Facile Synthesis of Sandwich-Type Porous Structured Ni(OH)₂/NCNWs/rGO Composite for High Performance Supercapacitor

Nickel hydroxide has ultra-high energy storage capacity in supercapacitors, but poor electrical conductivity limits their further application. The use of graphene to improve its conductivity is an effective measure, but how to suppress the stacking of graphene and improve the overall performance of composite materials has become a new challenge. In this work, a well-designed substrate of N-doped carbon nanowires with reduced graphene oxide (NCNWs/rGO) was fabricated by growing polypyrrole (PPy) nanowires between GO nanosheets layers and then calcining them at high temperatures. This NCNWs/rGO substrate can effectively avoid the stacking of rGO nanosheets, and provides sufficient sites for the subsequent in situ growth of Ni(OH)₂, forming a uniform and stable Ni(OH)₂/NCNWs/rGO composite material. Benefiting from the abundant pores, high specific surface area (107.2 m² g^-1), and conductive network throughout the NCNWs/rGO substrate, the deposited Ni(OH)₂ can not only realize an ultra-high loading ratio, but also exposes more active surfaces (221.3 m² g^-1). After a comprehensive electrochemical test, it was found that the Ni(OH)₂/NCNWs/rGO positive materials have a high specific capacitance of 2016.6 F g^-1 at a scan rate of 1 mV s^-1, and exhibit significantly better stability. The assembled Ni(OH)₂/NCNWs/rGO//AC asymmetric supercapacitor could achieve a high energy density of 85.2 Wh kg^-1 at power densities of 381 W kg^-1. In addition, the asymmetric supercapacitor has excellent stability and could retain 70.1% of initial capacitance after 10,000 cycles. These results demonstrate the feasibility of using NCNWs/rGO substrate to construct high-performance supercapacitor electrode materials, and it is also expected to be promoted in other active composite materials.