Influence of AlF3 coating on the electrochemical properties of LiFePO4/graphite Li-ion batteries

The influence of nanoscale AlF3 coating on the electrochemical properties of LiFePO4 cathode against graphite anode for Li-ion batteries was investigated in this paper. AlF3 coating was deposited on the LiFePO4 particle surface using a chemical precipitation method. High resolution transmission electron microscopy (HRTEM) shows that the AlF3 coating is an amorphous layer with a thickness of about 5 nm. The AlF3 coated LiFePO4 exhibits much higher capacity retention against mesocarbon microbead (MCMB) anode within a potential range of 2.2–3.8 V at 60 °C at 1 C rate than the pristine LiFePO4. Electrochemical impedance measurement reveals that the AlF3 coated LiFePO4 electrode has a lower charge transfer resistance than the pristine LiFePO4 electrode upon elevated temperature cycling. The AlF3 coating greatly reduces the dissolution of Fe of LiFePO4 in the LiPF6/EC-DEC electrolyte by working as a protective layer of the active LiFePO4.