A Dual-Functional Conductive Framework Embedded with TiN-VN Heterostructures for Highly Efficient Polysulfide and Lithium Regulation toward Stable Li–S Full Batteries

Lithium–sulfur (Li–S) batteries are strongly considered as next-generation energy storage systems because of their high energy density. However, the shuttling of lithium polysulfides (LiPS), sluggish reaction kinetics, and uncontrollable Li-dendrite growth severely degrade the electrochemical performance of Li–S batteries. Herein, a dual-functional flexible free-standing carbon nanofiber conductive framework in situ embedded with TiN-VN heterostructures (TiN-VN@CNFs) as an advanced host simultaneously for both the sulfur cathode (S/TiN-VN@CNFs) and the lithium anode (Li/TiN-VN@CNFs) is designed. As cathode host, the TiN-VN@CNFs can offer synergistic function of physical confinement, chemical anchoring, and superb electrocatalysis of LiPS redox reactions. Meanwhile, the well-designed host with excellent lithiophilic feature can realize homogeneous lithium deposition for suppressing dendrite growth. Combined with these merits, the full battery (denoted as S/TiN-VN@CNFs || Li/TiN-VN@CNFs) exhibits remarkable electrochemical properties including high reversible capacity of 1110 mAh g⁻¹ after 100 cycles at 0.2 C and ultralong cycle life over 600 cycles at 2 C. Even with a high sulfur loading of 5.6 mg cm⁻², the full cell can achieve a high areal capacity of 5.5 mAh cm⁻² at 0.1 C. This work paves a new design from theoretical and experimental aspects for fabricating high-energy-density flexible Li–S full batteries.     

A Combined Ordered Macro‐Mesoporous Architecture Design and Surface Engineering Strategy for High‐Performance Sulfur Immobilizer in Lithium–Sulfur Batteries

The practical application of lithium–sulfur (Li–S) batteries is hindered by the “shuttle” of lithium polysulfides (LiPS) and sluggish Li–S kinetics issues. Herein, a synergistic strategy combining mesoporous architecture design and defect engineering is proposed to synthesize multifunctional defective 3D ordered mesoporous cobalt sulfide (3DOM N‐Co₉S_8?x) to address the shuttling and sluggish reaction kinetics of polysulfide in Li–S batteries. The unique 3DOM design provides abundant voids for sulfur storage and enlarged active interfaces that reduce electron/ion diffusion pathways. Meanwhile, X‐ray absorption spectroscopy shows that the surface defect engineering tunes the CoS₄ tetrahedra to CoS₆ octahedra on Co₉S₈, endowing abundance of S vacancies on the Co₉S₈ octahedral sites. The ever‐increasing S vacancies over the course of electrochemical process further promotes the chemical trapping of LiPS and its conversion kinetics, rendering fast and durable Li–S chemistry. Benefiting from these features, the as‐developed 3DOM N‐Co₉S_8?x/S cathode delivers high areal capacity, superb rate capability, and excellent cyclic stability with ultralow capacity fading rate under raised sulfur loading and low electrolyte content. This design strategy promotes the development of practically viable Li–S batteries and sheds lights on the material engineering in related energy storage application.     

锂硫电池硫正极材料研究进展

由化石燃料的大量使用导致的全球能源和环境问题日益严重,已对人们的生产和生活产生了明显的影响.开发利用储量丰富的清洁能源(如太阳能、水能和风能等)有望较好地解决全球能源和环境问题.由于这些清洁能源存在地域性、间歇性等特点,高效的能量转化和存储技术是实现清洁能源规模化利用的关键和基础.锂离子电池作为绿色环保的储能器件,已在手机、笔记本电脑、相机等便携电子产品中广泛使用.近年来,锂离子电池开始在电动汽车等动力电池领域得到应用.但是,由于其能量密度不够高,导致锂离子电池电动汽车续航短、充电频繁及购车成本高.由金属锂为负极和硫为正极组成的锂硫电池的能量密度(2600 Wh·kg-1)远高于目前广泛使用的锂离子电池.此外,硫正极材料具有储量丰富、毒性低、价格便宜、环境友好等突出优点.因此,锂硫电池被认为是当前最具研究前景的高能量密度二次电池之一.硫正极材料的本征导电性差、在充放电过程中存在较大的体积膨胀和收缩,储放锂过程中形成的多硫化锂易溶于电解液,使得锂硫电池的倍率性能、循环寿命和库伦效率等电化学性能离实际应用仍有较大距离.迄今为止,关于硫正极材料的研究工作,主要集中于如何提升其导电性、抑制或消除由多硫化锂的溶解引起的穿梭效应以及在反复的循环过程中保持电极材料微结构的稳定性等方面.相关研究表明,将硫与不同形貌的碳材料复合构筑成具有特殊微观结构的硫/碳复合正极材料可显著提高其导电性、抑制多硫化锂的穿梭效应和减缓储放锂前后的体积变化,进而改善倍率性能、循环稳定性和充放电效率等.此外,在硫正极材料中引入异质元素掺杂碳材料、金属氧化物和导电集合物均可通过化学吸附实现对易溶解多硫化锂的有效吸附.将上述多种改性方法结合也可使硫正极材料具有优异的电化学储锂性能.本文从锂硫电池的工作原理出发,总结了硫正极材料存在的主要问题,综述了近几年锂硫电池复合正极材料的研究进展,最后对锂硫电池正极材料的研究思路与发展趋势进行了分析和展望.     

Low-Bandgap Se-Deficient Antimony Selenide as a Multifunctional Polysulfide Barrier toward High-Performance Lithium–Sulfur Batteries

The shuttling behavior and sluggish conversion kinetics of the intermediate lithium polysulfides (LiPSs) represent the main obstructions to the practical application of lithium–sulfur (Li–S) batteries. Herein, an anion-deficient design of antimony selenide (Sb₂Se_3−x) is developed to establish a multifunctional LiPS barrier toward the inhibition of polysulfide shuttling and enhancement of battery performance. The defect chemistry in the as-developed Sb₂Se_3−x promotes the intrinsic conductivity, strengthens the chemical affinity to LiPSs, and catalyzes the sulfur electrochemical conversion, which are verified by a series of computational and experimental results. Attributed to these unique superiorities, the obtained LiPS barrier efficiently promotes and stabilizes the sulfur electrochemistry, thus enabling excellent Li–S battery performance, e.g., outstanding cyclability over 500 cycles at 1.0 C with a minimum capacity fading rate of 0.027% per cycle, a superb rate capability up to 8.0 C, and a high areal capacity of 7.46 mAh cm⁻² under raised sulfur loading. This work offers a defect engineering strategy toward fast and durable sulfur electrochemistry, holding great promise in developing practically viable Li–S batteries as well as enlightening the material design of related energy storage and conversion systems.     

Approaching Ultrastable High‐Rate Li–S Batteries through Hierarchically Porous Titanium Nitride Synthesized by Multiscale Phase Separation

Porous architectures are important in determining the performance of lithium–sulfur batteries (LSBs). Among them, multiscale porous architecutures are highly desired to tackle the limitations of single‐sized porous architectures, and to combine the advantages of different pore scales. Although a few carbonaceous materials with multiscale porosity are employed in LSBs, their nonpolar surface properties cause the severe dissolution of lithium polysulfides (LiPSs). In this context, multiscale porous structure design of noncarbonaceous materials is highly required, but has not been exploited in LSBs yet because of the absence of a facile method to control the multiscale porous inorganic materials. Here, a hierarchically porous titanium nitride (h‐TiN) is reported as a multifunctional sulfur host, integrating the advantages of multiscale porous architectures with intrinsic surface properties of TiN to achieve high‐rate and long‐life LSBs. The macropores accommodate the high amount of sulfur, facilitate the electrolyte penetration and transportation of Li⁺ ions, while the mesopores effectively prevent the LiPS dissolution. TiN strongly adsorbs LiPS, mitigates the shuttle effect, and promotes the redox kinetics. Therefore, h‐TiN/S shows a reversible capacity of 557 mA h g^?1 even after 1000 cycles at 5 C rate with only 0.016% of capacity decay per cycle.     

Single Nickel Atoms on Nitrogen‐Doped Graphene Enabling Enhanced Kinetics of Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have arousing interest because of their high theoretical energy density. However, they often suffer from sluggish conversion of lithium polysulfides (LiPS) during the charge/discharge process. Single nickel (Ni) atoms on nitrogen‐doped graphene (Ni@NG) with Ni–N₄ structure are prepared and introduced to modify the separators of Li–S batteries. The oxidized Ni sites of the Ni–N₄ structure act as polysulfide traps, efficiently accommodating polysulfide ion electrons by forming strong S_x ^2????Ni? N bonding. Additionally, charge transfer between the LiPS and oxidized Ni sites endows the LiPS on Ni@NG with low free energy and decomposition energy barrier in an electrochemical process, accelerating the kinetic conversion of LiPS during the charge/discharge process. Furthermore, the large binding energy of LiPS on Ni@NG also shows its ability to immobilize the LiPS and further suppresses the undesirable shuttle effect. Therefore, a Li–S battery based on a Ni@NG modified separator exhibits excellent rate performance and stable cycling life with only 0.06% capacity decay per cycle. It affords fresh insights for developing single‐atom catalysts to accelerate the kinetic conversion of LiPS for highly stable Li–S batteries.     

利用二硫苏糖醇夹层抑制锂硫电池的穿梭效应

为了抑制锂硫电池的穿梭效应,改善锂硫电池的电化学性能,尝试以二硫苏糖醇(DTT)为剪切剂,对高阶多硫化物进行剪切以阻止其溶解。将二硫苏糖醇(DTT)掺入多壁碳纳米管(MWCNTs)纸中,制得DTT夹层,将该DTT夹层置于锂硫扣式半电池正极片和隔膜之间,正极片的载硫面密度约为2 mg/cm2。SEM观察结果证实DTT均匀分散在MWCNTs纸的表面和空隙中。电化学测试结果表明引入DTT夹层结构的锂硫电池在0.05C倍率首次放电比容量达到1 288 mAh/g,首次库伦效率接近100%,在0.5C、2C、4C倍率下充放电时的比容量分别达到650mAh/g、600mAh/g、410mAh/g。DTT夹层结构的引入可有效剪切高阶多硫化物并阻止其迁移到锂负极,从而抑制穿梭效应,改善锂硫电池的循环稳定性和库伦效率。     

Optimization of Microporous Carbon Structures for Lithium–Sulfur Battery Applications in Carbonate‐Based Electrolyte

Developing appropriate sulfur cathode materials in carbonate‐based electrolyte is an important research subject for lithium‐sulfur batteries. Although several microporous carbon materials as host for sulfur reveal the effect, methods for producing microporous carbon are neither easy nor well controllable. Moreover, due to the complexity and limitation of microporous carbon in their fabrication process, there has been rare investigation of influence on electrochemical behavior in the carbonate‐based electrolyte for lithium‐sulfur batteries by tuning different micropore size(0–2 nm) of carbon host. Here, we demonstrate an immediate carbonization process, self‐activation strategy, which can produce microporous carbon for a sulfur host from alkali‐complexes. Besides, by changing different alkali‐ion in the previous complex, the obtained microporous carbon exhibits a major portion of ultramicropore (<0.7 nm, from 54.9% to 25.8%) and it is demonstrated that the micropore structure of the host material plays a vital role in confining sulfur molecule. When evaluated as cathode materials in a carbonate‐based electrolyte for Li‐S batteries, such microporous carbon/sulfur composite can provide high reversible capacity, cycling stability and good rate capability.     

A Bifunctional Perovskite Promoter for Polysulfide Regulation toward Stable Lithium–Sulfur Batteries

Lithium‐sulfur (Li? S) batteries are strongly considered as the next‐generation rechargeable cells. However, both the shuttle of lithium polysulfides (LiPSs) and sluggish kinetics in random deposition of lithium sulfides (Li₂S) significantly degrade the capacity, rate performance, and cycling life of Li? S cells. Herein, bifunctional Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ perovskite nanoparticles (PrNPs) are proposed as a promoter to immobilize LiPSs and guide the deposition of Li₂S in a Li? S cell. The oxygen vacancy in PrNPs increases the metal reactivity to anchor LiPSs, and co‐existence of lithiophilic (O) and sulfiphilic (Sr) sites in PrNP favor the dual‐bonding (Li? O and Sr? S bonds) to anchor LiPSs. The high catalytic nature of PrNP facilitates the kinetics of LiPS redox reaction. The PrNP with intrinsic LiPS affinity serves as nucleation sites for Li₂S deposition and guides its uniform propagation. Therefore, the bifunctional LiPS promoter in Li? S cell yields high rate performance and ultralow capacity decay rate of 0.062% (a quarter of pristine Li? S cells). The proposed strategy to immobilize LiPSs, promotes the conversion of LiPS, and regulates deposition of Li₂S by an emerging perovskite promoter and is also expected to be applied in other energy conversion and storage devices based on multi‐electron redox reactions.     

Pyrrolic‐Type Nitrogen‐Doped Hierarchical Macro/Mesoporous Carbon as a Bifunctional Host for High‐Performance Thick Cathodes for Lithium‐Sulfur Batteries

Lithium‐sulfur (Li‐S) batteries are highly considered as a next‐generation energy storage device due to their high theoretical energy density. For practical viability, reasonable active‐material loading of >4.0 mg cm^?2 must be employed, at a cost to the intrinsic instability of sulfur cathodes. The incursion of lithium polysulfides (LiPS) at higher sulfur loadings results in low active material utilization and poor cell cycling capability. The use of high‐surface‐area hierarchical macro/mesoporous inverse opal (IOP) carbons to investigate the effects of pore volume and surface area on the electrochemical stability of high‐loading, high‐thickness cathodes for Li‐S batteries is presented here. The IOP carbons are additionally doped with pyrrolic‐type nitrogen groups (N‐IOP) to act as a polar polysulfide mediator and enhance the active‐material reutilization. With a high sulfur loading of 6.0 mg cm^?2, the Li‐S cells assembled with IOP and N‐IOP carbons are able to attain a high specific capacity of, respectively, 1242 and 1162 mA h g^?1. The N‐IOP enables the Li‐S cells to demonstrate good electrochemical performance over 300 cycles.     

In Situ 1D Carbon Chain-Mail Catalyst Assembly for Stable Lithium–Sulfur Full Batteries

The main obstacles for the commercial application of Lithium–Sulfur (Li–S) full batteries are the large volume change during charging/discharging process, the shuttle effect of lithium polysulfide (LiPS), sluggish redox kinetics, and the indisciplinable dendritic Li growth. Especially the overused of metal Li leads to the low utilization of active Li, which seriously drags down the actual energy density of Li–S batteries. Herein, an efficient design of dual-functional CoSe electrocatalyst encapsulated in carbon chain-mail (CoSe@CCM) is employed as the host both for the cathode and anode regulation simultaneously. The carbon chain-mail constituted by carbon encapsulated layer cross-linking with carbon nanofibers protects CoSe from the corrosion of chemical reaction environment, ensuring the high activity of CoSe during the long-term cycles. The Li–S full battery using this carbon chain-mail catalyst with a lower negative/positive electrode capacity ratio (N/P < 2) displays a high areal capacity of 9.68 mAh cm⁻² over 150 cycles at a higher sulfur loading of 10.67 mg cm⁻². Additionally, a pouch cell is stable for 80 cycles at a sulfur loading of 77.6 mg, showing the practicality feasibility of this design.     

Robust,Ultra‐Tough Flexible Cathodes for High‐Energy Li–S Batteries

Sulfur cathodes have become appealing for rechargeable batteries because of their high theoretical capacity (1675 mA h g^?1). However, the conventional cathode configuration borrowed from lithium‐ion batteries may not allow the pure sulfur cathode to put its unique materials chemistry to good use. The solid_(sulfur)–liquid_{(polysulfides)}–solid_(sulfides) phase transitions generate polysulfide intermediates that are soluble in the commonly used organic solvents in Li–S cells. The resulting severe polysulfide diffusion and the irreversible active‐material loss have been hampering the development of Li–S batteries for years. The present study presents a robust, ultra‐tough, flexible cathode with the active‐material fillings encapsulated between two buckypapers (B), designated as buckypaper/sulfur/buckypaper (B/S/B) cathodes, that suppresses the irreversible polysulfide diffusion to the anode and offers excellent electrochemical reversibility with a low capacity fade rate of 0.06% per cycle after 400 cycles. Engineering enhancements demonstrate that the B/S/B cathodes represent a facile approach for the development of high‐performance sulfur electrodes with a high areal capacity of 5.1 mA h cm^?2, which increases further to approach 7 mA h cm^?2 on coupling with carbon‐coated separators.     

Atomic Interlamellar Ion Path in High Sulfur Content Lithium‐Montmorillonite Host Enables High‐Rate and Stable Lithium–Sulfur Battery

Fast lithium ion transport with a high current density is critical for thick sulfur cathodes, stemming mainly from the difficulties in creating effective lithium ion pathways in high sulfur content electrodes. To develop a high‐rate cathode for lithium–sulfur (Li–S) batteries, extenuation of the lithium ion diffusion barrier in thick electrodes is potentially straightforward. Here, a phyllosilicate material with a large interlamellar distance is demonstrated in high‐rate cathodes as high sulfur loading. The interlayer space (≈1.396 nm) incorporated into a low lithium ion diffusion barrier (0.155 eV) significantly facilitates lithium ion diffusion within the entire sulfur cathode, and gives rise to remarkable nearly sulfur loading‐independent cell performances. When combined with 80% sulfur contents, the electrodes achieve a high capacity of 865 mAh g^?1 at 1 mA cm^?2 and a retention of 345 mAh g^?1 at a high discharging/charging rate of 15 mA cm^?2, with a sulfur loading up to 4 mg. This strategy represents a major advance in high‐rate Li–S batteries via the construction of fast ions transfer paths toward real‐life applications, and contributes to the research community for the fundamental mechanism study of loading‐independent electrode systems.     

Sulfur-impregnated disordered carbon nanotubes cathode for lithium-sulfur batteries

The commercialization of lithium-sulfur batteries is hindered by low cycle stability and low efficiency, which are induced by sulfur active material loss and polysulfide shuttle reaction through dissolution into electrolyte. In this study, sulfur-impregnated disordered carbon nanotubes are synthesized as cathode material for the lithium-sulfur battery. The obtained sulfur-carbon tube cathodes demonstrate superior cyclability and Coulombic efficiency. More importantly, the electrochemical characterization indicates a new stabilization mechanism of sulfur in carbon induced by heat treatment.     

α-MoC1–x纳米晶富集碳球修饰隔膜对锂硫电池性能的影响

采用自组装及热处理方法合成α-MoC1-x纳米晶富集的纳米碳球(α-MoC1-x/CNS),并将其涂覆在商用聚丙烯隔膜上,对隔膜实现了界面修饰。电化学性能显示,与普通的聚丙烯隔膜相比,采用修饰的α-MoC1-x/CNS-PP隔膜组装的锂硫电池的循环稳定性和倍率性能均得到明显提升,在0.5C条件下,电池首周放电比容量提升至1129.7 mAh/g,经过100周充放电循环后,电池仍具有855.5 mAh/g的放电比容量,且在此循环过程中,库伦效率始终大于98%。在自放电测试中,电池经过48h静置后的容量损失率仅为7.7%。结合α-MoC1-x/CNS的微观形貌及XPS分析可知,在锂硫电池充放电过程中,α-MoC1-x/CNS修饰层有效地阻挡了多硫化锂向负极侧的扩散迁移,且当α-MoC1-x与多硫离子接触时能产生Mo-S键、硫代和连多硫酸根产物,进一步巩固了活性物质被约束的程度,从而使电池性能得到提升。     

A Dual‐Function Na2SO4 Template Directed Formation of Cathode Materials with a High Content of Sulfur Nanodots for Lithium–Sulfur Batteries

The sulfur content in carbon–sulfur hybrid using the melt‐diffusion method is normally lower than 70 wt%, which greatly decreases the energy density of the cathode in lithium–sulfur (Li‐S) batteries. Here, a scalable method inspired by the commercialized production of Na₂S is used to prepare a hierarchical porous carbon–sulfur hybrid (denoted HPC‐S) with high sulfur content (≈85 wt%). The HPC‐S is characterized by the structure of sulfur nanodots naturally embedded in a 3D carbon network. The strategy uses Na₂SO₄ as the starting material, which serves not only as the sulfur precursor but also as a salt template for the formation of the 3D carbon network. The HPC‐S cathode with such a high sulfur content shows excellent rate performance and cycling stability in Li–S batteries because of the sulfur nanoparticles, the unique carbon framework, and the strong interaction between them. The production method can also be readily scaled up and used in practical Li–S battery applications.     

Integrating Conductivity,Immobility, and Catalytic Ability into High-N Carbon/Graphene Sheets as an Effective Sulfur Host

Lithium–sulfur (Li–S) batteries are considered to be one of the most promising candidate systems for next-generation electrochemical energy storage. The major challenge of this system is the polysulfide shuttle, which results in poor cycling efficiency. In this work, a highly N-doped carbon/graphene (NC/G) sheet is designed as a sulfur host, which combines the merits of abundant N active sites and high electrical conductivity to achieve in situ anchoring–conversion of lithium polysulfides (LiPSs). Such a host not only has strong binding with LiPSs but also promotes redox kinetics, which are revealed by both experimental investigations and theoretical studies. The sulfur cathode based on the NC/G host exhibits a high initial capacity of 1380 mA h g⁻¹ and a superior cycle stability with a low capacity decay of 0.037% per cycle within 500 cycles at 2 C. Steady areal capacity with a high sulfur loading (5.6 mg cm⁻²) is also attained even without the addition of LiNO₃ in the electrolyte. This work proposes and illustrates the importance of in situ anchoring–conversion of LiPSs, offering a new strategy to design multifunctional sulfur hosts for high-performance Li–S batteries.     

Ordered SnO nanoparticles in MWCNT as a functional host material for high-rate lithium-sulfur battery cathode

Lithium-sulfur battery has become one of the most promising candidates for next generation batteries,and it is still restricted due to the low sulfur conductivity,large volume expansion and severe polysulfide shuttling.Herein,we present a novel hybrid electrode with a ternary nanomaterial based on sulfur-impregnated multiwalled carbon nanotubes filled with ordered tin-monoxide nanoparticles (MWCNT-SnO/S).Using a dry plasma reduction method,a mechanically robust material is prepared as a cathode host material for lithium-sulfur batteries.The MWCNT-SnO/S electrode exhibits high conductivity,good ability to capture polysulfides,and small volume change during a repeated charge-discharge process.In situ transmission electron microscopy and ultraviolet-visible absorption results indicate that the MWCNT-SnO host efficiently suppresses volume expansion during lithiation and reduces polysulfide dissolution into the electrolyte.Furthermore,the ordered SnO nanoparticles in the MWCNTs facilitate fast ion/electron transfer during the redox reactions by acting as connective links between the walls of the MWCNTs.The MWCNT-SnO/S cathode with a high sulfur content of 70 wt.％ exhibits an initial discharge capacity of 1,682.4 mAh·g-1 at 167.5 mA·g-1 (0.1 C rate) and retains a capacity of 530.1 mAh·g-1 at 0.5 C after 1,000 cycles with nearly 100％ Coulombic efficiency.Furthermore,the electrode exhibits the high capacity even at a high current rate of 20 C.     

Highly Safe Electrolyte Enabled via Controllable Polysulfide Release and Efficient Conversion for Advanced Lithium–Sulfur Batteries

Conventional lithium–sulfur batteries often suffer from fatal problems such as high flammability, polysulfide shuttling, and lithium dendrites growth. Here, highly‐safe lithium–sulfur batteries based on flame‐retardant electrolyte (dimethoxyether/1,1,2,2‐tetrafluoroethyl 2,2,3,3‐tetrafluoropropyl ether) coupled with functional separator (nanoconductive carbon‐coated cellulose nonwoven) to resolve aforementioned bottle‐neck issues are demonstrated. It is found that this flame‐retardant electrolyte exhibits excellent flame retardancy and low solubility of polysulfide. In addition, Li/Li symmetrical cells using such flame‐retardant electrolyte deliver extraordinary long‐term cycling stability (less than 10 mV overpotential) for over 2500 h at 1.0 mA cm^?2 and 1.0 mAh cm^?2. Moreover, bare sulfur cathode–based lithium–sulfur batteries using this flame retardant electrolyte coupled with nanoconductive carbon‐coated cellulose separator can retain 83.6% discharge capacity after 200 cycles at 0.5 C. Under high charge/discharge rate (4 C), lithium–sulfur cells still show high charge/discharge capacity of ≈350 mAh g^?1. Even at an elevated temperature of 60 °C, discharge capacity of 870 mAh g^?1 can be retained. More importantly, high‐loading bare sulfur cathode (4 mg cm^?2)–based lithium–sulfur batteries can also deliver high charge/discharge capacity over 806 mAh g^?1 after 56 cycles. Undoubtedly, the strategy of flame retardant electrolyte coupled with carbon‐coated separator enlightens highly safe lithium–sulfur batteries at a wide range of temperature.     

Molybdenum Boride as an Efficient Catalyst for Polysulfide Redox to Enable High-Energy-Density Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries, despite having high theoretical specific energy, possess many practical challenges, including lithium polysulfide (LiPS) shuttling. To address the issues, here, hydrophilic molybdenum boride (MoB) nanoparticles are presented as an efficient catalytic additive for sulfur cathodes. The high conductivity and rich catalytically active sites of MoB nanoparticles allow for a fast kinetics of LiPS redox in high-sulfur-loading electrodes (6.1 mg cm⁻²). Besides, the hydrophilic properties and good wettability toward electrolyte of MoB can facilitate electrolyte penetration and LiPS redox, guaranteeing a high utilization of sulfur under a lean-electrolyte condition. Therefore, the cells with MoB achieve impressive electrochemical performance, including a high capacity (1253 mA h g⁻¹) and ultralong lifespan (1000 cycles) with a low capacity fade rate of 0.03% per cycle. Also, pouch cells fabricated with the MoB additive deliver an ultrahigh discharge capacity of 947 mA h g⁻¹, corresponding to a low electrolyte-to-capacity ratio of about 4.8 µL (mA h)⁻¹, and remain stable over 55 cycles under practically necessary conditions with a low electrolyte-to-sulfur ratio of 4.5 µL mg⁻¹.