Plasma-assisted lattice oxygen vacancies engineering recipe for high-performing supercapacitors in a model of birnessite-MnO2

Abstract

Defect engineering has been considered as an efficient strategy to enhance the electrochemical performance of transition metal oxides based energy storage devices. However, the electrochemical activity and stability were greatly determined by the defect located crystal and external environments, which dominate the electrochemical properties of its based electrode. Thus, regulating a defect engineering recipe becomes a vital and direct route to advance the performance of the electrode materials. Herein, a versatile recipe combining the mild H-plasma and O-plasma was demonstrated for prototypical birnessite-MnO2 to achieve the robust lattice oxygen vacancies in birnessite-MnO2 (LOV-MnO2), targeting to boost its electrochemical energy storage performance. Theoretical calculation reveals the facilitated ion intercalation and diffusion kinetics due to the lower energy barrier in the LOV-MnO2. The LOV-MnO2 demonstrates an exceptional electrochemical performance with a specific capacitance as high as 445.1 F g−1 (at the current density of 1 A g−1), and the diffusion-controlled capacitance contribution reaches unprecedented ~70% (at a scan rate of 5 mV s−1). Besides, the configured symmetrical supercapacitor device LOV-MnO2//LOV-MnO2 delivers remarkable performance with an energy density of 92.3 Wh kg−1 at a power density of 1100.3 W kg−1 with a widen working voltage of 2.2 V. An outstanding cyclic life of 92.2% capacitance retention was also achieved after 10,000 charge–discharge cycles. Such superior electrochemical performance suggests that the proposed defect engineering recipes here will aid in the future development of advanced electrode materials for electrochemical energy storage devices.