The Debate on LFP Battery Charging Challenges and Findings

TapTechNews August 26th news, electric vehicles are increasingly adopting lithium iron phosphate (LFP) batteries as they are cheaper, safer, and have a longer lifespan than traditional nickel manganese cobalt (NMC) batteries. However, LFP batteries have a lower energy density and are thus typically used in entry-level models.

TapTechNews noted that automakers recommend regularly charging LFP batteries to 100%, with Tesla suggesting once a week and Ford suggesting once a month. This helps calibrate the battery pack and ensures accurate range display on the dashboard for each drive. Automakers also say that doing so helps maintain battery health and avoid performance degradation.

For NMC batteries, the opposite is the case. Automakers recommend limiting daily charging to 80-90%, and charging them to 100% may reduce the energy storage capacity of the battery pack over time. This is because battery life is inversely related to heat and voltage. The fuller the charge, the higher the voltage and heat in the battery pack, accelerating aging.

However, new research published last week in the Journal of the Electrochemical Society contradicts automakers' claims about the LFP charging model. The research shows that repeatedly charging and cycling at higher charging states may damage LFP batteries over time. The research details how this process occurs at the most microscopic level.

Researchers found that fully charging LFP batteries creates harmful compounds in the battery pack that come from high voltage and high temperature. Frequently cycling the battery pack (that is, fully discharging and charging) causes these harmful compounds to deposit on the negative electrode and consume lithium, leading to aging. At higher charging states, the voltage is higher and the negative electrode reaction inside the electrolyte will accelerate, consuming the lithium inventory, the author said.

However, the research said that 0-25% charging cycles can extend battery life. This seems rather pointless for everyday users, especially without a home charging station. The research only focuses on battery life, not overall best charging practices.

Higher charging states are beneficial in most cases, such as for long trips, when the car needs to power the home in case of a power outage, when the range is shortened in winter, or just for peace of mind. In addition, modern batteries can travel hundreds of thousands of miles even with bad charging habits.

The most important thing is that the research authors do not recommend that users change their charging habits. They said, How practical is it to cycle battery cells only within the low charging state range? There is clearly a trade-off between useful capacity and capacity retention... It is not realistic to recommend only cycling LFP batteries between 0%-25% charging states because it is a waste of capacity.