CN111816839A - Lithium ion battery electrode, preparation method and application thereof, and lithium ion battery - Google Patents

Lithium ion battery electrode, preparation method and application thereof, and lithium ion battery Download PDF

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Publication number
CN111816839A
CN111816839A CN202010759017.0A CN202010759017A CN111816839A CN 111816839 A CN111816839 A CN 111816839A CN 202010759017 A CN202010759017 A CN 202010759017A CN 111816839 A CN111816839 A CN 111816839A
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electrode
lithium ion
ion battery
carbonate
active material
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CN111816839B (en
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郭明奎
苏树发
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Svolt Energy 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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 invention relates to the field of lithium ion batteries, and discloses a lithium ion battery electrode, a preparation method and application thereof, and a lithium ion battery. The lithium ion battery electrode comprises a current collector and a plurality of electrode material layers formed on the surface of the current collector, wherein the raw material for forming the electrode material layers contains electrode active material primary particles and/or secondary particles formed by the aggregation of the electrode active materials. The lithium ion battery prepared by the electrode has higher power and energy density.

Description

Lithium ion battery electrode, preparation method and application thereof, and lithium ion battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery electrode with a multi-layer electrode material layer structure formed by electrode active materials with different particle properties, a preparation method and application thereof, and a lithium ion battery
Background
With the development of electric vehicles, the requirements on the performance, especially the power, of the lithium ion battery as a power battery are higher and higher, and the energy density and the power as performance key points in three elements of the lithium ion battery design have great influence on the performance of the electric vehicle. In the prior art, the power can be improved by improving the binding rate of the electrode material to lithium ions, but the higher the binding rate, the smaller the energy density of the electrode material is, so that the power of the high-energy-density lithium ion battery is lower, and the energy density of the high-power lithium ion battery is lower.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provide a lithium ion battery electrode, a preparation method and application thereof and a lithium ion battery.
In order to achieve the above object, a first aspect of the present invention provides a lithium ion battery electrode comprising a current collector and a plurality of electrode material layers formed on a surface of the current collector, a raw material forming the electrode material layers containing primary particles of an electrode active material and/or secondary particles formed by aggregation of the electrode active material, wherein in the plurality of electrode material layers, a proportion of the secondary particles in the raw material forming the electrode material layers gradually increases in order in a direction from near to the current collector to far from the current collector.
The invention provides a lithium ion battery electrode, which comprises a current collector and a plurality of electrode material layers formed on the surface of the current collector, wherein the raw material for forming the electrode material layers contains electrode active material primary particles and/or secondary particles formed by the aggregation of the electrode active materials, and in the electrode material layers for multiple times, the proportion of the secondary particles in the raw material for forming the electrode material layers is gradually increased in the direction from the current collector to the direction far away from the current collector.
Preferably, in the adjacent electrode material layers, the median particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in the upper layer is smaller than the median particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in the lower layer by 4 μm or more; more preferably, in the adjacent electrode material layers, the electrode active material primary particles of the raw material forming the electrode material layer in the upper layer have a median particle diameter smaller by 6 to 12 μm than that of the electrode active material primary particles of the raw material forming the electrode material layer in the lower layer.
Preferably, the particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in close contact with the current collector is 15 to 30 μm.
Preferably, the primary particle diameter of the electrode active material of the raw material forming the electrode material layer in the electrode material layer farthest from the current collector is 1 to 10 μm.
Preferably, the electrode material layer is 2-5 layers.
Preferably, the electrode material layer is 2 layers, and when the electrode material layer in close contact with the current collector is a first layer, 80% or more of the first layer is formed of the electrode active material primary particles, and 80% or more of the second layer is formed of the secondary particles.
More preferably, 90% or more of the first layer is formed of the electrode active material primary particles, and 90% or more of the second layer is formed of the secondary particles.
Preferably, the primary particles of the electrode active material have a particle size of 1 to 30 μm.
Preferably, the secondary particles have a particle size of 5 to 15 μm.
Preferably, the electrode active material is a cathode active material or an anode active material.
Preferably, the cathode active material is one or more of lithium cobaltate, lithium manganate, lithium nickel cobalt aluminate and lithium iron phosphate.
Preferably, the anode active material is one or more of graphite, silicon dioxide, an aluminum-based alloy, a tin-based alloy, and a silicon-based alloy.
In a second aspect, the present invention provides a method for preparing an electrode for a lithium ion battery, which comprises the steps of mixing a binder, a conductive agent, and a solvent with two or more electrode active materials having different median particle diameters of primary particles and different proportions of formed secondary particles, respectively, then coating the mixture on a current collector in layers, and drying and rolling the coated current collector.
In a third aspect of the present invention, a lithium ion battery is provided, which contains a cathode, an anode, an organic electrolyte and a separator, wherein the organic electrolyte includes a lithium salt and an organic solvent, and the cathode and/or the anode are/is the lithium ion battery electrode provided by the present invention.
Preferably, the diaphragm is one or more of a polyolefin diaphragm, a polyamide diaphragm, a polysulfone diaphragm, a polyphosphazene diaphragm, a polyethersulfone diaphragm, a polyetheretherketone diaphragm, a polyetheramide diaphragm and a polyacrylonitrile diaphragm; more preferably, the separator is one or more of a polypropylene separator, a polyethylene separator, and a polyamide separator.
Preferably, the lithium salt is LiPF6、LiBF4、LiClO4、LiBOB、LiDFOB、LiN(SO2CF3)2、LiN(SO2C2F5)2、LiC(SO2CF3)3And LiN (SO)2F)2One or more of; more preferably, the lithium salt is LiPF6、LiBF4And LiClO4One or more of (a).
Preferably, the organic solvent is a carbonate compound.
Preferably, the carbonate-based compound is a cyclic carbonate and/or a linear carbonate.
Preferably, the cyclic carbonate is one or more of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate and fluoroethylene carbonate.
Preferably, the linear carbonate is one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate and propyl methyl carbonate.
More preferably, the organic solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate.
The fourth aspect of the invention provides the application of the lithium ion battery electrode provided by the invention in the preparation of a lithium ion battery.
According to the present invention, in the electrode provided by the present invention, the ratio of secondary particles formed in the raw material forming the electrode material layer farther from the current collector is higher, so that the lithium ion diffusion performance is good, and the ratio of secondary particles formed in the raw material forming the electrode material layer closer to the current collector is smaller, so that the battery energy density is high.
The lithium ion battery prepared by the lithium ion battery provided by the invention has higher energy density and power.
Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
In the present invention, when the contrary description is not given, the "upper layer" refers to a layer attached to the layer and located in a direction away from the current collector in the multilayer electrode material, and the "lower layer" refers to a layer attached to the layer and located in a direction close to the current collector in the multilayer electrode material. The "upper layer" refers to a layer in the multilayer electrode material that is relatively far from the current collector, and the "lower layer" refers to a layer in the multilayer electrode material that is relatively close to the current collector.
The invention provides a lithium ion battery electrode, which comprises a current collector and a plurality of electrode material layers formed on the surface of the current collector, wherein the raw material for forming the electrode material layers contains electrode active material primary particles and/or secondary particles formed by the aggregation of the electrode active materials, and in the electrode material layers for multiple times, the proportion of the secondary particles in the raw material for forming the electrode material layers is gradually increased in the direction from the current collector to the direction far away from the current collector.
The inventor of the present invention has surprisingly found that, by adopting the design of the multilayer electrode material layers, when the multilayer electrode material layers are sequentially and gradually increased in the direction from the current collector to the current collector according to the proportion of the secondary particles in the raw material, the obtained lithium ion battery has high energy density and power.
According to the present invention, the smaller the particle diameter of the electrode active material particles, the smaller the lithium ion solid phase diffusion path, the better the kinetic properties thereof, and the higher the battery power. However, because of the reduction of active sites, the number of sites for lithium intercalation is small, which leads to a reduction in the unit energy density of the material and a reduction in the battery capacity. The larger the particle diameter of the electrode active material particles, the longer the lithium ion solid phase diffusion path, the poorer the kinetic properties thereof, and the lower the battery power. However, due to the increase of active sites, the number of positions for lithium intercalation is large, the unit energy density of the material is improved, and the battery capacity is improved.
According to the present invention, from the viewpoint of balancing the difficulty of the manufacturing process, the power of the battery, and the energy density, in the adjacent electrode material layers, it is preferable that the median particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in the previous layer is smaller than the median particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in the next layer by 4 μm or more; more preferably, the median particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in the upper layer is smaller than the median particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in the lower layer by 6 to 12 μm.
Preferably, the particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in the electrode material layer closely attached to the current collector is 15 to 30 μm; more preferably, the particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in close contact with the current collector is 18 to 25 μm. By setting the particle diameter of the primary particles of the electrode active material of the raw material forming the electrode material layer in the electrode material layer to which the current collector is adhered within the above range, the amount of lithium intercalation sites at the lower layer is increased, and the unit mass capacity of the electrode material is improved.
Preferably, the primary particle diameter of the electrode active material of the raw material forming the electrode material layer in the electrode material layer farthest from the current collector is 1 to 10 μm; more preferably, the primary particle diameter of the electrode active material of the raw material forming the electrode material layer in the electrode material layer farthest from the current collector is 3 to 8 μm. The particle size of the primary particles of the electrode active material of the raw material forming the electrode material layer in the electrode material layer which is farthest away from the current collector is within the range, so that the solid phase diffusion coefficient of the upper layer is improved, and the power of the battery is increased.
In the present invention, the number of layers as the anode material layer in the multi-layered anode material layer is preferably 2 to 5 layers from the viewpoint of balancing the properties of the resulting battery and the complexity of the manufacturing process. Examples thereof include: 2 layers, 3 layers, 4 layers and 5 layers.
In a preferred embodiment of the present invention, the plurality of electrode material layers are 2 layers, and when the electrode material layer in close contact with the current collector is a first layer, 80% or more of the first layer is formed of the electrode active material primary particles, and 80% or more of the second layer is formed of the secondary particles; preferably, 90% or more of the first layer is formed of the electrode active material primary particles, and 90% or more of the second layer is formed of the secondary particles; more preferably, 98% or more of the first layer is formed of the electrode active material primary particles, and 90% or more of the second layer is formed of the secondary particles.
According to the invention, when the primary particle size of the electrode active material is smaller, the solid-phase diffusion performance of lithium ions is improved, but when the particle size is too small, the distribution is uneven, and the processing difficulty is increased. From the viewpoint of balancing performance and processing difficulty, it is preferable that the primary particles of the electrode active material have a particle diameter of 1 to 30 μm; more preferably, the primary particles of the electrode active material have a particle size of 3 to 8 μm.
According to the present invention, when the secondary particle diameter of the electrode active material is large, the number of active sites can be increased, and the unit energy density of the material can be increased, but when the secondary particle diameter is too large, the secondary particle is easily broken during charging and discharging, and the long-term capacity retention rate is affected, and from the viewpoint of balancing the battery capacity and the storage performance, the secondary particle preferably has a particle diameter of 5 to 15 μm; more preferably, the secondary particles have a particle size of 7 to 14 μm.
According to the present invention, the electrode active material is a cathode active material or an anode active material.
According to the present invention, the cathode active material is not particularly limited, and may be a cathode active material generally used in a lithium ion battery, and preferably, the cathode active material is one or more of lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, and lithium iron phosphate; more preferably, the cathode active material is one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate and lithium iron phosphate.
In a particularly preferred embodiment of the invention, the cathode active material is lithium nickel cobalt manganese oxide, for example of which the composition may consist of LiNi0.5Co0.2Mn0.3O2And (4) showing.
According to the present invention, the anode active material is not particularly limited, and may be an anode active material generally used in a lithium ion battery, and preferably, the anode active material is one or more of graphite, soft carbon, hard carbon, silicon, silica, an aluminum-based alloy, a tin-based alloy, and a silicon-based alloy; more preferably, the anode active material is one or more of graphite, soft carbon, and silica.
In a second aspect of the present invention, there is provided a method for producing an electrode for a lithium ion battery, comprising the steps of mixing a binder, a conductive agent and a solvent with two or more electrode active materials having different median particle diameters of primary particles and forming ratios of secondary particles, respectively, and then coating the mixture layer by layer on a current collector, and drying and pressing the mixture, wherein the ratio of the secondary particles is gradually increased in the raw materials forming the electrode material layer in the plurality of electrode material layers in the direction from the current collector toward the current collector.
In the method for producing an electrode for a lithium ion battery of the present invention, the electrode active material is as described above, and will not be described again here.
According to the present invention, the binder is not particularly limited, and a binder generally used in a lithium ion battery may be used, and may be one or more of styrene-butadiene rubber, sodium carboxymethyl cellulose, and polyvinylidene fluoride, for example.
According to the present invention, the conductive agent is not particularly limited, and a conductive agent generally used in a lithium ion battery may be used, and may be, for example, one or more of carbon black, conductive graphite, carbon nanotubes, carbon nanofibers, and graphene; preferably, the conductive agent is carbon black or conductive graphite.
In addition, the solvent may be N-methyl-2 pyrrolidone or water, and the amount of the solvent may be 0.3 to 3 times the total weight of the anode active material, the conductive agent, and the binder.
According to the present invention, the layered coating method is not particularly limited as long as a plurality of electrode material layers can be formed, and for example, a multi-cavity or multi-die one-step coating method may be used, or a single-cavity or single-die one-step coating method may be used in which a plurality of layers are coated.
According to the present invention, the drying conditions are not particularly limited, and drying conditions generally used in the preparation of lithium ion battery electrodes may be used, and for example, drying at 85 to 105 ℃ for 0.5 to 2 hours may be performed.
According to the invention, the pressing is preferably a rolling. The rolling conditions are not particularly limited, and rolling conditions generally used in the preparation of lithium ion battery electrodes may be employed, and from the viewpoint of forming good pores in the multilayer electrode material layer, the rolling conditions are preferably a rolling pressure of 1-2T, a roll diameter used for rolling of 500-1000mm, a rolling temperature of 25-45 ℃ and a rolling speed of 5-15 m/min. The number of rolling is preferably a plurality of times of rolling, and more preferably a second time of rolling.
In a third aspect of the present invention, a lithium ion battery is provided, which contains a cathode, an anode, an organic electrolyte and a separator, wherein the organic electrolyte includes a lithium salt and an organic solvent, and the cathode and/or the anode are/is the lithium ion battery electrode provided by the present invention.
According to the present invention, the separator is not particularly limited, and may be a separator generally used in a lithium ion battery, and preferably, the separator is one or more of a polyolefin-based separator, a polyamide-based separator, a polysulfone-based separator, a polyphosphazene-based separator, a polyethersulfone-based separator, a polyetheretherketone-based separator, a polyetheramide-based separator, and a polyacrylonitrile-based separator; more preferably, the separator is one or more of a polypropylene separator, a polyethylene separator, and a polyamide separator.
According to the present invention, the lithium salt is not particularly limited, and may be a lithium salt generally used in a lithium ion battery, and is preferably a lithium saltThe lithium salt is LiPF6、LiBF4、LiClO4、LiBOB、LiDFOB、LiN(SO2CF3)2、LiN(SO2C2F5)2、LiC(SO2CF3)3And LiN (SO)2F)2One or more of; more preferably, the lithium salt is LiPF6、LiBF4And LiClO4One or more of (a).
In a particularly preferred embodiment of the invention, the lithium salt is LiPF6。
The concentration of the lithium salt is not particularly limited, and may be a concentration generally used in a lithium ion battery, and preferably, the concentration of the lithium salt is 0.8 to 1.3 mol/L; more preferably, the concentration of the lithium salt is 0.9 to 1.2 mol/L.
According to the present invention, the organic solvent is not particularly limited, and may be an organic solvent generally used in a lithium ion battery, and preferably, the organic solvent is a carbonate compound, and the carbonate compound is a cyclic carbonate and/or a linear carbonate.
Preferably, the cyclic carbonate is one or more of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate and fluoroethylene carbonate.
Preferably, the linear carbonate is one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate and propyl methyl carbonate.
More preferably, the organic solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate.
In a particularly preferred embodiment of the present invention, the organic solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate, and the mass ratio of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate is 1: 1: 1.
according to the present invention, the lithium ion battery can be prepared in a manner commonly used in the art, for example, the following may be mentioned: and mixing and coating a cathode/anode active substance, a conductive material and a binder on metal to prepare a cathode/anode plate, sequentially laminating or winding the anode plate, a diaphragm and the cathode plate into a bare cell, putting the bare cell into a shell, baking, injecting an organic electrolyte into the obtained cell, and performing formation and sealing to obtain the lithium ion battery.
The fourth aspect of the invention provides the application of the lithium ion battery electrode in the preparation of a lithium ion battery.
In the electrode provided by the invention, the proportion of the secondary particles formed in the raw material of the electrode material layer which is farther away from the current collector is higher, so that the lithium ion diffusion performance is good, and the proportion of the secondary particles formed in the raw material of the electrode material layer which is closer to the current collector is smaller, so that the energy density of the battery is high.
The lithium ion battery prepared by using the lithium ion battery provided by the invention has higher energy density and power.
Examples
The present invention will be described in detail below by way of examples, but the present invention is not limited to the following examples.
In the following examples, the cathode LiNi0.5Co0.2Mn0.3O2The powder particle C-1 is purchased from Qingdao Gankuo Kagaku New Material Co., Ltd, and has a trade name of QY-901, and the cathode LiNi0.5Co0.2Mn0.3O2The powder particle C-2 was purchased from Qingdao Qianjin Gaokou New Material Co., Ltd under the designation QY-902. The anode artificial graphite powder particles A-1 are purchased from Guangdong Kaiki New energy science and technology Co., Ltd under the brand name AML400, and the anode artificial graphite powder particles A-2 are purchased from Guangdong Kaiki New energy science and technology Co., Ltd under the brand name AML 600.
The appearance and particle size of the powder particles were measured by SEM, the median particle diameters of the primary particles of A-1, A-2, C-1 and C-2 were 2 μm, 12 μm, 4 μm and 14 μm, respectively, the proportions of the secondary particles were 95%, 2%, 90% and 1%, respectively, and the median particle diameters of the secondary particles were 10 μm, 13 μm, 16 μm and 18 μm, respectively.
In the following examples, the membrane was a 16 μm thick polyethylene membrane (available from Shanghai Enjie New Material science and technology Co., Ltd., model No. ND9), and the organic electrolysis was carried outThe liquid is LiPF with a concentration of 1.12mol/L6The weight ratio of (1): 1:1 mixed solution of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate
Example 1
Preparation of cathode slurry
Reacting cathode LiNi0.5Co0.2Mn0.3O2The powder particles C-1, a binder polyvinylidene fluoride (purchased from Arkema, France, type HSV900) and a conductive agent carbon black (purchased from Yirui graphite & carbon company, Switzerland, type Super P-Li) are mixed according to the proportion of 95:3:2 by weight, 43 parts by weight of N-methyl-2 pyrrolidone is added into 100 parts by weight of the mixture, and the mixture is stirred and mixed to obtain cathode slurry C-1.
Reacting cathode LiNi0.5Co0.2Mn0.3O2The powder particles C-2, a binder polyvinylidene fluoride (purchased from Arkema, France, type HSV900) and a conductive agent carbon black (purchased from Yirui graphite & carbon company, Switzerland, type Super P-Li) are mixed according to the proportion of 95:3:2 by weight, 43 parts by weight of N-methyl-2 pyrrolidone is added into 100 parts by weight of the mixture, and the mixture is stirred and mixed to obtain cathode slurry C-2.
Preparation of anode slurry
Anode graphite particles a-1 were mixed with styrene-butadiene rubber (model SN307 available from Nippon a & L), sodium carboxymethylcellulose, and carbon black (model Super P-Li available from yirui graphite & carbon, switzerland) as a binder in a ratio of 95:2.5:1.5:1 by weight, 82 parts by weight of water was added to 100 parts by weight of the mixture, and the mixture was stirred and mixed to obtain anode slurry a-1.
Anode graphite particles a-2 were mixed with styrene-butadiene rubber (model SN307 available from Nippon a & L), sodium carboxymethylcellulose, and carbon black (model Super P-Li available from yirui graphite & carbon, switzerland) as a binder in a ratio of 95:2.5:1.5:1, 82 parts by weight of water was added to 100 parts by weight of the mixture, and the mixture was stirred and mixed to obtain anode slurry a-2.
(3) Preparation of cathode plate
A double-cavity coating die head (manufactured by Mannster, model number BG 01A-400-30) was usedB) The cathode slurry C-1 is introduced into the upper chamber and the cathode slurry C-2 is introduced into the lower chamber. Then the upper cavity slurry and the lower cavity slurry were coated on one side of the substrate to a total coating weight of 115g/m2The upper and lower layers are coated on both sides of a 12-micron aluminum foil substrate in a weight ratio of 1:1, and then dried, rolled, die-cut and punched into cathode pole pieces.
(4) Preparation of anode plate
The anode slurry A-1 was passed into the upper chamber and the anode slurry A-2 was passed into the lower chamber using a twin chamber coating die (model BG01A-400-30B, manufactured by Mannster). Then the upper cavity slurry and the lower cavity slurry are coated according to the total single-side coating weight of 65g/m2The upper layer and the lower layer are uniformly coated on two sides of a copper foil base material with the thickness of 8 mu m according to the coating weight ratio of 1:1, and then the anode pole piece is formed by drying, rolling, die cutting and punching.
(5) Preparation of lithium ion battery
And (3) placing the pole pieces (total 141 layers) layer by layer according to the sequence of the anode pole piece, the diaphragm, the cathode pole piece, the diaphragm and the anode pole piece to obtain a naked electric core, then putting the naked electric core into a shell, baking the naked electric core, injecting organic electrolyte, and performing formation and sealing to obtain the lithium ion battery.
Examples 2 to 11, comparative example 1
A battery cell was fabricated in the same manner as in example 1, except that the types of the slurry used for the upper and lower layers and the coating weight ratio of the upper and lower layers were as shown in table 1 below.
TABLE 1
Figure BDA0002612531690000121
Test example 1
The lithium ion batteries obtained in examples 1 to 11 and comparative example 1 were charged at a constant current and a constant voltage of 0.33C to 4.2V at room temperature (25 ℃) using a charge and discharge test chamber (manufactured by Shenzhen Xinrui New energy science and technology Co., Ltd., model No. MACCOR S4000H), and were discharged at 0.33C to 2.8V after being left for 10min, and the discharge capacities were measured.
The internal resistance of the lithium ion batteries of comparative examples and examples was measured using a resistance tester (model No. SB2230, manufactured by Shanghai BiCMOS instruments Ltd.).
The weight of the lithium ion batteries of comparative examples and examples was measured using an electronic scale (model number LP7680, manufactured by beijing langke business-oriented weighing apparatus ltd.), and the energy density of the weight of the lithium ion batteries was calculated according to the following formula:
gravimetric energy density (Wh/kg) ═ discharge capacity × discharge plateau voltage/cell weight.
The results are shown in Table 2.
TABLE 2
Capacity (Ah) Internal resistance (m omega) Energy Density (Wh/kg)
Example 1 162.9 0.56 238
Example 2 162.4 0.55 237
Example 3 162.3 0.55 237
Example 4 162.3 0.54 237
Example 5 162.3 0.54 237
Example 6 153.9 0.52 225
Example 7 159.6 0.55 233
Example 8 152.8 0.52 223
Example 9 158.2 0.53 231
Example 10 160.1 0.55 235
Example 11 159.3 0.53 233
Comparative example 1 151.3 0.51 221
Test example 2
The lithium ion batteries obtained in the comparative examples and examples were charged at room temperature (25 ℃) at a constant current and a constant voltage of 0.33C rate to 4.2V, then discharged at a 1C rate for 30min to a state of charge of 50%, and then discharged at a 4C rate for 10S, and the voltage values before and after 4C discharge were measured. The discharge dc impedance (m Ω) was calculated as follows:
discharge dc impedance (m Ω) — (voltage before discharge-voltage after discharge)/discharge current.
The discharge power (W) was calculated as follows:
discharge power (W) is discharge current × voltage after discharge.
The lithium ion batteries obtained in the comparative example and the example are charged to 4.2V at room temperature at a constant current and constant voltage of 0.33C, then discharged for 30min at a rate of 1C until the state of charge is 50%, charged for 10S at a current of 2C, and the voltage values before and after charging are recorded. The charging dc impedance (m Ω) is calculated as follows:
charging dc impedance (m Ω) — (voltage after charging-voltage before charging)/charging current.
The charging power (W) is calculated as follows:
the charging power (W) is (upper limit voltage-voltage before charging) × voltage before charging/charging dc impedance.
The results are shown in Table 3.
TABLE 3
Figure BDA0002612531690000141
Note: DCR refers to DC impedance
Test example 3
At room temperature (25 ℃), the lithium ion batteries obtained in comparative examples and examples were charged to 4.2V at a constant current and constant voltage at a rate of 0.33C, left for 5min, and then discharged to 2.8V at a rate of 0.33C, and the discharge capacity was measured, and the capacity retention ratio (%) was calculated as follows for one cycle:
capacity retention (%) — current discharge capacity/initial discharge capacity.
And repeatedly circulating until the capacity retention rate is lower than 80 percent to obtain 80 percent capacity circulation times.
And (3) charging the lithium ion batteries obtained in the comparative example and the example to 4.2V at room temperature by adopting a 0.33C constant current and constant voltage, then placing the battery cell in a high-temperature 45 ℃ thermostat, storing for 500 days, and measuring the capacity retention rate on the 500 th day.
The results are shown in Table 4.
TABLE 4
80% capacity cycle number Capacity retention at day 500
Example 1 2881 84
Example 2 2888 84
Example 3 2907 85
Example 4 2901 85
Example 5 2896 85
Example 6 2679 78
Example 7 2757 81
Example 8 2666 78
Example 9 2677 78
Example 10 2772 82
Example 11 2653 78
Comparative example 1 2627 77
The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.

Claims (10)

1. A lithium ion battery electrode, it includes the current collector and forms the multilayer electrode material layer on the surface of the current collector, the raw materials forming this electrode material layer contain electrode active material primary particle, and/or the said electrode active material gathers the secondary particle formed, characterized by that, in the said electrode material layer of many times, in the direction from getting close to the current collector to keeping away from the current collector, in forming the raw materials of the electrode material layer, the proportion of the secondary particle increases gradually in order.
2. The lithium ion battery electrode according to claim 1, wherein in adjacent electrode material layers, the median particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in the upper layer is smaller than the median particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in the lower layer by 4 μm or more, preferably 6 to 12 μm;
preferably, the particle diameter of the electrode active material primary particles of the raw material forming the electrode material layer in the electrode material layer closely attached to the current collector is 15 to 30 μm;
preferably, the primary particle diameter of the electrode active material of the raw material forming the electrode material layer in the electrode material layer farthest from the current collector is 1 to 10 μm.
3. A lithium-ion battery electrode according to claim 1, wherein the electrode material layer is 2-5 layers.
4. The lithium ion battery electrode according to claim 1, wherein the electrode material layer is 2 layers, and when the electrode material layer in close contact with the current collector is a first layer, 80% or more of the first layer is formed of the electrode active material primary particles, and 80% or more of the second layer is formed of the secondary particles;
preferably, 90% or more of the first layer is formed of the electrode active material primary particles, and 90% or more of the second layer is formed of the secondary particles.
5. The lithium ion battery electrode according to any one of claims 1 to 4, wherein the primary electrode active material particles have a particle diameter of 1 to 30 μm;
preferably, the secondary particles have a particle size of 5 to 15 μm.
6. The lithium ion battery electrode according to claim 1, wherein the electrode active material is a cathode active material or an anode active material;
preferably, the cathode active material is one or more of lithium cobaltate, lithium manganate, lithium nickel cobalt aluminate and lithium iron phosphate;
preferably, the anode active material is one or more of graphite, silicon dioxide, an aluminum-based alloy, a tin-based alloy, and a silicon-based alloy.
7. A preparation method of an electrode of a lithium ion battery is characterized by comprising the steps of respectively mixing a binder, a conductive agent and a solvent with two or more electrode active materials with different median particle diameters of primary particles and different proportions of formed secondary particles, then coating the mixture on a current collector in a layering manner, and drying and pressing the mixture, wherein the proportions of the secondary particles in raw materials forming electrode material layers in a plurality of electrode material layers are gradually increased in sequence from the direction close to the current collector to the direction far away from the current collector.
8. A lithium ion battery comprising a cathode, an anode, an organic electrolyte comprising a lithium salt and an organic solvent, and a separator, wherein the cathode and/or the anode is the lithium ion battery electrode of any one of claims 1 to 6.
9. The lithium ion battery of claim 7, wherein the membrane is one or more of a polyolefin membrane, a polyamide membrane, a polysulfone membrane, a polyphosphazene membrane, a polyethersulfone membrane, a polyetheretherketone membrane, a polyetheramide membrane, and a polyacrylonitrile membrane;
preferably, the membrane is one or more of a polypropylene membrane, a polyethylene membrane and a polyamide membrane;
preferably, the lithium salt is LiPF6、LiBF4、LiClO4、LiBOB、LiDFOB、LiN(SO2CF3)2、LiN(SO2C2F5)2、LiC(SO2CF3)3And LiN (SO)2F)2One or more of;
preferably, the lithium salt is LiPF6、LiBF4And LiClO4One or more of;
preferably, the organic solvent is a carbonate compound;
preferably, the carbonate compound is a cyclic carbonate and/or a linear carbonate;
preferably, the cyclic carbonate is one or more of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate and fluoroethylene carbonate;
preferably, the linear carbonate is one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate and propyl methyl carbonate;
preferably, the organic solvent is a mixture of ethylene carbonate, diethyl carbonate and ethyl methyl carbonate.
10. Use of a lithium ion battery electrode according to any of claims 1 to 6 for the preparation of a lithium ion battery.
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