退役磷酸铁锂电池容量一致性及衰减特征研究

2.3 退役电池容量衰减突变现象

在随机循环测试的12支退役单体电池中， #1电池在循环过程中出现容量衰减突变为0 mAh的现象。#1电池的初始放电容量为17.7 Ah，与新电池比，剩余容量为80.5%。在1243次循环之前，电池充放电容量与循环次数出现很好的线性关系，与#2～#4电池一样，每发生一次容量衰减突变，都会伴随有较为明显的容量下降趋势。在循环至1243次时，放电容量突然降至0.12 Ah，与新电池比，剩余容量为0.55%。此后继续衰减至接近0 Ah，如图8所示。

图6 #4退役单体电池的容量循环曲线

Fig.6 Capacity fading acteristic for #4 retired power cell in ging/disging condition

图7 #2～#4退役单体电池的容量衰减率曲线

Fig.7 Capacity fading rates for #2～#4 retired power cells in disging condition

图8 #1退役单体电池循环容量衰减曲线

Fig.8 Capacity fading and it’s mutation acteristic for #1 retired power cell in ging/disging condition

#1退役电池的容量衰减率曲线见图9，在循环至1242次之前，其衰减率平均为4.4%，且在1242次之前，容量衰减率与循环次数间保持较好的线性关系。循环至1243次及以后，容量衰减率突然增大近100%。

在本次抽样实验研究中，12支单体电池循环2000次左右后，仅#1电池出现了上述衰减突变现象，发生概率为8.3%。由此可见，退役电池性能衰减在2000次内突变是不可预测的现象，但存在发生可能性，且发生概率不低。这种容量衰减突变现象对梯次利用储能系统可靠运行是较大的挑战，一方面需要研究电池容量跳水等性能衰减、突变预警技术，另一方面应设计灵活的储能系统电气拓扑结构，以便可以隔离突然失效电池所在支路，保证尚未失效支路可以正常工作。

图9 #1退役单体电池容量衰减率曲线

Fig.9 Capacity fading rate for #1 retired power cell in disging condition

3 结论

(1)纯电动大巴和纯电动出租汽车两类退役磷酸铁锂电池模块容量测试结果表明，退役电池模块间容量差均较为明显，离散性突出，不利于电池重组。

(2)以退役单体电池为研究对象，抽样测试了12支单体电池的循环性能，2000次充放电循环试验数据表明，绝大多数退役电池仍具有较好的循环性能，其容量衰减与循环次数呈现明显的线性关系，其容量衰减率不超过8%，具有较理想的梯次利用价值。

(3)退役单体电池2000次充放电循环试验数据表明，个别退役电池存在容量突变为零的现象，本文研究抽样样本中，其发生概率为8.3%。为保证退役电池储能系统可靠性，应针对性开展容量跳水预警技术研究。

作者：

赵光金1,2，邱武斌1,2

(1. 国网河南省电力公司电力科学研究院，河南省 郑州市 450052;2. 国家电网公司电网废弃物资源化处理技术实验室，河南省 郑州市 450052)

国家电网公司科技项目(52170217000L)。

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原标题:退役磷酸铁锂电池容量一致性及衰减特征研究