A novel core-shell structure composed of polypyrrole shell and high-entropy oxide/carbon cloth core for high-performance supercapatteries

High-entropy oxides (HEOs) are promising candidates for supercapattery applications owing to their unique high entropy effect and abundant metal elements to provide high capacitance. However, their poor electrical conductivity, low specific capacitance, and limited stability still need to be addressed. Herein, coaxial core-shell structured electrodes (CoCrFeMnNi)3O4@CC-PPy are prepared by a two-step electrodeposition method. The core-shell electrode structure is formed by depositing (CoCrFeMnNi)3O4 (HEO) nanoparticles on a conductive carbon (CC) cloth followed by electrodeposition of a shell layer composed of highly conductive polypyrrole (PPy) nanospheres. The optimized HEO@CC-PPy-140s electrode prepared by electrodeposition for 140 s exhibits excellent specific capacitance reaching 791 F'g- 1 at a current density of 0.5 A'g- 1, and a specific capacitance retention of 63 % at a high current density of 10 A'g- 1. Importantly, the use of HEO@CC-PPy as a negative electrode in a supercapattery device assembled with an electrodeposited NiCo2O4@CC positive electrode displays a high energy density of 49.2 Wh'kg- 1 and good cycling stability, with a capacitance retention rate of 88.2 % after 3000 charge/discharge cycles. Overall, the proposed coaxial core-shell structure electrode design offers promising potential for the fabrication of supercapatteries with advanced characteristics.