Jeffrey G. Killian

Polypyrrole Composite Electrodes in an All‐Polymer Battery System

The authors have fabricated an all-polymer battery utilizing the redox properties of electrically conducting polymers for the anode and cathode in conjunction with an ionic conducting polymer gel electrolyte. The anode and cathode consist of pyrrole electropolymerized onto a graphite fiber substrate resulting in a high-surface-area, composite electrode. A polymer gel electrolyte, based on polyacrylonitrile, was solution cast onto the electrodes to form an all-polymer cell. This system exhibits a specific charge capacity of 22 mAh/g based on the electroactive mass of the cathode and discharging the system to 0.4 V. These cells show no loss of capacity when cycled to 100 cycles.

An all-polymer charge storage device

Conducting polymers that can be switched between a neutral state and a doped state are of interest for charge storage applications. We report on the fabrication of an all-polymer charge storage device incorporating derivatized polythiophene films electropolymerized onto graphite-coated polymeric supports and a polymer gel electrolyte film. The devices exhibited discharge voltages of about 2.4 V and capacities of 9.5–11.5 mAh g−1. The elimination of any metallic components or liquids and the lightweight and flexible construction provides a unique approach for the fabrication of organic power sources.

The electrochemistry of fluorine-substituted polyphenylthiophenes for charge storage applications

A series of thiophene-based conducting polymers has been synthesized. The properties of these polymers were characterized using electrochemical techniques. The polymerization potentials of the monomers were found to be related to the corresponding Hammett σ values. The maximum n-doping levels of the polymers were also found to be correlated with the Hammett σ values. No correlation was found with the maximum p-doping levels of the polymers. The doping densities were found to decrease on repeated cycling and were correlated with irreversible morphological changes in the films. Test cells were fabricated using conducting polymer films for both anode and cathode. These cells exhibited discharge voltages of about 2.5 V and capacities of 9.5 to 11.5 mA h g−1.

Synthesis and characterization of fluoro-substituted polyphenylthiophenes for charge storage applications

Abstract A series of fluoro-substituted phenylthiophene monomers has been synthesized with high isolated yields (71–90%). Generalized coupling reactions have been developed for the series with a Pd(dppf)Cl 2 catalyst and via Zn-complex mediated reactions. The controlled electropolymerization of monomers yielded polymeric materials which, when cycled, exhibited reversible redox reactions in both the n- and p-doped states with high cycling efficiencies. The doping levels and polymerization potentials were strongly correlated with the electronic character of the monomers based on the Hammett model. This methodology suggests a theoretical scheme for the development of other high charge-capacity polymeric materials.

Synthesis and characterization of a series of fluorine-substituted phenylene-thienyl polymers for battery applications

Abstract A series of fluorine-substituted phenylene-thienyl-based monomers (1,4-bis(2-thienyl)-benzene (THB), 1,4-bis(2-thienyl)-2-fluorophenylene (TFP),1,4-bis(2-thienyl)-2,5-difluorophenylene (TF2P), and 1,4-bis(2-thienyl)-2,3,5,6-tetrafluorophenylene (TF4P)) has been synthesized. Thin films of the polymers were deposited by controlled electropolymerization of the monomers, and the doping densities and cycling efficiencies were determined from electrochemical measurements. The polymers poly-1,4-bis(2-thienyl) -benzene (pTHB), poly-1,4-bis(2-thienyl)-2-fluorophenylene (pTFP), and poly-1,4-bis(2-thienyl)-2,5-difluorophenylene (pTF2P) exhibited reversible p-doping and n-doping, with doping densities in the range 0.12 to 0.45 electrons per monomer unit. The cycling efficiencies were higher for p-doping than for n-doping, with values in the range of 99.58 to 99.70% charge retained per cycle.