High-rate Lithium-sulfur Batteries Research Articles

Flexible CNT-Interpenetrating Hierarchically Porous Sulfurized Polyacrylonitrile (CIHP-SPAN) Electrodes for High-Rate Lithium-Sulfur (Li-S) Batteries

Sulfurized polyacrylonitrile (SPAN) is a promising cathode material for lithium-sulfur batteries owing to its reversible solid–solid conversion for high-energy-density batteries. However, the sluggish reaction kinetics of SPAN cathodes significantly limit their output capacity, especially at high cycling rates. Herein, a CNT-interpenetrating hierarchically porous SPAN electrode is developed by a simple phase-separation method. Flexible self-supporting SPAN cathodes with fast electron/ion pathways are synthesized without additional binders, and exceptional high-rate cycling performances are obtained even with substantial sulfur loading. For batteries assembled with this special cathode, an impressive initial discharge capacity of 1090 mAh g−1 and a retained capacity of 800 mAh g−1 are obtained after 1000 cycles at 1 C with a sulfur loading of 1.5 mg cm−2. Furthermore, by incorporating V2O5 anchored carbon fiber as an interlayer with adsorption and catalysis function, a high initial capacity of 614.8 mAh g−1 and a notable sustained capacity of 500 mAh g−1 after 500 cycles at 5 C are achieved, with an ultralow decay rate of 0.037% per cycle with a sulfur loading of 1.5 mg cm−2. The feasible construction of flexible SPAN electrodes with enhanced cycling performance enlists the current processing as a promising strategy for novel high-rate lithium-sulfur batteries and other emerging battery electrodes.

Nickel aerogel @ ultra-thin NiCo-LDH nanosheets integrated freestanding film as a collaborative adsorption and accelerated conversion cathode to improve the rate performance of lithium sulfur batteries

It is a great challenge to develop freestanding ultralight cathodes for lithium–sulfur battery exhibiting good electrochemical performances. Herein, ultrathin porous nickel–cobalt layered double hydroxide (NiCo-LDH) nanosheets were grown on the surface of ultra-light nickel microwire aerogels (NMWAs), and there is capillary action in the gaps formed by the ordered arrangement due to the presence of magnetic filed in the preparation process, which has the advantages of synergistic adsorption and accelerated conversion kinetics of lithium polysulfide. Because of the abundant hydrophilic hydroxyl groups on the surface of NiCo-LDH and the capillary action of NMWAs, the integrated freestanding film cathode sulfur host (NMWAs@NiCo-LDH/S) provides excellent rate performance as well as cycling stability. The film cathode has an ultra-high initial specific capacity of 1238.4 mAh g−1 at 0.1C and an excellent reversible capacity of 805.8 mAh/g at 5.0C. Even after 700 cycles at a high current density of 5.0C, it still provides a reversible capacity of 647.1 mAh g−1 with a capacity decay rate of only 0.018 % per cycle. This work provides a simple and new way for the design of high rate lithium–sulfur battery film cathodes with good cycle stability.

Effective d–p orbital hybridization of Co0.75Fe0.25P catalysts enabling high-rate and long-life lithium‒sulfur batteries

Lithium–sulfur (Li–S) batteries represent one of the potential next-generation energy storage devices. However, their commercialization is hindered by the severe shuttle effect of lithium polysulfides (LiPSs) and sluggish redox kinetics. A crucial strategy to address these issues involves the rational design of catalysts and a comprehensive understanding of interaction mechanisms between catalysts and sulfur species. In this study, Fe atoms were incorporated into CoP catalysts, and one-dimensional (1D) porous carbon-encapsulated Fe-doped CoP (Co1-xFexP@C) nanotube-like nanostructures were rationally designed and successfully synthesized. This design involves modifying the d–p orbital hybridization between the transition metal Co 3d orbitals and S 2p orbitals through the Fe 3d orbitals, thus creating catalysts with the most effective d–p orbital hybridization and, consequently, the strongest electrocatalytic activity. Detailed kinetic analysis reveals the Co0.75Fe0.25P@C catalyst, with an effective d–p orbital hybridization, can firmly anchor the LiPSs, inhibit the shuttle effect, and facilitate bidirectional Li2S redox, thereby enhancing sulfur utilization and promoting LiPS conversion. These findings enable high-rate and long-cycle-life Li–S batteries. Specifically, the Li–S battery using the Co0.75Fe0.25P@C catalyst demonstrates excellent cycling stability, with a low capacity decay rate of 0.05 % per cycle over 900 cycles at 2 C. More impressively, the Li–S battery also achieves outstanding high-rate performance, delivering 726.3 mAh g–1 at 6 C. This study introduces a new strategy for identifying catalysts with the strongest electrocatalytic activity, which holds promise for advancing the development of Li−S batteries.

Conductive V2O3 electrocatalyst on carbon hollow spheres to accelerate polysulfide conversion for long-cycle and high-rate lithium sulfur batteries

The V2O3/C-HS material was prepared by a hard template and impregnation method. When applied in lithium–sulfur batteries, it shows excellent long-cycle and high-rate performance.

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

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

A viologen auxiliary strategy to accelerate the catalytic efficiency of polyoxometalates for high-rate lithium–sulfur batteries

For lithium–sulfur (Li–S) batteries, the serious obstacles for sulfur cathode are the polysulfides shuttle effect and slow redox kinetics during cycles. The functionalizing separator modified by catalytic material can not only effectively prevent polysulfides from shuttling between the cathode and anode but also extremely facilitate polysulfides conversion reaction. Herein, we propose an auxiliary catalytic strategy by aminopropyl viologen-K3[PW12O40] (AV-PW12)composite as the separator modification material in Li–S batteries. AV as a good electron receiver can quickly obtain electrons and transfer them to PW12 through hydrogen bonding (N–H⋯O), which is conducive to enhancing the conductivity of PW12 and further promoting the catalytic reaction kinetics of PW12. The high-efficiency catalytic activity of AV-PW12 plays a pivotal role in improving the rate performance of Li–S batteries. Moreover, AV with certain capture capacity for polysulfides by electrostatic attraction assists the adsorption of PW12, improving the probability of lithium polysulfides being catalyzed by PW12. Therefore, when applied to modified separator material, the AV-PW12-based cell achieves the high initial discharge capacity of 1596 mAh/g at 0.5C and runs for 1000 cycles at 10 C within a low capacity decay of 0.041%. Even with a low electrolyte/sulfur ratio of 5 μL/mg, the reversible capacity can still retain 561.6 mAh/g at 0.5 C upon 200 cycles under a high sulfur loading of 4.5 mg/cm2. This work demonstrates an innovative method for the design of polyoxometalates-based composite at the molecular level, which gives more possibilities for the application of polyoxometalates as catalytic materials in Li–S batteries.

Transition Metal Dichalcogenides as Effective Catalysts for High-Rate Lithium–Sulfur Batteries

In today’s renaissance of high-energy-density secondary batteries, lithium–sulfur (Li–S) batteries represent one of the most promising candidates for the next generation of renewable energy storage systems due to sulfur’s high theoretical specific capacity of 1675 mA h g–1 and high earth abundance. However, despite decades of study, the issues associated with capacity fade via the polysulfide shuttle and sluggish kinetics remain. Through a rigorous and detailed electrochemical study of lithium polysulfides via rotating disk electrode (RDE) voltammetry, we have investigated the kinetics of the redox reactions and explored candidate catalysts to potentially overcome/mitigate the polysulfide shuttle effect. From these RDE studies, supported by comprehensive electronic structure calculations of conversion-type surface reactions, we determined that WSe2 can effectively catalyze the polysulfide redox reaction, though further studies are necessary to improve the overall Li–S battery performance.

Electronic structure adjustment of lithium sulfide by a single-atom copper catalyst toward high-rate lithium-sulfur batteries

• Developing a novel approach for enhancing catalytic efficiency toward Li 2 S deposition/dissolution by insulator-to-metal transition of Li 2 S. • Single-copper was screened out among single-atom catalysts to endow insulator-to-metal transition of Li 2 S. • Rapidly charge transfer on metallic Li 2 S nuclei leads to a morphology of spherical clusters other than conventional lateral film by continuous 3D nucleation & growth. • The catalytic efficiency of Li 2 S-covered catalytic sites is considerably enhanced, resulting in remarkable rate performance of Li-S batteries under high sulfur loading. Electrocatalytically reducing the energy barrier for Li 2 S deposition/dissociation is a promising strategy for high-rate Li-S batteries. However, the catalytic sites would be covered by the insulating Li 2 S product during discharge, which deteriorates the catalytic activity. Here, suggested by first-principles calculations, single-atom copper (SA-Cu) was screened out to endow the insulator-to-metal transition of adsorbed Li 2 S in view of the electronic structure. In addition to the thermodynamically reduced redox energy barrier, metallic Li 2 S nuclei deposited on SA-Cu decorated nitrogen-doped carbon fiber foam (SA-Cu@NCNF) with favorable electronic transport present 3D spherical clusters rather than conventional 2D lateral morphology by continuous 3D nucleation and growth. The Li 2 S deposition capacity and the catalytic efficiency of Li 2 S-covered catalytic sites are thus greatly improved. As a result, SA-Cu@NCNF based Li-S cells with a sulfur loading of 4 mg cm −2 retained an areal capacity of 1.60 mAh cm −2 at 5 C after 500 cycles (0.038% decay per cycle). A competitive areal capacity of 8.44 mAh cm −2 was obtained at 0.2 C with a sulfur loading of 10 mg cm −2 . The demonstration of the distinctive design of catalysts to adjust the electronic structure of adsorbed Li 2 S paves the way for developing high-rate and long-life Li-S batteries. Single-atom copper (SA-Cu) was screened out to adjust the electronic structure and endow the insulator-to-metal transition of adsorbed Li 2 S, so as to improve the electronic conductivity of Li 2 S. In Li-S batteries, a facile Li 2 S deposition/dissolution process and novel spherical cluster morphology were obtained by continuous 3D nucleation & growth, which greatly improve the reaction efficiency. Catalytic effectiveness value for Li 2 S deposition (CEV depo ) is proposed to prove SA-Cu an efficient electrocatalyst for Li-S battery system.

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.

Solid Carbon Spheres with Interconnected Open Pore Channels Enabling High-Efficient Polysulfide Conversion for High-Rate Lithium-Sulfur Batteries.

Hollow carbon spheres or core-sheath porous carbon spheres have been widely used in the S cathode of lithium-sulfur batteries. However, the sphere shells or the pore walls may block the free transport of active species to a certain extent and may have a negative influence on the effective accommodation of elemental sulfur. Herein, solid but porous carbon spheres (PNCS) with large porosity and high specific surface area are developed, which enable high sulfur loading and ample cathode/electrolyte contact area, and the interconnected open pore channels significantly shorten the ion/electron transport pathways. Together with high-conducting nitrogen-doped graphene (NG), facilitated polysulfide conversion kinetics is realized in the as-assembled Li-S batteries, which deliver a high initial discharge capacity of 1445 mAh g-1 at 0.2 C, excellent rate capability of 872 mAh g-1 at 4 C, and low capacity decay of 0.047% per cycle for 500 cycles at 1 C. Even under high sulfur loading of 5.5 mg cm-2 and low electrolyte/sulfur (E/S) ratio of 5 μL mg-1, the Li-S batteries still display high specific capacities of 896 mAh g-1 and 4.96 mAh cm-2. The real application of PNCS/NG is also demonstrated by the corresponding Li-S pouch cells showing high discharging capacity and stable open circuit voltage. This work exhibits the promising application of the solid carbon spheres as the S host for effectively addressing the polysulfide shuttle and propelling the development of high-performance Li-S batteries.

Fluoroalkyl ether electrolyte with sulfur-wetting and shuttling-inhibition functionalities for high-rate lithium sulfur batteries

Lithium-sulfur (Li–S) batteries have been acknowledged as one of the most fascinating energy storage devices due to their remarkable theoretical energy density. However, low conductivity and polysulfide shuttling are notorious challenges for their commercial applications. Here, by directly introducing fluoroalkyl ether 2,2,2-trifluoroethyl-1,1,2,3,3,3-hexafluoropropyl ether (THE) into commercial ether electrolytes, we design a fluoroalkyl ether electrolyte to improve high-rate cyclic performance of Li–S battery. As confirmed by density functional theory calculations, in-situ Raman, and electron density maps, the THE electrolyte, with abundant high-polarity CF3 and CF2 groups, fully wets the sulfur cathode and inhibits the polysulfide shuttling, owing to the intense repulsive interaction (1.97 eV) with polysulfide ions and the robust absorption interaction (−2.42 eV) with sulfur cathode. With the THE electrolyte, the Li–S battery cycling 500 times at 5 C (10.5 mA cm−2) delivers a capacity retention of 53.3%, holding promise for developing high-rate, long-period Li–S batteries.

NiCo2O4@PPy concurrently as cathode host material and interlayer for high-rate and long-cycle lithium sulfur batteries

The large-scale practical application of cost-efficient lithium sulfur (Li–S) battery with high energy density is impeded due to the shuttle effect and torpid kinetics of polysulfides. Hence, it is significant for Li–S battery to solve these disadvantages to boost the electrochemical performances and facilitate the popularization in various fields. Herein, we synthesized a conductive NiCo2O4@PPy micro-flower-like material via hydrothermal technique followed by subsequent in-situ vapor phase polymerization, and the material was assembled into Li–S batteries to obtain satisfactory electrochemical performances. Flower-like NiCo2O4 expedites the conversion of polysulfides through both physical adsorption and chemical anchoring. Polypyrrole can efficaciously confine polysulfides shuttling, increase the conductivity and concurrently promote lithium ions diffusion. NiCo2O4@PPy is simultaneously served as the effective cathode material and multi-functional interlayer for anchoring-catalyzing polysulfides, which can exhibit a satisfying initial capacity of 1588 mAh g−1 at 0.1C, and the average coulomb efficiency is 95.2%. The highest discharge specific capacity of 740 mAh g−1 is displayed at 2C and the capacity decay rate is 0.107% per cycle after 400 cycles. NiCo2O4@PPy composite is a favorable sulfur host material intimated by these new results, and it is also a competent candidate of interlayer in high-performance Li–S batteries.

Polysulfides immobilization and conversion by nitrogen-doped porous carbon/graphitized carbon nitride heterojunction for high-rate lithium-sulfur batteries

Improving efficiency of solid-liquid-solid multiphase conversion of sulfur to Li2S and suppressing lithium polysulfide shuttle phenomenon are crucial tasks for industrialization of lithium-sulfur batteries. In this study, a novel honeycomb-like nitrogen-doped porous carbon/graphitized carbon nitride (HPCG) heterojunction nanocatalyst is prepared using truncated rhombic dodecahedral zeolitic imidazolate framework-8 (TRD-ZIF-8) nanoparticles as a synthesis template. A unique hierarchical porous structure and abundant active catalytic sites of HPCG can effectively immobilize polysulfides, accelerate long-chain polysulfide conversion and promote Li2S nucleation, thereby inhibiting the shuttle effect. HPCG cells exhibit good rate performance and excellent high-rate cycling stability with only 0.073% capacity decay per cycle after 1000 cycles at 5 C. Specifically, a cell with a low electrolyte/sulfur (E/S) ratio of 9.6 µL mg−1 demonstrates stable operation over 300 cycles at 1C. This work is expected to deepen the understanding of interphase conversion process of complex lithium polysulfides and provide new ideas for designing sulfur host materials of lithium-sulfur batteries.

Electrospun Sulfurized Polyacrylonitrile Nanofibers for Long-Term Cycling Stability and High-Rate Lithium–Sulfur Batteries

Electrospun Sulfurized Polyacrylonitrile Nanofibers for Long-Term Cycling Stability and High-Rate Lithium–Sulfur Batteries

Mixed-Valence iron phosphate as an effective catalytic host for the High-Rate Lithium-Sulfur battery

Lithium-sulfur battery, one of the most attractive candidates for next-generation energy storage systems, commonly suffers from sluggish polysulfide conversion and detrimental shuttle mechanism. To solve these issues, finding novel catalytic hosts and strategies to facilitate polysulfide redox reaction is gaining much importance nowadays. Herein, we report oxidation-state-controlled amorphous FePO4 as an effective catalytic host for polysulfide conversion for the first time. For this study, we fabricated the FePO4-embedded 3D graphene composite by facile hydrothermal reaction and tailored the ratio of Fe2+/Fe3+ in the amorphous FePO4 by a thermal treatment in the reducing H2 atmosphere. A series of electrochemical tests showed that the mixed-valence FePO4 demonstrates enhanced catalytic ability than Fe3+-dominant FePO4. Surface and bandgap analyses indicate that such enhanced kinetics of mixed-valence FePO4 is attributed to the combined effects of promoted electron conduction and chemical interaction. By introducing mixed-valence FePO4 into the cathode, the battery showed robust cyclability delivering an excellent capacity of 784 mAh∙g−1 at 1C after 300 cycles (retained capacity of ∼ 78%) and superior rate performance exhibiting over 872 mAh∙g−1 at a high rate of 2C.

Construction of a fast Li-ion path in a MOF-derived Fe3O4@NC sulfur host enables high-rate lithium-sulfur batteries.

Besides the adjustment of the active centres, the precisely designed microstructures of the carbon hosts also play a significant role in improving the battery performance. Herein, MOF-derived Fe3O4@NCs were prepared through a molten salt-assisted calcination method at different carbonization temperatures. Compared with the materials obtained at 700 °C, LK450 calcined at a lower temperature of 450 °C maintains suitable pore sizes and more N-doping and exhibits excellent Li-ion transport performance. Thus, the S/LK450 cathode can achieve an outstanding rate performance of up to 5 C (∼528 mA h g-1) and an extremely low capacity decay of 0.037% per cycle after 500 cycles at 1C. Notably, even with a high sulfur loading (4.0 mg cm-2), the S/LK450 cathode can still deliver a high capacity of 673 mA h g-1 at 0.2C after 100 cycles. Briefly, this work demonstrates the superiorities to prepare the samples at relatively low carbonization temperatures, which guarantee a better ion path structure and sufficient N-doping in the carbon skeleton.

PPy-encapsulated hydrangea-type 1T MoS2 microspheres as catalytic sulfur hosts for long-life and high-rate lithium-sulfur batteries

Lithium-sulfur batteries are regarded as promising candidates for next-generation energy storage applications owing to their high theoretical specific capacity, low cost, and eco-friendliness. However, the poor conductivity, large volume variation of sulfur species during the charging/discharging process, complicated conversion reactions of sulfur species, shuttle effect of lithium polysulfide, and low sulfur loading greatly hinder the practical application of lithium-sulfur batteries. In this study, we propose an efficient approach to design polypyrrole (PPy)-encapsulated 1T-MoS2 microspheres with a hydrangea-like structure as catalytic sulfur hosts for lithium-sulfur batteries. The catalytic effect of 1T-MoS2 and the high conductivity of the PPy layer accelerated the adsorption/conversion of lithium polysulfides. The hydrangea-like structure of the 1T-MoS2 microspheres provided adequate number of active sites and sufficient space for sulfur loading. Meanwhile, the specific inter-porous/outer-coating layer structure could also restrain the expansion of sulfur electrode during the electrochemical reaction process. The obtained 1T-MoS2-S@PPy cathode material exhibited outstanding electrochemical performance with an excellent reversible capacity of 1434 mAh g−1 at 0.1C rate, a considerable capacity of 1023 mAh g−1 at 1C rate, and excellent cycling stability for over 800 cycles with a low cycling decay rate of 0.051% per cycle.

Ultra-lightweight ion-sieving membranes for high-rate lithium sulfur batteries

The practical application of lithium-sulfur (Li-S) batteries is impeded by the shuttle effect of intermediate polysulfides and the inherent sluggish kinetics. Herein, Mo2C nanocatalysts anchoring on holey graphene scaffold (Mo2C@HGr) is explored as a lightweight and ultrathin modified separator to conquer the above issues. The artificially customized holes on holey graphene sheets facilitate ionic transfer and electrolyte penetration, and further enhance the sulfur utilization under lean electrolyte conditions. The experimental results together with theoretic calculation demonstrate the favourable chemical adsorption ability of Mo2C sites that blocking the diffusion of LiPSs. Abundant triple-phase interfaces among Mo2C nanomediators, holey graphene and electrolyte boost the conversion kinetics of the intercepted LiPSs. As a result, the cell with Mo2C@HGr modified separator shows superior rate capability (836 mAh g−1) even at 5 C current with a negligible Mo2C@HGr loading of 0.08 mg cm−2. Furthermore, ultrahigh areal capacity of 5.9 mAh cm−2 is still attained with high sulfur loading of 6 mg cm−2 under lean electrolyte operation (E/S = 5.6 µL mg−1). This design concept can be extended to other graphene based multifunctional nanocomposite toward the development of more practical Li-S batteries.

Flower-like Ni/NiO microspheres decorated by sericin-derived carbon for high-rate lithium-sulfur batteries

Flower-like Ni/NiO microspheres decorated by sericin-derived carbon for high-rate lithium-sulfur batteries

Three-Dimensional Engineering of Sulfur/MnO2 Composites for High-Rate Lithium-Sulfur Batteries.

Herein, a three-dimensional interconnected sulfur (3DIS) system is used to construct a cathode of the lithium-sulfur battery. Compared with the traditional methods of encapsulating sulfur, the 3DIS system serves as a framework to grow MnO2, which ensures a high sulfur content of 91.5 wt % (the ratio of sulfur/host was 10.8) and a uniform distribution of sulfur. Due to the synergistic effect of the 3D interconnected architecture and the uniform coating layer of polar MnO2, 3DIS@MnO2 (3DISMO) delivers a capacity of 891 mA h g-1 after 900 cycles at 1 C. Even at a rate of 10 C, a capacity decay rate of 0.061% per cycle is achieved.