Current Transient-Based Electrochemical Method for Detecting Li Plating during Fast-Charging of Li-Ion Batteries
Authors: Shin Hong Rim , Yang Soo Young , Lee Jong-Won 
Published: December 2024

Li metal plating in Li-ion batteries (LIBs) has been recognized as a major obstacle for realizing fast-charging of LIBs, as Li metal deposits on graphite anodes often cause drastic capacity loss and may trigger internal short-circuiting, raising safety concerns. Therefore, extensive research efforts have been devoted to developing methods for detecting plated Li. However, proposed methods often required specialized equipment or sophisticated experimental methods, which cannot be implemented in practical cell operation conditions. Recently, diagnostic methods based on characteristic electrochemical signals of plating have been attracted significant research interest as they enable non-destructive, in operando detection that can be directly applied to the state-of-the-art battery management systems.
Herein, we present an electrochemical method for detecting Li plating based on the cell current transient during constant-voltage (CV) charging. To study the electrochemical behavior of full cells under fast-charging conditions, a three-dimensional (3D) full-cell model is constructed with a stochastically generated anode. To generate the geometry of graphite anodes with realistic particle shapes, we employ 3D Voronoi tessellation and Catmull-Clark subdivision methods. In the model, we assume that the plating/stripping reaction of Li-metal is partially reversible, to reflect the highly irreversible nature of Li metal deposits.
To extract the characteristic signal of Li plating from the electrochemical behavior of full cells, we simulate the charging process of full cells with three different reaction modes for the graphite anode: (i) intercalation reaction, (ii) intercalation and irreversible Li plating reaction, and (iii) intercalation and partially reversible Li plating/stripping reactions. The results of electrochemical modeling show that, without the Li stripping reaction, the cell current monotonously decreases as CV charging proceeds. Conversely, the cell with partially reversible Li plating/stripping reactions exhibits a characteristic peak in the cell current profile. The amount of plated Li metal and reaction current profiles suggest that the peak appears with the depletion of plated Li. Upon the depletion of plated Li, the Li stripping reaction current, which contributes to the cell current in an opposite direction to the intercalation reaction current, rapidly decreases, causing a transient increase in the cell current during CV charging. As a result, a peak or plateau appears in the current profile of the cell that experiences Li plating and stripping during charging. The effect of the reaction rates of intercalation, Li plating, and Li stripping reactions on the characteristic signal is further explored by electrochemical modeling. Specifically, the amount of plated Li and the reaction rate for Li stripping critically affect the detectability of the peak/plateau in the cell profile. Based on the simulation results, we demonstrate that the peak/plateau in cell current profiles during CV charging can be utilized as a characteristic electrochemical signal of Li plating. Moreover, experimental studies with [LiNi0.8Co0.1Mn0.1O2|graphite] full cells are conducted to demonstrate the practical applicability of the proposed electrochemical method for detecting Li plating during fast-charging cycling.