Lithium Iron Phosphate Battery: Discharge Characteristics and Lifespan Explained

Lithium iron phosphate (LiFePO4) batteries have gained significant attention in the battery industry due to their outstanding performance and stability. As a notable branch of lithium-ion batteries, LiFePO4 batteries offer unparalleled advantages in discharge characteristics, lifespan, and over-discharge tolerance. This article examines these features using the STL18650 LiFePO4 battery as an example.

1. Stable Discharge Characteristics
   The discharge curve of the STL18650 battery (1100mAh capacity) demonstrates exceptional stability across various discharge rates (0.5C to 10C):

Voltage Stability

During discharge, the voltage remains within 2.7V to 3.2V until the capacity reaches nearly 800mAh, where it slightly declines.
This stability ensures consistent output, making it ideal for applications requiring steady voltage.
High-Rate Discharge Capability

Even at a 10C discharge rate, the STL18650 battery maintains a reliable voltage profile, highlighting its suitability for high-power applications.

2. Temperature Adaptability
   LiFePO4 batteries excel in extreme temperature conditions, offering reliable performance across a wide range:

Temperature Impact on Capacity

At 23°C, the battery achieves 100% discharge capacity. At 0°C and -20°C, the capacity drops to 78% and 65%, respectively.
At +40°C, the battery slightly exceeds its nominal capacity, showcasing excellent high-temperature adaptability.
Low-Temperature Operation

The STL18650 operates effectively at -20°C, though with a 35% reduction in output energy, making it suitable for cold environments.

3. Exceptional Charge-Discharge Cycle Life
   Cycle life is a critical metric for assessing battery durability. The STL18650 excels in this area:

Test Conditions

The battery underwent 570 charge-discharge cycles at 1C charging and 2C discharging rates.
Capacity Retention

After 570 cycles, the battery retained 100% of its original capacity, demonstrating exceptional longevity.
This durability makes it ideal for high-frequency applications such as electric vehicles and energy storage systems.

4. Superior Over-Discharge Performance
   Over-discharge to zero voltage is often detrimental to batteries, but the STL18650 showcases remarkable resilience:

Zero Voltage Storage Test

After being discharged to 0V and stored for 7 days, the battery exhibited no leakage and retained 100% capacity. Even after 30 days of storage, the capacity only dropped to 98% and fully recovered after three charge-discharge cycles.
This result underscores the battery’s robustness, even under extreme conditions.
Comparative Advantage

Unlike other lithium-ion batteries, LiFePO4 batteries excel in over-discharge scenarios, enhancing reliability and user confidence.