Boosting the zinc-ion storage ability of MnO2 cathode by depositing oxygen-deficient CuOx layer

Abstract

MnO2 is subject to intensified examination as the foremost promising cathode material for aqueous zinc-ion batteries (AZIBs). However, achieving high stability and fast kinetics simultaneously is extremely challenging. Herein, an α-MnO2 cathode has been successfully engineered with an oxygen-deficient CuOx coating utilizing active screen plasma technology. The CuOx coating, abundant in oxygen vacancies (OVs), promotes the dissociation of adsorbed water molecules and the ensuing formation of hydroxyl groups, thereby bestowing several benefits on the electrochemical performance. At the atomic level, the OVs serve to markedly fortify electron transport and expedite charge transfer. At the molecular level, the introduction of negatively-charged hydroxyl groups augments surface wettability, which in turn improves the Zn2+ diffusion kinetics and promotes the aggregation of a higher concentration of Zn2+ in the vicinity of the cathode. Furthermore, the CuOx layer is instrumental in preserving the integrity of the electrode structure by inhibiting the Mn dissolution. The integration of these multifaceted advantages culminates in a cathode that manifests a remarkable specific capacity (345 mA h g-1 at 0.2 A g-1) and exemplary cyclic stability (240 mA h g−1 after 1200 cycles at 0.5 A g−1). Conclusively, pouch cells with a large area (5 × 7 cm2) have been fabricated, demonstrating extraordinary flexibility and practical utility.