The structures of CoFe2O4/PEDOT electrodes effect on the stability and specific capacity for electrochemical energy storage

Developing electrodes with high stability and high specific capacity are two strategies to promote the application of supercapacitors. However, high specific capacity electrodes possess poor cycling stability, and good cycling performance electrode possesses low specific capacity, so it is difficult to achieve a balance. The stability of nano-sized metal oxides is reduced due to the collapse of their nanostructures during the cyclic process. Thus, the channel of electron transmission is destroyed, and the conduction of charge is not smooth. Therefore, we select electrodes with highest specific capacity and better cycling performance from many structures of CoFe2O4 electrodes that are controllable designed by solvent ratio and structure-directing agent, such as chain, sphere, box, belt etc. In addition, we use an electrochemical method to coat the electrode with a layer of PEDOT to increase the conductivity and cyclic stability for practical application. Hence, the NF/CoFe2O4 sphere/PEDOT as cathode indicates an outstanding specific capacity of 299.2 mAh g−1 at 1 A g−1. The energy density is 230.4 Wh kg−1 (power density of 616 W kg−1). The aqueous hybrid supercapacitor shows a good cycle life, after 2000 cycles the capacity retention is 91.7%. The maximum current and self-discharge phenomena of mechanical energy charging are also studied and it is demonstrated that it has good tolerance to large current, which is suitable for mechanical energy charging.