Commonly used methods for measuring the K value of lithium batteries

K is equal to OCV1-OCV2 divided by t1-t2. 2. The standard deviation feedback of the pressure drop difference is often used by some Japanese and Korean companies: △OCVu003eaverage (△OCV)+4.5, judge NG1NG for a period of time, retest and filter; prompt: The average value (△OCV) is the average value of △OCV; it is the standard deviation of △OCV. The K value of a good battery is generally less than 2mV/d or 0.08mv/h. Important factors affecting the K value are: 1. Positive and negative electrode materials, electrolyte Type, thickness type of diaphragm: Since self-discharge mainly occurs between materials, the properties of materials have a great influence on self-discharge. Someone has done experiments to prove that the self-discharge of ternary materials is higher than that of lithium cobalt oxide batteries; 2. Storage time: The longer the storage time, on the one hand, the absolute value of the pressure drop will increase; on the other hand, it pretends to reduce the absolute error/pressure of the instrument. Decrease the value to make the result more accurate. However, if the storage time is too long, the capacity balance between the positive and negative electrodes will gradually break and deepen, and the decomposition of the electrolyte will also accumulate some irreversible capacity loss, which will increase the self-discharge. The longer the time, the smaller the k value. 3. Storage conditions: The increase in storage temperature and humidity will increase the degree of self-discharge. 4. It is also related to the self-consumption of the battery protection board. 5. Test initial voltage: the initial voltage (or primary voltage) is different, the K value obtained is also different. The higher the initial voltage, the higher the self-discharge rate; technically speaking, the self-discharge capacity attenuates, but don’t let the battery discharge to directly measure the remaining capacity without proper equipment, and can only measure the self-discharge indirectly by measuring the voltage. It is the K value. If the variation of the environmental conditions leads to the deviation of the test voltage, it may cause the K value measurement error. Even if the actual measurement is negative, this is obviously inconsistent with the meaning of self-discharge itself, so the equipment should be checked regularly and the measurement environment is consistent. . Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.