Li+ hopping mechanism in LiTFSI water-in-salt electrolyte identified by molecular dynamics simulations

Molecular dynamics (MD) simulations using carefully validated force field show that the Li+ conduction in the highly concentrated LiTFSI water-in-salt electrolyte follows a hopping mechanism.

Scientific Achievement

The high Li+ apparent transference number in the LiTFSI water-in-salt electrolyte was captured by MD simulations and the dominant Li+ conduction mechanism in the highly concentrated LiTFSI water-in-salt electrolyte was identified to be hopping between water and TFSI- anions.

Significance and Impact

The results show that water-rich and TFSI-rich nano-scale domains are not necessary for the high Li+ apparent transference number and therefore suggest a new mechanism to understand the electrochemical behavior in these highly concentrated water-in-salt electrolytes.

Research Details

  • MD simulations were carried out using a force field validated previously for the liquid structure and further validated here against experimental transport properties.
  • Calculated viscosity, self-diffusion coefficient, ionic conductivity, apparent transference number and inverse Haven ratio all agree with experimental results quantitatively.
  • Transport and Li+ dynamics were studied in depth with the validated MD simulations.

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DOI: 10.1021/acs.jpcb.1c07581

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