In recent years, reference documents in various countries around the world have carried out a lot of scientific research on the embrittlement system and regularity of lithium batteries. It is widely believed that the accumulation of lithium ion batteries, the increase in SEI film thickness and the damage of active materials are the cause of the embrittlement and volume attenuation of rechargeable batteries. The key reason is that the abuse of lithium batteries will accelerate the embrittlement of rechargeable batteries, and all normal charging and discharging will also endanger the physical and mental health of rechargeable batteries and accelerate the embrittlement of rechargeable batteries.
1. The harm of temperature to the SOH value of rechargeable batteries
It is generally believed that temperature is a key element that endangers battery health. Temperature has a two-way hazard to battery performance. On the one hand, high temperature will accelerate the chemical changes inside the rechargeable battery and improve the high efficiency and characteristics of the rechargeable battery. On the other hand, high temperature will make some irreversible. The chemical change produced by the rechargeable battery causes the active material in the rechargeable battery to decrease, resulting in the embrittlement of the rechargeable battery and the volume attenuation coefficient. Scientific research results show that high temperature will accelerate the growth and development of the SEI film of rechargeable batteries, increase the difficulty of lithium-ion batteries through the SEI film, and increase the internal resistance of the rechargeable battery.
2. The harm of charge and discharge current rate to SOH composition
Using the Sony 18650 rechargeable battery to carry out three different charge and discharge multiples of 300 cycle system tests, the results show: the respective attenuation coefficient of battery power, battery power reduction, battery internal resistance expansion, battery internal resistance expansion, battery internal resistance expansion, battery internal In addition, the charging and discharging of polymer cells will cause a lot of heat inside the rechargeable battery, which will accelerate the embrittlement of the rechargeable battery. According to the observation of the transmission electron microscope, the SEI film of the charge and discharge level of the polymer battery rechargeable battery is lower. Multiple charge and discharge film thickness.
3. The harm of deep discharge to the SOH value of rechargeable batteries
Battery charging is deeply related to the battery’s physical and mental health and embrittlement. Some insights believe that the battery has accumulated total migration kinetic energy. Based on the total migration kinetic energy, the volume attenuation coefficient and embrittlement of the battery are analyzed. According to the deep cycle system experiment on different charging and discharging of lithium batteries, Feixiang et al. analyzed the relationship between the accumulated migration kinetic energy of the battery and the battery capacity attenuation coefficient, and obtained the battery capacity attenuation coefficient to 85% before the battery is deep charged, deep discharge and shallow discharge The accumulation and migration kinetic energy under the two methods are basically the same. When the battery capacity attenuation coefficient reaches 85% to 75%, the accumulation and migration kinetic energy and the high efficiency of kinetic energy of the battery under the deep charge and deep discharge method are better than the shallow discharge method.
4. The harm of circulatory system spacing to the SOH concentration value of rechargeable batteries
The cycle system interval time of charging and discharging lithium battery packs will also endanger the whole process of embrittlement of rechargeable batteries. The interval time of the cycle system is different. The internal resistance of the matched battery is different, so the rechargeable battery is hot and the reaction is slightly different during the cycle. , Long-term operation will endanger the physical and mental health and embrittlement of rechargeable batteries. Experts believe that the SOC range of rechargeable batteries is 20% to 80%, which is beneficial to the physical and mental health of rechargeable batteries and the service life of the circulatory system.
5. The harm of battery charging cut-off voltage to SOH value
Excessive charging and loss of lithium battery packs will endanger the physical and mental health of rechargeable batteries, and poor working voltage upper and lower limits will also endanger the physical and mental health of lithium battery packs. Along with the reduction of the working voltage up to charging and discharging, the internal resistance of the battery expands, causing the internal battery to become hot. In addition, adverse reactions increase, the battery active material decreases, the negative-grade high-purity graphite sheet collapses, the battery accelerates embrittlement, and the attenuation coefficient volume. Too high battery charge cut-off voltage causes the internal resistance of the battery to expand, and the internal heat of the rechargeable battery increases. Too much charging of the battery will cause a negative level to cause a “lithium evolution” condition, which will cause an increase in adverse reactions and endanger battery power and embrittlement.
All in all, the operating temperature of the rechargeable battery, the charging rate of the battery, the depth of charge and discharge, the time interval of the circulatory system, and the battery charging cut-off voltage are all harmful to the physical and mental health and service life of the rechargeable battery. The scientific research on the factors affecting battery health is still in the qualitative analysis process at this stage. Qualitative analysis of such influencing factors and the coupling relationship between each element is a difficult problem for scientific research, and it is also a hot spot for future research on battery health and service life. .