Causes Of Lithium Battery Explosion

1. Large internal polarization;
2. The pole piece absorbs water and reacts with the electrolyte to cause air bulging;
3. Problems with the quality and performance of the electrolyte itself;
4. The amount of liquid injected during injection does not meet the process requirements;
5. The sealing performance of laser welding during the assembly process is poor, and air leaks during leakage testing;
6. Dust and pole piece dust are the first to cause micro short circuits;
7. The positive and negative pole pieces are thicker than the process range, making it difficult to enter the shell;
8. Liquid injection and sealing problems, poor sealing performance of steel balls leads to air bulging;
9. The shell wall of the incoming shell material is too thick, and the shell deformation affects the thickness;
10. Excessive external ambient temperature is also the main cause of the explosion.
Explosion type
Analysis of explosion type The types of battery cell explosions can be summarized into three types: external short circuit, internal short circuit, and overcharge. The external here refers to the outside of the battery cell, including short circuits caused by poor insulation design inside the battery pack. When a short circuit occurs outside the battery cell and the electronic components fail to cut off the circuit, high heat will be generated inside the battery cell, causing part of the electrolyte to vaporize and expand the battery shell. When the temperature inside the battery reaches 135 degrees Celsius, a good quality diaphragm paper will close the pores, the electrochemical reaction will terminate or almost terminate, the current will drop sharply, and the temperature will slowly drop, thereby avoiding the explosion. However, if the pore closing rate is too poor, or the pores of the diaphragm paper are not closed at all, the battery temperature will continue to rise, more electrolyte will vaporize, and finally the battery shell will be broken, and even the battery temperature will be raised to the point where the material burns and explodes. Internal short circuits are mainly caused by burrs on copper and aluminum foils penetrating the diaphragm, or dendrites of lithium atoms penetrating the diaphragm.
These tiny needle-like metals will cause micro short circuits. Since the needles are very thin and have a certain resistance value, the current may not be very large. The burrs on copper and aluminum foils are caused during the production process. The observable phenomenon is that the battery leaks too quickly, and most of them can be screened out by the battery cell factory or assembly plant. Moreover, because the burrs are small, they may be burned off sometimes, so that the battery returns to normal. Therefore, the probability of explosion caused by burr micro short circuit is not high. This statement can be statistically supported by the fact that there are often bad batteries with low voltage shortly after charging in each battery factory, but there are few explosions. Therefore, the explosion caused by internal short circuit is mainly caused by overcharging.
Because after overcharging, the electrode is full of needle-shaped lithium metal crystals, piercing points are everywhere, and micro short circuits occur everywhere. Therefore, the battery temperature will gradually rise, and finally the high temperature will gasify the electrolyte. In this case, whether the temperature is too high to cause the material to burn and explode, or the shell is broken first, allowing air to enter and violently oxidize with lithium metal, it will end in explosion. However, this explosion caused by internal short circuit caused by overcharging does not necessarily occur at the time of charging. It is possible that the battery temperature is not high enough to cause the material to burn, and the gas generated is not enough to break the battery shell, so consumers stop charging and take the phone out. At this time, the heat generated by numerous micro short circuits slowly raises the battery temperature, and after a period of time, the explosion occurs. Consumers often describe that they find their phones very hot when they pick them up, and they explode after they throw them away.
Based on the above types of explosions, the focus of explosion prevention can be placed on three aspects: prevention of overcharging, prevention of external short circuits, and improvement of battery cell safety. Among them, prevention of overcharging and external short circuits belong to electronic protection, which is closely related to battery system design and battery assembly. The focus of improving battery cell safety is chemical and mechanical protection, which is closely related to battery cell manufacturers.