Electrochemical Performance and Behavior Mechanism for Zn/LiFePO4 Battery in a Slightly Acidic Aqueous Electrolyte.

The electrochemical performances and process mechanisms of Zn/LiFePO4 cells in a slightly acidic 1.9 m Li2 SO4 -0.5 m ZnSO4 aqueous solution were investigated. The results showed that the hydrogen depletion side reaction on the surface of the zinc sheet led to an increase in pH of the electrolyte and fluctuations in specific capacity of the cells, and that the dissolution of Fe2+ ions and the lamination of LiFePO4 particles resulted in a decrease in the specific capacity of the cells. At pH 5.0, the initial discharge specific capacity of the Zn/LiFePO4 cell was about 120.0 mAh g-1 at 0.25 C, about 64.4 mAh g-1 at 3 C, with about 60.9 % capacity retention rate after 200 cycles at 1 C, and the Li+ ions diffusion coefficient was about 7.75×10-12  cm2 s-1 .