锂离子电池电-热-机耦合特性实验研究及关键参数辨识

Experimental Study on ETSS Coupling Mechanism and Identification of Key Parameter for Lithium-Ion Batteries

针对锂离子电池的电-热-机耦合特性,设计了一套耦合特性综合测试系统,进行了电池不同倍率充放电工况下电-热-机耦合特性的测试与分析,以探究电池电特性、形变、温度的时间演变规律与空间分布特性,可以得到电池荷电状态(state of charge,SOC)-形变曲线具有明显的分段特性,可以辅助磷酸铁锂电池SOC估计的修正。基于该系统测试结果研究了电池充放电过程形变产生的机理,并进行了电池热膨胀系数的参数辨识。实验结果表明:高倍率放电时,在放电初期和中期电池边缘部分膨胀,放电后期收缩,而中心位置在放电初期和中期收缩,后期膨胀;低倍率放电时,电池表现为放电初期和后期整体收缩,中期整体膨胀。研究结果可为电池内部电-热-机耦合特性的理论分析与测试管理提供依据。

The coupling mechanism of ETSS fields （electro-chemical field,temperature field and strain-stress field） is a hot spot in the lithium-ion battery design and management researches.A novel instrument is designed to simultaneously obtain the thermal,electric and mechanical behaviors of the battery under charge and discharge operations and to further ascertain the characteristics in both spatial and temporal domains.Conclusion is drawn that the battery deformation curve has an obvious piecewise characteristic related to SOC （state of charge）,and can be used to aid in the modification of the SOC estimation method for LiFePO4 battery.Based on the test results,the mechanism of battery deformation under charge and discharge is further investigated and the key parameter of thermal expansion coefficient is identified.The result shows that when discharge is at a high rate,the battery expands during the initial and middle stages,then shrinks during the final stage in the edge area,while battery shrinks during the initial and middle stages and expands during the final stage in the center area,and that when discharge is at a low rate,the battery shrinks during the initial and middle stages but expands in the final stage in both the edge and the center areas.These results may provide a basis for theoretical analysis,testing and management of battery ETSS fields.