Suppressed Shuttle via Inhibiting the Formation of Long‐Chain Lithium Polysulfides and Functional Separator for Greatly Improved Lithium–Organosulfur Batteries Performance

The development of lithium–sulfur batteries is limited by the poor conductivity of sulfur cathodes and soluble long‐chain lithium polysulfides (LPSs), which cause the low utilization of sulfur and the aversive shuttle effect, and further, give rise to self‐discharge, rapid reversible capacity fading, and low Coulombic efficiency. In this work, a novel configuration is built for high‐performance lithium–organosulfur batteries, in which the organosulfur hybrid material and lithium metal are used as the cathode and the anode, respectively, and are separated by a functional separator decorated with nitrogen and sulfur co‐doped reduced graphite oxide. The organosulfur in the cathode prevents the shuttle effect by inhibiting the formation of long‐chain LPSs. In addition, the functional separator effectively adsorbs LPSs escaping from the cathode by electrostatic interactions and further restrains the shuttle effect. These effects are confirmed by density‐functional theory calculations. As a result, this novel configuration provides a high initial discharge capacity of 1364 mAh g^?1 at 0.2 C and a high discharge capacity of 750 mAh g^?1 at 1 C after 700 cycles with a very low capacity decay rate of 0.037% per cycle.     

3D Hyperbranched Hollow Carbon Nanorod Architectures for High‐Performance Lithium‐Sulfur Batteries

Lithium‐sulfur batteries have been plagued for a long time by low Coulombic efficiency, fast capacity loss, and poor high rate performance. Here, the synthesis of 3D hyperbranched hollow carbon nanorod encapsulated sulfur nanocomposites as cathode materials for lithium‐sulfur batteries is reported. The sulfur nanocomposite cathodes deliver a high specific capacity of 1378 mAh g^‐1 at a 0.1C current rate and exhibit stable cycling performance. The as‐prepared sulfur nanocomposites also achieve excellent high rate capacities and cyclability, such as 990 mAh g^‐1 at 1C, 861 mAh g^‐1 at 5C, and 663 mAh g^‐1 at 10C, extending to more than 500 cycles. The superior electrochemical performance are ascribed to the unique 3D hyperbranched hollow carbon nanorod architectures and high length/radius aspect ratio of the carbon nanorods, which can effectively prevent the dissolution of polysulfides, decrease self‐discharge, and confine the volume expansion on cycling. High capacity, excellent high‐rate performance, and long cycle life render the as‐developed sulfur/carbon nanorod nanocomposites a promising cathode material for lithium‐sulfur batteries.     

Conductive and Catalytic Triple‐Phase Interfaces Enabling Uniform Nucleation in High‐Rate Lithium–Sulfur Batteries

Rechargeable lithium–sulfur batteries have attracted tremendous scientific attention owing to their superior energy density. However, the sulfur electrochemistry involves multielectron redox reactions and complicated phase transformations, while the final morphology of solid‐phase Li₂S precipitates largely dominate the battery's performance. Herein, a triple‐phase interface among electrolyte/CoSe₂/G is proposed to afford strong chemisorption, high electrical conductivity, and superb electrocatalysis of polysulfide redox reactions in a working lithium–sulfur battery. The triple‐phase interface effectively enhances the kinetic behaviors of soluble lithium polysulfides and regulates the uniform nucleation and controllable growth of solid Li₂S precipitates at large current density. Therefore, the cell with the CoSe₂/G functional separator delivers an ultrahigh rate cycle at 6.0 C with an initial capacity of 916 mAh g^?1 and a capacity retention of 459 mAh g^?1 after 500 cycles, and a stable operation of high sulfur loading electrode (2.69–4.35 mg cm^?2). This work opens up a new insight into the energy chemistry at interfaces to rationally regulate the electrochemical redox reactions, and also inspires the exploration of related energy storage and conversion systems based on multielectron redox reactions.     

A Multifunctional Separator Enables Safe and Durable Lithium/Magnesium–Sulfur Batteries under Elevated Temperature

Rechargeable metal–sulfur batteries encounter severe safety hazards and fast capacity decay, caused by the flammable and shrinkable separator and unwanted polysulfide dissolution under elevated temperatures. Herein, a multifunctional Janus separator is designed by integrating temperature endurable electrospinning polyimide nonwovens with a copper nanowire‐graphene nanosheet functional layer and a rigid lithium lanthanum zirconium oxide‐polyethylene oxide matrix. Such architecture offers multifold advantages: i) intrinsically high dimensional stability and flame‐retardant capability, ii) excellent electrolyte wettability and effective metal dendritic growth inhibition, and iii) powerful physical blockage/chemical anchoring capability for the shuttled polysulfides. As a consequence, the as constructed lithium–sulfur battery using a pure sulfur cathode displays an outstandingly high discharge capacity of 1402.1 mAh g^?1 and a record high cycling stability (approximately average 0.24% capacity decay per cycle within 300 cycles) at 80 °C, outperforming the state‐of‐the‐art results in the literature. Promisingly, a high sulfur mass loading of ≈3.0 mg cm^?2 and a record low electrolyte/sulfur ratio of 6.0 are achieved. This functional separator also performs well for a high temperature magnesium–sulfur battery. This work demonstrates a new concept for high performance metal–sulfur battery design and promises safe and durable operation of the next generation energy storage systems.     

An Efficient Separator with Low Li‐Ion Diffusion Energy Barrier Resolving Feeble Conductivity for Practical Lithium–Sulfur Batteries

Due to unprecedented features including high‐energy density, low cost, and light weight, lithium–sulfur batteries have been proposed as a promising successor of lithium‐ion batteries. However, unresolved detrimental low Li‐ion transport rates in traditional carbon materials lead to large energy barrier in high sulfur loading batteries, which prevents the lithium–sulfur batteries from commercialization. In this report, to overcome the challenge of increasing both the cycling stability and areal capacity, a metallic oxide composite (NiCo₂O₄@rGO) is designed to enable a robust separator with low energy barrier for Li‐ion diffusion and simultaneously provide abundant active sites for the catalytic conversion of the polar polysulfides. With a high sulfur‐loading of 6 mg cm^?2 and low sulfur/electrolyte ratio of 10, the assembled batteries deliver an initial capacity of 5.04 mAh cm^?2 as well as capacity retention of 92% after 400 cycles. The metallic oxide composite NiCo₂O₄@rGO/PP separator with low Li‐ion diffusion energy barrier opens up the opportunity for lithium–sulfur batteries to achieve long‐cycle, cost‐effective operation toward wide applications in electric vehicles and electronic devices.     

3D Ferroconcrete‐Like Aminated Carbon Nanotubes Network Anchoring Sulfur for Advanced Lithium–Sulfur Battery

To address the serious capacity fading in lithium–sulfur batteries, a 3D ferroconcrete‐like aminated carbon nanotubes network with polyaniline coating as an effective sulfur host to contain polysulfide dissolution is presented here. In this composite, the cross‐linked aminated carbon nanotubes framework provides a fast charge transport pathway and enhancement in the reaction kinetics of the active material to greatly improve the rate capability and sulfur utilization. The ethylenediamine moieties provide strong adhesion of polar discharge products to nonpolar carbon surfaces and thus efficiently prevent polysulfide dissolution to improve the cycle stability, confirmed by density functional theory calculations. The outside polyaniline layers structurally restrain polysulfides to prevent the shuttle effect and active material loss. Benefiting from these advantages, the synthesized composite exhibits a high initial capacity of 1215 mAh g^?1 and a capacity of 975 mAh g^?1 after 200 cycles at 0.2 C. Even after 200 cycles at 0.5 C, a capacity of 735 mAh g^?1 can be maintained, among the best performance reported. The strategy in this work can shed some light on modifying nonpolar carbon surfaces via the amination process to chemically attach sulfur species for high‐performance lithium–sulfur batteries.     

A Low-Cost Al(OH)3-Modified Fire-Retardant and Shuttle-Limiting Separator for Safe and Stable Lithium–Sulfur Batteries

Lithium–sulfur battery (LSB) possesses high theoretical energy density, but its poor cycling stability and safety issues significantly restrict progress in practical applications. Herein, a low-cost and simple Al(OH)₃-based modification of commercial separator, which renders the battery outstanding fire-retardant and stable cycling, is reported. The modification is carried out by a simple blade coating of an ultrathin composite layer, mainly consisting of Al(OH)₃ nanoparticles and conductive carbon, on the cathode side of the separator. The Al(OH)₃ shows strong chemical absorption ability toward Lewis-based polysulfides and outstanding fire retardance through a self-decomposition mechanism under high heat, while the conductive carbon material acts as a top current collector to prevent dead polysulfide. LSB using the Al(OH)₃-modified separator shows an extremely low average capacity decade per cycle during 1000 cycles at 2 C (0.029%, 1 C = 1600 mA g⁻¹). The pouch cell exhibiting high energy density (426 Wh kg⁻¹) can also steadily cycle for more than 100 cycles with high capacity retention (70.2% at 0.1 C). The effectiveness and accessibility of this Al(OH)₃ modification strategy will hasten the practical application progress of LSBs.     

Capture and Catalytic Conversion of Polysulfides by In Situ Built TiO2‐MXene Heterostructures for Lithium–Sulfur Batteries

The detrimental shuttle effect in lithium–sulfur batteries mainly results from the mobility of soluble polysulfide intermediates and their sluggish conversion kinetics. Herein, presented is a multifunctional catalyst with the merits of strong polysulfides adsorption ability, superior polysulfides conversion activity, high specific surface area, and electron conductivity by in situ crafting of the TiO₂‐MXene (Ti₃C₂T_x) heterostructures. The uniformly distributed TiO₂ on MXene sheets act as capturing centers to immobilize polysulfides, the hetero‐interface ensures rapid diffusion of anchored polysulfides from TiO₂ to MXene, and the oxygen‐terminated MXene surface is endowed with high catalytic activity toward polysulfide conversion. The improved lithium–sulfur batteries deliver 800 mAh g^?1 at 2 C and an ultralow capacity decay of 0.028% per cycle over 1000 cycles at 2 C. Even with a high sulfur loading of 5.1 mg cm^?2, the capacity retention of 93% after 200 cycles is still maintained. This work sheds new insights into the design of high‐performance catalysts with manipulated chemical components and tailored surface chemistry to regulate polysulfides in Li–S batteries.     

NiCo2O4 Nanofibers as Carbon‐Free Sulfur Immobilizer to Fabricate Sulfur‐Based Composite with High Volumetric Capacity for Lithium–Sulfur Battery

Both the energy density and cycle stability are still challenges for lithium–sulfur (Li–S) batteries in future practical applications. Usually, light‐weight and nonpolar carbon materials are used as the hosts of sulfur, however they struggle on the cycle stability and undermine the volumetric energy density of Li–S batteries. Here, heavy NiCo₂O₄ nanofibers as carbon‐free sulfur immobilizers are introduced to fabricate sulfur‐based composites. NiCo₂O₄ can accelerate the catalytic conversion kinetics of soluble intermediate polysulfides by strong chemical interaction, leading to a good cycle stability of sulfur cathodes. Specifically, the S/NiCo₂O₄ composite presents a high gravimetric capacity of 1125 mAh g^?1 at 0.1 C rate with the composite as active material, and a low fading rate of 0.039% per cycle over 1500 cycles at 1 C rate. In particular, the S/NiCo₂O₄ composite with the high tap density of 1.66 g cm^?3 delivers large volumetric capacity of 1867 mAh cm^?3, almost twice that of the conventional S/carbon composites.     

Interfacial Charge Field in Hierarchical Yolk–Shell Nanocapsule Enables Efficient Immobilization and Catalysis of Polysulfides Conversion

Inhibiting the shuttle effect of lithium polysulfides and accelerating their conversion kinetics are crucial for the development of high‐performance lithium–sulfur (Li–S) batteries. Herein, a modified template method is proposed to synthesize the robust yolk–shell sulfur host that is constructed by enveloping dispersive Fe₂O₃ nanoparticles within Mn₃O₄ nanosheet‐grafted hollow N‐doped porous carbon capsules (Fe₂O₃@N‐PC/Mn₃O₄‐S). When applied as a cathode for Li–S batteries, the as‐prepared Fe₂O₃@N‐PC/Mn₃O₄‐S can deliver capacities as high as 1122 mAh g^?1 after 200 cycles at 0.5 C and 639 mAh g^?1 after 1500 cycles at 10 C, respectively. Remarkably, even as the areal sulfur loading is increased to 5.1 mg cm^?2, the cathode can still maintain a high areal specific capacity of 5.08 mAh cm^?2 with a fading rate of only 0.076% per cycle over 100 cycles at 0.1 C. By a further combination analysis of electron holography and electron energy loss spectroscopy, the outstanding performance is revealed to be mainly traced to the oxygen‐vacancy‐induced interfacial charge field, which immobilizes and catalyzes the conversion of lithium polysulfides, assuring low polarization, fleet redox reaction kinetics, and sufficient utilization of sulfur. These new findings may shed light on the dependence of electrochemical performance on the heterostructure of sulfur hosts.     

Achieving a Quasi-Solid-State Conversion of Polysulfides via Building High Efficiency Heterostructure for Room Temperature Na–S Batteries

The practical application of room temperature sodium–sulfur (RT Na–S) batteries are prevented by the sulfur insulation, the severe shuttling effect of high-order sodium polysulfides (Na₂S_n, 4 ≤ n ≤ 8), and the sluggish reaction kinetics. Therefore, designing an ideal host material to suppress the polysulfides shuttle process and accelerate the redox reactions of soluble NaPSs to Na₂S₂/Na₂S is of paramount importance for RT Na–S batteries. Here, a quasi-solid-state transformation of NaPSs is realized by building high efficiency MoC-W₂C heterostructure in freestanding multichannel carbon nanofibers via electrospinning and calcination methods (MoC-W₂C-MCNFs). The multichannel carbon nanofibers are interlinked micro-mesoporous structures that can accommodate volume change of electrode materials and confine the entire redox process of NaPSs (restraining the polysulfides shuttle process). Meanwhile, the MoC-W₂C heterostructure with abundant heterointerfaces can facilitate electron/ion transport and accelerate conversion of NaPSs. Consequently, the S/MoC-W₂C-MCNFs cathode delivers a high capacity of 640 mAh g⁻¹ after 500 cycles at 0.2 A g⁻¹ and an excellent reversible performance of 200 mAh g⁻¹ after ultralong 3500 cycles at 4 A g⁻¹. What's more, the heterostructure catalytic mechanism (a quasi-solid-state transformation) is proposed and confirmed in carbonate electrolyte by combining experimentally and theoretically.     

High‐Performance and Low‐Temperature Lithium–Sulfur Batteries: Synergism of Thermodynamic and Kinetic Regulation

The intrinsic polysulfides shuttle, resulting from not only concentration‐gradient diffusion but also slow conversion kinetics of polysulfides, bears the primary responsibility for the poor capacity and cycle stability of lithium–sulfur batteries (LSBs). Here, it is first presented that enriched edge sites derived from vertical standing and ultrathin 2D layered metal selenides (2DLMS) can simultaneously achieve the thermodynamic and kinetic regulation for polysulfides diffusion, which is systematically elucidated through theoretical calculation, electrochemical characterization, and spectroscopic/microscopic analysis. When employed to fabricate compact coating layer of separator, an ultrahigh capacity of 1338.7 mA h g^?1 is delivered after 100 cycles at 0.2 C, which is the best among the reports. Over 1000 cycles, the cell still maintains the capacity of 546.8 mA h g^?1 at 0.5 C. Moreover, the cell exhibits outstanding capacities of 1106.2 and 865.7 mA h g^?1 after 100 cycles at stern temperature of 0 and ?25 °C. The superior low‐temperature performance is appealing for extended practical application of LSBs. Especially, in view of the economy, the 2DLMS is recycled as an anode of lithium‐ion and sodium‐ion batteries after finishing the test of LSBs. The low‐cost and scalable 2DLMS with enriched egde sites open a new avenue for the perfect regulation of the sulfur electrode.     

Boosting Polysulfide Redox Kinetics by Graphene‐Supported Ni Nanoparticles with Carbon Coating

Lithium–sulfur batteries have attracted extensive attention because of their high energy density. However, their application is still impeded by the inherent sluggish kinetics and solubility of intermediate products (i.e., polysulfides) of the sulfur cathode. Herein, graphene‐supported Ni nanoparticles with a carbon coating are fabricated by directly carbonizing a metal–organic framework/graphene oxide composite, which is then dispersed on a commercial glass fiber membrane to form a separator with electrocatalytic activity. In situ analysis and electrochemical investigation demonstrate that this modified separator can effectively suppress the shuttle effect and regulate the catalytic conversion of intercepted polysulfides, which is also confirmed by density functional theory calculations. It is found that Ni–C sites can chemically interact with polysulfides and stabilize the radical S₃^?? through Ni? S bonds to enable fast dynamic equilibrium with S₆^2?, while Ni nanoparticles reduce the oxidation barrier of Li₂S and accelerate ion/electron transport. As a result, the corresponding lithium–sulfur battery shows a high cycle stability (88% capacity retention over 100 cycles) even with a high sulfur mass loading of 8 mg cm^?2 and lean electrolyte (6.25 µ L mg^?1). Surprisingly, benefitting from the improved kinetics, the battery can work well at ?50 °C, which is rarely achieved by conventional Li–S batteries.     

Facile Synthesis of Crumpled Nitrogen‐Doped MXene Nanosheets as a New Sulfur Host for Lithium–Sulfur Batteries

Crumpled nitrogen‐doped MXene nanosheets with strong physical and chemical coadsorption of polysulfides are synthesized by a novel one‐step approach and then utilized as a new sulfur host for lithium–sulfur batteries. The nitrogen‐doping strategy enables introduction of heteroatoms into MXene nanosheets and simultaneously induces a well‐defined porous structure, high surface area, and large pore volume. The as‐prepared nitrogen‐doped MXene nanosheets have a strong capability of physical and chemical dual‐adsorption for polysulfides and achieve a high areal sulfur loading of 5.1 mg cm^–2. Lithium–sulfur batteries, based on crumpled nitrogen‐doped MXene nanosheets/sulfur composites, demonstrate outstanding electrochemical performances, including a high reversible capacity (1144 mA h g^–1 at 0.2C rate) and an extended cycling stability (610 mA h g^–1 at 2C after 1000 cycles).     

Highly Dispersed Cobalt Clusters in Nitrogen‐Doped Porous Carbon Enable Multiple Effects for High‐Performance Li–S Battery

The lithium–sulfur (Li–S) battery is considered a promising candidate for the next generation of energy storage system due to its high specific energy density and low cost of raw materials. However, the practical application of Li–S batteries is severely limited by several weaknesses such as the shuttle effect of polysulfides and the insulation of the electrochemical products of sulfur and Li₂S/Li₂S₂. Here, by doping nitrogen and integrating highly dispersed cobalt catalysts, a porous carbon nanocage derived from glucose adsorbed metal–organic framework is developed as the host for a sulfur cathode. This host structure combines the reported positive effects, including high conductivity, high sulfur loading, effective stress release, fast lithium‐ion kinetics, fast interface charge transport, fast redox of Li₂S_n, and strong physical/chemical absorption, achieving a long cycle life (86% of capacity retention at 1C within 500 cycles) and high rate performance (600 mAh g^?1 at 5C) for a Li–S battery. By combining experiments and density functional theoretical calculations, it is demonstrated that the well‐dispersed cobalt clusters play an important role in greatly improving the diffusion dynamics of lithium, and enhance the absorption and conversion capability of polysulfides in the host structure.     

Separator Modified by Cobalt‐Embedded Carbon Nanosheets Enabling Chemisorption and Catalytic Effects of Polysulfides for High‐Energy‐Density Lithium‐Sulfur Batteries

Lithium‐sulfur (Li‐S) batteries are considered to be one of the promising next‐generation energy storage systems. Considerable progress has been achieved in sulfur composite cathodes, but high cycling stability and discharging capacity at the expense of volumetric capacity have offset their advantages. Herein, a functional separator is presented by coating cobalt‐embedded nitrogen‐doped porous carbon nanosheets and graphene on one surface of a commercial polypropylene separator. The coating layer not only suppresses the polysulfide shuttle effect through chemical affinity, but also functions as an electrocatalyst to propel catalytic conversion of intercepted polysulfides. The slurry‐bladed carbon nanotubes/sulfur cathode with 90 wt% sulfur deliver high reversible capacity of 1103 mA h g^?1 and volumetric capacity of 1062 mA h cm^?3 at 0.2 C, and the freestanding carbon nanofibers/sulfur cathode provides a high discharging capacity of 1190 mA h g^?1 and volumetric capacity of 1136 mA h cm^?3 at high sulfur content of 78 wt% and sulfur loading of 10.5 mg cm^?2. The electrochemical performance is comparable with or even superior to those in the state‐of‐the‐art carbon‐based sulfur cathodes. The separator reported in this work holds great promise for the development of high‐energy‐density Li‐S batteries.     

Sulfiphilic Few‐Layered MoSe2 Nanoflakes Decorated rGO as a Highly Efficient Sulfur Host for Lithium‐Sulfur Batteries

Lithium‐sulfur batteries (LSBs) have been regarded as a competitive candidate for next‐generation electrochemical energy‐storage technologies due to their merits in energy density. The sluggish redox kinetics of the electrochemistry and the high solubility of polysulfides during cycling result in insufficient sulfur utilization, severe polarization, and poor cyclic stability. Herein, sulfiphilic few‐layered MoSe₂ nanoflakes decorated rGO (MoSe₂@rGO) hybrid has been synthesized through a facile hydrothermal method and for the first time, is used as a conceptually new‐style sulfur host for LSBs. Specifically, MoSe₂@rGO not only strongly interacts with polysulfides but also dynamically strengthens polysulfide redox reactions. The polarization problem is effectively alleviated by relying on the sulfiphilic MoSe₂. Moreover, MoSe₂@rGO is demonstrated to be beneficial for the fast nucleation and uniform deposition of Li₂S, contributing to the high discharge capacity and good cyclic stability. A high initial capacity of 1608 mAh g^?1 at 0.1 C, a slow decay rate of 0.042% per loop at 0.25 C, and a high reversible capacity of 870 mAh g^?1 with areal sulfur loading of 4.2 mg cm^?2 at 0.3 C are obtained. The concept of introducing sulfiphilic transition‐metal selenides into the LSBs system can stimulate engineering of novel architectures with enhanced properties for various energy‐storage devices.     

Tin Intercalated Ultrathin MoO3 Nanoribbons for Advanced Lithium–Sulfur Batteries

Heteroatom doping strategies have been widely developed to engineer the conductivity and polarity of 2D materials to improve their performance as the host for sulfur cathode in lithium–sulfur batteries. However, further improvement is limited by the inhomogeneity and the small amount of the doping atoms. An intercalation method to improve the conductivity and polarity of 2D‐layered α‐MoO₃ nanoribbons is developed here, thus, resulting in much improved electrochemical performance as sulfur host with better rate and cycle performance. The first principle calculations show that the binding energy of MoO₃ and lithium polysulfides, lithium sulfide and sulfur is significantly improved after Sn intercalation. The Sn_0.063MoO₃‐S cathode delivers an initial specific capacity of 1390.3 mAh g^?1 at 0.1 C with the Coulombic efficiency up to 99.7% and shows 79.6% retention of the initial capacity over 500 cycles at 1 C rate with a capacity decay of 0.04% per cycle. This intercalation method provides a new strategy to engineer the electrochemical properties of 2D materials.     

Catalytic Polysulfide Conversion and Physiochemical Confinement for Lithium–Sulfur Batteries

The lithium–sulfur (Li–S) battery is widely regarded as a promising energy storage device due to its low price and the high earth‐abundance of the materials employed. However, the shuttle effect of lithium polysulfides (LiPSs) and sluggish redox conversion result in inefficient sulfur utilization, low power density, and rapid electrode deterioration. Herein, these challenges are addressed with two strategies 1) increasing LiPS conversion kinetics through catalysis, and 2) alleviating the shuttle effect by enhanced trapping and adsorption of LiPSs. These improvements are achieved by constructing double‐shelled hollow nanocages decorated with a cobalt nitride catalyst. The N‐doped hollow inner carbon shell not only serves as a physiochemical absorber for LiPSs, but also improves the electrical conductivity of the electrode; significantly suppressing shuttle effect. Cobalt nitride (Co₄N) nanoparticles, embedded in nitrogen‐doped carbon in the outer shell, catalyze the conversion of LiPSs, leading to decreased polarization and fast kinetics during cycling. Theoretical study of the Li intercalation energetics confirms the improved catalytic activity of the Co₄N compared to metallic Co catalyst. Altogether, the electrode shows large reversible capacity (1242 mAh g^?1 at 0.1 C), robust stability (capacity retention of 658 mAh g^?1 at 5 C after 400 cycles), and superior cycling stability at high sulfur loading (4.5 mg cm^?2).     

Chemical Bonding and Physical Trapping of Sulfur in Mesoporous Magnéli Ti4O7 Microspheres for High‐Performance Li–S Battery

Various host materials have been investigated to address the intrinsic drawbacks of lithium sulfur batteries, such as the low electronic conductivity of sulfur and inevitable decay in capacity during cycling. Besides the widely investigated carbonaceous materials, metal oxides have drawn much attention because they form strong chemical bonds with the soluble lithium polysulfides. Here, mesoporous Magnéli Ti₄O₇ microspheres are prepared via an in situ carbothermal reduction that exhibit interconnected mesopores (20.4 nm), large pore volume (0.39 cm³ g^?1), and high surface area (197.2 m² g^?1). When the sulfur cathode is embedded in a matrix of mesoporous Magnéli Ti₄O₇ microspheres, it exhibits a superior reversible capacity of 1317.6 mA h g^?1 at moderate current (C/10) and a low decay in capacity of 12% after 400 cycles at C/5. Strong chemical bonding of the lithium polysulfides to Ti₄O₇, as well as effective physical trapping in the mesopores and voids in the matrix are considered responsible for the improved electrochemical performance. A mechanism of the physical and chemical interactions between mesoporous Magnéli Ti₄O₇ microspheres and sulfur is proposed based on systematic investigations.