CN-122000322-A - Composite positive electrode material, preparation method and application thereof, and simulation evaluation method of interface stress distribution of composite positive electrode material

CN122000322ACN 122000322 ACN122000322 ACN 122000322ACN-122000322-A

Abstract

The invention belongs to the technical field of solid-state batteries, and particularly relates to a composite positive electrode material, a preparation method and application thereof, and a simulation evaluation method of interface stress distribution of the composite positive electrode material. The composite positive electrode material comprises a modified positive electrode material and a sulfide type solid electrolyte, wherein the modified positive electrode material comprises positive electrode active particles and a coating layer coated on the surfaces of the positive electrode active particles, and the coating layer material is a polymer-lithium salt composite material with the elastic modulus of 0.1-5.0 GPa or a lithium-containing oxide material with the elastic modulus of 120-200 GPa. The key point of the invention is that the surface of the positive electrode active particles is coated with a polymer-lithium salt composite material or a lithium-containing oxide material with specific elastic modulus, so that the obtained composite positive electrode material enables the lithium ion solid-state battery to show remarkably improved multiplying power performance and cycle performance.

Inventors

DING FEI
MENG YUXIN
ZHANG RUI
LI LE
WANG NING
Wang Xingai
ZHANG HAICHANG

Assignees

河北工业大学

Dates

Publication Date: 20260508
Application Date: 20260126
Priority Date: 20260121

Claims (10)

1. The composite positive electrode material is characterized by comprising a modified positive electrode material and a sulfide type solid electrolyte, wherein the modified positive electrode material comprises positive electrode active particles and a coating layer coated on the surfaces of the positive electrode active particles, the coating layer is a polymer-lithium salt composite material with an elastic modulus of 0.1-5.0 GPa or a lithium-containing oxide material with an elastic modulus of 120-200 GPa, and the polymer in the polymer-lithium salt composite material is at least one selected from polyethylene oxide, polycarbonate, polymethyl methacrylate and polystyrene.
2. The composite positive electrode material according to claim 1, wherein the positive electrode active particles are selected from at least one of nickel cobalt lithium manganate particles, nickel cobalt lithium aluminate particles, lithium manganese iron phosphate particles; preferably, the lithium salt is lithium bistrifluoro-methanesulfonimide and/or lithium hexafluorophosphate; Preferably, the lithium-containing oxide material is selected from at least one of lithium niobate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide.
3. The composite positive electrode material according to claim 1, wherein the mass ratio of the modified positive electrode material to the sulfide-type solid electrolyte is 1 (0.3 to 0.5); Preferably, the mass ratio of the coating layer material to the positive electrode active particles is (1-3) 100; Preferably, the mass ratio of the polymer to the lithium salt in the polymer-lithium salt composite material is 5 (1-3).
4. A method for preparing a composite positive electrode material according to any one of claims 1 to 3, characterized in that the method comprises the steps of: S1, dissolving lithium salt and a polymer in a first organic solvent to form a mixed solution, and performing first ball milling treatment on the mixed solution and first positive electrode active particles to obtain a first modified positive electrode material with a polymer-lithium salt composite coating layer on the surface; or dispersing lithium-containing oxide in a second organic solvent to form a dispersion liquid, and performing second ball milling treatment on the dispersion liquid and second anode active particles to obtain a second modified anode material with a lithium-containing oxide coating layer on the surface; S2, performing third ball milling treatment on the first modified positive electrode material or the second modified positive electrode material and the sulfide solid electrolyte to obtain the composite positive electrode material.
5. The method of producing a composite positive electrode material according to claim 4, wherein in step S1, the mass ratio of the lithium salt to the polymer is (1 to 3): 5; preferably, the mass ratio of the first positive electrode active particles to the polymer in the mixed solution is 100 (1-3); Preferably, the mass ratio of the second positive electrode active particles to the lithium-containing oxide in the dispersion is 100 (1-3); Preferably, the conditions of the first ball milling treatment and the second ball milling treatment respectively and independently comprise the rotating speed of 150-200 rpm and the time of 6-10 h.
6. The method for producing a composite positive electrode material according to claim 4, wherein in step S1, the lithium salt is lithium bistrifluoro methanesulfonimide and/or lithium hexafluorophosphate; Preferably, the first and second positive electrode active particles are each independently selected from at least one of nickel cobalt lithium manganate particles, nickel cobalt lithium aluminate particles, lithium manganese iron phosphate particles; preferably, the first organic solvent and the second organic solvent are each independently selected from at least one of acetonitrile, methanol, ethanol, isopropanol, acetone, dimethylformamide.
7. The method for producing a composite positive electrode material according to claim 4, wherein in step S2, the mass ratio of the first modified positive electrode material or the second modified positive electrode material to the sulfide-type solid electrolyte is 1 (0.3 to 0.5); Preferably, the conditions of the third ball milling treatment comprise a rotating speed of 150-200 rpm and a time of 1-3 hours.
8. A composite positive electrode material prepared by the method of any one of claims 4 to 7.
9. Use of the composite positive electrode material according to any one of claims 1 to 3 and claim 8 in a solid state battery.
10. A simulation evaluation method for interface stress distribution of a composite positive electrode material is characterized by comprising the steps of preparing an electrode plate from a composite positive electrode material and a binder after ball milling, conducting CT scanning on the electrode plate, guiding an obtained CT image into image processing software for processing to obtain a three-dimensional microstructure model of the composite positive electrode material, guiding the obtained three-dimensional microstructure model into simulation software, inputting battery simulation parameters, an electrochemical model control equation and a stress model control equation, constructing an electrochemical field-mechanical field coupling simulation model, wherein the coupling principle is that the chemical strain is driven by lithium ion concentration change in an electrochemical field based on deformation of the mechanical field, setting charge and discharge test parameters for simulation test, obtaining an interface stress distribution cloud image, calculating the maximum value, the average value and the standard deviation of interface stress, and using the interface stress distribution cloud image, the maximum value, the average value and the standard deviation as quantization indexes for evaluating stress level and uniformity.

Description

Composite positive electrode material, preparation method and application thereof, and simulation evaluation method of interface stress distribution of composite positive electrode material Technical Field The invention belongs to the technical field of solid-state batteries, and particularly relates to a composite positive electrode material, a preparation method and application thereof, and a simulation evaluation method of interface stress distribution of the composite positive electrode material. Background Along with the rapid development of new energy technology and electronic technology, lithium ion batteries are widely applied to various fields such as new energy automobiles, and the capacity of the lithium ion batteries is inevitably attenuated in the use process, mainly because the composite positive electrode material is broken by particles due to expansion and shrinkage in the circulation process, the alleviation of mechanical failure of the positive electrode material is a key problem for improving the battery performance, and the lithium ion batteries have important significance in particular to the design of solid-state batteries. Currently, there is a need to find a method that can relieve the stress of the cathode material. Disclosure of Invention One of the purposes of the invention is to provide a composite positive electrode material, aiming at the problem that the lithium ion battery performance is seriously attenuated due to easy mechanical failure in the use process of the existing positive electrode material, and the interface stress of the positive electrode in the charge and discharge process is obviously reduced by coating a specific material layer on the surface of positive electrode house type particles, so that the performance of the lithium ion battery is improved. The composite positive electrode material comprises a modified positive electrode material and a sulfide type solid electrolyte, wherein the modified positive electrode material comprises positive electrode active particles and a coating layer coated on the surfaces of the positive electrode active particles, the coating layer material is a polymer-lithium salt composite material with the elastic modulus of 0.1-5.0 GPa or a lithium-containing oxide material with the elastic modulus of 120-200 GPa, and the polymer in the polymer-lithium salt composite material is at least one selected from polyethylene oxide, polycarbonate, polymethyl methacrylate and polystyrene. In a preferred embodiment, the positive electrode active particles are selected from at least one of nickel cobalt lithium manganate particles, nickel cobalt lithium aluminate particles, lithium manganese iron phosphate particles. In a preferred embodiment, the lithium salt is lithium bistrifluoro methanesulfonimide and/or lithium hexafluorophosphate. In a preferred embodiment, the lithium-containing oxide material is selected from at least one of lithium niobate, lithium lanthanum zirconium oxide, lithium lanthanum titanium oxide. In a preferred embodiment, the mass ratio of the modified cathode material to the sulfide-type solid electrolyte is 1 (0.3 to 0.5). In a preferred embodiment, the mass ratio of the coating layer material to the positive electrode active particles is (1-3) 100. In a preferred embodiment, the mass ratio of the polymer to the lithium salt in the polymer-lithium salt composite material is 5 (1-3). The second purpose of the invention is to provide a preparation method of the composite positive electrode material. The preparation method comprises the following steps: S1, dissolving lithium salt and a polymer in a first organic solvent to form a mixed solution, and performing first ball milling treatment on the mixed solution and first positive electrode active particles to obtain a first modified positive electrode material with a polymer-lithium salt composite coating layer on the surface; or dispersing lithium-containing oxide in a second organic solvent to form a dispersion liquid, and performing second ball milling treatment on the dispersion liquid and second anode active particles to obtain a second modified anode material with a lithium-containing oxide coating layer on the surface; S2, performing third ball milling treatment on the first modified positive electrode material or the second modified positive electrode material and the sulfide solid electrolyte to obtain the composite positive electrode material. In a preferred embodiment, in the step S1, the mass ratio of the lithium salt to the polymer is (1-3): 5. In a preferred embodiment, in step S1, the mass ratio of the first positive electrode active particles to the polymer in the mixed solution is 100 (1-3). In a preferred embodiment, in step S1, the mass ratio of the second positive electrode active particles to the lithium-containing oxide in the dispersion is 100 (1 to 3). In a preferred embodiment, in step S1, the conditions of the first ball milling treatment and the