Controllable growth of NiSe nanorod arrays via one-pot hydrothermal method for high areal-capacitance supercapacitors

To satisfy the ever-increasing demand of smart and miniaturized portable devices, supercapacitors have attracted tremendous attention owing to their short charging time, long cycling lifespan, and reliable safety. Nevertheless, the energy density of pseudocapacitors is the major obstacle because of its kinetically sluggish reactions, low mass loading of active materials, and/or high internal resistance. Herein we develop a one-pot hydrothermal method to synthesize NiSe nanorod arrays on nickel foam (NiSe NRA/NF), which exhibit ultrahigh areal capacitance of 6.81 F cm(-2) at current density of 5 mA cm(-2) as well as excellent cycling stability. The superior performance of NiSe NRA/NF can be attributed to metallic conductivity of nickel selenides, short diffusion length of ions from electrolyte to electrode materials, and fast electrons transport pathway between active materials and current collectors. For practical applications, an asymmetric supercapacitor was assembled by applying NiSe as positive electrode and reduced graphene oxide as negative electrode, delivering an energy density of 38.8 Wh kg(-1) at a power density of 629 W kg(-1) and 6.38 Wh kg(-1) at a power density of 13.5 kW kg(-1). Moreover, the devices retained 90.09% after 3000 cycles at high current density of 3.6 A g(-1), showing a promising application prospect. (C) 2017 Elsevier Ltd. All rights reserved.