Electrochemical Change Induced by Spherical Indentation in Lithium-Ion Batteries

Abstract

Since the Young’s modulus of the separator is weaker than that of the other materials inside a lithium-ion battery, local deformation may cause blockage or rupture of the separator, resulting in internal short-circuit or other disasters. This study collects the stress–strain relationship of various materials within the battery, and combines the mechanical model with the electrochemical model through the coupled relationship between the volumetric strain and the volume fractions of solid and liquid phases. From a two-dimensional electrochemical simulation of a spherical indentation on a layer-structured battery, it is found that there is local negative value of the side reaction overpotential on the negative electrode adjacent to the separator after the battery is deformed. A higher strain will cause a decrease in the negative overpotential, leading to a more serious deposition of lithium during the charge process. The deformation-dependent overpotential is evaluated and the lithium deposition is then quantified. Moreover, the issue of the separator thickness is explored. We find that under an indentation, the thickness does not affect the charging voltage, while a thinner layer will reduce the separator porosity and thus lower the overpotential and increase the chance of lithium deposition.

Keywords

• lithium-ion batteries
• spherical indentation
• mechanical-electrochemical coupling
• negative overpontential