Recent Progress for Concurrent Realization of Shuttle-Inhibition and Dendrite-Free Lithium-Sulfur Batteries

A multifunctional self-supporting LLTO/C interlayer for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are recognized as an encouraging alternative for future power storage technologies. However, their practical application is hindered by several significant challenges, including slow redox kinetics, the shuttle effect, and the formation of lithium dendrites. Here a binder-free, self-supporting multifunctional interlayer composed of lithium lanthanum titanate (LLTO) with amorphous carbon nanofiber matrices for Li-S batteries has been constructed. This multifunctional interlayer has been designed to facilitate the redox kinetics of lithium polysulfides (LiPSs), promote the nucleation of lithium sulfide (Li2S), and hinder the formation of lithium dendrites. The electrocatalytic properties of the interlayer were subjected to systematic evaluation through electrochemical testing, and the lithium deposition was assessed by examining the surface evolution of lithium metal in symmetric cells. The LLTO carbon matrix interlayer sustained a high specific capacity of 703.3 mA h g-1 after 200 cycles at 0.1C, with a sulfur loading of 5.5 mg cm-2. Furthermore, it demonstrated a high capacity of 905.9 mA h g-1 with a decay rate of 0.069% per cycle over 1000 cycles at a current density of 5C with a sulfur loading of 1 mg cm-2. This investigation highlights the potential of LLTO carbon composite materials as multifunctional interlayers, which could facilitate the optimization of advanced Li-S batteries.

Asymmetric Polarization Modulation of d-p Hybridization-Enhanced Bidirectional Sulfur Redox Kinetics with Heteronuclear Dual-Atom Catalysts

Lithium sulfur batteries (LiSBs) represent a highly promising avenue for future energy storage systems, offering high energy density and eco-friendliness. However, the sluggish kinetics of the sulfur redox reaction (SRR) poses a significant challenge to their widespread applications. To tackle this challenge, we have developed an efficient heteronuclear dual-atom catalyst (hetero-DAC) that leverages surface charge polarization to enhance the asymmetric adsorption of sulfur intermediates. This study investigates how asymmetric electronic redistribution of CoFe DACs modulates the d-p orbital hybridization with sulfur intermediates, revealing the mechanisms of moderate adsorption dynamics with enhanced catalytic performance. The dynamic switching between mono and dual adsorption sites, enabled by the heteronuclear polarized configuration, fine-tunes the orbital hybridization, boosting the bidirectional rate-determining steps, that is, the solid-solid conversion of Li2S2 to Li2S and the reverse dissociation of Li2S. Consequently, the thus-designed CoFe DACs cathode delivers impressive rate performance, achieving a high initial specific capacity of 703.9 mA h g-1 at 3 C, with a negligible decay rate of only 0.031% over 1000 cycles, demonstrating sustained long-term cycling stability. This work bridges geometric configurations and electronic structures, elucidating the mechanisms of asymmetric trapping and conversion enabled by hetero-DACs and offering fresh perspectives for catalyst design in LiSBs and beyond.

An In Situ Generated Organic/Inorganic Hybrid SEI Layer Enables Li Metal Anodes with Dendrite Suppression Ability, High-Rate Capability, and Long-Life Stability

High-quality solid electrolyte interphase (SEI) layers can effectively suppress the growth of Li dendrites and improve the cycling stability of lithium metal batteries. Herein, 1-(6-bromohexanoyl)-3-butylurea is used to construct an organic/inorganic hybrid (designated as LiBr-HBU) SEI layer that features a uniform and compact structure. The LiBr-HBU SEI layer exhibits superior electrolyte wettability and air stability as well as strong attachment to Li foils. The LiBr-HBU SEI layer achieves a Li+ conductivity of 2.75 × 10-4 S cm-1, which is ≈50-fold higher than the value measured for a native SEI layer. A Li//Li symmetric cell containing the LiBr-HBU SEI layer exhibits markedly improved cyclability when compared with the cell containing a native SEI layer, especially at a high current density (e.g., cycling life up to 1333 h at 15 mA cm-2). The LiBr-HBU SEI layer also improves the performance of lithium-sulfur cells, particularly the rate capability (548 mAh g-1 at 10 C) and cycling stability (513 mAh g-1 at 0.5 C after 500 cycles). The methodology described can be extended to the commercial processing of Li metal anodes as the artificial SEI layer also protects Li metal against corrosion.

Zinc Tellurium with Anionic Vacancies Anchored on Ordered Macroporous Carbon Skeleton Enabling Accelerated Polysulfide Conversion for Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) showcase great promise for large-scale energy storage systems, however, their practical commercialization is seriously hindered by the sluggish redox reaction kinetics and detrimental shuttle effect of soluble polysulfides. Herein, small ZnTe1- x nanoparticles with anionic vacancies firmly anchored on 3D ordered macroporous N-doped carbon skeleton (3DOM-ZnTe1- x@NC) are elaborately constructed as a high-efficiency electrocatalyst for LSBs. The ordered macroporous carbon skeleton not only greatly increases the external surface area to expose sufficient active sites but also facilitates the electrolyte penetration. Additionally, the experimental studies combined with theoretical calculations confirm the presence of Te vacancies optimizes the electronic structure to enhance the intrinsic catalytic activity and chemical absorption. Consequently, LSBs assembled with the 3DOM-ZnTe1- x@NC modified separators exhibit high specific discharge capacity, as well as superior rate performance and good long-term cycling stability. Even under a high sulfur loading of 6.5 mg cm-2 and lean electrolyte, an impressive areal capacity of 5.28 mAh cm-2 is achieved at 0.1 C after 100 cycles. More significantly, the 3DOM-ZnTe1- x@NC based pouch cells are also fabricated to demonstrate its potential for practical applications. This work highlights that the rational combination of 3DOM architecture and vacancy engineering is important for designing advanced Li-S electrocatalysts.

Construction of spontaneous built-in electric field on heterointerface furnishing continuous efficient adsorption-directional migration-conversion of polysulfides

Integrating sulfur with efficient electrocatalysts remains a pressing need in lithium-sulfur (Li-S) batteries for modulating the sluggish conversion kinetics and restricting the shuttle behavior of lithium polysulfides (LiPSs). Herein, a compact p-type Fe3O4 and n-type MoS2 heterostructure embedded on nitrogen-doped porous carbon (Fe3O4-MoS2-NPC-0.5) is meticulously constructed as dual-functional hosts that can facilitate continuous catalytic conversion of LiPSs. The p-type Fe3O4 exhibits a high affinity for polysulfides, while n-type MoS2 enables effective catalysis of LiPSs. The successful migration of LiPSs from Fe3O4 to MoS2 is bridged due to a spontaneous built-in electric field (BIEF) at the p-n heterojunction interface. The synergistic effect prevents the passivation of adsorption sites on Fe3O4 and enhances the efficient catalytic conversion capabilities of MoS2. Consequently, the battery with Fe3O4-MoS2-NPC-0.5/S exhibits a prominent initial capacity of 1120.6 mAh g-1 at 2 C, maintains outstanding cyclability with a capacity attenuation rate of 0.045 % per cycle at 0.5 C, and high sulfur utilization at large sulfur loadings. This work offers insights into optimizing the performance-enhanced Li-S battery electrodes by the formation of a dynamic "trapping-directional migration-conversion" reaction.

Garnet-Type Solid-State Electrolytes: Crystal-Phase Regulation and Interface Modification for Enhanced Lithium Metal Batteries

Due to their substantial energy density, rapid charging and discharging rates, and extended lifespan, lithium-ion batteries have attained broad application across various industries. However, their limited theoretical capacity struggles to meet the growing demand for battery capacity in consumer electronics, automotive, and aerospace applications. As a promising substitute, solid-state lithium-metal batteries (SSLBs) have emerged, utilizing a lithium-metal anode that boasts a significant theoretical specific capacity and non-flammable solid-state electrolytes (SSEs) to address energy density limitations and safety concerns. For SSLBs to attain large-scale commercial viability, SSEs require heightened ionic-conductivity, improved mechanical characteristics, and enhanced chemical and electrochemical stability. Furthermore, tackling the challenges related to interfacial contacts between SSEs and the lithium-metal anode is imperative. This review comprehensively overviews the primary methods used to prepare garnet SSEs and summarizes doping strategies for various sites on Li7La3Zr2O12 (LLZO) garnet SSEs, aiming to optimize the crystal phase to achieve more favorable properties in SSE applications. Additionally, it discusses strategies for modifying the interfacial contact between the lithium-metal anode and SSEs, classifying them into three areas: surface modification, interlayer-modification, and composite anodes. This review aims to serve as a valuable reference for future researchers working on high-performance garnet SSEs and effective interfacial-modification strategies.

Breaking the Passivation Effect for MnO2 Catalysts in Li-S Batteries by Anion-Cation Doping

Transition metal oxides (TMOs) are recognized as high-efficiency electrocatalyst systems for restraining the shuttle effect in lithium-sulfur (Li-S) batteries, owing to their robust adsorption capabilities for polysulfides. However, the sluggish catalytic conversion of Li2S redox and severe passivation effect of TMOs exacerbate polysulfide shuttling and reduce the cyclability of Li-S batteries, which significantly hinders the development of TMOs electrocatalysts. Here, through the anion-cation doping approach, dual incorporation of phosphorus and molybdenum into MnO2 (P,Mo-MnO2) was engineered, demonstrating effective mitigation of the passivation effect and allowing for the simultaneous immobilization of polysulfides and rapid redox kinetics of Li2S. Both experimental and theoretical investigations reveal the pivotal role of dopants in fine-tuning the d-band center and optimizing the electronic structure of MnO2. Furthermore, this well-designed configuration processes catalytic selectivity. Specifically, P-doping expedites rapid Li2S nucleation kinetics by minimizing reaction-free energy, while Mo-doping facilitates robust Li2S dissolution kinetics by mitigating decomposition barriers. This dual-doping approach equips P,Mo-MnO2 with robust bi-directional catalytic activity, effectively overcoming passivation effect and suppressing the notorious shuttle effect. Consequently, Li-S batteries incorporating P,Mo-MnO2-based separators demonstrate favorable performance than pristine TMOs. This design offers rational viewpoint for the development of catalytic materials with superior bi-directional sulfur electrocatalytic in Li-S batteries.

Electrochemically Active MoO3/TiN Sulfur Host Inducing Dynamically Reinforced Built-in Electric Field for Advanced Lithium-Sulfur Batteries

Although various electrocatalysts have been developed to ameliorate the shuttle effect and sluggish Li-S conversion kinetics, their electrochemical inertness limits the sufficient performance improvement of lithium-sulfur batteries (LSBs). In this work, an electrochemically active MoO3/TiN-based heterostructure (MOTN) is designed as an efficient sulfur host that can improve the overall electrochemical properties of LSBs via prominent lithiation behaviors. By accommodating Li ions into MoO3 nanoplates, the MOTN host can contribute its own capacity. Furthermore, the Li intercalation process dynamically affects the electronic interaction between MoO3 and TiN and thus significantly reinforces the built-in electric field, which further improves the comprehensive electrocatalytic abilities of the MOTN host. Because of these merits, the MOTN host-based sulfur cathode delivers an exceptional specific capacity of 2520 mA h g-1 at 0.1 C. Furthermore, the cathode exhibits superior rate capability (564 mA h g-1 at 5 C), excellent cycling stability (capacity fade rate of 0.034% per cycle for 1200 cycles at 2 C), and satisfactory areal capacity (6.6 mA h cm-2) under a high sulfur loading of 8.3 mg cm-2. This study provides a novel strategy to develop electrochemically active heterostructured electrocatalysts and rationally manipulate the built-in electric field for achieving high-performance LSBs.

Progresses and Perspectives of Carbon-Free Metal Compounds-Modified Separators for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) have the advantages of high theoretical specific capacity, excellent energy density, abundant elemental sulfur reserves. However, the LSBs is mainly limited by shuttling of lithium polysulfides (LiPSs), slow reaction kinetics of sulfur cathode. For solving the above problems, by developing high-performance battery separators, the reversible capacity, Coulombic efficiency (CE) and cycle life of LSBs can be effectively enhanced. Carbon-free based metal compounds are expected to be highly efficient separator modifiers for a new generation of high-performance LSBs by virtue of superior chemical adsorption capacity, strong catalytic properties and excellent lithophilicity to a certain extent. They can give play to the synergistic effect of their "adsorption-catalysis" sites to accelerate the redox kinetics of LiPSs, and their good lithophilicity can accelerate the Li+ transport kinetics, thus showing more remarkable electrochemical performances. However, a comprehensive summary of carbon-free metal compounds-modified separators for LSBs is still lacking. Here, this review systematically summarizes the researching progresses and performance characteristics of carbon-free-based metal compounds modified materials for separators of LSBs, and summarizes the corresponding mechanisms of using carbon-based separators to enhance the performance of LSBs. Finally, the review also looks forward to the prospects of LSBs using carbon-free metal compounds separators.

Xanthate-Mediated Oxidation of Li2S as the Lithium-Containing Cathode in Lithium-Sulfur Batteries with Extremely Low Overpotential

Lithium-sulfide (Li2S) has long been pursued as a lithium-containing cathode material for high-energy-density lithium-sulfur (Li-S) batteries. Unfortunately, its direct oxidation generally has a large overpotential, giving rise to low energy efficiency. The use of redox mediators to accelerate the conversion of solid Li2S to polysulfides represents a possible solution to lower the initial oxidation overpotential. However, most reported redox mediators exhibit significantly higher redox potentials than the desirable value. Herein, it is serendipitously found that lithium ethyl xanthate (LiEX) formed from the reaction among Li2S, ethanol, and CS2 at room temperature is an efficient redox mediator. It has a redox potential (≈2.3 V vs Li+/Li) close to the electrochemical oxidation potential of Li2S (2.25 V vs Li+/Li), which enables fast Li2S oxidation reaction kinetics, and more importantly, lowers the Li2S oxidation potential from ≈3.6 to ≈2.3 V. When further integrated with an Ni-NC catalyst in a tandem catalysis scheme, a remarkable specific capacity of ≈1100 mAh g-1 at 0.2 mA cm-2 and long cycle life of 1400 cycles with ∼73% capacity retention is achieved, outperforming those of other Li2S-based cathode materials from recent literature.

In Situ Synthesis of CoMoO4 Microsphere@rGO as a Matrix for High-Performance Li-S Batteries at Room and Low Temperatures

Lithium-sulfur batteries (Li-S batteries) have attracted wide attention due to their high theoretical energy density and the low cost of sulfur cathode material. However, the poor conductivity of the sulfur cathode, the polysulfide shuttle effect, and the slow redox kinetics severely affect their cycling performance and Coulombic efficiencies, especially under low-temperature conditions, where these effects are more exacerbated. To address these issues, this study designs and synthesizes a microspherical cobalt molybdate@reduced graphene oxide (CoMoO4@rGO) composite material as the cathode material for Li-S batteries. By growing CoMoO4 nanoparticles on the rGO surface, the composite material not only provides a good conductive network but also significantly enhances the adsorption capacity to polysulfides, effectively suppressing the shuttle effect. After 100 cycles at room temperature with a current density of 1 C, the reversible specific capacity of the battery stabilizes at 805 mAh g-1. Notably, at -20 °C, the S/CoMoO4@rGO composite achieves a reversible specific capacity of 840 mAh g-1. This study demonstrates that the CoMoO4@rGO composite has significant advantages in suppressing polysulfide diffusion and expanding the working temperature range of Li-S batteries, showing great potential for applications in next-generation high-performance Li-S batteries.

Iodine-doped carbon nanotubes boosting the adsorption effect and conversion kinetics of lithium-sulfur batteries

Compared with lithium-ion batteries (LIBs), lithium-sulfur batteries (LSBs), based on electrochemical reactions involving multi-step 16-electron transformations provide higher specific capacity (1672 mAh g-1) and specific energy (2600 Wh kg-1), exhibiting great potential in the field of energy storage. However, the inherent insulation of sulfur, slow electrochemical reaction kinetics and detrimental shuttle-effect of lithium polysulfides (LiPSs) restrict the development of LSBs in practical applications. Herein, the iodine-doped carbon nanotubes (I-CNTs) is firstly reported as sulfur host material to the enhance the adsorption-conversion kinetics of LSBs. Iodine doping can significantly improve the polarity of I-CNTs. Iodine atoms with lone pair electrons (Lewis base) in iodine-doped CNTs can interact with lithium cations (Lewis acidic) in LiPSs, thereby anchoring polysulfides and suppressing subsequent shuttling behavior. Moreover, the charge transfer between iodine species (electron acceptor) and CNTs (electron donor) decreases the gap band and subsequently improves the conductivity of I-CNTs. The enhanced adsorption effect and conductivity are beneficial for accelerating reaction kinetics and enhancing electrocatalytic activity. The in-situ Raman spectroscopy, quasi in-situ electrochemical impedance spectroscopy (EIS) and Li2S potentiostatic deposition current-time (i-t) curves were conducted to verify mechanism of complex sulfur reduction reaction (SRR). Owing to above advantages, the I-CNTs@S composite cathode exhibits an ultrahigh initial capacity of 1326 mAh g-1 as well as outstanding cyclicability and rate performance. Our research results provide inspirations for the design of multifunctional host material for sulfur/carbon composite cathodes in LSBs.

Biomimetic Aramid Nanofiber/β-FeOOH Composite Coating for Polypropylene Separators in Lithium-Sulfur Batteries

Aramid nanofibers (ANFs), with attractive mechanical and thermal properties, have attracted much attention as key building units for the design of high-performance composite materials. Although great progress has been made, the potential of ANFs as fibrous protein mimetics for controlling the growth of inorganic materials has not been fully revealed, which is critical for avoiding phase separation associated with typical solution blending. In this work, we show that ANFs could template the oriented growth of β-FeOOH nanowhiskers, which enables the synthesis of ANFs/β-FeOOH hybrids as composite coatings for polypropylene (PP) separators in Li-S batteries. The modified PP separator exhibits enhanced mechanical properties, heightened thermal performance, optimized electrolyte wettability, and improved ion conductivity, leading to superior electrochemical properties, including high initial specific capacity, better rate capability, and long cycling stability, which are superior to those of the commercial PP separators. Importantly, the addition of β-FeOOH to ANFs could further contribute to the suppression of lithium polysulfide shuttling by chemical immobilization, inhibition of the growth of lithium dendrites because of the intrinsic high modulus and hardness, and promotion of reaction dynamics due to the catalytic effect. We believe that our work may provide a potent biomimetic pathway for the development of advanced battery separators based on ANFs.

Cobalt-zinc carbides embedded in N-doped porous carbon nanospheres as polysulfide mediators for efficient lithium-sulfur batteries

Developing high-efficiency interlayer catalysts is a promising tactic for improving the cycling performance of rechargeable lithium-sulfur (Li-S) batteries. Herein, using the Prussian blue analogue as the precursor, cobalt-zinc carbide nanocrystal-embedded N-doped porous carbon (Co3ZnC@NC) is synthesized via simple post-carbonization. The obtained Co3ZnC@NC nanospheres exhibit a robust core-shell structure showing good conductivity, high porosity and available metal active sites, favoring the interfacial charge transfer and the electron transport upon electrochemical reactions. The results demonstrate that the Co3ZnC@NC catalyst is quite suitable for boosting the adsorption and redox conversion kinetics of soluble polysulfides. When acting as the separator interlayer, Co3ZnC@NC contributes to improved Li-S batteries with a high discharge specific capacity of 1659.8 mA h g-1 at 0.1C and superior cycling stability of over 250 cycles at 1.0C (high capacity retention of 84.1% after 100 cycles at 0.5C). Furthermore, the Co3ZnC@NC-based battery can maintain a high discharge capacity of 734.0 mA h g-1 at 5.0C, along with delivering a stable reversible capacity of 805.4 mA h g-1 (∼5 mA h cm-2) after 50 cycles even under a high sulfur loading of 6.2 mg cm-2. This study affords a viable way to construct highly dispersed bimetal/carbon composites for efficient catalysts and renewable energy devices.

Rechargeable alkali metal-chlorine batteries: advances, challenges, and future perspectives

The emergence of Li-SOCl2 batteries in the 1970s as a high-energy-density battery system sparked considerable interest among researchers. However, limitations in the primary cell characteristics have restricted their potential for widespread adoption in today's sustainable society. Encouragingly, recent developments in alkali/alkaline-earth metal-Cl2 (AM-Cl2) batteries have shown impressive reversibility with high specific capacity and cycle performance, revitalizing the potential of SOCl2 batteries and becoming a promising technology surpassing current lithium-ion batteries. In this review, the emerging AM-Cl2 batteries are comprehensively summarized for the first time. The development history and advantages of Li-SOCl2 batteries are traced, followed by the critical working mechanisms for achieving high rechargeability. The design concepts of electrodes and electrolytes for AM-Cl2 batteries as well as key characterization techniques are also demonstrated. Furthermore, the current challenges and corresponding strategies, as well as future directions regarding the battery are systematically discussed. This review aims to deepen the understanding of the state-of-the-art AM-Cl2 battery technology and accelerate the development of practical AM-Cl2 batteries for next-generation high-energy storage systems.

Dependence of Interlayer or Sulfur Host on Hollow Framework of Lithium-Sulfur Battery

Lithium-sulfur batteries are recognized as the next generation of high-specific energy secondary batteries owing to their satisfactory theoretical specific capacity and energy density. However, their commercial application is greatly limited by a series of problems, including disordered migration behavior, sluggish redox kinetics, and the serious shuttle effect of lithium polysulfides. One of the most efficient approaches to physically limit the shuttle effect is the rational design of a hollow framework as sulfur host. However, the influence of the hollow structure on the interlayers has not been clearly reported. In this study, the Mo2C/C catalysts with hollow(H-Mo2C/C) and solid(S-Mo2C/C) frameworks are rationally designed to explore the dependence of the hollow structure on the interlayer or sulfur host. In contrast to the physical limitations of the hollow framework as host, the hollow structure of the interlayer inhibited lithium-ion diffusion, resulting in poor electrochemical properties at high current densities. Based on the superiority of the various frameworks, the H-Mo2C/C@S | S-Mo2C/C@PP | Li cells are assembled and displayed excellent electrochemical performance. This work re-examines the design requirements and principles of catalyst frameworks in different battery units.

Pristine MOF Materials for Separator Application in Lithium-Sulfur Battery

Lithium-sulfur (Li-S) batteries have attracted significant attention in the realm of electronic energy storage and conversion owing to their remarkable theoretical energy density and cost-effectiveness. However, Li-S batteries continue to face significant challenges, primarily the severe polysulfides shuttle effect and sluggish sulfur redox kinetics, which are inherent obstacles to their practical application. Metal-organic frameworks (MOFs), known for their porous structure, high adsorption capacity, structural flexibility, and easy synthesis, have emerged as ideal materials for separator modification. Efficient polysulfides interception/conversion ability and rapid lithium-ion conduction enabled by MOFs modified layers are demonstrated in Li-S batteries. In this perspective, the objective is to present an overview of recent advancements in utilizing pristine MOF materials as modification layers for separators in Li-S batteries. The mechanisms behind the enhanced electrochemical performance resulting from each design strategy are explained. The viewpoints and crucial challenges requiring resolution are also concluded for pristine MOFs separator in Li-S batteries. Moreover, some promising materials and concepts based on MOFs are proposed to enhance electrochemical performance and investigate polysulfides adsorption/conversion mechanisms. These efforts are expected to contribute to the future advancement of MOFs in advanced Li-S batteries.

Developing Cathode Films for Practical All-Solid-State Lithium-Sulfur Batteries

The development of all-solid-state lithium-sulfur batteries (ASSLSBs) toward large-scale electrochemical energy storage is driven by the higher specific energies and lower cost in comparison with the state-of-the-art Li-ion batteries. Yet, insufficient mechanistic understanding and quantitative parameters of the key components in sulfur-based cathode hinders the advancement of the ASSLSB technologies. This review offers a comprehensive analysis of electrode parameters, including specific capacity, voltage, S mass loading and S content toward establishing the specific energy (Wh kg-1) and energy density (Wh L-1) of the ASSLSBs. Additionally, this work critically evaluates the progress in enhancing lithium ion and electron percolation and mitigating electrochemical-mechanical degradation in sulfur-based cathodes. Last, a critical outlook on potential future research directions is provided to guide the rational design of high-performance sulfur-based cathodes toward practical ASSLSBs.

Rare Earth Single-Atom Catalysis for High-Performance Li-S Full Battery with Ultrahigh Capacity

Lithium-sulfur (Li-S) batteries have many advantages but still face problems such as retarded polysulfides redox kinetics and Li dendrite growth. Most reported single atom catalysts (SACs) for Li-S batteries are based on d-band transition metals whose d orbital constitutes active valence band, which is inclined to occur catalyst passivation. SACs based on 4f inner valence orbital of rare earth metals are challenging for their great difficulty to be activated. In this work, we design and synthesize the first rare earth metal Sm SACs which has electron-rich 4f inner orbital to promote catalytic conversion of polysulfides and uniform deposition of Li. Sm SACs enhance the catalysis by the activated 4f orbital through an f-d-p orbital hybridization. Using Sm-N3C3 modified separators, the half cells deliver a high capacity over 600 mAh g-1 and a retention rate of 84.3 % after 2000 cycles. The fabricated Sm-N3C3-Li|Sm-N3C3@PP|S/CNTs full batteries can provide an ultra-stable cycling performance of a retention rate of 80.6 % at 0.2 C after 100 cycles, one of the best full Li-S batteries. This work provides a new perspective for the development of rare earth metal single atom catalysis in electrochemical reactions of Li-S batteries and other electrochemical systems for next-generation energy storage.

Organic Electrolyte Additive: Dual Functions Toward Fast Sulfur Conversion and Stable Li Deposition for Advanced Li-S Batteries

Lithium-sulfur (Li-S) battery is of great potential for the next generation energy storage device due to the high specific capacity energy density. However, the sluggish kinetics of S redox and the dendrite Li growth are the main challenges to hinder its commercial application. Herein, an organic electrolyte additive, i.e., benzyl chloride (BzCl), is applied as the remedy to address the two issues. In detail, BzCl can split into Bz· radical to react with the polysulfides, forming a Bz-S-Bz intermediate, which changes the conversion path of S and improves the kinetics by accelerating the S splitting. Meanwhile, a tight and robust solid electrolyte interphase (SEI) rich in inorganic ingredients namely LiCl, LiF, and Li2O, is formed on the surface of Li metal, accelerating the ion conductivity and blocking the decomposition of the solvent and lithium polysulfides. Therefore, the Li-S battery with BzCl as the additive remains high capacity of 693.2 mAh g-1 after 220 cycles at 0.5 C with a low decay rate of 0.11%. This work provides a novel strategy to boost the electrochemical performances in both cathode and anode and gives a guide on the electrolyte design toward high-performance Li-S batteries.

Multifunctional SnO2 QDs/MXene Heterostructures as Laminar Interlayers for Improved Polysulfide Conversion and Lithium Plating Behavior

Poor cycling stability in lithium-sulfur (Li-S) batteries necessitates advanced electrode/electrolyte design and innovative interlayer architectures. Heterogeneous catalysis has emerged as a promising approach, leveraging the adsorption and catalytic performance on lithium polysulfides (LiPSs) to inhibit LiPSs shuttling and improve redox kinetics. In this study, we report an ultrathin and laminar SnO2@MXene heterostructure interlayer (SnO2@MX), where SnO2 quantum dots (QDs) are uniformly distributed across the MXene layer. The combined structure of SnO2 QDs and MXene, along with the creation of numerous active boundary sites with coordination electron environments, plays a critical role in manipulating the catalytic kinetics of sulfur species. The Li-S cell with the SnO2@MX-modified separator not only demonstrates superior electrochemical performance compared to cells with a bare separator but also induces homogeneous Li deposition during cycling. As a result, an areal capacity of 7.6 mAh cm-2 under a sulfur loading of 7.5 mg cm-2 and a high stability over 500 cycles are achieved. Our work demonstrates a feasible strategy of utilizing a laminar separator interlayer for advanced Li-S batteries awaiting commercialization and may shed light on the understanding of heterostructure catalysis with enhanced reaction kinetics.

The role of electrocatalytic materials for developing post-lithium metal||sulfur batteries

The exploration of post-Lithium (Li) metals, such as Sodium (Na), Potassium (K), Magnesium (Mg), Calcium (Ca), Aluminum (Al), and Zinc (Zn), for electrochemical energy storage has been driven by the limited availability of Li and the higher theoretical specific energies compared to the state-of-the-art Li-ion batteries. Post-Li metal||S batteries have emerged as a promising system for practical applications. Yet, the insufficient understanding of quantitative cell parameters and the mechanisms of sulfur electrocatalytic conversion hinder the advancement of these battery technologies. This perspective offers a comprehensive analysis of electrode parameters, including S mass loading, S content, electrolyte/S ratio, and negative/positive electrode capacity ratio, in establishing the specific energy (Wh kg-1) of post-Li metal||S batteries. Additionally, we critically evaluate the progress in investigating electrochemical sulfur conversion via homogeneous and heterogeneous electrocatalytic approaches in both non-aqueous Na/K/Mg/Ca/Al||S and aqueous Zn||S batteries. Lastly, we provide a critical outlook on potential research directions for designing practical post-Li metal||S batteries.

Heterogenization-Activated Zinc Telluride via Rectifying Interfacial Contact to Afford Synergistic Confinement-Adsorption-Catalysis for High-Performance Lithium-Sulfur Batteries

The notorious shuttle effect and sluggish conversion kinetics of intermediate polysulfides (Li2S4, Li2S6, Li2S8) are severely hindered the large-scale development of Lithium-sulfur (Li-S) batteries. Rectifying interface effect has been a solution to regulate the electron distribution of catalysts via interfacial charge exchange. Herein, a ZnTe-ZnO heterojunction encapsulated in nitrogen-doped hierarchical porous carbon (ZnTe-O@NC) derived from metal-organic framework is fabricated. Theoretical calculations and experiments prove that the built-in electric field constructed at ZnTe-ZnO heterojunction via the rectifying interface contact, thus promoting the charge transfer as well as enhancing adsorption and conversion kinetics toward polysulfides, thereby stimulating the catalytic activity of the ZnTe. Meanwhile, the nitrogen-doped hierarchical porous carbon acts as confinement substrate also enables fast electrons/ions transport, combining with ZnTe-ZnO heterojunction realize a synergistic confinement-adsorption-catalysis toward polysulfides. As a result, the Li-S batteries with S/ZnTe-O@NC electrodes exhibit an impressive rate capability (639.7 mAh g-1 at 3 C) and cycling performance (70% capacity retention at 1 C over 500 cycles). Even with a high sulfur loading, it still delivers a superior electrochemical performance. This work provides a novel perspective on designing highly catalytic materials to achieve synergistic confinement-adsorption-catalysis for high-performance Li-S batteries.

Unveiling Confinement Engineering for Achieving High-Performance Rechargeable Batteries

The confinement effect, restricting materials within nano/sub-nano spaces, has emerged as an innovative approach for fundamental research in diverse application fields, including chemical engineering, membrane separation, and catalysis. This confinement principle recently presents fresh perspectives on addressing critical challenges in rechargeable batteries. Within spatial confinement, novel microstructures and physiochemical properties have been raised to promote the battery performance. Nevertheless, few clear definitions and specific reviews are available to offer a comprehensive understanding and guide for utilizing the confinement effect in batteries. This review aims to fill this gap by primarily summarizing the categorization of confinement effects across various scales and dimensions within battery systems. Subsequently, the strategic design of confinement environments is proposed to address existing challenges in rechargeable batteries. These solutions involve the manipulation of the physicochemical properties of electrolytes, the regulation of electrochemical activity, and stability of electrodes, and insights into ion transfer mechanisms. Furthermore, specific perspectives are provided to deepen the foundational understanding of the confinement effect for achieving high-performance rechargeable batteries. Overall, this review emphasizes the transformative potential of confinement effects in tailoring the microstructure and physiochemical properties of electrode materials, highlighting their crucial role in designing novel energy storage devices.

Multi-heterostructured MXene/NiS2/Co3S4 with S-Vacancies to Promote Polysulfide Conversion in Lithium-Sulfur Batteries

The severe shuttle effect of polysulfides (LiPSs) and the slow liquid-solid phase conversion are the main obstacles hindering the practical application of lithium-sulfur (Li-S) batteries. Separator modification with a high-activity catalyst can boost LiPSs conversion and suppress their shuttle effect. In this work, multi-heterostructured MXene/NiS2/Co3S4 with rich S-vacancies was constructed facilely with a hydrothermal and high-temperature annealing strategy for separator modification. The MXene sheet not only provides a physical barrier but also ensures a high conductivity and adsorption capacity of the catalyst; the dual active centers of NiS2 and Co3S4 catalyze LiPSs conversion. In addition, the vacancies and heterostructures can modulate the electronic structure of the catalyst, improve its intrinsic activity, and reduce the polysulfides reaction barrier, thus facilitating ion/electron transport and inhibiting the shuttle effect. Benefiting from these advantages, the Li-S battery with MXene/NiS2/Co3S4 modified separator exhibits exciting discharge capacities (1495.4 mAh g-1 at 0.1C and 549.0 mAh g-1 at 6C) and an excellent ultra-long cycle life (average capacity decay rate of 0.026% for 2000 cycles at 2C); at a high sulfur loading of 10.0 mg cm-2, the battery operates for nearly 80 cycles at 0.2C, giving a capacity retention rate of 75.76%. This work provides a high-activity catalyst for Li-S batteries.

MoP quantum dots based multifunctional efficient electrocatalyst for stable and long-life flexible lithium-sulfur batteries

The commercialization of lithium-sulfur (Li-S) batteries is challenging, owing to factors like the poor conductivity of S, the 'shuttle effect', and the slow reaction kinetics. To address these challenges, MoP quantum dots were decorated on hollow carbon spheres (MoPQDs/C) in this study and used as an efficient lithium polysulfides (LiPSs) adsorbents and catalysts. In this approach polysulfides are effectively trapped through strong chemisorption and physical adsorption while simultaneously facilitating LiPSs conversion by enhancing the reaction kinetics. MXene serves as a flexible physical barrier (MoPQDs/C@MXene), further enhancing the confinement of LiPSs. Moreover, both materials are conductive, significantly facilitating electron and charge transfer. Additionally, the flexible MoPQDs/C@MXene-S electrode offers a large specific surface area for sulfur loading and withstand volume expansion during electrochemical processes. As a result, the MoPQDs/C@MXene-S electrode exhibits excellent long-term cyclability and maintains a robust specific capacity of 992 mA h g-1 even after 800cycles at a rate of 1.0C (1C = 1675 mA g-1), with a minimal capacity decay rate of 0.034 % per cycle. This work proposes an efficient strategy to fabricate highly efficient electrocatalysts for advanced Li-S batteries.

Rechargeable Metal-Sulfur Batteries: Key Materials to Mechanisms

Rechargeable metal-sulfur batteries are considered promising candidates for energy storage due to their high energy density along with high natural abundance and low cost of raw materials. However, they could not yet be practically implemented due to several key challenges: (i) poor conductivity of sulfur and the discharge product metal sulfide, causing sluggish redox kinetics, (ii) polysulfide shuttling, and (iii) parasitic side reactions between the electrolyte and the metal anode. To overcome these obstacles, numerous strategies have been explored, including modifications to the cathode, anode, electrolyte, and binder. In this review, the fundamental principles and challenges of metal-sulfur batteries are first discussed. Second, the latest research on metal-sulfur batteries is presented and discussed, covering their material design, synthesis methods, and electrochemical performances. Third, emerging advanced characterization techniques that reveal the working mechanisms of metal-sulfur batteries are highlighted. Finally, the possible future research directions for the practical applications of metal-sulfur batteries are discussed. This comprehensive review aims to provide experimental strategies and theoretical guidance for designing and understanding the intricacies of metal-sulfur batteries; thus, it can illuminate promising pathways for progressing high-energy-density metal-sulfur battery systems.

Chlorine bridge bond-enabled binuclear copper complex for electrocatalyzing lithium-sulfur reactions

Engineering atom-scale sites are crucial to the mitigation of polysulfide shuttle, promotion of sulfur redox, and regulation of lithium deposition in lithium-sulfur batteries. Herein, a homonuclear copper dual-atom catalyst with a proximal distance of 3.5 Å is developed for lithium-sulfur batteries, wherein two adjacent copper atoms are linked by a pair of symmetrical chlorine bridge bonds. Benefiting from the proximal copper atoms and their unique coordination, the copper dual-atom catalyst with the increased active interface concentration synchronously guide the evolutions of sulfur and lithium species. Such a delicate design breaks through the activity limitation of mononuclear metal center and represents a catalyst concept for lithium-sulfur battery realm. Therefore, a remarkable areal capacity of 7.8 mA h cm-2 is achieved under the scenario of sulfur content of 60 wt.%, mass loading of 7.7 mg cm-2 and electrolyte dosage of 4.8 μL mg-1.

Surface-coated AlF3 nanolayers enable polysulfide confinement within biomass-derived nitrogen-doped hierarchical porous carbon microspheres for improved lithium-sulfur batteries

The electrically insulating and volumetric deformation of sulfur and the shuttle effect of the intermediate lithium polysulfide (LiPSs) have severely hindered the development of lithium-sulfur batteries (LSBs). Herein, a synergistic strategy of hierarchical porous nitrogen-doped carbon microspheres (PNCM) derived from low-cost biomass with surface-coated AlF3 nanolayer as a multifunctional sulfur host (denoted as PNCM@S@AlF3) was developed. The PNCM not only possesses an abundant pore structure, large surface area, and high electrical conductivity but also features an intrinsic N-doped and fluorinated framework, which effectively enhances the physical adsorption and chemical anchoring to LiPSs. In addition, the AlF3 nanolayer protects the open surface of the porous carbon to isolate sulfur species from the electrolyte to reduce irreversible losses while accelerating the redox kinetics of LiPSs through strong polar adsorption and bonding. Hence, the PNCM@S@AlF3 cathode exhibits an initial capacity as high as 1176.2 mAh/g at 0.2C, and the cycling stability and rate capability are superior to that of PNCM@S without AlF3 coating. Impressively, the PNCM@S@AlF3 cathode delivers stable long-term cycling performance at a high rate of 2C, with 95.6% capacity retention after 500 cycles. This work presents a facile, sustainable, and efficient synergistic strategy for developing advanced LSBs.

Hyphae Carbon Coupled with Gel Composite Assembly for Construction of Advanced Carbon/Sulfur Cathodes for Lithium-Sulfur Batteries

The design and fabrication of novel carbon hosts with high conductivity, accelerated electrochemical catalytic activities, and superior physical/chemical confinement on sulfur and its reaction intermediates polysulfides are essential for the construction of high-performance C/S cathodes for lithium-sulfur batteries (LSBs). In this work, a novel biofermentation coupled gel composite assembly technology is developed to prepare cross-linked carbon composite hosts consisting of conductive Rhizopus hyphae carbon fiber (RHCF) skeleton and lamellar sodium alginate carbon (SAC) uniformly implanted with polarized nanoparticles (V2O3, Ag, Co, etc.) with diameters of several nanometers. Impressively, the RHCF/SAC/V2O3 composites exhibit enhanced physical/chemical adsorption of polysulfides due to the synergistic effect between hierarchical pore structures, heteroatoms (N, P) doping, and polar V2O3 generation. Additionally, the catalytic conversion kinetics of cathodes are effectively improved by regulating the 3D carbon structure and optimizing the V2O3 catalyst. Consequently, the LSBs assembled with RHCF/SAC/V2O3-S cathode show exceptional cycle stability (capacity retention rate of 94.0% after 200 cycles at 0.1 C) and excellent rate performance (specific capacity of 578 mA h g-1 at 5 C). This work opens a new door for the fabrication of hyphae carbon composites via fermentation for electrochemical energy storage.

Cement/Sulfur for Lithium-Sulfur Cells

Lithium-sulfur batteries represent a promising class of next-generation rechargeable energy storage technologies, primarily because of their high-capacity sulfur cathode, reversible battery chemistry, low toxicity, and cost-effectiveness. However, they lack a tailored cell material and configuration for enhancing their high electrochemical utilization and stability. This study introduces a cross-disciplinary concept involving cost-efficient cement and sulfur to prepare a cement/sulfur energy storage material. Although cement has low conductivity and porosity, our findings demonstrate that its robust polysulfide adsorption capability is beneficial in the design of a cathode composite. The cathode composite attains enhanced cell fabrication parameters, featuring a high sulfur content and loading of 80 wt% and 6.4 mg cm-2, respectively. The resulting cell with the cement/sulfur cathode composite exhibits high active-material retention and utilization, resulting in a high charge storage capacity of 1189 mA∙h g-1, high rate performance across C/20 to C/3 rates, and an extended lifespan of 200 cycles. These attributes contribute to excellent cell performance values, demonstrating areal capacities ranging from 4.59 to 7.61 mA∙h cm-2, an energy density spanning 9.63 to 15.98 mW∙h cm-2, and gravimetric capacities between 573 and 951 mA∙h g-1 per electrode. Therefore, this study pioneers a new approach in lithium-sulfur battery research, opting for a nonporous material with robust polysulfide adsorption capabilities, namely cement. It effectively showcases the potential of the resulting cement/sulfur cathode composite to enhance fabrication feasibility, cell fabrication parameters, and cell performance values.

Accelerating Sulfur Redox Chemistry by Atomically Dispersed Zn-N4 Sites Coupled with Pyridine-N Defects on Porous Carbon Sheets

Single-atom catalysts (SACs) with specific N-coordinated configurations immobilized on the carbon substrates have recently been verified to effectively alleviate the shuttle effect of lithium polysulfides (LiPSs) in lithium-sulfur (Li─S) batteries. Herein, a versatile molten salt (KCl/ZnCl2 )-mediated pyrolysis strategy is demonstrated to fabricate Zn SACs composed of well-defined Zn-N4 sites embedded into porous carbon sheets with rich pyridine-N defects (Zn─N/CS). The electrochemical kinetic analysis and theoretical calculations reveal the critical roles of Zn-N4 active sites and surrounding pyridine-N defects in enhancing adsorption toward LiPS intermediates and catalyzing their liquid-solid conversion. It is confirmed by reducing the overpotential of the rate-determining step of Li2 S2 to Li2 S and the energy barrier for Li2 S decomposition, thus the Zn─N/CS guarantees fast redox kinetics between LiPSs and Li2 S products. As a proof of concept demonstration, the assembled Li─S batteries with the Zn─N/CS-based sulfur cathode deliver a high specific capacity of 1132 mAh g-1 at 0.1 C and remarkable capacity retention of 72.2% over 800 cycles at 2 C. Furthermore, a considerable areal capacity of 6.14 mAh cm-2 at 0.2 C can still be released with a high sulfur loading of 7.0 mg cm-2 , highlighting the practical applications of the as-obtained Zn─N/CS cathode in Li─S batteries.

Constructing Cooperative Interface via Bi-Functional COF for Facilitating the Sulfur Conversion and Li+ Dynamics

Lithium-sulfur (Li-S) batteries stand out for their high theoretical specific capacity and cost-effectiveness. However, the practical implementation of Li-S batteries is hindered by issues such as the shuttle effect, tardy redox kinetics, and dendrite growth. Herein, an appealingly designed covalent organic framework (COF) with bi-functional active sites of cyanide groups and polysulfide chains (COF-CN-S) is developed as cooperative functional promoters to simultaneously address dendrites and shuttle effect issues. Combining in situ techniques and theoretical calculations, it can be demonstrated that the unique chemical architecture of COF-CN-S is capable of performing the following functions: 1) The COF-CN-S delivers significantly enhanced Li+ transport capability due to abundant ion-hopping sites (cyano-groups); 2) it functions as a selective ion sieve by regulating the dynamic behavior of polysulfide anions and Li+ , thus inhibiting shuttle effect and dendrite growth; 3) by acting as a redox mediator, the COF-CN-S can effectively control the electrochemical behavior of polysulfides and enhance their conversion kinetics. Based on the above advantages, the COF-CN-S endows Li-S batteries with excellent performance. This study highlights the significance of interface modification and offers novel insights into the rational design of organic materials in the Li-S realm.

Co/Mon Invigorated Bilateral Kinetics Modulation for Advanced Lithium-Sulfur Batteries

Sluggish sulfur redox kinetics and Li-dendrite growth are the main bottlenecks for lithium-sulfur (Li-S) batteries. Separator modification serves as a dual-purpose approach to address both of these challenges. In this study, the Co/MoN composite is rationally designed and applied as the modifier to modulate the electrochemical kinetics on both sides of the sulfur cathode and lithium anode. Benefiting from its adsorption-catalysis function, the decorated separators (Co/MoN@PP) not only effectively inhibit polysulfides (LiPSs) shuttle and accelerate their electrochemical conversion but also boost Li+ flux, realizing uniform Li plating/stripping. The accelerated LiPSs conversion kinetics and excellent sulfur redox reversibility triggered by Co/MoN modified separators are evidenced by performance, in-situ Raman detection and theoretical calculations. The batteries with Co/MoN@PP achieve a high initial discharge capacity of 1570 mAh g-1 at 0.2 C with a low decay rate of 0.39%, uniform Li+ transportation at 1 mA cm-2 over 800 h. Moreover, the areal capacity of 4.62 mAh cm-2 is achieved under high mass loadings of 4.92 mg cm-2 . This study provides a feasible strategy for the rational utilization of the synergistic effect of composite with multifunctional microdomains to solve the problems of Li anode and S cathode toward long-cycling Li-S batteries.

Carbon Nanotube-encapsulated Chestnut Inner Shell O,N-doped Graded Porous Carbon as Stable and High-Sulfur Loading Electrode for Lithium-Sulfur Batteries

The shuttle effect of lithium-sulfur (Li-S) batteries and the poor conductivity of sulfur (S) and lithium polysulfide severely limit their practical applications. Currently, compounding carbon materials with S is one of the effective ways to solve this problem. Therefore, green, low-cost chestnut inner shell biochar (CISC) with graded porous structure was used as the S carrier in this experiment, and carbon nanotubes (CNTs) coating was employed as the S protective layer to improve the electrical conductivity and inhibit the shuttle effect. The results showed that the CISC prepared in this experiment had a relatively high specific surface area (1135.11 m2  g-1 ), and the S loading rate was as high as 65.72 %. The graded porous structure and high specific surface area of CISC can increase the loading rate of S and thus increase the battery capacity. Meanwhile, the naturally contained O and N elements can improve the chemisorption of S. The initial discharge capacity of the CISC@S/CNTs battery at 0.1 C is 967.3 mAh g-1 , and the capacity retention rate is 74.3 % after 500 cycles. The unique composite structure improves the battery's electrical conductivity, reduces the dissolution of polysulfides, and enhances the battery cycle stability.

Synergizing Spatial Confinement and Dual-Metal Catalysis to Boost Sulfur Kinetics in Lithium-Sulfur Batteries

Sluggish kinetics and parasitic shuttling reactions severely impede lithium-sulfur (Li-S) battery operation; resolving these issues can enhance the capacity retention and cyclability of Li-S cells. Therefore, an effective strategy featuring core-shell-structured Co/Ni bimetal-doped metal-organic framework (MOF)/sulfur nanoparticles is reported herein for addressing these problems; this approach offers unprecedented spatial confinement and abundant catalytic sites by encapsulating sulfur within an ordered architecture. The protective shells exhibit long-term stability, ion screening, high lithium-polysulfide adsorption capability, and decent multistep catalytic conversion. Additionally, the delocalized electrons of the MOF endow the cathodes with superior electron/lithium-ion transfer ability. Via multiple physicochemical and theoretical analysis, the resulting synergistic interactions are proved to significantly promote interfacial charge-transfer kinetics, facilitate sulfur conversion dynamics, and inhibit shuttling. The assembled Li-S batteries deliver a stable, highly reversible capacity with marginal decay (0.075% per cycle) for 400 cycles at 0.2 C, a pouch-cell areal capacity of 3.8 mAh cm-2 for 200 cycles under a high sulfur loading, as well as remarkably improved pouch-cell performance.

MoO2/t-C3N4 Heterogeneous Materials with Bidirectional Catalysis for the Rapid Conversion of S Species in Li-S Batteries

Li-S batteries have drawn a lot of attention for their high theoretical specific capacity and significant economic benefits. However, the shuttle effect of polysulfides prevents them from being used widely. To tackle this difficulty, a heterogeneous structure based on tubular carbon nitride with evenly dispersed molybdenum dioxide nanoparticles (MoO2/t-C3N4) as the S host is constructed in this work. As a polar material with a large specific surface area, MoO2/t-C3N4 has a strong anchoring effect on polysulfide. Additionally, the heterogeneous material has excellent bidirectional catalytic ability for the redox process of S species based on the action of the built-in electric field formed by electron directional transfer. Not only does it improve the reaction kinetics of the redox process of the polysulfides but it also prevents polysulfides from accumulating on the surface of the modified material and deactivating it, further improving the utilization of the active material. Thus, MoO2/t-C3N4/S shows the high initial-discharge specific capacity of 812.7 mAh g-1 at the current density of 5C, and the Coulombic efficiency is maintained at more than 95% after 400 charge/discharge cycles. Moreover, MoO2/t-C3N4/S achieved a capacity retention of 89% after 100 cycles at the current density of 0.1C under the high S loading. Therefore, the research results of this work provide a trustworthy reference for the future commercial application of Li-S batteries.

Establishing Transition Metal Phosphides as Effective Sulfur Hosts in Lithium-Sulfur Batteries through the Triple Effect of "Confinement-Adsorption-Catalysis"

Structurally optimized transition metal phosphides are identified as a promising avenue for the commercialization of lithium-sulfur (Li-S) batteries. In this study, a CoP nanoparticle-doped hollow ordered mesoporous carbon sphere (CoP-OMCS) is developed as a S host with a "Confinement-Adsorption-Catalysis" triple effect for Li-S batteries. The Li-S batteries with CoP-OMCS/S cathode demonstrate excellent performance, delivering a discharge capacity of 1148 mAh g-1 at 0.5 C and good cycling stability with a low long-cycle capacity decay rate of 0.059% per cycle. Even at a high current density of 2 C after 200 cycles, a high specific discharge capacity of 524 mAh g-1 is maintained. Moreover, a reversible areal capacity of 6.56 mAh cm-2 is achieved after 100 cycles at 0.2 C, despite a high S loading of 6.8 mg cm-2 . Density functional theory (DFT) calculations show that CoP exhibits enhanced adsorption capacity for sulfur-containing substances. Additionally, the optimized electronic structure of CoP significantly reduces the energy barrier during the conversion of Li2 S4 (L) to Li2 S2 (S). In summary, this work provides a promising approach to optimize transition metal phosphide materials structurally and design cathodes for Li-S batteries.