WO2023230832A1 - 镍锰酸锂正极活性材料及其制备方法、以及使用其的二次电池 - Google Patents

镍锰酸锂正极活性材料及其制备方法、以及使用其的二次电池 Download PDF

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WO2023230832A1
WO2023230832A1 PCT/CN2022/096216 CN2022096216W WO2023230832A1 WO 2023230832 A1 WO2023230832 A1 WO 2023230832A1 CN 2022096216 W CN2022096216 W CN 2022096216W WO 2023230832 A1 WO2023230832 A1 WO 2023230832A1
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active material
cathode active
lithium nickel
lithium
manganate cathode
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PCT/CN2022/096216
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English (en)
French (fr)
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张振国
王嗣慧
范敬鹏
柳娜
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宁德时代新能源科技股份有限公司
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Priority to CN202280046067.1A priority Critical patent/CN117581397A/zh
Priority to PCT/CN2022/096216 priority patent/WO2023230832A1/zh
Priority to EP22929210.7A priority patent/EP4312290A1/en
Publication of WO2023230832A1 publication Critical patent/WO2023230832A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Nickelates
    • C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
    • C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/54—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese of the type [Mn2O4]-, e.g. Li(NixMn2-x)O4, Li(MyNixMn2-x-y)O4
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to a lithium nickel manganate cathode active material for secondary batteries and a preparation method thereof, as well as secondary batteries, battery modules, battery packs and electrical devices using the lithium nickel manganate cathode active material.
  • the cathode active material is a key factor restricting the high-rate discharge capability and storage stability improvement of secondary batteries. Therefore, it is urgent to develop a cathode active material with high kinetic performance and high chemical stability.
  • This application was made in view of the above technical problems, and its purpose is to provide a spinel-structured lithium nickel manganese cathode active material with high kinetic performance and high chemical stability, so that it can simultaneously improve the use of the nickel manganese.
  • the high-rate discharge capability and long-term storage stability of secondary batteries using lithium acid lithium cathode active materials was made in view of the above technical problems, and its purpose is to provide a spinel-structured lithium nickel manganese cathode active material with high kinetic performance and high chemical stability, so that it can simultaneously improve the use of the nickel manganese.
  • the first aspect of the present application provides a lithium nickel manganate cathode active material, wherein,
  • composition formula of the positive active material is Li 1+x Ni y M z Mn 2-xyz O 4-k , -0.1 ⁇ x ⁇ 0.2, 0.4 ⁇ y ⁇ 0.6, 0 ⁇ z ⁇ 0.2, M is Cr, Mo, One or more of Nb, Ru, P, S, Ta, W, Tl and Ti,
  • the ratio of the charging capacity of 3.5V to 4.4V to the charging capacity of 3.5V to 4.95V is A, A satisfies 0.04 ⁇ A ⁇ 0.3, and the product of k and A It satisfies 0 ⁇ kA ⁇ 0.015, wherein the first-cycle charging curve is measured at a rate of 0.1C.
  • the obtained lithium nickel manganate cathode active material has both high kinetic performance and high chemical stability, and the corresponding secondary battery has both high-rate discharge capability and long-term storage stability.
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies: 0.11 ⁇ k+A ⁇ 0.18, optionally 0.11 ⁇ k+A ⁇ 0.15. This is because when the A value is large, the Mn 3+ content in the lithium nickel manganate cathode active material corresponding to the spinel structure is higher, and transition metal manganese is prone to dissolve, thereby reducing the chemical stability of the material, so the smaller The k value can improve the chemical stability of the material, so that the material has both good kinetic properties and chemical stability, and the corresponding secondary battery has both excellent high-rate discharge capability and long-term storage stability.
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies: 0.07 ⁇ A ⁇ 0.15.
  • the obtained lithium nickel manganate cathode active material has further improved kinetic properties, corresponding to the improvement of the high-rate discharge capability of the secondary battery.
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies: 0 ⁇ k ⁇ 0.1, optionally 0 ⁇ k ⁇ 0.05, optionally 0 ⁇ k ⁇ 0.03.
  • the obtained lithium nickel manganate cathode active material has further improved chemical stability, corresponding to improved long-term storage stability of the secondary battery.
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies: 0 ⁇ z ⁇ 0.2, optionally 0.001 ⁇ z ⁇ 0.15.
  • M is further one or two or more selected from Nb, Ru, P, Ta and T1.
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies that: the lithium nickel manganate cathode active material is single crystal and/or single crystal-like particles.
  • the chemical stability of the positive electrode active material is further improved, and the long-term storage performance of the secondary battery using the positive electrode active material is further improved.
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies: the volume median particle diameter (D V50 ) of the particles satisfies 1 ⁇ m ⁇ D V50 ⁇ 20 ⁇ m, optionally 2 ⁇ m ⁇ D V50 ⁇ 15 ⁇ m.
  • D V50 volume median particle diameter
  • the grain size is larger, its exposed surface is smaller, and the contact area with the electrolyte is smaller. Therefore, the stability of the lithium nickel manganese oxide cathode active material is improved.
  • too large grain size will deteriorate its dynamic performance.
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies: 0.06 ⁇ (k+A)/(D V50 0.3 ) ⁇ 0.12, optionally 0.06 ⁇ (k+A )/(D V50 0.3 ) ⁇ 0.10, where the unit of (k+A)/(D V50 0.3 ) is ⁇ m -0.3 .
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies: based on the total weight of the M element, along the radial direction of the surface layer of the cathode active material particles toward its geometric center, More than 80% of the M elements are located in the first 50% of the volume of the particles of the cathode active material; optionally, they are within the first 30% of the volume. Therefore, by concentrating the doping elements on the surface layer, the surface stabilizing effect of the doping elements on the cathode active material can be further improved, the oxygen defect content can be further reduced, the surface stability of the material can be improved, and the performance of secondary batteries using the cathode active material can be improved. Long term storage stability.
  • the second aspect of this application also provides a preparation method of lithium nickel manganate cathode active material, including the following steps:
  • S1 Provide a compound or mixture containing lithium, nickel, and manganese.
  • the compound or mixture contains M element;
  • composition formula of the positive active material is Li 1+x Ni y M z Mn 2-xyz O 4-k , -0.1 ⁇ x ⁇ 0.2, 0.4 ⁇ y ⁇ 0.6, 0 ⁇ z ⁇ 0.2, M is Cr, Mo, One or more of Nb, Ru, P, S, Ta, W, Tl and Ti,
  • the ratio of the charging capacity of 3.5V to 4.4V to the charging capacity of 3.5V to 4.95V is 0.04 ⁇ A ⁇ 0.3, and the product of k and A is 0 ⁇ kA ⁇ 0.015, wherein the charging curve is measured at a rate of 0.1C.
  • the oxygen partial pressure accounts for 80% to 100%.
  • the compound or mixture containing lithium, nickel, and manganese is heat-treated at 800 to 1100°C for 5 to 50 hours in an oxygen-containing atmosphere.
  • the nickel-manganese raw material in the mixture containing lithium, nickel, and manganese is selected from Ni y Mn 2-xyz (OH) 4-2x-2z , Ni y Mn 2-xyz (CO 3 ) 2- xz , Ni y Mn 2-xyz O 2-xz , Ni y Mn 2-xyz O 4-2x-2z , (Ni y Mn 2-xyz ) 3 O 4-2x-2z , Ni y Mn 2-xyz [O (OH)] 2-One or two or more of xz , -0.1 ⁇ x ⁇ 0.2, 0.4 ⁇ y ⁇ 0.6, 0 ⁇ z ⁇ 0.2.
  • the spinel structure lithium nickel manganate cathode active material prepared by the above preparation method of the present application has excellent dynamic properties and chemical stability.
  • a third aspect of the present application also provides a secondary battery, which includes the lithium nickel manganate cathode active material of the first aspect or the lithium nickel manganate cathode active material obtained by the preparation method of the second aspect.
  • the secondary battery has High-rate discharge capability and long-term storage stability are significantly improved.
  • a fourth aspect of the present application also provides a battery module, which includes the secondary battery of the third aspect.
  • a fifth aspect of the present application provides a battery pack, including the battery module of the fourth aspect of the present application.
  • a sixth aspect of the present application provides an electrical device, including at least one selected from the secondary battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, or the battery pack of the fifth aspect of the present application. kind.
  • the battery modules, battery packs, and electrical devices of the present application include the secondary battery cells of the present application, they have the same advantages as the secondary battery cells of the present application.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. 4 .
  • Figure 6 is a schematic diagram of an electrical device according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • Lithium nickel manganese oxide cathode active material is an excellent cathode active material with high voltage characteristics and has great commercial value.
  • the existing lithium nickel manganese oxide cathode active material has the following characteristics: the lithium nickel manganese oxide cathode active material with a spinel structure has a nickel-manganese disordered phase Fd3m and a nickel-manganese organic phase. There are two space group structures of sequence phase P4 3 32.
  • the spinel structure of the lithium manganate material is Lithium ions have stronger conductivity and thus have stronger discharge capability at high rates.
  • the proportion of Fd3m structure is relatively high, the surface oxygen defects of the spinel structure lithium nickel manganate cathode active material are many.
  • the spinel-structured lithium nickel manganese oxide cathode active material when the surface oxygen defects of the spinel-structured lithium nickel manganese oxide cathode active material are more, the side reactions (such as transition metals) between the lithium nickel manganese oxide cathode active material and the electrolyte will The dissolution of manganese, consumption of electrolyte and gas generation, etc.) become more significant, which leads to poor long-term storage performance of the secondary battery. That is to say, the spinel-structured lithium nickel manganate cathode active material in the prior art has never been able to achieve both high kinetic performance and high chemical stability.
  • this application developed a spinel-structured lithium nickel manganate cathode active material with high kinetic performance and high chemical stability through reasonable control of the preparation process, so that secondary batteries using this cathode active material can have both High rate discharge capability and long-term storage stability performance.
  • the first aspect of the embodiment of the present application proposes a lithium nickel manganate cathode active material.
  • the composition formula of the cathode active material is Li 1+x Ni y M z Mn 2-xyz O 4-k , -0.1 ⁇ x ⁇ 0.2, 0.4 ⁇ y ⁇ 0.6, 0 ⁇ z ⁇ 0.2, M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti,
  • the ratio of the charging capacity of 3.5V to 4.4V to the charging capacity of 3.5V to 4.95V is A, A satisfies 0.04 ⁇ A ⁇ 0.3, and the product of k and A It satisfies 0 ⁇ kA ⁇ 0.015, wherein the first-cycle charging curve is measured at a rate of 0.1C.
  • the spinel structure lithium manganate material when the proportion of Fd3m structure in the spinel structure lithium manganate material is relatively high, the spinel structure lithium manganate material has a stronger discharge capability at high rates.
  • the spinel structure lithium manganate material described in the first aspect of this application The proportion of Fd3m structure in the spar structure lithium manganate material is significantly increased, thereby significantly improving the lithium ion conductivity of the spinel structure lithium nickel manganate cathode active material, and significantly improving the spinel structure lithium manganate The kinetic properties of the cathode active material thereby significantly improve the high-rate discharge capability of the secondary battery prepared from the spinel structure lithium nickel manganate cathode active material.
  • the inventor creatively discovered that the proportion of Fd3m structure in the lithium nickel manganate cathode active material can be represented by A.
  • the measurement method of A is as follows: in the first cycle charging curve of the half-cell of the positive active material, the ratio of the charging capacity of 3.5V to 4.4V to the charging capacity of 3.5V to 4.95V, where, in the first cycle of testing, curve, first use lithium as the negative electrode and the spinel structure lithium nickel manganese oxide positive electrode active material of the present application as the positive electrode to prepare a button half cell, and then charge it to a voltage of 4.95V at a rate of 0.1C, and then obtain the first cycle Charging curve.
  • the value of A is the ratio of the charging capacity of 3.5V to 4.4V to the charging capacity of 3.5V to 4.95V. .
  • the value of A can characterize the proportion of the Fd3m structure in the lithium nickel manganese oxide cathode active material. Further reasons are as follows: In the Fd3m structure, because it contains more Mn 3+ , all lithium nickel manganese oxide cathode materials are removed during the charging process. In addition to the valence state changes of Ni 2+ /Ni 3+ /Ni 4+ that may occur, the valence state change of Mn 3+ /Mn 4+ unique to the Fd3m structure lithium nickel manganate will also occur. This element The change between valence states causes a voltage platform to appear in the charging curve in the range of 3.5V to 4.4V. Therefore, the ratio A of the charging capacity corresponding to the voltage platform to the charging capacity corresponding to 3.5V to 4.95V can characterize the Fd3m structure in nickel. Proportion of lithium manganate cathode active material.
  • the A value of the spinel structure lithium nickel manganate cathode active material of the present application satisfies 0.04 ⁇ A ⁇ 0.3.
  • the spinel structure lithium nickel manganate cathode active material is almost all Fd3m structure.
  • the proportion of Fd3m structure in the spinel structure lithium nickel manganate cathode active material increases, and the spinel structure
  • the structured lithium nickel manganate cathode active material has significantly improved kinetic properties, and the high-rate discharge capability of the secondary battery prepared from the spinel structured lithium nickel manganate cathode active material is significantly improved.
  • the cathode active material of the present application has the composition formula of Li 1+x Ni y M z Mn 2-xyz O 4-k , -0.1 ⁇ x ⁇ 0.2, 0.4 ⁇ y ⁇ 0.6, 0 ⁇ z ⁇ 0.2.
  • “1+x” represents the number of moles of lithium atoms in the composition formula
  • "y” represents the number of moles of nickel atoms in the composition formula
  • "z” represents the number of moles of M atoms in the composition formula.
  • “4-k” represents the number of moles of oxygen atoms in the composition formula.
  • k represents a quantitative index of surface oxygen defects in the lithium nickel manganese oxide with the spinel structure of the composition formula, that is, the size of k can characterize the spinel structure nickel manganese oxide of the present application.
  • the chemical stability of the lithium cathode active material can further affect the long-term storage stability of the secondary battery prepared from the spinel structure lithium nickel manganate cathode active material.
  • the k value of the spinel structure lithium nickel manganate cathode active material of the present application satisfies the following conditions: the product of k and A satisfies 0 ⁇ kA ⁇ 0.015.
  • the product kA of k and A can comprehensively characterize the comprehensive chemical stability and kinetic properties of the spinel structure lithium nickel manganese oxide cathode active material. Specifically, when A is larger, it means that the spinel structure nickel manganese
  • the Fd3m structure accounts for a high proportion in the lithium acid cathode active material and has good kinetic properties.
  • the surface of the lithium nickel manganate cathode active material corresponding to the spinel structure will have many oxygen defects and the material will be chemically unstable. It has poor performance and cannot comprehensively take into account the dynamic properties and chemical stability of the material.
  • the spar-structured lithium nickel-manganese oxide cathode active material satisfies the relationship of 0 ⁇ kA ⁇ 0.015
  • the spinel-structured lithium nickel-manganese oxide cathode active material has excellent comprehensive properties and has both good kinetic properties and chemical properties. Stability, the secondary battery thus prepared has excellent high-rate discharge performance and long-term storage stability.
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies: 0.11 ⁇ k+A ⁇ 0.18, optionally 0.11 ⁇ k+A ⁇ 0.15. This is because when the A value is large, the Mn 3+ content in the lithium nickel manganate cathode active material corresponding to the spinel structure is higher, and transition metal manganese is prone to dissolve, thereby reducing the chemical stability of the material, so the smaller The k value can improve the chemical stability of the material, so that the material has both good kinetic properties and chemical stability, and the corresponding secondary battery has both excellent high-rate discharge capability and long-term storage stability.
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies: 0 ⁇ k ⁇ 0.1, optionally 0 ⁇ k ⁇ 0.05, optionally 0 ⁇ k ⁇ 0.03.
  • the smaller the k value the fewer oxygen defects on the surface of spinel lithium manganate.
  • the chemical stability of the material can be significantly improved, the side reaction between the cathode material and the electrolyte can be slowed down, and the dissolution of Mn and the electrolyte can be slowed down. consumption and improve the long-term storage stability of secondary batteries.
  • the spinel structure lithium manganate material when z is not 0, contains the doping element M.
  • the doping element M can form a strong bond with oxygen, which is not only beneficial to the synthesis of a low-oxygen defective Fd3m structure, but also Moreover, it can further improve the structural stability of the material, thereby better improving the long-term stability of the secondary battery while taking into account high dynamic performance.
  • M is further selected from one or more of Nb, Ru, P, Ta and Tl.
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies: 0.07 ⁇ A ⁇ 0.15.
  • the spinel-structured lithium nickel manganate cathode active material has a higher proportion of Fd3m structure, and the dynamic properties of the material improve, thereby improving the high-rate charge and discharge capability of the secondary battery.
  • the Fd3m structure of the spinel-structured lithium nickel manganate cathode active material accounts for too much, resulting in a reduction in the total energy density of the secondary battery using this cathode active material.
  • the lithium nickel manganate cathode active material is single crystal and/or single crystal-like particles.
  • Single-crystal-like refers to materials with a cohesive structure composed of several to a dozen crystal grains forming an agglomerate-like morphology. This type of material with a quasi-single crystal morphology has the characteristics of being easy to synthesize and reducing the grain boundaries of secondary spherical particles. Advantage.
  • single crystal or single-crystal-like nickel manganese oxide Lithium materials can effectively avoid or reduce these problems, thereby further improving the surface stability of the cathode active material, and further improving the long-term storage performance of secondary batteries using the cathode active material.
  • the volume median particle size (D V50 ) of the spinel structure lithium nickel manganate material particles satisfies 1 ⁇ m ⁇ D V50 ⁇ 20 ⁇ m, optional 2 ⁇ m ⁇ D V50 ⁇ 15 ⁇ m.
  • D V50 volume median particle size
  • the grain size is larger, its exposed surface is smaller, and the contact area with the electrolyte is smaller. Therefore, the stability of the lithium nickel manganese oxide cathode active material is improved.
  • too large grain size will deteriorate its dynamic performance.
  • the spinel structure lithium nickel manganate cathode active material of the present application further satisfies 0.06 ⁇ (k+A)/(D V50 0.3 ) ⁇ 0.12, optionally 0.06 ⁇ (k+A)/ (D V50 0.3 ) ⁇ 0.10, where the unit of (k+A)/(D V50 0.3 ) is ⁇ m -0.3 .
  • the crystal grains are larger, the exposed surface is smaller, and the contact area with the electrolyte is small, so the stability of the lithium nickel manganate cathode active material is improved; but on the other hand, too large grains will deteriorate its dynamic performance.
  • the spinel structure lithium nickel manganate cathode active material requires a higher proportion of Fd3m structure; in addition, if there are a small amount of oxygen defects inside the particles (not on the surface) that promote ion transfer (reflected in an increase in the k value Large) will also have a certain promotion effect on the overall dynamic performance.
  • balancing k, A and D V50 through the above relationship is more conducive to the high-rate discharge performance and long-term storage stability of secondary batteries using spinel-structured lithium nickel manganate cathode active materials.
  • the spinel structure lithium nickel manganate cathode active material of the present application based on the total weight of the M element, is 80% in the radial direction from the surface layer of the particles of the cathode active material to its geometric center.
  • the above M element is located within the first 50% volume of the particles of the positive electrode active material; optionally, it is within the first 30% volume.
  • the surface stabilizing effect of the doping elements on the cathode active material can be further improved, the oxygen defect content can be further reduced, the surface stability of the material can be improved, and the performance of secondary batteries using the cathode active material can be improved. Long term storage stability.
  • the grain shape of the lithium nickel manganate cathode active material is an octahedron, a truncated octahedron, or a regular shape of an octahedron with sharp edges and edges.
  • the so-called truncated octahedron or the regular shape of the octahedron with sharpened edges refers to a shape in which the vertex corners of the octahedron are truncated or the edges of the octahedron are flattened, but the main crystal plane orientation of the octahedron is retained.
  • the octahedral or octahedral sharpened and edged grain shape indicates that the grain surface is a crystal plane with optimal dynamic properties and is relatively stable, thereby improving the dynamic properties of the cathode active material and reducing surface side reactions of the cathode active material, thus The high-rate discharge capability of the secondary battery using the positive electrode active material is further improved.
  • the second aspect of the embodiment of the present application proposes a method for preparing a lithium nickel manganate cathode active material.
  • the preparation method includes the following steps S1 and S2.
  • S1 Provide a compound or mixture containing lithium, nickel, and manganese.
  • the compound or mixture contains M element;
  • composition formula of the positive active material is Li 1+x Ni y M z Mn 2-xyz O 4-k , -0.1 ⁇ x ⁇ 0.2, 0.4 ⁇ y ⁇ 0.6, 0 ⁇ z ⁇ 0.2, M is Cr, Mo, One or more of Nb, Ru, P, S, Ta, W, Tl and Ti,
  • the ratio of the charging capacity of 3.5V to 4.4V to the charging capacity of 3.5V to 4.95V is 0.04 ⁇ A ⁇ 0.3, and the product of k and A is 0 ⁇ kA ⁇ 0.015, wherein the charging curve is measured at a rate of 0.1C.
  • step S1 “compounds of lithium, nickel, and manganese” refer to raw materials containing lithium, nickel, and manganese at the same time; “mixtures of lithium, nickel, and manganese” refer to lithium-containing raw materials, nickel-containing raw materials, manganese-containing raw materials, or The raw materials containing any two elements of lithium, nickel and manganese are physically mixed to form a mixed material containing three elements: lithium, nickel and manganese.
  • step S2 the higher the heat treatment temperature, the more conducive to the formation of the Fd3m space group structure, but the easier it is to form surface oxygen defects, so the heat treatment temperature is limited to 5 to 20 hours at a temperature of 800 to 900°C; in addition, by heating in the furnace Heat treatment in a furnace atmosphere where the internal pressure is positive relative to atmospheric pressure and the oxygen partial pressure is >50% can minimize the formation of surface oxygen defects; further, through appropriate heat treatment time, Fd3m with a higher content can be obtained Lithium nickel manganese oxide cathode active material with spinel structure but low content of surface oxygen defects.
  • step S1 powder containing an M source is further mixed, and the M is one or more of Cr, Mo, Nb, Ru, P, S, Ta, W, Tl and Ti.
  • M elements can form strong bonds with oxygen, which not only facilitates the synthesis of low-oxygen defective Fd3m structures, but also further improves the structural stability of the material, thereby better improving the long-term stability of the battery while taking into account the dynamic performance. sex.
  • the M element is preferably one or two or more selected from Nb, Ru, P, Ta and Tl.
  • the oxygen partial pressure ratio in step S2, can be selected from 80% to 100%.
  • a pre-sintering process is included in step S1.
  • Heat-treat compounds or mixtures containing lithium, nickel, and manganese at 800 to 1100°C for 5 to 50 hours in an oxygen-containing atmosphere. Since the temperature, atmosphere and firing time need to be accurately controlled in step S2, the target grain size requirements may not be achieved, especially the requirements for large-sized grains. Therefore, in order to obtain grains of the target size, pre-sintering can be carried out by heat treatment at 800-1100°C for 5-50 hours in an oxygen-containing atmosphere, so as to first produce a product that meets the target grain size, and then proceed to the formal firing process to obtain Lithium nickel manganate cathode active material with low surface oxygen defect content and a high proportion of Fd3m structure.
  • the compound or mixture containing lithium, nickel, manganese or the pre-calcinated powder can also be crushed using a pulverizer to obtain crushed powder.
  • the crushing process can reduce the particle size of the powder and improve the dispersibility, thereby dispersing single crystal-like particles into particles closer to single crystals.
  • the nickel-manganese raw material in the mixture containing lithium, nickel, and manganese is selected from Ni y Mn 2-xyz (OH) 4-2x-2z , Ni y Mn 2-xyz (CO 3 ) 2- xz , Ni y Mn 2-xyz O 2-xz , Ni y Mn 2-xyz O 4-2x-2z , (Ni y Mn 2-xyz ) 3 O 4-2x-2z , Ni y Mn 2-xyz [O (OH)] 2-One or two or more of xz , -0.1 ⁇ x ⁇ 0.2, 0.4 ⁇ y ⁇ 0.6, 0 ⁇ z ⁇ 0.2.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive electrode piece and the negative electrode piece.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is disposed between the positive electrode piece and the negative electrode piece, and mainly functions to prevent the positive and negative electrodes from being short-circuited and allows ions to pass through.
  • the secondary battery may be a lithium-ion battery.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the above-mentioned spinel structure lithium nickel manganate positive electrode active material or the tip prepared according to the above-mentioned preparation method. Lithium nickel manganate cathode active material with spar structure.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the spinel structure lithium nickel manganate cathode active material of the present application can also be mixed with other cathode active materials known in the art for batteries to improve the electrical performance of secondary batteries.
  • other cathode active materials may include any of the following materials: olivine-structured lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O
  • lithium-containing phosphates with an olivine structure may include but are not limited to phosphoric acid Lithium iron (such as LiFePO 4 (also referred to as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), composite materials of lithium manganese phosphate and carbon, lithium iron manganese phosphate, iron manganese phosphate Composite materials of lithium and carbon, etc.
  • Lithium iron such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • composite materials of lithium manganese phosphate and carbon lithium iron manganese phosphate, iron manganese phosphate Composite materials of lithium and carbon, etc.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared by: dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, lithium replenishing agent, binder and any other components in In a solvent (such as N-methylpyrrolidone), a positive electrode slurry is formed; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N-methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes. There is no specific restriction on the type of electrolyte in this application, and it can be selected according to needs.
  • the electrolyte is an electrolyte solution.
  • the electrolyte includes electrolyte salt and solvent.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from non-fluorinated solvents and/or fluorinated solvents, and the non-fluorinated solvents include one or more of carbonates, carboxylates, sulfones, and ethers.
  • the fluorinated solvent is one or more of fluorinated carbonate, fluorinated carboxylate, fluorinated sulfone, and fluorinated ether.
  • ethylene carbonate propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluorocarbonic acid
  • Ethylene methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butanate
  • the electrolyte optionally also includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 1 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 3 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, battery module or battery pack can be selected according to its usage requirements.
  • FIG. 6 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • the target composition Li 1.00 Ni 0.50 Mn 1.50 O 4-k, weigh the Li 2 CO 3 and Ni 0.5 Mn 1.5 (OH) 4 powders corresponding to the stoichiometric ratio, and then mix them evenly to obtain raw material mixture powder.
  • the raw material mixture powder is heated to 1000°C and kept for 8 hours in an air atmosphere to pre-sinter, to obtain a pre-sintered powder.
  • the above pre-sintered powder is heated to 800°C and kept for 10 hours under a positive pressure of 0.05Mpa relative to the atmospheric pressure and a mixed atmosphere of oxygen + nitrogen containing 50% oxygen partial pressure to obtain the finished spinel lithium nickel manganate. .
  • the above pre-sintered powder was heated to 860°C and kept for 10 hours in an oxygen + nitrogen mixed gas atmosphere with a positive pressure of 0.05Mpa relative to the atmospheric pressure and an oxygen partial pressure of 80%, to obtain the finished spinels of each embodiment.
  • the above-mentioned pre-sintered powder was heated to 860°C and kept for 10 hours in an oxygen+nitrogen mixed gas atmosphere with a positive pressure of 0.05Mpa relative to the atmospheric pressure and an oxygen partial pressure of 80%, to obtain the finished products of each embodiment and comparative example.
  • the raw material mixture powder is heated to 1000°C and kept for 8 hours in an air atmosphere to pre-sinter, to obtain a pre-sintered powder.
  • the above pre-calcinated powder was heated to 860°C and kept for 10 hours in an oxygen+nitrogen mixed gas atmosphere with a positive pressure of 0.05Mpa relative to the atmospheric pressure and an oxygen partial pressure of 80%, to obtain lithium nickel manganese oxide of each embodiment. .
  • the target components Li 1.00 Ni 0.50 Mn 1.50 O 4-k shown in Table 1 weigh the corresponding stoichiometric ratios of LiOH ⁇ H 2 O, Ni 0.5 Mn 1.5 (OH) 4 and powder, and then mix them evenly to obtain a raw material mixture Powder. Except for Example 26, in other examples, the raw material mixture powder was heated to the temperature shown in Table 1 for a corresponding time in an air atmosphere, and then pre-fired to obtain a pre-fired powder. In Examples 26-28, before firing, the calcined powder (Examples 27 and 28) or the raw material mixed powder (Example 26) was crushed using an airflow mill to obtain crushed powder.
  • Examples 29 and 30 The obtained calcined powder (Examples 29 and 30) or crushed powder (Examples 26-28) was exposed to oxygen + nitrogen at a positive pressure of 0.05 MPa relative to the atmospheric pressure and an oxygen partial pressure of 80%. In a mixed gas atmosphere, the temperature is raised to the firing temperature shown in Table 1 and kept for a corresponding time to obtain the finished product lithium nickel manganate.
  • the target composition Li 1.03 Ni 0.51 Nb 0.03 Ru 0.02 Mn 1.41 O 4-k
  • the raw material mixture powder is heated to 1000°C and kept for 8 hours in an air atmosphere to pre-sinter, to obtain a pre-sintered powder.
  • the spinel structure lithium nickel manganate positive active material of each example or comparative example was assembled into a half cell (button cell) according to the following steps:
  • the obtained positive electrode slurry is coated on the aluminum foil, and then dried to obtain a positive electrode piece.
  • the loading amount of lithium nickel manganese composite oxide on the positive electrode piece is 0.015g/cm 2 .
  • ⁇ Use a polypropylene film ( ⁇ 16mm) with a thickness of 12 ⁇ m as the isolation film, and place the lithium sheet, isolation film, and positive electrode sheet in order so that the isolation film is between the metal lithium sheet and the composite negative electrode sheet for isolation.
  • the button-type half-cells prepared from the positive active materials of each example and comparative example were charged at a constant current of 0.1C to a voltage of 4.95V, and the charging capacity of 4.4 to 3.5V was extracted from the original charging data ( C1) and 4.95 ⁇ 3.5V charging capacity (C2).
  • the finished spinel lithium nickel manganate can be controlled to have appropriate A values and kA values, that is, spinel nickel Lithium manganate has low oxygen defects and an appropriate content of Fd3m structure, and its finished lithium-ion battery can take into account both kinetic performance and long-term storage performance.
  • the firing temperature is outside the above range, it is impossible to achieve both the appropriate A value and kA value.
  • the temperature is lower than 800°C, the A value decreases significantly.
  • the firing temperature of Comparative Example 1 is 670°C, and the A value is only 0.032, that is, the Fd3m content is too small, which is not conducive to the dynamic performance.
  • the temperature is too high, it is conducive to the generation of oxygen defects, so the k value and kA value are difficult to reduce, which will aggravate the side reaction between the positive electrode material and the electrolyte and the dissolution of Mn, and reduce the service life of the battery.
  • doping elements Cr, Mo, Nb, Ru, P, Ta, and Tl can further reduce the k value (reduce oxygen defects). This is because these elements can form strong bonds with oxygen, thus slowing down the oxygen release of spinel lithium nickel manganese oxide at high temperatures. Among them, the k value of Examples 13-17 is smaller. It can be seen that the doping elements Nb, Ru, P, Ta, and Tl have a more significant effect on suppressing oxygen defects.
  • spinel lithium nickel manganate with suitable A value and kA value can be obtained by appropriately adjusting the contents of Li, Ni, and Mn. This is because the Li, Ni, and Mn elements in spinel lithium nickel manganate can partially replace each other.
  • the particle size of the particles can be controlled by adjusting the preparation process. As the maximum temperature increases and the holding time increases during pre-firing and formal firing in the preparation process, it is easier to generate single crystals and the grains are easier to grow, and the A value and kA value will also change accordingly.
  • the crushing process before formal firing can reduce the particle size D V50 and improve the dispersibility, thereby dispersing the quasi-single crystal into a quasi-single crystal or single crystal that is closer to a single crystal.
  • the lithium nickel manganese oxide cathode active material of each example and comparative example was prepared into a graphite negative electrode soft-pack battery according to the following method, and the discharge energy density E5C (Wh/Kg) at 5C rate and the normal temperature full charge storage time ts ( month), the results are shown in Table 3.
  • the graphite negative electrode soft pack battery of each example or comparative example was charged at a constant current of 0.3C until the voltage was 4.9V, and then charged at a constant voltage of 4.9V until the current was 0.05C. After leaving it alone for 5 minutes, the soft pack battery was charged. The battery pack is discharged at a constant current of 5C until the voltage is 3.5V. Extracting the corresponding discharge capacity and discharge energy is the 5C discharge capacity and 5C discharge energy of the soft pack battery. Dividing this capacity and this energy by the mass (g) of the positive active material in the battery is the 5C discharge gram capacity and 5C discharge energy density of the positive active material, which are shown in Table 3 respectively.
  • 5C is a large rate current, which can better reflect the advantages and disadvantages of materials and battery kinetic properties. Therefore, the 5C discharge capacity and discharge energy density reflect the use of electrode materials for secondary applications. Battery kinetic properties.
  • the graphite negative electrode soft-pack batteries of each example or comparative example were charged at a constant current of 0.3C until the voltage was 4.9V, and then charged at a constant voltage of 4.9V until the current was 0.05C. Then place the secondary battery at 25°C, perform full discharge and then full charge every 10 days, and extract the discharge capacity value until the extracted discharge capacity decays to 80% of the initial value, then the storage ends.
  • the total storage time at 25°C after full charging is the normal temperature full charging storage time ts, and are shown in Table 3. In this application, the normal temperature full charge storage time ts is used to represent the long-term stability of the material used in secondary batteries.
  • the comprehensive evaluation coefficient values of each Example and Comparative Example were calculated, and the results are shown in Table 3.
  • the lithium nickel manganate cathode active material Li 1+x Ni y M z Mn 2-xyz O 4-k satisfies the A value of 0.04 ⁇ A ⁇ 0.3, and 0 ⁇ kA ⁇ 0.015, 0.1 ⁇ x ⁇ 0.2, 0.4 ⁇ y ⁇ 0.6, 0 ⁇ z ⁇ 0.2, which has both good 5C discharge energy density and normal temperature full charge storage performance.
  • Comparative Example 1 when A is less than 0.04, the 5C discharge energy density is low; from Comparative Examples 2 and 3, it can be seen that when the value of kA is greater than 0.015, it is impossible to achieve both good 5C discharge energy density and normal temperature full charge storage performance. ; From Comparative Example 4, it can be seen that when the content of the doping element M is too high, it is impossible to achieve both good 5C discharge energy density and normal temperature full charge storage performance.
  • the doping of the M element improves the 5C discharge energy density and/or room temperature full charge storage performance of the material, and improves the value of the comprehensive evaluation coefficient R; the doping elements Nb, Ru, The modification effect of P, Ta and Tl is more significant.
  • Example 13 Comparing Example 13 and Examples 18-21, the room temperature storage of lithium nickel manganese oxide with a doped Nb element content that satisfies z ⁇ 0.2 has been significantly improved, and the comprehensive evaluation coefficient R>8, which takes into account good 5C discharge. Energy density and full charge storage performance at room temperature; the comprehensive evaluation coefficient of lithium nickel manganese oxide with a doped Nb element content of 0.001 ⁇ z ⁇ 0.15 is R>10, and the overall performance is better.
  • lithium nickel manganese oxide with a volume median particle size D V50 that satisfies 1 ⁇ m ⁇ D V50 ⁇ 20 ⁇ m has an average R > 6, which is a good balance between good 5C discharge energy density and full charge at room temperature.
  • Storage performance; 2 ⁇ m ⁇ D V50 ⁇ 15 ⁇ m lithium nickel manganate cathode active material has R>7, and the overall performance is better.
  • the lithium nickel manganese oxide active material has both good 5C discharge energy density and normal temperature full charge storage performance.

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Abstract

本申请提供了一种Li1+xNiyMzMn2-x-y-zO4-k的正极活性材料，-0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2，M为Cr、Mo、Nb、Ru、P、S、Ta、W、Tl和Ti中的一种或多种，在所述正极活性材料的半电池的首圈充电曲线中，3.5V～4.4V的充电容量与3.5V～4.95V充电容量的比值为A，A满足0.04≤A≤0.3，k与A的乘积满足0≤kA≤0.015，所述首圈充电曲线在0.1C的倍率下测得。本申请的正极活性材料兼顾高动力学性能和高化学稳定性，对应的二次电池兼具高倍率放电能力和长期存储稳定性。

Description

镍锰酸锂正极活性材料及其制备方法、以及使用其的二次电池 技术领域
本申请涉及一种二次电池用镍锰酸锂正极活性材料及其制备方法、以及使用了该镍锰酸锂正极活性材料的二次电池、电池模块、电池包和用电装置。
背景技术
近年来，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源***，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域，使用者对其高倍率放电能力、长期存储稳定性等综合性能提出了更高的要求。
正极活性材料是制约二次电池高倍率放电能力和存储稳定性提升的关键因素，因此亟待开发出一种高动力学性能和高化学稳定性的正极活性材料。
发明内容
本申请是鉴于上述技术问题而进行的，其目的在于，提供一种高动力学性能和高化学稳定性的尖晶石结构的镍锰酸锂正极活性材料，从而能够兼顾提高使用了该镍锰酸锂正极活性材料的二次电池的高倍率放电能力以及长期存储稳定性。
为了达到上述目的，本申请的第一方面提供一种镍锰酸锂正极活性材料，其中，
所述正极活性材料组成式为Li 1+xNi yM zMn 2-x-y-zO 4-k，-0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2，M为Cr、Mo、Nb、Ru、P、S、Ta、W、Tl和Ti中的一种或多种，
在所述正极活性材料的半电池的首圈充电曲线中，3.5V～4.4V的充电容量与3.5V～4.95V充电容量的比值为A，A满足0.04≤A≤0.3，k与 A的乘积满足0≤kA≤0.015，其中，所述首圈充电曲线在0.1C的倍率下测得。
由此，得到的镍锰酸锂正极活性材料兼顾高动力学性能和高化学稳定性，对应的二次电池兼具高倍率放电能力和长期存储稳定性。
在任意实施实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料进一步满足：0.11≤k+A≤0.18，可选0.11≤k+A≤0.15。这是由于当A值较大时，对应尖晶石结构的镍锰酸锂正极活性材料中Mn 3+含量更高，易发生过渡金属锰溶出，从而降低材料的化学稳定性，因此较小的k值才能提升材料的化学稳定性，使材料兼具良好的动力学性能和化学稳定性，对应的二次电池兼具优良的高倍率放电能力和长期存储稳定性。
在任意实施实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料进一步满足：0.07≤A≤0.15。由此，得到的镍锰酸锂正极活性材料具有进一步提高的动力学性能，对应二次电池的高倍率放电能力提高。
在任意实施实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料进一步满足：0≤k≤0.1，可选为0≤k≤0.05，可选为0≤k≤0.03。由此，得到的镍锰酸锂正极活性材料具有进一步提高的化学稳定性，对应二次电池的长期存储稳定性提高。
在任意实施实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料进一步满足：0＜z≤0.2，可选为0.001≤z≤0.15。
通过将上述M元素的含量控制在适量的范围的0＜z≤0.2，从而更容易实现全面均匀的掺杂，从而更好地兼顾了材料的动力学性能和长期使用的稳定性。进一步可选为0＜z≤0.2，可选为0.001≤z≤0.15。
在任意实施方式中，M进一步为选自Nb、Ru、P、Ta和Tl中的一种或两种以上。由此，可以进一步降低氧缺陷含量，提高材料化学稳定性，提高使用镍锰酸锂正极活性材料的二次电池的长期存储稳定性。
在任意实施实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料进一步满足：所述镍锰酸锂正极活性材料为单晶和/或类单晶的 颗粒。由此，进一步提高正极活性材料的化学稳定性，进而进一步提高使用了该正极活性材料的二次电池的长期存储性能。
在任意实施实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料进一步满足：所述颗粒的体积中值粒径(D V50)满足1μm≤D V50≤20μm，可选为2μm≤D V50≤15μm。当晶粒越大时，其外露的表面越小，与电解液的接触面积小镍锰酸锂正极活性材料稳定性因此有所提升，但另一方面，晶粒过大会恶化其动力学性能。
在任意实施实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料进一步满足：0.06≤(k+A)/(D V50 0.3)≤0.12，可选为0.06≤(k+A)/(D V50 0.3)≤0.10，其中(k+A)/(D V50 0.3)单位为μm -0.3。通过如上述关系式平衡k、A和D V50，更有利于兼顾尖晶石结构的镍锰酸锂正极活性材料的二次电池的高倍率放电性能和长期存储稳定性。
在任意实施实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料进一步满足：基于M元素的总重量，沿所述正极活性材料颗粒的表层向其几何中心的径向方向，80％以上的M元素位于所述正极活性材料的颗粒的前50％体积内；可选为前30％体积以内。由此，通过将掺杂元素集中于表层，能够进一步提高掺杂元素对正极活性材料的表面稳定作用，进一步降低氧缺陷含量，提高材料表面稳定性，提高使用该正极活性材料的二次电池的长期存储稳定性。
本申请第二方面还提供一种镍锰酸锂正极活性材料的制备方法，包括如下步骤，
S1：提供含锂、镍、锰的化合物或混合物，可选地，所述化合物或混合物中含有M元素；
S2：将所述化合物或混合物在炉内气压相对于大气压为正压且氧分压占比＞50％的炉内气氛中，升温到800～900℃热处理5～20h，得到所述正极活性材料，其中，
所述正极活性材料组成式为Li 1+xNi yM zMn 2-x-y-zO 4-k，-0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2，M为Cr、Mo、Nb、Ru、P、S、Ta、W、Tl和Ti中的一种或多种，
在所述正极活性材料的半电池的首圈充电曲线中，3.5V～4.4V的充 电容量与3.5V～4.95V充电容量的比值0.04≤A≤0.3，且k与A的乘积0≤kA≤0.015，其中，所述充电曲线在0.1C的倍率下测得。
在任意实施方式中，在所述S2中，所述氧分压占比为80％～100％。
在任意实施方式中，在所述S1中，所述含锂、镍、锰的化合物或混合物在含氧气氛中以800～1100℃热处理5～50h。
在任意实施方式中，所述含锂、镍、锰的混合物中的镍锰原材料选自Ni yMn 2-x-y-z(OH) 4-2x-2z、Ni yMn 2-x-y-z(CO 3) 2-x-z、Ni yMn 2-x-y-zO 2-x-z、Ni yMn 2-x-y-zO 4-2x-2z、(Ni yMn 2-x-y-z) 3O 4-2x-2z、Ni yMn 2-x-y-z[O(OH)] 2-x-z中的一种或两种以上，-0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2。
本申请上述制备方法制备的尖晶石结构的镍锰酸锂正极活性材料具有优良的动力学性能和化学稳定性。
本申请的第三方面还提供一种二次电池，其包括第一方面的镍锰酸锂正极活性材料或通过第二方面的制备方法获得的镍锰酸锂正极活性材料，该二次电池的高倍率放电能力以及长期存储稳定性显著提高。
本申请的第四方面还提供一种电池模块，其包括第三方面的二次电池。
本申请的第五方面提供一种电池包，包括本申请的第四方面的电池模块。
本申请的第六方面提供一种用电装置，包括选自本申请的第三方面的二次电池、本申请的第四方面的电池模块或本申请的第五方面的电池包中的至少一种。
本申请的电池模组、电池包、用电装置因包括本申请的二次电池单体，故具有与本申请二次电池单体具有同样的优势。
附图说明
图1是本申请一个实施方式的二次电池的示意图。
图2是图1所示的本申请一个实施方式的二次电池的分解图。
图3是本申请一个实施方式的电池模块的示意图。
图4是本申请一个实施方式的电池包的示意图。
图5是图4所示的本申请一个实施方式的电池包的分解图。
图6是本申请一个实施方式的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的二次电池、电池模块、电池包和电学装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
镍锰酸锂正极活性材料，特别是尖晶石结构的镍锰酸锂正极活性材料，是具有高电压特性的优良正极活性材料，具有重大商业价值。根据本领域技术人员当前的认知规律，现有技术的镍锰酸锂正极活性材料具有如下特点：尖晶石结构的镍锰酸锂正极活性材料内部存在镍锰无序相Fd3m和镍锰有序相P4 332两种空间群结构，因Fd3m空间群结构的无序性以及含有较多的+3价锰元素，故当Fd3m结构占比较高时，尖晶石结构的锰酸锂材料的锂离子导电能力更强，进而在高倍率下的放电能力更强。但是，当Fd3m结构占比较高时，尖晶石结构的镍锰酸锂正极活性材料的表面氧缺陷多。根据本领域技术人员当前的认知规律，当尖晶石结构的镍锰酸锂正极活性材料的表面氧缺陷越多，镍锰酸锂正极活性材料与电解液之间的副反应(比如过渡金属锰溶出、消耗电解液而产气等)越显著，进而导致二次电池的长期存储性能差。也就是说，现有技术的尖晶石结构的镍锰酸锂正极活性材料始终无法兼顾高动力学性能和高化学稳定性。
基于此，本申请通过合理调控制备工艺，开发出一种高动力学性能和高化学稳定性的尖晶石结构的镍锰酸锂正极活性材料，使使用该 正极活性材料的二次电池兼具高倍率放电能力和长期存储稳定性性能。
【正极活性材料】
基于此，本申请实施方式的第一方面提出一种镍锰酸锂正极活性材料，所述正极活性材料组成式为Li 1+xNi yM zMn 2-x-y-zO 4-k，-0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2，M为Cr、Mo、Nb、Ru、P、S、Ta、W、Tl和Ti中的一种或多种，
在所述正极活性材料的半电池的首圈充电曲线中，3.5V～4.4V的充电容量与3.5V～4.95V充电容量的比值为A，A满足0.04≤A≤0.3，k与A的乘积满足0≤kA≤0.015，其中，所述首圈充电曲线在0.1C的倍率下测得。
如前所述，尖晶石结构的锰酸锂材料中Fd3m结构占比较高时，尖晶石结构的锰酸锂材料在高倍率下的放电能力更强，本申请第一方面所述的尖晶石结构的锰酸锂材料中将Fd3m结构的占比显著提高，由此显著提高尖晶石结构的镍锰酸锂正极活性材料的锂离子导电能力，显著提高尖晶石结构的锰酸锂正极活性材料的动力学性能，从而显著提高由所述尖晶石结构的镍锰酸锂正极活性材料制备的二次电池的高倍率放电能力。
本申请中，发明人创造性地发现，Fd3m结构在镍锰酸锂正极活性材料中的占比能够用A来表示。所述A的测定方法如下：在所述正极活性材料的半电池的首圈充电曲线中，3.5V～4.4V的充电容量与3.5V～4.95V充电容量的比值，其中，在测试首圈充电曲线时，首先以锂作为负极，以本申请的尖晶石结构的镍锰酸锂正极活性材料作为正极制备成扣式半电池，然后以0.1C的倍率充电至4.95V电压，进而得到首圈充电曲线。利用得到的首圈充电曲线，计算3.5V～4.4V的充电容量以及3.5V～4.95V充电容量，A的值即为3.5V～4.4V的充电容量占3.5V～4.95V的充电容量的比值。
A的值能够表征Fd3m结构在镍锰酸锂正极活性材料中的占比进一步原因如下：在Fd3m结构中，因含有较多Mn 3+，故在充电过程中除发生所有镍锰酸锂正极材料均可能发生的Ni 2+/Ni 3+/Ni 4+的价态变化之外，还会发生Fd3m结构镍锰酸锂中独有的Mn 3+/Mn 4+的价态变化， 这种元素价态之间的变化使得充电曲线中在3.5V～4.4V范围内出现电压平台，因此所述电压平台对应的充电容量与3.5V～4.95V对应的充电容量的比值A能够表征Fd3m结构在镍锰酸锂正极活性材料中的占比。
进一步地，本申请的尖晶石结构的镍锰酸锂正极活性材料的A值满足0.04≤A≤0.3。当A满足0.04≤A≤0.3时，尖晶石结构的镍锰酸锂正极活性材料几乎全为Fd3m结构，尖晶石结构的镍锰酸锂正极活性材料中Fd3m结构占比提高，尖晶石结构的镍锰酸锂正极活性材料具有显著提高的动力学性能，由所述尖晶石结构的镍锰酸锂正极活性材料制备的二次电池的高倍率放电能力得到显著提升。
本申请的正极活性材料具有Li 1+xNi yM zMn 2-x-y-zO 4-k，-0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2的组成式。在所述组成式中，“1+x”表示锂原子在所述组成式中的摩尔数，“y”表示镍原子在所述组成式中的摩尔数，“z”代表M原子在所述组成式中的摩尔数。“4-k”表示氧原子在所述组成式中的摩尔数。
其中，“k”表示在具有所述组成式的尖晶石结构的镍锰酸锂中的表面氧缺陷的量化指标，也即，k的大小能够表征本申请的尖晶石结构的镍锰酸锂正极活性材料的化学稳定性，进一步地，能够影响由所述尖晶石结构的镍锰酸锂正极活性材料制备的二次电池的长期存储稳定性。
进一步地，本申请的尖晶石结构的镍锰酸锂正极活性材料的k值满足以下条件：k与A的乘积满足0≤kA≤0.015。k与A的乘积kA能够综合表征尖晶石结构的镍锰酸锂正极活性材料在化学稳定性和动力学性能的综合性能，具体地，当A较大时，说明尖晶石结构的镍锰酸锂正极活性材料中Fd3m结构占比高，动力学性能好，但是此时若k值过大，则对应尖晶石结构的镍锰酸锂正极活性材料的表面氧缺陷多，材料的化学稳定性差，无法综合兼顾材料动力学性能和化学稳定性。经过大量实验，当晶石结构的镍锰酸锂正极活性材料满足0≤kA≤0.015关系时，尖晶石结构的镍锰酸锂正极活性材料综合性能优良，兼具良好的动力学性能和化学稳定性，由此制备的二次电池具有极佳的高倍率放电性能和长期存储稳定性。
在一些实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材 料进一步满足：0.11≤k+A≤0.18，可选0.11≤k+A≤0.15。这是由于当A值较大时，对应尖晶石结构的镍锰酸锂正极活性材料中Mn 3+含量更高，易发生过渡金属锰溶出，从而降低材料的化学稳定性，因此较小的k值才能提升材料的化学稳定性，使材料兼具良好的动力学性能和化学稳定性，对应的二次电池兼具优良的高倍率放电能力和长期存储稳定性。
在一些实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料进一步满足：0≤k≤0.1，可选为0≤k≤0.05，可选为0≤k≤0.03。k值越小，尖晶石锰酸锂的表面氧缺陷越少，通过减少氧缺陷，从而可以显著提高材料的化学稳定性，减缓正极材料与电解液间的副反应，减缓Mn溶出和电解液消耗，提高二次电池的长期存储稳定性。
在一些实施方式中，当z不为0时，尖晶石结构的锰酸锂材料中包含掺杂元素M，掺杂元素M可与氧形成强键，不仅有利于合成低氧缺陷Fd3m结构，而且能够进一步提高材料的结构稳定性，从而在兼顾高动力学性能的同时，更好地提升了二次电池长期使用的稳定性。
进一步地，通过将上述M元素的含量控制在适量的范围的0＜z≤0.2，从而更容易实现全面均匀的掺杂，从而更好地兼顾了材料的动力学性能和长期使用的稳定性。进一步可选为0.001≤z≤0.15。
在一些实施方式中，M进一步选自Nb、Ru、P、Ta和Tl中的一种或两种以上。由此，可以进一步降低氧缺陷含量，提高材料表面稳定性，提高使用镍锰酸锂正极活性材料的二次电池的长期存储稳定性。
在一些实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料进一步满足：0.07≤A≤0.15。
随着A的增大，尖晶石结构的镍锰酸锂正极活性材料中具有更高占比的Fd3m结构，材料的动力学性能提高，从而提高了二次电池的高倍率充放电能力。但是当A过大，尖晶石结构的镍锰酸锂正极活性材料Fd3m结构占比过高，导致使用该正极活性材料的二次电池的总能量密度降低。
在一些实施方式中，镍锰酸锂正极活性材料为单晶和/或类单晶的颗粒。“类单晶”是指由几个至十几个晶粒形成类团聚体形貌的黏连结 构的材料，这种类单晶形貌的材料具有易于合成，减少二次球颗粒的晶界等优势。
由于多晶的颗粒内部存在大量晶界，晶界处受力后容易开裂，从而暴露不稳定的表面，加剧与电解液的副反应，导致性能恶化，所以单晶或类单晶的镍锰酸锂材料能够有效避免或减少这些问题，从而进一步提高正极活性材料的表面稳定性，进而进一步提高使用了该正极活性材料的二次电池的长期存储性能。
在一些实施方式中，从更容易兼顾较低的k值和较高的A值的观点出发，尖晶石结构的镍锰酸锂材料颗粒的体积中值粒径(D V50)满足1μm≤D V50≤20μm，可选为2μm≤D V50≤15μm。当晶粒越大时，其外露的表面越小，与电解液的接触面积小镍锰酸锂正极活性材料稳定性因此有所提升，但另一方面，晶粒过大会恶化其动力学性能。
在一些实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料进一步满足0.06≤(k+A)/(D V50 0.3)≤0.12，可选为0.06≤(k+A)/(D V50 0.3)≤0.10，其中(k+A)/(D V50 0.3)单位为μm -0.3。当晶粒越大时，其外露的表面越小，与电解液的接触面积小镍锰酸锂正极活性材料稳定性因此有所提升；但另一方面，晶粒过大会恶化其动力学性能，因此尖晶石结构的镍锰酸锂正极活性材料需更高占比的Fd3m结构；此外，若在颗粒内部(非表层)存在少量的对离子传递有促进作用的氧缺陷(体现为k值增大)也会对整体的动力学性能有一定促进作用。实验发现，通过如上述关系式平衡k、A和D V50，更有利于兼顾尖晶石结构的镍锰酸锂正极活性材料的二次电池的高倍率放电性能和长期存储稳定性。
在一些实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料，基于M元素的总重量，沿所述正极活性材料的颗粒的表层向其几何中心的径向方向，80％以上的M元素位于所述正极活性材料的颗粒的前50％体积内；可选为前30％体积以内。
由此，通过将掺杂元素集中于表层，能够进一步提高掺杂元素对正极活性材料的表面稳定作用，进一步降低氧缺陷含量，提高材料表面稳定性，提高使用该正极活性材料的二次电池的长期存储稳定性。
在一些实施方式中，镍锰酸锂正极活性材料的晶粒外形为八面体、截角八面体或八面体削尖去棱的规则外形。所谓截角八面体或八面体削尖去棱的规则外形是指将八面体的顶角截去、或者把八面体的棱边削平，但保留八面体的主要晶面取向的形状。八面体或八面体削尖去棱的晶粒形状表明晶粒表面为动力学性能最优且较稳定的晶面，由此提高正极活性材料的动力学性能和减少正极活性材料表面副反应，从而进一步提高使用了该正极活性材料的二次电池的高倍率放电能力。
【正极活性材料的制备方法】
本申请实施方式的第二方面提出一种镍锰酸锂正极活性材料的制备方法，该制备方法包括以下工序S1和S2。
S1：提供含锂、镍、锰的化合物或混合物，可选地，所述化合物或混合物中含有M元素；
S2：将所述化合物或混合物在炉内气压相对于大气压为正压且氧分压占比＞50％的炉内气氛中，升温到800～900℃热处理5～20h，得到所述正极活性材料，其中，
所述正极活性材料组成式为Li 1+xNi yM zMn 2-x-y-zO 4-k，-0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2，M为Cr、Mo、Nb、Ru、P、S、Ta、W、Tl和Ti中的一种或多种，
在所述正极活性材料的半电池的首圈充电曲线中，3.5V～4.4V的充电容量与3.5V～4.95V充电容量的比值0.04≤A≤0.3，且k与A的乘积0≤kA≤0.015，其中，所述充电曲线在0.1C的倍率下测得。
在步骤S1中，“锂、镍、锰的化合物”是指同时包含锂、镍、锰的原材料；“锂、镍、锰的混合物”是指含锂原材料、含镍原材料、含锰原材料、或者含锂镍锰中任意两种元素的原材料物理混合形成的同时含有锂、镍、锰三种元素的混合材料。
步骤S2中，热处理温度越高，越有利于Fd3m空间群结构的形成，但是也越容易形成表面氧缺陷，因此限定热处理温度为在800～900℃温度下处理5～20h；另外，通过在炉内气压相对于大气压为正压并且氧分压占比＞50％的炉内气氛中进行热处理，能够尽量减少表面氧缺陷的形成；进一步通过合适的热处理时间能够得到具有较高含量占比的Fd3m 结构但是低含量表面氧缺陷的尖晶石结构的镍锰酸锂正极活性材料。
在一些实施方式中，在步骤S1中，进一步混合含有M源的粉末，所述M为Cr、Mo、Nb、Ru、P、S、Ta、W、Tl和Ti中的一种或多种。这些M元素可与氧形成强键，从而不仅有利于合成低氧缺陷Fd3m结构，而且进一步提高了材料的结构稳定性，从而在兼顾动力学性能的同时，更好地提升了电池长期使用的稳定性。从进一步降低氧缺陷含量的观点出发，M元素优选为选自Nb、Ru、P、Ta和Tl中的一种或两种以上。
在一些实施方式中，为了能够更好地降低氧缺陷，在步骤S2中，氧分压占比可选为80％～100％。
在一些实施方式中，在步骤S1中包括预烧成工艺。将含锂、镍、锰的化合物或混合物在含氧气氛中以800～1100℃热处理5～50h。由于步骤S2中，需精确地控制温度、气氛以及烧成的时间，因此，不一定能够达到目标晶粒尺寸的需求，尤其是大尺寸晶粒的需求。因此为了得到目标尺寸的晶粒，可以在含氧气氛中以800～1100℃热处理5～50h进行预烧成，从而先制得符合目标晶粒大小的产品，然后再进行正式烧成工艺，从而得到表面氧缺陷含量低且具有较高的Fd3m结构占比的镍锰酸锂正极活性材料。
在一些实施方式中，在进行步骤S2之前，还可以对含锂、镍、锰的化合物或混合物或者经过预烧成的粉体使用粉碎机破碎，得到破碎后粉体。破碎过程可以减小粉体的粒径，提高分散性，从而可以将类单晶分散为更接近单晶的颗粒。
在一些实施方式中，所述含锂、镍、锰的混合物中的镍锰原材料选自Ni yMn 2-x-y-z(OH) 4-2x-2z、Ni yMn 2-x-y-z(CO 3) 2-x-z、Ni yMn 2-x-y-zO 2-x-z、Ni yMn 2-x-y-zO 4-2x-2z、(Ni yMn 2-x-y-z) 3O 4-2x-2z、Ni yMn 2-x-y-z[O(OH)] 2-x-z中的一种或两种以上，-0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2。
【二次电池】
本申请的一个实施方式中，提供一种二次电池。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返 嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过，所述二次电池可以为锂离子电池。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，该正极膜层包括以上所述的尖晶石结构的镍锰酸锂正极活性材料或按照上述制备方法制备的尖晶石结构的镍锰酸锂正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，本申请的尖晶石结构的镍锰酸锂正极活性材料还可以与本领域公知的用于电池的其他正极活性材料混合使用，以提高二次电池的电性能。作为示例，其他正极活性材料可包括以下材料中的任意种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等。橄榄石结构的含锂磷酸盐的 示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料等。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、补锂剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，其中，负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛 酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。
在一些实施方式中，电解质采用电解液。其中，电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自非氟代溶剂和/或氟代溶剂，所述非氟代溶剂包含碳酸酯、羧酸酯、砜类、醚类中的一种或者多种。所述氟代溶剂为氟代碳酸酯、氟代羧酸酯、氟代砜、氟代醚中的一种或 者多种。具体地如碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形 成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能***等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池 模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
【尖晶石结构的镍锰酸锂正极活性材料的制备及产品参数测试】
实施例1
按目标成分Li 1.00Ni 0.50Mn 1.50O 4-k称取对应化学计量比的Li 2CO 3、和Ni 0.5Mn 1.5(OH) 4粉体，然后混合均匀，得到原料混合物粉体。将原料混合物粉体在空气气氛中，升温到1000℃保温8小时进行预烧，得到预烧后粉体。
将上述预烧后粉体在相对于大气压为0.05Mpa的正压、且含有50％氧分压的氧气+氮气的混合气氛下，升温到800℃保温10h，得到成品尖晶石镍锰酸锂。
实施例2-10、比较例1-3
使用与上述实施例1中同样得到的预烧后粉体，在相对于大气压为0.05Mpa的正压的氧气+氮气混合气体或空气气氛中，按照表1调整烧成温度和氧分压，得到成品尖晶石镍锰酸锂。
实施例11-17
分别按照表1所示的目标成分Li 1.00Ni 0.50M 0.05Mn 1.45O 4-k称取对应化学计量比的Li 2CO 3、Ni 0.5Mn 1.45(OH) 3.9和Cr 2O 3、MoO 3、Nb 2O 5、RuO 2、NH 4H 2PO 4、Ta 2O 5、Tl 2O 3粉体，然后混合均匀，得到原料混合物粉体。将原料混合物粉体在空气气氛中，升温到1000℃保温8小时进行预烧， 得到预烧后粉体。
将上述预烧后粉体，在相对于大气压为0.05Mpa的正压、氧分压为80％的氧气+氮气混合气体气氛中，升温到860℃保温10小时，得到各实施例的成品尖晶石镍锰酸锂。
实施例18-21、比较例4
分别按照表1所示的目标成分Li 1.00Ni 0.50Nb zMn 1.5-zO 4-k称取对应化学计量比的Li 2CO 3、Ni 0.5Mn 1.5-zO 2-z和Nb 2O 5粉体，然后混合均匀，得到原料混合物粉体。将原料混合物粉体在空气气氛中，升温到1000℃保温8小时进行预烧，得到预烧后粉体。
将上述预烧后粉体在相对于大气压为0.05Mpa的正压、氧分压为80％的氧气+氮气混合气体气氛中，升温到860℃保温10小时，得到各实施例和比较例的成品尖晶石镍锰酸锂。
实施例22-25
分别按照表1所示的目标成分Li 1+xNi yMn 2-x-yO 4-k称取对应化学计量比的Li 2CO 3、Ni yMn 2-x-y(CO 3) 2-x粉体，然后混合均匀，得到原料混合物粉体。将原料混合物粉体在空气气氛中，升温到1000℃保温8小时进行预烧，得到预烧后粉体。
将上述预烧后粉体在相对于大气压为0.05Mpa的正压、氧分压为80％的氧气+氮气混合气体气氛中，升温到860℃保温10小时，得到各实施例的镍锰酸锂。
实施例26-30
按照表1所示的目标成分Li 1.00Ni 0.50Mn 1.50O 4-k称取对应化学计量比的LiOH·H 2O、Ni 0.5Mn 1.5(OH) 4、粉体，然后混合均匀，得到原料混合物粉体。除实施例26外，其它实施例中都将原料混合物粉体在空气气氛中，升温到表1所示温度保温相应时间，进行预烧，得到预烧后粉体。实施例26-28中，在烧成之前，对预烧后粉体(实施例27、28)或原料混合粉体(实施例26)，使用气流式粉碎机进行破碎，得到破碎后粉体。
将所得到的预烧后粉体(实施例29、30)或破碎后粉体(实施例26-28)，在相对于大气压为0.05Mpa的正压、氧分压为80％的氧气+氮 气混合气体气氛中，升温到表1所示烧成温度保温相应时间后制得成品镍锰酸锂。
实施例31
按目标成分Li 1.03Ni 0.51Nb 0.03Ru 0.02Mn 1.41O 4-k称取对应化学计量比的Li 2CO 3、Ni 0.51Mn 1.41(OH) 3.84、Nb 2O 5、RuO 2粉体，然后混合均匀，得到原料混合物粉体。将原料混合物粉体在空气气氛中，升温到1000℃保温8小时进行预烧，得到预烧后粉体。
在相对于大气压为0.05Mpa的正压、氧分压为99％的氧气+氮气混合气体气氛中，升温到860℃保温20小时，得到尖晶石结构镍锰酸锂的正极活性材料。
表1.镍锰酸锂正极活性材料制备工艺参数表
Figure PCTCN2022096216-appb-000001
对各实施例和对比例的物化参数进行以下测试表征，并将结果汇 总于表2中。
(1)参照EPA 6010D-2014电感耦合等离子体原子发射光谱法，测量所得到的各实施例和对比例正极活性材料中各元素的含量，并计算其k值。另外，也可通过XRD分析、XRF分析等确定元素含量、材料结构等。
(2)参照JY/T010-1996测试，使用ZEISS sigma 300扫描电子显微镜观察所得到的各实施例和对比例的正极活性材料的形貌，并判断其颗粒形貌为单晶、类单晶或多晶。本发明实施例的粉体颗粒形貌均为单晶或类单晶。
(3)参照GB/T 19077-2016粒度分析激光衍射法，使用Mastersizer 3000激光粒度仪测量各实施例和对比例的正极活性材料粉体的体积中值粒径D V50。
(4)对各实施和比较例所得到的正极活性材料进行以下扣电测试，得到首圈充电曲线并计算A值，将所得到的A值示于表2。
首先，以锂片为对电极，按照下述步骤将各实施例或比较例的尖晶石结构的镍锰酸锂正极活性材料组装为半电池(扣式电池)：
●将各实施例或比较例的镍锰酸锂正极活性材料与导电炭黑、PVDF按重量比90：5：5混合，加入适量N-甲基吡咯烷酮，搅拌均匀，获得正极浆料。将所得到的正极浆料涂布在铝箔上，涂布后烘干，获得正极极片。其中正极极片上锂镍锰复合氧化物的负载量为0.015g/cm 2。
●以含有1mol/L LiPF 6的碳酸脂、氟代碳酸酯、氟代醚等的混合溶液作为电解液。
●以厚度12μm的聚丙烯薄膜(φ16mm)作为隔离膜，将锂片、隔离膜、正极极片按顺序放好，使隔离膜处于金属锂片与复合负极极片中间起到隔离的作用。
●注入电解液，组装成CR2030扣式电池，静置24h，得半电池。
然后，在25℃下，将各实施例和比较例的正极活性材料制备的扣式半电池以0.1C恒流充电至电压为4.95V，从原始充电数据中截取4.4～3.5V的充电容量(C1)和4.95～3.5V充电容量(C2)。
其中，A＝C1/C2。
表2.尖晶石结构的正极活性材料产品参数表
Figure PCTCN2022096216-appb-000002
*：P＝(k+A)/(D V50 0.3)
由所有实施例和对比例可知，通过以800～900℃的温度、采用相对于大气压为正压且氧分压占比＞50％的炉内气氛中保温5～20h的条件下对满足条件的原料混合物进行烧成，可以得到0.04≤A≤0.3且0≤kA≤0.015的镍锰酸锂正极活性材料，镍锰酸锂正极活性材料中Fd3m空间群结构占比较高且氧缺陷较少。
由实施例1-6可知，通过调整烧成温度在800～900℃、搭配合适的氧分压，可控制成品尖晶石镍锰酸锂具有适宜的A值和kA值，即尖晶石镍锰酸锂具有低的氧缺陷和适宜含量的Fd3m结构，使用其成品的锂离子电池可以兼顾动力学性能和长期存储性能。烧成温度不在上述区间时，无法兼顾适宜的A值和kA值。当温度低于800℃时，A值明显降低，如比较例1烧成温度为670℃，其A值仅为0.032，即Fd3m含量过少，不利于动力学性能。而当温度过高时，有利于氧缺陷的产生，因此k值和kA值很难降低，会加剧正极材料与电解液的副反应和Mn溶出、降低电池的使用寿命。
由实施例7-10、比较例2可知，通过延长保温时间和增大氧分压，可以保持A值不变(Fd3m结构含量不变)的情况下，减小k值和kA值，即减少氧缺陷，将有利于尖晶石镍锰酸锂的结构稳定性和电池的使用寿命。
由实施例11-17可知，掺杂元素Cr、Mo、Nb、Ru、P、Ta、Tl可进一步使k值减小(降低氧缺陷)。这是因为这些元素可与氧形成强健，所以减缓了尖晶石镍锰酸锂在高温下的释氧。其中实施例13-17的k值更小一些，可知掺杂元素Nb、Ru、P、Ta、Tl对抑制氧缺陷的作用更显著。
由实施例18-21、比较例3可知，通过掺杂元素含量在适宜范围内从而能够更好地兼顾A值和kA值。而当掺杂元素含量过高，即z＞0.2时，对氧缺陷的降低不再有进一步效果，但因掺杂量过大而使得材料的实际活性物质明显减少，因为这些掺杂物质对应的尖晶石结构LiM 2O 4是几乎无活性的，影响电池的充放电容量。
由实施例22-25可知，适当调整Li、Ni、Mn的含量均可得到A值和kA值适宜的尖晶石镍锰酸锂。这是因为尖晶石镍锰酸锂中Li、Ni、 Mn元素是可以进入相互的位置部分替换的。
由实施例26-30可知，通过调整制备工艺，可以控制颗粒的粒径大小。随着制备工艺中预烧成和正式烧成中最高温度的升高和保温时间延长，更容易生成单晶且晶粒更容易增大，A值和kA值也会随之变化。另外，正式烧成前的破碎工序可以减小粒径D V50，提高分散性，从而将类单晶分散为更接近单晶的类单晶或单晶。
由实施例31可知，通过综合调整烧结工艺、掺杂改性、主要元素(Li、Ni、Mn)含量，可以得到k＝0(无氧缺陷)、A值(A＝0.109，kA＝0)适宜且粒径适宜(D V50＝6.7μm)的单晶型尖晶石镍锰酸锂正极活性材料。
【二次电池的制备以及性能测试】
将各实施例以及比较例的镍锰酸锂正极活性材料分别按照下述方法制备成石墨负极软包电池，测试5C倍率下的放电能量密度E5C(Wh/Kg)和常温满充存储时间ts(月)，将结果示于表3。
石墨负极软包电池的制备：
(1)将各实施例和比较例的镍锰酸锂正极活性材料与导电炭黑、PVDF按重量比96：2.5：1.5混合，加入适量N-甲基吡咯烷酮，搅拌均匀，获得正极浆料。将正极浆料涂布在铝箔上，涂布后烘干，获得正极极片。正极极片上锂镍锰复合氧化物的载量为0.02g/cm 2。
(2)将负极活性材料人造石墨、导电剂炭黑(Super P)、粘结剂丁苯橡胶、增稠剂羧甲基纤维素钠按照质量比96：1：1：2在适量的溶剂去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。负极集流体单侧上负极活性材料的负载量为0.008g/cm 2。
(3)以含有1mol/L LiPF 6的碳酸脂、氟代碳酸酯、氟代醚等的混合溶液作为电解液。
(4)以厚度12μm的聚丙烯薄膜(φ16mm)作为隔离膜，将上述制得的正极极片、隔离膜，负极极片按顺序放好，使隔离膜处于正负极片中间起到隔离的作用，卷绕成型，用铝塑袋包装。注入电解液，封装后进行化成容量，制得石墨负极软包电池。
石墨负极软包电池电性能测试：
(1)正极活性材料在石墨负极软包电池的5C放电克容量与5C放电能量密度测试：
在25℃下，将各实施例或比较例的石墨负极软包电池以0.3C恒流充电至电压为4.9V，然后以4.9V恒压充电至电流为0.05C，静置5min之后，将软包电池以5C恒流放电至电压为3.5V。提取对应的放电容量和放电能量即为该软包电池的5C放电容量和5C放电能量。用该容量与该能量除以电池中的正极活性物质的质量(g)即为正极活性物质的5C放电克容量和5C放电能量密度，并分别示于表3中。相比于常规的小倍率0.33C或1C的充放电，5C是大倍率电流，更能体现材料及电池动力学性能的优劣，所以5C放电容量和放电能量密度反映了电极材料用于二次电池的动力学性能。
(2)二次电池软包常温满充存储性能测试：
在25℃下，将各实施例或比较例的石墨负极软包电池以0.3C恒流充电至电压为4.9V，然后以4.9V恒压充电至电流为0.05C。然后将二次电池在25℃下放置，每隔10d做一次满充满放再满充，提取该放电容量值，直至提取的放电容量衰减为初始值的80％，则存储结束。满充后在25℃下存储的总时长即为常温满充存储时长ts，并分别示于表3中。本申请中用常温满充存储时间ts代表材料用于二次电池的长期稳定性。
(3)电性能综合评价系数R计算：
依照“全寿命里程＝单次续航×总寿命”的逻辑，设定电性能综合评价系数R＝(E5C-440)×(ts-12)/100，其中两个常数分别表示能量密度440Wh/kg和满充存储1年，是当前该材料体系有应用价值的基本条件。其中R值为负数时亦记为0。由该评价系数可直观地综合评价电池性能的差异性。通过计算将各实施例和比较例的综合评价系数值，并将结果示于表3。
表3.二次电池性能表
试样编号 5C放电能量密度E/(Wh/Kg) 常温满充存储ts/(月) 综合评价系数R
比较例1 443 25.1 0.4
实施例1 486 28.3 7.5
实施例2 497 27.2 8.7
实施例3 515 25.9 10.4
实施例4 532 23.4 10.5
实施例5 523 18.8 5.6
实施例6 521 16.5 3.6
比较例2 512 14.3 1.7
比较例3 531 11.6 0.0
实施例7 534 25.9 13.1
实施例8 545 24.8 13.4
实施例9 536 18.8 6.5
实施例10 533 16.2 3.9
实施例11 567 24.1 15.4
实施例12 541 27.8 15.9
实施例13 537 30.7 18.1
实施例14 541 31.2 19.4
实施例15 531 32.8 18.9
实施例16 523 33.7 18.0
实施例17 526 34.3 19.2
实施例18 533 26.8 13.8
实施例19 527 34.9 19.9
实施例20 498 35.8 13.8
实施例21 478 33.2 8.1
比较例4 405 31.5 0
实施例22 528 18.3 5.5
实施例23 502 27.9 9.9
实施例24 523 20.1 6.7
实施例25 508 27.4 10.5
实施例26 553 15.6 4.1
实施例27 545 18.1 6.4
实施例28 542 19.2 7.3
实施例29 518 21.0 7.0
实施例30 513 21.2 6.7
实施例31 537 37.8 25.0
通过对比实施例和对比例可知，满足A值在0.04≤A≤0.3，且0≤kA≤0.015的镍锰酸锂正极活性材料Li 1+xNi yM zMn 2-x-y-zO 4-k，0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2，其兼具良好的5C放电能量密度和常温满充存储 性能。由比较例1可知，当A小于0.04时，5C放电能量密度较低；由比较例2和比较例3可知，kA的值大于0.015时，无法兼顾良好的5C放电能量密度和常温满充存储性能；由比较例4可知，当掺杂元素M含量过高时，也无法兼顾良好的5C放电能量密度和常温满充存储性能。
对比实施例1-10，当0.11≤k≤0.22时，综合评价系数R＞5，较好地兼顾良好的5C放电能量密度和常温满充存储性能；进一步的0.11≤k+A≤0.18时，R＞6，综合性能进一步提升。
对比实施例1-3与实施例11-17，掺杂M元素提高了材料的5C放电能量密度和/或常温满充存储性能，提高了综合评价系数R的值；掺杂元素Nb、Ru、P、Ta和Tl的改性效果更显著。
对比实施例13、实施例18-21，掺杂Nb元素的含量满足z≤0.2的镍锰酸锂的常温存储得到了显著改善，且综合评价系数R＞8，良好地兼顾了良好的5C放电能量密度和常温满充存储性能；掺杂Nb元素的含量0.001≤z≤0.15的镍锰酸锂的综合评价系数R＞10，综合性能更优。
对比实施例4、实施例26-30，体积中值粒径D V50满足1μm≤D V50≤20μm的镍锰酸锂均R＞6，较好地兼顾了良好的5C放电能量密度和常温满充存储性能；2μm≤D V50≤15μm的镍锰酸锂正极活性材料的R＞7，综合性能更优。
对比实施例1-10、实施例27-30，当P＝(k+A)/(D V50 0.3)满足0.06≤P≤0.12时，综合评价系数R＞6，兼顾良好的5C放电能量密度和常温满充存储性能；进一步的0.06≤P≤0.10时，R＞7，综合性能进一步提升。
对比实施例31与其他实施例，经过综合调控A、kA、掺杂元素与掺杂量、粒径的镍锰酸锂活性材料兼顾良好的5C放电能量密度和常温满充存储性能。

Claims (18)

  1. 一种镍锰酸锂正极活性材料，其中，
    所述正极活性材料组成式为Li 1+xNi yM zMn 2-x-y-zO 4-k，-0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2，M为Cr、Mo、Nb、Ru、P、S、Ta、W、Tl和Ti中的一种或多种，
    在所述正极活性材料的半电池的首圈充电曲线中，3.5V～4.4V的充电容量与3.5V～4.95V充电容量的比值为A，A满足0.04≤A≤0.3，k与A的乘积满足0≤kA≤0.015，其中，所述首圈充电曲线在0.1C的倍率下测得。
  2. 根据权利要求1所述的镍锰酸锂正极活性材料，其中，所述A和k满足如下关系：
    0.11≤k+A≤0.18，可选0.11≤k+A≤0.15。
  3. 根据权利要求1或2所述的镍锰酸锂正极活性材料，其中，
    0.07≤A≤0.15。
  4. 根据权利要求1-3中任一项所述的镍锰酸锂正极活性材料，其中，
    所述k满足0≤k≤0.1，可选为0≤k≤0.05。
  5. 根据权利要求1-4中任一项所述的镍锰酸锂正极活性材料，其中，所述z满足如下关系：
    0＜z≤0.2，可选为0.001≤z≤0.15。
  6. 根据权利要求1-5中任一项所述的镍锰酸锂正极活性材料，其中，
    M为选自Nb、Ru、P、Ta和Tl中的一种或两种以上。
  7. 根据权利要求1-6中任一项所述的镍锰酸锂正极活性材料，其中，
    所述镍锰酸锂正极活性材料为单晶和/或类单晶的颗粒。
  8. 根据权利要求1-7中任一项所述的镍锰酸锂正极活性材料，其中，
    所述正极活性材料的颗粒的体积中值粒径D V50满足1μm≤D V50≤20μm，可选为2μm≤D V50≤15μm。
  9. 根据权利要求8所述的镍锰酸锂正极活性材料，其中，
    0.06≤(k+A)/(D V50 0.3)≤0.12，可选为0.06≤(k+A)/(D V50 0.3)≤0.10，其中(k+A)/(D V50 0.3)单位为μm -0.3。
  10. 根据权利要求1-9中任一项所述的镍锰酸锂正极活性材料，其中，
    基于M元素的总重量，沿正极活性材料的颗粒的表层向其几何中心的径向方向，80％以上的M元素位于所述颗粒的前50％体积内；可选为前30％体积以内。
  11. 一种镍锰酸锂正极活性材料的制备方法，包括如下步骤，
    S1：提供含锂、镍、锰的化合物或混合物，可选地，所述化合物或混合物中含有M元素；
    S2：将所述化合物或混合物在炉内气压相对于大气压为正压且氧分压占比＞50％的炉内气氛中，升温到800～900℃热处理5～20h，得到所述正极活性材料，其中，
    所述正极活性材料组成式为Li 1+xNi yM zMn 2-x-y-zO 4-k，-0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2，M为Cr、Mo、Nb、Ru、P、S、Ta、W、Tl和Ti中的一种或多种，
    在所述正极活性材料的半电池的首圈充电曲线中，3.5V～4.4V的充电容量与3.5V～4.95V充电容量的比值A满足0.04≤A≤0.3，且k与A 的乘积kA满足0≤kA≤0.015，其中，所述首圈充电曲线在0.1C的倍率下测得。
  12. 根据权利要求11中所述的制备方法，其中，
    在所述S2中，所述氧分压占比为80％～100％。
  13. 根据权利要求11或12所述的制备方法，其中，
    在所述S1中，将所述含锂、镍、锰的化合物或混合物在含氧气氛中以800～1100℃热处理5～50h。
  14. 根据权利要求11-13中任一项所述的制备方法，其中，
    所述含锂、镍、锰的混合物中的镍锰原材料选自Ni yMn 2-x-y-z(OH) 4-2x-2z、Ni yMn 2-x-y-z(CO 3) 2-x-z、Ni yMn 2-x-y-zO 2-x-z、Ni yMn 2-x-y-zO 4-2x-2z、(Ni yMn 2-x-y-z) 3O 4-2x-2z、Ni yMn 2-x-y-z[O(OH)] 2-x-z中的一种或两种以上，-0.1≤x≤0.2，0.4≤y≤0.6，0≤z≤0.2。
  15. 一种二次电池，其中，包含权利要求1-10中任一项所述的镍锰酸锂正极活性材料或者通过权利要求11-14中任一项所述的制备方法制得的镍锰酸锂正极活性材料。
  16. 一种电池模块，其特征在于，包括权利要求15所述的二次电池。
  17. 一种电池包，其特征在于，包括权利要求16所述的电池模块。
  18. 一种用电装置，其特征在于，包括选自权利要求15所述的二次电池、权利要求16所述的电池模块或权利要求17所述的电池包中的至少一种。
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