Influence of organic additive on the electrochemical performance of LiFePO4 cathode in an aqueous electrolyte solution

Abstract

The effect of the organic additive ethylene glycol (EtG) in 1 M Li2SO4 aqueous electrolyte on the electrochemical performance of the LiFePO4 cathode material in aqueous rechargeable batteries is investigated at various content (wt.%) of 0, 5, 10, 20, and 40 in this study. The suitable content of EtG is 5%, which greatly enhances the cycling stability (121 mAh g−1) and low surface resistance (75 Ohm) of the LiFePO4 electrode at 1 C rate after repeated charge and discharge cycling. Moreover, the EtG additive in the aqueous electrolyte solution forms a compact and uniform solid interface electrolyte (SEI) layer on the surface of LiFePO4 particles, suggesting fast lithium ion transport with low resistance compared to a sample without EtG additive. The SEI layer formed on the electrode surface is investigated using X-ray photoelectron spectroscopy. Furthermore, the SEI layer prevents the formation of side reaction components in aqueous electrolyte solutions. We can assume that the SEI layer, which has lower resistivity and high ionic conductivity, can play an important role in enhancing high specific capacities and has excellent rate capabilities.