Study on the limiting factors of the cycle life of alkaline poly(vinyl alcohol)-based zinc–air batteries

Flexible zinc–air batteries (FZABs) arouse extensive research interests due to their high energy density and extremely low cost. However, FZABs based on poly(vinyl alcohol) (PVA) alkaline gel polymer electrolyte (GPE) suffer from poor cycling life, which seriously hinders their commercial application. Although most previous efforts focus on optimizing and developing the electrodes and the electrolyte materials with high electrochemical performance to improve the battery cycle life, the limiting factors of the cycle life of the FZAB remain obscure. Herein, a PVA–KOH-based FZAB was assembled to explore the limiting factors of the battery cycle lifespan by setting an array of comparative experiments. The results demonstrate that the decline of the OH− ion content in the PVA–KOH GPE is the key factor in shortening the battery cycle life. The ZnO and carbonate formation in the GPE as well as the poor water retention capability of the GPE contribute to the decrease of OH− ion content in the PVA–KOH GPE. Due to the widely used PVA–KOH GPE in FZABs, this work can provide valuable theoretical guidance and reference for most of the research works centered on prolonging the cycle lifetime of the FZABs.