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

Abstract

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 MnO2 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 MnO2 film after heat treatment has minor charge transfer impedance and high ions diffusion coefficient. The morphology revolution upon cycling suggests that the MnO2 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.