Positive electrode active material and preparation method therefor, positive electrode sheet, battery, and electric device

Abstract

A positive electrode active material and a preparation method therefor, a positive electrode sheet, a battery, and an electric device. The positive electrode active material comprises a positive electrode active host material and a fluorine-phosphorus compound admixed in the positive electrode active host material, wherein the positive electrode active host material comprises lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide. By admixing the fluorine-phosphorus compound with the positive electrode active material, the positive electrode active material is modified, the service life at a high temperature is prolonged, and the electrochemical performance of a battery is optimized.

Description

Positive electrode active material and preparation method thereof, positive electrode sheet, battery and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application with application number 2024102332683 filed on February 29, 2024, and invention name “Positive electrode active material and preparation method thereof, positive electrode sheet, battery and electrical equipment”. Technical Field

[0003] The present application relates to the technical field of lithium batteries, and in particular to a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and an electrical device. Background Art

[0004] Lithium-ion batteries are currently the most widely used electrochemical energy storage devices in the energy sector. As the largest component of lithium-ion batteries, the cathode material significantly impacts the battery's overall performance. However, under high temperature and high pressure, the cathode material experiences severe side reactions, shortening the battery's lifespan. Consequently, the industrialization of lithium-ion batteries under these conditions is significantly limited.

[0005] Summary of the Invention

[0006] In view of this, the main technical problem to be solved by this application is the instability of the bulk structure of the positive electrode material under high temperature and high pressure, thereby providing a positive electrode active material and its preparation method, a positive electrode plate, a battery and an electrical equipment, which can stabilize the bulk structure of the positive electrode material and enhance the stability of the positive electrode material under high temperature and high pressure conditions.

[0007] In a first aspect, the present application provides a positive electrode active material. The positive electrode active material includes a positive electrode active host material and a fluorophosphorus compound. The positive electrode active host material includes lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide; the fluorophosphorus compound is admixed with the positive electrode active host material.

[0008] In the technical solution of the embodiments of the present application, the addition of a fluorophosphorus compound to the cathode active host material formed of lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide can inhibit the oxidation activity of the cathode active host material, stabilize the bulk structure of the cathode active host material, and enhance the stability of the cathode active material in high-temperature environments, thereby significantly improving the battery's storage performance and gas production issues. Furthermore, the fluorophosphorus compound is acidic and can react with residual alkali on the surface of the cathode active host material to reduce the decomposition of the residual alkali during the battery's charge and discharge process, which can lead to battery deterioration.

[0009] In any embodiment, the fluorophosphorus compound is located on the surface of the positive electrode active host material.

[0010] In the technical solutions of the embodiments of this application, the fluorophosphorus compound located on the surface of the positive electrode active host material can inhibit the oxidative activity of the positive electrode active host material and stabilize the bulk structure of the positive electrode active host material, thereby enhancing the stability of the positive electrode active material in high-temperature environments, thereby significantly improving the battery's storage performance and gas production issues. Furthermore, the fluorophosphorus compound is acidic and can react with residual alkali on the surface of the positive electrode active host material to reduce the decomposition of the residual alkali during the battery's charge and discharge process, which can lead to battery deterioration.

[0011] In any embodiment, the fluorophosphorus compound comprises a structural formula of Li p P q O r The compound of F2, wherein 0.8≤p≤1.2, 0.8≤q≤1.2, and 1.8≤r≤2.2.

[0012] In the technical solution of the embodiment of the present application, the structural formula is Li p P q O r The fluorophosphorus compound of F2 can enhance the stability of the overall structure of the positive electrode active material and maintain good electrical performance even at a high voltage of 4.5V.

[0013] In any embodiment, the cathode active host material comprises a structural formula of Li(Ni x Co y M z ) 1-u T u O2 material, wherein M includes Mn or Al, T includes one or more of Zr, Sr, B, Ti, Mg, Na, Si, Sn, Tb, W, Nb, Sb and Al, x+y+z=1, 0.3≤x≤0.9, 0.03≤y≤0.3, 0.05≤z≤0.4, 0.0003≤u≤0.004.

[0014] In the technical solution of the embodiment of the present application, the structural formula is Li(Ni x Co y M z ) 1-u T u The main active material of the positive electrode of O2 has a hexagonal crystal structure, which has a higher energy density, that is, it has better electrical energy storage performance under the same volume and mass; at the same time, it has higher chemical stability and is not prone to thermal runaway, so it has a longer service life.

[0015] In any embodiment, the positive electrode active host material is doped with fluorine and phosphorus.

[0016] In the technical solution of the embodiment of the present application, fluorine and phosphorus are doped in the positive electrode active main material formed by lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide. The fluorine element will be doped into the oxygen site of the hexagonal crystal system of the positive electrode active main material, and the phosphorus element will be doped into the hexagonal crystal lattice or / and the oxygen site of the hexagonal crystal system of the positive electrode active main material, so as to achieve the modification of the positive electrode active main material, inhibit the oxidation activity of the positive electrode active main material, stabilize the bulk structure of the positive electrode active main material, and enhance the stability of the positive electrode active material under high temperature conditions, thereby significantly improving the storage performance of the battery and gas production problems.

[0017] In any embodiment, the fluorinated phosphorus compound accounts for 0.015% to 0.4% of the total mass of the positive electrode active material. Optionally, the fluorinated phosphorus compound accounts for 0.03% to 0.3% of the total mass of the positive electrode active material. By controlling the content of the fluorinated phosphorus compound in the positive electrode active material, residual alkali on the surface of the positive electrode active material can be suppressed, and the stability of the positive electrode active material can be improved, resulting in a battery with excellent electrical performance.

[0018] In any embodiment, the volume average particle size DV50 of the positive electrode active material is 3 μm to 15 μm. By controlling the volume average particle size of the positive electrode active material to 3 μm to 15 μm, the sites for lithium insertion and removal of the positive electrode active material are larger, ensuring better power performance of the battery.

[0019] The volume average particle size DV50 of the positive electrode active material is common knowledge in the art, has a commonly known meaning in the art, and can be measured by methods and instruments in the art.

[0020] The second aspect of the present application also provides a method for preparing a positive electrode active material, which includes: spraying a difluorophosphate solution on a nickel-cobalt metal precursor so that the difluorophosphate is coated on the nickel-cobalt metal precursor, wherein the nickel-cobalt metal precursor includes a nickel-cobalt-manganese precursor or a nickel-cobalt-aluminum precursor; mixing the nickel-cobalt metal precursor coated with the difluorophosphate and a lithium source, and sintering them to form a lithium nickel-cobalt-manganese oxide or a lithium nickel-cobalt-aluminum oxide doped with a fluorine-phosphorus compound.

[0021] In the technical solution of the embodiment of the present application, the difluorophosphate solution is coated on the surface of the nickel-cobalt metal precursor in the form of a spray, so that the contact between the difluorophosphate and the nickel-cobalt metal precursor is more uniform, which can reduce the occurrence of difluorophosphate agglomeration, and make the surface distribution of the final lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide mixed with fluorophosphorus compounds more uniform and the difference in all directions is small.

[0022] In any embodiment, the spray coating time is 5 minutes to 60 minutes. Optionally, the spray coating time is 8 minutes to 30 minutes. Controlling the spray coating time within this time range facilitates more uniform and sufficient mixing of the difluorophosphate solution and the nickel-cobalt metal precursor.

[0023] In any embodiment, the mass ratio of difluorophosphate to nickel-cobalt metal precursor in the difluorophosphate solution is 3×10 -4 ~4×10 -3 : 1. By controlling the mass ratio of difluorophosphate to nickel-cobalt metal precursor, the residual alkali on the surface of the positive electrode active host material can be suppressed, and the stability of the positive electrode active material can be improved, so that the battery has excellent electrical performance.

[0024] In any embodiment, mixing a nickel-cobalt metal precursor coated with difluorophosphate and a lithium source comprises: mixing a nickel-cobalt metal precursor coated with difluorophosphate, a lithium source and a metal doping source, wherein the metal doping source comprises one or more metal oxides of Zr, Sr, B, Ti, Mg, Na, Si, Sn, Tb, W, Nb, Sb and Al.

[0025] In any embodiment, the nickel-cobalt metal precursor comprises a structural formula (Ni a Co b M c ) d (OH)2, 0.3≤a≤0.9, 0.01≤b≤0.4, 0.1≤c≤0.5, a+b+c=1, 0.95≤d≤1, M includes Mn or Al. Using this hydroxide precursor as a substance for preparing a positive electrode active material enables the prepared positive electrode active material to have the advantage of high specific capacity, good compatibility with the electrolyte, and wide application.

[0026] In any embodiment, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium sulfate, lithium nitrate, lithium acetate, and lithium phosphate. The lithium source is used to provide lithium, which has high electrochemical activity and can react chemically with other elements in the battery to release electrons and generate current.

[0027] In any embodiment, the mixing speed is 600 rpm to 2000 rpm, and the mixing time is 30 min to 300 min. This mixing method allows the nickel-cobalt metal precursor and the lithium source to be mixed more fully.

[0028] In any embodiment, the sintering temperature is 900° C. to 950° C., and the sintering time is 10 hours to 33 hours. In the embodiment of the present application, by controlling the sintering temperature and sintering time, the nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide are synthesized, and the volume average particle size DV50 of the nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide is made to be within a preset range, for example, within the range of 3 μm to 15 μm, so that the power performance of the battery is better.

[0029] The third aspect of the present application further provides a positive electrode sheet comprising the positive electrode active material of the first aspect of the present application and / or the positive electrode active material prepared by the method for preparing the positive electrode active material of the second aspect of the present application. Because the positive electrode sheet of the present application comprises the positive electrode active material provided herein, it has at least the same advantages as the positive electrode active material.

[0030] The fourth aspect of the present application further provides a battery comprising the positive electrode active material of the first aspect of the present application, and / or the positive electrode active material prepared by the method for preparing the positive electrode active material of the second aspect of the present application, or the positive electrode sheet of the third aspect of the present application. Because the battery of the present application comprises the positive electrode active material provided herein, it has at least the same advantages as the positive electrode active material.

[0031] The fifth aspect of the present application further provides an electrical device, comprising the battery of the fourth aspect of the present application. Since the electrical device of the present application comprises the battery provided by the present application, it has at least the same advantages as the battery.

[0032] The beneficial effects of the present application are as follows: Different from the prior art, the positive electrode active material of the present application includes a positive electrode active main material and a fluorophosphorus compound, and the fluorophosphorus compound is mixed in the positive electrode active main material. The fluorophosphorus compound can modify the positive electrode active main material, inhibit the oxidation activity of the positive electrode active main material, stabilize the bulk structure of the positive electrode active main material, and enhance the stability of the positive electrode active material in a high temperature environment, thereby significantly improving the storage performance and gas production problems of the battery. In addition, the fluorophosphorus compound can also react with the residual alkali on the surface of the positive electrode active main material to reduce the decomposition of the residual alkali during the battery charging and discharging process, thereby reducing the deterioration of the battery.

[0033] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0035] FIG1 is a schematic structural diagram of a battery cell according to an embodiment of the present application.

[0036] FIG2 is a schematic diagram of the exploded structure of a battery according to an embodiment of the present application.

[0037] FIG3 a is a schematic diagram of a partial structure of an electrical device according to an embodiment of the present application.

[0038] FIG3 b is a schematic diagram of an electrical device according to an embodiment of the present application. DETAILED DESCRIPTION

[0039] Below, the embodiments of the battery cells, batteries, and electrical equipment of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0040] The "ranges" disclosed herein are defined in terms of lower and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower and upper limits define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise indicated, the numerical range "a to b" is a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0042] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0043] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which indicates that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may further include step (c), which 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 may include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0044] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may indicate that other components not listed may also be included or that only the listed components are included.

[0045] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0046] As the main material with the largest proportion in lithium-ion batteries, the positive electrode active material has a great influence on the overall performance of the battery. In order to maximize the energy performance of the ternary positive electrode active material and minimize the cost in current technology, the operating voltage is often increased. However, under high voltage (3.7V~4.5V), the side reactions of the positive electrode active material are intense, resulting in a shortened lifespan. Therefore, the industrialization of high-voltage ternary positive electrode active materials is greatly limited. Conventional high-voltage ternary positive electrode active material modification methods mainly target the surface of the positive electrode active material, coating the surface of the positive electrode active material with a modified material to inhibit the side reaction between the surface of the positive electrode active material and the electrolyte. However, the surface polarization of the positive electrode active material coated with the modified material is too large, resulting in poor battery capacity. In addition, the surface coating layer blocks the channel for lithium ion transmission, resulting in serious gram capacity decay and serious battery cycle decay. On the other hand, the surface coating layer is not effective in inhibiting side reactions under high temperature and high pressure.

[0047] Based on this, the present application proposes a positive electrode active material. The positive electrode active material includes a positive electrode active main material and a fluorophosphorus compound. The positive electrode active main material includes lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide; the fluorophosphorus compound is admixed with the positive electrode active main material.

[0048] In embodiments of the present application, the addition of a fluorophosphorus compound to the cathode active host material formed from lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide can inhibit the oxidative activity of the cathode active host material, stabilize the bulk structure of the cathode active host material, and enhance the stability of the cathode active material in high-temperature environments, thereby significantly improving the battery's storage performance and gas production issues. Furthermore, the fluorophosphorus compound is acidic and can react with residual alkali on the surface of the cathode active host material to reduce the decomposition of the residual alkali during battery charge and discharge, which can lead to battery deterioration.

[0049] In some embodiments of the present application, the fluorophosphorus compound is located on the surface layer of the positive electrode active host material.

[0050] In the technical solutions of the embodiments of this application, the fluorophosphorus compound located on the surface of the positive electrode active host material can inhibit the oxidative activity of the positive electrode active host material and stabilize the bulk structure of the positive electrode active host material, thereby enhancing the stability of the positive electrode active material in high-temperature environments, thereby significantly improving the battery's storage performance and gas production issues. Furthermore, the fluorophosphorus compound is acidic and can react with residual alkali on the surface of the positive electrode active host material to reduce the decomposition of the residual alkali during the battery's charge and discharge process, which can lead to battery deterioration.

[0051] In some embodiments of the present application, the fluorophosphorus compound includes a structural formula of Li p P q O r F2 compound, wherein 0.8≤p≤1.2, 0.8≤q≤1.2, 1.8≤r≤2.2. The structural formula is Li p P q O r The fluorophosphorus compound F2 enhances the structural stability of the cathode active material, maintaining good electrical performance even at a high voltage of 4.5 V. Furthermore, the acidic nature of the fluorophosphorus compound allows it to react with residual alkali on the surface of the cathode active material, reducing the decomposition of the residual alkali during battery charge and discharge, which can lead to battery deterioration.

[0052] In some embodiments of the present application, the cathode active host material includes a structural formula of Li(Ni x Co y M z ) 1- u T uO2 material, wherein M includes Mn or Al, T includes one or more of Zr, Sr, B, Ti, Mg, Na, Si, Sn, Tb, W, Nb, Sb and Al, x+y+z+u=1, 0.3≤x≤0.9, 0.03≤y≤0.3, 0.05≤z≤0.4, 0.0003≤u≤0.004.

[0053] In the technical solution of the embodiment of the present application, the structural formula is Li(Ni x Co y M z ) 1-u T u The main active material of the positive electrode of O2 has a hexagonal crystal structure, which has a higher energy density, that is, it has better electrical energy storage performance under the same volume and mass; at the same time, it has higher chemical stability and is not prone to thermal runaway, so it has a longer service life.

[0054] In some embodiments of the present application, the positive electrode active host material is doped with fluorine and phosphorus.

[0055] In the technical solution of the embodiment of the present application, fluorine and phosphorus are doped in the positive electrode active main material formed by lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide. The fluorine element will be doped into the oxygen site of the hexagonal crystal system of the positive electrode active main material, and the phosphorus element will be doped into the hexagonal crystal lattice or / and the oxygen site of the hexagonal crystal system of the positive electrode active main material, so as to achieve the modification of the positive electrode active main material, inhibit the oxidation activity of the positive electrode active main material, stabilize the bulk structure of the positive electrode active main material, and enhance the stability of the positive electrode active material under high temperature conditions, thereby significantly improving the storage performance of the battery and gas production problems.

[0056] In some embodiments of the present application, the fluorophosphorus compound accounts for 0.015% to 0.4% of the total mass of the positive electrode active material, and optionally 0.03% to 0.3%. For example, it may be 0.015%, 0.03%, 0.059%, 0.15%, 0.19%, 0.26%, 0.29%, 0.3%, 0.34%, 0.4%, or a range consisting of any two of the above values, for example, 0.015% to 0.26%, 0.26% to 0.34%, 0.34% to 0.4%, or the like. By controlling the content of the fluorophosphorus compound in the positive electrode active material, it is possible to suppress residual alkali on the surface of the positive electrode active material and improve the stability of the positive electrode active material, resulting in a battery with excellent electrical performance.

[0057] In some embodiments of the present application, the volume average particle size DV50 of the positive electrode active material is 3μm to 15μm. By controlling the volume average particle size of the positive electrode active material to be 3μm to 15μm, the sites for lithium insertion and removal of the positive electrode active material are larger, ensuring better power performance of the battery cell. Among them, the volume average particle size DV50 of the positive electrode active material can be 3μm, 4.2μm, 5.5μm, 6.9μm, 9.4μm, 12.5μm, 15μm, etc., or a range consisting of any two of the above values, for example, 3μm to 6.9μm, 6.9μm to 12.5μm, 12.5μm to 15μm, etc. Among them, the volume average particle size DV50 of the positive electrode active material is common knowledge in the art, has a meaning known in the art, and can be measured by methods and instruments in the art.

[0058] The second technical solution adopted in the present application is: to provide a method for preparing a positive electrode active material, the method comprising: spraying a difluorophosphate solution on a nickel-cobalt metal precursor so that the difluorophosphate is coated on the nickel-cobalt metal precursor, wherein the nickel-cobalt metal precursor includes a nickel-cobalt-manganese precursor or a nickel-cobalt-aluminum precursor; mixing the nickel-cobalt metal precursor coated with the difluorophosphate and a lithium source, and sintering them to form a lithium nickel-cobalt-manganese oxide or a lithium nickel-cobalt-aluminum oxide doped with a fluorine-phosphorus compound.

[0059] Specifically, the method for preparing the positive electrode active material includes the following steps:

[0060] Step 1: Fully dissolve lithium difluorophosphate in deionized water to form a difluorophosphate solution, and coat the difluorophosphate solution on the nickel-cobalt-manganese precursor or the nickel-cobalt-aluminum precursor by wet spraying.

[0061] Lithium difluorophosphate is readily soluble in water. In this embodiment, harmless, non-polluting deionized water is preferably used as the solvent. The lithium difluorophosphate is dissolved in deionized water to form a difluorophosphate solution. This solution facilitates subsequent coating using a spraying method. Of course, in other embodiments, the lithium difluorophosphate may also be dissolved in an alcoholic solvent such as methanol or ethanol.

[0062] In this embodiment, the mass ratio of difluorophosphate to nickel-cobalt metal precursor in the difluorophosphate solution is 3×10 -4 ~4×10 -3 :1. By controlling the mass ratio of difluorophosphate to nickel-cobalt metal precursor, the residual alkali on the surface of the positive electrode active material can be suppressed, and the stability of the positive electrode active material can be improved, so that the battery has excellent electrical performance. Among them, the mass ratio of difluorophosphate to nickel-cobalt metal precursor in the difluorophosphate solution can be 3.0×10 -4 :1, 3.1×10 -4 :1, 4.1×10 -4:1, 5.5×10 -4 :1, 2.1×10 - 3 :1,3.8×10 -3 :1, 4×10 -3 :1, etc., or a range consisting of any two of the above values, for example, 3.0×10 -4 :1~5.5×10 -4 :1,5.5×10 -4 :1~2.1×10 -3 :1,2.1×10 -3 :1~4×10 -3 :1 etc.

[0063] The lithium difluorophosphate solution is then coated onto the surface of the nickel-cobalt-manganese precursor or the nickel-cobalt-aluminum precursor using a spray coating method. This spraying method allows the lithium difluorophosphate solution to be thoroughly mixed with the nickel-cobalt metal precursor, achieving uniform coating and reducing the occurrence of difluorophosphate agglomeration. This allows the lithium difluorophosphate to better exert its effects during subsequent sintering in a high-temperature environment, modifying the positive electrode active material, inhibiting its oxidative activity, and stabilizing its bulk structure, thereby enhancing the stability of the positive electrode active material in a high-temperature environment.

[0064] In this embodiment, the spray coating time is 5 minutes to 60 minutes, and optionally, the spray coating time is 8 minutes to 30 minutes. Controlling the spray coating time within this time range is conducive to more uniform and sufficient mixing of the difluorophosphate solution and the nickel-cobalt metal precursor. The spray coating time can be 5 minutes, 8 minutes, 15 minutes, 26 minutes, 30 minutes, 37 minutes, 45 minutes, 58 minutes, 60 minutes, etc., or a range consisting of any two of the above values, for example, 5 minutes to 26 minutes, 26 minutes to 45 minutes, 45 minutes to 60 minutes, etc.

[0065] Step 2: Mixing a nickel-cobalt metal precursor coated with difluorophosphate and a lithium source, and sintering them to form lithium nickel-cobalt-manganese oxide or lithium nickel-cobalt-aluminum oxide mixed with fluorine-phosphorus compounds.

[0066] Specifically, this step includes: mixing a nickel-cobalt metal precursor coated with difluorophosphate, a lithium source and a metal doping source. This embodiment does not limit the mixing order. The nickel-cobalt metal precursor coated with difluorophosphate can be first mixed with a lithium source and then mixed with a metal doping source. The nickel-cobalt metal precursor coated with difluorophosphate can also be first mixed with a metal doping source and then mixed with a lithium source. The nickel-cobalt metal precursor coated with difluorophosphate can also be mixed with a lithium source and a metal doping source at the same time. The metal doping source includes one or more metal oxides of Zr, Sr, B, Ti, Mg, Na, Si, Sn, Tb, W, Nb, Sb and Al. In the embodiment of the present application, lithium nickel cobalt manganese oxide mixed with fluorine-phosphorus compounds and lithium nickel cobalt aluminum oxide mixed with fluorine-phosphorus compounds can be prepared by further sintering.

[0067] In some embodiments of the present application, the nickel-cobalt metal precursor includes a structural formula (Ni a Co b M c ) d (OH)2, 0.3≤a≤0.9, 0.01≤b≤0.4, 0.1≤c≤0.5, a+b+c=1, 0.95≤d≤1, M includes Mn or Al. Using this hydroxide precursor as a material for preparing a positive electrode active material has the advantage of high specific capacity, good compatibility with the electrolyte, and wide application.

[0068] Lithium sources include one or more of lithium carbonate, lithium hydroxide, lithium sulfate, lithium nitrate, lithium acetate, and lithium phosphate. Lithium sources provide the element lithium, which has high electrochemical activity and can react chemically with other elements in the battery, releasing electrons and generating current.

[0069] In some embodiments of the present application, the nickel-cobalt metal precursor may include but is not limited to (Ni 0.3 Co 0.4 Mn 0.3 ) 0.95 (OH)2、(Ni 0.4 Co 0.2 Mn 0.4 ) 0.96 (OH)2、(Ni 0.6 Co 0.1 Mn 0.3 ) 0.97 (OH)2、(Ni 0.7 Co 0.05 Al 0.25 ) 0.98 (OH)2 and (Ni 0.9 Co 0.01 Al 0.09 )1(OH)2.

[0070] The nickel-cobalt metal precursor coated with difluorophosphate, the lithium source, and the metal doping source are mixed in an inclined roller mill or a high-speed mixer at a mixing speed of 600 to 2000 rpm for 30 to 300 minutes. This mixing method allows for more complete mixing of the nickel-cobalt metal precursor and the lithium source. The mixing speed can be 600 rpm, 780 rpm, 890 rpm, 1350 rpm, 1590 rpm, 1780 rpm, 1950 rpm, 2000 rpm, etc., or a range consisting of any two of the above values, for example, 600 rpm to 890 rpm, 890 rpm to 1590 rpm, 1590 rpm to 2000 rpm, etc.; the mixing time can be 30 min, 65 min, 95 min, 156 min, 210 min, 260 min, 300 min, etc., or a range consisting of any two of the above values, for example, 30 min to 95 min, 95 min to 210 min, 210 min to 300 min, etc.

[0071] After mixing, the mixture is sintered at a temperature of 900°C to 950°C for 10 to 33 hours. Related technologies use low-temperature coating technology at a temperature of 400°C to 500°C. This low-temperature sintering process typically only coats lithium difluorophosphate on the outer surface of the positive electrode active material, but cannot achieve internal mixing of the lithium difluorophosphate. Furthermore, lithium difluorophosphate decomposes incompletely, producing harmful substances such as hydrogen fluoride due to incomplete combustion. The sintering temperature of this embodiment is 900℃~950℃, while the decomposition temperature of fluorine-phosphorus compounds is relatively low, less than 300℃, so in fact, when the temperature is more than 300 degrees Celsius, lithium difluorophosphate has already decomposed. When the temperature is raised to 900℃~950℃, lithium difluorophosphate will decompose into fluorine and phosphorus elements, and the fluorine and phosphorus elements will migrate into the interior of the positive electrode active material and be doped into the bulk phase of the positive electrode active main material. Among them, the F element will be doped into the oxygen site of the hexagonal crystal system of the positive electrode active main material, and the P element will be doped into the hexagonal crystal lattice or / and the oxygen site of the hexagonal crystal system of the positive electrode active main material, thereby modifying the positive electrode active main material, inhibiting the oxidation activity of the positive electrode active main material, stabilizing the bulk structure of the positive electrode active main material, and enhancing the stability of the positive electrode active material under high temperature conditions, thereby significantly improving the storage performance and gas production problems of the battery. The embodiment of the present application controls the sintering temperature within the range of 900°C to 950°C and the sintering time within the range of 10h to 33h to control the synthesis of nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide, and makes the volume average particle size DV50 of the nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide within a preset range, for example, within the range of 3μm to 15μm, so as to achieve better power performance of the battery. The sintering temperature can be 900°C, 910°C, 925°C, 934°C, 945°C, 950°C, etc., or a range consisting of any two of the above values, for example, 900°C to 925°C, 925°C to 934°C, 934°C to 950°C, etc.; the sintering time can be 10h, 15h, 20h, 25h, 30h, 33h, etc., or a range consisting of any two of the above values, for example, 10h to 15h, 15h to 25h, 25h to 33h, etc.

[0072] It should be noted that during the production of the positive electrode active material, after sintering at 900°C to 950°C, the fluorine and phosphorus compounds in the positive electrode active material decompose to produce F and P elements, which are then doped into the lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide (i.e., the bulk phase of the positive electrode active host material). After sintering and cooling, firstly, some of the F and P elements remain doped into the lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide. The F element is doped into the hexagonal oxygen sites of the positive electrode active host material, and the P element is doped between the hexagonal lattices and / or into the hexagonal oxygen sites of the positive electrode active host material. This doping stabilizes the bulk structure of the positive electrode active host material and improves its structural stability. The F and P elements doped into the positive electrode active host material can be characterized by XRD refinement, observing shifts in characteristic peaks at oxygen sites or changes in other characteristic peaks. Secondly, after sintering and cooling, at least some of the decomposed F and P elements will reform into fluorine and phosphorus compounds. Therefore, after the final sintering is completed, fluorine-phosphorus compounds will appear in the positive electrode active material. The reformed fluorine-phosphorus compounds are located on the surface of the positive electrode active host material, stabilizing the interface and improving the stability of the positive electrode active host material. It should be noted that the reformed fluorine-phosphorus compounds cannot decompose into the elements F and P.

[0073] The positive electrode active material prepared using the above preparation process contains difluorophosphate. Under high temperature conditions greater than 300°C, i.e., 900°C to 950°C, the difluorophosphate will decompose to release F and P elements that are doped into the bulk phase of the positive electrode active main material, thereby modifying the positive electrode active main material, inhibiting the oxidation activity of the positive electrode active main material, and stabilizing the bulk structure of the positive electrode active main material. This enhances the stability of the positive electrode active material under high temperature conditions, thereby significantly improving the battery's storage performance and gas production problems. In addition, the difluorophosphate on the surface of the positive electrode active material is acidic and can react with residual alkali on the surface of the positive electrode active main material to reduce the decomposition of the residual alkali during the battery's charge and discharge process, which can lead to battery deterioration. The positive electrode active material prepared using the above preparation process has an excellent high-temperature storage life.

[0074] The third technical solution adopted by this application is to provide a positive electrode plate comprising the positive electrode active material of the first aspect of this application and / or the positive electrode active material prepared by the method for preparing the positive electrode active material of the second aspect of this application. Because the positive electrode plate of this application comprises the positive electrode active material provided herein, it has at least the same advantages as the positive electrode active material.

[0075] In addition, the battery cell, battery, and electric device of the present application will be described below with reference to the drawings as appropriate.

[0076] In the embodiment of the present application, a battery cell refers to the smallest unit that makes up a battery. A battery cell also includes an electrolyte and a separator. The separator is provided between the positive electrode and the negative electrode. It mainly prevents the positive and negative electrodes from short-circuiting while allowing ions to pass through. During the charge and discharge process of the battery, the active ions Li + The electrolyte is inserted and removed back and forth between the positive electrode and the negative electrode, and acts as a conductor of ions between the positive electrode and the negative electrode.

[0077] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes the positive electrode active material of the above embodiment of the present application.

[0078] As an example, the positive electrode current collector has two surfaces opposite to 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 electrode current collector.

[0079] In some embodiments, the positive electrode 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 material base and a metal layer formed on at least one surface of the polymer material base. 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0080] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0081] In some embodiments, the positive electrode film layer may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0082] In some embodiments, the positive electrode sheet can be prepared by the following method: the components used to prepare the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0083] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0084] As an example, the negative electrode current collector has two surfaces opposite to 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 electrode current collector.

[0085] 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 base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0086] In some embodiments, the negative electrode film layer may further 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).

[0087] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0088] In some embodiments, the negative electrode film layer may further include other additives, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0089] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0090] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. This application has no specific restrictions on the type of electrolyte, and it can be selected according to needs.

[0091] In some embodiments, the electrolyte solution includes an electrolyte salt and a solvent.

[0092] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0093] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0094] 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 properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0095] In some embodiments, the battery cell further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0096] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven 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.

[0097] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into a battery cell assembly through a winding process or a lamination process.

[0098] In some embodiments, as shown in FIG1 , a battery cell 10 may include an outer packaging. The outer packaging may be used to encapsulate the battery cell assembly 11 and the electrolyte. The outer packaging includes an end cap 12 , a housing 13 , and other functional components.

[0099] The end cap 12 refers to a component that covers the opening of the shell 13 to isolate the internal environment of the battery cell 10 from the external environment. Without limitation, the shape of the end cap 12 can be adapted to the shape of the shell 13 to match the shell 13. Optionally, the end cap 12 can be made of a material with a certain hardness and strength (such as an aluminum alloy). In this way, the end cap 12 is not easily deformed when squeezed or collided, so that the battery cell 10 can have a higher structural strength and improved safety performance. Functional components such as electrode terminals 12a can be provided on the end cap 12. The electrode terminals 12a can be used to electrically connect to the battery cell assembly 11 for outputting or inputting electrical energy into or out of the battery cell 10. In some embodiments, the end cap 12 can also be provided with a pressure relief mechanism for releasing internal pressure when the internal pressure or temperature of the battery cell 10 reaches a threshold. The material of the end cap 12 can also be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not impose any special restrictions on this. In some embodiments, an insulating member (not shown) may be provided inside the end cap 12 to isolate the electrical connection components in the housing 13 from the end cap 12 to reduce the risk of short circuits. For example, the insulating member may be made of plastic, rubber, or the like.

[0100] The housing 13 is a component that cooperates with the end cap 12 to form the internal environment of the battery cell 10. This internal environment can be used to accommodate the battery cell assembly 11, electrolyte, and other components. The housing 13 and the end cap 12 can be separate components. An opening can be provided in the housing 13, and the end cap 12 is placed over the opening to form the internal environment of the battery cell 10. Alternatively, the end cap 12 and the housing 13 can be integrated. Specifically, the end cap 12 and the housing 13 can form a common connection surface before other components are inserted into the housing. When the interior of the housing 13 needs to be enclosed, the end cap 12 is placed over the housing 13. The housing 13 can have a variety of shapes and sizes, such as a rectangular parallelepiped, a cylindrical shape, a hexagonal prism, etc. Specifically, the shape of the housing 13 can be determined based on the specific shape and size of the battery cell assembly 11. The housing 13 can be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and this embodiment of the present application does not impose any specific limitations on this.

[0101] The housing 13 may contain one or more battery cell assemblies 11. The portions of the positive and negative electrode sheets that do not contain active material each form a tab 11a. The positive and negative tabs may be located together at one end of the main body or separately at opposite ends. During the battery's charge and discharge processes, the positive and negative active materials react with the electrolyte, and the tabs 11a connect to the electrode terminals to form a current circuit.

[0102] Please refer to Figure 2, which is a schematic diagram of the exploded structure of a battery 100 provided in some embodiments of the present application. The battery 100 includes a housing 20 and a battery cell 10, with the battery cell 10 housed within the housing 20. The housing 20 provides a storage space for the battery cell 10 and can have various structures. In some embodiments, the housing 20 can include a first portion 21 and a second portion 22, which overlap each other and together define a storage space for the battery cell 10. The second portion 22 can be a hollow structure with one end open. The first portion 21 can be a plate-like structure, with the first portion 21 overlapping the open side of the second portion 22, so that the first and second portions 21 and 22 together define a storage space. Alternatively, the first and second portions 21 and 22 can each be a hollow structure with one end open, with the open side of the first portion 21 overlapping the open side of the second portion 22. Of course, the housing 20 formed by the first and second portions 21 and 22 can have various shapes, such as a cylinder or a rectangular parallelepiped.

[0103] In the battery 100, there may be multiple battery cells 10, and the multiple battery cells 10 may be connected in series, in parallel, or in a hybrid connection. A hybrid connection refers to a combination of series and parallel connections among the multiple battery cells 10. The multiple battery cells 10 may be directly connected in series, in parallel, or in a hybrid connection, and then the entire battery cell 10 may be housed within the housing 20. Of course, the battery 100 may also be formed by first connecting multiple battery cells 10 in series, in parallel, or in a hybrid connection to form a battery module, and then the multiple battery modules may be connected in series, in parallel, or in a hybrid connection to form an entire battery cell, and then housed within the housing 20. The battery 100 may also include other structures, for example, the battery 100 may further include a busbar component for electrically connecting the multiple battery cells 10.

[0104] The battery 100 in the embodiment of the present application includes a lithium-ion battery as a battery cell 10. In other embodiments, the battery 100 may further include any one or more of a lithium-sulfur battery, a sodium-ion battery, and a magnesium-ion battery, but is not limited thereto. The battery cell 10 may be cylindrical, flat, rectangular, or in other shapes.

[0105] In some embodiments, batteries may be assembled into a battery module. The number of batteries contained in the battery module may be one or more. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0106] In addition, the present application also provides an electric device, which includes at least one of the battery cells and / or batteries provided in the present application. The battery cells or battery packs can be used as power sources for electric devices, or as energy storage units for electric devices. Electric devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0107] As an electrical device, a battery cell and / or battery 100 may be selected according to its usage requirements.

[0108] Figures 3a and 3b show an electric device as an example. The electric device is a vehicle such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. A structural schematic diagram of a vehicle 1000 is specifically provided. A battery 100 is provided inside the vehicle 1000, and the battery 100 can be provided at the bottom, head, or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000, for example, the battery 100 can serve as an operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to power the motor 300, for example, for starting, navigating, and operating power requirements of the vehicle 1000 during driving.

[0109] In some embodiments of the present application, the battery 100 can serve not only as an operating power source for the vehicle 1000, but also as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0110] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0111] In the embodiments described below in this application, the amounts of lithium difluorophosphate (LiPO2F2), metal doping sources (raw materials containing T elements), such as ZrO2, AlO2, etc., are all based on nickel-cobalt metal precursors.

[0112] Example 1

[0113] Preparation method of positive electrode active material:

[0114] (1)Ni 0.55 Co 0.06 Mn0.39 The mass of the (OH)2 precursor was measured, and 1500 ppm of lithium difluorophosphate (LiPO2F2) was weighed and dissolved in water to obtain a difluorophosphate aqueous solution.

[0115] (2) In Ni 0.55 Co 0.06 Mn 0.39 The (OH)2 precursor was spray-coated with a difluorophosphate aqueous solution containing 1500 ppm, and the spraying time was 20 minutes.

[0116] (3) The precursor coated with difluorophosphate was mixed with lithium carbonate at a molar ratio of 1:1.05; 0.55 Co 0.06 Mn 0.39 The (OH)2 precursor was mixed with 1000 ppm ZrO2 in a high-speed mixer at 1500 rpm for 2 hours. The mixture was sintered in a kiln at 900°C for 13 hours, cooled to room temperature, and crushed to obtain the positive electrode active material.

[0117] Preparation method of positive electrode sheet:

[0118] Positive electrode active material 1, conductive carbon black (Super-P), and polyvinylidene fluoride (PVDF) in a weight ratio of 95.5:3:1.5 were mixed with N,N-dimethylpyrrolidone (NMP) and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry was evenly coated on both sides of aluminum foil. The electrode sheet was cold pressed and sliced ​​to produce a positive electrode sheet.

[0119] Preparation method of negative electrode sheet:

[0120] Artificial graphite, nano-silicon, conductive carbon black (Super-P), carbon nanotubes, sodium carboxymethyl cellulose (CMC-Na), and styrene-butadiene rubber (SBR) are mixed with deionized water in a weight ratio of 95:5:0.5:0.1:1:1.5 and stirred evenly to obtain a slurry for coating the negative electrode sheet. The viscosity can be adjusted with deionized water during the stirring process. The slurry is then applied to both sides of the negative electrode current collector at a certain width. The negative electrode sheet is produced by cold pressing and slicing. In the present embodiment, the negative electrode current collector is copper foil.

[0121] Preparation method of battery monomer:

[0122] The positive electrode sheet, the separator and the negative electrode sheet are wound into a battery cell assembly, and the battery cell is produced through the steps of tab welding, aluminum shell packaging, liquid injection, packaging formation and vacuum molding. The battery cell assembly has a width of 148 mm, a thickness of 28 mm, a height of 98 mm and a capacity of 60 Ah. Among them, the injected electrolyte is a 1 mol / L LiPF6 solution, and the solvent of the LiPF6 solution is ethylene carbonate (EC) and dimethyl carbonate (DMC), and the volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) is 1:2. In the embodiment of the present application, the separator adopts 7 μm thick polyethylene (PE).

[0123] Example 2

[0124] The difference from Example 1 lies in the preparation method of the positive electrode active material. Specifically, the preparation method of the positive electrode active material is:

[0125] (1) Based on Ni 0.55 Co 0.06 Mn 0.39 The mass of the (OH)2 precursor was measured, and 4000 ppm of lithium difluorophosphate (LiPO2F2) was weighed and dissolved in water until it was fully dissolved to obtain a difluorophosphate aqueous solution.

[0126] (2) In Ni 0.55 Co 0.06 Mn 0.39 The (OH)2 precursor was spray-coated with a difluorophosphate aqueous solution containing 4000 ppm, and the spraying time was 20 minutes.

[0127] (3) The precursor coated with difluorophosphate was mixed with lithium carbonate at a molar ratio of 1:1.05; 0.55 Co 0.06 Mn 0.39 The (OH)2 precursor was mixed with 1000 ppm ZrO2 in a high-speed mixer at 1500 rpm for 2 hours. The mixture was sintered in a kiln at 900°C for 13 hours, cooled to room temperature, and crushed to obtain the positive electrode active material.

[0128] Example 3

[0129] The difference from Example 1 lies in the preparation method of the positive electrode active material. Specifically, the preparation method of the positive electrode active material is:

[0130] (1) Based on Ni 0.55 Co 0.06 Mn 0.39 The mass of the (OH)2 precursor was measured, and 1500 ppm of lithium difluorophosphate (LiPO2F2) was weighed and dissolved in water until it was fully dissolved to obtain a difluorophosphate aqueous solution.

[0131] (2) In Ni 0.55 Co 0.06 Mn 0.39 The (OH)2 precursor was spray-coated with a difluorophosphate aqueous solution containing 1500 ppm, and the spraying time was 20 minutes.

[0132] (3) The precursor coated with difluorophosphate was mixed with lithium carbonate at a molar ratio of 1:1.05; 0.55 Co 0.06 Mn 0.39 The (OH)2 precursor was mixed with 1000 ppm AlO2 in a high-speed mixer at 1500 rpm for 2 hours. The mixture was sintered in a kiln at 900°C for 13 hours, cooled to room temperature, and crushed to obtain the positive electrode active material.

[0133] Example 4

[0134] The difference from Example 1 lies in the preparation method of the positive electrode active material. Specifically, the preparation method of the positive electrode active material is:

[0135] (1) Based on Ni 0.55 Co 0.06 Mn 0.39 The mass of the (OH)2 precursor was measured, and 1500 ppm of lithium difluorophosphate (LiPO2F2) was weighed and dissolved in water until it was fully dissolved to obtain a difluorophosphate aqueous solution.

[0136] (2) In Ni 0.55 Co 0.06 Mn 0.39 The (OH)2 precursor was spray-coated with a difluorophosphate aqueous solution containing 1500 ppm, and the spraying time was 20 minutes.

[0137] (3) The precursor coated with difluorophosphate was mixed with lithium carbonate at a molar ratio of 1:1.05; 0.55 Co 0.06 Mn 0.39 The (OH)2 precursor was mixed with 1000ppm AlO2 and 1000ppm ZrO2 in a high-speed mixer at 1500rpm for 2 hours. The mixture was sintered in a kiln at 900°C for 13 hours, cooled to room temperature, and crushed to obtain the positive electrode active material.

[0138] Example 5

[0139] The difference from Example 1 lies in the preparation method of the positive electrode active material. Specifically, the preparation method of the positive electrode active material is:

[0140] (1) Dissolve 1500 ppm of lithium difluorophosphate (LiPO2F2) in water until it is fully dissolved to obtain a difluorophosphate aqueous solution.

[0141] (2) In Ni 0.65 Co 0.12 Mn 0.23 The (OH)2 precursor was spray-coated with a difluorophosphate aqueous solution containing 1500 ppm, and the spraying time was 60 minutes.

[0142] (3) The difluorophosphate-coated precursor was mixed with lithium carbonate at a molar ratio of 1:1.05, and 1000 ppm of ZrO2 was added. The mixture was mixed in a high-speed mixer at 1500 rpm for 2 h. The mixture was sintered in a kiln at 900°C for 13 h, cooled to room temperature, and crushed to obtain the positive electrode active material.

[0143] Example 6

[0144] The difference from Example 1 lies in the preparation method of the positive electrode active material. Specifically, the preparation method of the positive electrode active material is:

[0145] (1) Dissolve 300 ppm of lithium difluorophosphate (LiPO2F2) in water until it is fully dissolved to obtain a difluorophosphate aqueous solution.

[0146] (2) In Ni 0.65 Co 0.12 Mn 0.23 The (OH)2 precursor was spray-coated with a 300 ppm aqueous solution of difluorophosphate, and the spraying time was 5 minutes.

[0147] (3) The difluorophosphate-coated precursor was mixed with lithium carbonate at a molar ratio of 1:1.05 in a high-speed mixer at 1500 rpm for 2 h. The mixture was sintered in a kiln at 950°C for 10 h, cooled to room temperature, and crushed to obtain the positive electrode active material.

[0148] Example 7

[0149] The difference from Example 1 lies in the preparation method of the positive electrode active material. Specifically, the preparation method of the positive electrode active material is:

[0150] (1) Dissolve 1500 ppm of lithium difluorophosphate (LiPO2F2) in water until it is fully dissolved to obtain a difluorophosphate aqueous solution.

[0151] (2) In Ni 0.9 Co 0.02 Mn 0.08 The (OH)2 precursor was spray-coated with a difluorophosphate aqueous solution containing 1500 ppm, and the spraying time was 20 minutes.

[0152] (3) The difluorophosphate-coated precursor was mixed with lithium carbonate at a molar ratio of 1:1.05 in a high-speed mixer at 1500 rpm for 2 h. The mixture was sintered in a kiln at 930°C for 33 h, cooled to room temperature, and crushed to obtain a positive electrode active material.

[0153] Example 8

[0154] The difference from Example 1 lies in the preparation method of the positive electrode active material. Specifically, the preparation method of the positive electrode active material is:

[0155] (1) Dissolve 1500 ppm of lithium difluorophosphate (LiPO2F2) in water until it is fully dissolved to obtain a difluorophosphate aqueous solution.

[0156] (2) In Ni 0.65 Co 0.12 Al 0.23 The (OH)2 precursor was spray-coated with a difluorophosphate aqueous solution containing 1500 ppm, and the spraying time was 20 minutes.

[0157] (3) The difluorophosphate-coated precursor was mixed with lithium carbonate at a molar ratio of 1:1.05, and 1000 ppm of ZrO2 was added. The mixture was mixed in a high-speed mixer at 1500 rpm for 2 h. The mixture was sintered in a kiln at 900°C for 13 h, cooled to room temperature, and crushed to obtain the positive electrode active material.

[0158] Comparative Example 1

[0159] The difference from Example 1 lies in the preparation method of the positive electrode active material. Specifically, the preparation method of the positive electrode active material of Comparative Example 1 is:

[0160] (1) Ni 0.55 Co 0.06 Mn 0.39 The (OH)2 precursor was mixed with lithium carbonate at a molar ratio of 1:1.05 in a high-speed mixer at 1500 rpm for 2 hours. The mixture was then sintered in a kiln at 900°C for 13 hours, cooled to room temperature, and crushed to obtain the positive electrode active material.

[0161] Comparative Example 2

[0162] The difference from Example 1 lies in the preparation method of the positive electrode active material. Specifically, the preparation method of the positive electrode active material is:

[0163] (1) Ni 0.65 Co 0.12 Mn 0.23The (OH)2 precursor was mixed with lithium carbonate at a molar ratio of 1:1.05 in a high-speed mixer at 1500 rpm for 2 hours. The mixture was then sintered in a kiln at 900°C for 13 hours, cooled to room temperature, and crushed to obtain the positive electrode active material.

[0164] Comparative Example 3

[0165] The difference from Example 1 lies in the preparation method of the positive electrode active material. Specifically, the preparation method of the positive electrode active material is:

[0166] (1) Ni 0.55 Co 0.06 Mn 0.39 The (OH)2 precursor was mixed with lithium carbonate at a molar ratio of 1:1.05, and 1000 ppm of ZrO2 was added. The mixture was mixed in a high-speed mixer at 1500 rpm for 2 hours. The mixture was sintered in a kiln at 900°C for 13 hours, cooled to room temperature, and crushed to obtain the positive electrode active material.

[0167] Comparative Example 4

[0168] The difference from Example 1 lies in the preparation method of the positive electrode active material. Specifically, the preparation method of the positive electrode active material is:

[0169] (1) Ni 0.65 Co 012 Al 0.23 The (OH)2 precursor was mixed with lithium carbonate at a molar ratio of 1:1.05, and 1000 ppm of ZrO2 was added. The mixture was mixed in a high-speed mixer at 1500 rpm for 2 hours. The mixture was sintered in a kiln at 900°C for 13 hours, cooled to room temperature, and crushed to obtain the positive electrode active material.

[0170] The positive electrode active materials of Examples 1 to 8 and Comparative Examples 1 to 4 were made into corresponding batteries 1, 2, 3, 4, 5, 6, 7, 8 and batteries 9, 10, 11, and 12, and battery performance tests were performed, as shown in Table 1. Specifically, the battery was tested for high-temperature gas generation, gram capacity, and high-temperature storage performance. The specific test conditions were:

[0171] 1. High temperature gas production test

[0172] The high-temperature gas generation test method for batteries involves fully charging the battery to 4.5V at 1C and then placing it in a 70°C incubator for 30 days. The initial volume and the volume after 30 days of standing are measured using the water displacement method to determine the battery's volume expansion rate. Battery volume expansion rate (%) = (volume after 30 days of standing / initial volume - 1) × 100%.

[0173] 2. Battery gram capacity test

[0174] The battery capacity test is to place the battery at a constant temperature of 25°C for 2 hours, then charge it to 4.5V at 1 / 3C, then charge it at 4.5V at a constant voltage until the current is ≤0.05mA, let it stand for 5 minutes, and then discharge it to 2.8V at 1C, and record the battery capacity C. 放 .

[0175] Gram capacity = battery capacity C 放 (mAh) / mass of positive electrode active material (g).

[0176] 3. High temperature storage performance test

[0177] At 25°C, the battery was charged to 4.5V at a constant current rate of 0.33C, then charged at a constant voltage until the current was less than or equal to 0.05C, and then discharged to 2.8V at a constant current rate of 0.33C. The initial discharge capacity of the battery was obtained by testing. At 25°C, the battery was charged to 4.5V at a constant current rate of 0.33C, then charged at a constant voltage until the current was less than or equal to 0.05C, and then the fully charged battery was placed in a 60°C oven. After 15 days of high-temperature storage, the battery was taken out and naturally cooled to 25°C, discharged to 2.8V at a constant current rate of 0.33C, then charged to 4.5V at a constant current rate of 0.33C, then charged at a constant voltage until the current was less than or equal to 0.05C, and then discharged to 2.8V at a constant current rate of 0.33C. The discharge capacity of the battery after 15 days of high-temperature storage was obtained by testing. It was then placed in a 60°C oven until the capacity retention rate was less than 80%. Repeat the test every 15 days.

[0178] Capacity retention rate (%) after 60 days of high-temperature storage = discharge capacity after 60 days of high-temperature storage / initial discharge capacity × 100%. The number of days for the capacity to decay to 80% is obtained by drawing a line based on the test data.

[0179] 4. Volume average particle size Dv50 test.

[0180] Equipment model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer, reference standard process: GB / T19077-2016 / ISO 13320:2009, specific test process: Take an appropriate amount of the sample to be tested (the sample concentration is 8% to 12% obscuration), add 20ml of deionized water, and ultrasonicate for 5min (53KHz / 120W) to ensure that the sample is completely dispersed. Then, the sample is measured according to GB / T19077-2016 / ISO 13320:2009 standard.

[0181] Table 2 Process parameters and performance parameters of the embodiments and comparative examples

[0182] As can be seen from the process parameters and performance parameters in Tables 1 and 2, based on Comparative Examples 1 to 4, the positive electrode active materials of Examples 1 to 8 of the present application significantly reduce the high-temperature gas production performance of the positive electrode active materials of Examples 1 to 8 of the present application to 20% to 43% by adding fluorine-phosphorus compounds to the positive electrode active main material, which is lower than the 58% to 70% of Comparative Examples 1 to 4. The high-temperature storage performance of the positive electrode active materials of Examples 1 to 8 of the present application is significantly improved, and the high-temperature storage can reach 480 days to 650 days, which is much higher than the 195 days to 210 days of Comparative Examples 1 to 4. The 1 / 3C capacity of the positive electrode active materials of Examples 1 to 8 of the present application is between 190 mAh / g and 198 mAh / g, and the positive electrode active materials of Examples 1 to 8 of the present application can also maintain a relatively high capacity. In Examples 1 to 8 of the present application, the positive electrode active main material includes a fluorine-phosphorus compound, and the fluorine-phosphorus compound includes lithium difluorophosphate. In Examples 1 to 8 of the present application, a difluorophosphate solution is coated on the surface of a nickel-cobalt-manganese precursor or a nickel-cobalt-aluminum precursor by spraying, so that the fluorine-phosphorus compound in the positive electrode active material is mixed uniformly on the surface of the positive electrode active main material, which is beneficial to improving the stability of the positive electrode active main material. In the positive electrode active main materials of Examples 1 to 8 of the present application, at a sintering temperature of 900°C to 950°C, the fluorine-phosphorus compound decomposes F and P elements and dopes them into the bulk phase of the positive electrode active main material, wherein the F element is doped into the oxygen site of the hexagonal system of the positive electrode active main material, and the P element is doped into the hexagonal lattice or / and the oxygen site of the hexagonal system of the positive electrode active main material, thereby modifying the positive electrode active main material, inhibiting the oxidation activity of the positive electrode active main material, stabilizing the bulk structure of the positive electrode active main material, and enhancing the stability of the positive electrode active material under high temperature conditions, thereby significantly improving the storage performance and gas production problems of the battery.

[0183] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode active material, wherein The positive electrode active material includes: A positive electrode active main material, wherein the positive electrode active main material comprises lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide; A fluorine-phosphorus compound is mixed into the positive electrode active host material.

2. The positive electrode active material according to claim 1, wherein The fluorine-phosphorus compound is located on the surface layer of the positive electrode active main material.

3. The positive electrode active material according to claim 1, wherein The fluorophosphorus compound includes a structural formula of Li p P q O r The compound of F2, wherein 0.8≤p≤1.2, 0.8≤q≤1.2, and 1.8≤r≤2.

2.

4. The positive electrode active material according to claim 1 or 2, wherein The positive electrode active main material includes a structural formula of Li(Ni x Co y M z ) 1-u T u O2 material, wherein M includes Mn or Al, T includes one or more of Zr, Sr, B, Ti, Mg, Na, Si, Sn, Tb, W, Nb, Sb and Al, x+y+z=1, 0.3≤x≤0.9, 0.03≤y≤0.3, 0.05≤z≤0.4, 0.0003≤u≤0.

004.

5. The positive electrode active material according to any one of claims 1 to 4, wherein The positive electrode active main material is doped with fluorine and phosphorus elements.

6. The positive electrode active material according to any one of claims 1 to 5, wherein The mass fraction of the fluorine-phosphorus compound to the total mass of the positive electrode active material is 0.015% to 0.4%.

7. The positive electrode active material according to any one of claims 1 to 6, wherein The volume average particle size DV50 of the positive electrode active material is 3 μm to 15 μm.

8. A method for preparing a positive electrode active material, wherein: include: Spraying a difluorophosphate solution onto a nickel-cobalt metal precursor so that the difluorophosphate is coated on the nickel-cobalt metal precursor, wherein the nickel-cobalt metal precursor includes a nickel-cobalt-manganese precursor or a nickel-cobalt-aluminum precursor; A nickel-cobalt metal precursor coated with difluorophosphate is mixed with a lithium source and sintered to form lithium nickel-cobalt-manganese oxide or lithium nickel-cobalt-aluminum oxide mixed with fluorine-phosphorus compounds.

9. The method for preparing a positive electrode active material according to claim 6, wherein: The spray coating spray time is 5 minutes to 60 minutes.

10. The method for preparing a positive electrode active material according to any one of claims 8 to 9, wherein: The mass ratio of the difluorophosphate in the difluorophosphate solution to the nickel-cobalt metal precursor is 3×10 -4 ~4×10 -3 :

1.

11. The method for preparing a positive electrode active material according to any one of claims 8 to 10, wherein: The method comprises mixing a nickel-cobalt metal precursor coated with difluorophosphate and a lithium source, comprising: Mixing a nickel-cobalt metal precursor coated with difluorophosphate, a lithium source, and a metal doping source, wherein the metal doping source comprises one or more metal oxides of Zr, Sr, B, Ti, Mg, Na, Si, Sn, Tb, W, Nb, Sb, and Al; Wherein, the nickel-cobalt metal precursor comprises a structural formula (Ni a Co b M c ) d (OH)2, 0.3≤a≤0.9, 0.01≤b≤0.4, 0.1≤c≤0.5, a+b+c=1, 0.95≤d≤1, M includes Mn or Al; or / and, The lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium sulfate, lithium nitrate, lithium acetate and lithium phosphate; or / and, The mixing speed is 600 rpm to 2000 rpm, and the mixing time is 30 min to 300 min.

12. The method for preparing a positive electrode active material according to any one of claims 8 to 11, wherein: The sintering temperature is 900° C. to 950° C., and the sintering time is 10 hours to 33 hours.

13. A positive electrode sheet, wherein: The positive electrode active material comprises the positive electrode active material according to any one of claims 1 to 7, and / or the positive electrode active material prepared by the method for preparing the positive electrode active material according to any one of claims 6 to 10.

14. A battery, wherein: The positive electrode active material comprises the positive electrode active material according to any one of claims 1 to 8, and / or the positive electrode active material prepared by the method for preparing the positive electrode active material according to any one of claims 6 to 10, or the positive electrode sheet according to claim 13.

15. An electrical device, wherein: Including the battery according to claim 14.

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