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CN-122025629-A - Composite positive electrode active material, preparation method thereof, positive electrode and battery

CN122025629ACN 122025629 ACN122025629 ACN 122025629ACN-122025629-A

Abstract

The embodiment of the application discloses a composite positive electrode active material, a preparation method thereof, a positive electrode and a battery, belonging to the technical field of batteries. The mass percentage of the first solid electrolyte in the composite positive electrode active material is 5-9%, the particle size D50 of the lithium manganese iron phosphate is A, the particle size D10 of the first solid electrolyte is B, the particle size D50 of the first solid electrolyte is C, and 0< (B-A)/3 <1.5, 1.2< (C-A)/7 <3.5 are satisfied. The composite positive electrode active material provided by the embodiment of the application can improve the defects of a lithium iron manganese phosphate system, improve the conductivity, ensure the multiplying power performance, reduce the precipitation of manganese in the lithium iron manganese phosphate, enhance the cycling stability and enlarge the electrochemical performance of a battery in a wide-temperature-range application scene.

Inventors

  • WEI HAITAO
  • JING LIQIANG

Assignees

  • 惠州亿纬锂能股份有限公司
  • 湖北亿纬动力有限公司

Dates

Publication Date
20260512
Application Date
20251231

Claims (12)

  1. 1. A composite positive electrode active material comprising lithium iron manganese phosphate and a first solid electrolyte; the mass percentage of the first solid electrolyte in the composite positive electrode active material is 5-9%, the particle size D50 of the lithium manganese iron phosphate is A, the particle size D10 of the first solid electrolyte is B, and the particle size D50 of the first solid electrolyte is C, wherein 0< (B-A)/3 <1.5, and 1.2< (C-A)/7 <3.5 are satisfied.
  2. 2. The composite positive electrode active material according to claim 1, wherein the first solid electrolyte has a particle diameter D10 of 2 μm to 5 μm, a particle diameter D50 of 8 μm to 20 μm, and a particle diameter D90 of 40 μm to 80 μm; And/or the particle diameter D50 of the lithium manganese iron phosphate is 0.7-1.7 mu m, and the particle diameter D90 is 2-15 mu m.
  3. 3. The composite positive electrode active material according to claim 1 or 2, wherein the first solid electrolyte comprises at least one of an oxide solid electrolyte, a polymer solid electrolyte, and a sulfide solid electrolyte; And/or the molar ratio of manganese element to iron element in the lithium iron manganese phosphate is 1:1.
  4. 4. A method for preparing a composite positive electrode active material, comprising: Ball-milling and mixing lithium iron manganese phosphate and the first solid electrolyte to obtain a composite positive electrode active material; the mass percentage of the first solid electrolyte in the composite positive electrode active material is 5-9%, the particle size D50 of the lithium manganese iron phosphate is A, the particle size D10 of the first solid electrolyte is B, and the particle size D50 of the first solid electrolyte is C, wherein 0< (B-A)/3 <1.5, and 1.2< (C-A)/7 <3.5 are satisfied.
  5. 5. A positive electrode comprising the composite positive electrode active material according to any one of claims 1 to 3, and/or the composite positive electrode active material produced by the method for producing a composite positive electrode active material according to claim 4.
  6. 6. The positive electrode of claim 5, wherein the positive electrode comprises a positive electrode current collector and a positive electrode active layer coated on at least one side of the positive electrode current collector, the positive electrode active layer comprising the composite positive electrode active material, a first conductive agent, and a first binder; The mass ratio of the composite positive electrode active material to the first conductive agent to the first binder is (96% -98.5%) (0.5% -1.5%) (1% -2.5%); And/or, the single-sided surface density of the positive electrode is 180g/m 2 -250g/m 2 ; And/or, the positive electrode active layer has a porosity of 29% -31%.
  7. 7. A battery comprising the positive electrode according to claim 5 or 6, a separator, and a negative electrode; the separator is positioned at one side of the positive electrode, which is close to the positive electrode active layer, and the negative electrode is positioned at one side of the separator, which is away from the positive electrode.
  8. 8. The battery according to claim 7, wherein the separator includes a base film and a solid electrolyte layer provided on a side of the base film near the anode, the solid electrolyte layer including a second solid electrolyte therein.
  9. 9. The battery of claim 8, wherein the second solid state electrolyte comprises at least one of an oxide solid state electrolyte, a polymer solid state electrolyte, and a sulfide solid state electrolyte; And/or the thickness of the solid electrolyte layer is 1 μm to 2 μm.
  10. 10. The battery according to any one of claims 7 to 9, wherein the CB value of the battery is 1 to 1.14.
  11. 11. The battery according to any one of claims 7 to 9, wherein the battery is a semi-solid state battery or a solid state battery.
  12. 12. The battery of claim 11, wherein the battery is a semi-solid battery, and further comprising an electrolyte having a fill factor in the battery of 2.5g/Ah to 2.8g/Ah.

Description

Composite positive electrode active material, preparation method thereof, positive electrode and battery Technical Field The application relates to the technical field of batteries, in particular to a composite positive electrode active material, a preparation method thereof, a positive electrode and a battery. Background Currently, lithium ion battery technology is rapidly evolving toward high energy density, high safety, and low cost. The lithium iron manganese phosphate (LMFP) shows remarkable advantages by virtue of the olivine structure, the introduction of manganese element enables the voltage platform to be increased to 4.1V, and the theoretical energy density is increased by 15% compared with that of the lithium iron phosphate (LFP). The lithium iron manganese phosphate (LMFP) forms a solid solution by partially replacing iron sites with manganese on the basis of inheriting a stable structure of lithium iron phosphate (LFP) olivine, and has higher thermal stability. The thermal stability of the lithium iron manganese phosphate is mainly characterized in that firstly, the Fe-O strong covalent bond which is the same as LFP can effectively inhibit oxygen release at high temperature and maintain skeleton stability, and secondly, the introduction of Mn-O bond does not damage the thermal decomposition resistance of the original structure, LMFP still maintains the initial temperature of thermal runaway above 250 ℃ and is equivalent to LFP, thus fundamentally guaranteeing the thermal safety of a battery system, leading the LMFP battery to show the safety performance of the same level as LFP in the extreme tests of needling, overcharging and the like, being obviously superior to that of lamellar ternary materials, and meanwhile, the raw material components of the LMFP are only 60% of ternary materials and do not contain noble metals such as cobalt, nickel and the like. However, the LMFP material system has the inherent defects that the electron conductivity is extremely low (only 10-9 S/cm level), the rate performance is severely restricted, the Jahn-Teller effect of Mn 3+ can cause lattice distortion to cause precipitation of Mn ions, and in addition, a two-phase reaction mechanism in the charge-discharge process can generate obvious polarization voltage to limit the performance of the LMFP material in a wide-temperature-range application scene. Disclosure of Invention The application provides a composite positive electrode active material, a preparation method thereof, a positive electrode and a battery, and aims to solve the problems that the conductivity of manganese iron lithium iron phosphate is low, manganese ions are easy to separate out, and performance in a wide temperature range is limited. According to a first aspect of the present application, there is provided a composite positive electrode active material comprising lithium iron manganese phosphate and a first solid state electrolyte; The mass percentage of the first solid electrolyte in the composite positive electrode active material is 5-9%, the particle size D50 of the lithium manganese iron phosphate is A, the particle size D10 of the first solid electrolyte is B, the particle size D50 of the first solid electrolyte is C, and 0< (B-A)/3 <1.5, 1.2< (C-A)/7 <3.5 are satisfied. The composite anode and the active material provided by the application comprise the lithium iron manganese phosphate and the first solid electrolyte, and the mass percentage of the first solid electrolyte in the anode active material is 5% -9%, so that the conductivity of the composite anode active material can be improved, the interface impedance can be reduced, and the conductivity of a lithium iron manganese phosphate anode system can be improved. The particle size D50A of the lithium manganese iron phosphate and the particle size D10B of the first solid electrolyte are enabled, the particle size D50C of the first solid electrolyte meets 0< (B-A)/3 <1.5, and 1.2< (C-A)/7 <3.5, so that A good stacking effect can be formed between the lithium manganese iron phosphate and the first solid electrolyte, A close stacking structure of the lithium manganese iron phosphate coated on the surface of the first solid electrolyte is formed, the compaction density is improved, the energy density of the positive electrode is ensured, A good conductive network is formed, the defect of lower conductivity of the lithium manganese iron phosphate is improved, and the multiplying power performance of the positive electrode is improved. Meanwhile, the crystal structure of the lithium iron manganese phosphate can be stabilized by introducing the first solid electrolyte, manganese precipitation is reduced, the high mechanical strength of the first solid electrolyte is also beneficial to inhibiting the growth of lithium dendrites, the cycle stability is enhanced, and the service life of the battery is prolonged. By introducing the first solid electrolyte into the composite positive electrod