Review and prospect of NiCo2O4-based composite materials for supercapacitor electrodes

Supercapacitors known as typical electrochemical capacitors have been considered as one of the most promising candidates of energy storage systems owing to their advantages such as high-power density, long life span and lower production cost. The electrode materials play a crucial role on properties of supercapacitors. Hence, many researches have been focused on the development of novel electrode materials for high-performance supercapacitors. NiCo2O4 as supercapacitor electrode material has drawn more and more attentions in recent years due to its outstanding advantages, such as high theoretical capacity, low cost, natural abundance and easy of synthesis. However, the NiCo2O4 always suffer from severe capacity deterioration because of the low electrical conductivity and small surface area. Hence, it is necessary to systematically and comprehensively summarize the progress in understanding and modifying NiCo2O4-based materials from various aspects. In this review, the structure and synthesis method of NiCo2O4-based materials are discussed in detail. And then, the major goal of this review is to highlight new progress in using proposed strategies to improve the cycling stability and rate capacity of NiCo2O4-based materials, including synthesis, control of special morphologies and design of composite materials. Finally, an insight into the future research and development of NiCo2O4-based materials for supercapacitors is prospected.