Graphene-doped lithium iron phosphate active material and method for preparing the same

A method for preparing a functional positive electrode active material, the method comprising:

• 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 the 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,
• wherein the functional positive electrode active material has a first crystallinity in a first state before a charging and discharging process of a lithium secondary battery that includes the functional positive electrode active material,
• wherein the functional positive electrode active material has a second crystallinity in a second state after the charging and discharging process,
• wherein the second crystallinity is higher than the first crystallinity as a result of performing the charging and discharging process,
• wherein the functional positive electrode active material has a disorder/defect band (“D band”) and a graphitic band (“G band”),
• wherein a ratio (ID/IG) value of intensity of the D band to intensity of the G band is greater than 1.98 and less than 3.26 when measuring a Raman spectrum,
• wherein the functional positive electrode active material has a graphene powder content greater than 1 at % and less than 3 at %, and
• wherein the functional positive electrode active material has a capacity value greater than a theoretical capacity value of 170 mAh g−1 for lithium iron phosphate.