Sulphur-polypyrrole composite positive electrode materials for rechargeable lithium batteries

Design of Coatings for Sulfur-Based Cathode Materials in Lithium-Sulfur Batteries: A review

Lithium-sulfur batteries (LSBs) are considered next-generation energy storage and conversion solutions owing to their high theoretical specific capacity and the high abundance/low-cost of sulfur-based cathode materials. However, LSBs still encounter significant challenges, including the low conductivities of sulfur-based materials, severe volumetric expansion of sulfur during the discharge process, and the persistent "shuttle effect" of polysulfides. In recent years, a tremendous amount of research has been conducted to address the above challenges by developing coating and compositing materials and corresponding fabrication strategies for sulfur-based cathode materials. In this study, the surface coating, compositing materials, and fabrication methodologies of LSB cathodes are comprehensively reviewed in terms of advanced materials, structure/component characterization, functional mechanisms, and performance validation. Some technical challenges are analyzed in detail, and possible future research directions are proposed to overcome the challenges toward practical applications of lithium-sulfur batteries.

Novel binary regulated silicon-carbon materials as high-performance anodes for lithium-ion batteries

The massive volume dilation, unsteady solid electrolyte interphase, and weak conductivity about Si have failed to bring it to practical applications, although its potential capacity is up to 4200 mAh g-1. For solving these problems, novel binary regulated silicon-carbon materials (Si/BPC) were done by a sol-gel procedure combined with single carbonization. Analytical techniques were systematically utilized to examine the effects of element doping at several gradients on morphology, structure and electrochemical properties of composites, thus the optimal content was identified. Si/BPC preserves a discharge specific capacity of 1021.6 mAh g-1with a coulomb efficiency of 99.27% after 180 cycles at 1000 mA g-1, within the upgrade than single-doped and undoped. In rate test, it has a specific capacity of 1003.2 mAh g-1at a high current density of 5000 mA g-1, quickly back towards 2838.6 mAh g-1at 200 mA g-1. The inclusion of B and P elements is linked to the electrochemical characteristics. In the co-doped carbon layers, the synergistic impact of doping B and P accelerates the diffusion kinetics of lithium ions, boosts diffusion rate of Li+, offers low electrochemical impedance (45.75 Ω). This brings more defects to provide transport carriers and induces a substantial amount of electrochemically active sites, which fosters the storage of Li+, thus making silicon material electrochemically more active and potential.

Attenuating the Polysulfide Shuttle Mechanism by Separator Coating

Lithium-sulfur batteries have a high energy density but lack cycle stability to reach market maturity. This is mainly due to the polysulfide shuttle mechanism, i. e., the leaching of active material from the cathode into the electrolyte and subsequent side reactions. We demonstrate how to attenuate the polysulfide shuttle by magnetron sputtering molybdenum oxysulfide, manganese oxide, and chromium oxide onto microporous polypropylene separators. The morphology of the amorphous coatings was analyzed by SEM and XRD. Electrochemical cyclization quantified how these coatings improved Coulombic efficiency and cycle stability. These tests were conducted in half cells. We compare the different performances of the different coatings with the known chemical and adsorption properties of the respective coating materials.

High-Performance Sulfurized Polyacrylonitrile Cathode by Using MXene as a Conductive and Catalytic Binder for Room-Temperature Na/S Batteries

Sulfurized polyacrylonitrile (PAN@S) is a promising cathode material for room-temperature Na/S batteries but suffers from low conductivity and insufficient electrochemical activity, resulting in unsatisfactory actual capacity and rate performance. Herein, Ti3C2Tx MXene nanosheets are used as a conductive and catalytic binder to establish the PAN@S electrode, wherein MXene constructs a highly conductive framework for fast charge transport and provides high catalytic effect to improve the active material utilization and accelerate the redox kinetics significantly. Therefore, the PAN@S electrode bonded by MXene shows an electronic conductivity of 5.05 S cm-1, 4 orders of magnitude higher than the conventional electrodes bonded by the insulative polymer binders, and much decreased activation energy barrier and resistance. Consequently, the PAN@S electrode displays superior performance in terms of high capacity (697.3 mAh g-1 at 200 mA g-1), unparalleled rate capability (189.0 mAh g-1 at 20 A g-1), and excellent high-rate cycling performance (a capacity decay rate of ∼0.04% per cycle during 1000 cycles at 5 A g-1). This work provides a high-performance electrode for room-temperature Na/S batteries and shows the promising potential of conductive and catalytic MXene binders in boosting the performance of active materials.

Tubular Polypyrrole with Chloride Ion Dopants as an Ultrafast Organic Anode for High-Power Lithium-Ion Batteries

Polypyrrole (PPy), as a representative p-type conductive polymer, attracts wide attention for energy storage materials. However, the sluggish reaction kinetics and low specific capacity of PPy impede its application in high-power lithium-ion batteries (LIBs). Herein, tubular PPy with chloride and methyl orange (MO) anionic dopants is synthesized and investigated as an anode for LIBs. The Cl^- and MO anionic dopants can increase the ordered aggregation and the conjugation length of pyrrolic chains, forming plentiful conductive domains and affecting the conduction channel inside the pyrrolic matrix, thereby achieving fast charge transfer and Li⁺ ion diffusion, low ion transfer energy barriers, and rapid reaction kinetics. On account of the above synergistic effect, PPy electrodes deliver a high specific capacity of 2067.8 mAh g^-1 at 200 mA g^-1 and a remarkable rate capacity of 1026 mAh g^-1 at 10 A g^-1 , realizing high energy density (724 Wh kg^-1 ) and power density (7237 W kg^-1 ) simultaneously.

Integration of porous graphitic carbon and carbon fiber framework for ultrahigh sulfur-loading lithium-sulfur battery

A lithium-sulfur battery, a potential next-generation secondary battery, is affected by poor conductivity of sulfur and the dissolution of intermediate polysulfides. Here we report a lithium-sulfur battery with ultrahigh sulfur loading and excellent cycling stability using porous graphitic carbon (PGC) as a high-conductivity carrier of sulfur and carbon fiber with crisscross conductive framework as an electric attachment site of sulfur. PGC is fabricated through a simple and environmentally friendly synthesis process involving high-temperature graphitization in a N₂ atmosphere followed by an annealing process in air. Due to the presence of porous graphitic structure, with C-O termination groups, PGC endows the lithium-sulfur battery system with excellent cycling performance. The lithium-sulfur battery cathode constructed by PGC with a sulfur loading of 2.5 mg cm^-2 still retains a high specific capacity of 734.4 mA h g^-1 after 200 cycles. Meanwhile, an ultrahigh sulfur loading of 12.8 mg cm^-2 for a CR2025 coin cell is achieved, which is the highest sulfur loading reported in the literature for the coin cell. The ultrahigh sulfur loading cell also shows good electrochemical properties, profiting from the mesopores terminated with C-O groups, high specific surface area of 1129.9 m² g^-1 and high-conductivity graphitic structure.

A New Graphitic Nitride and Reduced Graphene Oxide-Based Sulfur Cathode for High-Capacity Lithium-Sulfur Cells

Lithium-sulfur (Li-S) batteries can provide at least three times higher energy density than lithium-ion (Li-Ion) batteries. However, Li-S batteries suffer from a phenomenon called the polysulfide shuttle (PSS) that prevents the commercialization of these batteries. The PSS has several undesirable effects, such as depletion of active materials from the cathode, deleterious reactions between the lithium anode and electrolyte soluble lithium polysulfides, resulting in unfavorable coulombic efficiency, and poor cycle life of the battery. In this study, a new sulfur cathode composed of graphitic nitride as the polysulfide absorbing material and reduced graphene oxide as the conductive carbon host has been synthesized to rectify the problems associated with the PSS effect. This composite cathode design effectively retains lithium polysulfide intermediates within the cathode structure. The S@RGO/GN cathode displayed excellent capacity retention compared to similar RGO-based sulfur cathodes published by other groups by delivering an initial specific capacity of 1415 mA h g−1 at 0.2 C. In addition, the long-term cycling stability was outstanding (capacity decay at the rate of only 0.2% per cycle after 150 cycles).

Polymers in Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) hold great promise as one of the next-generation power supplies for portable electronics and electric vehicles due to their ultrahigh energy density, cost effectiveness, and environmental benignity. However, their practical application has been impeded owing to the electronic insulation of sulfur and its intermediates, serious shuttle effect, large volume variation, and uncontrollable formation of lithium dendrites. Over the past decades, many pioneering strategies have been developed to address these issues via improving electrodes, electrolytes, separators and binders. Remarkably, polymers can be readily applied to all these aspects due to their structural designability, functional versatility, superior chemical stability and processability. Moreover, their lightweight and rich resource characteristics enable the production of LSBs with high-volume energy density at low cost. Surprisingly, there have been few reviews on development of polymers in LSBs. Herein, breakthroughs and future perspectives of emerging polymers in LSBs are scrutinized. Significant attention is centered on recent implementation of polymers in each component of LSBs with an emphasis on intrinsic mechanisms underlying their specific functions. The review offers a comprehensive overview of state-of-the-art polymers for LSBs, provides in-depth insights into addressing key challenges, and affords important resources for researchers working on electrochemical energy systems.

Graphene-Based Materials for Flexible Lithium-Sulfur Batteries

The increasing demand for wearable electronic devices necessitates flexible batteries with high stability and desirable energy density. Flexible lithium-sulfur batteries (FLSBs) have been increasingly studied due to their high theoretical energy density through the multielectron chemistry of low-cost sulfur. However, the implementation of FLSBs is challenged by several obstacles, including their low practical energy density, short life, and poor flexibility. Various graphene-based materials have been applied to address these issues. Graphene, with good conductivity and flexibility, exhibits synergistic effects with other active/catalytic/flexible materials to form multifunctional graphene-based materials, which play a pivotal role in FLSBs. This review summarizes the recent progress of graphene-based materials that have been used as various FLSB components, including cathodes, interlayers, and anodes. Particular attention is focused on the precise nanostructures, graphene efficacy, interfacial effects, and battery layout for realizing FLSBs with good flexibility, energy density, and cycling stability.

Advances in Lithium-Sulfur Batteries: From Academic Research to Commercial Viability

Lithium-ion batteries, which have revolutionized portable electronics over the past three decades, were eventually recognized with the 2019 Nobel Prize in chemistry. As the energy density of current lithium-ion batteries is approaching its limit, developing new battery technologies beyond lithium-ion chemistry is significant for next-generation high energy storage. Lithium-sulfur (Li-S) batteries, which rely on the reversible redox reactions between lithium and sulfur, appears to be a promising energy storage system to take over from the conventional lithium-ion batteries for next-generation energy storage owing to their overwhelming energy density compared to the existing lithium-ion batteries today. Over the past 60 years, especially the past decade, significant academic and commercial progress has been made on Li-S batteries. From the concept of the sulfur cathode first proposed in the 1960s to the current commercial Li-S batteries used in unmanned aircraft, the story of Li-S batteries is full of breakthroughs and back tracing steps. Herein, the development and advancement of Li-S batteries in terms of sulfur-based composite cathode design, separator modification, binder improvement, electrolyte optimization, and lithium metal protection is summarized. An outlook on the future directions and prospects for Li-S batteries is also offered.

Accelerated polysulfide conversion on hierarchical porous vanadium-nitrogen-carbon for advanced lithium-sulfur batteries

With high theoretical specific density, low cost, and non-toxicity, Li-S batteries are regarded as a promising candidate for next-generation energy storage systems. However, the shuttling of soluble Li polysulfides (LiPSs) results in self-discharge and rapid capacity degradation. Herein, nitrogen-doped hierarchical porous carbon with embedded highly dispersed vanadium (v)-N_x sites (V-N-C) is developed as a high-performance Li-S battery cathode for the first time. The metal-organic polymer supramolecule structure formed by the electrostatic/hydrogen bond interaction of chitosan-VO₃^- strongly stabilizes V to generate a high density of V-N_x/C sites. During the discharge/charge process, the unique V-N_x/C active sites can serve as efficient catalysts to accelerate the redox kinetics of LiPSs, while the hierarchical porous carbon structure of V-N-C benefits the diffusion/transfer of Li⁺/e^- and suppresses the shuttling of LiPSs. As a result, the S/V-N-C composite delivers a high specific capacity of 1111.2 mA h g^-1 at 0.5C and maintains 573.6 mA h g^-1 at 5C with a low capacity decay rate of 0.087% per cycle (over 500 cycles at 1C). The rate performance of the developed V-N-C cathode in Li-S batteries is superior to that of most of the reported M-N-C and carbon material/metal compound composite electrodes.

Recent advances in cathode materials for rechargeable lithium-sulfur batteries

Lithium-sulfur batteries (Li-S) are regarded as a promising candidate for next-generation energy storage systems due to their high specific capacity (1675 mA h g^-1) and energy density (2600 W h kg^-1) as well as the abundance, safety and low cost of sulfur materials. However, many disadvantages hinder the further development of Li-S batteries, such as the insulating nature of the active materials, the dissolution of intermediate products, large volume expansion and safety concerns related to metal lithium anodes. During the past decade, tremendous efforts have been made in the design and synthesis of electrode materials. In this review, we briefly discuss the electrochemical mechanism of Li-S batteries and their practical problems. Then, we systematically summarize the current strategies for designing cathode materials with stable and long cycling performance, including sulfur cathodes and Li₂S cathodes; subsequently, the current development of solid-state electrolytes and protective strategies for lithium metal anodes are briefly discussed. Finally, the current challenges and future perspectives of Li-S batteries are presented.

Current Status and Future Prospects of Metal-Sulfur Batteries

Lithium-sulfur batteries are a major focus of academic and industrial energy-storage research due to their high theoretical energy density and the use of low-cost materials. The high energy density results from the conversion mechanism that lithium-sulfur cells utilize. The sulfur cathode, being naturally abundant and environmentally friendly, makes lithium-sulfur batteries a potential next-generation energy-storage technology. The current state of the research indicates that lithium-sulfur cells are now at the point of transitioning from laboratory-scale devices to a more practical energy-storage application. Based on similar electrochemical conversion reactions, the low-cost sulfur cathode can be coupled with a wide range of metallic anodes, such as sodium, potassium, magnesium, calcium, and aluminum. These new "metal-sulfur" systems exhibit great potential in either lowering the production cost or producing high energy density. Inspired by the rapid development of lithium-sulfur batteries and the prospect of metal-sulfur cells, here, over 450 research articles are summarized to analyze the research progress and explore the electrochemical characteristics, cell-assembly parameters, cell-testing conditions, and materials design. In addition to highlighting the current research progress, the possible future areas of research which are needed to bring conversion-type lithium-sulfur and other metal-sulfur batteries into the market are also discussed.

Housing Sulfur in Polymer Composite Frameworks for Li-S Batteries

Extensive efforts have been devoted to the design of micro-, nano-, and/or molecular structures of sulfur hosts to address the challenges of lithium-sulfur (Li-S) batteries, yet comparatively little research has been carried out on the binders in Li-S batteries. Herein, we systematically review the polymer composite frameworks that confine the sulfur within the sulfur electrode, taking the roles of sulfur hosts and functions of binders into consideration. In particular, we investigate the binding mechanism between the binder and sulfur host (such as mechanical interlocking and interfacial interactions), the chemical interactions between the polymer binder and sulfur (such as covalent bonding, electrostatic bonding, etc.), as well as the beneficial functions that polymer binders can impart on Li-S cathodes, such as conductive binders, electrolyte intake, adhesion strength etc. This work could provide a more comprehensive strategy in designing sulfur electrodes for long-life, large-capacity and high-rate Li-S battery.

Double-Layered Modified Separators as Shuttle Suppressing Interlayers for Lithium-Sulfur Batteries

The shuttling phenomena in lithium-sulfur batteries lead to drastic attenuation of the capacity. This can be suppressed effectively by modifying the separator. Herein, a double-layered separator composed of a macroporous polypropylene (PP) matrix layer and an arrayed poly(methyl methacrylate) (PMMA) microsphere retarding layer is designed as the separator for lithium-sulfur batteries. A sulfur positive electrode with the PP/PMMA separator exhibits a high initial capacity of 1100.10 mAh g^-1 at a current density of 0.1 mA cm^-2 along with a high Coulombic efficiency, which is higher than the corresponding first discharge capacity results obtained using the standard PP separator (948.60 mAh g^-1). In the double-layered separator, the arrayed PMMA microspheres can inhibit the diffusion of polysulfides through physical and chemical adsorption, thereby improving the electrochemical performance of lithium-sulfur batteries. In addition, the PMMA microspheres enhance the affinity of the separator to the electrolyte, which will increase the adsorption of the electrolyte to the separator and accelerate the diffusion rate of lithium ions.

Novel Non-Carbon Sulfur Hosts Based on Strong Chemisorption for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are considered as promising candidates for energy storage systems owing to their high theoretical capacity and high energy density. The application of Li-S batteries is hindered by several obstacles, however, including the shuttle effect, poor electrical conductivity, and the severe volume expansion of sulfur. The traditional method is to integrate sulfur with carbon materials. But the interaction between polysulfide intermediates and carbon is only weak physical adsorption, which easily leads to the escape of species from the framework (shuttle effect) of the material causing capacity loss. Recently, however, there has been a trend for the introduction of novel non-carbon materials as sulfur hosts based on the strong chemisorption. This review highlights recent research progress on novel non-carbon sulfur hosts based on strong chemisorption, in Li-S batteries. In comparison with carbon-based sulfur hosts, most non-carbon sulfur hosts have been demonstrated to be polar host materials that could efficiently adsorb polysulfide via strong chemisorption, mitigating their dissolution. The intrinsic mechanism associated with the role of non-carbon-based host materials in improving the performance of Li-S batteries is discussed.

Advances in Cathode Materials for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) represent a promising energy storage technology, and they show potential for next-generation high-energy systems due to their high specific capacity, abundant constitutive resources, non-toxicity, low cost, and environment friendliness. Unlike their ubiquitous lithium-ion battery counterparts, the application of LSBs is challenged by several obstacles, including short cycling life, limited sulfur loading, and severe shuttling effect of polysulfides. To make LSBs a viable technology, it is very important to design and synthesize outstanding cathode materials with novel structures and properties. In this review, we summarize recent progress in designs, preparations, structures, and properties of cathode materials for LSBs, emphasizing binary, ternary, and quaternary sulfur-based composite materials. We especially highlight the utilization of carbons to construct sulfur-based composite materials in this exciting field. An extensive discussion of the emerging challenges and possible future research directions for cathode materials for LSBs is provided.

Nitrogen-Doped Single-Walled Carbon Nanohorns as a Cost-Effective Carbon Host toward High-Performance Lithium-Sulfur Batteries

Nitrogen-doped single-walled carbon nanohorns (N-SWCNHs) are porous carbon material characterized by unique horn-shape structures with high surface areas and good conductivity. Moreover, they can be mass-produced (tons/year) using a novel proprietary process technology making them an attractive material for various industrial applications. One of the applications is the encapsulation of sulfur, which turns them as promising conductive host materials for lithium-sulfur batteries. Therefore, we explore for the first time the electrochemical performance of industrially produced N-SWCNHs as a sulfur-encapsulating conductive material. Fabrication of lithium-sulfur cells based on N-SWCNHs with sulfur composite could achieve a remarkable initial gravimetric capacity of 1650 mA h g^-1, namely equal to 98.5% of the theoretical capacity (1675 mA h g^-1), with an exceptional sulfur content as high as 80% in weight. Using cyclic chronopotentiometry and impedance spectroscopy, we also explored the dissolution mechanism of polysulfides inside the electrolyte.

A LiAlO2/nitrogen-doped hollow carbon spheres (NdHCSs) modified separator for advanced lithium–sulfur batteries

LiAlO₂/nitrogen-doped hollow carbon spheres (NdHCSs)-modified separators restrict the shuttle of the polysulfides.

In situ template synthesis of hierarchical porous carbon used for high performance lithium–sulfur batteries

Hierarchical porous carbon (HPC) consists of micropores, mesopores and macrospores which are synthesized by in situ formation of template followed by acid etching. The obtained pores are three-dimensional and interconnected, and evenly distributed in the carbon matrix. By adjusting the ratio of the raw materials, the high specific surface area and large pore volume is afforded. The obtained HPC-3 samples possess graphite flakes and locally graphited-carbon walls, which provide good electrical conductivity. These unique characteristics make these materials suitable cathode scaffolds for Li–S batteries. After encapsulating 61% sulfur into HPC-3 host, the S/HPC-3 composite exhibits excellent cycling stability, high columbic efficiency, and superior rate cycling as a cathode material. The S/HPC-3 composite cathode displays an initial discharge capacity of 1059 mA h g⁻¹, and a reversible capacity of 797 mA h g⁻¹ after 200 cycles at 0.2C. The discharge capacities of the S/HPC-3 composite cathode after every 10 cycles at 0.1, 0.2, 0.5, 1, and 2C are 1119, 1056, 982, 921, and 829 mA h g⁻¹, respectively.

In situ template synthesis of HPCs used for lithium–sulfur batteries, which exhibits excellent cycling stability and superior rate cycling.

The influence of different Si : C ratios on the electrochemical performance of silicon/carbon layered film anodes for lithium-ion batteries

With a high specific capacity (4200 mA h g⁻¹), silicon based materials have become the most promising anode materials in lithium-ions batteries.

Reverse Microemulsion Synthesis of Sulfur/Graphene Composite for Lithium/Sulfur Batteries

Due to its high theoretical capacity, high energy density, and easy availability, the lithium-sulfur (Li-S) system is considered to be the most promising candidate for electric and hybrid electric vehicle applications. Sulfur/carbon cathode in Li-S batteries still suffers, however, from low Coulombic efficiency and poor cycle life when sulfur loading and the ratio of sulfur to carbon are high. Here, we address these challenges by fabricating a sulfur/carboxylated-graphene composite using a reverse (water-in-oil) microemulsion technique. The fabricated sulfur-graphene composite cathode, which contains only 6 wt % graphene, can dramatically improve the cycling stability as well as provide high capacity. The electrochemical performance of the sulfur-graphene composite is further enhanced after loading into a three-dimensional heteroatom-doped (boron and nitrogen) carbon-cloth current collector. Even at high sulfur loading (∼8 mg/cm²) on carbon cloth, this composite showed 1256 mAh/g discharge capacity with more than 99% capacity retention after 200 cycles.

A MnO2/Graphene Oxide/Multi-Walled Carbon Nanotubes-Sulfur Composite with Dual-Efficient Polysulfide Adsorption for Improving Lithium-Sulfur Batteries

Lithium-sulfur batteries can potentially be used as a chemical power source because of their high energy density. However, the sulfur cathode has several shortcomings, including fast capacity attenuation, poor electrochemical activity, and low Coulombic efficiency. Herein, multi-walled carbon nanotubes (CNTs), graphene oxide (GO), and manganese dioxide are introduced to the sulfur cathode. A MnO₂/GO/CNTs-S composite with a unique three-dimensional (3D) architecture was synthesized by a one-pot chemical method and heat treatment approach. In this structure, the innermost CNTs work as a conducting additive and backbone to form a conducting network. The MnO₂/GO nanosheets anchored on the sidewalls of CNTs have a dual-efficient absorption capability for polysulfide intermediates as well as afford adequate space for sulfur loading. The outmost nanosized sulfur particles are well-distributed on the surface of the MnO₂/GO nanosheets and provide a short transmission path for Li⁺ and the electrons. The sulfur content in the MnO₂/GO/CNTs-S composite is as high as 80 wt %, and the as-designed MnO₂/GO/CNTs-S cathode displays excellent comprehensive performance. The initial specific capacities are up to 1500, 1300, 1150, 1048, and 960 mAh g^-1 at discharging rates of 0.05, 0.1, 0.2, 0.5, and 1 C, respectively. Moreover, the composite cathode shows a good cycle performance: the specific capacity remains at 963.5 mAh g^-1 at 0.2 C after 100 cycles when the area density of sulfur is 2.8 mg cm^-2.

Building better lithium-sulfur batteries: from LiNO3 to solid oxide catalyst

Lithium nitrate (LiNO₃) is known as an important electrolyte additive in lithium-sulfur (Li-S) batteries. The prevailing understanding is that LiNO₃ reacts with metallic lithium anode to form a passivation layer which suppresses redox shuttles of lithium polysulfides, enabling good rechargeability of Li-S batteries. However, this view is seeing more challenges in the recent studies, and above all, the inability of inhibiting polysulfide reduction on Li anode. A closely related issue is the progressive reduction of LiNO₃ on Li anode which elevates internal resistance of the cell and compromises its cycling stability. Herein, we systematically investigated the function of LiNO₃ in redox-shuttle suppression, and propose the suppression as a result of catalyzed oxidation of polysulfides to sulfur by nitrate anions on or in the proximity of the electrode surface upon cell charging. This hypothesis is supported by both density functional theory calculations and the nitrate anions-suppressed self-discharge rate in Li-S cells. The catalytic mechanism is further validated by the use of ruthenium oxide (RuO₂, a good oxygen evolution catalyst) on cathode, which equips the LiNO₃-free cell with higher capacity and improved capacity retention over 400 cycles.

Designing high-energy lithium–sulfur batteries

This review summarizes major developments in the field of lithium–sulfur batteries with a focus on successful material design strategies.

An in situ confinement strategy to porous poly(3,4-ethylenedioxythiophene)/sulfur composites for lithium–sulfur batteries

Porous poly(3,4-ethylenedioxythiophene)/sulfur composite was prepared throughin situautocatalytic polymerization of dibromized 3,4-ethylenedioxythiophene for lithium–sulfur batteries.