Preparation and electrochemical properties of Li5FeO4 cathode prelithiation material in lithium ion batteries

In order to develop lithium-ion batteries with high energy density, prelithium technology has attracted extensive attention. Li5FeO4was successfully prepared by molten salt method with LiNO3-LiOH mixed lithium salt as reaction medium and lithium source, and nano Fe2O3 as iron source in this work. Li5FeO4 as cathode prelithiation additive is applied to lithium-ion batteries. The synthesis conditions of Li5FeO4 were optimized by orthogonal experiment, and the effect of synthesis conditions on the electrochemical properties of the material was discussed. Li5FeO4 was added to the surface of LiFePO4 positive electrode and assembled with graphite negative electrode to form a full cell. Its effect on the electrochemical performance of the full cells and the mechanism of reducing the initial capacity loss of lithium-ion batteries were studied. The results show that Li5FeO4 cathode prelithiation additives with high purity, small particle size and outstanding electrochemical performance can be prepared by molten salt method. When Li5FeO4 with a mass fraction of 2.8%(based on the percentage of active materials mass) was added, the discharge specific capacity of first cycle for the LiFePO4/graphite full cell was 150 mAh·g-1 at 0.05 C, which was 8.5% higher than that without adding, after 100 cycles at 0.2 C. the capacity still increased by 7.1%, and the irreversible capacity of the svstem was restored.