Lithium ion batteries that are capable of extreme fast charging (XFC) are highly desirable to accelerate adoption of electric vehicles (EVs). To identify the rate limiting factors for XFC, we used both half cells and symmetric cells to investigate the fast charging behavior of the cathode and anode separately. The symmetric cells enabled accurate measurements of charge transfer at each electrode without complications from counter electrodes. The battery materials and electrode design were comparable to the state-of-the-art for EV cells. Under these conditions, the graphite anode is the rate limiting electrode for fast charging in NMC811/Graphite pouch cells. The effective N/P ratio falls below 1.0 at high charging rates, which also causes Li plating. The use of symmetric cells in this study provides new insights to identify the limiting electrode in Li-ion batteries, especially those designated for extreme fast charging applications.

能够快速充电（XFC）的锂离子电池非常需要加速电动汽车（EV）的采用。为了确定XFC的速率限制因素，我们使用半电池和对称电池分别研究了阴极和阳极的快速充电行为。对称电池能够精确测量每个电极上的电荷转移，而不会产生反电极带来的复杂情况。电池材料和电极设计可与EV电池的最新技术相媲美。在这些条件下，石墨阳极是NMC811 /石墨袋式电池中快速充电的限速电极。在高充电速率下，有效N / P比降至1.0以下，这也会导致Li镀层。