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 operational and safety concerns that must be addressed before expanding their applications. During charge-discharge cycles lithium dendrites form within the battery due to plating on Li-electrolyte surface inhomogeneities. Full penetration through the electrolyte to the cathode leads to a short-circuit, resulting in battery failure and sometimes fire. Thus, controlling the rate of lithium dendrite growth is imperative for creating safer and longer-lasting batteries. Dendrite growth occurs when the lithium deposition rate exceeds the stripping rate and increases when the current density at the peak of a surface inhomogeneity is greater than at the valley. Addition of mechanical stress due to both internal and external pressures can decrease the propensity for dendrite growth; for various system conditions, a critical pressure exists above which formation is suppressed. However, mechanical pressure also leads to other complications, including inhomogeneous transport through the separator caused by nonuniform contact of a rough Li surface. Pressure-driven creep of the Li surface additionally evolves the contact and mechanical landscape. In this work, we present a mesoscale model and parametrically study the effect of internal stress and material properties on dendrite growth. The model couples mechanical deformation in both Li and the separator with the electrochemical response during the charging phase. Both the effects of mechanical and transport properties of the liquid electrolyte are investigated. Phase maps of the conditions for which dendrite formation is encouraged or suppressed are created and can be used to inform battery manufacturing and material choices.This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program 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.