Electrochemistry-Based Diagnosis of Li Plating for Fast-Charging Li-Ion Batteries

Abstract

Recent innovations in battery technologies have facilitated the development and widespread use of electric vehicles (EVs), by increasing the energy density of batteries while lowering their cost. Despite the rapid growth of the EV market, the long charging time of lithium-ion batteries (LIBs) remains as a major obstacle for expanding customer acceptance of EVs. Typically, graphite-based anodes in the state-of-the-art LIBs suffer from Li plating under fast-charging conditions, which causes severe performance degradations and early cell failure of batteries. To prevent the Li plating-induced failure, extensive research efforts have been devoted to developing diagnostic methods capable of detecting Li plating. The electrochemical analysis of Li plating enables non-destructive, in operando detection without complicated experimental procedures or special equipment.Herein, we present a non-destructive method for detecting Li plating during fast-charge cycling by analyzing current transients during the constant-voltage charging step, based on electrochemical battery models. Three-dimensional (3D) and pseudo-two-dimensional (P2D) battery models are employed to predict the electrochemical behavior of full cells under fast-charging conditions. 3D model enables the evaluation of local electrochemical properties, such as local reaction current densities and electrode potentials, which are largely affected by the microstructure of the electrode. Furthermore, P2D models are employed to investigate the effect of changes in microstructural properties (e.g., porosity and fraction of active surface of the graphite anode) on electrochemical behavior of full cells.For 3D modeling, the 3D Voronoi tessellation and Catmull-Clark algorithm are employed to construct the model geometry of graphite anodes. 3D modeling results predict that upon fast-charging, the charge-transfer potential on the top surface of graphite anode rapidly drops below 0 V vs. Li/Li+, triggering Li plating. To extract the electrochemical signals of Li plating, the fast-charging behaviors of full cells are investigated by using the P2D model with a partially reversible Li plating–stripping reaction. In specific, the constant-current and constant-voltage (CC-CV) charging process of the full cells with graphite anodes is simulated with Li plating-induced degradation modes; reduction of (i) interparticle pores, (ii) active surface area for Li intercalation reaction, and (iii) cyclable Li amount. Modeling results demonstrate that an inflection point appears in the current transient curve, and it shows a positive shift when the Li plating-induced degradation occurs. Electrochemical tests and microstructural analyses further confirm the validity of proposed electrochemical detection of Li plating. This study provides an effective strategy to design electrochemical methods for Li plating detection during fast-charging batteries based on electrochemistry-based models.