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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 & LC-MS 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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