Room-temperature CoxB/CoyO Heterostructure coating for defect-engineered MnO2 cathodes in aqueous zinc-ion batteries

초록

Aqueous zinc-ion batteries (AZIBs) are promising energy storage systems due to their cost-effectiveness, environmental benignity, and inherent safety. However, manganese dioxide (MnO2), although an attractive cathode material with high theoretical capacity, suffers from low electronic conductivity, sluggish reaction kinetics, and rapid capacity decay caused by continuous Mn dissolution during cycling. This work enhances the electrochemical performance of MnO2 through the construction of a heterostructured CoxB/CoyO coating layer on its surface. Under a reducing environment, Co precursors with high oxygen affinity induce lattice oxygen migration toward the surface, which simultaneously generates oxygen vacancies within the MnO2 core and forms the CoxB/CoyO coating layer. The induced oxygen vacancies act as electrochemically active sites and improve electronic conductivity, which facilitates rapid electron and H+/Zn2+ ion transport. At the same time, the coating layer serves as a physical barrier that suppresses interfacial side reactions and structural collapse caused by Mn dissolution. As a result, the MnO2@CoxB/CoyO cathode delivers a reversible capacity of 228.2 mAh g−1 at 0.5 A g−1. It also retains a discharge capacity of 160.2 mAh g−1 after 800 cycles at 1 A g−1, which significantly exceeds that of the pristine nanorod MnO2 (76 mAh g−1). These results demonstrate that defect-engineered MnO2@CoxB/CoyO is a viable candidate for next-generation aqueous energy storage systems.

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