WO2024187741A1 - 正极活性材料、及其制备方法、二次电池和用电装置 - Google Patents

正极活性材料、及其制备方法、二次电池和用电装置 Download PDF

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Publication number
WO2024187741A1
WO2024187741A1 PCT/CN2023/124542 CN2023124542W WO2024187741A1 WO 2024187741 A1 WO2024187741 A1 WO 2024187741A1 CN 2023124542 W CN2023124542 W CN 2023124542W WO 2024187741 A1 WO2024187741 A1 WO 2024187741A1
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Prior art keywords
positive electrode
active material
electrode active
sodium
source
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PCT/CN2023/124542
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English (en)
French (fr)
Inventor
杨惠玲
赵玉珍
许跃
官英杰
温严
黄起森
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority claimed from CN202310232757.2A external-priority patent/CN118630153B/zh
Application filed by Contemporary Amperex Technology Co Ltd filed Critical Contemporary Amperex Technology Co Ltd
Priority to EP23927085.3A priority Critical patent/EP4618186A4/en
Publication of WO2024187741A1 publication Critical patent/WO2024187741A1/zh
Priority to US19/195,738 priority patent/US20250273674A1/en
Anticipated expiration legal-status Critical
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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—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
    • H01M4/58—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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/74—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by peak-intensities or a ratio thereof only
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of secondary batteries, and in particular to a positive electrode active material, a preparation method thereof, a secondary battery and an electrical device.
  • Sodium batteries have great application potential in large-scale energy storage due to their abundant reserves, low price and wide operating temperature.
  • Iron-based polyanion compounds are considered to be the most promising electrode materials due to their excellent structural stability, safety and suitable voltage platform.
  • sodium batteries using iron-based polyanion compounds as positive electrode materials still have many problems and cannot meet the application needs of the new generation of electrochemical systems.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode active material with higher crystallinity, which is beneficial to improve the first discharge capacity of the battery.
  • a positive electrode active material comprises a polyanion compound having a general formula as shown in Formula I.
  • the crystallinity of the positive electrode active material is 0.8 to 1. Na x Fe y1 M y2 (PO 4 ) z (P 2 O 7 ) kFormula I
  • M includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W and Pb; 1 ⁇ x ⁇ 7 , 1 ⁇ y1 + y2 ⁇ 4 , 1 ⁇ z ⁇ 2, 1 ⁇ k ⁇ 4.
  • the positive electrode active material with a crystallinity of 0.8 to 1 is beneficial to improving the initial discharge capacity of the battery, so that the battery has a higher charging capacity and improves the performance of the battery.
  • the ratio Id of the peak intensity of (602) to the peak intensity of (022) in the XRD diffraction spectrum of the positive electrode active material is 0.9 to 1.5.
  • the positive electrode active material further includes a carbon material located on at least a portion of the surface of the primary particles of the polyanion compound.
  • the carbon material located on the surface of the primary particles can significantly improve the poor conductivity of the iron-based polyanion compounds and greatly improve the electrochemical performance of the positive electrode active material.
  • the second aspect of the present application provides a method for preparing a positive electrode active material, comprising the following steps:
  • the raw material further includes an M source;
  • the positive electrode active material includes a polyanion compound having a general formula shown in Formula I, and the crystallinity of the positive electrode active material is 0.8 to 1.
  • M includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W and Pb; 1 ⁇ x ⁇ 7 , 1 ⁇ y1 + y2 ⁇ 4 , 1 ⁇ z ⁇ 2, 1 ⁇ k ⁇ 4.
  • the positive electrode active material with a crystallinity of 0.8 to 1 is beneficial to improving the initial discharge capacity of the battery, so that the battery has a higher charging capacity and improves the performance of the battery.
  • the raw materials comprising a sodium source, an iron source, and a phosphorus source are mixed with a solvent to obtain a mixed slurry, which specifically includes:
  • the raw materials including the sodium source, ferrous oxalate and phosphorus source are added to a solvent, stirred and ground to obtain a mixed slurry.
  • the mixed slurry is subjected to a homogenizing shear rate of 300S -1 to 900S -1 .
  • the homogenizing shear rate of stirring is controlled to be 300S -1 ⁇ 900S -1 .
  • a high homogenizing shear rate is beneficial to avoid or reduce the precursor generated by the reaction of the sodium source, phosphorus source and ferrous oxalate to wrap the unreacted ferrous oxalate, so as to fully expose the unreacted ferrous oxalate.
  • the reaction is carried out separately to improve the crystallinity of the positive electrode active material.
  • the median particle size Dv50 of the particles in the mixed slurry is 0.05 ⁇ m to 1.5 ⁇ m, and can be optionally 0.1 ⁇ m to 0.7 ⁇ m.
  • Controlling the median particle size Dv50 of the particles in the mixed slurry within an appropriate particle size range can avoid the need for a long grinding time due to too small a particle size, increase the risk of subsequent slurry physical gelation, reduce the difficulty of subsequent processing, and reduce the requirements for production equipment; it can also reduce the small crystallinity and more impurities of the positive electrode active material due to too large a particle size, thereby ensuring the kinetic performance of the positive electrode active material during the charge and discharge process.
  • the solid content of the mixed slurry is 15% to 50%, and optionally 25% to 40%.
  • Controlling the solid content of the mixed slurry within an appropriate range can avoid the mixed slurry's solid content being too low, which leads to a reduction in production capacity and inability to produce on a large scale, and can also avoid the mixed slurry's solid content being too high, which increases equipment losses and requirements for production equipment. It can take into account both production costs and production scale, making it suitable for industrial applications.
  • the mixed slurry includes a carbon source.
  • carbon source is beneficial to improving the conductivity of the positive electrode active material and increasing the initial discharge capacity of the battery.
  • the raw materials comprising a sodium source, an iron source, and a phosphorus source are added to a solvent to obtain a mixed slurry:
  • the raw materials including the sodium source, ferrous oxalate and phosphorus source are added to a solvent, stirred and ground until the median particle size Dv50 of the particles in the slurry is 0.05 ⁇ m to 1.5 ⁇ m, and then mixed with a carbon source to obtain a mixed slurry.
  • Controlling the median particle size Dv50 of the particles in the mixed slurry within an appropriate particle size range can avoid the need for a long grinding time due to too small a particle size, increase the risk of subsequent slurry physical gelation, reduce the difficulty of subsequent processing, and reduce the requirements for production equipment; it can also reduce the small crystallinity and more impurities of the positive electrode active material due to too large a particle size, thereby ensuring the kinetic performance of the positive electrode active material during the charge and discharge process.
  • the preparation method comprises:
  • the raw materials including the sodium source, ferrous oxalate, and phosphorus source are added to the solvent, stirred, and ground until the median particle size Dv50 of the particles in the slurry is 0.1 ⁇ m to 0.7 ⁇ m, and then mixed with the carbon source to obtain to the mixed slurry.
  • the median particle size Dv50 of the particles in the mixed slurry is further controlled to be 0.1 ⁇ m to 0.7 ⁇ m before mixing with the carbon source to reduce the difficulty of initial grinding.
  • the addition of the carbon source will significantly increase the viscosity of the slurry, increase the grinding power and grinding time.
  • the sodium source includes one or more of sodium carbonate, sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium pyrophosphate, sodium bicarbonate, sodium oxalate, sodium acetate, sodium citrate, sodium nitrate, and sodium hydroxide.
  • the phosphorus source includes one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium pyrophosphate, trisodium monohydrogen pyrophosphate, disodium dihydrogen pyrophosphate, monosodium trihydrogen pyrophosphate, phosphoric acid, and pyrophosphoric acid.
  • the solvent includes one or more of ethanol, water, and ethylene glycol.
  • the above solvents and dispersants are beneficial to the sufficient dissolution and dispersion of the raw materials, forming a uniformly mixed mixed slurry, which is convenient for controlling the particle size in the mixed slurry.
  • the carbon source includes an inorganic carbon source or an organic carbon source
  • the inorganic carbon source includes one or more of natural graphite, artificial graphite, carbon black, carbon nanotubes, and graphene
  • the organic carbon source includes one or more of sucrose, glucose, citric acid, starch, cyclodextrin, and asphalt.
  • Both inorganic carbon sources and organic carbon sources are beneficial to improving the conductivity of positive electrode active materials.
  • a third aspect of the present application provides a secondary battery, comprising a positive electrode plate and a negative electrode plate, wherein the positive electrode plate comprises the positive electrode active material of the first aspect or the positive electrode active material prepared by the preparation method of the second aspect.
  • the secondary battery is a negative electrode-free sodium secondary battery.
  • the negative electrode plate includes a negative electrode current collector and a primer layer disposed on at least one surface of the negative electrode current collector, and the primer layer includes one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.
  • the above-mentioned base coating layer not only has excellent conductivity, but also facilitates the uniform deposition of metal ions on the surface of the current collector, thereby improving the cycle performance and safety of the battery.
  • the surface density of the primer layer is 5 g/m 2 to 50 g/m 2 .
  • the base coating with a surface density of 5 g/m 2 to 50 g/m 2 is conducive to the uniform distribution of nucleation sites. It promotes uniform deposition of metals without affecting the transport behavior of electrons.
  • the thickness of the primer layer is 2 ⁇ m to 100 ⁇ m.
  • Controlling the thickness of the base coating to be 2 ⁇ m to 100 ⁇ m can provide enough nucleation sites to facilitate uniform deposition of metal ions and inhibit dendrites.
  • a fourth aspect of the present application provides an electrical device, comprising the secondary battery of the third aspect of the present application.
  • FIG. 1a is an X-ray diffraction pattern of a positive electrode active material precursor in some embodiments and comparative examples of the present application;
  • FIG1b is a standard X-ray diffraction pattern of ferrous oxalate
  • FIG2a is an X-ray diffraction pattern of the positive electrode active material in the examples and comparative examples of the present application.
  • FIG2 b is a standard X-ray diffraction pattern of sodium ferric pyrophosphate
  • FIG3 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG4 is an exploded view of the secondary battery of one embodiment of the present application shown in FIG3 ;
  • FIG5 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG6 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG7 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG6 ;
  • FIG. 8 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • “Scope” disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range.
  • the scope limited in this way can be including end values or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the terms “include” and “comprising” mentioned in this application may be open-ended or closed-ended.
  • the terms “include” and “comprising” may mean that other components not listed may also be included or that only the listed components may be included or that the components listed may be included. point.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • sodium iron phosphate pyrophosphate is usually used as the positive electrode material of sodium battery, but the existing process is difficult to prepare sodium iron phosphate pyrophosphate material with high crystallinity, which affects its electrochemical performance.
  • the applicant unexpectedly found that the crystallinity of sodium iron phosphate pyrophosphate is difficult to improve because in the mechanical solid phase synthesis process, the intermediate product (such as the precursor) is easily coated on the surface of the iron source, resulting in the iron source being unable to be exposed and continue to participate in the reaction.
  • the present application proposes a positive electrode active material, the positive electrode active material includes a polyanion compound having a formula I, and the crystallinity of the positive electrode active material is 0.8 to 1.
  • M includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W and Pb; 1 ⁇ x ⁇ 7 , 1 ⁇ y1 + y2 ⁇ 4 , 1 ⁇ z ⁇ 2, 1 ⁇ k ⁇ 4.
  • M comprises Mg. In some embodiments, M comprises Al. In some embodiments, M comprises V. In some embodiments, M comprises Mn.
  • x may be selected as 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, or a value in the range consisting of any two of the above points
  • y1 and y2 may be selected as 1, 1.5, 2, 2.5, 3, 3.5, 4, or a value in the range consisting of any two of the above points
  • z may be selected as 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a value in the range consisting of any two of the above points
  • k may be selected as 1, 1.5, 2, 2.5, 3, 3.5, 4, or a value in the range consisting of any two of the above points.
  • the crystallinity of the positive electrode active material can be measured by any known means, including but not limited to X-ray diffractometer.
  • the area of the (222) peak and the integrated area in the standard card are used as parameters to calculate the crystallinity.
  • the integrated area of the diffraction peak can be directly calculated using Jade.
  • the positive electrode active material with a crystallinity of 0.8 to 1 is beneficial to improving the initial discharge capacity of the battery, so that the battery has a higher charging capacity and improves the performance of the battery.
  • the ratio Id of the peak intensity of (602) to the peak intensity of (022) in the XRD diffraction spectrum of the positive electrode active material is 0.9 to 1.5.
  • the peak intensity can be directly calculated by Jade.
  • the ratio of the peak intensity of (602) to the peak intensity of (022) in the Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) 4 standard card is 1.15.
  • the ratio Id of the peak intensity of (602) to the peak intensity of (022) in the XRD diffraction spectrum of the positive electrode active material may be 0.9, 1, 1.1, 1.2, 1.3, 1.4 or 1.5.
  • the positive electrode active material further includes a carbon material located on at least a portion of the surface of the primary particles of the polyanion compound.
  • the carbon material is distributed in a particle form between primary particles of the polyanionic compound.
  • the carbon material is inorganic carbon, which has high crystallinity, high particle size, and strong conductivity, and can effectively improve the conductivity of the positive electrode active material.
  • the carbon material is coated on the surface of the primary particles of the polyanion compound in the form of a carbon film.
  • the introduction of carbon materials into the positive electrode active materials is beneficial to improving the conductivity and optimizing the coulombic efficiency and cycle performance of the battery.
  • the present application also provides a method for preparing a positive electrode active material, comprising the following steps:
  • the mixed slurry is dried and calcined to obtain a positive electrode active material
  • the positive electrode active material includes a polyanion compound represented by formula I
  • the crystallinity of the positive electrode active material is 0.8 to 1.
  • M includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W and Pb; 1 ⁇ x ⁇ 7 , 1 ⁇ y1 + y2 ⁇ 4 , 1 ⁇ z ⁇ 2, 1 ⁇ k ⁇ 4.
  • M comprises Mg. In some embodiments, M comprises Al. In some embodiments, M comprises V. In some embodiments, M comprises Mn.
  • x may be selected as 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, or a value in the range consisting of any two of the above points
  • y1 and y2 may be selected as 1, 1.5, 2, 2.5, 3, 3.5, 4, or a value in the range consisting of any two of the above points
  • z may be selected as 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, or a value in the range consisting of any two of the above points
  • k may be selected as 1, 1.5, 2, 2.5, 3, 3.5, 4, or a value in the range consisting of any two of the above points.
  • the positive electrode active material with a crystallinity of 0.8 to 1 is beneficial to improving the initial discharge capacity of the battery, so that the battery has a higher charging capacity and improves the performance of the battery.
  • the raw materials comprising a sodium source, an iron source, and a phosphorus source are added to a solvent to obtain a mixed slurry as follows:
  • the raw materials including the sodium source, ferrous oxalate and phosphorus source are added to a solvent, stirred and ground to obtain a mixed slurry.
  • the mixed slurry is subjected to a homogenizing shear rate of 300S -1 to 900S -1 .
  • the homogenizing shear rate may be 300 S -1 , 350 S -1 , 400 S -1 , 450 S -1 , 500 S -1 , 550 S -1 , 600 S -1 , 650 S -1 , 700 S -1 , 750 S -1 , 800 S -1 , 850 S -1 , 900 S -1 , or a value in a range consisting of any two of the above points.
  • the homogenization shear rate is a parameter comprehensively related to the stirring parameters, fluid viscosity, and volume, and can be calculated by any known method.
  • the homogenization shear rate for controlling the stirring is 300S -1 to 900S -1 .
  • a high homogenization shear rate is beneficial to avoid or reduce the precursor generated by the reaction of the sodium source, phosphorus source and ferrous oxalate to encapsulate the unreacted ferrous oxalate, so as to fully expose the unreacted ferrous oxalate to make it fully react and improve the crystallinity of the positive electrode active material.
  • the median particle size Dv50 of the particles in the mixed slurry is 0.05 ⁇ m to 1.5 ⁇ m, and can be optionally 0.1 ⁇ m to 0.7 ⁇ m.
  • the median particle size Dv50 of the particles in the mixed slurry can be selected to be 0.05 ⁇ m, 0.1 ⁇ m, 0.2 ⁇ m, 0.3 ⁇ m, 0.4 ⁇ m, 0.5 ⁇ m, 0.6 ⁇ m, 0.7 ⁇ m, 0.8 ⁇ m, 0.9 ⁇ m, 1 ⁇ m, 1.1 ⁇ m, 1.2 ⁇ m, 1.3 ⁇ m, 1.4 ⁇ m, 1.5 ⁇ m, or a value in the range consisting of any two of the above points.
  • the median particle size Dv50 of the particles in the mixed slurry can be measured by any known means, including but not limited to centrifugal sedimentation and laser particle size analyzer testing.
  • the sample is first centrifuged, sedimented, and filtered to obtain a particle sample in the initial mixed slurry, and then 0.1g to 0.13g of the particle sample to be tested is weighed in a 50mL beaker, 5g of acetone is added, and a stirring bar of about 2.5mm is placed in it and sealed with plastic wrap. After ultrasonic treatment for 5 minutes, the sample is transferred to a magnetic stirrer and stirred at 500 rpm for more than 20 minutes. Two samples are taken from each batch of products for testing. The Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK, is used for testing.
  • Controlling the median particle size Dv50 of the particles in the mixed slurry within an appropriate particle size range can avoid the need for a long grinding time due to too small a particle size, increase the risk of subsequent slurry physical gelation, reduce the difficulty of subsequent processing, and reduce the requirements for production equipment; it can also reduce the small crystallinity and more impurities of the positive electrode active material due to too large a particle size, thereby ensuring the kinetic performance of the positive electrode active material during the charge and discharge process.
  • the solid content of the mixed slurry is 15% to 50%, and optionally 25% to 40%.
  • the solid content of the mixed slurry may be selected to be 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a value in a range consisting of any two of the above points.
  • Controlling the solid content of the mixed slurry within an appropriate range can avoid the mixed slurry's solid content being too low, which leads to a reduction in production capacity and inability to produce on a large scale, and can also avoid the mixed slurry's solid content being too high, which increases equipment losses and requirements for production equipment. It can take into account both production costs and production scale, making it suitable for industrial applications.
  • a carbon source is included in the mixed slurry.
  • carbon source is beneficial to improve the conductivity of positive electrode active materials and improve the battery The first discharge capacity.
  • the mixed slurry further includes a dispersant, and the dispersant includes one or more of polyethylene glycol and polyvinyl alcohol.
  • the dispersant is beneficial for the uniform dispersion of the carbon source in the mixed slurry, thus facilitating the subsequent preparation of the positive electrode active material.
  • the raw materials comprising a sodium source, an iron source, and a phosphorus source are added to a solvent to obtain a mixed slurry as follows:
  • the raw materials including the sodium source, ferrous oxalate and phosphorus source are added to a solvent, stirred and ground until the median particle size Dv50 of the particles in the slurry is 0.05 ⁇ m to 1.5 ⁇ m, and then mixed with a carbon source to obtain a mixed slurry.
  • Controlling the median particle size Dv50 of the particles in the mixed slurry within an appropriate particle size range can avoid the need for a long grinding time due to too small a particle size, increase the risk of subsequent slurry physical gelation, reduce the difficulty of subsequent processing, and reduce the requirements for production equipment; it can also reduce the small crystallinity and more impurities of the positive electrode active material due to too large a particle size, thereby ensuring the kinetic performance of the positive electrode active material during the charge and discharge process.
  • the preparation method comprises:
  • the raw materials including the sodium source, ferrous oxalate and phosphorus source are added to a solvent, stirred and ground until the median particle size Dv50 of the particles in the slurry is 0.1 ⁇ m to 0.7 ⁇ m, and then mixed with a carbon source to obtain a mixed slurry.
  • the median particle size Dv50 of the particles in the mixed slurry is further controlled to be 0.1 ⁇ m to 0.7 ⁇ m before mixing with the carbon source to reduce the difficulty of initial grinding.
  • the addition of the carbon source will significantly increase the viscosity of the slurry, increase the grinding power and grinding time.
  • the sodium source includes one or more of sodium carbonate, sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium pyrophosphate, sodium bicarbonate, sodium oxalate, sodium acetate, sodium citrate, sodium nitrate, and sodium hydroxide.
  • the phosphorus source includes one or more of sodium dihydrogen phosphate, disodium hydrogen phosphate, sodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium pyrophosphate, trisodium monohydrogen pyrophosphate, disodium dihydrogen pyrophosphate, monosodium trihydrogen pyrophosphate, phosphoric acid, and pyrophosphoric acid.
  • the solvent is selected from one or more of ethanol, water, and ethylene glycol.
  • the above solvents and dispersants are beneficial to fully dissolve the raw materials, forming a uniformly mixed mixed slurry, which is convenient for controlling the particle size in the mixed slurry.
  • the carbon source includes an inorganic carbon source or an organic carbon source
  • the inorganic carbon source includes one or more of natural graphite, artificial graphite, carbon black, carbon nanotubes, and graphene
  • the organic carbon source includes one or more of sucrose, glucose, citric acid, starch, cyclodextrin, and asphalt.
  • Both inorganic carbon sources and organic carbon sources are beneficial to improving the conductivity of positive electrode active materials.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer formed on at least a portion of the surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material in some embodiments.
  • the positive electrode active material layer may further include a conductive agent to improve the conductivity of the positive electrode.
  • the conductive agent may be selected from one or more of Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene and carbon nanofibers.
  • the positive electrode active material layer may further include a binder to firmly bind the positive electrode active material and the optional conductive agent to the positive electrode current collector.
  • the binder may be selected from at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), sodium alginate (SA), polymethacrylic acid (PMA) and carboxymethyl chitosan (CMCS).
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PAA polyacrylic acid
  • PVA polyvinyl alcohol
  • EVA ethylene-vinyl acetate copolymer
  • SBR styrene-butadiene rubber
  • CMC carboxymethyl cellulose
  • SA sodium al
  • the positive electrode current collector may be a conductive carbon sheet, a metal foil, a carbon-coated metal foil, a porous metal plate or a composite current collector.
  • the conductive carbon material of the conductive carbon sheet may be selected from one or more of Super P, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene and carbon nanofibers
  • the metal material of the metal foil, the carbon-coated metal foil and the porous metal plate may be independently selected from at least one of copper, aluminum, nickel and stainless steel
  • the composite current collector may be a composite current collector formed by a metal foil and a polymer base film.
  • the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, The positive electrode plate can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the negative electrode sheet may only include a negative electrode current collector without including a negative electrode active material.
  • the negative electrode sheet may also be formed by pre-depositing a metal phase on 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 substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode plate includes a negative electrode current collector and a primer layer disposed on at least one surface of the negative electrode current collector, and the primer layer includes one or more of carbon nanotubes, graphite, graphene, silver composite carbon nanoparticles, and tin composite carbon nanoparticles.
  • the above-mentioned base coating layer not only has excellent conductivity, but also facilitates the uniform deposition of metal ions on the surface of the current collector, thereby improving the cycle performance and safety of the battery.
  • the surface density of the primer layer is 5 g/m 2 to 50 g/m 2 .
  • the surface density of the primer layer may be 5 g/ m2 , 10 g/ m2 , 15 g/ m2 , 20 g/ m2 , 25 g/ m2 , 30 g/ m2 , 35 g/ m2 , 40 g/ m2 , 45 g/ m2 , 50 g/ m2 , or a value in a range consisting of any two of the foregoing.
  • the undercoat layer with a surface density of 5 g/m 2 to 50 g/m 2 is conducive to the uniform distribution of nucleation sites and promotes the uniform deposition of metals, while not affecting the transmission behavior of electrons.
  • the primer layer has a thickness of 2 ⁇ m to 100 ⁇ m.
  • the thickness of the primer layer can be selected to be 2 ⁇ m, 5 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, 45 ⁇ m, 50 ⁇ m, 55 ⁇ m, 60 ⁇ m, 65 ⁇ m, 70 ⁇ m, 75 ⁇ m, 80 ⁇ m, 85 ⁇ m, 90 ⁇ m, 95 ⁇ m, 100 ⁇ m, or a value in the range formed by any two of the above points.
  • Controlling the thickness of the base coating to be 2 ⁇ m to 100 ⁇ m can provide enough nucleation sites to facilitate uniform deposition of metal ions and inhibit dendrites.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • a secondary battery comprises a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet comprises a positive electrode active material in some embodiments or a positive electrode active material prepared by a preparation method in some embodiments.
  • FIG3 is a secondary battery 5 of a square structure as an example.
  • the secondary battery further includes a separator and an electrolyte.
  • the secondary battery is a negative electrode-free sodium secondary battery.
  • Negative electrode-free sodium secondary battery refers to a battery that does not actively set a negative electrode active material layer on the negative electrode side during the battery manufacturing process. For example, during the battery manufacturing process, a sodium metal or carbonaceous active material layer is not set on the negative electrode through a coating or deposition process to form a negative electrode active material layer.
  • sodium ions obtain electrons on the anode side and metallic sodium is deposited on the current collector surface to form a sodium metal phase.
  • metallic sodium can be converted into sodium ions. The electrons return to the positive electrode to achieve cyclic charge and discharge.
  • the negative electrode-free sodium secondary battery can achieve higher energy density due to the lack of negative electrode active material layer.
  • the negative electrode side of the negative electrode-free sodium secondary battery may be provided with some conventional substances that can be used as negative electrode active materials, such as carbonaceous materials, metal oxides, alloys, etc. Although these materials have a certain capacity, due to the small amount of these materials, they are not used as the main negative electrode active materials in the battery, and therefore are not considered to form a negative electrode active material layer that plays a role in sodium insertion, and the sodium secondary battery thus constructed can still be considered as a negative electrode-free sodium secondary battery.
  • some conventional substances that can be used as negative electrode active materials such as carbonaceous materials, metal oxides, alloys, etc.
  • the CB value of the negative electrode-free sodium secondary battery is less than or equal to 0.1.
  • the CB value is the unit area capacity of the negative electrode plate in the secondary battery divided by the unit area capacity of the positive electrode plate. Since the negative electrode-free battery contains no or only a small amount of negative electrode active material, the unit area capacity of the negative electrode plate is small, and the CB value of the secondary battery is less than or equal to 0.1.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the non-Newtonian fluid electrolyte composition is infiltrated in 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 may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG5 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. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a storage space, a plurality of The secondary battery 5 is accommodated in the accommodation space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG6 and FIG7 are battery packs 1 as an example.
  • 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 body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of battery modules 4 can be arranged in the battery box in any manner.
  • an electric device comprising at least one of a secondary battery of any embodiment, a battery module of any embodiment, or a battery pack of any embodiment.
  • the electrical device includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device.
  • the electrical 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, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG8 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • a device is usually required to be light and thin, and a secondary battery may be used as a power source.
  • Sodium pyrophosphate, ferrous oxalate and ammonium dihydrogen phosphate were dissolved in deionized water at a molar ratio of 0.998:3:2, stirred continuously for 30 minutes at room temperature, and the homogenization shear rate was 630S -1 .
  • a carbon source was added and mixed to obtain a mixed slurry with a solid content of 35%.
  • the mixed slurry was spray dried with an inlet air temperature of 220°C and an outlet air temperature of 109°C to obtain a powdered positive electrode active material precursor.
  • the temperature was raised to 320°C at a heating rate of 2°C and kept warm for 4 hours, and then continued to be raised to 550 ° C at a heating rate of 2°C and kept warm for 10 hours.
  • the sintered product was crushed and sieved to obtain Na3.98Fe3 ( PO4 ) 2P2O7 positive electrode active material.
  • polyvinylidene fluoride binder 2.5wt% polyvinylidene fluoride binder was fully dissolved in N-methylpyrrolidone (NMP), and then 2.0wt% Super P, 1.0wt% carbon nanotubes and 94.5wt% of the above positive electrode active materials were added and stirred to obtain positive electrode slurry.
  • NMP N-methylpyrrolidone
  • the slurry was evenly coated on the surface of the current collector aluminum foil, and then transferred to a vacuum drying oven for complete drying. The dried electrode sheet was rolled and punched to obtain a positive electrode sheet.
  • Single-walled carbon nanotubes and carboxymethyl cellulose (CMC) were added to deionized water in a mass ratio of 1:0.4 and stirred into a uniform slurry.
  • the slurry was coated on the surface of the negative electrode current collector copper foil, and then transferred to a vacuum drying oven for complete drying, and then punched to obtain a negative electrode sheet without a negative electrode structure.
  • Polypropylene film is used as the isolation film.
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare cell, the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum shell, and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery.
  • the uncharged battery is then subjected to the processes of static, hot and cold pressing, formation, shaping, and capacity testing in sequence to obtain the negative electrode-free sodium metal battery product of Example 1.
  • the preparation methods of the batteries of Examples 2 to 11 are similar to those of the battery of Example 1, but the preparation parameters of the positive electrode active material are adjusted. The specific parameters are shown in Table 1.
  • Comparative Examples 1-4 are substantially similar to those in Example 1, but the homogenization shear rates are all adjusted to be less than 300 S ⁇ 1 .
  • the specific parameters are shown in Table 1.
  • the centrifugal sedimentation method and laser particle size analyzer were used for testing. First, the sample was centrifuged, sedimented, and filtered to obtain the particle sample in the initial mixed slurry. Then, 0.1g to 0.13g of the particle sample to be tested was weighed in a 50mL beaker, 5g of acetone was added, and a stirring bar of about 2.5mm was placed and sealed with plastic wrap. After ultrasonic treatment for 5min, the sample was transferred to a magnetic stirrer and stirred at 500 rpm for more than 20min. Two samples were taken from each batch of products for testing. The Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK, was used for testing.
  • the average shear rate is used to measure the homogenous shear rate of the fluid, which is the sum of the axial average shear rate and the radial average shear rate.
  • ⁇ is the liquid viscosity, Pa ⁇ S
  • L is the length (the axial length touched by the slurry), in m
  • ⁇ P is the inlet and outlet pressure, which is positively correlated with the slurry volume flow rate, in Pa.
  • X-ray diffraction method for measuring crystallinity - the area (As) obtained by integrating the strongest diffraction peak (i.e. (222) peak) is compared with the area (Ag) obtained by integrating the standard substance, and used as an index for calculating crystallinity, crystallinity As/Ag ⁇ 100%.
  • the XRD abscissa 2 ⁇ position of the (222) peak of the standard substance is 33.304°.
  • the ratio of the (602) peak intensity (the XRD abscissa 2 ⁇ position of the ( 602 ) peak is 34.304 °) to the (022) peak intensity (the XRD abscissa 2 ⁇ position of the (022) peak is 32.218°) in the Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) 4 standard card is 1.15.
  • the first discharge capacity test process is as follows: at 25°C, the prepared battery is charged to 3.75V at a constant current of 1C, then charged at a constant voltage of 3.75V until the current drops to 0.05C, and then discharged to 1.5V at a constant current of 1C to obtain the first cycle discharge capacity (Cd1).
  • the test process of the comparative example and other embodiments is the same as above.
  • the battery capacity retention rate test process is as follows: at 25°C, the prepared battery is charged to 3.75V at a constant current of 1C, then charged at a constant voltage of 3.75V until the current drops to 0.05C, and then discharged to 1.5V at a constant current of 1C, and the obtained capacity is recorded as the initial capacity (C0). Repeat the above steps for the same battery, and record the discharge capacity (Cn) of the battery after the nth cycle at the same time.
  • the battery capacity retention rate data corresponding to the embodiment or comparative example in Table 2 is the data measured after 100 cycles under the above test conditions, that is, the value of P100.
  • the test process of the comparative example and other embodiments is the same as above.
  • the precursor obtained after spray drying of the mixed slurry was characterized by XRD, and the results are shown in Figure 1a.
  • the precursor component in Comparative Example 1 still contains ferrous oxalate with high crystallinity, while in Example 5, by increasing the shear rate, the crystallinity of ferrous oxalate in the precursor is significantly reduced, and in Example 3, the shear rate is further increased, and the precursor is completely amorphous, indicating that the raw material ferrous oxalate is fully involved in the reaction.
  • the positive electrode active material obtained after calcination was characterized by XRD.
  • the results are shown in Figure 2a.
  • the standard card XRD spectrum of sodium iron phosphate pyrophosphate is compared in Figure 2b.
  • the ratio of the (602) peak intensity to the (022) peak intensity in the XRD diffraction spectrum of the positive electrode active material continues to increase. This is because the precursor is coated with ferrous oxalate, which limits the growth of the (602) crystal plane. As the raw material components completely enter the precursor, The crystallinity of the positive electrode active material is significantly improved after calcination.
  • Examples 1 to 11 all include a positive electrode active material, the positive electrode active material includes a polyanion compound represented by Formula I, and the crystallinity of the positive electrode active material is 0.8 to 1.
  • M includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W and Pb; 1 ⁇ x ⁇ 7 , 1 ⁇ y1 + y2 ⁇ 4 , 1 ⁇ z ⁇ 2, 1 ⁇ k ⁇ 4.

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Abstract

一种正极活性材料及其制备方法、二次电池和用电装置。该正极活性材料包括具有式I所示通式的聚阴离子化合物，正极活性材料的结晶度为0.8～1，式I：Na xFe y1M y2(PO 4) z(P 2O 7) k，其中，M包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W和Pb中的至少一种；1≤x≤7，1≤y1+y2≤4，1≤z≤2，1≤k≤4。该正极活性材料具有较高的结晶度，有利于提升电池的首次放电容量。

Description

正极活性材料、及其制备方法、二次电池和用电装置
交叉引用
本申请引用于2023年3月10日递交的名称为“正极活性材料、及其制备方法、二次电池和用电装置”的第202310232757.2号中国专利申请，其通过引用被全部并入本申请。
技术领域
本申请涉及二次电池技术领域，尤其涉及一种正极活性材料、及其制备方法、二次电池和用电装置。
背景技术
钠电池由于具有丰富的储量，较低的价格以及宽的工作温度，在大型储能方面具有巨大的应用潜力。
铁基聚阴离子化合物以优异的结构稳定性、安全性和合适的电压平台被认为是最有应用前景的一类电极材料。但目前以铁基聚阴离子化合物作为正极材料的钠电池仍然存在着诸多问题。无法满足新一代电化学体系的应用需要。
发明内容
本申请是鉴于上述课题而进行的，其目的在于提供一种具有较高结晶度的正极活性材料，有利于提升电池的首次放电容量。
本申请的第一方面，提供了一种正极活性材料，正极活性材料包括具有式I所示通式的聚阴离子化合物，正极活性材料的结晶度为0.8～1，
NaxFey1My2(PO4)z(P2O7)k    式I
其中，M包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W和Pb中的至少一种；1≤x≤7，1≤y1+y2≤4，1≤z≤2，1≤k≤4。
结晶度为0.8～1的正极活性材料，有利于提升电池的首次放电容量，以使电池具有较高的充电能力，改善电池的性能。
在任意实施方式中，正极活性材料的XRD衍射谱中(602)峰强与(022)峰强的比值Id为0.9～1.5。
申请人意外地发现XRD衍射谱中(602)峰强与(022)峰强的比值Id越高，正极活性材料的电化学表现越优异。
在任意实施方式中，正极活性材料还包括位于聚阴离子化合物一次粒子至少部分表面的碳材料。
碳材料位于一次粒子表面能够显著改善铁基聚阴离子化合物导电性差的问题，大幅度改善正极活性材料的电化学性能。
本申请的第二方面提供一种正极活性材料的制备方法，包括以下步骤：
将包含钠源、铁源、及磷源的原料与溶剂混合后得到混合浆料，可选地，原料还包括M源；
对混合浆料干燥、煅烧后得到正极活性材料，正极活性材料包括具有式I所示通式的聚阴离子化合物，正极活性材料的结晶度为0.8～1，
NaxFey1My2(PO4)z(P2O7)k     式I
其中，M包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W和Pb中的至少一种；1≤x≤7，1≤y1+y2≤4，1≤z≤2，1≤k≤4。
结晶度为0.8～1的正极活性材料，有利于提升电池的首次放电容量，以使电池具有较高的充电能力，改善电池的性能。
在任意实施方式中，将包含钠源、铁源、及磷源的原料与溶剂混合后得到混合浆料具体包括：
将包含钠源、草酸亚铁、及磷源的原料加入溶剂中搅拌、研磨后得到混合浆料，混合浆料受到的均质剪切速率为300S-1～900S-1。
控制搅拌的均质剪切速率为300S-1～900S-1，高均质剪切速率有利于避免或减少钠源、磷源与草酸亚铁反应生成的前驱体包裹未反应的草酸亚铁，便于将未反应的草酸亚铁充分暴露出来，以使其充 分反应，提高正极活性材料的结晶度。
在任意实施方式中，混合浆料中颗粒的中值粒径Dv50为0.05μm～1.5μm，可选为0.1μm～0.7μm。
控制混合浆料中颗粒的中值粒径Dv50在合适的粒径范围，既可避免由于粒径太小导致所需研磨时间较长、以及增加后续浆料物理凝胶的风险，降低了后续加工难度、以及对生产设备的要求；也可减少由于粒径太大导致的正极活性材料结晶度小、杂相较多，从而保证正极活性材料在充放电过程中的动力学性能。
在任意实施方式中，混合浆料的固含量为15％～50％，可选为25％～40％。
控制混合浆料的固含量在合适的范围内，既可以避免混合浆料的固含量过低导致产能的降低，无法大规模生产，又可以避免混合浆料的固含量过高增加了对设备的损耗、以及对生产设备的要求，能够兼顾生产成本和生产规模，使其适于工业化应用。
在任意实施方式中，混合浆料中包含碳源。
碳源的加入有利于提升正极活性材料的导电性能，提升其电池的首次放电容量。
在任意实施方式中，将包含钠源、铁源、及磷源的原料加入溶剂中得到混合浆料具体为：
将包含钠源、草酸亚铁、及磷源的原料加入溶剂中搅拌、研磨至浆料中颗粒的中值粒径Dv50为0.05μm～1.5μm后，与碳源混合得到混合浆料。
控制混合浆料中颗粒的中值粒径Dv50在合适的粒径范围，既可避免由于粒径太小导致所需研磨时间较长、以及增加后续浆料物理凝胶的风险，降低了后续加工难度、以及对生产设备的要求；也可减少由于粒径太大导致的正极活性材料结晶度小、杂相较多，从而保证正极活性材料在充放电过程中的动力学性能。
在任意实施方式中，制备方法包括：
将包含钠源、草酸亚铁、及磷源的原料加入溶剂中搅拌、研磨至浆料中颗粒的中值粒径Dv50为0.1μm～0.7μm后，与碳源混合得 到混合浆料。
进一步控制混合浆料中颗粒的中值粒径Dv50为0.1μm～0.7μm后再与碳源混合减少初始研磨难度，碳源的加入会显著提高浆料的粘度，增大研磨功率和研磨时间。
在任意实施方式中，钠源包括碳酸钠、磷酸钠、磷酸二氢钠、磷酸氢二钠、焦磷酸钠、碳酸氢钠、草酸钠、乙酸钠、柠檬酸钠、硝酸钠、氢氧化钠中的一种或多种。
在任意实施方式中，磷源包括磷酸二氢钠、磷酸氢二钠、磷酸钠、磷酸二氢铵、磷酸氢二铵、焦磷酸钠、焦磷酸一氢三钠、焦磷酸二氢二钠、焦磷酸三氢一钠、磷酸、焦磷酸中的一种或多种。
在任意实施方式中，溶剂包括乙醇、水、乙二醇中的一种或多种。
上述溶剂和分散剂均有利于原料的充分溶剂和分散，形成混合均匀的混合浆料，便于混合浆料中颗粒尺寸的控制。
在任意实施方式中，碳源包括无机碳源或有机碳源，无机碳源包括天然石墨、人造石墨、碳黑、纳米碳管、石墨烯中的一种或多种，有机碳源包括蔗糖、葡萄糖、柠檬酸、淀粉、环糊精、沥青中一种或多种。
无机碳源和有机碳源均有利于提升正极活性材料的导电性能。
本申请的第三方面提供一种二次电池，包括正极极片和负极极片，正极极片包括第一方面的正极活性材料或第二方面的制备方法制备的正极活性材料。
在任意实施方式中，二次电池是无负极钠二次电池。
在任意实施方式中，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的底涂层，底涂层包括碳纳米管、石墨、石墨烯、银复合碳纳米颗粒、锡复合碳纳米颗粒中的一种或多种。
上述底涂层不仅具有优异的导电性，还有利于金属离子在集流体表面的均匀沉积，提升电池的循环性能和安全性。
在任意实施方式中，底涂层的面密度为5g/m2～50g/m2。
面密度为5g/m2～50g/m2的底涂层有利于成核位点的均匀分布， 促进金属的均匀沉积，同时也不影响电子的传输行为。
在任意实施方式中，底涂层的厚度为2μm～100μm。
控制底涂层的厚度为2μm～100μm，可以提供足够多的成核位点有利于金属离子的均匀沉积，抑制枝晶。
本申请的第四方面提供一种用电装置，包括本申请第三方面的二次电池。
附图说明
图1a为本申请一些实施例与对比例中的正极活性材料前驱体的X射线衍射图谱；
图1b为草酸亚铁的X射线标准衍射图谱；
图2a为本申请实施例和对比例中的正极活性材料的X射线衍射图谱；
图2b为磷酸焦磷酸铁钠的标准X射线衍射图谱；
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。
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盖板。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的正极活性材料及其制备方法、二次电池、电池模块、电池包和电学装置的实施方式。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)。
现有技术中通常采用磷酸焦磷酸铁钠作为钠电池的正极材料，但是现有工艺难以制备具有高结晶度的磷酸焦磷酸铁钠材料，影响其电化学表现。申请人意外地发现，磷酸焦磷酸铁钠难以提高的结晶度是由于机械固相合成工艺中，中间产物(如前驱体)易于包覆在铁源表面，导致铁源无法裸露继续参与反应导致的。
[正极活性材料]
基于此，本申请提出了一种正极活性材料，正极活性材料包括具有式I所示的聚阴离子化合物，正极活性材料的结晶度为0.8～1，
NaxFey1My2(PO4)z(P2O7)k        式I
其中，M包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W和Pb中的至少一种；1≤x≤7，1≤y1+y2≤4，1≤z≤2，1≤k≤4。
在一些实施方式中，M包括Mg。在一些实施方式中，M包括Al。在一些实施方式中，M包括V。在一些实施方式中，M包括Mn。
在一些实施方式中，x可选为1、1.5、2、2.5、3、3.5、4、4.5、5、5.5、6、6.5、7、或由上述任意两点构成的范围中的数值，y1、y2可任选为1、1.5、2、2.5、3、3.5、4、或由上述任意两点构成的范围中的数值，z可选为1、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8、1.9、2、或由上述任意两点构成的范围中的数值，k可选为1、1.5、2、2.5、3、3.5、4、或由上述任意两点构成的范围中的数值。
正极活性材料的结晶度可以通过任意公知手段测得，包括但不限于X射线衍射仪。作为示例，在X射线衍射仪的谱图中，取最强衍射峰与标准物质卡片中该峰的积分所得面积(Ag)进行比较，作为结晶度的衡量参数，结晶度＝As/Ag×100％。对于本申请中提供的磷 酸焦磷酸铁钠，以(222)峰的面积与其标准卡片中的积分面积作为参数，进行结晶度的计算，衍射峰的积分面积可以通过Jade直接求出。
结晶度为0.8～1的正极活性材料，有利于提升电池的首次放电容量，以使电池具有较高的充电能力，改善电池的性能。
在一些实施方式中，正极活性材料的XRD衍射谱中(602)峰强与(022)峰强的比值Id为0.9～1.5。
正极活性材料的XRD衍射谱中(602)峰强与(022)峰强的比值Id可以通过任意公知手段测得，包括但不限于X射线衍射仪。作为示例，采用X射线法测试正极活性材料的XRD图谱，计算(602)峰强与(022)峰强的比值，即Id＝I(602)/I(022)。峰强可以通过Jade直接求出。Na4Fe3(PO4)2(P2O7)4标准卡片中(602)峰强与(022)峰强的比值为1.15。
在一些实施方式中，正极活性材料的XRD衍射谱中(602)峰强与(022)峰强的比值Id可选为0.9、1、1.1、1.2、1.3、1.4或1.5。
申请人意外地发现XRD衍射谱中(602)峰强与(022)峰强的比值Id越高，正极活性材料的电化学表现越优异。
在一些实施方式中，正极活性材料还包括位于聚阴离子化合物一次粒子至少部分表面的碳材料。
碳材料位于一次粒子表面能够显著改善铁基聚阴离子化合物导电性差的问题，大幅度改善正极活性材料的电化学性能。
在一些实施方式中，碳材料以颗粒状分布于聚阴离子化合物的一次粒子之间。
在一些实施方式中，碳材料为无机碳，结晶度高、颗粒度高、导电性强，能够有效改善正极活性材料的导电性能。
在一些实施方式中，碳材料以碳膜的形式包覆于聚阴离子化合物的一次粒子表面上。
在一些实施方式中，碳材料为无定形碳，通过包覆于聚阴离子化合物表面，增大与活性材料的接触面积，提高电子传导性。
正极活性材料中引入碳材料，有利于提升导电性能，优化电池的库伦效率和循环性能。
本申请还提供一种正极活性材料的制备方法，包括以下步骤：
将包含钠源、铁源、及磷源的原料加入溶剂中得到混合浆料，可选地，原料还包括M源；
对混合浆料干燥、煅烧后得到正极活性材料，正极活性材料包括具有式I所示的聚阴离子化合物，正极活性材料的结晶度为0.8～1，
NaxFey1My2(PO4)z(P2O7)k        式I
其中，M包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W和Pb中的至少一种；1≤x≤7，1≤y1+y2≤4，1≤z≤2，1≤k≤4。
在一些实施方式中，M包括Mg。在一些实施方式中，M包括Al。在一些实施方式中，M包括V。在一些实施方式中，M包括Mn。
在一些实施方式中，x可选为1、1.5、2、2.5、3、3.5、4、4.5、5、5.5、6、6.5、7、或由上述任意两点构成的范围中的数值，y1、y2可任选为1、1.5、2、2.5、3、3.5、4、或由上述任意两点构成的范围中的数值，z可选为1、1.1、1.2、1.3、1.4、1.5、1.6、1.7、1.8、1.9、2、或由上述任意两点构成的范围中的数值，k可选为1、1.5、2、2.5、3、3.5、4、或由上述任意两点构成的范围中的数值。
结晶度为0.8～1的正极活性材料，有利于提升电池的首次放电容量，以使电池具有较高的充电能力，改善电池的性能。
在一些实施方式中，将包含钠源、铁源、及磷源的原料加入溶剂中得到混合浆料具体为：
将包含钠源、草酸亚铁、及磷源的原料加入溶剂中搅拌、研磨后得到混合浆料，混合浆料受到的均质剪切速率为300S-1～900S-1。
在一些实施方式中，均质剪切速率可选为300S-1、350S-1、400S-1、450S-1、500S-1、550S-1、600S-1、650S-1、700S-1、750S-1、800S-1、850S-1、900S-1、或由上述任意两点构成的范围中的数值。
均质剪切速率是与搅拌参数、流体粘度、体积综合相关的参数，其可以通过任意公知方法计算而得。控制搅拌的均质剪切速率为300S-1～900S-1，高均质剪切速率有利于避免或减少钠源、磷源与草酸亚铁反应生成的前驱体包裹未反应的草酸亚铁，便于将未反应的草酸亚铁充分暴露出来，以使其充分反应，提高正极活性材料的结晶度。
在一些实施方式中，混合浆料中颗粒的中值粒径Dv50为0.05μm～1.5μm，可选为0.1μm～0.7μm。
在一些实施方式中，混合浆料中颗粒的中值粒径Dv50可选为0.05μm、0.1μm、0.2μm、0.3μm、0.4μm、0.5μm、0.6μm、0.7μm、0.8μm、0.9μm、1μm、1.1μm、1.2μm、1.3μm、1.4μm、1.5μm、或由上述任意两点构成的范围中的数值。
混合浆料中颗粒的中值粒径Dv50可以通过任意公知手段测得，包括但不限于离心沉降法和激光粒度分析仪测试。作为示例，首先将样品离心、沉积、过滤，得到初始混合浆料中的颗粒样品，然后用50mL烧杯称量0.1g～0.13g待测的颗粒样品，加入5g丙酮，放入约2.5mm搅拌子后用保鲜膜密封。样品超声处理5min后转移到磁力搅拌机，500转/分钟搅拌20min以上，每批次产品抽取2个样品测试。采用英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪进行测试。
控制混合浆料中颗粒的中值粒径Dv50在合适的粒径范围，既可避免由于粒径太小导致所需研磨时间较长、以及增加后续浆料物理凝胶的风险，降低了后续加工难度、以及对生产设备的要求；也可减少由于粒径太大导致的正极活性材料结晶度小、杂相较多，从而保证正极活性材料在充放电过程中的动力学性能。
在一些实施方式中，混合浆料的固含量为15％～50％，可选为25％～40％。
在一些实施方式中，混合浆料的固含量可选为15％、20％、25％、30％、35％、40％、45％、50％、或由上述任意两点构成的范围中的数值。
控制混合浆料的固含量在合适的范围内，既可以避免混合浆料的固含量过低导致产能的降低，无法大规模生产，又可以避免混合浆料的固含量过高增加了对设备的损耗、以及对生产设备的要求，能够兼顾生产成本和生产规模，使其适于工业化应用。
在一些实施方式中，混合浆料中包含碳源。
碳源的加入有利于提升正极活性材料的导电性能，提升其电池 的首次放电容量。
在一些实施方式中，混合浆料还包括分散剂，分散剂包括聚乙二醇、聚乙烯醇中的一种或多种。
分散剂有利于碳源在混合浆料中中均与分散，便于后续正极活性材料的制备。
在一些实施方式中，将包含钠源、铁源、及磷源的原料加入溶剂中得到混合浆料具体为：
将包含钠源、草酸亚铁、及磷源的原料加入溶剂中搅拌、研磨至浆料中颗粒的中值粒径Dv50为0.05μm～1.5μm后，与碳源混合得到混合浆料。
控制混合浆料中颗粒的中值粒径Dv50在合适的粒径范围，既可避免由于粒径太小导致所需研磨时间较长、以及增加后续浆料物理凝胶的风险，降低了后续加工难度、以及对生产设备的要求；也可减少由于粒径太大导致的正极活性材料结晶度小、杂相较多，从而保证正极活性材料在充放电过程中的动力学性能。
在一些实施方式中，制备方法包括：
将包含钠源、草酸亚铁、及磷源的原料加入溶剂中搅拌、研磨至浆料中颗粒的中值粒径Dv50为0.1μm～0.7μm后，与碳源混合得到混合浆料。
进一步控制混合浆料中颗粒的中值粒径Dv50为0.1μm～0.7μm后再与碳源混合减少初始研磨难度，碳源的加入会显著提高浆料的粘度，增大研磨功率和研磨时间。
在一些实施方式中，钠源包括碳酸钠、磷酸钠、磷酸二氢钠、磷酸氢二钠、焦磷酸钠、碳酸氢钠、草酸钠、乙酸钠、柠檬酸钠、硝酸钠、氢氧化钠中的一种或多种。
在一些实施方式中，磷源包括磷酸二氢钠、磷酸氢二钠、磷酸钠、磷酸二氢铵、磷酸氢二铵、焦磷酸钠、焦磷酸一氢三钠、焦磷酸二氢二钠、焦磷酸三氢一钠、磷酸、焦磷酸中的一种或多种。
在一些实施方式中，溶剂选自乙醇、水、乙二醇中的一种或多种。
上述溶剂和分散剂均有利于原料的充分溶剂，形成混合均匀的混合浆料，便于混合浆料中颗粒尺寸的控制。
在一些实施方式中，碳源包括无机碳源或有机碳源，无机碳源包括天然石墨、人造石墨、碳黑、纳米碳管、石墨烯中的一种或多种，有机碳源包括蔗糖、葡萄糖、柠檬酸、淀粉、环糊精、沥青中一种或多种。
无机碳源和有机碳源均有利于提升正极活性材料的导电性能。
[正极极片]
正极极片包括正极集流体及形成于正极集流体的至少部分表面上的正极活性材料层，正极活性材料层包括一些实施方式中的正极活性材料。
正极活性材料层还可以包括导电剂，以改善正极的导电性能。导电剂可选为Super P、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯及碳纳米纤维中的一种或几种。
正极活性材料层还可以包括粘结剂，以将正极活性材料和可选的导电剂牢固地粘结在正极集流体上。粘结剂可选为聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯酸(PAA)、聚乙烯醇(PVA)、乙烯-醋酸乙烯酯共聚物(EVA)、丁苯橡胶(SBR)、羧甲基纤维素(CMC)、海藻酸钠(SA)、聚甲基丙烯酸(PMA)及羧甲基壳聚糖(CMCS)中的至少一种。
正极集流体可以采用导电碳片、金属箔材、涂炭金属箔材、多孔金属板或复合集流体。导电碳片的导电碳材质可选为Super P、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯及碳纳米纤维中的一种或几种，金属箔材、涂炭金属箔材和多孔金属板的金属材质各自独立地选自铜、铝、镍及不锈钢中的至少一种，复合集流体可以为金属箔材与高分子基膜复合形成的复合集流体。
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]
负极极片可以仅包括负极集流体，不包含负极活性材料。负极极片也可以在负极集流体上预沉积金属相。
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，可以采用铝箔或铜箔。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的底涂层，底涂层包括碳纳米管、石墨、石墨烯、银复合碳纳米颗粒、锡复合碳纳米颗粒中的一种或多种。
上述底涂层不仅具有优异的导电性，还有利于金属离子在集流体表面的均匀沉积，提升电池的循环性能和安全性。
在一些实施方式中，底涂层的面密度为5g/m2～50g/m2。
在一些实施方式中，底涂层的面密度可选为5g/m2、10g/m2、15g/m2、20g/m2、25g/m2、30g/m2、35g/m2、40g/m2、45g/m2、50g/m2、或由上述任意两点构成的范围中的数值。
面密度为5g/m2～50g/m2的底涂层有利于成核位点的均匀分布，促进金属的均匀沉积，同时也不影响电子的传输行为。
在一些实施方式中，底涂层的厚度为2μm～100μm。
在一些实施方式中，底涂层的厚度可选为2μm、5μm、10μm、15μm、20μm、25μm、30μm、35μm、40μm、45μm、50μm、55μm、60μm、65μm、70μm、75μm、80μm、85μm、90μm、95μm、100μm、或由上述任意两点构成的范围中的数值。
控制底涂层的厚度为2μm～100μm，可以提供足够多的成核位点有利于金属离子的均匀沉积，抑制枝晶。
[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聚乙烯、聚丙烯、聚偏氟乙烯、芳纶、聚对苯二甲酸乙二醇酯、聚四氟乙烯、聚丙烯腈、聚酰亚胺，聚酰胺、聚酯和天然纤维中的至少一种。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。
[二次电池]
二次电池，包括正极极片和负极极片，正极极片包括一些实施方式中的正极活性材料或者一些实施方式中的制备方法制备的正极活性材料。
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，二次电池还包括隔离膜和电解液。
在一些实施方式中，二次电池为无负极钠二次电池。
无负极钠二次电池是指在电池的制造过程中，在负极侧不主动设置负极活性材料层而构成的电池，例如在电池的制造过程中不在负极处通过涂敷或沉积等工序设置钠金属或碳质活性材料层而形成负极活性材料层。首次充电时，钠离子在阳极侧得到电子以金属钠在集流体表面沉积形成钠金属相，放电时，金属钠能够转变为钠离 子回到正极，实现循环充放。相比于其他钠二次电池，无负极钠二次电池由于没有负极活性材料层，可以获得更高的能量密度。
在一些实施方式中，为了改善电池性能，无负极钠二次电池的负极侧可以设置一些常规可作为负极活性材料的物质，如碳质材料、金属氧化物、合金等。虽然这些材料具有一定容量，但是由于这些材料的量较少，其在电池中不是作为主要的负极活性材料使用，因此不被视为形成起到嵌钠作用的负极活性材料层，这样构成的钠二次电池仍然可被视为无负极钠二次电池。
在一些实施方式中，无负极钠二次电池的CB值小于等于0.1。
CB值为二次电池中负极极片的单位面积容量除以正极极片的单位面积容量。由于无负极电池中，不包含或者仅包含少量的负极活性材料，因此负极极片的单位面积容量较小，二次电池的CB值小于等于0.1。
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能够盖设于开口，以封闭容纳腔。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封装于容纳腔内。非牛顿流体电解质组合物浸润于电极组件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。
[电池模块]
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。
[电池包]
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。
[用电装置]
本申请的一个实施方式中，提供一种用电装置，包括任意实施方式的二次电池、任意实施方式的电池模块或任意实施方式的电池包中的至少一种。
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。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。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。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
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。
一、制备方法
实施例1
1)正极活性材料的制备
将焦磷酸钠、草酸亚铁和磷酸二氢铵按照0.998:3:2的摩尔比溶于去离子水中，室温下持续搅拌30min，均质剪切速率为630S-1，球磨至平均粒径为0.2μm后加入碳源混合，得到固含量为35％的混合浆料。将上述混合浆料喷雾干燥，进风温度为220℃，出风温度为109℃，得到粉状正极活性材料前驱体。最后，在N2气氛中，以2℃的升温速率升温至320℃保温4h，继续以2℃的升温速率升温至550℃保温10h。对烧结产物进行破碎，过筛，得到Na3.98Fe3(PO4)2P2O7正极活性材料。
2)正极极片的制备
将2.5wt％聚偏氟乙烯粘结剂充分溶解于N‐甲基吡咯烷酮(NMP)中，再加入2.0wt％Super P、1.0wt％碳纳米管与94.5wt％上述正极活性材料搅拌混合均匀，得到正极浆料。将浆料均匀涂敷在集流体铝箔表面，然后转移到真空干燥箱中完全干燥。将干燥后的极片进行辊压、冲切，得到正极极片。
3)负极极片的制备
将单壁碳纳米管和羧甲基纤维素(CMC)按照1:0.4的质量比加入到去离子水中搅拌成均匀的浆料，使浆料涂覆在负极集流体铜箔表面上，之后转移到真空干燥箱中完全干燥，再进行冲切，得到无负极结构的负极极片。
4)电解液
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将钠盐六氟磷酸钠NaPF6溶解于有机溶剂乙二醇二甲醚(DME)中，搅拌均匀， 得到钠盐浓度1.5mol/L的电解液。
5)隔离膜
以聚丙烯膜作为隔离膜。
6)电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，然后卷绕得到裸电芯，给裸电芯焊接极耳，并将裸电芯装入铝壳中，并在80℃下烘烤除水，随即注入电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得实施例1的无负极钠金属电池产品。
实施例2～11
实施例2～11的电池与实施例1的电池制备方法相似，但是调整了正极活性材料的制备参数，具体参数如表1所示。
对比例1～4
对比例1-4中的电池制备方法与实施例1基本相似，但是均质剪切速率均调整为小于300S-1，具体参数如表1所示。
二、性能测试
1、混合浆料
1)初始混合浆料粒径测试
采用离心沉降法和激光粒度分析仪测试，首先将样品离心、沉积、过滤，得到初始混合浆料中的颗粒样品，然后用50mL烧杯称量0.1g～0.13g待测的颗粒样品，加入5g丙酮，放入约2.5mm搅拌子后用保鲜膜密封。样品超声处理5min后转移到磁力搅拌机，500转/分钟搅拌20min以上，每批次产品抽取2个样品测试。采用英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪进行测试。
2)均质剪切速率测试
使用平均剪切速率衡量流体的均质剪切速率，平均剪切速率为轴向平均剪切速率和径向平均剪切速率之和。
径向平均剪切速率的计算公式为：
式中，为径向平均剪切速率，S-1；K为转子外径与定子外径之比，ω为转子角速度；
轴向平均剪切速率的计算公式为：
式中，为轴向平均剪切速率，S-1；R3为定子外径，单位为m；η为液体粘度，Pa·S；L为长度(料液触及到的轴长)，单位为m；ΔP为进出口压强，与浆料体积流量成正相关，单位为Pa。
2、正极活性材料浆料
1)结晶度测试
X射线衍射法测结晶度-将最强衍射峰(即(222)峰)积分所得的面积(As)与标准物质积分所得面积(Ag)进行比较，当作计算结晶度的指标，结晶度＝As/Ag×100％。标准物质的(222)峰XRD横坐标2θ位置在33.304°。
2)Id值测试--(602)晶面取向生长
采用X射线法测试正极活性材料的XRD图谱，计算(602)峰强与(022)峰强的比值，即Id＝I(602)/I(022)。Na4Fe3(PO4)2(P2O7)4标准卡片中(602)峰强((602)峰XRD横坐标2θ位置在34.304°)与(022)峰强((022)峰XRD横坐标2θ位置在32.218°)的比值为1.15。
3、电池性能测试
1)首次放电容量测试
首次放电容量测试过程如下：在25℃下，将制备的电池以1C的恒定电流充电至3.75V，之后以3.75V恒压充电至电流降到0.05C，再以1C的恒定电流放电至1.5V，得到首圈放电容量(Cd1)。
2)库伦效率测试
库伦效率测试过程如下：在25℃下，将制备的电池以1/5C的恒 定电流充电至3.75V，之后以3.75V恒压充电至电流降到0.05C，得到首次充电容量(Cc1)；再以1/5C的恒定电流放电至1.5V，得到首次放电容量(Cd1)，并按照下式计算电池库伦效率：电池库伦效率＝首次放电容量(Cd1)/首次充电容量(Cc1)。对比例以及其他实施例的测试过程同上。
3)电池循环容量保持率测试
电池容量保持率测试过程如下：在25℃下，将制备的电池，以1C恒流充电至3.75V，再以3.75V恒定电压充电至电流降到0.05C，再以1C的恒定电流放电至1.5V，所得容量记为初始容量(C0)。对上述同一个电池重复以上步骤，并同时记录循环第n次后电池的放电容量(Cn)，则每次循环后电池容量保持率Pn＝Cn/C0×100％，以P1、P2……100这100个点值为纵坐标，以对应的循环次数为横坐标，得到电池容量保持率与循环次数的曲线图。该测试过程中，第一次循环对应n＝1、第二次循环对应n＝2、……第100次循环对应n＝100，表2中实施例或对比例对应的电池容量保持率数据是在上述测试条件下循环100次之后测得的数据，即P100的值。对比例以及其他实施例的测试过程同上。
三、各实施例、对比例测试结果分析
按照上述方法分别制备各实施例和对比例的电池，并测量各项性能参数，结果见下表。
表1
表2
对混合浆料喷雾干燥后得到的前驱体进行XRD表征，结果如图1a所示。与图1b中展示的草酸亚铁的标准卡片对比，可以明显看出对比例1中的前驱体组分中还残留着高结晶度的草酸亚铁，而实施例5中通过提高剪切速率，前驱体中的草酸亚铁结晶度显著减小，而实施例3中剪切速度进一步提高，前驱体呈现完全非晶态，说明原料草酸亚铁全部参与反应中。
对煅烧后得到的正极活性材料进行XRD表征，结果如图2a所示，磷酸焦磷酸铁钠的标准卡片XRD图谱对比于图2b所示。由图2a可见，随着剪切速率的不断增大，正极活性材料XRD衍射谱中(602)峰强与(022)峰强的比值Id不断提高。这是由于前驱体包覆于草酸亚铁限制了(602)晶面的长大，随着原料组分完全进入前驱 体，煅烧后正极活性材料的结晶度显著提高。
实施例1～11中均包括正极活性材料，正极活性材料包括具有式I所示的聚阴离子化合物，正极活性材料的结晶度为0.8～1，
NaxFey1My2(PO4)z(P2O7)k
其中，M包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W和Pb中的至少一种；1≤x≤7，1≤y1+y2≤4，1≤z≤2，1≤k≤4。
从实施例1～11与对比例1～4的对比可见，控制正极活性材料的结晶度为0.8～1，有利于提升其电池的首次放电容量，改善电池的性能。
从实施例1～11与对比例1～4的对比可见，控制均质剪切速率为300S-1～900S-1，有利于提升正极活性材料的结晶度、以及提升其电池的首次放电容量，改善电池的性能。
从实施例1-4的对比可见，磷酸焦磷酸铁钠中存在钠空位或者铁空位的时候有助于进一步提升电池的容量和循环性能。
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 (19)

  1. 一种正极活性材料，其特征在于，所述正极活性材料包括具有式I所示通式的聚阴离子化合物，所述正极活性材料的结晶度为0.8～1，
    NaxFey1My2(PO4)z(P2O7)k   式I
    其中，M包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W和Pb中的至少一种；1≤x≤7，1≤y1+y2≤4，1≤z≤2，1≤k≤4。
  2. 根据权利要求1所述的正极活性材料，其特征在于，所述正极活性材料的XRD衍射谱中(602)峰强与(022)峰强的比值Id为0.9～1.5。
  3. 根据权利要求1或2所述的正极活性材料，其特征在于，所述正极活性材料还包括位于所述聚阴离子化合物一次粒子至少部分表面的碳材料。
  4. 一种正极活性材料的制备方法，其特征在于，包括以下步骤：
    将包含钠源、铁源、及磷源的原料与溶剂混合后得到混合浆料，可选地，所述原料还包括M源；
    对所述混合浆料干燥、煅烧后得到正极活性材料，所述正极活性材料包括具有式I所示通式的聚阴离子化合物，所述正极活性材料的结晶度为0.8～1，
    NaxFey1My2(PO4)z(P2O7)k    式I
    其中，M包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W和Pb中的至少一种；1≤x≤7，1≤y1+y2≤4，1≤z≤2，1≤k≤4。
  5. 根据权利要求4所述的正极活性材料的制备方法，其特征在于，所述将包含钠源、铁源、及磷源的原料与溶剂混合后得到混合浆料具体包括：
    将包含钠源、草酸亚铁、及磷源的原料加入溶剂中搅拌、研磨后得到混合浆料，所述混合浆料受到的均质剪切速率为300S-1～900S-1。
  6. 根据权利要求4或5所述的正极活性材料的制备方法，其特征在于，所述混合浆料中颗粒的中值粒径Dv50为0.05μm～1.5μm，可选为0.1μm～0.7μm。
  7. 根据权利要求4至6中任一项所述的正极活性材料的制备方法，其特征在于，所述混合浆料的固含量为15％～50％，可选为25％～40％。
  8. 根据权利要求4至7中任一项所述的制备方法，其特征在于，所述混合浆料中包含碳源。
  9. 根据权利要求8所述的正极活性材料的制备方法，其特征在于，所述制备方法包括：
    将包含钠源、草酸亚铁、及磷源的原料加入溶剂中搅拌、研磨至浆料中颗粒的中值粒径Dv50为0.1μm～1.3μm，可选为0.1μm～0.7μm后，与碳源混合得到混合浆料。
  10. 根据权利要求4至9中任一项所述的制备方法，其特征在于，所述钠源包括碳酸钠、磷酸钠、磷酸二氢钠、磷酸氢二钠、焦磷酸钠、碳酸氢钠、草酸钠、乙酸钠、柠檬酸钠、硝酸钠、氢氧化钠中的一种或多种。
  11. 根据权利要求4至10中任一项所述的制备方法，其特征在 于，所述磷源包括磷酸二氢钠、磷酸氢二钠、磷酸钠、磷酸二氢铵、磷酸氢二铵、焦磷酸钠、焦磷酸一氢三钠、焦磷酸二氢二钠、焦磷酸三氢一钠、磷酸、焦磷酸中的一种或多种。
  12. 根据权利要求4至11中任一项所述的制备方法，其特征在于，所述溶剂包括乙醇、水、乙二醇中的一种或多种。
  13. 根据权利要求10至12中任一项所述的制备方法，其特征在于，所述碳源包括无机碳源或有机碳源，所述无机碳源包括天然石墨、人造石墨、碳黑、纳米碳管、石墨烯中的一种或多种，所述有机碳源包括蔗糖、葡萄糖、柠檬酸、淀粉、环糊精、沥青中一种或多种。
  14. 一种二次电池，其特征在于，包括正极极片和负极极片，所述正极极片包括权利要求1至3中任一项所述的正极活性材料或权利要求4至13中任一项所述的正极活性材料的制备方法制备的正极活性材料。
  15. 根据权利要求14所述的二次电池，其特征在于，所述二次电池是无负极钠二次电池。
  16. 根据权利要求14或15所述的二次电池，其特征在于，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面的底涂层，所述底涂层包括碳纳米管、石墨、石墨烯、银复合碳纳米颗粒、锡复合碳纳米颗粒中的一种或多种。
  17. 根据权利要求16所述的二次电池，其特征在于，所述底涂层的面密度为5g/m2-50g/m2。
  18. 根据权利要求16或17所述的二次电池，其特征在于，所述 底涂层的厚度为2μm～100μm。
  19. 一种用电装置，其特征在于，包括权利要求14至18中任一项所述的二次电池。
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CN119660724A (zh) * 2025-02-18 2025-03-21 湖南先钠科技有限公司 一种仙人球状钠离子电池正极材料的制备方法

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