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CN-122010076-A - Method for regulating and controlling high exposure {010} crystal face of manganese-rich phosphate-based positive electrode material

CN122010076ACN 122010076 ACN122010076 ACN 122010076ACN-122010076-A

Abstract

The invention relates to the technical field of preparation of positive electrode materials of lithium ion batteries, in particular to a method for regulating and controlling a high-exposure {010} crystal face of a manganese-rich phosphate-based positive electrode material, which comprises the steps of weighing manganese salt （MnO 2 、MnC 2 O 4 ·2H 2 O、MnCO 3 、Mn(H 2 PO 4 ) 2 、MnC 4 H 6 O 4 ·4H 2 O and the like, ferric salt (FeSO 4 ·7H 2 O、Fe 2 O 3 、FePO 4 and the like), lithium salt (LiOH, li 2 CO 3 、CH 3 COOLi、LiH 2 PO 4 and the like), phosphate (NH 4 H 2 PO 4 ), sulfate (MgSO 4 、NaSO 4 、FeSO 4 ·7H 2 O and the like) according to the mass ratio of (1-n) n to 1:1:0.01, adding 10-50% of organic carbon, ball-milling in an absolute ethyl alcohol medium, drying at 80-110 ℃ to obtain a precursor, placing the precursor into a tubular furnace, presintering at 300 ℃ for 2-5 h in an argon atmosphere, naturally annealing, heating to 700 ℃, sintering for 6-10 h in an argon atmosphere, and naturally annealing to obtain the manganese-iron lithium phosphate positive electrode material with the high-exposure {010} crystal face. After the high-exposure {010} crystal face material LiMn 0.6 Fe 0.4 PO 4 prepared by the method is circulated for 300 times under 5C high multiplying power, the specific discharge capacity retention rate is as high as 95.7 percent and is far higher than that of an unmodified control sample by 50.4 percent.

Inventors

  • CUI XIAOLING
  • HE NING
  • WANG PENG
  • FU BIN
  • Zhang Ningshuang
  • ZHANG YUANYUAN

Assignees

  • 兰州理工大学

Dates

Publication Date
20260512
Application Date
20260116

Claims (10)

  1. 1. A method for regulating and controlling a high-exposure {010} crystal face of a manganese-rich phosphate-based positive electrode material is characterized by comprising the following steps of: S1, preparing a precursor, namely weighing raw materials according to the mole ratio of manganese salt, ferric salt, lithium salt, phosphate to sulfate of (1-n), wherein the range of the n is 0.4, 0.5, 0.6 or 0.7, adding an organic carbon source accounting for 10-50% of the total mass of the raw materials, mixing the weighed raw materials and the organic carbon source in an absolute ethanol medium, performing ball milling, and then drying at the temperature of 80-110 ℃ to obtain the precursor; s2, presintering, namely presintering the precursor in an argon atmosphere at 300 ℃, keeping the temperature for 2 to 5 hours, and then naturally cooling; and S3, sintering and crystallizing at high temperature, namely heating the presintered and cooled material to 700 ℃ in an argon atmosphere for sintering, keeping the temperature for 6 to 10 hours, and naturally cooling to obtain the lithium iron manganese phosphate anode material with the high-exposure {010} crystal face.
  2. 2. The method of claim 1, wherein the manganese salt is selected from at least one of MnO 2 、MnC 2 O 4 ·2H 2 O、MnCO 3 、Mn(H 2 PO 4 ) 2 and MnC 4 H 6 O 4 ·4H 2 O.
  3. 3. The method of claim 1, wherein the iron salt is selected from at least one of FeSO 4 ·7H 2 O、Fe 2 O 3 and FePO 4 .
  4. 4. The method of claim 1, wherein the lithium salt is selected from at least one of LiOH, li 2 CO 3 、CH 2 COOLi, and LiH 2 PO 4 .
  5. 5. The method of claim 1, wherein the phosphate is NH 4 H 2 PO 4 .
  6. 6. The method of claim 1, wherein the sulfate is selected from at least one of MgSO 4 、Na 2 SO 4 and FeSO 4 ·7H 2 O.
  7. 7. The method of claim 1, wherein the organic carbon source is selected from at least one of glucose, sucrose, and citric acid.
  8. 8. The lithium iron manganese phosphate positive electrode material prepared by the method according to any one of claims 1 to 7, wherein the positive electrode material has a highly exposed {010} crystal plane, and the diffraction peak intensity ratio I (020)/I (200) of the (020) crystal plane to the (200) crystal plane in the X-ray diffraction pattern is 2.2, which is greater than that of an unmodified control sample.
  9. 9. A lithium ion battery positive electrode comprising the lithium iron manganese phosphate positive electrode material according to claim 8.
  10. 10. A lithium ion battery comprising the positive electrode of claim 9.

Description

Method for regulating and controlling high exposure {010} crystal face of manganese-rich phosphate-based positive electrode material Technical Field The invention relates to the technical field of preparation of lithium ion battery anode materials, in particular to a method for regulating and controlling a high-exposure {010} crystal face of a manganese-rich phosphate-based anode material. Background Olivine-type phosphate-based positive electrode materials, particularly lithium manganese iron phosphate (LiMnFePO 4, abbreviated as LMFP), are considered as one of the ideal positive electrode materials for next-generation high-energy-density lithium ion batteries because of their high theoretical specific capacity (about 170 mAh/g), good structural stability, high safety, low cost, and environmental friendliness. However, the existence of two inherent defects in LiMnFePO 4 materials severely limits the electrochemical performance of the materials, particularly the application at high multiplying power, namely, extremely low electronic conductivity (about 10- 9~10⁻¹0 S/cm) and slow diffusion kinetics due to one-dimensional diffusion of lithium ions in the crystal structure mainly along the b-axis direction. Together, these two factors result in poor rate performance of the material. At present, the main strategy for improving the multiplying power performance of LiMnFePO 4 materials comprises carbon coating, namely coating a conductive carbon layer on the surface of the materials, and improving the electronic conductivity. However, too thick a carbon layer reduces the tap density and volumetric energy density of the material, and carbon itself does not contribute to capacity, potentially resulting in a decrease in overall specific capacity (see patent CN119349534 a). Nanocrystallization, namely reducing the particle size of the material to a nanoscale, and shortening the diffusion path of lithium ions. However, this results in a decrease in the compacted density of the material, a deterioration in the electrode processability, and easy agglomeration of nanoparticles (refer to patent CN118289728 a). Ion doping by introducing aliovalent cations into the lattice, may increase the intrinsic conductivity. However, doping may introduce electrochemically inert phases, reducing the active material content, and excessive doping may even block the lithium ion diffusion channels (see patent CN119503892 a). Crystal face regulation, namely, through controlling crystal growth, a specific crystal face which is favorable for rapid transmission of lithium ions is more exposed. The {010} crystal face is a main channel face of LiMnFePO 4 for diffusing lithium ions along the b axis, and the highly exposed {010} crystal face can effectively shorten the diffusion distance of the lithium ions in the bulk phase, so that the rate performance is remarkably improved. Currently, the dominant method for achieving {010} crystal plane regulation is solvothermal or hydrothermal. The method generally uses organic molecules such as alcohols, surfactants and the like as morphology inducers at high temperature and high pressure to control the growth of crystals along a specific direction. For example, patent CN116873893a discloses a method for preparing high-exposure {010} crystal face lithium iron manganese phosphate, but the method belongs to a typical liquid phase method. The solvothermal method has the remarkable defects of high reaction equipment cost and high requirement, a large amount of organic solvents are used, potential safety hazards and environmental protection hazards exist, the solvents need to be recycled, the process complexity and the cost are increased, continuous and large-scale production is difficult to realize, and the industrial application prospect is limited. Therefore, the preparation method of the high-exposure {010} crystal face LiMnFePO 4 material, which has the advantages of simple process, low cost, environmental friendliness and easiness in large-scale production, is developed, and has a vital significance for promoting the practical application of the material in high-performance lithium ion batteries. Disclosure of Invention The invention aims to overcome the defects of complex equipment, high cost, large pollution, difficult industrialization and the like existing in the prior art that a solvothermal method is adopted to prepare the high-exposure {010} crystal face lithium iron manganese phosphate material. The method is based on a synthesis route of a solid phase method, and by introducing a sulfate additive, liMnFePO 4 crystals are induced to preferentially grow along the {010} crystal face direction in the high-temperature sintering lithiation process of the material, so that the olivine-type lithium manganese iron phosphate positive electrode material with the high-exposure {010} crystal face is prepared. The method has the advantages of simple process, mild reaction conditions, no need of complex post-tr