Synergistic effects of engineered spinel hetero-metallic cobaltites on electrochemical pseudo-capacitive behaviors

Spinel metal cobaltites (MCo₂O₄) composed of different transition metals and their corresponding oxides are a significant class of materials for capacitive energy storage due to their novel-redox nature which enables faradaic kinetics of electrodes with high energy storage ability. It is also still important to investigate and adjust the logical selection of transition metal atoms in M sites of spinel metal cobaltites in order to positively affect their overall storage behavior. Herein, we report a strategy to design novel spinel metal cobaltite nanostructures with multiple transition metal heteroatoms so as to achieve optimized capacitive performance. We develop a Zn-Ni-Co₂O₄ electrode with hetero-transition metals (ZNCH) to simultaneously achieve a large capacitance, high conductivity, favorable ion diffusion, and stable structural integrity. The proposed combined atomic configuration of the electrode materials exhibits excellent energy storage characteristics with a capacitance of 5.58 F cm^-2 (1390.1 F g^-1) and a good energy density of 36.73 W h kg^-1, as well as a charge-discharge retention stability of 87.7% at a current density of 10 mA cm^-2 after 3000 cycles. Through the combined utilization of multiple transition metal heteroatoms, the synergistic integration of different electrochemical properties, such as high energy storage performance, and structural stability can be directly realized.