Synthesis and performance of LiVPO4F/C-based cathode material for lithium ion battery
(School of Metallurgy and Environment, Central South University, Changsha 410083, China)
Abstract: LiVPO4F/C-based material was prepared by heating a precursor, which was obtained through ball milling with slurry of H2C2O4·2H2O, NH4H2PO4, NH4VO3 and LiF. In this process, H2C2O4·2H2O was used as a reducing agent as well as carbon source. The properties of the precursor and the prepared sample were characterized by TG-DTA, XRD, SEM, TEM and C-S analysis. XRD analysis shows that the precursor is amorphous and the prepared LiVPO4F sample coexists with Li3V2(PO4)3, as well as a small amount of V2O3. Homogeneous powders with an average particle size of 2 μm are observed by TEM. HRTEM image shows that the crystal particles are coated by amorphous carbon uniformly, with a coating layer of about 2 nm. The synthesized material shows the specific discharge capacities of 151.3 and 102.5 mA·h/g at 0.1C and 10C respectively, in the voltage range of 3.0-4.4 V, and it keeps 90.4% of initial discharge capacity at 10C after 50 cycles. V3+/V4+ redox peaks corresponding to both LiVPO4F and Li3V2(PO4)3 are seen clearly in the CV curve.
Key words: lithium ion battery; LiVPO4F; ball milling; cathode material; carbon coating