WO2022077333A1 - 正极材料、电化学装置和电子设备 - Google Patents

正极材料、电化学装置和电子设备 Download PDF

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WO2022077333A1
WO2022077333A1 PCT/CN2020/121139 CN2020121139W WO2022077333A1 WO 2022077333 A1 WO2022077333 A1 WO 2022077333A1 CN 2020121139 W CN2020121139 W CN 2020121139W WO 2022077333 A1 WO2022077333 A1 WO 2022077333A1
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positive electrode
peak
aluminum oxide
lithium cobalt
electrode material
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PCT/CN2020/121139
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English (en)
French (fr)
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吴霞
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宁德新能源科技有限公司
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Priority to CN202080020022.8A priority Critical patent/CN113597693B/zh
Priority to PCT/CN2020/121139 priority patent/WO2022077333A1/zh
Publication of WO2022077333A1 publication Critical patent/WO2022077333A1/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
    • H01M4/52—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
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/16—Oxides
    • C30B29/22—Complex oxides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the technical field of electrochemistry, and in particular, to a positive electrode material, an electrochemical device and an electronic device.
  • electrochemical devices eg, lithium-ion batteries
  • electrochemical devices eg, lithium-ion batteries
  • an important way is to increase the voltage of electrochemical devices.
  • the cathode materials of electrochemical devices have unstable crystal structure at high voltage, the capacity decays rapidly, and the cycle performance is greatly reduced.
  • the cathode material of the present application includes lithium cobalt aluminum oxide of P6 3 mc crystal phase, and the intensity ratio ⁇ of the 002 peak and the 101 peak satisfies 3.9 ⁇ 5, which improves the crystal structure of the cathode material while ensuring the capacity of the cathode material. stability, thereby improving the cycling performance and storage performance of electrochemical devices.
  • Embodiments of the present application provide a positive electrode material, comprising:
  • Lithium cobalt aluminum oxide, lithium cobalt aluminum oxide has a P6 3 mc crystal phase structure
  • the diffraction angle corresponding to the 002 peak is between 17.5° and 19°.
  • the particles of lithium cobalt aluminum oxide have a porous structure and/or have gaps.
  • the lithium cobalt aluminum oxide includes primary particles, and the aspect ratio r of the primary particles satisfies 0 ⁇ r ⁇ 0.1.
  • the lithium cobalt aluminum oxide includes: Li x Na z Co 1-y A ly M m O 2 ;
  • M includes at least one of Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr or Zr one.
  • the positive electrode includes a current collector and a positive electrode active material layer disposed on the current collector, and the positive electrode active material layer includes any one of the above-mentioned positive electrode materials.
  • the specific surface area of the positive electrode material layer is 0.2 m 2 /g to 2 m 2 /g.
  • the X-ray diffraction pattern of the active material in the state of 0% SOC, includes a first diffraction peak and a second diffraction peak in the range of 16°-19°, and the angle of the first diffraction peak is greater than that of the second diffraction peak. Angle.
  • Embodiments of the present application also provide an electronic device, including the electrochemical device according to any one of the above.
  • the positive electrode material of the present application includes lithium cobalt aluminum oxide with a P6 3 mc crystal phase structure, and the intensity ratio of the 002 peak to the 101 peak in the X-ray diffraction pattern of the lithium cobalt aluminum oxide is ⁇ , 3.9 ⁇ 5, so,
  • the lithium ion in the positive electrode material has a fast diffusion rate and a stable crystal structure, which can stabilize the crystal structure while ensuring the capacity of the positive electrode material, thereby improving the cycle performance and storage performance of the electrochemical device.
  • FIG. 1 is a scanning electron microscope image of particles of a lithium cobalt aluminum oxide according to an embodiment of the present application.
  • FIG. 2 is a scanning electron microscope image of particles of another lithium cobalt aluminum oxide according to an embodiment of the present application.
  • FIG. 3 is a scanning electron microscope image of another lithium cobalt aluminum oxide according to an embodiment of the present application.
  • FIG. 4 is an X-ray diffraction pattern of a positive electrode material of an electrochemical device according to an embodiment of the present application in a state of 0% SOC.
  • Example 5 is an X-ray diffraction diagram of the positive electrode material in Example 1-1 of the present application.
  • Figure 6 is the X-ray diffraction pattern of the positive electrode material in Examples 1-5 of the present application.
  • the lithium cobalt oxide cathode material widely used in electrochemical devices has the R-3m crystal phase structure, and its theoretical capacity is 273.8mAh/g, which has good cycle performance and safety performance.
  • the material market occupies an important position.
  • lithium cobalt oxide materials are developing in the direction of high voltage.
  • lithium cobalt oxide materials have a capacity of only 190mAg/g when the charging voltage is 4.5V.
  • lithium ions are extracted from the crystal structure of lithium cobalt oxide to improve the capacity of lithium cobalt oxide materials, but with the further increase of voltage, lithium ions are extracted from the crystal structure of lithium cobalt oxide will lead to a series of irreversible phase transitions, making cobalt oxide
  • the cycle performance and storage performance of lithium cobalt oxide materials are greatly reduced, and the interfacial side reactions increase at high voltages, the dissolution of cobalt metal is serious, the decomposition of electrolyte increases, and the capacity attenuation of lithium cobalt oxide materials is very serious.
  • the structural stability of lithium cobalt oxide materials with R-3m crystal phase structure is improved by doping lithium cobalt oxide materials with metal cations such as Al, Mg, Ti, Zn, and Ni.
  • the irreversible phase transition of lithium materials improves the structural stability of lithium cobalt oxide materials, but when the voltage reaches 4.6V and above, the effect of this method to stabilize the crystal structure decreases, and doping will lead to a large increase in the capacity loss of lithium cobalt oxide materials.
  • the crystal structure of the cathode material cannot be stabilized while maintaining the high capacity of the cathode material, especially when the voltage reaches 4.6V, the stability of the crystal structure of the cathode material decreases and the capacity decays rapidly.
  • the positive electrode material of the present application includes lithium cobalt aluminum oxide of P6 3 mc crystal phase, and the intensity ratio of the 002 peak and the 101 peak is limited, which improves the stability of the crystal structure of the positive electrode material while ensuring the capacity of the positive electrode material, thereby improving the electrical conductivity. Cycling and storage performance of chemical devices.
  • a positive electrode material comprising: lithium cobalt aluminum oxide.
  • the lithium cobalt aluminum oxide has a P6 3 mc crystal phase structure, and the X-ray diffraction pattern of the lithium cobalt aluminum oxide has the 002 peak corresponding to the (002) crystal plane and the 101 peak corresponding to the (101) crystal plane.
  • the intensity is I 002
  • the intensity of the 101 peak is I 101
  • I 002 /I 101 ⁇ , where 3.9 ⁇ 5.
  • Lithium cobalt aluminum oxide has HCP (Hexagonal Closepacked Structure, hexagonal close-packed) oxygen structure, which contains Co-O bonds and Al-O bonds. As the number of Al-O bonds increases, the charge-discharge capacity of lithium cobalt aluminum oxide increases. There will be no obvious loss; and there are lithium vacancies in the crystal structure of the material, and lithium ions are released during the delithiation process.
  • the lithium cobalt aluminum oxide is very friendly to the electrolyte due to its special oxygen structure, the interface stability is very friendly to the electrolyte, the catalytic effect on the electrolyte is small, and the decomposition risk of the electrolyte is small. , so the structural stability can be ensured under high voltage (eg 4.6V), and its charge cut-off voltage can be as high as 4.8V.
  • the cathode material in this application has high structural stability due to the special crystal phase structure and excellent interfacial stability of lithium cobalt aluminum oxide, and can maintain a high capacity, thereby improving the Cycling performance and storage performance at high voltages (eg, 4.6V-4.8V) of electrochemical devices.
  • the diffraction angle corresponding to the 002 peak is between 17.5°-19°.
  • the 002 peak corresponds to the 002 crystal plane of lithium cobalt aluminum oxide, and its corresponding diffraction angle reflects the spacing of the 002 crystal plane.
  • the diffraction angle of the 002 peak is between 17.5° and 19°, it reflects the oxidation of lithium cobalt aluminum oxide.
  • the crystal phase structure of the material is in a stable state, which is beneficial to improve the cycle performance and storage performance of electrochemical devices at high voltages (eg, 4.6V).
  • the diffraction angle corresponding to the 101 peak is between 37° and 39°.
  • the particles of lithium cobalt aluminum oxide have a porous structure.
  • the particles of lithium cobalt aluminum oxide have gaps. For the lithium cobalt aluminum oxide particles, when they have a pore structure and/or a gap, they can fully infiltrate with the electrolyte and fully absorb the electrolyte.
  • the addition of aluminum element in the lithium cobalt aluminum oxide affects the morphology of the lithium cobalt aluminum oxide, so that the lithium cobalt aluminum oxide has a specific horizontal and vertical direction and increases the active lithium sites.
  • the lithium cobalt aluminum oxide includes primary particles, and the aspect ratio r of the primary particles satisfies 0 ⁇ r ⁇ 0.1.
  • the particles of the lithium cobalt aluminum oxide include secondary particles formed by the aggregation of the primary particles, and the morphology of the secondary particles can affect the lithium cobalt aluminum oxide.
  • the lithium cobalt aluminum oxide comprises: Li x Na z Co 1-y A ly M m O 2 ; wherein, 0.6 ⁇ x ⁇ 0.93, 0 ⁇ y ⁇ 0.15, 0 ⁇ z ⁇ 0.02 , 0 ⁇ m ⁇ 0.02, M includes at least one of Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr or Zr.
  • M includes at least one of Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr or Zr.
  • the cycle performance and stability of the positive electrode material are better.
  • the positive electrode material can ensure good cycle performance and storage performance at the same time.
  • Some embodiments of the present application also provide an electrochemical device, the electrochemical device includes: a positive electrode, a negative electrode, and a separator, and the separator is arranged between the positive electrode and the negative electrode.
  • the positive electrode includes a current collector and a positive electrode active material layer provided on the current collector, and the positive electrode active material layer includes any one of the above-mentioned positive electrode materials.
  • the specific surface area of the positive electrode material layer is 0.2 m 2 /g-2 m 2 /g. In some embodiments, when the specific surface area is in the above range, the cycle performance of the electrochemical device is the best.
  • the X-ray diffraction pattern of the cathode material in the state of 0% SOC (State Of Charge, state of charge), includes the first diffraction peak in the range of 16°-19° and the second diffraction peak, the angle of the first diffraction peak is greater than the angle of the second diffraction peak.
  • the number of diffraction peaks in the range of 16°-19° in the X-ray diffraction pattern of the X-ray diffraction pattern before the charge-discharge cycle was originally one, and at 0% SOC state , that is, in the fully discharged state, the number of diffraction peaks in the X-ray diffraction pattern of the cathode material in the range of 16°-19° has changed from one to two, which indicates that the cathode material has undergone a phase change during the cycle of the electrochemical device. , so that there are two different crystal phase structures in the cathode material, and the existence of the first diffraction peak and the second diffraction peak indicates the coexistence of two phases in the electrochemical device during the cycle.
  • the peak position difference D1 between the first diffraction peak and the second diffraction peak satisfies 1° ⁇ D1 ⁇ 2°.
  • the peak intensity ratio D2 of the second diffraction peak and the first diffraction peak satisfies 0 ⁇ D2 ⁇ 1.
  • the peak intensity ratio of the second diffraction peak and the first diffraction peak indicates the ratio of the content of the two phases in the cathode material after the phase transition occurs, since the content of the two phases changes with cycling of the electrochemical device.
  • the full width at half maximum FWHM1 of the second diffraction peak satisfies 0 ⁇ FWHM1 ⁇ 1; in some embodiments of the present application, the full width at half maximum FWHM2 of the first diffraction peak satisfies 0 ⁇ FWHM2 ⁇ 0.5.
  • the full width at half maximum FWHM1 of the second diffraction peak satisfies 0 ⁇ FWHM1 ⁇ 1; in some embodiments of the present application, the full width at half maximum FWHM2 of the first diffraction peak satisfies 0 ⁇ FWHM2 ⁇ 0.5.
  • the interlayer spacing of the two phases is different, and the number of atoms on each atomic layer is different.
  • the positive electrode current collector may use Al foil, and of course, other positive electrode current collectors commonly used in the art may also be used.
  • the thickness of the cathode current collector may be 4 ⁇ m-50 ⁇ m.
  • the positive electrode active material layer may only be coated on a partial area of the positive electrode current collector.
  • the thickness of the positive electrode active material layer may be 5 ⁇ m ⁇ 50 ⁇ m. It should be understood that these are exemplary only and other suitable thicknesses may be employed.
  • the release membrane includes at least one of polyethylene, polypropylene, polyvinylidene fluoride, polyethylene terephthalate, polyimide, or aramid.
  • the polyethylene includes at least one selected from high density polyethylene, low density polyethylene or ultra-high molecular weight polyethylene. Especially polyethylene and polypropylene, they have a good effect on preventing short circuits and can improve the stability of the battery through the shutdown effect.
  • the thickness of the isolation film is in the range of about 5 ⁇ m to 500 ⁇ m.
  • the surface of the isolation membrane may further include a porous layer, the porous layer is disposed on at least one surface of the isolation membrane, the porous layer includes inorganic particles and a binder, and the inorganic particles are selected from aluminum oxide (Al 2 O 3 ), Silicon oxide (SiO 2 ), magnesium oxide (MgO), titanium oxide (TiO 2 ), hafnium dioxide (HfO 2 ), tin oxide (SnO 2 ), ceria (CeO 2 ), nickel oxide (NiO), oxide Zinc (ZnO), calcium oxide (CaO), zirconium oxide (ZrO 2 ), yttrium oxide (Y 2 O 3 ), silicon carbide (SiC), boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or sulfuric acid at least one of barium.
  • the pores of the isolation membrane have diameters in the range of about 0.01 ⁇ m to 1 ⁇ m.
  • the binder of the porous layer is selected from polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, sodium carboxymethyl cellulose, polyamide At least one of vinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the porous layer on the surface of the separator can improve the heat resistance, oxidation resistance and electrolyte wettability of the separator, and enhance the adhesion between the separator and the pole piece.
  • the electrode assembly of the electrochemical device is a wound electrode assembly or a stacked electrode assembly.
  • the electrochemical device includes a lithium-ion battery, although the present application is not so limited.
  • the electrochemical device may also include an electrolyte.
  • the electrolyte may be one or more of a gel electrolyte, a solid electrolyte, and an electrolytic solution, and the electrolytic solution includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF6, LiBF4 , LiAsF6, LiClO4 , LiB ( C6H5 ) 4 , LiCH3SO3 , LiCF3SO3 , LiN ( SO2CF3 ) 2 , LiC ( SO2CF3 ) 3 , LiSiF 6 , LiBOB or one or more of lithium difluoroborate.
  • LiPF 6 is chosen as the lithium salt because it can give high ionic conductivity and improve cycle characteristics.
  • the non-aqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.
  • the carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.
  • chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl esters (MEC) and combinations thereof.
  • chain carbonate compounds are diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl carbonate Ethyl esters (MEC) and combinations thereof.
  • Examples of the cyclic carbonate compound are ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylethylene carbonate (VEC), or a combination thereof.
  • fluorocarbonate compound examples include fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonate -Difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, trifluoromethylethylene carbonate, or a combination thereof.
  • FEC fluoroethylene carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate Fluoroethylene, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-carbonate -Difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene
  • carboxylate compounds are methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, decolactone, Valerolactone, mevalonolactone, caprolactone, methyl formate, or a combination thereof.
  • ether compounds are dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxy Ethane, 2-methyltetrahydrofuran, tetrahydrofuran, or a combination thereof.
  • organic solvents examples include dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, methyl amide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphate esters or combinations thereof.
  • Embodiments of the present application also provide electronic devices including the above electrochemical devices.
  • the electronic device in the embodiment of the present application is not particularly limited, and it may be used in any electronic device known in the prior art.
  • electronic devices may include, but are not limited to, notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, assisted bicycles, bicycles, Lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large-scale household storage batteries and lithium-ion capacitors, etc.
  • the embodiment of the present application also proposes a method for preparing a positive electrode material, which can be used to prepare any of the above-mentioned positive electrode materials, and the preparation method includes the following steps:
  • the precursor of M element doped (Co 1-y A ly M m ) 3 O 4 was synthesized by liquid-phase precipitation and sintering.
  • soluble cobalt salts for example, cobalt chloride, cobalt acetate, cobalt sulfate, cobalt nitrate etc.
  • M salt eg, sulfate, etc.
  • a precipitant eg: sodium carbonate
  • complexing agent for example: ammonia water
  • lithium-containing molten salt eg, lithium nitrate, lithium chloride, lithium hydroxide, etc.
  • Preparation of positive electrode Dissolve the positive electrode material, conductive agent conductive carbon black, and binder polyvinylidene fluoride in N-methylpyrrolidone (NMP) solution in a weight ratio of 97:1.4:1.6 to form a positive electrode slurry.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry was coated on the positive electrode current collector with a coating weight of 17.2 mg/cm 2 , and the positive electrode was obtained after drying, cold pressing, cutting and welding tabs.
  • negative electrode active material The negative electrode active material, acrylic resin, and sodium carboxymethyl cellulose are dissolved in deionized water in a weight ratio of 95:4.0:1.0 to form a negative electrode active material layer slurry, wherein the negative electrode active material is artificial.
  • Graphite and silicon were mixed in a weight ratio of 9:1.
  • a 10 ⁇ m thick copper foil was used as the negative electrode current collector, the negative electrode slurry was coated on the negative electrode current collector with a coating weight of 6.27 mg/cm 2 , dried to obtain a negative electrode active material layer, and the negative electrode was obtained by cutting and welding the tabs.
  • the isolation film substrate is polyethylene (PE) with a thickness of 8 ⁇ m, and a 2 ⁇ m alumina ceramic layer is coated on both sides of the isolation film substrate for drying.
  • PE polyethylene
  • Preparation of lithium ion battery stack the positive electrode, the separator and the negative electrode in sequence, so that the separator is placed between the positive electrode and the negative electrode for isolation, and then the electrode assembly is obtained by winding.
  • the electrode assembly is placed in the outer packaging aluminum-plastic film, and after dehydration at 80°C, the above electrolyte is injected and packaged, and the lithium ion battery is obtained through the process of forming, degassing, and trimming.
  • Examples 1-2 to 1-8, Comparative Examples 1-1 to 1-5, Comparative Examples 2-1 to 2-7 and Comparative Examples 3-1 to 3-11 are based on the steps of Example 1-1
  • the difference between each embodiment and the comparative example is only in the positive electrode material used, and the specific positive electrode material used is shown in Table 1 to Table 3 below.
  • the first charge and discharge are performed, and constant current charging is performed at a charging current of 0.5C (that is, the current value that completely discharges the theoretical capacity within 2h) until the upper limit voltage is 4.8V; then, in Perform constant current discharge at a discharge current of 0.5C until the final voltage is 3V, record the discharge capacity of the first cycle; continue to the Nth charge and discharge cycle (where N can be determined according to actual needs), record the Nth cycle discharge capacity.
  • the capacity decay rate and capacity retention rate after the Nth cycle of the lithium-ion battery are calculated according to the following formulas:
  • the capacity decay rate after the Nth cycle (discharge capacity at the first cycle ⁇ discharge capacity at the Nth cycle)/discharge capacity at the first cycle ⁇ 100%.
  • Capacity retention rate after the Nth cycle discharge capacity at the Nth cycle/discharge capacity at the first cycle ⁇ 100%.
  • the positive electrode material was processed by an ion polishing machine (JEOL-IB-09010CP) to obtain a cross section.
  • the cross-section was photographed with a scanning electron microscope at a magnification of not less than 5.0K to obtain a particle image, and holes and cracks could be observed on the cross-sectional image.
  • the selection requirements for holes are: when the ratio of the longest axis of the closed area to the longest axis of the particle in a single particle is not higher than 10%, and the difference between the longest axis and the shortest axis of the closed area is less than 0.5 microns, it meets the counting requirements. the holes;
  • the requirements for the selection of cracks are as follows: when the ratio of the longest axis of the closed region to the longest axis of the particle in a single particle is not less than 70%, it is a crack that meets the counting requirements.
  • the selection method of the long and short axes connect any two points in the closed area, the longest distance is the longest axis, and the shortest distance is the shortest axis.
  • a closed area refers to an area enclosed by closed lines in a graph, and the line connecting any point inside the closed area and any point outside the area intersects the boundary of the area.
  • the powder of positive electrode material is analyzed and tested by iCAP7000 ICP detector;
  • NMP can be used to dissolve the polar piece, the powder is filtered and dried, and the iCAP7000 ICP detector is used for elemental analysis and testing.
  • test equipment is: BSD-BET400; test process: put the sample into a system filled with N2 gas, and the surface of the material undergoes physical adsorption at the temperature of liquid nitrogen.
  • test process put the sample into a system filled with N2 gas, and the surface of the material undergoes physical adsorption at the temperature of liquid nitrogen.
  • the physical adsorption is in equilibrium, by measuring the adsorption pressure and the flow rate of the adsorbed gas at equilibrium, the adsorption capacity of the monomolecular layer of the material can be obtained, thereby calculating the specific surface area of the sample
  • X-ray diffraction test Bruker D8 ADVANCE was used to obtain the XRD diffraction pattern of the cathode material.
  • Examples 1-1 to 1-8, Comparative Examples 1-1 to 1-5, Comparative Examples 2-1 to 2-7, and Comparative Examples 3-1 to 3-11 The positive electrode materials all satisfy the chemical formula Li x Na z Co 1-y A ly M m O 2 , and the comparative examples 1-6 have the R-3m crystal phase structure.
  • Table 1 shows the positive electrode materials and test results used in Examples 1-1 to 1-9, and Comparative Examples 1-1 to 1-5.
  • Example 1-1 By defining Li x Na z Co 1-y A ly M m O 2 to Example 1-9, the ratio of I 002 /I 101 is in the range of 3.9 to 5, compared to Comparative Example 1-1 to Comparative Example 1 -2 and Comparative Examples 1-4 can improve the capacity retention rate for 100 cycles while ensuring the discharge capacity of the first cycle. This is because the lithium ion diffusion rate is the fastest when the ratio of I 002 /I 101 is in the range of 3.9 to 5. And the crystal structure is the most stable.
  • Table 2 shows the positive electrode materials and test results used in Example 1-1, Example 2-1 to Example 2-6.
  • Example 1-1 and Example 2-5 By comparing Example 1-1 and Example 2-5 to Example 2-6, it can be seen that the capacity retention rate corresponding to Li x Na z Co 1-y A ly M m O 2 in Example 1-1 for 100 cycles is obvious higher than that of Examples 2-5 to 2-6, because the Li x Na z Co 1-y A ly M m O 2 particles of Example 1-1 have both holes and gaps, which can fully infiltrate the electrolyte, And effectively release the stress in the process of delithiation and intercalation, thereby improving the stability of the crystal structure and ensuring the cycle performance.
  • Example 2-1 By comparing Example 2-1 and Examples 2-3 to 2-4, it can be seen that when the aspect ratio r of Li x Na z Co 1-y A y M m O 2 satisfies 0 ⁇ r ⁇ 0.1, the electrochemical device The higher capacity retention rate after 100 cycles is due to the fact that the aspect ratio of the particles affects the morphology of the particles, and the morphology of the particles affects the ratio of I 002 /I 101 in the cathode material.
  • Table 3 shows the positive electrode materials and test results used in Examples 1-1, 1-5, 1-8, and Comparative Examples 3-1 to 3-11.

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Abstract

本申请提出了正极材料、电化学装置和电子设备。正极材料包括：锂钴铝氧化物，锂钴铝氧化物具有P63mc晶相结构；锂钴铝氧化物的X射线衍射图谱中具有对应于(002)晶面的002峰和对应于(101)晶面的101峰，002峰的强度为I002，101峰的强度为I 101，I002/I101＝η，其中，3.9<η<5。本申请提出的正极材料中的锂离子扩散速度快，且晶体结构稳定，能够在保证正极材料容量的同时稳定晶体结构，从而提高电化学装置的循环性能和存储性能。

Description

正极材料、电化学装置和电子设备 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、电化学装置和电子设备。
背景技术
随着电化学装置(例如，锂离子电池)的发展和进步，对其容量提出了越来越高的要求。为了提高电化学装置的容量，一个重要的途径是提高电化学装置的电压，然而电化学装置的正极材料在高电压下晶体结构不稳定，容量快速衰减，循环性能大幅降低。
发明内容
本申请的正极材料中包括P6 3mc晶相的锂钴铝氧化物，并且002峰和101峰的强度比η满足3.9<η<5，在保证正极材料容量的同时提高了正极材料晶体结构的稳定性，从而提升了电化学装置的循环性能和存储性能。
本申请的实施例提供了一种正极材料，包括：
锂钴铝氧化物，锂钴铝氧化物具有P6 3mc晶相结构；
锂钴铝氧化物的X射线衍射图谱中具有对应于(002)晶面的002峰和对应于(101)晶面的101峰，002峰的强度为I 002，101峰的强度为I 101，I 002/I 101＝η，其中，3.9<η<5。
在上述正极材料中，002峰对应的衍射角位于17.5°-19°之间。
在上述正极材料中，锂钴铝氧化物的颗粒具有孔洞结构和/或具有缝隙。
在上述正极材料中，锂钴铝氧化物包括：一次颗粒，一次颗粒的横纵比r满足0<r<0.1。
在上述正极材料中，锂钴铝氧化物包括：Li xNa zCo 1-yAl yM mO 2；
其中，0.6<x<0.93，0<y<0.15，0≤z<0.02，0≤m<0.02，M包括Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr或Zr中的至少一个。
本申请的实施例提供了一种电化学装置，包括：
正极；
负极；
隔离膜，设置在正极和负极之间；
其中，正极包括集流体和设置在集流体上的正极活性物质层，正极活性物质层包括上述任一项的正极材料。
在上述电化学装置中，正极材料层的比表面积为0.2m 2/g-2m 2/g。
在上述电化学装置中，在0％SOC状态下，活性材料的X射线衍射图谱在16°-19°范围内包含第一衍射峰和第二衍射峰，第一衍射峰角度大于第二衍射峰的角度。
在上述电化学装置中，满足如下条件(a)-(d)中的至少一个：
(a)第一衍射峰与第二衍射峰的峰位差D1满足1°≤D1≤2°；
(b)第二衍射峰与第一衍射峰的峰强比D2满足0＜D2＜1；
(c)第二衍射峰的半高宽FWHM1满足0＜FWHM1＜1；
(d)第一衍射峰的半高宽FWHM2满足0＜FWHM2＜0.5。
本申请的实施例还提供了一种电子装置，包括上述任一项的电化学装置。
本申请正极材料中包括具有P6 3mc晶相结构的锂钴铝氧化物，锂钴铝氧化物的X射线衍射图谱中002峰与101峰的强度比为η，3.9<η<5，如此，正极材料中的锂离子扩散速度快，且晶体结构稳定，能够在保证正极材料容量的同时稳定晶体结构，从而提高电化学装置的循环性能和存储性能。
附图说明
结合附图并参考以下具体实施方式，本申请各实施例的上述和其他特征、优点及方面将变得更加明显。贯穿附图中，相同或相似的附图标记表示相同或相似的元素。应当理解附图是示意性的，元件和元素不一定按照比例绘制。
图1是本申请实施例的一种锂钴铝氧化物的颗粒的扫描电镜图。
图2是本申请实施例的另一种锂钴铝氧化物的颗粒的扫描电镜图。
图3是本申请实施例的另一种锂钴铝氧化物的扫描电镜图。
图4是本申请实施例的一种电化学装置在0％SOC状态时正极材料的X射线衍射图。
图5是本申请实施例1-1中正极材料的X射线衍射图；
图6是本申请实施例1-5中正极材料的X射线衍射图.
具体实施方式
下面的实施例可以使本领域技术人员更全面地理解本申请，但不以任何方式限制本申请。
目前，电化学装置(例如，锂离子电池)中广泛使用的钴酸锂正极材料为R-3m晶相结构，其理论容量为273.8mAh/g，其具有良好的循环性能和安全性能，在正极材料市场占有重要地位。为了获得更高的比能量，钴酸锂材料正在朝着高电压的方向发展，目前钴酸锂材料在充电电压为4.5V时，容量也仅仅达到190mAg/g，人们尝试通过从钴酸锂材料的晶体结构中脱出更多的锂离子从而提高钴酸锂材料的容量，但随着电压的进一步升高，锂离子从钴酸锂的晶体结构中脱出将导致一系列不可逆的相变，使得钴酸锂材料的循环性能和存储性能大大降低，并且在高电压下界面副反应增加，钴金属溶出严重，电解液分解增加，钴酸锂材料的容量衰减十分严重。
一些技术中通过采用Al、Mg、Ti、Zn、Ni等金属阳离子对钴酸锂材料进行掺杂从而提高R-3m晶相结构的钴酸锂材料的结构稳定性，这些金属阳离子通过推迟钴酸锂材料不可逆相变从而提高钴酸锂材料的结构稳定性，但当电压达到4.6V及以上时，该方法稳定晶体结构的效果下降，并且掺杂会导致钴酸锂材料的容量损失大幅增加。
现有技术中，无法在保持正极材料的高容量的同时稳定晶体结构，特别是在电压达到4.6V的情况下，正极材料晶体结构的稳定性下降，容量快速衰减。
本申请正极材料中包括P6 3mc晶相的锂钴铝氧化物，并限定002峰和101峰的强度比，在保证正极材料容量的同时提高了正极材料晶体结构的稳定性，从而提升了电化学装置的循环性能和存储性能。
在本申请的一些实施例中，提出一种正极材料，包括：锂钴铝氧化物。锂钴铝氧化物具有P6 3mc晶相结构，锂钴铝氧化物的X射线衍射图谱中具有对应于(002)晶面的002峰和对应于(101)晶面的101峰，002峰的强度为I 002，101峰的强度为I 101，I 002/I 101＝η，其中，3.9<η<5。
本申请发明人发现，正极材料中P6 3mc晶相结构的锂钴铝氧化物在3.9<η<5时，材料中锂离子的扩散速率快，且晶体结构稳定。锂钴铝氧化物具有HCP(Hexagonal Closepacked Structure，密排六方)氧结构，其中包含Co-O键和Al-O键，随着Al-O键的数量增加，锂钴铝氧化物的充放电容量不会出现明显损失；并且该材料晶体结构中存在锂空位，在脱锂过程中脱出锂离子，打开锂离子通道后可以在嵌锂过程中容纳额外的锂离子，从而保障锂钴铝氧化物本身的容量；此外，在电压达到4.6V的情况下，该锂钴铝氧化物由于其特殊的氧结构，其界面稳定对电解液十分友好，对电解液的催化作用小，电解液的分解风险小，因此可以在高电压(例如4.6V)下保证结构稳定性，其充电截止电压可高达4.8V。由上可知，本申请中的正极材料，由于锂钴铝氧化物特殊的晶相结构和优异的界面稳定性，使其具有较高的结构稳定性，并且可以保持较高的容量，从而能够提高电化学装置的高电压(例如4.6V-4.8V)下的循环性能和存储性能。
在本申请的一些实施例中，002峰对应的衍射角位于17.5°-19°之间。002峰对应于锂钴铝氧化物的002晶面，其对应的衍射角反应了002晶面的间距，当002峰的衍射角位于17.5°-19°之间时，其反应了锂钴铝氧化物的晶相结构处于稳定的状态，有利于提高电化学装置在高电压(例如4.6V)下的循环性能和存储性能。
在本申请的一些实施例中，101峰对应的衍射角位于37°-39°之间。请参考图1和图2，在本申请的一些实施例中，锂钴铝氧化物的颗粒具有孔洞结构。在本申请的一些实施例中，锂钴铝氧化物的颗粒具有缝隙。对于锂钴铝氧化物颗粒，当其具有孔洞结构和/或缝隙时，能够与电解液充分浸润，充分吸收电解液。并且，当锂钴铝氧化物在高电压(例如4.8V及以上)进行充放电循环时，可以通过孔洞结构和/或缝隙释放锂离子脱嵌和嵌入过程中形成的巨大应力，抑制颗粒层间的不可逆的滑移，从而提高晶体的结构稳定性，改善循环性能。
在本申请的一些实施例中，锂钴铝氧化物中铝元素的加入影响锂钴铝氧化物的形貌，使锂钴铝氧化物具有特定的横纵，增加活性锂位。
在本申请的一些实施例中，请参考图3，锂钴铝氧化物包括：一次颗粒，一次颗粒的横纵比r满足0<r<0.1。一些实施例中，一次颗粒的横纵比在0-0.1 之间时，锂钴铝氧化物的颗粒包含由一次颗粒聚集形成的二次颗粒，二次颗粒的形貌可影响锂钴铝氧化物的101峰和002峰的强度比。
在本申请的一些实施例中，锂钴铝氧化物包括：Li xNa zCo 1-yAl yM mO 2；其中，0.6<x<0.93，0<y<0.15，0≤z<0.02，0≤m<0.02，M包括Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr或Zr中的至少一个。一些实施例中，在锂钴铝氧化物包括上述化学式的化合物时，正极材料的循环性能和稳定性能较好，在一些实施例中，当0≤y<0.025时，0.005≤z<0.02；当0.025≤y<0.1时，0≤z<0.005，在上述范围内，正极材料可同时保证良好的循环性能和存储性能。
本申请的一些实施例中还提出一种电化学装置，电化学装置包括：正极、负极以及隔离膜，隔离膜设置在正极和负极之间。正极包括集流体和设置在集流体上的正极活性物质层，正极活性物质层包括上述中任一项的正极材料。
在一些实施例中，正极材料层的比表面积为0.2m 2/g-2m 2/g。一些实施例中，比表面积在上述范围时，电化学装置的循环性能最好。
在本申请的一些实施例中，请参看图4，在0％SOC(State Of Charge，荷电状态)状态下，正极材料的X射线衍射图谱在16°-19°范围内包含第一衍射峰和第二衍射峰，第一衍射峰的角度大于第二衍射峰的角度。对于本实施例中提出的电化学装置中的正极材料，在未充放电循环前其X射线衍射图在16°-19°范围内的衍射峰的个数原本为一个，在0％SOC状态下，即满放状态下，正极材料的X射线衍射图在16°-19°范围内的衍射峰的个数由一个变为两个，这表明电化学装置在循环过程中正极材料发生了相变，使得正极材料中具有两种不同晶相结构的材料，第一衍射峰和第二衍射峰的存在表明了电化学装置在循环过程中存在两相共存。
在本申请的一些实施例中，第一衍射峰与第二衍射峰的峰位差D1满足1°≤D1≤2°。在本申请的一些实施例中，第二衍射峰与第一衍射峰的峰强比D2满足0＜D2＜1。一些实施例中，第二衍射峰和第一衍射峰的峰强比表明了发生相变之后正极材料中两相的含量的比值，由于两相含量随着电化学装置的循环而发生变化。
在本申请的一些实施例中，第二衍射峰的半高宽FWHM1满足0＜FWHM1＜1；在本申请的一些实施例中，第一衍射峰的半高宽FWHM2满足 0＜FWHM2＜0.5。在0％SOC状态下，正极材料中两相共存，两相的层间距不同，且各个原子层上的原子数量不同。
在一些实施例中，正极集流体可以采用Al箔，当然，也可以采用本领域常用的其他正极集流体。在一些实施例中，正极集流体的厚度可以为4μm-50μm。在一些实施例中，正极活性物质层可以仅涂覆在正极集流体的部分区域上。在一些实施例中，正极活性物质层的厚度可以为5μm～50μm。应该理解，这些仅是示例性的，可以采用其他合适的厚度。
在一些实施例中，隔离膜包括聚乙烯、聚丙烯、聚偏氟乙烯、聚对苯二甲酸乙二醇酯、聚酰亚胺或芳纶中的至少一种。例如，聚乙烯包括选自高密度聚乙烯、低密度聚乙烯或超高分子量聚乙烯中的至少一种。尤其是聚乙烯和聚丙烯，它们对防止短路具有良好的作用，并可以通过关断效应改善电池的稳定性。在一些实施例中，隔离膜的厚度在约5μm～500μm的范围内。
在一些实施例中，隔离膜表面还可以包括多孔层，多孔层设置在隔离膜的至少一个表面上，多孔层包括无机颗粒和粘结剂，无机颗粒选自氧化铝(Al 2O 3)、氧化硅(SiO 2)、氧化镁(MgO)、氧化钛(TiO 2)、二氧化铪(HfO 2)、氧化锡(SnO 2)、二氧化铈(CeO 2)、氧化镍(NiO)、氧化锌(ZnO)、氧化钙(CaO)、氧化锆(ZrO 2)、氧化钇(Y 2O 3)、碳化硅(SiC)、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。在一些实施例中，隔离膜的孔具有在约0.01μm～1μm的范围的直径。多孔层的粘结剂选自聚偏氟乙烯、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、聚四氟乙烯或聚六氟丙烯中的至少一种。隔离膜表面的多孔层可以提升隔离膜的耐热性能、抗氧化性能和电解质浸润性能，增强隔离膜与极片之间的粘接性。
在本申请的一些实施例中，电化学装置的电极组件为卷绕式电极组件或堆叠式电极组件。
在一些实施例中，电化学装置包括锂离子电池，但是本申请不限于此。在一些实施例中，电化学装置还可以包括电解质。电解质可以是凝胶电解质、固态电解质和电解液中的一种或多种，电解液包括锂盐和非水溶剂。 锂盐选自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、LiSiF 6、LiBOB或者二氟硼酸锂中的一种或多种。例如，锂盐选用LiPF 6，因为它可以给出高的离子导电率并改善循环特性。
非水溶剂可为碳酸酯化合物、羧酸酯化合物、醚化合物、其它有机溶剂或它们的组合。
碳酸酯化合物可为链状碳酸酯化合物、环状碳酸酯化合物、氟代碳酸酯化合物或其组合。
链状碳酸酯化合物的实例为碳酸二乙酯(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)及其组合。所述环状碳酸酯化合物的实例为碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)或者其组合。所述氟代碳酸酯化合物的实例为碳酸氟代亚乙酯(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、碳酸三氟甲基亚乙酯或者其组合。
羧酸酯化合物的实例为乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯、甲瓦龙酸内酯、己内酯、甲酸甲酯或者其组合。
醚化合物的实例为二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、乙氧基甲氧基乙烷、2-甲基四氢呋喃、四氢呋喃或者其组合。
其它有机溶剂的实例为二甲亚砜、1,2-二氧戊环、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、甲酰胺、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯、磷酸三辛酯、和磷酸酯或者其组合。
本申请的实施例还提供了包括上述电化学装置的电子装置。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，电子装置可以包括，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。
本申请的实施例中还提出一种正极材料的制备方法，其可以用于制备上述任一的正极材料，该制备方法包括如下步骤：
采用液相沉淀加烧结的方法合成M元素掺杂的(Co 1-yAl yM m) 3O 4前躯体，首先将可溶性钴盐(例如，氯化钴、醋酸钴、硫酸钴、硝酸钴等)和M盐(例如，硫酸盐等)按比例Co：Al：M＝(1-y):y：m溶入溶剂(例如，去离子水)中，加入沉淀剂(例如：碳酸钠)和络合剂(例如：氨水)，调节pH(例如，将pH值调节到5-9)，使之沉淀；然后对沉淀物进行烧结，研磨获得(Co 1-yAl yM m) 3O 4粉体。最后，将(Co 1-yAl yM m) 3O 4粉体与Na 2CO 3按预设化学计量比(例如：n：1-y)在700℃-900℃、空气气氛中反应36-48h，得到Na nCo 1-yAl yM mO 2，其中，0.6<x<0.93，0<y<0.15，0.6≤n<1，0≤m<0.02。
采用Na nCo 1-yAl yM mO 2作为前躯体，将其与含锂熔盐(例如，硝酸锂、氯化锂、氢氧化锂等)按比例优选Na：Li＝1：5混合均匀，在200℃-400℃、空气气氛中反应2h-8h，反应物经去离子水多次洗涤，待熔盐清洗干净，烘干粉体得到具有HCP氧结构的Li xNa zCo 1-yAl yM mO 2，0.6<x<0.93，0<y<0.15，0≤z<0.02，0≤m<0.02。反应物经去离子水多次洗涤，待熔盐清洗干净，烘干粉体得到正极材料。
下面列举了一些具体实施例和对比例以更好地对本申请进行说明，其中，采用锂离子电池作为示例。
实施例1-1
正极的制备：将正极材料、导电剂导电炭黑、粘结剂聚偏二氟乙烯按重量比97：1.4：1.6的比例溶于N-甲基吡咯烷酮(NMP)溶液中，形成正极浆料。采用铝箔作为正极集流体，将正极浆料涂覆于正极集流体上，涂布重量为17.2mg/cm 2，经过干燥、冷压、裁切焊接极耳后得到正极。
负极的制备：将负极活性材料、丙烯酸树脂、和羧甲基纤维素钠按重量比95：4.0：1.0的比例溶于去离子水中，形成负极活性物质层浆料，其中，负极活性材料中人造石墨和硅按照重量比9：1进行混合。采用10μm厚度铜箔作为负极集流体，将负极浆料涂覆于负极集流体上，涂布重量为6.27mg/cm 2，干燥得到负极活性物质层，经裁切、焊接极耳后得到负极。
隔离膜的制备：隔离膜基材为8μm厚的聚乙烯(PE)，在隔离膜基材的两侧各涂覆2μm氧化铝陶瓷层烘干。
电解液的制备：在含水量小于10ppm的环境下，将六氟磷酸锂与非水有机溶剂(碳酸乙烯酯(EC)：碳酸二乙酯(DEC)：碳酸亚丙酯(PC)：丙酸丙酯(PP)：氟代碳酸乙烯酯(FEC)＝20：30：20：28：2，重量比)按重量比8：92配制以形成电解液。
锂离子电池的制备：将正极、隔离膜、负极按顺序依次叠好，使隔离膜处于正极和负极中间起到隔离的作用，并卷绕得到电极组件。将电极组件置于外包装铝塑膜中，在80℃下脱去水分后，注入上述电解液并封装，经过化成，脱气，切边等工艺流程得到锂离子电池。
实施例1-2到1-8，对比例1-1到1-5、对比例2-1到2-7和对比例3-1到3-11是在实施例1-1步骤的基础上进行，各个实施例和对比例的区别仅在于所采用的正极材料不同，具体采用的正极材料如下表1至表3所示。
下面描述本申请的各个参数的测试方法。
容量衰减率/保持率测试：
在25℃的环境中，进行第一次充电和放电，在0.5C(即2h内完全放掉理论容量的电流值)的充电电流下进行恒流充电，直到上限电压为4.8V；然后，在0.5C的放电电流下进行恒流放电，直到最终电压为3V，记录首次循环的放电容量；继续进行到第N次充电和放电循环(其中N可以根据实际需要来确定)，记录第N次循环的放电容量。按照如下公式计算得到锂离子电池的第N次循环后的容量衰减率和容量保持率：
第N次循环后的容量衰减率＝(首次循环的放电容量-第N次循环的放电容量)/首次循环的放电容量×100％。
第N次循环后的容量保持率＝第N次循环的放电容量/首次循环的放电容量×100％。
孔洞和裂缝测试：
利用离子抛光机(日本电子-IB-09010CP)对正极材料加工，得到断面。利用扫描电子显微镜对其断面进行拍摄，拍摄倍数不低于5.0K，获得颗粒图像，断面图像上可观测到孔洞和裂缝。
孔洞选取要求为：单个颗粒中闭合区域的最长轴与颗粒最长轴的比不高于10％时，且闭合区域的最长轴与最短轴的差值小于0.5微米，即为符合计数要求的孔洞；
裂缝的选取要求为：单个颗粒中闭合区域的最长轴与颗粒最长轴的比不低于70％时，即为符合计数要求的裂缝。
长短轴的选取方式：连接闭合区域任意两点，最长的距离即为最长轴，最短的距离即为最短轴。
闭合区域是指图形中由封闭线条围成的一个区，闭合区域内部任何一点与区域外任何一点的连线都和区域的边界相交。
颗粒横纵比测试：
利用扫描电子显微镜对颗粒进行拍摄，拍摄倍数不低于5.0K，获得颗粒图像，通过标尺确定一次颗粒的纵向长度和横向长度，其中纵向长度是一次颗粒的最长径，横向长度是垂直于纵向长度的径，颗粒横纵比等于横向长度除以纵向长度。
元素组成测试：
对正极材料的粉体采用iCAP7000 ICP检测仪进行元素分析测试；
对于负载有正极材料的正极，可采用NMP溶解极片，过滤取粉体烘干，采用iCAP7000 ICP检测仪进行元素分析测试。
比表面积测试：
测试设备为：BSD-BET400；测试过程：将样品放入充满N2气体体系,材料的表面在液氮温度下发生物理吸附。当该物理吸附处于平衡时,通过测量平衡时的吸附压力和吸附气体的流量,可求出材料的单分子层吸附量,从而计算出试样的比表面积
X射线衍射测试：采用Bruker D8 ADVANCE获取正极材料的XRD衍射图谱。
实施例1-1到实施例1-8，对比例1-1到对比例1-5、对比例2-1到对比例2-7和对比例3-1到对比例3-11所采用的正极材料均满足化学式Li xNa zCo 1-yAl yM mO 2，对比例1-6为R-3m晶相结构。
表1示出了实施例1-1到实施例1-9，以及对比例1-1到1-5中所用的正极材料以及测试结果。
表1
Figure PCTCN2020121139-appb-000001
请参考图5和图6以及表1，通过比较实施例1-1到实施例1-9，以及对比例1-1到对比例1-2以及对比例1-4可知，实施例1-1到实施例1-9通过限定Li xNa zCo 1-yAl yM mO 2对应的I 002/I 101的比值在3.9到5范围内，相比于对比例1-1到对比例1-2以及对比例1-4可以在保证首圈放电容量的同时，提高循环100圈容量保持率，这是因为I 002/I 101的比值在3.9到5范围内时锂离子扩散速率最快，且晶体结构最稳定。
通过比较实施例1-1到实施例1-8，以及对比例1-3以及对比例1-5可知，通过限制002峰对应的衍射角在17.5°-19°能够提高循环100圈的容量保持率。
表2示出了实施例1-1、实施例2-1至实施例2-6中所用的正极材料以及测试结果。
表2
Figure PCTCN2020121139-appb-000002
通过比较实施例1-1以及实施例2-5到实施例2-6可知，实施例1-1的Li xNa zCo 1-yAl yM mO 2对应的循环100圈容量保持率明显高于实施例2-5到实施例2-6，这是因为实施例1-1的Li xNa zCo 1-yAl yM mO 2颗粒同时具有孔洞和缝隙，能够充分浸润电解液，并且有效释放在脱锂和嵌锂过程中的应力，从而提高了晶体结构的稳定性，保证了循环性能。
通过比较实施例2-1、实施例2-3到2-4可知，当Li xNa zCo 1-yAl yM mO 2的横纵比r满足0<r<0.1时，电化学装置循环100圈容量保持率较高，这是因为颗粒的横纵比会影响颗粒的形貌，而颗粒的形貌会影响正极材料中I 002/I 101的比值。
表3
表3示出了实施例1-1、1-5、1-8，以及对比例3-1到3-11中所用的正极材料以及测试结果。
Figure PCTCN2020121139-appb-000003
Figure PCTCN2020121139-appb-000004
通过比较实施例1-1、1-5、1-8以及实施例3-1到3-3可知，当锂钴铝氧化物对应的X射线衍射图在16°-19°范围内具有第一衍射峰和第二衍射峰时，电化学装置循环100圈容量保持率较高，这是因为实施例1-1、1-5、1-8中的锂钴铝氧化物的晶体结构的可逆性好，不易发生不可逆相变，因此循环性能得到提升。
通过比较实施例1-1、1-5、1-8以及实施例3-4到3-6可知，当锂钴铝氧化物的比表面积满足0.2m 2/g-2m 2/g时，电化学装置循环100圈容量保持率较高。
以上描述仅为本申请的较佳实施例以及对所运用技术原理的说明。本领域技术人员应当理解，本申请中所涉及的公开范围，并不限于上述技术特征的特定组合而成的技术方案，同时也应涵盖由上述技术特征或其等同特征进行任意组合而形成的其它技术方案。例如上述特征与本申请中公开的具有类似功能的技术特征进行互相替换而形成的技术方案。

Claims (10)

  1. 一种正极材料，其特征在于，包括：
    锂钴铝氧化物，所述锂钴铝氧化物具有P6 3mc晶相结构；
    所述锂钴铝氧化物的X射线衍射图谱中具有对应于(002)晶面的002峰和对应于(101)晶面的101峰，所述002峰的强度为I 002，所述101峰的强度为I 101，I 002/I 101＝η，其中，3.9<η<5。
  2. 根据权利要求1所述的正极材料，其特征在于，
    所述002峰对应的衍射角位于17.5°-19°之间。
  3. 根据权利要求1所述的正极材料，其特征在于，所述锂钴铝氧化物的颗粒具有孔洞结构和/或具有缝隙。
  4. 根据权利要求1所述的正极材料，其特征在于，所述锂钴铝氧化物包括：一次颗粒，所述一次颗粒的横纵比r满足0<r<0.1。
  5. 根据权利要求1所述的正极材料，其特征在于，
    所述锂钴铝氧化物包括：Li xNa zCo 1-yAl yM mO 2；
    其中，0.6<x<0.93，0<y<0.15，0≤z<0.02，0≤m<0.02，M包括Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr或Zr中的至少一个。
  6. 一种电化学装置，其特征在于，包括：
    正极；
    负极；
    隔离膜，设置在所述正极和所述负极之间；
    其中，所述正极包括集流体和设置在所述集流体上的正极活性物质层，所述正极活性物质层包括如权利要求1-5中任一项所述的正极材料。
  7. 根据权利要求6所述的电化学装置，其特征在于，所述正极材料层的比表面积为0.2m 2/g-2m 2/g。
  8. 根据权利要求6所述的电化学装置，其特征在于，在0％SOC状态下，所述正极材料的X射线衍射图谱在16°-19°范围内包含第一衍射峰和第二衍射峰，第一衍射峰角度大于第二衍射峰的角度。
  9. 根据权利要求8所述的电化学装置，其特征在于，满足如下条件(a)-(d)中的至少一个：
    (a)所述第一衍射峰与第二衍射峰的峰位差D1满足1°≤D1≤2°；
    (b)所述第二衍射峰与第一衍射峰的峰强比D2满足0＜D2＜1；
    (c)所述第二衍射峰的半高宽FWHM1满足0＜FWHM1＜1；
    (d)所述第一衍射峰的半高宽FWHM2满足0＜FWHM2＜0.5。
  10. 一种电子装置，其特征在于，包括权利要求6-9任一项所述的电化学装置。
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