Positive electrode material and its manufacturing method, battery

Abstract

The present application provides a positive electrode material, a method for producing the same, and a battery. The positive electrode material has the general formula: Li n Ni 1-x-y M x Mn y O2 (where 0.9≦n≦1.2, 0

Description

Detailed Description of the Invention

[0001] [Technical Field]

[0002] This application claims priority based on a Chinese patent application bearing application number 202311334878.4, filed with the State Intellectual Property Office of the People's Republic of China on October 13, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0003] The present invention relates to the technical field of positive electrode materials, and in particular to a positive electrode material, a manufacturing method thereof, and a battery. [Background technology]

[0004] Lithium-ion batteries have the advantages of high energy density, excellent safety, long cycle life, and environmental friendliness, making them widely used in fields such as laptops, mobile phones, and digital products. The development of positive electrode materials has been relatively slow compared to the development of high-capacity negative electrode materials (approximately 800mAh / g to 1000mAh / g). Therefore, researchers are currently focusing on developing high-capacity, high-voltage positive electrode materials to improve the energy density of lithium-ion batteries.

[0005] Common layered ternary cathode materials exhibit high capacity, high voltage, excellent cycle life, and excellent safety, making them the main cathode materials for power battery development. However, as the nickel content in ternary cathode materials increases, problems such as lithium-nickel mixing, structural degradation, reduced thermal stability, and increased residual base content inevitably occur, which leads to battery capacity degradation, reduced cycle life, and structural stability degradation, affecting its safety and high performance.

[0006] The hydroxide precursor produced by the conventional coprecipitation method is a nickel-cobalt-manganese hydroxide in which its components are uniformly distributed. In the sintering process with a lithium salt, the elemental ratios of Ni, Co, and Mn also remain uniformly distributed. Generally, in order to reduce the dislocation defects caused by lithium-nickel mixing, the nickel content (mass) can only be appropriately reduced, but this inevitably sacrifices the performance of the material such as high capacity and high initial efficiency.

[0007] Therefore, improving the specific capacity and high initial efficiency performance of the cathode material, as well as improving the structural stability and cycle performance, is still one of the problems to be solved at present.

Summary of the Invention

Problems to be Solved by the Invention

[0008] The object of the present application is to provide a cathode material, a method for manufacturing the same, and a battery. The cathode material according to the present application can effectively improve the specific capacity and high initial efficiency performance of the cathode material, and can also improve the structural stability and cycle performance.

Means for Solving the Problems

[0009] In a first aspect, the present application provides a material represented by the general formula: 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), including a first particle with a maximum diameter of 1.5 μm or less and a second particle with a maximum diameter of 2.5 μm or more, where the average value of the molar ratio of Ni element to Mn element in the first particle measured by energy dispersive spectroscopy (EDS) is denoted as R1, and the average value of the molar ratio of Ni element to Mn element in the second particle measured by energy dispersive spectroscopy (EDS) is denoted as R2, and a cathode material satisfying 0 < R2 - R1 is provided.

[0010] In a second aspect, the present application provides a method for producing a positive electrode material, the method comprising the steps of subjecting a mixture containing an oxide precursor of the positive electrode material, a lithium source, and a metal M-containing dopant to a primary sintering treatment, and crushing the primary sintered product to obtain a positive electrode material, wherein the oxide precursor of the positive electrode material has diffraction peaks in both the range of 34.4° to 36.4° and the range of 42.3° to 44.3° in an X-ray diffraction pattern.

[0011] In a third aspect, the present application provides a battery including a positive electrode material. [Effects of the Invention]

[0012] The present invention has the following advantageous effects compared to the prior art.

[0013] The cathode material provided herein is formed by agglomerating first particles with a maximum diameter of 1.5 μm or less and second particles with a maximum diameter of 2.5 μm or more, thereby stabilizing the crystalline structure dynamics of the larger second particles and improving the structural stability of the cathode material. The smaller first particles provide a large specific surface area, thereby increasing the number of lithium storage sites and increasing the discharge capacity of the cathode material. The present application further controls the molar ratio of Ni to Mn in the first particles to be different from the molar ratio of Ni to Mn in the second particles, thereby reducing the Ni content in the first particles and reducing the possibility of dislocation defects and oxygen precipitation due to Ni mixing in the first particles, thereby reducing side reactions on the particle surface. The large particle size of the second particles stabilizes the crystal structure dynamics of the second particles. In addition, the relatively high Ni content of the second particles reduces the internal stress caused by the overall size of the second particles, even if dislocation defects due to Ni mixing occur within the second particles. This reduces the deterioration of the crystal structure, reduces mixing and oxygen precipitation, and further reduces particle collapse. Therefore, when a positive electrode material satisfies the above particle size and element distribution relationship, the structural stability of the material is effectively improved, particle collapse is reduced, and its cycle performance and capacity retention rate are improved.

[0014] In the method for producing a positive electrode material according to the present application, the precursor of the positive electrode material employed has diffraction peaks in the range of 34.4° to 36.4° and the range of 42.3° to 44.3°. The phrase "having a diffraction peak in the range of 42.3° to 44.3°" refers to the presence of a rock salt phase in some of the particles of the precursor of the positive electrode material, such as NiO with a rock salt phase. The phrase "having a diffraction peak in the range of 34.4° to 36.4°" refers to the presence of a spinel phase in some of the particles of the precursor of the positive electrode material, such as NiMn2O4. During the sintering process with the lithium salt, rock salt phase precursor particles tend to form particles with relatively large particle diameters through nucleation and growth, resulting in a large maximum diameter for the primary particles after sintering. While the precursor has a high nickel content, the structure of its crystalline phase is more stable and can withstand a high nickel content without structural collapse. Furthermore, the spinel phase precursor particles have a high nucleation energy barrier during sintering with the lithium salt, which reduces the longest diameter of the sintered primary particles and the low nickel content, which reduces the possibility of lattice defects and oxygen precipitation due to Ni mixing and reduces side reactions on the particle surface. Therefore, the positive electrode material produced by sintering the precursor effectively improves the structural stability of the material, reduces particle collapse, and improves its cycle performance and capacity retention.

[0015] In order to more clearly describe the technical solutions of the embodiments of the present application or the prior art, the following briefly introduces drawings necessary for describing the embodiments or the prior art. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without requiring any inventive effort. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a flowchart showing a method for manufacturing a positive electrode material according to an embodiment of the present application. [Figure 2a] FIG. 2 is a diagram showing an XRD chart of an oxide precursor of a positive electrode material according to Example 1 of the present application. [Figure 2b]FIG. 2 is a view showing an SEM image of an oxide precursor of a positive electrode material according to Example 1 of the present application. [Figure 2c] FIG. 2 is a view showing an SEM image of the positive electrode material according to Example 1 of the present application. [Figure 2d] FIG. 2 shows a cross section of a positive electrode material according to Example 1 of the present application and the results of an EDS spectrum. [Figure 3a] FIG. 2 is a diagram showing an XRD chart of an oxide precursor of a positive electrode material according to Example 2 of the present application. [Figure 3b] FIG. 2 is a view showing an SEM image of an oxide precursor of a positive electrode material according to Example 2 of the present application. [Figure 3c] FIG. 2 is a view showing an SEM image of a positive electrode material according to Example 2 of the present application. [Figure 3d] FIG. 2 shows a cross section of a positive electrode material according to Example 2 of the present application and the results of an EDS spectrum. [Figure 4a] FIG. 2 is a diagram showing an XRD chart of an oxide precursor of a positive electrode material according to Comparative Example 1 of the present application. [Figure 4b] FIG. 2 is a view showing an SEM image of an oxide precursor of a positive electrode material according to Comparative Example 1 of the present application. [Figure 4c] FIG. 2 is a view showing an SEM image of a positive electrode material according to Comparative Example 1 of the present application. [Figure 4d] FIG. 2 shows a cross section of a positive electrode material according to Comparative Example 1 of the present application and the results of an EDS spectrum. DETAILED DESCRIPTION OF THE INVENTION

[0017] In order to better understand the technical solution of the present application, the following describes in detail the embodiments of the present application with reference to the accompanying drawings.

[0018] It is apparent that the described embodiments are only some of the embodiments of the present invention, and not all of the embodiments, and all other embodiments that a person skilled in the art can obtain based on the embodiments of the present invention without any inventive effort fall within the scope of protection of the present invention.

[0019] Also, the terms "first" and "second" are used merely for the purpose of explanation and should not be construed as indicating or implying relative importance or implicitly pointing out the number of the specified technical features. Therefore, the features limited by "first" and "second" may explicitly or implicitly include one or more of the said features.

[0020] For the purpose of facilitating the understanding of the present invention, specific terms are appropriately defined in this application. In the present invention, unless otherwise defined, scientific terms and technical terms used in the present invention have the meanings generally understood by those skilled in the art to which this application pertains.

[0021] As used herein, the term "substrate" refers to a lithium-based composite oxide synthesized by mixing a precursor and a lithium salt through a high-temperature solid-phase reaction, and contains lithium and a metal element.

[0022] As used herein, the term "primary particle" refers to a particle that exists alone without forming an aggregate.

[0023] As used herein, the term "secondary particle" refers to a particle formed by aggregation of the above primary particles.

[0024] This application relates to a material having the general formula: 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), comprising a first particle having a maximum diameter of 1.5 μm or less and a second particle having a maximum diameter of 2.5 μm or more, where the average value of the molar ratio of Ni element to Mn element in the first particle measured by energy dispersive spectroscopy (EDS) is denoted as R1, and the average value of the molar ratio of Ni element to Mn element in the second particle measured by energy dispersive spectroscopy (EDS) is denoted as R2, and 0 < R2 - R1 is satisfied, to provide a cathode material.

[0025] The positive electrode material according to the present invention comprises first particles having a maximum diameter of 1.5 μm or less and second particles having a maximum diameter of 2.5 μm or more. mixture By forming a cathode material using the first particles, the crystal structure dynamics of the larger second particles become more stable, improving the structural stability of the cathode material. The smaller first particles provide a larger specific surface area, thereby increasing the number of lithium storage sites and increasing the discharge capacity of the cathode material. The present application further controls the molar ratio of Ni to Mn in the first particles to be different from that in the second particles, thereby reducing the Ni content in the first particles and reducing the possibility of dislocation defects and oxygen precipitation due to Ni mixing in the first particles. This reduces side reactions on the particle surface. The larger second particles stabilize the crystal structure dynamics of the second particles. Furthermore, by increasing the Ni content in the second particles, even if a small amount of dislocation defects due to Ni mixing occur within the second particles, the internal stress generated by the overall size is alleviated, reducing deterioration of the crystal structure, reducing the likelihood of mixing and oxygen precipitation, and further reducing particle collapse. Therefore, when the positive electrode material satisfies the above relationship between particle size and element distribution, the structural stability of the material can be effectively improved, particle collapse can be reduced, and the cycle performance and capacity retention rate can be improved.

[0026] Specifically, n may range from 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, or may be any other value within the above ranges. x may range from 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 0.92, or the like, and y may range from 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, or the like.

[0027] In some embodiments, in the positive electrode material, R1 is greater than 0.5, specifically, it may 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., and is not limited thereto.

[0028] In some embodiments, in the positive electrode material, R2 is greater than 0.6, specifically, it may be 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, 2.1, 2.2, etc., and is not limited thereto.

[0029] In some embodiments, 0 < R2 - R1 < 0.5, specifically, it may be 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, etc., and is not limited thereto. That is, the R 2 -R 1 It is preferable that the value of R satisfies any one of the following conditions (1) to (5): 2 -R 1 is 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5, or a range consisting of both values ​​selected from these, or (2) 0.01≦R 2 -R 1 ≦0.05, or (3) 0.04≦R 2 -R 1 ≦0.08, or (4) 0.07≦R 2 -R 1 ≦0.22, or (5) 0.17≦R 2 -R 1 ≦0.41. When in the range of the R2 - R1 value, the Ni content of the large particles is high and the Ni content of the small particles is low, and after ensuring that the distribution of the whole main elements is uniform, it is possible to reach a Ni content having a gradient between the large particles and the small particles, thereby enabling the material to have higher structural stability, alleviating the collapse of the lattice structure, and improving the capacity and cycle performance.

[0030] In some embodiments, the average particle diameter of the first particles is 0.5 μm to 1.5 μm. By controlling the particle diameter within the above range, the occurrence of side reactions can be reduced and the structural stability of the particles can be improved.

[0031] In some embodiments, the average particle size of the second particles is 2.5 μm to 3.5 μm. Controlling the particle size within this range is advantageous for the diffusion transport of lithium ions, reduces the internal resistance between particles, and improves the capacity and fold-rate performance of the material. Preferably, the average particle size of the second particles is 2.6 μm to 3.5 μm.

[0032] In the present application, it is understood that the positive electrode material formed by the aggregation of first particles with a longest diameter of 1.5 μm or less and second particles with a longest diameter of 2.5 μm or more stabilizes the crystal structure dynamics of the larger second particles, and even if a small amount of dislocation defects due to Ni mixing occur internally, it can relieve internal stress caused by the overall size and mitigate deterioration of the crystal structure, making the phenomena of Ni mixing and oxygen precipitation less likely to occur, providing greater lithium storage activity and improving the capacity of the positive electrode material. The relatively small first particles have a low Ni content, which can originally reduce the possibility of lattice defects and oxygen precipitation due to Ni mixing, making the crystal structure more stable and reducing surface side reactions of the positive electrode material. The relatively large specific surface area of ​​the first particles provides high activity, increasing the number of lithium storage sites and increasing the discharge capacity of the positive electrode material.

[0033] In some embodiments, the positive electrode material has the general formula: Li n Ni 1-x-y M x Mn y M2 z O2 (where 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). Specifically, z may be in the range of 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.92, etc., and may of course be other values ​​within the above range.

[0034] In some embodiments, the positive electrode material has the general formula: Li n Ni 1-x-y M x Mny M2 z M3 u O2 (where 0 ≦ z < 1, 0 ≦ u < 1, the M2 metal contains at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Sb, Ta, Ca, B, Y, and W, and the M3 metal contains at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Y, B, and W).

[0035] In some embodiments, the sulfate content of the positive electrode material is 800 ppm or less. In the positive electrode material of the present application, SO4 2- has a great influence on the electrochemical performance of the material. SO4 2- When the content is high, SO4 2- combines with Li + and restrains a part of Li + , which is disadvantageous for the movement of Li and causes deterioration of the material capacity and rate. In addition, SO4 2- also affects the stability of the SEI film and reduces the cycle performance. By controlling the sulfate content in the positive electrode material of the present application within the above range, the adverse effects can be effectively suppressed, and the electrochemical performance of the positive electrode material can be further improved.

[0036] In some embodiments, the precursor of the positive electrode material has the general formula: Ni[[ID=%]] a M b Mn c O (where 0 < a < 1, 0 < b < 1, 0 < c < 1, and a + b + c = 1, and M is selected from Co and / or Al). Note that the precursor of the positive electrode material is a substance that can be converted into the positive electrode material of the present application.

[0037] In some embodiments, the precursor of the positive electrode material has the general formula: Ni a Co b Mn c (OH)2 (where 0 < a < 1, 0 < b < 1, 0 ≦ c < 1, and a + b + c = 1).

[0038] Specifically, XRD diffractionThe precursor of the positive electrode material was measured by FTIR diffraction, and the precursor of the positive electrode material had diffraction peaks at 35.4°±1° and 43.3°±1°, respectively. The phrase "having a diffraction peak at 35.4°±1°" indicates that some of the particles in the precursor of the positive electrode material have a rock salt phase, such as NiO having a rock salt phase. Some of the particles may have a spinel phase, such as NiMn2O4. The rock salt phase precursor particles are sintered to form particles with a relatively large particle size, and the sintered primary particles have a large longest diameter and a high nickel content. The spinel phase precursor particles are sintered to form particles with a relatively small particle size, and the sintered primary particles have a small longest diameter and a low nickel content.

[0039] In some embodiments, the positive electrode material is a single-crystal material comprising a plurality of crystal grains, each of which comprises a plurality of primary particles, each of which may comprise a first particle and / or a second particle, and all of the primary particles within at least one crystal grain have the same orientation. The average particle size of the single crystal grain is 1 μm to 5 μm. Compared to conventional polycrystalline materials, the single-crystal material has a more stable structure, a more uniform distribution of phase components, and better particle strength. This significantly reduces particle cracking during the electrode piece pressing process, improving the electrode piece pressing density and volumetric energy density, and benefiting the overall battery energy density. It also prevents microcracks from occurring within the polycrystalline material aggregates during cycling, thereby improving high-voltage performance and cycle stability. The single crystal grain in this application is formed by the aggregation of a plurality of primary particles, and both the first particle and the second particle are primary particles. The single crystal grain may consist of a first particle, a second particle, a combination of a first particle and a second particle, or a first particle, a second particle, and a primary particle whose maximum diameter is located between the first particle and the second particle.

[0040] In some embodiments, the positive electrode material is a single crystal material comprising a plurality of crystal grains, the crystal grains comprising a plurality of primary particles, the plurality of primary particles comprising first particles and / or second particles, the primary particles within at least one crystal grain having the same orientation, and the average particle size of the single crystal grain being 1 μm to 5 μm. Whether the positive electrode material comprises single crystal grains of the same orientation can be measured by electron backscatter diffraction (EBSD). By observing the color of a single primary particle within a single crystal grain, it can be determined whether all primary particles within the crystal grain comprise single crystal grains of the same orientation, and by observing an EBSD or SEM image, the particle size of the selected single particles of the same orientation (i.e., the average particle size of the single crystal grains) can be determined.

[0041] The orientation of primary particles within the crystal grains of the positive electrode material can be measured at least by electron backscatter diffraction (EBSD), where 100 single crystal grains having the same orientation are randomly selected, the particle size of each crystal grain is measured, and the arithmetic mean value is taken as the average particle size of the single crystal grains.

[0042] The difference between single-crystal positive electrode materials and polycrystalline ternary positive electrode materials (i.e., polycrystalline secondary particles) is that polycrystalline secondary particles are secondary particles formed by the aggregation of primary particles. Furthermore, in single-crystal positive electrode materials, the smallest particles are typically monomeric primary particles on the order of microns. In addition to EBSD measurement, other measurement methods, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD), can generally be used to determine whether a resulting positive electrode product is a single-crystal material. For typical single-crystal positive electrode materials, SEM is an important and reliable measurement method, as it determines whether the outer shape of the single-crystal particles is generally regular or irregular polyhedral and without significant particle aggregation. TEM is an auxiliary secondary measurement method, which observes whether the crystal plane orientation of the resulting product is consistent, and is further measured using selected-area electron diffraction (SAED). All of these methods are used to determine whether a product is a single-crystal positive electrode material. For ease of understanding, the single crystal positive electrode material of the present application is understood to include positive electrode material particles in which all primary particles within at least one crystal grain have the same orientation, and the average particle size of the single crystal grain is 1 μm to 5 μm.

[0043] In the present application, a single crystal grain may be understood to mean a single particle consisting of one primary particle. The single-crystal positive electrode material may contain a small amount of "pseudo-secondary particles" formed by the blocking of several single particles. A "primary particle" refers to the smallest particle unit identified when observing the positive electrode active material with a scanning electron microscope, and a "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles, resulting in a relatively rounded spherical shape. A "pseudo-secondary particle" refers to a particle formed by the blocking of several single particles. The particle diameter of a single particle in the pseudo-secondary particle is typically 1 μm to 5 μm, and the degree of roundness of the "pseudo-secondary particle" is generally lower than that of the typical "secondary particle."

[0044] It should be noted that "single-crystal positive electrode materials" known to those skilled in the art are not "single-crystal" in the strict sense. In crystallography, an ideal single crystal refers to a crystal with the exact same alignment and orientation. However, due to limitations of impurities, distortion, and crystal defects, ideal single crystals are extremely rare and difficult to produce in laboratories. Therefore, single-crystal positive electrode materials known in the art are often actually positive electrode materials with a "quasi-single-crystal morphology," which differs only in size from polycrystals, which are composed of many small primary particles, representing the large grain size of pseudo-single crystals.

[0045] In some embodiments, the median diameter of the positive electrode material satisfies 2.5 μm≦median diameter≦5 μm (provided that the median diameter is less than the particle diameter D 50 Yes Specifically, it is the particle diameter at which the cumulative volume ratio in the particle volume particle size distribution is 50%. If the particle size of the single crystal particles is too large, the ion transport path becomes long and the internal resistance of the particles becomes high, which slows the reaction kinetics of the positive electrode material and reduces the capacity and rate performance of the positive electrode material.

[0046] In some embodiments, the pH of the positive electrode material satisfies 11.0≦pH≦12.5, and may be, but is not limited to, 11.0, 11.2, 11.3, 11.5, 11.8, 12.0, 12.3, or 12.5. Controlling the pH of the positive electrode material within this range is advantageous for improving the processing performance of the positive electrode material.

[0047] In some embodiments, the amount of LiOH in the positive electrode material is 100 ppm by mass. <m LiOH The Li2CO3 content (mass) in the positive electrode material is ≦1500 ppm, and specifically may be, but is not limited to, 110 ppm, 150 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, 1100 ppm, 1200 ppm, or 1500 ppm. <m Li2CO3≦5000 ppm. Specifically, it may be, but is not limited to, 110 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 800 ppm, 1000 ppm, 1500 ppm, 2000 ppm, 3000 ppm, 4000 ppm, 4500 ppm, or 110 ppm. The alkaline impurities on the surface of the positive electrode material mainly refer to Li2CO3 and LiOH. It is understood that 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 the alkaline impurities on the positive electrode material, protect the structural stability of the positive electrode material, and be beneficial to improving the cycle stability of the positive electrode material.

[0048] In some embodiments, the free lithium content of the positive electrode material is 100 ppm <m Li ≦2000 ppm. Specifically, it may be, but is not limited to, 110 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 800 ppm, 1000 ppm, 1500 ppm, 2000 ppm, or the like.

[0049] In some embodiments, the specific surface area of ​​the positive electrode material is 0.5 m 2 / g~1.5m 2 / g, specifically, 0.5m 2 / g, 0.6m 2 / g, 0.72m 2 / g, 0.83m 2 / g, 1.01m 2 / g, 1.14m 2 / g, 1.27m 2 / g, 1.38m 2 / g, 1.45m 2 / g, etc., and of course, other values ​​within the above range may also be used, but are not limited to these. By controlling the specific surface area of ​​the positive electrode material within the above range, the positive electrode material can exhibit high capacity, high initial coulomb efficiency, high cycle stability, and low gas generation.

[0050] In some embodiments, the tap density of the cathode material is 1.5 g / cm 3 ~3.0g / cm 3Specifically, 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 3.0 g / cm 3 The tap density of the positive electrode material may be, but is not limited to, any other value within the above range. Controlling the tap density of the positive electrode material within the above range is advantageous for improving the processing performance of the material and increasing the energy density of the battery.

[0051] In some embodiments, the pressed density of the cathode 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 4.0 g / cm 3 Of course, other values ​​within the above range may also be used, but the press density is not limited to these. Controlling the press density of the positive electrode material within the above range is advantageous for improving the energy density of the battery.

[0052] In a second aspect, the present application provides a method for producing a cathode material, as shown in FIG. 1 , the method for producing a precursor of the cathode material includes: The method includes a step of obtaining a positive electrode material by subjecting a mixture containing an oxide precursor of a positive electrode material and a lithium source to a primary sintering treatment and crushing the primary sintered product, wherein the oxide precursor of the positive electrode material has diffraction peaks at 35.4°±1° and 43.3°±1°, respectively, in an X-ray diffraction pattern.

[0053] In the method for producing a positive electrode material according to the present application, the precursor of the positive electrode material employed has diffraction peaks at 35.4°±1° and 43.3°±1°, respectively. "Having a diffraction peak at 43.3°±1°" indicates that some particles in the positive electrode material precursor have a rock salt phase, such as NiO with a rock salt phase. "Having a diffraction peak at 35.4°±1°" indicates that some particles in the positive electrode material precursor have a spinel phase, such as NiMn2O4. Rock salt phase precursor particles are prone to forming particles with relatively large particle diameters through nucleation and growth during the sintering process with lithium salt. After sintering, the nickel content is high, the longest diameter of the particles is large, and the crystalline phase structure is more stable, allowing the precursor to withstand a high nickel content without structural collapse. Furthermore, the spinel phase precursor particles have a high nucleation energy barrier during sintering with the lithium salt, resulting in relatively small particle sizes, a small longest diameter, and a low nickel content after sintering, which reduces the possibility of lattice defects and oxygen precipitation due to Ni mixing and reduces side reactions on the particle surface. Therefore, the positive electrode material prepared by sintering the precursor effectively improves the structural stability of the material, reduces particle collapse, and improves its cycle performance and capacity retention.

[0054] The production method of the present invention will be specifically described below with reference to examples.

[0055] A mixture of an oxide precursor 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 has diffraction peaks in both the range of 34.4° to 36.4° and the range of 42.3° to 44.3° in an X-ray diffraction pattern.

[0056] In some embodiments, the oxide precursor of the positive electrode material includes NiO and NiMn₂O₄.

[0057] In some embodiments, the method further includes annealing the hydroxide precursor of the positive electrode material at 500°C to 900°C for 4 hours to 12 hours to dehydrate the hydroxide to form an oxide, thereby obtaining the oxide precursor of the positive electrode material. The oxide precursor has the general formula: Ni a M b Mn c O (where 0 < a < 1, 0 ≤ b < 1, 0 < c < 1, and a + b + c = 1, and M is selected from Co and / or Al).

[0058] In some embodiments, the annealing temperature is 500°C to 900°C. Specifically, it may be 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. The annealing time may be 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours, etc. Of course, it may also be other values within the above range and is not limited thereto.

[0059] 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.

[0060] In some embodiments, the amount of the lithium source and the precursor of the positive electrode material added satisfies the following: The ratio of the molar amount of Li to the total molar amount of all metals in the precursor of the positive electrode material is (0.87 to 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 are also possible, but are not limited to these. Within this range, the degree of Li / Ni cation mixing can be reduced, and the processability and safety can be prevented from being impaired when the amount of residual lithium on the surface of the fired product is too high.

[0061] In some embodiments, the mixture further comprises a dopant comprising a metal M2, where the metal M2 comprises at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Y, and W. Specifically, the mixture may comprise a salt or oxide that may comprise the metal M2.

[0062] In some embodiments, the dopant comprises at least one of Nb2O5, Nb2O3, MoO3, WO2, WO3, VO5, VO3, Sr(OH)2, SrO, TiO2, ZrO2, Zr(OH)4, YO3, BaO, Cr2O3, ZnO, CuO, MgO, and Mg(OH)2. Preferably, the dopant comprising the metal M2 is a compound of Zr or Ti.

[0063] In some embodiments, the mixing conditions for obtaining the mixture are solid-phase mixing at 10° C. to 50° C. for 0.3 hours to 3 hours.

[0064] In some embodiments, the solid-phase mixing temperature may 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 may be 0.3 hours, 0.4 hours, 0.5 hours, 0.6 hours, 0.8 hours, 1 hour, 1.5 hours, 1.8 hours, 2.5 hours, or 3 hours, or may be other values ​​within the above ranges, but is not limited thereto. Preferably, the solid-phase mixing temperature is 10°C to 35°C.

[0065] In some embodiments, the amounts of the dopant and the precursor of the positive electrode material added satisfy the following: the ratio of the molar amount of M2 to the total molar amount of metals in the precursor of the positive electrode material is (0.01 to 0.04:1), and may be specifically, but not limited to, 0.01:1, 0.02:1, 0.03:1, 0.04:1, etc., or other values ​​within the above range.

[0066] In some embodiments, the method of solid-phase mixing may be, but is not limited to, dry grinding, ball milling, or the like, as long as each component is mixed uniformly.

[0067] 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.

[0068] In some embodiments, the primary sintering process is carried out in an oxygen-containing atmosphere, and the oxygen-containing atmosphere has an oxygen gas content of 95% or more.

[0069] In some embodiments, the temperature of the primary sintering treatment is 700°C to 1000°C, and may be 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 listed values, and other unlisted values ​​within the range also apply. This range can promote the oxidation of divalent nickel to trivalent nickel and reduce the mixing of Li / Ni cations.

[0070] In some embodiments, the incubation time for the primary sintering treatment is 6 hours to 48 hours, and may be specifically 6 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 24 hours, 36 hours, or 48 hours, but is not limited to the recited values, and other unrecited values ​​within the range also apply.

[0071] In some embodiments, when the metal M2-containing dopant is a compound of Zr or Ti, the temperature of the primary sintering treatment is 800° C. to 900° C., and the temperature retention time is 8 hours to 10 hours.

[0072] In some embodiments, the method includes mixing the crushed substrate material with a metal M3-containing coating, followed by a secondary sintering process to obtain a positive electrode material.

[0073] In some embodiments, the median diameter of the substrate material after crushing is between 2.5 μm and 4.5 μm.

[0074] In some embodiments, the width of the particle size distribution of the substrate material after crushing is 1.1≦(D 90 -D 10 ) / D 50 The particle size distribution of the substrate material is preferably ≦1.7, and may be, but is not limited to, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, etc. The substrate material has a wide particle size distribution, which is advantageous for improving the lamination press density of the positive electrode material and further improving the gram capacity of the positive electrode material.

[0075] In some embodiments, the crushing method includes at least one of a double roll crusher, a plowshare mixer / crusher, and an airflow crusher.

[0076] In some embodiments, in the metal M3-containing coating, M3 is at least one selected from Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Y, and W. The metal M3-containing coating may be a salt or oxide of the metal M3. Preferably, the metal M3-containing coating contains a compound of Nb and / or a compound of W.

[0077] In some embodiments, the secondary sintering process is carried out in an oxygen-containing atmosphere, and the oxygen-containing atmosphere has an oxygen gas content of 95% or more.

[0078] In some embodiments, the temperature of the secondary sintering treatment is 300°C to 800°C, and may be 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, but is not limited to the listed values, and other unlisted values ​​within the range also apply.

[0079] In some embodiments, the incubation time for the secondary sintering treatment is 6 hours to 24 hours, and may be specifically 6 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, or 24 hours, but is not limited to the recited values, and other unrecited values ​​within the range also apply.

[0080] In some embodiments, when the metal M3-containing coating agent contains a Nb compound and / or a W compound, the temperature of the secondary sintering treatment is 500°C to 600°C, and the temperature retention time of the secondary sintering treatment is 6 hours to 8 hours.

[0081] In some embodiments, the method further comprises cooling, sizing, and sieving the product after secondary sintering, wherein the sizing comprises at least one of crushing, grinding, ball milling, or airflow milling.

[0082] In some embodiments, the mesh number of the screen mesh used for sieving is 300 mesh to 400 mesh.

[0083] In a third aspect, the present application provides a battery comprising the above-described positive electrode material or a positive electrode material produced by the above-described production method.

[0084] The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

[0085] The present invention will be further described below with reference to several examples, but the present invention is not limited to the following specific examples, which may be modified as appropriate without changing the scope of the main claims.

[0086] Measurement method: (1) Measurement of the molar content of the main elements (Li / Ni / M / Mn) of the precursor and cathode material: Equipment: Agilent 5110 ICP-OES plasma inductive coupling tester. Method: Aqua regia was added to 0.3 g of sample to decompose it, and after cooling and volumetric determination, 1 mL of the decomposition solution was taken and diluted 100 times to measure the mass content of the main elements Li / Ni / M / Mn. The content (mass) was converted to obtain the molar content.

[0087] (2) Measurement of XRD diffraction peaks of the precursor of the positive electrode material: Equipment: X'Pert Powder (PANalytical) or Bruker X-ray diffraction tester products. Method: Fill the sample cell with powder and flatten the top surface with a glass sheet to ensure that the top surface of the sample is parallel to the cell edge. The scanning range is 2θ = 10° ~ 90°, and the total scanning time is more than 5 minutes. After the scanning is completed, open the Jade software and automatically perform a peak search by selecting Analysis → Find Peaks to identify the position and height of the diffraction peak.

[0088] (3) Measurement of alkaline impurities in the positive electrode material: In a sealed glass flask, 5.0 g of the positive electrode material powder was immersed in 100 mL of deionized water and stirred for 10 minutes. After thorough stirring, the suspension was filtered to obtain a clear solution. Then, while stirring, 90 mL of the clear solution was titrated to pH 3 while adding 0.1 mol / L HCl solution at a rate of 0.5 mL / min, recording the pH curve. LiOH and Li2CO3 dissolved in low concentrations in deionized water were determined by titration, and a reference voltage curve was obtained. The first plateau, with an end point y1 (unit: mL) between pH 8 and pH 9, was determined by the OH. - The second plateau, with an end point y2 (unit: mL) between pH 4 and pH 6, is the determined HCO3 - The inflection point y1 between the first and second plateaus and the inflection point y2 after the second plateau were obtained from the corresponding minimum values ​​of the derivative dpH / dVol of the pH curve. These are then expressed as the percentages (by weight) of LiOH, LiCO3, and free lithium (Free Li) as shown in the following equations (3), (4), and (5).

number

[0089] (4) pH measurement of positive electrode material: A sample of approximately 5g of positive electrode material was taken, 45mL of water was added, and the sample was ultrasonically treated for 5 minutes. After that, the sample was removed and allowed to stand for 10 minutes. After calibrating with a pH meter, the composite electrode was inserted into the supernatant liquid to be measured. The pH of the solution was calculated from the potential difference between the measurement electrode and the reference electrode.

[0090] (5) Measurement method for volume median diameter of positive electrode material: The volume distribution range of particle diameters of the positive electrode material was measured using a Malvern laser particle size analyzer, and the median diameter D 50 obtained.

[0091] (6) Measurement method for the specific surface area of ​​the positive electrode material: Apparatus: A Micro Tristar 3020 specific surface area and hole diameter analyzer is used to measure the specific surface area of ​​the positive electrode material. Method: Weigh the mass of an empty sample tube (m1), take 3 g of sample, and introduce it into the sample tube through a long funnel. Degas it under vacuum at 300°C for 1 hour. After cooling, weigh the mass of the sample tube (m2). The sample mass is m = m2 - m1. The sample tube was placed in liquid nitrogen, and the nitrogen gas adsorption capacity (V) of the sample was measured at a series of relative pressures (P / P0) to obtain an adsorption isotherm. The P / P0 ratios were set to 0.05 / 0.1 / 0.15 / 0.20 / 0.25 / 0.30. The isotherm was fitted, and the saturated monolayer adsorption capacity (Vm) was calculated from the slope and intercept. The specific surface area was then calculated from Vm.

[0092] (7) Measurement of the Quantatap density of the positive electrode material: Apparatus: A tap density meter manufactured by Quantachrome (model number: DAT-4-220) is used. Method: After cleaning the measuring cylinder, weigh the mass m1 of the measuring cylinder, add approximately 50g of sample to the measuring cylinder, make sure the sample surface is as horizontal as possible, wipe the periphery with tissue paper, weigh the total mass m2 of the sample and measuring cylinder, place the measuring cylinder on the vibration table, secure it with three symmetrical fixed legs, activate the instrument, set the vibration frequency to 5000, press the vibration switch, the instrument will vibrate the specified number of times and then automatically stop, remove the measuring 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 value V of the highest and lowest readings, and the tapped density = (m2 - m1) / V.

[0093] (8) Measurement of pressed density of positive electrode material: The press density of the positive electrode material is measured by the American Carver 4350. The steps are as follows: weigh 1 g of sample and put it into a mold, pressurize it at a pressure of 3 T for 30 s, and then measure the height to calculate the pressurization.

[0094] (9) Measurement of the average particle size of the positive electrode material: Cross-sectional SEM measurement of the positive electrode material was performed, and an image magnified 3000 times was selected. The particle diameters of all primary particles were measured using Nano Measure software. The longest diameter of the particles was selected during measurement. After measurement of all particles in the image was completed, the longest diameters of all first particles with a longest diameter of less than 1.5 μm were averaged to obtain the average particle diameter of the first particles. The longest diameters of all second particles with a longest diameter of more than 2.5 μm were averaged to obtain the average particle diameter of the second particles. The longest diameters of all particles in the image were averaged to obtain the average particle diameter of the positive electrode material.

[0095] (10) SEM and EDS measurements of cathode materials: Equipment: Hitachi S4800 scanning electron microscope, OXFORD Instrument energy dispersive spectroscopic tester. SEM measurement method: When measuring powder samples, adhere the powder sample with tools such as tweezers, spread it on a flat surface with conductive adhesive, and measure it under electron beam conditions of 5kV / 10mA. When measuring cross-sectional samples, apply the material to aluminum foil using a general electrode manufacturing method, cut it with a focused ion beam (FIB), and measure it under the same conditions as measuring powder samples with SEM. EDS measurement method: After adjusting the SEM electron beam voltage to 15 kV or higher, EDS measurements were performed on a selected area, covering the central portion of each single crystal particle. To determine the average Ni / Mn element ratio, 10 particles with a longest diameter of less than 1.5 μm (i.e., first particles) and 10 particles with a longest diameter of more than 2.5 μm (i.e., second particles) were selected and subjected to EDS measurement. The Ni / Mn ratios of the 10 first particles and the 10 second particles were obtained, respectively. The maximum and minimum values ​​were removed from the Ni / Mn ratios of the 10 first particles, and the remaining eight values ​​were averaged to obtain R1. The maximum and minimum values ​​were removed from the Ni / Mn ratios of the 10 second particles, and the remaining eight values ​​were averaged to obtain R2.

[0096] (11) SO in cathode materials 4 2- Measurement method for content: SO4 2-The method for measuring the sulfate content involves pre-treating the sample solution, separating it using an ion chromatography column, and then quantitatively analyzing it using the relationship between the concentration of separated sulfate ions and the detection signal. Ion chromatography typically uses a conductivity detector as the detection means, and the sulfate ion concentration is determined by monitoring the change in conductivity. The measurement results are shown in Table 2.

[0097] (12) Electrochemical performance measurement: The positive electrode materials obtained in the examples and comparative examples were assembled into button batteries. Specifically, the positive electrode material, conductive carbon, and polyvinylidene fluoride (PVDF) were added to N-methyl-2-pyrrolidone (NMP) in a mass ratio of 96:2:2 and mixed uniformly to prepare a positive electrode slurry. The slurry was then applied to a positive electrode current collector, vacuum dried, and then formed into a positive electrode sheet (the press density of the sheet was 2.8 g / cm). 3 The resulting cathode was assembled into a 2016 button cell in a glove box using a lithium sheet as the negative electrode. Measurements were carried out using a CT2001A battery detection system manufactured by WuhanLAND Electronic Co. Ltd. under the condition of a 1C theoretical capacity of 250mAh / g in the 3.0V to 4.3V discharge range. Details of the measurement results are shown in Table 3.

[0098] (13) Measurement of primary particle orientation of crystal grains: Apparatus: An electron backscattered diffractometer (EBSD) mounted on a scanning electron microscope, model number Gemini SEM300. Method: By observing and measuring the color of a single primary particle within a crystal grain, it can be determined whether the crystal grain contains a single crystal grain in which all primary particles have the same orientation. If all primary particles within a crystal grain have the same color, it is determined that all primary particles within the crystal grain have the same orientation.

[0099] Example 1 (1) Select the oxide precursor of the positive electrode material prepared by pyrolysis, and as shown in Table 1, its general formula is Ni 0.6 Co 0.1 Mn 0.3 O x(The molar content of each major element is within ±1%.) The precursor of the positive electrode material was measured by XRD and found to have two diffraction peaks at 35.9° and 43.4°, respectively, as shown in Figure 2a. As shown in Figure 2b, the morphology of the precursor of the positive electrode material is secondary particles formed by the aggregation of multiple primary particles. (2) The precursor of the positive electrode material and Li2CO3 were mixed so that the molar ratio of Li / Me (Me is the total molar content of Ni, Co, and Mn) was 1.02:1, and 2000 ppm of TiO2 was added relative to the content (mass) of the precursor of the positive electrode material. The mixture was then subjected to primary sintering in an oxygen atmosphere at 900°C for 10 hours. (3) The primary sintered product was crushed in a plowshare crusher for 30 seconds to obtain the substrate material. (4) The substrate material was mixed with 1000 ppm of Nb2O5, and then secondary sintered in an oxygen atmosphere at 500°C for 6 hours. The secondary sintered product was sieved through a 325 mesh screen to obtain a positive electrode material.

[0100] As shown in FIG. 2c, the positive electrode material produced in the examples of the present application has a morphology of a single particle with rounded particles, and has few cross sections due to fractures on the surface.

[0101] As shown in Figure 2d, the results of cross-sectional SEM and EDS measurements showed that the Ni / Mn ratios at 10 points on the first particles within the particle diameter range of 1.5 μm or less were 1.85, 1.87, 1.90, 1.79, 1.85, 1.91, 1.90, 1.89, 1.91, and 1.79, respectively, with an average R1 of 1.87 excluding the highest and lowest values. The Ni / Mn ratios at 10 points on the second particles within the particle diameter range of 2.5 μm or more were 1.83, 1.87, 1.86, 1.88, 1.96, 1.91, 1.92, 1.89, 1.87, and 1.94, respectively, with an average R2 of 1.89 excluding the highest and lowest values. The remaining measurement results are shown in Table 2.

[0102] Example 2 (1) Select the oxide precursor of the positive electrode material prepared by pyrolysis, and as shown in Table 1, its general formula is Ni0.9 Co 0.05 Mn 0.05 O x (The molar content of each major element is within ±1%.) The precursor of the positive electrode material was measured by XRD and found to have two diffraction peaks at 35.9° and 43.3°, respectively, as shown in Figure 3a. As shown in Figure 3b, the morphology of the precursor of the positive electrode material is secondary particles formed by the aggregation of multiple primary particles. (2) The precursor of the positive electrode material and Li2CO3 were mixed at a molar ratio of Li / Me (Me is the sum of Ni, Co, and Mn) of 1.01:1, and 2000 ppm of TiO2 was added relative to the content (mass) of the precursor of the positive electrode material. Primary sintering was performed at 800°C for 8 hours in an oxygen atmosphere. The sintering temperature was lower than in Example 1 due to the high Ni content. Depending on the characteristics of the ternary material, the sintering temperature should be inversely proportional to the Ni content to ensure similar crystal grain sizes. (3) The primary sintered product was crushed for 30 seconds with a plowshare crusher to obtain a substrate material. (4) The substrate material was mixed with 2000 ppm of WO3, and then secondary sintered in an oxygen atmosphere at 550°C for 8 hours. The secondary sintered product was sieved through a 325 mesh screen to obtain a positive electrode material.

[0103] figure 3 As shown in Fig. 3c, the positive electrode material produced in the examples of the present application has a morphology of a single particle with rounded particles, and has few cross sections due to fractures on the surface.

[0104] As shown in Figure 3d, the cross-sectional SEM and EDS measurements showed that the Ni / Mn ratios at 10 points on the first particles within the particle diameter range of 1.5 μm or less 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 R1, excluding the highest and lowest values, was 19.74. The Ni / Mn ratios at 10 points on the second particles within the particle diameter range of 2.5 μm or more 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 R2, excluding the highest and lowest values, was 19.80. The remaining measurement results are shown in Table 2.

[0105] Example 3 It differs from Example 1 in the following points. (1) Select the oxide precursor of the positive electrode material prepared by pyrolysis. As shown in Table 1, the general formula is Ni 0.67 Co 0.05 Mn 0.28 O x (The deviation of the molar content of each main element is within ±1%), and the precursor of the positive electrode material further contains 85 ppm of Ca.

[0106] Example 4 It differs from Example 1 in the following points. (4) The substrate material was mixed with 1000 ppm of ZrO2, and then secondary sintered in an oxygen atmosphere at 850°C for 8 hours. The secondary sintered product was sieved through a 325 mesh screen to obtain a positive electrode material.

[0107] Example 5 It differs from Example 2 in the following points. (4) The substrate material was mixed with 1000 ppm of WO3, and then secondary sintered in an oxygen atmosphere at 880°C for 8 hours. The secondary sintered product was sieved through a 325 mesh screen to obtain a positive electrode material.

[0108] Example 6 It differs from Example 3 in the following points. (4) The substrate material was mixed with 1000 ppm of MgO, and the mixture was subjected to secondary sintering in an oxygen atmosphere at 960°C for 8 hours. The secondary sintered product was sieved through a 325 mesh screen to obtain a positive electrode material.

[0109] Example 7 It differs from Example 1 in the following points. (4) The substrate material was mixed with 1000 ppm of WO3, and then secondary sintered in an oxygen atmosphere at 920°C for 12 hours. The secondary sintered product was sieved through a 325 mesh screen to obtain a positive electrode material.

[0110] Example 8 It differs from Example 1 in the following points. Step (4) is not performed.

[0111] Example 9 It differs from Example 2 in the following points. The oxide precursor of the cathode material prepared by pyrolysis selected in step (1) has the general formula Ni 0.92 Al 0.02 Mn 0.06 O x (The deviation of the molar content of each major element is within ±1%).

[0112] Example 10 It differs from Example 1 in the following points. In step (1), the selected Ni was prepared by coprecipitation. 0.6 Co 0.1 Mn 0.3 The hydroxide precursor was (OH)2, and annealed at 730 °C for 8 hours to obtain the oxide precursor for the cathode material. As shown in Table 1, the general formula is Ni 0.6 Co 0.1 Mn 0.3 O x (The molar content of each main element is within ±1%.) The sulfate content of the produced cathode material is as high as 830 ppm, and Li +Due to the inhibition of migration, the material is inferior to Example 1 in capacity, rate and capacity.

[0113] Example 11 The following points were different from Example 1: The temperature of the primary sintering was reduced from 900°C to 820°C.

[0114] Example 12 The difference from Example 1 is as follows: In step (1), Ni prepared by the sol-gel method was selected. 0.6 Co 0.1 Mn 0.3 (OH)2 hydroxide precursor, and was annealed at 600 °C for 4 hours to obtain the oxide precursor of the positive electrode material. The general formula is Ni 0.6 Co 0.1 Mn 0.3 O x (The deviation of the molar content of each main element is within ±1%). The content of sulfate radicals in the obtained positive electrode material is as high as 1240 ppm.

[0115] Example 13 The difference from Example 1 is as follows: The oxide precursor of the positive electrode material prepared by the pyrolysis method was selected, and as shown in Table 1, the general formula was Ni 0.34 Co 0.33 Mn 0.33 O x (The deviation of the molar content of each major element is within ±1%).

[0116] Example 14 The difference from Example 1 is as follows: The oxide precursor of the positive electrode material prepared by the pyrolysis method was selected, and as shown in Table 1, the general formula was Ni 0.45 Co 0.25 Mn 0.30 O x (The deviation of the molar content of each major element is within ±1%).

[0117] Example 15 The difference from Example 1 is as follows: The oxide precursor of the positive electrode material prepared by the pyrolysis method was selected, and as shown in Table 1, the general formula was Ni 0.55 Co 0.12 Mn 0.33 O x (The deviation of the molar content of each major element is within ±1%).

[0118] Example 16 The difference from Example 1 is as follows: The oxide precursor of the positive electrode material prepared by the pyrolysis method was selected, and as shown in Table 1, the general formula was Ni 0.83 Co 0.08 Mn 0.09 O x (The deviation of the molar content of each major element is within ±1%).

[0119] Comparative Example 1 It differs from Example 1 in the following points. (1) Select the oxide precursor of the cathode material prepared by the general coprecipitation method. As shown in Table 1, the general formula is Ni 0.6 Co 0.1 Mn 0.3 O x (The molar content of each major element is within ±1%.) As shown in Figure 4a, the precursor of the positive electrode material was measured by XRD and found to have one diffraction peak at 19.3°, but no diffraction peaks at 35.4° or 43.3°. As shown in Figure 4b, the morphology of the precursor of the positive electrode material is secondary particles formed by the aggregation of multiple primary particles.

[0120] As shown in Figure 4c, the morphology of the positive electrode material is a relatively angular single-crystal particle, and cross sections due to fractures can be observed on the surface. As shown in Figure 4d, SEM and EDS measurements of the particle cross sections of the positive electrode material revealed that the Ni / Mn ratios at 10 points on the first particles in the particle diameter range of 1.5 μm or less were 1.86, 1.89, 1.90, 1.89, 1.86, 1.92, 1.81, 1.88, 1.92, and 1.93, respectively, with an average R1 of 1.89 excluding the highest and lowest values. The Ni / Mn ratios at 10 points on the second particles in the particle diameter range of 2.5 μm or more were 1.80, 1.79, 1.86, 1.86, 1.97, 1.88, 1.85, 1.75, 1.87, and 1.97, respectively, with an average R2 of 1.86 excluding the highest and lowest values.

[0121] Comparative Example 2 It differs from Example 2 in the following points. (1) Select the oxide precursor of the cathode material prepared by the general coprecipitation method. As shown in Table 1, the general formula is Ni 0.9 Co 0.05 Mn 0.05 O x (The molar content of each main element is within ±1%.) The precursor of the positive electrode material was measured by XRD and found to have one diffraction peak at 19.3°, but no diffraction peaks at 35.4° and 43.3°.

[0122] Comparative Example 3 It differs from Example 3 in the following points. (1) ICP measurement was performed on selected oxide precursors of cathode materials prepared by a general coprecipitation method. As shown in Table 1, the general formula is Ni 0.67 Co 0.05 Mn 0.28 O x (The molar content of each main element is within ±1%.) The precursor of the positive electrode material was measured by XRD and found to have one strong diffraction peak at 19.4°, but no diffraction peaks at 35.4° and 43.3°.

[0123] Table 1: Comparison of positive electrode materials between Examples and Comparative Examples TIFF2026503791000020.tif108152

[0124] Table 2: Comparison of positive electrode materials between Examples and Comparative Examples TIFF2026503791000021.tif120130

[0125] Cathode material manufacturing The cathode precursors prepared in each example and comparative example were mixed with LiOH at a molar ratio of 1:1.02, and doping amounts of 1600 ppm Al(OH)3, 800 ppm TiO2, and 600 ppm Sr(OH)2 were added and mixed. The mixture was sintered at 730°C for 25 hours in a 95% oxygen atmosphere, cooled, crushed, and sieved to obtain the cathode materials.

[0126] The button cell battery was assembled and electrochemical measurements were carried out. The results are shown in Table 3.

[0127] Table 3: Comparison of positive electrode materials between Examples and Comparative Examples TIFF2026503791000022.tif96162

[0128] The positive electrode materials of Examples 1 to 7 differ in the molar ratio of Ni to Mn in the positive electrode material containing two types of particles. The molar ratio of nickel to manganese in the larger particles is higher than that in the smaller particles. This relatively lowers the Ni content in the first particles with particle diameters less than 1.5 μm, thereby reducing the possibility of lattice defects and oxygen precipitation due to Ni mixing and reducing side reactions on the particle surface. Meanwhile, the specific surface area of ​​the first particles with particle diameters less than 1.5 μm is relatively increased, resulting in high activity, increased lithium storage sites, and improved specific capacity of the material. The positive electrode material effectively improves the specific capacity and high initial efficiency of the positive electrode material, as well as structural stability and cycle performance.

[0129] As can be seen from the parameter data of the cathode material precursors of Example 1 and Comparative Example 1, Comparative Example 1 uses a common hydroxide precursor and does not have two material phases with different Ni contents, the spinel phase and the rock salt phase. Therefore, after sintering, the Ni element distribution does not have the advantage of a high gradient of large particles and a low gradient of small particles, and therefore the R2-R1 value of the cathode material precursor is less than 0. Compared to the electrochemical performance of cathode materials prepared with this cathode material precursor, Example 1 has high discharge capacity and initial coulombic efficiency, and its cycle stability at both room temperature and high temperature is clearly superior. This result indicates that single-crystal materials without a Ni gradient distribution are more susceptible to structural collapse, and Ni mixing increases lattice defects and oxygen precipitation, slightly reducing the structural stability and cycle performance of the cathode material.

[0130] Similarly, based on ternary materials with different Ni / Co / Mn contents, a comparison was made between Comparative Example 2 and Example 2, and a comparison was made between Comparative Example 3 and Example 3. The results show that a relatively high Ni content in large particles and a relatively low Ni content in small particles both have advantages in electrochemical performance in different ternary systems.

[0131] Furthermore, by comparing different material parameters under different manufacturing conditions based on the above examples, more preferred embodiments can be found.

[0132] As can be seen from the measurement data of Examples 1, 4, 7, and 8, all of these examples are based on a ternary positive electrode material system with a Ni:Co:Mn=6:1:3 ratio. The different doping aids used during the sintering process result in differences in the distribution of Ni, which affects parameters such as particle size, surface residual lithium, tap density, and press density. Comparing the electrochemical performance of the positive electrode materials, Example 1 demonstrates optimal capacity, rate, and cycle performance. The effect of Nb doping on the electrochemical performance of the positive electrode material is superior to that of Zr and W doping. While W doping results in a slight increase in surface residual lithium, which is consistent with the patent protection, it is not the most desirable solution. Example 8, which does not employ doping, exhibits low capacity and initial efficiency. Therefore, selecting and doping appropriate elements during the manufacturing process of the positive electrode material is beneficial for improving the electrochemical performance of the positive electrode material.

[0133] As can be seen from the measurement data of Examples 2 and 5, both are made from ternary positive electrode materials with a high nickel content of Ni:Co:Mn=90:5:5. The difference between the two is the doped W content. As the W content increases, the R2-R1 value of the resulting positive electrode material precursor increases significantly. By comparing the electrochemical performance of the positive electrode materials obtained from the precursors of these positive electrode materials, it can be seen that the R2-R1 value of the positive electrode material precursor in Example 5 is high, resulting in poor structural stability of the positive electrode material. As a result, the discharge capacity and cycle stability of Example 5 are lower than those of Example 2.

[0134] As can be seen from the measurement data of Examples 3 and 6, both were manufactured using ternary positive electrode materials with an element ratio of Ni:Co:Mn=67:5:28, and the value of R2-R1 of the Nb-doped Example 3 was lower than that of the Mg-doped Example 6. Comparing the electrochemical performance of Example 6 and Example 3, it was found that a high value of R2-R1 within a certain range is beneficial to improving the structural stability of the positive electrode material, leading to better discharge specific capacity and high-temperature cycle performance of Example 6. However, a combined analysis of Examples 2 and 5 reveals that if the value of R2-R1 is too high, the distribution of metal elements in the positive electrode material will be unbalanced, which may result in poor structural stability of the positive electrode material.

[0135] As can be seen from the measurement data of Examples 1 and 11, in Example 11, the sintering temperature was lowered, resulting in insufficient grain growth energy, and instead of forming single crystal grains with a size of 1 μm to 5 μm, a polycrystalline morphology was formed with a single crystal grain size of only 0.88 μm. In this morphology, there are many grain boundaries between the materials, and when charging and discharging, lithium ions are frequently released and absorbed, resulting in severe grain boundary dislocations, poor crystal structure stability, and poor cycle stability.

[0136] As can be seen from the measurement data in Examples 1 and 12, the free SO4 2- High SO4 content adversely affects the capacity and rate of the material, and too much free SO4 2- This also affects the stability of the SEI film and reduces the cycle performance.

[0137] As can be seen from the measurement data of Examples 13 to 16, when the particle size and distribution rules of Ni and Mn elements of the present invention are satisfied based on positive electrode materials of ternary materials with different Ni / Co / Mn contents, all of them have good material structural stability, high cycle performance, and capacity retention rate.

[0138] The above is merely a preferred embodiment of the present invention, and is not intended to limit the present invention. Those skilled in the art will appreciate that the present invention may have various modifications and variations. Any modifications, equivalent replacements, improvements, etc. made within the scope of the spirit and principles of the present invention should be understood to be included in the scope of protection of the present application.

Claims

1. General formula: Li ｎ Ni １－ｘ－ｙ M ｘ Mn ｙ O ２ (wherein 0.9≦n≦1.2, 0<x<1, 0<y<1, and M is selected from Co and / or Al), A positive electrode material comprising first particles having a longest diameter of 1.5 μm or less and second particles having a longest diameter of 2.5 μm or more, The average value of the molar ratio of Ni element to Mn element in the first particles measured by energy dispersive spectroscopy (EDS) is R １ and the average value of the molar ratio of Ni element to Mn element in the second particles measured by energy dispersive spectroscopy (EDS) is R ２ Then, 0<R ２ -R １ Satisfying the needs of cathode materials.

2. The positive electrode material according to claim 1, which satisfies at least one of the following characteristics (1) to (3): (1) In the positive electrode material, R １ >0.

5. (2) In the positive electrode material, R ２ >0.

6. (3) In the positive electrode material, 0<R ２ -R １ <0.

5.

3. The positive electrode material according to claim 1, which satisfies at least one of the following characteristics (1) to (2): (1) The first particles have an average particle size of 0.5 μm to 1.5 μm. (2) The average particle size of the second particles is 2.5 μm to 3.5 μm.

4. The positive electrode material according to claim 1, which satisfies at least one of the following characteristics (1) to (2): (1) The positive electrode material has the general formula: Li ｎ Ni １－ｘ－ｙ M ｘ Mn ｙ M2 ｚ O ２ (wherein 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). (2) The positive electrode material has the general formula: Li ｎ Ni １－ｘ－ｙ M ｘ Mn ｙ M2 ｚ M3 ｕ O ２ (wherein 0≦z<1, 0≦u<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, and M3 metal includes at least one of Zr, Mg, Ti, Ba, Sr, Cr, Zn, V, Cu, Nb, Mo, Y, B and W).

5. The positive electrode material according to claim 1, which satisfies at least one of the following technical features (1) to (2). (1) The positive electrode material is a single crystal material including a plurality of crystal grains, the crystal grains including a plurality of primary particles, the plurality of primary particles including first particles and / or second particles, and the orientation of all the primary particles within at least one of the crystal grains is similar. (2) The positive electrode material is a single crystal material including a plurality of crystal grains, the crystal grains including a plurality of primary particles, the plurality of primary particles including first particles and / or second particles, all of the primary particles in at least one of the crystal grains having a similar orientation, and the average particle size of the primary particles being 1 μm to 5 μm.

6. The positive electrode material according to claim 1 , wherein the median diameter satisfies 2.5 μm≦median diameter≦5 μm.

7. 2. The positive electrode material according to claim 1, wherein the content of sulfate radicals is 800 ppm or less.

8. The positive electrode material according to claim 1, which satisfies at least one of the following characteristics (1) to (3): (1) The pH of the positive electrode material satisfies 11.0≦pH≦12.

5. (2) The content (mass) of LiOH in the positive electrode material is 100 ppm < m ＬｉＯＨ ≦1500 ppm. (3) Li in the positive electrode material ２ CO ３ The content (mass) of is 100 ppm < m Ｌｉ２ＣＯ３ ≦5000 ppm.

9. The positive electrode material according to claim 1, which satisfies at least one of the following characteristics (1) to (4): (1) The content (mass) of free lithium in the positive electrode material is 100 ppm < m Ｌｉ ≦2000 ppm. (2) The specific surface area of ​​the positive electrode material is 0.5 m ２ / g to 1.5m ２ / g. (3) The tap density of the positive electrode material is 1.5 g / cm ３ ~3.0 g / cm ３ is. (4) The press density of the positive electrode material is 2.5 g / cm ３ ~4.0 g / cm ３ is.

10. 1. A method for producing a positive electrode material, comprising: subjecting a mixture containing an oxide precursor of a positive electrode material and a lithium source to a primary sintering treatment; and crushing the primary sintered product to obtain a positive electrode material, the oxide precursor of the positive electrode material has diffraction peaks in both the range of 34.4° to 36.4° and the range of 42.3° to 44.3° in an X-ray diffraction pattern.

11. annealing the hydroxide precursor of the positive electrode material at 500°C to 900°C for 4 hours to 12 hours to obtain an oxide precursor of the positive electrode material; The oxide precursor of the positive electrode material has the general formula: Ni ａ M ｂ Mn ｃ 11. The method according to claim 10, wherein 0 is represented by the formula (wherein 0<a<1, 0≦b<1, 0<c<1, and a+b+c=1, and M is selected from Co and / or Al).

12. The manufacturing method according to claim 10, which satisfies at least one of the following characteristics (1) to (4): (1) The lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate, and lithium oxalate. (2) The amounts of the lithium source and the precursor of the positive electrode material added satisfy the ratio of the molar amount of Li to the total molar amount of all metals in the precursor of the positive electrode material of (0.87 to 1.25):

1. (3) The mixture further comprises a metal M2-containing dopant, 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 contains a dopant containing a metal M2, and the amounts of the dopant and the oxide precursor of the positive electrode material added satisfy a ratio of the molar amount of M2 to the total molar amount of metals in the oxide precursor of the positive electrode material of (0.01 to 0.04):

1.

13. The manufacturing method according to claim 10, which satisfies at least one of the following characteristics (1) to (4): (1) The mixing conditions for obtaining the mixture are solid-state mixing at 10°C to 50°C for 0.3 to 3 hours. (2) The primary sintering treatment is carried out in an oxygen-containing atmosphere, and the oxygen gas content in the oxygen-containing atmosphere is 95% or more. (3) The temperature of the primary sintering treatment is 700°C to 1000°C. (4) The temperature retention time for the primary sintering treatment is 6 to 48 hours.

14. The method according to claim 10, further comprising: mixing the crushed substrate material with a coating agent containing the metal M3, followed by secondary sintering to obtain a positive electrode material.

15. A battery comprising the positive electrode material according to any one of claims 1 to 9.

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