Ultrathin Nickel-Cobalt Phosphate 2D Nanosheets for Electrochemical Energy Storage under Aqueous/Solid-State Electrolyte

摘要

2D materials are ideal for constructing flexible electrochemical energy storage devices due to their great advantages of flexibility, thinness, and transparency. Here, a simple one-step hydrothermal process is proposed for the synthesis of nickel-cobalt phosphate 2D nanosheets, and the structural influence on the pseudocapacitive performance of the obtained nickel-cobalt phosphate is investigated via electrochemical measurement. It is found that the ultrathin nickel-cobalt phosphate 2D nanosheets with an Ni/Co ratio of 4: 5 show the best electrochemical performance for energy storage, and the maximum specific capacitance up to 1132.5 F g(-1). More importantly, an aqueous and solidstate flexible electrochemical energy storage device has been assembled. The aqueous device shows a high energy density of 32.5 Wh kg(-1) at a power density of 0.6 kW kg(-1), and the solid-state device shows a high energy density of 35.8 Wh kg(-1) at a power density of 0.7 kW kg(-1). These excellent performances confirm that the nickel-cobalt phosphate 2D nanosheets are promising materials for applications in electrochemical energy storage devices.