Charles W. Walker

Improvement of Ionic Conductivity in Plasticized PEO‐Based Solid Polymer Electrolytes

The ionic conductivity of a solid polymer electrolyte based on a lithium salt dissolved in a poly(ethylene oxide) (PEO) host was significantly improved with the use of plasticizing agents. Either a plasticizing salt, solvent, or combinations of both were incorporated into free-standing solution-cast films of (PEO){sub x}(LiCF{sub 3}SO{sub 3}). The greatest enhancement of conductivity was observed when a plasticizing salt (LiN[CF{sub 3}SO{sub 2}]{sub 2}) and solvent (diethyl phthalate) were combined, with the most notable improvement occurring below the melting temperature of PEO ({approx}66 C). Conductivity increased from 7.7 {times} 10{sup {minus}7} S/cm at 20 C to 4.6 {times} 10{sup {minus}5} S/cm with the addition of both plasticizers.

Proton-Conducting Interpenetrating Polymer Network with Reduced Methanol Permeability

A freestanding polymer electrolyte membrane was developed having low permeability to methanol while maintaining high permeability to water and proton conductivity. A two-polymer composite formed an interpenetrating polymer network (IPN) composed of proton-conducting 2-acrylamido-2-methyl propanesulfonic acid and a second polymer, poly(vinyl alcohol), serving as a methanol barrier. Ion conductivity and methanol permeability were controlled by adjusting polymer ratios and the extent of cross-linking of the two polymers. Compared to Nafion, the IPNs had up to fifteen times greater selectivity for water over methanol and proton conductivity about an order of magnitude lower.

Optimization of carbon cathodes for Li/SO2Cl2 cells

Five carbon blacks were evaluated for use as cathode materials in lithium-sulfuryl chloride half-cells. The best overall performance at high discharge rates was obtained with Cabots CSX-179B. Cathode load voltage and capacity were dramatically increased at 40 mA/sq cm current density without resorting to catalysts or additives by chemically treating either Shawinigan acetylene black or CSX-179B powder with acetone prior to cathode fabrication. 13 references.

Calorimetric Studies of Deuterated Pd Electrodes

This paper reports on calorimetric experiments conducted to verify the caloric claims by Fleischmann and Pons. A twin-cell heat conduction calorimeter was used, rather than the quasi-adiabatic instrumentation of the original investigation. Under similar electrochemical conditions, the output of heat powers from experimental cells of Pd in 0.1M LiOD/D{sub 2}O and that from control cells of Pd in 0.1M LiOH/H{sub 2}O and Pt in 0.1M LiOD/D{sub 2}O were all in close agreement with input heat powers using simple theory. These results show no anomalous excess heat as claimed.

Performance of Poly 3-Methylthiophene Cathodes in Li∕SO[sub 2] Rechargeable Cells

This paper reports on electrochemically formed, conducting ply 3-methylthiophene that was used as a rechargeable cathode material in lithium/sulfur dioxide cells. Good capacity and very high volumetric energy density were obtained with thin (0.41-1.4 {mu}m thick) cathodes in Li(SO{sub 2}){sub 3} AlCl{sub 4} electrolyte. Recharge was achieved at potentials below 3.9 V, which should preclude the corrosive effects of formed chlorine.

Low Temperature Performance Characterization of Lithium Sulfuryl Chloride Cells

Lithium sulfuryl chloride cells containing various concentrations of LiAlCl/sub 4/ were constructed and discharged at 2.5 mA/cm/sup 2/ constant current at 25/sup 0/ and -32/sup 0/C. The solid discharge product in cathode was analyzed and found to contain only LiCl. No sulfur or other lithium salt was found. An explanation of the reduced capacity and decreased operational voltage of these cells discharged at -32/sup 0/C is offered. At electrolyte concentrations less than or equal to 0.75M cathode capacity is primarily limited by conductivity, while for electrolyte concentrations less than or equal to 0.75M, diffusion appears to be the limiting factor. The decreased operational voltage for cells discharged at -32/sup 0/C is due to a decrease in the amount of catalytically produced Cl/sub 2/.

The Effect of Ru on Unsupported Pt-Ru Alloys for Methanol Electro-Oxidation at Different Temperatures

Unsupported different atomic ratios of platinum-ruthenium bulk alloys were prepared. The alloys were characterized by cyclic voltammetry, X-ray diffraction and energy dispersive X-ray spectroscopy. These alloys were also tested as anodes for methanol electro-oxidation in sulfuric acid over a range of temperatures. Ruthenium is inactive for methanol electro-oxidation at 25 °C, but becomes active at higher temperatures. When a comparison is made on the basis of “true” (hydrogen adsorption) surface area, a 30 atomic percent Ru electrocatalyst provides the highest activity for methanol electro-oxidation as measured at either 0.4 or 0.5V vs. RHE at both 25 and 60 °C.