Regulating the Microcrystalline Structure of Anthracite via Thermal Treatment Strategies for Enhanced Sodium-Ion Storage Performance

Regulating the Microcrystalline Structure of Anthracite via Thermal Treatment Strategies for Enhanced Sodium-Ion Storage Performance | 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 Regulating the Microcrystalline Structure of Anthracite via Thermal Treatment Strategies for Enhanced Sodium-Ion Storage Performance Yulong Zhang, Deping Xiong, Yan dong Xie, Qu Wang, Zuyong Feng This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7693425/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Sodium-ions and lithium ions are in the same main group, have the same chemical properties, and are low in price, so they are expected to replenish lithium-ion batteries. Among the various anode materials for sodium-ion batteries, anthracite has attracted much attention due to its low price and carbon content exceeding 90%. Although significant progress has been made in the research of hard carbon derived from anthracite-based carbon materials, the reversible capacity and initial Coulombic efficiency (ICE) of anthracite-based soft carbon are still not satisfactory. This paper uses anthracite as raw material and adjusts the specific surface area and defects through mechanical shearing, and regulates the interlayer spacing through temperature. Achieve a relatively high capacity of anthracite at 304.4 mAh g -1 and an ICE of 89.3%. Low-cost anthracite coal, low-cost processes, and high initial coulombic efficiency—these outstanding performance characteristics meet the requirements of practical applications and lay the foundation for the large-scale industrial production of low-cost, high-performance sodium-ion batteries for energy storage. Anthracite Ball milling Two-step carbonization Initial coulomb efficiency Plateau capacity Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 INTRODUCTION Recently, with the gradual deterioration of the ecological environment, the efficient utilization of renewable energy resources has already become an urgent task for creating a healthy ecological environment and a sustainable energy structure [ 1 ]. Among various energy storage systems, secondary batteries are a good choice. Among secondary batteries, lithium-ion batteries (LIBs), which have been successfully developed as power sources for portable electronic devices, are a promising alternative source due to their high reversible capacity and initial Coulombic efficiency [ 2 ]. However, the rarity and non-uniform geographic distribution of lithium resources may severely restrict LIBs' prospective applications in grid-scale energy storage [ 3 , 4 ]. Sodium ions and lithium ions are located in the same main group, have similar structures and properties, and are low in cost, evenly distributed and abundant in resources. Therefore, sodium-ion batteries (SIBs) are regarded as an important supplement and partial replacement for LIBs energy storage technology [ 5 – 9 ]. The radius of sodium ions (Na⁺) is larger than that of lithium ions (Li⁺). This characteristic leads to a relatively slower diffusion rate of sodium ions within electrode materials, thereby affecting their reversible sodium storage capacity. As a result, the graphite anode materials commonly used in commercial LIBs are unsuitable for Na⁺ storage in SIBs [ 10 , 11 ]. Therefore, finding suitable SIB anode materials is very important and urgent. Disordered carbon materials are considered to be very promising SIB anode materials due to their amorphous structure and large interlayer spacing [ 12 , 13 ]. To date, many carbon materials with different structures have been developed, such as soft carbon [ 14 ], hard carbon [ 15 ], and hybrid carbon [ 1 ]. Currently, the large-scale, low-cost use of precursors is one of the common methods for producing hard carbon materials, such as coal [ 16 – 18 ], resins [ 19 – 21 ], asphalt [ 22 ], and oxygen-rich biomass [ 23 – 25 ]. Anthracite, as a coal-based material, possesses distinct advantages over other coal resources: its graphite structure is clearly ordered, it boasts a high carbon content, and it is cost-effective. Consequently, it has been extensively researched for energy storage applications [ 26 – 28 ]. However, coal-based carbon primarily consists of polynuclear fused aromatic hydrocarbons, which readily form carbon layers during carbonisation. This results in a highly ordered graphite structure with narrow interlayer spacing and few defects, rendering it unfavourable for sodium ion storage. Therefore, the development of high-performance SIB anodes with suitable interlayer spacing and a high proportion of graphitic microcrystals is imperative. To address this issue, numerous researchers have made tremendous efforts, Hu and co-workers prepared coal-based carbon by the direct pyrolysis of anthracite, and the anode delivers a high sodium storage capacity of 222 mAh g − 1 with good rate performance and long cycle life [ 28 ]. However, the reversible capacity remains relatively low, and the ICE is 81%, which is not sufficient for large-scale production requirements. Liu et al. used anthracite as the carbon source and utilized the effect of surface hydrogen bonds to self-assemble melamine-cyanuric acid onto the surface of anthracite, successfully constructing N-doped carbon materials with customized microstructure and expanded interlayer spacing [ 29 ]. Although they achieved high reversible capacity and rate performance, melamine-cyanuric acid exhibits certain toxicity, is costly, and possesses a low initial coulombic efficiency of only 74.2%. However, due to the complexity of the internal structure of anthracite, the performance of the final hard carbon product has always been difficult to meet the requirements of industrialization, especially the reversible capacity and ICE remain challenges. In this study, we introduced a method that combines mechanical shearing and segmented calcination to regulate the internal graphite microcrystals of anthracite-based hard carbon materials, thereby increasing the degree of material defects and providing more active sites for sodium ion storage. At 0.1 C, the reversible capacity is 304.4 mAh g -1 , the initial Coulomb efficiency is 89.3%, and after 100 cycles, the reversible capacity is 280.5 mAh g -1 . This work provides a feasible approach for the large-scale preparation of smokeless coal-based hard carbon materials. EXPERIMENTAL SECTION Method of Preparation Crush and sieve anthracite. Select anthracite with a particle size of less than 1000 mesh and ball mill it in a ball mill at a speed of 500 for 12 h. Add 5% concentration hydrochloric acid and 20 mL of ethanol, and oil bath in an oil bath pot with a rotational speed of 500 and 80 ℃ for 12 h. After the oil bath, the sample was centrifuged at 10,000 RPM for 3 min, and the precipitate (tris-water, tris-alcohol) was retained. Take out the sediment and filter it in a vacuum filtration instrument until the liquid is clear. Then dry it in a forced convection drying oven for 12 h. Replace hydrochloric acid with hydrogen fluoride and repeat the steps. Take out the samples and dry them in a forced convection drying oven for 12 h. In the tube furnace, the pre-carbonization at 600 ℃, 700 ℃, and 800 ℃ (heating at 3 ℃ min -1 , argon gas, holding for 2 h) and carbonization at 1400 ℃ (heating at 5 ℃ min -1 , argon gas, holding for 2 h) were respectively named as follows: ASC600-1400, ASC700-1400, ASC800-1400. Materials characterization X-ray diffraction (XRD (D-MAX 2200 VPC, Rigaku, Japan) was performed using a powder X-ray diffractometer. Raman spectra (inVia, Reflex, UK) were recorded using a micro-Raman spectrometer with an excitation wavelength of 532 nm. Scanning electron microscope (SEM) images were obtained through ultra-high resolution field emission scanning electron microscopy. The pyrolysis behavior of carbon precursors was characterized by thermogravimetric analyzer (TGA, air atmosphere, STA 449 F3, Netzsch, Germany) at a constant heating rate of 10 ℃ min -1 from 25 ℃ to 800 ℃ in an air atmosphere. The nitrogen adsorption and desorption isotherms were collected at 77.3 K using a nitrogen adsorption analyzer (BSD-660M A6B3M instrument. Images for characterizing the lattice morphology were collected using high-resolution transmission electron microscopy (HR-TEM, F200 X G2, FEI Talos). The closed-pore structure characteristics were studied by the small-angle X-ray scattering (SAXS, Xeuss 3.0, Xenocs) testing method, and the specific surface area (SSA) of micropores (Smic) and mesopores (Smes) was determined by the Barret-Joyner-Halenda method (BJH). Use XPS to measure the functional groups contained in carbon materials. Electrochemical measurements All electrochemical tests were conducted on button cells. The negative electrode was prepared by mixing active materials, Super P, carboxymethyl cellulose (CMC), and polymerized styrene-butadiene rubber (SBR) in weight ratios of 95:1.74:0.96:2.3. The mixture was then evenly mixed with deionized water to form a slurry, which was applied to the copper foil. The electrode was vacuum-dried at 80 degrees Celsius in a vacuum drying oven for 12 h. After cutting the pieces, the batteries are assembled in a glove box filled with argon gas. 1.0 mol L − 1 NaPF6 (EC/DMC/DEC = 1:1:1 in volume) were used as electrolytes for SIBs.. The glass fiber membrane (GF/D, Whatman) was used as the separator, and the sodium metal was used as the counter electrode. The battery system undergoes discharge and charge tests at various C rates within a voltage range of 0.01 ~ 2 V in a constant temperature and humidity chamber. Full battery test method The cathode material comprises sodium iron manganese oxide, while the anode utilises sample carbon material with an N:P ratio of 1.3. 1.0 mol L − 1 NaPF6 (EC/DMC/DEC = 1:1:1 in volume) were used as electrolytes for SIBs. RESULTS AND DISCUSSION Physical characterization In order to visually observe the microstructure of the samples, we conducted a series of tests using both TEM and SEM. As demonstrated in (Fig. 1 (a-f)), the ASC600-1400, ASC700-1400, and ASC800-1400 all manifest long-range disordered and short-range ordered structures, with the ASC700-1400 displaying a preponderance of closed-cell structures. All the samples exhibited dispersed diffraction rings, yet diffraction spots of individual crystals were discernible. Subsequent analysis of the substance indicated that it was elemental silicon. As is apparent from the results of the SEM analysis, the sizes of the particles under consideration are all less than 9 µm. Because the same ball milling method is adopted, there is no obvious difference in their morphologie. Through thermogravimetric analysis, the weight change of anthracite was not significant between 25 ℃ and 430 ℃, but it decreased sharply between 430 ℃ and 600 ℃. After 600 ℃, it remained stable, but still contained 3.3% impurities (Fig. 2 a). The following analysis shows that it is elemental silicon. According to reports, elemental silicon does not store sodium, so it has no impact on this experiment. The unique crystal structure of hard carbon was observed in the XRD pattern, and the peaks near 24° and 43° provided direct information from the (002) and (100) crystal planes(Fig. 2 b). Calculate the interlayer spacing according to Formula 1. The interlayer spacing of ASC700-1400 (3.74 nm) is greater than that of ASC600-1400 (3.67 nm) and ASC800-1400 (3.72 nm). This is attributed to the unique carbonization evolution process of Anthracite. At low temperatures, small molecules are released, and the closed pores increase. As the temperature rises, the interlayer spacing becomes larger and larger. When a certain temperature is reached, the microcrystalline structure begins to repair itself, gradually becoming graphitised, and the interlayer spacing decreases. Therefore, ASC700-1400 has a relatively high interlayer spacing. From the XRD image, it can be seen that there are still a small amount of impurities. Through analysis, it is found to be elemental silicon. According to relevant literature reports, silicon has very low curing activity, resulting in limited sodium storage capacity [ 30 ]. The specific surface area and pore size distribution of anthracite coal-t material were comprehensively analysed using nitrogen adsorption-desorption isotherm technology. As shown in Fig. 2 c, a typical Type IV isotherm curve was observed, indicating the material contains abundant mesoporous material with a pore size range of 0–50 nm. The specific surface area ranges from 12 to 18 m 2 g − 1 . The pore diameters were calculated from the desorption branches of the isotherms using the BJH method. Among them, the pore volume of ASC700-1400 was the smallest, and that of ASC600-1400 was the largest in Fig. 2 (c, d). The analysis results of pore size and volume by the BJH method (calculated based on desorption isotherms) are presented in Table S1 . We employed small-angle scattering (SAXS) specifically to characterize ASC700-1400 as shown in Fig. 2 (e, f). According to the SAXS diagram (Fig. 2 e), a distinct peak is produced near 0.1 A − 1 . The scattering shape of closed pores is as shown in Fig. 2 f. The closed-cell radius ranges from 0.17 to 10 nm. In order to further ascertain the chemical composition and chemical state of the material, Fig. 3 (a, b) displays the X-ray photoelectron spectroscopy (XPS) scan of ASC700-1400. The sample displays clear C1s and O1s signals. As illustrated in Fig. 3 a, the C1s spectral profile can be decomposed in order to reveal graphite carbon (C-C peak at 284.8 eV), as well as C-O derived from epoxy or phenolic functional groups at 286.2 eV, and carbon-oxygen double bonds (C = O at 288.9 eV) [ 31 ]. As illustrated in Fig. 3 b, the O1s spectra are predominantly fitted as two peaks of oxygen atoms bonded to the carbon double bond (C = O carbonyl at 531.8 eV) and oxygen atoms bonded to the carbon single bond (C-O alkyl, 532.6 eV [ 32 ]. As demonstrated in Tables S1-S2, within the O1s spectrum, the carbon-oxygen double bond (C = O carbonyl) accounts for 96.41%, while the carbon-oxygen single bond (C-O alkyl) constitutes 87.3%. In the C1s spectrum, the carbon-oxygen double bond (C = O) accounts for 33.64%, the carbon-oxygen single bond (C-O) accounts for 44.48%, and graphitic carbon (C-C) accounts for 56.55%. As demonstrated in Fig. 3 (c-e), Raman spectroscopy can be employed to analyse the degree of graphitization of the material under investigation. Two characteristic peaks are evident at 1345 cm − 1 and 1585 cm − 1 , corresponding to the D band and G band, respectively. These bands are associated with turbostratic defects (sp³) and crystalline graphite (sp²) structures [ 33 ]. The next step is to fit and deconvolve the Raman spectrum in order to obtain more specific information [ 34 ]. The following essay will provide a comprehensive overview of the relevant literature on the subject. The spectral curves were divided at 1200 (D4), 1340 (D1), 1500 (D3), and 1580 cm − 1 (G) [ 35 ]. The intensity ratio of D1 to G bands (A D1 /A G ) has been shown to reflect the defect concentration of disordered carbon [ 36 ]. The A D1 /A G ratio exhibited an upward trend, initially rising from 1.39 of ASC600-1400 to 1.41 of ASC700-1400, and subsequently reaching 1.61 of ASC800-1400. The gradual increase of A D1 /A G has been shown to result in a decrease in the degree of graphitization [ 37 ]. As demonstrated in Fig. 3 f, there is a gradual increase in A D1 /A G , whilst A D3 /A G initially decreases and subsequently increases. The following essay will provide a comprehensive overview of the relevant literature on the subject. Electrochemical measurements In order to further explore the influence of the microstructure of the material on the sodium storage behavior, the electrochemical performance of Anthracite under different conditions was studied by using the half-cell test method with sodium as the counter electrode, and the tests were carried out on the constant current charge-discharge curve of 20 mA g − 1 . The voltage distribution of all Anthracite electrodes shows two distinct regions; (1) At a platform near 0.1V, (2) The voltage gradually increases around 0.1-2 V. As shown in Fig. 4 a, the ASC700-1400 demonstrated a maximum reversible capacity of 304.36 mAh g − 1 and a maximum initial Coulombic efficiency of 89.32%, and the platform capacity was 201.9 mAh g − 1 , accounting for 66.34%. The reversible capacity and initial coulombic efficiency of the ASC600-1400 and ASC800-1400 samples were 274.7 mAh g − 1 , 85.15%, 295 mAh g − 1 , and 87.2% respectively, and the platform capacity and platform capacity proportion were 181.4 mAh g − 1 , 66.03%, 182 mAh g − 1 , and 61.52% respectively Shown in Fig S1 . Intercalation capacity is shown in Fig S2, where ASC700-1400 accounts for the highest proportion at 61%, while ASC600-1400 and ASC800-1400 both stand at 58%. Based on the existing relevant literature, the slope corresponds to the storage of sodium ions by carbon defects and active sites, and the platform corresponds to the storage of sodium ions by closed pores. The smaller interlayer spacing is not conducive to the intercalation/deintercalation of sodium ions, resulting in the capacity of ASC600-1400、ASC800-1400 being lower than that of ASC700-1400 [ 38 ]. The increase in platform area capacity and ICE is due to the synergistic effect of high-temperature treatment to obtain closed micropores and the formation of a stable SEI film. As shown in the Fig. 4 b, the cycling performance of ASC600-1400, ASC700-1400, and ASC800-1400 at 0.1 C for 100 cycles is presented. Among them, ASC700-1400 and ASC800-1400 have better cycling stability than ASC600-1400. After 100 cycles, ASC700-1400 maintains a reversible capacity of 280.5 mAh g -1 , and the capacity retention rate after cycling is close to 100%. This excellent cycling performance is very likely due to the unique amorphous carbon material having good mechanical properties and high electronic conductivity. The EIS test results are shown in Fig. 4 c. The ASC600-1400 and ASC700-1400 exhibit the smallest internal resistance, indicating better dynamic performance. The internal resistance of ASC600-1400 and ASC700-1400 is 100 Ω, while that of ASC700-1400 is 148 Ω. The characteristics of larger interlayer spacing, higher defect density, and abundant nano-pore structure promote rapid charge transfer, enhance ion diffusion kinetics, thereby reducing the internal resistance of ion and charge transport processes in the material, and exhibiting high reversible intercalation-uncalation properties. In Fig. 4 d, the rate performance of Anthracite electrodes was further studied in detail at various rates ranging from 20 mA g -1 to 500 mA g -1 to evaluate the influence of carbonization temperature on electrochemical performance. The ASC700-1400 has a reversible capacity of 50 mAh g -1 at 500 mA g -1 . The reversible capacities of the ASC600-1400 and ASC800-1400 are lower than that of the ASC700-1400 under the same current. All three samples can maintain relatively good reversible capacity at a current density of 20 mA g -1 after a high current density. We conducted a 200 mA high current long cycle test on the ASC700-1400, and the results showed that there was only a 50 mA g -1 reversible capacity after 500 cycles. The high-current cycling performance is poor. The cycling performance of the ASC700-1400 at a current of 200 mA g -1 is shown in Fig. 4 e. The results indicate that the charging specific capacity drops sharply in the first few laps, tends to level off after 10 laps, and only has a capacity of 50 mAh g -1 after 500 laps, with poor high-current cycling. After ball milling, the specific surface area increases, defects increase, leading to an increase in adsorption capacity, which results in poorer rate performance. Figure 5 (a, d, g) shows the CV curves of the first three turns of different carbon materials at a scanning rate of 0.1 mV s -1 . For sodium ion storage, the ΔV values of ASC600-1400 (Δ V = 0.188 V), ASC700-1400 (Δ V = 0.145 V), and ASC800-1400 (Δ V = 0.145 V) tend to be consistent. These results indicate that the high overlap of CV curves measured after the activation of sodium-ion batteries suggests that a stable SEI film can be formed during the activation process. Figure 5 (b, e, h) shows the CV curves of three different electrodes at different scanning rates. With the increase of scanning rate, all Anthracite exhibited a lower sodium storage potential, similar oxidation/reduction peaks, and produced smaller irreversible regions, indicating less electrolyte decomposition, and rapid sodification and desodification kinetics. A pair of sharp oxidation/reduction peaks that appear near 0.1 and 0.01 V are suitable for the process insertion and extraction of Na + . The existence of the difference between the oxidation peak and the reduction peak indicates that there is polarization lag between them. In addition, except for the REDOX peak, the scanning curves of other cycles overlap well, vividly demonstrating the excellent electrochemical robustness of Anthracite throughout the discharge-recharge cycle. $$\:\begin{array}{c}\text{I}\text{=}\text{a}{\text{v}}^{\text{b}}\#\text{（}\text{1}\text{）}\end{array}$$ The aim is to quantitatively explore the Na + storage principle, according to Eq. 1. The correlation between the anode current density ( i ) and the scanning rate ( v ) has been thoroughly and carefully examined. The derived index b value of 0.5 indicates the diffusion-controlled storage mechanism, while the b value of 1.0 indicates the main capacitive storage contribution [ 39 , 40 ]. Figure 5 (c, f, i) shows that the material exhibits a favorable linear correlation between the logarithmic current density (log i ) and the logarithmic scan rate (log v ). The range of b values between 0.5 and 1.0 indicates that the total charge storage capacity involves a mixing mechanism that combines diffusion-dominant and capacitive effects, with a b value of approximately 0.5. It indicates that the total charge storage is mainly contributed by the diffusion control process [ 41 ]. The values of the constant b of ASC600-1400, ASC700-1400 and ASC800-1400 are 0.75, 0.56 and 0.54 respectively. \(\:\begin{array}{c}\text{I}\left(\text{v}\right)\text{=}{\text{k}}_{\text{1}}\text{v}\text{+}{\text{k}}_{\text{2}}{\text{v}}^{\text{1/2}}\#\text{（}\text{2}\text{）}\end{array}\) According to Eq. 2, The current ( i ) at a specific potential was separated into an embedded component (proportional to k 2 v 1/2 ) and a capacitive component (linearly proportional to k 1 v ) for current separation analysis to obtain the percentage contributions of these two processes, as shown in Fig S3, S4 [ 42 ]. The ASC700-1400 can achieve a diffusion control percentage of 63% at a low scanning rate of 0.1 mV s -1 , indicating more capacitive processes. As the scanning speed increases, the proportion of capacitance gradually decreases. Additionally, GITT measurements were conducted to, analyse ion diffusion kinetics. As shown in Fig S5–S7, during the 0.1–0.01 V sodium-ionation process, the sodium ion diffusion coefficients (D Na⁺ ) for ASC600-1400, ASC700-1400, and ASC800-1400 all exhibited a decrease followed by an increase. This phenomenon arises from the sequential intercalation and subsequent pore filling of sodium clusters [ 43 ]. The preliminary electrochemical measurement results of the full battery are shown in Fig. 6 . Each group of batteries is charged to 3.8 V at a current rate of 0.1 C and then discharged to 2 V. As shown in Fig. 6 a, the ASC700-1400 exhibits a charging specific capacity of 129 mAh g − 1 , a discharging specific capacity of 88.5 mAh g − 1 , and an ICE of 68.6%. As shown in Fig. 6 b, the ASC600-1400 exhibits a charging specific capacity of 127.4 mAh g − 1 , a discharging specific capacity of 87 mAh g − 1 , and an ICE of 68.29%. As shown in Fig. 6 c, the ASC800-1400 exhibits a charging specific capacity of 129.1 mAh g − 1 , a discharging specific capacity of 87.6 mAh g − 1 , and an ICE of 67.85%. Among the three full-battery comparison samples, the ASC700-1400 had the best cycling performance, with a reversible capacity of 55 mAh g − 1 after 100 cycles Fig. 6 d. As shown in Fig. 7 , anthracite starts to release small molecules (such as water, carbon dioxide, etc.) from 0 to 600 ℃, forming open pores and increasing the interlayer spacing. At 600 to 700 ℃, it continues to release small molecules more fully, reaching the maximum interlayer spacing. At 700 to 800 ℃, it begins to repair the microcrystalline structure, with the interlayer spacing decreasing. At 1400 ℃, closed pores are formed. At around 700 ℃, the release of small molecules is more thorough, so the final interlayer spacing is larger and the performance is better. The findings of this study are applicable to anthracite from various origins. As illustrated in the Fig. 8 , the ICE and reversible capacity values are as follows: ASC700-1400-Y1 at 81.2% and 218.7 mAh g − 1 ; ASC700-1400-Y2 at 87.4% and 295.8 mAh g − 1 ; ASC7000-1400-Y3 at 87.8% and 276.4 mAh g − 1 . The proportion of anthracite platform capacity from different sources is shown in Fig. 8 d. CONCLUSIONS This work optimized the performance of anthracite in the anode application of sodium-ion batteries by controlling the ball milling and two-step carbonization temperatures, and explained the influence of ball milling and carbonization temperatures on anthracite. The results show that ball milling will increase the specific surface area and defect degree of anthracite, thereby achieving a higher capacity. Control the temperature of the first carbonization step to obtain a larger interlayer spacing, thereby achieving a high initial Coulombic efficiency. Throughout the entire experiment, ASC700-1400 had the best performance, with a reversible capacity of 304.4 mAh g -1 and an initial Coulombic efficiency of 89.3%. And it has excellent cycling performance and rate performance. It provides strategies for the optimization of anthracite in the future. Declarations Supporting Information Supplementary Information The online version contains supplementary material available at. Author contribution Yulong Zhang: Writing – review & editing, Writing – original draft, Methodology, Investigation, Conceptualization. Yandong Xie: Methodology, Investigation. Zuyong Feng: Investigation, Data curation. Qu Wang: Formal analysis, Data curation. Deping Xiong: Writing – review & editing, Supervision, Project administration. Conflict of interest The authors declare no competing interests. AUTHOR INFORMATION Corresponding Author Deping Xiong - School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China. E -mail: [email protected] . Yandong Xie - School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China. E -mail: [email protected] . Authors Yulong Zhang - School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China. Qu Wang - School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China. Zuyong Feng - School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China. Funding This work was generously supported by the project of sci & tech of Zhongshan ( 2023A4011). References Li, Y.; Hu, Y. S.; Li, H.; Chen, L.; Huang, X. A superior low-cost amorphous carbon anode made from pitch and lignin for sodium-ion batteries[J]. 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ACS Applied Energy Materials. 2018 , 1(5): 2295-2305. https://doi.org/10.1021/acsaem.8b00354 Additional Declarations No competing interests reported. Supplementary Files SupportingInformation2.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 18 Oct, 2025 Reviews received at journal 02 Oct, 2025 Reviewers agreed at journal 29 Sep, 2025 Reviews received at journal 28 Sep, 2025 Reviewers agreed at journal 28 Sep, 2025 Reviewers agreed at journal 28 Sep, 2025 Reviewers invited by journal 27 Sep, 2025 Editor assigned by journal 26 Sep, 2025 Submission checks completed at journal 26 Sep, 2025 First submitted to journal 23 Sep, 2025 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. 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1","display":"","copyAsset":false,"role":"figure","size":106426,"visible":true,"origin":"","legend":"\u003cp\u003eTypical TEM, SEM and SAED images. (a) TEM- ASC600-1400. (b) TEM-ASC700-1400. (C) TEM- ASC800-1400. (d) SEM- ASC600-1400. (e) SEM- ASC700-1400. (f) SEM- ASC800-1400\u003c/p\u003e","description":"","filename":"floatimage1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7693425/v1/7f94e83ea813335a9bc3c115.jpg"},{"id":93124885,"identity":"6fbc68a7-7cd6-4605-b018-8ced70f6b48f","added_by":"auto","created_at":"2025-10-09 10:17:53","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":624603,"visible":true,"origin":"","legend":"\u003cp\u003eStructural characterization. (a) TG-DTG curves of Anthracite. (b) Comparative XRD patterns. (C) N\u003csub\u003e2\u003c/sub\u003e adsorption−desorption isotherms. (d) pore size distribution. (e) SAXS patterns of ASC700-1400. (f) SAXS 2d spectral structure of ASC700-1400\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-7693425/v1/165f17a9eb6dc3dd3ddcc4a7.png"},{"id":93124886,"identity":"74d9d6c6-ff38-4fed-90a0-15b90bf6a6bb","added_by":"auto","created_at":"2025-10-09 10:17:53","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":229237,"visible":true,"origin":"","legend":"\u003cp\u003eChemical structure characterizations. (a) High-resolution C1s spectra of ASC700-1400. (b) High-resolution O1s spectra of ASC700-1400. (c-e) Fitted Raman spectra of Anthracites carbonized under different condition. (f) Values of A\u003csub\u003eD1\u003c/sub\u003e/A\u003csub\u003eG \u003c/sub\u003eand A\u003csub\u003eD3\u003c/sub\u003e/A\u003csub\u003eG\u003c/sub\u003e\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7693425/v1/37368f44d0d1ee98319ce42b.png"},{"id":93125806,"identity":"d8a8c0f4-600e-4024-b4e2-a0e54bafd49b","added_by":"auto","created_at":"2025-10-09 10:25:53","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":212360,"visible":true,"origin":"","legend":"\u003cp\u003e(a) GCD curves at 20 mA g\u003csup\u003e-1\u003c/sup\u003e. (b) Their cycle performance at 20 mA g\u003csup\u003e-1\u003c/sup\u003e. (c) Nyquist plots of Anthracite. (d) The rate capacity under different current densities. (e) Cycle capacity at high current (200 mA g\u003csup\u003e-1\u003c/sup\u003e)\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-7693425/v1/36492cb48dc58b3297c13b3d.png"},{"id":93124897,"identity":"a162cd6c-5194-4d0c-bac0-c75e2cc7b501","added_by":"auto","created_at":"2025-10-09 10:17:53","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":269796,"visible":true,"origin":"","legend":"\u003cp\u003e(a, d, g) The CV curves of the first three turns at a sweep rate of 0.1mV/s. \u0026nbsp;(b, e, h)The CV curves at different rates of Anthracite. (c, f, i) A linear relationship between log (Peak Currents) and log (Sweep Rate)\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-7693425/v1/b0e8051ace243c1e20b488fb.png"},{"id":93124887,"identity":"d9995b78-dd14-4079-a0b0-d7265a7b5f62","added_by":"auto","created_at":"2025-10-09 10:17:53","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":199875,"visible":true,"origin":"","legend":"\u003cp\u003eThe performance of the coin-type Na\u003csup\u003e+\u003c/sup\u003e full battery. (a) The first three laps of ASC600-1400. (b) The first three laps of ASC700-1400. (c) The first three laps of ASC800-1400\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-7693425/v1/4ddf9564b81fd3a387570416.png"},{"id":93125809,"identity":"b533efbb-5b57-48d7-b22f-cdce8cae99f8","added_by":"auto","created_at":"2025-10-09 10:25:53","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":180168,"visible":true,"origin":"","legend":"\u003cp\u003eCarbonization mechanism diagram\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-7693425/v1/efdc6f17df41ab110e1e3318.png"},{"id":93125808,"identity":"a8e0138a-1cb9-451c-bec8-f80441f7f009","added_by":"auto","created_at":"2025-10-09 10:25:53","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":163240,"visible":true,"origin":"","legend":"\u003cp\u003e(a, b, c) GCD curves of anthracite from different origins at 20 mA g⁻¹. (d) Platform capacity share from different origins\u003c/p\u003e","description":"","filename":"floatimage8.png","url":"https://assets-eu.researchsquare.com/files/rs-7693425/v1/d09de1f1be3b6549ca2fde84.png"},{"id":93127048,"identity":"7e270110-bf2f-483d-ae77-275dd2fff167","added_by":"auto","created_at":"2025-10-09 10:41:55","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2364654,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7693425/v1/97d11c46-ac60-438d-ac2d-0d2828e74d62.pdf"},{"id":93124882,"identity":"e1832358-716c-4d67-a107-fcd4b861edd8","added_by":"auto","created_at":"2025-10-09 10:17:53","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":1746416,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation2.docx","url":"https://assets-eu.researchsquare.com/files/rs-7693425/v1/98ad4cbc4bd04b8362fb2962.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Regulating the Microcrystalline Structure of Anthracite via Thermal Treatment Strategies for Enhanced Sodium-Ion Storage Performance","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eRecently, with the gradual deterioration of the ecological environment, the efficient utilization of renewable energy resources has already become an urgent task for creating a healthy ecological environment and a sustainable energy structure [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Among various energy storage systems, secondary batteries are a good choice. Among secondary batteries, lithium-ion batteries (LIBs), which have been successfully developed as power sources for portable electronic devices, are a promising alternative source due to their high reversible capacity and initial Coulombic efficiency [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. However, the rarity and non-uniform geographic distribution of lithium resources may severely restrict LIBs' prospective applications in grid-scale energy storage [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Sodium ions and lithium ions are located in the same main group, have similar structures and properties, and are low in cost, evenly distributed and abundant in resources. Therefore, sodium-ion batteries (SIBs) are regarded as an important supplement and partial replacement for LIBs energy storage technology [\u003cspan additionalcitationids=\"CR6 CR7 CR8\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe radius of sodium ions (Na⁺) is larger than that of lithium ions (Li⁺). This characteristic leads to a relatively slower diffusion rate of sodium ions within electrode materials, thereby affecting their reversible sodium storage capacity. As a result, the graphite anode materials commonly used in commercial LIBs are unsuitable for Na⁺ storage in SIBs [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Therefore, finding suitable SIB anode materials is very important and urgent. Disordered carbon materials are considered to be very promising SIB anode materials due to their amorphous structure and large interlayer spacing [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTo date, many carbon materials with different structures have been developed, such as soft carbon [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e], hard carbon [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], and hybrid carbon [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Currently, the large-scale, low-cost use of precursors is one of the common methods for producing hard carbon materials, such as coal [\u003cspan additionalcitationids=\"CR17\" citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e], resins [\u003cspan additionalcitationids=\"CR20\" citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], asphalt [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], and oxygen-rich biomass [\u003cspan additionalcitationids=\"CR24\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Anthracite, as a coal-based material, possesses distinct advantages over other coal resources: its graphite structure is clearly ordered, it boasts a high carbon content, and it is cost-effective. Consequently, it has been extensively researched for energy storage applications [\u003cspan additionalcitationids=\"CR27\" citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. However, coal-based carbon primarily consists of polynuclear fused aromatic hydrocarbons, which readily form carbon layers during carbonisation. This results in a highly ordered graphite structure with narrow interlayer spacing and few defects, rendering it unfavourable for sodium ion storage. Therefore, the development of high-performance SIB anodes with suitable interlayer spacing and a high proportion of graphitic microcrystals is imperative.\u003c/p\u003e\u003cp\u003eTo address this issue, numerous researchers have made tremendous efforts, Hu and co-workers prepared coal-based carbon by the direct pyrolysis of anthracite, and the anode delivers a high sodium storage capacity of 222 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e with good rate performance and long cycle life [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. However, the reversible capacity remains relatively low, and the ICE is 81%, which is not sufficient for large-scale production requirements. Liu et al. used anthracite as the carbon source and utilized the effect of surface hydrogen bonds to self-assemble melamine-cyanuric acid onto the surface of anthracite, successfully constructing N-doped carbon materials with customized microstructure and expanded interlayer spacing [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eAlthough they achieved high reversible capacity and rate performance, melamine-cyanuric acid exhibits certain toxicity, is costly, and possesses a low initial coulombic efficiency of only 74.2%. However, due to the complexity of the internal structure of anthracite, the performance of the final hard carbon product has always been difficult to meet the requirements of industrialization, especially the reversible capacity and ICE remain challenges.\u003c/p\u003e\u003cp\u003eIn this study, we introduced a method that combines mechanical shearing and segmented calcination to regulate the internal graphite microcrystals of anthracite-based hard carbon materials, thereby increasing the degree of material defects and providing more active sites for sodium ion storage. At 0.1 C, the reversible capacity is 304.4 mAh g\u003csup\u003e-1\u003c/sup\u003e, the initial Coulomb efficiency is 89.3%, and after 100 cycles, the reversible capacity is 280.5 mAh g\u003csup\u003e-1\u003c/sup\u003e. This work provides a feasible approach for the large-scale preparation of smokeless coal-based hard carbon materials.\u003c/p\u003e"},{"header":"EXPERIMENTAL SECTION","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003eMethod of Preparation\u003c/h2\u003e\u003cp\u003eCrush and sieve anthracite. Select anthracite with a particle size of less than 1000 mesh and ball mill it in a ball mill at a speed of 500 for 12 h. Add 5% concentration hydrochloric acid and 20 mL of ethanol, and oil bath in an oil bath pot with a rotational speed of 500 and 80 ℃ for 12 h. After the oil bath, the sample was centrifuged at 10,000 RPM for 3 min, and the precipitate (tris-water, tris-alcohol) was retained. Take out the sediment and filter it in a vacuum filtration instrument until the liquid is clear. Then dry it in a forced convection drying oven for 12 h. Replace hydrochloric acid with hydrogen fluoride and repeat the steps. Take out the samples and dry them in a forced convection drying oven for 12 h. In the tube furnace, the pre-carbonization at 600 ℃, 700 ℃, and 800 ℃ (heating at 3 ℃ min\u003csup\u003e-1\u003c/sup\u003e, argon gas, holding for 2 h) and carbonization at 1400 ℃ (heating at 5 ℃ min\u003csup\u003e-1\u003c/sup\u003e, argon gas, holding for 2 h) were respectively named as follows: ASC600-1400, ASC700-1400, ASC800-1400.\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eMaterials characterization\u003c/h3\u003e\n\u003cp\u003eX-ray diffraction (XRD (D-MAX 2200 VPC, Rigaku, Japan) was performed using a powder X-ray diffractometer. Raman spectra (inVia, Reflex, UK) were recorded using a micro-Raman spectrometer with an excitation wavelength of 532 nm. Scanning electron microscope (SEM) images were obtained through ultra-high resolution field emission scanning electron microscopy. The pyrolysis behavior of carbon precursors was characterized by thermogravimetric analyzer (TGA, air atmosphere, STA 449 F3, Netzsch, Germany) at a constant heating rate of 10 ℃ min\u003csup\u003e-1\u003c/sup\u003e from 25 ℃ to 800 ℃ in an air atmosphere. The nitrogen adsorption and desorption isotherms were collected at 77.3 K using a nitrogen adsorption analyzer (BSD-660M A6B3M instrument. Images for characterizing the lattice morphology were collected using high-resolution transmission electron microscopy (HR-TEM, F200 X G2, FEI Talos). The closed-pore structure characteristics were studied by the small-angle X-ray scattering (SAXS, Xeuss 3.0, Xenocs) testing method, and the specific surface area (SSA) of micropores (Smic) and mesopores (Smes) was determined by the Barret-Joyner-Halenda method (BJH). Use XPS to measure the functional groups contained in carbon materials.\u003c/p\u003e\n\u003ch3\u003eElectrochemical measurements\u003c/h3\u003e\n\u003cp\u003eAll electrochemical tests were conducted on button cells. The negative electrode was prepared by mixing active materials, Super P, carboxymethyl cellulose (CMC), and polymerized styrene-butadiene rubber (SBR) in weight ratios of 95:1.74:0.96:2.3. The mixture was then evenly mixed with deionized water to form a slurry, which was applied to the copper foil. The electrode was vacuum-dried at 80 degrees Celsius in a vacuum drying oven for 12 h. After cutting the pieces, the batteries are assembled in a glove box filled with argon gas. 1.0 mol L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e NaPF6 (EC/DMC/DEC\u0026thinsp;=\u0026thinsp;1:1:1 in volume) were used as electrolytes for SIBs.. The glass fiber membrane (GF/D, Whatman) was used as the separator, and the sodium metal was used as the counter electrode. The battery system undergoes discharge and charge tests at various C rates within a voltage range of 0.01\u0026thinsp;~\u0026thinsp;2 V in a constant temperature and humidity chamber.\u003c/p\u003e\n\u003ch3\u003eFull battery test method\u003c/h3\u003e\n\u003cp\u003eThe cathode material comprises sodium iron manganese oxide, while the anode utilises sample carbon material with an N:P ratio of 1.3. 1.0 mol L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e NaPF6 (EC/DMC/DEC\u0026thinsp;=\u0026thinsp;1:1:1 in volume) were used as electrolytes for SIBs.\u003c/p\u003e"},{"header":"RESULTS AND DISCUSSION","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003ePhysical characterization\u003c/h2\u003e\u003cp\u003eIn order to visually observe the microstructure of the samples, we conducted a series of tests using both TEM and SEM. As demonstrated in (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e(a-f)), the ASC600-1400, ASC700-1400, and ASC800-1400 all manifest long-range disordered and short-range ordered structures, with the ASC700-1400 displaying a preponderance of closed-cell structures. All the samples exhibited dispersed diffraction rings, yet diffraction spots of individual crystals were discernible. Subsequent analysis of the substance indicated that it was elemental silicon. As is apparent from the results of the SEM analysis, the sizes of the particles under consideration are all less than 9 \u0026micro;m. Because the same ball milling method is adopted, there is no obvious difference in their morphologie.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThrough thermogravimetric analysis, the weight change of anthracite was not significant between 25 ℃ and 430 ℃, but it decreased sharply between 430 ℃ and 600 ℃. After 600 ℃, it remained stable, but still contained 3.3% impurities (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). The following analysis shows that it is elemental silicon. According to reports, elemental silicon does not store sodium, so it has no impact on this experiment. The unique crystal structure of hard carbon was observed in the XRD pattern, and the peaks near 24\u0026deg; and 43\u0026deg; provided direct information from the (002) and (100) crystal planes(Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). Calculate the interlayer spacing according to Formula 1. The interlayer spacing of ASC700-1400 (3.74 nm) is greater than that of ASC600-1400 (3.67 nm) and ASC800-1400 (3.72 nm).\u003c/p\u003e\u003cp\u003eThis is attributed to the unique carbonization evolution process of Anthracite. At low temperatures, small molecules are released, and the closed pores increase. As the temperature rises, the interlayer spacing becomes larger and larger. When a certain temperature is reached, the microcrystalline structure begins to repair itself, gradually becoming graphitised, and the interlayer spacing decreases. Therefore, ASC700-1400 has a relatively high interlayer spacing. From the XRD image, it can be seen that there are still a small amount of impurities. Through analysis, it is found to be elemental silicon. According to relevant literature reports, silicon has very low curing activity, resulting in limited sodium storage capacity [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe specific surface area and pore size distribution of anthracite coal-t material were comprehensively analysed using nitrogen adsorption-desorption isotherm technology. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec, a typical Type IV isotherm curve was observed, indicating the material contains abundant mesoporous material with a pore size range of 0\u0026ndash;50 nm. The specific surface area ranges from 12 to 18 m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The pore diameters were calculated from the desorption branches of the isotherms using the BJH method. Among them, the pore volume of ASC700-1400 was the smallest, and that of ASC600-1400 was the largest in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(c, d). The analysis results of pore size and volume by the BJH method (calculated based on desorption isotherms) are presented in Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e. We employed small-angle scattering (SAXS) specifically to characterize ASC700-1400 as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e(e, f). According to the SAXS diagram (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ee), a distinct peak is produced near 0.1 A\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The scattering shape of closed pores is as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef. The closed-cell radius ranges from 0.17 to 10 nm.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eIn order to further ascertain the chemical composition and chemical state of the material, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(a, b) displays the X-ray photoelectron spectroscopy (XPS) scan of ASC700-1400. The sample displays clear C1s and O1s signals. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, the C1s spectral profile can be decomposed in order to reveal graphite carbon (C-C peak at 284.8 eV), as well as C-O derived from epoxy or phenolic functional groups at 286.2 eV, and carbon-oxygen double bonds (C\u0026thinsp;=\u0026thinsp;O at 288.9 eV) [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, the O1s spectra are predominantly fitted as two peaks of oxygen atoms bonded to the carbon double bond (C\u0026thinsp;=\u0026thinsp;O carbonyl at 531.8 eV) and oxygen atoms bonded to the carbon single bond (C-O alkyl, 532.6 eV [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. As demonstrated in Tables S1-S2, within the O1s spectrum, the carbon-oxygen double bond (C\u0026thinsp;=\u0026thinsp;O carbonyl) accounts for 96.41%, while the carbon-oxygen single bond (C-O alkyl) constitutes 87.3%. In the C1s spectrum, the carbon-oxygen double bond (C\u0026thinsp;=\u0026thinsp;O) accounts for 33.64%, the carbon-oxygen single bond (C-O) accounts for 44.48%, and graphitic carbon (C-C) accounts for 56.55%.\u003c/p\u003e\u003cp\u003eAs demonstrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c-e), Raman spectroscopy can be employed to analyse the degree of graphitization of the material under investigation. Two characteristic peaks are evident at 1345 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and 1585 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, corresponding to the D band and G band, respectively. These bands are associated with turbostratic defects (sp\u0026sup3;) and crystalline graphite (sp\u0026sup2;) structures [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The next step is to fit and deconvolve the Raman spectrum in order to obtain more specific information [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The following essay will provide a comprehensive overview of the relevant literature on the subject. The spectral curves were divided at 1200 (D4), 1340 (D1), 1500 (D3), and 1580 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (G) [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe intensity ratio of D1 to G bands (A\u003csub\u003eD1\u003c/sub\u003e/A\u003csub\u003eG\u003c/sub\u003e) has been shown to reflect the defect concentration of disordered carbon [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. The A\u003csub\u003eD1\u003c/sub\u003e/A\u003csub\u003eG\u003c/sub\u003e ratio exhibited an upward trend, initially rising from 1.39 of ASC600-1400 to 1.41 of ASC700-1400, and subsequently reaching 1.61 of ASC800-1400. The gradual increase of A\u003csub\u003eD1\u003c/sub\u003e/A\u003csub\u003eG\u003c/sub\u003e has been shown to result in a decrease in the degree of graphitization [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. As demonstrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef, there is a gradual increase in A\u003csub\u003eD1\u003c/sub\u003e/A\u003csub\u003eG\u003c/sub\u003e, whilst A\u003csub\u003eD3\u003c/sub\u003e/A\u003csub\u003eG\u003c/sub\u003e initially decreases and subsequently increases. The following essay will provide a comprehensive overview of the relevant literature on the subject.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\n\u003ch3\u003eElectrochemical measurements\u003c/h3\u003e\n\u003cp\u003eIn order to further explore the influence of the microstructure of the material on the sodium storage behavior, the electrochemical performance of Anthracite under different conditions was studied by using the half-cell test method with sodium as the counter electrode, and the tests were carried out on the constant current charge-discharge curve of 20 mA g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The voltage distribution of all Anthracite electrodes shows two distinct regions; (1) At a platform near 0.1V, (2) The voltage gradually increases around 0.1-2 V. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, the ASC700-1400 demonstrated a maximum reversible capacity of 304.36 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and a maximum initial Coulombic efficiency of 89.32%, and the platform capacity was 201.9 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, accounting for 66.34%. The reversible capacity and initial coulombic efficiency of the ASC600-1400 and ASC800-1400 samples were 274.7 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 85.15%, 295 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 87.2% respectively, and the platform capacity and platform capacity proportion were 181.4 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, 66.03%, 182 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and 61.52% respectively Shown in Fig \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e. Intercalation capacity is shown in Fig S2, where ASC700-1400 accounts for the highest proportion at 61%, while ASC600-1400 and ASC800-1400 both stand at 58%. Based on the existing relevant literature, the slope corresponds to the storage of sodium ions by carbon defects and active sites, and the platform corresponds to the storage of sodium ions by closed pores. The smaller interlayer spacing is not conducive to the intercalation/deintercalation of sodium ions, resulting in the capacity of ASC600-1400、ASC800-1400 being lower than that of ASC700-1400 [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe increase in platform area capacity and ICE is due to the synergistic effect of high-temperature treatment to obtain closed micropores and the formation of a stable SEI film. As shown in the Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, the cycling performance of ASC600-1400, ASC700-1400, and ASC800-1400 at 0.1 C for 100 cycles is presented. Among them, ASC700-1400 and ASC800-1400 have better cycling stability than ASC600-1400. After 100 cycles, ASC700-1400 maintains a reversible capacity of 280.5 mAh g\u003csup\u003e-1\u003c/sup\u003e, and the capacity retention rate after cycling is close to 100%. This excellent cycling performance is very likely due to the unique amorphous carbon material having good mechanical properties and high electronic conductivity.\u003c/p\u003e\u003cp\u003eThe EIS test results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec. The ASC600-1400 and ASC700-1400 exhibit the smallest internal resistance, indicating better dynamic performance. The internal resistance of ASC600-1400 and ASC700-1400 is 100 Ω, while that of ASC700-1400 is 148 Ω. The characteristics of larger interlayer spacing, higher defect density, and abundant nano-pore structure promote rapid charge transfer, enhance ion diffusion kinetics, thereby reducing the internal resistance of ion and charge transport processes in the material, and exhibiting high reversible intercalation-uncalation properties.\u003c/p\u003e\u003cp\u003eIn Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed, the rate performance of Anthracite electrodes was further studied in detail at various rates ranging from 20 mA g\u003csup\u003e-1\u003c/sup\u003e to 500 mA g\u003csup\u003e-1\u003c/sup\u003e to evaluate the influence of carbonization temperature on electrochemical performance. The ASC700-1400 has a reversible capacity of 50 mAh g\u003csup\u003e-1\u003c/sup\u003e at 500 mA g\u003csup\u003e-1\u003c/sup\u003e. The reversible capacities of the ASC600-1400 and ASC800-1400 are lower than that of the ASC700-1400 under the same current. All three samples can maintain relatively good reversible capacity at a current density of 20 mA g\u003csup\u003e-1\u003c/sup\u003e after a high current density. We conducted a 200 mA high current long cycle test on the ASC700-1400, and the results showed that there was only a 50 mA g\u003csup\u003e-1\u003c/sup\u003e reversible capacity after 500 cycles. The high-current cycling performance is poor. The cycling performance of the ASC700-1400 at a current of 200 mA g\u003csup\u003e-1\u003c/sup\u003e is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee. The results indicate that the charging specific capacity drops sharply in the first few laps, tends to level off after 10 laps, and only has a capacity of 50 mAh g\u003csup\u003e-1\u003c/sup\u003e after 500 laps, with poor high-current cycling. After ball milling, the specific surface area increases, defects increase, leading to an increase in adsorption capacity, which results in poorer rate performance.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a, d, g) shows the CV curves of the first three turns of different carbon materials at a scanning rate of 0.1 mV s\u003csup\u003e-1\u003c/sup\u003e. For sodium ion storage, the ΔV values of ASC600-1400 (Δ\u003cem\u003eV\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.188 V), ASC700-1400 (Δ\u003cem\u003eV\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.145 V), and ASC800-1400 (Δ\u003cem\u003eV\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.145 V) tend to be consistent. These results indicate that the high overlap of CV curves measured after the activation of sodium-ion batteries suggests that a stable SEI film can be formed during the activation process.\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(b, e, h) shows the CV curves of three different electrodes at different scanning rates. With the increase of scanning rate, all Anthracite exhibited a lower sodium storage potential, similar oxidation/reduction peaks, and produced smaller irreversible regions, indicating less electrolyte decomposition, and rapid sodification and desodification kinetics.\u003c/p\u003e\u003cp\u003eA pair of sharp oxidation/reduction peaks that appear near 0.1 and 0.01 V are suitable for the process insertion and extraction of Na\u003csup\u003e+\u003c/sup\u003e. The existence of the difference between the oxidation peak and the reduction peak indicates that there is polarization lag between them. In addition, except for the REDOX peak, the scanning curves of other cycles overlap well, vividly demonstrating the excellent electrochemical robustness of Anthracite throughout the discharge-recharge cycle.\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\begin{array}{c}\\text{I}\\text{=}\\text{a}{\\text{v}}^{\\text{b}}\\#\\text{（}\\text{1}\\text{）}\\end{array}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eThe aim is to quantitatively explore the Na\u003csup\u003e+\u003c/sup\u003e storage principle, according to Eq.\u0026nbsp;1. The correlation between the anode current density (\u003cem\u003ei\u003c/em\u003e) and the scanning rate (\u003cem\u003ev\u003c/em\u003e) has been thoroughly and carefully examined. The derived index \u003cem\u003eb\u003c/em\u003e value of 0.5 indicates the diffusion-controlled storage mechanism, while the \u003cem\u003eb\u003c/em\u003e value of 1.0 indicates the main capacitive storage contribution [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(c, f, i) shows that the material exhibits a favorable linear correlation between the logarithmic current density (log \u003cem\u003ei\u003c/em\u003e) and the logarithmic scan rate (log \u003cem\u003ev\u003c/em\u003e). The range of \u003cem\u003eb\u003c/em\u003e values between 0.5 and 1.0 indicates that the total charge storage capacity involves a mixing mechanism that combines diffusion-dominant and capacitive effects, with a \u003cem\u003eb\u003c/em\u003e value of approximately 0.5. It indicates that the total charge storage is mainly contributed by the diffusion control process [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. The values of the constant \u003cem\u003eb\u003c/em\u003e of ASC600-1400, ASC700-1400 and ASC800-1400 are 0.75, 0.56 and 0.54 respectively.\u003c/p\u003e\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\begin{array}{c}\\text{I}\\left(\\text{v}\\right)\\text{=}{\\text{k}}_{\\text{1}}\\text{v}\\text{+}{\\text{k}}_{\\text{2}}{\\text{v}}^{\\text{1/2}}\\#\\text{（}\\text{2}\\text{）}\\end{array}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003cp\u003eAccording to Eq.\u0026nbsp;2, The current (\u003cem\u003ei\u003c/em\u003e) at a specific potential was separated into an embedded component (proportional to k\u003csub\u003e2\u003c/sub\u003e\u003cem\u003ev\u003c/em\u003e\u003csup\u003e1/2\u003c/sup\u003e) and a capacitive component (linearly proportional to k\u003csub\u003e1\u003c/sub\u003e\u003cem\u003ev\u003c/em\u003e) for current separation analysis to obtain the percentage contributions of these two processes, as shown in Fig S3, S4 [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. The ASC700-1400 can achieve a diffusion control percentage of 63% at a low scanning rate of 0.1 mV s\u003csup\u003e-1\u003c/sup\u003e, indicating more capacitive processes. As the scanning speed increases, the proportion of capacitance gradually decreases.\u003c/p\u003e\u003cp\u003eAdditionally, GITT measurements were conducted to, analyse ion diffusion kinetics. As shown in Fig S5\u0026ndash;S7, during the 0.1\u0026ndash;0.01 V sodium-ionation process, the sodium ion diffusion coefficients (D\u003csub\u003eNa⁺\u003c/sub\u003e) for ASC600-1400, ASC700-1400, and ASC800-1400 all exhibited a decrease followed by an increase. This phenomenon arises from the sequential intercalation and subsequent pore filling of sodium clusters [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe preliminary electrochemical measurement results of the full battery are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. Each group of batteries is charged to 3.8 V at a current rate of 0.1 C and then discharged to 2 V. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea, the ASC700-1400 exhibits a charging specific capacity of 129 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, a discharging specific capacity of 88.5 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and an ICE of 68.6%. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb, the ASC600-1400 exhibits a charging specific capacity of 127.4 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, a discharging specific capacity of 87 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and an ICE of 68.29%. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec, the ASC800-1400 exhibits a charging specific capacity of 129.1 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, a discharging specific capacity of 87.6 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, and an ICE of 67.85%. Among the three full-battery comparison samples, the ASC700-1400 had the best cycling performance, with a reversible capacity of 55 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003eafter 100 cycles Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eAs shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, anthracite starts to release small molecules (such as water, carbon dioxide, etc.) from 0 to 600 ℃, forming open pores and increasing the interlayer spacing. At 600 to 700 ℃, it continues to release small molecules more fully, reaching the maximum interlayer spacing. At 700 to 800 ℃, it begins to repair the microcrystalline structure, with the interlayer spacing decreasing. At 1400 ℃, closed pores are formed. At around 700 ℃, the release of small molecules is more thorough, so the final interlayer spacing is larger and the performance is better.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eThe findings of this study are applicable to anthracite from various origins. As illustrated in the Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e, the ICE and reversible capacity values are as follows: ASC700-1400-Y1 at 81.2% and 218.7 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; ASC700-1400-Y2 at 87.4% and 295.8 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e; ASC7000-1400-Y3 at 87.8% and 276.4 mAh g\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The proportion of anthracite platform capacity from different sources is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ed.\u003c/p\u003e"},{"header":"CONCLUSIONS","content":"\u003cp\u003eThis work optimized the performance of anthracite in the anode application of sodium-ion batteries by controlling the ball milling and two-step carbonization temperatures, and explained the influence of ball milling and carbonization temperatures on anthracite. The results show that ball milling will increase the specific surface area and defect degree of anthracite, thereby achieving a higher capacity. Control the temperature of the first carbonization step to obtain a larger interlayer spacing, thereby achieving a high initial Coulombic efficiency. Throughout the entire experiment, ASC700-1400 had the best performance, with a reversible capacity of 304.4 mAh g\u003csup\u003e-1\u003c/sup\u003e and an initial Coulombic efficiency of 89.3%. And it has excellent cycling performance and rate performance. It provides strategies for the optimization of anthracite in the future.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eSupporting Information\u0026nbsp;\u003c/strong\u003eSupplementary Information The online version contains supplementary material available at.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contribution\u0026nbsp;\u003c/strong\u003eYulong Zhang: Writing \u0026ndash; review \u0026amp; editing, Writing \u0026ndash; original draft, Methodology, Investigation, Conceptualization. Yandong Xie: Methodology, Investigation. Zuyong Feng: Investigation, Data curation. Qu Wang: Formal analysis, Data curation. Deping Xiong: Writing \u0026ndash; review \u0026amp; editing, Supervision, Project administration.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eConflict of interest The authors declare no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAUTHOR INFORMATION\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorresponding Author\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eDeping Xiong\u003cstrong\u003e-\u0026nbsp;\u003c/strong\u003e\u003cem\u003eSchool of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eE -mail: [email protected].\u003c/p\u003e\n\u003cp\u003eYandong Xie - \u003cem\u003eSchool of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eE -mail: [email protected].\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eYulong Zhang -\u003cem\u003e\u0026nbsp;School of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eQu Wang - \u003cem\u003eSchool of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eZuyong Feng - \u003cem\u003eSchool of Physics and Optoelectronic Engineering, Guangdong University of Technology, Guangzhou 510006, China.\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e This work was generously supported by the project of sci \u0026amp; tech of Zhongshan ( 2023A4011).\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eLi, Y.; Hu, Y. 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ACS Applied Energy Materials. \u003cstrong\u003e2018\u003c/strong\u003e, 1(5): 2295-2305. https://doi.org/10.1021/acsaem.8b00354\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"ionics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":" Learn more about [Ionics](https://www.springer.com/journal/11581) ","snPcode":"11581","submissionUrl":"https://mc.manuscriptcentral.com/ionics","title":"Ionics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Anthracite, Ball milling, Two-step carbonization, Initial coulomb efficiency, Plateau capacity","lastPublishedDoi":"10.21203/rs.3.rs-7693425/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7693425/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eSodium-ions and lithium ions are in the same main group, have the same chemical properties, and are low in price, so they are expected to replenish lithium-ion batteries. Among the various anode materials for sodium-ion batteries, anthracite has attracted much attention due to its low price and carbon content exceeding 90%. Although significant progress has been made in the research of hard carbon derived from anthracite-based carbon materials, the reversible capacity and initial Coulombic efficiency (ICE) of anthracite-based soft carbon are still not satisfactory. This paper uses anthracite as raw material and adjusts the specific surface area and defects through mechanical shearing, and regulates the interlayer spacing through temperature. Achieve a relatively high capacity of anthracite at 304.4 mAh g\u003csup\u003e-1\u003c/sup\u003e and an ICE of 89.3%. Low-cost anthracite coal, low-cost processes, and high initial coulombic efficiency\u0026mdash;these outstanding performance characteristics meet the requirements of practical applications and lay the foundation for the large-scale industrial production of low-cost, high-performance sodium-ion batteries for energy storage.\u003c/p\u003e","manuscriptTitle":"Regulating the Microcrystalline Structure of Anthracite via Thermal Treatment Strategies for Enhanced Sodium-Ion Storage Performance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-09 10:17:48","doi":"10.21203/rs.3.rs-7693425/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-18T21:13:09+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-02T11:55:59+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"126352262368982761085945606872186906731","date":"2025-09-29T20:40:47+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-29T03:53:57+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"58374460914242916162322008336007648854","date":"2025-09-28T08:01:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"45943538520418097956432107993678080789","date":"2025-09-28T07:31:05+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-09-27T19:49:29+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-09-26T11:45:06+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-09-26T11:42:36+00:00","index":"","fulltext":""},{"type":"submitted","content":"Ionics","date":"2025-09-23T10:46:23+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"ionics","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":" Learn more about [Ionics](https://www.springer.com/journal/11581) ","snPcode":"11581","submissionUrl":"https://mc.manuscriptcentral.com/ionics","title":"Ionics","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"78ed71e8-3071-4143-855e-5b3769b1584b","owner":[],"postedDate":"October 9th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-12-06T00:38:13+00:00","versionOfRecord":[],"versionCreatedAt":"2025-10-09 10:17:48","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7693425","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7693425","identity":"rs-7693425","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}