P14-07 小型リチウムイオン二次電池の発熱挙動の研究

Abstract

The overvoltage resistances and the entropy changes, which are the heat sources for small lithium ion secondary batteries, have been measured by several methods. The calculated temperature rises and the heat production rates of the batteries at the discharge cycle by using the measured results were compared with the experimental temperature rises and the heat production rates. The overvoltage resistance was estimated by four kinds of measurement methods, i. e. the voltage-current characteristics of batteries at constant-current discharge, the difference between the open circuit voltage and the cell voltage, the voltage change by the 60 seconds intermittent discharge, and the AC impedance measurement. The overvoltage resistance by the voltage-current characteristics is almost the same with the one by the difference between the open circuit voltage and the cell voltage. However, in some cases the resistances by the intermittent discharge and the AC impedance are shown to be smaller than the above two methods. The entropy change ΔS measured by the temperature change of open circuit voltage is shown to agree almost with the measured ΔS by the temperature rise difference between charge and discharge cycle. The cell temperature rises and the heat production rates of the batteries calculated by the overvoltage resistances by the voltage-current characteristics, and by the difference between the open circuit voltage and the cell voltage agree well with the measured for two kinds of batteries.