What are the calendar life and cycle life of lithium batteries? With the large-scale promotion and operation of electric vehicles, the marketization of electric vehicles is becoming increasingly apparent, and consumers' focus is largely on the power lithium batteries. Battery life includes cycle life and calendar life. Existing standards provide specific test methods for calendar life and cycle life, but only a few foreign test manuals cover calendar life. Below, we will explain what the calendar life and cycle life of lithium batteries are.
What is the calendar life of a lithium battery?
The calendar life of a lithium battery refers to the period from the date of manufacture to the end of its life, measured in years. This period includes various stages such as storage, aging, high and low temperature testing, cycling, and simulated operating conditions. The end of the life of one battery in a system often affects the operation of the entire system, causing overall system failure. Therefore, accurate estimation of battery health and research on calendar life can further guide battery operation.
The aging process of lithium batteries is extremely complex. Predicting their lifespan requires not only relevant empirical values and data accumulation, but also the development of models based on the battery's aging mechanism for more accurate predictions. Calendar life prediction for lithium batteries is of great significance for further guiding battery maintenance, extending battery lifespan, and reducing battery usage risks.
External factors affecting the calendar life of lithium batteries include temperature, state of charge, charge/discharge rate, cutoff voltage, and discharge window. The presence of unstable factors in the electrolyte at high temperatures accelerates battery aging, while low-temperature charging also negatively impacts battery performance. Furthermore, charging and discharging at different rates also accelerates lithium battery aging.
What is the cycle life of a lithium battery?
Battery standard cycle life refers to the number of charge and discharge cycles a battery can withstand before its capacity decays to a specified value under a certain charge and discharge regime. One cycle consists of one full charge plus one full discharge. Operating condition cycle life, on the other hand, is more commonly used for power lithium batteries in electric vehicles. It primarily assesses the battery's lifespan according to operating condition curves. This is important because the conditions encountered by a vehicle during driving are much more complex; different terrains and traffic conditions can all affect battery performance.
How to improve the cycle life of lithium batteries
1. During the electrolysis of lithium ions, the electrolyte primarily contains ester solvents, which are highly reactive and easily decomposed, resulting in poor stability in lithium batteries. However, ether solvents offer relatively better stability and can inhibit the growth of lithium dendrites. Therefore, we can see that ester solvents in lithium batteries exhibit more side effects during the reaction, significantly reducing the battery's cycle life and overall lifespan.
2. We know that lithium metal is very reactive and has strong reducing properties. The density it has during the deposition process is very important. This substance can effectively reduce the contact area between lithium metal and electrolyte, and at the same time avoid some side effects, thereby promoting the increase of cycle life.
3. To improve the stability and cycle life of lithium batteries, the composition of the electrolyte can be improved, increasing the proportion of substances with stronger stability, thereby improving battery density and other performance characteristics. In short, improving the cycle life of lithium batteries requires not only improving the high concentration of ether solvents in the electrolyte but also improving the deposition characteristics of lithium metal itself.
The cycle life of lithium batteries is influenced by many factors, directly affecting their usage time and quality. Only by effectively managing all factors affecting cycle life during research and development and production can companies gain a competitive edge in the fierce market. The calendar life and cycle life of lithium batteries have a non-linear relationship. The impact of external factors and changes in the battery's internal structure on performance degradation is significant for the study of calendar life.
