Excellent rate performance enabled by Ni-doping for Co3O4 nanosheet electrodes in supercapacitors

Maintaining a high energy density without sacrificing the intrinsic high power density is the research focus in supercapacitors; however, it is far from satisfactory because of the low capacitance retention under a high current. We report herein a facile molten salt method to deposit nanosheet-structured Co3O4 with Ni in-situ doping on Ni foam. Density functional theory (DFT) calculations indicate that the Ni doping leads to higher conductivity and favorable OH− adsorptions. The optimized Ni-doped Co3O4 (Ni-Co3O4) exhibits an excellent capacitance and rate performance, maintaining 86.12% of the original specific capacitance (3360.0 mF cm−2/2710.3 F g−1) when the current density increases from 2 to 200 mA cm−2. After 10000 cycles at 10 mA cm−2, the capacitance retention is 84.71%. An asymmetric supercapacitor assembled using the electrode and activated carbon paper achieves a high areal energy density of 0.19 mWh cm−2 at a power density of 97.04 mW cm−2, with a capacitance retention of 71.50% after 10000 cycles. The device shows promising comprehensive performances when works under a high current density, which could have great prospects in high-rate energy storages.