Cathodic electrodeposition of porous MnO2 film as binder-free cathode for high performance rechargeable Zinc-ion battery

Rechargeable aqueous Zinc-ion batteries (ZIBs) are highly desirable for meeting ever-growing demands from large-scale energy storage fields due to their high energy density, high safety, low cost and environmental friendliness. Here, we report a binder-free porous MnO 2 film achieved by cathodic electrodeposition coupled with subsequent high temperature heat treatment as cathode for aqueous ZIBs. Benefiting from the binder-free and porous structure, this electrode exhibits a stable capacity of about 94[Formula: see text]mAh[Formula: see text]g[Formula: see text] at 1.8[Formula: see text]A g[Formula: see text] over 1500 cycles. The capacity at 6.0[Formula: see text]A[Formula: see text]g[Formula: see text] remains 61[Formula: see text]mAh[Formula: see text]g[Formula: see text], which is 36% of that at 0.3[Formula: see text]A[Formula: see text]g[Formula: see text]. Electrochemical impedance spectroscopy (EIS) results indicate the MnO 2 film after heat treatment has minor charge transfer impedance and high ions diffusion coefficient. The morphology revolution upon cycling suggests that the MnO 2 film after heat treatment is easily transformed into nanosheet arrays with abundant voids facilitating ions transport and possess better structure stability. This work may offer an efficient pathway to explore a promising cathode for aqueous ZIBs.