WO2024036502A1 - 正极材料、电化学装置及电子设备 - Google Patents

正极材料、电化学装置及电子设备 Download PDF

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WO2024036502A1
WO2024036502A1 PCT/CN2022/112965 CN2022112965W WO2024036502A1 WO 2024036502 A1 WO2024036502 A1 WO 2024036502A1 CN 2022112965 W CN2022112965 W CN 2022112965W WO 2024036502 A1 WO2024036502 A1 WO 2024036502A1
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composite oxide
cathode material
nickel composite
single crystal
lithium nickel
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PCT/CN2022/112965
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English (en)
French (fr)
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程世杨
下羽淳平
郎野
徐磊敏
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宁德新能源科技有限公司
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Priority to CN202280010312.3A priority Critical patent/CN116918106A/zh
Priority to PCT/CN2022/112965 priority patent/WO2024036502A1/zh
Publication of WO2024036502A1 publication Critical patent/WO2024036502A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—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
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of electrochemistry technology, and in particular to a cathode material, electrochemical device and electronic equipment.
  • electrochemical devices With the popularity of consumer electronics products such as laptops, mobile phones, tablets, mobile power supplies and drones, the requirements for the electrochemical devices in them are becoming more and more stringent.
  • electrochemical devices are not only required to be lightweight, but also have high capacity and long operating life.
  • lithium-ion batteries have occupied a mainstream position in the market due to their outstanding advantages such as high energy density, high safety, no memory effect and long working life.
  • lithium-ion batteries In order to pursue higher energy density, lithium-ion batteries have been developing in the direction of increasing voltage and increasing the amount of lithium removal. At the same time, in actual use, high temperature conditions will inevitably exist. Under high voltage, high delithiation capacity and high temperature conditions, the problems of surface oxygen release and structural phase change of the cathode material are also fully exposed, causing problems such as battery cycle diving and gas production.
  • the present application provides a cathode material, electrochemical device and electronic equipment to at least partially solve the above problems existing in the prior art.
  • the present application provides a cathode material.
  • the cathode material includes first single crystal particles; the first single crystal particles have a first aspect ratio L 1 , and L 1 satisfies 2 ⁇ L 1 ⁇ 5.
  • the positive electrode material includes first single crystal particles with a first aspect ratio L 1. Since the first single crystal particles have a high aspect ratio, they are beneficial to reducing the active crystal planes where side reactions occur on the surface of the positive electrode material, inhibiting the positive electrode. The structural phase change of materials and the occurrence of interface side reactions help improve the cycle performance and storage performance of electrochemical devices under high voltage and high temperature conditions.
  • the first single crystal particle has a first crack on its surface.
  • the cracks on the surface of the first single crystal particle can make the first single crystal particle have a larger specific surface area to promote the deintercalation of lithium ions inside the first single crystal particle, thereby increasing the energy density of the electrochemical device; on the other hand,
  • the stress and strain caused by the expansion and contraction caused by the deintercalation of lithium in the long diameter direction will be larger.
  • the cracks on the surface of the first single crystal particles can buffer the first single crystal particles. The expansion and contraction of the single crystal particles in the long diameter direction reduces the risk of cracking of the first single crystal particles, thereby improving the cycle performance and storage performance of the electrochemical device under high voltage and high temperature conditions.
  • the first single crystal particles have an average particle diameter D 1 of 10 ⁇ m to 25 ⁇ m.
  • the first crack wall contains at least one of P element, F element or N element.
  • the first crack contains at least one of P element, F element or N element inside, which can improve the stability of the crystal structure of the first single crystal particle at the first crack and suppress the phase change of the crystal structure and interface side reactions there. occurs, thereby improving the cycle performance and storage performance of electrochemical devices under high voltage and high temperature conditions.
  • the width h of the first crack is less than or equal to 0.1 ⁇ m.
  • the width h of the first crack is within the above range, which helps to suppress the occurrence of interface side reactions, thereby improving the cycle performance and storage performance of the electrochemical device under high voltage and high temperature conditions.
  • the first single crystal particle includes a first lithium nickel composite oxide.
  • the first lithium nickel composite oxide includes Ni element, Na element, optional Co element, optional Mn element, optional M element and optional R element, the M element Including B, Mg, Al, Si, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, Sr , Ca, Ba, Ta, Hf or Ce; the R element includes at least one of P, F or N.
  • the molar percentage content of the Na element in the first lithium nickel composite oxide 1% to 10%.
  • the molar percentage content of the M element in the first lithium nickel composite oxide is 0.1% to 20%.
  • the molar percentage content of the R element in the first lithium nickel composite oxide 1% to 10%.
  • the molar percentage content of the Ni element in the first lithium nickel composite oxide Greater than or equal to 50%.
  • the first lithium nickel composite oxide includes Li x1 Na w1 Ni y1 Co z1 Mn k1 M q1 O 2 ⁇ a R a ; wherein, 0.2 ⁇ x1 ⁇ 1.2, 0.5 ⁇ y1 ⁇ 1, 0 ⁇ z1 ⁇ 0.5, 0 ⁇ k1 ⁇ 0.5, 0 ⁇ q1 ⁇ 0.2, 0.01 ⁇ w1 ⁇ 0.1 and 0 ⁇ a ⁇ 0.1.
  • the cathode material further includes second single crystal particles; the second single crystal particles have a second aspect ratio L 2 , L 2 satisfies 1 ⁇ L 2 ⁇ 2; the first single crystal particles
  • the number of particles is N 1
  • the number of second single crystal particles is N 2 , wherein N 1 /(N 1 +N 2 ) ranges from 20% to 50%, and N 2 /(N 1 +N 2 ) ranges from 50% to 80%.
  • the second single crystal particle includes a second lithium nickel composite oxide.
  • the second lithium nickel composite oxide includes Ni element, Na element, optional Co element, optional Mn element, optional M' element and optional R' element; said M' elements include B, Mg, Al, Si, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, At least one of Ge, Sr, Ca, Ba, Ta, Hf or Ce; the R' element includes at least one of P, F or N.
  • the molar percentage of Na element in the second lithium nickel composite oxide Content is 1% to 10%.
  • the molar amount of the M' element in the second lithium nickel composite oxide is The content is 0.1% to 20%.
  • the molar amount of the R' element in the second lithium nickel composite oxide is The content is 1% to 10%.
  • the molar percentage of Ni element in the second lithium nickel composite oxide is greater than or equal to 50%.
  • the second lithium nickel composite oxide includes Li x2 Na w2 Ni y2 Co z2 Mn k2 M' q2 O 2 ⁇ b R' b ; wherein, 0.2 ⁇ x2 ⁇ 1.2, 0.5 ⁇ y2 ⁇ 1 , 0 ⁇ z2 ⁇ 0.5, 0 ⁇ k2 ⁇ 0.5, 0 ⁇ q2 ⁇ 0.2, 0.01 ⁇ w2 ⁇ 0.1 and 0 ⁇ b ⁇ 0.1.
  • the second single crystal particles have an average particle diameter D2 of 2 ⁇ m to 8 ⁇ m.
  • (Dv90-Dv10)/Dv50 ⁇ 2 where Dv90 is the particle diameter when the cumulative volume particle size distribution of the cathode material reaches 90%, and Dv10 is the cumulative particle size in the volume particle size distribution of the cathode material. The particle size reaches 10%, and Dv50 is the particle size when the volume particle size distribution of the cathode material reaches 50%.
  • the half-maximum width FWHM (003) of the (003) peak in the XRD diffraction pattern of the cathode material in the range of 18° to 19.2° satisfies: 0.14° ⁇ FWHM (003) ⁇ 0.2°.
  • FWHM (003) Within this range, the regularity of the active crystal plane for deintercalation of lithium in the lithium-nickel composite oxide is relatively high. On the one hand, it is conducive to the deintercalation of lithium ions inside the lithium-nickel composite oxide, thereby improving the electrochemical device.
  • the unit cell parameter a of the cathode material satisfies:
  • the unit cell parameter c of the cathode material satisfies:
  • the cathode material includes a Li layer and an O layer
  • the interlayer spacing range between the Li layer and the O layer is to The Li-O layer spacing within the above range can promote the extraction and insertion of lithium ions, thereby increasing the energy density of the electrochemical device.
  • the present application provides an electrochemical device including the cathode material as described above.
  • the present application provides an electronic device including the electrochemical device as described above.
  • This application sets the cathode material to include first single crystal particles with a first aspect ratio L 1. Since the first single crystal particles have a high aspect ratio, they are beneficial to reducing the active crystal planes where side reactions occur on the surface of the cathode material. , inhibiting the structural phase change of the cathode material and the occurrence of interface side reactions, thereby helping to improve the cycle performance and storage performance of the electrochemical device under high voltage and high temperature conditions.
  • Figure 1 is an SEM image of the cathode material powder of Example 7 of the present application.
  • Figure 2 is an SEM image of the first crack on the surface of the first single crystal particle in Example 7 of the present application
  • Figure 3 is the XRD diffraction pattern of the cathode material in Example 7 of the present application.
  • Figure 4 is an SEM image of the cross-section of the cathode material in Example 7 of the present application.
  • Figure 5 is the SEM-EDX distribution diagram of Ni element at the cross section in Figure 4.
  • Figure 6 is the SEM-EDX distribution diagram of Co element at the cross section in Figure 4.
  • Figure 7 is the SEM-EDX distribution diagram of Na element at the cross section in Figure 4.
  • a list of items connected by the term "at least one of,” “at least one of,” “at least one of,” or other similar terms may mean that the listed items any combination of.
  • the phrase “at least one of A and B” means only A; only B; or A and B.
  • the phrase “at least one of A, B, and C” means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B and C.
  • Item A may contain a single component or multiple components.
  • Item B may contain a single component or multiple components.
  • Item C may contain a single component or multiple components.
  • the present application provides a cathode material.
  • the cathode material includes first single crystal particles; the first single crystal particles have a first aspect ratio L 1 , L 1 satisfies 2 ⁇ L 1 ⁇ 5, where the first aspect ratio is The ratio of the long diameter to the short diameter of a single crystal particle.
  • the long diameter of the first single crystal particle is the longest diameter of the first single crystal particle in the electron microscope photo, that is, the distance between the two furthest edge points, and The distance between the two edge points located perpendicular to the long diameter in the electron microscope photo is the short diameter of the first single crystal particle.
  • the positive electrode material includes first single crystal particles with a first aspect ratio L 1.
  • the first single crystal particles have a high aspect ratio, they are beneficial to reducing the active crystal planes where side reactions occur on the surface of the positive electrode material, inhibiting the positive electrode.
  • the structural phase change of materials and the occurrence of interface side reactions help improve the cycle performance and storage performance of electrochemical devices under high voltage and high temperature conditions.
  • the first single crystal particle has a first crack on its surface.
  • the cracks on the surface of the first single crystal particle can make the first single crystal particle have a larger specific surface area to promote the deintercalation of lithium ions inside the first single crystal particle, thereby increasing the energy density of the electrochemical device; on the other hand,
  • the stress and strain caused by the expansion and contraction caused by the deintercalation of lithium in the long diameter direction will be larger.
  • the cracks on the surface of the first single crystal particles can buffer the first single crystal particles.
  • FIG 2 it is an SEM image of the first crack on the surface of the first single crystal particle in an embodiment of the present application. It can be seen from Figure 2 that there are first cracks on the surface of the first single crystal particle in multiple places, one of which is The width of the first crack at one location is 0.05 ⁇ m, and the width of the first crack at another location is 0.06 ⁇ m.
  • the first crack wall contains at least one of P element, F element or N element. That is, the wall surface layer inside the first crack contains at least one of P element, F element or N element, which can improve the stability of the crystal structure of the first single crystal particle at the first crack, inhibit the phase change of the crystal structure there and Interfacial side reactions occur, thereby improving the cycle performance and storage performance of electrochemical devices under high voltage and high temperature conditions.
  • the width h of the first crack is less than or equal to 0.1 ⁇ m.
  • the first crack is an irregular crack, and the maximum width of the irregular crack is 0.1 ⁇ m.
  • the width of the first crack is less than or equal to 0.1 ⁇ m, which helps to suppress the occurrence of interface side reactions, thereby improving the cycle performance and storage performance of the electrochemical device under high voltage and high temperature conditions.
  • the ratio of the depth of the first crack to the particle diameter of the first single crystal particle is less than or equal to 10% to suppress the occurrence of interface side reactions, thereby improving the cycle performance of the electrochemical device under high voltage and high temperature conditions. and storage performance.
  • the particle diameter of the first single crystal particle is the longest diameter of the cross section of the first single crystal particle.
  • the average particle diameter D 1 of the first single crystal particles is 10 ⁇ m to 25 ⁇ m.
  • the first single crystal particle includes a first lithium nickel composite oxide.
  • the first lithium nickel composite oxide includes Ni element, Na element, optional Co element, optional Mn element, optional M element and optional R element, the M element Including B, Mg, Al, Si, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, Sr , Ca, Ba, Ta, Hf or Ce; the R element includes at least one of P, F or N.
  • the first lithium-nickel composite oxide includes Ni element and Co element, as shown in Figure 4, which is an SEM image of the cross-section of the cathode material in an embodiment of the present application (ie, subsequent Embodiment 7); Figure 5 The SEM-EDX distribution diagram of the Ni element in the cross section in Figure 4 is shown, and Figure 6 is the SEM-EDX distribution diagram of the Co element in the cross section in Figure 4.
  • the molar percentage content of Na element in the first lithium nickel composite oxide is 1% to 10%.
  • Figure 7 is the SEM-EDX distribution diagram of Na element at the cross section in Figure 4.
  • the molar percentage content of the M element in the first lithium nickel composite oxide is greater than or equal to 0.1 % to 20%.
  • the molar percentage content of the R element in the first lithium nickel composite oxide is greater than or equal to 1 % and less than or equal to 10%.
  • the molar percentage content of Ni element in the first lithium nickel composite oxide is greater than or equal to 50 %.
  • the surface energy of the cathode material can be adjusted, the sintering activity of the material can be improved, the grain size growth can be promoted during the sintering process, the surface side reaction activity of the material can be reduced, and the surface stability of the material can be improved. , thereby inhibiting the oxygen release and gas production of the cathode material during high-temperature cycles.
  • doping the lithium layer with elements with high ionic radius can increase the interlayer spacing between the lithium layer and the oxygen layer, improving the dynamic performance of the cathode material.
  • the first lithium nickel composite oxide includes Li x1 Na w1 Ni y1 Co z1 Mn k1 M q1 O 2 ⁇ a R a ; wherein, 0.2 ⁇ x1 ⁇ 1.2, 0.5 ⁇ y1 ⁇ 1, 0 ⁇ z1 ⁇ 0.5, 0 ⁇ k1 ⁇ 0.5, 0 ⁇ q1 ⁇ 0.2, 0.01 ⁇ w1 ⁇ 0.1 and 0 ⁇ a ⁇ 0.1; M includes B, Mg, Al, Si, S, Ti, Cr, Fe, Cu, At least one of Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, Sr, Ca, Ba, Ta, Hf or Ce; R includes P At least one of , F or N.
  • the cathode material further includes second single crystal particles; the second single crystal particles have a second aspect ratio L 2 , L 2 satisfies 1 ⁇ L 2 ⁇ 2; wherein, the second aspect ratio The ratio is the ratio of the long diameter to the short diameter of the second single crystal particle.
  • the long diameter of the second single crystal particle is the longest diameter of the second single crystal particle in the electron microscope photo, that is, the distance between the two farthest edge points. distance, and the distance between the two edge points located on the vertical line in the long diameter in the electron microscope photo is the short diameter of the second single crystal particle.
  • FIG. 1 it is a scanning electron microscope (SEM) image of the cathode material powder in one embodiment of the present application (that is, the subsequent embodiment 7).
  • the number of the first single crystal particles is N 1 and the number of the second single crystal particles is N 2 , wherein N 1 /(N 1 +N 2 ) ranges from 20% to 50%, N 2 /(N 1 +N 2 ) ranges from 50% to 80%.
  • the second single crystal particle has a lower aspect ratio, and the deintercalation path of lithium ions in the second single crystal particle is shorter, thereby improving the dynamic performance of the cathode material; on the other hand, by converting the first single crystal particle
  • the number N 1 of crystal particles and the number N 2 of second single crystal particles are controlled within the above range, which is conducive to mutual embedding and close packing of the two, thereby improving the energy density of the electrochemical device.
  • N 1 /(N 1 +N 2 ) can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, and any two of these point values.
  • Range and any value in the range; N 2 / (N 1 + N 2 ) can be 50%, 55%, 60%, 65%, 70%, 75%, 80% and any two of these point values The range formed and any value within the range.
  • the second single crystal particle includes a second lithium nickel composite oxide.
  • the second lithium nickel composite oxide includes Ni element, Na element, optional Co element, optional Mn element, optional M' element and optional R' element; said M' elements include B, Mg, Al, Si, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, At least one of Ge, Sr, Ca, Ba, Ta, Hf or Ce; the R' element includes at least one of P, F or N.
  • the molar percentage of Na element in the second lithium nickel composite oxide Content is 1% to 10%.
  • the molar amount of the M' element in the second lithium nickel composite oxide is The content is 0.1% to 20%.
  • the molar amount of the R' element in the second lithium nickel composite oxide is The content is 1% to 10%.
  • the molar percentage of Ni element in the second lithium nickel composite oxide is greater than or equal to 50%.
  • the second lithium nickel composite oxide includes Li x2 Na w2 Ni y2 Co z2 Mn k2 M' q2 O 2 ⁇ b R' b ; wherein, 0.2 ⁇ x2 ⁇ 1.2, 0.5 ⁇ y2 ⁇ 1 , 0 ⁇ z2 ⁇ 0.5, 0 ⁇ k2 ⁇ 0.5, 0 ⁇ q2 ⁇ 0.2, 0.01 ⁇ w2 ⁇ 0.1 and 0 ⁇ b ⁇ 0.1; M' includes B, Mg, Al, Si, S, Ti, Cr, Fe, At least one of Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, Sr, Ca, Ba, Ta, Hf or Ce; R 'Includes at least one of P, F or N.
  • the second single crystal particles have an average particle diameter D 2 of 2 ⁇ m to 8 ⁇ m.
  • (Dv90-Dv10)/Dv50 ⁇ 2 where Dv90 is the particle diameter when the cumulative volume particle size distribution of the cathode material reaches 90%, and Dv10 is the cumulative particle size in the volume particle size distribution of the cathode material.
  • the particle size reaches 10%, and Dv50 is the particle size when the volume particle size distribution of the cathode material reaches 50%. Satisfying the above relationship can prevent the particle size distribution range of the cathode material particles from being too wide, resulting in the compaction density of the cathode material being too small.
  • the half-maximum width FWHM (003) of the (003) peak in the XRD diffraction pattern of the cathode material in the range of 18° to 19.2° satisfies: 0.14° ⁇ FWHM (003) ⁇ 0.2°, and the FWHM (003) is within this range, the active crystal plane for deintercalation of lithium in the lithium-nickel composite oxide has a high regularity.
  • the unit cell parameter a of the cathode material satisfies:
  • the unit cell parameter c of the cathode material satisfies:
  • the cathode material includes a Li layer and an O layer, and the interlayer spacing between the Li layer and the O layer ranges from to The Li-O layer spacing within the above range can promote the extraction and insertion of lithium ions, thereby increasing the energy density of the electrochemical device.
  • Embodiments of the present application also provide an electrochemical device, including a positive electrode sheet, a negative electrode sheet, a separator, an electrolyte and an outer packaging.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer.
  • the positive electrode active layer is provided on at least one surface of the positive electrode current collector.
  • the positive electrode active layer includes the positive electrode material as described above.
  • the positive electrode current collector in this application is not particularly limited.
  • the positive electrode current collector can be any positive electrode current collector known in the art, such as aluminum foil, aluminum alloy foil or composite current collector.
  • the positive active layer also includes a conductive agent and a binder.
  • a conductive agent includes but is not limited to at least one of carbon nanotubes, carbon fibers, conductive carbon black, acetylene black, graphene, and Ketjen black.
  • the binder includes but is not limited to polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, and polyacrylic acid.
  • the binder, conductive agent and positive electrode material are added to the solvent and mixed evenly to obtain the positive electrode slurry.
  • the positive electrode slurry is coated on the surface of the positive electrode current collector, and the positive electrode slurry is dried and then rolled
  • the positive electrode active layer is obtained by pressing, and the compacted density of the positive electrode active layer is greater than or equal to 3.5g/cc.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer.
  • the negative electrode active layer is disposed on at least one surface of the negative electrode current collector.
  • the negative electrode active layer includes negative electrode material.
  • the negative electrode sheet of this application is not particularly limited.
  • the negative electrode material can be any negative electrode material in the prior art.
  • the negative electrode material includes at least one of graphite, hard carbon, soft carbon, silicon, silicon carbon or silicon oxide; the negative electrode current collector It can be any negative electrode current collector known in the art, such as copper foil, aluminum foil, aluminum alloy foil or composite current collector.
  • the separator of the present application is not particularly limited.
  • the separator may be made of materials that are stable to the electrolyte of the present application, so that the ions in the electrolyte can pass through the separator, so that the ions in the electrolyte can pass through the positive electrode sheet and the negative electrode.
  • the separator may include polyethylene (PE), etc.
  • the separator is disposed between the positive electrode sheet and the negative electrode sheet.
  • the negative electrode sheet, separator and positive electrode sheet can be stacked or wound in sequence along the thickness direction of the negative electrode sheet, and can be accommodated in the internal space of the outer package.
  • the electrolyte solution in this application is not particularly limited, any electrolyte solution known in the art can be used, and the electrolyte solution can be in any of gel state, solid state, and liquid state.
  • the electrolyte is a liquid electrolyte
  • the liquid electrolyte includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is not particularly limited. Any lithium salt known in the art can be used as long as the purpose of the present application can be achieved.
  • the lithium salt can include LiTFSI, LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 At least one of H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiC (SO 2 CF 3 ) 3 , LiPO 2 F 2, etc.
  • the non-aqueous solvent is not particularly limited as long as it can achieve the purpose of the present application.
  • the non-aqueous solvent may include at least one of carbonate compounds, carboxylate compounds, ether compounds, nitrile compounds or other organic solvents, carbonic acid
  • the ester compound may include diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC) ), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,2-carbonate Difluoroethylene, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoroethylene carbonate 2-Methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-
  • the electrochemical device also includes a positive electrode ear and a negative electrode ear.
  • the positive electrode ear is electrically connected to the positive current collector
  • the negative electrode ear is electrically connected to the negative current collector. Both the positive electrode ear and the negative electrode ear are led out of the outer package and used for electrical connection with the external circuit. It is used to charge and discharge the electrochemical device and monitor the internal working status of the electrochemical device.
  • the present application also provides an electronic device, which includes the electrochemical device as described above.
  • electronic devices include, but are not limited to: notebook computers, pen computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headsets, video recorders, LCD TV, portable cleaner, portable CD player, mini CD, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, backup power supply, motor, automobile, motorcycle, power-assisted bicycle, bicycle, lighting equipment , toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • Morphology and particle number ratio test Carl Zeiss ZEISS SIGMA-500 field emission scanning electron microscope was used to observe the morphology of the sample and test the crack width, average particle diameter and aspect ratio. Take SEM photos at a suitable magnification to observe whether there are cracks on the surface of the first single crystal particle. Use image processing software to randomly count the maximum width of the cracks on the surface of 10 first single crystal particles, and take the average value as the first single crystal particle.
  • Width of surface cracks h random statistics of the longest diameter and aspect ratio of 50 first single crystal particles, and take their average values as the average particle diameter D 1 and aspect ratio L 1 of the first single crystal particles; random statistics The longest diameter and aspect ratio of 50 second single crystal particles were averaged as the average particle diameter D 2 and aspect ratio L 2 of the second single crystal particle; the aspect ratio of 100 particles was randomly counted, Determine the total number of first single crystal particles and the total number of second single crystal particles, and obtain their respective proportions.
  • Element type and content testing The element type and content of the first single crystal particle and the second single crystal particle in the cathode material are tested by SEM-EDX; the element type and content of the cathode material as a whole are tested by inductively coupled plasma emission Spectrometer (ICP) for testing; the element types at the crack wall are processed by transferring the cathode material into a scanning electron microscope (model: FEI Vion Plasma FIB) equipped with a focused ion beam and can be used for transmission scanning electron microscopy (STEM, model: For samples analyzed by FEI Titan3 G2 60-300), the sample surface is required to be protected with Pt and processed with Ga ion beam.
  • a scanning electron microscope model: FEI Vion Plasma FIB equipped with a focused ion beam and can be used for transmission scanning electron microscopy (STEM, model: For samples analyzed by FEI Titan3 G2 60-300
  • the sample thickness does not exceed 100nm; and is cleaned in low voltage mode to remove the residual surface of the sample processing.
  • the volume particle size distribution of the cathode material is obtained through laser particle size analyzer testing, and the Dv10, Dv50 and Dv90 of the cathode material are obtained.
  • Capacity loss rate and thickness expansion rate after 7 days of storage at 60°C Charge the lithium-ion battery to 4.35V at a constant current of 0.2C at 25°C, so that the lithium-ion battery reaches a fully charged state (100% SOC), and then 0.2C constant current discharge to 2.8V, so that the lithium-ion battery reaches the full discharge state, and the discharge capacity at this time is recorded as the starting capacity; repeat the above charging process, so that the lithium-ion battery reaches the full charge state (100% SOC), use a micrometer Measure the thickness of the lithium-ion battery at this time as H0. Store the lithium-ion battery in an oven at 60°C for 7 days.
  • Capacity loss rate (initial capacity - recovery capacity after shelving)/initial capacity ⁇ 100%.
  • Thickness expansion ratio (H1-H0)/H0 ⁇ 100%.
  • the assembled button battery is charged and discharged at a cut-off voltage of 2.7 to 4.3V, at 25°C, with a current of 0.2C, and its gram capacity is tested.
  • Gram capacity discharge capacity/quality of positive electrode material.
  • High-temperature cycle capacity retention test At 45°C, charge to 4.35V with a constant current of 0.5C and discharge to 2.8V with a constant current of 1C. After 500 cycles, calculate the amount of electricity released in the 500th discharge compared with the first time. The ratio of discharge capacity is the high temperature cycle capacity retention rate.
  • the chemical formula of the nickel-containing hydroxide precursor is Ni y Co z Mn k (OH) 2 ;
  • the raw materials of the M elements Sr, Y, Ti, Zr, Nb, Al, and B are respectively represented by SrCO 3 , Y 2 O 3 , TiO 2 , ZrO 2 , Nb 2 O 5 , Al 2 O 3 , H 3 BO 3 exist;
  • the raw material of R element F exists as NH 4 F.
  • the nickel-containing hydroxide precursor, sodium carbonate, optional M element source and optional R element source Weigh and mix the nickel-containing hydroxide precursor, sodium carbonate, optional M element source and optional R element source to obtain a primary mixture, in which the molar ratio of Na element to metal elements other than Na is 1.05:1 , metal elements other than Na are proportioned according to Table 1; the primary mixture is sintered once to obtain the sodium precursor.
  • the primary sintering temperature is shown in Table 1, and the primary sintering time is 12h.
  • the secondary mixture is subjected to secondary sintering to obtain the primary product.
  • the secondary sintering temperature is shown in Table 1 and the secondary sintering time is 6 hours.
  • the primary product is put into deionized water and washed for 10 minutes according to the liquid-to-solid ratio of 1:1.
  • the solid-liquid separation is followed by drying to prepare a positive electrode material in which the first single crystal particles and the second single crystal particles are mixed.
  • Example 21 The difference between Example 21 and Example 4 is that lithium nitrate is used instead of lithium carbonate in the ion exchange step to promote the fusion and growth of small particles, and a cathode material containing only the first single crystal particles is screened.
  • Polyethylene (PE) porous polymer film is used as the isolation membrane.
  • the negative electrode slurry Mix the negative electrode material artificial graphite, the binder styrene-butadiene rubber and the thickener sodium carboxymethyl cellulose (abbreviated as CMC) in an appropriate amount of deionized water at a weight ratio of 96:2:2 to form a uniform
  • the negative electrode slurry ; apply the negative electrode slurry evenly on one surface of the negative electrode current collector copper foil, dry it, and repeat the above steps on the other surface of the copper foil to obtain a double-sided coated negative electrode sheet, which is evenly coated Cold pressing and cutting to obtain the negative electrode sheet.
  • the nickel-containing hydroxide precursor and mix it with lithium hydroxide to obtain a primary mixture, in which the molar ratio of Li element to metal elements other than Li is 1.05:1; perform primary sintering of the primary mixture to obtain the cathode material.
  • the primary sintering temperature is shown in Table 1, and the primary sintering time is 12h.
  • the molar percentages and calcination temperatures of each element in the cathode materials of each Example and Comparative Example 1 are as shown in Table 1. Among them, the molar percentage of each element is calculated based on the sum of the molar contents of Ni, Co, Mn and M elements being 100%.
  • the relevant parameters of the first single crystal particles and the second single crystal particles in the cathode material in each embodiment are as shown in Table 2.
  • the positive electrode active material includes first single crystal particles with an aspect ratio of 2 ⁇ L 1 ⁇ 5
  • the lithium ion battery is convenient.
  • the performance has been improved, especially the cycle performance and storage performance under high voltage and high temperature conditions.
  • the cathode material includes first single crystal particles with a first aspect ratio L 1.
  • the first single crystal particles have a high aspect ratio, which is beneficial to reducing the active crystals that cause side reactions on the surface of the cathode material. surface, inhibiting the structural phase change of the cathode material and the occurrence of interface side reactions, thereby helping to improve the cycle performance and storage performance of lithium-ion batteries under high voltage and high temperature conditions.
  • the first single crystal particles have cracks on the surface, which can improve the cycle performance and storage of lithium-ion batteries under high voltage and high temperature conditions. performance; the possible reason is that due to the high length-to-diameter ratio of the first single crystal particle, the stress and strain generated by the expansion and contraction caused by the deintercalation of lithium in the long diameter direction will be larger, and the cracks on the surface of the first single crystal particle will It can buffer the expansion and contraction of the first single crystal particles in the long diameter direction and reduce the risk of rupture of the first single crystal particles, thereby improving the cycle performance and storage performance of lithium-ion batteries under high voltage and high temperature conditions.
  • the M element can play a pillar role in the layered lithium-nickel composite oxide, suppressing lattice defects and structural collapse; on the other hand, the doping of M
  • the element and/or R element can improve the stability of the crystal structure of the first single crystal particle at the first crack, inhibit the phase change of the crystal structure and the occurrence of interface side reactions, thereby improving the performance of lithium-ion batteries at high voltage and high temperature. Cycling performance and storage performance under conditions.
  • Example 21 and Example 4 in Tables 1 to 3 it can be seen that the selection of lithium salt for ion exchange can regulate the proportion of small particles.
  • LiNO 3 is used as the lithium salt
  • the small particles crystallize into large particles. Pure large particle material was obtained.
  • the first single crystal particles with high aspect ratio and the second single crystal particles with low aspect ratio in Example 4 can form better particle accumulation, and the pressure The solid density is high, and a good conductive network can be formed at a higher compacted density, thereby increasing the gram capacity of the cathode material.

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Abstract

本申请公开了一种正极材料、电化学装置及电子设备。正极材料包括第一单晶颗粒；第一单晶颗粒具有第一长径比L1，L1满足2≤L1≤5。通过正极材料包括具有第一长径比L1的第一单晶颗粒，该第一单晶颗粒由于具有较高的长径比，有利于减少正极材料表面发生副反应的活性晶面，抑制正极材料的结构相变及界面副反应的发生，从而有助于提升电化学装置在高电压和高温条件下的循环性能和存储性能。

Description

正极材料、电化学装置及电子设备 技术领域
本申请涉及电化学技术领域，尤其涉及一种正极材料、电化学装置及电子设备。
背景技术
随着消费电子类的产品如笔记本电脑、手机、平板电脑、移动电源和无人机等的普及，对其中的电化学装置的要求越来越严格。例如，不仅要求电化学装置轻便，而且还要求电化学装置拥有高容量和较长的工作寿命。其中，锂离子电池凭借其具有能量密度高、安全性高、无记忆效应和工作寿命长等突出的优点已经在市场上占据主流地位。
为了追求更高的能量密度，锂离子电池一直在朝着提高电压、提高脱锂量的方向发展。同时，在实际使用过程中，不可避免的会存在高温工况。而在高电压、高脱锂量以及高温工况下，正极材料的表面释氧和结构相变的问题也充分暴露出来，带来电池循环跳水、产气等问题。
发明内容
有鉴于此，本申请提供一种正极材料、电化学装置及电子设备，以至少部分解决现有技术存在的上述问题。
第一方面，本申请提供了一种正极材料，所述正极材料包括第一单晶颗粒；所述第一单晶颗粒具有第一长径比L 1，L 1满足2≤L 1≤5。通过正极材料包括具有第一长径比L 1的第一单晶颗粒，该第一单晶颗粒由于具有较高的长径比，有利于减少正极材料表面发生副反应的活性晶面，抑制正极材料的结构相变及界面副反应的发生，从而有助于提升电化学装置在高电压和高温条件下的循环性能和存储性能。
在一些实施方式中，所述第一单晶颗粒表面具有第一裂纹。一方面，第一单晶颗粒表面的裂纹可使第一单晶颗粒具有更大的比表面积，以促进第一单晶颗粒内部锂离子的脱嵌，从而提升电化学装置的能量密度；另一方面，由于第一单晶颗粒长径比较高，在长径方向由于脱嵌锂导致的膨胀和收缩所产生的应力和应变将较大，通过第一单晶颗粒表面的裂纹，可缓冲第一单晶颗粒在长径方向的膨胀和收缩，降低第一单晶颗粒破裂的风险，从而提升电化学装置在高电压和高温条件下的循环性能和存储性能。
在一些实施方式中，所述第一单晶颗粒的平均粒径D 1为10μm至25μm。
在一些实施方式中，所述第一裂纹壁面包含P元素、F元素或N元素中的至少一种。第一裂纹内部包含P元素、F元素或N元素中的至少一种，可提高第一单晶颗粒于第一裂纹处晶体结构的稳定性，抑制该处晶体结构的相变以及界面副反应的发生，从而提升电化学装置在高电压和高温条件下的循环性能 和存储性能。
在一些实施方式中，所述第一裂纹的宽度h小于或等于0.1μm。第一裂纹的宽度h在上述范围内，有助于抑制界面副反应的发生，从而提升电化学装置在高电压和高温条件下的循环性能和存储性能。
在一些实施方式中，所述第一单晶颗粒包括第一锂镍复合氧化物。
在一些实施方式中，所述第一锂镍复合氧化物包括Ni元素、Na元素、可选的Co元素、可选的Mn元素、可选的M元素以及可选的R元素，所述M元素包括B、Mg、Al、Si、S、Ti、Cr、Fe、Cu、Zn、Ga、Y、Zr、Mo、Ag、W、In、Sn、Pb、Sb、V、Nb、La、Ge、Sr、Ca、Ba、Ta、Hf或Ce中的至少一种；所述R元素包括P、F或N中的至少一种。
在一些实施方式中，基于所述第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，所述第一锂镍复合氧化物中Na元素的摩尔百分含量为1％至10％。
在一些实施方式中，基于所述第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，所述第一锂镍复合氧化物中M元素的摩尔百分含量为0.1％至20％。
在一些实施方式中，基于所述第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，所述第一锂镍复合氧化物中R元素的摩尔百分含量为1％至10％。
在一些实施方式中，基于所述第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，所述第一锂镍复合氧化物中Ni元素的摩尔百分含量大于或等于50％。
在一些实施方式中，所述第一锂镍复合氧化物包括Li x1Na w1Ni y1Co z1Mn k1M q1O 2±aR a；其中，0.2≤x1≤1.2、0.5≤y1≤1、0≤z1≤0.5、0≤k1≤0.5、0≤q1≤0.2、0.01≤w1≤0.1以及0≤a≤0.1。
在一些实施方式中，所述正极材料还包括第二单晶颗粒；所述第二单晶颗粒具有第二长径比L 2，L 2满足1≤L 2＜2；所述第一单晶颗粒的数量为N 1，所述第二单晶颗粒的数量为N 2，其中，N 1/(N 1+N 2)的范围为20％至50％，N 2/(N 1+N 2)的范围为50％至80％。通过将第一单晶颗粒的数量N 1和第二单晶颗粒的数量N 2控制在上述范围内，有利于两者的相互嵌入和紧密堆积，从而提升电化学装置的能量密度。同时，由于低长径比的第二单晶颗粒的存在，能够减少由于压实后的高长径比第一单晶颗粒的晶格应力较大而产生的缺陷，进而改善电化学装置的高温循环和存储性能。
在一些实施方式中，所述第二单晶颗粒包括第二锂镍复合氧化物。
在一些实施方式中，所述第二锂镍复合氧化物包括Ni元素、Na元素、可选的Co元素、可选的Mn元素、可选的M’元素以及可选的R’元素；所述M’元素包括B、Mg、Al、Si、S、Ti、Cr、Fe、Cu、Zn、Ga、Y、Zr、Mo、Ag、W、In、Sn、Pb、Sb、V、Nb、La、Ge、Sr、Ca、Ba、Ta、Hf或Ce中的至少一种；所述R’元素包括P、F或N中的至少一种。
在一些实施方式中，基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中Na元素的摩尔百分含量为1％至10％。
在一些实施方式中，基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中M’元素的摩尔百分含量为0.1％至20％。
在一些实施方式中，基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中R’元素的摩尔百分含量为1％至10％。
在一些实施方式中，基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中Ni元素的摩尔百分含量大于或等于50％。
在一些实施方式中，所述第二锂镍复合氧化物包括Li x2Na w2Ni y2Co z2Mn k2M’ q2O 2±bR’ b；其中，0.2≤x2≤1.2、0.5≤y2≤1、0≤z2≤0.5、0≤k2≤0.5、0≤q2≤0.2、0.01≤w2≤0.1以及0≤b≤0.1。
在一些实施方式中，所述第二单晶颗粒的平均粒径D 2为2μm至8μm。
在一些实施方式中，9μm≤Dv50≤20μm，其中，Dv50为所述正极材料的体积粒度分布中累计达到50％时的粒径。
在一些实施方式中，(Dv90-Dv10)/Dv50≤2，其中，Dv90为所述正极材料的体积粒度分布中累计达到90％时的粒径，Dv10为所述正极材料的体积粒度分布中累计达到10％时的粒径，Dv50为所述正极材料的体积粒度分布中累计达到50％时的粒径。
在一些实施方式中，所述正极材料的XRD衍射图谱在18°到19.2°范围内(003)峰的半峰宽FWHM(003)满足：0.14°≤FWHM(003)≤0.2°。FWHM(003)在该范围内，锂镍复合氧化物中脱嵌锂的活性晶面的规整度较高，一方面，有利于锂镍复合氧化物内部锂离子的脱嵌，从而提高电化学装置的能量密度；另一方面，能够提高活性晶面的结构稳定性，抑制活性晶面晶体结构的相变和界面副反应的发生，从而提升电化学装置在高电压和高温条件下的循环性能和存储性能。
在一些实施方式中，所述正极材料的晶胞参数a满足：
Figure PCTCN2022112965-appb-000001
所述正极材料的晶胞参数c满足：
Figure PCTCN2022112965-appb-000002
此时，锂镍复合氧化物的层状结构稳定、有序性较好，有助于提升电化学装置在高电压和高温条件下的循环性能和存储性能。
在一些实施方式中，所述正极材料包括Li层和O层，所述Li层与所述O层的层间距范围为
Figure PCTCN2022112965-appb-000003
至
Figure PCTCN2022112965-appb-000004
Li-O层间距在上述范围内，能够促进锂离子的脱出和嵌入，从而提升电化学装置的能量密度。
第二方面，本申请提供一种电化学装置，其包括如上所述的正极材料。
第三方面，本申请提供一种电子设备，其包括如上所述的电化学装置。
本申请通过设置正极材料包括具有第一长径比L 1的第一单晶颗粒，该第一单晶颗粒由于具有较高的长径比，有利于减少正极材料表面发生副反应的活性晶面，抑制正极材料的结构相变及界面副反应的发生，从而有助于提升电化学装置在高电压和高温条件下的循环性能和存储性能。
附图说明
为了更清楚地说明本申请实施例中的技术方案，下面将对实施例描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域技术人员来讲，还可以根据这些附图获得其他的附图。
图1为本申请实施例7的正极材料粉末的SEM图；
图2为本申请实施例7的第一单晶颗粒表面具有第一裂纹的SEM图；
图3为本申请实施例7的正极材料的XRD衍射图谱；
图4为本申请实施例7的正极材料截面的SEM图像；
图5为图4中截面处Ni元素的SEM-EDX分布图；
图6为图4中截面处Co元素的SEM-EDX分布图；
图7为图4中截面处Na元素的SEM-EDX分布图。
具体实施方式
本申请的实施例将会被详细的描示在下文中。在此所描述的实施例为说明性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。
另外，有时在本文中以范围格式呈现量、比率和其它数值。应理解，此类范围格式是用于便利及简洁起见，且应灵活地理解，不仅包含明确地指定为范围限制的数值，而且包含涵盖于所述范围内的所有个别数值或子范围，如同明确地指定每一数值及子范围一般。
在具体实施方式及权利要求书中，由术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个元件或多个元件。项目B可包含单个元件或多个元件。项目C可包含单个元件或多个元件。
本申请提供一种正极材料，正极材料包括第一单晶颗粒；第一单晶颗粒具有第一长径比L 1，L 1满足2≤L 1≤5，其中，第一长径比为第一单晶颗粒的长径与短径之比，第一单晶颗粒的长径为电镜照片中第一单晶颗粒的最长直径，即距离最远的两个边缘点之间的距离，且该电镜照片中位于长径中垂线的两个边缘点之间的距离即为第一单晶颗粒的短径。通过正极材料包括具有第一长径比L 1的第一单晶颗粒，该第一单晶颗粒由于具有较高的长径比，有利于减少正极材料表面发生副反应的活性晶面，抑制正极材料的结构相变及界面副反应的发生，从而有助于提升电化学装置在高电压和高温条件下的循环性能和存储性能。
在一些实施例中，第一单晶颗粒表面具有第一裂纹。一方面，第一单晶颗粒表面的裂纹可使第一单 晶颗粒具有更大的比表面积，以促进第一单晶颗粒内部锂离子的脱嵌，从而提升电化学装置的能量密度；另一方面，由于第一单晶颗粒长径比较高，在长径方向由于脱嵌锂导致的膨胀和收缩所产生的应力和应变将较大，通过第一单晶颗粒表面的裂纹，可缓冲第一单晶颗粒在长径方向的膨胀和收缩，降低第一单晶颗粒破裂的风险，从而提升电化学装置在高电压和高温条件下的循环性能和存储性能。如图2所示，为本申请一实施例中第一单晶颗粒的表面具有第一裂纹的SEM图，从图2中可以看出第一单晶颗粒表面多处具有第一裂纹，其中一处第一裂纹的宽度为0.05μm，另一处第一裂纹的宽度为0.06μm。
在一些实施例中，第一裂纹壁面包含P元素、F元素或N元素中的至少一种。即第一裂纹内部的壁面表层包含P元素、F元素或N元素中的至少一种，可提高第一单晶颗粒于第一裂纹处晶体结构的稳定性，抑制该处晶体结构的相变以及界面副反应的发生，从而提升电化学装置在高电压和高温条件下的循环性能和存储性能。
在一些实施例中，第一裂纹的宽度h小于或等于0.1μm。例如，第一裂纹为非规则裂纹，非规则裂纹的最大宽度为0.1μm。第一裂纹的宽度小于或等于0.1μm，有助于抑制界面副反应的发生，从而提升电化学装置在高电压和高温条件下的循环性能和存储性能。
在一些实施例中，第一裂纹的深度与第一单晶颗粒粒径的比值小于或等于10％，以抑制界面副反应的发生，从而提升电化学装置在高电压和高温条件下的循环性能和存储性能。其中，第一单晶颗粒的粒径为第一单晶颗粒截面的最长直径。
在一些实施例中，所述第一单晶颗粒的平均粒径D 1为10μm至25μm。
在一些实施例中，第一单晶颗粒包括第一锂镍复合氧化物。在一些实施例中，所述第一锂镍复合氧化物包括Ni元素、Na元素、可选的Co元素、可选的Mn元素、可选的M元素以及可选的R元素，所述M元素包括B、Mg、Al、Si、S、Ti、Cr、Fe、Cu、Zn、Ga、Y、Zr、Mo、Ag、W、In、Sn、Pb、Sb、V、Nb、La、Ge、Sr、Ca、Ba、Ta、Hf或Ce中的至少一种；所述R元素包括P、F或N中的至少一种。在一些实施例中，第一锂镍复合氧化物包含Ni元素和Co元素，如图4所示，为本申请一实施例(也即后续实施例7)中正极材料截面的SEM图；图5为图4中截面处Ni元素的SEM-EDX分布图，图6为图4中截面处Co元素的SEM-EDX分布图。
在一些实施例中，基于第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，第一锂镍复合氧化物中Na元素的摩尔百分含量为1％至10％。图7为图4中截面处Na元素的SEM-EDX分布图。
在一些实施例中，基于第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，第一锂镍复合氧化物中M元素的摩尔百分含量为大于等于0.1％至20％。
在一些实施例中，基于第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，第一锂镍复合氧化物中R元素的摩尔百分含量为大于等于1％且小于等于10％。
在一些实施例中，基于第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，第一锂镍复合氧化物中Ni元素的摩尔百分含量大于或等于50％。
通过掺杂如上所述的Na元素、M元素或R元素可以调节正极材料的表面能，改善材料的烧结活性，促进烧结过程中晶粒度生长，降低材料表面副反应活性，提升材料表面稳定性，从而抑制正极材料在高温循环中的释氧产气。同时，在锂层掺杂高离子半径的元素，可增大锂层和氧层的层间距，提升了正极材料的动力学性能。
具体地，在一些实施例中，第一锂镍复合氧化物包括Li x1Na w1Ni y1Co z1Mn k1M q1O 2±aR a；其中，0.2≤x1≤1.2、0.5≤y1≤1、0≤z1≤0.5、0≤k1≤0.5、0≤q1≤0.2、0.01≤w1≤0.1以及0≤a≤0.1；M包括B、Mg、Al、Si、S、Ti、Cr、Fe、Cu、Zn、Ga、Y、Zr、Mo、Ag、W、In、Sn、Pb、Sb、V、Nb、La、Ge、Sr、Ca、Ba、Ta、Hf或Ce中的至少一种；R包括P、F或N中的至少一种。
在一些实施例中，所述正极材料还包括第二单晶颗粒；所述第二单晶颗粒具有第二长径比L 2，L 2满足1≤L 2＜2；其中，第二长径比为第二单晶颗粒的长径与短径之比，第二单晶颗粒的长径为电镜照片中第二单晶颗粒的最长直径，即距离最远的两个边缘点之间的距离，且该电镜照片中位于长径中垂线的两个边缘点之间的距离即为第二单晶颗粒的短径。如图1所示，为本申请一实施例(也即后续实施例7)中正极材料粉末的扫描电子显微镜(SEM)图。
在一些实施例中，所述第一单晶颗粒的数量为N 1，所述第二单晶颗粒的数量为N 2，其中，N 1/(N 1+N 2)的范围为20％至50％，N 2/(N 1+N 2)的范围为50％至80％。一方面，第二单晶颗粒具有较低的长径比，锂离子在第二单晶颗粒中的脱嵌路径较短，从而提升正极材料的动力学性能；另一方面，通过将第一单晶颗粒的数量N 1和第二单晶颗粒的数量N 2控制在上述范围内，有利于两者的相互嵌入和紧密堆积，从而提升电化学装置的能量密度。同时，由于低长径比的第二单晶颗粒的存在，能够减少由于压实后的高长径比第一单晶颗粒的晶格应力较大而产生的缺陷，进而改善电化学装置的高温循环和存储性能。典型但非限制性的，N 1/(N 1+N 2)可以为20％、25％、30％、35％、40％、45％、50％以及这些点值中的任意两个构成的范围及范围中的任意值；N 2/(N 1+N 2)可以为50％、55％、60％、65％、70％、75％、80％以及这些点值中的任一两个构成的范围及范围中的任意值。
在一些实施例中，所述第二单晶颗粒包括第二锂镍复合氧化物。在一些实施例中，所述第二锂镍复合氧化物包括Ni元素、Na元素、可选的Co元素、可选的Mn元素、可选的M’元素以及可选的R’元素；所述M’元素包括B、Mg、Al、Si、S、Ti、Cr、Fe、Cu、Zn、Ga、Y、Zr、Mo、Ag、W、In、Sn、Pb、Sb、V、Nb、La、Ge、Sr、Ca、Ba、Ta、Hf或Ce中的至少一种；所述R’元素包括P、F或N中的至少一种。
在一些实施例中，基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中Na元素的摩尔百分含量为1％至10％。
在一些实施例中，基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中M’元素的摩尔百分含量为0.1％至20％。
在一些实施例中，基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中R’元素的摩尔百分含量为1％至10％。
在一些实施例中，基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中Ni元素的摩尔百分含量大于或等于50％。
在一些实施例中，所述第二锂镍复合氧化物包括Li x2Na w2Ni y2Co z2Mn k2M’ q2O 2±bR’ b；其中，0.2≤x2≤1.2、0.5≤y2≤1、0≤z2≤0.5、0≤k2≤0.5、0≤q2≤0.2、0.01≤w2≤0.1以及0≤b≤0.1；M’包括B、Mg、Al、Si、S、Ti、Cr、Fe、Cu、Zn、Ga、Y、Zr、Mo、Ag、W、In、Sn、Pb、Sb、V、Nb、La、Ge、Sr、Ca、Ba、Ta、Hf或Ce中的至少一种；R’包括P、F或N中的至少一种。
在一些实施例中，所述第二单晶颗粒的平均粒径D 2为2μm至8μm。
在一些实施例中，9μm≤Dv50≤20μm，其中，Dv50为所述正极材料的体积粒度分布中累计达到50％时的粒径。
在一些实施例中，(Dv90-Dv10)/Dv50≤2，其中，Dv90为所述正极材料的体积粒度分布中累计达到90％时的粒径，Dv10为所述正极材料的体积粒度分布中累计达到10％时的粒径，Dv50为所述正极材料的体积粒度分布中累计达到50％时的粒径。满足上述关系，可防止正极材料颗粒的粒度分布范围过宽，而导致正极材料压实密度过小。
在一些实施例中，正极材料的XRD衍射图谱在18°到19.2°范围内(003)峰的半峰宽FWHM(003)满足：0.14°≤FWHM(003)≤0.2°，FWHM(003)在该范围内，锂镍复合氧化物中脱嵌锂的活性晶面的规整度较高，一方面，有利于锂镍复合氧化物内部锂离子的脱嵌，从而提高电化学装置的能量密度；另一方面，能够提高活性晶面的结构稳定性，抑制活性晶面晶体结构的相变和界面副反应的发生，从而提升电化学装置在高电压和高温条件下的循环性能和存储性能。如图3所示，为本申请一实施例(即后续实施例7)中的正极材料的XRD衍射图谱，18°到19.2°范围内正极材料的(003)峰的半峰宽FWHM为0.152°。
在一些实施例中，正极材料的晶胞参数a满足：
Figure PCTCN2022112965-appb-000005
正极材料的晶胞参数c满足：
Figure PCTCN2022112965-appb-000006
此时，锂镍复合氧化物的层状结构稳定、有序性较好，有助于提升电化学装置在高电压和高温条件下的循环性能和存储性能。
在一些实施例中，正极材料包括Li层和O层，且Li层与O层的层间距范围为
Figure PCTCN2022112965-appb-000007
至
Figure PCTCN2022112965-appb-000008
Li-O层间距在上述范围内，能够促进锂离子的脱出和嵌入，从而提升电化学装置的能量密度。
本申请实施例还提供了一种电化学装置，包括正极片、负极片、隔膜、电解液和外包装。
正极片包括正极集流体和正极活性层，正极活性层设于正极集流体的至少一个表面上，正极活性层 包括如上所述的正极材料。本申请的正极集流体没有特别限制，正极集流体可以为本领域公知的任何正极集流体，如铝箔、铝合金箔或复合集流体等。
正极活性层还包括导电剂和粘结剂。本申请对导电剂的材料不做限定，例如，导电剂包括但不限于碳纳米管、碳纤维、导电炭黑、乙炔黑、石墨烯、科琴黑中的至少一种。本申请对粘结剂的材料不做限定，例如，粘结剂包括但不限于聚偏氟乙烯、偏氟乙烯-六氟丙烯的共聚物、聚酰胺、聚丙烯腈、聚丙烯酸酯、聚丙烯酸、聚丙烯酸盐、羧甲基纤维素钠、聚乙烯呲咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯、聚六氟丙烯、丁苯橡胶中的至少一种。其中，在制备正极片时，将粘结剂、导电剂以及正极材料加入溶剂中，混合均匀，获得正极浆料，将正极浆料涂布于正极集流体表面，干燥正极浆料后对其辊压获得正极活性层，正极活性层的压实密度大于等于3.5g/cc。
负极片包括负极集流体和负极活性层，负极活性层设于负极集流体的至少一个表面上，负极活性层包括负极材料。本申请的负极片没有特别限制，负极材料可以为现有技术的任何负极材料，负极材料包括石墨、硬碳、软碳、硅、硅碳或硅氧化物等中的至少一种；负极集流体可以为本领域公知的任何负极集流体，如铜箔、铝箔、铝合金箔或复合集流体等。
本申请的隔膜没有特别限制，例如，隔膜可包括由对本申请的电解液稳定的材料制得，使电解液内的离子可从隔膜穿过，以使电解液内的离子能够在正极片和负极片之间活动，例如隔膜可包括聚乙烯(PE)等。
隔膜设于正极片和负极片之间，其中，负极片、隔膜和正极片可沿负极片厚度方向依次层叠设置或绕卷设置，并容置于外包装的内部空间。
本申请的电解液没有特别限制，可以使用本领域公知的任何电解液，电解液可以是凝胶态、固态和液态中的任一种。当电解液为液态电解液时，液态电解液包括锂盐和非水溶剂。锂盐没有特别限制，可以使用本领域公知的任何锂盐，只要能实现本申请的目的即可，例如，锂盐可以包括LiTFSI、LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3或LiPO 2F 2等中的至少一种。非水溶剂没有特别限定，只要能实现本申请的目的即可，例如，非水溶剂可以包括碳酸酯化合物、羧酸酯化合物、醚化合物、腈化合物或其它有机溶剂等中的至少一种，碳酸酯化合物可以包括碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)、碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)、碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯或碳酸三氟甲基亚乙酯等中的至少一种。
电化学装置还包括正极耳和负极耳，正极耳与正集流体电性连接，负极耳与负集流体电性连接，且正极耳和负极耳均引出外包装并用于与外部电路电性连接，以对电化学装置进行充放电，以及用于监测 电化学装置内部工作状态。
本申请还提供了一种电子装置，所述电子装置包含如上所述的电化学装置。
本申请实施例的电子装置没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，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、家庭用大型蓄电池和锂离子电容器等。
以下将以电化学装置为锂离子电池为例，结合具体实施例对本申请作进一步详细的说明。
一、锂离子电池性能测试方法
(1)形貌及颗粒数占比测试：采用卡尔蔡司ZEISS SIGMA-500型场发射扫描电子显微镜对样品进行形貌观察以及裂纹宽度、平均粒径和长径比的测试。在合适的倍率下拍摄SEM照片，观察第一单晶颗粒表面是否存在裂纹，使用图像处理软件，随机统计10个第一单晶颗粒表面裂纹的最大宽度，取其平均值作为第一单晶颗粒表面裂纹的宽度h；随机统计50个第一单晶颗粒的最长直径和长径比，分别取其平均值作为第一单晶颗粒的平均粒径D 1和长径比L 1；随机统计50个第二单晶颗粒的最长直径和长径比，分别取其平均值作为第二单晶颗粒的平均粒径D 2和长径比L 2；随机统计100个颗粒的长径比，确定第一单晶颗粒总数以及第二单晶颗粒总数，得出各自占比。
(2)元素种类及含量测试：正极材料中第一单晶颗粒和第二单晶颗粒各自的元素种类和含量通过SEM-EDX进行测试；正极材料整体的元素种类和含量采用电感耦合等离子体发射光谱仪(ICP)进行测试；裂纹壁面处的元素种类，通过将正极材料转移至配备聚焦离子束的扫描电镜(型号：FEI Vion Plasma FIB)腔体内，加工得到可用于透射扫描电镜(STEM，型号：FEI Titan3 G2 60-300)分析的样品，要求样品表面用Pt保护，并且用Ga离子束加工，样品厚度不超过100nm；并且用低电压模式进行清洗，除去样品加工的残留表面。将样品在STEM下观察，在合适的倍率下利用EDX功能对裂纹壁面处进行数据采集，确定裂纹壁面处的元素种类。
(3)XRD测试：将正极材料样品保持表面平整，放置在XRD测试仪器(型号布鲁克，D8)样品台中，使用2°/min的扫描速率，扫描角度范围10°至90°，得到XRD图谱。
(4)粒度测试：通过激光粒度仪测试获得正极材料的体积粒度分布，得到正极材料的Dv10、Dv50和Dv90。
(5)60℃存储7天容量损失率和厚度膨胀率：将锂离子电池在25℃下以0.2C恒流充电至4.35V，使锂离子电池达到满充状态(100％SOC)，再以0.2C恒流放电至2.8V，使锂离子电池达到满放状态，记录此时的放电容量为起始容量；重复上述充电流程，使锂离子电池达到满充状态(100％SOC)，利用千分 尺测量此时锂离子电池的厚度为H0，将锂离子电池搁置于60℃烘箱中存储7天，冷却至25℃后利用千分尺测量此时锂离子电池的厚度为H1，然后在25℃下采用0.2C的电流重复上述充放电流程3次，测量第3次锂离子电池的放电容量记为搁置后恢复容量。
容量损失率＝(起始容量-搁置后恢复容量)/起始容量×100％。
厚度膨胀率＝(H1-H0)/H0×100％。
(6)扣电测试：将正极片的一面正极活性层用N-甲基吡咯烷酮(NMP)清洗干净，85℃真空烘烤2h，冲切2025扣式电池所需的小圆片，按照泡沫镍、锂片、隔离膜、正极圆片，组装成扣式电池，注入50微升的电解液，电解液的组成为EC：PC：DEC质量比＝1：1：1，且电解液中LiPF 6的质量浓度为12.5％。
将组装好的扣式电池在2.7至4.3V截止电压下，在25℃条件下，0.2C电流充放电，测试其克容量，克容量＝放电容量/正极材料的质量。
(7)高温循环容量保持率测试：在45℃下，以0.5C恒流充电至4.35V后以1C恒流放电至2.8V，循环500次后，计算第500次放电所放出的电量与初次放电容量的比值，即为高温循环容量保持率。
二、锂离子电池的制备方法
其中，以下各实施例中，含镍氢氧化物前驱体，化学式为Ni yCo zMn k(OH) 2；M元素Sr、Y、Ti、Zr、Nb、Al、B的原料分别对应地以SrCO 3、Y 2O 3、TiO 2、ZrO 2、Nb 2O 5、Al 2O 3、H 3BO 3存在；R元素F的原料以NH 4F存在。
(1)正极材料的制备
(1a)钠前驱体的制备
称取含镍氢氧化物前驱体、碳酸钠、可选的M元素源以及可选的R元素源混合，获得一次混合料，其中，Na元素与除Na以外金属元素的摩尔比为1.05：1，除Na以外金属元素按表1配比；将一次混合料进行一次烧结，得到钠前驱体。其中，一次烧结温度参见表1，一次烧结时间为12h。
(1b)离子交换
称取钠前驱体和碳酸锂混合获得二次混合料，其中，钠前驱体中钠元素的摩尔量与碳酸锂中锂元素的摩尔量之比为1:10。将二次混合料进行二次烧结，得到初级产品，其中，二次烧结温度参见表1，二次烧结时间为6h；冷却后将初级产品按照液固比1:1投入去离子水中洗涤10min，固液分离后烘干，制得第一单晶颗粒与第二单晶颗粒混合的正极材料。
其中，实施例21与实施例4的区别在于，在离子交换步骤中采用硝酸锂替代碳酸锂，促进小颗粒融并生长，并筛选得到仅含第一单晶颗粒的正极材料。
(3)正极片的制备
将正极材料、导电剂导电炭黑(Super P)、粘结剂聚偏氟乙烯(PVDF)按照98：1：1的重量比混合，然后加入适量的N-甲基吡咯烷酮(简写为NMP)作为溶剂，充分搅拌混合均匀，调配成固含量为75％ 的正极浆料。然后将正极浆料均匀涂覆在正极集流体铝箔的一个表面上，80℃烘干，在铝箔的另一个表面上重复以上步骤，得到双面涂覆的正极片，之后经冷压、裁切，得到正极片。
(4)隔离膜的制备
以聚乙烯(PE)多孔聚合薄膜作为隔离膜。
(5)负极片的制备
将负极材料人造石墨、粘结剂丁苯橡胶和增稠剂羧甲基纤维素钠(简写为CMC)按照96：2：2的重量比在适量的去离子水中充分搅拌混合，使其形成均匀的负极浆料；将负极浆料均匀涂覆在负极集流体铜箔的一个表面上，烘干，在铜箔的另一个表面上重复以上步骤，得到双面涂覆的负极片，均匀涂覆冷压、裁切，得到负极片。
(6)锂离子电池的制备
将制得的正极片、隔离膜、负极片按顺序叠好，使隔离膜处于正极片和负极片之间起到隔离的作用，然后卷绕得到裸电芯。将裸电芯置于外包装铝塑膜中，留下注液口，从注液口灌注电解液(电解液的组成为EC：PC：DEC质量比＝1：1：1，且电解液中LiPF 6的质量浓度为12.5％)，经过真空封装、静置、化成、整形等工序，即完成锂离子电池的制备。
对比例1
称取含镍氢氧化物前驱体与氢氧化锂混合，获得一次混合料，其中，Li元素与除Li以外金属元素的摩尔比为1.05：1；将一次混合料进行一次烧结，得到正极材料。其中，一次烧结温度参见表1，一次烧结时间为12h。
各实施例和对比例1的正极材料中各元素的摩尔百分含量和煅烧温度如表1所示。其中，各元素的摩尔百分含量均以Ni、Co、Mn和M元素的摩尔含量之和为100％计。
表1
Figure PCTCN2022112965-appb-000009
Figure PCTCN2022112965-appb-000010
各实施例中正极材料中的第一单晶颗粒和第二单晶颗粒相关参数如表2所示。
表2
Figure PCTCN2022112965-appb-000011
Figure PCTCN2022112965-appb-000012
各实施例中锂离子电池的性能测试结果如表3所示。
表3
Figure PCTCN2022112965-appb-000013
根据表1至表3中对比例1和实施例1-21的结果可以看出，当正极活性材料中包括2≤长径比L 1≤5 的第一单晶颗粒时，锂离子电池各方便的性能均得到提升，特别是在高电压和高温条件下的循环性能和存储性能。这是由于，通过正极材料包括具有第一长径比L 1的第一单晶颗粒，该第一单晶颗粒由于具有较高的长径比，有利于减少正极材料表面发生副反应的活性晶面，抑制正极材料的结构相变及界面副反应的发生，从而有助于提升锂离子电池在高电压和高温条件下的循环性能和存储性能。
根据表1至表3中实施例1-3和实施例4-5的结果可以看出，第一单晶颗粒表面具有裂纹，可以提升锂离子电池在高电压和高温条件下的循环性能和存储性能；可能的原因在于，由于第一单晶颗粒长径比较高，在长径方向由于脱嵌锂导致的膨胀和收缩所产生的应力和应变将较大，第一单晶颗粒表面的裂纹，可缓冲第一单晶颗粒在长径方向的膨胀和收缩，降低第一单晶颗粒破裂的风险，从而提升锂离子电池在高电压和高温条件下的循环性能和存储性能。
根据表1至表3中实施例1-5和实施例6-20的结果可以看出，当制备正极活性材料时，向其中掺杂M元素(Sr、Y、Ti、Zr、Nb、Al、B)和/或R元素(F)等掺杂元素中的一种或多种时，能够进一步提升锂离子电池在高电压和高温条件下的循环性能和存储性能。这是由于，掺杂M元素和/或R元素，一方面，M元素可以在层状锂镍复合氧化物中起到支柱的作用，抑制晶格缺陷和结构坍塌；另一方面，掺杂M元素和/或R元素，可提高第一单晶颗粒于第一裂纹处晶体结构的稳定性，抑制该处晶体结构的相变以及界面副反应的发生，从而提升锂离子电池在高电压和高温条件下的循环性能和存储性能。
根据表1至表3中实施例21和实施例4的结果可以看出，离子交换的锂盐选择可以调控小颗粒的占比，当采用LiNO 3作为锂盐时，小颗粒结晶成大颗粒，得到纯大颗粒材料，对比实施例21，由于级配的改善，实施例4中高长径比的第一单晶颗粒和低长径比的第二单晶颗粒能够形成较好的颗粒堆积，压实密度较高，在较高的压实密度下，也能够形成良好的导电网络，从而提高正极材料的克容量。同时，由于低长径比的第二单晶颗粒的存在，能够减少由于压实后的高长径比第一单晶颗粒的晶格应力较大而产生的缺陷，进而改善锂离子电池的高温循环和存储性能。
尽管已经演示和描述了说明性实施例，本领域技术人员应该理解上述实施例不能被解释为对本申请的限制，并且可以在不脱离本申请的精神、原理及范围的情况下对实施例进行改变，替代和修改。

Claims (10)

  1. 一种正极材料，其特征在于，所述正极材料包括第一单晶颗粒；
    所述第一单晶颗粒具有第一长径比L 1，L 1满足2≤L 1≤5。
  2. 根据权利要求1所述的正极材料，其特征在于，所述正极材料满足下列条件中的至少一者：
    (1)所述第一单晶颗粒表面具有第一裂纹；
    (2)所述第一单晶颗粒的平均粒径D 1为10μm至25μm。
  3. 根据权利要求2所述的正极材料，其特征在于，所述正极材料满足下列条件中的至少一者：
    (1)所述第一裂纹壁面包含P元素、F元素或N元素中的至少一种；
    (2)所述第一裂纹的宽度h小于或等于0.1μm。
  4. 根据权利要求1所述的正极材料，其特征在于，所述第一单晶颗粒包括第一锂镍复合氧化物，所述第一锂镍复合氧化物包括Ni元素、Na元素、可选的Co元素、可选的Mn元素、可选的M元素以及可选的R元素，所述M元素包括B、Mg、Al、Si、S、Ti、Cr、Fe、Cu、Zn、Ga、Y、Zr、Mo、Ag、W、In、Sn、Pb、Sb、V、Nb、La、Ge、Sr、Ca、Ba、Ta、Hf或Ce中的至少一种；所述R元素包括P、F或N中的至少一种；所述正极材料满足下列条件中的至少一者：
    (1)基于所述第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，所述第一锂镍复合氧化物中Na元素的摩尔百分含量为1％至10％；
    (2)基于所述第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，所述第一锂镍复合氧化物中M元素的摩尔百分含量为0.1％至20％；
    (3)基于所述第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，所述第一锂镍复合氧化物中R元素的摩尔百分含量为1％至10％；
    (4)基于所述第一锂镍复合氧化物中Ni元素、Co元素、Mn元素和M元素的总摩尔量，所述第一锂镍复合氧化物中Ni元素的摩尔百分含量大于或等于50％；
    (5)所述第一锂镍复合氧化物包括Li x1Na w1Ni y1Co z1Mn k1M q1O 2±aR a；其中，0.2≤x1≤1.2、0.5≤y1≤1、0≤z1≤0.5、0≤k1≤0.5、0≤q1≤0.2、0.01≤w1≤0.1以及0≤a≤0.1。
  5. 根据权利要求1所述的正极材料，其特征在于，所述正极材料还包括第二单晶颗粒；所述第二单晶颗粒具有第二长径比L 2，L 2满足1≤L 2＜2；
    所述第一单晶颗粒的数量为N 1，所述第二单晶颗粒的数量为N 2，其中，N 1/(N 1+N 2)的范围为20％至50％， N 2/(N 1+N 2)的范围为50％至80％。
  6. 根据权利要求5所述的正极材料，其特征在于，所述第二单晶颗粒包括第二锂镍复合氧化物，所述第二锂镍复合氧化物包括Ni元素、Na元素、可选的Co元素、可选的Mn元素、可选的M’元素以及可选的R’元素；所述M’元素包括B、Mg、Al、Si、S、Ti、Cr、Fe、Cu、Zn、Ga、Y、Zr、Mo、Ag、W、In、Sn、Pb、Sb、V、Nb、La、Ge、Sr、Ca、Ba、Ta、Hf或Ce中的至少一种；所述R’元素包括P、F或N中的至少一种；所述正极材料满足下列条件中的至少一者：
    (1)基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中Na元素的摩尔百分含量为1％至10％；
    (2)基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中M’元素的摩尔百分含量为0.1％至20％；
    (3)基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中R’元素的摩尔百分含量为1％至10％；
    (4)基于所述第二锂镍复合氧化物中Ni元素、Co元素、Mn元素和M’元素的总摩尔量，所述第二锂镍复合氧化物中Ni元素的摩尔百分含量大于或等于50％；
    (5)所述第二锂镍复合氧化物包括Li x2Na w2Ni y2Co z2Mn k2M’ q2O 2±bR’ b；其中，0.2≤x2≤1.2、0.5≤y2≤1、0≤z2≤0.5、0≤k2≤0.5、0≤q2≤0.2、0.01≤w2≤0.1以及0≤b≤0.1。
  7. 根据权利要求5所述的正极材料，其特征在于，所述正极材料满足下列条件中的至少一者：
    (1)所述第二单晶颗粒的平均粒径D 2为2μm至8μm。
    (2)9μm≤Dv50≤20μm，其中，Dv50为所述正极材料的体积粒度分布中累计达到50％时的粒径；
    (3)(Dv90-Dv10)/Dv50≤2，其中，Dv90为所述正极材料的体积粒度分布中累计达到90％时的粒径，Dv10为所述正极材料的体积粒度分布中累计达到10％时的粒径，Dv50为所述正极材料的体积粒度分布中累计达到50％时的粒径。
  8. 根据权利要求1所述的正极材料，其特征在于，所述正极材料满足下列条件中的至少一者：
    (1)所述正极材料的XRD衍射图谱在18°到19.2°范围内(003)峰的半峰宽FWHM(003)满足：0.14°≤FWHM(003)≤0.2°；
    (2)所述正极材料的晶胞参数a满足：
    Figure PCTCN2022112965-appb-100001
    所述正极材料的晶胞参数c满足：
    Figure PCTCN2022112965-appb-100002
    (3)所述正极材料包括Li层和O层，所述Li层与所述O层的层间距范围为
    Figure PCTCN2022112965-appb-100003
    至
    Figure PCTCN2022112965-appb-100004
  9. 一种电化学装置，其包括根据权利要求1-8中任一项所述的正极材料。
  10. 一种电子设备，其包括根据权利要求9所述的电化学装置。
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KR20190032119A (ko) * 2017-09-19 2019-03-27 주식회사 엘지화학 리튬 이차전지용 양극 활물질, 이의 제조방법, 이를 포함하는 리튬 이차전지용 양극 및 리튬 이차전지
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