Lithium-containing nickel-manganese composite oxide, method for preparing the same, and positive electrode sheet, secondary battery, and electric device comprising the same

Abstract

The application provides a lithium-containing nickel-manganese composite oxide, a preparation method thereof, a positive electrode sheet containing the lithium-containing nickel-manganese composite oxide, a secondary battery and an electric device, and the lithium-containing nickel-manganese composite oxide has a core-shell structure, comprising an inner core and a shell coated on the surface of the inner core, the inner core comprises Li x (Ni y Mn 2‑y ) 1‑m M m O4, M comprises one or more selected from Mg, a fourth sub-group element to a sixth sub-group element, a third main group element to a fifth main group element and a lanthanide series element, 0.95≤x≤1.10, 0.40≤y≤0.60, 0.001≤m≤0.015, and the shell comprises aluminum lithium phosphate and optionally comprises aluminum lithium phosphate and aluminum phosphate. The lithium-containing nickel-manganese composite oxide provided by the application can make the secondary battery simultaneously have high energy density, good cycle performance and storage performance and low gas production.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and particularly relates to a lithium-containing nickel-manganese composite oxide, a preparation method thereof, a positive electrode sheet containing the lithium-containing nickel-manganese composite oxide, a secondary battery and an electric device. BACKGROUND

[0002] In recent years, secondary batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the application and promotion of secondary batteries, people's demand for secondary batteries with high energy density, safety and reliability, and low cost is growing. The cobalt-free spinel lithium nickel-manganese oxide has become one of the most concerned positive active materials due to its high energy density, good thermal stability and low cost. However, its high working voltage hinders its compatibility with conventional electrolytes, and can cause serious side reactions and deterioration of the positive electrode-electrolyte interface, thereby hindering its practical application. SUMMARY

[0003] The purpose of the present application is to provide a lithium-containing nickel-manganese composite oxide, a preparation method thereof, a positive electrode sheet containing the lithium-containing nickel-manganese composite oxide, a secondary battery and an electric device, which can simultaneously achieve high energy density, good cycle performance and storage performance, and low gas production.

[0004] The first aspect of the present application provides a lithium-containing nickel-manganese composite oxide having a core-shell structure, comprising a core and a shell coated on the surface of the core, wherein the core comprises Li x (Ni y Mn 2-y ) 1-m M m O4, M comprises one or more selected from Mg, fourth sub-group elements to sixth sub-group elements, third main group elements to fifth main group elements, lanthanide series elements, optionally comprises one or more elements selected from Zr, W, Sb, P, Ti, B, Ta, Nb, Ce, Al, Mo and Mg, 0.95≤x≤1.10, 0.40≤y≤0.60, 0.001≤m≤0.015, and the shell comprises aluminum lithium phosphate, optionally comprises aluminum lithium phosphate and aluminum phosphate.

[0005] The lithium-containing nickel-manganese composite oxide provided in the application has a core-shell structure. The inner core has a low oxygen defect content, high crystal structure stability, and low rock salt phase content; the shell is coated on the surface of the inner core, which can effectively reduce the positive electrode-electrolyte interface side reaction and reduce the dissolution of manganese ions; the shell includes lithium aluminum phosphate, which can construct lithium ion conduction channels and avoid capacity reduction due to coating the shell on the surface of the inner core. Therefore, the secondary battery using the lithium-containing nickel-manganese composite oxide provided in the application can simultaneously have high energy density, good cycle performance and storage performance, and low gas production.

[0006] In any embodiment of the application, M includes one or more elements selected from W, P, B, Ta, Nb, and Mo, and can optionally include two or more elements selected from W, P, B, Ta, Nb, and Mo. In this way, the cycle performance and storage performance of the secondary battery can be further improved.

[0007] In any embodiment of the application, 0.003≤m≤0.007. In this way, the crystal structure stability can be improved, the dissolution of manganese ions can be reduced, the oxygen defect and rock salt phase content can be reduced, and the lithium ion diffusion coefficient can also be improved.

[0008] In any embodiment of the application, 0.45≤y≤0.55, and y can optionally be 0.50.

[0009] In any embodiment of the application, the inner core satisfies 0<(A1 / A2) 1 / 2 ≤0.2, and can optionally satisfy 0<(A1 / A2) 1 / 2 ≤0.1, A1 represents the peak area of the diffraction peak at 2θ of 43.7±0.2° in the X-ray diffraction spectrum of the inner core measured by a powder X-ray diffractometer using Cu Kα1 rays, and A2 represents the peak area of the diffraction peak at 2θ of 18.8±0.1° in the X-ray diffraction spectrum of the inner core measured by a powder X-ray diffractometer using Cu Kα1 rays. The inner core of the lithium-containing nickel-manganese composite oxide provided in the application has a low oxygen defect.

[0010] In any embodiment of the application, the thickness of the shell is uniform and continuous. In this way, the positive electrode-electrolyte interface can be better stabilized, the dissolution of manganese ions can be reduced, and the shell can also have uniform lithium ion conduction channels, thereby improving the charge and discharge efficiency.

[0011] In any embodiment of the application, the lithium aluminum phosphate is inlaid in the shell and is discretely distributed. In this way, it is helpful to better construct lithium ion conduction channels and avoid capacity reduction due to coating the shell on the surface of the inner core.

[0012] In any embodiment of the present application, the content of element P in the lithium aluminum phosphate in the shell is greater than 0 and less than or equal to 50 wt%, optionally 10 wt%-25 wt%, based on the total weight of element P in the shell. In this way, the promoting effect of lithium aluminum phosphate on lithium ion conduction and the stabilizing effect of aluminum phosphate on the positive electrode interface can be fully exerted, and the shell has high structural stability, which can not only play a role in isolating the electrolyte and reducing the positive electrode-electrolyte interface side reaction, but also play a role in conducting lithium ions.

[0013] In any embodiment of the present application, the thickness of the shell is 30 nm or less, optionally 5 nm-30 nm, and more optionally 5 nm-20 nm. When the thickness of the shell is within a suitable range, the positive electrode-electrolyte interface side reaction can be reduced while the capacity is not affected, and even a good lithium ion conduction channel can be constructed to improve the charge and discharge efficiency of the material.

[0014] In any embodiment of the present application, the volume particle size Dv50 of the lithium-containing nickel-manganese composite oxide is 5 μm-15 μm, optionally 5 μm-10 μm. In this way, the positive electrode-electrolyte interface side reaction can be effectively reduced, and the cycle performance and storage performance of the secondary battery can be improved.

[0015] In any embodiment of the present application, the span (Dv90-Dv10) / Dv50 of the lithium-containing nickel-manganese composite oxide is ≤1.0, and optionally, (Dv90-Dv10) / Dv50 is ≤0.8. In this way, the positive electrode-electrolyte interface side reaction can be effectively reduced, and the cycle performance and storage performance of the secondary battery can be improved.

[0016] In any embodiment of the present application, the BET specific surface area of the lithium-containing nickel-manganese composite oxide is 0.3 m 2 / g-1.0 m 2 / g, optionally 0.3 m 2 / g-0.7 m 2 / g. In this way, the positive electrode-electrolyte interface side reaction can be effectively reduced, and the cycle performance and storage performance of the secondary battery can be improved.

[0017] In any embodiment of the present application, the particle morphology of the lithium-containing nickel-manganese composite oxide is single crystal or single crystal-like, and optionally single crystal. In this way, the cracking phenomenon of the particles during cold pressing and use can be effectively reduced, thereby improving the overall performance of the secondary battery.

[0018] In any embodiment of this application, the grain shape of the lithium-containing nickel-manganese composite oxide is an octahedron with passivated edges and corners. This reduces stress corrosion, decreases the surface activity of the material, and reduces the contact area with the electrolyte, thereby further reducing side reactions at the cathode-electrolyte interface, reducing manganese ion dissolution, and lowering oxygen defects and rock salt phase content.

[0019] The second aspect of this application provides a method for preparing a lithium-containing nickel-manganese composite oxide, comprising the following steps: S1, mixing a source of element Ni, a source of element Mn, a source of element M, and a source of element Li in a predetermined ratio to obtain a mixture; S2, heating the mixture obtained in S1 to a first temperature T1 under an oxygen-containing atmosphere and a first pressure P1 and holding it at that temperature for a first time t1, thereby obtaining a core; S3, adding the core obtained in S2 to a solution containing aluminum salt and phosphate, adjusting the pH to allow the aluminum salt and phosphate to react, thereby obtaining a mixed solution; S4, separating the solid and liquid components of the mixed solution obtained in S3, drying it, and sieving it to obtain an intermediate product; S5, mixing the intermediate product obtained in S4 with a source of element Li in a predetermined ratio, heating it to a second temperature T2 under an oxygen-containing atmosphere and a second pressure P2 and holding it at that temperature for a second time t2, thereby obtaining a lithium-containing nickel-manganese composite oxide, wherein the lithium-containing nickel-manganese composite oxide has a core-shell structure, comprising a core and a shell covering the surface of the core, wherein the core comprises Li x (Ni y Mn 2-y ) 1-m M m O4, M includes one or more elements selected from Mg, Group IV to Group VI elements, Group III to Group V elements, and lanthanides, and optionally includes one or more elements selected from Zr, W, Sb, P, Ti, B, Ta, Nb, Ce, Al, Mo, and Mg, with 0.95≤x≤1.10, 0.40≤y≤0.60, and 0.001≤m≤0.015. The shell includes lithium aluminum phosphate, and optionally includes lithium aluminum phosphate and aluminum phosphate.

[0020] The preparation method provided in this application can prepare lithium-containing nickel-manganese composite oxides at a lower sintering temperature, while effectively controlling the morphology of the product, reducing oxygen defects and rock salt phase content, improving crystal structure stability, reducing side reactions at the cathode-electrolyte interface, and reducing manganese ion dissolution.

[0021] In any embodiment of this application, in S1, the source of the element Ni and the source of the element Mn are nickel manganese hydroxide.

[0022] In any embodiment of this application, in S1, the source of element M includes one or more selected from nitrates, hydrochlorides, sulfates, carbonates and acetates of element M.

[0023] In any embodiment of this application, in S1, the source of the element Li includes one or more selected from lithium hydroxide, lithium carbonate, and lithium oxide.

[0024] In any embodiment of this application, in S1, the ratio of the amount of element Li in the mixture to the total amount of elements Ni and Mn is (0.45-0.55):1.

[0025] In any embodiment of this application, in S1, the molar ratio of element Li to element M in the mixture is 1:(0.001-0.015), optionally 1:(0.003-0.007). This improves crystal structure stability, reduces manganese ion dissolution, lowers oxygen defects and rock salt phase content, and also improves the lithium ion diffusion coefficient.

[0026] In any embodiment of this application, in S2, the heating rate is ≤5℃ / min, optionally ≤3℃ / min. This helps to make the obtained lithium-containing nickel-manganese composite oxide primary particles more uniform and have a narrower particle size distribution.

[0027] In any embodiment of this application, in S2, the oxygen concentration of the oxygen-containing atmosphere is >60% by volume, optionally 80%-100% by volume.

[0028] In any embodiment of this application, in S2, the first pressure P1 is a relative atmospheric pressure of 0.02MPa-0.08MPa, and can be selected as 0.02MPa-0.04MPa.

[0029] When the oxygen concentration and / or the first pressure in the oxygen-containing atmosphere are within a suitable range, the content of small particles in the product can be reduced, while also helping to reduce the oxygen defect content of the obtained lithium-containing nickel-manganese composite oxide.

[0030] In any embodiment of this application, in S2, the first temperature T1 is 500℃-1200℃, and can be selected as 700℃-1200℃.

[0031] In any embodiment of this application, in S2, the first time t1 is 5h-40h, and can be selected as 5h-30h.

[0032] When the first temperature and / or the first time are within a suitable range, it helps to regulate the morphology, size, and spacing of the obtained lithium-containing nickel-manganese composite oxide particles.

[0033] In any embodiment of this application, in step S3, the core obtained in step S2 is added to an aluminum salt solution, followed by a phosphate solution. The pH is then adjusted to allow the aluminum salt and phosphate to react, resulting in a mixed solution. This allows a coating layer to be formed in situ on the core surface, and the coating layer is denser and more uniform in thickness.

[0034] In any embodiment of this application, in S3, the aluminum salt includes one or more selected from aluminum nitrate, aluminum chloride, aluminum sulfate, and aluminum carbonate.

[0035] In any embodiment of this application, in S3, the phosphate includes one or more selected from ammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate.

[0036] In any embodiment of this application, in step S3, the pH during the reaction of aluminum salt and phosphate is controlled to be 5-9, optionally 6-8. This allows for the acquisition of a dense and uniformly thick aluminum phosphate coating layer.

[0037] In any embodiment of this application, in S3, the ratio of the amount of element Al in the aluminum salt to the amount of element P in the phosphate is 1:1.

[0038] In any embodiment of this application, in S3, the amount of phosphate added is such that the mass of element P is 0.05wt%-1wt%, optionally 0.1wt%-0.5wt%, based on the mass of the kernel.

[0039] In any embodiment of this application, in S5, the heating rate is ≤5℃ / min, optionally ≤3℃ / min. This helps to make the obtained lithium-containing nickel-manganese composite oxide primary particles more uniform and narrower in size distribution, while also compensating for oxygen defects in the core.

[0040] In any embodiment of this application, in S5, the oxygen concentration of the oxygen-containing atmosphere is >60% by volume, optionally 80%-100% by volume.

[0041] In any embodiment of this application, in S5, the second pressure P2 is a relative atmospheric pressure of 0.02MPa-0.08MPa, and can be selected as 0.02MPa-0.04MPa.

[0042] When the oxygen concentration and / or second pressure in an oxygen-containing atmosphere are within a suitable range, the content of small particles in the product can be reduced, while also compensating for oxygen defects in the core. This further reduces the oxygen defects in the obtained lithium-containing nickel-manganese composite oxide and effectively reduces Mn. 3+ The content of [unclear] reduces manganese ion dissolution and lowers the content of rock salt phase. Furthermore, it facilitates the source reaction of aluminum phosphate with elemental Li to form a dense and uniformly thick coating layer.

[0043] In any embodiment of this application, in S5, the second temperature T2 is 400℃-700℃, and can be selected as 500℃-700℃.

[0044] In any embodiment of this application, in S5, the second time t2 is 5h-40h, and can be selected as 5h-30h.

[0045] When the second temperature and / or the second time are within a suitable range, it helps to compensate for the oxygen defects in the core, improve the coating effect of the shell, and obtain a dense and uniformly thick coating layer. At the same time, it also helps to form lithium aluminum phosphate and aluminum phosphate with higher crystal content, thereby further improving the structural stability of the shell, thus better isolating the electrolyte, reducing the side reactions at the cathode-electrolyte interface, and also helping to better conduct lithium ions.

[0046] In any embodiment of this application, the ratio of the amount of element Li in the source of element Li in S5 to the amount of element P in the phosphate in S3 is ≤0.75, and optionally ≤0.375. This allows the generated lithium aluminum phosphate to be embedded in the aluminum phosphate coating layer and to be discretely distributed, thereby facilitating the construction of lithium-ion conduction channels by the lithium aluminum phosphate and avoiding capacity reduction due to the coating on the core surface.

[0047] In any embodiment of this application, the source of element Li in S5 includes one or more selected from lithium hydroxide, lithium carbonate, and lithium oxide.

[0048] A third aspect of this application provides a positive electrode sheet, comprising a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, wherein the positive electrode film layer comprises a lithium-containing nickel-manganese composite oxide of the first aspect of this application or a lithium-containing nickel-manganese composite oxide prepared by the method of the second aspect of this application, wherein the content of the lithium-containing nickel-manganese composite oxide in the positive electrode film layer is 1wt%-99wt%, optionally 85wt%-99wt%, based on the total weight of the positive electrode film layer.

[0049] The fourth aspect of this application provides a secondary battery, including the positive electrode sheet of the third aspect of this application.

[0050] The fifth aspect of this application provides an electrical device, including the secondary battery of the fourth aspect of this application.

[0051] The lithium-containing nickel-manganese composite oxide provided in this application has a core-shell structure. The core has low oxygen defect content, high crystal structure stability, and low rock salt phase content; the shell coats the surface of the core, which can effectively reduce side reactions at the cathode-electrolyte interface and reduce manganese ion dissolution; the shell includes lithium aluminum phosphate, which can construct lithium-ion conduction channels and avoid capacity reduction due to the shell coating on the core surface. Therefore, the secondary battery using the lithium-containing nickel-manganese composite oxide provided in this application can simultaneously achieve high energy density, good cycle performance and storage performance, and low gas production. The power device of this application includes the secondary battery provided in this application, and therefore has at least the same advantages as the secondary battery. Attached Figure Description

[0052] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0053] Figure 1 This is a schematic diagram of the lithium-containing nickel-manganese composite oxide of this application.

[0054] Figure 2 This is a schematic diagram of one embodiment of the secondary battery of this application.

[0055] Figure 3 yes Figure 2 An exploded view of the implementation method of the secondary battery.

[0056] Figure 4 This is a schematic diagram of one embodiment of the battery module of this application.

[0057] Figure 5 This is a schematic diagram of one embodiment of the battery pack of this application.

[0058] Figure 6 yes Figure 5 An exploded view of an embodiment of the battery pack shown.

[0059] Figure 7 This is a schematic diagram of one embodiment of an electrical device that uses a secondary battery as a power source, as described in this application.

[0060] Figure 8 The X-ray diffraction pattern of the lithium-containing nickel-manganese composite oxide prepared in Example 1 was determined using a Cu Kα1 powder X-ray diffraction apparatus.

[0061] Figure 9 This is a scanning electron microscope image of the lithium-containing nickel-manganese composite oxide prepared in Example 1.

[0062] Figure 10 The X-ray diffraction pattern of the lithium-containing nickel-manganese composite oxide prepared in Comparative Example 1 was determined using a Cu Kα1 powder X-ray diffraction apparatus.

[0063] Figure 11 This is a scanning electron microscope image of the lithium-containing nickel-manganese composite oxide prepared in Comparative Example 1.

[0064] Figure 12 The X-ray diffraction pattern of the lithium-containing nickel-manganese composite oxide prepared in Comparative Example 5 was determined using a Cu Kα1 powder X-ray diffraction apparatus.

[0065] Figure 13 This is a scanning electron microscope image of the lithium-containing nickel-manganese composite oxide prepared in Comparative Example 5.

[0066] In the accompanying drawings, the figures may not be drawn to scale. The reference numerals are explained as follows: 1 Battery pack, 2 Upper casing, 3 Lower casing, 4 Battery module, 5 Secondary battery, 51 Housing, 52 Electrode assembly, 53 Cover plate, 10 Lithium-containing nickel-manganese composite oxide, 101 Core, 102 Shell, 102a Aluminum phosphate, 102b Lithium aluminum phosphate. Detailed Implementation

[0067] The following detailed description, with appropriate reference to the accompanying drawings, discloses the lithium-containing nickel-manganese composite oxide, its preparation method, and embodiments thereof, including a positive electrode, a secondary battery, and an electrical device. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a thorough understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0068] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 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. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0069] Unless otherwise specified, all embodiments and optional embodiments of this application may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this application.

[0070] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions, and such technical solutions shall be deemed to be included in the disclosure of this application.

[0071] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0072] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0073] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the 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).

[0074] In this application, the terms "multiple" or "various" refer to two or more kinds.

[0075] In this application, "about" a certain value represents a range, specifically a range of ±10% of that value.

[0076] Unless otherwise stated, the terms used in this application have the common meanings as commonly understood by those skilled in the art.

[0077] Unless otherwise stated, the values ​​of the parameters mentioned in this application can be determined using various testing methods commonly used in the art, for example, they can be determined according to the testing methods provided in this application.

[0078] Spinel-type lithium nickel manganese oxide (LiNi) 0.5 Mn 1.5 O4 exhibits a high discharge voltage plateau of 4.7V and a theoretical discharge specific capacity of 147mAh / g, thus possessing the advantage of high specific energy density. Spinel-type lithium nickel manganese oxide contains significantly less Li and Ni than ternary cathode active materials, and its preparation process is simple, resulting in low production costs. Spinel-type lithium nickel manganese oxide also boasts high thermal stability and a large tolerance for overcharge and over-discharge, thus offering superior safety performance.

[0079] Therefore, spinel-type lithium nickel manganese oxide is a promising low-cost, high-energy-density cathode active material. However, most current spinel-type lithium nickel manganese oxides are synthesized under high-temperature conditions, which easily leads to oxygen deficiency, resulting in a large number of oxygen vacancies and rock-salt phase structures. This, in turn, reduces its structural stability and deteriorates its cycle performance. Furthermore, under high-temperature and high-voltage operating conditions, the Mn content in the bulk phase of spinel-type lithium nickel manganese oxide... 3+ It is prone to disproportionation reaction to form Mn 4+ and Mn 2+ And the Mn formed 2+ It will dissolve in the electrolyte, causing the spinel structure to break down. Furthermore, Mn... 2+ Further reduction reactions will occur on the surface of the negative electrode, resulting in deposition. Under high temperature and high voltage operating conditions, spinel-type lithium nickel manganese oxide is also prone to oxidizing and decomposing the organic solvent in the electrolyte, which leads to thickening of the positive electrode-electrolyte interface and increase in interfacial impedance, thus seriously affecting the electrochemical performance of the secondary battery.

[0080] In view of the above problems, the inventors of this application have conducted extensive research to provide a lithium-containing nickel-manganese composite oxide with low oxygen defects.

[0081] Lithium-containing nickel-manganese composite oxide

[0082] The first aspect of this application provides a lithium-containing nickel-manganese composite oxide having a core-shell structure, including a core and a shell covering the surface of the core, wherein the core comprises Li x (Ni y Mn 2-y ) 1-m M m O4, M includes one or more elements selected from Mg, Group IV to Group VI elements, Group III to Group V elements, and lanthanides, with 0.95≤x≤1.10, 0.40≤y≤0.60, and 0.001≤m≤0.015. The shell includes lithium aluminum phosphate (Li3Al(PO4)2).

[0083] The lithium-containing nickel-manganese composite oxide provided in this application has a core-shell structure. The core has low oxygen defect content, high crystal structure stability, and low rock salt phase content; the shell, covering the core surface, can effectively reduce side reactions at the cathode-electrolyte interface and reduce manganese ion dissolution; the shell includes lithium aluminum phosphate, which can construct lithium-ion conduction channels and avoid capacity reduction due to the shell covering the core surface. Therefore, the secondary battery using the lithium-containing nickel-manganese composite oxide provided in this application can simultaneously achieve high energy density, good cycle performance and storage performance, and low gas production.

[0084] In the core, M includes one or more elements selected from Mg, Group IV to Group VI elements, Group III to Group V elements, and lanthanides. In some embodiments, M optionally includes one or more elements selected from Zr, W, Sb, P, Ti, B, Ta, Nb, Ce, Al, Mo, and Mg. The aforementioned dopant element M can enter the crystal lattice of the grain and occupy transition metal sites and vacancies. Furthermore, the bond energy of the MO bond formed by Mn is greater than that of the Mn-O bond, thereby stabilizing the spinel structure while weakening the Li-O bond energy. This improves crystal structure stability, reduces manganese ion dissolution, decreases oxygen defects and rock salt phase content, and also increases the lithium ion diffusion coefficient. The aforementioned dopant element M can also passivate edges and improve morphology, thereby reducing the specific surface area of ​​the material and reducing side reactions at the cathode-electrolyte interface. The aforementioned dopant element M can also accelerate the growth of primary particles during material preparation, allowing the material to be sintered at a lower temperature and reach the target size, thus effectively reducing oxygen defects.

[0085] In some embodiments, M optionally includes one or more elements selected from W, P, B, Ta, Nb, and Mo, and more preferably includes two or more elements selected from W, P, B, Ta, Nb, and Mo, such as a combination of W and Nb, a combination of Ta and Mo, or a combination of P and W. This can further improve the cycle performance and storage performance of the secondary battery.

[0086] In the core, the content of dopant element M satisfies 0.001 ≤ m ≤ 0.015. For example, m can be 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.010, 0.011, 0.012, 0.013, 0.014, 0.015, or any value within any range of the above. Optionally, 0.001 ≤ m ≤ 0.012, 0.001 ≤ m ≤ 0.010, and 0.003 ≤ m ≤ 0.007. This improves crystal structure stability, reduces manganese ion dissolution, lowers oxygen defects and rock salt phase content, and also improves the lithium-ion diffusion coefficient. When the content of dopant element M is too high, the capacity utilization of the material will decrease significantly, which is detrimental to the energy density of the secondary battery.

[0087] In the kernel, 0.40 ≤ y ≤ 0.60. For example, y can be 0.40, 0.42, 0.44, 0.46, 0.48, 0.50, 0.52, 0.54, 0.56, 0.58, 0.60, or any range of the above values. Optionally, 0.45 ≤ y ≤ 0.55. More alternatively, y is 0.50.

[0088] The lithium-containing nickel-manganese composite oxide core provided in this application has low oxygen defects. In some embodiments, the core satisfies 0 < (A1 / A2). 1 / 2 ≤0.2, optionally, 0<(A1 / A2) 1 / 2 ≤0.18, 0<(A1 / A2) 1 / 2 ≤0.16, 0<(A1 / A2) 1 / 2 ≤0.14, 0<(A1 / A2) 1 / 2 ≤0.12, 0<(A1 / A2) 1 / 2 ≤0.1, 0<(A1 / A2) 1 / 2 ≤0.08, A1 represents the peak area of ​​the diffraction peak at 2θ of 43.7±0.2° in the X-ray diffraction pattern of the kernel measured using a powder X-ray diffraction device with Cu Kα1 rays, and A2 represents the peak area of ​​the diffraction peak at 2θ of 18.8±0.1° in the X-ray diffraction pattern of the kernel measured using a powder X-ray diffraction device with Cu Kα1 rays.

[0089] In some embodiments, the lithium-containing nickel-manganese composite oxide has a grain shape of octahedron with passivated edges. Currently prepared spinel-type lithium nickel manganese oxide grains are mostly octahedral or truncated octahedral. Due to their many sharp edges, these edges are prone to stress corrosion, which degrades the performance of the secondary battery. The doping element M provided in this application also helps to passivate the edges of the octahedron, reduce stress corrosion, reduce material surface activity, and reduce the contact area with the electrolyte, thereby further reducing side reactions at the cathode-electrolyte interface, reducing manganese ion dissolution, and reducing oxygen defects and rock salt phase content.

[0090] In some embodiments, the lithium-containing nickel-manganese composite oxide particles have a single crystal or near-single crystal morphology, and may be selected as single crystals. The lithium-containing nickel-manganese composite oxide provided in this application consists of single crystal or near-single crystal particles. The single crystal particles do not contain grain boundaries, while the near-single crystal particles are composed of several or a dozen aggregated grains with very few grain boundaries inside. This effectively reduces the occurrence of particle cracking during cold pressing and use, thereby improving the overall performance of the secondary battery.

[0091] In this application, "grain" and "particle" are two completely different concepts. In this application, a particle refers to an aggregate that cannot be further dispersed by methods such as ultrasonic dispersion, and it may be composed of one or more grains. When a particle consists of a single grain, it is a monocrystalline particle; when a particle consists of multiple grains, it is a polycrystalline particle. In this application, the term "quasi-monocrystalline" refers to a particle composed of several or a dozen grains.

[0092] In some embodiments, the shell of the lithium-nickel-manganese composite oxide comprises lithium aluminum phosphate and aluminum phosphate. Aluminum phosphate has poor lithium-ion conductivity, which affects the material's capacity. Lithium aluminum phosphate can construct lithium-ion conduction channels, thereby preventing capacity reduction due to the shell coating on the core surface and even improving the material's charge-discharge efficiency. When the shell simultaneously comprises lithium aluminum phosphate and aluminum phosphate, both the lithium aluminum phosphate's promoting effect on lithium-ion conduction and the aluminum phosphate's stabilizing effect on the positive electrode interface can be utilized. Therefore, the shell can both isolate the electrolyte and reduce side reactions at the positive electrode-electrolyte interface, and also conduct lithium ions, preventing capacity reduction due to the shell coating on the core surface.

[0093] Lithium aluminum phosphate (LAP) has lower stability than aluminum phosphate, which can easily lead to instability at the cathode interface, potentially affecting the cycle performance and storage performance of the secondary battery. Therefore, its content should not be too high. In some embodiments, the shell comprises lithium aluminum phosphate and aluminum phosphate, wherein the content of element P in the lithium aluminum phosphate in the shell is greater than 0 and less than or equal to 50 wt%, optionally 10 wt%-35 wt%, 10 wt%-30 wt%, or 10 wt%-25 wt%, based on the total weight of element P in the shell. This allows the promoting effect of lithium aluminum phosphate on lithium-ion conduction and the stabilizing effect of aluminum phosphate on the cathode interface to be fully utilized. Consequently, the shell has high structural stability, effectively isolating the electrolyte, reducing side reactions at the cathode-electrolyte interface, and conducting lithium ions.

[0094] In some embodiments, the lithium aluminum phosphate is embedded in the shell (e.g., embedded in the aluminum phosphate) and is discretely distributed, which helps to better construct lithium-ion conduction channels and avoids capacity reduction due to the shell covering the core surface.

[0095] The aluminum phosphate and lithium aluminum phosphate can be crystalline, amorphous, or both. In some embodiments, optionally, both the aluminum phosphate and lithium aluminum phosphate are crystalline. This helps to further improve the structural stability of the shell, thereby better isolating the electrolyte, reducing side reactions at the cathode-electrolyte interface, and also facilitating better lithium-ion conduction.

[0096] In some embodiments, the shell has a uniform and continuous thickness. This better stabilizes the positive electrode-electrolyte interface, reduces manganese ion dissolution, and also provides the shell with uniform lithium-ion conduction channels, improving charge and discharge efficiency. In some embodiments, the shell can be formed in situ on the surface of the core, thereby making the shell thickness uniform and continuous.

[0097] In some embodiments, the thickness of the shell is less than 30 nm, preferably 5 nm-30 nm, and more preferably 5 nm-20 nm, 5 nm-15 nm, or 5 nm-10 nm. The shell covers the surface of the core, effectively isolating the electrolyte, reducing side reactions at the cathode-electrolyte interface, and reducing manganese ion dissolution. When the shell thickness is within a suitable range, it can reduce side reactions at the cathode-electrolyte interface without affecting capacity performance, and may even construct a good lithium-ion conduction channel, improving the charge-discharge efficiency of the material. If the shell is too thick, it may significantly reduce the material's capacity performance. At the same time, the shell should not be too thin, as it is prone to detachment and lose its protective function.

[0098] In some embodiments, the volumetric particle size Dv50 of the lithium-containing nickel-manganese composite oxide is 5μm-15μm, and can be selected as 5μm-10μm.

[0099] In some embodiments, the radial distance (Dv90-Dv10) / Dv50 of the lithium-containing nickel-manganese composite oxide is ≤1.0, and optionally, (Dv90-Dv10) / Dv50 is ≤0.9, (Dv90-Dv10) / Dv50 is ≤0.8, (Dv90-Dv10) / Dv50 is ≤0.7, and (Dv90-Dv10) / Dv50 is ≤0.6.

[0100] In some embodiments, the BET specific surface area of ​​the lithium-containing nickel-manganese composite oxide is 0.3 m². 2 / g-1.0m 2 / g, optional 0.3m 2 / g-0.7m 2 / g.

[0101] Lithium-containing nickel-manganese composite oxides have a large primary particle size, a small BET specific surface area, a narrow particle size distribution, and high uniformity, which can effectively reduce side reactions at the cathode-electrolyte interface and help improve the cycle performance and storage performance of secondary batteries.

[0102] The lithium-containing nickel-manganese composite oxide provided in this application is described below with reference to the accompanying drawings. Figure 1 This is a schematic diagram of the lithium-containing nickel-manganese composite oxide 10 of this application. (As shown...) Figure 1 As shown, the lithium-containing nickel-manganese composite oxide 10 includes a core 101 and a shell 102 covering the surface of the core 101. The shell 102 includes aluminum phosphate 102a and lithium aluminum phosphate 102b, which can be embedded in the shell 102 and are discretely distributed.

[0103] Preparation method

[0104] The second aspect of this application provides a method for preparing a lithium-containing nickel-manganese composite oxide, which can prepare the lithium-containing nickel-manganese composite oxide of the first aspect of this application.

[0105] The preparation method includes the following steps: S1, mixing a source of element Ni, a source of element Mn, a source of element M, and a source of element Li in a predetermined ratio to obtain a mixture; S2, heating the mixture obtained in S1 to a first temperature T1 under an oxygen-containing atmosphere and a first pressure P1 and holding it at that temperature for a first time t1, after which a core is obtained; S3, adding the core obtained in S2 to a solution containing aluminum salt and phosphate, adjusting the pH to allow the aluminum salt and phosphate to react, after which a mixed solution is obtained; S4, separating the solid and liquid components of the mixed solution obtained in S3, drying it, and sieving it to obtain an intermediate product; S5, mixing the intermediate product obtained in S4 with a source of element Li in a predetermined ratio, heating it to a second temperature T2 under an oxygen-containing atmosphere and a second pressure P2 and holding it at that temperature for a second time t2, after which a lithium-containing nickel-manganese composite oxide is obtained, wherein the lithium-containing nickel-manganese composite oxide has a core-shell structure, comprising a core and a shell covering the surface of the core, the core comprising Li x (Ni y Mn 2-y ) 1-m M m O4, M includes one or more elements selected from Mg, Group IV to Group VI elements, Group III to Group V elements, and lanthanides, and optionally includes one or more elements selected from Zr, W, Sb, P, Ti, B, Ta, Nb, Ce, Al, Mo, and Mg, with 0.95≤x≤1.10, 0.40≤y≤0.60, and 0.001≤m≤0.015. The shell includes lithium aluminum phosphate, and optionally includes lithium aluminum phosphate and aluminum phosphate.

[0106] The preparation method provided in this application can prepare lithium-containing nickel-manganese composite oxides at a lower sintering temperature, while effectively controlling the morphology of the product, reducing oxygen defects and rock salt phase content, improving crystal structure stability, reducing side reactions at the cathode-electrolyte interface, and reducing manganese ion dissolution.

[0107] In S1, the source of each element can be a compound known in the art that can be used to prepare lithium-containing nickel-manganese composite oxides. In some embodiments, in S1, the source of element Ni and the source of element Mn are nickel-manganese hydroxides. In some embodiments, in S1, the source of element M includes one or more selected from nitrates, hydrochlorides, sulfates, carbonates, and acetates of element M. In some embodiments, in S1, the source of element Li includes one or more selected from lithium hydroxide, lithium carbonate, and lithium oxide.

[0108] In some embodiments, in S1, the ratio of the amount of element Li in the mixture to the total amount of elements Ni and Mn is (0.45-0.55):1.

[0109] In some embodiments, in S1, the molar ratio of element Li to element M in the mixture is 1:(0.001-0.015), optionally 1:(0.003-0.007). This can improve crystal structure stability, reduce manganese ion dissolution, reduce oxygen defects and rock salt phase content, and also improve the lithium ion diffusion coefficient.

[0110] In some embodiments, in S1, the mixing can be carried out in a plow mixer, a high-speed mixer, or an inclined mixer.

[0111] In some embodiments, in S2, the heating rate is ≤5℃ / min, optionally ≤3℃ / min. The heating rate affects the heating of the particles during the crystallization process. A lower heating rate allows for more uniform heating during particle growth and fewer oxygen defects, thereby helping to obtain more uniform primary particles with a narrower particle size distribution of lithium-containing nickel-manganese composite oxide.

[0112] In some embodiments, in S2, the oxygen concentration of the oxygen-containing atmosphere is >60% by volume, optionally 80%-100% by volume; and / or, the first pressure P1 is 0.02MPa-0.08MPa relative to atmospheric pressure, optionally 0.02MPa-0.04MPa. This can reduce the content of small particles in the product, while also helping to reduce the oxygen defect content of the obtained lithium-containing nickel-manganese composite oxide.

[0113] In some embodiments, in S2, the first temperature T1 is 500°C-1200°C, for example, it can be about 550°C, about 600°C, about 700°C, about 800°C, about 900°C, about 1000°C, about 1100°C, about 1200°C, or any range of any of the above values. Optionally, the first temperature T1 is 700°C-1200°C, 800°C-1200°C, 900°C-1200°C, or 1000°C-1200°C.

[0114] In some embodiments, in S2, the first time t1 is 5h-40h, and can be selected as 5h-30h, 10h-30h, or 10h-20h.

[0115] When the first temperature and / or the first time are within a suitable range, it helps to regulate the morphology, size, and spacing of the obtained lithium-containing nickel-manganese composite oxide particles.

[0116] In some embodiments, the preparation method may further include the step of: after S2 and before S3, crushing and sieving the kernel obtained in S2 to obtain powder. Optionally, the crushing is ball milling or air jet milling. Optionally, the crushing can be performed using a planetary ball mill.

[0117] In some embodiments, in S3, the aluminum salt includes one or more selected from aluminum nitrate, aluminum chloride, aluminum sulfate, and aluminum carbonate.

[0118] In some embodiments, in S3, the phosphate includes one or more selected from ammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate.

[0119] In some embodiments, in S3, the aluminum salt and the phosphate can be added to the solvent simultaneously or separately. The solvent used is a solvent commonly used in the art. For example, the solvent can be water (e.g., deionized water) or an organic solvent (e.g., ethanol).

[0120] In some embodiments, in S3, the core obtained in S2 is added to an aluminum salt solution, followed by a phosphate solution. The pH is then adjusted to allow the aluminum salt and phosphate to react, resulting in a mixture. The core material is insoluble in the aluminum salt solution, allowing a uniform layer of aluminum ions to adhere to the surface of the core material, forming an atomic-level coating on the core. This enables the in-situ generation of a coating layer on the core surface, resulting in a denser and more uniform coating layer.

[0121] In some embodiments, in S3, the pH of the reaction between the aluminum salt and phosphate is controlled to be 5-9, optionally 6-8, thereby obtaining a dense and uniformly thick aluminum phosphate coating. It should be noted that the pH can be adjusted in this application using methods commonly used in the art, such as by adding acid or base to the reaction system. If the pH is too low, the aluminum salt and phosphate cannot react to form aluminum phosphate; if the pH is too high, the aluminum salt readily reacts with hydroxide ions to form aluminum hydroxide precipitate instead of aluminum phosphate.

[0122] In some embodiments, in S3, the ratio of the amount of element Al in the aluminum salt to the amount of element P in the phosphate is 1:1, and / or the amount of phosphate added is such that the mass of element P is 0.05wt%-1wt%, optionally 0.1wt%-0.5wt%, based on the mass of the core.

[0123] In some embodiments, in S5, the mixing can be carried out in a plow mixer, a high-speed mixer, or an inclined mixer.

[0124] In some embodiments, in S5, the source of the element Li includes one or more selected from lithium hydroxide, lithium carbonate, and lithium oxide.

[0125] In some embodiments, in S5, the heating rate is ≤5℃ / min, optionally ≤3℃ / min. The heating rate affects the heating conditions during particle crystallization. A lower heating rate allows for more uniform heating during particle growth, which helps to make the obtained lithium-containing nickel-manganese composite oxide primary particles more uniform and have a narrower particle size distribution, while also compensating for oxygen defects in the core.

[0126] In some embodiments, in S5, the oxygen concentration of the oxygen-containing atmosphere is >60% by volume, optionally 80%-100% by volume, and / or the second pressure P2 is a relative atmospheric pressure of 0.02MPa-0.08MPa, optionally 0.02MPa-0.04MPa.

[0127] When the oxygen concentration and / or second pressure in an oxygen-containing atmosphere are within a suitable range, the content of small particles in the product can be reduced, while also compensating for oxygen defects in the core. This further reduces the oxygen defects in the obtained lithium-containing nickel-manganese composite oxide and effectively reduces Mn. 3+ The content of [unclear] reduces manganese ion dissolution and lowers the content of rock salt phase. Furthermore, it facilitates the source reaction of aluminum phosphate with elemental Li to form a dense and uniformly thick coating layer.

[0128] In some embodiments, in S5, the second temperature T2 is 400°C-700°C, for example, it can be about 400°C, about 500°C, about 600°C, about 700°C, or any range of any of the above values. Optionally, the second temperature T2 is 500°C-700°C.

[0129] In some embodiments, in S5, the second time t2 is 5h-40h, and can be selected as 5h-30h, 10h-30h, or 10h-20h.

[0130] When the second temperature and / or the second time are within a suitable range, it helps to compensate for the oxygen defects in the core, improve the coating effect of the shell, and obtain a dense and uniformly thick coating layer. At the same time, it also helps to form lithium aluminum phosphate and aluminum phosphate with higher crystal content, thereby further improving the structural stability of the shell, thus better isolating the electrolyte, reducing the side reactions at the cathode-electrolyte interface, and also helping to better conduct lithium ions.

[0131] In some embodiments, the ratio of the amount of element Li in the source of element Li in S5 to the amount of element P in the phosphate in S3 is ≤0.75, optionally ≤0.525, ≤0.450, or ≤0.375. This allows the generated lithium aluminum phosphate to be embedded in the aluminum phosphate coating layer and to be discretely distributed, thereby facilitating the construction of lithium-ion conduction channels by the lithium aluminum phosphate and avoiding capacity reduction due to the coating on the core surface.

[0132] In some embodiments, the preparation method may further include the steps of crushing and sieving the product obtained in S5. Optionally, the crushing is ball milling or air jet milling. Optionally, the crushing can be performed using a planetary ball mill.

[0133] In some embodiments, the preparation method includes the following steps: S2, mixing nickel manganese hydroxide, a source of element M, and a source of element Li in a predetermined ratio to obtain a mixture; S2, heating the mixture obtained in S1 to 500℃-1200℃ and holding it at a first pressure P1 of 0.02MPa-0.08MPa (optionally 0.02MPa-0.04MPa) under an oxygen-containing atmosphere with an oxygen concentration >60% by volume (optionally 80%-100% by volume) and a relative atmospheric pressure of 0.02MPa-0.08MPa (optionally 0.02MPa-0.04MPa) for 5h-40h, after which a core is obtained; S3, adding the core obtained in S2 to an aluminum salt solution, then adding a phosphate solution, and then adjusting the pH to allow the aluminum salt and phosphate to react, after which a core is obtained. S4: After solid-liquid separation of the mixture obtained in S3, the mixture is dried and sieved to obtain an intermediate product; S5: The intermediate product obtained in S4 is mixed with a source of elemental Li in a predetermined ratio and heated to 400℃-700℃ under a second pressure P2 at an oxygen concentration of >60% (optional, 80%-100% by volume) and a relative atmospheric pressure of 0.02MPa-0.08MPa (optional, 0.02MPa-0.04MPa) and held for 5h-40h. After the heating is completed, a lithium-containing nickel-manganese composite oxide is obtained. The lithium-containing nickel-manganese composite oxide has a core-shell structure, which includes a core and a shell covering the surface of the core. The core includes Li. x (Ni y Mn 2-y ) 1-m M m O4, M includes one or more elements selected from Mg, Group IV to Group VI elements, Group III to Group V elements, and lanthanides, and optionally includes one or more elements selected from Zr, W, Sb, P, Ti, B, Ta, Nb, Ce, Al, Mo, and Mg, with 0.95≤x≤1.10, 0.40≤y≤0.60, and 0.001≤m≤0.015. The shell includes lithium aluminum phosphate, and optionally includes lithium aluminum phosphate and aluminum phosphate.

[0134] In the process of preparing lithium-containing nickel-manganese composite oxides, some parameters of lithium-containing nickel-manganese composite oxides (such as the types and contents of doping elements) can be referred to the lithium-containing nickel-manganese composite oxides of the first aspect of this application, and will not be repeated here.

[0135] Unless otherwise specified, all raw materials used in the preparation method of the second aspect of this application can be obtained commercially.

[0136] Positive electrode sheet

[0137] A third aspect of this application provides a positive electrode sheet, comprising a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector. The positive electrode film layer comprises a lithium-containing nickel-manganese composite oxide according to the first aspect of this application or a lithium-containing nickel-manganese composite oxide prepared by the preparation method of the second aspect of this application. The content of the lithium-containing nickel-manganese composite oxide in the positive electrode film layer is 1 wt%-99 wt%, optionally 85 wt%-99 wt%, based on the total weight of the positive electrode film layer. The positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0138] The positive electrode film layer may also include other positive electrode active materials known in the art for use in secondary batteries. For example, these other positive electrode active materials may include one or more of lithium transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Examples of lithium-containing phosphates may include one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their respective modified compounds. In this application, the modified compounds of the above-mentioned positive electrode active materials may be those obtained by doping and / or surface coating modification of the positive electrode active materials.

[0139] In some embodiments, the positive electrode film may optionally include a positive electrode conductive agent. This application does not impose any particular limitation on the type of positive electrode conductive agent. As an example, the positive electrode conductive agent includes one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0140] In some embodiments, the positive electrode film layer may optionally include a positive electrode binder. This application does not impose any particular limitation on the type of positive electrode binder. As an example, the positive electrode binder may include one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0141] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. An example of a metal material may be one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. An example of a polymer substrate may be one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0142] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, optional conductive agent, optional binder, and any other components in a solvent and stirring until homogeneous. The solvent may be N-methylpyrrolidone (NMP), but is not limited to this.

[0143] Secondary battery

[0144] A fourth aspect of this application provides a secondary battery, which includes the positive electrode sheet of the third aspect of this application. A secondary battery, also known as a rechargeable battery or accumulator, is a battery that can be recharged after discharge to activate its active materials and continue to be used. Typically, a secondary battery includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode sheet, a negative electrode sheet, and a separator. During the charging and discharging process, lithium ions repeatedly insert and extract between the positive and negative electrode sheets. The separator is disposed between the positive and negative electrode sheets, primarily serving to prevent short circuits between the positive and negative electrodes while allowing lithium ions to pass through. The electrolyte, located between the positive and negative electrode sheets, conducts lithium ions.

[0145] [Positive electrode plate]

[0146] The positive electrode used in the secondary battery of this application is the positive electrode described in any embodiment of the third aspect of this application.

[0147] [Negative electrode plate]

[0148] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative current collector has two surfaces opposite each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative current collector.

[0149] The negative electrode active material may be any negative electrode active material known in the art for use in secondary batteries. As an example, the negative electrode active material includes, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based material may include one or more of elemental tin, tin oxide, and tin alloy materials. This application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0150] In some embodiments, the negative electrode film layer may optionally include a negative electrode conductive agent. This application does not impose any particular limitation on the type of negative electrode conductive agent. As an example, the negative electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0151] In some embodiments, the negative electrode film layer may optionally include a negative electrode binder. This application does not impose any particular limitation on the type of negative electrode binder. As an example, the negative electrode binder may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0152] In some embodiments, the negative electrode film may optionally include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0153] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymer substrate and a metal material layer formed on at least one surface of the polymer substrate. As an example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymer substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0154] The negative electrode film layer is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0155] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet of this application further includes a conductive undercoat layer (e.g., composed of a conductive agent and an adhesive) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of this application further includes a protective layer covering the surface of the negative electrode film layer.

[0156] [Electrolytes]

[0157] This application does not impose specific limitations on the type of electrolyte, which can be selected according to requirements. For example, the electrolyte may include at least one selected from solid electrolytes and liquid electrolytes (i.e., electrolyte solutions).

[0158] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0159] The type of electrolyte salt is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the electrolyte salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0160] The type of solvent is not specifically limited and can be selected according to actual needs. In some embodiments, as an example, the solvent may include one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE).

[0161] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0162] [Isolation membrane]

[0163] Secondary batteries using electrolytes, as well as some secondary batteries using solid electrolytes, also include a separator. The separator is disposed between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes while allowing lithium ions to pass through. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0164] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer may be the same or different.

[0165] In some embodiments, the positive electrode, the separator, and the negative electrode can be fabricated into an electrode assembly using a winding process or a stacking process.

[0166] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0167] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0168] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. Figure 2 This is an example of a square-structured secondary battery 5.

[0169] In some embodiments, such as Figure 3 As shown, the outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 is used to cover the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be adjusted according to requirements.

[0170] The method for preparing the secondary battery described in this application is well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a secondary battery. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding or stacking process. The electrode assembly is then placed in an outer packaging, dried, and injected with an electrolyte. After vacuum sealing, settling, formation, and shaping, a secondary battery is obtained.

[0171] In some embodiments of this application, the secondary battery according to this application can be assembled into a battery module. The number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.

[0172] Figure 4 This is a schematic diagram of battery module 4 as an example. Figure 4 As shown, in battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0173] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0174] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0175] Figure 5 and Figure 6 This is a schematic diagram of battery pack 1 as an example. Figure 5 and Figure 6 As shown, the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0176] Electric device

[0177] A fifth aspect of this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack described in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0178] The electrical device can be equipped with a secondary battery, battery module, or battery pack according to its usage requirements.

[0179] Figure 7 This is a schematic diagram of an example electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0180] Another example of an electrical device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use rechargeable batteries as their power source.

[0181] Example

[0182] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0183] Example 1

[0184] (1) Preparation of lithium-containing nickel-manganese composite oxides

[0185] S1, according to the kernel target component being Li(Ni) 0.5 Mn 1.5 ) 0.996 Nb 0.004 Weigh out Ni in the corresponding stoichiometric ratio using O4. 0.5 Mn 1.5 (OH)4 (as a source of elements Ni and Mn), Li2CO3 (as a source of element Li) and Nb2O5 (as a source of element M) are mixed evenly in a plow-type mixer to obtain a mixture.

[0186] S2. The above mixture is placed in a furnace and heated to 1000℃ at a rate of 1℃ / min under conditions of 95% oxygen concentration and a furnace pressure P1 relative to atmospheric pressure of 0.03 MPa. The temperature is then held for 10 hours, and finally cooled to room temperature to obtain the core. The elemental content of the core can be determined using inductively coupled plasma atomic emission spectrometry (ICP) according to EPA 6010D-2014.

[0187] S3. The obtained kernels were ball-milled into powder using a planetary ball mill and then added to an aqueous solution of aluminum nitrate. Following this, an aqueous solution of ammonium phosphate was added, and the pH of the reaction solution was adjusted to 7 to allow the aluminum nitrate and ammonium phosphate to react. A mixed solution was obtained after the reaction. The molar ratio of aluminum nitrate to ammonium phosphate was 1:1, and the amount of ammonium phosphate added was such that the mass of elemental phosphorus (P) was 0.30 wt%, based on the mass of the kernels.

[0188] S4. The obtained mixture is centrifuged, then dried and sieved to obtain the intermediate product.

[0189] S5. The obtained intermediate product and LiOH are mixed evenly in a plow-type mixer at a Li / P molar ratio of 0.15:1. Then, the mixture is placed in a kiln and heated to 700℃ at a rate of 1℃ / min under the conditions of oxygen concentration of 95% by volume and furnace pressure P2 relative to atmospheric pressure of 0.03MPa, and held for 10h. After the end of the process, lithium-containing nickel-manganese composite oxide is obtained by air-jet crushing.

[0190] (2) Preparation of button cell (half-cell)

[0191] The lithium-containing nickel-manganese composite oxide prepared above was mixed with conductive carbon black and polyvinylidene fluoride at a weight ratio of 90:5:5, and an appropriate amount of NMP solvent was added. The mixture was stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry was coated onto a positive electrode current collector aluminum foil and dried to obtain a positive electrode sheet. The loading of the lithium-containing nickel-manganese composite oxide on the positive electrode sheet was 0.015 g / cm³. 2 .

[0192] A lithium sheet was used as the counter electrode, and a solution of 1 mol / L LiPF6 in ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1 was used as the electrolyte. A 12 μm thick polypropylene film was used as the separator. Together with the positive electrode sheet prepared above, they were assembled into a CR2030 coin cell in a coin cell box and left to stand for 24 hours to obtain a half cell.

[0193] (3) Preparation of secondary batteries (full batteries)

[0194] The lithium-containing nickel-manganese composite oxide prepared above was mixed with conductive carbon black and polyvinylidene fluoride at a weight ratio of 96:2.5:1.5, and an appropriate amount of solvent NMP was added. The mixture was stirred evenly to obtain a positive electrode slurry. The positive electrode slurry was coated on both surfaces of the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.

[0195] Artificial graphite (negative electrode active material), carbon black (Super P) (conductive agent), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) are thoroughly mixed in an appropriate amount of deionized water at a weight ratio of 96:1:1:2 to form a negative electrode slurry. The negative electrode slurry is then coated onto both surfaces of the copper foil (negative electrode current collector), and after drying and cold pressing, a negative electrode sheet is obtained.

[0196] A 12μm thick polypropylene film is used as a separator. It is placed in sequence with the positive and negative electrode sheets prepared above, so that the separator is in the middle of the positive and negative electrode sheets to play a role in isolation. Then, the electrode assembly is wound to obtain the electrode assembly. The electrode assembly is placed in an outer packaging aluminum-plastic bag, dried, and then injected with the same electrolyte as the button cell prepared above. After vacuum sealing, standing, formation, capacity testing and other processes, a secondary battery is obtained.

[0197] Example 2-33

[0198] Except for the preparation of the lithium-containing nickel-manganese composite oxide, the preparation of the coin cell and the secondary cell were the same as in Example 1. The differences in the preparation process of the lithium-containing nickel-manganese composite oxide are detailed in Table 1.

[0199] Comparative Example 1

[0200] Except for the preparation of lithium-containing nickel-manganese composite oxide, the preparation of coin cells and secondary cells is the same as in Example 1.

[0201] Ni 0.5 Mn 1.5 (OH)4 and Li2CO3 were mixed evenly in a plow-type mixer at a molar ratio of 1:0.5 to obtain a mixture. The mixture was placed in a kiln and heated to 1000℃ at a rate of 1℃ / min under conditions of 95% oxygen concentration and a furnace pressure P1 relative to atmospheric pressure of 0.03MPa. After holding at this temperature for 10 hours, the mixture was crushed by airflow to obtain a lithium-containing nickel-manganese composite oxide.

[0202] Comparative Example 2

[0203] Except for the preparation of lithium-containing nickel-manganese composite oxide, the preparation of coin cells and secondary cells is the same as in Example 1.

[0204] According to the target component is Li(Ni) 0.5 Mn 1.5 ) 0.996 Nb 0.004 Weigh out Ni in the corresponding stoichiometric ratio using O4. 0.5 Mn 1.5 (OH)4 (as a source of elements Ni and Mn), Li2CO3 (as a source of element Li), and Nb2O5 (as a source of element M) are mixed evenly in a plow-type mixer to obtain a mixture. The mixture is then placed in a kiln and heated to 1000℃ at a rate of 1℃ / min under conditions of 95% oxygen concentration and a furnace pressure P1 relative to atmospheric pressure of 0.03MPa, and held at that temperature for 10 hours. After the holding time, the mixture is crushed by airflow to obtain a lithium-containing nickel-manganese composite oxide.

[0205] Comparative Example 3

[0206] Except for the preparation of lithium-containing nickel-manganese composite oxide, the preparation of coin cells and secondary cells is the same as in Example 1.

[0207] Ni 0.5 Mn 1.5(OH)4 and Li2CO3 were mixed uniformly in a plow-type mixer at a molar ratio of 1:0.5 to obtain a mixture. This mixture was placed in a kiln and heated to 1000℃ at a rate of 1℃ / min under conditions of 95% oxygen concentration and a furnace pressure P1 relative to atmosphere of 0.03 MPa, and held at that temperature for 10 hours. After cooling to room temperature, the core was obtained. The obtained core was ball-milled into powder using a planetary ball mill and added to an aqueous solution of aluminum nitrate. Then, an aqueous solution of ammonium phosphate was added to adjust the pH of the reaction solution to 7, allowing the aluminum nitrate and ammonium phosphate to react. A mixed solution was obtained after the reaction. The obtained mixed solution was centrifuged, dried, and sieved to obtain an intermediate product. The obtained intermediate product was mixed with LiOH in a plow-type mixer at a Li / P molar ratio of 0.15:1. The mixture was then placed in a kiln and heated to 700°C at a rate of 1°C / min under conditions of 95% oxygen concentration and a furnace pressure P2 relative to atmospheric pressure of 0.03 MPa. The mixture was then held for 10 hours. After the process, the lithium-containing nickel-manganese composite oxide was obtained by air jet crushing.

[0208] Comparative Example 4

[0209] Except for the preparation of lithium-containing nickel-manganese composite oxide, the preparation of coin cells and secondary cells is the same as in Example 1.

[0210] According to the kernel target component is Li(Ni) 0.5 Mn 1.5 ) 0.996 Nb 0.004 Weigh out Ni in the corresponding stoichiometric ratio using O4. 0.5 Mn 1.5 (OH)4 (as a source of elements Ni and Mn), Li2CO3 (as a source of element Li), and Nb2O5 (as a source of element M) were mixed uniformly in a plow-type mixer to obtain a mixture. This mixture was placed in a kiln and heated to 1000℃ at a rate of 1℃ / min under conditions of 95% oxygen concentration and a furnace pressure P1 relative to atmosphere of 0.03 MPa, and held at that temperature for 10 hours. After cooling to room temperature, the core was obtained. The obtained core was ball-milled into powder using a planetary ball mill and added to an aqueous solution of aluminum nitrate, followed by an aqueous solution of ammonium phosphate. The pH of the reaction solution was adjusted to 7 to allow the aluminum nitrate and ammonium phosphate to react, resulting in a mixed solution. The obtained mixed solution was centrifuged, dried, and sieved to obtain an intermediate product. The obtained intermediate product was placed in a kiln and heated to 700°C at a rate of 1°C / min under conditions of oxygen concentration of 95% by volume and furnace pressure P2 relative to atmospheric pressure of 0.03 MPa, and held for 10 hours. After the process, lithium-containing nickel-manganese composite oxide was obtained by airflow crushing.

[0211] Comparative Examples 5-10

[0212] Except for the preparation of the lithium-containing nickel-manganese composite oxide, the preparation of the coin cell and the secondary cell were the same as in Example 1. The differences in the preparation process of the lithium-containing nickel-manganese composite oxide are detailed in Table 1.

[0213] Test section

[0214] (1) Morphology test of lithium-containing nickel-manganese composite oxide

[0215] The lithium-containing nickel-manganese composite oxide prepared above was tested using a scanning electron microscope, and then tested according to JY / T010-1996, and the morphology of the sample was observed. The testing instrument can be a ZEISS Sigma 300.

[0216] (2) Thickness test of shell containing lithium nickel manganese composite oxide

[0217] In this application, the thickness of the shell of the lithium nickel manganese composite oxide has a meaning known in the art and can be measured using instruments and methods known in the art. For example, a thin slice of approximately 100 nm thickness can be cut from the middle of a single lithium nickel manganese composite oxide particle using a focused ion beam, and then the shell thickness can be measured and determined using a transmission electron microscope. During the test, the thickness can be measured at three locations on the selected particle, and the average value is taken.

[0218] (3) Volume particle size tests of lithium nickel manganese composite oxides: Dv90, Dv50, and Dv10

[0219] In this application, the volumetric particle sizes Dv90, Dv50, and Dv10 of the lithium-nickel-manganese composite oxide have meanings known in the art, representing the particle size corresponding to a cumulative volume distribution percentage of 90%, 50%, and 10%, respectively, and can be determined using instruments and methods known in the art. For example, they can be conveniently determined using a laser particle size analyzer in accordance with GB / T 19077-2016. The testing instrument can be a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK.

[0220] (4) BET specific surface area test of lithium nickel manganese composite oxide

[0221] In this application, the BET specific surface area of ​​lithium nickel manganese composite oxides has a meaning known in the art and can be determined using instruments and methods known in the art. For example, it can be tested using the nitrogen adsorption specific surface area analysis method according to GB / T 19587-2017, and calculated using the BET method. The testing instrument can be the Tri-Star 3020 specific surface area and pore size analyzer from Micromeritics, USA.

[0222] (5) Test of oxygen defect content in the core of lithium nickel manganese composite oxide

[0223] The X-ray diffraction pattern of lithium-containing nickel-manganese composite oxide was determined using a Cu Kα1 powder X-ray diffraction apparatus. The square root (A1 / A2) of the ratio of the peak area A1 of the diffraction peak at 2θ of 43.7±0.2° to the peak area A2 of the diffraction peak at 2θ of 18.8±0.1° was used. 1 / 2 This indicates the oxygen defect content in the core of the lithium nickel manganese composite oxide. The test method includes the following steps: (1) Sample preparation: the sample groove is 1 mm deep and 25 mm in diameter, and the plate sample preparation method is used; (2) Test: the starting angle is 15°, the ending angle is 70°, the step size is 0.01671°, the duration of each step is 0.24 s, the voltage is 40 KV, the current is 40 mA, and the anti-scattering slit is 1 mm; (3) Data processing: the data is processed using X'Pert HighScore Plus to obtain the peak area A1 of the diffraction peak at 2θ of 43.7 ± 0.2° and the peak area A2 of the diffraction peak at 2θ of 18.8 ± 0.1°. The test instrument can be a Bruker X-ray diffractometer, model D8DISCOVER, and the test standard reference procedure is: JIS / K0131-1996 General Rules for X-ray Diffraction Analysis.

[0224] (6) Measurement of initial discharge capacity of button cell (half-cell)

[0225] At 25°C, the coin cell prepared above is charged at a constant current of 0.1C to a voltage of 4.9V, and then charged at a constant voltage of 4.9V to a current of 0.05C. After standing for 5 minutes, the coin cell is discharged at a constant current of 0.1C to a voltage of 3.5V. The discharge capacity obtained at this time is the initial discharge capacity of the coin cell.

[0226] (7) Initial discharge capacity test of secondary battery (full battery)

[0227] At 25°C, the secondary battery prepared above is charged at a constant current of 0.33C to a voltage of 4.9V, and then charged at a constant voltage of 4.9V to a current of 0.05C. After standing for 5 minutes, the secondary battery is discharged at a constant current of 0.33C to a voltage of 3.5V. The discharge capacity obtained at this time is the initial discharge capacity of the secondary battery.

[0228] (8) Cyclic performance test of secondary battery (full battery) at 25℃

[0229] At 25°C, the prepared secondary battery was charged at a constant current of 0.33C to a voltage of 4.9V, then charged at a constant voltage of 4.9V to a current of 0.05C. After standing for 5 minutes, the secondary battery was discharged at a constant current of 0.33C to a voltage of 3.5V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the secondary battery after the first cycle. The aforementioned charge-discharge cycle was repeated, and the discharge capacity after each cycle was recorded.

[0230] The capacity retention rate of a secondary battery after 300 cycles at 25°C = discharge capacity after 300 cycles / discharge capacity after the first cycle.

[0231] (9) Cyclic performance test of secondary battery (full battery) at 45℃

[0232] At 45°C, the prepared secondary battery was charged at a constant current of 0.33C to a voltage of 4.9V, then charged at a constant voltage of 4.9V to a current of 0.05C. After standing for 5 minutes, the secondary battery was discharged at a constant current of 0.33C to a voltage of 3.5V. This constitutes one charge-discharge cycle, and the discharge capacity of this cycle is the discharge capacity of the secondary battery after the first cycle. The aforementioned charge-discharge cycle was repeated, and the discharge capacity after each cycle was recorded.

[0233] The capacity retention rate of a secondary battery after 200 cycles at 45°C = discharge capacity after 200 cycles / discharge capacity after the first cycle.

[0234] (10) Storage performance test of secondary battery (full battery) at 45℃

[0235] At 25°C, the prepared secondary battery was charged at a constant current of 0.33C to a voltage of 4.9V, and then charged at a constant voltage of 4.9V to a current of 0.05C. At this point, the secondary battery was in a fully charged state (100% SOC). The fully charged secondary battery was placed in a constant temperature chamber at 45°C and stored until the discharge capacity decreased to 80% of the initial discharge capacity of the secondary battery. The test was then stopped, and the number of days of storage was recorded.

[0236] The lithium-containing nickel-manganese composite oxide provided in this application has a core-shell structure. The core has low oxygen defect content, high crystal structure stability, and low rock salt phase content. The shell, covering the core surface, effectively reduces side reactions at the cathode-electrolyte interface and reduces manganese ion dissolution. The shell simultaneously comprises lithium aluminum phosphate and aluminum phosphate, thus leveraging both the lithium aluminum phosphate's promoting effect on lithium-ion conduction and the aluminum phosphate's stabilizing effect on the cathode interface. Therefore, the shell provided in this application can both isolate the electrolyte and reduce side reactions at the cathode-electrolyte interface, and also conduct lithium ions, preventing capacity reduction due to the shell covering the core surface. The test results in Table 2 show that the secondary battery using the lithium-containing nickel-manganese composite oxide with the core-shell structure provided in this application can simultaneously achieve high initial discharge capacity, good cycle performance, and storage performance.

[0237] The lithium-containing nickel-manganese composite oxides prepared in Comparative Examples 1 and 2 do not have a core-shell structure, while the lithium-containing nickel-manganese composite oxides prepared in Comparative Examples 3 and 4 do have a core-shell structure. However, the core of Comparative Example 3 does not contain the doping element provided in this application, and the shell of Comparative Example 4 does not contain lithium aluminum phosphate. Therefore, neither of them can enable the secondary battery to simultaneously achieve high initial discharge capacity and good cycle performance and storage performance.

[0238] Figure 8 The X-ray diffraction pattern of the lithium-containing nickel-manganese composite oxide prepared in Example 1 was determined using a Cu Kα1 powder X-ray diffraction apparatus. Figure 9 This is a scanning electron microscope image of the lithium-containing nickel-manganese composite oxide prepared in Example 1. Figure 10 The X-ray diffraction pattern of the lithium-containing nickel-manganese composite oxide prepared in Comparative Example 1 was determined using a Cu Kα1 powder X-ray diffraction apparatus. Figure 11 This is a scanning electron microscope image of the lithium-containing nickel-manganese composite oxide prepared in Comparative Example 1. Figure 12 The X-ray diffraction pattern of the lithium-containing nickel-manganese composite oxide prepared in Comparative Example 5 was determined using a Cu Kα1 powder X-ray diffraction apparatus. Figure 13 This is a scanning electron microscope image of the lithium-containing nickel-manganese composite oxide prepared in Comparative Example 5. (From...) Figure 8 , Figure 10 and Figure 12 It is evident that the lithium-containing nickel-manganese composite oxide core provided in this application has a low oxygen defect content. (From...) Figure 9 , Figure 11 and Figure 13 It is known that the grain shape of the lithium-containing nickel-manganese composite oxide provided in this application is an octahedron with blunted edges and corners.

[0239] Based on the test results of Examples 1, 4-8 and Comparative Examples 1, 5-6, it can be seen that when the core material does not contain the doping element provided in this application, the prepared lithium-nickel-manganese composite oxide has a high oxygen defect content and sharp edges in its grain shape. Therefore, the secondary battery cannot simultaneously achieve high initial discharge capacity, good cycle performance, and good storage performance. A possible reason is that the doping element M provided in this application can enter the crystal lattice of the grain and occupy transition metal sites and vacancies. Furthermore, the bond energy of the MO bond it forms is greater than that of the Mn-O bond, thereby stabilizing the spinel structure, improving crystal structure stability, reducing manganese ion dissolution, and decreasing oxygen defects and rock salt phase content. The doping element M provided in this application also helps to passivate the edges of the octahedron.

[0240] Based on the test results of Examples 1, 21-22 and Comparative Examples 7-8, it can be seen that when the reaction of aluminum salt and phosphate does not meet the pH requirement between 5 and 9, a shell containing lithium aluminum phosphate or both lithium aluminum phosphate and aluminum phosphate cannot be formed. As a result, the lithium-ion conductivity of this shell is poor, which leads to a low initial discharge capacity of the battery.

[0241] Based on the test results of Examples 1-3 and Comparative Examples 9-10, it can be seen that when the content of doping elements is within a suitable range, it can improve the stability of the crystal structure, reduce the dissolution of manganese ions, reduce oxygen defects and rock salt phase content, and also improve the lithium ion diffusion coefficient. In this way, the secondary battery can simultaneously achieve high initial discharge capacity, good cycle performance, and storage performance.

[0242] The test results from Examples 1-33 also show that when the oxygen defect content of the core material further satisfies 0 < (A1 / A2)... 1 / 2 ≤0.2, optionally, 0<(A1 / A2) 1 / 2 When the value is ≤0.1, it helps to further improve the overall performance of the secondary battery.

[0243] The test results from Examples 1-33 also show that when lithium-containing nickel-manganese composite oxides have suitable particle size, BET specific surface area, and particle size distribution, they can help to further improve the overall performance of secondary batteries.

[0244] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

[0245]

[0246]

[0247]

[0248]

Claims

1. A lithium-containing nickel-manganese composite oxide having a core-shell structure, comprising a core and a shell covering the surface of the core, wherein, The kernel includes Li x (Ni y Mn 2-y ) 1-m M m O4, M includes one or more elements selected from Mg, Group IV to Group VI elements, Group III to Group V elements, and lanthanides, with 0.95 ≤ x ≤ 1.10, 0.40 ≤ y ≤ 0.60, and 0.001 ≤ m ≤ 0.

015. The shell includes lithium aluminum phosphate and aluminum phosphate.

2. The lithium-containing nickel-manganese composite oxide according to claim 1, wherein, M includes one or more elements selected from Zr, W, Sb, P, Ti, B, Ta, Nb, Ce, Al, Mo, and Mg.

3. The lithium-containing nickel-manganese composite oxide according to claim 1, wherein, M includes one or more elements selected from W, P, B, Ta, Nb, and Mo, and / or, 0.003 ≤ m ≤ 0.007; and / or, 0.45 ≤ y ≤ 0.55。 4. The lithium-containing nickel-manganese composite oxide according to claim 1, wherein, M includes two or more elements selected from W, P, B, Ta, Nb, and Mo.

5. The lithium-containing nickel-manganese composite oxide according to claim 1, wherein, y is 0.

50.

6. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The kernel satisfies 0 < (A1 / A2) 1 / 2 ≤0.2, A1 represents the peak area of ​​the diffraction peak at 2θ of 43.7±0.2° in the X-ray diffraction pattern of the kernel measured using a powder X-ray diffraction device with Cu Kα1 rays, and A2 represents the peak area of ​​the diffraction peak at 2θ of 18.8±0.1° in the X-ray diffraction pattern of the kernel measured using a powder X-ray diffraction device with Cu Kα1 rays.

7. The lithium-containing nickel-manganese composite oxide according to claim 6, wherein, The kernel satisfies 0 < (A1 / A2) 1 / 2 ≤0.

1.

8. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The shell has a uniform and continuous thickness.

9. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The lithium aluminum phosphate is embedded in the shell and is discretely distributed.

10. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The content of element P in the lithium aluminum phosphate in the shell is greater than 0 and less than or equal to 50 wt%, based on the total weight of element P in the shell.

11. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The content of element P in the lithium aluminum phosphate in the shell is 10wt%-25wt%, based on the total weight of element P in the shell.

12. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The thickness of the shell is less than 30 nm.

13. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The thickness of the shell is 5nm-30nm.

14. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The thickness of the shell is 5nm-20nm.

15. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The volumetric particle size Dv50 of the lithium-containing nickel-manganese composite oxide is 5 μm-15 μm; and / or, The radial distance (Dv90-Dv10) / Dv50 of the lithium-containing nickel-manganese composite oxide is ≤1.0; and / or, The BET specific surface area of ​​the lithium-containing nickel-manganese composite oxide is 0.3 m². 2 / g-1.0m 2 / g.

16. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The volumetric particle size Dv50 of the lithium-containing nickel-manganese composite oxide is 5 μm-10 μm; and / or, The radial distance (Dv90-Dv10) / Dv50 of the lithium-containing nickel-manganese composite oxide is ≤0.8; and / or, The BET specific surface area of ​​the lithium-containing nickel-manganese composite oxide is 0.3 m². 2 / g-0.7m 2 / g.

17. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The lithium-containing nickel-manganese composite oxide has a particle morphology of single crystal or near-single crystal. The grain shape of the lithium-containing nickel-manganese composite oxide is an octahedron with blunted edges and corners.

18. The lithium-containing nickel-manganese composite oxide according to any one of claims 1 to 5, wherein, The lithium-containing nickel-manganese composite oxide has a single-crystal morphology.

19. A method for preparing lithium-containing nickel-manganese composite oxide, comprising the following steps: S1, mixing a source of element Ni, a source of element Mn, a source of element M, and a source of element Li in a predetermined ratio to obtain a mixture; S2, heating the mixture obtained in S1 to a first temperature T1 under an oxygen-containing atmosphere and a first pressure P1 and holding it at that temperature for a first time t1, thereby obtaining a core; S3, adding the core obtained in S2 to a solution containing aluminum salt and phosphate, adjusting the pH to allow the aluminum salt and phosphate to react, thereby obtaining a mixed solution; S4, separating the solid and liquid components of the mixed solution obtained in S3, drying it, and sieving it to obtain an intermediate product; S5, mixing the intermediate product obtained in S4 with a source of element Li in a predetermined ratio, heating it to a second temperature T2 under an oxygen-containing atmosphere and a second pressure P2 and holding it at that temperature for a second time t2, thereby obtaining a lithium-containing nickel-manganese composite oxide, wherein... The lithium-containing nickel-manganese composite oxide has a core-shell structure, comprising a core and a shell covering the surface of the core, wherein the core comprises Li x (Ni y Mn 2-y ) 1- m M m O4, M includes one or more elements selected from Mg, Group IV to Group VI elements, Group III to Group V elements, and lanthanides, with 0.95 ≤ x ≤ 1.10, 0.40 ≤ y ≤ 0.60, and 0.001 ≤ m ≤ 0.

015. The shell includes lithium aluminum phosphate and aluminum phosphate.

20. The method according to claim 19, wherein, S4, M includes one or more elements selected from Zr, W, Sb, P, Ti, B, Ta, Nb, Ce, Al, Mo, and Mg.

21. The method according to claim 19, wherein, In S1, The source of the element Ni and the source of the element Mn are nickel-manganese hydroxide; and / or, The source of element M includes one or more selected from nitrates, hydrochlorides, sulfates, carbonates, and acetates of element M; and / or, The source of the element Li includes one or more selected from lithium hydroxide, lithium carbonate, and lithium oxide.

22. The method according to any one of claims 19 to 21, wherein, In S1, The ratio of the amount of element Li to the total amount of elements Ni and Mn in the mixture is (0.45-0.55):1; and / or, The ratio of the amount of element Li to the amount of element M in the mixture is 1:(0.001-0.015).

23. The method according to any one of claims 19 to 21, wherein, In S1, the ratio of the amount of element Li to the amount of element M in the mixture is 1:(0.003-0.007).

24. The method according to any one of claims 19 to 21, wherein, In S2, The heating rate is ≤5℃ / min; and / or, The oxygen concentration in the oxygen-containing atmosphere is >60% by volume; and / or, The first pressure P1 is a relative atmospheric pressure of 0.02 MPa - 0.08 MPa; and / or, The first temperature T1 is 500℃-1200℃; and / or, The first time interval t1 is 5h-40h.

25. The method according to any one of claims 19 to 21, wherein, In S2, The heating rate is ≤3℃ / min; and / or, The oxygen concentration in the oxygen-containing atmosphere is 80%-100% by volume; and / or, The first pressure P1 is a relative atmospheric pressure of 0.02 MPa-0.04 MPa; and / or, The first temperature T1 is 700℃-1200℃; and / or, The first time interval t1 is 5h-30h.

26. The method according to any one of claims 19 to 21, wherein, In S3, the kernels obtained in S2 are added to an aluminum salt solution, followed by a phosphate solution. The pH is then adjusted to allow the aluminum salt and phosphate to react, resulting in a mixed solution.

27. The method according to any one of claims 19 to 21, wherein, In S3, The aluminum salt includes one or more selected from aluminum nitrate, aluminum chloride, aluminum sulfate, and aluminum carbonate; and / or, The phosphate includes one or more selected from ammonium hydrogen phosphate, ammonium dihydrogen phosphate, and ammonium phosphate; and / or, The pH of the reaction between aluminum salts and phosphates should be controlled between 5 and 9; and / or, The molar ratio of element Al in the aluminum salt to the molar ratio of element P in the phosphate is 1:1; and / or, The amount of phosphate added is such that the mass of element P is 0.05wt%-1wt%, based on the mass of the kernel.

28. The method according to any one of claims 19 to 21, wherein, In S3, The pH of the reaction between aluminum salts and phosphates should be controlled at 6-8; and / or, The amount of phosphate added is such that the mass of element P is 0.1wt%-0.5wt%, based on the mass of the kernel.

29. The method according to any one of claims 19 to 21, wherein, In S5, The heating rate is ≤5℃ / min; and / or, The oxygen concentration in the oxygen-containing atmosphere is >60% by volume; and / or, The second pressure P2 is a relative atmospheric pressure of 0.02 MPa - 0.08 MPa; and / or, The second temperature T2 is 400℃-700℃; and / or, The second time t2 is 5h-40h.

30. The method according to any one of claims 19 to 21, wherein, In S5, The heating rate is ≤3℃ / min; and / or, The oxygen concentration in the oxygen-containing atmosphere is 80%-100% by volume; and / or, The second pressure P2 is a relative atmospheric pressure of 0.02 MPa - 0.04 MPa; and / or, The second temperature T2 is 500℃-700℃; and / or, The second time t2 is 5h-30h.

31. The method according to any one of claims 19 to 21, wherein, The ratio of the amount of element Li in the source of element Li in S5 to the amount of element P in the phosphate in S3 is ≤0.75; and / or, The source of element Li in S5 includes one or more selected from lithium hydroxide, lithium carbonate, and lithium oxide.

32. The method according to any one of claims 19 to 21, wherein, The ratio of the amount of element Li in the source of element Li in S5 to the amount of element P in the phosphate in S3 is ≤0.

375.

33. A positive electrode sheet, comprising a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, wherein, The positive electrode film layer comprises the lithium-containing nickel-manganese composite oxide as described in any one of claims 1-18 or the lithium-containing nickel-manganese composite oxide prepared by the method described in any one of claims 19-32, wherein the content of the lithium-containing nickel-manganese composite oxide in the positive electrode film layer is 1wt%-99wt%, based on the total weight of the positive electrode film layer.

34. The positive electrode sheet according to claim 33, wherein, The content of the lithium-containing nickel-manganese composite oxide in the positive electrode film is 85wt%-99wt%, based on the total weight of the positive electrode film.

35. A secondary battery comprising the positive electrode sheet as described in claim 34.

36. An electrical device comprising the secondary battery of claim 35.

Images