Montmorillonite (MONT) Complex and their Application
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MONTMORILLONITE
(MONT)
COMPLEX AND THEIR APPLICATION
YU, WENHAI AND LIU WANYU Department of Materials Science and Engineering, University of Science and Technology of China Hefei, Anhui 230026, the People's Republic of China
ABSTRACT Montmorillonite(Mont) has been proved to be a kind of very promising solid electrolyte in recent years because of its good electric properties. It can be composed by polymer to prepare a mont-polymer complex which has high ionic conductivity and excellent plasticity. The film made of mont-polymer complex with room temperature ionic conduction has been used in solid state battery as solid electrolyte. It may be a new type of function material with futher application. INTRODUCTION Montmorillonite (abbr. mont) is main component of bentonite, abundant in resources and chim in price. The ideal mont is possessed of a layer structure1 '. Its ideal composition is Si0 2 66.7%, A1 2 0 3 28.3%, H2 0 5% (uncluding interlayer matter), and its practical composition can be expressed generally with a formula as following. l/2(Ca,Na)
0
.7(AI,Mg,Fe)
4
(Si,AI)
8
0 2 0 (OH)
4
nH2 0.
Its crystal-unit is composed of two silica tetrahedral sheep with a 3 middle alumina octahedral sheet. Owing to that the S' anl Al + re xeplaced by some low-valence ions such as Ali+ Fe , Mg 2, Ca + etc under normal conditions, so that the crystal -unit is charged with negative charge. Therefore various cations as well as water molecules or other polar molecules can be adsorbed into the interlayer region between two neighbouring units. The cations may be migrated in the interlayer channel as a quasi-liquid under an external electric field so that the ionic conductance was expressed. The natural monts are generally classified according to their impurities, e.g. Ca-mont, Na-mont etc, and can be turned into fast ionic conductors by ion-exchange methods, i.e. subMtuting Mn+ for Ca or Na4 , where M was Li, Zn, Mg, Cu, Fe, etc'' . The a.c. and d.c. conductivities of valrious M-monts have been determined to be 10and 10-'Scm-' in order of magnitude respectively as shown in table 1. DENATURE OF MONT WITH ORGANIC MOLECULES to
The natural and denatured monts generally contain water 13--16% of the entire weight so that difficult to apply
Mat. Res. Soc. Symp. Proc. Vol. 210. 01991 Materials Research Society
up in
494
high density batteries as solid electrolytes for oxidation of anodes. For overcoming this difficulty tW.% interlayer water was replaced by some polar organic molecules 1. The organic-monts prepared in our Lab are propylene carbonate--mont (pc-mont), butyrolatone--mont ( -BL-mont), N'N- dimethyl fomamide--mont (DMF-mont), N'N-dimethyl acetamide--mont (DMA-mont) and dimethyl sulphoxide--mont (DMSO-mont). Their electric properties determined are listed in table 2. It -s sewn that the conductivities of the organic-monts are 10- -- 10-Scmhaving the same order of magnitude with that of M-monts, and the activation energies are 0.2--0.3eV in 10--90 0 C region. Table
1. Conductivities
and
activation
energies
for
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