CN109004176B - Electrode and lithium ion battery - Google Patents

Electrode and lithium ion battery Download PDF

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Publication number
CN109004176B
CN109004176B CN201810204412.5A CN201810204412A CN109004176B CN 109004176 B CN109004176 B CN 109004176B CN 201810204412 A CN201810204412 A CN 201810204412A CN 109004176 B CN109004176 B CN 109004176B
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material layer
electrode
thickness
lithium ion
average particle
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CN109004176A (en
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钟华炜
杨帆
苏义松
林超旺
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to CN201810204412.5A priority Critical patent/CN109004176B/en
Priority to CN202110396594.2A priority patent/CN113130848B/en
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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
    • H01M4/13—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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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

Abstract

The present application provides an electrode and a lithium ion battery comprising the electrode, the electrode comprising: a first layer of material comprising particles; wherein the relationship between the thickness T of the first material layer and the average particle diameter Dv50 of the particles in the first material layer satisfies: t is Dv50 (1+ A), wherein A is not less than 0 and not more than 60. The method and the device can achieve the purpose of improving the safety performance of the lithium ion battery on the premise of not sacrificing the energy density of the lithium ion battery.

Description

Electrode and lithium ion battery
Technical Field
The present application relates to batteries, and more particularly, to electrodes and lithium ion batteries.
Background
Lithium ion batteries have entered our daily lives with technological advances and increased environmental requirements. With the great popularization of lithium ion batteries, the safety problem caused by the fact that the lithium ion battery is punctured by external force occasionally occurs at a user end, the safety performance of the lithium ion battery is more and more emphasized by people, and particularly, continuous fermentation of some mobile phone explosion events causes new requirements on the safety performance of the lithium ion battery by users, after-sales terminals and lithium ion battery manufacturers.
At present, methods for improving the safety of the lithium ion battery mainly include methods of increasing the thickness of a ceramic coating diaphragm, changing a material formula, increasing the stability of materials, arranging a coating on the surfaces of a positive electrode plate and a negative electrode plate, and the like, and the methods have no exception of influencing the capacity and the thickness of the lithium ion battery, so that the volume energy density of the lithium ion battery is reduced. Therefore, a technical means capable of remarkably improving the safety performance of the lithium ion battery under the condition of higher volume energy density is urgently needed to be provided.
Disclosure of Invention
The electrode comprises a material layer, the material layer contains particles, the thickness T of the material layer and the average particle diameter Dv50 of the particles in the material layer meet the requirement of T & ltdv & gt 50 & ltx (1+ A), wherein A is more than or equal to 0 and less than or equal to 60, and the purpose of improving the safety performance of the lithium ion battery can be achieved on the premise of not sacrificing the energy density of the lithium ion battery.
Some embodiments of the present application provide an electrode comprising: a first layer of material comprising particles; wherein the relationship between the thickness T of the first material layer and the average particle diameter Dv50 of the particles in the first material layer satisfies: t is Dv50 (1+ A), wherein A is not less than 0 and not more than 60.
In the above electrode, wherein the electrode comprises a current collector.
In the above electrode, wherein the first material layer is in contact with the current collector.
In the above electrode, wherein the particles of the first material layer have an average particle diameter Dv50 ≦ 8 μm.
In the above electrode, wherein the electrode further comprises a second material layer in contact with the first material layer.
In the above electrode, the first material layer contains a first active material.
In the above electrode, the first active material is at least one selected from the group consisting of a metal oxide having a layered structure, a metal oxide having a spinel structure, and a metal oxide having a phosphate type.
In the above electrode, wherein the first material layer further comprises a conductive agent, and the conductive agent comprises carbon nanotubes.
In the above electrode, wherein the second material layer contains a second active material.
In the above electrode, the second active material is at least one selected from the group consisting of lithium cobaltate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, a lithium rich manganese based material, and lithium iron phosphate.
In the above electrode, wherein the first material layer and the second material layer each include a binder.
In the above electrode, wherein a mass percentage of the binder in the first material layer is larger than a mass percentage of the binder in the second material layer.
Some embodiments of the present application also provide a lithium ion battery comprising the above-described electrode.
The present application satisfies the following relationship by relating the thickness T of the first material layer in the electrode to the average particle diameter Dv50 of the particles in the first material layer: t is Dv50 x (1+ A), wherein A is more than or equal to 0 and less than or equal to 60, so that the high bonding property of the first material layer is ensured, and the purpose of improving the safety performance of the lithium ion battery is achieved on the premise of not sacrificing the energy density of the lithium ion battery.
Detailed Description
Lithium ion batteries typically include a positive pole piece, a separator, and a negative pole piece stacked or wound together, with the separator disposed between the positive and negative pole pieces. The positive electrode sheet may include a positive electrode current collector (e.g., aluminum foil) and a material layer. The negative electrode tab may include a negative electrode current collector (e.g., copper foil) and a material layer.
The needling is one of the methods for simulating the short circuit in the lithium ion battery, and the needling test is taken as a mode for evaluating the safety performance of the lithium ion battery. In the lithium ion battery needling process, the extension of the aluminum foil burrs leads to the contact of the positive current collector and the material layer of the negative pole piece, thereby causing the occurrence of short circuit, or the material layers of the aluminum foil and the negative pole piece are directly conducted through a steel nail, namely the contact of the material layers of the positive current collector, the steel nail and the negative pole piece occurs, thereby causing the occurrence of short circuit, and the two short circuit modes are the most dangerous short circuit modes. Avoiding these two short circuits is one of the main means to improve the safety performance of lithium ion batteries. The high-adhesion material layer is coated on the surface of the aluminum foil to protect the aluminum foil and inhibit extension of aluminum foil burrs in the needling process, so that the most dangerous material layer short circuit mode of the positive current collector and the negative pole piece is converted into a safer material layer short circuit mode of the high-adhesion material layer and the negative pole piece.
In order to avoid the above two dangerous short circuit modes, the first material layer of the electrode of the lithium ion battery has a certain thickness, specifically, the relation between the thickness T of the first material layer and the average particle diameter Dv50 of the active material in the first material layer satisfies: t is Dv50 (1+ A), wherein A is not less than 0 and not more than 60. This first material layer has high impedance characteristic for the contact resistance of acupuncture process is big, and the heat production power is little, makes acupuncture lithium ion battery can not become invalid.
As will be appreciated by those skilled in the art, to avoid the above two dangerous short circuit modes, the first material layer may be formed on either the positive or negative electrode of the lithium ion battery. However, for the sake of simplicity of description, the present application is illustrated with the first material layer formed on the positive electrode as an example, but the present application is not limited thereto. In addition, the electrode may include or not include a current collector, and when the electrode includes a current collector, the first material layer may be formed on the current collector. Other material layers may or may not be formed between the current collector and the first material layer, and when no other material layers are formed between the current collector and the first material layer, the first material layer is in contact with the current collector.
In some embodiments, the active material in the first material may be a particle. The small particle active material of the first material layer has a large specific surface area and interaction force between particles is large, so that adhesion between the first material layer and a current collector (e.g., aluminum foil) can be increased. In some embodiments, the average particle size Dv50 of the active material of the first material layer is 8 μm or less.
In some embodiments, the first material layer includes an active material containing at least one of a metal oxide of a layered structure, a metal oxide of a spinel structure, and a metal oxide of a phosphate type. The metal oxide having a layered structure may include lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, such as LiCoO2、LiNiO2、LiNi0.5Co0.2Mn0.3O2、LiNi1/3Co1/3Mn1/3O2、Li2MnO3. The spinel-structured metal oxide may include Li2MnO4、LiCo0.5Ni0.25Mn1.25O4. The phosphate type metal oxide may include LiFePO4、LiCoPO4、LiMnPO4. The metal oxide may also include metal oxides with transition metal element doping, such as Al, Mg, Cr, etc., and metal oxides with anion doping, such as F, S, N, etc.
In some embodiments, the first material layer further includes a binder, which may include polyvinylidene fluoride or the like. The mass percentage of the binder in the first material layer is 2% to 4%, and may be 3%, for example. If the content of the binder is too low, it is not advantageous to improve the adhesion between the first material layer and the aluminum foil. If the binder content is too high, the volumetric energy density of the lithium ion battery may be lost.
In some embodiments, the first material layer may further include a conductive agent, which may include carbon black (SP), Carbon Nanotubes (CNT), graphene, and the like. For example, the conductive agent of the first material layer may include carbon nanotubes, and the adhesive force between the aluminum foil and the first material layer may be well increased due to the chain-like structure of the carbon nanotubes.
In some embodiments, the electrode further comprises a second material layer, and the first material layer may be disposed between the current collector and the second material layer. The second material layer may be in direct contact with the first material layer. The first material layer may be in simultaneous contact with the second material and the current collector. The second material layer may include an active material, a binder, and a conductive agent. The binder of the second material layer may include polyvinylidene fluoride or the like. The conductive agent of the second material layer may include carbon black (SP), Carbon Nanotube (CNT), graphene, and the like. The active material in the second material layer may include a combination of one or more of lithium cobaltate, lithium nickel cobalt manganese, lithium nickel cobalt aluminate, lithium rich manganese based materials, lithium iron phosphate, for example, LiCoO2、LiNi1/3Co1/3Mn1/3O2、LiNi0.85Co0.1Al0.05O2、Li2MnO3、LiFePO4。
In some embodiments, the mass percentage of binder in the first material layer is greater than the mass percentage of binder in the second material layer. Generally, the content of the active material in the second material layer is higher than that of the first material layer to increase the energy density of the lithium ion battery.
For example, the adhesion between the material layer of the conventional positive electrode sheet and the positive electrode current collector is generally about 10N/m, which is insufficient for protecting the aluminum foil and suppressing the extension of burrs of the aluminum foil. If a high-adhesion first material layer containing an active material is coated on the surface of the aluminum foil, the adhesion between the first material layer and the aluminum foil is at least more than 50N/m and even as high as 200N/m, the extension of burrs of the aluminum foil can be well inhibited. When the second material layer is coated, the adhesive force of the whole positive pole piece can be improved from 10N/m to more than 100N/m. In the cold pressing process, the degree of embedding of the particles of the second material layer is small, the particles of the second material layer are not contacted with the aluminum foil, and the impedance internal resistance (alternating current, 1kHz) increase fluctuation and the needling passage rate fluctuation of the lithium ion battery are small.
The present application also provides lithium ion batteries that include the above-described electrodes (e.g., positive electrode, negative electrode). The lithium ion battery comprises a positive pole piece, a negative pole piece, an isolating membrane, electrolyte and the like. The negative electrode tab may include a negative electrode current collector and a negative electrode material layer coated on the negative electrode current collector, the negative electrode material layer including a negative electrode active material, a conductive agent, and a binder. The negative electrode collector may employ a copper foil, however, other negative electrode collectors commonly used in the art may be employed. The binder of the material layer of the negative electrode may include polyvinylidene fluoride or the like. The conductive agent of the material layer of the negative electrode may include carbon black (SP), Carbon Nanotubes (CNT), graphene, and the like. The negative active material includes, but is not limited to, one of soft carbon, hard carbon, mesocarbon microbeads (MCMB), mesocarbon fibers, artificial graphite, and natural graphite, and a combination thereof, and includes a negative active material doped or coated in the related art.
The separator includes a Polyethylene (PE) separator, a polypropylene (PP) separator, and the like. Further, the separator includes one of a bare separator without a coating layer, an inorganic particle-coated separator, and a polymer-coated separator, and a combination thereof, according to whether the surface of the separator contains a coating layer and the kind of the coating layer. The electrolyte comprises at least two of dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC), Ethylene Carbonate (EC), Propylene Carbonate (PC) and Propyl Propionate (PP). In addition, the electrolyte may additionally include at least one of Vinylene Carbonate (VC), fluoroethylene carbonate (FEC), and a dinitrile compound as an electrolyte additive, wherein the dinitrile compound includes Succinonitrile (SN).
And winding or stacking the positive pole piece, the isolating membrane and the negative pole piece in sequence to form a bare cell, then putting the bare cell into a shell, such as an aluminum-plastic film, injecting electrolyte, forming and packaging to obtain the lithium ion battery. And then, performing performance test and cycle test on the prepared lithium ion battery.
Those skilled in the art will appreciate that the above-described methods of making lithium ion batteries are examples only. Other methods commonly used in the art may be employed without departing from the disclosure herein.
Examples 1-54 and comparative examples 1-6 are listed below to better illustrate the present application.
Example 1
Adopting an aluminum foil as a positive current collector, and uniformly coating slurry of a first material layer on the surface of the aluminum foil, wherein the slurry comprises 96.0 wt% of LiNi0.5Co0.2Mn0.3O2And drying 3 wt% of polyvinylidene fluoride (PVDF), 0.5 wt% of Carbon Nano Tube (CNT) and 0.5 wt% of conductive carbon black (SP) at 85 ℃, then carrying out cold pressing, cutting into pieces and slitting, and drying for 4 hours at 85 ℃ under a vacuum condition to prepare the positive pole piece. Wherein the thickness of the first material layer is 60 μm, and the average particle diameter Dv50 of the particles in the first material layer is 5 μm.
The method comprises the steps of taking a copper foil as a negative current collector, uniformly coating a layer of graphite slurry on the surface of the copper foil, drying the slurry at 85 ℃, then carrying out cold pressing, cutting into pieces and slitting, and drying for 4 hours at 85 ℃ under the vacuum condition, thus obtaining the negative pole piece.
And winding the positive pole piece and the negative pole piece after stripping, and separating the positive pole piece and the negative pole piece by a polyethylene isolating film so as to prepare the winding naked battery cell. And (3) carrying out top side sealing, code spraying, vacuum drying, electrolyte injection, high-temperature standing and formation and capacity treatment on the bare cell to obtain the finished product lithium ion battery.
Example 2
In accordance with the manufacturing method of example 1, except that the thickness of the first material layer in example 2 was 50 μm.
Example 3
In accordance with the manufacturing method of example 1, except that the thickness of the first material layer in example 3 was 40 μm.
Example 4
In accordance with the manufacturing method of example 1, except that the thickness of the first material layer in example 4 was 30 μm.
Example 5
In accordance with the manufacturing method of example 1, except that the thickness of the first material layer in example 5 was 20 μm.
Example 6
In accordance with the manufacturing method of example 1, except that the thickness of the first material layer in example 6 was 15 μm.
Example 7
In accordance with the manufacturing method of example 1, except that the thickness of the first material layer in example 7 was 10 μm.
Example 8
In accordance with the manufacturing method of example 1, except that the thickness of the first material layer in example 8 was 5 μm.
Comparative example 1
In accordance with the manufacturing method of example 1, except that the first material layer was not formed in comparative example 1, that is, the thickness of the first material layer was 0.
Example 9
An aluminum foil is adopted as a positive current collector, and a layer of LiNi is uniformly coated on the surface of the aluminum foil0.5Co0.2Mn0.3O2Slurry having a composition of 96.0 wt% LiNi0.5Co0.2Mn0.3O23 wt% polyvinylidene fluoride (PVDF), 0.5 wt% Carbon Nanotube (CNT) and 0.5 wt% conductive carbon black (SP), and drying at 85 ℃; continuously coating a layer of lithium cobaltate slurry as a second material layer on the first material layer coated with the lithium nickel cobalt manganese oxide slurry, wherein the slurry composition is 97.0 wt% LiCoO2Drying the polyvinylidene fluoride (PVDF) 1.6 wt% and the conductive carbon black 1.4 wt% at 85 ℃, cold pressing, cutting into pieces, cutting, and drying for 4 hours at 85 ℃ under a vacuum condition to prepare the positive pole piece. Wherein the particles in the first material layer have an average particle diameter Dv50 of5 μm, the thickness of the first material layer is 60 μm and the thickness of the second material layer is 25 μm.
The method comprises the steps of taking a copper foil as a negative current collector, uniformly coating a layer of graphite slurry on the surface of the copper foil, drying the slurry at 85 ℃, then carrying out cold pressing, cutting into pieces and slitting, and drying for 4 hours at 85 ℃ under the vacuum condition, thus obtaining the negative pole piece.
And winding the positive pole piece and the negative pole piece after stripping, and separating the positive pole piece and the negative pole piece by a polyethylene isolating film so as to prepare the winding naked battery cell. And (3) carrying out top side sealing, code spraying, vacuum drying, electrolyte injection, high-temperature standing and formation and capacity treatment on the bare cell to obtain the finished product lithium ion battery.
Example 10
In accordance with the manufacturing method of example 9, except that the thickness of the first material layer in example 10 was 50 μm.
Example 11
In accordance with the manufacturing method of example 9, except that the thickness of the first material layer in example 11 was 40 μm.
Example 12
In accordance with the manufacturing method of example 9, except that the thickness of the first material layer in example 12 was 30 μm.
Example 13
In accordance with the manufacturing method of example 9, except that the thickness of the first material layer in example 13 was 20 μm.
Example 14
In accordance with the manufacturing method of example 9, except that the thickness of the first material layer in example 14 was 15 μm.
Example 15
In accordance with the manufacturing method of example 9, except that the thickness of the first material layer in example 15 was 10 μm.
Example 16
In accordance with the manufacturing method of example 9, except that the thickness of the first material layer in example 16 was 5 μm.
Comparative example 2
In accordance with the manufacturing method of example 9, except that the first material layer was not formed in comparative example 2, that is, the thickness of the first material layer was 0.
Example 17
In accordance with the production method of example 1, except that the active material of the first material layer in example 17 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm.
Example 18
In accordance with the production method of example 1, except that the active material of the first material layer in example 18 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 50 μm.
Example 19
In accordance with the production method of example 1, except that the active material of the first material layer in example 19 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 40 μm.
Example 20
In accordance with the production method of example 1, except that the active material of the first material layer in example 20 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 30 μm.
Example 21
In accordance with the production method of example 1, except that the active material of the first material layer in example 21 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 20 μm.
Example 22
In keeping with the method of preparation of example 1, except that the first material layer of example 22 was activatedThe material is LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 15 μm.
Example 23
In accordance with the production method of example 1, except that the active material of the first material layer in example 23 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 10 μm.
Example 24
In accordance with the production method of example 1, except that the active material of the first material layer in example 24 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 5 μm.
Example 25
In accordance with the production method of example 1, except that the active material of the first material layer in example 25 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 3 μm.
Comparative example 3
In accordance with the manufacturing method of example 1, except that the first material layer was not formed in comparative example 3, that is, the thickness of the first material layer was 0.
Example 26
In accordance with the production method of example 9, except that the active material of the first material layer in example 26 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm.
Example 27
In accordance with the production method of example 9, except that the active material of the first material layer in example 27 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 50 μm.
Example 28
In accordance with the production method of example 9, except that the active material of the first material layer in example 28 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 40 μm.
Example 29
In accordance with the production method of example 9, except that the active material of the first material layer in example 29 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 30 μm.
Example 30
In accordance with the production method of example 9, except that the active material of the first material layer in example 30 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 20 μm.
Example 31
In accordance with the production method of example 9, except that the active material of the first material layer in example 31 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 15 μm.
Example 32
In accordance with the production method of example 9, except that the active material of the first material layer in example 32 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 10 μm.
Example 33
In accordance with the production method of example 9, except that the active material of the first material layer in example 33 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 5 μm.
Example 34
In accordance with the production method of example 9, except that the active material of the first material layer in example 34 was LiNi1/3Co1/3Mn1/3O2The average particle diameter Dv50 of the particles in the first material layer was 3 μm, and the thickness of the first material layer was 3 μm.
Comparative example 4
In accordance with the manufacturing method of example 9, except that the first material layer was not formed in comparative example 4, that is, the thickness of the first material layer was 0.
Example 35
Consistent with the preparation method of example 1, except that the active material of the first material layer in example 35 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm.
Example 36
Consistent with the preparation method of example 1, except that the active material of the first material layer in example 36 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 50 μm.
Example 37
Consistent with the preparation method of example 1, except that the active material of the first material layer in example 37 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 40 μm.
Example 38
Consistent with the preparation method of example 1, except that the active material of the first material layer in example 38 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 30 μm.
Example 39
Consistent with the preparation method of example 1, except that the active material of the first material layer in example 39 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 20 μm.
Example 40
And implementation ofThe preparation method of example 1 was identical, except that the active material of the first material layer in example 40 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 15 μm.
EXAMPLE 41
Consistent with the preparation method of example 1, except that the active material of the first material layer in example 41 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 10 μm.
Example 42
Consistent with the preparation method of example 1, except that the active material of the first material layer in example 42 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 5 μm.
Example 43
Consistent with the preparation method of example 1, except that the active material of the first material layer in example 43 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 2 μm.
Example 44
Consistent with the preparation method of example 1, except that the active material of the first material layer in example 44 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 1 μm.
Comparative example 5
In accordance with the manufacturing method of example 1, except that the first material layer was not formed in comparative example 5, that is, the thickness of the first material layer was 0.
Example 45
Consistent with the preparation method of example 9, except that the active material of the first material layer in example 45 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm.
Example 46
Consistent with the preparation method of example 9, except that the active material of the first material layer in example 46 was LiFePO4Of 1 atThe particles in one layer had an average particle size Dv50 of 1 μm and the thickness of the first layer was 50 μm.
Example 47
Consistent with the preparation method of example 9, except that the active material of the first material layer in example 47 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 40 μm.
Example 48
Consistent with the preparation method of example 9, except that the active material of the first material layer in example 48 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 30 μm.
Example 49
Consistent with the preparation method of example 9, except that the active material of the first material layer in example 49 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 20 μm.
Example 50
Consistent with the preparation method of example 9, except that the active material of the first material layer in example 50 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 15 μm.
Example 51
Consistent with the preparation method of example 9, except that the active material of the first material layer in example 51 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 10 μm.
Example 52
Consistent with the preparation method of example 9, except that the active material of the first material layer in example 52 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 5 μm.
Example 53
Consistent with the preparation method of example 9, except that the active material of the first material layer in example 53 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 2 μm.
Example 54
Consistent with the preparation method of example 9, except that the active material of the first material layer in example 54 was LiFePO4The average particle diameter Dv50 of the particles in the first material layer was 1 μm, and the thickness of the first material layer was 1 μm.
Comparative example 6
In accordance with the manufacturing method of example 9, except that the first material layer was not formed in comparative example 6, that is, the thickness of the first material layer was 0.
And then testing the needling passing rate of the lithium ion battery.
The needling test method comprises the following steps:
and (3) placing the lithium ion battery in a constant temperature box at 25 ℃, and standing for 30 minutes to keep the temperature of the lithium ion battery constant. The lithium ion battery reaching the constant temperature was charged at a constant current of 0.5C to a voltage of 4.4V, and then charged at a constant voltage of 4.4V to a current of 0.025C. And transferring the fully charged lithium ion battery to a needling tester, keeping the test environment temperature at 25 +/-2 ℃, using a steel nail with the diameter of 4mm to uniformly penetrate through the center of the lithium ion battery at the speed of 30mm/s, keeping for 300s, and recording that the lithium ion battery passes when the lithium ion battery is not fired and is not exploded. And testing 10 lithium ion batteries each time, and taking the number of the lithium ion batteries passing the needling test as an index for evaluating the safety performance of the lithium ion batteries.
Experimental parameters and measurement results for the respective examples and comparative examples are shown in table 1 below.
TABLE 1
Figure BDA0001595446550000161
Figure BDA0001595446550000171
Figure BDA0001595446550000181
As can be seen from comparing examples 1 to 8 with comparative example 1, when the relationship between the thickness T of the first material layer and the average particle diameter Dv50 of the particles in the first material layer satisfies T Dv50 × (1+ a), where 0 ≦ a ≦ 60, the lithium ion battery has a good needle penetration rate, where a is 11 in example 1. When the relation between the thickness T of the first material layer and the average particle diameter Dv50 of the particles in the first material layer does not satisfy T ═ Dv50 × (1+ A), wherein A is greater than or equal to 0 and less than or equal to 60, the lithium ion battery has a poor needle penetration rate.
Referring to examples 9 to 17 and comparative example 2, at this time, a second material layer was formed on the first material layer. When the relation between the thickness T of the first material layer and the average particle diameter Dv50 of the particles in the first material layer satisfies T ═ Dv50 × (1+ A), wherein A is greater than or equal to 0 and less than or equal to 60, the lithium ion battery has a better needling pass rate. When the relationship between the thickness T of the first material layer and the Dv50 of the particles in the first material layer does not satisfy T ═ Dv50 × (1+ a), where 0 ≦ a ≦ 60, the needle penetration rate of the lithium ion battery sharply decreases.
Similarly, referring to examples 17 to 25 and comparative example 3, and examples 26 to 34 and comparative example 4, the active material of the first material layer was LiNi1/3Co1/3Mn1/3O2And Dv50 of the first material layer is 3 μm, when the relationship between the thickness T of the first material layer and the average particle diameter Dv50 of the particles in the first material layer satisfies T ═ Dv50 × (1+ a), wherein a is 0 ≦ a ≦ 60, and the lithium ion battery has a preferable needle penetration rate. When the relationship between the thickness T of the first material layer and the average particle diameter Dv50 of the particles in the first material layer does not satisfy T ═ Dv50 × (1+ a), where 0 ≦ a ≦ 60, the puncture passage rate of the lithium ion battery sharply decreases.
Similarly, referring to examples 35 to 44 and comparative example 5, and examples 45 to 54 and comparative example 6, the active material of the first material layer was LiFePO4And when the Dv50 of the first material layer is 1 μm, when the relationship between the thickness T of the first material layer and the average particle diameter Dv50 of the particles in the first material layer satisfies T ═ Dv50 × (1+ a), where a is 0 ≦ 60, the lithium ion battery has a better needle penetration rate. When the thickness T of the first material layer is equal to that of the first material layerWhen the relation of the average particle diameter Dv50 in (a) does not satisfy T ═ Dv50 × (1+ a), where 0. ltoreq. a.ltoreq.60, the puncture passage rate of the lithium ion battery sharply decreases.

Claims (9)

1. An electrode, comprising:
a current collector;
a first material layer comprising a first active material, the first material layer in contact with the current collector;
a second material layer comprising a second active material, the second material layer in contact with the first material layer;
wherein a relationship between the thickness T of the first material layer and the average particle diameter Dv50 of the first active material in the first material layer satisfies: t is Dv50 x (1+ A), wherein A is more than or equal to 0 and less than or equal to 60, and T is more than or equal to 1 mu m and less than or equal to 60 mu m;
wherein the first material layer and the second material layer both comprise a binder, and the mass percentage of the binder in the first material layer is greater than the mass percentage of the binder in the second material layer.
2. The electrode of claim 1, wherein the current collector is aluminum foil.
3. The electrode of claim 2, wherein the adhesion between the first material layer and the current collector is greater than 50N/m.
4. The electrode according to claim 1, wherein the first active material of the first material layer has an average particle diameter Dv50 ≦ 8 μm.
5. The electrode according to claim 1, wherein the first active material is at least one selected from the group consisting of a metal oxide having a layered structure, a metal oxide having a spinel structure, and a metal oxide having a phosphate type.
6. The electrode of claim 1, wherein the first material layer further comprises a conductive agent, the conductive agent comprising carbon nanotubes.
7. The electrode of claim 1, wherein the second active material is selected from at least one of lithium cobaltate, lithium nickel cobalt manganese, lithium nickel cobalt aluminate, a lithium rich manganese based material, lithium iron phosphate.
8. The electrode of claim 1, wherein the binder in the first material layer is 2-4% by mass.
9. A lithium ion battery comprising an electrode according to any one of claims 1-8.
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