WO2022022520A1 - 一种负极片及其制备方法和包含该负极片的锂离子电池 - Google Patents

一种负极片及其制备方法和包含该负极片的锂离子电池 Download PDF

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WO2022022520A1
WO2022022520A1 PCT/CN2021/108700 CN2021108700W WO2022022520A1 WO 2022022520 A1 WO2022022520 A1 WO 2022022520A1 CN 2021108700 W CN2021108700 W CN 2021108700W WO 2022022520 A1 WO2022022520 A1 WO 2022022520A1
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negative electrode
active material
electrode active
material layer
current collector
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PCT/CN2021/108700
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English (en)
French (fr)
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金丹丹
彭冲
李俊义
徐延铭
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珠海冠宇电池股份有限公司
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Priority to EP21848556.3A priority Critical patent/EP4187641A1/en
Publication of WO2022022520A1 publication Critical patent/WO2022022520A1/zh
Priority to US18/160,294 priority patent/US20230187606A1/en

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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
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    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/531—Electrode connections inside a battery casing
    • H—ELECTRICITY
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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
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    • 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
    • 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 belongs to the technical field of lithium ion batteries, and in particular relates to a negative electrode sheet, a preparation method thereof, and a lithium ion battery comprising the negative electrode sheet.
  • Lithium-ion batteries are widely used in portable electronic devices, such as mobile phones and notebook computers, due to their high platform voltage, good cycle life, high energy density, and no memory effect.
  • STP Specific Cell Process
  • this structure also has certain disadvantages, the most prominent of which is that lithium is easily precipitated at the position of the pole piece close to the pole ear, especially when charging at a high rate. This will lead to the continuous diffusion of the lithium deposition area of the cell during the cycle, speed up the consumption of the electrolyte, and eventually lead to the failure and deformation of the cell, which brings great hidden dangers.
  • the reason for the above-mentioned lithium precipitation problem is mainly that during the charging process, the current density at the middle tab position is larger than that at other positions.
  • the present invention provides a negative electrode sheet, a preparation method thereof, and a lithium ion battery comprising the negative electrode sheet.
  • the negative electrode sheet of the present invention can solve the problem of lithium precipitation at the tab position in the special cell technology structure in the middle of the tab, that is, in the STP structure, thereby improving the cycle life of the cell.
  • placing the tabs in the middle is a different way of disposing the tabs in the empty foil area of the head of the negative electrode sheet, which is different from the conventional tabs.
  • the special cell process structure with the middle of the tab refers to that the tab is welded at the middle position of the paste-coated area on the surface of the negative electrode sheet.
  • a negative electrode sheet the negative electrode sheet comprises a negative electrode current collector, a first negative electrode active material layer, a second negative electrode active material layer, and a negative electrode tab, wherein the negative electrode tab is arranged on one side surface of the negative electrode current collector and is close to the negative electrode current collector.
  • the first negative electrode active material layer is coated on the surface of the negative electrode current collector at the negative electrode tab and on the side where the negative electrode tab is arranged, and the second negative electrode active material layer is coated on the surface of the negative electrode current collector away from the negative electrode tab and on the side where the negative electrode tab is arranged. material layer;
  • the first negative electrode active material layer includes a first negative electrode active material
  • the second negative electrode active material layer includes a second negative electrode active material
  • the rate at which the first negative electrode active material layer accepts lithium ions is higher than that of the second negative electrode active material layer. The speed at which the negative electrode active material layer accepts and deintercalates lithium ions.
  • the kinetic performance of the first negative electrode active material layer is better than the kinetic performance of the second negative electrode active material layer.
  • the kinetic performance refers to the deintercalation speed of lithium ions, and the faster the deintercalation speed, the better the kinetic performance.
  • the factors affecting the deintercalation speed of lithium ions mainly include: (1) the amount of charging current that the active material can support, the larger the charging current that can be supported, the better the kinetic performance; (2) the amount of lithium ions accepted per unit time , that is, the speed of accepting lithium ions, the faster the speed of accepting lithium ions, the better the kinetic performance.
  • the extraction speed of lithium ions of the first negative electrode active material layer is greater than the extraction speed of lithium ions of the second negative electrode active material layer.
  • the supportable charging current of the first negative electrode active material layer is greater than the supportable charging current of the second negative electrode active material layer.
  • the lithium evolution window of the first negative electrode active material layer is larger than the lithium evolution window of the second negative electrode active material layer.
  • the lithium evolution window of the first negative electrode active material layer can be reflected by the dissection of the first negative electrode active material (such as graphite) whether or not lithium is deposited.
  • the dissection of the negative electrode active material is reflected by whether it is lithium-deposited; in the embodiment of the present invention, the lithium-evolution window of the above-mentioned first negative-electrode active material is greater than or equal to 1.5C.
  • the above-mentioned first negative electrode active material is a negative electrode that supports 1.5C fast charging active substance.
  • a first negative electrode active material layer is coated on both sides of the negative electrode current collector near the negative electrode tab, and a second negative electrode active material layer is coated on both sides of the negative electrode current collector far from the negative electrode tab.
  • the lengths of the first negative electrode active material layers on both sides of the negative electrode current collector are the same or different, preferably the same.
  • the first negative active material layers on both sides of the negative electrode current collector are symmetrically arranged on both sides of the negative electrode current collector with the negative electrode current collector as the symmetry axis.
  • the lengths of the second negative electrode active material layers on both sides of the negative electrode current collector are the same or different, preferably the same.
  • the second negative active material layers on both sides of the negative electrode current collector are symmetrically arranged on both sides of the negative electrode current collector with the negative electrode current collector as the symmetry axis.
  • the negative electrode is a pole-tab center structure.
  • the second negative electrode active material layer is connected to the first negative electrode active material layer, that is, there is no blank area in the second negative electrode active material layer and the first negative electrode active material layer.
  • the length and width of the negative electrode current collector are not particularly defined, and current collectors with different lengths and widths are selected according to different cells required.
  • the length of the negative electrode current collector is 500-1000 mm, eg, 885 ⁇ 2 mm
  • the width of the negative electrode current collector is 400-900 mm, eg, 773 ⁇ 2 mm.
  • the thickness of the first negative electrode active material layer and the thickness of the second negative electrode active material layer are the same or different, preferably the same, preferably 90-120 ⁇ m, such as 90 ⁇ m, 95 ⁇ m, 100 ⁇ m, 105 ⁇ m, 110 ⁇ m , 115 ⁇ m or 120 ⁇ m.
  • the surface of the negative electrode current collector further optionally includes a blank area, and the blank area is arranged on one side of the second negative electrode active material layer.
  • the blank area is to avoid cutting Due to the second negative electrode active material layer on the surface of the negative electrode current collector, the length of the blank area may be, for example, 0.5-2 mm, such as 1 mm.
  • the negative electrode sheet includes a negative electrode current collector, a first negative electrode active material layer (BC segment and FG segment), a second negative electrode active material layer (AB segment, CD segment, EF segment and GH segment) section), negative electrode tabs, the negative electrode tabs are arranged on the surface of one side of the negative electrode current collector, and the surfaces on both sides of the negative electrode current collector near the negative electrode tabs are coated with the first negative electrode active material layer (section BC and section FG). ), a second negative electrode active material layer (AB segment, CD segment, EF segment and GH segment) is coated on both sides of the negative electrode current collector away from the negative electrode tab.
  • a second negative electrode active material layer (AB segment, CD segment, EF segment and GH segment) is coated on both sides of the negative electrode current collector away from the negative electrode tab.
  • the first negative electrode active material layer includes a first negative electrode active material, a first conductive agent, a first dispersant and a first binder
  • the second negative electrode active material layer includes a second negative electrode active material substance, a second conductive agent, a second dispersant, and a second binder.
  • first negative electrode active material and the second negative electrode active material forming the first negative electrode active material layer and the second negative electrode active material layer are the same or different
  • first conductive agent and the second conductive agent are the same or different
  • first conductive agent is the same or different
  • the binder and the second binder are the same or different
  • the first dispersant and the second dispersant are the same or different.
  • the mass percentage content of each component in the first negative electrode active material layer is:
  • the mass percentage of each component in the first negative electrode active material layer is:
  • the mass percentage of each component in the second negative electrode active material layer is:
  • the mass percentage of each component in the second negative electrode active material layer is:
  • the content of the first conductive agent forming the first negative electrode active material layer is greater than the content of the second conductive agent forming the second negative electrode active material layer.
  • Such selection can ensure that the electronic conductivity of the first negative electrode active material layer is better than that of the second negative electrode active material layer . Therefore, this selection can ensure that the kinetic performance of the first negative electrode active material layer is superior to that of the second negative electrode active material layer.
  • the first conductive agent and the second conductive agent are the same or different, and are independently selected from conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder, carbon fiber, graphene at least one of them.
  • the first conductive agent and the second conductive agent are different doses.
  • the first conductive agent is selected from at least one of graphene and carbon nanotubes
  • the second conductive agent is selected from conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, metal At least one of powder and carbon fiber; such selection can ensure that the electronic conductivity of the first negative electrode active material layer is better than that of the second negative electrode active material layer, mainly because the electrons of graphene and carbon nanotubes Better conductivity.
  • the first binder and the second binder are the same or different, and are independently selected from sodium carboxymethyl cellulose, styrene-butadiene latex, styrene-acrylate emulsion, polytetrafluoroethylene, polyethylene oxide at least one of them.
  • the first binder and the second binder are different.
  • the first binder is selected from styrene-acrylate emulsion
  • the second binder is selected from sodium carboxymethyl cellulose, styrene-butadiene latex, benzene polytetrafluoroethylene, and polyethylene oxide.
  • this selection can ensure that the electronic conductivity of the first negative electrode active material layer is better than that of the second negative electrode active material layer, mainly because of the electrolyte affinity of the styrene-acrylate emulsion. Better than other binders.
  • the first negative electrode active material and the second negative electrode active material are the same or different, and are independently selected from at least one of modified or unmodified following materials: artificial graphite, natural graphite, mesophase carbon Ball, lithium titanate, silicon oxide, wherein the modification includes doping, particle size regulation or coating.
  • the particle size of the first negative electrode active material is smaller than the particle size of the second negative electrode active material, or the coating amount of the first negative electrode active material is greater than the coating amount of the second negative electrode active material.
  • Small particle size can shorten the path of Li + transport, while increasing the coating amount can increase the path of Li + insertion, both of which can improve the diffusion ability of Li + inside the anode active material layer, so this choice can guarantee all
  • the kinetic performance of the first negative electrode active material layer is better than that of the second negative electrode active material layer.
  • first dispersant and the second dispersant are the same or different, and are independently selected from at least one of carboxymethyl cellulose and sodium carboxymethyl cellulose.
  • the present invention also provides a method for preparing the negative electrode sheet, the method comprising the following steps:
  • step 1) the solid content of the slurry for forming the first negative electrode active material layer and the slurry for forming the second negative electrode active material layer is 40wt% to 45wt%.
  • step 1) comprises the following steps:
  • the first step add the first negative electrode active material, the first conductive agent, the first binder and the first dispersant into the stirring tank according to a certain mass ratio, and then add deionized water to make the negative electrode slurry;
  • the second step the second negative electrode active material, the second conductive agent, the second binder and the second dispersant are added into the stirring tank according to a certain mass ratio, and then deionized water is added to prepare the negative electrode slurry.
  • step 2) comprises the following steps:
  • the slurry for forming the second negative electrode active material layer is coated on the surface of the negative electrode current collector away from the negative electrode tab and on the side where the negative electrode tab is arranged to form the second negative electrode active material layer.
  • step 2) comprises the following steps:
  • step 2) comprises the following steps:
  • the slurry for forming the first negative electrode active material layer is coated on the BC section of the negative electrode current collector surface to form the first negative electrode active material layer; the second negative electrode active material layer will be formed The slurry is coated on the AB segment and CD segment on the surface of the negative electrode current collector, and the BC segment is skipped during coating to form the second negative electrode active material layer;
  • the slurry for forming the first negative electrode active material layer is coated on the surface FG section of the negative electrode current collector to form the first negative electrode active material layer;
  • the slurry of the second negative electrode active material layer is coated on the EF segment and the GH segment on the surface of the negative electrode current collector, and the FG segment is skipped during coating to form the second negative electrode active material layer.
  • the method further comprises the steps of:
  • step 3 comprises the following steps:
  • the prepared negative electrode sheet was dried at a temperature of 100°C, and then cut into strips by rolling, laser-cleaned the tab groove on the area where the first negative electrode active material layer was located, and welded the nickel tab to obtain the negative electrode sheet .
  • the present invention also provides a lithium-ion battery, which includes the above-mentioned negative electrode sheet.
  • the battery further includes a positive electrode sheet and a separator.
  • the capacity retention rate of the lithium ion battery is ⁇ 82% after being cycled for 1000 cycles under a charge-discharge regime of 3C/1C at 25°C.
  • the expansion rate of the battery cell is less than or equal to 12% after the lithium ion battery is cycled for 1000 cycles under the charge-discharge regime of 3C/1C at 25°C.
  • the invention provides a negative electrode sheet and a preparation method thereof, and a lithium ion battery comprising the negative electrode sheet;
  • the negative electrode sheet of the present invention can effectively improve the phenomenon of lithium precipitation at the pole ear position of the STP structure lithium ion battery, and improve the cycle life of the lithium ion battery; At the same time, it can also effectively alleviate the problem of lithium precipitation deformation of the battery cell caused by lithium precipitation.
  • Fig. 1 Schematic diagram of the structure of the negative electrode sheet of the present invention.
  • Figure 2 Schematic diagram of the structure of the existing negative electrode sheet.
  • the particle size of the artificial graphite A and the artificial graphite B are equivalent, and the difference is only that the surface of the artificial graphite has a coating layer structure, so the dynamic performance of the artificial graphite A is better than that of the artificial graphite B.
  • the particle size of the artificial graphite C is smaller than that of the artificial graphite B, so the dynamic performance of the artificial graphite C is better than that of the artificial graphite B.
  • Embodiment 1 A preparation method of a negative electrode sheet and a preparation method of a lithium ion battery comprising the same are as follows:
  • the first step prepare the first active material slurry: combine the first negative electrode active material (artificial graphite B), the first conductive agent (conductive carbon black), the first binder (styrene-butadiene latex), the first dispersant ( Carboxymethyl cellulose) was added into the stirring tank according to the mass ratio of 96.4:1:1.3:1.4, then deionized water was added to make a negative electrode slurry, and the mixture was stirred through a known batching process to obtain a solid content of 40% to 45%. % slurry;
  • the second step preparation of the second active material slurry: the second negative electrode active material (artificial graphite B), the second binder (styrene-butadiene latex), the second dispersant (carboxymethyl cellulose) according to 97.4:1.3
  • the mass ratio of: 1.4 is added into the stirring tank, then deionized water is added to form a negative electrode slurry, and the slurry is stirred by a known batching process to obtain a slurry with a solid content of 40% to 45%;
  • the third step preparation of the negative electrode sheet: use a jump coater to coat twice, and coat the two active material slurries on the negative electrode current collector copper foil.
  • the surface of one side of the negative electrode sheet coating can be started from either end A or D, and the second active material slurry is coated on the AB segment and CD segment through the first jump coating, and the coating
  • the first active material slurry passes through the second jump coating, the coating area is the BC section, and the thickness of the coating layers on the surfaces of the three coating sections is the same.
  • the surface of the other side of the negative electrode sheet it can be coated from either end of the E or H end.
  • the second active material slurry is coated on the EF segment and the GH segment through the first jump coating, and the FG segment is skipped during coating.
  • the first active material slurry passes through the second jump coating, the coating area is the FG section, and the thickness of the coating layers on the surfaces of the three coating sections is the same.
  • the prepared negative electrode sheet was dried at a temperature of 100° C., and then cut into strips by rolling, and the tab grooves were cleaned by laser, and the nickel tab was welded to obtain the negative electrode sheet.
  • the fourth step preparation of positive electrode plate: the main material of lithium cobalt oxide positive electrode, conductive agent and polyvinylidene fluoride are added into the stirring tank according to the mass ratio of 97:1.5:1.5, and then NMP solvent is added to prepare the positive electrode slurry.
  • the solid content of the slurry is 70% to 75%, and then the slurry is coated on the aluminum foil by a coating machine, dried at a temperature of 120 ° C for 8 hours, and then cut into small strips after drying, and then cleaned with a scraper.
  • the welding position of the positive electrode lug is then compacted by a roller press, and the aluminum electrode lug is welded to obtain the positive electrode pole piece;
  • Step 5 Assemble the battery cell: wind the positive and negative electrode sheets obtained in the above two steps together with the diaphragm to form a roll core, wrap it with aluminum-plastic film, bake it to remove moisture, and then inject the electrolyte, and then use the hot-pressing process to form it. Get batteries.
  • the first step prepare the first active material slurry: combine the first negative electrode active material (artificial graphite A), the first conductive agent (conductive carbon black), the first binder (styrene-butadiene latex), the first dispersant ( Carboxymethyl cellulose) was added into the stirring tank according to the mass ratio of 96.4:1:1.3:1.4, then deionized water was added to make a negative electrode slurry, and the mixture was stirred through a known batching process to obtain a solid content of 40% to 45%. % slurry;
  • the second step prepare the second active material slurry: the second negative electrode active material (artificial graphite B), the second conductive agent (conductive carbon black), the second binder (styrene-butadiene latex), the second dispersant ( Carboxymethyl cellulose) was added into the stirring tank according to the mass ratio of 96.4:1:1.3:1.4, then deionized water was added to make a negative electrode slurry, and the mixture was stirred through a known batching process to obtain a solid content of 40% to 45%. % slurry.
  • the second negative electrode active material artificial graphite B
  • the second conductive agent conductive carbon black
  • the second binder styrene-butadiene latex
  • the second dispersant Carboxymethyl cellulose
  • the first step prepare the first active material slurry: combine the first negative electrode active material (artificial graphite C), the first conductive agent (conductive carbon black), the first binder (styrene-butadiene latex), the first dispersant ( Carboxymethyl cellulose) was added into the stirring tank according to the mass ratio of 96.4:1:1.3:1.4, then deionized water was added to make a negative electrode slurry, and the mixture was stirred through a known batching process to obtain a solid content of 40% to 45%. % slurry;
  • the second step prepare the second active material slurry: the second negative electrode active material (artificial graphite B), the second conductive agent (conductive carbon black), the second binder (styrene-butadiene latex), the second dispersant ( Carboxymethyl cellulose) was added into the stirring tank according to the mass ratio of 96.4:1:1.3:1.4, then deionized water was added to make a negative electrode slurry, and the mixture was stirred through a known batching process to obtain a solid content of 40% to 45%. % slurry.
  • the second negative electrode active material artificial graphite B
  • the second conductive agent conductive carbon black
  • the second binder styrene-butadiene latex
  • the second dispersant Carboxymethyl cellulose
  • the first step prepare the first active material slurry: combine the first negative electrode active material (artificial graphite B), the first conductive agent (conductive carbon black), the first binder (styrene-acrylate emulsion), the first The dispersant (carboxymethyl cellulose) was added to the stirring tank according to the mass ratio of 96.4:1:1.3:1.4, and then deionized water was added to form a negative electrode slurry, and the mixture was stirred by a known batching process to obtain a solid content of 40. % ⁇ 45% of slurry;
  • the second step prepare the second active material slurry: the second negative electrode active material (artificial graphite B), the second conductive agent (conductive carbon black), the second binder (styrene-butadiene latex), the second dispersant ( Carboxymethyl cellulose) was added into the stirring tank according to the mass ratio of 96.4:1:1.3:1.4, then deionized water was added to make a negative electrode slurry, and the mixture was stirred through a known batching process to obtain a solid content of 40% to 45%. % slurry.
  • the second negative electrode active material artificial graphite B
  • the second conductive agent conductive carbon black
  • the second binder styrene-butadiene latex
  • the second dispersant Carboxymethyl cellulose
  • the first step prepare the first active material slurry: combine the first negative electrode active material (artificial graphite B), the first conductive agent (carbon nanotubes, the first binder (styrene-butadiene latex), the first dispersant (carboxyl Methyl cellulose) is added into the stirring tank according to the mass ratio of 96.4:1:1.3:1.4, then deionized water is added to make a negative electrode slurry, and the mixture is stirred by a known batching process to obtain a solid content of 40% to 45%. slurry;
  • the second step prepare the second active material slurry: the second negative electrode active material (artificial graphite B), the second conductive agent (conductive carbon black), the second binder (styrene-butadiene latex), the second dispersant ( Carboxymethyl cellulose) was added into the stirring tank according to the mass ratio of 96.4:1:1.3:1.4, then deionized water was added to make a negative electrode slurry, and the mixture was stirred through a known batching process to obtain a solid content of 40% to 45%. % slurry.
  • the second negative electrode active material artificial graphite B
  • the second conductive agent conductive carbon black
  • the second binder styrene-butadiene latex
  • the second dispersant Carboxymethyl cellulose
  • the first step prepare the active material slurry: mix the negative active material (artificial graphite A), conductive agent (conductive carbon black), binder (styrene-butadiene latex), and dispersant (carboxymethyl cellulose) according to 96.4:1
  • the mass ratio of :1.3:1.4 is added to the stirring tank, and then deionized water is added to make the negative electrode slurry.
  • the solid content of the negative electrode slurry is 40% to 45%, and then the slurry is coated on the copper foil by a coating machine.
  • the coating structure was dried at a temperature of 100° C. according to Figure 2, and then rolled, cut into strips, laser-cleaned to remove the tab grooves, and welded with nickel tabs to obtain a negative electrode sheet.
  • the first step prepare the active material slurry: mix the negative active material (artificial graphite B), conductive agent (conductive carbon black), binder (styrene-butadiene latex), and dispersant (carboxymethyl cellulose) according to 96.4:1
  • the mass ratio of :1.3:1.4 was added to the stirring tank, and then deionized water was added to make the negative electrode slurry.
  • the solid content of the negative electrode slurry was 40% to 45%, and then the slurry was coated on the copper foil by a coating machine.
  • the coating structure was dried at a temperature of 100° C. according to Figure 2, and then rolled, cut into strips, laser-cleaned to remove the tab grooves, and welded with nickel tabs to obtain a negative electrode sheet.
  • the surface of one side of the negative electrode sheet can be coated from either end A or D, the first active material slurry is coated on the AB segment and CD segment through the first jump coating, and the coating
  • the BC section is skipped, the second active material slurry passes through the second jump coating, the coating area is the BC section, and the thickness of the coating layers on the surfaces of the three coating sections is the same.
  • the surface of the other side of the negative electrode sheet it can be coated from either end of the E or H end.
  • the first active material slurry is coated on the EF segment and the GH segment through the first jump coating, and the FG segment is skipped during coating.
  • the second active material slurry passes through the second jump coating, the coating area is the FG section, and the thickness of the coating layers on the surfaces of the three coating sections is the same.
  • the pole pieces prepared in each example and the comparative example were assembled into soft-packed cells with a model of 386283, and the capacity of the cells was tested by 0.2C/0.2C charge and discharge at 25°C, according to capacity ⁇ voltage/thickness/width/height , calculate the energy density of the battery, and test the cycle performance of 3C/1C at 25°C.
  • the battery was disassembled under different cycles to confirm the lithium precipitation at the position of the battery tabs. The disassembly results and energy density are listed in Table 1.
  • the battery cell prepared by the method of the present invention can significantly improve the lithium deposition at the electrode lug of the battery cell, significantly improve the deformation and expansion of the battery cell caused by the lithium deposition, and improve the efficiency of the battery cell. cycle life of the core.

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Abstract

本发明提供了一种负极片及其制备方法和包含该负极片的锂离子电池；所述负极片包括负极集流体、第一负极活性物质层、第二负极活性物质层、负极极耳，所述负极极耳设置在负极集流体一侧表面上，靠近所述负极极耳处且设置负极极耳一侧的负极集流体表面涂布第一负极活性物质层，远离所述负极极耳处且设置负极极耳一侧的负极集流体表面涂布第二负极活性物质层；所述第一负极活性物质层包括第一负极活性物质，所述第二负极活性物质层包括第二负极活性物质，本发明的负极片可以有效改善STP结构锂离子电池极耳位置析锂现象，改善锂离子电池的循环寿命；同时还可以有效缓解因为析锂带来的电芯析锂变形问题。

Description

一种负极片及其制备方法和包含该负极片的锂离子电池
本申请要求于2020年07月27日提交中国专利局、申请号为202010733533.6、申请名称为“一种负极片及其制备方法和包含该负极片的锂离子电池”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
本发明属于锂离子电池技术领域，尤其涉及一种负极片及其制备方法和包含该负极片的锂离子电池。
背景技术
锂离子电池因其平台电压高、循环寿命好、能量密度高、无记忆效应等优点，被广泛应用在便携式电子设备上，如手机、笔记本电脑等。随着技术的不断发展，尤其是5G时代已经到来，市场对电池能量密度和充电速度的需求越来越高，常规的卷绕结构已经无法满足客户需求。一些电池厂商开发出了极耳中置的特殊电芯工艺(Special Tab Process，简称为STP)结构。这种结构一方面减少了空箔区面积，提升了能量密度，另一方面降低了电芯的阻抗，提升了电芯充电速度。但是这种结构也有一定的弊端，其中最突出的弊端就是极片靠近极耳位置处容易析锂，尤其是采用大倍率充电时。这会导致电芯在循环中析锂区域不断扩散，加快电解液消耗，最终导致电芯失效变形，带来很大的隐患。上述析锂问题的原因主要是充电过程中，中间极耳位置电流密度比其他位置大。
发明内容
为了改善现有技术的不足，本发明提供一种负极片及其制备方法和包含 该负极片的锂离子电池。本发明的负极片可以解决极耳中置的特殊电芯工艺结构、即STP结构中极耳位置析锂的问题，从而改善电芯的循环寿命。
本发明中，极耳中置是一种不同于常规的极耳设置在负极片头部空箔区域的极耳设置方式。所述的极耳中置的特殊电芯工艺结构是指极耳焊接在负极片表面涂膏涂覆区域的中间位置。极耳焊接时，先将焊接部位的涂膏清洗掉，露出负极集流体，再将负极极耳焊接在负极集流体表面；或在涂布过程中，集流体的极耳焊接区域不涂覆活性物质。
本发明目的是通过如下技术方案实现的：
一种负极片，所述负极片包括负极集流体、第一负极活性物质层、第二负极活性物质层、负极极耳，所述负极极耳设置在负极集流体一侧表面上，靠近所述负极极耳处且设置负极极耳一侧的负极集流体表面涂布第一负极活性物质层，远离所述负极极耳处且设置负极极耳一侧的负极集流体表面涂布第二负极活性物质层；
所述第一负极活性物质层包括第一负极活性物质，所述第二负极活性物质层包括第二负极活性物质，所述第一负极活性物质层接受锂离子脱嵌的速度大于所述第二负极活性物质层接受锂离子脱嵌的速度。
本发明中，所述第一负极活性物质层的动力学性能优于所述第二负极活性物质层的动力学性能。
根据本发明，所述动力学性能是指锂离子的脱嵌速度，脱嵌速度越快，动力学性能越好。影响锂离子的脱嵌速度的因素主要包括：(1)活性物质可支持的充电电流大小，可支持的充电电流越大，动力学性能越好；(2)单位时间内接受的锂离子的量、即接受锂离子的速度，接受锂离子的速度越快，动力学性能越好。
示例性地，所述第一负极活性物质层的锂离子的脱嵌速度大于第二负极活性物质层的锂离子的脱嵌速度。
示例性地，所述第一负极活性物质层的可支持的充电电流大于第二负极 活性物质层的可支持的充电电流。
示例性地，所述第一负极活性物质层的析锂窗口大于第二负极活性物质层的析锂窗口。
所述第一负极活性物质层的析锂窗口可以通过第一负极活性物质(如石墨)的解剖是否析锂来体现，同理，所述第二负极活性物质层的析锂窗口可以通过第二负极活性物质的解剖是否析锂来体现；在本发明实施例中，上述第一负极活性物质的析锂窗口大于或等于1.5C，举例说明，若上述第一负极活性物质的析锂窗口为1.5C，在统一采用现有的正极+第一负极活性物质+涂胶隔膜+电解液的体系对上述第一负极活性物质的析锂窗口进行评判的情况下，使用上述第一负极活性物质的电池在1.5C下充放电20T(周期)，解剖不析锂，即解剖后极片呈现金黄色，无灰色的析锂区域；换句话说，上述第一负极活性物质为支持1.5C快充的负极活性物质。
根据本发明，所述第一负极活性物质层的长度占整个负极集流体表面涂膏的1/6-1/3，即L A/(L A+L B)＝1/6-1/3，其中，L A为所述第一负极活性物质层的长度，L B为所述第二负极活性物质层的长度。
根据本发明，所述第二负极活性物质层的长度占整个负极集流体表面涂膏的2/3-5/6，即L B/(L A+L B)＝2/3-5/6，其中，L A为所述第一负极活性物质层的长度，L B为所述第二负极活性物质层的长度。
根据本发明，在靠近所述负极极耳处的负极集流体两侧表面涂布第一负极活性物质层，远离所述负极极耳处的负极集流体两侧表面涂布第二负极活性物质层。
根据本发明，负极集流体两侧的第一负极活性物质层的长度相同或不同，优选为相同。示例性地，负极集流体两侧的第一负极活性物质层以负极集流体为对称轴对称地设置在负极集流体两侧。
根据本发明，负极集流体两侧的第二负极活性物质层的长度相同或不同，优选为相同。示例性地，负极集流体两侧的第二负极活性物质层以负极集流 体为对称轴对称地设置在负极集流体两侧。
根据本发明，所述负极为极耳中置结构。
根据本发明，所述第二负极活性物质层和所述第一负极活性物质层相连设置，即所述第二负极活性物质层、所述第一负极活性物质层中没有空白区域。
根据本发明，所述负极集流体的长度和宽度没有特别的定义，根据需要的电芯的不同选取不同长度、不同宽度的集流体。示例性地，针对386283型号的电池，所述负极集流体的长度为500-1000mm，例如为885±2mm，所述负极集流体的宽度为400-900mm，例如为773±2mm。
根据本发明，所述第一负极活性物质层的厚度和所述第二负极活性物质层的厚度相同或不同，优选为相同，优选为90-120μm，例如为90μm、95μm、100μm、105μm、110μm、115μm或120μm。
根据本发明，所述负极集流体表面还任选地包括空白区域，所述空白区域设置在第二负极活性物质层一侧，所述空白区域例如是在负极片的生产过程中为了避免剪裁到负极集流体表面的第二负极活性物质层而产生的，所述空白区域的长度例如可以是0.5-2mm，如1mm。
根据本发明，如图1所示，所述负极片包括负极集流体、第一负极活性物质层(BC段和FG段)、第二负极活性物质层(AB段、CD段、EF段和GH段)、负极极耳，所述负极极耳设置在负极集流体一侧表面上，靠近所述负极极耳处的负极集流体两侧表面涂布第一负极活性物质层(BC段和FG段)，远离所述负极极耳处的负极集流体两侧表面涂布第二负极活性物质层(AB段、CD段、EF段和GH段)。
根据本发明，所述第一负极活性物质层中包括第一负极活性物质、第一导电剂、第一分散剂和第一粘结剂，所述第二负极活性物质层中包括第二负极活性物质、第二导电剂、第二分散剂和第二粘结剂。
其中，形成所述第一负极活性物质层和第二负极活性物质层的第一负极 活性物质和第二负极活性物质相同或不同，第一导电剂和第二导电剂相同或不同，第一粘结剂和第二粘结剂相同或不同，第一分散剂和第二分散剂相同或不同。
根据本发明，所述第一负极活性物质层中各组分的质量百分含量为：
70-98.5wt％的第一负极活性物质、0.5-10wt％的第一导电剂、0.5-10wt％的第一粘结剂、0.5-10wt％的第一分散剂。
优选地，所述第一负极活性物质层中各组分的质量百分含量为：
85-97wt％的第一负极活性物质、1-5wt％的第一导电剂、1-5wt％的第一粘结剂、1-5wt％的第一分散剂。
根据本发明，所述第二负极活性物质层中各组分的质量百分含量为：
83-99.5wt％的第二负极活性物质、0-2wt％的第二导电剂、0.5-15wt％的第二粘结剂。
优选地，所述第二负极活性物质层中各组分的质量百分含量为：
90-99wt％的第二负极活性物质、0-2wt％的第二导电剂、1-8wt％的第二粘结剂。
根据本发明，形成所述第一负极活性物质层的第一导电剂的含量大于形成所述第二负极活性物质层的第二导电剂的含量。这样选择可以保证所述第一负极活性物质层的电子导电能力优于第二负极活性物质层的电子导电能力，导电剂的增加不仅可以提高负极活性物质的导电能力，还能有效改善Li +在负极活性物质内部的扩散能力，所以这样选择可以保证所述第一负极活性物质层的动力学性能优于第二负极活性物质层的动力学性能。
其中，所述第一导电剂和第二导电剂相同或不同，彼此独立地选自导电炭黑、乙炔黑、科琴黑、导电石墨、导电碳纤维、碳纳米管、金属粉、碳纤维、石墨烯中的至少一种。
根据本发明，当形成所述第一负极活性物质层的第一导电剂的含量等于形成所述第二负极活性物质层的第二导电剂的含量时，所述第一导电剂和第 二导电剂不同。示例性地，所述第一导电剂选自石墨烯和碳纳米管中的至少一种，所述第二导电剂选自导电炭黑、乙炔黑、科琴黑、导电石墨、导电碳纤维、金属粉、碳纤维中的至少一种；这样选择可以保证所述第一负极活性物质层的电子导电能力优于第二负极活性物质层的电子导电能力，这主要是因为石墨烯和碳纳米管的电子导电能力更优。
其中，所述第一粘结剂和第二粘结剂相同或不同，彼此独立地选自羧甲基纤维素钠、丁苯胶乳、苯乙烯-丙烯酸酯乳液、聚四氟乙烯、聚氧化乙烯中的至少一种。优选地，所述第一粘结剂和第二粘结剂不同。示例性的，所述第一粘结剂选自苯乙烯-丙烯酸酯乳液，所述第二粘结剂选自羧甲基纤维素钠、丁苯胶乳、苯聚四氟乙烯、聚氧化乙烯中的至少一种；这样选择可以保证所述第一负极活性物质层的电子导电能力优于第二负极活性物质层的电子导电能力，这主要是因为苯乙烯-丙烯酸酯乳液的电解液亲和性比其他粘结剂更好。
其中，所述第一负极活性物质和第二负极活性物质相同或不同，彼此独立地选自改性或未改性的下述物质中的至少一种：人造石墨、天然石墨、中间相碳微球、钛酸锂、氧化硅，其中，所述改性包括掺杂、粒径调控或包覆。其中第一负极活性物质的粒径小于第二负极活性物质的粒径，或第一负极活性物质的包覆量大于第二负极活性物质的包覆量。小粒径可以缩短Li +传输的路径，而包覆量增加则可以增加Li +插入的路径，这两种措施都可以改善Li +在负极活性物质层内部的扩散能力，所以这样选择可以保证所述第一负极活性物质层的动力学性能优于第二负极活性物质层的动力学性能。
其中，所述第一分散剂和第二分散剂相同或不同，彼此独立地选自羧甲基纤维素、羧甲基纤维素钠中的至少一种。
本发明还提供上述负极片的制备方法，所述方法包括如下步骤：
1)分别配制形成第一负极活性物质层的浆料、形成第二负极活性物质层的浆料；
2)使用涂布机进行涂布，将形成第一负极活性物质层的浆料涂覆在靠近 所述负极极耳处且设置负极极耳一侧的负极集流体表面，将形成第二负极活性物质层的浆料涂覆在远离所述负极极耳处且设置负极极耳一侧的负极集流体表面，制备得到所述负极片。
根据本发明，步骤1)中，所述形成第一负极活性物质层的浆料、形成第二负极活性物质层的浆料的固含量为40wt％～45wt％。
根据本发明，所述步骤1)包括如下步骤：
第一步：将第一负极活性物质、第一导电剂、第一粘结剂和第一分散剂按照一定的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料；
第二步：将第二负极活性物质、第二导电剂、第二粘结剂和第二分散剂按照一定的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料。
根据本发明，所述步骤2)包括如下步骤：
将形成第一负极活性物质层的浆料涂覆在靠近所述负极极耳处且设置负极极耳一侧的负极集流体表面，形成第一负极活性物质层；
将形成第二负极活性物质层的浆料涂覆在远离所述负极极耳处且设置负极极耳一侧的负极集流体表面，形成第二负极活性物质层。
根据本发明，所述步骤2)包括如下步骤：
将形成第一负极活性物质层的浆料涂覆在靠近所述负极极耳处的负极集流体两侧表面，形成第一负极活性物质层；
将形成第二负极活性物质层的浆料涂覆在远离所述负极极耳处的负极集流体两侧表面，形成第二负极活性物质层。
根据本发明，所述步骤2)包括如下步骤：
在设置负极极耳的负极集流体一侧表面，将形成第一负极活性物质层的浆料涂覆在负极集流体表面BC段，形成第一负极活性物质层；将形成第二负极活性物质层的浆料涂覆在负极集流体表面AB段和CD段，涂布时跳开BC段，形成第二负极活性物质层；
任选地，在与设置负极极耳一侧相对的另一侧表面，将形成第一负极活 性物质层的浆料涂覆在负极集流体表面FG段，形成第一负极活性物质层；将形成第二负极活性物质层的浆料涂覆在负极集流体表面EF段和GH段，涂布时跳开FG段，形成第二负极活性物质层。
根据本发明，所述方法还包括如下步骤：
3)将制备的负极片在100℃温度下烘干，然后通过辊压，分切成条，激光清洗出极耳槽，焊接镍极耳，即得到负极片。
根据本发明，所述步骤3)包括如下步骤：
将制备的负极片在100℃温度下烘干，然后通过辊压，分切成条，在第一负极活性物质层所在的区域上激光清洗出极耳槽，焊接镍极耳，即得到负极片。
本发明还提供一种锂离子电池，所述电池包括上述的负极片。
根据本发明，所述电池还包括正极片和隔膜。
根据本发明，所述锂离子电池在25℃下3C/1C的充放电制度下循环1000圈后的容量保持率为≥82％。
根据本发明，所述锂离子电池在25℃下3C/1C的充放电制度下循环1000圈后电芯的膨胀率为≤12％。
本发明的有益效果：
本发明提供了一种负极片及其制备方法和包含该负极片的锂离子电池；本发明的负极片可以有效改善STP结构锂离子电池极耳位置析锂现象，改善锂离子电池的循环寿命；同时还可以有效缓解因为析锂带来的电芯析锂变形问题。
附图说明
图1：本发明的负极片的结构示意图。
图2：现有负极片的结构示意图。
具体实施方式
下文将结合具体实施例对本发明做更进一步的详细说明。应当理解，下列实施例仅为示例性地说明和解释本发明，而不应被解释为对本发明保护范围的限制。凡基于本发明上述内容所实现的技术均涵盖在本发明旨在保护的范围内。
下述实施例中所使用的实验方法如无特殊说明，均为常规方法；下述实施例中所用的试剂、材料等，如无特殊说明，均可从商业途径得到。
下述实施例中所使用的人造石墨A为经过硬碳包覆的球形石墨，其粒径为D 10＝8.0μm，D 50＝15.2μm，D 90＝29.3μm，其中，所述包覆方法为液相包覆。
下述实施例中所使用的人造石墨B为未经包覆和掺杂的球形石墨，其粒径为D 10＝8.2μm，D 50＝15.8μm，D 90＝28.8μm。
下述实施例中所使用的人造石墨C为未经包覆和掺杂的球形石墨，其粒径为D 10＝6.1μm，D 50＝13.9μm，D 90＝22.7μm。
其中，所述人造石墨A与所述人造石墨B的粒径相当，区别仅在于人造石墨表面还有包覆层结构，因此所述人造石墨A的动力学性能优于所述人造石墨B的动力学性能；所述人造石墨C的粒径小于所述人造石墨B的粒径，因此所述人造石墨C的动力学性能优于所述人造石墨B的动力学性能。
在本发明的描述中，需要说明的是，术语“第一”、“第二”等仅用于描述目的，而并非指示或暗示相对重要性。
实施例1.一种负极片的制备方法及包含其的锂离子电池制备方法如下：
第一步：配制第一活性物质浆料：将第一负极活性物质(人造石墨B)、第一导电剂(导电炭黑)、第一粘结剂(丁苯乳胶)、第一分散剂(羧甲基纤维素)按照96.4:1:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料，通过公知的配料工艺进行搅拌，得到固含量为40％～45％的浆料；
第二步：配制第二活性物质浆料：将第二负极活性物质(人造石墨B)、 第二粘结剂(丁苯乳胶)、第二分散剂(羧甲基纤维素)按照97.4:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料，通过公知的配料工艺进行搅拌，得到固含量为40％～45％的浆料；
第三步：制备负极片：使用跳涂机涂布两次，将两种活性物质浆料涂布在负极集流体铜箔上。如附图1所示，负极片一侧表面：可以从A端或D端任意一端开始涂覆，第二活性物质浆料通过第一次跳涂，涂布在AB段和CD段，涂布时跳开BC段，第一活性物质浆料通过第二次跳涂，涂布区域为BC段，三个涂覆段表面的涂覆层的厚度相同。负极片另一侧表面：可以从E端或H端任意一端开始涂覆，第二活性物质浆料通过第一次跳涂，涂布在EF段和GH段，涂布时跳开FG段，第一活性物质浆料通过第二次跳涂，涂布区域为FG段，三个涂覆段表面的涂覆层的厚度相同。
将制备的负极片在100℃温度下烘干，然后通过辊压，分切成条，激光清洗出极耳槽，焊接镍极耳，即得到负极片。
第四步：制备正极极片：将钴酸锂正极主料、导电剂和聚偏氟乙烯按照97:1.5:1.5的质量比加入到搅拌罐中，然后加入NMP溶剂配成正极浆料，正极浆料固含量70％～75％，再利用涂布机将浆料涂覆到铝箔上，在120℃温度下烘干8h，烘干后先分切成小条，再采用刮刀清洗，洗出正极耳焊接位置，然后通过辊压机压实，焊接铝极耳，即得到正极极片；
第五步：组装电芯：将上述两步得到的正负极片和隔膜一起卷绕形成卷芯，用铝塑膜包装，烘烤去除水分后注入电解液，采用热压化成工艺化成即可得到电芯。
实施例2
其他同实施例1，区别仅在于：
第一步：配制第一活性物质浆料：将第一负极活性物质(人造石墨A)、第一导电剂(导电炭黑)、第一粘结剂(丁苯乳胶)、第一分散剂(羧甲基纤维素)按照96.4:1:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成 负极浆料，通过公知的配料工艺进行搅拌，得到固含量为40％～45％的浆料；
第二步：配制第二活性物质浆料：将第二负极活性物质(人造石墨B)、第二导电剂(导电炭黑)、第二粘结剂(丁苯乳胶)、第二分散剂(羧甲基纤维素)按照96.4:1:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料，通过公知的配料工艺进行搅拌，得到固含量为40％～45％的浆料。
实施例3
其他同实施例1，区别仅在于：
第一步：配制第一活性物质浆料：将第一负极活性物质(人造石墨C)、第一导电剂(导电炭黑)、第一粘结剂(丁苯乳胶)、第一分散剂(羧甲基纤维素)按照96.4:1:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料，通过公知的配料工艺进行搅拌，得到固含量为40％～45％的浆料；
第二步：配制第二活性物质浆料：将第二负极活性物质(人造石墨B)、第二导电剂(导电炭黑)、第二粘结剂(丁苯乳胶)、第二分散剂(羧甲基纤维素)按照96.4:1:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料，通过公知的配料工艺进行搅拌，得到固含量为40％～45％的浆料。
实施例4
其他同实施例1，区别仅在于：
第一步：配制第一活性物质浆料：将第一负极活性物质(人造石墨B)、第一导电剂(导电炭黑)、第一粘结剂(苯乙烯-丙烯酸酯乳液)、第一分散剂(羧甲基纤维素)按照96.4:1:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料，通过公知的配料工艺进行搅拌，得到固含量为40％～45％的浆料；
第二步：配制第二活性物质浆料：将第二负极活性物质(人造石墨B)、第二导电剂(导电炭黑)、第二粘结剂(丁苯乳胶)、第二分散剂(羧甲基纤维素)按照96.4:1:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料，通过公知的配料工艺进行搅拌，得到固含量为40％～45％的浆料。
实施例5
其他同实施例1，区别仅在于：
第一步：配制第一活性物质浆料：将第一负极活性物质(人造石墨B)、第一导电剂(碳纳米管、第一粘结剂(丁苯乳胶)、第一分散剂(羧甲基纤维素)按照96.4:1:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料，通过公知的配料工艺进行搅拌，得到固含量为40％～45％的浆料；
第二步：配制第二活性物质浆料：将第二负极活性物质(人造石墨B)、第二导电剂(导电炭黑)、第二粘结剂(丁苯乳胶)、第二分散剂(羧甲基纤维素)按照96.4:1:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料，通过公知的配料工艺进行搅拌，得到固含量为40％～45％的浆料。
对比例1
其他同实施例1，区别仅在于第一步至第三步用下述第一步进行替换：
第一步：配制活性物质浆料：将负极活性物质(人造石墨A)、导电剂(导电炭黑)、粘结剂(丁苯乳胶)、分散剂(羧甲基纤维素)按照96.4:1:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料，负极浆料固含量40％～45％，再利用涂布机将浆料涂覆到铜箔上，涂布结构按照附图2，在100℃温度下烘干，然后通过辊压，分切成条，激光清洗出极耳槽，焊接镍极耳，即得到负极片。
对比例2
其他同实施例1，区别仅在于第一步至第三步用下述第一步进行替换：
第一步：配制活性物质浆料：将负极活性物质(人造石墨B)、导电剂(导电炭黑)、粘结剂(丁苯乳胶)、分散剂(羧甲基纤维素)按照96.4:1:1.3:1.4的质量比加入到搅拌罐中，然后加入去离子水配成负极浆料，负极浆料固含量40％～45％，再利用涂布机将浆料涂覆到铜箔上，涂布结构按照附图2，在100℃温度下烘干，然后通过辊压，分切成条，激光清洗出极耳槽，焊接镍极耳，即得到负极片。
对比例3
其他同实施例1，区别仅在于：
第三步：制备负极片：使用跳涂机涂布两次，将两种活性物质浆料涂布在负极集流体铜箔上。如附图1所示，负极片一侧表面：可以从A端或D端任意一端开始涂覆，第一活性物质浆料通过第一次跳涂，涂布在AB段和CD段，涂布时跳开BC段，第二活性物质浆料通过第二次跳涂，涂布区域为BC段，三个涂覆段表面的涂覆层的厚度相同。负极片另一侧表面：可以从E端或H端任意一端开始涂覆，第一活性物质浆料通过第一次跳涂，涂布在EF段和GH段，涂布时跳开FG段，第二活性物质浆料通过第二次跳涂，涂布区域为FG段，三个涂覆段表面的涂覆层的厚度相同。
将各实施例及对比例制备的极片组装成型号为386283的软包电芯，在25℃条件下进行0.2C/0.2C充放电测试电芯容量，按照容量×电压/厚度/宽度/高度，计算电池的能量密度，并测试25℃下3C/1C的循环性能，在不同循环次数下拆解电池确认电池极耳位置处析锂情况，拆解结果和能量密度列于表1中。
表1.各实施例和对比例的能量密度及循环过程中极耳处析锂情况、容量保持率和电芯厚度膨胀率对比数据
Figure PCTCN2021108700-appb-000001
从表1中可以看出，采用本发明中的方法制备的电芯可以明显改善电芯极耳处的析锂情况，显著改善了电芯因析锂导致的电芯变形膨胀，并提高了电芯的循环寿命。
以上，对本发明的实施方式进行了说明。但是，本发明不限定于上述实施方式。凡在本发明的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种负极片，其中，所述负极片包括负极集流体、第一负极活性物质层、第二负极活性物质层、负极极耳，所述负极极耳设置在负极集流体一侧表面上，靠近所述负极极耳处且设置负极极耳一侧的负极集流体表面涂布第一负极活性物质层，远离所述负极极耳处且设置负极极耳一侧的负极集流体表面涂布第二负极活性物质层；
    所述第一负极活性物质层包括第一负极活性物质，所述第二负极活性物质层包括第二负极活性物质，所述第一负极活性物质层接受锂离子脱嵌的速度大于所述第二负极活性物质层接受锂离子脱嵌的速度。
  2. 根据权利要求1所述的负极片，其中，L A/(L A+L B)＝1/6-1/3；其中，L A为所述第一负极活性物质层的长度，L B为所述第二负极活性物质层的长度。
  3. 根据权利要求1或2所述的负极片，其中，L B/(L A+L B)＝2/3-5/6；其中，L A为所述第一负极活性物质层的长度，L B为所述第二负极活性物质层的长度。
  4. 根据权利要求1-3任一项所述的负极片，其中，所述第一负极活性物质层的锂离子的脱嵌速度大于第二负极活性物质层的锂离子的脱嵌速度；和/或，
    所述第一负极活性物质层的可支持的充电电流大于第二负极活性物质层的可支持的充电电流；和/或，
    所述第一负极活性物质层的析锂窗口大于第二负极活性物质层的析锂窗口。
  5. 根据权利要求1-4任一项所述的负极片，其中，所述第一负极活性物质层中包括第一负极活性物质、第一导电剂、第一分散剂和第一粘结剂，所述第二负极活性物质层中包括第二负极活性物质、第二导电剂、第二分散剂和第二粘结剂。
  6. 根据权利要求1-5任一项所述的负极片，其中，所述第一负极活性物质层中各组分的质量百分含量为：
    70-98.5wt％的第一负极活性物质、0.5-10wt％的第一导电剂、0.5-10wt％ 的第一粘结剂、0.5-10wt％的第一分散剂；
    所述第二负极活性物质层中各组分的质量百分含量为：
    83-99.5wt％的第二负极活性物质、0-2wt％的第二导电剂、0.5-15wt％的第二粘结剂。
  7. 根据权利要求1-6任一项所述的负极片，其中，在靠近所述负极极耳处的负极集流体两侧表面涂布第一负极活性物质层，远离所述负极极耳处的负极集流体两侧表面涂布第二负极活性物质层。
  8. 根据权利要求1-7任一项所述的负极片，其中，形成所述第一负极活性物质层的第一导电剂的含量大于形成所述第二负极活性物质层的第二导电剂的含量；和/或，
    所述第一导电剂选自石墨烯和碳纳米管中的至少一种，所述第二导电剂选自导电炭黑、乙炔黑、科琴黑、导电石墨、导电碳纤维、金属粉、碳纤维中的至少一种；和/或，
    所述第一粘结剂选自苯乙烯-丙烯酸酯乳液；和/或，
    所述第二粘结剂选自羧甲基纤维素钠、丁苯胶乳、苯聚四氟乙烯、聚氧化乙烯中的至少一种；和/或，
    第一负极活性物质的粒径小于第二负极活性物质的粒径；和/或，
    第一负极活性物质的包覆量大于第二负极活性物质的包覆量。
  9. 根据权利要求1-8任一项所述的负极片，其中，负极为极耳中置结构。
  10. 一种锂离子电池，所述电池包括权利要求1-9任一项所述的负极片。
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