CN-122025513-A - Lithium iron phosphate positive electrode material, and preparation method and application thereof

CN122025513ACN 122025513 ACN122025513 ACN 122025513ACN-122025513-A

Abstract

The application relates to the technical field of batteries, and provides a lithium iron phosphate positive electrode material, a preparation method and application thereof, wherein iron phosphate and a first lithium source are mixed according to a mass ratio of 1:0.2-0.3, a first carbon source with a mass of 3-6% of iron phosphate and a solvent are added for mixing, grinding and spraying to obtain a spray material A, the spray material A and a second carbon source with a mass of 2.0-5.0% of the spray material A are mixed to obtain a polycrystalline precursor B, the iron phosphate and the second lithium source are mixed according to a mass ratio of 1:0.2-0.3, a doping agent with a mass of 0.5-2.0% of the iron phosphate, the solvent and a first carbon source with a mass of 6-15% of the iron phosphate are added for mixing, grinding and spraying to obtain a spray material C, the spray material C and the second carbon source with a mass of 0.5-2.5% of the spray material B are mixed according to a mass ratio of 5:5-3:7, sintering and air-crushing. The compaction density is 2.6-3.0 g/cm 3 , and the 1C discharge is more than 140mAh/g.

Inventors

MIAO LINPING
JING RUYI
MAO YANYONG
Mo Chengqian

Assignees

四川天力锂能有限公司

Dates

Publication Date: 20260512
Application Date: 20251231

Claims (10)

1. The preparation method of the lithium iron phosphate anode material is characterized by comprising the following steps of: S1, mixing ferric phosphate and a first lithium source according to a mass ratio of 1:0.2-0.3, adding a first carbon source and a solvent, mixing and grinding, spray drying to obtain a spray material A, mixing the spray material A and a second carbon source, and uniformly stirring to obtain a polycrystalline precursor B, wherein the mass of the first carbon source is 3-6% of that of the ferric phosphate in the step, and the mass of the second carbon source in the step is 2.0-5.0% of that of the spray material A; S2, mixing ferric phosphate and a second lithium source according to a mass ratio of 1:0.2-0.3, adding a doping agent, a solvent and a first carbon source, mixing, grinding, spray drying to obtain a spray material C, mixing the spray material C and the second carbon source, and uniformly stirring to obtain a monocrystal precursor D, wherein the mass of the doping agent is 0.5-2.0% of the mass of the ferric phosphate in the step, the mass of the first carbon source is 6-15% of the mass of the ferric phosphate in the step, and the mass of the second carbon source in the step is 0.5-2.5% of the mass of the spray material C; s3, mixing, sintering and air-crushing the polycrystalline precursor B and the monocrystalline precursor D according to the mass ratio of 3:7-5:5 to obtain the lithium iron phosphate positive electrode material, wherein the sum of the mass ratio of the polycrystalline precursor B to the monocrystalline precursor D is 10.
2. The preparation method of the lithium iron phosphate positive electrode material according to claim 1, wherein the iron phosphate is prepared by an ammonium process, a sodium process or an iron oxide red process, the first lithium source and the second lithium source are at least one of lithium carbonate, lithium dihydrogen phosphate and lithium hydroxide, the first carbon source is at least one of glucose, fructose, sucrose, maltose, starch, cellulose, N-methylpyrrolidone, polyethylene glycol with a molecular weight of 2000-20000, polyvinyl alcohol with a molecular weight of less than 20000 and polyvinylpyrrolidone with a molecular weight of k 10-120, the second carbon source is at least one of glycerol, stearic acid, glycerol monostearate and asphalt, and the doping agent is at least one of titanium dioxide, titanyl oxalate, titanium citrate, ammonium metavanadate, vanadium pentoxide, magnesium oxide, magnesium carbonate, magnesium hydroxide and zirconium oxide.
3. The method for preparing a lithium iron phosphate positive electrode material according to claim 1, wherein the particle size of the particles obtained after mixing and grinding in the step S1 is 0.4 to 0.8 μm, and the median D50 of the particle size of the spray material a is 2 to 10 μm.
4. The method for preparing a lithium iron phosphate positive electrode material according to claim 3, wherein the median D50 of the particle diameter of the spray material a in step S1 is 3 to 6 μm.
5. The method for preparing a lithium iron phosphate positive electrode material according to claim 1, wherein the particle size of the particles obtained after mixing and grinding in the step S2 is 0.2 to 0.4 μm, the particle size D50 of the spray material C is more than 15 μm, and the particle size D50 of the single crystal precursor D is 1.0 to 4.0 μm.
6. The method for producing a lithium iron phosphate positive electrode material according to claim 5, wherein the single crystal precursor D has a particle diameter D50 of 2.0 to 3.0. Mu.m.
7. The method for preparing the lithium iron phosphate positive electrode material according to claim 1, wherein the sintering temperature in the step S3 is 750-820 ℃, the constant temperature time in the sintering process is 6-10 h, and the gas crushing classification frequency is 100-130 Hz.
8. The lithium iron phosphate positive electrode material prepared by the preparation method according to any one of claims 1 to 7, wherein the lithium iron phosphate positive electrode material comprises large polycrystalline particles, large monocrystalline particles, middle monocrystalline particles and small monocrystalline particles, the particle size of the large polycrystalline particles is 2-10 microns and accounts for 15-25 wt% of the mass of the lithium iron phosphate positive electrode material, the particle size of the large monocrystalline particles is 0.5-2.0 microns and accounts for 15-25 wt% of the mass of the lithium iron phosphate positive electrode material, the particle size of the middle monocrystalline particles is 0.2-0.5 microns and accounts for 30-50 wt% of the mass of the lithium iron phosphate positive electrode material, the particle size of the small monocrystalline particles is less than 0.2 microns and accounts for less than 20wt% of the mass of the lithium iron phosphate positive electrode material, and the outermost layer of the lithium iron phosphate positive electrode material is coated by a carbon coating layer formed by a second carbon source.
9. The lithium iron phosphate positive electrode material according to claim 8, wherein the powder of the lithium iron phosphate positive electrode material is compacted to 2.60-2.75 g/cm 3 .
10. A lithium battery, characterized in that the positive electrode of the lithium battery is mainly made of the lithium iron phosphate positive electrode material according to claim 8 or 9.

Description

Lithium iron phosphate positive electrode material, and preparation method and application thereof Technical Field The application belongs to the technical field of batteries, and particularly relates to a lithium iron phosphate positive electrode material, and a preparation method and application thereof. Background The lithium ion battery is widely applied to the storage fields of power, energy storage, consumption and the like as a secondary electrochemical energy storage system. At present, factors influencing the capacity, the cycle life, the safety, the price and the like of the lithium ion battery are mainly positive electrode materials. In recent years, lithium iron phosphate cathode materials are highly favored in the market by virtue of low cost, high safety, and excellent cycle performance. In the field of power batteries, lithium iron phosphate positive electrode materials become mainstream, and the market share is far beyond ternary positive electrode materials. However, a major problem in limiting the dynamic performance of lithium iron phosphate batteries is that it is difficult to simultaneously achieve both the compacted density and the rate capability of the material. The compacted density of the lithium iron phosphate anode material which is commercially applied at present is generally 2.1-2.65g/cm 3, and the multiplying power performance of the material is gradually reduced along with the improvement of the compacted density. The 1C rate discharge of the lithium iron phosphate anode material with the compacted density in the range of 2.1-2.3g/cm 3 can be 150-160mAh/g, the 1C rate discharge of the lithium iron phosphate anode material with the compacted density of 2.38-2.50g/cm 3 and 2.50-2.60g/cm 3 can be 135-145mAh/g, and the powder of the lithium iron phosphate anode material prepared by the conventional one-firing process can be compacted to be more than 2.60g/cm 3, the qualification rate of the lithium iron phosphate anode material with the compacted 1C rate discharge of 135-140mAh/g is less than 30%, and even the lithium iron phosphate anode material is hard to break through 140mAh/g. The higher the rate discharge capacity of the positive electrode material, the better the quick charge and low temperature performance. In order to meet the requirements of the power battery market on quick charge and low temperature, the improvement of the multiplying power performance is particularly critical while the compaction density of the material is improved. At present, the method for improving the multiplying power performance of the high-compaction lithium iron phosphate positive electrode material is generally realized by adopting a grain size grading mode, wherein the main grading mode is 2, namely, the first and the second lithium iron phosphate positive electrode materials with different compaction densities are used for grading finished products, secondary sintering is assisted, a fourth-generation energy storage product can be prepared barely, the requirement of high-end power on high multiplying power is difficult to meet, and the second CN118373397A discloses a secondary grinding and secondary sintering process which grinds primary burned materials with different grain sizes to prepare high-compaction high-multiplying power products with large, medium and small grain sizes, but the process adopts secondary grinding, secondary sintering, and is complex in process and extremely high in processing cost. Therefore, the exploration of an adaptive one-time sintering process for preparing the high-compaction high-magnification product has important research significance and market demand. Disclosure of Invention The application aims to provide a lithium iron phosphate positive electrode material, a preparation method and application thereof, and aims to solve the problems of complex process and extremely high processing cost although a high-compaction high-magnification product can be obtained by the existing secondary grinding and secondary sintering process. In order to achieve the purposes of the application, the technical scheme adopted by the application is as follows: the application provides a preparation method of a lithium iron phosphate anode material, which comprises the following steps: S1, mixing ferric phosphate and a first lithium source according to a mass ratio of 1:0.2-0.3, adding a first carbon source and a solvent, mixing and grinding, spray drying to obtain a spray material A, mixing the spray material A and a second carbon source, and uniformly stirring to obtain a polycrystalline precursor B, wherein the mass of the first carbon source is 3-6% of that of the ferric phosphate in the step, and the mass of the second carbon source in the step is 2.0-5.0% of that of the spray material A; S2, mixing ferric phosphate and a second lithium source according to a mass ratio of 1:0.2-0.3, adding a doping agent, a solvent and a first carbon source, mixing, grinding, spray drying