Refined potential for LiTFSI-Acetonitrile electrolyte system

LiTFSI-Acetonitrile electrolytes have been widely investigated for a variety of applications due to their outstanding properties, such as high conductivity and excellent stability. Molecular Dynamics (MD) simulation is an important technique to elucidate key mechanisms at the molecular level, but depends critically on the priori force field. However, only structure was included in previous development of force field. Herein, we report both structure and dynamics need to be considered when developing a force field according to MD simulation results using parameters from different quantum chemistry calculations. All the force fields parameter yield structures in good agreement with the neutron PDF but dramatically different dynamics. In the extreme case, the simulated self-diffusion coefficient can be one order of magnitude different from the NMR measurement. Furthermore, reducing the charge of oxygen in TFSI and lithium ions yield both structures and dynamics in good agreement experiments. These results suggest that although the force field gives the correct structure, the dynamics may be completely wrong. Therefore, dynamics must be also considered when developing a force field.