Ion Flux Optimization via Hollow Carbon Nanoreactors for High-Power and Energy-Dense Li-Cl2 Batteries

Ion Flux Optimization via Hollow Carbon Nanoreactors for High-Power and Energy-Dense Li-Cl2 Batteries | 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 Article Ion Flux Optimization via Hollow Carbon Nanoreactors for High-Power and Energy-Dense Li-Cl 2 Batteries Wei Chen, Yan Xu, Jiejun Ye, Zhipeng Wang, Peichao Zou, Lidong Sun, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6516066/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 Rechargeable Li-Cl 2 batteries are a promising high-energy-density technology but having critical challenges of limited rates and capacities. Insufficient and uneven ion flux in the interior of cathode is a crucial factor that hinders the rate performance and specific capacity of Li-Cl 2 battery. Herein, we propose and develop hollow carbon nanoreactors (HCNRs) as cathode materials for extremely high-power and high-energy Li-Cl 2 batteries. By confining electrolytes within tailored cavities, HCNRs facilitate enhanced and spatially homogenized ion flux in the interior of cathode, eliminating the reliance on bulk electrolyte diffusion and prohibiting rapid electrode degradation. This design enables the as-assembled Li-Cl 2 cell to achieve an ultrahigh current density of 120 mA/cm 2 during the charge/discharge process (charging to 500 mAh/g in 15 s) and a record-breaking specific capacity of 8000 mAh/g (9 mAh/cm 2 ), superior to the reported literature. Furthermore, we demonstrate the scalability of this design in a 1-Ah-scale pouch cell, achieving a practical cell-specific energy of 106 Wh/kg. This hollow nanoreactor design highlights the potential of Li-Cl 2 batteries as high-power and energy-dense systems, paving the way for their practical applications. Physical sciences/Energy science and technology/Energy storage/Batteries Physical sciences/Materials science/Materials for energy and catalysis/Batteries rechargeable Li-Cl2 battery hollow carbon nanoreactor ion flux high-power high-energy density Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction The development of high-energy-density batteries is critical to meeting the growing demands of electric vehicles and electric aircrafts 1 – 4 . Lithium-ion batteries (LIBs) are currently the most ideal options, offering an energy density of ~ 250 Wh/kg 5–8 . However, further advancements are urgently needed to extend the cruising range of these applications 9 – 13 . Recently, rechargeable lithium-chlorine (Li-Cl 2 ) batteries using thionyl chloride (SOCl 2 ) as the electrolyte, Li metal as the anode, and porous materials as the cathode have gathered much attention due to their high theoretical energy density 14 – 23 . Despite their promises, Li-Cl₂ batteries face significant challenges, including low cycling current densities (< 5 mA/cm²) and limited specific capacities (< 4000 mAh/g), leading to low power density and limited energy density. We evaluated the commonly applied cathode materials in Li-Cl 2 batteries, and found that they feature solid structures 17 , 20 – 22 , 24 with inadequate electrolyte retention capacity. Therefore, in traditional cathode materials, the Li + or Cl - ion transport in the interior of cathode faces two critical challenges (Fig. 1 a): (1) insufficient ionic flux due to the prolonged diffusion length ( l ) from the bulk electrolyte reservoirs, and (2) non-uniform ionic flux distribution along the thickness direction of cathode during cell operation. The inhomogeneous ionic flux distribution induces the reactive sites of cathode near the separator being covered by a solid LiCl layer due to the excessive ion flux around this area, which obstructs subsequent ion transport. Consequently, active materials approaching to the current collector is electrochemically inactive, resulting in significantly compromised specific capacity and power density. To address these challenges, we hypothesize that by designing a cathode material with a hollow structure that capable of intrinsic electrolyte confinement in the cavity (Fig. 1 b), the hollow structure could promote ion flux, effectively reduce the diffusion length and homogenize ion distribution compared to the conventional solid material. Hollow carbon materials have demonstrated remarkable potential in improving electrochemical reaction kinetics and modulating microenvironments in the fields of catalysis 25 – 27 and energy storage 28 , 29 . This has motivated us to explore hollow carbon materials to improve the electrochemical kinetics in Li-Cl 2 batteries. In this work, we demonstrate that the N-doped hollow carbon nanoreactors (HCNRs) can significantly enhance the performance of Li-Cl 2 batteries in terms of power density and energy density. The N-doped HCNRs play a dual role in improving the performance of the battery. Firstly, the hollow design of HCNR helps to improve the ion diffusion of Li + and Cl - ions and reduces diffusion length by confining electrolyte in the cavity, allowing for fast charge/discharge rates of Li/Cl 2 batteries. At a specific capacity of 500 mAh/g, our rechargeable Li/Cl 2 battery demonstrates an impressive cycling current density of 120 mA/cm 2 , achieving a full charge/discharge cycle in only 30 seconds. Secondly, the homogenization of Li + and Cl - ions along the thickness of cathode prohibits the premature electrode, enabling Li-Cl 2 battery to achieve a specific capacity as high as 8000 mAh/g (9 mAh/cm 2 ). Notably, the Li-Cl 2 pouch cell utilizing HCNRs as cathode materials exhibits a practical energy density of around 106 Wh/kg at the entire-cell level. Our findings suggest the potential of this hollow cathode material design in addressing the trade-off between energy density and power density in Li-Cl 2 batteries. Results and Discussion 2.1 Preparation and Characterization of HCNRs HCNRs were prepared by a hard template method according to the reported literature 30 . To prepare HCNRs with different-sized cavities, MgO nanoparticles with different diameters were selected as the hard template. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the microstructures and the corresponding morphologies of HCNRs. As can be seen from SEM images, the HCNs maintain a spherical morphology (Figure S1 ). TEM images give the clear hollow feature of HCNRs (Fig. 2 a- 2 b). The diameter of the obtained HCNRs is mainly distributed in the range of 16–24 nm and 40–55 nm, with average diameters of 21 nm and 47 nm, respectively (Figure S2). In the following text, the obtained HCNRs with different sizes are denoted as HCNR-20 nm and HCNR-50 nm, respectively. HRTEM confirms the graphitic lattice of both HCNR-50 nm and HCNR-20 nm with measured wall thicknesses 6.0 nm and 4.3 nm, respectively (Fig. 2 a- 2 b inset image and Figure S3), respectively. To elucidate the critical role of hollow nanostructure, commercial carbon material, ketjenblack (KJ Black), was chosen as a contrast, which showed solid-structure with similar graphitic lattice (Fig. 2 c and Figure S4). The N 2 adsorption/desorption measurements (77 K) were employed to assess the structure and porosity of HCNRs. As shown in Fig. 2 d- 2 f, the N 2 adsorption-desorption isotherms of HCNR-50 nm, HCNR-20 nm and KJ Black exhibited the characteristics of typical Type-II curves, indicating the coexistence of micropores and mesopores in these carbon materials. In the low-pressure range (0-0.1 P/P 0 ), the cumulative N 2 uptake is 330, 113, and 299 cm 3 /g for HCNR-50 nm, HCNR-20 nm and KJ Black, respectively, indicating that HCNR-50 nm and KJ Black have similar micropore structure. The micropore size distribution of HCNRs and KJ Black was analyzed using nonlocal density functional theory (NLDFT), concentrated in the range of 0.5–1.4 nm (Figure S5). However, at high pressure rang (near 1.0 P/P 0 ), the cumulative N 2 uptake for HCNR-50 nm, HCNR-20 nm was 3894 and 2302 cm 3 /g, higher than that of KJ Black, suggesting that inner macropore in HCNR can storge more condensed N 2 . The Brunauer–Emmett–Teller (BET) surface area of HCNR-50 nm and HCNR-20 nm were 1352 and 502 m 2 /g, respectively. The BET surface area of KJ Black was ~ 1034 m 2 /g, comparable to HCN-50 nm. Notably, the presence of micropores within the HCNR walls facilitates electrolyte permeation into the interior hollow cavities, enabling efficient ion transport pathways. To evaluate the Cl₂ storage capacity, static adsorption experiments of Cl 2 gas were conducted at room temperature. Figure 2 g shows that the adsorption amount of Cl 2 was 1.0, 3.5, and 2.6 mmol per gram for KJ Black, HCNR-50 nm, and HCNR-20 nm, respectively. This result unambiguously demonstrates the superior Cl 2 storage capability of our hollow nanoreactor architecture, highlighting its unique advantage in confining reactive Cl₂ species within the engineered cavities. X-ray diffraction (XRD) and Raman were applied to analyze the electronic conductivity of HCNR-50 nm, HCNR-20 nm and KJ Black. The XRD patterns of these three carbon materials exhibit broad peaks at ~ 26° (Figure S6), corresponding to the (002) plane of graphitic carbon. Raman spectra were further applied to investigate the degree of graphitization. As shown in Fig. 2 h, the intensity ratio of D and G bands of HCNR-50 nm, HCNR-20 nm and KJ Black were 1.15, 1.22 and 1.71, respectively, suggesting that HCNR-50 nm possesses the highest graphitization degree, which was beneficial to fast electron transport. The electron conductivity of these three carbon materials was further tested by a powder resistivity tester, and HCNR-50 nm has the highest electron conductivity (Figure S7). In order to exclude the influence of electron conductivity, a kind of carbon nanotube (CNT) with characteristics of high electron conductivity would be introduced into HCNR-50 nm, HCNR-20 nm and KJ Black electrodes. Figure S8 shows HCNRs were connected by the CNTs, which could construct the fast electron transport pathways. X-ray photoelectron spectroscopy (XPS) was further applied to analyze the compositions of HCNR. The survey spectra revealed N and O heteroatoms contained in HCNRs and the contents of N and O were ~ 6 at% and 3 at% (Figure S9 and Table S1 ). The N 1s spectra showed two peaks at 401.0 and 398.1 eV (Fig. 2 i), corresponding to pyrrolic N and pyridinic N, which were considered as active sites for the capture of LiCl and Cl 2 . 15 , 16 Subsequently, the samples after the adsorption of Cl 2 were analyzed by XPS. Figure S10 shows that the Cl signal was detected in the samples of HCNRs, but not in the sample of KJ Black, suggesting that the successful adsorption of Cl 2 by HCNRs involved chemisorption, but the failed adsorption of Cl 2 by KJ Black. Further mechanistic insight was gained through N 1s XPS analysis (Figure S11), which revealed a 0.2 eV higher energy shift, indicating that the electron density on N atoms decreased due to the interaction between Cl 2 and N atoms in HCNRs. This result confirms the critical role of nitrogen active sites in facilitating strong chemisorption interactions. 2.2 Electrochemical Performance of Li-Cl Battery To investigate the correlation between the HCNR architecture and the Li + and Cl - ion diffusion kinetics, electrochemical impedance spectroscopy (EIS) was first conducted to Li-Cl 2 battery after charging 1 mAh using different cathode materials. As shown in Fig. 3 a, the ion diffusion resistance of Li-Cl 2 @KJ Black battery was much larger than that of Li-Cl 2 @HCNR-50 nm battery and Li-Cl 2 @HCNR-20 nm battery (Figure S12). More importantly, the Z W in the Nyquist plot of Li-Cl 2 battery using HCNR-50 nm and HCNR-20 nm was an inclined straight line in the low-frequency region, while for Li-Cl 2 @KJ Black battery, the plot became an arc in the low-frequency region (Fig. 3 a). This implies that the diffusion of Li + and Cl - ions was semi-infinite diffusion in HCNR-50 nm and HCNR-20 nm electrodes due to sufficient ion supply, and the diffusion of Li + and Cl - ions was finite diffusion in KJ Black electrode due to the limited ion concentration in the bulky electrode. In the Bode plots shown in Fig. 3 b, the ionic diffusion coefficient (D) was decreased in the order of HCNR-20 nm, HCNR-50 nm and KJ Black. If D value was large, the active species can be supplied rapidly to the electrode, and this result agrees well with the result in Fig. 3 a. Further, the ion diffusion kinetics were investigated in Li-Cl 2 battery at various current densities from 2 mA/cm 2 to 120 mA/cm 2 . As shown in Fig. 3 c, the discharge and charge plateaus of Li-Cl 2 @HCNRs cells were positioned at 3.34 V and 4.09 V at a low current density of 5 mA/cm 2 , leading to a polarization voltage of 0.75 V. In sharp contrast, the Li-Cl 2 @KJ Black cell exhibited a higher polarization voltage of 0.95 V with the discharge and charge plateaus positioned at 3.23 V and 4.18 V, respectively. The fast Li + and Cl - ion transfer in Li-Cl 2 @HCNRs battery contributes to the lower polarization voltage. Remarkably, even at a high current density of 50 mA/cm 2 , the Li-Cl 2 @HCNR-50 nm battery exhibited a discharge plateau at 2.92 V and a charge plateau at 4.40 V with a Coulombic efficiency (CE) ~ 100% (Fig. 3 d). The Li-Cl 2 @KJ Black battery even cannot tolerate such a high current density of 50 mA/cm 2 with a sharp increased charge voltage due to the limited ion diffusion kinetics. The highest current density that Li-Cl 2 @HCNR-50 nm battery could survive was 120 mA/cm 2 (charged in 15 s to 500 mAh/g, Fig. 3 e) with a CE of ~ 95% (Figure S13) and a discharge plateau at 2.58 V (Figure S14). These results, especially cycling at extremely high current density with high CE (Fig. 3 f), far surpasses those of previous high-energy battery systems like Li-S 3 , 31 , Li-CO 2 32,33 , Li-I 2 34,35 and Li-O 2 36 batteries. Notably, the Li-Cl 2 @HCNR-20 nm battery exhibited a maximal tolerant current density was 80 mA/cm 2 , which could be ascribed to the limited cavity volume in HCNR-20 nm cavity structure, supplying insufficient ions. Therefore, the optimal size of HCNR for high-power Li-Cl 2 battery is 50 nm. The encapsulation effect based on the hollow structure enhanced the Li + and Cl - ions flux, leading to the smallest ion diffusion polarization and the highest current density tolerance. The long-term cycling performance of Li-Cl 2 @HCNR-50 nm battery at high current density was further explored. As shown in Fig. 3 g, the Li-Cl 2 @HCNR-50 nm battery delivered a remarkable capacity of 740 mAh/g with an ultralong cycling life of 400 cycles and a CE nearly 100% at a high current density of 20 mA/cm 2 . These excellent electrochemical performances promise the Li-Cl 2 @HCNRs battery could retain high power delivery. The unique structure of HCNR could homogenize the ion flux along the thickness of cathode, ensuring the full utilization of cathode materials, leading to enhanced specific capacity. To verify the above effect by heteroatom-doped HCNRs, Li-Cl 2 batteries were evaluated at specific capacities ranging from 2000 mAh/g to 8000 mAh/g. As shown in Fig. 4 a and Figure S15, the CE of Li-Cl 2 @HCNR-50 nm, Li-Cl 2 @HCNR-20 nm and Li-Cl 2 @KJ Black batteries could be maintained at ~ 100% under moderate specific capacities of 2000–4000 mAh/g. As shown in Fig. 4 a, even at a high specific capacity of 6000 mAh/g and ultrahigh specific capacity of 8000 mAh/g (equivalent to 9–10 mAh/cm 2 ), the CE of Li-Cl 2 @HCNR-50 nm battery remained at ~ 100%, demonstrating the excellent homogenization of ion flux by HCNRs. In contrast, the CE of Li-Cl 2 @KJ Black battery were merely ~ 80% and 70% (Fig. 4 a) at the specific capacity of 6000 mAh/g and 8000 mAh/g, respectively, due to the insufficient ion flux at the interior of cathode materials. Notably, the CE of Li-Cl 2 @HCNR-20 nm battery could be maintained at ~ 100% across the entire range of specific capacities from 2000 to 8000 mAh/g. However, during the late charge process after several cycles at a specific capacity of 8000 mAh/g, the charge voltage suddenly increased to 5 V (Figure S15), likely due to the limited cavity space or the aggregation of LiCl blocking the micropores of HCNR-20 nm. 20 The voltage profiles of Li-Cl 2 @HCNR-50 nm, Li-Cl 2 @HCNR-20 nm and Li-Cl 2 @KJ Black batteries were compared at a specific capacity of 6000 mAh/g. As shown in Fig. 4 b, the Li-Cl 2 @ KJ Black battery demonstrated the highest polarization with the charge/discharge voltages recorded at 4.07 V and 3.38 V, respectively, attributing to the sluggish ion diffusion in KJ Black. The Li-Cl 2 @HCNR-50 nm battery and the Li-Cl 2 @HCNR-20 nm battery displayed identical charge voltages at 3.96 V. The discharge voltages for the Li-Cl 2 @HCNR-50 nm battery and Li-Cl 2 @HCNR-20 nm battery were measured at 3.56 V and 3.47 V, respectively, consistent with the findings in Fig. 3 c. High areal capacity is critical to obtain high-energy density battery, therefore, the long cycle lives of Li-Cl 2 cells utilizing different cathode materials were assessed at a high areal capacity of 7 mAh/cm 2 (2500 mAh/g). As depicted in Fig. 4 c and 4 d, the Li-Cl 2 @HCNR-50 nm battery demonstrated a cycling life exceeding 120 cycles in a stable charge and discharge voltage plateaus with a CE of approximately 100%. Conversely, the cycling lifetime of the Li-Cl 2 @HCNR-20 nm battery was less than 90 cycles with sharply increased charge voltage due to the limited cavity space (Fig. 4 c and S17). The Li-Cl 2 @KJ Black battery presented the shortest cycle life of 60 cycles and unstable discharge voltage due to the diffusion pathway blocked by LiCl (Fig. 4 c and 4 e). Upon increasing the areal capacity of the Li-Cl 2 @HCNR-50 nm battery to 9 mAh/cm 2 (~ 5600 mAh/g), the Li-Cl 2 @HCNR-50 nm battery still could exhibit a cycle life exceeding 90 cycles with a CE nearing 100% (Fig. 4 f), indicating its exceptional utilization rate of the whole cathode. We compared our work with the state-of-the-art cathode materials for rechargeable Li-Cl 2 batteries including carbon dioxide activated porous carbon (KJCO 2 ) 18 , acetylene black with molecular catalyst of I 2 (AB with I 2 ) 37 , AB with SO 2 23 , graphite 19 , TpPa-NH 2 COF 38 and porous organic nanocage (POC) 22 in the aspects of areal and specific capacities, as summarized in Fig. 4 g. Specifically, the Li-Cl 2 @HCNR-50 nm cell exhibited impressive performances, achieving a maximal areal capacity of 9 mAh/cm 2 over 90 cycles with an accumulative capacity of 810 mAh/cm 2 . Among the compared materials, only KJCO 2 demonstrated a comparable areal capacity, but its cycle life was limited to merely 3 cycles, highlighting the exceptional cycling stability of our HCNR-based system. Furthermore, the Li-Cl 2 @HCNR-50 nm cell achieved an extraordinary specific capacity of 8000 mAh/g, surpassing the best-reported value by 3000 mAh/g. These significant advancements illustrate the potential of HCNRs as a highly effective cathode material for high-performance rechargeable Li-Cl 2 batteries. 2.3 Mechanism Investigation of Battery Reactions in the HCNR To elucidate the influence of the HCNR architecture on ion diffusion in Li-Cl₂ batteries, finite element method (FEM) simulations were employed. Given that LiCl distribution reflects the spatial arrangement of Li⁺ and Cl⁻ ions, the simulations focused on modeling LiCl formation during the electrochemical reduction of Cl₂. The HCNR-50 nm was represented as a hollow spherical structure with open pores in its walls, immersed in an electrolyte and filled with Cl₂ molecules both inside and outside the cavity. The simulation results revealed that Cl₂ molecules could diffuse through the pores and undergo reduction to form LiCl on both the inner and outer surfaces of the HCNR-50 nm (Figure S18a). Consequently, LiCl was uniformly distributed within the cavity and on the outer surface of the HCNR (Fig. 5 a). This dual-pathway diffusion and deposition mechanism facilitated the generation of Li⁺ and Cl⁻ ion fluxes within the cavity, significantly enhancing ion flux and homogenizing ion distribution across the cathode interior. In contrast, for solid carbon materials such as KJ Black, Cl₂ diffusion was restricted to the outer surface, leading to LiCl deposition exclusively on the external surface (Fig. 5 b and Figure S18b). This surface-limited deposition obstructed ion diffusion pathways, resulting in underutilization of active cathode materials near the current collector, particularly at high C-rates. Figure 5 c shows the concentration distribution curve of LiCl. For the solid KJ black material, the LiCl concentration reaches its maximum near the outer surface and progressively decreases with distance from the surface. In contrast, the hollow carbon materials demonstrate a distinct dual-concentration characteristic: they maintain a high LiCl concentration at the outer surface, and they also preserve an even greater concentration within their interior cavities. This unique dual-concentration configuration ensures sufficient ion flux throughout the electrochemical reaction process. To confirm electrolyte infiltration into the HCNR cavities, HCNR-50 nm was immersed in the electrolyte. As shown in Fig. 5 d, the settling of HCNR-50 nm at the bottom of the electrolyte confirmed successful penetration into the cavities. The distribution of LiCl in HCNR-50 nm after the first discharge was investigated by TEM and energy-dispersive X-ray spectroscopy (EDS). As shown in Fig. 5 e and 5 f, LiCl was presented within the cavities and at the surface of the HCNRs, which was identical to the FEM simulation results. The selected area electron diffraction (SAED) pattern of the deposited LiCl (Fig. 5 f) exhibited characteristic (200)/(110)/(220)/(311) reflections, consistent with the XRD results (Fig. 5 g), confirming the crystalline nature of the LiCl deposits. Notably, the LiCl deposition amount within the cavities exceeded that on the outer surface, as evidenced by scanning electron microscopy (SEM) images showing exposed HCNR structures after complete discharge (Fig. 5 i). In stark contrast, LiCl deposition on the KJ Black electrode was severely aggregated on the surface (Fig. 5 j), highlighting the inefficiency of solid carbon materials in achieving uniform ion flux distribution. These findings underscore the critical role of the HCNR-50 nm architecture in optimizing ion flux distribution, enabling efficient utilization of active materials and enhancing the overall performance of Li-Cl₂ batteries. The unique hollow structure of HCNRs not only facilitates dual-pathway ion diffusion but also ensures uniform LiCl deposition, addressing key limitations of conventional solid carbon cathodes. 2.4 Ah-scale Li-Cl pouch cells To investigate the viability of the Li-Cl 2 @HCNRs battery in practical applications, pouch cells were constructed and tested. Figure 6 a illustrates the battery setup, which includes a HCNRs cathode with an area of 20.4 cm 2 , a Li anode, a glass fiber separator, and an electrolyte containing SOCl 2 . The cathode and anode were stacked in 5 layers. As shown in Figure S19, the Li-Cl 2 @HCNR-50 nm pouch cell delivered a capacity of 3400 mAh at the first discharge process, corresponding to 350 Wh/kg when considering all components. The calculation details of energy density can be found in Table S2. Benefiting from the unique structure of HCNRs, the pouch cell was able to cycle stably for 20 cycles with a charge capacity of 1000 mAh (Fig. 6 b) and maintained a stable discharge voltage of ~ 3.42 V over 14 cycles (Fig. 6 c). Solar energy is a clean and renewable resource. By storing solar energy in Li-Cl 2 batteries during the day and utilizing it at night (Fig. 6 d), carbon emissions can be reduced. Therefore, we recharged the Li-Cl 2 pouch cell using a 6 W, 9 V photovoltaic panel for 1 hour, with a charge current of approximately 120 mA throughout (Fig. 6 e). Remarkably, the Li-Cl 2 pouch cells were capable of powering a series of lights overnight (Fig. 6 f), demonstrating their consistent voltage output. The promising electrochemical performance of these high-energy density pouch cells paves the way for their future use in electrical energy storage applications. Conclusion In summary, we have developed heteroatom-doped hollow structured carbon nanoreactors (HCNRs) as cathode materials for high-rate and energy-dense Li-Cl 2 batteries. The unique structure of HCNRs improved ion diffusion flux in the interior of cathode and reduced diffusion length by pre-storing electrolyte in the cavity of HCNRs. Additionally, the ion flux was homogenized by HCNRs, which ensured the full utilization of whole cathode, further improving the specific capacity of battery performance. Benefiting from the enhanced ion diffusion flux and encapsulation capabilities of HCNRs, a rechargeable Li-Cl 2 battery was able to achieve a maximum discharge current of 120 mA/cm 2 and a maximum reversible capacity of 8000 mAh/g (equivalent to ~ 9 mAh/cm 2 ), much superior to previous reports. Moreover, a pouch cell with a capacity exceeding 1 Ah demonstrated an energy density of 106 Wh/kg when considering all components, marking a significant advancement towards practical applications of the Li-Cl 2 battery. These results signify a breakthrough in addressing the trade-off between energy density and power density in energy storage systems, positioning HCNRs as promising contenders for sustainable energy storage solutions. Declarations Notes The authors declare no competing financial interest. Acknowledgements The authors gratefully acknowledge support from the National Key Research and Development Program of China (2022YFB3805903), the National Natural Science Foundation of China (22309127, 22208229, 92372122, 52471242, 52071225), the Natural Science Foundation of Jiangsu Province (BK20220501, BK20230499), the Fundamental Research Funds for the Central Universities (WK2060000040, KY2060000150, GG2060127001) and General Programs of Jiangsu Province Universities (23KJB150030), the European Union’s Horizon Europe Research and Innovation Program (No. 101087143) (Electron Beam Emergent Additive Manufacturing (EBEAM)) and REFRESH-Research Excellence for Region Sustainability and High-tech Industries project (No. CZ.10.03.01/00/22_003/0000048) via the Operational Program Just Transition. References Meng, Y.S., Srinivasan, V., and Xu, K.. Designing better electrolytes. Science 378 , eabq3750 (2022). Li, X.-T., Chou, J., Zhu, Y.-H., Wang, W.-P., Xin, S., and Guo, Y.-G. 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Transforming a Primary Li-SOCl 2 Battery into a High-Power Rechargeable System via Molecular Catalysis. J. Am. Chem. Soc. 145 , 22158-22167 (2023). Xu, Y., Zhang, S., Wang, M., Meng, Y., Xie, Z., Sun, L., Huang, C., and Chen, W. Enrichment of Chlorine in Porous Organic Nanocages for High-Performance Rechargeable Lithium–Chlorine Batteries. J. Am. Chem. Soc. 145 , 27877-27885 (2023). Chen, G., Liu, X., Hou, H., Gao, X., Hu, L., Dong, S., and Cui, G. Regulating reversibility of Li-SOCl 2 batteries by elucidating intrinsic charging conversion strategy. Sci. Bull. 70, 140-143 (2024). Liang, P., Zhu, G., Huang, C.-L., Li, Y.-Y., Sun, H., Yuan, B., Wu, S.-C., Li, J., Wang, F., Hwang, B.-J. , et al . Rechargeable Li/Cl 2 Battery Down to −80 °C. 36 , 2307192 (2024). Tian, Q., Jing, L., Du, H., Yin, Y., Cheng, X., Xu, J., Chen, J., Liu, Z., Wan, J., Liu, J. , et al . Mesoporous carbon spheres with programmable interiors as efficient nanoreactors for H 2 O 2 electrosynthesis. Nat. 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Li, P., Li, X., Guo, Y., Li, C., Hou, Y., Cui, H., Zhang, R., Huang, Z., Zhao, Y., Li, Q. , et al . Highly Thermally/Electrochemically Stable I − /I 3 − Bonded Organic Salts with High I Content for Long-Life Li–I 2 Batteries. Adv. Energy Mater. 12 , 2103648 (2022). Zhu, F., Li, Z., Wang, Z., Fu, Y., and Guo, W. From Inorganic to Organic Iodine: Stabilization of I + Enabling High-Energy Lithium–Iodine Battery. J. Am. Chem. Soc. 146 , 11193-11201 (2024). Liu, Y., Cai, J., Zhou, J., Zang, Y., Zheng, X., Zhu, Z., Liu, B., Wang, G., and Qian, Y. Tailoring the adsorption behavior of superoxide intermediates on nickel carbide enables high-rate Li–O 2 batteries. eScience 2 , 389-398 (2022). Chen, G., Li, W., Du, X., Wang, C., Qu, X., Gao, X., Dong, S., Cui, G., and Chen, L. Transforming a Primary Li-SOCl 2 Battery into a High-Power Rechargeable System via Molecular Catalysis. J. Am. Chem. Soc. 145 , 22158-22167 (2023). Xu, Y., Wang, M., Sajid, M., Meng, Y., Xie, Z., Sun, L., Jin, J., Chen, W., and Zhang, S. Organocatalytic Lithium Chloride Oxidation by Covalent Organic Frameworks for Rechargeable Lithium-Chlorine Batteries. Angew. Chem. Int. Ed. 63 , e202315931 (2024). Additional Declarations There is NO Competing Interest. Supplementary Files 20250411SILiCl2BatteriesEnabledbyHollowCarbonNanoreactor1.docx Supplementary information 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. 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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-6516066","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":452965319,"identity":"7dc1940e-430f-4de9-8f0a-a3791e8b6983","order_by":0,"name":"Wei Chen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA3ElEQVRIiWNgGAWjYFACxgZmIMnDD+cSq0VGsgGimhgtDAwgLTYGB4jVYnC8ufFzQcUdHuMb6c8f/GCwkd1wgPnZA7xazhxslp5x5hmP2Y0cw8YehjTjDQfYzA3waTG7kdjGzNt2GKSFsZmB4XDihgM8bBJ4tdx/CNTy7zCP8Yz0h0At/4nQcoMRqKXhMI+BRIIhUMsBwlrszyQ2S/McO8wjceaN4cweg2TjmYfZzPBqkWw//vAzT81he/729AcfflTYyfYdb36GVwsaAAUVMwnqR8EoGAWjYBRgBwA13kqkQiZOWQAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-8018-4529","institution":"University of Science and Technology of China","correspondingAuthor":true,"prefix":"","firstName":"Wei","middleName":"","lastName":"Chen","suffix":""},{"id":452965320,"identity":"7da683c3-ad71-44b9-9ad1-9bd0a0ea6285","order_by":1,"name":"Yan Xu","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Yan","middleName":"","lastName":"Xu","suffix":""},{"id":452965321,"identity":"9394b3dc-2329-49cb-aaf7-73589ecb540a","order_by":2,"name":"Jiejun Ye","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Jiejun","middleName":"","lastName":"Ye","suffix":""},{"id":452965322,"identity":"6d27fb7f-e207-422d-8d32-4a42af067669","order_by":3,"name":"Zhipeng Wang","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Zhipeng","middleName":"","lastName":"Wang","suffix":""},{"id":452965323,"identity":"f4b1ed1e-8a59-42b8-9d1a-cb53c1a79cb4","order_by":4,"name":"Peichao Zou","email":"","orcid":"https://orcid.org/0000-0003-0148-7482","institution":"University of California, Irvine","correspondingAuthor":false,"prefix":"","firstName":"Peichao","middleName":"","lastName":"Zou","suffix":""},{"id":452965324,"identity":"a3f6ce1b-979d-416d-a136-42e7c57fa387","order_by":5,"name":"Lidong Sun","email":"","orcid":"","institution":"University of Science and Technology of China","correspondingAuthor":false,"prefix":"","firstName":"Lidong","middleName":"","lastName":"Sun","suffix":""},{"id":452965325,"identity":"ffc30fa8-4141-482d-bc9c-740059d1c76d","order_by":6,"name":"Liyao Wang","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Liyao","middleName":"","lastName":"Wang","suffix":""},{"id":452965326,"identity":"cf2a59f7-301e-450e-92ce-b23632f1699d","order_by":7,"name":"Qi Liu","email":"","orcid":"https://orcid.org/0000-0002-9377-8529","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Qi","middleName":"","lastName":"Liu","suffix":""},{"id":452965327,"identity":"e927d2b3-7a29-494b-bd94-6bcc4e8d33d1","order_by":8,"name":"Mark Rummeli","email":"","orcid":"","institution":"Soochow University","correspondingAuthor":false,"prefix":"","firstName":"Mark","middleName":"","lastName":"Rummeli","suffix":""},{"id":452965328,"identity":"1eeb47a9-9034-44ba-b4be-c30c45e61cdc","order_by":9,"name":"Shenxiang Zhang","email":"","orcid":"","institution":"Soochow Univeristy","correspondingAuthor":false,"prefix":"","firstName":"Shenxiang","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2025-04-24 01:30:20","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6516066/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6516066/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":82243042,"identity":"21628e5e-c817-40fa-bb1c-7715aaeada99","added_by":"auto","created_at":"2025-05-08 08:37:23","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":10023185,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic diagram of LiCl distribution and corresponding Li\u003csup\u003e+\u003c/sup\u003e or Cl\u003csup\u003e-\u003c/sup\u003e ion diffusion paths using (a) commercial carbon and (b) HCNRs.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-6516066/v1/72e79f2fa68f6660ebd13e01.png"},{"id":82243022,"identity":"10e4e97a-c114-434e-ae81-3125bcc2a935","added_by":"auto","created_at":"2025-05-08 08:37:21","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":472194,"visible":true,"origin":"","legend":"\u003cp\u003eCharacterization of HCNRs. TEM images of (a) HCNR-50 nm, (b) HCNR-20 nm and (c) KJ Black. Scale bar of inset image: 10 nm. N\u003csub\u003e2 \u003c/sub\u003eadsorption and desorption isotherms of (d) HCNR-50 nm, (e) HCNR-20 nm and (f) KJ Black at 77 K. (g) The \u0026nbsp;\u0026nbsp;adsorption amount of Cl\u003csub\u003e2\u003c/sub\u003e by HCNR-50 nm, HCNR-20 nm and KJ Black. (h) Raman spectra and (i) N 1s XPS of pristine HCNR-50 nm, pristine HCNR-20 nm and KJ Black.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-6516066/v1/96c56778c5c8ec6f9f5470e3.png"},{"id":82243024,"identity":"c0957b0c-6533-4a92-b86a-bd42ba10254b","added_by":"auto","created_at":"2025-05-08 08:37:21","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":5242078,"visible":true,"origin":"","legend":"\u003cp\u003eElectrochemical performance of Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries. (a) EIS and (b) Bode plot of Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries using HCNR-50 nm, HCNR-20 nm and KJ Black cathode materials. Voltage profiles of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery, Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm and Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black battery at the current density of (c) 5 mA/cm\u003csup\u003e2\u003c/sup\u003e and (d) 50 mA/cm\u003csup\u003e2\u003c/sup\u003e. (e) Electrochemical performance Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery, Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm battery and Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black battery under the current densities from 2 mA/cm\u003csup\u003e2\u003c/sup\u003e to 120 mA/cm\u003csup\u003e2\u003c/sup\u003e. (f) Comparison areal and mass current densities of Li-Cl\u003csub\u003e2\u003c/sub\u003e battery with Li-S, Li-CO\u003csub\u003e2\u003c/sub\u003e, Li-I\u003csub\u003e2\u003c/sub\u003e and Li-O\u003csub\u003e2\u003c/sub\u003e batteries. (g) Cycling performance of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery under the current density of 20 mA/cm\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-6516066/v1/da8d9737db03446705b090ed.png"},{"id":82243027,"identity":"50285213-3a96-49bb-9272-cfd73365ba80","added_by":"auto","created_at":"2025-05-08 08:37:21","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":6566676,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Electrochemical performance of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery, Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm battery and Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black battery under the specific capacities from 2000 mAh/g to 8000 mAh/g. (b) Voltage profiles of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery, Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm battery and Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black battery at a specific capacity of 6000 mAh/g. (c) Cycling performance of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery, Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm battery and Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black battery at an areal capacity of 7 mAh/cm\u003csup\u003e2\u003c/sup\u003e (equivalent to 2500 mAh/g). Voltage profiles of (d) Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery and (e) Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black battery under different cycles. (f) Cycling performance of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery at areal capacity of 9 mAh/cm\u003csup\u003e2\u003c/sup\u003e (equivalent to 5600 mAh/g). (g) Comparison of our work with other reports in terms of areal and specific capacities.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-6516066/v1/e0f5c6219b6b4e175a4d36e6.png"},{"id":82243023,"identity":"0e04df29-cfb5-46b5-89f5-de721617c843","added_by":"auto","created_at":"2025-05-08 08:37:21","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":426234,"visible":true,"origin":"","legend":"\u003cp\u003eSimulated LiCl species distribution on (a) HCNRs and (b) KJ Black. Scale bar is the relative concentration of LiCl. (c) LiCl concentration distribution curve according to the FEM simulation at 10 μs. (d) Digital photograph of HCNR-50 nm immersed into the electrolyte. (e) TEM image of HCNR-50 nm cathode material after fully discharge, and the corresponding (f) Cl element mapping and (g) SAED pattern. (h) XRD pattern of HCNR-50 nm cathode after fully discharge. (i) SEM image of HCNR-50 nm electrode and (j) KJ Black electrode after fully discharge.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-6516066/v1/6ecc8613ea6fdb6484058ca6.png"},{"id":82243038,"identity":"a0dd263a-8540-4e6f-ac19-ad21dd142d98","added_by":"auto","created_at":"2025-05-08 08:37:21","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":216398,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Schematic diagram of constructed Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm pouch cell. (b) The electrochemical performance and (c) voltage profiles of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm pouch cell. Inset image: the voltage profile at the 1\u003csup\u003est\u003c/sup\u003e discharge process. (d) Schematic diagram of the integration of photovoltaics and energy storage system. (e) Change in charging current over time. Inset image: Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm pouch cell charged by photovoltaics and the charge current was monitored by multimeter. (f) Digital photographs of a charged Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm pouch cell powered a series of lights.\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-6516066/v1/445385e5d3eacc8164e1bc66.png"},{"id":91386889,"identity":"869fc57e-39b0-4639-bd2e-c6dcab67bacb","added_by":"auto","created_at":"2025-09-16 02:48:38","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":22355972,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6516066/v1/248bada2-d9ef-4845-bb16-540fbedd295a.pdf"},{"id":82243021,"identity":"6644e534-0944-4107-b36f-e7f7d8e4313d","added_by":"auto","created_at":"2025-05-08 08:37:21","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1100179,"visible":true,"origin":"","legend":"Supplementary information","description":"","filename":"20250411SILiCl2BatteriesEnabledbyHollowCarbonNanoreactor1.docx","url":"https://assets-eu.researchsquare.com/files/rs-6516066/v1/02f814630504ba16d4014ecd.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"\u003cp\u003eIon Flux Optimization via Hollow Carbon Nanoreactors for High-Power and Energy-Dense Li-Cl\u003csub\u003e2\u003c/sub\u003e Batteries\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe development of high-energy-density batteries is critical to meeting the growing demands of electric vehicles and electric aircrafts\u003csup\u003e\u003cspan additionalcitationids=\"CR2 CR3\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Lithium-ion batteries (LIBs) are currently the most ideal options, offering an energy density of ~\u0026thinsp;250 Wh/kg\u003csup\u003e5\u0026ndash;8\u003c/sup\u003e. However, further advancements are urgently needed to extend the cruising range of these applications\u003csup\u003e\u003cspan additionalcitationids=\"CR10 CR11 CR12\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Recently, rechargeable lithium-chlorine (Li-Cl\u003csub\u003e2\u003c/sub\u003e) batteries using thionyl chloride (SOCl\u003csub\u003e2\u003c/sub\u003e) as the electrolyte, Li metal as the anode, and porous materials as the cathode have gathered much attention due to their high theoretical energy density\u003csup\u003e\u003cspan additionalcitationids=\"CR15 CR16 CR17 CR18 CR19 CR20 CR21 CR22\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e. Despite their promises, Li-Cl₂ batteries face significant challenges, including low cycling current densities (\u0026lt;\u0026thinsp;5 mA/cm\u0026sup2;) and limited specific capacities (\u0026lt;\u0026thinsp;4000 mAh/g), leading to low power density and limited energy density.\u003c/p\u003e \u003cp\u003eWe evaluated the commonly applied cathode materials in Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries, and found that they feature solid structures\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan additionalcitationids=\"CR21\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e with inadequate electrolyte retention capacity. Therefore, in traditional cathode materials, the Li\u003csup\u003e+\u003c/sup\u003e or Cl\u003csup\u003e-\u003c/sup\u003e ion transport in the interior of cathode faces two critical challenges (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea): (1) insufficient ionic flux due to the prolonged diffusion length (\u003cem\u003el\u003c/em\u003e) from the bulk electrolyte reservoirs, and (2) non-uniform ionic flux distribution along the thickness direction of cathode during cell operation. The inhomogeneous ionic flux distribution induces the reactive sites of cathode near the separator being covered by a solid LiCl layer due to the excessive ion flux around this area, which obstructs subsequent ion transport. Consequently, active materials approaching to the current collector is electrochemically inactive, resulting in significantly compromised specific capacity and power density. To address these challenges, we hypothesize that by designing a cathode material with a hollow structure that capable of intrinsic electrolyte confinement in the cavity (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb), the hollow structure could promote ion flux, effectively reduce the diffusion length and homogenize ion distribution compared to the conventional solid material. Hollow carbon materials have demonstrated remarkable potential in improving electrochemical reaction kinetics and modulating microenvironments in the fields of catalysis\u003csup\u003e\u003cspan additionalcitationids=\"CR26\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e and energy storage\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. This has motivated us to explore hollow carbon materials to improve the electrochemical kinetics in Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries.\u003c/p\u003e \u003cp\u003eIn this work, we demonstrate that the N-doped hollow carbon nanoreactors (HCNRs) can significantly enhance the performance of Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries in terms of power density and energy density. The N-doped HCNRs play a dual role in improving the performance of the battery. Firstly, the hollow design of HCNR helps to improve the ion diffusion of Li\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e-\u003c/sup\u003e ions and reduces diffusion length by confining electrolyte in the cavity, allowing for fast charge/discharge rates of Li/Cl\u003csub\u003e2\u003c/sub\u003e batteries. At a specific capacity of 500 mAh/g, our rechargeable Li/Cl\u003csub\u003e2\u003c/sub\u003e battery demonstrates an impressive cycling current density of 120 mA/cm\u003csup\u003e2\u003c/sup\u003e, achieving a full charge/discharge cycle in only 30 seconds. Secondly, the homogenization of Li\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e-\u003c/sup\u003e ions along the thickness of cathode prohibits the premature electrode, enabling Li-Cl\u003csub\u003e2\u003c/sub\u003e battery to achieve a specific capacity as high as 8000 mAh/g (9 mAh/cm\u003csup\u003e2\u003c/sup\u003e). Notably, the Li-Cl\u003csub\u003e2\u003c/sub\u003e pouch cell utilizing HCNRs as cathode materials exhibits a practical energy density of around 106 Wh/kg at the entire-cell level. Our findings suggest the potential of this hollow cathode material design in addressing the trade-off between energy density and power density in Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Preparation and Characterization of HCNRs\u003c/h2\u003e \u003cp\u003eHCNRs were prepared by a hard template method according to the reported literature\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. To prepare HCNRs with different-sized cavities, MgO nanoparticles with different diameters were selected as the hard template. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the microstructures and the corresponding morphologies of HCNRs. As can be seen from SEM images, the HCNs maintain a spherical morphology (Figure \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). TEM images give the clear hollow feature of HCNRs (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea-\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). The diameter of the obtained HCNRs is mainly distributed in the range of 16\u0026ndash;24 nm and 40\u0026ndash;55 nm, with average diameters of 21 nm and 47 nm, respectively (Figure S2). In the following text, the obtained HCNRs with different sizes are denoted as HCNR-20 nm and HCNR-50 nm, respectively. HRTEM confirms the graphitic lattice of both HCNR-50 nm and HCNR-20 nm with measured wall thicknesses 6.0 nm and 4.3 nm, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea-\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb inset image and Figure S3), respectively. To elucidate the critical role of hollow nanostructure, commercial carbon material, ketjenblack (KJ Black), was chosen as a contrast, which showed solid-structure with similar graphitic lattice (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec and Figure S4).\u003c/p\u003e \u003cp\u003eThe N\u003csub\u003e2\u003c/sub\u003e adsorption/desorption measurements (77 K) were employed to assess the structure and porosity of HCNRs. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ed-\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ef, the N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms of HCNR-50 nm, HCNR-20 nm and KJ Black exhibited the characteristics of typical Type-II curves, indicating the coexistence of micropores and mesopores in these carbon materials. In the low-pressure range (0-0.1 P/P\u003csub\u003e0\u003c/sub\u003e), the cumulative N\u003csub\u003e2\u003c/sub\u003e uptake is 330, 113, and 299 cm\u003csup\u003e3\u003c/sup\u003e/g for HCNR-50 nm, HCNR-20 nm and KJ Black, respectively, indicating that HCNR-50 nm and KJ Black have similar micropore structure. The micropore size distribution of HCNRs and KJ Black was analyzed using nonlocal density functional theory (NLDFT), concentrated in the range of 0.5\u0026ndash;1.4 nm (Figure S5). However, at high pressure rang (near 1.0 P/P\u003csub\u003e0\u003c/sub\u003e), the cumulative N\u003csub\u003e2\u003c/sub\u003e uptake for HCNR-50 nm, HCNR-20 nm was 3894 and 2302 cm\u003csup\u003e3\u003c/sup\u003e/g, higher than that of KJ Black, suggesting that inner macropore in HCNR can storge more condensed N\u003csub\u003e2\u003c/sub\u003e. The Brunauer\u0026ndash;Emmett\u0026ndash;Teller (BET) surface area of HCNR-50 nm and HCNR-20 nm were 1352 and 502 m\u003csup\u003e2\u003c/sup\u003e/g, respectively. The BET surface area of KJ Black was ~\u0026thinsp;1034 m\u003csup\u003e2\u003c/sup\u003e/g, comparable to HCN-50 nm. Notably, the presence of micropores within the HCNR walls facilitates electrolyte permeation into the interior hollow cavities, enabling efficient ion transport pathways. To evaluate the Cl₂ storage capacity, static adsorption experiments of Cl\u003csub\u003e2\u003c/sub\u003e gas were conducted at room temperature. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eg shows that the adsorption amount of Cl\u003csub\u003e2\u003c/sub\u003e was 1.0, 3.5, and 2.6 mmol per gram for KJ Black, HCNR-50 nm, and HCNR-20 nm, respectively. This result unambiguously demonstrates the superior Cl\u003csub\u003e2\u003c/sub\u003e storage capability of our hollow nanoreactor architecture, highlighting its unique advantage in confining reactive Cl₂ species within the engineered cavities.\u003c/p\u003e \u003cp\u003eX-ray diffraction (XRD) and Raman were applied to analyze the electronic conductivity of HCNR-50 nm, HCNR-20 nm and KJ Black. The XRD patterns of these three carbon materials exhibit broad peaks at ~\u0026thinsp;26\u0026deg; (Figure S6), corresponding to the (002) plane of graphitic carbon. Raman spectra were further applied to investigate the degree of graphitization. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eh, the intensity ratio of D and G bands of HCNR-50 nm, HCNR-20 nm and KJ Black were 1.15, 1.22 and 1.71, respectively, suggesting that HCNR-50 nm possesses the highest graphitization degree, which was beneficial to fast electron transport. The electron conductivity of these three carbon materials was further tested by a powder resistivity tester, and HCNR-50 nm has the highest electron conductivity (Figure S7). In order to exclude the influence of electron conductivity, a kind of carbon nanotube (CNT) with characteristics of high electron conductivity would be introduced into HCNR-50 nm, HCNR-20 nm and KJ Black electrodes. Figure S8 shows HCNRs were connected by the CNTs, which could construct the fast electron transport pathways. X-ray photoelectron spectroscopy (XPS) was further applied to analyze the compositions of HCNR. The survey spectra revealed N and O heteroatoms contained in HCNRs and the contents of N and O were ~\u0026thinsp;6 at% and 3 at% (Figure S9 and Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). The N 1s spectra showed two peaks at 401.0 and 398.1 eV (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ei), corresponding to pyrrolic N and pyridinic N, which were considered as active sites for the capture of LiCl and Cl\u003csub\u003e2\u003c/sub\u003e.\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e Subsequently, the samples after the adsorption of Cl\u003csub\u003e2\u003c/sub\u003e were analyzed by XPS. Figure S10 shows that the Cl signal was detected in the samples of HCNRs, but not in the sample of KJ Black, suggesting that the successful adsorption of Cl\u003csub\u003e2\u003c/sub\u003e by HCNRs involved chemisorption, but the failed adsorption of Cl\u003csub\u003e2\u003c/sub\u003e by KJ Black. Further mechanistic insight was gained through N 1s XPS analysis (Figure S11), which revealed a 0.2 eV higher energy shift, indicating that the electron density on N atoms decreased due to the interaction between Cl\u003csub\u003e2\u003c/sub\u003e and N atoms in HCNRs. This result confirms the critical role of nitrogen active sites in facilitating strong chemisorption interactions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003e2.2 Electrochemical Performance of Li-Cl Battery\u003c/h3\u003e\n\u003cp\u003eTo investigate the correlation between the HCNR architecture and the Li\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e-\u003c/sup\u003e ion diffusion kinetics, electrochemical impedance spectroscopy (EIS) was first conducted to Li-Cl\u003csub\u003e2\u003c/sub\u003e battery after charging 1 mAh using different cathode materials. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea, the ion diffusion resistance of Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black battery was much larger than that of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery and Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm battery (Figure S12). More importantly, the Z\u003csub\u003eW\u003c/sub\u003e in the Nyquist plot of Li-Cl\u003csub\u003e2\u003c/sub\u003e battery using HCNR-50 nm and HCNR-20 nm was an inclined straight line in the low-frequency region, while for Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black battery, the plot became an arc in the low-frequency region (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). This implies that the diffusion of Li\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e-\u003c/sup\u003e ions was semi-infinite diffusion in HCNR-50 nm and HCNR-20 nm electrodes due to sufficient ion supply, and the diffusion of Li\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e-\u003c/sup\u003e ions was finite diffusion in KJ Black electrode due to the limited ion concentration in the bulky electrode. In the Bode plots shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb, the ionic diffusion coefficient (D) was decreased in the order of HCNR-20 nm, HCNR-50 nm and KJ Black. If D value was large, the active species can be supplied rapidly to the electrode, and this result agrees well with the result in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea.\u003c/p\u003e \u003cp\u003eFurther, the ion diffusion kinetics were investigated in Li-Cl\u003csub\u003e2\u003c/sub\u003e battery at various current densities from 2 mA/cm\u003csup\u003e2\u003c/sup\u003e to 120 mA/cm\u003csup\u003e2\u003c/sup\u003e. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec, the discharge and charge plateaus of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNRs cells were positioned at 3.34 V and 4.09 V at a low current density of 5 mA/cm\u003csup\u003e2\u003c/sup\u003e, leading to a polarization voltage of 0.75 V. In sharp contrast, the Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black cell exhibited a higher polarization voltage of 0.95 V with the discharge and charge plateaus positioned at 3.23 V and 4.18 V, respectively. The fast Li\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e-\u003c/sup\u003e ion transfer in Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNRs battery contributes to the lower polarization voltage. Remarkably, even at a high current density of 50 mA/cm\u003csup\u003e2\u003c/sup\u003e, the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery exhibited a discharge plateau at 2.92 V and a charge plateau at 4.40 V with a Coulombic efficiency (CE)\u0026thinsp;~\u0026thinsp;100% (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). The Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black battery even cannot tolerate such a high current density of 50 mA/cm\u003csup\u003e2\u003c/sup\u003e with a sharp increased charge voltage due to the limited ion diffusion kinetics. The highest current density that Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery could survive was 120 mA/cm\u003csup\u003e2\u003c/sup\u003e (charged in 15 s to 500 mAh/g, Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee) with a CE of ~\u0026thinsp;95% (Figure S13) and a discharge plateau at 2.58 V (Figure S14). These results, especially cycling at extremely high current density with high CE (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ef), far surpasses those of previous high-energy battery systems like Li-S\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e, Li-CO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e32,33\u003c/sup\u003e, Li-I\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e34,35\u003c/sup\u003e and Li-O\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e36\u003c/sup\u003e batteries. Notably, the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm battery exhibited a maximal tolerant current density was 80 mA/cm\u003csup\u003e2\u003c/sup\u003e, which could be ascribed to the limited cavity volume in HCNR-20 nm cavity structure, supplying insufficient ions. Therefore, the optimal size of HCNR for high-power Li-Cl\u003csub\u003e2\u003c/sub\u003e battery is 50 nm. The encapsulation effect based on the hollow structure enhanced the Li\u003csup\u003e+\u003c/sup\u003e and Cl\u003csup\u003e-\u003c/sup\u003e ions flux, leading to the smallest ion diffusion polarization and the highest current density tolerance.\u003c/p\u003e \u003cp\u003eThe long-term cycling performance of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery at high current density was further explored. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eg, the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery delivered a remarkable capacity of 740 mAh/g with an ultralong cycling life of 400 cycles and a CE nearly 100% at a high current density of 20 mA/cm\u003csup\u003e2\u003c/sup\u003e. These excellent electrochemical performances promise the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNRs battery could retain high power delivery.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe unique structure of HCNR could homogenize the ion flux along the thickness of cathode, ensuring the full utilization of cathode materials, leading to enhanced specific capacity. To verify the above effect by heteroatom-doped HCNRs, Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries were evaluated at specific capacities ranging from 2000 mAh/g to 8000 mAh/g. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea and Figure S15, the CE of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm, Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm and Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black batteries could be maintained at ~\u0026thinsp;100% under moderate specific capacities of 2000\u0026ndash;4000 mAh/g. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea, even at a high specific capacity of 6000 mAh/g and ultrahigh specific capacity of 8000 mAh/g (equivalent to 9\u0026ndash;10 mAh/cm\u003csup\u003e2\u003c/sup\u003e), the CE of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery remained at ~\u0026thinsp;100%, demonstrating the excellent homogenization of ion flux by HCNRs. In contrast, the CE of Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black battery were merely\u0026thinsp;~\u0026thinsp;80% and 70% (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea) at the specific capacity of 6000 mAh/g and 8000 mAh/g, respectively, due to the insufficient ion flux at the interior of cathode materials. Notably, the CE of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm battery could be maintained at ~\u0026thinsp;100% across the entire range of specific capacities from 2000 to 8000 mAh/g. However, during the late charge process after several cycles at a specific capacity of 8000 mAh/g, the charge voltage suddenly increased to 5 V (Figure S15), likely due to the limited cavity space or the aggregation of LiCl blocking the micropores of HCNR-20 nm.\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e\u003c/p\u003e \u003cp\u003eThe voltage profiles of Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm, Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm and Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black batteries were compared at a specific capacity of 6000 mAh/g. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb, the Li-Cl\u003csub\u003e2\u003c/sub\u003e@ KJ Black battery demonstrated the highest polarization with the charge/discharge voltages recorded at 4.07 V and 3.38 V, respectively, attributing to the sluggish ion diffusion in KJ Black. The Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery and the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm battery displayed identical charge voltages at 3.96 V. The discharge voltages for the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery and Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm battery were measured at 3.56 V and 3.47 V, respectively, consistent with the findings in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec. High areal capacity is critical to obtain high-energy density battery, therefore, the long cycle lives of Li-Cl\u003csub\u003e2\u003c/sub\u003e cells utilizing different cathode materials were assessed at a high areal capacity of 7 mAh/cm\u003csup\u003e2\u003c/sup\u003e (2500 mAh/g). As depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed, the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery demonstrated a cycling life exceeding 120 cycles in a stable charge and discharge voltage plateaus with a CE of approximately 100%. Conversely, the cycling lifetime of the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-20 nm battery was less than 90 cycles with sharply increased charge voltage due to the limited cavity space (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec and S17). The Li-Cl\u003csub\u003e2\u003c/sub\u003e@KJ Black battery presented the shortest cycle life of 60 cycles and unstable discharge voltage due to the diffusion pathway blocked by LiCl (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec and \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee). Upon increasing the areal capacity of the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery to 9 mAh/cm\u003csup\u003e2\u003c/sup\u003e (~\u0026thinsp;5600 mAh/g), the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm battery still could exhibit a cycle life exceeding 90 cycles with a CE nearing 100% (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ef), indicating its exceptional utilization rate of the whole cathode.\u003c/p\u003e \u003cp\u003eWe compared our work with the state-of-the-art cathode materials for rechargeable Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries including carbon dioxide activated porous carbon (KJCO\u003csub\u003e2\u003c/sub\u003e)\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e, acetylene black with molecular catalyst of I\u003csub\u003e2\u003c/sub\u003e (AB with I\u003csub\u003e2\u003c/sub\u003e)\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e, AB with SO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e23\u003c/sup\u003e, graphite\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e, TpPa-NH\u003csub\u003e2\u003c/sub\u003e COF\u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e and porous organic nanocage (POC)\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e in the aspects of areal and specific capacities, as summarized in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eg. Specifically, the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm cell exhibited impressive performances, achieving a maximal areal capacity of 9 mAh/cm\u003csup\u003e2\u003c/sup\u003e over 90 cycles with an accumulative capacity of 810 mAh/cm\u003csup\u003e2\u003c/sup\u003e. Among the compared materials, only KJCO\u003csub\u003e2\u003c/sub\u003e demonstrated a comparable areal capacity, but its cycle life was limited to merely 3 cycles, highlighting the exceptional cycling stability of our HCNR-based system. Furthermore, the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm cell achieved an extraordinary specific capacity of 8000 mAh/g, surpassing the best-reported value by 3000 mAh/g. These significant advancements illustrate the potential of HCNRs as a highly effective cathode material for high-performance rechargeable Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003e2.3 Mechanism Investigation of Battery Reactions in the HCNR\u003c/h3\u003e\n\u003cp\u003eTo elucidate the influence of the HCNR architecture on ion diffusion in Li-Cl₂ batteries, finite element method (FEM) simulations were employed. Given that LiCl distribution reflects the spatial arrangement of Li⁺ and Cl⁻ ions, the simulations focused on modeling LiCl formation during the electrochemical reduction of Cl₂. The HCNR-50 nm was represented as a hollow spherical structure with open pores in its walls, immersed in an electrolyte and filled with Cl₂ molecules both inside and outside the cavity. The simulation results revealed that Cl₂ molecules could diffuse through the pores and undergo reduction to form LiCl on both the inner and outer surfaces of the HCNR-50 nm (Figure S18a). Consequently, LiCl was uniformly distributed within the cavity and on the outer surface of the HCNR (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). This dual-pathway diffusion and deposition mechanism facilitated the generation of Li⁺ and Cl⁻ ion fluxes within the cavity, significantly enhancing ion flux and homogenizing ion distribution across the cathode interior. In contrast, for solid carbon materials such as KJ Black, Cl₂ diffusion was restricted to the outer surface, leading to LiCl deposition exclusively on the external surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb and Figure S18b). This surface-limited deposition obstructed ion diffusion pathways, resulting in underutilization of active cathode materials near the current collector, particularly at high C-rates. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec shows the concentration distribution curve of LiCl. For the solid KJ black material, the LiCl concentration reaches its maximum near the outer surface and progressively decreases with distance from the surface. In contrast, the hollow carbon materials demonstrate a distinct dual-concentration characteristic: they maintain a high LiCl concentration at the outer surface, and they also preserve an even greater concentration within their interior cavities. This unique dual-concentration configuration ensures sufficient ion flux throughout the electrochemical reaction process.\u003c/p\u003e \u003cp\u003eTo confirm electrolyte infiltration into the HCNR cavities, HCNR-50 nm was immersed in the electrolyte. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ed, the settling of HCNR-50 nm at the bottom of the electrolyte confirmed successful penetration into the cavities. The distribution of LiCl in HCNR-50 nm after the first discharge was investigated by TEM and energy-dispersive X-ray spectroscopy (EDS). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ee and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef, LiCl was presented within the cavities and at the surface of the HCNRs, which was identical to the FEM simulation results. The selected area electron diffraction (SAED) pattern of the deposited LiCl (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ef) exhibited characteristic (200)/(110)/(220)/(311) reflections, consistent with the XRD results (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eg), confirming the crystalline nature of the LiCl deposits. Notably, the LiCl deposition amount within the cavities exceeded that on the outer surface, as evidenced by scanning electron microscopy (SEM) images showing exposed HCNR structures after complete discharge (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ei). In stark contrast, LiCl deposition on the KJ Black electrode was severely aggregated on the surface (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ej), highlighting the inefficiency of solid carbon materials in achieving uniform ion flux distribution. These findings underscore the critical role of the HCNR-50 nm architecture in optimizing ion flux distribution, enabling efficient utilization of active materials and enhancing the overall performance of Li-Cl₂ batteries. The unique hollow structure of HCNRs not only facilitates dual-pathway ion diffusion but also ensures uniform LiCl deposition, addressing key limitations of conventional solid carbon cathodes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003e2.4 Ah-scale Li-Cl pouch cells\u003c/h3\u003e\n\u003cp\u003eTo investigate the viability of the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNRs battery in practical applications, pouch cells were constructed and tested. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea illustrates the battery setup, which includes a HCNRs cathode with an area of 20.4 cm\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e, a Li anode, a glass fiber separator, and an electrolyte containing SOCl\u003csub\u003e2\u003c/sub\u003e. The cathode and anode were stacked in 5 layers. As shown in Figure S19, the Li-Cl\u003csub\u003e2\u003c/sub\u003e@HCNR-50 nm pouch cell delivered a capacity of 3400 mAh at the first discharge process, corresponding to 350 Wh/kg when considering all components. The calculation details of energy density can be found in Table S2. Benefiting from the unique structure of HCNRs, the pouch cell was able to cycle stably for 20 cycles with a charge capacity of 1000 mAh (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eb) and maintained a stable discharge voltage of ~\u0026thinsp;3.42 V over 14 cycles (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ec). Solar energy is a clean and renewable resource. By storing solar energy in Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries during the day and utilizing it at night (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ed), carbon emissions can be reduced. Therefore, we recharged the Li-Cl\u003csub\u003e2\u003c/sub\u003e pouch cell using a 6 W, 9 V photovoltaic panel for 1 hour, with a charge current of approximately 120 mA throughout (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ee). Remarkably, the Li-Cl\u003csub\u003e2\u003c/sub\u003e pouch cells were capable of powering a series of lights overnight (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ef), demonstrating their consistent voltage output. The promising electrochemical performance of these high-energy density pouch cells paves the way for their future use in electrical energy storage applications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, we have developed heteroatom-doped hollow structured carbon nanoreactors (HCNRs) as cathode materials for high-rate and energy-dense Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries. The unique structure of HCNRs improved ion diffusion flux in the interior of cathode and reduced diffusion length by pre-storing electrolyte in the cavity of HCNRs. Additionally, the ion flux was homogenized by HCNRs, which ensured the full utilization of whole cathode, further improving the specific capacity of battery performance. Benefiting from the enhanced ion diffusion flux and encapsulation capabilities of HCNRs, a rechargeable Li-Cl\u003csub\u003e2\u003c/sub\u003e battery was able to achieve a maximum discharge current of 120 mA/cm\u003csup\u003e2\u003c/sup\u003e and a maximum reversible capacity of 8000 mAh/g (equivalent to ~\u0026thinsp;9 mAh/cm\u003csup\u003e2\u003c/sup\u003e), much superior to previous reports. Moreover, a pouch cell with a capacity exceeding 1 Ah demonstrated an energy density of 106 Wh/kg when considering all components, marking a significant advancement towards practical applications of the Li-Cl\u003csub\u003e2\u003c/sub\u003e battery. These results signify a breakthrough in addressing the trade-off between energy density and power density in energy storage systems, positioning HCNRs as promising contenders for sustainable energy storage solutions.\u003c/p\u003e "},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eNotes\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare no competing financial interest.\u003cstrong\u003e\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors gratefully acknowledge support from the National Key Research and Development Program of China (2022YFB3805903), the National Natural Science Foundation of China (22309127, 22208229, 92372122, 52471242, 52071225), the Natural Science Foundation of Jiangsu Province (BK20220501, BK20230499), the Fundamental Research Funds for the Central Universities (WK2060000040, KY2060000150, GG2060127001) and General Programs of Jiangsu Province Universities (23KJB150030), the European Union\u0026rsquo;s Horizon Europe Research and Innovation Program (No. 101087143) (Electron Beam Emergent Additive Manufacturing (EBEAM)) and REFRESH-Research Excellence for Region Sustainability and High-tech Industries project (No. CZ.10.03.01/00/22_003/0000048) via the Operational Program Just Transition.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMeng, Y.S., Srinivasan, V., and Xu, K.. 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Ed. \u003cem\u003e63\u003c/em\u003e, e202315931 (2024).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"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":"rechargeable Li-Cl2 battery, hollow carbon nanoreactor, ion flux, high-power, high-energy density","lastPublishedDoi":"10.21203/rs.3.rs-6516066/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6516066/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eRechargeable Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries are a promising high-energy-density technology but having critical challenges of limited rates and capacities. Insufficient and uneven ion flux in the interior of cathode is a crucial factor that hinders the rate performance and specific capacity of Li-Cl\u003csub\u003e2\u003c/sub\u003e battery. Herein, we propose and develop hollow carbon nanoreactors (HCNRs) as cathode materials for extremely high-power and high-energy Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries. By confining electrolytes within tailored cavities, HCNRs facilitate enhanced and spatially homogenized ion flux in the interior of cathode, eliminating the reliance on bulk electrolyte diffusion and prohibiting rapid electrode degradation. This design enables the as-assembled Li-Cl\u003csub\u003e2\u003c/sub\u003e cell to achieve an ultrahigh current density of 120 mA/cm\u003csup\u003e2\u003c/sup\u003e during the charge/discharge process (charging to 500 mAh/g in 15 s) and a record-breaking specific capacity of 8000 mAh/g (9 mAh/cm\u003csup\u003e2\u003c/sup\u003e), superior to the reported literature. Furthermore, we demonstrate the scalability of this design in a 1-Ah-scale pouch cell, achieving a practical cell-specific energy of 106 Wh/kg. This hollow nanoreactor design highlights the potential of Li-Cl\u003csub\u003e2\u003c/sub\u003e batteries as high-power and energy-dense systems, paving the way for their practical applications.\u003c/p\u003e","manuscriptTitle":"Ion Flux Optimization via Hollow Carbon Nanoreactors for High-Power and Energy-Dense Li-Cl2 Batteries","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-08 08:37:16","doi":"10.21203/rs.3.rs-6516066/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":"1e4bcc1a-7705-4e33-a413-29aee9cac537","owner":[],"postedDate":"May 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":48241466,"name":"Physical sciences/Energy science and technology/Energy storage/Batteries"},{"id":48241467,"name":"Physical sciences/Materials science/Materials for energy and catalysis/Batteries"}],"tags":[],"updatedAt":"2025-09-16T02:40:17+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-08 08:37:16","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6516066","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6516066","identity":"rs-6516066","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}