Self heating function of lithium ion battery
We often need to adjust the electrolyte and electrode to improve the low-temperature performance of lithium-ion battery at the cost of high cost and performance sacrifice. Recently, researchers put forward a new idea, not changing the low-temperature electrolyte and electrode ratio, only starting from the battery structure, by inserting Ni foil coated with polymer insulating layer between the internal plates of the battery, lithium-ion battery is realized The self heating function of lithium-ion battery can heat the lithium-ion battery from - 30 ℃ to 0 ℃ in 30 seconds, which only consumes 5.5% of the battery energy.
At present, there are two ways to heat the battery: external heating and internal heating. The external heating is mainly realized by heat conduction or heat convection, and the battery is heated by PTC material or heating film. However, the heating is uneven and the heating efficiency is low. Internal heating directly generates heat in the battery, so the heating efficiency is higher and the heating is more uniform.
Due to the low thermal conductivity of lithium-ion battery structure, when the surface temperature of the battery rises from - 20 ℃ to 0 ℃, the temperature of Ni foil in the middle of the battery reaches about 30 ℃, which forms a large temperature gradient between the inside and the surface of the battery. This temperature difference will lead to the difference of discharge rate of different cells. Due to the existence of large temperature gradient, the self heating process has a bad effect on the performance of lithium battery, and also leads to the high heating energy consumption of lithium battery.