Why Lithium Iron Phosphate Batteries Are Safer Than Ternary Lithium Batteries

Lithium iron phosphate (LiFePO4) battery and ternary lithium battery differ in several ways, particularly when it comes to "energy density" and "safety." While ternary lithium batteries offer higher energy density, their safety is often a concern. In comparison, lithium iron phosphate batteries have lower energy density, but they are widely regarded as safer.

For example, with 18650 battery (diameter: 18mm, height: 65mm), ternary lithium battery can have a capacity of up to 3500mAh, while a LiFePO4 battery maxes out at around 2000mAh in the same volume.

1. Higher Thermal Stability

LiFePO4 batteries have a higher thermal runaway temperature (~270°C or 518°F), compared to ternary lithium batteries (~200°C or 392°F).

Thermal runaway is a condition where excessive heat causes a chain reaction that may lead to fire or explosion. The higher the thermal stability, the safer the battery, particularly under extreme conditions like overcharging, overheating, or external damage.

This makes LiFePO4 less likely to catch fire, even if exposed to high temperatures, overcharging, or short circuits.

2. Chemical Stability

The chemical structure of LiFePO4 is inherently more stable than the materials used in ternary lithium batteries.

Iron phosphate (FePO4) is more resistant to oxidation and decomposition, reducing the likelihood of hazardous reactions.

Ternary lithium batteries, containing cobalt and nickel, are more reactive and volatile, which increases the risk of thermal runaway and fire.

3. Non-Combustible Nature

LiFePO4 batteries are non-combustible. Even in extreme conditions such as physical damage (e.g., puncturing), the battery’s chemical structure does not react violently, which significantly reduces the chances of a fire or explosion.

In contrast, ternary lithium batteries are more likely to release flammable gases and catch fire when punctured or damaged.

4. Improved Safety with Overcharging

LiFePO4 batteries are more tolerant of overcharging without risking catastrophic failure. Their safer charging characteristics reduce the potential for short circuits, swelling, or overheating, which are common risks in other lithium-ion chemistries.

Ternary lithium batteries can heat up rapidly if overcharged, increasing the risk of fire.

5. Lower Heat Generation

LiFePO4 generates less heat during charging and discharging, further minimizing the risks of overheating or failure due to excessive heat buildup. This is especially important in applications requiring high current or power, where overheating could lead to dangerous scenarios.

Ternary lithium batteries, on the other hand, can heat up significantly during rapid charging or discharging, which adds to the safety concerns.

6. Environmentally Friendly and Non-Toxic

LiFePO4 batteries do not contain toxic heavy metals like cobalt or nickel, which are used in ternary lithium batteries.

This not only makes them safer for humans in case of leaks or damage but also reduces the risk of environmental contamination.

The non-toxic materials make LiFePO4 batteries safer to handle, recycle, and dispose of.

7. Longer Cycle Life, Less Degradation

LiFePO4 batteries typically have a longer cycle life, meaning they degrade more slowly over time. This reduces the risk of capacity loss, which can lead to overheating or unsafe conditions in aging batteries.

Ternary lithium batteries degrade faster, which can result in a higher likelihood of safety issues as the battery ages.

8. Wide Temperature Tolerance

LiFePO4 performs better in extreme temperature environments, particularly in high-temperature settings, which helps maintain safety during use.

Ternary lithium batteries are more sensitive to temperature fluctuations and tend to degrade faster, which could lead to dangerous overheating in hot environments or poor performance in cold temperatures.

9. Safer in High Discharge Scenarios

LiFePO4 is capable of handling high discharge rates without compromising safety. In applications requiring heavy energy demand, such as electric vehicles or industrial applications, this is a key safety feature.

Ternary lithium batteries, under high discharge, may become unstable and pose a higher risk of overheating or fire.

Summary of Safety Factors

LiFePO4 batteries are safer than ternary lithium batteries because they:

Resist overheating and maintain stability at higher temperatures.

Have a chemically stable structure that is non-combustible and less prone to violent reactions.

Are more tolerant to overcharging and produce less heat during charging and discharging.

Do not contain toxic heavy metals, making them safer for both users and the environment.

Have a longer cycle life with less degradation over time, reducing the chance of safety failures.

These safety advantages make LiFePO4 batteries a better choice for applications where safety, longevity, and stability are critical concerns.