Si nanocrystallites embedded in hard TiFeSi2 matrix as an anode material for Li-ion batteries

A Si–TiFeSi2 composite was synthesized in large-scale using arc melting followed by rapid quenching. The composite showed that active Si nanocrystallites of approximately 50 nm were embedded in an inactive TiFeSi2 hard matrix. Crystalline Si reacted with Li to form the Li21Si8 phase and transformed into amorphous Si when Li was extracted, while the TiFeSi2 matrix remained inactive to Li and unchanged throughout the electrochemical cycling. The composite showed a reversible capacity of 1200 mAh g−1 over 50 cycles with a Coulombic efficiency of 89% for the first cycle. Nanosized cracks were observed only at the Si crystallites parts within the Si–TiFeSi2 particles, indicating that the TiFeSi2 matrix was hard enough to withstand the stress generated during lithiation which explained the excellent capacity retention.