Coated positive electrode material, preparation method thereof, positive electrode sheet and lithium ion battery

Abstract

The application provides a coated positive electrode material, a preparation method of the coated positive electrode material, a positive electrode sheet and a lithium ion battery. The coated positive electrode material comprises a multi-element positive electrode material substrate and a coating layer coated on at least part of the surface of the multi-element positive electrode material substrate. The coating layer comprises a material with a chemical formula of Li r V s Nb t O u F v wherein 1.0<=r<=1.5, 0.2<=s<=0.8, 0.01<=t<=0.5, 1.6<=u<=2.0 and 0<=v<=0.4. The coating layer has low strain, can effectively inhibit the volume expansion of the multi-element positive electrode material substrate during the cycle process, and maintain the structural stability of the multi-element positive electrode material substrate. Therefore, the coated positive electrode material can improve the capacity retention rate of the lithium ion battery when applied to the lithium ion battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a coated positive electrode material, a preparation method thereof, a positive electrode sheet and a lithium ion battery. BACKGROUND

[0002] With the development of lithium ion battery technology, people have higher use requirements for lithium ion batteries. The volume of lithium ion battery positive electrode materials often changes during the cycle process, which poses a great challenge to the development of lithium ion batteries in the direction of high energy density and high safety.

[0003] Since the energy density of ternary positive electrode materials is high, ternary positive electrode materials are increasingly occupying the mainstream market in the fields of power automobiles, electric tools and energy storage devices. In related technologies, when ternary positive electrode materials are used in lithium ion batteries, the capacity retention rate of the lithium ion batteries is often reduced while the energy density is improved. SUMMARY

[0004] Therefore, it is necessary to provide a coated positive electrode material capable of improving the capacity retention rate of a lithium ion battery, a preparation method thereof, a positive electrode sheet and a lithium ion battery.

[0005] The first aspect of the embodiment of the present application provides a coated positive electrode material, comprising:

[0006] a multi-element positive electrode material matrix; and

[0007] a coating layer coated on at least part of the surface of the multi-element positive electrode material matrix, the coating layer comprising a material with a chemical formula of Li r V s Nb t O u F v , wherein 1.0≤r≤1.5, 0.2≤s≤0.8, 0.01≤t≤0.5, 1.6≤u≤2.0, and 0≤v≤0.4.

[0008] In some embodiments, the multi-element positive electrode material matrix comprises a material with a chemical formula of LiNi x Co y M 1-x-y O2, wherein M comprises one or more of Mn, Al, Mg, Ti, Zr, Y, Nb, W, Ce, Sb, Sr and Ta, 0.20

[0009] In some embodiments, the mass ratio of the multi-element positive electrode material matrix and the coating layer is (0.0001-0.03):1.

[0010] In some embodiments, the coating layer has a thickness of 2-50 nm, and the coated cathode material has a volume average particle size Dv50 of 1.3-15 μm.

[0011] The second aspect of the embodiments of the present application provides a method for preparing a coated cathode material, comprising the following steps:

[0012] mixing the multi-component cathode material matrix with raw materials for forming the coating layer, and then performing calcination to form the coating layer on at least part of the surface of the multi-component cathode material matrix, thereby obtaining the coated cathode material;

[0013] Optionally, the raw materials for forming the coating layer comprise a first lithium source, a vanadium compound, a niobium compound, and optionally a first material, wherein the optional first material is a fluoride.

[0014] In some embodiments, the preparation of the coated cathode material comprises at least one of the following conditions:

[0015] (1) the molar ratio of lithium element contained in the multi-component cathode material matrix, the first lithium source, vanadium element contained in the vanadium compound, niobium element contained in the niobium compound, and fluorine element contained in the fluoride is 1:(0.001-0.05):(0.001-0.03):(0.001-0.02):(0.0001-0.02);

[0016] (2) the first lithium source comprises one or more of lithium hydroxide and lithium carbonate;

[0017] (3) the vanadium compound comprises one or more of vanadium monoxide, divanadium trioxide, divanadium dioxide, and divanadium pentoxide;

[0018] (4) the niobium compound comprises one or more of niobium monoxide, divanadium dioxide, divanadium trioxide, and divanadium pentoxide;

[0019] (5) the fluoride comprises one or more of lithium fluoride, ammonium fluoride, sodium fluoride, and sodium hydrogen fluoride;

[0020] (6) the calcination temperature is 500-850°C;

[0021] (7) the calcination time is 6-15 h.

[0022] In some embodiments, the method further comprises a step of preparing the multi-component cathode material matrix:

[0023] mixing a multi-component cathode material precursor, a second lithium source, and an optional second material to obtain an intermediate, wherein the optional second material is a metal compound, and the multi-component cathode material precursor comprises a chemical formula of Ni m Co n M1-m-n The material is (M1-xMn)xLi(m-n)Mn(n)(OH)2, wherein M includes one or more of Mn, Al, Mg, Ti, Zr, Y, Nb, W, Ce, Sb, Sr and Ta, 0.20 < m < 0.98, 0 < n < 0.45, and m + n < 1;

[0024] The intermediate is subjected to a calcination treatment to obtain the multi-element positive electrode material matrix.

[0025] In some embodiments, the preparation of the multi-element positive electrode material matrix comprises at least one of the following conditions:

[0026] (1) the molar ratio of the multi-element positive electrode material precursor, the metal elements contained in the metal compound, and the lithium elements contained in the second lithium source is 1:(0-0.02):(0.95-1.08);

[0027] (2) the metal compound comprises one or more of metal oxides, metal hydroxides and metal carbonates; the metal contained in the metal compound includes one or more of Al, Mg, Ti, Zr, Y, Nb, W, Ce, Sb, Sr and Ta;

[0028] (3) the second lithium source comprises one or more of lithium hydroxide and lithium carbonate;

[0029] (4) the calcination temperature when the intermediate is subjected to the calcination treatment is 600-1100°C;

[0030] (5) the calcination time when the intermediate is subjected to the calcination treatment is 6-20h.

[0031] The third aspect of the embodiments of the present application provides a positive electrode tab, comprising:

[0032] a positive electrode current collector;

[0033] a positive electrode active material layer on at least one surface of the positive electrode current collector, the positive electrode active material layer comprising the coated positive electrode material of the first aspect or the coated positive electrode material prepared by the method of the second aspect.

[0034] The fourth aspect of the embodiments of the present application provides a lithium ion battery comprising the coated positive electrode material of the first aspect, the coated positive electrode material prepared by the method of the second aspect, or the positive electrode tab of the third aspect.

[0035] The fifth aspect of the embodiments of the present application provides an electric device comprising the lithium ion battery of the fourth aspect.

[0036] The coating type positive electrode material provided in the above, the preparation method thereof, the positive electrode sheet and the lithium ion battery, wherein the coating type positive electrode material is provided with a coating layer containing a material with a chemical formula of Li r V s Nb t O u F v on at least part of the surface of the multi-element positive electrode material substrate, the coating layer has low strain property, can effectively inhibit the volume expansion of the multi-element positive electrode material substrate during the cycle process, and maintain the structural stability thereof, so that the coating type positive electrode material applied to the lithium ion battery can improve the capacity retention rate of the lithium ion battery. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 SEM image of the coating type positive electrode material prepared in Example 1;

[0038] Figure 2 SEM image of the coating type positive electrode material prepared in Example 5;

[0039] Figure 3 XRD image of the coating type positive electrode material prepared in Example 1;

[0040] Figure 4 Variation diagram of the capacity retention rate with the cycle number of Example 1, Example 5, Comparative Example 1 and Comparative Example 2. DETAILED DESCRIPTION

[0041] In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the accompanying drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present application can be more thoroughly and completely understood.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terminology used in the description of the present application herein only for the purpose of describing the specific embodiments of the present application, and is not intended to limit the present application. The term "and / or" used herein includes any and all combinations of one or more of the listed items.

[0043] Herein, in the technical features described in an open manner, both the closed technical solution consisting of the listed features and the open technical solution containing the listed features are included.

[0044] In the present text, with reference to numerical intervals, unless specifically stated otherwise, the numerical intervals are considered to be continuous and to include the minimum and maximum values of the range, as well as every value between the minimum and maximum values of the range. Further, when ranges are provided, the range includes every integer within the range. Also, when a range is provided, the range includes every integer within the range. In other words, unless otherwise specified, all ranges disclosed herein are to be understood as encompassing any and all sub-ranges of the same.

[0045] In the present text, with reference to units of data, if only the unit is provided after the right end point, it means that the units of the left end point and the right end point are the same. For example, 6-15h means that the units of the left end point "6" and the right end point "15" are both h (hour).

[0046] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, as can any upper limit with any other upper limit. In addition, each individual disclosed point or single numerical value can itself be combined with any other point or single numerical value or with other lower limits or upper limits to form a range not explicitly recited.

[0047] The temperature parameters in the present text, unless specifically limited, allow both constant temperature treatment and treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument.

[0048] In the present text, the terms "first", "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited. In the description of the application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise specifically limited.

[0049] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0050] If not otherwise specified, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c), which means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0051] The embodiment of the present application provides a coated positive electrode material, comprising: a multi-element positive electrode material substrate and a coating layer coated on at least part of the surface of the multi-element positive electrode material substrate, wherein the coating layer comprises a material with a chemical formula of Li r V s Nb t O u F v , wherein 1.0≤r≤1.5, 0.2≤s≤0.8, 0.01≤t≤0.5, 1.6≤u≤2.0, and 0≤v≤0.4.

[0052] It should be noted that the coating layer can be coated on part of the surface of the multi-element positive electrode material substrate, or can be coated on the entire surface of the multi-element positive electrode material substrate; preferably, the coating layer is coated on the entire surface of the multi-element positive electrode material substrate. The coating layer comprises a material with a chemical formula of Li r V s Nb t O u F v , and the coating layer is an LVNOF coating layer.

[0053] The multi-element positive electrode material can be a ternary positive electrode material, a quaternary positive electrode material or a quinary positive electrode material, and the specific type is not limited.

[0054] The coating layer comprises a material with a chemical formula of Li r V s Nb t O u F v , wherein r can be 1.0, 1.1, 1.2, 1.3, 1.4 or 1.5, and the specific type is not limited; s can be 0.2, 0.3, 0.4, 0.5, 0.6, 0.7 or 0.8, and the specific type is not limited; t can be 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5, and the specific type is not limited; u can be 1.6, 1.7, 1.8, 1.9 or 2.0, and the specific type is not limited; and v can be 0, 0.1, 0.2, 0.3 or 0.4, and the specific type is not limited.

[0055] Understandably, by setting the coated positive electrode material as coated with a coating layer containing a material with a chemical formula of Li r V s Nb t O u F v on at least part of the surface of the multi-element positive electrode material matrix, the coating layer has low strain, which can effectively inhibit the volume expansion of the multi-element positive electrode material matrix during the cycle process, maintain its structural stability, and thus the coated positive electrode material applied to the lithium ion battery can improve the capacity retention rate of the lithium ion battery.

[0056] The coating layer is a spinel structure, and under the premise of ensuring the free shuttle of lithium ions, the volume change of the coating layer is relatively small compared with the layered structure, thereby inhibiting the cracking and decomposition of the multi-element positive electrode material matrix and maintaining the structural stability of the ternary material.

[0057] In addition, the coating layer carries active Li + material, which can release / embed Li + ions during the electrochemical process, thereby providing part of the capacity and improving the specific discharge capacity and coulombic efficiency of the lithium ion battery; and the coating layer compensates the charge of the multi-element positive electrode material matrix through V 3+ / V 5+ redox pair, inhibits the redox of oxygen in the multi-element positive electrode material matrix, and reduces the loss of lattice oxygen, thereby improving the cycle stability and safety performance of the lithium ion battery.

[0058] In some embodiments, the multi-element positive electrode material matrix comprises a material with a chemical formula of LiNi x Co y M 1-x-y O2, wherein M is selected from one or more of Mn, Al, Mg, Ti, Zr, Y, Nb, W, Ce, Sb, Sr and Ta, 0.20 x Co y M 1-x-y O2, wherein M is selected from one or more of Mn, Al, Mg, Ti, Zr, Y, Nb, W, Ce, Sb, Sr and Ta, 0.20

[0059] In some embodiments, the mass ratio of the multi-element positive electrode material matrix and the coating layer is (0.0001-0.03):1; for example, it can be (0.0005-0.03):1, (0.001-0.03):1, (0.005-0.03):1, (0.01-0.03):1, (0.015-0.03):1, (0.02-0.03):1, (0.025-0.03):1, (0.0001-0.01):1 or (0.0003-0.02):1, etc., which is not specifically limited. When the mass ratio of the multi-element positive electrode material matrix and the coating layer is in the above range, the coating layer can fully play the role of maintaining the structural stability of the multi-element positive electrode material and improving the capacity.

[0060] In some embodiments, the thickness of the coating layer is 2-50 nm, and the volume average particle size Dv50 of the coated positive electrode material is 1.3-15 μm.

[0061] The embodiments of the present application also provide a preparation method of the coated positive electrode material, comprising the following steps: mixing a multi-element positive electrode material matrix and raw materials for forming a coating layer, and then performing roasting, so as to form the coating layer on at least part of the surface of the multi-element positive electrode material matrix, thereby obtaining the coated positive electrode material.

[0062] In some embodiments, the raw materials for forming the coating layer comprise a first lithium source, a vanadium compound, a niobium compound, and an optional first material, and the optional first material is fluoride.

[0063] In some embodiments, when the coated positive electrode material is prepared, the molar ratio of the multinary positive electrode material base, lithium element contained in the first lithium source, vanadium element contained in the vanadium compound, niobium element contained in the niobium compound, and fluorine element contained in the fluoride is 1 : (0.001-0.05) : (0.001-0.03) : (0.001-0.02) : (0-0.02); for example, it can be 1 : (0.003-0.05) : (0.005-0.03) : (0.005-0.02) : (0.0005-0.02), 1 : (0.01-0.05) : (0.01-0.03) : (0.01-0.02) : (0.001-0.02), 1 : (0.015-0.05) : (0.018-0.03) : (0.013-0.02) : (0.005-0.02), 1 : (0.02-0.05) : (0.02-0.03) : (0.015-0.02) : (0.01-0.02), 1 : (0.03-0.05) : (0.023-0.03) : (0.017-0.02) : (0.013-0.02), 1 : (0.04-0.05) : (0.025-0.03) : (0.018-0.02) : (0.015-0.02), 1 : (0.045-0.05) : (0.027-0.03) : (0.013-0.02) : (0.017-0.02), or 1 : (0.001-0.35) : (0.001-0.02) : (0.001-0.01) : (0.0001-0.01), etc. Further, the molar ratio of the multinary positive electrode material base, lithium element contained in the first lithium source, vanadium element contained in the vanadium compound, niobium element contained in the niobium compound, and fluorine element contained in the fluoride can be 1 : 0.001 : 0.001 : 0.001 : 0, 1 : 0.002 : 0.002 : 0.002 : 0.0001, 1 : 0.003 : 0.005 : 0.005 : 0.0003, 1 : 0.005 : 0.008 : 0.008 : 0.0005, 1 : 0.01 : 0.01 : 0.01 : 0.001, 1 : 0.02 : 0.015 : 0.012 : 0.005, 1 : 0.03 : 0.02 : 0.015 : 0.01, 1 : 0.04 : 0.025 : 0.018 : 0.015, or 1 : 0.05 : 0.03 : 0.02 : 0.02, etc., and is not particularly limited. When the molar ratio of the multinary positive electrode material base, lithium element contained in the first lithium source, vanadium element contained in the vanadium compound, niobium element contained in the niobium compound, and fluorine element contained in the fluoride is within the above range, a stable and uniform coating layer can be formed.

[0064] In some embodiments, the first lithium source used in the preparation of the coated cathode material includes one or more of lithium hydroxide and lithium carbonate.

[0065] In some embodiments, the vanadium compound used in the preparation of the coated cathode material includes one or more of vanadium monoxide, vanadium sesquioxide, vanadium dioxide and vanadium pentoxide.

[0066] In some embodiments, the niobium compound used in the preparation of the coated cathode material includes one or more of niobium monoxide, niobium dioxide, niobium sesquioxide and niobium pentoxide.

[0067] In some embodiments, the fluoride used in the preparation of the coated cathode material includes one or more of lithium fluoride, ammonium fluoride, sodium fluoride and sodium hydrogen fluoride.

[0068] In some embodiments, the calcination temperature used in the preparation of the coated cathode material is 500-850°C; for example, it can be 550-850°C, 600-850°C, 650-850°C, 700-850°C, 750-850°C, 800-850°C or 500-750°C, etc., without limitation.

[0069] In some embodiments, the calcination time used in the preparation of the coated cathode material is 6-15h. For example, it can be 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h, etc., without limitation.

[0070] In some embodiments, the method for preparing the coated cathode material further includes a step of preparing a multi-element cathode material matrix: mixing a multi-element cathode material precursor, a second lithium source and an optional second material to obtain an intermediate; the optional second material is a metal compound, and the multi-element cathode material precursor includes a material with a chemical formula of Ni m Co n M 1-m-n (OH)2, wherein M includes one or more of Mn, Al, Mg, Ti, Zr, Y, Nb, W, Ce, Sb, Sr and Ta, 0.20

[0071] The intermediate is subjected to a calcination treatment to obtain the multi-element cathode material matrix.

[0072] It should be noted that the multi-element cathode material precursor can be commercially available or prepared according to conventional methods well known to those skilled in the art.

[0073] In the preparation of the multi-element positive electrode material matrix, the metal compound is added to enable the metal element to play a supporting role between the transition metal layers and increase the kinetic performance of the multi-element positive electrode material matrix, thereby ensuring the stability of the layered structure of the multi-element positive electrode material matrix and improving the transportability of lithium ions.

[0074] In some embodiments, the molar ratio of the metal element contained in the multi-element positive electrode material precursor, the metal compound and the lithium element contained in the second lithium source is 1:(0-0.02):(0.95-1.08); for example, it can be 1:(0.005-0.02):(1.0-1.08), 1:(0.01-0.02):(1.03-1.08), 1:(0.015-0.02):(1.05-1.08) or 1:(0-0.01):(0.95-1.05), etc. Alternatively, the molar ratio of the metal element contained in the multi-element positive electrode material precursor, the metal compound and the lithium element contained in the second lithium source is 1:0:0.95, 1:0.001:0.96, 1:0.002:0.965, 1:0.003:0.97, 1:0.005:0.98, 1:0.008:0.99, 1:0.01:1.00, 1:0.015:1.01, 1:0.02:1.05 or 1:0.01:1.08, etc., without limitation. When the molar ratio of the metal element contained in the multi-element positive electrode material precursor, the metal compound and the lithium element contained in the second lithium source is within the above range, a multi-element positive electrode matrix material with stable structure and excellent capacity performance can be prepared.

[0075] In some embodiments, the metal compound used in the preparation of the multi-element positive electrode material matrix includes one or more of metal oxides, metal hydroxides and metal carbonates; the metal contained in the metal compound includes one or more of Al, Mg, Ti, Zr, Y, Nb, W, Ce, Sb, Sr and Ta.

[0076] In some embodiments, the second lithium source used in the preparation of the multi-element positive electrode material matrix includes one or more of lithium hydroxide and lithium carbonate.

[0077] In some embodiments, the calcination temperature for the intermediate during the calcination treatment in the preparation of the multi-element positive electrode material matrix is 600-1100°C; for example, it can be 600°C, 700°C, 750°C, 800°C, 900°C or 1100°C, etc., without limitation.

[0078] In some embodiments, the calcination time of the intermediate during the calcination process for preparing the multi-element positive electrode material matrix is 6-20 hours; for example, it can be 6 hours, 8 hours, 10 hours, 12 hours, 13 hours, 15 hours, 18 hours or 20 hours, and the specific value is not limited.

[0079] The embodiments of the present application also provide a positive electrode tab, comprising: a positive electrode current collector and a positive electrode active material layer on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the coated positive electrode material or the coated positive electrode material prepared by the method described above.

[0080] The embodiments of the present application also provide a lithium ion battery, comprising the coated positive electrode material, the coated positive electrode material prepared by the method described above or the positive electrode tab described above.

[0081] The technical solutions are described in detail below in combination with specific embodiments.

[0082] I. Preparation of the coated positive electrode material

[0083] Embodiment 1

[0084] Ni 0.60 Co 0.05 Mn 0.35 (OH)2, Li2CO3 and Al2O3 are mixed according to a molar ratio of 1:0.51:0.001, and the intermediate is obtained after sufficient mixing;

[0085] The intermediate is calcined at 920℃ for 14 hours to obtain a multi-element positive electrode material matrix;

[0086] The multi-element positive electrode material matrix, Li2CO3, V2O5 and Nb2O3 are mixed according to a molar ratio of 1:0.02:0.0026:0.002, and the coated positive electrode material is obtained after sufficient mixing and calcination at 750℃ for 11 hours, and the chemical formula of the coated positive electrode material is LiNi 0.600 Co 0.050 Mn 0.348 Al 0.002 O2@Li 1.30 V 0.4 Nb 0.3 O2.

[0087] The volume average particle size Dv50 of the coated positive electrode material is 2.5-4.5 μm, the mass ratio of the multi-element positive electrode material matrix and the coating layer is 1:0.001, and the thickness of the coating layer is 3-8 nm.

[0088] 2. Embodiment 2

[0089] Ni 0.68 Co 0.12 Mn0.20 (OH)2, Li2CO3 and TiO2 were mixed in a molar ratio of 1:0.52:0.001, and an intermediate was obtained after thorough mixing;

[0090] The intermediate was calcined at 890°C for 13.5h to obtain a multi-element positive electrode material matrix;

[0091] The multi-element positive electrode material matrix, LiOH, V2O5 and Nb2O5 were mixed in a molar ratio of 1:0.03:0.0035:0.0018, and after thorough mixing, the mixture was calcined at 700°C for 10h to obtain a coated positive electrode material with a chemical formula of LiNi 0.678 Co 0.120 Mn 0.200 Ti 0.002 O2@Li 1.3 V 0.5 Nb 0.24 O2.

[0092] The coated positive electrode material has a volume average particle size Dv50 of 3-5μm, the mass ratio of the multi-element positive electrode material matrix and the coating layer is 1:0.002, and the thickness of the coating layer is 5-10nm.

[0093] Example 3

[0094] Ni 0.82 Co 0.12 Mn 0.06 (OH)2, LiOH and ZrO2 were mixed in a molar ratio of 1:1.04:0.0015, and an intermediate was obtained after thorough mixing;

[0095] The intermediate was calcined at 780°C for 12h to obtain a multi-element positive electrode material matrix;

[0096] The multi-element positive electrode material matrix, LiOH, V2O5 and NbO2 were mixed in a molar ratio of 1:0.02:0.009:0.005, and after thorough mixing, the mixture was calcined at 650°C for 8h to obtain a coated positive electrode material with a chemical formula of LiNi 0.817 Co 0.120 Mn 0.060 Zr 0.003 O2@Li 1.28 V 0.54 Nb 0.22 O2.

[0097] The coated positive electrode material has a volume average particle size Dv50 of 8-11μm, the mass ratio of the multi-element positive electrode material matrix and the coating layer is 1:0.005, and the thickness of the coating layer is 10-20nm.

[0098] Example 4

[0099] Ni 0.89 Co 0.10 Al 0.01 OH)2, LiOH and SrO were proportioned at a molar ratio of 1:1.045:0.002, and after being mixed thoroughly, an intermediate was obtained;

[0100] The intermediate was calcined at 720℃ for 11h to prepare a multi-element positive electrode material matrix;

[0101] The multi-element positive electrode material matrix, LiOH, VO2 and NbO2 were proportioned at a molar ratio of 1:0.018:0.021:0.0055, and after being mixed thoroughly, the mixture was calcined at 620℃ for 8.5h to prepare a coated positive electrode material with a chemical formula of LiNi 0.888 Co 0.100 Al 0.010 Sr 0.002 O2@Li 1.48 V 0.59 Nb 0.15 O2.

[0102] The coated positive electrode material has a volume average particle size Dv50 of 8-11μm, the mass ratio of the multi-element positive electrode material matrix and the coating layer is 1:0.01, and the thickness of the coating layer is 10-30nm.

[0103] Example 5

[0104] Ni 0.93 Co 0.05 Mn 0.01 Al 0.01 OH)2, LiOH and ZrO2 were proportioned at a molar ratio of 1:1.045:0.002, and after being mixed thoroughly, an intermediate was obtained;

[0105] The intermediate was calcined at 760℃ for 14h to prepare a multi-element positive electrode material matrix;

[0106] The multi-element positive electrode material matrix, LiOH, VO2, NbO2 and LiF were proportioned at a molar ratio of 1:0.016:0.025:0.0065:0.002, and after being mixed thoroughly, the mixture was calcined at 550℃ for 6.5h to prepare a coated positive electrode material with a chemical formula of LiNi 0.92 8Co 0.050 Mn 0.010 Al 0.010 Zr 0.002 O2@Li 1.25 V 0.55 Nb 0.2 O 1.9 F 0.1 .

[0107] The volume average particle size Dv50 of the coated positive electrode material is 11-14 μm, the mass ratio of the multi-element positive electrode material matrix and the coating layer is 1:0.015, and the thickness of the coating layer is 10-50 nm.

[0108] Comparative Example 1

[0109] Comparative Example 1 and Example 1 are different in that after the multi-element positive electrode material matrix is prepared, the coating layer coated on the surface of the multi-element positive electrode material matrix is not continuously prepared, and the others are the same. The specific process is as follows:

[0110] Ni 0.60 Co 0.05 Mn 0.35 (OH)2, Li2CO3 and Al2O3 are proportioned according to a molar ratio of 1:0.51:0.001, and an intermediate is obtained after being fully mixed;

[0111] The intermediate is calcined at 920℃ for 14h to prepare a multi-element positive electrode material matrix, and the chemical formula of the multi-element positive electrode material matrix is: LiNi 0.600 Co 0.050 Mn 0.348 Al 0.002 O2.

[0112] The volume average particle size Dv50 of the multi-element positive electrode material matrix is 2.5-4.5 μm.

[0113] Comparative Example 2

[0114] Comparative Example 2 and Example 4 are different in that after the multi-element positive electrode material matrix is prepared, VO2 and NbO2 are not added when the multi-element positive electrode material matrix is subjected to subsequent treatment, and the others are the same. The specific process is as follows:

[0115] Ni 0.89 Co 0.10 Al 0.01 (OH)2, LiOH and SrO are proportioned according to a molar ratio of 1:1.045:0.002, and an intermediate is obtained after being fully mixed;

[0116] The intermediate is calcined at 720℃ for 11h to prepare a multi-element positive electrode material matrix;

[0117] The multi-element positive electrode material matrix and LiOH are proportioned according to a molar ratio of 1:0.018, and an intermediate is obtained after being fully mixed, and is calcined at 620℃ for 8.5h to prepare a multi-element positive electrode material with a chemical formula of LiNi 0.888 Co 0.100 Al 0.010 Sr 0.002 O2.

[0118] The volume average particle size Dv50 of the multi-element positive electrode material matrix is 8-11 μm.

[0119] Comparative Example 3

[0120] Comparative Example 3 and Example 4 differ in that after the preparation of the multi-element positive electrode material matrix, no V02 is added during the subsequent treatment, and the other conditions are the same. The specific process is as follows:

[0121] Ni 0.89 Co 0.10 Al 0.01 (OH)2, LiOH and SrO are proportioned according to a molar ratio of 1:1.045:0.002, and after being fully mixed, an intermediate is obtained;

[0122] The intermediate is calcined at 720°C for 11h to prepare a multi-element positive electrode material matrix;

[0123] The multi-element positive electrode material matrix, LiOH and Nb02 are proportioned according to a molar ratio of 1:0.018:0.0055, and after being fully mixed, they are calcined at 620°C for 8.5h to prepare a coated positive electrode material, whose chemical formula is LiNi 0.888 Co 0.100 Al 0.010 Sr 0.00 2O2@Li 1.50 Nb 0.50 O2.

[0124] The volume average particle size Dv50 of the coated positive electrode material is 8-11μm, the mass ratio of the multi-element positive electrode material matrix and the coating layer is 1:0.002, and the thickness of the coating layer is 5-15nm.

[0125] Comparative Example 4

[0126] Comparative Example 4 and Example 4 differ in that after the preparation of the multi-element positive electrode material matrix, no Nb02 is added during the subsequent treatment, and the other conditions are the same. The specific process is as follows:

[0127] Ni 0.89 Co 0.10 Al 0.01 (OH)2, LiOH and SrO are proportioned according to a molar ratio of 1:1.045:0.002, and after being fully mixed, an intermediate is obtained;

[0128] The intermediate is calcined at 720°C for 11h to prepare a multi-element positive electrode material matrix;

[0129] The multi-element positive electrode material matrix, LiOH and V02 are proportioned according to a molar ratio of 1:0.018:0.021, and after being fully mixed, they are calcined at 620°C for 8.5h to prepare a coated positive electrode material, whose chemical formula is LiNi 0.888 Co 0.100 Al0.010 Sr 0.002 O2@Li 1.40 V 1.20 O2。。

[0130] The volume average particle size Dv50 of the coated positive electrode material is 8-11 μm, the mass ratio of the multi-element positive electrode material matrix and the coating layer is 1:0.008, and the thickness of the coating layer is 10-25 nm.

[0131] II. Performance test experiment

[0132] 1. Scanning electron microscopy was used to characterize the morphology of the coated positive electrode material prepared in Example 1 and Example 5, respectively. The results of Example 1 are shown in FIG. 1, and the results of Example 5 are shown in FIG. 2. Figure 1 Figure 2

[0133] As can be seen from FIG. 1, the coated positive electrode material prepared in Example 1 has a single crystal structure, and the surface is smooth and uniform without aggregates. As can be seen from FIG. 2, the coated positive electrode material prepared in Example 5 has a polycrystalline structure, and the surface is smooth and uniform without aggregates. Figure 1 Figure 2

[0134] 2. The coated positive electrode material prepared in Example 1 was subjected to XRD test, and the results are shown in FIG. 3. As can be seen from FIG. 3, the coated positive electrode material prepared in Example 1 has sharp diffraction peaks, indicating that the coated positive electrode material provided by the technical scheme has a good crystal structure and high crystallinity. Figure 3 Figure 3

[0135] 3. Each of the positive electrode materials in Examples 1-5 and Comparative Examples 1-4 was assembled into a positive electrode sheet together with a conductive agent and PVDF according to a mass ratio of 96:2:2, and then each of the positive electrode sheets was assembled into a button cell together with a negative electrode sheet, a separator, and an electrolyte.

[0136] Each of the button cells was subjected to first discharge specific capacity test, first efficiency test, and capacity retention rate test after 200 cycles. The test conditions for the first capacity and cycle test of the button cell were LR 2032, 0.3C, 2.5-4.25V, vs. Li + / Li.

[0137] The test results are shown in Table 1 below.

[0138] Table 1

[0139] Positive electrode material Initial discharge specific capacity (mA h / g) Initial efficiency (%) 200 cycle capacity retention (%) Example 1 184.2 89.1 95.4 Example 2 191.8 89.4 94.2 Example 3 206.5 90.8 96.3 Example 4 221.4 92.5 94.3 Example 5 220.8 92.7 94.7 Comparative Example 1 181.2 88.7 78.6 Comparative Example 2 219.6 90.1 70.2 Comparative Example 3 219.9 90.2 85.4 Comparative Example 4 220.6 90.4 88.7

[0140] ​​​​​​As can be seen from the results of examples 1-5 in table 1, the coated positive electrode material provided in the application has good kinetic performance, and when it is applied to a lithium ion battery, the lithium ion battery has high initial specific discharge capacity, high capacity retention rate and good cycle performance, and can be widely applied in the field of lithium ion batteries.

[0141] As can be seen from the results of examples 1 and comparative example 1, and examples 4 and comparative examples 2-4, in comparative example 1, the multi-element positive electrode material substrate is not subjected to secondary calcination, and no coating layer is formed on the surface, resulting in a decrease in the initial specific discharge capacity and the initial efficiency; in comparative examples 2-4, no LVNOF coating layer is formed on the surface of the multi-element positive electrode material substrate, resulting in a decrease in the initial specific discharge capacity and the initial efficiency, and the decrease in the initial efficiency is more obvious; in comparative examples 1-4, the capacity retention rate at 200 cycles is significantly decreased, and the reason analyzed by the technical personnel of the application is that: in comparative examples 1-4, no LVNOF coating layer is formed on the surface of the multi-element positive electrode material substrate, and the multi-element positive electrode material substrate is subjected to Li + After multiple deintercalation / intercalation, the volume shrinks / expands greatly, and the lattice oxygen is gradually lost, resulting in serious damage to the structure of the multi-element positive electrode material substrate and a significant decrease in the cycle performance.

[0142] As can be seen from the results of example 4 and comparative examples 23-4, compared with the preparation of a coating layer only by using a vanadium compound or a niobium compound, the preparation of an LVNOF coating layer by simultaneously using a vanadium compound and a niobium compound has a synergistic effect.

[0143] The capacity retention rate of examples 1, 5, comparative example 1 and comparative example 2 with the change of cycle number is shown in Figure 4 As can be seen from the results of Figure 4 Compared with comparative examples 1 and 2, the capacity retention rate of examples and example 5 with the change of cycle number is significantly reduced, indicating that the coated positive electrode material has good kinetic performance, and when it is applied to a lithium ion battery, the capacity retention rate is high and the cycle performance is good.

[0144] The technical features of the above-described examples can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above-described examples are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the description.

[0145] The above-described examples only express several embodiments of the application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the application, a number of modifications and improvements can be made, which are within the scope of the application. Therefore, the protection scope of the patent of the application should be subject to the appended claims.

Claims

1. A coated cathode material, characterized in that, include: The multi-element cathode material matrix includes materials with the chemical formula LiNi. x Co y M 1-x-y The material of O2, wherein M includes one or more of Mn, Al, Mg, Ti, Zr, Y, Nb, W, Ce, Sb, Sr and Ta, 0.20<x≤0.98, 0≤y<0.45, x+y≤1; as well as A coating layer is applied to at least a portion of the surface of the multi-element cathode material matrix, the coating layer comprising a chemical formula of Li. r V s Nb t O u F v The material has the following properties: 1.0≤r≤1.5, 0.2≤s≤0.8, 0.01≤t≤0.5, 1.6≤u≤2.0, 0<v≤0.4; the coating layer has a spinel structure.

2. The coated cathode material as described in claim 1, characterized in that, The thickness of the coating layer is 2~50nm, and the volume average particle size Dv50 of the coated cathode material is 1.3~15μm.

3. A method for preparing a coated cathode material as described in any one of claims 1 to 2, characterized in that, Includes the following steps: A coating cathode material is prepared by mixing a multi-element cathode material matrix with raw materials for forming a coating layer and then calcining the mixture to form a coating layer on at least a portion of the surface of the multi-element cathode material matrix. The raw materials used to form the coating layer include a first lithium source, a vanadium compound, a niobium compound, and a first material, wherein the first material is a fluoride.

4. The method for preparing the coated cathode material as described in claim 3, characterized in that, The preparation of coated cathode materials includes at least one of the following conditions: (1) The molar ratio of the multi-element cathode material matrix, the lithium element contained in the first lithium source, the vanadium element contained in the vanadium compound, the niobium element contained in the niobium compound, and the fluorine element contained in the fluoride is 1:(0.001~0.05):(0.001~0.03):(0.001~0.02):(0~0.02); (2) The first lithium source includes one or more of lithium hydroxide and lithium carbonate; (3) The vanadium compound includes one or more of vanadium monoxide, vanadium trioxide, vanadium dioxide, and vanadium pentoxide; (4) The niobium compound includes one or more of niobium monoxide, niobium dioxide, niobium trioxide and niobium pentoxide; (5) The fluoride includes one or more of lithium fluoride, ammonium fluoride, sodium fluoride and sodium hydrogen fluoride; (6) The roasting temperature is 500~850℃; (7) The roasting time is 6~15h.

5. The method for preparing the coated cathode material according to any one of claims 3 to 4, characterized in that, It also includes the step of preparing the multi-element cathode material matrix: An intermediate is prepared by mixing a multi-component cathode material precursor, a second lithium source, and a second material; the second material is a metal compound, and the multi-component cathode material precursor includes materials with the chemical formula Ni. m Co n M 1-m-n The material is (OH)2, wherein M includes one or more of Mn, Al, Mg, Ti, Zr, Y, Nb, W, Ce, Sb, Sr and Ta, 0.20<m≤0.98, 0≤n<0.45, and m+n≤1; The intermediate was calcined to obtain a multi-element cathode material matrix.

6. The method for preparing the coated cathode material as described in claim 5, characterized in that, The preparation of the multi-element cathode material matrix includes at least one of the following conditions: (1) The molar ratio of the metal element contained in the multi-element cathode material precursor, the metal element contained in the metal compound, and the lithium element contained in the second lithium source is 1:(0~0.02):(0.95~1.08); (2) The metal compound includes one or more of metal oxides, metal hydroxides and metal carbonates; the metal contained in the metal compound includes one or more of Al, Mg, Ti, Zr, Y, Nb, W, Ce, Sb, Sr and Ta; (3) The second lithium source includes one or more of lithium hydroxide and lithium carbonate; (4) The calcination temperature for calcining the intermediate is 600~1100℃; (5) The roasting time for roasting the intermediate is 6 to 20 hours.

7. A positive electrode sheet, characterized in that, include: Positive current collector; A positive electrode active material layer is located on at least one surface of the positive electrode current collector, and the positive electrode active material layer comprises a coated positive electrode material as described in any one of claims 1 to 2 or a coated positive electrode material prepared by the method as described in any one of claims 3 to 6.

8. A lithium-ion battery, characterized in that, It includes the coated positive electrode material as described in any one of claims 1 to 2, the coated positive electrode material prepared by the method as described in any one of claims 3 to 6, or the positive electrode sheet as described in claim 7.

9. An electrical device, characterized in that, Including the lithium-ion battery as described in claim 8.

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