2010 Volume 78 Issue 5 Pages 435-437
An investigation of the thermal deterioration characteristics of a lithium-ion secondary cell is inevitable for in utilization for electric vehicles. An accelerating rate calorimeter study revealed that the thermal runaway of the cell occurs over 130°C. In the present study, the thermal deterioration characteristics of a lithium-ion secondary cell during a 100°C storage have been investigated by varying the state of charge (SOC). The measured impedance spectra have been analyzed based on an equivalent circuit, which consists of resistances of the anode and cathode (R1 and R2). Based on the analyses, the increasing rates of R1 and R2 can be defined. The rate of R1 is lower than that of R2 for an SOC of 87%; conversely, that of R1 is greater than that of R2 for SOCs of 66 and 44%. Moreover, the increasing rates of both R1 and R2 are found to become significant when the magnitude of the SOC increases. The increasing rate of R2 more strongly depends on the SOC than that of R1. These results mean that the cathode material is thermally unstable when the extent of lithium deterioration is high.
