Abstract
The overpotential resistances and the entropy changes of two kinds of small Lithium-ion secondary batteries, which are the heat source terms for batteries, have been measured by several methods. And the temperature rises and the heat production rates of the batteries were calculated during the discharge cycle by using the measured results, being compared with the experimental temperature rises and the heat production rates. The overpotential 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 overpotential 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 measurements. The entropy change ΔSmeasured by the temperature change of open circuit voltage is shown to agree almost with the measured ΔShy the temperature rise difference between charge and discharge cycle. The cell temperature rises and the heat production rates of the batteries calculated by the overpotential resistances by the voltage-current characteristics and ΔSby the temperature change of open circuit voltage agree well with the measured for two kinds of batteries.
