Direct measurement of internal temperatures of commercially-available 18650 lithium-ion batteries

Abstract

Direct access to internal temperature readings in lithium-ion batteries provides the opportunity to infer physical information to study the effects of increased heating, degradation, and thermal runaway. In this context, a method to insert temperature sensors into commercial 18650 cells to determine the short- and long-term effects through characterization testing is developed. Results show that sensor insertion only causes a decrease in capacity of 0.5–2.3%, and an increase in DC resistance of approximately 15 mΩ. The temperatures of the modified cells are approximately 0.5 °C higher than the control cells, the difference between the internal and external temperature readings of the modified cells is approximately 0.4 °C, and the modified cells exhibit the same temperature behavior and trend during cycling as the control cells. The cells are able to operate and collect data for 100–150 cycles before their capacities fade and resistances increase beyond what is observed in the control cells. The results of the testing show that cells modified with internal temperature sensors provide useful internal temperature data for cells that have experienced little or no cyclic aging.

Multiscale correlative imaging reveals sequential and heterogeneous degradations in fast-charging batteries

“…14,49 Heat could be another factor promoting the electrolyte decomposition as it was previously reported that the temperature was higher at the inner region than the outer region for the cylindrical cells. 31,[50][51][52] This issue could become more severe for larger size cylindrical cells, such as 46 800. As the battery transitioned from electrolyte-rich to electrolyte-lean, side reactions at the anode side, including Li-plating, transition-metal crossover and deposition, and accumulation of electrolytedecomposition byproducts, aggravated and exhibited significant spatial-heterogeneity.…”