Polyglycerol-functionalized microporous carbon/sulfur cathode for Li-S battery

Lithium–sulfur (Li-S) batteries are promising next-generation rechargeable devices that have low cost and high energy densities. However, the commercialization of Li-S batteries is challenging because lithium polysulfide (Li2Sn), which forms during the charge–discharge process, dissolves in the electrolyte. To suppress Li2Sn dissolution, we propose a method of modifying microporous carbon with polyglycerol, in which only microporous carbon materials and monomers are mixed and heated. Using a sulfur cathode with polyglycerol-treated microporous carbon as a host material for the sulfur, the capacity retention (discharge capacity at the 50th cycle divided by the discharge capacity at the 2nd cycle) improved from 57.6 to 75.2%. We also used Fourier-transform infrared spectroscopy to reveal that polyglycerol treatment suppresses the dissolution of Li2Sn from the cathode. Finally, polyglycerol treatment is shown to improve the cycle performance of Li-S batteries.