Chemo-Mechanical Model for Internal Stress Impact on Lithium Dendrite Growth

Abstract

Lithium-ion batteries have the potential for greater efficiency and lifetime than current commercial options; however, there are operation and safety concerns that must be addressed before expanding their applications. During operation lithium dendrites form due to plating on Li-electrolyte surface inhomogeneities, which leads to battery failure once the dendrite reaches the cathode and short-circuits the cell. Addition of mechanical stress due to both internal and external pressures has been observed to decrease the propensity for dendrite growth. However, this addition leads to other complications, including inhomogeneous transport through the separator caused by inhomogeneous contact of a rough Li surface. In this work, we present a mesoscale model of a lithium protrusion brought into contact with a typical porous separator. The model couples mechanical deformation in both the lithium and separator with the electrochemical response during the charging phase. The nature of the model allows these materials to be brought into full or partial contact; the latter creates an electrolyte-filled gap, which drastically changes the electrochemical behavior across the 3-dimensional contact interface. The effects of internal stress and various model properties on the reaction rate across the protrusion surface are explored; through this, the propensity of plating across the interface may be predicted. Specific properties studied include the protrusion shape, separator porosity and modulus, liquid electrolyte diffusivity, and applied current density. Phase maps of the conditions for which dendrite formation is encouraged or suppressed are created and may be used to inform battery manufacturing and material choices.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.