CN118676298A - Lithium battery negative electrode plate and preparation method and application thereof - Google Patents
Lithium battery negative electrode plate and preparation method and application thereof Download PDFInfo
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- CN118676298A CN118676298A CN202310699269.2A CN202310699269A CN118676298A CN 118676298 A CN118676298 A CN 118676298A CN 202310699269 A CN202310699269 A CN 202310699269A CN 118676298 A CN118676298 A CN 118676298A
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 82
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 81
- 238000002360 preparation method Methods 0.000 title abstract description 15
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Landscapes
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a lithium battery negative electrode plate, a preparation method and application thereof, wherein the lithium battery negative electrode plate comprises: a current collector; and a negative electrode active material layer provided at least on one side of the current collector; the negative electrode active material layer comprises a first negative electrode active material layer and a second negative electrode active material layer, the first negative electrode active material layer is arranged on the current collector, the second negative electrode active material layer is arranged on one side, far away from the current collector, of the first negative electrode active material layer, the first negative electrode active material layer and the second negative electrode active material layer comprise a first binder, the first binder comprises polyacrylic acid, and the content of the first binder in the first negative electrode active material layer or the second negative electrode active material layer is 1.2-1.3 wt%. The lithium battery negative electrode plate, the preparation method and the application thereof provided by the invention can improve the dynamic performance and the cycle performance of the lithium battery.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a lithium battery negative electrode plate and a preparation method and application thereof.
Background
There is still a great room for improvement in performance of lithium batteries as a new type of high-energy battery, and improvement in performance of negative electrode active materials is a key point thereof. The negative electrode active material should have the properties of large capacity, good charge and discharge cycle performance, stable discharge voltage, small irreversible capacity loss, stable electrolyte and the like. The graphite anode active material has the advantages of large reserve, low cost, safety, no toxicity and the like, and becomes a main stream anode active material.
The development of lithium batteries needs to meet the requirements of fast charge performance and better cycle, and the current single graphite serving as a negative electrode active material cannot meet the requirements of high dynamics, high charge and discharge efficiency, high cycle performance and the like.
Disclosure of Invention
The lithium battery negative electrode plate and the preparation method and application thereof can ensure the capacity performance of the lithium battery negative electrode plate, improve the uniformity and consistency of the lithium battery negative electrode plate, and simultaneously meet the high dynamics and long cycle performance of the lithium battery.
In order to solve the technical problems, the invention is realized by the following technical scheme.
The invention provides a lithium battery negative electrode plate, which at least comprises:
A current collector; and
A negative electrode active material layer provided at least on one side of the current collector;
The negative electrode active material layer comprises a first negative electrode active material layer and a second negative electrode active material layer, the first negative electrode active material layer is arranged on the current collector, the second negative electrode active material layer is arranged on one side, far away from the current collector, of the first negative electrode active material layer, the first negative electrode active material layer and the second negative electrode active material layer comprise a first binder, the first binder comprises polyacrylic acid, and the content of the first binder in the first negative electrode active material layer or the second negative electrode active material layer is 1.2-1.3 wt%.
In an embodiment of the present invention, the first anode active material layer includes a first anode active material having a Dv50 of 13 μm to 17 μm;
wherein Dv50 represents that 50% of the particles of the first anode active material have a particle size distribution on a volume basis smaller than this value.
In an embodiment of the present invention, the second anode active material layer includes a second anode active material layer, and a difference in Dv50 of the first anode active material and the second anode active material is 0 to 7 μm.
In one embodiment of the present invention, the gram-capacity of the first negative electrode active material is smaller than the gram-capacity of the second negative electrode active material.
In one embodiment of the present invention, the total thickness of the anode active material layer is 140 μm to 280 μm.
In one embodiment of the present invention, the ratio of the thickness of the first anode active material layer to the thickness of the second anode active material layer is ε, and ε is 0.62 ε 1.32.
In an embodiment of the present invention, the first anode active material layer and the second anode active material layer include a second binder including a methylcellulose-based binder, and the content of the second binder in the first anode active material layer or the second anode active material layer is 0.4wt% to 0.5wt%.
In an embodiment of the present invention, the first and second anode active material layers include a third binder including a styrene-butadiene rubber binder, and the third binder is contained in the first or second anode active material layer in an amount of 0.4wt% to 0.5wt%.
The invention also provides a preparation method of the lithium battery negative electrode plate, which at least comprises the following steps:
providing a current collector;
Preparing a first slurry and a second slurry;
Coating the first slurry on at least one side of the current collector to form a first slurry layer, and drying;
Coating the second slurry on the dried first slurry layer to form a second slurry layer;
and drying, rolling and shearing the first slurry layer and the second slurry layer to form the lithium battery negative electrode plate.
In one embodiment of the invention, the viscosity of the first slurry is 4800-7000 mPa.s, and the solid content is 54-57 wt%.
In one embodiment of the invention, the viscosity of the second slurry is 5000-8000 mPas and the solid content is 54-57 wt%.
The invention also provides an electrochemical device comprising the lithium battery negative electrode plate.
In summary, the lithium battery negative electrode piece, the preparation method and the application thereof provided by the invention have the advantages that the negative electrode active material layers formed by different negative electrode active materials can ensure the capacity and the cycle performance of the lithium battery, and simultaneously ensure the fast charge/fast discharge and the high and low temperature performance of the lithium battery, thereby ensuring that the lithium battery has good high and low temperature performance and cycle stability. The content of the negative electrode active material is improved, and the capacity performance of the negative electrode plate of the lithium battery is further ensured. The uniformity and consistency of the negative pole piece of the lithium battery can be improved, and the performance of the lithium battery is improved. The thickness of the negative electrode active material layer is increased to increase the capacity of the lithium battery. The multi-layer anode active material layer selects anode active materials with different performances, and the lithium battery can simultaneously meet high dynamics and long cycle performance.
Of course, it is not necessary for any of the above described advantages to be achieved simultaneously in practicing any of the embodiments of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a negative electrode tab of a lithium battery according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a negative electrode tab of a lithium battery according to another embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a lithium battery according to an embodiment of the present invention.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention.
It should be understood that the present invention may be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Furthermore, the terms "first," "second," and the like, as used herein, are used for descriptive and distinguishing purposes only and are not to be construed as indicating or implying a relative importance.
The technical solution of the present invention will be described in further detail below with reference to several embodiments and the accompanying drawings, and it is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Lithium batteries have been increasingly used in a variety of fields, having advantages of high specific energy, no memory effect, and long cycle life. The lithium battery comprises a positive electrode, a negative electrode, electrolyte and a diaphragm, wherein the negative electrode is a carrier of lithium ions and electrons in the charging process of the battery, plays roles in energy storage and release, and mainly influences the first efficiency, the cycle performance, the multiplying power (quick charge) and the like of the lithium battery. The lithium battery negative electrode plate, the preparation method and the application thereof provided by the invention have high dynamics and long cycle performance, and can improve the performance of the lithium battery.
Referring to fig. 1 to 2, in an embodiment of the present invention, a negative electrode tab of a lithium battery is provided, the negative electrode tab includes a current collector 10 and a negative electrode active material layer 20, and the negative electrode active material layer 20 is disposed at least on one side of the current collector 10. Wherein the anode active material layer 20 includes a first anode active material layer 21 and a second anode active material layer 22, the first anode active material layer 21 is disposed on the current collector 10, and the second anode active material layer 22 is disposed on a side of the first anode active material layer 21 away from the current collector 10. Wherein the first anode active material layer 21 includes a first anode active material, the second anode active material layer 22 includes a second anode active material, and the particle size, specific surface area, gram capacity, and the like of the first anode active material and the second anode active material are different. And the first anode active material layer 21 and the second anode active material layer 22 include a plurality of binders therein, the total content of the binders is reduced, the capacity performance of the anode sheet is improved, and the interface performance of the anode active material layer is improved while satisfying high kinetics and long cycle performance.
Referring to FIGS. 1 to 2, in one embodiment of the present invention, the total thickness of the anode active material layer 20 is, for example, 140 μm to 280 μm, and the ratio of the thickness of the first anode active material layer 21 to the thickness of the second anode active material layer 22 is ε, which is 0.62 ε.ltoreq.1.32. In the present embodiment, the anode active material layers 20 are provided on both sides of the current collector 10, for example, and the thicknesses of the first anode active material layers 21 on both sides of the current collector 10 are the same, and the thicknesses of the second anode active material layers 22 on both sides of the current collector 10 are the same. In other embodiments, the thickness of the first anode active material layer 21 and/or the second anode active material layer 22 may be different on both sides of the current collector 10 according to manufacturing requirements.
Referring to fig. 1 to 2, in an embodiment of the present invention, the current collector 10 is, for example, a copper foil current collector, a composite copper foil current collector, a carbon current collector, a foam copper current collector, or a stainless steel current collector, and the thickness of the current collector 10 is, for example, 8 μm-12 μm. The negative electrode active material layer 20 is provided on the surface of the current collector 10, and the negative electrode active material layer 20 is provided at least on one side of the current collector 10, that is, the negative electrode active material layer 20 may be provided on both sides of the current collector 10, or the negative electrode active material layer 20 may be provided on one side of the current collector 10, specifically, may be selected according to the manufacturing requirements.
Referring to fig. 1 to 2, in an embodiment of the present invention, the first anode active material layer 21 includes a first anode active material, and the second anode active material layer 22 includes a second anode active material. The negative electrode active material is a material capable of intercalating and deintercalating lithium, and includes, but is not limited to, carbon materials such as crystalline carbon (natural graphite, artificial graphite, and the like), amorphous carbon, carbon-coated graphite, and resin-coated graphite, and may be oxide materials such as indium oxide, silicon oxide, tin oxide, lithium titanate, zinc oxide, and lithium oxide, or may be lithium metal or a metal material capable of forming an alloy with lithium. Among them, a metal material forming an alloy with lithium, for example Cu, sn, si, co, mn, fe, sb, ag, or the like, may be used, and a binary or ternary alloy containing these metals and lithium may be used as the negative electrode active material. These negative electrode active materials may be used alone or in combination of two or more. From the viewpoint of increasing the energy density, a carbon material such as graphite may be used in combination with a Si-based material such as Si, si alloy, or Si oxide.
Referring to fig. 1 to 2, in an embodiment of the present invention, the first negative electrode active material includes, for example, a first graphite, the second negative electrode active material includes, for example, a second graphite, and the performance parameters of the first graphite and the second graphite are shown in table 1. In this example, the first graphite is artificial graphite prepared from petroleum coke, for example, and has Dv50 of 13 μm to 17 μm, for example, the specific surface area (Special Surface Area, SSA) of the first graphite is 1.38m 2/g, the bulk density (TAP DENSITY, TD) is 1.08g/cc, the gram capacity is 348mAh/g, and the first efficiency is 93.1%, for example, i.e., the first graphite is high-energy-ratio graphite, wherein Dv50 represents that 50% of the particle size of the anode active material in the volume-based particle size distribution is smaller than this value. The second graphite is artificial graphite prepared from needle coke, for example, and has a Dv50 of 10 μm to 13 μm, for example, a specific surface area (Special Surface Area, SSA) of 1.02m 2/g, a bulk density (TAP DENSITY, TD) of 1.08g/cc, a gram capacity of 355mAh/g, and a first efficiency of 93.4%, for example, i.e., the second graphite is a high kinetic graphite, for example. The difference between Dv50 of the first anode active material and Dv50 of the second anode active material is, for example, 0-7 μm, i.e., the particle size of the second anode active material is less than or equal to the particle size of the first anode active material, and the gram capacity of the first anode active material is less than the gram capacity of the second anode active material. Through set up the negative pole active material layer including different negative pole active material on the mass flow body, the capacity and the cyclic performance of lithium cell can be guaranteed to the first negative pole active material that is close to the mass flow body, and the second negative pole active material that keeps away from the mass flow body can guarantee the quick charge/quick release and the high low temperature performance of lithium cell to ensure that lithium cell possesses good low temperature performance and cyclic stability.
Table 1, performance parameters of the first graphite and the second graphite
Referring to fig. 1 to 2, in an embodiment of the present invention, the first anode active material layer 21 and the second anode active material layer 22 include a plurality of binders, specifically, for example, a first binder, a second binder, a third binder, and the like. The first binder includes, for example, a Polyacrylic Acid (PAA) binder, and the content of the first binder in the first anode active material layer 21 or the second anode active material layer 22 is, for example, 1.2wt% to 1.3wt%. The second binder includes, for example, a carboxymethyl cellulose (Carboxymethyl Cellulose, CMC) type binder, specifically, sodium carboxymethyl cellulose or other carboxymethyl cellulose salt, etc., and the content of the second binder in the first anode active material layer 21 or the second anode active material layer 22 is, for example, 0.4wt% to 0.5wt%. The third binder includes, for example, styrene-butadiene rubber (Polymerized Styrene Butadiene Rubbe, SBR) binder, and the content of the third binder in the first anode active material layer 21 and the second anode active material layer 22 is, for example, 0.4wt% to 0.5wt%. Through the mixed use of the binders, the first binder is a binder with a surface structure, has good binding performance, good wettability in a water system solvent and small expansion coefficient, can reduce the dosage of the second binder in slurry, improves the content of the anode active material, and further ensures the capacity performance of the anode pole piece.
The invention also provides a preparation method of the lithium battery negative electrode plate, which at least comprises the steps S11-S15.
Step S11, providing a current collector, and cleaning and drying the current collector.
Step S12, preparing a first slurry and a second slurry.
And S13, coating a first slurry on the current collector to form a first slurry layer, and drying.
And step S14, coating the second slurry on the dried first slurry layer to form a second slurry layer.
And S15, drying, rolling and shearing the first slurry layer and the second slurry layer to form the negative electrode plate.
In an embodiment of the present invention, in step S11, the type of the current collector is selected according to the manufacturing requirement, and the current collector is processed. In this embodiment, the current collector is cleaned in an ultrasonic cleaner sequentially with absolute ethanol, acetone and deionized water to remove oil stains on the current collector, and then dried in a vacuum drying oven at a drying temperature of 60-80 ℃ for 20-30 min. The effect of pollutants on the current collector on the battery performance is reduced by treating the current collector.
In an embodiment of the present invention, in step S12, the first binder, the first anode active material, and the conductive agent required for preparation are premixed dry-mixed at the time of preparing the first slurry. After mixing well, for example, adding a solvent in an amount of 30wt% to 50wt% of the total solvent in the first slurry, dispersing at a high speed for, for example, 25min to 35min, adding a second binder, and continuing dispersing at a high speed for, for example, 80min to 100min. And continuously adding 50-70wt% of solvent in the total solvent amount in the first slurry, adding a third binder when the solid content in the first slurry is regulated to be 54-57 wt%, dispersing at a low speed for 25-35 min, and defoaming to obtain the first slurry.
In an embodiment of the present invention, in step S12, the first binder, the second anode active material, and the conductive agent required for preparation are premixed dry-blended in preparing the second slurry. After mixing well, for example, adding a solvent in an amount of 30wt% to 50wt% of the total solvent in the second slurry, dispersing at a high speed for, for example, 25min to 35min, adding a second binder, and continuing dispersing at a high speed for, for example, 80min to 100min. And continuously adding 50-70wt% of solvent in the total solvent amount in the second slurry, adding a third binder when the solid content in the second slurry is regulated to be 54-57 wt%, dispersing at a low speed for 25-35 min, and defoaming to obtain the second slurry.
In an embodiment of the present invention, in step S12, the conductive agent is any one or more of conductive carbon black (Super P, SP), acetylene black, carbon nanotubes (Carbon Nanotube, CNT), graphene, and the like, and in this embodiment, the conductive agent is conductive carbon black, for example. In the first slurry or the second slurry, the content of the conductive agent is, for example, 0.42wt% to 0.60wt%, the content of the first binder is, for example, 1.2wt% to 1.3wt%, the content of the second binder is, for example, 0.4wt% to 0.5wt%, and the content of the third binder is, for example, 0.4wt% to 0.5wt%, in terms of 100%.
In an embodiment of the present invention, in step S12, the first negative electrode active material is, for example, first graphite, and in the first slurry, the content of the first negative electrode active material is, for example, 97.2wt% to 97.5wt% in terms of 100% of the substances other than the solvent. The second anode active material is, for example, second graphite, and in the second slurry, the content of the second anode active material is, for example, 97.2wt% to 97.5wt% in terms of 100% of the substances other than the solvent.
In one embodiment of the present invention, in step S12, the solvent in the first slurry and the second slurry is, for example, deionized water, and the first slurry and the second slurry are dispersed, for example, on a magnetic stirrer or a vacuum stirrer. In other embodiments, the solvent may be selected according to the manufacturing requirements, and the dispersion manner and dispersion speed may be adjusted according to the production. In the first slurry and the second slurry, except for the anode active materials, the formulations of the slurries are the same, so that the arrangement consistency of graphite particles at the contact surface of the first anode active material layer and the second anode active material layer can be improved, the phenomenon of graphite slippage caused by different binding force of the upper layer and the lower layer is avoided, and the ordered arrangement of graphite in the anode pole piece is ensured. Namely, the first sizing agent and the second sizing agent are used for preparing the negative electrode plate by adopting the same formula, so that the uniformity and consistency of the negative electrode plate can be improved, and the performance of the lithium battery can be improved.
In an embodiment of the present invention, in step S13, before the first slurry and the second slurry are coated, other coatings may be coated on the current collector processed in step S11, or the first slurry may be directly coated, which is specifically selected according to the manufacturing requirements of the lithium battery, and the present invention is not limited specifically. The first slurry is applied as a single layer by doctor blade coating, roll coating, slot die coating, or the like, specifically by a coating head, for example. Wherein the solid content in the first slurry is, for example, 54-57 wt%, the shipment viscosity of the first slurry is, for example, 4800 mPa.s-7000 mPa.s, and the maximum fineness of the first slurry shipment is less than or equal to 35 mu m. The first slurry layer is formed on one side or both sides of the current collector, and the first slurry layer is subjected to a drying process, for example, in a vacuum dryer or a heating box.
In an embodiment of the present invention, in step S14, after the first slurry layer is dried, a second slurry is coated on the first slurry layer, and the second slurry is coated in a single layer, for example, by doctor blade coating, roll coating, slot die coating, or the like, specifically, by a coating grinding head, that is, by single die double layer coating on the current collector. Wherein the solid content in the second slurry is, for example, 54-57 wt%, the shipment viscosity of the second slurry is, for example, 5000-8000 mPa.s, and the maximum fineness of the second slurry shipment is less than or equal to 35 μm. A second slurry layer is formed on the first slurry layer on one or both sides.
In an embodiment of the present invention, in step S15, after the second slurry is applied, the first slurry layer and the second slurry layer are dried, for example, in a vacuum dryer or a heating box, etc. And after the slurry layer is dried, rolling, shearing and the like are carried out on the current collector to form a negative electrode plate, and in the rolling process, the highest compaction density of the first negative electrode active material and/or the second negative electrode active material is considered, so that the defects of cracks or breakage and the like of the negative electrode active material layer caused by overlarge pressure are avoided. In this embodiment, the first slurry layer forms the first anode active material layer after being dried and rolled, and the second slurry layer forms the second anode active material layer after being dried and rolled. In this embodiment, for example, the first anode active material layer and the second anode active material layer are provided on both sides of the current collector, and the total thickness of the first anode active material layer and the second anode active material layer is, for example, 140 μm to 280 μm. The thickness of the negative electrode active material layer is increased by double-layer coating to increase the capacity of the lithium battery.
Referring to fig. 3, the present invention further provides a lithium battery, which includes a negative electrode plate 100, a positive electrode plate 200, a separator 300 and an electrolyte 400, wherein the separator 300 is located between the negative electrode plate 100 and the positive electrode plate 200, the electrolyte 400 is filled between the negative electrode plate 100, the positive electrode plate 200 and the separator 300, and the negative electrode plate 100 is the negative electrode plate obtained by the above method. The lithium battery is, for example, a primary battery or a secondary battery, and is, for example, a secondary battery. And lithium ion secondary batteries are, for example, pouch batteries, hard case batteries, cylindrical batteries, and the like.
Referring to fig. 3, in an embodiment of the present invention, the positive electrode tab 200 includes, for example, a positive electrode current collector, and a positive electrode active material layer disposed on the positive electrode current collector. The positive current collector is, for example, a foil formed by surface treatment of nickel, titanium, aluminum, nickel, silver, stainless steel or carbon, and the surface of the positive current collector is smooth, or fine grains and the like can be formed on the surface of the positive current collector, so that the adhesion between the positive active material and the positive current collector is improved. The positive electrode current collector may be used in combination of any one or more of a plurality of forms such as a film, a mesh, a porous form, a foam, and a nonwoven fabric, in addition to the foil.
In one embodiment of the present invention, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material is selected from one or more of LiMnO2、LiFeO2、LiMn2O4、Li2FeSiO4、LiNi1/3Co1/3Mn1/3O2、LiNi5CO2Mn3O2、LiFePO4、LizNi(1-x-y)CoxMyO2、LiNiaCobMncMepO2, li mCo(1-n)MxO2, and the like. Wherein in Li zNi(1-x-y)CoxMyO2, x is more than or equal to 0.01 and less than or equal to 0.20, y is more than or equal to 0 and less than or equal to 0.20, z is more than or equal to 0.97 and less than or equal to 1.20, and M is at least one element selected from Mn, V, mg, mo, nb and Al. In LiNi aCobMncMepO2, a+b+c=1, 0.ltoreq.p.ltoreq.0.1, and me is selected from Zr, zn, cu, cr, mg, fe, V, ti, sr, sb, Y, W, nb or a combination of one or more of Al. In Li mCo(1-n)MnO2, n is more than or equal to 0 and less than or equal to 0.1, m is more than or equal to 0.97 and less than or equal to 1.20, and M is selected from one or a combination of more of Mn, ni, V, mg, mo, nb and Al.
In an embodiment of the present invention, the positive electrode active material layer further includes a binder, a conductive agent, and the like, and the addition amount may be adjusted in 1 to 50wt% of the total amount of the positive electrode active material according to different requirements. The conductive agent is, for example, a graphite material such as natural graphite or artificial graphite, a carbon black material such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black or thermal black, a conductive fiber such as carbon fiber or metal fiber, a metal powder such as carbon fluoride powder, aluminum powder or nickel powder, a conductive whisker such as zinc oxide or potassium titanate, a conductive metal oxide such as titanium dioxide, or a polyphenylene derivative, or a reagent for ensuring good charge/discharge performance of the electrode. The binder is selected from, for example, polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber or fluororubber, and various copolymers, etc., to facilitate bonding between the positive electrode active material and the conductive agent, and to facilitate bonding of the positive electrode active material and the positive electrode current collector.
Referring to fig. 3, in an embodiment of the invention, the positive electrode active material is selected from LiNi 0.8Co0.1Mn0.1O2, the binder is selected from polyvinylidene fluoride, the conductive agent is selected from acetylene black, the positive electrode active material, the binder and the conductive agent are mixed according to a mass ratio of 98:1:1, and a proper amount of solvent N-methyl pyrrolidone (N-Methylpyrrolidone, NMP) is added, and the mixture is stirred by a vacuum stirrer until the positive electrode slurry is uniformly transparent, thereby obtaining the positive electrode slurry. The positive electrode slurry is uniformly coated on an aluminum foil current collector of 16 mu m, dried at room temperature, transferred to an oven, dried at 80-120 ℃ for 6 hours, and cold-pressed and cut to obtain a positive electrode sheet 200.
Referring to fig. 3, in an embodiment of the present invention, the separator 300 is, for example, a Polyethylene (PE), a Polypropylene (PP), a glass fiber film, a Polyethylene film, or the like. Wherein the thickness of the separator 300 is, for example, 9 μm to 18 μm, the porosity is, for example, 30% to 50%, the pore size is 5 μm to 300 μm, and the air permeability is 180s/100mL to 380s/100mL. The separator 300 has high ion permeability, high mechanical strength, chemical resistance, and hydrophobicity to ensure insulation between the negative electrode tab 100 and the positive electrode tab 200.
Referring to fig. 3, in an embodiment of the present invention, the electrolyte 400 includes, for example, an organic solvent, a lithium salt, an additive, and the like. The organic solvent is selected, for example, from dimethyl carbonate (Dimethyl Carbonate, DMC), diethyl carbonate (Diethyl Carbonate, DEC), dipropyl carbonate (Dipropyl Carbonate, DPC), methylpropyl carbonate (Methyl Propyl Carbonate, MPC), ethylpropyl carbonate (Ethylpropyl Carbonate, EPC), methylethyl carbonate (MEC), methylethyl carbonate (ETHYL METHYL Carbonate, EMC), ethylene carbonate (Ethylene Carbonate, EC), propylene carbonate (Propylene Carbonate, PC) and butylene carbonate (Butylene Carbonate, BC). The lithium salt is at least one selected from LiPF 6、LiBF4、LiN(SO2F)2 (abbreviated as LiFSI), liClO 4、LiAsF6、LiB(C2O4)2 (abbreviated as LiBOB), liBF 2(C2O4 (abbreviated as libfob), liN (SO 2RF)2) and LiN (SO 2 F) (abbreviated as SO 2RF), for example. The additive is selected from, for example, one or more of vinylene carbonate (Vinylene Carbonate, VC), fluoroethylene carbonate (Fluoroethylene Carbonate, FEC), ethylene carbonate (4-Vinyl-1, 3-dioxolan-2-one, VEC), ethylene sulfate (DTD), vinylene sulfate, 1,3-propane sultone (1, 3-Propanesultone, PS), propenyl sultone or 1,4-butane sultone (1, 4-Butanesultone), and the like. and the amount of the additive in the electrolyte 400 is, for example, 1wt% to 4wt% of the electrolyte, and is, for example, 2wt%. In this embodiment, the organic solvent is, for example, a mixed solution of Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC), wherein the volume ratio of EC, EMC and DEC is, for example, 20:20:60, and in an argon atmosphere glove box with a water content of less than 10ppm, the LiPF 6 that is sufficiently dried is dissolved in the above mixed organic solvent, and the electrolyte is obtained after uniform mixing, wherein the concentration of LiPF 6 is 1mol/L.
For a further understanding of the present invention, reference will now be made in detail to the present embodiments, which are not to be construed as limiting. Appropriate modifications may be made within the scope consistent with the gist of the invention, which fall within the technical scope of the invention.
Example 1
Preparing a positive electrode plate: mixing an anode active material LiNi 0.8Co0.1Mn0.1O2, an adhesive polyvinylidene fluoride and a conductive agent acetylene black according to a mass ratio of 98:1:1, adding a solvent N-methyl pyrrolidone, and stirring in a vacuum stirrer until the anode active material is uniform and transparent, thus obtaining anode slurry. And uniformly coating the positive electrode slurry on an aluminum foil current collector with the thickness of 16 mu m, airing the current collector at room temperature, transferring the current collector to an oven, drying the current collector at the temperature of 100 ℃ for 6 hours, and then carrying out cold pressing and slitting to obtain the positive electrode plate.
Preparing a negative electrode plate: the current collector is selected from copper foil, and is washed in an ultrasonic cleaner by absolute ethyl alcohol, acetone and deionized water in sequence, and is dried for 30min at 70 ℃ in a vacuum drying oven. Dry-mixing 1.3wt% of a first binder, 97.3wt% of first graphite and 0.4wt% of a conductive agent, adding water, stirring for 30min after uniformly mixing, adding 0.5wt% of a second binder, continuing high-speed dispersion for 90min, adding 0.5wt% of a third binder, stirring for 30min slowly when adding water to adjust the solid content of the slurry to 55wt%, and defoaming to obtain the first slurry. Dry-mixing 1.3wt% of a first binder, 97.3wt% of second graphite and 0.4wt% of a conductive agent, adding water, stirring for 30min, adding 0.5wt% of a second binder, continuing high-speed dispersion for 90min, adding 0.5wt% of a third binder, stirring for 30min slowly when the solid content of the slurry is adjusted to 55wt% by adding water, and defoaming to obtain a second slurry. Wherein the first binder is a PAA binder, the conductive agent is conductive carbon black, the second binder is a CMC binder, and the third binder is an SBR binder. And coating the first slurry on two sides of the current collector through a coating grinding head in a single layer to form a first slurry layer, and drying the first slurry layer. Wherein the D50 of the first slurry discharge is 10.4 μm. After the first slurry layer is dried, a second slurry layer is formed by coating a single layer of the second slurry on the first slurry layer on both sides of the current collector by a coating grinding head. Wherein the D50 of the second slurry discharge was 24.8. Mu.m. And drying the first slurry layer and the second slurry layer to form a first anode active material layer and a second anode active material layer, wherein the total thickness of the first anode active material layer and the second anode active material layer is 180 mu m, and the ratio epsilon of the total thickness of the first anode active material layer and the total thickness of the second anode active material layer is 0.64. The current collector is then rolled and sheared, etc., to form the negative electrode sheet.
Preparation of electrolyte: mixing ethylene carbonate, methyl ethyl carbonate and diethyl carbonate according to the volume ratio of 20:20:60. In an argon atmosphere glove box with the water content of less than 10ppm, the fully dried LiPF 6 is dissolved in a mixed organic solvent, and the electrolyte is obtained after uniform mixing, wherein the concentration of the LiPF 6 is 1mol/L.
Selection of a diaphragm: a polypropylene separator of 12 μm thickness was selected.
Preparation of the battery: and sequentially laminating the prepared positive pole piece, the diaphragm and the negative pole piece, so that the diaphragm is positioned between the positive pole piece and the negative pole piece to play a role in isolation. And then coating an aluminum plastic film, transferring the film into a vacuum oven, drying at 120 ℃, injecting electrolyte solution of 3.0g/Ah, sealing, and performing the procedures of standing, hot and cold pressing, formation, clamping, capacity division and the like to prepare the soft-package battery with the capacity of 1 Ah. The formation step is to charge the battery at 0.02C for 17min in a hot-press environment at a pressure of, for example, 0.1MPa and a temperature of, for example, 45C after pouring the electrolyte. Then standing for 5min, then charging 0.02C to 0.3Ah, then cutting off the air bag, vacuum packaging, and standing for 48h at normal temperature, thereby completing formation of the electrolyte.
Example 2
The total thickness of the first anode active material layer was 90 μm, and the total thickness of the second anode active material layer was 90 μm, that is, the ratio ε of the total thickness of the first anode active material layer and the total thickness of the second anode active material layer was 1, and the other operations were the same as in example 1.
Example 3
The total thickness of the first anode active material layer was 104 μm, the total thickness of the second anode active material layer was 76 μm, that is, the ratio ε of the total thickness of the first anode active material layer and the total thickness of the second anode active material layer was 1.36, and the other operations were the same as in example 1.
Comparative example 1
Only the first anode active material layer was provided on the current collector, and the total thickness of the first anode active material layer was 180 μm, and the other operations were the same as in example 1.
Comparative example 2
Only the second anode active material layer was provided on the current collector, and the total thickness of the second anode active material layer was 180 μm, and the other operations were the same as in example 1.
To verify the performance of the negative electrode tabs obtained in examples 1-3 and comparative examples 1-2, the initial direct current resistance (DIRECTIVE CURRENT RESISTANCE, DCR), initial capacity and capacity retention at 1C current density of 500 cycles of the batteries composed of different negative electrode tabs were tested under conditions such as 25 ℃.
The performance of the lithium batteries prepared with the negative electrode tabs of examples 1 to 3 and comparative examples 1 to 2 was tested, and the test results are shown in table 2.
Table 2, examples 1-3 and comparative examples 1-2 performance of lithium batteries
Referring to table 2, in combination with examples 1 to 3 and comparative example 1, when only the first negative active material layer is provided on the current collector, the cycle performance of the lithium battery is good, but the initial DCR value of the lithium battery is high, and the fast charge performance of the lithium battery cannot be ensured. In combination with examples 1 to 3 and comparative example 2, when only the second negative active material layer was provided on the current collector, the initial DCR value of the lithium battery was low, the quick charge performance of the lithium battery was good, but the capacity and cycle performance of the lithium battery were poor. In combination with examples 1 to 3 and comparative examples 1 to 2, when the first negative electrode active material layer and the second negative electrode active material layer are simultaneously provided on the current collector, the initial DCR value, capacity and cycle performance of the lithium battery can be simultaneously considered, i.e., the capacity and cycle performance of the lithium battery can be ensured, and meanwhile, the quick charge/quick discharge and high and low temperature performance of the lithium battery can be ensured, thereby obtaining a lithium battery with good capacity and cycle stability.
In summary, according to the lithium battery negative electrode piece, the preparation method and the application thereof, the negative electrode active material layers comprising different negative electrode active materials are arranged on the current collector, the first negative electrode active material close to the current collector can ensure the capacity and the cycle performance of the lithium battery, and the second negative electrode active material far away from the current collector can ensure the fast charge/fast discharge and the high and low temperature performance of the lithium battery, so that the lithium battery is ensured to have good low temperature performance and cycle stability. The content of the negative electrode active material is improved by mixing the binder, so that the capacity performance of the negative electrode plate is ensured. The first sizing agent and the second sizing agent are used for preparing the negative electrode plate by adopting the same formula, so that the uniformity and consistency of the negative electrode plate can be improved, and the performance of the lithium battery can be improved. The thickness of the negative electrode active material layer is increased by double-layer coating to increase the capacity of the lithium battery. The current collector is provided with a plurality of anode active material layers, and the anode active material layers are made of anode active materials with different performances, so that high dynamics and long cycle performance can be simultaneously met.
The above description is only a preferred embodiment of the present application and the description of the technical principle applied, and it should be understood by those skilled in the art that the scope of the present application is not limited to the specific combination of the above technical features, but also covers other technical features formed by any combination of the above technical features or the equivalent features thereof without departing from the inventive concept, for example, the technical features disclosed in the present application (but not limited to) are replaced with technical features having similar functions. Other technical features besides those described in the specification are known to those skilled in the art, and are not described herein in detail to highlight the innovative features of the present application.
Claims (12)
1. A lithium battery negative electrode tab, comprising:
A current collector; and
A negative electrode active material layer provided at least on one side of the current collector;
The negative electrode active material layer comprises a first negative electrode active material layer and a second negative electrode active material layer, the first negative electrode active material layer is arranged on the current collector, and the second negative electrode active material layer is arranged on one side, far away from the current collector, of the first negative electrode active material layer;
The first and second anode active material layers include a first binder including polyacrylic acid, and the content of the first binder in the first or second anode active material layer is 1.2wt% to 1.3wt%.
2. The lithium battery negative electrode tab according to claim 1, wherein the first negative electrode active material layer comprises a first negative electrode active material having a Dv50 of 13 μιη -17 μιη;
wherein Dv50 represents that 50% of the particles of the first anode active material have a particle size distribution on a volume basis smaller than this value.
3. The negative electrode tab for a lithium battery according to claim 2, wherein the second negative electrode active material layer includes a second negative electrode active material layer, and a difference in Dv50 of the first negative electrode active material and the second negative electrode active material is 0-7 μm.
4. The lithium battery negative electrode tab of claim 3, wherein the gram capacity of the first negative electrode active material is less than the gram capacity of the second negative electrode active material.
5. The negative electrode tab for a lithium battery according to claim 1, wherein the total thickness of the negative electrode active material layer is 140 μm to 280 μm.
6. The negative electrode tab for a lithium battery according to claim 1, wherein a ratio of a thickness of the first negative electrode active material layer to a thickness of the second negative electrode active material layer is ∈ and satisfies 0.62 ∈ 1.32.
7. The negative electrode tab for a lithium battery according to claim 1, wherein the first negative electrode active material layer and the second negative electrode active material layer include a second binder including a methylcellulose-based binder, and the content of the second binder in the first negative electrode active material layer or the second negative electrode active material layer is 0.4wt% to 0.5wt%.
8. The negative electrode tab for a lithium battery according to claim 1, wherein the first negative electrode active material layer and the second negative electrode active material layer include a third binder including a styrene-butadiene rubber binder, and the content of the third binder in the first negative electrode active material layer or the second negative electrode active material layer is 0.4wt% to 0.5wt%.
9. A method for preparing a negative electrode sheet for a lithium battery according to any one of claims 1 to 8, comprising at least the steps of:
providing a current collector;
Preparing a first slurry and a second slurry;
Coating the first slurry on at least one side of the current collector to form a first slurry layer, and drying;
Coating the second slurry on the dried first slurry layer to form a second slurry layer;
and drying, rolling and shearing the first slurry layer and the second slurry layer to form the lithium battery negative electrode plate.
10. The method for preparing a negative electrode plate of a lithium battery according to claim 9, wherein the viscosity of the first slurry is 4800-7000 mPa-s, and the solid content is 54-57 wt%.
11. The method for preparing a negative electrode plate of a lithium battery according to claim 9, wherein the viscosity of the second slurry is 5000-8000 mPa-s, and the solid content is 54-57 wt%.
12. An electrochemical device comprising the lithium battery negative electrode tab of any one of claims 1-8.
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