CN113113682A - Lithium supplement current collector, preparation method thereof, lithium supplement electrode piece and lithium battery - Google Patents

Lithium supplement current collector, preparation method thereof, lithium supplement electrode piece and lithium battery Download PDF

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CN113113682A
CN113113682A CN202110388129.4A CN202110388129A CN113113682A CN 113113682 A CN113113682 A CN 113113682A CN 202110388129 A CN202110388129 A CN 202110388129A CN 113113682 A CN113113682 A CN 113113682A
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lithium
current collector
polymer
supplement
lithium supplement
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CN113113682B (en
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赵晓宁
蔡挺威
刘永飞
梁世硕
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Kunshan Bao Innovative Energy Technology Co Ltd
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Kunshan Bao Innovative Energy Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0409—Methods of deposition of the material by a doctor blade method, slip-casting or roller coating
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H01M4/0435—Rolling or calendering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Composite Materials (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention discloses a lithium supplement current collector which comprises a metal foil and a lithium supplement layer loaded on the metal foil, wherein the lithium supplement layer comprises conductive carbon, a lithium-containing additive, a first polymer and/or a derivative thereof and a second polymer and/or a derivative thereof, the first polymer is selected from one or more of polyacrylic acid, polymethyl methacrylate, polyvinyl alcohol, polystyrene, polyvinylidene fluoride, carboxymethyl cellulose, epoxy resin and phenolic resin, and the second polymer is polytetrafluoroethylene. The invention also discloses a preparation method of the lithium supplement current collector, which comprises the following steps: placing the lithium supplement slurry between preheated rollers of a roller press for rolling to obtain a self-supporting lithium supplement coating, wherein the preheating temperature of the rollers is 50-150 ℃; and (3) placing the self-supporting lithium supplement coating on the metal foil, and performing hot-pressing compounding between preheated rollers. The invention also discloses a negative plate. The invention also discloses a lithium battery.

Description

Lithium supplement current collector, preparation method thereof, lithium supplement electrode piece and lithium battery
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a lithium supplement current collector, a preparation method of the lithium supplement current collector, a lithium supplement electrode sheet and a lithium battery.
Background
In recent years, the market share of new energy automobiles in passenger cars and special cars is gradually increased. However, the problem of short driving range of new energy vehicles in the market at present generally exists, and particularly low-end entrance vehicles limit further popularization of the new energy vehicles. Therefore, how to increase the driving mileage of the new energy automobile and reduce the production cost of the new energy automobile becomes a problem which needs to be solved urgently in the new energy industry.
The lithium ion battery is used as a core component of a new energy automobile, provides corresponding power output for the running of the automobile, and the main means for improving the running mileage of the automobile is to improve the energy density of the lithium ion battery. In view of the current industry development and the current technical situation, the methods for improving the energy density of the battery cell are many, and can be roughly divided into two layers of the battery cell and the material. In the aspect of the battery cell, the proportion of active components is improved to the maximum extent by optimizing the structural design of the battery cell, but the improvement effect is limited. The material is diversified in means, and problems can be fundamentally solved, for example, high-specific-capacity negative electrode materials (silicon carbon negative electrodes, silicon negative electrodes and lithium metal negative electrodes), high-specific-capacity positive electrodes (high-nickel and lithium-rich positive electrodes), high-voltage positive electrodes (lithium cobaltate and lithium manganate) and the like are adopted, but innovation in the material aspect is often the most difficult, and a large amount of time is needed for optimization.
The silicon negative electrode material is gradually popularized and applied as the most conventional material for improving the energy density of the battery cell in the current market. The technical means is mainly that a part of silicon materials are used for replacing conventional graphite materials to achieve the improvement of the capacity of a negative electrode, the specific capacity of a battery cell is improved, and the purpose of improving the energy density of the battery cell is further achieved; the silicon material as a negative electrode material with high specific capacity can actually realize great improvement of the negative electrode capacity, but the silicon material also has the problems of large self volume expansion, low first charge-discharge efficiency, poor cyclicity and the like. Therefore, how to apply silicon materials while still maintaining high first-effect and cycle performance becomes an urgent problem to be solved.
The negative electrode lithium supplement technology is a practical and effective means, can improve the first efficiency and the cycle performance of the battery cell, and makes up lithium consumed due to the formation of an SEI film and the generation of irreversible substances. At present, conventional lithium supplementing methods include lithium foil lithium supplementing, lithium powder lithium supplementing and the like, for example, a lithium supplementing method using porous lithium foil as a third pole is proposed in the patent publication No. CN107768743A of the euthanasia of the traditional chinese countries, which can achieve the purpose of lithium supplementing, but the introduced third pole greatly increases the difficulty of cell assembly, and the electrochemical method using the third pole to supplement lithium greatly affects the lithium supplementing speed and efficiency, and the lithium foil is too soft and has poor strength, so that the lithium foil is not suitable for assembling a large number of cells, and the safety in the assembling process is also considered; in addition, the Hunan Culten New energy science and technology, Inc. patent publication No. CN 109728306A states that a porous lithium foil layer is tightly adhered between two slurry layers to achieve the purpose of improving the first efficiency and the cycle performance, but the lithium foil between the two layers inevitably affects the adhesive force between the two slurry layers, the risk of falling off of a pole piece slurry layer exists in the battery cell cycle process, and the lithium foil has excessive limitation on the selection of a slurry solvent. Therefore, the existing lithium supplement technology is not mature enough, and has the problems of instability and poor safety.
Disclosure of Invention
Therefore, it is necessary to provide a lithium supplement current collector, a preparation method thereof, a lithium supplement electrode sheet and a lithium battery aiming at the problems of instability and poor safety of the conventional lithium supplement technology.
A lithium supplement current collector comprises a metal foil and a lithium supplement layer loaded on the metal foil, wherein the lithium supplement layer comprises conductive carbon, a lithium-containing additive, a first polymer and/or a derivative thereof, and a second polymer and/or a derivative thereof, the first polymer is selected from one or more of polyacrylic acid, polymethyl methacrylate, polyvinyl alcohol, polystyrene, polyvinylidene fluoride, carboxymethyl cellulose, epoxy resin and phenolic resin, and the second polymer is polytetrafluoroethylene.
In some embodiments, the mass percentage of the first polymer in the lithium supplement slurry is 1% to 50%, and the mass percentage of the second polymer in the lithium supplement slurry is 0.1% to 20%.
In some of these embodiments, the lithium-containing additive has a particle size of 500nm or less.
In some of these embodiments, the lithium supplement layer has a thickness of 0.1 μm to 12 μm.
In some embodiments, the conductive carbon is selected from any one or more of acetylene black, ketjen black, nano graphite, carbon nanotubes, and carbon black, and the mass percentage of the conductive carbon in the lithium supplement slurry is 20% to 90%.
In some of these embodiments, the lithium-containing additive is selected from any one or more of passivated lithium metal powder, lithium-rich metal oxide, and lithium-containing alloy.
In some of these embodiments, the metal foil is a copper foil or a stainless steel foil.
The preparation method of the lithium supplement current collector comprises the following steps:
placing the lithium supplement slurry between preheated rollers of a roller press for rolling to obtain a self-supporting lithium supplement coating, wherein the preheating temperature of the rollers is 50-150 ℃;
and placing the self-supporting lithium supplementing coating on the metal foil, and performing hot-pressing compounding between the preheated rollers.
In some embodiments, the preparation method of the lithium supplement slurry comprises the following steps:
mixing conductive carbon and a lithium-containing additive to obtain a primary mixed material;
mixing the primary blend, the first polymer, and the second polymer under air shear.
The negative plate comprises the lithium supplement current collector and a negative active material layer loaded on the lithium supplement current collector.
In some of these embodiments, the negative active material layer has silicon powder therein.
A lithium battery comprises a positive plate, a negative plate, a diaphragm and electrolyte.
The invention provides a lithium supplement current collector which solves the problems of low first effect, poor circulation and the like caused by lithium consumption due to the formation of an SEI film or the generation of irreversible substances in a battery cell. Lithium with required lithium supplement amount is introduced into the current collector in advance, the advantage of improving the multiplying power performance of the battery cell by combining the carbon-coated foil is combined, and the lithium supplement additive and the conductive carbon are simultaneously loaded on the surface of the current collector, so that the double effects of lithium supplement and multiplying power improvement are achieved; the method does not influence the preparation process of the subsequent pole piece slurry layer, does not influence the structure of the slurry layer, is suitable for the existing cell manufacturing procedure, and has obvious effect when being particularly used for a silicon-containing system. The scheme of adding the lithium supplement layer in the current collector is not only simpler to realize, but also can not cause the problems of safety and stability. Furthermore, a first polymer and a second polymer in the lithium supplement layer are matched with each other, and the addition of the first polymer can enhance the adhesive force between the lithium-containing coating and the metal foil, increase the adhesive force between the active material layer and the current collector and enhance the overall electrochemical performance of the electrode plate; in addition, the addition of the first polymer can effectively encapsulate the lithium-containing additive, thereby improving the activity stability of the lithium-containing additive in the battery. The second polymer provides support for the lithium supplement coating during rolling after air flow shear fiberization.
Drawings
Fig. 1 is a schematic structural diagram of a lithium replenishing current collector according to an embodiment of the present invention.
Detailed Description
To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different 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.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
Referring to fig. 1, an embodiment of the present invention provides a lithium supplement current collector, including a metal foil 1 and a lithium supplement layer loaded on the metal foil 1, where the lithium supplement layer includes conductive carbon 3, a lithium-containing additive 2, a first polymer and/or a derivative thereof, and a second polymer and/or a derivative thereof, the first polymer is selected from any one or more of polyacrylic acid (PAA), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), Polystyrene (PS), polyvinylidene fluoride (PVDF), carboxymethyl cellulose, epoxy resin, and phenolic resin, and the second polymer is polytetrafluoroethylene.
The invention provides a lithium supplement current collector which solves the problems of low first effect, poor circulation and the like caused by lithium consumption due to the formation of an SEI film or the generation of irreversible substances in a battery cell. Lithium with required lithium supplement amount is introduced into the current collector in advance, the advantage of improving the multiplying power performance of the battery cell by combining the carbon-coated foil is combined, and the lithium supplement additive and the conductive carbon 3 are simultaneously loaded on the surface of the current collector, so that the double effects of lithium supplement and multiplying power improvement are achieved; the method does not influence the preparation process of the subsequent pole piece slurry layer, does not influence the structure of the slurry layer, is suitable for the existing cell manufacturing procedure, and has obvious effect when being particularly used for a silicon-containing system. The scheme of adding the lithium supplement layer in the current collector is not only simpler to realize, but also can not cause the problems of safety and stability. Further, the first polymer and the second polymer in the lithium supplement layer are matched with each other, and the first polymer and the second polymer are crosslinked into the polymer fiber 4. The addition of the first polymer can enhance the adhesive force between the lithium-containing coating and the metal foil 1, increase the adhesive force between the active material layer and the current collector and enhance the overall electrochemical performance of the electrode plate; in addition, the addition of the first polymer can effectively encapsulate the lithium-containing additive 2, thereby improving the activity stability of the lithium-containing additive 2 in the battery. The second polymer provides support for the lithium supplement coating during rolling after air flow shear fiberization. .
The lithium supplement slurry may be composed of conductive carbon 3, lithium-containing additive 2, first polymer and/or its derivative, and second polymer and/or its derivative, and may also contain a suitable amount of other additives as needed.
In some embodiments, the mass percentage of the first polymer in the lithium supplement slurry is 1% to 50%, and the mass percentage of the second polymer in the lithium supplement slurry is 0.1% to 20%. Specifically, the mass percentage of the first polymer in the lithium supplement slurry can be 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%. The mass percentage of the second polymer in the lithium supplement slurry is 0.1%, 0.5%, 1%, 5%, 10%, 15% and 20%. Preferably, the mass percentage of the first polymer in the lithium supplement slurry is 1-30%, and the mass percentage of the second polymer in the lithium supplement slurry is 0.5-15%.
Preferably, the lithium-containing additive 2 is encapsulated by the first polymer in the lithium supplement layer.
In some embodiments, the lithium-containing additive 2 has a particle size of 500nm or less. The specific particle diameter may be 500nm, 400nm, 300nm, 200nm, 100nm, or the like.
In some embodiments, the lithium supplement layer has a thickness of 0.1 μm to 12 μm. . Preferably 1 to 6 μm.
In some embodiments, the conductive carbon 3 is selected from any one or more of acetylene black, ketjen black, nano graphite, carbon nanotubes, and carbon black, and the mass percentage of the conductive carbon 3 in the lithium supplement slurry is 20% to 90%. Specifically, the concentration may be 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%. Preferably, the mass percentage of the conductive carbon 3 in the lithium supplement slurry is 50-90%.
In some embodiments, the lithium-containing additive 2 is selected from any one or more of passivated lithium metal powder, lithium-rich metal oxide, and lithium-containing alloy. The amount of the lithium-containing additive 2 can be calculated according to the actual requirement of the amount of lithium supplement required by the pole piece.
In some embodiments, the metal foil 1 is a copper foil or a stainless steel foil.
The embodiment of the invention also provides a preparation method of the lithium supplement current collector, which comprises the following steps:
placing the lithium supplement slurry between preheated rollers of a roller press for rolling to obtain a self-supporting lithium supplement coating, wherein the preheating temperature of the rollers is 50-150 ℃;
and placing the self-supporting lithium supplementing coating on the metal foil 1, and performing hot-pressing compounding between the preheated rollers.
In the embodiment, the roller of the roller press is preheated to a proper temperature, the gap between the two rollers of the roller press is adjusted, a proper amount of powder is taken and placed on the roller of the roller press, rolling is carried out at a certain rolling speed, and the self-supporting lithium supplement coating with a certain thickness is prepared. In the process, the first polymer forms certain migration and mutual adhesion in the coating film due to heating to form a package for the lithium-containing additive 2, and the package is attached to the fiberized second polymer to form a uniform and compact coating, and the second polymer can be further fiberized in the hot pressing process, so that the fibers are directly overlapped with each other, and the coating strength is further improved.
The preheating temperature of the roller can be 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃ and 150 ℃, preferably 80 ℃ to 120 ℃.
In some embodiments, the gap of the roller can be 0.01um to 50um, and specifically can be 0.01um, 0.1um, 1um, 0.1um, 5um, 10um, 15um, 20um, 25um, 30um, 35um, 40um, 45um, 50 um. Preferably 0.1um to 10 um. More preferably 1um to 5 um.
In some embodiments, the rolling speed may be 1rpm to 20rpm, and specifically may be 1rpm, 2rpm, 3rpm, 4rpm, 5rpm, 6rpm, 7rpm, 8rpm, 9rpm, 10rpm, 11rpm, 12rpm, 13rpm, 14rpm, 15rpm, 16rpm, 17rpm, 18rpm, 19rpm, 20 rpm. Preferably 5rpm to 15 rpm.
In some embodiments, the method for preparing the lithium supplement slurry comprises the following steps:
mixing conductive carbon 3 and a lithium-containing additive 2 to obtain a primary mixed material;
mixing the primary blend, the first polymer, and the second polymer under air shear.
The mixing mode of the conductive carbon 3 and the lithium-containing additive 2 can be any one or combination of a plurality of mechanical stirring, ultrasonic dispersion, ball milling mixing, extruder mixing, vibration mixing and defoaming mixing.
As used herein, the term "first polymer" refers to a first polymer and/or derivative thereof, and "second polymer" refers to a second polymer and/or derivative thereof.
The primary mixing, the first polymer and the second polymer can be premixed before the gas flow shearing mixing, and the premixing mode can be any one or combination of more of mechanical stirring, ultrasonic dispersion, ball milling mixing, extruder mixing, vibration mixing and defoaming mixing. The premixing is preferably carried out under high shear.
The mixing time in the preparation process of the lithium supplementing slurry can be pulse mixing, namely, a part of pause time period exists in the stirring process, so that heat generation in the mixing process can be fully dissipated.
Fully mixing conductive carbon 3 and a lithium-containing additive 2 in a proper proportion to uniformly disperse the conductive carbon 3 and the lithium-containing additive to obtain a primary mixed material; then the secondary mixed material is obtained by high-speed shearing and mixing with the first polymer and the second polymer, so that the secondary mixed material is further fully and uniformly dispersed, and the second polymer is partially fiberized to generate a certain bonding effect, thereby realizing effective bonding of particle materials; and further shearing the mixed material by high-speed airflow to realize sufficient fiberization of the second polymer and obtain uniformly dispersed powder with certain viscosity.
The lithium-supplementing current collector is suitable for positive electrodes, negative electrodes, liquid batteries, semi-solid batteries and solid batteries.
The embodiment of the invention also provides a negative plate which comprises the lithium supplement current collector and a negative active material layer loaded on the lithium supplement current collector.
In some embodiments, the negative active layer has silicon powder therein.
The embodiment of the invention also provides a lithium battery which comprises a positive plate, a negative plate, a diaphragm and electrolyte. The negative electrode sheet may be selected from the negative electrode sheets of any of the above embodiments.
The nonaqueous electrolyte may be a nonaqueous electrolyte solution or a solid electrolyte membrane. The lithium ion battery using the nonaqueous electrolyte solution further includes a separator disposed between the positive electrode material layer and the negative electrode material layer. The lithium battery adopting the solid electrolyte membrane arranges a diaphragm between the positive pole piece and the negative pole piece. The non-aqueous electrolyte comprises a solvent and a solute dissolved in the solvent, and the solvent can be one or more of cyclic carbonate, chain carbonate, cyclic ether, chain ether, nitrile and amide, such as ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, gamma-butyrolactone, tetrahydrofuran, 1, 2-dimethoxyethane, acetonitrile and dimethylformamide. The solute may be exemplified by LiPF6、LiBF4、LiCF3SO3、LiAsF6、LiCIO4And LiBOB.
The material of the separator may be selected from polyolefin based polymer materials.
The positive electrode tab may include a current collector and a positive active layer on the current collector. The positive active layer may be a conventional positive active material for a lithium battery, and will not be described herein.
Compared with the common current collector with the conductive coating, the novel current collector with the lithium supplement function provided by the invention can further realize the lithium supplement effect on the basis of improving the conductive performance. Lithium supplement and conductivity are integrated, and the functionalization of the current collector is improved. Is a preparation method of the current collector coating without any solvent. Compared with the conventional pole piece lithium supplementing method (lithium foil or lithium powder), the method has the advantages that the practicability is more convenient, and the influence on the capacity exertion of the pole piece caused by solvent screening and lithium byproduct residue inside the pole piece is avoided. And a specific lithium supplement coating can be designed according to the pole piece information, so that a specific lithium supplement current collector is obtained. The method has no influence on the existing pole piece preparation process, can realize continuous and large-scale production, has no influence on the whole cell production process, and enlarges the practical application of lithium supplement.
The following are specific examples.
Example 1
Fully mixing conductive carbon 3 acetylene black (70 mass percent) and passivated lithium metal powder (10 mass percent) in an ultrasonic dispersion mode, wherein the ultrasonic mixing time is 10min, and the power is 20K; then, sequentially adding polyacrylic acid (15% by mass) and polytetrafluoroethylene (5% by mass) to the mixture, and shearing and mixing the mixture for 20min at the speed of 15000rpm by using a high-speed ball mill (pulse mixing is adopted, namely the mixture is mixed for 2min, and the next mixture is mixed for 2min after the rest of 1 min), so that different materials are fully and uniformly dispersed and a certain bonding effect is generated; and further transferring the powder into a jet mill for high-speed jet shearing to realize the sufficient fiberization of PTFE and obtain agglomerated powder with certain viscosity.
Preheating a roller of a vertical roller press to 100 ℃, adjusting a gap between two rollers of the roller press to be 4um, taking a proper amount of powder to be placed between the two rollers of the roller press, repeatedly rolling at a rolling speed of 8rpm, in the hot pressing process, PAA wrapping lithium metal powder attached to PTFE fibers, simultaneously increasing the hot pressing times, further improving the PTFE fibrosis degree, further increasing the compactness degree of a coating film, and finally manufacturing a self-supporting film with the thickness of about 5 um. Further, the diaphragm and the 6um copper foil are adjusted to a proper roller gap for hot-pressing compounding at the temperature, the diaphragm can show proper viscosity at the temperature and is tightly attached to the copper foil, and finally the copper foil lithium-supplement current collector containing a lithium-supplement layer (4um) with the thickness of about 10um is obtained.
Further, coating the silicon-containing negative electrode slurry on the current collector by using the mixed negative electrode slurry through a coating process, quickly drying the silicon-containing negative electrode slurry through an air-blast drying oven, and then fully drying the silicon-containing negative electrode slurry in a vacuum drying oven; further, the dried pole piece is hot-pressed to the required thickness and the required compaction density under a heating roller press (100 ℃) to obtain the required pole piece. In the rolling process, the slurry layer is fully contacted with the current collector layer, and the PAA coated with the lithium metal powder can creep under the influence of temperature and pressure and can also increase the adhesive force between the slurry layer and the current collector; in addition, a part of the lithium metal powder also comes into contact with the active material of the slurry layer, thereby achieving preferential lithiation of a part of the active material.
Comparative example 1
As a comparative example, coating was performed using the same slurry as in example 1 above, with the only difference that a conventional carbon-coated copper foil was used as a current collector (no lithium supplement layer) during the coating process.
Example 2
Fully mixing the conductive carbon 3 Keqin black (80% by mass) and the passivated lithium metal powder (5% by mass) in a mechanical stirring manner, wherein the stirring speed is 20000rpm, and the stirring time is 10 min; sequentially adding polyvinylidene fluoride (12% by mass) and polytetrafluoroethylene (3% by mass) into a high-speed ball mill, and shearing and mixing at 12000rpm for 15min (pulse mixing is adopted, namely mixing is carried out for 2min, and the next mixing is carried out for 2min after 1min of pause) so that different materials are fully and uniformly dispersed and a certain bonding effect is generated; further transferring the powder into a jet mill, and carrying out high-speed jet shearing to realize full fiberization of PTFE and obtain agglomerated powder with certain viscosity;
preheating a roller of a vertical roller press to 115 ℃, adjusting the gap between two rollers of the roller press to be 3um, taking a proper amount of powder to be placed between the two rollers of the roller press, repeatedly rolling at the rolling speed of 10rpm, and finally preparing the self-supporting membrane with the thickness of about 4 um. Further, the diaphragm and the 6um stainless steel foil are adjusted to a proper roller gap at the temperature for hot-pressing compounding, and finally the stainless steel foil current collector containing the lithium supplement coating (3um) with the thickness of about 9um is obtained.
Further, coating the mixed negative electrode slurry on the current collector, quickly drying the current collector by using an air drying oven, and then fully drying the current collector in a vacuum drying oven; further, the dried pole piece is hot-pressed to the required thickness and the required compaction density under a heating roller press (100 ℃) to obtain the required pole piece. The slurry layer is fully contacted with the current collector layer in the rolling process, and the lithium metal powder in the current collector coating layer can be contacted with the active material of the slurry layer due to the influence of temperature and pressure, so that the preferential lithiation of part of the active material is realized; in addition, the lithium ion battery also has the effect of continuously replenishing consumed lithium during charge and discharge. Meanwhile, the polymer in the coating can also increase the adhesive force between the slurry layer and the current collector, and the pole piece is ensured not to fall off in the operation process.
Comparative example 2
The same slurry as that in example 2 was used to coat and make a pole piece, the coating current collector was a carbon-coated stainless steel foil current collector (no lithium-supplement layer), and finally the pole piece maintained the same thickness, areal density and compacted density as the pole piece in example 2.
Example 3
Fully mixing conductive carbon 3 nano graphite (85 mass percent) and passivated lithium metal powder (3 mass percent) in a mechanical stirring manner, wherein the stirring speed is 15000rpm, and the stirring time is 10 min; sequentially adding carboxymethyl cellulose (9% by mass) and polytetrafluoroethylene (3% by mass) to mechanically stir at a speed of 15000rpm, shearing and mixing for 10min, so that different materials are fully and uniformly dispersed and a certain bonding effect is generated; further transferring the powder into a jet mill, and carrying out high-speed jet shearing to realize full fiberization of PTFE and obtain agglomerated powder with certain viscosity;
preheating a roller of a vertical roller press to 95 ℃, adjusting the gap between two rollers of the roller press to be 4um, taking a proper amount of powder, placing the powder between the two rollers of the roller press, repeatedly rolling at the rolling speed of 12rpm, and finally preparing the self-supporting membrane with the thickness of about 5 um. Further, the diaphragm and the 6um copper foil are subjected to hot-pressing compounding by adjusting a proper roller gap at the temperature, and finally the copper foil current collector containing the lithium supplement coating (4um) with the thickness of about 10um is obtained.
Further, coating the mixed negative electrode slurry on the current collector, quickly drying the current collector by using an air drying oven, and then fully drying the current collector in a vacuum drying oven; further, the dried pole piece is hot-pressed to the required thickness and the required compaction density under a heating roller press (95 ℃) to obtain the required pole piece.
Comparative example 3
The same slurry as that in example 3 was used to coat and make a pole piece, the coated current collector was a carbon-coated copper foil current collector (no lithium-supplement layer), and finally the pole piece maintained the same thickness, areal density and compacted density as the pole piece in example 3.
Comparative example 4
Fully mixing conductive carbon 3 acetylene black (70 mass percent) and passivated lithium metal powder (10 mass percent) in an ultrasonic dispersion mode, wherein the ultrasonic mixing time is 10min, and the power is 20K; adding polytetrafluoroethylene (the mass ratio is 20%) and shearing and mixing the polytetrafluoroethylene for 20min at the speed of 15000rpm by a high-speed ball mill (pulse mixing is adopted, namely the materials are mixed for 2min, and the next 2min of mixing is carried out after 1min of pause), so that different materials are fully and uniformly dispersed and a certain bonding effect is generated; further transferring the powder into a jet mill, and carrying out high-speed jet shearing to realize full fiberization of PTFE and obtain agglomerated powder with certain viscosity;
the agglomerated powder was subjected to the same hot pressing process as in example 1 to obtain a copper foil current collector having a lithium supplement coating (4um) with a thickness of about 10 um.
Further, the same negative electrode slurry as in example 1 was coated on the current collector by a coating process with a silicon-containing negative electrode, dried rapidly by an air-blast drying oven, and then sufficiently dried in a vacuum drying oven; further, the dried pole piece was hot-pressed to the same thickness as in example 1 by a hot roller press (100 ℃ C.) to obtain a desired pole piece.
Because the coating of the lithium-supplement current collector does not contain PAA (Polymer 1), the adhesive force between the coating and the metal foil 1 and the adhesive force between the active material layer and the current collector are reduced; in addition, the lithium metal powder lacks the effective package of PPA, and partial lithium metal powder is failed.
The electrode sheets prepared in the examples and comparative examples were used as negative electrode sheets. Then preparing the same positive plate and electrolyte, and assembling the positive plate and the electrolyte into the battery under the same conditions.
Preparing a positive plate:
mixing Li (Ni)0.5Co0.2Mn0.3)O2Mixing the positive electrode active material, SP and PVDF binder at a mass ratio of 94:3:3, adding N-methylpyrrolidone (NMP) to obtain positive electrode active slurry, and coating the positive electrode active slurry on the functional surface of the carbon-coated Al foil to obtain a positive electrode sheet.
And assembling the obtained negative plate, the obtained positive plate and the diaphragm into a battery, and injecting electrolyte to prepare the soft package full battery.
Electrochemical tests were performed under the same conditions on the batteries prepared in the examples and comparative examples, and the results are shown in table 1 below.
TABLE 1 test results for different samples
Figure BDA0003015835020000111
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
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 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.

Claims (10)

1. The lithium supplement current collector is characterized by comprising a metal foil and a lithium supplement layer loaded on the metal foil, wherein the lithium supplement layer comprises conductive carbon, a lithium-containing additive, a first polymer and/or a derivative thereof, and a second polymer and/or a derivative thereof, the first polymer is selected from one or more of polyacrylic acid, polymethyl methacrylate, polyvinyl alcohol, polystyrene, polyvinylidene fluoride, carboxymethyl cellulose, epoxy resin and phenolic resin, and the second polymer is polytetrafluoroethylene.
2. The lithium replenishing current collector of claim 1, wherein the mass percent of the first polymer in the lithium replenishing slurry is between 1 and 50 percent, and the mass percent of the second polymer in the lithium replenishing slurry is between 0.1 and 20 percent.
3. The lithium replenishing current collector of claim 1, wherein the lithium-containing additive has a particle size of 500nm or less.
4. The lithium replenishment current collector of claim 1, wherein the lithium replenishment layer has a thickness of 0.1 μ ι η to 12 μ ι η.
5. The lithium supplementing current collector according to any one of claims 1 to 4,
the conductive carbon is selected from one or more of acetylene black, Ketjen black, nano graphite, carbon nano tubes and carbon black, and the mass percentage of the conductive carbon in the lithium supplement slurry is 20-90%; and/or the presence of a gas in the gas,
the lithium-containing additive is selected from any one or more of passivated lithium metal powder, lithium-rich metal oxide and lithium-containing alloy; and/or the presence of a gas in the gas,
the metal foil is copper foil or stainless steel foil.
6. A method for preparing a lithium supplementing current collector as claimed in any one of claims 1 to 5, comprising the steps of:
placing the lithium supplement slurry between preheated rollers of a roller press for rolling to obtain a self-supporting lithium supplement coating, wherein the preheating temperature of the rollers is 50-150 ℃;
and placing the self-supporting lithium supplementing coating on the metal foil, and performing hot-pressing compounding between the preheated rollers.
7. The method for preparing the lithium replenishing current collector of claim 6, wherein the method for preparing the lithium replenishing slurry comprises the following steps:
mixing conductive carbon and a lithium-containing additive to obtain a primary mixed material;
mixing the primary blend, the first polymer, and the second polymer under air shear.
8. A negative electrode sheet comprising the lithium replenishing current collector according to any one of claims 1 to 5 and a negative electrode active material layer supported on the lithium replenishing current collector.
9. The negative electrode sheet according to claim 8, wherein the negative active material layer has silicon powder therein.
10. A lithium battery comprising a positive electrode sheet, the negative electrode sheet according to any one of claims 8 to 9, a separator, and an electrolyte.
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CN114551900A (en) * 2022-04-27 2022-05-27 华中科技大学 Multifunctional current collector and preparation method and application thereof
CN114744207A (en) * 2022-03-29 2022-07-12 佛山市中技烯米新材料有限公司 Lithium supplement current collector and lithium supplement electrode
CN115425304A (en) * 2022-10-10 2022-12-02 湖北亿纬动力有限公司 Composite lithium supplement agent and preparation method and application thereof
CN115842094A (en) * 2022-05-19 2023-03-24 宁德时代新能源科技股份有限公司 Negative pole piece and preparation method thereof, secondary battery, battery module, battery pack and electric device

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Publication number Priority date Publication date Assignee Title
CN114744207A (en) * 2022-03-29 2022-07-12 佛山市中技烯米新材料有限公司 Lithium supplement current collector and lithium supplement electrode
CN114744207B (en) * 2022-03-29 2023-02-10 佛山市中技烯米新材料有限公司 Lithium supplement current collector and lithium supplement electrode
CN114551900A (en) * 2022-04-27 2022-05-27 华中科技大学 Multifunctional current collector and preparation method and application thereof
CN115842094A (en) * 2022-05-19 2023-03-24 宁德时代新能源科技股份有限公司 Negative pole piece and preparation method thereof, secondary battery, battery module, battery pack and electric device
CN115842094B (en) * 2022-05-19 2024-03-22 宁德时代新能源科技股份有限公司 Negative electrode plate, preparation method thereof, secondary battery, battery module, battery pack and power utilization device
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CN115425304B (en) * 2022-10-10 2024-03-15 湖北亿纬动力有限公司 Composite lithium supplementing agent and preparation method and application thereof

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