The ionic conductivities of liquid electrolyte blends that contained LiPF6 and varying amounts of fluorinated, nitrile-containing organosilicon molecules, ethyl methyl carbonate (EMC), and ethylene carbonate (EC) were determined using Electrochemical Impedance Spectroscopy (EIS). Liquid electrolytes are attractive for lithium-ion battery applications because they provide a fluid medium for ion transport, which promotes conductivity. Current state of the art batteries face performance and safety disadvantages such as poor stability and cycling capacity as well as high flammability and reactivity towards moisture. In contrast, organosilicon-based electrolytes have low flammability, high thermal and electrochemical stability, and low toxicity. The ionic conductivities of ten electrolyte blends were measured in the temperature range from 0°C to 50°C. Measured ionic conductivity data was complemented with molar conductivity data from pulsed-field gradient NMR experiments, which assumes that all of the lithium salt ions dissociate and participate in transport. By comparing the measured EIS conductivity with the ideal predicted molar conductivity (NMR), the degree of ion dissociation in these samples was determined and its dependence on temperature was analyzed. Arrhenius plots for the ionic conductivity of these electrolytes displayed a Vogel-Tamman-Fulcher (VTF) type dependence on temperature, which was used to find the activation energy of ion transport and other electrolyte-specific parameters. The ionic conductivities of the electrolyte blends depended greatly on their viscosity and the analogue of the organosilyl molecule that was used. All electrolyte blends tested exceeded the conductivity threshold of 1.0 mScm-1 at 298 K with some blends equaling the ionic conductivity of the all-carbonate control electrolyte.

Impedance studies of silyl/carbonate electrolyte blends

253rd National Meeting (2017)

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