Sulfur Cathode Research Articles

Rational design of bidirectional electrocatalysts and accelerated sulfur redox reactions in lithium-sulfur batteries

Lithium–sulfur (Li–S) batteries have emerged as one of the most promising energy storage solutions. However, its commercial application still faces a significant challenge: the sluggish redox reaction kinetics of the reversible lithium polysulfide (LiPS) conversion process. The strategic design of cathode structures and electrocatalysts can help accelerate polysulfide conversion. In this study, systematic density functional theory (DFT) calculations predict that the incorporation of platinum (Pt) nanoparticles, as a model electrocatalyst, into biomass carbon materials can effectively promote the bidirectional conversion of polysulfides. Detailed kinetic analyses reveal that Pt-doped biomass carbon materials possess exceptional electrocatalytic abilities for Li2S nucleation and dissociation. These findings are further elucidated by ex situ X–ray photoelectron spectroscopy measurements, elucidating the bidirectional mechanism of Pt. The sulfur cathode delivers a remarkable specific discharge capacity of 1386.9 mAh g–1 at 0.1 C. Even more impressive is its potential for practical applications, exemplified by a high initial capacity of 1218.7/1015.3 mAh g−1 and excellent cycling stability under a high sulfur loading of 4.5/7.5 mg cm−2, which achieved substantial capacity retention (83.9/81.1%) after 100 cycles. This bidirectional electrocatalysis, achieved through the synergy of metal with biomass carbon materials, presents an attractive approach for advancing Li–S systems.

Tuning of d-p band centers with M-A (M = Co, Ni, Cu; A = N, P, O, Se) co-doped FeS2 for enhanced Li-S redox chemistry

The sulfur host material has both excellent conductivity and catalytic performance, which is the key to highly efficient Li-S redox chemistry in lithium‑sulfur batteries (LSBs). FeS2, as the sulfur cathode host, shows high theoretical specific capacity. However, FeS2 is still insufficient in accelerating the kinetics of lithium polysulfide (LiPS) transformation and inhibiting the shuttle effect. Using first-principles calculations, we explore the physicochemical properties of M-A (M = Co, Ni, Cu; A = N, P, O, Se) co-doped FeS2, including the formation energy, conductivity, Li+ diffusion, chemical adsorption, catalytic performance and Li2S decomposition. Co-A (A = O, P) co-doped FeS2 shows lower formation energy and lattice distortion compared to other co-doping elements. Fe0.875Co0.125O0.125S1.875 has high electronic conductivity and low Li+ diffusion barrier, followed by Fe0.875Co0.125P0.125S1.875. Fe0.875Co0.125P0.125S1.875 (001) shows great potential in accelerating the kinetics of LiPS conversion and suppressing shuttle effects due to low Δɛ↓(d–p) band center. Fe0.875Co0.125A0.125S1.875(001) is favorable for the Li2S decomposition. Overall, Fe0.875Co0.125P0.125S1.875 as sulfur cathode host has potential application value in promoting Li-S redox chemistry. This work deepens the understanding of the co-doping strategy and provides theoretical guidance for the design and development of the sulfur cathode host to improve the Li-S redox chemistry in LSBs.

Phosphorous-Based Heterostructure for the Effective Catalysis of Polysulfide Reactions with Phase Changes in High-Sulfur-Loading Lithium-Sulfur Batteries.

High sulfur loading and long cycle life are the design targets of commercializable lithium-sulfur (Li-S) batteries. The sulfur electrochemical reactions from Li2 S4 to Li2 S, which account for 75% of the battery's theoretical capacity, involve liquid-to-solid and solid-to-solid phase changes in all Li-S battery electrolytes in use today. These are kinetically hindered processes that are exacerbated by a high sulfur loading. In this study, it is observed that an in situ grown bimetallic phosphide/black phosphorus (NiCoP/BP) heterostructure can effectively catalyze the Li2 S4 to Li2 S reactions to increase the sulfur utilization at high sulfur loadings. The NiCoP/BP heterostructure is a good polysulfide adsorber, and the electric field prevailing at the Mott-Schottky junction of the heterostructure can facilitate charge transfer in the Li2 S4 to Li2 S2 liquid-to-solid reaction and Li+ diffusion in the Li2 S2 to Li2 S solid-state reaction. Consequently, a sulfur cathode with the NiCoP/BP catalyst can deliver a specific capacity of 830 mAh g-1 at the sulfur loading of 6mg cm-2 for 500 cycles at the 0.5 C rate. High sulfur utilization is also possible at a higher sulfur loading of 8mg cm-2 for 440 cycles at the 1 C rate.

Remarkable chemical adsorption and catalysis of monodisperse metallic cobalt sulfide nanoparticles enable long-cycling Li–S battery with high areal capacity and low shuttle constant

High-energy density lithium-sulfur battery is considered as one of the most potential new-generation energy-storage technologies. Nevertheless, the capacity decays rapidly due to severe volumetric change of sulfur, dissolution and slow redox kinetics of intermediate polysulfides, and instability of lithium anode. Herein, a novel highly conductive porous sulfur cathode host composed of graphene aerogel and polar Co9S8 nanoparticle is designed to address these obstacles. The porous conductive framework not only provides channels for rapid conduction of electron and lithium ion, but also provides adequate space to physically confine the lithium polysulfides and accommodate the volume expansion. Both experimental and theoretical calculations demonstrate that the in-situ uniformly deposited Co9S8 nanoparticles can effectively bind polar lithium polysulfides and catalyze their interconversion, and the shuttle effect is therefore effectively suppressed. The Co9S8-GA/S cathode exhibits high specific discharge capacity (1219.1 mAh g−1) and high areal specific capacity (14.3 mAh m−2) at 0.1 C, low shuttle constant (0.15 h−1), excellent rate performance (625.6 mAh g−1/7.4 mAh m−2 at 5 C), outstanding long cyclic stability (low decay of 0.024 %/cycle during 1000 cycles at 2 C). This study demonstrates a promising aerogel strategy to design high-performance composite cathode for lithium-sulfur battery.

Bifunctional Additive for Lithium-Sulfur Batteries Based on the Metal-Phthalocyanine Complex.

With extremely high specific capacity and high energy density, lithium-sulfur batteries (LSBs) have attracted enormous interest as promising candidates for energy storage devices. However, several problems, such as the shuttle effect and sluggish redox kinetics, hinder the successful realization of LSBs on an industrial scale. Therefore, designing an efficient electrode material to inhibit the shuttle effect and improve the reaction kinetics of polysulfides (LiPS) is of utmost significance. Herein, a bifunctional additive with excellent polysulfide adsorption and superior catalytic behavior is developed using the phthalocyanine-tetrasulfonic acid nickel complex tetrasodium salt (Ni-PCTs) additive. Ni-PCTs provide effective trapping of LiPS due to their abundant sulfonic acid groups. Moreover, Ni-PCTs exhibit effective catalytic conversion of LiPS due to the presence of N atoms in the phthalocyanine ring as well as the central Ni atoms. Consequently, the as-assembled LSBs, with a 10 wt % Ni-PCTs additive, exhibit a significant increase in specific capacities, such as the high initial specific capacity of 1283 mA h g-1 at 0.15 mA/cm2 and a stable specific capacity of 623 mA h g-1 after 400 cycles. The current study demonstrates the promise of metal phthalocyanines for sulfur cathodes, opening up avenues for further research and development of LSBs.

Platinum Electrocatalyst Promoting Redox Kinetics of Li2S and Regulating Li2S Nucleation for Lithium-Sulfur Batteries.

The development of lithium-sulfur batteries (LSBs) is impeded by the shuttle effect of polysulfides (LiPSs) and the sluggish nucleation of Li2S. To address these challenges, incorporating electrocatalysts into sulfur host materials represents an effective strategy for promoting polysulfide conversion, in tandem with the rational design of multifunctional sulfur host materials. In this study, Pt nanoparticles are integrated into biomass-derived carbon materials by solution deposition method. Pt, as an electrocatalyst, not only enhances the electrical conductivity of sulfur cathodes and effectively immobilizes LiPSs but also catalyzes the redox reactions of sulfur species bidirectionally. Additionally, Pt helps regulate the 3D deposition and growth of Li2S while reducing the reaction energy barrier. Consequently, this accelerates the conversion of LiPSs in LSBs. Furthermore, the catalytic ability of Pt for the redox reactions of sulfur species, along with its influence on the 3D deposition and growth of Li2S, is elucidated using electrochemical kinetic analyses and classical models of electrochemical deposition. The cathodes exhibit a high initial specific capacity of 1019.1mAhg-1 at 1C and a low decay rate of 0.045% over 1500 cycles. This study presents an effective strategy to regulate Li2S nucleation and enhance the kinetics of polysulfide conversion in LSBs.

Chemical and spatial dual-confinement engineering for stable Na-S batteries with approximately 100% capacity retention.

Sodium-sulfur (Na-S) batteries are attracting intensive attention due to the merits like high energy and low cost, while the poor stability of sulfur cathode limits the further development. Here, we report a chemical and spatial dual-confinement approach to improve the stability of Na-S batteries. It refers to covalently bond sulfur to carbon at forms of C-S/N-C=S bonds with high strength for locking sulfur. Meanwhile, sulfur is examined to be S1-S2 small species produced by thermally cutting S8 large molecules followed by sealing in the confined pores of carbon materials. Hence, the sulfur cathode achieves a good stability of maintaining a high-capacity retention of 97.64% after 1000 cycles. Experimental and theoretical results show that Na+ is hosted via a coordination structure (N···Na···S) without breaking the C-S bond, thus impeding the formation and dissolution of sodium polysulfide to ensure a good cycling stability. This work provides a promising method for addressing the S-triggered stability problem of Na-S batteries and other S-based batteries.

Chemically tuned nitrogen-doped sulfur host for a reversible and stable room-temperature sodium-sulfur batteries

The fast transition of long-chain polysulfide to short-chain polysulfide causes a sharp decay in the performance of room-temperature sodium sulfur (RT-Na/S) batteries. The nitrogen-doped sulfur host is identified as effective in slowing the transition process by entrapping the sodium polysulfide. However, precise control over the amount of nitrogen remained a challenge. We report a chemical route to fine-tune nitrogen doping in the sulfur host. The nitrogen content in the sulfur host is identified to vary from 7 to 19 at. % by varying the reaction time from 4 to 12 h. The optimized reaction time of about 8 h results in the highest pyridinic and pyrrolic nitrogen content. In addition to nitrogen doping, the sulfur host with a hierarchical pore structure could be achieved with 8 h of reaction time. The as-developed sulfur host serves as a sulfur cathode and is used to fabricate an RT-Na/S battery. The cell could function stably for over 500 cycles at 1C, with a high Coulombic efficiency of ~99.5 % and a capacity decay of 0.28 mAh g−1 per cycle at 1C. The cell could function reversibly and stably at various C-rates (0.2C – 2C). This study paves a path for the researcher to revisit the design of the sulfur host to construct a stable cathode for RT-Na/S batteries.

An Electron/Ion Dual Conductive Integrated Cathode Using Cationic/Anionic Redox for High‐Energy‐Density All‐Solid‐State Lithium‐Sulfur Batteries

AbstractAll‐solid‐state lithium‐sulfur batteries (ASSLSB), composed of sulfur cathode and lithium metal anode with high theoretical capacity, have a potentially higher energy density by weight than a typical lithium‐ion battery (LIB). However, due to insulating sulfur, a relatively large proportion of electronic (carbon) and ionic (solid electrolyte) conductors are mixed for cathode fabrication, leading to inferior practical capacity. Herein, we report a novel integrated cathode Li2S‐LiI‐MoS2 which has relatively high electronic and ionic conductivities (the order of 10−4 S cm−1) without any carbon and solid electrolyte. The ASSLSB with integrated Li2S‐LiI‐MoS2 cathode delivers a remarkably high energy density of 1020 Wh kg−1 at the cathode level at room temperature. By applying precise X‐ray diffraction, pair distribution function analysis and X‐ray computed tomography, it is found that the formation of an ionic conducting phase composed mainly of LiI during discharge is responsible for the high rate capability. Furthermore, X‐ray absorption fine structure (XAFS) has also revealed the charge compensation mechanism and ascertained the involvement of both Mo 3d and S 3p orbitals during the charging and discharging process. It is believed the strategy will pave the way for developing high practical energy density at room temperature for all‐solid‐state batteries.

Freeze-Drying-Assisted ZIF-67 Template-Derived Co@NCS Porous Composite as Sulfur Cathode Host for Improved Li-S Battery Performance: Deconvolution of Diffusive and Capacitive Li+ Storage.

A zeolitic imidazole framework (ZIF-67) template-derived cobalt@nitrogen-doped carbon-sulfur composite (ZIF-Co@NCS) was synthesized using a freeze-drying method and explored for lithium-sulfur (Li-S) batteries. Material characterizations confirmed the formation of the ZIF-Co@NCS composite. To fabricate the Li-S battery in a coin-type CR-2032 cell, the as-synthesized ZIF-Co@NCS composite having a sulfur content of ∼65% was used as a cathode material and coupled with a lithium metal anode. This battery demonstrated exceptional cycling stability over 600 charge-discharge cycles with a steady capacity of 550 mAh g-1 at 0.05 C-rate. The good electrochemical performance of the cathode was ascribed to the nanofeatures associated with the freeze-dried porous carbon structure, which offered enough space for the sulfur cathode. The enhanced trapping of polysulfide facilitated by the presence of the Co-N sites in the ZIF-Co@NCS composite led to excellent cycling stability. The derived cathode composite showed a high specific capacity, outstanding rate capability, and excellent cyclic stability rendering it a promising candidate for high-performance Li-S batteries. Detailed Li+ ion charge storage examined by means of Dunn's method revealed a significant capacitive mode of charge storage both at peak currents and nonpeak currents. The post-mortem analysis of the cycled cathode using X-ray diffraction and scanning electron microscopy at different depth-of-discharge (DOD) values revealed the stepwise formation of discharge products.

Double-shelled ZnS@CoS2 nanocages with heterojunctions for high performance cathodes in lithium−sulfur batteries

The intelligent design of electrocatalytic sulfur host materials is an essential step to achieving high-performance lithium−sulfur (LiS) batteries. Herein, we report double-shelled ZnS@CoS2 nanocages as sulfur hosts to electrocatalytically enhance sulfur cathode kinetics and suppress the shuttle effect of polysulfides. Combining theoretical calculations and experimental tests, we reveal that the built-in electric field formed at the ZnS@CoS2 heterojunction is uniquely suited to promoting sulfur cathode electrochemistry; the double-shelled ZnS@CoS2 nanocages facilitate Li+ transport while at the same time enabling the immobilization and rapid electrocatalytic conversion of key polysulfides. Consequently, LiS cells prepared from ZnS@CoS2 as sulfur host exhibit a high specific capacity (e.g., 1443 mA h g−1 at the current rate of 0.1 C) and an impressive cycling stability (e.g., an initial specific capacity of 801 mA h g−1 achieved at 2 C and 507 mA h g−1 retained after 650 cycles). Our new concept of designing a heterojunction to promote sulfur cathodic reactions can be potentially extended to other contemporary energy-storage systems.

Graphene‐Based Sulfur Cathodes and Dual Salt‐Based Sparingly Solvating Electrolytes: A Perfect Marriage for High Performing, Safe, and Long Cycle Life Lithium‐Sulfur Prototype Batteries

AbstractThe growing requirements for electrified applications entail exploring alternative battery systems. Lithium‐sulfur batteries (LSBs) have emerged as a promising, cost‐effective, and sustainable solution; however, their practical commercialization is impeded by several intrinsic challenges. With the aim of surpassing these challenges, the implementation of a holistic LSB concept is proposed. To this end, the effectiveness of coupling a high‐performing 2D graphene‐based sulfur cathode with a well‐suited sparingly solvating electrolyte (SSE) is reported. The incorporation of bis(fluorosulfonyl)imide (LiFSI) salt to tune sulfolane and 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropylether based SSE enables the formation of a robust and compact lithium fluoride‐rich solid electrolyte interphase. Consequently, the lithium compatibility is improved, achieving a high Coulombic efficiency (CE) of 98.8% in the Li||Cu cells and enabling thin and dense lithium depositions. When combined with a high‐performing 2D graphene‐based sulfur cathode, a symbiotic effect is shown, leading to high discharge capacities, remarkable rate capability (2.5 mAh cm−2 at C/2), enhanced cell stability, and wide temperature applicability. Furthermore, the scalability of this strategy is successfully demonstrated by assembling high‐performing monolayer prototype cells with a total capacity of 93 mAh, notable capacity retention of 70% after 100 cycles, and a high average CE of 99%.

Sustainable Dual‐Layered Interface for Long‐Lasting Stabilization of Lithium Metal Anodes

AbstractLithium metal anodes (LMAs) offer substantial promise for high‐energy‐density rechargeable batteries, but managing the complex electrolyte–anode interface is a challenge. Herein, a sustainable dual‐layered interface (SDI) protected Li anode is developed using a joint electrospinning‐rolling technique. In this SDI, polyacrylonitrile (PAN) nanofibers normalize Li‐ion flux across the bulk electrolyte and mitigate electrode volume expansion. More significantly, the continuous release of lithiophilic metal ions aids in constructing alloy interphase in situ, which facilitates Li‐ion transport and uniform lithium deposition. With the dynamic protection of SDI films, cracks in the alloy layer can be promptly repaired during cycling, ensuring efficient control of the electrolyte–anode interface and prolonged stabilization of LMAs. As validation, using a PAN/SnCl2 film as an SDI prototype, the symmetric cells achieve ultra‐long cycling of 5200 h (≈7 months) at 5 mA cm−2 and 5 mAh cm−2. When paired with a sulfur cathode (in ether electrolyte) or a LiNi0.8Co0.1Mn0.1O2 cathode (in ester electrolyte), the full cells exhibit exceptional stability and rate performance. This sustainable protection strategy for LMAs opens a path to suppress dendrite growth, creating new opportunities for advanced lithium metal batteries.

Unraveling the Coupling Effect between Cathode and Anode toward Practical Lithium-Sulfur Batteries.

The localized reaction heterogeneity of the sulfur cathode and the uneven Li deposition on the Li anode are intractable issues for lithium-sulfur (Li-S) batteries under practical operation. Despite impressive progress in separately optimizing the sulfur cathode or Li anode, a comprehensive understanding of the highly coupled relationship between the cathode and anode is still lacking. In this work, inspired by the Butler-Volmer equation, a binary descriptor (IBD ) assisting the rational structural design of sulfur cathode by simultaneously considering the mass-transport index (Imass ) and the charge-transfer index (Icharge ) is identified, and subsequently the relationship between IBD and the morphological evolution of Li anode is established. Guided by the IBD , a scalable electrode providing interpenetrated flow channels for efficient mass/charge transfer, full utilization of active sulfur, and mechanically elastic support for aggressive electrochemical reactions under practical conditions is reported. These characteristics induce a homogenous distribution of local current densities and reduced reaction heterogeneity on both sides of the cathode and anode. Impressive energy density of 318Wh kg-1 and 473Wh L-1 in an Ah-level pouch cell can be achieved by the design concept. This work offers a promising paradigm for unlocking the interaction between cathode and anode and designing high-energy practical Li-S batteries.

Two-Step Catalytic Against Polysulfide Shuttling to Enhance Redox Conversion for Advanced Lithium-Sulfur Batteries.

The development of lithium-sulfur batteries is seriously hindered by the shuttle effect of lithium polysulfides (LiPSs) and the low electrical conductivity of sulfur. To solve these problems, efficient catalysts can be used to improve the conversion rate of LiPSs and the conductivity of sulfur cathode. Herein, annealed melamine foam supported MoSe2 (NCF@MoSe2) is used as interlayer and the MoSe2/MoP heterojunction obtained by phosphating MoSe2 is further used as the catalyst material for metal fusion with a sulfur element. The interlayer can not only improve the electrical conductivity and effectively adsorb and catalyze LiPSs, but more importantly, the MoSe2/MoP heterojunction can also effectively adsorb and catalyze LiPSs, so that the batteries have a dual inhibition shuttling effect strategy. Furthermore, the rapid anchor-diffusion transition of LiPSs, and the suppression of shuttling effects by catalyst materials are elucidated using theoretical calculations and in situ Raman spectroscopy. The two-step catalytic strategy exhibits a high reversibility of 983mAhg-1 after 200 cycles at 0.5C and a high-rate capacity of 889mAhg-1 at 5C. This work provides a feasible solution for the rational design of interlayer and heterojunction materials and is also conducive to the development of more advanced Li-S batteries.

Toward Sustainable Li-S Battery Using Scalable Cathode and Safe Glyme-Based Electrolyte.

The search for safe electrolytes to promote the application of lithium-sulfur (Li-S) batteries may be supported by the investigation of viscous glyme solvents. Hence, electrolytes using nonflammable tetraethylene glycol dimethyl ether added by lowly viscous 1,3-dioxolane (DOL) are herein thoroughly investigated for sustainable Li-S cells. The electrolytes are characterized by low flammability, a thermal stability of ∼200 °C, ionic conductivity exceeding 10-3 S cm-1 at 25 °C, a Li+ transference number of ∼0.5, electrochemical stability window from 0 to ∼4.4 V vs Li+/Li, and a Li stripping-deposition overpotential of ∼0.02 V. The progressive increase of the DOL content from 5 to 15 wt % raises the activation energy for Li+ motion, lowers the transference number, slightly limits the anodic stability, and decreases the Li/electrolyte resistance. The electrolytes are used in Li-S cells with a composite consisting of sulfur and multiwalled carbon nanotubes mixed in the 90:10 weight ratio, exploiting an optimized current collector. The cathode is preliminarily studied in terms of structure, thermal behavior, and morphology and exploited in a cell using standard electrolyte. This cell performs over 200 cycles, with sulfur loading increased to 5.2 mg cm-2 and the electrolyte/sulfur (E/S) ratio decreased to 6 μL mg-1. The above sulfur cathode and the glyme-based electrolytes are subsequently combined in safe Li-S batteries, which exhibit cycle life and delivered capacity relevantly influenced by the DOL content within the studied concentration range.

Zwitterionic Covalent Organic Framework Based Electrostatic Field Electrocatalysts for Durable Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are one of the most promising candidates for next-generation energy storage systems. To develop long-life LSBs, there is an urgent need to develop functional materials with higher catalytic activity toward polysulfides and reduced dendritic lithium growth. Herein, an electrostatic field electrocatalyst is designed in a zwitterionic covalent organic framework (COF) with a "two birds with one stone" ability for simultaneously overcoming obstacles in the lithium metal anode and sulfur cathode. The synergism between cationic and anionic moieties in the zwitterionic COF creates an electrostatic field for bidirectionally catalyzing S cathode conversion. Besides, the rational design of zwitterionic COF as a separator modification layer allows lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dissociation and fast lithium-ion conduction, which alleviates lithium dendrite growth and thus improves the cycling life of LSBs. This contribution not only pioneers the application of zwitterionic COF in the field of LSBs but also highlights the potential of electrostatic field electrocatalysts.

Interfacial Engineering and Coupling of MXene/Reduced Graphene Oxide/C3 N4 Aerogel with Optimized d-Band Center as a Free-Standing Sulfur Carrier for High-Performance Li-S Batteries.

To overcome the shuttle effect and improve the energy density of Li-S batteries, developing free-standing sulfur carriers with high capture and catalytic effect towards polysulfides is an effective strategy. Herein, a MXene/reduced graphene oxide/C3 N4 aerogel (MG/C3 N4 ) with three-dimensional architecture prepared through low-temperature hydrothermal approach followed by thermal treatment is used as sulfur carrier for free-standing cathode of Li-S batteries. In the MG/C3 N4 , MXene and rGO construct a highly conductive framework, and the MXene nanosheets offer chemical capture and catalytic activity towards lithium polysulfides, in favor of good cycling stability. The introduction of g-C3 N4 further enhances the reactivity of C-Ti-N at the hetero-interface by engineering the electronic state of Ti atoms, leading to the optimized metal d-band for expediting the multistep conversion of sulfur electrochemistry. Therefore, the free-standing sulfur cathode with MG/C3 N4 carrier achieves excellent performance with a capacity of 1315.6 mAh g-1 at 0.2 C and a capacity retention of 97.5% after 100 cycles as well as superior rate capability with 1167.4 mAh g-1 at 2 C. Even at a high sulfur loading of 4.92mg cm-2 , the cathode remains 940.3 mAh g-1 (4.62 mAh cm-2 ) after 200 cycles, indicating its promising potential for achieving high-performance Li-S batteries.

An examination and prospect of stabilizing Li metal anode in lithium–sulfur batteries: A review of latest progress

AbstractThe Li metal anode emerges as a formidable competitor among anode materials for lithium–sulfur (Li‐S) batteries; nevertheless, safety issues pose a significant hurdle in its path toward commercial viability. This review enumerates three historical challenges inherent to the Li metal anode: unavoidable volume expansion, multifunctional solid electrolyte interface formation, and uncontrollable lithium dendrite growth. In particular, when paired with a sulfur cathode, the Li anode presents an additional unique hurdle: the shuttle effect. To address these issues, this article offers a thorough examination of the latest innovations aimed at stabilizing the Li metal anode within Li‐S batteries. We categorize these approaches into five classifications: liquid electrolyte optimization, enhancement of non‐liquid‐state electrolytes, Li metal surface modification, Li anode architecture design, and Li alloy improvement. For several noteworthy results within these categories, we have compiled their electrochemical performance into tables, facilitating direct comparison. This detailed analysis illuminates feasible strategies and suggests directions warranting further exploration for optimizing the capability and safety of Li metal anodes in Li‐S batteries.

Dual Functionalities of Rb Cation in Lean Electrolyte Lithium Sulfur Batteries

Achieving large discharge capacity and high cycling stability under high sulfur loading and lean electrolyte condition is critical for practical lithium sulfur batteries. However, it is impeded by the large overpotential for lithium sulfide (Li2S) nucleation at the cathode, caused by the sluggish reduction kinetics of lithium polysulfide and the short-circuit triggered by inhomogeneous Li electroplating at the anode. In this study, we report that adding rubidium cation to lean electrolyte in an additive level (0.05 M) can address the two challenges owing to the modifications of the cathode and anode surfaces by the formation of rubidium sulfide. At the sulfur cathode, the rubidium sulfide acts as a catalyst, accelerating the reduction of lithium polysulfides. At the Li metal anode, a rubidium sulfide-enriched inner SEI quickly passivates the surface, suppressing electrolyte decomposition and promoting uniform lithium deposition due to its lithiophilicity. The drop-in-solution leads to impressive results, delivering more than 3 mAh cm−2 over approximately 80 cycles at a sulfur loading of 3.8 mgsulfur cm−2 and an electrolyte to sulfur ratio of 3 μl mg−1.