Shuttle Effect Of Polysulfides Research Articles

Revealing the Multifunctional Electrocatalysis of Indium‐Modulated Phthalocyanine for High‐Performance Lithium‐Sulfur Batteries

The sluggish kinetics of complicated multiphase conversions and the severe shuttling effect of lithium polysulfides (LiPSs) significantly hinder the applications of Li‐S battery, which is one of the most promising candidates for the next‐generation energy storage system. Herein, a bifunctional electrocatalyst, indium phthalocyanine self‐assembled with carbon nanotubes (InPc@CNT) composite material, is proposed to promote the conversion kinetics of both reduction and oxidation processes, demonstrating a bidirectional catalytic effect on both nucleation and dissolution of Li2S species. The theoretical calculation shows that the unique electronic configuration of InPc@CNT is conducive to trapping soluble polysulfides in the reduction process, as well as the modulation of electron transfer dynamics also endows the dissolution of Li2S in the oxidation reaction, which will accelerate the effectiveness of catalytic conversion and facilitate sulfur utilization. Moreover, the InPc@CNT modified separator displays lower overpotential for polysulfide transformation, alleviating polarization of electrode during cycling. The integrated spectroscopy analysis, HRTEM, and electrochemical study reveal that the InPc@CNT acts as an efficient multifunctional catalytic center to satisfy the requirements of accelerating charging and discharging processes. Therefore, the Li–S battery with InPc@CNT‐modified separator obtains a discharge‐specific capacity of 1415 mAh g−1 at a high rate of 0.5 C. Additionally, the 2 Ah Li–S pouch cells deliver 315 Wh kg−1 and achieved 80% capacity retention after 50 cycles at 0.1 C with a high sulfur loading of 10 mg cm−2. Our study provides a practical method to introduce bifunctional electrocatalysts for boosting the electrochemical properties of Li–S batteries.

Synthesis of the Ni2P–Co Mott–Schottky Junction as an Electrocatalyst to Boost Sulfur Conversion Kinetics and Application in Separator Modification in Li-S Batteries

To overcome the shuttling effect and sluggish conversion kinetics of polysulfides, a large number of catalysts have been designed for lithium-sulfur (Li-S) batteries. Herein, a Mott-Schottky junction catalyst composed of Co nanoparticles and Ni2P was designed to improve polysulfide kinetics. Our investigations reveal the rearrangement of charges at the Schottky junction interface and the construction of the built-in electric field are crucial for lowering the activation energy of the dissolved Li2Sn reduction and Li2S nucleation reaction. Furthermore, a series of experimental and electrochemical tests were performed to demonstrate that the Schottky catalytic effect enhanced the synergistic catalytic effect. With a Ni2P-Co@CNT catalyst, the battery exhibits an initial specific capacity of 874 mAh g-1 at a rate of 4.0 C, and the decay rate per cycle is 0.049% in 700 cycles. Meanwhile, the battery shows 0.118% decay rate per cycle at 0.5 C in 100 cycles at a high sulfur loading of 10 mg cm-2. The Schottky heterojunction structure proposed here has been shown to have a good catalytic effect on the reduction of Li2Sn and nucleation of Li2S, which provides a profound guidance for efficient and rational catalyst design.

Anchoring and Boosting: Ferrocene-Based Separators Used to Eliminate the Polysulfide Shuttle Effect for Li-S Batteries

Anchoring and Boosting: Ferrocene-Based Separators Used to Eliminate the Polysulfide Shuttle Effect for Li-S Batteries

Highly-dispersed nickel on 2D graphitic carbon nitrides (g-C3N4) for facilitating reaction kinetics of lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are promising next-generation energy storage devices due to high theoretical energy density and low-cost. Nevertheless, the practical applications are hindered by polysulfide shuttling effect, low electrical conductivity of sulfur, and slower conversion kinetics. Here, the graphited g-C3N4 assembled with highly-dispersed nickel (HDNi@g-C3N4) is designed as a catalyst to accelerate the reaction kinetics of lithium polysulfide. The oxidized Ni sites of HDNi@g-C3N4 molecules significantly accommodate the orbital for the electron clouds of polysulfide by forming Sn2–‧‧‧Ni-N active site, thus efficiently improving redox kinetics and mitigating shuttle effects. Based on density functional theory (DFT) calculations, HDNi@g-C3N4 exhibits a superior metallicity with increased density of states (DOS) at the Fermi energy level. Then, the narrowed energy gap between the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) level contributes to the enhanced conductivity of catalyst molecular and fast combination between electrons and Li+ ions. Moreover, the positive Gibbs free energy change is significantly decreased for the HDNi@g-C3N4 cathode. The Li-S battery exhibits a high reversible capacity of 1, 271.6 mAh g−1 at 0.1 C and a high rate capacity of 571.96 mAh g−1 at 2.0 C, a preferable cycling stability with a capacity retention of 53 % even after 500 cycles at a 1.0 C, and an average decay rate of 0.733 % per cycle.

Novel Adsorption-Catalysis Design of CuO Impregnated CeO2 Nanorods As Cathode Modifier for Lithium-Sulfur Battery

Lithium sulfur batteries (LSBs) are a promising candidate to be used in modern commodities like electric vehicles, grid energy storage, electric aviation, and many others because of the exceptionally high theoretical capacity of sulfur (1675 mAh g-1), almost 5 times higher than the conventional lithium-ion batteries. However, the problem of polysulfide shuttling effect originating from the dissolved lithium polysulfides in the electrolyte results in poor cycling stability, hindering the commercialization of LSB. Significant advancement has been made over the years due to a great deal of research on novel materials development and structural design for lithium polysulfide (Li2Sn: 4≤ n ≤8) adsorption synergy to counter the polysulfide shuttling effect 1. However, rather than focusing only on the adsorption synergy (Physical confinement and chemical binding), novel catalysts that can accelerate the polysulfide conversion reaction kinetics are needed to design the next generation LSB. Previously, our group investigated shape-controlled cerium oxide (CeO2) to accelerate the polysulfide conversion reactions by generating the intermediate steps of thiosulfate and polythionate 2, 3. Copper oxide (CuO), being a p-type semiconducting material, is another promising material that can activate thiosulfate formation as its redox potential is 2.53 V vs Li/Li+, which lies in the potential window of 2.4 V < E° ≤ 3.05 V that selectively triggers the formation of thiosulfate. Herein, we investigated 10 wt% of CuO impregnated on the CeO2 nanorods (10 wt%CuO/CeO2) as a cathode host for LSB. The CuO impregnation on the surface of CeO2 nanorods attributed strong interaction between the surface defect rich CeO2 nanorods and the copper oxides (CuOx: Cu2O and CuO) promoting excellent electrocatalytic activity. The 10 wt%CuO/CeO2 sample provides adsorption-catalysis dual synergy to chemically bind and further catalyze the polysulfide conversion by polythionate and thiosulfate generation. As a result, the derived LSB exhibited excellent electrochemical performance with high capacity of 1141 mAh g-1 at 0.2 C with a sulfur loading of 1.33 mg cm-2 and a capacity loss of only 0.04% per cycle after 60 cycles. Key words: lithium sulfur batteries, lithium polysulfides, shuttle effect, cerium oxide, catalysis. Xiong, D. G.; Zhang, Z.; Huang, X. Y.; Huang, Y.; Yu, J.; Cai, J. X.; Yang, Z. Y., Boosting the polysulfide confinement in B/N–codoped hierarchically porous carbon nanosheets via Lewis acid–base interaction for stable Li–S batteries. Journal of Energy Chemistry 2020, 51, 90-100. Azam, S.; Wei, Z.; Wang, R., Cerium oxide nanorods anchored on carbon nanofibers derived from cellulose paper as effective interlayer for lithium sulfur battery. J Colloid Interface Sci 2022, 615, 417-431. Wei, Z.; Li, J.; Wang, R., Surface engineered polar CeO2-based cathode host materials for immobilizing lithium polysulfides in High-performance Li-S batteries. Applied Surface Science 2022, 580.

Emerging Strategies for Gel Polymer Electrolytes with Improved Dual-Electrode Side Regulation Mechanisms for Lithium-Sulfur Batteries.

Although GPE still has the risk of shuttling due to the incomplete removal of liquid electrolytes compared to SPE, which has the most promise of eliminating polysulfide shuttling, researchers have made abundant efforts to eliminate as much of the polysulfide shuttling effect as possible while retaining the unique advantages of GPE. For example, physical barrier to polysulfides by improving the pore size of GPE or fabricating multidimensional structures by different preparation methods. Further chemical adsorption of polysulfides by adding nanofillers to increase polar sites to create polar-polar interactions with polysulfides or to create Lewis acid-base interactions. However, although chemical adsorption can indeed highly immobilize polysulfides, it still brings disadvantages such as loss of active material. Therefore, other researchers have employed GPE with ion-selective permeability that has electrostatic repulsive force or steric hindrance to polysulfides to better inhibit polysulfide shuttling. However, modifying only the cathode side is not enough to enhance this overall properties of Li-S cells. These problems of poor Li+ transport, lithium dendrite growth, and poor SEI due to uneven lithium ion deposit on Li anode side still affect the overall performance of Li-S cells. Therefore, a GPE to improve these problems on the Li anode side is summarized below. Compared with an all-solid electrolyte, GPE, which has a partially liquid electrolyte, clearly has advantages such as strong interfacial contact, good anode interface compatibility, and high flexibility. However, it is still not comparable to the ionic conductivity, etc. of pure liquid electrolyte only. Therefore, the problems on the lithium metal anode side are mainly focused on the lithium ion transport problems and the problems of lithium dendrite growth and inhomogeneous SEI at the lithium anode interface. Facing the problems in these two aspects, researchers have given many improvement solutions respectively. For the lithium ion transport problem, researchers have instead provided pathways for lithium ion transport by adding amorphous nanofibers or nanofillers to reduce the crystallinity of the polymer and improve the ionic conductivity. Alternatively, the migration number of lithium ions can be increased by limiting the anions in the electrolyte. As for the interfacial problems of lithium anodes, researchers have effectively suppressed the growth of lithium dendrites or inhomogeneous lithium plating/stripping phenomena mainly by adding nanofillers to increase the mechanical strength of GPE or by participating in the generation of SEI.

Highly active CoP-Co2N confined in nanocarbon enabling efficient electrocatalytic immobilizing-conversion of polysulfide targeting high-rate lithium-sulfur batteries

Lithium-sulfur batteries suffer from poor cycling stability because of the intrinsic shuttling effect of intermediate polysulfides and sluggish reaction kinetics, especially at high rates and high sulfur loading. Herein, we report the construction of a CoP-Co2N@N-doped carbon polyhedron uniformly anchored on three-dimensional carbon nanotubes/graphene (CoP-Co2N@NC/CG) scaffold as a sulfur reservoir to achieve the trapping-diffusion-conversion of polysulfides. Highly active CoP-Co2N shows marvelous catalytic effects by effectively accelerating the reduction of sulfur and the oxidation of Li2S during the discharging and charging process, respectively, while the conductive NC/CG network with massive mesoporous channels ensures fast and continuous long-distance electron/ion transportation. DFT calculations demonstrate that the CoP-Co2N with excellent intrinsic conductivity serves as job-synergistic immobilizing-conversion sites for polysulfides through the formation of P···Li/N···Li and Co···S bonds. As a result, the S@CoP-Co2N@NC/CG cathode (sulfur content 1.7 mg cm−2) exhibits a high capacity of 988 mAh g−1 at 2 C after 500 cycles, which is superior to most of the electrochemical performance reported. Even under high sulfur content (4.3 mg cm−2), it also shows excellent cyclability with high capacity at 1 C.

Metal‐Organic Frameworks Functionalized Separators for Lithium‐Sulfur Batteries

Lithium sulfur batteries (LSBs) have attracted tremendous attention owing to their high theoretical specific capacity and specific energy. However, their practical applications are hindered by poor cyclic life, mainly caused by polysulfide shuttling. The development of advanced materials to mitigate the polysulfide shuttling effect is urgently demanded. Metal-organic frameworks (MOFs) have been exploited as multifunctional materials for the decoration of separators owing to their high surface area, structural diversity, tunable pore size, and easy tailor ability. In this review, we aim to present the state-of-the-art MOF-based separators for LSBs. Particular attention is paid to the rational design (pore aperture, metal node, functionality, and dimension) of MOFs with enhanced ability for anchoring polysulfides and facilitating Li+ transportation. Finally, the challenges and perspectives are provided regarding to the future design MOF-based separators for high-performance LSBs.

Ultra-Fast Synthesis of Single Atoms for All-Solid-State Lithium-Sulfur Batteries

All-solid-state lithium-sulfur (Li-S) battery has attracted the most attention in the past decades due to its high theoretical energy density (2600 Wh kg-1), high safety, low cost, and environmentally friendly feature. However, several issues need to be addressed before commercializing all-solid-state Li-S battery. The insulating nature of charged product sulfur and discharged product lithium sulfide results in low active material utilization. The dissolution of polysulfides intermediate and shuttling effect leads to fast capacity decay. Incorporating catalysts into the cathode or separator has proven to be very effective for promoting the sluggish Li-S reaction kinetics, suppress the shuttling effect of polysulfides, thus achieving superior cycling performance of Li-S battery using the liquid electrolyte. Single atom catalyst with the maximum atom utilization, unique coordination environment attracted particular attention. Whether single atom sites are feasible in the solid-state electrolyte is still unexplored. Herein, we synthesized single atom catalysts using ultra-fast approach. High-angle annular dark-field aberration corrected scanning transmission electron microscopy image and extended X-ray absorption fine spectroscopy verified the presence of single atoms on the support. The optimized absorption sites of single atoms were further studied with density functional theories. Using polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide infiltrated polyimide as the solid polymer electrolyte, we evaluated the cycling performance of all-solid-state Li-S battery. Single atoms incorporated sulfur cathodes exhibits higher cycling performance than the bare sulfur cathodes due to the significantly enhance lithium-sulfur redox reaction kinetics. The fast Li-S redox reaction kinetics were also revealed by calculating the energy barrier from sulfur to lithium sulfide using density functional theories. The formation of lithium sulfide from lithium disulfide was found to be the rate-limiting step for discharging sulfur. With the help of single atoms, the energy barrier of the rate-limiting step is significantly reduced. Our work provides new insights to improve the capacity and cycling life of all-solid-state Li-S batteries for commercializing Li-S technology.

Mesoporous Ti4 O7 Nanosheets with High Polar Surface Area for Catalyzing Separator to Reduce the Shuttle Effect of Soluble Polysulfides in Lithium-sulfur Batteries.

In the effort to accelerate adsorption and catalytic conversion of lithium polysulfides (Li-PSs) and suppress the shuttle effect of lithium-sulfur batteries (LSBs), the Ti4 O7 nanosheets/carbon material-modified separator is successfully fabricated to reducing soluble Li-PSs' crossover from cathode to anode. The catalyst of mesoporous Ti4 O7 nanosheets with O-Ti-O units synthesized at low temperature shows both excellent conductivity and high surface area. The modified separator can serve as a diffusion barrier of Li-PSs and catalyst for converting soluble low-chain sulfides into insoluble ones and then remarkably enhance the sulfur utilization and electrochemical performance of the LSB. This work provides a feasible avenue in both design and synthesis of mesoporous catalyst materials for suppressing the shuttle effect of lithium-sulfur batteries.

A Sustainable Multipurpose Separator Directed Against the Shuttle Effect of Polysulfides for High‐Performance Lithium–Sulfur Batteries

AbstractThe success of lithium–sulfur batteries will reduce the expected Co, Ni resource challenges from the wide adoption of lithium‐ion batteries. Unfortunately, the shuttle effect of soluble polysulfides brings many problems. Anchoring or blocking polysulfides on the cathode side using functional separators is the dominant strategy for addressing this. However, the blocked polysulfides gradually aggregate on the separator to form the so‐called “dead sulfur” and withdraw from cycling. Herein, a multipurpose separator is proposed that enables catalytic activation of the blocked polysulfides to prevent the formation of “dead sulfur”, and contribute to capacity. The multifunctionality is supported by montmorillonite (MMT) that provides sufficient channels for lithium‐ion transport, and selenium‐doped sulfurized‐polyacrylonitrile (Se0.06SPAN) that catalyzes conversion of “dead sulfur” and simultaneously contributes capacity. The theoretical calculations reveal Se0.06SPAN/MMT has a low migration barrier for Li+ and a low decomposition barrier for Li2S, facilitating the conversion and minimizing “dead sulfur”. Consequently, the Li–S battery with the Se0.06SPAN/MMT@PP (polypropylene) separator shows a low fading rate of 0.034% during 1000 cycles and achieves a super‐high areal capacity (33.07 mAh cm–2) under high sulfur loading (26.75 mg cm–2) and lean electrolyte conditions (4.5 µL mg–1). Moreover, the multipurpose separator has encouraging performance in stability, flexibility, and sustainability.

Copolymerization of Sulfur Chains with Vinyl Functionalized Metal−Organic Framework for Accelerating Redox Kinetics in Lithium−Sulfur Batteries

AbstractLithium−sulfur batteries (LSBs) are regarded as one of the most promising candidates for energy storage devices. However, the severe shuttling effect of soluble polysulfides (PSs) limits its further application. Metal−organic frameworks (MOFs) have emerged as a new kind of sulfur host for their talents in confining and trapping PSs. However, the shuttle effect has not been fully stressed as a significant drawback for most MOFs that leads to sluggish redox kinetics, resulting in low specific capacity and short lifetime, especially at high sulfur loading. In this work, a MOF‐sulfur copolymer (CNT@UiO‐66‐V‐S) is elaborated by copolymerization of sulfur with vinyl functionalized MOFs. Systematic electrochemical experiments and in situ Raman spectroscopy analysis indicate that the cathode exhibits a radical reaction mechanism and can accelerates LiPSs conversion. The CNT@UiO‐66‐V‐S cathode delivers over 100% improved discharge capacity and lowers decay rate at both low and high (5.6 mg cm–2) sulfur loadings compared to the physically mixed MOF/S cathode. The strategy of MOF‐sulfur copolymerization provides a new solution for promoting reaction kinetics and tackling the shuttle effect, and is expected to inspire the design of advanced sulfur hosts applied for high‐performance LSBs.

Facile Synthesis of Heterostructured MoS2–MoO3 Nanosheets with Active Electrocatalytic Sites for High-Performance Lithium–Sulfur Batteries

In order to overcome the shuttling effect of soluble polysulfides in lithium-sulfur (Li-S) batteries, we have designed and synthesized a creative MoS2-MoO3/carbon shell (MoS2-MoO3/CS) composite by a H2O2-enabled oxidizing process under mild conditions, which is further used for separator modification. The MoS2-MoO3 heterostructures can conform to the CS morphology, forming two-dimensional nanosheets, and thus shorten the transport path of lithium ion and electrons. Based on our theoretical calculations and experiments, the heterostructures show strong surface affinity toward polysulfides and good catalytic activity to accelerate polysulfide conversion. Benefiting from the above merits, the Li-S battery with a MoS2-MoO3/CS modified separator exhibits good electrochemical performance: it delivers a high discharge capacity of 1531 mAh g-1 at 0.2 C; the initial capacity can be maintained by 92% after 600 cycles at 1 C, and the discharge capacity decay rate is only 0.0135% per cycle. Moreover, the MoS2-MoO3/CS battery still achieves good cycling stability with 78% capacity retention after 100 cycles at 0.2 C with a high sulfur loading of 5.9 mg cm-2. This work offers a facile design to construct the MoS2-MoO3 heterostructures for high-performance Li-S batteries, and may also improve one's understanding on the heterostructure contribution during polysulfide adsorption and conversion.

Interfacial Assembled CeO2–x/Co@N-Doped Carbon Hollow Nanohybrids for High-Performance Lithium–Sulfur Batteries

Despite their high theoretical specific energy, lithium–sulfur (Li–S) batteries still suffer from a significant shuttling effect and sluggish redox conversion of lithium polysulfides (LiPSs), which seriously hinders their practical application. Here, we develop a heterostructure comprising hollow oxygen-deficient CeO2 (H-CeO2–x)/Co nanocrystals@N-doped carbon (NC) nanospheres as a multifunctional sulfur host for Li–S batteries. The resulting H-CeO2–x/Co@NC effectively prevents the shuttling effect and accelerates trapping–diffusion–conversion of LiPSs through the interconnection of conductive networks and exposure of adsorptive/catalytic planes with different components. Theoretical calculations reveal that the introduction of oxygen vacancies and the formation of heterogeneous interfaces strengthen the combination of H-CeO2–x/Co@NC with LiPSs and accelerate the decomposition of Li2S. The introduction of Co induces an electric field in CeO2, which generates highly active interfaces to improve the adsorption ability and redox conversion for LiPSs. Consequently, the H-CeO2–x/Co@NC-sulfur cathode exhibits an outstanding rate performance (626 mAh g–1 at 5 C), superior cycling stability with a capacity retention of 81.6% after 1000 cycles at 2 C, and a high areal capacity of 5.3 mAh cm–2 at 0.1 C with a high sulfur loading (5.4 mg cm–2). This work provides insights for the rational design of heterostructures for high-performance Li–S batteries through interface control and defect chemistry.

A robust polymeric binder based on complementary multiple hydrogen bonds in lithium-sulfur batteries

The practical application of sulfur cathodes in traditional lithium–sulfur batteries has been hindered by the substantial deterioration of the sulfur electrode due to the polysulfide shuttling effect and the large volume expansion of the electrode during charge/discharge cycling. The resolving of this issue demands for a robust binder to hold the polysulfide/sulfur particles, but without causing severe disintegration of the electrode. A polar polymeric binder with high mechanical strength was designed and synthesized for use in high-performance sulfur cathodes. The complementary multiple hydrogen bonds formed in the polymeric binder significantly enhanced the adhesive strength of the binder, and buffered the dramatic volume expansion of the sulfur cathode during cycling. The strong physical and chemical interactions between the functional groups (e.g. carboxyl and tertiary amine groups) of the binder and the polysulfides effectively mitigated the shuttling effect in the Li–S batteries. As a consequence, the sulfur cathode exhibited excellent electrochemical performance at a high sulfur loading, yielding an initial discharge capacity of 627.8 mA h g−1 with sulfur loading up to 9.610 mg cm−2 at a rate of 0.2C, corresponding to an aerial capacity of 6.03 mA h cm−1. The present work opens a new avenue for constructing a high-performance Li–S battery using a simple and effective binder.

Metal Organic Framework Derived Magnesium Oxide/Carbon Interlayer for Long-Life Lithium-Sulfur Batteries

i-S battery, with abundant S sources and high theoretical capacity, is one of the promising future battery technology. S cathode has a theoretical capacity of 1672 mAhg-1, which is an order of magnitude higher than the transition metal oxides’ of commercial lithium-ion batteries. However, the commercialization of Li-S battery is still struggling due to poor cyclic stability and limited kinetics. These problems come from the low electrical conductivity of S, LiS and Li2S, polysulfide shuttling effect and large volume change during cycling. Polysulfide shuttling effect is a phenomenon that polysulfide intermediate species, generated during charging and discharging of S and Li2S, gets dissolved into electrolyte and cause loss of capacity. Herein, the Mg-MOF-74-derived MgO/carbon interlayer is synthesized. Carbon substrate is known to provide additional electrical conductivity to S cathode, and according to Tao, X., et al, MgO is a good choice to balance between sulfide-adsorption and diffusion on the oxides. Therefore, MOF-derived MgO particles are expected to effectively mitigate polysulfide shuttling and reutilize dissolved polysulfide. Inserting MOF-derived MgO/carbon interlayer, the Li-S cell show excellent cycling stability (87.5% retention within 100 cycles) at 0.2 C with sulfur loading mass 2.6 mg cm-2, whereas the pristine and carbon interlayer sample show 60.0% and 64.3%. The capacity retention still holds at higher loading mass of sulfur electrode. Due to low electrical conductivity and polysulfide dissolution of the sulfur cathode, increasing sulfur content and loading mass of the sulfur electrode, and amount of electrolyte could be detrimental to Li-S cell performance. However, with Mg-MOF-74-derived MgO/carbon interlayer, this limitation could be overcome.

Multifunctional Trilayer Separator for High-Performance Lithium-Sulfur Batteries Under Extreme Conditions

Lithium-ion Batteries (LIBs) have transformed mankind's lives beyond imagination in the past few decades. They have found their use in a variety of applications such as defense, transportation, portable electronics, and space explorations. To keep up with the demand, stress is applied for discovering materials with higher capacity and energy densities. High capacity anodes like silicon, tin, antimony, carbon composites have been identified. However, limited cathode materials are available at disposal viz., LiCoO2, LiMnNiCoO2, LiFePO4, LiMn2O4. Most of these cathodes have capacities <250 mAh g-1, and thus LIBs cannot keep up with the ever-growing demand from the applications. The high-theoretical capacity chemistry of lithium-sulfur comes to the rescue. It is the lightest element to be used as a cathode, which has attractive properties such as capacity of 1672 mAh g-1, economical (~$50 per metric tonne), and abundance in nature. However, chemistry suffers from three critical issues viz., poor sulfur conductivity, polysulfide shuttling, and lithium dendrite growth. To tackle the insulative sulfur and polysulfide shuttling effect approaches such as coating sulfur with metal sulfide or oxides, mesoporous carbon, conductive polymers, inverse vulcanization have been applied. Unfortunately, these techniques lead to a reduction in the energy density of the system, involve complex fabrication steps or raw materials are expensive. On the issue of lithium metal dendrites growth, electrolytic additives, exotic electrode coatings, and special shutdown separators are used. The downside to all of these is that they impede cell performance or are uneconomical.Here we report, the use of a multifunctional trilayer separator in Li-S battery to tackle all three issues simultaneously. Modified separator acted as a barricade for polysulfide from shuttling by trapping them preferably due to the favorable interactions. The performance of Li-S cells with and without modified separator was compared for long term cycling and rate studies. It was found that cells with modified separator outperformed those with pristine separator. Modified separator cell exhibited capacities of 925, 833, 644, 480, 326, 260, and 220 mAh g-1 at 0.1C, 0.2C, 0.5C, 1C, 2C, 3C and 4C rates, respectively with 95% capacity retention. The choice of electrolyte affects battery performance drastically. However, using 1M LiTFSI in 1:1 (v/v) 1, 3-Dioxolane (DOL): 1, 2-Dimethoxyethane (DME) with additives, provided remarkable results at low and high-temperature ranges. At 0 ℃, the cell with the modified separator yielded about 350 mAh g-1 capacity at 0.5C over 200 cycles. The performance of the cells was stellar even at 50 ℃ with 500 mAh g-1 capacity at 0.5C rate after 100 cycles. Multiple module calorimetry provided the thermal heat signature to elucidate the safety features of the Li-S system with the modified separator and compared with the existing LIBs. High-performance Li-S batteries proposed here can be valuable to a variety of applications like defense, transportation, and space explorations, where drastic conditions affect the battery functionalities, in the times ahead.

The promises, challenges and pathways to room-temperature sodium-sulfur batteries.

Room-temperature sodium-sulfur batteries (RT-Na-S batteries) are attractive for large-scale energy storage applications owing to their high storage capacity as well as the rich abundance and low cost of the materials. Unfortunately, their practical application is hampered by severe challenges, such as low conductivity of sulfur and its reduced products, volume expansion, polysulfide shuttling effect and Na dendrite formation, which can lead to rapid capacity fading. The review discusses the Na-S-energy-storage chemistry, highlighting its promise, key challenges and potential strategies for large-scale energy storage systems. Specifically, we review the electrochemical principles and the current technical challenges of RT-Na-S batteries, and discuss the strategies to address these obstacles. In particular, we give a comprehensive review of recent progresses in cathodes, anodes, electrolytes, separators and cell configurations, and provide a forward-looking perspective on strategies toward robust high-energy-density RT-Na-S batteries.

Suppressed shuttling effect of polysulfides using three-dimensional nickel hydroxide polyhedrons for advanced lithium-sulfur batteries

In this work, controlled-size hollow polyhedron assembled by crumpled nickel hydroxide (Ni(OH)2) nanosheets from silicon dioxide (SiO2)-covered zeolitic imidazole framework-67 (ZIF-67@SiO2) is prepared via a template-sacrificed method. It is found that SiO2 plays an essential role in keeping intact polyhedrons and suppressing particle growth. Benefiting from structural and compositional advantages, the Ni(OH)2@S electrode exhibits high specific capacity, excellent rate performance, and stable cycle life at 1C with a small capacity decay of 0.067% per cycle. The Ni(OH)2 hollow polyhedrons can accommodate the volume expansion to maintain the integrity of the electrode and suppress the shuttling effect of polysulfides via abundant hydroxyl groups. Hence, this strategy is beneficial to anticipate the material for large-scale applications.

Direct trapping and rapid conversing of polysulfides via a multifunctional Nb2O5-CNT catalytic layer for high performance lithium-sulfur batteries

Practical application of high-energy-density lithium-sulfur (Li–S) battery is greatly impeded by the detrimental shuttling effect and sluggish redox kinetics of polysulfides. Herein, a multifunctional Nb2O5-carbon nanotube (CNT) catalytic interface is designed and fabricated onto the separator, which can directly trap the polysulfides and then rapidly catalyze their redox conversion for advanced Li–S batteries. The construction of conductive and catalytic Nb2O5-CNT interface could afford long-distance electron transfer network, strong chemisorptive properties, and rich catalytic sites for accelerating polysulfide conversion kinetics and regulating Li2S nucleation/dissolution. The sulfur cathode with the assistant of Nb2O5-CNT interface could deliver an initial discharge capacity of 1286 mAh g−1 and remain 992 mAh g−1 with a capacity retention of 77.0%, corresponding to a low capacity attenuation rate of 0.23% per cycle during 100 cycles at 0.2C. Meanwhile, the Nb2O5-CNT interface can greatly suppress the self-discharge and effectively reduce the formation of lithium dendrite due to the inhibition of the shuttling effect. This work provides instructive insights to suppress the shuttle effect and accelerate redox conversion via designing a multifunctional catalytic interface for Li–S chemistry.