磷酸铁锂电池外短路损伤特性及熔断防护研究

电池外短路损伤特性研究对于高可靠性熔断防护设计具有重要意义。基于自主开发的最小时间为0.1 ms、最大过流为5000 A的可控外短路测试平台,以磷酸铁锂圆柱型锂离子电池为研究对象,进行了不同电流与时间组合的外短路测试。研究证明磷酸铁锂电池外短路存在破裂泄漏、内部熔断以及累积损伤3种损伤模式。电池外短路安全边界、熔断边界和性能损伤边界均具有反时限特征,且前两个边界在电流有效值30C处存在交点。电流小于交点值容易触及安全边界发生破裂泄漏事故,安全风险增加;电流大于交点值优先触及熔断边界发生熔断保护,防护可靠性提高。对于未发生熔断或破裂的电池,存在多次外短路冲击累积失效的风险。基于研究结论,充分考虑电池外短路损伤特性,能够保证电池系统在发生外短路时不产生过度损伤,提高系统安全性。

External short-circuit damage characteristics and fusion protection forlithium-iron phosphate batteries

The study of battery external short-circuit (ESC) damage characteristics is of great significance for the design of high-reliability fusing protection. Based on the self-developed controllable ESC test platform with a minimum time of 0.1 ms and a maximum overcurrent of 5000 A, taking lithium-iron phosphate cylindrical lithium-ion batteries as the research object, ESC tests with different current and time combinations are carried out. The study proves that there are three damage modes in the ESC of lithium-iron phosphate batteries: rupture leakage, internal fusing and cumulative damage. The ESC safety, fusing and performance damage boundaries all have inverse time characteristics, and the first two boundaries have an intersection point at the RMS current value of 30C. If the current is less than the intersection value, it is easy to touch the safety boundary to cause rupture and leakage accidents, increasing the safety risk; if the current is greater than the intersection value, it is preferred to touch the fuse boundary and fuse protection will occur, and the protection reliability is improved. For batteries that have not fused or ruptured, there is a risk of cumulative failure from multiple ESC impacts. Based on the findings, full consideration of the ESC damage characteristics of a battery can ensure that the battery system does not produce excessive damage in the case of ESC and thereby improve system safety.