An introduction to the internal resistance standard of lithium batteries and the internal resistance characteristics of lithium batteries

The internal resistance, static internal resistance and operating internal resistance of lithium batteries are often different. In different environments, the internal resistance also changes with different temperatures. Temperature Ambient temperature is an important factor affecting the resistance of various lithium batteries, and directly determines the speed of electrochemical reaction and the speed of ion movement. The standard resistance of the internal resistance of a lithium battery indicates the degree of resistance of a circuit element to the current transmission. The unit is ohm. For lithium batteries, the internal resistance of lithium batteries is divided into ohmic internal resistance and polarization internal resistance. The ohmic internal resistance is composed of electrode material, electrolyte, diaphragm resistance and the contact resistance of each part. The internal polarization resistance refers to the resistance caused by the polarization during the electrochemical reaction, including the resistance caused by the electrochemical polarization and the concentration polarization. The ohmic resistance is mainly composed of the electrode material, electrolyte, diaphragm resistance, current collector, and the touch resistance of the connection of the tabs. It is related to the size, structure, and connection method of the battery. Polarization resistance, the resistance that appears at the moment when current is applied, is the sum of various trends in the battery that prevent charged ions from reaching their destination. Polarization resistance can be divided into two parts: electrochemical polarization and concentration polarization. The accurate calculation of the internal resistance of a lithium battery is quite complicated, and it will constantly change during the battery use process. According to relevant experience, the larger the volume of the lithium battery, the smaller the internal resistance; and vice versa. The internal resistance of the 18650 lithium battery that performs well at present is about 12 milliohms, and generally about 13-15 milliohms; because the impedance will affect the performance of the battery, generally 50 milliohms is normal, and 50-100 can be It is used, but the performance begins to decay. It must be used in parallel when it is above 100, and it cannot be used when it is above 200. The internal resistance is an important parameter to measure the power performance of the lithium battery and evaluate the life of the lithium battery. The initial internal resistance of the lithium battery is mainly determined by the structural design of the battery, the performance of the raw materials and the manufacturing process. In actual use, the change of battery internal resistance is also affected by various factors such as temperature and SOC. The internal resistance characteristics of lithium batteries. With the use of lithium batteries, battery performance continues to decay, which is mainly manifested in capacity decay, increase in internal resistance, and power drop. The change in battery internal resistance is affected by various conditions such as temperature and depth of discharge. Internal resistance is one of the important indicators for evaluating the performance of lithium batteries. Regarding the application of large lithium battery packs, such as power supply systems for electric vehicles, due to the limitations of test equipment, it is impossible or inconvenient to directly test the AC internal resistance. Generally, the characteristics of the battery pack are evaluated by the DC internal resistance. In practical applications, DC internal resistance is also used to evaluate the health of the battery, to predict the life, and to estimate the system SOC, output/input capabilities, etc. Disclaimer: Some pictures and content of articles published on this site are from the Internet, please contact to delete if there is any infringement. Previous: Comparison of the advantages of graphene batteries and lithium batteries