Unexpected capacity fade and recovery mechanism of LiFePO4/graphite cells for grid operation
Unexpected capacity fade and recovery mechanism of LiFePO4/graphite cells for grid operation
复制标题
电网运行LiFePO4/石墨电池的意外容量衰减及恢复机制
DOI：
10.1016/j.jpowsour.2019.227502
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发表时间：
2020
影响因子：
9.2
通讯作者：
Y. Mita
中科院分区：
文献类型：
--
作者：
Yo Kobayashi;H. Miyashiro;Atsuko Yamazaki;Y. Mita
研究了大型LiFePO 4/石墨电池（>100 Wh）浅荷电状态（SOC）循环容量衰减机理。在浅SOC操作的情况下，对于在40%和60%的SOC之间的ΔSOC = 20%，电池在操作250天后显示出容量衰减。然而，试验性损失的容量通过随后的全SOC循环操作恢复，并且在恢复循环之后在C/2处记录了20%的最高容量恢复。这种现象不能用以前报道的负电极悬垂模型或锂的部分电镀来解释。在这项研究中，我们已经提出了一个模型，其中的LiFePO 4平面表面的不均匀性引起的容量下降，因为平坦的潜在的操作区域的LiFePO 4，这种减少的电池容量可以恢复全SOC操作。连接到电网的大容量能量存储系统需要使用LiFePO 4/石墨电池用于中等SOC操作，因为安装成本低并且需要电池系统的快速响应。在这种情况下，我们应该考虑电池中电极的特性。
The capacity fade mechanism of large-scale LiFePO4/graphite cells (>100 Wh) with shallow state of charge (SOC) cycling was investigated. In the case of shallow SOC operation, for ΔSOC = 20% between SOCs of 40% and 60%, the cells showed capacity fade after 250 days of operation. However, the tentatively lost capacity was recovered by subsequent full SOC cycling operation, and the highest capacity recovery of 20% was recorded at C/2 after the recovery cycling. The phenomena cannot be explained by the previously reported negative electrode overhung model or the partial plating of lithium. In this study, we have proposed a model where an inhomogeneity of the LiFePO4planar surface induces the decrease in capacity because of the flat potential operating region of LiFePO4, and this decrease in the cell capacity can be restored by full SOC operation. Large capacity energy storage systems connected to the electric grid require the use LiFePO4/graphite cells for medial SOC operation because of the low installation cost and the requirement for rapid response of the battery system. In such cases, we should consider the properties of the electrodes in the cell.