119 Sn Mössbauer spectroscopy, X-ray diffraction (XRD) and electrochemical experiments were carried out to characterise the reaction mechanism of lithium with spinel phases Cu x In y Sn z S4. The electrochemical investigations have shown interesting reversible capacities for these materials, and their possible use as anode materials in lithium-ion cells. This analysis reveals a multi-phase mechanism linked to the reduction of the cations involving a spinel to rocksalt transformation followed by a structural breakdown. Density functional calculations by the linearised augmented plane wave (LAPW) method give a good interpretation of experimental results for crystalline phases.