Lithium‐ion batteries are applied to many portable devices, but when internal short circuits occur, high electrochemical energy is converted into thermal energy, and there are consumer safety issues such as heat generation and fire/explosion of battery packs. Herein, the internal short circuit was simulated by damaging the battery pack in smartphones to investigate the cause of heat generation and fire/explosion. This battery pack simulating the internal short circuit confirmed that the internal short‐circuit resistance depends on leakage current, state of charge, and cycle. Furthermore, it is found that the battery pack with crushed jelly roll electrode plates has a probability of internal short circuit, which can develop into a firing at high temperature and high current charging. Safety was improved by screening the defective electrode geometry through X‐ray inspection of the battery pack, and various structures were proposed to improve its internal electrode geometry. However, X‐ray inspection may cause temporary, permanent, or potential characteristic changes or failures in semiconductors (integrated circuits (ICs)/field‐effect transistors (FETs)) used in battery packs due to high‐energy X‐rays. The influence of ICs/FETs performing the protection operation of the battery pack according to the time or number of X‐ray irradiation was tested. Particularly, the overcharge detection voltage and delay time were most affected by X‐rays among the protection operations of the battery pack. After X‐ray irradiation, it was confirmed that there was no additional characteristic change depending on temperature/humidity/time through environmental evaluation. By measuring the characteristic change of semiconductors according to the X‐ray irradiation dose, we found the X‐ray threshold irradiation dose applicable to the battery pack. By inspecting the battery pack below the X‐ray threshold irradiation dose, safety was improved and the X‐ray effect on the semiconductors in battery packs was minimized.
Kim et al. (Sun,) studied this question.