Engineering active sites on hierarchical ZnNi layered double hydroxide architectures with rich Zn vacancies boosting battery-type supercapacitor performances

Designing metal-cation defects with desired architectures is a big challenge for boosting electrochemical performances. Herein, we report ultrathin ZnNi layered double hydroxide (LDH) nanosheets with rich Zn vacancies (VZn) uniformly anchored on CuO nanowire skeletons for high performance capacitive electrode via a zeolitic imidazolate frameworks-8 derived approach. The optimized VZn-defect electrode displays high area capacity of 3967 mF cm−2 at a current density of 2.0 mA cm−2. Moreover, an all solid-state hybrid supercapacitor constructed with the VZn-defect sample and activated carbon delivers a maximum energy density of 1.03 mWh cm−3 at a power density of 9.3 mW cm−3. Mechanism studies indicate that VZn regulates the electronic structure of ZnNi LDH nanosheets for electron conductivity and surface Faradaic reactions. The work may disclose the role of metal-cation defects in affecting the electrochemical activity at atomic level for developing high performance supercapacitors.