Development Of Lithium-sulfur Batteries Research Articles

Advanced Li-S Battery Configuration Featuring Sulfur-Coated Separator and Interwoven rGO/CNT Fabric Current Collector.

The development of lithium-sulfur batteries (LSBs) marks a crucial milestone in advancing energy storage solutions essential for sustainable energy transitions. With high theoretical specific capacity, cost-effectiveness, and reduced ecological footprint, LSBs promise to enhance electric vehicle ranges, extend portable electronics' operational times, and stabilize grids integrated with renewable energy. However, challenges like complex processing, electrode instability, and poor cycling stability hinder their commercialization. This study introduces a novel battery design that addresses these issues by coating sulfur directly onto the separator instead of the current collector, demonstrating that active sulfur can be effectively utilized without being incorporated into the electrode structure. Using an interwoven substrate made from carbon nanotube (CNT) fabric adorned with reduced graphene oxide (rGO), this setup enhances manufacturing scalability, supports optimal sulfur utilization, and improves battery performance. The rGO decoration provides multiple highly conductive polysulfide trapping sites, enhancing active material reutilization, while the flexibility and mechanical strength of CNT fabric contribute to electrode integrity. This combination boosts electrical conductivity and polysulfide-capturing capability, effectively managing migrating sulfur species during charge-discharge cycles and mitigating sulfur loss and polysulfide shuttling. The results demonstrate superior cycling stability and efficiency, highlighting the potential of this approach in advancing LSB technology.

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

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

Bimetallic NiCo@C with a Hollow Sea Urchin Structure Enables Li-S Batteries to Hasten the Reaction Kinetics and Effectively Inhibit the Shuttling of Polysulfides.

The "shuttle effect" and several issues related to it are seen as "obstacles" to the study and development of lithium-sulfur batteries (LSBs). This work aims at finding how to fully expose bimetallic sites and quicken the battery reaction kinetics. Here, a bimetallic NiCo-MOF and its derivative NiCo@C with a hollow sea urchin structure are produced. The obtained NiCo@C possesses a micromesoporous structure and fully disclosed bimetallic active sites because of its distinctive structure. The experimental findings demonstrate that fully exposed bimetallic active sites take on chemical adsorbents and collaborate with micromesopores as physical constraints to effectively suppress the "shuttle effect". Furthermore, the hollow sea urchin structure of NiCo@C enables a highly conductive grid, which provides channels to facilitate the movement of solvated Li+. Thanks to these advantages, the NiCo@C-based sulfur cathode offers a high initial discharge specific capacity of 924.41 mAh g-1 at 0.1 C and sustains 390.35 mAh g-1 discharge specific capacity after 100 cycles. The quick transfer of solvated lithium ions (DLi+ = 1.81 × 10-8 cm2 s-1) enables the battery to still contribute a discharge specific capacity of 367.54 mAh g-1 at 1 C. This work provides a new understanding for the structural design of positive electrodes in LSBs.

Mesoporous Carbons Produced from Tannin Biomass for Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) are promising alternatives since sulfur can provide a theoretical specific capacity of 1675 mA h g-1 when combined with lithium [1]. Thus, LSBs can achieve a theoretical energy density (2500 W h kg-1) that is much greater than that of conventional lithium-ion batteries [1]. However, several problems must be resolved to enable commercial production on a large scale, such as the formation of soluble species of lithium polysulfides [2]. Various approaches have been used to minimize this problem, including the development of carbon-based hosts capable of retaining these polysulfides. Among these, the development of cathodes based on carbon‒sulfur composites using carbon from biomass is an alternative that benefits from the possibility of obtaining materials with a modifiable surface area and porosity at low cost [2]. On this basis, this work reports the synthesis of mesoporous carbons (MCs) from tannin biomass, the incorporation of sulfur and the development of lithium-sulfur batteries. The MC sample was produced using the solvent-free method [3] and was named C. The incorporation of sulfur into mesoporous carbons was carried out using melt diffusion methodology [4]. Two quantities of sulfur were added to the carbon host by mass, and the materials were named CS1 and CS2 at ratios of 1:1 and 2:1, respectively, in relation to sulfur:MC. Coin cells (CR 2032) were assembled using the produced materials on the cathode, metallic Li on the anode and the electrolyte 1 M LiTFSI and 1% (w/v) LiNO3 in 1,2-dimethoxyethane/1,3-dioxolane (DME/DOL) and characterized by cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) cycling. The mesoporous carbon C presented a type IV isotherm characteristic of mesoporous materials, with a BET surface area of 539 m2g-1, average pore size of 7.7 nm and total pore volume of 0.747 cm3g-1. There was a decrease in the area and pore volume of the materials after sulfur incorporation, reaching 70 m2g-1 and 0.195 cm3g-1 for CS1 and 3 m2g-1 and 0.012 cm3g-1 for CS2, respectively. The sulfur contents were determined by thermogravimetric analysis (TGA) and were 39% and 61% for CS1 and CS2, respectively. The sulfur contents determined by TGA were close to those obtained by elemental analysis (CHNS), which were 45% and 63% for CS1 and CS2, respectively. The CV data showed that both cells presented cathodic and anodic potentials typical of Li-S batteries. The GCD data show that the cell containing the cathode with the material with a higher elemental sulfur content (CS 2) is stable and maintains specific capacities on the order of 550 mA h g-1 after 45 galvanostatic cycles at different current densities. However, this cell showed a more abrupt decrease in capacity at the highest rates (2C and 4C), Figure 1. Most likely, the higher sulfur content used in this sample did not result in total impregnation of the porous structure, resulting in sulfur deposition on the surface of the particles. As a result, the interparticle contact resistance in the electrodes increases, which limits the performance at higher current demands. For the cell built with the sample containing 39% S (CS1), excellent performance is obtained at high C rates. At 0.1 C, the cathode operates above 900 mA h g-1 in the initial cycles and above 550 mA h g-1 at 0.5 C, and no significant capacity drop is observed between 1 C and 2 C (≈500 mA h g-1). At 4C, a decrease in the specific capacity is noted, but the specific capacity remains above 350 mA h g-1. These results demonstrate the potential of carbon materials obtained from biomass for building high-performance Li-S batteries.Acknowledgments: The authors thank the financial support from the Rota 2030 Program at Fundep – Brazil.

Spontaneous Built-In Electric Field in C3N4-CoSe2 Modified Multifunctional Separator with Accelerating Sulfur Evolution Kinetics and Li Deposition for Lithium-Sulfur Batteries.

The discovery of the heterostructures that is combining two materials with different properties has brought new opportunities for the development of lithium sulfur batteries (LSBs). Here, C3N4-CoSe2 composite is elaborately designed and used as a functional coating on the LSBs separator. The abundant chemisorption sites of C3N4-CoSe2 form chemical bonding with polysulfides, provides suitable adsorption energy for lithium polysulfides (LiPSs). More importantly, the spontaneously formed internal electric field accelerates the charge flow in the C3N4-CoSe2 interface, thus facilitating the transport of LiPSs and electrons and promotingthe bidirectional conversion of sulfur. Meanwhile, the lithiophilic C3N4-CoSe2 sample with catalytic activity can effectively regulate the uniform distribution of lithium when Li+ penetrates the separator, avoiding the formation of lithium dendrites in the lithium (Li) metal anode. Therefore, LSBs based on C3N4-CoSe2 functionalized membranes exhibit a stable long cycle life at 1C (with capacity decay of 0.0819% per cycle) and a large areal capacity of 10.30mAhcm-2 at 0.1C (sulfur load: 8.26mgcm-2, lean electrolyte 5.4µLmgs -1). Even under high-temperature conditions of 60°C, a capacity retention rate of 81.8% after 100 cycles at 1C current density is maintained.

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.

Efficient Polysulfides Conversion Kinetics Enabled by Ni@CNF Interlayer for Lithium Sulfur Batteries

Recent advances in the development of lithium-sulfur batteries (Li-S) demonstrated their high effectiveness owing to their tremendous theoretical specific capacity and high theoretical gravimetrical energy. Nevertheless, the potential commercialization of Li-S is significantly held by the insulating nature of sulfur and complicated RedOx reactions during the electrochemical charge-discharge processes. This paper presents nickel nanoparticles embedded carbon nanofibers interlayer (Ni@CNF) between a cathode and a separator as an additional physical barrier against lithium polysulfides shuttle for their efficient conversion during the charge-discharge cycling. Furthermore, the interlayer provides an auxiliary electron pathway with subsequent lowering of the charge transfer resistance. The electrochemical analysis of a Li-S cell with the Ni@CNF interlayer demonstrated high initial discharge capacities of 1441.2 mAh g-1 and 1194.2 mAh g-1 at 0.1 and 1.0 C rates, respectively, with remarkable capacity retention of ~83% after 100 cycles. This study revealed the advantageous impact of Ni@CNF towards solving the major issues of lithium-sulfur batteries, i.e., sluggish kinetics and the shuttle effect.

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.

Facile synthesis of MoS2 confined in yolk-shell hollow mesoporous carbon spheres with enhanced polysulfide binding for high-rate Li-S batteries

Lithium-sulfur (Li-S) batteries are one of the most potential energy storage systems because of their high theoretical density, environmental friendliness. However, the practical application of Li-S batteries is currently hampered by several intrinsic problems including the shuttle effects of polysulfides and sluggish electrode reaction kinetics. Herein, a flower-like MoS2 nanosheets confined and in situ grown inside yolk-shell hollow mesoporous carbon spheres (abbreviated as MoS2 @YHMCs) was fabricated as advanced sulfur immobilizer, which can effectively inhibit shuttle effect and conversion of polysulfides. The yolk-shell hollow mesoporous carbon spheres can restrain the volume variation during lithiation-delithiation processes, expose abundant active interfaces and furnish a shortened ion/electron transmission route for facilitated redox reactions. Furthermore, the few layered MoS2 nanosheets have strong LiPS adsorption and catalyzation, thereby achieving rapid redox conversion and enhanced reaction kinetics. Owing to these structural advantages, the delicately-designed MoS2 @S@YHMCs cathode shows good Li-S battery performance, i.e., high initial discharge capacity (1145 mAh g−1), desirable rate capability (770 mAh g−1 at 4 C), and superior cycling performance (583 mAh g−1 after 200 cycles at 1 C), suggesting great application prospects in the development of Li-S batteries.

Regulating Electrochemical Kinetics of CoP by Incorporating Oxygen on Surface for High-Performance Li-S Batteries.

Lithium-sulfur (Li-S) batteries are widely studied because of their high theoretical specific capacity and environmental friendliness. However, the further development of Li-S batteries is hindered by the shuttle effect of lithium polysulfides (LiPSs) and the sluggish redox kinetics. Since the adsorption and catalytic conversion of LiPSs mainly occur on the surface of the electrocatalyst, regulating the surface structure of electrocatalysts is an advisable strategy to solve the obstacles in Li-S batteries. Herein, CoP nanoparticles with high oxygen content on surface embedded in hollow carbon nanocages (C/O-CoP) is employed to functionalize the separators and the effect of the surface oxygen content of CoP on the electrochemical performance is systematically explored. Increasing the oxygen content on CoP surface can enhance the chemical adsorption to lithium polysulfides and accelerate the redox conversions kinetics of polysulfides. The cell with C/O-CoP modified separator can achieve the capacity of 1033 mAh g-1 and maintain 749mAh g-1 after 200 cycles at 2C. Moreover, DFT calculations are used to reveal the enhancement mechanism of oxygen content on surface of CoP in Li-S chemistry. This work offers a new insight into developing high-performance Li-S batteries from the perspective of surface engineering.

Tubular C3N4 Nanotubes as Metal-Free Sulfur Hosts toward Stable Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) with high energy density have the potential to replace current commercial lithium-ion batteries. However, the shuttle effect and the low conversion kinetics of lithium polysulfide (LiPS) remain the main challenges in the development of LSBs. In this study, a metal-free and simple-to-prepare carbon nitride with a high surface area and tubular morphology (CN-nt) is used as the sulfur host for LSBs. Due to its unique nanostructure and rich active sites, it not only effectively disperses the active sulfur material and anchors soluble polysulfide species, but it also promotes the nucleation process of Li2S, thus achieving fast and sustainable Li-S redox reactions. Experimental results show that the obtained S@CN-nt electrodes exhibit a high sulfur utilization of 1296.2 mAh g−1 at 0.1 C and a significant rate capability of 689.4 mAh g−1 at the high current rate of 3C. More importantly, the capacity retention reaches 87.7% after 500 cycles. This simple strategy of engineering unique carbon-based nanostructured hosts can inspire new ideas for developing cost-effective and metal-free host materials for sulfur-based batteries.

Boosted Polysulfide Conversion by Co, Mn Bimetallic-Modulated Nitrogen–Carbon Material for Advanced Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) are regarded as one of the most promising future generation rechargeable battery energy storage devices due to their high theoretical specific capacity and energy density. However, the development of LSBs is largely influenced by the shuttle effect and slow kinetics of lithium polysulfides, which seriously hinder their commercial applications. Based on this, we propose a bimetallic modulating strategy to synthesize carbon tube embedded with Co and Mn bimetals anchored on a nitrogen-doped carbon nanosheet (Co/Mn-GC@N–C) function separator to catalytic polysulfide conversion and enhance the electrochemical performance. Co/Mn-GC@N–C possesses high electrical conductivity and large specific surface area, which can offer a lot of active sites for anchoring polysulfides, stimulating their redox reaction and quickening the electrode reaction kinetics. The comprehensive test results show that the cell with Co/Mn-GC@N–C exhibits a specific discharge capacity of 1215 mAh g–1 at 0.5C and a high Coulombic efficiency of 99.4% after 300 cycles; even the Co/Mn-GC@N–C cell with a high sulfur loading of 6.6 mg cm–2 shows a high area capacity of 5 mAh cm–2. Therefore, this bimetallic modulating strategy provides an option for the design of advanced high-performance lithium–sulfur battery separator materials.

Creating Edge Sites within the 2D Metal‐Organic Framework Boosts Redox Kinetics in Lithium–Sulfur Batteries (Adv. Energy Mater. 42/2022)

Metal-Organic Frameworks In article number 2201960, Jiantao Wang, Xin Wang, Zhongwei Chen, and co-workers adopted a simple method to design a material that can create edge sites and defects on two-dimensional metal-organic frameworks as the cathode for lithium sulfur batteries, which can be used to catalyze the conversion of polysulfides. The creation of edge active sites provides a new strategic perspective for the adsorption and catalysis of polysulfides and has great prospects for promoting the future development of lithium sulfur batteries.

Discarded COVID-19 masks-derived-doped porous carbon for lithium-sulfur batteries.

SummaryDespite the high theoretical capacity and energy density of lithium‐sulfur (Li‐S) batteries, the development of Li‐S batteries has been slow due to the poor electrical conductivity and the shuttle effect of the electrode materials, resulting in low sulfur utilization and fast long‐term cycling capacity decay. The modified carbon materials are often used as sulfur hosts to significantly improve the cycling performance of the materials, but also bring high‐cost issues. Here, the porous carbon materials are synthesized quickly and conveniently by the microwave cross‐linking method using discarded medical masks as carbon sources and concentrated sulfuric acid as solvent. However, poor surface and structural properties limit the application of materials. The porous carbon material is modified with p‐toluene disulfide and urea as the sulfur and nitrogen sources by the microwave cross‐linking method, which not only improves the porosity and specific surface area of the porous carbon material, but also improved the electrical conductivity and interlayer spacing of the material. As synthesized SN‐doped porous carbon is employed as the sulfur host, which exhibits a high discharge capacity (1349.3 mAh g−1) at 0.1°C, the S‐porous C/S, N‐porous C/S, and SN‐porous C/S can maintain 78.1, 43.9, and 59.5% of the initial capacity after 500 cycles. The results indicate that the doping of S and N atoms provides sufficient active sites for the chemisorbed lithium polysulfides (LiPSs) to improve the reaction kinetics of the materials.

Approaches to Combat the Polysulfide Shuttle Phenomenon in Li–S Battery Technology

Lithium–sulfur battery (LSB) technology has tremendous prospects to substitute lithium-ion battery (LIB) technology due to its high energy density. However, the escaping of polysulfide intermediates (produced during the redox reaction process) from the cathode structure is the primary reason for rapid capacity fading. Suppressing the polysulfide shuttle (PSS) is a viable solution for this technology to move closer to commercialization and supersede the established LIB technology. In this review, we have analyzed the challenges faced by LSBs and outlined current methods and materials used to address these problems. We conclude that in order to further pioneer LSBs, it is necessary to address these essential features of the sulfur cathode: superior electrical conductivity to ensure faster redox reaction kinetics and high discharge capacity, high pore volume of the cathode host to maximize sulfur loading/utilization, and polar PSS-resistive materials to anchor and suppress the migration of polysulfides, which can be developed with the use of nanofabrication and combinations of the PSS-suppressive qualities of each component. With these factors addressed, our world will be able to forge ahead with the development of LSBs on a larger scale—for the efficiency of energy systems in technology advancement and potential benefits to outweigh the costs and performance decay.

Progress study on the development of lithium-sulfur batteries

With the rapid development of the new energy industry in recent years, the demand for lithium batteries is very urgent, and at the same time, the requirements for the performance of lithium batteries are getting higher and higher. Lithium-sulfur batteries, as a very competitive lithium battery, can reach as much as five times the energy density of traditional lithium batteries. However, due to various limitations in the reaction process, Li-S batteries also need to undergo various performance improvements to improve the efficiency of Li-S batteries and industrial applications. This paper introduces the advantages and disadvantages of lithium-sulfur batteries as well as future challenges. It also introduces the recent developments in lithium-sulfur batteries from three different aspects, i.e., material modification, structure-based modifications, and discussion from the perspective of electrolyte additives.

Niobium Diboride Nanoparticles Accelerating Polysulfide Conversion and Directing Li2S Nucleation Enabled High Areal Capacity Lithium-Sulfur Batteries.

The shuttle effect of polysulfides and Li2S sluggish nucleation are the major problems hampering the further development of lithium-sulfur batteries. The reasonable design for sulfur host materials with catalytic function has been an effective strategy for promoting polysulfide conversion. Compared with other types of transition metal compounds, transition metal borides with high conductivity and catalytic capability are more suitable as sulfur host materials. Herein, a niobium diboride (NbB2) nanoparticle with abundant and high-efficiency catalytic sites has been synthesized by facile solid-phase reaction. The NbB2 with both high conductivity and catalytic nature could regulate 3D-nucleation and growth of Li2S, decrease the reaction energy barrier, and accelerate the transformation of polysulfides. Thus, the NbB2 cathode could retain a high capacity of 1014 mAh g-1 after 100 cycles. In addition, the high initial specific capacities of 703/609 mAh g-1 are also achieved at 5 C/10 C and could run for 1000/1300 cycles within a low decay rate of 0.057%/0.051%. Even with a high sulfur loading up to 16.5 mg cm-2, an initial areal capacity of 17 mAh cm-2 could be achieved at 0.1 C. This work demonstrates a successful method for enhancing the kinetics of polysulfide conversion and directing Li2S nucleation.

Uniform coverage of high-loading sulfur on cross-linked carbon nanofibers for high reaction kinetics in Li–S batteries with low electrolyte/sulfur ratio

Aggregation of high loading sulfur on host materials at low carbon/sulfur ratio results in the limited S↔Li2S reaction kinetics, which is a bottleneck for the development of lithium sulfur batteries with high energy densities.

Two-Dimensional Conductive Metal-Organic Frameworks as Highly Efficient Electrocatalysts for Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LiSBs) which are expected to fulfill the increasing demands of high-density energy storage have been under intensive investigation. However, the development of LiSBs is facing many obstacles, such as the poor electronic conductivity of sulfur, shuttling effects of lithium polysulfides (LiPSs), sluggish Li2S decomposition, and low discharging/charging efficiency. Suitable electrocatalysts that can solve the above problems are promising in the development of LiSBs. Herein, 13 two-dimensional (2D) metal-organic frameworks (MOFs) of nitrogen-, sulfur-, and oxygen-coordinated transition-metal (TM) atoms (Co, Ni, Cu, and Zn) are selected and constructed to reveal the structure-activity relationship of 2D MOFs in terms of the electrocatalytic performance. Among all the 2D MOFs investigated, Cu3(HITP)2, Zn3(HITP)2, and Cu3(C18H9O3N3)2 offer moderate binding strength to LiPSs, which effectively suppresses Li2Sn dissolution and shuttling. Cu3(HITP)2 exhibits good electrical conductivity, a low Gibbs free energy barrier, effective electrocatalytic ability for Li2S decomposition, and a high sulfur loading amount. A descriptor φ is proposed to correlate the binding energies of the 2D MOFs to the coordination environment and the electronegativity of the TM atoms in the LiPSs via an implicit volcano plot. These findings are helpful for understanding the electrocatalytic effect of 2D MOFs in LiSBs and represent a promising approach for the development of future LiSBs.