Search Results (19)

In this study, nitrogen- and sulfur-co-doped MXene (NS-MXene) was developed as a high-performance cathode material for lithium–sulfur (Li-S) batteries. Heterocyclic Se₂S₆ molecules were successfully confined within the NS-MXene structure using a simple melt impregnation method. The resulting NS-MXene exhibited a unique wrinkled morphology with a stable structure which facilitated rapid ion transport and provided a physical barrier to mitigate the shuttle effect of polysulfide. The introduction of nitrogen and sulfur heteroatoms into the MXene structure not only shifted the Ti d-band center towards the Fermi level but also significantly polarizes the MXene, enhancing the conversion kinetics and ion diffusion capability while preventing the accumulation of Li₂S₆. Additionally, the incorporation of Se and S in Se₂S₆ improved the conductivity compared to S alone, resulting in reduced polarization and enhanced electrical properties. Consequently, NS-MXene/Se₂S₆ exhibited excellent cycling stability, high reversible capacity, and reliable performance at high current densities and under extreme conditions, such as high sulfur loading and low electrolyte-to-sulfur ratios. This work presents a simple and effective strategy for designing heteroatom-doped MXene materials, offering promising potential for the development of high-performance, long-lasting Li-S batteries for practical applications. Full article

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/Ti₃C₂T_x Mxene@selenium (S/Ti₃C₂T_x@Se) cathode of a LSB is synthesized by a simple hydrothermal method to address these challenges. In this composite, Ti₃C₂T_x forms a conductive framework and Se is tightly anchored on the framework. The Se inhibits the agglomeration of Ti₃C₂T_x and prevents the collapse of Ti₃C₂T_x. The S/Ti₃C₂T_x@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. Full article

Se_xS_y composite cathode materials, which offer superior theoretical capacity compared to pure selenium and improved electrochemical properties relative to pure sulfur, have aroused considerable interest in recent decades on account of their applications in electric vehicles and energy storage grids. In the current work, the feasibility of a Co@C₂N monolayer as a promising host candidate for the cathode material of Li-Se_xS_y batteries has been evaluated using first-principles calculations, and particular efforts have been devoted to underscoring the anchoring mechanism and catalytic performance of the Co@C₂N monolayer. The pronounced synergistic effects of Co-S and Li-N bonds lead to increased anchoring performance for Li₂Se_xS_y/Se_xS_y clusters on the surface of Co@C₂N monolayer, which effectively inhibit the shuttle effect. The charge density difference and Mulliken charge analysis underscores a substantial charge transfer from the Li₂Se_xS_y and Se_xS_y clusters to the Co@C₂N monolayer, which indicates a noticeable chemical interaction between them. Further electronic property calculations show that the Co@C₂N monolayer can improve the electrical conductivity of cathode materials for Li-Se_xS_y batteries by maintaining semi-metallic characteristics after anchoring of Li₂Se_xS_y/Se_xS_y clusters. Additionally, the catalytic performance of the Co@C₂N monolayer is evaluated in terms of the reduction pathway of Se₈ and the decomposition energy barrier of the Li₂SeS cluster, which highlights the catalytic role of the Co@C₂N monolayer in the formation and decomposition of the Li₂SeS cluster during the cycle processes. Overall, the Co@C₂N monolayer emerges as a promising host material and catalyst for Li-Se_xS_y batteries with remarkable anchoring and catalytic performance. Full article

Sluggish transfer kinetics caused by solid–solid contact at the lithium (Li)/solid-state electrolyte (SE) interface is an inherent drawback of all-solid-state Li metal batteries (ASSLMBs) that not only limits the cell power density but also induces uneven Li deposition as well as high levels of interfacial stress that deteriorates the internal structure and cycling stability of ASSLMBs. Herein, a fast Li⁺ transfer scaffold is proposed to overcome the sluggish kinetics at the Li/SE interface in ASSLMBs using an α-MnO₂-decorated carbon paper (CP) structure (α-MnO₂@CP). At an atomic scale, the tunnel structure of α-MnO₂ exhibits a great ability to facilitate Li⁺ adsorption and transportation across the inter-structure of α-MnO₂@CP, leading to a high critical current density of 3.95 mA cm⁻² at the Li/SE interface. Meanwhile, uniform Li deposition can be guided along the skeletons of α-MnO₂@CP with minimized volume expansion, significantly improving the structural stability of the Li/SE interface. Based on these advantages, the ASSLMBs using α-MnO₂@CP protected the Li anode and can stably cycle up to very high charge/discharge rates of 10C/10C, paving the way for developing high-power ASSLMBs. Full article

Lithium–sulfur (Li-S) batteries are regarded as highly promising energy storage devices due to their high theoretical specific capacity and high energy density. Nevertheless, the commercial application of Li-S batteries is still restricted by poor electrochemical performance. Herein, beaded nanofibers (BNFs) consisting of carbon and CoSe₂ nanoparticles (CoSe₂/C BNFs) were prepared by electrospinning combined with carbonization and selenization. Benefitting from the synergistic effect of physical adsorption and chemical catalysis, the CoSe₂/C BNFs can effectively inhibit the shuttle effect of lithium polysulfides and improve the rate performance and cycle stability of Li-S batteries. The three-dimensional conductive network provides a fast electron and ion transport pathway as well as sufficient space for alleviating the volume change. CoSe₂ can not only effectively adsorb the lithium polysulfides but also accelerate their conversion reaction. The CoSe₂/C BNFs-S cathode has a high reversible discharge specific capacity of 919.2 mAh g⁻¹ at 0.1 C and presents excellent cycle stability with a low-capacity decay rate of 0.05% per cycle for 600 cycles at 1 C. The combination of the beaded carbon nanofibers and polar metal selenides sheds light on designing high-performance sulfur-based cathodes. Full article

Li-SeS₂ batteries balance the opposing and complimentary qualities of Li-S and Li-Se batteries by having a high specific capacity and high electrical conductivity. However, there is still a lack of knowledge regarding the electrochemical characteristics of Li-SeS₂ all-solid-state batteries (ASSB). Herein, transmission electron microscopy (TEM) is used to reveal the electrochemistry of a Li-SeS₂ battery. It is discovered that, without the Polyethylene glycol (PEG), amorphous SeS₂ in Li-SeS₂ ASSB change into crystalline selenium and a small amount of sulfur. The continuous loss of sulfur from the active material may be related to the failure of the cell at 15 cycles and the severe instability of the Coulombic efficiency. It was found that the PEG coating selenium disulfide graphene composite (PEG@rGO-SeS₂) cathode maintained a specific capacity of 258 mAh g⁻¹ and a stable Coulombic efficiency of about 97% after 50 cycles. TEM analysis shows that the charging product remains as a granular amorphous selenium disulfide with a constant Se/S ratio during cycling. The PEG-protected selenium disulfide can effectively limit the loss of elemental sulfur and regulate the reaction mechanism of the Li-SeS₂ batteries. Full article

Due to the limitations of organic liquid electrolytes, current development is towards high performance all-solid-state lithium batteries (ASSLBs). For high performance ASSLBs, the most crucial is the high ion-conducting solid electrolyte (SE), with a focus on interface analysis between SE and active materials. In the current study, we successfully synthesized the high ion-conductive argyrodite-type (Li₆PS₅Cl) solid electrolyte, which has 4.8 mS cm⁻¹ conductivity at room temperature. Additionally, the present study suggests the quantitative analysis of interfaces in ASSLBs. The measured initial discharge capacity of a single particle confined in a microcavity electrode was 1.05 nAh for LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622)-Li₆PS₅Cl solid electrolyte materials. The initial cycle result shows the irreversible nature of active material due to the formation of the solid electrolyte interphase (SEI) layer on the surface of the active particle; further second and third cycles demonstrate high reversibility and good stability. Furthermore, the electrochemical kinetic parameters were calculated through the Tafel plot analysis. From the Tafel plot, it is seen that asymmetry increases gradually at high discharge currents and depths, which rise asymmetricity due to the increasing of the conduction barrier. However, the electrochemical parameters confirm the increasing conduction barrier with increased charge transfer resistance. Full article

Metal–sulfur batteries, especially lithium/sodium–sulfur (Li/Na-S) batteries, have attracted widespread attention for large-scale energy application due to their superior theoretical energy density, low cost of sulfur compared to conventional lithium-ion battery (LIBs) cathodes and environmental sustainability. Despite these advantages, metal–sulfur batteries face many fundamental challenges which have put them on the back foot. The use of ether-based liquid electrolyte has brought metal–sulfur batteries to a critical stage by causing intermediate polysulfide dissolution which results in poor cycling life and safety concerns. Replacement of the ether-based liquid electrolyte by a solid electrolyte (SEs) has overcome these challenges to a large extent. This review describes the recent development and progress of solid electrolytes for all-solid-state Li/Na-S batteries. This article begins with a basic introduction to metal–sulfur batteries and explains their challenges. We will discuss the drawbacks of the using liquid organic electrolytes and the advantages of replacing liquid electrolytes with solid electrolytes. This article will also explain the fundamental requirements of solid electrolytes in meeting the practical applications of all solid-state metal–sulfur batteries, as well as the electrode–electrolyte interfaces of all solid-state Li/Na-S batteries. Full article

Selenium disulfide that combines the advantages of S and Se elements is a new material for Li-chalcogen battery cathodes. However, like Li-S batteries, the shuttle effect seriously restricts the performance of Li-SeS₂ batteries. In this work, we have synthesized a kind of nitrogen-rich lithophilic covalent organic framework (ATG-DMTZ-COF) as a separator coating material for Li-SeS₂ batteries. Here, the N atom in the ATG-DMTZ-COF channel preferentially interacts with the lithium ion in the electrolyte to form N…Li bond, which significantly improves the diffusion coefficient of lithium ions during the charge and discharge. More importantly, we prove that the pore size of ATG-DMTZ-COF will decrease sharply because there is a large amount of TFSI^- in the channel, and finally the shuttling of polysulfide and polyselenide is suppressed by the sieving effect. As a consequence, Li-SeS₂ batteries using the ATG-DMTZ-COF separator coating show excellent performances with an initial discharge capacity of 1028.7 mAh g⁻¹ at 0.5 C under a SeS₂ loading of 2.38 mg cm⁻². Furthermore, when the current density is 1C, the specific capacity of 404.7 mAh g⁻¹ can be maintained after 700 cycles. Full article

Selenium (Se)-based cathode materials have garnered considerable interest for lithium-ion batteries due to their numerous advantages, including low cost, high volumetric capacity (3268 mAh cm⁻³), high density (4.82 g cm⁻³), ability to be cycled to high voltage (4.2 V) without failure, and environmental friendliness. However, they have low electrical conductivity, low coulombic efficiency, and polyselenide solubility in electrolytes (shuttle effect). These factors have an adverse effect on the electrochemical performance of Li-Se batteries, rendering them unsuitable for real-world use. In this study, we briefly examined numerous approaches to overcoming these obstacles, including selecting an adequate electrolyte, the composition of Se with carbonaceous materials, and the usage of metal selenide base electrodes. Furthermore, we examined the effect of introducing interlayers between the cathode and the separator. Finally, the remaining hurdles and potential study prospects in this expanding field are proposed to inspire further insightful work. Full article

Conventional lithium-ion batteries with a limited energy density are unable to assume the responsibility of energy-structure innovation. Lithium-selenium (Li-Se) batteries are considered to be the next generation energy storage devices since Se cathodes have high volumetric energy density. However, the shuttle effect and volume expansion of Se cathodes severely restrict the commercialization of Li-Se batteries. Herein, a facile solid-phase synthesis method is successfully developed to fabricate novel pre-lithiated Li₂Se-LiTiO₂ composite cathode materials. Impressively, the rationally designed Li₂Se-LiTiO₂ composites demonstrate significantly enhanced electrochemical performance. On the one hand, the overpotential of Li₂Se-LiTiO₂ cathode extremely decreases from 2.93 V to 2.15 V. On the other hand, the specific discharge capacity of Li₂Se-LiTiO₂ cathode is two times higher than that of Li₂Se. Such enhancement is mainly accounted to the emergence of oxygen vacancies during the conversion of Ti⁴⁺ into Ti³⁺, as well as the strong chemisorption of LiTiO₂ particles for polyselenides. This facile pre-lithiated strategy underscores the potential importance of embedding Li into Se for boosting electrochemical performance of Se cathode, which is highly expected for high-performance Li-Se batteries to cover a wide range of practical applications. Full article

The safety problem caused by lithium dendrite of lithium metal anode and the rapid capacity decay problem caused by the shuttle effect of polysulfide and polyselenide during the charge and discharge of selenium disulfide cathode limit the application of lithium selenium disulfide batteries significantly. Here, a fibrous ATFG-COF, containing rich carbonyl and amino functional groups, was applied as the separator coating layer. Density Functional Theory (DFT) theoretical calculations and experimental results showed that the abundant carbonyl group in ATFG-COF had a positive effect on lithium ions, and the amino group formed hydrogen bonds with bis ((trifluoromethyl) sulfonyl) azanide anionics (TFSI⁻), which fixed TFSI⁻ in the channel, so as to improve the transfer number of lithium ions and narrow the channels. Therefore, ATFG-COF fiber coating can not only form a rapid and uniform lithium-ion flow on the lithium anode to inhibit the growth of lithium dendrites, but also effectively screen polysulfide and polyselenide ions to suppress the shuttle effect. The Li-SeS₂ cell with ATFG-COF/polypropylene (ATFG-COF/PP) separator exhibited good cycle stability at 0.5 C and maintained a specific capacity of 509 mAh/g after 200 cycles. Our work provides insights into the design of dual-function separators with high-performance batteries. Full article

Transition metal dichalcogenides (TMDs) such as MoSe₂ have continued to generate interest in the engineering community because of their unique layered morphology—the strong in-plane chemical bonding between transition metal atoms sandwiched between two chalcogen atoms and the weak physical attraction between adjacent TMD layers provides them with not only chemical versatility but also a range of electronic, optical, and chemical properties that can be unlocked upon exfoliation into individual TMD layers. Such a layered morphology is particularly suitable for ion intercalation as well as for conversion chemistry with alkali metal ions for electrochemical energy storage applications. Nonetheless, host of issues including fast capacity decay arising due to volume changes and from TMD’s degradation reaction with electrolyte at low discharge potentials have restricted use in commercial batteries. One approach to overcome barriers associated with TMDs’ chemical stability functionalization of TMD surfaces by chemically robust precursor-derived ceramics or PDC materials, such as silicon oxycarbide (SiOC). SiOC-functionalized TMDs have shown to curb capacity degradation in TMD and improve long term cycling as Li-ion battery (LIBs) electrodes. Herein, we report synthesis of such a composite in which MoSe₂ nanosheets are in SiOC matrix in a self-standing fiber mat configuration. This was achieved via electrospinning of TMD nanosheets suspended in pre-ceramic polymer followed by high temperature pyrolysis. Morphology and chemical composition of synthesized material was established by use of electron microscopy and spectroscopic technique. When tested as LIB electrode, the SiOC/MoSe₂ fiber mats showed improved cycling stability over neat MoSe₂ and neat SiOC electrodes. The freestanding composite electrode delivered a high charge capacity of 586 mAh g⁻¹_electrode with an initial coulombic efficiency of 58%. The composite electrode also showed good cycling stability over SiOC fiber mat electrode for over 100 cycles. Full article

All-solid-state batteries (ASSBs) are a promising response to the need for safety and high energy density of large-scale energy storage systems in challenging applications such as electric vehicles and grid integration. ASSBs based on sulfide solid electrolytes (SEs) have attracted much attention because of their high ionic conductivity and wide electrochemical windows of the sulfide SEs. Here, we study the electrochemical performance of ASSBs using composite electrodes prepared via two processes (simple mixture and solution processes) and varying the ionic conductor additive (80Li₂S∙20P₂S₅ and argyrodite-type Li₆PS₅Cl). The composite electrodes consist of lithium-silicate-coated LiNi_1/3Mn_1/3Co_1/3O₂ (NMC), a sulfide SE, and carbon additives. The charge-transfer resistance at the interface of the solid electrolyte and NMC is the main parameter related to the ASSB’s status. This value decreases when the composite electrodes are prepared via a solution process. The lithium silicate coating and the use of a high-Li-ion additive conductor are also important to reduce the interfacial resistance and achieve high initial capacities (140 mAh g⁻¹). Full article

Carbon–selenium composite positive electrode (CSs@Se) is engineered in this project using a melt diffusion approach with glucose as a precursor, and it demonstrates good electrochemical performance for lithium–selenium batteries. X-ray diffraction (XRD) and scanning electron microscopy (SEM) with EDS analysis are used to characterize the newly designed CSs@Se electrode. To complete the evaluation, electrochemical characterization such as charge–discharge (rate performance and cycle stability), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) tests are done. The findings show that selenium particles are distributed uniformly in mono-sized carbon spheres with enormous surface areas. Furthermore, the charge–discharge test demonstrates that the CSs@Se cathode has a rate performance of 104 mA h g⁻¹ even at current density of 2500 mA g⁻¹ and can sustain stable cycling for 70 cycles with a specific capacity of 270 mA h g⁻¹ at current density of 25 mA g⁻¹. The homogeneous diffusion of selenium particles in the produced spheres is credited with an improved electrochemical performance. Full article