US-12620596-B2 - Graphene-doped lithium iron phosphate active material and method for preparing the same

US12620596B2US 12620596 B2US12620596 B2US 12620596B2US-12620596-B2

Abstract

A method for preparing a positive electrode active material is provided. The method for preparing a positive electrode active material may comprise the steps of: preparing a lithium precursor, an iron precursor, a phosphorus precursor, and abase 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 comprising a compound of lithium, iron, phosphorus, and oxygen.

Inventors

Jung-Ho Lee
Sambhaji Shivaji Shinde
Dong-hyung KIM

Assignees

INDUSTRY-UNIVERSITY COOPERATION FOUNDATION HANYANG UNIVERSITY ERICA CAMPUS

Dates

Publication Date: 20260505
Application Date: 20220415
Priority Date: 20191015

Claims (5)

1 . 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 (I D /I G ) 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.
2 . The method of claim 1 , wherein the first solvent and the second solvent are a same solvent.
3 . The method of claim 2 , wherein the first solvent and the second solvent comprises N-methyl-2-pyrrolidone (NMP).
4 . The method of claim 1 , wherein providing the second stock solution comprises: preparing a graphene colloid having the graphene powder by mixing the graphene powder with an oxidizing agent and heat-treating a mixture of the graphene powder and the oxidizing agent; obtaining the graphene powder from the graphene colloid; and dispersing the graphene powder in the second solvent.
5 . The method of claim 4 , wherein the oxidizing agent is hydrogen peroxide.

Description

TECHNICAL FIELD The present application relates to a positive electrode active material and a method for preparing the same, and more particularly, to a positive electrode active material including a compound of lithium, iron, phosphorus, and oxygen and a method for preparing the same. BACKGROUND ART Small IT devices such as smart phones, etc., took lead in initial growth of a global secondary battery market, but recently, a secondary battery market for vehicles is rapidly growing with the growth of an electric vehicle market. Secondary batteries for vehicles are leading the growth of the electric vehicle market while enabling mass production through product standardization and achieving low price and stable performance through technology development, and the market is rapidly expanding as a short mileage, which was pointed out as a limitation of electric vehicles, has been resolved by improving battery performance. With an explosive increase in the demand for secondary batteries, next-generation secondary batteries are also being actively developed to meet the safety issues of secondary batteries and the demand for increased battery capacity. For example, Korean Unexamined Patent Registration Publication No. 10-1808373 discloses a positive electrode active material for a lithium secondary battery, which includes a core including a particle of lithium transition metal oxide represented by equation 1 below and a coating layer located on a surface of the core, in which the coating layer includes niobium (Nb) and the particle of lithium transition metal oxide of above formula 1 is doped with tungsten, in which the tungsten is distributed in a concentration gradient manner that decreases from the surface of the particle of lithium transition metal oxide to a center thereof: [Equation 1] Li (Ni1−x−y−zMnxCoyMz)aWl−aO2 (in above formula 1, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and x, y, z and a are 1≤x+y+z≤1, 0≤x<a<1 as an atomic fraction of independent elements, respectively.). DISCLOSURE Technical Problem One technical object of the present application is to provide a positive electrode active material and a method for preparing the same. Another technical object of the present application is to provide a positive electrode active material including a compound of lithium, iron, phosphorus, and oxygen and a method for preparing the same. Still another technical object of the present application is to provide a positive electrode active material capable of enhancing charge/discharge properties and a method for preparing the same. Still another technical object of the present application is to provide a positive electrode active material capable of enhancing high-speed charge/discharge properties and a method for preparing the same. Still another technical object of the present application is to provide a positive electrode active material having high stability and long life and a method for preparing the same. Still another technical object of the present application is to provide a positive electrode active material, which is easily mass-produced, and a method for preparing the same. The technical objects of the present application are not limited to the above. Technical Solution To solve the above technical objects, the present application may provide a method for preparing a positive electrode active material. According to one embodiment, the method for preparing a positive electrode active material may include: 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. According to one embodiment, the chelating agent may include at least any one of pyrrole and citric acid, and a conversion of Fe3+ into Fe2+ may be suppressed to suppress a production of Fe(OH)2 by the chelating agent. According to one embodiment, the lithium precursor may include at least any one of Li2CO3, LiOH H2O, LiH2PO4, Li(CH3C00), LiCl, LiNO3, lithium citrate (Li3C6H5O7) or LiI. According to one embodiment, the iron precursor may include at least any one of Fe(NO3)3, FeSO4, Fe2O3, FeCl2 4H2O, FePO4, FeC6H5O7, iron acetate, and iron citrate (FeC6H6O7). According to one embodiment, the phosphorus precursor may include at least any one of C7H11NO7P2, C6H18O24P6, (NH4)2HPO4, H3PO4, or LiH2PO4. According to one embodiment, the base solvent may include N-methyl-2-pyrrolidone (NMP). According to one embodiment, the base solvent may further include ethylene glycol and deio