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The Mott-Schottky heterostructure formed by the contact of intermetallic compound Co-B with N-type semiconductor NiMoO4helps to overcome the ion diffusion barrier and charge transport resistance during the charge and discharge process.

Lithium-ion batteries are widely used in various fields of social life because of their good cycle performance and high energy density. The excellent performance of the anode electrode material directly determines the performance of the prepared battery. In recent years, bimetallic oxides with the spinel structure have been widely studied. However, the volume change in its structure during charge and discharge leads to its electrochemical instability, which cannot meet the needs of lithium batteries. Inspired by this, the NiGa2O4/RGO composite electrode material with a special structure was successfully designed and prepared by a simple hydrothermal method and subsequent heat treatment. The electrochemical properties of composites and pure materials are analyzed and compared. From the test results, it can be seen that NiGa2O4/RGO has outstanding electrochemical properties and fast kinetic behavior. After 200 charge/discharge cycles, the discharge specific capacity of the composite NiGa2O4/RGO is stably maintained at 610.5 mA h g–1and the Coulomb efficiency can reach about 99%. Moreover, in this article, we analyzed the capacitance characteristics of NiGa2O4/RGO rarely reported in other articles, which enriched the research on the electrochemical properties of such substances. Finally, it contributes to promoting the feasibility of such bimetallic oxides in practical applications.

Thanks to the combination of the advantages of batteries and supercapacitors, battery-supercapacitor hybrid devices (BSHD) with higher power densities than batteries and higher energy densities than supercapacitors have aroused extensive concerns. Through the reasonable design of the capacity and kinetic characteristics of the cathode and anode, BSHD can provide individual advantages such as excellent properties, low cost, and safety. Li-ion BSHD has been widely studied because of lithium’s low potential and small ionic radius. However, the anode with slow electrode process dynamics is a great challenge for developing high-performance Li-ion BSHD. Consequently, it is essential to develop an electrode material with better electrical conductivity and a faster electrochemical reaction process. Here, an inverse spinel oxide iron gallium oxide (FeGa2O4, FGO) is designed with Fe2+occupying octahedral sites and Ga3+occupying tetrahedral sites. FGO pure phase was successfully synthesized by controlling the calcination temperature and atmosphere, and the experimental results were verified by X-ray diffraction (XRD). Subsequently, the electrochemical test of the half-cell shows that the capacity is stable at 500 mAh g–1after 200 cycles at a current density of 0.1 A g–1, showing that the electrode has extraordinary cycle stability. Meanwhile, the kinetics of the electrode process of the material was tested by pseudocapacitance calculations, electrochemical impedance spectra (EIS), and the galvanostatic intermittent titration technique (GITT). The results show that the material is suitable for Li-ion BSHD. The assembled Li-ion BSHD exhibits high energy density (up to 107.19 Wh kg–1), high power density (up to 4126.01 W kg–1), and long cycle life in a wide working voltage range (0.5–4.0 V). Therefore, this work has carried out a new research direction for Li-ion BSHD’s electrode materials with high performance.

Interfacial engineering has proved to be an effective strategy for improving the performance of electrode materials in many applications. Herein, we report the disorder-order engineering of VO2nanorods, and construct a crystal core and a surface-amorphized shell heterostructure (denoted as A-VO2) by simple hydrothermal method and reduction reaction, as a promising anode of lithium ion capacitor (LIC). The tunable amorphous layer introduces a large number of oxygen vacancy, which can efficiently improve electronic conductivity and enhance Li ion storage capacity. The crystalline-amorphous heterointerface generated in A-VO2can significantly reduce the surface energy of VO2and Li+diffusion barrier, as well as increase the charge storage sites. The crystalline-amorphous heterogeneous phases work synergistically to facilitate ion and electron transport and maintain structural stability in discharge/charge process. The A-VO2-2 nanorods electrode possesses high capacity of 309 mAh g−1at 0.1 A g−1after 300 cycles, obviously larger than the crystalline VO2electrode. In addition, the LIC, assembled with A-VO2-2 nanorods as anode and commercial active carbon (AC) as cathode, exhibit great energy density of 76.75 and 22.05 W h kg−1at power density of 195 and 9360 W kg−1. It can remain 38.9 % of the initial capacity after 5000 cycles, demonstrating an instructive paradigm for disorder-order engineering in LIC electrode materials.

The paramount focus in the construction of lithium-ion capacitors (LICs) is the development of anode materials with high reversible capacity and fast kinetics to overcome the mismatch of kinetics and capacity between the anode and cathode. Herein, a strategy is presented for the controllable synthesis of cobalt-based phosphides with various morphologies by adjusting the time of the phosphidation process, including 3D hierarchical needle-stacked diabolo-shaped CoP nanorods, 3D hierarchical stick-stacked diabolo-shaped Co2P nanorods, and 3D hierarchical heterostructure CoP@Co2P nanorods. 3D hierarchical nanostructures and a highly conductive project to accommodate volume changes are rational designs to achieve a robust construction, effective electron-ion transportation, and rapid kinetics characteristics, thus leading to excellent cycling stability and rate performance. Owing to these merits, the 3D hierarchical CoP, Co2P, and CoP@Co2P nanorods demonstrate prominent specific capacities of 573, 609, and 621 mA h g–1at 0.1 A g–1over 300 cycles, respectively. In addition, a high-performance CoP@Co2P//AC LIC is successfully constructed, which can achieve high energy densities of 166.2 and 36 W h kg–1at power densities of 175 and 17524 W kg–1(83.7% capacity retention after 12000 cycles). Therefore, the controllable synthesis of various simultaneously constructed crystalline phases and morphologies can be used to fabricate other advanced energy storage devices.

Exploring better electrochemical energy storage devices is a great challenge. Lithium‐ion capacitors have attracted much attention because they combine the advantages of Li‐ion batteries and supercapacitors, but the mismatch between the kinetics and capacity of the cathode and anode is still an extraordinary gap. In order to address this issue, a cubic‐phase perovskite fluoride KMnF3via a simple and safe coprecipitation way is synthesized. The KMnF3electrode exhibits a cubic‐phase structure and a pseudocapacitive kinetics by X‐ray diffractometer and cyclic voltammetry. The high specific capacity (189 mAh g−1at 0.1 A g−1for 500 cycles) and fast pseudocapacitive control dynamics (at the sweep speed of 0.2 mV s−1, the pseudocapacitance ratio is 62.12%) can be demonstrated in half cell, while the b‐value is up to 0.95. Further assembled with activate carbon to form lithium‐ion capacitors (LICs), KMnF3//AC delivers high energy density (24 Wh kg−1), high power density (3900 kW kg−1), and long cycle life over 4000 cycles. The findings shed lights on developing advanced electrode materials for high‐performance electrochemical LICs. The development of transition metal fluorides has been limited by the disadvantages of their inherent insulation and poor electronic conductivity. In order to effectively address this drawback, a simple coprecipitation method is used to synthesize the perovskite fluoride KMnF3material. Subsequently, a high energy density and power density energy storage device is obtained through a series of electrochemical tests.

•MnF2with high crystallinity was prepared by a simple one-step solvothermal method.•MnF2electrodes show an abnormal increase in specific capacity during cycling.•The causes of abnormal capacity growth were investigated using impedance analysis and SEM analysis.•A LIHC with MnF2as the anode and AC as the cathode was constructed to study the application of MnF2in energy storage devices.

The pseudocapacitive behavior is a hot research topic in the electrochemical field. There are two most widely studied types of pseudocapacitors: (i) based on the redox reaction pseudocapacitance represented by RuO2·xH2O, MnO2, and so on and (ii) the intercalation pseudocapacitive materials such as Nb2O5. It is important to study the pseudocapacitive mechanism and discover new materials with pseudocapacitive behavior for a clearer understanding of pseudocapacitive characteristics. Here, we discover and report the pseudocapacitive behavior of copper tungstate hydrate for the first time. Its cyclic voltammetry curve shape is similar to that of MXene (Ti3C2Tx), its potential window (−0.4 to 0.2 V) is also close to that of MXene, and its charge–discharge curve is almost an ideal isosceles triangle. These electrochemical analysis results indicate that the electrochemical behavior of CuWO4is a new type of intercalation pseudocapacitive behavior. In addition, because of the higher density of CuWO4(7.5 g cm–3), it exhibits an excellent volumetric specific capacitance of 743 F cm–3at 0.5 A g–1(similar to that of MXenes). The novel pseudocapacitive behavior of CuWO4reported in this work facilitates the development of a new material system for pseudocapacitive research. The follow-up studies are more concerned with how the pseudocapacitive behavior of this material occurs.

•The ammonia reduction reaction method provides a new pathway to converts the material from semiconductor to conductor.•The ammonia reduction reaction strategy can optimize the electronic conductivity.•The synthesized metallic Cu has good specific capacitance and excellent cycle performance (keep 114% of initial capacitance over 40,000 cycles).

So far, there are still some difficulties in controlling the pore structure of porous carbon materials. Exploring the relationship between the structure and electrochemical behavior of porous carbon through optimizing pore structure is of great significance for its application in the field of energy storage.Here, we employ the interpenetrating polymer networks as the precursor to prepare ultra-microporous carbon with a pore diameter of 0.6 nm, and regulate the mesoporous content by chemical activation. The relationship between mesoporosity and electrochemical performance was studied. In our experimental results, the optimized sample has a mesoporous ratio of 55.1% and the specific surface area of 2453 m2g−1. As electrode material, its specific capacity reaches 247F g−1with excellent cycle performance. As the symmetric device, its specific energy reached 17.75Wh kg−1.