▎ 摘　　要

NOVELTY - Lithium secondary battery (21) comprises a negative electrode (22), a positive electrode (23), and an electrolyte disposed between the negative electrode and the positive electrode. The negative electrode comprises: a silicon composite comprising silicon, a silicon oxide (I) disposed on the silicon, and a graphene disposed on the silicon oxide; or a carbonaceous composite comprising the silicon composite, and a carbonaceous material, which is different from the graphene. USE - The lithium secondary battery is useful as a flexible battery (claimed), in electric vehicles, and in hybrid vehicles e.g. plug-in hybrid electric vehicles. ADVANTAGE - The lithium secondary battery exhibits enhanced capacity retention, and excellent charging/discharging efficiency and lifespan characteristics. DETAILED DESCRIPTION - Lithium secondary battery (21) comprises a negative electrode (22), a positive electrode (23), and an electrolyte disposed between the negative electrode and the positive electrode. The negative electrode comprises: a silicon composite comprising silicon, a silicon oxide of formula (I) disposed on the silicon, and a graphene disposed on the silicon oxide; or a carbonaceous composite comprising the silicon composite, and a carbonaceous material, which is different from the graphene, where at least one of the negative electrode and the electrolyte comprises an ionic liquid containing a fluorosulfonyl imide anion and a lithium salt. x = greater than 0 to less than 2. DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the lithium secondary battery. Lithium secondary battery (21) Negative electrode (22) Positive electrode (23) Separator (24) Battery case (25)