Lithium Sulfur Research Articles

Supercritical CO2 in the Development of Highly Efficient Composite Cathodes for Li-S Batteries.

Conventional Li-S battery cathode synthesis routes are time-consuming, energy-intensive, use toxic solvents, and yet fail to effectively confine sulfur into carbon matrices, reducing the cathode efficiency. Supercritical CO₂ (scCO2) presents notable benefits as a "green solvent" due to its affordability, chemical inertness, recyclability, non-flammability, and non-toxicity. It eliminates the need for energy-intensive post-heat treatments, providing a more sustainable and efficient option. CO2 in supercritical state gains unique gas-like and liquid-like properties that enable precise sulfur loading, uniform encapsulation, and improved sulfur-carbon interactions, which enhance conductivity and reaction kinetics. Recent studies show that cathodes prepared using scCO2 exhibit exceptional electrochemical performance, including long-term cycling stability and high coulombic efficiency. The versatility of scCO2 in infiltrating various host architectures also makes it suitable for a wide range of cathode designs. Despite its tremendous potential, this advanced synthesis technology is often overlooked in textbooks, underscoring the need for awareness within the research community. This review highlights the remarkable features of scCO2 and examine up-to-date research progress, focusing on its application in developing high-performance carbon/sulfur composite cathodes. An application-focused audience would benefit from a summary of this review, as they reveal new Li-S cathode synthesis technologies that haven't been widely explored or discussed.

A Promising Approach to Ultra-Flexible 1 Ah Lithium-Sulfur Batteries Using Oxygen-Functionalized Single-Walled Carbon Nanotubes.

Lithium-sulfur (Li-S) batteries represent a promising solution for achieving high energy densities exceeding 500Wh kg-1, leveraging cathode materials with theoretical energy densities up to 2600Wh kg-1. These batteries are also cost-effective, abundant, and environment-friendly. In this study, an innovative approach is proposed utilizing highly oxidized single-walled carbon nanotubes (Ox-SWCNTs) as a conductive fibrous scaffold and functional interlayer in sulfur cathodes and separators, respectively, to demonstrate large-area and ultra-flexible Li-S batteries with enhanced energy density. The free-standing sulfur cathodes in the Li-S cells exhibit high energy density maintaining 806 mAh g-1 even after 100 charge-discharge cycles. Additionally, oxygen-containing functional groups on the SWCNTs significantly improve electrochemical performance by promoting the adsorption of lithium polysulfides. Employing Ox-SWCNTs in both cathodes and interlayers, the study achieves high-capacity Li-S pouch cells that consistently deliver a capacity of 1.06 Ah and a high energy density of 909 mAh g-1 over 50 charge-discharge cycles. This strategy not only significantly enhances the electrochemical performance of Li-S batteries but also maintains excellent mechanical flexibility under severe deformation, positioning this Ox-SWCNT-based architecture as a viable, light-weight, and ultra-flexible energy storage solution suitable for commercializing rechargeable Li-S batteries.

Nano-Sized Graphene Cages Realize Highly Loaded “Solid-Solid” Process in Cathode Materials of Lithium Sulfur Batteries

Abstract The effects of polysulfide shuttle and volume expansion in lithium sulfur batteries limit their practical applications. In this work, a two-dimensional fabric with graphene cage interweaving was designed by the chemical vapor deposition method to resolve these issues. It has a large number of micropores, mesopores, and macropores. Sulfur was deposited in these pores by melting method to form sulfur/graphene complex. Polysulfides were confined within these pores, making them less likely to diffuse and shuttle. Graphene walls have strong flexibility and can alleviate the volume expansion effect during charge and discharge process. Sulfur/graphene complex as active materials were directly coated on aluminum foil by graphene oxide to build lithium-sulfur battery, where graphene oxide served not only as an adhesive but also as a conductive agent to improve the electrochemical performances of batteries. The lithium-sulfur battery had an initial capacity of 1400 mAh g-1 and high capacity retention (500 mAh g-1 after 200 cycles at 0.2 C rate). These results suggest that the reasonable design of material morphology for sulfur loading will effectively improve the performance of lithium sulfur batteries.

Facile Synthesis of S/Ti3C2Tx Mxene@Se Cathode for High-Sulfur-Loading Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) are gaining much attention because they offer a much higher theoretical energy density compared to traditional lithium-ion batteries. However, the cycling performance of LSBs with high sulfur mass loading is poor due to the shuttle effect, limiting the practical application of LSBs. In this work, a unique porous sulfur/Ti3C2Tx Mxene@selenium (S/Ti3C2Tx@Se) cathode of a LSB is synthesized by a simple hydrothermal method to address these challenges. In this composite, Ti3C2Tx forms a conductive framework and Se is tightly anchored on the framework. The Se inhibits the agglomeration of Ti3C2Tx and prevents the collapse of Ti3C2Tx. The S/Ti3C2Tx@Se composite can adsorb lithium polysulfides (LiPSs) and suppresses the shuttle effect and volume changes during cycling, improving the cycling stability of LSBs with high S loading. A high capacity of 812.2 mAh g−1 at 0.1 C with 5.0 mg cm−2 sulfur mass loading after 100 cycles is obtained. This work could inspire further research into high-performance S host materials for high-S-loading LSBs.

Alloying Strategy Regulating Size and Electronic Structure of Mo0.25Nb0.75Se2 to Achieve High‐Performance Lithium–Sulfur Batteries

The utilization of catalysts in lithium−sulfur batteries has proven to be an efficacious avenue for enhancing the kinetics of polysulfide conversion. Specially, the size and electronic structure of catalysts play a pivotal role in harnessing the active sites and intrinsic catalysis activity. Outstanding MoSe2 and NbSe2 are selected from 16 universal transition metal selenides based on the proposed binary descriptor. Then, an alloying strategy is devised to prepare Mo0.25Nb0.75Se2 flakelets for further improvement of the intrinsic catalysis. The integration of density functional theory calculations and electrochemical analysis demonstrates that alloying Mo with Nb can regulate the surface energy and indexes of band match and lattice mismatch, thereby enabling Mo0.25Nb0.75Se2 to possess a small size, suitable adsorption energy and low reaction energy barrier. This optimization enhances the catalysis of sulfur reduction/evolution reaction and the reversible deposition/stripping of lithium. Consequently, an assembled Ah‐level pouch cell is realized with dramatic cycle stability. With the electrolyte/sulfur ratio of 2.36 μL mg S–1, the cell can deliver a high energy density of up to 505.4 Wh kgtotal−1. This work pioneers a universal strategy for sculpting the geometric configurations and electronic structures of catalysts, to achieve enhanced catalytic activity and precise interpretation of structure−activity relationships.

A polyolefin separator reinforced inorganic/organic composite electrolyte for quasi-solid-state Lithium-sulfur batteries with high cycle stability and long lifespan

Lithium-sulfur (Li-S) batteries are considered a promising next-generation energy storage system due to the high energy density and the low cost. However, the severe shuttle effect of polysulfide and the security issue caused by organic liquid electrolyte and lithium metal anode have hindered their commercial application. Herein we achieved a polyolefin commercial separator reinforced inorganic/organic composite electrolyte (denoted as Com-LATP) via coating the polypropylene (PP) separator with the composite of polymethyl methacrylate/poly(vinylidene fluoride) (PMMA/PVDF) modified with Li1.3Al0.3Ti1.7(PO4)3 (LATP). The Com-LATP electrolyte (thickness: ∼30 um) exhibits remarkable tensile strength of 103 MPa, an ionic conductivity of 0.47·mS cm-1 with the Li+ transfer number of 0.45, which is beneficial for the uniform Li+ flux and the stable striping and plating of Li metal. The Li symmetrical batteries equipped with this Com-LATP exhibited stable cycling for over 350 h. Meanwhile, the Com-LATP electrolyte with the special dense structure can hinder the polysulfide diffusion. The developed quasi-solid-state lithium-sulfur batteries have demonstrated impressive cycling stability with an initial specific capacity of 1184.8 mA h g-1 at a discharge rate of 0.2 C, maintaining performance over 200 cycles. Additionally, they exhibited outstanding rate capability, retaining a reversible capacity of 710.4 mA h g-1 even at a higher discharge rate of 2 C. This research introduces an innovative structural design approach for high-performance quasi-solid-state Li-S batteries, which holds significant promise for advancing the commercialization of lithium-sulfur battery technology.

Supramolecular macrocycle grafted Nb-MXene nanosheets constructing self-supporting framework for high-performance lithium-sulphur batteries

The advancement of lithium-sulphur (Li-S) batteries with high-energy density has been hindered by the high energy conversion barrier of sulphur and the shuttle effect of polysulfides. In this study, we successfully graft monocarboxylic pillar[5]arene (PA5-COOH) onto niobium carbide MXene (Nb2CTx) through an esterification reaction to obtain the PA5-COOH/Nb2C hybrid multi-functional separator. The incorporation of organic molecules increases the interlayer spacing, creating more active sites for capturing polysulfides. Through a combination of experimental and theoretical calculations, we find that the presence of the organic macromolecular structure can facilitate rapid polysulfide conversion, while Nb2CTx provides support sites for PA5-COOH and its larger specific surface area helps mitigate sulphur volume changes. By equipping Li-S batteries with a PA5-COOH/Nb2C separator, the Li-S battery supports an impressive reversible specific capacity of 1317mAh g−1 at 0.2C and demonstrates exceptional rate performance (303 mAh g−1 at 10C). The incorporation of the PA5-COOH/Nb2C hybrid separator expands the application potential of organic macrocyclic molecules and presents a stable self-support structure for developing high-performance lithium-sulphur batteries using macrocycle organic molecules.

Heterostructured MoO2@rGO facilitates enhanced kinetics in lithium-sulfur battery

MoO2 is heterogeneously grafted onto reduced graphene oxide (rGO) to create a MoO2@rGO heterostructure, which acts as a host material for sulfur in lithium-sulfur batteries (LSBs). The transition metal compounds MoO2 enhance the adsorption capacity for lithium polysulfides (LiPSs) and promote catalytic conversion processes. The MoO2@rGO cathode exhibits high sulfur loading (70 wt.%), elevated specific capacity (1136 mAh g-1 at 0.3 C, 9 mg cm-2), and excellent rate performance. Importantly, MoO2@rGO/S (12 mg cm-2) demonstrates a localized capacity of 11.60 mAh in the first discharge. After 110 cycles under a current density of 2.01 mA cm-2, it still retains residual capacity of 6.12 mAh, with a specific discharge capacity of 536 mAh g-1, showcasing superior cycling competence. The MoO2@rGO/S-100 mg pouch cell achieves an initial specific capacity of 1128 mAh g-1. After 110 cycles at 0.2 C, it retains a specific capacity of 738 mAh g-1 (65.4%), with a coulombic efficiency stabilizing around 99.2%. Two series-connected MoO2@rGO/S pouch cells-powered drone run continuously for 115 s. Hence, heterostructured MoO2@rGO can serve as a LiPS catcher, accelerate the redox kinetics of sulfur, and hold promise for constructing next-generation LSBs with outstanding electrochemical performance.

DFT insights into the role of penta-SiC₂ in enhancing Li-S battery performance through polysulfide anchoring

The interactions between soluble Li2Sn species (S8, Li2S8, Li2S6, Li2S4, Li2S2, and Li2S) and the penta-SiC2 (p-SiC2) surface were examined to assess its suitability as an anchoring material for Li-S batteries using Density Functional Theory (DFT) calculations. Our analysis of the structural and electronic properties of these species revealed their most stable configurations and associated binding energies. The findings indicate that p-SiC2 has moderate binding energies with Li2Sn species, which implies that it can serve as a moderate anchoring material, helping to prevent the dissolution of polysulfides into the electrolyte. Bader charge analysis confirmed the transfer of charge from Li atoms to S atoms and highlighted the role of p-SiC2 as a charge acceptor, thereby enhancing its anchoring effect. Furthermore, Gibbs free energy calculations showed that the reduction of Li2S2 to Li2S is the rate-limiting step in the sulfur redox reaction, underscoring the catalytic role of p-SiC2. This study offers valuable insights into the potential application of p-SiC2 as a functional material in Li-S batteries, effectively balancing the interaction between Li2Sn species and the anchoring surface to enhance battery performance.

Ion selective rapid transport enabled by functionalized CeO2/LiX zeolite modified separator in high performance lithium sulfur batteries

With regard to the issues in the application of lithium sulfur batteries (LSBs), for instance, the low-rate performance due to the difficulty in Li+/S2-n diffusion, and the poor cycling stability caused by lithium dendrites and polysulfide shuttle. This work reports a unique strategy for protecting lithium anode, that is, using the “size sieving” and “Donnan effect” of CeO2/LiX modified separator to simultaneously regulate the transfer behavior of Li+/S2-n based on the differences in size and charge. The CeO2, which is carefully constructed with oxygen defects, together with the negatively charged properties of zeolite framework, exhibits a synergistic relationship in controlling the flux and diffusion rate of Li+ and suppressing the polysulfide shuttling, which is confirmed by the experimental and theoretical investigations. As a result, the symmetric cell assembled with CeO2/LiX modified separator achieves stable cycling for 5000 h at 5 mA cm−2 and 5 mA h cm−2, and a deep Li stripping/plating for more than 2000 h at 10 mA h cm−2. The corresponding full battery shows a competitive areal capacity of 4.7 mA h cm−2 under a high sulfur loading of 4.0 mg cm−2. This strategy offers a low-cost solution to achieve the practical application of LSBs.

Defect-riched prussian blue analogues with superior adsorption-catalysis toward lithium polysulfides for high performance lithium-sulfur batteries

Lithium‑sulfur batteries (LiS) garner significant interest within the energy storage industry, because of their exceptional theoretical energy density coupled with employment of environmental materials. Nevertheless, the broader implementation of LiS batteries faces challenges, primarily due to the lithium polysulfide (LiPSs) shuttle effect and the sluggish conversion kinetics associated with LiPSs. In this work, we introduce a reduction-induced dissolution process to fabricate a mesoporous CoFePB rich in crystal defects via a facile solvothermal method. The experimental results indicate that the abundance of crystal defects originate from the phase transition from Co3[FeIII(CN)6]2 to Co2[FeII(CN)6]. The subsequent adsorption tests and electrochemical evaluations have shown that the defect-rich CoFePB possesses enhanced LiPSs absorption capacity and improved cycling performance in contrast to the pristine CoFePB, which is primarily ascribed to proliferation of active sites emerging as a result of the crystal defects. Consequently, the D-CoFePB-S cathode demonstrates remarkable rate performance with 583 mAh g−1 at a substantial 5C current rate, superior long-term stability with capacity retention of 64.3 % over 2000 cycles at current rate of 2C and outstanding areal capacity of 4.9 mAh cm−2 at 0.1C, even under a substantial sulfur loading of 5.0 mg cm−2.

Advances and prospects of g-C 3N 4 in lithium-sulfur batteries

Advances and prospects of g-C ₃N ₄ in lithium-sulfur batteries

Interfacial synergy in twinborn CoS2/CoS1.097 heterojunction to promote sulfur conversion kinetics in lithium-sulfur batteries

The rational design of sulfur hosts is essential for mitigating the shuttle effect of lithium polysulfides (LiPSs) and improving the sluggish conversion kinetics of sulfur during multi-step phase transition. Herein, a twinborn CoS2/CoS1.097 heterojunction encapsulated in N-doped hollow carbon polyhedrons and in-situ generated CNTs (CoS2/CoS1.097@NC/CNT) was elaborately synthesized and utilized as the electrocatalyst in sulfur cathodes. The CoS2/CoS1.097 heterojunction provides abundant chemisorption sites that facilitate the formation of chemical bonds with polysulfides, thereby effectively adsorbing LiPSs. More importantly, the spontaneously generated internal electric field at the CoS2/CoS1.097 interface accelerates electron transfer, which promotes the reversible transformation between LiPSs and Li2S. Additionally, the hollow carbon polyhedrons and grafted CNTs not only effectively confine sulfur, but also provide extra buffer space for the sulfur evolution reaction. Benefiting from these characteristics, the battery assembled with CoS2/CoS1.097@NC/CNT/S cathode exhibits a remarkable initial capacity of 1454.4mAh/g at 0.1C), excellent rate capability of 674.7mAh/g at 4C, and outstanding capacity retention of 604.7mAh/g over 500 cycles at 2C (∼73.1 % of initial capacity).

Coupling 5 d metallic and conductive Network for promoting polysulfide conversion

The reaction kinetics of lithium-sulfur (Li-S) battery mainly depends on the capture and catalytic conversion efficiency of lithium polysulfide (LiPSs). The unique electron configuration of the 5d metal and the high electrical conductivity of MXene can enhance the interaction between the catalyst and LiPSs. However, the challenge of enhancing the adsorption of LiPSs by regulating the electronic structure of the catalyst with 5d metal and MXene remains unresolved and obscure. In this work, we have developed molybdenum disulfide (MoS2)-tungsten disulfide (WS2) @MXene (MoS2-WS2@MX) heterostructure catalysts for separator coatings in Li-S batteries by introducing W and MXene for the first time. Theoretical calculations demonstrate that the 5 d metallic and conductive MXene coupling effectively modulate the orbital hybridization degree between the catalyst and LiPSs, thereby reducing the energy barrier for LiPSs conversion. Electrochemical test and in situ tests verify the effectiveness of the strategy on the adsorption and conversion of LiPSs. Consequently, the MoS2-WS2@MX based batteries exhibit high initial reversible capacity of 950.3 mAh g−1 and low capacity decay of 0.066 % per cycle over 500 cycles at 2 C, which is superior to most reported catalysts. This study provides a dual regulatory strategy for enhancing catalytic activity, offering valuable insights for the advancement of high-performance Li-S batteries.

Co/Co3O4@NC-CNTs modified separator of Li-S battery achieving the synergistic effect of adsorption-directional migration-catalysis via built-in electric field

The shuttle effect of lithium polysulfides (LiPSs) and sluggish sulfur conversion kinetics have seriously hindered the commercial application of lithium-sulfur (Li-S) batteries. Currently, the adsorption and catalysis processes are emphasized; however, the diffusion process is often neglected. The delayed diffusion of the adsorbed LiPSs significantly reduce battery performance. Herein, the directional migration of Sn2- was realized by adjusting the characteristics of heterostructure materials. The heterostructure consists of Co with a high Fermi level and excellent catalytic activity and Co3O4 with a low Fermi level and strong adsorption ability. This configuration regulated the direction of the built-in electric field (BIEF) at the heterogeneous interface, which promoted the migration of Sn2− from Co3O4 to Co side and realised a continuous “adsorption-directional migration-catalysis” mechanism. Experimental and theoretical results indicated that the Co/Co3O4 heterostructure modified by nitrogen-doped carbon nanotubes (Co/Co3O4@NC-CNTs), as the separator of Li-S batteries, not only enhanced the adsorption of LiPSs but also accelerated the kinetic conversion process. Consequently, the battery modified by the Co/Co3O4@NC-CNTs separator exhibited a high initial specific capacity of 1423 mAh g−1 at 0.2C, and maintained 735.5 mAh g−1 at a current density of 1C after 400 cycles.

Confined Biomimetic Catalysts Boost LiNO3-Free Lithium-Sulfur Batteries via Enhanced LiTFSI Decomposition

Lithium-sulfur batteries face a critical challengeLiNO3 limits the electrochemical stability window of electrolyte and poses safety risks. This study presents FePC@NH2-MIL-68, a biomimetic enzyme catalyst stable in ether-based electrolytes, to address these issues, which can replace LiNO3 and facilitate Li-anion decomposition. Theoretical and spectroscopic investigations show it promotes LiTFSI decomposition, forms robust CEI and SEI interfaces, and enhances sulfur conversions. Consequently, the FePC@NH2-MIL-68 cell, without LiNO3 additive, delivers a high discharge capacity of 1549 mAh g−1 at 0.2 C and a low capacity decay rate of 0.067% over 1000 cycles at 1.5 C. Even under high sulfur loading of 7.9 mg cm−2 and low electrolyte-to-sulfur ratio of 5.5 μL mg−1, the cells maintain 720 mAh g−1. This work emphasizes that in developing sulfur conversion catalysts, special attention must be paid to their effects on other lithium salt components, which provides a guidance for new catalysts design for metal-sulfur batteries.

Emerging redox kinetics promoters for the advanced lithium-sulfur batteries

Emerging redox kinetics promoters for the advanced lithium-sulfur batteries

Conductive nanofabrics as multifunctional interlayer of sulfur-loading cathode towards durable lithium-sulfur batteries

Conductive nanofabrics as multifunctional interlayer of sulfur-loading cathode towards durable lithium-sulfur batteries

ZnS/MoS2 heterostructures on MXene: A strategy for improved polysulfide adsorption and conversion in Li-S batteries

The shuttle effect of polysulfides (LiPSs) and the sluggish sulfur redox kinetics are critical challenges hindering the practical application of lithium-sulfur (Li-S) batteries. This paper introduces ZnS/MoS2 heterostructures uniformly anchored on MXene (ZnS/MoS2@MXene) for use in Li-S batteries via a modified separator. The heterogeneous interface of ZnS/MoS2@MXene facilitates efficient adsorption, catalysis, and conversion of LiPSs, thereby suppressing the shuttle effect and significantly enhancing sulfur redox kinetics. The redox kinetics and the mechanism behind the enhanced chemisorption effect of ZnS/MoS2@MXene are thoroughly investigated using density functional theory (DFT) calculations. As anticipated, Li-S batteries employing ZnS/MoS2@MXene demonstrate remarkable rate performance and long-term cycling stability. The specific capacity of the ZnS/MoS2@MXene battery reaches 1504.4 mAh g−1 at 0.1C. The ZnS/MoS2@MXene battery retains a high discharge specific capacity of 741 mAh g−1 after 500 cycles at 1C, with a per-cycle decay rate of just 0.067 %. Notably, with a sulfur loading of 5.6 mg cm−2, the areal specific capacity remains at 3.6 mAh cm−2 after 100 cycles at 0.2C. This study presents a viable strategy for developing more efficient heterostructure catalysts for Li-S batteries.

Understanding Rate and Capacity Limitations in Li-S Batteries Based on Solid-State Sulfur Conversion in Confinement.

Li-S batteries with an improved cycle life of over 1000 cycles have been achieved using cathodes of sulfur-infiltrated nanoporous carbon with carbonate-based electrolytes. In these cells, a protective cathode-electrolyte interphase (CEI) is formed, leading to solid-state conversion of S to Li2S in the nanopores. This prevents the dissolution of polysulfides and slows capacity fade. However, there is currently little understanding of what limits the capacity and rate performance of these Li-S batteries. Here, we aim to deepen our understanding of the capacity and rate limitation using a variety of structure-sensitive and electrochemical techniques, such as operando small-angle neutron scattering (SANS), operando X-ray diffraction (XRD), electrochemical impedance spectroscopy, and galvanostatic charge/discharge. Operando SANS and XRD data give direct evidence of CEI formation and solid-state sulfur conversion occurring inside the nanopores. Electrochemical measurements using two nanoporous carbons with different pore sizes suggest that charge transfer at the active material interfaces and the specific CEI/active material structure in the nanopores play the dominant role in defining capacity and rate performance. This work helps define strategies to increase the sulfur loading while maximizing sulfur usage, rate performance, and cycle life.