CN111799456A - Preparation method of composite anode for lithium ion battery - Google Patents

Preparation method of composite anode for lithium ion battery Download PDF

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CN111799456A
CN111799456A CN202010703412.7A CN202010703412A CN111799456A CN 111799456 A CN111799456 A CN 111799456A CN 202010703412 A CN202010703412 A CN 202010703412A CN 111799456 A CN111799456 A CN 111799456A
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谈益
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E60/10—Energy storage using batteries

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Abstract

The invention provides a preparation method of a composite positive electrode for a lithium ion battery, wherein the positive electrode comprises a current collector and an active substance layer positioned on the current collector, and the active substance layer comprises a first active substance and a second active substance; the preparation method comprises the steps of mixing a first active substance and a second active substance according to the mass ratio of 7:3-8:2 and preparing a first slurry; the preparation method comprises the steps of mixing a first active substance and a conductive agent according to the mass ratio of 1:9-2:8, preparing conductive slurry, sequentially coating and drying the conductive slurry, the first slurry and the second slurry, and performing hot pressing to obtain the lithium ion battery composite anode.

Description

Preparation method of composite anode for lithium ion battery
Technical Field
The invention relates to a preparation method of a composite anode for a lithium ion battery.
Background
The lithium ion battery has the advantages of large capacity and high working voltage. The charge holding capacity is strong, and the allowable working temperature range is wide. The lithium ion battery has excellent high and low temperature discharge performance, and the high temperature discharge performance is higher than that of other various batteries. The battery has long cycle service life, the battery capacity is still not lower than 60 percent of the rated value after 1200 times of continuous charge and discharge, and is far higher than other various batteries, and the battery has long-term use economy. High safety, and can be charged and discharged safely and rapidly. The lithium ion battery has the characteristics of short circuit resistance, overcharge resistance, overdischarge resistance, impact resistance, vibration resistance, gunshot, needling, no fire, no explosion and the like, and can be charged and discharged under the condition of 1C charging rate, so that the safety performance is greatly improved. No environmental pollution. The battery does not contain harmful substances such as cadmium, lead and mercury. Has no memory effect. Can be repeatedly charged and discharged for use at any time. Small volume, light weight and high specific energy. The positive electrode of the lithium ion battery is mostly a composite positive electrode at present, and how to enable the composite positive electrode to obtain the best stability and improve the cycle life is a research hotspot of the composite positive electrode at present.
Disclosure of Invention
The invention provides a preparation method of a composite positive electrode for a lithium ion battery, wherein the positive electrode comprises a current collector and an active substance layer positioned on the current collector, and the active substance layer comprises a first active substance and a second active substance; the first active substance has a D50 of 2.4-2.5 microns, a D10 of 1.8-1.9 microns, and a D90 of 3.2-3.3 microns; the second active substance has D50 of 1.9-2.0 micrometer, D10 of 1.0-1.1 micrometer, and D90 of 2.4-2.5 micrometer; the preparation method comprises the steps of mixing a first active substance and a second active substance according to a ratio of 7:3-8:2 and preparing a first slurry; mixing the first active material and the second active material according to a predetermined mass ratio and preparing a second slurry, wherein the mass ratio of the first active material/the second active material/the first active material D50/the first active material D50 is 0.66-0.67, and k is 0.45-0.46; the preparation method comprises the steps of mixing a first active substance and a conductive agent according to the mass ratio of 1:9-2:8, preparing conductive slurry, sequentially coating and drying the conductive slurry, the first slurry and the second slurry, and performing hot pressing to obtain the lithium ion battery composite anode.
The specific scheme is as follows:
a preparation method of a composite positive electrode for a lithium ion battery comprises a current collector and an active material layer positioned on the current collector, wherein the active material layer comprises a first active material and a second active material; the first active substance has a D50 of 2.4-2.5 microns, a D10 of 1.8-1.9 microns, and a D90 of 3.2-3.3 microns; the second active substance has D50 of 1.9-2.0 micrometer, D10 of 1.0-1.1 micrometer, and D90 of 2.4-2.5 micrometer; the preparation method comprises the following steps:
1) uniformly mixing a first active substance and a second active substance according to a mass ratio of 7:3-8:2, adding an organic solvent into a stirring kettle, sequentially adding a binder and a conductive agent under a stirring state, uniformly mixing, then adding the mixed active substances, and vacuumizing and stirring to obtain a first slurry;
2) uniformly mixing the first active substance and the second active substance according to a predetermined mass ratio, wherein the mass ratio of the first active substance to the second active substance is r-k, the mass ratio of the second active substance is D50 of the second active substance to the mass ratio of the first active substance is D50 of the first active substance, wherein r is 0.65-0.67, and k is 0.46; adding an organic solvent into a stirring kettle, sequentially adding a binder and a conductive agent under the stirring state, uniformly mixing, then adding a mixed active substance, vacuumizing and stirring to obtain a second slurry;
3) uniformly mixing a first active substance and a conductive agent according to a mass ratio of 1:9-2:8, adding an organic solvent into a stirring kettle, sequentially adding a binder under a stirring state, adding a mixed material after uniformly mixing, and vacuumizing and stirring to obtain a conductive slurry;
4) sequentially coating the conductive slurry, the first slurry and the second slurry on a current collector, drying and hot-pressing to obtain the lithium ion battery composite anode; wherein the coating thickness of each paste, the thickness of the conductive paste: thickness of the first slurry: the thickness of the second slurry is 3-5: 40-70: 10-20.
Further, the first active material is LiMn0.65Ni0.1Co0.25O2The first active material has a D50 of 2.4 microns, a D10 of 1.9 microns, and a D90 of 3.2 microns.
Further, the second active material is LiFe0.95Co0.05PO4The second active material has a D50 of 2.0 microns, a D10 of 1.1 microns, and a D90 of 2.4 microns.
Further, in the first slurry, the ratio of active material: adhesive: the conductive agent is 100:4: 4.
Further, in the second slurry, the ratio of active material: adhesive: the conductive agent is 100:4: 5.
Further, the conductive agent in the conductive paste is carbon fiber with the length of 40-80 microns, and the active substance in the conductive paste is: conductive agent: binder 15:80: 5.
Further, the thickness of the conductive paste: thickness of the first slurry: thickness of the second slurry was 4: 60: 15.
the invention has the following beneficial effects:
1) the inventors have found that the active material LiMn0.65Ni0.1Co0.25O2And LiFe0.95Co0.05PO4The composite anode obtained by matching can obtain higher rate performance and cycle performance, and when the particle size distribution of each active substance is within the range of the invention, the two materials are matched with each other to obtain better rate performance, cycle performance and energy density;
2) and a larger amount of ternary materials are adopted in the first slurry, so that a higher working voltage is obtained, and a higher energy density is obtained.
3) And the second slurry is used as a stabilizing layer, and is mixed according to a specific proportion, wherein the mass ratio of the first active material to the second active material is R-k, the second active material is D50 of the second active material to D50 of the first active material, wherein r is 0.65-0.67, k is 0.46, the obtained slurry has extremely high stability, the structural stability of the obtained coating layer is greatly improved, the active material can be prevented from falling off in circulation, and the surface layer of the active material layer can improve the circulation performance of the electrode.
4) The conductive layer contains a large amount of linear conductive agents and a small amount of active substances, the multiplying power performance of the electrode can be improved, and meanwhile, the conductive layer can generate a small amount of volume change during charging and discharging due to the addition of the small amount of active substances, so that the intermediate layer serving as a current collector and the first slurry layer can alleviate stress difference caused by the volume change of the two layers.
Detailed Description
The present invention will be described in more detail below with reference to specific examples, but the scope of the present invention is not limited to these examples. In the present invention, the first active material is LiMn0.65Ni0.1Co0.25O2The first active material has a D50 of 2.4 microns, a D10 of 1.9 microns, and a D90 of 3.2 microns. The second active material is LiFe0.95Co0.05PO4The second active material has a D50 of 2.0 microns, a D10 of 1.1 microns, and a D90 of 2.4 microns.
Example 1
1) Uniformly mixing a first active substance and a second active substance according to a mass ratio of 7:3, adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black under a stirring state, uniformly mixing, then adding the mixed active substances, and vacuumizing and stirring to obtain a first slurry; in the first slurry, active material: PVDF: conductive carbon black 100:4: 4;
2) uniformly mixing the first active material and the second active material according to a predetermined mass ratio, wherein the mass ratio of the first active material to the second active material is 0.267, r is 0.65, and k is 0.46; adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black in a stirring state, uniformly mixing, then adding mixed active substances, and carrying out vacuum-pumping stirring to obtain second slurry, wherein in the second slurry, the active substances: PVDF: conductive carbon black 100:4: 5;
3) uniformly mixing a first active substance and carbon fibers with the length of 40 micrometers according to the mass ratio of 1:9, adding NMP into a stirring kettle, sequentially adding PVDF under the stirring state, uniformly mixing, then adding a mixed material, vacuumizing and stirring to obtain a conductive slurry, wherein the active substance in the conductive slurry is as follows: carbon fiber: PVDF 15:80: 5;
4) sequentially coating the conductive slurry, the first slurry and the second slurry on a current collector, drying and hot-pressing to obtain the lithium ion battery composite anode; wherein the total thickness of coating is 80 microns, the coating thickness of each paste, the thickness of the conductive paste: thickness of the first slurry: thickness of the second slurry 3: 40: 10.
example 2
1) Uniformly mixing a first active substance and a second active substance according to a mass ratio of 8:2, adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black under a stirring state, uniformly mixing, then adding the mixed active substances, and vacuumizing and stirring to obtain a first slurry; in the first slurry, active material: PVDF: conductive carbon black 100:4: 4;
2) uniformly mixing the first active substance and the second active substance according to a predetermined mass ratio, wherein the mass ratio of the first active substance/the second active substance is 0.287, wherein r is 0.67, and k is 0.46; adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black in a stirring state, uniformly mixing, then adding mixed active substances, and carrying out vacuum-pumping stirring to obtain second slurry, wherein in the second slurry, the active substances: PVDF: conductive carbon black 100:4: 5;
3) uniformly mixing a first active substance and carbon fibers with the length of 40-80 micrometers according to the mass ratio of 2:8, adding NMP into a stirring kettle, sequentially adding PVDF in a stirring state, uniformly mixing, then adding a mixed material, vacuumizing and stirring to obtain a conductive slurry, wherein the active substance in the conductive slurry is as follows: carbon fiber: PVDF 15:80: 5;
4) sequentially coating the conductive slurry, the first slurry and the second slurry on a current collector, drying and hot-pressing to obtain the lithium ion battery composite anode; wherein the total thickness of coating is 80 microns, the coating thickness of each paste, the thickness of the conductive paste: thickness of the first slurry: the thickness of the second slurry was 5: 70: 20.
example 3
1) Uniformly mixing a first active substance and a second active substance according to a mass ratio of 3:1, adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black under a stirring state, uniformly mixing, then adding the mixed active substances, and vacuumizing and stirring to obtain a first slurry; in the first slurry, active material: PVDF: conductive carbon black 100:4: 4;
2) uniformly mixing the first active substance and the second active substance according to a predetermined mass ratio, wherein the mass ratio of the first active substance/the second active substance is 0.277, wherein r is 0.66, and k is 0.46; adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black in a stirring state, uniformly mixing, then adding mixed active substances, and carrying out vacuum-pumping stirring to obtain second slurry, wherein in the second slurry, the active substances: PVDF: conductive carbon black 100:4: 5;
3) uniformly mixing a first active substance and carbon fibers with the length of 60 micrometers according to the mass ratio of 3:17, adding NMP into a stirring kettle, sequentially adding PVDF under the stirring state, uniformly mixing, then adding a mixed material, vacuumizing and stirring to obtain a conductive slurry, wherein the active substance in the conductive slurry is as follows: carbon fiber: PVDF 15:80: 5;
4) sequentially coating the conductive slurry, the first slurry and the second slurry on a current collector, drying and hot-pressing to obtain the lithium ion battery composite anode; wherein the total thickness of coating is 80 microns, the coating thickness of each paste, the thickness of the conductive paste: thickness of the first slurry: thickness of the second slurry was 4: 60: 15.
comparative example 1
1) Uniformly mixing a first active substance and a second active substance according to a mass ratio of 3:1, adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black under a stirring state, uniformly mixing, then adding the mixed active substances, and vacuumizing and stirring to obtain a first slurry; in the first slurry, active material: PVDF: conductive carbon black 100:4: 4;
2) the first active material and the second active material are uniformly mixed according to a preset mass ratio, wherein the mass ratio of the first active material to the second active material is 0.25, NMP is added into a stirring kettle, PVDF and conductive carbon black are sequentially added in a stirring state, the mixed active materials are added after uniform mixing, the second slurry is obtained after vacuum pumping and stirring, and in the second slurry, the active materials: PVDF: conductive carbon black 100:4: 5;
3) uniformly mixing a first active substance and carbon fibers with the length of 60 micrometers according to the mass ratio of 3:17, adding NMP into a stirring kettle, sequentially adding PVDF under the stirring state, uniformly mixing, then adding a mixed material, vacuumizing and stirring to obtain a conductive slurry, wherein the active substance in the conductive slurry is as follows: carbon fiber: PVDF 15:80: 5;
4) sequentially coating the conductive slurry, the first slurry and the second slurry on a current collector, drying and hot-pressing to obtain the lithium ion battery composite anode; wherein the total thickness of coating is 80 microns, the coating thickness of each paste, the thickness of the conductive paste: thickness of the first slurry: thickness of the second slurry was 4: 60: 15.
comparative example 2
1) Uniformly mixing a first active substance and a second active substance according to a mass ratio of 3:1, adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black under a stirring state, uniformly mixing, then adding the mixed active substances, and vacuumizing and stirring to obtain a first slurry; in the first slurry, active material: PVDF: conductive carbon black 100:4: 4;
2) the method comprises the following steps of uniformly mixing a first active substance and a second active substance according to a preset mass ratio, wherein the mass ratio of the first active substance to the second active substance is 0.30, adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black in a stirring state, uniformly mixing, adding the mixed active substances, vacuumizing and stirring to obtain a second slurry, wherein in the second slurry, the active substances: PVDF: conductive carbon black 100:4: 5;
3) uniformly mixing a first active substance and carbon fibers with the length of 60 micrometers according to the mass ratio of 3:17, adding NMP into a stirring kettle, sequentially adding PVDF under the stirring state, uniformly mixing, then adding a mixed material, vacuumizing and stirring to obtain a conductive slurry, wherein the active substance in the conductive slurry is as follows: carbon fiber: PVDF 15:80: 5;
4) sequentially coating the conductive slurry, the first slurry and the second slurry on a current collector, drying and hot-pressing to obtain the lithium ion battery composite anode; wherein the total thickness of coating is 80 microns, the coating thickness of each paste, the thickness of the conductive paste: thickness of the first slurry: thickness of the second slurry was 4: 60: 15.
comparative example 3
1) Uniformly mixing a first active substance and a second active substance according to a mass ratio of 3:1, adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black under a stirring state, uniformly mixing, then adding the mixed active substances, and vacuumizing and stirring to obtain a first slurry; in the first slurry, active material: PVDF: conductive carbon black 100:4: 4;
2) uniformly mixing the first active substance and the second active substance according to a predetermined mass ratio, wherein the mass ratio of the first active substance/the second active substance is 0.277, wherein r is 0.66, and k is 0.46; adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black in a stirring state, uniformly mixing, then adding mixed active substances, and carrying out vacuum-pumping stirring to obtain second slurry, wherein in the second slurry, the active substances: PVDF: conductive carbon black 100:4: 5;
3) uniformly mixing a first active substance and conductive carbon black according to a mass ratio of 3:17, adding NMP into a stirring kettle, sequentially adding PVDF in a stirring state, uniformly mixing, then adding a mixed material, vacuumizing and stirring to obtain conductive slurry, wherein the active substance in the conductive slurry is as follows: conductive carbon black: PVDF 15:80: 5;
4) sequentially coating the conductive slurry, the first slurry and the second slurry on a current collector, drying and hot-pressing to obtain the lithium ion battery composite anode; wherein the total thickness of coating is 80 microns, the coating thickness of each paste, the thickness of the conductive paste: thickness of the first slurry: thickness of the second slurry was 4: 60: 15.
comparative example 4
1) Uniformly mixing a first active substance and a second active substance according to a mass ratio of 3:1, adding NMP into a stirring kettle, sequentially adding PVDF and conductive carbon black under a stirring state, uniformly mixing, then adding the mixed active substances, and vacuumizing and stirring to obtain a first slurry; in the first slurry, active material: PVDF: conductive carbon black 100:4: 4;
3) uniformly mixing a first active substance and carbon fibers with the length of 60 micrometers according to the mass ratio of 3:17, adding NMP into a stirring kettle, sequentially adding PVDF under the stirring state, uniformly mixing, then adding a mixed material, vacuumizing and stirring to obtain a conductive slurry, wherein the active substance in the conductive slurry is as follows: carbon fiber: PVDF 15:80: 5;
4) sequentially coating conductive slurry and first slurry on a current collector, drying and hot-pressing to obtain the lithium ion battery composite anode; wherein the total thickness of coating is 80 microns, the coating thickness of each paste, the thickness of the conductive paste: thickness of the first slurry was 4: 60.
test and results
Testing the positive electrodes of examples 1 to 3 and comparative examples 1 to 4, and the counter electrode lithium sheet to constitute a test cell, injecting an electrolyte solution, which is a mixed solvent of dimethyl carbonate and ethylene carbonate in a volume ratio of 1:2, an electrolyte salt being 1 mol per liter of lithium hexafluorophosphate, and circulating 100 times and 300 times at a current of 0.5C to measure a capacity retention rate; and the second slurries of examples 1 to 3 and comparative examples 1 to 2 were left to stand at normal temperature for 10 hours, the solid contents at positions 5cm below the liquid level before and after the standing were measured, and the solid content retention rate, i.e., the stability of the slurries, was calculated, and the results are shown in table 1. As can be seen from the data in table 1, when the component ratio of the two active materials in the second slurry is slightly changed, the balance of the stability of the slurry is broken, thereby affecting the coating performance and further affecting the cycle stability, while the addition of the carbon fiber also has a great influence on the improvement of the stability, the greatest influence should be the presence of the second slurry, and when the second slurry is not present, the cycle decay of the material is serious.
TABLE 1
Figure BDA0002593730440000071
Figure BDA0002593730440000081
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention.

Claims (7)

1. A preparation method of a composite positive electrode for a lithium ion battery comprises a current collector and an active material layer positioned on the current collector, wherein the active material layer comprises a first active material and a second active material; the first active substance has a D50 of 2.4-2.5 microns, a D10 of 1.8-1.9 microns, and a D90 of 3.2-3.3 microns; the second active substance has D50 of 1.9-2.0 micrometer, D10 of 1.0-1.1 micrometer, and D90 of 2.4-2.5 micrometer; the preparation method comprises the following steps:
1) uniformly mixing a first active substance and a second active substance according to a mass ratio of 7:3-8:2, adding an organic solvent into a stirring kettle, sequentially adding a binder and a conductive agent under a stirring state, uniformly mixing, then adding the mixed active substances, and vacuumizing and stirring to obtain a first slurry;
2) uniformly mixing the first active substance and the second active substance according to a predetermined mass ratio, wherein the mass ratio of the first active substance to the second active substance is r-k, the mass ratio of the second active substance is D50 of the second active substance to the mass ratio of the first active substance is D50 of the first active substance, wherein r is 0.65-0.67, and k is 0.46; adding an organic solvent into a stirring kettle, sequentially adding a binder and a conductive agent under the stirring state, uniformly mixing, then adding a mixed active substance, vacuumizing and stirring to obtain a second slurry;
3) uniformly mixing a first active substance and a conductive agent according to a mass ratio of 1:9-2:8, adding an organic solvent into a stirring kettle, sequentially adding a binder under a stirring state, adding a mixed material after uniformly mixing, and vacuumizing and stirring to obtain a conductive slurry;
4) sequentially coating the conductive slurry, the first slurry and the second slurry on a current collector, drying and hot-pressing to obtain the lithium ion battery composite anode; wherein the coating thickness of each paste, the thickness of the conductive paste: thickness of the first slurry: the thickness of the second slurry is 3-5: 40-70: 10-20.
2. The method of the preceding claim, wherein the first active material is LiMn0.65Ni0.1Co0.25O2The first active material has a D50 of 2.4 microns, a D10 of 1.9 microns, and a D90 of 3.2 microns.
3. The method of claim, wherein the second active material is LiFe0.95Co0.05PO4The second active material has a D50 of 2.0 microns, a D10 of 1.1 microns, and a D90 of 2.4 microns.
4. The method of the preceding claim, wherein, in the first slurry, the ratio of active material: adhesive: the conductive agent is 100:4: 4.
5. The method of the preceding claim, wherein, in the second slurry, the ratio of active material: adhesive: the conductive agent is 100:4: 5.
6. The method as claimed in the preceding claim, wherein the conductive agent in the conductive paste is carbon fibers having a length of 40-80 μm, and the active material in the conductive paste: conductive agent: binder 15:80: 5.
7. The method of the preceding claim, wherein the thickness of the conductive paste is: thickness of the first slurry: thickness of the second slurry was 4: 60: 15.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2024164791A (en) * 2023-05-15 2024-11-27 遠景動力技術（江蘇）有限公司 Positive electrode active material composition and its application

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2024164791A (en) * 2023-05-15 2024-11-27 遠景動力技術（江蘇）有限公司 Positive electrode active material composition and its application
JP7811199B2 (en) 2023-05-15 2026-02-04 遠景動力技術（江蘇）有限公司 Positive electrode active material composition and its application

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