N,P-co-doped 2D Carbon Nanosheets for High Energy Density Zinc-Ion Capacitors

Zinc-ion capacitors (ZICs) are regarded as highly promising candidates for electrical energy storage systems (EESs). However, some challenges must be met to achieve high energy density and long cycling life in practical applications. Herein, we report on design and preparation of 2D nanosheets of N,P-co-doped hierarchical porous carbon (GNPCs) by a one-step process. Benefitting from the mesopores supporting rapid diffusive ion transport, sufficient micropores for charge storage, and high electrical conductivity enabled by N,P-doping, the resulting GNPC cathodes for ZICs achieved a high capacity of 401 F g(-1). In a complete device a high energy density of 180 Wh kg(-1) was obtained at a power density of 85 W kg(-1) at 0.1 A g(-1). More importantly, the ZICs exhibit a good cycling stability with a capacity retention of 95 % after 10 000 cycles at a current density of 5 A g(-1). Our work presents a good strategy for developing high-performance carbon-based cathodes for ZICs.