Chemo-Mechanical Model of Lithium Dendrite Growth Impacted By External Pressure

Abstract

The use of lithium metal anodes within commercial batteries is of great interest due to their high energy density and low coulombic efficiency; however, several challenges must be addressed before lithium anodes are implemented in a wide range of applications. Lithium plating and stripping during cell operation leads to the loss of active lithium and the formation of dendrites, which decrease battery capacity and lead to dangerous modes of failure such as fire. Application of external pressure has been shown to mitigate plating to an extent, as it alters the cell morphology and locations of high current density along the anode. In this work we present a 3-D, mesoscale model of lithium plating on an inhomogeneity characteristic of the rough lithium anode surface. The interplay between interfacial growth, state of stress, and ionic transport is explored in a coupled mechanics-electrochemical model. Local stress-induced changes in separator porosity and tortuosity limit bulk and surface ion transport, encouraging Li plating in regions of low stress and contact with liquid electrolyte. The initial electrochemical response across the Li anode surface is studied parametrically with respect to applied pressure, charge rate, and various material properties. The developed finite-element model is then used to simulate plating and stripping by moving the Li surface according to the local reaction rate; the evolution of the interface may thus be studied parametrically. Preliminary results show non-uniform plating across the protrusion that is highly dependent on applied pressure. As the interface evolves, changes in anode-separator contact redirect current and local stresses, leading to various modes of protrusion growth or flattening. This work will provide insight into the modes of protrusion growth based on material properties, applied pressure, and charging rate, and will inform cell design and manufacturing processes in order to mitigate plating and increase battery lifetime and safety.Supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.