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Electrolyte Dependence of Li+ Transport Mechanisms in Small Molecule Solvents from Classical Molecular Dynamics
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DOI：10.1021/acs.jpcb.3c07999.png)
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Abstract
En 中文
As demands on Li-ion battery performance increase, the need for electrolytes with high ionic conductivity and a high Li+ transference number (t (Li)) becomes crucial to boost power density. Unfortunately, t (Li) in liquid electrolytes is typically <0.5 due to Li+ migrating via a vehicular mechanism, whereby Li+ diffuses along with its solvation shell, making its diffusivity slower than the counteranion. Designing liquid electrolytes where the Li+ ion diffuses independently of its solvation shell is of significant interest to enhance the transference number. In this work, we elucidate how the properties of the solvent influence the Li+ transport mechanism. Using classical molecular dynamics simulations, we find that a vehicular mechanism can be increasingly preferred with a decreasing solvent viscosity and increasing interaction energy between the solvent and Li+. Thus, a weaker interaction energy can enhance t (Li) through a solvent-exchange mechanism, ultimately improving Li-ion battery performance. Finally, metadynamics simulations show that in electrolytes where a solvent-exchange mechanism is preferable, the energy barrier to changing the coordination environment of Li+ is much lower than in electrolytes where a vehicular mechanism dominates.
Keywords:
LITHIUM-ION
INITIAL CONFIGURATIONS
TRANSFERENCE NUMBER
COUPLING STRENGTH
CONDUCTIVITY
SIMULATIONS
SOLVATION
CARBONATE
LITFSI
SALTS
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