Soy protein isolate/MXene decorated acidified carbon paper interlayer for long-cycling Li–S batteries

The terrible shuttling of lithium polysulfides (LiPSs) is a major obstacle for commercializing lithium–sulfur (Li–S) batteries as high-performance energy storage systems. In this study, a carbon-based interlayer with effective suppression capability on the shuttle effect is developed by simply coating a well-dispersed mixture of soybean protein isolate/MXene onto the acidified carbon paper (ACP). The resultant composite interlayer (SM@ACP) is able to synergistically diminish the shuttle effect through chemical adsorption and physical blocking. Meanwhile, this interlayer displays excellent conductivity and facilitates the diffusion of Li ions due to the composite coating to promote both electron/ion conduction as well as the porous structure of ACP. Benefiting from the unique properties of the composite interlayer, the as-assembled Li–S batteries with SM@ACP interlayers show a great improvement in the cycling stability and rate performance, delivering a very low-capacity decay rate of 0.071% per cycle at 0.5 C even after 800 cycles. This work provides a feasible route to realize rational design and commercial mass production of desirable interlayers for promoting the commercialization of Li–S batteries.     

Fast,Reversible Lithium Storage with a Sulfur/Long‐Chain‐Polysulfide Redox Couple

The cathodic reactions in Li–S batteries can be divided into two steps. Firstly, elemental sulfur is transformed into long‐chain polysulfides (S₈?Li₂S₄), which are highly soluble in the electrolyte. Next, long‐chain polysulfides undergo nucleation reaction and convert into solid‐state Li₂S₂ and Li₂S (Li₂S₄?Li₂S) by slow processes. As a result, the second‐step of the electrochemical reaction hinders the high‐rate application of Li–S batteries. In this report, the kinetics of the sulfur/long‐chain‐polysulfide redox couple (theoretical capacity=419 mA h g^?1) are experimentally demonstrated to be very fast in the Li–S system. A Li–S cell with a blended carbon interlayer retains excellent cycle stability and possesses a high percentage of active material utilization over 250 cycles at high C rates. The meso‐/micropores in the interlayer are responsible for accommodating the shuttling polysulfides and offering sufficient electrolyte accessibility. Therefore, utilizing the sulfur/long‐chain polysulfide redox couple with an efficient interlayer configuration in Li–S batteries may be a promising choice for high‐power applications.     

Sulfur‐Impregnated Core–Shell Hierarchical Porous Carbon for Lithium–Sulfur Batteries

Core–shell hierarchical porous carbon spheres (HPCs) were synthesized by a facile hydrothermal method and used as host to incorporate sulfur. The microstructure, morphology, and specific surface areas of the resultant samples have been systematically characterized. The results indicate that most of sulfur is well dispersed over the core area of HPCs after the impregnation of sulfur. Meanwhile, the shell of HPCs with void pores is serving as a retard against the dissolution of lithium polysulfides. This structure can enhance the transport of electron and lithium ions as well as alleviate the stress caused by volume change during the charge–discharge process. The as‐prepared HPC‐sulfur (HPC‐S) composite with 65.3 wt % sulfur delivers a high specific capacity of 1397.9 mA h g^?1 at a current density of 335 mA g^?1 (0.2 C) as a cathode material for lithium–sulfur (Li‐S) batteries, and the discharge capacity of the electrode could still reach 753.2 mA h g^?1 at 6700 mA g^?1 (4 C). Moreover, the composite electrode exhibited an excellent cycling capacity of 830.5 mA h g^?1 after 200 cycles.     

Correlating Polysulfide Solvation Structure with Electrode Kinetics towards Long-Cycling Lithium–Sulfur Batteries

Lithium–sulfur (Li−S) batteries are promising due to ultrahigh theoretical energy density. However, their cycling lifespan is crucially affected by the electrode kinetics of lithium polysulfides. Herein, the polysulfide solvation structure is correlated with polysulfide electrode kinetics towards long-cycling Li−S batteries. The solvation structure derived from strong solvating power electrolyte induces fast anode kinetics and rapid anode failure, while that derived from weak solvating power electrolyte causes sluggish cathode kinetics and rapid capacity loss. By contrast, the solvation structure derived from medium solvating power electrolyte balances cathode and anode kinetics and improves the cycling performance of Li−S batteries. Li−S coin cells with ultra-thin Li anodes and high-S-loading cathodes deliver 146 cycles and a 338 Wh kg⁻¹ pouch cell undergoes stable 30 cycles. This work clarifies the relationship between polysulfide solvation structure and electrode kinetics and inspires rational electrolyte design for long-cycling Li−S batteries.     

Nitrogen-doped hierarchical porous carbon derived from metal–organic aerogel for high performance lithium–sulfur batteries

Nitrogen-doped three-dimensional(3 D) porous carbon materials have numerous applications due to their highly porous structures, abundant structural nitrogen heteroatom decoration and low densities. Herein,nitrogen doped hierarchical 3 D porous carbons(NHPC) were prepared via a novel metal–organic aerogel(MOA), using hexamethylenetetramine(HMT), 1,3,5-benzenetricarboxylic acid and copper(II) as starting materials. The morphology, porous structure of the building blocks in the NHPC can be tuned readily using different amount of HMT, which makes elongation of the pristine octahedron of HKUST-1 to give rise to different aspect ratio rod-like structures. The as-prepared NHPC with rod-like carbons exhibit high performance in lithium sulfur battery due to the rational ion transfer pathways, high N-doped doping and hierarchical porous structures. As a result, the initial specific capacity of 1341 m A h/g at rate of 0.5 C(1 C = 1675 m A h/g) and high-rate capability of 354 m A h/g at 5 C was achieved. The decay over 500 cycles is 0.08% per cycle at 1 C, highlighting the long-cycle Li–S batteries.     

Electrolyte Design for Improving Mechanical Stability of Solid Electrolyte Interphase in Lithium–Sulfur Batteries

Practical lithium–sulfur (Li−S) batteries are severely plagued by the instability of solid electrolyte interphase (SEI) formed in routine ether electrolytes. Herein, an electrolyte with 1,3,5-trioxane (TO) and 1,2-dimethoxyethane (DME) as co-solvents is proposed to construct a high-mechanical-stability SEI by enriching organic components in Li−S batteries. The high-mechanical-stability SEI works compatibly in Li−S batteries. TO with high polymerization capability can preferentially decompose and form organic-rich SEI, strengthening mechanical stability of SEI, which mitigates crack and regeneration of SEI and reduces the consumption rate of active Li, Li polysulfides, and electrolytes. Meanwhile, DME ensures high specific capacity of S cathodes. Accordingly, the lifespan of Li−S batteries increases from 75 cycles in routine ether electrolyte to 216 cycles in TO-based electrolyte. Furthermore, a 417 Wh kg⁻¹ Li−S pouch cell undergoes 20 cycles. This work provides an emerging electrolyte design for practical Li−S batteries.     

Multifunctional Metal Phosphides as Superior Host Materials for Advanced Lithium-Sulfur Batteries

For the past few years, a new generation of energy storage systems with large theoretical specific capacity has been urgently needed because of the rapid development of society. Lithium–sulfur (Li−S) batteries are regarded as one of the most promising candidates for novel battery systems, since their resurgence at the end of the 20th century Li−S batteries have attracted ever more attention, attributed to their notably high theoretical energy density of 2600 W h kg⁻¹, which is almost five times larger than that of commercial lithium-ion batteries (LIBs). One of the determining factors in Li−S batteries is how to design/prepare the sulfur cathode. For the sulfur host, the major technical challenge is avoiding the shuttling effect that is caused by soluble polysulfides during the reaction. In past decades, though the sulfur cathode has developed greatly, there are still some enormous challenges to be conquered, such as low utilization of S, rapid decay of capacity, and poor cycle life. This article spotlights the recent progress and foremost findings in improving the performance of Li−S batteries by employing multifunctional metal phosphides as host materials. The current state of development of the sulfur electrode of Li−S batteries is summarized by emphasizing the relationship between the essential properties of metal phosphide-based hybrid nanomaterials, the chemical reaction with lithium polysulfides and the latter′s influence on electrochemical performance. Finally, trends in the development and practical application of Li−S batteries are also pointed out.     

Chemistry-Performance Relationships of Polymer Gel-Electrolytes for Mg−S and Li−S Batteries: Influence of Network Cation Solvation Capacity on Polymer-Polysulfide Interactions

Metal-sulfur batteries are a promising next-generation energy storage technology, offering high theoretical energy densities with low cost and good sustainability. An active area of research is the development of electrolytes that address unwanted migration of sulfur and intermediate species known as polysulfides during operation of metal-sulfur batteries, a phenomenon that leads to low energy efficiency and short life-spans. A particular class of electrolytes, gel polymer electrolytes, are especially attractive for their ability to repel polysulfides on the basis of structure, electrostatics, and other polymer properties. Herein, within the context of magnesium- and lithium-sulfur batteries, we investigate the impact of gel polymer electrolyte cation solvation capacity, a property related to network dielectric constant and chemistry, on sulfur/polysulfide-polymer interactions, an understudied property-performance relationship. Polymers with lower cation solvation capacity are found to permanently absorb less polysulfide active material, which increases sulfur utilization for Li−S batteries and significantly increases charge efficiency and life-span for Li−S and Mg−S batteries.     

Utilizing the Alterable Solubility of Chitosan in Aqueous Solution to Synthesize Nanosized Sulfur for High Performance Li–S Batteries

We demonstrate the synthesis of cathode material with nanosized sulfur by a precipitation method making use of the alterable solubility of chitosan (CTS) in aqueous solution. Mesoporous Ketjen Black (KB) and carbon nanotube (CNT) are added as conductive agents to provide the three‐dimensional electric channels. This method can reduce the size of the sulfur particles, thus the nanosized sulfur obtained can fully contact with the conductive agent, which could increase the utilization of sulfur and improve the capacity of Li‐S batteries. Moreover, CTS with abundant hydroxyl and amine groups has strong interaction with polysulfides, which can improve the stability of Li‐S batteries. As a result, the obtained CTS/C‐S cathode containing 76 wt% sulfur delivers an impressively initial discharge specific capacity of 1141.6 mA·h·g^–1 at 0.5 C and maintains a capacity of 842.3 mA·h·g^–1 after 300 cycles. Our finding paves a way for the rational design of high‐performance sulfur cathodes for advanced Li‐S batteries.     

Bimetal-Organic Framework Nanoboxes Enable Accelerated Redox Kinetics and Polysulfide Trapping for Lithium-Sulfur Batteries

Lithium-sulfur (Li−S) batteries are considered as promising candidates for next-generation energy storage systems in view of the high theoretical energy density and low cost of sulfur resources. The suppression of polysulfide diffusion and promotion of redox kinetics are the main challenges for Li−S batteries. Herein, we design and prepare a novel type of ZnCo-based bimetallic metal–organic framework nanoboxes (ZnCo-MOF NBs) to serve as a functional sulfur host for Li−S batteries. The hollow architecture of ZnCo-MOF NBs can ensure fast charge transfer, improved sulfur utilization, and effective confinement of lithium polysulfides (LiPSs). The atomically dispersed Co−O₄ sites in ZnCo-MOF NBs can firmly capture LiPSs and electrocatalytically accelerate their conversion kinetics. Benefiting from the multiple structural advantages, the ZnCo-MOF/S cathode shows high reversible capacity, impressive rate capability, and prolonged cycling performance for 300 cycles.     

Large Scale Synthesis of Three-dimensional Hierarchical Porous Framework with High Conductivity and its Application in Lithium Sulfur Battery

Quick capacity loss due to the polysulfide shuttle effects and poor rate performance caused by low conductivity of sulfur have always been obstacles to the commercial application of lithium sulfur batteries. Herein, an in-situ doped hierarchical porous biochar materials with high electron-ion conductivity and adjustable three-dimensional (3D) macro-meso-micropore is prepared successfully. Due to its unique physical structure, the resulting material has a specific surface area of 2124.9 m² g⁻¹ and a cumulative pore volume of 1.19 cm³ g⁻¹. The presence of micropores can effectively physically adsorb polysulfides and mesopores ensure the accessibility of lithium ions and active sites and give the porous carbon material a high specific surface area. The large pores provide channels for the storage of electrolyte and the transmission of ions on the surface of the substrate. The combined effect of these three kinds of pores and the N doping formed in-situ can effectively promote the cycle and rate performance of the battery. Therefore, prepared cathode can still reach a reversible discharge capacity of 616 mAh g⁻¹ at a rate of 5 C. After 400 charge–discharge cycles at 1 C, the reversible capacity is maintained at 510.0 mAh g⁻¹. This new strategy has provided a new approach to the research and industrial-scale production of adjustable hierarchical porous biochar materials.     

Oxygen and nitrogen tailoring carbon fiber aerogel with platinum electrocatalysis interfaced lithium/sulfur (Li/S) batteries

Sluggish kinetics of lithium/sulfur (Li/S) conversion chemistry and the ion channels formation in the cathode is still a bottleneck for developing future Li/S batteries with high-rate, long-cycling and high-energy. Here, a rational cathode structure design of an oxygen (O) and nitrogen (N) tailoring carbon fiber aerogel (OCNF) as a host material integrated with platinum (Pt) electrocatalysis interface is employed to regulate Li/S conversion chemistry and ion channel. The Pt nanoparticles were uniformly sprayed onto the S surface to construct the electrocatalysis interface (Pt/S/OCNF) for generating ion channels to promote the effective penetration of electrolyte into the cathode. This Pt/S/OCNF gives the cathode a high sulfur utilization of 77.5%, an excellent rate capacity of 813.2 mAh/g (2 C), and an outstanding long-cycling performance with a capacitance retention of 82.6% and a decay of 0.086% per cycle after 200 cycles at 0.5 C. Density functional theory (DFT) calculations reveal that the Pt electrocatalysis interface makes the cathode a high density of state (DOS) at Fermi level to facilitate the electrical conductivity, charge transfer kinetics and electrocatalysis to accelerate the lithium polysulfides (LiPSs) electrochemical conversion. Furthermore, the unique chemisorption structure and adsorption ability of Li₂S_n (n = 1, 2, 4, 6, 8) and S₈ on OCNF are attributed to the bridging effects of interfacial Pt and the bonding of N-Li. The Pt electrocatalysis interface combined with the unique 3D hierarchical porous structure and abundant functional active sites at OCNF guarantee strong adsorption confinement, fast Li/S electrocatalytic conversion and unblocked ion channels for electrolyte permeation in cathode.     

Constructing Atomic Fe and N Co-doped Hollow Carbon Nanospheres with a Polymer Encapsulation Strategy for High-Performance Lithium-Sulfur Batteries with Accelerated Polysulfide Conversion

As competitive next-generation rechargeable batteries, lithium-sulfur batteries (LSBs) suffer from the shuttle effect and the sluggish kinetics of intermediate polysulfides during charge and discharge processes, adversely affecting their electrochemical performances and actual applications. Herein, we demonstrate a polymer encapsulation strategy to synthesize atomic Fe and N co-doped hollow carbon nanospheres (Fe−NHC) with Fe−N_x sites for modifying commercial PP separator of LSBs to suppress the shuttle effect and promote the kinetics of intermediate polysulfides. Benefiting from the excellent structural design, the doped-N with positive charges could effectively adsorb negatively charged soluble polysulfides, help attract the soluble polysulfides to the Fe atoms and boost the catalytic transformation of the soluble polysulfides. Additionally, such a thin carbon shell could provide a short mass diffusion pathway and hence promote the adsorption and the catalytic conversion. Therefore, the battery with the Fe−NHC/PP separator delivers outstanding cycling and rate performances. At the large current density of 1 C, the specific capacity is 1079 mA h g⁻¹ and maintains a low loss of 0.076 % per cycle within 500 cycles. Even at a harsh current density of 4 C, a high capacity of 824 mA h g⁻¹ is still achieved, indicating the advantage of the Fe−NHC/PP separator in LSBs.     

Engineering Functional Interface with Built-in Catalytic and Self-Oxidation Sites for Highly Stable Lithium–Sulfur Batteries

Lithium−sulfur (Li−S) batteries have attracted great attention due to their high theoretical energy density. The rapid redox conversion of lithium polysulfides (LiPS) is effective for solving the serious shuttle effect and improving the utilization of active materials. The functional design of the separator interface with fast charge transfer and active catalytic sites is desirable for accelerating the conversion of intermediates. Herein, a graphene-wrapped MnCO₃ nanowire (G@MC) was prepared and utilized to engineer the separator interface. G@MC with active Mn²⁺ sites can effectively anchor the LiPS by forming the Mn−S chemical bond according to our theoretical calculation results. In addition, the catalytic Mn²⁺ sites and conductive graphene layer of G@MC could accelerate the reversible conversion of LiPS via the spontaneous “self-redox” reaction and the rapid electron transfer in electrochemical process. As a result, the G@MC-based battery exhibits only 0.038 % capacity decay (per cycle) after 1000 cycles at 2.0 C. This work affords new insights for designing the integrated functional interface for stable Li−S batteries.     

Coaxial Carbon/MnO2 Hollow Nanofibers as Sulfur Hosts for High‐Performance Lithium‐Sulfur Batteries

Lithium‐sulfur (Li‐S) batteries have recently attracted a large amount of attention as promising candidates for next‐generation high‐power energy storage devices because of their high theoretical capacity and energy density. However, the shuttle effect of polysulfides and poor conductivity of sulfur are still vital issues that constrain their specific capacity and cyclic stability. Here, we design coaxial MnO₂‐graphitic carbon hollow nanofibers as sulfur hosts for high‐performance lithium‐sulfur batteries. The hollow C/MnO₂ coaxial nanofibers are synthesized via electrospinning and carbonization of the carbon nanofibers (CNFs), followed by an in situ redox reaction to grow MnO₂ nanosheets on the surface of CNFs. The inner graphitic carbon layer not only maintains intimate contact with sulfur and outer MnO₂ shell to significantly increase the overall electrical conductivity but also acts as a protective layer to prevent dissolution of polysulfides. The outer MnO₂ nanosheets restrain the shuttle effect greatly through chemisorption and redox reaction. Therefore, the robust S@C/MnO₂ nanofiber cathode delivers an extraordinary rate capability and excellent cycling stability with a capacity decay rate of 0.044 and 0.051 % per cycle after 1000 cycles at 1.0 C and 2.0 C, respectively. Our present work brings forward a new facile and efficient strategy for the functionalization of inorganic metal oxide on graphitic carbons as sulfur hosts for high performance Li‐S batteries.     

氮硫共掺杂多孔碳材料的制备及其在锂硫电池中的应用

锂硫电池因其较高的理论容量和对环境友好等优势被视为极具发展潜力的储能装置,但是多硫化物的穿梭效应极大地限制了锂硫电池的实际应用。本文以葡萄糖为碳源,离子液体为氮源和硫源,KCl和ZnCl₂为模板剂,KOH为活化剂,通过热解工艺合成了氮硫共掺杂多孔碳（NSPC）。XPS和极性吸附实验表明N、S杂原子成功引入并且提高了碳材料对多硫化物的吸附能力,有效缓解多硫化物的穿梭效应,而较高的比表面积（1290.67 m²·g^-1）有助于提高硫负载量。负载70.1wt.%的硫后（S@NSPC）作为锂硫电池的正极材料表现出了良好的电化学性能。在167.5 mA·g^-1的电流密度下S@NSPC的首次放电容量为1229.2 mAh·g^-1,远高于S@PC的861.6 mAh·g^-1,且S@NSPC循环500圈后容量为328.1 mAh·g^-1。当电流密度从3350 mA·g^-1恢复至167.5 mA·g^-1时,可逆容量达到首圈放电比容量的80%,几乎恢复至其初始值。     

A Supramolecular Capsule for Reversible Polysulfide Storage/Delivery in Lithium‐Sulfur Batteries

Supramolecular materials, in which small organic molecules are assembled into regular structures by non‐covalent interactions, attract tremendous interests because of their highly tunable functional groups and porous structure. Supramolecular adsorbents are expected to fully expose their abundant adsorptive sites in a dynamic framework. In this contribution, we introduced cucurbit[6]uril as a supramolecular capsule for reversible storage/delivery of mobile polysulfides in lithium‐sulfur (Li‐S) batteries to control undesirable polysulfide shuttle. The Li‐S battery equipped with the supramolecular capsules retains a high Coulombic efficiency and shows a large increase in capacity from 300 to 900 mAh g⁻¹ at a sulfur loading of 4.2 mg cm⁻². The implementation of supramolecular capsules offers insights into intricate multi‐electron‐conversion reactions and manifests as an effective and efficient strategy to enhance Li‐S batteries and analogous applications that involve complex transport phenomena and intermediate manipulation.     

Three‐Dimensional Hierarchical Constructs of MOF‐on‐Reduced Graphene Oxide for Lithium–Sulfur Batteries

A three‐dimensional (3D) hierarchical MOF‐on‐reduced graphene oxide (MOF‐on‐rGO) compartment was successfully synthesized through an in situ reduced and combined process. The unique properties of the MOF‐on‐rGO compartment combining the polarity and porous features of MOFs with the high conductivity of rGO make it an ideal candidate as a sulfur host in lithium–sulfur (Li‐S) batteries. A high initial discharge capacity of 1250 mAh g^?1 at a current density of 0.1 C (1.0 C=1675 mAh g^?1) was reached using the MOF‐on‐rGO based electrode. At the rate of 1.0 C, a high specific capacity of 601 mAh g^?1 was still maintained after 400 discharge–charge cycles, which could be ascribed to the synergistic effect between MOFs and rGO. Both the hierarchical structures of rGO and the polar pore environment of MOF retard the diffusion and migration of soluble polysulfide, contributing to a stable cycling performance. Moreover, the spongy‐layered rGO can buffer the volume expansion and contraction changes, thus supplying stable structures for Li‐S batteries.     

Low-cost,porous carbon current collector with high sulfur loading for lithium–sulfur batteries

Li–S batteries with a porous carbon current collector (PCCC), high sulfur loading (2.3 mg cm^− 2, equal to 80 wt.% sulfur content), high capacity, and long cycle life have been fabricated with a simple one-step paste absorption method. The intimate contact between the insulating sulfur and the embedded conductive matrix allows high active material loading. The high absorptivity of electrolyte by the PCCC facilitates efficient retention of soluble polysulfides within the PCCC, so the 3D cathode architecture stabilizes the electrochemical reaction within the porous space.     

Porous carbon framework nested nickel foam as freestanding host for high energy lithium sulfur batteries

Constructing 3 D multifunctional conductive framework as stable sulfur cathode contributes to develop advanced lithium-sulfur(Li-S) batteries.Herein,a freestanding electrode with nickel foam framework and nitrogen doped porous carbon(PC) network is presented to encapsulate active sulfur for Li-S batteries.In such a mutually embedded architecture with high stability,the interconnected carbon network and nickel foam matrix can expedite ionic/electro nic tra nsport and sustain volume variations of sulfur.Furthermore,rationally designed porous structures provide sufficient internal space and large surface area for high active sulfur loading and polar polysulfides anchoring.Benefiting from the synergistic superiority,the Ni/PC-S cathode exhibits a high initial capacity of around 1200 mAh/g at 0.2 C,excelle nt rate perfo rmance,and high cycling stability with a low decay rate of 0.059% per cycle after 500 cycles.This work provides a useful strategy to exploit freestanding porous framework for diverse applications.