When a Li–metal
electrode immerses in the electrolytes containing
organic solvents, it is always covered by a thin layer of solid electrolyte
interphase (SEI) containing both inorganic and organic compounds.
While simulating the electrochemical reactions occurring at this interface
is essential to understand electrolyte decomposition and Li dendrite
formation that impact the life and safety of Li-ion batteries, conventional
density functional theory (DFT) or force field methods are either
limited by size or by accuracy. Therefore, the self-consistent-charge
density functional tight-binding (SCC-DFTB) approach was taken in
this research. We first developed a parametrization scheme for mixed
valence lithium (Li0 and Li+) within the SCC-DFTB
framework and then developed a new set of parameters for Li–X
(X = Li, H, O, and C) interactions. The newly developed parameters
were validated through comparison with DFT predictions for a range
of materials, including Li, Li2O, and Li2CO3, and Li+ ions dissolved in ethylene carbonate
(EC) solvent. The SCC-DFTB calculated properties, including electric,
structural, surface, and interface properties, and Li+ solvation
energy and diffusion coefficient in liquid EC agreed well with DFT
results. The effect of SEI thickness in blocking electron transfer
and preventing electrolyte reduction was captured by a Li/Li2CO3/liquid-EC interface model. The newly developed SCC-DFTB
parameters provide a reliable and transferable method to simulate
charge transfer reactions at the complex Li–metal/SEI/electrolyte
for Li-ion batteries.