Electrodeposited partially oxidized Bi & NiCo alloy based thin films for aqueous hybrid high energy microcapacitor

Abstract Electrochemical energy storage (EES) devices play an important role in meeting the demand for the electrical energy. Particularly, electrochemical hybrid capacitors (HCs) are considered as one of the potential candidates for fulfilling the energy requirement. In this work, aqueous electrolyte-based high voltage HC is fabricated and its electrochemical characteristics are analyzed. Here, electrochemically prepared NiCo and Bi thin films on stainless steel substrate were used as positive and negative electrodes, respectively. The phase structure and crystalline size of the electrodeposited films are confirmed from XRD and AFM. It is observed that the as prepared NiCo film showed an excellent specific capacitance value of 83.33 mF cm−2 at 0.5 mA cm−2; on the other side, Bi film also showed a good storage capacity of 32.2 μA h cm−2 at 1 mA cm−2; To realize the high energy density, Bi||NiCo combination of the thin film HC is fabricated and the HC devices showed excellent performance at a tested potential window of 1.5 V. The cell plateau voltage is observed at 0.8 V. The maximum specific energy density of 7.3 μW h was achieved at a specific power density is 0.3 mW cm−2. Maximum specific power of 7.5 mW cm−2 at an energy density of 1.875 μW h was obtained from HSC. This indicates the excellent performance of the HC at various conditions. Thus, the binder-free, electrodeposited active electrode materials of the present work will play a significant role in the various electronic applications by supplying the energy demand.