Thermal runaway is the main cause of battery safety problems, so what causes thermal runaway of lithium batteries?
 
First, the external factors of the battery. If the ambient temperature of the battery is too high, and the battery does not dissipate heat well, or the internal winding is poor, resulting in poor battery heat dissipation. In addition, companies need to pay special attention to another situation, that is, the battery spine is sometimes hot. The metal spine of the battery has copper and aluminum and has a relatively good thermal conductivity. For circuits in components with some high heat sources, it is important to ensure that they are kept away from the battery spine to adequately dissipate heat.
 
Again, the internal factors of the battery. One is a micro-short circuit. There are two types of micro-short circuits.
 
One is the short circuit in the battery production process, including burrs; the other is the use of the process in the short circuit, these situations will lead to the micro-short circuit and make the local temperature of the battery is higher than the thermal runaway temperature, which in turn leads to thermal runaway phenomenon.
 
The second reason is the battery overcharge, which will reduce the thermal runaway temperature of the material after overcharging. In the use in the later stages, the capacity of the battery will drop. At this point, the battery itself is already in an overcharged state, and the thermal runaway temperature will naturally drop; the third is the amount of electrolyte. If the amount is too much, the explosion will be very harmful and the flame will be ejected very high or even far, so the amount of electrolyte must be strictly controlled.
 
Taking flexible pack batteries as an example, flexible pack lithium batteries are another name for polymer batteries. Compared with cylindrical and square lithium batteries, they have the advantages of small size, lightweight, high specific energy, high safety and design flexibility. The main difference between them is the stainless steel case or aluminum case used for square and cylindrical batteries. Flexible packaged batteries are manufactured using stacked manufacturing methods, so they are smaller in size and weight for the same bulk density and weight. lightest. However, there are still many practical issues on the technology path for flexible packaging batteries. First of all, the high cost and limited technology level of aluminum-plastic film technology, especially in terms of control of the lamination technology, requires more winding.
 
Quality control issues will directly affect battery life and safety issues. Therefore, manufacturers of flexible packaging lithium batteries place great emphasis on internal inspection. The development of flexible packaging batteries has benefited from the trend towards smaller, thinner and lighter consumer electronics. Smaller size means more difficult to inspect.