Solid–liquid–solid mediated artificial SEI coated stable lithium and high-sulfur percentage SPAN for high performance Li–S batteries

Abstract

Lithium–sulfur batteries (LSBs) are a next generation battery that are an attractive alternative to lithium-ion batteries. Although, LSBs are conventionally reliant on ether electrolytes that promote the unwanted polysulfide shuttling effect and lead to safety concerns due to low flash points. Another major issue is the instability of lithium metal at the anode. These two issues hinder the scaling up of this chemistry from coin cells to pouch cells. Herein, we present a novel synthesis method to produce sulfurized polyacrylonitrile (SPAN), a material that can avoid polysulfide formation and is compatible with carbonate electrolytes. Our synthesis method results in an 18% increase in sulfur content, compared to a traditional synthesis method. The new synthesis method also creates smaller cathode agglomerations which improves cell performance. We also studied the influence of a polymeric artificial SEI on the stability of the lithium metal anode. Using postmortem XPS, we found an increase in LiF with this anode treatment. We combined these materials in a Li-SPAN pouch cell to investigate their performance at a larger scale and found it to be electrochemically stable in a commercial carbonate electrolyte. It yielded an initial stable capacity of 1068 mA h g_sulfur⁻¹ (572 mA h g_SPAN⁻¹) with a capacity retention of 82% after 200 cycles. This treated pouch cell lasted nearly five times longer than a conventional pouch cell with no lithium treatment.