Effect of different carbon-coating ways on the microstructure and electrochemical performance of LiFePO4/C cathodes

Through comparative studying on LiFePO4/C preparation process of adding carbon source in precursor and pre-sintered material, marked as LFP-1 (in-situ carbon coating) and LFP-2 respectively, by means of C-S test, XRD, SEM, BET, Raman, the effects of carbon content, morphology, particle size and surface carbon structure on the electrochemical performance of LiFePO4/C cathodes were investigated. SEM images showed that particle sizes of LFP-1 and LFP-2 are about 10μm and 100nm respectively. The EIS and galvnostatic charge-discharge tests indicated that LFP-1 has lower charge transfer resistance (Rct), better rate and cycle performance than that of LFP-2, which can be attributed to the different microstructure and the higher degree of graphitized carbon of LiFePO4/C. Raman spectroscopic analysis showed that the ratio of the ID/IG and Asp3/Asp2 of LFP-1 is lower that of LFP-2, which means the degree of graphitized carbon of LFP-1 is higher than that of LEP-2. These results have important significance for improving the overall performance of olivine cathode materials for lithium ion batteries.