Introduction Lithium/sulfur battery is very attractive for rechargeable lithium battery due to its high theoretical specific capacity of 1675 mAh/g-sulfur , high theoretical energy density of 2600 Wh/kg, low cost, and environmental friendliness [1]. Unfortunately, during the charge-discharge process, the lithium polysulfide dissolves into electrolyte, which causes the loss of sulfur active material. Therefore, Li/S battery has bad cyclic durability at room temperature.[2] To overcome such problems, the polysulfide dissolution into electrolyte should be retarded or prohibited. So, in this study, in order to improve the cycle life of Li/S battery. nano-sized Al2O3 was added to sulfur cathode as a additive to adsorb soluble polysulfide within sulfur cathode.