CoP/Cu3P heterostructured nanoplates for high-rate supercapacitor electrodes

•A facile strategy is proposed to construct CoP/Cu3P heterostructured nanoplate.•The prepared electrode shows an improved specific capacitance and rate capability.•Theoretical calculations further confirm the enhanced electrical conductivity. CoP is considered as a promising electrode material for supercapacitors owing to the concomitant covalent and metallic bonds which lead to high electrical conductivity and high theoretical capacitance. However, the practical low specific capacitance and poor rate capability limit its further applications. Here, a novel CoP/Cu3P heterostructured nanoplate is fabricated via a facile phosphorization process. Due to the synergistic effects of heterostructure, the ionic and electronic diffusion kinetics in the CoP/Cu3P are significantly improved. The CoP/Cu3P electrode manifests an excellent electrochemical performance of 734.2 F g−1 at 1.0 A g−1, a state-of-the-art rate capability of 53.2% capacitance retention even when the current density increases to 50.0 A g−1, and an excellent cycling performance. A hybrid asymmetric device constructed with CoP/Cu3P as positive electrode delivers a high energy density of 28.6 Wh kg−1 at the power density of 775.0 W kg−1, and an ultra-high power density of 38.8 kW kg−1 at 9.7 Wh kg−1. Theoretical calculations further confirm that the heterostructure can effectively tune the electronic structure of CoP and Cu3P, and improve the charge transport. This study provides insight into the rational design of high-rate performance electrode materials in energy storage.