Nanoparticles of Polypyrrole and Their Effect on Mediating Li Ion Transport from Liquid Electrolyte to Cathode
- PDF / 560,888 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 31 Downloads / 139 Views
Nanoparticles of Polypyrrole and Their Effect on Mediating Li Ion Transport from Liquid Electrolyte to Cathode Yong Pang, Ningpine Chen, and Liang Hong Department of Chemical & Environmental Engineering National University of Singapore Singapore 119260 ABSCTRACT Nano-scale particles of polypyrrole (PPy) have been synthesized by polymerizing the respect monomer in the presence of its substituted homologue with oxyethylene (POE) oligomers as the substitute groups. The polymerization was carried out by introducing an aqueous solution of oxidant into the tetrahydrofurane (THF) solution of the monomers. The particles obtained possess brush-like architectures in the dispersing medium, and their sizes in dry state fall into the range of 10 to 40 nm according to TEM analysis. When dispersed by a low content (< 0.1 wt %) in an aprotic organic solvent, the nanoparticles synthesized have been found to affect the conduction of lithium ion. The effect is interpreted as a significant reduction in the electrical resistance at the electrode/electrolyte interface according to gain-phase impedance measurement. This has been attributed to the mediating role of the graft POE chains on the colloidal particles. INTRODUCTION The conventional procedures of the preparation of conducting polymer colloids rely on emulsion polymerization by using water-soluble polymers, such as poly(vinyl alcohol-co-vinyl acetate), PEO, and cellulosic derivatives etc., as steric stabilizers [1]. In this way, the stabilizer is physically adsorbed onto the surface of the PPy particles. The average particle diameter of the colloidal particles varies over the range 66~300 nm. Recently, Simmons et al. have reported a “reactive stabilizer” route leading to colloidal PPy [2]. By this method, water-soluble monomers such as N-vinylpyrrolidone was copolymerised with various vinylic (bi)thiophene comonomers to obtain water-soluble statistical copolymers. After the in situ polymerization of the pyrrole monomer, resulting PPy particles were typically 100~150 nm in diameter. The present paper proposes an alternative approach that results in even smaller PPy nanoparticles. By this method, large organic molecules containing polyoxyethylene (PEO) moiety are bound to pyrrole or aniline molecule via a spacer, tolylene diisocyanate (TDI). Besides the synthesis of the PPy nanoparticles, their application for improving ionic conductivity of liquid electrolyte of lithium is also explored in this study.
EXPERIMENTAL DETAILS Preparation of the grafted polypyrrole nanoparticles THF 40ml, pyrrole (0.70ml, 10.1 mmol), TDI (1.45ml, 10.1mmol) were added into a 100ml conical flask. The mixture was stirred for 36h at room temperature. Then oxyethyl-containing oligomer (11 mmol) and dibutyl tin dilauriate (DBTDL, ca. 0.3 ml) were added into the solution. After that, the reaction was allowed to extend for 24 more hours at room temperature. An aqueous solution consisting of (NH4)2S2O8 (2.77g, 12.1 mmol) and deionized water (DIW) 40ml was introduced into the organic solution, and the two-liquid
Data Loading...
