Date of Award
Campus Access Dissertation
Branko N. Popov
The dissertation discusses the synthesis and characterization of polymer composite materials used in lithium primary batteries and capacitors. The objective of the first part of the dissertation is to develop cathode materials based on silver vanadium oxide (SVO) coated with polypyrrole (PPy) having lower particle-to-particle resistance, lower initial voltage drop, higher discharge capacity and higher rate-capability than state-of-the-art SVO. PPy/SVO composite cathode materials were synthesized by polymerizing pyrrole onto the surface of pure SVO particles. Electrochemical characterization was carried out by performing galvanostatic discharge, pulse discharge and AC-impedance experiments. The composite electrodes yielded a higher discharge capacity and a better pulse discharge capability when compared to the pristine SVO electrode. The pulse discharge and AC-impedance studies indicated that PPy forms an effective conductive network on the SVO surface and thereby reduces the particle-to-particle contact resistance and facilitates the interfacial charge transfer kinetics. To determine the thermal stability of the composite cathode, galvanostatic discharge and AC-impedance experiments were performed at different temperatures. The capacity increased with temperature due to enhanced charge transfer kinetics and low mass transfer limitations. The peak capacity was obtained at 60 oC, after which the performance degraded with any further increase in temperature.
The second part of the dissertation reports on the dielectric characterization of polystyrene composites containing a variety of titanates, aluminates, and novel mixed metal phosphonates. We investigated BaTiO3 materials, covalently surface-modified BaTiO3, and novel mixed metal phosphonates, ATi(O3PC6H5)3 (A = Ba, Sr) to assess the effect of particle size and surface treatment on the composites' effective dielectric permittivity. In all cases, polystyrene composites containing mixed metal phosphonates exhibited higher dielectric constants and higher dielectric loss values than polystyrene composites containing the corresponding titanates. The relatively high dielectric constant exhibited by the mixed metal phosphonates could be due to their organic-inorganic hybrid layered structures. This suggests the possibility that interfacial polarization changes could account for the relatively high dielectric constants of the mixed metal phosphonate systems. We also studied CaCu3Ti4O12 (CCTO) - polymer composite systems to assess its dielectric properties. CCTO/P(VDF-HFP) system having 20 volume percent of the filler particles gave the highest energy density of 12.3 J/cm3.
Anguchamy, Y.(2010). Synthesis and Characterization of Polymer Composite Materials For Lithium Battery Cathodes and Capacitors. (Doctoral dissertation). Retrieved from http://scholarcommons.sc.edu/etd/127