Diffusion Of Lithium Polysulfides Research Articles

Modification and Functionalization of Separators for High Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSB) have been recognized as a prominent potential next-generation energy storage system, owing to their substantial theoretical specific capacity (1675 mAh g-1) and high energy density (2600 Wh kg-1). In addition, sulfur's abundance, low cost, and environmental friendliness make commercializing LSB feasible. However, challenges such as poor cycling stability and reduced capacity, stemming from the formation and diffusion of lithium polysulfides (LiPSs), hinder LSB's practical application. Introducing functional separators represents an effective strategy to surmount these obstacles and enhance the electrochemical performance of LSBs. Here, we have conducted a comprehensive review of recent advancements in functional separators for LSBs about various (i) carbon and metal compound materials, (ii) polymer materials, and (iii) novel separators in recent years. The detailed preparation process, morphology and performance characterization, and advantages and disadvantages are summarized, aiming to fundamentally understand the mechanisms of improving battery performance. Additionally, the development potential and future prospects of advanced separators are also discussed.

A Ternary (P, Se, S) Covalent Inorganic Framework as a Shuttle Effect-Free Cathode for Li-S Batteries.

Developing new cathode materials to avoid shuttle effect of Li-S batteries at source is crucial for practical high-energy applications, which, however, remains a great challenge. Herein, a new class of sulfur-containing ternary covalent inorganic framework (CIF), P4 Se6 S40 , is explored, by simply comelting powders of P, S, and Se. The P4 Se6 S40 CIF with open framework enables all active sites available during electrochemical reactions, giving a high capacity delivery. Moreover, introducing Se atoms can improve intrinsic electronic conductivity of S chains yet without remarkably compromising the capacity because Se is also electrochemical active to lithium storage. More importantly, Se atoms in S-Se chains can serve as a heteroatom barrier to block the bonding of S atoms around, effectively avoiding the formation of long-chain polysulfides during cycling. Besides, stable Li3 PS4 with a tetrahedral configuration formed after lithiation works as not only a good ionic conductor to promote Li ion diffusion, but a three-dimensional spatial barrier and chemical anchor to suppress the dissolution and diffusion of lithium polysulfides (LiPS), further inhibiting the shuttle effect. Consequently, the P4 Se6 S40 cathode delivers high capacity and excellent capacity retention with even a high loading of 10.5 mg cm-2 which far surpasses the requirement for commercial applications.

Perspectives of High‐Performance Li–S Battery Electrolytes

AbstractLithium–sulfur batteries with high energy density are considered to be one of the most promising candidates for the next‐generation energy storage devices. Electrolyte as the medium for Li+ transportation between the electrodes, also plays a crucial role in inhibiting the dissolution and diffusion of lithium polysulfides in Li–S batteries. The working mechanism of Li–S batteries in different electrolytes is classified into “solid‐liquid‐solid” and “solid‐solid” conversions. Under the “solid‐liquid‐solid” conversion, Li–S batteries would inevitably face the challenges such as “shuttle effect” that lead to poor cycle performance, and under the “solid‐solid” conversion, they would face interface mismatch that limits the utilization of sulfur with low energy density, while both conversion mechanisms cause uncontrollable Li dendrites on anode. According to the conversion mechanism, electrolytes can be divided into ether‐based, ionic liquid‐based, gel polymer electrolytes, and polymer‐based solid‐state electrolytes with “solid‐liquid‐solid” conversion, as well as carbonate‐based electrolytes and oxide/sulfide‐based solid‐state electrolytes with “solid‐solid” conversion. Based on the conversion mechanism of active materials in different electrolytes, the current status on the strategies from multiple perspectives are summarized to improve the electrochemical performance, with the hope to provide a comprehensive guideline toward the development of suitable electrolytes for Li–S batteries.

Ab Initio Molecular Dynamics Simulations of Amorphous Metal-Polysulfides as Cathode Materials for Lithium-Ion Batteries

Lithium-sulfur batteries offer a few advantages, including high energy density and low cost, compared to our current battery technology. However, various polysulfide intermediates formed during charging and discharging lead to the polysulfide shuttle effect, which hinders their commercial application. It has been shown that amorphous metal sulfides can reduce the formation of polysulfides, although a fundamental understanding is lacking. In this research, amorphous molybdenum and titanium sulfides with different sulfur concentrations were generated by the simulated melt-quench process using ab initio molecular dynamics simulations. Different numbers of lithium ions were added at the cathode/electrolyte interface to simulate the electrochemical conversion process in these materials. It is observed that the behavior of amorphous metal sulfides is different from that of sulfur, and the formation and diffusion of lithium polysulfides have been greatly reduced. Insights obtained from this work could help to develop new strategies to effectively inhibit the polysulfide shuttle effect.

Cooperative catalytic platinum species accelerating polysulfide redox reactions for Li-S batteries

The shuttle effect derived from diffusion of lithium polysulfides (LiPSs) and sluggish redox kinetic bring about poor cycling stability and low utilization of sulfur, which have always been the key challenging issues for the commercial application of lithium-sulfur (Li-S) batteries. Rational design of cathode materials to catalyze Li2S dissociation/nucleation processes is an appealing and valid strategy to develop high-energy practical Li-S batteries. Herein, considering the synergistic effect of bidirectional catalysis on LiPSs conversion and enhanced chemical immobilization for LiPSs by heteroatom doping, Pt nanoparticles loaded on nitrogen-doped carbon spheres (Pt/NCS composites) were constructed as cathode materials. According to the dynamic evolution of Pt catalysts and sulfur species, Pt0 and Pt2+ species were identified as active species for the accelerated dissociation and nucleation of Li2S, respectively. Meanwhile, in-situ Raman results demonstrated the expedited conversion of sulfur species resulted from bidirectional catalysis of active Pt species, corresponding to boosted redox kinetics. Consequently, Pt/NCS cathode exhibited improved long-term cyclability with high initial capacity, along with enhanced rate capability. This work provides a facile approach to construct cathode materials with bidirectional catalysis on Li2S dissociation/nucleation, and sheds light on a more global understanding of the catalytic mechanism of metal catalysts during LiPSs conversion.

Adsorption-catalysis design with cerium oxide nanorods supported nickel-cobalt-oxide with multifunctional reaction interfaces for anchoring polysulfides and accelerating redox reactions in lithium sulfur battery

The charge and discharge working mechanisms in lithium sulfur batteries contain multi-step complex reactions involving two-electron transfer and multiple phase transformations. The dissolution and diffusion of lithium polysulfides cause a huge loss of active material and fast capacity decay, preventing the practical use of lithium sulfur batteries. Herein, CeO2 nanorods supported bimetallic nickel cobalt oxide (NiCo2Ox) was investigated as a cathode host material for lithium sulfur batteries, which can provide adsorption-catalysis dual synergy to restrain the shuttle of polysulfides and stimulate rapid redox reaction for the conversion of polysulfides. The polar CeO2 nanorods with abundant surface defects exhibit chemisorption towards lithium polysulfides and the excellent electrocatalytic activity of NiCo2Ox nanoclusters can rev up the chain transformation of lithium polysulfides. The electrochemical results show that the battery with NiCo2Ox/CeO2 nanorods can demonstrate high discharge capacity, stable cycling, low voltage polarization and high sulfur utilization. The battery with NiCo2Ox/CeO2 nanorods unveils a high specific capacity of 1236 mAh g−1 with a very low capacity fading of 0.09% per cycle after 100 cycles at a 0.2C current rate. Moreover, the excellent performance with high sulfur loading (>5 mg cm−2) verifies a huge promise for future commercial applications.

Electrically and thermally conductive Al2O3/C nanofiber membrane filled with organosilicon as a multifunctional integrated interlayer for lithium-sulfur batteries under lean-electrolyte and thermal gradient

The development of lithium-sulfur (Li-S) batteries is dogged not only by severe limitations in cycling and rate performances arising from the shuttle effect of lithium polysulfides (LiPSs) but also severe degradation under harsh evaluation conditions of high sulfur loading, lean-electrolyte, and prominent thermal gradient. To achieve high performance and safety in Li-S batteries, a flexible and multifunctional integrated interlayer consisting of dual-functional alumina/carbon (Al2O3/C) nanofiber skeleton and organosilicon (OSi) filler is fabricated. Electrically and thermally conductive nanofibers are continuous and interlaced, enhancing the reutilization of LiPSs and the homogenization of temperature gradient through constructed dual-conductive networks. The interval-filled OSi helps in the diffusion of LiPSs and the absorption and retention of electrolytes, providing significant support to stabilize the Li-S batteries for long-term cycling. As a result, considerable enhancements in cycle stability and rate performance either under a high sulfur loading of ∼5.5 mg cm-2, low electrolyte/sulfur (E/S) rate of 4 μL mg-1, or artificial temperature gradients are achieved for a typical sulfur/carbon black cathode simply by incorporating multifunctional Al2O3/C@OSi interlayer. The new design and configuration of the interlayer may practically be used in high-energy applications since it can effectively address severe limitations of the current Li-S batteries.

Chemisorption of polysulfides by keto groups modified Li4Ti5O12 nanofibers with 3D interwove network structure for LSBs

Lithium-sulfur batteries (LSBs) possess high energy density but suffer from severe capacity fading due to the dissolution of lithium polysulfide (LiPSs). Novel design and mechanisms to encapsulate LiPSs are greatly desired by high-performance LSBs towards practical applications. Herein, we report a strategy of preparing Lithium titanate (Li4Ti5O12, LTO) nanofibers using bacterial cellulose as excellent biomimetic mineralization template at room temperature. Natural abundant organic molecule of Anthraquinone (AQ) combine with the zero strain fast ionic conductor of LTO can inhibit the dissolution and diffusion of LiPSs through redox reactions during cycling. The keto groups (C = O) of AQ play a critical role in forming strong Lewis acid-based chemical bonding. The 3D interwove network structure of LTO nanofibers also hinders the shuttle effect of LiPSs. Polydopamine (PDA) coated on the outermost layer not only improves the conductivity of the whole electrode, but also enhances the wettability of the electrolyte. The long-term stability of S-based electrode is ensured by the synergistic effect of the three. This mechanism leads to a long cycling stability of S-based electrodes. With a high sulfur content of ∼ 70%, a low capacity decay of 0.042%, 0.063% and 0.061% per cycle for 500 cycles at the current densities of 1, 2 and 4C, respectively. The water-soluble binder was adopted, which was a solid step for the practical application of LSBs. This finding and understanding paves an alternative avenue for the future design of S-based cathodes toward the practical application of LSBs.

Insight into Lithium–Sulfur Batteries with Novel Modified Separators: Recent Progress and Perspectives

Lithium-sulfur (Li-S) batteries have been found to have sky-scraping theoretical gravimetric energy density and have gained a lot of interest. However, owing to low electrical conductivity, a conducting substance must be coupled with the sulfur cathode. The first important concern in Li-S is diffusion of lithium polysulfides (PSs), resulting in a shuttle linking both the cathode and anode and rapid capacity of degradation. Plating conventional separators is a kind of alleviation of the shuttle issue. To achieve an advanced Li-S battery, understanding of the structure of PSs needs to be considered to design efficient separator coating materials. The main object of this work is to review the most promising recent challenges and address the application of modified coatings on the polypropylene (PP), polyethylene (PE), and glass fiber (GF) separators for high-performance Li-S batteries. The particular focus has been placed on functioning of various functional layers on the surface of PP, PE, and GF, including polymers, carbons, nanomaterials, and their composites. Finally, the polar host materials in the cathode that influence the Li-S performance are summarized. © 2021 American Chemical Society. All rights reserved.

Yolk@Shell Structured MnS@Nitrogen-Doped Carbon as a Sulfur Host and Polysulfide Conversion Booster for Lithium/Sodium Sulfur Batteries

Lithium-sulfur (Li-S) batteries have been regarded as an important candidate for next-generation energy storage devices due to their low cost and high theoretical energy density. However, several factors retard the practical use of Li-S batteries including the slow kinetics of lithium polysulfide (LiPS) transformation as well as the shuttle effect induced by the diffusion of LiPS that damages the cycling stability of Li-S batteries. In this study, a yolk@shell structured MnS@nitrogen-doped carbon (MnS@N-C) is developed as the S host and polysulfide conversion booster, which offers both the physical confinement of S species and accelerated kinetics toward LiPS catalytic conversion. As a result, the developed S/yolk@shell MnS@N-C delivers a higher rate performance compared to S/yolk@shell MnO@N-C and S/N-C and long cycle life with a remaining capacity of 636.1 mAh g–1 after 330 cycles at 0.5C. When equipped with MnS@N-C functional separators, S/yolk@shell MnS@N-C retains a capacity of 504.2 mAh g–1 after 1000 cycles at 1C. In addition, S/yolk@shell MnS@N-C also delivers a decent capacity decay of 0.16% per cycle after 300 cycles at 0.5C in a room-temperature Na-S battery.

Metal Nanoparticles Supported on Nitrogen-Doped Porous Carbon As a Cathode Material for Lithium-Sulfur Batteries

Increasing demands of lithium-ion batteries (LIBs) in devices with high energy demands such as electronic vehicles and energy storage systems have exposed the vulnerability of the state-of-the-art LIBs. Low energy-to-weight ratios and high production costs have shed light on the increasing demands for batteries with higher energy density. Lithium-sulfur batteries (LSBs) with high theoretical capacity and lower price-to-energy ratio are the prime candidate for the replacement of LIBs.1,2 To compete with LIBs, there are few practical requirements that LSBs should have: 1) sufficient sulfur content (> 70 wt.%), 2) high areal sulfur loading (> 5 mg cm−1), and 3) low electrolyte to sulfur rations (< 4 µL mg−1). On the other hand, few intrinsic characteristics of LSBs need to be addressed before their commercialization, poor conductivity of S8, and Li2S and the large change in the volume during the reduction reaction that takes place in the discharge process. Loss of lithium polysulfide (LiPS) leads to the loss of active materials and poor stability. The diffusion of LiPS from anode to cathode can hamper the columbic efficiency of LSBs. To address these problems in the cathode a development of a conductive framework which is also a sulfur and LiPS adsorbent is crucial.Functionalized supports are widely utilized in energy conversion and energy storage applications. High surface area porous carbon materials have been introduced as a highly active cathode material for LSBs.3 The electrochemical performance of the LSBs can be largely improved by the efficient reversible conversion of LiPS to Li2S during discharge and to elemental sulfur during charge.4 In this study, we have developed a high surface area nitrogen-doped carbon framework as a support for highly distributed small Ni nanoparticles (NPs). The introduction Ni NPs enhances the conductivity and acts as active sites for the adsorption of LiPS during reduction reaction. The porous carbon framework helps with trapping the insoluble Li2S2/ Li2S species at the end of the discharge half-cycle. Nickel NPs act as active centers for the adsorption of polysulfides during the discharge process and rapidly convert them to Li2S while catalyzing Li2S oxidation to sulfur in the reverse process. The addition of Ni NPs improves the reaction kinetics and activity retention of the LSBs. References (1) Ding, Y.; Cano, Z. P.; Yu, A.; Lu, J.; Chen, Z. Automotive Li-Ion Batteries: Current Status and Future Perspectives. Electrochem. Energy Rev. 2019, 2 (1), 1–28. https://doi.org/10.1007/s41918-018-0022-z.(2) Yin, Y. X.; Xin, S.; Guo, Y. G.; Wan, L. J. Lithium-Sulfur Batteries: Electrochemistry, Materials, and Prospects. Angew. Chemie - Int. Ed. 2013, 52 (50), 13186–13200. https://doi.org/10.1002/anie.201304762.(3) Ji, X.; Lee, K. T.; Nazar, L. F. A Highly Ordered Nanostructured Carbon-Sulphur Cathode for Lithium-Sulphur Batteries. Nat. Mater. 2009, 8 (6), 500–506. https://doi.org/10.1038/nmat2460.(4) Lim, W. G.; Kim, S.; Jo, C.; Lee, J. A Comprehensive Review of Materials with Catalytic Effects in Li–S Batteries: Enhanced Redox Kinetics. Angew. Chemie - Int. Ed. 2019, 58 (52), 18746–18757. https://doi.org/10.1002/anie.201902413.

Layer-by-layer self-assembled covalent triazine framework/electrical conductive polymer functional separator for Li-S battery

Lithium-sulfur (Li-S) battery is attracting intense attention due to its extremely high theoretical specific capacity and low cost. However, the dissolution and diffusion of lithium polysulfides (LiPS), as well as the insulating property of sulfur and its discharge products, limit the practical application of Li-S battery. In this work, we developed an ultralight functional separator (LBL-fseparator) with orderly structure and multifunctional properties through electrostatic layer-by-layer (LBL) self-assembly of positively charged poly(diallyl dimethyl ammonium chloride) (PDDA) wrapped covalent triazine framework (CTF) (CTF@PDDA) and negatively charged poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT: PSS) to effectively retard LiPS shuttle and improve the utilization of active sulfur material. The CTF@PDDA as LiPS shuttle inhibiting layers displays strong LiPS-anchor ability through physical/chemical interaction as well as excellent electrolyte uptake capacity due to its large specific surface area and porous structure, while the PEDOT: PSS as the conductive layers improves electron transfer as well as excellent interface stabilizer and adhesion binder. It was demonstrated that the proposed LBL-fseparator assembled with general S-cathode and Li metal anode displays commendable cycling stability (0.052% capacity fade-rate per cycle over 1000 cycles at 1C), superb utilization of sulfur (90.7% at 0.1C and 59.2% at 2C), and enhanced protection ability of the Li metal. The excellent battery performance and easily mass-produced method provide a useful strategy for industrial-scale production.

Cellulose-Derived Carbon Microfiber Mesh for Binder-Free Lithium-Sulfur Batteries.

The practical application of lithium-sulfur batteries (LSBs) has been impeded by several chronic problems related to the insulating nature of sulfur and lithium sulfide, in addition to the dissolution and diffusion of lithium polysulfides. In view of these problems, a large variety of carbonaceous materials have been employed to enhance the electronic conductivity of the cathode and/or sequester lithium polysulfides within conductive matrixes. Although they may exhibit impressive electrochemical performance, the fabrication of most carbon materials involves costly precursors and complicated procedures. Waste paper-the main constituent of municipal waste-is composed of carbohydrates, and can be an ideal precursor for carbon materials. Herein, carbon microfiber meshes (CMFMs) obtained by the pyrolysis of common filter paper in argon (A-CMFM) or ammonia (N-CMFM) were used to form sulfur cathodes. Compared with LSBs based on A-CMFM, those based on N-CMFM demonstrated higher specific capacity and better rate capability, with a capacity of 650 mA h g-1 at 0.2 C and 550 mA h g-1 at 0.5 C. This was owing to the strong immobilization of lithium polysulfides resulting from the heteroatom doping and hydrophilicity of N-CMFM. The results indicate that cellulose paper-derived carbon is a promising candidate for application in high-performance LSBs.

High Cycling Performance Li‐S Battery via Fenugreek Gum Binder Through Chemical Bonding of the Binder with Polysulfides in Nanosulfur@CNFs Cathode

AbstractThe dissolution and diffusion of lithium polysulfides are one of the main intrinsic bottlenecks in the development of lithium‐sulfur (Li−S) batteries with long term cycling stability. Appropriate binders could play a key role of anchoring the lithium polysulfides in S‐cathode through strong chemical bonds, thus boosts the electrochemical performance of Li−S battery. Herein, we report a new binder (fenugreek gum, FG) that has enhanced significantly the cycling performance of Li−S batteries with S@CNFs composite as cathode. The Li−S cell with FG binder delivers a large initial capacity of 900 mAh g−1 at 2 C, and a reversible capacity retention of 45.6 % after 1300 cycles, superior to the cycling performance of Li−S cell with conventional PVDF or previous reported guar gum (GG) binder. This enhancement in cycling performance of Li−S batteries could be attributed to the formation of the S−O and Li−O bonds between the O‐relevant functional groups in the binder and the polysulfides in S‐cathode as manifested by XPS data of the discharged and charged electrodes. Furthermore, the tensile strain rate of the FG binder is as high as 32 %, which can effectively restrain the volume expansion of the S‐cathode during the discharge/charge process and ensure the integrity of the electrode.

Single-atom Fe and N co-doped graphene for lithium-sulfur batteries: a density functional theory study

Shuttle effect caused by the dissolution and diffusion of lithium polysulfides (Li2Sn) in electrolytes is the main reason that hinders the application of lithium-sulfur batteries. The introduction of anchoring materials to adsorb Li2Sn is an effective way to overcome this problem and achieve long-term cycling stability. In this work, a systematical density functional theory study of single-atom Fe and N co-doped graphene (FeNx (x = 1, 2, 3, 4)) is conducted to elaborate the anchoring mechanism. We investigate the adsorption of Li2Sn on FeNx and study the detailed interaction and electronic structure. It is proved that there is strong interaction between FeNx and Li2Sn, which will inhibit the dissolution and diffusion of Li2Sn (n = 4, 6, 8) and is beneficial to the uniform nucleation of Li2S and Li2S2. In addition, the stability of FeNx can be improved by increasing the number of N coordination. Finally, the adsorption energy can be adjusted by doping concentration of atoms. Hence, our work reveals in detail the mechanism how FeNx improve the performance of lithium-sulfur batteries. It is of guiding significance to the screening and design of anchoring materials in the future.

Anchoring effects of S-terminated Ti2C MXene for lithium-sulfur batteries: A first-principles study

The low cycle stability and low efficiency of lithium-sulfur (Li-S) batteries stemming from the dissolution and diffusion of lithium polysulfides in the electrolyte severely hinder their commercialization. Using first-principles calculations, we demonstrate that the strong Ti-S interaction leads to stable S-terminated Ti2C MXene (Ti2CS2). Compared with other surface-functionalized Ti2C MXenes, such as Ti2CO2 and Ti2CF2, Ti2CS2 has the highest binding energy to polysulfides and thus highest efficiency to suppress the shuttle phenomenon of polysulfides. In addition, the metallic features of Ti2CS2 facilitate the electrochemical activity during the charge (or discharge) process. The diffusion of Li ions on Ti2CS2 experiences a relatively low energy barrier which is expected to assist the electrochemical process. These results provide a surface-functionalization strategy to design of sulfur host materials for high performance Li-S batteries.

Novel Conductive Metal-Organic Framework for a High-Performance Lithium-Sulfur Battery Host: 2D Cu-Benzenehexathial (BHT).

Despite the high theoretical capacity of lithium-sulfur (Li-S) batteries, their commercialization is severely hindered by low cycle stability and low efficiency, stemming from the dissolution and diffusion of lithium polysulfides (LiPSs) in the electrolyte. In this study, we propose a novel two-dimensional conductive metal-organic framework, namely, Cu-benzenehexathial (BHT), as a promising sulfur host material for high-performance Li-S batteries. The conductivity of Cu-BHT eliminates the insulating nature of most S-based electrodes. The dissolution of LiPSs into the electrolyte is largely prevented by the strong interaction between Cu-BHT and LiPSs. In addition, orientated deposition of Li2S on Cu-BHT facilitates the kinetics of the LiPS redox reaction. Therefore, the use of Cu-BHT for Li-S battery cathodes is expected to suppress the LiPS shuttle effect and to improve the overall performance, which is ideal for practical application of Li-S batteries.

Adsorption and diffusion of lithium polysulfides over blue phosphorene for Li-S batteries.

Lithium-sulphur (Li-S) batteries suffer from capacity loss due to the dissolution of lithium polysulfides (LiPSs). Although finding cathodes that can trap LiPSs strongly is a possible solution to suppress the "shuttle" effect, fast diffusion of lithium and LiPSs is also pivotal to prevent agglomeration. We report that monolayer blue phosphorene (BP), a recently synthesized two-dimensional material, possesses these characteristics as a cathode in Li-S batteries. Density functional theory calculations showed that while the adsorption energies (Eb) of various LiPSs over pristine BP are reasonably strong (from -0.86 eV to -2.45 eV), defect engineering of the lattice by introducing a single vacancy (SV) increased the binding strength significantly, with Eb in the range of -1.41 eV to -4.34 eV. Ab-initio molecular dynamics simulations carried out at 300 K showed that the single vacancies trap the Li atoms in the LiPSs compared to pristine BP. Projected density of states revealed that the creation of an SV induces metallicity in the cathode. Furthermore, an increase in the adsorption strength did not cause significant structural deformation, implying that the soluble large LiPSs did not decompose, which is essential to suppress capacity fading. The energy barriers for LiPSs' migration over pristine BP are minimal to ensure ultrafast diffusion, with the lowest diffusion energy barriers being 0.23 eV, 0.13 eV and 0.18 eV for Li2S4, Li2S6 and Li2S8, respectively. Furthermore, the energy barrier associated with the catalytic oxidation of Li2S over pristine and defective BP was found to be greater than three times smaller compared to graphene, which suggests that charging processes could be faster by orders of magnitude. Therefore, BP with a suitable combination of defects would be an excellent cathode material in Li-S batteries.

Sulfur Immobilization by “Chemical Anchor” to Suppress the Diffusion of Polysulfides in Lithium–Sulfur Batteries

AbstractLithium–sulfur (Li–S) battery is considered to be one of the most promising contenders for the next generation high‐energy storages due to their high theoretical energy density (≈2600 Wh kg−1), which is nearly five times higher than that of the commercial LiCoO2/graphite batteries. However, a series of issues especially for the dissolution of lithium polysulfides (LiPSs) and their “shuttle effect” greatly limit their widely commercial applications. Starting from a brief overview of conventional methods to solve these problems, the achievements spotlighted in this review mainly show that the diffusion of LiPSs can be effectively suppressed by forming strong “chemical anchor” between LiPSs and host materials. The synthetic methods and characterization techniques are reviewed according to different types of chemical bonding between LiPSs and the host materials. Theoretical calculation methods are also summarized here to further understanding the role of these “chemical anchors.” Proposing with some perspectives and future research efforts, this review is hoped to provide an in‐depth understanding and offer avenues in the rational design of Li–S batteries with long cycle life and high energy/power density in the near future.

High electrochemical performance of hierarchical CoMoS3.13/SnO2 nanocomposites as lithium-sulfur battery cathode

Hierarchical CoMoS3.13/SnO2 nanocomposites as cathode of lithium-sulfur (Li-S) battery are prepared by a two-step method. The synergistic effect between CoMoS3.13 and SnO2 leads to high capacity, cyclability and rate capability. The reversible capacity of hierarchical CoMoS3.13/SnO2 nanocomposites is up to 770mAhg−1 at 0.3C rate (~3h per half cycle) and maintains 718mAhg−1 after 50 cycles, much higher than that of pure CoMoS3.13 nanosheets. And the diffusion of lithium polysulfide can be restrained by SnO2 nanoparticles shell, avoiding the loss of material during cycling. The present results indicate that hierarchical CoMoS3.13/SnO2 nanocomposites are good candidates for the cathode of Li-S battery.