Direct growth of honeycomb-like NiCo2O4@Ni foam electrode for pouch-type high-performance asymmetric supercapacitor

Abstract

Abstract This study focuses on the binder-free direct growth of a honeycomb-like NiCo2O4 structure on Ni foam by a simple combustion method and its application as a supercapacitor electrode. With glycine as a fuel and nitrate as an oxidizer, an appropriate glycine-to-nickel/cobalt-nitrate molar ratio was used for the formation of the honeycomb-like NiCo2O4@Ni foam (NF). The mass loading of NiCo2O4 on NF was optimized using different concentrations of glycine and nickel/cobalt nitrate. The honeycomb-like NiCo2O4@NF electrode exhibited a high specific capacitance of 646.6 F g−1 at a current density of 1 A g−1 and a comparable rate performance of 32% capacitance retention at 9 A g−1. Furthermore, two-electrode pouch-type asymmetric supercapacitors with NiCo2O4@NF as the cathode and sugar-derived carbon (SC) as the anode were fabricated (NiCo2O4@NF//SC) using 6 M KOH. The NiCo2O4@NF//SC electrode exhibited a high charge storage capacity with a specific capacitance of 169 F g−1 at a current density of 1.5 A g−1. More importantly, the asymmetric supercapacitor exhibited a high energy density of 48 W h kg−1 at a power density of 1076 W kg−1 and outstanding cycling stability with 96.5% capacitance retention after 3000 cycles. These results suggest that this honeycomb-structured NiCo2O4@NF material could be a promising cathode electrode for supercapacitors.