Solid polymer electrolytes based on polyacrylonitrile and organically modified ceramics ( Ormocers)
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Date
2000
Authors
Perera, G. A. K. Sandhya
Journal Title
Journal ISSN
Volume Title
Publisher
University of Peradeniya
Abstract
PAN based electrolytes were made by complexing EC and PC with different salts namely, CuCNS, Cu(CF₃SO₃)₂, Mg(CIO₄)₂, and LiCF₃SO₃ Sample preparation was done using the hot pressed technique. All systems yielded free standing electrolyte films.
System with 21 mol% PAN : 30 mol% EC : 45 mol% PC : 4 mol% CuCNS has a room temperature conductivity of 3.3 x 10⁻⁵ S cm⁻¹ while the system with 20 mol% PAN : 41 mol% EC : 34 mol% PC : 5 mol% Cu(CF₃SO₃)₂ has a room temperature conductivity of 4.1 x 10⁻³ S cm⁻¹ Conductivity variations with temperature of the two systems show Arrhenius and VTF behaviours respectively. Former system seems to be an anionic conductor and the latter system a mixed conductor with cationic and electronic contributions. Electrolytes made with Cu(CF₃SO₃)₂ has been used in cells of the form, Cu/PAN: EC: PC : Cu(CF₃SO₃)₂ / PPy : DBS where DBS stands for polypyrrole polymerized in the presence of DBS. Open circuit voltage was approximately 180 mV. A capacity of about 12 μA h under a load resistor of 50 kΩ was obtained.
When Mg(CIO₄)₂ was incorporated with PAN : EC : PC, a room temperature conductivity of 3.2 x 10⁻³ S cm⁻¹ can be obtained from the composition 18 mol% PAN : 64 mol% EC : 14 mol% PC : 4 mol% Mg(CIO₄)₂ . Conductivity variation with the temperature takes the form of Arrhenius behaviour. Secondary solid state cells have been fabricated with this electrolyte in the form, Mg / PAN : EC : PC : Mg(CIO₄)₂ / PPy : DBS. Open circuit voltage lies around 1.5 V. Estimated capacity values are around 0.18 mA h.
System based on LiCF₃SO₃ has a room temperature conductivity of 1.2 x 10⁻³ S cm⁻¹. Corresponding composition is 15 mol% PAN : 42 mol% EC : 36 mol% PC : 7 mol% LiCF₃SO₃. Conductivity variation with temperature followed VTF behaviour. Stability of the electrolyte with lithium is somewhat acceptable. Test cells in the configuration, Li / PAN : EC : PC : LiCF₃SO₃ / PPy : X (X : CF₃SO₃, DBS’, AS) have open circuit voltages around 4 V. It is possible to get more than 800 cycles with an efficiency of 99.95%. Artificial muscles in the form, PPy : X / PAN : EC : PC : LiCF₃SO₃ / PPy : X (X : CF₃SO₃, DBS’) have been fabricated. Their movements were observed between two voltages. It is seen that the movements are faster when the assembly is thin.
Ormocer electrolytes are having somewhat considerable conductivity values. But, those values should be enhanced further to make them proper candidates for applications. Concept of all solid state cells may be feasible with ormocers.
Description
Keywords
Polymer , Polymer electrolytes , Polyacrylonitrile , Ceramics