Jay C. Henderson

Batteries and electrochemical capacitors

Present and future applications of electrical energy storage devices are stimulating research into innovative new materials and novel architectures.

Dithienylcyclopentenes-containing transition metal bisterpyridine complexes directed toward molecular electronic applications.

There is continuing interest in the design and synthesis of functional materials for applications in molecular electronics and information storage. Of particular interest are systems that can provide multiple means for controlling transport through well-defined and stable electronic and/or redox states. We report herein the synthesis and characterization of a system containing transition-metal complexes along with dithienylethene (DTE) units so as to achieve photo and redox control of transport. A facile synthetic methodology was developed to assemble and couple metal terpyridine (M-tpy) complexes with the photochromic DTE unit in a linear structure with M-DTE-M or DTE-M-DTE arrangements, with emphasis on the latter series. The photochromic properties of these assemblies were examined by monitoring the changes in their UV/vis spectra upon irradiation at specific wavelengths capable of triggering the open/closed isomerization in the DTE units. Their electrochromic properties were studied via cyclic voltammetry and controlled potential electrolysis experiments. Complexes 10 (PhDTE-Fe-DTEPh) and 11 (PhDTE-Co-DTEPh) with phenyl-ending groups were found to be both photochromic and electrochromic, so they represent excellent candidates for further elaborations. The Fe(II)-containing complex 8 (ClDTE-Fe-DTECl) with chloride-ending groups was photochromically inactive but could undergo the electrochemically induced open-to-closed isomerization. On the contrary, the electrochromically inactive complex 9 (ClDTE-Co-DTECl) underwent cyclization under ultraviolet irradiation.

4-Amino- 4H-1,2,4-triazole-3,5-dithiol A Modifiable Organosulfur Compound as a High-Energy Cathode for Lithium-Ion Rechargeable Batteries

We have studied the electrochemistry of the organosulfur compound, 4-amino-4H-1,2,4-triazole-3,5-dithiol (ATAD), as a potential cathode electroactive material for lithium-ion rechargeable batteries. The redox behavior was investigated via cyclic voltammetry, and the charge-transfer kinetics of ATAD were compared to those of 2,5-dimercapto-1,3,4-thiadiazole (DMcT) and thiophene-2,5-bis(thiolate) (TBT). The redox reactions of ATAD were ascribed to the thiol groups at the 2 and 5 positions, forming a disulfide polymer during oxidation and cleaving the disulfide bonds during reduction. In addition to its chemical tunablity via the amine group, an important feature that DMcT does not possess, ATAD exhibited comparable charge-transfer kinetics to DMcT. Moreover, the charge-transfer kinetics of ATAD were significantly greater than those of TBT, which possesses chemically tunable points. These results point to the importance of heteroatoms adjacent to the thiolate groups to obtain fast charge-transfer kinetics. Furthermore, it was revealed that the redox reactions of ATAD could be accelerated by the conducting polymer poly(3,4-ethylenedioxythiophene). The chemical tunability of ATAD and the fast charge-transfer kinetics, as well as the high positive potential of the redox reactions, could enable the practical use of this organosulfur compound as a charge-storage material in lithium-ion rechargeable batteries.

Synthesis, computational and electrochemical characterization of a family of functionalized dimercaptothiophenes for potential use as high-energy cathode materials for lithium/lithium-ion batteries

We present a family of a novel class of organosulfur compounds based on dimercaptothiophene and its derivatives, with a variety of functional groups (electron-donating or electron-withdrawing groups) and regiochemistries, designed as potential high-energy cathode materials with sufficient charge/discharge cyclability for lithium/lithium-ion rechargeable batteries. This study uses as a point of departure the electrochemical and computational understanding of the electrocatalytic effect of poly(3,4-ethylenedioxythiophene) (PEDOT) towards the redox reactions of 2,5-dimercapto-1,3,4-thiadiazole (DMcT). The effective redox potentials of these materials exhibited good correlation with the highest-occupied molecular orbital (HOMO) levels predicted via computational modeling. Furthermore, the redox reactions of all the compounds studied were electrocatalytically accelerated at PEDOT film-coated glassy carbon electrodes (GCEs), although some materials exhibited higher energy output than others. By using this approach we have identified several compounds that exhibit clear promise as potential cathode materials and have characterized the molecular interactions between the organosulfur compounds and PEDOT film surfaces involved in the electrocatalytic reactions.