What factors affect the performance of lithium-ion batteries?

There are many influencing factors that affect the capacity of lithium-ion batteries. Factors such as operating temperature, charge and discharge current, and charge-discharge cut-off voltage will all affect the rate of degradation of lithium-ion batteries. The mechanism that causes the capacity decline of lithium-ion batteries can be divided into three categories: internal resistance and polarization loss of new positive and negative active materials, Li loss, and different external factors have different effects on these three. For example, lithium-ion batteries made of LiFePO4 material have very good cycle performance, but different use conditions have an important impact on the cycle life of lithium-ion batteries. Experiments have proved that 15C pulse discharge and 15C continuous discharge are performed on 26650 lithium ion batteries. The two discharge systems have completely different effects on 26650 lithium ion batteries. The 26650 lithium ion battery with 15C pulse discharge has a very rapid capacity decline. After 40 cycles of charging and discharging, 15C discharge can no longer be performed, but 1C discharge can still be performed. The 15C continuous discharge battery capacity decays slowly, and 15C discharge can still be performed after 60 times, but the decay rate of the 1C rate is faster than the 15C pulse discharge. The mechanism analysis concludes that the 15C pulse discharge battery has more LiF in the SEI film of the negative electrode, and LiF hinders the diffusion of lithium ions more, which makes the Li+ diffusion resistance and charge exchange resistance of the battery increase rapidly, thus making The polarization voltage of the battery is too large during the charging and discharging process, which leads to the rapid decline of the high-current discharge capacity of LiFePO4. Lithium-ion battery charging strategy Research on the impact of lithium-ion battery life decay can better guide our design of lithium-ion batteries. In the following, the impact of different charge control strategies on the life decline of lithium-ion batteries is studied, and its use mechanism is studied, and a life decline model of lithium-ion batteries is proposed. Research experiments have shown that when the charging current and cut-off voltage exceed a certain value, the decay of lithium-ion batteries will be greatly accelerated. In order to reduce the decay rate of lithium-ion batteries, it is necessary to select appropriate charging for different systems. Discharge current and cut-off voltage. It can be seen from the data that as the charging rate increases, the decay rate of lithium-ion batteries is also rapidly increasing, and from the slope of the curve, there are three different stages in the decay rate of the battery. The stage with a faster decay rate (stage 1), the stable stage with a slower decay rate in the middle (stage 2), and the later stage of decay rate acceleration (stage 3). According to the research on the decay mechanism of the three-stage battery, stage 1 may be because the growth of the battery SEI film consumes a part of Li+, so the decay rate is faster. In stage 2, as the structure of the SEI membrane becomes stable, the interior is relatively stable, so the decay rate is slower. In stage 3, as the battery ages, the loss of active materials begins to occur, and the active interface of the electrode decreases, making the battery very sensitive to current. Figure C is an experiment on the influence of different cut-off voltages on the battery decay speed. From the experimental results, it can be seen that when the charge cut-off voltage is increased to 4.3V, the cycle performance of the battery will deteriorate sharply. Lowering the charge cut-off voltage can be effective Improve the cycle performance of the battery. The analysis of the dynamic internal resistance of the battery is shown in the figure. From the test results of Figure a, when the charging current is less than 1C, the dynamic internal resistance of the battery changes with the battery cycle almost the same, but when the charging current exceeds 1C , The increase speed of the dynamic internal resistance of the battery will increase rapidly with the increase of the charging rate. From the test results in Figure b, when the charge cut-off voltage is 4.3V, the dynamic internal resistance of the battery increases very quickly, indicating that the high cut-off voltage will deteriorate the dynamic conditions of the battery. When the cut-off voltage is 4.1V and 4.2V, the dynamic internal resistance of the battery The increase in resistance is slower. 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 charge correctly to prevent cell phone battery explosion?