WO2023184275A1 - 正极材料、电化学装置及用电设备 - Google Patents

正极材料、电化学装置及用电设备 Download PDF

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WO2023184275A1
WO2023184275A1 PCT/CN2022/084200 CN2022084200W WO2023184275A1 WO 2023184275 A1 WO2023184275 A1 WO 2023184275A1 CN 2022084200 W CN2022084200 W CN 2022084200W WO 2023184275 A1 WO2023184275 A1 WO 2023184275A1
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compound
coating
cathode material
cobalt oxide
lithium
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PCT/CN2022/084200
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English (en)
French (fr)
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刘小浪
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宁德新能源科技有限公司
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Priority to PCT/CN2022/084200 priority Critical patent/WO2023184275A1/zh
Publication of WO2023184275A1 publication Critical patent/WO2023184275A1/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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—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 electrochemical energy storage, and in particular to a cathode material, an electrochemical device and electrical equipment containing the cathode material.
  • Lithium-ion batteries have the advantages of high energy density, good cycle stability, high operating voltage, and environmental friendliness. They dominate the field of energy storage and are widely used in portable electronic devices, energy storage grids, electric vehicles, and other fields.
  • lithium cobalt oxide has become the mainstream cathode material for lithium-ion batteries used in consumer electronics due to its high volumetric energy density.
  • more lithium ions need to be extracted from the lattice of lithium cobalt oxide materials.
  • the most direct way is to increase the charging voltage of lithium cobalt oxide, but this method
  • the lithium cobalt oxide in the battery has the problem of rapid cycle attenuation under high voltage, which affects the life of the battery.
  • this application provides a cathode material with a coating structure, which has a base body of P6 3 mc structure and a coating of R-3m structure.
  • the cathode material with the coating structure can perform at high voltages.
  • the present application also provides electrochemical devices and electrical equipment including the aforementioned cathode material with a coating structure.
  • a cathode material which includes a base body and a coating located on at least part of the surface of the base body; wherein the base body includes a first compound having a P6 3 mc structure, and the coating The compound includes a second compound having the structure R-3m.
  • the coating has a thickness of 10 nm to 300 nm. In some embodiments, the coating has a thickness of 30 nm to 200 nm.
  • the first compound is lithium cobalt oxide, and the first compound includes Co element and optional T element, wherein the T element includes Ni, Mn, Ti, Zn, Y, La , at least one of Zr, Mg, Fe, Cu, Nb, Cr or Al; in the first compound, the sum of the molar amounts of the Co element and the T element is n Co+T , and the T element The molar amount is n T , and the ratio y1 of n T to n Co+T satisfies 0 ⁇ y1 ⁇ 0.15.
  • the first compound further includes the Na element.
  • the molar amount of the Na element is n Na
  • the ratio z1 of the n Na to the n Co+T satisfies 0 ⁇ z1 ⁇ 0.03.
  • the second compound is lithium cobalt oxide, and the second compound includes Co element and optional Q element, wherein the Q element includes Ni, Mn, Ti, Zn, Y, La , at least one of Zr, Mg, Fe, Cu, Nb, Cr or Al; in the second compound, the sum of the molar amounts of the Co element and the Q element is m Co+Q , and the Q element The molar amount is m Q , and the ratio y2 of the m Q to the m Co+Q satisfies 0 ⁇ y2 ⁇ 0.5.
  • the second compound further includes Na element.
  • the molar amount of Na element is m Na
  • the ratio z2 of m Na to m Co+Q satisfies 0 ⁇ z2 ⁇ 0.03.
  • the peak intensity of the strongest diffraction peak with a 2 ⁇ diffraction angle in the range of 18°-19° is I 1
  • the 2 ⁇ diffraction angle is in the range of 44°-46°.
  • the peak intensity of the strongest diffraction peak is I 2 , which satisfies 1% ⁇ I 2 /I 1 ⁇ 11%.
  • the mass ratio m of the coating in the cathode material satisfies 0 ⁇ m ⁇ 10%, where m is obtained through XRD refined quantitative phase analysis.
  • the average particle size Dv50 of the cathode material is 10 ⁇ m to 25 ⁇ m.
  • an electrochemical device which includes a positive electrode piece, and the positive electrode piece includes the positive electrode material according to any one of the preceding items.
  • an electrical equipment which includes the electrochemical device described in the second aspect of the present application.
  • the cathode material with R-3m@P6 3 mc coating structure is used as the cathode active material to make a lithium-ion battery.
  • a high voltage such as 4.6V
  • high gram capacity and cycle stability can be achieved.
  • Figure 1 is a schematic diagram of a cathode material with an R-3m@P6 3 mc coating structure in an embodiment of the present application;
  • Figure 2 is an XRD pattern of lithium cobalt oxide with an R-3m structure prepared in Comparative Example 1 of the present application;
  • Figure 3 is the XRD pattern of the three materials prepared in Comparative Example 2 of the present application.
  • the three XRD patterns from bottom to top respectively correspond to the cobalt oxide precursor prepared in Comparative Example 2.
  • the material prepared in Comparative Example 2 has P6 3 /mmc structure sodium-containing cobalt oxide precursor, Comparative Example 2 prepared with P6 3 mc structure lithium-containing cobalt oxide precursor;
  • Figure 4 is an XRD pattern of lithium cobalt oxide with an R-3m@P6 3 mc coating structure prepared in Example 4 of the present application;
  • Figure 5 is an XRD pattern of the remaining P6 3 mc structure matrix after the lithium cobalt oxide with R-3m@P6 3 mc coating structure prepared in Example 4 of the present application is treated with aqua regia.
  • LiCoO2 materials usually have an R-3m crystal structure, which can extract more lithium from the crystal lattice when charged to high voltages (such as ⁇ 4.6V vs. Li + /Li) Lithium-ion for higher capacity.
  • high voltages such as ⁇ 4.6V vs. Li + /Li
  • irreversible phase changes such as O3 to H1-3
  • the positive electrode material and the electrolyte will change.
  • Side reactions occur at the interface, causing rapid deterioration of the cycle.
  • high-concentration doping such as Al, Mg, Ti, etc.
  • Lithium cobalt oxides belonging to the P6 3 mc space group have a low-temperature metastable state and can be produced by ion-exchanging sodium in sodium-containing oxides with lithium at low temperatures.
  • the advantage of this lithium cobalt oxide material is that even if it is charged to a high voltage (such as ⁇ 4.6V vs. Li + /Li), the lithium in the crystal lattice is almost completely released, and its crystal structure can still remain intact.
  • lithium cobalt oxide belonging to the P6 3 mc space group has better structural reversibility at high voltages.
  • the shortcomings of lithium cobalt oxide belonging to the P6 3 mc space group are also significant.
  • This lithium cobalt oxide material is unstable at high temperatures and easily undergoes phase changes when heated above 300°C. It cannot resemble the traditional R-3m structure lithium High-temperature coating treatment like cobalt oxide is used to stabilize the material interface, but low-temperature coating is difficult to achieve. This results in the material being basically exposed in the battery and in direct contact with the electrolyte, which is prone to serious interface vices. reaction, and cobalt ions continue to dissolve during the cycle, destroying the anode SEI (solid electrolyte interphase) film, causing the long-term cycle performance of the battery to fail to meet actual application needs.
  • SEI solid electrolyte interphase
  • phase coating method has complex processes, high costs, and difficulty in industrial production.
  • a cathode material with a coating structure which includes a base body and a coating located on at least part of the surface of the base body; wherein the base body includes a first compound with a P6 3 mc structure, including The coating includes a second compound having the structure R-3m.
  • the coating structure of this cathode material can be recorded as R-3m@P6 3 mc coating structure.
  • Figure 1 is a schematic diagram of a cathode material with an R-3m@P6 3 mc coating structure in an embodiment of the present application; it includes a base 100 with a P6 3 mc structure and a coating 200 with an R-3m structure.
  • the coating 200 exists on a partial area of the surface of the base 100 , that is, the base is only partially wrapped, and the covering 200 exists on part of the surface of the base. In some embodiments, the coating 200 exists on the entire surface area of the substrate 100 , that is, the substrate is completely covered, and the coating exists on the entire surface of the substrate.
  • the cathode material has a matrix of P6 3 mc structure and a coating of R-3m structure, at high voltage (such as greater than 4.5V), the P6 3 mc structure of the cathode material matrix has a high reversibility capacity, and the R-3m structure of the coating can undergo spinel phase change, thereby forming a stable spinel phase change layer, which plays a good protective role on the surface of the P6 3 mc structure of the cathode material matrix, and can also Inhibit the dissolution of transition metals.
  • lithium-ion batteries made of this cathode material with R-3m@P6 3 mc coating structure as the cathode active material high gram capacity and cycle stability can be achieved when charged to a high voltage (such as ⁇ 4.6V) sex.
  • the matrix consists essentially of the first compound. In some embodiments, the coating consists essentially of the second compound. In some embodiments, the matrix consists essentially of the first compound and the coating consists essentially of the second compound.
  • structure A consists mainly of material a
  • material a is the main active material that provides the active function of structure A.
  • structure A only includes material a, but does not completely exclude the existence of other coexisting substances.
  • mass proportion of material a in structure A is relatively high, such as greater than 80%, greater than 85%, greater than 90%, greater than 95%, greater than 99%, etc., such as 100%.
  • the first compound is a first lithium cobalt oxide.
  • the second compound is a second lithium cobalt oxide.
  • lithium cobalt oxide refers to a substance containing at least Li element, Co element and O element.
  • the matrix in the cathode material with a coating structure, includes a first lithium cobalt oxide with a P6 3 mc crystal structure, and the coating includes a second lithium cobalt oxide with an R-3m crystal structure.
  • the matrix in the cathode material with a coating structure, is a first lithium cobalt oxide with a P6 3 mc crystal structure, and the coating is a second lithium cobalt oxide with an R-3m crystal structure.
  • the advantages of the above-mentioned cathode material with R-3m@P6 3 mc coating structure include but are not limited to: (1) During the delithiation/lithium insertion process, the first lithium cobalt oxide with P6 3 mc structure in the cathode material matrix The phase change reversibility under high voltage is higher than that of traditional R-3m structure lithium cobalt oxide, and has a very high reversible capacity; (2) At high voltage (such as greater than 4.5V), the coating has R The second lithium cobalt oxide with the -3m structure undergoes spinel phase transformation to form a stable spinel phase change layer.
  • the interface is very stable, and can provide a good solution to the first lithium cobalt oxide with the P6 3 mc structure in the matrix. It has a protective effect and inhibits the dissolution of transition metals, so it has better high-voltage cycle stability than pure P6 3 mc structure lithium cobalt oxide; (3)
  • the cathode material can be obtained in the following ways: by simply adding The disadvantages of the original spinel phase change are transformed into the technical advantages in this application.
  • the lithium cobalt oxide belonging to the P6 3 mc space group is annealed at a certain temperature (such as below 300°C), and R- occurs on the surface layer.
  • the 3m in-situ phase transformation forms a coating structural material whose matrix belongs to the P6 3 mc space group and the coating belongs to the R-3m space group. It not only provides a new direction for the modification of lithium cobalt oxide cathode materials, but also has a simple preparation process. , low cost, strong practicability, and has great potential for industrial application.
  • the mass proportion of the coating in the cathode material (denoted as m) satisfies 0 ⁇ m ⁇ 10%, where m is obtained through XRD refined quantitative phase analysis.
  • m can also be ⁇ 5.5% (that is, 0 ⁇ m ⁇ 5.5%), can also be ⁇ 5%, and can also be ⁇ 4.5%.
  • m can also be selected from any one of the following percentages or a percentage interval composed of any two percentages: 0.1%, 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3 %, 3.5%, 4%, 4.2%, 4.4%, 4.5%, 4.6%, 4.8%, 5%, 5.5%, 6%, 7%, 8%, 9%, 10%, etc.
  • the coating has a thickness of 10 nm to 300 nm.
  • the thickness of the coating can also be selected from any one of the following ratios or an interval composed of any two ratios: 10nm, 20nm, 50nm, 80nm, 100nm, 120nm, 150nm, 170nm, 190nm, 200nm, 250nm, 300nm.
  • the average particle size Dv50 of the cathode material is 10 ⁇ m to 25 ⁇ m.
  • the types of chemical elements of the matrix and the coating can be the same or different, but they should satisfy that the matrix has a P6 3 mc structure and the coating has an R-3m structure.
  • the first compound includes Co element and optional T element, wherein the T element includes Ni, Mn, Ti, Zn, Y, La, Zr, Mg, Fe, Cu, Nb, At least one of Cr or Al.
  • the sum of the molar amounts of the Co element and the T element is n Co+T
  • the molar amount of the T element is n T
  • the ratio y1 of Co+T satisfies 0 ⁇ y1 ⁇ 0.15.
  • the first compound further includes Li element.
  • the molar amount of Li element is n Li
  • the ratio x1 of n Li to n Co+T satisfies 0.6 ⁇ x1 ⁇ 0.95.
  • the first compound further includes Na element.
  • the molar amount of the Na element is n Na
  • the ratio z1 of the n Na to the n Co+T satisfies 0 ⁇ z1 ⁇ 0.03.
  • the first compound is Li x1 Na z1 Co 1-y1 T y1 O 2 ⁇ b1 , wherein 0.6 ⁇ x1 ⁇ 0.95, 0 ⁇ z1 ⁇ 0.03, 0 ⁇ y1 ⁇ 0.15; 0 ⁇ b1 ⁇ 0.2 .
  • the second compound includes Co element and optional Q element, wherein the Q element includes Ni, Mn, Ti, Zn, Y, La, Zr, Mg, Fe, Cu, Nb, At least one of Cr or Al.
  • the sum of the molar amounts of the Co element and the Q element is m Co+Q
  • the molar amount of the Q element is m Q
  • the ratio y2 of Co+Q satisfies 0 ⁇ y2 ⁇ 0.5.
  • the second compound further includes Li element.
  • the molar amount of Li element is m Li
  • the ratio x2 of m Li to m Co+Q satisfies 0.6 ⁇ x2 ⁇ 1.2. In some embodiments, 0.8 ⁇ x2 ⁇ 1.1.
  • the second compound further includes Na element.
  • the molar amount of the Na element is m Na
  • the ratio z2 of the m Na to the m Co+Q satisfies 0 ⁇ z2 ⁇ 0.03.
  • the second compound is Li x2 Na z2 Co 1-y2 Q y2 O 2 ⁇ b2 , wherein 0.6 ⁇ x2 ⁇ 1.2, 0 ⁇ z2 ⁇ 0.03, 0 ⁇ y2 ⁇ 0.15, 0 ⁇ b2 ⁇ 0.2 .
  • the crystal structure of the matrix and coating can be identified by the characteristic diffraction peaks in the XRD pattern obtained by the X-ray diffraction (XRD) method.
  • Cu-K ⁇ radiation is used to obtain the X-ray diffraction pattern, and the target material for XRD testing is Cu-K ⁇ .
  • the strongest diffraction peak of the matrix is the (002) crystal plane diffraction peak of the P6 3 mc structure.
  • the (002) The crystal plane diffraction peak is located in the range of 18°-19°.
  • the strongest diffraction peak of the coating is the (003) crystal plane diffraction peak of the R-3m structure.
  • the (003) crystal plane diffraction peak 003) The crystal plane diffraction peak is located in the range of 18°-19°.
  • the peak intensity of the strongest diffraction peak with a 2 ⁇ diffraction angle in the range of 18°-19° is I 1
  • the peak intensity of the strongest diffraction peak with a 2 ⁇ diffraction angle in the range of 44°-46° is I 2 , satisfying 1% ⁇ I/I ⁇ 10%.
  • there is only one characteristic diffraction peak in the 2 ⁇ diffraction angle range of 44°-46° (it should be understood that noise is not considered).
  • the diffraction peak with a 2 ⁇ diffraction angle in the range of 44°-46° corresponds to the (104) crystal plane diffraction peak of the R-3m structure lithium cobalt oxide, and can be used as a characteristic diffraction to identify the presence or absence of the R-3m structure lithium cobalt oxide. peak.
  • a method for preparing a cathode material with a coating structure which can be used to prepare the cathode material with a coating structure in the first aspect of the application, but is not limited to preparing the cathode material with a coating structure in the first aspect of the application.
  • a cathode active material with a P6 3 mc structure is used to undergo in-situ phase transformation on the surface layer to form a coating with an R-3m structure, thereby preparing a cathode material with a coating structure.
  • a method for preparing a cathode material with a coating structure including the following steps: providing a cathode active material with a P6 3 mc structure; annealing the cathode active material with a P6 3 mc structure to have a P6
  • the surface layer of the cathode active material with a 3 mc structure undergoes in-situ phase transformation to form a coating with an R-3m structure, and a cathode material with a coating structure is obtained.
  • the annealing temperature increases, the R-3m phase transformation of the surface layer of the cathode active material with P6 3 mc structure gradually increases, and the relative content of the coating with R-3m structure increases.
  • the annealing temperature exceeds 300°C, the phase transformation is significantly accelerated, and the relative content of the coating with the R-3m structure also increases extremely rapidly.
  • the annealing temperature can be selected from 250°C to 300°C.
  • the annealing temperature can also be selected from any one of the following temperatures or a temperature range composed of any two temperatures: 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 285°C, 290°C, 295°C wait.
  • the relative content of the coating having the R-3m structure gradually increases.
  • the annealing time can be selected from 0.5h to 4h.
  • the annealing time can also be selected from any one of the following time lengths or an interval composed of any two time lengths: 0.5h (30min), 0.75h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, etc.
  • Annealing temperature and annealing time can be combined in a suitable manner.
  • the annealing temperature ranges from 250°C to 300°C
  • the annealing time ranges from 0.5h to 4h.
  • the annealing temperature and annealing time may be selected from appropriate values or ranges in any of the above embodiments.
  • the cathode active material having a P6 3 mc structure can be obtained by a preparation method including the following steps: (1) using raw materials including soluble cobalt salts, through liquid phase precipitation, sintering, crushing, and optionally sieving to obtain a cobalt oxide precursor; wherein the raw materials optionally include soluble T salts containing T elements; (2) mix the cobalt oxide precursor with sodium salt, and obtain sodium-containing cobalt oxide by solid-phase synthesis. (3) The sodium-containing cobalt oxide precursor and the lithium salt solution are heated to reflux, washed, dried, and screened to obtain a cathode active material with a P6 3 mc structure.
  • the soluble cobalt salt may be selected from one or more of the following groups: cobalt chloride, cobalt acetate, cobalt sulfate, cobalt nitrate, and the like.
  • the soluble T salt containing element T is a sulfate salt.
  • the solvent for the liquid phase precipitation method is selected from water.
  • the liquid phase precipitation method performs precipitation in the presence of a precipitating agent.
  • examples of suitable precipitating agents include, but are not limited to, ammonium carbonate.
  • the liquid phase precipitation method performs precipitation under appropriate pH conditions.
  • a suitable pH value is, for example, 5 to 9.
  • Suitable pH values can also be selected from any one of the following pH values or a pH range between any two: 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, etc.
  • the sintering temperature of the solid-phase synthesis method in step (2) is selected from 700°C to 1000°C.
  • the sintering time is selected from 36h to 56h.
  • the sintering atmosphere is oxygen atmosphere.
  • the lithium salt in the lithium salt solution may be selected from lithium bromide.
  • the solvent in the lithium salt solution may be selected from alcoholic solvents.
  • the alcohol solvent can be hexanol.
  • the reaction temperature for heating and refluxing in step (3) is selected from 175°C to 185°C, for example, 180°C.
  • the reaction time of heating and refluxing is selected from 7.5h to 8.5h.
  • the preparation method of the second aspect of the application can be realized in the following way: converting the disadvantages of the original spinel phase change into the technical advantages of the application in a simple way, generally speaking, using lithium belonging to the P6 3 mc space group
  • the surface layer undergoes an R-3m in-situ phase transformation, thereby forming a coating structural material in which the matrix belongs to the P6 3 mc space group and the coating belongs to the R-3m space group.
  • This method not only provides a new direction for the modification of lithium cobalt oxide cathode materials, but also has a simple preparation process, low cost, strong practicability, and has great potential for industrial application.
  • a positive electrode sheet including a positive active material layer, which contains the positive electrode material with a coating structure of the first aspect of the present application or the second aspect of the present application.
  • the positive electrode material with a coating structure is prepared by the preparation method.
  • the positive electrode sheet further includes a positive current collector, which includes a positive active material layer and a positive current collector.
  • the positive active material layer is located on at least one surface of the positive current collector.
  • the positive active material layer is located on only one surface of the positive current collector.
  • the cathode active material layers are located on two opposite surfaces of the cathode current collector.
  • the positive electrode current collector may be aluminum foil, and similarly, other positive electrode current collectors commonly used in the art may also be used.
  • the positive active material layer may also include one or more of a conductive agent and a binder.
  • the conductive agent in the cathode active material layer may include one or more of carbon nanotubes, acetylene black, graphene, Ketjen black, conductive carbon black, and the like.
  • the binder in the positive active material layer may include one or more of polyvinylidene fluoride, carboxymethylcellulose, styrene-butadiene rubber, and the like.
  • the mass ratio of the cathode material, conductive agent and binder in the cathode active material layer is (84-98): (0.5-10): (0.5-5). It should be understood that the materials and mass ratios described above are only exemplary and are not intended to limit the application, and other suitable materials and mass ratios may be used.
  • an electrochemical device which includes the positive electrode piece of the third aspect of the present application, a negative electrode piece, and a separation film disposed between the positive electrode piece and the negative electrode piece.
  • the negative electrode plate may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.
  • negative active material layers are provided on opposite sides of the negative current collector. In other embodiments, the negative active material layer is provided only on one side of the negative current collector.
  • the negative active material layer includes a negative active material including one or more of carbon materials, silicon materials, and the like.
  • the carbon material includes one or more of graphite, hard carbon, and the like.
  • the silicon material includes one or more of silicon, silicon oxide compounds, silicon carbon compounds, silicon alloys, and the like.
  • the negative electrode current collector may include one or more of copper foil, aluminum foil, nickel foil, or carbon-based current collector.
  • the negative active material layer may also include one or more of a conductive agent and a binder.
  • the conductive agent in the negative active material layer includes one or more of conductive carbon black, acetylene black, carbon nanotubes, Ketjen black, conductive graphite, graphene, and the like.
  • the mass percentage of the conductive agent in the negative active material layer is 0.5% to 10%.
  • the binder in the negative active material layer includes polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, One or more of sodium carboxymethylcellulose, polyvinylpyrrolidone, polyvinyl ether, polymethylmethacrylate, polytetrafluoroethylene, polyhexafluoropropylene, styrene-butadiene rubber, etc.
  • the mass percentage of the binder in the negative active material layer is 0.5% to 10%. It should be understood that the above is only exemplary and not intended to limit the application.
  • the isolation membrane includes polymers or inorganic substances formed of materials that are stable to the electrolyte of the present application.
  • the isolation film may include a base material layer and a surface treatment layer.
  • the base material layer is a non-woven fabric, film or composite film with a porous structure, and the material of the base material layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate or polyimide.
  • polypropylene porous membrane, polyethylene porous membrane, polypropylene non-woven fabric, polyethylene non-woven fabric or polypropylene-polyethylene-polypropylene porous composite membrane can be used.
  • a surface treatment layer is provided on at least one surface of the base layer.
  • the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic layer.
  • the inorganic layer includes inorganic particles and binders.
  • the inorganic particles include aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, oxide At least one of yttrium, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide or barium sulfate.
  • Binders include polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, poly At least one of methyl methacrylate, polytetrafluoroethylene or polyhexafluoropropylene.
  • the polymer layer contains a polymer, and the polymer material includes polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polyvinylidene fluoride or poly( At least one of vinylidene fluoride-hexafluoropropylene).
  • the isolation film has a thickness of 5 ⁇ m to 500 ⁇ m.
  • the electrochemical device in the present application also includes an electrolyte, and the electrolyte includes a lithium salt and a non-aqueous solvent.
  • the lithium salt is selected from LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , One or more of LiC(SO 2 CF 3 ) 3 , LiSiF 6 , LiBOB and lithium difluoroborate.
  • the lithium salt can be LiPF 6 .
  • the non-aqueous solvent may include carbonate compounds, carboxylate compounds, ether compounds, or any suitable combination thereof.
  • the carbonate compound may be selected from chain carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or any suitable combination thereof.
  • the chain carbonate compound may be selected from diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC) and their combinations.
  • the cyclic carbonate compound may be selected from ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC) or combinations thereof.
  • the fluorocarbonate compound may be selected from the group consisting of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, and 1,1,2-trifluoroethylene carbonate.
  • the carboxylate compound may be selected from the group consisting of methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, gamma-butyrolide ester, decanolide, valerolactone, caprolactone, methyl formate or any suitable combination thereof.
  • the ether compound may be selected from dibutyl ether, tetraglyme, diglyme, 1,2-dimethoxyethane, 1,2-diethoxyethane , ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran or any suitable combination thereof.
  • the electrochemical device of the present application includes, but is not limited to: all kinds of primary batteries or secondary batteries.
  • the electrochemical device is a lithium secondary battery.
  • lithium secondary batteries include, but are not limited to: lithium metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, or lithium ion polymer secondary batteries.
  • an electrical equipment which includes the electrochemical device of the fourth aspect of the present application.
  • the powered device may include, but is not limited to, a notebook computer, a pen input computer, a mobile computer, an e-book player, a portable telephone, a portable fax machine, a portable copier, a portable printer, and a stereo headset , VCR, 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 fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • X-ray powder diffractometer instrument model: Bruker D8 ADVANCE
  • the target material was Cu K ⁇ ; the voltage and current were 40KV/35mA, the scanning angle range was 10° to 90°, and the scanning rate was 0.02°/s.
  • the intensity of the strongest diffraction peak is required to be greater than 10,000, in counts.
  • the collected XRD spectra were refined using Fullprof software to determine the phase structure and I 2 /I 1 .
  • the cathode material element composition test the content of elements such as Li, Na and transition metals was measured by the Optima7000DV inductively coupled plasma spectrometer (ICP) tester of the American PE company.
  • ICP inductively coupled plasma spectrometer
  • the average particle size Dv50 of the cathode material was measured using a laser particle size analyzer.
  • the instrument model is MasterSizer 3000, the sampling system is Hydro 2000SM&Hydro 2000MU, the measuring range is 0.01-3500um, the detection angle range is 0.0153-144°, the test snapshot rate is 1000 times/s, the detector is photosensitive silicon material, and the test reference standard is GB /T19077-2016/ISO 13320:2009. Before the test, take an appropriate amount of the sample to be tested, add deionized water, and ultrasonic for 5 minutes with a power of 120W to disperse it evenly.
  • the samples were observed under STEM and the thickness of the coating was measured. Collect at least 3 different locations and take the average.
  • CoSO 4 cobalt sulfate
  • NiSO 4 nickel sulfate
  • MnSO 4 manganese sulfate
  • Lithium carbonate (Li 2 CO 3 ) and the above-mentioned metal oxides were weighed and mixed evenly according to a molar ratio of 1.05:1, and kept at 900°C for 12 hours. After post-processing, the corresponding lithium cobalt oxide material (recorded as Comparative Example 1 material ).
  • the Dv50 of the material of Comparative Example 1 is 13 ⁇ m.
  • the XRD test results can be seen in the XRD pattern shown in Figure 2.
  • the results show that the obtained lithium cobalt oxide has an R-3m structure.
  • the ICP test results can be seen in Table 1.
  • the results show that the elemental composition of the cathode material obtained in Comparative Example 1 is Li 1.002 Co 0.857 Ni 0.053 Mn 0.090 O 2 .
  • the material of Comparative Example 1 of the above R-3m structure was used as the cathode active material, conductive carbon (SP) was used as the conductive agent, and polyvinylidene fluoride (PVDF) was used as the binder.
  • the material was mixed according to the mass ratio of 90:5:5, and the solvent was added.
  • NMP N-Methyl-2-pyrrolidone
  • NMP was made into a slurry and coated on an aluminum foil with a thickness of 12 ⁇ m. Then, it was dried in a blast drying oven at 90°C for 4 hours, and then baked in a vacuum drying oven at 110°C for 24 hours.
  • the fully dried pole pieces are subjected to processes such as cold pressing, punching, and weighing to obtain the positive electrode.
  • the above-mentioned positive electrode, separator, negative electrode and electrolyte are used to assemble a buckle-charge half cell.
  • the negative electrode is lithium metal;
  • the electrolyte ethylene carbonate (EC) and dimethyl carbonate (DMC) with a volume ratio of 1:1, and the concentration of LiPF 6 is 1 mol/L.
  • the above-mentioned assembled button battery was tested for electrochemical performance, and the first discharge capacity was measured to be 205.7mAh/g, and the capacity retention rate after 80 cycles was 68.2%.
  • Sodium carbonate (Na 2 CO 3 ) and the above-mentioned precursor 1 were weighed and mixed evenly at a molar ratio of 0.35:1, kept at 800°C for 48 hours, and post-processed to obtain a composition of Na 0.7 Co 0.85 Ni 0.05 Mn 0.10 O 2
  • Sodium-containing cobalt oxide precursor 2 (corresponding to the aforementioned sodium-containing cobalt oxide precursor, denoted as precursor 2).
  • XRD test results show that the obtained sodium-containing cobalt oxide has a P6 3 /mmc structure.
  • the XRD test results can be seen in the XRD pattern shown in Figure 3.
  • the test results show that the cathode material obtained in Comparative Example 2 is a pure phase belonging to the P6 3 mc crystal structure.
  • the ICP test results can be seen in Table 1.
  • the test results show that the elemental composition of the material of Comparative Example 2 is Li 0.912 Na 0.007 Co 0.854 Ni 0.052 Mn 0.094 O 2 .
  • the subsequent assembly and testing methods of the buckle battery using the material of Comparative Example 2 as the positive active material are exactly the same as those of Comparative Example 1.
  • the first discharge gram capacity of the material of Comparative Example 2 was measured experimentally to be 218.4 mAh/g, and the capacity retention rate after 80 cycles was 78.3%.
  • Example 1 to Example 5. Changing the annealing temperature
  • Comparative Example 2 material of P6 3 mc structure place it in a tube furnace, heat it to the preset holding temperature (T, corresponding to the aforementioned annealing temperature) at a heating rate of 1.5°C/min, and then hold it for 30 minutes. After the furnace is cooled, a composite material with a P6 3 mc structure and an R-3m structure as the matrix and the coating is obtained (a cathode material with an R-3m@P6 3 mc coating structure). The subsequent production and testing methods of the obtained cathode material are the same as those in Comparative Example 2.
  • the insulation temperatures T of the material from Example 1 to Example 5 are respectively 250°C, 270°C, 280°C, 290°C, and 300°C.
  • the obtained positive electrode materials are respectively recorded as the material of Example 1, the material of Example 2, and the material of Example 5. 3 materials, Example 4 materials, and Example 5 materials.
  • the subsequent testing process of the obtained cathode material was the same as Comparative Example 2. Among them, the powder test results and electrochemical performance test results of the materials can be seen in Table 1.
  • Example 6 to Example 9. Changing the annealing time
  • the obtained positive electrode materials are respectively recorded as the material of Example 6, the material of Example 7, the material of Example 8, and the material of Example 9. .
  • the subsequent testing process of the obtained cathode material was the same as Comparative Example 2. Among them, the powder test results and electrochemical performance test results of the materials from Example 6 to Example 9 can be seen in Table 1.
  • cobalt sulfate CoSO 4
  • zinc sulfate ZnSO4
  • add deionized water and stir quickly to dissolve then add ammonium carbonate and adjust the pH to 8 until the reaction is completed to form homogeneous carbonic acid Salt precipitate, sinter the precipitate at 650°C for 12 hours, and undergo crushing and screening processes to obtain cobalt-zinc metal oxide precursor 1 (corresponding to the aforementioned cobalt oxide precursor).
  • Sodium carbonate (Na 2 CO 3 ) and the above-mentioned precursor 1 were weighed and mixed evenly at a molar ratio of 0.35:1, kept at 800°C for 48 hours, and post-processed to obtain a zinc-doped composition of Na 0.7 Co 0.85 Zn 0.15 O 2 Mixed sodium-containing cobalt oxide precursor 2 (corresponding to the aforementioned sodium-containing cobalt oxide precursor).
  • Example 10 materials Take about 10g of the zinc-doped lithium cobalt oxide material with the above-mentioned P6 3 mc structure, place it in a tube furnace, heat it to 270°C at a heating rate of 1.5°C/min, and then keep it warm for 45 minutes. After cooling in the furnace, the zinc-doped lithium cobalt oxide material is obtained.
  • the hybrid matrix and coating are respectively P6 3 mc structure and R-3m structure composite materials (positive electrode materials of R-3m@P6 3 mc coating structure) (recorded as Example 10 materials).
  • the subsequent testing process of the obtained cathode material was the same as Comparative Example 2. Among them, the test results of the material powder and the electrochemical performance test results of Example 10 can be seen in Table 1.
  • Example 11 except that zinc sulfate is replaced by aluminum nitrate, manganese sulfate, yttrium nitrate, zirconium nitrate, lanthanum nitrate, nickel sulfate and titanium nitrate in sequence, and these soluble salts are added to deionized water together with cobalt sulfate.
  • the remaining steps of material preparation and testing process up to Example 17 are the same as those in Example 10. Among them, the powder test results and electrochemical performance test results of the materials can be seen in Table 1.
  • I 2 /I 1 is the intensity of the diffraction peak (I 1 ) with a 2 ⁇ diffraction angle in the range of 44°-46° and the strongest diffraction in the 2 ⁇ diffraction angle in the range of 18°-19° in the XRD pattern.
  • m represents the mass percentage of the R-3m structure in the cathode material of the R-3m@P6 3 mc coating structure. Among them, m is obtained through XRD refined quantitative phase analysis.
  • the lithium cobalt oxide cathode material with a coating structure prepared in this application mainly consists of two parts. Among them, the matrix and the coating have the crystal structures of P6 3 mc and R-3m respectively (denoted as R-3m@P6 3 mc cladding structure).
  • the XRD pattern of the material of Example 4 was first tested.
  • the XRD test results can be seen in the XRD pattern shown in Figure 4.
  • the test results show that the phase composition of the material in Example 4 is the main phase P6 3 mc compounded with a small amount of R-3m structure lithium cobalt oxide.
  • the mass percentage content m of the R-3m structure material obtained through XRD structure refinement is 5.24%.
  • the hot aqua regia can slowly erode lithium from the surface.
  • Cobalt oxide material After soaking for about 30 minutes, the residual powder is filtered out, washed, and dried, and then the material is tested by XRD again.
  • the XRD test results can be seen in the XRD pattern shown in Figure 5. The test results show that after the material of Example 4 is treated with aqua regia, only the P6 3 mc structure phase of the material remains, while the original R-3m structure has been completely dissolved.
  • the cathode material prepared in this application has a coating structure of R-3m@P6 3 mc.
  • Example 4 By comparing the XRD diffraction spectra of Example 4 and Comparative Example 2, it can be seen that there is an additional set of diffraction spectra of the R-3m structure in the XRD diffraction spectra of the material of Example 4.
  • the diffraction peak of the R-3m structure (003) crystal plane in the material of Example 4 is located at about 18.5°, which highly overlaps with the diffraction peak of the main phase P6 3 mc structure (002) crystal plane, indicating that the R-3m structure lithium cobalt oxide
  • the material is also in a lithium-deficient state, which is the same as the P6 3 mc structure lithium cobalt oxide before the aqua regia heat treatment of the material in Example 4, and further illustrates the R-3m structure lithium cobalt oxide in the materials of each example (including the material in Example 4).
  • the material is obtained by in-situ conversion of P6 3 mc structure lithium cobalt oxide material.
  • lithium cobalt oxide For pure P6 3 mc structure lithium cobalt oxide (such as the material in Comparative Example 2), its first discharge gram capacity is significantly better than that of the R-3m structure lithium cobalt oxide material, mainly due to its ability to maintain the structure in a high delithiation state. It has stable material properties, but due to the lack of interface protection on the material surface, the dissolution of transition metal elements during the cycle is very serious, resulting in a capacity retention rate of only 75.3% after 80 cycles. It can be concluded from Table 1 that the lithium cobalt oxide material with R-3m@P6 3 mc coating structure provided by this application has obvious advantages.

Abstract

本申请涉及一种正极材料、电化学装置及用电设备，该正极材料包括基体以及位于所述基体至少部分表面的包覆物；其中，基体包含具有P6 3mc结构的第一化合物，包覆物包含具有R-3m结构的第二化合物。该正极材料在高电压下能够具有高的克容量和循环稳定性。

Description

正极材料、电化学装置及用电设备 技术领域
本申请涉及电化学储能领域，特别涉及一种正极材料、包含该正极材料的电化学装置及用电设备。
背景技术
锂离子电池具有能量密度高、循环稳定性好、工作电压高、环境友好等优点，在储能领域占据主导地位，被广泛应用于便携式电子设备、储能电网和电动汽车等领域。在商业上可获得的常见正极材料中，钴酸锂凭借其较高的体积能量密度而成为消费类电子产品用锂离子电池的主流正极材料。为了满足对锂离子电池日益增长的高能量密度需求，需要从钴酸锂材料的晶格中提取出更多的锂离子，其中最直接的方式就是提升钴酸锂的充电电压，但这种方式中的钴酸锂存在着高电压下的循环快速衰减问题，影响到电池的寿命。
发明内容
鉴于上述技术问题，本申请提供了一种具有包覆结构的正极材料，其具有P6 3mc结构的基体和R-3m结构的包覆物，该具有包覆结构的正极材料在高电压下能够具有高的克容量和循环稳定性。本申请还提供了包括前述具有包覆结构的正极材料的电化学装置和用电设备。
在本申请的第一方面，提供一种正极材料，其包括基体以及位于所述基体至少部分表面的包覆物；其中，所述基体包含具有P6 3mc结构的第一化合物，所述包覆物包含具有R-3m结构的第二化合物。
在一些实施方式中，所述包覆物的厚度为10nm至300nm。在一些实施方式中，所述包覆物的厚度为30nm至200nm。
在一些实施方式中，所述第一化合物为锂钴氧化物，所述第一化合物包含Co元素和可选的T元素，其中，所述T元素包含Ni、Mn、Ti、Zn、Y、La、Zr、Mg、Fe、Cu、Nb、Cr或Al中的至少一种；所述第一化合物中，Co元素和所述T元素的摩尔量之和为n Co+T，所述T元素的摩尔量为n T，所述n T与所述n Co+T的比值y1，满足0≤y1≤0.15。
在一些实施方式中，所述第一化合物还包含Na元素，所述第一化合物中，Na元素的摩尔量为n Na，所述n Na与所述n Co+T的比值z1，满足0<z1≤0.03。
在一些实施方式中，所述第二化合物为锂钴氧化物，所述第二化合物包含Co元素和可选的Q元素，其中，所述Q元素包含Ni、Mn、Ti、Zn、Y、La、Zr、Mg、Fe、Cu、Nb、 Cr或Al中的至少一种；所述第二化合物中，Co元素和所述Q元素的摩尔量之和为m Co+Q，所述Q元素的摩尔量为m Q，所述m Q与所述m Co+Q的比值y2满足0≤y2≤0.5。
在一些实施方式中，所述第二化合物还包括Na元素，所述第二化合物中，Na元素的摩尔量为m Na，所述m Na与所述m Co+Q的比值z2，满足0<z2≤0.03。
在一些实施方式中，所述正极材料的X射线衍射谱中，2θ衍射角在18°-19°范围内的最强衍射峰的峰强为I 1，2θ衍射角在44°-46°范围内的最强衍射峰的峰强为I 2，满足1％≤I 2/I 1≤11％。
在一些实施方式中，所述包覆物在所述正极材料中的质量占比m满足0<m≤10％，其中，m通过XRD精修定量相分析获得。
在一些实施方式中，所述正极材料的平均粒径Dv50为10μm至25μm。
在本申请的第二方面，提供一种电化学装置，其包括正极极片，所述正极极片包含前述任一项所述的正极材料。
在本申请的第三方面，提供一种用电设备，其包括本申请的第二方面所述电化学装置。
本申请研究发现，当正极材料具有P6 3mc结构的基体和R-3m结构的包覆物时，这种包覆结构可记为R-3m@P6 3mc包覆结构，在高电压(如大于4.5V)下，该正极材料基体的P6 3mc结构具有高的可逆容量，而包覆物的R-3m结构可发生尖晶石相变，从而形成稳定的尖晶石相变层，对正极材料基体P6 3mc结构的表面起到很好的保护作用，还可抑制过渡金属的溶出。因此，采用该具有R-3m@P6 3mc包覆结构的正极材料作为正极活性材料制成锂离子电池，充电至高电压(如4.6V)时，可实现高的克容量和循环稳定性。
附图说明
为了更清楚地说明本申请实施例中的技术方案、更完整地理解本申请及其有益效果，下面将对实施例描述中所需要使用的附图作简单的介绍。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，对本领域技术人员来说，还可以根据这些附图获得其他的附图。
图1为本申请的一实施例中的具有R-3m@P6 3mc包覆结构的正极材料的示意图；
图2为本申请的对比例1制备的具有R-3m结构的锂钴氧化物的XRD图；
图3为本申请的对比例2中制备的三种材料的XRD图，其中，自下而上的三个XRD图谱分别对应对比例2制备的钴氧化物前驱体，对比例2制备的具有P6 3/mmc结构的含钠钴氧化物前驱体，对比例2制备的具有P6 3mc结构的含锂钴氧化物；
图4为本申请的实施例4制备的具有R-3m@P6 3mc包覆结构的锂钴氧化物的XRD图；
图5为本申请的实施例4制备的具有R-3m@P6 3mc包覆结构的锂钴氧化物经王水处理后剩余的P6 3mc结构基体的XRD图。
附图标记说明：100，基体；200，包覆物。
具体实施方式
下面结合附图、实施方式和实施例，对本申请作进一步详细的说明。应理解，这些实施方式和实施例仅用于说明本申请而不用于限制本申请的范围，提供这些实施方式和实施例的目的是使对本申请公开内容理解更加透彻全面。还应理解，本申请可以以许多不同的形式来实现，并不限于本申请所描述的实施方式和实施例，本领域技术人员可以在不违背本申请内涵的情况下作各种改动或修改，得到的等价形式同样落于本申请的保护范围。
除非另有定义，本申请所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本申请中在本申请的说明书中所使用的术语只是为了描述实施方式和实施例的目的，不是旨在于限制本申请。
传统的锂钴氧化物材料(通常为LiCoO 2材料)通常具有R-3m晶体结构，在充电至高电压(如≥4.6V vs.Li +/Li)时，可以从晶格中提取出更多的锂离子，从而获得更高的容量。然而，对于传统的锂钴氧化物材料来说，在高电压下，特别是锂离子提取超过0.5mol以后，极易发生不可逆相变(如O3到H1-3)，并在正极材料与电解液界面发生副反应，导致循环极速恶化。通过高浓度掺杂(例如Al、Mg、Ti等)，在一定程度上可以缓解不可逆相变，但会导致容量发挥显著恶化。
属于P6 3mc空间群的锂钴氧化物具有低温亚稳态，可通过在低温下利用锂对含钠氧化物中的钠进行离子交换制得。该锂钴氧化物材料的优势在于，即使充电至高电压(如≥4.6V vs.Li +/Li)，晶格中的锂接近完全脱出，其晶体结构仍能保持完整。换言之，属于P6 3mc空间群的锂钴氧化物在高电压下具有更好的结构可逆性。然而，属于P6 3mc空间群的锂钴氧化物的缺点也很显著，该锂钴氧化物材料在高温下不稳定，加热至300℃以上极易发生相变，无法像传统R-3m结构锂钴氧化物那样进行高温包覆处理方式来稳定材料界面，而低温包覆又很难实现，这就导致材料在电池中基本处于裸露的状态，会与电解液直接接触，易发生严重的界面副反应，而且循环过程中钴离子持续溶出，破坏阳极SEI(solid electrolyte interphase)膜，造成电池长期循环性能无法满足实际应用需求。传统技术中，针对P6 3mc结构的锂钴氧化物材料，只能采用低温液相包覆方式，难以实现有效的表面包覆，高电压下的界面副反应难以从根本上得到抑制，而且液相包覆方式工艺复杂，成本较高，工业化生产难度大。
本申请的第一方面
在本申请的第一方面，提供一种具有包覆结构的正极材料，其包括基体以及位于所述基体至少部分表面的包覆物；其中，基体包含具有P6 3mc结构的第一化合物，包覆物包含具有R-3m结构的第二化合物。该正极材料中包覆结构可记为R-3m@P6 3mc包覆结构。
图1为本申请的一实施例中的具有R-3m@P6 3mc包覆结构的正极材料的示意图；包括具有P6 3mc结构的基体100和具有R-3m结构的包覆物200。
在一些实施例中，包覆物200存在于基体100的表面的部分区域上，也即仅对基体进行了部分包裹，包覆物存在于基体的部分表面上。在一些实施例中，包覆物200存在于基体100的表面的全部区域上，也即实现了对基体的完全包覆，包覆物存在于基体的全部表面上。
本申请研究发现，当正极材料具有P6 3mc结构的基体和R-3m结构的包覆物时，在高电压(如大于4.5V)时，该正极材料基体的P6 3mc结构具有高的可逆容量，而包覆物的R-3m结构可发生尖晶石相变，从而形成稳定的尖晶石相变层，对正极材料基体P6 3mc结构的表面起到很好的保护作用，还可抑制过渡金属的溶出。因此，对于采用该具有R-3m@P6 3mc包覆结构的正极材料作为正极活性材料制成的锂离子电池，充电至高电压(如≥4.6V)时，可实现高的克容量和循环稳定性。
在一些实施方式中，基体主要由第一化合物组成。在一些实施方式中，包覆物主要由第二化合物组成。在一些实施方式中，基体主要由第一化合物组成，包覆物主要由第二化合物组成。
在本申请中，“结构A主要由材料a组成”表示材料a是提供结构A之活性功能的主要活性材料。一般情形中，结构A仅包括材料a，但不完全排除其它可共存物质的存在，但应理解，即使存在其他共存物质，这些共存物质也不会影响到材料a主体性能的发挥。应当理解，材料a在结构A中的质量占比较高，比如大于80％，大于85％，大于90％，大于95％，大于99％等，还比如100％。
在一些实施方式中，第一化合物为第一锂钴氧化物。在一些实施方式中，第二化合物为第二锂钴氧化物。
在本申请中，涉及“锂钴氧化物”是指至少具有Li元素、Co元素和O元素的物质。
在一些实施例中，具有包覆结构的正极材料中，基体包含具有P6 3mc晶体结构的第一锂钴氧化物，包覆物包含具有R-3m晶体结构的第二锂钴氧化物。在其中的一些实施例中，具有包覆结构的正极材料中，基体为具有P6 3mc晶体结构的第一锂钴氧化物，包覆物为具有R-3m晶体结构的第二锂钴氧化物。
上述具有R-3m@P6 3mc包覆结构的正极材料的优点包括但不限于：(1)在脱锂/嵌锂过程中，正极材料基体中具有P6 3mc结构的第一锂钴氧化物在高电压下的相变可逆性高于传统的R-3m结构的锂钴氧化物，具有非常高的可逆容量；(2)在高电压(如大于4.5V)时，包覆物中具有R-3m结构的第二锂钴氧化物发生尖晶石相变，形成稳定的尖晶石相变层，界面十分稳定，对基体中具有P6 3mc结构的第一锂钴氧化物可提供很好的保护作用，抑制过渡金属 的溶出，因而具有比纯P6 3mc结构的锂钴氧化物更好的高电压循环稳定性；(3)该正极材料可通过如下的方式获得：通过简便的方式将原有的尖晶石相变弊端转化为本申请中的技术优势，概括地，利用属于P6 3mc空间群的锂钴氧化物在一定温度(如300℃以下)经退火处理，表层发生R-3m原位相转变，从而形成基体属于P6 3mc空间群、包覆物属于R-3m空间群的包覆结构材料，不仅提供了锂钴氧化物正极材料改性的新方向，而且制备工艺简单、成本低、实用性强，具有较大的工业化应用潜力。
在一些实施方式中，包覆物在正极材料中的质量占比(记为m)满足0<m≤10％，其中，m通过XRD精修定量相分析获得。其中，m还可以≤5.5％(也即0<m≤5.5％)，还可以≤5％，还可以≤4.5％。m还可选自以下任一百分比或者任两种百分比构成的百分比区间：0.1％、0.2％、0.4％、0.5％、0.6％、0.8％、1％、1.5％、2％、2.5％、3％、3.5％、4％、4.2％、4.4％、4.5％、4.6％、4.8％、5％、5.5％、6％、7％、8％、9％、10％等。
在一些实施方式中，所述包覆物的厚度为10nm至300nm。包覆物的厚度还可选自以下任一比值或者任两种比值构成的区间：10nm、20nm、50nm、80nm、100nm、120nm、150nm、170nm、190nm、200nm、250nm、300nm。
在一些实施方式中，正极材料的平均粒径Dv50为10μm至25μm。
关于基体和包覆物的化学元素种类，可以相同，也可以不同，但应满足基体具有P6 3mc结构且包覆物具有R-3m结构。
在一些实施方式中，所述第一化合物包含Co元素和可选的T元素，其中，所述T元素包含Ni、Mn、Ti、Zn、Y、La、Zr、Mg、Fe、Cu、Nb、Cr或Al中的至少一种。
在一些实施方式中，所述第一化合物中，Co元素和所述T元素的摩尔量之和为n Co+T，所述T元素的摩尔量为n T，所述n T与所述n Co+T的比值y1，满足0≤y1≤0.15。
在一些实施方式中，第一化合物还包含Li元素，第一化合物中，Li元素的摩尔量为n Li，所述n Li与所述n Co+T的比值x1，满足0.6≤x1≤0.95。
在一些实施方式中，第一化合物还包含Na元素。
在一些实施方式中，第一化合物中，Na元素的摩尔量为n Na，所述n Na与所述n Co+T的比值z1，满足0<z1≤0.03。
在一些实施方式中，第一化合物为Li x1Na z1Co 1-y1T y1O 2±b1，其中，0.6≤x1≤0.95，0<z1≤0.03，0≤y1≤0.15；0≤b1≤0.2。
在一些实施方式中，所述第二化合物包含Co元素和可选的Q元素，其中，所述Q元素包含Ni、Mn、Ti、Zn、Y、La、Zr、Mg、Fe、Cu、Nb、Cr或Al中的至少一种。
在一些实施方式中，所述第二化合物中，Co元素和所述Q元素的摩尔量之和为m Co+Q， 所述Q元素的摩尔量为m Q，所述m Q与所述m Co+Q的比值y2满足0≤y2≤0.5。
在一些实施方式中，第二化合物还包含Li元素，第二化合物中，Li元素的摩尔量为m Li，所述m Li与所述m Co+Q的比值x2，满足0.6≤x2≤1.2。在一些实施方式中，0.8≤x2≤1.1。
在一些实施方式中，第二化合物还包含Na元素。
在一些实施方式中，所述第二化合物中，Na元素的摩尔量为m Na，所述m Na与所述m Co+Q的比值z2，满足0<z2≤0.03。
在一些实施方式中，第二化合物为Li x2Na z2Co 1-y2Q y2O 2±b2，其中，0.6≤x2≤1.2，0≤z2≤0.03，0≤y2≤0.15，0≤b2≤0.2。
基体和包覆物的晶体结构可通过X射线衍射(XRD)方法获得的XRD图谱中的特征衍射峰进行鉴定。
在一些实施方式中，使用Cu-Kα辐射获得X射线衍射图，此时进行XRD测试的靶材为Cu-Kα。
在一些实施方式中，在具有包覆结构的正极材料的X射线衍射谱中，基体的最强衍射峰为P6 3mc结构的(002)晶面衍射峰，一些实施方式中，该(002)晶面衍射峰位于18°-19°范围内。
在一些实施方式中，在具有包覆结构的正极材料的X射线衍射谱中，包覆物的最强衍射峰为R-3m结构的(003)晶面衍射峰，一些实施方式中，该(003)晶面衍射峰位于18°-19°范围内。
在一些实施方式中，2θ衍射角在18°-19°范围内的最强衍射峰的峰强为I 1，2θ衍射角在44°-46°范围内的最强衍射峰的峰强为I 2，满足1％≤I/I≤10％。在其中的一些实施例中，在2θ衍射角44°-46°范围内只有一个特征衍射峰(应当理解，不考虑噪音)。该2θ衍射角在44°-46°范围内的衍射峰对应R-3m结构锂钴氧化物的(104)晶面衍射峰，可作为鉴别R-3m结构锂钴氧化物存在与否的特征衍射峰。
本申请的第二方面
在本申请的第二方面，提供一种具有包覆结构的正极材料的制备方法，可用于制备本申请的第一方面的具有包覆结构的正极材料，但并不局限于制备本申请的第一方面的具有包覆结构的正极材料。
在一些实施方式中，利用具有P6 3mc结构的正极活性材料在表层发生原位相转变而形成具有R-3m结构的包覆物，从而制得具有包覆结构的正极材料。
在一些实施方式中，提供一种具有包覆结构的正极材料的制备方法，包括如下步骤：提供具有P6 3mc结构的正极活性材料；将具有P6 3mc结构的正极活性材料进行退火，具有P6 3mc结构的正极活性材料的表层发生原位相转变而形成具有R-3m结构的包覆物，获得具有包覆结构的正极材料。
随着退火温度的升高，具有P6 3mc结构的正极活性材料表层的R-3m相变逐渐增多，具有R-3m结构的包覆物的相对含量增大。本申请的一些实施例中发现，当退火温度超过300℃时，相变明显加速，具有R-3m结构的包覆物的相对含量也极速增加。
在一些实施方式中，退火温度可以选自250℃～300℃。退火温度还可以选自如下任一种温度或者任两种温度构成的温度区间：250℃、255℃、260℃、265℃、270℃、275℃、280℃、285℃、290℃、295℃等。
在一些实施例中，随着退火时间的延长，具有R-3m结构的包覆物的相对含量逐渐增加。
在一些实施方式中，退火时间可以选自0.5h～4h。退火时间还可以选自如下任一种时长或者任两种时长构成的区间：0.5h(30min)、0.75h、1h、1.5h、2h、2.5h、3h、3.5h、4h等。
退火温度和退火时间可以进行合适方式的组合。在一些实施方式中，退火温度为250℃～300℃，退火时间为0.5h～4h。退火温度和退火时间可以选自上述任一实施方式中的合适值或合适范围。
在一些实施方式中，具有P6 3mc结构的正极活性材料可通过包括如下步骤的制备方法获得：(1)采用包括可溶性钴盐的原料，通过液相沉淀法、烧结、破碎，可选地筛分，获得钴氧化物前驱体；其中，原料还可选地包括含有T元素的可溶性T盐；(2)将钴氧化物前驱体与钠盐混合，通过固相合成法，获得含钠钴氧化物前驱体；(3)将含钠钴氧化物前驱体与锂盐溶液进行加热回流、洗涤、干燥、过筛，获得具有P6 3mc结构的正极活性材料。
在一些实施方式中，可溶性钴盐可以选自如下群组中的一种或更多种：氯化钴、醋酸钴、硫酸钴、硝酸钴等。
在一些实施方式中，含有T元素的可溶性T盐为硫酸盐。
在一些实施方式中，液相沉淀法的溶剂选自水。
在一些实施方式中，液相沉淀法在沉淀剂存在条件下进行沉淀。
在一些实施方式中，合适的沉淀剂的举例包括但不限于碳酸铵。
在一些实施方式中，液相沉淀法在合适的pH值条件下进行沉淀。合适的pH值举例如5～9。合适的pH值还可以选自如下pH值中的任一种或任两种之间的pH范围：5、5.5、6、6.5、7、7.5、8、8.5、9等。
在一些实施方式中，步骤(2)中固相合成法的烧结温度选自700℃～1000℃。烧结时间选自36h～56h。烧结的气氛为氧气气氛。
在一些实施方式中，锂盐溶液中的锂盐可以选自溴化锂。
在一些实施方式中，锂盐溶液中的溶剂可以选自醇类溶剂。其中，醇类溶剂可以己醇。
在一些实施方式中，步骤(3)中加热回流的反应温度选自175℃～185℃，举例如180℃。加热回流的反应时间选自7.5h～8.5h。
本申请的第二方面的制备方法可通过如下方式实现：通过简便的方式将原有的尖晶石相变弊端转化为本申请中的技术优势，概括地，利用属于P6 3mc空间群的锂钴氧化物在一定温度(如300℃以下)经退火处理，表层发生R-3m原位相转变，从而形成基体属于P6 3mc空间群、包覆物属于R-3m空间群的包覆结构材料，该方法不仅提供了锂钴氧化物正极材料改性的新方向，而且制备工艺简单、成本低、实用性强，具有较大的工业化应用潜力。
本申请的第三方面
在本申请的第三方面，提供一种正极极片，包括正极活性材料层，该正极活性材料层包含本申请的第一方面的具有包覆结构的正极材料或者包含本申请的第二方面的制备方法制备得到的具有包覆结构的正极材料。
在一些实施方式中，正极极片还包括正极集流体，此时包括正极活性材料层和正极集流体，其中的一些实施方式中，正极活性材料层位于正极集流体的至少一个表面上。
在一些实施方式中，正极活性材料层位于正极集流体的仅一个表面上。
在一些实施方式中，正极活性材料层位于正极集流体相对的两个表面上。
在一些实施例中，正极集流体可以采用铝箔，同样，也可以采用本领域常用的其他正极集流体。
正极活性材料层还可以包括导电剂和粘结剂中的一种或更多种。在一些实施例中，正极活性材料层中的导电剂可以包括碳纳米管、乙炔黑、石墨烯、科琴黑、导电碳黑等中的一种或更多种。在一些实施例中，正极活性材料层中的粘结剂可以包括聚偏氟乙烯、羧甲基纤维素、丁苯橡胶等中的一种或更多种。在一些实施例中，正极活性材料层中的正极材料、导电剂和粘结剂的质量比为(84-98)：(0.5-10)：(0.5-5)。应该理解，以上描述的材料和质量比仅是示例性的，而不用于限制本申请，可以其他合适的材料和质量比。
本申请的第四方面
在本申请的第四方面，提供一种电化学装置，其包括本申请的第三方面的正极极片，还包括负极极片以及设置在正极极片和负极极片之间的隔离膜。
在一些实施例中，负极极片可以包括负极集流和设置在负极集流体的至少一个表面上的负极活性材料层。在一些实施例中，在负极集流体相对的两侧均设置有负极活性材料层。在另一些实施例中，仅在负极集流体的一侧设置负极活性材料层。
在一些实施例中，负极活性材料层包括负极活性材料，负极活性材料包括碳材料、硅材料等中的一种或更多种。在一些实施例中，碳材料包括石墨、硬碳等中的一种或更多种。在 一些实施例中，硅材料包括硅、硅氧化合物、硅碳化合物、硅合金等中的一种或更多种。在一些实施例中，负极集流体可以包括铜箔、铝箔、镍箔或碳基集流体中的一种或更多种。
负极活性材料层还可以包括导电剂和粘结剂中的一种或更多种。在一些实施例中，负极活性材料层中的导电剂包括导电炭黑、乙炔黑、碳纳米管、科琴黑、导电石墨、石墨烯等中的一种或更多种。在一些实施例中，导电剂在负极活性材料层中的质量百分含量为0.5％至10％。在一些实施例中，负极活性材料层中的粘结剂包括聚偏氟乙烯、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、聚乙烯吡咯烷酮、聚乙烯醚、聚甲基丙烯酸甲酯、聚四氟乙烯、聚六氟丙烯、丁苯橡胶等中的一种或更多种。在一些实施例中，粘结剂在负极活性材料层中的质量百分含量为0.5％至10％。应该理解，以上仅是示例性的，而不用于限制本申请。
在一些实施例中，隔离膜包括由对本申请的电解液稳定的材料形成的聚合物或无机物等。例如，隔离膜可包括基材层和表面处理层。基材层为具有多孔结构的无纺布、膜或复合膜，基材层的材料包括聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯或聚酰亚胺中的至少一种。具体地，可选用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。无机物层包括无机颗粒和粘结剂，无机颗粒包括氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、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。粘结剂包括聚偏氟乙烯、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、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。聚合物层中包含聚合物，聚合物的材料包括聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯呲咯烷酮、聚乙烯醚、聚偏氟乙烯或聚(偏氟乙烯-六氟丙烯)中的至少一种。在一些实施例中，隔离膜的厚度为5μm至500μm。
在本申请的电化学装置还包括电解液，电解液包括锂盐和非水溶剂。
在一些实施例中，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和二氟硼酸锂中的一种或多种。举例来说，锂盐可以选用LiPF 6。
在一些实施例中，非水溶剂可包括碳酸酯化合物、羧酸酯化合物、醚化合物或它们的任意合适的组合。
在一些实施例中，碳酸酯化合物可选自链状碳酸酯化合物、环状碳酸酯化合物、氟代碳 酸酯化合物或其任意合适的组合。
在一些实施例中，链状碳酸酯化合物可选自碳酸二乙酯(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可选自碳酸亚乙酯(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可选自碳酸氟代亚乙酯(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任意合适的组合。
在一些实施例中，羧酸酯化合物可选自乙酸甲酯、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、己内酯、甲酸甲酯或者其任意合适的组合。
在一些实施例中，醚化合物可选自二丁醚、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、四氢呋喃或者其任意合适的组合。
根据本申请的一些实施方式，本申请的电化学装置包括，但不限于：所有种类的一次电池或二次电池。在一些实施例中，所述电化学装置是锂二次电池。在一些实施例中，锂二次电池包括，但不限于：锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
本申请的第五方面
在本申请的第五方面，提供一种用电设备，其包括本申请的第四方面的电化学装置。
本申请的实施例的用电设备没有特别限定，其可以是用于目前已有的任何电子装置。在一些实施例中，用电设备可以包括，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。
下面将结合实施例对本申请的实施方案进行详细描述。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
测试方法：
1、XRD测试
采用X射线粉末衍射仪(XRD，仪器型号：Bruker D8 ADVANCE)测试正极材料，靶材为Cu Kα；电压电流为40KV/35mA，扫描角度范围为10°至90°，扫描速率0.02°/s，要求最强衍射峰强度大于10000，单位counts。通过Fullprof软件对采集到的XRD谱进行精修，确定物相结构以及I 2/I 1。
2、正极材料元素组成测试
正极材料元素组成测试，其中Li、Na和过渡金属等元素含量由美国PE公司Optima7000DV电感耦合等离子光谱(ICP)测试仪测得。
3、放电克容量及循环容量保持率测试
将扣电池经恒温(25℃)陈化24h后，在3V至4.6V(相对于Li/Li +)电压范围内反复进行50次充放电测试。其中，前2圈采用0.2C倍率的低电流充放电，对电池进行活化；从第3圈起，采用1C倍率的电流进行充放电。其中，1C＝273mA/g。
其中，以第3圈放电克容量作为循环克容量衰减的参考基准，即第n次容量保留率＝第n次放电容量/第3次放电容量×100％。
4.平均粒径Dv50测试
采用激光粒度仪测量获得正极材料的平均粒径Dv50。其中仪器型号为MasterSizer 3000，进样系统为Hydro 2000SM&Hydro 2000MU，量程为0.01-3500um，检测角范围为0.0153-144°，测试快照速率为1000次/s，检测器为光敏硅材料，测试参考标准GB/T19077-2016/ISO 13320:2009。测试前，取待测样品适量，加入去离子水，超声5min，功率120W，使之分散均匀。
5.包覆物的厚度测试
将锂离子电池在0.05C的电流密度下满放至3.5V以下，并且静置10min后在手套箱内拆解获得正极极片；将正极极片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，测量包覆物的厚度。采集至少3处不同位置，取平均值。
对比例1.
按照摩尔比0.85:0.05:0.15分别称取硫酸钴(CoSO 4)、硫酸镍(NiSO 4)和硫酸锰(MnSO 4)，加入去离子水快速搅拌溶解，然后加入碳酸铵，调节pH为8，直至反应完全进行，形成均相 碳酸盐沉淀物，将沉淀物于650℃烧结12h，经破碎和筛分处理等过程，得到钴镍锰的氧化物前驱体。
将碳酸锂(Li 2CO 3)与上述金属氧化物按照摩尔比为1.05:1称量混合均匀，在900℃下保温12h，经后处理得到相应锂钴氧化物材料(记为对比例1材料)。对比例1材料的Dv50为13μm。
XRD测试结果可参见图2所示的XRD图谱。结果表明，所得锂钴氧化物为R-3m结构。ICP测试结果可参见表1。结果表明，对比例1所得正极材料的元素组成为Li 1.002Co 0.857Ni 0.053Mn 0.090O 2。
将上述R-3m结构的对比例1材料作为正极活性材料，以导电碳(SP)作为导电剂、聚偏氟乙烯(PVDF)作为粘接剂，按照质量比90:5:5混合，加入溶剂N-甲基-2-吡咯烷酮(NMP)制成浆料，涂布在厚度为12μm的铝箔上。然后，先在90℃鼓风干燥箱中干燥4h，在110℃真空干燥箱烘烤24h。将充分干燥后的极片，进行冷压、冲切、称重等过程，得到正极。
在惰性气氛下，用上述正极与隔离膜、负极和电解液组装成扣电半电池。其中，负极为锂金属；电解液：体积比为1:1的碳酸亚乙酯(EC)和碳酸二甲酯(DMC)，LiPF 6的浓度为1mol/L。
将上述组装好的扣电池进行电化学性能测试，测得首次放电克容量为205.7mAh/g，循环80圈以后的容量保持率为68.2％。
对比例2.
按照摩尔比0.85:0.05:0.10分别称取硫酸钴(CoSO 4)、硫酸镍(NiSO 4)和硫酸锰(MnSO 4)，加入去离子水快速搅拌溶解，然后加入碳酸铵，调节pH为8，直至反应完全进行，形成均相碳酸盐沉淀物，将沉淀物于650℃烧结12h，经破碎和筛分处理等过程，得到钴镍锰的金属氧化物前驱体1(对应前述的钴氧化物前驱体，记为前驱体1)。
将碳酸钠(Na 2CO 3)与上述前驱体1按照摩尔比为0.35:1称量混合均匀，在800℃下保温48h，经后处理得到组成为Na 0.7Co 0.85Ni 0.05Mn 0.10O 2的含钠钴氧化物前驱体2(对应前述的含钠钴氧化物前驱体，记为前驱体2)。XRD测试结果表明所得含钠钴氧化物为P6 3/mmc结构。
将上述含钠钴氧化物前驱体2与5mol/L的LiBr的己醇溶液，按照20g:600ml的质量体积比例，混合均匀；然后采用回流法在180℃保温12h，直至反应完全进行；反应结束后，将所得粉末过滤，用甲醇洗涤后，置于真空烘箱180℃烘干；最后，将干燥后的粉末过200目筛，即可得到锂钴氧化物材料(可记为对比例2材料)。
XRD测试结果可参见图3所示的XRD图谱。测试结果表明，对比例2所得正极材料为 属于P6 3mc晶体结构的纯相。ICP测试结果可参见表1，测试结果表明对比例2材料的元素组成为Li 0.912Na 0.007Co 0.854Ni 0.052Mn 0.094O 2。
后续采用对比例2材料作为正极活性材料的扣电池组装及测试的方法与对比例1完全相同。实验测得对比例2材料的首次放电克容量为218.4mAh/g，循环80圈以后的容量保持率为78.3％。
实施例1至实施例5.改变退火温度
取P6 3mc结构的对比例2材料10g左右，置于管式炉中，以1.5℃/min的升温速率升温至预设的保温温度(T，对应前述的退火温度)，然后保温30min，随炉冷却后得到基体和包覆物分别为P6 3mc结构、R-3m结构的复合材料(R-3m@P6 3mc包覆结构的正极材料)。所得正极材料后续扣电制作及测试的方法与对比例2相同。其中，实施例1材料至实施例5材料的保温温度T分别为250℃、270℃、280℃、290℃、300℃，所得正极材料分别记为实施例1材料、实施例2材料、实施例3材料、实施例4材料、实施例5材料。所得正极材料的后续测试过程与对比例2相同。其中，材料的粉末测试结果及电化学性能测试结果可参见表1。
实施例6至实施例9.改变退火时间
取P6 3mc结构的对比例2材料10g左右，置于管式炉中，以1.5℃/min的升温速率升温至270℃，然后保温一定时间(t，对应前述的退火时间)，随炉冷却后得到基体和包覆物分别为P6 3mc结构、R-3m结构复合材料(R-3m@P6 3mc包覆结构的正极材料)。所得正极材料后续扣电制作及测试的方法与对比例2相同。其中，实施例6材料至实施例9材料的保温时间t分别为15min、45min、60min、75min，所得正极材料分别记为实施例6材料、实施例7材料、实施例8材料、实施例9材料。所得正极材料后续测试过程与对比例2相同。其中，实施例6材料至实施例9材料的粉末测试结果及电化学性能测试结果可参见表1。
实施例10.改变掺杂元素
按照摩尔比0.85:0.15分别称取硫酸钴(CoSO 4)、硫酸锌(ZnSO4)，加入去离子水快速搅拌溶解，然后加入碳酸铵，调节pH为8，直至反应完全进行，形成均相碳酸盐沉淀物，将沉淀物于650℃烧结12h，经破碎和筛分处理等过程，得到钴锌的金属氧化物前驱体1(对应前述的钴氧化物前驱体)。
将碳酸钠(Na 2CO 3)与上述前驱体1按照摩尔比为0.35:1称量混合均匀，在800℃下保温48h，经后处理得到组成为Na 0.7Co 0.85Zn 0.15O 2的锌掺杂含钠钴氧化物前驱体2(对应前述的含钠钴氧化物前驱体)。
将上述锌掺杂含钠钴氧化物前驱体2与5mol/L的LiBr的己醇溶液，按照20g:600mL的质量体积比例，混合均匀；然后采用回流法在180℃保温12h，直至反应完全进行；反应结 束后，将所得粉末过滤，用甲醇洗涤后，置于真空烘箱180℃烘干；最后，将干燥后的粉末过200目筛，即可得到P6 3mc结构的锌掺杂锂钴氧化物材料。
取将上述P6 3mc结构的锌掺杂锂钴氧化物材料10g左右，置于管式炉中，以1.5℃/min的升温速率升温至270℃，然后保温45min，随炉冷却后得到锌掺杂的基体和包覆物分别为P6 3mc结构、R-3m结构复合材料(R-3m@P6 3mc包覆结构的正极材料)(记为实施例10材料)。所得正极材料后续测试过程与对比例2相同。其中，实施例10材料粉末测试结果及电化学性能测试结果可参见表1。
实施例11至实施例17.改变掺杂元素
除了将硫酸锌替换依次替换为硝酸铝、硫酸锰、硝酸钇、硝酸锆、硝酸镧、硫酸镍和硝酸钛，将这些可溶盐与硫酸钴一起加入到去离子水中存在不同以外，实施例11至实施例17材料制备的其余步骤和测试过程与实施例10相同。其中，材料的粉末测试结果及电化学性能测试结果可参见表1。
表1中，I 2/I 1是XRD图谱中，2θ衍射角在44°-46°范围内的衍射峰的强度(I 1)与2θ衍射角在18°-19°范围内的最强衍射峰的强度(I 1)之间的比值。
表1中，m表示R-3m结构在R-3m@P6 3mc包覆结构的正极材料中的质量百分含量。其中，m是通过XRD精修定量相分析得到。
表1.
Figure PCTCN2022084200-appb-000001
Figure PCTCN2022084200-appb-000002
本申请制备的具有包覆结构的锂钴氧化物正极材料主要由两部分组成，其中，基体和包覆物分别具有P6 3mc、R-3m的晶体结构(记为R-3m@P6 3mc包覆结构)。
为了证实该结构，首先测试了实施例4材料的XRD图谱，XRD测试结果可参见图4所示的XRD图谱。测试结果表明，实施例4材料的物相组成为主相P6 3mc复合少量R-3m结构锂钴氧化物，通过XRD结构精修得到R-3m结构材料的质量百分含量m为5.24％。
进一步地，取少量实施例4材料，置于80℃的王水溶液(浓盐酸和浓硝酸的体积比V 浓 HCl:V 浓HNO3＝3:1)，热的王水可以从表面缓慢的侵蚀锂钴氧化物材料。浸泡约30分钟后，将残余粉料滤出、洗涤、烘干，然后再次对材料进行XRD测试。XRD测试结果可参见图5所示的XRD图，测试结果表明，实施例4材料经王水处理后，所得材料仅剩余P6 3mc结构的物相，而原R-3m结构已经完全溶解，具体表现为45°附近特征衍射峰消失。由此说明R-3m结构锂钴氧化物主要存在于材料表层(也即包覆层)，本申请制备的正极材料具有R-3m@P6 3mc的包覆结构。
通过比较实施例4和对比例2的XRD衍射谱，可以看到二者实施例4材料的XRD衍射谱中多出了一套R-3m结构的衍射谱。其中，实施例4材料中的R-3m结构(003)晶面衍射峰位于18.5°左右，与主相P6 3mc结构(002)晶面衍射峰高度重合，表明R-3m结构锂钴氧化物材料也是一种缺锂态，与实施例4材料王水热处理前的P6 3mc结构锂钴氧化物相同，进而说明各实施例材料(包括实施例4材料)中的R-3m结构锂钴氧化物材料是由P6 3mc结构锂钴氧化物材料原位转化得到。另外，还可以看到，45°衍射角附近只有一个衍射峰，属于R-3m结构锂钴氧化物的(104)晶面衍射峰，可以用作鉴别R-3m结构锂钴氧化物存在与否的特征衍射峰。
比较实施例1至实施例17与对比例1、对比例2材料的测试数据，可以看出，各正极材料的综合电性能方面：R-3m@P6 3mc结构>P6 3mc结构>R-3m结构。在组分相近的情况下，R-3m结构的锂钴氧化物材料的首次放电克容量和循环稳定性表现最差，如对比例1材料，充电至4.6V，其首次放电克容量为205mAh/g，循环80圈后的容量保持率为62.2％。对于纯P6 3mc结构的锂钴氧化物(如对比例2材料)，其首次放电克容量明显优于R-3m结构锂钴氧化物材料，主要源于其高脱锂态下仍能维持结构稳定的材料特性，但是由于材料表面缺乏界面保护，循环过程中过渡金属元素溶出非常严重，导致其循环80圈后的容量保持率也仅为75.3％。 通过表1可以得出，本申请提供的R-3m@P6 3mc包覆结构的锂钴氧化物材料具有明显优势。
以上各实施方式和实施例的各技术特征可以进行任意合适方式的组合，为使描述简洁，未对上述实施方式和实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为在本说明书记载的范围中。
以上各实施例仅表达了本申请的几种实施方式，便于具体和详细地理解本申请的技术方案，但并不能因此而理解为对本申请保护范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。此外应理解，在阅读了本申请的上述讲授内容之后，本领域技术人员可以对本申请作各种改动或修改，得到的等价形式同样落于本申请的保护范围。还应当理解，本领域技术人员在本申请提供的技术方案的基础上，通过合乎逻辑的分析、推理或者有限的试验得到的技术方案，均在本申请所附权利要求的保护范围内。因此，本申请的保护范围应以所附权利要求的内容为准，说明书及附图可以用于解释权利要求的内容。

Claims (10)

  1. 一种正极材料，其包括基体以及位于所述基体至少部分表面的包覆物；其中，所述基体包含具有P6 3mc结构的第一化合物，所述包覆物包含具有R-3m结构的第二化合物。
  2. 根据权利要求1所述的正极材料，所述包覆物的厚度为10nm至300nm。
  3. 根据权利要求1所述的正极材料，其中，所述第一化合物为锂钴氧化物，所述第一化合物包含Co元素和可选的T元素，其中，所述T元素包含Ni、Mn、Ti、Zn、Y、La、Zr、Mg、Fe、Cu、Nb、Cr或Al中的至少一种；所述第一化合物中，Co元素和所述T元素的摩尔量之和为n Co+T，所述T元素的摩尔量为n T，所述n T与所述n Co+T的比值y1，满足0≤y1≤0.15。
  4. 根据权利要求3所述的正极材料，其中，所述第一化合物还包含Na元素，所述第一化合物中，Na元素的摩尔量为n Na，所述n Na与所述n Co+T的比值z1，满足0<z1≤0.03。
  5. 根据权利要求1所述的正极材料，其中，所述第二化合物为锂钴氧化物，所述第二化合物包含Co元素和可选的Q元素，其中，所述Q元素包含Ni、Mn、Ti、Zn、Y、La、Zr、Mg、Fe、Cu、Nb、Cr或Al中的至少一种；所述第二化合物中，Co元素和所述Q元素的摩尔量之和为m Co+Q，所述Q元素的摩尔量为m Q，所述m Q与所述m Co+Q的比值y2满足0≤y2≤0.5。
  6. 根据权利要求5所述的正极材料，其中，所述第二化合物还包括Na元素，所述第二化合物中，Na元素的摩尔量为m Na，所述m Na与所述m Co+Q的比值z2，满足0<z2≤0.03。
  7. 根据权利要求1所述的正极材料，其中，所述正极材料的X射线衍射谱中，2θ衍射角在18°-19°范围内的最强衍射峰的峰强为I 1，2θ衍射角在44°-46°范围内的最强衍射峰的峰强为I 2，满足1％≤I 2/I 1≤11％。
  8. 根据权利要求1所述的正极材料，其满足以下条件中的至少一个：
    条件a1：所述包覆物在所述正极材料中的质量占比m满足0<m≤10％，其中，m通过XRD精修定量相分析获得；
    条件a2：所述正极材料的平均粒径Dv50为10μm至25μm。
  9. 一种电化学装置，其包括正极极片，所述正极极片包含权利要求1至8中任一项所述的正极材料。
  10. 一种用电设备，其包括权利要求9所述电化学装置。
PCT/CN2022/084200 2022-03-30 2022-03-30 正极材料、电化学装置及用电设备 WO2023184275A1 (zh)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103582971A (zh) * 2011-05-31 2014-02-12 三洋电机株式会社 非水电解质电池
WO2014083834A1 (ja) * 2012-11-29 2014-06-05 三洋電機株式会社 非水電解質二次電池
JP2015176644A (ja) * 2014-03-13 2015-10-05 三洋電機株式会社 非水電解質二次電池用正極活物質及び非水電解質二次電池
CN107507973A (zh) * 2016-06-14 2017-12-22 三星电子株式会社 复合正极活性材料、包括复合正极活性材料的正极和锂电池及制备复合正极活性材料的方法

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103582971A (zh) * 2011-05-31 2014-02-12 三洋电机株式会社 非水电解质电池
WO2014083834A1 (ja) * 2012-11-29 2014-06-05 三洋電機株式会社 非水電解質二次電池
JP2015176644A (ja) * 2014-03-13 2015-10-05 三洋電機株式会社 非水電解質二次電池用正極活物質及び非水電解質二次電池
CN107507973A (zh) * 2016-06-14 2017-12-22 三星电子株式会社 复合正极活性材料、包括复合正极活性材料的正极和锂电池及制备复合正极活性材料的方法

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