Comparative supercapacitive analysis of 2-methylimidazole derived cobalt nickel oxides (CoNiO2 and Co2NiO4) and subsequent fabrication of asymmetric supercapacitor devices

An attempt to pursue optimization study of a bi-metal organic framework derived cobalt nickel oxides has been demonstrated here to achieve best supercapacitive performance. The synthesis process was started with formation of Co-MOF by coordination of Co 2+ metal ion with organic ligand 2-MeIM, following coordination of Ni 2+ to the Co-MOF to construct Co 2+ and Ni 2+ dual metal coordinated organic cluster. The final oxides CoNiO 2 (abbreviated as CNOa) and Co 2 NiO 4 (abbreviated as CNOb), were obtained by breakdown of the organic moiety in a high temperature annealing process . While, the starting Co-MOF material yielded only C s of 768 F g −1 (with 67% C s retention after 8000 cycles) but the optimized CNOa with composition of Co: Ni molar ratio 1:1 revealed higher C s of 1624 F g −1 with 86.5% C s retention after 8000 cycles. The electrode material CNOb with Co:Ni molar ratio: 2:1 demonstrated C s of 1329 F g −1 with 72.8% C s retention. The superior specific capacitance, electrochemical reversibility and elevated cycle stability in CNOa was achieved from several positive virtues inherited in electrode material, such as: hierarchical nanoleaves with rough surface, bigger pore volume, thinner surface thickness of active material and definitely higher surface area. Two sets of asymmetric supercapacitor devices (CNOa//GNP, CNOb//GNP) were fabricated for comparison of the energy and power output. Superior energy density of 48.12 Wh Kg −1 was perceived from CNOa//GNP with commendable cycle stability of 92.8% whereas, CNOb//GNP delivered energy density of 40.18 Wh Kg −1 with 85.2% cycle stability experimented after 8000 GCD cycles. • Different Co Ni oxides were derived from a Co-MOF ZIF-67 and nickel precursor. The amount of Co-MOF was altered to obtain two variant of cobalt nickel oxides. • The optimized CNOa (with 1:1 Co:Ni ratio) exhibited a C s of 1624 F g −1 which is superior in comparison to CNOb (with 2:1 Co:Ni ratio) with C s 1329 F g −1 and Co-MOF (768 F g −1 ) with cycle stability of 86.5%, 72.8% and 67% for CNOa, CNOb and Co-MOF, respectively. • CNOa//GNP accomplished energy density of 48.12 Wh kg −1 at power density of 750 W kg −1 whereas, energy density of 40.18 Wh kg −1 at similar power density was achieved from CNOb//GNP. Moreover, ~ 92.8 and 85.2% C s values were persisted after 8000 consecutive GCD cycles in respective CNOa//GNP and CNOb//GNP devices.