Graphene Oxide/Carbon Nanotube Bilayer Flexible Membrane for High-Performance Li–S Batteries with Superior Physical and Electrochemical Properties

Developing a highly effective interlayer inserted between the sulfur electrode and separator is one of the most important issues in Li–S battery research, because this interlayer enhances the cycle performance of the Li–S battery by trapping the lithium polysulfides in the sulfur electrode. Among various interlayer materials, carbon materials such as graphene and carbon nanotubes are particularly appealing because of their high electrical conductivity. Here, a new flexible carbon membrane interlayer consisting of graphene oxide (GO) and carbon nanotubes (CNTs) is developed by a facile vacuum filtration approach to trap the lithium polysulfides in the sulfur electrode. When the GO/CNT bilayer membrane is used as an interlayer between the sulfur electrode and separator (glass fiber), the Li–S battery delivers an initial discharge capacity of 1591.56 mAh g ⁻¹ and maintains a capacity of about 1000 mAh g ⁻¹ over 50 cycles at 0.2C with a low potential difference of 150 mV. This reflects higher electrochemical performance than a GO or CNT monolayer unilaterally. This is attributed to the hydrophilic functional group of the GO layer strongly adsorbing lithium polysulfides dissolved in liquid electrolyte and the CNT layer enhancing the ion conductivity.