Heat Generation Of Lithium Ion Battery During Cycling Under Adiabatic Condition

In this paper, an Accelerating Rate Calorimeter combined with battery charging and discharging cycler was employed to study the heat release mechanism of a lithium ion battery during cycling under adiabatic condition. Thermal behavior of lithium cobalt oxide battery under different cycle rates was researched, and the influence of cycle rate, battery capacity and ambient temperature on the thermal stability of lithium cobalt oxide battery was studied. In addition, thermal behavior of lithium titanate battery, which was widely adopted in the field of energy storage, was tested and its thermal runaway behavior and cycle rate effect were also analyzed.The test on lithium cobalt oxide battery shows that, temperature rises in the process of discharging while keeps constant during charging. With the cycle process going on, temperature of battery keeps rising and reaches135℃, leading to occurrence of battery thermal runaway, which causes surface temperature of battery sharply increasing to at least330℃and maximum temperature rise rate to140℃min-1. The released heat due to thermal runaway is much greater than that during battery cycling, representing a majority of the total heat production, whose value exceeds7500J.Results of the tests to study the cyclic rate effect on heat production of lithium cobalt oxide shows that, with the increase of cycle rate, general trend of both average self-heating rate and heat generation of each discharging process augments correspondingly. Moreover, battery thermal runaway onset temperature decreases with the increase of cycle rate. In addition, capacity and ambient temperature effect on battery thermal stability was also investigated. The results show that, the increase in both capacity and ambient temperature will lead to rise in heat production rate and temperature rise rate, and finally cause decreasing of the thermal stability of lithium cobalt oxide battery.Unlike with the lithium cobalt oxide battery, when lithium titanate battery cycling under adiabatic condition, temperature rise exists in both charging and discharging processes, while the quantitative value of temperature rise and heat production is relatively low. When cycle times set at5, heat generation was not large enough to cause thermal runaway. However, when lithium titanate battery cycling many times with rate of1.5C, thermal runaway finally occurs at temperature of125℃, leading surface temperature of battery increasing to366.0℃, with total heat production of15243.5J/Ah.Research of cycle rate effect on thermal stability of lithium titanate battery shows that, its total heat production rate is positively correlated to its cycle rate. That is to say, the higher cycle rate was set, the larger heat production rate was obtained. Furthermore, by comparing the test results of lithium cobalt oxide and lithium titanate battery, it was found that, thermal stability of lithium titanate battery is significantly higher than that of commercial widely used lithium cobalt battery. Therefore, lithium titanate battery may be an appropriate choice for areas with high security requirements.