Electrolytic behavior and application to lithium batteries of monofluorinated dimethyl carbonate

• Published in: Solid state ionics 2006-01, Vol.177 (3), p.299-303
• Main Authors: Sasaki, Yukio, Takehara, Masahiro, Watanabe, Susumu, Oshima, Masato, Nanbu, Noritoshi, Ue, Makoto
• Format: Article
• Language: English
• Subjects: Cycling efficiency; Direct fluorination of dimethyl carbonate; Electrolytic conductivity; Lithium batteries
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/j.ssi.2005.10.022

Dimethyl carbonate (DMC) was fluorinated by F 2 gas (direct fluorination) to form four fluorinated DMC derivatives, such as monofluorinated DMC (MFDMC), two difluorinated DMCs (DFDMC(a) and DFDMC(b)) and trifluorinated DMC (TFDMC). The electrolytic behavior and charge–discharge characteristics of the lithium electrode were examined in MFDMC and MFDMC-ethylene carbonate (EC) equimolar binary solutions. The dielectric constant and viscosity of MFDMC are higher than those of DMC. This means that the molecular interaction in MFDMC becomes larger due to the introduction of a high electron withdrawing fluorine atom. In addition, oxidation durability of MFDMC is higher than that of DMC. The specific conductivity in EC-MFDMC equimolar binary solution containing 1 M LiPF 6 is 8.5 mS cm − 1 at 25 °C which means a good electrolyte for lithium batteries. The lithium electrode cycling efficiency in EC-MFDMC equimolar binary solution containing 1 M LiPF 6 is higher than 70%. The surface of the film formed on the electrode in the solution is homogeneous, and consists of the uniform and small grain size.