Self-templated flower-like NiCoZn-carbonate hydroxide hollow nanospheres for asymmetric supercapacitors with high performance

Abstract

With the increasing demand for energy resources, it is crucial to explore electrode materials with high specific capacitance and cycling stability for supercapacitors. Herein, flower-like NiCoZn-carbonate hydroxide (NiCoZn-CH) hollow nanospheres are prepared using self-templated NiCoZn-glycerate solid nanospheres through the Kirkendall effect in a solvothermal reaction. Benefiting from a flower-like morphology, NiCoZn-CH not only provides large contact areas on the electrolyte-electrode and an abundant number of active sites but also shortens the ion transportation pathway. Meanwhile, the hollow structure also improves cycling stability by relieving stresses. Furthermore, Zn²⁺ can accelerate the ion transfer and improve the electrochemical activity. Therefore, the Ni₁Co₁Zn_0.25-CH electrode shows an attractive specific capacitance of 1585.2 F g^-1 at 1 A g^-1 and excellent cycling stability. Additionally, the asymmetric supercapacitor Ni₁Co₁Zn_0.25-CH//AC delivers a superior cycling stability of 99.9% after 15 000 cycles at 10 A g^-1 and an energy density of 33.7 W h kg^-1 at a power density of 400 W kg^-1. This work provides a simple and efficient route for the fabrication of various carbonate hydroxides.