Poreless Separator and Electrolyte Additive for Lithium–Sulfur Batteries with High Areal Energy Densities

Despite the attractive theoretical capacity of sulfur over 1600 mA h g−1, lithium–sulfur (Li–S) batteries suffer from insufficient cycle lives mainly due to fatal polysulfide dissolution. This chronic drawback becomes amplified at high areal capacities, especially close to commercial levels (i.e., >3 mA h cm−2). Here, we introduce an integrated approach of adopting poreless urea–urethane copolymer (spandex) separator and cesium nitrate (CsNO3) electrolyte additive. The spandex separator prevents soluble polysulfides from reaching Li metal anode and also suppresses Li dendrite growth via its intrinsic wet adhesion. When combined with a sulfur–carbon composite cathode, the cell based on the spandex separator and the electrolyte additive delivers a high areal capacity of 4 mA h cm−2 with decent cycling performance, such as 79.2 % capacity retention after 200 cycles with respect to the capacity in the second cycle. An integrated approach of poreless separator and electrolyte additive enhances lithium–sulfur battery cycle life even at commercial levels of areal energy density.