Multi-factor aging in Lithium Iron phosphate batteries: Mechanisms and insights

Lithium-ion batteries are extensively employed in transportation and the integration of renewable energy sources. However, the aging process significantly impacts their performance, and the mechanisms behind this aging during operation are not completely understood. This study involved designing a 5-factor, 3-level orthogonal experiment with commercial lithium iron phosphate (LFP) batteries to assess the factors associated with aging and to clarify the aging mechanisms. The factors examined included environmental temperature (T), charging current (I_chg), discharging current (I_dis), charging voltage limit (V_chg), and discharging voltage limit (V_dis). The findings indicated that the factors affecting the degradation of battery performance, ranked from most to least influential, are T, V_chg, I_chg, I_dis, and V_dis. We quantitatively analyzed the degradation mechanisms using a new half-cell model at a temperature of 25 °C. This model significantly improved accuracy, achieving a 28.1 % reduction in root mean square error and substantial decreases in relative errors of 92.5 %, 61.5 %, and 98.9 % at critical points that outline the voltage curve. The analysis revealed that the degradation of active materials in the negative and positive electrodes accelerates with higher charging current and charging voltage limit, respectively. These insights can provide useful guidance for accelerated aging research and effective lifespan management of LFP batteries.