Many electric vehicles (EVs) are equipped with lithium-ion batteries (Li-ion or LIB) that offer high energy and power density. Although the lifespan of EV batteries typically averages eight to 15 years, factors such as climate, driving habits, and charging cycles influence how slowly or quickly an EV battery ages.
Figure 1. The EV battery lifespan: capacity and power fade over time.
This article explores the effects of these variables on battery lifespan, the impact of battery aging on EV range and performance, and strategies to prolong battery life.
Understanding capacity fade
Every battery’s ability to hold a charge diminishes over time. In the context of EVs, this is known as capacity fade, leading to a reduced driving range. For example, a brand-new EV might initially offer a 300-mile range. However, regular use could decrease the projected range to 250 miles or even less.
This decline stems from:
- Electrode degradation: Both the anode and cathode in EV batteries deteriorate over time due to repeated charging and discharging. This results in cracking, dissolution, or structural changes, reducing the ability to store and release ions and, by extension, energy.
- Solid-electrolyte interface (SEI) growth: When an SEI layer forms on the anode during initial charge cycles, it’s beneficial because this layer protects the anode. However, continuous growth increases internal resistance and captures lithium ions, limiting the active lithium available for subsequent cycles.
Electrolytes, crucial for transporting lithium ions between electrodes, undergo degradation as EV batteries age. This degradation causes increased resistance and reduced ion movement, leading to excessive heat generation. A significant loss of electrolytes can even produce localized hotspots, heightening fire risks.
The nuances of power fade
While capacity fade impacts how far a vehicle can drive, power fade affects how quickly and responsively it moves and functions. A decline in peak power caused by an aging EV battery can affect acceleration and essential automotive systems such as regenerative braking. Since many EVs use regenerative braking to recapture energy when slowing down, the power fade significantly reduces the amount of reclaimed and stored energy.
Moreover, power fade impacts the efficiency and performance of auxiliary systems such as climate control and infotainment. In aging EV batteries, power fade is caused by many of the same factors described in the capacity fade section above, including electrode degradation, increased internal resistance, SEI growth, and decreased active or available lithium.
Factors accelerating battery aging
Several elements expedite EV battery aging, including:
- Temperature: Batteries are sensitive to temperature extremes. Prolonged exposure to high temperatures increases internal resistance and accelerates degradation. Conversely, charging at extremely low temperatures can lead to lithium plating (metallic lithium deposits on the anode surface), which affects battery life and performance.
- State of charge (SOC): Constant overcharging or consistently maintaining a battery near or at full capacity shortens its lifespan.
- Charging habits: While fast charging is convenient for EV owners, excessive use strains the battery and accelerates the aging process, as do frequent deep discharges.
- Driving style: In addition to causing vehicle wear and tear, aggressive driving speeds battery degradation due to high current draws. Rapid acceleration, hauling heavy loads, and frequently driving up steep inclines all reduce vehicle range.
Figure 2. The energy band of an aging EV battery. (Image: Battery University).
Extending EV battery life
Many EVs feature advanced battery management systems (BMS) that monitor the state of health (SOH), optimize charge and discharge cycles, and regulate temperature.
Grace capacity — extra battery capacity beyond the advertised amount — is often incorporated by the EV manufacturer as a buffer against natural degradation and provides an additional safety margin against harmful charging practices.
EV owners can also employ several strategies to extend battery life. These include parking in shaded areas or temperature-controlled environments, maintaining an optimal charging range (between 20% to 80%), and practicing smooth driving.
Batteries past their prime for EVs might still serve other second-life purposes, such as stationary energy storage or backup power sources.
Summary
EV batteries typically last eight to 15 years, with factors such as climate, charging patterns, and driving behavior influencing their aging rate. The primary outcomes of battery aging are capacity and power fade, which affect range and vehicle performance. While EV battery aging is inevitable, strategies such as optimal charging, advanced BMS, and proper storage can mitigate its effects.
References
- All-Electric Vehicles, US Department of Energy
- Battery Aging in an Electric Vehicle (EV), Battery University
- Electrode Degradation in Lithium-Ion Batteries, ACS Nano
- Solid Electrolyte Interphase Growth in Lithium Metal Cells with Normal Electrolyte Flow, Frontiers
- Understanding EV Battery Life, Sustainable Energy Authority of Ireland
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Filed Under: Batteries, FAQs