WO2023184329A1 - 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

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WO2023184329A1
WO2023184329A1 PCT/CN2022/084385 CN2022084385W WO2023184329A1 WO 2023184329 A1 WO2023184329 A1 WO 2023184329A1 CN 2022084385 W CN2022084385 W CN 2022084385W WO 2023184329 A1 WO2023184329 A1 WO 2023184329A1
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positive electrode
optionally
monomer unit
polymer
group
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PCT/CN2022/084385
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English (en)
French (fr)
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刘会会
冯凌云
范艳煌
张文梦
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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 EP22917641.7A priority Critical patent/EP4280308A4/en
Priority to PCT/CN2022/084385 priority patent/WO2023184329A1/zh
Priority to CN202280050821.9A priority patent/CN117678092A/zh
Priority to US18/222,503 priority patent/US20230420677A1/en
Publication of WO2023184329A1 publication Critical patent/WO2023184329A1/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
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
    • H01M4/602—Polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—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
    • 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 relates to the field of battery technology, and in particular to a positive electrode plate, a secondary battery and an electrical device.
  • secondary batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields.
  • energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields.
  • secondary batteries have achieved great development, higher requirements have been placed on their energy density, cycle performance, etc.
  • the related art uses a conductive undercoat layer between the active material of the positive electrode plate and the current collector to improve one or more properties of the secondary battery.
  • the new positive electrode sheet includes a new positive active material and a new conductive undercoat layer, which are described separately below.
  • a first aspect of the present application provides a positive electrode sheet, including a positive electrode current collector, a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and a conductive primer located between the positive electrode current collector and the positive electrode film layer. layer, where,
  • the positive electrode film layer includes a positive electrode active material with a core-shell structure, and the positive electrode active material includes a core and a shell covering the core,
  • the shell includes a first cladding layer covering the core and a second cladding layer covering the first cladding layer, wherein,
  • the first coating layer includes pyrophosphate MP 2 O 7 and phosphate XPO 4 , and the M and X are each independently selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr , one or more of Nb or Al;
  • the second cladding layer includes carbon
  • the conductive undercoat layer includes a first polymer, a first aqueous binder and a first conductive agent,
  • the first polymer includes:
  • At least one second monomer unit selected from the group consisting of the monomer unit represented by Formula 2 and the monomer unit represented by Formula 3;
  • At least one third monomer unit selected from the group consisting of the monomer unit represented by Formula 4 and the monomer unit represented by Formula 5;
  • R 1 , R 2 and R 3 each independently represent H, carboxyl group, ester group and the following substituted or unsubstituted groups: C1 to C10 alkyl group, C1 to C10 alkyl group Oxygen group, C2-C10 alkenyl group, C6-C10 aryl group, R 4 represents H, and the following substituted or unsubstituted groups: C1-C10 alkyl group, C1-C10 alkoxy group, C2-C10 Alkenyl group, C6 ⁇ C10 aryl group;
  • the mass percentage of the first monomer unit is M1, and M1 is 10% to 55%, optionally 25% to 55%; and/or,
  • the mass percentage of the second monomer unit is M2, and M2 is 40% to 80%, optionally 50% to 70%; and/or,
  • the mass percentage of the third monomer unit is M3, and M3 is 0% to 10%, optionally 0.001% to 2%; and/or,
  • the mass percentage of the fourth monomer unit is M4, and M4 is 0% to 10%, optionally 0.1% to 1%.
  • M3/(M2+M3) is 0% to 5%, optionally 0.001% to 1%.
  • the first polymer includes one or more selected from hydrogenated nitrile rubber and hydrogenated carboxyl nitrile rubber; and/or, the weight average molecular weight of the first polymer is 50,000 ⁇ 1.5 million, optionally 200,000 ⁇ 400,000.
  • the first water-based binder includes one selected from the group consisting of water-based polyacrylic resin and its derivatives, water-based amino-modified polypropylene resin and its derivatives, polyvinyl alcohol and its derivatives, or Multiple, optionally including selected from water-based acrylic acid-acrylate copolymer; and/or, the weight average molecular weight of the first water-based binder is 200,000 to 1.5 million, optionally 300,000 to 400,000.
  • the first conductive agent includes one selected from the group consisting of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, or Multiple types, optionally including one or more selected from carbon nanotubes, graphene, and carbon nanofibers.
  • the mass percentage of the first polymer is X1, and X1 is 5% to 20%, optionally 5% to 10%; and/or,
  • the mass percentage of the first water-based binder is X2, and X2 is 30% to 80%, optionally 40% to 50%; and/or,
  • the mass percentage of the first conductive agent is X3, and X3 is 10% to 50%, optionally 40% to 50%.
  • the thickness of the conductive undercoat layer ranges from 1 ⁇ m to 20 ⁇ m, optionally from 3 ⁇ m to 10 ⁇ m.
  • the positive electrode film layer further includes one or more selected from the group consisting of a wetting agent and a dispersing agent.
  • the positive electrode film layer also includes both a wetting agent and a dispersing agent.
  • the surface tension of the sizing agent is 20 mN/m to 40 mN/m.
  • the sizing agent includes one or more selected from the group consisting of small molecule organic solvents and low molecular weight polymers,
  • the small molecule organic solvent includes one or more selected from the group consisting of alcohol amine compounds, alcohol compounds, and nitrile compounds.
  • the number of carbon atoms of the alcohol amine compound is 1 to 16, optionally 2 to 6;
  • the low molecular weight polymer includes one or more selected from the group consisting of maleic anhydride-styrene copolymer, polyvinylpyrrolidone, and polysiloxane.
  • the low molecular weight polymer The weight average molecular weight is below 6000, optionally 3000-6000.
  • the dispersant includes a second polymer, and the second polymer includes:
  • At least one sixth monomer unit selected from the group consisting of a monomer unit represented by Formula 8 and a monomer unit represented by Formula 9;
  • At least one seventh monomer unit selected from the group consisting of the monomer unit represented by Formula 10 and the monomer unit represented by Formula 11;
  • the mass percentage of the fifth monomer unit is M5, and M5 is 10% to 55%, optionally 25% to 55%; and/or,
  • the mass percentage of the sixth monomer unit is M6, and M6 is 40% to 80%, optionally 50% to 70%; and/or,
  • the mass percentage of the seventh monomer unit is M7, and M7 is 0% to 10%, optionally 0.001% to 2%.
  • M7/(M6+M7) is 0% to 5%, optionally 0.001% to 1%.
  • the second polymer is hydrogenated nitrile rubber; and/or,
  • the weight average molecular weight of the second polymer is 50,000-500,000, optionally 150,000-350,000.
  • the mass percentage of the dispersant is Y1, and Y1 is 0.05% to 1%, optionally 0.1% to 0.5%; and/or, The mass percentage of the sizing agent is Y2, and Y2 is 0.05% to 2%, optionally 0.2% to 0.8%.
  • Y1/Y2 is 0.05-20, optionally 0.1-1, further 0.3-0.8.
  • the mass ratio of the first polymer to the second polymer is 1.5-5, optionally 2-3.
  • the interplanar spacing of the phosphate of the first coating layer is 0.345-0.358 nm, and the angle between the crystal directions (111) is 24.25°-26.45°;
  • the interplanar spacing of phosphate is 0.293-0.326nm, and the angle between the crystal orientation (111) is 26.41°-32.57°.
  • the ratio of y to 1-y is 1:10 to 10:1, optionally 1:4 to 1:1; and/or, in the kernel, z
  • the ratio to 1-z is 1:9 to 1:999, optionally 1:499 to 1:249.
  • the coating amount of the first coating layer is greater than 0% by weight and less than or equal to 7% by weight, optionally 4-5.6% by weight, based on the weight of the core.
  • the weight ratio of pyrophosphate and phosphate in the first coating layer is 1:3 to 3:1, optionally 1:3 to 1:1.
  • the crystallinity of the pyrophosphate and phosphate salts each independently ranges from 10% to 100%, optionally from 50% to 100%.
  • the coating amount of the second coating layer is greater than 0% by weight and less than or equal to 6% by weight, optionally 3-5% by weight, based on the weight of the core.
  • the A is selected from at least two of Fe, Ti, V, Ni, Co and Mg.
  • the Li/Mn anti-site defect concentration of the cathode active material is 4% or less, optionally 2% or less.
  • the lattice change rate of the cathode active material is 6% or less, optionally 4% or less.
  • the surface oxygen valence state of the cathode active material is -1.88 or less, optionally -1.98 to -1.88.
  • the positive active material has a compacted density of 2.0 g/cm or more at 3 tons, optionally 2.2 g/cm or more.
  • the specific surface area of the positive active material is 15 m 2 /g ⁇ 25 m 2 /g, and the coating weight of one side of the positive current collector is 20 mg/cm 2 ⁇ 40 mg/cm 2 .
  • the specific surface area of the cathode active material is 15m 2 /g ⁇ 25m 2 /g and the coating weight of one side of the cathode current collector is 20mg/cm 2 ⁇ 40mg/cm 2
  • the film release phenomenon is prone to occur during the coating process.
  • This application uses a new type of conductive undercoat to increase the bonding strength between the positive active material layer and the current collector.
  • a second aspect of the present application provides a secondary battery, including the positive electrode plate described in any one of the above.
  • a third aspect of the present application provides an electrical device, including the above-mentioned secondary battery.
  • the cathode active material with a core-shell structure includes a core and a shell covering the core,
  • the shell includes a first cladding layer covering the core and a second cladding layer covering the first cladding layer,
  • the first coating layer includes pyrophosphate MP 2 O 7 and phosphate XPO 4 , wherein M and X are each independently selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, One or more of Ag, Zr, Nb or Al;
  • the second cladding layer includes carbon.
  • the above limitation on the numerical range of y is not only a limitation on the stoichiometric number of each element as A, but also on the stoichiometric number of each element as A.
  • Limitation of the sum of stoichiometric numbers For example, when A is two or more elements A1, A2...An, the stoichiometric numbers y1, y2...yn of A1, A2...An each need to fall within the numerical range of y defined in this application, and y1 , y2...yn and the sum must also fall within this numerical range.
  • the limitation on the numerical range of the R stoichiometric number in this application also has the above meaning.
  • the inventor of the present application found in actual work that during the deep charge and discharge process of the lithium manganese phosphate cathode active material, manganese dissolution is relatively serious. Although there are attempts in the prior art to coat lithium manganese phosphate with lithium iron phosphate to reduce interface side reactions, this coating cannot prevent the migration of eluted manganese into the electrolyte. The eluted manganese is reduced to metallic manganese after migrating to the negative electrode. The metal manganese produced is equivalent to a "catalyst", which can catalyze the decomposition of the SEI film (solid electrolyte interphase, solid electrolyte interface film) on the surface of the negative electrode.
  • Part of the by-products produced are gases, which can easily cause the battery to expand and affect the safety of the secondary battery. Performance, and the other part is deposited on the surface of the negative electrode, blocking the passage of lithium ions in and out of the negative electrode, causing the impedance of the secondary battery to increase and affecting the dynamic performance of the battery. In addition, in order to replenish the lost SEI film, the electrolyte and active lithium inside the battery are continuously consumed, which has an irreversible impact on the capacity retention rate of the secondary battery.
  • the inventor found that for lithium manganese phosphate cathode active materials, problems such as severe manganese dissolution and high surface reactivity may be caused by the Ginger-Taylor effect of Mn 3+ after delithiation and the change in the size of the Li + channel.
  • the inventor modified lithium manganese phosphate to obtain a cathode active material that can significantly reduce manganese dissolution and lattice change rate, and thus has good cycle performance, high-temperature storage performance and safety performance.
  • the lithium manganese phosphate cathode active material of the present application has a core-shell structure with two coating layers.
  • the positive active material includes a core 91 and a shell covering the core.
  • the shell includes a first coating layer 92 that wraps the core and a second coating layer 93 that wraps the first coating layer 92 .
  • the core includes Li 1+x Mn 1-y A y P 1-z R z O 4 .
  • the element A doped in the manganese position of lithium manganese phosphate in the core helps to reduce the lattice change rate of lithium manganese phosphate during the lithium deintercalation process, improves the structural stability of the lithium manganese phosphate cathode material, and greatly reduces the dissolution of manganese. And reduce the oxygen activity on the particle surface.
  • the element R doped at the phosphorus site helps change the ease of Mn-O bond length change, thereby reducing the lithium ion migration barrier, promoting lithium ion migration, and improving the
  • the first coating layer of the cathode active material of the present application includes pyrophosphate and phosphate. Since the migration barrier of transition metals in pyrophosphate is high (>1eV), it can effectively inhibit the dissolution of transition metals. Phosphate has excellent ability to conduct lithium ions and can reduce the surface miscellaneous lithium content. In addition, since the second coating layer is a carbon-containing layer, it can effectively improve the conductive properties and desolvation ability of LiMnPO 4 . In addition, the "barrier" function of the second coating layer can further hinder the migration of manganese ions into the electrolyte and reduce the corrosion of the active material by the electrolyte.
  • this application can effectively suppress the dissolution of Mn during the process of deintercalation of lithium, and at the same time promote the migration of lithium ions, thereby improving the rate performance of the battery core and improving the secondary Battery cycle performance and high temperature performance.
  • Figure 10 is a comparison chart between the XRD spectrum of Example 1-1 of the present application before the first coating layer and the second coating layer are not coated, and the standard XRD spectrum of lithium manganese phosphate (00-033-0804). It should be pointed out that, as shown in Figure 10, in this application, by comparing the XRD spectra before and after LiMnPO 4 doping, it can be seen that the positions of the main characteristic peaks of the cathode active material of this application and LiMnPO 4 before doping are basically consistent, indicating that the doping
  • the mixed lithium manganese phosphate cathode active material has no impurity phase.
  • the improvement in secondary battery performance mainly comes from element doping, not the impurity phase.
  • the interplanar spacing of the phosphate of the first coating layer is 0.345-0.358 nm, and the angle between the crystal directions (111) is 24.25°-26.45°; the first coating layer The interplanar spacing of pyrophosphate is 0.293-0.326nm, and the angle between the crystal orientation (111) is 26.41°-32.57°.
  • the angle between the interplanar spacing and the crystal direction (111) of the phosphate and pyrophosphate in the first coating layer is within the above range, the impurity phase in the coating layer can be effectively avoided, thereby increasing the gram capacity of the material and improving cycle performance. performance and rate capabilities.
  • the ratio of y to 1-y is 1:10 to 10:1, optionally 1:4 to 1:1.
  • y represents the sum of stoichiometric numbers of Mn-site doping elements.
  • the ratio of z to 1-z is 1:9 to 1:999, optionally 1:499 to 1:249.
  • y represents the sum of stoichiometric numbers of P-site doping elements.
  • the coating amount of the first coating layer is greater than 0% by weight and less than or equal to 7% by weight, optionally 4-5.6% by weight, based on the weight of the core.
  • the coating amount of the first coating layer is within the above range, manganese dissolution can be further suppressed and the transport of lithium ions can be further promoted. And can effectively avoid the following situations: if the coating amount of the first coating layer is too small, the inhibitory effect of pyrophosphate on manganese dissolution may be insufficient, and the improvement of lithium ion transport performance is not significant; if If the coating amount of a coating layer is too large, the coating layer may be too thick, increase the battery impedance, and affect the dynamic performance of the battery.
  • the weight ratio of pyrophosphate and phosphate in the first coating layer is 1:3 to 3:1, optionally 1:3 to 1:1.
  • the appropriate ratio of pyrophosphate and phosphate is conducive to giving full play to the synergistic effect of the two. And can effectively avoid the following situations: if there is too much pyrophosphate and too little phosphate, it may cause the battery impedance to increase; if there is too much phosphate and too little pyrophosphate, the effect of inhibiting manganese dissolution is not significant.
  • the crystallinity of the pyrophosphate and phosphate salts each independently ranges from 10% to 100%, optionally from 50% to 100%.
  • pyrophosphate and phosphate with a certain degree of crystallinity are beneficial to maintaining the structural stability of the first coating layer and reducing lattice defects.
  • this is conducive to giving full play to the role of pyrophosphate in hindering manganese dissolution.
  • it is also conducive to the phosphate reducing the surface miscellaneous lithium content and reducing the valence state of surface oxygen, thereby reducing the interface side reactions between the cathode material and the electrolyte and reducing The consumption of electrolyte improves the cycle performance and safety performance of the battery.
  • the crystallinity of pyrophosphate and phosphate can be adjusted, for example, by adjusting the process conditions of the sintering process, such as sintering temperature, sintering time, and the like.
  • the crystallinity of pyrophosphate and phosphate can be measured by methods known in the art, such as by X-ray diffraction, density, infrared spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance absorption methods.
  • the coating amount of the second coating layer is greater than 0% by weight and less than or equal to 6% by weight, optionally 3-5% by weight, based on the weight of the core.
  • the carbon-containing layer as the second coating layer can function as a "barrier” to avoid direct contact between the positive active material and the electrolyte, thereby reducing the corrosion of the active material by the electrolyte and improving the safety performance of the battery at high temperatures.
  • it has strong electrical conductivity, which can reduce the internal resistance of the battery, thereby improving the dynamic performance of the battery.
  • the carbon material has a low gram capacity, when the amount of the second coating layer is too large, the overall gram capacity of the cathode active material may be reduced. Therefore, when the coating amount of the second coating layer is within the above range, the kinetic performance and safety performance of the battery can be further improved without sacrificing the gram capacity of the cathode active material.
  • the A is selected from at least two of Fe, Ti, V, Ni, Co and Mg.
  • Doping the manganese site in the lithium manganese phosphate cathode active material with two or more of the above elements at the same time is beneficial to enhancing the doping effect. On the one hand, it further reduces the lattice change rate, thereby inhibiting the dissolution of manganese and reducing the loss of electrolyte and active lithium. consumption, on the other hand, it is also conducive to further reducing surface oxygen activity and reducing interface side reactions between the positive active material and the electrolyte, thereby improving the cycle performance and high-temperature storage performance of the battery.
  • the Li/Mn anti-site defect concentration of the cathode active material is 4% or less, optionally 2% or less.
  • the Li/Mn anti-site defect refers to the interchange of positions of Li + and Mn 2+ in the LiMnPO 4 crystal lattice. Since the Li + transport channel is a one-dimensional channel, Mn 2+ is difficult to migrate in the Li + transport channel. Therefore, the anti-site defective Mn 2+ will hinder the transport of Li + .
  • the anti-site defect concentration can be measured based on JIS K0131-1996, for example.
  • the lattice change rate of the cathode active material is 6% or less, optionally 4% or less.
  • the lithium deintercalation process of LiMnPO 4 is a two-phase reaction.
  • the interface stress of the two phases is determined by the lattice change rate. The smaller the lattice change rate, the smaller the interface stress and the easier Li + transport. Therefore, reducing the lattice change rate of the core will be beneficial to enhancing the Li + transport capability, thereby improving the rate performance of secondary batteries.
  • the average discharge voltage of the cathode active material is more than 3.5V, and the discharge capacity is more than 140mAh/g; optionally, the average discharge voltage is more than 3.6V, and the discharge capacity is more than 145mAh. /g or above.
  • the average discharge voltage of undoped LiMnPO 4 is above 4.0V, its discharge gram capacity is low, usually less than 120mAh/g. Therefore, the energy density is low; adjusting the lattice change rate by doping can make it The discharge gram capacity is greatly increased, and the overall energy density is significantly increased while the average discharge voltage drops slightly.
  • the surface oxygen valence state of the cathode active material is -1.88 or less, optionally -1.98 ⁇ -1.88.
  • the higher the valence state of oxygen in the compound the stronger its ability to obtain electrons, that is, the stronger its oxidizing property.
  • the reactivity on the surface of the cathode material can be reduced, and the interface side reactions between the cathode material and the electrolyte can be reduced, thereby improving the secondary Battery cycle performance and high temperature storage performance.
  • the compacted density of the positive active material at 3 tons (T) is above 2.0 g/cm 3 , optionally above 2.2 g/cm 3 .
  • the compacted density of the positive active material that is, the greater the weight of the active material per unit volume, the more conducive it will be to increasing the volumetric energy density of the battery.
  • the compacted density can be measured according to GB/T 24533-2009, for example.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the lithium manganese phosphate positive electrode active material of the present application or is prepared according to the method of the present application. lithium manganese phosphate cathode active material, and the content of the cathode active material in the cathode film layer is more than 10% by weight, based on the total weight of the cathode film layer.
  • the content of the cathode active material in the cathode film layer is 90-99.5% by weight, based on the total weight of the cathode film layer.
  • the positive electrode current collector has two surfaces facing each other in its own 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 positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can 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 base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • 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 cathode film layer of the present application includes 90-99.5% of the lithium manganese phosphate cathode active material of the present application, 0.4-5.5% of binder, 0.1-2.5% of conductive carbon and 0.001-1% of Other additives, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer of the present application may also include other additives such as dispersants, wetting agents, rheology modifiers and other additives commonly used in the art.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the coating weight of the positive electrode film layer of the present application is 0.28-0.45g/1540.25mm 2 , and the compacted density reaches 2.2-2.8g/cm 3 .
  • the median particle diameter Dv 50 refers to the particle diameter corresponding to when the cumulative volume distribution percentage of the positive active material reaches 50%.
  • the median particle diameter Dv 50 of the positive electrode active material can be measured using laser diffraction particle size analysis. For example, refer to the standard GB/T 19077-2016 and use a laser particle size analyzer (such as Malvern Master Size 3000) for measurement.
  • coating layer refers to a material layer coated on the core.
  • the material layer may completely or partially cover the core.
  • the use of “coating layer” is only for convenience of description and is not intended to limit this article. invention.
  • the term “thickness of the coating layer” refers to the thickness of the material layer coating the core in the radial direction of the core.
  • source refers to a compound that is the source of a certain element.
  • types of “source” include but are not limited to carbonates, sulfates, nitrates, elements, halides, and oxides. and hydroxides, etc.
  • This application modified lithium manganese phosphate to obtain a cathode active material that can significantly reduce manganese dissolution and lattice change rate, and thus has good cycle performance, high-temperature storage performance and safety performance.
  • the first coating layer of the cathode active material of the present application includes pyrophosphate and phosphate. Since the migration barrier of transition metals in pyrophosphate is high (>1eV), it can effectively inhibit the dissolution of transition metals. Phosphate has excellent ability to conduct lithium ions and can reduce the surface miscellaneous lithium content. In addition, since the second coating layer is a carbon-containing layer, it can effectively improve the conductive properties and desolvation ability of LiMnPO 4 .
  • the "barrier" function of the second coating layer can further hinder the migration of manganese ions into the electrolyte and reduce the corrosion of the active material by the electrolyte. Therefore, by performing specific element doping and surface coating on lithium manganese phosphate, this application can effectively suppress the dissolution of Mn during the process of deintercalation of lithium, and at the same time promote the migration of lithium ions, thereby improving the rate performance of the battery core and improving the secondary Battery cycle performance and high temperature performance.
  • the first polymer in the conductive undercoat layer will dissolve again after contacting the solvent NMP. , thereby mutually diffusing with the positive electrode active material slurry. After solidification, the active material layer can be integrated with the base coating, thereby effectively increasing the bonding strength between the positive electrode film layer and the positive electrode current collector.
  • the first water-based binder in the conductive undercoat layer is acrylic-acrylate copolymer (weight average molecular weight: 200000 ⁇ 1500000), the polarity of the binder is strong and can be combined with the current collector (aluminum foil ) good adhesion.
  • acrylic acid-acrylate copolymer has good stability in electrolyte, high temperature resistance, corrosion resistance, and low electrolyte absorption efficiency (low swelling degree).
  • the conductive agent in the conductive undercoat layer is selected from one or two types of carbon black, acetylene black, carbon fiber, graphite, and carbon nanotubes, it can reduce the interface resistance and improve the charge and discharge rate performance of the battery. and extend battery cycle life.
  • Figure 1 is a schematic diagram of a positive electrode plate according to an embodiment of the present application.
  • Figure 2 is a schematic flow chart of measuring the adhesive force of pole pieces according to an embodiment of the present application
  • FIG. 3 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 4 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 3 .
  • FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 6 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 7 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 6 .
  • FIG. 8 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • Figure 9 is a schematic diagram of a cathode active material with a core-shell structure according to an embodiment of the present application.
  • Figure 10 is a comparison chart between the XRD spectrum of Example 1-1 of the present application before the first coating layer and the second coating layer are not coated, and the standard XRD spectrum of lithium manganese phosphate (00-033-0804).
  • 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).
  • 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 normally includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte.
  • active ions such as lithium ions
  • 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 is between the positive electrode piece and the negative electrode piece and mainly plays the role of conducting active ions.
  • a first aspect of the present application provides a positive electrode sheet, including a positive electrode current collector, a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and a conductive primer located between the positive electrode current collector and the positive electrode film layer. layer, where,
  • the positive electrode film layer includes a positive electrode active material with a core-shell structure, and the positive electrode active material includes a core and a shell covering the core,
  • the shell includes a first cladding layer covering the core and a second cladding layer covering the first cladding layer, wherein,
  • the first coating layer includes pyrophosphate MP 2 O 7 and phosphate XPO 4 , and the M and X are each independently selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr , one or more of Nb or Al;
  • the second cladding layer includes carbon
  • the conductive undercoat layer includes a first polymer, a first aqueous binder and a first conductive agent,
  • the first polymer includes:
  • At least one second monomer unit selected from the group consisting of the monomer unit represented by Formula 2 and the monomer unit represented by Formula 3;
  • At least one third monomer unit selected from the group consisting of the monomer unit represented by Formula 4 and the monomer unit represented by Formula 5;
  • R 1 , R 2 and R 3 each independently represent H, carboxyl group, ester group and the following substituted or unsubstituted groups: C1 to C10 alkyl group, C1 to C10 alkyl group Oxygen group, C2-C10 alkenyl group, C6-C10 aryl group, R 4 represents H, and the following substituted or unsubstituted groups: C1-C10 alkyl group, C1-C10 alkoxy group, C2-C10 Alkenyl group, C6 ⁇ C10 aryl group;
  • the positive electrode film layer and the positive electrode current collector have enhanced bonding strength.
  • the cathode active material slurry containing solvent N-methylpyrrolidone, NMP for short
  • the first polymer in the conductive undercoat layer will Dissolved again, thereby mutually diffusing with the positive electrode active material slurry.
  • the active material layer can be integrated with the base coating, thereby effectively increasing the bonding strength between the positive electrode film layer and the positive electrode current collector.
  • the first polymer is a random copolymer.
  • Nitrile butadiene rubber is a random copolymer formed by polymerization (such as emulsion polymerization) of acrylonitrile and butadiene monomers. Its general structural formula is:
  • connection mode of butadiene (B) and acrylonitrile (A) chain links is generally the triplet of BAB, BBA or ABB, ABA and BBB.
  • BAB butadiene
  • ABB acrylonitrile
  • AABAA acrylonitrile
  • sequence distribution of butadiene is mainly trans-1,4 structure, and its microstructure is related to the polymerization conditions.
  • Hydrogenated nitrile butadiene rubber refers to a product obtained by hydrogenating the carbon-carbon double bonds on the molecular chain of nitrile butadiene rubber until it is partially or fully saturated.
  • the chemical formula of fully saturated hydrogenated nitrile rubber is as follows:
  • HNBR hydrogenated nitrile rubber
  • the so-called hydrogenated carboxybutyl rubber refers to the further introduction of carboxyl groups on the basis of hydrogenated nitrile rubber.
  • Esters of unsaturated carboxylic acids are, for example, esters of ⁇ , ⁇ -unsaturated monocarboxylic acids.
  • Useful esters of ⁇ , ⁇ -unsaturated monocarboxylic acids are their alkyl esters and alkoxyalkyl esters.
  • an alkyl ester of ⁇ , ⁇ -unsaturated monocarboxylic acid such as C1-C18 alkyl ester
  • optionally is an alkyl ester of acrylic acid or methacrylic acid such as C1-C18 alkyl ester
  • alkoxyalkyl esters of ⁇ , ⁇ -unsaturated monocarboxylic acids optionally alkoxyalkyl esters of acrylic acid or methacrylic acid, for example C2-C12-alkanes of acrylic acid or methacrylic acid.
  • Oxyalkyl esters particularly methoxymethyl acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate and methoxyethyl (meth)acrylate.
  • Mixtures of alkyl esters, such as those described above, and alkoxyalkyl esters, such as those described above, may also be used.
  • Hydroxyalkyl acrylate and hydroxyalkyl methacrylate in which the number of carbon atoms in the hydroxyalkyl group is 1-12 can also be used, optionally 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and acrylic acid. 3-hydroxypropyl ester.
  • epoxy-containing esters may be used, such as glycidyl methacrylate.
  • Cyanoalkyl acrylate and cyanoalkyl methacrylate with 2-12 C atoms in the cyanoalkyl group can also be used, and ⁇ -cyanoethyl acrylate and ⁇ -cyanoethyl acrylate are optional. and cyanobutyl methacrylate.
  • Acrylates or methacrylates containing fluorine-substituted benzyl groups can also be used, and fluorobenzyl acrylate and fluorobenzyl methacrylate are optional.
  • Fluoroalkyl-containing acrylates and methacrylates can also be used, with optional trifluoroethyl acrylate and tetrafluoropropyl methacrylate.
  • Amino-containing ⁇ , ⁇ -unsaturated carboxylic acid esters such as dimethylaminomethyl acrylate and diethylaminoethyl acrylate may also be used.
  • the mass percentage of the first monomer unit is M1, and M1 is 10% to 55%, optionally 25% to 55%; and/or,
  • the mass percentage of the second monomer unit is M2, and M2 is 40% to 80%, optionally 50% to 70%; and/or,
  • the mass percentage of the third monomer unit is M3, and M3 is 0% to 10%, optionally 0.001% to 2%; and/or,
  • the mass percentage of the fourth monomer unit is M4, and M4 is 0% to 10%, optionally 0.1% to 1%.
  • the conductive undercoat based on this solution can be moderately dissolved during the coating process, thereby forming an enhanced bond with the positive electrode film layer.
  • the mass percentage of the first monomer unit is M1, and M1 is 10% to 55%, optionally 10%-15%, 15%-20%, 20%-25%, 25%-30% , 30%-35%, 35%-40%, 40%-45%, 45%-50% or 50%-55%; and/or,
  • the mass percentage of the second monomer unit is M2, and M2 is 40% to 80%, optionally 40%-45%, 45%-50%, 50%-55%, 55%-60% , 60%-65%, 65%-70%, 70%-75% or 75%-80%; and/or,
  • the mass percentage of the third monomer unit is M3, and M3 is 0% to 10%, optionally 0.001%-1%, 1%-2%, 2%-3%, 3%-4% , 4%-5%, 5%-6%, 6%-7%, 7%-8%, 8%-9% or 9%-10%; and/or,
  • the mass percentage of the fourth monomer unit is M4, and M4 is 0% to 10%, optionally 0.01%-1%, 1%-2%, 2%-3%, 3%-4% , 4%-5%, 5%-6%, 6%-7%, 7%-8%, 8%-9% or 9%-10%;.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the conductive undercoat based on this solution can be moderately dissolved during the coating process, thereby forming an enhanced bond with the positive electrode film layer.
  • M3/(M2+M3) is 0% to 5%, optionally 0.001% to 1%.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • M3/(M2+M3) is 0.01%-1%, 1%-2%, 2%-3%, 3%-4%, or 4%-5%.
  • the first polymer includes one or more selected from hydrogenated nitrile rubber and hydrogenated carboxyl nitrile rubber; and/or, the weight average molecular weight of the first polymer is 50,000 ⁇ 1.5 million, optionally 200,000 ⁇ 400,000.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the weight average molecular weight of the first polymer is 100,000-300,000, 300,000-500,000, 500,000-700,000, 700,000-900,000, 900,000-1.1 million, 1.10-1.3 million, or 130-150 Ten thousand.
  • the first water-based binder includes one selected from the group consisting of water-based polyacrylic resin and its derivatives, water-based amino-modified polypropylene resin and its derivatives, polyvinyl alcohol and its derivatives, or A variety, optionally including selected from waterborne acrylic-acrylate copolymers; and/or,
  • the weight average molecular weight of the first aqueous binder is 200,000 to 1.5 million, optionally 300,000 to 400,000.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the weight average molecular weight of the first aqueous binder is 100,000-300,000, 300,000-500,000, 500,000-700,000, 700,000-900,000, 900,000-1.1 million, or 1.10-1.3 million.
  • the first conductive agent includes one selected from the group consisting of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, carbon nanofibers, or Multiple types, optionally including one or more selected from carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the mass percentage of the first polymer is X1, and X1 is 5% to 20%, optionally 5% to 10%; and/or,
  • the mass percentage of the first water-based binder is X2, and X2 is 30% to 80%, optionally 40% to 50%; and/or,
  • the mass percentage of the first conductive agent is X3, and X3 is 10% to 50%, optionally 40% to 50%.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the thickness of the conductive undercoat layer ranges from 1 ⁇ m to 20 ⁇ m, optionally from 3 ⁇ m to 10 ⁇ m.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the positive electrode film layer further includes one or more selected from the group consisting of a wetting agent and a dispersing agent.
  • the positive electrode film layer also includes both a wetting agent and a dispersing agent.
  • the surface tension of the sizing agent is 20 mN/m to 40 mN/m.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • surface tension can be measured using the Wilhelmy Plate Method.
  • Specific test steps can refer to general standards in the field, such as GBT/22237-2008 Determination of surfactant-surface tension, such as ASTM D1331-14.
  • the sizing agent includes one or more selected from the group consisting of small molecule organic solvents and low molecular weight polymers,
  • the small molecule organic solvent includes one or more selected from the group consisting of alcohol amine compounds, alcohol compounds, and nitrile compounds.
  • the number of carbon atoms of the alcohol amine compound is 1 to 16, optionally 2 to 6;
  • the low molecular weight polymer includes one or more selected from the group consisting of maleic anhydride-styrene copolymer, polyvinylpyrrolidone, and polysiloxane.
  • the low molecular weight polymer The weight average molecular weight is below 6000, optionally 3000-6000.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the dispersant includes a second polymer, and the second polymer includes:
  • At least one sixth monomer unit selected from the group consisting of the monomer unit represented by Formula 8 and the monomer unit represented by Formula 9;
  • At least one seventh monomer unit selected from the group consisting of the monomer unit represented by Formula 10 and the monomer unit represented by Formula 11;
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the mass percentage of the fifth monomer unit is M5, and M5 is 10% to 55%, optionally 25% to 55%; and/or,
  • the mass percentage of the sixth monomer unit is M6, and M6 is 40% to 80%, optionally 50% to 70%; and/or,
  • the mass percentage of the seventh monomer unit is M7, and M7 is 0% to 10%, optionally 0.001% to 2%.
  • the mass percentage of the fifth monomer unit is M5, and M5 is 10% to 55%, optionally 10%-15%, 15%-20%, 20%-25%, 25%-30% , 30%-35%, 35%-40%, 40%-45%, 45%-50% or 50%-55%; and/or,
  • the mass percentage of the sixth monomer unit is M6, and M6 is 40% to 80%, optionally 40%-45%, 45%-50%, 50%-55%, 55%-60% , 60%-65%, 65%-70%, 70%-75% or 75%-80%; and/or,
  • the mass percentage of the seventh monomer unit is M7, and M7 is 0% to 10%, optionally 0.01%-1%, 1%-2%, 2%-3%, 3%-4% , 4%-5%, 5%-6%, 6%-7%, 7%-8%, 8%-9% or 9%-10%.
  • M7/(M6+M7) is 0% to 5%, optionally 0.001% to 1%.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the second polymer is hydrogenated nitrile rubber; and/or,
  • the weight average molecular weight of the second polymer is 50,000-500,000, optionally 150,000-350,000.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the mass percentage of the dispersant is Y1, and Y1 is 0.05% to 1%, optionally 0.1% to 0.5%; and/or, The mass percentage of the sizing agent is Y2, and Y2 is 0.05% to 2%, optionally 0.2% to 0.8%.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • Y1/Y2 is 0.05-20, optionally 0.1-1, further 0.3-0.8.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the mass ratio of the first polymer to the second polymer is 1.5-5, optionally 2-3.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the interplanar spacing of the phosphate of the first coating layer is 0.345-0.358 nm, and the angle between the crystal directions (111) is 24.25°-26.45°;
  • the interplanar spacing of phosphate is 0.293-0.326nm, and the angle between the crystal orientation (111) is 26.41°-32.57°.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the ratio of y to 1-y is 1:10 to 10:1, optionally 1:4 to 1:1; and/or, in the kernel, z
  • the ratio to 1-z is 1:9 to 1:999, optionally 1:499 to 1:249.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the coating amount of the first coating layer is greater than 0% by weight and less than or equal to 7% by weight, optionally 4-5.6% by weight, based on the weight of the core.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the weight ratio of pyrophosphate and phosphate in the first coating layer is 1:3 to 3:1, optionally 1:3 to 1:1.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the crystallinity of the pyrophosphate and phosphate salts each independently ranges from 10% to 100%, optionally from 50% to 100%.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the coating amount of the second coating layer is greater than 0% by weight and less than or equal to 6% by weight, optionally 3-5% by weight, based on the weight of the core.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the A is selected from at least two of Fe, Ti, V, Ni, Co and Mg.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the Li/Mn anti-site defect concentration of the cathode active material is 4% or less, optionally 2% or less.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the lattice change rate of the cathode active material is 6% or less, optionally 4% or less.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the surface oxygen valence state of the cathode active material is -1.88 or less, optionally -1.98 to -1.88.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the positive active material has a compacted density of 2.0 g/cm or more at 3 tons, optionally 2.2 g/cm or more.
  • the positive electrode sheet based on this solution is used in secondary batteries, and one or more properties of the secondary battery are significantly improved.
  • the present application provides a secondary battery including the positive electrode sheet described in any one of the above.
  • the present application provides an electrical device, including the above-mentioned secondary battery.
  • the positive electrode sheet generally includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material.
  • Figure 1 shows a schematic diagram of a positive electrode plate according to an embodiment.
  • a positive electrode sheet includes a positive electrode current collector 11, a positive electrode film layer 13 provided on at least one surface 112 of the positive electrode current collector 11, and a positive electrode film layer 13 located between the positive electrode current collector 11 and the positive electrode film layer 13.
  • Conductive primer layer 12 between.
  • the positive electrode current collector has two surfaces facing each other in its own 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 positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can 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 base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer. At least one of a meta-copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • 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 positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • 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, where the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own 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 composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative 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, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials 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 film layer optionally further includes a binder.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), At least one of polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes 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 negative electrode film layer optionally also includes other auxiliaries, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • auxiliaries such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is liquid and includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte optionally also includes additives.
  • 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 or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • 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 film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film 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 material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 3 shows a square-structured secondary battery 5 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 can 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 more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 5 is a 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.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number 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 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with 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 present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include 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, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • Figure 8 is 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.
  • a battery pack or battery module can be used.
  • the reaction kettle was heated to 80°C and stirred at a rotation speed of 600 rpm for 6 hours until the reaction was terminated (no bubbles were generated) to obtain a manganese oxalate suspension co-doped with Fe, Co, V and S.
  • the suspension was then filtered, and the filter cake was dried at 120° C. and then ground to obtain Fe, Co and V co-doped manganese oxalate dihydrate particles with a median particle size Dv50 of 100 nm.
  • Preparation of lithium manganese phosphate co-doped with Fe, Co, V and S combine the manganese oxalate dihydrate particles obtained in the previous step (1793.4g), 369.0g lithium carbonate (calculated as Li 2 CO 3 , the same below), 1.6g Dilute sulfuric acid with a concentration of 60% (calculated as 60% H 2 SO 4 , the same below) and 1148.9g ammonium dihydrogen phosphate (calculated as NH 4 H 2 PO 4 , the same below) were added to 20 liters of deionized water, and the mixture was Stir for 10 hours to mix evenly and obtain a slurry.
  • lithium iron pyrophosphate powder Dissolve 4.77g lithium carbonate, 7.47g ferrous carbonate, 14.84g ammonium dihydrogen phosphate and 1.3g oxalic acid dihydrate in 50ml deionized water. The pH of the mixture was 5, and the reaction mixture was stirred for 2 hours to fully react. The reacted solution was then heated to 80°C and maintained at this temperature for 4 hours to obtain a suspension containing Li 2 FeP 2 O 7. The suspension was filtered, washed with deionized water, and dried at 120°C for 4 hours. , get powder. The powder was sintered at 650° C. in a nitrogen atmosphere for 8 hours, and then naturally cooled to room temperature and then ground to obtain Li 2 FeP 2 O 7 powder.
  • lithium iron phosphate suspension Dissolve 11.1g lithium carbonate, 34.8g ferrous carbonate, 34.5g ammonium dihydrogen phosphate, 1.3g oxalic acid dihydrate and 74.6g sucrose (calculated as C 12 H 22 O 11 , the same below) In 150 ml of deionized water, a mixture was obtained, and then stirred for 6 hours to allow the above mixture to fully react. The reacted solution was then heated to 120°C and maintained at this temperature for 6 hours to obtain a suspension containing LiFePO4 .
  • the double-layer coated lithium manganese phosphate cathode active material prepared above, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) in a weight ratio of 92:2.5:5.5 ), stir and mix evenly to obtain positive electrode slurry. Then, the positive electrode slurry is evenly coated on the aluminum foil at a density of 0.280g/ 1540.25mm2 , dried, cold pressed, and cut to obtain the positive electrode piece.
  • negative active material artificial graphite artificial graphite, hard carbon, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethylcellulose (CMC-Na) in a weight ratio of 90:5:2:2 : 1 Dissolve in solvent deionized water, stir and mix evenly to prepare negative electrode slurry.
  • the negative electrode slurry is evenly coated on the negative electrode current collector copper foil at a density of 0.117g/1540.25mm 2 , and then dried, cold pressed, and cut to obtain negative electrode pieces.
  • a commercially available PP-PE copolymer microporous film with a thickness of 20 ⁇ m and an average pore diameter of 80 nm was used.
  • the positive electrode piece, isolation film, and negative electrode piece obtained above are stacked in order, so that the isolation film is between the positive and negative electrodes to play an isolation role, and the bare battery core is obtained by winding.
  • the bare battery core is placed in the outer packaging, the above-mentioned electrolyte is injected and packaged to obtain a full battery (hereinafter also referred to as "full battery").
  • the double-layer coated lithium manganese phosphate cathode active material prepared above, PVDF, and acetylene black were added to NMP in a weight ratio of 90:5:5, and stirred in a drying room to form a slurry.
  • the above slurry is coated on aluminum foil, dried and cold pressed to form a positive electrode sheet.
  • the coating amount is 0.02g/cm 2 and the compacted density is 2.0g/cm 3 .
  • Lithium sheets were used as the negative electrode, and a solution of 1 mol/L LiPF 6 in ethylene carbonate (EC) + diethyl carbonate (DEC) + dimethyl carbonate (DMC) with a volume ratio of 1:1:1 was used as the electrolyte.
  • liquid, together with the positive electrode sheet prepared above, are assembled into a button battery (hereinafter also referred to as a "button battery") in a buckle box.
  • the coating amount shown in Table 1 is the same as that in Example 1.
  • the ratio of the coating amount corresponding to -1 is adjusted accordingly, so that the amounts of Li 2 FeP 2 O 7 /LiFePO 4 in Examples 1-2 to 1-6 are 12.6g/37.7g, 15.7g/47.1g, and 18.8 respectively. g/56.5g, 22.0/66.0g and 25.1g/75.4g.
  • the other conditions are the same as in Example 1-1 except that the amount of sucrose used is 37.3g.
  • the amounts of various raw materials are adjusted accordingly according to the coating amounts shown in Table 1 so that the amounts of Li 2 FeP 2 O 7 /LiFePO 4 are 23.6g/39.3g respectively. , 31.4g/31.4g, 39.3g/23.6g and 47.2g/15.7g, the conditions of Examples 1-11 to 1-14 were the same as Example 1-7.
  • Examples 1-15 were the same as Examples 1-14 except that 492.80 g of ZnCO3 was used instead of ferrous carbonate in the preparation process of the co-doped lithium manganese phosphate core.
  • Examples 1-16 used 466.4g NiCO 3 , 5.0g zinc carbonate and 7.2g titanium sulfate instead of ferrous carbonate in the preparation process of the co-doped lithium manganese phosphate core.
  • 455.2g of ferrous carbonate and 8.5g of vanadium dichloride were used in the preparation process of the lithium manganese phosphate core.
  • 455.2g of ferrous carbonate was used in the preparation process of the co-doped lithium manganese phosphate core.
  • 4.9g of vanadium dichloride and 2.5g of magnesium carbonate the conditions of Examples 1-17 to 1-19 were the same as Example 1-7.
  • Examples 1-19 used 369.4g of lithium carbonate and 1.05g of 60% concentrated dilute nitric acid instead of dilute sulfuric acid in the preparation process of the co-doped lithium manganese phosphate core.
  • the conditions of Examples 1-19 to 1-20 were the same as those of Example 1-18, except that 369.7g of lithium carbonate was used and 0.78g of silicic acid was used instead of dilute sulfuric acid.
  • Example 1-21 632.0g manganese carbonate, 463.30g ferrous carbonate, 30.5g vanadium dichloride, 21.0g magnesium carbonate and 0.78g silicic acid were used in the preparation process of the co-doped lithium manganese phosphate core. ;
  • Example 1-22 uses 746.9g manganese carbonate, 289.6g ferrous carbonate, 60.9g vanadium dichloride, 42.1g magnesium carbonate and 0.78g silicic acid in the preparation process of co-doped lithium manganese phosphate core. Except for this, the conditions of Examples 1-21 to 1-22 were the same as those of Example 1-20.
  • Example 1-24 In the preparation process of co-doped lithium manganese phosphate core, 862.1g manganese carbonate, 173.8g ferrous carbonate, 1155.1g ammonium dihydrogen phosphate, 1.86g boric acid (mass fraction 99.5% ) and 371.6 g of lithium carbonate, the conditions of Examples 1-23 to 1-24 were the same as those of Example 1-22.
  • Example 1-25 uses 370.1g lithium carbonate, 1.56g silicic acid and 1147.7g ammonium dihydrogen phosphate in the preparation process of the co-doped lithium manganese phosphate core, the conditions of Examples 1-25 are the same as those of Examples 1-20 are the same.
  • Examples 1-26, 368.3g lithium carbonate, 4.9g dilute sulfuric acid with a mass fraction of 60%, 919.6g manganese carbonate, 224.8g ferrous carbonate, and 3.7g dichloride were used in the preparation process of the co-doped lithium manganese phosphate core.
  • the conditions of Examples 1-26 were the same as Examples 1-20 except for vanadium, 2.5g magnesium carbonate and 1146.8g ammonium dihydrogen phosphate.
  • Example 1-27 used 367.9g lithium carbonate, 6.5g dilute sulfuric acid with a concentration of 60% and 1145.4g ammonium dihydrogen phosphate in the preparation process of the co-doped lithium manganese phosphate core.
  • the conditions of Example 1-27 Same as Examples 1-20.
  • Examples 1-28 to 1-33 are the same as those of Example 1-20, except that the usage amounts of dilute sulfuric acid with a concentration of 60% are: 8.2g, 9.8g, 11.4g, 13.1g, 14.7g and 16.3g respectively. .
  • the sintering temperature in the powder sintering step is 550°C and the sintering time is 1h to control the crystallinity of Li 2 FeP 2 O 7 to 30%.
  • the sintering temperature in the coating sintering step is 650°C and the sintering time is 2 hours to control the crystallinity of LiFePO 4 to 30%.
  • Other conditions are the same as in Example 1-1.
  • the sintering temperature in the powder sintering step is 550°C and the sintering time is 2h to control the crystallinity of Li 2 FeP 2 O 7 to 50%.
  • the sintering temperature in the coating sintering step is 650°C and the sintering time is 3 hours to control the crystallinity of LiFePO 4 to 50%.
  • Other conditions are the same as in Example 1-1.
  • the sintering temperature in the powder sintering step is 600°C and the sintering time is 3h to control the crystallinity of Li 2 FeP 2 O 7 to 70%.
  • the sintering temperature in the coating sintering step is 650°C and the sintering time is 4 hours to control the crystallinity of LiFePO 4 to 70%.
  • Other conditions are the same as in Example 1-1.
  • the sintering temperature in the powder sintering step is 650°C and the sintering time is 4h to control the crystallinity of Li 2 FeP 2 O 7 to 100%.
  • the sintering temperature in the coating sintering step is 700°C and the sintering time is 6 hours to control the crystallinity of LiFePO 4 to 100%.
  • Other conditions are the same as in Example 1-1.
  • the heating temperature/stirring time in the reaction kettle of Example 3-1 is 60°C/120 minutes respectively; the heating temperature in the reaction kettle of Example 3-2 The temperature/stirring time is 70°C/120 minutes respectively; the heating temperature/stirring time in the reaction kettle of Example 3-3 is 80°C/120 minutes respectively; the heating temperature/stirring time in the reaction kettle of Example 3-4 is respectively 90°C/120 minutes; the heating temperature/stirring time in the reaction kettle of Example 3-5 is 100°C/120 minutes respectively; the heating temperature/stirring time in the reaction kettle of Example 3-6 is 110°C/120 minutes respectively; The heating temperature/stirring time in the reaction kettle of Example 3-7 is 120°C/120 minutes respectively; the heating temperature/stirring time in the reaction kettle of Example 3-8 is 130°C/120 minutes respectively; the reaction of Example 3-9 The heating temperature/stirring time in the kettle is 100°C/60 minutes respectively;
  • Examples 4-1 to 4-4 Except in the preparation process of lithium iron pyrophosphate (Li 2 FeP 2 O 7 ), the drying temperature/drying time in the drying step are respectively 100°C/4h, 150°C/6h, 200°C/6h and 200°C/6h; in the preparation process of lithium iron pyrophosphate (Li 2 FeP 2 O 7 ), the sintering temperature and sintering time in the sintering step are 700°C/6h, 700°C/6h, 700 respectively Except for °C/6h and 600°C/6h, other conditions are the same as Example 1-7.
  • Embodiments 4-5 to 4-7 In addition to the drying temperature/drying time in the drying step during the coating process being 150°C/6h, 150°C/6h and 150°C/6h respectively; in the sintering process during the coating process The other conditions are the same as Examples 1-12 except that the sintering temperature and sintering time in the step are 600°C/4h, 600°C/6h and 800°C/8h respectively.
  • Preparation of manganese oxalate Add 1149.3g of manganese carbonate to the reaction kettle, and add 5 liters of deionized water and 1260.6g of oxalic acid dihydrate (calculated as C 2 H 2 O 4 ⁇ 2H 2 O, the same below). Heat the reaction kettle to 80°C and stir at 600 rpm for 6 hours until the reaction is terminated (no bubbles are generated) to obtain a manganese oxalate suspension, then filter the suspension, dry the filter cake at 120°C, and then proceed After grinding, manganese oxalate dihydrate particles with a median particle size Dv50 of 100 nm were obtained.
  • Preparation of carbon-coated lithium manganese phosphate Take 1789.6g of the manganese oxalate dihydrate particles obtained above, 369.4g of lithium carbonate (calculated as Li 2 CO 3 , the same below), 1150.1g of ammonium dihydrogen phosphate (calculated as NH 4 H 2 PO 4 , the same below) and 31g sucrose (calculated as C 12 H 22 O 11 , the same below) were added to 20 liters of deionized water, and the mixture was stirred for 10 hours to mix evenly to obtain a slurry. Transfer the slurry to spray drying equipment for spray drying and granulation, set the drying temperature to 250°C, and dry for 4 hours to obtain powder. In a protective atmosphere of nitrogen (90 volume %) + hydrogen (10 volume %), the above powder was sintered at 700° C. for 4 hours to obtain carbon-coated lithium manganese phosphate.
  • Comparative Example 2 Other conditions of Comparative Example 2 were the same as Comparative Example 1 except that 689.5 g of manganese carbonate was used and 463.3 g of additional ferrous carbonate were added.
  • Comparative Example 3 Other conditions of Comparative Example 3 were the same as Comparative Example 1 except that 1148.9 g of ammonium dihydrogen phosphate and 369.0 g of lithium carbonate were used, and 1.6 g of 60% concentration dilute sulfuric acid was additionally added.
  • Comparative Example 4 Except for using 689.5g of manganese carbonate, 1148.9g of ammonium dihydrogen phosphate and 369.0g of lithium carbonate, and additionally adding 463.3g of ferrous carbonate and 1.6g of 60% concentration of dilute sulfuric acid, the other conditions of Comparative Example 4 were the same as those of Comparative Example 4. Same as scale 1.
  • lithium iron phosphate suspension Dissolve 14.7g lithium carbonate, 46.1g ferrous carbonate, 45.8g ammonium dihydrogen phosphate and 50.2g oxalic acid dihydrate in 500ml deionized water, and then stir for 6 hours. The mixture reacted fully. The reacted solution was then heated to 120°C and maintained at this temperature for 6 hours to obtain a suspension containing LiFePO 4 .
  • the sintering temperature in the coating sintering step during the preparation of lithium iron phosphate (LiFePO 4 ) was 600°C.
  • Comparative Example 6 The other conditions of Comparative Example 6 were the same as Comparative Example 4 except that the sintering time was 4h to control the crystallinity of LiFePO 4 to 8%. When preparing carbon-coated materials, the amount of LiFePO 4 was 62.8g.
  • lithium iron pyrophosphate powder Dissolve 2.38g lithium carbonate, 7.5g ferrous carbonate, 7.4g ammonium dihydrogen phosphate and 8.1g oxalic acid dihydrate in 50ml deionized water. The pH of the mixture was 5, and the reaction mixture was stirred for 2 hours to fully react. The reacted solution was then heated to 80°C and maintained at this temperature for 4 hours to obtain a suspension containing Li 2 FeP 2 O 7. The suspension was filtered, washed with deionized water, and dried at 120°C for 4 hours. , get powder. The powder was sintered at 500° C. in a nitrogen atmosphere for 4 hours, and then naturally cooled to room temperature and then ground to control the crystallinity of Li 2 FeP 2 O 7 to 5%.
  • lithium iron phosphate suspension Dissolve 11.1g lithium carbonate, 34.7g ferrous carbonate, 34.4g ammonium dihydrogen phosphate, 37.7g oxalic acid dihydrate and 37.3g sucrose (calculated as C 12 H 22 O 11 , the same below) in 1500 ml deionized water, and then stirred for 6 hours to fully react the mixture. The reacted solution was then heated to 120°C and maintained at this temperature for 6 hours to obtain a suspension containing LiFePO4 .
  • the drying temperature/drying time in the drying step is respectively 80°C/3h, 80°C/3h, and 80°C/ 3h; in the preparation process of lithium iron pyrophosphate (Li 2 FeP 2 O 7 ), the sintering temperature and sintering time in the sintering step are respectively 400°C/3h, 400°C/3h, and 350°C in Comparative Examples 8-10.
  • the drying temperature/drying time in the drying step during the preparation process of lithium iron phosphate (LiFePO 4 ) in Comparative Example 11 is 80°C/3h; and Li 2 FeP 2 O 7 /LiFePO in Comparative Examples 8-11 Except that the dosage of 4 is 47.2g/15.7g, 15.7g/47.2g, 62.8g/0g, and 0g/62.8g respectively, other conditions are the same as those in Examples 1-7.
  • the button battery prepared above was left for 5 minutes in a constant temperature environment of 25°C, discharged at 0.1C to 2.5V, left for 5 minutes, charged at 0.1C to 4.3V, and then charged at a constant voltage of 4.3V until the current was less than Equal to 0.05mA, let stand for 5 minutes; then discharge to 2.5V according to 0.1C.
  • the discharge capacity at this time is the initial gram capacity, recorded as D0, the discharge energy is the initial energy, recorded as E0, and the average discharge voltage V of the buckle is E0 /D0.
  • the above-prepared full cell was stored at 100% state of charge (SOC) at 60°C. Measure the open circuit voltage (OCV) and AC internal resistance (IMP) of the battery cells before, after and during storage to monitor SOC, and measure the volume of the battery cells. The full battery was taken out after every 48 hours of storage, and the open circuit voltage (OCV) and internal resistance (IMP) were tested after leaving it for 1 hour. After cooling to room temperature, the cell volume was measured using the drainage method. The drainage method is to first separately measure the gravity F 1 of the battery cell using a balance that automatically converts units based on the dial data, then completely places the battery core in deionized water (density is known to be 1g/cm 3 ), and measures the battery core at this time.
  • the positive active material sample is prepared into a buckle, and the above buckle is charged at a small rate of 0.05C until the current is reduced to 0.01C. Then take out the positive electrode piece from the battery and soak it in dimethyl carbonate (DMC) for 8 hours. Then it is dried, scraped into powder, and particles with a particle size less than 500nm are screened out. Take a sample and calculate its unit cell volume v1 in the same way as the above-mentioned test of fresh samples, and use (v0-v1)/v0 ⁇ 100% as the lattice change rate (unit cell volume change rate) before and after complete deintercalation of lithium. in the table.
  • DMC dimethyl carbonate
  • the positive electrode active material sample prepared above Take 5 g of the positive electrode active material sample prepared above and prepare a buckle according to the above buckle preparation method. Charge with a small rate of 0.05C until the current is reduced to 0.01C. Then take out the positive electrode piece from the battery and soak it in dimethyl carbonate (DMC) for 8 hours. Then it is dried, scraped into powder, and particles with a particle size less than 500nm are screened out. The obtained particles were measured with electron energy loss spectroscopy (EELS, the instrument model used was Talos F200S) to obtain the energy loss near-edge structure (ELNES), which reflects the state density and energy level distribution of the element. According to the density of states and energy level distribution, the number of occupied electrons is calculated by integrating the valence band density of states data, thereby deducing the valence state of the charged surface oxygen.
  • DMC dimethyl carbonate
  • the crystallinity is the ratio of the crystalline part scattering to the total scattering intensity.
  • the specific embodiments related to the new conductive undercoat layer are added with a suffix [’] after the number.
  • Example 1-1 (positive electrode active material of Example 1-1)
  • the first polymer is a hydrogenated carboxyl nitrile rubber, which contains a first monomer unit, a second monomer unit, a third monomer unit and a fourth monomer unit.
  • the weight percentages of the first monomer unit, the second monomer unit, the third monomer unit and the fourth monomer unit in the polymer, and the weight average molecular weight of the first polymer are as shown in Table 1P.
  • the first monomer unit is the monomer unit represented by Formula 1;
  • the second monomer unit is selected from at least the group consisting of the monomer unit represented by Formula 2 and the monomer unit represented by Formula 3.
  • At least the third monomer unit is selected from the group consisting of the monomer unit represented by Formula 4 and the monomer unit represented by Formula 5.
  • the fourth monomer unit is the monomer unit represented by Formula 6:
  • R 1 , R 2 and R 3 are all H, and R 4 is n-butyl.
  • the first polymer, the first water-based binder (polyacrylic acid-acrylate copolymer, weight average molecular weight 340,000) and the first conductive agent (SP) are mixed in a weight ratio of 15:40:45, and dissolved/dispersed In NMP solvent, prepare conductive primer slurry.
  • the conductive primer slurry is applied to both sides of the aluminum foil, and after drying, a conductive primer with a thickness of 5 ⁇ m is formed on each side.
  • Aluminum foil with a conductive base coating is obtained.
  • the double-layer-coated lithium manganese phosphate cathode active material of Example 1-1 above was mixed with the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) in a weight ratio of 92:2.5:5.5 in N-methyl After mixing evenly in the pyrrolidone solvent system, the positive electrode slurry is obtained. The positive electrode slurry is coated on both sides of the aluminum foil with a conductive undercoat, dried, and cold pressed to form a positive electrode film layer, and a positive electrode piece is obtained. The density of one side of the positive electrode film layer is 0.025g/cm 2 and the compacted density is 2.4g/cm 3 .
  • the density of one side of the negative electrode film layer is 0.013g/cm 2 and the compacted density is 1.7g/cm 3 .
  • PE polyethylene
  • the weight of the positive active material in a single full battery is 565.66g; the weight of the negative active material is 309.38g.
  • Examples 1-2’ to 1-33’ positive electrode active materials of Examples 1-2 to 1-33
  • Example 1-1' The difference between Examples 1-2' to 1-33' and Example 1-1' lies in step 3). Other step parameters are the same as those in Example 1-1'.
  • the cathode active materials used in step 3) of Examples 1-2' to 1-33' are the cathode active materials of the above Examples 1-2 to 1-33 respectively.
  • Examples 2-1’ to 2-3’ positive electrode active materials of Examples 2-1 to 2-3
  • Example 1-1' The difference between Examples 2-1' to 2-3' and Example 1-1' lies in step 3). Other step parameters are the same as those in Example 1-1'.
  • the cathode active materials used in step 3) of Examples 2-1' to 2-3' are the cathode active materials of the above Examples 2-1 to 2-3 respectively.
  • the cathode active materials used in step 3) of Comparative Examples 1' to 7' are the cathode active materials of Comparative Examples 1-1 to 1-7 above, respectively.
  • the cathode active material used in step 3) of Comparative Example 8' is the cathode active material of Example 1-1 above.
  • step 2 The difference between Comparative Example 9' and Example 1-1' lies in step 2).
  • Other step parameters are the same as those in Example 1-1'.
  • step 2 the first water-based binder (polyacrylic acid-acrylate copolymer) and the first conductive agent (SP) were mixed in a weight ratio of 40:45, and dissolved/dispersed in deionized water. water to prepare a conductive primer slurry. The conductive undercoat slurry is applied to the aluminum foil and dried to form a conductive undercoat with a thickness of 5 ⁇ m. Aluminum foil with a conductive base coating is obtained.
  • the first water-based binder polyacrylic acid-acrylate copolymer
  • SP first conductive agent
  • step 2 The difference between Comparative Example 10' and Example 1-1' lies in step 2).
  • Other step parameters are the same as those in Example 1-1'.
  • step 2 the first polymer, the first water-based binder (polyacrylic acid-acrylate copolymer) and the first conductive agent (SP) were mixed in a weight ratio of 15:40:45 , dissolved/dispersed in deionized water, to prepare a conductive primer slurry.
  • the conductive undercoat slurry is applied to the aluminum foil and dried to form a conductive undercoat with a thickness of 5 ⁇ m.
  • Aluminum foil with a conductive base coating is obtained.
  • the difference between the first polymer and the first polymer lies in the composition of the polymer.
  • the composition and weight average molecular weight of the first polymer are as shown in Table 2P below.
  • step 2 The difference between Comparative Example 11' and Example 1-1' lies in step 2).
  • Other step parameters are the same as those in Example 1-1'.
  • step 2 the first polymer, the first binder (polyacrylic acid, weight average molecular weight 350,000) and the first conductive agent (SP) were mixed in a weight ratio of 15:40:45 , dissolved/dispersed in deionized water, to prepare a conductive primer slurry.
  • the conductive undercoat slurry is applied to the aluminum foil and dried to form a conductive undercoat with a thickness of 5 ⁇ m.
  • Aluminum foil with a conductive base coating is obtained.
  • FIG. 2 show a flow chart of the peel test.
  • a steel plate 510 is first provided, with dimensions of 30 mm wide and 100 mm long.
  • a piece of double-sided tape 520 is then provided. The size of the double-sided tape 520 is 20 mm wide ⁇ 30 mm long.
  • the double-sided tape 520 is attached to the steel plate 510, with one wide edge of the double-sided tape 520 Aligned with one wide edge of steel plate 510.
  • a pole piece 530 to be tested is then provided. The size of the pole piece 530 to be tested is 20 mm wide by 180 mm long.
  • the direction of the stretching force is perpendicular to the steel plate 510 and is at a certain distance from the surface of the steel plate 510 .
  • the steel plate moves upward to keep the stretching direction perpendicular to the pole piece peeling position.
  • the stretching causes the pole piece 530 to be gradually peeled off from the steel plate.
  • the stretching speed of the clamp is 50mm/min.
  • record the tensile force of the clamp After the tensile force stabilizes, continue to peel off a length of 40 mm.
  • the average tensile force under the peeling length is the bonding force (unit N).
  • the DC impedance value of the battery of Example 1-1' is 100%, and the changes in other Examples and Comparative Examples relative to Example 1-1' are expressed in the form of percentages.
  • Battery’s 45°C capacity retention rate is 80% cycles (hereinafter referred to as “80% capacity cycles”)
  • the positive electrode sheets of Examples 1-1' to 1-33' and Examples 2-1' to 2-3' show improved adhesion, and the positive electrode sheets of Examples 1-1' to 1-33 ', the batteries of Examples 2-1' to 2-3' showed reduced DC resistance and improved cycle capacity retention rate.
  • Comparative Example 8' (no conductive undercoat layer is provided), Comparative Example 9' (not containing the first polymer), Comparative Example 10' (replacing the first polymer with the first polymer), Comparative Example 11' (using the first polymer) 1 binder instead of the first water-based binder) failed to achieve the above-mentioned improved effect.
  • Example 3-1' to 3-7' lies in step 2).
  • Other step parameters are the same as those in Example 1-1'.
  • step 2) the composition of the first polymer used in Examples 3-1' to 3-7' is different from that in Example 1-1', specifically the weight percentage of the second monomer unit and the third monomer unit. Different from Example 1-1'.
  • the component composition of the first polymer of Examples 3-1' to 3-7' is shown in Table 4P below.
  • Example 3-8' to 3-12' lies in step 2).
  • Other step parameters are the same as those in Example 1-1'.
  • step 2) the thickness of the conductive undercoat layer of Examples 3-8' to 3-12' is different from that of Example 1-1', see Table 5P for details.
  • Example 1-1' The difference between Examples 3-13' to 3-18' and Example 1-1' lies in step 2).
  • Other step parameters are the same as those in Example 1-1'.
  • step 2) the conductive undercoat components (the ratio of the first polymer, the first aqueous binder and the first conductive agent) of Examples 3-13' to 3-18' are the same as those of Example 1-1 'Different, see Table 6P for details.
  • the adhesion force of the positive electrode sheet prepared in the above embodiments 1-1', 3-1' to 3-18', the DC resistance value of the battery and the 45°C capacity retention rate of the battery were 80 % cycle number was tested, and the results are shown in Table 7P below.
  • Example 3-1 13 100% 1650
  • Example 3-1 12.7 100% 1700
  • Example 3-2’ 13 97% 1688
  • Example 3-3 12.5 100% 1703
  • Example 3-4 13.1 99% 1600
  • Example 3-5 13.8 98% 1660
  • Example 3-6 13.9 99% 1655
  • Example 3-7 12 258% 731
  • Example 3-8 8.5 110% 1540
  • Example 3-9 7.3 101% 1720
  • Example 3-10 9.9 100% 1779
  • Example 3-11’ 21.1 120% 1600
  • Example 3-13’ 8.1 100% 1630
  • Example 3-14’ 10.5 105% 1680
  • Example 3-15’ 11.6 103% 1701
  • Example 3-16’ 10.7 145% 1600
  • Example 3-17’ 14.5 130% 1635
  • Example 3-18’ 15 110% 1630
  • Example 4-1' to 4-9' lies in step 3).
  • Other step parameters are the same as those in Example 1-1'.
  • step 3) of Examples 4-1' to 4-9' the double-layer coated lithium manganese phosphate cathode active material of Example 1-1 above is mixed with the conductive agent acetylene black and the binder polyylidene fluoride.
  • Ethylene (PVDF), dispersant and sizing agent are mixed evenly in the N-methylpyrrolidone solvent system according to the weight ratio (92-Y 1 -Y 2 ): 2.5: 5.5: Y 1 : Y 2 to obtain the positive electrode slurry.
  • the positive electrode slurry is coated on both sides of the aluminum foil with a conductive undercoat, dried and cold pressed to form a positive electrode film layer to obtain a positive electrode piece.
  • the density of one side of the positive electrode film layer is 0.025g/cm 2 and the compacted density is 2.4g/cm 3 .
  • the sizing agent in Examples 4-1' to 4-9' is maleic anhydride-styrene copolymer (molecular weight 5000).
  • the dispersant of Examples 4-1' to 4-9' is the second polymer.
  • the second polymer is a hydrogenated nitrile rubber containing a fifth monomer unit, a sixth monomer unit and a seventh monomer unit.
  • the weight percentages of the five monomer units, the sixth monomer unit and the seventh monomer unit in the polymer, and the weight average molecular weight of the second polymer are shown in Table 8P.
  • the fifth monomer unit is the monomer unit represented by Formula 1;
  • the sixth monomer unit is at least one selected from the group consisting of the monomer unit represented by Formula 8 and the monomer unit represented by Formula 9.
  • the seventh monomer unit is at least one selected from the group consisting of the monomer unit represented by Formula 10 and the monomer unit represented by Formula 11;
  • the mass ratio of the first polymer (from the conductive undercoat layer) and the second polymer (from the positive electrode film layer) is 2:1.
  • the ratio Y 1/ Y 2 is shown in Table 9P below.
  • Example 4-1 0.2 0.3 0.67
  • Example 4-2 0.1 0.5 0.20
  • Example 4-3 0.5 0.5 1.00
  • Example 4-4 1 0.5 2.00
  • Example 4-5 0.25 0.05 5.00
  • Example 4-6 0.25 0.2 1.25
  • Example 4-7 0.25 0.3 0.83
  • Example 4-8 0.25 0.8 0.31
  • Example 4-9 0.25 2 0.13
  • Example 1-1 13 100% 1650
  • Example 4-1 64 93% 1762
  • Example 4-2 60 95% 1770
  • Example 4-3 178 104% 1310
  • Example 4-4 193 160% 1308
  • Example 4-5 105 100% 1700
  • Example 4-6 105 99% 1830
  • Example 4-7 110 98% 1781
  • Example 4-8’ 108 106% 1690
  • Example 4-9’ 109 116% 1410
  • the adhesion of the electrode piece can be further improved, and/or the DC resistance of the battery can be reduced, and /or improve battery cycle performance.
  • the positive electrode plate includes a new positive active material and a new conductive undercoat.
  • New cathode active materials have achieved better results in one or even all aspects of cycle performance, high-temperature storage performance and safety performance.
  • the new conductive undercoating achieves better results in one or even all aspects of providing adhesion to the pole pieces, reducing the DC resistance of the battery, and improving the cycle performance of the battery.

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Abstract

本申请提供一种正极极片、二次电池及用电装置。其中，正极极片，包括正极集流体、设置在所述正极集流体至少一个表面的正极膜层以及位于所述正极集流体和所述正极膜层之间的导电底涂层，其中，所述正极膜层包括所述正极膜层包括具有核-壳结构的正极活性材料，所述正极活性材料包括内核及包覆所述内核的壳，导电底涂层包括第一聚合物、第一水性粘结剂以及第一导电剂。

Description

正极极片、二次电池及用电装置 技术领域
本申请涉及电池技术领域，尤其涉及一种正极极片、二次电池及用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，二次电池广泛应用于水力、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。由于二次电池取得了极大的发展，因此对其能量密度、循环性能等也提出了更高的要求。
相关技术采用在正极极片的活性材料和集流体之间设置导电底涂层以改善二次电池的一项或多项性能。
为了进一步提升电池性能，现有技术需要更优的正极极片。
发明内容
鉴于上述课题，本申请提供一种新型正极极片、二次电池及用电装置。该新型正极极片包括新型正极活性材料和新型导电底涂层，下面分别描述。
本申请第一方面提供一种正极极片，包括正极集流体、设置在所述正极集流体至少一个表面的正极膜层以及位于所述正极集流体和所述正极膜层之间的导电底涂层，其中，
所述正极膜层包括具有核-壳结构的正极活性材料，所述正极活性材料包括内核及包覆所述内核的壳，
所述内核包括Li 1+xMn 1-yA yP 1-zR zO 4，x＝-0.100～0.100，y＝0.001～0.500，z＝0.001～0.100，所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，所述R选自B、Si、N和S中的一种或多种；
所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，
所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；
所述第二包覆层包含碳；
所述导电底涂层包括第一聚合物、第一水性粘结剂以及第一导电剂，
所述第一聚合物包括：
式1表示的第一单体单元；
选自式2表示的单体单元和式3表示的单体单元组成的组中的至少一种的第二单 体单元；
选自式4表示的单体单元和式5表示的单体单元组成的组中的至少一种的第三单体单元；以及
式6表示的第四单体单元，R 1、R 2、R 3各自独立地表示H、羧基、酯基以及取代或未取代的如下基团：C1～C10的烷基、C1～C10的烷氧基、C2～C10的烯基、C6～C10的芳基，R 4表示H、以及取代或未取代的如下基团：C1～C10的烷基、C1～C10的烷氧基、C2～C10的烯基、C6～C10的芳基；
Figure PCTCN2022084385-appb-000001
在一些实施方式中，基于所述第一聚合物的总质量，
所述第一单体单元的质量百分含量为M1，M1为10％～55％，可选地为25％～55％；和/或，
所述第二单体单元的质量百分含量为M2，M2为40％～80％，可选地为50％～70％；和 /或，
所述第三单体单元的质量百分含量为M3，M3为0％～10％，可选地为0.001％～2％；和/或，
所述第四单体单元的质量百分含量为M4，M4为0％～10％，可选地为0.1％～1％。
在一些实施方式中，M3/(M2+M3)为0％～5％，可选地为0.001％～1％。
在一些实施方式中，所述第一聚合物包括选自氢化丁腈橡胶、氢化羧基丁腈橡胶中的一种或多种；和/或，所述第一聚合物的重均分子量为5万～150万，可选地为20万～40万。
在一些实施方式中，所述第一水性粘结剂包括选自水性聚丙烯酸树脂及其衍生物、水性氨基改性聚丙烯树脂及其衍生物、聚乙烯醇及其衍生物中的一种或多种，可选地包括选自水性丙烯酸-丙烯酸酯共聚物；和/或，所述第一水性粘结剂的重均分子量为20万～150万，可选地为30万～40万。
在一些实施方式中，所述第一导电剂包括选自超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的一种或多种，可选地包括选自碳纳米管、石墨烯、碳纳米纤维中的一种或多种。
在一些实施方式中，基于所述导电底涂层的总质量计，
所述第一聚合物的质量百分含量为X1，X1为5％～20％，可选地为5％～10％；和/或，
所述第一水性粘结剂的质量百分含量为X2，X2为30％～80％，可选地为40％～50％；和/或，
所述第一导电剂的质量百分含量为X3，X3为10％～50％，可选地为40％～50％。
在一些实施方式中，所述导电底涂层的厚度为1μm～20μm，可选为3μm～10μm。
在一些实施方式中，所述正极膜层还包括选自浸润剂、分散剂中的一种或多种，可选地，所述正极膜层还同时包括浸润剂和分散剂。
在一些实施方式中，所述浸润剂的表面张力为20mN/m～40mN/m，可选地，所述浸润剂包括如下官能团中的至少一种：-CN、-NH 2、-NH-、-N-、-OH、-COO-、-C(＝O)-O-C(＝O)-。
在一些实施方式中，所述浸润剂包括选自小分子有机溶剂、低分子量聚合物中的一种或多种，
可选地，所述小分子有机溶剂包括选自醇胺类化合物、醇类化合物、腈类化合物中的一种或多种，可选地，所述醇胺类化合物的碳原子数为1～16，可选地为2～6；
可选地，所述低分子量聚合物包括选自马来酸酐-苯乙烯共聚物、聚乙烯基吡咯烷酮、聚硅氧烷中的一种或多种，可选地，所述低分子量聚合物的重均分子量在6000以下，可选地为3000～6000。
在一些实施方式中，所述分散剂包括第二聚合物，并且所述第二聚合物包括：
式7表示的第五单体单元；
选自式8表示的单体单元和式9表示的单体单元组成的组中的至少一种的第六单 体单元；以及
选自式10表示的单体单元和式11表示的单体单元组成的组中的至少一种的第七单体单元；
Figure PCTCN2022084385-appb-000002
在一些实施方式中，基于所述第二聚合物的总质量，
所述第五单体单元的质量百分含量为M5，M5为10％～55％，可选地为25％～55％；和/或，
所述第六单体单元的质量百分含量为M6，M6为40％～80％，可选地为50％～70％；和/或，
所述第七单体单元的质量百分含量为M7，M7为0％～10％，可选地为0.001％～2％。
在一些实施方式中，M7/(M6+M7)为0％～5％，可选地为0.001％～1％。
在一些实施方式中，所述第二聚合物为氢化丁腈橡胶；和/或，
所述第二聚合物的重均分子量为5万～50万，可选地为15万～35万。
在一些实施方式中，基于所述正极膜层的总质量，所述分散剂的质量百分含量为Y1，Y1为0.05％～1％，可选地为0.1％～0.5％；和/或，所述浸润剂的质量百分含量为Y2，Y2为0.05％～2％，可选地为0.2％～0.8％。
在一些实施方式中，Y1/Y2为0.05～20，可选地为0.1～1，进一步地为0.3～0.8。
在一些实施方式中，在所述正极极片中，所述第一聚合物与所述第二聚合物的质量比为1.5～5，可选地为2～3。
在一些实施方式中，所述第一包覆层的磷酸盐的晶面间距为0.345-0.358nm，晶向(111)的夹角为24.25°-26.45°；所述第一包覆层的焦磷酸盐的晶面间距为0.293-0.326nm，晶向(111)的夹角为26.41°-32.57°。
在一些实施方式中，在所述内核中，y与1-y的比值为1：10至10：1，可选为1：4至1：1；和/或，在所述内核中，z与1-z的比值为1：9至1：999，可选为1：499至1：249。
在一些实施方式中，所述第一包覆层的包覆量大于0重量％且小于等于7重量％，可选为4-5.6重量％，基于所述内核的重量计。
在一些实施方式中，所述第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。
在一些实施方式中，所述焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。
在一些实施方式中，所述第二包覆层的包覆量为大于0重量％且小于等于6重量％，可选为3-5重量％，基于所述内核的重量计。
在一些实施方式中，所述A选自Fe、Ti、V、Ni、Co和Mg中的至少两种。
在一些实施方式中，所述正极活性材料的Li/Mn反位缺陷浓度为4％以下，可选为2％以下。
在一些实施方式中，所述正极活性材料的晶格变化率为6％以下，可选为4％以下。
在一些实施方式中，所述正极活性材料的表面氧价态为-1.88以下，可选地为-1.98～-1.88。
在一些实施方式中，所述正极活性材料在3吨下的压实密度为2.0g/cm 3以上，可选地为2.2g/cm 3以上。
在一些实施方案中，正极活性材料的比表面积为15m 2/g～25m 2/g，正极集流体单侧的涂布重量为20mg/cm 2～40mg/cm 2。当正极活性材料的比表面积为15m 2/g～25m 2/g，正极集流体单侧的涂布重量为20mg/cm 2～40mg/cm 2时，在涂布过程中容易出现脱膜现象。本申请采用了新型的导电底涂层增加了提高正极活性材料层与集流体的粘结强度。
本申请第二方面提供一种二次电池，包括上述任一项所述的正极极片。
本申请第三方面提供一种用电装置，包括上述的二次电池。
关于本申请提供的具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，
所述内核包括Li 1+xMn 1-yA yP 1-zR zO 4，其中x＝-0.100～0.100，例如x可以为0.006、0.004、0.003、0.002、0.001、0、-0.001、-0.003、-0.004、-0.005、-0.006、-0.007、-0.008、-0.009、-0.10；y＝0.001～0.500，例如y可以为0.1、0.2、0.25、0.3、0.35、0.4、0.45；z＝0.001～0.100， 例如z可以为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.009、0.1；所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，所述R选自B、Si、N和S中的一种或多种；
所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，
其中，所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，其中所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；
所述第二包覆层包含碳。
除非另有说明，否则上述化学式中，当A为两种以上元素时，上述对于y数值范围的限定不仅是对每种作为A的元素的化学计量数的限定，也是对各个作为A的元素的化学计量数之和的限定。例如当A为两种以上元素A1、A2……An时，A1、A2……An各自的化学计量数y1、y2……yn各自均需落入本申请对y限定的数值范围内，且y1、y2……yn之和也需落入该数值范围内。类似地，对于R为两种以上元素的情况，本申请中对R化学计量数的数值范围的限定也具有上述含义。
本申请发明人在实际作业中发现：磷酸锰锂正极活性材料在深度充放电过程中，锰溶出比较严重。虽然现有技术中有尝试对磷酸锰锂进行磷酸铁锂包覆，从而减少界面副反应，但这种包覆无法阻止溶出的锰向电解液中的迁移。溶出的锰在迁移到负极后，被还原成金属锰。这些产生的金属锰相当于“催化剂”，能够催化负极表面的SEI膜(solid electrolyte interphase，固态电解质界面膜)分解，产生的副产物一部分为气体，容易导致电池发生膨胀，影响二次电池的安全性能，另一部分沉积在负极表面，阻碍锂离子进出负极的通道，造成二次电池的阻抗增加，影响电池的动力学性能。此外，为补充损失的SEI膜，电解液和电池内部的活性锂被不断消耗，给二次电池的容量保持率带来不可逆的影响。
发明人经过大量研究后发现，对于磷酸锰锂正极活性材料，锰溶出严重和表面反应活性高等问题可能是由于脱锂后Mn 3+的姜-泰勒效应和Li +通道大小变化引起的。为此，发明人通过对磷酸锰锂进行改性，得到了能够显著降低锰溶出和降低晶格变化率，进而具备良好的循环性能、高温存储性能和安全性能的正极活性材料。
如图9所示，本申请的磷酸锰锂正极活性材料为具有两层包覆层的核-壳结构。正极活性材料包括内核91及包覆所述内核的壳，所述壳包括包覆所述内核的第一包覆层92以及包覆所述第一包覆层92的第二包覆层93。其中内核包括Li 1+xMn 1-yA yP 1-zR zO 4。所述内核在磷酸锰锂的锰位掺杂的元素A有助于减小脱嵌锂过程中磷酸锰锂的晶格变化率，提高磷酸锰锂正极材料的结构稳定性，大大减少锰的溶出并降低颗粒表面的氧活性。在磷位掺杂的元素R有助于改变Mn-O键长变化的难易程度，从而降低锂离子迁移势垒，促进锂离子迁移，提高二次电池的倍率性能。
本申请的正极活性材料的第一包覆层包括焦磷酸盐和磷酸盐。由于过渡金属在焦磷酸 盐中的迁移势垒较高(>1eV)，能够有效抑制过渡金属的溶出。而磷酸盐具有优异的导锂离子的能力，并可减少表面杂锂含量。另外，由于第二包覆层为含碳层，因而能够有效改善LiMnPO 4的导电性能和去溶剂化能力。此外，第二包覆层的“屏障”作用可以进一步阻碍锰离子迁移到电解液中，并减少电解液对活性材料的腐蚀。
因此，本申请通过对磷酸锰锂进行特定的元素掺杂和表面包覆，能够有效抑制脱嵌锂过程中的Mn溶出，同时促进锂离子的迁移，从而改善电芯的倍率性能，提高二次电池的循环性能和高温性能。
图10为本申请实施例1-1在未包覆第一包覆层和第二包覆层之前的XRD谱图与磷酸锰锂XRD标准谱图(00-033-0804)的对比图。需要指出的是，如图10所示，本申请中通过对比LiMnPO 4掺杂前后XRD谱图，可见，本申请的正极活性材料与LiMnPO 4掺杂前的主要特征峰的位置基本一致，说明掺杂的磷酸锰锂正极活性材料没有杂质相，二次电池性能的改善主要来自元素掺杂，而不是杂质相导致的。
在一些实施方式中，可选地，所述第一包覆层的磷酸盐的晶面间距为0.345-0.358nm，晶向(111)的夹角为24.25°-26.45°；第一包覆层焦磷酸盐的晶面间距为0.293-0.326nm，晶向(111)的夹角为26.41°-32.57°。
当第一包覆层中磷酸盐和焦磷酸盐的晶面间距和晶向(111)的夹角在上述范围时，能够有效避免包覆层中的杂质相，从而提升材料的克容量，循环性能和倍率性能。
在一些实施方式中，可选地，在所述内核中，y与1-y的比值为1：10至10：1，可选为1：4至1：1。此处y表示Mn位掺杂元素的化学计量数之和。在满足上述条件时，正极活性材料的能量密度和循环性能可进一步提升。
在一些实施方式中，可选地，在所述内核中，z与1-z的比值为1：9至1：999，可选为1：499至1：249。此处y表示P位掺杂元素的化学计量数之和。在满足上述条件时，正极活性材料的能量密度和循环性能可进一步提升。
在一些实施方式中，可选地，所述第一包覆层的包覆量为大于0重量％且小于等于7重量％，可选为4-5.6重量％，基于所述内核的重量计。
当所述第一包覆层的包覆量在上述范围内时，能够进一步抑制锰溶出，同时进一步促进锂离子的传输。并能够有效避免以下情况：若第一包覆层的包覆量过小，则可能会导致焦磷酸盐对锰溶出的抑制作用不充分，同时对锂离子传输性能的改善也不显著；若第一包覆层的包覆量过大，则可能会导致包覆层过厚，增大电池阻抗，影响电池的动力学性能。
在一些实施方式中，可选地，所述第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。
焦磷酸盐和磷酸盐的合适配比有利于充分发挥二者的协同作用。并能够有效避免以下情况：如果焦磷酸盐过多而磷酸盐过少，则可能导致电池阻抗增大；如果磷酸盐过多而焦磷酸盐过少，则抑制锰溶出的效果不显著。
在一些实施方式中，可选地，所述焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。
在本申请磷酸锰锂正极活性材料的第一包覆层中，具备一定结晶度的焦磷酸盐和磷酸盐有利于保持第一包覆层的结构稳定，减少晶格缺陷。这一方面有利于充分发挥焦磷酸盐阻碍锰溶出的作用，另一方面也有利于磷酸盐减少表面杂锂含量、降低表面氧的价态，从而减少正极材料与电解液的界面副反应，减少对电解液的消耗，改善电池的循环性能和安全性能。
需要说明的是，在本申请中，焦磷酸盐和磷酸盐的结晶度例如可通过调整烧结过程的工艺条件例如烧结温度、烧结时间等进行调节。焦磷酸盐和磷酸盐的结晶度可通过本领域中已知的方法测量，例如通过X射线衍射法、密度法、红外光谱法、差示扫描量热法和核磁共振吸收方法等方法测量。
在一些实施方式中，可选地，所述第二包覆层的包覆量为大于0重量％且小于等于6重量％，可选为3-5重量％，基于所述内核的重量计。
作为第二包覆层的含碳层一方面可以发挥“屏障”功能，避免正极活性材料与电解液直接接触，从而减少电解液对活性材料的腐蚀，提高电池在高温下的安全性能。另一方面，其具备较强的导电能力，可降低电池内阻，从而改善电池的动力学性能。然而，由于碳材料的克容量较低，因此当第二包覆层的用量过大时，可能会降低正极活性材料整体的克容量。因此，第二包覆层的包覆量在上述范围时，能够在不牺牲正极活性材料克容量的前提下，进一步改善电池的动力学性能和安全性能。
在一些实施方式中，可选地，所述A选自Fe、Ti、V、Ni、Co和Mg中的至少两种。
在磷酸锰锂正极活性材料中的锰位同时掺杂两种以上的上述元素有利于增强掺杂效果，一方面进一步减小晶格变化率，从而抑制锰的溶出，减少电解液和活性锂的消耗，另一方面也有利于进一步降低表面氧活性，减少正极活性材料与电解液的界面副反应，从而改善电池的循环性能和高温储存性能。
在一些实施方式中，可选地，所述正极活性材料的Li/Mn反位缺陷浓度为4％以下，可选为2％以下。
在本申请的正极活性材料中，Li/Mn反位缺陷是指LiMnPO 4晶格中，Li +和Mn 2+的位置发生互换。由于Li +传输通道为一维通道，Mn 2+在Li +传输通道中难以迁移，因此，反位缺陷的Mn 2+会阻碍Li +的传输。通过将Li/Mn反位缺陷浓度控制在低水平，能够改善LiMnPO 4的克容量和倍率性能。本申请中，反位缺陷浓度例如可根据JIS K0131-1996测定。
在一些实施方式中，可选地，所述正极活性材料的晶格变化率为6％以下，可选为4％以下。
LiMnPO 4的脱嵌锂过程是两相反应。两相的界面应力由晶格变化率大小决定，晶格变化率越小，界面应力越小，Li +传输越容易。因此，减小内核的晶格变化率将有利于增强Li + 的传输能力，从而改善二次电池的倍率性能。
在一些实施方式中，可选地，所述正极活性材料的扣电平均放电电压为3.5V以上，放电克容量在140mAh/g以上；可选为平均放电电压3.6V以上，放电克容量在145mAh/g以上。
尽管未掺杂的LiMnPO 4的平均放电电压在4.0V以上，但它的放电克容量较低，通常小于120mAh/g，因此，能量密度较低；通过掺杂调整晶格变化率，可使其放电克容量大幅提升，在平均放电电压微降的情况下，整体能量密度有明显升高。
在一些实施方式中，可选地，所述正极活性材料的表面氧价态为-1.88以下，可选地为-1.98～-1.88。
这是由于氧在化合物中的价态越高，其得电子能力越强，即氧化性越强。而在本申请的磷酸锰锂正极活性材料中，通过将氧的表面价态控制在较低水平，可降低正极材料表面的反应活性，减少正极材料与电解液的界面副反应，从而改善二次电池的循环性能和高温储存性能。
在一些实施方式中，可选地，所述正极活性材料在3吨(T)下的压实密度为2.0g/cm 3以上，可选地为2.2g/cm 3以上。
正极活性材料的压实密度越高，即单位体积活性物质的重量越大，将更有利于提升电池的体积能量密度。本申请中，压实密度例如可根据GB/T 24533-2009测定。
关于本申请提供的正极极片，其包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括本申请的磷酸锰锂正极活性材料或根据本申请的方法制备的磷酸锰锂正极活性材料，并且所述正极活性材料在所述正极膜层中的含量为10重量％以上，基于所述正极膜层的总重量计。
在一些实施方式中，可选地，所述正极活性材料在所述正极膜层中的含量为90-99.5重量％，基于所述正极膜层的总重量计。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述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。
在一些实施方式中，正极膜层还可选地包括粘结剂。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。
在一些实施方式中，正极膜层还可选地包括导电剂。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。
在一些实施方式中，本申请的正极膜层包括90-99.5％的本申请的磷酸锰锂正极活性材料、0.4-5.5％的粘结剂、0.1-2.5％的导电碳和0.001-1％的其他添加剂，基于所述正极膜层的总重量计。
在一些实施方式中，可选地，本申请的正极膜层中还可包括其他添加剂如分散剂、润湿剂、流变改性剂等本领域通常使用的添加剂。
在一些实施方式中，可以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；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
在一些实施方式中，本申请正极膜层的涂覆重量为0.28-0.45g/1540.25mm 2，压实密度达到2.2-2.8g/cm 3。
需要说明的是，在本文中，中值粒径Dv 50是指，所述正极活性材料累计体积分布百分数达到50％时所对应的粒径。在本申请中，正极活性材料的中值粒径Dv 50可采用激光衍射粒度分析法测定。例如参照标准GB/T 19077-2016，使用激光粒度分析仪(例如Malvern Master Size 3000)进行测定。
在本文中，术语“包覆层”是指包覆在内核上的物质层，所述物质层可以完全或部分地包覆内核，使用“包覆层”只是为了便于描述，并不意图限制本发明。同样地，术语“包覆层的厚度”是指包覆在内核上的所述物质层在内核径向上的厚度。
在本文中，术语“源”是指作为某种元素的来源的化合物，作为实例，所述“源”的种类包括但不限于碳酸盐、硫酸盐、硝酸盐、单质、卤化物、氧化物和氢氧化物等。
有益效果
本申请一个或多个实施方式具有以下一项或多项有益效果：
(1)本申请通过对磷酸锰锂进行改性，得到了能够显著降低锰溶出和降低晶格变化率，进而具备良好的循环性能、高温存储性能和安全性能的正极活性材料。本申请的正极活性材料的第一包覆层包括焦磷酸盐和磷酸盐。由于过渡金属在焦磷酸盐中的迁移势垒较高(>1eV)，能够有效抑制过渡金属的溶出。而磷酸盐具有优异的导锂离子的能力，并可减少表面杂锂含量。另外，由于第二包覆层为含碳层，因而能够有效改善LiMnPO 4的导电性能和去溶剂化能力。此外，第二包覆层的“屏障”作用可以进一步阻碍锰离子迁移到电解液中，并减少电解液对活性材料的腐蚀。因此，本申请通过对磷酸锰锂进行特定的元素掺杂和表面包覆，能够有效抑制脱嵌锂过程中的Mn溶出，同时促进锂离子的迁移，从而改善电芯的倍率性能，提高二次电池的循环性能和高温性能。
(2)当正极活性材料的BET比表面积较大，小颗粒较多时，容易导致正极活性材料与集流体(铝箔)的结合强度较弱，在涂布过程中出现脱膜现象。本申请采用了新型的导电底涂层增加了提高正极活性材料层与集流体的粘结强度。
(3)在导电底涂层表面涂布正极活性材料浆料(含溶剂N-甲基吡咯烷酮，简称NMP)的过程中，导电底涂层中的第一聚合物在接触溶剂NMP后会再次溶解，从而与正极活性材料浆料相互扩散，固化后，活性材料层能够与底涂层融为一体，进而有效增加正极膜层与正极集流体之间的结合强度。
(4)当导电底涂层中的第一水性粘结剂采用丙烯酸-丙烯酸酯共聚物(重均分子量：200000～1500000)时，该粘结剂的极性较强可以实现与集流体(铝箔)的良好粘结。另外，丙烯酸-丙烯酸酯共聚物在电解液中稳定性好、耐高温、耐腐蚀、吸收电解液效率低(溶胀度低)。
(5)当导电底涂层中的导电剂选至炭黑、乙炔黑、碳纤维、石墨、碳纳米管中的一种或两种时，能降低界面电阻，提高电池的充、放电倍率性能，并延长电池的循环寿命。
附图说明
图1是本申请一实施例的正极极片的示意图
图2是本申请一实施例测量极片粘结力的流程示意图；
图3是本申请一实施方式的二次电池的示意图。
图4是图3所示的本申请一实施方式的二次电池的分解图。
图5是本申请一实施方式的电池模块的示意图。
图6是本申请一实施方式的电池包的示意图。
图7是图6所示的本申请一实施方式的电池包的分解图。
图8是本申请一实施方式的二次电池用作电源的用电装置的示意图。
图9为本申请一实施方式的具有核壳结构的正极活性材料的示意图。
图10为本申请实施例1-1在未包覆第一包覆层和第二包覆层之前的XRD谱图与磷酸锰锂XRD标准谱图(00-033-0804)的对比图。
附图标记说明：
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顶盖组件；11正极集流体；112表面；12导电底涂层；13正极膜层；510钢板；520双面胶；530极片；
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负极活性材料及其制造方法、正 极极片、负极极片、二次电池、电池模块、电池包和装置的实施方式。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。
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。
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)。
[二次电池]
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、隔离膜及电解液。在电池充放电过程中，活性离子(例如锂离子)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。电解液在正极极片和负极极片之间，主要起到传导活性离子的作用。
[正极极片]
本申请第一方面提供一种正极极片，包括正极集流体、设置在所述正极集流体至少一个表面的正极膜层以及位于所述正极集流体和所述正极膜层之间的导电底涂层，其中，
所述正极膜层包括具有核-壳结构的正极活性材料，所述正极活性材料包括内核及包覆所述内核的壳，
所述内核包括Li 1+xMn 1-yA yP 1-zR zO 4，x＝-0.100～0.100，y＝0.001～0.500，z＝0.001～0.100，所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，所述R选自B、Si、N和S中的一种或多种；
所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，
所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；
所述第二包覆层包含碳；
所述导电底涂层包括第一聚合物、第一水性粘结剂以及第一导电剂，
所述第一聚合物包括：
式1表示的第一单体单元；
选自式2表示的单体单元和式3表示的单体单元组成的组中的至少一种的第二单体单元；
选自式4表示的单体单元和式5表示的单体单元组成的组中的至少一种的第三单体单元；以及
式6表示的第四单体单元，R 1、R 2、R 3各自独立地表示H、羧基、酯基以及取代或未取代的如下基团：C1～C10的烷基、C1～C10的烷氧基、C2～C10的烯基、C6～C10的芳基，R 4表示H、以及取代或未取代的如下基团：C1～C10的烷基、C1～C10的烷氧基、C2～C10的烯基、C6～C10的芳基；
Figure PCTCN2022084385-appb-000003
Figure PCTCN2022084385-appb-000004
基于上述方案的正极极片中，正极膜层与正极集流体具有增强的结合强度。不受理论限制，在导电底涂层表面涂布正极活性材料浆料(含溶剂N-甲基吡咯烷酮，简称NMP)的过程中，导电底涂层中的第一聚合物在接触溶剂NMP后会再次溶解，从而与正极活性材料浆料相互扩散，固化后，活性材料层能够与底涂层融为一体，进而有效增加正极膜层与正极集流体之间的结合强度。
在一些实施方案中，所述第一聚合物为无规共聚物。
丁腈橡胶(NBR)是由丙烯腈与丁二烯单体聚合(例如乳液聚合)而成的无规共聚物，其结构通式为：
Figure PCTCN2022084385-appb-000005
在丁腈橡胶中，丁二烯(B)和丙烯腈(A)链节的联接方式一般为BAB、BBA或ABB、ABA和BBB三元组，但随丙烯腈含量的增加，也有呈AABAA五元组联接者，甚至成为丙烯腈的本体聚合物。在丁腈橡胶中，丁二烯的序列分布主要是反式-1,4结构，其微观结构与聚合条件有关。
氢化丁腈橡胶(HNBR)是指是丁腈橡胶中分子链上的碳碳双键加氢至部分或全部饱和得到的产物。全部饱和的氢化丁腈橡胶的化学式如下：
Figure PCTCN2022084385-appb-000006
氢化丁腈橡胶(HNBR)的制备方法主要有三种：乙烯-丙烯腈共聚法、NBR溶液加氢法和NBR乳液加氢法。
氢化羧基丁基橡胶(HXNBR)是由腈(例如丙烯腈)、共轭二烯(例如丁二烯)和不饱和羧酸的酯共聚后形成聚合物，再选择氢化C＝C制得的聚合物。所谓的氢化羧基丁基橡胶是指在氢化丁腈橡胶的基础上进一步引入了羧基基团。
不饱和羧酸的酯例如是α,β-不饱和一元羧酸的酯。可采用的α,β-不饱和一元羧酸的酯是其烷基酯和烷氧基烷基酯。可选的是α,β-不饱和一元羧酸的烷基酯，例如是C1-C18烷基酯，可选的是丙烯酸或甲基丙烯酸的烷基酯，例如是C1-C18烷基酯，例如是丙烯酸甲酯、丙烯酸乙酯、丙烯酸丙酯、丙烯酸正丁酯、丙烯酸叔丁酯、丙烯酸2-乙基己酯、丙烯酸正十二烷基酯、甲基丙烯酸甲酯、甲基丙烯酸乙酯、甲基丙烯酸丁酯和甲基丙烯酸2-乙基己酯。还可选的是α,β-不饱和一元羧酸的烷氧基烷基酯，可选丙烯酸或甲基丙烯酸的烷氧基烷基酯，例如是丙烯酸或甲基丙烯酸的C2-C12-烷氧基烷基酯，极其可选丙烯酸甲氧基甲酯、(甲基)丙烯酸甲氧基乙酯、(甲基)丙烯酸乙氧基乙酯和(甲基)丙烯酸甲氧基乙酯。也可采用烷基酯(例如上述那些)与烷氧基烷基酯(例如呈上述那些的形式)的混合物。也可采用其中羟烷基中的碳原子数为1-12的丙烯酸羟烷基酯和甲基丙烯酸羟烷基酯，可选丙烯酸2-羟乙酯、甲基丙烯酸2-羟乙酯和丙烯酸3-羟丙酯。同样，可以采用含环氧基的酯，例如甲基 丙烯酸缩水甘油酯。还可采用其中氰基烷基中有2-12个C原子的丙烯酸氰基烷基酯和甲基丙烯酸氰基烷基酯，可选丙烯酸α-氰基乙酯、丙烯酸β-氰基乙酯和甲基丙烯酸氰基丁酯。也可采用含氟取代的苄基的丙烯酸酯或甲基丙烯酸酯，可选丙烯酸氟苄基酯和甲基丙烯酸氟苄基酯。也可采用含氟烷基的丙烯酸酯和甲基丙烯酸酯，可选丙烯酸三氟乙酯和甲基丙烯酸四氟丙酯。也可采用含氨基的α,β-不饱和羧酸酯，诸如丙烯酸二甲基氨基甲酯和丙烯酸二乙基氨基乙酯。
在一些实施方式中，基于所述第一聚合物的总质量，
所述第一单体单元的质量百分含量为M1，M1为10％～55％，可选地为25％～55％；和/或，
所述第二单体单元的质量百分含量为M2，M2为40％～80％，可选地为50％～70％；和/或，
所述第三单体单元的质量百分含量为M3，M3为0％～10％，可选地为0.001％～2％；和/或，
所述第四单体单元的质量百分含量为M4，M4为0％～10％，可选地为0.1％～1％。
基于此方案的导电底涂层在涂布的过程中能够适度地溶解，进而与正极膜层形成增强的结合。
在一些实施方式中，基于所述第一聚合物的总质量，
所述第一单体单元的质量百分含量为M1，M1为10％～55％，可选地为10％-15％、15％-20％、20％-25％、25％-30％、30％-35％、35％-40％、40％-45％、45％-50％或50％-55％；和/或，
所述第二单体单元的质量百分含量为M2，M2为40％～80％，可选地为40％-45％、45％-50％、50％-55％、55％-60％、60％-65％、65％-70％、70％-75％或75％-80％；和/或，
所述第三单体单元的质量百分含量为M3，M3为0％～10％，可选地为0.001％-1％、1％-2％、2％-3％、3％-4％、4％-5％、5％-6％、6％-7％、7％-8％、8％-9％或9％-10％；和/或，
所述第四单体单元的质量百分含量为M4，M4为0％～10％，可选地为0.01％-1％、1％-2％、2％-3％、3％-4％、4％-5％、5％-6％、6％-7％、7％-8％、8％-9％或9％-10％；。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。基于此方案的导电底涂层在涂布的过程中能够适度地溶解，进而与正极膜层形成增强的结合。
在一些实施方式中，M3/(M2+M3)为0％～5％，可选地为0.001％～1％。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，M3/(M2+M3)为0.01％-1％、1％-2％、2％-3％、3％-4％或4％-5％。
在一些实施方式中，所述第一聚合物包括选自氢化丁腈橡胶、氢化羧基丁腈橡胶中的一种或多种；和/或，所述第一聚合物的重均分子量为5万～150万，可选地为20万～40万。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方案中，所述第一聚合物的重均分子量为10-30万、30-50万、50-70万、70-90万、90-110万、110-130万或130-150万。
在一些实施方式中，所述第一水性粘结剂包括选自水性聚丙烯酸树脂及其衍生物、水性氨基改性聚丙烯树脂及其衍生物、聚乙烯醇及其衍生物中的一种或多种，可选地包括选自水性丙烯酸-丙烯酸酯共聚物；和/或，
所述第一水性粘结剂的重均分子量为20万～150万，可选地为30万～40万。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方案中，所述第一水性粘结剂的重均分子量为10-30万、30-50万、50-70万、70-90万、90-110万或110-130万。
在一些实施方式中，所述第一导电剂包括选自超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的一种或多种，可选地包括选自碳纳米管、石墨烯、碳纳米纤维中的一种或多种。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，基于所述导电底涂层的总质量计，
所述第一聚合物的质量百分含量为X1，X1为5％～20％，可选地为5％～10％；和/或，
所述第一水性粘结剂的质量百分含量为X2，X2为30％～80％，可选地为40％～50％；和/或，
所述第一导电剂的质量百分含量为X3，X3为10％～50％，可选地为40％～50％。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述导电底涂层的厚度为1μm～20μm，可选为3μm～10μm。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述正极膜层还包括选自浸润剂、分散剂中的一种或多种，可选地，所述正极膜层还同时包括浸润剂和分散剂。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述浸润剂的表面张力为20mN/m～40mN/m，可选地，所述浸润剂包括如下官能团中的至少一种：-CN、-NH 2、-NH-、-N-、-OH、-COO-、-C(＝O)-O-C(＝O)-。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方案中，表面张力可以采用铂金板法(Wilhelmy Plate Method)测得。具体测试步骤可以参考本领域通用标准，例如GBT/22237-2008表面活性剂-表面张力的测定，例如ASTM D1331-14.涂料溶液，溶剂，表面活性剂溶液及相关材料的表面张力与界面张力的标准试验方法。
在一些实施方式中，所述浸润剂包括选自小分子有机溶剂、低分子量聚合物中的一种或多种，
可选地，所述小分子有机溶剂包括选自醇胺类化合物、醇类化合物、腈类化合物中的 一种或多种，可选地，所述醇胺类化合物的碳原子数为1～16，可选地为2～6；
可选地，所述低分子量聚合物包括选自马来酸酐-苯乙烯共聚物、聚乙烯基吡咯烷酮、聚硅氧烷中的一种或多种，可选地，所述低分子量聚合物的重均分子量在6000以下，可选地为3000～6000。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述分散剂包括第二聚合物，并且所述第二聚合物包括：
式7表示的第五单体单元；
选自式8表示的单体单元和式9表示的单体单元组成的组中的至少一种的第六单体单元；以及
选自式10表示的单体单元和式11表示的单体单元组成的组中的至少一种的第七单体单元；
Figure PCTCN2022084385-appb-000007
基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，基于所述第二聚合物的总质量，
所述第五单体单元的质量百分含量为M5，M5为10％～55％，可选地为25％～55％；和/或，
所述第六单体单元的质量百分含量为M6，M6为40％～80％，可选地为50％～70％；和/或，
所述第七单体单元的质量百分含量为M7，M7为0％～10％，可选地为0.001％～2％。
在一些实施方式中，基于所述第二聚合物的总质量，
所述第五单体单元的质量百分含量为M5，M5为10％～55％，可选地为10％-15％、15％-20％、20％-25％、25％-30％、30％-35％、35％-40％、40％-45％、45％-50％或50％-55％；和/或，
所述第六单体单元的质量百分含量为M6，M6为40％～80％，可选地为40％-45％、45％-50％、50％-55％、55％-60％、60％-65％、65％-70％、70％-75％或75％-80％；和/或，
所述第七单体单元的质量百分含量为M7，M7为0％～10％，可选地为0.01％-1％、1％-2％、2％-3％、3％-4％、4％-5％、5％-6％、6％-7％、7％-8％、8％-9％或9％-10％。
在一些实施方式中，M7/(M6+M7)为0％～5％，可选地为0.001％～1％。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述第二聚合物为氢化丁腈橡胶；和/或，
所述第二聚合物的重均分子量为5万～50万，可选地为15万～35万。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，基于所述正极膜层的总质量，所述分散剂的质量百分含量为Y1，Y1为0.05％～1％，可选地为0.1％～0.5％；和/或，所述浸润剂的质量百分含量为Y2，Y2为0.05％～2％，可选地为0.2％～0.8％。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，Y1/Y2为0.05～20，可选地为0.1～1，进一步地为0.3～0.8。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，在所述正极极片中，所述第一聚合物与所述第二聚合物的质量比为1.5～5，可选地为2～3。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述第一包覆层的磷酸盐的晶面间距为0.345-0.358nm，晶向(111)的夹角为24.25°-26.45°；所述第一包覆层的焦磷酸盐的晶面间距为0.293-0.326nm，晶向(111)的夹角为26.41°-32.57°。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，在所述内核中，y与1-y的比值为1：10至10：1，可选为1：4至1：1；和/或，在所述内核中，z与1-z的比值为1：9至1：999，可选为1：499至1：249。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述第一包覆层的包覆量大于0重量％且小于等于7重量％，可选为4-5.6重量％，基于所述内核的重量计。基于此方案的正极极片用于二次电池，二次电池 的一项或多项性能有显著改善。
在一些实施方式中，所述第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述第二包覆层的包覆量为大于0重量％且小于等于6重量％，可选为3-5重量％，基于所述内核的重量计。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述A选自Fe、Ti、V、Ni、Co和Mg中的至少两种。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述正极活性材料的Li/Mn反位缺陷浓度为4％以下，可选为2％以下。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述正极活性材料的晶格变化率为6％以下，可选为4％以下。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述正极活性材料的表面氧价态为-1.88以下，可选地为-1.98～-1.88。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方式中，所述正极活性材料在3吨下的压实密度为2.0g/cm 3以上，可选地为2.2g/cm 3以上。基于此方案的正极极片用于二次电池，二次电池的一项或多项性能有显著改善。
在一些实施方案中，本申请提供一种二次电池，包括上述任一项所述的正极极片。
在一些实施方案中，本申请提供一种用电装置，包括上述的二次电池。
在一些实施方案中，正极极片通常包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括正极活性材料。
图1示出一个实施例的正极极片的示意图。如图所示，一种正极极片，包括正极集流体11、设置在所述正极集流体11至少一个表面112的正极膜层13以及位于所述正极集流体11和所述正极膜层13之间的导电底涂层12。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，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。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，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。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，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。
在一些实施方式中，可以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；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[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，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。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。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。
在一些实施方式中，负极膜层还可选地包括粘结剂。作为示例，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。
在一些实施方式中，负极膜层还可选地包括导电剂。作为示例，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。
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。
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；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[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，电解质为液态的，且包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，电解液还可选地包括添加剂。作为示例，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，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。
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。 例如，图3是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图4，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52。电极组件52封装于所述容纳腔内。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多个，本领域技术人员可根据具体实际需求进行选择。
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。
图5是作为一个示例的电池模块4。参照图5，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。
图6和图7是作为一个示例的电池包1。参照图6和图7，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能够盖设于下箱体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。
另外，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。所述用电装置可以包括移动设备(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，但不限于此。
作为所述用电装置，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8是作为一个示例的用电装置。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二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
有关新型正极活性材料类的具体实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所 描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。本发明实施例中各成分的含量，如果没有特别说明，均以不含结晶水的质量计。
本申请实施例涉及的原材料来源如下：
名称 化学式 厂家 规格
碳酸锰 MnCO 3 山东西亚化学工业有限公司 1Kg
碳酸锂 Li 2CO 3 山东西亚化学工业有限公司 1Kg
碳酸镁 MgCO 3 山东西亚化学工业有限公司 1Kg
碳酸锌 ZnCO 3 武汉鑫儒化工有限公司 25Kg
碳酸亚铁 FeCO 3 西安兰之光精细材料有限公司 1Kg
硫酸镍 NiCO 3 山东西亚化学工业有限公司 1Kg
硫酸钛 Ti(SO 4) 2 山东西亚化学工业有限公司 1Kg
硫酸钴 CoSO 4 厦门志信化学有限公司 500g
二氯化钒 VCl 2 上海金锦乐实业有限公司 1Kg
二水合草酸 C 2H 2O 4·2H 2O 上海金锦乐实业有限公司 1Kg
磷酸二氢铵 NH 4H 2PO 4 上海澄绍生物科技有限公司 500g
蔗糖 C 12H 22O 11 上海源叶生物科技有限公司 100g
硫酸 H 2SO 4 深圳海思安生物技术有限公司 质量分数60％
硝酸 HNO 3 安徽凌天精细化工有限公司 质量分数60％
亚硅酸 H 2SiO 3 上海源叶生物科技有限公司 100g
硼酸 H 3BO 3 常州市启迪化工有限公司 1Kg
实施例1-1
【双层包覆的磷酸锰锂正极活性材料的制备】
(1)共掺杂磷酸锰锂内核的制备
制备Fe、Co和V共掺杂的草酸锰：将689.5g碳酸锰(以MnCO 3计，下同)、455.2g碳酸亚铁(以FeCO 3计，下同)、4.6g硫酸钴(以CoSO 4计，下同)和4.9g二氯化钒(以VCl 2计，下同)在混料机中充分混合6小时。将混合物转移至反应釜中，并加入5升去离子水和1260.6g二水合草酸(以C 2H 2O 4.2H 2O计，下同)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，直至反应终止(无气泡产生)，得到Fe、Co、V和S共掺杂的草酸锰悬浮液。然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv50为100nm的Fe、Co和V共掺杂的二水草酸锰颗粒。
制备Fe、Co、V和S共掺杂的磷酸锰锂：将前一步骤获得的二水草酸锰颗粒(1793.4g)、 369.0g碳酸锂(以Li 2CO 3计，下同)，1.6g浓度为60％的稀硫酸(以60％H 2SO 4计，下同)和1148.9g磷酸二氢铵(以NH 4H 2PO 4计，下同)加入到20升去离子水中，将混合物搅拌10小时使其混合均匀，得到浆料。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到粉料。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结4小时，得到1572.1g的Fe、Co、V和S共掺杂的磷酸锰锂。
(2)焦磷酸铁锂和磷酸铁锂的制备
制备焦磷酸铁锂粉末：将4.77g碳酸锂、7.47g碳酸亚铁、14.84g磷酸二氢铵和1.3g二水合草酸溶于50ml去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4h，得到粉末。将所述粉末在650℃、氮气气氛下烧结8小时，并自然冷却至室温后进行研磨，得到Li 2FeP 2O 7粉末。
制备磷酸铁锂悬浊液：将11.1g碳酸锂、34.8g碳酸亚铁、34.5g磷酸二氢铵、1.3g二水合草酸和74.6g蔗糖(以C 12H 22O 11计，下同)溶于150ml去离子水中，得到混合物，然后搅拌6小时使上述混合物充分反应。然后将反应后的溶液升温到120℃并保持该温度6小时，得到包含LiFePO 4的悬浊液。
(3)包覆
将1572.1g上述Fe、Co、V和S共掺杂的磷酸锰锂与15.72g上述焦磷酸铁锂(Li 2FeP 2O 7)粉末加入到上一步骤制备获得的磷酸铁锂(LiFePO 4)悬浊液中，搅拌混合均匀后转入真空烘箱中在150℃下干燥6小时。然后通过砂磨分散所得产物。在分散后，将所得产物在氮气气氛中、在700℃下烧结6小时，得到目标产物双层包覆的磷酸锰锂。
【正极极片的制备】
将上述制备的双层包覆的磷酸锰锂正极活性材料、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为92：2.5：5.5加入到N-甲基吡咯烷酮(NMP)中，搅拌混合均匀，得到正极浆料。然后将正极浆料按0.280g/1540.25mm 2均匀涂覆于铝箔上，经烘干、冷压、分切，得到正极极片。
【负极极片的制备】
将负极活性物质人造石墨、硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照重量比为90：5：2：2：1溶于溶剂去离子水中，搅拌混合均匀后制备成负极浆料。将负极浆料按0.117g/1540.25mm 2均匀涂覆在负极集流体铜箔上，经过烘干、冷压、分切得到负极极片。
【电解液的制备】
在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，作为有机溶剂，将碳酸亚乙酯(EC)/碳酸甲乙酯(EMC)按照体积比3/7混合均匀，加入12.5重量％(基于所述有机溶剂的重量计)LiPF 6溶解于上述有机溶剂中，搅拌均匀，得到电解液。
【隔离膜】
使用市售的厚度为20μm、平均孔径为80nm的PP-PE共聚物微孔薄膜(来自卓高电子科技公司，型号20)。
【全电池的制备】
将上述获得的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入上述电解液并封装，得到全电池(下文也称“全电”)。
【扣式电池的制备】
将上述制备的双层包覆的磷酸锰锂正极活性材料、PVDF、乙炔黑以90：5：5的重量比加入至NMP中，在干燥房中搅拌制成浆料。在铝箔上涂覆上述浆料，干燥、冷压制成正极极片。涂覆量为0.02g/cm 2，压实密度为2.0g/cm 3。
采用锂片作为负极，采用1mol/L的LiPF 6在体积比1：1：1的碳酸亚乙酯(EC)+碳酸二乙酯(DEC)+碳酸二甲酯(DMC)中的溶液作为电解液，与上述制备的正极极片一起在扣电箱中组装成扣式电池(下文也称“扣电”)。
实施例1-2至1-6
在共掺杂磷酸锰锂内核的制备过程中，除不使用二氯化钒和硫酸钴、使用463.4g的碳酸亚铁，1.6g的60％浓度的稀硫酸，1148.9g的磷酸二氢铵和369.0g碳酸锂以外，实施例1-2至1-6中磷酸锰锂内核的制备条件与实施例1-1相同。
此外，在焦磷酸铁锂和磷酸铁锂的制备过程以及包覆第一包覆层和第二包覆层的过程中，除所使用的原料按照表1中所示包覆量与实施例1-1对应的包覆量的比值对应调整，以使实施例1-2至1-6中Li 2FeP 2O 7/LiFePO 4的用量分别为12.6g/37.7g、15.7g/47.1g、18.8g/56.5g、22.0/66.0g和25.1g/75.4g，实施例1-2至1-6中蔗糖的用量为37.3g以外，其他条件与实施例1-1相同。
实施例1-7至1-10
除蔗糖的用量分别为74.6g、149.1g、186.4g和223.7g以使作为第二包覆层的碳层的对 应包覆量分别为31.4g、62.9g、78.6g和94.3g以外，实施例1-7至1-10的条件与实施例1-3相同。
实施例1-11至1-14
除在焦磷酸铁锂和磷酸铁锂的制备过程中按照表1中所示包覆量对应调整各种原料的用量以使Li 2FeP 2O 7/LiFePO 4的用量分别为23.6g/39.3g、31.4g/31.4g、39.3g/23.6g和47.2g/15.7g以外，实施例1-11至1-14的条件与实施例1-7相同。
实施例1-15
除在共掺杂磷酸锰锂内核的制备过程中使用492.80g ZnCO 3代替碳酸亚铁以外，实施例1-15的条件与实施例1-14相同。
实施例1-16至1-18
除实施例1-16在共掺杂磷酸锰锂内核的制备过程中使用466.4g的NiCO 3、5.0g的碳酸锌和7.2g的硫酸钛代替碳酸亚铁，实施例1-17在共掺杂的磷酸锰锂内核的制备过程中使用455.2g的碳酸亚铁和8.5g的二氯化钒，实施例1-18在共掺杂的磷酸锰锂内核的制备过程中使用455.2g的碳酸亚铁、4.9g的二氯化钒和2.5g的碳酸镁以外，实施例1-17至1-19的条件与实施例1-7相同。
实施例1-19至1-20
除实施例1-19在共掺杂磷酸锰锂内核的制备过程中使用369.4g的碳酸锂、和以1.05g的60％浓度的稀硝酸代替稀硫酸，实施例1-20在共掺杂的磷酸锰锂内核的制备过程中使用369.7g的碳酸锂、和以0.78g的亚硅酸代替稀硫酸以外，实施例1-19至1-20的条件与实施例1-18相同。
实施例1-21至1-22
除实施例1-21在共掺杂磷酸锰锂内核的制备过程中使用632.0g碳酸锰、463.30g碳酸亚铁、30.5g的二氯化钒、21.0g的碳酸镁和0.78g的亚硅酸；实施例1-22在共掺杂磷酸锰锂内核的制备过程中使用746.9g碳酸锰、289.6g碳酸亚铁、60.9g的二氯化钒、42.1g的碳酸镁和0.78g的亚硅酸以外，实施例1-21至1-22的条件与实施例1-20相同。
实施例1-23至1-24
除实施例1-23在共掺杂磷酸锰锂内核的制备过程中使用804.6g碳酸锰、231.7g碳酸亚铁、1156.2g的磷酸二氢铵、1.2g的硼酸(质量分数99.5％)和370.8g碳酸锂；实施例1-24 在共掺杂磷酸锰锂内核的制备过程中使用862.1g碳酸锰、173.8g碳酸亚铁、1155.1g的磷酸二氢铵、1.86g的硼酸(质量分数99.5％)和371.6g碳酸锂以外，实施例1-23至1-24的条件与实施例1-22相同。
实施例1-25
除实施例1-25在共掺杂磷酸锰锂内核的制备过程中使用370.1g碳酸锂、1.56g的亚硅酸和1147.7g的磷酸二氢铵以外，实施例1-25的条件与实施例1-20相同。
实施例1-26
除实施例1-26在共掺杂磷酸锰锂内核的制备过程中使用368.3g碳酸锂、4.9g质量分数为60％的稀硫酸、919.6g碳酸锰、224.8g碳酸亚铁、3.7g二氯化钒、2.5g碳酸镁和1146.8g的磷酸二氢铵以外，实施例1-26的条件与实施例1-20相同。
实施例1-27
除实施例1-27在共掺杂磷酸锰锂内核的制备过程中使用367.9g碳酸锂、6.5g浓度为60％的稀硫酸和1145.4g的磷酸二氢铵以外，实施例1-27的条件与实施例1-20相同。
实施例1-28至1-33
除实施例1-28至1-33在共掺杂磷酸锰锂内核的制备过程中使用1034.5g碳酸锰、108.9g碳酸亚铁、3.7g二氯化钒和2.5g碳酸镁，碳酸锂的使用量分别为：367.6g、367.2g、366.8g、366.4g、366.0g和332.4g，磷酸二氢铵的使用量分别为：1144.5g、1143.4g、1142.2g、1141.1g、1139.9g和1138.8g，浓度为60％的稀硫酸的使用量分别为：8.2g、9.8g、11.4g、13.1g、14.7g和16.3g以外，实施例1-28至1-33的条件与实施例1-20相同。
实施例2-1至2-4
实施例2-1
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为550℃，烧结时间为1h以控制Li 2FeP 2O 7的结晶度为30％，在磷酸铁锂(LiFePO 4)的制备过程中在包覆烧结步骤中的烧结温度为650℃，烧结时间为2h以控制LiFePO 4的结晶度为30％以外，其他条件与实施例1-1相同。
实施例2-2
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为550℃，烧结时间为2h以控制Li 2FeP 2O 7的结晶度为50％，在磷酸铁锂(LiFePO 4)的制备过程中在包覆烧结步骤中的烧结温度为650℃，烧结时间为3h以控制LiFePO 4的结晶度为50％以外， 其他条件与实施例1-1相同。
实施例2-3
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为600℃，烧结时间为3h以控制Li 2FeP 2O 7的结晶度为70％，在磷酸铁锂(LiFePO 4)的制备过程中在包覆烧结步骤中的烧结温度为650℃，烧结时间为4h以控制LiFePO 4的结晶度为70％以外，其他条件与实施例1-1相同。
实施例2-4
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为650℃，烧结时间为4h以控制Li 2FeP 2O 7的结晶度为100％，在磷酸铁锂(LiFePO 4)的制备过程中在包覆烧结步骤中的烧结温度为700℃，烧结时间为6h以控制LiFePO 4的结晶度为100％以外，其他条件与实施例1-1相同。
实施例3-1至3-12
除制备Fe、Co和V共掺杂的草酸锰颗粒的过程中，实施例3-1反应釜内的加热温度/搅拌时间分别为60℃/120分钟；实施例3-2反应釜内的加热温度/搅拌时间分别为70℃/120分钟；实施例3-3反应釜内的加热温度/搅拌时间分别为80℃/120分钟；实施例3-4反应釜内的加热温度/搅拌时间分别为90℃/120分钟；实施例3-5反应釜内的加热温度/搅拌时间分别为100℃/120分钟；实施例3-6反应釜内的加热温度/搅拌时间分别为110℃/120分钟；实施例3-7反应釜内的加热温度/搅拌时间分别为120℃/120分钟；实施例3-8反应釜内的加热温度/搅拌时间分别为130℃/120分钟；实施例3-9反应釜内的加热温度/搅拌时间分别为100℃/60分钟；实施例3-10反应釜内的加热温度/搅拌时间分别为100℃/90分钟；实施例3-11反应釜内的加热温度/搅拌时间分别为100℃/150分钟；实施例3-12反应釜内的加热温度/搅拌时间分别为100℃/180分钟以外，实施例3-1至3-12的其他条件与实施例1-1相同。
实施例4-1至4-7
实施例4-1至4-4：除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在干燥步骤中的干燥温度/干燥时间分别为100℃/4h、150℃/6h、200℃/6h和200℃/6h；在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在烧结步骤中的烧结温度和烧结时间分别为700℃/6h、700℃/6h、700℃/6h和600℃/6h以外，其它条件与实例1-7相同。
实施例4-5至4-7：除在包覆过程中在干燥步骤中的干燥温度/干燥时间分别为150℃/6h、150℃/6h和150℃/6h；在包覆过程中在烧结步骤中的烧结温度和烧结时间分别为600℃/4h、600℃/6h和800℃/8h以外，其它条件与实例1-12相同。
对比例1
制备草酸锰：将1149.3g碳酸锰加至反应釜中，并加入5升去离子水和1260.6g二水合草酸(以C 2H 2O 4·2H 2O计，下同)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，直至反应终止(无气泡产生)，得到草酸锰悬浮液，然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv50为100nm的二水草酸锰颗粒。
制备碳包覆的磷酸锰锂：取1789.6g上述获得的二水草酸锰颗粒、369.4g碳酸锂(以Li 2CO 3计，下同)，1150.1g磷酸二氢铵(以NH 4H 2PO 4计，下同)和31g蔗糖(以C 12H 22O 11计，下同)加入到20升去离子水中，将混合物搅拌10小时使其混合均匀，得到浆料。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到粉料。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结4小时，得到碳包覆的磷酸锰锂。
对比例2
除使用689.5g的碳酸锰和额外添加463.3g的碳酸亚铁以外，对比例2的其他条件与对比例1相同。
对比例3
除使用1148.9g的磷酸二氢铵和369.0g碳酸锂，并额外添加1.6g的60％浓度的稀硫酸以外，对比例3的其他条件与对比例1相同。
对比例4
除使用689.5g的碳酸锰、1148.9g的磷酸二氢铵和369.0g碳酸锂，并额外添加463.3g的碳酸亚铁、1.6g的60％浓度的稀硫酸以外，对比例4的其他条件与对比例1相同。
对比例5
除额外增加以下步骤：制备焦磷酸铁锂粉末：将9.52g碳酸锂、29.9g碳酸亚铁、29.6g磷酸二氢铵和32.5g二水合草酸溶于50ml去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4h，得到粉末。将所述粉末在500℃、氮气气氛下烧结4小时，并自然冷却至室温后进行研磨，控制Li 2FeP 2O 7的结晶度为5％，制备碳包覆的材料时，Li 2FeP 2O 7的用量为62.8g以外，对比例5的其它条件与对比例4相同。
对比例6
除额外增加以下步骤：制备磷酸铁锂悬浊液：将14.7g碳酸锂、46.1g碳酸亚铁、45.8g磷酸二氢铵和50.2g二水合草酸溶于500ml去离子水中，然后搅拌6小时使混合物充分反应。然后将反应后的溶液升温到120℃并保持该温度6小时，得到包含LiFePO 4的悬浊液，在磷酸铁锂(LiFePO 4)的制备过程中在包覆烧结步骤中的烧结温度为600℃，烧结时间为4h以控制LiFePO 4的结晶度为8％以外，制备碳包覆的材料时，LiFePO 4的用量为62.8g以外，对比例6的其它条件与对比例4相同。
对比例7
制备焦磷酸铁锂粉末：将2.38g碳酸锂、7.5g碳酸亚铁、7.4g磷酸二氢铵和8.1g二水合草酸溶于50ml去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4h，得到粉末。将所述粉末在500℃、氮气气氛下烧结4小时，并自然冷却至室温后进行研磨，控制Li 2FeP 2O 7的结晶度为5％。
制备磷酸铁锂悬浊液：将11.1g碳酸锂、34.7g碳酸亚铁、34.4g磷酸二氢铵、37.7g二水合草酸和37.3g蔗糖(以C 12H 22O 11计，下同)溶于1500ml去离子水中，然后搅拌6小时使混合物充分反应。然后将反应后的溶液升温到120℃并保持该温度6小时，得到包含LiFePO 4的悬浊液。
将得到的焦磷酸铁锂粉末15.7g，加入上述磷酸铁锂(LiFePO 4)和蔗糖悬浊液中，制备过程中在包覆烧结步骤中的烧结温度为600℃，烧结时间为4h以控制LiFePO 4的结晶度为8％以外，对比例7的其它条件与对比例4相同，得到非晶态焦磷酸铁锂、非晶态磷酸铁锂、碳包覆的正极活性材料。
对比例8-11
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在干燥步骤中的干燥温度/干燥时间在对比例8-10中分别为80℃/3h、80℃/3h、80℃/3h；在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在烧结步骤中的烧结温度和烧结时间在对比例8-10中分别为400℃/3h、400℃/3h、350℃/2h，对比例11在磷酸铁锂(LiFePO 4)的制备过程中在干燥步骤中的干燥温度/干燥时间为80℃/3h；以及在对比例8-11中Li 2FeP 2O 7/LiFePO 4的用量分别为47.2g/15.7g、15.7g/47.2g、62.8g/0g、0g/62.8g以外，其他条件与实施例1-7相同。
上述实施例和对比例的【正极极片的制备】、【负极极片的制备】、【电解液的制备】、【隔离膜】和【电池的制备】均与实施例1-1的工艺相同。
【相关参数测试】
1.扣式电池初始克容量测试：
在2.5～4.3V下，将上述制得的扣式电池按照0.1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA，静置5min，然后按照0.1C放电至2.0V，此时的放电容量为初始克容量，记为D0。
2.扣电平均放电电压(V)测试：
将上述制得的扣式电池在25℃恒温环境下，静置5min，按照0.1C放电至2.5V，静置5min，按照0.1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA，静置5min；然后按照0.1C放电至2.5V，此时的放电容量为初始克容量，记为D0，放电能量为初始能量，记为E0，扣电平均放电电压V即为E0/D0。
3.全电池60℃胀气测试：
在60℃下，存储100％充电状态(SOC)的上述制得的全电池。在存储前后及过程中测量电芯的开路电压(OCV)和交流内阻(IMP)以监控SOC，并测量电芯的体积。其中在每存储48h后取出全电池，静置1h后测试开路电压(OCV)、内阻(IMP)，并在冷却至室温后用排水法测量电芯体积。排水法即先用表盘数据自动进行单位转换的天平单独测量电芯的重力F 1，然后将电芯完全置于去离子水(密度已知为1g/cm 3)中，测量此时的电芯的重力F 2，电芯受到的浮力F 浮即为F 1-F 2，然后根据阿基米德原理F 浮＝ρ×g×V 排，计算得到电芯体积V＝(F 1-F 2)/(ρ×g)。
由OCV、IMP测试结果来看，本实验过程中直至存储结束，全部实施例的电池始终保持99％以上的SOC。
存储30天后，测量电芯体积，并计算相对于存储前的电芯体积，存储后的电芯体积增加的百分比。
另外，测量电芯残余容量。在2.5～4.3V下，将全电池按照1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5min，记录此时的充电容量为电芯残余容量。
4.全电池45℃下循环性能测试：
在45℃的恒温环境下，在2.5～4.3V下，将上述制得的全电池按照1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5min，然后按照1C放电至2.5V，记录此时的放电容量为D0。重复前述充放电循环，直至放电容量降低到D0的80％。记录此时电池经过的循环圈数。
5.晶格变化率测试：
在25℃恒温环境下，将上述制得的正极活性材料样品置于XRD(型号为Bruker D8 Discover)中，采用1°/min对样品进行测试，并对测试数据进行整理分析，参照标准PDF卡片，计算出此时的晶格常数a0、b0、c0和v0(a0、b0和c0表示晶胞各个方面上的长度大小，v0表示晶胞体积，可通过XRD精修结果直接获取)。
采用上述扣电制备方法，将所述正极活性材料样品制备成扣电，并对上述扣电以0.05C小倍率进行充电，直至电流减小至0.01C。然后将扣电中的正极极片取出，并置于碳酸二甲酯(DMC)中浸泡8小时。然后烘干，刮粉，并筛选出其中粒径小于500nm的颗粒。取样并按照与上述测试新鲜样品同样的方式计算出其晶胞体积v1，将(v0-v1)/v0×100％作为其完全脱嵌锂前后的晶格变化率(晶胞体积变化率)示于表中。
6.Li/Mn反位缺陷浓度测试：
将“晶格变化率测量方法”中测试的XRD结果与标准晶体的PDF(Powder Diffraction File)卡片对比，得出Li/Mn反位缺陷浓度。具体而言，将“晶格变化率测量方法”中测试的XRD结果导入通用结构分析系统(GSAS)软件中，自动获得精修结果，其中包含了不同原子的占位情况，通过读取精修结果获得Li/Mn反位缺陷浓度。
7.过渡金属溶出测试：
将45℃下循环至容量衰减至80％后的全电池采用0.1C倍率进行放电至截止电压2.0V。然后将电池拆开，取出负极极片，在负极极片上随机取30个单位面积(1540.25mm 2)的圆片，用Agilent ICP-OES730测试电感耦合等离子体发射光谱(ICP)。根据ICP结果计算其中Fe(如果正极活性材料的Mn位掺杂有Fe的话)和Mn的量，从而计算循环后Mn(以及Mn位掺杂的Fe)的溶出量。测试标准依据EPA-6010D-2014。
8.表面氧价态测试：
取5g上述制得的正极活性材料样品按照上述扣电制备方法制备成扣电。对扣电采用0.05C小倍率进行充电，直至电流减小至0.01C。然后将扣电中的正极极片取出，并置于碳酸二甲酯(DMC)中浸泡8小时。然后烘干，刮粉，并筛选出其中粒径小于500nm的颗粒。将所得颗粒用电子能量损失谱(EELS，所用仪器型号为Talos F200S)进行测量，获取能量损失近边结构(ELNES)，其反映元素的态密度和能级分布情况。根据态密度和能级分布，通过对价带态密度数据进行积分，算出占据的电子数，从而推算出充电后的表面氧的价态。
9.压实密度测量：
取5g的上述制得的正极活性材料粉末放于压实专用模具(美国CARVER模具，型号13mm)中，然后将模具放在压实密度仪器上。施加3T的压力，在设备上读出压力下粉末 的厚度(卸压后的厚度，用于测试的容器的面积为1540.25mm 2)，通过ρ＝m/v，计算出压实密度。
10.X射线衍射法测试焦磷酸盐和磷酸盐的结晶度
取5g上述制得的正极活性材料粉末，通过X射线测得总散射强度，它是整个空间物质的散射强度之和，只与初级射线的强度、化学结构、参加衍射的总电子数即质量多少有关，而与样品的序态无关；然后从衍射图上将结晶散射和非结晶散射分开，结晶度即是结晶部分散射与散射总强度之比。
11.晶面间距和夹角
取1g上述制得的各正极活性材料粉末于50mL的试管中，并在试管中注入10mL质量分数为75％的酒精，然后进行充分搅拌分散30分钟，然后用干净的一次性塑料吸管取适量上述溶液滴加在300目铜网上，此时，部分粉末将在铜网上残留，将铜网连带样品转移至TEM(Talos F200s G2)样品腔中进行测试，得到TEM测试原始图片，保存原始图片格式(xx.dm3)。
将上述TEM测试所得原始图片在DigitalMicrograph软件中打开，并进行傅里叶变换(点击操作后由软件自动完成)得到衍射花样，量取衍射花样中衍射光斑到中心位置的距离，即可得到晶面间距，夹角根据布拉格方程进行计算得到。
Figure PCTCN2022084385-appb-000008
Figure PCTCN2022084385-appb-000009
Figure PCTCN2022084385-appb-000010
Figure PCTCN2022084385-appb-000011
Figure PCTCN2022084385-appb-000012
Figure PCTCN2022084385-appb-000013
Figure PCTCN2022084385-appb-000014
Figure PCTCN2022084385-appb-000015
Figure PCTCN2022084385-appb-000016
Figure PCTCN2022084385-appb-000017
Figure PCTCN2022084385-appb-000018
有关新型导电底涂层的具体实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
为了上文有关新型正极材料的具体实施例相区别，有关新型导电底涂层的具体实施例在编号后加后缀[’]。
实施例1-1’(实施例1-1的正极活性材料)
1.提供第一聚合物
以下实施例中，第一聚合物是一种氢化羧基丁腈橡胶，其含有第一单体单元，第二单体单元、第三单体单元和第四单体单元。第一单体单元、第二单体单元、第三单体单元和第四单体单元在聚合物中的重量百分比、以及第一聚合物的重均分子量如表1P所示。
第一单体单元为式1表示的单体单元；
Figure PCTCN2022084385-appb-000019
第二单体单元选自式2表示的单体单元和式3表示的单体单元组成的组中的至少
一种的
Figure PCTCN2022084385-appb-000020
第三单体单元选自式4表示的单体单元和式5表示的单体单元组成的组中的至少
一种；
Figure PCTCN2022084385-appb-000021
Figure PCTCN2022084385-appb-000022
第四单体单元为式6表示的单体单元：
Figure PCTCN2022084385-appb-000023
本实施例中，R 1、R 2和R 3均为H，R 4为正丁基。
表1P
Figure PCTCN2022084385-appb-000024
2.制备具有导电底涂层的铝箔
将第一聚合物、第一水性粘结剂(聚丙烯酸-丙烯酸酯共聚物，重均分子量34万)和第一导电剂(SP)按照15:40:45的重量比配比，溶解/分散于NMP溶剂，配制成导电底涂层浆料。
将导电底涂层浆料涂布于铝箔的两侧，干燥后每侧形成厚度为5μm的导电底涂层。获得具有导电底涂层的铝箔。
3)制备正极极片
将上文实施例1-1的双层包覆的磷酸锰锂正极活性材料与导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比92：2.5：5.5在N-甲基吡咯烷酮溶剂体系中混合均匀后得到正极浆料，将正极浆料涂覆于带具有导电底涂层的铝箔两侧上并烘干、冷压，形成正极膜层，得到正极极片。正极膜层的单侧面密度为0.025g/cm 2，压实密度为2.4g/cm 3。
4)制备负极极片
将负极活性材料人造石墨、硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照重量比90：5：2：2：1在去离子水中混合均匀后，涂覆于铜箔上烘干、冷压，形成正极膜层，得到负极极片。负极膜层的单侧面密度为0.013g/cm 2，压实密度为1.7g/cm 3。
5)全电池的组装
以聚乙烯(PE)多孔聚合薄膜作为隔离膜，将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入电解液并封装，得到全电池(下文也称“全电”)。
单个全电池中正极活性物质的重量为565.66g；负极活性物质的重量为309.38g。
实施例1-2’至1-33’(实施例1-2至1-33的正极活性材料)
实施例1-2’至1-33’与实施例1-1’的区别在于步骤3)。其他步骤参数与实施例1-1’无异。
实施例1-2’至1-33’在步骤3)采用的正极活性材料分别为上文实施例1-2至1-33的正极活性材料。
实施例2-1’至2-3’(实施例2-1至2-3的正极活性材料)
实施例2-1’至2-3’与实施例1-1’的区别在于步骤3)。其他步骤参数与实施例1-1’无异。
实施例2-1’至2-3’在步骤3)采用的正极活性材料分别为上文实施例2-1至2-3的正极活性材料。
对比例1’至8’(未设置导电底涂层)
对比例1’至8’与实施例1-1’的区别在于步骤2)和3)。其他步骤参数与实施例1-1’无异。
对比例1’至8’在步骤2)和3)中，没有制备具有导电底涂层的铝箔，而是，直接将正极浆料涂覆于铝箔上并烘干、冷压，形成正极膜层，得到正极极片。
对比例1’至7’在步骤3)采用的正极活性材料分别为上文对比例1-1至1-7的正极活性材料。
对比例8’在步骤3)采用的正极活性材料为上文实施例1-1的正极活性材料。
对比例9’(不含第一聚合物)
对比例9’与实施例1-1’的区别在于步骤2)。其他步骤参数与实施例1-1’无异。
对比例9’在步骤2)中，将第一水性粘结剂(聚丙烯酸-丙烯酸酯共聚物)和第一导电剂(SP)按照40:45的重量比配比，溶解/分散于去离子水，配制成导电底涂层浆料。将导电底涂层浆料涂布于铝箔，干燥后形成厚度为5μm的导电底涂层。获得具有导电底涂层的铝箔。
对比例10’(用第I聚合物替换第一聚合物)
对比例10’与实施例1-1’的区别在于步骤2)。其他步骤参数与实施例1-1’无异。
对比例10’在步骤2)中，将第I聚合物、第一水性粘结剂(聚丙烯酸-丙烯酸酯共聚物)和第一导电剂(SP)按照15:40:45的重量比配比，溶解/分散于去离子水，配制成导电底涂层浆料。将导电底涂层浆料涂布于铝箔，干燥后形成厚度为5μm的导电底涂层。获得具有导电底涂层的铝箔。
第I聚合物与第一聚合物的区别在于聚合物的组成不同，第I聚合物的组成以及重均分子量如下表2P所示。
表2P
Figure PCTCN2022084385-appb-000025
对比例11’(用第I粘结剂替换第一水性粘结剂)
对比例11’与实施例1-1’的区别在于步骤2)。其他步骤参数与实施例1-1’无异。
对比例11’在步骤2)中，将第一聚合物、第I粘结剂(聚丙烯酸，重均分子量35万)和第一导电剂(SP)按照15:40:45的重量比配比，溶解/分散于去离子水，配制成导电底涂层浆料。将导电底涂层浆料涂布于铝箔，干燥后形成厚度为5μm的导电底涂层。获得具有导电底涂层的铝箔。
分析检测
1.正极极片的粘结力测试
图2的(a)～(d)示出剥离测试的流程图。如图2的(a)所示，首先提供一块钢板510，钢板尺寸宽30mm×长100mm。如图2的(b)所示，然后提供一块双面胶520，双面胶520的尺寸为宽20mm×长30mm，将双面胶520贴在钢板510上，双面胶520的一个宽边与钢板510的一个宽边对齐。如图2的(c)所示，然后提供一块待测试极片530，待测试极片530的尺寸为宽20mm×长180mm。将待测试极片530覆盖在双面胶520上(两边对齐)，极片530的涂布面朝向双面胶520。由于待测试极片530的长度大于双面胶520的长度，故待测试极片520的部分区域未与双面胶粘接。如图2的(d)所示，将钢板510固定在拉伸试验机的基座上，用夹具夹持待测试极片530未与双面胶粘接的一端，然后使夹具向另一端的方向(如箭头所示方向)拉伸，拉伸的力的方向垂直于钢板510，且与钢板510表面存在一定距离。在向纸面外拉伸剥离极片的同时，钢板向上移动，以保持拉伸方向 与极片剥离位置垂直。在拉伸过程中，拉伸使极片530从钢板上被逐渐剥离。在拉伸过程中，夹具的拉伸速度为50mm/min。拉伸过程中，记录夹具的拉力，待拉力稳定后继续剥离40mm长度，以该剥离长度下的平均拉力为粘结力(单位N)。
2电池的直流阻抗值测试
在25℃下，以1.0C恒流恒压将电池充电至4.3V(1.0C指的是标称容量)；1.0C倍率下调整电池电量至50％SOC，静置5min后4C恒流(I m)放电30s(每1s采集一次电压数据)，记录初始电压U 0和放电30s后的电压U 30，按下式计算的直流阻抗(DCR)值。
直流阻抗值＝(U 0-U 30)/I m
以实施例1-1’的电池的直流阻抗值为100％，其它实施例和对比例相对于实施例1-1’的变动以百分比的形式体现。
3.电池的45℃容量保持率80％循环周数(以下简称“80％容量周数”)
在45℃的恒温环境下，在2.5～4.3V下，将全电池按照1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5min，然后按照1C放电至2.5V，记录此时的放电容量为D0。重复前述充放电循环，直至放电容量降低到D0的80％。记录此时电池经过的循环周数。
按照上述检测分析方法，对上文的实施例1-1’至1-33’、实施例2-1’至2-3’和对比例1’至11’制备的正极极片的粘结力、电池的直流阻抗值和电池的45℃容量保持率80％循环周数进行检测，结果如下表3P所示。
表3P
Figure PCTCN2022084385-appb-000026
Figure PCTCN2022084385-appb-000027
Figure PCTCN2022084385-appb-000028
由表3P可知，实施例1-1’至1-33’、实施例2-1’至2-3’的正极极片表现出提高的粘结力，实施例1-1’至1-33’、实施例2-1’至2-3’的电池表现出降低的直流阻抗和提高的循环容量保持率。
对比例8’(未设置导电底涂层)、对比例9’(不含第一聚合物)、对比例10’(用第I聚合物替换第一聚合物)、对比例11’(用第I粘结剂替换第一水性粘结剂)没能取得上述改善的效果。
实施例3-1’至3-7’(第一聚合物的成分变动)
实施例3-1’至3-7’与实施例1-1’的区别在于步骤2)。其他步骤参数与实施例1-1’无异。
在步骤2)中，实施例3-1’至3-7’使用的第一聚合物的成分与实施例1-1’不同，具体为第二单体单元和第三单体单元的重量百分比与实施例1-1’不同。实施例3-1’至3-7’的第一聚合物的成分组成如下表4P所示。
表4P
Figure PCTCN2022084385-appb-000029
实施例3-8’至3-12’(导电底涂层厚度的变动)
实施例3-8’至3-12’与实施例1-1’的区别在于步骤2)。其他步骤参数与实施例1-1’无异。
在步骤2)中，实施例3-8’至3-12’的导电底涂层厚度与实施例1-1’不同，详见表5P。
表5P
Figure PCTCN2022084385-appb-000030
实施例3-13’至3-18’(导电底涂层成分的变动)
实施例3-13’至3-18’与实施例1-1’的区别在于步骤2)。其他步骤参数与实施例1-1’无异。
在步骤2)中，实施例3-13’至3-18’的导电底涂层成分(第一聚合物、第一水性粘结剂和第一导电剂的配比)与实施例1-1’不同，详见表6P。
表6P
Figure PCTCN2022084385-appb-000031
按照上述检测分析方法，对上文的实施例1-1’、3-1’至3-18’制备的正极极片的粘结力、电池的直流阻抗值和电池的45℃容量保持率80％循环周数进行检测，结果如下表7P所示。
表7P
  极片粘结力 直流阻抗 80％容量周数
实施例1-1’ 13 100％ 1650
实施例3-1’ 12.7 100％ 1700
实施例3-2’ 13 97％ 1688
实施例3-3’ 12.5 100％ 1703
实施例3-4’ 13.1 99％ 1600
实施例3-5’ 13.8 98％ 1660
实施例3-6’ 13.9 99％ 1655
实施例3-7’ 12 258％ 731
实施例3-8’ 8.5 110％ 1540
实施例3-9’ 7.3 101％ 1720
实施例3-10’ 9.9 100％ 1779
实施例3-11’ 21.1 120％ 1600
实施例3-12’ 32.5 150％ 1678
实施例3-13’ 8.1 100％ 1630
实施例3-14’ 10.5 105％ 1680
实施例3-15’ 11.6 103％ 1701
实施例3-16’ 10.7 145％ 1600
实施例3-17’ 14.5 130％ 1635
实施例3-18’ 15 110％ 1630
由表7P可知，实施例1-1’、3-1’至3-18’的正极极片表现出提供的粘结力，实施例1-1’、3-1’至3-18’的电池表现出降低的直流阻抗和提高的循环容量保持率。当M3/(M2+M3)的值为0～5％时，电池的质量阻抗表现出显著的降低。
实施例4-1’至4-9’
实施例4-1’至4-9’与实施例1-1’的区别在于步骤3)。其他步骤参数与实施例1-1’无异。
实施例4-1’至4-9’的步骤3)中，将上文实施例1-1的双层包覆的磷酸锰锂正极活性材料与导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)、分散剂和浸润剂按重量比(92-Y 1-Y 2)：2.5：5.5：Y 1：Y 2在N-甲基吡咯烷酮溶剂体系中混合均匀后得到正极浆料，将正极浆料涂覆于带具有导电底涂层的铝箔两侧上并烘干、冷压，形成正极膜层，得到正极极片。正极 膜层的单侧面密度为0.025g/cm 2，压实密度为2.4g/cm 3。
实施例4-1’至4-9’的浸润剂为马来酸酐-苯乙烯共聚物(分子量5000)。实施例4-1’至4-9’的分散剂为第二聚合物。
第二聚合物是一种氢化丁腈橡胶，其含有第五单体单元，第六单体单元和第七单体单元。五单体单元、第六单体单元和第七单体单元在聚合物中的重量百分比、以及第二聚合物的重均分子量如表8P所示。
第五单体单元为式1表示的单体单元；
Figure PCTCN2022084385-appb-000032
第六单体单元选自式8表示的单体单元和式9表示的单体单元组成的组中的至少一种的
Figure PCTCN2022084385-appb-000033
第七单体单元选自式10表示的单体单元和式11表示的单体单元组成的组中的至少一种；
Figure PCTCN2022084385-appb-000034
表8P
Figure PCTCN2022084385-appb-000035
实施例4-1’至4-9’的正极极片中，第一聚合物(来自导电底涂层)和第二聚合物(来自正极膜层)的质量比为2：1。
实施例4-1’至4-9’在步骤3)中采用的分散剂(第二聚合物)比例Y 1和浸润剂(马来酸酐-苯乙烯共聚物)的比例Y 2以及二者的比值Y 1/Y 2如下表9P所示。
表9P
  Y 1 Y 2 Y 1/Y 2
实施例4-1’ 0.2 0.3 0.67
实施例4-2’ 0.1 0.5 0.20
实施例4-3’ 0.5 0.5 1.00
实施例4-4’ 1 0.5 2.00
实施例4-5’ 0.25 0.05 5.00
实施例4-6’ 0.25 0.2 1.25
实施例4-7’ 0.25 0.3 0.83
实施例4-8’ 0.25 0.8 0.31
实施例4-9’ 0.25 2 0.13
按照上述检测分析方法，对上文的实施例1-1’和实施例4-1’至4-9’制备的正极极片的粘结力、电池的直流阻抗值和电池的45℃容量保持率80％循环周数进行检测，结果如下表10P所示。
表10P
  极片粘结力 直流阻抗 循环圈数
实施例1-1’ 13 100％ 1650
实施例4-1’ 64 93％ 1762
实施例4-2’ 60 95％ 1770
实施例4-3’ 178 104％ 1310
实施例4-4’ 193 160％ 1308
实施例4-5’ 105 100％ 1700
实施例4-6’ 105 99％ 1830
实施例4-7’ 110 98％ 1781
实施例4-8’ 108 106％ 1690
实施例4-9’ 109 116％ 1410
如表10P所示，在上述新型导电底涂层的基础上，结合含有分散剂和浸润剂的新型正极膜层，能够进一步改善极片的粘结力，和/或降低电池的直流阻抗，和/或改善电池的循环性能。
由以上实验数据可知，本申请提供一种新型的正极极片、二次电池及用电装置。该正极极片包括新型正极活性材料和新型的导电底涂层。
新型正极活性材料均在循环性能、高温存储性能和安全性能中的一个甚至全部方面实现了更优的效果。
新型导电底涂层在提供极片的粘结力，降低电池的直流阻抗，改善电池的循环性能中的一个甚至全部方面实现了更优的效果。
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。

Claims (31)

  1. 一种正极极片，包括正极集流体、设置在所述正极集流体至少一个表面的正极膜层以及位于所述正极集流体和所述正极膜层之间的导电底涂层，其中，
    所述正极膜层包括具有核-壳结构的正极活性材料，所述正极活性材料包括内核及包覆所述内核的壳，
    所述内核包括Li 1+xMn 1-yA yP 1-zR zO 4，x＝-0.100～0.100，y＝0.001～0.500，z＝0.001～0.100，所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，所述R选自B、Si、N和S中的一种或多种；
    所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，
    所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；
    所述第二包覆层包含碳；
    所述导电底涂层包括第一聚合物、第一水性粘结剂以及第一导电剂，
    所述第一聚合物包括：
    式1表示的第一单体单元；
    选自式2表示的单体单元和式3表示的单体单元组成的组中的至少一种的第二单体单元；
    选自式4表示的单体单元和式5表示的单体单元组成的组中的至少一种的第三单体单元；以及
    式6表示的第四单体单元，R 1、R 2、R 3各自独立地表示H、羧基、酯基以及取代或未取代的如下基团：C1～C10的烷基、C1～C10的烷氧基、C2～C10的烯基、C6～C10的芳基，R 4表示H、以及取代或未取代的如下基团：C1～C10的烷基、C1～C10的烷氧基、C2～C10的烯基、C6～C10的芳基；
    Figure PCTCN2022084385-appb-100001
    Figure PCTCN2022084385-appb-100002
  2. 根据权利要求1所述的正极极片，其中，基于所述第一聚合物的总质量，
    所述第一单体单元的质量百分含量为M1，M1为10％～55％，可选地为25％～55％；和/或，
    所述第二单体单元的质量百分含量为M2，M2为40％～80％，可选地为50％～70％；和/或，
    所述第三单体单元的质量百分含量为M3，M3为0％～10％，可选地为0.001％～2％；和/或，
    所述第四单体单元的质量百分含量为M4，M4为0％～10％，可选地为0.1％～1％。
  3. 根据权利要求2所述的正极极片，其中，M3/(M2+M3)为0％～5％，可选地为0.001％～1％。
  4. 根据权利要求1-3中任一项所述的正极极片，其中，
    所述第一聚合物包括选自氢化丁腈橡胶、氢化羧基丁腈橡胶中的一种或多种；和/或，
    所述第一聚合物的重均分子量为5万～150万，可选地为20万～40万。
  5. 根据权利要求1-4中任一项所述的正极极片，其中，
    所述第一水性粘结剂包括选自水性聚丙烯酸树脂及其衍生物、水性氨基改性聚丙烯树脂及其衍生物、聚乙烯醇及其衍生物中的一种或多种，可选地包括选自水性丙烯酸-丙烯酸酯共聚物；和/或，
    所述第一水性粘结剂的重均分子量为20万～150万，可选地为30万～40万。
  6. 根据权利要求1-5中任一项所述的正极极片，其中，所述第一导电剂包括选自超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的一种或多种，可选地包括选自碳纳米管、石墨烯、碳纳米纤维中的一种或多种。
  7. 根据权利要求1-6中任一项所述的正极极片，其中，基于所述导电底涂层的总质量计，
    所述第一聚合物的质量百分含量为X1，X1为5％～20％，可选地为5％～10％；和/或，
    所述第一水性粘结剂的质量百分含量为X2，X2为30％～80％，可选地为40％～50％；和/或，
    所述第一导电剂的质量百分含量为X3，X3为10％～50％，可选地为40％～50％。
  8. 根据权利要求1-7中任一项所述的正极极片，其中，所述导电底涂层的厚度为1μm～20μm，可选为3μm～10μm。
  9. 根据权利要求1-8中任一项所述的正极极片，其中，所述正极膜层还包括选自浸润剂、分散剂中的一种或多种，可选地，所述正极膜层还同时包括浸润剂和分散剂。
  10. 根据权利要求9所述的正极极片，其中，所述浸润剂的表面张力为20mN/m～40mN/m，可选地，所述浸润剂包括如下官能团中的至少一种：-CN、-NH 2、-NH-、-N-、-OH、-COO-、-C(＝O)-O-C(＝O)-。
  11. 根据权利要求9或10所述的正极极片，其中，
    所述浸润剂包括选自小分子有机溶剂、低分子量聚合物中的一种或多种，
    可选地，所述小分子有机溶剂包括选自醇胺类化合物、醇类化合物、腈类化合物中的一种或多种，可选地，所述醇胺类化合物的碳原子数为1～16，可选地为2～6；
    可选地，所述低分子量聚合物包括选自马来酸酐-苯乙烯共聚物、聚乙烯基吡咯烷酮、聚硅氧烷中的一种或多种，可选地，所述低分子量聚合物的重均分子量在6000以下，可选地为3000～6000。
  12. 根据权利要求9-11中任一项所述的正极极片，其中，所述分散剂包括第二聚合物，并且所述第二聚合物包括：
    式7表示的第五单体单元；
    选自式8表示的单体单元和式9表示的单体单元组成的组中的至少一种的第六单体单元；以及
    选自式10表示的单体单元和式11表示的单体单元组成的组中的至少一种的第七单体单元；
    Figure PCTCN2022084385-appb-100003
  13. 根据权利要求12所述的正极极片，其中，基于所述第二聚合物的总质量，
    所述第五单体单元的质量百分含量为M5，M5为10％～55％，可选地为25％～55％；和/或，
    所述第六单体单元的质量百分含量为M6，M6为40％～80％，可选地为50％～70％；和/或，
    所述第七单体单元的质量百分含量为M7，M7为0％～10％，可选地为0.001％～2％。
  14. 根据权利要求13所述的正极极片，其中，M7/(M6+M7)为0％～5％，可选地为0.001％～1％。
  15. 根据权利要求12-14中任一项所述的正极极片，其中，
    所述第二聚合物为氢化丁腈橡胶；和/或，
    所述第二聚合物的重均分子量为5万～50万，可选地为15万～35万。
  16. 根据权利要求9-15中任一项所述的正极极片，其中，基于所述正极膜层的总质量，
    所述分散剂的质量百分含量为Y1，Y1为0.05％～1％，可选地为0.1％～0.5％；和/或，
    所述浸润剂的质量百分含量为Y2，Y2为0.05％～2％，可选地为0.2％～0.8％。
  17. 根据权利要求16所述的正极极片，其中，Y1/Y2为0.05～20，可选地为0.1～1，进一步地为0.3～0.8。
  18. 根据权利要求9-17中任一项所述的正极极片，其中，在所述正极极片中，所述第一聚合物与所述第二聚合物的质量比为1.5～5，可选地为2～3。
  19. 根据权利要求1-18中任一项所述的正极极片，其中，所述第一包覆层的磷酸盐的晶面间距为0.345-0.358nm，晶向(111)的夹角为24.25°-26.45°；所述第一包覆层的焦磷酸盐的晶面间距为0.293-0.326nm，晶向(111)的夹角为26.41°-32.57°。
  20. 根据权利要求1-19中任一项所述的正极极片，其中，
    在所述内核中，y与1-y的比值为1：10至10：1，可选为1：4至1：1；和/或，
    在所述内核中，z与1-z的比值为1：9至1：999，可选为1：499至1：249。
  21. 根据权利要求1-20中任一项所述的正极极片，其中，所述第一包覆层的包覆量大于0重量％且小于等于7重量％，可选为4-5.6重量％，基于所述内核的重量计。
  22. 根据权利要求1-21中任一项所述的正极极片，其中，所述第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。
  23. 根据权利要求1-22中任一项所述的正极极片，其中，所述焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。
  24. 根据权利要求1-23中任一项所述的正极极片，其中，所述第二包覆层的包覆量为大于0重量％且小于等于6重量％，可选为3-5重量％，基于所述内核的重量计。
  25. 根据权利要求1-24中任一项所述的正极极片，其中，所述A选自Fe、Ti、V、Ni、Co和Mg中的至少两种。
  26. 根据权利要求1-25中任一项所述的正极极片，其中，所述正极活性材料的Li/Mn反位缺陷浓度为4％以下，可选为2％以下。
  27. 根据权利要求1-26中任一项所述的正极极片，其中，所述正极活性材料的晶格变化率为6％以下，可选为4％以下。
  28. 根据权利要求1-27中任一项所述的正极极片，其中，所述正极活性材料的表面氧价态为-1.88以下，可选地为-1.98～-1.88。
  29. 根据权利要求1-28中任一项所述的正极极片，其中，所述正极活性材料在3吨下的压实密度为2.0g/cm 3以上，可选地为2.2g/cm 3以上。
  30. 一种二次电池，包括根据权利要求1-29中任一项所述的正极极片。
  31. 一种用电装置，包括根据权利要求30所述的二次电池。
PCT/CN2022/084385 2022-03-31 2022-03-31 正极极片、二次电池及用电装置 WO2023184329A1 (zh)

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