How to Extend the Lifespan of Lithium Batteries?
Lithium batteries are found in various devices in our daily lives. As consumers, we care about what usage habits can extend their lifespan. In the article of lithium battery evaluation metrics, it was described that battery lifespan includes cycle life and calendar life. Cycle life simply refers to the number of charge-discharge cycles, while calendar life denotes the duration of storage. Below, we will discuss each separately, and finally, explain what usage habits help extend lifespan for different products.
Cycle Life
The cycle life of lithium-ion batteries is primarily determined by several factors: charge/discharge current, temperature, and charge/discharge range. To enhance user experience, battery development trends prioritize rapid charging and discharging capabilities. From OPPO’s 2015 R7 series slogan “5 minutes of charging for 2 hours of talk time” to BYD’s recent megawatt flash charging technology touting “5 minutes of charging for 400 km of range,” the emphasis has been on rapid charging capabilities. However, fast charging is detrimental from the perspective of battery cycle life. On one hand, high-current charging causes significant battery heating, and elevated temperatures accelerate side reactions within the battery. On the other hand, high currents themselves catalyze internal side reactions like dendrite growth, particle fragmentation, and thickening of the SEI film. Therefore, daily opt for slower charging with lower currents when time permits. For instance, with a phone supporting up to 100W charging, using a 65W charger can effectively extend battery life and maintaining a satisfactory user experience. For electric vehicles, opt for overnight slow charging whenever possible. This avoids disrupting travel plans and takes advantage of cheaper off-peak electricity rates. It’s also important to note that a battery’s fast-charging capability diminishes over time. Consequently, batteries with longer usage histories should be particularly avoided from high-current fast charging. Battery operating temperature significantly impacts cycle life. Charging at both high and low temperatures accelerates aging. High-temperature aging is primarily driven by intensified electrolyte side reactions and thickening of the SEI film, while low-temperature aging is mainly caused by lithium dendrite growth. Consequently, the recommended operating temperature range for batteries is 10–35°C.
The charge-discharge range refers to the minimum and maximum levels at which a battery is charged and discharged. Most users experience range anxiety below 30% capacity and charge to 100%. However, from a cycle life extension perspective, this 30%-100% habit is suboptimal. Various experimental data consistently show that for all types of lithium-ion batteries[1~3], the cycle life in the higher charge range (30%–100%) is significantly shorter than in the intermediate range (20%–90%), which deliver nearly identical total energy. This occurs because at higher charge levels, the cathode exhibits stronger oxidation tendencies and the anode stronger reduction tendencies, accelerating side reactions. Furthermore, charging at high charge levels increases the likelihood of lithium plating. If you examine the charging power of smartphones or electric vehicles closely, you’ll notice that even fast-charging batteries reduce their charging power at high charge levels.
Therefore, from a cycle life perspective, the methods to extend battery lifespan are: reduce charging power, operate within the appropriate temperature range (10–35°C), and use the battery within the mid-range charge level (20%–90%).
Calendar Life
Calendar life significantly impacts overall lifespan yet is often overlooked. Rarely do smartphone, EV, or battery manufacturer presentations highlight calendar life metrics. This stems partly from the difficulty in obtaining accurate calendar life test data, as lithium-ion battery calendar life is measured in years—a timeframe severely mismatched with today’s short product development cycles.On the other hand, product replacement cycles are often shorter than the calendar life of batteries. The calendar life of lithium batteries also varies significantly across different application fields. Typically, lithium-ion batteries in consumer and power applications have a calendar life of 3 to 8 years, while those in energy storage applications often last 10 to 20 years. However, this does not mean that calendar life becomes irrelevant if batteries do not reach the required lifespan before product replacement. It not only impacts the end-of-life user experience but also affects the product’s residual value. Once the lithium battery recycling industry matures, batteries will inevitably be recycled and repurposed in tiers based on their health status. Furthermore, for most home electric vehicles, driving and charging/discharging time constitute a very small proportion of their operational time. They spend the majority of their time parked and idle. Therefore, greater attention should be paid to how calendar life affects overall battery lifespan.
The calendar life of lithium-ion batteries is primarily determined by the state of charge (SOC) and temperature during storage. Higher SOC levels and higher temperatures accelerate calendar life degradation. Taking lithium iron phosphate batteries as an example, their calendar life at 45°C/100%SOC is less than one-quarter of that at 25°C/50%SOC—a significant disparity. Thus, to maximize calendar life, extend battery longevity by parking vehicles at moderate temperatures, minimizing summer outdoor exposure, and avoiding prolonged storage at high charge levels.
In summary, good habits for extending lithium battery life in consumer products include: using a charger with lower wattage than advertised, avoiding full charges, and steering clear of extreme temperatures during use. For lithium-ion electric vehicles, beneficial practices encompass: prioritizing overnight slow charging, avoiding full charges, avoiding operation in extreme temperatures, preventing prolonged exposure to high heat, and avoiding extended storage at high charge levels.