A GexS1-x alloy electrode is useful for addressing the shortcomings of a Si negative electrode for lithium-ion batteries. To further improve the electrochemical performance of a GexS1-x negative electrode, a film-forming additive and the formation of a composite with LaSi2 were applied. A Ge0.1Si0.9 electrode exhibited better cyclability in the additive-containing electrolyte with a discharge capacity of 1240 mA h g(-1) at the 400th cycle. In addition, a Ge0.1Si0.9/LaSi2 composite electrode showed better cycle performance than a Ge0.1Si0.9 electrode.