Lithium-ion batteries have become the dominant rechargeable battery technology for consumer electronics like smartphones and laptops, as well as electric vehicles. However, lithium-ion batteries still have limitations on how long they last before degrading and eventually failing. Understanding the factors that reduce lithium-ion battery lifespan can help you take steps to prolong their useful life.
Chemical degradation
The heart of a lithium-ion battery is the electrolyte, a liquid that allows lithium ions to flow between the positive and negative electrodes. However, the commonly used electrolytes in lithium-ion batteries are unstable and decomposed over time during charging and discharging. This electrolyte decomposition leads to permanent loss of lithium ions, reducing battery capacity over the battery’s lifetime.
Another chemical process that degrades lithium-ion batteries is the growth of metallic lithium dendrites on the negative electrode. Dendrites reduce performance and can eventually cause internal short circuits, leading to complete battery failure. New electrolyte additives and composite electrode materials are being researched to suppress dendrite growth.
High temperatures
Exposure to high temperatures accelerates unwanted chemical reactions inside lithium-ion batteries. Studies have found that storing or operating lithium-ion batteries above 30°C significantly shortens their lifespan compared to storage around 20°C. High temperatures reduce cycle life more rapidly than calendar life for stationary applications.
The negative impact of temperature on battery degradation is even more severe for electric vehicles. The battery pack temperature can spike much higher than ambient conditions during fast charging or driving. Research suggests limiting maximum battery temperature to around 45°C could double the lifetime of electric vehicle batteries.
Ways to reduce high temperature damage
- Avoid leaving devices or vehicles containing lithium-ion batteries in hot environments for extended periods.
- Use thermal management systems with cooling capabilities to keep battery temperature in check.
- Design battery packs to minimize internal heat generation and improve passive cooling.
- Charge batteries slower to reduce heat buildup.
Overcharging
Charging lithium-ion batteries too high leads to accelerated loss of battery capacity. Most lithium-ion batteries are designed to operate safely between around 3.0-4.2V per cell. Charging to higher voltages causes electrolyte oxidation and electrode degradation.
Overcharging can also lead to plating of metallic lithium, especially on the graphite negative electrode. Reducing the maximum charge voltage extends cycle life but decreases usable capacity. Battery management systems prevent overcharging by limiting charge voltage.
Ways to prevent overcharging damage
- Use a quality battery charger or device that follows manufacturer charge voltage limits.
- Don’t leave batteries plugged into chargers for extended periods after reaching full charge.
- Replace older batteries that may have faulty charge management.
Deep discharge cycles
Discharging lithium-ion batteries below around 2.5V per cell also causes premature capacity loss. The copper component of the negative electrode dissolves at low voltages, reducing stability over cycles. Deep discharge events are especially harmful at higher temperatures.
Battery management systems avoid overly deep discharges by shutting down the battery when cell voltage gets too low. However, imperfect cell balancing can lead to individual cells dropping below safe levels prematurely.
Ways to avoid deep discharge damage
- Recharge batteries before they become completely depleted.
- Do not store batteries in a discharged state for extended periods.
- Replace unbalanced battery packs prone to individual cell under-voltage.
High current loads
Drawing high levels of current from lithium-ion batteries generates internal resistance heating and accelerates cell degradation. Continuous current loads above 1C generally have a more negative impact on lifespan than intermittent pulses. This effect depends on cell construction.
Electric vehicle battery packs experience high load currents during acceleration and fast charging. Improved cooling systems and lower resistance electrode materials can help minimize damage from high current operations.
Ways to protect against current stress
- Avoid frequently demanding maximum output current from the battery.
- Use lower current chargers for longer battery life.
- Choose batteries designed for high drain applications.
Mechanical damage
Lithium-ion batteries contain thin electrodes and separators pressed together inside a metal can or pouch. Internal mechanical damage can occur if the battery is crushed, penetrated by a sharp object, or deformed from swelling.
Mechanical abuse crushes active materials and separates internal components, often causing immediate battery failure. Swelling commonly results from cell imbalance, overcharging, or short circuits.
Ways to avoid mechanical damage
- Protect batteries from crushing and puncturing with sturdy cases.
- Do not open or deform battery housings.
- Inspect batteries for swelling and replace if detected.
- Use metal can cells instead of pouches when needed for ruggedness.
Age and cycling
Lithium-ion batteries have a finite lifetime even if all other degradation factors are minimized. Gradual loss of active lithium ions, breakdown of electrodes, and loss of electrolyte performance occurs over time and repeated charge/discharge cycles.
Battery capacity slowly fades during use until dropping below 80% of original capacity, which is considered end-of-life for most applications. The total lifespan depends on battery materials, usage conditions, and other factors below optimal temperatures.
| Battery Type | Estimated Lifespan |
|---|---|
| Smartphone | 300-500 cycles |
| Electric vehicle | 1,000-3,000 cycles |
| Energy storage | 5,000-10,000 cycles |
Ways to maximize cycle life
- Use moderate charge and discharge rates.
- Avoid exposing batteries to high temperatures.
- Charge to lower maximum voltage when possible.
- Do not fully discharge batteries.
Poor cell balancing
Lithium-ion battery packs contain multiple cells connected in series and parallel. Mismatched cells degrade unevenly and can limit the lifetime of the overall pack.
Individual cells vary slightly in capacity and internal resistance due to manufacturing inconsistencies. Weaker cells tend to get over-discharged or overcharged first. Active and passive cell balancing helps, but imbalance can still occur over time.
Ways to improve cell balancing
- Use batteries with advanced active balancing ICs.
- Avoid using low-quality bargain battery packs.
- Charge fully once in a while to calibrate cell voltages.
- Replace unbalanced packs showing uneven cell voltages.
Conclusion
Lithium-ion batteries are complex electrochemical systems with many modes of degradation over their operational lifetime. While battery technology continues to improve, taking steps to avoid damage from heat exposure, overcharging, deep discharging, mechanical abuse, and imbalanced cells can help maximize lifespan. However, all lithium-ion batteries will eventually fail as age and cycling irreversibly damage cell components.