Identifying cathode and anode polarizations during practical high‐rate charging/discharging in different Li‐ion pouch batteries
Li Wang, Leqiong Xie, Youzhi Song, Xiaomei Liu, Hao Zhang, Xiangming He
Abstract
Abstract Cell design is effective to improve the performances of lithium‐ion batteries (LIBs). For identifying the bottleneck of a full battery used for high‐rate charging/discharging, we developed a simple method, by a reference electrode in practical pouch cells, to quick obtain the polarizations of the cathode and the anode. For a Li(Ni 0.6 Co 0.2 Mn 0.2 )O 2 /graphite full cell, 63.9% and 97.0% of the polarizations originate from the anode at 50% state of charge (SOC) during 2.0 C charging and discharging rates, respectively. While for LiFePO 4 /graphite system, 62.5% and 55.8% of the polarizations originate from the anode at the same charging and discharging conditions. These indicate that the anode is the limitation during fast charging/discharging, which is consistent with the common understanding but in contrary to the results obtained by coin cells reported previously. While the rate limitation from anode in LiFePO 4 /graphite system during fast charging/discharging is significantly changed to both cathode and anode compared with Li(Ni 0.6 Co 0.2 Mn 0.2 )O 2 /graphite. Besides, graphite anodes in LiFePO 4 /graphite cells more readily dive to the Li‐metal plating potential at high charging rate. This leads to safety concerns of LiFePO 4 /graphite cells during fast charging. This is a facile strategy for fast distinguishing polarizations from cathodes and anodes of high‐rate LIBs.