Amorphous cobalt boride–activated carbon was synthesized via a one-step liquid phase reduction method and its electrochemical performance was studied.

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Interfacial engineering is one of the feasible pathways to tune the characteristics and functions of nanomaterials. In this report, we successfully synthesized crystalline CoWO 4 /amorphous Co−B heterostructures that enable superior electrochemical performance. The electrodes overcome the defect of low conductivity of cobalt tungstate and also expose more active sites. The optimized CoWO 4 /Co−B electrode has a remarkable specific capacity of 177.4 C g −1 at 0.5 A g −1 and a great specific capacity retention of 100% at 5 A g −1 after 10,000 cycles with reasonable cycling stability. Moreover, the Co−B/CoWo 4 electrode and activated carbon electrode are combined to assemble an asymmetric supercapacitor, which achieves 22.26 W h kg −1 maximum energy density at 200 W kg −1 and a capacity retention of 95.65% after 10,000 cycles at 2 A g −1 . In general, the work shows the unique characteristics of the crystalline/amorphous nanoheterostructure and provides a direction for future studies on increasing the electrochemical character and application of nanomaterials through regulating the interface contact of composites.

Lithium-ion hybrid capacitors (LIHCs) are considered as promising energy storage devices due to their high energy density of lithium-ion batteries and excellent power density of supercapacitors. The electrode material is the key to the performance of LIHCs. Therefore, a rod-like nanostructure of NiF 2 with a clear morphology was prepared by a simple hydrothermal method. The nanorod structure of NiF 2 shortens the transport distance of lithium ions and provides more active sites, thus showing excellent electrochemical performance. The specific capacity of the NR-NiF 2 electrode can reach 379 mA h g −1 after 500 cycles at 0.1 A g −1 and remains at 61 mA h g −1 after 10,000 cycles (a current density of 2 A g −1 ). Meanwhile, according to the fitting results of the peak current and sweep rate, b = 0.95 is obtained, indicating that the electrochemical behavior of the NR-NiF 2 material is dominated by pseudocapacitance. Furthermore, the LIHCs of NR-NiF 2 //AC are constructed and exhibit a high energy density of 87 W h kg −1 (at 96 W kg −1 ), a high power density of 6079 W kg −1 (at 27 W h kg −1 ), and an excellent cycle stability (capacity retention of 69% after 5000 cycles at 1 A g −1 ). Hence, NiF 2 nanorods with fast kinetic properties are a promising choice as an anode material for LIHCs.

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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 NiGa 2 O 4 /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 NiGa 2 O 4 /RGO has outstanding electrochemical properties and fast kinetic behavior. After 200 charge/discharge cycles, the discharge specific capacity of the composite NiGa 2 O 4 /RGO is stably maintained at 610.5 mA h g −1 and the Coulomb efficiency can reach about 99%. Moreover, in this article, we analyzed the capacitance characteristics of NiGa 2 O 4 /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.

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