▎ 摘　　要

NOVELTY - Producing yolk-shell structure, comprises (a) forming a graphene layer on surface of the silicon particles, and (b) performing vapor phase etching on outer surface of the silicon particles present inside the graphene. USE - The yolk-shell structure is useful in cathode for lithium secondary battery (claimed). ADVANTAGE - The method is economical and simple, improves yield of yolk-shell structure compared to conventional method of manufacturing graphene/silicon yolk-shell structure using wet etching process, and stability of battery, does not include step of oxidizing silica surface, and makes volume expansion less than or equal to 450% of core without deformation of shell structure. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) yolk-shell structure prepared by above method, where voids exist between the graphene and the silicon particles; and (2) cathode comprising cathode active material and water-soluble polymer including the yolk-shell structure. DESCRIPTION OF DRAWING(S) - The drawing shows a flowchart illustrating the method for producing yolk-shell structure (Drawing includes non-English language text).