A new technique to produce Li2S/C composites and Li2S cathodes as well as their application in high-capacity Li–S batteries is demonstrated. The simple but effective method converts an easy-to-handle lithium salt-containing composite or electrode to Li2S using H2S. The main advantage is that the conversion to Li2S can be performed towards the final stage of the electrode preparation process, which significantly reduces the need of controlled atmosphere otherwise required for Li2S handling. LiOH is used to demonstrate the technique, and such fabricated Li2S electrode is successfully used in a Li–S battery (half-cell) where it shows discharge capacities of up to 770 mAh g−1 (Li2S) and retained >410 mAh g−1 (Li2S) after 100 cycles at C/5.