Safety of High Power Type Lithium-Ion Batteries with Different Novel Cathode Materials

Compared to the currently used LiCoO2 and LiMn2O4 oxide cathode materials, LiFePO4 and LiNi1/3Co1/3Mn1/3O2 are the alternative cathode materials for large scale lithium ion battery application, due to the advantages of lower cost, high structure stability, and high safety. In this study, a high power of 40113 type of lithium ion battery has developed by using LiMn2O4, LiFePO4 and LiNi1/3Co1/3Mn1/3O2 as cathode materials. The design of the specific power density of the batteries with three cathode materials can meet the target of the Freedom Car project for HEV application. The abuse tests including nail penetration, crush, overcharge and hot box test were investigated. From table 1, the cell with LiFePO4 material showed the higher safety behavior than the cell with LiMn2O4 and LiNi1/3Co1/3Mn1/3O2 materials. In order to understand the safety contributed by the different cathode materials, the charged electrode with different cathode materials were examined for its thermal stability by differential scanning calorimetry (DSC). In the present experiment, LiMn2O4, LiFePO4 and LiNi1/3Co1/3Mn1/3O2 were charged at 4.3 V vs. Li/Li. Fig. 2 shows the results of DSC measurements of electrodes at full charged state. The LiFePO4 electrode showed lower heat generation than that of LiMn2O4 and LiNi1/3Co1/3Mn1/3O2. The thermo-gravimetric analysis (TGA) and time resolved X-ray diffraction (XRD) will be also discussed. These thermal properties analysis can help us to understand the safety related characteristics and the mechanism of thermal degradation of the electrodes in Li-ion cells.