Among all environmental factors, temperature has the greatest impact on the charge discharge performance of the battery. The electrochemical reaction at the electrode/electrolyte interface is related to the ambient temperature. The output power of the lithium-ion battery will increase when the temperature rises. The temperature also affects the transmission speed of electrolyte. If the temperature rises, the transmission speed will be accelerated. If the transmission temperature drops, the transmission speed will be slowed down, and the battery charging and discharging performance will also be affected. However, if the temperature is too high and exceeds 45 ℃, the chemical balance in the battery will be destroyed, leading to side reactions.

The influence of temperature on discharge performance is directly related to discharge capacity and voltage. As the temperature decreases, the internal resistance of the battery increases, the electrochemical reaction speed slows down, the internal polarization resistance increases rapidly, and the discharge capacity and discharge platform of the battery decrease, affecting the output of battery power and energy. The capacity decline of lithium ion battery has the influence of battery polarization, that is, the lithium ion diffusion speed can not keep up with the electron transfer speed, which makes the lithium ion contained in the battery cathode less and less. This polarization process is further intensified at the high temperature of 60 ℃, which is the fundamental reason for the capacity degradation of lithium ion batteries.

The failure mechanism of lithium ion battery at high temperature is far more complicated than previous reports, and it is difficult to distinguish the loss of active lithium from the loss of active materials in practical research. In the process of lithium insertion of lithium iron phosphate materials, some lithium iron phosphate phases embedded with lithium will be isolated from the electronic conductive channel formed by the conductive agent due to the internal stress use, which will lead to the loss of active materials due to irreversible lithium deinterlation.