Energy storage and conversion materials: Part 1: Synthesis and characterization of ruthenium tris-bipyridine based fullerene charge transfer salts as a new class of tunable thermoelectric materials; Part 2: Synthesis and characterization of polymer thin films for use as a lithium ion battery separator.

摘要

PART 1: SYNTHESIS AND CHARACTERIZATION OF RUTHENIUM TRIS-BIPYRIDINE BASED FULLERENE CHARGE-TRANSFER SALTS AS A NEW CLASS OF TUNABLE THERMOELECTRIC MATERIALS.;A class of highly tunable charge-transfer salts was used to investigate relationships between structure and thermoelectric properties. The ultimate goal of the project was to find methods of tuning the electrical conductivity of a material independent of the thermal conductivity. This goal was to be achieved by synthesizing a host of charge transfer fullerene salts of the general form [MLnp+ ]a(C60a-) p where M is ruthenium, L is a bipyridine based ligand; p+ = 1+, 2+; and a- = 1-. These salts were expected to exhibit semiconductor behavior and large Seebeck coefficients. Structural data were collected on single crystals through XRD but only three crystals afforded publishable data due to the fullerene being disordered in the crystal lattice. Seebeck coefficients and electrical conductivity values were calculated from a two probe measurement on pressed powders. Values ranging from 100 to -400 μV/K for Seebeck coefficient and 5.6 x 10-2 to 3.3 x 10-5 S/cm for electrical conductivity were achieved. Seebeck values varied significantly from one batch to the next, showing how sensitive Seebeck coefficients were to doping levels.;PART 2: SYNTHESIS AND CHARACTERIATION OF POLYMER THIN FILMS FOR USE AS A LITHIUM-ION BATTERY SEPARATOR MATERIAL.;The first system explored was a radical initiated aqueous electrodeposition of poly(ethylene glycol) diacrylate. Initial work was done in a glove box with harsh organic solvents, so the first goal was to transition the technique to an aqueous solution on the bench-top. Once optimized, poly(ethylene glycol) diacrylate was deposited onto indium tin oxide planar, copper antimonide planar and 3-D structured electrodes. Monitoring film thickness as a function of deposition time, temperature, and monomer concentration was also achieved. Film thickness was measured using SEM imaging from freeze fractured samples. Impedance spectroscopy was used to determine the ionic conductivity of the solid polymer electrolyte, which was 6.1 x 10-7 S/cm. Film thickness was controllable and films as thin as 2 microns were achieved for this system. A half cell was constructed and cycling was demonstrated, but only when the separator was plasticized.;The second system explored was the direct electrodeposition of diazonium salts to achieve an ultra-thin separator material. The goal of this project was a conformal coating that was under 100 nm thick and grafted to the electrode surface. The goal was chosen because the first project afforded films on the micron scale that were not grafted, which led to many shorted cells plus a thickness that was not practical for nanostructured batteries. In this project, a new class of diazonium salts with poly(ethylene glycol) moieties were synthesized and characterized by NMR and IR spectroscopy. The salts were electrodeposited onto glassy carbon electrodes, showing remarkable self-limiting properties. During a fifteen minute deposition, current dropped up to 5 orders in magnitude due to the self-limiting nature of diazonium salts. Redox probe experiments confirmed a conformal and pinhole-free film was deposited. Redox probe experiments also show permeation of the film is possible and likely has a size dependency, which is favorable for lithium permeation. Impedance spectroscopy was used to determine the resistance and thickness of the films, around 5-10 Ω and 3 nm, respectively. (Abstract shortened by UMI.).