Electrochemistry-based method for determining Li plating-induced degradation of fast-charging Li-ion batteries

초록

Despite the rapid growth of the electric vehicle market, the long charging time of commercial Li-ion batteries (LIBs) remains a major obstacle to expanding customer acceptance of electric vehicles. However, the realization of fast-charging LIBs has been hindered by Li plating on the anode surface, which causes severe capacity decay and raises safety concerns. For safe utilization of fast-charging LIBs, in this study, we present an electrochemical method for determining Li plating-induced degradation based on the transient cell current during constant-voltage (CV) charging. A three-dimensional electrochemical model with a stochastically generated anode is constructed and utilized to find any characteristic signals specific to Li plating under fast-charging conditions. The electrochemical modeling shows that after high-rate charging, a potential variation over a plateau region in the potential profile during CV charging causes the appearance of an inflection point in the current profile, which can be characterized as a peak in the differential current profile. In case that Li plating proceeds continuously on the anode, thus consuming active Li and blocking Li+ transport, the characteristic peak in the differential current profile shifts gradually toward a higher normalized CV capacity. Based on computational and experimental studies, we confirm that the characteristic electrochemical signal can be used to in-situ monitor the Li plating-induced degradation during fast-charging cycling, which is distinguished from the degradation due to the loss of cathode active materials. This study provides an effective strategy for developing diagnostic methods to analyze degradation behaviors of fast-charging LIBs.

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