Lithium-Ion: Electrolyte

Salt Inhomogeneity Induced By Electrolyte Motion – A Novel Aging Mechanism In Large-Format Lithium-Ion Cells Researchers at BWM, Solchenbach et al., propose an underexplored mechanism for degradation in cells - electrolyte motion induced salt inhomogeneity EMSI. In the proposed mechanism, the electrolyte expelled from the jellyroll upon charge is at a lower than average salt concentration.

HYPOTHESIS SUPPORTED BY

X-ray CT

Moment of inertia

Cell dissection

IC & LCMS of salt and solvent amount sampled along jellyroll height (z-axis)

Capacity, DCIR, DCh end slippage over cycles

P2D simulation

Source: Solchenbach et al. Energy Environ. Sci. 2024.

Over cycles, a polarization in salt concentration builds because it takes weeks to months for the salt concentration to re-equilibrate along the height of the jellyroll 95mm.

The polarized salt distribution leads to localized degradation and Li-plating, accelerating capacity fade and internal resistance growth. This is exacerbated in cells with larger dimensions, subject to higher C-rates. The effects are not as pronounced in cells with lower electrolyte loading (no net electrolyte expelled out of the jellyroll even at 100% SOC

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