119Sn Mössbauer spectroscopy, X-ray diffraction and electrochemical experiments were carried out to characterize the reaction mechanism of lithium with spinel phases of the Cu2S–In2S3–SnS2 system. This analysis reveals an irreversible part of the mechanism linked to the reduction of the cations involving a spinel to rocksalt transformation followed by a structural breakdown, and a reversible part linked to the formation of lithium-metal alloys. The electrochemical investigation has shown interesting reversible capacities for these materials, and their possible use as anode materials in lithium-ion cells.