论文标题
库仑效率和能力保留不是细胞衰老的通用描述。
Coulombic efficiency and capacity retention are not universal descriptors of cell aging
论文作者
论文摘要
在假设这些数量可以直接见解有关固体电解质相（SEI）的增长时，容量和库仑效率通常用于评估锂离子电池的性能。在这里，我们表明电极特性实际上可以更改可以直接从容量测量中检索到老化的信息的量。在全细胞的循环过程中，仅访问阴极和阳极的电压轮廓的一部分，而在两个电极上存储了可环的Li+的储层。该储层的大小和可用性取决于电压轮廓的形状，并且访问此额外的LI+可以抵消SEI消耗的某些容量。因此，容量和效率测量有时可能会严重低估细胞所经历的副反应速率。例如，我们表明，相同的SEI生长速率会导致LIFEPO4的容量淡出比NMC细胞中更快，并且衰老的感知作用取决于测试变量，例如排放深度。简单地测量能力可能不足以衡量由锂离子电池忍受的衰老程度。
Capacity and coulombic efficiency are often used to assess the performance of Li-ion batteries, under the assumption that these quantities can provide direct insights about the rate of electron consumption due to growth of the solid electrolyte interphase (SEI). Here, we show that electrode properties can actually change the amount of information about aging that can be directly retrieved from capacity measurements. During cycling of full-cells, only portions of the voltage profiles of the cathode and anode are accessible, leaving a reservoir of cyclable Li+ stored at both electrodes. The size and availability of this reservoir depends on the shape of the voltage profiles, and accessing this extra Li+ can offset some of the capacity that is consumed by the SEI. Consequently, capacity and efficiency measurements can, at times, severely underestimate the rate of side reactions experienced by the cell. We show, for example, that a same rate of SEI growth would cause faster capacity fade in LiFePO4 than in NMC cells, and that the perceived effects of aging depend on testing variables such as depth of discharge. Simply measuring capacity may be insufficient to gauge the true extent of aging endured by Li-ion batteries.
