The Kinetics and Cyclability of Various Types of Polyacetylene Electrodes in Nonaqueous Lithium Cells

Abstract

The electrochemical doping process of polyacetylene has been investigated in lithium cells using lithium perchlorate in propylene carbonate as the electrolytic solution. The kinetics and the cyclability of this process have been examined by cyclic voltammetry, charge‐discharge curves, and EPR analysis. The results show that, for film‐type polyacetylene electrodes, the kinetics are controlled by the diffusion of the dopant species throughout the polymer. This diffusion appears particularly slow from the bulk to the surface of the polymer so that constant‐current charge‐discharge cycles of polyacetylene film electrodes may sustain only low rates (i.e., in the range of microamperes per square centimeter), and have a poor coulombic efficiency (i.e., of the order of 50%). Much better performance is offered by foam‐type polyacetylene electrodes, where the intrinsic high porosity produces an improved surface morphology, which in turn favors the diffusion of the dopant species. Indeed, constant‐current, charge‐discharge cycles at reasonably high rates (i.e., in the range of milliamperes per square centimeter) and reasonably good coulombic efficiencies (i.e., of the order of 85%), have been obtained with lithium cells using this type of polyacetylene electrodes.