A highly efficient double-hierarchical sulfur host for advanced lithium-sulfur batteries

Exquisitely constructing hierarchical carbon nanoarchitectures decorated with sulfides for high-performance Li-S batteries

The sluggish reaction kinetics and notorious shuttle effect of polysulfides significantly hinder the practical application of lithium-sulfur batteries (LSBs). Therefore, polysulfides are anchored and their conversion reactions are catalyzed to enhance the performance of LSBs. Herein, an exquisite hierarchical carbon nanoarchitecture decorated with sulfides is designed and introduced into LSBs. Systematic experiments show that the nanoarchitecture not only enables rapid electron/ion migration but also functions as an active catalyst to increase polysulfide conversion, thus effectively reducing the shuttle effect. As a result, LSBs with the nanoarchitecture modified separator exhibited outstanding rate capacity (724.9 mA h g-1 at 5C), low self-discharge capacity loss (4.1% capacity loss after 72 h), and exceptional reversible capacity (1518.3 mA h g-1 at 0.1C and 25.6% capacity loss after 100 cycles). Through the design of a multifunctional separator, this study offers an effective way to minimize the shuttle effect and speed up redox conversion. The strategy of constructing nanoarchitectures provides an innovative route for hierarchical heterocatalyst design for LSBs.

DFT Simulation-Based Design of 1T-MoS2 Cathode Hosts for Li-S Batteries and Experimental Evaluation

The main challenge in lithium sulphur (Li-S) batteries is the shuttling of lithium polysulphides (LiPSs) caused by the rapid LiPSs migration to the anode and the slow reaction kinetics in the chain of LiPSs conversion. In this study, we explore 1T-MoS₂ as a cathode host for Li-S batteries by examining the affinity of 1T-MoS₂ substrates (pristine 1T-MoS₂, defected 1T-MoS₂ with one and two S vacancies) toward LiPSs and their electrocatalytic effects. Density functional theory (DFT) simulations are used to determine the adsorption energy of LiPSs to these substrates, the Gibbs free energy profiles for the reaction chain, and the preferred pathways and activation energies for the slow reaction stage from Li₂S₄ to Li₂S. The obtained information highlights the potential benefit of a combination of 1T-MoS₂ regions, without or with one and two sulphur vacancies, for an improved Li-S battery performance. The recommendation is implemented in a Li-S battery with areas of pristine 1T-MoS₂ and some proportion of one and two S vacancies, exhibiting a capacity of 1190 mAh/g at 0.1C, with 97% capacity retention after 60 cycles in a schedule of different C-rates from 0.1C to 2C and back to 0.1C.

Understanding the interactions between lithium polysulfides and anchoring materials in advanced lithium-sulfur batteries using density functional theory

Lithium-sulfur batteries (LSBs) are promising energy storage devices because of their high theoretical capacity and energy density. However, the "shuttle" effect in lithium polysulfides (LiPSs) is an unresolved issue that can hinder their practical commercial application. Research on LSBs has focused on finding appropriate materials that suppress this effect by efficiently anchoring the LiPSs intermediates. Quantum chemical computations are a useful tool for understanding the mechanistic details of chemical interaction involving LiPSs, and they can also offer strategies for the rational design of LiPSs anchoring materials. In this perspective, we highlight computational and theoretical work performed on this topic. This includes elucidating and characterizing the adsorption mechanisms, and the dominant types of interactions, and summarizing the binding energies of LiPSs on anchoring materials. We also give examples and discuss the potential of descriptors and machine learning approaches to predict the adsorption strength and reactivity of materials. We believe that both approaches will become indispensable in modelling future LSBs.

Ternary Transition Metal Sulfide as High Real Energy Cathode for Lithium-Sulfur Pouch Cell Under Lean Electrolyte Conditions

Fabrication of a highly porous sulfur host and using excess electrolyte is a common strategy to enhance sulfur utilization. However, flooded electrolyte limits the practical energy density of Li-S pouch cells. In this study, a novel Fe_0.34 Co_0.33 Ni_0.33 S₂ (FCN) is proposed as host for sulfur to realize Ah-level Li-S full cells demonstrating excellent electrochemical performances under 2 µL mg^-1 lean electrolyte conditions. Moreover, Kelvin probe force microscopy shows that the FCN surface contains positive charge with a potential of ≈70 mV, improving the binding of polysulfides through Lewis acid base interaction. In particular, the FCN@S possesses inherent electrochemical activity of simultaneous anionic and cationic redox for lithium storage in the voltage window of 1.8-2.1 V, which additionally contributes to the specific capacity. Due to the low carbon content (≈10 wt%), the sulfur loading is as high as ≈6 mg cm^-2 , approaching an outstanding energy density of 394.9 and 267.2 Wh kg^-1 at the current density of 1.5 and 4 mA cm^-2 , respectively. Moreover, after 60 cycles at 1.5 mA cm^-2 , the pouch cell still retains an energy of 300.2 Wh kg^-1 . This study represents a milestone in the practical applications of high-energy Li-S batteries.

Ion-Selective Covalent Organic Framework Membranes as a Catalytic Polysulfide Trap to Arrest the Redox Shuttle Effect in Lithium-Sulfur Batteries

In the wake of shaping the energy future through materials innovation, lithium-sulfur batteries (LSBs) are top-of-the-line energy storage system attributed to their high theoretical energy density and specific capacity inclusive of low material costs. Despite their strengths, LSBs suffer from the cross-over of soluble polysulfide redox species to the anode, entailing fast capacity fading and inferior cycling stability. Adding to the concern, the insulating character of polysulfides lends to sluggish reaction kinetics. To address these challenges, we construct optimized polysulfide blockers-cum-conversion catalysts by accommodating the battery separator with covalent organic framework@Graphene (COF@G) composites. We settle on a crystalline TAPP-ETTB COF in the interest of its nitrogen-enriched scaffold with a regular pore geometry, providing ample lithiophilic sites for strong chemisorption and catalytic effect to polysulfides. On another front, graphene enables high electron mobility, boosting the sulfur redox kinetics. Consequently, a lithium-sulfur battery with a TAPP-ETTB COF@G-based separator demonstrates a high reversible capacity of 1489.8 mA h g^-1 at 0.2 A g^-1 after the first cycle and good cyclic performance (920 mA h g^-1 after 400 cycles) together with excellent rate performance (827.7 mA h g^-1 at 2 A g^-1). The scope and opportunities to harness the designability and synthetic structural control in crystalline organic materials is a promising domain at the interface of sustainable materials, energy storage, and Li-S chemistry.

Polysulfide Catalytic Materials for Fast-Kinetic Metal-Sulfur Batteries: Principles and Active Centers

Benefiting from the merits of low cost, ultrahigh-energy densities, and environmentally friendliness, metal-sulfur batteries (M-S batteries) have drawn massive attention recently. However, their practical utilization is impeded by the shuttle effect and slow redox process of polysulfide. To solve these problems, enormous creative approaches have been employed to engineer new electrocatalytic materials to relieve the shuttle effect and promote the catalytic kinetics of polysulfides. In this review, recent advances on designing principles and active centers for polysulfide catalytic materials are systematically summarized. At first, the currently reported chemistries and mechanisms for the catalytic conversion of polysulfides are presented in detail. Subsequently, the rational design of polysulfide catalytic materials from catalytic polymers and frameworks to active sites loaded carbons for polysulfide catalysis to accelerate the reaction kinetics is comprehensively discussed. Current breakthroughs are highlighted and directions to guide future primary challenges, perspectives, and innovations are identified. Computational methods serve an ever-increasing part in pushing forward the active center design. In summary, a cutting-edge understanding to engineer different polysulfide catalysts is provided, and both experimental and theoretical guidance for optimizing future M-S batteries and many related battery systems are offered.

Basal-Plane-Activated Molybdenum Sulfide Nanosheets with Suitable Orbital Orientation as Efficient Electrocatalysts for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are one of the most promising candidates for next-generation energy storage systems because of their high theoretical energy density. However, the shuttling behavior and sluggish conversion kinetics of lithium polysulfides (LiPSs) limit their practical application. Herein, B-doped MoS₂ nanosheets are synthesized on carbon nanotubes (denoted as CNT@MoS₂-B) to function as catalysts to boost the performance of Li-S batteries. The poor catalytic performance of the pristine MoS₂ is revealed to be the result of unsuitable orbital orientation of the basal plane, which hinders the orbital overlap with sulfur species. B in CNT@MoS₂-B is sp³ hybridized, and it has a vacant σ orbital perpendicular to the basal plane, which can maximize the head-on orbital overlap with S. The incorporation of B significantly increases the reactivity of MoS₂ basal plane, which can facilitate the kinetics of Li₂S formation and dissolution. With these merits, the S/CNT@MoS₂-B cathodes deliver high rate capability and outstanding cycling stability, holding great promise for both scientific research and practical application. This work affords fresh insights for developing effective catalysts to accelerate LiPS conversion.

Metal-Organic-Framework-Derived Nanostructures as Multifaceted Electrodes in Metal-Sulfur Batteries

Metal-sulfur batteries (MSBs) are considered up-and-coming future-generation energy storage systems because of their prominent theoretical energy density. However, the practical applications of MSBs are still hampered by several critical challenges, i.e., the shuttle effects, sluggish redox kinetics, and low conductivity of sulfur species. Recently, benefiting from the high surface area, regulated networks, molecular/atomic-level reactive sites, the metal-organic frameworks (MOFs)-derived nanostructures have emerged as efficient and durable multifaceted electrodes in MSBs. Herein, a timely review is presented on recent advancements in designing MOF-derived electrodes, including fabricating strategies, composition management, topography control, and electrochemical performance assessment. Particularly, the inherent charge transfer, intrinsic polysulfide immobilization, and catalytic conversion on designing and engineering of MOF nanostructures for efficient MSBs are systematically discussed. In the end, the essence of how MOFs' nanostructures influence their electrochemical properties in MSBs and conclude the future tendencies regarding the construction of MOF-derived electrodes in MSBs is exposed. It is believed that this progress review will provide significant experimental/theoretical guidance in designing and understanding the MOF-derived nanostructures as multifaceted electrodes, thus offering promising orientations for the future development of fast-kinetic and robust MSBs in broad energy fields.

An Emerging Energy Storage System: Advanced Na-Se Batteries

Sodium-selenium (Na-Se) batteries have aroused enormous attention due to the large abundance of the element sodium as well as the high electronic conductivity and volumetric capacity of selenium. In this battery system, some primary advances in electrode materials have been achieved, mainly involving the design of Se-based cathode materials. In this Review, the electrochemical mechanism is discussed, thus revealing the main challenges in Na-Se batteries. Then, the advances in the design of Se-based cathode materials for Na-ion storage are systemically summarized, classified, and discussed, including Se/carbon composite, Se/polar material/carbon composites, and hybrid Se_xS_y alloys. Some potential strategies enabling the improvement of crucial challenges and enhancement of electrochemical performance are also proposed to provide guidelines for the enhancements of Na-ion storage. An outlook for future valuable research directions is proposed to understand more deeply the electrochemical mechanism of Na-Se batteries and promote their further developments in full cell performance and commercialization.

Advanced High-Performance Potassium-Chalcogen (S, Se, Te) Batteries

Current great progress on potassium-chalcogen (S, Se, Te) batteries within much potential to become promising energy storage systems opens a new avenue for the rapid development of potassium batteries as a complementary option to lithium ion batteries. The discussion mainly concentrates on recent research advances of potassium-chalcogen (S, Se, Te) batteries and their corresponding cathode materials in this review. Initially, the development of cathode materials for four types of batteries is introduced, including: potassium-sulfur (K-S), potassium-selenium (K-Se), potassium-selenium sulfide (K-Se_x S_y ), and potassium-tellurium (K-Te) batteries. Next, critical challenges for chalcogen-based electrodes in devices operation are summarized. In addition, some pragmatic strategies are proposed as well to relieve the low electronic conductivity, large volumetric expansion, shuttle effect, and potassium dendrite growth. At last, the perspectives on designing advanced cathode materials for potassium-chalcogen batteries are provided with the goal of developing high-performance potassium storage devices.

Metal-Based Electrocatalysts for High-Performance Lithium-Sulfur Batteries: A Review

The lithium-sulfur (Li-S) redox battery system is considered to be the most promising next-generation energy storage technology due to its high theoretical specific capacity (1673 mAh g−1), high energy density (2600 Wh kg−1), low cost, and the environmentally friendly nature of sulfur. Though this system is deemed to be the next-generation energy storage device for portable electronics and electric vehicles, its poor cycle life, low coulombic efficiency and low rate capability limit it from practical applications. These performance barriers were linked to several issues like polysulfide (LiPS) shuttle, inherent low conductivity of charge/discharge end products, and poor redox kinetics. Here, we review the recent developments made to alleviate these problems through an electrocatalysis approach, which is considered to be an effective strategy not only to trap the LiPS but also to accelerate their conversion reactions kinetics. Herein, the influence of different chemical interactions between the LiPS and the catalyst surfaces and their effect on the conversion of liquid LiPS to solid end products are reviewed. Finally, we also discussed the challenges and perspectives for designing cathode architectures to enable high sulfur loading along with the capability to rapidly convert the LiPS.

Atomically Engineered Transition Metal Dichalcogenides for Liquid Polysulfide Adsorption and Their Effective Conversion in Li-S Batteries

Curtailing the polysulfide shuttle by anchoring the intermediate lithium polysulfides (LiPS) within the electrode structure is essential to impede the rapid capacity fade in lithium-sulfur (Li-S) batteries. While most of the contemporary Li-S cathode surfaces are capable of entrapping certain LiPS, developing a unique electrode material that can adsorb all the intermediates of sulfur redox is imperative. Herein, we report doping of the MoS₂ atomic structure with nickel (Ni@1TMoS₂) to modulate its absorption capability toward all LiPS and function as an electrocatalyst for Li-S redox. Detailed in situ and ex situ spectroscopic analysis revealed that both Ni and Mo sites chemically anchor all the intermediate of LiPS. Electrochemical studies and detailed kinetics analysis suggested that the conversion of liquid LiPS to solid end products are facilitated on the Ni@1TMoS₂ electrocatalytic surface. Further, the employment of the Ni@1TMoS₂ electrocatalyst enhances the Li⁺ diffusion coefficient, thus contributing to the realization of a high capacity of 1107 mA h g^-1 at 0.2C with a very limited capacity fade of 0.19% per cycle for over 100 cycles. In addition, this cathode demonstrated an excellent high rate and long cycling performance for over 300 cycles at a 1C rate.

Built-In Catalysis in Confined Nanoreactors for High-Loading Li-S Batteries

A cathode host with strong sulfur/polysulfide confinement and fast redox kinetics is a challenging demand for high-loading lithium-sulfur batteries. Recently, porous carbon hosts derived from metal-organic frameworks (MOFs) have attracted wide attention due to their unique spatial structure and customizable reaction sites. However, the loading and rate performance of Li-S cells are still restricted by the disordered pore distribution and surface catalysis in these hosts. Here, we propose a concept of built-in catalysis to accelerate lithium polysulfide (LiPSs) conversion in confined nanoreactors, i.e., laterally stacked ordered crevice pores encompassed by MoS₂-decorated carbon thin layers. The functions of S-fixability and LiPS catalysis in these mesoporous cavity reactors benefit from the 2D interface contact between ultrathin catalytic MoS₂ and conductive C pyrolyzed from Al-MOF. The integrated function of adsorption-catalysis-conversion endows the sulfur-infused C@MoS₂ electrode with a high initial capacity of 1240 mAh g^-1 at 0.2 C, long life cycle stability of at least 1000 cycles at 2 C, and high rate endurance up to 20 C. This electrode also exhibits commercial potential in view of considerable capacity release and reversibility under high sulfur loading (6 mg cm^-2 and ∼80 wt %) and lean electrolyte (E/S ratio of 5 μL mg^-1). This study provides a promising design solution of a catalysis-conduction 2D interface in a 3D skeleton for high-loading Li-S batteries.

Nickel Hollow Spheres Concatenated by Nitrogen-Doped Carbon Fibers for Enhancing Electrochemical Kinetics of Sodium-Sulfur Batteries

The high energy density of room temperature (RT) sodium-sulfur batteries (Na-S) usually rely on the efficient conversion of polysulfide to sodium sulfide during discharging and sulfur recovery during charging, which is the rate-determining step in the electrochemical reaction process of Na-S batteries. In this work, a 3D network (Ni-NCFs) host composed by nitrogen-doped carbon fibers (NCFs) and Ni hollow spheres is synthesized by electrospinning. In this novel design, each Ni hollow unit not only can buffer the volume fluctuation of S during cycling, but also can improve the conductivity of the cathode along the carbon fibers. Meanwhile, the result reveals that a small amount of Ni is polarized during the sulfur-loading process forming a polar Ni-S bond. Furthermore, combining with the nitrogen-doped carbon fibers, the Ni-NCFs composite can effectively adsorb soluble polysulfide intermediate, which further facilitates the catalysis of the Ni unit for the redox of sodium polysulfide. In addition, the in situ Raman is employed to supervise the variation of polysulfide during the charging and discharging process. As expected, the freestanding S@Ni-NCFs cathode exhibits outstanding rate capability and excellent cycle performance.

A one-pot synthesis of hetero-Co9S8–NiS sheets on graphene to boost lithium–sulfur battery performance

Graphene decorated with hetero-Co₉S₈–NiS sheets have abundant active sites, which can efficiently catalyze the electrochemical conversion of lithium polysulfides in Li–S battery.

Design and Construction of Sodium Polysulfides Defense System for Room-Temperature Na-S Battery

Room-temperature Na-S batteries are facing one of the most serious challenges of charge/discharge with long cycling stability due to the severe shuttle effect and volume expansion. Herein, a sodium polysulfides defense system is presented by designing and constructing the cathode-separator double barriers. In this strategy, the hollow carbon spheres are decorated with MoS2 (HCS/MoS2) as the S carrier (S@HCS/MoS2). Meanwhile, the HCS/MoS2 composite is uniformly coated on the surface of the glass fiber as the separator. During the discharge process, the MoS2 can adsorb soluble polysulfides (NaPSs) intermediates and the hollow carbon spheres can improve the conductivity of S as well as act as the reservoir for electrolyte and NaPSs, inhibiting them from entering the anode to make Na deteriorate. As a result, the cathode-separator group applied to room-temperature Na-S battery can enable a capacity of ≈1309 mAh g-1 at 0.1 C and long cycling life up to 1000 cycles at 1 C. This study provides a novel and effective way to develop durable room-temperature Na-S batteries.

Rational Construction of Fe2N@C Yolk-Shell Nanoboxes as Multifunctional Hosts for Ultralong Lithium-Sulfur Batteries

Rationally constructing inexpensive sulfur hosts that have high electronic conductivity, large void space for sulfur, strong chemisorption, and rapid redox kinetics to polysulfides is critically important for their practical use in lithium-sulfur (Li-S) batteries. Herein, we have designed a multifunctional sulfur host based on yolk-shelled Fe₂N@C nanoboxes (Fe₂N@C NBs) through a strategy of etching combined with nitridation for high-rate and ultralong Li-S batteries. The highly conductive carbon shell physically confines the active material and provides efficient pathways for fast electron/ion transport. Meanwhile, the polar Fe₂N core provides strong chemical bonding and effective catalytic activity for polysulfides, which is proved by density functional theory calculations and electrochemical analysis techniques. Benefiting from these merits, the S/Fe₂N@C NBs electrode with a high sulfur content manifests a high specific capacity, superior rate capability, and long-term cycling stability. Specifically, even after 600 cycles at 1 C, a capacity of 881 mAh g^-1 with an average fading rate of only 0.036% can be retained, which is among the best cycling performances reported. The strategy in this study provides an approach to the design and construction of yolk-shelled iron-based compounds@carbon nanoarchitectures as inexpensive and efficient sulfur hosts for realizing practically usable Li-S batteries.

Highly Puffed Co9S8/Carbon Nanofibers: A Functionalized S Carrier for Superior Li-S Batteries

Li-S batteries have triggered global research interest because of their higher theoretical energy density and lower cost than popularized Li-ion cells. However, they still do not have practical implementations because of issues induced by intermediate polysulfide dissolution. To better confine both S and polysulfides in cathode regions and prolong the cyclic lifespan, we purposely design the unique highly puffed Co₉S₈/carbon nanofibers (Co₉S₈@CNFs) as efficient S carriers. Such fibrous products made of interconnected hollow/porous Co₉S₈/C nanopolyhedra can provide ample places to load the large amount of S, convenient pathways for both Li⁺ and electrons transfer, and extra reversible capacity contribution. Particularly, each individual Co₉S₈ subunit is physically robust, metallic, and polarized, synergistically enabling the spatial confinement and chemical bonding to restrict S volume expansions and anchor the soluble polysulfides during cycling. The as-built highly puffed S⊆Co₉S₈@CNFs cathodes can exhibit a large specific capacity of ∼1080 mA h g^-1, admirable cyclic stability/lifespan (capacity loss rate: ∼0.03% per cycle), and excellent rate capabilities. Our work may hold a great potential in rational design of superior cathodes for applicable Li-S cell systems.

Metal-Organic Frameworks/Conducting Polymer Hydrogel Integrated Three-Dimensional Free-Standing Monoliths as Ultrahigh Loading Li-S Battery Electrodes

The lithium-sulfur (Li-S) system is a promising material for the next-generation of high energy density batteries with application extending from electrical vehicles to portable devices and aeronautics. Despite progress, the energy density of current Li-S technologies is still below that of conventional intercalation-type cathode materials due to limited stability and utilization efficiency at high sulfur loading. Here, we present a conducting polymer hydrogel integrated highly performing free-standing three-dimensional (3D) monolithic electrode architecture for Li-S batteries with superior electrochemical stability and energy density. The electrode layout consists of a highly conductive three-dimensional network of N,P codoped carbon with well-dispersed metal-organic framework nanodomains of ZIF-67 and HKUST-1. The hierarchical monolithic 3D carbon networks provide an excellent environment for charge and electrolyte transport as well as mechanical and chemical stability. The electrically integrated MOF nanodomains significantly enhance the sulfur loading and retention capabilities by inhibiting the release of lithium polysulfide specificities as well as improving the charge transfer efficiency at the electrolyte interface. Our optimal 3D carbon-HKUST-1 electrode architecture achieves a very high areal capacity of >16 mAh cm^-2 and volumetric capacity (C_V) of 1230.8 mAh cm^-3 with capacity retention of 82% at 0.2C for over 300 cycles, providing an attractive candidate material for future high-energy density Li-S batteries.

Lithiated Defect Sites in Zr Metal-Organic Framework for Enhanced Sulfur Utilization in Li-S Batteries

Lithium sulfur (Li-S) battery technology is one of the most promising candidates for next-generation energy storage devices; however, it is still hindered by limited capacity yield and poor long-term stability. The complexity of these devices has hindered efforts to study electrochemical determinants of battery performance, impeding advancement of the field. Due to the ease of functionalization, metal-organic frameworks (MOFs) are unique platforms to explore such reactions, where integration of defects into the crystalline structure provides a convenient method for introducing synthetic handles. In Zr-based MOFs such as UiO-66, the engineered defect sites contain acidic protons that can be replaced with lithium ions, transforming defected MOFs into a range of materials with tunable lithium content. Our results demonstrate the capability of this facile lithiation procedure to create novel cathode additives and evaluate their influence on Li-S battery performance. By improving ionic conductivity and dispersion of sulfur species, lithiated MOFs enhance both sulfur utilization and capacity retention at a variety of cycling rates compared to the as-synthesized MOFs. Our general synthetic strategy has the potential to be applied to technologies beyond MOFs, including polymeric and inorganic materials. Ultimately, we illustrate that defected MOFs can be used to systematically control lithiation, currently unprecedented in conventional inorganic materials, and provide a window to examine heterogeneous reactions relevant to energy conversion and storage.

An N-doped porous carbon/MXene composite as a sulfur host for lithium–sulfur batteries

The sulfur content of the composite can reach 80%, and the composite has multiple adsorption for polysulfides.

A Flexible All-in-One Lithium-Sulfur Battery

The recent boom in flexible and wearable electronic devices has increased the demand for flexible energy storage devices. The flexible lithium-sulfur (Li-S) battery is considered to be a promising candidate due to its high energy density and low cost. Herein, a flexible Li-S battery was fabricated based on an all-in-one integrated configuration, where a multiwalled carbon nanotubes/sulfur (MWCNTs/S) cathode, MWCNTs/manganese dioxide (MnO₂) interlayer, polypropylene (PP) separator, and Li anode were integrated together by combining blade coating with vacuum evaporation methods. Each component of the all-in-one structure can be seamlessly connected with the neighboring layers. Such an optimal interfacial connection can effectively enhance electron- and/or load-transfer capacity by avoiding the relative displacement or detachment between two neighboring components at bending strain. Therefore, the flexible all-in-one Li-S batteries display fast electrochemical kinetics and have stable electrochemical performance under different bending states.

Self-Supported FeCo2S4 Nanotube Arrays as Binder-Free Cathodes for Lithium-Sulfur Batteries

Inhibiting the shuttle effect, buffering the volume expansion, and improving the utilization of sulfur have been the three strategic points for developing a high-performance lithium-sulfur (Li-S) battery. Driven by this background, a flexible sulfur host material composed of FeCo₂S₄ nanotube arrays grown on the surface of carbon cloth is designed for a binder-free cathode of the Li-S battery through two-step hydrothermal method. Among the rest, the interconnected carbon fiber skeleton of the composite electrode ensures the basic electrical conductivity, whereas the FeCo₂S₄ nanotube arrays not only boost the electron and electrolyte transfer but also inhibit the dissolution of polysulfides because of their strong chemical adsorption. Meanwhile, the hollow structures of these arrays can provide a large inner space to accommodate the volume expansion of sulfur. More significantly, the developed composite electrode also reveals a catalytic action for accelerating the reaction kinetic of the Li-S battery. As a result, the FeCo₂S₄/CC@S electrode delivers a high discharge capacity of 1384 mA h g^-1 at the current density of 0.1 C and simultaneously exhibits a stable Coulombic efficiency of about 98%.

A high performance lithium-ion-sulfur battery with a free-standing carbon matrix supported Li-rich alloy anode

A high-performance lithium-ion–sulfur battery has been built by using a carbon supported Li-rich alloy anode and sulfurized polyacrylonitrile (S@pPAN) cathode.

Although the lithium–sulfur battery exhibits high capacity and energy density, the cycling performance is severely retarded by dendrite formation and side-reactions of the lithium metal anode and the shuttle effect of polysulfides. Therefore, exploring lithium rich-alloy (or compound) anodes and suppressing the shuttling of polysulfides have become practical technical challenges for the commercialization of lithium–sulfur batteries. Here, a lithium ion sulfur full battery system combining a lithium-rich Li–Si alloy anode and sulfurized polyacrylonitrile (S@pPAN) cathode has been proposed. The free-standing CNF matrix supported Li–Si alloy anode is prepared by a simple and effective method, which is practical for scale-up production. The obtained Li–Si alloy anode demonstrates high cycling stability without dendrite growth, while the use of the S@pPAN cathode avoids the shuttle effect in carbonate electrolytes. The constructed Li–Si/S@pPAN battery could be cycled more than 1000 times at 1C and 3000 times at 3C, with a capacity fading rate of 0.01% and 0.03% per cycle. The exceptional performance should originate from the stable integrated anode structure and the excellent compatibility of the S@pPAN cathode and Li–Si alloy anode with carbonate electrolytes.

A Conductive Ni2 P Nanoporous Composite with a 3D Structure Derived from a Metal-Organic Framework for Lithium-Sulfur Batteries

Sulfur cathodes have attracted significant attention as next-generation electrode material candidates due to their considerable theoretical energy density. The main challenge in developing long-life Li-S batteries is to simultaneously suppress the shuttle effect and high areal mass loading of sulfur required for practical applications. To solve this problem, we have designed a novel nickel phosphide nanoporous composite derived from metal-organic frameworks (MOFs) as sulfur host materials. Homogeneous distribution of Ni₂ P nanoparticles significantly avoids soluble polysulfides migrating out of the framework through strong chemical interactions, and the conductive 3D skeleton offers an accelerating electron transport. As a result, S@Ni₂ P/NC has exhibited an enhanced performance of 1357 mAh g^-1 initially at 0.2 C (1 C=1675 mA g^-1 ) and remaining at 946 mAh g^-1 after 300 cycles. Even at an areal mass loading of sulfur as high as 4.6 mg cm^-2 , the electrode still showed an excellent specific capacity of 918 mAh g^-1 .

Vanadium Dioxide-Graphene Composite with Ultrafast Anchoring Behavior of Polysulfides for Lithium-Sulfur Batteries

The lithium-sulfur (Li-S) battery has been deemed as one of the most promising energy-storage systems owing to its high energy density, low cost, and environmental benignancy. However, the capacity decay and kinetic sluggishness stemming from polysulfide shuttle effects have by far posed a great challenge to practical performance. We herein demonstrate the employment of low-cost, wet-chemistry-derived VO₂ nanobelts as the effective host additives for the graphene-based sulfur cathode. The VO₂ nanobelts displayed an ultrafast anchoring behavior of polysulfides, managing to completely decolor the polysulfide solution in 50 s. Such a fast and strong anchoring ability of VO₂ was further investigated and verified by experimental and theoretical investigations. Benefitting from the synergistic effect exerted by VO₂ in terms of chemical confinement and catalytic conversion of polysulfides, the Li-S batteries incorporating VO₂ and graphene manifested excellent cycling and rate performances. Notably, the batteries delivered an initial discharge capacity of 1405 mAh g^-1 when cycling at 0.2 C, showed an advanced rate performance of ∼830 mAh g^-1 at 2 C, and maintained a stable cycling performance at high current densities of 1, 2, and 5 C over 200 cycles, paving a practical route toward cost-effective and environmentally benign cathode design for high-energy Li-S batteries.

Thermal Instability Induced Oriented 2D Pores for Enhanced Sodium Storage

Hierarchical porous structures are highly desired for various applications. However, it is still challenging to obtain such materials with tunable architectures. Here, this paper reports hierarchical nanomaterials with oriented 2D pores by taking advantages of thermally instable bonds in vanadium-based metal-organic frameworks (MOFs). High-temperature calcination of these MOFs accompanied by the loss of coordinated water molecules and other components enables the formation of orderly slit-like 2D pores in vanadium oxide/porous carbon nanorods (VO_x /PCs). This unique combination leads to an increase of the reactive surface area. In addition, optimized VO_x /PCs demonstrate high-rate capability and ultralong cycling life for sodium storage. The assembled full cells also show high capacity and cycling stability. This report provides an effective strategy for producing MOFs-derived composites with hierarchical porous architectures for energy storage.