Office: PHSC 330D Phone: (405) 325-3831 Email: rfrech@ou.edu

Roger Frech Professor B.S. (Massachusetts lnstitute of Technology) 1963 Ph.D. (Minnesota) 1968. Edith Gaylord Harper Presidential Professor, 1997-2001 American Chemical Society Oklahoma Chemist of the Year, 1998 Alexander von Humboldt Research Fellowship: 9/80-8/81, 9/88-  12/88 Regents' Award for Superior Accomplishment in Research, 1985 Oklahoma Center for Photonic and Electronic Materials and Devices; Scientific Steering Committee Chair, 1995-2001. Oklahoma Laboratory for Electronic Properties of Materials; Co-Director, 1992-2001

Division: Physical Chemistry; Material Science Research Interests Vibrational spectroscopy (including 2-D correlation methods and in situ techniques), polymer electrolytes, intercalation electrodes, rechargeable lithium batteries, fuel cells.

Research Description

My research programs lie in two complementary areas: rechargeable lithium polymer batteries and proton exchange membrane (PEM) fuel cells. Fuel cells and rechargeable batteries both have wide applications ranging from portable communications devices, through a variety of transportation systems, to large stationary power stations. My primary research emphasis is on the discovery and development of advanced materials for use in these "next generation" energy systems.

Rechargeable Lithium Batteries

In this program, we seek to understand fundamental factors such as structure, dynamics, and thermodynamics which underlie the electrochemical behavior and charge transport in ion-conducting polymer electrolytes and intercalation electrode materials. In order to develop new ion-conducting polymers with enhanced conductivities and desirable mechanical properties, we study factors controlling ionic conductivity: (1) the structure and dynamics of cation-anion interactions, (2) local structural changes of the polymer backbone resulting from cation-polymer interactions, and (3) the segmental motion of the polymer backbone and its dynamic coupling with ionic transport.

We are developing in situ spectroscopic techniques to aid our studies of lithium insertion/extraction reactions in a number of intercalation cathode materials including lithium manganese oxide, lithium vanadium oxide, and a large family of phosphate-based olivine compounds. Here the key scientific issues are the factors controlling reversibility and capacity in these materials. The nature of the interaction between the host cathode and the intercalated cation is especially important. We are examining the structural changes in the cathode accompanying the intercalation process, with particular attention to subtle modifications in the local structure of the host to accommodate the intercalated cation.

Fuel Cells

Our group is interested in proton exchange membrane (PEM) fuel cells, focusing on the need for a mechanically robust, thermally stable polymer membrane with high protonic conductivity at appropriate operating temperatures. Our goal is a fundamental, molecular-level understanding of charge transport through the membrane, the interaction of the membrane with the catalyst and how factors such as temperature and relative humidity affect the stability of the membrane during prolonged operation.

We are developing fuel cells that permit in situ vibrational spectroscopic measurements of the membrane and membrane/electrode regions.  With these systems we will address issues such as: (1) the nature and relative concentrations of protonated species in the membrane, (2) the interactions of those species with the membrane host, and (3) structural/compositional changes in the membrane during long term fuel cell operation.

In collaboration with Professor Dan Glatzhofer of this department, we have been working with new polymer membranes based on linear poly(ethylenimine) that has been cross-linked through the backbone nitrogen atoms.  These membranes are mechanically robust and enable good fuel cell performance at temperatures greater than 100 °C without the need for external humidification.

Experimental Techniques

We primarily use Raman scattering and infrared vibrational spectroscopy to examine local structure, composition, and dynamics in electrolytes and electrode materials. We have developed in situ spectroscopic techniques to examine the cathode and anode regions of an operating rechargeable lithium battery. We also utilize impedance spectroscopy to measure the ionic conductivities of these materials. We measure phase transition temperatures and enthalpies using differential scanning calorimetry. X-ray diffraction methods provide information about long range structure while EXAFS gives us insight into local structure. Nuclear magnetic resonance spectroscopy is also used to study the structure and dynamics of mobile ion species as well as that of the supporting matrix.

Selected Recent Publications (165 total)

C. P. Rhodes and R. Frech, "Local Structures in Crystalline and Amorphous Phases of Diglylme-LiCF₃SO₃ and Poly(ethylene oxide- LiCF₃SO₃ Systems:  Implications for the Mechanism of Ionic Transport", Macromolecules. 34, 2660-2666 (2001).

A. Yu and R. Frech, "Mesoporous Tin Oxides as Lithium Intercalation Anode Materials", J. Power Sources 104, 97-100 (2002).

R. Frech, V. Seneviratne, Z. Gadjourova, and P. G. Bruce, "A Vibrational Study of the Crystalline Phases of (CH₃(OCH₂CH₂)₂OCH₃)₂LiSbF₆ and P(EO)₆LiMF₆ (M=P, As, Sb)", J. Phys. Chem. B 107, 11255-11260 (2003).

R. Frech, S. York, H. Allcock and C. Kellam, "Ionic Transport in Polymer Electrolytes:  The Essential Role of Associated Ionic Species", Macromolecules 37, 8699-8702 (2004)

C. M. Burba and R. Frech, " A Raman and FTIR Spectroscopic Study of Li_xFePO₄ (0 £ x £ 1)", J. Electrochem. Soc.  151(7), A1032-A1038 (2004).

R. Frech, G. A. Giffin, F. Yepez Castillo, D. T. Glatzhofer, J. Eisenblätter, "Spectroscopic Studies of Polymer Electrolytes Based on Poly(N-ethylethylenimine) and Poly(N-methylethylenimine)", Electrochim. Acta  50(19), 3963-3968 (2005).

M. Burba and R. Frech, "Electrochemical, Spectroscopic, and Thermal Investigations of LiSn₂(PO₄)₃ and Sn₃(PO₄)₂ Anodes During the First Discharge", J. Electrochem. Soc. 152(6), A1233-1240 (2005).

D. T. Glatzhofer, M. J. Erickson, R. Frech, F. Yepez and J. Furneaux, "Polymer Electrolytes Based on Cross-Linked Linear Poly(ethylenimine) Hydrochloride/Phosphoric Acid Systems", Solid State Ionics 176(39-40), 2861-2865 (2005).

N. M. Rocher and R. Frech, "Hydrogen Bonding and the Inductive Effect in Crystalline and Solution Phases of Hexylamine-LiCF₃SO₃ and Dipropylamine-LiCF₃SO₃: Applications to Branched Poly(ethylenimine". J. Phys. Chem. B 109, 20679-20706 (2005).