Lithium surface protection by polyacetylene in situ polymerization

Direct acetylene polymerization at ambient temperature on a Li metal surface and polyolefin separator with Ziegler-Natta catalyst was developed. Thin conducting polyacetylene films with strong adhesion to Li or polyolefin surface was formed and studied by electrochemical methods. AC impedance measurements and charge/discharge tests were applied for prepared coin cells with LiCoO2 as a cathode material in the presence of 1 M LiPF6 in dimethyl carbonate, ethylene carbonate, propylene carbonate (5:3:2 vol) electrolyte. Three kinds of polyolefins were used to prepare composite separators with polyacetylene: polypropylene (PP), polyethylene (PE) and three-layer type: PP-PE-PP. The polyacetylene film thickness on Li metal or polyolefin separator was easily controlled by catalyst concentration and polymerization time. It was shown that high ionic conductivity (7.5 x 10(-5) S cm(-1)) might be achieved due to higher porosity of a polyethylene separator. Li-polyacetylene electrodes showed highest ionic conductivity and stability in charge/discharge tests. (c) 2006 Elsevier B.V. All rights reserved.