With the large-scale promotion and operation of electric vehicles, the marketization of electric vehicles is becoming more and more obvious, and most of the consumers' concerns about electric vehicles focus on the power battery. Battery life includes cycle life and calendar life. Existing standards give specific test methods for regular life and cycle life, but only a few foreign test manuals cover calendar life. What is the calendar life and cycle life of Li-ion battery?
What is the calendar life of Li-ion battery?
The calendar life of a Li-ion battery is the period of time from the date of production to the end of life of the battery measured in years, which includes different aspects such as shelving, aging, high and low temperature, cycling, and working condition simulation. The end of battery life of one battery in a system often affects the work of the whole system and causes the overall system failure, so the correct estimation of battery health and the study of calendar life can further guide the operation of the battery.
The aging process of Li-ion battery is an extremely complex process, and the prediction of its life requires not only the empirical values and data accumulation about the battery, but also a model based on the aging mechanism of the battery to predict more accurately. The calendar life prediction of Li-ion battery is important to further guide the battery maintenance, extend the battery life and reduce the risk of battery use.
The external factors of Li-ion battery calendar life include temperature, charge state, charge/discharge rate, degree of cut-off voltage and discharge window, etc. The presence of unstable factors in the electrolyte at high temperature makes the battery aging faster, while low temperature charging will also adversely affect the decay of battery performance, in addition, the charge/discharge process at different rates will also accelerate the aging of Li-ion batteries.
What is the cycle life of Li-ion battery?
The standard cycle life of a battery refers to the number of charge and discharge cycles the battery can withstand before its capacity decays to a certain specified value under a certain charge and discharge regime. One cycle means one full charge + one full discharge. The working cycle life is mostly used for the power battery of electric vehicles, which is mainly assessed by the battery according to the working condition profile to test the service life of the power battery. This is mainly because the conditions of the car in the process of driving will be much more complex, different terrain, different traffic conditions, etc. will affect the working conditions of the battery.
How to improve the cycle life of lithium-ion batteries
1, lithium ion in the work of electrolysis occurs when the electrolyte contains substances mainly ester solvent, which has a relatively high reactivity and can be easily decomposed, so it is less stable when used in lithium batteries; but another substance ether solvent, which has relatively good stability, but also inhibits the growth of lithium metal dendrites. So we can see that the ester solvent in lithium batteries in the reaction, will produce more side effects, making the battery cycle times greatly reduced, life will also be reduced as a result.
2, we know that the performance of lithium metal is very active, reduction is also strong, it is very important in the process of deposition of the presence of a dense, this substance can well reduce the lithium metal and electrolyte contact area, but also to avoid the occurrence of some side effects, thereby promoting the growth of cycle life.
3, if you want to make lithium-ion batteries have stronger stability and cycle life to get better growth, you can improve the composition of the electrolyte ratio of substances, the proportion of substances with greater stability can be floated, so as to improve the battery density and other performance. In short, to improve the cycle life of lithium-ion batteries not only need to improve the electrolyte inside the high concentration of ether solvents but also to improve some deposition characteristics of lithium metal itself.
The factors affecting the cycle life of lithium-ion batteries are many, cycle life directly affects the use of lithium-ion battery time and quality, only in the development and production process will affect the cycle life of the various factors are well grasped, the enterprise can take the initiative in the fierce competition in the market. The calendar life of lithium-ion batteries and their cycle life into a non-linear relationship, the battery external factors and changes in the internal structure of the battery on the battery performance decay, the study of the calendar life has a certain degree of significance.
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