CN113161510A - Electrode pole piece, preparation method thereof and lithium ion battery - Google Patents

Electrode pole piece, preparation method thereof and lithium ion battery Download PDF

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Publication number
CN113161510A
CN113161510A CN202110302510.4A CN202110302510A CN113161510A CN 113161510 A CN113161510 A CN 113161510A CN 202110302510 A CN202110302510 A CN 202110302510A CN 113161510 A CN113161510 A CN 113161510A
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electrode
active material
material layer
electrode active
carbon
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张淇
莫玉迪
邱俊敏
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Sunwoda Electric Vehicle Battery Co Ltd
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Sunwoda Electric Vehicle Battery 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The application discloses an electrode plate, a preparation method thereof and a lithium ion battery. The design of the electrode plate is suitable for preparing the thick electrode, wherein the carbon-based porous conductive material layer has a porous structure and can be used as a framework, the mechanical property of the carbon-based porous conductive material layer is excellent, the processing property of the thick electrode can be improved, and the structural stability of the electrode plate is improved; the porous structure of the conductive network can improve the power performance of the electrode plate, can improve the long-term cycle performance of the battery when applied to the lithium ion battery, can reduce the polarization phenomenon of the electrode plate, optimizes the rate performance of the battery, and improves the energy density of the lithium ion battery.

Description

Electrode pole piece, preparation method thereof and lithium ion battery
Technical Field
The application relates to the technical field of batteries, in particular to an electrode plate, a preparation method thereof and a lithium ion battery.
Background
With the development of lithium ion batteries, the trend that the lithium ion batteries enter the automobile field to become main power components of automobiles is inevitable, which promotes the continuous and rapid development of the lithium ion batteries, and further promotes the technical innovation, so that the lithium ion batteries have longer driving mileage and gradually replace fuel engines. At present, the surface density of an electrode is improved and the inactive material component ratio is reduced by optimizing the electrode structure so as to improve the battery capacity to the maximum extent, and the improvement of the energy density plays a positive role in improving the endurance mileage for the limited automobile space. The conventional manufacturing process for manufacturing the electrode by increasing the thickness of the coating can effectively increase the energy density, but brings many disadvantages, on one hand, the resistance of the lithium ions to longitudinal transmission in the pole piece is increased, and on the other hand, the structural stability of the electrode is deteriorated. Therefore, it is necessary to develop an electrode pad to improve the above problems.
Disclosure of Invention
The present application is directed to solving at least one of the problems in the prior art. Therefore, the application provides an electrode plate, a preparation method thereof and a lithium ion battery.
In a first aspect of the present application, there is provided an electrode sheet, comprising:
a current collector;
an electrode active material layer disposed on at least one surface of the current collector; the electrode active material layer comprises a first electrode active material layer, a carbon-based porous conductive material layer and a second electrode active material layer which are sequentially stacked.
The electrode piece according to the embodiment of the application has at least the following beneficial effects: the electrode plate is provided with an electrode active material layer comprising a first electrode active material layer, a carbon-based porous conductive material layer and a second electrode active material layer which are arranged in a stacked manner on at least one surface of a current collector. The electrode is suitable for the preparation of thick electrodes, wherein the carbon-based porous conductive material layer has a porous structure and can be used as an intermediate interlayer to improve the overall porosity of an electrode pole piece and improve the infiltration efficiency of electrolyte, and the carbon-based porous conductive material layer is a higher conductive material and can improve the conductivity of the electrode pole piece; the carbon-based porous conductive material with the porous structure can form a framework, has excellent mechanical properties, can improve the processing performance of a thick electrode, and increases the structural stability of an electrode plate; the porous structure of the lithium ion battery can form a conductive network, the power performance of an electrode pole piece can be improved, and the long-term cycle performance of the lithium ion battery can be improved when the lithium ion battery is applied to the lithium ion battery; in addition, the method can reduce the polarization phenomenon of the electrode plate, optimize the rate capability of the battery, improve the energy density of the lithium ion battery and improve the performance of the battery.
According to some embodiments of the present application, the carbon-based porous conductive material layer is at least one of carbon paper, carbon cloth, and carbon felt, and preferably carbon paper is used. Compared with the traditional ceramic and metal porous materials, the carbon-based porous conductive material layer can overcome the problems that the ceramic material has poor conductivity and can reduce the performance of the battery, and the electrochemical reaction of the first electrode active material layer and the second electrode active material layer can be influenced due to the close functions of the metal material and the current collector.
According to some embodiments of the present application, the carbon paper has an areal density of 3 to 15g/m2The thickness is 25 to 75 μm, and the fiber diameter is 0.25 to 1.00 μm. Preferably, the surface density of the carbon paper is 5-15 g/m2The thickness is 25 to 75 μm, and the fiber diameter is 0.25 to 0.50 μm. The thickness is specifically the thickness of the carbon paper in the direction perpendicular to the joint surface with the current collector; the fiber diameter is specifically the diameter of the fibers constituting the carbon paper. The area density, thickness and fiber diameter of the carbon paper generally need to be controlled in the above ranges, and if the area density is too low, the thickness is too low and the fiber diameter is too thin, the mechanical property of the carbon paper is influenced, and further the processing property is influenced; if the carbon paper with the surface density, the thickness and the fiber density larger than the reference values is adopted, the occupation ratio of the interlayer carbon paper in the electrode active material layer is too large, and the electrode piece is reducedEnergy density.
According to some embodiments of the present application, the material of the first electrode active material layer includes a first electrode active material, a first binder, and a first conductive agent; the material of the second electrode active material layer includes a second electrode active material, a second binder, and a second conductive agent; the first electrode active material and the second electrode active material are positive electrode active materials of a lithium ion battery or negative electrode active materials of the lithium ion battery. Wherein, the material of the first electrode active material layer and the material of the second electrode active material layer can be the same or different; in the actual preparation process, the types and the proportions of the materials can be changed and adjusted according to requirements so as to change the porosity and the conductivity of the electrode plate. Specifically, the material of the first electrode active material layer may include 85 to 96 wt% of a first electrode active material, 1.5 to 10 wt% of a first binder, and 1.5 to 5 wt% of a first conductive agent, and the material of the second electrode active material layer may include 85 to 96 wt% of a second electrode active material, 1.5 to 10 wt% of a second binder, and 1.5 to 5 wt% of a second conductive agent.
According to some embodiments of the present application, the first electrode active material and the second electrode active material are lithium ion electrode negative electrode active materials, and the material of the first electrode active material layer further includes a first thickener, and the material of the second electrode active material further includes a second thickener. The viscosity of the slurry can be adjusted in the process of preparing the electrode active material layer by adding the thickening agent, so that the coating processing capacity of the slurry is improved. The first thickener and the second thickener can be sodium carboxymethylcellulose (CMC); the mass percentage of the first thickening agent in the material of the first electrode active material layer and the mass percentage of the second thickening agent in the second electrode active material layer are generally 1-3%, and the addition amount of the thickening agents is controlled in the above range, so that the viscosity of the slurry for preparing the electrode active material layer is controlled in the range of 3000-5000 mPa · s, and the processing capacity of slurry coating is improved.
According to some embodiments of the present application, the lithium ion battery positive active material is selected from at least one of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium manganese phosphate, lithium vanadium phosphate, lithium nickel manganate, and ternary nickel cobalt manganese materials;
the negative active material of the lithium ion battery is selected from at least one of natural graphite, artificial graphite, metallic lithium, silicon-based alloy, silicon-based oxide, tin-based alloy, tin-based oxide, lithium titanate, titanium dioxide, tin oxide, iron oxide and cobalt oxide;
the first binder and the second binder are selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, polyacrylate multipolymer and modified styrene-butadiene rubber (SBR);
the first conductive agent and the second conductive agent are selected from at least one of graphite, conductive carbon black, acetylene black, activated carbon, carbon nanotubes, carbon fibers and graphene.
According to some embodiments of the present application, the electrode active material layer is partially disposed on both side surfaces of the current collector. Through the equal electrode active material layer that sets up in the both sides surface of mass flow body, be favorable to guaranteeing battery stable performance, reduce the inefficacy risk, avoid the inhomogeneous battery performance that causes in mass flow body both sides unstable, the problem that the inefficacy risk improves.
According to some embodiments of the present application, the thickness of the electrode plate is generally controlled to be 250-400 μm. Through controlling the thickness of the electrode plate in the range, the energy density can be improved on the premise of ensuring the dynamic performance by combining the technology of the application.
In a second aspect of the present application, there is provided a method for preparing any one of the electrode sheets provided in the first aspect of the present application, including the following steps:
s1, dissolving the material of the first electrode active material layer in a first solvent to prepare first electrode slurry; dissolving the material of the second electrode active material layer in a second solvent to prepare second electrode slurry;
s2, coating the first electrode slurry on the surface of the current collector to form a first electrode slurry layer;
s3, arranging a carbon-based porous conductive material layer on the surface, deviating from the current collector, of the first electrode slurry layer, and then drying;
and S4, coating the second electrode slurry on the carbon-based porous conductive material layer, and then drying and rolling.
The preparation method of the electrode piece according to the embodiment of the application has at least the following beneficial effects: the preparation method comprises the steps of adding a coating process design of a carbon-based porous conductive material layer on at least one surface of a current collector, specifically, coating and arranging a first electrode slurry layer on the surface of the current collector, then arranging the carbon-based porous conductive material layer on the first electrode slurry layer, drying, then coating and arranging a second electrode slurry layer on the carbon-based porous conductive material layer, and further drying and rolling to obtain the electrode piece. Generally, the increase of the coating thickness can narrow the rolling process window, so that the design compaction is difficult to achieve, and the design of the coating process by adding the carbon-based porous conductive material layer can increase the processing window and reduce the adverse effect of the coating thickness on the rolling process; meanwhile, the porosity of the two-time coating interface can be increased, and the electrolyte wetting effect of the first electrode active material layer formed by drying the first electrode slurry layer is improved; the conductivity of the two coating interfaces of the electrode can be increased, and the electron conduction capability from a second electrode active material layer correspondingly formed on the second electrode slurry layer to the current collector is improved; in addition, the mechanical property of the electrode plate can be enhanced, and when the electrode plate is applied to a lithium ion battery, the long-term cycle performance of the battery can be improved; the dynamic performance of the electrode plate is improved, the polarization phenomenon of the electrode plate is reduced, and the rate performance of the battery is optimized. The electrode pole piece design process is suitable for preparing the thick electrode, the controllable adjustment of the performance of the thick electrode can be realized by adding the carbon-based porous conductive material layer technology in the two coating processes, on one hand, the uniform stress of the thick electrode in the rolling pressure-extending direction is improved, on the other hand, the dynamic performance of the thick electrode can be improved, and further, the electrode pole piece design process can be applied to a lithium ion battery, the energy density of the battery can be improved, and the cycle performance and the rate capability of the battery are improved.
In step S1, the first solvent and the second solvent may be at least one selected from N-methylpyrrolidone (NMP) and deionized water. Generally, if the electrode plate is a positive electrode plate, the first solvent and the second solvent are N-methylpyrrolidone (NMP), and if the electrode plate is a negative electrode plate, the first solvent and the second solvent are deionized water.
The solid contents of the first electrode slurry and the second electrode slurry can be the same or different; furthermore, the types and the ratios of the materials of the first electrode active material layer and the second electrode active material layer can be adjusted according to requirements, so that the porosity and the conductivity of the electrode pole piece can be changed, and the designability of the first electrode paste and the second electrode paste can be improved. In addition, generally, the viscosity of the electrode slurry is affected by the solid content of the electrode slurry, the technical waste is caused by too low solid content, and the adhesive is easy to float upwards in the drying process; if the viscosity of the electrode slurry is too high, the fluidity of the electrode slurry is poor, the coating quality is directly poor, and finally, the prepared pole piece is not uniform, so that the performance of the battery is affected. Therefore, in the actual production preparation process, the solid contents of the first electrode slurry and the second electrode slurry can be controlled to ensure that the electrode slurry is uniformly coated. Specifically, the electrode plate can be designed as a positive electrode plate or a negative electrode plate, if the prepared electrode plate is the positive electrode plate, the solid contents of the first electrode slurry and the second electrode slurry are generally controlled to be 60-75%, and the solid content of the first electrode slurry is controlled to be larger than that of the second electrode slurry; if the prepared electrode plate is a negative electrode plate, the solid contents of the first electrode slurry and the second electrode slurry are generally controlled to be 50-60%, and the solid content of the first electrode slurry is controlled to be larger than that of the second electrode slurry. Through the solid content control, the uniform coating is facilitated, the performance of the electrode plate is ensured, and the resource waste is avoided.
In step S3, a carbon-based porous conductive material layer is disposed on the first electrode slurry layer in a wet film state, and the electrode slurry in the wet film state can partially infiltrate into pores of the carbon-based porous conductive material layer, and the carbon-based porous conductive material layer forms a skeleton due to its porous structure, and has excellent mechanical properties, so that the processability and structural stability of the whole electrode plate can be enhanced, and the dynamic properties of the electrode plate can be improved by forming a conductive network with its porous structure.
In addition, in step S4, a second electrode paste is coated on the carbon-based porous conductive material layer to form a second electrode paste layer, where the coating width of the second electrode paste layer is generally greater than the width of the first electrode paste layer, so as to ensure that the second electrode paste layer covers the first electrode paste layer. Specifically, the coating width of the second electrode paste layer may be 5-10 mm greater than that of the first electrode paste layer.
In a third aspect of the present application, a lithium ion battery is provided, which includes any one of the electrode pads provided in the first aspect of the present application.
Drawings
The present application is further described with reference to the following figures and examples, in which:
fig. 1 is a schematic view of an electrode active material layer coated and disposed on a current collector in example 1 of the present application;
FIG. 2 is a schematic structural diagram of a positive electrode sheet obtained in example 1 of the present application;
FIG. 3 shows the results of the cycle performance test of the lithium ion battery prepared in example 1 of the present application;
fig. 4 is a result of rate capability test of the lithium ion battery prepared in example 1 of the present application.
Reference numerals: a current collector 100, a first positive electrode slurry layer 200, carbon paper 300, a first roller 410, a second roller 420, a first positive electrode active material layer 500, and a second positive electrode active material layer 600.
Detailed Description
The conception and the resulting technical effects of the present application will be clearly and completely described below in conjunction with the embodiments to fully understand the objects, features and effects of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, and not all embodiments, and other embodiments obtained by those skilled in the art without inventive efforts based on the embodiments of the present application belong to the protection scope of the present application.
Example 1
The embodiment prepares the lithium ion battery, and the specific process comprises the following steps:
s1, preparing the middle sandwich carbon paper and adopting the surface densityDegree of 5g/m2Carbon paper with the fiber diameter of 300nm and the thickness of 25 mu m;
s2, preparing positive electrode slurry, including:
A. preparing a first positive electrode slurry: the positive electrode active material, a binder polyvinylidene fluoride (PVDF) and a conductive agent conductive carbon black (Super P) are mixed according to a mass ratio of 96%: 2%: dissolving 2% of the mixed solution in N-methylpyrrolidone (NMP), and uniformly stirring to prepare first positive electrode slurry; the positive active material may be a commercially available positive active material such as a nickel-cobalt-manganese (NCM) ternary material (811/622/532, etc.), a lithium iron phosphate material, etc., and in this embodiment, the positive active material is a nickel-cobalt-manganese ternary material 622; the solid content of the first positive electrode slurry is controlled to be 68-75%, and the viscosity is controlled to be 3000-5000 mPa & s.
B. Preparing a second positive electrode slurry: preparing first positive electrode slurry according to the method, adding N-methyl pyrrolidone (NMP), and respectively reducing the solid content and the viscosity of the first positive electrode slurry to 64-66% and 2500-3000 mPa & s to obtain second positive electrode slurry.
S3, preparing a positive pole piece, including:
A. as shown in fig. 1, an electrode active material layer is disposed on a current collector by using a coater modified with a double-roller device at a coating end, the coater specifically comprises a first roller 410 and a second roller 420, the first roller 410 is used for conveying the current collector 100, and the second roller 420 is located behind the coating roller and is used for conveying the carbon paper 300 prepared in step S1; specifically, can adopt the control of high accuracy screw pump, the first positive pole thick liquids of even coating in a surface of anodal mass flow body aluminium foil forms wet film (being first positive pole thick liquids layer 200), first positive pole thick liquids layer 200 thickness is 200 ~ 300 mu m, the width is 192mm, simultaneously through the second cylinder 420 of drive coiling carbon paper, evenly cover carbon paper 300 on wet film, then dry, first positive pole thick liquids layer corresponds and forms first positive active material layer, the surface that deviates from anodal mass flow body on it is equipped with carbon paper 300. The first positive active material layer and the carbon paper 300 are disposed on the other surface of the aluminum foil of the positive current collector using the same method.
B. And respectively and uniformly coating second anode slurry on the surface of the carbon paper 300, which deviates from the first anode active material layer, to form a second anode slurry layer with the thickness of 200-300 microns, wherein the coating width of the second anode slurry layer is larger than the width of the first anode slurry layer by 8mm, and then drying and rolling to obtain the anode piece. The positive pole piece comprises a current collector 100 and positive active material layers arranged on the surfaces of two sides of the current collector 100, wherein the positive active material layers comprise a first positive active material layer 500, carbon paper 300 and a second positive active material layer 600 which are sequentially stacked.
S4, preparing anode slurry, including:
A. preparing first cathode slurry: the preparation method comprises the following steps of mixing a negative electrode active material artificial graphite, a water-based binder styrene-butadiene emulsion, a thickening agent CMC and a conductive agent conductive carbon black according to a mass ratio of 95%: 1.5%: 1.5%: dissolving 2% of the mixed solution in deionized water, and uniformly stirring to prepare first cathode slurry; the solid content of the first negative electrode slurry is controlled to be 58-68%, and the viscosity is controlled to be 3000-5000 mPa & s.
B. Preparing a second cathode slurry: preparing the first negative electrode slurry according to the method, adding deionized water, and respectively reducing the solid content and the viscosity of the first negative electrode slurry to 54-56% and 2500-3000 mPa & s to obtain the second negative electrode slurry.
S5, preparing a negative pole piece, comprising:
A. arranging an electrode active material layer on the copper foil of the negative current collector by adopting a coating machine with a double-roller device at the coating end modified similarly to the step A in the step S3; specifically, a high-precision screw pump control can be adopted, first negative electrode slurry is uniformly coated on one surface of a negative electrode current collector copper foil to form a wet film (namely a first negative electrode slurry layer), the thickness of the first negative electrode slurry layer is 200-300 microns, the width of the first negative electrode slurry layer is 192mm, meanwhile, the wet film is uniformly covered with carbon paper prepared in the step S1, then drying is carried out, the first negative electrode slurry layer correspondingly forms a first negative electrode active material layer, and the carbon paper is arranged on the surface of the first negative electrode slurry layer, which deviates from the negative electrode current collector. And arranging a first negative active material layer and carbon paper on the other surface of the negative current collector copper foil by adopting the same method.
B. And respectively and uniformly coating second negative electrode slurry on the surfaces of the carbon paper, which are far away from the first negative electrode active material layer, to form a second negative electrode slurry layer with the thickness of 200-300 microns, wherein the coating width of the second negative electrode slurry layer is larger than the width of the first negative electrode slurry layer by 8mm, and then drying and rolling to obtain the negative electrode plate. The negative pole piece comprises a negative pole current collector and negative pole active material layers arranged on the surfaces of the two sides of the negative pole current collector, wherein the negative pole active material layers comprise a first negative pole active material layer, carbon paper and a second negative pole active material layer which are sequentially stacked.
S5, preparing the lithium ion battery, including: and (3) arranging a diaphragm between the positive pole piece prepared in the step S3 and the negative pole piece prepared in the step S5, then winding a winding core of a winding structure with the positive pole wrapped outside by using a winding machine, packaging by adopting an aluminum-plastic film, baking for 48 hours in a vacuum state to remove moisture, then injecting electrolyte, and then carrying out formation and capacity grading on the battery to obtain a product lithium ion battery, which is marked as C1. Wherein the electrolyte is prepared by adopting a conventional electrolyte formula: LiPF6+ solvent (ethylene carbonate EC + polycarbonate PC + diethyl carbonate DEC).
Example 2
This example, which is different from example 1 in that: the middle sandwich carbon paper prepared in step S1 is the one used in this embodiment and has an areal density of 5g/m2A carbon paper blank having a fiber diameter of 300nm was pre-rolled into a carbon paper having a thickness of 50 μm, and the other operations were carried out in the same manner as in example 1 to obtain a lithium ion battery, which was designated as C2.
Example 3
This example, which is different from example 1 in that: in the middle sandwich carbon paper prepared in step S1, the middle sandwich carbon paper used in this embodiment has an areal density of 5g/m2A carbon paper blank having a fiber diameter of 300nm was pre-rolled into a carbon paper having a thickness of 75 μm, and a lithium ion battery, designated as C3, was obtained in the same manner as in example 1.
Example 4
This example, which is different from example 1 in that: the intermediate interlayer prepared in step S1The carbon paper of the middle interlayer adopted in the embodiment adopts the surface density of 10g/m2A carbon paper blank having a fiber diameter of 300nm was pre-rolled into carbon paper having a thickness of 25 μm, and a lithium ion battery, designated as C4, was obtained in the same manner as in example 1.
Example 5
This example, which is different from example 1 in that: the middle sandwich carbon paper prepared in step S1 is the one with the surface density of 15g/m2A carbon paper blank having a fiber diameter of 300nm was pre-rolled into carbon paper having a thickness of 25 μm, and a lithium ion battery, designated as C5, was obtained in the same manner as in example 1.
Example 6
This example, which is different from example 1 in that: the middle sandwich carbon paper prepared in step S1 is the one used in this embodiment and has an areal density of 5g/m2A carbon paper blank having a fiber diameter of 500nm was pre-rolled into carbon paper having a thickness of 25 μm, and otherwise the same operation as in example 1 was carried out to obtain a lithium ion battery, which was designated as C6.
Example 7
This example, which is different from example 1 in that: the middle sandwich carbon paper prepared in step S1 is the one used in this embodiment and has an areal density of 5g/m2A carbon paper blank having a fiber diameter of 1 μm was pre-rolled into a carbon paper having a thickness of 25 μm, and a lithium ion battery was obtained as C7 in the same manner as in example 1.
Example 8
This example, which is different from example 1 in that: the middle sandwich carbon paper prepared in step S1 is prepared by the present embodiment using the middle sandwich carbon paper with the surface density of 30g/m2Carbon paper blank with the fiber diameter of 1 mu m is rolled into carbon paper with the thickness of 75 mu m by a pre-roller, and other operations are the same as the example 1 to prepare the lithium ion battery which is marked asC8。
Comparative example 1
This comparative example, which was different from example 1 in that: the same operations as in example 1 were performed except that step S1 was omitted, and the carbon paper was not disposed on the first positive electrode slurry layer in step S3, and the carbon paper was not disposed on the first negative electrode slurry layer in step S5, to obtain a lithium ion battery, denoted as C0.
Comparative example 2
This comparative example differs from example 1 in that: the middle layer carbon paper prepared in step S1 is the one with the surface density of 2g/m2A carbon paper blank having a fiber diameter of 300nm was pre-rolled to form a carbon paper A having a thickness of 25 μm, and the operation was otherwise the same as in example 1.
Comparative example 3
This comparative example differs from example 1 in that: the middle layer carbon paper prepared in step S1 is the one with the surface density of 5g/m2A carbon paper blank having a fiber diameter of 100nm was pre-rolled to form carbon paper B having a thickness of 25 μm, and the other operations were the same as in example 1.
Comparative example 4
This comparative example differs from example 1 in that: the middle layer carbon paper prepared in step S1 is the one with the surface density of 5g/m2A carbon paper blank having a fiber diameter of 300nm was pre-rolled to form carbon paper C having a thickness of 20 μm, and the operation was otherwise the same as in example 1.
In the comparative examples 2 to 4, since the mechanical properties of the intermediate interlayer carbon paper are far lower than the processing requirements, the intermediate interlayer carbon paper has different band breakage phenomena in the preparation process of the lithium ion battery, the consistency of the prepared lithium ion battery is poor, and the lithium ion battery meeting the expected performance cannot be prepared.
Test examples
The experimental example tests the cycle performance and rate capability of the lithium ion battery prepared in example 1, wherein:
the cycle performance was specifically tested in a charge-discharge cycle at 25 ℃ and a current density of 1C, and the test results are shown in fig. 3. As can be seen from fig. 3, the lithium ion battery prepared in example 1 has excellent long-term cycle stability.
The rate capability is specifically measured by performing a capacity volatilization test at 25 ℃ and at current densities of 1C, 10C, 20C and 30C, respectively, and the obtained test results are shown in FIG. 4. As can be seen from fig. 4, the lithium ion battery prepared in example 1 has excellent rate capability.
In addition, the gram capacity, the first effect and the capacity after 2000 cycles at 25 ℃ of the lithium ion batteries C0-C8 prepared in comparative example 1 and examples 1-8 were respectively tested. Wherein, the capacity is obtained by 1C discharge, and the gram capacity is obtained by dividing the mass of active materials in the battery; obtaining the ratio of the charging capacity to the discharging capacity as a first effect through 1C charging and discharging; after the mixture is cycled for 2000 circles at 25 ℃, the ratio of the final discharge capacity to the first discharge capacity is the capacity. The results obtained by the tests are shown in table 1:
TABLE 1
Figure BDA0002986813050000101
As can be seen from table 1 above, compared with the lithium ion battery C0 prepared in comparative example 1, in the lithium ion batteries C1 to C8 prepared in examples 1 to 8, the carbon paper interlayer is additionally arranged between the first electrode active material layer and the second electrode active material layer on the electrode active material layer of the electrode plate, so that the batteries C1 to C8 can ensure good cycle stability on the premise of ensuring gram capacity and first effect, because the arrangement of the carbon paper interlayer can increase the processability of the electrode plate, improve the interface state of the first electrode active material layer and the second electrode active material layer, provide a channel for improving the dynamic performance of the electrode plate, and ensure the performance of the electrode plate. In addition, the carbon paper interlayer can also improve the mechanical property of the electrode pole piece, ensure the stability of the pole piece after long-term circulation and reduce the capacity loss.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present application. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application.

Claims (10)

1. An electrode sheet, comprising:
a current collector;
an electrode active material layer disposed on at least one surface of the current collector; the electrode active material layer comprises a first electrode active material layer, a carbon-based porous conductive material layer and a second electrode active material layer which are sequentially stacked.
2. The electrode sheet according to claim 1, wherein the carbon-based porous conductive material layer is at least one of carbon paper, carbon cloth, and carbon felt.
3. The electrode sheet according to claim 2, wherein the carbon paper has an areal density of 3 to 15g/m2The thickness is 25 to 75 μm, and the fiber diameter is 0.25 to 1.00 μm.
4. The electrode sheet according to claim 1, wherein the material of the first electrode active material layer comprises a first electrode active material, a first binder and a first conductive agent; the material of the second electrode active material layer includes a second electrode active material, a second binder, and a second conductive agent; the first electrode active material and the second electrode active material are positive electrode active materials of a lithium ion battery or negative electrode active materials of the lithium ion battery.
5. The electrode sheet according to claim 4, wherein the first electrode active material and the second electrode active material are lithium ion battery negative electrode active materials, and the material of the first electrode active material layer further comprises a first thickener, and the material of the second electrode active material layer further comprises a second thickener.
6. The electrode sheet according to claim 4, wherein the lithium ion battery positive active material is selected from at least one of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium manganese phosphate, lithium vanadium phosphate, lithium nickel manganate and ternary nickel cobalt manganese materials; the negative active material of the lithium ion battery is selected from at least one of natural graphite, artificial graphite, metallic lithium, silicon-based alloy, silicon-based oxide, tin-based alloy, tin-based oxide, lithium titanate, titanium dioxide, tin oxide, iron oxide and cobalt oxide; the first binder and the second binder are selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, polyacrylate multipolymer and modified styrene-butadiene rubber;
the first conductive agent and the second conductive agent are selected from at least one of graphite, conductive carbon black, acetylene black, activated carbon, carbon nanotubes, carbon fibers and graphene.
7. The electrode tab of claim 1, wherein the electrode active material layer is partially disposed on both side surfaces of the current collector.
8. The electrode sheet according to any one of claims 1 to 7, wherein the thickness of the electrode sheet is 250 to 400 μm.
9. The method for preparing an electrode sheet according to any one of claims 1 to 8, comprising the steps of:
s1, dissolving the material of the first electrode active material layer in a first solvent to prepare first electrode slurry; dissolving the material of the second electrode active material layer in a second solvent to prepare second electrode slurry;
s2, coating the first electrode slurry on the surface of the current collector to form a first electrode slurry layer;
s3, arranging a carbon-based porous conductive material layer on the surface, deviating from the current collector, of the first electrode slurry layer, and then drying;
and S4, coating the second electrode slurry on the carbon-based porous conductive material layer, and then drying and rolling.
10. A lithium ion battery comprising the electrode sheet of any one of claims 1 to 8.
CN202110302510.4A 2021-03-22 2021-03-22 Electrode pole piece, preparation method thereof and lithium ion battery Pending CN113161510A (en)

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