▎ 摘　　要

NOVELTY - Preparing functional positive electrode active material involves providing a first stock solution in which a base positive electrode active material including a compound of lithium, iron, phosphorus, and oxygen is dispersed in a first solvent; providing a second stock solution in which graphene powder is dispersed in a second solvent; and preparing a functional positive electrode active material in which the graphene powder is doped into the base positive electrode active material by mixing and heat-treating the first stock solution and the second stock solution. USE - Method for preparing functional positive electrode active material used in lithium secondary battery for vehicles, smartphones. ADVANTAGE - The functional positive electrode active material has high stability against high-speed charge/discharge and a long lifespan, increases battery capacity and demand in market. The positive electrode active material is prepared with an easy mass production and less production cost and time, has high charge/discharge properties by configuring a lithium secondary battery together with the solid electrolyte. The graphene powder can not only enhance the conductivity of a positive electrode, but also function as an active material that occludes and desorbs lithium ions along with the base positive electrode active material, thereby enhancing a charge/discharge capacity. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) a functional positive electrode active material, which comprises a base positive electrode active material including a compound of lithium, iron, phosphorus, and oxygen; and graphene powder doped into the base positive electrode active material, where ratio (ID/IG) value of intensity of a D band to intensity of a G band is greater than 1.98 and less than 3.26 when measuring the Raman spectrum; (2) a method for preparing a positive electrode active material, which involves providing a lithium precursor, an iron precursor, a phosphorus precursor, and a base solvent; mixing the base solvent and the lithium precursor to prepare a first source, mixing the base solvent and the iron precursor to prepare a second source, and mixing the base solvent and the phosphorus precursor to prepare a third source; and mixing the first source, the second source, the third source, and a chelating agent and allowing a reaction to occur in the mixture by a heat treatment method to prepare a positive electrode active material including a compound of lithium, iron, phosphorus, and oxygen; (3) a lithium secondary battery, which comprises a positive electrode having a positive electrode active material including a compound of lithium, iron, phosphorus, and oxygen; and a negative electrode on the positive electrode; and a solid electrolyte between the positive electrode and the negative electrode; and (4) a positive electrode active material including a compound of lithium, iron, phosphorus, and oxygen, where the positive electrode active material has a first crystallinity in a state before charging and discharging of a lithium secondary battery including the positive electrode active material, and has a second crystallinity in a state after charging and discharging of the lithium secondary battery, and the second crystallinity is higher than the first crystallinity.