Self‐Assembled Cu ₃ P@NiCo ₂ O ₄ Core–Shell Heterostructure Electrodes for High‐Energy All‐Solid‐State Supercapacitor

Core-shell electrodes provide a potential and innovative approach for significantly enhancing the performance and capacity of supercapacitors (SCs) by combining two distinct materials. The capabilities of these advanced electrodes surpass those of conventional single electrodes. Specifically, these exhibit better energy storage, higher power density, and improved overall performance. In this study, 1D core-shell Cu₃P@NiCo₂O₄ heterostructure is synthesized on copper foam (CF) and utilized as a positive electrode for an all-solid-state SC (ASS-SC). The interconnected core-shell heterostructure of the micro-nanorods improves both electrochemical activity and stability via interfacial electronic reconstruction, thereby yielding an exceptional electrochemical performance, as supported by density functional theory (DFT) calculations. These advantages enable the engineered electrode material to exhibit a high specific capacity of 604.836 C g^-1 at 1 A g^-1, and a high-capacity retention (of 88.2%) over 20 000 cycles. Significantly, the ASS-SC shows specific capacitances of 100.8 F g^-1 (1.07 F cm^-3 volumetric capacitance) at 1 A g^-1, respectively. The energy density of the device is 31.5 Wh kg^-1 at 774.8 W kg^-1, and the capacity retention is 97.6% over 5000 charge/discharge cycles. The remarkable electrochemical performance of the ASS-SC prototype device demonstrates the potential of Cu₃P@NiCo₂O₄ electrodes for future energy storage systems.