Physical and Electrolytic Properties of Partially Fluorinated Methyl Propyl Carbonate and Its Application to Lithium Batteries

The physical and electrolytic properties, and charge-discharge characteristics for secondary lithium batteries of partially fluorinated methyl propyl carbonate (MPC) derivatives were examined. Dielectric constants of the fluorinated MPC derivatives except 2,2,3,3,3-pentafluoropropyl methyl carbonate (PFPMC) tend to increase with increasing the number of fluorine atom. Viscosity of PFPMC with the highest molar volume is lower than those of other fluorinated MPC derivatives. Donor numbers (DN) of the fluorinated MPC derivatives were estimated by 29Si NMR chemical shifts of triphenylsilanol. DN of the fluorinated MPC derivatives except PFPMC tends to decrease with increasing the number of fluorine atom. 3-Fluoropropyl methyl carbonate (FPMC) shows the highest specific conductivity at the temperature above about 25°C. Oxidative decomposition potentials of the fluorinated MPC derivatives tend to increase with increasing the number of fluorine atom. PC-FPMC electrolyte shows higher lithium electrode cycling efficiency. Every PC-based fluorinated MPC derivative electrolyte shows higher discharge capacities for Li|LiCoO2 cells.