Parameterized evaluation of thermal characteristics for a lithium-ion battery

Abstract

Parameterized evaluation of thermal characteristics for a lithium ion battery is a challenge due to the facts: 1) heat generated by a battery is extremely hard to be measured; 2) the measured surface temperature is unable to reflect the entire thermal status. In this study, thermal energy conversion efficiency is proposed to evaluate the thermal behaviors. Results show thermal energy conversion efficiencies at 2 C are about 4.6% and 8.1% when charging and discharging, respectively, showing the former is significantly less than the later. The elevated temperature also shows the similar trend. The increased max temperatures at 2 C are about 16 K and 30 K when charging and discharging, respectively. It is found that the irreversible thermal energy is higher when discharging than when charging. The linear relations between thermal energy conversion efficiencies, and the max and min temperature are discovered, proving that temperature distribution is determined by the thermal energy conversion efficiency. The increased max and min temperatures as function of a current rate and state of charge (SOC) or depth of discharge (DOD) are estimated and plotted as three-dimensional figures. Thus, the temperature range can be known according to the ranges of SOC/DOD and current rates.