Ni0.9Co1.92Se4 nanostructures: binder-free electrode of coral-like bimetallic selenide for supercapacitors

Abstract

Coral-like Ni_0.9Co_1.92Se₄ nanostructured materials have been prepared through a simple and controlled two-step solvothermal method, which present a handsome electrochemical performance. The specific capacitance reaches 1021.1 F g⁻¹ under the current density of 2 mA cm⁻² over a 0.5 V electrode potential window with an areal capacitance of 6.43 F cm⁻². A superior rate capability of 77% is achieved with discharge rates increasing from 2 to 50 mA cm⁻², as well as a good cycling stability of 88.39% after 5000 cycles. Furthermore, a good energy density of 26.29 W h kg⁻¹ is achieved under the power density of 265 W kg⁻¹ when assembled into a Ni_0.9Co_1.92Se₄//AC asymmetric supercapacitor with the operating potential window extended to 1.5 V. The high performance can be attributed to the coral-like architectures with rich redox reactions, high conductivity and transport rate for both electrons and electrolyte ions. Our results suggest that the coral-like Ni_0.9Co_1.92Se₄ nanostructured electrode materials may be a good choice for supercapacitors.