Reaction of butyllithium with 3-D Cu3NbS4 leads to redox extraction of copper and formation of 2-D LiNbS2. Action of iodine on the intercalated material allows NbS2 (2H variety) to be obtained. For both Cu3NbS4 and Cu3VS4, the electrochemical study shows an irreversible multi-phase transformation of the starting material during the first intercalation-deintercalation cycle. Cyclability is observed over a large composition domain (similar to 5 Li per formula unit) corresponding to capacities larger than that of the Li-TiS2 system.