A polyaniline (PANi)-coated sulfur cathode was prepared by in-situ polymerization to improve the performance of Li-S batteries and prevent polysulfide dissolution. Because PANi polymerization requires only the addition of sulfur powder, the polymerization method was simple. Battery performance testing was conducted using various sulfur ratios, with the best performance being exhibited by the 31 wt% sulfur PANi composite (approximately 500 mAh g −1 S after 50 cycles from an initial capacity of 903 mAh g −1 S). Transmission electron microscopy images confirmed that sulfur was coated by an approximately 10-nm-thick layer of PANi. Cycle testing was conducted at a rate of 0.2 C with an electrode loading of 2 mg cm −2 of sulfur. Thus, a highly homogenous distribution of sulfur particles in PANi was achieved, resulting in sulfur-coated composite materials and allowing for the preparation of a conductive polymer by a relatively simple sulfur distribution method.