One-dimensional metal oxide-carbon hybrid nanostructures for electrochemical energy storage

Development of Cellulose Nanofiber-SnO2 Supported Nanocomposite as Substrate Materials for High-Performance Lithium-Ion Batteries

The large volumetric expansion of conversion-type anode materials (CTAMs) based on transition-metal oxides is still a big challenge for lithium-ion batteries (LIBs). An obtained nanocomposite was established by tin oxide (SnO₂) nanoparticles embedding in cellulose nanofiber (SnO₂-CNFi), and was developed in our research to take advantage of the tin oxide's high theoretical specific capacity and the cellulose nanofiber support structure to restrain the volume expansion of transition-metal oxides. The nanocomposite utilized as electrodes in lithium-ion batteries not only inhibited volume growth but also contributed to enhancing electrode electrochemical performance, resulting in the good capacity maintainability of the LIBs electrode during the cycling process. The SnO₂-CNFi nanocomposite electrode delivered a specific discharge capacity of 619 mAh g^-1 after 200 working cycles at the current rate of 100 mA g^-1. Moreover, the coulombic efficiency remained above 99% after 200 cycles showing the good stability of the electrode, and promising potential for commercial activity of nanocomposites electrode.

Reversible flowering of CuO nanoclusters via conversion reaction for dual-ion Li metal batteries

Dual-ion Li metal batteries based on non-flammable SO₂-in-salt inorganic electrolytes ( Li-SO₂ batteries) offer high safety and energy density. The use of cupric oxide (CuO) as a self-activating cathode material achieves a high specific capacity with cost-effective manufacturing in Li-SO₂ batteries, but its cycle retention performance deteriorates owing to the significant morphological changes of the cathode active materials. Herein, we report the catalytic effect of carbonaceous materials used in the cathode material of Li-SO₂ batteries, which act as templates to help recrystallize the active materials in the activation and conversion reactions. We found that the combination of oxidative-cyclized polyacrylonitrile (PAN) with N-doped carbonaceous materials and multi-yolk-shell CuO (MYS-CuO) nanoclusters as cathode active materials can significantly increase the specific capacity to 315.9 mAh g^- 1 (93.8% of the theoretical value) at 0.2 C, which corresponds to an energy density of 1295 Wh kg_CuO^-1, with a capacity retention of 84.46% at the 200th cycle, and the cathode exhibited an atypical blossom-like morphological change.

A Review on the Application of Cobalt-Based Nanomaterials in Supercapacitors

Among many electrode materials, cobalt-based nanomaterials are widely used in supercapacitors because of their high natural abundance, good electrical conductivity, and high specific capacitance. However, there are still some difficulties to overcome, including poor structural stability and low power density. This paper summarizes the research progress of cobalt-based nanomaterials (cobalt oxide, cobalt hydroxide, cobalt-containing ternary metal oxides, etc.) as electrode materials for supercapacitors in recent years and discusses the preparation methods and properties of the materials. Notably, the focus of this paper is on the strategies to improve the electrochemical properties of these materials. We show that the performance of cobalt-based nanomaterials can be improved by designing their morphologies and, among the many morphologies, the mesoporous structure plays a major role. This is because mesoporous structures can mitigate volume changes and improve the performance of pseudo capacitance. This review is dedicated to the study of several cobalt-based nanomaterials in supercapacitors, and we hope that future scholars will make new breakthroughs in morphology design.

Electrospinning-Based Carbon Nanofibers for Energy and Sensor Applications

Carbon nanofibers (CNFs) are the most basic structure of one-dimensional nanometer-scale sp2 carbon. The CNF’s structure provides fast current transfer and a large surface area and it is widely used as an energy storage material and as a sensor electrode material. Electrospinning is a well-known technology that enables the production of a large number of uniform nanofibers and it is the easiest way to mass-produce CNFs of a specific diameter. In this review article, we introduce an electrospinning method capable of manufacturing CNFs using a polymer precursor, thereafter, we present the technologies for manufacturing CNFs that have a porous and hollow structure by modifying existing electrospinning technology. This paper also discusses research on the applications of CNFs with various structures that have recently been developed for sensor electrode materials and energy storage materials.

Core-shell NiSe/Ni(OH)2with NiSe nanorods and Ni(OH)2nanosheets as battery-type electrode for hybrid supercapacitors

Novel core-shell nanostructure electrodes benefit from the excellent properties of their constituent materials, as well as the synergy between them. However, it is challenging to fabricate such structures efficiently. In this study, NiSe nanorods were fabricated using Ni foam as the conductive substrate and reactant via a one-step hydrothermal process, and Ni(OH)₂nanosheets were coated on the surface of the nanorods via one-step electrodeposition. The effect of the structure and morphology on the properties of the material was explored using scanning electron microscopy, x-ray diffraction, and electrochemical technology. The obtained core-shell NiSe/Ni(OH)₂exhibited an areal capacity of 1.89 mAh cm^-2at a current density of 5 mA cm^-2. The assembled NiSe/Ni(OH)₂//AC hybrid supercapacitor exhibited excellent energy and power densities, indicating that NiSe/Ni(OH)₂has great potential for use as a battery-type electrode in energy storage systems.

Rational Design and Engineering of One-Dimensional Hollow Nanostructures for Efficient Electrochemical Energy Storage

The unique structural characteristics of one-dimensional (1D) hollow nanostructures result in intriguing physicochemical properties and wide applications, especially for electrochemical energy storage applications. In this Minireview, we give an overview of recent developments in the rational design and engineering of various kinds of 1D hollow nanostructures with well-designed architectures, structural/compositional complexity, controllable morphologies, and enhanced electrochemical properties for different kinds of electrochemical energy storage applications (i.e. lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-selenium sulfur batteries, lithium metal anodes, metal-air batteries, supercapacitors). We conclude with prospects on some critical challenges and possible future research directions in this field. It is anticipated that further innovative studies on the structural and compositional design of functional 1D nanostructured electrodes for energy storage applications will be stimulated.

K2Ti6O13/carbon core-shell nanorods as a superior anode material for high-rate potassium-ion batteries

Bunches of oriented K2Ti6O13 nanorods coated by a thin carbon layer (4-7 nm) were prepared by combining hydrothermal and heat treatment in sequence. The K2Ti6O13 nanorods possess long- and short-axis crystal orientations of <010> and <001>, respectively, contributing to fast K+ diffusion, and the carbon-coating layer improves the electron conductivity. In addition, the obtained K2Ti6O13/carbon has a high compaction density, which is beneficial for realizing high volumetric specific capacity. When evaluated as a potassium-ion battery anode, the nanorods demonstrated a superior rate capability (122.5, 104.3, 92.3, 78.6 and 65.1 mA h g-1 at current densities of 20, 50, 100, 200 and 500 mA g-1, respectively), a favourable cycle life (118.5 mA h g-1 at 25 mA g-1 for 200 cycles) and high capacity retention.

Flexible 3D carbon cloth as a high-performing electrode for energy storage and conversion

High-performance energy storage and conversion devices with high energy density, power density and long-term cycling life are of great importance in current consumer electronics, portable electronics and electric vehicles. Carbon materials have been widely investigated and utilized in various energy storage and conversion devices due to their excellent conductivity, mechanical and chemical stability, and low cost. Abundant excellent reviews have summarized the most recent progress and future outlooks for most of the current prime carbon materials used in energy storage and conversion devices, such as carbon nanotubes, fullerene, graphene, porous carbon and carbon fibers. However, the significance of three-dimensional (3D) commercial carbon cloth (CC), one of the key carbon materials with outstanding mechanical stability, high conductivity and flexibility, in the energy storage and conversion field, especially in wearable electronics and flexible devices, has not been systematically summarized yet. In this review article, we present a careful investigation of flexible CC in the energy storage and conversion field. We first give a general introduction to the common properties of CC and the roles it has played in energy storage and conversion systems. Then, we meticulously investigate the crucial role of CC in typical electrochemical energy storage systems, including lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries and supercapacitors. Following a description of the wide application potential of CC in electrocatalytic hydrogen evolution, oxygen evolution/reduction, full-water splitting, etc., we will give a brief introduction to the application of CC in the areas of photocatalytically and photoelectrochemically induced solar energy conversion and storage. The review will end with a brief summary of the typical superiorities that CC has in current energy conversion and storage systems, as well as providing some perspectives and outlooks on its future applications in the field. Our main interest will be focused on CC-based flexible devices due to the inherent superiority of CC and the increasing demand for flexible and wearable electronics.

Fabrication of Fe7S8/C flexible nanofibers with nano-buffered spaces and their application in Li-ion batteries

The Fe₇S₈/C flexible nanofibers with nano-buffered spaces are prepared without using any template, and exhibit excellent electrochemical properties.

Rationally engineered 3D-dendritic cell-like morphologies of LDH nanostructures using graphene-based core-shell structures

Functionalization of graphene-based materials using chemical moieties not only modify the electronic structure of the underlying graphene but also enable in limited enhancement of targeted properties. Surface modification of graphene-based materials using other nanostructures enhances the effective properties by minimally modifying the properties of pristine graphene backbone. In this pursuit, we have synthesized bio-inspired hierarchical nanostructures based on Ni-Co layered double hydroxide on reduced graphene oxide core-shells using template based wet chemical approach. The material synthesized have been characterized structurally and electrochemically. The fabricated dendritic morphology of the composite delivers a high specific capacity of 1056 Cg^-1. A cost effective solid state hybrid supercapacitor device was also fabricated using the synthesized electrode material which shows excellent performance with high energy density and fast charging capability.

1D Carbon-Based Nanocomposites for Electrochemical Energy Storage

Electrochemical energy storage (EES) devices have attracted immense research interests as an effective technology for utilizing renewable energy. 1D carbon-based nanostructures are recognized as highly promising materials for EES application, combining the advantages of functional 1D nanostructures and carbon nanomaterials. Here, the recent advances of 1D carbon-based nanomaterials for electrochemical storage devices are considered. First, the different categories of 1D carbon-based nanocomposites, namely, 1D carbon-embedded, carbon-coated, carbon-encapsulated, and carbon-supported nanostructures, and the different synthesis methods are described. Next, the practical applications and optimization effects in electrochemical energy storage devices including Li-ion batteries, Na-ion batteries, Li-S batteries, and supercapacitors are presented. After that, the advanced in situ detection techniques that can be used to investigate the fundamental mechanisms and predict optimization of 1D carbon-based nanocomposites are discussed. Finally, an outlook for the development trend of 1D carbon-based nanocomposites for EES is provided.

Hydrothermal Coating of Patterned Carbon Nanotube Forest for Structured Lithium-Ion Battery Electrodes

Controlling the arrangement and interface of nanoparticles is essential to achieve good transfer of charge, heat, or mechanical load. This is particularly challenging in systems requiring hybrid nanoparticle mixtures such as combinations of organic and inorganic materials. This work presents a process to coat vertically aligned carbon nanotube (CNT) forests with metal oxide nanoparticles using microwave-assisted hydrothermal synthesis. Hydrothermal processes normally damage delicate CNT forests, which is addressed here by a combination of lithographic patterning, transfer printing, and reduction of the synthesis time. This process is applied for the fabrication of structured Li-ion battery (LIB) electrodes where the aligned CNTs provide a straight electron transport path through the electrode and the hydrothermal coating process is used to coat the CNTs with conversion anode materials for LIBs. These nanoparticles are anchored on the surface of the CNTs and batteries fabricated following this process show a fourfold longer cyclability. Finally, this process is used to create thick electrodes (350 µm) with a gravimetric capacity of over 900 mAh g^-1 .

From fluorene molecules to ultrathin carbon nanonets with an enhanced charge transfer capability for supercapacitors

It is a big challenge to synthesize ultrathin carbon nanonets with an enhanced charge transfer capability for high-performance energy storage devices. Herein, ultrathin carbon nanonets (UCNs) were successfully synthesized for the first time from fluorene, a typical aromatic molecule, by a template strategy for supercapacitors. The formation mechanism of UCNs was determined using Density Functional Theory and Materials Studio, in which the fluorene-derived radicals were assembled into UCNs in the template-confinement space with the assistance of KOH. The as-made UCNs feature interconnected high-conductivity net-like architectures with enhanced charge transfer capability, evidenced by their high capacitance, excellent rate performance and cycling stability for symmetrical supercapacitors in a KOH electrolyte. This finding may provide a significant step forward in understanding the formation mechanism of graphene-like materials from more complicated aromatic hydrocarbon molecules, and our work may draw wide attention in the fields of aromatic chemistry and carbon-based energy storage materials.

Cobalt Sulfide Confined in N-Doped Porous Branched Carbon Nanotubes for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are considered new generation of large-scale energy-storage devices. However, LIBs suffer from a lack of desirable anode materials with excellent specific capacity and cycling stability. In this work, we design a novel hierarchical structure constructed by encapsulating cobalt sulfide nanowires within nitrogen-doped porous branched carbon nanotubes (NBNTs) for LIBs. The unique hierarchical Co₉S₈@NBNT electrode displayed a reversible specific capacity of 1310 mAh g^-1 at a current density of 0.1 A g^-1, and was able to maintain a stable reversible discharge capacity of 1109 mAh g^-1 at a current density of 0.5 A g^-1 with coulombic efficiency reaching almost 100% for 200 cycles. The excellent rate and cycling capabilities can be ascribed to the hierarchical porosity of the one-dimensional Co₉S₈@NBNT internetworks, the incorporation of nitrogen doping, and the carbon nanotube confinement of the active cobalt sulfide nanowires offering a proximate electron pathway for the isolated nanoparticles and shielding of the cobalt sulfide nanowires from pulverization over long cycling periods.

A ternary Ag–TiO2/reduced graphene oxide nanocomposite as the anode material for lithium ion batteries

A Ag–TiO₂/rGO nanocomposite exhibits enhanced electrochemical performance with good stability, as the intra-/inter-grain connectivity is increased between nanosized Ag and TiO₂ particles on the reduced graphene oxide surface.

Ultralong Ca2B2O5·H2O nanowires: water-bath pretreated eco-friendly hydrothermal synthesis, optical and rare earth-doped photoluminescence properties

A facile water-bath pretreated hydrothermal route is developed for ultralong Ca₂B₂O₅·H₂O nanowires (length: <230 μm) as a promising photoluminescent host candidate.

Bottom-Up Construction of Reduced-Graphene-Oxide-Anchored MnO with an Nitrogen-Doped Carbon Coating for Synergistically Improving Lithium-Ion Storage

Designing an advanced architecture to overcome the innate issue of MnO-based anode materials in terms of low electrical conductivity and severe volume change during cycling is still a challenge toward which more effort needs devoted. Here, an intriguing hybrid involving the architecture of reduced graphene oxide (RGO)-anchored MnO within an nitrogen-codoped carbon coating (RGO-MnO@NC) is reported via a simple and facile approach and regarded as a promising lithium-ion (Li⁺) anode material with high rate capacity, large specific capacity, and a long cycle lifespan simultaneously. The resulting porous conductive carbon layer could not only promote the electron/ion transfer but also alleviate the volume variation for retaining a relatively stable solid electrolyte interphase and prevent MnO from direct contact with the electrolyte to reduce unexpected lithium consumption. The existing internal voids offer the space to accommodate volume expansion in the lithiation/delithiation processes, and RGO could build a large conductive network for better electron transfer. Consequently, the RGO-MnO@NC electrode presents high Li⁺ storage capacity (699 mAh g^-1 at 0.1 A g^-1), excellent cycling performance (607 mAh g^-1 at 1 A g^-1 over 550 cycles), and a remarkable rate performance. Through kinetic analysis, it is revealed that RGO-MnO@NC exhibits an enhanced capacitive contribution for Li⁺ storage, showing a typical faradaic surface pseudocapacitive mechanism. This work proposes a new strategy to ameliorate the deficiency of the electrode material toward the conductivity and volume change for enhanced Li⁺ storage.

The Design and Synthesis of Hollow Micro-/Nanostructures: Present and Future Trends

Hollow micro-/nanostructures have attracted tremendous interest owing to their intriguing structure-induced physicochemical properties and great potential for widespread applications. With the development of modern synthetic methodology and analytical instruments, a rapid structural/compositional evolution of hollow structures from simple to complex has occurred in recent decades. Here, an updated overview of research progress made in the synthesis of hollow structures is provided. After an introduction of definition and classification, achievements in synthetic approaches for these delicate hollow architectures are presented in detail. According to formation mechanisms, these strategies can be categorized into four different types, including hard-templating, soft-templating, self-templated, and template-free methods. In particular, the rationales and emerging innovations in conventional templating syntheses are in focus. The development of burgeoning self-templating strategies based on controlled etching, outward diffusion, and heterogeneous contraction is also summarized. In addition, a brief overview of template-free methods and recent advances on combined mechanisms is provided. Notably, the strengths and weaknesses of each category are discussed in detail. In conclusion, a perspective on future trends in the research of hollow micro-/nanostructures is given.

Molecular-Scale Functionality on Graphene To Unlock the Energy Capabilities of Metal Hydrides for High-Capacity Lithium-Ion Batteries

Metal hydrides have attracted great intentions as anodes for lithium-ion batteries (LIBs) due to their extraordinary theoretical capacity. It is an unsolved challenge, however, to achieve high capacity with stable cyclability, owing to their insulating property and large volume expansion upon lithium storage. Here, we introduce self-initiated polymerization to realize molecular-scale functionality of metal hydrides with conductive polymer, that is, polythiophene (PTh), on graphene, leading to the formation of MgH₂@PTh core-shell nanoparticles on graphene. The nanoscale characteristics of MgH₂ not only relieve the induced stress upon volume changes but also allow fast diffusivity and high reactivity for Li-ion transport. More importantly, the conformal coating of ultrathin PTh membrane can effectively suppress the detrimental reactions between MgH₂ and electrolyte, provide enhanced performance with facile electron and Li⁺ transport, and preserve its structural integrity, attributed to the strong molecular interaction between PTh and MgH₂ as well as its various products during electrochemical reactions. With this structure, a high reversible specific capacity of 1311 mAh g^-1 at 100 mA g^-1, excellent rate performance of 1025 mAh g^-1 at 2000 mA g^-1, and a capacity retention of 84.5% at 2000 mA g^-1 after 500 cycles are observed for MgH₂@PTh nanoparticles as anode for LIBs.

Fabrication of a 3D Hierarchical Sandwich Co9 S8 /α-MnS@N-C@MoS2 Nanowire Architectures as Advanced Electrode Material for High Performance Hybrid Supercapacitors

Supercapacitors suffer from lack of energy density and impulse the energy density limit, so a new class of hybrid electrode materials with promising architectures is strongly desirable. Here, the rational design of a 3D hierarchical sandwich Co₉ S₈ /α-MnS@N-C@MoS₂ nanowire architecture is achieved during the hydrothermal sulphurization reaction by the conversion of binary mesoporous metal oxide core to corresponding individual metal sulphides core along with the formation of outer metal sulphide shell at the same time. Benefiting from the 3D hierarchical sandwich architecture, Co₉ S₈ /α-MnS@N-C@MoS₂ electrode exhibits enhanced electrochemical performance with high specific capacity/capacitance of 306 mA h g^-1 /1938 F g^-1 at 1 A g^-1 , and excellent cycling stability with a specific capacity retention of 86.9% after 10 000 cycles at 10 A g^-1 . Moreover, the fabricated asymmetric supercapacitor device using Co₉ S₈ /α-MnS@N-C@MoS₂ as the positive electrode and nitrogen doped graphene as the negative electrode demonstrates high energy density of 64.2 Wh kg^-1 at 729.2 W kg^-1 , and a promising energy density of 23.5 Wh kg^-1 is still attained at a high power density of 11 300 W kg^-1 . The hybrid electrode with 3D hierarchical sandwich architecture promotes enhanced energy density with excellent cyclic stability for energy storage.

MnWO4 nanoparticles as advanced anodes for lithium-ion batteries: F-doped enhanced lithiation/delithiation reversibility and Li-storage properties

F-Doped MnWO4 nano-particles were synthesized by a one-pot hydrothermal reaction. When evaluated as an electrode material for a Li ion battery, the F-doped nano-MnWO4 delivers a theoretical capacity of 708 mA h g-1 and a long cycle life, as demonstrated by more than 85% capacity retention when cycled for 150 cycles.

Latest advances in supercapacitors: from new electrode materials to novel device designs

Notably, many significant breakthroughs for a new generation of supercapacitors have been reported in recent years, related to theoretical understanding, material synthesis and device designs. Herein, we summarize the state-of-the-art progress toward mechanisms, new materials, and novel device designs for supercapacitors. Firstly, fundamental understanding of the mechanism is mainly focused on the relationship between the structural properties of electrode materials and their electrochemical performances based on some in situ characterization techniques and simulations. Secondly, some emerging electrode materials are discussed, including metal-organic frameworks (MOFs), covalent organic frameworks (COFs), MXenes, metal nitrides, black phosphorus, LaMnO₃, and RbAg₄I₅/graphite. Thirdly, the device innovations for the next generation of supercapacitors are provided successively, mainly emphasizing flow supercapacitors, alternating current (AC) line-filtering supercapacitors, redox electrolyte enhanced supercapacitors, metal ion hybrid supercapacitors, micro-supercapacitors (fiber, plane and three-dimensional) and multifunctional supercapacitors including electrochromic supercapacitors, self-healing supercapacitors, piezoelectric supercapacitors, shape-memory supercapacitors, thermal self-protective supercapacitors, thermal self-charging supercapacitors, and photo self-charging supercapacitors. Finally, the future developments and key technical challenges are highlighted regarding further research in this thriving field.

Group 6 transition metal dichalcogenide nanomaterials: synthesis, applications and future perspectives

Group 6 transition metal dichalcogenides (G6-TMDs), most notably MoS₂, MoSe₂, MoTe₂, WS₂ and WSe₂, constitute an important class of materials with a layered crystal structure. Various types of G6-TMD nanomaterials, such as nanosheets, nanotubes and quantum dot nano-objects and flower-like nanostructures, have been synthesized. High thermodynamic stability under ambient conditions, even in atomically thin form, made nanosheets of these inorganic semiconductors a valuable asset in the existing library of two-dimensional (2D) materials, along with the well-known semimetallic graphene and insulating hexagonal boron nitride. G6-TMDs generally possess an appropriate bandgap (1-2 eV) which is tunable by size and dimensionality and changes from indirect to direct in monolayer nanosheets, intriguing for (opto)electronic, sensing, and solar energy harvesting applications. Moreover, rich intercalation chemistry and abundance of catalytically active edge sites make them promising for fabrication of novel energy storage devices and advanced catalysts. In this review, we provide an overview on all aspects of the basic science, physicochemical properties and characterization techniques as well as all existing production methods and applications of G6-TMD nanomaterials in a comprehensive yet concise treatment. Particular emphasis is placed on establishing a linkage between the features of production methods and the specific needs of rapidly growing applications of G6-TMDs to develop a production-application selection guide. Based on this selection guide, a framework is suggested for future research on how to bridge existing knowledge gaps and improve current production methods towards technological application of G6-TMD nanomaterials.

Towards flexible solid-state supercapacitors for smart and wearable electronics

Flexible solid-state supercapacitors (FSSCs) are frontrunners in energy storage device technology and have attracted extensive attention owing to recent significant breakthroughs in modern wearable electronics. In this study, we review the state-of-the-art advancements in FSSCs to provide new insights on mechanisms, emerging electrode materials, flexible gel electrolytes and novel cell designs. The review begins with a brief introduction on the fundamental understanding of charge storage mechanisms based on the structural properties of electrode materials. The next sections briefly summarise the latest progress in flexible electrodes (i.e., freestanding and substrate-supported, including textile, paper, metal foil/wire and polymer-based substrates) and flexible gel electrolytes (i.e., aqueous, organic, ionic liquids and redox-active gels). Subsequently, a comprehensive summary of FSSC cell designs introduces some emerging electrode materials, including MXenes, metal nitrides, metal-organic frameworks (MOFs), polyoxometalates (POMs) and black phosphorus. Some potential practical applications, such as the development of piezoelectric, photo-, shape-memory, self-healing, electrochromic and integrated sensor-supercapacitors are also discussed. The final section highlights current challenges and future perspectives on research in this thriving field.

Auto-generated iron chalcogenide microcapsules ensure high-rate and high-capacity sodium-ion storage

Sodium-ion batteries (SIBs) are regarded as promising alternative energy-storage devices to lithium-ion batteries (LIBs). However, the trade-off of between energy density and power density under high mass-loading conditions restricts the application of SIBs. Herein, we synthesized an FeSe@FeS material via a facile solid-state reaction. A microcapsule architecture was spontaneously achieved in this process, which facilitated electron transport and provided stable diffusion paths for Na ions. The FeSe@FeS material exhibits a high capacity retention (485 mA h g^-1 at 3 A g^-1 after 1400 cycles) and superior rate capability (230 mA h g^-1 at 10 A g^-1 after 1600 cycles) in the half-cell test. Furthermore, superior cycling stability is achieved in the full-cell test. The high mass-loaded FeSe@FeS electrodes (8 mg cm^-2) realize a high areal capacity retention of 2.8 mA h cm^-2 and high thermal stability.

Design and synthesis of nanoporous carbon materials using Cd-based homochiral metal–organic frameworks as precursors for supercapacitor application

Design and synthesis of nanoporous carbon materials using Cd-based homochiral metal–organic frameworks as precursors for supercapacitor application.

In Situ Fabrication of Hierarchically Branched TiO2 Nanostructures: Enhanced Performance in Photocatalytic H2 Evolution and Li-Ion Batteries

1D branched TiO₂ nanomaterials play a significant role in efficient photocatalysis and high-performance lithium ion batteries. In contrast to the typical methods which generally have to employ epitaxial growth, the direct in situ growth of hierarchically branched TiO₂ nanofibers by a combination of the electrospinning technique and the alkali-hydrothermal process is presented in this work. Such the branched nanofibers exhibit improvement in terms of photocatalytic hydrogen evolution (0.41 mmol g^-1 h^-1 ), in comparison to the conventional TiO₂ nanofibers (0.11 mmol g^-1 h^-1 ) and P25 (0.082 mmol g^-1 h^-1 ). Furthermore, these nanofibers also deliver higher lithium specific capacity at different current densities, and the specific capacity at the rate of 2 C is as high as 201. 0 mAh g^-1 , roughly two times higher than that of the pristine TiO₂ nanofibers.

Nanoflakes of Ni-Co LDH and Bi2O3 Assembled in 3D Carbon Fiber Network for High-Performance Aqueous Rechargeable Ni/Bi Battery

For aqueous nickel/metal batteries, low energy density and poor rate properties are among the limiting factors for their applications, although they are the energy storage systems with high safety, high capacity, and low production cost. Here, we have developed a class of active materials consisting of porous nanoflakes of Ni-Co hydroxides and Bi₂O₃ that are successfully assembled on carbon substrates of carbon cloth/carbon nanofiber 3D network (CC/CNF). The combination of the porous Ni-Co hydroxides/Bi₂O₃ nanoflakes with carbon substrate of 3D network is able to provide a large surface area, excellent conductivity, and promote synergistic effects, as a result of the interaction between the active materials and the carbon matrix. With the porous Ni-Co hydroxides and Bi₂O₃ nanoflakes, the Ni/Bi battery can deliver a high capacity of ∼110 mA h g^-1 at a current density of 2 A g^-1. About 80% of its capacity (85 mA h g^-1) can be retained when the current density increases to 20 A g^-1. The full cell can also maintain 93% of the initial capacity after 1000 charge/discharge cycles, showing great potential for Ni/Bi battery.

Tuning the Shell Number of Multishelled Metal Oxide Hollow Fibers for Optimized Lithium-Ion Storage

Searching the long-life transition-metal oxide (TMO)-based materials for future lithium-ion batteries (LIBs) is still a great challenge because of the mechanical strain resulting from volume change of TMO anodes during the lithiation/delithiation process. To well address this challenging issue, we demonstrate a controlled method for making the multishelled TMO hollow microfibers with tunable shell numbers to achieve the optimal void for efficient lithium-ion storage. Such a particularly designed void can lead to a short diffusion distance for fast diffusion of Li⁺ ions and also withstand a large volume variation upon cycling, both of which are the key for high-performance LIBs. Triple-shelled TMO hollow microfibers are a quite stable anode material for LIBs with high reversible capacities (NiO: 698.1 mA h g^-1 at 1 A g^-1; Co₃O₄: 940.2 mA h g^-1 at 1 A g^-1; Fe₂O₃: 997.8 mA h g^-1 at 1 A g^-1), excellent rate capability, and stability. The present work opens a way for rational design of the void of multiple shells in achieving the stable lithium-ion storage through the biomass conversion strategy.

Porous One-Dimensional Nanomaterials: Design, Fabrication and Applications in Electrochemical Energy Storage

Electrochemical energy storage technology is of critical importance for portable electronics, transportation and large-scale energy storage systems. There is a growing demand for energy storage devices with high energy and high power densities, long-term stability, safety and low cost. To achieve these requirements, novel design structures and high performance electrode materials are needed. Porous 1D nanomaterials which combine the advantages of 1D nanoarchitectures and porous structures have had a significant impact in the field of electrochemical energy storage. This review presents an overview of porous 1D nanostructure research, from the synthesis by bottom-up and top-down approaches with rational and controllable structures, to several important electrochemical energy storage applications including lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, lithium-oxygen batteries and supercapacitors. Highlights of porous 1D nanostructures are described throughout the review and directions for future research in the field are discussed at the end.

Metastable Marcasite-FeS2 as a New Anode Material for Lithium Ion Batteries: CNFs-Improved Lithiation/Delithiation Reversibility and Li-Storage Properties

Marcasite (m-FeS₂) exhibits higher electronic conductivity than that of pyrite (p-FeS₂) because of its lower semiconducting gap (0.4 vs 0.7 eV). Meanwhile, as demonstrates stronger Fe-S bonds and less S-S interactions, the m-FeS₂ seems to be a better choice for electrode materials compared to p-FeS₂. However, the m-FeS₂ has been seldom studied due to its sophisticated synthetic methods until now. Herein, a hierarchical m-FeS₂ and carbon nanofibers composite (m-FeS₂/CNFs) with grape-cluster structure was designed and successfully prepared by a straightforward hydrothermal method. When evaluated as an electrode material for lithium ion batteries, the m-FeS₂/CNFs exhibited superior lithium storage properties with a high reversible capacity of 1399.5 mAh g^-1 after 100 cycles at 100 mA g^-1 and good rate capability of 782.2 mAh g^-1 up to 10 A g^-1. The Li-storage mechanism for the lithiation/delithiation processes of m-FeS₂/CNFs was systematically investigated by ex situ powder X-ray diffraction patterns and scanning electron microscopy. Interestingly, the hierarchical m-FeS₂ microspheres assembled by small FeS₂ nanoparticles in the m-FeS₂/CNFs composite converted into a mimosa with leaves open shape during Li⁺ insertion process and vice versa. Accordingly, a "CNFs accelerated decrystallization-recrystallization" mechanism was proposed to explain such morphology variations and the decent electrochemical performance of m-FeS₂/CNFs.