WO2023184243A1 - 正极组合物、水系正极浆料及其制备方法、水系正极极片、二次电池及用电装置 - Google Patents

正极组合物、水系正极浆料及其制备方法、水系正极极片、二次电池及用电装置 Download PDF

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WO2023184243A1
WO2023184243A1 PCT/CN2022/084093 CN2022084093W WO2023184243A1 WO 2023184243 A1 WO2023184243 A1 WO 2023184243A1 CN 2022084093 W CN2022084093 W CN 2022084093W WO 2023184243 A1 WO2023184243 A1 WO 2023184243A1
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positive electrode
lithium
optionally
organic solvent
water
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PCT/CN2022/084093
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English (en)
French (fr)
Inventor
陈均桄
程丛
裴海乐
张盛武
李世松
王亚龙
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/084093 priority Critical patent/WO2023184243A1/zh
Priority to CN202280011839.8A priority patent/CN117157779A/zh
Publication of WO2023184243A1 publication Critical patent/WO2023184243A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • 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

  • This application belongs to the field of battery technology, and specifically relates to a positive electrode composition, aqueous positive electrode slurry and a preparation method thereof, aqueous positive electrode sheets, secondary batteries and electrical devices.
  • the positive electrode plate is one of the key factors that determine the performance of the secondary battery.
  • the solvent used for the existing positive electrode slurry is usually an oil-based solvent, such as N-methylpyrrolidone (NMP).
  • NMP N-methylpyrrolidone
  • NMP has high dosage, is volatile, and difficult to Recycling, high toxicity and high cost defects will not only cause serious pollution to the environment, but also endanger people's health. Therefore, it is necessary to develop a low-cost, environmentally friendly and excellent-performance water-based cathode plate.
  • the purpose of this application is to provide a positive electrode composition, aqueous positive electrode slurry and a preparation method thereof, aqueous positive electrode sheets, secondary batteries and electrical devices, which can reduce the irreversible loss of lithium elements and transition metal elements in the positive electrode sheets. , and enable secondary batteries to take into account high energy density and good cycle performance, rate performance and safety performance.
  • a first aspect of the present application provides a cathode composition, including a lithium-containing cathode active material and an organic solvent coating covering at least a portion of the surface of the lithium-containing cathode active material, wherein the lithium-containing cathode active material includes lithium elements and transition metal elements, the boiling point Tm of the organic solvent coating is below 100°C, and the solubility of the organic solvent coating in water at room temperature is below 10%.
  • the surface of the lithium-containing cathode active material particles is less likely to form bound water and lithium on the particle surface.
  • the cathode sheet prepared therefrom has less irreversible loss of lithium elements and transition metal elements, which can improve the energy density and cycle performance of secondary batteries; in addition, the cathode prepared therefrom
  • the pole piece has less moisture content, which can reduce the risk of bulging, corrosion, and severe self-discharge in the secondary battery, and can also reduce the internal resistance of the secondary battery. Therefore, the secondary battery using the cathode composition provided by the present application can simultaneously achieve high energy density and good cycle performance, rate performance and safety performance.
  • the transition metal element includes one or more of Fe, Ni, Co, Mn, Al, Cu, Zn, and Ti.
  • the organic solvent coating has a boiling point Tm between 30°C and 100°C, optionally between 40°C and 60°C.
  • Tm boiling point
  • the boiling point of the organic solvent coating is within a suitable range, it is beneficial to further reduce the internal resistance of the secondary battery and significantly improve the rate performance and cycle performance of the secondary battery.
  • the solubility of the organic solvent coating in water at room temperature is below 1%, optionally between 0.01% and 1%.
  • the solubility of the organic solvent coating is within a suitable range, it is conducive to giving full play to its protective effect on the surface of the lithium-containing cathode active material particles, thereby further reducing the internal resistance of the secondary battery and significantly improving the rate performance and performance of the secondary battery. Cycle performance.
  • the organic solvent coating includes aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, alcohols, phenols, esters, ketones, ethers, alcohol ethers, ester ethers, nitriles, and sulfides. one or more.
  • the organic solvent coating includes benzene, hexane, isohexane, n-heptane, isooctane, 2,2-dimethylpentane, 3-methylpentane, cyclopentane, cyclopentane, One or more of hexane, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, carbon disulfide, methyl acetate, and ethyl acetate.
  • organic solvent coatings have appropriate boiling points and solubility, which can better prevent the surface of lithium-containing cathode active material particles from combining with the solvent water in the slurry to form bound water, and at the same time effectively reduce the amount of lithium elements on the surface of lithium-containing cathode active material particles. With the dissolution of transition metal elements, the secondary battery can better balance high energy density with good cycle performance and rate performance. In addition, these organic solvent coatings can also speed up water removal efficiency, reduce the moisture content of the positive electrode piece, and alleviate the cracking of the positive electrode film.
  • the positive electrode composition further includes one or more of a dispersant, an aqueous binder, and a conductive agent.
  • the mass percentage of the lithium-containing cathode active material is 88%-99%, optionally 90%-94%.
  • the mass percentage of the organic solvent coating is 0.01%-10%, optionally 3%-7%.
  • the content of the organic solvent coating is within an appropriate range, it can better prevent the surface of the lithium-containing cathode active material particles from combining with the solvent water in the slurry to form bound water, while further reducing the lithium element on the surface of the lithium-containing cathode active material particles. and the dissolution of transition metal elements, further improving the energy density and cycle performance of secondary batteries.
  • the mass percentage of the dispersant is less than 0.7%, optionally 0.1%-0.5%.
  • the mass percentage of the aqueous binder is less than 5%, optionally 2%-4%.
  • the mass percentage of the conductive agent is less than 5%, optionally 0.5%-3%.
  • the dispersant includes anionic dispersant, cationic dispersant, nonionic dispersant, amphoteric dispersant, electrically neutral dispersant, polymer dispersant, and controlled free radical dispersant.
  • One or more of the dispersants optionally include one or more of polyethyleneimine, sodium dodecyl sulfonate, polyvinyl alcohol, and polyethylene glycol octylphenyl ether.
  • the aqueous binder includes methylcellulose and salts thereof, xanthan gum and salts thereof, chitosan and salts thereof, alginic acid and salts thereof salt, polyethyleneimine and its salts, polyacrylamide, acrylonitrile-acrylic acid copolymer and its derivatives, or mixtures thereof.
  • the aqueous adhesive includes a compound mixture of xanthan gum and polyethyleneimine.
  • the mass ratio of the xanthan gum and the polyethyleneimine is 2:1-0.2:2.8.
  • the number average molecular weight of the xanthan gum is 300000-2000000, and the number average molecular weight of the polyethyleneimine is 2000-50000.
  • the aqueous binder includes a compound mixture of acrylonitrile-(meth)acrylic acid copolymer and polyethyleneimine.
  • the mass ratio of the acrylonitrile-(meth)acrylic acid copolymer and the polyethyleneimine is 2:1-0.2:2.8.
  • the number average molecular weight of the acrylonitrile-(meth)acrylic acid copolymer is 300,000-2,000,000, and the number average molecular weight of the polyethyleneimine is 2,000-70,000.
  • a second aspect of the application provides an aqueous cathode slurry, including solvent water and the cathode composition of the first aspect of the application.
  • the solid content of the aqueous cathode slurry is 40%-90%, optionally 50%-70%.
  • the water-based cathode slurry has better dispersion and higher stability.
  • the cathode sheet prepared therefrom has a lower moisture content and the film layer is less likely to crack.
  • the viscosity of the aqueous cathode slurry is 100cp-10000cp, optionally 3000cp-7000cp.
  • the viscosity of the water-based cathode slurry is within a suitable range, the water-based cathode slurry has better dispersion and higher stability.
  • the cathode sheet prepared therefrom has a lower moisture content and the film layer is less likely to crack.
  • the third aspect of this application provides a method for preparing a water-based cathode slurry, which is used to prepare the water-based cathode slurry of the second aspect of this application, including the step of: S100, uniformly mixing the lithium-containing cathode active material and the organic solvent coating to form Dump; S200, mix the obtained dough, conductive agent, water-based binder and solvent water evenly to obtain a water-based positive electrode slurry.
  • an organic solvent coating material with a T m of 100° C. or less and a room temperature solubility of 10% or less is added, and the organic solvent coating material is coated on at least part of the surface of the lithium-containing cathode active material particles. Then mixed with other components, it can prevent the surface of the lithium-containing cathode active material particles from combining with the solvent water in the slurry to form bound water, and at the same time reduce the dissolution of lithium elements and transition metal elements on the surface of the lithium-containing cathode active material particles, thereby preparing it
  • the irreversible loss of lithium elements and transition metal elements in the positive electrode sheet is less, and the secondary battery has higher energy density and better cycle performance.
  • the positive electrode sheet obtained through the preparation method of the present application has less moisture content and less residual organic solvent coating. It can also reduce the risk of bulging, corrosion, and severe self-discharge in the secondary battery, and reduce the internal resistance of the secondary battery. .
  • a fourth aspect of the present application provides a water-based positive electrode sheet, including a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, wherein the positive electrode film layer is the water-based positive electrode slurry of the second aspect of the present application.
  • the mass fraction W 1 of the transition metal element in the region 100 nm away from the surface of the lithium-containing cathode active material particles is equal to the mass fraction W 1 of the transition metal element in the region 100 nm away from the center of the lithium-containing cathode active material particle.
  • the ratio of W2 is ⁇ , ⁇ is 60%-100%, optionally 70%-100%.
  • the thickness of the positive electrode film layer is H, the porosity P 1 in the area of the positive electrode film layer H/3 from the surface, and the distance in the positive electrode film layer H/3 from the positive electrode current collector.
  • the ratio of the porosity P2 in the area is ⁇ , and ⁇ is 1.15-2.0, optionally 1.40-1.60.
  • the positive electrode film layer of the present application exhibits the characteristic that the porosity of the surface area is significantly higher than that of the inner layer area, which is beneficial to the electrolyte to better infiltrate the positive electrode film layer, accelerate the transmission of lithium ions, and reduce the internal resistance of the battery, so it can further Improve the energy density, cycle performance and rate performance of secondary batteries.
  • the mass content of the organic solvent coating is below 5000 ppm, optionally below 200 ppm.
  • the moisture mass content of the water-based positive electrode sheet after vacuum drying at 80° C. for 6 hours is below 400 ppm, optionally below 200 ppm.
  • a fifth aspect of the present application provides a secondary battery, including the aqueous positive electrode sheet of the fourth aspect of the present application.
  • a sixth aspect of the present application provides an electrical device, including the secondary battery of the fifth aspect of the present application.
  • the water-based positive electrode sheet of the present application can have lower moisture content and organic solvent coating residue, and the irreversible loss of lithium elements and transition metal elements is also less; at the same time, the positive electrode film layer of the present application also shows a surface area.
  • the porosity is significantly higher than the inner layer area, which helps the electrolyte to better infiltrate the positive electrode film layer, accelerate the transmission of lithium ions, and reduce the internal resistance of the battery. Therefore, the secondary battery using the water-based positive electrode sheet of the present application can simultaneously take into account high energy density and good cycle performance, rate performance and safety performance.
  • the electrical device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. 1 .
  • FIG. 3 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of a power consumption device including the secondary battery of the present application as a power source.
  • Figure 7 is a scanning electron microscope (SEM) picture of the positive electrode plate prepared in Example 1.
  • Figure 8 is an X-ray energy spectrometer (EDS) spectrum of the positive electrode plate prepared in Example 1.
  • Embodiments specifically disclosing the cathode composition, the aqueous cathode slurry and the preparation method thereof, the aqueous cathode sheet, the secondary battery and the electrical device of the present application will be described in detail below with appropriate reference to the drawings. However, unnecessary detailed explanations may be omitted. For example, detailed descriptions of well-known matters may be omitted, or descriptions of substantially the same structure may be repeated. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • 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.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: 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).
  • room temperature refers to 20°C ⁇ 2°C.
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.
  • a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte, a separator, etc.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through.
  • the electrolyte plays a role in conducting active ions between the positive electrode piece and the negative electrode piece.
  • Aqueous cathode slurries using water as solvent have attracted more and more attention from researchers due to their low cost and environmental friendliness.
  • the inventor's research found that lithium ions and transition metal ions are easily precipitated on the surface of the positive electrode active material particles in the presence of solvent water, which affects the energy density and cycle performance of the secondary battery.
  • the water-based cathode slurry also has defects such as poor fluidity and difficulty in dispersion.
  • the cathode sheets prepared using the water-based cathode slurry also have defects such as difficulty in removing water, high moisture content, and easy cracking of the cathode film layer.
  • the inventor of the present application has proposed a cathode composition suitable for use in aqueous cathode slurry after extensive research and practice.
  • the first aspect of the embodiment of the present application provides a cathode composition, including a lithium-containing cathode active material and an organic solvent coating covering at least a part of the surface of the lithium-containing cathode active material.
  • the lithium-containing cathode active material includes Lithium element and transition metal element, the boiling point Tm of the organic solvent coating material is below 100°C, and the solubility of the organic solvent coating material in water at room temperature is below 10%.
  • the inventor found that after coating at least part of the surface of the lithium-containing cathode active material particles with an organic solvent coating with a Tm below 100°C and a room temperature solubility below 10%, the activity of the lithium-containing cathode can be reduced.
  • the dissolution of lithium elements and transition metal elements on the surface of the material particles also serves to prevent the surface of the lithium-containing cathode active material particles from combining with the solvent water in the slurry to form bound water.
  • the organic solvent coating used in this application has the characteristics of low boiling point and low solubility, it can also reduce the overall boiling point of the slurry, increase the water removal efficiency of the positive electrode piece, and reduce the moisture content of the positive electrode piece.
  • the organic solvent coating of the present application can also play a certain plasticizing effect in the slurry, thereby improving the dispersion of the slurry and alleviating the problem of cracking of the positive electrode film.
  • the surface of the lithium-containing cathode active material particles is less likely to form bound water and particles.
  • the positive electrode sheet has less moisture content, which can reduce the risk of bulging, corrosion, and severe self-discharge in the secondary battery, and can also reduce the internal resistance of the secondary battery. Therefore, the secondary battery using the cathode composition provided by the present application can simultaneously achieve high energy density and good cycle performance, rate performance and safety performance.
  • the boiling point Tm of the organic solvent coating When the boiling point Tm of the organic solvent coating is below 100°C, it can reduce its residual amount in the positive electrode piece, which is beneficial to reducing the internal resistance of the secondary battery and improving the rate performance and cycle performance of the secondary battery.
  • the boiling point Tm of the organic solvent coating may be between 30°C and 100°C, between 30°C and 90°C, between 30°C and 80°C, and between 30°C and 70°C. , between 30°C and 60°C, between 40°C and 100°C, between 40°C and 90°C, between 40°C and 80°C, between 40°C and 70°C, between 40°C and 60°C.
  • the boiling point of the organic solvent coating When the boiling point of the organic solvent coating is within a suitable range, it is beneficial to further reduce the internal resistance of the secondary battery and significantly improve the rate performance and cycle performance of the secondary battery.
  • the solubility of the organic solvent coating in water at room temperature is less than 10%, which is beneficial to ensure that the organic solvent coating is coated on the surface of the lithium-containing cathode active material particles during the stirring and dispersion process of the cathode slurry, preventing the large amount of organic solvent coating from occurring. Dissolved in solvent water and loses its protective effect on the surface of lithium-containing cathode active material particles.
  • the solubility of the organic solvent coating in water at room temperature may be below 8%, below 5%, below 3%, below 2%, or below 1%.
  • the solubility of the organic solvent coating in water at room temperature is 0.01%-5%, 0.01%-3%, 0.01%-2%, or 0.01%-1%.
  • solubility of the organic solvent coating is within a suitable range, it is conducive to fully exerting its protective effect on the surface of the lithium-containing cathode active material particles, thereby further reducing the internal resistance of the battery and significantly improving the rate performance and cycle performance of the secondary battery.
  • the boiling point Tm of the organic solvent coating is between 40°C and 60°C, and the solubility of the organic solvent coating in water at room temperature is 0.01%-1%.
  • the organic solvent coating can fully exert the protective effect on the surface of the lithium-containing cathode active material particles and reduce the internal resistance of the battery. Therefore, the secondary battery can not only have high energy density, but also have significantly improved rate performance and cycle performance. performance.
  • the organic solvent coating includes aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, alcohols, phenols, esters, ketones, ethers, alcohol ethers, ester ethers, nitriles, and sulfides. one or more.
  • the organic solvent coating includes benzene, hexane, isohexane, n-heptane, isooctane, 2,2-dimethylpentane, 3-methylpentane, cyclopentane, cyclopentane, One or more of hexane, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, carbon disulfide, methyl acetate, and ethyl acetate.
  • the organic solvent coating includes one or more of hexane, isohexane, cyclopentane, carbon tetrachloride, carbon disulfide, methyl acetate, and ethyl acetate.
  • the organic solvent coating includes one or more of isohexane, cyclopentane, and carbon disulfide.
  • organic solvent coatings have appropriate boiling points and solubility, which can better prevent the surface of lithium-containing cathode active material particles from combining with the solvent water in the slurry to form bound water, and at the same time effectively reduce the amount of lithium elements on the surface of lithium-containing cathode active material particles. With the dissolution of transition metal elements, the secondary battery can better balance high energy density with good cycle performance and rate performance. In addition, these organic solvent coatings can also speed up water removal efficiency, reduce the moisture content of the positive electrode piece, and alleviate the cracking of the positive electrode film.
  • the organic solvent coating may cover more than 70% of the surface of the lithium-containing cathode active material.
  • the organic solvent coating covers more than 80% of the surface of the lithium-containing cathode active material.
  • the organic solvent coating covers more than 90% of the surface of the lithium-containing cathode active material. In particular, the organic solvent coating completely covers the surface of the lithium-containing cathode active material.
  • the organic solvent coating When the organic solvent coating is located on most or even all surfaces of the lithium-containing cathode active material, it can better prevent the surface of the lithium-containing cathode active material particles from combining with the solvent water in the slurry to form bound water, while further reducing the risk of lithium-containing cathode active materials.
  • the dissolution of lithium elements and transition metal elements from the surface of active material particles further improves the energy density and cycle performance of secondary batteries.
  • the transition metal element includes one or more of Fe, Ni, Co, Mn, Al, Cu, Zn, and Ti.
  • the lithium-containing cathode active material includes LiFePO 4 (LFP), LiMnPO 4 , LiFe 0.9 Mn 0.1 PO 4 , LiFe 0.8 Mn 0.2 PO 4 , LiFe 0.7 Mn 0.3 PO 4 , LiFe 0.6 Mn 0.4 PO 4 , LiFe 0.5 Mn 0.5 PO 4 , Li(Ni 0.5 Co 0.2 Mn 0.3 )O 2 (NCM523), Li(Ni 0.6 Co 0.2 Mn 0.2 )O 2 (NCM622), Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 (NCM811) , one or more of Li(Ni 0.8 Co 0.15 Al 0.05 )O 2 .
  • LFP LiFePO 4
  • LiMnPO 4 LiFe 0.9 Mn 0.1 PO 4
  • LiFe 0.8 Mn 0.2 PO 4 LiFe 0.7 Mn 0.3 PO 4
  • LiFe 0.6 Mn 0.4 PO 4 LiFe 0.5 M
  • the cathode composition further includes an aqueous binder.
  • the water-based adhesive can bond the positive active material, conductive agent, etc. to the current collector, enhance the contact between the positive active material and the conductive agent and between the positive active material and the current collector, and stabilize the structure of the positive electrode piece.
  • oil-based adhesives such as polyvinylidene fluoride
  • water-based adhesives are lower in cost, more environmentally friendly, and safer to use.
  • the water-based adhesive may include an aqueous dispersion solution or emulsion with a solid component content of more than 5%.
  • the water-based adhesive may also include solids that can form a stable dispersion with water with a solid component content of more than 1%.
  • the water-based adhesive includes soluble polysaccharides and their derivatives, water-soluble or water-dispersed polymers, or mixtures thereof.
  • the water-based adhesive includes but is not limited to methylcellulose and its salts (such as lithium methylcellulose, sodium methylcellulose, potassium methylcellulose, etc.), xanthan gum and its salts, chitosan Sugar and its salts, alginic acid and its salts (such as lithium alginate, sodium alginate, potassium alginate, etc.), polyethyleneimine and its salts, polyacrylamide, acrylonitrile-(meth)acrylic acid copolymer and its derivatives, or mixtures thereof.
  • methylcellulose and its salts such as lithium methylcellulose, sodium methylcellulose, potassium methylcellulose, etc.
  • xanthan gum and its salts such as lithium methylcellulose, sodium methylcellulose, potassium methylcellulose, etc.
  • chitosan Sugar and its salts such as lithium alginate, sodium alginate, potassium alginate,
  • the aqueous adhesive includes a compound mixture of xanthan gum and polyethyleneimine.
  • the mass ratio of the xanthan gum and the polyethyleneimine is 2:1-0.2:2.8.
  • the number average molecular weight of the xanthan gum is 300000-2000000, and the number average molecular weight of the polyethyleneimine is 2000-50000.
  • the water-based adhesive includes a compound mixture of acrylonitrile-(meth)acrylic acid copolymer and polyethyleneimine.
  • the mass ratio of the acrylonitrile-(meth)acrylic acid copolymer and the polyethyleneimine is 2:1-0.2:2.8.
  • the number average molecular weight of the acrylonitrile-(meth)acrylic acid copolymer is 300,000-2,000,000, and the number average molecular weight of the polyethyleneimine is 2,000-70,000.
  • the cathode composition further includes a conductive agent.
  • a conductive agent This application has no particular limitation on the type of conductive agent.
  • it may include one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. or more.
  • the positive electrode composition further includes a dispersant, which can further improve the stability of the slurry and make it less likely to settle.
  • the dispersant includes one of anionic dispersants, cationic dispersants, nonionic dispersants, amphoteric dispersants, electrically neutral dispersants, polymer dispersants, and controlled free radical dispersants. or more.
  • the dispersant includes, but is not limited to, one or more of polyethyleneimine, sodium dodecyl sulfonate, polyvinyl alcohol, and polyethylene glycol octylphenyl ether.
  • the positive electrode composition further includes two or more types of aqueous binders, conductive agents, and dispersants.
  • the mass percentage of the lithium-containing cathode active material is 88%-99% based on the total mass of the cathode composition.
  • the mass percentage of the lithium-containing cathode active material is 90%-94%.
  • the mass percentage of the organic solvent coating is 0.01%-10% based on the total mass of the cathode composition.
  • the mass percentage of the organic solvent coating is 3%-7%.
  • the content of the organic solvent coating is within an appropriate range, it can better prevent the surface of the lithium-containing cathode active material particles from combining with the solvent water in the slurry to form bound water, while further reducing the lithium element on the surface of the lithium-containing cathode active material particles. and the dissolution of transition metal elements, further improving the energy density and cycle performance of secondary batteries.
  • the content of the organic solvent coating should not be too much.
  • the residual amount of the organic solvent coating in the prepared positive electrode sheet may increase, which may affect the internal resistance of the secondary battery; the content of the organic solvent coating
  • the stability of the slurry may decrease, for example, sedimentation may occur more easily.
  • the drying time of the slurry is shortened and the drying speed is accelerated, and the film layer in the cathode sheet prepared thereby may Will be more susceptible to cracking.
  • the mass percentage of the dispersant is less than 0.7% based on the total mass of the cathode composition.
  • the mass percentage of the dispersant is 0.1%-0.5%.
  • the mass percentage of the aqueous binder is less than 5% based on the total mass of the cathode composition.
  • the mass percentage of the water-based adhesive is 2%-4%.
  • the mass percentage of the conductive agent is less than 5% based on the total mass of the cathode composition.
  • the mass percentage of the conductive agent is 0.5%-3%.
  • the second aspect of the embodiment of the present application provides an aqueous cathode slurry, including solvent water and the positive electrode composition of the first aspect of the embodiment of the present application.
  • the solid content of the aqueous cathode slurry is 40%-90%.
  • the solid content of the aqueous cathode slurry is 50%-70%.
  • the water-based cathode slurry has better dispersion and higher stability.
  • the cathode sheet prepared therefrom has a lower moisture content and the film layer is less likely to crack.
  • the stability of the slurry may decrease, for example, it is more likely to settle.
  • the solvent content is high, so that during the drying process of the slurry The drying time required is longer and the drying temperature is higher, and the film layer in the cathode sheet prepared by this method may be more susceptible to cracking.
  • the uniformity of the slurry may become poor and coating of the slurry may become difficult.
  • the viscosity of the aqueous cathode slurry (in this application, the viscosity at room temperature) is 100 cp-10000 cp.
  • the viscosity of the aqueous cathode slurry is 3000cp-7000cp.
  • the water-based cathode slurry has better dispersion and higher stability.
  • the cathode sheet prepared therefrom has a lower moisture content and the film layer is less likely to crack.
  • the stability of the slurry may decrease, for example, settlement is more likely to occur.
  • the viscosity of the water-based cathode slurry is low, the solvent content is high, which requires a large amount of solvent during the drying process of the slurry. If the drying time is longer and the drying temperature is higher, the film layer in the cathode sheet prepared by this method may be more susceptible to cracking.
  • the viscosity of the aqueous cathode slurry is high, it may become difficult to apply the slurry.
  • the viscosity of the slurry has a well-known meaning in the art and can be measured using instruments and methods well-known in the art. For example, you can refer to GB/T 2794-2013 "Determination of Adhesive Viscosity by Single Cylinder Rotational Viscometer Method" for measurement.
  • the third aspect of the embodiment of the present application provides a method for preparing aqueous cathode slurry, including the steps: S100, mix the lithium-containing cathode active material and the organic solvent coating to form a dough; S200, mix the obtained dough The material, conductive agent, water-based binder and solvent water are evenly mixed to obtain a water-based positive electrode slurry.
  • the preparation method of aqueous cathode slurry provided in this application can prepare the aqueous cathode slurry of the second aspect of the embodiment of this application.
  • an organic solvent coating material with a T m of 100° C. or less and a room temperature solubility of 10% or less is added, and the organic solvent coating material is coated on at least part of the surface of the lithium-containing cathode active material particles. Then mixed with other components, it can prevent the surface of the lithium-containing cathode active material particles from combining with the solvent water in the slurry to form bound water, and at the same time reduce the dissolution of lithium elements and transition metal elements on the surface of the lithium-containing cathode active material particles, thereby preparing it
  • the irreversible loss of lithium elements and transition metal elements in the positive electrode sheet is less, and the secondary battery has higher energy density and better cycle performance.
  • the positive electrode sheet obtained through the preparation method of the present application has less moisture content and less residual organic solvent coating. It can also reduce the risk of bulging, corrosion, and severe self-discharge in the secondary battery, and reduce the internal resistance of the secondary battery. .
  • a dispersant can also be added to S200.
  • the fourth aspect of the embodiment of the present application provides a water-based positive electrode sheet, including a positive current collector and a positive electrode film layer located on at least one surface of the positive current collector, wherein the positive electrode film layer is the second aspect of the embodiment of the present application.
  • the positive electrode film layer may be formed by coating the aqueous positive electrode slurry on the positive electrode current collector and subjecting it to processes such as drying and cold pressing.
  • the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the water-based positive electrode sheet of the present application can have lower moisture content and organic solvent coating residue, and the irreversible loss of lithium elements and transition metal elements is also less; at the same time, the positive electrode film layer of the present application also shows a surface area.
  • the porosity is significantly higher than the inner layer area, which helps the electrolyte to better infiltrate the positive electrode film layer, accelerate the transmission of lithium ions, and reduce the internal resistance of the battery. Therefore, the secondary battery using the water-based positive electrode sheet of the present application can simultaneously take into account high energy density and good cycle performance, rate performance and safety performance.
  • the mass fraction W 1 of the transition metal element in the region 100 nm from the surface of the lithium-containing cathode active material particles is equal to the 100 nm distance between the lithium-containing cathode active material particles and the center of the particle.
  • the ratio of the mass fraction W 2 of transition metal elements in the region is ⁇ , and ⁇ is 60%-100%.
  • ⁇ can be 70%-100%, 75%-100%, 80%-100%.
  • the higher the ⁇ value the less the surface of the lithium-containing cathode active material particles is affected by the solvent water, the less transition metals are eluted, and the more stable the particle crystal structure is.
  • ⁇ is more than 60%, more than 70%, more than 75%, or even more than 80%.
  • the “particle center” refers to the center of the sphere; when the positive active material particles are irregularly shaped, the intersection of the longest diagonal line and the shortest diagonal line of the particle can be taken as particle center.
  • the parameter ⁇ of the lithium-containing cathode active material in the aqueous cathode plate can be obtained by the following test method.
  • Cut a sample of a certain area from the water-based positive electrode piece for example, the length is 4cm to 8cm, the width is 4cm to 8cm
  • a CP ion cross-section polisher such as IB-19500 model
  • Surface samples use a scanning electron microscope (SEM, such as ZEISSsigma 300 model) and an X-ray energy spectrometer (EDS, such as Horiba 7021-H model) for SEM-EDS testing.
  • SEM scanning electron microscope
  • EDS X-ray energy spectrometer
  • JY/T 010-1996 you can refer to JY/T 010-1996 to observe the sample Distribution of elements in the medium; select the cross section of the lithium-containing cathode active material particle in the SEM-EDX picture, test the mass fraction W 1 of the transition metal element in any area 100nm from the surface of the cross section, and then test the mass fraction W 1 of the transition metal element 100nm from the center of the particle.
  • the mass fraction W 2 of transition metal elements in any region, parameter ⁇ (W 1 /W 2 ) ⁇ 100%.
  • multiple areas of the cross-section of the lithium-containing cathode active material particles can be tested and then averaged.
  • test on the positive electrode plate can be performed by sampling and testing during the preparation process of the secondary battery, or by sampling and testing from the prepared secondary battery.
  • the sampling can be performed as follows.
  • Discharge the secondary battery for safety reasons, generally keep the battery in a fully discharged state; remove the positive electrode piece after disassembling the battery, and soak the positive electrode piece in dimethyl carbonate (DMC) for a certain period of time (for example, 2-10 hours); then take out the positive electrode piece and dry it at a certain temperature and time (for example, 60°C, 4 hours). After drying, take out the positive electrode piece.
  • DMC dimethyl carbonate
  • the lithium-containing positive electrode activity can be taken during the test.
  • the mass fraction of transition metal elements in the region 120nm to 220nm from the surface of the cross-section of the material particles is regarded as W 1 to ensure the accuracy of the test results.
  • the thickness H of the positive electrode film layer is not specifically limited, and may be, for example, 50 ⁇ m-500 ⁇ m.
  • the thickness of the positive electrode film layer has a well-known meaning in the art, and can be measured using methods known in the art, such as using a spiral micrometer.
  • the thickness of the positive electrode film layer is H, the porosity P 1 in the area H/3 of the positive electrode film layer from the surface, and the distance of H/3 of the positive electrode film layer from the positive electrode current collector.
  • the ratio of porosity P 2 in the region is ⁇ , and ⁇ is 1.15-2.0.
  • ⁇ is 1.20-2.0, 1.25-2.0, 1.30-2.0, 1.35-2.0, 1.40-2.0, 1.20-1.70, 1.25-1.70, 1.30-1.70, 1.35-1.70, 1.40-1.70, 1.20-1.60, 1.25-1.60, 1.30-1.60, 1.35-1.60 or 1.40-1.60.
  • the positive electrode film layer of the present application exhibits the characteristic that the porosity of the surface area is significantly higher than that of the inner layer area, which is beneficial to the electrolyte to better infiltrate the positive electrode film layer, accelerate the transmission of lithium ions, and reduce the internal resistance of the battery, so it can further Improve the energy density, cycle performance and rate performance of secondary batteries.
  • the organic solvent coating used in this application has the characteristics of low boiling point and low solubility, which is easier to float during the slurry drying process. Therefore, the porosity of the surface area of the positive electrode film layer will be significantly higher than that of the inner layer. area.
  • the porosity of the positive electrode film layer has a meaning known in the art, and can be tested using methods known in the art. For example, it can be measured with reference to GB/T 24586-2009.
  • the mass content (ie, residual amount) of the organic solvent coating is less than 5000 ppm.
  • the mass content of the organic solvent coating is below 2000 ppm, below 1000 ppm, below 500 ppm, below 200 ppm, below 100 ppm, or even below 80 ppm.
  • the mass content of the organic solvent coating can be measured using gas chromatography-mass spectrometry (GC-MS).
  • the moisture mass content (i.e., residual amount) of the positive electrode piece after vacuum drying at 80° C. for 6 hours can be below 400 ppm.
  • the moisture mass content of the positive electrode piece after vacuum drying at 80° C. for 6 hours can be below 300 ppm, below 200 ppm, or even below 180 ppm.
  • the moisture content of the positive electrode sheet after vacuum drying at 80°C for 6 hours can be tested as follows: Coat the aqueous positive electrode slurry on the positive electrode current collector, and then place it in a drying room (dew point ⁇ -30°C) Vacuum dry in a vacuum oven at 80°C for 6 hours to obtain the dried positive electrode film layer; weigh 0.6g-1g powder sample from the dried positive electrode film layer (for example, use a blade to scrape the powder for sampling) and place it in the moisture test box Check moisture content.
  • the moisture test box is a Karl Fischer moisture meter, and the weighing instrument can be an electronic balance.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys.
  • the polymer material base layer may include polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) one or more.
  • the above-mentioned tests on the positive electrode plates can be performed by sampling and testing during the preparation process of the secondary battery, or by sampling and testing from the prepared secondary battery.
  • the above test method given in this application is for the positive electrode film layer on one side of the positive electrode current collector. When the positive electrode film layer is arranged on both sides of the positive electrode current collector, the test results of the positive electrode film layer on either side are If this application is satisfied, it is deemed to fall within the protection scope of this application.
  • a fifth aspect of the embodiment of the present application provides a secondary battery, including a positive electrode plate, a negative electrode plate and an electrolyte.
  • a secondary battery including a positive electrode plate, a negative electrode plate and an electrolyte.
  • active ions are embedded and detached back and forth between the positive electrode piece and the negative electrode piece, and the electrolyte acts as a conductor between the positive electrode piece and the negative electrode piece. The role of active ions.
  • the positive electrode sheet used in the secondary battery of the present application is the water-based positive electrode sheet of the fourth aspect of the embodiment of the present application.
  • 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.
  • the negative electrode current collector has two surfaces opposite 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 can be a metal foil or a composite current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer may include polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) one or more.
  • the negative electrode film layer usually contains negative electrode active materials, optional binders, optional conductive agents, and other optional auxiliaries.
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry coating is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or water, but is not limited thereto.
  • the adhesive used for the negative electrode film layer may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, polysodium acrylate PAAS ), one or more of polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS).
  • the conductive agent used for the negative electrode film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • Other optional auxiliaries may include thickeners (eg, sodium carboxymethylcellulose CMC), PTC thermistor materials, etc.
  • the negative active material a negative active material for secondary batteries known in the art can be used.
  • the negative active material may include natural graphite, artificial graphite, soft carbon, hard carbon, mesophase microcarbon spheres, silicon-based materials, tin-based materials, lithium titanate, Li-Sn alloy, Li-Sn-O alloy, One or more Li-Al alloys.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitride composite, and silicon alloy materials.
  • the tin-based material may include one or more of elemental tin, tin oxide, and tin alloy materials.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode sheet of the present application does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode sheet of the present application further includes a conductive undercoat layer (for example, composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector.
  • the negative electrode sheet of the present application further includes a protective layer covering the surface of the negative electrode film layer.
  • the electrolyte may include one or more of a solid electrolyte and a liquid electrolyte (i.e., electrolyte).
  • the electrolyte is an electrolyte solution including an electrolyte salt and a solvent.
  • the types of the electrolyte salt and the solvent are not specifically limited and can be selected according to actual needs.
  • the electrolyte salt may include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonimide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonate borate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), one or more of lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium perchlorate
  • the solvent may include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropylene carbonate Ester (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), acetic acid Propyl ester (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4- One or more of butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).
  • EC ethylene carbonate
  • the electrolyte optionally further includes additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery performance. Additives for low temperature power performance, etc.
  • the additive may include, but is not limited to, one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), and 1,3-propanesultone (PS).
  • Secondary batteries using electrolytes and some secondary batteries using solid electrolytes also include a separator.
  • the isolation film is disposed between the positive electrode piece and the negative electrode piece, and mainly functions to prevent the positive and negative electrodes from short-circuiting, and at the same time, allows active ions to pass through.
  • the material of the isolation membrane may be selected from one or more of fiberglass, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film may be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different.
  • the positive electrode piece, the multi-layer composite isolation film and the negative electrode piece can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and 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 bag, such as a bag-type soft bag.
  • the soft bag may be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.
  • This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. As shown in FIG. 1 , a square-structured secondary battery 5 is shown as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or several, and can be adjusted according to needs.
  • the secondary batteries according to the present application can be assembled into a battery module.
  • the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a schematic diagram of the battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte may be assembled to form a secondary battery.
  • the positive electrode sheet, isolation film, and negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process.
  • the electrode assembly is placed in an outer package, dried, and then injected with electrolyte. After vacuum packaging, standing, and Through processes such as formation and shaping, secondary batteries are obtained.
  • a sixth aspect of the embodiment of the present application provides an electrical device.
  • the electrical device includes one or more of the secondary battery, battery module, or battery pack of the present application.
  • the secondary battery, battery module or battery pack may be used as a power source for the electrical device or as an energy storage unit for the electrical device.
  • the electrical device may be, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric Golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the power-consuming device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 6 is a schematic diagram of an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • battery packs or battery modules can be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the electrical device is usually required to be light and thin, and secondary batteries can be used as power sources.
  • the water-based adhesive is a mixture of acrylonitrile-acrylic acid copolymer LA-133 and polyethyleneimine with a mass ratio of 1:1.
  • the solvent deionized water is thoroughly stirred and mixed to form a negative electrode slurry; the negative electrode slurry is evenly coated on the surface of the negative electrode current collector copper foil, and after drying, cold pressing, and cutting, the negative electrode pieces are obtained.
  • Polypropylene film is used as the isolation film.
  • the above-mentioned positive electrode sheets, isolation films, and negative electrode sheets are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer packaging aluminum shell, baked at 80°C, the above-mentioned electrolyte is added, and then vacuum sealed , standing, hot and cold pressing, formation, shaping, capacity testing and other processes, the secondary battery is obtained.
  • the preparation method of the secondary battery is similar to Example 1, except that the preparation parameters of the positive electrode sheet are different. See Table 1 for details.
  • the preparation method of the secondary battery is similar to Example 1, except that the organic solvent coating isohexane is not added during the preparation process of the positive electrode sheet.
  • the moisture test box is a Karl Fischer moisture meter, and the weighing instrument can be an electronic balance.
  • Discharge the secondary battery (for safety reasons, generally keep the battery in a fully discharged state); remove the positive electrode piece after disassembling the battery, and soak the positive electrode piece in dimethyl carbonate (DMC) for 4 hours; then remove the positive electrode piece. Take out the piece and dry it at 60°C for 4 hours. After drying, take out the positive electrode piece and scrape the powder.
  • the obtained powder will be sent to a gas chromatography-mass spectrometer (GC-MS) for testing. Specifically, the powder was placed in an Al 2 O 3 crucible, shaken flat, and covered with a lid. The parameters were set to: nitrogen atmosphere, purge gas 60 mL/min, and protective gas 20 mL/min. The temperature rise program is set to: 10°C/min, 35°C to 600°C.
  • Cut a sample of about 6cm ⁇ 6cm from the freshly prepared positive electrode sheet, and polish it using the IB-19500CP ion cross-section polisher to obtain a polished sample with a cut surface refer to JY/T 010-1996, use ZEISS sigma 300 scanning electron microscope and Horiba 7021-H X-ray energy spectrometer for SEM-EDS testing to observe the distribution of elements in the sample; select the cross-section of the positive active material particles in the SEM-EDX picture and test the cross-section to be 100nm from the surface
  • the mass fraction W 1 of the transition metal element in the region is measured, and then the mass fraction W 2 of the transition metal element in the region 100 nm away from the center of the particle is measured.
  • the parameter ⁇ W 1 /W 2 .
  • ⁇ the less the loss of transition metal elements on the surface of the cathode active material particles.
  • multiple points for example, 5 to 10 can be randomly selected for testing on the surface of the positive active material particles and corresponding areas in the center of the particles, and then the average value is taken as the test result.
  • the capacity retention rate of the secondary battery after 300 cycles (discharge capacity after the 300th cycle/initial capacity) ⁇ 100%.
  • the internal resistance growth rate of the secondary battery after 300 cycles (internal resistance after the 300th cycle/internal resistance after the first cycle) ⁇ 100%.
  • Table 1 shows the test results of Examples 1-17 and Comparative Examples 1-7.
  • the possible reason is that the organic solvent coating can prevent the surface of the lithium-containing cathode active material particles from combining with the solvent water in the slurry to form bound water, and at the same time reduce the dissolution of lithium elements and transition metal elements from the surface of the lithium-containing cathode active material particles, thus
  • the cathode sheet prepared by the method has less irreversible loss of lithium elements and transition metal elements; at the same time, the cathode sheet of the present application has less moisture content and organic solvent coating residue, and the cathode film layer shows a surface area
  • the porosity is significantly higher than the characteristics of the inner layer area, which helps the electrolyte to better infiltrate the positive electrode film layer, accelerate the transmission of lithium ions and reduce the internal resistance of the battery.
  • Figures 7 and 8 show the SEM-EDS test results of the cathode electrode sheet prepared in Example 1.
  • Area a represents the area about 100 nm from the surface of the cathode active material particles
  • area b represents the area about 100 nm from the center of the particles. It can be seen from Figure 8 that the Fe element distribution in the cathode active material particles in the cathode electrode sheet prepared in this application is relatively uniform. In particular, the Fe element content on the surface of the particles is still high, and no large amount of Fe element is eluted.

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Abstract

本申请提供一种正极组合物、水系正极浆料及其制备方法、水系正极极片、二次电池及用电装置，所述正极组合物包括含锂正极活性材料以及包覆于所述含锂正极活性材料至少一部分表面的有机溶剂包覆物，其中，所述含锂正极活性材料包括锂元素和过渡金属元素，所述有机溶剂包覆物的沸点T m在100℃以下，并且室温下所述有机溶剂包覆物在水中的溶解度在10％以下。本申请可以减少正极极片中锂元素和过渡金属元素的不可逆损失，并且使二次电池同时兼顾高能量密度以及良好的循环性能、倍率性能和安全性能。

Description

正极组合物、水系正极浆料及其制备方法、水系正极极片、二次电池及用电装置 技术领域
本申请属于电池技术领域，具体涉及一种正极组合物、水系正极浆料及其制备方法、水系正极极片、二次电池及用电装置。
背景技术
近年来，二次电池被广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。随着二次电池的应用及推广，其成本问题和环境污染问题受到越来越多的关注。正极极片是决定二次电池性能的关键因素之一，用于现有正极浆料的溶剂通常为油系溶剂，例如N-甲基吡咯烷酮(NMP)，但是NMP存在用量高、易挥发、难回收、毒性高且成本高的缺陷，不仅会对环境造成严重污染，而且还会危害人的身体健康。因此，有必要开发一种低成本、环境友好并且性能优异的水系正极极片。
发明内容
本申请的目的在于提供一种正极组合物、水系正极浆料及其制备方法、水系正极极片、二次电池及用电装置，其可以减少正极极片中锂元素和过渡金属元素的不可逆损失，并且使二次电池同时兼顾高能量密度以及良好的循环性能、倍率性能和安全性能。
本申请第一方面提供一种正极组合物，包括含锂正极活性材料以及包覆于所述含锂正极活性材料至少一部分表面的有机溶剂包覆物，其中，所述含锂正极活性材料包括锂元素和过渡金属元素，所述有机溶剂包覆物的沸点T m在100℃以下，并且室温下所述有机溶剂包覆物在水中的溶解度在10％以下。
将T m在100℃以下、室温溶解度在10％以下的有机溶剂包覆物包覆在含锂正极活性材料颗粒的至少一部分表面后，含锂正极活性材料颗粒表面不易形成结合水、颗粒表面锂元素和过渡金属元素的溶出较少，由其制备的正极极片中锂元素和过渡金属元素的不可逆损失较少，从而能够提升二次电池的能量密度和循环性能；此外，由其制备的正极极片水分含量较少，从而可以减少二次电池出现鼓包、腐蚀、严重自放电的风险，同时还可以降低二次电池内阻。由此，采用本申请提供的正极组合物的二次电池能够同时兼顾高能量密度以及良好的循环性能、倍率性能和安全性能。
在一些实施方式中，所述过渡金属元素包括Fe、Ni、Co、Mn、Al、Cu、Zn、Ti中的一种或多种。
在一些实施方式中，所述含锂正极活性材料包括LiFe mMn 1-mPO 4、Li(Ni xCo yMn zAl aCu bZn cTi d)O 2中的一种或多种，0≤m≤1，x+y+z+a+b+c+d＝1，0.5≤x＜1， 0.05≤y＜1，0≤z＜0.5，0≤a≤0.1，0≤b≤0.1，0≤c≤0.1，0≤d≤0.1。
在一些实施方式中，所述有机溶剂包覆物的沸点T m在30℃至100℃之间，可选地在40℃至60℃之间。有机溶剂包覆物的沸点在合适的范围内时，有利于进一步降低二次电池内阻，并明显提高二次电池的倍率性能和循环性能。
在一些实施方式中，室温下所述有机溶剂包覆物在水中的溶解度在1％以下，可选地为0.01％-1％。有机溶剂包覆物的溶解度在合适的范围内时，有利于充分发挥其对含锂正极活性材料颗粒表面的保护作用，从而进一步降低二次电池内阻，并明显提高二次电池的倍率性能和循环性能。
在一些实施方式中，所述有机溶剂包覆物包括芳香烃、脂肪烃、脂环烃、卤代烃、醇、酚、酯、酮、醚、醇醚、酯醚、腈、硫化物中的一种或多种。可选地，所述有机溶剂包覆物包括苯、己烷、异己烷、正庚烷、异辛烷、2,2-二甲基戊烷、3-甲基戊烷、环戊烷、环己烷、二氯甲烷、三氯甲烷、四氯化碳、1,2-二氯乙烷、二硫化碳、醋酸甲酯、醋酸乙酯中的一种或多种。这些有机溶剂包覆物具有合适的沸点和溶解度，能够更好地阻碍含锂正极活性材料颗粒表面与浆料中的溶剂水结合形成结合水，同时有效减少含锂正极活性材料颗粒表面锂元素和过渡金属元素的溶出，此时二次电池可以更好地兼顾高能量密度以及良好的循环性能和倍率性能。此外，这些有机溶剂包覆物还可以起到加快除水效率、减少正极极片水分含量、缓解正极膜层开裂的作用。
在一些实施方式中，所述正极组合物还包括分散剂、水性粘接剂、导电剂中的一种或多种。
在一些实施方式中，基于所述正极组合物的总质量计，所述含锂正极活性材料的质量百分含量为88％-99％，可选地为90％-94％。
在一些实施方式中，基于所述正极组合物的总质量计，所述有机溶剂包覆物的质量百分含量为0.01％-10％，可选地为3％-7％。有机溶剂包覆物的含量在合适的范围内时，能够更好地阻碍含锂正极活性材料颗粒表面与浆料中的溶剂水结合形成结合水，同时进一步减少含锂正极活性材料颗粒表面锂元素和过渡金属元素的溶出，进一步提升二次电池的能量密度和循环性能。
在一些实施方式中，基于所述正极组合物的总质量计，所述分散剂的质量百分含量为0.7％以下，可选地为0.1％-0.5％。
在一些实施方式中，基于所述正极组合物的总质量计，所述水性粘接剂的质量百分含量为5％以下，可选地为2％-4％。
在一些实施方式中，基于所述正极组合物的总质量计，所述导电剂的质量百分含量为5％以下，可选地为0.5％-3％。
在一些实施方式中，所述分散剂包括阴离子型分散剂、阳离子型分散剂、非离子型分散剂、两性型分散剂、电中性型分散剂、高分子型分散剂、受控自由基型分散剂中的一种或多种，可选地包括聚乙烯亚胺、十二烷基磺酸钠、聚乙烯醇、聚乙二醇辛基苯基醚中的一种或多种。
在一些实施方式中，基于所述正极组合物的总质量计，所述水性粘接剂包括甲基纤维素及其盐、黄原胶及其盐、壳聚糖及其盐、海藻酸及其盐、聚乙烯亚胺及其盐、聚丙烯酰胺、丙烯腈-丙烯酸共聚物及其衍生物、或其混合物。
在一些实施方式中，所述水性粘接剂包括黄原胶和聚乙烯亚胺的复配混合物。
可选地，所述黄原胶和所述聚乙烯亚胺的质量比为2:1-0.2:2.8。
可选地，所述黄原胶的数均分子量为300000-2000000，所述聚乙烯亚胺的数均分子量为2000-50000。
在一些实施方式中，基于所述正极组合物的总质量计，所述水性粘接剂包括丙烯腈-(甲基)丙烯酸共聚物和聚乙烯亚胺的复配混合物。
可选地，所述丙烯腈-(甲基)丙烯酸共聚物和所述聚乙烯亚胺的质量比为2:1-0.2:2.8。
可选地，所述丙烯腈-(甲基)丙烯酸共聚物的数均分子量为300000-2000000，所述聚乙烯亚胺的数均分子量为2000-70000。
本申请第二方面提供一种水系正极浆料，包括溶剂水以及本申请第一方面的正极组合物。
在一些实施方式中，所述水系正极浆料的固含量为40％-90％，可选地为50％-70％。水系正极浆料的固含量在合适的范围内时，水系正极浆料的分散性较好、稳定性较高，同时由其制备的正极极片水分含量较低并且膜层不易开裂。
在一些实施方式中，所述水系正极浆料的粘度为100cp-10000cp，可选地为3000cp-7000cp。水系正极浆料的粘度在合适的范围内时，水系正极浆料的分散性较好、稳定性较高，同时由其制备的正极极片水分含量较低并且膜层不易开裂。
本申请第三方面提供一种水系正极浆料的制备方法，用于制备本申请第二方面的水系正极浆料，包括步骤：S100，将含锂正极活性材料、有机溶剂包覆物混合均匀形成团状物；S200，将所得到的团状物、导电剂、水性粘接剂与溶剂水混合均匀，得到水系正极浆料。
在浆料的预搅拌工序中加入T m在100℃以下、室温溶解度在10％以下的有机溶剂包覆物，并使有机溶剂包覆物包覆在含锂正极活性材料颗粒的至少一部分表面后再与其他组分混合，能够阻碍含锂正极活性材料颗粒表面与浆料中的溶剂水结合形成结合水，同时减少含锂正极活性材料颗粒表面锂元素和过渡金属元素的溶出，从而由其制备的正极极片中锂元素和过渡金属元素的不可逆损失较少，二次电池的能量密度较高、循环性能较好。同时，通过本申请制备方法得到的正极极片水分含量和有机溶剂包覆物残留量均较少，还可以减少二次电池出现鼓包、腐蚀、严重自放电的风险，并降低二次电池内阻。
本申请第四方面提供一种水系正极极片，包括正极集流体以及位于所述正极集流体至少一个表面上的正极膜层，其中，所述正极膜层为本申请第二方面的水系正极浆料干燥后形成的层、或通过本申请第三方面的方法得到的水系正极浆料干燥后形成的层。
在一些实施方式中，所述含锂正极活性材料颗粒距离表面100nm的区域中过渡金属元素的质量分数W 1与所述含锂正极活性材料颗粒距离颗粒中心100nm的区域中过渡金属元素的质量分数W 2的比值为α，α为60％-100％，可选地为70％-100％。
在一些实施方式中，所述正极膜层的厚度为H，所述正极膜层中距离表面H/3区域内的孔隙率P 1和所述正极膜层中距离所述正极集流体H/3区域内的孔隙率P 2的比值为β，β为1.15-2.0，可选地为1.40-1.60。本申请的正极膜层呈现出表层区域的孔隙率明显高 于内层区域的特性，从而有利于电解液更好地浸润正极膜层、加快锂离子的传输、减小电池内阻，因此能够进一步提升二次电池的能量密度、循环性能以及倍率性能。
在一些实施方式中，基于所述水系正极极片的总质量，所述有机溶剂包覆物的质量含量在5000ppm以下，可选地在200ppm以下。
在一些实施方式中，所述水系正极极片80℃真空干燥6h后的水分质量含量在400ppm以下，可选地在200ppm以下。
本申请第五方面提供一种二次电池，包括本申请第四方面的水系正极极片。
本申请第六方面提供一种用电装置，包括本申请第五方面的二次电池。
本申请的水系正极极片可具有较低的水分含量和有机溶剂包覆物残留量，锂元素和过渡金属元素的不可逆损失也较少；同时，本申请的正极膜层还呈现出表层区域的孔隙率明显高于内层区域的特性，从而有利于电解液更好地浸润正极膜层、加快锂离子的传输以及减小电池内阻。因此，采用本申请水系正极极片的二次电池能够同时兼顾高能量密度以及良好的循环性能、倍率性能和安全性能。本申请的用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍。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是本申请的二次电池的一实施方式的示意图。
图2是图1的二次电池的实施方式的分解示意图。
图3是本申请的电池模块的一实施方式的示意图。
图4是本申请的电池包的一实施方式的示意图。
图5是图4所示的电池包的实施方式的分解示意图。
图6是包含本申请的二次电池作为电源的用电装置的一实施方式的示意图。
图7是实施例1制备的正极极片的扫描电子显微镜(SEM)图。
图8是实施例1制备的正极极片的X射线能谱仪(EDS)谱图。
在附图中，附图未必按照实际的比例绘制。其中，附图标记说明如下：1电池包，2上箱体，3下箱体，4电池模块，5二次电池，51壳体，52电极组件，53盖板。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的正极组合物、水系正极浆料及其制备方法、水系正极极片、二次电池及用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
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，并且这样的技术方案应被认为包含在本申请的公开内容中。
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，并且这样的技术方案应被认为包含在本申请的公开内容中。
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。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或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)。
在本文的描述中，除非另有说明，“以上”、“以下”为包含本数。
在本文的描述中，除非另有说明，“多种”、“多个”、“多者”的含义是两种、两个或两者以上。
在本申请中，术语“室温”是指20℃±2℃。
二次电池又称为充电电池或蓄电池，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，二次电池包括正极极片、负极极片、电解质以及隔离膜等。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，主要起到防止正负极短路的作用，同时可以使活性离子通过。电解质在正极极片和负极极片之间起到传导活性离子的作用。
随着二次电池的应用及推广，其成本问题和环境污染问题受到越来越多的关注。采用水作为溶剂的水系正极浆料由于具有成本低廉且环境友好的特点，受到研究者越来 越多的关注。但是，发明人研究发现正极活性材料颗粒表面在溶剂水存在下容易析出锂离子和过渡金属离子，影响了二次电池的能量密度和循环性能。此外，水系正极浆料还存在流动性差、不易分散等缺陷，并且采用水系正极浆料制备的正极极片还存在除水难度大、水分含量高、正极膜层易开裂等缺陷。
鉴于此，本申请的发明人经过大量研究与实践，提出了一种适合用于水系正极浆料的正极组合物。
正极组合物
本申请实施方式第一方面提供了一种正极组合物，包括含锂正极活性材料以及包覆于所述含锂正极活性材料至少一部分表面的有机溶剂包覆物，所述含锂正极活性材料包括锂元素和过渡金属元素，所述有机溶剂包覆物的沸点T m在100℃以下，并且室温下所述有机溶剂包覆物在水中的溶解度在10％以下。
发明人经过大量研究与实践发现，将T m在100℃以下、室温溶解度在10％以下的有机溶剂包覆物包覆在含锂正极活性材料颗粒的至少一部分表面后，能够减少含锂正极活性材料颗粒表面锂元素和过渡金属元素的溶出，并同时起到阻碍含锂正极活性材料颗粒表面与浆料中的溶剂水结合形成结合水的作用。
同时，由于本申请采用的有机溶剂包覆物具有低沸点、低溶解度的特性，其还可以降低浆料整体的沸点，起到增加正极极片除水效率、降低正极极片水分含量的作用。此外，本申请的有机溶剂包覆物在浆料中也可以起到一定的增塑作用，从而还可以提高浆料分散性并缓解正极膜层开裂的问题。
因此，将T m在100℃以下、室温溶解度在10％以下的有机溶剂包覆物包覆在含锂正极活性材料颗粒的至少一部分表面后，含锂正极活性材料颗粒表面不易形成结合水、颗粒表面锂元素和过渡金属元素的溶出较少，由其制备的正极极片中锂元素和过渡金属元素的不可逆损失较少，从而能够提升二次电池的能量密度和循环性能；此外，由其制备的正极极片水分含量较少，从而可以减少二次电池出现鼓包、腐蚀、严重自放电的风险，同时还可以降低二次电池内阻。由此，采用本申请提供的正极组合物的二次电池能够同时兼顾高能量密度以及良好的循环性能、倍率性能和安全性能。
有机溶剂包覆物的沸点T m在100℃以下时，能够减少其在正极极片中的残留量，有利于降低二次电池内阻，提高二次电池的倍率性能和循环性能。在一些实施例中，所述有机溶剂包覆物的沸点T m可以在30℃至100℃之间、30℃至90℃之间、30℃至80℃之间、30℃至70℃之间、30℃至60℃之间、40℃至100℃之间、40℃至90℃之间、40℃至80℃之间、40℃至70℃之间、40℃至60℃之间。有机溶剂包覆物的沸点在合适的范围内时，有利于进一步降低二次电池内阻，并明显提高二次电池的倍率性能和循环性能。
室温下有机溶剂包覆物在水中的溶解度在10％以下，有利于保证正极浆料搅拌分散过程中有机溶剂包覆物包覆在含锂正极活性材料颗粒表面，防止由于有机溶剂包覆物大量溶于溶剂水中而失去对含锂正极活性材料颗粒表面的保护作用。在一些实施例中，室温下所述有机溶剂包覆物在水中的溶解度可以在8％以下、5％以下、3％以下、2％以下或1％以下。可选地，室温下有机溶剂包覆物在水中的溶解度为0.01％-5％、0.01％-3％、0.01％-2％、0.01％-1％。有机溶剂包覆物的溶解度在合适的范围内时，有利于充分发挥其对含锂正极活性材料颗粒表面的保护作用，从而进一步降低电池内阻，并明显提高二次 电池的倍率性能和循环性能。
在一些实施例中，所述有机溶剂包覆物的沸点T m在40℃至60℃之间，室温下有机溶剂包覆物在水中的溶解度为0.01％-1％。此时，能够充分发挥有机溶剂包覆物对含锂正极活性材料颗粒表面的保护作用并降低电池内阻，从而二次电池能在具有高能量密度的同时，还具有明显提高的倍率性能和循环性能。
在一些实施例中，所述有机溶剂包覆物包括芳香烃、脂肪烃、脂环烃、卤代烃、醇、酚、酯、酮、醚、醇醚、酯醚、腈、硫化物中的一种或多种。
可选地，所述有机溶剂包覆物包括苯、己烷、异己烷、正庚烷、异辛烷、2,2-二甲基戊烷、3-甲基戊烷、环戊烷、环己烷、二氯甲烷、三氯甲烷、四氯化碳、1,2-二氯乙烷、二硫化碳、醋酸甲酯、醋酸乙酯中的一种或多种。进一步地，所述有机溶剂包覆物包括己烷、异己烷、环戊烷、四氯化碳、二硫化碳、醋酸甲酯、醋酸乙酯中的一种或多种。特别地，所述有机溶剂包覆物包括异己烷、环戊烷、二硫化碳中的一种或多种。
这些有机溶剂包覆物具有合适的沸点和溶解度，能够更好地阻碍含锂正极活性材料颗粒表面与浆料中的溶剂水结合形成结合水，同时有效减少含锂正极活性材料颗粒表面锂元素和过渡金属元素的溶出，此时二次电池可以更好地兼顾高能量密度以及良好的循环性能和倍率性能。此外，这些有机溶剂包覆物还可以起到加快除水效率、减少正极极片水分含量、缓解正极膜层开裂的作用。
在一些实施例中，有机溶剂包覆物可以包覆于含锂正极活性材料70％以上的表面。可选地，有机溶剂包覆物包覆于含锂正极活性材料80％以上的表面。进一步地，有机溶剂包覆物包覆于含锂正极活性材料90％以上的表面。特别地，有机溶剂包覆物完全包覆含锂正极活性材料的表面。
有机溶剂包覆物位于含锂正极活性材料大部分表面甚至全部表面上时，能够更好地阻碍含锂正极活性材料颗粒表面与浆料中的溶剂水结合形成结合水，同时进一步减少含锂正极活性材料颗粒表面锂元素和过渡金属元素的溶出，进一步提升二次电池的能量密度和循环性能。
在一些实施例中，所述过渡金属元素包括Fe、Ni、Co、Mn、Al、Cu、Zn、Ti中的一种或多种。
本申请对含锂正极活性材料的种类没有特别的限制。在一些实施例中，所述含锂正极活性材料包括但不限于LiFe mMn 1-mPO 4、Li(Ni xCo yMn zAl aCu bZn cTi d)O 2中的一种或多种，0≤m≤1，x+y+z+a+b+c+d＝1，0.5≤x＜1，0.05≤y＜1，0≤z＜0.5，0≤a≤0.1，0≤b≤0.1，0≤c≤0.1，0≤d≤0.1。可选地，所述含锂正极活性材料包括LiFePO 4(LFP)、LiMnPO 4、LiFe 0.9Mn 0.1PO 4、LiFe 0.8Mn 0.2PO 4、LiFe 0.7Mn 0.3PO 4、LiFe 0.6Mn 0.4PO 4、LiFe 0.5Mn 0.5PO 4、Li(Ni 0.5Co 0.2Mn 0.3)O 2(NCM523)、Li(Ni 0.6Co 0.2Mn 0.2)O 2(NCM622)、Li(Ni 0.8Co 0.1Mn 0.1)O 2(NCM811)、Li(Ni 0.8Co 0.15Al 0.05)O 2中的一种或多种。
在一些实施例中，所述正极组合物还包括水性粘接剂。水性粘接剂可以将正极活性材料、导电剂等粘接于集流体上，增强正极活性材料与导电剂之间以及正极活性材料与集流体之间的接触、稳定正极极片的结构。水性粘接剂相比于油系粘接剂，例如聚偏氟乙烯等，成本更低、对环境更加友好且使用更安全。
所述水性粘接剂可以包含固体组分含量在5％以上的水分散溶液或乳液。所述水 性粘接剂还可以包含可与水形成固体组分含量在1％以上的稳定分散液的固体。
在一些实施例中，所述水性粘接剂包括可溶性多糖类及其衍生物、水溶性或水分散液高分子聚合物或其混合物。例如，所述水性粘接剂包括但不限于甲基纤维素及其盐(例如甲基纤维素锂、甲基纤维素钠、甲基纤维素钾等)、黄原胶及其盐、壳聚糖及其盐、海藻酸及其盐(例如海藻酸锂、海藻酸钠、海藻酸钾等)、聚乙烯亚胺及其盐、聚丙烯酰胺、丙烯腈-(甲基)丙烯酸共聚物及其衍生物、或其混合物。
在一些实施例中，所述水性粘接剂包括黄原胶和聚乙烯亚胺的复配混合物。可选地，所述黄原胶和所述聚乙烯亚胺的质量比为2:1-0.2:2.8。可选地，所述黄原胶的数均分子量为300000-2000000，所述聚乙烯亚胺的数均分子量为2000-50000。
在一些实施例中，所述水性粘接剂包括丙烯腈-(甲基)丙烯酸共聚物和聚乙烯亚胺的复配混合物。可选地，所述丙烯腈-(甲基)丙烯酸共聚物和所述聚乙烯亚胺的质量比为2:1-0.2:2.8。可选地，所述丙烯腈-(甲基)丙烯酸共聚物的数均分子量为300000-2000000，所述聚乙烯亚胺的数均分子量为2000-70000。
在一些实施例中，所述正极组合物还包括导电剂。本申请对所述导电剂的种类没有特别的限制，例如可以包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中一种或多种。
在一些实施例中，所述正极组合物还包括分散剂，分散剂可以进一步改善浆料的稳定性，使其不易沉降。所述分散剂包括阴离子型分散剂、阳离子型分散剂、非离子型分散剂、两性型分散剂、电中性型分散剂、高分子型分散剂、受控自由基型分散剂中的一种或多种。作为示例，所述分散剂包括但不限于聚乙烯亚胺、十二烷基磺酸钠、聚乙烯醇、聚乙二醇辛基苯基醚中的一种或多种。
在一些实施例中，所述正极组合物还包括水性粘接剂、导电剂、分散剂中的两种以上。
在一些实施例中，基于所述正极组合物的总质量计，所述含锂正极活性材料的质量百分含量为88％-99％。可选地，所述含锂正极活性材料的质量百分含量为90％-94％。
在一些实施例中，基于所述正极组合物的总质量计，所述有机溶剂包覆物的质量百分含量为0.01％-10％。可选地，所述有机溶剂包覆物的质量百分含量为3％-7％。有机溶剂包覆物的含量在合适的范围内时，能够更好地阻碍含锂正极活性材料颗粒表面与浆料中的溶剂水结合形成结合水，同时进一步减少含锂正极活性材料颗粒表面锂元素和过渡金属元素的溶出，进一步提升二次电池的能量密度和循环性能。
有机溶剂包覆物的含量也不宜过多，此时制备的正极极片中有机溶剂包覆物的残留量可能增加，由此可能会影响二次电池的内阻；有机溶剂包覆物的含量较多时，浆料的稳定性可能下降，例如更容易出现沉降；此外，有机溶剂包覆物的含量较多时，浆料干燥时间缩短、干燥速度加快，由此制备的正极极片中膜层可能会更易开裂。
在一些实施例中，基于所述正极组合物的总质量计，所述分散剂的质量百分含量为0.7％以下。可选地，所述分散剂的质量百分含量为0.1％-0.5％。
在一些实施例中，基于所述正极组合物的总质量计，所述水性粘接剂的质量百分含量为5％以下。可选地，所述水性粘接剂的质量百分含量为2％-4％。
在一些实施例中，基于所述正极组合物的总质量计，所述导电剂的质量百分含量 为5％以下。可选地，所述导电剂的质量百分含量为0.5％-3％。
水系正极浆料
本申请实施方式第二方面提供一种水系正极浆料，包括溶剂水以及本申请实施方式第一方面的正极组合物。
在一些实施例中，所述水系正极浆料的固含量为40％-90％。可选地，所述水系正极浆料的固含量为50％-70％。水系正极浆料的固含量在合适的范围内时，水系正极浆料的分散性较好、稳定性较高，同时由其制备的正极极片水分含量较低并且膜层不易开裂。
水系正极浆料的固含量较低时，浆料的稳定性可能下降，例如更容易出现沉降；此外，水系正极浆料的固含量较低时，溶剂的含量较多，从而浆料干燥过程中所需干燥时间较长、干燥温度较高，由此制备的正极极片中膜层可能会更易开裂。水系正极浆料的固含量较高时，浆料的均一性可能变差并且浆料的涂布也可能会变得比较困难。
在一些实施例中，所述水系正极浆料的粘度(在本申请中为室温下的粘度)为100cp-10000cp。可选地，所述水系正极浆料的粘度为3000cp-7000cp。水系正极浆料的粘度在合适的范围内时，水系正极浆料的分散性较好、稳定性较高，同时由其制备的正极极片水分含量较低并且膜层不易开裂。
水系正极浆料的粘度较低时，浆料的稳定性可能下降，例如更容易出现沉降；此外，水系正极浆料的粘度较低时，溶剂的含量较多，从而浆料干燥过程中所需干燥时间较长、干燥温度较高，由此制备的正极极片中膜层可能会更易开裂。水系正极浆料的粘度较高时，浆料的涂布可能会变得比较困难。
浆料的粘度为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以参考GB/T 2794-2013《胶黏剂粘度的测定单圆筒旋转粘度计法》进行测定。
水系正极浆料的制备方法
本申请实施方式第三方面提供一种水系正极浆料的制备方法，包括步骤：S100，将含锂正极活性材料、有机溶剂包覆物混合均匀形成团状物；S200，将所得到的团状物、导电剂、水性粘接剂与溶剂水混合均匀，得到水系正极浆料。
本申请提供的水系正极浆料的制备方法能够制备本申请实施方式第二方面的水系正极浆料。
在浆料的预搅拌工序中加入T m在100℃以下、室温溶解度在10％以下的有机溶剂包覆物，并使有机溶剂包覆物包覆在含锂正极活性材料颗粒的至少一部分表面后再与其他组分混合，能够阻碍含锂正极活性材料颗粒表面与浆料中的溶剂水结合形成结合水，同时减少含锂正极活性材料颗粒表面锂元素和过渡金属元素的溶出，从而由其制备的正极极片中锂元素和过渡金属元素的不可逆损失较少，二次电池的能量密度较高、循环性能较好。同时，通过本申请制备方法得到的正极极片水分含量和有机溶剂包覆物残留量均较少，还可以减少二次电池出现鼓包、腐蚀、严重自放电的风险，并降低二次电池内阻。
在一些实施例中，S200中还可以加入分散剂。
水系正极极片
本申请实施方式第四方面提供一种水系正极极片，包括正极集流体以及位于所述正极集流体至少一个表面上的正极膜层，其中，所述正极膜层为本申请实施方式第二方 面的水系正极浆料干燥后形成的层、或通过本申请实施方式第三方面的制备方法备得到的水系正极浆料干燥后形成的层。正极膜层可以是将上述水系正极浆料涂布在所述正极集流体上，经干燥、冷压等工序后而形成的。正极集流体具有在自身厚度方向相对的两个表面，正极膜层设置于正极集流体的两个相对表面中的任意一者或两者上。
本申请的水系正极极片可具有较低的水分含量和有机溶剂包覆物残留量，锂元素和过渡金属元素的不可逆损失也较少；同时，本申请的正极膜层还呈现出表层区域的孔隙率明显高于内层区域的特性，从而有利于电解液更好地浸润正极膜层、加快锂离子的传输以及减小电池内阻。因此，采用本申请水系正极极片的二次电池能够同时兼顾高能量密度以及良好的循环性能、倍率性能和安全性能。
在一些实施例中，在所述水系正极极片中，所述含锂正极活性材料颗粒距离表面100nm的区域中过渡金属元素的质量分数W 1与所述含锂正极活性材料颗粒距离颗粒中心100nm的区域中过渡金属元素的质量分数W 2的比值为α，α为60％-100％。例如，α可以为70％-100％，75％-100％，80％-100％。α数值越高，表明含锂正极活性材料颗粒表面受到溶剂水影响越小，过渡金属溶出越少，颗粒晶体结构越稳定。本申请的正极极片中，α为60％以上，70％以上，75％以上，甚至80％以上。由此，采用其的二次电池可以同时兼顾高能量密度和良好的循环性能。
在本申请中，当颗粒为球形或类球形时，“颗粒中心”即表示球心；当正极活性材料颗粒为不规则形状时，可取颗粒最长对角线与最短对角线的交叉点作为颗粒中心。
水系正极极片中含锂正极活性材料的参数α可通过如下测试方法得到。
从水系正极极片中裁切出一定面积的样品(例如长度为4cm至8cm，宽度为4cm至8cm)，采用CP离子截面抛光仪(例如IB-19500型)进行抛光处理，得到抛光后带切割面的样品；用扫描电子显微镜(SEM，例如ZEISSsigma 300型)和X射线能谱仪(EDS，例如Horiba 7021-H型)进行SEM-EDS测试，例如可以参照JY/T 010-1996，观测样品中元素分布情况；在SEM-EDX图片中选取含锂正极活性材料颗粒的横剖面，测试该横剖面距离表面100nm的任一区域中过渡金属元素的质量分数W 1，然后测试距离颗粒中心100nm的任一区域中过渡金属元素的质量分数W 2，参数α＝(W 1/W 2)×100％。为了保证测试结果的准确性，可以取含锂正极活性材料颗粒横剖面的多个区域进行测试，然后取平均值。
需要说明的是，上述针对正极极片的测试，可以在二次电池制备过程中取样测试，也可以从制备好的二次电池中取样测试。当上述测试样品是从制备好的二次电池中取样时，作为示例，可以按如下步骤进行取样。
将二次电池做放电处理(为了安全起见，一般使电池处于满放状态)；将电池拆卸后取出正极极片，使用碳酸二甲酯(DMC)将正极极片浸泡一定时间(例如2-10小时)；然后将正极极片取出并在一定温度和时间下干燥处理(例如60℃，4h)，干燥后取出正极极片。
同时，在对从制备好的二次电池中取出的正极极片样品进行测试时，由于含锂正极活性材料颗粒表面可能形成了具有一定厚度的保护膜，因此在测试时可以取含锂正极活性材料颗粒的横剖面距离表面120nm至220nm的区域中过渡金属元素的质量分数作为W 1，以保证测试结果的准确性。
在一些实施例中，所述正极膜层的厚度H不受具体的限制，例如可以为50μm-500μm。在本申请中，正极膜层的厚度为本领域公知的含义，可采用本领域已知的方法进行测试，例如采用螺旋测微仪进行测定。
在一些实施例中，所述正极膜层的厚度为H，所述正极膜层中距离表面H/3区域内的孔隙率P 1和所述正极膜层中距离所述正极集流体H/3区域内的孔隙率P 2的比值为β，β为1.15-2.0。可选地，β为1.20-2.0，1.25-2.0，1.30-2.0，1.35-2.0，1.40-2.0，1.20-1.70，1.25-1.70，1.30-1.70，1.35-1.70，1.40-1.70、1.20-1.60，1.25-1.60，1.30-1.60，1.35-1.60或1.40-1.60。
本申请的正极膜层呈现出表层区域的孔隙率明显高于内层区域的特性，从而有利于电解液更好地浸润正极膜层、加快锂离子的传输、减小电池内阻，因此能够进一步提升二次电池的能量密度、循环性能以及倍率性能。可能的原因在于，本申请采用的有机溶剂包覆物具有低沸点、低溶解度的特性，其在浆料烘干工序中更容易上浮，因此正极膜层表层区域的孔隙率会明显高于内层区域。
在本申请中，正极膜层的孔隙率为本领域公知的含义，可采用本领域已知的方法进行测试，例如可以参照GB/T 24586-2009进行测定。
在一些实施例中，基于所述水系正极极片的总质量，所述有机溶剂包覆物的质量含量(即残留量)在5000ppm以下。可选地，所述有机溶剂包覆物的质量含量在2000ppm以下，1000ppm以下，500ppm以下，在200ppm以下，100ppm以下，甚至80ppm以下。在本申请中，有机溶剂包覆物的质量含量可采用气相色谱-质谱联用仪(GC-MS)进行测定。
在一些实施例中，所述正极极片80℃真空干燥6h后的水分质量含量(即残留量)可以在400ppm以下。可选地，所述正极极片80℃真空干燥6h后的水分质量含量可以在300ppm以下，200ppm以下，甚至180ppm以下。
在本申请中，正极极片80℃真空干燥6h后的水分质量含量可按照如下方法进行测试：将水系正极浆料涂布在正极集流体上，之后置于干燥间(露点＜-30℃)的真空烘箱中于80℃真空干燥6h得到干燥后的正极膜层；从干燥后的正极膜层中称取0.6g-1g粉末样品(例如选用刀片刮粉取样)后置于水分测试检测箱中检测水分含量。其中水分测试检测箱为卡尔费休法水分测定仪，称量仪器可为电子天平。
在一些实施例中，所述正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可包括铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的一种或多种。作为示例，高分子材料基层可包括聚丙烯(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)中的一种或多种。
需要说明的是，除非另有说明，上述针对正极极片的各项测试，均可以在二次电池制备过程中取样测试，也可以从制备好的二次电池中取样测试。另外，本申请所给的上述测试方法是针对正极集流体单侧的正极膜层，当所述正极膜层设置在所述正极集流体的两侧时，其中任意一侧的正极膜层测试结果满足本申请，即认为落入本申请的保护范围内。
二次电池
本申请实施方式的第五方面提供一种二次电池，包括正极极片、负极极片以及电解质。在二次电池充放电过程中，活性离子在所述正极极片和所述负极极片之间往返嵌入和脱出，所述电解质在所述正极极片和所述负极极片之间起到传导活性离子的作用。
[正极极片]
本申请的二次电池采用的正极极片为本申请实施方式第四方面的水系正极极片。
[负极极片]
在一些实施例中，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面的负极膜层。例如，所述负极集流体具有在自身厚度方向相对的两个表面，所述负极膜层设置在所述负极集流体的两个相对表面中的任意一者或两者上。
所述负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可包括铜、铜合金、镍、镍合金、钛、钛合金、银、银合金中的一种或多种。作为示例，高分子材料基层可包括聚丙烯(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)中的一种或多种。
负极膜层通常包含负极活性材料、可选的粘接剂、可选的导电剂以及其他可选的助剂。负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。负极浆料涂通常是将负极活性材料、可选的导电剂、可选地粘接剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或水，但不限于此。作为示例，用于负极膜层的粘接剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水系丙烯酸树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、羧甲基壳聚糖(CMCS)中的一种或多种。作为示例，用于负极膜层的导电剂可包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中一种或多种。其他可选的助剂可包括增稠剂(例如，羧甲基纤维素钠CMC)、PTC热敏电阻材料等。
负极活性材料可采用本领域公知的用于二次电池的负极活性材料。作为示例，负极活性材料可包括天然石墨、人造石墨、软炭、硬炭、中间相微碳球、硅基材料、锡基材料、钛酸锂、Li-Sn合金、Li-Sn-O合金、Li-Al合金中的一种或多种。硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物、硅合金材料中的一种或多种。锡基材料可包括单质锡、锡氧化物、锡合金材料中的一种或多种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池负极活性材料的传统公知的材料。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。
本申请的负极极片并不排除除了负极膜层之外的其他附加功能层。例如在一些实施例中，本申请的负极极片还包括夹在负极集流体和负极膜层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘接剂组成)。在另外一些实施例中，本申请的负极极片还包括覆盖在负极膜层表面的保护层。
[电解质]
本申请对所述电解质的种类没有具体的限制，可根据需求进行选择。例如，所述 电解质可以包括固态电解质及液态电解质(即电解液)中的一种或多种。
在一些实施例中，所述电解质采用电解液，所述电解液包括电解质盐和溶剂。所述电解质盐和所述溶剂的种类不受具体的限制，可根据实际需求进行选择。
作为示例，所述电解质盐可包括六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、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)、四氟草酸磷酸锂(LiTFOP)中的一种或多种。
作为示例，所述溶剂可包括碳酸乙烯酯(EC)、碳酸亚丙酯(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)中的一种或多种。
在一些实施例中，所述电解液还可选地包括添加剂。例如，所述添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，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、改善电池高温性能的添加剂、改善电池低温功率性能的添加剂等。作为示例，所述添加剂可以包括但不限于碳酸亚乙烯酯(VC)、氟代碳酸乙烯酯(FEC)、1,3-丙磺酸内酯(PS)中的一种或多种。
[隔离膜]
采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还包括隔离膜。所述隔离膜设置在所述正极极片和所述负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。本申请对所述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。
在一些实施例中，所述隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或多种。所述隔离膜可以是单层薄膜，也可以是多层复合薄膜。所述隔离膜为多层复合薄膜时，各层的材料相同或不同。
在一些实施例中，所述正极极片、所述多层复合隔离膜和所述负极极片可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施例中，所述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液。
在一些实施例中，所述二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。所述二次电池的外包装也可以是软包，例如袋式软包。所述软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或多种。
本申请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5。
在一些实施例中，如图2所示，外包装可包括壳体51和盖板53。其中，壳体51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51具有与容纳腔 连通的开口，盖板53用于盖设所述开口，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52。电极组件52封装于所述容纳腔。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或几个，可根据需求来调节。
在本申请的一些实施例中，根据本申请的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多个，具体数量可根据电池模块的应用和容量来调节。
图3是作为一个示例的电池模块4的示意图。如图3所示，在电池模块4中，多个二次电池5可以是沿电池模块4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5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施例中，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根据电池包的应用和容量进行调节。
图4和图5是作为一个示例的电池包1的示意图。如图4和图5所示，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
本申请的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
用电装置
本申请实施方式第六方面提供一种用电装置。所述用电装置包括本申请的二次电池、电池模块、或电池包中的一种或多种。所述二次电池、电池模块或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电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。
所述用电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6是作为一个示例的用电装置的示意图。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使 用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
正极极片的制备
将92质量份LiFePO 4(LFP，含锂正极活性材料)与4质量份异己烷(有机溶剂包覆物)混合均匀形成团状物后，再与2质量份导电剂炭黑(SuperP)、2质量份水性粘接剂混合均匀，之后加入适量溶剂水搅拌分散均匀后配置成固含量为50％的正极浆料；将正极浆料均匀涂覆于正极集流体铝箔的表面上，之后置于干燥间(露点＜-30℃)的真空烘箱中于80℃真空干燥6h，然后经过冷压、分切等工序，得到正极极片。其中，水性粘接剂采用丙烯腈-丙烯酸共聚物LA-133与聚乙烯亚胺质量比1:1的混合物。
负极极片的制备
将负极活性材料人造石墨、导电剂炭黑(Super P)、粘接剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比96.2:0.8:0.8:1.2在适量的溶剂去离子水中充分搅拌混合形成负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，经烘干、冷压、分切后，得到负极极片。
电解液的制备
在氩气气氛手套箱中(H 2O＜0.1ppm，O 2＜0.1ppm)，将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)按照体积比3:7混合，得到有机溶剂；将LiPF 6均匀溶解在上述有机溶剂中得到电解液，其中，LiPF 6的质量分数为12.5％。
隔离膜的制备
采用聚丙烯膜作为隔离膜。
二次电池的制备
将上述正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件放入外包装铝壳中，在80℃下烘烤后加入上述电解液，然后经真空封装、静置、热冷压、化成、整形、容量测试等工序后，得到二次电池。
实施例2-17和对比例2-7
二次电池的制备方法与实施例1类似，不同之处在于正极极片的制备参数不同，具体详见表1。
对比例1
二次电池的制备方法与实施例1类似，不同之处在于正极极片的制备过程中未加入有机溶剂包覆物异己烷。
测试部分
(1)正极极片的水分含量测试
从上述80℃真空干燥6h后、冷压前的正极膜层中称取0.6g-1g粉末样品，之后将粉末样品置于水分测试检测箱中检测水分含量。其中水分测试检测箱为卡尔费休法水分测定仪，称量仪器可为电子天平。
(2)正极极片的有机溶剂包覆物残留量测试
将二次电池做放电处理(为了安全起见，一般使电池处于满放状态)；将电池拆卸后取出正极极片，使用碳酸二甲酯(DMC)将正极极片浸泡4小时；然后将正极极片取出并在60℃干燥4小时，干燥后取出正极极片进行刮粉处理，将获得的粉末送气相色 谱-质谱联用仪(GC-MS)进行测试。具体地，将粉末置于Al 2O 3坩埚中，抖平，盖上盖子，参数设置为：氮气气氛，吹扫气60mL/min，保护气20mL/min。温升程序设定为：10℃/min，35℃至600℃。
(3)正极活性材料颗粒中元素分布测试
从新鲜制备的正极极片中裁切出约6cm×6cm的样品，采用IB-19500CP离子截面抛光仪进行抛光处理，得到抛光后带切割面的样品；参照JY/T 010-1996，用ZEISS sigma 300扫描电子显微镜和Horiba 7021-H型X射线能谱仪进行SEM-EDS测试，观测样品中元素分布情况；在SEM-EDX图片中选取正极活性材料颗粒的横剖面，测试该横剖面距离表面100nm的区域中过渡金属元素的质量分数W 1，然后测试距离颗粒中心100nm的区域中过渡金属元素的质量分数W 2，参数α＝W 1/W 2。α越高，正极活性材料颗粒表面过渡金属元素的损失越少。为了保证测试结果的准确性，测试时可分别在正极活性材料颗粒表面和颗粒中心对应区域中随机取多个点(例如5个至10个)进行测试，然后取平均值作为测试结果。
(4)正极极片的孔隙率测试
通过胶带剥离正极膜层，参照GB/T 24586-2009测试正极膜层中距离表面H/3区域内的孔隙率P 1和正极膜层中距离正极集流体H/3区域内的孔隙率P 2，参数β＝P 1/P 2。
(5)正极活性材料的初始克容量测试
在25℃下，将二次电池以1/3C恒流充电至3.65V，再以3.65V恒压充电至电流为0.05C；静置5min后以1/3C恒流放电至2.5V，得到二次电池的初始容量。
正极活性材料的初始克容量(mAh/g)＝二次电池的初始容量/正极活性材料的质量。
(6)二次电池的循环性能测试
在25℃下，将二次电池以1/3C恒流充电至3.65V，再以3.65V恒压充电至电流为0.05C；静置5min后以1/3C恒流放电至2.5V，所得放电容量记为二次电池初始容量。将二次电池按照上述方法进行循环充放电测试，记录每圈循环后的放电容量。
二次电池循环300圈后的容量保持率＝(第300圈循环后的放电容量/初始容量)×100％。
(7)二次电池的直流阻抗测试
在25℃下，将二次电池以1/3C恒流充电至3.65V，再以3.65V恒压充电至电流为0.05C，静置5min后，记录此时的电压V 1；将二次电池以1/3C恒流放电30s，记录此时的电压V 2，则以(V 2-V 1)/(1/3C)表示首圈循环后的内阻。
重复以上步骤，并同时记录二次电池每圈循环后的内阻。
二次电池循环300圈后的内阻增长率＝(第300圈循环后的内阻/首圈循环后的内阻)×100％。
表1给出实施例1-17和对比例1-7的测试结果。
从表1的测试结果可以看出，在浆料的预搅拌工序中加入T m在100℃以下、室温溶解度在10％以下的有机溶剂包覆物，并使有机溶剂包覆物包覆在含锂正极活性材料颗粒的至少一部分表面后再与其他组分混合，能够使二次电池同时兼具高能量密度、良好的循环性能和较低的内阻。可能的原因在于，有机溶剂包覆物能够阻碍含锂正极活性材料 颗粒表面与浆料中的溶剂水结合形成结合水，同时减少含锂正极活性材料颗粒表面锂元素和过渡金属元素的溶出，从而由其制备的正极极片中锂元素和过渡金属元素的不可逆损失较少；同时，本申请的正极极片水分含量和有机溶剂包覆物残留量均较少，并且正极膜层呈现出表层区域的孔隙率明显高于内层区域的特性，从而有利于电解液更好地浸润正极膜层、加快锂离子的传输以及减小电池内阻。
图7和图8示出实施例1制备的正极极片的SEM-EDS测试结果，区域a表示距离正极活性材料颗粒表面约100nm的区域，区域b表示距离颗粒中心约100nm的区域。从图8可以看出，本申请制备的正极极片中正极活性材料颗粒中Fe元素分布比较均一，特别地，颗粒表面Fe元素含量依旧较高，未出现大量Fe元素溶出。
从实施例1-16和对比例2-4的测试结果可以看出，当在浆料的预搅拌工序中加入的有机溶剂包覆物的沸点T m高于100℃时，尽管含锂正极活性材料颗粒表面锂元素和过渡金属元素的溶出较少，但是正极极片水分含量和有机溶剂包覆物残留量均较高，并且正极膜层表层区域孔隙率与内层区域的孔隙率接近，从而并不能有效地促进电解液的浸润、加快锂离子的传输以及减小电池内阻。因此，此时二次电池不能同时兼具高能量密度、良好的循环性能和较低的内阻。
从实施例1-16和对比例5-7的测试结果可以看出，当在浆料的预搅拌工序中加入的有机溶剂包覆物的室温溶解度高于10％时，有机溶剂包覆物大量溶于溶剂水中而失去对含锂正极活性材料颗粒表面的保护作用，从而含锂正极活性材料颗粒表面锂元素和过渡金属元素的溶出较多，因此，此时二次电池也不能同时兼具高能量密度、良好的循环性能和较低的内阻。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。
Figure PCTCN2022084093-appb-000001

Claims (19)

  1. 一种正极组合物，包括含锂正极活性材料以及包覆于所述含锂正极活性材料至少一部分表面的有机溶剂包覆物，
    所述含锂正极活性材料包括锂元素和过渡金属元素，
    所述有机溶剂包覆物的沸点T m在100℃以下，并且室温下所述有机溶剂包覆物在水中的溶解度在10％以下。
  2. 根据权利要求1所述的正极组合物，其中，所述过渡金属元素包括Fe、Ni、Co、Mn、Al、Cu、Zn、Ti中的一种或多种。
  3. 根据权利要求1或2所述的正极组合物，其中，所述含锂正极活性材料包括LiFe mMn 1-mPO 4、Li(Ni xCo yMn zAl aCu bZn cTi d)O 2中的一种或多种，0≤m≤1，x+y+z+a+b+c+d＝1，0.5≤x＜1，0.05≤y＜1，0≤z＜0.5，0≤a≤0.1，0≤b≤0.1，0≤c≤0.1，0≤d≤0.1。
  4. 根据权利要求1-3中任一项所述的正极组合物，其中，
    所述有机溶剂包覆物的沸点T m在30℃至100℃之间，可选地在40℃至60℃之间；和/或，
    室温下所述有机溶剂包覆物在水中的溶解度在1％以下，可选地为0.01％-1％。
  5. 根据权利要求1-4中任一项所述的正极组合物，其中，所述有机溶剂包覆物包括芳香烃、脂肪烃、脂环烃、卤代烃、醇、酚、酯、酮、醚、醇醚、酯醚、腈、硫化物中的一种或多种，
    可选地，所述有机溶剂包覆物包括苯、己烷、异己烷、正庚烷、异辛烷、2,2-二甲基戊烷、3-甲基戊烷、环戊烷、环己烷、二氯甲烷、三氯甲烷、四氯化碳、1,2-二氯乙烷、二硫化碳、醋酸甲酯、醋酸乙酯中的一种或多种。
  6. 根据权利要求1-5中任一项所述的正极组合物，其中，所述正极组合物还包括分散剂、水性粘接剂、导电剂中的一种或多种。
  7. 根据权利要求6所述的正极组合物，其中，基于所述正极组合物的总质量计，
    所述含锂正极活性材料的质量百分含量为88％-99％，可选地为90％-94％；和/或，
    所述有机溶剂包覆物的质量百分含量为0.01％-10％，可选地为3％-7％；和/或，
    所述分散剂的质量百分含量为0.7％以下，可选地为0.1％-0.5％；和/或，
    所述水性粘接剂的质量百分含量为5％以下，可选地为2％-4％；和/或，
    所述导电剂的质量百分含量为5％以下，可选地为0.5％-3％。
  8. 根据权利要求6所述的正极组合物，其中，
    所述分散剂包括阴离子型分散剂、阳离子型分散剂、非离子型分散剂、两性型分散剂、电中性型分散剂、高分子型分散剂、受控自由基型分散剂中的一种或多种，可选地包括聚乙烯亚胺、十二烷基磺酸钠、聚乙烯醇、聚乙二醇辛基苯基醚中的一种或多种；和/或，
    所述水性粘接剂包括甲基纤维素及其盐、黄原胶及其盐、壳聚糖及其盐、海藻酸及其盐、聚乙烯亚胺及其盐、聚丙烯酰胺、丙烯腈-丙烯酸共聚物及其衍生物、或其混合物。
  9. 根据权利要求8所述的正极组合物，其中，所述水性粘接剂包括黄原胶和聚乙烯亚 胺的复配混合物，
    可选地，所述黄原胶和所述聚乙烯亚胺的质量比为2:1-0.2:2.8；
    可选地，所述黄原胶的数均分子量为300000-2000000，所述聚乙烯亚胺的数均分子量为2000-50000。
  10. 根据权利要求8所述的正极组合物，其中，所述水性粘接剂包括丙烯腈-(甲基)丙烯酸共聚物和聚乙烯亚胺的复配混合物，
    可选地，所述丙烯腈-(甲基)丙烯酸共聚物和所述聚乙烯亚胺的质量比为2:1-0.2:2.8；
    可选地，所述丙烯腈-(甲基)丙烯酸共聚物的数均分子量为300000-2000000，所述聚乙烯亚胺的数均分子量为2000-70000。
  11. 一种水系正极浆料，包括溶剂水以及根据权利要求1-10中任一项所述的正极组合物。
  12. 根据权利要求11所述的水系正极浆料，其中，
    所述水系正极浆料的固含量为40％-90％，可选地为50％-70％；和/或，
    所述水系正极浆料的粘度为100cp-10000cp，可选地为3000cp-7000cp。
  13. 一种水系正极浆料的制备方法，用于制备权利要求11或12所述的水系正极浆料，包括步骤：
    S100，将含锂正极活性材料、有机溶剂包覆物混合均匀形成团状物；
    S200，将所得到的团状物、导电剂、水性粘接剂与溶剂水混合均匀，得到水系正极浆料。
  14. 一种水系正极极片，包括正极集流体以及位于所述正极集流体至少一个表面上的正极膜层，其中，所述正极膜层为根据权利要求11或12所述的水系正极浆料干燥后形成的层、或通过权利要求13所述的方法得到的水系正极浆料干燥后形成的层。
  15. 根据权利要求14所述的水系正极极片，其中，
    所述含锂正极活性材料颗粒距离表面100nm的区域中过渡金属元素的质量分数W 1与所述含锂正极活性材料颗粒距离颗粒中心100nm的区域中过渡金属元素的质量分数W 2的比值为α，α为60％-100％，可选地为70％-100％。
  16. 根据权利要求14或15所述的水系正极极片，其中，所述正极膜层的厚度为H，所述正极膜层中距离表面H/3区域内的孔隙率P 1和所述正极膜层中距离所述正极集流体H/3区域内的孔隙率P 2的比值为β，β为1.15-2.0，可选地为1.40-1.60。
  17. 根据权利要求14-16中任一项所述的水系正极极片，其中，
    基于所述水系正极极片的总质量，所述有机溶剂包覆物的质量含量在5000ppm以下，可选地在200ppm以下；和/或，
    所述水系正极极片80℃真空干燥6h后的水分质量含量在400ppm以下，可选地在200ppm以下。
  18. 一种二次电池，包括根据权利要求14至17中任一项所述的水系正极极片。
  19. 一种用电装置，包括根据权利要求18所述的二次电池。
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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014130775A (ja) * 2012-12-28 2014-07-10 Toyota Motor Corp 非水電解質二次電池およびその製造方法
CN105244508A (zh) * 2015-11-06 2016-01-13 中国科学院青岛生物能源与过程研究所 一种锂离子电池高电压正极材料表面包覆方法
JP2016149357A (ja) * 2015-02-10 2016-08-18 Tdk株式会社 リチウムイオン二次電池用正極活物質、リチウムイオン二次電池用正極及びリチウムイオン二次電池
CN111883746A (zh) * 2020-06-19 2020-11-03 广东工业大学 一种改性的富锂锰基氧化物正极材料及其制备方法和应用
CN113363484A (zh) * 2021-05-20 2021-09-07 贵州梅岭电源有限公司 一种提升富锂正极材料库伦效率和循环稳定性的方法

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014130775A (ja) * 2012-12-28 2014-07-10 Toyota Motor Corp 非水電解質二次電池およびその製造方法
JP2016149357A (ja) * 2015-02-10 2016-08-18 Tdk株式会社 リチウムイオン二次電池用正極活物質、リチウムイオン二次電池用正極及びリチウムイオン二次電池
CN105244508A (zh) * 2015-11-06 2016-01-13 中国科学院青岛生物能源与过程研究所 一种锂离子电池高电压正极材料表面包覆方法
CN111883746A (zh) * 2020-06-19 2020-11-03 广东工业大学 一种改性的富锂锰基氧化物正极材料及其制备方法和应用
CN113363484A (zh) * 2021-05-20 2021-09-07 贵州梅岭电源有限公司 一种提升富锂正极材料库伦效率和循环稳定性的方法

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