Chemical Lithiation-Induced Oxygen Vacancies in MnO2 at Room Temperature for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) have attracted extensiveattentiondue to their high safety, low cost, and environment-friendliness.However, the use of AZIBs is limited by the unsatisfactory conductivity,poor cycle life, and low specific capacity of MnO2 cathodematerials. Herein, the layered oxygen-deficient delta-MnO2 (birnessite, V-O-MnO2) with an inter-layerdistance of around 7.0 angstrom is synthesized at room temperature throughchemical prelithiation of MnO2 in lithium naphthalene solution.The results confirm that the existence of oxygen vacancies improvesthe conductivity, provides accessible channels for Zn2+ and/or H+, facilitates reversible adsorption/desorptionof Zn2+ and/or H+, and enables the fast transportof electron and ion. The as-designed V-O-MnO2@CNF cathode achieves a high capacity of 303 mA h g(-1) at 300 mA g(-1), excellent rate capability (148mA h g(-1) at 1000 mA g(-1)), andlong-term cycling performance (a reversible capacity of 135 mA h g(-1) at 1000 mA g(-1) after 740 cycles).The results provide a potential of the V-O-MnO2@CNF cathode for AZIB, which is expected to be used in practicalapplications. This work paves the way to guide the future electrodematerials for high performance AZIBs via defect engineering at roomtemperature.

Automated summary

Aqueous zinc-ion batteries (AZIBs) suffer from poor conductivity, unsatisfactory cycle life, and low specific capacity of cathode materials. By synthesizing oxygen-deficient V-O-MnO2@CNF cathode at room temperature, the conductivity and ion/electron transport are improved, resulting in high capacity, excellent rate capability, and long-term cycling performance. This work provides potential for future electrode materials in high-performance AZIBs through defect engineering at room temperature.