Simulation of Lithium Plating Due to Spatial Inhomogeneous Separator Strain in Lithium-Ion-Cells

Abstract

The electrodes and especially the separator of a lithium-ion-cell are exposed to mechanical stress due to expansion of electrode materials during operation if the electrodes are integrated in a stiff cell casing e.g. in a 18650 cell. As a result, the porosity and therefore the lithiumdiffusion characteristics are altered. In this paper a simulative study of spatially resolved effects from inhomogeneous separator porosity reduction induced by mechanical strain is presented. The findings show significantly changed spatial current densities and local anode voltage potentials that match findings of post-mortem investigations.

Microstructure Evolution of Lithium‐Ion Battery Separator under Compressive Loading: In Situ Experiments and Image‐Based Finite Simulations

“…[15,16] Many studies have been carried out to study the mechanical behaviors of separators under stress, including the evolution of thickness, mechanical strength, porosity, and tortuosity. [17,18] When the separator is compressed, internal characteristic changes, such as decreasing porosity, increasing tortuosity, and decreasing ion conductivity, can dramatically affect the transmission of Li þ [19,20] and accelerate the degradation of battery performance. [21] Moreover, changes in the microstructure of the separator caused by compressive strain may lead to different degrees of lithium deposition and cause safety hazards to LIBs.…”

“…[21] Moreover, changes in the microstructure of the separator caused by compressive strain may lead to different degrees of lithium deposition and cause safety hazards to LIBs. [14,20,22,23] In previous investigations, considerable work has been conducted on the microstructure evolution of separators. For example, the pressure effect of the thickness direction of a separator was studied, the permeability change in the separator after deformation was tested, and the deformation form of the microstructure was analyzed via scanning electron microscopy (SEM) images.…”

Simulation of Spatial Strain Inhomogeneities in Lithium-Ion-Cells Due to Electrode Dilation Dependent on Internal and External Cell Structures

“…On cell level, electrode dilation can result in significant material strain; this can especially affect the soft polymer separator layers. Increased strain of the separator results in reduced porosity of the separator, which leads to increased internal resistance of the cell, but can also cause localized lithium-plating due to mechanically induced balancing currents on electrode level [15][16][17][18]. Non-uniform/inhomogeneous pressure distribution was found to induce accelerated cell aging e.g.…”

“…Hence, the mechanical structure of a cell clearly has an impact on (spatial) lithium plating behavior. [15], pouch-type-cell [32] and prismatic hardcasetype cell [33].…”

Simulation of Spatial Strain Inhomogeneities in Lithium-Ion-Cells Due to Electrode Dilation Dependent on Internal and External Cell Structures

“…Hence, the mechanical structure of the cell clearly has an impact on (spatial) plating behavior. [15], pouch-type-cell [32] and prismatic hard case-type cell [33].…”