Positive electrode material and preparation method thereof, and battery

Abstract

The present application provides a positive electrode material and a preparation method thereof, and a battery. The positive electrode material is a positive electrode material having the general chemical formula of Li n Ni 1‑x‑y M x Mn y O2, wherein 0.9≤n≤1.2, 0≤x<1, 0<y<1, wherein M is selected from Co and / or Al; the positive electrode material contains first particles within a particle size range of ≤1.5μm and second particles within a particle size range of ≥2.5μm, and when the first particles within the particle size range of ≤1.5μm are characterized by energy dispersive spectroscopy (EDS), the average molar ratio of the Ni element to the Mn element is recorded as R1; when the second particles within the particle size range of ≥2.5μm are characterized by energy dispersive spectroscopy (EDS), the average molar ratio of the Ni element to the Mn element is recorded as R2, 0<R2‑R1. The positive electrode material of the present application can effectively improve the specific capacity and high first-efficiency performance of the positive electrode material while improving the structural stability and cycle performance.

Description

[0001] This application claims priority to the invention patent application submitted to the State Intellectual Property Office on October 13, 2023, with application number 2023113348784 and application name "Positive electrode material and preparation method thereof, battery", all contents of which are incorporated by reference in this application. Technical Field

[0002] The present invention belongs to the technical field of positive electrode materials, and in particular relates to positive electrode materials, preparation methods thereof, and batteries. Background Art

[0003] Lithium-ion batteries are widely used in laptops, mobile phones, and digital products due to their high energy density, excellent safety, long cycle life, and environmental friendliness. However, the development of cathode materials has been slower than that of high-capacity anode materials (approximately 800-1000 mAh / g). Therefore, researchers are currently focusing their efforts on developing high-capacity and high-voltage cathode materials to increase the energy density of lithium-ion batteries.

[0004] Commonly used layered ternary cathode materials exhibit high capacity, high voltage, long cycle life, and excellent safety, making them the primary cathode material for power battery development. However, increasing nickel content in ternary cathode materials inevitably leads to problems such as lithium-nickel intermixing, structural degradation, reduced thermal stability, and increased residual alkali. This leads to battery capacity degradation, reduced cycle life, and poor structural stability, compromising safety and high performance.

[0005] The hydroxide precursor prepared by the conventional co-precipitation method is composed of uniformly distributed nickel-cobalt-manganese hydroxides. During the sintering process with lithium salts, the element ratios of Ni, Co, and Mn are also kept uniformly distributed. Generally, in order to reduce the dislocation defects caused by the mixing of lithium and nickel, the mass content of nickel can only be appropriately reduced. However, this will inevitably require sacrificing the material's high capacity, high initial efficiency and other properties.

[0006] Therefore, how to improve the specific capacity and high initial efficiency performance of the positive electrode material while improving the structural stability and cycle performance is one of the problems that still needs to be solved. Summary of the Invention

[0007] The purpose of this application is to provide a positive electrode material, a preparation method thereof, and a battery. The positive electrode material of this application can effectively improve the specific capacity and high initial efficiency performance of the positive electrode material while improving the structural stability and cycle performance.

[0008] In the first aspect, the present application provides a positive electrode material, the chemical formula of the positive electrode material is Li n Ni 1-x- y M x Mny O2, wherein 0.9≤n≤1.2, 0≤x<1, 0<y<1, wherein M is selected from Co and / or Al;

[0009] The positive electrode material comprises first particles with a particle size of ≤1.5 μm and second particles with a particle size of ≥2.5 μm, wherein the first particles with a particle size of ≤1.5 μm are characterized by energy dispersive spectroscopy (EDS), and the average molar ratio of Ni to Mn is recorded as R1;

[0010] When the second particles with a particle size of ≥2.5 μm are characterized by energy dispersive spectroscopy (EDS), the average molar ratio of Ni element to Mn element is recorded as R2, where 0<R2-R1.

[0011] In some embodiments, in the positive electrode material, R1>0.5.

[0012] In some embodiments, in the positive electrode material, R2>0.6.

[0013] In some embodiments, in the positive electrode material, 0<R2-R1<0.5.

[0014] In some embodiments, the average particle size of the first particles within the particle size range of ≤1.5 μm is 0.5 μm to 1.5 μm.

[0015] In some embodiments, the average particle size of the second particles within the particle size range of ≥2.5 μm is 2.5 μm to 3.5 μm.

[0016] In some embodiments, the chemical formula of the positive electrode material is Li n Ni 1-x-y M x Mn y M2 z O2, 0≤z<1, M2 metal includes at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Sb, Ta, Ca, B, Y and W.

[0017] In some embodiments, the chemical formula of the cathode material precursor is Ni a M b Mn c O, wherein 0<a<1, 0≤b<1, 0<c<1, and a+b+c=1, and M is selected from Co and / or Al.

[0018] In some embodiments, the cathode material is a single crystal material.

[0019] In some embodiments, in the positive electrode material, the second particles are selected from single crystal particles with a particle size range of 2.5 μm ≤ ≤ 5 μm.

[0020] In some embodiments, the pH of the positive electrode material satisfies: 11.0≤pH≤12.5.

[0021] In some embodiments, the mass content of LiOH in the positive electrode material is 100ppm<m LiOH <1500ppm.

[0022] In some embodiments, the mass content of Li2CO3 in the positive electrode material is 100ppm<m Li2CO3 <5000ppm.

[0023] In some embodiments, the free lithium content in the positive electrode material is 100 ppm < m Li <2000ppm.

[0024] In some embodiments, the specific surface area of the positive electrode material is 5.5 m 2 / g~10m 2 / g;

[0025] In some embodiments, the tap density of the positive electrode material is 1.5 g / cm 3 ~3.0g / cm 3 ;

[0026] In some embodiments, the compacted density of the positive electrode material is 2.5 g / cm 3 ~4.0g / cm 3 .

[0027] In a second aspect, the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0028] A mixture of an oxide precursor of a positive electrode material, a lithium source, and a dopant containing metal M is subjected to a primary sintering treatment, and the primary sintering product is crushed to obtain a positive electrode material, wherein the positive electrode material precursor is measured using XRD rays, and the positive electrode material precursor has diffraction peaks at 35.4°±1° and 43.3°±1°, respectively.

[0029] In some embodiments, the method further comprises annealing the hydroxide precursor of the positive electrode material at 500°C to 900°C for 4h to 12h to obtain an oxide precursor of the positive electrode material, wherein the chemical formula of the oxide precursor of the positive electrode material is Ni a M b Mn c O, wherein 0<a<1, 0≤b<1, 0<c<1, and a+b+c=1, and M is selected from Co and / or Al.

[0030] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate, and lithium oxalate.

[0031] In some embodiments, the added amounts of the lithium source and the cathode material precursor satisfy the following conditions: the ratio of the molar amount of Li to the total molar amount of all metals in the cathode material precursor is (0.87-1.25):1.

[0032] In some embodiments, the mixture further comprises a dopant comprising a metal M2, wherein the M2 metal comprises at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Sb, Ta, Ca, B, Y, and W.

[0033] In some embodiments, the mixture further comprises a dopant containing metal M2, wherein the dopant comprises at least one of Nb2O5, Nb2O3, MoO3, WO2, WO3, V2O5, V2O3, Sr(OH)2, SrO, SrCO3, TiO2, ZrO2, Zr(OH)4, Y2O3, BaO, Cr2O3, ZnO, CuO, Ta2O5, CaO, Sb2O3, Sb2O5, H3BO3, MgO and Mg(OH)2.

[0034] In some embodiments, the mixing conditions for obtaining the mixture are: solid phase mixing at 10° C. to 50° C. for 0.3 h to 3 h.

[0035] In some embodiments, the primary sintering process is performed in an oxygen-containing atmosphere, and the oxygen content in the oxygen-containing atmosphere is ≥95%.

[0036] In some embodiments, the temperature of the primary sintering process is 700°C to 1000°C.

[0037] In some embodiments, the holding time of the primary sintering treatment is 6 hours to 48 hours.

[0038] In some embodiments, when the lithium salt is lithium carbonate and the dopant containing the metal M2 is a compound of Zr or Ti, the temperature of the primary sintering treatment is 800° C. to 900° C. and the holding time is 8 h to 10 h.

[0039] In some embodiments, the method further comprises: mixing the crushed base material with a coating agent containing metal M, and then performing a secondary sintering process to obtain a positive electrode material.

[0040] In some embodiments, the coating agent containing metal M2, M2 is selected from at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Y, B and W.

[0041] In some embodiments, the secondary sintering process is performed in an oxygen-containing atmosphere, and the oxygen content in the oxygen-containing atmosphere is ≥95%.

[0042] In some embodiments, the temperature of the secondary sintering process is 300°C to 800°C.

[0043] In some embodiments, the holding time of the secondary sintering treatment is 6 hours to 24 hours.

[0044] In some embodiments, the coating agent containing the metal M2 includes a Nb compound and / or a W compound.

[0045] In some embodiments, the coating agent containing metal M2 includes a Nb compound and / or a W compound, the temperature of the secondary sintering treatment is 500° C. to 600° C., and the holding time of the secondary sintering treatment is 6 h to 8 h.

[0046] In a third aspect, the present application provides a battery comprising a positive electrode material.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The positive electrode material provided by the present application is such that the molar ratio of Ni to Mn in the positive electrode materials of the two particles is different, and the molar ratio of nickel and manganese in the larger particles is greater than that in the smaller particles, that is, the Ni content in the first particles within the particle size range of ≤1.5μm is relatively low, which can reduce the possibility of lattice defects and oxygen precipitation caused by Ni mixing, thereby reducing side reactions on the particle surface. On the other hand, the specific surface area of the first particles within the particle size range of ≤1.5μm is relatively large, and they have higher activity, which increases the lithium storage sites and improves the specific capacity of the material. The Ni content in the second particles within the particle size range of ≥2.5μm is relatively high, and they have more stable physicochemical properties, better particle strength, and can reduce particle collapse. Therefore, the positive electrode material containing these two types of particles can effectively improve the structural stability of the material, reduce particle collapse, and improve its cycle performance and capacity retention rate.

[0049] The preparation method of the positive electrode material provided in the present application uses a positive electrode material precursor having diffraction peaks at 35.4°±1° and 43.3°±1°, respectively. Among them, the diffraction peak at 43.3°±1° indicates that some particles in the positive electrode material precursor have a rock salt phase, for example, it can be NiO with a rock salt phase; the diffraction peak at 35.4°±1° indicates that some particles in the positive electrode material precursor have a spinel phase, for example, it can be NiMn2O4. During the sintering process with lithium salt, the precursor particles of the rock salt phase easily nucleate and grow to form particles with relatively large particle size. The nickel content of the particles after sintering is high, but its crystal structure is more stable and can withstand a high nickel content without structural collapse. During the sintering process with lithium salt, the precursor particles of the spinel phase have a relatively small particle size after sintering due to the high nucleation energy barrier of the precursor particles. The nickel content is low, which can reduce the possibility of lattice defects and oxygen precipitation caused by Ni mixing, thereby reducing side reactions on the particle surface. Therefore, the positive electrode material made by sintering the above-mentioned precursor can effectively improve the structural stability of the material, reduce particle collapse, and improve its cycle performance and capacity retention rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0051] Figure 1 A schematic flow chart of the method for preparing the positive electrode material provided in an embodiment of the present application.

[0052] Figure 2a This is the XRD pattern of the positive electrode material oxide precursor provided in Example 1 of the present application.

[0053] Figure 2b This is an SEM image of the positive electrode material oxide precursor provided in Example 1 of the present application.

[0054] Figure 2c This is an SEM image of the positive electrode material provided in Example 1 of the present application.

[0055] Figure 2d The cross section and EDS spectrum results of the positive electrode material provided in Example 1 of the present application.

[0056] Figure 3a This is the XRD image of the positive electrode material oxide precursor provided in Example 2 of the present application.

[0057] Figure 3bThis is an SEM image of the positive electrode material oxide precursor provided in Example 2 of the present application.

[0058] Figure 3c This is an SEM image of the positive electrode material provided in Example 2 of the present application.

[0059] Figure 3d This is the cross-section and EDS spectrum results of the positive electrode material provided in Example 2 of the present application.

[0060] Figure 4a This is the XRD image of the positive electrode material oxide precursor provided in Comparative Example 1 of the present application.

[0061] Figure 4b This is an SEM image of the positive electrode material oxide precursor provided in Comparative Example 1 of the present application.

[0062] Figure 4c This is the SEM image of the positive electrode material provided in Comparative Example 1 of this application.

[0063] Figure 4d The cross section and EDS spectrum results of the positive electrode material provided in Comparative Example 1 of this application. DETAILED DESCRIPTION

[0064] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0065] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0066] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features.

[0067] In order to easily understand the present invention, specific terms are appropriately defined in this application. Unless otherwise defined herein, scientific terms and technical terms used in the present invention have the meanings commonly understood by those skilled in the art to which the present invention belongs.

[0068] As used herein, the term "matrix" refers to a lithium composite oxide synthesized by mixing a precursor with a lithium salt through a high-temperature solid-phase reaction, and includes lithium and metal elements.

[0069] As used herein, the term "primary particles" refers to particles that exist individually without forming agglomerates.

[0070] As used herein, the term "secondary particles" refers to particles formed by agglomeration of the above-mentioned primary particles.

[0071] The present application provides a positive electrode material, which is a single crystal positive electrode material. The chemical formula of the positive electrode material is Li n Ni 1-x-y M x Mn y O2, wherein 0.9≤n≤1.2, 0≤x<1, 0<y<1, wherein M is selected from Co and / or Al;

[0072] The positive electrode material comprises first particles with a particle size of ≤1.5 μm and second particles with a particle size of ≥2.5 μm, wherein the first particles with a particle size of ≤1.5 μm are characterized by energy dispersive spectroscopy (EDS), and the average molar ratio of Ni to Mn is recorded as R1;

[0073] When the second particles with a particle size of ≥2.5 μm are characterized by energy dispersive spectroscopy (EDS), the average molar ratio of Ni element to Mn element is recorded as R2, where 0<R2-R1.

[0074] The positive electrode material provided by the present application has different molar ratios of Ni and Mn elements in the positive electrode materials of the two particles. The nickel-manganese molar ratio of the larger particles is greater than the nickel-manganese molar ratio of the smaller particles, that is, the Ni content in the first particles within the particle size range of ≤1.5μm is relatively low, which can reduce the possibility of lattice defects and oxygen precipitation caused by Ni mixing, thereby reducing side reactions on the particle surface. On the other hand, the specific surface area of the first particles within the particle size range of ≤1.5μm is relatively large, and it has higher activity, which increases the lithium storage sites and improves the specific capacity of the material. The Ni content in the second particles within the particle size range of ≥2.5μm is relatively high, but it has more stable physicochemical properties and better particle strength, which can reduce particle collapse. Therefore, the positive electrode material containing these two types of particles can effectively improve the structural stability of the material, reduce particle collapse, and improve its cycle performance and capacity retention rate.

[0075] Specifically, the value range of n can be 0.9, 0.92, 0.94, 0.95, 0.98, 1.0, 1.02, 1.05, 1.08, 1.1, 1.12, 1.14, 1.16, 1.18 or 1.2, etc., and of course it can also be other values within the above range. The value range of x can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 0.92, the value range of y can be 0, 0.06, 0.1, 0.2, 0.28, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 0.92, and the value range of z can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 0.92, etc.

[0076] In some embodiments, in the positive electrode material, R1>0.5, specifically can be 0.52, 0.6, 0.7, 0.8, 0.9, 1.0, 1.3, 1.4, 1.5, 1.6, 1.8, 1.87, 1.9, etc., which is not limited here.

[0077] In some embodiments, in the positive electrode material, R2>0.6, specifically 0.65, 0.7, 0.8, 0.9, 1.0, 1.2, 1.5, 1.8, 1.9, 1.93, 1.94, 1.95, 2.0, 2.01, 2.2, etc., which are not limited here.

[0078] In some embodiments, 0<R2-R1<0.5, specifically 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, etc., are not limited here. Within this R2-R1 value range, the advantages of high Ni content in large particles and low Ni content in small particles are achieved. While ensuring uniform distribution of the main elements overall, a gradient of Ni content between large and small particles is achieved, resulting in a material with higher structural stability, mitigating lattice structure collapse, and thus improving capacity and cycle performance.

[0079] In some embodiments, the average particle size of the first particles within the particle size range of ≤1.5 μm is 0.5 μm to 1.5 μm. Controlling the particle size within the above range can reduce the occurrence of side reactions and improve the structural stability of the particles.

[0080] In some embodiments, the average particle size of the second particles within the particle size range of ≥2.5 μm is 2.5 μm to 3.5 μm. Controlling the particle size within the above range facilitates the diffusion and transport of lithium ions, reduces the internal resistance between particles, and improves the capacity and rate performance of the material.

[0081] It can be understood that the present application uses a mixture of first particles with a particle size of ≤1.5μm and second particles with a particle size of ≥2.5μm to form a positive electrode material. The crystal structure of the larger second particles is more mechanically stable. Even if a small amount of dislocation defects caused by Ni mixing appear inside, the internal stress generated can be alleviated by the overall size, which alleviates the degradation of the crystal structure. Mixing and oxygen evolution are not likely to occur, and more lithium storage activity can be provided to increase the capacity of the positive electrode material. The first particles with a relatively small size have a low content of Ni, which can reduce the possibility of lattice defects and oxygen precipitation caused by Ni mixing from the source. The crystal structure is more stable, reducing the surface side reactions of the positive electrode material, and the specific surface area of the first particles is relatively larger, which can provide high activity to increase lithium storage sites and increase the discharge capacity of the positive electrode material.

[0082] In some embodiments, the chemical formula of the positive electrode material is Li n Ni 1-x-y M x Mn y M2 z O2, 0≤z<1, M2 metal includes at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Sb, Ta, Ca, B, Y and W.

[0083] In some embodiments, the chemical formula of the cathode material precursor is Ni a M b Mn c O, wherein 0<a<1, 0≤b<1, 0<c<1, and a+b+c=1, and M is selected from Co and / or Al.

[0084] In some embodiments, the chemical formula of the cathode material precursor is Ni a Co b Mn c (OH)2, wherein 0<a<1, 0≤b<1, 0≤c<1, and a+b+c=1.

[0085] Specifically, the cathode material precursor was measured using XRD rays, and the cathode material precursor had diffraction peaks at 35.4°±1° and 43.3°±1°, respectively. The presence of a diffraction peak at 35.4°±1° indicates that some particles in the cathode material precursor have a rock salt phase, such as NiO having a rock salt phase; and some particles have a spinel phase, such as NiMn2O4. The precursor particles in the rock salt phase sinter to form particles with a relatively large particle size, while the precursor particles in the spinel phase sinter to form particles with a relatively small particle size.

[0086] In some embodiments, the positive electrode material is a single crystal material. Compared to traditional polycrystalline materials, single crystal materials have a relatively higher electrode compaction density, which is beneficial to the overall energy density of the battery. They can also avoid the generation of microcracks in polycrystalline material agglomerates during cycling, thereby achieving higher high-voltage performance and cycling stability.

[0087] In some embodiments, in the positive electrode material, the second particles are selected from single crystal particles with a particle size range of 2.5 μm ≤ ≤ 5 μm. If the particle size of the single crystal particles is too large, the ion transport path will be extended, the internal resistance of the particles will increase, and the reaction kinetics of the positive electrode material will be slowed down, thereby reducing the capacity and rate performance of the positive electrode material.

[0088] In some embodiments, the pH of the positive electrode material satisfies the following range: 11.0 ≤ pH ≤ 12.5, and specifically can be 11.0, 11.2, 11.3, 11.5, 11.8, 12.0, 12.3, or 12.5, etc., without limitation herein. Controlling the pH of the positive electrode material within the above range is beneficial to improving the processing performance of the positive electrode material.

[0089] In some embodiments, the mass content of LiOH in the positive electrode material is 100ppm<m LiOH <1500ppm, specifically 110ppm, 150ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm or 1500ppm, etc., which are not limited here. The mass content of Li2CO3 in the positive electrode material is 100ppm <m Li2CO3 <5000ppm. Specifically, it can be 110ppm, 200ppm, 300ppm, 400ppm, 500ppm, 800ppm, 1000ppm, 1500ppm, 2000ppm, 3000ppm, 4000ppm, 4500ppm or 5000ppm, etc., which are not limited here. It can be understood that the surface alkaline impurities of the positive electrode material mainly refer to Li2CO3 and LiOH. Controlling the content of LiOH and Li2CO3 on the surface of the positive electrode material within the above range can reduce the corrosion effect of alkaline impurities on the positive electrode material, protect the structural stability of the positive electrode material, and help improve the cycle stability of the positive electrode material.

[0090] In some embodiments, the free lithium content in the positive electrode material is 100 ppm < m Li<2000ppm. Specifically, it can be 110ppm, 200ppm, 300ppm, 400ppm, 500ppm, 800ppm, 1000ppm, 1500ppm or 2000ppm, etc., which is not limited here.

[0091] In some embodiments, the specific surface area of the positive electrode material is 5.5 m 2 / g~10m 2 / g; specifically, it can be 5.5m 2 / g、6m 2 / g, 6.5m 2 / g, 6.8m 2 / g、7m 2 / g, 7.2m 2 / g, 7.5m 2 / g, 7.8m 2 / g、7.9m 2 / g, 8.2m 2 / g、8.5m 2 / g, 9.2m 2 / g, 9.5m 2 / g, 9.8m 2 / g or 10m 2 By controlling the specific surface area of the positive electrode material within the above range, the positive electrode material can exhibit higher capacity, initial coulombic efficiency, cycle stability, and lower gas production.

[0092] In some embodiments, the tap density of the positive electrode material is 1.5 g / cm 3 ~3.0g / cm 3 , specifically 1.5 g / cm 3 , 1.6g / cm 3 , 1.7g / cm 3 , 1.8g / cm 3 , 1.9g / cm 3 , 2.0g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3 , 2.4g / cm 3 , 2.5g / cm 3 , 2.8g / cm 3 or 3.0g / cm 3 Of course, it can also be other values within the above range, which is not limited here. Controlling the tap density of the positive electrode material within the above range is beneficial to improving the processing performance of the material and increasing the energy density of the battery.

[0093] In some embodiments, the compacted density of the positive electrode material is 2.5 g / cm 3 ~4.0g / cm 3 , specifically 2.5 g / cm 3 , 2.6g / cm 3 , 2.7g / cm 3 , 2.8g / cm 3 , 2.9g / cm 3 , 3.0g / cm 3 , 3.1g / cm 3 、3.2g / cm 3 、3.4g / cm 3 , 3.5g / cm 3 、3.8g / cm 3 or 4.0g / cm 3 Of course, it can also be other values within the above range, which is not limited here. Controlling the compaction density of the positive electrode material within the above range is beneficial to improving the energy density of the battery.

[0094] In a second aspect, the present application provides a method for preparing a positive electrode material, such as Figure 1 As shown, the preparation method of the positive electrode material precursor includes the following steps:

[0095] S10, performing a primary sintering treatment on a mixture of an oxide precursor of a positive electrode material and a lithium source, and crushing the primary sintering product to obtain a positive electrode material, wherein the positive electrode material precursor is measured using XRD rays, and the oxide precursor of the positive electrode material has diffraction peaks at 35.4°±1° and 43.3°±1°, respectively.

[0096] The preparation method of the positive electrode material provided in the present application uses a positive electrode material precursor having diffraction peaks at 35.4°±1° and 43.3°±1°, respectively. Among them, the diffraction peak at 43.3°±1° indicates that some particles in the positive electrode material precursor have a rock salt phase, for example, it can be NiO with a rock salt phase; the diffraction peak at 35.4°±1° indicates that some particles in the positive electrode material precursor have a spinel phase, for example, it can be NiMn2O4. During the sintering process with lithium salt, the precursor particles of the rock salt phase easily nucleate and grow to form particles with relatively large particle size. The nickel content of the particles after sintering is high, but its crystal structure is more stable and can withstand a high nickel content without structural collapse. During the sintering process with lithium salt, the precursor particles of the spinel phase have a relatively small particle size after sintering due to the high nucleation energy barrier of the precursor particles. The nickel content is low, which can reduce the possibility of lattice defects and oxygen precipitation caused by Ni mixing, thereby reducing side reactions on the particle surface. Therefore, the positive electrode material made by sintering the above-mentioned precursor can effectively improve the structural stability of the material, reduce particle collapse, and improve its cycle performance and capacity retention rate.

[0097] The preparation method of the present application is described in detail below with reference to the examples:

[0098] S10, performing a primary sintering treatment on a mixture of an oxide precursor of a positive electrode material and a lithium source, and crushing the primary sintering product to obtain a positive electrode material, wherein the positive electrode material precursor is measured using XRD rays, and the oxide precursor of the positive electrode material has diffraction peaks at 35.4°±1° and 43.3°±1°, respectively.

[0099] In some embodiments, the oxide precursor of the positive electrode material includes NiO and NiMn2O4.

[0100] In some embodiments, the method further comprises annealing the hydroxide precursor of the positive electrode material at 500°C to 900°C for 4h to 12h to dehydrate the hydroxide to form an oxide, thereby obtaining the oxide precursor of the positive electrode material, wherein the general chemical formula of the oxide precursor is Ni a M b Mn c O, wherein 0<a<1, 0≤b<1, 0<c<1, and a+b+c=1, and M is selected from Co and / or Al.

[0101] In some embodiments, the annealing temperature is 500°C to 900°C, specifically 500°C, 550°C, 580°C, 600°C, 630°C, 650°C, 680°C, 700°C, 750°C, 780°C, 800°C, 850°C or 900°C, and the annealing time can be 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h or 12h, etc., and of course it can also be other values within the above range, which is not limited here.

[0102] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate, and lithium oxalate. Preferably, the lithium salt is lithium carbonate.

[0103] In some embodiments, the amount of the lithium source and the cathode material precursor added satisfies: the ratio of the molar amount of Li to the total molar amount of all metals in the cathode material precursor is (0.87-1.25):1, specifically 0.87:1, 0.89:1, 0.92:1, 0.95:1, 0.98:1, 1.02:1, 1.05:1, 1.1:1, 1.17:1 or 1.25:1, etc., and of course other values within the above range can also be used, which are not limited here. Within this range, the degree of Li / Ni cation mixing can be reduced, and the excessive residual lithium on the surface of the sintered product can be prevented from affecting the processing performance and safety performance.

[0104] In some embodiments, the mixture further includes a dopant containing metal M2, and the M2 metal includes at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Y, and W. Specifically, the mixture may contain a salt or oxide of metal M2.

[0105] In some embodiments, the dopant includes at least one of Nb2O5, Nb2O3, MoO3, WO2, WO3, V2O5, V2O3, Sr(OH)2, SrO, TiO2, ZrO2, Zr(OH)4, Y2O3, BaO, Cr2O3, ZnO, CuO, MgO, and Mg(OH)2. Preferably, the metal M2-containing dopant is a compound of Zr or Ti.

[0106] In some embodiments, the mixing conditions for obtaining the mixture are: solid phase mixing at 10° C. to 50° C. for 0.3 h to 3 h.

[0107] In some embodiments, the temperature of the solid-phase mixing can be 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, or 50°C, and the solid-phase mixing time can be 0.3 h, 0.4 h, 0.5 h, 0.6 h, 0.8 h, 1 h, 1.5 h, 1.8 h, 2.5 h, or 3 h, etc., and of course other values within the above ranges can also be used, and are not limited here. Preferably, the temperature of the solid-phase mixing is 10°C to 35°C.

[0108] In some embodiments, the added amounts of the dopant and the positive electrode material precursor satisfy: the ratio of the molar amount of M to the total molar amount of metal in the positive electrode material precursor is (0.01 to 0.04):1, specifically 0.01:1, 0.02:1, 0.03:1, 0.04:1, etc., and of course it can also be other values within the above range, which is not limited here.

[0109] In some embodiments, the solid phase mixing method can be dry grinding, ball milling, etc., which is not limited here, as long as the components are mixed evenly.

[0110] In some embodiments, the mixing device may be at least one of a ball mill, a three-dimensional mixer, a high-speed mixer, and a VC mixer.

[0111] In some embodiments, the primary sintering process is performed in an oxygen-containing atmosphere, and the oxygen content in the oxygen-containing atmosphere is ≥95%.

[0112] In some embodiments, the primary sintering temperature is 700°C to 1000°C, specifically 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 780°C, 800°C, 850°C, 900°C, or 1000°C, but is not limited to the values listed above. Other values not listed within this range are also applicable. Within this range, sufficient air can promote the oxidation of divalent nickel to trivalent nickel and reduce Li / Ni cation mixing.

[0113] In some embodiments, the holding time of the primary sintering treatment is 6h to 48h, specifically 6h, 8h, 10h, 12h, 15h, 18h, 24h, 36h or 48h, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0114] In some embodiments, when the dopant containing the metal M2 is a compound of Zr or Ti, the temperature of the primary sintering treatment is 800° C. to 900° C., and the holding time is 8 h to 10 h.

[0115] In some embodiments, the method further comprises: mixing the crushed base material with a coating agent containing metal M, and then performing a secondary sintering process to obtain a positive electrode material.

[0116] In some embodiments, the median particle size of the crushed matrix material is 2.5 μm to 4.5 μm.

[0117] In some embodiments, the particle size distribution width of the crushed matrix material satisfies: 1.1≤(D 90 -D 10 ) / D 50 ≤1.7, specifically 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, etc., are not limited here. The matrix material has a wide particle size distribution, which is beneficial to improving the stacking density of the positive electrode material and thus increasing the specific capacity of the positive electrode material.

[0118] In some embodiments, the crushing method includes at least one of a double roller, a plowshare mixer / crusher, and a jet mill.

[0119] In some embodiments, the coating agent containing metal M2, M2 is selected from at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Y, and W. The coating agent containing metal M2 can be a salt or oxide of metal M2. Preferably, the coating agent containing metal M2 includes a Nb compound and / or a W compound.

[0120] In some embodiments, the secondary sintering process is performed in an oxygen-containing atmosphere, and the oxygen content in the oxygen-containing atmosphere is ≥95%.

[0121] In some embodiments, the temperature of the secondary sintering treatment is 300°C to 800°C, specifically 300°C, 320°C, 330°C, 350°C, 380°C, 400°C, 450°C, 500°C, 550°C, 650°C, 700°C or 800°C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0122] In some embodiments, the holding time of the secondary sintering treatment is 6h to 24h, specifically 6h, 8h, 10h, 12h, 15h, 18h or 24h, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0123] In some embodiments, when the coating agent containing metal M2 includes a Nb compound and / or a W compound, the temperature of the secondary sintering treatment is 500° C. to 600° C., and the holding time of the secondary sintering treatment is 6 h to 8 h.

[0124] In some embodiments, the preparation method further comprises cooling, shaping, and screening the product after secondary sintering. The shaping comprises at least one of pulverizing, grinding, ball milling, or gas crushing.

[0125] In some embodiments, the sieving uses a sieve with a mesh size of 300 to 400 mesh.

[0126] In a third aspect, the present application provides a battery, which comprises the above-mentioned positive electrode material or the positive electrode material prepared by the above-mentioned preparation method.

[0127] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

[0128] The following further describes the embodiments of the present invention in multiple embodiments. The embodiments of the present invention are not limited to the following specific embodiments. Within the scope of the unchanged main rights, appropriate changes can be made to the implementation.

[0129] Test method:

[0130] (1) ICP characterization of cathode materials

[0131] Equipment: Agilent 5110 ICP-OES plasma inductively coupled plasma analyzer.

[0132] Method: Take 0.3g sample and add aqua regia to digest it. After cooling and constant volume, take 1mL of digestion solution and dilute it 100 times to test the main elements Li / Ni / M / Mn and impurity elements.

[0133] (2) XRD characterization of cathode material precursor

[0134] Equipment: XPert Powder (PANalytical) or Bruker X-ray diffraction tester products.

[0135] Method: Place the powder sample into a sample well and flatten the top surface with a glass slide, ensuring it is parallel to the edge of the well. Scan the sample over a range of 2θ = 10-90°C for at least 5 minutes. After scanning, open the sample in Jade software and use the "Analyze" → "Find Peaks" function to automatically identify the diffraction peak positions and heights.

[0136] (3) Alkaline impurity test of positive electrode material: 5.0 g of positive electrode material powder was immersed in 100 mL of deionized water and stirred in a sealed glass flask for 10 minutes. After sufficient stirring, the suspension was filtered to obtain a clear solution. Then, 90 mL of the clear solution was titrated by recording the pH curve while adding 0.1 mol / L HCl solution at a rate of 0.5 mL / min under stirring until the pH reached 3. The reference voltage curve was obtained by titrating the low concentrations of LiOH and Li2CO3 dissolved in deionized water. The first platform with an end point y1 (in mL) between pH 8 and 9 is the determined OH - / H2O mass content, the second platform with end point y2 (in mL) between pH 4 and 6 is determined by HCO3 - / H2CO3 mass content. The inflection point y1 between the first and second plateaus and the inflection point y2 after the second plateau are obtained from the corresponding minimum values of the derivative dpH / dVol of the pH curve. The results are then expressed as the weight percentages of LiOH and Li2CO3 as shown in the following equations (3) and (4):

[0137]

[0138]

[0139] Free Liwt%=LiOHwt%*6.94 / 23.95+Li2CO3wt%*6.94*2 / 73.89(5).

[0140] (4) pH characterization of cathode materials:

[0141] Take approximately 5g of the positive electrode material sample, add 45mL of water, and sonicate for 5 minutes. Then remove and let it sit for 10 minutes. After the pH meter is calibrated, insert the composite electrode into the supernatant to be measured. Calculate the pH value of the solution based on the potential difference between the measuring electrode and the reference electrode.

[0142] (5) Testing method for particle size of positive electrode materials:

[0143] The particle size distribution range of the positive electrode material was measured by Malvern laser particle size analyzer to obtain D 90 、D 50 and D 10 .

[0144] (6) Testing method for specific surface area of positive electrode material:

[0145] Equipment: Micromeritics Tristar 3020 surface area and pore size analyzer was used to test the surface area of the cathode material.

[0146] Method: Weigh the empty sample tube (m1). Add 3 g of sample to the tube via a long-necked funnel. Degas under vacuum at 300°C for 1 hour. After cooling, weigh the tube (m2). The sample mass is calculated as m2 - m1. The tube is placed in liquid nitrogen, and the nitrogen adsorption capacity (V) of the sample is measured at a range of relative pressures (P / P0) of 0.05, 0.1, 0.15, 0.20, 0.25, and 0.30. The isotherm is fitted, and the monolayer saturation adsorption capacity (Vm) is calculated based on the slope and intercept. The specific surface area is then calculated based on Vm.

[0147] (7) Kanta tap density test of positive electrode material:

[0148] Equipment: American Quantacon tap density tester (model: DAT-4-220)

[0149] Method: Clean the graduated cylinder and weigh it as m1. Add approximately 50g of sample to the cylinder, keeping the sample surface as horizontal as possible and wiping the surrounding area with a paper towel. Weigh the total mass of the sample and cylinder as m2. Place the cylinder on a vibrating table and secure it with three symmetrical legs. Turn on the instrument and set the vibration frequency to 5000. Turn on the vibration switch, and the instrument will automatically stop after the specified number of vibrations. Remove the graduated cylinder and read the volume of the sample. If the sample surface is horizontal after tapping, read the volume directly. If it is diagonal, take the average of the readings at the highest and lowest points (V). Tap density = (m2 - m1) / V.

[0150] (8) Compaction density test of positive electrode material:

[0151] The compaction density of the positive electrode material is tested using the American carver 4350. The steps are as follows: weigh 1g of sample and put it into a mold and press it with a pressure of 3T for 30s. After pressing, the height is measured to calculate the compaction.

[0152] (9) Average particle size test of positive electrode material:

[0153] A cross-sectional SEM test was performed on the positive electrode material. An image with a magnification of 3000 times was selected, and the particle size of all primary particles was measured using Nano Measure software. The longest inner diameter of the particles was selected during measurement. After all particles in the image were measured, the particle sizes of all first particles with a particle size less than 1.5 μm were counted and averaged to obtain the average particle size of the first particles; the particle sizes of all second particles with a particle size greater than 2.5 μm were counted and averaged to obtain the average particle size of the second particles.

[0154] (10) SEM and EDS characterization of cathode materials:

[0155] Equipment: Hitachi S4800 scanning electron microscope, OXFORD Instrument's energy dispersive spectrometer.

[0156] SEM method: For powder sample testing, use tweezers or other tools to pick up the powder sample, spread it flat on a conductive adhesive, and flatten it. Testing is performed under 5kV / 10mA electron beam conditions. For cross-section testing, the material is coated on aluminum foil using conventional electrode preparation techniques, then cut using a focused ion beam (FIB). The SEM is then tested under the same conditions as for powder samples.

[0157] EDS method: Adjust the electron beam voltage of the SEM to above 15kV, then use EDS to perform a selected area test, with the selected area being the center of each single crystal particle. To calculate the average Ni / Mn element ratio, select 10 particles with the longest diameter less than 1.5μm and 10 particles with the longest diameter greater than 2.5μm, and perform EDS tests on each of the 10 obtained Ni / Mn ratio values. Remove the maximum and minimum values, and then average the remaining 8 values.

[0158] (11) Electrochemical performance test:

[0159] The positive electrode materials obtained in the examples and comparative examples were assembled into button batteries: the positive electrode material, conductive carbon and polyvinylidene fluoride (PVDF) were added to N-methyl-2-pyrrolidone (NMP) at a mass ratio of 96:2:2, and the mixture was uniformly mixed to form a positive electrode slurry, which was then coated on the positive electrode current collector and vacuum dried to form a positive electrode sheet (the compacted density of the sheet was 2.8 g / cm 3 ), with lithium sheet as negative electrode, assembled into 2016 button batteries in a glove box.

[0160] The battery was tested in the 3.0V-4.3V discharge range and with a theoretical capacity of 250mAh / g at 1C using the CT2001A battery testing system from Wuhan Blue Electric Electronics Co., Ltd. The test results are detailed in Table 1.

[0161] Example 1

[0162] (1) The oxide precursor of the positive electrode material prepared by thermal decomposition is selected, and its chemical formula can be expressed as Ni 0.6 Co 0.1 Mn 0.3 O x (The deviation of the content of each main element is within ±1%), as shown in Table 1. The cathode material precursor was characterized by XRD, as shown in Figure 2a As shown in , it has a diffraction peak at 35.9° and 43.4° respectively; Figure 2b As shown, the morphology of the cathode material precursor is secondary particles assembled from nanoparticles.

[0163] (2) The cathode material precursor was mixed with Li2CO3 at a Li / Me (Me is the sum of Ni, Co, and Mn) molar ratio of 1.02:1, and TiO2 with a mass content of 2000 ppm relative to the cathode material precursor was added, and sintered at 900°C for 10 h in an oxygen atmosphere.

[0164] (3) The primary sintered product was crushed by a plowshare crusher for 30 seconds to obtain a matrix material.

[0165] (4) The matrix material was mixed with 1000 ppm of Nb2O5, and secondary sintered at 500°C for 6 h in an oxygen atmosphere. The secondary sintered product was sieved through a 325-mesh sieve to obtain the positive electrode material.

[0166] The positive electrode material prepared in the embodiment of the present application is as follows: Figure 2c As shown, its morphology is single particles with round particles and few cross sections caused by crushing on the surface.

[0167] The SEM and EDS characterization results of the cross section showed that Figure 2d As shown, the Ni / Mn ratios of the first particles with a particle size of ≤1.5μm at 10 locations are 1.85, 1.87, 1.90, 1.79, 1.85, 1.91, 1.90, 1.89, 1.91, and 1.79, respectively. The average value R1 after removing the highest and lowest values is 1.87; the Ni / Mn ratios of the second particles with a particle size of ≥2.5μm at 10 locations are 1.83, 1.87, 1.86, 1.88, 1.96, 1.91, 1.92, 1.89, 1.87, and 1.94, respectively. The average value R2 after removing the highest and lowest values is 1.89; the other test results are shown in Table 2.

[0168] Example 2

[0169] (1) The oxide precursor of the positive electrode material prepared by thermal decomposition is selected, and its chemical formula is Ni 0.9 Co 0.05 Mn 0.05 O x (The deviation of the content of each main element is within ±1%), as shown in Table 1. The cathode material precursor was characterized by XRD, as shown in Figure 3a As shown, it has a diffraction peak at 35.9° and 43.3° respectively; Figure 3b As shown, the morphology of the cathode material precursor is secondary particles assembled from nanoparticles.

[0170] (2) The cathode material precursor was mixed with Li2CO3 at a Li / Me (Me is the sum of Ni, Co, and Mn) molar ratio of 1.01:1, and TiO2 with a mass content of 2000 ppm relative to the cathode material precursor was added, and sintered at 800°C for 8 hours in an oxygen atmosphere.

[0171] (3) The primary sintered product was crushed by a plowshare crusher for 30 seconds to obtain a matrix material.

[0172] (4) The matrix material was mixed with 2000 ppm of WO3 and secondary sintered at 550°C for 8 h in an oxygen atmosphere. The secondary sintered product was sieved through a 325-mesh sieve to obtain the positive electrode material.

[0173] The positive electrode material prepared in the embodiment of the present application is as follows: Figure 2c As shown, its morphology is single particles with round particles and few cross sections caused by crushing on the surface.

[0174] The SEM and EDS characterization results of the cross section showed that Figure 3d As shown in Figure 2, the Ni / Mn ratios at 10 locations for the first particles with a particle size of ≤1.5 μm were 19.05, 19.59, 18.42, 19.02, 23.66, 21.32, 20.37, 20.51, 19.64, and 17.60, respectively. The average value (R1) after removing the highest and lowest values was 19.74. The Ni / Mn ratios at 10 locations for the second particles with a particle size of ≥2.5 μm were 19.55, 19.04, 15.59, 22.68, 19.15, 19.17, 18.17, 20.65, 21.54, and 21.13, respectively. The average value (R2) after removing the highest and lowest values was 19.80. The remaining test results are shown in Table 2.

[0175] Example 3

[0176] The difference from Example 1 is that:

[0177] (1) The oxide precursor of the positive electrode material prepared by thermal decomposition is selected, and its chemical formula is Ni 0.67 Co 0.05 Mn 0.28 O x (The deviation of the content of each main element is within ±1%). As shown in Table 1, the positive electrode material precursor also contains 85 ppm of Ca.

[0178] Example 4

[0179] The difference from Example 1 is that:

[0180] (4) The matrix material was mixed with 1000 ppm of ZrO2 and secondary sintered at 850°C for 8 h in an oxygen atmosphere. The secondary sintered product was sieved through a 325-mesh sieve to obtain a positive electrode material.

[0181] Example 5

[0182] The difference from Example 2 is that:

[0183] (4) The matrix material was mixed with 1000 ppm of WO3 and secondary sintered at 880°C for 8 h in an oxygen atmosphere. The secondary sintered product was sieved through a 325-mesh sieve to obtain the positive electrode material.

[0184] Example 6

[0185] The difference from Example 3 is that:

[0186] (4) The base material was mixed with 1000 ppm of MgO, and secondary sintered at 960°C for 8 h in an oxygen atmosphere. The secondary sintered product was sieved through a 325-mesh sieve to obtain a positive electrode material.

[0187] Example 7

[0188] The difference from Example 1 is that:

[0189] (4) The matrix material was mixed with 1000 ppm of WO3 and secondary sintered at 920°C for 12 h in an oxygen atmosphere. The secondary sintered product was sieved through a 325-mesh sieve to obtain the positive electrode material.

[0190] Example 8

[0191] The difference from Example 1 is that:

[0192] Step (4) is not performed.

[0193] Example 9

[0194] The difference from Example 2 is that:

[0195] The oxide precursor of the positive electrode material obtained by the pyrolysis method selected in step (1) can be represented by the chemical formula Ni 0.92 Al 0.02 Mn 0.06 O x (The content deviation of each main element is within ±1%).

[0196] Example 10

[0197] The difference from Example 1 is that:

[0198] In step (1), Ni is obtained by coprecipitation. 0.6 Co 0.1 Mn0.3 The (OH)2 hydroxide precursor is annealed at 730℃ for 8h to obtain the oxide precursor of the positive electrode material. The general chemical formula can be expressed as Ni 0.6 Co 0.1 Mn 0.3 O x , (the deviation of the content of each main element is within ±1%), as shown in Table 1.

[0199] Comparative Example 1

[0200] The difference from Example 1 is that:

[0201] (1) The oxide precursor of the cathode material prepared by conventional co-precipitation is selected, and its general chemical formula can be expressed as Ni 0.6 Co 0.1 Mn 0.3 O x (The deviation of the content of each main element is within ±1%), as shown in Table 1. The cathode material precursor was characterized by XRD, as shown in Figure 4a As shown in , it has a diffraction peak at 19.3°, but no diffraction peaks at 35.4° and 43.3°; Figure 4b As shown, the morphology of the cathode material precursor is secondary microspheres assembled from nanosheets.

[0202] like Figure 4c As shown in the figure, the morphology of the cathode material is a single crystal particle with relatively clear edges and corners, and the cross section caused by surface crushing can be observed. The SEM and EDS characterization results of the particle cross section of the cathode material show that Figure 4d As shown, the Ni / Mn ratios of the first particles with a particle size of ≤1.5μm at 10 locations are 1.86, 1.89, 1.90, 1.89, 1.86, 1.92, 1.81, 1.88, 1.92, and 1.93, respectively. The average value R1 excluding the highest and lowest values is 1.89; the Ni / Mn ratios of the second particles with a particle size of ≥2.5μm at 10 locations are 1.80, 1.79, 1.86, 1.86, 1.97, 1.88, 1.85, 1.75, 1.87, and 1.97, respectively. The average value R2 excluding the highest and lowest values is 1.86.

[0203] Comparative Example 2

[0204] The difference from Example 2 is that:

[0205] (1) The oxide precursor of the cathode material prepared by conventional co-precipitation is selected, and its general chemical formula can be expressed as Ni 0.9 Co 0.05 Mn 0.05 O x(The deviation of the content of each main element is within ±1%), as shown in Table 1. The cathode material precursor was characterized by XRD, which showed a diffraction peak at 19.3°, but no diffraction peaks at 35.4° and 43.3°.

[0206] Comparative Example 3

[0207] The difference from Example 3 is that:

[0208] (1) The oxide precursor of the cathode material prepared by conventional coprecipitation was selected for ICP characterization. Its chemical formula can be expressed as Ni 0.67 Co 0.05 Mn 0.28 O x (The deviation of the content of each main element is within ±1%), as shown in Table 1. The cathode material precursor was characterized by XRD, which showed a strong diffraction peak at 19.4°, but no diffraction peaks at 35.4° and 43.3°.

[0209] Table 1 Comparison of positive electrode material precursors of the embodiment and the comparative example

[0210]

[0211] Preparation of positive electrode materials

[0212] The cathode material precursors prepared in the examples and comparative examples were mixed with LiOH at a molar ratio of 1:1.02, and then doped with 1600 ppm of Al(OH)3, 800 ppm of TiO2, and 600 ppm of Sr(OH)2. The mixture was sintered at 730°C for 25 hours in a 95% oxygen atmosphere, cooled, crushed, and sieved to obtain a cathode material.

[0213] The cells were assembled into button-type batteries and subjected to electrochemical tests. The test results are shown in Table 2 below.

[0214] Table 2 Comparison of positive electrode materials of the embodiment and the comparative example

[0215]

[0216] The positive electrode materials provided in Examples 1-7 have different molar ratios of Ni and Mn in the two types of positive electrode materials. The larger particles have a greater nickel-manganese molar ratio than the smaller particles, i.e., the first particles within a particle size range of <1.5 μm have a relatively low Ni content, which can reduce the possibility of lattice defects and oxygen precipitation caused by Ni mixing, thereby reducing side reactions on the particle surface. On the other hand, the first particles within a particle size range of <1.5 μm have a relatively large specific surface area, which has higher activity, increases lithium storage sites, and improves the specific capacity of the material. The positive electrode material can effectively improve the specific capacity and high initial efficiency performance of the positive electrode material while improving structural stability and cycle performance.

[0217] According to the precursor parameter data of the positive electrode materials of Example 1 and Comparative Example 1, since Comparative Example 1 uses a conventional hydroxide precursor, it does not have two physical phases with different Ni contents, namely, spinel phase and rock salt phase. Therefore, after sintering, the distribution of its Ni element does not have a gradient advantage of large particles being higher and small particles being lower, so the R2-R1 value of the positive electrode material precursor is less than 0. By comparing the electrochemical properties of the positive electrode materials prepared from the positive electrode material precursors, the discharge capacity and the first coulombic efficiency of Example 1 are both higher, and the cycle stability at room temperature and high temperature has obvious advantages. This result shows that the structure of the single crystal material without Ni gradient distribution is more likely to collapse, and the Ni mixing leads to lattice defects and increased oxygen precipitation, and the structural stability and cycle performance of the positive electrode material are slightly reduced.

[0218] Similarly, Comparative Example 2 relative to Example 2 and Comparative Example 3 relative to Example 3 are comparisons based on ternary materials with different Ni / Co / Mn contents, which can also illustrate that the higher Ni content in large particles and the lower Ni content in small particles have electrochemical performance advantages under different ternary systems.

[0219] In addition, based on the above embodiments, a more preferred implementation scheme can be found by comparing different material parameters caused by different preparation conditions.

[0220] According to the test data of Example 1, Example 4, Example 7, and Example 8, the above examples are all based on the ternary positive electrode material system of Ni: Co: Mn = 6: 1: 3, but the doping auxiliary materials in the sintering process are different, which leads to differences in the distribution of the Ni element, thereby affecting parameters such as particle size, surface residual lithium, tap density, and compaction density. By comparing the electrochemical properties of the positive electrode materials, it can be found that the capacity, rate and cycle performance of Example 1 are the best, indicating that the effect of doping with Nb element on the electrochemical properties of the positive electrode material is better than that of doping with Zr element and W element. Among them, the doping of W element will cause a slight increase in the residual lithium on the surface. Although it is also in line with the content protected by this patent, it is not the most preferred option. The capacity and first efficiency of Example 8, which is not doped, are both low. Therefore, selecting suitable elements for doping during the preparation of the positive electrode material is beneficial to improving the electrochemical properties of the positive electrode material.

[0221] According to the test data of Example 2 and Example 5, both are prepared based on the ternary positive electrode material with a high nickel content of Ni:Co:Mn=90:5:5. The difference lies in the different W content of doping. As the W content increases, the R2-R1 value of the obtained positive electrode material precursor increases significantly. By comparing the electrochemical properties of the positive electrode material prepared from this positive electrode material precursor, the discharge capacity and cycle stability of Example 5 are lower than those of Example 2, indicating that the high R2-R1 value of the positive electrode material precursor will also lead to poor structural stability of the positive electrode material.

[0222] According to the test data of Example 3 and Example 6, both are prepared based on a ternary positive electrode material with an element ratio of Ni:Co:Mn=67:5:28. The R2-R1 value of Example 3 doped with Nb is lower than that of Example 6 doped with Mg, and the discharge specific capacity and high-temperature cycle performance of Example 6 are better, indicating that within a certain range, an increase in the R2-R1 value is beneficial to improving the structural stability of the positive electrode material. However, if the R2-R1 value is too high, the distribution of metal elements in the positive electrode material is unbalanced, which may also cause the structural stability of the positive electrode material to deteriorate.

[0223] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A positive electrode material, characterized in that The chemical general formula of the positive electrode material is Li n Ni 1-x-y M x Mn y O2, where 0.9 ≤ n ≤ 1.2, 0 ≤ x < 1, 0 < y < 1, and M is selected from Co and / or Al; The positive electrode material is a single crystal material, comprising first particles with a particle size of ≤1.5 μm and second particles with a particle size of 2.5 μm to 5 μm, wherein the first particles are characterized by energy dispersive spectroscopy (EDS), and the average molar ratio of Ni to Mn is denoted as R1, and R1 is greater than 0.5; When the second particles are characterized by energy dispersive spectroscopy (EDS), the average molar ratio of Ni to Mn is recorded as R2, R2>0.6, and 0<R2-R1<0.

5.

2. The positive electrode material according to claim 1, characterized in that It meets at least one of the following technical features: (1) the average particle size of the first particles within the particle size range of ≤1.5 μm is in the range of 0.5 μm to 1.5 μm; (2) the average particle size of the second particles within the particle size range of 2.5 μm or more is in the range of 2.5 μm to 3.5 μm; (3) The chemical formula of the positive electrode material is Li n Ni 1-x-y M x Mn y M2 z O2, 0≤z<1, M2 metal includes at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Sb, Ta, Ca, B, Y and W; (4) The chemical formula of the positive electrode material precursor is Ni a M b Mn c O, wherein 0<a<1, 0≤b<1, 0<c<1, and a+b+c=1, and M is selected from Co and / or Al.

3. The positive electrode material according to claim 1 or 2, characterized in that It meets at least one of the following technical features: (1) The pH of the positive electrode material satisfies: 11.0≤pH≤12.5; (2) The mass content of LiOH in the positive electrode material is 100ppm<m LiOH <1500ppm; (3) The mass content of Li2CO3 in the positive electrode material is 100ppm<m Li2CO3 <5000ppm; (4) The free lithium content in the positive electrode material is 100 ppm < m Li <2000ppm; (5) The specific surface area of the positive electrode material is 5.5 m 2 / g~10m 2 / g; (6) The tap density of the positive electrode material is 1.5 g / cm 3 ~3.0g / cm 3 ; (7) The compaction density of the positive electrode material is 2.5 g / cm 3 ~4.0g / cm 3 .

4. A method for preparing the positive electrode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: A mixture of an oxide precursor of a positive electrode material and a lithium source is subjected to a primary sintering treatment, and the primary sintered product is crushed to obtain a positive electrode material, wherein the oxide precursor of the positive electrode material is measured by XRD ray, and the oxide precursor of the positive electrode material has diffraction peaks at 35.4°±1° and 43.3°±1° respectively; wherein the chemical formula of the oxide precursor of the positive electrode material is Ni a M b Mn c O, wherein 0<a<1, 0≤b<1, 0<c<1, and a+b+c=1, and M is selected from Co and / or Al.

5. The preparation method according to claim 4, characterized in that The method further comprises annealing the hydroxide precursor of the positive electrode material at 500° C. to 900° C. for 4 hours to 12 hours to obtain the oxide precursor of the positive electrode material.

6. The preparation method according to claim 4, characterized in that It meets at least one of the following technical features: (1) The lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate and lithium oxalate; (2) The amount of the lithium source and the positive electrode material precursor added satisfies the following conditions: the ratio of the molar amount of Li to the total molar amount of all metals in the positive electrode material precursor is (0.87-1.25):1; (3) The mixture further comprises a dopant containing a metal M2, wherein the M2 metal comprises at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Sb, Ta, Ca, B, Y, and W; (4) the mixture further comprises a dopant containing a metal M2, wherein the dopant comprises at least one of Nb2O5, Nb2O3, MoO3, WO2, WO3, V2O5, V2O3, Sr(OH)2, SrO, SrCO3, TiO2, ZrO2, Zr(OH)4, Y2O3, BaO, Cr2O3, ZnO, CuO, Ta2O5, CaO, Sb2O3, Sb2O5, H3BO3, MgO and Mg(OH)2; (5) The mixing conditions for obtaining the mixture are: solid phase mixing at 10°C to 50°C for 0.3h to 3h; (6) The primary sintering treatment is carried out in an oxygen-containing atmosphere, wherein the oxygen content in the oxygen-containing atmosphere is ≥95%; (7) The temperature of the primary sintering treatment is 700° C. to 1000° C.; (8) The holding time of the primary sintering treatment is 6 hours to 48 hours; (9) When the lithium source is lithium carbonate and the metal M2-containing dopant is a Zr or Ti compound, the temperature of the primary sintering treatment is 800° C. to 900° C. and the holding time is 8 h to 10 h.

7. The preparation method according to claim 4, characterized in that The method further comprises: The crushed base material is mixed with a coating agent containing metal M2 and then subjected to a secondary sintering treatment to obtain a positive electrode material.

8. The preparation method according to claim 7, characterized in that The preparation method meets at least one of the following technical characteristics: (1) The coating agent containing metal M2, M2 is selected from at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Y, B and W; (2) The secondary sintering treatment is carried out in an oxygen-containing atmosphere, wherein the oxygen content in the oxygen-containing atmosphere is ≥95%; (3) The temperature of the secondary sintering treatment is 300° C. to 800° C.; (4) The holding time of the secondary sintering treatment is 6 hours to 24 hours; (5) The coating agent containing metal M2 includes a Nb compound and / or a W compound; (6) The coating agent containing metal M2 includes a Nb compound and / or a W compound, the temperature of the secondary sintering treatment is 500°C to 600°C, and the holding time of the secondary sintering treatment is 6h to 8h.

9. A battery, characterized in that: The battery comprises the positive electrode material according to any one of claims 1 to 3.

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