WO2024092684A1 - 正极极片、二次电池及用电装置 - Google Patents

正极极片、二次电池及用电装置 Download PDF

Info

Publication number
WO2024092684A1
WO2024092684A1 PCT/CN2022/129727 CN2022129727W WO2024092684A1 WO 2024092684 A1 WO2024092684 A1 WO 2024092684A1 CN 2022129727 W CN2022129727 W CN 2022129727W WO 2024092684 A1 WO2024092684 A1 WO 2024092684A1
Authority
WO
WIPO (PCT)
Prior art keywords
positive electrode
active material
electrode sheet
particle size
lithium
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/CN2022/129727
Other languages
English (en)
French (fr)
Inventor
靳超
叶永煌
任苗苗
严观福生
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Contemporary Amperex Technology Co Ltd
Original Assignee
Contemporary Amperex Technology Co Ltd
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
Publication date
Application filed by Contemporary Amperex Technology Co Ltd filed Critical Contemporary Amperex Technology Co Ltd
Priority to CN202280098184.2A priority Critical patent/CN119547214A/zh
Priority to EP22963994.3A priority patent/EP4507019A4/en
Priority to PCT/CN2022/129727 priority patent/WO2024092684A1/zh
Publication of WO2024092684A1 publication Critical patent/WO2024092684A1/zh
Priority to US18/945,251 priority patent/US20250070186A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H01M4/662—Alloys
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/663—Selection of materials containing carbon or carbonaceous materials as conductive part, e.g. graphite, carbon fibres
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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 present application belongs to the technical field of secondary batteries, and specifically relates to a positive electrode sheet, a secondary battery and an electrical device.
  • Secondary batteries are widely used in various consumer electronic products and new energy vehicles due to their outstanding features such as light weight, no pollution, and no memory effect. With the continuous development of the new energy industry, customers have put forward higher requirements for the use of secondary batteries. For example, the energy density design of secondary batteries is getting higher and higher.
  • increasing the compaction density of the positive electrode is one of the ways to increase the energy density of secondary batteries.
  • the energy density is often increased, which often leads to the destruction of the oxide film on the surface of the aluminum foil under high pressure, exposing fresh aluminum, and the electrolyte corroding the aluminum foil, thus causing battery safety problems.
  • the present application provides a positive electrode plate, a secondary battery and an electrical device, aiming to improve the energy density of the secondary battery while improving the safety of the secondary battery.
  • a positive electrode sheet comprising:
  • a primer layer located on at least one side of the positive electrode current collector, the primer layer comprising a conductive agent and a binder;
  • a positive electrode active material layer located on a side of the undercoat layer away from the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material;
  • the thickness of the primer layer is recorded as L, and the thickness of the primer layer satisfies:
  • Dv50 is the particle size corresponding to when the cumulative particle size distribution number of particles in the volume distribution of the positive electrode active material reaches 50%, and the unit is ⁇ m; PD represents the compaction density of the positive electrode sheet, and the unit is g/cm 3 .
  • the present application at least has the following beneficial effects:
  • the positive electrode sheet of the present application is provided with a primer layer.
  • the primer layer can improve or even prevent the oxide film on the surface of the aluminum foil from being crushed by the positive electrode active material, thereby improving the safety of the secondary battery.
  • the oxide film on the surface of the aluminum foil can be protected without affecting the energy density of the secondary battery. In this way, the above-mentioned positive electrode sheet is applied to the secondary battery, which can improve the safety of the secondary battery while improving the energy density of the secondary battery.
  • the nickel content in the positive electrode active material is ⁇ 80%.
  • the volume average particle size Dv50 of the positive electrode active material is denoted as D4, and the volume average particle size Dv50 of the positive electrode active material satisfies: 5 ⁇ m ⁇ D4 ⁇ 15 ⁇ m; optionally, 5 ⁇ m ⁇ D4 ⁇ 9 ⁇ m.
  • the mass ratio of the binder to the conductive agent is (2-10):10.
  • the binder includes an acrylic resin
  • the acrylic resin includes one or more of cross-linked polyacrylic acid, lithium polyacrylate, sodium polyacrylate and polyacrylic acid-polyacrylonitrile copolymer.
  • the conductive agent includes one or more of acetylene black, carbon black, graphite, Ketjen black and graphene.
  • the base coating layer further includes active material particles.
  • the volume average particle size Dv10 of the active material particles is recorded as D1
  • the volume average particle size Dv50 of the active material particles is recorded as D2
  • the volume average particle size Dv90 of the active material particles is recorded as D3, then the active material particles satisfy: D2 ⁇ 2 ⁇ m, (D3-D1)/D2 ⁇ 2.8.
  • the thickness of the primer layer satisfies:
  • D2 is the volume average particle size Dv50 of the active material particles.
  • the active material particles include one or more of NCM ternary materials, lithium iron phosphate and lithium supplement agent;
  • the chemical formula of the NCM ternary material is LiNi x Co y Mn 1-xy O 2 , wherein 0.3 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 0.5;
  • the lithium supplement includes one or more of lithium-containing oxides, lithium-containing nitrides, lithium-containing sulfides and lithium-containing metal salts.
  • the mass ratio of the binder, the conductive agent and the active material particles is (2-10):10:(1-10).
  • the thickness of the primer layer satisfies: 0 ⁇ L ⁇ 5 ⁇ m; optionally, 1 ⁇ L ⁇ 2 ⁇ m.
  • the positive electrode active material includes lithium nickel cobalt manganese oxide.
  • the current collector is selected from aluminum foil.
  • a second aspect of the present application provides a secondary battery, comprising the positive electrode sheet as described in the first aspect of the present application.
  • the secondary battery further includes an electrolyte, and the electrolyte contains lithium bis(fluorosulfonyl)imide.
  • a third aspect of the present application provides an electrical device, comprising the secondary battery of the second aspect of the present application.
  • FIG. 1 is a schematic diagram of one embodiment of a secondary battery.
  • FIG. 2 is an exploded view of FIG. 1 .
  • FIG. 3 is a schematic diagram of an embodiment of a battery pack.
  • FIG. 4 is a schematic diagram of an embodiment of an electric device using a secondary battery as a power source.
  • any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range.
  • each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range.
  • the range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive. That is, the phrase “A or (or) B” means “A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • the terms used in this application have the well-known meanings commonly understood by those skilled in the art.
  • the numerical values of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).
  • high-nickel ternary materials have high energy density
  • using high-nickel ternary materials as positive electrode materials is also one of the means to improve the energy density of secondary batteries in related technologies. Due to the poor high-temperature structural stability of high-nickel ternary materials, oxygen release is likely to occur at high temperatures, resulting in rapid decay of the storage life of secondary batteries and reduced safety.
  • high-nickel ternary materials are used as positive electrode materials, the storage life of secondary batteries can often be effectively improved by adding lithium bis(fluorosulfonyl)imide (LiFSI) to the electrolyte, thereby improving safety.
  • LiFSI lithium bis(fluorosulfonyl)imide
  • the electrolyte containing LiFSI is easy to corrode aluminum foil under high pressure, and it is easy to cause aluminum foil to break brittlely in the later stage of the cycle, causing secondary battery safety accidents.
  • the secondary battery has poor shallow puncture tolerance, and the electrolyte has poor high-voltage stability, and the risk of overcharge failure is high.
  • the technical personnel of this application analyzed and found that it was mainly the positive electrode material particles that crushed the aluminum foil under high pressure density, the surface oxide film of the aluminum foil was destroyed, and the fresh aluminum foil was exposed. The fresh aluminum foil reacted with the electrolyte, thereby causing aluminum foil corrosion, causing secondary battery safety accidents.
  • the positive electrode sheet provided in the present application comprises: a positive electrode current collector, a primer layer located on at least one side of the positive electrode current collector, and a positive electrode active material layer located on a side of the primer layer away from the positive electrode current collector;
  • the primer layer comprises a binder and a conductive agent;
  • the positive electrode active material layer comprises a positive electrode active material, the thickness of the primer layer is denoted as L, and the thickness of the primer layer satisfies:
  • Dv50 is the particle size corresponding to when the cumulative particle size distribution number of particles in the volume distribution of the positive electrode active material reaches 50%, and the unit is ⁇ m;
  • PD represents the compaction density of the positive electrode sheet, and the unit is g/cm 3 .
  • the undercoat layer is located on at least one side of the positive electrode current collector, and the undercoat layer may be in contact with the positive electrode current collector or may not be in contact with the positive electrode current collector.
  • the positive electrode active material layer may include one positive electrode active material or two or more positive electrode active materials. If the positive electrode active material layer includes two or more positive electrode active materials, Dv50 is the particle size corresponding to 50% of the volume distribution of all positive electrode active materials.
  • the thickness of the primer layer satisfies:
  • the positive electrode sheet of the present application is provided with a primer layer.
  • the primer layer can improve or even prevent the oxide film on the surface of the aluminum foil from being crushed by the positive electrode active material, thereby improving the safety of the secondary battery.
  • the oxide film on the surface of the aluminum foil can be protected without affecting the energy density of the secondary battery. In this way, the above-mentioned positive electrode sheet is applied to the secondary battery, which can improve the safety of the secondary battery while increasing the energy density of the secondary battery.
  • volume average particle size Dv50 is that particles with a particle size smaller than (or larger than) it account for 50%.
  • the volume average particle size Dv50 of the positive electrode active material mentioned above can be conveniently measured by referring to GB/T 19077-2016 Particle Size Distribution Laser Diffraction Method using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK.
  • the thickness of the above-mentioned undercoat layer can be measured by the following method: perform cross-sectional CP characterization on the positive electrode sheet, measure the total thickness of the positive electrode sheet, the thickness of the positive electrode active material layer and the thickness of the positive electrode current collector, and then obtain the thickness of the undercoat layer based on the formula: total thickness of the positive electrode sheet - thickness of the positive electrode active material layer - thickness of the positive electrode current collector.
  • the inventors have found through in-depth research that when the positive electrode plate of the present application satisfies the above-mentioned design conditions and optionally satisfies one or more of the following conditions, the energy density, kinetic performance and shallow puncture safety of the secondary battery can be further improved.
  • the nickel content in the positive electrode active material is ⁇ 80%.
  • the positive electrode plate adopts a high-nickel ternary material as the positive electrode active material.
  • LiFSI is adaptively added to the electrolyte; if the positive electrode active material is in direct contact with the aluminum foil, when the compaction density of the positive electrode active material layer is large, the positive electrode active material is easy to damage the oxide film on the surface of the aluminum foil and expose the fresh aluminum foil.
  • the LiFSI in the electrolyte contacts the aluminum foil, it reacts and corrodes the aluminum foil.
  • the primer layer located between the positive electrode active material layer and the positive electrode current collector can slow down or even avoid the damage of the positive electrode active material particles to the oxide film on the surface of the aluminum foil when the compaction density is large, thereby avoiding the corrosion of the aluminum foil caused by the contact between the fresh aluminum foil and the electrolyte, and improving the safety of the secondary battery.
  • the nickel content in the above-mentioned positive electrode active material can be measured by an ICAP6300 spectrometer.
  • the volume average particle size Dv50 of the positive electrode active material is recorded as D4, and the volume average particle size Dv50 of the positive electrode active material satisfies: 5 ⁇ m ⁇ D4 ⁇ 15 ⁇ m; for example, it can be 6 ⁇ m ⁇ D4 ⁇ 15 ⁇ m, 7 ⁇ m ⁇ D4 ⁇ 14 ⁇ m, 8 ⁇ m ⁇ D4 ⁇ 13 ⁇ m, 9 ⁇ m ⁇ D4 ⁇ 12 ⁇ m, 10 ⁇ m ⁇ D4 ⁇ 11 ⁇ m or 5 ⁇ m ⁇ D4 ⁇ 13 ⁇ m, etc.
  • the volume average particle size Dv50 of the positive electrode active material is within the above range, if the compaction density of the positive electrode sheet is high and the positive electrode active material layer is in direct contact with the positive electrode current collector, the positive electrode active material particles are more likely to damage the oxide film on the surface of the aluminum foil.
  • the volume average particle size Dv50 of the positive electrode active material satisfies: 5 ⁇ m ⁇ D4 ⁇ 9 ⁇ m.
  • the mass ratio of the binder to the conductive agent is (2-10):10; for example, the mass ratio of the binder to the conductive agent can be (2-9):10, (3-8):10, (4-7):10, (5-6):10, (4.5-5.5):10 or (5.5-6.5):10, etc.
  • the mass ratio of the binder to the conductive agent is within the given range, the shear strength requirements between the primer layer and the positive electrode current collector and the positive electrode active material layer can be met, and the filtration of the primer slurry during preparation is facilitated, and the solid content in the primer slurry is reduced.
  • the binder includes an acrylic resin; optionally, the acrylic resin includes one or more of cross-linked polyacrylic acid, lithium polyacrylate, sodium polyacrylate, and polyacrylic acid-polyacrylonitrile copolymer.
  • the conductive agent includes one or more of acetylene black, carbon black, graphite, Ketjen black and graphene.
  • the bottom coating layer further includes active material particles. Adding active material particles to the bottom coating layer can enable the bottom coating layer to also play a capacity replenishment role, thereby increasing the overall capacity of the secondary battery and reducing or compensating for the loss of energy density caused by the provision of the bottom coating layer.
  • the volume average particle size Dv10 of the active material particles is recorded as D1
  • the volume average particle size Dv50 of the active material particles is recorded as D2
  • the volume average particle size Dv90 of the active material particles is recorded as D3, then the active material particles satisfy: D2 ⁇ 2 ⁇ m, (D3-D1)/D2 ⁇ 2.8.
  • the volume average particle size Dv50 of the active material particles exceeds the above range, the active material particles are also easy to crush the positive electrode current collector, and the thickness of the primer layer needs to be increased, which may lead to the deterioration of the shear strength of the primer layer, the energy density of the secondary battery is reduced, the DCR is increased, and the cost is increased.
  • the active material particles are easy to agglomerate, which may cause the primer slurry to produce filter residue, which in turn causes the shear strength of the primer layer to deteriorate, and the corrosion of the electrolyte to the positive electrode current collector will be further aggravated, while increasing the DCR of the secondary battery.
  • the compressive resistance of the base coating can be improved, and it is also easier to obtain a dense and thin coating, which is beneficial to improving the base coating's ability to resist mechanical damage such as shallow punctures.
  • volume average particle size Dv10 refers to the particle size corresponding to when the cumulative particle size distribution number of the active material particles reaches 10% in the volume cumulative distribution curve of the active material particles.
  • volume average particle size Dv50 refers to the particle size corresponding to when the cumulative particle size distribution number of the active material particles reaches 50% in the volume cumulative distribution curve of the active material particles.
  • volume average particle size Dv90 refers to the particle size corresponding to when the cumulative particle size distribution number of the active material particles reaches 90% in the volume cumulative distribution curve of the active material particles.
  • Dv10, Dv50 and Dv90 can be conveniently measured by using a laser particle size analyzer with reference to the particle size distribution laser diffraction method of GB/T 19077-2016, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK.
  • the thickness of the base coating layer satisfies:
  • D2 is the volume average particle size Dv50 of the active material particles.
  • the active material particles include one or more of NCM ternary materials, lithium iron phosphate and lithium supplement;
  • the chemical formula of the NCM ternary material is LiNi x Co y Mn 1-xy O 2 , wherein 0.3 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 0.5;
  • the lithium supplement includes three categories: one or more of binary lithium-containing compounds (such as Li2O, Li2O2, LiF, Li2S, Li3N, etc.), ternary lithium-containing compounds (Li4FeO5, Li6CoO4, Li2NiO2, etc.), and organic lithium salts (Li2DHBN, Li2C2O4, etc.).
  • binary lithium-containing compounds such as Li2O, Li2O2, LiF, Li2S, Li3N, etc.
  • ternary lithium-containing compounds Li4FeO5, Li6CoO4, Li2NiO2, etc.
  • organic lithium salts Li2DHBN, Li2C2O4, etc.
  • the active material particles may also include olivine-structured lithium-containing phosphates, including but not limited to at least one of a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • olivine-structured lithium-containing phosphates including but not limited to at least one of a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • the mass ratio of the binder, the conductive agent and the active material particles is (2-10):10:(1-10); for example, the mass ratio of the binder, the conductive agent and the active material particles can be (2-9):10:(2-10), (3-8):10:(4-7), (5-6):10:(4-8), (4.5-5.5):10:(5-7), (5.5-6.5):10:(5-6) or (5-10):10:(1-3), etc.
  • the mass ratio of the binder, the conductive agent and the active material particles is within the given range, a stable slurry can be formed, the membrane is well bonded, and the addition of an appropriate amount of active material helps the battery to have both high volume energy density (VED) and safety.
  • VED volume energy density
  • the thickness of the primer layer satisfies: 0 ⁇ L ⁇ 5 ⁇ m; for example, it can be 0.01 ⁇ L ⁇ 5 ⁇ m, 0.1 ⁇ L ⁇ 5 ⁇ m, 0.5 ⁇ L ⁇ 3.5 ⁇ m, 1 ⁇ L ⁇ 3 ⁇ m, 1.5 ⁇ L ⁇ 2.5 ⁇ m, 2 ⁇ L ⁇ 2.5 ⁇ m, 0.5 ⁇ L ⁇ 1 ⁇ m, 1.5 ⁇ L ⁇ 2 ⁇ m or 1 ⁇ L ⁇ 1.5 ⁇ m, etc.
  • the thickness of the primer layer satisfies: 1 ⁇ L ⁇ 2 ⁇ m.
  • the positive electrode active material includes lithium nickel cobalt manganese oxide.
  • the positive electrode active material may also include other positive electrode active materials for batteries known in the art.
  • the positive electrode active material may include at least one of the following materials: lithium-containing phosphates of olivine structure, lithium transition metal oxides and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, at least one of lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and their modified compounds.
  • lithium cobalt oxide such as LiCoO 2
  • lithium nickel oxide such as LiNiO 2
  • lithium manganese oxide such as LiMnO 2 , LiMn 2 O 4
  • lithium nickel cobalt oxide lithium manganese cobalt oxide
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • the weight ratio of the positive electrode active material in the positive electrode film layer is 80-100 weight %, based on the total weight of the positive electrode film layer.
  • the present application also provides a method for preparing a primer slurry, comprising the following steps:
  • the base coating slurry has a solid content of 5-20 wt % and a viscosity of 500-2000 mPa ⁇ s at room temperature.
  • the mass ratio of the binder, the conductive agent and the active material particles in the primer slurry is (2-20):10:(1-10).
  • the binder when preparing slurry A, is in the form of a binder aqueous solution with a solid content of 25%, and is prepared together with the conductive agent to prepare slurry A.
  • the sum of the mass percentages of the binder, the conductive agent, the active material particles and the deionized water in the finally prepared primer slurry is 100%.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material layer may also optionally include a binder, a conductive agent, and other optional auxiliary agents.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the positive electrode active material layer is 0-20 weight %, based on the total weight of the positive electrode active material layer.
  • the positive electrode sheet can be prepared in the following way:
  • the components for preparing the positive electrode sheet such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, wherein the positive electrode slurry has a solid content of 40-80wt% and a viscosity at room temperature adjusted to 5000-25000mPa ⁇ s;
  • a solvent such as N-methylpyrrolidone
  • the positive electrode slurry is coated on the surface of the base coating, dried and then cold-pressed by a cold rolling mill to form a positive electrode sheet; the positive electrode powder coating unit surface density is 150-350 mg/m 2 , and the positive electrode sheet compaction density is 3.0-3.6 g/cm 3 , and can be optionally 3.3-3.5 g/cm 3 .
  • a secondary battery is a battery that can be recharged to activate the active materials after being discharged and continue to be used.
  • a secondary battery includes the positive electrode sheet, the negative electrode sheet, the separator and the electrolyte provided above in the present application.
  • active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet.
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet to play an isolating role.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may adopt the negative electrode active material for batteries known in the art.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxides, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used.
  • These negative electrode active materials may be used alone or in combination of two or more.
  • the weight ratio of the negative electrode active material in the negative electrode film layer is 70-100% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer may further include a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the weight ratio of the conductive agent in the negative electrode film layer is 0-20 weight %, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer may further include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)), etc.
  • a thickener such as sodium carboxymethyl cellulose (CMC-Na)
  • the weight ratio of the other additives in the negative electrode film layer is 0-15% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity at room temperature is adjusted to 2000-10000mPa ⁇ s; the obtained negative electrode slurry is coated on the negative electrode collector, and after a drying process, cold pressing such as rolling, a negative electrode sheet is obtained.
  • the negative electrode powder coating unit area density is 75-220mg/ m2
  • the negative electrode sheet compaction density is 1.2-2.0g/ m3 .
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte contains lithium bis(fluorosulfonyl)imide (LiFSI).
  • the electrolyte salt may also be selected from one or more of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobisoxalatophosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).
  • the concentration of the electrolyte salt is generally 0.5-5 mol/L.
  • the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (FEC),
  • the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the isolation film has a thickness of 6-40 ⁇ m, and optionally 12-20 ⁇ m.
  • the secondary battery of the present application is a lithium ion secondary battery.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package that can be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • the secondary battery can be prepared according to conventional methods in the art, for example, the positive electrode sheet, the separator, and the negative electrode sheet are wound (or stacked) in sequence, so that the separator is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, to obtain a battery cell, the battery cell is placed in an outer package, the electrolyte is injected and sealed, and the secondary battery is obtained.
  • FIG1 is a secondary battery 4 of a square structure as an example.
  • the outer package may include a shell 41 and a cover plate 43.
  • the shell 41 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 41 has an opening connected to the receiving cavity, and the cover plate 43 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the separator can be wound or laminated to form an electrode assembly 42.
  • the electrode assembly 52 is encapsulated in the housing cavity.
  • the electrolyte is infiltrated in the electrode assembly 42.
  • the number of electrode assemblies 42 contained in the secondary battery 4 can be one or more, which can be adjusted according to needs.
  • secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • multiple secondary batteries can be arranged in sequence along the length direction of the battery module. Of course, they can also be arranged in any other way. Further, the multiple secondary batteries can be fixed by fasteners.
  • the battery module can also include a housing with a storage space, and multiple secondary batteries are accommodated in the storage space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the secondary batteries described above may also be assembled into a battery pack, and the number of secondary batteries contained in the battery pack may be adjusted according to the application and capacity of the battery pack.
  • FIG3 is a battery pack 1 as an example.
  • the battery pack 1 may include a battery box and a plurality of secondary batteries or battery modules disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3.
  • the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating secondary batteries or battery modules.
  • the plurality of secondary batteries or battery modules can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module or battery pack provided in the present application.
  • the secondary battery, battery module or battery pack can be used as a power source for the device, or as an energy storage unit for the device.
  • the device can be, but is not limited to, a mobile device (such as a mobile phone, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc.
  • the device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • Fig. 4 is an example of an electric device 5.
  • the electric device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack may be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • a device is usually required to be light and thin, and a secondary battery may be used as a power source.
  • slurry A 10g of conductive agent acetylene black (as a conductive agent) and 40g of cross-linked polyacrylic acid solution (as a binder, with a solid content of 25%) to prepare slurry A; dissolve 10g of lithium iron phosphate (LFP, as active material particles) in deionized water and fully dissolve to prepare slurry B; add slurry A to slurry B, stir and mix thoroughly to obtain a primer slurry. Filter the primer slurry, and the residue content in the primer slurry and the filtration time of the primer slurry are shown in Table 1. The filtered primer slurry is evenly coated on the positive electrode current collector and dried to obtain a substrate with a primer layer.
  • LFP lithium iron phosphate
  • the positive electrode active material LiNi 0.50 Co 0.06 Mn 0.44 O 2 , the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) were dissolved in a solvent N-methylpyrrolidone (NMP) at a weight ratio of 96.5:1.5:2, and the mixture was fully stirred and mixed to obtain a positive electrode slurry; the positive electrode slurry was then evenly coated on a positive electrode current collector with a primer, and then dried, cold pressed and cut to obtain a positive electrode sheet.
  • NMP N-methylpyrrolidone
  • the preparation method of the positive electrode plate in Example 2-11 is basically similar to the preparation method of the positive electrode plate in Example 1, and the main difference is that when preparing the substrate with the primer layer, at least one of the type and/or amount of the conductive agent, the type and/or amount of the binder, the type and/or amount of the active material particles, and the thickness of the primer layer is different. See Table 1 for details.
  • the preparation method of the positive electrode sheet in Example 12 is substantially similar to the preparation method of the positive electrode sheet in Example 2, with the main difference being that when preparing the positive electrode active material layer, the positive electrode active material used is LiNi 0.80 Co 0.12 Mn 0.08 O 2 , and the rest are the same.
  • the preparation method of the positive electrode sheet in Example 13 is substantially similar to the preparation method of the positive electrode sheet in Example 2, with the main difference being that when preparing the positive electrode active material layer, the positive electrode active material used is LiNi 0.90 Co 0.08 Mn 0.02 O 2 , and the rest are the same.
  • the positive electrode sheet in Comparative Example 1-9 is not provided with a primer layer, and its preparation method is as follows:
  • the positive electrode active material NCM, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are dissolved in the solvent N-methylpyrrolidone (NMP) in a weight ratio of 96.5:1.5:2, and the positive electrode slurry is obtained after being fully stirred and mixed; the positive electrode slurry is then evenly coated on the positive electrode collector, and then dried, cold pressed, and cut to obtain the positive electrode sheet.
  • NMP N-methylpyrrolidone
  • the positive electrode sheet was subjected to cross-sectional CP characterization, and the total thickness of the positive electrode sheet, the thickness of the positive electrode active material layer and the thickness of the positive electrode current collector were measured. Then, based on the formula: total thickness of the positive electrode sheet - thickness of the positive electrode active material layer - thickness of the positive electrode current collector, the thickness of the basecoat layer was obtained.
  • D1, D2, D3, D4 in the above embodiments and D4 in the comparative examples can be conveniently measured by referring to the particle size distribution laser diffraction method according to GB/T 19077-2016, using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer produced by Malvern Instruments Ltd., UK.
  • a laser particle size analyzer such as the Mastersizer 2000E laser particle size analyzer produced by Malvern Instruments Ltd., UK.
  • the filtration time of the primer slurry, the content of the filter residue, the compaction density of the positive electrode sheet, the shear strength of the primer layer, and the volume average particle size Dv50 of the positive electrode active material in the preparation process of the positive electrode sheets of the above-mentioned embodiments and comparative examples are shown in Table 1 respectively.
  • D1 represents the volume average particle size Dv10 of the active material particles
  • D2 represents the volume average particle size Dv50 of the active material particles
  • D3 represents the volume average particle size Dv90 of the active material particles
  • SPAN (D3-D1)/D2
  • D4 represents the volume average particle size Dv50 of the positive electrode active material
  • PD represents the compaction density of the positive electrode sheet
  • L represents the thickness of the base coating.
  • the filter residue content in the primer slurry, and the shear strength of the primer layer From the filtration time of the primer slurry of each embodiment in Table 1, the filter residue content in the primer slurry, and the shear strength of the primer layer, it can be seen that when the mass proportion of the binder in the primer slurry is 2-10%, the mass proportion of the conductive agent is 10%, the mass proportion of the active material particles is 1-10%, the volume average particle size of the active material particles is Dv50 ⁇ 2 ⁇ m and SPAN ⁇ 2.8, the filtration time of the primer slurry is appropriate ( ⁇ 60s) and the primer slurry does not contain filter residue, and the shear strength of the primer layer can meet the bonding requirements ( ⁇ 0.7Mpa).
  • Example 2 and 8-10 in Table 1 The difference between Examples 2 and 8-10 in Table 1 is that the amount of binder in the primer slurry is different; the amount of binder in Example 8 is the largest, and the amount of binder in Example 10 is the smallest.
  • the filtering time of the primer slurry in Examples 8 and 10 is too long, and the primer slurry contains filter residue. The technicians analyzed the reason.
  • the mass proportion of the binder in the primer slurry is higher than 10%, the viscosity of the primer slurry is too large, which may lead to prolonged filtering time of the primer slurry and the material in the primer slurry is easy to agglomerate to form filter residue;
  • the mass proportion of the binder in the primer slurry is lower than 2%, due to the low viscosity of the primer slurry, the conductive agent and active material particles in the primer slurry will agglomerate between themselves, which also leads to prolonged filtering time of the primer slurry and containing filter residue.
  • the mass proportion of the binder in the primer slurry is lower than 2%, the shear strength of the primer layer is significantly reduced and cannot meet the bonding requirements.
  • the negative electrode active material graphite, silicon, conductive agent acetylene black, high molecular polymer, and thickener sodium carboxymethyl cellulose (CMC) were dissolved in deionized water at a weight ratio of 90:5:2:2:1, and then uniformly mixed with deionized water to prepare a negative electrode slurry.
  • the negative electrode slurry was coated on a copper foil, dried, and then cold-pressed and cut to obtain an anode electrode sheet.
  • Diaphragm Polyethylene film (PE) is used as the isolation membrane, and the surface is coated with PVDF and alumina coating.
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then LiPF6:LiFSI (2:8) was uniformly dissolved in the above solution to obtain an electrolyte.
  • LiPF6:LiFSI (2:8) was uniformly dissolved in the above solution to obtain an electrolyte.
  • the concentration of lithium salt is 1 mol/L.
  • the positive electrode sheets, separators, and negative electrode sheets in the above embodiments and comparative examples are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare cell, and the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum shell, and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery.
  • the uncharged battery is then subjected to the processes of static, hot and cold pressing, formation, shaping, and capacity testing in sequence to obtain a secondary battery.
  • Each secondary battery was placed at 25°C for 30 minutes, charged to 4.25V at a rate of 1/3C, and then the constant voltage was reached at 0.05C. After being placed at rest for 30 minutes, the battery was discharged to 2.8V at a rate of 1/3C, and the released energy was E0.
  • the prepared secondary batteries were discharged at 25°C at a rate of 1/3C to 2.8V, left standing for 60 minutes, and charged at a rate of 1/3C to 4.25V, and the constant voltage was terminated to 0.05C; left standing for 60 minutes, part of the shell was removed, and the voltage, internal resistance and weight of the battery cell were recorded.
  • the nail penetration test was carried out at 25°C.
  • the nail diameter was 1mm and the speed was 0.1mm/s.
  • the nail was inserted at a uniform speed perpendicular to the direction of the battery plate, and the insertion position was close to the geometric center of the punctured surface.
  • the penetration depth was 4mm and the voltage drop was monitored.
  • the test environment was observed for 1h. If there was no failure, the penetration depth was changed to 5mm and the above steps were repeated until failure.
  • the voltage, internal resistance and weight of the battery cell at the time of failure were recorded.
  • Each secondary battery was placed at 25°C for 30 minutes, charged to 4.25V at a rate of 1/3C, and ended at a constant voltage of 0.05C. After being placed at rest for 10 minutes, the battery was discharged at a rate of 1/3C0 until the battery cell's capacity was 50% of the full charge, which was called 50% SOC; after being placed at rest for 60 minutes, the battery was discharged at a rate of 4C0 for 10 seconds, and the DCR value of the battery cell was recorded.
  • the positive electrode plate adopts NCM ternary material with a nickel content of ⁇ 80%.
  • the positive electrode material particles crush the aluminum foil under the high compaction density, and LiFSI corrodes the aluminum foil.
  • Example 1 4.2 80% Low 90% 120%
  • Example 2 4.2 80% Low 92% 110%
  • Example 3 4.2 80% Low 88% 130%
  • Example 4 4.2 80% Low 92% 115%
  • Example 5 4.2 80% Low 92% 110%
  • Example 6 4.2 80% Low 92% 110%
  • Example 7 4.2 80% Low 95% 110%
  • Example 8 4.2 80% Low 92% 140%
  • Example 9 4.2 80% Low 92% 110%
  • Example 10 4.2 80% middle 92% 110%
  • Embodiment 11 4.2 80% Low 85% 110%
  • Example 12 4.2 80% Low 95% 107%
  • Comparative Example 2 4.2 50% high / / Comparative Example 3 4.2 50% middle / / Comparative Example 4 4.2 50% high / / Comparative Example 5 4.1 50% Low / / Comparative Example 6 4.3 50% high / / Comparative Example 7 4.2 30% Low / / Comparative Example 8 4.2 80% high / / Comparative Example 9 4.2 50% High 100% 100% 100%
  • ED in Table 2 represents energy density. Based on the measured secondary battery energy density and discharge DCR when the volume average particle size Dv50 of the positive electrode active material is 9 ⁇ m, the compaction density of the positive electrode sheet is 3.6 g/cm 3 , the mass proportion of LiFSI in the electrolyte is 50%, the upper limit voltage of the secondary battery is 4.2 V, and the primer layer is not applied, the change percentages of the secondary battery energy density and discharge DCR after applying the primer layer are measured.
  • Example 1-3 The difference between Examples 1-3 is that the volume average particle size Dv50 of the active material particles is different; from the results of Examples 1-3, it can be seen that when the volume average particle size Dv50 of the active material particles is greater than 2 ⁇ m, as the volume average particle size Dv50 of the active material particles increases, the thickness of the base coating will increase, which may lead to a decrease in the energy density of the secondary battery and an increase in DCR.
  • Example 2 and Examples 4-5 The difference between Example 2 and Examples 4-5 is that the SPAN of the active material particles is different; from the results of Examples 1 and Examples 4-5, it can be seen that when the SPAN of the active material particles is less than 2.8, during the preparation of the positive electrode sheet, the filtration time of the primer slurry is significantly increased and filter residue is present, the risk of corrosion of the electrolyte to the current collector is increased, and the DCR of the secondary battery is increased; the technicians analyzed the reason and found that it may be because when the SPAN of the active material particles is less than 2.8, the active material particles are easy to agglomerate, which may cause the primer slurry to produce filter residue and prolong the filtration time, further aggravate the corrosion of the electrolyte to the current collector, and increase the DCR of the secondary battery.
  • Example 2 and Examples 6-7 The difference between Example 2 and Examples 6-7 is that the mass proportion of active material particles is different; from the results of Examples 2 and 6-7, it can be seen that when the mass proportion of active material particles in the primer slurry is higher than 10%, the shear strength of the primer layer decreases and the risk of corrosion of the electrolyte to the positive electrode current collector increases.
  • the technicians analyzed the reason and found that it may be due to the increase in the mass proportion of active material particles in the primer slurry, which leads to the decrease in the shear strength of the primer layer, further increasing the risk of corrosion of the electrolyte to the positive electrode current collector.
  • Example 2 and Examples 8-10 The difference between Example 2 and Examples 8-10 is that the mass proportion of the binder in the primer slurry is different; from the results of Example 2 and Examples 8-10, it can be seen that when the mass proportion of the binder in the primer slurry is lower than 2%, the filtration time of the primer slurry is significantly prolonged and filter residue is produced, the shear strength of the primer layer cannot meet the use requirements, and the corrosion risk of the electrolyte to the positive electrode collector is increased; when the mass proportion of the binder in the primer slurry is higher than 10%, the filtration time of the primer slurry is also significantly prolonged and filter residue is produced, and the DCR of the secondary battery is significantly increased.
  • Example 11 The difference between Example 11 and Example 2 is that no active material particles are added to the primer slurry; from the results of Example 2 and Example 11, it can be seen that by adding active material particles to the primer slurry, the loss of energy density caused by setting the primer layer can be reduced or compensated compared with not adding active material particles to the primer slurry.
  • Comparative Examples 1-2 and 9 The difference between Comparative Examples 1-2 and 9 is that the volume average particle size Dv50 of the positive electrode active material is different; from the results of Comparative Examples 1-2 and 9, it can be seen that the larger the volume average particle size Dv50 of the positive electrode active material, the greater the corrosion risk.
  • Comparative Examples 3-4 and 9 The difference between Comparative Examples 3-4 and 9 is that the compaction density of the positive electrode sheets is different; from the results of Comparative Examples 3-4 and 9, it can be seen that the greater the compaction density of the positive electrode sheets, the greater the corrosion risk.
  • Comparative Examples 5-6 and 9 The difference between Comparative Examples 5-6 and 9 is that the upper limit voltage used by the secondary battery is different; from the results of Comparative Examples 5-6 and 9, it can be seen that the greater the upper limit voltage used by the secondary battery, the greater the corrosion risk.
  • Comparative Examples 7-9 The difference between Comparative Examples 7-9 is that the mass proportion of LiFSI in the electrolyte is different; from the results of Comparative Examples 7-9, it can be seen that the greater the mass proportion of LiFSI in the electrolyte, the greater the corrosion risk.

Landscapes

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

Abstract

一种正极极片、二次电池（4）及用电装置（5）。正极极片包括：正极集流体；底涂层，位于正极集流体的至少一侧，底涂层包括导电剂和粘结剂；正极活性物质层，位于底涂层远离正极集流体的一侧，正极活性物质层包括正极活性材料；底涂层的厚度记为L，则底涂层的厚度满足: （I）；其中，Dv50为正极活性材料体积分布中颗粒的累计粒度分布数达到50％时所对应的粒度尺寸，单位为μm；PD表示正极极片的压实密度，单位为g/cm 3。

Description

正极极片、二次电池及用电装置 技术领域
本申请属于二次电池技术领域，具体涉及一种正极极片、二次电池及用电装置。
背景技术
二次电池因具有重量轻、无污染、无记忆效应等突出特点，被广泛应用于各类消费类电子产品和新能源汽车中。随着新能源行业的不断发展，客户对二次电池提出了更高的使用需求。例如，二次电池的能量密度设计越来越高。
相关技术中，提高正极极片的压实密度是提高二次电池的能量密度的途径之一。但是，采用提高正极极片的压实密度的手段，在提高能量密度的同时，往往导致高压密下对于铝箔表面氧化膜的破坏，暴露新鲜的铝，电解液腐蚀铝箔从而引发电池安全问题。
发明内容
鉴于背景技术中存在的技术问题，本申请提供一种正极极片、二次电池及用电装置，旨在提高二次电池能量密度的同时提高二次电池的安全性。
为了实现上述目的，本申请的第一方面提供一种正极极片，包括：
正极集流体；
底涂层，位于所述正极集流体的至少一侧，所述底涂层包括导电剂和粘结剂；
正极活性物质层，位于所述底涂层远离所述正极集流体的一侧，所述正极活性物质层包括正极活性材料；
所述底涂层的厚度记为L，则所述底涂层的厚度满足：
Figure PCTCN2022129727-appb-000001
其中，Dv50为正极活性材料体积分布中颗粒的累计粒度分布数达到50％时所对应的粒度尺寸，单位为μm；PD表示正极极片的压实密度，单位为g/cm 3。
相对于现有技术，本申请至少包括如下所述的有益效果：
本申请的正极极片，其设置有底涂层，在正极活性物质层具有高的压实密度时，底涂层可改善甚至避免铝箔表层的氧化膜被正极活性材料压伤，提高二次电池的安全性；此外，通过基于正极极片的压实密度和正极活性材料的体积平均粒径Dv50确定适宜的 底涂层厚度，可在不影响二次电池能量密度的同时对铝箔表面的氧化膜起到保护作用。如此上述正极极片应用于二次电池，可在提高二次电池能量密度的同时提高二次电池的安全性。
在本申请任意实施方式中，所述正极活性材料中的镍含量≥80％。
在本申请任意实施方式中，所述正极活性材料的体积平均粒径Dv50记为D4，则所述正极活性材料的体积平均粒径Dv50满足：5μm≤D4≤15μm；可选地，5μm≤D4≤9μm。
在本申请任意实施方式中，所述粘结剂和所述导电剂的质量比为(2-10):10。
在本申请任意实施方式中，所述粘结剂包括丙烯酸类树脂；
可选地，所述丙烯酸类树脂包括交联型聚丙烯酸、聚丙烯酸锂、聚丙烯酸钠和聚丙烯酸-聚丙烯腈共聚物中的一种或多种。
在本申请任意实施方式中，所述导电剂包括乙炔黑、炭黑、石墨、科琴黑和石墨烯中的一种或多种。
在本申请任意实施方式中，所述底涂层还包括活性物质颗粒。
在本申请任意实施方式中，所述活性物质颗粒的体积平均粒径Dv10记为D1，所述活性物质颗粒的体积平均粒径Dv50记为D2，所述活性物质颗粒的体积平均粒径Dv90记为D3，则所述活性物质颗粒满足：D2≤2μm，(D3-D1)/D2≥2.8。
在本申请任意实施方式中，所述底涂层的厚度满足：
Figure PCTCN2022129727-appb-000002
其中，D2为所述活性物质颗粒的体积平均粒径Dv50。
在本申请任意实施方式中，所述活性物质颗粒包括NCM三元材料、磷酸铁锂和补锂剂中的一种或多种；
可选地，所述NCM三元材料的化学式为LiNi xCo yMn 1-x-yO 2，其中，0.3≤x≤1，0≤y≤0.5；
可选地，所述补锂剂包括含锂氧化物、含锂氮化物、含锂硫化物和含锂金属酸盐中的一种或多种。
在本申请任意实施方式中，所述粘结剂、所述导电剂和所述活性物质颗粒的质量比为(2-10):10:(1-10)。
在本申请任意实施方式中，所述底涂层的厚度满足：0＜L≤5μm；可选地，1≤L≤2μm。
在本申请任意实施方式中，所述正极活性材料包括锂镍钴锰氧化物。
在本申请任意实施方式中，所述集流体选自铝箔。
本申请的第二方面提供了一种二次电池，包括如本申请第一方面的正极极片。
在本申请任意实施方式中，所述二次电池还包括电解液，所述电解液中含有双氟磺酰亚胺锂。
本申请的第三方面提供了一种用电装置，包括本申请第二方面的二次电池。
附图说明
为了更清楚地说明本申请的技术方案，下面将对本申请中所使用的附图作简单介绍。显而易见地，下面所描述的附图仅仅是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是二次电池的一实施方式的示意图。
图2是图1的分解图。
图3是电池包的一实施方式的示意图。
图4是二次电池用作电源的用电装置的一实施方式的示意图。
附图标记说明：
1、电池包；2、上箱体；3、下箱体；4、二次电池；41、壳体；42、电极组件；43、盖板；5、用电装置。
具体实施方式
下面结合具体实施方式，进一步阐述本申请。应理解，这些具体实施方式仅用于说明本申请而不用于限制本申请的范围。
为了简明，本文仅具体地公开了一些数值范围。然而，任意下限可以与任意上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、 2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
在本文的描述中，需要说明的是，除非另有说明，“以上”、“以下”为包括本数，“一种或几种”中“几种”的含义是两种及两种以上。
在本文的描述中，除非另有说明，术语“或(or)”是包括性的。也就是说，短语“A或(or)B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法进行测试)。
随着新能源行业的不断发展，客户对二次电池的能量密度提出了更高的需求。相关技术中，提高正极极片的压实密度是提高二次电池的能量密度的途径之一。但是，采用提高正极极片的压实密度的手段，在提高能量密度的同时，往往导致对于铝箔表面氧化膜的破坏，引发电池安全问题。
此外，由于高镍三元材料具有高的能量密度，采用高镍三元材料作为正极材料也是相关技术中提高二次电池能量密度的手段之一。由于高镍三元材料的高温结构稳定性差，高温容易发生释氧，导致二次电池存储寿命衰减快，安全性下降。当采用高镍三元材料作为正极材料时，往往可通过在电解液中添加双氟磺酰亚胺锂(LiFSI)，有效改善二次电池的存储寿命，提高安全性。但是，含有LiFSI的电解液在高压下易腐蚀铝箔，循环后期容易造成铝箔脆断，引发二次电池安全事故。此外，二次电池浅刺耐受性差，并且电解液高压稳定性差，过充失效风险高。本申请的技术人员分析发现主要是高压密度下正极材料颗粒压伤铝箔，铝箔表层氧化膜被破坏，暴露新鲜的铝箔，新鲜的铝箔与电解液发生反应，从而发生铝箔腐蚀，引发二次电池安全事故。
本申请提供的正极极片，包括：正极集流体、位于正极集流体的至少一侧的底涂层以及位于底涂层远离正极集流体的一侧的正极活性物质层；底涂层包括粘结剂和导电剂；正极活性物质层包括正极活性材料，底涂层的厚度记为L，则底涂层的厚度满足：
Figure PCTCN2022129727-appb-000003
其中，Dv50为正极活性材料体积分布中颗粒的累计粒度分布数达到50％时所对应的粒度尺寸，单位为μm；PD表示正极极片的压实密度，单位为g/cm 3。
需要说明的是，底涂层位于正极集流体的至少一侧，底涂层可以与正极集流体相接触，也可以与正极集流体不接触。
需要说明的是，正极活性物质层内可包括一种正极活性材料，也可包括两种或两种以上的正极活性材料。若正极活性物质层包括两种或两种以上的正极活性材料，则Dv50为所有正极活性材料体积分布中50％所对应的粒度尺寸。
底涂层中仅含有粘结剂和导电剂时，底涂层的厚度满足：
Figure PCTCN2022129727-appb-000004
不希望限于任何理论，本申请的正极极片，其设置有底涂层，在正极活性物质层具有高的压实密度时，底涂层可改善甚至避免铝箔表层的氧化膜被正极活性材料压伤，提高二次电池的安全性；此外，通过基于正极极片的压实密度和正极活性材料的体积平均粒径Dv50确定适宜的底涂层厚度，可在不影响二次电池能量密度的同时对铝箔表面的氧化膜起到保护作用。如此上述正极极片应用于二次电池，可在提高二次电池能量密度的同时提高二次电池的安全性。
需要说明的是，体积平均粒径Dv50的物理意义是粒径小于(或大于)它的颗粒占50％。作为示例，上述提及的正极活性材料的体积平均粒径Dv50可以参照GB/T 19077-2016 粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。
上述提及的正极极片的压实密度可采用如下方法测得：刮取单位面积的极片，称重获得极片涂布面密度。待极片烘干冷压之后，使用游标卡尺测量极片的总厚度，扣除集流体的厚度就可以计算出涂布厚度。根据涂布面密度及涂布厚度两个参数，基于公式：压实密度＝面密度/涂布厚度，即可计算极片的压实密度。需要说明的是，对于设置有底涂层的正极极片，涂布面密度为底涂层和正极活性物质层的整合面密度，涂布厚度为底涂层和正极活性物质层的整合厚度。
上述提及的底涂层的厚度可采用如下方法测得：对正极极片进行截面CP表征，测量正极极片总厚度以及正极活性物质层厚度和正极集流体厚度，然后基于公式：正极极片总厚度-正极活性物质层厚度-正极集流体厚度，即得底涂层厚度。
本发明人经深入研究发现，当本申请的正极极片在满足上述设计条件的基础上，若还可选地满足下述条件中的一个或几个时，可以进一步提升二次电池的能量密度、动力学性能、浅刺安全性。
在其中的一些实施例中，正极活性材料中的镍含量≥80％。正极极片采用高镍三元材料作为正极活性材料，如此正极极片应用于二次电池时，电解液中适配性的加入LiFSI；若正极活性材料与铝箔直接接触，正极活性物质层的压实密度较大时，正极活性材料易损伤铝箔表面的氧化膜而暴露新鲜的铝箔，电解液中的LiFSI与铝箔接触时发生反应腐蚀铝箔。位于正极活性物质层与正极集流体之间的底涂层，可减缓甚至避免在压实密度较大时正极活性材料颗粒对铝箔表面的氧化膜的损伤，从而避免由于新鲜的铝箔与电解液接触而导致的铝箔腐蚀，提高二次电池安全性。
上述提及的正极活性材料中的镍含量可通过ICAP6300光谱仪测量得到。
在其中的一些实施例中，正极活性材料的体积平均粒径Dv50记为D4，则正极活性材料的体积平均粒径Dv50满足：5μm≤D4≤15μm；例如，可以为6μm≤D4≤15μm、7μm≤D4≤14μm、8μm≤D4≤13μm、9μm≤D4≤12μm、10μm≤D4≤11μm或5μm≤D4≤13μm等。正极活性材料的体积平均粒径Dv50位于上述范围时，若正极极片的压实密度高且正极活性物质层与正极集流体直接接触，正极活性材料颗粒更容易损伤铝箔表面的氧化膜。通过在正极活性物质层与正极集流体之间设置底涂层，可减缓甚至避免正极活性材料颗粒对铝箔表面的氧化膜造成破损。进一步地，正极活性材料的体积平均粒径Dv50 满足：5μm≤D4≤9μm。
在其中的一些实施例中，粘结剂和导电剂的质量比为(2-10):10；例如，粘结剂和导电剂的质量比可以为(2-9):10、(3-8):10、(4-7):10、(5-6):10、(4.5-5.5):10或(5.5-6.5):10等。粘结剂和导电剂的质量比位于所给范围内时，可满足底涂层与正极集流体及正极活性物质层之间的剪切强度需求，同时便于底涂浆料制备时的过滤，并减少底涂浆料中的固含量。
在其中的一些实施例中，粘结剂包括丙烯酸类树脂；可选地，丙烯酸类树脂包括交联型聚丙烯酸、聚丙烯酸锂、聚丙烯酸钠和聚丙烯酸-聚丙烯腈共聚物中的一种或多种。
在其中的一些实施例中，导电剂包括乙炔黑、炭黑、石墨、科琴黑和石墨烯中的一种或多种。
在其中的一些实施例中，底涂层还包括活性物质颗粒。底涂层中添加活性物质颗粒，可使底涂层也能发挥容量补给作用，提高二次电池的整体容量，降低或弥补由于设置底涂层而造成的能量密度的损失。
可选地，活性物质颗粒的体积平均粒径Dv10记为D1，活性物质颗粒的体积平均粒径Dv50记为D2，活性物质颗粒的体积平均粒径Dv90记为D3，则活性物质颗粒满足：D2≤2μm，(D3-D1)/D2≥2.8。活性物质颗粒的体积平均粒径Dv50超过上述范围时，活性物质颗粒亦容易压伤正极集流体，则需增加底涂层的厚度，进而可导致底涂层的剪切强度变差，二次电池的能量密度降低、DCR增大，同时增加成本。(D3-D1)/D2低于上述范围时，活性物质颗粒易团聚，可导致底涂浆料产生滤渣，进而导致底涂层的剪切强度变差，且电解液对正极集流体的腐蚀情况将会进一步恶化，同时增大二次电池的DCR。通过对底涂层中活性物质颗粒的尺寸进行调配，可提高底涂层的抗压能力，也更易获得致密且薄的涂层，利于提高底涂层对浅刺等机械损伤的抵挡能力。
需要说明的是，体积平均粒径Dv10是指在活性物质颗粒的体积累积分布曲线中，活性物质颗粒的累计粒度分布数达到10％时所对应的粒径。体积平均粒径Dv50是指在活性物质颗粒的体积累积分布曲线中，活性物质颗粒的累计粒度分布数达到50％时所对应的粒径。体积平均粒径Dv90是指在活性物质颗粒的体积累积分布曲线中，活性物质颗粒的累计粒度分布数达到90％时所对应的粒径。作为示例，Dv10、Dv50及Dv90可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。
在其中的一些实施例中，底涂层中还含有活性物质颗粒时，底涂层的厚度满足：
Figure PCTCN2022129727-appb-000005
其中，D2为活性物质颗粒的体积平均粒径Dv50。
在其中的一些实施例中，活性物质颗粒包括NCM三元材料、磷酸铁锂和补锂剂中的一种或多种；
可选地，NCM三元材料的化学式为LiNi xCo yMn 1-x-yO 2，其中，0.3≤x≤1，0≤y≤0.5；
可选地，补锂剂包括三类：二元含锂化合物(如Li2O、Li2O2、LiF、Li2S、Li3N等)、三元含锂化合物(Li4FeO5、Li6CoO4、Li2NiO2等)、有机锂盐(Li2DHBN、Li2C2O4等)中的一种或多种。
可选地，活性物质颗粒还可包括橄榄石结构的含锂磷酸盐，包括但不限于磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在其中的一些实施例中，粘结剂、导电剂和活性物质颗粒的质量比为(2-10):10:(1-10)；例如，粘结剂、导电剂和活性物质颗粒的质量比可以为(2-9):10:(2-10)、(3-8):10:(4-7)、(5-6):10:(4-8)、(4.5-5.5):10:(5-7)、(5.5-6.5):10:(5-6)或(5-10):10:(1-3)等。粘结剂、导电剂和活性物质颗粒的质量比在所给范围内时，可形成稳定的浆料，膜片粘结良好，添加适量的活性物质有助于电池兼顾高体积能量密度(VED)和安全性。
在其中的一些实施例中，底涂层的厚度满足：0＜L≤5μm；例如，可以为0.01≤L≤5μm、0.1≤L≤5μm、0.5≤L≤3.5μm、1≤L≤3μm、1.5≤L≤2.5μm、2≤L≤2.5μm、0.5≤L≤1μm、1.5≤L≤2μm或1≤L≤1.5μm等。底涂层的厚度在所给范围内时，能够在不影响二次电池能量密度的同时，有效改善正极材料颗粒对铝箔的破坏。可选地，底涂层的厚度满足：1≤L≤2μm。
在其中的一些实施例中，正极活性材料包括锂镍钴锰氧化物。
在其中的一些实施例中，正极活性材料还可包括本领域公知的其他用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸 铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。所述正极活性材料在正极膜层中的重量比为80-100重量％，基于正极膜层的总重量计。
本申请还提供了一种底涂浆料的制备方法，包括如下步骤：
将导电剂、粘结剂和活性物质颗粒干混，得到均匀分散的粉末；
加入去离子水缓慢搅拌预溶解，高速搅拌得到均匀分散的底涂浆料。
在一些实施例中，所述底涂浆料的固含量为5-20wt％，室温下的粘度为500-2000mPa·s。
在其中的一些实施例中，底涂浆料中粘结剂、导电剂及活性物质颗粒的质量比为(2-20):10:(1-10)。
作为示例，制备浆料A时，粘结剂以固含量为25％的粘结剂水溶液的形式，与导电剂共同制备浆料A。最后制得的底涂浆料中粘结剂、导电剂、活性物质颗粒及去离子水的质量百分比之和为100％。
在一些实施例中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
正极活性物质层通常还可选地包括粘结剂、导电剂和其他可选助剂。
作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。所述粘结剂在正极活性物质层中的重量比为0-20重量％，基于正极活性物质层的总重量计。
作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。所述导电剂在正极活性物质层中的重量比为0-20重量％，基于正极活性物质层的总重量计。
作为示例，可通过以下方式制备正极极片：
将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他 的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料，其中所述正极浆料固含量为40-80wt％，室温下的粘度调整到5000-25000mPa·s；
将底涂浆料涂覆在正极集流体的表面，烘干，形成底涂层；
将正极浆料涂覆在底涂层的表面，烘干后经过冷轧机冷压后形成正极极片；正极粉末涂布单位面密度为150-350mg/m 2，正极极片压实密度为3.0-3.6g/cm 3，可选为3.3-3.5g/cm 3。
上述原料未特别说明的均可以通过市购获得。
二次电池
二次电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括本申请上述提供的正极极片、负极极片、隔离膜及电解液。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。电解液在正极极片和负极极片之间起到传导离子的作用。
负极极片
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化 合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。所述负极活性材料在负极膜层中的重量比为70-100重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。所述粘结剂在负极膜层中的重量比为0-30重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。所述导电剂在负极膜层中的重量比为0-20重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。所述其他助剂在负极膜层中的重量比为0-15重量％，基于负极膜层的总重量计。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料，其中所述负极浆料固含量为30-70wt％，室温下的粘度调整到2000-10000mPa·s；将所得到的负极浆料涂覆在负极集流体上，经过干燥工序，冷压例如对辊，得到负极极片。负极粉末涂布单位面密度为75-220mg/m 2，负极极片压实密度1.2-2.0g/m 3。
电解质
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施例中，电解液中含有双氟磺酰亚胺锂(LiFSI)。
在一些实施方式中，电解质盐还可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟 甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)及四氟草酸磷酸锂(LiTFOP)中的一种或几种。所述电解质盐的浓度通常为0.5-5mol/L。
在一些实施方式中，溶剂可选自氟代碳酸乙烯酯(FEC)、碳酸亚乙酯(EC)、碳酸亚丙基酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
隔离膜
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，所述隔离膜的厚度为6-40μm，可选为12-20μm。
在一些实施方式中，本申请的二次电池为锂离子二次电池。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
可以按照本领域常规方法制备二次电池，例如将正极极片、隔离膜、负极极片按顺 序卷绕(或叠片)，使隔离膜处于正极极片与负极极片之间起到隔离的作用，得到电芯，将电芯置于外包装中，注入电解液并封口，得到二次电池。
本申请实施例对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。如图1是作为一个示例的方形结构的二次电池4。
在一些实施例中，参照图2，外包装可包括壳体41和盖板43。其中，壳体41可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体41具有与容纳腔连通的开口，盖板43能够盖设于所述开口，以封闭所述容纳腔。
正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件42。电极组件52封装于所述容纳腔。电解液浸润于电极组件42中。二次电池4所含电极组件42的数量可以为一个或多个，可根据需求来调节。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。在电池模块中，多个二次电池可以是沿电池模块的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池进行固定。电池模块还可以包括具有容纳空间的外壳，多个二次电池容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
在一些实施例中，上述二次电池还可以组装成电池包，电池包所含二次电池的数量可以根据电池包的应用和容量进行调节。
图3是作为一个示例的电池包1。在电池包1中可以包括电池箱和设置于电池箱中的多个二次电池或电池模块。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳二次电池或电池模块的封闭空间。多个二次电池或电池模块可以按照任意的方式排布于电池箱中。
用电装置
本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块或电池包中的至少一种。所述二次电池、电池模块或电池包可以用作所述装置的电源，也可以作为所述装置的能量存储单元。所述装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、 储能系统等。
所述装置可以根据其使用需求来选择二次电池、电池模块或电池包。
图4是作为一个示例的用电装置5。该用电装置5为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对二次电池的高功率和高能量密度的需求，可以采用电池包。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
以下结合实施例进一步说明本申请的有益效果。
实施例
为了使本申请所解决的技术问题、技术方案及有益效果更加清楚，以下将结合实施例和附图进行进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。以下对至少一个示例性实施例的描述实际上仅仅是说明性的，决不作为对本申请及其应用的任何限制。基于本申请中的实施例，本领域普通技术人员在没有付出创造性劳动前提下所获得的所有其他实施例都属于本申请保护的范围。本申请的实施例和对比例中所用的材料均可以通过商购获得。
一、正极极片的的制备
实施例1
将10g导电剂乙炔黑(作为导电剂)、40g交联型聚丙烯酸溶液(作为粘结剂，固含量为25％)混合制备浆料A；将10g磷酸铁锂(LFP，作为活性物质颗粒)溶于去离子水中，充分溶解制备浆料B；将浆料A加入浆料B中，充分搅拌混合均匀后得到底涂浆料。过滤底涂浆料，底涂浆料中的滤渣含量及底涂浆料的过滤时间如表1所示。将过滤后的底涂浆料均匀涂覆于正极集流体上，烘干得到带有底涂层的基材。
其中，磷酸铁锂颗粒(作为活性物质颗粒)的体积平均粒径Dv50为2μm，且(体积平均粒径Dv90-体积平均粒径Dv10)/体积平均粒径Dv50＝2.8；底涂层的厚度为3μm；底涂层的剪切强度为15Mpa。
将正极活性材料LiNi 0.50Co 0.06Mn 0.44O 2、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为96.5:1.5:2溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料；之后将正极浆料均匀涂覆于带有底涂的正极集流体上，之后经过烘干、冷压、 分切，得到正极极片。
实施例2-11
实施例2-11中正极极片的制备方法和实施例1中正极极片的制备方法基本相似，区别主要在于：制备带有底涂层的基材时，采用的导电剂的种类和/或用量、粘结剂的种类和/或用量、活性物质颗粒的种类和/或用量、底涂层的厚度中的至少一项不同，具体详见表1。
实施例12
实施例12中正极极片的制备方法和实施例2中正极极片的制备方法基本相似，区别主要在于：制备正极活性物质层时，采用的正极活性材料为LiNi 0.80Co 0.12Mn 0.08O 2，其他均相同。
实施例13
实施例13中正极极片的制备方法和实施例2中正极极片的制备方法基本相似，区别主要在于：制备正极活性物质层时，采用的正极活性材料为LiNi 0.90Co 0.08Mn 0.02O 2，其他均相同。
对比例1-9
对比例1-9中的正极极片未设置底涂层，其制备方法如下：
将正极活性材料NCM、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为96.5:1.5:2溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料；之后将正极浆料均匀涂覆于正极集流体上，之后经过烘干、冷压、分切，得到正极极片。
需要说明的是，上述各实施例和对比例中正极极片的压实密度可采用如下方法进行测定：
刮取单位面积的极片，称重获得极片涂布面密度。待极片烘干冷压之后，使用游标卡尺测量极片的总厚度，扣除集流体和底涂层的厚度就可以计算出涂布厚度。根据涂布面密度及涂布厚度两个参数，基于公式：压实密度＝面密度/涂布厚度，即可计算极片的压实密度。需要说明的是，对于设置有底涂层的正极极片，涂布面密度为底涂层和正极活性物质层的整合面密度，涂布厚度为底涂层和正极活性物质层的整合厚度。对于未设置有底涂层的正极极片，涂布面密度为正极活性物质层的面密度，涂布厚度为正极活性物质层的厚度。
上述各实施例中底涂层的厚度可采用如下方法进行测定：
对正极极片进行截面CP表征，测量正极极片总厚度以及正极活性物质层厚度和正极集流体厚度，然后基于公式：正极极片总厚度-正极活性物质层厚度-正极集流体厚度，即得底涂层厚度。
上述各实施例中的D1、D2、D3、D4以及各对比例中的D4可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。
上述各实施例中底涂层的剪切强度可采用如下方法测得：
取待测试极片，使用模切工具冲裁宽度为20mm、长度为100mm的试样。选取外观平整钢板，棉纱布蘸酒精，擦拭钢板表面，并烘干。双面胶纸粘结在钢板上，胶带底边与钢板底边距离＞1cm，用刀片轻轻刮掉胶带上层离型纸。截取的极片试样端部周圈贴上皱纹胶，再贴在双面胶上，测试面朝下。使用2kg的压辊来回辊压3次。打开拉力机电源，指示灯亮，调整限位块到合适位置。将钢板未贴极片的一端用下夹具固定。上夹具夹持在皱纹胶位置。打开与拉力机链接的专用电脑，双击桌面“U60”软件图标。设置拉力机参数。测试速度10mm/min。测试曲线出现峰值，极片与钢板完全分开，自动停止测试。导出原始数据。选取曲线的峰值作为极片的最大剪切力Fs(N)，根据Q＝Fs/S计算极片的剪切强度，单位Mpa。
上述各实施例和对比例的正极极片制备过程中的底涂浆料过滤时间、滤渣含量、正极极片的压实密度、底涂层的剪切强度、正极活性材料的体积平均粒径Dv50分别如表1所示。
表1
Figure PCTCN2022129727-appb-000006
Figure PCTCN2022129727-appb-000007
其中，表1中D1表示活性物质颗粒的体积平均粒径Dv10，D2表示活性物质颗粒的体积平均粒径Dv50，D3表示活性物质颗粒的体积平均粒径Dv90，SPAN＝(D3-D1)/D2；D4表示正极活性材料的体积平均粒径Dv50；PD表示正极极片的压实密度；L表示底涂层的厚度。
由表1中各实施例底涂浆料的过滤时间、底涂浆料中的滤渣含量、底涂层的剪切强度可知，底涂浆料中粘结剂的质量占比为2-10％、导电剂的质量占比为10％、活性物质颗粒的质量占比为1-10％、活性物质颗粒的体积平均粒径Dv50≤2μm且SPAN≥2.8时， 底涂浆料过滤时间适宜(≤60s)且底涂浆料内不含有滤渣，同时底涂层的剪切强度可满足粘结需求(≥0.7Mpa)。
由表1中实施例2、8-10的区别在于底涂浆料中粘结剂的用量不同；实施例8中粘结剂用量最大，实施例10中粘结剂用量最小，实施例8和实施例10中底涂浆料的过滤时间均过长，且底涂浆料中均含有滤渣。技术人员分析其原因，这可能是由于当底涂浆料中粘结剂的质量占比高于10％时，底涂浆料的粘度过大，可导致底涂浆料过滤时间延长且底涂浆料中的物料易结块形成滤渣；当底涂浆料中粘结剂的质量占比低于2％时，由于底涂浆料的粘度过低，底涂浆料中的导电剂及活性物质颗粒将会发生自身之间的粉末团聚，从而亦导致底涂浆料过滤时间延长且含有滤渣。此外，当底涂浆料中粘结剂的质量占比低于2％时，底涂层的剪切强度显著降低，不能满足粘结需求。
二、电池的制备
1、负极极片的制备
将负极活性材料石墨、硅、导电剂乙炔黑、高分子聚合物、增稠剂羧甲基纤维素钠(CMC)按照重量比为90:5:2:2:1溶于去离子水中，与去离子水均匀混合后制备成负极浆料，将负极浆料涂布在铜箔上，烘干后经过冷压分切，获得阳极极片
2、隔膜：以聚乙烯膜(PE)作为隔离膜，表面涂敷PVDF和氧化铝涂层。
3、电解液的制备
将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，然后将LiPF6：LiFSI(2:8)均匀溶解在上述溶液中，得到电解液。该电解液中，锂盐的浓度为1mol/L。
4、二次电池的制备：将上述各实施例和对比例中的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，然后卷绕得到裸电芯，给裸电芯焊接极耳，并将裸电芯装入铝壳中，并在80℃下烘烤除水，随即注入电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得二次电池。
三、电池性能测试
1、二次电池能量密度测试
将制作好的各二次电池于25℃静置30min，以1/3C的倍率充电至4.25V，恒压至0.05C结束。静置30min，以1/3C的倍率放电至2.8V，放出的能量即为E0。基于公式 电池能量密度＝E0/电芯体积，计算二次电池能量密度；其中，电芯体积可通过测量二次电池的长、宽、高计算得到。
2、浅刺测试
将制作好的各二次电池于25℃以1/3C的倍率放电至2.8V，静置60min，以1/3C的倍率充电至4.25V，恒压至0.05C结束；静置60min，去除部分壳体，记录此时电芯的电压、内阻和重量。
在25℃下进行穿钉实验，钉子直径为1mm，速度为0.1mm/s，匀速垂直于电池极板的方向刺入，刺入位置靠近被刺面几何中心；刺入深度为4mm，监控压降；试验环境下观察1h；若无失效，刺入深度改为5mm，重复上述步骤，直至失效为止；记录失效时电芯的电压、内阻和重量。
3、二次电池放电DCR测试
将制作好的各二次电池于25℃静置30min，以1/3C的倍率充电至4.25V，恒压至0.05C结束。静置10min，以1/3C0的倍率放电至电芯的电量为满充时的50％，将其称之为50％SOC；静置60min，以4C0的倍率放电10s，记录电芯的DCR值。
4、腐蚀风险系数
正极极片采用镍含量≥80％的NCM三元材料，电解液中含有LiFSI的二次电池中，高的压实密度下正极材料颗粒压伤铝箔，LiFSI腐蚀铝箔，腐蚀风险系数记为S，则S＝(V/4.2)*(PD/3.5)*(w/50％)；其中，V表示二次电池使用的上限电压，w表示LiFSI在电解液中的质量占比；腐蚀风险系数≥1时发生腐蚀。
各实施例和对比例制得的二次电池的性能测试结果如下表2所示。
表2
组别 V w 腐蚀风险 ED/wh/L DCR
实施例1 4.2 80％ 偏低 90％ 120％
实施例2 4.2 80％ 低 92％ 110％
实施例3 4.2 80％ 偏低 88％ 130％
实施例4 4.2 80％ 偏低 92％ 115％
实施例5 4.2 80％ 低 92％ 110％
实施例6 4.2 80％ 低 92％ 110％
实施例7 4.2 80％ 偏低 95％ 110％
实施例8 4.2 80％ 低 92％ 140％
实施例9 4.2 80％ 低 92％ 110％
实施例10 4.2 80％ 中 92％ 110％
实施例11 4.2 80％ 低 85％ 110％
实施例12 4.2 80％ 偏低 95％ 107％
实施例13 4.2 80％ 偏低 102％ 98％
对比例1 4.2 50％ 中 / /
对比例2 4.2 50％ 高 / /
对比例3 4.2 50％ 中 / /
对比例4 4.2 50％ 高 / /
对比例5 4.1 50％ 低 / /
对比例6 4.3 50％ 高 / /
对比例7 4.2 30％ 低 / /
对比例8 4.2 80％ 高 / /
对比例9 4.2 50％ 偏高 100％ 100％
其中，表2中ED表示能量密度。以正极活性材料的体积平均粒径Dv50为9μm、正极极片的压实密度为3.6g/cm 3、LiFSI在电解液中的质量占比为50％、二次电池使用的上限电压为4.2v，且未施加底涂层时，测得的二次电池能量密度、放电DCR为基础，分别测量施加底涂层后二次电池能量密度、放电DCR的变化百分比。
实施例1-3的区别在于活性物质颗粒的体积平均粒径Dv50不同；由实施例1-3的结果可知，活性物质颗粒的体积平均粒径Dv50大于2μm时，随着活性物质颗粒的体积平均粒径Dv50的增加，底涂层的厚度将会增加，可导致二次电池的能量密度降低、DCR增大。
实施例2和实施例4-5的区别在于活性物质颗粒的SPAN不同；由实施例1和实施例4-5的结果可知，活性物质颗粒的SPAN小于2.8时，正极极片制备过程中，底涂浆料的过滤时间显著增加且存在滤渣，电解液对集流体的腐蚀风险增加，且二次电池的DCR增大；技术人员分析其原因，可能是由于活性物质颗粒的SPAN小于2.8时，活性物质颗粒易团聚，从而可导致底涂浆料产生滤渣并延长过滤时间，并进一步恶化电解液对集流体的腐蚀情况，且增大二次电池的DCR。
实施例2和实施例6-7的区别在于活性物质颗粒的质量占比不同；由实施例2和实施例6-7的结果可知，当底涂浆料中活性物质颗粒的质量占比高于10％时，底涂层的剪切强度降低、电解液对正极集流体的腐蚀风险增大。技术人员分析其原因，可能是由于底涂浆料中活性物质颗粒的质量占比增加，导致底涂层的剪切强度降低，进一步增加了电解液对正极集流体的腐蚀风险。
实施例2和实施例8-10的区别在于底涂浆料中粘结剂的质量占比不同；由实施例2和实施例8-10的结果可知，底涂浆料中粘结剂的质量占比低于2％时，底涂浆料的过滤时间显著延长且产生滤渣，底涂层的剪切强度不能满足使用需求，且电解液对正极集流体的腐蚀风险增大；底涂浆料中粘结剂的质量占比高于10％时，底涂浆料的过滤时间亦显著延长且产生滤渣，同时二次电池的DCR显著增大。
实施例11和实施例2的区别在于底涂浆料中未添加活性物质颗粒；由实施例2和实施例11的结果可知，与底涂浆料中未添加活性物质颗粒相比，通过在底涂浆料中添加活性物质颗粒，可降低或弥补由于设置底涂层而造成的能量密度的损失。
对比例1-2和9的区别在于正极活性材料的体积平均粒径Dv50不同；由对比例1-2和9的结果可知，正极活性材料的体积平均粒径Dv50越大，腐蚀风险越大。
对比例3-4和9的区别在于正极极片的压实密度不同；由对比例3-4和9的结果可知，正极极片的压实密度越大，腐蚀风险越大。
对比例5-6和9的区别在于二次电池使用的上限电压不同；由对比例5-6和9的结果可知，二次电池使用的上限电压越大，腐蚀风险越大。
对比例7-9的区别在于LiFSI在电解液中的质量占比不同；由对比例7-9的结果可知，LiFSI在电解液中的质量占比越大，腐蚀风险越大。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (16)

  1. 一种正极极片，包括：
    正极集流体；
    底涂层，位于所述正极集流体的至少一侧，所述底涂层包括导电剂和粘结剂；
    正极活性物质层，位于所述底涂层远离所述正极集流体的一侧，所述正极活性物质层包括正极活性材料；
    所述底涂层的厚度记为L，则所述底涂层的厚度满足：
    Figure PCTCN2022129727-appb-100001
    其中，Dv50为正极活性材料体积分布中颗粒的累计粒度分布数达到50％时所对应的粒度尺寸，单位为μm；PD表示正极极片的压实密度，单位为g/cm 3。
  2. 如权利要求1所述的正极极片，其中所述正极活性材料中的镍含量≥80％。
  3. 如权利要求1至2任一项所述的正极极片，其中所述正极活性材料的体积平均粒径Dv50记为D4，则所述正极活性材料的体积平均粒径Dv50满足：5μm≤D4≤15μm；可选地，5μm≤D4≤9μm。
  4. 如权利要求1至3任一项所述的正极极片，其中所述粘结剂和所述导电剂的质量比为(2-10):10。
  5. 如权利要求1至4任一项所述的正极极片，其中所述粘结剂包括丙烯酸类树脂；
    可选地，所述丙烯酸类树脂包括交联型聚丙烯酸、聚丙烯酸锂、聚丙烯酸钠和聚丙烯酸-聚丙烯腈共聚物中的一种或多种。
  6. 如权利要求1至5任一项所述的正极极片，其中所述导电剂包括乙炔黑、炭黑、石墨、科琴黑和石墨烯中的一种或多种。
  7. 如权利要求1至6任一项所述的正极极片，其中所述底涂层还包括活性物质颗粒。
  8. 如权利要求7所述的正极极片，其中所述活性物质颗粒的体积平均粒径Dv10记为D1，所述活性物质颗粒的体积平均粒径Dv50记为D2，所述活性物质颗粒的体积平均粒径Dv90记为D3，则所述活性物质颗粒满足：D2≤2μm，(D3-D1)/D2≥2.8。
  9. 如权利要求7至8中任一项所述的正极极片，其中所述底涂层的厚度满足：
    Figure PCTCN2022129727-appb-100002
    其中，D2为所述活性物质颗粒的体积平均粒径Dv50。
  10. 如权利要求7至9任一项所述的正极极片，其中所述活性物质颗粒包括NCM三元材料、磷酸铁锂和补锂剂中的一种或多种；
    可选地，所述NCM三元材料的化学式为LiNi xCo yMn 1-x-yO 2，其中，0.3≤x≤1，0≤y≤0.5；
    可选地，所述补锂剂包括含锂氧化物、含锂氮化物、含锂硫化物和含锂金属酸盐中的一种或多种。
  11. 如权利要求7至10任一项所述的正极极片，其中所述粘结剂、所述导电剂和所述活性物质颗粒的质量比为(2-10):10:(1-10)。
  12. 如权利要求1至11任一项所述的正极极片，其中所述底涂层的厚度满足：0＜L≤5μm；可选地，1≤L≤2μm。
  13. 如权利要求1至12任一项所述的正极极片，其中所述正极活性材料包括锂镍钴锰氧化物。
  14. 一种二次电池，包括如权利要求1至13任一项所述的正极极片。
  15. 如权利要求14所述的二次电池，其中所述二次电池还包括电解液，所述电解液中含有双氟磺酰亚胺锂。
  16. 一种用电装置，包括如权利要求14-15任一项所述的二次电池。
PCT/CN2022/129727 2022-11-04 2022-11-04 正极极片、二次电池及用电装置 Ceased WO2024092684A1 (zh)

Priority Applications (4)

Application Number Priority Date Filing Date Title
CN202280098184.2A CN119547214A (zh) 2022-11-04 2022-11-04 正极极片、二次电池及用电装置
EP22963994.3A EP4507019A4 (en) 2022-11-04 2022-11-04 POSITIVE ELECTRODE SHEET, SECONDARY BATTERY AND ELECTRICAL APPLIANCE
PCT/CN2022/129727 WO2024092684A1 (zh) 2022-11-04 2022-11-04 正极极片、二次电池及用电装置
US18/945,251 US20250070186A1 (en) 2022-11-04 2024-11-12 Positive electrode sheet, secondary battery, and electrical device

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2022/129727 WO2024092684A1 (zh) 2022-11-04 2022-11-04 正极极片、二次电池及用电装置

Related Child Applications (1)

Application Number Title Priority Date Filing Date
US18/945,251 Continuation US20250070186A1 (en) 2022-11-04 2024-11-12 Positive electrode sheet, secondary battery, and electrical device

Publications (1)

Publication Number Publication Date
WO2024092684A1 true WO2024092684A1 (zh) 2024-05-10

Family

ID=90929217

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2022/129727 Ceased WO2024092684A1 (zh) 2022-11-04 2022-11-04 正极极片、二次电池及用电装置

Country Status (4)

Country Link
US (1) US20250070186A1 (zh)
EP (1) EP4507019A4 (zh)
CN (1) CN119547214A (zh)
WO (1) WO2024092684A1 (zh)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118888684A (zh) * 2024-09-27 2024-11-01 浙江蓝京新能工业科技有限公司 一种快充电池极片及其制备方法、制造装置和锂离子电池
CN119133635A (zh) * 2024-11-15 2024-12-13 珠海冠宇电池股份有限公司 电芯和电池

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN119920999B (zh) * 2025-02-18 2025-11-11 欣旺达动力科技股份有限公司 一种二次电池及用电装置
CN119993981B (zh) * 2025-04-11 2025-09-12 宁德时代新能源科技股份有限公司 电池单体、电池装置和用电装置
CN121460683A (zh) * 2025-05-12 2026-02-03 宁德时代新能源科技股份有限公司 电池单体、电池装置、用电装置以及储能装置

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002151055A (ja) * 2000-08-28 2002-05-24 Nissan Motor Co Ltd リチウムイオン二次電池
CN109004170A (zh) * 2018-02-26 2018-12-14 宁德新能源科技有限公司 极片和锂离子电池
CN110943201A (zh) * 2019-04-15 2020-03-31 宁德时代新能源科技股份有限公司 一种正极极片和电化学装置
CN110943223A (zh) * 2019-04-15 2020-03-31 宁德时代新能源科技股份有限公司 一种正极极片和电化学装置
WO2021163926A1 (zh) * 2020-02-19 2021-08-26 宁德新能源科技有限公司 正极极片与包含其的电化学装置及电子装置

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105406083A (zh) * 2015-12-17 2016-03-16 湖南高远电池有限公司 一种可快速充放电的锂离子电池及其制造方法
US10516154B2 (en) * 2016-07-01 2019-12-24 Lg Chem, Ltd. Positive electrode for lithium secondary battery and method for preparing the same
CN107154499B (zh) * 2017-04-14 2020-05-15 宁德时代新能源科技股份有限公司 一种含有集流体的锂电池及其制备方法
CN110660995B (zh) * 2018-12-29 2021-03-09 宁德时代新能源科技股份有限公司 一种电极极片和电化学装置

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2002151055A (ja) * 2000-08-28 2002-05-24 Nissan Motor Co Ltd リチウムイオン二次電池
CN109004170A (zh) * 2018-02-26 2018-12-14 宁德新能源科技有限公司 极片和锂离子电池
CN110943201A (zh) * 2019-04-15 2020-03-31 宁德时代新能源科技股份有限公司 一种正极极片和电化学装置
CN110943223A (zh) * 2019-04-15 2020-03-31 宁德时代新能源科技股份有限公司 一种正极极片和电化学装置
WO2021163926A1 (zh) * 2020-02-19 2021-08-26 宁德新能源科技有限公司 正极极片与包含其的电化学装置及电子装置

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See also references of EP4507019A4 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118888684A (zh) * 2024-09-27 2024-11-01 浙江蓝京新能工业科技有限公司 一种快充电池极片及其制备方法、制造装置和锂离子电池
CN119133635A (zh) * 2024-11-15 2024-12-13 珠海冠宇电池股份有限公司 电芯和电池

Also Published As

Publication number Publication date
US20250070186A1 (en) 2025-02-27
EP4507019A4 (en) 2025-12-24
EP4507019A1 (en) 2025-02-12
CN119547214A (zh) 2025-02-28

Similar Documents

Publication Publication Date Title
WO2022032624A1 (zh) 二次电池及其制备方法与包含二次电池的电池模块、电池包及装置
US20230187655A1 (en) Composite current collector, electrode sheet, secondary battery, battery module, battery pack, and electrical apparatus
WO2024092684A1 (zh) 正极极片、二次电池及用电装置
CN116435504B (zh) 电极极片及其制备方法、二次电池、电池模块和电池包
CN118843960A (zh) 正极极片、二次电池及用电装置
EP4235832A1 (en) Positive electrode composite material for lithium-ion secondary battery, positive electrode, and battery
CN115882160A (zh) 复合隔离膜、电化学储能装置及用电装置
CN115832290A (zh) 负极活性材料及其制备方法、负极极片、二次电池、电池模块、电池包和用电装置
EP4528905A1 (en) Separator film and preparation method therefor, secondary battery, and electrical device
CN115810717A (zh) 负极极片及其制备方法、二次电池、电池模块、电池包和用电装置
EP4636929A1 (en) Separator and preparation method therefor, secondary battery and preparation method therefor, and electric device
WO2023130204A1 (zh) 二次电池、电池模块、电池包和用电装置
CN117043983A (zh) 负极极片及其制备方法、二次电池、电池模块、电池包及用电装置
CN115472773A (zh) 电化学装置及用电装置
EP4235902A1 (en) Negative electrode sheet and preparation method therefor, secondary battery, battery module, battery pack, and power-consuming apparatus
WO2024212200A1 (zh) 负极极片以及包含其的二次电池和用电装置
WO2024164109A1 (zh) 预锂化电极材料及其制备方法、二次电池和用电装置
CN118841519A (zh) 负极极片、电池和用电装置
CN118507653A (zh) 负极添加剂、负极极片、二次电池和用电装置
CN119029487A (zh) 隔离膜、二次电池及用电装置
WO2023078071A1 (zh) 正极材料极片、制备方法、二次电池、电池模组、电池包及用电装置
WO2024065764A1 (zh) 负极极片及其制备方法、二次电池和用电装置
CN118020163A (zh) 负极极片、二次电池、电池模组、电池包及用电装置
CN115911748A (zh) 隔膜及其制备方法、二次电池和用电装置
WO2023133805A1 (zh) 一种用于锂离子二次电池的正极复合材料、正极和电池

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 22963994

Country of ref document: EP

Kind code of ref document: A1

WWE Wipo information: entry into national phase

Ref document number: 2022963994

Country of ref document: EP

ENP Entry into the national phase

Ref document number: 2022963994

Country of ref document: EP

Effective date: 20241107

WWE Wipo information: entry into national phase

Ref document number: 202280098184.2

Country of ref document: CN

WWP Wipo information: published in national office

Ref document number: 202280098184.2

Country of ref document: CN

NENP Non-entry into the national phase

Ref country code: DE