A Flexible Nanostructured Paper of a Reduced Graphene Oxide-Sulfur Composite for High-Performance Lithium-Sulfur Batteries with Unconventional Configurations

Two-dimensional phosphorus carbides (β-PC) as highly efficient metal-free electrocatalysts for lithium-sulfur batteries: a first-principles study

Li-S batteries are considered as the next-generation batteries due to their exceptional theoretical capacity. However, their practical application is hampered by the shuttling effects of lithium polysulfides (LiPSs) and the sluggish Li2S decomposition, particularly the slow conversion from Li2S2 to Li2S. Addressing these challenges, the quest for effective catalysts that can accelerate the conversion of LiPSs and enhance the performance of Li-S batteries is crucial. In this study, we explored the electrocatalytic activity of two-dimensional phosphorus carbides (β0-PC and β1-PC) in Li-S batteries based on first-principles calculations. Our findings reveal that these materials demonstrate optimal binding strengths (ranging from 1.09 to 1.83 eV) with long-chain LiPSs, effectively preventing them from dissolving into the electrolyte. Additionally, they show remarkable catalytic activity during the sulfur redox reaction (SRR), with ΔG being only 0.37 eV for β0-PC and 0.13 eV for β1-PC. The low energy barrier induced by β-PC enhances ion migration barrier and significantly expedites the charge/discharge cycles of Li-S batteries. Furthermore, we investigated the conversion dynamics of Li2S2 to Li2S, employing the computational lithium electrode (CLE) model. The excellent performance in these aspects underscores the potential of these materials as electrocatalysts for Li-S batteries, paving the way for advanced high-efficiency energy storage solutions.

Multiscale Structural Design of 2D Nanomaterials-based Flexible Electrodes for Wearable Energy Storage Applications

2D nanomaterials play a critical role in realizing high-performance flexible electrodes for wearable energy storge devices, owing to their merits of large surface area, high conductivity and high strength. The electrode is a complex system and the performance is determined by multiple and interrelated factors including the intrinsic properties of materials and the structures at different scales from macroscale to atomic scale. Multiscale design strategies have been developed to engineer the structures to exploit full potential and mitigate drawbacks of 2D materials. Analyzing the design strategies and understanding the working mechanisms are essential to facilitate the integration and harvest the synergistic effects. This review summarizes the multiscale design strategies from macroscale down to micro/nano-scale structures and atomic-scale structures for developing 2D nanomaterials-based flexible electrodes. It starts with brief introduction of 2D nanomaterials, followed by analysis of structural design strategies at different scales focusing on the elucidation of structure-property relationship, and ends with the presentation of challenges and future prospects. This review highlights the importance of integrating multiscale design strategies. Finding from this review may deepen the understanding of electrode performance and provide valuable guidelines for designing 2D nanomaterials-based flexible electrodes.

Macroscopic assembly of 2D materials for energy storage and seawater desalination

Since the discovery of graphene in 2004, two-dimensional (2D) materials have attracted widespread attention due to their excellent physical and chemical properties in the fields of energy, environment, catalysis, and optoelectronics. However, there are still many key problems in the process of practical application. To further promote the potential of 2D materials for practical applications, macroscopic assembly of 2D materials is crucial for the continued development of 2D materials, especially in the fields of energy storage and seawater desalination. Therefore, this review focuses on the latest progress and current status related to the macroscopic assembly of 2D materials, including 1D fibers, 2D films, and 3D architectures. In addition, the application of macroscopic bodies assembled based on 2D materials in the fields of energy storage and seawater desalination is also introduced. Finally, future directions for the macroscopic assembly of 2D materials and their applications are prospected.

High-Energy Aqueous/Organic Hybrid Batteries Enabled by Cu2+ Redox Charge Carriers

Lithium||sulfur (Li||S) batteries are considered as one of the promising next-generation batteries due to the high theoretical capacity and low cost of S cathodes, as well as the low redox potential of Li metal anodes (-3.04 V vs. standard hydrogen electrode). However, the S reduction reaction from S to Li2 S leads to limited discharge voltage and capacity, largely hindering the energy density of Li||S batteries. Herein, high-energy Li||S hybrid batteries were designed via an electrolyte decoupling strategy. In cathodes, S electrodes undergo the solid-solid conversion reaction from S to Cu2 S with four-electron transfer in a Cu2+ -based aqueous electrolyte. Such an energy storage mechanism contributes to enhanced electrochemical performance of S electrodes, including high discharge potential and capacity, superior rate performance and stable cycling behavior. As a result, the assembled Li||S hybrid batteries exhibit a high discharge voltage of 3.4 V and satisfactory capacity of 2.3 Ah g-1 , contributing to incredible energy density. This work provides an opportunity for the construction of high-energy Li||S batteries.

MoSe2 @rGO as Highly Efficient Host and Catalyst for Li-Organosulfide Battery

Organosulfides are promising high-capacity cathode materials for rechargeable lithium batteries. However, sluggish kinetics and inferior utilization impede its practical application in batteries. Rationally designing redox mediators and identifying their active moieties remain formidable challenges. Currently, as a rising star of transition metal dichalcogenides, few-layered MoSe2 decorated reduced graphene oxide (rGO) (MoSe2 @rGO) with high electronic conductivity and narrow energy band is used to manipulate electrocatalytic redox kinetics of organosulfides, thereby enhancing the battery performance. Here, an exotic MoSe2 @rGO is reported with Se defects material obtained from 2D MoSe2 growing on rGO for Li-dipentamethylenethiuram tetrasulfide (Li-PMTT) batteries. MoSe2 @rGO with Se defects has a large specific surface area, and sufficient pores, as well as exce llent catalytic ability for organosulfides conversion reactions. Therefore, the PMTT@MoSe2 @rGO cathode delivers a high reversible capacity of 405 mAh g-1 in the first cycle at 0.5 C and can maintain 238.3 mAh g-1 specific capacity after 300 cycles. This work offers an understanding of organosulfides electrochemistry toward fast and durable performance, holding great promise for developing practically feasible lithium-organosulfides battery material designs.

Lithium Azides Induced SnS Quantum Dots for Ultra-Fast and Long-Term Sodium Storage

Tin sulfide (SnS) is an attractive anode for sodium ion batteries (NIBs) because of its high theoretical capacity, while it seriously suffers from the inherently poor conductivity and huge volume variation during the cycling process, leading to inferior lifespan. To intrinsically maximize the sodium storage of SnS, herein, lithium azides (LiN3 )-induced SnS quantum dots (QDs) are first reported using a simple electrospinning strategy, where SnS QDs are uniformly distributed in the carbon fibers. Taking the advantage of LiN3 , which can effectively prevent the growth of crystal nuclei during the thermal treatment, the well-dispersed SnS QDs performs superior Na+ transfer kinetics and pseudocapacitive when used as an anode material for NIBs. The 3D SnS quantum dots embedded uniformly in N-doped nanofibers (SnS QDs@NCF) electrodes display superior long cycling life-span (484.6 mAh g-1 after 5800 cycles at 2 A g-1 and 430.9 mAh g-1 after 7880 cycles at 10 A g-1 ), as well as excellent rate capability (422.3 mAh g-1 at 20 A g-1 ). This fabrication of transition metal sulfides QDs composites provide a feasible strategy to develop NIBs with long life-span and superior rate capability to pave its practical implementation.

A computational study on bifunctional 1T-MnS2 with an adsorption-catalysis effect for lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are promising rechargeable energy storage systems with a high energy density, environmental friendliness and low cost. However, the commercialization process of Li-S batteries has been seriously hindered by the shuttling of lithium polysulfides (LiPSs) and the sluggish kinetics of conversion reaction among sulfur species. In this work, the adsorption-catalysis performance of five transition metal disulfide 1T-MS₂ (M = Mn, V, Ti, Zr, and Hf) surfaces is investigated by evaluating the adsorption energy of sulfur species, Li-ion diffusion energy barrier, decomposition energy barrier of Li₂S, and the Gibbs free energy barrier of the sulfur reduction reaction based on first-principles calculations. Our results show that the sulfiphilicity of 1T-MS₂ plays an important role in the adsorption behavior of short-chain sulfur species, in addition to lithiophilicity. Remarkably, among the five 1T-MS₂ materials, our results confirm that 1T-TiS₂ and 1T-VS₂ show excellent adsorption-catalysis performance and it is predicted that 1T-MnS₂ is an even better candidate catalyst to inhibit the shuttle effect and accelerate delithiation/lithiation kinetics. Moreover, the outstanding performance of 1T-MnS₂ persists in a solvent environment and under strain modulation. Our results not only demonstrate that 1T-MnS₂ is an excellent potential catalyst for high-performance Li-S batteries, but also provide great insights into the adsorption-catalysis mechanism during the cycling process.

Petal-like Mn-doped α-Ni(OH)2 nanosheets for high-performance Li-S cathode material

Lithium-sulphur (Li-S) batteries are high-energy-density and cost-effective batteries. Herein, petal-like Ni_1-x Mn _x (OH)₂ (x ≈ 0.04) nanosheets were synthesised using a hydrothermal method and the electrical conductivity of Ni(OH)₂ was improved by applying the cathode functional materials in Li-S batteries. With up to 5 mg cm^-2 of S content in the cathode, the fabricated Ni_1-x Mn _x (OH)₂ electrode exhibited specific discharge capacities up to 1375 and 1150 mA h g^-1 at 0.2 and 0.5C, and retained this capacity at 813 and 714 mA h g^-1 after 200 cycles, respectively. Electrochemical measurement results show that Ni_1-x Mn _x (OH)₂ plays a critical role in Li-S batteries as it has a larger specific surface area than Ni(OH)₂, which has superior adsorption performance toward lithium polysulphides. Moreover, the conductivity performance of Ni_1-x Mn _x (OH)₂ is significantly better than that of Ni(OH)₂, which improves the electrochemical reaction kinetics of the Li-S batteries.

Ultrafine Co-Species Interspersed g-C3N4 Nanosheets and Graphene as an Efficient Polysulfide Barrier to Enable High Performance Li-S Batteries

Lithium-sulfur (Li-S) batteries are regarded as one of the promising advanced energy storage systems due to their ultrahigh capacity and energy density. However, their practical applications are still hindered by the serious shuttle effect and sluggish reaction kinetics of soluble lithium polysulfides. Herein, g-C₃N₄ nanosheets and graphene decorated with an ultrafine Co-species nanodot heterostructure (Co@g-C₃N₄/G) as separator coatings were designed following a facile approach. Such an interlayer can not only enable effective polysulfide affinity through the physical barrier and chemical binding but also simultaneously have a catalytic effect on polysulfide conversion. Because of these superior merits, the Li-S cells assembled with Co@g-C₃N₄/G-PP separators matched with the S/KB composites (up to ~70 wt% sulfur in the final cathode) exhibit excellent rate capability and good cyclic stability. A high specific capacity of ~860 mAh g^-1 at 2.0 C as well as a capacity-fading rate of only ~0.035% per cycle over 350 cycles at 0.5 C can be achieved. This bifunctional separator can even endow a Li-S cell at a low current density to exhibit excellent cycling capability, with a capacity retention rate of ~88.4% at 0.2 C over 250 cycles. Furthermore, a Li-S cell with a Co@g-C₃N₄/G-PP separator possesses a stable specific capacity of 785 mAh g^-1 at 0.2 C after 150 cycles and a superior capacity retention rate of ~84.6% with a high sulfur loading of ~3.0 mg cm^-2. This effective polysulfide-confined separator holds good promise for promoting the further development of high-energy-density Li-S batteries.

Carbon Coated Metal-Based Composite Electrode Materials for Lithium Sulfur Batteries: A Review

Lithium-sulfur battery is one of the most promising secondary battery systems due to their high energy density and low material cost. During the past decade, great progress has been achieved in promoting the performances of Li-S batteries by addressing the challenges at the laboratory-level model systems. With growing attention paid to the application of Li-S batteries, new challenges at practical cell scales emerge as the bottleneck. However, challenges remain for the commercialization of lithium-sulfur batteries. The current review mainly focused on metal-based catalysts decorated-carbon materials for enhanced lithium sulfur battery performance. Firstly, the synthesis methods of various carbon-sulfur composites are discussed, as well as the influence of different material structures on the electrochemical performance. Secondly, a variety of catalysts, including metal atoms, metal oxides, sulfides, phosphides, nitrides, and carbide-decorated carbon nanomaterials, are systematically introduced to determine how lithium can be enhanced by suppressing polysulfides and promoting redox conversion reactions. Also, analyzed the multi-step electrochemical reaction mechanism of the battery during the charging and discharging process, and provide a feasible path for the practical application of high energy density lithium-sulfur batteries.

Facile Dissolution-Crystallization Strategy to Achieve Rapid and Uniform Distribution of Sulfur on Porous Carbon for Lithium-Sulfur Batteries

In this work, we proposed a facile dissolution-crystallization strategy based on density functional theory calculations to achieve rapid as well as uniform distribution of sulfur on porous carbon. Sulfur-containing solution can completely penetrate porous material and in preference remove into the pores under the influence of capillary force, and sulfur tends to crystallize on the defective even non-defective carbon matrix rather than agglomerate. The S/PC composites prepared by this method can still achieve uniform distribution of sulfur when the sulfur content is as high as 85%. All operations can be completed within a few minutes without any heating. Compared with common melt-diffusion and vapor-phase infusion, this approach has lower energy consumption and is simple, safe, continuous, and rapid.

A graphene oxide scaffold-encapsulated microcapsule for polysulfide-immobilized long life lithium-sulfur batteries

Engineering high-performance cathodes for high energy-density lithium-sulfur (Li-S) batteries is quite significant to achieve commercialization. Here, we develop a graphene oxide scaffold/sulfur composite-encapsulated microcapsule (GSM) for high-performance Li-S batteries, which is prepared through the co-flow focusing (CFF) approach. The GSM-based cathode displays a high capacity of 1004 mA h g^-1 at 0.2C after cycling 200 times, a long-term cycling stability after 1000 cycles at 2C, and a good rate-performance. At temperatures of -5 °C and 45 °C, the electrochemical performance is also excellent. The computational calculations based on density functional theory (DFT) verify the high adsorption energies of the microcapsules towards polysulfides, suppressing the shuttle effect efficiently. It is expected that the GSM system developed based on the CFF method here and its high electrochemical performance will enable it to be applicable for preparing many other emerging energy-storage materials and secondary batteries.

A Comparative Study of Cobalt Chalcogenides as the Electrode Materials on Lithium-Sulfur Battery Performance

Lithium-sulfur batteries, as viable options for energy storage, have gained popularity because of their high energy density. However, the poor conductivity of sulfur and Li₂ S, as well as the shuttling effect of lithium polysulfides, seriously limits their commercialization. Herein, cobalt chalcogenides (Co₃ O₄ , CoS, and Co₃ Se₄ ) supported by reduced graphene oxide are synthesized as the electrode materials, which feature high conductivity, rapid kinetic conversion, and catalytic effect. Based on complementary experimental outputs and advanced computation, it is revealed that the change in anion results in distinctive performance. Among them, the cathode material based on Co₃ Se₄ /reduced graphene oxide is the best. The reasons can be ascribed to the conductive and catalytic improvement. This comparative study provides guidelines in the design of lithium-sulfur batteries via the meticulous regulation of the anions.

An integrated flexible film as cathode for High-Performance Lithium-Sulfur battery

Poor cycling stability and low volumetric capacity of sulfur cathode prevents practical application of Lithium-sulfur (Li-S) batteries. Herein, we demonstrate a strategy to address the two drawbacks of sulfur cathode by synthesizing a compact and flexible film cathode with bilayer structure using a two-step vacuum filtration method. Two layers make up the sulfur cathode, active layer (sulfur-acethlene black (SC) spheres) and barrier layer (three dimensional MnO₂-graphene oxide-multi-walled carbon nanotubes (MnO₂-GO-CNTs) composites), which are integrated together by reduced graphene oxide (rGO) through self-binding. The rGO sheets provide an electrical conductive framework and a stable architecture to accommodate volume changes of sulfur. SC spheres stacked orderly between the rGO layers facilitate fast Li⁺ storage and energy release. Polar MnO₂-GO-CNTs composites with large specific surface area have not only afforded efficient sites for chemically binding polysulfides, but also provided fast electron transfer for accelerating polysulfides redox reaction. Consequently, the integrated film cathode exhibits an unprecedented cycling stability of ~0.0279% capacity decay per cycle over more than 600 cycles at 1C and high volumetric capacity of 1021.9 Ah L^-1 at 2C. Meanwhile, a foldable Li-S battery based on this flexible cathode is fabricated and shows excellent mechanical and electrochemical properties. The integrated flexible sulfur cathode of this study sheds light on the design strategies for application in flexible high volumetric capacity system.

Organosulfur polymer-based cathode materials for rechargeable batteries

Organosulfur polymer cathode materials have shown promising electrochemical performances in rechargeable batteries. This review covers recent developments of the polymer cathodes and the remaining challenges and future prospects are discussed.

Graphene-Based Nanomaterials for Flexible and Stretchable Batteries

Recently, as flexible and wearable electronic devices have become widely popular, research on light weight and large-capacity batteries suitable for powering such devices has been actively conducted. In particular, graphene has attracted considerable attention from researchers in the battery field owing to its good mechanical properties and its applicability in various processes to fabricate electrodes for batteries. Graphene is classified into two types: flake-type, fabricated from graphite, and film-type, synthesized using chemical vapor deposition. The unique processes involved in these two types enable the fabrication of flexible and stretchable batteries with various shapes and functions. In this article, the recent progress in the development of flexible and stretchable batteries based on graphene, as well as its important technical issues are reviewed.

Boron nitride nanosheets wrapped by reduced graphene oxide for promoting polysulfides adsorption in lithium-sulfur batteries

The polysulfides shuttling and slow redox kinetics of sulfur-based cathodes have severely hindered the commercialization of lithium-sulfur (Li-S) batteries. Herein, distinctive three-dimensional microspheres composed of boron nitride (BN) nanosheets and reduced graphene oxide (rGO) were applied to act as efficient sulfur cathode hosts for the first time using in a spray-drying process. Using this construction, the robust microsphere structure could shorten ion diffusion pathways and supply sufficient spaces to alleviate the volumetric expansion of sulfur during lithiation. Besides, the synergistic effect between BN and rGO significantly enhanced polysulfides adsorption capability and accelerated their conversion, verified by the density functional theory (DFT) calculations and adsorption experiments. Consequently, the S-BN@rGO cathode could manifest the high initial capacity (1137 mAh g^-1 at 0.2 C) and remarkable cycling/stability performance (572 mAh g^-1 at 1 C after 500 cycles). These results shed light on a design concept of high-performance sulfur cathode host materials.

Pathways of Developing High-Energy-Density Flexible Lithium Batteries

Flexible lithium-based batteries (FLBs) enable the seamless implementation of power supply to flexible and wearable electronics. They not only enhance the energy capacity by fully utilizing the available space but also revolutionize the form factors of future device design. To date, how to simultaneously acquire high energy density and excellent mechanical flexibility is the major challenge of FLBs. Here, a critical discussion for guiding the future development of FLBs toward high energy density and high flexibility is presented. First, the industrial criteria of FLBs for several desirable applications of flexible and wearable electronics are summarized. Then, strategies to achieve flexibility of FLBs are discussed, with highlights of representative examples. The performance of FLBs is benchmarked with a flexible battery plot. New materials and cell design principles are analyzed to realize high-energy-density and high-flexibility FLBs. Other important aspects of FLBs including materials to improve the cycling stability and safety are also discussed.

Graphene-Based Materials for Flexible Lithium-Sulfur Batteries

The increasing demand for wearable electronic devices necessitates flexible batteries with high stability and desirable energy density. Flexible lithium-sulfur batteries (FLSBs) have been increasingly studied due to their high theoretical energy density through the multielectron chemistry of low-cost sulfur. However, the implementation of FLSBs is challenged by several obstacles, including their low practical energy density, short life, and poor flexibility. Various graphene-based materials have been applied to address these issues. Graphene, with good conductivity and flexibility, exhibits synergistic effects with other active/catalytic/flexible materials to form multifunctional graphene-based materials, which play a pivotal role in FLSBs. This review summarizes the recent progress of graphene-based materials that have been used as various FLSB components, including cathodes, interlayers, and anodes. Particular attention is focused on the precise nanostructures, graphene efficacy, interfacial effects, and battery layout for realizing FLSBs with good flexibility, energy density, and cycling stability.

Graphene-Based Nanomaterials as the Cathode for Lithium-Sulfur Batteries

The global energy crisis and environmental problems are becoming increasingly serious. It is now urgent to vigorously develop an efficient energy storage system. Lithium-sulfur batteries (LSBs) are considered to be one of the most promising candidates for next-generation energy storage systems due to their high energy density. Sulfur is abundant on Earth, low-cost, and environmentally friendly, which is consistent with the characteristics of new clean energy. Although LSBs possess numerous advantages, they still suffer from numerous problems such as the dissolution and diffusion of sulfur intermediate products during the discharge process, the expansion of the electrode volume, and so on, which severely limit their further development. Graphene is a two-dimensional crystal material with a single atomic layer thickness and honeycomb bonding structure formed by sp2 hybridization of carbon atoms. Since its discovery in 2004, graphene has attracted worldwide attention due to its excellent physical and chemical properties. Herein, this review summarizes the latest developments in graphene frameworks, heteroatom-modified graphene, and graphene composite frameworks in sulfur cathodes. Moreover, the challenges and future development of graphene-based sulfur cathodes are also discussed.

A special core-shell ZnS-CNTs/S@NH cathode constructed to elevate electrochemical performances of lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are regarded as promising candidates for next-generation electrochemical energy storage systems due to their low cost and high energy density. However, the insulative sulfur, the volume expansion and high soluble polysulfides are three roots impeding their practical applications, and consequently bring challenges of low sulfur utilization, poor cyclic stability and sluggish redox kinetics. Herein, a special core-shell ZnS-CNTs/S@Ni(OH)₂ (labeled as ZnS-CNTs/S@NH) cathode has been designed to overcome above obstacles and elevate the electrochemical performance. The ZnS-CNTs/S@NH cathode is synthesized via a facile step-by-step strategy, in which ZnS-decorated CNTs was used as a framework to load sulfur and followed with a ultrathin Ni(OH)₂ (NH) layer encapsulation. The ZnS-CNT core combines merits of CNT network and polar ZnS quantum dots (QDs), accommodating the volume change, offering efficient pathways for fast electron/ion transport, and anchoring polysulfides through polar interactions. The outer Ni(OH)₂ shell physically confines the active material and meanwhile provides plenty of catalytic sites for effective polysulfide chemisorption. Benefiting from these merits, the ZnS-CNTs/S@NH cathode exhibits excellent cell performances in comparison with ZnS-CNTs/S and CNTs/S. Its discharge capacity at different C-rates is optimal in the three cathodes, which decreases from 1037.0 mAh g^-1 at 0.1 C to 646.1 mAh g^-1 at 2.0 C. Its cyclic capacity also manifests the slowest reduction from 861.1 to 760.1 mAh g^-1 after 150 cycles at 0.5 C, showing a high retention (88.3%) and a tiny average fading rate (0.078%). The strategy in this work provides a feasible approach to design and construct core-shell cathode materials for realizing practically usable Li-S batteries.

Efficient polysulfide trapping in lithium-sulfur batteries using ultrathin and flexible BaTiO3/graphene oxide/carbon nanotube layers

Ultrathin and flexible layers containing BaTiO₃ (BTO) nanoparticles, graphene oxide (GO) sheets, and carbon nanotube (CNT) films (BTO/GO@CNT) are used to trap solvated polysulfides and alleviate the shuttle effect in lithium-sulfur (Li-S) batteries. In the functional layers, the CNT films build a conductive framework, and the GO sheets form a support membrane for the uniform dispersion of BTO nanoparticles. BTO nanoparticles without ferroelectricity (nfBTO) can trap polysulfides more effectively by chemical interaction compared to BTO nanoparticles with ferroelectricity (fBTO). A Li-S cell with the nfBTO/GO@CNT functional layer exhibits a reversible capacity of 824.5 mA h g^-1 over 100 cycles at 0.2 C. At a high sulfur loading of 5.49 mg cm^-2, an electrode with the functional layer shows an areal capacity of 5.15 mA h cm^-2 at 0.1 C, demonstrating the nfBTO/GO@CNT functional layer's potential in developing high-performance Li-S batteries.

Scallion-Inspired Graphene Scaffold Enabled High Rate Lithium Metal Battery

Graphene-based one-dimensional macroscopic assemblies (GBOMAs) have attracted great attention and extensive efforts have been devoted to enabling great progress. However, their applications are still restricted to less functionalized electronics, and the superior potentials remain scarce. Herein, inspired by natural scallion structure, a novel strategy was introduced to effectively improve battery performances through the mesoscale scallion-like wrapping of graphene. The obtained RGO/Ag-Li anodes demonstrated an ultralow overpotential of ∼11.3 mV for 1800 h at 1 mA cm^-2 in carbonate electrolytes, which is superior to those of the most previous reports. Besides, this strategy can also be further expanded to the high mass loading of various cathode nanomaterials, and the resulting RGO/LiFePO₄ cathodes exhibited remarkable rate performance and cycle stability. This work opens a new avenue to explore and broaden the applications of GBOMAs as scaffolds in fabricating full lithium batteries via maximizing their advantages derived from the unique structure and properties.

A flexible and conductive MXene-coated fabric integrated with in situ sulfur loaded MXene nanosheets for long-life rechargeable Li-S batteries

Lithium-sulfur (Li-S) batteries with high energy density, which show great application potential in flexible electronic products, have attracted a lot of research enthusiasm. However, the low utilization of sulfur and shuttle effect limit the application of Li-S batteries. Materials with a void structure and high conductivity can be used as a sulfur host to overcome these issues. Herein, a flexible MXene-coated textile fabric electrode (MF@Ti₃C₂T_x/S) is designed by integrating the MXene-coated textile fabric (MF) with in situ sulfur loaded MXene nanosheets (Ti₃C₂T_x/S). The MF provides a flexible 3D conductive framework, which is covered with Ti₃C₂T_x/S nanosheets to form the layer-by-layer structure. This unique structure not only provides enough space for volume expansion to maintain the structural stability in the electrochemical process, but also promotes the physical encapsulation and chemical adsorption of lithium polysulfides (LiPSs). Consequently, the MF@Ti₃C₂T_x/S50 electrode exhibits a high initial capacity of 916 mA h g^-1 at 1C and an ultralong-term cycling stability of 674 mA h g^-1 at 1C after 1000 cycles. Furthermore, this electrode also exhibits excellent rate performance at a high energy density (290 mA h g^-1 at 5C after 800 cycles). A pouch cell is prepared by using the MF@Ti₃C₂T_x/S50 electrode and shows excellent cycle performances at different bending angles, which indicates that this study is valuable in the field of flexible energy storage. This work provides a new concept design for flexible Li-S batteries, which have great application potential as wearable and portable electronic devices.

An Ultra-Long-Life Flexible Lithium-Sulfur Battery with Lithium Cloth Anode and Polysulfone-Functionalized Separator

Flexible and high-performance batteries are urgently required for powering flexible/wearable electronics. Lithium-sulfur batteries with a very high energy density are a promising candidate for high-energy-density flexible power source. Here, we report flexible lithium-sulfur full cells consisting of ultrastable lithium cloth anodes, polysulfone-functionalized separators, and free-standing sulfur/graphene/boron nitride nanosheet cathodes. The carbon cloth decorated with lithiophilic three-dimensional MnO₂ nanosheets not only provides the lithium anodes with an excellent flexibility but also limits the growth of the lithium dendrites during cycling, as revealed by theoretical calculations. Commercial separators are functionalized with polysulfone (PSU) via a phase inversion strategy, resulting in an improved thermal stability and smaller pore size. Due to the synergistic effect of the PSU-functionalized separators and boron nitride-graphene interlayers, the shuttle of the polysulfides is significantly inhibited. Because of successful control of the shuttle effect and dendrite formation, the flexible lithium-sulfur full cells exhibit excellent mechanical flexibility and outstanding electrochemical performance, which shows a superlong lifetime of 800 cycles in the folded state and a high areal capacity of 5.13 mAh cm^-2. We envision that the flexible strategy presented herein holds promise as a versatile and scalable platform for large-scale development of high-performance flexible batteries.

Synthesis and Electrochemical Performance of Graphene @ Halloysite Nanotubes/Sulfur Composites Cathode Materials for Lithium-Sulfur Batteries

Natural halloysite nanotubes (HNTs) and reduced graphene oxide (RGO) were introduced into the S cathode material to form HNTs/S and RGO@HNTs/S composite electrode to improve the electrochemical performance of Li-S batteries. The effect of acid etching temperature on the morphology and pore structure of HNTs was explored and the morphological characteristics and electrochemical performance of composite electrodes formed by HNTs that after treatment with different acid etching temperatures and RGO were compared. The result shows that the cycling stability and the utilization rate of active substances of the Li-S battery were greatly improved because the pore structure and surface polarity functional groups of HNTs and the introduction of RGO provide a conductive network for insulating sulfur particles. The RGO@HNTs treated by acid treatment at 80 °C (RGO@HNTs-80/S) composite electrode at 0.1 C has an initial capacity of 1134 mAh g-1, the discharge capacity after 50 cycles retains 20.1% higher than the normal S electrode and maintains a specific discharge capacity of 556 mAh g-1 at 1 C. Therefore, RGO and HNTs can effectively improve the initial discharge specific capacity, cycle performance and rate performance of Li-S batteries.

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.

A waste newspaper/multi-walled carbon nanotube/TiO2 interlayer for improving the cycling stability of lithium-sulfur batteries by anchoring polysulfides

Owing to the high theoretical specific capacity and energy density, lithium-sulfur (Li-S) batteries are considered an ideal candidate for next-generation rechargeable batteries. Whereas, the shuttle effect of polysulfides limits the utilization of active materials, reducing the electrochemical performance of lithium-sulfur batteries. Herein, by directly using waste newspapers as a substrate, a waste newspaper/multi-walled carbon nanotube/TiO2 (NMT) interlayer has been prepared for stable Li-S batteries. In the composite interlayer, the newspaper functions as the basic frame for loading materials. Carbon materials absorbed by the newspaper provide both a conductive pathway and physical adsorption of lithium polysulfides (LiPS). Meanwhile, TiO2 inhibits the dissolution of LiPS in the electrolyte by strong chemical bonding. The morphology and spectra prove that the newspaper plays a key frame role in the functional composite interlayer. The electrochemical analyses demonstrate that the as-fabricated interlayer can obviously improve the cycling performance of Li-S battery. At a 0.5 C (1.0 C = 1675 mA h g-1) charge-discharge current density, after 500 cycles, the Li-S battery with NMT interlayer still exhibits a discharge capacity of 463.7 mA h g-1 with a low capacity decay per cycle of 0.071%.

Recent Progress in the Development of Composite Membranes Based on Polybenzimidazole for High Temperature Proton Exchange Membrane (PEM) Fuel Cell Applications

The rapid increasing of the population in combination with the emergence of new energy-consuming technologies has risen worldwide total energy consumption towards unprecedent values. Furthermore, fossil fuel reserves are running out very quickly and the polluting greenhouse gases emitted during their utilization need to be reduced. In this scenario, a few alternative energy sources have been proposed and, among these, proton exchange membrane (PEM) fuel cells are promising. Recently, polybenzimidazole-based polymers, featuring high chemical and thermal stability, in combination with fillers that can regulate the proton mobility, have attracted tremendous attention for their roles as PEMs in fuel cells. Recent advances in composite membranes based on polybenzimidazole (PBI) for high temperature PEM fuel cell applications are summarized and highlighted in this review. In addition, the challenges, future trends, and prospects of composite membranes based on PBI for solid electrolytes are also discussed.

3D-metal-embroidered electrodes: dreaming for next generation flexible and personalizable energy storage devices

Flexible and Personalizable battery is a promising candidate for energy storage, but suffers from the weldablity and large-scale producibility of the electrode. To address the issues, we design a nickel foam catalyzed electroless deposition (NFED) derived 3D-metal-pattern embroidered electrodes. This is the first attempt to utilize this type of electrode in battery field. It is found that the current collector can be embroidered on any selected areas of any complex-shape electrodes, with high controllability and economical feasibility. As a result, the electronic conductivity of the flexible electrodes can be improved by nearly one order of magnitude, which can be easily and firmly weldded to the metal tab using the industry generic ultrasonic heating process. The embroidered electrodes could substantially promote the electrochemical performance under bending deformation, with both Li-S and Li-LiFePO₄ batteries as the models. This innovation is also suitable to embroider all the VIII group elements on any electrodes with personalized shapes, which is widely attractive for the development of next generation flexible and personalizable energy storage devices.

Tellurium: A High-Volumetric-Capacity Potassium-Ion Battery Electrode Material

Currently, exploring high-volumetric-capacity electrode materials that allow for reversible (de-)insertion of large-size K⁺ ions remains challenging. Tellurium (Te) is a promising alternative electrode for storage of K⁺ ions due to its high volumetric capacity, confirmed in lithium-/sodium-ion batteries, and the intrinsic good electronic conductivity. However, the charge storage capability and mechanism of Te in potassium-ion batteries (KIBs) have not been unveiled until now. Here, a novel K-Te battery is constructed, and the K⁺ -ion storage mechanism of Te is revealed to be a two-electron conversion-type reaction of 2K + Te ↔ K₂ Te, resulting in a high theoretical volumetric capacity of 2619 mAh cm^-3 . Consequently, the rationally fabricated tellurium/porous carbon electrodes deliver an ultrahigh reversible volumetric capacity of 2493.13 mAh cm^-3 at 0.5 C (based on Te), a high-rate capacity of 783.13 mAh cm^-3 at 15 C, and superior long-term cycling stability for 1000 cycles at 5 C. This excellent electrochemical performance proves the feasibility of utilizing Te as a high-volumetric-capacity active material for storage of K⁺ ions and will advance the practical application of KIBs.

Enhanced Multiple Anchoring and Catalytic Conversion of Polysulfides by Amorphous MoS3 Nanoboxes for High-Performance Li-S Batteries

The practical implementation of lithium-sulfur batteries is obstructed by poor conductivity, sluggish redox kinetics, the shuttle effect, large volume variation, and low areal loading of sulfur electrodes. Now, amorphous N-doped carbon/MoS₃ (NC/MoS₃ ) nanoboxes with hollow porous architectures have been meticulously designed as an advanced sulfur host. Benefiting from the enhanced conductivity by the N-doped carbon, reduced shuttle effect by the strong chemical interaction between unsaturated Mo and lithium polysulfides, improved redox reaction kinetics by the catalytic effect of MoS₃ , great tolerance of volume variation and high sulfur loading arising from flexible amorphous materials with hollow-porous structures, the amorphous NC/MoS₃ nanoboxes enabled sulfur electrodes to deliver a high areal capacity with superior rate capacity and decent cycling stability. The synthetic strategy can be generalized to fabricate other amorphous metal sulfide nanoboxes.