Ternary Hybrids of Amorphous Nickel Hydroxide-Carbon Nanotube-Conducting Polymer for Supercapacitors with High Energy Density, Excellent Rate Capability, and Long Cycle Life

The utilization of Ni(OH)(2) as a pseudocapacitive material for high performance supercapacitors is hindered by its low electrical conductivity and short cycle life. A coaxial ternary hybrid material comprising of amorphous Ni(OH)(2) deposited on multiwalled carbon nanotubes wrapped with conductive polymer (poly (3,4-ethylenedioxythiophene)-poly(styrenesulfonate)) is demonstrated. A thin layer of disordered amorphous Ni(OH)(2) is deposited by an effective coordinating etching and precipitating method, resulting in an ultrahigh specific capacitance of 3262 F g(-1) at 5 mV s(-1) and excellent rate capability (71.9% capacitance retention at 100 mV s(-1)). More importantly, the polymer layer prevents the degradation of the nanostructure and dissolution of Ni ion during repeated charge-discharge cycling for 30 000 cycles, a phenomenon which often plagues Ni(OH)(2) nanomaterials. Using the ternary Ni(OH)(2) hybrid and the reduced graphene oxide/carbon nanotube hybrid as the positive and negative electrodes, respectively, the assembled asymmetric supercapacitors exhibit high energy density of 58.5 W h kg(-1) at the power density of 780 W kg(-1) as well as long cycle life (86% capacitance retention after 30 000 cycles). The ternary hybrid architecture design for amorphous Ni(OH)(2) can be regarded as a general approach to obtain pseudocapacitive materials for supercapacitors with both high energy density, excellent rate capability, and long cycle life.