Advanced Lithium Sulfur Batteries Research Articles

Emerging redox kinetics promoters for the advanced lithium-sulfur batteries

Emerging redox kinetics promoters for the advanced lithium-sulfur batteries

General and Fast Gas–Solid Synthesis of Functional MXenes and Derivatives on the Scale of Tens of Grams

The rising of MXenes not only enriches the two‐dimensional material family but also brings more opportunities for diverse functional applications. However, the controllable synthesis of MXenes is still unsatisfied via the common liquid‐solid etching route, considering the unsolved problems like safety risk, time cost and easy oxidation. Herein, a facile yet efficient gas‐solid (G‐S) reaction methodology is devised by using hydrogen fluoride gas derived from fluorinated organics as the MAX etchant toward high‐efficiency fabrication of multiple MXenes and their derivatives. The innovative G‐S reaction strategy exhibits superb versatility to achieve different gram‐level MXenes (V2C, Ti3C2, Nb2C, Ti2N, Ti3CN, (Mo2/3Y1/3)2C) in a very short time, and even realizes in‐situ heteroatom doping or synchronous phase conversion of MXenes directly from MAX phases. The obtained MXenes and their derivatives exhibit excellent structure stability and high electron/ion conductivity, making them promising materials for electrochemical applications. In particular, the N‐doped V2C MXene shows superior adsorption and catalytic activity toward lithium polysulfides for advanced lithium sulfur batteries.

Favorable Moderate Adsorption of Polysulfide on FeNi3 Intermetallic Compound Accelerating Conversion Kinetics for Advanced Lithium-Sulfur Batteries.

Sluggish conversion kinetics of polysulfides during discharge and the severe shuttle effect significantly hinder the practical application of lithium-sulfur (Li-S) batteries. In this work, the lattice engineering strategy of Fe hybridization is employed to manipulate the bulk phase spacing of FeNi3 (space group Pm3m) intermetallic compounds to adjust the 3d electronic structure, optimizing the adsorption of polysulfides, thereby accelerating the catalytic conversion. As a result, FeNi2.25@OC achieves favorable moderate adsorption toward polysulfides. Due to the larger number of electrons occupying the lowest occupied molecular orbital of Li2S4, the S-S bonds are weakened and broken. Temperature-dependent experiments confirm that FeNi2.25@OC exhibits the lowest activation energy and can effectively accelerate the catalytic conversion of polysulfides. The Li-S cell assembled with FeNi2.25@OC modified PP separator delivers a high initial discharge specific capacity of 1219.5 mAh g-1 at 0.2 C. Even at a high sulfur loading of 6.06mg cm-2 and lean electrolyte conditions (6 µL mg-1), it can cycle stably for 60 cycles.

Atomic substitution engineering-induced domino synergistic catalysis in Li-S batteries

Atomic substitution engineering is considered as effective strategy to activate the basal plane of molybdenum disulfide (MoS2) which has been demonstrated effective catalytic cathode in lithium-sulfur (Li-S) batteries. Rationally designing atomic substitution structure is vital to figure out the origin of catalytic activity in doped-MoS2 based catalytic cathodes. Herein, an “adjacent period, adjacent group” atomic substitution engineering is constructed to investigate the role of foreign atoms in sulfur redox reaction, and reveal the origin of catalytic activity. Theoretical calculations reveal that the real active sites are the S atoms adjacent to the doped atoms. It has been demonstrated that Nb atomic substitution acts as an initiator to trigger a “Domino Effect” of activating the S sites, enhancing the adsorption ability, facilitating the conversion reaction of sulfur species, and accelerating the Li+ diffusion. Enlightened by the theoretical guidance, Nb-doped MoS2 ultrathin nanosheets assembled hollow nanotubes (Mo1-xNbxS2 HNTs) are fabricated as efficient “adsorption-conversion” sulfur hosts, which exhibit high initial discharge capacities (1163 mAh g−1 at 0.2 C, 971 mAh g−1 at 0.5 C). An initial capacity of 613 mAh g−1 could be achieved under high sulfur loading (3.13 mg cm−2) and lean electrolyte (5.6 μL mg−1). This work provides pivotal guidance to design highly efficient catalytic cathodes for advanced Li-S batteries.

Carbon/Co3O4 heterostructures as new energy storage materials for advanced lithium-sulfur batteries

Carbon/Co3O4 heterostructures as new energy storage materials for advanced lithium-sulfur batteries

High-performance S cathode through a decoupled ion-transport mechanism

A high-performance sulfur (S) cathode is essential for advanced lithium-sulfur (LiS) batteries. Issues such as shuttle effect of polysulfides and low conductivity of S need to be resolved. Here, we report a S-cathode prepared via constructing unique decoupled ion-transport network formed from soy protein-based ionic conductor with well-dispersed graphene, leading to mitigated shuttle effect and excellent dual-conductive capabilities, i.e., high electronic and ionic conductivities. The decoupled ion-transport mechanism, which is unconventional in polymeric systems, is enabled by appropriately maintaining the denatured soy protein structure during the cathode preparation, facilitating polysulfide trapping and providing high adhesion for the S cathode, confirmed by the experiment and simulation results. Consequently, the LiS battery with the protein-based S cathode demonstrates excellent rate performance and long cycling stability. In specific, the LiS battery with the protein-based S cathode shows ∼70 % capacity retention (∼504 mAh g−1) after 600 cycles under the current density of 0.5 A g−1. This work will initiate new scientific studies on introducing an unconventional ion-transport mechanism into electrodes for producing high-performance batteries.

Nitrogen-Doped Graphene-Supported Tungsten Oxynitride Nanoparticles as an Efficient Bidirectional Polysulfide Convertor for Advanced Lithium-Sulfur Batteries.

Catalytic materials are considered pivotal in addressing the sluggish kinetics and shuttle effect in lithium-sulfur batteries (LSBs). However, effectively harnessing the utilization rate of active sites within catalytic materials remains a pivotal challenge. In this study, a novel conductive nitrogen-doped graphene-loaded tungsten oxynitride nanoparticle (WNO/NG) with abundant active sites is prepared through a polymer-assisted templating method for serving as a sulfur host. Electrochemical analysis coupled with in situ XRD confirm the dual-directional electrocatalytic behavior of WNO/NG for accelerating the conversion of lithium polysulfide (LiPSs). Theoretical calculations demonstrate that the intrinsic mechanism underlying the performance enhancement is attributed to the high inherent conductivity of WNO/NG and the efficient interface charge transfer with LiPSs. The assembled 500 mAh pouch cell delivers a 97% capacity retention after 25 cycles. This strategy provides valuable insights for designing catalytic materials with abundant activity sites and sheds light on the mechanisms of catalytic enhancement in Li-S chemistry.

N-doped carbon nanotubes and CoS@NC composites as a multifunctional separator modifier for advanced lithium-sulfur batteries

Lithium-sulfur batteries (LSBs), with their high theoretical energy density and specific capacity, are considered optimal candidates for next-generation energy storage systems. However, significant challenges remain in their cycle life and efficiency for practical applications, primarily due to the shuttle effect of lithium polysulfides (LiPSs) and the poor electrical conductivity of sulfur materials. The key to addressing these challenges lies in designing materials with excellent dispersion, good electrical conductivity, and high catalytic activity. In this work, we have designed and successfully synthesized a unique structural material consisting of in-situ grown cobalt sulfide nanoparticles embedded in zeolite imidazolate frameworks (ZIFs), which are derived from N-doped carbon wrapped around polypyrrole-derived N-doped carbon nanotubes (CoS@NC/NCNT). This design effectively mitigates the shuttle effect of lithium polysulfides (LiPSs) and enhances the conductivity of the material. As a result, batteries with CoS@NC/NCNT-modified separators achieved a high specific discharge capacity of 1518 mAh g−1 at 0.1 C. This work provides a reliable design strategy for synthesizing N-doped carbon nanotube/high-activity transition metal sulfide composite materials and opens new avenues for enhancing the modification and separation of high-performance lithium-sulfur batteries (LSBs).

Elucidating the dominant role of all-amorphous heterostructure on optimized built-in electric field with abundant active sites for advanced lithium–sulfur batteries

While various transition metal compound-based electrocatalysts have been developed to mitigate the shuttle effect of lithium–sulfur (Li–S) batteries, few studies have examined the effectiveness of their crystal structures. Herein, by integrating amorphous MoS2 nanosheets and TiO2 layers, an all-amorphous heterostructure is designed as a multifunctional electrocatalyst. The highly disordered atomic arrangement of the components provides abundant active sites and creates additional energy levels within the band gaps. Moreover, this unique crystal structures shift the Fermi level. Due to these synergistic effects, a well-aligned strong built-in electric field is generated, thereby exhibiting specific capacity of 1135 mA h g–1 at a current rate of 1 C, along with a stable long-term lifespan of 500 cycles at 2 C. This work provides a novel strategy for optimizing built-in electric field and amplifying active sites by constructing an all-amorphous heterostructure, which is crucial for the advanced Li–S batteries.

High-entropy sulfides enhancing adsorption and catalytic conversion of lithium polysulfides for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries with high energy density suffer from the soluble lithium polysulfide species. Traditional metal sulfides containing a single metal element used as electrocatalysts for Li-S batteries commonly have limited catalytic abilities to improve battery performance. Herein, based on the Hume-Rothery rule and solvothermal method, the high-entropy sulfide NiCoCuTiVSx derived from Co9S8 was designed and synthesized, to realize the combination of small local strain and excellent catalytic performance. With all five metal elements (Ni, Co, Cu, Ti, and V) capable of chemical interactions with soluble polysulfides, NiCoCuTiVSx exhibited strong chemical confinement of polysulfides and promoted fast kinetics for polysulfides conversion. Consequently, the S/NiCoCuTiVSx cathode can maintain a high discharge capacity of 968.9 mA h g−1 after 200 cycles at 0.5 C and its capacity retention is 1.3 times higher than that of S/Co9S8. The improved cycle stability can be attributed to the synergistic effect originating from the multiple metal elements, coupled with the reduced nucleation and activation barriers of Li2S. The present work opens a path to explore novel electrocatalyst materials based on high entropy materials for the achievement of advanced Li-S batteries.

Spatial structure design of interlayer for advanced lithium–sulfur batteries

The practical application of lithium-sulfur (Li–S) batteries has been hindered by the lithium polysulfide shuttle effect. An effective way to solve this problem is to utilize interlayer engineering to confine polysulfides and promote their catalytic conversion. From a spatial perspective, we designed a carbon nanofiber conductive layer (CNF, without Sn content, labeled as 0) and two Sn-doped carbon nanofiber catalytic layers (SCNF, with 10 wt% and 20 wt% Sn content, labeled as 1 and 2, respectively) with different contents of catalyst content, and verified an efficient interlayer structure by adjusting the order of preferential contact between the conductive layer and the catalytic layer with the sulfur cathode to form a hierarchical system for the inhibition and conversion of lithium polysulfide. Electrochemical measurements show that different spatial configurations have significant discrepancies on the electrochemical performance of Li–S batteries. Thus, the space configuration of 210 enables the Li–S battery to provide a specific capacity of up to 1088 mAh g−1 after 100 cycles at 0.2C. Even under the harsh conditions of high sulfur loading (5.6 mg cm−2) and lean electrolyte (E/S = 10 μL mg−1), the Li–S battery was able to cycle stably for 94 cycles at 0.2C with 87 % capacity retention. This study provides a novel spatial strategy for advancing the spatial design of high-performance Li–S batteries.

Bifunctional Role of High-Entropy Selenides in Accelerating Redox Conversion and Modulating Lithium Plating towards Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries, recognized as one of the most promising next-generation energy storage systems, are still limited by the "shuttle effect" of soluble polysulfides (LiPSs) on the cathode and the uncontrolled growth of lithium dendrites on the anode. These issues are critical obstacles to their practical application. Currently, many researchers have addressed these challenges from a unilateral perspective. Herein, we propose bifunctional hosts based on high-entropy selenides (HE-Se) to simultaneously tackle the persistent problems on both the positive and negative electrodes of Li-S batteries. On the one hand, HE-Se interacts with polysulfides to promote their conversion, effectively mitigating the shuttle effect. On the other hand, HE-Se provides multiple lithophilic sites during the initial nucleation of Li+, which reduces overpotential and exhibits excellent lithophilicity and cyclic stability. As a result, Li-S batteries incorporating the HE-Se hosts demonstrate outstanding performance in terms of rate capability and cycling stability. Additionally, the porous lithophilic HE-Se structure offers sufficient nucleation sites, inhibits the growth of dendritic lithium, and accommodates volume changes during charging and discharging cycles. This study highlights the potential of sulphophilic/lithophilic high-entropy materials in designing advanced Li-S batteries and encourages further exploration in this area.

Operando Fabricated Quasi-Solid-State Electrolyte Hinders Polysulfide Shuttles in an Advanced Li-S Battery

Lithium-sulfur (Li-S) batteries are a promising option for energy storage due to their theoretical high energy density and the use of abundant, low-cost sulfur cathodes. Nevertheless, several obstacles remain, including the dissolution of lithium polysulfides (LiPS) into the electrolyte and a restricted operational temperature range. This manuscript presents a promising approach to addressing these challenges. The manuscript describes a straightforward and scalable in situ thermal polymerization method for synthesizing a quasi-solid-state electrolyte (QSE) by gelling pentaerythritol tetraacrylate (PETEA), azobisisobutyronitrile (AIBN), and a dual salt lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium nitrate (LiNO3)-based liquid electrolyte. The resulting freestanding quasi-solid-state electrolyte (QSE) effectively inhibits the polysulfide shuttle effect across a wider temperature range of −25 °C to 45 °C. The electrolyte’s ability to prevent LiPS migration and cluster formation has been corroborated by scanning electron microscopy (SEM) and Raman spectroscopy analyses. The optimized QSE composition appears to act as a physical barrier, thereby significantly improving battery performance. Notably, the capacity retention has been demonstrated to reach 95% after 100 cycles at a 2C rate. Furthermore, the simple and scalable synthesis process paves the way for the potential commercialization of this technology.

A fresh perspective to synthesizing and designing carbon/sulfur composite cathodes using supercritical CO2 technology for advanced Li-S battery cathodes

The morphology and surface chemistry of the sulfur host within lithium-sulfur (Li-S) batteries significantly influence the overall battery performance. To investigate this relationship, we employed a non-toxic heat treatment to produce reduced graphene oxide (rGO) with varying degrees of reduction, resulting in distinct surface chemistries. The physicochemical characteristics and electrochemical properties of four differently reduced GO samples and rGO/sulfur composite cathodes developed with supercritical CO2 technology were examined. Our study established a clear correlation between the specific surface area and porosity of rGO and the electrochemical performance of the corresponding rGO/sulfur composite cathodes. Notably, rGO samples reduced at 350°C (rGO350) exhibited superior discharge capacity and long-term cycling stability compared to those reduced at higher temperatures. This performance enhancement can be attributed to the combination of high surface area, porosity, and an open morphology in rGO350. These findings underscore the importance of optimizing carbon chemistry, microstructure, and cathode synthesis strategies in Li-S batteries. By effectively controlling sulfur loading and distribution within the rGO network, we can enhance active material utilization, boost electronic conductivity, and ensure the long-term stability of rGO/sulfur composite cathodes. Our research suggests that SC-CO2-assisted synthesis offers a promising approach for designing high-performance carbon/sulfur composite cathodes for Li-S batteries. This method provides a versatile platform for tailoring the rGO morphology and surface chemistry, optimizing battery performance. By carefully considering the interplay between these factors, we can unlock the full potential of Li-S batteries for various applications.

Ultrathin 2D-2D MXene-LDH Interlayer with High Polysulfide Adsorption Ability for Advanced Li-S Batteries.

Lithium-sulfur (Li-S) batteries are considered as promising energy storage systems due to the high energy density of 2600 W h kg-1. However, the practical application of Li-S batteries is hindered by the inadequate conductivity of sulfur and Li2S, as well as the shuttle effect caused by polysulfides during the charge-discharge process. Introducing a conductive interlayer between the cathode and the separator to physically resist polysulfides represents an effective and straightforward approach to mitigate the shuttle effect in Li-S batteries. In this paper, an ultrathin (<1 μm) 2D-2D MXene-LDH interlayer with high polysulfide adsorption ability was introduced to Li-S batteries. The synergistic effect between MXene and layered double hydroxide greatly improved the adsorption effect of the interlayers: the conductive Ti3C2Tx MXene chemically adsorbs polysulfides and promotes their fast transfer, and the NiCo-LDH alleviates the restack of MXene and facilitates Li+ diffusion. After inserting the MXene-LDH interlayer, the Li-S batteries exhibit an enhanced specific capacity of 1137.6 mA h g-1 at 0.1 C and retain 622.6 mA h g-1 after 100 cycles. The ultrathin 2D-2D interlayer offers a feasible way for the development of highly efficient and lightweight interlayers in Li-S batteries.

Construction and regulation of a perovskite-type sulfur reduction catalyst based on oxygen vacancy engineering for advanced lithium-sulfur batteries

Lithium-sulfur batteries are considered as a promising energy storage solution due to their considerably high theoretical capacity of 1675 mAh g−1 and high energy density of 2600 Wh kg−1. Nevertheless, the lithium-sulfur batteries in commercial application is facing some challenges such as the shuttle effect. In this paper, the perovskite-type La2Ti2O7-x with oxygen defect is developed and applied as an advanced catalyst in lithium-sulfur batteries. It is found that La2Ti2O7-x with oxygen defects can not only strengthen the chemical binding between the metal sites and LiPSs, but also provide additional adsorption and catalytic sites. The as-prepared La2Ti2O7-x/S cathodes exhibit a high initial discharge specific capacity of 1047 mAh g−1 at 1 C (1 C = 1675 mA g−1), and a capacity decay rate of merely 0.089 % per cycle after 500 cycles. Therefore, this study demonstrates a significant approach to producing high-performance lithium-sulfur batteries using perovskite transition metal oxides as high efficiency electrocatalyst.

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.

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.

Accelerating catalytic conversion and chemisorption of polysulfides for advanced Li-S batteries from incorporating Fe0.64Ni0.36@Co5.47N hetero-nanocrystals into boron carbonitride nanotubes

With the rapid development of large-scale clean energy, lithium-sulfur (Li-S) batteries are considered to be one of the most promising energy storage devices. In this manuscript, the polymetallic hetero-nanocrystal of iron nickel@cobalt nitride encapsulating into boron carbonitride nanotubes (Fe0.64Ni0.36@Co5.47N@BCN) was designed and optimized for use as a modified material for commercial polypropylene (PP) separators. The prepared Fe0.64Ni0.36@Co5.47N@BCN-12 hybrid material presents strong chemisorption and catalytic conversion capabilities, which endows the Fe0.64Ni0.36@Co5.47N@BCN-12//PP separator with enhanced polysulfide shuttling inhibition. The assembled Li-S cells with Fe0.64Ni0.36@Co5.47N@BCN-12//PP separators have minimized charge transfer resistance and faster redox kinetics. Additionally, cells with Fe0.64Ni0.36@Co5.47N@BCN-12//PP separator provide high reversible capacity of 674 mAh/g for 400 cycles at 0.5C and excellent cyclability for 1000 cycles at 2C with a low decay rate of 0.05 % per cycle. Therefore, this study provides a feasible functionalization route for improving the electrochemical performance of Li-S batteries through separator modification.

Activation of the Radical‐Mediated Pathway and Facilitation of the Li2S Conversion by N‐Doped Carbon‐Embedded Ti1–xCoxN Nanowires as a Multifunctional Separator with a High Donor‐Number Solvent toward Advanced Lithium–Sulfur Batteries

Electrolyte modification with a high donor‐number solvent is necessary to increase sulfur utilization, but it also presents poor compatibility with lithium metal. The amount of the solvent should be optimized to maximize sulfur utilization at the cathode and minimize side reactions with Li metal at the anode. An electrolyte solution comprising 1 vol% N,N‐dimethylacetamide (DMA) in a 1,2‐dimethoxyethane (DME)/1,3‐dioxolane (DOL) co‐solvent demonstrated increased discharge capacity and reduced overpotential compared to DME/DOL and DMA/DOL. In addition to electrolyte, modification that creates radical‐mediated pathways from a high donor‐number solvent, long‐cycle performance is achieved by effectively mitigating the shuttling effect and enhancing reaction kinetics with an efficient electrocatalyst. Cobalt doping into TiN introduced an upshift of the d‐band center with ferromagnetic properties that suppressed the shuttling effect, activated radical‐mediated pathways, and facilitated the Li2S conversion. A multifunctional separator fabricated with N‐doped carbon‐embedded cobalt‐doped titanium nitride nanowires (NC‐Ti0.95Co0.05N NWs) under 1 vol% DMA electrolyte achieved a discharge capacity of 464.4 mA h g−1 even after 200 cycles at a decay rate of 0.093% per cycle through the synergistic effects of electrolyte and electrocatalyst modifications. This work highlights the importance of ferromagnetic catalysts with a high donor‐number solvent for lithium–sulfur (Li–S) batteries.