Boosting Li–S battery performance using an in-cell electropolymerized conductive polymer

Abstract

Lithium–sulfur (Li–S) batteries represent a promising high-density energy storage technology. The use of conductive polymers to enhance the performance of Li–S batteries has received much attention. In this work, a convenient and low-cost in-cell electropolymerization method is developed for the preparation of a conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), as a cathode binder inside a Li–S battery. The cell with this electropolymerized PEDOT (ePEDOT) shows notably improved specific capacity, cycling stability, and rate performance in comparison with the cell using the chemically synthesized commercial PEDOT:PSS (cPEDOT:PSS) as the binder. The performance enhancement is attributed to the formation of tightly integrated interfaces between ePEDOT and other components in the sulfur cathode. Moreover, this study revealed that the electrochemical dedoping of PEDOT is likely to occur during the Li–S battery cycling and thus the contribution of PEDOT (and some other conductive polymers) to the enhancement of the electrical conductivity of the sulfur cathode may not be as significant as expected.