What are the factors that affect the low-temperature performance of lithium-ion batteries.

With the rapid development of lithium-ion batteries in the fields of electric vehicles and military industry, the disadvantage of their low-temperature performance not being able to adapt to special low-temperature weather or extreme environments has become increasingly apparent. Under low temperature conditions, the effective discharge capacity and energy of lithium-ion batteries will significantly decrease, and they are almost non rechargeable in environments below -10 ℃, which seriously restricts the application of lithium-ion batteries.

Lithium ion batteries are mainly composed of positive electrode materials, negative electrode materials, separators, and electrolytes. Lithium ion batteries in low-temperature environments have characteristics such as a decrease in discharge voltage plateau, low discharge capacity, fast capacity decay, and poor rate performance. The main factors that restrict the low-temperature performance of lithium-ion batteries are as follows:

The three-dimensional structure of positive electrode materials restricts the diffusion rate of lithium ions, especially at low temperatures. The positive electrode materials of lithium-ion batteries include commercialized lithium iron phosphate, nickel cobalt manganese ternary materials, lithium manganese oxide, lithium cobalt oxide, etc., as well as high-voltage positive electrode materials in the development stage such as lithium nickel manganese oxide, lithium iron manganese phosphate, lithium vanadium phosphate, etc. Different positive electrode materials have different three-dimensional structures. Currently, the main positive electrode materials used in electric vehicle power batteries are lithium iron phosphate, nickel cobalt manganese ternary materials, and lithium manganese oxide. Wu Wendi et al. studied the discharge performance of lithium iron phosphate batteries and nickel cobalt manganese ternary batteries at -20 ℃, and found that the discharge capacity of lithium iron phosphate batteries at -20 ℃ can only reach 67.38% of room temperature capacity, while nickel cobalt manganese ternary batteries can reach 70.1%. Du Xiaoli and others found that the discharge capacity of lithium manganese oxide batteries can reach 83% of their room temperature capacity at -20 ℃.

Due to the presence of high melting point solvents in the mixed solvent of electrolyte, the viscosity of lithium-ion battery electrolyte increases at low temperatures. When the temperature is too low, electrolyte solidification occurs, leading to a decrease in the transmission rate of lithium ions in the electrolyte.

The diffusion rate of lithium ions in graphite negative electrodes decreases under low temperature conditions. Xiangyu System studied the effect of graphite negative electrode on the low-temperature discharge performance of lithium-ion batteries and proposed that the increase in charge transfer impedance of lithium-ion batteries in low-temperature environments leads to a decrease in the diffusion rate of lithium ions in the graphite negative electrode, which is an important reason affecting the low-temperature performance of lithium-ion batteries.

Summary

At present, multiple factors affect the low-temperature performance of lithium-ion batteries, such as the structure of the positive electrode, the migration rate of lithium ions in various parts of the battery, the thickness and chemical composition of the SEI film, and the selection of lithium salts and solvents in the electrolyte.

The low-temperature performance limits the application of lithium-ion batteries in the fields of electric vehicles, military industry, and extreme environments. Developing lithium-ion batteries with excellent low-temperature performance is an urgent demand in the market.

Guangzhou Battsys Co., Ltd (NEEQ:837375), was founded in 2006, which is a join-stock high-tech enterprise engaging in ODM and OEM , specially for customized and diverse research&production of lithium-ion battery，BATTSYS annual production capacity is tens of millions battery cells. The products are exported to dozens of countries & regions such as Europe, America & Asia etc.