Defect-Engineered VS2 Electrocatalysts for Lithium-Sulfur Batteries.

Defective two-dimensional transition metal dichalcogenides can be effective electrocatalysts for Li-S batteries, but the relationship between defect types and battery performance is unclear. In this work, we designed S vacancy-type SV-VS2 and V self-intercalated-type VI-VS2 and measured their catalytic activities in Li-S batteries. Compared with self-intercalating V atoms, S vacancies accelerated Li+ diffusion and SV-VS2 as a Li+ "reservoir" promoted the sulfur conversion kinetics significantly. In addition, the presence of sulfur vacancies promoted the lithiation behavior of SV-VS2 during discharge, leading to an enhancement of the catalytic ability of SV-VS2. However, this lithiation phenomenon weakened the catalytic activity of VI-VS2. Overall, SV-VS2 had better adsorption and catalytic activity. Li-S batteries with SV-VS2-coated separators delivered high rate performance and excellent cycling stability, with a capacity decay rate of 0.043% over 880 cycles at 1.0 C. This work provides an effective strategy for designing efficient Li-S battery electrocatalysts using defect engineering.

The Structural and Electronic Engineering of Molybdenum Disulfide Nanosheets as Carbon-Free Sulfur Hosts for Boosting Energy Density and Cycling Life of Lithium-Sulfur Batteries.

The compact sulfur cathodes with high sulfur content and high sulfur loading are crucial to promise high energy density of lithium-sulfur (Li-S) batteries. However, some daunting problems, such as low sulfur utilization efficiency, serious polysulfides shuttling, and poor rate performance, are usually accompanied during practical deployment. The sulfur hosts play key roles. Herein, the carbon-free sulfur host composed of vanadium-doped molybdenum disulfide (VMS) nanosheets is reported. Benefiting from the basal plane activation of molybdenum disulfide and structural advantage of VMS, high stacking density of sulfur cathode is allowed for high areal and volumetric capacities of the electrodes together with the effective suppression of polysulfides shuttling and the expedited redox kinetics of sulfur species during cycling. The resultant electrode with high sulfur content of 89 wt.% and high sulfur loading of 7.2 mg cm-2 achieves high gravimetric capacity of 900.9 mAh g-1 , the areal capacity of 6.48 mAh cm-2 , and volumetric capacity of 940 mAh cm-3 at 0.5 C. The electrochemical performance can rival with the state-of-the-art those in the reported Li-S batteries. This work provides methodology guidance for the development of the cathode materials to achieve high-energy-density and long-life Li-S batteries.

Binary Sulfiphilic Nickel Boride on Boron-Doped Graphene with Beneficial Interfacial Charge for Accelerated Li-S Dynamics.

The "shuttle effect" and slow conversion kinetics of lithium polysulfides (LiPSs) are stumbling block for high-energy-density lithium-sulfur batteries (LSBs), which can be effectively evaded by advanced catalytic materials. Transition metal borides possess binary LiPSs interactions sites, aggrandizing the density of chemical anchoring sites. Herein, a novel core-shelled heterostructure consisting of nickel boride nanoparticles on boron-doped graphene (Ni3 B/BG), is synthesized through a graphene spontaneously couple derived spatially confined strategy. The integration of Li2 S precipitation/dissociation experiments and density functional theory computations demonstrate that the favorable interfacial charge state between Ni3 B and BG provides smooth electron/charge transport channel, which promotes the charge transfer between Li2 S4 -Ni3 B/BG and Li2 S-Ni3 B/BG systems. Benefitting from these, the facilitated solid-liquid conversion kinetics of LiPSs and reduced energy barrier of Li2 S decomposition are achieved. Consequently, the LSBs employed the Ni3 B/BG modified PP separator deliver conspicuously improved electrochemical performances with excellent cycling stability (decay of 0.07% per cycle for 600 cycles at 2 C) and remarkable rate capability of 650 mAh g-1 at 10 C. This study provides a facile strategy for transition metal borides and reveals the effect of heterostructure on catalytic and adsorption activity for LiPSs, offering a new viewpoint to apply boride in LSBs.

Dual Active Sites of Oversaturated Fe-N5 and Fe2 O3 Nanoparticles for Accelerating Redox Kinetics of Polysulfides.

The shuttling effect and sluggish reaction kinetics are the main bottlenecks for the commercial viability of lithium-sulfur (Li-S) batteries. Metal-nitrogen-carbon single atom catalysts have attracted much attention to overcoming these obstacles due to their novel electrocatalytic activity. Herein, a novel cooperative catalytic interface with dual active sites (oversaturated Fe-N5 and polar Fe2 O3 nanocrystals) are co-embedded in nitrogen-doped hollow carbon spheres (Fe2 O3 /Fe-SA@NC) is designed by fine atomic regulation mechanism. Both experimental verifications and theoretical calculations disclose that the dual active sites (Fe-N5 and Fe2 O3 ) in this catalyst (Fe2 O3 /Fe-SA@NC) tend to form "FeS" and "LiN/O" bond, synchronically enhancing chemical adsorption and interface conversion ability of polysulfides, respectively. Specially, the Fe-N5 coordination with 3D configuration and sulfiphilic superfine Fe2 O3 nanocrystals exhibit the strong adsorption ability to facilitate the subsequent conversion reaction at dual-sites. Meanwhile, the nitrogen-doped hollow carbon spheres can promote Li+ /electron transfer and physically suppress polysulfides shuttling. Consequently, Li-S battery with the Fe2 O3 /Fe-SA@NC-modified separator exhibits a high capacity retention of 78% after 800 cycles at 1 C (pure S cathode, S content: 70 wt.%). Furthermore, the pouch cell with this separator shows good performance at 0.1 C for practical application (S loading: 4 mg cm-2 ).

Dual-Functional Hosts for Polysulfides Conversion and Lithium Plating/Stripping towards Lithium-Sulfur Full Cells.

The practical application of lithium-sulfur (Li-S) batteries is greatly hindered by the shuttle effect of dissolved polysulfides in the sulfur cathode and the severe dendritic growth in the lithium anode. Adopting one type of effective host with dual-functions including both inhibiting polysulfide dissolution and regulating Li plating/stripping, is recently an emerging research highlight in Li-S battery. This review focuses on such dual-functional hosts and systematically summarizes the recent research progress and application scenarios. Firstly, this review briefly describes the stubborn issues in Li-S battery operations and the sophisticated counter measurements over the challenges by dual-functional behaviors. Then, the latest advances on dual-functional hosts for both cathode and anode in Li-S full cells are catalogued as species, including metal chalcogenides, metal carbides, metal nitrides, heterostuctures, and the possible mechanisms during the process. Besides, we also outlined the theoretical calculation tools for the dual-functional host based on the first principles. Finally, several sound perspectives are also rationally proposed for fundamental research and practical development as guidelines.

A Multifunctional Coating on Sulfur-Containing Carbon-Based Anode for High-Performance Sodium-Ion Batteries.

A sulfur doping strategy has been frequently used to improve the sodium storage specific capacity and rate capacity of hard carbon. However, some hard carbon materials have difficulty in preventing the shuttling effect of electrochemical products of sulfur molecules stored in the porous structure of hard carbon, resulting in the poor cycling stability of electrode materials. Here, a multifunctional coating is introduced to comprehensively improve the sodium storage performance of a sulfur-containing carbon-based anode. The physical barrier effect and chemical anchoring effect contributed by the abundant C-S/C-N polarized covalent bond of the N, S-codoped coating (NSC) combine to protect SGCS@NSC from the shuttling effect of soluble polysulfide intermediates. Additionally, the NSC layer can encapsulate the highly dispersed carbon spheres inside a cross-linked three-dimensional conductive network, improving the electrochemical kinetic of the SGCS@NSC electrode. Benefiting from the multifunctional coating, SGCS@NSC exhibits a high capacity of 609 mAh g-1 at 0.1 A g-1 and 249 mAh g-1 at 6.4 A g-1. Furthermore, the capacity retention of SGCS@NSC is 17.6% higher than that of the uncoated one after 200 cycles at 0.5 A g-1.

Multifunctional Atomic Molybdenum on Graphene with Distinctive Coordination to Solve Li and S Electrochemistry.

The improvement of lithium-sulfur batteries is still impeded by notorious shuttling effect and sluggish kinetics on the S cathode, and rampant Li dendrite formation on the Li anode makes it worse. Herein, a type of single-atom dispersed Mo on nitrogen-doped graphene (Mo/NG) with a distinctive Mo-N2 O2 -C coordination structure first serving as a multifunctional material is designed by a structure-oriented strategy to solve Li and S electrochemistry. Mo/NG with superior intrinsic properties endowed by the unique coordination configuration adsorbs soluble polysulfides and promotes bidirectional conversion of LiPSs at the cathode side. Meanwhile, the suitable binding strength of Mo/NG with lithium ions endows it with an attractive lithiophilic feature. Specifically, Mo/NG is able to work as the adaptor to redistribute lithium ions on the interface of separator and homogenize the lithium ion flux. Due to the suitable binding ability with Li+ , it does not interfere with the diffusion of lithium ions across and provides tunnels exclusive to lithium ions to generate fast and homogeneous flux. Ascribed to such unique multifunctionality, Li-S batteries assembled with Mo/NG exhibit excellent electrochemical performance including long cycling stability over 1000 cycles and high areal capacities under high sulfur mass loading.

WSe2 Flakelets on N-Doped Graphene for Accelerating Polysulfide Redox and Regulating Li Plating.

The practical application of lithium-sulfur batteries is still limited by the lithium polysulfides (LiPSs) shuttling effect on the S cathode and uncontrollable Li-dendrite growth on the Li anode. Herein, elaborately designed WSe2 flakelets immobilized on N-doped graphene (WSe2 /NG) with abundant active sites are employed to be a dual-functional host for satisfying both the S cathode and Li anode synchronously. On the S cathode, the WSe2 /NG with a strong interaction towards LiPSs can act as a redox accelerator to promote the bidirectional conversion of LiPSs. On the Li anode, the WSe2 /NG with excellent lithiophilic features can regulate the uniform Li plating/stripping to mitigate the growth of Li dendrite. Taking advantage of these merits, the assembled Li-S full batteries exhibit remarkable rate performance and stable cycling stability even at a higher sulfur loading of 10.5 mg cm-2 with a negative to positive electrode capacity (N/P) ratio of 1.4 : 1.

Dual-Functional MgO Nanocrystals Satisfying Both Polysulfides and Li Regulation toward Advanced Lithium-Sulfur Full Batteries.

Lithium-sulfur battery (LSB) is regarded as a preferential option for next-generation energy-storage system, but the lithium polysulfides (LiPSs) shuttling effect and the uncontrollable growth of dendritic Li in the anode impede its commercial viability. To address both of the issues simultaneously, a well-designed hybrid of MgO ultrafine nanocrystals dispersed on graphene-supported carbon nanosheets (MCG) is developed via a facile self-template strategy as dual-functional host for both sulfur and lithium. Relying on the coordination of strong LiPS-capturing capability, the shuttling effect is inhibited. Furthermore, the lithiophilic configuration with high specific surface area induce homogenous Li deposition, thus preventing the formation of disordered lithium dendrite. Integrating all these advantages, a full cell based on S@MCG cathode and Li@MCG@Cu anode exhibits a stable capacity at 0.5 C for 150 cycles with a low capacity fading rate. Furthermore, the full cell achieves a high capacity retention of 85.5% at a high S areal loading of 3.82 mg cm-2 under the condition of a low electrolyte/sulfur ratio (E/S) of 6.5 µL mg-1 and negative/positive capacity ratio (N/P) of 3. This strategy satisfying both cathode and anode host provides a viable approach to realize high-energy-density and dendrite-free LSBs.

Bacteria-Derived Biological Carbon Building Robust Li-S Batteries.

Lithium sulfur (Li-S) batteries are attracting increasing interest for high-density energy storage. However, the practical application is limited by the rapid capacity fading over repeated charge/discharge cycles which is largely attributed to the formation and shuttling of soluble polysulfide species. To address these issues, we develop a hierarchical structure composite with triple protection strategy via graphene, organic conductor PEDOT, and nitrogen and phosphorus codoped biological carbon to encapsulate sulfur species (GOC@NPBCS). This unique hierarchical structure can effectively immobilize the sulfur species while at the same time improve the electrical conductivity and ensure efficient lithium ion transport to enable excellent Li-S battery performance. In particular, the biological carbon derived from natural bacteria features inherent nitrogen and phosphorus codoping with a strong absorption to lithium polysulfides, which can greatly suppress the dissolution and shuttling of polysulfides that are responsible for rapid capacity fading. With these synergistic effects, the GOC@NPBCS cathode exhibits exceptionally stable cycling stability (an ultralow capacity fading rate of 0.045% per cycle during 1000 cycles at the current rate of 5 C), high specific capacity (1193.8 mAh g-1 at 0.5 C based on sulfur weight), and excellent rate capability.

rGO@TiO2-x Schottky heterojunction for enhanced bidirectional catalysis in polysulfide conversion.

The shuttling and sluggish conversion kinetics of lithium polysulfides (LiPSs) lead to poor cycling performance and low energy efficiency in lithium-sulfur batteries (LSBs). In this work, a hierarchically structured nanocomposite, synthesized through a surfactant-directed hydrothermal growth following dopamine-protected pyrolysis, serves as a bidirectional catalyst for LSBs. This nanocomposite comprises N-doped reduced graphene oxide (rGO) nanosheets anchored with uniformly distributed TiO2-x nanoparticles via interfacial N-Ti and C-Ti bonding, resulting in the formation of abundant 2D/0D Schottky heterojunctions (rGO/TiO2-x). Density functional theory (DFT) calculations and in situ Raman characterizations demonstrate that rGO/TiO2-x effectively inhibits the shuttling of LiPSs with enhanced redox kinetics, achieving high utilization of the sulfur cathode and improving the overall reversibility. A high areal capacity is attained at a high sulfur loading and a low electrolyte/sulfur ratio. The initial specific capacity reaches 1010 mA h g-1 at a current density of 0.2C (1C = 1675 mA g-1), and a retention of 86.4 % is attained over 100 cycles. A light-emitting diode (LED) screen using two LSBs with rGO/TiO2-x demonstrates their high potential for practical applications.

Constructing Orbital Coupling-Modulated Homogeneous Dual-Atom Fe-Fe Sites for Boosting Bidirectional Conversion of Polysulfides.

Homogeneous dual-atom catalysts (HDACs) have garnered significant attention for their potential to overcome the shuttling effect and sluggish reaction kinetics in lithium-sulfur (Li-S) batteries. However, modulating the electron structure of metal atomic orbitals for HDACs to dictate the catalytic activity toward polysulfides has remained meaningful but unexplored so far. Herein, an interfacial cladding strategy is developed to obtain a new type of dual-atom iron matrix with a unique FeN2P1-FeN2P1 coordination structure (Fe2@NCP). The 3d orbital electrons of the Fe centers are redistributed by incorporating phosphorus atoms into the first coordination sphere. The theoretical calculations disclose that the strong coupling between the Fe d orbital and the S p orbital exhibits an enhanced Fe-S bond and improved reactivity toward polysulfides. Moreover, the Fe2@NCP catalyst achieves robust adsorption ability toward Li2Sn (1 ≤ n ≤ 8) and significantly boosts bidirectional sulfur redox reaction kinetics by lowering the Li2S deposition/decomposition energy barriers. Consequently, the assembled Li-S batteries present a high retention ratio of 77.3% after 500 cycles at 1C. Furthermore, the Li-S pouch cell also exhibits good performance at 0.1C (80.2% retention over 100 cycles) for practical application with a sulfur loading of 4.0 mg/cm2. The outcome of this study will facilitate the design of homogeneous dual-atom catalysts for Li-S batteries.

Confining Iodine into Metal-Organic Framework Derived Metal-Nitrogen-Carbon for Long-Life Aqueous Zinc-Iodine Batteries.

Aqueous zinc-iodine batteries (AZIBs) are highly appealing for energy requirements owing to their safety, cost-effectiveness, and scalability. However, the inadequate redox kinetics and severe shuttling effect of polyiodide ions impede their commercial viability. Herein, several Zn-MOF-derived porous carbon materials are designed, and the further preparation of iron-doped porous carbon (Fe-N-C, M9) with varied Fe doping contents is optimized based on a facile self-assembly/carbonization approach. M9, with atomic Fe coordinated to nitrogen atoms, is employed as an efficient cathode host for AZIBs. Functional modifications of porous carbon hosts involving the doping species and levels are investigated. The adsorption tests, in situ Raman spectroscopy, and in situ UV-vis results demonstrate the adsorption capability and charge-discharge mechanism for the iodine species. Furthermore, experimental findings and theoretical analyses have proven that the redox conversion of iodine is enhanced through a physicochemical confinement effect. This study offers basic principles for the strategic design of single-atom dispersed carbon as an iodine host for high-performance AZIBs. Flexible soft-pack battery and wearable microbattery applications also have implications for future long-life aqueous battery designs.

Heterostructures Regulating Lithium Polysulfides for Advanced Lithium-Sulfur Batteries.

Sluggish reaction kinetics and severe shuttling effect of lithium polysulfides seriously hinder the development of lithium-sulfur batteries. Heterostructures, due to unique properties, have congenital advantages that are difficult to be achieved by single-component materials in regulating lithium polysulfides by efficient catalysis and strong adsorption to solve the problems of poor reaction kinetics and serious shuttling effect of lithium-sulfur batteries. In this review, the principles of heterostructures expediting lithium polysulfides conversion and anchoring lithium polysulfides are detailedly analyzed, and the application of heterostructures as sulfur host, interlayer, and separator modifier to improve the performance of lithium-sulfur batteries is systematically reviewed. Finally, the problems that need to be solved in the future study and application of heterostructures in lithium-sulfur batteries are prospected. This review will provide a valuable reference for the development of heterostructures in advanced lithium-sulfur batteries.

Construction of Co3 O4 /ZnO Heterojunctions in Hollow N-Doped Carbon Nanocages as Microreactors for Lithium-Sulfur Full Batteries.

Lithium-sulfur (Li-S) batteries are promising alternatives of conventional Li-ion batteries attributed to their remarkable energy densities and high sustainability. However, the practical applications of Li-S batteries are hindered by the shuttling effect of lithium polysulfides (LiPSs) on cathode and the Li dendrite formation on anode, which together leads to inferior rate capability and cycling stability. Here, an advanced N-doped carbon microreactors embedded with abundant Co3 O4 /ZnO heterojunctions (CZO/HNC) are designed as dual-functional hosts for synergistic optimization of both S cathode and Li metal anode. Electrochemical characterization and theoretical calculations confirm that CZO/HNC exhibits an optimized band structure that effectively facilitates ion diffusion and promotes bidirectional LiPSs conversion. In addition, the lithiophilic nitrogen dopants and Co3O4/ZnO sites together regulate dendrite-free Li deposition. The S@CZO/HNC cathode exhibits excellent cycling stability at 2 C with only 0.039% capacity fading per cycle over 1400 cycles, and the symmetrical Li@CZO/HNC cell enables stable Li plating/striping behavior for 400 h. Remarkably, Li-S full cell using CZO/HNC as both cathode and anode hosts shows an impressive cycle life of over 1000 cycles. This work provides an exemplification of designing high-performance heterojunctions for simultaneous protection of two electrodes, and will inspire the applications of practical Li-S batteries.

High-Rate Lithium-Selenium Batteries Boosted by a Multifunctional Janus Separator Over a Wide Temperature Range of -30 °C to 60 °C.

Lithium-selenium batteries are characterized by high volumetric capacity comparable to Li-S batteries, while ≈1025 times higher electrical conductivity of Se than S is favorable for high-rate capability. However, they also suffer from the "shuttling effect" of lithium polyselenides (LPSes) and Li dendrite growth. Herein, a multifunctional Janus separator is designed by coating hierarchical nitrogen-doped carbon nanocages (hNCNC) and AlN nanowires on two sides of commercial polypropylene (PP) separator to overcome these hindrances. At room temperature, the Li-Se batteries with the Janus separator exhibit an unprecedented high-rate capability (331 mAh g-1 at 25 C) and retain a high capacity of 408 mAh g-1 at 3 C after 500 cycles. Moreover, the high retained capacities are achieved over a wide temperature range from -30 °C to 60 °C, showing the potential application under extreme environments. The excellent performances result from the "1+1>2" synergism of suppressed LPSes shuttling by chemisorption and electrocatalysis of hNCNC on the cathode side and suppressed Li-dendrite growth by thermally conductive AlN-network on the anode side, which can be well understood by the "Bucket Effect". This Janus separator provides a general strategy to develop high-performance lithium-chalcogen (Se, S, SeS2 ) batteries.

Ce-Doped Three-Dimensional Ni/Fe LDH Composite as a Sulfur Host for Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) have become the most promising choice in the new generation of energy storage/conversion equipment due to their high theoretical capacity of 1675 mAh g-1 and theoretical energy density of 2600 Wh kg-1. Nevertheless, the continuous shuttling of lithium polysulfides (LiPSs) restricts the commercial application of LSBs. The appearance of layered double hydroxides (LDH) plays a certain role in the anchoring of LiPSs, but its unsatisfactory electronic conductivity and poor active sites hinder its realization as a sulfur host for high-performance LSBs. In this paper, metal organic framework-derived and Ce ion-doped LDH (Ce-Ni/Fe LDH) with a hollow capsule configuration is designed rationally. The hollow structure of Ce-Ni/Fe LDH contains a sufficient amount of sulfur. Fe, Ni, and Ce metal ions effectively trap LiPSs; speed up the conversion of LiPSs; and firmly anchor LiPSs, thus effectively inhibiting the shuttle of LiPSs. The electrochemical testing results demonstrate that a lithium-sulfur battery with capsule-type S@Ce-Ni/Fe LDH delivers the initial discharge capacities of 1207 mAh g-1 at 0.1 C and 1056 mAh g-1 at 0.2 C, respectively. Even at 1 C, a lithium-sulfur battery with S@Ce-Ni/Fe LDH can also cycle 1000 times. This work provides new ideas to enhance the electrochemical properties of LSBs by constructing a hollow capsule configuration.

MOF-Derived Nitrogen-Doped Porous Carbon Polyhedrons/Carbon Nanotubes Nanocomposite for High-Performance Lithium-Sulfur Batteries.

Nanocomposites that combine porous materials and a continuous conductive skeleton as a sulfur host can improve the performance of lithium-sulfur (Li-S) batteries. Herein, carbon nanotubes (CNTs) anchoring small-size (~40 nm) N-doped porous carbon polyhedrons (S-NCPs/CNTs) are designed and synthesized via annealing the precursor of zeolitic imidazolate framework-8 grown in situ on CNTs (ZIF-8/CNTs). In the nanocomposite, the S-NCPs serve as an efficient host for immobilizing polysulfides through physical adsorption and chemical bonding, while the interleaved CNT networks offer an efficient charge transport environment. Moreover, the S-NCP/CNT composite with great features of a large specific surface area, high pore volume, and short electronic/ion diffusion depth not only demonstrates a high trapping capacity for soluble lithium polysulfides but also offers an efficient charge/mass transport environment, and an effective buffering of volume changes during charge and discharge. As a result, the Li-S batteries based on a S/S-NCP/CNT cathode deliver a high initial capacity of 1213.8 mAh g-1 at a current rate of 0.2 C and a substantial capacity of 1114.2 mAh g-1 after 100 cycles, corresponding to a high-capacity retention of 91.7%. This approach provides a practical research direction for the design of MOF-derived carbon materials in the application of high-performance Li-S batteries.

Bifunctional Separator with Ultra-Lightweight MnO2 Coating for Highly Stable Lithium-Sulfur Batteries.

The severe shuttling behavior in the discharging-charging process largely hampers the commercialization of lithium-sulfur (Li-S) batteries. Herein, we design a bifunctional separator with an ultra-lightweight MnO2 coating to establish strong chemical adsorption barriers for shuttling effect alleviation. The double-sided polar MnO2 layers not only trap the lithium polysulfides through extraordinary chemical bonding but also ensure the uniform Li+ flux on the lithium anode and inhibit the side reaction, resulting in homogeneous plating and stripping to avoid corrosion of the Li anode. Consequently, the assembled Li-S battery with the MnO2-modified separator retains a capacity of 665 mA h g-1 at 1 C after 1000 cycles at the areal sulfur loading of 2.5 mg cm-2, corresponding to only 0.028% capacity decay per cycle. Notably, the areal loading of ultra-lightweight MnO2 coating is as low as 0.007 mg cm-2, facilitating the achievement of a high energy density of Li-S batteries. This work reveals that the polar metal oxide-modified separator can effectively inhibit the shuttle effect and protect the Li anode for high-performance Li-S batteries.

Application of Inorganic Quantum Dots in Advanced Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have emerged as one of the most attractive alternatives for post-lithium-ion battery energy storage systems, owing to their ultrahigh theoretical energy density. However, the large-scale application of Li-S batteries remains enormously problematic because of the poor cycling life and safety problems, induced by the low conductivity , severe shuttling effect, poor reaction kinetics, and lithium dendrite formation. In recent studies, catalytic techniques are reported to promote the commercial application of Li-S batteries. Compared with the conventional catalytic sites on host materials, quantum dots (QDs) with ultrafine particle size (<10 nm) can provide large accessible surface area and strong polarity to restrict the shuttling effect, excellent catalytic effect to enhance the kinetics of redox reactions, as well as abundant lithiophilic nucleation sites to regulate Li deposition. In this review, the intrinsic hurdles of S conversion and Li stripping/plating reactions are first summarized. More importantly, a comprehensive overview is provided of inorganic QDs, in improving the efficiency and stability of Li-S batteries, with the strategies including composition optimization, defect and morphological engineering, design of heterostructures, and so forth. Finally, the prospects and challenges of QDs in Li-S batteries are discussed.