The high-performance MoO3−x/MXene cathodes for zinc-ion batteries based on oxygen vacancies and electrolyte engineering

Increasingly severe energy and environmental issues have prompted the development of high-quality energy storage. Aqueous zinc ion batteries (AZIBs) are one of the most attractive candidate devices because they have the advantages of safety and moderate energy density. MoO3 is considered as a promising cathode material for energy storage with huge potential windows due to its higher theoretical capacity and excellent electrochemical activity. However, the low conductivity and poor stability of MoO3 in aqueous seriously affect its wide application. To solve the problems, Ti3C2Tx MXenes with a two-dimensional (2D) layered structure and hydrophobic trifluoromethane sulfonate (OTf-) were introduced into the AZIBs. The MXenes not only causes partial reduction of MoO3 to form oxygen vacancies but also reduces the hydrophilicity of MoO3. The OTf- in zinc trifluoromethane sulfonate (Zn(OTf)2) electrolyte is conducive to prevent cathode from dissolving. As expected, a paper of MoO3−x/MXene delivers exceptional high capacity of 369.8 mAh g−1 at 0.20 A g−1 and an outstanding cycling life of 46.7% capacity retention after 1600 cycles. A zinc ion micro-battery (ZIMB) employing the MoO3−x/MXene paper as cathode demonstrates superior performance and a high capacity. This study paves a new strategy for the design of cathode materials with high capacity, stability, and commercialization of AZIBs.