Power lithium batteries used in electric vehicles have reached the end of their service life, meaning that the decay of the battery reaches 20% of its initial capacity. The service life of the power lithium battery in the electric vehicle is repeatedly charged and discharged, due to the continuous occurrence of adverse reactions in the lithium ion battery, the material properties of the battery body will decline. This decline is due to the following aspects: changes in the lattice structure of electrode materials; The decomposition, peeling or corrosion of the electrode material will reduce the active material; The decrease of conductivity and increase of impedance caused by electrolyte decomposition and consumption; The removable lithium ions are consumed due to negative evolution of lithium or side reactions; The gas and insoluble material generated by the side reaction, as well as the modification of the binder and the corrosion caused by the fluid collector increase the impedance.

From the point of view of the actual environment conditions, the factors that affect the service life of the power lithium battery include the charge and discharge cut-off voltage, the charge and discharge ratio, the service temperature and the shelving conditions.

Many literatures have shown that the cycle life of different charging cut-off voltages decreases with the higher charging voltage in a certain range. This shows that the charge cutoff voltage has a great influence on the battery life. High charging cut-off voltage will aggravate the occurrence of adverse reactions and shorten the battery life. When the power lithium battery is used in the whole vehicle, due to the various driving conditions of the electric vehicle, the battery is prone to decline, and the performance of the battery decreases more seriously when charging and discharging in the higher potential area.

In order to meet different driving conditions, different charging and discharging rates are adopted in the use of power lithium batteries in electric vehicles. The research on charging and discharging rate of power lithium battery shows that charging and discharging at high rate will accelerate the decay of battery capacity. The larger the charging and discharging rate is, the faster the battery capacity decays. This is mainly due to the change of the structure and properties of the anode material and the thickening of the anode surface film, which leads to the difficulty of lithium ion diffusion. If the charge and discharge rate is too large, there may be overheating of the single battery, short circuit caused by explosion, etc.

Different power lithium batteries have different optimal service temperature, too high or too low temperature will affect the service life of the battery. With the decrease of temperature, the discharge capacity of Li-ion battery will decrease. This is because with the decrease of temperature, the ionic conductivity of the electrolyte decreases, causing the rapid increase of the internal resistance of the battery, resulting in the deterioration of the output performance of the battery at low temperature.

Power lithium battery in use under the condition of not in use, due to the nature of the battery itself self-discharge, positive and negative material passivation, electrolyte decomposition and so on. The experimental results show that the unstable performance of the negative SEI will lead to rapid decay of the anode active material and easy to precipitate lithium metal. The lithium ion battery with stable SEI film can be stored at high temperature for more than 4 years. At the same time, different electrolyte components have different effects on the decline of the electrode material.