Understanding the reactivity of lithium toward new materials proposed for electrodes in lithium ion batteries is an important step to improve material performances. In this work, the reactivity with Li of a new negative electrode material with atomic composition Ni0.14Sn0.17Si0.32Al0.037C0.346 is carried out. Powerful characterization methods (Operando XRD, Transmission Mössbauer Spectroscopy TMS and Cyclic Voltammetry CV) have been used to investigate electrochemical and structural transformations along cycling. The excellent behavior of this new composite is achieved thanks to the reversible reactions of all components with lithium, namely Si, Ni3,4Sn4 and C phases. Formation of Li–Sn and Li–Si alloys is identified and discussed.