WO2022143210A1 - 极片及电池 - Google Patents

极片及电池 Download PDF

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Publication number
WO2022143210A1
WO2022143210A1 PCT/CN2021/139024 CN2021139024W WO2022143210A1 WO 2022143210 A1 WO2022143210 A1 WO 2022143210A1 CN 2021139024 W CN2021139024 W CN 2021139024W WO 2022143210 A1 WO2022143210 A1 WO 2022143210A1
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WIPO (PCT)
Prior art keywords
active material
pole piece
thickness
layer
lithium
Prior art date
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PCT/CN2021/139024
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English (en)
French (fr)
Inventor
张双虎
张健
孙雷明
Original Assignee
珠海冠宇电池股份有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
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Application filed by 珠海冠宇电池股份有限公司 filed Critical 珠海冠宇电池股份有限公司
Priority to KR1020237009172A priority Critical patent/KR20230051567A/ko
Priority to CN202180093956.9A priority patent/CN116897440A/zh
Priority to EP21913951.6A priority patent/EP4145562A1/en
Priority to JP2022574383A priority patent/JP2023528447A/ja
Publication of WO2022143210A1 publication Critical patent/WO2022143210A1/zh
Priority to US18/060,570 priority patent/US20230115059A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/40—Alloys based on alkali metals
    • H01M4/405—Alloys based on lithium
    • 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
    • H01M4/70—Carriers or collectors characterised by shape or form
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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

Definitions

  • the invention relates to the field of batteries, in particular to a pole piece and a battery using the pole piece.
  • Lithium-ion batteries are widely used in consumer electronics and electric vehicles due to their environmental friendliness, high operating voltage, large specific capacity and long cycle life. It is of great significance for the practical promotion and application of batteries.
  • the wound battery is a relatively common type of battery. It is mainly composed of positive electrode sheets, separators, and negative electrode sheets, which are stacked and then wound to form a battery cell, which is then made by liquid injection, packaging, and chemical formation.
  • the core is usually too thick near the pole piece and the tab part, especially when the pole piece is designed with the pole piece in the middle (not the end) of the pole piece, due to the need to attach adhesive tape to the pole piece, etc. It is more prone to over-thickness near the tabs, exceeding the thickness specification, resulting in lithium precipitation and increased internal resistance of the battery, which is not conducive to the safety of the battery, the volumetric energy density of the battery, and the charge-discharge rate.
  • the present invention provides a pole piece to at least solve the problems existing in the prior art that the battery cell is too thick near the pole piece tab, resulting in low battery safety and poor charge-discharge rate performance.
  • the invention also provides a battery, which adopts the above-mentioned pole piece, which can effectively avoid the problem of excessive thickness of the battery core near the pole piece and the tab, and has good charge and discharge rate performance, safety and long service life.
  • a pole piece which includes a current collector and a functional layer located on a first surface of the current collector, the first surface is provided with a tab, and the functional layer on the first surface is composed of a normal electrode away from the tab.
  • the thickness of the recessed area is smaller than the thickness of the normal area.
  • the functional layer includes an undercoat layer and an active material layer, the undercoat layer is located between the surface of the current collector and the active material layer, and the raw material of the undercoat layer includes an active material, a bonding agent
  • the raw material of the active material layer includes an active material, a binder and a conductive agent, and the content of the binder in the primer layer is higher than the content of the binder in the active material layer.
  • the thickness of the recessed region is 5-125 ⁇ m smaller than that of the normal region.
  • the thickness of the primer layer in the recessed area is 0-15 ⁇ m
  • the thickness of the active material layer in the recessed area is 0-105 ⁇ m
  • the thickness of the primer layer in the normal area is 5-15 ⁇ m
  • the thickness of the active material layer in the normal region is 90-110 ⁇ m.
  • the width of the recessed area is 3-50 mm.
  • the primer layer has a porous structure with a porosity of 20%-45%; and/or the active material layer is a porous structure with a porosity of 25%-50%.
  • the mass content of the active material in the raw materials of the primer layer, is 49-94%, the mass content of the binder is 4-50%, and the mass content of the conductive agent is 1-5% and/or, in the raw materials of the active material layer, the mass content of the active material is 93-96%, the mass content of the binder is 0.9-1.5%, and the mass content of the conductive agent is 1-3%.
  • the pole piece is a positive electrode piece
  • the active material includes lithium cobalt oxide, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium iron manganese phosphate, and vanadium phosphate. At least one of lithium, lithium vanadyl phosphate, lithium-rich manganese-based material, lithium nickel cobalt aluminate and lithium titanate.
  • the pole piece is a negative electrode piece
  • the active material includes graphite, mesocarbon microspheres, soft carbon, hard carbon, silicon material, silicon oxygen material, silicon carbon material, lithium titanate material at least one of them.
  • Another aspect of the present invention provides a battery including the above-mentioned pole piece.
  • the pole piece provided by the present invention has good safety through the above-mentioned special structural design. When it is applied to a battery, it can effectively avoid problems such as excessive thickness of the part of the battery cell close to the pole ear, and improve the safety and charge-discharge rate of the battery. and other qualities; the battery provided by the present invention adopts the above-mentioned pole piece, which has good performances such as safety and charge-discharge rate, and has greater practical significance in the industry.
  • FIG. 1 is a schematic structural diagram of a pole piece according to an embodiment of the present invention.
  • FIG. 2 is a schematic diagram of a cell winding structure of a battery according to an embodiment of the present invention
  • FIG. 3 is a schematic diagram of a gravure roll used when preparing a pole piece in an embodiment of the present invention
  • a pole piece is provided. As shown in FIG. 1 , the pole piece includes a current collector 1 and a functional layer located on a first surface of the current collector 1 .
  • the functional layer is composed of a normal area 31 away from the tab and a concave area 32 close to the tab, and the thickness of the concave area 32 is smaller than that of the normal area.
  • the pole piece provided by the present invention can effectively avoid the problem that the thickness of the battery core formed by using the pole piece is too thick near the tab ear through the design of the recessed area, thereby ensuring the safety of the battery and the quality of the charge and discharge rate.
  • the above-mentioned functional layer can include a primer layer 2 and an active material layer 3, the primer layer 2 is located between the surface of the current collector 1 and the active material layer 3, the raw material of the primer layer 2 includes an active material, a binder and a conductive agent, and the active
  • the raw materials of the material layer 3 include active materials, a binder and a conductive agent, and the content of the binder in the primer layer 2 is higher than the content of the binder in the active material layer 3.
  • layer) has a high adhesion to the surface of the current collector, which can further improve the safety and other properties of the pole piece.
  • the tab 4 may be located in the middle (ie, not the end) of the pole piece, and the functional layer is arranged around the tab.
  • the thickness of the tab 4 is not greater than the thickness of the recessed area 32, that is, on the surface (ie, the first surface) of the current collector on which the tab is provided, the height of the tab 4 is not greater than the surface of the current collector. greater than the height of the recessed region 32 .
  • a functional layer may be provided only on the first surface of the current collector 1, or a functional layer may be provided on the second surface opposite to the first surface at the same time (functional layers are provided on both the front and back surfaces of the current collector), preferably In the latter case, characteristics such as the energy density of the pole piece can be further improved.
  • the positions corresponding to the tabs on the second surface may be coated with a functional layer, or may be an uncoated area without a coating, preferably an uncoated area without a coating
  • the coverage area is more conducive to avoiding the super-thick phenomenon of the battery core, and is also more conducive to the production of the pole piece; in a specific embodiment, when the two surfaces of the current collector 1 are provided with functional layers, the second surface is provided with a functional layer.
  • Uncoated area 6 without coating corresponds to the position of the tab 4 on the first surface, and the functional layer on the second surface may not have a concave area, or it may be in a position close to the uncoated area 6
  • the concave area is set at the place (that is, the functional layer of the second surface includes a concave area close to the uncoated area 6 and a normal area far away from the uncoated area 6), the concave area of the first surface, the shape of the concave area of the second surface, Parameters such as area size and thickness can be the same or different, and are preferably the same.
  • the thickness of the above-mentioned recessed area can generally be 5-125 ⁇ m smaller than that of the normal area, that is, H1 is 5-125 ⁇ m, further can be 10-125 ⁇ m, such as 10-100 ⁇ m or 10-90 ⁇ m or 10- 80 ⁇ m or 10-70 ⁇ m or 10-65 ⁇ m or 20-65 ⁇ m or 30-65 ⁇ m or 40-65 ⁇ m or 45-65 ⁇ m or 50-65 ⁇ m or 55-65 ⁇ m or 60-65 ⁇ m.
  • the thickness of the recessed area 32 is substantially equal to the sum of the thickness of the primer layer in the recessed area 32 and the thickness of the active material layer in the recessed area 32.
  • the thickness of the primer layer in the recessed area can be 0-15 ⁇ m, such as
  • the thickness of the active material layer in the recessed region may be 0-105 ⁇ m, for example, may be 45-105 ⁇ m.
  • the thickness of the recessed region is 0-125 ⁇ m, further can be 0-120 ⁇ m, and further can be 50-112 ⁇ m, for example, can be 50 ⁇ m, 57 ⁇ m, 63 ⁇ m, 74 ⁇ m, 90 ⁇ m, 101 ⁇ m, 110 ⁇ m, 112 ⁇ m.
  • the thickness of the normal area 31 of the present invention can be set according to the thickness of the conventional pole piece coating in the field, and the thickness of the normal area 31 is substantially equal to the sum of the thickness of the primer layer in the normal area and the thickness of the active material layer in the normal area.
  • the thickness of the primer layer in the normal area is 5-15 ⁇ m, and further can be 5-12 ⁇ m, such as 5-8 ⁇ m, which is beneficial to make the pole piece have both good safety and low internal resistance; the active material in the normal area
  • the thickness of the layer is 90-110 ⁇ m, which is beneficial to further improve the energy density and other characteristics of the pole piece.
  • the width of the above-mentioned recessed area 32 may generally be 3-50 mm, further may be 3-30 mm, for example, may be 10-30 mm or 20-30 mm or 25-30 mm.
  • the above-mentioned primer layer 2 is a porous structure, and its porosity can be 20%-45%; and/or, the active material layer 3 is a porous structure, and its porosity can be 25%-50%.
  • the mass content of the active material is 49-94%; and/or the mass content of the binder is 4-50%, and the mass content of the conductive agent is 1-5% ;
  • the mass content of the active material is 93-96%, such as 94-96%; and/or, the mass content of the binder is 0.9-1.5%, such as 2-3.5%, conductive
  • the mass content of the agent is 1-3%, such as 1-2%.
  • the active material, the binder, and the conductive agent can all be conventional materials in the art.
  • the binder can include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile , polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene, polyhexafluoropropylene and styrene butadiene rubber (SBR)
  • At least one of the conductive agents may include at least one of carbon black, carbon fibers, carbon nanotubes, graphite, graphene, metal materials, and conductive ceramic materials.
  • the above-mentioned pole piece can be a positive pole piece or a negative pole piece.
  • the above-mentioned pole piece is a positive pole piece
  • the above-mentioned active material can be a lithium-containing active material and other conventional positive active materials in the field, for example, it can include cobalt At least one of lithium oxide, lithium manganate, lithium nickelate, lithium nickel cobalt manganate, lithium iron phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadium phosphate, lithium-rich manganese-based materials, and lithium nickel cobalt aluminate
  • the above-mentioned pole piece is a negative pole piece
  • the above-mentioned active material can include graphite, mesocarbon microspheres, soft carbon, hard carbon, silicon At least one of materials, silicon-oxygen materials, silicon-carbon materials, lithium titanate materials, etc.
  • the above-mentioned current collector may be a conventional negative
  • the raw material of the primer layer 2 and/or the raw material of the active material layer 3 may also include a dispersant, and the mass content of the dispersant in the primer layer 2 may be 1.5-2.5%, and the active material layer The mass content of the dispersant in 3 can be 1.5-2.5%, and the dispersant can be a common dispersant such as sodium carboxymethyl cellulose (CMC).
  • CMC sodium carboxymethyl cellulose
  • the pole piece of the present invention can be prepared according to conventional methods in the art such as a coating method.
  • the preparation method may specifically include: after coating the surface of the current collector 1 with a primer layer 2, and then coating the primer layer on the surface of the current collector 1. 2.
  • the active material layer 3 is coated on the surface, and after removing the primer layer and the active material layer at the preset tab position, the tab is welded on the current collector at the preset tab position, and the width and thickness of the recessed area are determined according to the preset width and thickness.
  • the above-mentioned active material layer can also be coated by a gravure coating method; the coating layer at the preset tab position can be removed by a conventional method in the art, such as laser or scraper scraping or the combination of the two.
  • the slurry of the primer coating can be applied to the current collector first, and then dried/drying (the drying temperature can be controlled to 100-130°C, such as 110°C) to form on the current collector. Undercoat, and then apply the slurry of the active material layer on the surface of the undercoat. After the coating is completed, it is dried (the drying temperature can be 80-110 ° C) and rolled, and then it can be cleaned with a step blade or laser. The functional layer in the preset recessed area is removed to form a recessed area, and all the functional layers in the preset tab position are removed to expose the current collector, and the tabs are welded on the current collector to obtain a pole piece.
  • the solvent of the above slurry can be a conventional solvent in the field such as N-methylpyrrolidone (NMP).
  • the above-mentioned gravure roll includes a roll body, and the surface of the roll body is provided with at least one coating area corresponding to the pole piece coating, and the coating area includes an engraved area 8 engraved with anilox and unengraved
  • the tab position 9 is reserved, and the rest are the unengraved area (ie, the non-coated area) 10 .
  • the above-mentioned preset tab position is used for welding the tab, and its surface shape and size are the same as the shape and size of the bottom surface of the tab to be welded.
  • the shape and size of the above-mentioned reserved tab position 9 can be set according to the shape and size of the tab to be welded.
  • the shape of the reserved tab position is generally similar to the shape of the preset tab position, and its size is generally slightly larger than the size of the preset tab position.
  • the gravure coater formed by using the above-mentioned gravure roll may specifically include a trough for holding the coating slurry, a gravure roll located above the gravure roll, and a rubber roll (usually located above the gravure roll) matched with the gravure roll. ), and a scraper (usually located on the side of the gravure roll and pressed on the gravure roll) that cooperates with the gravure roll; wherein, the material trough, the rubber roll, the scraper and their positions are all conventional settings in the art, and will not be repeated.
  • the base coating material can be placed in a solvent to form a coating slurry, and after setting parameters or conditions such as blade pressure, rubber roller pressure, coating speed, oven temperature, etc., the above slurry is placed in gravure coating.
  • the substrates such as current collectors
  • a primer layer is formed on the substrate to obtain a coil coated with the primer layer, and then the coil is dried.
  • the positive electrode active layer is coated on the material, it is rolled and cut into pole pieces that meet the preset shape, size and other parameters.
  • the conditions for the above-mentioned gravure coating may be: the coating speed is 10-30m/min, such as 20m/min; the blade pressure is 0.2-0.6MPa, such as 0.4MPa; the rubber roller pressure is 0.2-0.6MPa, Such as 0.4MPa.
  • Using the above method to prepare the pole piece can not only improve the performance of the pole piece, such as safety, charge and discharge rate, but also improve the manufacturing yield of the pole piece, which is beneficial to industrialized production and application.
  • Another aspect of the present invention further provides a battery comprising the above-mentioned pole piece.
  • the battery of the present invention may include a positive electrode sheet with the above-mentioned structural design (that is, the above-mentioned electrode sheet is a positive electrode sheet), or a negative electrode sheet with the above-mentioned structural design (that is, the above-mentioned electrode sheet is a negative electrode sheet), or may also include the above-mentioned structural design.
  • the positive electrode sheet and the negative electrode sheet with the above-mentioned structural design that is, the above-mentioned electrode sheet includes a positive electrode sheet and a negative electrode sheet).
  • the above-mentioned battery also includes a positive pole piece, and the positive pole piece can also be a conventional positive pole piece in the field; when the above-mentioned pole piece is a positive pole piece, the above-mentioned battery also includes a negative pole piece, and the negative pole piece can be this Conventional negative electrode sheet in the field, as in one embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode functional layer located on the negative electrode current collector, the thickness of the negative electrode functional layer can be 100-120 ⁇ m, and its raw materials include negative electrode active materials, bonding agent and conductive agent, wherein the mass content of the negative electrode active material can be 94-96%, the mass content of the binder can be 2-3.5%, the mass content of the dispersant can be 1.5-2.5%, and the mass content of the conductive agent It can be 1-2%, and the binder, the conductive agent, the negative electrode active material, and the dispersant can be the conventional materials as
  • the above-mentioned battery also includes a separator between the positive electrode sheet and the negative electrode sheet, the separator is used to separate the positive electrode sheet and the negative electrode sheet, which can be a conventional separator in the art, which is not particularly limited in the present invention.
  • an adhesive tape 5 is attached to a surface of the pole piece provided with the tabs, and the adhesive tape 5 and the tabs 4 and at least part of the concave area 32 surrounding the tab 4 (the concave area 32 near the tab) are adhered to Then, the tab 4 is located in the cavity surrounded by the recessed area 32, the adhesive paper 5 and the current collector 1, and the upper surface of the adhesive paper 5 is located below the surface of the normal area 31, that is, the upper surface of the adhesive paper 5 reaches the normal area 31.
  • the distance H2 from the surface the thickness of the normal area 31 - the distance from the upper surface of the tape 5 to the surface of the current collector on the side where the tape is located, H2>0.
  • functional layers are provided on both surfaces of the current collector 1 , an uncoated area 6 is provided on the second surface, and the uncoated area 6 is provided with the first surface.
  • the positions of the tabs 4 correspond to each other, the functional layers on the two surfaces are provided with recessed areas 32, and the two surfaces are attached with adhesive tape 5.
  • the adhesive tape 5 is attached to the second surface in the same way as the first surface.
  • the adhesive tape 5 is bonded to at least part of the concave area 32 surrounding the uncoated area 6 (the concave area close to the uncoated area), and the uncoated area 6 is located in the concave area 32, the adhesive In the cavity enclosed by the paper 5 and the current collector 1 , the upper surface of the adhesive paper 5 is located below the surface of the normal area 32 .
  • the thickness of the adhesive paper can generally be 16-30 ⁇ m.
  • the above-mentioned battery can be a wound lithium-ion battery.
  • the positive electrode sheet with the positive electrode tab 4 and the negative electrode sheet with the negative electrode tab 7 are separated by a diaphragm, and there is no excessive thickness near the electrode tab. .
  • the above-mentioned wound battery can be prepared according to conventional methods in the art.
  • the positive electrode sheet, the separator and the negative electrode sheet can be stacked and arranged through winding, assembly, vacuum baking, liquid injection, standing, encapsulation, chemical formation, volume separation, etc. After the treatment, the wound lithium-ion battery is obtained.
  • the above-mentioned winding, assembling, vacuum baking, liquid injection, standing, packaging, forming, and volume separation can all be conventional procedures in the field, and the used diaphragm, electrolyte, etc. can be Conventional materials in this field will not be repeated here.
  • the gravure coating machine used in the coating process by the gravure coating method includes: a trough for holding the coating slurry, a gravure roll located above the trough, The rubber roller matched with the gravure roll (usually located above the gravure roll), and the doctor blade matched with the gravure roll (usually located on the side of the gravure roll and pressed on the gravure roll); wherein the gravure roll includes a roll body, and the roll body
  • the surface is provided with at least one coating area corresponding to the coating of the pole piece.
  • the coating area includes the normal area with engraved pattern and the reserved pole ear position without engraving, and the rest are non-coating areas; when coating, control the coating area.
  • the cloth speed is 20m/min; the blade pressure is 0.4MPa; the rubber roller pressure is 0.4MPa.
  • the positive electrode sheet of this embodiment includes a positive electrode current collector and a positive electrode functional layer coated on both surfaces of the positive electrode current collector.
  • One surface of the positive electrode current collector is provided with a positive electrode tab (the positive electrode tab is located in the middle of the positive electrode sheet), and the positive electrode on the surface is
  • the functional layer is composed of a normal area away from the positive electrode tab and a recessed area close to the positive electrode tab, the thickness of the recessed area is smaller than the thickness of the normal area;
  • the other surface of the positive electrode current collector is provided with an uncoated area corresponding to the position of the positive electrode tab , the positive electrode functional layer on the other surface is the same as the positive electrode functional layer on the surface provided with the positive electrode lug (composed of the above-mentioned normal area and the depression area);
  • the positive electrode functional layer on the above-mentioned two surfaces comprises a primer layer and a positive electrode active material layer, The coating is located between the surface of the positive electrode current collector and the positive electrode active material layer; wherein,
  • the above-mentioned positive electrode sheet and the wound lithium-ion battery formed by the positive electrode sheet are specifically prepared according to the following process:
  • Lithium iron phosphate, polyvinylidene fluoride and carbon black are uniformly mixed in NMP according to the mass ratio of 65:30:5 to form a primer coating slurry (solid content is 15%); In the trough of the gravure coater, open the coating, coat it on both sides of the aluminum foil, and then dry at 110 ° C to obtain the coil coated with the primer layer;
  • Lithium cobalt oxide, polyvinylidene fluoride and carbon black are mixed uniformly in NMP according to the mass ratio of 97:1.3:1.4 to form a positive electrode active layer slurry, which is coated on the above-mentioned roll material by a slot extrusion coating equipment.
  • the positive electrode sheet precursors of 1000mm ⁇ 65mm are cut into 1000mm ⁇ 65mm by roller pressing; after cleaning the coating of the pre-set tab positions of the positive electrode sheet precursors, the electrode tabs are welded to obtain a positive electrode sheet ;
  • the above-mentioned positive electrode sheet and negative electrode sheet are used to make a wound battery.
  • tape is attached to both surfaces of the positive electrode sheet, and on the surface provided with the positive electrode tab, the tape is bonded to the positive electrode tab and the recessed area surrounding the positive electrode tab.
  • the upper surface of the adhesive tape In the cavity enclosed by the current collector, the upper surface of the adhesive tape is located below the surface of the normal area, and on the surface with the uncoated area, the adhesive tape is bonded to the concave area surrounding the uncoated area, and the uncoated area is located by In the cavity enclosed by the concave area, the adhesive paper and the positive electrode current collector, the upper surface of the adhesive paper is located below the surface of the normal area; the thickness of the adhesive paper used is 16 ⁇ m.
  • Example 1 The difference between this example and Example 1 is that the thickness of the primer layer is 7 ⁇ m, the thickness of the positive active material layer in the recessed area is 50 ⁇ m, and the depth of the recessed area is 60 ⁇ m, and other conditions are the same as those in Example 1.
  • Example 1 The difference between this example and Example 1 is that the thickness of the primer layer is 8 ⁇ m, the thickness of the positive active material layer in the recessed area is 55 ⁇ m, and the depth of the recessed area is 55 ⁇ m, and other conditions are the same as those in Example 1.
  • Example 1 The difference between this example and Example 1 is that the thickness of the primer layer is 9 ⁇ m, the thickness of the positive active material layer in the recessed area is 65 ⁇ m, and the depth of the recessed area is 45 ⁇ m, and other conditions are the same as in Example 1.
  • the difference between this example and Example 1 is that the thickness of the primer layer is 10 ⁇ m, the thickness of the positive active material layer in the recessed area is 80 ⁇ m, and the depth of the recessed area is 30 ⁇ m.
  • Example 1 The difference between this example and Example 1 is that the thickness of the primer layer is 11 ⁇ m, the thickness of the positive active material layer in the recessed area is 90 ⁇ m, and the depth of the recessed area is 20 ⁇ m, and other conditions are the same as in Example 1.
  • the difference between this example and Example 1 is that the thickness of the primer layer is 12 ⁇ m, the thickness of the positive active material layer in the recessed area is 100 ⁇ m, and the depth of the recessed area is 10 ⁇ m.
  • Example 1 The difference between this comparative example and Example 1 is that the depth of the recessed area is 5 ⁇ m, the thickness of the positive electrode active material layer in the recessed area is 105 ⁇ m, and other conditions are the same as those of Example 1.
  • Example 1 The difference between this comparative example and Example 1 is that the width of the concave region of the positive electrode sheet is set to 50 mm, and other conditions are the same as those of Example 1.
  • Example 1 The difference between this comparative example and Example 1 is that no primer layer is provided, the thickness of the recessed area is the same as that of the normal area (that is, no recessed area is provided), the tabs are arranged at the end of the pole piece, and the rest are the same as those of Example 1. The conditions are the same.
  • Example 1 The difference between this comparative example and Example 1 is that the thickness of the recessed area is the same as that of the normal area (ie, no recessed area is provided), and other conditions are the same as those of Example 1.
  • the battery internal resistance, 2C charging rate, super-thickness ratio of the cell, and acupuncture pass rate of the lithium ion batteries of Examples 1-9 and Comparative Examples 1 and 2 were measured as shown in Table 1.
  • the depth of the recessed area, the width of the recessed area, the thickness of the primer layer, and the capacity of the battery are also summarized in Table 1.
  • each test method is as follows:
  • Battery internal resistance When the battery cell is charged to 50% SOC, use a 1KHZ voltage internal resistance tester to detect the internal resistance of the battery cell or battery.
  • Acupuncture pass rate In the normal temperature environment, charge the lithium-ion battery with a constant current of 0.5C to a voltage of 4.35V, and then charge it with a constant voltage to a current of 0.025C; transfer the lithium-ion battery to the nail penetration test equipment , keep the test environment temperature at 25°C, use a steel nail with a diameter of 4mm to pass through the lithium-ion battery negative ear side 7mm from the cell side at a constant speed of 30mm/s, and keep it for 300s, the lithium-ion battery will not catch fire and will not explode Recorded as passed.
  • the results of the above examples and comparative examples show that the present invention can effectively solve the problem of ultra-thick battery cells, improve the safety of the battery, and at the same time improve the battery capacity, charge Discharge rate and other properties.

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Abstract

本发明提供一种极片及电池，该极片包括集流体和位于集流体第一表面的功能层，第一表面设有极耳，功能层由远离极耳的正常区和靠近极耳的凹陷区组成，凹陷区的厚度小于正常区的厚度。本发明能够有效避免电芯靠近极耳的部位过厚等问题，提高电池的安全性和充放电倍率等品质。

Description

极片及电池
本申请要求于2020年12月30日提交中国专利局、申请号为202011628643.2、申请名称为“极片及电池”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及电池领域，具体涉及一种极片及采用该极片的电池。
背景技术
锂离子电池由于具有环境友好、工作电压高、比容量大和循环寿命长等优点而被广泛应用于消费电子产品及电动汽车等领域，提高锂离子电池的快充能力以及寿命和安全性等品质，对于电池的实际推广应用具有重要意义。
卷绕式电池是比较常用的一类电池，其主要由正极片、隔膜、负极片层叠设置后再经卷绕形成电芯，再经注液、封装、化成等工艺制成，然而，常规电芯通常靠近极片极耳部位处过厚，尤其是采用将极耳设计在极片的中间(而非端部)的极片时，由于需要在极耳部位贴附胶纸等原因，电芯靠近极耳部位处更易出现过厚现象，超出厚度规格，导致析锂、电池内阻增大等问题，不利于电池的安全性、电芯体积能量密度和充放电倍率等性能。
发明内容
本发明提供一种极片，以至少解决上述现有技术中所存在的电芯中靠近极片极耳部位处过厚以及由此导致的电池安全性低、充放电倍率性能差等问题。
本发明还提供一种电池，采用上述极片，能够有效避免其电芯靠近极片极耳部位处过厚等问题，具有良好的充放电倍率性能、安全性和较长的使用寿命。
本发明的一方面，提供一种极片，包括集流体和位于集流体第一表面的功能层，所述第一表面设有极耳，所述第一表面的功能层由远离极耳的正常 区和靠近极耳的凹陷区组成，所述凹陷区的厚度小于正常区的厚度。
根据本发明的一实施方式，所述功能层包括底涂层和活性材料层，所述底涂层位于集流体表面和活性材料层之间，所述底涂层的原料包括活性材料、粘结剂和导电剂，所述活性材料层的原料包括活性材料、粘结剂和导电剂，所述底涂层中的粘结剂的含量高于活性材料层中的粘结剂的含量。
根据本发明的一实施方式，所述凹陷区的厚度比正常区的厚度小5-125μm。
根据本发明的一实施方式，所述凹陷区的底涂层的厚度为0-15μm，凹陷区的活性材料层的厚度为0-105μm；和/或，所述正常区的底涂层的厚度为5-15μm，所述正常区的活性材料层的厚度为90-110μm。
根据本发明的一实施方式，所述凹陷区的宽度为3-50mm。
根据本发明的一实施方式，所述底涂层为多孔结构，其孔隙率为20％-45％；和/或，所述活性材料层为多孔结构，其孔隙率为25％-50％。
根据本发明的一实施方式，所述底涂层的原料中，活性材料的质量含量为49-94％，粘结剂的质量含量为4-50％，导电剂的质量含量为1-5％；和/或，所述活性材料层的原料中，活性材料的质量含量为93-96％，粘结剂的质量含量为0.9-1.5％，导电剂的质量含量为1-3％。
根据本发明的一实施方式，所述极片为正极片，所述活性材料包括钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、磷酸铁锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、富锂锰基材料、镍钴铝酸锂和钛酸锂中的至少一种。
根据本发明的一实施方式，所述极片为负极片，所述活性材料包括石墨、中间相碳微球、软碳、硬碳、硅材料、硅氧材料、硅碳材料、钛酸锂材料中的至少一种。
本发明的另一方面，提供一种电池，包括上述极片。
本发明提供的极片，通过上述特殊结构设计，具有良好的安全性，将其应用于电池时，能够有效避免电芯靠近极耳的部位过厚等问题，提高电池的安全性和充放电倍率等品质；本发明提供的电池，采用上述极片，具有良好的安全性和充放电倍率等性能，在产业上具有更大的实用意义。
附图说明
图1为本发明一实施方式的极片的结构示意图；
图2为本发明一实施方式的电池的电芯卷绕结构示意图；
图3为本发明一实施方式中制备极片时所用凹版辊示意图；
附图标记说明：1：集流体；2：底涂层；3：活性材料层；31：正常区；32：凹陷区；4：极耳；5：胶纸；6：未涂覆区；7：负极耳；8：雕刻区；9：预留极耳位；10：未雕刻区；H1：凹陷区深度；H2：胶纸上表面至正常区表面的距离。
具体实施方式
为使本领域技术人员更好地理解本发明的方案，下面结合附图对本发明作进一步地详细说明。
本发明的一方面，提供一种极片，如图1所示，该极片包括集流体1和位于集流体1第一表面的功能层，第一表面设有极耳4，第一表面的功能层由远离极耳的正常区31和靠近极耳的凹陷区32组成，凹陷区32的厚度小于正常区的厚度。
本发明提供的极片，通过上述凹陷区设计，能够有效避免采用该极片形成的电芯中靠近极耳部位处的厚度过厚的问题，进而保证电池的安全性和充放电倍率等品质。
上述功能层可以包括底涂层2和活性材料层3，底涂层2位于集流体1表面和活性材料层3之间，底涂层2的原料包括活性材料、粘结剂和导电剂，活性材料层3的原料包括活性材料、粘结剂和导电剂，底涂层2中的粘结剂的含量高于活性材料层3中的粘结剂的含量，上述底涂层(或称安全涂层)具有较高的与集流体表面的粘附力，可进一步提高极片的安全性等性能。
具体地，本发明中，极耳4可以位于极片的中部(即非端部)，功能层围绕极耳设置。一般情况下，极耳4的厚度不大于凹陷区32的厚度，即在集流体设有极耳的表面(即第一表面)上，以集流体的该表面为基准，极耳4的高度不大于凹陷区32的高度。
本发明中，可以只在集流体1的第一表面设置功能层，也可以同时在与第一表面相对的第二表面设置功能层(集流体的正反两个表面均设置功能层)，优选后者，能够进一步提高极片的能量密度等特性。当在两个表面均设有功 能层时，第二表面上与极耳对应的位置处可以涂覆有功能层，也可以是没有涂层的未涂覆区，优选为没有涂层的未涂覆区，更利于避免电芯的超厚现象，同时也更利于极片的制作；在一具体实施方式中，在集流体1的两个表面均设有功能层时，第二表面上设有无涂层的未涂覆区6，未涂敷区6与第一表面的极耳4位置对应，第二表面的功能层可以不设有凹陷区，也可以在靠近未涂覆区6的位置处设置凹陷区(即第二表面的功能层包括靠近未涂敷区6的凹陷区和远离未涂敷区6的正常区)，第一表面的凹陷区、第二表面的凹陷区的形状、面积大小、厚度等参数可以相同或不同，优选为相同。
本发明中，正常区31的底涂层和凹陷区32的底涂层的厚度可以相同或不同，只要满足凹陷区32的厚度小于正常区31的厚度即可，意即，凹陷区深度H1＝正常区的厚度-凹陷区的厚度，H1＞0。根据本发明的研究，上述凹陷区的厚度一般可以比正常区的厚度小5-125μm，即H1为5-125μm，进一步可以为10-125μm，比如可以为10-100μm或10-90μm或10-80μm或10-70μm或10-65μm或20-65μm或30-65μm或40-65μm或45-65μm或50-65μm或55-65μm或60-65μm。
上述凹陷区32的厚度基本等于凹陷区32的底涂层厚度和凹陷区32的活性材料层厚度之和，在一优选实施方式中，凹陷区的底涂层厚度可以为0-15μm，比如可以为5-12μm，凹陷区的活性材料层的厚度可以为0-105μm，比如可以为45-105μm。
具体地，在本发明的一实施方式中，凹陷区的厚度为0-125μm，进一步可以为0-120μm，更进一步可以为50-112μm，比如可以为为50μm、57μm、63μm、74μm、90μm、101μm、110μm、112μm。
本发明正常区31的厚度可以按照本领域常规极片涂层厚度设置，正常区31的厚度基本等于正常区的底涂层厚度和正常区的活性材料层厚度之和，在一优选实施方式中，正常区的底涂层的厚度为5-15μm，进一步可以为5-12μm，比如可以为5-8μm，利于使极片兼具良好的安全性和较低的内阻；正常区的活性材料层的厚度为90-110μm，利于进一步提高极片的能量密度等特性。
进一步地，上述凹陷区32的宽度一般可以为3-50mm，进一步可以为3-30mm，比如可以为10-30mm或20-30mm或25-30mm。
一般情况下，上述底涂层2为多孔结构，其孔隙率可以为20％-45％；和/或，活性材料层3为多孔结构，其孔隙率可以为25％-50％。
经进一步研究，上述底涂层2的原料中，活性材料的质量含量为49-94％；和/或，粘结剂的质量含量为4-50％，导电剂的质量含量为1-5％；上述活性材料层3的原料中，活性材料的质量含量为93-96％，例如94-96％；和/或，粘结剂的质量含量为0.9-1.5％，例如2-3.5％，导电剂的质量含量为1-3％，例如1-2％。
本发明中，活性材料、粘结剂、导电剂均可以是本领域常规材料，例如，粘结剂可以包括聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素钠、聚乙烯吡咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯、聚六氟丙烯和丁苯橡胶(SBR)中的至少一种，导电剂可以包括碳黑、碳纤维、碳纳米管、石墨、石墨烯、金属材料、导电陶瓷材料中的至少一种。
具体地，上述极片可以是正极片或者负极片，例如，在一实施方式中，上述极片为正极片，上述活性材料可以是含锂活性材料等本领域常规正极活性材料，例如可以包括钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、磷酸铁锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、富锂锰基材料、镍钴铝酸锂中的至少一种，上述集流体可以是铝箔等本领域常规正极集流体；在另一实施方式中，上述极片为负极片，上述活性材料可以包括石墨、中间相碳微球、软碳、硬碳、硅材料、硅氧材料、硅碳材料、钛酸锂材料等中的至少一种，上述集流体可以是铜箔等本领域常规负极集流体。
当上述极片为负极片时，底涂层2的原料和/或活性材料层3的原料还可以包括分散剂，底涂层2中分散剂的质量含量可以为1.5-2.5％，活性材料层3中分散剂的质量含量可以为1.5-2.5％，该分散剂可以是羧甲基纤维素钠(CMC)等常用分散剂。
本发明的极片可以按照涂覆法等本领域常规方法制得，如在一实施方式中，其制备方法具体可以包括：在集流体1表面涂布底涂层2后，再在底涂层2表面涂布活性材料层3，然后除去预设极耳位的底涂层和活性材料层后，在预设极耳位的集流体上焊接极耳，并根据预设凹陷区的宽度、厚度等参数除去预设凹陷区的功能层形成凹陷区32，得到极片；其中，采用凹版涂布法涂布底涂层，如图3所示，凹版涂布法所用的凹版辊设有预留极耳位9，集流体1上的预设极耳位与凹版辊的预留极耳位9的位置对应；可以采用转移涂布、挤压涂布、丝网印刷等常规方法涂布上述活性材料层，亦可以采用凹版 涂布法涂布上述活性材料层；可采用激光或刮刀刮除或二者的配合等本领域常规方式除去预设极耳位的涂层。
一般情况下，可以先将底涂层的浆料涂敷于集流体后，再经干燥/烘干处理(烘干的温度可以控制为100-130℃，比如110℃)，在集流体上形成底涂层，然后在底涂层表面涂覆活性材料层的浆料，涂覆完成后，再经干燥(干燥温度可以为80-110℃)和辊压处理，随后可采用台阶刮刀或激光清洗等方式除去预设凹陷区的功能层形成凹陷区，并除去预设极耳位的全部功能层，露出集流体，在集流体上焊接极耳，得到极片。其中，上述浆料的溶剂可以是N-甲基吡咯烷酮(NMP)等本领域常规溶剂。
具体地，如图3所示，上述凹版辊包括辊体，辊体表面设有至少一个对应极片涂层的涂布区，涂布区包括雕刻有网纹的雕刻区8和未经雕刻的预留极耳位9，其余为未雕刻区(即非涂布区)10。上述预设极耳位用于焊接极耳，其表面形状大小均与待焊接极耳的底面形状大小相同，上述预留极耳位9的形状大小可以根据待焊接极耳的形状大小进行设定，通常预留极耳位的形状与预设极耳位的形状类似，而其尺寸一般稍大于预设极耳位的尺寸。
采用上述凹版辊形成的凹版涂布机具体可以包括用于盛放涂层浆料的料槽、位于所述料槽上方的凹版辊、与该凹版辊配合的胶辊(通常位于凹版辊的上方)、以及与该凹版辊配合的刮刀(通常位于凹版辊的侧面并压在凹版辊上)；其中，料槽、胶辊、刮刀及其位置均为本领域常规设置，不再赘述。具体实施时，可以将底涂层原料置于溶剂中形成涂层浆料，设定刮刀压力、胶辊压力、涂布速度、烘箱温度等参数或条件后，将上述浆料置于凹版涂布机的料槽中，开始对集流体等基材进行涂布；涂布完成后，经干燥处理，在基材上形成底涂层，得到涂覆有底涂层的卷料，然后在该卷料上涂覆正极活性层后，再辊压分切成符合预设形状、大小等参数的极片。具体地，上述凹版涂布的条件可以为：涂布速度为10-30m/min，比如可以为20m/min；刮刀压力为0.2-0.6MPa，比如0.4MPa；胶辊压力为0.2-0.6MPa，比如0.4MPa。
采用上述方法制备极片，不仅能够提升极片的安全性、充放电倍率等性能，还能够提高极片的制造良率，利于产业化生产和应用。
本发明的另一方面，还提供一种电池，包括上述极片。
本发明的电池可以包括具有上述结构设计的正极片(即上述极片为正极片)，或者包括具有上述结构设计的负极片(即上述极片为负极片)，或者 可以同时包括具有上述结构设计的正极片和具有上述结构设计的负极片(即上述极片包括正极片和负极片)。当上述极片为负极片时，上述电池还包括正极片，该正极片亦可以是本领域常规正极片；当上述极片为正极片时，上述电池还包括负极片，该负极片可以是本领域常规负极片，如在一实施方式中，该负极片包括负极集流体和位于负极集流体上的负极功能层，该负极功能层厚度可以为100-120μm，其原料包括负极活性材料、粘结剂和导电剂，其中，负极活性材料的质量含量可以为94-96％，粘结剂的质量含量可以为2-3.5％，分散剂的质量含量可以为1.5-2.5％，导电剂的质量含量可以为1-2％，粘结剂、导电剂、负极活性材料、分散剂可以是如上所述的常规材料，不再赘述。
上述电池还包括位于正极片和负极片之间的隔膜，该隔膜用于间隔正极片和负极片，其可以是本领域常规隔膜，本发明对此亦不做特别限制。
一般情况下，在极片设有极耳的一表面上贴附有胶纸5，胶纸5和极耳4、环绕极耳4的至少部分凹陷区32(靠近极耳的凹陷区32)粘接，极耳4位于由凹陷区32、胶纸5、集流体1围成的腔内，胶纸5的上表面位于正常区31表面的下方，意即，胶纸5上表面至正常区31表面的距离H2＝正常区31的厚度-胶纸5上表面至该胶纸所在侧的集流体表面的距离，H2＞0。
在本发明的一优选实施方式中，在集流体1的两个表面均设有功能层，第二表面上设有无涂层的未涂覆区6，未涂敷区6与第一表面的极耳4位置对应，两个表面的功能层均设有凹陷区32，两个表面均贴附有胶纸5，胶纸5在第二表面的贴附方式与在第一表面的贴附方式相同，即，在第二表面，胶纸5和环绕未涂覆区6的至少部分凹陷区32(靠近未涂覆区的凹陷区)粘接，未涂覆区6位于由凹陷区32、胶纸5、集流体1围成的腔内，胶纸5的上表面位于正常区32表面的下方。
本发明可以采用本领域常规胶纸，在一优选实施方式中，胶纸厚度一般可以为16-30μm。
如图2所示，上述电池可以是卷绕式锂离子电池，带有正极耳4的正极片与带有负极耳7的负极片之间通过隔膜隔开，靠近极耳的部位没有过厚现象。
上述卷绕式电池可以按照本领域常规方法制得，如可以将正极片、隔膜、负极片层叠设置后经卷绕、组装、真空烘烤、注液、静置、封装、化成、分容等处理后制得卷绕式锂离子电池，上述卷绕、组装、真空烘烤、注液、静 置、封装、化成、分容均可以是本领域常规工序，所用隔膜、电解液等均可以是本领域常规材料，不再赘述。
为使本发明的目的、技术方案和优点更加清楚，下面将结合本发明的实施例，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
如无特别说明，以下实施例中，采用凹版涂布法进行涂布的过程所用的凹版涂布机包括：用于盛放涂层浆料的料槽、位于所述料槽上方的凹版辊、与该凹版辊配合的胶辊(通常位于凹版辊的上方)、以及与该凹版辊配合的刮刀(通常位于凹版辊的侧面并压在凹版辊上)；其中，凹版辊包括辊体，辊体表面设有至少一个对应极片涂层的涂布区，涂布区包括雕刻有网纹的正常区和未经雕刻的预留极耳位，其余为非涂布区；涂布时，控制涂布速度为20m/min；刮刀压力为0.4MPa；胶辊压力为0.4MPa。
实施例1
本实施例的正极片包括正极集流体和涂敷于正极集流体两个表面的正极功能层，正极集流体的一表面上设有正极耳(正极耳位于正极片的中部)，该表面的正极功能层由远离正极耳的正常区和靠近正极耳的凹陷区组成，所述凹陷区的厚度小于正常区的厚度；正极集流体的另一表面上设有与正极耳位置对应的未涂覆区，该另一表面的正极功能层与设有正极耳的表面的正极功能层相同(由上述正常区和凹陷区组成)；上述两表面的正极功能层包括底涂层和正极活性材料层，底涂层位于正极集流体表面和正极活性材料层之间；其中，凹陷区的底涂层与正常区的底涂层厚度相同，底涂层厚度为5μm，凹陷区的正极活性材料层厚度为45μm，正常区的正极活性材料层厚度为110μm，凹陷区深度H1为65μm，凹陷区宽度30mm；底涂层的孔隙率为28％，正极活性层的孔隙率为35％；正极集流体为铝箔。
上述正极片及采用该正极片形成的卷绕式锂离子电池具体按照如下过程制得：
(1)将磷酸铁锂、聚偏氟乙烯和碳黑按照质量比65:30:5于NMP中混合 均匀形成底涂层浆料(固含量为15％)；将上述底涂层浆料置于凹版涂布机的料槽中，开启涂布，将其涂布于铝箔两面，然后经110℃烘干后，得到涂覆有底涂层的卷料；
将钴酸锂、聚偏氟乙烯和碳黑按照质量比97：1.3：1.4于NMP中混合均匀形成正极活性层浆料，采用狭缝式挤压涂布设备将其涂布于上述卷料的两面，于100℃干燥2-5min后，经辊压分切成1000mm×65mm的正极片前体；清洗掉正极片前体的预设极耳位的涂层后，焊接极耳，得到正极片；
(2)将石墨、CMC、SBR和碳黑按照质量比95：1.5：1.5：2于去离子水中混合均匀形成负极活性层浆料，将该浆料涂敷于铜箔的两个表面上，于70～100℃烘干2～5min，然后辊压分切成1100mm×66.5mm的负极片；其中，负极片功能层(其上述浆料经干燥、辊压后形成的涂层)的厚度为120μm；
(3)按照常规的锂电池卷绕工艺，采用上述正极片、负极片制作成卷绕式电池。其中，在正极片的两个表面均贴附有胶纸，在设有正极耳的表面，胶纸和正极耳、环绕正极耳的凹陷区粘接，正极耳位于由凹陷区、胶纸、正极集流体围成的腔内，胶纸的上表面位于正常区表面的下方，在设有未涂敷区的表面，胶纸和环绕未涂覆区的凹陷区粘接，未涂覆区位于由凹陷区、胶纸、正极集流体围成的腔内，胶纸的上表面位于正常区表面的下方；所用胶纸的厚度为16μm。
实施例2
本实施例与实施例1的区别在于，底涂层厚度为7μm，凹陷区的正极活性材料层厚度为50μm，凹陷区深度为60μm，其余条件与实施例1相同。
实施例3
本实施例与实施例1的区别在于，底涂层的厚度为8μm，凹陷区的正极活性材料层厚度为55μm，凹陷区深度为55μm，其余条件与实施例1相同。
实施例4
本实施例与实施例1的区别在于，底涂层的厚度为9μm，凹陷区的正极活性材料层厚度为65μm，凹陷区深度为45μm，其余条件与实施例1相同。
实施例5
本实施例与实施例1的区别在于，底涂层的厚度为10μm，凹陷区的正极活性材料层厚度为80μm，凹陷区深度为30μm，其余条件与实施例1相同。
实施例6
本实施例与实施例1的区别在于，底涂层的厚度为11μm，凹陷区的正极活性材料层厚度为90μm，凹陷区深度为20μm，其余条件与实施例1相同。
实施例7
本实施例与实施例1的区别在于，底涂层的厚度为12μm，凹陷区的正极活性材料层厚度为100μm，凹陷区深度为10μm，其余条件与实施例1相同。
实施例8
该对比例与实施例1的区别在于，凹陷区的深度为5μm，凹陷区的正极活性材料层厚度为105μm，其余条件与实施例1相同。
实施例9
该对比例与实施例1的区别在于，正极片凹陷区宽度设置为50mm，其余条件与实施例1相同。
对比例1
该对比例与实施例1的区别在于，未设置底涂层，凹陷区的厚度和正常区的厚度相同(即未设置凹陷区)，极耳设置在极片的端部，其余与实施例1条件相同。
对比例2
该对比例与实施例1的区别在于，凹陷区的厚度和正常区的厚度相同(即未设置凹陷区)，其余条件与实施例1相同。
性能测试
测得实施例1-9、对比例1和2的锂离子电池的电池内阻、2C充电倍率、 电芯超厚比例、针刺通过率如表1所示，各实施例和对比例中的凹陷区深度、凹陷区宽度、底涂层厚度、电池的容量亦汇总于表1。
其中，各测试方法如下：
(1)电池内阻：电芯充电至50％SOC时，用1KHZ电压内阻测试仪检测电芯或电池的内阻。
(2)2C充放电倍率
倍率充电：在25℃±5℃条件下，将电芯以0.2C电流恒流放电到3.0V，静置10min，再以2C恒流充电至4.35V；然后改为恒压充电，直到充电电流≤0.02C；其中，恒流阶段充电容量计为Cc1，总充电容量计为C1，恒流充入比＝Cc1/C1。
倍率放电：在25℃±5℃条件下，将电芯以0.2C电流恒流放电到3.0V，然后按照0.2C恒流恒压充电至4.35V截止电压，再以0.2C和2C放电至3.0V；其中，0.2C放电容量记为C0，2C放电容量记为C2，放电容量比＝C2/C0。
(3)电芯超厚比例
按照如下过程分别测定各实施例和对比例的电芯超厚比例：采用平面测厚仪测量200个电芯厚度数值(各实施例和对比例的电芯厚度不超过3.965mm为宜)，超过规格限(3.965+0.08mm)的电芯个数记为N，超厚比例＝N/50。
(4)针刺通过率：在常温环境下，将锂离子电池以0.5C恒流充电至电压为4.35V，然后恒压充电至电流为0.025C；将锂离子电池转移至穿钉测试设备上，保持测试环境温度为25℃，用直径为4mm的钢钉，以30mm/s的速度匀速穿过锂离子电池负极耳侧距电芯侧边7mm处，保留300s，锂离子电池不起火不爆炸记为通过。每实施例/对比例测试5只锂离子电池，以穿钉测试通过率作为评价锂离子电池安全性的指标，其中，针刺测试通过率＝针刺通过电池数量/针刺总电池数。
表1
Figure PCTCN2021139024-appb-000001
Figure PCTCN2021139024-appb-000002
从表1结果可以看出，相对于对比例1和2，实施例1-9的电池电芯超厚比例极低，大部分超厚比例为0，而同时具有较高的针刺通过率、较低的电池内阻、较高的电芯容量以及倍率性能等优势，尤其是实施例1-9的电池兼具更优异的电芯容量、充放电倍率、针刺通过率等综合性能。更具体来说，从实施例1-7可以看出，随着底涂层厚度增加，电池针刺通过率增加，说明底涂层厚度增加对电池的安全性提升效果明显，但过高会影响电池内阻等性能；从实施例1、8、9可以看出，随着凹陷区深度增大，电池超厚比例降低，但凹陷区过大，会影响电池的容量，而凹陷区深度过低，电池的超厚比例稍高，即相对存在较高的超厚风险；从实施例1和对比例1-2可以看出，正极片凹陷区设计，可以使得正极片卷绕形成的电池电芯中，正极片、隔膜、负极片之间接触更加紧密，有利于电芯内阻降低和充放电倍率性能的发挥。
因此，上述实施例及对比例结果表明，本发明通过在正极片极耳位设置上述特定的凹陷区，可以有效解决电芯超厚问题，提升电池的安全性，同时兼顾提高电池的容量、充放电倍率等性能。

Claims (10)

  1. 一种极片，其特征在于，包括集流体和位于集流体第一表面的功能层，所述第一表面设有极耳，所述第一表面的功能层由远离极耳的正常区和靠近极耳的凹陷区组成，所述凹陷区的厚度小于正常区的厚度。
  2. 根据权利要求1所述的极片，其特征在于，所述功能层包括底涂层和活性材料层，所述底涂层位于集流体表面和活性材料层之间，所述底涂层的原料包括活性材料、粘结剂和导电剂，所述活性材料层的原料包括活性材料、粘结剂和导电剂，所述底涂层中的粘结剂的含量高于活性材料层中的粘结剂的含量。
  3. 根据权利要求1所述的极片，其特征在于，所述凹陷区的厚度比正常区的厚度小5-125μm。
  4. 根据权利要求2所述的极片，其特征在于，所述凹陷区的底涂层的厚度为0-15μm，凹陷区的活性材料层的厚度为0-105μm；和/或，所述正常区的底涂层的厚度为5-15μm，所述正常区的活性材料层的厚度为90-110μm。
  5. 根据权利要求1或3所述的极片，其特征在于，所述凹陷区的宽度为3-50mm。
  6. 根据权利要求2所述的极片，其特征在于，所述底涂层为多孔结构，其孔隙率为20％-45％；和/或，所述活性材料层为多孔结构，其孔隙率为25％-50％。
  7. 根据权利要求2所述的极片，其特征在于，所述底涂层的原料中，活性材料的质量含量为49-94％，粘结剂的质量含量为4-50％，导电剂的质量含量为1-5％；和/或，所述活性材料层的原料中，活性材料的质量含量为93-96％，粘结剂的质量含量为0.9-1.5％，导电剂的质量含量为1-3％。
  8. 根据权利要求2所述的极片，其特征在于，所述极片为正极片，所述活性材料包括钴酸锂、锰酸锂、镍酸锂、镍钴锰酸锂、磷酸铁锂、磷酸锰铁锂、磷酸钒锂、磷酸钒氧锂、富锂锰基材料、镍钴铝酸锂和钛酸锂中的至少一种。
  9. 根据权利要求2所述的极片，其特征在于，所述极片为负极片，所述活性材料包括石墨、中间相碳微球、软碳、硬碳、硅材料、硅氧材料、硅碳材料、钛酸锂材料中的至少一种。
  10. 一种电池，其特征在于，包括权利要求1-9任一项所述的极片。
PCT/CN2021/139024 2020-12-30 2021-12-17 极片及电池 WO2022143210A1 (zh)

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