Heat dissipation&insulation In Li ion Battery Cell Explaination
Because of its own internal resistance, the single cell will produce a certain amount of heat while outputting electric energy, making its temperature higher. When its temperature exceeds its normal operating temperature range, the performance and life of the battery will be affected. When the highest temperature of the battery exceeds 60 C, the safety problem of the battery caused by overheating will occur. 20 ~ 45 C is the ideal working temperature range of the battery. It can be said that, of all the batteries, the hottest batteries determine the safety of the whole battery pack, the coldest batteries determine the performance of the whole battery pack, a battery and the maximum temperature difference between the battery pack determines the life of the whole battery pack. In order to improve the safety and long-term performance of the battery pack, the thermal management system in the battery pack must ensure that the temperature of any one of the cells in the battery pack should not exceed the permissible maximum operating temperature, and the maximum temperature difference between all the cells in the battery pack and the maximum temperature difference of each cell should not exceed 5%. Therefore, in order to ensure that the temperature between the cores meets the above requirements, there must be a good heat sink between the cores. The heat dissipation between the cores is usually achieved by cooling fluid on the heat sink.
The energy storage part of the battery pack and the energy conversion part exist in the same space, which can easily cause chain exothermic reaction under the condition of overcharging, needling and collision, resulting in thermal runaway accidents such as smoke, fire and even explosion. Thermal runaway is the most serious safety accident of power battery, which directly threatens the life safety of users. In recent years, the problem of thermal runaway propagation of battery pack is mainly solved by thermal protection technology. In addition to the batteries, thermal protection is also required between the battery modules and between the battery compartment and passenger compartment to improve the thermal resistance of thermal runaway batteries to other systems of the battery, thus preventing the spread of thermal runaway. At present, the research on thermal runaway of power battery system mainly focuses on the safety problem of thermal runaway triggered by single cell thermal runaway and then spread to the whole battery pack. This is because when a single cell triggers the thermal runaway, it will generate a sudden increase in heat, heat dissipation is far less than heat production, resulting in heat transfer to the surrounding battery, will quickly lead to large-scale thermal runaway surrounding batteries, forming a security risk. In other words, the thermal runaway of single cell is the source of thermal runaway of the whole battery pack, so we mainly discuss the thermal protection between the cells. The thermal protection between the cells is to add a thermal insulation layer between the cells to prevent the thermal runaway from spreading from the runaway monomer to the surrounding cells, and to reduce the damage of the battery pack and the incidental damage.