Enhanced energy storage with TiO2/NiO/ZnO core-shell heterostructures in hybrid battery-supercapacitor applications

Abstract

We reported the synthesis of novel TiO₂/NiO/ZnO ternary core-shell arrays (TCSA) by a one-pot electrospinning method via an ex-situ wet-chemical assisted route for battery-supercapacitor hybrid systems (BSCHs). The structural examinations revealed the obtained TiO₂/NiO/ZnO TCSA with high purity and crystallinity. The charge storage and capacitive properties of pure TiO₂, binary TiO₂/NiO, and TiO₂/NiO/ZnO TCSA were examined by cyclic voltammetry, impedance spectroscopy, and discharge/charge techniques. We obtained the battery-supercapacitor hybrid charge storage with remarkable capacitive properties. Interestingly, the TiO₂/NiO/ZnO TCSA achieves a maximum capacitance of 438 F/g and the lowest charge transfer resistance, which supports faster diffusion of electrolyte ions in the host electrode than that of pure TiO₂, and binary TiO₂/NiO composite at the same conditions. An asymmetric battery-supercapacitor hybrid system (BSCHs) was constructed utilizing battery-type electrode materials, TiO₂/NiO/ZnO TCSA as anode and capacitive-type activated carbon (AC) as cathode, represented as TiO₂/NiO/ZnO||AC BSCHs). This BSCHs achieved a high energy density of 43.9 Wh/kg with 749 W/kg power density at 1 A/g current rate, and the power density outreach to 3350 W/kg with 17.68 Wh/kg energy density at higher current rates. Also, a remarkable stability was displayed with 94.9% capacitance retention after 3000 cycles by assembling a BSCHs. The aid of an optimum voltage of 1.5 V coupled with a high capacitance of 140.6 F/g realizes the considerable energy storage performance, which can be effectively extended to construct other oxide-based low-cost electrodes for electronic devices.