In-situ formation of α-Co(OH)2 nanosheet arrays on magnesium cobaltate nanowires for hybrid supercapacitors with enhanced electrochemical performance

In this work, the MgCo2O4@α-Co(OH)2 core–shell structure (MgCo2O4@α-Co(OH)2/NF) on foam nickel was prepared using hydrothermal annealing and chemical bath deposition processes to form a supercapacitor positive electrode. MgCo2O4@α-Co(OH)2/NF-2 composite material, with a deposition time of 20 min in a chemical bath, showed a specific capacitance of 1634.8 F g−1 at 1 A g−1, a long cycle stability of 89.4% (in 10,000 cycles) and a rate performance of 78.29%, with excellent electrochemical impedance performance (Rs ≈ 0.507 Ω). The MgCo2O4@α-Co(OH)2/NF-2//AC asymmetric supercapacitors (ASCs) showed a specific capacitance of 185.46 F g−1 at 1 A g−1, with a good long-cycle stability of 91.7% preservation rate after 10,000 cycles. At a power density of 773.19 W kg−1, the energy density is high (65.94 Wh kg−1). We demonstrated that three prepared ASCs devices can produce a diode with a rated voltage of 3 V that continues to emit light for 10 min. This study shows that the MgCo2O4@α-Co(OH)2/NF-2 electrode can be used as a positive electrode for high-efficiency energy storage devices.