Lithium nickel manganese acid cathode material, preparation method thereof, cathode and lithium ion battery

Abstract

The application provides a lithium nickel-manganese oxide positive electrode material and a preparation method, a positive electrode and a lithium ion battery thereof, and relates to the field of secondary batteries. a‑z Mn b‑ x Nb x F y Al z O 4‑y , wherein 0.3<=a<=0.8, 1.2<=b<=1.7, a+b=2, 0

Description

Technical Field

[0001] The present application relates to the field of secondary batteries, and in particular to a lithium nickel manganese oxide positive electrode material and a preparation method thereof, a positive electrode and a lithium ion battery. Background Art

[0002] As society develops, fossil energy and environmental issues are becoming increasingly serious, creating an urgent need for renewable, clean energy to address this predicament. Lithium-ion batteries are widely used in energy supply and storage devices due to their high cycle performance and high energy density. These performance characteristics are crucially dependent on the cathode material. Lithium nickel manganese oxide (LiMnO) cathode materials are considered one of the most promising due to their high voltage, high energy density, and low cost.

[0003] However, lithium nickel manganese oxide positive electrode materials still have some problems, such as poor lithium ion conductivity, which will reduce their electrochemical performance and thus limit their practical application effects.

[0004] Therefore, it is necessary to improve the lithium nickel manganese oxide positive electrode material. Summary of the Invention

[0005] The purpose of this application is to provide a lithium nickel manganese oxide positive electrode material and a preparation method thereof, a positive electrode and a lithium ion battery to solve the above problems.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] The present application provides a lithium nickel manganese oxide positive electrode material, the chemical formula of which is LiNi a- z Mn b-x Nb x F y Al z O 4-y , where 0.3≤a≤0.8, 1.2≤b≤1.7, a+b=2, 0 <x≤0.3,0<y≤0.2,0<z≤0.5;

[0008] Preferably, 0.05≤x≤0.2, 0.05≤y≤0.1, and 0.15≤z≤0.4.

[0009] According to an embodiment of the present application, the lithium nickel manganese oxide positive electrode material is a single crystal primary particle, and the particle size of the single crystal primary particle is 400-3000 nm, preferably 600-2200 nm, and more preferably 653-2124 nm;

[0010] And / or, the specific surface area of ​​the lithium nickel manganese oxide positive electrode material is 0.9-1.5m 2 / g, preferably 0.9-1.3m2 / g.

[0011] According to an embodiment of the present application, the single-crystal primary particles have a spinel crystal structure, and the morphology of the single-crystal primary particles is a polyhedron with 6 to 12 crystal faces. It should be noted that a quasi-single crystal is an aggregate of multiple single crystals, and has a particle morphology between single crystal materials and polycrystalline materials. In the embodiments of the present application, the main body is a single crystal particle.

[0012] The present application also provides a method for preparing the lithium nickel manganese oxide positive electrode material as described above, comprising:

[0013] Mixing nickel manganese hydroxide, an aluminum-containing compound, a niobium-containing compound, a fluorine-containing compound, and a lithium source to obtain a mixture;

[0014] The mixture is sintered to obtain a lithium nickel manganese oxide positive electrode material.

[0015] According to the embodiment of the present application, the chemical formula of the nickel manganese hydroxide is Ni a’ Mn b’ (OH)2, wherein a' is 0.15-0.4, b' is 0.6-0.85, a'+b'=1, preferably Ni 0.25 Mn 0.75( OH)2;

[0016] The aluminum-containing compound includes one or two of Al2O3 and Al(OH)3;

[0017] The niobium-containing compound includes one or more of Nb2O3, NbO, and Nb2O5;

[0018] The fluorine-containing compound includes LiF;

[0019] The lithium source includes one or both of Li2CO3 and LiOH.

[0020] According to an embodiment of the present application, the nickel manganese hydroxide (precursor) is a polycrystalline particle, and the particle size Dv50 of the polycrystalline particle is 3.0-7.5 μm;

[0021] And / or, the specific surface area of ​​the nickel manganese hydroxide is 30-40m 2 / g;

[0022] And / or, the tap density of the nickel manganese hydroxide is 0.5-1.5 g / cm 3 .

[0023] According to an embodiment of the present application, the sintering temperature is 800-900°C;

[0024] And / or, the method further comprises: increasing the temperature to the sintering temperature at a heating rate of 1-6°C / min.

[0025] According to an embodiment of the present application, the sintering time is 15-20 hours.

[0026] The present application also provides a positive electrode, which includes a current collector and a positive electrode active material layer. The positive electrode active material layer includes the lithium nickel manganese oxide positive electrode material described above or includes the lithium nickel manganese oxide positive electrode material prepared by the preparation method described above.

[0027] The present application also provides a lithium-ion battery, which includes the positive electrode described above.

[0028] Compared with the prior art, the advantages of this application include:

[0029] The present application utilizes specific doping levels of Al, Nb, and F, with these doping elements occupying the Ni, Mn, and O positions, respectively. These doping elements, Al, Nb, and F, functionally support and cooperate with each other, stabilizing the crystal structure and making the positive electrode material particles single-crystallized. This significantly improves the lithium ion conductivity, discharge capacity, and structural stability of the positive electrode material, thereby effectively improving the electrochemical performance of the lithium-ion battery. The use of the lithium nickel manganese oxide positive electrode material of the present application can effectively improve the discharge capacity, cycle performance, rate performance, and other electrochemical properties of the lithium battery.

[0030] The preparation method of lithium nickel manganese oxide positive electrode material can be used to prepare a positive electrode material with excellent electrochemical properties.

[0031] The positive electrode and lithium-ion battery of the present application have excellent electrochemical properties and can significantly improve market competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0033] Figure 1 Ni in Example 1 0.25 Mn 0.75( OH)2 SEM image;

[0034] Figure 2 Ni in Example 1 0.25 Mn 0.75( OH)2 cross-section SEM image;

[0035] Figure 3 is a SEM image of the lithium nickel manganese oxide positive electrode material prepared in Example 1;

[0036] Figure 4 is a SEM image of the lithium nickel manganese oxide positive electrode material prepared in Example 2;

[0037] Figure 5 is a SEM image of the lithium nickel manganese oxide positive electrode material prepared in Example 3;

[0038] Figure 6 is a SEM image of the lithium nickel manganese oxide positive electrode material prepared in Example 4;

[0039] Figure 7 is a SEM image of the lithium nickel manganese oxide positive electrode material prepared in Example 5;

[0040] Figure 8 is a SEM image of the lithium nickel manganese oxide positive electrode material prepared in Example 6;

[0041] Figure 9 is a SEM image of the lithium nickel manganese oxide positive electrode material prepared in Example 7;

[0042] Figure 10 is a SEM image of the lithium nickel manganese oxide positive electrode material prepared in Example 8;

[0043] Figure 11 This is an SEM image of the lithium nickel manganese oxide positive electrode material prepared in Comparative Example 1;

[0044] Figure 12 This is an SEM image of the lithium nickel manganese oxide positive electrode material prepared in Comparative Example 2;

[0045] Figure 13 This is an SEM image of the lithium nickel manganese oxide positive electrode material prepared in Comparative Example 3;

[0046] Figure 14 This is a comparison curve of the cycle performance of the buckle prepared with lithium nickel manganese oxide positive electrode materials of Example 1 and Comparative Example 1 at 1C. DETAILED DESCRIPTION

[0047] In order to better illustrate the technical solution provided by this application, before the embodiments, an overall description of the technical solution is first given, as follows:

[0048] The present application provides a lithium nickel manganese oxide positive electrode material, the chemical formula of which is LiNi a- z Mn b-x Nb x F y Al z O 4-y , where 0.3≤a≤0.8, 1.2≤b≤1.7, a+b=2, 0 <x≤0.3,0<y≤0.2,0<z≤0.5;

[0049] Preferably, 0.05≤x≤0.2, 0.05≤y≤0.1, and 0.15≤z≤0.4.

[0050] Preferably, 0.2≤az≤0.6, 1.1≤bx≤1.45.

[0051] The present application can effectively improve the electrochemical performance of the positive electrode material by doping specific contents of elements Al, Nb, and F. Specifically, the doping element Al occupies the Ni position, Nb occupies the Mn position, and F occupies the O position. The introduction of Al and Nb can stabilize the lattice structure, refine the particles, reduce the mixing of Li / Ni, and increase the diffusion rate of lithium ions. F has strong oxidizing properties and can increase the discharge capacity of the material; moreover, F occupies the O position, and fluorine and transition metals can form chemical bonds, which increases the stability of the crystal structure, makes it difficult for O in the material to detach and reduces the mixing of Li / Ni, thereby reducing the activation energy of lithium ion migration.

[0052] Furthermore, if z is too small, that is, the aluminum content in the cathode material is too low, the crystal structure may not be effectively stabilized. If z is too large, that is, the aluminum content in the cathode material is too high, it may cause excessive shrinkage of the unit cell volume, resulting in local tension imbalance in the lattice, affecting the discharge capacity and preventing single crystallization. If x is too small, that is, the niobium content in the cathode material is too low, it may cause the particles to be unable to form single crystals and the particles cannot be refined. If x is too large, that is, the niobium content in the cathode material is too high, impurities may form on the particle surface, increasing the resistance to lithium ion diffusion and reducing the cycling stability of the material. If y is too small, that is, the F content in the cathode material is too low, it may reduce structural stability. If y is too large, that is, the F content in the cathode material is too high, it may increase the degree of Li / Ni mixing and reduce the discharge capacity of the material.

[0053] According to some embodiments of the present application, x can be 0.05, 0.1, or 0.2, z can be 0.15, 0.2, or 0.4, y can be 0.05, 0.08, or 0.1, and the chemical formula of the lithium nickel manganese oxide positive electrode material can be LiNi 0.35 Mn 1.45 Nb 0.05 F 0.05 Al 0.15 O 3.95 、LiNi 0.3 Mn 1.4 Nb 0.1 F 0.08 Al 0.2 O 3.92 、LiNi 0.1 Mn 1.3 Nb 0.2 F 0.1 Al 0.4 O 3.9 .

[0054] According to an embodiment of the present application, the lithium nickel manganese oxide positive electrode material is a single crystal primary particle, and the particle size of the single crystal primary particle is 400-3000nm; thus, it is conducive to achieving a balance between battery energy density and stability. If the particle size of the single crystal primary particle is too large, the lithium ion transmission path will be increased, the lithium ion transmission rate will be reduced, and thus the discharge capacity will be reduced; moreover, the excessively large particle size will cause the contact area between the particle and the electrolyte to be smaller, reducing the reaction area, and thus causing a decrease in discharge capacity. If the particle size of the single crystal primary particle is too small, the internal compactness will increase when the battery is assembled, resulting in the inability to remove internal heat and gas, reducing safety; moreover, particles that are too small are prone to agglomeration and water absorption, affecting the electrochemical performance of the battery.

[0055] According to some embodiments of the present application, the particle size of the single crystal primary particles is preferably 600-2200 nm, more preferably 653-2124 nm.

[0056] It should be noted that the equivalent particle size of the single crystal primary particles can be obtained from a scanning electron microscope (SEM) image, and the particle size of the single crystal primary particles refers to the average equivalent particle size of the single crystal primary particles.

[0057] And / or, the specific surface area of ​​the lithium nickel manganese oxide positive electrode material is 0.9-1.5m 2 / g. Thus, it is beneficial to achieve a balance between battery energy density and stability. If the specific surface area is too large, the particle size of the positive electrode material is small, which easily causes particle agglomeration and affects the electrochemical cycle stability. If the specific surface area is too small, the particle size of the positive electrode material is large, which leads to a low discharge capacity. The specific surface area of ​​the lithium nickel manganese oxide positive electrode material is preferably 0.9-1.3m 2 / g.

[0058] According to an embodiment of the present application, the single-crystal primary particles have a spinel crystal structure, and the morphology of the single-crystal primary particles is a polyhedron with 6 to 12 crystal faces. When the above conditions are met, the electrochemical performance of the lithium nickel manganese oxide positive electrode material can be further improved. If the number of crystal faces of the polyhedron is too few or too many, it will lead to poor electrochemical performance.

[0059] In some embodiments of the present application, the single-crystal primary particle has a morphology of a polyhedron with 8 crystal faces.

[0060] The present application also provides a method for preparing the lithium nickel manganese oxide positive electrode material as described above, comprising:

[0061] Mixing nickel manganese hydroxide, an aluminum-containing compound, a niobium-containing compound, a fluorine-containing compound, and a lithium source to obtain a mixture;

[0062] The mixture is sintered to obtain a lithium nickel manganese oxide positive electrode material.

[0063] Furthermore, the cathode material LiNi a-z Mn b-x Nb x F y Al z O 4-y The molar ratio of each element in the mixture is calculated, and the masses of the nickel manganese hydroxide, the aluminum-containing compound, the niobium-containing compound, the fluorine-containing compound, and the lithium source are calculated. Subsequently, the nickel manganese hydroxide, the aluminum-containing compound, the niobium-containing compound, the fluorine-containing compound, and the lithium source are weighed and mixed to obtain a mixture.

[0064] According to the embodiment of the present application, the chemical formula of the nickel manganese hydroxide is Ni a’ Mn b’ (OH)2, wherein a' is 0.15-0.4, b' is 0.6-0.85, a'+b'=1, preferably Ni 0.25 Mn 0.75( OH)2;

[0065] Furthermore, nickel manganese hydroxide can be prepared by a coprecipitation method.

[0066] The aluminum-containing compound includes one or two of Al2O3 and Al(OH)3;

[0067] The niobium-containing compound includes one or more of Nb2O3, NbO, and Nb2O5;

[0068] The fluorine-containing compound includes LiF;

[0069] The lithium source includes one or both of Li2CO3 and LiOH.

[0070] According to an embodiment of the present application, the nickel manganese hydroxide is a polycrystalline particle, and the particle size Dv50 of the polycrystalline particle is 3.0-7.5 μm; through the method of the present application, the polycrystalline particles can be broken, which is conducive to the formation of single crystal primary particles of positive electrode material with smaller particle size.

[0071] And / or, the specific surface area of ​​the nickel manganese hydroxide is 3.0-4.0m 2 / g;

[0072] And / or, the tap density of the nickel manganese hydroxide is 0.5-1.5 g / cm 3 When the tap density of nickel-manganese hydroxide is within the above range, its interior is loose. At the same particle size, if the tap density is too high, the interior of the particles is relatively dense, which is not conducive to single crystallization. If the tap density is too low, the particles are too loose, which may cause the conductivity of the positive electrode material to decrease, thereby affecting the electrochemical performance.

[0073] According to the embodiments of the present application, the sintering temperature is 800-900°C; this sintering temperature is conducive to the formation of single-crystalline primary particles with smaller particle sizes, thereby improving the discharge capacity. If the sintering temperature is too low, the spherical morphology of the raw material cannot be destroyed, single crystallization cannot be achieved, and a complete spinel structure cannot be formed, which hinders the insertion and extraction of lithium ions. If the sintering temperature is too high, it will cause particle agglomeration and even destroy the internal properties of the material, thereby reducing the discharge capacity.

[0074] While conventional materials require temperatures exceeding 900°C to form single crystals, the present invention can produce single-crystal primary particles with smaller particle sizes at lower sintering temperatures of 800-900°C. This means that compared to conventional methods for preparing single-crystal cathode materials, the present invention can lower the sintering temperature while ensuring a uniform distribution of the single-crystal particles formed after sintering.

[0075] Furthermore, the sintering temperature may be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C or any value between 800-900°C.

[0076] And / or, the method further comprises: increasing the temperature to the sintering temperature at a heating rate of 1-6°C / min.

[0077] Furthermore, the heating rate may be 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min or any value between 1-6°C / min.

[0078] According to an embodiment of the present application, the sintering time is 15-20 hours. During the above-mentioned sintering time, it is possible to ensure that the raw materials fully react with each other, which is conducive to the formation of single-crystal primary particles with smaller particle size, and can effectively improve the discharge capacity and cycle retention rate of the positive electrode material. If the sintering time is too short, it may cause incomplete reaction of the raw materials, affecting the chemical composition and crystal structure of the material, thereby reducing the electrochemical performance. If the sintering time is too long, it may cause particle agglomeration and reduce the ion diffusion rate. Moreover, high-temperature treatment for too long may induce side reactions and affect the purity of the positive electrode material.

[0079] Furthermore, the sintering time can be 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours or any value between 15 and 20 hours.

[0080] The present application also provides a positive electrode, which includes a current collector and a positive electrode active material layer. The positive electrode active material layer includes the lithium nickel manganese oxide positive electrode material described above or includes the lithium nickel manganese oxide positive electrode material prepared by the preparation method described above.

[0081] The present application also provides a lithium-ion battery, which includes the positive electrode described above.

[0082] As used herein:

[0083] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0084] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0085] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0086] Example 1

[0087] Example 1 provides a lithium nickel manganese oxide positive electrode material LiNi 0.3 Mn 1.4 Nb 0.1 F 0.08 Al 0.2 O 3.92 , and its preparation method comprises the following steps:

[0088] Step S1: According to the target chemical formula LiNi 0.3 Mn 1.4 Nb 0.1 F 0.08 Al 0.2 O 3.92 Calculate the amount of raw materials based on the molar ratio of each element in the raw materials, weigh Ni 0.25 Mn 0.75(OH)2, aluminum oxide, niobium pentoxide, lithium fluoride and lithium carbonate are added into a high-speed mixer, and the raw materials are mixed at a rotation speed of 300 rpm for 5 minutes, and then at a rotation speed of 650 rpm for 20 minutes, and mixed uniformly to obtain a mixture.

[0089] Among them, Ni 0.25 Mn 0.75( OH)2 SEM image and cross-section SEM image as shown Figure 1 and Figure 2 As shown, Ni 0.25 Mn 0.75( The particle size Dv50 of OH)2 is 3.0 μm, and Ni 0.25 Mn 0.75( The specific surface area of ​​OH)2 is 32.8 m 2 / g, Ni 0.25 Mn 0.75( The tap density of OH)2 is 1.04 g / cm 3 .

[0090] Step S2, sintering the mixture of step S1, specifically, heating the temperature to 850°C at a rate of 3°C / min, and sintering for 18 hours. After sintering, the sintered product was crushed by a jet mill with a crushing frequency of 40 Hz, and passed through a 325 mesh sieve to obtain a single crystal morphology of lithium nickel manganese oxide positive electrode material LiNi 0.3 Mn 1.4 Nb 0.1 F 0.08 Al 0.2 O 3.92 .

[0091] Depend on Figure 3 It can be seen that the lithium nickel manganese oxide positive electrode material of Example 1 is a single crystal primary particle having a spinel crystal structure and a polyhedron with 8 crystal faces. The particle size of the single crystal primary particle is 700 nm.

[0092] The precursor Ni in Example 1 0.25 Mn 0.75( OH)2 is a polycrystalline particle, which is composed of multiple particles agglomerated. After heat preservation and sintering, the polycrystalline particles will crack and grow and crystallize again. Therefore, the particle size of the prepared positive electrode material will be smaller than that of the precursor Ni 0.25 Mn 0.75( OH)2 particle size.

[0093] The specific surface area of ​​the lithium nickel manganese oxide positive electrode material of Example 1 is 1.18 m 2 / g.

[0094] Example 2

[0095] Example 2 provides a lithium nickel manganese oxide positive electrode material LiNi 0.35 Mn 1.45 Nb 0.05 F 0.05 Al 0.15 O 3.95 , its preparation method is different from that of Example 1 in that:

[0096] Example 2 According to the target chemical formula LiNi 0.35 Mn 1.45 Nb 0.05 F 0.05 Al 0.15 O 3.95 The amount of raw materials charged is calculated based on the molar ratio of each element in the mixture. The amount of raw materials charged in Example 2 is different from that in Example 1.

[0097] like Figure 4 As shown, the lithium nickel manganese oxide positive electrode material of Example 2 is a single crystal primary particle having a spinel crystal structure and a polyhedron having 8 crystal faces. The particle size of the single crystal primary particle is 760 nm.

[0098] The specific surface area of ​​the lithium nickel manganese oxide positive electrode material of Example 2 is 1.15 m 2 / g.

[0099] Example 3

[0100] Example 3 provides a lithium nickel manganese oxide positive electrode material LiNi 0.2 Mn 1.3 Nb 0.2 F 0.1 Al 0.3 O 3.9 , its preparation method is different from that of Example 1 in that:

[0101] Example 3 According to the target chemical formula LiNi 0.2 Mn 1.3 Nb 0.2 F 0.1 Al 0.3 O 3.9 The amount of raw materials charged is calculated based on the molar ratio of each element in the mixture. The amount of raw materials charged in Example 3 is different from that in Example 1.

[0102] like Figure 5 As shown, the lithium nickel manganese oxide positive electrode material of Example 3 is a single crystal primary particle having a spinel crystal structure and a polyhedron having 8 crystal faces. The particle size of the single crystal primary particle is 862 nm.

[0103] The specific surface area of ​​the lithium nickel manganese oxide positive electrode material of Example 3 is 1.11 m2 / g.

[0104] Example 4

[0105] Example 4 provides a lithium nickel manganese oxide positive electrode material LiNi 0.3 Mn 1.4 Nb 0.1 F 0.08 Al 0.2 O 3.92 , its preparation method is different from that of Example 1 in that:

[0106] The sintering temperature in step S2 of Example 4 is 800°C.

[0107] like Figure 6 As shown, the lithium nickel manganese oxide positive electrode material of Example 4 is a single crystal primary particle having a spinel crystal structure and a polyhedron having 8 crystal faces. The particle size of the single crystal primary particle is 687 nm.

[0108] The specific surface area of ​​the lithium nickel manganese oxide positive electrode material of Example 4 is 1.21 m 2 / g.

[0109] Example 5

[0110] Example 5 provides a lithium nickel manganese oxide positive electrode material LiNi 0.3 Mn 1.4 Nb 0.1 F 0.08 Al 0.2 O 3.92 , its preparation method is different from that of Example 1 in that:

[0111] The sintering temperature in step S2 of Example 5 is 900°C.

[0112] like Figure 7 As shown, the lithium nickel manganese oxide positive electrode material of Example 5 is a single crystal primary particle having a spinel crystal structure and a polyhedron having 8 crystal faces. The particle size of the single crystal primary particle is 914 nm.

[0113] The specific surface area of ​​the lithium nickel manganese oxide positive electrode material of Example 5 is 1.08 m 2 / g.

[0114] Example 6

[0115] Example 6 provides a lithium nickel manganese oxide positive electrode material LiNi 0.3 Mn 1.4 Nb 0.1 F 0.08 Al 0.2 O 3.92, its preparation method is different from that of Example 1 in that:

[0116] The sintering time in step S2 of Example 6 is 15 hours.

[0117] like Figure 8 As shown, the lithium nickel manganese oxide positive electrode material of Example 6 is a single crystal primary particle having a spinel crystal structure and a polyhedron having 8 crystal faces. The particle size of the single crystal primary particle is 653 nm.

[0118] The specific surface area of ​​the lithium nickel manganese oxide positive electrode material of Example 6 is 1.30 m 2 / g.

[0119] Example 7

[0120] Example 7 provides a lithium nickel manganese oxide positive electrode material LiNi 0.3 Mn 1.4 Nb 0.1 F 0.08 Al 0.2 O 3.92 , its preparation method is different from that of Example 1 in that:

[0121] The sintering time in step S2 of Example 7 is 20 hours.

[0122] like Figure 9 As shown, the lithium nickel manganese oxide positive electrode material of Example 7 is a single crystal primary particle having a spinel crystal structure and a polyhedron having 3-9 crystal faces. The particle size of the single crystal primary particle is 2124 nm.

[0123] The specific surface area of ​​the lithium nickel manganese oxide positive electrode material of Example 7 is 0.91 m 2 / g.

[0124] Example 8

[0125] Example 8 provides a lithium nickel manganese oxide positive electrode material LiNi 0.6 Mn 1.1 Nb 0.1 F 0.08 Al 0.2 O 3.92 .

[0126] In step S1 of Example 1, Ni 0.25 Mn 0.75( OH)2 is replaced by Ni 0.4 Mn 0.6( OH)2, and the others are the same as in Example 1.

[0127] like Figure 10As shown, the lithium nickel manganese oxide positive electrode material of Example 8 is a single crystal primary particle having a spinel crystal structure and a polyhedron having 6-10 crystal faces. The particle size of the single crystal primary particle is 642 nm.

[0128] The specific surface area of ​​the lithium nickel manganese oxide positive electrode material of Example 8 is 1.23 m 2 / g.

[0129] Comparative Example 1

[0130] The positive electrode material of Comparative Example 1 is doped with Nb and F.

[0131] The difference between Comparative Example 1 and Example 1 is that aluminum oxide is not added in step S1 of Comparative Example 1.

[0132] like Figure 11 As shown, the positive electrode material prepared in Comparative Example 1 is single crystal-like particles.

[0133] Comparative Example 2

[0134] The positive electrode material of Comparative Example 2 is doped with Al and Nb.

[0135] The difference between Comparative Example 2 and Example 1 is that lithium fluoride is not added in step S1 of Comparative Example 2.

[0136] like Figure 12 As shown, the positive electrode material prepared in Comparative Example 2 is single crystal-like particles.

[0137] Comparative Example 3

[0138] The positive electrode material of Comparative Example 3 is doped with Al and F.

[0139] The difference between Comparative Example 3 and Example 1 is that niobium pentoxide is not added in step S1 of Comparative Example 3.

[0140] like Figure 13 As shown, the positive electrode material prepared in Comparative Example 3 is single crystal-like particles.

[0141] The positive electrode materials prepared in the examples and comparative examples were fabricated into button-type batteries using the same method, and the electrochemical performance of the batteries was examined under the same test conditions. Super P was used as the conductive agent, and PVDF was used as the binder. The conductive agent and binder were mixed with the positive electrode material, and NMP was added dropwise. After mixing and stirring, a positive electrode slurry was prepared and coated onto the current collector to obtain the positive electrode. The positive electrode was then assembled with a lithium sheet negative electrode, a separator, and an electrolyte to form a lithium-ion button-type battery. Testing at room temperature yielded a voltage range of 3.0-4.95V.

[0142] A blue-electric test cabinet was used to test the electrochemical properties of the battery. The test method was constant current and constant voltage charge and discharge. For example, at 25°C, the charge and discharge cycle characteristics of the button battery were detected using a blue-electric test cabinet. The battery was charged and discharged at a charge and discharge rate of 0.1C within a voltage range of 3.0-4.95V. Specifically, the battery was charged at a constant current of 0.1C to 4.95V, and then charged at a constant voltage at a voltage of 4.95V to a cutoff current of 0.02C, left for 5 minutes, and discharged at 0.1C to 3.0V, left for 5 minutes. The charge and discharge capacity after the first charge and discharge was recorded, and the first coulombic efficiency was calculated.

[0143] Again, charge at a constant current of 1C to 4.95V, then charge at a constant voltage at 4.95V to a cutoff current of 0.02C, let it sit for 5 minutes, discharge at 1C to 3.0V, let it sit for 5 minutes, and repeat this cycle. After 100 charge / discharge cycles, record the charge and discharge capacity after the 100th cycle, and calculate the cycle capacity retention rate after the 100th cycle.

[0144] Capacity retention rate after the 100th cycle (%)=(100th cycle discharge capacity / 1st cycle discharge capacity)×100%.

[0145] The test results are shown in Table 1.

[0146] Table 1 Comparison of electrochemical performance of Examples 1-8 and Comparative Examples 1-3

[0147]

[0148] Through Table 1 and Figure 14 It can be seen that the discharge capacity and cycle stability of the positive electrode materials of Examples 1-8 are superior to those of Comparative Examples 1-3. This may be due to the simultaneous introduction of Al, Nb, and F elements into the positive electrode materials of Examples 1-8. The co-introduction of Al, Nb, and F stabilizes the crystal structure, increases the diffusion rate of lithium ions, and exerts a synergistic effect of the three elements. The positive electrode materials prepared in Examples 1-8 are essentially single crystals, while the positive electrode materials prepared in Comparative Examples 1-3 are all quasi-single crystals, indicating that the co-introduction of Al, Nb, and F elements is conducive to the synthesis of single crystal particles and improves the cycle stability of the material.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

[0150] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and to form distinct embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is intended solely to enhance understanding of the overall background of this application and should not be construed as an admission or any implication that such information constitutes prior art known to those skilled in the art.

Claims

1. A lithium nickel manganese oxide positive electrode material, characterized in that The chemical formula of the lithium nickel manganese oxide positive electrode material is LiNi a- z Mn b-x Nb x F y Al z O 4-y , where 0.3≤a≤0.8, 1.2≤b≤1.7, a+b=2, 0 <x≤0.3,0<y≤0.2,0<z≤0.5; The lithium nickel manganese oxide positive electrode material is a single crystal primary particle, and the particle size of the single crystal primary particle is 400-3000nm.

2. The lithium nickel manganese oxide positive electrode material according to claim 1, characterized in that The specific surface area of ​​the lithium nickel manganese oxide positive electrode material is 0.9-1.5m 2 / g.

3. The lithium nickel manganese oxide positive electrode material according to claim 2, characterized in that The single crystal primary particle has a spinel crystal structure, and the morphology of the single crystal primary particle is a polyhedron with 6 to 12 crystal faces.

4. A method for preparing the lithium nickel manganese oxide positive electrode material according to any one of claims 1 to 3, characterized in that: include: Mixing nickel manganese hydroxide, an aluminum-containing compound, a niobium-containing compound, a fluorine-containing compound, and a lithium source to obtain a mixture; sintering the mixture to obtain a lithium nickel manganese oxide positive electrode material; Wherein, the nickel manganese hydroxide is a polycrystalline particle, and the particle size Dv50 of the polycrystalline particle is 3.0-7.5 μm; The specific surface area of ​​the nickel manganese hydroxide is 30-40m 2 / g; The tap density of the nickel manganese hydroxide is 0.5-1.5 g / cm 3 ; The sintering temperature is 800-900°C; The sintering time is 15-20 hours.

5. The preparation method according to claim 4, characterized in that The chemical formula of the nickel manganese hydroxide is Ni a’ Mn b’ (OH)2, where a' is 0.15-0.4, b' is 0.6-0.85, and a'+b'=1; The aluminum-containing compound includes one or two of Al2O3 and Al(OH)3; The niobium-containing compound includes one or more of Nb2O3, NbO, and Nb2O5; The fluorine-containing compound includes LiF; The lithium source includes one or both of Li2CO3 and LiOH.

6. The preparation method according to claim 4, characterized in that The method further comprises: increasing the temperature to the sintering temperature at a heating rate of 1-6° C. / min.

7. A positive electrode, characterized in that The positive electrode includes a current collector and a positive electrode active material layer, and the positive electrode active material layer includes the lithium nickel manganese oxide positive electrode material according to any one of claims 1 to 3 or the lithium nickel manganese oxide positive electrode material prepared by the preparation method according to any one of claims 4 to 6.

8. A lithium ion battery, characterized in that: The lithium-ion battery comprises the positive electrode according to claim 7.

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