WO2022267529A1 - 正极活性材料、电化学装置与电子设备 - Google Patents

正极活性材料、电化学装置与电子设备 Download PDF

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WO2022267529A1
WO2022267529A1 PCT/CN2022/079167 CN2022079167W WO2022267529A1 WO 2022267529 A1 WO2022267529 A1 WO 2022267529A1 CN 2022079167 W CN2022079167 W CN 2022079167W WO 2022267529 A1 WO2022267529 A1 WO 2022267529A1
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positive electrode
active material
electrode active
carbon
shell
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PCT/CN2022/079167
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English (en)
French (fr)
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曾毓群
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宁德时代新能源科技股份有限公司
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Priority to JP2023525942A priority Critical patent/JP2023547189A/ja
Priority to KR1020237014143A priority patent/KR20230078732A/ko
Priority to EP22827034.4A priority patent/EP4220765A1/en
Publication of WO2022267529A1 publication Critical patent/WO2022267529A1/zh
Priority to US18/322,824 priority patent/US20230299275A1/en

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    • H—ELECTRICITY
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
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    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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    • 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
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    • 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
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • H—ELECTRICITY
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
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    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • 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
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    • 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
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    • H01M4/00—Electrodes
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    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
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    • 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, in particular to a positive electrode active material, an electrochemical device and an electronic device.
  • Lithium-ion batteries have been widely used as an important new energy storage device in recent years due to their high energy density and good cycle performance.
  • the cost of batteries has always been high, and at the same time they are facing serious problems such as the depletion of related resources, so it is necessary to develop other low-cost metal-ion secondary battery systems.
  • Sodium-ion batteries have become a hot research direction in recent years due to their advantages such as low cost, abundant sodium metal resources, and similar manufacturing processes to lithium-ion batteries.
  • pyrophosphate-based cathode materials have been widely concerned due to their good cycle performance and low cost.
  • direct use will affect the performance of the gram capacity of the pyrophosphate-based cathode material and its electrochemical performance is poor, which seriously hinders its large-scale application.
  • the present application provides a positive electrode active material, an electrochemical device and an electronic device, which can effectively improve the conductivity of the positive electrode active material, improve the gram capacity and kinetic performance of the material, reduce the occurrence of side reactions, and improve the cycle performance of the positive electrode active material.
  • the present application provides a positive electrode active material
  • the positive electrode active material includes a conductive matrix material and an active material distributed on the conductive matrix material;
  • the active material has a core-shell structure, and the core-shell structure consists of A core layer material and a shell layer material are formed, wherein the core layer material includes a phosphate-based sodium salt material, the shell layer material includes a metal oxide, and the conductive matrix material includes a carbon material.
  • the metal oxide includes at least one of WO 3 , Al 2 O 3 , ZnO, CuO, and TiO 2 .
  • the positive electrode active material has at least one of the following characteristics:
  • the chemical formula of the sodium phosphate salt material is Na x1 R y1 (PO 4 ) Z1 , wherein, 1 ⁇ x 1 ⁇ 3, 1 ⁇ y 1 ⁇ 2, 1 ⁇ z 1 ⁇ 3, R includes Mg, At least one of Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W and Pb;
  • the chemical formula of the sodium phosphate salt material is Na x2 R y2 (P 2 O 7 ) Z2 , wherein, 1 ⁇ x 2 ⁇ 7, 1 ⁇ y 2 ⁇ 3, 1 ⁇ z 2 ⁇ 4, 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;
  • the chemical formula of the sodium phosphate salt material is Na x3 R y3 (PO 4 ) Z3 (P 2 O 7 ) k3 , wherein, 1 ⁇ x 3 ⁇ 7, 1 ⁇ y 3 ⁇ 4, 1 ⁇ z 3 ⁇ 2, 1 ⁇ k 3 ⁇ 4, R includes Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W and at least one of Pb;
  • the chemical formula of the sodium phosphate salt material is Na x4 R y4 (PO 4 ) Z4 M l1 , wherein, 1 ⁇ x 4 ⁇ 3, 1 ⁇ y 4 ⁇ 2, 1 ⁇ z 4 ⁇ 2 , 1 ⁇ l1 ⁇ 3, 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 , M includes at least one of F, Cl, Br.
  • the sodium phosphate salt material includes NaFePO 4 , Na 3 V 2 (PO 4 ) 3 , Na 2 FeP 2 O 7 , Na 2 MnP 2 O 7 , NaCoP 2 O 7 , Na 7 V 3 (P 2 O 7 ) 4 , Na 2 FePO 4 F, Na 3 V 2 (PO 4 ) 2 F 3 , Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ), Na 4 Mn 3 (PO 4 ) 2 (P 2 O 7 ), Na 4 Co 3 (PO 4 ) 2 (P 2 O 7 ), Na 4 Ni 3 (PO 4 ) 2 (P 2 O 7 ), Na 7 V 4 (PO 4 ) At least one of (P 2 O 7 ) 4 .
  • the mass of actual oxygen atoms in the metal oxide is 70%-95% of the mass of theoretical oxygen atoms in the metal oxide.
  • the positive electrode active material has at least one of the following characteristics:
  • the thickness of the shell material is 50nm ⁇ 400nm
  • the mass content of the shell material in the positive electrode active material is 1% to 10%
  • the mass content of the core layer material in the positive electrode active material is 90% to 99%
  • the mass content of the conductive matrix material in the positive electrode active material is 1% to 10%
  • the positive electrode active material has at least one of the following characteristics:
  • the carbon material includes at least one of carbon nanotubes, graphene, carbon fibers, natural graphite, and artificial graphite;
  • the carbon material includes an oxygen-containing group, and the oxygen-containing group is selected from at least one of carboxyl, hydroxyl and ether groups;
  • the carbon material includes oxygen-containing groups, and the mass content of oxygen atoms in the carbon material is ⁇ 0.1%;
  • the conductive base material is a carbon material.
  • the positive electrode active material has at least one of the following characteristics:
  • the positive electrode active material has a resistivity of 0.005 ⁇ cm to 100 ⁇ cm under a pressure of 20MPa;
  • the average particle size of the positive electrode active material is 5 ⁇ m to 20 ⁇ m;
  • the gram capacity of the positive electrode active material is 100mAh/g to 180mAh/g.
  • the present application provides an electrochemical device, comprising a positive pole piece, a negative pole piece, a separator, and an electrolyte, wherein the positive pole piece includes the above-mentioned positive pole active material.
  • the present application provides an electronic device, which includes the above-mentioned electrochemical device.
  • the application provides a positive electrode active material, which is coated with a metal oxide on the surface of the phosphate-based sodium salt material.
  • the metal oxide has strong mechanical strength and can still maintain the stability of the coating layer when the volume of the material changes during charge and discharge. At the same time, a large number of oxygen vacancies bring certain conductivity.
  • metal oxides can form metal sodium salts with high sodium ion conductivity with shuttled sodium ions, improving the kinetic properties of the material.
  • this coating layer can improve the conductivity of the sodium phosphate salt material to enhance its gram capacity and dynamic performance, and on the other hand, it can prevent the sodium phosphate salt material from being in direct contact with the electrolyte and reduce side reactions.
  • the high conductivity of the conductive matrix material can be used to further improve the conductivity of the material, so that the positive electrode active material with a conductive polymer coating structure and a conductive matrix material can play Higher gram capacity, better kinetic performance and cycle performance.
  • Figure 1 is a schematic structural view of a positive electrode active material provided in the embodiment of the present application.
  • Figure 2 is a schematic structural view of the active material in the positive electrode active material provided by the embodiment of the present application.
  • connection can be a fixed connection or a detachable connection, or an integrated connection, or Electrical connection; either directly or indirectly through an intermediary.
  • the present application provides a positive electrode active material
  • Fig. 1 is a schematic structural view of a positive electrode active material provided in an embodiment of the present application
  • the positive electrode active material includes a conductive matrix material 1 and is distributed on Active substance 2 on material 1.
  • the active material 2 has a core-shell structure.
  • Figure 2 is a schematic structural view of the active material in the positive electrode active material provided by the embodiment of the present application.
  • the core-shell structure is composed of a core material 21 and a shell material 22.
  • the core layer material 21 includes a sodium phosphate material
  • the shell layer material 22 includes a metal oxide
  • the conductive matrix material 1 includes a carbon material.
  • the conductive matrix material 1 is used to construct a conductive network, and the active material 2 can be adhered to the surface of the conductive matrix material 1, or attached to the hole structure of the conductive matrix material 1, etc., which is not limited here.
  • the active material 2 By attaching the active material 2 to the conductive matrix material 1, the high conductivity of the conductive matrix material can be utilized to improve the conductivity of the positive electrode active material.
  • the conductive matrix material 1 is a carbon material, wherein the carbon material includes at least one of carbon nanotubes, graphene, carbon fibers, natural graphite, and artificial graphite.
  • the carbon material includes oxygen-containing groups, and the oxygen-containing groups are at least one selected from carboxyl groups, hydroxyl groups and ether groups.
  • the mass content of oxygen atoms in the oxygen-containing group is ⁇ 0.1%.
  • the mass content of the oxygen atoms in the oxygen-containing group can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6% , 0.7%, 0.8%, 0.9%, 1%, etc., are not limited here.
  • the overpotential of the conductive matrix material can be reduced, the phenomenon of poor affinity between the active material and the positive electrode current collector can be improved, and the binding force between the active material and the positive electrode current collector can be improved.
  • the mass content of the conductive matrix material 1 in the positive electrode active material is 1% to 10%.
  • the mass content of the conductive matrix material in the positive electrode active material can be 1%, 2%, or 3%. %, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc., are not limited here. If the mass content of the conductive matrix material 1 in the positive electrode active material is too high, there will be too many carbon materials with high specific surface area, no capacity, and low compaction density, and the battery capacity will become smaller, thereby reducing the energy density and cycle life of the battery.
  • the mass content of the conductive matrix material 1 in the positive electrode active material may be 4% to 8%.
  • the active material 2 on the conductive matrix material 1 has a core-shell structure
  • the core-shell structure is composed of a core material 21 and a shell material 22
  • the core material 21 is covered by the shell material 22
  • the cladding structure is Full coating or half coating
  • the coating method can be solid phase coating method, liquid phase coating method or gas phase coating method, etc.
  • the specific coating method can be selected according to actual needs, and is not limited here.
  • the shell material 22 and the core material 21 of the active material 2 are closely connected by the Coulomb attraction of charges or by strong chemical bonds between the core material 21 and the shell material 22 .
  • the composition of the core layer material 21 includes a sodium phosphate salt material
  • the chemical formula of the sodium phosphate salt material includes Na x1 R y1 (PO 4 ) Z1 , Na x2 R y2 (P 2 O 7 ) Z2 , Na x3 R y3 At least one of (PO 4 ) Z3 (P 2 O 7 ) k3 , Na x4 R y4 (PO 4 ) Z4 M l1 .
  • 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, and M includes F , Cl, Br at least one.
  • the sodium phosphate salt material can specifically be NaFePO 4 , Na 3 V 2 (PO 4 ) 3 , Na 2 FeP 2 O 7 , Na 2 MnP 2 O 7 , NaCoP 2 O 7 , Na 7 V 3 (P 2 O 7 ) 4 , Na 2 FePO 4 F, Na 3 V 2 (PO 4 ) 2 F 3 , Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ), Na 4 Mn 3 (PO 4 ) 2 ( P 2 O 7 ), Na 4 Co 3 (PO 4 ) 2 (P 2 O 7 ), Na 4 Ni 3 (PO 4 ) 2 (P 2 O 7 ), Na 7 V 4 (PO 4 ) (P 2 O 7 ) 4 etc. are not limited here.
  • the sodium phosphate salt material may be Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ).
  • the shell material 22 used to cover the core material 21 includes metal oxide, wherein the metal oxide includes at least one of WO 3 , Al 2 O 3 , ZnO, CuO, and TiO 2 .
  • the actual atomic mass of oxygen in the metal oxide is 70% to 95% of the theoretical atomic mass of oxygen in the metal oxide.
  • the actual atomic mass of oxygen in the metal oxide is 70%, 75%, 80%, 85%, 90%, 95%, etc. of the theoretical atomic mass of oxygen in the metal oxide, which is not limited herein.
  • the difference between the actual atomic mass of oxygen and the theoretical atomic mass of oxygen in metal oxides is due to the presence of oxygen vacancy defects, that is, the original metal oxide surface loses some oxygen to form a disordered structure rich in oxygen vacancy defects layer, thereby forming a certain amount of oxygen vacancies on the surface of the metal oxide. Too many oxygen vacancies will make the metallicity of the material too high, resulting in a decrease in mechanical strength, and at the same time reduce the proportion of metal sodium salts with high ionic conductivity formed by bonding with sodium ions, reducing the conductivity of sodium ions.
  • the actual atomic mass of oxygen in the metal oxide is 85% of the theoretical atomic mass of oxygen in the metal oxide.
  • the metal oxide-coated positive electrode active material has more excellent reversibility during charge and discharge. Since metal oxides have better mechanical strength and higher electrical conductivity, on the one hand, they can improve the electrical conductivity of the positive electrode active material, and improve the gram capacity and kinetic performance of the positive electrode active material. On the other hand, it can prevent the direct contact between the positive electrode active material and the electrolyte, reduce the occurrence of side reactions, and improve the cycle performance of the positive electrode active material.
  • the active material 2 is loaded on the conductive matrix material 1, and a large number of isolated active materials 2 can be connected through an externally constructed one-dimensional or two-dimensional conductive network to further improve the conductivity.
  • the oxygen-containing functional groups of the conductive matrix material 1 are increased, and the oxygen-containing functional groups are used to form stronger hydrogen bonds with the shell material 22 on the surface of the active material 2 to improve the binding strength between the active material 2 and the conductive matrix material 1 .
  • the mass content of the core layer material 21 in the positive electrode active material is 90% to 99%.
  • the mass content of the core layer material 21 in the positive electrode active material may specifically be 90%, 91%, 92%, 93%, 96%, 97%, 98%, 99%, etc., which is not limited herein. If the mass content of the core layer material 21 in the positive electrode active material is too large, and the proportion of the metal oxide covering the core layer material is too small, the conductivity of the positive electrode active material will be reduced, which will affect the gram capacity and kinetic performance of the battery.
  • the mass content of the core layer material 21 in the positive electrode active material is too small, and the proportion of the phosphate-based sodium salt material with good cycle performance is too small, resulting in a decrease in the cycle performance of the battery.
  • the mass content of the core layer material 21 in the positive electrode active material may be 95%.
  • the mass content of the shell material 22 in the positive electrode active material is 1% to 10%.
  • the mass content of the shell material 22 in the positive electrode active material can be specifically 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.
  • the thickness of the shell material is 50nm to 400nm, optional, the thickness of the shell material can be 50nm, 100nm, 150nm, 200nm, 350nm , 300nm, 350nm, 400nm, 450nm, 500nm, etc. are not limited here.
  • the mass content and thickness of the shell material 22 in the positive electrode active material are too high, the shell layer will be too thick, the mass ratio of the metal oxide will be too high, and the mass ratio of the phosphate-based sodium salt material with good cycle performance in the core layer material will change. Small, ultimately affecting the cycle performance of the battery.
  • the mass content and thickness of the shell material 22 in the positive electrode active material are too low, the metal oxide cladding layer coated on the core layer material is too thin, the conductivity of the positive electrode active material decreases, and the surface of the positive electrode active material is easy to contact with the electrolytic Direct contact with the liquid may cause side reactions.
  • the mass content of the shell material 22 in the positive electrode active material may be 4% to 8%, and the thickness of the shell material may be 100nm to 300nm.
  • the average particle size of the positive electrode active material satisfies 5 ⁇ m ⁇ Dv50 ⁇ 20 ⁇ m.
  • the average particle size Dv50 of the positive electrode active material can specifically be 5 ⁇ m, 7 ⁇ m, 9 ⁇ m, 11 ⁇ m, 13 ⁇ m, 15 ⁇ m, 17 ⁇ m, 19 ⁇ m, 20 ⁇ m, etc. are not limited here. If the average particle size of the positive electrode active material is too small, agglomeration of particles of the positive electrode active material is likely to occur, and side reactions with the electrolyte are likely to occur.
  • the particle size Dv50 of the positive electrode active material satisfies 8 ⁇ m ⁇ Dv50 ⁇ 15 ⁇ m.
  • the present application provides an electrochemical device, including a positive pole piece, a negative pole piece, a separator, and an electrolyte, and the positive pole piece includes the above-mentioned positive electrode active material.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector, and the positive electrode active material layer includes the positive electrode active material of the first aspect above.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector.
  • the negative active material layer includes a negative active material.
  • the negative electrode active material includes at least one of graphite, silicon material, silicon-oxygen material, tin material, tin-oxygen material or silicon-carbon composite material.
  • the negative electrode active material layer includes a binder
  • the binder includes, but is not limited to: polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl alcohol Vinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, Styrene butadiene rubber, acrylic (ester) styrene butadiene rubber, epoxy resin or nylon, etc.
  • the negative electrode active material layer also includes conductive materials, which include, but are not limited to: natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, metal fiber, Copper, nickel, aluminum, silver or polyphenylene derivatives, etc.
  • the negative electrode current collector includes, but is not limited to: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite current collector.
  • Aluminum-based current collectors are preferred, including any one of aluminum foil, aluminum alloy foil, and aluminum-based composite current collectors.
  • Aluminum-based composite current collectors include polymer Base film and aluminum foil and/or aluminum alloy foil formed on both sides of the polymer base film. Specifically, the aluminum-based composite current collector has a "sandwich" structure, and the polymer base film is located in the middle, with aluminum foils on both sides, or aluminum alloy foils on both sides, or one side of the polymer base film. Aluminum foil with aluminum foil on the other side.
  • the polymer base film can be polyamide, polyethylene terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polypara Any of butylene phthalate, poly-p-phenylene terephthalamide, polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, polycarbonate A sort of.
  • the aluminum-based composite current collector selected in this application has better ductility, which is conducive to maintaining the integrity of the electrode during the sodium deposition/extraction process.
  • the isolation film can be various materials suitable for the isolation film of electrochemical energy storage devices in the field, for example, it can include, but not limited to: polyethylene, polypropylene, polyvinylidene fluoride, At least one of aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fibers.
  • the electrochemical device further includes an electrolytic solution, and the electrolytic solution includes an organic solvent, a sodium salt and an additive.
  • the organic solvent of the electrolytic solution according to the present application can be any organic solvent known in the prior art that can be used as a solvent for the electrolytic solution.
  • the electrolyte used in the electrolytic solution according to the present application is not limited, and it may be any electrolyte known in the prior art.
  • the additive of the electrolytic solution according to the present application may be any additive known in the prior art as an additive to the electrolytic solution.
  • the organic solvent includes, but is not limited to: ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), vinylene carbonate, fluoroethylene carbonate, propylene carbonate, propyl propionate or ethyl propionate.
  • EC ethylene carbonate
  • PC propylene carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • DMC dimethyl carbonate
  • vinylene carbonate fluoroethylene carbonate
  • propylene carbonate propyl propionate or ethyl propionate.
  • the sodium salt includes at least one of organic sodium salt or inorganic sodium salt.
  • sodium salts include, but are not limited to: sodium hexafluorophosphate (NaPF 6 ), sodium tetrafluoroborate (NaBF 4 ), sodium difluorophosphate (NaPO 2 F 2 ), bistrifluoromethanesulfonyl Sodium amine NaN(CF 3 SO 2 ) 2 (NaTFSI), sodium bis(fluorosulfonyl)imide Na(N(SO 2 F) 2 )(NaFSI), sodium bisoxalate borate NaB(C 2 O 4 ) 2 ( NaBOB), sodium difluorooxalate borate NaBF 2 (C 2 O 4 ) (NaDFOB), or sodium perchlorate.
  • NaPF 6 sodium hexafluorophosphate
  • NaBF 4 sodium tetrafluoroborate
  • NaPO 2 F 2 sodium difluorophosphate
  • NaTFSI bistrifluoromethanesulfonyl Sodium amine NaN(CF 3 SO
  • the electrochemical device of the present application includes, but is not limited to: all kinds of primary batteries and secondary batteries.
  • the battery includes at least one of a soft pack, a square aluminum case, a square steel case, a cylindrical aluminum case and a cylindrical steel case battery.
  • the present application provides an electronic device, which includes the above-mentioned electrochemical device. Electrochemical devices can be used to provide power to electronic devices.
  • the electronic devices include, but are not limited to: notebook computers, pen-input computers, mobile computers, e-book players, portable phones, portable fax machines, portable copiers, portable printers, head-mounted Stereo headphones, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, power assist Bicycles, bicycles, lighting appliances, toys, game consoles, clocks, electric tools, flashlights, cameras, large household batteries, energy storage or sodium ion capacitors, etc.
  • the present application also provides a method for preparing a positive electrode active material, the preparation method comprising the following steps:
  • the average particle size of the carbon material after ultrasonic dispersion is 50nm to 20um
  • the inlet temperature of the spray drying is 150°C to 250°C
  • the outlet temperature of the spray drying is 80°C to 150°C.
  • the stirring time is 2h-8h
  • the adjusted pH value is 10-12
  • the calcination time is 4h-10h
  • the pore size of the sieved positive electrode active material satisfies 8 ⁇ m ⁇ Dv50 ⁇ 15 ⁇ m.
  • the positive active material is finally obtained.
  • the carbon material was first put into a mixed solution of concentrated sulfuric acid and concentrated nitric acid with a volume ratio of 3:1 and stirred for 4 hours, washed with deionized water, filtered, put into an oven, and dried at 80°C.
  • the carbon material and the high molecular polymer are added into N-methylpyrrolidone and stirred to form a uniform slurry, and the slurry is coated on the copper foil and dried to obtain the carbon material coating used.
  • Under Ar atmosphere put the sodium metal into a stainless steel crucible and heat it to 200°C to make it melt completely, then add the alloy component powder into the liquid sodium metal and stir for 2 hours to ensure that the metal powder and the sodium metal liquid are evenly mixed, After cooling, the sodium metal alloy active material can be obtained.
  • the sodium metal alloy active material is compounded on the surface of the carbon material coating by cold pressing to obtain the sodium metal negative electrode sheet.
  • Ethylene glycol dimethyl ether (DME) was used as an organic solvent, and then fully dried sodium salt NaPF 6 was dissolved in the mixed organic solvent to prepare an electrolyte solution with a concentration of 1mol/L.
  • the above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play the role of isolation, and the above-mentioned electrolyte is added to assemble a button battery.
  • Examples 1-22 and Comparative Examples 1-7 were prepared according to the above method, and the specific parameters are shown in Table 1.
  • Resistivity of the positive electrode active material the positive electrode active material powder was tested with a powder resistance tester under a pressure of 20 MPa.
  • the batteries prepared in Examples and Comparative Examples were charged to 4V at a rate of 0.1C, discharged to 1V at a rate of 0.1C, and a full charge and discharge test was performed to obtain the discharge capacity as the gram capacity of the material.
  • the positive electrode active materials with different compositions have slight differences in the gram capacity of the prepared batteries and the number of cycles of the batteries.
  • the positive electrode active material is Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ).
  • the mass content of the shell material in the positive electrode active material is too low, the metal oxide coating layer coated on the core layer material is too thin, the conductivity of the positive electrode active material decreases, and the surface of the positive electrode active material is easily in direct contact with the electrolyte , resulting in side reactions.
  • the mass content of the shell layer material in the positive electrode active material is 4% to 8%.
  • the mass content of the conductive matrix material in the positive electrode active material is too low, it will be difficult to form an effective conductive network between the active materials, the battery conduction rate will decrease, and the gram capacity of the active material will be difficult to exert, thereby reducing the battery life.
  • the mass content of the conductive matrix material in the positive electrode active material is 4% to 8%.
  • the shell material can be TiO 2 .
  • the average particle size of the positive electrode active material is in the range of 5 ⁇ m to 20 ⁇ m, the gram capacity and cycle performance of the battery are the best.
  • the average particle size of the positive electrode active material is too small, which is prone to agglomeration and side reactions with the electrolyte. If the average particle size of the positive electrode active material is too large, the diffusion rate of active ions in the material will be reduced, the kinetic performance will be reduced, and the gram capacity and cycle performance of the battery will be affected.
  • the average particle size of the positive electrode active material satisfies 8 ⁇ m ⁇ Dv50 ⁇ 15 ⁇ m.

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Abstract

本申请提供一种正极活性材料、电化学装置与电子设备。正极活性材料包括导电基体材料及分布于导电基体材料上的活性物质，活性物质具有核壳结构，核壳结构由核层材料和壳层材料组成。核层材料包括磷酸基钠盐材料，壳层材料包括金属氧化物，导电基体材料包括碳材料。本申请提供的正极活性材料、电化学装置与电子设备，可以有效提高正极活性材料的导电性，提高材料的克容量及动力学性能，减少副反应的发生，提升正极活性材料的循环性能。

Description

正极活性材料、电化学装置与电子设备
相关申请的交叉引用
本申请要求享有于2021年06月26日提交的名称为“正极活性材料、电化学装置与电子设备”的中国专利申请第202110742609.6号的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请涉及二次电池技术领域，具体地涉及一种正极活性材料、电化学装置与电子设备。
背景技术
随着能源与环境问题的日益凸显，新能源产业得到了越来越多的重视。锂离子电池因其能量密度高、循环性能好等特点，近年来作为一种重要的新型储能装置被广泛应用。然而，由于锂离子电池相关活性物质资源稀缺，电池成本始终居高不下，而且同时面临相关资源枯竭等严峻问题，因此需要开发其他低成本金属离子二次电池体系。
钠离子电池由于其成本低、钠金属资源丰富、与锂离子电池制造工艺相仿等优势使其成为近年来热门研究方向。在钠离子二次电池体系中，焦磷酸基正极材料由于其循环性能好，成本低廉一直受到广泛关注。但是，由于焦磷酸基正极材料本身导电性较差，直接使用会影响焦磷酸基正极材料克容量的发挥且电化学性能较差，严重阻碍了其大规模应用。
发明内容
本申请提供一种正极活性材料、电化学装置与电子设备，可以有效提高正极活性材料的导电性，提高材料的克容量及动力学性能，减少副反应的发生，提升正极活性材料的循环性能。
第一方面，本申请提供一种正极活性材料，所述正极活性材料包括导电基体材料及分布于所述导电基体材料上的活性物质；所述活性物质具有核壳结构，所 述核壳结构由核层材料和壳层材料构成，其中，所述核层材料包括磷酸基钠盐材料，所述壳层材料包括金属氧化物，所述导电基体材料包括碳材料。
根据本申请第一方面的实施方式，所述金属氧化物包括WO 3、Al 2O 3、ZnO、CuO、TiO 2中的至少一种。
根据本申请第一方面的实施方式，所述正极活性材料具有如下特征中的至少一种：
(1)所述磷酸基钠盐材料的化学式为Na x1R y1(PO 4) Z1，其中，1≤x 1≤3，1≤y 1≤2，1≤z 1≤3，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；
(2)所述磷酸基钠盐材料的化学式为Na x2R y2(P 2O 7) Z2，其中，1≤x 2≤7，1≤y 2≤3，1≤z 2≤4，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；
(3)所述磷酸基钠盐材料的化学式为Na x3R y3(PO 4) Z3(P 2O 7) k3，其中，1≤x 3≤7、1≤y 3≤4、1≤z 3≤2、1≤k 3≤4，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；
(4)所述磷酸基钠盐材料的化学式为Na x4R y4(PO 4) Z4M l1，其中，1≤x 4≤3，1≤y 4≤2，1≤z 4≤2，1≤l1≤3，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，M包括F、Cl、Br中的至少一种。
根据本申请第一方面的实施方式，所述磷酸基钠盐材料包括NaFePO 4、Na 3V 2(PO 4) 3、Na 2FeP 2O 7、Na 2MnP 2O 7、NaCoP 2O 7、Na 7V 3(P 2O 7) 4、Na 2FePO 4F、Na 3V 2(PO 4) 2F 3、Na 4Fe 3(PO 4) 2(P 2O 7)、Na 4Mn 3(PO 4) 2(P 2O 7)、Na 4Co 3(PO 4) 2(P 2O 7)、Na 4Ni 3(PO 4) 2(P 2O 7)、Na 7V 4(PO 4)(P 2O 7) 4中的至少一种。
根据本申请第一方面的实施方式，所述金属氧化物中实际氧原子的质量为所述金属氧化物中理论氧原子的质量的70％～95％。
根据本申请第一方面的实施方式，所述正极活性材料具有如下特征中的至少一种：
(5)所述壳层材料的厚度为50nm～400nm；
(6)所述壳层材料在所述正极活性材料中的质量含量为1％至10％；
(7)所述核层材料在所述正极活性材料中的质量含量为90％至99％；
(8)所述导电基体材料在所述正极活性材料中的质量含量为1％至10％；
根据本申请第一方面的实施方式，所述正极活性材料具有如下特征中的至少一种：
(9)所述碳材料包括碳纳米管、石墨烯、碳纤维、天然石墨、人造石墨中的至少一种；
(10)所述碳材料包括含氧基团，所述含氧基团选自羧基、羟基和醚基中的至少一种；
(11)所述碳材料包括含氧基团，所述碳材料中的氧原子的质量含量≥0.1％；
(12)所述导电基体材料为碳材料。
根据本申请第一方面的实施方式，所述正极活性材料具有如下特征中的至少一种：
(13)所述正极活性材料在20MPa压力下的电阻率为0.005Ω·cm至100Ω·cm；
(14)所述正极活性材料的平均粒径为5μm至20μm；
(15)所述正极活性材料的克容量为100mAh/g至180mAh/g。
第二方面，本申请提供一种电化学装置，包括正极极片、负极极片、隔离膜及电解液，所述正极极片包括上述的正极活性材料。
第三方面，本申请提供一种电子设备，所述电子设备包括上述的电化学装置。
本申请提供的技术方案至少具有以下有益效果：
本申请提供一种正极活性材料，在磷酸基钠盐材料表面包覆金属氧化物，金属氧化物具有较强的机械强度，在材料充放电发生体积变化时仍能保持包覆层的稳定性，同时具有大量氧空位带来了一定的导电性，此外，金属氧化物可以与穿梭的钠离子形成具有高钠离子电导率的金属钠盐，提升材料动力学性能。综上所述，此包覆层一方面可以改善磷酸基钠盐材料的导电性以提升其克容量发挥与动力学性能，另一方面防止磷酸基钠盐材料与电解液直接接触，减少副反应发生，提升正极活性材料循环性能。过将包覆后的活性物质附着在导电基体材料上，可以利用导电基体材料的高导电性能，进一步提高材料的导电性，使得具有导电聚合物包覆结构以及导电基体材料的正极活性材料可以发挥更高的克容量、更好的动力学性能及循环性能。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对实施例中所需要使用的附图作简单地介绍，应当理解，以下附图仅示出了本申请的某些实施例，因此不应被看作是对本申请范围的限定。
图1为本申请实施例提供的一种正极活性材料的结构示意图；
图2为本申请实施例提供的正极活性材料中的活性物质的结构示意图；
附图标记：
1-导电基体材料；
2-活性物质；21-核层材料；22-壳层材料。
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
在本说明书的描述中，除非另有明确的规定和限定，术语“第一”、“第二”仅用于描述的目的，而不能理解为指示或暗示相对重要性；除非另有规定或说明，术语“多个”是指两个或两个以上；术语“连接”、“固定”等均应做广义理解，例如“连接”可以是固定连接或者是可拆卸连接，或一体的连接，或电连接；可以是直接相连，也可以通过中间媒介间接相连。
对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
本说明书的描述中，需要理解的是，本申请实施例所描述的“上”、“下”等方位词是以附图所示的角度来进行描述的，不应理解为对本申请实施例的限定。此外，在上下文中，还需要理解的是，当提到一个元件连接在另一个元件“上”或者“下”时，其不仅能够直接连接在另一个元件“上”或者“下”，也可以通过中间元件间接连接在另一个元件“上”或者“下”。
第一方面，本申请提供一种正极活性材料，图1为本申请实施例提供的一种正极活性材料的结构示意图；如图1所示，正极活性材料包括导电基体材料1及分布于导电基体材料1上的活性物质2。活性物质2具有核壳结构，图2为本申请实施例提供的正极活性材料中的活性物质的结构示意图，如图2所示，核壳结 构由核层材料21和壳层材料22构成。其中，核层材料21包括磷酸基钠盐材料，壳层材料22包括金属氧化物，导电基体材料1包括碳材料。
在本申请中，导电基体材料1用于构建导电网络，活性物质2可以粘附于导电基体材料1的表面，或者附着在导电基体材料1的孔洞结构内等，在此不做限定。通过将活性物质2附着在导电基体材料1上，可以利用导电基体材料的高导电性，提高正极活性材料的导电性能。
在上述方案中，导电基体材料1为碳材料，其中，碳材料包括碳纳米管、石墨烯、碳纤维、天然石墨、人造石墨中的至少一种。具体的，碳材料包括含氧基团，含氧基团选自羧基、羟基和醚基中的至少一种。含氧基团中的氧原子的质量含量≥0.1％，可选的，含氧基团中的氧原子的质量含量具体可以为0.1％、0.2％、0.3％、0.4％、0.5％、0.6％、0.7％、0.8％、0.9％、1％等，在此不做限定。通过控制碳材料中的氧原子的质量含量，可以降低导电基体材料的过电势，可以改善活性物质与正极集流体的亲和性不佳的现象，提升活性物质与正极集流体的粘结力。
在实际应用过程中，导电基体材料1在正极活性材料中的质量含量为1％至10％，可选的，导电基体材料在正极活性材料中的质量含量具体可以为1％、2％、3％、4％、5％、6％、7％、8％、9％、10％等，在此不做限定。导电基体材料1在正极活性材料中的质量含量过高，会造成高比表面积、无容量、低压实密度的碳材料过多，电池容量变小，从而造成电池能量密度及循环寿命的降低。导电基体材料1在正极活性材料中的质量含量过低，会造成活性物质2之间难以形成有效的导电网络，导电速率降低，电池导电性能与寿命降低。优选的，导电基体材料1在正极活性材料中的质量含量可以为4％至8％。
在上述方案中，导电基体材料1上的活性物质2具有核壳结构，核壳结构由核层材料21和壳层材料22构成，核层材料21被壳层材料22包覆，包覆结构为全包覆或者半包覆，包覆的方式可以为固相包覆法、液相包覆法或气相包覆法等，具体包覆方式可根据实际需要选择，在此不做限定。具体的，活性物质2的壳层材料22与核层材料21通过电荷的库伦引力吸附或依靠核层材料21与壳层材料22之间牢固的化学键紧密连接。
具体的，核层材料21的组成包括磷酸基钠盐材料，磷酸基钠盐材料的化学式包括Na x1R y1(PO 4) Z1、Na x2R y2(P 2O 7) Z2、Na x3R y3(PO 4) Z3(P 2O 7) k3、Na x4R y4(PO 4) Z4M l1中的至少一种。其中，1≤x 1≤3，1≤y 1≤2，1≤z 1≤3，1≤x 2≤7，1≤y 2≤3，1≤z 2≤4，1≤x 3≤7、1≤y 3≤4、1≤z 3≤2、1≤k 3≤4，1≤x 4≤3，1≤y 4≤2，1≤z 4≤2，1≤l 1≤3，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，M包括F、Cl、Br中的至少一种。
可选的，磷酸基钠盐材料具体可以为NaFePO 4、Na 3V 2(PO 4) 3、Na 2FeP 2O 7、Na 2MnP 2O 7、NaCoP 2O 7、Na 7V 3(P 2O 7) 4、Na 2FePO 4F、Na 3V 2(PO 4) 2F 3、Na 4Fe 3(PO 4) 2(P 2O 7)、Na 4Mn 3(PO 4) 2(P 2O 7)、Na 4Co 3(PO 4) 2(P 2O 7)、Na 4Ni 3(PO 4) 2(P 2O 7)、Na 7V 4(PO 4)(P 2O 7) 4等，在此不做限定。优选的，磷酸基钠盐材料可以为Na 4Fe 3(PO 4) 2(P 2O 7)。
用于包覆核层材料21的壳层材料22包括金属氧化物，其中，金属氧化物包括包括WO 3、Al 2O 3、ZnO、CuO、TiO 2中的至少一种。具体的，金属氧化物中的实际氧原子质量为金属氧化物中的理论氧原子质量的70％～95％。可选的，金属氧化物中的实际氧原子质量为金属氧化物中的理论氧原子质量的70％、75％、80％、85％、90％、95％等，在此不做限定。需要说明的是，金属氧化物中的实际氧原子质量与理论氧原子质量有差别，是因为存在氧空位缺陷，即原来的金属氧化物表面失去部分氧而形成富含氧空位缺陷的无序结构层，从而在金属氧化物表面形成一定量的氧空位。氧空位过多，会使得材料金属性过高，造成机械强度下降，同时减少与钠离子键合形成具有高离子电导率的金属钠盐的比例，降低钠离子电导率。氧空位过少，氧离子不能在其中自由移动，不能实现电致电阻效应中电场对氧离子运动的调控。优选的，金属氧化物中的实际氧原子质量为金属氧化物中的理论氧原子质量的85％。
作为本申请可选的技术方案，金属氧化物包覆结构的正极活性材料在充放电过程中具有更优异的可逆性。由于金属氧化物具有较好的机械强度、较高的导电性，一方面可以改善正极活性材料的导电性，提升正极活性材料的克容量发挥及动力学性能。另一方面可以防止正极活性材料与电解液直接接触，减少副反应发生，提升正极活性材料的循环性能。在正极活性材料中，活性物质2负载在导电基体材料1上，可将大量孤立的活性物质2通过外部构建的一维或二维导电网络连接起来，进一步提升导电性。并且，增加导电基体材料1的含氧官能团，利用含氧官能团与活性物质2表面的壳层材料22形成结合力更强的氢键，提高活性物质2与导电基体材料1的结合强度。
在实际应用过程中，核层材料21在正极活性材料中的质量含量为90％至99％。可选的，核层材料21在正极活性材料中的质量含量具体可以为90％、91％、92％、93％、96％、97％、98％、99％等，在此不做限定。核层材料21在正极活 性材料中的质量含量过大，包覆核层材料的金属氧化物占比过小，正极活性材料的导电性会降低，影响电池的克容量发挥与动力学性能。核层材料21在正极活性材料中的质量含量过小，具有良好循环性能的磷酸基钠盐材料占比过小，导致电池的循环性能降低。优选的，核层材料21在正极活性材料中的质量含量可以为95％。
壳层材料22在正极活性材料中的质量含量为1％至10％，可选的，壳层材料22在正极活性材料中的质量含量具体可以为1％、2％、3％、4％、5％、6％、7％、8％、9％、10％等，壳层材料的厚度为50nm至400nm，可选的，壳层材料的厚度具体可以为50nm、100nm、150nm、200nm、350nm、300nm、350nm、400nm、450nm、500nm等，在此不做限定。壳层材料22在正极活性材料中的质量含量及厚度过高，会造成壳层过厚，金属氧化物质量占比过高，核层材料中循环性能良好的磷酸基钠盐材料质量占比变小，最终影响电池的循环性能。壳层材料22在正极活性材料中的质量含量及厚度过低，包覆在核层材料上的金属氧化物包覆层过薄，正极活性材料的导电性下降，且正极活性材料表面易与电解液直接接触，造成副反应发生。优选的，壳层材料22在正极活性材料中的质量含量可以为4％至8％，壳层材料的厚度可以为100nm至300nm。
作为本申请可选的技术方案，正极活性材料的平均粒径满足5μm≤Dv50≤20μm，可选的，正极活性材料的平均粒径Dv50具体可以为5μm、7μm、9μm、11μm、13μm、15μm、17μm、19μm、20μm等，在此不做限定。正极活性材料平均粒径过小，易出现正极活性材料颗粒团聚现象，且容易与电解液发生副反应。正极活性材料平均粒径过大，会降低活性离子在正极活性材料内部的扩散速率，导致动力学性能降低，影响正极活性材料克容量发挥与电池循环性能。优选的，正极活性材料径粒Dv50满足8μm≤Dv50≤15μm。
第二方面，本申请提供一种电化学装置，包括正极极片、负极极片、隔离膜及电解液，正极极片包括上述的正极活性材料。
正极极片包括正极集流体及位于正极集流体上的正极活性材料层，正极活性材料层包括上述第一方面的正极活性材料。
负极极片包括负极集流体及位于负极集流体上的负极活性材料层。负极活性材料层包括负极活性材料。
作为本申请可选的技术方案，负极活性材料包括石墨、硅材料、硅氧材料、锡材料、锡氧材料或硅碳复合材料中的至少一种。
作为本申请可选的技术方案，负极活性材料层包括粘合剂，粘合剂包括，但不限于：聚乙烯醇、羧甲基纤维素、羟丙基纤维素、二乙酰基纤维素、聚氯乙烯、羧化的聚氯乙烯、聚氟乙烯、含亚乙基氧的聚合物、聚乙烯吡咯烷酮、聚氨酯、聚四氟乙烯、聚偏1,1-二氟乙烯、聚乙烯、聚丙烯、丁苯橡胶、丙烯酸(酯)化的丁苯橡胶、环氧树脂或尼龙等。
作为本申请可选的技术方案，负极活性材料层还包括导电材料，导电材料包括，但不限于：天然石墨、人造石墨、碳黑、乙炔黑、科琴黑、碳纤维、金属粉、金属纤维、铜、镍、铝、银或聚亚苯基衍生物等。
作为本申请可选的技术方案，负极集流体包括，但不限于：铜箔、镍箔、不锈钢箔、钛箔、泡沫镍、泡沫铜或复合集流体。
由于钠离子不与铝形成合金，基于降本和减重的考虑，优先采用铝基集流体，包括铝箔、铝合金箔和铝基复合集流体中任意一种，铝基复合集流体包括高分子基膜及形成于所述高分子基膜的两侧的铝箔和/或铝合金箔。具体地，铝基复合集流体为“三明治”结构，高分子基膜位于中间，其两侧设有铝箔，或者其两侧设有铝合金箔，还可以是高分子基膜的一侧设有铝箔，另一侧设有铝合金箔。高分子基膜可以为聚酰胺、聚对苯二甲酸酯、聚酰亚胺、聚乙烯、聚丙烯、聚苯乙烯、聚氯乙烯、丙烯腈-丁二烯-苯乙烯共聚物、聚对苯二甲酸丁二醇酯、聚对苯二甲酰对苯二胺、聚丙乙烯、聚甲醛、环氧树脂、酚醛树脂、聚四氟乙烯、聚偏氟乙烯、硅橡胶、聚碳酸酯中任意一种。优选地，本申请选择铝基复合集流体具有更好的延展性，有利于在钠沉积/脱出过程中保持电极的完整性。
作为本申请可选的技术方案，隔离膜可以是本领域各种适用于电化学储能装置隔离膜的材料，例如，可以是包括，但不限于：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。
作为本申请可选的技术方案，电化学装置还包括电解液，所述电解液包括有机溶剂、钠盐和添加剂。
根据本申请的电解液的有机溶剂可为现有技术中已知的任何可作为电解液的溶剂的有机溶剂。根据本申请的电解液中使用的电解质没有限制，其可为现有技术中已知的任何电解质。根据本申请的电解液的添加剂可为现有技术中已知的任何可作为电解液添加剂的添加剂。
在具体实施例中，所述有机溶剂包括，但不限于：碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、碳酸二甲酯(DMC)、碳酸亚乙烯酯、氟代碳酸乙烯酯、碳酸亚丙酯、丙酸丙酯或丙酸乙酯中的至少一种。
在具体实施例中，钠盐包括有机钠盐或无机钠盐中的至少一种。
在具体实施例中，钠盐包括，但不限于：六氟磷酸钠(NaPF 6)、四氟硼酸钠(NaBF 4)、二氟磷酸钠(NaPO 2F 2)、双三氟甲烷磺酰亚胺钠NaN(CF 3SO 2) 2(NaTFSI)、双(氟磺酰)亚胺钠Na(N(SO 2F) 2)(NaFSI)、双草酸硼酸钠NaB(C 2O 4) 2(NaBOB)、二氟草酸硼酸钠NaBF 2(C 2O 4)(NaDFOB)或高氯酸钠。
作为本申请可选的技术方案，本申请的电化学装置包括，但不限于：所有种类的一次电池、二次电池。所述电池包括软包、方形铝壳、方形钢壳、圆柱铝壳和圆柱钢壳电池中的至少一种。
第三方面，本申请提供一种电子设备，电子设备包括上述的电化学装置。电化学装置可用于为电子设备提供电源。
作为本申请可选的技术方案，所述电子装置包括，但不限于：笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池、储能或钠离子电容器等。
第四方面，本申请还提供一种正极活性材料的制备方法，制备方法包括以下步骤：
S10.将碳材料放入浓硫酸：浓硝酸＝3：1的溶液中搅拌4h，用去离子水洗涤、过滤后放入烘箱中，在80℃条件下烘干；其中，过滤筛孔径大小选择为400目。
S20.将上述处理后的碳材料放入水中超声分散，然后和化学计量比的硝酸铁、磷酸二氢钠溶液混合搅拌均匀，接着利用喷雾干燥技术制出前驱体粉末。
其中，超声分散后的碳材料平均径粒大小满足50nm至20um、喷雾干燥的进口温度为150℃至250℃、喷雾干燥的出风口温度为80℃至150℃。
S30.在600℃高温将前驱体粉末煅烧6小时后放入金属氧化物溶液中充分搅拌，通过调节PH值将前驱体凝胶包覆在磷酸基钠盐材料表面，然后在400℃至800℃，氢气气氛下进行煅烧，将得到的产物过筛后得到正极活性材料。
其中，搅拌时间为2h-8h，调节后的PH值为10-12，煅烧时间为4h-10h，筛 分后的正极活性材料孔径满足8μm≤Dv50≤15μm。
通过上述制备方法及壳层材料质量分数、导电基体材料质量分数、壳层材料种类、正极活性材料粒径的调整，最终得到正极活性材料。
为使本领域技术人员更好地理解本申请的技术方案，下面结合具体实施方式对本申请做进一步详细描述。
实施例1：
(1)负极极片的制备：
先将碳材料放入体积比为3:1的浓硫酸与浓硝酸的混合溶液中搅拌4h，用去离子水洗涤、过滤后放入烘箱中，在80℃条件下烘干。将碳材料和高分子聚合物加到N-甲基吡咯烷酮中搅拌成均匀的浆料，使浆料涂覆在铜箔上并烘干即得到所用碳材料涂层。在Ar气氛下，将钠金属放入到不锈钢坩埚中加热至200℃使其完全融化，然后将合金组分粉末加入到液态钠金属中并充分搅拌2h，确保金属粉末与钠金属液体均匀混合，冷却后即可得到钠金属合金活性物质。将钠金属合金活性物质通过冷压复合在碳材料涂层表面，得到钠金属负极极片。
(2)正极极片的制备：
将10wt％聚偏氟乙烯粘结剂充分溶解于N-甲基吡咯烷酮中，加入10wt％炭黑导电剂与80wt％正极活性材料制成分散均匀的浆料。将浆料均匀涂敷在锆表面，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，然后进行冲裁，得到目标圆片。
(3)隔离膜的制备：
采用聚丙烯聚合物薄膜。
(4)电解液的制备：
将乙二醇二甲醚(DME)作为有机溶剂，接着将充分干燥的钠盐NaPF 6溶解于混合后的有机溶剂中，配制成浓度为1mol/L的电解液。
(5)扣式电池的制备：
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，加入上述电解液组装成扣式电池。
根据上述方法制得实施例1～22及对比例1～7，具体参数详见表1。
表1
Figure PCTCN2022079167-appb-000001
性能测试：
(1)正极活性材料的电阻率：采用粉末电阻测试仪在20MPa的压力下对正极活性材料粉末进行测试。
(2)正极活性材料的克容量：
在25℃下，将实施例和对比例制备得到的电池以0.1C倍率充电到4V、以0.1C倍率放电到1V，进行满充满放测试，得到放电容量成为材料克容量。
(3)电池的循环性能：在25℃下，将实施例和对比例制备得到的电池以0.1C 倍率充电到4V、以0.1C倍率放电到1V，进行满充满放循环测试，直至钠离子电池的容量小于初始容量的80％，记录循环圈数，其测试结果如表2所示。
表2
序号 正极活性材料的电阻率(Ω·m) 克容量(mAh/g) 循环圈数
实施例1 85 148 791
实施例2 104 84 725
实施例3 76 121 763
实施例4 60 123 987
实施例5 88 118 851
实施例6 69 121 921
实施例7 61 122 937
实施例8 61 120 901
实施例9 61 118 882
实施例10 92 115 829
实施例11 69 121 931
实施例12 55 122 976
实施例13 50 120 963
实施例14 48 118 942
实施例15 70 120 887
实施例16 63 121 927
实施例17 66 119 864
实施例18 60 124 891
实施例19 62 123 932
实施例20 68 121 955
实施例21 70 121 966
实施例22 74 120 949
对比例1 102 113 762
对比例2 61 116 838
对比例3 125 110 618
对比例4 47 117 901
对比例5 56 124 877
对比例6 79 118 914
对比例7 110 110 687
由实施例1至4可知，组成成分不同的正极活性材料，制备出的电池克容量发挥及电池循环圈数稍有差异。优选的，正极活性材料为Na 4Fe 3(PO 4) 2(P 2O 7)。
由实施例5至9及对比例1至2可知，当壳层材料在正极活性材料中的质量含量在1％至10％范围内时，电池的克容量发挥、动力学性能及循环性能好。壳层材料在正极活性材料中的质量含量过高，核层厚度过高，金属氧化物质量占比过高，核层材料中循环性能好的磷酸基钠盐材料质量占比变小，最终影响电池的循环性能。壳层材料在正极活性材料中的质量含量过低，包覆在核层材料上的金属氧化物包覆层过薄，正极活性材料的导电性下降，且正极活性材料表面易与电解液直接接触，造成副反应发生。优选的，壳层材料在正极活性材料中的质量含量为4％至8％。
由实施例10至14及对比例3至4可知，当导电基体材料在正极活性材料中的质量含量在1％至10％范围内时，材料导电性能提高，材料的克容量提升。导电基体材料在正极活性材料中的质量含量过高，会造成高比表面积、无容量、低压实密度的碳材料过多，电池容量变小，从而造成电池能量密度及循环寿命的降低。导电基体材料在正极活性材料中的质量含量过低，会造成活性物质之间难以形成有效的导电网络，电池导电速率降低，活性物质的克容量难以发挥，从而降低电池寿命。优选的，导电基体材料在正极活性材料中的质量含量为4％至8％。
由实施例15至实施例17可知，金属氧化物种类的选择会对电池的克容量发挥与循环寿命产生影响。优选的，壳层材料可以为TiO 2。
由实施例18至22及对比例5至6可知，当正极活性材料的平均粒径在5μm至20μm范围内时，电池的克容量发挥及循环性能最好。正极活性材料平均粒径过小，易出现团聚，且容易与电解液发生副反应。正极活性材料平均粒径过大，会降低活性离子在材料内部的扩散速率，降低动力学性能，影响电池的克容量发挥与电池循环性能。优选的，正极活性材料平均粒径满足8μm≤Dv50≤15μm。
从实施例1至22、对比例7可知的数据可以看出，在实施例1至22中，随着导电基体材料质量分数、壳层材料种类、正极活性材料粒径的变化，会略有影响正极活性材料的克容量发挥，会略有影响电池的循环寿命；但是，相比于对比例7，其在核层材料的表面未包覆壳层材料，使得正极活性材料的导电性下降， 电阻率升高，使得材料的克容量大幅下降；并且，核层材料与电解液直接接触，造成副反应发生，电池的循环性能下降。
本领域技术人员应能理解，上述实施例均是示例性而非限制性的。在不同实施例中出现的不同技术特征可以进行组合，以取得有益效果。本领域技术人员在研究附图、说明书及权利要求书的基础上，应能理解并实现所揭示的实施例的其他变化的实施例。在权利要求书中，术语“包括”并不排除其他装置或步骤；物品没有使用数量词修饰时旨在包括一个/种或多个/种物品，并可以与“一个/种或多个/种物品”互换使用”；术语“第一”、“第二”用于标示名称而非用于表示任何特定的顺序。权利要求中的任何附图标记均不应被理解为对保护范围的限制。权利要求中出现的多个部分的功能可以由一个单独的硬件或软件模块来实现。某些技术特征出现在不同的从属权利要求中并不意味着不能将这些技术特征进行组合以取得有益效果。。

Claims (10)

  1. 一种正极活性材料，包括：
    导电基体材料；及
    分布于所述导电基体材料上的活性物质，所述活性物质具有核壳结构，所述核壳结构由核层材料和壳层材料构成，
    其中，所述导电基体材料包括碳材料，所述核层材料包括磷酸基钠盐材料，所述壳层材料包括金属氧化物。
  2. 根据权利要求1所述的正极活性材料，其中，所述金属氧化物包括WO 3、Al 2O 3、ZnO、CuO、TiO 2中的至少一种。
  3. 根据权利要求1所述的正极活性材料，其中，所述正极活性材料具有如下特征中的至少一种：
    (1)所述磷酸基钠盐材料的化学式为Na x1R y1(PO 4) Z1，其中，1≤x 1≤3，1≤y 1≤2，1≤z 1≤3，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；
    (2)所述磷酸基钠盐材料的化学式为Na x2R y2(P 2O 7) Z2，其中，1≤x 2≤7，1≤y 2≤3，1≤z 2≤4，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；
    (3)所述磷酸基钠盐材料的化学式为Na x3R y3(PO 4) Z3(P 2O 7) k3，其中，1≤x 3≤7、1≤y 3≤4、1≤z 3≤2、1≤k 3≤4，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；
    (4)所述磷酸基钠盐材料的化学式为Na x4R y4(PO 4) Z4M l1，其中，1≤x 4≤3，1≤y 4≤2，1≤z 4≤2，1≤l1≤3，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，M包括F、Cl、Br中的至少一种。
  4. 根据权利要求1或2所述的正极活性材料，其中，所述磷酸基钠盐材料包括NaFePO 4、Na 3V 2(PO 4) 3、Na 2FeP 2O 7、Na 2MnP 2O 7、NaCoP 2O 7、Na 7V 3(P 2O 7) 4、Na 2FePO 4F、Na 3V 2(PO 4) 2F 3、Na 4Fe 3(PO 4) 2(P 2O 7)、Na 4Mn 3(PO 4) 2(P 2O 7)、Na 4Co 3(PO 4) 2(P 2O 7)、Na 4Ni 3(PO 4) 2(P 2O 7)、Na 7V 4(PO 4)(P 2O 7) 4中的至少一种。
  5. 根据权利要求1所述的正极活性材料，其中，所述金属氧化物中实际氧 原子的质量为所述金属氧化物中理论氧原子的质量的70％～95％。
  6. 根据权利要求1或2所述的正极活性材料，其中，所述正极活性材料具有如下特征中的至少一种：
    (5)所述壳层材料的厚度为50nm～400nm；
    (6)所述壳层材料在所述正极活性材料中的质量含量为1％至10％；
    (7)所述核层材料在所述正极活性材料中的质量含量为90％至99％；
    (8)所述导电基体材料在所述正极活性材料中的质量含量为1％至10％。
  7. 根据权利要求1或2所述的正极活性材料，其中，所述正极活性材料具有如下特征中的至少一种：
    (9)所述碳材料包括碳纳米管、石墨烯、碳纤维、天然石墨、人造石墨中的至少一种；
    (10)所述碳材料包括含氧基团，所述含氧基团选自羧基、羟基和醚基中的至少一种；
    (11)所述碳材料包括含氧基团，所述碳材料中的氧原子的质量含量≥0.1％；
    (12)所述导电基体材料为碳材料。
  8. 权利要求1所述的正极活性材料，其中，所述正极活性材料具有如下特征中的至少一种：
    (13)所述正极活性材料在20MPa压力下的电阻率为0.005Ω·cm至100Ω·cm；
    (14)所述正极活性材料的平均粒径为5μm至20μm；
    (15)所述正极活性材料的克容量为100mAh/g至180mAh/g。
  9. 一种电化学装置，包括正极极片、负极极片、隔离膜及电解液，其中，所述正极极片包括权利要求1～8任一项所述的正极活性材料。
  10. 一种电子设备，包括权利要求9所述的电化学装置。
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