How does the voltage and current affect the life of the ternary lithium battery during the electric process?

Generally speaking, the ternary data we often refer to mainly refers to NMC data, including NCA data. The capacity of layered data is affected by its structural stability, because the chemical stability of Ni3+ is better than that of Co. Therefore, during the charging process, the NMC material can release more Li, which makes the capacity of the material greatly improved. Conversely, the structural stability of the layered oxide cathode material is also affected by the amount of de-Li. Excessive de-Li may cause the layered structure of the data to collapse. Therefore, in order to ensure the structural stability of the NMC data, the charging of the data must be cut off. The voltage is constrained to ensure the long-term cycle stability of the data. The impact of the charge cut-off voltage The amount of delithiation of the NMC material is proportional to the charge cut-off voltage, that is to say, the higher the charge cut-off voltage, the greater the delithiation of the NMC material, and the correspondingly more unstable the structure of the data. The figure below shows the cyclic function curve of NCM811 data under different charge cut-off voltages. It can be seen that after the cut-off voltage is increased, the data capacity has improved significantly, but the data decay rate is accelerated. Comparing the cycle data under different cut-off voltages, it is found that although the specific capacity is the highest at the fifth discharge at the cut-off voltage of 4.6V, the capacity drops rapidly after 53 cycles, which is lower than the NMC111 at the cut-off voltages of 4.5V and 4.4V. Capacity. This statement blindly improves the charging cut-off voltage, although the capacity of the data will be greatly improved, but it will cause a significant decrease in the cycle stability of the data, so it is necessary to choose a reasonable charge based on the planned life of the battery Cut-off voltage. The following figure shows the data of NMC111, NMC532, NMC622, NMC811 and NCA. After 53 cycles of different cut-off voltages, the discharge energy and discharge energy retention rate curve, as can be seen from the figure, after 53 cycles, the discharge energy density The highest is not the battery with the highest cut-off voltage. Regarding the NMC811 data, the highest discharge energy density was obtained at the 4.3V cut-off voltage. The NMC622, NMC532, and NCA data achieved the highest discharge energy density at the 4.4V charge cut-off voltage, and the NMC111 data was 4.5 V achieved the highest energy density. This is only the data after 53 cycles. With the increase of the number of cycles, the data under the higher cut-off voltage has a faster decay rate. According to the trend of the cycle curve in the figure above, when the cut-off voltage is the lowest, the discharge energy density will be Will be the highest. In addition, it can be seen from the figure below that no matter which kind of material increases with the charge cut-off voltage, it will cause the acceleration of the capacity decline, especially the NMC111, NMC532 and NMC622 materials with lower Ni content are more affected by the cut-off voltage. This indicates that the structural stability of the materials with lower Ni content is worse. The influence of ambient temperature In the actual use of lithium batteries, the high temperature stability of the data also needs to be considered. Johannes Kasnatscheew has conducted a research on the cycle function of NMC622, NMC811 and NCA data at room temperature and 60℃. The results are shown in the figure below. Generally speaking, increasing the temperature can improve the kinetic conditions in the battery, thereby improving the function of the battery. This can be clearly seen from the capacity of the battery at 60℃, but high temperature will definitely affect the cycle stability of the data. Impact. For example, at a normal temperature of 20°C, the three materials have a relatively close cycle function in the first 50 cycles, but after the temperature is increased to 60°C, the capacity retention rate of the NMC811 and NCA materials after 50 cycles is significantly lower than that of the NMC622 material , This declares that NMC622 data has higher thermal stability. Johannes Kasnatscheew analyzed the factors that affect the ternary data circulation function, such as the charging cut-off voltage and the formed voltage and current, and the influence of the ambient temperature on the NMC and NCA data circulation function. Essentially, it follows the new lithium removal quantity of the NMC data. Increase will cause the structural stability of the data to decrease and affect the circulation function. In addition, high temperature will also have a negative impact on the stability of the data, resulting in a decline in the data circulation function. Johannes Kasnatscheew also planned a new charging system based on the characteristics of the NMC data. It cuts off the capacity constraint and adjusts the charging voltage to ensure that the capacity of the battery is the same every time, so as to overcome the charging capacity and the charging capacity caused by the over-potential of the battery. The decline in discharge capacity greatly improves the cycle function of the battery. 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: How to repair the lithium battery of electric vehicles and what are the common faults?