WO2024152193A1 - 正极活性材料、其制备方法及包含其的正极极片、二次电池和用电装置 - Google Patents

正极活性材料、其制备方法及包含其的正极极片、二次电池和用电装置 Download PDF

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Publication number
WO2024152193A1
WO2024152193A1 PCT/CN2023/072597 CN2023072597W WO2024152193A1 WO 2024152193 A1 WO2024152193 A1 WO 2024152193A1 CN 2023072597 W CN2023072597 W CN 2023072597W WO 2024152193 A1 WO2024152193 A1 WO 2024152193A1
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Prior art keywords
positive electrode
electrode active
active material
optionally
water content
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PCT/CN2023/072597
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English (en)
French (fr)
Inventor
许跃
杨惠玲
官英杰
秦猛
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 to EP23916683.8A priority Critical patent/EP4597627A4/en
Priority to PCT/CN2023/072597 priority patent/WO2024152193A1/zh
Priority to CN202380043121.1A priority patent/CN119256409B/zh
Publication of WO2024152193A1 publication Critical patent/WO2024152193A1/zh
Priority to US19/192,436 priority patent/US20250256965A1/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
    • 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
    • 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
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • 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
    • 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
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • 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 sodium batteries, and in particular to a positive electrode active material, and a positive electrode sheet, a secondary battery and an electrical device comprising the positive electrode active material.
  • Secondary batteries are one of the ideal choices for energy storage technology. Although lithium-ion secondary batteries have achieved great success in a variety of application fields, due to the relative scarcity and high cost of lithium resources, people have turned their attention to sodium, which has similar performance to lithium but is abundant and easy to obtain. Sodium-ion secondary batteries are also considered to be one of the strong candidates for future energy storage systems. However, the water content in the sodium-ion positive electrode active material in the existing technology is relatively high, which may affect the electrochemical performance, energy density, and safety performance of the electrode and battery.
  • the present application provides a positive electrode active material, and a positive electrode sheet, a secondary battery and an electrical device containing the same.
  • the first aspect of the present application provides a positive electrode active material, which is a composite of NaxRy ( PO4 ) z ( P2O7 ) k and C, wherein 1 ⁇ x ⁇ 7, 1 ⁇ y ⁇ 4, 1 ⁇ z ⁇ 2 , 1 ⁇ k ⁇ 4 , and R 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; wherein the water content of the positive electrode active material is not higher than 1600ppm.
  • the positive electrode active material of the embodiment of the present application has a low water content, which can effectively improve or avoid the instability of the slurry of the positive electrode active material (e.g., condensation). glue) problem, thereby significantly improving its processability and making the positive electrode sheet have a higher charge and discharge specific capacity and a higher first-cycle coulombic efficiency.
  • the water content is not higher than 1400ppm, optionally not higher than 1200ppm, optionally not higher than 1000ppm, optionally not higher than 900ppm, optionally not lower than 50ppm, more optionally not lower than 70ppm, and more optionally 200-800ppm.
  • the positive electrode active material having the above water content range is more cost-effective on the basis of ensuring that the material has the above favorable properties.
  • the chemical composition of the positive electrode active material satisfies at least one of the following conditions:
  • Such positive electrode active materials have a high energy density.
  • a second aspect of the present application provides a method for preparing a positive electrode active material, wherein the positive electrode active material is a composite of NaxRy ( PO4 ) z ( P2O7 ) k and C, wherein 1 ⁇ x ⁇ 7, 1 ⁇ y ⁇ 4, 1 ⁇ z ⁇ 2, 1 ⁇ k ⁇ 4 , and R 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; wherein the water content of the positive electrode active material is not higher than 1600ppm; and the method comprises the following steps:
  • a) preparing a precursor material preparing a mixed slurry including an R source compound, a sodium source compound, a phosphorus source compound and a carbon source compound, and drying the mixed slurry to obtain the precursor material;
  • the precursor material in a sintering atmosphere to obtain the positive electrode active material, wherein the ratio between the ventilation volume of the sintering atmosphere and the weight of the precursor material is 0.85-3.42 m 3 /kg, optionally 1.70-3.42 m 3 /kg, more optionally 2.27-3.42 m 3 /kg.
  • the positive electrode active material prepared by the above method has a low water content, good processability, and gives the positive electrode sheet and battery containing the material a high charge and discharge specific capacity and Higher first-cycle Coulomb efficiency.
  • the heating rate is 0.5-5°C/min, optionally 2-5°C/min. Such a heating rate is helpful to obtain a positive electrode active material with a lower water content.
  • the sintering atmosphere comprises nitrogen and/or argon.
  • the nitrogen flow rate is 2-10 L/min, optionally 5-10 L/min; and/or the sintering time is about 10-30 hours, optionally about 18-23 hours.
  • Adopting the above conditions in step b) can further help the prepared positive electrode active material to have a lower water content.
  • the method of the present application further comprises the following steps:
  • pulverizing the positive electrode active material wherein the pulverizing is performed at an ambient humidity of no more than 10%, optionally at an ambient humidity of 2% to 10%. Controlling the ambient humidity of the material during the pulverizing step is conducive to making the pulverized positive electrode active material have a water content equivalent to or even lower than that of the discharged material.
  • the method of the present application further comprises the following steps:
  • the drying step can further reduce the water content of the material.
  • the third aspect of the present application further provides a positive electrode plate, comprising the positive electrode active material of the first aspect or the positive electrode active material obtained by the method of the second aspect of the present application.
  • the fourth aspect of the present application also provides a secondary battery, comprising the positive electrode plate of the third aspect of the present application.
  • the fifth aspect of the present application further provides an electrical device, comprising the secondary battery of the fourth aspect of the present application.
  • the present application provides a phosphate-based sodium salt positive electrode active material with a low water content, which can effectively improve the processability of the positive electrode active material (for example, slurry gel), thereby enabling the battery positive electrode plate to have a higher charge and discharge specific capacity.
  • the positive electrode active material for example, slurry gel
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.
  • FIG. 6 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 "ab” 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" have been listed in this article, 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 “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • 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).
  • Secondary batteries are one of the ideal choices for energy storage technology. Although lithium-ion secondary batteries have achieved great success in a variety of application fields, due to the relative scarcity and high cost of lithium resources, people have turned their attention to sodium, which has similar performance to lithium but is abundant and easy to obtain. Sodium-ion secondary batteries are also considered to be one of the strong candidates for future energy storage systems.
  • sodium phosphate salts are considered to be the most promising positive electrode active materials for sodium ion secondary batteries because they combine multiple advantages including low cost, environmental friendliness, high theoretical capacity, high average operating voltage and low volume expansion.
  • water content of such materials in the prior art is relatively high. In the preparation of non-aqueous slurries, the water content of the materials is more sensitive. Even a very small amount of water may cause the slurry to coagulate. Glue makes coating difficult, further affecting the electrochemical performance and energy density of the electrode and battery.
  • the increase in water content of the positive electrode active material will make it easier for sodium in the material phase to escape, resulting in residual alkali on the surface of the material, namely sodium bicarbonate, sodium hydroxide, sodium ions, etc., which reduces the kinetic performance of the electrode material during charging and discharging, causing battery bloating during the cycle.
  • the art generally adopts a drying method to reduce the moisture content of the material, the ability of drying to reduce the moisture content is very limited and cannot meet the demand.
  • the present application provides a low-water content sodium phosphate salt positive electrode active material and a method for preparing a low-water content sodium phosphate salt positive electrode active material, which can effectively improve or even avoid the gel problem of the positive electrode active material during the processing, thereby making the battery positive electrode plate have a higher charge and discharge specific capacity.
  • a positive electrode active material which is a complex of NaxRy ( PO4 ) z ( P2O7 ) k and C, wherein 1 ⁇ x ⁇ 7, 1 ⁇ y ⁇ 4, 1 ⁇ z ⁇ 2, 1 ⁇ k ⁇ 4 , and R 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; wherein the water content of the positive electrode active material is not higher than 1600ppm.
  • the positive electrode active material of the embodiments of the present application has a low water content, which can effectively improve or avoid the problem of slurry instability (such as gel) of the positive electrode active material, thereby significantly improving its processability and enabling the positive electrode plate to have a higher charge and discharge specific capacity and a higher first-cycle coulombic efficiency.
  • gel problem refers to the situation where the slurry is jelly-like and has no fluidity, so it cannot be applied normally.
  • the positive electrode active material of the embodiment of the present application can have a lower water content, improve the processability of the slurry, and thus improve the performance of the pole piece and the battery, such as the charge-discharge specific capacity and the first cycle coulomb efficiency.
  • water content means the amount of water contained in a unit mass of the positive electrode active material.
  • the water content is measured according to GB/T11133-2015 (Determination of Water Content in Petroleum Products, Lubricants and Additives - Karl Fischer Coulometric Titration).
  • the positive electrode active material means a material having the above chemical composition, and it can be In different states, including, for example, a discharging state, a crushing state and a drying state.
  • the water content of the positive electrode active material includes the discharging water content, the water content after crushing and the water content after drying.
  • the discharging state is defined as the positive electrode active material after sintering (optionally preliminarily screened), and the water content of the material at this time is the discharging water content.
  • the crushing state is defined as the powder obtained by crushing the material in the above discharging state, and the water content of the material at this time is the water content after crushing.
  • the drying state is defined as the product obtained after drying the above powder, and the water content of the material at this time is the water content after drying.
  • the complex of NaxRy ( PO4 ) z ( P2O7 ) k and C is NaxRy ( PO4 ) z ( P2O7 ) k with carbon coating, wherein x, y, z , k and R are as defined above.
  • the water content of the positive electrode active material is not higher than 1400ppm, optionally not higher than 1200ppm, optionally not higher than 1100ppm, optionally not higher than 1000ppm, optionally not higher than 950ppm, optionally not higher than 900ppm, optionally not higher than 850ppm, optionally not higher than 800ppm, optionally not higher than 750ppm, optionally not higher than 700ppm, optionally not higher than 650ppm.
  • the water content of the positive electrode active material is not less than 50ppm, optionally not less than 70ppm, optionally not less than 200ppm, optionally not less than 300ppm, optionally not less than 350ppm, optionally not less than 400ppm, optionally not less than 450ppm, optionally not less than 500ppm, optionally not less than 550ppm.
  • the water content of the positive electrode active material is 200-800ppm.
  • the chemical composition of the positive electrode active material satisfies at least one of the following conditions:
  • Such positive electrode active materials have a high energy density.
  • Another aspect of the present application provides a method for preparing the positive electrode active material described above.
  • the method comprises the following steps:
  • a) preparing a precursor material preparing a mixed slurry including an R source compound, a sodium source compound, a phosphorus source compound and a carbon source compound, and drying the mixed slurry to obtain the precursor material;
  • the positive electrode active material prepared by the above method has a low water content, good processability, and gives the positive electrode sheet and battery containing the material a higher charge and discharge specific capacity and a higher first-cycle coulomb efficiency.
  • the method of the embodiment of the present application effectively reduces the water content (especially the discharge water content) of the positive electrode active material by controlling the sintering step.
  • Low discharge water content is conducive to maintaining or even further reducing the water content of the positive electrode active material in possible further processing (such as crushing and/or drying).
  • the ratio between the ventilation value of the sintering atmosphere in cubic meters in the sintering step and the weight value of the precursor material in kilograms is controlled within the above range to achieve a low water content of the positive electrode active material.
  • the discharge water content of the positive electrode active material obtained by the above steps is not higher than 1400ppm, optionally not higher than 1200ppm, optionally not higher than 1100ppm, optionally not higher than 1000ppm, optionally not higher than 950ppm, optionally not higher than 900ppm, optionally not higher than 850ppm, optionally not higher than 800ppm, optionally not higher than 750ppm, optionally not higher than 700ppm, optionally not higher than 650ppm.
  • the water content of the positive electrode active material is not less than 50ppm, optionally not less than 70ppm, optionally not less than 200ppm, optionally not less than 300ppm, optionally not less than 350ppm, optionally not less than 400ppm, optionally not less than 450ppm, optionally not less than 500ppm, optionally not less than 550ppm. In some embodiments, the water content of the positive electrode active material is 200-800ppm.
  • the amount of nitrogen is the same, the longer the sintering time, the smaller the corresponding nitrogen flow rate; the shorter the sintering time, the larger the corresponding nitrogen flow rate.
  • sintering time means the sum of the heating time, the holding time and the cooling time in the sintering step.
  • the mixed slurry in step a), can be prepared, for example, by adding an R source compound, a sodium source compound, and a phosphorus source compound to a solvent to prepare a slurry; and then adding a carbon source compound to the slurry to obtain the mixed slurry.
  • the solvent in step a), may be, for example, water (optionally, deionized water) or ethanol.
  • the slurry and the mixed slurry can be prepared by one or more methods such as grinding and solvent dispersion.
  • the grinding in step a), can be performed in a conventional manner in the art, for example, the grinding can be ball milling, sand milling, vibration milling or tumbling milling.
  • the grinding can be performed by conventional equipment in the art (e.g., ball mill, sand mill, vibration mill or tumbling mill).
  • the R source compound may be any compound in the art that can provide the R element.
  • the R source compound may be, for example, at least one of ferrous oxalate, ferric nitrate, ferric citrate, and ammonium ferric citrate.
  • the sodium source compound can be any compound in the art that can provide sodium element.
  • a compound can be, for example, at least one of sodium pyrophosphate, sodium acetate, sodium nitrate, sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate and disodium hydrogen phosphate.
  • the phosphorus source compound can be any compound in the art that can provide phosphorus element.
  • a compound can be, for example, at least one of ammonium dihydrogen phosphate, phosphoric acid, diammonium hydrogen phosphate, ammonium phosphate, disodium hydrogen phosphate, sodium pyrophosphate and sodium dihydrogen phosphate.
  • the carbon source compound is any compound in the art that can provide carbon.
  • a compound can be, for example, at least one of oxalic acid, ascorbic acid, formaldehyde, acetaldehyde, n-butyraldehyde, lactic acid, citric acid, malic acid, oxalic acid, adipic acid, citric acid, soluble starch, ascorbic acid, sucrose and glucose. To improve the conductivity of the material.
  • the average particle size D v 50 of the solid material contained in the mixed slurry obtained after grinding may be 0.1-0.8 ⁇ m. Such a particle size range is conducive to further reaction of the material during the sintering process.
  • average particle size D v 50 means the particle size corresponding to 50% of the particles in the volume distribution.
  • the average particle size can be measured by conventional methods in the art, for example, by using a laser particle size analyzer.
  • step a) the drying is performed by at least one of the following methods: forced air drying, vacuum drying, freeze drying and spray drying.
  • the sintering atmosphere in the step b), includes nitrogen and/or argon; optionally, the sintering atmosphere also includes hydrogen. In some embodiments, the sintering atmosphere is nitrogen. Generally, sintering atmospheres are divided into inert atmospheres or reducing atmospheres. Herein, if the sintering atmosphere is nitrogen and/or argon, it is an inert sintering atmosphere; and if the sintering atmosphere is a nitrogen-hydrogen mixed gas or an argon-hydrogen mixed gas, it is a reducing atmosphere. In some embodiments, in the step b), the sintering atmosphere is nitrogen.
  • the sintering atmosphere in step b), has an oxygen content of less than 100 ppm, optionally 30-50 ppm. Controlling the oxygen content within the above range is beneficial to reducing side reactions and improving the conductivity of the material.
  • the sintering atmosphere is introduced after the system (e.g., in the sintering furnace) is evacuated; the oxygen content is the amount of oxygen remaining in the system after evacuation.
  • the nitrogen flow rate is 2-10 L/min, optionally 5-10 L/min.
  • the sintering time is about 10-30 hours, optionally about 18-23 hours.
  • using the sintering time and/or nitrogen flow rate within the above respective ranges can further facilitate the prepared positive electrode active material to have a lower water content (especially the water content of the discharge material).
  • the heating rate is 0.5-5°C/min. In some embodiments, optionally, the heating rate is 2-5°C/min. Without wishing to be bound by any theory, such a heating rate is advantageous for ensuring sufficient reaction and at the same time ensuring sufficient reaction.
  • the water that should be produced can be discharged in time, which helps to obtain positive electrode active materials with lower water content (especially water content of the output material).
  • the sintering is performed by at least one selected from the following equipment: a tube furnace, a vacuum box furnace, an explosion-proof box furnace, a push plate kiln, a roller kiln, a bell kiln and a rotary kiln.
  • the sintering of step b) includes a low-temperature sintering stage and a high-temperature sintering stage.
  • the low-temperature sintering can be kept at a temperature of 300-350°C for 3-5 hours.
  • the high-temperature sintering can be kept at a temperature of 500-550°C for 7-11 hours, optionally for about 10 hours.
  • the holding time as described above means the sum of the low-temperature sintering holding time and the high-temperature sintering holding time.
  • the heating time as described above means the sum of the time required for the temperature to rise from the initial temperature (e.g., ambient temperature or room temperature (25°C)) to the low-temperature sintering temperature and from the low-temperature sintering temperature to the high-temperature sintering temperature.
  • the initial temperature e.g., ambient temperature or room temperature (25°C)
  • the method further comprises the following steps:
  • pulverizing the positive electrode active material wherein the pulverizing is performed at an ambient humidity of no more than 10%, optionally at an ambient humidity of 2% to 10%.
  • controlling the ambient humidity of the material during the pulverizing step is beneficial for the pulverized positive electrode active material to have a water content equivalent to or even lower than that of the discharged material.
  • the water content of the positive electrode active material after crushing is not higher than 1500ppm, optionally not higher than 1200ppm, optionally not higher than 1100ppm, optionally not higher than 1000ppm, optionally not higher than 950ppm, optionally not higher than 900ppm, optionally not higher than 850ppm, optionally not higher than 800ppm, optionally not higher than 750ppm, optionally not higher than 700ppm, optionally not higher than 650ppm.
  • the water content of the positive electrode active material after crushing is not less than 50ppm, optionally not less than 70ppm, optionally not less than 200ppm, optionally not less than 300ppm, optionally not less than 350ppm, optionally not less than 400ppm, optionally not less than 450ppm. In some embodiments, the water content of the positive electrode material after crushing is 200-800ppm.
  • the method further comprises the following steps:
  • the drying step in the present application can be carried out by conventional drying methods in the art, for example, vacuum drying.
  • the drying temperature is 100°C-200°C, optionally 110°C-150°C.
  • the drying time is 12h-36h.
  • the water content of the positive electrode active material after drying is not higher than 1200ppm, optionally not higher than 1150ppm, optionally not higher than 1000ppm, optionally not higher than 900ppm, optionally not higher than 850ppm, optionally not higher than 800ppm, optionally not higher than 750ppm, optionally not higher than 700ppm. In some embodiments, the water content of the positive electrode active material after drying is not less than 50ppm, optionally not less than 70ppm, optionally not less than 200ppm, optionally not less than 250ppm. In some embodiments, the water content of the positive electrode active material after drying is 200-800ppm.
  • One aspect of the present application also provides a positive electrode active material prepared by the method described above.
  • Another aspect of the present application provides a positive electrode plate, which includes the positive electrode active material of the present application or the positive electrode active material obtained by the method of the present application.
  • the positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode active material of the embodiment of the present application.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil may be used.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a conductive agent which may include, for example, 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 in the following manner: 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 collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • Yet another aspect of the present application provides a secondary battery.
  • the secondary battery includes a battery cell form, a battery module form, and a battery pack form.
  • Another aspect of the present application provides an electrical device, comprising the secondary battery of the embodiment of the present application.
  • a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • a metal foil a copper foil may be used.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material base (such as polypropylene (PP), poly(terephthalate)). It is formed on a substrate such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may adopt the negative electrode active material for the battery known in the art.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon 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 negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • a conductive agent which 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 may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from sodium hexafluorophosphate (NaPF 6 ), One or more of sodium borate (NaBF4), NaN(SO2F)2 (abbreviated as NaFSI), NaClO4, NaAsF6, NaB(C2O4)2 (abbreviated as NaBOB), NaBF2(C2O4 ) ( abbreviated as NaDFOB), NaN(SO2RF)2 and NaN(SO2F)(SO2RF ) ; wherein RF represents CbF2b + 1 , b is an integer in the range of 1-10, and can be optionally an integer in the range of 1-3 , and more optionally, RF is -CF3 , -C2F5 or -CF2CF2CF3 .
  • the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the 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 battery cell may include an outer package for packaging the positive electrode sheet, the negative electrode sheet and the electrolyte.
  • the positive electrode sheet, the negative electrode sheet and the separator may be stacked or wound to form a stacked structure battery cell or a wound structure battery cell, and the battery cell is packaged in the outer package; the electrolyte is impregnated in the battery cell.
  • the number of battery cells in the battery cell may be one or more, which can be adjusted according to demand.
  • the present application provides an electrode assembly.
  • the positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly by a winding process or a lamination process.
  • the outer packaging can be used to encapsulate the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the battery cell may be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.
  • the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the present application has no particular restrictions on the shape of the battery cell, which may be cylindrical, square, or any other shape.
  • FIG. 1 is a battery cell 5 of a square structure as an example.
  • 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 film 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 electrolyte is infiltrated in the electrode assembly 52.
  • the number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the battery cells may be assembled into a battery module or a battery pack.
  • the number of battery cells contained in the battery module or the battery pack 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 or the battery pack.
  • FIG3 is a battery module 4 as an example.
  • a plurality of battery cells 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 battery cells 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.
  • the battery cells or the battery modules described above may be assembled into a battery pack.
  • the battery pack may contain one or more battery cells or battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the 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 cover the lower box body 3 and 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 embodiment of the present application further provides an electric device, which includes at least one of the battery cells, battery modules or battery packs provided in the present application.
  • the battery cells, battery modules or battery packs can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric 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, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • a battery cell, a battery module or a battery pack may be selected according to its usage requirements.
  • Fig. 6 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.
  • the precursor material was first heated from room temperature (25°C) to 300°C at a heating rate of 2°C/min, and calcined at 300°C for 4 hours, then heated to 550°C at a heating rate of 2°C/min, and calcined at 550°C for 10 hours, and then cooled to 100°C at a cooling rate of 2°C/min to obtain a product.
  • the product was confirmed to be the desired positive electrode active material Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 and C complex (carbon-coated Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 ) by X-ray diffraction (XRD) analysis and infrared carbon-sulfur analyzer.
  • the amount of nitrogen introduced during the sintering time is 6.825 m 3 , and its ratio to the weight of the precursor (in kg) is 1.70625.
  • the material is transferred to the drying room for preliminary crushing and screening. At this time, the positive electrode active material is in the discharge state. The water content of the discharge is measured and recorded in Table 1.
  • the positive electrode active material obtained by sintering ie, the positive electrode active material in the discharged state
  • the water content after pulverization was measured and recorded in Table 1.
  • the positive electrode active material powder was placed in a drying oven at 120° C. and dried for 24 h to obtain the dried positive electrode active material powder (dried state).
  • the water content of the positive electrode active material ie, the water content after drying was measured and recorded in Table 1.
  • the polyvinylidene fluoride binder was fully dissolved in N-methylpyrrolidone, and then the carbon black conductive agent and the dried positive electrode active material powder were added to make the weight ratio of the positive electrode active material powder, the carbon black conductive agent and the binder 7:2:1 to prepare a uniformly dispersed positive electrode slurry.
  • the positive electrode slurry was evenly coated on the surface of the aluminum foil (the thickness of the aluminum foil was 13 ⁇ m, and the loading was 43.42mg/ 1540.25mm2 ), and then transferred to a vacuum drying oven for complete drying. The electrode sheet is rolled and then punched to obtain the positive electrode sheet.
  • the carbon nanotube material, the binder sodium carboxymethyl cellulose and deionized water were stirred into a uniform slurry at a weight ratio of 4:1.6:94.4, and the slurry was coated on the surface of the copper foil (the copper foil thickness was 8 ⁇ m, and the loading amount was 2 mg/1540.25 mm 2 ), and then transferred to a vacuum drying oven for complete drying, and then punched to obtain a negative electrode sheet.
  • sodium hexafluorophosphate NaPF 6 was dissolved in an organic solvent, ethylene glycol dimethyl ether DME, and stirred evenly to obtain an electrolyte with a sodium salt concentration of 0.5 mol/L.
  • Polypropylene film is used as the isolation film.
  • the positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to play an isolating role.
  • 0.5 g of the above electrolyte is added to assemble a laminated battery.
  • the test is carried out according to GB/T11133-2015 (Determination of water content in petroleum products, lubricants and additives - Karl Fischer coulometric titration).
  • the secondary battery prepared above was charged to 3.75V at 25°C with a constant current of 1/3C, then charged at a constant voltage of 3.75V until the current dropped to 0.05C, and the first cycle charge capacity (C c1 ) was measured; then discharged to 1.5V with a constant current of 1/3C, and the first cycle discharge capacity (C d1 ) was measured.
  • the first cycle coulomb efficiency of the secondary battery was calculated according to the following formula:
  • Example 2-18 Except for the amount of nitrogen introduced (keeping the sintering time unchanged, changing the nitrogen amount by changing the nitrogen flow rate) and the sintering weight ratio or heating rate with the precursor (see Table 1 below for details), the other steps of Examples 2-18 are the same as those of Example 1.
  • Comparative Example 1 is substantially the same as Example 1, except that the ratio of the amount of nitrogen to the weight of the precursor is changed.
  • the examples of the present application (the ratio between the ventilation volume value of the sintering atmosphere and the weight value of the precursor material is in the range of 0.85-3.42 m 3 /kg) obtain positive electrode active materials with lower water content, and the water content of the positive electrode active materials in the examples of the present application is lower than 1600ppm.

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Abstract

本申请提供了一种正极活性材料，所述正极活性材料为NaxRy(PO4)Z(P2O7)k与C的复合物，其中1≤x≤7，1≤y≤4，1≤z≤2，1≤k≤4，且R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；其中所述正极活性材料的含水量不高于1600ppm。本申请还提供了包含该正极活性材料的制备方法，以及包含该材料的正极极片、二次电池及用电装置。本申请的正极活性材料具有较低的含水量，可有效改善或避免正极活性材料的可加工性，并使包含该材料的正极极片和二次电池具有较高充放电比容量和较高的首圈库伦效率。

Description

正极活性材料、其制备方法及包含其的正极极片、二次电池和用电装置 技术领域
本申请涉及钠电池技术领域，尤其涉及一种正极活性材料，以及包含该正极活性材料的正极极片、二次电池和用电装置。
背景技术
二次电池是储能技术的理想选择之一。虽然锂离子二次电池在多种应用领域取得了巨大的成功，然而由于锂资源相对稀缺，成本高昂，使人们将目光投向与锂性能相似但丰富易得的钠，而钠离子二次电池也被认为是未来储能系统的有力候选者之一。但是，现有技术中钠离子正极活性材料中含水量偏高，可能会影响极片和电池的电化学性能、能量密度以及安全性能等等。
鉴于上述问题，需要提供一种低水含量的磷酸基钠盐正极活性材料，可有效改善甚至避免正极活性材料在浆料加工过程中与含水量向关联的问题，从而使电池正极极片和二次电池具有较高的充、放电比容量和首圈库伦效率。
发明内容
为了达到上述目的，本申请提供了一种正极活性材料，以及包含其的正极极片、二次电池和用电装置。
本申请的第一方面提供了一种正极活性材料，所述正极活性材料为NaxRy(PO4)z(P2O7)k与C的复合物，其中1≤x≤7，1≤y≤4，1≤z≤2，1≤k≤4，且R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；其中所述正极活性材料的含水量不高于1600ppm。本申请实施例的正极活性材料含水量较低，可有效改善或避免正极活性材料的浆料不稳定(如，凝 胶)问题，从而显著改善其可加工性，并使正极极片具有较高充放电比容量和较高的首圈库伦效率。
在任意实施方式中，所述含水量不高于1400ppm，可选地不高于1200ppm，可选地不高于1000ppm，可选地不高于900ppm，可选地不低于50ppm，更可选地不低于70ppm，再更可选地为200-800ppm。具有上述含水量范围的正极活性材料在确保了材料具备上述有利性能的基础上，更具成本有效性。
在任意实施方式中，所述正极活性材料的化学组成满足以下条件中的至少一项：
(1)3≤x≤5；
(2)2≤y≤4；
(3)1.5≤z≤2；
(4)1≤k≤1.5；
(5)R为Fe。
这样的正极活性材料具有较高的能量密度。
本申请的第二方面提供了一种制备正极活性材料的方法，所述正极活性材料为NaxRy(PO4)z(P2O7)k与C的复合物，其中1≤x≤7，1≤y≤4，1≤z≤2，1≤k≤4，且R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；其中所述正极活性材料的含水量不高于1600ppm；所述方法包括以下步骤：
a)制备前驱体材料：制备包括R源化合物、钠源化合物、磷源化合物和碳源化合物的混合浆料，并将所述混合浆料干燥，得到所述前驱体材料；
b)在烧结气氛中烧结所述前驱体材料得到所述正极活性材料，其中所述烧结气氛的通气量体积值和前驱体材料重量值之间的比值为0.85-3.42m3/kg，可选地为1.70-3.42m3/kg，更可选地为2.27-3.42m3/kg。
由上述方法制备得到的正极活性材料的含水量较低，具有良好的可加工性，并赋予包含该材料的正极极片和电池较高充放电比容量和 较高的首圈库伦效率。
在任意实施方式中，在所述步骤b)中，升温速率为0.5-5℃/min，可选地为2-5℃/min。采用这样的升温速率，有助于得到含水量较低的正极活性材料。
在任意实施方式中，在所述步骤b)中，所述烧结气氛包括氮气和/或氩气。
在任意实施方式中，在所述步骤b)中，氮气流量为2-10L/min可选地为5-10L/min；和/或烧结时间为约10-30小时，可选地为约18-23小时。
步骤b)中采用上述条件，能够进一步有利于所制得的正极活性材料具有较低的含水量。
在任意实施方式中，本申请的方法还包括以下步骤：
c)粉碎所述正极活性材料，其中所述粉碎在不大于10％的环境湿度下，可选地在2％～10％的环境湿度下进行。控制粉碎步骤中材料所处的环境湿度，有利于使粉碎后的正极活性材料具有与出料时相当，甚至更低的水含量。
在任意实施方式中，本申请的方法还包括以下步骤：
d)烘干所述正极活性材料。通过烘干步骤可进一步降低材料的含水量。
本申请的第三方面还提供了一种正极极片，包括第一方面的正极活性材料或通过本申请第二方面的方法得到的正极活性材料。
本申请的第四方面还提供了一种二次电池，包括本申请第三方面的正极极片。
本申请的第五方面还提供了一种用电装置，包括本申请第四方面的二次电池。
本申请提供一种低水含量的磷酸基钠盐正极活性材料，可有效改善正极活性材料的可加工性(例如，浆料凝胶)，从而使电池正极极片具有较高充、放电比容量。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6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电池单体；51壳体；52电极组件；53顶盖组件
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实施例的正极活性材料及其制备方法、正极极片、二次电池和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。 另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
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)。
二次电池是储能技术的理想选择之一。虽然锂离子二次电池在多种应用领域取得了巨大的成功，然而由于锂资源相对稀缺，成本高昂，使人们将目光投向与锂性能相似但丰富易得的钠，而钠离子二次电池也被认为是未来储能系统的有力候选者之一。
目前已报道多种钠离子电池用正极活性材料，其中磷酸基钠盐因其综合了多种优点包括低成本、环境友好、高理论容量、高平均工作电压和低体积膨胀，而被认为最具潜力的钠离子二次电池正极活性材料。然而，现有技术中此类材料中含水量偏高。在非水浆料制备中，对于材料的含水量更为敏感，即使极少量的水也可能造成浆料产生凝 胶，造成涂布困难，进一步影响极片和电池的电化学性能和能量密度。另外，正极活性材料的水含量的增加会导致材料体相中钠比较容易脱出，导致材料表面残余碱即碳酸氢钠、氢氧化钠、钠离子等，降低电极材料在充放电过程中的动力学性能，造成循环过程中电池胀气。
尽管为了改善上述问题，本领域一般会采用烘干方法来降低材料的含水量，但烘干降低水含量的能力十分有限，并不能满足需求。
鉴于上述问题，本申请提供一种低水含量的磷酸基钠盐正极活性材料以及制备低水含量的磷酸基钠盐正极活性材料的方法，可有效改善甚至避免正极活性材料在加工过程中的凝胶问题，从而使电池正极极片具有较高充、放电比容量。
正极活性材料及其制备方法
本申请的一方面是一种正极活性材料，所述正极活性材料为NaxRy(PO4)z(P2O7)k与C的复合物，其中1≤x≤7，1≤y≤4，1≤z≤2，1≤k≤4，且R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；其中所述正极活性材料的含水量不高于1600ppm。
不希望囿于任何理论，本申请实施例的正极活性材料含水量较低，可有效改善或避免正极活性材料的浆料不稳定(如，凝胶)问题，从而显著改善其可加工性，并使正极极片具有较高充放电比容量和较高的首圈库伦效率。
本文中，“凝胶问题”是指浆料呈果冻状，不具备流动性，因而无法正常涂布的情况。
尽管浆料制备之前，对正极活性材料进行烘干可在一定程度上降低其含水量，但仍不能满足本领域内对于材料低含水量的要求。然而，本申请实施例正极活性材料能够具有更低含水量，改善浆料的可加工性，从而改善极片和电池的性能，如充放电比容量和首圈库伦效率等。
本文中，“含水量”意为单位质量的正极活性材料所含水分的量。含水量根据GB/T11133-2015(《石油产品、润滑油和添加剂中水含量的测定卡尔费休库伦滴定法》)测得。
本文中，正极活性材料意为具有上述化学组成的材料，并且其可 处于不同状态，包括例如出料状态、粉碎状态和烘干状态。相应地，正极活性材料的含水量包括出料含水量、粉碎后含水量和烘干后含水量。出料状态定义为经烧结(任选地初步过筛)后的正极活性材料，此时材料的含水量为出料含水量。粉碎状态定义为将上述出料状态的材料进行粉碎后得到的粉料，此时材料的含水量为粉碎后含水量。烘干状态定义为将上述粉料烘干后得到的产品，此时材料的含水量为烘干后含水量。
在一些实施方式中，所述NaxRy(PO4)z(P2O7)k与C的复合物是具有碳包覆的NaxRy(PO4)z(P2O7)k，其中x、y、z、k和R如上文定义。
在一些实施方式中，所述正极活性材料的含水量不高于1400ppm，可选地不高于1200ppm，可选地不高于1100ppm，可选地不高于1000ppm，可选地不高于950ppm，可选地不高于900ppm，可选地不高于850ppm，可选地不高于800ppm，可选地不高于750ppm，可选地不高于700ppm，可选地不高于650ppm。在一些实施方式中，可选地，所述正极活性材料的含水量不低于50ppm，可选地不低于70ppm，可选地不低于200ppm，可选地不低于300ppm，可选地不低于350ppm，可选地不低于400ppm，可选地不低于450ppm，可选地不低于500ppm，可选地不低于550ppm。在一些实施方式中，所述正极活性材料的含水量为200-800ppm。尽管正极活性材料具有更低含水量是符合期望的，但是上述含水量范围的正极活性材料在确保了材料具备有利性能的基础上，更具成本有效性。
在一些实施方式中，所述正极活性材料的化学组成满足以下条件中的至少一项：
(1)3≤x≤5，可选地为4；
(2)2≤y≤4，可选地为3；
(3)1.5≤z≤2，可选地为2；
(4)1≤k≤1.5，可选地为1；
(5)R为Fe。
这样的正极活性材料具有较高的能量密度。
本申请的另一方面提供一种制备上文所述的正极活性材料的方 法，所述方法包括以下步骤：
a)制备前驱体材料：制备包括R源化合物、钠源化合物、磷源化合物和碳源化合物的混合浆料，并将所述混合浆料干燥，得到所述前驱体材料；
b)烧结：在烧结气氛中烧结所述前驱体材料得到所述正极活性材料，其中所述烧结气氛的通气量值和前驱体材料重量值之间的比值为0.85-3.42m3/kg，可选地为1.70-3.42m3/kg，更可选地为2.27-3.42m3/kg。
由上述方法制备得到的正极活性材料的含水量较低，具有良好的可加工性，并赋予包含该材料的正极极片和电池较高充放电比容量和较高的首圈库伦效率。不希望囿于任何理论，本申请实施例的方法通过控制烧结步骤，有效降低了正极活性材料的含水量(特别是出料含水量)。低出料含水量，有利于正极活性材料在可能的进一步处理(诸如粉碎和/或烘干等)保持甚至进一步降低含水量。特别地，将烧结步骤中以立方米为单位的所述烧结气氛的通气量值和以千克为单位的前驱体材料重量值之间的比值控制在上述范围内，实现了正极活性材料的低含水量。
通过上述步骤获得的所述正极活性材料的出料含水量不高于1400ppm，可选地不高于1200ppm，可选地不高于1100ppm，可选地不高于1000ppm，可选地不高于950ppm，可选地不高于900ppm，可选地不高于850ppm，可选地不高于800ppm，可选地不高于750ppm，可选地不高于700ppm，可选地不高于650ppm。在一些实施方式中，可选地，所述正极活性材料的含水量不低于50ppm，可选地不低于70ppm，可选地不低于200ppm，可选地不低于300ppm，可选地不低于350ppm，可选地不低于400ppm，可选地不低于450ppm，可选地不低于500ppm，可选地不低于550ppm。在一些实施方式中，所述正极活性材料的含水量为200-800ppm。
本文中，“通气量”意为烧结时间内通入烧结设备中烧结气氛气体的总体积；也即，通气量(单位m3)＝烧结气氛气体的流量*烧结时间。例如，当烧结气氛为氮气时，氮气量(单位m3)＝氮气流量(单 位L/min)*烧结时间(单位h)*0.06。在氮气量相等的情况下，烧结时间越长，对应的氮气流量越小；烧结时间越短，对应的氮气流量越大。
本文中，“烧结时间”意指烧结步骤中升温时间、保温时间和降温时间之和。
在一些实施方式中，在步骤a)中，所述混合浆料可以例如通过以下方式制备：将R源化合物、钠源化合物、磷源化合物加入溶剂中，然后制成浆料；再向所述浆料中加入碳源化合物，得到所述混合浆料。
在一些实施方式中，所述步骤a)中，溶剂可为，例如，水(可选地，去离子水)或者乙醇。
在一些实施方式中，所述步骤a)中，所述浆料和所述混合浆料可采用研磨、溶剂分散等方式中的一种或多种来制备。
在一些实施方式中，所述步骤a)中，所述研磨可以用本领域常规的方式进行，例如，所述研磨可以是球磨、砂磨、振磨或滚磨。所述研磨可通过本领域常规的设备(例如球磨机、砂磨机、振磨机或滚磨机)进行。
在一些实施方式中，R源化合物可以是本领域中能够提供R元素的任意化合物。当R元素为Fe时，R源化合物可以是，例如，草酸亚铁、硝酸铁、柠檬酸铁和柠檬酸铁铵中的至少一种。
在一些实施方式中，钠源化合物可以是本领域中能够提供钠元素的任意化合物。这样的化合物可以是，例如，焦磷酸钠、醋酸钠、硝酸钠、碳酸钠、碳酸氢钠、磷酸二氢钠和磷酸氢二钠中的至少一种。
在一些实施方式中，磷源化合物可以是本领域中能够提供磷元素的任意化合物。这样的化合物可以是，例如，磷酸二氢铵、磷酸、磷酸氢二铵、磷酸铵、磷酸氢二钠、焦磷酸钠和磷酸二氢钠中的至少一种。
在一些实施方式中，碳源化合物是本领域中能够提供碳元素的任意化合物。这样的化合物可以是，例如，草酸、抗坏血酸、甲醛、乙醛、正丁醛、乳酸、柠檬酸、苹果酸、乙二酸、己二酸、柠檬酸、可溶性淀粉、抗坏血酸、蔗糖和葡萄糖中的至少一种。碳源化合物有助 于提高材料的导电性。
在一些实施方式中，所述步骤a)中，研磨后得到的所述混合浆料中所含的固体物质的平均粒径Dv50可以为0.1-0.8微米。这样的粒径范围有利于材料在烧结过程中更进一步反应充分。
本文中，“平均粒径Dv50”意为体积分布中50％的颗粒所对应的粒度。平均粒径可采用本领域常规方式检测，例如，采用激光粒度仪测试。
在一些实施方式中，所述步骤a)中，所述干燥通过以下方法中的至少一种进行：鼓风干燥、真空干燥、冷冻干燥和喷雾干燥。
在一些实施方式中，所述步骤b)中，所述烧结气氛包括氮气和/或氩气；可选地，所述烧结气氛还包括氢气。在一些实施方式中，烧结气氛为氮气。一般地，烧结气氛分为惰性气氛或还原气氛。本文中，烧结气氛为氮气和/或氩气，则为惰性烧结气氛；而烧结气氛为氮氢混合气体或氩氢混合气体，则为还原气氛。在一些实施方式中，所述步骤b)中，所述烧结气氛为氮气。
在一些实施方式中，在所述步骤b)中，所述烧结气氛具有小于100ppm，可选地在30-50ppm的氧含量。将氧含量控制在上述范围内，有利于减少副反应和提高材料导电性。烧结气氛是在体系(例如，烧结炉具内)抽真空后通入的；所述氧含量是抽真空后，体系中剩余的氧气的量。
在一些实施方式中，在所述步骤b)中，氮气流量为2-10L/min，可选地为5-10L/min。。
在一些实施方式中，在所述步骤b)中，烧结时间为约10-30小时，可选地约18-23小时。
不希望囿于任何理论，采用在上述各自范围内的烧结时间和/或氮气流量，能够进一步有利于所制得的正极活性材料具有较低的含水量(特别是出料含水量)。
在一些实施方式中，在所述步骤b)中，升温速率为0.5-5℃/min。在一些实施方式中，可选地，升温速率为2-5℃/min。不希望囿于任何理论，采用这样的升温速率，在确保反应充分的同时，有利于使反 应产生的水能够及时排出，有助于得到含水量(特别是出料含水量)较低的正极活性材料。
在一些实施方式中，所述步骤b)中，所述烧结通过选自以下设备中的至少一种进行：管式炉、真空箱式炉、防爆箱式炉、推板窑、辊道窑、钟罩窑和回转窑。
在一些实施方式中，所述步骤b)的烧结包括低温烧结阶段和高温烧结阶段。所述低温烧结可以在300-350℃的温度下保温3-5小时。所述高温烧结可以在500-550℃的温度下保温7-11小时，可选地约10小时。此时，如上文所述的保温时间意为低温烧结保温时间和高温烧结保温时间之和。如上文所述的升温时间意为温度从初始温度(例如，环境温度或室温(25℃))升高至低温烧结温度和从低温烧结温度升高至高温烧结温度所需的时间之和。
在一些实施方式中，所述方法还包括以下步骤：
c)粉碎所述正极活性材料，其中所述粉碎在在不大于10％的环境湿度下，可选地在2％～10％的环境湿度下进行。不希望囿于任何理论，控制粉碎步骤中材料所处的环境湿度，有利于使粉碎后的正极活性材料具有与出料时相当，甚至更低的水含量。
经粉碎后的正极活性材料的含水量不高于1500ppm，可选地不高于1200ppm，可选地不高于1100ppm，可选地不高于1000ppm，可选地不高于950ppm，可选地不高于900ppm，可选地不高于850ppm，可选地不高于800ppm，可选地不高于750ppm，可选地不高于700ppm，可选地不高于650ppm。在一些实施方式中，经粉碎后的正极活性材料的含水量不低于50ppm，可选地不低于70ppm，可选地不低于200ppm，可选地不低于300ppm，可选地不低于350ppm，可选地不低于400ppm，可选地不低于450ppm。在一些实施方式中，经粉碎后的正极材料的含水量为200-800ppm。
在一些实施方式中，所述方法还包括以下步骤：
d)烘干所述正极活性材料。
本申请中的烘干步骤可以本领域常规的烘干方法进行，例如，真空烘干。烘干温度为100℃-200℃，可选地为110℃-150℃。烘干时间 为12h-36h。
经烘干后的正极活性材料的含水量不高于1200ppm，可选地不高于1150ppm，可选地不高于1000ppm，可选地不高于900ppm，可选地不高于850ppm，可选地不高于800ppm，可选地不高于750ppm，可选地不高于700ppm。在一些实施方式中，经烘干后的正极活性材料的含水量不低于50ppm，可选地不低于70ppm，可选地不低于200ppm，可选地不低于250ppm。在一些实施方式中，经烘干后的正极活性材料的含水量为200-800ppm。
本申请的一个方面还提供了一种如上文所述的方法制备的正极活性材料。
正极极片、二次电池和用电装置
本申请的再一方面提供了一种正极极片，其包括本申请的正极活性材料或由本申请的方法得到的正极活性材料。
正极极片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实施例的正极活性材料。
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，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。
本申请的又一方面提供一种二次电池。
本文中，二次电池包括电池单体形式、电池模块形式、电池包形式。
本申请的再一方面提供一种用电装置，包括本申请实施例的二次电池。
下文中适当参照附图对本申请实施例的电池单体、电池模块、电池包和用电装置进行说明。
通常情况下，电池单体包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。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，同时可以使离子通过。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲 酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
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，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸钠(NaPF6)、六氟 硼酸钠(NaBF4)、NaN(SO2F)2(简写为NaFSI)、NaClO4、NaAsF6、NaB(C2O4)2(简写为NaBOB)、NaBF2(C2O4)(简写为NaDFOB)、NaN(SO2RF)2和NaN(SO2F)(SO2RF)中的一种或多种；其中，RF代表CbF2b+1，b为1-10范围内的整数，可选为1-3范围内的整数，更可选地，RF为-CF3、-C2F5或-CF2CF2CF3。
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，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，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。
[外包装]
在一些实施方式中，电池单体可以包括外包装，用于封装正极极片、负极极片和电解质。作为一个示例，正极极片、负极极片和隔离膜可经叠片或卷绕形成叠片结构电芯或卷绕结构电芯，电芯封装在外包装内；电解质浸润于电芯中。电池单体中电芯的数量可以为一个或几个，可以根据需求来调节。
在一个实施方式中，本申请提供一种电极组件。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。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，电池单体的外包装可以是软包，例如袋式软包。软包的材质可以是塑料，如可包括聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或几种。在一些实施方式中，电池单体的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。本申请对电池单体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1是作为一个示例的方形结构的电池单体5。
在一些实施方式中，参照图2，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。电池单体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，电池单体可以组装成电池模块或电池包。电池模块或电池包中所含的电池单体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或电池包的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个电池单体可以是沿电池模块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电池单体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，多个电池单体5容纳于该容纳空间。
在一些实施方式中，电池单体或上述电池模块可以组装成电池包，电池包所含电池单体或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4和图5是作为一个示例的电池包1。参照图4和图5，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，本申请实施例还提供一种用电装置，所述用电装置包括本申请提供的电池单体、电池模块或电池包中的至少一种。所述电池单体、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电池单体、电池模块或电池包。
图6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。
实施例1
1.正极活性材料Na4Fe3(PO4)2P2O7与C的复合物的制备
a)制备前驱体材料：
按照化学式Na4Fe3(PO4)2P2O7中的Na、Fe、P的原子摩尔比将十水合焦磷酸钠(Na4P2O7.10H2O)1.164kg、二水合草酸亚铁 (FeC2O4.2H2O)1.367kg和磷酸二氢铵(NH4H2PO4)0.6kg加入6L水中研磨混合；再向其中加入葡萄糖0.117kg作为碳源化合物，然后搅拌砂磨，得到混合浆料，之后将混合浆料喷雾干燥，得到前驱体材料；
b)烧结：
将4kg前驱体材料置于烧结炉内，将烧结炉抽真空，使氧含量控制在30-50ppm，烧结气氛为氮气，氮气流量为5.14L/min。先将前驱体材料以2℃/min的升温速率将温度由室温(25℃)升至300℃，保持在300℃煅烧4小时，然后以2℃/min的升温速率将温度升至550℃，保持在550℃煅烧10h，然后以2℃/min的降温速率降温至100℃，得到产物，经X射线衍射(XRD)分析和红外碳硫仪确认产物为期望的正极活性材料Na4Fe3(PO4)2P2O7与C的复合物(碳包覆的Na4Fe3(PO4)2P2O7)。烧结时间内通入的氮气量为6.825m3，其与前驱体重量(单位kg)比值为1.70625。将材料转移至干燥房，进行初步破碎过筛，此时正极活性材料为出料状态，测得出料含水量，记录于表1中。
c)粉碎：
将烧结得到的正极活性材料(也即，出料状态的正极活性材料)在小于10％的环境湿度下进行气流粉碎，得到正极活性材料粉料(粉碎状态)。测定经粉碎后含水量，记录于表1中。
d)烘干：
将正极活性材料粉料放在干燥箱中在120℃烘干24h，得到烘干后的正极活性材料粉料(烘干状态)，测得正极活性材料含水量(也即，烘干后含水量)记录于表1中。
2.正极极片的制备
将聚偏氟乙烯粘结剂充分溶解于N-甲基吡咯烷酮中，再加入炭黑导电剂与上述经烘干的正极活性材料粉料，使正极活性材料粉料、炭黑导电剂和粘结剂的重量比为7∶2∶1，制成分散均匀的正极浆料。将正极浆料均匀涂覆在铝箔表面(铝箔厚度为13μm，负载量为43.42mg/1540.25mm2)，然后转移到真空干燥箱中完全干燥。将得到 的极片进行辊压，然后进行冲切，得到正极极片。
3.负极极片的制备
将碳纳米管材料、粘结剂羧甲基纤维素钠和去离子水按照重量比为4∶1.6∶94.4搅拌成均匀的浆料，将浆料涂覆在铜箔表面上(铜箔厚度为8μm，负载量为2mg/1540.25mm2)，然后转移到真空干燥箱中完全干燥，然后进行冲切，得到负极极片。
4.电解液的制备
在氩气气氛手套箱中(H2O＜0.1ppm，O2＜0.1ppm)，将六氟磷酸钠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0.5mol/L的电解液。
5.隔离膜
以聚丙烯膜作为隔离膜。
6.二次电池制备
将上述正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间，起到隔离的作用，加入0.5g上述电解液组装成叠片电池。
7.含水量测试
根据GB/T11133-2015(《石油产品、润滑油和添加剂中水含量的测定卡尔费休库伦滴定法》)进行检测。
8.充、放电比容量及首圈库伦效率测试
将上述制得的二次电池在25℃下以1/3C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，测得首圈充电比容量(Cc1)；再以1/3C的恒定电流放电至1.5V，测得首圈放电比容量(Cd1)。按照下式计算二次电池的首圈库伦效率：
实施例2-18
除通入氮气量(保持烧结时间不变，通过改变氮气流量来改变氮气量)及与前驱体烧结重量比值或升温速率不同以外(详见下表1)，实施例2-18的其他步骤与实施例1相同。
对比例1、2
对比例1基本与实施例1相同，其中不同之处在于改变了氮气量与前驱体重量比值。
上述实施例和对比例中的烧结和烘干的条件及测试结果请见下表1所示。

由表1可见，在实施例中，当前驱体重量、升温速率相同时，满足上述范围内的比值越大，含水量越少(或性能越好)。与对比例1-2相比，本申请的实施例(其烧结气氛的通气量体积值和前驱体材料重量值之间的比值在0.85-3.42m3/kg范围内)得到了含水量更低的正极活性材料，并且本申请实施例中的正极活性材料的含水量均低于1600ppm。
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 (12)

  1. 一种正极活性材料，所述正极活性材料为NaxRy(PO4)Z(P2O7)k与C的复合物，其中1≤x≤7，1≤y≤4，1≤z≤2，1≤k≤4，且R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；其中所述正极活性材料的含水量不高于1600ppm。
  2. 根据权利要求1所述的正极活性材料，其中所述含水量不高于1400ppm，可选地不高于1200ppm，可选地不高于1000ppm，可选地不高于900ppm，可选地不低于50ppm，更可选地不低于70ppm，再更可选地为200-800ppm。
  3. 根据权利要求1或2所述的正极活性材料，其中所述正极活性材料的化学组成满足以下条件中的至少一项：
    (1)3≤x≤5；
    (2)2≤y≤4；
    (3)1.5≤z≤2；
    (4)1≤k≤1.5；
    (5)R为Fe。
  4. 一种制备正极活性材料的方法，所述正极活性材料为NaxRy(PO4)Z(P2O7)k与C的复合物，其中1≤x≤7，1≤y≤4，1≤z≤2，1≤k≤4，且R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；其中所述正极活性材料的含水量不高于1600ppm；所述方法包括以下步骤：
    a)制备前驱体材料：制备包括R源化合物、钠源化合物、磷源化合物和碳源化合物的混合浆料，并将所述混合浆料干燥，得到所述前驱体材料；
    b)在烧结气氛中烧结所述前驱体材料得到所述正极活性材料， 其中所述烧结气氛的通气量体积值和前驱体材料重量值之间的比值为0.85-3.42m3/kg，可选地为1.70-3.42m3/kg，更可选地为2.27-3.42m3/kg。
  5. 根据权利要求4中任一项所述的方法，其中在所述步骤b)中，升温速率为0.5-5℃/min，可选地为2-5℃/min。
  6. 根据权利要求4或5所述的方法，其中在所述步骤b)中，所述烧结气氛包括氮气和/或氩气。
  7. 根据权利要求6所述的方法，其中在所述步骤b)中，氮气流量为2-10.5L/min可选地为5-10.5L/min；和/或烧结时间为约10-30小时，可选地为约18-23小时。
  8. 根据权利要求4至7中任一项所述的方法，还包括以下步骤：
    c)粉碎所述正极活性材料，其中所述粉碎在不大于10％的环境湿度下，可选地在2％～10％的环境湿度下进行。
  9. 根据权利要求4至8中任一项所述的方法，还包括以下步骤：
    d)烘干所述正极活性材料。
  10. 一种正极极片，包括权利要求1至3中任一项所述的正极活性材料或通过权利要求4至9中任一项所述的方法得到的正极活性材料。
  11. 一种二次电池，包括权利要求10所述的正极极片。
  12. 一种用电装置，包括权利要求11所述的二次电池。
PCT/CN2023/072597 2023-01-17 2023-01-17 正极活性材料、其制备方法及包含其的正极极片、二次电池和用电装置 Ceased WO2024152193A1 (zh)

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