Transition metal oxide@hydroxide assemblies as electrode materials for asymmetric hybrid capacitors with excellent cycling stabilities

Abstract

In this work, three-dimensional cactus-like Co₃O₄@Ni(OH)₂ electrode materials are grown directly on Ni foam via a two-step hydrothermal method. The as-prepared products possess a specific capacitance of 464.5 C g⁻¹ at 0.5 A g⁻¹ and 91.67% capacitance retention after 20 000 cycles. The as-assembled device using the as-synthesized samples as positive electrodes delivers an energy density of 112.5 W h kg⁻¹ at a power density of 1350 W h kg⁻¹. The superior electrochemical performance of the electrode materials can be attributed to their unique structure, the synergistic effect between Co₃O₄ and Ni(OH)₂ materials and reversible reaction kinetics. It suggests that the products are potential alternatives in future energy storage devices.