Electrolytic Solvation Effects in Fluoroethylene Carbonate and Trifluoropropylene Carbonate: A Comparative Study Based on First-Principles Calculation
Owing to its high energy density, high specific capacity, and low self-discharge rate, the Li-ion battery (LIB) has been implemented in a wide area of applications starting from small electronic devices to large electric vehicles. However, the use of LIBs in electric vehicles has not yet been commercialized on a large scale due to the unavailability of suitable␣electrolytic solvents for high-voltage LIBs. Recently, fluorinated carbonates have gained much attention as potential high-voltage electrolytes for having desirable physical properties such as low melting points, low flammability, and high electrochemical stability. However, the solvation properties of Li+ in electrolytic fluorinated carbonates solvents require detailed investigations. With the first-principles calculations, the present work provides a comparative study of the structural, electronic, thermochemical and solvation properties of Li+ solvated by fluoroethylene carbonate (FEC), trifluoropropylene carbonate (TFPC), i.e., Li+-(FEC)n and Li+-(TFPC)n, where n = 1–4. We have found that the structural properties, e.g., bond length C=O (of carbonyl) and associated infrared (IR) frequency, show similar variation for both the fluorinated Li-carbonate complexes. However, higher solvation energy and lower desolvation energy for the TFPC than the FEC show the opposite nature of their respective pristine carbonate counterparts. Our result, i.e., superior solvation energy of TFPC compared to FEC, is in good agreement with the experimentally developed solvating power series. Based on the solvation/desolvation energy, we conclude that TFPC could be a better high-voltage electrolyte for LIBs.