One-pot ball-milling synthesis of a Ni-Ti-Si based composite as anode material for Li-ion batteries

One-step ball-milling method is proposed to synthesize Ni-Ti-Si composites as anode materials for Li-ion batteries. From this approach it is possible to obtain the ternary compound Ni4Ti4Si7, which is poorly crystallized and does not show significant electrochemical activity. More interesting performances have been obtained for the Si-rich composite with the chemical composition Ni0.12Ti0.12Si0.76. The specific capacity is of about 700 mAh g−1 with a coulombic efficiency of 99.8% at the 50th cycle. This composite is formed by small Si particles embedded in a matrix mainly composed of the binary phases of the Ni-Ti-Si system and Ni4Ti4Si7. The analysis of the reaction mechanism by differential capacity and in situ X-ray diffraction (XRD) indicates that Si particles react with Li to form LixSi amorphous phases while most of the intermetallic phases are electrochemically inactive. A particular attention has been devoted to the evaluation of the integral intensity of some XRD structures to determine the main trends in the formation of species during the first discharge-charge cycle. The results confirm the electrochemical inactivity of the matrix that maintains the dispersion of the Si particles and buffers the volume variations.