In this work, the performance degradation mechanism of the retired power cells is investigated after 400 and 800 cycles at 25 °C and 45 °C to determine whether they satisfy the secondary utilization requirement under the simulated energy storage systems. The results confirm that the capacity of retired cells show a linear relationship with cycle number. When the cycle numbers are more than 2400 times (at 25 °C), the capacity of the retired cells is decreased to less than 80% of initial capacity, which means the retired cells have the value of secondary utilization. In contrast to stable capacity delivering of LiFePO₄, graphite anode shows obvious capacity fading. Further, the lithium loss at the LiFePO₄ cathode accounts for more than 70% of the retired cells capacity loss, and exceeding 85% of the consumed lithium-ion can be found at the graphite anode, leading to the formation of SEI film consisting of Li₂CO₃ and LiF inorganic salts.

中文翻译：

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淘汰的LiFePO 4 /石墨动力电池性能下降机理分析

在这项工作中，在25°C和45°C下进行400和800次循环后，研究了退休电池的性能下降机理，以确定它们是否满足模拟储能系统的二次利用要求。结果证实，退休细胞的容量与周期数呈线性关系。当循环次数大于2400次（在25°C下）时，已淘汰电池的容量会降低到初始容量的80％以下，这意味着已淘汰电池具有二次利用的价值。与稳定的LiFePO ₄容量输送相反，石墨阳极显示出明显的容量衰减。此外，LiFePO ₄处的锂损失阴极占了退休电池容量损失的70％以上，而在石墨阳极上发现的锂离子消耗量超过了85％，导致形成了由Li ₂ CO ₃和LiF无机盐组成的SEI膜。