Analysis of performance degradation of lithium iron phosphate power battery under slightly overcharging cycles

Lithium-ion batteries may be slightly overcharged due to the errors in the Battery Management System (BMS) state estimation when used in the field of vehicle power batteries, which may lead to problems such as battery performance degradation and battery stability degradation. Therefore, this paper conducts an experimental study on the influence of slightly overcharging cycles on battery performance degradation, and builds a semi-empirical capacity degradation model under slightly overcharging cycles on this basis. The experimental results show that the slightly overcharging cycle causes the capacity decay of the battery to be significantly accelerated, and its capacity decay will also cause the capacity “diving” phenomenon at the end of its life under normal cycle conditions. The slightly overcharging cycle has little effect on the internal polarization resistance of the battery. But it has a greater impact on the ohmic internal resistance due to the thickening of the SEI film.