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CN-122025607-A - Lithium manganese iron phosphate positive electrode material, preparation method thereof, positive plate and lithium ion battery

CN122025607ACN 122025607 ACN122025607 ACN 122025607ACN-122025607-A

Abstract

The embodiment of the application provides a lithium iron manganese phosphate positive electrode material, a preparation method thereof, a positive plate and a lithium ion battery. The lithium iron manganese phosphate positive electrode material comprises a lithium iron manganese phosphate matrix and a carbon layer existing on at least part of the surface of the lithium iron manganese phosphate matrix, wherein in the lithium iron manganese phosphate positive electrode material, the proportion of the mole number of divalent manganese elements to the total mole number of manganese elements is 87.6% -99.6%. According to the application, the proportion of the mole number of the divalent manganese element in the lithium iron manganese phosphate anode material to the total mole number of the manganese element is improved to prevent excessive divalent manganese element from being oxidized into trivalent manganese element, so that the collapse of the lithium iron manganese phosphate material structure caused by the ginger-Taylor effect (Jahn-Teller effect) can be avoided, and the cycle stability and the rate capability of the lithium ion battery are improved.

Inventors

  • SHI YANING
  • LI RONG
  • GUO YONGXING
  • LIU XIANGZHE
  • QI SHIBO
  • XIE PU
  • HUANG JIEYANG
  • WEI XIAOYAN

Assignees

  • 浙江吉利控股集团有限公司
  • 浙江吉曜通行能源科技有限公司
  • 湖州耀宁固态电池研究院有限公司

Dates

Publication Date
20260512
Application Date
20260330

Claims (10)

  1. 1. The lithium iron manganese phosphate anode material is characterized by comprising a lithium iron manganese phosphate matrix and a carbon layer existing on at least part of the surface of the lithium iron manganese phosphate matrix, wherein the proportion of the mole number of divalent manganese elements to the total mole number of manganese elements in the lithium iron manganese phosphate anode material is 87.6% -99.6%.
  2. 2. The lithium iron manganese phosphate positive electrode material according to claim 1, wherein the conductivity of the lithium iron manganese phosphate positive electrode material is 0.5 x 10 -1 S/cm ~1.5×10 - to 1S/cm.
  3. 3. The lithium iron manganese phosphate positive electrode material according to any one of claims 1 or 2, characterized in that the carbon content in the lithium iron manganese phosphate positive electrode material is 1 wt% -2 wt%; and/or the thickness of the carbon layer is 2 nm-5.5 nm; And/or the chemical formula of the lithium iron manganese phosphate matrix is LiMn x Fe 1-x PO 4 , 0< x <1.
  4. 4. A method for preparing the lithium iron manganese phosphate positive electrode material according to any one of claims 1 to 3, comprising the steps of: And calcining the mixed material comprising the manganese iron phosphate precursor, a lithium source and a first carbon source to obtain the manganese iron lithium phosphate anode material, wherein the first carbon source is carbonized in the calcining process and generates reducing gas.
  5. 5. The method for producing a lithium iron manganese phosphate positive electrode material according to claim 4, wherein the reducing gas comprises sulfur dioxide and/or hydrogen sulfide; And/or, the first carbon source comprises methanesulfonic acid; and/or the mass of the first carbon source accounts for 1.2% -5% of the mass of the mixed material.
  6. 6. The method for producing a lithium iron manganese phosphate positive electrode material according to any one of claims 4 or 5, wherein the mixed material further comprises a second carbon source that is carbonized during the calcination treatment; And/or the calcination treatment comprises a pre-calcination stage and a main calcination stage which are sequentially carried out, wherein the temperature of the pre-calcination stage is 300-400 ℃ and the time is 2-4 hours, and the temperature of the main calcination stage is 600-750 ℃ and the time is 4-6 hours.
  7. 7. The method for preparing a lithium iron manganese phosphate positive electrode material according to claim 4, wherein the particle size Dv50 of the precursor of manganese iron phosphate is 100nm to 200nm; And/or the preparation process of the manganese iron phosphate precursor comprises the steps of carrying out gelation treatment on a mixed solution comprising an iron source, a manganese source, a phosphorus source, a dispersing agent and a solvent, and then drying to obtain the manganese iron phosphate precursor, wherein the dispersing agent comprises ethylenediamine tetraacetic acid.
  8. 8. The method for preparing a lithium iron manganese phosphate positive electrode material according to claim 7, wherein the ratio of the number of moles of the dispersant to the total number of moles of iron ions in the iron source and manganese ions in the manganese source is (0.2 to 0.5): 1; and/or, adjusting the pH value of the mixed solution to 4-6, and then carrying out gelation treatment; And/or, subjecting the mixed solution to the gelation treatment in a stirred state; And/or the temperature of the gelation treatment is 80-90 ℃ and the time is 2-4 hours; and/or, the drying is performed by adopting a spray drying mode.
  9. 9. A positive electrode sheet, characterized by comprising the lithium iron manganese phosphate positive electrode material according to any one of claims 1 to 3 or the lithium iron manganese phosphate positive electrode material produced by the method for producing the lithium iron manganese phosphate positive electrode material according to any one of claims 4 to 8.
  10. 10. A lithium ion battery comprising the positive electrode sheet of claim 9.

Description

Lithium manganese iron phosphate positive electrode material, preparation method thereof, positive plate and lithium ion battery Technical Field The application relates to the technical field of batteries, in particular to a lithium iron manganese phosphate positive electrode material, a preparation method thereof, a positive electrode plate and a lithium ion battery. Background The lithium iron manganese phosphate material is a lithium ion battery anode material widely applied in the industry, has higher theoretical specific capacity, good thermal stability and safety, rich raw material resources and low preparation cost. However, the existing preparation method of the lithium iron manganese phosphate material still has some problems, such as that divalent manganese ions are easily oxidized into trivalent manganese ions under the high-temperature condition in the preparation process, ginger-Taylor effect (Jahn-Teller effect) is caused, the structure of the lithium iron manganese phosphate material collapses, the capacity of a lithium ion battery decays, hydroxide precipitation is easily formed in a solution by metal ions, the precursor is unevenly mixed, the material performance is influenced, conventional carbon sources such as glucose and sucrose are easily agglomerated at high temperature, and carbon coating is unevenly influenced, and the conductivity of the material is influenced. Therefore, development of the lithium iron manganese phosphate positive electrode material with high cycle stability and rate capability, a preparation method thereof, a positive plate and a lithium ion battery have important practical significance. Disclosure of Invention The embodiment of the application provides a lithium manganese iron phosphate positive electrode material, a preparation method thereof, a positive plate and a lithium ion battery, which can avoid collapse of the structure of the lithium manganese iron phosphate material caused by overhigh trivalent manganese element, thereby improving the cycle stability and the rate capability of the lithium ion battery. In a first aspect, an embodiment of the application provides a lithium iron manganese phosphate positive electrode material, which comprises a lithium iron manganese phosphate matrix and a carbon layer existing on at least part of the surface of the lithium iron manganese phosphate matrix, wherein in the lithium iron manganese phosphate positive electrode material, the proportion of the mole number of divalent manganese elements to the total mole number of manganese elements is 87.6% -99.6%. In one possible embodiment, the conductivity of the lithium iron manganese phosphate positive electrode material is 0.5X10 -1 S/cm ~1.5×10- to 1S/cm. In one possible embodiment, the carbon content in the lithium manganese iron phosphate positive electrode material is 1 wt% -2 wt%. In one possible embodiment, the carbon layer has a thickness of 2 nm to 5.5 nm. In one possible embodiment, the lithium manganese iron phosphate matrix has the chemical formula LiMn xFe1-xPO4, 0< x <1. In a second aspect, the embodiment of the application provides a preparation method of a lithium iron manganese phosphate positive electrode material, which comprises the following steps of calcining a mixed material comprising a lithium iron manganese phosphate precursor, a lithium source and a first carbon source to obtain the lithium iron manganese phosphate positive electrode material, wherein the first carbon source is carbonized in the calcining process and generates reducing gas. In one possible embodiment, the reducing gas comprises sulfur dioxide and/or hydrogen sulfide. In one possible embodiment, the first carbon source comprises methanesulfonic acid. In one possible embodiment, the mass of the first carbon source is 1.2% -5% of the mass of the mixture. In one possible embodiment, the mixture further comprises a second carbon source that is carbonized during the calcination process. In one possible implementation, the calcination treatment comprises a pre-calcination stage and a main calcination stage which are sequentially carried out, wherein the temperature of the main calcination stage is 600-750 ℃ and the time is 4-6 hours, and the temperature of the pre-calcination stage is 300-400 ℃ and the time is 2-4 hours. In one possible embodiment, the particle size Dv50 of the ferromanganese phosphate precursor is 100nm to 200nm. In one possible embodiment, the preparation process of the manganese iron phosphate precursor comprises the steps of carrying out gelation treatment on a mixed solution comprising an iron source, a manganese source, a phosphorus source, a dispersing agent and a solvent, and then drying to obtain the manganese iron phosphate precursor, wherein the dispersing agent comprises ethylenediamine tetraacetic acid. In one possible embodiment, the ratio of the number of moles of the dispersant to the total number of moles of iron ions in the iron source and manganese io