Why does the capacity of lithium batteries decrease in winter?

Why does the capacity of lithium batteries decrease in winter? Since their listing, lithium batteries have been widely used because of their long service life, large specific capacity, and no recall effect. In low-temperature use of lithium batteries, there are problems such as low capacity, severe attenuation, poor cycle ratio function, obvious lithium disconnection, and unbalanced lithium disconnection. However, with the continuous expansion of application fields, the low-quality restriction brought by the low-temperature performance of lithium batteries has become more obvious. According to reports, the discharge capacity of lithium batteries at -20°C is only about 31.5% of that at room temperature. The operating temperature of traditional lithium batteries is between -20°C and +55°C. However, in the fields of aerospace, military, electric vehicles, etc., batteries can only work normally at -40°C. Therefore, improving the low-temperature performance of lithium batteries is of great significance. Factors restricting the low-temperature performance of lithium batteries at low temperatures, the viscosity of the electrolyte increases, and some of them even condense, resulting in a decrease in the conductivity of the lithium battery. At low temperatures, the compatibility of the electrolyte with the negative electrode and the separator becomes poor. At low temperatures, the negative electrode of the lithium battery is severely precipitated, and the lithium ions precipitated by the metal lithium react with the electrolyte, and the accumulation of the product causes the thickness of the solid electrolyte interface (SEI) to increase. At low temperatures, the charge transfer resistance (Rct) of lithium batteries increases significantly as the dispersion system in the active material decreases. Why does the capacity of lithium batteries decrease in winter? Discussion on the decisive factors affecting the low temperature performance of lithium batteries Expert opinion 1: The electrolyte has the greatest impact on the low temperature function of lithium batteries. The composition and physical and chemical properties of the electrolyte have an important influence on the low-temperature performance of the battery. At low temperatures, the battery cycle will face the following problems: the viscosity of the electrolyte increases, and the ion conduction speed becomes slower, resulting in a mismatch in the electron removal speed of the external circuit, causing serious polarization of the battery, and a sharp decline in charge and discharge capacity. Especially when charging at low temperature, lithium ions will form lithium dendrites on the surface of the negative electrode, causing the battery to fail. The low temperature function of the electrolyte is closely related to the conductivity of the electrolyte itself. Electrolyte with high conductivity has a fast ion transport speed and can exert greater capacity at low temperatures. The more lithium ions in the electrolyte are dissociated, the higher the removal rate of lithium ions, and the higher the conductivity of lithium ions. The higher the conductivity, the faster the ion conductivity, the smaller the polarization, and the better the battery's low-temperature performance. Therefore, high conductivity is a necessary condition for achieving good low-temperature performance of lithium batteries. The conductivity of the electrolyte is related to the composition of the electrolyte. Reducing solvent viscosity is one of the ways to improve electrolyte conductivity. The excellent fluidity of the solvent at low temperature is the key to ensure ion transport and the negative electrode formed by the solid electrolyte membrane electrolyte at low temperature also affects the lithium ion conduction and resi is the important impedance of the lithium battery in the low temperature environment. Expert 2: The important factor restricting the low-temperature performance of lithium batteries is the sharp increase of lithium ion dispersion impedance at low temperatures, not SEI. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Which is better for electric vehicle lithium battery or lead-acid battery