Construction of Three-Dimensional Co(PO3)2/Cu3P Heterostructure for High-Rate Supercapacitors

The exploration for pseudocapacitive materials that employ surface Faradaic reactions to store charges in supercapacitors is highly desirable. However, the traditional transition metal oxides with poor electronic conductivity and sluggish reaction kinetics lead to a poor rate capability. In this study, a Co(PO3)2/Cu3P heterostructure is fabricated by a facile in situ phosphorization process. Benefiting from the formation of heterojunctions and modified electronic structures, the electronic transfer and ionic diffusion kinetics have been significantly improved. Specifically, the Co(PO3)2/Cu3P heterostructure electrode exhibits a capacitance of 787.1 F g–1 at 1.0 A g–1 and a superior rate capability of 78.4% capacitance retention at 20.0 A g–1. The fabricated Co(PO3)2/Cu3P//AC asymmetric supercapacitor device with this Co(PO3)2/Cu3P heterostructure as the positive electrode shows an excellent energy density of 39.8 Wh kg–1 at a power density of 936.7 W kg–1 and satisfactory cyclic stability. This design of a metaphosphate based heterostructure provides a path to explore electrode materials with both high capacitance and superior rate capability.