Electrochemically Induced Defects Promotional High-Performance Binder-Free MnO@CC Cathodes for Flexible Quasi-Solid-State Zinc-Ion Battery

Aqueous Zn-ion batteries (ZIBs) have attracted ever-increasing attention because of their features of a cheaper cost, high safety level, and environment protection. Manganese-based oxides stand out among the many cathode material candidates because of their high voltage platform (1.4 V vs Zn²⁺/Zn). Nevertheless, manganese ion dissolution still is an essential issue in the application of manganese-based cathodes, and the strategy of using manganese ion dissolution to activate electrode materials is rarely achieved. Here, a high-capacity and stable binder-free MnO@CC cathode was prepared by facile electrochemical deposition and carbothermal reduction methods. Based on the MnO@CC cathode and a homemade gel polymer electrolyte, a flexible quasi-solid state ZIB was assembled and exhibited a high reversible capacity, a significant energy output of 345 Wh kg^-1, and excellent long-term cycling performance. The ultradispersed and well-crystallized octahedral MnO nanoparticle provides an improved ion transfer interface, and abundant Mn vacancy during the initial charging process provides sufficient inserted channels and available active sites for subsequent ion insertion and storage. In addition, for the as-activated MnO@CC electrode, the reversible coinsertion mechanism (H⁺and Zn²⁺) is also monitored in the aqueous ZIBs. This work may provide insights into manufacturing advanced flexible aqueous ZIBs for wearable electronics via defect engineering.