Investigation of ilmenite structured NiMnO3-metal oxide composites as positive electrodes in supercapacitors

In this study, NiMnO 3 (NMO), NiCo 2 O 4 (NCO), and MnCo 2 O 4 (MCO) metal oxides were successfully synthesized by hydrothermal method with optimization studies. Co-precipitation method was used for the synthesis of α-MnO 2 (MO). The performance of each synthesized metal oxide has been investigated in case it is used as a positive electrode in supercapacitors. Furthermore, the performance of electrodes fabricated by physically mixing NMO, which possesses properties similar to the ilmenite structure selected as the primary metal oxide, with other metal oxides in ratios of 1:0, 0:1, 1:1, 1:3, and 1:7 was examined to enhance the use of NMO as a supercapacitor electrode. The cyclic voltammetry curves obtained at a scan rate of 10 mV/s revealed that the specific capacitance value for the NMO:3MO electrode increased from 120 F/g to 189 F/g compared to NMO. It was observed that the combination of NMO with an NMO:NCO ratio increased the specific capacitance value of NMO from 120 F/g to 285 F/g, and the combination of the electrode with an NMO:3MCO ratio increased the specific capacitance value of NMO from 120 F/g to 241 F/g. The effects of this doping on the specific capacitance and the effects on the charge-discharge rate are different, and these electrode materials can be purposefully selected by the user according to the desired property in a supercapacitor.The NMO-3MO electrode material is advantageous for a system where fast charge-discharge application is at the forefront, while the use of NMO-NCO electrode is recommended when high load capacity is desired.