▎ 摘　　要

NOVELTY - Preparation of composite fiber involves mixing a polymer and a solvent to prepare a coating solution, and providing the coating solution to graphene fiber to prepare composite fiber, in which uniformity of the coating film in the composite fibers can be controlled according to the molecular weight average molecular weight of the polymer or viscosity of the coating solution. USE - Preparation of composite fiber used as strategic core material. Uses include but are not limited to display, secondary battery, solar cell, automobile, and lighting. ADVANTAGE - The method is simple, and enables preparation of composite fiber with excellent mechanical properties such as elongation, and tensile strength, uniformity, and mechanical strength. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for composite fiber, which comprises coating film, graphene fiber conformally wraps, and graphene sheet structure is stacked in thickness direction, and several of graphene sheet structure is spaced apart from each other.