Development of 3D compound structures and highly wettable carbonate hydroxide electrodes for high-performance supercapacitors

Abstract

A facile hydrothermal method was employed to fabricate tailored NiCo(CO₃)(OH)₂ electrodes for high-performance supercapacitors. Ni and Co ions, transition metals with versatile oxidation states, were used, promoting redox reactions. Additionally, a comparative analysis of the characteristics and electrochemical properties between electrodes fabricated with 3D Ni foam substrates and those without substrates was conducted. This comparison emphasizes the critical role of 3D substrate selection in enhancing electrochemical performance during electrode fabrication. Furthermore, carbonate/hydroxide-based transition metal electrodes have been fabricated. Carbonate-based transition metals can substantially increase the wettability of the electrode surface due to their hydrophilicity, which has proven beneficial in aqueous electrolytes. The NiCo(CO₃)(OH)₂ electrodes with Ni foam substrates and without Ni foam substrates exhibit impressive specific capacitances of 2576.4 and 1460.2 F g⁻¹, respectively, at 3 A g⁻¹. Furthermore, an asymmetric supercapacitor configuration is introduced, utilizing the NiCo(CO₃)(OH)₂ electrode with a Ni foam substrate and graphene as positive and negative electrodes, respectively. A remarkable energy density of 35.5 W h kg⁻¹ and a power density of 2555.6 W kg⁻¹ at a current density of 2 A g⁻¹ are exhibited by this configuration. Notably, excellent cycling stability is displayed by the asymmetric supercapacitor, with approximately ∼71.3% of its capacity retained after 10 000 cycles. These results highlight the promising potential of the fabricated electrodes and asymmetric supercapacitor configuration for practical energy storage applications.