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CN-121983558-A - Composite modified lithium manganate positive electrode material, preparation method and application

CN121983558ACN 121983558 ACN121983558 ACN 121983558ACN-121983558-A

Abstract

The invention discloses a composite modified lithium manganate positive electrode material, a preparation method and application thereof, and belongs to the technical field of positive electrode materials. The structural formula of the composite modified lithium manganate positive electrode material is LiX a O b @LiYO 2 /LiMn 2 O 4 , which comprises an inner core composed of LiYO 2 and LiMn 2 O 4 and a LiX a O b coating layer coated on at least part of the surface of the inner core, wherein LiMn 2 O 4 has a porous structure, and LiYO 2 is filled in a pore canal of LiMn 2 O 4 . According to the lithium manganate positive electrode material, the lithium manganate substrate is filled with LiYO 2 in the pore canal of the substrate, the surface of the substrate is coated with LiX a O b , and the lithium manganate positive electrode material can not influence the specific capacity of the positive electrode material on the basis of reducing the Jahn-Teller effect of the lithium manganate by filling LiYO 2 in the pore canal, and the lithium ion diffusion rate can be accelerated by LiYO 2 , so that the rate capability of the material is improved.

Inventors

  • ZHANG YINGCHUN
  • LUO KUN
  • Zhou Qiangrong

Assignees

  • 四川长宏新能源技术有限公司

Dates

Publication Date
20260505
Application Date
20260403

Claims (10)

  1. 1. A composite modified lithium manganate positive electrode material is characterized by comprising a LiX a O b @LiYO 2 /LiMn 2 O 4 , an inner core and a LiX a O b coating layer, wherein the inner core consists of LiYO 2 and LiMn 2 O 4 , the LiX a O b coating layer is coated on at least part of the surface of the inner core, the LiMn 2 O 4 is of a porous structure, liYO 2 is filled in a pore canal of the LiMn 2 O 4 , X is one or more of Ti, bi and Sb, Y is one or more of Al, co and Fe, and a is more than or equal to 1 and less than or equal to 1.25,2 and b is more than or equal to 3.
  2. 2. The method for preparing the composite modified lithium manganate positive electrode material according to claim 1, which is characterized by comprising the following steps: (1) Preparing a mixed salt solution from manganese salt and zinc salt, adding ammonia water, and performing hydrothermal reaction to obtain a ZnO-Mn 3 O 4 composite material, adding the ZnO-Mn 3 O 4 composite material into an alkali solution, and etching to obtain porous Mn 3 O 4 ; (2) Dispersing porous Mn 3 O 4 in a Y metal salt solution, adjusting the pH of the reaction solution under a pressurized condition to perform precipitation reaction to obtain a reaction solution containing Y hydroxide filled Mn 3 O 4 , adding an X metal source into the reaction solution containing Y hydroxide filled Mn 3 O 4 under normal pressure, and performing hydrolysis reaction to obtain a precursor; (3) And mixing the precursor with a lithium source, and performing lithiation sintering to obtain the composite modified lithium manganate anode material.
  3. 3. The preparation method of the composite modified lithium manganate positive electrode material according to claim 2, which is characterized in that in the step (1), manganese salt is one or more of manganese acetate, manganese nitrate and manganese sulfate, and zinc salt is one or more of zinc acetate, zinc nitrate and zinc sulfate; And/or the molar ratio of manganese salt to zinc salt is (2.8-3.5): 0.1-0.3); And/or the total concentration of metal ions in the mixed salt solution is 1.9-2.6 mol/L; and/or the mass concentration of ammonia water is 28-29%; and/or the molar volume ratio of manganese salt to ammonia water is (2.8-3.5) mol (0.4-0.6) L; and/or the alkali solution is sodium hydroxide solution or potassium hydroxide solution, and the concentration of the alkali solution is 2-4 mol/L.
  4. 4. The preparation method of the composite modified lithium manganate positive electrode material according to claim 2, which is characterized in that in the step (1), the hydrothermal reaction temperature is 160-220 ℃, and the hydrothermal reaction time is 10-24 hours; And/or in the step (1), the etching temperature is 30-50 ℃ and the etching time is 4-10 h.
  5. 5. The preparation method of the composite modified lithium manganate positive electrode material according to claim 2, which is characterized in that in the step (2), the metal salt of Y is one or two of nitrate and sulfate, and the molar ratio of the metal salt of Y to the porous Mn 3 O 4 material is (0.05-0.3) (2-4); and/or adjusting the pH of the reaction solution to 5-9, the precipitation reaction temperature to 20-30 ℃, the time of the precipitation reaction to 0.5-5 h, and the pressurizing pressure to 0.3-1 MPa.
  6. 6. The method for preparing the composite modified lithium manganate positive electrode material according to claim 5, wherein when Y is an Al element, the pH value of the reaction solution is adjusted to 5-6, and when Y is one or both of Co and Fe, the pH value of the reaction solution is adjusted to 7-8.
  7. 7. The preparation method of the composite modified lithium manganate positive electrode material according to claim 2 is characterized in that in the step (2), the X metal source is one or more of tetrabutyl titanate, bismuth chloride and antimony chloride, and the molar ratio of the X metal source to the porous Mn 3 O 4 material is 1 (20-40); and/or the hydrolysis reaction time is 8-20 h.
  8. 8. The method for preparing the composite modified lithium manganate positive electrode material according to claim 2, wherein in the step (3), the lithium source is one or more of lithium hydroxide, lithium acetate and lithium nitrate, and the mole number of Li in the lithium source is the sum of 0.5-0.55 times of the mole number of Mn in the precursor, 0.8-1.05 times of the mole number of Y and 1-1.03 times of the mole number of X.
  9. 9. The method for preparing the composite modified lithium manganate positive electrode material according to claim 2, wherein in the step (3), the lithiation sintering temperature is 880-1000 ℃ and the lithiation sintering time is 8-16 h.
  10. 10. A lithium battery is characterized by comprising the composite modified lithium manganate positive electrode material disclosed in claim 1 or prepared by the preparation method disclosed in any one of claims 2-9.

Description

Composite modified lithium manganate positive electrode material, preparation method and application Technical Field The invention belongs to the technical field of positive electrode materials, and particularly relates to a composite modified lithium manganate positive electrode material, a preparation method and application thereof. Background The lithium manganese oxide with the spinel structure is considered as one of the positive electrode materials of the lithium ion battery with development prospect due to the characteristics of good safety, low cost, no toxicity and the like. However, after the LiMn 2O4 cathode material is assembled into a battery, the specific discharge capacity is seriously attenuated in the electrochemical cycle process, and the reason is mainly that the spinel structure of lithium manganate is changed from a cubic phase to a tetragonal phase under the effect of Jahn-Teller effect, so that the volume change and the structural collapse of spinel crystal lattice are caused, and then, the electrolyte is etched to cause the disproportionation reaction of trivalent manganese ions to generate Mn 2+ and Mn 4+, wherein Mn 2+ is dissolved in the electrolyte to damage the LiMn 2O4 structure, so that the performance of the battery is further deteriorated. In order to solve the problems, some researchers strengthen the structure and stability of the material by bulk ion doping, such as Al 3+、Ti4+、Cr3+, but the doping of a single element has limited effect on improving the performance of the material, and the bulk ion doping damages the crystalline phase structure of lithium manganate, so that the chemical activity is reduced, and the specific capacity is reduced. Disclosure of Invention In view of the above, the invention aims to provide a composite modified lithium manganate positive electrode material, a preparation method and application thereof. In the first aspect, the invention provides a composite modified lithium manganate positive electrode material, which has a structural formula of LiX aOb@LiYO2/LiMn2O4, and comprises an inner core composed of LiYO 2 and LiMn 2O4 and a LiX aOb coating layer coated on at least part of the surface of the inner core, wherein LiMn 2O4 has a porous structure, liYO 2 is filled in a pore channel of LiMn 2O4, X is one or more of Ti, bi and Sb, Y is one or more of Al, co and Fe, and a is more than or equal to 1 and less than or equal to 1.25,2 and b is more than or equal to 3. In a second aspect, the invention provides a composite modified lithium manganate positive electrode material, which comprises the following steps: (1) Preparing a mixed salt solution from manganese salt and zinc salt, adding ammonia water, and performing hydrothermal reaction to obtain a ZnO-Mn 3O4 composite material, adding the ZnO-Mn 3O4 composite material into an alkali solution, and etching to obtain porous Mn 3O4; (2) Dispersing porous Mn 3O4 in a Y metal salt solution, adjusting the pH of the reaction solution under a pressurized condition to perform precipitation reaction to obtain a reaction solution containing Y hydroxide filled Mn 3O4, adding an X metal source into the reaction solution containing Y hydroxide filled Mn 3O4 under normal pressure, and performing hydrolysis reaction to obtain a precursor; (3) And mixing the precursor with a lithium source, and performing lithiation sintering to obtain the composite modified lithium manganate anode material. Preferably, in the step (1), manganese salt is one or more of manganese acetate, manganese nitrate and manganese sulfate, zinc salt is one or more of zinc acetate, zinc nitrate and zinc sulfate, the molar ratio of manganese salt to zinc salt is (2.8-3.5): (0.1-0.3), the total concentration of metal ions in the mixed salt solution is 1.9-2.6 mol/L, the mass concentration of ammonia water is 28-29%, and the molar volume ratio of manganese salt to ammonia water is (2.8-3.5) mol (0.4-0.6) L. Preferably, in the step (1), the hydrothermal reaction temperature is 160-220 ℃ and the hydrothermal reaction time is 10-24 hours. Preferably, in the step (1), the alkali solution is sodium hydroxide solution or potassium hydroxide solution, and the concentration of the alkali solution is 2-4 mol/L. Preferably, in the step (1), the etching temperature is 30-50 ℃ and the etching time is 4-10 hours. Preferably, in the step (2), the metal salt of Y is one or two of nitrate and sulfate, and the molar ratio of the metal salt of Y to the porous Mn 3O4 material is (0.05-0.3) (2-4). Preferably, in the step (2), the pH of the reaction solution is adjusted to 5-9, the time of precipitation reaction is 0.5-5 h, and the pressurizing pressure is 0.3-1 MPa. Further preferably, when Y is an Al element, the pH value of the reaction solution is adjusted to 5-6, and when Y is one or both of Co and Fe, the pH value of the reaction solution is adjusted to 7-8. Preferably, in the step (2), the X metal source is one or more of tetrabutyl titanate, bismuth chlor