WO2024045937A1 - 一种正极活性材料及其应用 - Google Patents

一种正极活性材料及其应用 Download PDF

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Publication number
WO2024045937A1
WO2024045937A1 PCT/CN2023/108256 CN2023108256W WO2024045937A1 WO 2024045937 A1 WO2024045937 A1 WO 2024045937A1 CN 2023108256 W CN2023108256 W CN 2023108256W WO 2024045937 A1 WO2024045937 A1 WO 2024045937A1
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Prior art keywords
active material
lithium
cathode active
metal oxide
positive electrode
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PCT/CN2023/108256
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English (en)
French (fr)
Inventor
曾家江
夏定国
李素丽
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珠海冠宇电池股份有限公司
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Priority claimed from CN202211072399.5A external-priority patent/CN115275171A/zh
Priority claimed from CN202211075101.6A external-priority patent/CN115995550A/zh
Application filed by 珠海冠宇电池股份有限公司 filed Critical 珠海冠宇电池股份有限公司
Publication of WO2024045937A1 publication Critical patent/WO2024045937A1/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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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 embodiments of the present application relate to pole piece materials, in particular to a cathode active material and its application, which belong to the technical field of secondary batteries.
  • the capacity of the positive active material plays a crucial role in the capacity of the lithium-ion battery.
  • the most commonly used method at present is to increase its charge and discharge voltage.
  • the crystal structure of the positive active material will collapse, which will lead to a series of problems such as rapid capacity fading and a significant reduction in cycle performance of the battery.
  • embodiments of the present application provide a cathode active material.
  • the special composition and crystal phase structure of the cathode active material help to improve the specific capacity and cycle performance of the battery, especially under high-voltage conditions, and still enable the battery to perform excellently. .
  • the present application provides a positive electrode sheet, which includes the above-mentioned positive electrode active material, thereby helping to improve the relevant electrical performance of the battery.
  • the present application also provides a lithium-ion battery, which includes the above-mentioned positive electrode sheet. Therefore, the lithium-ion battery has excellent performance in terms of specific capacity and cycle performance.
  • the present application provides a cathode active material, wherein the cathode active material is composed of matrix particles including lithium metal oxide and a graphite coating layer covering at least part of the surface of the matrix particles;
  • the lithium metal oxide has the structure shown in Formula 1;
  • the lithium metal oxide is in the Cmca space group of the cubic crystal system, and has a 002 peak with a 2 ⁇ of 17.9°-18.1°, and a 131 peak with a 2 ⁇ of 67.0°-67.5°; Li ny Na y Co 1-a M a O 2Formula 1
  • M is the doping element.
  • M1 is selected from at least one of Te, W, Al, B, P and K; M2 is a doping element different from M1.
  • the mass percentage W of the graphite coating layer satisfies: 0 ⁇ W ⁇ 1%.
  • the peak intensity I G of the lithium metal oxide at a wavelength of about 1560 ⁇ 30cm -1 is the same as that of the lithium metal oxide at a wavelength of about 1360 ⁇ 30cm -1
  • the peak intensity of I D satisfies: I D / IG ⁇ 68%.
  • the present application provides a cathode active material, wherein the cathode active material includes lithium metal oxide, and the lithium metal oxide has the molecular formula shown in Formula 1;
  • the lithium metal oxide is in the Cmca space group of the cubic crystal system, and has a 002 peak with a 2 ⁇ of 17.9°-18.1°, and a 131 peak with a 2 ⁇ of 67.0°-67.5°; Li ny Na y Co 1-a M a O 2Formula 1
  • the ratio m1 of the molar content of Li element and Na element satisfies: 12 ⁇ m1 ⁇ 80;
  • M is the doping element.
  • M1 is selected from at least one of Te, W, Al, B, P and K; M2 is a doping element different from M1.
  • cathode active material as described above, wherein the cathode active material is composed of matrix particles including the lithium metal oxide and a coating layer covering at least part of the surface of the matrix particles.
  • the present application provides a positive electrode sheet, wherein the positive electrode sheet includes the positive electrode active material as described above.
  • the positive electrode sheet as described above, wherein the positive electrode sheet includes a current collector, a safety layer and a positive electrode active layer;
  • the safety layer is sandwiched between the current collector and the positive active layer, and the positive active layer includes the positive active material.
  • the compacted density of the positive electrode active layer is greater than or equal to 3.5g/cm 3 .
  • the present application provides a lithium ion battery, wherein the lithium ion battery includes the positive electrode sheet as described above.
  • the cathode active material of this application has a special crystal phase structure and chemical composition. After it is used in a battery, the cycle performance and gram capacity of the battery are significantly improved. Even under high-voltage conditions of 4.5V and above, the cathode active material is used The battery can still maintain excellent electrical performance and will not suffer from structural collapse due to poor voltage resistance of the positive active material.
  • Figure 1 is a schematic structural diagram of an embodiment of the negative electrode sheet in the lithium-ion battery of the present application
  • Figure 2 is an SEM image of the cathode active material in Example 1A of the present application.
  • Figure 3 is an SEM image of the cathode active material in Example 1C of the present application.
  • Figure 4 is an SEM image of the cathode active material in Comparative Example 1C of the present application.
  • Figure 5 is a Raman test chart of the positive electrode active material in Example 1A and Example 9A of the present application;
  • Figure 6 is an XRD pattern of the cathode active material in Example 8A and Example 1B of the present application.
  • a first aspect of the present application provides a cathode active material, which is composed of matrix particles including lithium metal oxide and a graphite coating layer covering at least part of the surface of the matrix particles;
  • Lithium metal oxide has the structure shown in Formula 1;
  • lithium metal oxide is in the Cmca space group of the cubic crystal system, and has a 002 peak with a 2 ⁇ of 17.9° to 18.1°, and a 131 peak with a 2 ⁇ of 67.0° to 67.5°; Li ny Na y Co 1-a M a O 2Formula 1
  • M is the doping element.
  • the graphite coating layer can cover part of the surface of the matrix particles, or can cover the entire surface of the collective particles. This application does not specifically limit the graphite coating layer.
  • the graphite coating layer is a graphene coating layer and/or a reduced graphene oxide coating layer.
  • the lithium metal oxide mentioned above in this application specifically includes at least oxides of lithium, cobalt and sodium. Furthermore, it can also be doped with M. This application does not limit the specific selection of M, and it can be a common doping element in the art. For example, it may be at least one of W, Mg, Ti, Mn, Al, Te, Ni, Nb, Zr, La, F, Ce, Sr, Y, K, B and P elements.
  • y is 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.010, 0.012, 0.015, 0.018, 0.020, 0.022, 0.024, 0.025, 0.026, 0.028, 0.03, 0.0 4 or 0.05;
  • a is 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.010, 0.012, 0.015, 0.018, 0.020, 0.022, 0.024, 0.025, 0.026, 0.028, 0.030, 0.032, 0. 034, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09 or 0.095.
  • n refers to the molar amount of lithium per unit mole of lithium metal oxide in the positive electrode active material that has not undergone any charge and discharge treatment. It can be understood that when the positive active material is applied to a lithium-ion battery for any charge and discharge process, the molar amount of lithium in a unit mole of lithium metal oxide is different under different charge and discharge mechanisms and charge and discharge nodes.
  • the oxidized cathode active material compared with other positive electrode active materials, it will include the lithium gold After the oxidized cathode active material is used in lithium-ion batteries, the specific capacity and cycle performance of the lithium-ion battery are significantly improved. Even under high-voltage working conditions, the electrical performance of the lithium-ion battery will not deteriorate.
  • the present application provides a graphite coating layer so that the positive electrode active material has a core-shell structure including a core of lithium metal oxide and a graphite coating layer covering the core.
  • the coating helps to reduce or inhibit the side reactions of lithium metal oxide and electrolyte. Even when the battery is operating in a high-pressure environment, a stable interface can still be formed between the positive active material and the electrolyte. By avoiding the contamination of the positive active ions The transitional dissolution of metal ions and the avoidance of liquid shortage improve the cycle performance of the battery.
  • the suppression or reduction of side reactions can also reduce the gas production inside the battery, thereby ensuring the safety performance of the battery;
  • graphite The coating layer itself has good electron transmission properties, so that the cathode active material including the graphite coating layer can further improve the conductivity of the cathode active material, thereby increasing the charge and discharge capacity of the lithium-ion battery;
  • the material with the above crystal characteristics Lithium metal oxide has a more complete layered crystal phase structure, which can reduce or inhibit the occurrence of internal mixing of crystal phases, thereby enabling smooth deintercalation of lithium ions, especially during high-voltage charge and discharge processes.
  • a small charging and discharging platform is a small charging and discharging platform.
  • the lithium metal oxide has the structure shown in Formula 2; Li ny Na y Co 1-a1-a2 M1 a1 M2 a2 O 2Formula 2
  • M1 is selected from at least one of Te, W, Al, B, P and K; M2 is a doping element different from M1.
  • the lithium metal oxide of the present application can also have the structure shown in Formula 2, specifically an oxide including at least lithium, cobalt, sodium and M1. Furthermore, it can also be doped with M2 that is different from M1. This application does not limit the specific selection of M2, and it can be a common doping element in the art. For example, it may be at least one of Mg, Ti, Mn, Al, Te, Ni, Nb, Zr, La, F, Ce, Sr, Y, K, B and P elements.
  • a1 is 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.010, 0.012, 0.015, 0.018, 0.020, 0.022, 0.024, 0.025, 0.026, 0.028, 0.030, 0.032, 0.034, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09 or 0.095;
  • a2 is 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.010, 0.012, 0.015, 0.018, 0.020, 0.022, 0.024, 0.025, 0.026, 0.028, 0.030, 0.032, 0.034, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0 .075, 0.08, 0.085, 0.09
  • the cathode active material including the lithium metal oxide of Formula 2 is applied to the lithium-ion battery, the specific capacity and cycle performance of the lithium-ion battery can be further improved, so that the lithium-ion battery can operate for a longer time under high-voltage operating conditions. No deterioration occurs.
  • the inventor believes that it may be that the doping of M1 helps to support the structure of lithium metal oxide and improves the structural stability of lithium metal oxide to a certain extent. Therefore, no matter in normal conditions In high-pressure or high-pressure working environments, structurally stable lithium metal oxides are more helpful to improve the efficiency of lithium ion deintercalation and promote the improvement of lithium-ion battery cycle performance and specific capacity.
  • the mass percentage of the graphite coating layer in the positive electrode active material can be further selected in order to maximize the advantages of the graphite coating layer and lithium metal oxide and improve the performance of the positive electrode active material.
  • the mass percentage content W of the graphite coating layer satisfies: 0 ⁇ W ⁇ 1%.
  • the cathode active material when the graphite coating layer is a reduced graphene oxide coating layer, the cathode active material has more excellent properties, including lithium prepared from the cathode active material of the reduced graphene oxide coating layer. Ion batteries have better specific capacity and cycle performance. The reason is that reduced graphene oxide has a two-dimensional crystal structure, which has better conductive properties. When used in the cathode active material, it can further improve the gram capacity of the battery, and the two-dimensional crystal structure can increase the electrolyte of the cathode active material. The contact area between them enables the electrolyte and the positive active material to react more fully, more effectively reduces the side reactions between the positive active material and the electrolyte, and improves the capacity and cycle performance of the battery.
  • reduced graphene oxide refers to defective graphene obtained by reducing graphene oxide. Furthermore, the present application can also control the reduction degree of reduced graphene oxide in the reduced graphene oxide layer to maximize the role of the reduced graphene oxide layer and improve the capacity and cycle performance of the battery. The degree of reduction of reduced graphene oxide can be determined by observing the characteristic peaks of lithium metal oxide in the Raman spectrum.
  • the lithium metal oxide in the Raman spectrum, has a wavelength of 1560
  • the peak intensity I G of ⁇ 30cm -1 and the peak intensity I D of lithium metal oxide at a wavelength of about 1360 ⁇ 30cm -1 satisfy: I D / IG ⁇ 68%.
  • the cathode active material including the reduced graphene oxide coating layer of the present application has a Raman spectrum with a wavelength range in the range of 1000 to 2000cm -1 and includes a G band located near 1560cm -1 and a G band located at 1360cm -1
  • the peak intensity I G of the characteristic peak of the nearby D band and G band and the peak intensity I D of the characteristic peak of the D band satisfy: I D /I G ⁇ 68%. It can be understood that when I D / IG ⁇ 68%, the reduced graphene oxide has a better degree of reduction, and the cathode active material including the reduced graphene oxide layer has better performance. Further, 80% ⁇ ID / IG ⁇ 90 %.
  • n is between 0.6 and 0.8.
  • the positive electrode sheet including the positive electrode active material and the lithium metal negative electrode sheet are assembled into a battery and then charged and discharged, when the remaining power SOC of the battery is 0 (that is, it is in a fully discharged state) and the discharge cut-off voltage is 3.0 ⁇ 3.6V, lithium
  • the n of metal oxides is between 0.7 and 1.0. It should be noted that the change in n means that the number of charge and discharge cycles is within 10. Specifically, after the aforementioned lithium metal oxide is charged and discharged, its composition will change, especially the molar amount of lithium ions will increase significantly.
  • the lithium metal oxide with the aforementioned crystal structure has some vacancies. Therefore, when it is used for charging and discharging, the vacancies can accept lithium atoms from the lithium negative electrode, thereby making the molar amount of lithium ions compared to Improved before charging and discharging applications. This feature helps further improve the cycle performance and specific capacity of the battery.
  • the cathode active material of the present application can be in a single crystal morphology or a polycrystalline morphology, and the specific morphology is related to the selection and proportion of its doping elements. Specifically, when it is a polycrystalline morphology, it is a spherical or spherical-like particle; when it is a single crystal morphology, it can be a whisker, a flake, or any other irregular shape.
  • the median particle diameter of the cathode active material of the present application is 12 to 20 ⁇ m, such as 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m or 20 ⁇ m.
  • the inventor found that when the median particle size of the positive electrode active material meets the above requirements, on the one hand, its corresponding specific surface area can meet the deintercalation of more lithium ions; on the other hand, the agglomeration phenomenon between the positive electrode active materials is effectively controlled. , so that it can be stably dispersed in the slurry during the pulping process.
  • the first-stage discharge capacity of the positive electrode active material accounts for C1/C0 ⁇ 9%, and the second-stage discharge capacity accounts for C2/C0 ⁇ 25%; wherein, C0 includes the positive electrode active material
  • C1 includes the positive electrode active material
  • the above discharge capacity is performed under a special discharge mechanism. Specifically, after the half-battery composed of the positive electrode sheet of the positive electrode active material and the lithium metal negative electrode is charged until the SOC is 100% (the charging mechanism is not particularly limited), it is discharged at 0.1C at 3.0-4.55V. Among them, when discharging from 4.55V to 4.4V at 0.1C, the amount of electricity released is C1, and continuing to discharge. When discharging from 3.8V to 3.7V, the amount of electricity released in the step-down stage is C2, and continues to discharge to 3.0V (at this time, the SOC is 0), the total amount of electricity initially released by self-discharge is C0.
  • the cathode active material including the lithium metal oxide of the present application has strong voltage resistance, so that the specific capacity of the battery can be increased by subjecting it to a voltage boosting process.
  • the lithium metal oxide of the present application can be prepared by a method including the following steps: 1) sodium metal oxide represented by formula 1a Mix with a lithium compound and undergo ion treatment to obtain matrix particles; 2) Conduct a coating reaction on the matrix particles and graphite material to obtain the lithium metal oxide of the present application.
  • the above-mentioned ion exchange treatment is a heat treatment process, which specifically refers to mixing sodium metal oxide and lithium compound and then performing heat treatment at 80°C to 300°C for no more than 10 hours. After the ion exchange treatment, the ion exchanged system is washed and dried to finally obtain lithium metal oxide. Among them, the drying temperature is 80-180°C and the drying time is at least 10 hours. There is no limit to the equipment and drying equipment for ion exchange treatment.
  • the equipment for ion exchange treatment can be a closed container equipment with a sealing function and stirring ability, such as wet coating reaction equipment, co-precipitation reaction equipment, etc.; drying equipment It can be a blast oven, vacuum drying oven, rotary kiln, plate dryer, oven, etc.
  • the above-mentioned lithium compound may be a lithium source compound commonly used in the art, such as at least one of lithium carbonate, lithium chloride, lithium bromide, lithium iodide, lithium nitrate, lithium hydroxide, and lithium fluoride.
  • the mass ratio of the lithium compound and the sodium metal oxide is not less than 1:1, preferably (1-3):1.
  • sodium metal compound represented by formula 1a for example, it can be prepared by a method including the following process:
  • At least the cobalt source and the sodium source are mixed according to the target ratio and then calcined to obtain the sodium metal compound represented by formula 1a.
  • the temperature of the calcination treatment is 700 to 900°C, and the time is 8 to 50 hours.
  • the calcination treatment can be performed in an oxygen or air atmosphere.
  • the equipment for the calcination treatment may be, for example, high-temperature sintering equipment such as muffle furnaces, tunnel furnaces, roller kilns, and tube furnaces.
  • each of the above sources can be performed by high-speed mixing equipment, sand grinding equipment, ball milling equipment, plow mixing equipment, inclined mixing equipment, etc. It should be noted that if sand grinding equipment, ball milling equipment and ball milling or When adding solvent (water, ethanol or other solvent media) during the sanding process, the mixed system needs to be dried after the mixing process is completed. Generally, the mixing time is no longer than 4 hours.
  • the lithium metal oxide of the present application can also be prepared by a method including the following steps: 1) mixing the sodium metal oxide shown in Formula 2a with a lithium compound and performing ion treatment to obtain matrix particles; 2) converting the matrix particles into Carry out coating reaction with graphite material to obtain the lithium metal oxide of the present application. It is prepared by mixing the sodium metal oxide represented by Formula 2a with a lithium compound and subjecting it to ion treatment. Na x Co 1-a1-a2 M1 a1 M2 a2 O 2Formula 2a
  • the M1 source, M2 source, cobalt source, and sodium source can be mixed according to the target ratio and then calcined to obtain the sodium metal compound represented by Formula 2a.
  • cobalt source is selected from one or more of cobalt hydroxide, cobalt tetroxide, doped cobalt tetroxide, cobalt oxide, cobalt oxyhydroxide, cobalt nitrate, cobalt sulfate, etc.
  • the sodium source is selected from sodium carbonate, sodium nitrate , sodium hydroxide, sodium bicarbonate, sodium sulfate, etc.
  • the M1 source can be any compound containing M1, for example, containing M1 oxide, when M1 is W, the M1 source is, for example, tungstic acid and /or sodium tungstate, etc.; when M1 is Te, the M1 source is, for example, telluric acid and/or sodium tellurate, etc.; when M1 is Al, the M1 source is, for example, one of aluminum sulfate, aluminum nitrate, aluminum hydroxide,
  • M1 is B
  • the source of M1 is, for example, boric acid and/or sodium borate
  • M1 is P
  • the source of M1 is, for example, phosphoric acid and/or sodium phosphate, etc.
  • M1 is K
  • the source of M1 is, for example, boric acid and/or sodium borate, etc.
  • the M2 source example can be any compound containing M2, such as an oxide containing M2, such as basic magnesium carbonate , one or more of magnesium hydroxide, zirconium oxide, yttrium oxide, lanthanum oxide, lanthanum fluoride, nickel oxide, niobium oxide, etc.
  • the second aspect of the application also provides another cathode active material, the cathode active material includes lithium metal oxide, and the lithium metal oxide has the molecular formula shown in Formula 1;
  • lithium metal oxide is in the Cmca space group of the cubic crystal system, and has a 002 peak with a 2 ⁇ of 17.9° to 18.1°, and a 131 peak with a 2 ⁇ of 67.0° to 67.5°; Li ny Na y Co 1-a M a O 2Formula 1
  • the ratio m1 of the molar content of Li element and Na element satisfies: 12 ⁇ m1 ⁇ 80;
  • M is the doping element.
  • the lithium metal oxide mentioned above in this application specifically includes at least oxides of cobalt, lithium and sodium. Furthermore, it can also be doped with M. This application does not limit the specific selection of M, and it can be a common doping element in the art. For example, it may be at least one of W, Mg, Ti, Mn, Al, Te, Ni, Nb, Zr, La, F, Ce, Sr, Y, K, B and P elements.
  • y is 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.010, 0.012, 0.015, 0.018, 0.020, 0.022, 0.024, 0.025, 0.026, 0.028, 0.03, 0.0 4 or 0.05;
  • m1 is 12, 13, 15, 20, 40, 50, 65, 78 or 80;
  • a is 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.010, 0.012, 0.015, 0.018, 0.020, 0.022, 0.024, 0.025, 0.026, 0.028, 0.030, 0.032, 0.034, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09, or 0.095.
  • n refers to the molar amount of lithium per unit mole of lithium metal oxide in the positive electrode active material that has not undergone any charge and discharge treatment.
  • m1 refers to the ratio of the molar content of Li element to the molar content of Na element in unit mole of lithium metal oxide in the positive electrode active material without any charge and discharge treatment. Further, m1 is 22-73.
  • the molar amount of lithium in a unit mole of lithium metal oxide is different under different charge and discharge mechanisms and charge and discharge nodes.
  • the ratio of the molar content of Li element to the molar content of Na element in unit mole of lithium metal oxide is also different.
  • the cathode active material including the lithium metal oxide is applied to the lithium-ion battery, the specific capacity and cycleability of the lithium-ion battery will be improved. It can be significantly improved, and the electrical performance of lithium-ion batteries will not deteriorate even under high-voltage working conditions.
  • the inventor believes that it may be that when the molar content ratio of Li element to Na element is within a certain range, lithium metal oxide has a more complete T2 structure, and part of the sodium element plays a supporting role in the structure. This allows lithium metal to increase the deintercalation efficiency of lithium ions in the Cmca space group of the cubic crystal system and promote the improvement of the cycle performance and specific capacity of lithium-ion batteries.
  • the lithium metal oxide has the molecular formula shown in Formula 2; Li ny Na y Co 1-a1-a2 M1 a1 M2 a2 O 2Formula 2
  • M1 is selected from at least one of Te, W, Al, B, P and K; M2 is a doping element different from M1.
  • the lithium metal oxide of the present application has the molecular formula shown in Formula 2, specifically an oxide including at least cobalt, lithium, sodium and M1. Furthermore, it can also be doped with M2 that is different from M1. This application does not limit the specific selection of M2, and it can be a common doping element in the art. For example, it may be at least one of Mg, Ti, Mn, Al, Te, Ni, Nb, Zr, La, F, Ce, Sr, Y, K, B and P elements.
  • y is 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.010, 0.012, 0.015, 0.018, 0.020, 0.022, 0.024, 0.025, 0.026, 0.028, 0.03, 0.0 4 or 0.05;
  • a1 is 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.010, 0.012, 0.015, 0.018, 0.020, 0.022, 0.024, 0.025, 0.026, 0.028, 0.030, 0.032, 0 .034, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, 0.08, 0.085, 0.09 or 0.095;
  • a2 is 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.010, 0.012, 0.015 ,0.018
  • the cathode active material including the lithium metal oxide of Formula 2 is applied to the lithium-ion battery, the specific capacity and cycle performance of the lithium-ion battery can be further improved, so that the lithium-ion battery can operate for a longer time under high-voltage operating conditions. No deterioration occurs.
  • the inventor believes that It may be:
  • the doping of M1 helps to support the structure of lithium metal oxide, which improves the structural stability of lithium metal oxide to a certain extent. Therefore, it can be used in normal or high-pressure working environments.
  • lithium metal oxide with a stable structure is more helpful to improve the efficiency of lithium ion deintercalation and promote the improvement of lithium-ion battery cycle performance and specific capacity; on the other hand, the lithium metal oxide with the above crystal characteristics has more
  • the perfect layered crystal phase structure can reduce or inhibit the occurrence of internal mixing of the crystal phase, thereby enabling smooth deintercalation of lithium ions, especially during high-voltage charging and discharging processes, multiple small charging and discharging platforms are displayed.
  • the positive active material has a core-shell structure including a core of lithium metal oxide and the coating layer covering the core.
  • This coating helps to reduce or inhibit the side reactions of lithium metal oxide and electrolyte. Even when the battery is operating in a high-pressure environment, a stable interface can still be formed between the positive active material and the electrolyte.
  • the cycle performance of the battery is improved by the transitional dissolution of metal ions in the ions and the avoidance of liquid shortage. At the same time, the suppression or reduction of side reactions can also reduce the amount of gas produced inside the battery, thus ensuring the safety performance of the battery.
  • the coating layer can be made of carbon-containing compounds, fast ion conductors and other materials.
  • n is between 0.6 and 0.8, and the molar content ratio m1 of the Li element and the Na element is between 12 and 80.
  • the positive electrode sheet including the positive active material and the lithium metal negative electrode sheet are assembled into a battery and then charged and discharged, and the number of charge and discharge cycles is less than 10 cycles, when the remaining power SOC of the battery is 0 (that is, it is in a fully discharged state) and the discharge is cut off
  • the voltage is 3.0 ⁇ 3.6V
  • n of lithium metal oxide is between 0.7 ⁇ 1.0, and the ratio m2 of the molar content of Li element to Na element is between 16-93.
  • the lithium metal oxide with the aforementioned crystal structure has some vacancies. Therefore, when it is used for charging and discharging, the vacancies can accept lithium atoms from the lithium negative electrode, thereby making the molar amount of lithium ions compared to Improved before charging and discharging applications. This feature helps further improve the cycle performance and specific capacity of the battery.
  • the battery has a more excellent specific capacity.
  • the n of the lithium metal oxide is between 0.7 ⁇ 1.0, and the Li element and the Na element
  • the molar content ratio m2 is between 26-93, and when the difference between m2 and m1 is greater than 3, the battery has better cycle performance and specific capacity.
  • the cathode active material of the present application can be in a single crystal morphology or a polycrystalline morphology, and the specific morphology is related to the selection and proportion of its doping elements. Specifically, when it is a polycrystalline morphology, it is a spherical or spherical-like particle; when it is a single crystal morphology, it can be a whisker, a flake, or any other irregular shape.
  • the median particle diameter of the cathode active material of the present application is 12-20 ⁇ m, such as 3 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m or 20 ⁇ m.
  • the inventor found that when the median particle size of the positive electrode active material meets the above requirements, on the one hand, its corresponding specific surface area can meet the deintercalation of more lithium ions; on the other hand, the agglomeration phenomenon between the positive electrode active materials is effectively controlled. , so that it can be stably dispersed in the slurry during the pulping process.
  • the cathode active material including the lithium metal oxide of the present application has strong voltage resistance, so that the specific capacity of the battery can be increased by subjecting it to a voltage boosting process.
  • the lithium metal oxide of the second aspect of the application can be prepared by the preparation method of the lithium metal oxide of the first aspect. It can be understood that by controlling the added amounts of the sodium metal oxide and the lithium compound, the lithium metal oxide with a specific molar content ratio of the Li element and the Na element in the second aspect of the present application can be obtained.
  • a third aspect of the present application provides a cathode sheet, which includes the cathode active material of the first aspect and/or the cathode active material of the second aspect.
  • the cathode sheet of the present application helps to improve the cycle performance and specific capacity of the lithium-ion battery.
  • the cathode sheet of the present application includes a cathode current collector and a cathode active layer disposed on at least one surface of the cathode current collector.
  • the cathode active layer includes the aforementioned cathode active material.
  • the positive active layer also includes a conductive agent and a binder.
  • the cathode active layer includes 70-99wt% cathode active material, 0.5-15wt% conductive agent, 0.5-15wt% binder in terms of mass percentage, and further includes 80-98wt% cathode activity Material, 1-10wt% conductive agent, 1-10wt% binder.
  • the selection of conductive agent and binder is not special and can be conventionally selected in this field.
  • the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, single-wall carbon nanotubes, multi-arm carbon nanotubes, and carbon fibers
  • the binder is selected from the group consisting of: From at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyacrylic lithium (PAALi).
  • a safety layer can also be provided between the positive electrode active layer and the current collector.
  • the material of the safety layer is generally a non-conductive safety material, such as iron-containing compounds (such as lithium iron phosphate, lithium phosphate, etc.), aluminum-containing compounds (such as ceramic alumina), etc.
  • the security layer also includes adhesive, and the ratio of adhesive and security material can be further determined according to specific needs.
  • the cycle performance and specific capacity of the battery can be further improved.
  • the fourth aspect of the present application also provides a lithium-ion battery.
  • the ion battery includes the above-mentioned positive electrode sheet and therefore has outstanding performance in terms of cycle performance and specific capacity.
  • the lithium-ion battery also includes a negative electrode sheet, a separator and an electrolyte.
  • the electrolyte is a conventional electrolyte known in the art including lithium salts and solvents.
  • the solvent contains ethylene carbonate (abbreviated as EC), diethyl carbonate (abbreviated as DEC), propylene carbonate (abbreviated as PC). ), fluoroethylene carbonate (abbreviated as FEC).
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • FEC fluoroethylene carbonate
  • an additive represented by formula T is also included, the mass percentage of which is 0.1 to 10% in the electrolyte.
  • the negative electrode sheet may be a negative electrode sheet rich in lithium metal, such as a lithium foil or a negative electrode sheet as shown in FIG. 1 .
  • the negative electrode sheet in Figure 1 includes a stacked negative electrode current collector. 101. Negative active layer 20 and lithium material layer 30.
  • the negative electrode sheet in FIG. 1 is provided on both sides. Of course, it may also be a negative electrode sheet in which the negative electrode active layer 20 and the lithium material layer 30 are provided on only one side of the negative electrode current collector.
  • the lithium material layer is, for example, lithium foil.
  • the areal density of metallic lithium in the lithium material layer is 0.09 mg/cm 2 to 3.5 mg/cm 2 ; the negative electrode active layer includes a negative electrode active material, a conductive agent, and a binder.
  • the negative active layer includes 70-99wt% negative active material, 0.5-15wt% conductive agent, 0.5-15wt% binder according to mass percentage, and further includes 80-98wt % negative active material, 1-10wt% conductive agent, 1-10wt% binder.
  • the negative active material is selected from one or more of artificial graphite, natural graphite, hard carbon, mesocarbon microspheres, lithium titanate, silicon carbon, and silicon oxide.
  • the separator is a polypropylene-based material, or a rubber-coated separator coated with ceramic on one or both sides.
  • the lithium-ion battery of the present application is suitable for high-voltage systems. Specifically, under the condition that the lithium-ion button battery including the aforementioned positive electrode sheet is ⁇ 4.55V (relative to lithium), the gram capacity of the positive electrode sheet is ⁇ 225mAh/g, and at ⁇ 4.50 V (corresponding to the aforementioned negative electrode sheet) also has excellent cycle performance.
  • the lithium-ion battery of this application has good cycle stability and high gram capacity at higher voltages such as 4.50V, which can meet the needs of high-end digital products to be thinner and lighter.
  • step (3) Take a reaction vessel and weigh lithium hydroxide monohydrate with a weight of 10.49g and lithium nitrate particles with a mass of 17.24g. Add the two lithium compounds to the reaction vessel respectively, and weigh the mass to 10g.
  • Na 0.69 CoO 2 synthesized in step (2) is poured into the reaction vessel and initially mixed, and then ion exchanged at 280°C for 0.5h to obtain the crude product;
  • sample 1B# was obtained after drying at 90°C for 8 hours;
  • step (4) Weigh 5g of sample 1B# powder and 25mg of graphene oxide (GO) obtained in step (4), put sample 1B# powder and graphene oxide into a beaker container, add 15ml of deionized water, and heat at 45°C The coating reaction is carried out with mechanical stirring at low temperature. The coating reaction time is 30 minutes. Then the temperature is raised to 65°C until the water in the beaker container is basically evaporated. Then it is further reduced and dried under vacuum at 100°C. The sample is taken out to obtain 1A# sample. ;
  • the 1A# sample was tested with a Raman spectrometer, and the test results are shown in Table 2A.
  • the preparation method of the cathode active material in this embodiment is basically the same as that in Embodiment 1A, except that in step (5), 35 mg of graphene oxide is weighed.
  • the preparation method of the positive active material of this embodiment is basically the same as that of Embodiment 1A, except that in step (5), 15 mg of graphene oxide is weighed.
  • the preparation method of the positive active material of this embodiment is basically the same as that of Embodiment 1A, except that in step (5), the coating reaction time is 60 minutes.
  • the preparation method of the positive active material of this embodiment is basically the same as that of Embodiment 1A, except that:
  • Step (1) is: take 36.56g sodium carbonate powder, 0.21g potassium carbonate powder, 282.31g hexahydrate cobalt nitrate powder and 1.21g nanometer magnesium oxide powder, and put them into a high-speed mixing equipment, Set the mixing program, mix at 300rpm for 3 minutes, mix at 500rpm for 5 minutes, then mix at 1000rpm for 10 minutes, take out the mixture and confirm that there are no white sodium carbonate spots in the mixture. The mixture is considered uniform;
  • the sodium metal oxide obtained in step (2) is Na 0.69 K 0.003 Co 0.97 Mg 0.03 O 2 ;
  • step (5) After processing in step (5), sample 5A#rGO/Li 0.71 Na 0.02 K 0.003 Co 0.97 Mg 0.03 O 2 was obtained.
  • the preparation method of the positive active material of this embodiment is basically the same as that of Embodiment 1A, except that:
  • Step (1) is: take 36.56g sodium carbonate powder, 1.53g nano-alumina powder, 276.50g hexahydrate cobalt nitrate powder and 0.806g nano-magnesium oxide powder, and put them into a high-speed mixing equipment , set the mixing program, mix at 300rpm for 3 minutes, mix at 500rpm for 5 minutes, then mix at 1000rpm for 10 minutes, take out the mixture, and confirm that there are no white sodium carbonate spots in the mixture. Mix evenly;
  • the sodium metal oxide obtained in step (2) is Na 0.69 Co 0.95 Al 0.03 Mg 0.02 O 2 ;
  • step (4) sample 6B#Li 0.71 Na 0.02 Co 0.95 Al 0.03 Mg 0.02 O 2 is obtained;
  • step (5) sample 6A#rGO/Li 0.71 Na 0.02 Co 0.95 Al 0.03 Mg 0.02 O 2 was obtained.
  • the preparation method of the positive active material of this embodiment is basically the same as that of Embodiment 1A, except that:
  • Step (1) is: take 36.56g of sodium carbonate powder, 1.854g of boric acid powder, and 282.32g of cobalt nitrate hexahydrate powder, put them into a high-speed mixing equipment, set the mixing program, and mix at 300 rpm. After mixing for 3 minutes, mix at 500rpm for 5 minutes, then mix at 1000rpm for 10 minutes. Take out the mixture and confirm that there are no white sodium carbonate spots in the mixture. The mixture is considered to be uniform;
  • the sodium metal oxide obtained in step (2) is Na 0.69 Co 0.97 B 0.03 O 2 ;
  • step (4) After being processed in step (4), sample 7B#Li 0.71 Na 0.02 Co 0.97 B 0.03 O 2 is obtained;
  • step (5) After processing in step (5), sample 7A#rGO/Li 0.71 Na 0.02 Co 0.97 B 0.03 O 2 was obtained.
  • the preparation method of the cathode active material in this embodiment is basically the same as that in Embodiment 1A, except that At:
  • Step (1) is: take 36.56g of sodium carbonate powder, 6.889g of telluric acid powder, and 282.32g of cobalt nitrate hexahydrate powder, put them into a high-speed mixing equipment, set the mixing program, and use 300rpm After mixing for 3 minutes, mix at 500rpm for 5 minutes, then mix at 1000rpm for 10 minutes. Take out the mixture. After confirming that there are no white sodium carbonate spots in the mixture, the mixture is considered to be uniform;
  • the sodium metal oxide obtained in step (2) is Na 0.69 Co 0.97 Te 0.03 O 2 ;
  • step (4) After being processed in step (4), sample 8B#Li 0.71 Na 0.02 Co 0.97 Te 0.03 O 2 is obtained;
  • step (5) sample 8A#rGO/Li 0.71 Na 0.02 Co 0.97 Te 0.03 O 2 was obtained.
  • the preparation method of the cathode active material of this embodiment is basically the same as that of Embodiment 1A, except that in step (5):
  • the coating reaction was carried out with mechanical stirring at 25°C, the coating reaction time was 10 minutes, and sample 9A# was obtained.
  • the preparation method of the cathode active material of this embodiment is basically the same as that of Embodiment 1A, except that in step (5):
  • the cathode active material in this comparative example is a conventional high-voltage doped coated lithium cobalt oxide cathode material, and its chemical composition is Li 1.0027 Co 0.97 Al 0.03 O 2 .
  • the preparation method includes the following steps:
  • the preparation method of the cathode active material of this comparative example is basically the same as that of Example 5A. The difference is that the process of step (5) is not performed, and the 5A# sample obtained in step (4) is directly used as the cathode active material.
  • the preparation method of the positive active material of this embodiment is basically the same as that of Embodiment 1C, except that:
  • step (3) perform ion exchange at 260°C for 1.2h to obtain the crude product; after treatment in step (4), Sample 2C#Li 0.70 Na 0.025 CoO 2 was obtained.
  • the preparation method of the positive active material of this embodiment is basically the same as that of Embodiment 1C, except that:
  • step (3) perform ion exchange at 95°C for 3.4h to obtain a crude product; after treatment in step (4), sample 3C#Li 0.72 Na 0.023 CoO 2 is obtained.
  • the preparation method of the positive active material of this embodiment is basically the same as that of Embodiment 1C, except that:
  • step (3) ion exchange was carried out at 105°C for 3.0h to obtain a crude product; after treatment in step (4), sample 4C#Li 0.73 Na 0.017 CoO 2 was obtained.
  • the preparation method of the positive active material of this embodiment is basically the same as that of Embodiment 1C, except that:
  • Step (1) is: take 36.56g of sodium carbonate powder, 0.21g of potassium carbonate powder, 282.31g of cobalt nitrate hexahydrate powder and 1.21g of nanometer magnesium oxide powder, and put them into a high-speed mixing equipment. Set the mixing program, mix at 300rpm for 3 minutes, mix at 500rpm for 5 minutes, and then mix at 1000rpm for 10 minutes. Take out the mixture and confirm that there are no white sodium carbonate dots in the mixture. It is considered mixed. Material is uniform;
  • the sodium metal oxide obtained in step (2) is Na 0.69 K 0.003 Co 0.97 Mg 0.03 O 2 ;
  • the preparation method of the cathode active material in this embodiment is basically the same as that in Embodiment 5C, except that:
  • step (3) perform ion exchange at 100°C for 2.8h to obtain a crude product; after treatment in step (4), sample 6C#Li 0.72 Na 0.021 K 0.003 Co 0.97 Mg 0.03 O 2 is obtained.
  • the preparation method of the cathode active material in this embodiment is basically the same as that in Embodiment 5C, except that:
  • step (3) perform ion exchange at 260°C for 1.5h to obtain a crude product; after treatment in step (4), sample 7C#Li 0.73 Na 0.017 K 0.003 Co 0.97 Mg 0.03 O 2 is obtained.
  • the preparation method of the cathode active material of this comparative example is basically the same as that of Example 1C, except that:
  • step (3) perform ion exchange at 75°C for 24 hours to obtain a crude product; after treatment in step (4), sample 1a#Li 0.50 Na 0.48 CoO 2 is obtained.
  • the preparation method of the cathode active material of this comparative example is basically the same as that of Example 1C, except that:
  • step (3) perform ion exchange at 90°C for 24 hours to obtain a crude product; after treatment in step (4), sample 2a#Li 0.89 Na 0.005 CoO 2 is obtained.
  • the preparation method of the cathode active material of this comparative example is basically the same as that of Example 5C, except that:
  • step (3) perform ion exchange at 280°C for 0.1h to obtain a crude product; after treatment in step (4), sample 3a#Li 0.39 Na 0.60 K 0.003 Co 0.97 Mg 0.03 O 2 is obtained.
  • the preparation method of the cathode active material of this comparative example is basically the same as that of Example 5C, except that:
  • step (3) perform ion exchange at 85°C for 30 hours to obtain a crude product; after treatment in step (4), sample 4a#Li 0.86 Na 0.006 K 0.003 Co 0.97 Mg 0.03 O 2 is obtained.
  • the preparation method of the cathode active material of this comparative example is basically the same as that of Example 5C, except that:
  • step (3) perform ion exchange at 280°C for 0.35h to obtain a crude product; after treatment in step (4), sample 5a#Li 0.69 Na 0.06 K 0.003 Co 0.97 Mg 0.03 O 2 is obtained.
  • the preparation method of the cathode active material of this comparative example is basically the same as that of Example 1C, except that:
  • step (3) perform ion exchange at 280°C for 15 hours to obtain a crude product; after treatment in step (4), sample 6a#Li 0.93 Na 0.03 CoO 2 is obtained.
  • FIG. 1 is an SEM image of the cathode active material in Example 1A of the present application. It can be seen from Figure 2 that the cathode material particles of the present application have flaky defective graphene layers and matrix particles, and the defective graphene layer is attached to the surface of the matrix particles.
  • Example 1C SEM was used to test the morphology of the cathode active materials of Example 1C and Comparative Example 1C respectively. As shown in Figures 3 and 4, the cathode active material in Example 1C has a larger particle size dispersion and can more fully perform dehydration. Embedding lithium ions helps improve the specific capacity and cycle performance of the battery.
  • Figure 5 is a Raman test chart of the positive electrode active material in Example 1A and Example 9A of the present application. As can be seen from Figure 5, the ID / IG in Example 1A is 80.20%, and the ID / IG in Example 9A is 65.38%.
  • Figure 6 is an XRD pattern of the cathode active material in Example 8A and Example 1B of the present application. It can be seen from Figure 6 that the lithium metal oxide prepared in the embodiment of the present application has a 002 peak (2 ⁇ is 17.9°-18.1°) and a 131 peak (2 ⁇ is 67.0°-67.5°), and it is a cubic Cmca Space group, with T2 structure.
  • a lithium material layer is superimposed on the surface of the negative electrode active layer by rolling.
  • the lithium material layer is lithium foil.
  • the areal density of metallic lithium is 1.0 mg/cm 2 .
  • a negative electrode sheet containing lithium metal is obtained.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • PC propylene carbonate
  • FEC fluoroethylene carbonate
  • LiPF 6 lithium hexafluorophosphate
  • the additive shown in Formula T the additive content accounts for 2% of the total electrolyte content.
  • the capacity retention rate of each obtained lithium-ion battery was tested.
  • the specific test method is: at 25°C, charge with a constant current to 4.50V at a charging rate of 1C, and then charge with a constant voltage to 4.50V at a charging rate of 0.05C. Then discharge to 3.0V at a discharge rate of 1C, repeat this charge and discharge cycle 500 times, measure the discharge capacity at the first cycle and the 500th cycle, and calculate the capacity after 500 cycles according to the following formula Retention rate, the results are shown in Tables 2A and 2C.
  • Capacity retention rate Q (Discharge capacity at the 500th cycle)/(Discharge capacity at the first cycle)*100%
  • the cathode active materials in the examples and comparative examples were mixed with conductive carbon black (SP) and PVDF according to the The mixture was mixed at a weight ratio of 80%:10%:10% and dispersed to obtain a positive electrode slurry.
  • the slurry is coated on the aluminum foil current collector, and rolled to prepare a positive electrode sheet.
  • the positive electrode sheet is then punched into a small disc with a diameter of 12 mm using a membrane tool. After drying and weighing, the gloves are placed under an Ar protective atmosphere.
  • a 2025 button battery shell is used, a Li metal disc is used as the negative electrode, and a conventional high-voltage lithium cobalt oxide electrolyte is used to assemble a button battery.
  • the first charge and discharge capacity test was performed.
  • the test conditions were: charging from 0.1C to 4.55V, constant voltage charging to 0.025C, and then leaving for 3 minutes. Discharge to 3.0V.
  • the discharge process record the discharge capacity C1 of 4.4 ⁇ 4.55V, the discharge capacity C2 of 3.7 ⁇ 3.8V, the first full discharge capacity C0, and the first charge capacity, and calculate the first efficiency and the first stage discharge capacity ratio C1/C0 And the second stage discharge capacity ratio C2/C0.
  • Tables 2A and 2C The results are shown in Tables 2A and 2C.
  • Example 5A and Comparative Example 2A it can be seen that the cathode active material prepared in the embodiment of the present application has better gram capacity and cycle performance when applied to lithium ion batteries, indicating that the positive electrode active material used in the present application Preparing cathode active materials by coating matrix materials with redox graphene can improve the electrochemical properties of cathode active materials.
  • the cathode active material prepared in the embodiment of the present application has better gram capacity and cycle performance when used in lithium-ion batteries.

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Abstract

本申请提供一种正极活性材料及其应用。该正极活性材料特殊的组成以及晶相结构有助于提升电池的比容量以及循环性能，尤其在高压条件下，依旧能够使电池表现优异。

Description

一种正极活性材料及其应用
本申请要求于2022年09月02日提交中国专利局、申请号为202211075101.6、申请名称为“一种正极活性材料及其应用”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
本申请要求于2022年09月02日提交中国专利局、申请号为202211072399.5、申请名称为“一种正极活性材料及其应用”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请实施例涉及极片材料，尤其涉及一种正极活性材料及其应用，属于二次电池技术领域。
背景技术
随着锂离子电池技术的发展和进步，对其容量提出了越来越高的要求。在锂离子电池的组成中，正极活性材料容量的高低，对锂离子电池的容量起着至关重要的作用。
为了提高锂离子电池的容量，目前最常用的方法就是提高其充放电电压。但是随着电压的提高，正极活性材料会出现晶体结构坍塌的现象，进而导致电池出现容量快速衰减和循环性能大幅降低等一系列问题。
因此，开发出一种具有高比容量、循环性能好的锂离子电池正极活性材料是本领域亟待解决的技术问题。
发明内容
有鉴于此，本申请实施例提供一种正极活性材料，该正极活性材料特殊的组成以及晶相结构有助于提升电池的比容量以及循环性能，尤其在高压条件下，依旧能够使电池表现优异。
本申请提供一种正极片，该正极片包括上述正极活性材料，因此有助于提升电池的相关电性能。
本申请还提供一种锂离子电池，该锂离子电池包括上述正极片，因此该锂离子电池在比容量和循环性能方面具有优异表现。
本申请提供一种正极活性材料，其中，所述正极活性材料由包括锂金属氧化物的基体颗粒和覆盖所述基体颗粒至少部分表面的石墨包覆层构成；
所述锂金属氧化物具有式1所示的结构；
在X射线衍射图谱中，所述锂金属氧化物为立方晶系的Cmca空间群，且具有2θ为17.9°～18.1°的002峰，以及2θ为67.0°～67.5°的131峰；
Lin-yNayCo1-aMaO2    式1
式1中，0.6≤n≤0.8，0＜y≤0.05，0≤a≤0.2；
其中，M为掺杂元素。
如上所述的正极活性材料，其中，所述锂金属氧化物具有式2所示的结构；
Lin-yNayCo1-a1-a2M1a1M2a2O2    式2
式2中，0＜a1≤0.1，0≤a2≤0.1，a1+a2＝a；
其中，M1选自Te、W、Al、B、P和K中的至少一种；M2为不同于M1的掺杂元素。
如上所述的正极活性材料，其中，基于所述正极活性材料的重质量，所述石墨包覆层的质量百分含量W满足：0＜W≤1％。
如上所述的正极活性材料，其中，所述石墨包覆层为还原氧化石墨烯包覆层。
如上所述的正极活性材料，其中，在拉曼光谱图中，所述锂金属氧化物在波长1560±30cm-1左右的峰强度IG，与锂金属氧化物在波长1360±30cm-1左右的峰强度为ID满足：ID/IG≥68％。
如上所述的正极活性材料，其中，80％≤ID/IG≤90％。
如上所述的正极活性材料，其中，所述正极活性材料在截止电压为3.0～3.6V且SOC为零时，0.7≤n≤1.0。
如上所述的正极活性材料，其中，所述正极活性材料的中值粒径为12μm～20μm。
本申请提供一种正极活性材料，其中，所述正极活性材料包括锂金属氧化物，所述锂金属氧化物具有式1所示的分子式；
在X射线衍射图谱中，所述锂金属氧化物为立方晶系的Cmca空间群，且具有2θ为17.9°～18.1°的002峰，以及2θ为67.0°～67.5°的131峰；
Lin-yNayCo1-aMaO2    式1
式1中，0.6≤n≤0.8，0＜y≤0.05，0≤a≤0.2；
Li元素与Na元素的摩尔含量之比m1满足：12≤m1≤80；
其中，M为掺杂元素。
如上所述的正极活性材料，其中，m1为22-73。
如上所述的正极活性材料，其中，所述的锂金属氧化物具有式2所示的分子式；
Lin-yNayCo1-a1-a2M1a1M2a2O2    式2
式2中，0＜a1≤0.1，0≤a2≤0.1，a1+a2＝a；
其中，M1选自Te、W、Al、B、P和K中的至少一种；M2为不同于M1的掺杂元素。
如上所述的正极活性材料，其中，所述正极活性材料由包括所述锂金属氧化物的基体颗粒和覆盖所述基体颗粒至少部分表面的包覆层构成。
如上所述的正极活性材料，其中，所述正极活性材料在截止电压为3.0～3.6V且SOC为零时，0.7≤n≤1.0，且Li元素与Na元素的摩尔含量之比m2满足：16≤m2≤93。
如上所述的正极活性材料，其中m2-m1＞3。
如上所述的正极活性材料，其中，所述正极活性材料的中值粒径为12μm～20μm。
本申请提供一种正极片，其中，所述正极片包括如上所述的正极活性材料。
如上所述的正极片，其中，所述正极片包括集流体、安全层以及正极活性层；
其中，所述安全层夹设在所述集流体和正极活性层之间，所述正极活性层包括所述正极活性材料。
如上所述的正极片，其中，所述正极片包括如上所述的正极活性材料， 所述正极活性层的压实密度大于等于3.5g/cm3。
本申请提供一种锂离子电池，其中，所述锂离子电池包括如上所述的正极片。
如上所述的锂离子电池，其中，所述锂离子电池中的负极片为含锂负极片。
本申请的正极活性材料具有特殊晶相结构和化学组成，其在应用于电池中后，电池的循环性能和克容量得到显著提升，即使在4.5V及以上的高压条件下，使用该正极活性材料的电池依旧能够保持相关电性能的优异表现，不会发生由于正极活性材料耐压性差而出现结构坍塌的问题。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作一简单地介绍，而易见地，下面描述中的附图是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为本申请锂离子电池中的负极片一实施例的结构示意图；
图2为本申请实施例1A中正极活性材料的SEM图；
图3为本申请实施例1C中正极活性材料的SEM图；
图4为本申请对比例1C中正极活性材料的SEM图；
图5为本申请实施例1A和实施例9A中正极活性材料的拉曼测试图；
图6为本申请实施例8A以及实施例1B中正极活性材料的XRD图。
附图标记说明：
20：负极活性层；
30：锂材料层；
101：负极集流体。
具体实施方式
为使本申请实施例的目的、技术方案和优点更加清楚，下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。基于 本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
本申请第一方面提供一种正极活性材料，该正极活性材料由包括锂金属氧化物的基体颗粒和覆盖基体颗粒至少部分表面的石墨包覆层构成；
锂金属氧化物具有式1所示的结构；
在X射线衍射图谱中，锂金属氧化物为立方晶系的Cmca空间群，且具有2θ为17.9°～18.1°的002峰，以及2θ为67.0°～67.5°的131峰；
Lin-yNayCo1-aMaO2    式1
式1中，0.6≤n≤0.8，0＜y≤0.05，0≤a≤0.2；
其中，M为掺杂元素。
可以理解，石墨包覆层可以覆盖基体颗粒的部分表面，也可以覆盖集体颗粒的整个表面。本申请对石墨包覆层不做具体限定，例如，石墨包覆层为石墨烯包覆层和/或还原氧化石墨烯包覆层。
本申请上述的锂金属氧化物，具体是至少包括锂、钴以及钠的氧化物。进一步地，其还可以掺杂M，本申请不限定M的具体选择，可以为本领域常见的掺杂元素。例如可以是W、Mg、Ti、Mn、Al、Te、Ni、Nb、Zr、La、F、Ce、Sr、Y、K、B和P元素中的至少一种。
本申请对在上述限定范围内的y以及a不做过多的限制。
例如，式1中，y为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.010、0.012、0.015、0.018、0.020、0.022、0.024、0.025、0.026、0.028、0.03、0.04或0.05；a为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.010、0.012、0.015、0.018、0.020、0.022、0.024、0.025、0.026、0.028、0.030、0.032、0.034、0.035、0.04、0.045、0.05、0.055、0.06、0.065、0.07、0.075、0.08、0.085、0.09或0.095。
需要强调的是，上述对n的限定是指未经过任何充放电处理的正极活性材料中，单位摩尔锂金属氧化物中锂的摩尔量。能够理解，当将该正极活性材料应用于锂离子电池中进行任何充放电处理后，在不同的充放电机制以及充放电节点下，单位摩尔锂金属氧化物中锂的摩尔量是有差异的。
根据本申请提供的上述方案，相较于其他正极活性材料，将包括该锂金 属氧化的正极活性材料应用于锂离子电池后，锂离子电池的比容量和循环性能得到显著提升，即使在高电压的工作条件下，锂离子电池的电性能也不会出现劣化。
发明人基于此现象进行分析，认为可能是：一方面，本申请通过设置石墨包覆层，使正极活性材料为包括锂金属氧化物的内核、石墨包覆层覆盖内核的核壳结构，该包覆层有助于减少或抑制锂金属氧化物和电解液的副反应，即使当电池在高压环境下工作时，正极活性材料和电解液之间依旧能够形成稳定的界面，通过避免正极活性离子中金属离子的过渡溶出以及避免缺液现象而使电池的循环性能得到改善，同时，副反应的抑制或减少也能够降低电池内部的产气量，从而也保证了电池的安全性能；另一方面，石墨包覆层本身就具有良好的电子传输性能，使正极活性材料包括石墨包覆层可以进一步提高正极活性材料的导电性能，进而提高锂离子电池的充放电克容量；同时，具有上述晶体特征的该锂金属氧化物具有更为完善的层状晶相结构，得以减少或抑制晶相内部混排现象的发生，进而能够使锂离子发生顺利的脱嵌，尤其在高压的充放电过程中展现出多个充放电小平台。
进一步地，发明人发现通过对锂金属氧化物中的掺杂元素进行分类，能够进一步提高正极活性材料的性能。在本申请的一些实施方式中，锂金属氧化物具有式2所示的结构；
Lin-yNayCo1-a1-a2M1a1M2a2O2    式2
式2中，0＜a1≤0.1，0≤a2≤0.1，a1+a2＝a；
其中，M1选自Te、W、Al、B、P和K中的至少一种；M2为不同于M1的掺杂元素。
可以理解，本申请的锂金属氧化物还可以具有式2所示的结构，具体是至少包括锂、钴、钠以及M1的氧化物。进一步地，其还可以掺杂不同于M1的M2，本申请不限定M2的具体选择，可以为本领域常见的掺杂元素。例如，可以是Mg、Ti、Mn、Al、Te、Ni、Nb、Zr、La、F、Ce、Sr、Y、K、B和P元素中的至少一种。
本申请对在上述限定范围内的a1以及a2不做过多的限制。
例如，式2中，a1为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.010、0.012、0.015、0.018、0.020、0.022、0.024、0.025、0.026、0.028、 0.030、0.032、0.034、0.035、0.04、0.045、0.05、0.055、0.06、0.065、0.07、0.075、0.08、0.085、0.09或0.095；a2为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.010、0.012、0.015、0.018、0.020、0.022、0.024、0.025、0.026、0.028、0.030、0.032、0.034、0.035、0.04、0.045、0.05、0.055、0.06、0.065、0.07、0.075、0.08、0.085、0.09或0.095。
本申请中，包括式2的锂金属氧化物的正极活性材料应用于锂离子电池后，能够进一步提升锂离子电池的比容量和循环性能，使锂离子电池在高电压工作条件下能够更长时间不发生劣化。发明人基于此现象进行分析，认为可能是：M1的掺杂有助于对锂金属氧化物的结构进行支撑作用，使锂金属氧化物的结构稳定性在一定程度上得到提升，因此无论在常压或者高压的工作环境中，结构稳定的锂金属氧化物更有助于提升锂离子脱嵌的效率，促进锂离子电池循环性能和比容量的改善。
本申请中，可以对正极活性材料中，石墨包覆层的质量百分含量进行进一步的选择，以期最大化发挥石墨包覆层以及锂金属氧化物的优点，改善正极活性材料的性能。在本申请的一些实施方式中，基于正极活性材料的总质量，石墨包覆层的质量百分含量W满足：0＜W≤1％。
在本申请的一些实施方式中，当石墨包覆层为还原氧化石墨烯包覆层时，正极活性材料具有更为优异的性能，包括还原氧化石墨烯包覆层的正极活性材料所制备的锂离子电池具有更为优异的比容量和循环性能。原因在于，还原氧化石墨烯具有二维晶体结构，其具有更为优异的导电性能，应用于正极活性材料中时能够进一步改善电池的克容量，并且二维晶体结构能够增加正极活性材料的电解液之间的接触面积，使电解液和正极活性材料更加充分的反应，更有效的减少正极活性材料与电解液之间的副反应，改善电池的容量和循环性能。
本申请中，还原氧化石墨烯指的是对氧化石墨烯进行还原得到的缺陷石墨烯。进一步地，本申请还可以通过控制还原氧化石墨烯层中的还原氧化石墨烯的还原程度，以最大化发挥还原氧化石墨烯层的作用，改善电池的容量和循环性能。可以通过观察锂金属氧化物在拉曼光谱图中的特征峰以确定还原氧化石墨烯的还原程度。
在本申请的一些实施方式中，在拉曼光谱图中，锂金属氧化物在波长1560 ±30cm-1的峰强度IG，与锂金属氧化物在波长1360±30cm-1左右的峰强度为ID满足：ID/IG≥68％。
本申请的包括还原氧化石墨烯包覆层的正极活性材料，其拉曼光谱图的波长范围在1000～2000cm-1范围内，并且包含有位于1560cm-1附近的G带，和位于1360cm-1附近的D带，G带特征峰的峰强度IG与D带特征峰的峰强度ID满足：ID/IG≥68％。可以理解，当ID/IG≥68％时，还原氧化石墨烯具有更好的还原度，包含该还原氧化石墨烯层的正极活性材料具有更优异的性能。进一步地，80％≤ID/IG≤90％。
如前述，未经过任何充放电处理的锂金属氧化物中，n在0.6～0.8之间。当将包括正极活性材料的正极片和锂金属负极片组装为电池后进行充放电后，当电池的剩余电量SOC为0(即处于完全放电状态)且放电截止电压为3.0～3.6V时，锂金属氧化物的n在0.7～1.0之间。需要说明的是，n的变化是指充放电循环圈数在10之内。具体地，满足前述锂金属氧化物在进行充放电应用后，其组成会发生变化，尤其是锂离子的摩尔量会明显提升。原因在于，具有前述晶型结构的锂金属氧化物中具有部分空位，因此当将其进行充放电应用时，其空位能够接受来自于锂负极的锂原子，进而使锂离子的摩尔量相较于充放电应用前得到提升。该特性有助于进一步提升电池的循环性能和比容量。
本申请正极活性材料可以是单晶形貌或多晶形貌，具体形貌与其掺杂元素的选择以及比例相关。具体地，当为多晶形貌时，其为球状或类球状颗粒；当为单晶形貌时，其可以为须状、片状、或其他任意不规则的形状。
进一步地，本申请正极活性材料的中值粒径为12～20μm，例如为13μm、14μm、15μm、16μm、17μm、18μm、19μm或20μm。发明人发现，当正极活性材料的中值粒径满足上述要求时，一方面，其对应比表面积能够满足更多锂离子的脱嵌；另一方面，正极活性材料之间的团聚现象得到有效控制，从而在制浆过程中能够稳定分散在浆料中。
发明人发现，当锂金属氧化物中的锂在晶型内分布的更加均匀时，其充放电过程中的多个放电小平台均表现出较为优异的放电量。
在一种具体实施方式中，正极活性材料的第一阶段放电容量占比C1/C0≥9％，第二阶段放电容量占比C2/C0≥25％；其中，C0为包括正极活性材料 的半电池在3.0～4.55V电压下进行放电处理时的放电容量；放电处理中，半电池由初始放电电压放电至4.4V时的容量定义为C1，半电池在3.8放电至3.7V时放出的容量定义为C2。
需要解释的是，上述放电容量是在特殊的放电机制下进行的。具体地，包括正极活性材料的正极片和锂金属负极组成的半电池充电至SOC为100％后(对充电机制不做特殊限定)，在3.0～4.55V下以0.1C进行放电处理。其中自4.55V以0.1C放电至4.4V时其释放的电量为C1，继续放电当从3.8V放电至3.7V时该降压阶段释放的电量为C2，继续放电至3.0V(此时SOC为0)时其自放电初始释放的全部电量为C0。
很明显，在高压环境下的放电处理中，第一阶段放电电量占比和第二阶段放电容量占比皆表现优异。因此，包括本申请锂金属氧化物的正极活性材料耐压性强，从而能够通过对其进行升压处理而提升电池的比容量。
本申请不限定上述锂金属氧化物的制备方法，在一种具体实施方式中，本申请的锂金属氧化物可以通过包括以下步骤的方法制备得到：1)将式1a所示的钠金属氧化物与锂化合物混合并进行离子处理得到基体颗粒；2)将基体颗粒和石墨材料进行包覆反应得到本申请的锂金属氧化物。
NaxCo1-aMaO2   式1a
式1a中，0.68＜x＜0.74，0<a≤0.2。
上述离子交换处理是一种热处理过程，具体是指将钠金属氧化物和锂化合物混合后在80℃～300℃下进行不高于10h的热处理。在离子交换处理后，通过对离子交换后的体系进行洗涤、干燥，最终得到锂金属氧化物。其中，干燥的温度为80～180℃，时间至少为10h。对进行离子交换处理的设备和干燥设备不做限定，例如离子交换处理的设备可以是带有密闭功能和搅拌能力的密闭容器设备，如湿法包覆反应设备，共沉淀反应设备等；干燥设备可以是鼓风烘箱、真空干燥烘箱、回转窑、盘式干燥机、烤箱等。
上述锂化合物可以是本领域常用的锂源化合物，例如碳酸锂、氯化锂、溴化锂、碘化锂、硝酸锂、氢氧化锂、氟化锂中的至少一种。离子交换处理中，锂化合物和钠金属氧化物的质量比为不低于1:1，优选为(1-3)：1。
对于式1a所示的钠金属化合物，示例性，可以通过包括以下过程的方法制备得到：
至少将钴源以及钠源按照目标比例混合后进行煅烧处理，得到式1a所示的钠金属化合物。
具体地，煅烧处理的温度为700～900℃，时间为8～50h，煅烧处理可以在氧气或空气气氛下进行。煅烧处理的设备例如可以是马弗炉、隧道炉、辊道窑炉、管式炉等高温烧结设备。
上述各个源的混合可以通过高速混料设备、砂磨设备、球磨设备、犁刀混料设备、斜式混料设备等执行，需要注意的是，若使用砂磨设备、球磨设备且在球磨或砂磨过程中加入溶剂(水、乙醇或者其它溶剂介质)时，在混合处理结束后需要对混合后的体系进行干燥。一般的，混合时间不高于4h。
优选地，本申请的锂金属氧化物还可以通过包括以下步骤的方法制备得到：1)将式2a所示的钠金属氧化物与锂化合物混合并进行离子处理得到基体颗粒；2)将基体颗粒和石墨材料进行包覆反应得到本申请的锂金属氧化物。将式2a所示的钠金属氧化物与锂化合物混合并进行离子处理的方法制备得到。
NaxCo1-a1-a2M1a1M2a2O2    式2a
式2中，0＜a1≤0.1，0≤a2≤0.1，a1+a2＝a。
可以将M1源、M2源、钴源、钠源按照目标比例混合后进行煅烧处理，得到式2a所示的钠金属化合物。
本申请不限定钴源、钠源、M1源以及M2源的具体选择。示例性地，钴源选自氢氧化钴、四氧化三钴、掺杂型四氧化三钴、氧化亚钴、羟基氧化钴、硝酸钴、硫酸钴等中的一种或多种；钠源选自碳酸钠、硝酸钠、氢氧化钠、碳酸氢钠、硫酸钠等中的一种或多种；M1源可以是任何含有M1的化合物，例如，含有M1氧化物，当M1为W时，M1源例如为钨酸和/或钨酸钠等；当M1为Te时，M1源例如为碲酸和/或碲酸钠等；当M1为Al时，M1源例如为硫酸铝、硝酸铝、氢氧化铝等中的一种或多种；当M1为B时，M1源例如为硼酸和/或硼酸钠等；当M1为P时，M1源例如为磷酸和/或磷酸钠等；当M1为K时，M1源例如为碳酸钾、硝酸钾、氢氧化钾、碳酸氢钾、硫酸钾等中的一种或多种；M2源例可以是任何含有M2的化合物，例如含有M2的氧化物，例如为碱式碳酸镁、氢氧化镁、氧化锆、氧化钇、氧化镧、氟化镧、氧化镍、氧化铌等中的一种或多种。
本申请第二方面还提供另一种正极活性材料，该正极活性材料包括锂金属氧化物，锂金属氧化物具有式1所示的分子式；
在X射线衍射图谱中，锂金属氧化物为立方晶系的Cmca空间群，且具有2θ为17.9°～18.1°的002峰，以及2θ为67.0°～67.5°的131峰；
Lin-yNayCo1-aMaO2    式1
式1中，0.6≤n≤0.8，0＜y≤0.05，0≤a≤0.2；
Li元素与Na元素的摩尔含量之比m1满足：12≤m1≤80；
其中，M为掺杂元素。
本申请上述的锂金属氧化物，具体是至少包括钴、锂以及钠的氧化物。进一步地，其还可以掺杂M，本申请不限定M的具体选择，可以为本领域常见的掺杂元素。例如可以是W、Mg、Ti、Mn、Al、Te、Ni、Nb、Zr、La、F、Ce、Sr、Y、K、B和P元素中的至少一种。
本申请对在上述限定范围内的y、m1以及a不做过多的限制。
例如，式1中，y为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.010、0.012、0.015、0.018、0.020、0.022、0.024、0.025、0.026、0.028、0.03、0.04或0.05；m1为12、13、15、20、40、50、65、78或80；a为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.010、0.012、0.015、0.018、0.020、0.022、0.024、0.025、0.026、0.028、0.030、0.032、0.034、0.035、0.04、0.045、0.05、0.055、0.06、0.065、0.07、0.075、0.08、0.085、0.09或0.095。
需要强调的是，上述对n的限定是指未经过任何充放电处理的正极活性材料中，单位摩尔锂金属氧化物中锂的摩尔量。上述对m1的限定是指未经任何充放电处理的正极活性材料中，单位摩尔锂金属氧化物中Li元素的摩尔含量与Na元素的摩尔含量之比，进一步地，m1为22-73。
能够理解，当将该正极活性材料应用于锂离子电池中进行任何充放电处理后，在不同的充放电机制以及充放电节点下，单位摩尔锂金属氧化物中锂的摩尔量是有差异的，单位摩尔锂金属氧化物中Li元素的摩尔含量与Na元素的摩尔含量之比也是有差异的。
根据本申请提供的上述方案，相较于其他正极活性材料，将包括该锂金属氧化的正极活性材料应用于锂离子电池后，锂离子电池的比容量和循环性 能得到显著提升，即使在高电压的工作条件下，锂离子电池的电性能也不会出现劣化。发明人基于此现象进行分析，认为可能是：Li元素与Na元素的摩尔含量之比在一定的范围内时，锂金属氧化物具有更完善的T2结构，部分钠元素在结构中其支撑作用，使得锂金属在立方晶系的Cmca空间群能提升锂离子脱嵌效率，促进锂离子电池循环性能和比容量的改善。
进一步地，发明人发现通过对锂金属氧化物中的掺杂元素进行分类，能够进一步提高正极活性材料的性能。在本申请的一些实施方式中，锂金属氧化物具有式2所示的分子式；
Lin-yNayCo1-a1-a2M1a1M2a2O2    式2
式2中，0＜a1≤0.1，0≤a2≤0.1，a1+a2＝a；
其中，M1选自Te、W、Al、B、P和K中的至少一种；M2为不同于M1的掺杂元素。
可以理解，本申请的锂金属氧化物具有式2所示的分子式，具体是至少包括钴、锂、钠以及M1的氧化物。进一步地，其还可以掺杂不同于M1的M2，本申请不限定M2的具体选择，可以为本领域常见的掺杂元素。例如，可以是Mg、Ti、Mn、Al、Te、Ni、Nb、Zr、La、F、Ce、Sr、Y、K、B和P元素中的至少一种。
本申请对在上述限定范围内的y、a1以及a2不做过多的限制。
例如，式2中，y为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.010、0.012、0.015、0.018、0.020、0.022、0.024、0.025、0.026、0.028、0.03、0.04或0.05；a1为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.010、0.012、0.015、0.018、0.020、0.022、0.024、0.025、0.026、0.028、0.030、0.032、0.034、0.035、0.04、0.045、0.05、0.055、0.06、0.065、0.07、0.075、0.08、0.085、0.09或0.095；a2为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.010、0.012、0.015、0.018、0.020、0.022、0.024、0.025、0.026、0.028、0.030、0.032、0.034、0.035、0.04、0.045、0.05、0.055、0.06、0.065、0.07、0.075、0.08、0.085、0.09或0.095。
本申请中，包括式2的锂金属氧化物的正极活性材料应用于锂离子电池后，能够进一步提升锂离子电池的比容量和循环性能，使锂离子电池在高电压工作条件下能够更长时间不发生劣化。发明人基于此现象进行分析，认为 可能是：一方面，M1的掺杂有助于对锂金属氧化物的结构进行支撑作用，使锂金属氧化物的结构稳定性在一定程度上得到提升，因此无论在常压或者高压的工作环境中，结构稳定的锂金属氧化物更有助于提升锂离子脱嵌的效率，促进锂离子电池循环性能和比容量的改善；另一方面，具有上述晶体特征的该锂金属氧化物具有更为完善的层状晶相结构，得以减少或抑制晶相内部混排现象的发生，进而能够使锂离子发生顺利的脱嵌，尤其在高压的充放电过程中展现出多个充放电小平台。
除了上述锂金属氧化物对电池相关电性能的正向促进作用之外，当在锂金属氧化物的至少部分表面覆盖包覆层时，电池的表现会得到更进一步的改善。通过设置包覆层，正极活性材料为包括锂金属氧化物的内核、包覆层覆盖内核的核壳结构。该包覆层有助于减少或抑制锂金属氧化物和电解液的副反应，即使当电池在高压环境下工作时，正极活性材料和电解液之间依旧能够形成稳定的界面，通过避免正极活性离子中金属离子的过渡溶出以及避免缺液现象而使电池的循环性能得到改善。同时，副反应的抑制或减少也能够降低电池内部的产气量，从而也保证了电池的安全性能。
本申请不限定包覆层材料的选择，只要能够抑制副反应并保证锂离子的正常迁移即可。为了进一步提升锂离子电导率，包覆层可以选用含碳化合物、快离子导体等材料。
如前述，未经过任何充放电处理的锂金属氧化物中，n在0.6～0.8之间，Li元素与Na元素的摩尔含量之比m1在12-80之间。当将包括正极活性材料的正极片和锂金属负极片组装为电池后进行充放电后，充放电循环次数＜10圈时，当电池的剩余电量SOC为0(即处于完全放电状态)且放电截止电压为3.0～3.6V时，锂金属氧化物的n在0.7～1.0之间，Li元素与Na元素的摩尔含量之比m2在16-93之间。具体地，满足前述锂金属氧化物在进行充放电应用后，其组成会发生变化，尤其是锂离子的摩尔量会明显提升。原因在于，具有前述晶型结构的锂金属氧化物中具有部分空位，因此当将其进行充放电应用时，其空位能够接受来自于锂负极的锂原子，进而使锂离子的摩尔量相较于充放电应用前得到提升。该特性有助于进一步提升电池的循环性能和比容量。
进一步地，当m2与m1的差值大于3时，电池具有更为优异的比容量。
尤其是，当电池的剩余电量SOC为0(即处于完全放电到3.0V时)且放电截止电压为3.0～3.6V时，锂金属氧化物的n在0.7～1.0之间，Li元素与Na元素的摩尔含量之比m2在26-93之间，并且，m2与m1的差值大于3时，电池具有更为优异的循环性能和比容量。
本申请正极活性材料可以是单晶形貌或多晶形貌，具体形貌与其掺杂元素的选择以及比例相关。具体地，当为多晶形貌时，其为球状或类球状颗粒；当为单晶形貌时，其可以为须状、片状、或其他任意不规则的形状。
进一步地，本申请正极活性材料的中值粒径为12～20μm，例如为3μm、14μm、15μm、16μm、17μm、18μm、19μm或20μm。发明人发现，当正极活性材料的中值粒径满足上述要求时，一方面，其对应比表面积能够满足更多锂离子的脱嵌；另一方面，正极活性材料之间的团聚现象得到有效控制，从而在制浆过程中能够稳定分散在浆料中。
发明人发现，通过对锂金属氧化物的掺杂元素含量和元素种类参数进行进一步限定，其充放电过程中的多个放电小平台均表现出较为优异的放电量。
很明显，在高压环境下的放电处理中，第一阶段放电电量占比和第二阶段放电容量占比皆表现优异。因此，包括本申请锂金属氧化物的正极活性材料耐压性强，从而能够通过对其进行升压处理而提升电池的比容量。
本申请不限定上述锂金属氧化物的制备方法，在一种具体实施方式中，本申请第二方面的锂金属氧化物可以通过第一方面的锂金属氧化物的制备方法制备得到。能够理解，通过控制钠金属氧化物与锂化合物的添加量，可以得到本申请第二方面具有特定Li元素与Na元素的摩尔含量比的锂金属氧化物。
本申请第三方面提供一种正极片，该正极片包括上述第一方面的正极活性材料和/或第二方面的正极活性材料。
基于第一方面的正极活性材料和/或第二方面的正极活性材料的特性，本申请的正极片有助于改善锂离子电池的循环性能和比容量。
在一种具体实施方式中，本申请的正极片包括正极集流体和设置在正极集流体至少一表面的正极活性层，该正极活性层包括前述正极活性材料。
能够理解，除了正极活性材料之外，正极活性层还包括导电剂和粘结剂。 示例性地，正极活性层按照质量百分含量包括70-99wt％的正极活性材料、0.5-15wt％的导电剂、0.5-15wt％的粘结剂，进一步地，包括80-98wt％的正极活性材料、1-10wt％的导电剂、1-10wt％的粘结剂。
导电剂和粘结剂的选择并无特殊，可以为本领域常规选择。例如，导电剂选自导电炭黑、乙炔黑、科琴黑、导电石墨、导电碳纤维、碳纳米管、单壁碳纳米管、多臂碳纳米管、碳纤维中的至少一种，粘结剂选自聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯酸锂(PAALi)中的至少一种。
进一步地，为了提升安全性能，还可以在正极活性层和集流体之间设置安全层。安全层的材料一般为非导电性的安全材料，例如含铁的化合物(如磷酸铁锂、磷酸锂等)、含铝的化合物(如陶瓷氧化铝)等。当然，安全层中也包括粘结剂，粘结剂和安全材料的比例可以根据具体需求而进一步确定。
在本申请的一些实施方式中，当正极片包括第二方面的正极活性材料时，正极活性层的压实密度大于等于3.5g/cm3时，能够进一步提高电池的循环性能和比容量。
本申请第四方面还提供一种锂离子电池，该离子电池包括上述正极片，因此在循环性能和比容量方面表现突出。
根据本申请，锂离子电池还包括负极片、隔膜和电解液。
示例性地，电解液为本领域已知的包括锂盐和溶剂的常规电解液，溶剂含有碳酸乙烯酯(简写为EC)、碳酸二乙酯(简写为DEC)、碳酸丙烯酯(简写为PC)、氟代碳酸乙烯酯(简写为FEC)。进一步地，还包括一种式T所示的添加剂，其在电解液中的质量百分含量为0.1～10％等。
示例性地，负极片可以为是富含锂金属的负极片，例如可以是锂箔或者如图1所示的负极片。具体地，图1中的负极片包括层叠设置的负极集流体 101、负极活性层20和锂材料层30。图1中的负极片为双面设置，当然也可以为仅在负极集流体单面设置负极活性层20和锂材料层30的负极片。锂材料层例如为锂箔，进一步地，锂材料层中金属锂的面密度为0.09mg/cm2～3.5mg/cm2；负极活性层包括负极活性材料、导电剂以及粘结剂。
在一种具体实施方式中，负极活性层按照质量百分含量包括70-99wt％的负极活性材料、0.5-15wt％的导电剂、0.5-15wt％的粘结剂，进一步地，包括80-98wt％的负极活性材料、1-10wt％的导电剂、1-10wt％的粘结剂。其中，负极活性材料选自人造石墨、天然石墨、硬炭、中间相碳微球、钛酸锂、硅碳、氧化亚硅中的一种或多种。
示例性地，隔膜为聚丙烯为基材的材料，或在此基础上单面或双面涂覆陶瓷的涂胶隔膜。
本申请的锂离子电池适用于高压体系，具体的，包括前述正极片的的锂离子扣式电池≥4.55V(相对锂)的条件下，正极片克容量发挥≥225mAh/g，且在≥4.50V(对应前述负极片)同时具有优异的循环性能。
因此，本申请在4.50V等更高电压具有良好的循环稳定性和较高的克容量的锂离子电池，可满足高端数码产品轻薄化的使用需求。
以下，将结合具体的实施例对本申请的技术方案进行进一步的解释说明。
实施例1A
本实施例的正极活性材料按照以下方法制备：
(1)称取重量为36.56g的碳酸钠粉末和291.05g的六水合硝酸钴粉末，将其放入高速混料设备中，设定混料程序，用300rpm混料3分钟后，用500rpm混料5分钟，再用1000rpm混料10分钟后取出混合料，确认混合料中没有白色的碳酸钠小白点存在后，认为混料均匀；
(2)取30g左右混合均匀的混合料，均匀装入陶瓷坩埚中，使用设备型号为VBF-1200X的井式马弗炉进行高温烧结，烧结的升温曲线为5℃/min，升温至750℃时进行恒温烧结10h，烧结后自然降温至常温后将样品取出，经电感耦合等离子光谱发生仪(ICP)检测得到钠金属氧化物Na0.69CoO2；
(3)取一个反应容器里先称取重量为10.49g的一水合氢氧化锂和质量为17.24g的硝酸锂颗粒，将两种锂的化合物分别加入反应容器中，称取质量为10g 的步骤(2)合成的Na0.69CoO2，倒入反应容器中初步混合后，于280℃离子交换0.5h，得到粗品；
(4)粗品经过3次去离子水抽滤洗涤后，在90℃，干燥8h后得到样品1B#；
利用ICP对1B#进行检测分析，具体结果见表1A；
(5)称取5g步骤(4)得到的样品1B#粉末、25mg氧化石墨烯(GO)，将样品1B#粉末和氧化石墨烯放入一个烧杯容器中，加入15ml去离子水，在45℃下用机械搅拌进行包覆反应，包覆反应时间为30min，然后将其升温至65℃直至烧杯容器中的水分基本蒸干后，进一步在100℃下真空还原干燥，将样品取出得到1A#样品；
对1A#样品进行拉曼光谱仪测试，测试结果见表2A。
实施例2A
本实施例的正极活性材料的制备方法与实施例1A基本相同，不同之处在于：步骤(5)中，称取35mg氧化石墨烯。
实施例3A
本实施例的正极活性材料的制备方法与实施例1A基本相同，不同之处在于：步骤(5)中，称取15mg氧化石墨烯。
实施例4A
本实施例的正极活性材料的制备方法与实施例1A基本相同，不同之处在于：步骤(5)中，包覆反应时间为60min。
实施例5A
本实施例的正极活性材料的制备方法与实施例1A基本相同，不同之处在于：
步骤(1)为：取重量为36.56g的碳酸钠粉末、0.21g的碳酸钾粉末、282.31g的六水合硝酸钴粉末和1.21g的纳米氧化镁粉末，将其放入高速混料设备中，设定混料程序，用300rpm混料3分钟后，用500rpm混料5分钟，再用1000rpm混料10分钟后取出混合料，确认混合料中没有白色的碳酸钠小白点存在后， 认为混料均匀；
步骤(2)得到的钠金属氧化物为Na0.69K0.003Co0.97Mg0.03O2；
经步骤(4)处理后，得到样品5B#Li0.71Na0.02K0.003Co0.97Mg0.03O2；
经步骤(5)处理后，得到样品5A#rGO/Li0.71Na0.02K0.003Co0.97Mg0.03O2。
实施例6A
本实施例的正极活性材料的制备方法与实施例1A基本相同，不同之处在于：
步骤(1)为：取重量为36.56g的碳酸钠粉末、1.53g的纳米氧化铝粉末、276.50g的六水合硝酸钴粉末和0.806g的纳米氧化镁粉末，将其放入高速混料设备中，设定混料程序，用300rpm混料3分钟后，用500rpm混料5分钟，再用1000rpm混料10分钟后取出混合料，确认混合料中没有白色的碳酸钠小白点存在后，认为混料均匀；
步骤(2)得到的钠金属氧化物为Na0.69Co0.95Al0.03Mg0.02O2；
经步骤(4)处理后，得到样品6B#Li0.71Na0.02Co0.95Al0.03Mg0.02O2；
经步骤(5)处理后，得到样品6A#rGO/Li0.71Na0.02Co0.95Al0.03Mg0.02O2。
实施例7A
本实施例的正极活性材料的制备方法与实施例1A基本相同，不同之处在于：
步骤(1)为：取重量为36.56g的碳酸钠粉末、1.854g的硼酸粉末、282.32g的六水合硝酸钴粉末，将其放入高速混料设备中，设定混料程序，用300rpm混料3分钟后，用500rpm混料5分钟，再用1000rpm混料10分钟后取出混合料，确认混合料中没有白色的碳酸钠小白点存在后，认为混料均匀；
步骤(2)得到的钠金属氧化物为Na0.69Co0.97B0.03O2；
经步骤(4)处理后，得到样品7B#Li0.71Na0.02Co0.97B0.03O2；
经步骤(5)处理后，得到样品7A#rGO/Li0.71Na0.02Co0.97B0.03O2。
实施例8A
本实施例的正极活性材料的制备方法与实施例1A基本相同，不同之处在 于：
步骤(1)为：取重量为36.56g的碳酸钠粉末、6.889g的碲酸粉末、282.32g的六水合硝酸钴粉末，将其放入高速混料设备中，设定混料程序，用300rpm混料3分钟后，用500rpm混料5分钟，再用1000rpm混料10分钟后取出混合料，确认混合料中没有白色的碳酸钠小白点存在后，认为混料均匀；
步骤(2)得到的钠金属氧化物为Na0.69Co0.97Te0.03O2；
经步骤(4)处理后，得到样品8B#Li0.71Na0.02Co0.97Te0.03O2；
经步骤(5)处理后，得到样品8A#rGO/Li0.71Na0.02Co0.97Te0.03O2。
实施例9A
本实施例的正极活性材料的制备方法与实施例1A基本相同，不同之处在于步骤(5)中：
在25℃下用机械搅拌进行包覆反应，包覆反应时间为10min，得到样品9A#。
实施例10A
本实施例的正极活性材料的制备方法与实施例1A基本相同，不同之处在于步骤(5)中：
称取75mg氧化石墨烯(GO)，包覆反应时间为10min，得到10A#；
对比例1A
本对比例的正极活性材料为常规高电压掺杂包覆钴酸锂正极材料，其化学组成为Li1.0027Co0.97Al0.03O2。
制备方法包括如下步骤：
(1)按摩尔比例Li:Co＝100.27:97称取碳酸锂和市面上购买的常规的带有掺杂Al的球形Co3O4颗粒，该Co3O4颗粒的化学计量比为Co:Al＝97:3.0将两种物质使用与实验例相同的搅拌设备，将其放入高速混料设备中，设定混料程序，用300rpm混料3分钟后，用500rpm混料5分钟，再用1000rpm混料10分钟后取出混合料，确认混合料中没有白色的碳酸锂小白点存在后，认为混料均匀；
(2)取30g左右混合均匀的混合料，均匀装入陶瓷坩埚中，使用设备型 号为VBF-1200X的井式马弗炉进行高温烧结，烧结的升温曲线为5℃/min，升温至1030℃时进行恒温烧结10h，烧结后自然降温至常温后将样品取出，得到Li1.0027Co0.97Al0.03O2。
对比例2A
本对比例的正极活性材料的制备方法与实施例5A基本相同，不同之处在于：不进行步骤(5)的处理，直接使用步骤(4)得到的5A#样品作为正极活性材料。
实施例1C
本实施例的正极活性材料按照以下方法制备：
(1)称取重量为36.56g的碳酸钠粉末和291.05g的六水合硝酸钴粉末，将其放入高速混料设备中，设定混料程序，用300rpm混料3分钟后，用500rpm混料5分钟，再用1000rpm混料10分钟后取出混合料，确认混合料中没有白色的碳酸钠小白点存在后，认为混料均匀；
(2)取30g左右混合均匀的混合料，均匀装入陶瓷坩埚中，使用设备型号为VBF-1200X的井式马弗炉进行高温烧结，烧结的升温曲线为5℃/min，升温至750℃时进行恒温烧结10h，烧结后自然降温至常温后将样品取出，经电感耦合等离子光谱发生仪(ICP)检测得到钠金属氧化物Na0.69CoO2；
(3)取一个反应容器先称取重量为10.49g的一水合氢氧化锂和质量为17.24g的硝酸锂颗粒，将两种锂的化合物分别加入反应容器中，称取质量为10g的步骤(2)合成的Na0.69CoO2，倒入反应容器中初步混合后，于280℃离子交换0.5h，得到粗品；
(4)粗品经过3次去离子水抽滤洗涤后，在90℃，干燥8h后得到样品1C#。
利用ICP对1C#进行检测分析，具体结果见表1C。
实施例2C
本实施例的正极活性材料的制备方法与实施例1C基本相同，不同之处在于：
步骤(3)中，于260℃离子交换1.2h，得到粗品；经步骤(4)处理后， 得到样品2C#Li0.70Na0.025CoO2。
实施例3C
本实施例的正极活性材料的制备方法与实施例1C基本相同，不同之处在于：
步骤(3)中，于95℃离子交换3.4h，得到粗品；经步骤(4)处理后，得到样品3C#Li0.72Na0.023CoO2。
实施例4C
本实施例的正极活性材料的制备方法与实施例1C基本相同，不同之处在于：
步骤(3)中，于105℃离子交换3.0h，得到粗品；经步骤(4)处理后，得到样品4C#Li0.73Na0.017CoO2。
实施例5C
本实施例的正极活性材料的制备方法与实施例1C基本相同，不同之处在于：
步骤(1)为：取重量为36.56g的碳酸钠粉末、0.21g的碳酸钾粉末、282.31g的六水合硝酸钴粉末和1.21g的纳米氧化镁粉末，将其放入高速混料设备中，设定混料程序，用300rpm混料3分钟后，用500rpm混料5分钟，再用1000rpm混料10分钟后取出混合料，确认混合料中没有白色的碳酸钠小白点存在后，认为混料均匀；
步骤(2)得到的钠金属氧化物为Na0.69K0.003Co0.97Mg0.03O2；
经步骤(4)处理后，得到样品5C#Li0.71Na0.02K0.003Co0.97Mg0.03O2。
实施例6C
本实施例的正极活性材料的制备方法与实施例5C基本相同，不同之处在于：
步骤(3)中，于100℃离子交换2.8h，得到粗品；经步骤(4)处理后，得到样品6C#Li0.72Na0.021K0.003Co0.97Mg0.03O2。
实施例7C
本实施例的正极活性材料的制备方法与实施例5C基本相同，不同之处在于：
步骤(3)中，于260℃离子交换1.5h，得到粗品；经步骤(4)处理后，得到样品7C#Li0.73Na0.017K0.003Co0.97Mg0.03O2。
对比例1C
本对比例的正极活性材料的制备方法与实施例1C基本相同，不同之处在于：
步骤(3)中，于75℃离子交换24h，得到粗品；经步骤(4)处理后，得到样品1a#Li0.50Na0.48CoO2。
对比例2C
本对比例的正极活性材料的制备方法与实施例1C基本相同，不同之处在于：
步骤(3)中，于90℃离子交换24h，得到粗品；经步骤(4)处理后，得到样品2a#Li0.89Na0.005CoO2。
对比例3C
本对比例的正极活性材料的制备方法与实施例5C基本相同，不同之处在于：
步骤(3)中，280℃离子交换0.1h，得到粗品；经步骤(4)处理后，得到样品3a#Li0.39Na0.60K0.003Co0.97Mg0.03O2。
对比例4C
本对比例的正极活性材料的制备方法与实施例5C基本相同，不同之处在于：
步骤(3)中，85℃离子交换30h，得到粗品；经步骤(4)处理后，得到样品4a#Li0.86Na0.006K0.003Co0.97Mg0.03O2。
对比例5C
本对比例的正极活性材料的制备方法与实施例5C基本相同，不同之处在于：
步骤(3)中，280℃离子交换0.35h，得到粗品；经步骤(4)处理后，得到样品5a#Li0.69Na0.06K0.003Co0.97Mg0.03O2。
对比例6C
本对比例的正极活性材料的制备方法与实施例1C基本相同，不同之处在于：
步骤(3)中，280℃离子交换15h，得到粗品；经步骤(4)处理后，得到样品6a#Li0.93Na0.03CoO2。
试验例1
1、使用SEM测试实施例1A的正极活性材料的形貌，图2为本申请实施例1A中正极活性材料的SEM图。从图2可以看出，本申请正极材料颗粒具有片状的缺陷石墨烯层和基体颗粒，缺陷石墨烯层贴合在基体颗粒的表面。
分别使用SEM测试实施例1C和对比例1C的正极活性材料的形貌，如图3和图4所示，实施例1C中的正极活性材料的粒径分散度较大，能够更充分的进行脱嵌锂离子，有助于改善电池的比容量以及循环性能。
2、对实施例1A-10A和对比例1A-2A的产品进行拉曼测试，结果见表2A。
图5为本申请实施例1A和实施例9A中正极活性材料的拉曼测试图。从图5可以看出，实施例1A中ID/IG为80.20％，实施例9A中ID/IG为65.38％。
3、对所有实施例和对比例的产品进行XRD衍射测试，测试结果见表2A以及2C。
图6为本申请实施例8A以及实施例1B中正极活性材料的XRD图。从图6可知，本申请实施例中制备得到的锂金属氧化物具有002峰(2θ为17.9°～18.1°)以及131峰(2θ为67.0°～67.5°)，且其为立方晶系的Cmca空间群，具有T2结构。
试验例2
将所有实施例和对比例中的产品制作为正极片后，与负极片、电解液以及隔膜按照以下方法组装得到锂离子电池。方法包括：
1)将实施例和对比例中的正极活性材料分别与导电碳黑、PVDF按照96％:2％:2％的重量比混合，通过分散得到正极浆料。将该浆料涂布在铝箔集流体上，辊压制备得到正极片；
2)将人造石墨、苯乙烯二烯橡胶(SBR)、及羧甲基纤维素钠、导电碳黑以94％:3％:2％:1％的重量比混合，将混合物分散于水中通过双行星混合后得到负极浆液。将该浆液涂覆于铜集流体上，接着进行辊压及干燥；
随后通过轧制方式在负极活性层表面叠加锂材料层，锂材料层为锂箔，金属锂的面密度为1.0mg/cm2，最终得到含有锂金属的负极片。
3)然后将正极片、负极片和隔膜组装成锂离子电池，并注入非水电解液。
其中，电解液为本领域已知的常规电解液，按碳酸乙烯酯(简写为EC)：碳酸二乙酯(简写为DEC)：碳酸丙烯酯(简写为PC)＝2：5：3的质量比混合后，加入占电解液总质量的5％的氟代碳酸乙烯酯(简写为FEC)、加入占电解液总质量的13％的六氟磷酸锂(简写为LiPF6)，以及式T所示的添加剂，添加剂含量占电解液总含量的2％。
对得到的各个锂离子电池的容量保持率进行测试，具体测试方法为：在25℃下，以1C的充电倍率恒流充电至4.50V，再以0.05C的充电倍率恒压充电至4.50V，然后以1C的放电倍率放电至3.0V，反复500次这种充放电循环，测定第一次循环时的放电容量和第500次循环时的放电容量，按照下式求出500圈循环后的容量保持率，结果见表2A以及2C。
容量保持率Q＝(第500次循环时的放电容量)/(第一次循环时的放电容量)*100％
试验例3
将所有实施例和对比例中的产品制作为正极片后，与负极片、电解液以及隔膜按照以下方法组装得到扣式电池。方法包括：
将实施例和对比例中的正极活性材料分别与导电碳黑(SP)、PVDF按照 80％:10％:10％的重量比混合，通过分散得到正极浆料。将该浆料涂布在铝箔集流体上，辊压制备得到正极片，然后将正极片用膜具冲型直径为12mm的小圆片，烘干称重处理后，在Ar保护气氛下的手套箱中，使用2025的扣式电池壳，用Li金属圆片做负极，常规高电压钴酸锂电解液一起组装成扣式电池。
对得到的各个扣式电池在常规环境下静置4h后，进行首次充放电容量测试，测试条件为：0.1C充电至4.55V，恒压充电至0.025C截止后，静置3min后，0.1C放电至3.0V。在放电过程中，分别记录4.4～4.55V的放电电量C1、3.7～3.8V的放电电量C2、首次放电全电量C0、首次充电容量，并计算首次效率、第一阶段放电容量占比C1/C0以及第二阶段放电容量占比C2/C0。结果见表2A以及2C。
表1A
表2A

根据表1A和表2A可知：
1、根据实施例和对比例，不同的制备参数如反应温度、反应时间、原料选择差异等，对锂金属氧化物的组成以及晶型结构均有一定的影响，并最终影响锂离子电池的相关表现。
2、从表2A中，实施例5A和对比例2A可以看出，本申请实施例制备的正极活性材料应用于锂离子电池时，具有更为优异的克容量和循环性能，说明本申请中使用氧化还原石墨烯包覆基体材料制备正极活性材料能够改善正极活性材料的电化学性能。
3、从实施例1A-4A可以看出，石墨包覆层的含量对正极活性材料的晶型有轻微影响，表现在特征峰的位置发生轻微变化，但是可以忽略。
表1C
表2C

根据表1C和表2C可知：
1、根据实施例和对比例，不同的制备参数如反应温度、反应时间、原料选择差异等，对锂金属氧化物的组成以及晶型结构均有一定的影响，并最终影响锂离子电池的相关表现。尤其是，需要严格控制合成条件，才能得到纯相的正极活性材料。
2、从表2C可以看出，本申请实施例制备的正极活性材料应用于锂离子电池时，具有更为优异的克容量和循环性能。
3、从实施例1C-4C与实施例5C-7C可以看出，与无掺杂元素的正极活性材料相比，具有掺杂元素的正极活性材料应用于锂离子电池时，其克容量基本不变，循环性能明显增强。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围。

Claims (20)

  1. 一种正极活性材料，其中，所述正极活性材料由包括锂金属氧化物的基体颗粒和覆盖所述基体颗粒至少部分表面的石墨包覆层构成；
    所述锂金属氧化物具有式1所示的结构；
    在X射线衍射图谱中，所述锂金属氧化物为立方晶系的Cmca空间群，且具有2θ为17.9°～18.1°的002峰，以及2θ为67.0°～67.5°的131峰；
    Lin-yNayCo1-aMaO2   式1
    式1中，0.6≤n≤0.8，0＜y≤0.05，0≤a≤0.2；
    其中，M为掺杂元素。
  2. 根据权利要求1所述的正极活性材料，其中，所述锂金属氧化物具有式2所示的结构；
    Lin-yNayCo1-a1-a2M1a1M2a2O2   式2
    式2中，0＜a1≤0.1，0≤a2≤0.1，0<a1/1-a2<0.1，a1+a2＝a；
    其中，M1选自Te、W、Al、B、P和K中的至少一种；M2为不同于M1的掺杂元素。
  3. 根据权利要求1或2所述的正极活性材料，其中，基于所述正极活性材料的总质量，所述石墨包覆层的质量百分含量W满足：0＜W≤1％。
  4. 根据权利要求1-3任一项所述的正极活性材料，其中，所述石墨包覆层为还原氧化石墨烯包覆层。
  5. 根据权利要求4所述的正极活性材料，其中，在拉曼光谱图中，所述锂金属氧化物在波长1560±30cm-1的峰强度IG，与锂金属氧化物在波长1360±30cm-1的峰强度为ID满足：ID/IG≥68％。
  6. 根据权利要求5所述的正极活性材料，其中，80％≤ID/IG≤90％。
  7. 根据权利要求1-6任一项所述的正极活性材料，其中，所述正极活性材料在截止电压为3.0～3.6V且SOC为零时，0.7≤n≤1.0。
  8. 根据权利要求1-7任一项所述的正极活性材料，其中，所述正极活性材料的中值粒径为12μm～20μm。
  9. 一种正极活性材料，其中，所述正极活性材料包括锂金属氧化物，所述锂金属氧化物具有式1所示的分子式；
    在X射线衍射图谱中，所述锂金属氧化物为立方晶系的Cmca空间群， 且具有2θ为17.9°～18.1°的002峰，以及2θ为67.0°～67.5°的131峰；
    Lin-yNayCo1-aMaO2   式1
    式1中，0.6≤n≤0.8，0＜y≤0.05，0≤a≤0.2；
    Li元素与Na元素的摩尔含量之比m1满足：12≤m1≤80；
    其中，M为掺杂元素。
  10. 根据权利要求9所述的正极活性材料，其中，m1为22-73。
  11. 根据权利要求9或10所述的正极活性材料，其中，所述的锂金属氧化物具有式2所示的分子式；
    Lin-yNayCo1-a1-a2M1a1M2a2O2   式2
    式2中，0＜a1≤0.1，0≤a2≤0.1，a1+a2＝a；
    其中，M1选自Te、W、Al、B、P和K中的至少一种；M2为不同于M1的掺杂元素。
  12. 根据权利要求9-11任一项所述的正极活性材料，其中，所述正极活性材料由包括所述锂金属氧化物的基体颗粒和覆盖所述基体颗粒至少部分表面的包覆层构成。
  13. 根据权利要求9-12任一项所述的正极活性材料，其中，所述正极活性材料在截止电压为3.0～3.6V且SOC为零时，0.7≤n≤1.0，且Li元素与Na元素的摩尔含量之比m2满足：16≤m2≤93。
  14. 根据权利要求13所述的正极活性材料，其中，m2-m1＞3。
  15. 根据权利要求9-14任一项所述的正极活性材料，其中，所述正极活性材料的中值粒径为12μm～20μm。
  16. 一种正极片，其中，所述正极片包括权利要求1-15任一项所述的正极活性材料。
  17. 根据权利要求16所述的正极片，其中，所述正极片包括集流体、安全层以及正极活性层；
    其中，所述安全层夹设在所述集流体和正极活性层之间，所述正极活性层包括所述正极活性材料。
  18. 根据权利要求17所述的正极片，其中，所述正极片包括权利要求9-15任一项所述的正极活性材料，所述正极活性层的压实密度大于等于3.5g/cm3。
  19. 一种锂离子电池，其中，所述锂离子电池包括权利要求16-18任一项 所述的正极片。
  20. 根据权利要求19所述的锂离子电池，其中，所述锂离子电池中的负极片为含锂负极片。
PCT/CN2023/108256 2022-09-02 2023-07-19 一种正极活性材料及其应用 WO2024045937A1 (zh)

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CN114784269A (zh) * 2022-06-20 2022-07-22 北京大学 一种空间群为Cmca的T2型钴酸锂正极材料及其制备方法
CN115275171A (zh) * 2022-09-02 2022-11-01 珠海冠宇电池股份有限公司 一种正极活性材料及其应用
CN115295789A (zh) * 2022-09-02 2022-11-04 珠海冠宇电池股份有限公司 一种正极活性材料及其应用
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