Impact of State of Charge (SOC) on Battery Degradation During Fast Charging
The state of charge (SOC) significantly influences degradation rates during fast charging due to its effect on lithium-ion diffusion and plating risks:
- High SOC risks: At high states of charge (e.g., above 80%), lithium ions face fewer available spaces in the graphite anode during charging. This increases the likelihood of lithium plating, where ions deposit as metallic lithium instead of intercalating into the anode. Plating accelerates capacity loss and can lead to permanent damage.
- Combined stressors: Fast charging at high SOC compounds degradation by forcing ions into the anode at accelerated rates, further straining the battery. High currents and elevated temperatures during fast charging exacerbate chemical instability, particularly when the battery is already near full capacity.
Mitigation Strategies
Mitigation strategies used by modern EVs include:
- Charging buffers: Most EVs limit the usable SOC range (e.g., capping at 80-90% for daily use) to reduce stress on the battery.
- Thermal management: Systems actively cool batteries during fast charging to maintain optimal temperatures (around 25°C), reducing plating risks while balancing SEI layer growth.
For drivers using fast chargers frequently, minimizing high SOC charging (e.g., charging to 80% instead of 100%) can help preserve battery health.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/how-does-the-state-of-charge-influence-battery-degradation-when-using-fast-chargers/
