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

Abstract

The application relates to the technical field of lithium batteries, in particular to a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and an electric device. The positive electrode active material comprises a positive electrode active main material and a fluorophosphorus compound. The positive electrode active main material comprises a lithium nickel cobalt manganese oxide or / and a lithium nickel cobalt aluminum oxide. The fluorophosphorus compound is mixed in the positive electrode active main material. The application realizes the modification of the positive electrode active material by mixing the fluorophosphorus compound in the positive electrode active material, stabilizes the bulk structure of the positive electrode active material, improves the storage life under high-temperature conditions, and optimizes the electrochemical performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery, and particularly relates to a positive electrode active material, a preparation method thereof, a positive electrode sheet, a battery and an electric device. BACKGROUND

[0002] Lithium ion battery is the most widely used electrochemical energy storage device in the field of energy. As the main material with the largest proportion in the lithium ion battery, the positive electrode material has a great influence on the overall performance of the battery. However, the side reaction of the positive electrode material is intense under high temperature and high pressure, which leads to the shortening of the service life of the battery, and thus the industrialization of the lithium ion battery under high temperature and high pressure is greatly limited. SUMMARY

[0003] Therefore, the present application mainly solves the technical problem of the instability of the bulk structure of the positive electrode material under high temperature and high pressure, and provides a positive electrode active material, a preparation method thereof, a positive electrode sheet, a battery and an electric device, 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.

[0004] The first aspect of the present application provides a positive electrode active material. The positive electrode active material comprises a positive electrode active host material and a fluorophosphorus compound. The positive electrode active host material comprises lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide; and the fluorophosphorus compound is doped in the positive electrode active host material.

[0005] In the technical scheme of the present application, the fluorophosphorus compound is doped in the positive electrode active host material formed by lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide, which can inhibit the oxidation activity of the positive electrode active host material, stabilize the bulk structure of the positive electrode active host material, and enhance the stability of the positive electrode active material under high temperature environment, so that the storage performance and gas production problem of the battery can be obviously improved. In addition, the fluorophosphorus compound is acidic, and can also react with residual alkali on the surface of the positive electrode active host material to reduce the decomposition of the residual alkali in the charging and discharging process of the battery and cause the battery to deteriorate.

[0006] In any embodiment, the fluorophosphorus compound is located on the surface layer of the positive electrode active host material.

[0007] In the technical scheme of the present application, the fluorophosphorus compound located on the surface layer of the positive electrode active host material can inhibit the oxidation activity of the positive electrode active host material, stabilize the bulk structure of the positive electrode active host material, and enhance the stability of the positive electrode active material under high temperature environment, so that the storage performance and gas production problem of the battery can be obviously improved. In addition, the fluorophosphorus compound is acidic, and can also react with residual alkali on the surface of the positive electrode active host material to reduce the decomposition of the residual alkali in the charging and discharging process of the battery and cause the battery to deteriorate.

[0008] In any embodiment, the fluorophosphorus compound includes a compound of structural formula Li p P q O r F2, wherein 0.8≤p≤1.2, 0.8≤q≤1.2, and 1.8≤r≤2.2.

[0009] In the technical solution of the embodiment of the application, the fluorophosphorus compound is a compound of structural formula Li p P q O r F2, which can enhance the stability of the overall structure of the positive electrode active material and maintain good electrical performance at a high voltage of 4.5 V.

[0010] In any embodiment, the positive electrode active host material includes a material of structural formula Li(Ni x Co y M z ) 1-u T u O2, 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, and 0.0003≤u≤0.004.

[0011] In the technical solution of the embodiment of the application, the positive electrode active host material is a material of structural formula Li(Ni x Co y M z ) 1-u T u O2, which has a hexagonal crystal structure, has a high energy density, that is, has better electrical energy storage performance under the same volume and mass, and has high chemical stability and is not prone to thermal runaway, thereby having a longer service life.

[0012] In any embodiment, the positive electrode active host material is doped with fluorine elements and phosphorus elements.

[0013] In the technical solution of the embodiment of the application, the positive electrode active host material formed by lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide is doped with fluorine elements and phosphorus elements. The fluorine elements are doped in the oxygen sites of the hexagonal crystal system of the positive electrode active host material, and the phosphorus elements are doped in the crystal lattice of the hexagonal crystal system or / and the oxygen sites of the hexagonal crystal system, so as to modify the positive electrode active host material, inhibit the oxidation activity of the positive electrode active host material, stabilize the bulk structure of the positive electrode active host material, and enhance the stability of the positive electrode active material under high temperature conditions, thereby obviously improving the storage performance and gas production problems of the battery.

[0014] In any embodiment, the fluorophosphorus compound accounts for 0.015% to 0.4% of the total mass of the positive electrode active material. Alternatively, the fluorophosphorus compound accounts for 0.03% to 0.3% of the total mass of the positive electrode active material. By controlling the content of the fluorophosphorus compound in the positive electrode active material, both the residual alkali on the surface of the positive electrode active host material and the stability of the positive electrode active material can be inhibited, so that the battery has excellent electrical performance.

[0015] 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 be 3 μm to 15 μm, the sites for lithium intercalation and deintercalation of the positive electrode active material are large, ensuring that the battery has good power performance.

[0016] 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 be 3 μm to 15 μm, the sites for lithium intercalation and deintercalation of the positive electrode active material are large, ensuring that the battery has good power performance.

[0017] The second aspect of the present application also provides a preparation method of a positive electrode active material, which comprises: spraying a difluorophosphate solution on a nickel-cobalt metal precursor to coat the difluorophosphate on the nickel-cobalt metal precursor, wherein the nickel-cobalt metal precursor comprises 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 to form a lithium nickel cobalt manganese oxide or a lithium nickel cobalt aluminum oxide doped with a fluorophosphorus compound.

[0018] In the technical solution of the embodiments of the present application, the difluorophosphate solution is coated on the surface of the nickel-cobalt metal precursor in the form of spraying, so that the contact between the difluorophosphate and the nickel-cobalt metal precursor is more uniform, the agglomeration of the difluorophosphate can be reduced, and the surface distribution of the lithium nickel cobalt manganese oxide or the lithium nickel cobalt aluminum oxide doped with the fluorophosphorus compound formed finally is more uniform and has small differences in different directions.

[0019] In any embodiment, the spraying time of the spraying coating is 5 min to 60 min. Alternatively, the spraying time is 8 min to 30 min. Controlling the spraying coating time within this range facilitates the uniform and sufficient mixing of the difluorophosphate solution and the nickel-cobalt metal precursor.

[0020] In any embodiment, the mass ratio of the difluorophosphate in the difluorophosphate solution to the nickel-cobalt metal precursor is 3 x 10 -4 to 4 x 10 -3 : 1. By controlling the mass ratio of the difluorophosphate to the nickel-cobalt metal precursor, both the residual alkali on the surface of the positive electrode active host material and the stability of the positive electrode active material can be inhibited, so that the battery has excellent electrical performance.

[0021] In any embodiment, the mixing of the nickel-cobalt metal precursor coated with difluorophosphate and the lithium source comprises: mixing the nickel-cobalt metal precursor coated with difluorophosphate, the 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.

[0022] In any embodiment, the nickel-cobalt metal precursor comprises a structural formula of (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, and M comprises Mn or Al. Using the hydroxide precursor as a material for preparing a positive electrode active material, the prepared positive electrode active material has the advantage of high specific capacity, and has good compatibility with electrolyte and is widely used.

[0023] In any embodiment, the lithium source comprises 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 elements, which have high electrochemical activity and can chemically react with other elements in the battery to release electrons and generate current.

[0024] In any embodiment, the mixing speed is 600 rpm-2000 rpm, and the mixing time is 30 min-300 min. This mixing method makes the mixing of the nickel-cobalt metal precursor and the lithium source more sufficient.

[0025] In any embodiment, the sintering temperature is 900℃-950℃, and the sintering time is 10 h-33 h. In the embodiment of the application, the sintering temperature and the sintering time are controlled to facilitate the synthesis of nickel-cobalt-manganese oxide or / and lithium-nickel-cobalt-aluminum oxide, and to make the volume average particle size DV50 of the nickel-cobalt-manganese oxide or / and lithium-nickel-cobalt-aluminum oxide within a predetermined range, for example, within a range of 3 μm-15 μm, so that the power performance of the battery is better.

[0026] The third aspect of the application also provides a positive electrode tab comprising the positive electrode active material of the first aspect of the application, and / or the positive electrode active material prepared by the preparation method of the second aspect of the application. Since the positive electrode tab of the application comprises the positive electrode active material provided by the application, it at least has the same advantages as the positive electrode active material.

[0027] 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 preparation method of the positive electrode active material of the second aspect of the present application, or the positive electrode tab of the third aspect of the present application. Since the battery of the present application comprises the positive electrode active material provided by the present application, it at least has the same advantages as the positive electrode active material.

[0028] The fifth aspect of the present application further provides an electric device comprising the battery of the fourth aspect of the present application. Since the electric device of the present application comprises the battery provided by the present application, it at least has the same advantages as the battery.

[0029] The beneficial effects of the present application are: different from the prior art, the positive electrode active material of the present application comprises 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, so that the stability of the positive electrode active material is enhanced in a high temperature environment, thereby the storage performance and the gas production problem of the battery are obviously improved. 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 in the battery charging and discharging process to cause the battery to deteriorate.

[0030] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented according to the content of the specification, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a structural schematic diagram of a battery monomer of an embodiment of the present application.

[0032] Figure 2 is a disassembled structural schematic diagram of a battery of an embodiment of the present application.

[0033] Figure 3a is a partial structural schematic diagram of an electric device of an embodiment of the present application.

[0034] Figure 3b is a schematic diagram of an electric device of an embodiment of the present application. DETAILED DESCRIPTION

[0035] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0036] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" 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.

[0037] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0038] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0039] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means 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.

[0040] If not specifically stated, "including" and "comprising" as used herein are open-ended and also include the other components not listed. For example, "including" and "comprising" can mean that other components can also be included or can also include only the listed components.

[0041] If not specifically stated, the term "or" in the present application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any one of the following conditions satisfies the condition "A or B": 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 A and B are both true (or exist).

[0042] The positive active material, as the largest main material in lithium ion batteries, has a great influence on the overall performance of the battery. In the current technology, in order to maximize the energy of the ternary positive active material and minimize the cost, the use voltage is often increased. However, under high voltage (3.7V-4.5V), the side reaction of the positive active material is severe, which leads to a short service life. Therefore, the industrialization of high-voltage ternary positive active materials is greatly limited. The conventional modification method of high-voltage ternary positive active materials is mainly aimed at the surface of the positive active material, and a modified material is coated on the surface of the positive active material to inhibit the side reaction between the surface of the positive active material and the electrolyte. However, the surface polarization of the positive active material coated with the modified material is too large, which causes poor battery capacity performance. In addition, the surface coating layer hinders the lithium ion transmission channel, which causes serious capacity fading and serious cycle fading of the battery. On the other hand, the surface coating layer has poor inhibition effect on the side reaction under high temperature and high pressure.

[0043] Based on this, the present application provides a positive active material. The positive active material comprises a positive active host material and a fluorophosphorus compound. The positive active host material comprises lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide; and the fluorophosphorus compound is mixed in the positive active host material.

[0044] In the embodiments of the present application, the fluorophosphorus compound is mixed in the positive active host material formed by lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide, which can inhibit the oxidation activity of the positive active host material, stabilize the bulk structure of the positive active host material, and enhance the stability of the positive active material under high temperature environment, so that the storage performance and gas production problems of the battery can be obviously improved. In addition, the fluorophosphorus compound is acidic, and can also react with residual alkali on the surface of the positive active host material to reduce the decomposition of the residual alkali during the charging and discharging process of the battery, thereby preventing the battery from deteriorating.

[0045] In some embodiments of the present application, the fluorophosphorus compound is located on the surface layer of the positive active host material.

[0046] The fluorophosphorus compound located on the surface layer of the positive electrode active host material can inhibit the oxidation activity of the positive electrode active host material, stabilize the bulk structure of the positive electrode active host material, and enhance the stability of the positive electrode active material in a high-temperature environment, so that the storage performance and gas production problems of the battery are obviously improved. In addition, the fluorophosphorus compound is acidic, and can also react with residual alkali on the surface of the positive electrode active host material to reduce the decomposition of the residual alkali in the battery charging and discharging process and cause the battery to deteriorate.

[0047] In some embodiments of the present application, the fluorophosphorus compound includes a compound with a structural formula of Li p P q O r F2, wherein 0.8≤p≤1.2, 0.8≤q≤1.2, and 1.8≤r≤2.2. The fluorophosphorus compound with a structural formula of Li p P q O r F2 can enhance the stability of the structure of the positive electrode active material and maintain good electrical performance at a high voltage of 4.5V. At the same time, the fluorophosphorus compound is acidic and can also react with residual alkali on the surface of the positive electrode active host material to reduce the decomposition of the residual alkali in the battery charging and discharging process and cause the battery to deteriorate.

[0048] In some embodiments of the present application, the positive electrode active host material includes a material with a structural formula of Li(Ni x Co y M z ) 1-u T u O2, 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, and 0.0003≤u≤0.004.

[0049] In the technical solution of the embodiments of the present application, the positive electrode active host material with a structural formula of Li(Ni x Co y M z ) 1-u T u O2 has a hexagonal crystal structure, has a high energy density, that is, has better electrical energy storage performance under the same volume and mass, and has high chemical stability and is not prone to thermal runaway, so has a longer service life.

[0050] In some embodiments of the present application, the positive electrode active host material is doped with fluorine elements and phosphorus elements.

[0051] In the technical scheme of the embodiments of the present application, the positive electrode active host material formed by lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide is doped with fluorine elements and phosphorus elements. The fluorine elements are doped in the oxygen sites of the hexagonal system of the positive electrode active host material, and the phosphorus elements are doped in the crystal lattices of the hexagonal system or / and the oxygen sites of the hexagonal system of the positive electrode active host material. In this way, the modification of the positive electrode active host material is realized, the oxidation activity of the positive electrode active host material is inhibited, the bulk structure of the positive electrode active host material is stabilized, the stability of the positive electrode active material is enhanced under high temperature conditions, and thus the storage performance and the gas production problem of the battery are obviously improved.

[0052] 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 accounts for 0.03% to 0.3%. For example, it can be 0.015%, 0.03%, 0.059%, 0.15%, 0.19%, 0.26%, 0.29%, 0.3%, 0.34%, 0.4%, etc., or a range composed of any two of the above values, for example, 0.015% to 0.26%, 0.26% to 0.34%, 0.34% to 0.4%, etc. By controlling the content of the fluorophosphorus compound in the positive electrode active material, both the residual alkali on the surface of the positive electrode active host material and the stability of the positive electrode active material can be improved, so that the battery has excellent electrical performance.

[0053] In some embodiments of the present application, 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 be 3 μm to 15 μm, the lithium insertion and deintercalation sites of the positive electrode active material are larger, and the power performance of the battery monomer is ensured to be better. The volume average particle size DV50 of the positive electrode active material can be 3 μm, 4.2 μm, 5.5 μm, 6.9 μm, 9.4 μm, 12.5 μm, 15 μm, etc., or a range composed of any two of the above values, for example, 3 μm to 6.9 μm, 6.9 μm to 12.5 μm, 12.5 μm to 15 μm, etc. The volume average particle size DV50 of the positive electrode active material is a common knowledge in the art and has the meaning known in the art, and can be measured by the methods and instruments in the art.

[0054] The second technical scheme adopted in the present application is to provide a preparation method of a positive electrode active material, which comprises: spraying a difluorophosphate solution on a nickel-cobalt metal precursor to coat the difluorophosphate on the nickel-cobalt metal precursor, wherein the nickel-cobalt metal precursor comprises 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 to form lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide doped with a fluorophosphorus compound.

[0055] Specifically, the preparation method of the positive electrode active material comprises the following steps:

[0056] Step one: after lithium difluorophosphate is fully dissolved in deionized water to form a lithium difluorophosphate solution, the lithium difluorophosphate solution is coated on the nickel-cobalt-manganese precursor or the nickel-cobalt-aluminum precursor by using a wet spraying method.

[0057] Lithium difluorophosphate is easily soluble in water, and in this embodiment, deionized water, which is harmless and non-polluting, is used as the solvent. Lithium difluorophosphate is dissolved in deionized water to form a lithium difluorophosphate solution. After the solution is formed, the subsequent coating is performed by using a spraying method. Of course, in other embodiments, lithium difluorophosphate can also be dissolved in alcohol solvents such as methanol or ethanol.

[0058] In this embodiment, the mass ratio of lithium difluorophosphate in the lithium difluorophosphate solution to the nickel-cobalt metal precursor is 3×10 -4 ~4×10 -3 :1. By controlling the mass ratio of lithium difluorophosphate to the nickel-cobalt metal precursor, the residual alkali on the surface of the positive electrode active host material can be inhibited, and the stability of the positive electrode active material can be improved, so that the battery has excellent electrical properties. The mass ratio of lithium difluorophosphate in the lithium difluorophosphate solution to the nickel-cobalt metal precursor 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, or a range composed 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.

[0059] Then, the lithium difluorophosphate solution is coated on the surface of the nickel-cobalt-manganese precursor or the nickel-cobalt-aluminum precursor by using a spraying coating method. The spraying method can mix the lithium difluorophosphate solution and the nickel-cobalt metal precursor sufficiently, achieve uniform coating, reduce the occurrence of agglomeration of lithium difluorophosphate, and better play the effect of lithium difluorophosphate during subsequent sintering in a high-temperature environment, so as to realize the modification of the positive electrode active host material, inhibit the oxidation activity of the positive electrode active host material, stabilize the bulk structure of the positive electrode active host material, and enhance the stability of the positive electrode active material in a high-temperature environment.

[0060] In the embodiment, the spraying time for the spraying coating is 5-60 minutes, and the spraying time is optionally 8-30 minutes. Controlling the spraying time within the time range facilitates more uniform and sufficient mixing of the difluorophosphate solution and the nickel-cobalt metal precursor. The spraying time can be 5 minutes, 8 minutes, 15 minutes, 26 minutes, 30 minutes, 37 minutes, 45 minutes, 58 minutes, 60 minutes, or a range formed by any two of the above values, for example, 5-26 minutes, 26-45 minutes, 45-60 minutes, etc.

[0061] Step two: mixing the nickel-cobalt metal precursor coated with difluorophosphate and a lithium source, and sintering to form a lithium nickel cobalt manganese oxide or a lithium nickel cobalt aluminum oxide doped with a fluorophosphorus compound.

[0062] Specifically, the step includes mixing the nickel-cobalt metal precursor coated with difluorophosphate, a lithium source, and a metal doping source. The embodiment does not limit the mixing order. The nickel-cobalt metal precursor coated with difluorophosphate can be mixed with the lithium source first and then mixed with the metal doping source, or the nickel-cobalt metal precursor coated with difluorophosphate can be mixed with the metal doping source first and then mixed with the lithium source, or the nickel-cobalt metal precursor coated with difluorophosphate can be mixed with the lithium source and the 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, a lithium nickel cobalt manganese oxide doped with a fluorophosphorus compound or a lithium nickel cobalt aluminum oxide doped with a fluorophosphorus compound can be prepared by further sintering.

[0063] In some embodiments of the application, the nickel-cobalt metal precursor includes a structural formula of (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, and M includes Mn or Al. Using the hydroxide precursor as a substance for preparing a positive electrode active material has the advantages of high specific capacity and good compatibility with electrolyte, and is widely used.

[0064] 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 elements, which have high electrochemical activity and can chemically react with other elements in the battery to release electrons and generate current.

[0065] In some embodiments of the application, the nickel-cobalt metal precursor can include but is not limited to (Ni 0.3 Co0.4 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)2and (Ni 0.9 Co 0.01 Al 0.09 )1(OH)2.

[0066] The mixing of the nickel-cobalt metal precursor coated with difluorophosphate, the lithium source and the metal doping source is carried out in a tilting mill or a high-speed mixer, the mixing speed is 600 rpm-2000 rpm, and the mixing time is 30 min-300 min. This mixing method makes the mixing of the nickel-cobalt metal precursor and the lithium source more sufficient. 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 composed of any two of the above values, for example, 600 rpm-890 rpm, 890 rpm-1590 rpm, 1590 rpm-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 composed of any two of the above values, for example, 30 min-95 min, 95 min-210 min, 210 min-300 min, etc.

[0067] After mixing, sintering is performed, and the sintering temperature is 900-950°C, and the sintering time is 10-33h. In the related art, a low-temperature coating technique is used, and the low-temperature sintering temperature is 400-500°C. The low-temperature sintering can only coat lithium difluorophosphate on the outer surface of the positive electrode active material, and cannot realize mixing in the interior of the positive electrode active material. At the same time, the lithium difluorophosphate is not completely decomposed, and produces hydrogen fluoride and other incomplete combustion harmful substances. The sintering temperature of the present embodiment is 900-950°C, and the decomposition temperature of fluorophosphorus compounds is lower than 300°C. Therefore, in fact, at more than 300°C, the lithium difluorophosphate has been decomposed. When the temperature is increased to 900-950°C, the lithium difluorophosphate is decomposed into fluorine and phosphorus elements, which migrate to the interior of the positive electrode active material, and realize doping in the bulk phase of the positive electrode active material. The F element is doped in the oxygen site of the hexagonal crystal system of the positive electrode active material, and the P element is doped in the crystal lattice of the hexagonal crystal system or / and the oxygen site of the hexagonal crystal system, so as to realize modification of the positive electrode active material, inhibit the oxidation activity of the positive electrode active material, stabilize the bulk phase structure of the positive electrode active material, and enhance the stability of the positive electrode active material under high-temperature conditions, so that the storage performance and gas production problems of the battery are obviously improved. In the present embodiment, the sintering temperature is controlled in the range of 900-950°C, and the sintering time is controlled in the range of 10-33h, so as to control the synthesis of nickel-cobalt-manganese oxide or / and lithium-nickel-cobalt-aluminum oxide, and make the volume average particle size DV50 of the nickel-cobalt-manganese oxide or / and lithium-nickel-cobalt-aluminum oxide in a preset range, for example, in the range of 3-15μm, so that the power performance of the battery is better. The sintering temperature can be 900°C, 910°C, 925°C, 934°C, 945°C, 950°C, or a range composed of any two of the above values, for example, 900-925°C, 925-934°C, 934-950°C, etc. The sintering time can be 10h, 15h, 20h, 25h, 30h, 33h, or a range composed of any two of the above values, for example, 10-15h, 15-25h, 25-33h, etc.

[0068] It should be noted that, in the process of preparing the positive electrode active material, after sintering at 900-950°C, the fluorophosphorus compound in the positive electrode active material will decompose F elements and P elements, and the F elements and P elements will be doped into the lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide (i.e. the bulk phase of the positive electrode active material). After sintering is completed and cooling, first, part of the F elements and P elements are still doped in the lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide. The F elements will be doped in the oxygen sites of the hexagonal system of the positive electrode active material, and the P elements will be doped between the lattices of the hexagonal system of the positive electrode active material and / or doped in the oxygen sites of the hexagonal system, which can stabilize the bulk phase structure of the positive electrode active material and improve the structural stability. Among them, the F elements and P elements doped in the positive electrode active material can be characterized by observing the shift of the oxygen site characteristic peak or the change of other characteristic peaks through XRD refinement. Second, after sintering is completed and cooling, at least part of the decomposed F elements and P elements will re-form fluorophosphorus compounds. Therefore, after the final sintering is completed, the positive electrode active material will exhibit fluorophosphorus compounds, and the re-formed fluorophosphorus compounds are located in the surface layer of the positive electrode active material, which can stabilize the interface and improve the stability of the positive electrode active material. It should be noted that the re-formed fluorophosphorus compounds cannot decompose F elements and P elements.

[0069] The positive electrode active material prepared by the above preparation process contains difluorophosphate, which will decompose F elements and P elements doped in the bulk phase of the positive electrode active material at a high temperature of greater than 300°C, i.e. 900-950°C, to achieve modification of the positive electrode active material, inhibit the oxidation activity of the positive electrode active material, stabilize the bulk phase structure of the positive electrode active material, and enhance the stability of the positive electrode active material in a high temperature environment, so that the storage performance and gas production problems of the battery are obviously improved. In addition, the difluorophosphate in the surface layer of the positive electrode active material is acidic, which can also react with residual alkali on the surface of the positive electrode active material to reduce the decomposition of residual alkali during the charging and discharging process of the battery, thereby preventing the battery from deteriorating. The positive electrode active material prepared by the above preparation process has excellent high-temperature storage life.

[0070] The third technical solution adopted in the present application is to provide a positive electrode tab, which comprises the positive electrode active material of the first aspect of the present application and / or the positive electrode active material prepared by the preparation method of the second aspect of the present application. Since the positive electrode tab of the present application comprises the positive electrode active material provided by the present application, it at least has the same advantages as the positive electrode active material.

[0071] In addition, the battery cell, battery and electric device of the present application are described below with appropriate reference to the accompanying drawings.

[0072] In the embodiment of the present application, the battery cell refers to the smallest unit of a battery. The battery cell further includes an electrolyte and a separator. The separator is arranged between the positive electrode sheet and the negative electrode sheet, and mainly functions to prevent short circuit between the positive electrode and the negative electrode, and meanwhile allows ions to pass through. In the process of charging and discharging of the battery, active ions Li + The active ions Li+ and e- are reversibly embedded and extracted between the positive electrode sheet and the negative electrode sheet. The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet.

[0073] 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. The positive electrode film layer includes the positive electrode active material of the above-mentioned embodiments of the present application.

[0074] For example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof. The positive electrode film layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0075] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0076] In some embodiments, the positive electrode film layer can further optionally include a binder. For example, the binder can 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 acrylic ester resin.

[0077] In some embodiments, the positive electrode film layer can further optionally include a conductive agent. For example, the conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0078] In some embodiments, the positive electrode sheet can be prepared by dispersing components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and then performing processes such as drying, cold pressing, etc. to obtain the positive electrode sheet.

[0079] 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, the negative electrode film layer including a negative electrode active material.

[0080] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0081] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0082] In some embodiments, the negative electrode film layer can further optionally include a binder. The binder can 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).

[0083] In some embodiments, the negative electrode film layer can further optionally include a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0084] In some embodiments, the negative electrode film layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na), etc.

[0085] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on the negative electrode current collector, and then performing processes such as drying, cold pressing, etc., to obtain the negative electrode sheet.

[0086] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of the electrolyte is not specifically limited in the present application, and can be selected as needed.

[0087] In some embodiments, the electrolyte includes an electrolyte salt and a solvent.

[0088] 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 difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0089] In some embodiments, 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.

[0090] 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.

[0091] In some embodiments, the battery cell 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.

[0092] 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.

[0093] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into a cell assembly using a winding or stacking process.

[0094] In some implementations, such as Figure 1 As shown, the battery cell 10 may include an outer packaging. This outer packaging can be used to encapsulate the aforementioned cell assembly 11 and electrolyte. The outer packaging includes an end cap 12, a housing 13, and other functional components.

[0095] The end cover 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 cover 12 can be adapted to the shape of the shell 13 to fit the shell 13. Optionally, the end cover 12 can be made of a material with certain hardness and strength, such as aluminum alloy, so that the end cover 12 is less likely to deform when subjected to extrusion collision, allowing the battery cell 10 to have higher structural strength and improved safety performance. The end cover 12 can be provided with functional components such as electrode terminals 12a. The electrode terminals 12a can be used to electrically connect with the cell assembly 11 for outputting or inputting the electrical energy of the battery cell 10. In some embodiments, the end cover 12 can also be provided with a pressure relief mechanism for releasing the internal pressure when the internal pressure or temperature of the battery cell 10 reaches a threshold value. The material of the end cover 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 make special limitations thereon. In some embodiments, an insulating member (not shown in the figure) can also be provided on the inner side of the end cover 12, which can be used to isolate the electrical connection components in the shell 13 from the end cover 12 to reduce the risk of short circuit. Exemplarily, the insulating member can be plastic, rubber, etc.

[0096] The shell 13 is a component for fitting the end cover 12 to form the internal environment of the battery cell 10, wherein the formed internal environment can be used to accommodate the cell assembly 11, the electrolyte and other components. The shell 13 and the end cover 12 can be independent components, and an opening can be provided on the shell 13, and the end cover 12 is made to cover the opening to form the internal environment of the battery cell 10. Without limitation, the end cover 12 and the shell 13 can also be integrated, specifically, the end cover 12 and the shell 13 can form a common connecting surface before other components enter the shell, and when it is necessary to seal the inside of the shell 13, the end cover 12 is made to cover the shell 13. The shell 13 can be various shapes and sizes, such as cuboid, cylinder, hexagonal prism, etc. Specifically, the shape of the shell 13 can be determined according to the specific shape and size of the cell assembly 11. The material of the shell 13 can be various, such as copper, iron, aluminum, stainless steel, aluminum alloy, plastic, etc., and the embodiments of the present application do not make special limitations thereon.

[0097] The shell 13 can contain one or more cell assemblies 11. The parts of the positive and negative electrode sheets without active material each constitute a tab 11a. The positive and negative tabs can be located together at one end of the main body or at two ends of the main body respectively. During the charging and discharging process of the battery, the positive and negative active materials react with the electrolyte, and the tabs 11a are connected to the electrode terminals to form a current loop.

[0098] Please refer to Figure 2 , Figure 2A schematic diagram of a battery 100 is provided in some embodiments of the present application. The battery 100 includes a box 20 and a battery cell 10, wherein the battery cell 10 is accommodated in the box 20. The box 20 is used to provide a space for accommodating the battery cell 10, and the box 20 can have various structures. In some embodiments, the box 20 can include a first part 21 and a second part 22, wherein the first part 21 and the second part 22 are overlapped with each other, and the first part 21 and the second part 22 together define a space for accommodating the battery cell 10. The second part 22 can be a hollow structure with one end open, and the first part 21 can be a plate structure, wherein the first part 21 is overlapped with the open end of the second part 22 to define the space together with the second part 22. Alternatively, the first part 21 and the second part 22 can both be hollow structures with one side open, and the open end of the first part 21 is overlapped with the open end of the second part 22. Of course, the box 20 formed by the first part 21 and the second part 22 can have various shapes, such as a cylinder, a cuboid, etc.

[0099] In the battery 100, the battery cell 10 can be multiple, and the multiple battery cells 10 can be connected in series, in parallel, or in a mixed connection. The mixed connection means that the multiple battery cells 10 are connected in series and in parallel. The multiple battery cells 10 can be directly connected in series, in parallel, or in a mixed connection, and then the whole of the multiple battery cells 10 is accommodated in the box 20. Of course, the battery 100 can also be that the multiple battery cells 10 are first connected in series, in parallel, or in a mixed connection to form a battery module, and then the multiple battery modules are connected in series, in parallel, or in a mixed connection to form a whole, and the whole is accommodated in the box 20. The battery 100 can further include other structures, for example, the battery 100 can further include a busbar component for realizing the electrical connection between the multiple battery cells 10.

[0100] In the battery 100 in the embodiments of the present application, the battery cell 10 can be a lithium ion battery. In other embodiments, the battery 100 can further include any one or several of a lithium-sulfur battery, a sodium ion battery, and a magnesium ion battery, but is not limited thereto. The battery cell 10 can have a cylindrical shape, a flat shape, a cuboid shape, or other shapes, etc.

[0101] In some embodiments, the battery can be assembled into a battery module, and the number of batteries contained in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0102] In addition, the application also provides a power utilization device, which comprises at least one of the battery monomer and / or the battery provided by the application. The battery monomer or the battery pack can be used as a power supply of the power utilization device, or can be used as an energy storage unit of the power utilization device. The power utilization device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0103] As the power utilization device, the battery monomer and / or the battery 100 can be selected according to the use requirement thereof.

[0104] Figure 3a and Figure 3b As shown in FIG. 1, the power utilization device is a vehicle, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. A structure schematic diagram of the vehicle 1000 is specifically provided. The vehicle 1000 is internally provided with the battery 100, which can be arranged at the bottom, the head or the tail of the vehicle 1000. The battery 100 can be used for power supply of the vehicle 1000, for example, the battery 100 can be used as an operating power supply of the vehicle 1000. The vehicle 1000 can further comprise a controller 200 and a motor 300, and the controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the working power requirement of the vehicle 1000 during starting, navigation and driving.

[0105] In some embodiments of the application, the battery 100 can not only be used as an operating power supply of the vehicle 1000, but also be used as a driving power supply of the vehicle 1000, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1000.

[0106] Hereinafter, the embodiments of the application are described. The embodiments described below are exemplary and are only used to explain the application, and cannot be understood as a limitation of the application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument used is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0107] In the embodiments described below, the amount of lithium difluorophosphate (LiPO2F2) and the metal doping source (raw material containing T element), such as ZrO2, AlO2, etc., is based on the nickel-cobalt metal precursor.

[0108] Embodiment 1

[0109] Preparation method of the positive active material:

[0110] (1) Ni 0.55 Co0.06 Mn 0.39 The mass of the (OH)2precursor was weighed, 1500 ppm of lithium difluorophosphate (LiPO2F2) was added, and the lithium difluorophosphate aqueous solution was prepared by dissolving the lithium difluorophosphate in water.

[0111] (2) The Ni 0.55 Co 0.06 Mn 0.39 The (OH)2precursor was sprayed with the lithium difluorophosphate aqueous solution containing 1500 ppm, and the spraying time was 20 min.

[0112] (3) The precursor coated with the lithium difluorophosphate was mixed with lithium carbonate at a molar ratio of 1:1.05; based on the mass of the Ni 0.55 Co 0.06 Mn 0.39 The mass of the (OH)2precursor was weighed, 1000 ppm of ZrO2was added, and the mixture was mixed in a high-speed mixer at a speed of 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.

[0113] Method for preparing the positive electrode sheet:

[0114] The positive electrode active material 1, conductive carbon black (Super-P), and polyvinylidene fluoride (PVDF) were mixed at a weight ratio of 95.5:3:1.5 with N,N-dimethylformamide (NMP) to obtain a slurry for the positive electrode sheet. The slurry for the positive electrode sheet was uniformly coated on both sides of an aluminum foil. The positive electrode sheet was prepared by cold pressing and slicing.

[0115] Method for preparing the negative electrode sheet:

[0116] Artificial graphite, nano-silicon, conductive carbon black (Super-P), carbon nanotubes, carboxymethyl cellulose sodium (CMC-Na), and butadiene-styrene rubber (SBR) were mixed at a weight ratio of 95:5:0.5:0.1:1:1.5 with deionized water to obtain a slurry for coating the negative electrode sheet. The viscosity of the slurry was adjusted by deionized water during the stirring process. Then, the slurry was coated on both sides of a negative electrode current collector at a certain width, and the negative electrode sheet was prepared by cold pressing and slicing. In the present application, the negative electrode current collector is a copper foil.

[0117] Method for preparing the battery cell:

[0118] The positive electrode sheet, the separator, and the negative electrode sheet are wound into an electrode assembly, and a battery monomer is prepared through tab welding, packaging of an aluminum shell, injection, packaging formation, and air extraction. The width of the electrode assembly is 148 mm, the thickness is 28 mm, the height is 98 mm, and the capacity is 60 Ah. The injected electrolyte is a 1 mol / L LiPF6 solution, the solvent of the LiPF6 solution is ethylene carbonate (EC) and dimethyl carbonate (DMC), and the volume ratio of the ethylene carbonate (EC) and the dimethyl carbonate (DMC) is 1:2. In the embodiment of the present application, the separator is a 7-micron-thick polyethylene (PE).

[0119] Example 2

[0120] The difference from Example 1 is the preparation method of the positive electrode active material, specifically, the preparation method of the positive electrode active material:

[0121] (1) Based on the mass of the Ni 0.55 Co 0.06 Mn 0.39 (OH)2 precursor, 4000 ppm of lithium difluorophosphate (LiPO2F2) is weighed and dissolved in water to obtain a lithium difluorophosphate aqueous solution.

[0122] (2) The Ni 0.55 Co 0.06 Mn 0.39 (OH)2 precursor is sprayed and coated with the lithium difluorophosphate aqueous solution containing 4000 ppm, and the spraying time is 20 min.

[0123] (3) The precursor coated with lithium difluorophosphate is mixed with lithium carbonate at a molar ratio of 1:1.05; based on the mass of the Ni 0.55 Co 0.06 Mn 0.39 (OH)2 precursor, 1000 ppm of ZrO2 is added, and mixed in a high-speed mixer at a speed of 1500 rpm for 2 h. Sintering is performed at 900°C for 13 h in a kiln, and the positive electrode active material is obtained after cooling to room temperature and crushing.

[0124] Example 3

[0125] The difference from Example 1 is the preparation method of the positive electrode active material, specifically, the preparation method of the positive electrode active material:

[0126] (1) Based on the mass of the Ni 0.55 Co 0.06 Mn 0.39 (OH)2 precursor, 1500 ppm of lithium difluorophosphate (LiPO2F2) is weighed and dissolved in water to obtain a lithium difluorophosphate aqueous solution.

[0127] (2) Spray coating of the Ni 0.55 Co 0.06 Mn 0.39 (OH)2precursor with a 1500 ppm aqueous solution of difluorophosphate salt for 20 min.

[0128] (3) Mixing the precursor coated with difluorophosphate salt with lithium carbonate at a molar ratio of 1 : 1.05; based on the mass of the Ni 0.55 Co 0.06 Mn 0.39 (OH)2precursor, adding 1000 ppm AlO2, and mixing in a high-speed mixer at a speed of 1500 rpm for 2 h. Sintering in a kiln at 900°C for 13 h, and breaking after cooling to room temperature to obtain the positive electrode active material.

[0129] Example 4

[0130] The difference from Example 1 is the preparation method of the positive electrode active material, specifically, the preparation method of the positive electrode active material:

[0131] (1) Based on the mass of the Ni 0.55 Co 0.06 Mn 0.39 (OH)2precursor, weighing 1500 ppm lithium difluorophosphate (LiPO2F2) and dissolving it in water to obtain an aqueous solution of difluorophosphate salt.

[0132] (2) Spray coating of the Ni 0.55 Co 0.06 Mn 0.39 (OH)2precursor with a 1500 ppm aqueous solution of difluorophosphate salt for 20 min.

[0133] (3) Mixing the precursor coated with difluorophosphate salt with lithium carbonate at a molar ratio of 1 : 1.05; based on the mass of the Ni 0.55 Co 0.06 Mn 0.39 (OH)2precursor, adding 1000 ppm AlO2 and 1000 ppm ZrO2, and mixing in a high-speed mixer at a speed of 1500 rpm for 2 h. Sintering in a kiln at 900°C for 13 h, and breaking after cooling to room temperature to obtain the positive electrode active material.

[0134] Example 5

[0135] The difference from Example 1 is the preparation method of the positive electrode active material, specifically, the preparation method of the positive electrode active material:

[0136] (1) 1500 ppm of lithium difluorophosphate (LiPO2F2) was dissolved in water to obtain a lithium difluorophosphate aqueous solution.

[0137] (2) The Ni 0.65 Co 0.12 Mn 0.23 (OH)2 precursor was spray coated with the lithium difluorophosphate aqueous solution containing 1500 ppm, and the spray coating time was 60 min.

[0138] (3) The precursor coated with lithium difluorophosphate 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 a rotation speed of 1500 rpm for 2 h. The mixture was placed in a kiln and sintered at 900°C for 13 h. After cooling to room temperature, the positive electrode active material was obtained by crushing.

[0139] Example 6

[0140] The difference from Example 1 is the preparation method of the positive electrode active material, specifically, the preparation method of the positive electrode active material:

[0141] (1) 300 ppm of lithium difluorophosphate (LiPO2F2) was dissolved in water to obtain a lithium difluorophosphate aqueous solution.

[0142] (2) The Ni 0.65 Co 0.12 Mn 0.23 (OH)2 precursor was spray coated with the lithium difluorophosphate aqueous solution containing 300 ppm, and the spray coating time was 5 min.

[0143] (3) The precursor coated with lithium difluorophosphate was mixed with lithium carbonate at a molar ratio of 1:1.05, and mixed in a high-speed mixer at a rotation speed of 1500 rpm for 2 h. The mixture was placed in a kiln and sintered at 950°C for 10 h. After cooling to room temperature, the positive electrode active material was obtained by crushing.

[0144] Example 7

[0145] The difference from Example 1 is the preparation method of the positive electrode active material, specifically, the preparation method of the positive electrode active material:

[0146] (1) 1500 ppm of lithium difluorophosphate (LiPO2F2) was dissolved in water to obtain a lithium difluorophosphate aqueous solution.

[0147] (2) The Ni 0.9 Co 0.02 Mn 0.08 (OH)2 precursor was spray coated with the lithium difluorophosphate aqueous solution containing 1500 ppm, and the spray coating time was 20 min.

[0148] (3) The precursor coated with difluorophosphate was mixed with lithium carbonate at a molar ratio of 1 : 1.05, mixed in a high-speed mixer at a speed of 1500 rpm for 2 h. Sintering was performed in a kiln at 930°C for 33 h, and the positive electrode active material was obtained after cooling to room temperature and crushing.

[0149] Example 8

[0150] The difference from Example 1 is the preparation method of the positive electrode active material, specifically, the preparation method of the positive electrode active material:

[0151] (1) 1500 ppm of lithium difluorophosphate (LiPO2F2) was dissolved in water to obtain a difluorophosphate aqueous solution.

[0152] (2) The Ni 0.65 Co 0.12 Al 0.23 (OH)2precursor was sprayed with a difluorophosphate aqueous solution containing 1500 ppm, and the spraying time was 20 min.

[0153] (3) The precursor coated with difluorophosphate was mixed with lithium carbonate at a molar ratio of 1 : 1.05, 1000 ppm of ZrO2 was added, mixed in a high-speed mixer at a speed of 1500 rpm for 2 h. Sintering was performed in a kiln at 900°C for 13 h, and the positive electrode active material was obtained after cooling to room temperature and crushing.

[0154] Comparative Example 1

[0155] The difference from Example 1 is the preparation method of the positive electrode active material, specifically, the preparation method of the positive electrode active material of Comparative Example 1:

[0156] (1) The Ni 0.55 Co 0.06 Mn 0.39 (OH)2precursor was mixed with lithium carbonate at a molar ratio of 1 : 1.05, mixed in a high-speed mixer at a speed of 1500 rpm for 2 h. Sintering was performed in a kiln at 900°C for 13 h, and the positive electrode active material was obtained after cooling to room temperature and crushing.

[0157] Comparative Example 2

[0158] The difference from Example 1 is the preparation method of the positive electrode active material, specifically, the preparation method of the positive electrode active material:

[0159] (1) The Ni 0.65 Co 0.12 Mn 0.23The LiNi0.5Mn0.5O2 precursor was mixed with lithium carbonate at a molar ratio of 1:1.05, 1000 ppm ZrO2 was added, and mixed in a high-speed mixer at a speed of 1500 rpm for 2 h. After sintering at 900°C for 13 h in a kiln, the positive electrode active material was obtained after cooling to room temperature and crushing.

[0160] Comparative Example 3

[0161] The difference from Example 1 is the preparation method of the positive electrode active material, specifically, the preparation method of the positive electrode active material:

[0162] (1) Ni 0.55 Co 0.06 Mn 0.39 The LiNi0.5Mn0.5O2 precursor was mixed with lithium carbonate at a molar ratio of 1:1.05, 1000 ppm ZrO2 was added, and mixed in a high-speed mixer at a speed of 1500 rpm for 2 h. After sintering at 900°C for 13 h in a kiln, the positive electrode active material was obtained after cooling to room temperature and crushing.

[0163] Comparative Example 4

[0164] The difference from Example 1 is the preparation method of the positive electrode active material, specifically, the preparation method of the positive electrode active material:

[0165] (1) Ni 0.65 Co 012 Al 0.23 The LiNi0.5Mn0.5O2 precursor was mixed with lithium carbonate at a molar ratio of 1:1.05, 1000 ppm ZrO2 was added, and mixed in a high-speed mixer at a speed of 1500 rpm for 2 h. After sintering at 900°C for 13 h in a kiln, the positive electrode active material was obtained after cooling to room temperature and crushing.

[0166] The positive electrode active materials of Examples 1-8 and Comparative Examples 1-4 above were made into corresponding batteries 1, 2, 3, 4, 5, 6, 7, 8 and batteries 9, 10, 11, 12, and battery performance tests were conducted to obtain Table 1. Specifically, battery high-temperature gas production tests, gram capacity tests, and high-temperature storage performance tests were conducted. The specific test conditions were:

[0167] 1. High-temperature gas production test

[0168] The battery high-temperature gas production test method is to charge the battery to 4.5V at 1C full charge, then place it in a 70°C constant temperature oven for 30 days. The initial volume and the volume after 30 days of standing are measured by the drainage method to obtain the volume expansion rate of the battery. The volume expansion rate of the battery (%) = (volume after 30 days of standing / initial volume-1) x 100%.

[0169] 2. Gram capacity test of the battery

[0170] The battery capacity test involved placing the battery at a constant temperature of 25°C for 2 hours, then charging it at 1 / 3C to 4.5V within the range of 2.8V to 4.5V, followed by constant voltage charging at 4.5V until the current ≤0.05mA, allowing it to rest for 5 minutes, and finally discharging it at 1C to 2.8V. The battery capacity C was then recorded. 放 .

[0171] Gram capacity = Battery capacity C 放 (mAh) / Mass of positive electrode active material (g).

[0172] 3. High-Temperature Storage Performance Test

[0173] At 25℃, the battery was charged at a constant current rate of 0.33C to 4.5V, then charged at a constant voltage rate until the current was less than or equal to 0.05C, and then discharged at a constant current rate of 0.33C to 2.8V. The initial discharge capacity of the battery was measured. At 25℃, the battery was charged at a constant current rate of 0.33C to 4.5V, then charged at a constant voltage rate until the current was less than or equal to 0.05C. The fully charged battery was then placed in a 60℃ oven. After 15 days, the battery was removed from the high-temperature storage and allowed to cool naturally to 25℃. It was then discharged at a constant current rate of 0.33C to 2.8V, then charged at a constant current rate of 0.33C to 4.5V, then charged at a constant voltage rate until the current was less than or equal to 0.05C, and then discharged at a constant current rate of 0.33C to 2.8V. The discharge capacity of the battery after 15 days of high-temperature storage was measured. Finally, the battery was placed back in a 60℃ oven until the capacity retention was below 80%. Repeat the test every 15 days.

[0174] Battery 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 it takes for the capacity to decay to 80% is calculated by drawing a line based on the test data.

[0175] 4. Volume average particle size Dv50 test.

[0176] Equipment Model: Malvern 2000 (MasterSizer 2000) laser particle size analyzer; Reference Standard Procedure: GB / T19077-2016 / ISO 13320:2009; Specific Test Procedure: Take an appropriate amount of the sample to be tested (the sample concentration should be 8%~12% opacity), add 20ml of deionized water, and sonicate for 5min (53KHz / 120W) to ensure complete dispersion of the sample. Then, measure the sample according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0177]

[0178] Table 2. Process parameters and performance parameters of the examples and comparative examples.

[0179]

[0180] As can be seen from the process parameters and performance parameters in Table 1 and Table 2, based on Comparative Examples 1-4, the positive electrode active material of the present application Examples 1-8 is mixed with fluorophosphorus compounds in the positive electrode active host material, so that the high-temperature gas production performance of the positive electrode active material of the present application Examples 1-8 is significantly reduced to 20%-43%, lower than 58%-70% of Comparative Examples 1-4. The high-temperature storage performance of the positive electrode active material of the present application Examples 1-8 is significantly improved, and the high-temperature storage can reach 480 days-650 days, much higher than 195 days-210 days of Comparative Examples 1-4. The 1 / 3C capacity of the positive electrode active material of the present application Examples 1-8 is 190 mAh / g-198 mAh / g, and the positive electrode active material of the present application Examples 1-8 can also maintain a high capacity. In the present application Examples 1-8, the positive electrode active host material includes fluorophosphorus compounds, and the fluorophosphorus compounds contain lithium difluorophosphate. The present application Examples 1-8 use a spraying method to coat the lithium difluorophosphate solution on the surface of the nickel-cobalt-manganese precursor or the nickel-cobalt-aluminum precursor, so that the uniformity of the fluorophosphorus compounds in the positive electrode active material mixed on the surface of the positive electrode active host material is higher, which is conducive to improving the stability of the positive electrode active host material. The positive electrode active host material of the present application Examples 1-8 is sintered at a temperature of 900°C-950°C, and the fluorophosphorus compounds will decompose F elements and P elements doped in the bulk phase of the positive electrode active host material, wherein the F elements are doped in the oxygen sites of the hexagonal system of the positive electrode active host material, and the P elements are doped in the crystal lattice of the hexagonal system or / and the oxygen sites of the hexagonal system, so as to realize the modification of the positive electrode active host material, inhibit the oxidation activity of the positive electrode active host material, stabilize the bulk phase structure of the positive electrode active host material, and enhance the stability of the positive electrode active material under high temperature conditions, so that the storage performance and gas production problems of the battery are obviously improved.

[0181] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and embodiments having the same technical idea and substantially the same effects as the technical idea within the scope of the technical solution of the present application are also included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications of the embodiments that can be thought of by those skilled in the art, and other ways constructed by combining part of the components of the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode active material, characterized by, The positive electrode active material comprises: The positive electrode active host material comprises lithium nickel cobalt manganese oxide or / and lithium nickel cobalt aluminum oxide; The fluorophosphorus compound is doped in the positive electrode active host material; The fluorophosphorus compound is located in the surface layer of the positive electrode active host material; The positive electrode active host material is doped with fluorine element and phosphorus element; The fluorine element is doped in the oxygen site of the hexagonal system of the positive electrode active host material, and the phosphorus element is doped in the lattice of the hexagonal system or / and the oxygen site of the hexagonal system.

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

2.

3. The positive electrode active material according to claim 1, wherein The positive active body material includes a material with a structural formula of Li(Ni x Co y M z ) 1-u T u O2, 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.

4. The positive electrode active material according to any one of claims 1-3, wherein The mass fraction of the fluorophosphorus compound in the total mass of the positive electrode active material is 0.015%-0.4%.

5. The positive electrode active material according to claim 1, wherein The volume average particle size DV50 of the positive electrode active material is 3-15 μm.

6. A method for producing a positive electrode active material, characterized by, Comprising: Spray coating 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 comprises a nickel-cobalt-manganese precursor or a nickel-cobalt-aluminum precursor; Mixing the nickel-cobalt metal precursor coated with difluorophosphate and a lithium source, and sintering to form lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide doped with a fluorophosphorus compound; The sintering temperature is 900-950°C, and the sintering time is 10-33 h.

7. The preparation method of the positive electrode active material according to claim 6, wherein The spray coating time is 5-60 min.

8. The method for producing a positive electrode active material according to claim 6 or 7, characterized by, The mass ratio of the difluorophosphate in the difluorophosphate solution to the nickel-cobalt metal precursor is 3 x 10 -4 4 x 10 -3 :

1.

9. The preparation method of the positive electrode active material according to claim 6, wherein The mixing of the nickel-cobalt metal precursor coated with difluorophosphate and the lithium source comprises: Mixing the 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; The nickel-cobalt metal precursor includes a structural formula of (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 comprises one or more of lithium carbonate, lithium hydroxide, lithium sulfate, lithium nitrate, lithium acetate, and lithium phosphate; or / and, The rotation speed of the mixing is 600-2000 rpm, and the mixing time is 30-300 min.

10. A positive electrode sheet characterized by comprising: Comprising the positive electrode active material according to any one of claims 1-5, or the positive electrode active material prepared by the preparation method of the positive electrode active material according to any one of claims 6-9.

11. A battery, characterized by Comprising the positive electrode active material according to any one of claims 1-5, or the positive electrode active material prepared by the preparation method of the positive electrode active material according to any one of claims 6-9, or comprising the positive electrode sheet according to claim 10.

12. An electrical device, characterized by Comprising the battery according to claim 11.

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