锂离子电池极速自加热中的电-热耦合特性及建模

Electrochemical Thermal Coupling Characteristics and Modeling for Lithium-ion Battery Operating with Extremely Self-fast Heating

动力电池低温下充放电时存在严重析锂、内阻增大、容量骤降等现象,导致其低温应用时能量不足,性能衰退增速以及安全事故频发等问题。针对当前锂离子动力电池低温加热速度慢制约全气候应用的难题,发现电触发极速生热特性,开发了间歇式极速加热系统;设计出系统的加热试验方法研究极速生热行为,明晰加热频率、占空比以及初始电量对电池温升速率和安全性的影响规律;发现加热温升与占空比和初始电量均呈正相关,加热使用的周期性电流是影响温升的关键,精确控制电流是加热策略实施的基础;建立低温加热电化学-热耦合模型,分析加热过程中颗粒锂离子浓度分布,结果表明,提出的极速加热方法不影响活性颗粒整体可循环锂浓度,证实了加热频率及占空比对加热效果的影响规律。

The serious lithium plating, high internal impedance and available capacity plummeting of the battery at low temperature condition lead to the shortage of energy, performance degradation and the aggravation of the potential safety problems. Aiming at the problem that the heating speed under low temperature condition of lithium-ion battery is slow, which restricts the application in the all-climate environment. The characteristics of extremely fast heat generation by electric trigger heating method are discovered, by which an intermittent fast heating system for battery is developed. A systematic heating experiment is designed to study the extremely fast heat generation behavior, and the effects of heating frequency, duty cycle and initial state of charge on the temperature rise and safety of the battery are clarified. It is found that the heating temperature rise has obvious positive correlation with duty cycle and initial state of charge. The current of the heating cycle is the key factor for the temperature rise. Therefore, the accurate control of the current is the basis of the low temperature heating. The electrochemical thermal coupling model of heating at low temperature is established, and the lithium-ion concentration distribution of the particles during the heating process is analyzed. The results show that the extremely fast heating method adopted will not affect the overall recyclable lithium-ion concentration of particles, and the effects of heating frequency and duty cycle on heating are verified.