Caroline Willuhn, University of Rhode Island


Although advantageous in many regards, solid polymer electrolytes have the major disadvantage of low ionic conductivity, preventing commercial utilization. Amorphous polymers have a higher lithium-ion conductivity than crystalline polymers. This is why many attempts are made to decrease their crystallinity. The integration of nanoparticles has been shown toeffectively reduce a polymer’s degree of crystallinity, thus enabling faster Li-ion transport.This work studies the integration of carboxyl-terminated carbon black (CB) and bariumtitanate nanoparticles into a PEO/LiTFSI polymer electrolyte (PE) with the final goal of enhancing its Li-ion conductivity. Differential Scanning Calorimetry (DSC) was carried out and showed a decrease in glass transition temperature, melting temperature, and degree of crystallinity for the nanoparticle-doped PE. DSC therefore confirmed the increase in amorphousness, which also agrees with findings from X-Ray Diffraction. Impedance measurements show that the ionic conductivity slightly increases with adding either type of nanoparticle but eventually reaches a maximum. At 60∞C and 70∞C the ionic conductivities of the PEO/LiTFSI electrolyte are 3.96 ∑ 10−4 S/cm and 9.46 ∑ 10−4 S/cm, respectively. The addition of 1wt% CB at 60∞C raises the ionic conductivity to 1.14 ∑ 10−3 S/cm. Adding 6wt% of BaTiO3 at 70∞C leads to an ionic conductivity of 1.18 ∑ 10−3 S/cm. With the obtained PE, full cells were built with an LTO anode and LFP cathode, showing that the cells cycle but have very high internal resistances, leading to low capacities.