Dual-protection of a graphene-sulfur composite by a compact graphene skin and an atomic layer deposited oxide coating for a lithium-sulfur battery

Elucidating the Synergic Effect in Nanoscale MoS2 /TiO2 Heterointerface for Na-Ion Storage

Interface engineering in electrode materials is an attractive strategy for enhancing charge storage, enabling fast kinetics, and improving cycling stability for energy storage systems. Nevertheless, the performance improvement is usually ambiguously ascribed to the "synergetic effect", the fundamental understanding toward the effect of the interface at molecular level in composite materials remains elusive. In this work, a well-defined nanoscale MoS₂ /TiO₂ interface is rationally designed by immobilizing TiO₂ nanocrystals on MoS₂ nanosheets. The role of heterostructure interface between TiO₂ and MoS₂ by operando synchrotron X-ray diffraction (sXRD), solid-state nuclear magnetic resonance, and density functional theory calculations is investigated. It is found that the existence of a hetero-interfacial electric field can promote charge transfer kinetics. Based on operando sXRD, it is revealed that the heterostructure follows a solid-solution reaction mechanism with small volume changes during cycling. As such, the electrode demonstrates ultrafast Na⁺ ions storage of 300 mAh g^-1 at 10 A g^-1 and excellent reversible capacity of 540 mAh g^-1 at 0.2 A g^-1 . This work provides significant insights into understanding of heterostructure interface at molecular level, which suggests new strategies for creating unconventional nanocomposite electrode materials for energy storage systems.

Cationic polymer-grafted graphene oxide/CNT cathode-coating material for lithium-sulfur batteries

A cathode-coating material composed of cationic polymer-grafted graphene oxide (CPGO) and carbon nanotube (CNT) was prepared, where the CPGO was synthesized by grafting quaternized 2-(dimethylamino)ethyl methacrylate (QDMAEMA) onto graphene oxide (GO) via atom transfer radical polymerization (ATRP). GO has good compatibility with carbon black, the main component of the cathode in lithium–sulfur (Li–S) batteries. Here, the cationic polymer having the QDMAEMA unit was intentionally grafted onto GO to decrease the shuttle effect by increasing the chemical adsorption of polysulfide (PS). In addition, when CNT was mixed with CPGO, the compatibility with carbon black was found to be further increased. The lithium–sulfur (Li–S) battery with a sulfur-deposited Super P® carbon black (S/C) cathode coated with a mixture of CPGO and CNT was found to have much improved cell performance compared to those coated without any coating material, with only CPGO, with the mixture of GO and CNT, and with the mixture of PQDMAEMA and CNT. For example, the Li–S battery with the cathode coated using the mixture of CPGO and CNT retained a discharge capacity of 744 mA h g⁻¹ after 50 cycles at 0.2C-rate, while those of the Li–S batteries with bare S/C and CPGO-S/C cathodes were found to be much smaller, i.e., 488 mA h g⁻¹ and 641 mA h g⁻¹, respectively, under the same conditions. Therefore, the mixture of CPGO with CNT as the cathode-coating material showed a synergetic effect to enhance the cell performance of the Li–S battery system.

A cathode-coating material composed of cationic polymer-grafted graphene oxide (CPGO) and carbon nanotube (CNT) was prepared and used as a cathode-coating material for lithium sulfur batteries.

Advances in Lithium-Sulfur Batteries: From Academic Research to Commercial Viability

Lithium-ion batteries, which have revolutionized portable electronics over the past three decades, were eventually recognized with the 2019 Nobel Prize in chemistry. As the energy density of current lithium-ion batteries is approaching its limit, developing new battery technologies beyond lithium-ion chemistry is significant for next-generation high energy storage. Lithium-sulfur (Li-S) batteries, which rely on the reversible redox reactions between lithium and sulfur, appears to be a promising energy storage system to take over from the conventional lithium-ion batteries for next-generation energy storage owing to their overwhelming energy density compared to the existing lithium-ion batteries today. Over the past 60 years, especially the past decade, significant academic and commercial progress has been made on Li-S batteries. From the concept of the sulfur cathode first proposed in the 1960s to the current commercial Li-S batteries used in unmanned aircraft, the story of Li-S batteries is full of breakthroughs and back tracing steps. Herein, the development and advancement of Li-S batteries in terms of sulfur-based composite cathode design, separator modification, binder improvement, electrolyte optimization, and lithium metal protection is summarized. An outlook on the future directions and prospects for Li-S batteries is also offered.

Nanoscale Drug Delivery Systems for Glaucoma: Experimental and In Silico Advances

In this review, nanoscale-based drug delivery systems, particularly in relevance to the antiglaucoma drugs, have been discussed. In addition to that, the latest computational/in silico advances in this field are examined in brief. Using nanoscale materials for drug delivery is an ideal option to target tumours, and the drug can be released in areas of the body where traditional drugs may fail to act. Nanoparticles, polymeric nanomaterials, single-wall carbon nanotubes (SWCNTs), quantum dots (QDs), liposomes and graphene are the most important nanomaterials used for drug delivery. Ocular drug delivery is one of the most common and difficult tasks faced by pharmaceutical scientists because of many challenges like circumventing the blood-retinal barrier, corneal epithelium and the blood-aqueous barrier. Authors found compelling empirical evidence of scientists relying on in-silico approaches to develop novel drugs and drug delivery systems for treating glaucoma. This review in nanoscale drug delivery systems will help us understand the existing queries and evidence gaps and will pave the way for the effective design of novel ocular drug delivery systems.

Reasonably Introduced ZnIn2S4@C to Mediate Polysulfide Redox for Long-Life Lithium-Sulfur Batteries

In consideration of the inferior rate performance and low sulfur utilization of lithium-sulfur batteries (LSBs), an effective strategy via combining polar materials with the conductive carbon sulfur host is widely applied. Herein, metal organic framework-derived in situ-developed ZnIn₂S₄@C is innovatively synthesized to mediate lithium polysulfide (LPS) conversion based on high electron conductivity and strong chemical interactions for advanced LSBs. Polar ZnIn₂S₄ possesses strong chemisorption in keeping with the DFT calculation results and catalytic for LPSs, ensuring a high sulfur utilization. Meanwhile, the hollow non-polar carbon frame possessing hierarchical pores not only provides internal space to contain active species but also accommodates efficient electronic transferring and diffusion of lithium ions in the process of cycling. The above advantages make the electrode possess promising stability and good rate performances, achieving long-term and high-rate cycling. Thus, under a sulfur loading of 1.5 mg cm^-2, after 500 cycles, at 2 and 5 C, the as-prepared ZnIn₂S₄@C@S delivers reversible capacities of 734 mA h g^-1 (75.7% of the initial capacity with a dropping rate of 0.015% per cycle) and 504 mA h g^-1 (68.5% of the primal capacity with a dropping rate of 0.029% per cycle), respectively. Even at a high sulfur loading of 5.0 mg cm^-2, at 5 C, 65.6% of the initial capacity can be maintained with a low fading rate of 0.430% per cycle after 500 loops with a high Coulombic efficiency of around 99.8%.

Atomic/molecular layer deposition for energy storage and conversion

Energy storage and conversion systems, including batteries, supercapacitors, fuel cells, solar cells, and photoelectrochemical water splitting, have played vital roles in the reduction of fossil fuel usage, addressing environmental issues and the development of electric vehicles. The fabrication and surface/interface engineering of electrode materials with refined structures are indispensable for achieving optimal performances for the different energy-related devices. Atomic layer deposition (ALD) and molecular layer deposition (MLD) techniques, the gas-phase thin film deposition processes with self-limiting and saturated surface reactions, have emerged as powerful techniques for surface and interface engineering in energy-related devices due to their exceptional capability of precise thickness control, excellent uniformity and conformity, tunable composition and relatively low deposition temperature. In the past few decades, ALD and MLD have been intensively studied for energy storage and conversion applications with remarkable progress. In this review, we give a comprehensive summary of the development and achievements of ALD and MLD and their applications for energy storage and conversion, including batteries, supercapacitors, fuel cells, solar cells, and photoelectrochemical water splitting. Moreover, the fundamental understanding of the mechanisms involved in different devices will be deeply reviewed. Furthermore, the large-scale potential of ALD and MLD techniques is discussed and predicted. Finally, we will provide insightful perspectives on future directions for new material design by ALD and MLD and untapped opportunities in energy storage and conversion.

Implanting Atomic Cobalt within Mesoporous Carbon toward Highly Stable Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries hold great promise to serve as next-generation energy storage devices. However, the practical performances of Li-S batteries are severely limited by the sulfur cathode regarding its low conductivity, huge volume change, and the polysulfide shuttle effect. The first two issues have been well addressed by introducing mesoporous carbon hosts to the sulfur cathode. Unfortunately, the nonpolar nature of carbon materials renders poor affinity to polar polysulfides, leaving the shuttling issue unaddressed. In this contribution, atomic cobalt is implanted within the skeleton of mesoporous carbon via a supramolecular self-templating strategy, which simultaneously improves the interaction with polysulfides and maintains the mesoporous structure. Moreover, the atomic cobalt dopants serve as active sites to improve the kinetics of the sulfur redox reactions. With the atomic-cobalt-decorated mesoporous carbon host, a high capacity of 1130 mAh g_S ^-1 at 0.5 C and a high stability with a retention of 74.1% after 300 cycles are realized. Implanting atomic metal in mesoporous carbon demonstrates a feasible strategy to endow nanomaterials with targeted functions for Li-S batteries and broad applications.

3D Starfish-Like FeOF on Graphene Sheets: Engineered Synthesis and Lithium Storage Performance

To address the problems associated with poor conductivity and large volume variation in practical applications as a conversion cathode, engineering of hierarchical nanostructured FeOF coupled with conductive decoration is highly desired, yet rarely reported. Herein, 3D starfish-like FeOF on reduced graphene oxide sheets (FeOF/rGO) is successfully prepared, for the first time, through a combination of solvothermal reaction, self-assembly, and thermal reduction. Integrating the structural features of the 3D hierarchical nanostructure, which favorably shorten the path for electron/ion transport and alleviate volumetric changes, with those of graphene wrapping, which can further enhance the electrical conductivity and maintain the structural stability of the electrode, the as-prepared FeOF/rGO composite exhibits a superior lithium-storage performance, including a high reversible capacity (424.5 mA h^-1  g^-1 at 50 mA g^-1 ), excellent stability (0.016 % capacity decay per cycle during 180 cycles), and remarkable rate capability (275.8 mA h^-1  g^-1 at 2000 mA g^-1 ).

Natural chalcopyrite as a sulfur source and its electrochemical performance for lithium–sulfur batteries

Natural chalcopyrite with high capacity and good cycling performance is used as a sulfur source for lithium–sulfur batteries.

Recent Advances in 3D Graphene Architectures and Their Composites for Energy Storage Applications

Graphene is widely applied as an electrode material in energy storage fields. However, the strong π-π interaction between graphene layers and the stacking issues lead to a great loss of electrochemically active surface area, damaging the performance of graphene electrodes. Developing 3D graphene architectures that are constructed of graphene sheet subunits is an effective strategy to solve this problem. The graphene architectures can be directly utilized as binder-free electrodes for energy storage devices. Furthermore, they can be used as a matrix to support active materials and further improve their electrochemical performance. Here, recent advances in synthesizing 3D graphene architectures and their composites as well as their application in different energy storage devices, including various battery systems and supercapacitors are reviewed. In addition, their challenges for application at the current stage are discussed and future development prospects are indicated.

A PPy/ZnO functional interlayer to enhance electrochemical performance of lithium/sulfur batteries

To enhance the electrochemical performance of the lithium/sulfur batteries, a novel interlayer was prepared by coating the slurry of PPy/ZnO composite onto the surface of a separator. Owing to a three-dimensional hierarchical network structure, PPy/ZnO composite serves as a polysulfide diffusion absorbent that can intercept the migrating soluble polysulfides to enhance the electrochemical performance of the Li/S batteries. The specific capacity of the cell with PPy/ZnO interlayer remained at 579 mAh g^-1 after 100 cycles at 0.2 C. This interlayer can provide novel avenues for the commercial applications of Li/S batteries.

Novel Non-Carbon Sulfur Hosts Based on Strong Chemisorption for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are considered as promising candidates for energy storage systems owing to their high theoretical capacity and high energy density. The application of Li-S batteries is hindered by several obstacles, however, including the shuttle effect, poor electrical conductivity, and the severe volume expansion of sulfur. The traditional method is to integrate sulfur with carbon materials. But the interaction between polysulfide intermediates and carbon is only weak physical adsorption, which easily leads to the escape of species from the framework (shuttle effect) of the material causing capacity loss. Recently, however, there has been a trend for the introduction of novel non-carbon materials as sulfur hosts based on the strong chemisorption. This review highlights recent research progress on novel non-carbon sulfur hosts based on strong chemisorption, in Li-S batteries. In comparison with carbon-based sulfur hosts, most non-carbon sulfur hosts have been demonstrated to be polar host materials that could efficiently adsorb polysulfide via strong chemisorption, mitigating their dissolution. The intrinsic mechanism associated with the role of non-carbon-based host materials in improving the performance of Li-S batteries is discussed.

Dual-Functional Graphene Carbon as Polysulfide Trapper for High-Performance Lithium Sulfur Batteries

The lithium sulfur (Li-S) battery has attracted much attention due to its high theoretical capacity and energy density. However, its cycling stability and rate performance urgently need to improve because of its shuttle effect. Herein, oxygen-doped carbon on the surface of reduced graphene oxide (labeled as ODC/rGO) was fabricated to modify the separators of Li-S batteries to limit the dissolution of the lithium polysulfides. The mesoporous structure in ODC/rGO can not only serve as the physical trapper, but also provide abundant channels for fast ion transfer, which is beneficial for effective confinement of the dissoluble intermediates and superior rate performance. Moreover, the oxygen-containing groups in ODC/rGO are able to act as chemical adsorption sites to immobilize the lithium polysulfides, suppressing their dissolution in electrolyte to enhance the utilization of sulfur cathode in Li-S batteries. As a result, because of the synergetic effects of physical adsorption and chemical interaction to immobilize the soluble polysulfides, the Li-S batteries with the ODC/rGO-coated separator exhibit excellent rate performance and good long-term cycling stability with 0.057% capacity decay per cycle at 1.0 C after 600 cycles.

Hierarchically porous graphene for batteries and supercapacitors

Hierarchical porous graphene based materials are explored for their application as electrochemical storage devices due to their large specific surface area, high electrical and thermal conductivity, and excellent specific capacity.

Nanostructured Metal Oxides and Sulfides for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries with high energy density and long cycle life are considered to be one of the most promising next-generation energy-storage systems beyond routine lithium-ion batteries. Various approaches have been proposed to break down technical barriers in Li-S battery systems. The use of nanostructured metal oxides and sulfides for high sulfur utilization and long life span of Li-S batteries is reviewed here. The relationships between the intrinsic properties of metal oxide/sulfide hosts and electrochemical performances of Li-S batteries are discussed. Nanostructured metal oxides/sulfides hosts used in solid sulfur cathodes, separators/interlayers, lithium-metal-anode protection, and lithium polysulfides batteries are discussed respectively. Prospects for the future developments of Li-S batteries with nanostructured metal oxides/sulfides are also discussed.

Core-Shell Structure and Interaction Mechanism of γ-MnO2 Coated Sulfur for Improved Lithium-Sulfur Batteries

Lithium-sulfur batteries have attracted worldwide interest due to their high theoretical capacity of 1672 mAh g^-1 and low cost. However, the practical applications are hampered by capacity decay, mainly attributed to the polysulfide shuttle. Here, the authors have fabricated a solid core-shell γ-MnO₂ -coated sulfur nanocomposite through the redox reaction between KMnO₄ and MnSO₄ . The multifunctional MnO₂ shell facilitates electron and Li⁺ transport as well as efficiently prevents polysulfide dissolution via physical confinement and chemical interaction. Moreover, the γ-MnO₂ crystallographic form also provides one-dimensional (1D) tunnels for the Li⁺ incorporation to alleviate insoluble Li₂ S₂ /Li₂ S deposition at high discharge rate. More importantly, the MnO₂ phase transformation to Mn₃ O₄ occurs during the redox reaction between polysulfides and γ-MnO₂ is first thoroughly investigated. The S@γ-MnO₂ composite exhibits a good capacity retention of 82% after 300 cycles (0.5 C) and a fade rate of 0.07% per cycle over 600 cycles (1 C). The degradation mechanism can probably be elucidated that the decomposition of the surface Mn₃ O₄ phase is the cause of polysulfide dissolution. The recent work thus sheds new light on the hitherto unknown surface interaction mechanism and the degradation mechanism of Li-S cells.

Polysulfide Anchoring Mechanism Revealed by Atomic Layer Deposition of V2O5 and Sulfur-Filled Carbon Nanotubes for Lithium-Sulfur Batteries

Despite the promise of surface engineering to address the challenge of polysulfide shuttling in sulfur-carbon composite cathodes, melt infiltration techniques limit mechanistic studies correlating engineered surfaces and polysulfide anchoring. Here, we present a controlled experimental demonstration of polysulfide anchoring using vapor phase isothermal processing to fill the interior of carbon nanotubes (CNTs) after assembly into binder-free electrodes and atomic layer deposition (ALD) coating of polar V₂O₅ anchoring layers on the CNT surfaces. The ultrathin submonolayer V₂O₅ coating on the CNT exterior surface balances the adverse effect of polysulfide shuttling with the necessity for high sulfur utilization due to binding sites near the conductive CNT surface. The sulfur loaded into the CNT interior provides a spatially separated control volume enabling high sulfur loading with direct sulfur-CNT electrical contact for efficient sulfur conversion. By controlling ALD coating thickness, high initial discharge capacity of 1209 mAh/g_S at 0.1 C and exceptional cycling at 0.2 C with 87% capacity retention after 100 cycles and 73% at 450 cycles is achieved and correlated to an optimal V₂O₅ anchoring layer thickness. This provides experimental evidence that surface engineering approaches can be effective to overcome polysulfide shuttling by controlled design of molecular-scale building blocks for efficient binder free lithium sulfur battery cathodes.

A polymer enhanced sulfur/graphene aerogel as a no-slurry cathode for lithium–sulfur batteries

We presented a facile no-slurry method to synthesize a three-dimensional polyvinylpyrrolidone–sulfur/graphene aerogel composite, which can be pressed into flexible sheets and directly used as a cathode without any additives.

A review of flexible lithium–sulfur and analogous alkali metal–chalcogen rechargeable batteries

This review summarizes recent progress in flexible Li–S and analogous alkali metal–chalcogen batteries, including flexible chalcogen cathodes, flexible alkali metal anodes, flexible solid-state electrolytes, and flexible battery prototypes.

High performance of electrochemical lithium storage batteries: ZnO-based nanomaterials for lithium-ion and lithium-sulfur batteries

As one of the most promising electrode materials, zinc oxide-based nanomaterials have attracted great attention in recent decades for remarkable features such as relatively low cost, relatively high reversible capacity and good physical and chemical stability. In this article, we aim to present a general review of synthetic methods of zinc oxide-based nanomaterials and related morphologies. In addition, recent advances in lithium storage batteries are summarized and discussed (lithium-ion and lithium-sulfur batteries). Tentative conclusions and assessments aim to promote the next generation of electrochemical lithium storage devices.

Polysulfides Capture-Copper Additive for Long Cycle Life Lithium Sulfur Batteries

Copper powder was introduced into the lithium sulfur battery system to capture intermediate polysulfides and Cu_xS (x = 1 or 2) species was generated depending on the chain length of polysulfides. This phenomenon was verified by X-ray absorption near edge structure technique. The results indicated that copper can be oxidized to CuS by Li₂S_x (x ≥ 6), and a mixture of Cu₂S and CuS was obtained when x ranges from 3 to 6. While Cu₂S is eventually formed in the presence of Li₂S₃. After several cycles activation, the polysulfide-shuttle effect and self-discharge phenomenon which hinder the application of lithium sulfur batteries are found nearly eliminated Further experiments demonstrated that in the case of Cu₂S generation, a high specific sulfur capacity of 1300 mAh g^-1 could be delivered, corresponding to 77.6% sulfur utilization, while the Coulombic efficiency approximates around 100%. Self-discharge experiment further demonstrated that polysulfides almost disappear in the electrolyte, which verified the polysulfide-capture capability of copper.

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

Flexible nanostructured reduced graphene oxide-sulfur (rGO-S) composite films are fabricated by synchronously reducing and assembling GO sheets with S nanoparticles on a metal surface. The nanostructured architecture in such composite films not only provides effective pathways for electron transport, but also suppresses the diffusion of polysulfides. Furthermore, they can serve as the cathodes of flexible Li-S batteries.

Synergistic Design of Cathode Region for the High-Energy-Density Li-S Batteries

The synergistic design of cathode region was conducted to minimize the shuttle effect of polysulfides and decrease the loading of inactive components in order to acquire high-energy-density lithium-sulfur (Li-S) batteries. The well-designed cathode region presented two special characteristics: one was the intertwined nanofibers interlayer based on ultrafine TiO₂ nanocrystal uniformly embedded within N-doping porous carbon; the other was the lightweight and three-dimensional current collector of fibrous cellulose paper coated by reduced graphene oxide. In consequence, the decent reversible capacity of 874.8 mA h g^-1 was acquired at 0.1 C with a capacity retention of 91.83% after 100 cycles. Besides, the satisfactory capacity of 670 mA h g^-1 was delivered after 300 cycles at 1 C with the small decay rate of only 0.08%. Because of higher capacity and lower loading of inactive component in cathode region, the energy density of cell increased more than five times compared with unmodified cell. Moreover, to further enhance the energy density, the high-sulfur-loading electrode was fabricated. A good areal capacity of 4.27 mA h cm^-2 was retained for the cell with the active material of 4 mg cm^-2 and the cycle stability was also well-maintained. In addition, due to the flexibility of interlayer and current collector, Li-S full cell (in pouch cell format) was easily curved. Therefore, the synergistic design for cathode region, which combines the flexible and mass-produced interlayer and current collector together, provides an effective access to Li-S batteries with high energy density and flexibility for practical application.

Recent Development of Advanced Electrode Materials by Atomic Layer Deposition for Electrochemical Energy Storage

Electrode materials play a decisive role in almost all electrochemical energy storage devices, determining their overall performance. Proper selection, design and fabrication of electrode materials have thus been regarded as one of the most critical steps in achieving high electrochemical energy storage performance. As an advanced nanotechnology for thin films and surfaces with conformal interfacial features and well controllable deposition thickness, atomic layer deposition (ALD) has been successfully developed for deposition and surface modification of electrode materials, where there are considerable issues of interfacial and surface chemistry at atomic and nanometer scale. In addition, ALD has shown great potential in construction of novel nanostructured active materials that otherwise can be hardly obtained by other processing techniques, such as those solution-based processing and chemical vapor deposition (CVD) techniques. This review focuses on the recent development of ALD for the design and delivery of advanced electrode materials in electrochemical energy storage devices, where typical examples will be highlighted and analyzed, and the merits and challenges of ALD for applications in energy storage will also be discussed.

A review of recent developments in rechargeable lithium-sulfur batteries

The research and development of advanced energy-storage systems must meet a large number of requirements, including high energy density, natural abundance of the raw material, low cost and environmental friendliness, and particularly reasonable safety. As the demands of high-performance batteries are continuously increasing, with large-scale energy storage systems and electric mobility equipment, lithium-sulfur batteries have become an attractive candidate for the new generation of high-performance batteries due to their high theoretical capacity (1675 mA h g^-1) and energy density (2600 Wh kg^-1). However, rapid capacity attenuation with poor cycle and rate performances make the batteries far from ideal with respect to real commercial applications. Outstanding breakthroughs and achievements have been made to alleviate these problems in the past ten years. This paper presents an overview of recent advances in lithium-sulfur battery research. We cover the research and development to date on various components of lithium-sulfur batteries, including cathodes, binders, separators, electrolytes, anodes, collectors, and some novel cell configurations. The current trends in materials selection for batteries are reviewed and various choices of cathode, binder, electrolyte, separator, anode, and collector materials are discussed. The current challenges associated with the use of batteries and their materials selection are listed and future perspectives for this class of battery are also discussed.

Efficient Fabrication of Hierarchically Porous Graphene-Derived Aerogel and Its Application in Lithium Sulfur Battery

Hierarchically porous carbon/graphene aerogel (CGA) with relatively high surface area and pore volume is synthesized through an efficient fabrication strategy, which involves forming hydrothermal carbon layer on the pore wall as upholder and directly carbonizing the wet hydrogel from hydrothermal reaction, without using any special drying techniques. Cassava powder is used as carbon precursor which enables sustainable synthesis. Carbonizing the wet hydrothermal product is found to be a self-activation process, through which abundant pores are generated. The aerogel is used as host to encapsulate sulfur for lithium sulfur battery. Graphene, served as highly conductive scaffold, accelerates the transport of the electrons. The hierarchically porous structure is in favor of improving the electrochemical performance of lithium sulfur battery. Therefore, the cathode with high sulfur loading and high sulfur content can deliver very good performance.

Silicon dioxide molecular sieve with mono-layer carbon deposited in the channels and carbon nanotubes on the outside for lithium–sulfur batteries

A novel sulfur host matrix prepared by the deposition of mono-layer carbon into silicon dioxide molecular sieve channels and carbon nanotubes on the molecular sieve surface is proposed as an electrode material for lithium sulfur batteries.

A facile synthesis of three dimensional graphene sponge composited with sulfur nanoparticles for flexible Li–S cathodes

A novel 3DGS was fabricatedviaa reduction induced self-assembly method. When used as a sulfur cathode, it shows high rate discharge capacity retention up to 500 cycles.

Encapsulating sulfur into highly graphitized hollow carbon spheres as high performance cathode for lithium–sulfur batteries

Encapsulating sulfur into a highly graphitized hollow carbon sphere (GHCS) is proposed as sulfur cathode, the S@GHCS delivers a high discharge capacity of ∼800 mA h g⁻¹at 4C rate and high capacity retention of 93.7% after 240 cycles.

Three-dimensional sandwich-type graphene@microporous carbon architecture for lithium–sulfur batteries

The hierarchical microporous carbon and graphene stacked materials with high pore volume and ultrahigh surface area were designed for lithium–sulfur batteries.

Porous Carbon Mat as an Electrochemical Testing Platform for Investigating the Polysulfide Retention of Various Cathode Configurations in Li-S Cells

Two optimized cathode configurations (a porous current collector and an interlayer) are utilized to determine the better architecture for improving the cycle stability and reversibility of lithium-sulfur (Li-S) cells. The electrochemical analysis on the upper-plateau discharge capacity (QH) and the lower-plateau discharge capacity (QL) is introduced for assessing, respectively, the polysulfide retention and the electrochemical reactivity of the cell. The analysis results in line with the expected materials chemistry principles suggest that the interlayer configuration offers stable cell performance for sulfur cathodes. The significance of the interlayer is to block the free migration of the dissolved polysulfides, which is a key factor for immobilizing and continuously utilizing the active material in sulfur cathodes. Accordingly, the carbon mat interlayers provide sulfur cathodes with a high discharge capacity of 864 mA h g(-1) at 1 C rate with a high capacity retention rate of 61% after 400 cycles.

Controlling the shell formation in hydrothermally reduced graphene hydrogel

Graphene hydrogels/aerogels are emerging three-dimensional graphene macroscopic assemblies of potential use in many applications including energy storage, pollutant adsorption, and gas sensing. In this Letter, we identify, characterize and control the formation of the exterior shell structure of graphene hydrogels prepared via hydrothermal reduction of graphene oxide. Unlike the porous bulk of the hydrogel, the shell is a compact, highly ordered layer with a higher electrical conductivity. Shell formation is dependent upon the surface anchoring of graphene oxide at the liquid-air and liquid-container interfaces. By purposefully weakening surface anchoring of graphene oxide using mild thermal or chemical prereduction method prior to hydrothermal reduction, we have succeeded in completely suppressing shell formation in the graphene hydrogel. The resulting graphene hydrogel shows a lower volume reduction with a porous bulk structure immediately accessible from the surface, in contrast to graphene hydrogels prepared under conventional conditions.

Fabrication of a nano-Li+-channel interlayer for high performance Li–S battery application

Nano-Li⁺-channel membranes were first proposed and prepared for a Li–S battery, based on a concept of separating the polysulfide particles via size exclusion. This concept could help overcome the polysulfide permeating problems and provide more options for Li–S development.