Full-cell C/SiO2ǁNa3V2(PO4)3 high-performance Na-ion battery: Diffusion kinetics and N/P optimization

Full-cell C/SiO2ǁNa3V2(PO4)3 high-performance Na-ion battery: Diffusion kinetics and N/P optimization | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Full-cell C/SiO 2 ǁNa 3 V 2 (PO 4 ) 3 high-performance Na-ion battery: Diffusion kinetics and N/P optimization Nguyen Kim Yen Chuong, My Loan Phung Le, Tan Phat Vu, Van Man Tran This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3996186/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract C/SiO 2 composite derived from rice husks (RHs) have gained significant attention in the development of abundant anode materials for sodium-ion battery due to their unique features, simple synthesis process without using additional sources of silica and carbon and affordable price. Despite the extensive research reported, a part of the expensive hard carbon, the choice of anode materials is still limited leading to the challenges in the commercialization of SIBs... In this study, full-cell C/SiO 2 ǁNa 3 V 2 (PO 4 ) 3 was optimized the assembly conditions, achieving the highest and most stable capacity. In detail, N/P ratio surveys using presodiation C/SiO 2 materials is the remaining factor. Besides, evaluations of the diffusion process kinetics in C/SiO 2 have been conducted through Electrochemical Impedance Spectroscopy (EIS) and Galvanostatic Intermittent Titration Technique (GITT) studies. Within the pre-sodiation anode, full-cell C/SiO 2 ǁNa 3 V 2 (PO 4 ) 3 at N/P ~ 1.2 offers the highest capacity of 126.3 mAh.g − 1 and capacity retention of 83.7% after 50 cycles. Moreover, other electrochemical evaluation techniques were also used in this study, such as: EIS ex-situ, CV, C-rate, GCPL. Finally, with the information of this study, the optimization of Na-ion battery assembly conditions from material C/SiO 2 has been explored, opening a new future for cost-effective batteries. Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. INTRODUCTION Na-ion batteries are becoming a favorable option for energy storage compared to Li-ion batteries due to their cost-effectiveness and abundant sodium supply [ 1 ]. In the past few decades, extensive research has focused on evolving electrode materials that exhibit favorable electrochemical properties [ 2 ]. The most popular cathode materials today can refer to polyphosphate-based compounds such as (Na 3 V 2 (PO 4 ) 3 , Na 2 FeP 2 O 7 ) or Prussian blue NaFe[Fe(CN) 6 ], Na 2 CoFe(CN) 6 ). These materials all have high specific capacities ranging 80 mAh.g − 1 to 128 mAh.g − 1 [ 3 ][ 4 ]. Furthermore, various anode materials, including hard carbon, alloys (Sn, Sb, Si, and P), and metal oxides/sulfides (SiO 2 , TiO 2 , Sb 2 S 3 ), have been studied. They possess high specific capacities ranging from 300 mAh.g − 1 to 1800 mAh.g − 1 [ 4 ]–[ 9 ]. Among them, C/SiO 2 material is considered a new material for use in Na-ion batteries with criteria such as: Low cost, high theoretical capacity, high Coulumbic performance and impressive capacity retention [ 6 ]. In addition, previous studies about this material mainly focused on optimizing synthesis condition and evaluating the properties of individual electrodes without considering their compatibility in the full-cell. The knowledge from full-cell assembly elements is quite limited, thus greatly affecting the efficiency and performance of the battery. The main reason for the low initial-cycle Coulomb efficiency (ICE) in SIBs is the involvement of active sodium ions in electrolyte cross-linking, which occurs at both electrodes and becomes irreversible [ 10 ]. A reduced ICE necessitates a larger quantity of cathode material for compensation, ultimately leading to a decrease in the energy density of the full-cell. Presodiation methods have been found to replenish the amount of irreversible sodium ions that can be compensated. In the case of a sodium ion-rich cathode (O3), addition of sodium results in a reduction of sodium ions within the lattice structure [ 11 ]. As a result, cathode materials exhibit greater stability and longer electrochemical cycles. With the sodium ion-poor cathode (P2), sodium ions will be replenished from the electrolyte due to the cathode's inability to compensate for the irreversible number of ions [ 11 ]. Providing sodium through presodiation will help to compensate for the loss of sodium ions in the electrolyte [ 10 ]. Since then, the concentration of sodium ions in the electrolyte is also more stable and greatly improves the life of the full-cell [ 10 ]. For the anode, the presodiation method also shows that the potential region of the charge-discharge curve is reduced and flatter. This means that both active potential area of ​​the full-cell and the capacity density both increase [ 7 ]. The presodiation process in this study utilized Electrochemical (EC) as the preferred method. EC involves the assembly and disassembly of a half-cell, which consists of a working electrode that requires intercalation of sodium ions and sodium metal acting as counter electrodes [ 2 ]. Wang et al. conducted an EC method on NaNi 0.5 Mn 0.3 Ti 0.2 O 2 ǁHC (hard carbon) full-cell [ 7 ]. After three charge-discharge cycles, HC was used to assemble the full-cell. The results showed that the reversible capacity was as high as 131 mAh.g − 1 . Coulombic efficiency was maintained at 85% after 50 cycles, which is 9% higher than full-cell not subjected to presodiation by the EC method. The second factor is balance between the amount of sodium ions that can be stored in the anode and the amount of sodium ions that can be accommodated in the cathode. Many independent studies have been conducted on half-cell with the counter electrode being a sodium metal. In contrast, there is a lack of information about their electrochemical properties when operating in a full-cell battery [ 12 ]–[ 14 ]. In SIB, the positive electrode acts as a supplier of sodium ions. The anode receives sodium ions from the cathode during the initial cycle and beyond. A portion of the sodium gets absorbed into the anode's structure, where it is trapped as irreversible capacity and cannot be sent back to the cathode. As a result, the reversible and irreversible capacities of both electrodes will dictate the total capacity of the battery. In practical cell design, it is essential that the capacities of the opposing electrodes are "matched". In a full-cell battery, the cathode and anode must possess identical active areas and exchange equivalent capacities during the charging process [ 15 ]. The ratio of the capacity of the anode to the cathode (N/P) represents the relative amount of sodium ions that can be intercalated into the anode and de-intercalated from the cathode during the charging and discharging processes. A high N/P ratio generally means that more sodium ions can be stored in the battery, resulting in a higher energy density. However, a higher N/P ratio can also lead to increased structural strain and potential safety issues, such as lithium plating on the anode. Hence, optimizing the N/P ratio is crucial to strike a balance between performance and safety. By carefully optimizing the N/P ratio, both the anode and cathode are fully utilized during the charge and discharge cycles, maximizing the battery's capacity and efficiency. In the process of assembling a full-cell, it is crucial to consider not only the N/P ratio compatibility but also the significance of diffusion coefficient. This factor is a fundamental property that characterizes the transport of species in a material. In full-cell assembly, this parameter plays a crucial role in influencing the cell's performance, especially its power density and efficiency. Factors that can influence the diffusion coefficient in a full cell assembly include temperature, electrode thickness, porosity, electrolyte concentration, and the size and shape of the active materials [ 16 ]. Other factors such as the type of electrolyte and the electrode material can also affect the diffusion coefficient [ 1 ]. If the diffusion coefficients of the anode and cathode are not compatible, it can lead to several issues. Firstly, it can cause an uneven distribution of lithium ions during charge and discharge cycles, leading to uneven electrode degradation and decreased battery performance and capacity over time. Secondly, the mismatch in diffusion coefficients can lead to concentration polarization, where a concentration gradient is developed near the electrode-electrolyte interface. This can increase the resistance to ion transport, leading to lower battery efficiency and slower charging/discharging rates. In general, enhancing the compatibility of diffusion coefficients is a key aspect to think about when designing and optimizing Na-ion batteries. One way to solve compatibility problems in Na-ion batteries is by utilizing advanced materials for the anode and cathode that have higher diffusion coefficients and can more effectively align with each other's characteristics. In there, the diffusion coefficients of anode material should be higher than cathode material for fast-rate aplication [ 17 ]. The diffusion coefficient of the cathode is constant during cyling process [ 16 ], so that the full-cell performance will depend on ion diffusion into the anode electrode. This research uses C/SiO 2 as anode materials synthesized from rice husks for the full-cell C/SiO 2 ǁNa 3 V 2 (PO 4 ) 3 . C/SiO 2 material has been previously researched by our research team with potential features for SIB batteries such as high specific capacity and cost-effectiveness [ 6 ], [ 18 ], [ 19 ]. However, one major obstacle in the full-cell assembly of these batteries is the significant irreversible capacity loss (over 50%) observed after the initial cycle [ 6 ], [ 18 ]–[ 20 ]. In this study, full-cell C/SiO 2 ǁNa 3 V 2 (PO 4 ) 3 was optimized the assembly conditions, achieving the highest and most stable capacity. In detail, N/P ratio surveys using presodiation C/SiO 2 materials is studied specifically. As well as the issue of diffusion coefficient of C/SiO 2 material with porous structure also needs to be investigated. When liquid is restricted within a porous medium, the diffusion coefficient tends to be lower compared to that in the bulk liquid [ 1 ]. Research involving Electrochemical Impedance Spectroscopy (EIS) and Galvanostatic Intermittent Titration Technique (GITT) has been carried out on C/SiO 2 in order to comprehend the kinetics of sodiation and desodiation. Based on our findings, C/SiO2 emerges as a prospective choice for anode material in upcoming SIB applications. 2. EXPERIMENTAL We utilized the process of synthesizing C/SiO 2 materials from rice husks based on previous research [ 6 ], [ 18 ], [ 19 ]. Through the process of surface activation of rice husk ash with KOH, the surface area of ​​C/SiO 2 material will be improved, and the material will then perform presodiation by the EC method. Since Na is a reactive metal in air, this assembly and disassembly process requires an argon-filled glovebox ( MB 20 G, MBRAUN). After five charge-discharge cycles of the C/SiO 2 ǁNa with a C/10 current density and 0.01-2V potential region, Na + ions will be interwoven into the material’s structure. The cut-off voltage during the last discharge cycles was set at 0.3 V. Lastly, the sodium metal as counter electrode was substituted with an NVP electrode to explore deeper into the electrochemical characteristics of the full-cell. The cathode electrode was prepared using a combination of NaV 2 (PO 4 ) 3 , C65 (Imerys) and a PVdF/NMP (Sigma Aldrich) binder (~ 10% wt) in a mass ratio of 80:15:5. The ingredients are mixed into a mixture, then coated with aluminum foil using the Doctor Blade technique. The resulting cathode membrane was dried under vacuum for 12 hours. Finally, the electrode membrane was cut into a circular shape with a diameter of 12 mm (NVP mass is about 3.408 mg – 4.992 mg). Similarly, the anode electrode was made up of a mixture of C/SiO 2 , C65 (Imerys) and CMC (Sigma Aldrich) binder (phase in water, ~ 1.4% wt ) in a mass ratio of 70:25:5. This mixture was coated onto copper foil and cut into circular shapes (SiO 2 /C mass is about 3.247 mg – 4.185 mg). The Swagelok model was used to investigate both half-cell and full-cell, which used a Whatman glass separator (GF/C) with electrolyte permeation of 1 M NaClO 4 / EC:DEC (1:1, v/v ). The electrode materials were investigated in different potential regions to determine the specific capacity at the C/10 rate. The NVP cathode was examined in the potential range of 2.4-4 V, while the C/SiO 2 anode was tested from 0.01-3V. Full-cell C/SiO 2 ǁNa 3 V 2 (PO 4 ) 3 was investigated with 4 N/P ratios of 1.0, 1.1, 1.2 and 1.3, respectively, in the potential region from 1-3.5 V at C/10 rate. For the C-rate measurement, the discharge-charge rate changed every five cycles as follows: C/10, C/5, C/2, 1C and then back to C/10 again. The electrochemical measurements were tested on the MPG-2 (Biologic) device using EC-Lab software. Full-cell results with the suitable N/P ratio will be evaluated using CV (rate of 0.1 mV.s − 1 , vs Na + /Na) and EIS 200.000 kHz to 100.000 mHz with an amplitude of 10 mV, VSP-2 Biologic measuring instrument) measurements. 3. RESULTS AND DISCUSSION 3.1. Diffusion kinetics using EIS and GITT methods EIS is an effective technique for analyzing the movement of sodium ions into and out of the electrode. Figure 1 a displays the Nyquist plot at various discharge stages. The plot displays a depressed semicircle in the high-frequency range, along with the Warburg region, and then shows a linear slope as the frequency decreases. The low-frequency semicircle is attributed to the interfacial charge transfer of sodium ions (R ct ), in conjunction with capacitance (CPE ct ) at the electrode/surface film interface [ 11 ][ 21 ]. During the first discharge, the total impedance value of C/SiO 2 material almost does not change much, in the range of 200–250 Ω which is higher than that of Hard carbon material abour 50 Ω [ 22 ]. However, the degree of variation and trend are the same. When discharge reaches the low voltage region, the total impedance value tends to decrease. This can be clarified by the easier kinetic process of interlocking Na ions into the material structure, the enhanced electrical conductivity of the sodium-carbon material during sodiation, which in turn facilitates the kinetics of the electrochemical reactions [ 22 ]. We can verify this argument by the calculated diffusion coefficient values below. The impedance of Warburg is associated with the solid state diffusion of Na + within the active particles [ 11 ]. As a result, the Warburg component can be utilized to estimate D Na+ using the equation below [ 23 ][ 24 ]: $$D=\frac{{R}^{2}{T}^{2}}{2{A}^{2}{n}^{4}{F}^{4}{C}^{2}{\sigma }^{2}} \left(1\right)$$ Impedance curves below 0.41 V do not display a distinct diffusion extension within the measured frequency range and are therefore not taken into consideration for further analysis. This is due to the fact that the sluggish interfacial kinetics dominate over the diffusion process [ 11 ]. The Nyquist plot illustrates the infinite Warburg impedance as a slanted line with an angle of 45 o (Fig. 1 b). Beyond a potential of 0.74 V, the Warburg line deviates from the expected slope condition. So that, the calculation of the diffusion coefficient is limited to potential ranges above 0.74 V [ 25 ][ 26 ]. Table 1 illustrates that the \({D}_{{Na}^{+}}\) values obtained from the EIS method range between 10 −15 and 10 − 14 cm 2 .s −1 , depending on the applied voltages. It is observed that \({D}_{{Na}^{+}}\) values exhibit a decreasing trend as the cell discharges to 0.01 V. Due to the discharge process, the space for sodium ion insertion in the lithiated C/SiO 2 structure gradually decreases. This suggests that towards the end of the discharge process, it becomes increasingly challenging for Na + ions to be inserted. The galvanostatic intermittent titration technique (GITT), pioneered by Weppner and Huggins, provides researchers with a valuable method to investigate and measure Na + diffusion coefficients in different electrode materials, significantly contributing to the advancement of our comprehension of electrochemical systems' behavior [ 17 ][ 27 ]. As shown in Fig. 2 a, the GITT curves for the C/SiO 2 anode were obtained within a voltage range of 2.0-0.01 V. In the GITT test, a discharge current of 0.1 mA is applied for 10 minutes, after which there is a 40-minute relaxation period with an open-circuit condition to enable the cell voltage to reach a stable state. This procedure is repeated throughout the entire voltage window from 2.0 V to 0.01 V. Based on Fick's second law, it is possible to calculate the diffusion coefficients of lithium ions using the following Eq. ( 2 ) [ 28 ]. $$D=\frac{4}{\pi }\times (\frac{I\times {V}_{m}}{{Z}_{A}\times F\times S}{)}^{2}\times (\frac{dE/d{\delta }}{dE/d\sqrt{t}}{)}^{2}$$ 2 The calculated \({D}_{{Na}^{+}}\) values from GITT measurements fal within the range of 10 −12 to 10 − 10 cm 2 .s −1 during discharge processes. As the voltage decreases during the discharge process, there is a slight decrease in the diffusion coefficient. However, when the voltage reaches 0.2 V, there is a rapid increase in the diffusion coefficient until the discharge process ends at 0.01 V (Fig. 2 c). This phenomenon is explained that the value range from 0.2 − 0.01 V is the typical window voltage of C/SiO 2 material [ 6 ]. Therefore, the process of interlocking Na ions takes place more smoothly, leading to an increase in the diffusion coefficient in this potential range. The cathode used in this work is Na 3 V 2 (PO 4 ) 3 . Its diffusion coefficient has been found to be range approximately 10 −11 (cm 2 .s −1 ) in previous studies [ 29 ]–[ 32 ]. C/SiO 2 material has a diffusion coefficient approximately similar to the Na 3 V 2 (PO 4 ) 3 material, so it indicate the potential for the fast-rate application [ 17 ]. The \({D}_{{Na}^{+}}\) value obtained from GITT (10 −12 to 10 − 10 cm 2 .s −1 ) is higher than that obtained from EIS (10 −15 and 10 − 14 cm 2 .s −1 ). This disparity can be attributed to the fact that the two methods were conducted under different equilibrium conditions [ 11 ]. In real experimental settings, the GITT method uses a brief pulse with sufficient relaxation time to remove any unwanted background current interference in the measured response. This significantly reduces errors when determining the diffusion coefficient compared to using EIS data [ 33 ]. Furthermore, the utilization of GITT becomes appealing when the inherent kinetics of phase transitions of the active material influence the corresponding electroanalytical responses [ 33 ]. Meanwhile, the EIS method is associated with the solid state diffusion of Na + within the active particles [ 11 ]. Additionally, the EIS outcomes were acquired under conditions closer to equilibrium, enabling an extended relaxation period for the electrode. Moreover, in our calculations, we consider the surface area in contact with the electrolyte as the geometric area of the electrode [ 34 ]. Nevertheless, it is important to recognize that the effective contact area between the C/SiO 2 electrode and electrolyte will exceed the geometric surface area due to the penetration of electrolyte into the C/SiO 2 electrode. This penetration will lead to a decrease in D Na+ , but the alteration of D Na+ with cell voltage remains unchanged in the potential range from 1.1 to 0.8 V. The calculated diffusion coefficient values obtained from GITT in this work demonstrate consistency with findings from earlier research, such as mesoporous soft carbon obtained from EIS by Cao et al. ( \(1.85\times {10}^{-11}\) cm 2 .s − 1 ) [ 35 ], soft carbon ( \(1.85\times {10}^{-11}\) cm 2 .s − 1 ) or hard carbon (3.6 \(\times {10}^{-12}\) cm 2 .s − 1 ) from Cheng et al. [ 36 ]. 3.2. Survey N/P conditions for full-cell C/SiO 2 ǁNa 3 V 2 (PO 4 ) 3 GCPL results (Fig. 5 a) show that the capacity of C/SiO 2 materials reaches 471.5 mAh.g − 1 at the first cycle. After 50 cycles, the capacity of C/SiO 2 remains at 150 mAh.g − 1 . Because of the capacity irreversibility after the first cycle, the electrode activation process is performed for this material [ 6 ], [ 18 ], [ 19 ], [ 37 ]. C/SiO 2 material is assembled into a half-cell with Na metal. After 5 charging cycles, this material is continued to assemble a full-cell with NVP cathode material. The capacity of the first cycle NVP material reaches 105.6 mAh.g − 1 (Fig. 3 b), a result that is close to the theoretical capacity of the NVP material (117 mAh.g − 1 ). Capacity reaches nearly the same after 50 cycles, approximately 110 mAh.g − 1 . This electrochemical result shows that the commercial NVP material used has high chemical properties as well as high structural stability during interlocking/release in the investigated potential region. In addition, the charge-discharge curve shows a characteristic flat potential at 3.4 V, which is typical for the flat potential region of the oxidation-reduction pair V 4+ /V 3+ [ 38 ]. From the above results, the actual capacity of C/SiO 2 and NVP materials will be fixed at 150 mAh.g − 1 and 110 mAh.g − 1 respectively, for implementation in formula (3) [ 39 ]. $$\frac{\text{N}}{\text{P}}=\frac{{\text{C}}_{\text{a}\text{n}\text{o}\text{d}\text{e}}}{{\text{C}}_{\text{c}\text{a}\text{t}\text{h}\text{o}\text{d}\text{e}}}=\frac{{\text{C}\text{a}\text{p}\text{a}\text{c}\text{i}\text{t}\text{y}}_{\text{a}\text{n}\text{o}\text{d}\text{e}} \times {\text{m}}_{\text{a}\text{c}\text{t}\text{i}\text{v}\text{e} \text{a}\text{n}\text{o}\text{d}\text{e} \text{m}\text{a}\text{t}\text{e}\text{r}\text{i}\text{a}\text{l}}}{{\text{C}\text{a}\text{p}\text{a}\text{c}\text{i}\text{t}\text{y}}_{\text{c}\text{a}\text{t}\text{h}\text{o}\text{d}\text{e} }\times {\text{m}}_{\text{a}\text{c}\text{t}\text{i}\text{v}\text{e} \text{c}\text{a}\text{t}\text{h}\text{o}\text{d}\text{e} \text{m}\text{a}\text{t}\text{e}\text{r}\text{i}\text{a}\text{l}}}$$ 3 The results of the GCPL survey of full-cell C/SiO 2 ǁNa 3 V 2 (PO 4 ) 3 at N/P ratios are shown in Fig. 4 . In the first cycle, the discharge capacity of N/P ratios 1.0 and 1.1, reaches 96.3 mAh.g − 1 , 112,0 mAh.g − 1 , respectively. However, the capacity decreased rapidly, as shown by the specific capacity results at cycles 50, reaching 15.5 mAh.g − 1 and 17.8 mAh.g − 1 . At the 50th cycle, the ratio N/P = 1.0 maintained 16.1% capacity retention, higher than the result of the ratio N/P = 1.1 only 15.9% (Table 2 ). Meanwhile, the discharge capacity at the first cycle of the N/P 1.2 reaches 126.3 mAh.g − 1 . After 50 cycles, the specific capacity still maintained is 105.7 mAh.g − 1 (83.7% retention compared to the first cycle, Table 2 ). Besides, the discharge capacity at the first cycle of the ratio N/P = 1.3 reached 93.6 mAh.g − 1 , after 50 cycles, the specific capacity obtained was 97.7 mAh.g − 1 . The specific capacity with the ratio N/P = 1.2 gradually decreases over the cycle. Surveying the cycling of a full-cell with 4 different N/P ratios over 50 cycles at C/10 rate (Fig. 5 a) shows that, at the ratio N/P = 1.0, the capacity decreases rapidly during 50 cycles, the Coulomb efficiency remains ~ 90%. Full-cell with the ratio N/P = 1.1 shows a significantly decreasing trend of specific capacity. In contrast, the Coulomb efficiency increased gradually, from period 25 onwards, maintaining ~ 96%. With the ratio N/P = 1.2 and 1.3, a general trend is that the specific capacity of the early cycles decreases, however from the 10th period onwards, the specific capacity increases. Especially at the ratio N/P = 1.3, the specific capacity increases, resulting in the 50th cycle the discharge capacity is higher than the first cycle (97.7 > 93.6 mAh.g − 1 ). Coulomb efficiency of full cell with and N/P = 1.2 ratio increases follow cycling process, at the 50th cycle, the stable efficiency ~ 98%. As a result, the Coulumbic efficiency gradually increases after charge-discharge cycles due to the formation of a stable SEI layer, resulting in the discharging-charging process becoming more reversible. The rate capability results of ratios N/P = 1.1; 1.2 and 1.3 have quite high and stable Coulomb efficiency (approximately 98%). As the current rate increases, the specific capacity of the full-cell decreases. Especially at the ratio N/P = 1.0, the specific capacity is limited. At all 4 N/P ratios, the full-cell when returning to the C/10 showed a reduction in capacity compared to the first 5 cycles at the same current (Fig. 5 b). With the ratio N/P = 1.2, the N/P 1.2 gives a specific capacity of 113.7 mAh.g − 1 when returning to C/10 rate (99.1% capacity retention). From this, it can be concluded that the ratio N/P = 1.2 has the ability to work well at different discharge-charge current rates. The cyclic voltammetry (CV) at the 1st, 3rd and 5th cycles of the full-cell with an N/P ratio = 1.2 are investigated in the potential range from 0.5–3.5 V at scan rate 0.1 mV/s (Fig. 6 ). The results show that the process of interlocking and releasing Na + ions take place in the range of 0.15–3.5 V. In all 3 cycles, the CV curve shows a pair of peaks at 3.4 and 3.2 V, which represent the V 3+ oxidized form and the V 4+ reduced form, respectively [ 40 ]. In the 1st, the oxidation peak at 3.4 V (0.26 mA) has a much higher intensity than the reduction peak at 3.2 V (0.07 mA), showing that the oxidation process requires higher current rate than the reduction process [ 41 ]. In the remaining cycles, the intensity of the two peaks narrows the gap and the CV curve shape is almost the same. In addition, in the discharge cycle, in the potential range from 1.3 to 2.7 V, a wide active region appears with unclear peak shape. It shows that the sodium interlocking reaction on the anode also occurs in this potential region [ 42 ]. The operating potential region results of the CV curve are also consistent with the appearance of two flat shoulder regions at 1.0 and 2.5 V of the GCPL results (full-cell N/P ratio = 1.2). The intensity of the reduction peak is lower than the oxidation peak, showing that the ion release diffusion from the anode is slower than that from the cathode. This result is consistent with the diffusion coefficient results examined. Figure 7 shows the electrochemical impedance spectra of the full-cell C/SiO 2 ǁNa 3 V 2 (PO 4 ) 3 with an N/P ratio = 1.2 at pristine and different potential values. The battery in its initial state shows two semicircles. The semicircles detected in the high and medium frequency ranges are probably attributed to the surface film resistance at the electrode-electrolyte interface, along with the charge transfer resistance. The remaining component - linear region is associated with the Warburg diffusion of Na + cations within the bulk material [ 22 ]. However, after being operated, the battery only shows one semicircle at various potential values. This phenomenon can be explained in the following manner. When two electrodes are involved in charge transfer processes or when two processes occur on one electrode simultaneously with similar frequencies, a semicircle can appear. At the beginning, before the charging process takes place, the system consists of two different-natured electrodes [ 43 ]. As a result, there will be as many charge transfer semicircles as there are interfaces, and these semicircles will typically be distinct and separate. It is highly unlikely for them to coincide. During charging-discharging process, changes in the concentration of oxidizing/reducing substances and alterations in the composition of the interfacial layer on an electrode lead to modifications in charge transfer resistance for each electrode. Whether or not a semicircle can be observed and how separated it appears depends on specific circumstances that cannot be predicted accurately. When the battery is newly installed (pristine), the EIS spectrum depicts an imperfect semicircle due to the lack of electrical energy activation in the electrode. At this stage, Na + diffusion is sluggish, and it has not yet penetrated the electrode structure. However, after operation, the total impedance value decreases significantly. The semicircle is reduced by nearly 100 times compared to its original state and becomes more complete, indicating the successful participation of Na + ions in the C/SiO 2 structure. 4. CONCLUSION The presodiation process using the Electrochemical method (EC) was successfully carried out on C/SiO 2 anode derived from rice husk. The sodium diffusion coefficient of C/SiO 2 calculated using the GITT method is higher, ranging from 10 –12 to 10 –10 (cm 2 s -1 ) compared to that calculated using the EIS method, which ranges from 10 –15 to 10 –14 (cm 2 s -1 ). This is because the two methods were conducted under different equilibrium conditions. It is noteworthy that the diffusion coefficient value derived from GITT aligns with findings from prior studies. The full-cell C/SiO 2 ║Na 3 V 2 (PO 4 ) 3 with N/P ratios of 1.1 and 1.2 achieved specific capacity of 112.0 and 126.3 mAh.g -1 , respectively. The full-cell with a N/P ratio of 1.2 retained up to 83.7% of its capacity after 50 cycles. When the current density increases, the full-cell with a N/P ratio of 1.1 and 1.2 results in specific capacity of 58.6 and 67.4 mAh.g -1 at 1C, respectively. The battery maintains over 58% of its capacity when the current density is back to C/10. Significantly, the work presented here provides information on the kinetics and optimal values ​​for cost-effective assembly of SIBs. DECLARATIONS CONFLICT OF INTEREST The authors declare that they have no conflict of interest. Author Contribution Le My Loan Phung, Tran Van Man and Vu Tan Phat came up with a research idea- Chuong Nguyen Kim Yen and Vu Tan Phat did the experiment- Chuong Nguyen Kim Yen and Vu Tan Phat wrote the main manuscript text- Le My Loan Phung and Tran Van Man edited the manuscript until it was complete REFERENCES C. Pean, B. Daffos, B. Rotenberg, P. Levitz, M. Haefele, P. L. Taberna, P. Simon, and M. Salanne “Confinement, Desolvation, and Electrosorption Effects on the Diffusion of Ions in Nanoporous Carbon Electrodes,” J. Am. Chem. Soc. , vol. 137, no. 39, pp. 12627–12632, 2015, doi: 10.1021/jacs.5b07416. E. de la Llave, V. Borgel, K. J. Parka, J. Y Hwang, Y. K. Suna, P. 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Kumagai, “Effect of negative/positive capacity ratio on the rate and cycling performances of LiFePO 4 /graphite lithium-ion batteries,” J. Energy Storage , vol. 19, no. February, pp. 96–102, 2018, doi: 10.1016/j.est.2018.07.012. D. R. Kumar, I. Kanagaraj, G. Dhakal, A. S. Prakash, and J. J. Shim, “Palmyra Palm tree biomass-derived carbon low-voltage plateau region capacity on Na-ion battery and its full cell performance,” J. Environ. Chem. Eng. , vol. 9, no. 4, p. 105698, 2021, doi: 10.1016/j.jece.2021.105698. X. Huang et al. , “Cyclic Voltammetry in Lithium–Sulfur Batteries—Challenges and Opportunities,” Energy Technol. , vol. 7, no. 8, 2019, doi: 10.1002/ente.201801001. M. Lu, Y. Huang, and C. Chen, “Cedarwood Bark-Derived Hard Carbon as an Anode for High-Performance Sodium-Ion Batteries,” Energy and Fuels , vol. 34, no. 9, pp. 11489–11497, 2020, doi: 10.1021/acs.energyfuels.0c01841. L. A. Middlemiss, A. J. R. Rennie, R. Sayers, and A. R. West, “Characterisation of batteries by electrochemical impedance spectroscopy”, Energy Reports , vol. 6, pp. 232–241, 2020, doi: 10.1016/j.egyr.2020.03.029. Tables Tables 1 and 2 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Table1.jpg Table2.jpg Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3996186","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":275507431,"identity":"14d47d06-a7bb-4ee5-a132-7d5755bdccf2","order_by":0,"name":"Nguyen Kim Yen Chuong","email":"","orcid":"","institution":"Applied Physical Chemistry Laboratory, VNUHCM-University of Science","correspondingAuthor":false,"prefix":"","firstName":"Nguyen","middleName":"Kim Yen","lastName":"Chuong","suffix":""},{"id":275507432,"identity":"96cce9d8-7639-4c7d-bb68-f7c19b359000","order_by":1,"name":"My Loan Phung 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Nyquist plots of C/SiO\u003csub\u003e2\u003c/sub\u003e at different discharge states (b) The correlation between the real part of impedance (Z') and the square root of frequency (w\u003csup\u003e-1/2\u003c/sup\u003e) at various voltages within the Warburg region\u003c/p\u003e","description":"","filename":"Figure1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3996186/v1/82199f72bcc45eb060c0a814.jpg"},{"id":51872406,"identity":"adc9fa3a-d573-40cc-85c6-c8b8b42bb979","added_by":"auto","created_at":"2024-03-01 17:03:21","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":549412,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Galvanostatic intermittent titration curve with a pulse of 10 mAg\u003csup\u003e-1\u003c/sup\u003e (b) The correlation between voltage change and the square root of interrupt time (c) Diffusion coefficients of lithium ions in C/SiO\u003csub\u003e2\u003c/sub\u003e results from GITT\u003c/p\u003e","description":"","filename":"Figure2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3996186/v1/5a8b5c34befce533339219cf.jpg"},{"id":51871343,"identity":"e3c5dbc7-f1fc-40b5-a5a1-630e6fa53510","added_by":"auto","created_at":"2024-03-01 16:55:22","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":455554,"visible":true,"origin":"","legend":"\u003cp\u003eCharge-discharge curve at 1\u003csup\u003est\u003c/sup\u003e, 2\u003csup\u003end\u003c/sup\u003e, 10\u003csup\u003eth\u003c/sup\u003e, 25\u003csup\u003eth\u003c/sup\u003e and 50\u003csup\u003eth\u003c/sup\u003e period at C/10 rate of (a) C/SiO\u003csub\u003e2\u003c/sub\u003e material in potential region 0.01 – 3.0 V and (b) NVP in potential region 2, 4 – 4.0 V\u003c/p\u003e","description":"","filename":"Figure3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3996186/v1/84cda9eddb9e895e7f9a2ee0.jpg"},{"id":51871341,"identity":"aa3baa70-a798-42f8-bb1e-a031193b5acf","added_by":"auto","created_at":"2024-03-01 16:55:21","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":589555,"visible":true,"origin":"","legend":"\u003cp\u003eCharge-discharge curve at (a) 1\u003csup\u003est \u003c/sup\u003eand (b) 50\u003csup\u003eth\u003c/sup\u003e cycles at C/10 rate of full-cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e in potential region 0.5 – 3.5 V with N/P ratios at 1.0, 1.1, 1.2 and 1.3.\u003c/p\u003e","description":"","filename":"Figure4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3996186/v1/ee69b77b82547d56a9ca8598.jpg"},{"id":51871338,"identity":"aadb6f0f-c383-4fbd-93c4-98e9c19e6ff8","added_by":"auto","created_at":"2024-03-01 16:55:20","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":642925,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Discharge capacity and Coulomb efficiency of the full-cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3 \u003c/sub\u003ein 50 cycles and (b) rates capacity with 4 N/P ratios 1.0, 1.1, 1.2 and 1.3.\u003c/p\u003e","description":"","filename":"Figure5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3996186/v1/82b54cc2131290c61a563fa8.jpg"},{"id":51871340,"identity":"5f84fb82-6474-4a7e-95c6-06fa2f2d9644","added_by":"auto","created_at":"2024-03-01 16:55:20","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":225129,"visible":true,"origin":"","legend":"\u003cp\u003eThe cyclic vorammtry result of full cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3 \u003c/sub\u003ewith N/P ratio = 1.2\u003c/p\u003e","description":"","filename":"Figure6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3996186/v1/3315d39b3a87555162808ce8.jpg"},{"id":51871344,"identity":"75f7be85-6ef4-4149-bbd9-a396510d1be4","added_by":"auto","created_at":"2024-03-01 16:55:22","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":130861,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Nyquist plot of the full cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3 \u003c/sub\u003eat pristine and various potential values, and (b) its magnified plots\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-3996186/v1/fc67a34fa1eb9f305a8b5ed0.png"},{"id":52845076,"identity":"3376dacd-bf03-4b4e-8ed3-194b6745f931","added_by":"auto","created_at":"2024-03-17 16:52:55","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":851048,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3996186/v1/62fac0ed-25ee-4c31-8fc6-a4e963cfd93f.pdf"},{"id":51871337,"identity":"58cbb1a6-ee0d-48ac-968b-caafca5708f1","added_by":"auto","created_at":"2024-03-01 16:55:19","extension":"jpg","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":411743,"visible":true,"origin":"","legend":"","description":"","filename":"Table1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3996186/v1/6c63ed2e63ed5d3f93747a29.jpg"},{"id":51871339,"identity":"c7ed4047-211f-4bd5-be92-0dc7d633da8c","added_by":"auto","created_at":"2024-03-01 16:55:20","extension":"jpg","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":279186,"visible":true,"origin":"","legend":"","description":"","filename":"Table2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3996186/v1/392a3be6abbac8349af1c6ff.jpg"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eFull-cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e high-performance Na-ion battery: Diffusion kinetics and N/P optimization\u003c/p\u003e","fulltext":[{"header":"1. INTRODUCTION","content":"\u003cp\u003eNa-ion batteries are becoming a favorable option for energy storage compared to Li-ion batteries due to their cost-effectiveness and abundant sodium supply [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In the past few decades, extensive research has focused on evolving electrode materials that exhibit favorable electrochemical properties [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The most popular cathode materials today can refer to polyphosphate-based compounds such as (Na\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e, Na\u003csub\u003e2\u003c/sub\u003eFeP\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e) or Prussian blue NaFe[Fe(CN)\u003csub\u003e6\u003c/sub\u003e], Na\u003csub\u003e2\u003c/sub\u003eCoFe(CN)\u003csub\u003e6\u003c/sub\u003e). These materials all have high specific capacities ranging 80 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 128 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e][\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Furthermore, various anode materials, including hard carbon, alloys (Sn, Sb, Si, and P), and metal oxides/sulfides (SiO\u003csub\u003e2\u003c/sub\u003e, TiO\u003csub\u003e2\u003c/sub\u003e, Sb\u003csub\u003e2\u003c/sub\u003eS\u003csub\u003e3\u003c/sub\u003e), have been studied. They possess high specific capacities ranging from 300 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e to 1800 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e [\u003cspan additionalcitationids=\"CR5 CR6 CR7 CR8\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]\u0026ndash;[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Among them, C/SiO\u003csub\u003e2\u003c/sub\u003e material is considered a new material for use in Na-ion batteries with criteria such as: Low cost, high theoretical capacity, high Coulumbic performance and impressive capacity retention [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In addition, previous studies about this material mainly focused on optimizing synthesis condition and evaluating the properties of individual electrodes without considering their compatibility in the full-cell. The knowledge from full-cell assembly elements is quite limited, thus greatly affecting the efficiency and performance of the battery.\u003c/p\u003e \u003cp\u003eThe main reason for the low initial-cycle Coulomb efficiency (ICE) in SIBs is the involvement of active sodium ions in electrolyte cross-linking, which occurs at both electrodes and becomes irreversible [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. A reduced ICE necessitates a larger quantity of cathode material for compensation, ultimately leading to a decrease in the energy density of the full-cell. Presodiation methods have been found to replenish the amount of irreversible sodium ions that can be compensated. In the case of a sodium ion-rich cathode (O3), addition of sodium results in a reduction of sodium ions within the lattice structure [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. As a result, cathode materials exhibit greater stability and longer electrochemical cycles. With the sodium ion-poor cathode (P2), sodium ions will be replenished from the electrolyte due to the cathode's inability to compensate for the irreversible number of ions [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Providing sodium through presodiation will help to compensate for the loss of sodium ions in the electrolyte [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Since then, the concentration of sodium ions in the electrolyte is also more stable and greatly improves the life of the full-cell [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. For the anode, the presodiation method also shows that the potential region of the charge-discharge curve is reduced and flatter. This means that both active potential area of ​​the full-cell and the capacity density both increase [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The presodiation process in this study utilized Electrochemical (EC) as the preferred method. EC involves the assembly and disassembly of a half-cell, which consists of a working electrode that requires intercalation of sodium ions and sodium metal acting as counter electrodes [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Wang \u003cem\u003eet al.\u003c/em\u003e conducted an EC method on NaNi\u003csub\u003e0.5\u003c/sub\u003eMn\u003csub\u003e0.3\u003c/sub\u003eTi\u003csub\u003e0.2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003eǁHC (hard carbon) full-cell [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. After three charge-discharge cycles, HC was used to assemble the full-cell. The results showed that the reversible capacity was as high as 131 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Coulombic efficiency was maintained at 85% after 50 cycles, which is 9% higher than full-cell not subjected to presodiation by the EC method.\u003c/p\u003e \u003cp\u003eThe second factor is balance between the amount of sodium ions that can be stored in the anode and the amount of sodium ions that can be accommodated in the cathode. Many independent studies have been conducted on half-cell with the counter electrode being a sodium metal. In contrast, there is a lack of information about their electrochemical properties when operating in a full-cell battery [\u003cspan additionalcitationids=\"CR13\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u0026ndash;[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. In SIB, the positive electrode acts as a supplier of sodium ions. The anode receives sodium ions from the cathode during the initial cycle and beyond. A portion of the sodium gets absorbed into the anode's structure, where it is trapped as irreversible capacity and cannot be sent back to the cathode. As a result, the reversible and irreversible capacities of both electrodes will dictate the total capacity of the battery. In practical cell design, it is essential that the capacities of the opposing electrodes are \"matched\". In a full-cell battery, the cathode and anode must possess identical active areas and exchange equivalent capacities during the charging process [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. The ratio of the capacity of the anode to the cathode (N/P) represents the relative amount of sodium ions that can be intercalated into the anode and de-intercalated from the cathode during the charging and discharging processes. A high N/P ratio generally means that more sodium ions can be stored in the battery, resulting in a higher energy density. However, a higher N/P ratio can also lead to increased structural strain and potential safety issues, such as lithium plating on the anode. Hence, optimizing the N/P ratio is crucial to strike a balance between performance and safety. By carefully optimizing the N/P ratio, both the anode and cathode are fully utilized during the charge and discharge cycles, maximizing the battery's capacity and efficiency.\u003c/p\u003e \u003cp\u003eIn the process of assembling a full-cell, it is crucial to consider not only the N/P ratio compatibility but also the significance of diffusion coefficient. This factor is a fundamental property that characterizes the transport of species in a material. In full-cell assembly, this parameter plays a crucial role in influencing the cell's performance, especially its power density and efficiency. Factors that can influence the diffusion coefficient in a full cell assembly include temperature, electrode thickness, porosity, electrolyte concentration, and the size and shape of the active materials [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Other factors such as the type of electrolyte and the electrode material can also affect the diffusion coefficient [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. If the diffusion coefficients of the anode and cathode are not compatible, it can lead to several issues. Firstly, it can cause an uneven distribution of lithium ions during charge and discharge cycles, leading to uneven electrode degradation and decreased battery performance and capacity over time. Secondly, the mismatch in diffusion coefficients can lead to concentration polarization, where a concentration gradient is developed near the electrode-electrolyte interface. This can increase the resistance to ion transport, leading to lower battery efficiency and slower charging/discharging rates. In general, enhancing the compatibility of diffusion coefficients is a key aspect to think about when designing and optimizing Na-ion batteries. One way to solve compatibility problems in Na-ion batteries is by utilizing advanced materials for the anode and cathode that have higher diffusion coefficients and can more effectively align with each other's characteristics. In there, the diffusion coefficients of anode material should be higher than cathode material for fast-rate aplication [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. The diffusion coefficient of the cathode is constant during cyling process [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], so that the full-cell performance will depend on ion diffusion into the anode electrode.\u003c/p\u003e \u003cp\u003eThis research uses C/SiO\u003csub\u003e2\u003c/sub\u003e as anode materials synthesized from rice husks for the full-cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e. C/SiO\u003csub\u003e2\u003c/sub\u003e material has been previously researched by our research team with potential features for SIB batteries such as high specific capacity and cost-effectiveness [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. However, one major obstacle in the full-cell assembly of these batteries is the significant irreversible capacity loss (over 50%) observed after the initial cycle [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], [\u003cspan additionalcitationids=\"CR19\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]\u0026ndash;[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. In this study, full-cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e was optimized the assembly conditions, achieving the highest and most stable capacity. In detail, N/P ratio surveys using presodiation C/SiO\u003csub\u003e2\u003c/sub\u003e materials is studied specifically. As well as the issue of diffusion coefficient of C/SiO\u003csub\u003e2\u003c/sub\u003e material with porous structure also needs to be investigated. When liquid is restricted within a porous medium, the diffusion coefficient tends to be lower compared to that in the bulk liquid [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Research involving Electrochemical Impedance Spectroscopy (EIS) and Galvanostatic Intermittent Titration Technique (GITT) has been carried out on C/SiO\u003csub\u003e2\u003c/sub\u003e in order to comprehend the kinetics of sodiation and desodiation. Based on our findings, C/SiO2 emerges as a prospective choice for anode material in upcoming SIB applications.\u003c/p\u003e"},{"header":"2. EXPERIMENTAL","content":"\u003cp\u003eWe utilized the process of synthesizing C/SiO\u003csub\u003e2\u003c/sub\u003e materials from rice husks based on previous research [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e], [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. Through the process of surface activation of rice husk ash with KOH, the surface area of ​​C/SiO\u003csub\u003e2\u003c/sub\u003e material will be improved, and the material will then perform presodiation by the EC method. Since Na is a reactive metal in air, this assembly and disassembly process requires an argon-filled glovebox (\u003cem\u003eMB 20 G, MBRAUN).\u003c/em\u003e After five charge-discharge cycles of the C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa with a C/10 current density and 0.01-2V potential region, Na\u003csup\u003e+\u003c/sup\u003e ions will be interwoven into the material\u0026rsquo;s structure. The cut-off voltage during the last discharge cycles was set at 0.3 V. Lastly, the sodium metal as counter electrode was substituted with an NVP electrode to explore deeper into the electrochemical characteristics of the full-cell.\u003c/p\u003e \u003cp\u003eThe cathode electrode was prepared using a combination of NaV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e, C65 \u003cem\u003e(Imerys)\u003c/em\u003e and a PVdF/NMP \u003cem\u003e(Sigma Aldrich)\u003c/em\u003e binder (~\u0026thinsp;10% wt) in a mass ratio of 80:15:5. The ingredients are mixed into a mixture, then coated with aluminum foil using the Doctor Blade technique. The resulting cathode membrane was dried under vacuum for 12 hours. Finally, the electrode membrane was cut into a circular shape with a diameter of 12 mm (NVP mass is about 3.408 mg \u0026ndash; 4.992 mg). Similarly, the anode electrode was made up of a mixture of C/SiO\u003csub\u003e2\u003c/sub\u003e, C65 \u003cem\u003e(Imerys)\u003c/em\u003e and CMC \u003cem\u003e(Sigma Aldrich)\u003c/em\u003e binder (phase in water, ~ 1.4% \u003cem\u003ewt\u003c/em\u003e) in a mass ratio of 70:25:5. This mixture was coated onto copper foil and cut into circular shapes (SiO\u003csub\u003e2\u003c/sub\u003e/C mass is about 3.247 mg \u0026ndash; 4.185 mg). The Swagelok model was used to investigate both half-cell and full-cell, which used a Whatman glass separator \u003cem\u003e(GF/C)\u003c/em\u003e with electrolyte permeation of 1 M NaClO\u003csub\u003e4\u003c/sub\u003e/ EC:DEC (1:1, \u003cem\u003ev/v\u003c/em\u003e).\u003c/p\u003e \u003cp\u003eThe electrode materials were investigated in different potential regions to determine the specific capacity at the C/10 rate. The NVP cathode was examined in the potential range of 2.4-4 V, while the C/SiO\u003csub\u003e2\u003c/sub\u003e anode was tested from 0.01-3V. Full-cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e was investigated with 4 N/P ratios of 1.0, 1.1, 1.2 and 1.3, respectively, in the potential region from 1-3.5 V at C/10 rate. For the C-rate measurement, the discharge-charge rate changed every five cycles as follows: C/10, C/5, C/2, 1C and then back to C/10 again. The electrochemical measurements were tested on the MPG-2 (Biologic) device using EC-Lab software. Full-cell results with the suitable N/P ratio will be evaluated using CV (rate of 0.1 mV.s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, \u003cem\u003evs\u003c/em\u003e Na\u003csup\u003e+\u003c/sup\u003e/Na) and EIS 200.000 kHz to 100.000 mHz with an amplitude of 10 mV, VSP-2 Biologic measuring instrument) measurements.\u003c/p\u003e"},{"header":"3. RESULTS AND DISCUSSION","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n\u003ch2\u003e3.1. Diffusion kinetics using EIS and GITT methods\u003c/h2\u003e\n\u003cp\u003eEIS is an effective technique for analyzing the movement of sodium ions into and out of the electrode. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003ea displays the Nyquist plot at various discharge stages. The plot displays a depressed semicircle in the high-frequency range, along with the Warburg region, and then shows a linear slope as the frequency decreases. The low-frequency semicircle is attributed to the interfacial charge transfer of sodium ions (R\u003csub\u003ect\u003c/sub\u003e), in conjunction with capacitance (CPE\u003csub\u003ect\u003c/sub\u003e) at the electrode/surface film interface [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e][\u003cspan class=\"CitationRef\"\u003e21\u003c/span\u003e]. During the first discharge, the total impedance value of C/SiO\u003csub\u003e2\u003c/sub\u003e material almost does not change much, in the range of 200\u0026ndash;250 Ω which is higher than that of Hard carbon material abour 50 Ω [\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e]. However, the degree of variation and trend are the same. When discharge reaches the low voltage region, the total impedance value tends to decrease. This can be clarified by the easier kinetic process of interlocking Na ions into the material structure, the enhanced electrical conductivity of the sodium-carbon material during sodiation, which in turn facilitates the kinetics of the electrochemical reactions [\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e]. We can verify this argument by the calculated diffusion coefficient values below.\u003c/p\u003e\n\u003cp\u003eThe impedance of Warburg is associated with the solid state diffusion of Na\u003csup\u003e+\u003c/sup\u003e within the active particles [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]. As a result, the Warburg component can be utilized to estimate D\u003csub\u003eNa+\u003c/sub\u003e using the equation below [\u003cspan class=\"CitationRef\"\u003e23\u003c/span\u003e][\u003cspan class=\"CitationRef\"\u003e24\u003c/span\u003e]:\u003c/p\u003e\n\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\n\u003cdiv id=\"FileID_Equa\" class=\"mathdisplay\"\u003e$$D=\\frac{{R}^{2}{T}^{2}}{2{A}^{2}{n}^{4}{F}^{4}{C}^{2}{\\sigma }^{2}} \\left(1\\right)$$\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eImpedance curves below 0.41 V do not display a distinct diffusion extension within the measured frequency range and are therefore not taken into consideration for further analysis. This is due to the fact that the sluggish interfacial kinetics dominate over the diffusion process [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]. The Nyquist plot illustrates the infinite Warburg impedance as a slanted line with an angle of 45\u003csup\u003eo\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003eb). Beyond a potential of 0.74 V, the Warburg line deviates from the expected slope condition. So that, the calculation of the diffusion coefficient is limited to potential ranges above 0.74 V [\u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e][\u003cspan class=\"CitationRef\"\u003e26\u003c/span\u003e]. Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e illustrates that the \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({D}_{{Na}^{+}}\\)\u003c/span\u003e\u003c/span\u003e values obtained from the EIS method range between 10\u003csup\u003e\u0026minus;15\u003c/sup\u003e and 10\u003csup\u003e\u0026minus;\u0026thinsp;14\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e.s\u003csup\u003e\u0026minus;1\u003c/sup\u003e, depending on the applied voltages. It is observed that \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({D}_{{Na}^{+}}\\)\u003c/span\u003e\u003c/span\u003e values exhibit a decreasing trend as the cell discharges to 0.01 V. Due to the discharge process, the space for sodium ion insertion in the lithiated C/SiO\u003csub\u003e2\u003c/sub\u003e structure gradually decreases. This suggests that towards the end of the discharge process, it becomes increasingly challenging for Na\u003csup\u003e+\u003c/sup\u003e ions to be inserted.\u003c/p\u003e\n\u003cp\u003eThe galvanostatic intermittent titration technique (GITT), pioneered by Weppner and Huggins, provides researchers with a valuable method to investigate and measure Na\u003csup\u003e+\u003c/sup\u003e diffusion coefficients in different electrode materials, significantly contributing to the advancement of our comprehension of electrochemical systems' behavior [\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e][\u003cspan class=\"CitationRef\"\u003e27\u003c/span\u003e]. As shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea, the GITT curves for the C/SiO\u003csub\u003e2\u003c/sub\u003e anode were obtained within a voltage range of 2.0-0.01 V. In the GITT test, a discharge current of 0.1 mA is applied for 10 minutes, after which there is a 40-minute relaxation period with an open-circuit condition to enable the cell voltage to reach a stable state. This procedure is repeated throughout the entire voltage window from 2.0 V to 0.01 V. Based on Fick's second law, it is possible to calculate the diffusion coefficients of lithium ions using the following Eq.\u0026nbsp;(\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e) [\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e\n\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\n\u003cdiv id=\"FileID_Equ1\" class=\"mathdisplay\"\u003e$$D=\\frac{4}{\\pi }\\times (\\frac{I\\times {V}_{m}}{{Z}_{A}\\times F\\times S}{)}^{2}\\times (\\frac{dE/d{\\delta }}{dE/d\\sqrt{t}}{)}^{2}$$\u003c/div\u003e\n\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eThe calculated \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({D}_{{Na}^{+}}\\)\u003c/span\u003e\u003c/span\u003e values from GITT measurements fal within the range of 10\u003csup\u003e\u0026minus;12\u003c/sup\u003e to 10\u003csup\u003e\u0026minus;\u0026thinsp;10\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e.s\u003csup\u003e\u0026minus;1\u003c/sup\u003e during discharge processes. As the voltage decreases during the discharge process, there is a slight decrease in the diffusion coefficient. However, when the voltage reaches 0.2 V, there is a rapid increase in the diffusion coefficient until the discharge process ends at 0.01 V (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ec). This phenomenon is explained that the value range from 0.2\u0026thinsp;\u0026minus;\u0026thinsp;0.01 V is the typical window voltage of C/SiO\u003csub\u003e2\u003c/sub\u003e material [\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e]. Therefore, the process of interlocking Na ions takes place more smoothly, leading to an increase in the diffusion coefficient in this potential range. The cathode used in this work is Na\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e. Its diffusion coefficient has been found to be range approximately 10\u003csup\u003e\u0026minus;11\u003c/sup\u003e (cm\u003csup\u003e2\u003c/sup\u003e.s\u003csup\u003e\u0026minus;1\u003c/sup\u003e) in previous studies [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]\u0026ndash;[\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e]. C/SiO\u003csub\u003e2\u003c/sub\u003e material has a diffusion coefficient approximately similar to the Na\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e material, so it indicate the potential for the fast-rate application [\u003cspan class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eThe \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({D}_{{Na}^{+}}\\)\u003c/span\u003e\u003c/span\u003e value obtained from GITT (10\u003csup\u003e\u0026minus;12\u003c/sup\u003e to 10\u003csup\u003e\u0026minus;\u0026thinsp;10\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e.s\u003csup\u003e\u0026minus;1\u003c/sup\u003e) is higher than that obtained from EIS (10\u003csup\u003e\u0026minus;15\u003c/sup\u003e and 10\u003csup\u003e\u0026minus;\u0026thinsp;14\u003c/sup\u003e cm\u003csup\u003e2\u003c/sup\u003e.s\u003csup\u003e\u0026minus;1\u003c/sup\u003e). This disparity can be attributed to the fact that the two methods were conducted under different equilibrium conditions [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]. In real experimental settings, the GITT method uses a brief pulse with sufficient relaxation time to remove any unwanted background current interference in the measured response. This significantly reduces errors when determining the diffusion coefficient compared to using EIS data [\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e]. Furthermore, the utilization of GITT becomes appealing when the inherent kinetics of phase transitions of the active material influence the corresponding electroanalytical responses [\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e]. Meanwhile, the EIS method is associated with the solid state diffusion of Na\u003csup\u003e+\u003c/sup\u003e within the active particles [\u003cspan class=\"CitationRef\"\u003e11\u003c/span\u003e]. Additionally, the EIS outcomes were acquired under conditions closer to equilibrium, enabling an extended relaxation period for the electrode. Moreover, in our calculations, we consider the surface area in contact with the electrolyte as the geometric area of the electrode [\u003cspan class=\"CitationRef\"\u003e34\u003c/span\u003e]. Nevertheless, it is important to recognize that the effective contact area between the C/SiO\u003csub\u003e2\u003c/sub\u003e electrode and electrolyte will exceed the geometric surface area due to the penetration of electrolyte into the C/SiO\u003csub\u003e2\u003c/sub\u003e electrode. This penetration will lead to a decrease in D\u003csub\u003eNa+\u003c/sub\u003e, but the alteration of D\u003csub\u003eNa+\u003c/sub\u003e with cell voltage remains unchanged in the potential range from 1.1 to 0.8 V. The calculated diffusion coefficient values obtained from GITT in this work demonstrate consistency with findings from earlier research, such as mesoporous soft carbon obtained from EIS by Cao et al. (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(1.85\\times {10}^{-11}\\)\u003c/span\u003e\u003c/span\u003e cm\u003csup\u003e2\u003c/sup\u003e.s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) [\u003cspan class=\"CitationRef\"\u003e35\u003c/span\u003e], soft carbon (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(1.85\\times {10}^{-11}\\)\u003c/span\u003e\u003c/span\u003ecm\u003csup\u003e2\u003c/sup\u003e.s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) or hard carbon (3.6\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\times {10}^{-12}\\)\u003c/span\u003e\u003c/span\u003ecm\u003csup\u003e2\u003c/sup\u003e.s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) from Cheng et al. [\u003cspan class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n\u003ch2\u003e3.2. Survey N/P conditions for full-cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e\u003c/h2\u003e\n\u003cp\u003eGCPL results (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea) show that the capacity of C/SiO\u003csub\u003e2\u003c/sub\u003e materials reaches 471.5 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e at the first cycle. After 50 cycles, the capacity of C/SiO\u003csub\u003e2\u003c/sub\u003e remains at 150 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Because of the capacity irreversibility after the first cycle, the electrode activation process is performed for this material [\u003cspan class=\"CitationRef\"\u003e6\u003c/span\u003e], [\u003cspan class=\"CitationRef\"\u003e18\u003c/span\u003e], [\u003cspan class=\"CitationRef\"\u003e19\u003c/span\u003e], [\u003cspan class=\"CitationRef\"\u003e37\u003c/span\u003e]. C/SiO\u003csub\u003e2\u003c/sub\u003e material is assembled into a half-cell with Na metal. After 5 charging cycles, this material is continued to assemble a full-cell with NVP cathode material. The capacity of the first cycle NVP material reaches 105.6 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e3\u003c/span\u003eb), a result that is close to the theoretical capacity of the NVP material (117 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). Capacity reaches nearly the same after 50 cycles, approximately 110 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. This electrochemical result shows that the commercial NVP material used has high chemical properties as well as high structural stability during interlocking/release in the investigated potential region. In addition, the charge-discharge curve shows a characteristic flat potential at 3.4 V, which is typical for the flat potential region of the oxidation-reduction pair V\u003csup\u003e4+\u003c/sup\u003e/V\u003csup\u003e3+\u003c/sup\u003e [\u003cspan class=\"CitationRef\"\u003e38\u003c/span\u003e]. From the above results, the actual capacity of C/SiO\u003csub\u003e2\u003c/sub\u003e and NVP materials will be fixed at 150 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 110 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e respectively, for implementation in formula (3) [\u003cspan class=\"CitationRef\"\u003e39\u003c/span\u003e].\u003c/p\u003e\n\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\n\u003cdiv id=\"FileID_Equ2\" class=\"mathdisplay\"\u003e$$\\frac{\\text{N}}{\\text{P}}=\\frac{{\\text{C}}_{\\text{a}\\text{n}\\text{o}\\text{d}\\text{e}}}{{\\text{C}}_{\\text{c}\\text{a}\\text{t}\\text{h}\\text{o}\\text{d}\\text{e}}}=\\frac{{\\text{C}\\text{a}\\text{p}\\text{a}\\text{c}\\text{i}\\text{t}\\text{y}}_{\\text{a}\\text{n}\\text{o}\\text{d}\\text{e}} \\times {\\text{m}}_{\\text{a}\\text{c}\\text{t}\\text{i}\\text{v}\\text{e} \\text{a}\\text{n}\\text{o}\\text{d}\\text{e} \\text{m}\\text{a}\\text{t}\\text{e}\\text{r}\\text{i}\\text{a}\\text{l}}}{{\\text{C}\\text{a}\\text{p}\\text{a}\\text{c}\\text{i}\\text{t}\\text{y}}_{\\text{c}\\text{a}\\text{t}\\text{h}\\text{o}\\text{d}\\text{e} }\\times {\\text{m}}_{\\text{a}\\text{c}\\text{t}\\text{i}\\text{v}\\text{e} \\text{c}\\text{a}\\text{t}\\text{h}\\text{o}\\text{d}\\text{e} \\text{m}\\text{a}\\text{t}\\text{e}\\text{r}\\text{i}\\text{a}\\text{l}}}$$\u003c/div\u003e\n\u003cdiv class=\"EquationNumber\"\u003e3\u003c/div\u003e\n\u003c/div\u003e\n\u003cp\u003eThe results of the GCPL survey of full-cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e at N/P ratios are shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e4\u003c/span\u003e. In the first cycle, the discharge capacity of N/P ratios 1.0 and 1.1, reaches 96.3 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 112,0 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, respectively. However, the capacity decreased rapidly, as shown by the specific capacity results at cycles 50, reaching 15.5 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 17.8 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. At the 50th cycle, the ratio N/P\u0026thinsp;=\u0026thinsp;1.0 maintained 16.1% capacity retention, higher than the result of the ratio N/P\u0026thinsp;=\u0026thinsp;1.1 only 15.9% (Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). Meanwhile, the discharge capacity at the first cycle of the N/P 1.2 reaches 126.3 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. After 50 cycles, the specific capacity still maintained is 105.7 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (83.7% retention compared to the first cycle, Table \u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e). Besides, the discharge capacity at the first cycle of the ratio N/P\u0026thinsp;=\u0026thinsp;1.3 reached 93.6 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, after 50 cycles, the specific capacity obtained was 97.7 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The specific capacity with the ratio N/P\u0026thinsp;=\u0026thinsp;1.2 gradually decreases over the cycle.\u003c/p\u003e\n\u003cp\u003eSurveying the cycling of a full-cell with 4 different N/P ratios over 50 cycles at C/10 rate (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003ea) shows that, at the ratio N/P\u0026thinsp;=\u0026thinsp;1.0, the capacity decreases rapidly during 50 cycles, the Coulomb efficiency remains\u0026thinsp;~\u0026thinsp;90%. Full-cell with the ratio N/P\u0026thinsp;=\u0026thinsp;1.1 shows a significantly decreasing trend of specific capacity. In contrast, the Coulomb efficiency increased gradually, from period 25 onwards, maintaining\u0026thinsp;~\u0026thinsp;96%. With the ratio N/P\u0026thinsp;=\u0026thinsp;1.2 and 1.3, a general trend is that the specific capacity of the early cycles decreases, however from the 10th period onwards, the specific capacity increases. Especially at the ratio N/P\u0026thinsp;=\u0026thinsp;1.3, the specific capacity increases, resulting in the 50th cycle the discharge capacity is higher than the first cycle (97.7\u0026thinsp;\u0026gt;\u0026thinsp;93.6 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e). Coulomb efficiency of full cell with and N/P\u0026thinsp;=\u0026thinsp;1.2 ratio increases follow cycling process, at the 50th cycle, the stable efficiency\u0026thinsp;~\u0026thinsp;98%. As a result, the Coulumbic efficiency gradually increases after charge-discharge cycles due to the formation of a stable SEI layer, resulting in the discharging-charging process becoming more reversible.\u003c/p\u003e\n\u003cp\u003eThe rate capability results of ratios N/P\u0026thinsp;=\u0026thinsp;1.1; 1.2 and 1.3 have quite high and stable Coulomb efficiency (approximately 98%). As the current rate increases, the specific capacity of the full-cell decreases. Especially at the ratio N/P\u0026thinsp;=\u0026thinsp;1.0, the specific capacity is limited. At all 4 N/P ratios, the full-cell when returning to the C/10 showed a reduction in capacity compared to the first 5 cycles at the same current (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003eb). With the ratio N/P\u0026thinsp;=\u0026thinsp;1.2, the N/P 1.2 gives a specific capacity of 113.7 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e when returning to C/10 rate (99.1% capacity retention). From this, it can be concluded that the ratio N/P\u0026thinsp;=\u0026thinsp;1.2 has the ability to work well at different discharge-charge current rates.\u003c/p\u003e\n\u003cp\u003eThe cyclic voltammetry (CV) at the 1st, 3rd and 5th cycles of the full-cell with an N/P ratio\u0026thinsp;=\u0026thinsp;1.2 are investigated in the potential range from 0.5\u0026ndash;3.5 V at scan rate 0.1 mV/s (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e). The results show that the process of interlocking and releasing Na\u003csup\u003e+\u003c/sup\u003e ions take place in the range of 0.15\u0026ndash;3.5 V. In all 3 cycles, the CV curve shows a pair of peaks at 3.4 and 3.2 V, which represent the V\u003csup\u003e3+\u003c/sup\u003e oxidized form and the V\u003csup\u003e4+\u003c/sup\u003e reduced form, respectively [\u003cspan class=\"CitationRef\"\u003e40\u003c/span\u003e]. In the 1st, the oxidation peak at 3.4 V (0.26 mA) has a much higher intensity than the reduction peak at 3.2 V (0.07 mA), showing that the oxidation process requires higher current rate than the reduction process [\u003cspan class=\"CitationRef\"\u003e41\u003c/span\u003e]. In the remaining cycles, the intensity of the two peaks narrows the gap and the CV curve shape is almost the same. In addition, in the discharge cycle, in the potential range from 1.3 to 2.7 V, a wide active region appears with unclear peak shape. It shows that the sodium interlocking reaction on the anode also occurs in this potential region [\u003cspan class=\"CitationRef\"\u003e42\u003c/span\u003e]. The operating potential region results of the CV curve are also consistent with the appearance of two flat shoulder regions at 1.0 and 2.5 V of the GCPL results (full-cell N/P ratio\u0026thinsp;=\u0026thinsp;1.2). The intensity of the reduction peak is lower than the oxidation peak, showing that the ion release diffusion from the anode is slower than that from the cathode. This result is consistent with the diffusion coefficient results examined.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003e shows the electrochemical impedance spectra of the full-cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e with an N/P ratio\u0026thinsp;=\u0026thinsp;1.2 at pristine and different potential values. The battery in its initial state shows two semicircles. The semicircles detected in the high and medium frequency ranges are probably attributed to the surface film resistance at the electrode-electrolyte interface, along with the charge transfer resistance. The remaining component - linear region is associated with the Warburg diffusion of Na\u003csup\u003e+\u003c/sup\u003e cations within the bulk material [\u003cspan class=\"CitationRef\"\u003e22\u003c/span\u003e]. However, after being operated, the battery only shows one semicircle at various potential values. This phenomenon can be explained in the following manner. When two electrodes are involved in charge transfer processes or when two processes occur on one electrode simultaneously with similar frequencies, a semicircle can appear. At the beginning, before the charging process takes place, the system consists of two different-natured electrodes [\u003cspan class=\"CitationRef\"\u003e43\u003c/span\u003e]. As a result, there will be as many charge transfer semicircles as there are interfaces, and these semicircles will typically be distinct and separate. It is highly unlikely for them to coincide. During charging-discharging process, changes in the concentration of oxidizing/reducing substances and alterations in the composition of the interfacial layer on an electrode lead to modifications in charge transfer resistance for each electrode. Whether or not a semicircle can be observed and how separated it appears depends on specific circumstances that cannot be predicted accurately. When the battery is newly installed (pristine), the EIS spectrum depicts an imperfect semicircle due to the lack of electrical energy activation in the electrode. At this stage, Na\u003csup\u003e+\u003c/sup\u003e diffusion is sluggish, and it has not yet penetrated the electrode structure. However, after operation, the total impedance value decreases significantly. The semicircle is reduced by nearly 100 times compared to its original state and becomes more complete, indicating the successful participation of Na\u003csup\u003e+\u003c/sup\u003e ions in the C/SiO\u003csub\u003e2\u003c/sub\u003e structure.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. CONCLUSION","content":"\u003cp\u003eThe presodiation process using the Electrochemical method (EC) was successfully carried out on C/SiO\u003csub\u003e2\u003c/sub\u003e anode derived from rice husk. The sodium diffusion coefficient of C/SiO\u003csub\u003e2\u003c/sub\u003e calculated using the GITT method is higher, ranging from 10\u003csup\u003e\u0026ndash;12\u003c/sup\u003e to 10\u003csup\u003e\u0026ndash;10\u003c/sup\u003e (cm\u003csup\u003e2\u003c/sup\u003es\u003csup\u003e-1\u003c/sup\u003e) compared to that calculated using the EIS method, which ranges from 10\u003csup\u003e\u0026ndash;15\u003c/sup\u003e to 10\u003csup\u003e\u0026ndash;14\u003c/sup\u003e (cm\u003csup\u003e2\u003c/sup\u003es\u003csup\u003e-1\u003c/sup\u003e). This is because the two methods were conducted under different equilibrium conditions. It is noteworthy that the diffusion coefficient value derived from GITT aligns with findings from prior studies. The full-cell C/SiO\u003csub\u003e2\u003c/sub\u003e║Na\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e with N/P ratios of 1.1 and 1.2 achieved specific capacity of 112.0 and 126.3 mAh.g\u003csup\u003e-1\u003c/sup\u003e, respectively. The full-cell with a N/P ratio of 1.2 retained up to 83.7% of its capacity after 50 cycles. When the current density increases, the full-cell with a N/P ratio of 1.1 and 1.2 results in specific capacity of 58.6 and 67.4 mAh.g\u003csup\u003e-1\u003c/sup\u003e at 1C, respectively. The battery maintains over 58% of its capacity when the current density is back to C/10. Significantly, the work presented here provides information on the kinetics and optimal values ​​for cost-effective assembly of SIBs.\u003c/p\u003e"},{"header":"DECLARATIONS","content":"\u003ch2\u003eCONFLICT OF INTEREST\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no conflict of interest.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eLe My Loan Phung, Tran Van Man and Vu Tan Phat came up with a research idea- Chuong Nguyen Kim Yen and Vu Tan Phat did the experiment- Chuong Nguyen Kim Yen and Vu Tan Phat wrote the main manuscript text- Le My Loan Phung and Tran Van Man edited the manuscript until it was complete\u003c/p\u003e"},{"header":"REFERENCES","content":"\u003col\u003e\n\u003cli\u003eC. Pean, B. Daffos, B. Rotenberg, P. Levitz, M. Haefele, P. L. Taberna, P. Simon, and M. Salanne \u0026ldquo;Confinement, Desolvation, and Electrosorption Effects on the Diffusion of Ions in Nanoporous Carbon Electrodes,\u0026rdquo; \u003cem\u003eJ. Am. 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West, \u0026ldquo;Characterisation of batteries by electrochemical impedance spectroscopy\u0026rdquo;, \u003cem\u003eEnergy Reports\u003c/em\u003e, vol. 6, pp. 232\u0026ndash;241, 2020, doi: 10.1016/j.egyr.2020.03.029.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 and 2 are available in the Supplementary Files section.\u003c/p\u003e "}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-3996186/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3996186/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eC/SiO\u003csub\u003e2\u003c/sub\u003e composite derived from rice husks (RHs) have gained significant attention in the development of abundant anode materials for sodium-ion battery due to their unique features, simple synthesis process without using additional sources of silica and carbon and affordable price. Despite the extensive research reported, a part of the expensive hard carbon, the choice of anode materials is still limited leading to the challenges in the commercialization of SIBs... In this study, full-cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e was optimized the assembly conditions, achieving the highest and most stable capacity. In detail, N/P ratio surveys using presodiation C/SiO\u003csub\u003e2\u003c/sub\u003e materials is the remaining factor. Besides, evaluations of the diffusion process kinetics in C/SiO\u003csub\u003e2\u003c/sub\u003e have been conducted through Electrochemical Impedance Spectroscopy (EIS) and Galvanostatic Intermittent Titration Technique (GITT) studies. Within the pre-sodiation anode, full-cell C/SiO\u003csub\u003e2\u003c/sub\u003eǁNa\u003csub\u003e3\u003c/sub\u003eV\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e at N/P\u0026thinsp;~\u0026thinsp;1.2 offers the highest capacity of 126.3 mAh.g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and capacity retention of 83.7% after 50 cycles. Moreover, other electrochemical evaluation techniques were also used in this study, such as: EIS ex-situ, CV, C-rate, GCPL. Finally, with the information of this study, the optimization of Na-ion battery assembly conditions from material C/SiO\u003csub\u003e2\u003c/sub\u003e has been explored, opening a new future for cost-effective batteries.\u003c/p\u003e","manuscriptTitle":"Full-cell C/SiO2ǁNa3V2(PO4)3 high-performance Na-ion battery: Diffusion kinetics and N/P optimization","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-03-01 16:55:10","doi":"10.21203/rs.3.rs-3996186/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"7f52cd34-2b71-4e63-84e3-9a7ab6d4530f","owner":[],"postedDate":"March 1st, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-03-17T16:44:34+00:00","versionOfRecord":[],"versionCreatedAt":"2024-03-01 16:55:10","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3996186","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3996186","identity":"rs-3996186","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}