Rational design of CoP@Ni(OH)2 bilayer nanosheets for high-performance supercapacitors

Abstract

Cobalt phosphide has excellent electrical conductivity, metallic properties, and thermal stability. However, its application is limited due to the few active sites exposed in electrochemical reactions and poor structural stability. Herein, we adopt the strategies of material compounding and structural design to construct CoP@Ni(OH)₂ bilayer nanosheets. The bilayer nanosheet structure can provide abundant transport paths for electrons and ions while also exposing more electroactive sites. In addition, the close contact and mutual support of the bilayer nanosheet structure can significantly alleviate material morphological collapse during charging/discharging processes, improving the cycle stability. The advantages of multiple components were combined in CoP@Ni(OH)₂ to provide multiple valances for the faradaic redox reactions. The CoP@Ni(OH)₂ manifested a specific capacity of 1697.8 C g⁻¹ at 1 A g⁻¹ and maintained a high rate capability of 35.0% even at 20 A g⁻¹. Moreover, the electrode, had great cycling stability, retaining 83.9% of its capacity at 6 A g⁻¹ after 7000 cycles. The asymmetric supercapacitor made of CoP@Ni(OH)₂//activated carbon delivered 53.2 W h kg⁻¹ at 800 W kg⁻¹.