Tailoring the Supercapacitance of Hydrothermally Synthesized Co3O4 Nanorods via Ni‐Doping and Fabrication of Symmetric and Asymmetric Supercapacitors

Abstract

Herein, cost‐effective and highly efficient Co3−XNiXO4 electrodes with various Ni concentrations (X = 0.1 to 0.5) are synthesized for supercapacitors. Ni‐doping effects are elucidated by various structural, morphological, and spectroscopic characterizations. The electrochemical studies show a ≈2‐fold increase in the specific capacitance for X = 0.5 when compared to its pristine counterpart. With varying concentrations of Ni, the specific capacitance of Co3O4, Co3−0.2Ni0.2O4, Co3−0.5Ni0.5O4 nanorods exhibits 473, 657, and 892 Fg−1 at a current density of 1 Ag−1 with a capacitance retention rate of 94%, 91%, and 93%, respectively, up to 8000 cycles. Significant enhancement in specific capacitance without compromising the cycling stability is due to the low charge transfer and internal resistances. Symmetric and asymmetric supercapacitors are fabricated using the sample with maximum performance, i.e., X = 0.5. The symmetric supercapacitor exhibits a specific capacitance of 222 Fg−1 at 1 Ag−1 and a capacitance retention of 89.3% over 1000 cycles at 5 Ag−1. For the asymmetric supercapacitor (ASC) fabrication, Co3Ni0.5O4 and activated carbon are used as positive and negative electrodes, respectively. The ASC device shows an excellent energy density of 39.4 Wh kg−1 at a power density of 754.8 Wh kg−1 with a retention rate of 98.4%.