CN113285062B - Thick electrode material, preparation method thereof and lithium ion battery - Google Patents

Thick electrode material, preparation method thereof and lithium ion battery Download PDF

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CN113285062B
CN113285062B CN202110526195.3A CN202110526195A CN113285062B CN 113285062 B CN113285062 B CN 113285062B CN 202110526195 A CN202110526195 A CN 202110526195A CN 113285062 B CN113285062 B CN 113285062B
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electrode
slurry
electrode slurry
thick
coating
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CN113285062A (en
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尚德华
杨泽乾
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Aopu Shanghai New Energy Co Ltd
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    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/34—Applying different liquids or other fluent materials simultaneously
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
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    • B05D1/36—Successively applying liquids or other fluent materials, e.g. without intermediate treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B05D5/12—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures to obtain a coating with specific electrical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/24—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials for applying particular liquids or other fluent materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/50—Multilayers
    • B05D7/52—Two layers
    • B05D7/54—No clear coat specified
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/50—Multilayers
    • B05D7/56—Three layers or more
    • B05D7/58—No clear coat specified
    • H—ELECTRICITY
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    • 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
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    • 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
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    • H01M4/00—Electrodes
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
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    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • 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
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention is suitable for the technical field of lithium ion batteries, and provides a thick electrode material and a preparation method thereof, and a lithium ion battery, wherein the thick electrode material comprises the following components: adding a conductive agent, a thickening agent, a binder and a solvent into the electrode active material with small particle size to prepare first electrode slurry; adding a conductive agent, a thickening agent, a binder and a solvent into the electrode active material with large particle size to prepare second electrode slurry; and respectively conveying the first electrode slurry and the second electrode slurry to corresponding die heads of a double-die-head coating machine through two sets of slurry conveying systems to simultaneously coat the first electrode slurry and the second electrode slurry in a clearance mode for an even number of times, keeping the first electrode slurry above the second electrode slurry or keeping the second electrode slurry above the first electrode slurry during each coating, and drying and rolling to obtain the electrode material. The invention can ensure the consistency of the obtained thick electrode material, and the through holes are naturally distributed, the electrolyte can be quickly and uniformly infiltrated, the manufacturing process is simple, and the problems of difficult infiltration, poor conductivity and poor consistency of the thick electrode are solved.

Description

Thick electrode material, preparation method thereof and lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a thick electrode material, a preparation method of the thick electrode material and a lithium ion battery.
Background
In the field of secondary batteries, lithium ion batteries are widely applied to the fields of new energy vehicles, energy storage systems, consumer electronics and the like due to the excellent characteristics of environmental protection, high energy power density, high working voltage and the like. Along with the popularization of new energy electric vehicles and energy storage, people have higher and higher requirements on lithium ions, especially energy density and cost, the driving mileage of new energy can be increased due to the high energy density, the popularization of new energy vehicles and the improvement of energy storage benefits are facilitated due to the low cost, the lithium ion battery manufactured by pole pieces with the conventional thickness cannot meet the requirements, and the lithium ion battery is developed towards a large capacity and a large volume. The current collectors with the same area of the thick electrode can bear more electrode materials, and the materials such as the current collectors are reduced, so that the energy density can be improved and the cost can be reduced. The performance of the manufactured battery is affected by the problems of low conductivity and poor consistency caused by the thick electrode.
For the problems caused by the thick electrode, the prior art schemes usually have certain disadvantages by improving the original design or by adopting a step electrode manufacturing method, that is, by adopting slurries (usually different in conductivity or porosity) of different combinations to coat for multiple times to manufacture the thick electrode, or by trying to add a transport channel or an electrolyte layer in the thickness direction on the thick electrode to ensure the performance of the thick electrode. The method with different conductivities or porosities needs to prepare different sizing agents and also needs to coat for multiple times with different thicknesses, the porosity is difficult to control, the process is complex, the design difficulty is high, and the electrolyte is difficult to infiltrate and different due to the difference of the porosities of different layers, so that the distribution of the electrolyte in the thickness direction is influenced. The method that the transport channel can be added on the thick electrode has the through hole diameter reaching several microns or even dozens of microns, and besides the high difficulty of the through hole adding technology, the coating electrode material is lost in the length direction and the width direction of the pole piece, so that the coating electrode material is not paid.
Therefore, the existing thick electrode preparation method has the problems of complex process, high technical difficulty and incapability of exerting the effective value of the thick electrode due to the cost of sacrificing other performances.
Disclosure of Invention
The embodiment of the invention aims to provide a preparation method of a thick electrode material, and aims to solve the problems that the existing preparation method of the thick electrode has complex process and high technical difficulty, and the thick electrode cannot exert the effective value due to the fact that other properties are sacrificed.
The embodiment of the invention is realized in such a way that the preparation method of the thick electrode material comprises the following steps:
adding a conductive agent, a thickening agent, a binder and a solvent into the electrode active material with small particle size to prepare first electrode slurry;
adding a conductive agent, a thickening agent, a binder and a solvent into the electrode active material with large particle size to prepare second electrode slurry;
and respectively conveying the first electrode slurry and the second electrode slurry to corresponding die heads of a double-die-head coating machine through two sets of slurry conveying systems to simultaneously coat the first electrode slurry and the second electrode slurry in a clearance mode for an even number of times, keeping the first electrode slurry above the second electrode slurry or keeping the second electrode slurry above the first electrode slurry during each coating, and drying and rolling to obtain the electrode material.
Another object of an embodiment of the present invention is to provide a thick electrode material, which is prepared by the method for preparing the thick electrode material.
Another object of an embodiment of the present invention is a lithium ion battery comprising said thick electrode material.
According to the preparation method of the thick electrode material provided by the embodiment of the invention, the double dies are adopted to coat two kinds of slurry with different particle sizes simultaneously, the two kinds of slurry are close to each other on the current collector, the small particle size slurry is coated above the original large particle size slurry during the second coating, the large particle size slurry is coated above the original small particle size slurry, and the coating is repeated in sequence, so that the capacity and other performances in the thickness direction can be basically consistent after the coating is finally carried out for even number of times, the consistency of the obtained thick electrode material is ensured, straight through holes are naturally distributed, the electrolyte can be quickly and uniformly infiltrated, the preparation process is simple, and the problems that the thick electrode is difficult to infiltrate, the conductivity is poor and the consistency is poor are solved.
Drawings
FIG. 1 is a schematic structural diagram of a thick electrode material provided by an embodiment of the present invention;
fig. 2 is a schematic diagram of gap coating of a thick electrode material according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Although the thick electrode can greatly increase the energy density of the lithium ion battery and reduce the cost, the increase of the thickness of the pole piece also causes the lengthening of the transmission path and the deterioration of the conductivity, and on the other hand, the deterioration of the uniformity due to the deterioration of the dispersion uniformity causes the deterioration of the uniformity, so that the capacity of a partial region cannot be sufficiently exerted, and therefore, the thick electrode needs to be improved to exert the excellent performance.
The embodiment of the invention provides a preparation method of a thick electrode material, aiming at solving the problems that the prior preparation method of the thick electrode has complex process and high technical difficulty and needs to sacrifice other performances, so that the thick electrode can not exert the effective value of the thick electrode, the preparation method of the thick electrode material adopts a double-mold head to coat two kinds of sizing agents with different particle sizes at the same time, and the two kinds of sizing agents are close to a current collector, coating small-particle size slurry on the original large-particle size slurry during the second coating, coating large-particle size slurry on the original small-particle size slurry, and the process is repeated in turn, and the capacity and other performances in the thickness direction can be ensured to be basically consistent by finally coating for even number of times, the consistency of the obtained thick electrode material is ensured, through holes are naturally distributed, the electrolyte can be quickly and uniformly infiltrated, the manufacturing process is simple, and the problems that the thick electrode is difficult to infiltrate, the conductivity is poor and the consistency is poor are solved.
The embodiment of the invention provides a preparation method of a thick electrode material, which comprises the following steps:
adding a conductive agent, a thickening agent, a binder and a solvent into the electrode active material with small particle size to prepare first electrode slurry;
adding a conductive agent, a thickening agent, a binder and a solvent into the electrode active material with large particle size to prepare second electrode slurry;
and (2) respectively conveying the first electrode slurry and the second electrode slurry to corresponding die heads of a double-die-head coating machine through two sets of slurry conveying systems to carry out simultaneous coating for an even number of times, keeping the first electrode slurry above the second electrode slurry or keeping the second electrode slurry above the first electrode slurry, and drying and rolling to obtain the thick electrode material shown in the structural schematic diagram of the thick electrode material shown in the figure 1 and the thick electrode material gap coating schematic diagram shown in the figure 2.
In the embodiment of the invention, the particle diameter ratio of the electrode active material with small particle diameter to the electrode active material with large particle diameter is 1: 1.2-100. Wherein the particle size range of the electrode active material with small particle size is 0.1 um-50 um; the particle size range of the electrode active material with a large particle size is 0.12um to 5000 um.
In the embodiment of the invention, in the first electrode slurry and the second electrode slurry, the mass ratio of the electrode active material to the conductive agent to the thickening agent to the binder is 90.5-97.5: 0.2-3.0: 0-3.0: 0.8 to 3.6.
In the embodiment of the invention, the conductive agent is one or more of a single-walled carbon nanotube, a multi-walled carbon nanotube, graphene, conductive graphite, conductive carbon black and carbon fiber.
In the embodiment of the invention, the binder is one or more of polyacrylic acid, polyvinyl alcohol, styrene butadiene rubber and acrylonitrile.
In the embodiment of the present invention, the thick electrode material may be a positive electrode material (positive electrode plate) or a negative electrode material (negative electrode plate), and specifically, when the electrode active material is a positive electrode active material, the thick electrode material obtained correspondingly is the positive electrode plate; when the electrode active material is a negative electrode active material, the thick electrode material obtained correspondingly is a negative electrode plate.
Specifically, when preparing a positive electrode material (positive electrode sheet), the specific preparation method comprises the following steps (the following contents are all in mass percent):
step S11: preparing first anode slurry: the method comprises the steps of preparing a first positive electrode slurry with a solid content of 40-70% and a viscosity of 4000-10000 mPa.S by using a positive electrode active material with a small particle size, wherein the positive electrode active material comprises 90.5-97.5%, a conductive agent comprises 0.2-3.0%, a binder comprises 0.8-3.6%, and a solvent.
Step S12: preparing a second anode slurry: the second anode slurry with the solid content of 40-70% and the viscosity of 4000-10000 mPa.S is prepared by adopting an anode active material with large particle size, the content of the anode active material is 90.5-97.5%, the content of the conductive agent is 0.2-3.0%, the content of the binder is 0.8-3.6% and adding a solvent.
Wherein, the solvent in the steps S11 and S12 is one or more of NMP, water and ethanol.
Step S13: the first anode slurry and the second anode slurry are respectively conveyed to the corresponding die heads of the double-die-head coating machine through two sets of slurry conveying systems.
Step S14: when coating, the first positive electrode slurry and the second positive electrode slurry are simultaneously coated at intervals (preferably in a range of more than the maximum particle size and less than 1 ten thousand times of the maximum particle size) to form a complete coating surface, the width of the coating stripes of the first positive electrode slurry and the second positive electrode slurry (preferably in a range of more than the maximum particle size and less than 1 ten thousand times of the maximum particle size) is consistent, and the range of the coating stripes is more than the maximum particle size and less than 1 ten thousand times of the maximum particle size.
Step S15: and coating the pole piece after primary coating and drying again on the pole piece, and keeping the first positive electrode slurry above the second positive electrode slurry or keeping the second positive electrode slurry above the first positive electrode slurry.
Step S16: and (5) repeating the step (S14) and the step (S15), and after finishing even-numbered coating, drying, rolling and cutting to prepare the corresponding positive pole piece.
Specifically, when preparing a negative electrode material (negative electrode sheet), the specific preparation method comprises the following steps (the following contents are all mass percent):
step S21: preparing a first negative electrode slurry: the first cathode and anode slurry with the solid content of 40-60% and the viscosity of 2000-6000 mPa.S is prepared by adopting a cathode active material with a small particle size, wherein the content of the cathode active material is 90.5-97.5%, the content of a conductive agent is 0.2-3.0%, the content of a thickening agent is 0.8-3.0%, and the content of a binder is 0.8-3.6%, and adding a solvent.
Step S22: preparing a second negative electrode slurry: the second negative electrode slurry with the solid content of 40-60% and the viscosity of 2000-6000 mPa.S is prepared by adopting a negative electrode active material with large particle size, wherein the content of the negative electrode active material is 90.5-97.5%, the content of the conductive agent is 0.2-3.0%, the content of the thickening agent is 0.8-3.0%, and the content of the binder is 0.8-3.6%, and adding a solvent.
Wherein, the solvent in step S21 and step S22 is one or more of water, benzene and ethanol.
Step S23: the first negative electrode slurry and the second negative electrode slurry are respectively conveyed to the corresponding die heads of the double-die-head coating machine through the two sets of slurry conveying systems.
Step S24: the first negative electrode slurry and the second negative electrode slurry are simultaneously gapped at the time of coating (the preferable range is more than the maximum particle size and less than 1 ten thousand times the maximum particle size). The coating forms a complete dressing surface, the width of the dressing stripes (preferably in the range of more than the maximum particle size and less than 1 ten thousand times the maximum particle size) of the first negative electrode slurry and the second negative electrode slurry are consistent, and the range of more than the maximum particle size and less than 1 ten thousand times the maximum particle size.
Step S25: and coating the pole piece subjected to primary coating and drying again on the pole piece, and keeping the first negative electrode slurry above the second negative electrode slurry or keeping the second negative electrode slurry above the first negative electrode slurry.
Step S26: and (5) repeating the step (S24) and the step (S25), and after finishing coating for even number of times, drying, rolling and cutting to prepare the corresponding negative pole piece.
The embodiment of the invention also provides a thick electrode material, and the thick electrode material is prepared by the preparation method of the thick electrode material.
The embodiment of the invention also provides a lithium ion battery which comprises the thick electrode material.
The following is only an example of preparing a graphite negative electrode material, and the purpose is not to limit the scope of the present invention, and other negative electrode materials and positive electrode materials are not illustrated because of similar principles.
In addition, it should be noted that the numerical values given in the following examples are as precise as possible, but those skilled in the art will understand that each numerical value should be understood as a divisor rather than an absolutely exact numerical value due to measurement errors and experimental operational problems that cannot be avoided. For example, due to an error of a weighing instrument, it should be understood that the weight value of each raw material for preparing the graphite negative electrode material with respect to each example may have an error of ± 2% or ± 1%.
Example 1
1) Preparing first negative electrode slurry: the first negative electrode slurry with the solid content of 50% and the viscosity of 3500mPa.S is prepared by adding deionized water into 96% of graphite material with the particle size D50 of 8um, the content of a conductive agent of Super-P of 0.5%, the content of a thickening agent of sodium carboxymethylcellulose of 1.5%, and the content of a binder of SBR of 2%.
2) Preparing a second negative electrode slurry: the graphite material with the particle size D50 of 15 microns is adopted, the content of the graphite material is 96%, the content of the conductive agent is Super-P is 0.5%, the content of the thickening agent is 1.5% of sodium carboxymethylcellulose, the content of the binder is 2%, and deionized water is added to prepare the second negative electrode slurry with the solid content of 50% and the viscosity of 3800 mPa.S.
3) The first negative electrode slurry and the second negative electrode slurry are respectively conveyed to the corresponding die heads of the double-die-head coating machine through the two sets of slurry conveying systems.
4) First negative pole thick liquids and second negative pole thick liquids clearance coating simultaneously constitute complete dressing face during the coating, and the coating clearance is 10mm, and the dressing stripe width of first negative pole thick liquids and second negative pole thick liquids is unanimous, and the width is 10mm, and thickness is 50 um.
5) The pole piece after the primary coating and drying is coated on the first negative pole slurry again, the second negative pole slurry is kept above the first negative pole slurry, the dressing thickness is also 50 microns, and the coating is carried out for 2 times, so that the total thickness of the single surface is 100 microns.
6) And (3) drying, rolling and cutting the negative pole piece finished in the step 5) to prepare a corresponding negative pole piece.
Example 2
The first negative electrode slurry and the second negative electrode slurry obtained in example 1 were respectively transferred to the respective corresponding die heads of a double-die head coater through two sets of slurry transport systems. First negative pole thick liquids and second negative pole thick liquids clearance coating simultaneously constitute complete dressing face during the coating, and the coating clearance is 10mm, and the dressing stripe width of first negative pole thick liquids and second negative pole thick liquids is unanimous, and the width is 10mm, and thickness is 25 um. The pole piece after the primary coating and drying is coated on the first negative pole slurry again, the second negative pole slurry is kept above the first negative pole slurry, the dressing thickness is 25 microns, the dressing thickness is coated for 4 times, and the total thickness of the single surface is 100 microns.
Example 3
The first negative electrode slurry and the second negative electrode slurry obtained in example 1 were respectively transferred to the respective corresponding die heads of a double-die head coater through two sets of slurry transport systems. First negative pole thick liquids and second negative pole thick liquids clearance coating simultaneously constitute complete dressing face during the coating, and the coating clearance is 20mm, and the dressing stripe width of first negative pole thick liquids and second negative pole thick liquids is unanimous, and the width is 20mm, and thickness is 50 um. The pole piece after the primary coating and drying is coated on the first negative pole slurry again, the second negative pole slurry is kept above the first negative pole slurry, the dressing thickness is also 50 microns, the dressing thickness is coated for 2 times, and the total thickness of the single surface is 100 microns.
Comparative example 1
The first negative electrode slurry obtained in example 1 was applied continuously 1 time, and the thickness of one side was 100 μm.
Comparative example 2
The second negative electrode slurry obtained in example 1 was applied continuously 1 time, and the thickness of one side was 100 μm.
Cutting the graphite negative pole pieces prepared in the examples 1-3 and the comparative examples 1-2 into a plurality of pole pieces with 3 x 4cm by using a sampler, taking 5 pieces with flat and undamaged surfaces, accurately taking 50uL of electrolytic liquid drops on the surfaces of the pole pieces by using a micrometer, recording the disappearance time of the electrolytic liquid drops, and taking an average number to evaluate the wettability; in addition, the graphite negative electrode sheets prepared in examples 1 to 3 and comparative examples 1 to 2 were each prepared into 2016-type button cells (lithium sheet as a positive electrode; 1mol/L LiPF6 as an electrolyte, and an electrolyte having a solvent ratio (EC: EMC: DEC: 3:5: 2)), and the capacity and 50-cycle performance were measured at 1/3C, and the results are shown in table 1.
TABLE 1
Test items Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2
Soaking time 55s 50s 52s 59s 47s
Capacity of 3.52mAh 3.58mAh 3.55mAh 3.65mAh 3.42mAh
Circulation of 92.4％ 92.9％ 92.3％ 90.5％ 91.2％
As can be seen from Table 1, according to the test results of the embodiments 1-3 and the comparative examples 1-2, the negative electrode plate prepared by the preparation method of the thick electrode material of the embodiments 1-3 can exert the advantages of good wettability of large particles and high conductivity of small particles, so that the cycle performance is improved; in addition, the examples 1 and 2 respectively adopt different coating thicknesses and coating layer numbers, and the examples 1 and 3 respectively adopt different coating gaps, and the comprehensive performance of the coating with multi-layer coating or smaller gaps is better according to the test results of the examples 1 to 3.
Example 4
1) Preparing first anode slurry: a lithium iron phosphate material with the particle size D50 of 1um is adopted, the content of the lithium iron phosphate material is 96.5%, the content of a conductive agent is 1% of CNT (carbon nano tube), the content of a binder is 2.5% of PVDF, NMP is added, and a first anode slurry with the solid content of 55% and the viscosity of 6300mPa.S is prepared.
2) Preparing a second anode slurry: the lithium iron phosphate material with the particle size D50 of 5um is adopted, the content of the lithium iron phosphate material is 96.5%, the content of the conductive agent is 1% of CNT (carbon nano tube), the content of the binder is 2.5% of PVDF, and NMP is added to prepare the second anode slurry with the solid content of 55% and the viscosity of 5500 mPa.S.
3) The first anode slurry and the second anode slurry are respectively conveyed to the corresponding die heads of the double-die-head coating machine through two sets of slurry conveying systems.
4) First positive pole thick liquids and the anodal thick liquids of second clearance coating simultaneously constitute complete dressing face during the coating, and the coating clearance is 10mm, and the dressing stripe width of first positive pole thick liquids and the anodal thick liquids of second is unanimous, and the width is 10mm, and thickness is 60 um.
5) The pole piece after the primary coating and drying is coated on the first positive pole slurry again, the second positive pole slurry is kept above the first positive pole slurry, the dressing thickness is also 60 micrometers, and the coating is coated for 2 times, so that the total thickness of the single surface is 120 micrometers.
6) And (3) drying, rolling and cutting the positive pole piece finished in the step 5) to prepare a corresponding positive pole piece.
Example 5
The first positive electrode slurry and the second positive electrode slurry obtained in example 4 were respectively conveyed to the respective dies of the double-die coater through two sets of slurry conveying systems. First positive pole thick liquids and the anodal thick liquids of second clearance coating simultaneously constitute complete dressing face during the coating, and the coating clearance is 10mm, and the dressing stripe width of first positive pole thick liquids and the anodal thick liquids of second is unanimous, and the width is 10mm, and thickness is 30 um. The pole piece after the primary coating and drying is coated on the first positive pole piece again, the second positive pole slurry is kept above the first positive pole slurry, the dressing thickness is also 30 micrometers, the coating is carried out for 4 times, and the total thickness of the single surface is 120 micrometers.
Example 6
The first positive electrode slurry and the second positive electrode slurry obtained in example 4 were mixed in the same ratio, except that the mixture ratio was changed to 95.5% for the first positive electrode slurry and 1.5% for the Super-P, and 2.5% for the PVDF as the binder, and NMP was added to prepare the first positive electrode slurry and the second positive electrode slurry, respectively, and the other materials were kept unchanged, thereby obtaining a positive electrode sheet with a total thickness of 120um on one side.
Comparative example 3
The first positive electrode slurry obtained in example 4 was applied by 1-pass continuous coating, and the thickness of one side was 120 μm.
Comparative example 4
The second positive electrode slurry obtained in example 1 was applied by 1-pass continuous coating, and the thickness of one side was 120 μm.
Cutting the lithium iron phosphate positive pole pieces prepared in the examples 4-6 and the comparative examples 3-4 into a plurality of pole pieces with the size of 3 x 4cm by using a sampler respectively, taking 5 pieces with smooth and unbroken surfaces, accurately taking 50uL of electrolytic liquid drops on the surfaces of the pole pieces by using a micrometer, recording the disappearance time of the electrolytic liquid drops, and taking the average number to evaluate the wettability; in addition, the lithium iron phosphate positive electrode pieces prepared in examples 4 to 6 and comparative examples 3 to 4 were respectively prepared into 2016 type button cells (wherein, the negative electrode is a lithium piece, 1mol/L LiPF6 is adopted as an electrolyte, and the solvent ratio is (EC: EMC: DEC: 3:5:2), and the capacity and 50-cycle performance of the lithium iron phosphate positive electrode pieces were tested at 1/3C, and the test results are shown in Table 2.
TABLE 2
Test items Example 4 Example 5 Example 6 Comparative example 3 Comparative example 4
Soaking time 95s 91s 94s 99s 89s
Capacity of 3.31mAh 3.30mAh 3.18mAh 3.35mAh 3.27mAh
Circulation of 95.5％ 94.8％ 93.5％ 94.6％ 94.3％
As can be seen from Table 2, according to the test results of the embodiments 4-6 and the comparative examples 3-4, the positive electrode plate prepared by the preparation method of the thick electrode material of the embodiments 4-6 can exert the advantages of good wettability of large particles and high conductivity of small particles, thereby improving the cycle performance; in addition, different coating thicknesses and coating layer numbers are respectively adopted in the examples 4 and 5, different proportions are respectively adopted in the examples 4 and 6, and according to the test results of the examples 4 to 6, the comprehensive performance of the multilayer coating is better, and under the condition that the proportion is not changed greatly, the influence on the wettability is smaller, and the other performances of the pole piece are influenced.
To sum up, the thick electrode material preparation method provided by the embodiment of the invention adopts the double-die head to simultaneously coat two kinds of slurry with different particle sizes, the two kinds of slurry are close to each other on the current collector, the small particle size slurry is coated above the original large particle size slurry during the second coating, the large particle size slurry is coated above the original small particle size slurry, and the coating is repeated in turn, so that the capacity and other performances in the thickness direction can be basically consistent after the slurry is finally coated for even number of times, the consistency of the obtained thick electrode material is ensured, the through holes are naturally distributed, the electrolyte can be quickly and uniformly infiltrated, the preparation process is simple, and the problems that the thick electrode is difficult to infiltrate, the conductivity is poor and the consistency is poor are solved.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. The preparation method of the thick electrode material is characterized by comprising the following steps of:
adding a conductive agent, a thickening agent, a binder and a solvent into the electrode active material with small particle size to prepare first electrode slurry;
adding a conductive agent, a thickening agent, a binder and a solvent into the electrode active material with large particle size to prepare second electrode slurry;
primary coating: the first electrode slurry and the second electrode slurry are respectively conveyed to corresponding die heads of a double-die-head coating machine through two sets of slurry conveying systems, simultaneous gap coating is carried out along the width direction of a current collector, the first electrode slurry and the second electrode slurry are close to each other on the current collector and coated at intervals, a complete first-layer coating surface is formed by coating, and the lengths, the widths and the thicknesses of the coating stripes of the first negative electrode slurry and the second negative electrode slurry are consistent;
drying after primary coating, and performing secondary coating on the dried pole piece: the secondary coating is the same as the primary coating, second electrode slurry is coated above the position where the first electrode slurry is originally coated, the first electrode slurry is coated above the position where the second electrode slurry is originally coated, and a complete second-layer coating surface is formed by coating; the width and the thickness of the dressing stripes of the first negative electrode slurry and the second negative electrode slurry which are coated for the second time are consistent, and the width and the thickness of the dressing stripes which are coated for the first time are also consistent;
repeating the steps, coating for even times, drying and rolling to obtain the thick electrode, which can ensure that the capacity in the thickness direction is basically consistent and through holes are naturally distributed, so that the electrolyte can be quickly and uniformly soaked.
2. The method for preparing a thick electrode material according to claim 1, wherein the ratio of the particle size of the electrode active material having a small particle size to the particle size of the electrode active material having a large particle size is 1:1.2 to 100.
3. The method for preparing a thick electrode material according to claim 1, wherein the mass ratio of the electrode active material, the conductive agent, the thickening agent and the binder in the first electrode slurry to the second electrode slurry is 90.5-97.5: 0.2-3.0: 0-3.0: 0.8 to 3.6.
4. The method for preparing a thick electrode material according to any one of claims 1 to 3, wherein the electrode active material is a negative electrode active material or a positive electrode active material;
the negative active material is one or more of graphite, silicon, soft carbon, hard carbon and MCMB;
the positive active material is one or more of lithium iron phosphate, lithium cobaltate, spinel lithium manganate, ternary NMC, ternary NCA and lithium nickelate.
5. The method for preparing a thick electrode material according to claim 1 or 3, wherein the conductive agent is one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, graphene, conductive graphite, conductive carbon black and carbon fibers.
6. The method for preparing a thick electrode material according to claim 1 or 3, wherein the binder is one or more of polyacrylic acid, polyvinyl alcohol, styrene butadiene rubber and acrylonitrile.
7. The method of claim 1, wherein the thickener is sodium carboxymethyl cellulose; the solvent is one or more of NMP, water, benzene and ethanol.
8. The method for preparing a thick electrode material according to any one of claims 1 to 3, wherein when the electrode active material is a negative electrode active material, the solid content of the first electrode slurry and the second electrode slurry is 40% to 60%, and the viscosity is 2000 to 6000 mPa.S;
when the electrode active material is a positive electrode active material, the solid content of the first electrode slurry and the solid content of the second electrode slurry are 40% -70%, and the viscosity is 4000-10000 mPa.S.
9. A thick electrode material, wherein the thick electrode material is prepared by the method for preparing the thick electrode material according to any one of claims 1 to 8.
10. A lithium ion battery comprising the thick electrode material of claim 9.
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