Lithium Sulfur Research Articles

Titanium-containing high entropy oxide (Ti-HEO): A redox expediting electrocatalyst towards lithium polysulfides for high performance Li-S batteries

Titanium-containing high entropy oxide (Ti-HEO): A redox expediting electrocatalyst towards lithium polysulfides for high performance Li-S batteries

Scalable Ni12P5-Coated Carbon Cloth Cathode for Lithium–Sulfur Batteries

As a better alternative to lithium-ion batteries (LIBs), lithium–sulfur batteries (LSBs) stand out because of their multi-electron redox reactions and high theoretical specific capacity (1675 mA h g−1). However, the long-term stability of LSBs and their commercialization are significantly compromised by the inherently irreversible transition of soluble lithium polysulfides (LiPS) into solid short-chain S species (Li2S2 and Li2S) and the resulting substantial density change in S. To address these issues, we used activated carbon cloth (ACC) coated with Ni12P5 as a porous, conductive, and scalable sulfur host material for LSBs. ACC has the benefit of high electrical conductivity, high surface area, and a three-dimensional (3D) porous architecture, allowing for ion transport channels and void spaces for the volume expansion of S upon lithiation. Ni12P5 accelerates the breakdown of Li2S to increase the efficiency of active materials and trap soluble polysulfides. The highly effective Ni12P5 electrocatalyst supported on ACC drastically reduced the severity of the LiPS shuttle, affected the abundance of adsorption–diffusion–conversion interfaces, and demonstrated outstanding performance. Our cells achieved near theoretical capacity (>1611 mA h g−1) during initial cycling and superior capacity retention (87%) for >250 cycles following stabilization with a 0.05% decay rate per cycle at 0.2 C.

Zein protein-functionalized separator through a viable method for trapping polysulfides and regulating ion transport in Li[sbnd]S batteries

Commercialization of lithium‑sulfur (LiS) batteries as a promising energy storage system, is primarily impeded by polysulfide shuttling and uncontrollable lithium dendrite growth. To address the issues for improving the performance of LiS batteries, we decorate the separator with zein (corn protein) via a simple soaking process. Owing to strong zein–polysulfide interactions, the zein-soaked separator effectively enhances the polysulfide-trapping capability. Moreover, abundant functional groups of zein also stabilize Li-ion deposition, and thus suppresses the growth of Li dendrites. As a result, the resulting LiS batteries exhibited enhanced electrochemical performance in terms of cycling stability, capacity retention, and rate capability. The soaking method used for coating zein on pristine separator offers a scalable solution for generating multifunctional separators toward commercialization.

An anthraquinone derivative for modulating the energy levels of polysulfide molecular orbitals to enhance the kinetics of redox reactions

The shuttle effect of lithium polysulfides (LiPSs) and the slow kinetics of sulfur redox reactions severely hinder the commercialization of lithium-sulfur (Li–S) batteries. In this study, 2,6-dihydroxyanthraquinone (DHAQ) is absorbed onto the surface of carbon materials through π-π interactions to facilitate the adsorption and catalytic conversion of LiPSs. Electrostatic potential (ESP) results indicate that introducing hydroxyl groups into the molecule enhances the carbonyl group's ability to adsorb LiPSs and thereby facilitates the formation of covalent Li-O bonds for their immobilization. The interaction between DHAQ and LiPSs results in a complex with a higher energy level for the highest occupied molecular orbital (HOMO) and a lower energy level for the lowest unoccupied molecular orbital (LUMO). This leads to enhanced redox activity, which accelerates the kinetics of LiPSs conversion reactions. Consequently, the S@DHAQ/C composite demonstrates a capacity decay rate of just 0.040 % per cycle after 600 cycles at 1 C. At a sulfur loading of 5 mg cm−2, it retains an initial discharge specific capacity of 643 mAh g−1 at 0.2 C. This work introduces a novel approach to improving polysulfide adsorption capacity through organic molecules while also accelerating the kinetics of redox reactions.

Enhanced performance of Lithium–Sulfur cells via novel nano-sized iron-plated sulfur composites

Lithium–sulfur cells are promising energy-storage systems because of their high energy density and the desirable electrochemical utilization rates of cost-effective sulfur cathodes. However, the commercialization of high-performance lithium–sulfur cells, which are characterized by a high discharge capacity and cyclic stability, necessitates simultaneous optimization of both the cell-fabrication parameters and cell-performance values. Here, we introduce a novel iron-plated sulfur composite featuring nano-sized conductive iron plating applied to micro-sized insulating sulfur particles through an innovative electroless-iron plating method. The iron-plated sulfur composite facilitates the realization of a lean-electrolyte lithium–sulfur cell at a low electrolyte-to-sulfur ratio of 5 μL mg−1, enabling high-loading sulfur cathodes (sulfur loadings of 10–14 mg cm−2) to attain a reversible discharge capacity (945–1033 mAh g−1) and a cycle life of 400 cycles. These well-controlled cell-fabrication parameters, coupled with the high cell performance, result in improved performance metrics, such as high areal capacity (10–13 mAh cm−2), improved energy density (22–28 mWh cm−2), and a low electrolyte-to-capacity ratio (4.8 μL mAh−1). These advancements are attributable to the incorporation of plated nano-sized iron, which endows the cathode with rapid electron/ion transfer, robust polysulfide retention, and heightened electrocatalysis capabilities for conversion-type battery chemistry.

Universal design of three-dimensional porous graphene-iron based promotors for kinetically rationalized lithium-sulfur chemistry

Lithium-sulfur (Li-S) batteries are widely deemed to be one of the most potential candidates for future secondary batteries because of their remarkable energy density. Nevertheless, notorious polysulfide shuttling and retarded sulfur reaction kinetics pose significant obstacles to the further application of Li-S batteries. While rationally designed highly active electrocatalysts can facilitate polysulfide conversion, the universal and scalable synthesis strategies need to be developed. Herein, a universal synthetic strategy to construct a series of three-dimensional (3D) porous graphene-iron (3DGr-Fe) based electrocatalysts involving 3DGr-FeP, 3DGr-Fe3C, and 3DGr-Fe3Se4 is exploited for manipulating the Li-S redox reactions. It has been observed that the implementation of a 3D porous Gr architecture leads to the well-designed conductive networks, while the uniformly dispersed iron nanoparticles introduce an abundance of active sites, fostering the lithium polysulfide conversion, thereby bolstering the overall electrochemical performance. The Li-S battery with the 3DGr-Fe based electrocatalyst exhibits remarkable capacity retention of 94.8% upon 100 times at 0.2 C. Moreover, the soft-packaged Li-S pouch cell based on such a 3DGr-Fe electrocatalyst delivers superior capacity of 1060.71 mA h g−1 and guarantees for the continuous 30 min work of fan toy. This investigation gives comprehensive insights into the design, synthesis, and mechanism of 3DGr-Fe based electrocatalysts with high activity toward efficient and durable Li-S batteries.

Preparation of MoSe2 nanosheets/nitrogen-doped carbon nanotubes and their electrochemical energy storage properties

Lithium-sulfur batteries can be used as excellent energy storage devices, but they still face some challenges in the practical application, such as the poor electrical conductivity of sulfur, the volume expansion of sulfur during the discharge process, and the dissolution of polysulfides. In this study, polypyrrole-coated molybdenum trioxide nanorods were used as templates for the simultaneous in-situ growth of MoSe2 nanosheets on the outer/inner sides of nitrogen-doped carbon nanotubes. When the MoSe2/N-carbon nanotubes (MoSe2/NC NTs) were used as sulfur carriers for lithium-sulfur battery, the large specific surface area of the N-carbon nanotubes facilitated the homogeneous loading of MoSe2 nanosheets and exposed more catalytically active sites of the MoSe2 nanosheets, increasing the contact area of electrolyte. In addition, the N-doped carbon nanotubes have excellent electrical conductivity, which greatly promotes the electrical conductivity of the cathode. The density functional theory calculations, adsorption experiments, and XPS results all confirm that the MoSe2/NC NTs are able to anchor lithium polysulfides through strong adsorption, thus effectively mitigating the shuttle effect of polysulfides. This study supplies a novel route for the preparation of sulfur host for advanced lithium-sulfur batteries.

Preparation of MoS2 nanosheets/nitrogen-doped carbon nanotubes/MoS2 nanoparticles and their electrochemical energy storage properties

Inferior electrical conductivity, huge volume swell, shuttle effect and slow redox reactions in Li-S batteries restrict their practical applications. In this study, molybdenum disulfide nanosheets anchored on nitrogen-doped carbon nanotubes encapsulating molybdenum disulfide nanoparticles (MoS2/NC/MoS2 NTs) were prepared by heat treatment, ammonia etching, high-temperature sulfurization, and solvent-thermal in-situ growth using polypyrrole-coated molybdenum trioxide nanorods (MoO3 NRs) as templates. The hollow structure of nitrogen-doped carbon nanotubes and the high specific surface area are conducive to increasing sulfur loading, increasing the contact area of electrolyte, accelerating the electron transport, and shortening the lithium ion transport route. The MoS2 nanosheets on the outer layer of the nitrogen-doped carbon tubes and the MoS2 particles wrapped inside can anchor polysulfides by chemisorption, slowing down the shuttle effect and enhancing the energy storage performance of lithium-sulfur batteries. The MoS2/NC/MoS2/S nanotubes (MoS2/NC/MoS2/S NTs) maintain a capacity of 498.9 mAh g−1 over 500 cycles at 1.0 A g−1, with an average single-cycle capacity decay rate of 0.061 %. The density functional theory calculations, the adsorption experiments, and the X-ray photoelectron spectroscopy results all confirm that the MoS2/NC/MoS2 NTs are able to anchor lithium polysulfides through strong adsorption, thus effectively mitigating the shuttle effect of polysulfides. The synthesis of MoS2/NC/MoS2/S NTs in this study is of important significance for the development of advanced lithium-sulfur batteries.

Revealing a volcano correlation of sulfur reduction catalytic activity and elements doping in cobalt-based sulfides for Li-S batteries

The effective utilization of Li-S batteries still necessitates the incorporation of an efficient catalytic medium to address the challenges posed by shuttle effects and sluggish reaction kinetics. Furthermore, the structure-activity relationship of catalysts for the sulfur reduction reaction remains inadequately understood. In this study, we utilize Co9S8 as a template to investigate the correlation between the doping of co-periodic elements (Fe, Ni, Cu and Zn) and their catalytic effects on the sulfur reduction reaction. There is a “volcano peak” correlation between the catalytic performance and the type of doped elements from Fe to Zn, and research indicates that the Ni-doped Co9S8 (NCS) demonstrates superior performance compared to other samples. The NCS not only maintains the inherent advantages of Co9S8 but also effectively lowers the apparent activation energy necessary for Li-S batteries. Consequently, this enhancement facilitates a more rapid and complete conversion of soluble lithium polysulfides, thereby endowing Li-S batteries with an enhanced reaction kinetics. When the sulfur areal loading is elevated to 5.2 mg cm−2, the maximum areal capacity of the cell can attain 5.2 mAh cm−2 at 0.05 C. This work further substantiates the efficacy of the element doping strategy in enhancing the catalytic performance of reduction reaction catalysts, and it also offers significant insights or considerations for the development of practical catalysts, thereby facilitating the practical application of Li-S batteries.

Nitrogen-doped 3D carbon hybrids based on modified lignin as sulfur host for high-performance lithium-sulfur batteries

Constructing a sulfur host with strong adsorption and catalytic conversion of polysulfides is significant in improving the electrochemical performance of lithium-sulfur batteries. In this work, we obtained nitrogen-doped 3D carbon hybridized materials (lignin porous carbon/carbon nanotubes, LPC/CNTs) by self-assembly and in situ activation methods. This is the first time to achieve nitrogen-doped carbon hybrids by melamine modification lignin as raw material. The results show that the construction of the nitrogen-doped 3D carbon hybridization network is highly correlated with the modification treatment of lignin. As sulfur host material, it can reach a specific capacity of 1300.18 mAh g−1 at 0.1 C for the first time and still has a specific capacity of 582.84 mAh g−1 at 1 C for 400 cycles. In addition, carbon hybridized materials show excellent rate performance and high current adaptability in the rate performance test compared with the carbon materials prepared from unmodified lignin. The excellent electrochemical performance is mainly attributed to the synergistic effect within the 3D interconnection network, which enhances the physical confinement and chemical adsorption of polysulfides, as well as the catalytic conversion. This work provides new insights into biomass application in the sulfur hosts of lithium-sulfur batteries.

Sulfonic Acid-Functionalized Graphdiyne for Effective Li-S Battery Separators.

Lithium-sulfur (Li-S) batteries enable a promising high-energy-storage system while facing practical challenges regarding lithium dendrites and lithium polysulfides (LiPSs) shuttling. Herein, a fascinating SO3H-functionalized graphdiyne (SOGDY) was developed by grafting SO3H onto GDY to modify the separator in Li-S batteries. It realizes structure-retained material transformation, that is, SOGDY retains the crystalline all-carbon network and uniform subnanopores from the initial GDY. The abundant SO3H and uniform pores create a rapid Li+ transport relay station, benefit rapid Li+ transport and even lithium deposition, and prevent lithium dendrite growth. The spatial obstruction and strong polar adsorption sites from SO3H effectively inhibit LiPS shuttling. Additionally, SOGDY establishes a fast electron-transfer pathway to facilitate the LiPS conversion. The SOGDY/PP separator exhibited steady cycling at 1 mA cm-2 over 3500 h in the Li∥Li symmetric battery and achieved outstanding low-temperature and high-rate performance in the Li-S battery with a high initial specific capacity of 804.5 mA h g-1 and a final capacity of 504.9 mA h g-1 after 500 cycles at 3 C and -10 °C. This work demonstrates that introducing a stable all-carbon network and uniform functionalized nanopores is an effective strategy to modify the Li-S battery separator.

A Homogeneous Janus Membrane Based on Functionalized MOFs Crosslinked by Aramid Nanofibers for Quasi-Solid-State Lithium Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are considered as promising candidates in the next generation of high energy density devices. However, the serious shuttle effect, irreversible dendrite growth of Li metal anode, and the potential safety hazard impede the practical application of LSBs. Herein, a novel homogeneous Janus membrane based on functionalized MOFs crosslinked by aramid nanofibers is designed and synthesized to simultaneously solve the above challenges in quasi-solid-state LSBs. The aramid nanofibers with good mechanical properties and thermal stability act as a homogeneous scaffold to crosslink the MOF particles with different ligands on both sides and this Janus membrane upgrades the stability and safety on both the cathode and anode. Specifically, the amino ligand-decorated MOFs contribute to homogenize Li-ion flux and stabilize the lithium anode, and the sulfonic ligand-decorated MOFs effectively suppress the shuttle effect by the dual effects of chemical adsorption and electrostatic repulsion. The quasi-solid-state LSBs assembled with this homogeneous Janus membrane deliver excellent rate performance and cycling stability. Moreover, it exhibits a high initial capacity of 923.4 mAh g-1 at 1C at 70°C, and 697.3 mAh g-1 is retained after 100 cycles, indicating great potential for its application in high-safety LSBs.

Progresses and Perspectives of Carbon-Free Metal Compounds-Modified Separators for High-Performance Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) have the advantages of high theoretical specific capacity, excellent energy density, abundant elemental sulfur reserves. However, the LSBs is mainly limited by shuttling of lithium polysulfides (LiPSs), slow reaction kinetics of sulfur cathode. For solving the above problems, by developing high-performance battery separators, the reversible capacity, Coulombic efficiency (CE) and cycle life of LSBs can be effectively enhanced. Carbon-free based metal compounds are expected to be highly efficient separator modifiers for a new generation of high-performance LSBs by virtue of superior chemical adsorption capacity, strong catalytic properties and excellent lithophilicity to a certain extent. They can give play to the synergistic effect of their "adsorption-catalysis" sites to accelerate the redox kinetics of LiPSs, and their good lithophilicity can accelerate the Li+ transport kinetics, thus showing more remarkable electrochemical performances. However, a comprehensive summary of carbon-free metal compounds-modified separators for LSBs is still lacking. Here, this review systematically summarizes the researching progresses and performance characteristics of carbon-free-based metal compounds modified materials for separators of LSBs, and summarizes the corresponding mechanisms of using carbon-based separators to enhance the performance of LSBs. Finally, the review also looks forward to the prospects of LSBs using carbon-free metal compounds separators.

P‐doped RuSe2 on Porous N‐doped Carbon Matrix as Catalysts for Accelerated Sulfur Redox Reactions

Monocomponent catalysts exhibit the limited catalytic conversion of polysulfides due to their intrinsic electronic structure, but their catalytic activity can be improved by introducing heteroatoms to regulate its electronic structure. However, the rational selection principles of doping elements remain unclear. Here, we are guided by theoretical calculations to select the suitable doping elements based on the balanced relationship between the adsorption strength of lithium polysulfides (LiPSs) and catalytic activity of lithium sulfide. We apply the screening method to develop a new catalyst of phosphorus doped RuSe2, manifesting the further enhanced conductivity compared with original RuSe2, facilitating charge transfer and further modulating the d–band center of RuSe2, thereby augmenting its effectiveness in interacting with LiPSs. Consequently, the assembled cell exhibits an areal capacity of 7.7 mAh cm–2, even under high sulfur loading of 8.0 mg cm–2 and a lean electrolyte condition (5.0 μL mg–1). This rational screening strategy offers a robust solution for the design of advanced catalysts in the field of lithium–sulfur batteries and potentially other domains as well.

P-doped RuSe2 on Porous N-Doped Carbon Matrix as Catalysts for Accelerated Sulfur Redox Reactions.

Monocomponent catalysts exhibit the limited catalytic conversion of polysulfides due to their intrinsic electronic structure, but their catalytic activity can be improved by introducing heteroatoms to regulate its electronic structure. However, the rational selection principles of doping elements remain unclear. Here, we are guided by theoretical calculations to select the suitable doping elements based on the balanced relationship between the adsorption strength of lithium polysulfides (LiPSs) and catalytic activity of lithium sulfide. We apply the screening method to develop a new catalyst of phosphorus doped RuSe2, manifesting the further enhanced conductivity compared with original RuSe2, facilitating charge transfer and further modulating the d-band center of RuSe2, thereby augmenting its effectiveness in interacting with LiPSs. Consequently, the assembled cell exhibits an areal capacity of 7.7 mAh cm-2, even under high sulfur loading of 8.0 mg cm-2 and a lean electrolyte condition (5.0 μL mg-1). This rational screening strategy offers a robust solution for the design of advanced catalysts in the field of lithium-sulfur batteries and potentially other domains as well.

Hydrogen-bonded organic framework-sulfur composite for high performance lithium–sulfur batteries

With the rapid development of energy storage devices, lithium–sulfur batteries are considered as one of the promising candidates due to their high energy density (2600 Wh Kg−1) and low cost of sulfur. Despite these advantages, the application of lithium–sulfur batteries is limited by many issues, such as the shuttle effect of polysulfide and slow redox reactions. In this paper, hydrogen-bonded organic frameworks (HOFs) materials are chosen for the first time to improve the performance of sulfur cathodes by exploiting their unique properties. Thanks to the abundant hydrogen bond of HOFs materials, which can interact with lithium polysulfide, this S-HOF composite can inhibit the shuttle of polysulfide and enhance the transformation of polysulfide. As a result, the HOF-S composite has a high initial capacity of 1100 mAh g−1 at 0.1 C and 530 mAh g−1 at 1 C. In this paper, hydrogen-bonded organic frameworks (HOFs) materials are chosen for the first time to improve the performance of sulfur cathodes. In the S-HOF, abundant hydrogen bond sites can interact with lithium polysulfide to inhibit the shuttle of polysulfide and accelerate the redox conversion of polysulfide. Therefore, the S-HOF composite has higher capacity and cycle stability. The initial capacity of the S-HOF composite is 1100 mAh g–1 at 0.1 C and 530 mAh g–1 at 1 C.

Metal–Organic Frameworks with Axial Cobalt–Oxygen Coordination Modulate Polysulfide Redox for Lithium–Sulfur Batteries

AbstractAlthough the ultrahigh theoretical energy density and cost‐effectiveness, lithium–sulfur (Li‐S) batteries suffer from sluggish conversion kinetics and the shuttling effect of soluble lithium polysulfides (LiPSs). Herein, conductive hexagonal cobalt‐organic framework (Co‐HTP) nanosheets are anchored in situ on carboxyl graphene (CG) substrates and serve as host catalysts to modulate the polysulfide redox. Substantial characterizations identify that the local coordination environment of the quadrilateral Co–N4 units transforms into an asymmetric penta‐coordinated O–Co–N4 with axial Co─O coordination, which triggers spin polarization and remarkable electron delocalization of Co 3d orbital. The higher spin state and lower local electron density of the O–Co–N4 sites induce more active electronic states in Co‐HTP/CG and facilitate orbital hybridization with polysulfides to form more stable bond orders. Such optimized electronic structure significantly accelerates redox kinetics and enhances the adsorption strength of polysulfides. These merit the lithium–sulfur battery based on Co‐HTP/CG with a high reversible capacity, impressive rate capability, and prolonged cycling performance over 500 cycles. This work will enrich the design philosophy of modulating the spintronic structure of electrocatalysts for advanced Li–S batteries and beyond.

Flexible composite fiber paper as robust and stable lithium-sulfur battery cathode

Flexible composite fiber paper as robust and stable lithium-sulfur battery cathode

Investigating PEDOT:PSS Binder as an Energy Extender in Sulfur Cathodes for Li-S Batteries.

Although lithium-sulfur (Li-S) batteries offer a high theoretical energy density, shuttling of dissolved sulfur and polysulfides is a major factor limiting the specific capacity, energy density, and cyclability of Li-S batteries with a liquid electrolyte. Cathode host materials with a microstructure to restrict the migration of active material may not totally eliminate the shuttling effect or may create additional problems that limit the full dissolution and redox conversion of all active cathode materials. Selecting a cathode coating binder with a multifunctional role offers a universal solution suitable for various cathode hosts. PEDOT:PSS is investigated as such a binder in this study via experimental testing and material characterization as well as multiscale modeling. The study is based on Li-S cells with a sulfur cathode in hollow porous particles as the cathode host and the 10 wt % PEDOT:PSS binder and electrolyte 1 M LiTFSI in 1:1 DOL:DME 1:1 v/v. A reference supercapacitor cell with the same electrolyte and electrodes comprising a coating of the same hollow porous particles and 10 wt % PEDOT:PSS revealed the pseudocapacitive effect of PEDOT:PSS following a surface redox mechanism that dominates the charge phase, which is equivalent to the discharge phase of the Li-S battery cell. A multipore continuum model for supercapacitors and Li-S cells is extended to incorporate the pseudocapacitive effects of PEDOT:PSS with the Li+ ions and the adsorption effects of PEDOT:PSS with respect to sulfur and lithium sulfides in Li-S cells, with the adsorption energies determined via molecular and ab initio simulations in this study. Experimental data and predictions of multiscale simulations concluded a 7-9% extension of the specific capacity of Li-S battery cells due to the surface redox effect of PEDOT:PSS and elimination of lithium sulfides from the anode by slowing down their migration and shuttling via their adsorption by the PEDOT:PSS binder.

The “d-p orbital hybridization”-guided design of novel two-dimensional MOFs with high anchoring and catalytic capacities in Lithium − Sulfur batteries

The energy system of lithium-sulfur batteries is quite promising, however, lithium-sulfur batteries still suffer from considerable problems, such as the abominable shuttle effect of polysulfides (LiPSs), the low conductivity of the solid-phase products, the slow redox kinetics during charging and discharging, and the volume expansion. Herein, the hybridization pattern between the d-orbitals of various transition metal atoms and the p-orbitals of sulfides is revealed grounded in the theory of density function, which explains the high adsorption strength of two-dimensional metal–organic frameworks (MOFs) with LiPSs and accelerates the screening of high-performance anchoring and catalytic materials. The results elucidate that the coordinated transition metal–organic frameworks (Mo-NH MOF) monolayers increase the capacity of LiPSs to anchor by forming more π-bonds from the hybridization of the S p orbitals and Mo d orbitals. Notably, Mo-NH MOF exhibits bifunctional catalytic activity for sulfur reduction as well as Li2S decomposition reactions during charging and discharging, which improves the conversion efficiency of redox reactions. As a result, new MOF materials featuring unique active centers and the potential mechanism by which the active centers modulate the performance of the substrate materials are revealed, and this finding may accelerate the development of high-performance Li-S batteries.