Quantum Chemical Calculation of Lithium Polysulfide in EMI-Tfsi Solution: SMD (Universal Solvation Model Based on Solute Electron Density and a Continuum Model of the Solvent) Model

摘要

One of the problem of the sulfur-based electrode for the all-solid-Lithium-Sulfur battery cells is the chemical (or electrochemical) decomposition of lithium polysulfide Li_2S_n. Kinoshita et al have shown that the EMI-TFSI (1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) ionic liquid contained all-solid-Lithium-Sulfur battery has a good battery performance. In this study we have calculated the quantum chemical calculation of lithium polysulfide Li_2S_n. in continuum which has the dielectric constant and optical constant is the same as EMI-TFSI ionic liquid. The solvation effect is included by the SMD (Universal Solvation Model Based on Solute Electron Density and a Continuum Model of the Solvent) model. The Austin-Frisch-Petersson functional with dispersion is used in the calculation. From the total energy difference of the enthalpy of the reaction 2Li~+ +S_n → (LiSn)~(2+), 2Li~+ + S_n~(2-) → LiS_n, and decomposition reactions. The enthalpy of the reactions have been compared with the experimental results given by Uchimoto and Yamamoto.