When the temperature is low, the power characteristics of lithium iron phosphate batteries will greatly decrease, and in severe cases, it will affect normal use. Therefore, anti freezing measures should be taken. Lithium iron phosphate batteries cannot be used at temperatures below minus 10 degrees Celsius. Whether it is a ternary lithium battery or a lithium iron phosphate battery, temperatures below minus 10 degrees Celsius will have a certain impact on the performance of the battery.
At low temperatures, the internal resistance and capacity of lithium iron phosphate batteries will decrease, and even cause irreversible damage to the battery's structure. Compared with ternary lithium batteries, lithium iron phosphate batteries do perform very poorly in winter. When the ambient temperature is minus 10 ℃, the capacity of lithium iron phosphate batteries will decay by 40-50%; When the temperature reaches minus 20 ℃, the battery is likely to lose its discharge capacity directly. Therefore, the lower limit of the working temperature of lithium iron phosphate batteries is around minus 20 ℃ (about minus 30 ℃ for ternary lithium batteries).
The reason why lithium iron phosphate batteries have such poor discharge performance in low temperature environments in winter is still due to the characteristics of its raw materials. The positive electrode material of the battery, lithium iron phosphate, has poor conductivity and is prone to polarization, leading to battery capacity degradation.
The viscosity of the electrolyte inside lithium iron phosphate batteries also increases in low temperature environments, leading to an increase in the migration impedance of lithium ions, a slower diffusion rate of lithium ions, and a decrease in battery activity. At the same time, the binder of lithium iron phosphate batteries is also affected by low temperature, resulting in a decrease in battery performance.
In addition, in low-temperature environments, the SEI film on the negative electrode of lithium iron phosphate batteries will also become thicker, and its impedance will increase accordingly, leading to a decrease in the rate of lithium ion conduction between the SEI films. Therefore, severe endurance degradation of lithium iron phosphate batteries in winter is a characteristic of their materials. Currently, major automakers can only alleviate capacity degradation by installing battery temperature management systems and providing low-temperature heating functions.
