(435g) Dielectric Saturation of Liquid Propylene Carbonate in Electrical Energy Storage Applications

Dielectric characteristics of modelled propylene carbonate are evaluated in preparation for molecular scale simulation of electrochemical capacitors based on nanotube forests. The calculated linear-response dielectric constant for the bulk liquid, and its temperature dependence, is in good agreement with experiment. Simulation of liquid propylene carbonate confined between charged parallel graphite electrodes demonstrates that the dielectric susceptibility is non-linear for the strong fields possible in nanometer wide slits. The capacitance then depends significantly on the electric potential difference in those thin films. An effective dielectric constant inferred from that capacitance is significantly less than the uniform liquid dielectric constant, but that inferred value is consistent with results obtained directly for a dielectric ratio at the strong electric fields in the propylene carbonate film.