Supercapacitive Performances of Ternary CuCo2S4 Sulfides.

Currently, ternary CuCo2S4 sulfides are intensively investigated as electrode materials for electrochemical capacitors due to their low cost, high conductivity, and synergistic effect. The research of CuCo2S4 materials for energy storage has gradually grown from 2016. The supercapacitive performances of CuCo2S4 electrodes for electrochemical capacitors are briefly reviewed in this work. The structure, morphology, and particle size of CuCo2S4 are related to the synthesis conditions and electrochemical performances. The thin films of CuCo2S4 nanostructures deposited on conductive substrates and their composites both show better properties than single CuCo2S4. CuCo2S4 and its composites reveal large potential for asymmetric capacitors, delivering high energy densities. However, there is still much new space remaining for future research. The possible development directions, challenges, and opportunities for CuCo2S4 materials are also discussed.

The Synthesis of NiCo2O4-MnO2 Core-Shell Nanowires by Electrodeposition and Its Supercapacitive Properties.

Hierarchical composite films grown on current collectors are popularly reported to be directly used as electrodes for supercapacitors. Highly dense and conductive NiCo2O4 nanowires are ideal backbones to support guest materials. In this work, low crystalline MnO2 nanoflakes are electrodeposited onto the surface of NiCo2O4 nanowire films pre-coated on nickel foam. Each building block in the composite films is a NiCo2O4-MnO2 core-shell nanowire on conductive nickel foam. Due to the co-presence of MnO2 and NiCo2O4, the MnO2@NiCo2O4@Ni electrode exhibits higher specific capacitance and larger working voltage than the NiCo2O4@Ni electrode. It can have a high specific capacitance of 1186 F·g-1 at 1 A·g-1. When the core-shell NiCo2O4-MnO2 composite and activated carbon are assembled as a hybrid capacitor, it has the highest energy density of 29.6 Wh·kg-1 at a power density of 425 W·kg-1 with an operating voltage of 1.7 V. This work shows readers an easy method to synthesize composite films for energy storage.

Research Progress of NiMn Layered Double Hydroxides for Supercapacitors: A Review.

The research on supercapacitors has been attractive due to their large power density, fast charge/discharge speed and long lifespan. The electrode materials for supercapacitors are thus intensively investigated to improve the electrochemical performances. Various transition metal layered double hydroxides (LDHs) with a hydrotalcite-like structure have been developed to be promising electrode materials. Earth-abundant metal hydroxides are very suitable electrode materials due to the low cost and high specific capacity. This is a review paper on NiMn LDHs for supercapacitor application. We focus particularly on the recent published papers using NiMn LDHs as electrode materials for supercapacitors. The preparation methods for NiMn LDHs are introduced first. Then, the structural design and chemical modification of NiMn LDH materials, as well as the composites and films derived from NiMn LDHs are discussed. These approaches are proven to be effective to enhance the performance of supercapacitor. Finally, the reports related to NiMn LDH-based asymmetric supercapacitors are summarized. A brief discussion of the future development of NiMn LDHs is also provided.

The effects of melamine on the formation of carbon xerogel derived from resorcinol and formaldehyde and its performance for supercapacitor.

Carbon aerogel/xerogel can be easily tuned to have hierarchical pores ranging from micropores to macropores. Nitrogen doping is considered to enhance the wettability and conductivity of the carbon electrode, hence improve the electrochemical performance. To prepare N-doped carbon xerogel and study the effects on the structure and the electrochemical performance of resorcinol and formaldehyde derived carbon xerogel, a series of Resorcinol-Melamine-Formaldehyde derived N-doped carbon xerogel were prepared by a facile sol-gel process and ambient drying method. With the increasing amount of melamine, the inside channels become larger, which contributes to faster ion transport and smaller charge transfer resistance (Rct). The Nitrogen content in carbon xerogel is also increased, enhancing the capacitance of carbon electrode by pseudocapacity effect, while damaging the rate performance by introducing more defects and larger degree of disorder. As a result, the best electrochemical performance is achieved in the RM-6-4 sample (resorcinol:melamine = 6:4), showing the largest capacitance of 139 F g-1.