Construction of Zn‐based anodes for electrolytic Zn‐MnO2 batteries with high discharge voltage and good durability

Rechargeable aqueous Zn-MnO2 batteries have attracted a great attention owing to their advantages on safety, power density, and cost. In strong acidic environment, the capacity of MnO2-based cathode can reach 616 mAh g-1 through a two-electrons-transfer process of Mn2+↔MnO2. However, in acidic environment, Zn corrosion, dendrites, and hydrogen evolution reaction (HER) on the anode are rather serious, resulting in low Columbic efficiency (CE) and poor durability. Towards these issues, ZnO with dual-protection, including C and polyvinyl alcohol (PVA) coating (ZnO@C-PVA), is developed as initial anode material herein. Compared with bare CC, ZnO, and ZnO@C, reversibility of the ZnO@C-PVA electrode is largely enhanced. CE of an electrolytic full system using ZnO@C-PVA as anode and bare carbon cloth (CC) as cathode can be as high as 90% at 5 mA cm-2, and discharge voltage is up to 1.85 V (mid-value), which can be maintained for 1,600 cycles, indicating rather good stability. It is believed that the existence of initial ZnO can tune the local pH around the anode, resulting in the decrease of HER and the enhancement of Zn plating. Besides, corrosion and Zn dendrites also can be inhibited effectively by the PVA layer.