Layered Transition Metal Dichalcogenide-Based Nanomaterials for Electrochemical Energy Storage

The rapid development of electrochemical energy storage (EES) systems requires novel electrode materials with high performance. A typical 2D nanomaterial, layered transition metal dichalcogenides (TMDs) are regarded as promising materials used for EES systems due to their large specific surface areas and layer structures benefiting fast ion transport. The typical methods for the preparation of TMDs and TMD-based nanohybrids are first summarized. Then, in order to improve the electrochemical performance of various kinds of rechargeable batteries, such as lithium-ion batteries, lithium–sulfur batteries, sodium-ion batteries, and other types of emerging batteries, the strategies for the design and fabrication of layered TMD-based electrode materials are discussed. Furthermore, the applications of layered TMD-based nanomaterials in supercapacitors, especially in untraditional supercapacitors, are presented. Finally, the existing challenges and promising future research directions in this field are proposed.     

Research Advances of Amorphous Metal Oxides in Electrochemical Energy Storage and Conversion

Amorphous metal oxides (AMOs) have aroused great enthusiasm across multiple energy areas over recent years due to their unique properties, such as the intrinsic isotropy, versatility in compositions, absence of grain boundaries, defect distribution, flexible nature, etc. Here, the materials engineering of AMOs is systematically reviewed in different electrochemical applications and recent advances in understanding and developing AMO‐based high‐performance electrodes are highlighted. Attention is focused on the important roles that AMOs play in various energy storage and conversion technologies, such as active materials in metal‐ion batteries and supercapacitors as well as active catalysts in water splitting, metal–air batteries, and fuel cells. The improvements of electrochemical performance in metal‐ion batteries and supercapacitors are reviewed regarding the enhancement in active sites, mechanical strength, and defect distribution of amorphous structures. Furthermore, the high electrochemical activities boosted by AMOs in various fundamental reactions are elaborated on and they are related to the electrocatalytic behaviors in water splitting, metal–air batteries, and fuel cells. The applications in electrochromism and high‐conducting sensors are also briefly discussed. Finally, perspectives on the existing challenges of AMOs for electrochemical applications are proposed, together with several promising future research directions.     

Three‐Dimensional Self‐Supported Metal Oxides for Advanced Energy Storage

The miniaturization of power sources aimed at integration into micro‐ and nano‐electronic devices is a big challenge. To ensure the future development of fully autonomous on‐board systems, electrodes based on self‐supported 3D nanostructured metal oxides have become increasingly important, and their impact is particularly significant when considering the miniaturization of energy storage systems. This review describes recent advances in the development of self‐supported 3D nanostructured metal oxides as electrodes for innovative power sources, particularly Li‐ion batteries and electrochemical supercapacitors. Current strategies for the design and morphology control of self‐supported electrodes fabricated using template, lithography, anodization and self‐organized solution techniques are outlined along with different efforts to improve the storage capacity, rate capability, and cyclability.     

Advanced Materials for Energy Storage

Popularization of portable electronics and electric vehicles worldwide stimulates the development of energy storage devices, such as batteries and supercapacitors, toward higher power density and energy density, which significantly depends upon the advancement of new materials used in these devices. Moreover, energy storage materials play a key role in efficient, clean, and versatile use of energy, and are crucial for the exploitation of renewable energy. Therefore, energy storage materials cover a wide range of materials and have been receiving intensive attention from research and development to industrialization. In this Review, firstly a general introduction is given to several typical energy storage systems, including thermal, mechanical, electromagnetic, hydrogen, and electrochemical energy storage. Then the current status of high‐performance hydrogen storage materials for on‐board applications and electrochemical energy storage materials for lithium‐ion batteries and supercapacitors is introduced in detail. The strategies for developing these advanced energy storage materials, including nanostructuring, nano‐/microcombination, hybridization, pore‐structure control, configuration design, surface modification, and composition optimization, are discussed. Finally, the future trends and prospects in the development of advanced energy storage materials are highlighted.     

金属氰胺化合物的结构、合成及电化学储能应用

金属氰胺化合物M_x(NCN)_y作为类氧硫族化合物, 是一类新兴的无机功能材料。准线性[NCN]^2-阴离子赋予其空旷和具有孔道的晶体结构、独特的电子结构和新奇的物化性质, 金属氰胺化合物在固态发光、光/电催化及电化学储能等诸多领域展现出应用前景, 近年来逐渐成为研究热点。本文简要回顾了金属氰胺化合物的研究历史, 概述了金属氰胺化合物的晶体结构及物化性质, 总结了常见合成方法及策略, 探讨了金属氰胺化合物在电化学储能领域的应用, 重点论述了其作为锂钠离子电池新型负极材料的电化学性能及存储机制。     

Recent Advances in Layered Ti3C2Tx MXene for Electrochemical Energy Storage

Ti₃C₂T_x, a typical representative among the emerging family of 2D layered transition metal carbides and/or nitrides referred to as MXenes, has exhibited multiple advantages including metallic conductivity, a plastic layer structure, small band gaps, and the hydrophilic nature of its functionalized surface. As a result, this 2D material is intensively investigated for application in the energy storage field. The composition, morphology and texture, surface chemistry, and structural configuration of Ti₃C₂T_x directly influence its electrochemical performance, e.g., the use of a well‐designed 2D Ti₃C₂T_x as a rechargeable battery anode has significantly enhanced battery performance by providing more chemically active interfaces, shortened ion‐diffusion lengths, and improved in‐plane carrier/charge‐transport kinetics. Some recent progresses of Ti₃C₂T_x MXene are achieved in energy storage. This Review summarizes recent advances in the synthesis and electrochemical energy storage applications of Ti₃C₂T_x MXene including supercapacitors, lithium‐ion batteries, sodium‐ion batteries, and lithium–sulfur batteries. The current opportunities and future challenges of Ti₃C₂T_x MXene are addressed for energy‐storage devices. This Review seeks to provide a rational and in‐depth understanding of the relation between the electrochemical performance and the nanostructural/chemical composition of Ti₃C₂T_x, which will promote the further development of 2D MXenes in energy‐storage applications.     

Flexible and Stretchable Energy Storage: Recent Advances and Future Perspectives

Energy‐storage technologies such as lithium‐ion batteries and supercapacitors have become fundamental building blocks in modern society. Recently, the emerging direction toward the ever‐growing market of flexible and wearable electronics has nourished progress in building multifunctional energy‐storage systems that can be bent, folded, crumpled, and stretched while maintaining their electrochemical functions under deformation. Here, recent progress and well‐developed strategies in research designed to accomplish flexible and stretchable lithium‐ion batteries and supercapacitors are reviewed. The challenges of developing novel materials and configurations with tailored features, and in designing simple and large‐scaled manufacturing methods that can be widely utilized are considered. Furthermore, the perspectives and opportunities for this emerging field of materials science and engineering are also discussed.     

MOF‐Derived Metal Oxide Composites for Advanced Electrochemical Energy Storage

Over the past two decades, metal–organic frameworks (MOFs), a type of porous material, have aroused great interest as precursors or templates for the derivation of metal oxides and composites for the next generation of electrochemical energy storage applications owing to their high specific surface areas, controllable structures, and adjustable pore sizes. The electrode materials, which affect the performance in practical applications, are pivotal components of batteries and supercapacitors. Metal oxide composites derived from metal–organic frameworks possessing high reversible capacity and superior rate and cycle performance are excellent electrode materials. In this Review, potential applications for MOF‐derived metal oxide composites for lithium‐ion batteries, sodium‐ion batteries, lithium–oxygen batteries, and supercapacitors are studied and summarized. Finally, the challenges and opportunities for future research on MOF‐derived metal oxide composites are proposed on the basis of academic knowledge from the reported literature as well as from experimental experience.     

Conjugated Polymers for Flexible Energy Harvesting and Storage

Since the discovery of conjugated polymers in the 1970s, they have attracted considerable interest in light of their advantages of having a tunable bandgap, high electroactivity, high flexibility, and good processability compared to inorganic conducting materials. The above combined advantages make them promising for effective energy harvesting and storage, which have been widely studied in recent decades. Herein, the key advancements in the use of conjugated polymers for flexible energy harvesting and storage are reviewed. The synthesis, structure, and properties of conjugated polymers are first summarized. Then, their applications in flexible polymer solar cells, thermoelectric generators, supercapacitors, and lithium‐ion batteries are described. The remaining challenges are then discussed to highlight the future direction in the development of conjugated polymers.     

Ti‐Based Oxide Anode Materials for Advanced Electrochemical Energy Storage: Lithium/Sodium Ion Batteries and Hybrid Pseudocapacitors

Titanium‐based oxides including TiO₂ and M‐Ti‐O compounds (M = Li, Nb, Na, etc.) family, exhibit advantageous structural dynamics (2D ion diffusion path, open and stable structure for ion accommodations) for practical applications in energy storage systems, such as lithium‐ion batteries, sodium‐ion batteries, and hybrid pseudocapacitors. Further, Ti‐based oxides show high operating voltage relative to the deposition of alkali metal, ensuring full safety by avoiding the formation of lithium and sodium dendrites. On the other hand, high working potential prevents the decomposition of electrolyte, delivering excellent rate capability through the unique pseudocapacitive kinetics. Nevertheless, the intrinsic poor electrical conductivity and reaction dynamics limit further applications in energy storage devices. Recently, various work and in‐depth understanding on the morphologies control, surface engineering, bulk‐phase doping of Ti‐based oxides, have been promoted to overcome these issues. Inspired by that, in this review, the authors summarize the fundamental issues, challenges and advances of Ti‐based oxides in the applications of advanced electrochemical energy storage. Particularly, the authors focus on the progresses on the working mechanism and device applications from lithium‐ion batteries to sodium‐ion batteries, and then the hybrid pseudocapacitors. In addition, future perspectives for fundamental research and practical applications are discussed.     

Localized Electrons Enhanced Ion Transport for Ultrafast Electrochemical Energy Storage

The rate-determining process for electrochemical energy storage is largely determined by ion transport occurring in the electrode materials. Apart from decreasing the distance of ion diffusion, the enhancement of ionic mobility is crucial for ion transport. Here, a localized electron enhanced ion transport mechanism to promote ion mobility for ultrafast energy storage is proposed. Theoretical calculations and analysis reveal that highly localized electrons can be induced by intrinsic defects, and the migration barrier of ions can be obviously reduced. Consistently, experiment results reveal that this mechanism leads to an enhancement of Li/Na ion diffusivity by two orders of magnitude. At high mass loading of 10 mg cm⁻² and high rate of 10C, a reversible energy storage capacity up to 190 mAh g⁻¹ is achieved, which is ten times greater than achievable by commercial crystals with comparable dimensions.     

Silica‐Mediated Formation of Nickel Sulfide Nanosheets on CNT Films for Versatile Energy Storage

An effective, nondestructive, and universal strategy to homogeneously modify freestanding carbon nanotube (CNT) films with various active species is essential to achieve functional electrodes for flexible electrochemical energy storage, which is challenging and has attracted considerable research interest. In this work, a generalizable concept, to utilize silicon oxide as the intermediate to uniformly decorate various metal sulfide nanostructures throughout CNT films is reported. Taking nickel sulfide nanosheet/CNT (NS/CNT) films, in which the NS nanosheets are homogeneously attached on the intact few‐walled CNTs, as an example, the sheet‐like NS provides sufficient active sites for redox reactions and the CNT network acts as an efficient electron highway, maintaining the structural integrity of the composite and also buffering volume changes. These merits enable NS/CNT films to meet the requirements of versatile energy storage applications. When used for supercapacitors, a high specific capacitance (2699.7 F g^?1/10 A g^?1), outstanding rate performance at extremely high rates (1527 F g^?1/250 A g^?1), remarkable cycling stability, and excellent flexibility can be achieved, among the best performance so far. Moreover, it also delivers excellent performance in the storage of Li and Na ions, meaning it is also potentially suitable for Li/Na ion batteries.     

Cellulose‐Based Nanomaterials for Energy Applications

Cellulose is the most abundant natural polymer on earth, providing a sustainable green resource that is renewable, degradable, biocompatible, and cost effective. Recently, nanocellulose‐based mesoporous structures, flexible thin films, fibers, and networks are increasingly developed and used in photovoltaic devices, energy storage systems, mechanical energy harvesters, and catalysts components, showing tremendous materials science value and application potential in many energy‐related fields. In this Review, the most recent advancements of processing, integration, and application of cellulose nanomaterials in the areas of solar energy harvesting, energy storage, and mechanical energy harvesting are reviewed. For solar energy harvesting, promising applications of cellulose‐based nanostructures for both solar cells and photoelectrochemical electrodes development are reviewed, and their morphology‐related merits are discussed. For energy storage, the discussion is primarily focused on the applications of cellulose‐based nanomaterials in lithium‐ion batteries, including electrodes (e.g., active materials, binders, and structural support), electrolytes, and separators. Applications of cellulose nanomaterials in supercapacitors are also reviewed briefly. For mechanical energy harvesting, the most recent technology evolution in cellulose‐based triboelectric nanogenerators is reviewed, from fundamental property tuning to practical implementations. At last, the future research potential and opportunities of cellulose nanomaterials as a new energy material are discussed.     

Mesoporous Nanoarchitectures for Electrochemical Energy Conversion and Storage

Mesoporous materials have attracted considerable attention because of their distinctive properties, including high surface areas, large pore sizes, tunable pore structures, controllable chemical compositions, and abundant forms of composite materials. During the last decade, there has been increasing research interest in constructing advanced mesoporous nanomaterials possessing short and open channels with efficient mass diffusion capability and rich accessible active sites for electrochemical energy conversion and storage. Here, the synthesis, structures, and energy-related applications of mesoporous nanomaterials are the main focus. After a brief summary of synthetic methods of mesoporous nanostructures, the delicate design and construction of mesoporous nanomaterials are described in detail through precise tailoring of the particle sizes, pore sizes, and nanostructures. Afterward, their applications as electrode materials for lithium-ion batteries, supercapacitors, water-splitting electrolyzers, and fuel cells are discussed. Finally, the possible development directions and challenges of mesoporous nanomaterials for electrochemical energy conversion and storage are proposed.     

锂离子电池正极材料LiNiO2的制备和性能研究

本文介绍了以氢氧化锂和氢氧化镍为原料通过高温法合成镍酸锂的方法,并讨论了合成了条件对产物电化学性能的影响。实验结果表明,合成反应温度,反应时间,Ｌｉ／Ｎｉ摩尔比对镍酸锂电化学性能有较大的影响,合成出具有电化学活性的镍酸锂需要严格控制反应条件。     

Heterocarbides Reinforced Electrochemical Energy Storage

The feasibility of transition metal carbides (TMCs) as promising high‐rate electrodes is still hindered by low specific capacity and sluggish charge transfer kinetics. Improving charge transport kinetics motivates research toward directions that would rely on heterostructures. In particular, heterocomposing with carbon‐rich TMCs is highly promising for enhancing Li storage. However, due to limited synthesis methods to prepare carbon‐rich TMCs, understanding the interfacial interaction effect on the high‐rate performance of TMCs is often neglected. In this work, a novel strategy is proposed to construct a binary carbide heteroelectrode, i.e. incorporating the carbon‐rich TMC (M=Mo) with its metal‐rich TMC nanowires (nws) via an ingenious in situ disproportionation reaction. Results show that the as‐prepared MoC‐Mo₂C‐heteronanowires (hnws) electrode could fully recover its capacity after high‐rates testing, and also possesses better lithium accommodation performance. Kinetic analysis verified that both electron and ion transfer in MoC‐Mo₂C‐hnws are superior to those of its singular counterparts. Such improvements suggest that by taking utilization of the interfacial component interactions of stoichiometry tunable heterocarbides, the electrochemical performance, especially high‐rate capability of carbides, could be significantly enhanced.     

碳纳米管的电化学贮锂性能研究

以纳米镍粉为催化剂,热分解法制备了碳纳米管.应用X射线衍射对碳纳米管的结构进行了研究,透射电子显微镜观察了碳纳米管的形貌.碳纳米管的直径在15nm左右,长>100nm,d₀₀₂为0.338nm.在结构上,纳米碳管具有与石墨类似的良好规整性,具有较高的可石墨化度,又具有纳米级的孔径,因此具有良好的贮锂性能.对碳纳米管的充放电性能研究结果表明,碳纳米管初始放电比容量为654mAh/g,高于纯石墨的理论容量372mAh/g,循环性能较好.     

High Areal Capacity Li‐Ion Storage of Binder‐Free Metal Vanadate/Carbon Hybrid Anode by Ion‐Exchange Reaction

Storing more energy in a limited device area is very challenging but crucial for the applications of flexible and wearable electronics. Metal vanadates have been regarded as a fascinating group of materials in many areas, especially in lithium‐ion storage. However, there has not been a versatile strategy to synthesize flexible metal vanadate hybrid nanostructures as binder‐free anodes for Li‐ion batteries so far. A convenient and versatile synthesis of M_xV_yO_x+2.5y@carbon cloth (M = Mn, Co, Ni, Cu) composites is proposed here based on a two‐step hydrothermal route. As‐synthesized products demonstrate hierarchical proliferous structure, ranging from nanoparticles (0D), and nanobelts (1D) to a 3D interconnected network. The metal vanadate/carbon hybrid nanostructures exhibit excellent lithium storage capability, with a high areal specific capacity up to 5.9 mAh cm^?2 (which equals to 1676.8 mAh g^?1) at a current density of 200 mA g^?1. Moreover, the nature of good flexibility, mixed valence states, and ultrahigh mass loading density (over 3.5 mg cm^?2) all guarantee their great potential in compact energy storage for future wearable devices and other related applications.