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 .