Multiphysics-constrained Optimal Charging of Lithium-ion Battery

The lithium-ion battery(LIB) is prone to the expected over-heating and quick degradation during the fast charging. Therefore, it is of great significance to constrain the key intermediate physical states of LIB actively within a reasonable range, while pursuing the speed of charging. Motivated by this, a multiple physics-constrained fast charging strategy is proposed for the LIB. A comprehensive electro-thermal-aging model is established and validated under typical charging scenarios. On this basis, a model-based observer is designed to estimate the state of charge and internal temperature of LIB in real time. Accounting for multiple conflicting objectives, i.e., the charging speed, temperature rise and degradation rate, a model predictive control-based strategy is proposed to optimize the charging process of LIB. Experimental results suggest that the proposed charging strategy can actively constrain the internal temperature of battery below the predetermined threshold. With a comparable charging speed, the proposed charging strategy leads to a slower degradation than the widely-used constant-current-constant-voltage charging strategy. The capacity decays within 200 charge-discharge cycles are 2.12% and 4.88%, respectively, for the two strategies. Based on the model predictive control, the proposed fast charging strategy constrains the battery internal states effectively, while a comprehensive promotion in terms of rapidity, safety and life extension is realized. © 2023 Editorial Office of Chinese Journal of Mechanical Engineering. All rights reserved.