According to reports, the discharge capacity of lithium-ion batteries at -20°C is only about 31.5% of that at room temperature. The operating temperature of traditional lithium-ion batteries is between -20 and +55 °C. However, in aerospace, military and other fields, the battery is required to work normally at a temperature of -40°C or lower. Therefore, it is of great significance to improve the low-temperature properties of lithium batteries.
In terms of its influencing factors and reasons, it is actually its electrolyte. The electrolyte has the greatest impact on the low temperature performance of lithium batteries, and the composition and physicochemical properties of the electrolyte have an important impact on the low temperature performance of the battery. The problems faced by the battery at low temperature are: the viscosity of the electrolyte will increase, the ion conduction speed will become slower, resulting in the mismatch of the electron migration speed of the external circuit, so the battery will be severely polarized, and the charge and discharge capacity will decrease sharply.
Especially when charging at low temperature, lithium ions easily form lithium dendrites on the surface of the negative electrode, resulting in battery failure. The low temperature performance of the electrolyte is closely related to the size of the conductivity of the electrolyte itself. The electrolyte with high conductivity transmits ions quickly and can exert more capacity at low temperature. The more dissociated the lithium salt in the electrolyte, the higher the number of migrations and the higher the conductivity. The higher the electrical conductivity, the faster the ion conduction rate, the less the polarization, and the better the performance of the battery at low temperature. Therefore, higher electrical conductivity is a necessary condition to achieve good low-temperature performance of lithium-ion batteries.
The conductivity of the electrolyte is related to the composition of the electrolyte, and reducing the viscosity of the solvent is one of the ways to improve the conductivity of the electrolyte. The good fluidity of the solvent at low temperature is the guarantee of ion transport, and the solid electrolyte film formed by the electrolyte at the negative electrode at low temperature is also the key to affecting the conduction of lithium ions, and RSEI is the main impedance of the lithium battery pack in the low temperature environment.
It is not difficult for us to analyze that the electrolyte is one of the low-temperature characteristics that affect its lithium battery pack. But as long as the battery is used, the lithium battery pack is indispensable. Therefore, at low temperature, we can only use low-temperature cells as low-temperature lithium battery packs. It can work at -40 degrees, but if it is lower than this temperature, our technology needs to go further, but everything depends on technology. Progress and development, the future can be expected