Ion modified cobalt-based layered double hydroxides and its derivatives as electrode materials for supercapacitors: A review and perspective

The transition metal cobalt is located in the eighth group of the fourth cycle and has a variety of chemically active valence states, which can form polyvalent cobalt-based compounds. Among them, cobalt based layered double hydroxides (LDH), as a promising anode material for pseudocapacitance, has a wide range of applications in electrochemical energy storage. However, the disadvantages of LDH such as the high resistance and the easy structure collapse in the process of charging and discharging lead to poor cycling performance, and the high price of cobalt metal limits its wide application. Therefore, doped metal elements replacing Co or phase transitions based on LDH designs can not only improve the structural stability and conductivity of materials, but also avoid expensive costs. In this paper, the structure characteristics, conduction mechanism and common synthesis methods of cobalt-based LDH in recent years are reviewed. Then, the recent progress in the field of supercapacitors of cationic doping Co-LDH and its derivatives (obtained by the phase transition of cobalt-based LDH) is summarized, with the emphasis on their conduction processes. Finally, the paper summarizes these works and puts forward some prospects.