Visualization of the Secondary Phase in LiFePO4 Ingots with Advanced Mapping Techniques

LiFePO4 has been widely used as a cathode material in lithium ion batteries. However, some impurity phases existing in LiFePO4 have a significant influence on its electrochemical performance. Therefore, detection of the impurity phases is necessary for the manufacturer in order to improve the quality of LiFePO4. In particular, visualization of the impurity and secondary phase distributions immersed in the bulk LiFePO4 crystal can help to understand the origin of the impurity and secondary phases, providing clear guidance towards the synthesis of high purity LiFePO4. The results show that with the combination of Raman and EDS, we are capable of identifying the low melting lithium phosphate phase in LFP ingot. Through micro XRF mapping, more detailed information about the LFP materials after carbon coating are observed. The secondary phases are easily defined due to the high sensitivity of this technology.