Improving the Performance of Lithium–Sulfur Batteries by Conductive Polymer Coating

TLDR

Lithium–sulfur batteries promise high energy density, low cost, and safety, yet their commercialization is hindered by rapid capacity fading caused by polysulfide dissolution and uncontrolled redeposition, which porous carbon matrices can trap but still allow to diffuse without an effective capping layer. This study investigates whether coating mesoporous carbon/sulfur particles with a conducting polymer can suppress polysulfide diffusion. The authors applied a poly(3,4‑ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) coating onto the mesoporous carbon/sulfur particles to create an effective capping layer. The PEDOT:PSS coating raised coulombic efficiency from 93 % to 97 %, cut capacity decay from 40 % to 15 % over 100 cycles, and increased discharge capacity by ~10 % to 1140 mAh g⁻¹ initially and >600 mAh g⁻¹ after 150 cycles at C/5, demonstrating a promising route for enhancing Li–S battery performance and potentially other lithium‑ion electrodes.

Abstract

Rechargeable lithium–sulfur (Li–S) batteries hold great potential for next-generation high-performance energy storage systems because of their high theoretical specific energy, low materials cost, and environmental safety. One of the major obstacles for its commercialization is the rapid capacity fading due to polysulfide dissolution and uncontrolled redeposition. Various porous carbon structures have been used to improve the performance of Li–S batteries, as polysulfides could be trapped inside the carbon matrix. However, polysulfides still diffuse out for a prolonged time if there is no effective capping layer surrounding the carbon/sulfur particles. Here we explore the application of conducting polymer to minimize the diffusion of polysulfides out of the mesoporous carbon matrix by coating poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS) onto mesoporous carbon/sulfur particles. After surface coating, coulomb efficiency of the sulfur electrode was improved from 93% to 97%, and capacity decay was reduced from 40%/100 cycles to 15%/100 cycles. Moreover, the discharge capacity with the polymer coating was ∼10% higher than the bare counterpart, with an initial discharge capacity of 1140 mAh/g and a stable discharge capacity of >600 mAh/g after 150 cycles at C/5 rate. We believe that this conductive polymer coating method represents an exciting direction for enhancing the device performance of Li–S batteries and can be applicable to other electrode materials in lithium ion batteries.