Li-S battery system is advantageous due to theoretically higher energy density (2,600 Wh kg−1 assuming the redox reaction of 2Li + S⇄ Li2S), and thus research and development for sulfur electrode had started in 1960–1970s [1, 2, 3].
The difficulty in Li-S battery operated at ambient temperature lies in two points: conductivity and the solubility of partly lithiated polysulfides, LixS8. S powder is usually a yellow powder and it has poor conductivity. So the conduction pathway should be ensured. At present, preparation of composite of S and carbons has been attracting many researcher for improvement. Present status will be outlined later in the next section.