Lead Acid replacement for solar street lights: the reason for the decline of Lead Acid replacement capacity in winter
Lithium batteries have been widely used since they entered the market. The reason is that the Lead Acid replacement has the characteristics of large capacity, small size, and no pollution to the environment. However, in a low temperature environment, the application of Lead Acid replacement packs has problems such as low capacity, severe attenuation, and poor cycle rate performance.
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, it is required that the battery can 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 will affect the low temperature function of the Lead Acid replacement pack, and the composition and physicochemical function of the electrolyte have an important impact on the low temperature function 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, and the electron transfer speed of the external circuit will not match, so the battery will show severe polarization 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 can transfer ions quickly and can exert more capacity at low temperature. The more the lithium salt in the electrolyte dissociates, the more the number of migrations and the higher the conductivity. The higher the conductivity, the faster the ion conduction rate, the smaller the polarization, and the better the function of the battery at low temperature. Therefore, higher electrical conductivity is a condition for achieving good low-temperature function of lithium-ion batteries.