Performance Of Lithium-sulfur Batteries Research Articles

Regulating Li2S Deposition and Accelerating Conversion Kinetics through Intracavity ZnS toward Low-Temperature Lithium-Sulfur Batteries.

The uncontrolled deposition behavior and sluggish conversion kinetics of the discharging product (solid Li2S) severely deteriorate the electrochemical performance of lithium-sulfur (Li-S) batteries, especially under high S loading and low-temperature conditions. Herein, a multifunctional S cathode host consisting of ZnS nanoparticles (NPs) confined in hollow porous carbon spheres (ZnS@HPCS) is synthesized via a unique capillary force-driven melting-diffusion strategy. The porous carbon shell of ZnS@HPCS provides a space-confined reservoir for soluble polysulfides and solid Li2S, while the intracavity ZnS NPs trap polysulfides, induce Li2S inside deposition, and accelerate conversion kinetics. Thus, Li-S batteries with ZnS@HPCS-S cathodes exhibit excellent electrochemical performance at both room and low temperatures (-40 °C) and high reversible capacities under high S loading (5.2 mg cm-2). Furthermore, Li2S nucleation/deposition, in situ Raman, and theoretical analyses reveal the underlying mechanism. This work offers fundamental insights into regulating Li2S deposition and designing S hosts for high-performance Li-S batteries.

Balanced d-Band Model: A Framework for Balancing Redox Reactions in Lithium-Sulfur Batteries.

Managing the redox reactions of polysulfides is crucial for improving the performance of lithium-sulfur batteries (LSBs). Herein, we introduce a progressive theoretical framework: the balanced d-band model, which is based on classical d-band center theory. Specifically, by optimizing the position of the d-band center in the middle between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of each sulfur species, balanced and fast oxidation and reduction reactions of the sulfur species can be achieved simultaneously. To validate this theory, we synthesized a catalyst featuring an in situ phosphorized heterostructure (NOP) based on nickel oxide (NiO), which effectively optimizes the d-band center at the middle between the HOMO and LUMO of each sulfur species. Aided by the balanced oxidation and reduction kinetics of the sulfur species, the NOP-based cell achieved a high reversible capacity, superior cycling stability, and prolonged cycle life. This study extends the conventional d-band center theory and introduces an innovative theoretical model to expand our understanding of the internal reaction mechanisms in LSBs.

Review and prospect on Metal-organic framework-based Separators for Lithium–Sulfur Battery

With the continuous advancement of technology, wearable smart devices and electric vehicles (EVs) have become an integral part of our daily lives. The increasing demand for energy from these devices and vehicles has driven the pursuit of high-performance rechargeable battery technology. In particular, the widespread adoption of electric vehicles has set higher standards for the energy density and cycle life of batteries. However, the energy density of the widely used lithium-ion batteries is currently limited by the theoretical capacity of commercial cathode materials, and there are certain challenges in terms of safety and cost-effectiveness. Therefore, the development of a new generation of rechargeable batteries with higher energy density, better safety, and more economical cost is particularly urgent. Lithium-sulfur batteries, due to their high energy density, high economic benefits, and high environmental friendliness, are considered to be one of the most promising successors to the widely used lithium-ion batteries. However, in practical applications, the electrochemical performance of lithium-sulfur batteries still needs to be improved. In particular, the poor conductivity of sulfur/lithium and the shuttle effect of polysulfides make the cycle life of the battery less than ideal, and lithium-sulfur batteries (LSB) are still far from achieving large-scale commercialization. The separator used in lithium-sulfur batteries plays a crucial role in its cycle performance and safety. The current commercial separator lacks the ability to effectively regulate the shuttle of polysulfides and is prone to thermal runaway at high temperatures. Therefore, to improve these issues, various functional materials have been used to modify the separator. Among them, as a new type of porous coordination polymer, metal organic frameworks (MOFs) have become a promising material for modifying separators due to their large specific surface area and highly ordered tunable nano-holes.At the same time, their rich inorganic nodes and designable organic ligands allow for the customization of pore chemistry at the molecular level, which can interact with the electroactive components in lithium-sulfur batteries in a tunable manner. This article reviews the reaction mechanism of lithium-sulfur batteries and the structural advantages of MOFs in terms of pore chemistry and morphology and briefly introduces the research progress of MOF-based interfacial layers for the functionalization of LSB separators in recent years. It elaborates on the mechanisms by which various modified separators improve electrochemical performance and provides a prospect for the development prospects of the field.

Enhanced Performance of Lithium-Sulfur Batteries Using Construction Wastes: A Sustainable Approach to High-Loading Sulfur Cathodes.

Advancing lithium-sulfur battery technology requires addressing both extrinsic cell-fabrication and intrinsic material challenges to improve efficiency, cyclability, and environmental sustainability. A key challenge is the low conductivity of sulfur cathodes, which is typically managed by incorporating conductive carbon materials. These materials enhance the performance of sulfur cathodes by facilitating high sulfur loading and improving polysulfide retention. In line with green chemistry principles and circular economy concepts, this study explores the use of recycled materials-specifically recycled quartz and board-as substrates for graphene coatings in lithium-sulfur cells. Recycled quartz bricks and blocks, predominantly SiO2, and recycled shelf boards, rich in Al2O3, are successfully coated with graphene, which significantly improves polysulfide adsorption and overall battery performance. The graphene-coated quartz exhibits high sulfur loading (8 mg cm-2), exceptional charge-storage capacity (1,114 mA·h g-1), and long cycle stability (200 cycles) with an energy density of 19 mW·h cm-2. This approach enhances the electrochemical performance of the lithium-sulfur cells and also aligns with sustainability goals by repurposing waste materials and minimizing environmental impact. This novel methodology demonstrates that integrating recycled materials can effectively address key challenges in lithium-sulfur battery technology, advancing both performance and environmental sustainability.

Electronic structure modulation of yttrium sites with heteroanions coordination enhances the bidirectional catalytic performance of lithium-sulfur batteries

Oxyfluorides exhibit unique properties, including catalytic activity and electrical conductivity. However, to date, there has been minimal application of oxyfluorides in the field of lithium-sulfur (Li-S) batteries. This study synthesizes yttrium oxyfluoride-doped semi-encapsulated porous carbon nanofibers (YOF@PCNFs) using through electrospinning strategy for the separator coating in Li-S batteries. The precisely engineered OF heteroanionic environment surrounding the Y cation can adjust the lattice spacing and electronic density of the catalyst. This enhancement improves interactions between the active sites and the reactants, intermediates, and products, reduces the energy barrier for polysulfide (LiPSs) conversion, and enhances the bidirectional catalytic conversion capability of LiPSs. Furthermore, the semi-encapsulated structure helps inhibit polysulfide shuttle and ensures uniform Li-ion deposition. Improved catalysts and the interconnected special structure can establish a series of polysulfides conversion factories which operate efficiently over the long term through a “confinement-adsorption-catalysis-desorption” process, thereby enhancing battery cycling stability. The assembled Li-S full cell exhibits a high initial capacity of 1013.2 mAh/g at 1 mA cm−2 and maintains steady operation over 1500 cycles, with a minimal capacity decay rate of only 0.039 % per cycle. Even at a high current density of 4 mA cm−2, it operates for 200 cycles with an exceptionally low decay rate of 0.081 % per cycle. The study provides an anion hybrid strategy for typical metal catalysts, offering design guidelines for tailored advanced Li-S catalysts.

Lithium‑sulfur batteries for next-generation automotive power batteries carbon emission assessment and sustainability study in China

The rise of electric vehicles has ushered in a revolution in the automotive industry, propelling the global automotive sector towards sustainable development. However, considerable controversy persists regarding the comprehensive performance of electric vehicle batteries and their environmental impact. The development of next-generation power batteries, aimed at enhancing energy storage performance while mitigating environmental consequences, has become a focal point of research in this field. Lithium‑sulfur batteries (LSBs), with their innovative structural design and environmentally friendly materials, not only enhance energy storage performance but also harbor significant environmental potential. When coupled with an all-solid-state battery structure, the all-solid-state lithium‑sulfur battery (A-LSB) demonstrates even more superior performance. This combination represents an ideal next-generation power battery for automotive applications, offering heightened efficiency and environmental sustainability. This study conducts a prospective life cycle assessment (LCA) to examine the environmental performance, particularly carbon emissions, during the production processes of LSBs and A-LSBs in the Chinese region. The primary objective is to uncover the potential for sustainable development in the future of lithium‑sulfur battery technologies. During the research process, we conducted comparative validation by comparing with traditional ternary lithium-ion batteries (NCM) and lithium iron phosphate batteries (LFP). Experimental setups were designed to simulate both laboratory and industrial production scenarios, with a primary focus on analyzing the sustainable performance of LSB and A-LSB. The results indicate that, compared to traditional lithium-ion batteries, both LSB and A-LSB exhibit lower carbon emissions and superior environmental performance, with A-LSB showing particular promise. However, A-LSB demonstrates higher sensitivity to environmental impacts, displaying significant variations before and after industrial production. Additionally, it exhibits a greater dependency on regional resources and energy structures. In contrast, LSB displays better regional adaptability.

Coordinatively Unsaturated Co Single-Atom Catalysts Enhance the Performance of Lithium-Sulfur Batteries by Triggering Strong d-p Orbital Hybridization.

The catalytic activities displayed by single-atom catalysts (SACs) depend on the coordination structure. SACs supported on carbon materials often adopt saturated coordination structures with uneven distributions because they require high-temperature conditions during synthesis. Herein, bisnitrogen-chelated Co SACs that are coordinatively unsaturated are prepared by integrating a Co complex into a conjugated microporous polymer (CMP-CoN2). Compared with saturated analogues, i.e., tetranitrogen-chelated Co SACs (denoted as CMP-CoN4), CMP-CoN2 exhibits higher electrocatalytic activity in polysulfide conversions due to an enhanced hybridization between the 3d orbitals of the Co atoms and the 3p orbitals of the S atoms in the polysulfide. As a result, sulfur cathodes prepared with CoN2 deliver outstanding performance metrics, including a high specific capacity (1393 mA h g-1 at 0.1 C), a superior rate capacity (673.2 mA h g-1 at 6 C), and a low capacity decay rate (of only 0.045% per cycle at 2 C over 1000 cycles). They also outperform sulfur cathodes that contain CMP-CoN4 or CMPs that are devoid of Co SACs. This work reveals how the catalytic activity displayed by SACs is affected by their coordination structures, and the rules that underpin the structure-activity relationship may be extended to designing electrocatalysts for use in other applications.

Modification and Functionalization of Separators for High Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSB) have been recognized as a prominent potential next-generation energy storage system, owing to their substantial theoretical specific capacity (1675 mAh g-1) and high energy density (2600 Wh kg-1). In addition, sulfur's abundance, low cost, and environmental friendliness make commercializing LSB feasible. However, challenges such as poor cycling stability and reduced capacity, stemming from the formation and diffusion of lithium polysulfides (LiPSs), hinder LSB's practical application. Introducing functional separators represents an effective strategy to surmount these obstacles and enhance the electrochemical performance of LSBs. Here, we have conducted a comprehensive review of recent advancements in functional separators for LSBs about various (i) carbon and metal compound materials, (ii) polymer materials, and (iii) novel separators in recent years. The detailed preparation process, morphology and performance characterization, and advantages and disadvantages are summarized, aiming to fundamentally understand the mechanisms of improving battery performance. Additionally, the development potential and future prospects of advanced separators are also discussed.

Tailoring eco-friendly siloxane-based electrolytes for high-performance lithium–sulfur batteries

Lithium–sulfur batteries (LSBs), with their ultra-high theoretical energy density (2600 Wh kg−1), are considered one of the most attractive high-energy batteries. However, the “shuttling effect” of polysulfides and the uncontrolled growth of lithium (Li) dendrites pose significant challenges to the practical implementation of LSBs. Herein, a lightweight and eco-friendly diethoxydimethylsilane (DEMS) is chosen as a multi-functional solvent for LSBs. The low polarity of DEMS promotes the “solid–solid” conversion of sulfurized polyacrylonitrile (SPAN) during charge–discharge processes, eliminating the shuttle effect of polysulfides. Moreover, the DEMS-based electrolyte enables highly reversible Li plating/stripping processes across a wide temperature range spanning from −20 to 60 °C. As a result, the Li/SPAN batteries using the DEMS electrolyte exhibit excellent cyclic stability at 0.2 C with retainable capacities of 524.4 mAh/g after 200 cycles, 598.8 mAh/g after 100 cycles, and 318.6 mAh/g after 50 cycles at 26, 60 and −20 °C, respectively. This study aims to identify low-cost and highly stable electrolytes through solvent screening to enhance the electrochemical performance of LSBs.

Modulation of d-Orbital Interactions in Dual-Atom Catalysts for Enhanced Polysulfide Anchoring and Kinetics in Lithium-Sulfur Batteries.

Modulating the electronic structure is essential for improving the anchoring and catalytic capabilities of catalysts in lithium-sulfur batteries (LSBs). This study delves into the modulation of d-orbitals in transition metal dual-atom catalysts (DACs) supported by boron nitride and graphene (BNC) hybrid sheets for LSBs. This study reveals that the d-band center of the DACs, a key determinant of material chemical properties, is primarily determined by the electronic configuration of the dyz and dx2-y2 orbitals. Furthermore, the interaction between dz2 of transition metals and S_3 p orbitals is critical for the binding strength of LiPSs. By understanding these interactions, the functionality of DACs can be customized for optimal performance in LSBs. For example, the MnCrBNC catalyst with 10 d-electrons exhibits the optimal d-band center and demonstrates exceptional LiPSs binding capability, the lowest Li2S decomposition energy barrier, and the lowest Gibbs free energy of reaction for the rate-determining step of sulfur reduction. This study elucidates the fundamental mechanisms for designing high-performance LSB catalysts through electronic structure modulation.

Nitrogen-Doped Graphene Uniformly Loaded with Large Interlayer Spacing MoS2 Nanoflowers for Enhanced Lithium-Sulfur Battery Performance.

Lithium-sulfur (Li-S) batteries offer a high theoretical energy density but suffer from poor cycling stability and polysulfide shuttling, which limits their practical application. To address these challenges, we developed a PANI-modified MoS2-NG composite, where MoS2 nanoflowers were uniformly grown on graphene oxide (GO) through PANI modification, resulting in an increased interlayer spacing of MoS2. This expanded spacing exposed more active sites, enhancing polysulfide adsorption and catalytic conversion. The composite was used to prepare MoS2-NG/PP separators for Li-S batteries, which achieved a high specific capacity of 714 mAh g-1 at a 3 C rate and maintained a low capacity decay rate of 0.085% per cycle after 500 cycles at 0.5 C. The larger MoS2 interlayer spacing was key to improving redox reaction kinetics and suppressing the shuttle effect, making the MoS2-NG composite a promising material for enhancing the performance and stability of Li-S batteries.

Nanosized CeO2C2 with rich oxygen vacancies embedded in hollow mesoporous carbon as a multifunctional sulfur-loaded matrix for lithium-sulfur batteries

The innovative structural and compositional design of sulfur-loaded matrices is an effective strategy to improve the performance of lithium-sulfur batteries (LSBs). Herein, nanosized CeO2C2 with rich oxygen vacancies embedded in hollow mesoporous carbon composites (HMC/CeO2C2) were synthesized by hydrothermal and annealing reduction processes. This structure has several advantages: the large specific surface area and mesoporous carbon walls facilitate sulfur penetration and electron/ion transport; the abundant mesopores and hollow inner cavities provide the structural basis for sulfur storage and buffer its volume expansion; the oxygen vacancy-rich CeO2C2 nanoparticles grown in situ in HMC and in close contact with carbon form an electrically favorable CeO2C2/C heterointerface as an efficient catalyst, which is conducive to catalyzing the redox reaction of sulfur. Consequently, the retention capacity of the HMC/CeO2C2/S electrode is 728 mAh g−1 after 500 cycles at 0.5 C with a decay rate of 0.056 % per cycle, and it maintains a high reversible area capacity of 3.18 mAh cm−2 and excellent cycling performance even under a high sulfur loading of 4.7 mg cm−2. It provides an idea for the development of multifunctional sulfur-loaded materials with high sulfur loading, high conductivity, and high catalytic activity.

Nd2O3/KB-coated separator constructs adsorption-catalytic bifunctional framework to improve lithium-sulfur battery performance

Nd2O3/KB-coated separator constructs adsorption-catalytic bifunctional framework to improve lithium-sulfur battery performance

Bi-Functional Materials for Sulfur Cathode and Lithium Metal Anode of Lithium-Sulfur Batteries: Status and Challenges.

Over the past decade, the most fundamental challenges faced by the development of lithium-sulfur batteries (LSBs) and their effective solutions have been extensively studied. To further transfer LSBs from the research phase into the industrial phase, strategies to improve the performance of LSBs under practical conditions are comprehensively investigated. These strategies can simultaneously optimize the sulfur cathode and Li-metal anode to account for their interactions under practical conditions, without involving complex preparation or costly processes. Therefore, "two-in-one" strategies, which meet the above requirements because they can simultaneously improve the performance of both electrodes, are widely investigated. However, their development faces several challenges, such as confused design ideas for bi-functional sites and simplex evaluation methods (i. e. evaluating strategies based on their bi-functionality only). To date, as few reviews have focused on these challenges, the modification direction of these strategies is indistinct, hindering further developments in the field. In this review, the advances achieved in "two-in-one" strategies and categorizing them based on their design ideas are summarized. These strategies are then comprehensively evaluated in terms of bi-functionality, large-scale preparation, impact on energy density, and economy. Finally, the challenges still faced by these strategies and some research prospects are discussed.

Engineering rare earth metal Ce-N coordination as catalyst for high redox kinetics in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are a key area of research in energy storage due to their high theoretical energy density, low cost, and environmental friendliness. However, the shuttle effect caused by lithium polysulfides (LiPSs) intermediates often results in poor cycling stability. Therefore, constructing rational cathode structures to achieve fast reaction kinetics in adsorbing and catalyzing LiPSs is the key to obtain high-performance Li-S batteries. Metallic single-atom catalysts (SACs), known for their 100 % atomic utilization rate and low cost, have demonstrated excellent catalytic activity and selectivity in the redox reactions of Li-S batteries, positioning them as one of the most promising catalysts in this field. Rare earth metallic SACs with versatile oxidation states, diverse coordination chemistry and environmentally friendly are rarely investigated in Li-S system. Herein, we fabricate a rare earth metal-based single-atom catalyst (CeSAs) supported on a three-dimensional porous N-doped carbon (3DCeSA-N-WS), and systematically study its performance in Li-S batteries. Benefitting from the atomic dispersion and versatile oxidation states (Ce3+/Ce4+), the 3DCeSA-N-WS demonstrates excellent performance in anchoring and catalyzing LiPSs, significantly enhancing the redox reaction kinetics. Consequently, the prepared sulfur cathode exhibits exceptional electrochemical performance, with a high initial specific discharge capacity of 1225 mAh g−1 at 0.2 C and a capacity retention of 76.1 % after 160 cycles. The assembled 100 mAh-level pouch cellmaintains a high specific discharge capacity of 877 mAh g−1 after 50 cycles at 0.5 C. This work provides new insights into the design of sulfur cathode catalysts, thereby contributing to the realization of high-performance Li-S batteries.

Corrigendum to “Host-guest regulations in functionalized metal and covalent organic frameworks raise the performance of lithium sulfur batteries” [DeCarbon 4 (2024) 100049]

Corrigendum to “Host-guest regulations in functionalized metal and covalent organic frameworks raise the performance of lithium sulfur batteries” [DeCarbon 4 (2024) 100049]

Synergistic implementation of efficient adsorption-diffusion-conversion in lithium-sulfur batteries via built-in electric field constructed by transition metal selenides

The adsorption of lithium polysulfides (LiPSs), the transport of lithium ions, and the redox kinetics collectively play pivotal roles in determining the application of lithium-sulfur (Li-S) batteries. Herein, a defect-rich p-Co3Se4/n-ZnSe p-n junction (ZCSNC) is engineered by chemical vapor deposition (CVD)-selenation. The n-type semiconductor ZnSe and the p-type semiconductor Co3Se4 contained in ZCSNC effectively anchor LiPSs and promote the catalytic reaction kinetics through synergistic effects, respectively. Meanwhile, the presence of heterogeneous interfaces in the p-n junction and the difference in work functions spontaneously form a built-in electric field, which promotes the transport and transfer of lithium ions and LiPSs. Therefore, the ZCSNC functional material contributes to improving the electrochemical performance of Li-S batteries through the process of adsorption-diffusion-conversion. The Li-S cells with ZCSNC-modified separators show excellent rate performance (741.1 mAh/g at 5C) and long-lasting cycling performance (only 0.04 % capacity decay per cycle over 1000 cycles). Notably, the ZCSNC still has excellent rate discharge capacities (683.9 and 649.7 mAh/g at 2C, respectively) at high sulfur loading and low temperature of 0 °C. This study illustrates that a p-n junction containing a built-in electric field can effectively modulate the kinetics of redox reactions of LiPSs through synergistic interactions.

Accelerated Reversible Conversion of Li2S2 to Li2S by Spidroin Regulated Li+ Flux for High-performance Li-Sulfur Batteries.

Regulating the transformation of sulfur species is the key to improving the electrochemical performance of lithium-sulfur (Li-S) batteries, in particular, to accelerate the reversible conversion between solid phase Li2S2 and Li2S. Herein, we introduced Spidroin, which is a main protein in spider silk, as a dual functional separator coating in Li-S batteries to effectively adsorb polysulfides via the sequence of amino acids in its primary structure and regulate Li+ flux through the β-sheet of its secondary structure, thus accelerating the reversible transformation between Li2S2 and Li2S. Spidroin-based Li-S cells exhibited an exceptional electrochemical performance with a high specific capacity of 744.1 mAh g-1 at 5 C and a high areal capacity of 7.5 mAh cm-2 at a low electrolyte-to-sulfur (E/S) ratio of 6 μL mgs -1 and a sulfur loading of 8.6 mgs cm-2.

Development and Optimization of Thin-Lithium-Metal Anodes with a Lithium Lanthanum Titanate Stabilization Coating for Enhancement of Lithium-Sulfur Battery Performance.

Lithium-ion batteries are dominating high-energy-density energy storage for 30 years. However, their development approaches theoretical limits, spurring the development of lithium-sulfur cells that achieve high energy densities through reversible electrochemical conversion reactions. Nevertheless, the commercialization of lithium-sulfur cells is hindered by practical challenges associated primarily with the use of thick-lithium anodes, low-loading sulfur cathodes, and high electrolyte-to-sulfur ratios, which prevent realization of the cells' full potential in terms of electrochemical and material performance. To solve these extrinsic and intrinsic problems, the effect of lithium-metal thickness on the electrochemical behavior of lithium-sulfur cells with high-loading sulfur cathodes in lean-electrolyte configurations is investigated. Specifically, lithium lanthanum titanate (LLTO), a solid electrolyte, is utilized to form an ionically/electronically conductive coating to stabilize lithium-metal anodes, thereby enhancing their lithium-ion pathways and interfacial charge transfer. Electrochemical analyses reveal that an LLTO coating significantly reduces excessive reactions between lithium metal and an electrolyte, thereby minimizing lithium consumption and electrolyte depletion. Further, LLTO-stabilized lithium anodes improve lithium-sulfur cell performance, and most importantly, allow the fabrication of thin-lithium, high-loading-sulfur cells that open a pathway toward high-energy-density batteries.

Utilization of CoSe2-loaded carbon nanofibers for enhancing separator performance in lithium-sulfur batteries: Polysulfide immobilization and redox conversion enhancement

Lithium‑sulfur batteries (LSBs) are recognized as promising candidates for the next generation of secondary batteries due to their high energy density, high theoretical capacity, and low environmental impact. However, the poor electrical conductivity of sulfur and Li2S, the “shuttle effect” of polysulfides, and the slow kinetics of redox reactions have significantly hindered the practical application of LSBs. In this work, CoSe2-loaded carbon nanofibers (CoSe2@CNF) derived from metal-organic frameworks were successfully prepared by electrospinning and used as a functional coating on the polypropylene separator. The three-dimensional network structure of CNFs not only improves the electrical conductivity of the material but also provides channels to facilitate ion and electron transport, while the CoSe2 particles distributed on the surface effectively act as adsorption and catalytic active sites for lithium polysulfides. Under the synergistic effect, the CoSe2@CNF-modified separator suppressed the shuttle effect and significantly enhanced the kinetics of redox reactions. The LSBs assembled with CoSe2@CNF-modified separator exhibited excellent electrochemical performance, achieving an initial capacity of 1445.6 mAh g−1 at 0.5C and maintaining a discharge specific capacity of 849.5 mAh g−1 after 275 cycles.