There are several things that can shorten the lifespan of a lithium ion battery, but they all come down to heat. Heat is generated through several means and leads to a cascade of detrimental effects on the battery's chemistry and physical structure. The most common ways heat damages a battery are by leaving it in direct sunlight, running too much current for too long, or using the battery for prolonged periods towards the lower end of its voltage range. To extend the life of your lithium battery when not in use, learn the best storage methods from our other articles.

Heats Effect on Lithium-Ion Degradation

There are so many ways heat can affect a battery. Whether it's internally generated from an external source, heat is the primary factor affecting a lithium-ion battery’s overall lifespan. Something as simple as exposing a battery to direct sunlight for long periods of time can drastically shorten its lifespan. When a battery is left in direct sunlight, it absorbs energy from the sun, leading to an increase in its temperature. Another avenue is high current demands; drawing excessive current from a battery causes an increase in internal resistance, which in turn generates heat.

Also, low-voltage operations contribute to this issue. As the battery discharges and its voltage drops, the internal resistance increases, further elevating the temperature. These factors combined can significantly impact the efficiency and safety of lithium-ion batteries.

Chemistry & Heats Impact on Battery Lifespan

Lithium-ion batteries, based on complex chemical reactions, are highly sensitive to temperature variations:

  • Chemical Instability: The chemistry of lithium-ion batteries is inherently unstable and temperature-dependent. Elevated temperatures can disrupt these chemical processes, leading to efficiency losses and potential hazards.
  • Resistance and Heat: Electrical resistance in batteries increases with temperature. This increase in resistance can create a positive feedback loop, further raising the temperature and exacerbating the problem.

Internal Resistance and Its Consequences

Internal resistance plays a pivotal role in how heat affects lithium-ion batteries:

  • Resistance Measurement: A typical lithium-ion cell has an internal resistance ranging from 15 to 30 milliohms.
  • Heat Generation: Current flowing through this resistance generates heat. For instance, 3 to 5 watts of heat loss in a battery can significantly increase its temperature, reducing its lifespan.

Voltage Level Considerations

Voltage levels within a lithium-ion battery also influence its thermal behavior. As the voltage drops below certain levels (below around 3 volts), the internal resistance increases, causing more heat generation and accelerating battery degradation. 

So, however much heat your battery generates under a 30 amp load when it's fully charged will be a whole lot different than the same load when the battery is almost dead.

Extending Battery Life

Lithium-ion batteries function through the movement of lithium ions between the anode and cathode in a solvent, typically lithium salt in an organic solvent. Charging a battery moves the ions to the anode while discharging them moves them back to the cathode. This process is susceptible to wear and degradation from heat, high voltages, and deep discharges.

Here is a basic run down and some things you can do to extend the life of a lithium-ion battery:

1. Optimal Charge Levels

Do Not Fully Charge or Deep Discharge: It’s best to charge lithium-ion batteries to about 80% and not let them drain below 20%. This helps in avoiding the stress that full charges or deep discharges can impose on the batteries. Battery University studies have shown that partial discharges, with occasional full discharges for calibration, can significantly extend battery life.

2. Appropriate Charging Practices

Use the Right Charger: Always use a charger that has the correct voltage and current that your battery needs. Using non-compatible chargers can affect charging cycles and degrade the battery.

Avoid Fast Charging: Constant use of fast chargers can degrade lithium batteries quicker. Fast charging works by increasing the voltage, which can heat up the battery and accelerate degradation.

3. Temperature Management

Keep Batteries Cool: Store and charge batteries in a cool environment. High temperatures cause lithium-ion batteries to degrade much faster. According to research, a lithium-ion battery operating at 25°C (77°F) will have a longer lifespan compared to one operating at 40°C (104°F). Find out if it's better to store lithium batteries charged or uncharged by checking our detailed guide in another article.

Avoid Cold Temperatures: Just as high temperatures can degrade batteries, exposing them to too cold temperatures can cause permanent damage, especially if charged while cold. The optimal storage temperature for a lithium-ion battery is around 15°C (59°F). Discover ways to keep batteries warm by exploring our tips in other articles.

4. Avoid Deep Discharges

Charge Before Empty: Lithium-ion batteries do not have a memory effect, so there is no need to fully discharge them before recharging, as was necessary with older battery types. Deep discharges can strain the battery; hence, charging periodically and making sure to discharge to no more than 20% is optimal. 

5. Handling and Care

Physical Protection: Avoid dropping or physically stressing the battery. Physical damage can lead to internal shorts, leading to battery degradation or failure. For lithium-ion battery safety tips, check out our detailed articles covering essential precautions and concerns.

Use Battery Cases: If possible, use a protective case for batteries, especially for those used in harsh environments to avoid mechanical stresses and punctures.

6. Proper Storage

Long-Term Storage: If storing a lithium-ion battery for a long period, charge it to about 50% every six months to maintain battery health and prevent it from going into a deep discharge state.

Finding the Perfect Trade-Off

Balancing battery usage and preservation involves finding a middle ground:

  • Charge-Discharge Levels: Charging to 80% and discharging to 20% can extend the battery's life by 2.5 to 3 times while sacrificing some capacity.
  • Watt-Hour Efficiency: This strategy, while reducing immediate capacity, increases the total watt-hours extracted from the battery over its lifespan.

Heat is the primary factor that shortens the life of lithium-ion batteries. By understanding and mitigating the sources of heat generation, such as exposure to sunlight, high current demands, and low voltage operation, the lifespan of these batteries can be significantly extended. Managing the internal resistance, optimal charging, and discharging practices are key to preserving the health and efficiency of lithium-ion batteries, thereby enhancing their longevity and overall performance in various applications.

It’s important to remember that charging, discharging, and even storage are part of the heat cycle for lithium ion batteries. The closer you keep your battery to room temperature, the longer its going to last.