Briefly describe the explosion conditions of large-capacity polymer batteries and battery protection methods

Analyzed the explosion conditions of polymer batteries and battery protection methods. The explosion or combustion of large-capacity polymer batteries is due to the strong chemical reaction inside the battery, which generates a lot of heat and gas. In order to promote the strong chemical reaction inside the battery, some necessary external conditions must be met: 1. The battery is seriously overcharged. The chemical system of the lithium battery determines that when the battery is overcharged, the LiCoO2 in the battery becomes Co3O4, which is a strong oxidant. , Can react with electrolyte and attack gas (O2). Oxygen continues to react with electrolyte water (H2O), water can continue to react with lithium, electrolyte, so the internal heat of the battery will attack a lot of gas, and the response will follow the rise and rise of the voltage. Generally speaking, if the battery voltage exceeds 4.2V, there is When this reaction reaches close to 5V, the battery voltage and the internal temperature and gas pressure of the battery increase, and most batteries will burn because of internal short-circuit attack (polymer battery) or blasting rigid package (liquid). The specific response process is as follows: 2. The battery is heated by high temperature, and when the battery is heated by high temperature, the electrolyte will evaporate and decompose together. As the internal pressure of the battery increases, the separator inside the battery may melt, causing the battery to short circuit and incinerate. The higher the battery voltage, the shorter the high temperature resistance. The figure below shows the Joule heating characteristic curve of different data: 3. The battery is short-circuited. When the battery is fully charged, it will suddenly short-circuit. 1) External short-circuit batteries, liquid rigid pack batteries, because the temperature of the battery rises, the internal electrolyte decomposes and evaporates, which may cause the internal pressure of the battery to be too large, the current explosion, and some batteries due to various reasons, the initial internal pressure has been very high. Large, short circuit, battery, or blast under high temperature applications. Batteries in soft packaging may bulge or crack when used in short-circuit applications. No burning. 2) Short circuit inside the battery. When the battery is fully charged, due to various reasons, when the positive and negative electrodes inside the battery are short-circuited, the temperature will rise sharply, which will cause a serious reaction inside the battery. In this case, the core of the hard shell bag will explode, while the core of the polymer flexible bag will burn. The above problems have been solved. Now it is important to maintain the battery with maintenance boards, PTCs, special chargers and fuses. Maintain the board to charge and discharge the battery and over-current level maintenance, PTC is a large short-circuit current situation, the battery is overheated and the cut-off current is the second-level maintenance of the battery, the charger is the battery charging current and voltage, and is connected with a small fuse, now it is important The purpose is to completely cut off the cohesion of the battery and the open circuit when the battery voltage or current is abnormal, to ensure that the battery will not be used again, and to ensure that the safety of the battery will not cause serious accidents. Therefore, the reliability of these maintenance equipment directly affects the safety application of the battery, and attention should be paid to satisfaction. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Lithium iron phosphate battery will be most suitable for the development of electric vehicles in the future