CN111933896A - Method for preparing cathode of lithium ion battery - Google Patents

Method for preparing cathode of lithium ion battery Download PDF

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Publication number
CN111933896A
CN111933896A CN202010830236.3A CN202010830236A CN111933896A CN 111933896 A CN111933896 A CN 111933896A CN 202010830236 A CN202010830236 A CN 202010830236A CN 111933896 A CN111933896 A CN 111933896A
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active material
material layer
layer
particles
uniformly stirring
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吴浩扬
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Suzhou Jingcheng Intelligent Technology Co ltd
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Suzhou Jingcheng Intelligent Technology Co ltd
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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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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Abstract

The invention provides a method for preparing a cathode of a lithium ion battery, wherein the cathode comprises a current collector and a conducting layer positioned on the surface of the current collector, wherein a first active material layer, a second active material layer and a third active material layer are sequentially laminated on the conducting layer; the cathode prepared by the invention has good rate performance and high energy density, the volume change difference of each layer is controlled in a balanced state, the stress change among the layers is not obvious, and the cathode has high cycling stability.

Description

Method for preparing cathode of lithium ion battery
Technical Field
The present invention relates to a method for preparing a cathode for a lithium ion battery.
Background
Lithium ion batteries are being considered to satisfy the increasing demand for portable electronic devices, electric and hybrid vehiclesThe energy requirement of (1). Lithium ion batteries have been used in numerous civil and military applications, such as mobile phones, notebook computers, video cameras, digital cameras, and the like. The ternary active material is a layered material mainly composed of three main elements of nickel, manganese and cobalt, and has the following characteristics: high voltage, high capacity, small internal resistance, less self-discharge, more cycle times, good safety and the like. The inventors found that LiNi0.15Mn0.62Co0.20Al0.01Mg0.02O2Such materials have good properties and are not critical to the particle size distribution, a wider range of particle size distributions can be used and still obtain good properties.
Disclosure of Invention
The invention provides a method for preparing a cathode of a lithium ion battery, wherein the cathode comprises a current collector and a conducting layer positioned on the surface of the current collector, wherein a first active material layer, a second active material layer and a third active material layer are sequentially laminated on the conducting layer; wherein the conductive layer, the first active material layer, the second active material layer and the third active material layer each contain active material particles, and the composition of the active material particles of each layer is the same and is LiNi0.15Mn0.62Co0.20Al0.01Mg0.02O2(ii) a The active material particles of the respective layers have different average particle diameters, wherein the average particle diameters D50 of the active material particles of the conductive layer, the first active material layer, the second active material layer, and the third active material layer decrease in this order, and satisfy the following relational expression: conductive layer active material particles D50/first active material layer active material particles D50 ═ 1.65 to 1.70, and second active material layer active material particles D50/(0.85 ×, first active material layer active material particles D50+1.15 ×, third active material layer active material particles D50) ═ 0.53 to 0.55; and the third active material layer active material particles D50 are 1.6 to 1.8 μm; the conductive layer comprises a conductive agent, carboxymethyl cellulose, a binder and active substance particles; the third active material layer includes a conductive agent, a binder, a metal oxide, and active material particles. The method comprises separately preparing a conductive layer, a first active material layer, a second active material layer and a third active material layerThe cathode prepared by the invention has good rate performance and high energy density, the volume change difference of each layer is controlled in a relatively balanced state, the stress change among the layers is not obvious, and the cathode has very high cycle stability.
The specific scheme is as follows:
a method for preparing a cathode of a lithium ion battery comprises a current collector, a conductive layer positioned on the surface of the current collector, and a first active material layer, a second active material layer and a third active material layer which are sequentially laminated on the conductive layer; wherein the conductive layer, the first active material layer, the second active material layer and the third active material layer all contain active material particles, and the composition of the active material particles of each layer is the same, and the average particle diameter of the active material particles of each layer is different, and satisfies the following relational expression: conductive layer active material particles D50/first active material layer active material particles D50 ═ 1.65 to 1.70, and second active material layer active material particles D50/(0.85 ×, first active material layer active material particles D50+1.15 ×, third active material layer active material particles D50) ═ 0.53 to 0.55; and the third active material layer active material particles D50 are 1.6 to 1.8 μm; the method comprises the following steps:
1) adding carboxymethyl cellulose and a binder into an organic solvent, uniformly stirring, adding a conductive agent, uniformly stirring, and uniformly mixing active substance particles to obtain conductive layer slurry;
2) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the first active material layer active material particles, and uniformly stirring to obtain first active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:3-5: 3-5;
3) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the active substance particles of the second active substance layer, and uniformly stirring to obtain second active substance layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:3-5: 3-5;
4) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent and the metal oxide, uniformly stirring, then adding the active substance particles of the third active substance layer, and uniformly stirring to obtain third active substance layer slurry; wherein the mass ratio of the active substance particles is as follows: metal oxide(s): adhesive: the conductive agent is 100:8-10:3-5: 3-5;
5) and coating the conductive layer slurry, the first active material layer slurry, the second active material layer slurry and the third active material layer slurry on a current collector in sequence, and drying to obtain the cathode.
Further, the molecular formulas of the active substances are all LiNi0.15Mn0.62Co0.20Al0.01Mg0.02O2.
Further, the average particle diameter D50 of the active material particles of the conductive layer, the first active material layer, the second active material layer, and the third active material layer is decreased in this order.
Further, the active material particles D50 of the first active material layer are 2.4 to 2.6 μm.
Further, the organic solvent is NMP, and the binder is PVDF.
Further, the metal oxide is selected from nanoparticles of aluminum oxide and magnesium oxide.
Further, the particle size of the metal oxide is 150-300 nm.
The invention has the following beneficial effects:
1) the inventors have found that LiNi0.15Mn0.62Co0.20Al0.01Mg0.02O2The usable particle size distribution range is wider; that is, the material has excellent structural stability over a wide range of particle diameters without causing structural collapse during circulation due to excessively large particle diameters, and the material also has excellent electrolyte stability without causing decomposition of the electrolyte on the surface thereof due to excessively small particle diameters, and therefore, the inventors have found that a structured cathode active material layer structure can be constructed only with a single-component material, and particles having large particle diameters have a high energy density, and particles having small particle diameters have a high active layer structureStability;
2) the inventors have found that the particle diameter of the cathode active material layer decreases gradually from the direction of the current collector toward the surface of the active material layer, and that a relatively stable active material layer and a high energy density can be obtained.
3) The conductive layer is added with part of active substance particles with large particle size, so that the conductive layer has partial volume change degree in the charging and discharging process, and the stress difference between the current collector and the first active substance layer can be relieved;
4) when the conductive layer active material particles D50/the first active material layer active material particles D50 is 1.65 to 1.70, the second active material layer active material particles D50/(0.85 × the first active material layer active material particles D50+1.15 × the third active material layer active material particles D50) is 0.53 to 0.55; and when the active material particles D50 of the third active material layer are 1.6-1.8 microns, the volume change difference between the layers is relatively uniform, so that the stress difference between the layers is relatively balanced, the stability between the layers of the active material layer is improved, and the separation phenomenon between the layers caused by overlarge volume change difference between the layers is avoided.
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. The molecular formula of the positive electrode active material in the invention is LiNi0.15Mn0.62Co0.20Al0.01Mg0.0 2O2The organic solvent is NMP, the binder is PVDF, and the conductive agent is conductive carbon black.
Example 1
1) Adding carboxymethyl cellulose and a binder into an organic solvent, uniformly stirring, adding a conductive agent, uniformly stirring, and uniformly mixing to obtain conductive layer slurry, wherein the active substance particles have a particle size D50 of 4 microns, and the active substance particles are prepared by mixing: carboxymethyl cellulose: conductive agent: binder 100:6:15: 5;
2) adding the binder into an organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding first active material layer active material particles with the particle size D50 of 2.4 microns, and uniformly stirring to obtain first active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:3: 3;
3) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the active material particles of the second active material layer, wherein the D50 of the active material particles of the second active material layer is 2.06 micrometers, and uniformly stirring to obtain second active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:3: 3;
4) adding a binder into an organic solvent, uniformly stirring, adding a conductive agent and a metal oxide, wherein the metal oxide is alumina with the particle size of 150 nanometers, uniformly stirring, then adding active substance particles of a third active substance layer, wherein the active substance particles D50 of the third active substance layer are 1.6 micrometers, and uniformly stirring to obtain third active substance layer slurry; wherein the mass ratio of the active substance particles is as follows: metal oxide(s): adhesive: the conductive agent is 100:8:3: 3;
5) and coating the conductive layer slurry, the first active material layer slurry, the second active material layer slurry and the third active material layer slurry on a current collector in sequence, wherein the coating thickness ratio of each layer is 1:3:3:2, the total thickness of the coating slurry layer is 80 microns, and drying to obtain the cathode.
Example 2
1) Adding carboxymethyl cellulose and a binder into an organic solvent, uniformly stirring, adding a conductive agent, uniformly stirring, and uniformly mixing active substance particles with the particle size D50 of 4.4 micrometers to obtain conductive layer slurry, wherein the active substance: carboxymethyl cellulose: conductive agent: binder 100:6:15: 5;
2) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the first active material layer active material particles with the particle size D50 of 2.6 microns, and uniformly stirring to obtain first active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:5: 5;
3) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the active material particles of the second active material layer, wherein the D50 of the active material particles of the second active material layer is 2.35 microns, and uniformly stirring to obtain second active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:5: 5;
4) adding a binder into an organic solvent, uniformly stirring, adding a conductive agent and a metal oxide, wherein the metal oxide is aluminum oxide with the particle size of 300 nanometers, uniformly stirring, then adding active substance particles of a third active substance layer, wherein the active substance particles D50 of the third active substance layer are 1.8 micrometers, and uniformly stirring to obtain third active substance layer slurry; wherein the mass ratio of the active substance particles is as follows: metal oxide(s): adhesive: the conductive agent is 100:10:5: 5;
5) and coating the conductive layer slurry, the first active material layer slurry, the second active material layer slurry and the third active material layer slurry on a current collector in sequence, wherein the coating thickness ratio of each layer is 1:3:3:2, the total thickness of the coating slurry layer is 80 microns, and drying to obtain the cathode.
Example 3
1) Adding carboxymethyl cellulose and a binder into an organic solvent, uniformly stirring, adding a conductive agent, uniformly stirring, and uniformly mixing active substance particles with the particle size D50 of 4.2 micrometers to obtain conductive layer slurry, wherein the active substance: carboxymethyl cellulose: conductive agent: binder 100:6:15: 5;
2) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the first active material layer active material particles with the particle size D50 of 2.5 micrometers, and uniformly stirring to obtain first active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:4: 4;
3) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the active material particles of the second active material layer, wherein the D50 of the active material particles of the second active material layer is 2.2 microns, and uniformly stirring to obtain second active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:4: 4;
4) adding a binder into an organic solvent, uniformly stirring, adding a conductive agent and a metal oxide, wherein the metal oxide is alumina with the particle size of 200 nanometers, uniformly stirring, then adding active substance particles of a third active substance layer, and uniformly stirring to obtain third active substance layer slurry, wherein the third active substance layer active substance particles D50 are 1.7 micrometers; wherein the mass ratio of the active substance particles is as follows: metal oxide(s): adhesive: the conductive agent is 100:9:4: 4;
5) and coating the conductive layer slurry, the first active material layer slurry, the second active material layer slurry and the third active material layer slurry on a current collector in sequence, wherein the coating thickness ratio of each layer is 1:3:3:2, the total thickness of the coating slurry layer is 80 microns, and drying to obtain the cathode.
Comparative example 1
1) Adding carboxymethyl cellulose and a binder into an organic solvent, uniformly stirring, adding a conductive agent, uniformly stirring, and uniformly mixing to obtain conductive layer slurry, wherein the active substance particles have a particle size D50 of 5 micrometers, and the active substance particles are prepared by mixing: carboxymethyl cellulose: conductive agent: binder 100:6:15: 5;
2) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the first active material layer active material particles with the particle size D50 of 2.5 micrometers, and uniformly stirring to obtain first active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:4: 4;
3) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the active material particles of the second active material layer, wherein the D50 of the active material particles of the second active material layer is 2 microns, and uniformly stirring to obtain second active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:4: 4;
4) adding a binder into an organic solvent, uniformly stirring, adding a conductive agent and a metal oxide, wherein the metal oxide is alumina with the particle size of 200 nanometers, uniformly stirring, then adding active substance particles of a third active substance layer, and uniformly stirring to obtain third active substance layer slurry, wherein the third active substance layer active substance particles D50 are 1.5 micrometers; wherein the mass ratio of the active substance particles is as follows: metal oxide(s): adhesive: the conductive agent is 100:9:4: 4;
5) and coating the conductive layer slurry, the first active material layer slurry, the second active material layer slurry and the third active material layer slurry on a current collector in sequence, wherein the coating thickness ratio of each layer is 1:3:3:2, the total thickness of the coating slurry layer is 80 microns, and drying to obtain the cathode.
Comparative example 2
1) Adding carboxymethyl cellulose and a binder into an organic solvent, uniformly stirring, adding a conductive agent, uniformly stirring, and uniformly mixing active substance particles with the particle size D50 of 2.5 micrometers to obtain conductive layer slurry, wherein the active substance: carboxymethyl cellulose: conductive agent: binder 100:6:15: 5;
2) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the first active material layer active material particles with the particle size D50 of 2.5 micrometers, and uniformly stirring to obtain first active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:4: 4;
3) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the active material particles of the second active material layer, wherein the D50 of the active material particles of the second active material layer is 2.5 microns, and uniformly stirring to obtain second active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:4: 4;
4) adding a binder into an organic solvent, uniformly stirring, adding a conductive agent and a metal oxide, wherein the metal oxide is alumina with the particle size of 200 nanometers, uniformly stirring, then adding active substance particles of a third active substance layer, and uniformly stirring to obtain third active substance layer slurry, wherein the third active substance layer active substance particles D50 are 2.5 micrometers; wherein the mass ratio of the active substance particles is as follows: metal oxide(s): adhesive: the conductive agent is 100:9:4: 4;
5) and coating the conductive layer slurry, the first active material layer slurry, the second active material layer slurry and the third active material layer slurry on a current collector in sequence, wherein the coating thickness ratio of each layer is 1:3:3:2, the total thickness of the coating slurry layer is 80 microns, and drying to obtain the cathode.
Comparative example 3
1) Adding carboxymethyl cellulose and a binder into an organic solvent, uniformly stirring, adding a conductive agent, uniformly stirring, and uniformly mixing to obtain conductive layer slurry, wherein the active substance particles have a particle size D50 of 4 microns, and the active substance particles are prepared by mixing: carboxymethyl cellulose: conductive agent: binder 100:6:15: 5;
2) adding a binder into an organic solvent, uniformly stirring, adding a conductive agent, uniformly stirring, then adding first active material layer active material particles with the particle size D50 of 3 microns, and uniformly stirring to obtain first active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:4: 4;
3) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the active material particles of the second active material layer, wherein the D50 of the active material particles of the second active material layer is 2 microns, and uniformly stirring to obtain second active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:4: 4;
4) adding a binder into an organic solvent, uniformly stirring, adding a conductive agent and a metal oxide, wherein the metal oxide is alumina with the particle size of 200 nanometers, uniformly stirring, then adding active substance particles of a third active substance layer, and uniformly stirring to obtain third active substance layer slurry, wherein the third active substance layer active substance particles D50 are 1.5 micrometers; wherein the mass ratio of the active substance particles is as follows: metal oxide(s): adhesive: the conductive agent is 100:9:4: 4;
5) and coating the conductive layer slurry, the first active material layer slurry, the second active material layer slurry and the third active material layer slurry on a current collector in sequence, wherein the coating thickness ratio of each layer is 1:3:3:2, the total thickness of the coating slurry layer is 80 microns, and drying to obtain the cathode.
Comparative example 4
1) Adding carboxymethyl cellulose and a binder into an organic solvent, uniformly stirring, adding a conductive agent, uniformly stirring, and uniformly mixing active substance particles with the particle size D50 of 4.2 micrometers to obtain conductive layer slurry, wherein the active substance: carboxymethyl cellulose: conductive agent: binder 100:6:15: 5;
2) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the first active material layer active material particles with the particle size D50 of 2.5 micrometers, and uniformly stirring to obtain first active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:4: 4;
3) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the active material particles of the second active material layer, wherein the D50 of the active material particles of the second active material layer is 1.8 microns, and uniformly stirring to obtain second active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:4: 4;
4) adding a binder into an organic solvent, uniformly stirring, adding a conductive agent and a metal oxide, wherein the metal oxide is alumina with the particle size of 200 nanometers, uniformly stirring, then adding active substance particles of a third active substance layer, and uniformly stirring to obtain third active substance layer slurry, wherein the third active substance layer active substance particles D50 are 1.7 micrometers; wherein the mass ratio of the active substance particles is as follows: metal oxide(s): adhesive: the conductive agent is 100:9:4: 4;
5) and coating the conductive layer slurry, the first active material layer slurry, the second active material layer slurry and the third active material layer slurry on a current collector in sequence, wherein the coating thickness ratio of each layer is 1:3:3:2, the total thickness of the coating slurry layer is 80 microns, and drying to obtain the cathode.
Test and results
The cathodes of examples 1 to 3 and comparative examples 1 to 4 were tested to constitute test cells with a lithium plate as a counter electrode, and the cycle capacity retention ratio of the cells was measured by performing charge and discharge cycles 500 times at a voltage interval of 2.8 to 4.2V at a current of 1C, and the results are shown in table 1. As can be seen from table 1, when the particle diameter range of each active layer does not satisfy the range defined in the present invention, the cycle performance of the material may be degraded, and when the conductive layer active material particle D50/first active material layer active material particle D50 is 1.65 to 1.70, the second active material layer active material particle D50/(0.85: first active material layer active material particle D50+ 1.15: third active material layer active material particle D50) is 0.53 to 0.55; and when the active material particles D50 of the third active material layer are 1.6-1.8 microns, the volume change difference between the layers is relatively uniform, so that the stress difference between the layers is relatively balanced, the stability between the layers of the active material layer is improved, and the separation phenomenon between the layers caused by overlarge volume change difference between the layers is avoided. By adjusting the particle size, the circulation capacity can be improved by 3-4%.
TABLE 1
Figure BDA0002637688160000071
Figure BDA0002637688160000081
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 method for preparing a cathode of a lithium ion battery comprises a current collector, a conductive layer positioned on the surface of the current collector, and a first active material layer, a second active material layer and a third active material layer which are sequentially laminated on the conductive layer; wherein the conductive layer, the first active material layer, the second active material layer and the third active material layer all contain active material particles, and the composition of the active material particles of each layer is the same, and the average particle diameter of the active material particles of each layer is different, and satisfies the following relational expression: conductive layer active material particles D50/first active material layer active material particles D50 ═ 1.65 to 1.70, and second active material layer active material particles D50/(0.85 ×, first active material layer active material particles D50+1.15 ×, third active material layer active material particles D50) ═ 0.53 to 0.55; and the third active material layer active material particles D50 are 1.6 to 1.8 μm; the method comprises the following steps:
1) adding carboxymethyl cellulose and a binder into an organic solvent, uniformly stirring, adding a conductive agent, uniformly stirring, and uniformly mixing active substance particles to obtain conductive layer slurry;
2) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the first active material layer active material particles, and uniformly stirring to obtain first active material layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:3-5: 3-5;
3) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent, uniformly stirring, then adding the active substance particles of the second active substance layer, and uniformly stirring to obtain second active substance layer slurry; wherein the mass ratio of the active substance particles is as follows: adhesive: the conductive agent is 100:3-5: 3-5;
4) adding the binder into the organic solvent, uniformly stirring, adding the conductive agent and the metal oxide, uniformly stirring, then adding the active substance particles of the third active substance layer, and uniformly stirring to obtain third active substance layer slurry; wherein the mass ratio of the active substance particles is as follows: metal oxide(s): adhesive: the conductive agent is 100:8-10:3-5: 3-5;
5) and coating the conductive layer slurry, the first active material layer slurry, the second active material layer slurry and the third active material layer slurry on a current collector in sequence, and drying to obtain the cathode.
2. The method of claim, wherein the active material has the formula LiNi0.15Mn0.62Co0.20Al0.01Mg0.02O2。
3. The method according to the preceding claim, wherein the average particle diameter D50 of the active material particles of the conductive layer, the first active material layer, the second active material layer and the third active material layer decreases in this order.
4. The method according to the preceding claim, the active material particles D50 of the first active material layer being 2.4 to 2.6 microns.
5. The method of the preceding claim, wherein the organic solvent is NMP and the binder is PVDF.
6. The method of the preceding claim, wherein the metal oxide is selected from nanoparticles of alumina, magnesia.
7. The method as claimed in the preceding claim, wherein the metal oxide has a particle size of 150-300 nm.
CN202010830236.3A 2020-08-18 2020-08-18 Method for preparing cathode of lithium ion battery Pending CN111933896A (en)

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CN110690410A (en) * 2019-10-18 2020-01-14 陆晨杰 Preparation method for positive electrode of lithium ion battery
CN111029532A (en) * 2020-01-02 2020-04-17 朱虎 Preparation method of lithium ion battery anode
CN111370669A (en) * 2020-03-19 2020-07-03 陆晨杰 Preparation method of composite positive electrode of power battery
CN111463410A (en) * 2019-01-22 2020-07-28 深圳市贝特瑞纳米科技有限公司 Positive electrode material, and preparation method and application thereof

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170346133A1 (en) * 2016-05-30 2017-11-30 Samsung Sdi Co., Ltd. Positive electrode for rechargeable lithium battery and rechargeable lithium battery including the same
CN111463410A (en) * 2019-01-22 2020-07-28 深圳市贝特瑞纳米科技有限公司 Positive electrode material, and preparation method and application thereof
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