Structural Dynamics of Polymer Electrolytes
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STRUCTURAL DYNAMICS OF POLYMER ELECTROLYTES G-A. Nazri, D.M. MacArthur, J.F. O'Gara, General Motors Research Laboratories, Warren, MI 48090 and Ricardo Aroca, Chemistry Department, University of Windsor, Ontario N9B 3P4 Canada ABSTRACT The structure of polyethylene oxide doped with lithium perchlorate was studied. The macroscopic structure of the polymer-salt complexes was studied by thermal analysis and xray diffraction. The microscopic structure and polymer dynamics were studied by infrared, Raman and nuclear magnetic resonance spectroscopy. Thermal analysis and x-ray diffraction studies clearly revealed the change of crystalline phase to an The vibrational amorphous phase by the addition of salt. analysis showed a conformational transformation of the polymer Vibrational analysis also showed chain by the addition of salt. cluster in clearly the formation of free ion, ion-pair and salt increased. the polymer as the concentration of the salt
INTRODUCTION Polymer electrolytes have gained a great deal of attention and adhesivness decade due to their flexibility during the last which provide excellent processability for fabrication in film various solid state devices. Fabrication of an ultra-thin is very of polymer electrolyte (to avoid high resistivity) attractive for application in miniature and large scale high energy density batteries. Polymer electrolytes were first reported in 1975 by Wright (1-3). He described the formation of a conductive complex when polyethylene oxide (PEO) was mixed with KSCN, NaSCN, NaI, or LiClO4 . Armand et al. used polymer electrolytes in electrochemical devices (4,5). Armand's work motivated several laboratories to search for new polymer electrolytes with high ionic conductivity and good stability versus reactive electrodes. It is found that polymers containing ionizable subunits either on the backbone or as the side chain form conductive complexes when mixed with low Polyethers such as polyethylene and lattice-energy salts. polypropylene oxides and polymers containing etheric side chains are among the most studied polymer electrolytes (6-14). The use of polymer electrolytes is a rather new concept compared with conventional liquid and solid electrolytes and many fundamental questions regarding the structure, mass and charge transport and the nature of the dissociated salt, remain to be studied. No unified theory to explain the properties of polymer electrolytes exists. The nature of ion-ion and ionpolymer interactions are the subject of extensive studies at several laboratories world-wide (6,9,10,15-19). Polymer conventional electrolytes, during charge shell of the
differences compared to electrolytes have distinct liquid and solid electrolytes. In a liquid the solvated ions carry their solvation shell transport. In polymer electrolytes the solvation ions has a very limited translational movement.
Mat. Res. Soc. Symp. Proc. Vol. 210. @1991 Materials Research Society
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Charge transport in solid inorganic electrolytes has been described mostly by a defect migration or ion hoppin
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