Improved Electrochemical Performance of Lanthanum Silicide/Silicon Composite Electrode with Nickel Substitution for Lithium-Ion Batteries

The effect of nickel substitution on the electrochemical performance of a lanthanum silicide (LaSi 2 )/silicon (Si) composite electrode for lithium-ion batteries was studied. The results of X-ray diffraction analysis showed that LaSi 2 forms a substitutional solid solution with Ni, and that only the Si site in LaSi 2 is substituted by Ni, whereas elemental Si in the crystal structure is not substituted. Although the charge–discharge capacity of a LaNi x Si 2– x electrode ( x = 0.06 and 0.12) was lower than that of a LaSi 2 electrode, the LaNi x Si 2– x electrode exhibited a high-rate performance. A LaNi 0.10 Si 1.90 /Si (70:30 wt %) composite electrode showed a large initial discharge capacity and a superior long-term cycle performance compared to electrodes composed of Si alone and LaSi 2 /Si composite, and suppressed the decrease in the initial Coulombic efficiency of the Si electrode. The LaNi 0.10 Si 1.90 /Si electrode also exhibited an excellent high-rate performance with a reversible capacity of 2240 mA h g(Si) −1 at a rate of 10 C. The results of computational chemistry demonstrated that LaNi 0.25 Si 1.75 favors Li migration in the pathway compared to LaSi 2 . These results indicate that Ni substitution in a LaSi 2 /Si composite negative electrode significantly improves its electrochemical performance.