Which factors affect the life of lithium-ion power lithium-ion battery

Regarding the end of the service life of the power lithium-ion battery used in electric vehicles, it means that the attenuation of the battery reaches 20% of the initial capacity. The service life of the power lithium-ion battery will be degraded due to the continuous occurrence of side reactions inside the lithium battery when the battery is repeatedly charged and discharged in the electric vehicle. This decline is due to the following aspects: changes in the lattice structure of the electrode material; reduction of active materials due to analysis, peeling or corrosion of the electrode material; decrease in conductivity and increase in impedance caused by the consumption of electrolyte analysis; due to lithium evolution in the negative electrode Or the side reaction causes the deintercalation of lithium ions to be consumed; the gas generated by the side reaction, insoluble substances, and the increase in impedance caused by the modification of the binder and the corrosion of the current collector. From the actual use of environmental conditions, the factors that affect the service life of power lithium-ion battery cells include the charge-discharge cut-off voltage, charge-discharge rate, use temperature, and shelf conditions. There have been many documents claiming that within a certain range, the cycle life of different charging cut-off voltages decreases with the higher the charging voltage. This shows that the charge cut-off voltage has a great impact on the battery life. A high charge cut-off voltage will aggravate the occurrence of battery side reactions and shorten the battery life. When the power lithium-ion 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 declines more severely when charging and discharging in the higher potential area. Lithium batteries are produced and customized. Different power lithium-ion batteries have different optimum operating temperatures, and excessively high or low temperatures will affect the service life of the battery. As the temperature decreases, the discharge capacity of lithium-ion power lithium-ion batteries will decrease. This is because as the temperature decreases, the ionic conductivity of the electrolyte decreases, causing the internal resistance of the battery to increase rapidly, resulting in poor output performance of the battery at low temperatures. When the power lithium-ion battery is left unused, self-discharge, passivation of positive and negative materials, and electrolyte analysis will occur due to the nature of the battery itself. Some test results stated that the instability of negative electrode SEI performance will lead to rapid decline of negative electrode active materials and prone to lithium metal precipitation. Lithium batteries that form a stable SEI film can be stored under high temperature conditions for more than 4 years. At the same time, different electrolyte components The degree of influence of the decline of the electrode material is different. The power lithium-ion battery adopts different charging and discharging rates in order to meet different driving conditions during the use of electric vehicles. Research on the rate charge and discharge of power lithium-ion batteries states that high rate charge and discharge will accelerate the attenuation of battery capacity. The greater the charge and discharge rate, the faster the battery capacity decays. This is mainly due to the change in the structure and properties of the positive electrode material and the thickening of the negative electrode surface film, which results in the difficulty of lithium ion diffusion. If the charge-discharge rate is too large, it may also cause the single battery to overheat, short-circuit and cause an explosion. The impact of the inconsistency of the monomers on the power lithium-ion battery pack. In the process of forming the single batteries, if the inconsistency of the voltage is large, it will cause the low-voltage battery to become the load of the battery pack when used together with the normal battery. Because when there is a low-voltage battery in the two batteries connected in parallel, mutual charging will occur, and other batteries will charge the battery. This connection method will increase the capacity of the low-voltage battery by a small margin and greatly reduce the capacity of the high-voltage battery, and the energy loss in mutual charging will not achieve the ideal external output. The inconsistency of the battery cells mainly occurs during the manufacturing process. Due to the level of technology, there are slight differences in the thickness of the battery plate, the microporosity, and the activation degree of the active material. This inconsistency in the internal structure of the battery will make it impossible to completely match the voltage, capacity, internal resistance, etc. of the same type of battery manufactured in the same batch. The influence of the inconsistency of the single battery on the service life of the power lithium-ion battery pack is divided into the inconsistency of the voltage, the inconsistency of the capacity, and the inconsistency of the internal resistance. The inconsistency of internal resistance makes the voltage and current distribution of the single lithium battery in the battery pack uneven, and local overvoltage charging or undervoltage discharge occurs. The inconsistency of internal resistance will also cause the heat loss of the single battery during the discharge process to be unequal. The greater the internal resistance, the faster the temperature rises, which may eventually cause thermal runaway. The initial capacity inconsistency has been greatly reduced after screening before the batteries are grouped, although the individual battery cells can be individually charged to balance the differences in the initial capacity of the single cells during use. However, the continued charging and discharging cycle process of electric vehicles will magnify this inconsistency to a certain extent. The decay rate of capacity varies with the cycle. As the number of battery cycles increases, the difference in capacity will become larger and larger. This will make the capacity of the single battery attenuate intensified and drive the capacity attenuation of the entire battery pack. Various inconsistencies such as voltage, capacity, internal resistance, etc. lead to differences in battery cell life and battery pack life. It is important to show the current temperature difference, charge-discharge rate difference, discharge depth difference, and available capacity difference. For example, the difference in the depth of discharge, due to the difference in the initial capacity of the battery cells, most of the batteries are still in the state of shallow discharge, and the low-capacity battery cells have been deeply discharged. 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: Why do new energy vehicles favor nickel-metal hydride batteries?