Enhancement in electrochemical performance of electrode materials has been the recent focus for material development of electrochemical energy storage devices. For the first time, we turn a post transition metal oxide, indium oxide (In2O3), into a high capacity, excellent stability and rate capability electrode by introducing suitable cations. Various electrode materials M-In2O3 (where M is Co, Fe, Mg, Mn, Ni, and Zn) have been prepared by simple and inexpensive cation substitution route. Among all, the optimal promoter Co–In2O3 electrode deliver higher specific capacity (4.8 times) and rate capability (1.3 times) than bare In2O3. The capacitive contribution and diffusion contribution reactions have been studied for all the electrodes. The capacitive distribution has been increased by Mg and Zn substitution and the diffusion contribution has been enhanced with Co, Fe, Mn, and Ni substitution. Furthermore, structural and electronic properties of In2O3 substituted with the cations have been studied through first principles density functional theory calculations. Moreover, seven asymmetric supercapacitor devices have been assembled by using In2O3 and M-In2O3 as the positive and the reduced graphene oxide as the negative electrode materials. The wrist watch, stop watch, and LEDs have been successfully operated, illustrate the prospective of electrode materials towards practical applications.