Positive electrode active material, battery cell, battery, and power using device

Abstract

This application provides a positive electrode active material, a battery cell, a battery, and an electrical device. The positive electrode active material includes a matrix, wherein the chemical formula of the matrix is ​​Li[Li] x Ni a Co b Mn c M d O2, M includes at least one of Mg, Nb, Cr, Ce, Fe, Ta, B, Al, V, Ti, Zr, Sn, P, and Mo, wherein x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, and d≥0; the coating layer is disposed on the surface of the substrate and includes a boron-containing alloy. The technical solution of this application can improve the energy retention rate and initial specific capacity of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to positive electrode active materials, battery cells, batteries and electrical devices. Background Technology

[0002] In recent years, lithium batteries have been applied in increasingly wider fields, such as energy storage power systems for wind, hydro, thermal power generation and solar power plants, as well as in electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other areas. While lithium batteries have made great strides, higher requirements have also been placed on their energy retention rate and energy density.

[0003] Therefore, improving the energy retention rate and initial specific capacity of batteries is an urgent problem to be solved. Summary of the Invention

[0004] This application is made in view of the above-mentioned issues, and its purpose is to provide positive electrode active materials, battery cells, batteries and power devices, wherein the energy retention rate and initial specific capacity of the battery can be improved.

[0005] The first aspect of this application provides a positive electrode active material, comprising: a matrix, wherein the chemical formula of the matrix is ​​Li[Li] x Ni a Co b Mn c M d O2, M includes at least one of Mg, Nb, Cr, Ce, Fe, Ta, B, Al, V, Ti, Zr, Sn, P, and Mo, wherein x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, and d≥0; the coating layer is disposed on the surface of the substrate, and the coating layer includes a boron-containing alloy.

[0006] In this embodiment, the positive electrode active material includes a matrix and a coating layer disposed on the surface of the matrix; further, the chemical formula of the matrix is ​​Li[Li x Ni a Co b Mn c M dO2, M includes at least one of Mg, B, Al, V, Ti, Zr, Sn, La, P and Mo, and x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, d≥0, the coating layer is a boron-containing alloy. By setting a boron-containing alloy coating layer on the substrate surface, the coating layer forms a molten fluid state at high temperature, has good wettability at grain boundaries with high surface energy, and can be uniformly distributed on the substrate; and the boron-containing alloy has high electronic conductivity, which can not only protect the di-coordinated oxygen atoms on the substrate grain boundaries, but also improve the migration kinetics of lithium ions on the surface of the positive electrode active material, thereby accelerating the migration speed of active lithium ions in the battery, reducing energy loss, decay and polarization in the battery during long cycles, and thus improving the energy retention rate and initial specific capacity of the battery.

[0007] In some embodiments, the boron-containing alloy comprises boron and a transition metal, wherein the transition metal comprises at least one of Co, Hf, Zr, and Ti.

[0008] In this embodiment, the boron-containing alloy can enhance the migration kinetics of lithium ions on the surface of the positive electrode active material, thereby reducing energy loss and degradation of the lithium battery during long cycles. By incorporating transition metals and boron into the boron-containing alloy, the compound composed of transition metals and boron possesses good structural stability and high-temperature resistance, which can further improve the energy retention rate of the battery.

[0009] In some embodiments, the boron-containing alloy comprises CoB n HfB n ZrB n TiB n WB n At least one of them, 0 < n ≤ 3.

[0010] In this embodiment of the application, CoB n HfB n ZrB n TiB n WB n Where 0 < n ≤ 3, it not only possesses good structural stability and high-temperature resistance, but also has readily available raw materials and is relatively simple to prepare. By making CoB... n HfB n ZrB n TiB n WB n Where 0 < n ≤ 3, it is set as a coating layer on the surface of the substrate and together with the substrate forms the positive electrode active material, which can not only improve the energy retention rate of the battery, but also facilitate its wide application.

[0011] In some embodiments, the boron-containing alloy further includes lithium and oxygen.

[0012] In this embodiment, when a boron-containing alloy comprising transition metals, lithium, and oxygen is deposited as a coating layer on the substrate surface and used together as the positive electrode active material of the lithium battery, the coating layer releases lithium ions during long-term battery cycling. These lithium ions can participate in the battery reaction as active lithium ions, compensating for the lithium ion consumption during long-term cycling, further reducing battery degradation during long-term cycling and improving the battery's energy retention rate.

[0013] In some embodiments, the microstress of the positive electrode active material ranges from 0.05% to 1%, and optionally from 0.1% to 0.5%.

[0014] In this embodiment, to improve lithium-ion migration kinetics, a boron-containing alloy coating layer is applied to the surface of the substrate, and both are used as the positive electrode active material of the battery. However, current positive electrode active materials exhibit significant stress differences within their micropores, making them prone to fatigue. This makes lithium-ion insertion / extraction increasingly difficult, leading to battery energy decay. By maintaining the micro-stress range of the positive electrode active material at 0.05%-1%, particularly 0.1%-0.5%, the overall flexibility of the positive electrode active material can be improved. This makes lithium-ion insertion / extraction easier during long-term battery cycling, further reducing battery energy decay.

[0015] In some embodiments, the peak intensity ratio of Mn-O to Ni-O in the positive electrode active material is 20-50, and optionally 25-35.

[0016] In this embodiment, by maintaining the peak intensities of Mn-O and Ni-O in the positive electrode active material at 20-50, especially 25-35, the surface of the positive electrode active material can be kept relatively stable, thereby improving the energy retention of the battery during long cycles.

[0017] In some embodiments, the coating layer has a coating amount of 200-15000 ppm, optionally 500-10000 ppm, based on the total weight of the metal elements in the coating layer relative to the substrate.

[0018] In this embodiment of the application, by maintaining the coating amount of the coating layer in the positive electrode active material at 200-15000ppm, especially 500-10000ppm, the coating layer can perform its function, while saving costs and avoiding unnecessary waste of the coating layer.

[0019] In some embodiments, the surface residual alkali of the positive electrode active material is 200-2000 ppm (w / w), and optionally, it is 500-1000 ppm (w / w).

[0020] In this embodiment, when the alkaline content in the positive electrode active material is too high, it will lead to a low initial coulombic efficiency and discharge specific capacity of the battery. By making the surface residual alkali of the positive electrode active material 200-2000 ppm (w / w), especially 500-1000 ppm (w / w), the initial specific capacity of the battery can be improved.

[0021] In some embodiments, the specific surface area of ​​the positive electrode active material is 0.5-9 m². 2 / g, optionally, is 0.7-3.5m 2 / g.

[0022] In this embodiment, appropriately reducing the specific surface area of ​​the positive electrode active material enriches its porosity, which helps improve the initial specific capacity of the battery. However, if the specific surface area is too large, the positive electrode active material becomes porous, which is not conducive to the intercalation and deintercalation of metal ions. By making the specific surface area of ​​the positive electrode active material 0.5-9m², 2 / g, especially 0.7-3.5m 2 / g, which helps metal ions to be properly inserted and extracted in the positive electrode active material.

[0023] In some embodiments, the oxygen defect of the positive electrode active material is 1.5-4, and optionally, 1.8-3.5.

[0024] In this embodiment, oxygen defects in the positive electrode active material can alter the local electronic structure of the material, thereby generating active lithium-ion adsorption sites and increasing the lithium-ion transport rate. By setting the oxygen defect ratio of the positive electrode active material to 1.5-4, particularly 1.8-3.5, it helps to further improve the lithium-ion migration kinetics, thereby further improving the cycle performance and energy density of the battery.

[0025] In some embodiments, the volume average particle size Dv50 of the positive electrode active material is 2-20 μm, and optionally, it is 5-12 μm.

[0026] In this embodiment of the application, by maintaining the volume average particle size Dv50 of the positive electrode active material at 2-20 μm, especially 5-12 μm, the battery can have a high discharge specific capacity and first coulombic efficiency, and the possibility of the positive electrode active material becoming porous, in which lithium ions are unstable to be inserted and extracted.

[0027] In some embodiments, the compaction density of the positive electrode active material is 2-3.5 g / cm³. 3 Optionally, it is 2.6-3.5 g / cm³. 3 .

[0028] In this embodiment, if the compaction density of the positive electrode active material is too low, the electrolyte may seep into the positive electrode active material, leading to severe side reactions and causing significant battery degradation during long cycles. By setting the compaction density of the positive electrode active material to 2-3.5 g / cm³, [further improvements can be achieved]. 3 Especially at 2.6-3.5 g / cm³ 3 This helps to further improve the battery's energy retention rate.

[0029] A second aspect of this application provides a method for preparing a positive electrode active material, comprising the following steps: providing a matrix, wherein the chemical formula of the matrix is ​​Li[Li] x Ni a Co b Mn c M d O2, M includes at least one of Mg, Nb, Cr, Ce, Fe, Ta, B, Al, V, Ti, Zr, Sn, P, and Mo, wherein x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, and d≥0; the matrix is ​​dispersed in an acidic solution and stirred to obtain a matrix mixture solution, optionally, the pH of the acidic solution is 1-3; the matrix mixture solution is solidified and dried to obtain a matrix mixture powder; the matrix mixture powder is mixed with a coating layer powder to obtain a positive electrode active material precursor, the coating layer powder including a boron-containing alloy; the positive electrode active material precursor is sintered to obtain the positive electrode active material, the positive electrode active material including: the matrix, the chemical formula of the matrix being Li[Li x Ni a Co b Mn c M d O2, M includes at least one of Mg, Nb, Cr, Ce, Fe, Ta, B, Al, V, Ti, Zr, Sn, P, and Mo, wherein x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, and d≥0; the coating layer is disposed on the surface of the substrate, and the coating layer includes the boron-containing alloy.

[0030] In this embodiment, by treating the substrate in an acidic solution with a pH of 1-3 and then mixing it with the coating powder, the residual alkali on the surface of the substrate can be removed in a gentler way to avoid dissolving the active material in the positive electrode active material. This helps to improve the specific capacity of the battery and thus improve the energy density of the battery.

[0031] In some embodiments, the acid in the acidic solution includes at least one of sulfuric acid, nitric acid, ammonium persulfate, citric acid, oxalic acid, sodium citrate, ammonium citrate, hydrogen citrate, fruit acid, salicylic acid, succinic acid, or succinic anhydride.

[0032] In this embodiment, the acid in the acidic solution includes at least one of sulfuric acid, nitric acid, ammonium persulfate, citric acid, oxalic acid, sodium citrate, ammonium citrate, hydrogen citrate, fruit acid, salicylic acid, succinic acid, or succinic anhydride. That is, the matrix is ​​treated in an acidic solution containing any of the above acids. These acidic solutions are relatively mild and will not dissolve the active substances in the matrix.

[0033] In some embodiments, the acidic solution further includes ethanol or water.

[0034] In this embodiment, the acidic solution also includes ethanol or water. Both ethanol and water are good solvents for dissolving acids such as succinic acid and succinic anhydride. By including ethanol or water in the acidic solution, acids such as succinic acid and succinic anhydride can be dissolved uniformly and thoroughly, thereby ensuring uniform matrix treatment.

[0035] In some embodiments, the mass ratio of the acidic solution to the matrix is ​​6-35, and optionally, 10-20.

[0036] In the embodiments of this application, acids such as succinic acid and succinic anhydride are dissolved in ethanol or water to form an acidic solution for treating the substrate. By making the mass ratio of the acidic solution to the substrate 6-35, especially 10-20, the residual alkali on the substrate surface can be fully treated.

[0037] In some embodiments, the acid in the acidic solution has a mass fraction of 0.1%-30%, optionally 10%-20%.

[0038] In the embodiments of this application, by making the mass fraction of acid in the acidic solution 0.1%-30%, especially 10%-20%, residual alkali on the substrate surface can be removed in a gentler manner.

[0039] In some embodiments, sintering the positive electrode active material precursor includes sintering the positive electrode active material precursor in an oxygen atmosphere or an inert gas atmosphere.

[0040] In the embodiments of this application, unnecessary side reactions can be avoided by sintering the positive electrode active material precursor in an oxygen atmosphere or an inert gas atmosphere.

[0041] In some embodiments, the sintering temperature in the inert gas atmosphere is 250-400°C.

[0042] In this embodiment of the application, when using inert gas to sinter the positive electrode active material precursor, maintaining the sintering temperature at 250-400℃ can ensure that the positive electrode active material precursor is sintered completely.

[0043] In some embodiments, the sintering temperature in an oxygen atmosphere is 500-700°C.

[0044] In the embodiments of this application, when oxygen is used to sinter the positive electrode active material precursor, maintaining the sintering temperature at 500-700℃ can ensure that the positive electrode active material precursor is sintered completely.

[0045] In some embodiments, the sintering time is 3-10 hours.

[0046] In this embodiment of the application, by sintering the positive electrode active material precursor for 3-10 hours, the positive electrode active material precursor can be completely sintered.

[0047] The third aspect of this application provides a battery cell including the positive electrode active material described in any embodiment of the first aspect of this application or the positive electrode active material prepared by the method for preparing the positive electrode active material described in the second aspect.

[0048] A fourth aspect of this application provides a battery comprising the battery cell described in the third aspect of this application.

[0049] The fifth aspect of this application provides an electrical device including the battery described in the fourth aspect of this application. Attached Figure Description

[0050] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced 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.

[0051] Figure 1 This is a schematic diagram of the structure of the positive electrode active material according to one embodiment of this application;

[0052] Figure 2 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0053] Figure 3 This is a schematic diagram of the structure of a battery cell according to another embodiment of this application;

[0054] Figure 4 This is a schematic diagram of the structure of a battery according to one embodiment of this application;

[0055] Figure 5 This is a schematic diagram of a vehicle according to one embodiment of this application. Detailed Implementation

[0056] The embodiments of the positive electrode active material, battery cell, battery, and power device of this application are described in detail below with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of matters well-known to the public or repeated descriptions of actually identical structures may be omitted. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0057] 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 specific 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 expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. 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.

[0058] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0059] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0060] Unless otherwise specified, all steps of 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 method may also include step (c), indicating 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.

[0061] 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.

[0062] The terms “above,” “below,” “greater than,” or “less than” used in this application include the number itself, such as “at least one” meaning one or more, and “at least one of A and B” meaning “A,” “B,” or “A and B.”

[0063] 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).

[0064] Lithium-ion batteries are widely used in consumer electronics due to their high energy density, high power density, and long cycle life. In recent years, with the continuous development of electric vehicles and energy storage systems, the requirements for batteries have been constantly increasing. Therefore, developing large-scale energy storage systems with high initial specific capacity and stable energy retention is particularly important.

[0065] For some existing cathode materials, LiCoO2's actual usable capacity is only about half of its theoretical capacity due to the strong oxidation of the electrolyte during deep charging and the structural damage caused by excessive delithiation; LiNi 1 / 3 Co 1 / 3 Mn 1 / 3O2 and LiNi 1 / 2 Mn 1 / 2 While O2 and other substances have reduced material costs and toxicity and significantly improved material safety, the actual specific capacity of these layered materials has not seen major breakthroughs; three-dimensional tunnel structure spinel cathode materials, such as LiMnO4 and LiNi... 0.5 Mn 1.5 While O4 and polyanionic cathode materials offer high safety performance, their theoretical specific capacity falls far short of the performance requirements for cathode materials in high-energy-density lithium batteries. Therefore, layered lithium-rich manganese-based materials with a theoretical capacity exceeding 230 mAh / g have become one of the important candidate cathode materials for next-generation lithium batteries.

[0066] However, lithium-rich manganese-based cathode materials have low electronic conductivity, leading to severe battery polarization during cycling and rapid energy decay, especially during long cycles. Furthermore, lithium-rich manganese-based cathode materials also result in low initial specific capacity in lithium-ion batteries. These drawbacks have become technical bottlenecks limiting the application of lithium-rich manganese-based cathode materials. To address the rapid energy decay, existing technologies mostly employ conductive carbon coating; however, this method may reduce manganese from the lithium-rich manganese base, causing structural distortion and affecting its stability. To address the low initial specific capacity, existing technologies mostly treat the lithium-rich manganese base with strong acids; however, this method leaches active lithium from the material surface, reducing the battery's energy density. Therefore, developing large-scale energy storage systems with high initial specific capacity and stable energy retention during cycling is particularly important.

[0067] The following description, with reference to the accompanying drawings, illustrates the positive electrode active material, battery cell, battery, and power device of this application.

[0068] [Positive electrode active material]

[0069] The first aspect of this application provides a positive electrode active material. Figure 1 This is a schematic diagram of the structure of a positive electrode active material according to an embodiment of this application. The positive electrode active material 31 includes a matrix, the chemical formula of which is Li[Li] x Ni a Co b Mn c M d O2, M includes at least one of Mg, Nb, Cr, Ce, Fe, Ta, B, Al, V, Ti, Zr, Sn, P, and Mo, wherein x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, and d≥0; cladding layer 312 is disposed on the surface of substrate 311, and cladding layer 312 includes a boron-containing alloy.

[0070] Research has shown that coating the surface of the substrate 311 with a boron-containing alloy coating layer 312 can not only improve the energy retention rate of the battery, but also increase the initial specific capacity of the battery.

[0071] A coating layer 312, made of a boron-containing alloy, is formed on the surface of the substrate 311. This coating layer 312 forms a molten fluid state at high temperatures, exhibiting good wettability at grain boundaries with high surface energy, and can be uniformly distributed on the substrate 311. Furthermore, the boron-containing alloy possesses high electronic conductivity, which not only effectively protects the dicoordinated cations at the grain boundaries of the substrate 311 but also enhances the migration kinetics of lithium ions on the surface of the positive electrode active material 31. This accelerates the migration rate of active lithium ions in the battery, reduces energy loss, degradation, and polarization during long-term cycling, and ultimately improves the battery's energy retention rate and initial specific capacity.

[0072] In some embodiments, the boron-containing alloy comprises boron and a transition metal, wherein the transition metal comprises at least one of Co, Hf, Zr, and Ti.

[0073] In the above scheme, by making the boron-containing alloy include transition metals and boron, the compound composed of transition metals and boron has good structural stability and high temperature resistance, which can further improve the energy retention rate of the battery.

[0074] In some embodiments, the boron-containing alloy includes CoB n HfB n ZrB n TiB n WB n At least one of them, 0 < n ≤ 3.

[0075] In the above scheme, by making CoB n HfB n ZrB n TiB n WB n Where 0 < n ≤ 3, it serves as a coating layer 312 on the surface of the substrate 311, and together with the substrate 311, forms the positive electrode active material 31. CoB n HfB n ZrB n TiB n WB n It not only has good structural stability and high temperature resistance, but also the raw materials are easy to obtain and the preparation is relatively simple. This can improve the cycle performance of the battery and facilitate its wide application.

[0076] In some embodiments, the boron-containing alloy also includes lithium and oxygen.

[0077] In the above scheme, when a boron-containing alloy comprising transition metals, lithium, and oxygen is disposed as a coating layer 312 on the surface of the substrate 311 and together they serve as the positive electrode active material 31 of the lithium battery, the coating layer releases lithium ions during long-term battery cycling. These lithium ions can participate in the battery reaction as active lithium ions, compensating for the lithium ion consumption during long-term cycling, further reducing battery degradation during long-term cycling and improving battery cycle performance.

[0078] In some embodiments, the microstress of the positive electrode active material 31 ranges from 0.05% to 1%, and optionally from 0.1% to 0.5%.

[0079] In the above scheme, by maintaining the micro-stress range of the positive electrode active material 31 within 0.05%-1%, especially 0.1%-0.5%, the overall flexibility of the positive electrode active material can be improved, preventing fatigue phenomena in the positive electrode active material 31 that would make lithium ion insertion / extraction increasingly difficult. In other words, during long-term battery cycling, lithium ion insertion / extraction in the positive electrode active material becomes easier, thereby further reducing battery capacity decay and improving cycle performance.

[0080] It should be noted here that the micro-stress of a material refers to the stress between the microstructures of the material. Its scale is on the same order of magnitude as the grain size, maintaining equilibrium within or between grains.

[0081] In some embodiments, the peak intensity ratio of Mn-O to Ni-O in the positive electrode active material is 20-50, and optionally 25-35.

[0082] In the above scheme, by keeping the peak intensities of Mn-O and Ni-O in the positive electrode active material between 20-50, especially 25-35, the surface of the positive electrode active material can be kept strong, thereby improving the long-cycle performance stability of the battery.

[0083] In some embodiments, the coating layer 312 has a coating amount of 200-15000 ppm, optionally 500-10000 ppm, based on the total weight of the metal elements in the coating layer 312 relative to the substrate 311.

[0084] In the above scheme, by maintaining the coating amount of the coating layer 312 in the positive electrode active material 31 at 200-15000ppm, especially 500-10000ppm, the coating layer 312 can perform its function, while saving costs and avoiding unnecessary waste of the coating layer 312.

[0085] In some embodiments, the surface residual alkali of the positive electrode active material 31 is 200-2000 ppm (w / w), and optionally, it is 500-1000 ppm (w / w).

[0086] In the above scheme, by making the surface residual alkali of the positive electrode active material 31 200-2000ppm (w / w), especially 500-1000ppm (w / w), the initial coulombic efficiency and discharge specific capacity of the battery can be improved, thereby increasing the energy density of the battery.

[0087] In some embodiments, the specific surface area of ​​the positive electrode active material 31 is 0.5-9 m². 2 / g, optionally, is 0.7-3.5m 2 / g.

[0088] In the above scheme, the specific surface area of ​​the positive electrode active material 31 is made to be 0.5-9 m². 2 / g, especially 0.7-3.5m 2 / g, which helps lithium ions to be properly inserted and extracted in the positive electrode active material 31.

[0089] In some embodiments, the oxygen vacancy of the positive electrode active material 31 is 1.5-4, and optionally, 1.8-3.5.

[0090] In the above scheme, by making the oxygen defect of the positive electrode active material 31 1.5-4, especially 1.8-3.5, it helps to further improve the migration kinetics of lithium ions, thereby further improving the cycle performance and energy density of the battery.

[0091] It should be noted here that oxygen defects refer to defects in the oxygen element within oxide materials. These defects can be quantitative or morphological.

[0092] In some embodiments, the volume average particle size Dv50 of the positive electrode active material 31 is 2-20 μm, and optionally, it is 5-12 μm.

[0093] In the above scheme, by maintaining the volume average particle size Dv50 of the positive electrode active material 31 at 2-20 μm, especially 5-12 μm, the battery can have a high discharge specific capacity and first coulombic efficiency, and the positive electrode active material 31 can be prevented from becoming loose, which would cause lithium ions to be unstable in insertion and extraction.

[0094] It should be noted that the volume average particle size Dv50 here refers to the fact that in the positive electrode active material 31, particles larger than and smaller than this particle size each account for 50%.

[0095] In some embodiments, the compaction density of the positive electrode active material 31 is 2-3.5 g / cm³. 3Optionally, it is 2.6-3.5 g / cm³. 3 .

[0096] In the above scheme, if the compaction density of the positive electrode active material 31 is too low, the electrolyte may seep into the positive electrode active material 31, leading to serious side reactions and causing severe battery degradation during long cycles. By adjusting the compaction density of the positive electrode active material 31 to 2-3.5 g / cm³, [the solution can be achieved]. 3 Especially at 2.6-3.5 g / cm³ 3 This will help to further improve the energy density of the battery.

[0097] This application also provides a method for preparing a positive electrode active material, the method comprising:

[0098] Provide a matrix with the chemical formula Li[Li] x Ni a Co b Mn c M d O2, M includes at least one of Mg, Nb, Cr, Ce, Fe, Ta, B, Al, V, Ti, Zr, Sn, P, and Mo, wherein x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, and d≥0.

[0099] The matrix is ​​dispersed in an acidic solution and stirred to obtain a matrix mixture solution with a pH of 2-3.

[0100] The matrix mixture solution is solidified and dried to obtain the matrix mixture powder.

[0101] The matrix powder and the coating powder are mixed to obtain the precursor of the positive electrode active material.

[0102] The positive electrode active material precursor is sintered to obtain the positive electrode active material, which includes: a matrix with the chemical formula Li[Li] x Ni a Co b Mn c M d O2, M includes at least one of Mg, Nb, Cr, Ce, Fe, Ta, B, Al, V, Ti, Zr, Sn, P, and Mo, wherein x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, and d≥0; the coating layer is disposed on the surface of the substrate, and the coating layer includes a boron-containing alloy.

[0103] In the above scheme, by treating the substrate in an acidic solution with a pH of 1-3 and then mixing it with the coating powder, the residual alkali on the surface of the substrate can be removed in a gentler way to avoid dissolving the active material in the positive electrode active material. This helps to improve the specific capacity of the battery and thus improve the energy density of the battery.

[0104] In some embodiments, the acid in the acidic solution includes at least one of sulfuric acid, nitric acid, ammonium persulfate, citric acid, oxalic acid, sodium citrate, ammonium citrate, hydrogen citrate, fruit acid, salicylic acid, succinic acid, or succinic anhydride.

[0105] In the above scheme, the acid in the acidic solution includes at least one of sulfuric acid, nitric acid, ammonium persulfate, citric acid, oxalic acid, sodium citrate, ammonium citrate, hydrogen citrate, fruit acid, salicylic acid, succinic acid, or succinic anhydride. That is, the matrix is ​​treated in an acidic solution containing any of the above acids. These acidic solutions are relatively mild and will not dissolve the active substances in the matrix.

[0106] In some embodiments, the acidic solution also includes ethanol or water.

[0107] In the above scheme, the acidic solution also includes ethanol or water. Both ethanol and water are good solvents for dissolving acids such as succinic acid and succinic anhydride. By including ethanol or water in the acidic solution, the acids such as succinic acid and succinic anhydride can be dissolved evenly and completely, thereby ensuring uniform matrix treatment.

[0108] In some embodiments, the mass ratio of the acidic solution to the matrix is ​​6-35, and optionally, 10-20.

[0109] In the above scheme, by making the mass ratio of acidic solution to substrate 6-35, especially 10-20, the residual alkali on the substrate surface can be fully treated.

[0110] In some embodiments, the mass fraction of the acid in the acidic solution is 0.1%-30%, optionally 10%-20%.

[0111] In the above scheme, by making the mass fraction of acid in the acidic solution 0.1%-30%, especially 10%-20%, residual alkali on the substrate surface can be removed in a gentler manner.

[0112] In some embodiments, the positive electrode active material precursor is sintered in an oxygen atmosphere or an inert gas atmosphere.

[0113] In the above scheme, unnecessary side reactions can be avoided by sintering the positive electrode active material precursor in an oxygen atmosphere or an inert gas atmosphere.

[0114] In some embodiments, the sintering temperature in an inert gas atmosphere is 250-400°C.

[0115] In the above scheme, when using inert gas to sinter the positive electrode active material precursor, keeping the sintering temperature at 250-400℃ can ensure that the positive electrode active material precursor is sintered completely.

[0116] In some embodiments, the sintering temperature in an oxygen atmosphere is 500-700°C.

[0117] In the above scheme, when oxygen is used to sinter the positive electrode active material precursor, keeping the sintering temperature at 500-700℃ can ensure that the positive electrode active material precursor is sintered completely.

[0118] In some implementations, the sintering time is 3-10 hours.

[0119] In the above scheme, by sintering the positive electrode active material precursor for 3-10 hours, the positive electrode active material precursor can be completely sintered.

[0120] [Positive electrode plate]

[0121] The positive electrode includes 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 includes the positive electrode active material described in any of the above embodiments.

[0122] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0123] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0124] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0125] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0127] [Negative electrode plate]

[0128] 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, the negative electrode film layer including a negative electrode active material.

[0129] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0130] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0131] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0132] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0133] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0134] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0135] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0136] Electrolyte

[0137] The electrolyte plays a role in conducting ions between the positive and negative electrode plates.

[0138] In some embodiments, the electrolyte further includes a solvent. The solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0139] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0140] [Isolation membrane]

[0141] In some embodiments, the lithium battery also includes a separator. 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.

[0142] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0143] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0144] In some embodiments, the lithium battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0145] In some implementations, the outer packaging of the lithium battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the lithium battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0146] This application does not impose any particular limitation on the shape of the lithium battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 This is an example of a square-structured battery cell, 300.

[0147] Furthermore, this application does not limit the type of lithium battery; the battery cell 300 can be a lithium-ion battery or a lithium metal battery. The following embodiments use a lithium-ion battery as an example for illustration.

[0148] Figure 3 This is a schematic diagram of the structure of a battery cell according to another embodiment of this application. In some embodiments, refer to Figure 3 The outer packaging may include a housing 31 and a cover plate 33. The housing 31 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 31 has an opening communicating with the receiving cavity, and the cover plate 33 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and solid electrolyte may be formed into electrode assemblies 32 via a winding process or a stacking process. The electrode assemblies 32 are encapsulated within the receiving cavity. The number of electrode assemblies 32 contained in the battery cell 300 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0149] Figure 4 This is a schematic diagram of the structure of a battery 500 according to one embodiment of this application. Figure 4 As shown, in battery 500, multiple battery cells 300 can be arranged sequentially along the length of battery 500. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 300 can be fixed in place using fasteners.

[0150] Please continue to refer to Figure 4 The battery 500 may include a battery box and a plurality of battery cells 300 disposed within the battery box. The battery box includes an upper box 501 and a lower box 502, the upper box 501 covering the lower box 502 to form a closed space for accommodating the battery cells 300. The plurality of battery cells 300 may be arranged in any manner within the battery box.

[0151] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0152] In some embodiments, the battery modules described above can also be assembled into a battery. The number of battery modules contained in the battery can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery.

[0153] In addition, this application also provides an electrical device, which includes at least one of the positive electrode active material, battery cell, or battery provided in this application. The battery cell or battery 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 include, 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.

[0154] For example, Figure 5 This is a structural schematic diagram of a vehicle according to one embodiment of this application. For example... Figure 5 As shown, vehicle 1 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A motor 400, a controller 600, and a battery 500 can be installed inside vehicle 1. The controller 600 controls the battery 500 to supply power to the motor 400. For example, the battery 500 can be installed at the bottom, front, or rear of vehicle 1. The battery 500 can be used to power vehicle 1; for example, it can serve as the operating power source for the vehicle 1's electrical system, such as for the power requirements of starting, navigation, and operation. In another embodiment of this application, the battery 500 can not only serve as the operating power source for vehicle 1 but also as the driving power source, replacing or partially replacing gasoline or natural gas to provide driving power to vehicle 1.

[0155] As the electrical device, the positive electrode active material, battery cell or battery can be selected according to its usage requirements.

[0156] The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the battery, battery cells or batteries can be used.

[0157] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0158] [Example]

[0159] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0160] [Example 1]

[0161] I. Preparation of Lithium-ion Batteries

[0162] 1.1) Preparation of the positive electrode sheet

[0163] 1.11) Preparation of the matrix: Ni 0.35 Co 0.05 Mn 0.60 (OH)₂ and lithium hydroxide were weighed at a molar ratio of 1.0:1.25 and mixed in a high-speed mixer. The mixed material was sintered in air for 10–15 h at a sintering temperature of 780–900 °C at a heating rate of 2–5 °C / min to obtain a cathode intermediate product 1 after one sintering. The cathode intermediate product 1 was mechanically ground and sieved to obtain a lithium-rich manganese-based cathode material matrix, hereinafter referred to as the matrix, with the chemical formula Li[Li]. 0.11 Ni 0.31 Co 0.04 Mn 0.54 O2.

[0164] 1.12) Preparation of positive electrode active material: Ammonium citrate was dissolved in deionized water to prepare an acidic solution with a pH of 2.57; then, the solution was stirred and acid-washed with a matrix weighed according to a certain liquid-solid ratio for 0.5 h, while stirring at a rate of 900 r / min; after acid washing, the solution was filtered, rinsed with deionized water, filtered again, and then dried at 80℃ for 10 h; after mechanical grinding and sieving, a matrix mixed powder was obtained; the matrix mixed powder obtained in the above steps and cobalt boride (CoB) were mixed at a mass ratio of 1:0.003 and placed in a furnace, and then subjected to a second calcination in an air atmosphere for 10 h at a sintering temperature of 450℃ and a heating rate of 2℃ / min. After sintering, the material was mechanically ground and sieved to obtain a lithium sodium composite manganese-based positive electrode active material. The positive electrode active material exhibits a micro-stress of 0.30%, a peak intensity ratio of Mn-O to Ni-O of 30, a CoB coating amount of 2000 ppm, a surface residual alkali content of 500 ppm (w / w), and a specific surface area of ​​0.8 m². 2 / g, oxygen vacancies 2, particle size 7μm.

[0165] 1.13) Preparation of the positive electrode sheet: The positive active material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) prepared above were mixed in a mass ratio of 96:2:2 for 30 minutes for a second dry mixing process; N-methylpyrrolidone (NMP) solvent was added, and the mixture was rapidly stirred under vacuum to form a positive electrode slurry. The positive electrode slurry was uniformly coated on both sides of an aluminum foil with a thickness of 12 μm. The coated electrode sheet was dried in an oven at 100-130℃ for half an hour to obtain the positive electrode sheet. The positive active material loading of the positive electrode sheet was 21.5 mg / cm³. 2 .

[0166] 1.2) Preparation of the negative electrode: Artificial graphite (anode active material), hard carbon, acetylene black (conductive agent), styrene-butadiene rubber (SBR) (binder), and sodium carboxymethyl cellulose (CMC) (thickener) were prepared in a weight ratio of 90:5:2:2:1. The mixture was thoroughly stirred and mixed evenly in a deionized water solvent system to obtain the negative electrode slurry. The negative electrode slurry was coated onto copper foil, dried, and cold-pressed to obtain the negative electrode sheet.

[0167] 1.3). Separator: Polyethylene (PE) film is used as the separator.

[0168] 1.4) Electrolyte: 1 mol / L LiPF6 / (EC+EMC+DMC), with the volume ratio of EC, EMC and DMC in the solvent being 1:1:1.

[0169] 1.5) Assembly of lithium-ion batteries: The positive electrode, separator, and negative electrode are stacked and wound in sequence to obtain the electrode assembly; the electrode assembly is installed in an aluminum shell, the top cover is welded, and after drying, the electrolyte is injected. After standing, formation, sealing and welding, aging, and capacity testing, the lithium-ion battery is obtained.

[0170] [Example 2]

[0171] The preparation of the lithium-ion battery in Example 2 is basically the same as that in Example 1, except that in the preparation of the positive electrode active material, the matrix material and TiB2 are mixed at a mass ratio of 1:0.003.

[0172] [Example 3]

[0173] The preparation of the lithium-ion battery in Example 3 is basically the same as that in Example 1, except that in the preparation of the positive electrode active material, the matrix material and HfB2 are mixed at a mass ratio of 1:0.003.

[0174] [Example 4]

[0175] The preparation of the lithium-ion battery in Example 4 is basically the same as that in Example 1, except that the micro-stress of the positive electrode active material is 0.10%.

[0176] [Example 5]

[0177] The preparation of the lithium-ion battery in Example 5 is basically the same as that in Example 1, except that the micro-stress of the positive electrode active material is 0.50%.

[0178] [Example 6]

[0179] The preparation of the lithium-ion battery in Example 6 is basically the same as that in Example 1, except that the peak intensity ratio of Mn-O to Ni-O in the positive electrode active material is 35.

[0180] [Example 7]

[0181] The preparation of the lithium-ion battery in Example 7 is basically the same as that in Example 1, except that the peak intensity ratio of Mn-O to Ni-O in the positive electrode active material is 25.

[0182] [Example 8]

[0183] The preparation of the lithium-ion battery in Example 8 was basically the same as that in Example 1, except that the CoB coating amount was 1000 ppm.

[0184] [Example 9]

[0185] The preparation of the lithium-ion battery in Example 9 was basically the same as that in Example 1, except that the CoB coating amount was 5000ppm.

[0186] [Example 10]

[0187] The preparation of the lithium-ion battery in Example 10 was basically the same as that in Example 1, except that the residual alkali on the surface of the positive electrode active material was 800 ppm (w / w).

[0188] [Example 11]

[0189] The preparation of the lithium-ion battery in Example 11 was basically the same as that in Example 1, except that the residual alkali on the surface of the positive electrode active material was 1000 ppm (w / w).

[0190] [Example 12]

[0191] The preparation of the lithium-ion battery in Example 12 was basically the same as that in Example 1, except that the specific surface area of ​​the positive electrode active material was 2.3 m². 2 / g.

[0192] [Example 13]

[0193] The preparation of the lithium-ion battery in Example 13 was basically the same as that in Example 1, except that the specific surface area of ​​the positive electrode active material was 1.5 m². 2 / g.

[0194] [Example 14]

[0195] The preparation of the lithium-ion battery in Example 14 was basically the same as that in Example 1, except that the specific surface area of ​​the positive electrode active material was 3m². 2 / g.

[0196] [Example 15]

[0197] The preparation of the lithium-ion battery in Example 15 is basically the same as that in Example 1, except that the oxygen defect of the positive electrode active material is 2.5.

[0198] [Example 16]

[0199] The preparation of the lithium-ion battery in Example 16 was basically the same as that in Example 1, except that the particle size of the positive electrode active material was 10 μm.

[0200] [Example 17]

[0201] The preparation of the lithium-ion battery in Example 17 is basically the same as that in Example 1, except for the preparation of the substrate material: Ni 0.35 Co 0.05 Mn 0.60(OH)₂, lithium hydroxide, and MgO were weighed in a molar ratio of 1.0:1.25:0.0025 and mixed in a high-speed mixer. The mixed material was sintered in air for 10-15 hours at a sintering temperature of 780-900℃ and a heating rate of 2-5℃ / min to obtain the cathode intermediate product 1 after one sintering. The cathode intermediate product 1 was mechanically ground and sieved to obtain the lithium-rich manganese-based cathode material matrix, hereinafter referred to as the matrix. The chemical formula of the matrix is ​​Li[Li 0.11 Ni 0.31 Co 0.04 Mn 0.535 Mg 0.005 O2.

[0202] [Example 18]

[0203] The preparation of the lithium-ion battery in Example 18 is basically the same as that in Example 17, except that in the preparation of the positive electrode active material, the matrix material and TiB2 are mixed at a mass ratio of 1:0.003.

[0204] [Example 19]

[0205] The preparation method of the lithium-ion battery in Example 19 is basically the same as that in Example 1, except for the preparation of the substrate material: Ni 0.35 Co 0.05 Mn 0.60 (OH)₂, lithium hydroxide, and MoS₂ were weighed in a molar ratio of 1.0:1.25:0.0025 and mixed in a high-speed mixer. The mixed material was sintered in air for 10-15 hours at a sintering temperature of 780-900℃ and a heating rate of 2-5℃ / min to obtain a cathode intermediate product 1 after one sintering. The cathode intermediate product 1 was mechanically ground and sieved to obtain a lithium-rich manganese-based cathode material matrix, hereinafter referred to as the matrix. The chemical formula of the matrix is ​​Li[Li 0.11 Ni 0.31 Co 0.04 Mn 0.535 Mo 0.005 O2.

[0206] [Example 20]

[0207] The preparation of the lithium-ion battery in Example 20 is basically the same as that in Example 1, except that the peak intensity ratio of Mn-O to Ni-O in the positive electrode active material is 10.

[0208] [Example 21]

[0209] The preparation of the lithium-ion battery in Example 21 is basically the same as that in Example 1, except that the peak intensity ratio of Mn-O to Ni-O in the positive electrode active material is 100.

[0210] [Example 22]

[0211] The preparation of the lithium-ion battery in Example 22 was basically the same as that in Example 1, except that the CoB coating amount was 100 ppm.

[0212] [Example 23]

[0213] The preparation of the lithium-ion battery in Example 23 was basically the same as that in Example 1, except that the CoB coating amount was 20,000 ppm.

[0214] [Comparative Example 1]

[0215] The preparation of the lithium-ion battery in Comparative Example 1 is basically the same as that in Example 1, except that the positive electrode active material is only the matrix material.

[0216] [Comparative Example 2]

[0217] The preparation of the lithium-ion battery in Comparative Example 2 was basically the same as that in Example 1, except that the matrix material and Cr2O3 were mixed at a mass ratio of 1:0.003 in the preparation of the positive electrode active material.

[0218] [Comparative Example 3]

[0219] The preparation of the lithium-ion battery in Comparative Example 3 was basically the same as that in Example 1, except that in the preparation of the positive electrode active material, the matrix material and MgO were mixed at a mass ratio of 1:0.003.

[0220] [Comparative Example 4]

[0221] The preparation of the lithium-ion battery in Comparative Example 4 was basically the same as that in Example 1, except that Ni was used in the preparation of the substrate. 0.29 Mn 0.71 (OH)₂ and lithium hydroxide were weighed at a molar ratio of 1.0:1.30 and mixed in a high-speed mixer to obtain a matrix with the chemical formula Li[Li]. 0.17 Ni 0.27 Mn 0.56 O2.

[0222] II. Characterization of Positive Electrode Active Materials

[0223] 2.1) Measurement of micro-stress: MS% = (β) hkl ×Cosθ hkl ) / (4sinθ hkl ), where θ hkl β represents the diffraction angle of the crystal plane of the lithium-sodium composite manganese-based cathode material (hkl) in the XRD diffraction pattern. hkl The value is the full width at half maximum (FWHM) of the crystal plane of the lithium-sodium composite manganese-based cathode material (hkl) in the XRD diffraction pattern.

[0224] 2.2) Peak intensity measurement of Mn-O and Ni-O: The method for confirming the peak intensity of Mn-O is the 600-620 cm⁻¹ peak in the infrared spectrum. -1 The method for confirming the intensity of the Ni-O peak is to examine the diffraction peak at 730-750 cm⁻¹ in the infrared spectrum. -1 The intensity of the diffraction peak.

[0225] 2.3) Measurement of residual alkali on the surface: Refer to GB / T 9736-2008 General Method for Determination of Acidity and Alkalinity of Chemical Reagents. Weigh 10-30g of powder, add 100ml of pure water and stir for 30min. After standing for 10min, filter and transfer a certain amount of filtrate. Use 0.05mol / L hydrochloric acid standard solution, drain the liquid to remove air bubbles from the burette, and select the corresponding sensor and program to start the potentiometric titration test.

[0226] 2.4) Measurement of specific surface area: Refer to GB / T 19587-2004 standard for details.

[0227] 2.41) Pretreatment: Take an appropriate amount of sample in a special sample tube, heat and degas for 2 hours, and weigh the total weight after cooling to room temperature. Subtract the mass of the sample tube to obtain the sample mass.

[0228] 2.42). Test: The sample tube is placed in the workstation and the amount of gas adsorbed on the solid surface under different adsorption pressures is measured at a constant low temperature. Based on the BET multilayer adsorption theory and its formula, the amount of monolayer adsorption of the sample is obtained, and the specific surface area of ​​the solid sample per unit mass is calculated.

[0229] 2.43) Adsorbed gas: nitrogen; Adsorption pressure points: 0.05, 0.10, 0.15, 0.20, 0.25, 0.30; Test atmosphere: high-purity liquid nitrogen atmosphere.

[0230] 2.5) Oxygen defect index test: The XRD spectrum of the test sample was scanned slowly (<2° / min) in the 35-50° range, and the image was processed by smoothing and filtering to obtain the diffraction peak areas I of the (101) crystal plane and the (012) crystal plane. 101 I 012 , through (I 101 / I 012 ) 0.5 To calculate the oxygen defect index.

[0231] 2.6) Measurement of volume average particle size Dv50: A Malvern 2000 (MasterSizer 2000) laser particle size analyzer was used; for details, refer to GB / T19077-2016 / ISO 13320:2009. Take an appropriate amount of the sample to be tested (the sample concentration should be 8-12% opacity), add 20 ml of deionized water, and simultaneously incubate for 5 min (53 kHz / 120 W) to ensure complete dispersion of the sample. Then, measure the sample according to the standard GB / T19077-2016 / ISO 13320:2009.

[0232] 2.7) Measurement of compaction density: Refer to GB / T 24533-2009 for details. Take a certain amount of powder and place it in a special compaction mold. Then place the mold on a compaction density instrument, set different pressures, and the thickness of the powder under different pressures (thickness after depressurization) can be read on the equipment. Calculate the compaction density using ρ = m / v.

[0233] Table 1. Specific parameters of Examples 1-23 and Comparative Examples 1-4

[0234]

[0235]

[0236] III. Battery Performance Testing

[0237] 3.1) Energy retention rate test

[0238] Under constant temperature conditions of 25℃, the voltage is charged to 4.45V at a 1C rate under a voltage range of 2.5-4.45V. Then, it is charged at a constant voltage of 4.45V until the current is ≤0.05mA. After standing for 5 minutes, it is discharged to 2.5V at a 1C rate. The discharge energy is recorded. The previous process is repeated to obtain the energy retention rate after 500 cycles. The energy retention rate = discharge energy in the first cycle / discharge energy at the specified number of cycles × 100%. The test results are shown in Table 2.

[0239] 3.2) Initial specific capacity test

[0240] Under constant temperature conditions of 25℃, the voltage is charged at 0.1C to 4.55V within the range of 2.5-4.55V. Then, it is charged at a constant voltage at 4.55V until the current is ≤0.05mA. After standing for 2 minutes, the charging capacity at this point is recorded as C0. Then, it is discharged at 0.1C to 2.5V. The discharge capacity at this point is the initial specific capacity, recorded as D0. Please refer to Table 2 for the test results.

[0241] Table 2 Battery performance of Examples 1-23 and Comparative Examples 1-4

[0242]

[0243]

[0244] As can be seen from Examples 1-23 and Comparative Example 1, the 500-cycle energy retention rate and initial specific capacity of the lithium-ion battery coated with boron alloy are higher than those of the uncoated lithium-ion battery. In other words, by coating the surface of the composite material with a coating layer, the energy retention rate and initial specific capacity of the lithium-ion battery can be improved.

[0245] As can be seen from Examples 1-3 and Examples 17-18, coating the surface of the substrate material with different boron-containing alloy materials can improve the energy retention rate and initial specific capacity of lithium-ion batteries.

[0246] As can be seen from Examples 1, 17 and 19, coating the surface of various matrix materials with a coating layer can improve the energy retention rate and initial specific capacity of lithium-ion batteries.

[0247] As can be seen from Examples 1, 6-7 and 20-21, maintaining the peak intensity ratio of Mn-O to Ni-O in the positive electrode active material of the lithium-ion battery within a suitable range, namely 20-50, is beneficial to improving the energy retention rate and initial specific capacity of the lithium-ion battery.

[0248] As can be seen from Examples 1, 8-9 and 22-23, maintaining the coating amount of the positive electrode active material in the lithium-ion battery within a suitable range, i.e., 200-15000ppm, is beneficial to improving the energy retention rate and initial specific capacity of the lithium-ion battery.

[0249] As can be seen from Examples 1-22 and Comparative Examples 1-3, coating the surface of the matrix material in the positive electrode active material with at least one of CoB, HfB2, and TiB2 is beneficial to further improve the energy retention rate and initial specific capacity of the lithium-ion battery.

[0250] As can be seen from Examples 1-23 and Comparative Example 4, the positive electrode active material contains the chemical formula Li[Li] x Ni a Co b Mn c M d O2, M includes at least one of Mg, Nb, Cr, Ce, Fe, Ta, B, Al, V, Ti, Zr, Sn, P, and Mo, wherein the matrix x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, and d≥0 is beneficial for further improving the energy retention rate and initial specific capacity of lithium-ion batteries.

[0251] As can be seen from the above embodiments and comparative examples, by coating the surface of the matrix material in the positive electrode active material with a coating layer, lithium-ion batteries can achieve both good energy retention and high initial specific capacity.

[0252] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are merely examples.

[0253] Any implementation method that has the same structure and performs the same function as the technical concept within the scope of this application is included in the scope of this application. Furthermore, without departing from the spirit of this application, various modifications that can be conceived by those skilled in the art to the implementation method, and other methods of constructing by combining some of the constituent elements of the implementation method, are also included in the scope of this application.

Claims

1. A positive electrode active material, comprising: The matrix, the chemical formula of which is Li[Li] x Ni a Co b Mn c M d O2, M includes at least one of Mg, Nb, Cr, Ce, Fe, Ta, B, Al, V, Ti, Zr, Sn, P, and Mo, wherein x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, and d≥0; A coating layer is disposed on the surface of the substrate, the coating layer comprising a boron-containing alloy; The peak intensity ratio of Mn-O to Ni-O in the positive electrode active material is 20-50.

2. The positive electrode active material according to claim 1, wherein, The boron-containing alloy comprises boron and a transition metal, wherein the transition metal comprises at least one of Co, Hf, Zr, and Ti.

3. The positive electrode active material according to claim 1 or 2, wherein, The boron-containing alloy includes CoB. n HfB n ZrB n TiB n WB n At least one of them, 0 < n ≤ 3.

4. The positive electrode active material according to any one of claims 1 to 3, wherein, The boron-containing alloy also includes lithium and oxygen.

5. The positive electrode active material according to any one of claims 1 to 4, wherein, The micro-stress of the positive electrode active material ranges from 0.05% to 1%.

6. The positive electrode active material according to any one of claims 1 to 5, wherein, The micro-stress range of the positive electrode active material is 0.1%-0.5%.

7. The positive electrode active material according to any one of claims 1 to 6, wherein, The peak intensity ratio of Mn-O to Ni-O in the positive electrode active material is 25-35.

8. The positive electrode active material according to any one of claims 1 to 7, wherein, The coating amount is 200-15000 ppm, based on the total weight of the metal elements in the coating relative to the substrate.

9. The positive electrode active material according to any one of claims 1-8, wherein, The coating amount is 500-10000 ppm, based on the total weight of the metal elements in the coating relative to the substrate.

10. The positive electrode active material according to any one of claims 1 to 9, wherein, The residual alkali on the surface of the positive electrode active material is 200-2000 ppm (w / w).

11. The positive electrode active material according to any one of claims 1 to 10, wherein, The residual alkali on the surface of the positive electrode active material is 500-1000 ppm (w / w).

12. The positive electrode active material according to any one of claims 1 to 11, wherein, The specific surface area of ​​the positive electrode active material is 0.5-9 m². 2 / g.

13. The positive electrode active material according to any one of claims 1 to 12, wherein, The specific surface area of ​​the positive electrode active material is 0.7-3.5 m². 2 / g.

14. The positive electrode active material according to any one of claims 1 to 13, wherein, The oxygen defect of the positive electrode active material is 1.5-4.

15. The positive electrode active material according to any one of claims 1 to 14, wherein, The oxygen defect of the positive electrode active material is 1.8-3.

5.

16. The positive electrode active material according to any one of claims 1 to 15, wherein, The volume average particle size Dv50 of the positive electrode active material is 2-20 μm.

17. The positive electrode active material according to any one of claims 1 to 16, wherein, The volume average particle size Dv50 of the positive electrode active material is 5-12 μm.

18. The positive electrode active material according to any one of claims 1 to 17, wherein, The compaction density of the positive electrode active material is 2-3.5 g / cm³. 3 .

19. The positive electrode active material according to any one of claims 1 to 18, wherein, The compaction density of the positive electrode active material is 2.6-3.5 g / cm³. 3 .

20. A method for preparing a positive electrode active material, comprising the following steps: Provide a matrix having the chemical formula Li[Li] x Ni a Co b Mn c M d O2, M includes at least one of Mg, Nb, Cr, Ce, Fe, Ta, B, Al, V, Ti, Zr, Sn, P, and Mo, wherein x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, and d≥0; The matrix is ​​dispersed in an acidic solution and stirred to obtain a matrix mixture solution; The matrix mixture solution is solidified and dried to obtain a matrix mixture powder; The matrix powder is mixed with the coating powder to obtain a positive electrode active material precursor, wherein the coating powder includes a boron-containing alloy. The positive electrode active material precursor is sintered to obtain the positive electrode active material. The positive electrode active material includes: The matrix has the chemical formula Li[Li] x Ni a Co b Mn c M d O2, M includes at least one of Mg, Nb, Cr, Ce, Fe, Ta, B, Al, V, Ti, Zr, Sn, P, and Mo, wherein x+a+b+c+d=1, x>0, a>0, 0<b<0.1, c>0, and d≥0; The coating layer is disposed on the surface of the substrate, and the coating layer includes the boron-containing alloy; The peak intensity ratio of Mn-O to Ni-O in the positive electrode active material is 20-50.

21. The method according to claim 20, wherein, The pH value of the acidic solution is 1-3.

22. The method according to claim 20 or 21, wherein, The acid in the acidic solution includes at least one of sulfuric acid, nitric acid, ammonium persulfate, citric acid, oxalic acid, sodium citrate, ammonium citrate, hydrogen citrate, fruit acid, salicylic acid, succinic acid, or succinic anhydride.

23. The method according to claim 20 or 22, wherein, The acidic solution may also include ethanol or water.

24. The method according to any one of claims 20 to 23, wherein, The mass ratio of the acidic solution to the matrix is ​​6-35.

25. The method according to any one of claims 20 to 24, wherein, The mass ratio of the acidic solution to the matrix is ​​10-20.

26. The method according to any one of claims 20 to 25, wherein, The mass fraction of the acid in the acidic solution is 0.1%-30%.

27. The method according to any one of claims 20 to 26, wherein, The acid has a mass fraction of 10%-20% in the acidic solution.

28. The method according to any one of claims 20 to 27, wherein, The sintering of the positive electrode active material precursor includes: The positive electrode active material precursor is sintered in an oxygen atmosphere or an inert gas atmosphere.

29. The method of claim 28, wherein, The sintering temperature in the inert gas atmosphere is 250-400℃.

30. The method of claim 28, wherein, The sintering temperature in an oxygen atmosphere is 500-700 ℃.

31. The method according to any one of claims 20 to 30, wherein, The sintering time is 3-10 h.

32. A battery cell comprising the positive electrode active material according to any one of claims 1 to 19, or the positive electrode active material prepared by any one of claims 20 to 31.

33. A battery comprising a battery cell as described in claim 32.

34. An electrical device comprising the battery as claimed in claim 33, the battery being used to provide electrical energy.

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