Electrochemical performance of ZnCo2O4@Mn-Ni(OH)2 core-shell composites for high-efficiency supercapacitors

Abstract

Enhancing the capacitance of supercapacitors represents a critical direction in the advancement of energy storage technologies. Therefore, a novel core–shell structure (ZnCo₂O₄@Mn-Ni(OH)₂) with ZnCo₂O₄ nanosheets as the core scaffold and Mn-doped Ni(OH)₂ nanosheets as the active shells was successfully synthesized. Notably, the bimetallic ZnCo₂O₄ nanosheets acted as the core to accelerate electron transfer, improve the mechanical stability of the electrodes, and provide abundant attaching points for shell growth. Specifically, the successful integration of Mn atoms into Ni(OH)₂ resulted in two significant outcomes: an increase in redox sites to enhance capacitance, and a concomitant acceleration in electron and ion migration rates to improve reaction kinetics. In consequence, the ZnCo₂O₄@Mn-Ni(OH)₂ composite material exhibited excellent capacitance (12.66 F cm⁻² at 2 mA cm⁻²) and capacity maintenance of 85.6 % following 4000 cycles. The ZnCo₂O₄@Mn-Ni(OH)₂//AC hybrid supercapacitors (HSC) device assembled with an activated carbon (AC) electrode achieved 0.38 mWh cm⁻² at 3.00 mW cm⁻². In particular, after 4000 cycles, the HSC device still had 94.4 % capacity retention. Two HSC devices in a serially connected could power a red light-emitting diode (LED) for a duration of over 80 min. These findings provide a new strategy for improving electrochemical performance and show great potential for practical applications.