Two-Dimensional Modeling of Lithium Deposition during Cell Charging

Empirical observations have shown that lithium deposition occurs preferentially at electrode edges and that extending the negative electrode beyond the edge of the positive by approximately 1 mm can prevent deposition from occurring. In this work, we use a simplified COMSOL Multiphysics model to explain this behavior and to investigate the conditions under which deposition occurs, paying particular attention to the magnitude of edge effects. Model results show that geometric effects generate overpotential at the edge of the electrode and create conditions which favor plating, despite unused capacity in the center of the electrode. Extending the negative electrode beyond the edge of the positive provides excess capacity where it is needed and prevents deposition from occurring before the cutoff potential is reached. Under the assumptions of this model, an extension of 0.4 mm is sufficient to prevent the onset of lithium deposition until after the cutoff potential is reached. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3095513] All rights reserved.