Safety Charging Boundary Prediction of Ternary Lithium-Ion Batteries Based on the SP+ Model

The fast charging technology is the trend in the development of new energy vehicles. Due to the lack of precise expression about the coupling relationship between the charging conditions and the internal reaction mechanisms of the battery, it leads to several problems such as low charging efficiency, rapid battery aging, and insufficient safety prediction, which may significantly impact the promotion of new energy vehicles. This paper focused on ternary lithium-ion batteries and established a relationship between the operating voltage, equilibrium potential, internal resistance polarization potential, and solid–liquid phase polarization potential during the charging process of ternary lithium-ion batteries based on the improvement of the single-particle model (SP+). The models about equilibrium potential, internal resistance polarization potential, and solid–liquid phase polarization potential were built individually. According to the phenomenon that the negative electrode electromotive force will be lower than 0 when the battery is overcharged, the decoupling method for the positive and negative electrode potentials of ternary lithium-ion batteries was proposed and the safety charging constraint equation for ternary lithium-ion batteries was established. A 2 Ah 18,650 batteries were carried out in the multicondition battery tests and the coefficients of the operating voltage relationship expression can be solved. According to the charging constraint equation, the safety charging boundary map can be drawn based on the safety charging current and duration. In order to verify the effectiveness of the method proposed, a comparison test was carried out based on different charging conditions for 2, 3, and 4 C and 1000 cycle capacities at 25°C. The results showed that the proposed method can effectively improve the battery charging efficiency and the service life and the proposed method had a short system computation time and was suitable for real-time applications in embedded systems. It can be a solution for rapid energy replenishment of new energy vehicles.