磷酸铁锂电极的路径依赖

Path dependence of lithium iron phosphate electrode

理论研究表明,磷酸铁锂存在诱导极化记忆效应和路径依赖特性。记忆效应指的是在充电/放电期间,在先前终止了部分充电/放电的荷电状态(SOC)处的不寻常极化。路径依赖指的是电池从同一状态出发,通过不同路径,例如短暂充放电,或者静置,达到同一状态时,其电压或者容量会产生差异。发现磷酸铁锂电池放电后,如果进行部分充电,其放电容量会大于充电容量。同时发现,部分充电后,静置30 min再放电时,放电电压低于不静置电池的放电电压。验证了磷酸铁锂材料电极中的路径依赖特性。对1.3 Ah的18650磷酸铁锂电池进行了测试研究,并验证了2.2 Ah 18650三元电池不具有磷酸铁锂电池类似的现象。该测试研究结果提醒动力电池工程师,对磷酸铁锂动力电池的性能评估、SOC估算及建模等方面均应考虑磷酸铁锂的记忆效应和路径依赖。

Theoretical studies show that lithium iron phosphate has characteristics of induced polarization memory effect and path dependence.Memory effect refers to the unusual polarization at the charging state(SOC)where partial charging/discharging was previously terminated during charging/discharging.Path dependence refers to the difference in voltage or capacity of batteries when they start from the same state and reach the same state through different paths,such as short charging and discharging,or rest.This study found that,if the lithium iron phosphate battery is partially charged after full discharging,its discharging capacity will be larger than the charged capacity.It is also found that the voltage of discharge curve is lower than that of the non-rest battery when the battery is rested for 30 minutes after charging.The path dependence characteristics of lithium iron phosphate material electrodes was verified.1.3 Ah 18650 lithium iron phosphate batteries were tested and studied.It is also verified that the 2.2 Ah 18650 NCM batteries do not have the similar phenomenon of lithium iron phosphate battery.The test results remind power battery engineers that memory effect and path dependence of lithium iron phosphate should be fully considered in performance evaluation,SOC estimation and modeling of lithium iron phosphate power battery.