Positive electrode material and method for manufacturing the same, 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 the Chinese patent application filed with the China National Intellectual Property Administration on 13 October 2023, application number 202311334878.4, and incorporates all of its disclosures herein.

[0003] This invention belongs to the technical field of positive electrode materials, and more particularly to positive electrode materials, methods for manufacturing the same, and batteries. [Background technology]

[0004] Lithium-ion batteries are widely used in fields such as laptops, mobile phones, and digital products due to their advantages of high energy density, superior safety, long cycle life, and environmental friendliness. The development of cathode materials has been relatively slower compared to the development of high-capacity anode materials (approximately 800 mAh / g to 1000 mAh / g). Therefore, current researchers are focusing on developing high-capacity and high-voltage cathode materials to improve the energy density of lithium-ion batteries.

[0005] Conventional layered ternary cathode materials exhibit characteristics such as high capacity, high voltage, excellent cycle life, and superior safety, making them the main cathode materials used in power battery development. However, increasing the nickel content in ternary cathode materials inevitably leads to problems such as lithium-nickel mixing, structural degradation, decreased thermal stability, and increased residual base content. This results in degradation of battery capacity, reduced cycle life, and structural stability, affecting their safety and high-performance use.

[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, only the nickel content (mass) can 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 positive electrode 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 positive electrode material, a method for manufacturing the same, and a battery. The positive electrode material according to the present application can effectively improve the specific capacity and high initial efficiency performance of the positive electrode 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 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 defined 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 defined as R2, and a positive electrode material satisfying 0 < R2 - R1 is provided.

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

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

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

[0013] The cathode material provided in this application is formed by agglomerating 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. This stabilizes the crystal structure mechanics of the larger second particles, improving the structural stability of the cathode material. The smaller first particles provide a large specific surface area, thereby increasing the lithium storage sites and increasing the discharge capacity of the cathode material. Furthermore, by controlling the molar ratio of Ni to Mn in the first particles to differ from that in the second particles, the Ni content in the first particles is relatively reduced, thereby decreasing the possibility of dislocation defects and oxygen deposition due to Ni mixing in the first particles and reducing side reactions on the particle surface. Because the second particle has a larger particle size, the crystal structure mechanics of the second particle is made more stable. In addition, the Ni content of the second particle is relatively high. Thus, even if dislocation defects occur inside the second particle due to a small amount of Ni mixing, the internal stress caused by the overall size is mitigated, the degradation of the crystal structure can be reduced, mixing and oxygen precipitation become less likely to occur, and particle disintegration can be further reduced. Therefore, when the cathode material satisfies the above relationship between particle size and elemental distribution, the structural stability of the material can be effectively improved, particle disintegration can be reduced, and its cycle performance and capacity retention rate can be improved.

[0014] In the method for manufacturing a positive electrode material according to the present invention, the precursor of the positive electrode material used has diffraction peaks in the ranges of 34.4° to 36.4° and 42.3° to 44.3°, respectively. "Having diffraction peaks in the range of 42.3° to 44.3°" indicates that some of the particles in the precursor of the positive electrode material have a rock salt phase, and may be, for example, NiO having a rock salt phase. "Having diffraction peaks in the range of 34.4° to 36.4°" indicates that some of the particles in the precursor of the positive electrode material have a spinel phase, and may be, for example, NiMn2O4. The precursor particles of the rock salt phase tend to form particles with relatively large particle diameters due to nucleation and growth during the sintering process with lithium salt, resulting in a larger maximum diameter of the primary particles after sintering and a higher nickel content. However, the structure of its crystal phase is more stable, allowing it to withstand high nickel content and preventing structural collapse. Furthermore, the spinel phase precursor particles have a high nucleation energy barrier during the sintering process with lithium salt, which reduces the maximum diameter of the primary particles after sintering, resulting in a lower nickel content, reduced lattice defects and oxygen deposition due to Ni mixing, and reduced side reactions on the particle surface. Therefore, the cathode material produced by sintering the above precursor effectively improves the structural stability of the material, reduces particle collapse, and improves its cycle performance and capacity retention rate.

[0015] To more clearly explain the embodiments of this application or the technical solutions of the prior art, the following drawings necessary for describing the embodiments or the prior art are briefly introduced. Clearly, the drawings described below are only a few embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without requiring any work commensurate with inventive step. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows a flowchart of the method for manufacturing a cathode material according to an embodiment of the present application. [Figure 2a] This figure shows the XRD chart of the oxide precursor of the cathode material according to Example 1 of the present application. [Figure 2b]This figure shows an SEM image of the oxide precursor of the cathode material according to Example 1 of the present application. [Figure 2c] This figure shows an SEM image of the cathode material according to Example 1 of the present application. [Figure 2d] This figure shows the cross-sectional view and EDS spectrum results of the cathode material according to Example 1 of the present application. [Figure 3a] This figure shows the XRD chart of the oxide precursor of the cathode material according to Example 2 of the present application. [Figure 3b] This figure shows an SEM image of the oxide precursor of the cathode material according to Example 2 of the present application. [Figure 3c] This figure shows an SEM image of the cathode material according to Example 2 of the present application. [Figure 3d] This figure shows the cross-sectional view and EDS spectrum results of the cathode material according to Example 2 of the present application. [Figure 4a] This figure shows the XRD chart of the oxide precursor of the cathode material according to Comparative Example 1 of the present application. [Figure 4b] This figure shows an SEM image of the oxide precursor of the cathode material according to Comparative Example 1 of the present application. [Figure 4c] This figure shows an SEM image of the cathode material relating to Comparative Example 1 of the present application. [Figure 4d] This figure shows the cross-sectional view and EDS spectrum results of the cathode material relating to Comparative Example 1 of the present application. [Modes for carrying out the invention]

[0017] To better understand the technical proposal of this application, the embodiments of this application will be described in detail below with reference to the attached drawings.

[0018] As is clear, the embodiments described represent only some, and not all, embodiments of the present invention. All other embodiments that a person skilled in the art could obtain based on the embodiments of the present invention without performing work worthy of inventive step are all within the scope of the protection of the present invention.

[0019] Also, the terms "first" and "second" are used merely for the purpose of explanation and should not be understood 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 belongs.

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

[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 the aggregation of the above primary particles.

[0024] This application relates to a material having a 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), which includes 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, and provides a cathode material satisfying 0 < R2 - R1, 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 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 R2.

[0025] The positive electrode material relating to this application comprises 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. mixture By forming the cathode material in this way, the crystal structure mechanics of the larger second particles are made more stable, improving the structural stability of the cathode material. The smaller first particles provide a large specific surface area, thereby increasing the lithium storage sites and increasing the discharge capacity of the cathode material. Furthermore, by controlling the molar ratio of Ni and Mn in the first particles to be different from that of the second particles, the Ni content in the first particles is made relatively low, reducing the possibility of dislocation defects and oxygen deposition due to Ni mixing in the first particles. This reduces side reactions on the particle surface. The larger size of the second particles makes the crystal structure mechanics of the second particles more stable. In addition, the relatively high Ni content of the second particles allows for the mitigation of internal stress caused by small amounts of Ni mixing within the second particles, even if dislocation defects occur due to small amounts of Ni mixing. This reduces the internal stress caused by the overall size, mitigating degradation of the crystal structure, making mixing and oxygen deposition less likely, and further reducing particle collapse. Therefore, when the cathode material satisfies the above relationship between particle size and elemental distribution, it is possible to effectively improve the structural stability of the material, reduce particle breakdown, and improve its cycle performance and capacity retention rate.

[0026] Specifically, the range of n may 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, and of course, it may be any other value within the above range. The range of x may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 0.92, and the range of y may be 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, etc.

[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 satisfies any of the following conditions (1) to (5): (1) The R 2 -R 1 The value of is within the range of 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5, or any two numbers selected from these, or (2) 0.01 ≤ R 2 -R 1 (3) 0.04 ≤ R 2 -R 1 (4) 0.07 ≤ R 2 -R 1 (5) 0.17 ≤ R 2 -R 1 The value is ≤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, which has the advantage. After ensuring that the distribution of the whole main element is uniform, it can reach the Ni content with a gradient between the large particles and the small particles. Thereby, the material has higher structural stability, alleviates the collapse of the lattice structure, and improves 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 diameter of the second particles is 2.5 μm to 3.5 μm. Controlling the particle diameter within the above range is advantageous for the diffusion and transport of lithium ions, reduces the internal resistance between particles, and improves the capacity and rate performance of the material. Preferably, the average particle diameter of the second particles is 2.6 μm to 3.5 μm.

[0032] In the present application, by aggregating the first particles having a maximum diameter of 1.5 μm or less and the second particles having a maximum diameter of 2.5 μm or more to form a cathode material, the crystal structure mechanics of the larger-sized second particles can be made more stable. Even if dislocation defects due to a small amount of Ni mixing occur inside, the internal stress generated by the overall size can be relaxed, the deterioration of the crystal structure can be alleviated, the phenomena of mixing and oxygen precipitation are less likely to occur, and more lithium storage activity can be provided, thereby improving the capacity of the cathode material. It is understood that the first particles with a relatively small size have a low content of Ni, can originally reduce the possibility of lattice defects and oxygen precipitation due to Ni mixing, make the crystal structure more stable, reduce the surface side reactions of the cathode material, and the specific surface area of the first particles is relatively large, providing high activity to increase the lithium storage sites and increase the discharge capacity of the cathode material.

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

[0034] In some embodiments, the cathode 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 + , restrains a part of Li + , is disadvantageous to 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 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] <s Specifically, XRD diffractionThe precursor of the positive electrode material was measured, and the precursor of the positive electrode material had diffraction peaks at 35.4°±1° and 43.3°±1°, respectively. Note that "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, and may be, for example, NiO having a rock salt phase. Some of the particles have a spinel phase, and may be, for example, NiMn2O4. When the particles of the rock salt phase precursor are sintered, they form particles with a relatively large particle size, and the longest diameter of the primary particles after sintering is large and the nickel content is high. When the precursor particles of the spinel phase are sintered, they form particles with a relatively small particle size, and the longest diameter of the primary particles after sintering is small and the nickel content is low.

[0039] In some embodiments, the positive electrode material is a single-crystal material comprising a plurality of crystal grains, each crystal grain comprising a plurality of primary particles, each primary particle comprising a first particle and / or a second particle, and the orientation of all primary particles within at least one crystal grain is the same. The average particle diameter of the single crystal grain is 1 μm to 5 μm. Compared to conventional polycrystalline materials, single-crystal materials have a more stable structure, a more uniform distribution of body phase components, and better particle strength, significantly reducing particle cracking during the electrode piece pressing process, improving the pressing density and volumetric energy density of the electrode piece, which is advantageous for the overall energy density of the battery, and avoiding the occurrence of microcracks during the cycle process within the aggregate of the polycrystalline material, thereby providing high high-voltage performance and cycle stability. In this application, a single crystal grain is formed by the aggregation of a plurality of primary particles, and both the first and second particles are primary particles. Furthermore, a 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 interposed between the first particle and the second particle.

[0040] In some embodiments, the cathode material is a single-crystal material comprising a plurality of crystal grains, each crystal grain comprising a plurality of primary particles, each primary particle comprising a first particle and / or a second particle, the orientation of the primary particles within at least one crystal grain being the same, and the average particle diameter of the single crystal grain being 1 μm to 5 μm. The presence of a single crystal grain with the same orientation in the cathode material can be measured by electron backscatter diffraction (EBSD), and by observing the color of a single primary particle within a single crystal grain, it can be determined whether all primary particles within that crystal grain are a single crystal grain with the same orientation, and by observing the EBSD or SEM image, the particle diameter of the selected single particle with the same orientation (i.e., the average particle diameter of the single crystal grain) can be determined.

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

[0042] The difference between single-crystal cathode materials and polycrystalline ternary cathode materials (i.e., polycrystalline secondary particles) lies in the fact that polycrystalline secondary particles are secondary particles formed by the aggregation of primary particles. Furthermore, in single-crystal cathode materials, the smallest particles are typically monomeric primary particles on the order of microns. Generally, in addition to EBSD measurement, scanning electron microscopes (SEM), transmission electron microscopes (TEM), and X-ray diffraction (XRD) can be used to determine whether the obtained cathode product is a single-crystal material. Even for general single-crystal cathode materials, SEM is an important and reliable measurement method, as the external shape of the single-crystal particles is generally regular or irregular polyhedral, and there is no significant particle aggregation. TEM is a supplementary second measurement method used to observe whether the orientation of the crystal planes of the obtained product matches, and further measurements are performed in conjunction with limited-field electron diffraction (SAED). All of the above methods are used to determine whether or not the material is a single-crystal cathode material. For ease of understanding, the single-crystal cathode material of the present invention is understood to include cathode material particles in which all primary particles within at least one crystal grain have the same orientation, and the average particle diameter of the single crystal grain is 1 μm to 5 μm.

[0043] In this application, a single crystal grain is understood to be a single particle consisting of one primary particle. In the above single-crystal cathode material, a small amount of "pseudo-secondary particles" formed by the blocking of several single particles may be present. "Primary particle" refers to the smallest particle unit identified when observing the cathode active material with a scanning electron microscope, and "secondary particle" refers to a secondary structure formed by the aggregation of multiple primary particles, which exhibits a relatively rounded spherical shape. "Pseudo-secondary particle" refers to a particle formed by the blocking of several single particles, and the particle diameter of a single particle in the above pseudo-secondary particle is usually 1 μm to 5 μm, and generally, the degree of roundness of the "pseudo-secondary particle" is lower than that of the above general "secondary particle".

[0044] It should be noted that "single-crystal cathode materials" known to those skilled in the art are not "single crystals" in the strict sense. In crystallography, an ideal single crystal refers to a crystal with perfectly identical arrangement and orientation. However, due to limitations imposed by impurities, strain, and crystal defects, ideal single crystals are extremely rare and difficult to produce in the laboratory. Therefore, single-crystal cathode materials known in this art are often actually cathode materials in a "pseudo-single-crystal form," and only in size do they represent the large particle size of a pseudo-single crystal, differing from polycrystalline materials composed of many small primary particles.

[0045] In some embodiments, the median diameter of the positive electrode material satisfies 2.5 μm ≤ median diameter ≤ 5 μm (where the median diameter is equal to the particle diameter D). 50 dea Specifically, this refers to the particle size at which the cumulative volume proportion in the particle volume size distribution is 50%. If the particle size of the single crystal particles is too large, the ion transport pathway becomes longer, increasing the internal resistance of the particles. This slows down the reaction kinetics of the cathode material, reducing its capacity and rate performance.

[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 the above range is advantageous for improving the processing performance of the positive electrode material.

[0047] In some embodiments, the LiOH content (by mass) in the positive electrode material is 100 ppm. <m LiOH The limit is ≤1500 ppm, and may specifically 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. The Li2CO3 content (mass) in the positive electrode material is 100 ppm. <m Li2CO3The limit is ≤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 cathode material mainly refer to Li2CO3 and LiOH, and it is understood that controlling the content of LiOH and Li2CO3 on the surface of the cathode material within the above range reduces the corrosive effect of alkaline impurities on the cathode material, protects the structural stability of the cathode material, and is advantageous in improving the cycle stability of the cathode material.

[0048] In some embodiments, the free lithium content in the cathode material is 100 ppm. <m Li The limit is ≤2000 ppm. Specifically, this may be, but is not limited to, 110 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 800 ppm, 1000 ppm, 1500 ppm, or 2000 ppm.

[0049] In some embodiments, the specific surface area of ​​the positive electrode material is 0.5 m². 2 / g~1.5m 2 It is / 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 It may be / g, or of course, any other value within the above range, and is not limited to these. By controlling the specific surface area of ​​the cathode material within the above range, the cathode 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 positive electrode material is 1.5 g / cm³. 3 ~3.0g / cm 3Specifically, 1.5 g / cm³ 3 1.6 g / cm³ 3 1.7 g / cm³ 3 1.8 g / cm³ 3 1.9 g / cm³ 3 2.0 g / cm³ 3 , 2.1 g / cm³ 3 , 2.2 g / cm³ 3 2.4 g / cm³ 3 2.5 g / cm³ 3 2.8 g / cm³ 3 Or 3.0 g / cm³ 3 It may be any of the above values, and of course, it may be any other value within the above range, and is not limited to these. 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 press density of the positive electrode material is 2.5 g / cm³. 3 ~4.0g / cm 3 Specifically, 2.5 g / cm³ 3 2.6 g / cm³ 3 2.7 g / cm³ 3 2.8 g / cm³ 3 2.9 g / cm³ 3 3.0 g / cm³ 3 3.1 g / cm³ 3 3.2 g / cm³ 3 3.4 g / cm³ 3 3.5 g / cm³ 3 3.8 g / cm³ 3 Or 4.0 g / cm³ 3 It may be any of the above values, and of course, it may be any other value within the above range, and 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 embodiment, the present application provides a method for manufacturing a cathode material, the method for manufacturing the precursor of the cathode material as shown in Figure 1, The method includes the step of obtaining a cathode material by subjecting a mixture containing an oxide precursor of a cathode material and a lithium source to a primary sintering treatment, and crushing the primary sintering product, wherein the oxide precursor of the cathode material has diffraction peaks at 35.4°±1° and 43.3°±1°, respectively, in the X-ray diffraction pattern.

[0053] In the method for manufacturing the positive electrode material according to the present invention, the positive electrode material precursor used has diffraction peaks at 35.4°±1° and 43.3°±1°, respectively. "Having a diffraction peak at 43.3°±1°" indicates that some of the particles in the positive electrode material precursor have a rock salt phase, and may be, for example, NiO having a rock salt phase. "Having a diffraction peak at 35.4°±1°" indicates that some of the particles in the positive electrode material precursor have a spinel phase, and may be, for example, NiMn2O4. The rock salt phase precursor particles tend to form particles with relatively large particle diameters through nucleation and growth during the sintering process with lithium salt, resulting in a high nickel particle content after sintering, a large maximum particle diameter, and a more stable crystalline phase structure that can withstand high nickel content and does not collapse. Furthermore, in the sintering process with lithium salt, the spinel phase precursor particles have a high nucleation energy barrier. As a result, the size of the sintered particles is relatively small, the longest particle diameter is small, and the nickel content is low. This reduces the possibility of lattice defects and oxygen deposition due to Ni mixing, and decreases side reactions on the particle surface. Therefore, the cathode material produced by sintering the aforementioned precursor can effectively improve the structural stability of the material, reduce particle collapse, and improve its cycle performance and capacity retention rate.

[0054] The manufacturing method of this invention will be described in detail below with reference to the examples.

[0055] A mixture of an oxide precursor and a lithium source is subjected to primary sintering treatment, and the primary sintering product is crushed to obtain a cathode material in which the oxide precursor of the cathode material has diffraction peaks in both the range of 34.4° to 36.4° and the range of 42.3° to 44.3° in the 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 temperature of the annealing treatment 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 time of the annealing treatment 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 amounts of lithium source and cathode material precursor added satisfy the following: 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, and may specifically be 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, and of course may be other values ​​within the above range, but are not limited to these. Within this range, the degree of Li / Ni cation mixing can be reduced, and the processability and safety that would be compromised if the amount of residual lithium on the surface of the calcined product is too high can be prevented.

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

[0062] In some embodiments, the dopant comprises 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 dopant containing the metal M2 is a compound of Zr or Ti.

[0063] In some embodiments, the mixing conditions for obtaining the mixture involve solid-phase mixing at 10°C to 50°C for 0.3 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, and of course, it may be other values ​​within the above range, and is not limited to these. Preferably, the solid-phase mixing temperature is 10°C to 35°C.

[0065] In some embodiments, the amounts of the dopant and cathode material precursor added satisfy the following: the molar amount of M2 is in a ratio of (0.01 to 0.04) to the total molar amount of metal in the cathode material precursor, which may be 0.01:1, 0.02:1, 0.03:1, 0.04:1, etc., and of course may be other values ​​within the above range, but are not limited to these.

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

[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 treatment is carried out in an oxygen-containing atmosphere, where the oxygen gas content in the oxygen-containing atmosphere is 95% or more.

[0069] In some embodiments, the temperature of the primary sintering process 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 these values, and other unlisted values ​​within this range are also applicable. This range promotes the oxidation of divalent nickel to trivalent nickel and reduces the mixing of Li / Ni cations.

[0070] In some embodiments, the holding time for the primary sintering process is 6 to 48 hours, specifically 6, 8, 10, 12, 15, 18, 24, 36, or 48 hours, but is not limited to these values, and other unlisted values ​​within that range are also applicable.

[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 holding time is 8 to 10 hours.

[0072] In some embodiments, the method includes mixing a crushed substrate material with a metal M3-containing coating agent, 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 2.5 μm to 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 value must satisfy ≤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 broad particle size distribution, which is advantageous for improving the lamination press density of the cathode material and further improving the gram capacity of the cathode material.

[0075] In some embodiments, the crushing method includes at least one of a double-roll crusher, a plow shear mixer / crusher, and an air-jet 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 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, where the oxygen gas content in the oxygen-containing atmosphere is 95% or more.

[0078] In some embodiments, the temperature of the secondary sintering process 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, but is not limited to the values ​​listed above, and other unlisted values ​​within that range are also applicable.

[0079] In some embodiments, the holding time for the secondary sintering process is 6 to 24 hours, and specifically may be 6 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, or 24 hours, but is not limited to the values ​​listed above, and other values ​​within that range that are not listed are also applicable.

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

[0081] In some embodiments, the manufacturing method further includes cooling, sizing, and sieving the product after secondary sintering. The sizing includes at least one of grinding, polishing, ball milling, or air-jet grinding.

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

[0083] In a third embodiment, the present application provides a battery comprising the above-described positive electrode material or a positive electrode material manufactured by the above-described manufacturing method.

[0084] The foregoing are merely preferred embodiments of the present invention and are not intended to limit it. Any modifications, substitutions with equivalents, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0085] The present invention will be further described below with reference to several embodiments. However, the embodiments of the present invention are not limited to the following specific embodiments. They 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) in the precursor and cathode materials: Equipment: Agilent 5110 ICP-OES plasma inductive coupling tester. Method: Aqua regia was added to 0.3 g of the sample to decompose it, and after cooling to a fixed volume, 1 mL of the decomposed solution was taken, and the mass content of the main elements Li / Ni / M / Mn, diluted 100-fold, was measured. The molar content was then obtained by converting the content (mass).

[0087] (2) Measurement of XRD diffraction peaks of cathode material precursors: Equipment: X'Pert Powder (Panalytical) or Bruker X-ray diffraction tester products. Method: Fill the sample cell with the powder sample, flatten the top surface with a glass sheet, and ensure that the sample top surface and the cell edge are parallel. The scanning range is 2θ = 10° to 90°, and the total scanning time is 5 minutes or more. After scanning is complete, open the sample in Jade software and perform an automatic peak search using Analysis → Find Peaks to identify the position and height of the diffraction peaks.

[0088] (3) Measurement of alkali impurities in the cathode material: In a sealed glass flask, 5.0 g of cathode 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, a 0.1 mol / L HCl solution was added at a rate of 0.5 mL / min, and the pH curve was recorded while titrating 90 mL of the clear solution until the pH reached 3. The titration determined the low concentrations of LiOH and Li2CO3 dissolved in the deionized water, and a reference voltage curve was obtained. The first plateau, with an endpoint y1 (unit: mL) between pH 8 and pH 9, was determined to be the OH - The second plateau, which has an endpoint y2 (unit: mL) between pH 4 and pH 6, is determined by the HCO3 content (mass). - This represents the content (mass) of H2CO3. 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. Subsequently, the percentages (weight) of LiOH, Li2CO3, and free lithium (Free Li) are expressed as shown in equations (3), (4), and (5) below.

number

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

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

[0091] (6) Method for measuring the specific surface area of ​​the positive electrode material: Equipment: The specific surface area of ​​the cathode material is measured using a Tristar 3020 type microphone, which measures specific surface area and hole diameter. Method: The mass m1 of an empty sample tube was weighed, 3g of sample was taken and introduced into the sample tube through a long funnel, degassed under vacuum at 300°C for 1 hour, and after cooling, the mass m2 of the sample tube was weighed, so the mass of the sample is m = m2 - m1. The sample tube was placed in liquid nitrogen, and the amount of nitrogen gas adsorbed by the sample V was measured at a series of relative pressures P / P0 to obtain adsorption isotherms. P / P0 was set to 0.05 / 0.1 / 0.15 / 0.20 / 0.25 / 0.30. The isothermal adsorption curves were fitted, and the monolayer saturated adsorption amount Vm was calculated from the slope and intercept, and then the specific surface area was calculated from Vm.

[0092] (7) Measurement of the Kantap density of the cathode material: Equipment: A tap density meter manufactured by Cantachrome (model number: DAT-4-220) will be used. Method: After cleaning the graduated cylinder, weigh the mass m1 of the graduated cylinder, place approximately 50g of sample into the graduated cylinder, make the sample surface as horizontal as possible, wipe the area around it with tissue paper, weigh the total mass m2 of the sample and graduated cylinder, place the graduated cylinder on the vibrating table, secure it with the three symmetrical fixing legs, activate the instrument, set the number of vibrations to 5000, press the vibration switch, and after the instrument vibrates for the specified number of times it will stop automatically, remove the graduated cylinder, and read the volume of the sample. If the sample surface after tapping is horizontal, read the volume directly; if it is slanted, take the average reading V of the highest and lowest points, and the tap density = (m2-m1) / V.

[0093] (8) Measurement of press density of positive electrode material: The press density of the cathode material was measured using a Carver 4350 in the USA. The procedure involved weighing 1g of sample, introducing it into the mold, pressurizing it at a pressure of 3T for 30s, and then measuring the height after pressurization to calculate the press density.

[0094] (9) Measurement of the average particle size of the positive electrode material: Cross-sectional SEM measurements were performed on the cathode material. An image with a magnification of 3000x was selected, and the particle diameter of all primary particles was measured using Nano Measure software. The longest particle diameter was selected during measurement, and after the measurement of all particles in the image was completed, the longest diameters of the first particles, all of which were less than 1.5 μm, were statistically calculated and the average value was obtained to obtain the average particle diameter of the first particles. The longest diameters of the second particles, all of which were greater than 2.5 μm, were statistically calculated and the average value was obtained to obtain the average particle diameter of the second particles. The average particle diameter of the cathode material was determined by averaging the longest diameters of all particles in the image.

[0095] (10) Measurement of cathode material by SEM and EDS: Equipment: Hitachi S4800 scanning electron microscope, OXFORD Instruments energy-dispersive spectrometer. SEM measurement method: When measuring powder samples, the powder sample is attached using an instrument such as tweezers, spread flat on a conductive adhesive, and measured under electron beam conditions of 5kV / 10mA. When measuring cross-sectional samples, the material is coated onto aluminum foil using a general electrode manufacturing method, cut with a focused ion beam (FIB), and then measured under the same conditions as when measuring powder samples with an SEM. EDS measurement method: After adjusting the electron beam voltage of the SEM to 15kV or higher, the limited field of view is measured by EDS, and the range of the limited field of view is the central part of each single crystal grain. To determine the average value of the Ni / Mn elemental 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) are selected and EDS measurements are performed on each, and the Ni / Mn ratios of the 10 first particles and the 10 second particles are obtained, respectively. The maximum and minimum values ​​are removed from the obtained Ni / Mn ratios of the 10 first particles, and the average value of the remaining 8 values ​​is calculated to obtain R1. The maximum and minimum values ​​are removed from the obtained Ni / Mn ratios of the 10 second particles, and the average value of the remaining 8 values ​​is calculated to obtain R2.

[0096] (11) SO in positive electrode materials 4 2- Method for measuring the content: SO4 2-Regarding the method for measuring the content, after pretreating the sample solution, it is separated by an ion chromatography column, and quantitative analysis is performed using the relationship between the separated sulfate ion concentration and the detection signal. Ion chromatography usually uses a conductivity detector as the detection means, and determines the concentration of sulfate ions by monitoring the change in conductivity. The measurement results are shown in Table 2.

[0097] (12) Measurement of electrochemical properties: 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) at a mass ratio of 96:2:2, uniformly mixed to produce a positive electrode slurry, applied to a positive electrode current collector, and vacuum dried. After that, a positive electrode sheet (the press density of the sheet is 2.8 g / cm 3 is formed), and a lithium sheet is used as the negative electrode and assembled into a 2016 button battery in a glove box. In the discharge range of 3.0 V to 4.3 V, under the condition of a 1C theoretical capacity of 250 mAh / g, measurements were carried out using a CT2001A type battery detection system manufactured by WuhanLAND Electronic Co., Ltd., and the details of the measurement results are shown in Table 3.

[0098] (13) Measurement of the orientation of primary grains in crystal grains: Equipment: A backscattered electron diffraction meter (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 is possible to determine whether a single crystal grain containing all primary particles with the same orientation exists within the crystal grain. If the colors of all primary particles within the crystal grain are the same, it is determined that the orientations of all primary particles within the crystal grain are the same.

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

[0100] As shown in Figure 2c, the cathode material manufactured in the embodiment of the present invention has a morphology in which the particles are single, rounded particles with few cross-sectional areas due to fracture on the surface.

[0101] As shown in Figure 2d, the results of cross-sectional SEM and EDS measurements show that the Ni / Mn ratios at 10 locations for the first particle with a particle diameter 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 value R1 of 1.87 excluding the highest and lowest values. The Ni / Mn ratios at 10 locations for the second particle with a particle diameter 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 value R2 of 1.89 excluding the highest and lowest values. The remaining measurement results are shown in Table 2.

[0102] Example 2 (1) Select an oxide precursor of the cathode material produced by the pyrolysis method, and as shown in Table 1, its general formula is Ni0.9 Co 0.05 Mn 0.05 O x (The deviation in the molar content of each major element is within ±1%). The cathode material precursor was measured by XRD and, as shown in Figure 3a, has one diffraction peak at 35.9° and 43.3°, respectively, and as shown in Figure 3b, the morphology of the cathode material precursor is secondary particles formed by the aggregation of multiple primary particles. (2) The cathode material precursor and Li2CO3 were mixed so that the molar ratio of Li / Me (where Me is the sum of Ni, Co, and Mn) was 1.01:1. 2000 ppm of TiO2 was added relative to the content (mass) of the cathode material precursor, and primary sintering was performed at 800°C for 8 hours under an oxygen atmosphere. The reason the sintering temperature was lower than in Example 1 is the higher Ni content. In order to ensure a similar grain size according to the properties of the ternary material, the sintering temperature should be inversely proportional to the Ni content. (3) The primary sintering product was crushed in a plow shear for 30 seconds to obtain the substrate material. (4) The substrate material and 2000 ppm WO3 were mixed and secondary sintered at 550°C for 8 hours in an oxygen atmosphere. The secondary sintered product was then sieved through a 325 mesh screen to obtain the cathode material.

[0103] figure 3 As shown in c, the cathode material manufactured in the embodiment of the present application has a morphology in which the particles are single, rounded particles with few cross-sectional areas due to fracture on the surface.

[0104] As shown in Fig. 3d, from the results of cross-sectional SEM and EDS measurements, the Ni / Mn ratios at 10 locations of the first particles within the range of particle size of 1.5 μm or less are 19.05, 19.59, 18.42, 19.02, 23.66, 21.32, 20.37, 20.51, 19.64, and 17.60 respectively. Excluding the highest and lowest values, the average value R1 is 19.74. The Ni / Mn ratios at 10 locations of the second particles within the range of particle size of 2.5 μm or more are 19.55, 19.04, 15.59, 22.68, 19.15, 19.17, 18.17, 20.65, 21.54, and 21.13 respectively. Excluding the highest and lowest values, the average value R2 is 19.80. The remaining measurement results are shown in Table 2.

[0105] Example 3 Example 1 is different from the above in the following points. (1) An oxide precursor of the cathode material manufactured by the thermal decomposition method is selected. 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 cathode material further contains 85 ppm of Ca.

[0106] Example 4 Example 1 is different from the above in the following points. (4) The substrate material and 1000 ppm of ZrO2 are mixed, and secondary sintering is performed at 850 °C for 8 hours in an oxygen atmosphere. After sieving the secondary sintering product with a 325-mesh screen mesh, the cathode material is obtained.

[0107] Example 5 Example 2 is different from the above in the following points. (4) The substrate material and 1000 ppm of WO3 are mixed, and secondary sintering is performed at 880 °C for 8 hours in an oxygen atmosphere. After sieving the secondary sintering product with a 325-mesh screen mesh, the cathode material is obtained.

[0108] Example 6 This differs from Example 3 in the following respects. (4) The substrate material was mixed with 1000 ppm MgO and secondary sintered at 960°C for 8 hours in an oxygen atmosphere. The secondary sintered product was then sieved through a 325 mesh screen to obtain the cathode material.

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

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

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

[0112] Example 10 This differs from Example 1 in the following respects. In step (1), the selected material was Ni produced by the coprecipitation method. 0.6 Co 0.1 Mn 0.3 The hydroxide precursor is (OH)2, and by annealing at 730°C for 8 hours, an oxide precursor for the cathode material was obtained, and as shown in Table 1, the general formula is Ni 0.6 Co 0.1 Mn 0.3 O x (The deviation in the molar content of each principal element is within ±1%). The sulfate content of the manufactured cathode material is high at 830 ppm, and Li +Because movement is inhibited, the material is inferior to the volume, rate, and capacity of Example 1.

[0113] Example 11 This method differs from Example 1 in the following respects: The primary sintering temperature was reduced from 900°C to 820°C.

[0114] Example 12 This differs from Example 1 in the following respects: In step (1), the selected material was Ni produced by the sol-gel method. 0.6 Co 0.1 Mn 0.3 (OH)2 hydroxide precursor, annealed at 600°C for 4 hours, yields an oxide precursor for the cathode material, and its general formula is Ni 0.6 Co 0.1 Mn 0.3 O x (The deviation in the molar content of each principal element is within ±1%). The sulfate content of the resulting cathode material is high at 1240 ppm.

[0115] Example 13 This differs from Example 1 in the following respects. An oxide precursor of the cathode material produced by the thermal decomposition method was selected, and as shown in Table 1, the general formula is Ni 0.34 Co 0.33 Mn 0.33 O x (The deviation in the molar content of each principal element is within ±1%).

[0116] Example 14 This differs from Example 1 in the following respects. An oxide precursor of the cathode material produced by the thermal decomposition method was selected, and as shown in Table 1, the general formula is Ni 0.45 Co 0.25 Mn 0.30 O x (The deviation in the molar content of each principal element is within ±1%).

[0117] Example 15 This differs from Example 1 in the following respects. An oxide precursor of the cathode material produced by the thermal decomposition method was selected, and as shown in Table 1, the general formula is Ni 0.55 Co 0.12 Mn 0.33 O x (The deviation in the molar content of each principal element is within ±1%).

[0118] Example 16 This differs from Example 1 in the following respects. An oxide precursor of the cathode material produced by the thermal decomposition method was selected, and as shown in Table 1, the general formula is Ni 0.83 Co 0.08 Mn 0.09 O x (The deviation in the molar content of each principal element is within ±1%).

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

[0120] As shown in Figure 4c, the morphology of the cathode material is relatively angular single-crystal grains, and cross-sections due to fracture on the surface can be observed. As shown in Figure 4d, from the results of SEM and EDS measurements of the particle cross-section of the cathode material, the Ni / Mn ratios at 10 locations for the first particles in the range of particle diameter 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 value R1 of 1.89 excluding the highest and lowest values. The Ni / Mn ratios at 10 locations for the second particles in the range of particle diameter 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 value R2 of 1.86 excluding the highest and lowest values.

[0121] Comparative Example 2 This differs from Example 2 in the following respects. (1) Select an oxide precursor of cathode material manufactured by a general coprecipitation method, and as shown in Table 1, the general formula is Ni 0.9 Co 0.05 Mn 0.05 O x (The deviation in the molar content of each major element is within ±1%). The cathode material precursor 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 This differs from Example 3 in the following respects. (1) Select an oxide precursor of the cathode material manufactured by a general coprecipitation method and perform ICP measurement. As shown in Table 1, the general formula is Ni 0.67 Co 0.05 Mn 0.28 O x (The deviation in the molar content of each major element is within ±1%). The cathode material precursor 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 table of cathode materials between examples and comparative examples. TIFF0007880501000002.tif108152

[0124] Table 2: Comparison table of cathode materials between examples and comparative examples. TIFF0007880501000003.tif120130

[0125] Manufacturing of positive electrode materials The cathode material precursors produced in each example and comparative example were mixed with LiOH in 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 mixed mixture was sintered at 730°C for 25 hours in a 95% oxygen atmosphere, cooled, crushed, and sieved to obtain the cathode material.

[0126] Button-type batteries were assembled, electrochemical measurements were performed, and the measurement results are shown in Table 3.

[0127] Table 3: Comparison table of cathode materials between examples and comparative examples. TIFF0007880501000004.tif96162

[0128] The cathode materials according to Examples 1 to 7 have different molar ratios of Ni and Mn elements in the cathode material containing two types of particles, and the molar ratio of nickel to manganese in the larger particles is made greater than the molar ratio of nickel to manganese in the smaller particles. That is, by relatively lowering the Ni content in the first particles within the range of particle diameter less than 1.5 μm, the possibility of lattice defects and oxygen deposition due to Ni mixing can be reduced, and side reactions on the particle surface can be reduced. On the other hand, the specific surface area of ​​the first particles within the range of particle diameter less than 1.5 μm is relatively increased, resulting in high activity, an increase in lithium storage sites, and an improvement in the specific capacity of the material. The cathode material can effectively improve the specific capacity and high initial efficiency performance of the cathode material, as well as improve structural stability and cycle performance.

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

[0130] Similarly, a comparison was made between Comparative Example 2 and Example 2, and between Comparative Example 3 and Example 3, based on ternary materials with different Ni / Co / Mn content. The results showed that in both different ternary systems, a relatively high Ni content in larger particles and a relatively low Ni content in smaller particles resulted in superior electrochemical performance.

[0131] Furthermore, based on the above examples, a more preferable embodiment can be discovered by comparing different material parameters under different manufacturing conditions.

[0132] As can be seen from the measurement data of Examples 1, 4, 7, and 8, all of the above examples are based on a ternary cathode material system of Ni:Co:Mn=6:1:3, but because the doping auxiliary materials used in the sintering process differ, differences occur in the distribution of Ni elements, affecting parameters such as particle size, surface residual lithium, tap density, and press density. By comparing the electrochemical performance of the cathode materials, it was found that Example 1 had optimal capacity, rate, and cycle performance, and that doping with Nb element had a superior effect on the electrochemical performance of the cathode material compared to doping with Zr and W element. Although doping with W element results in a slight increase in surface residual lithium and is consistent with the protections of this patent, it is not the most preferable solution. Example 8, which does not use doping, has low capacity and initial efficiency. Therefore, selecting and doping with appropriate elements during the manufacturing process of the cathode material is advantageous for improving the electrochemical performance of the cathode material.

[0133] As can be seen from the measurement data of Example 2 and Example 5, both were manufactured using a ternary cathode material with a high nickel content of Ni:Co:Mn=90:5:5. The difference between the two lies in the doping content of W. As the W content increases, the R2-R1 value of the resulting cathode material precursor clearly increases. By comparing the electrochemical performance of the cathode materials obtained by manufacturing these cathode material precursors, it can be seen that the R2-R1 value of the cathode material precursor in Example 5 is higher, the structural stability of the cathode material deteriorates, and 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 a ternary cathode material with an elemental ratio of Ni:Co:Mn = 67:5:28. The R2-R1 value of Example 3, which was doped with Nb, was lower than that of Example 6, which was doped with Mg. Comparing the electrochemical performance of Example 6 and Example 3, it can be seen that a higher R2-R1 value within a certain range is advantageous for improving the structural stability of the cathode material, resulting in better discharge ratio capacity and high-temperature cycle performance of Example 6. However, a comprehensive analysis of Examples 2 and 5 reveals that if the R2-R1 value is too high, the distribution of metal elements in the cathode material becomes unbalanced, which may worsen the structural stability of the cathode material.

[0135] As can be seen from the measurement data of Example 1 and Example 11, Example 11 has a lower sintering temperature, resulting in insufficient energy for grain growth. It does not form single-crystal grains with a single grain size in the range of 1 μm to 5 μm, but rather a polycrystalline form with a single grain size of only 0.88 μm. In this form, many grain boundaries exist between the materials, and during charging and discharging, lithium ions are frequently released and absorbed, leading to intense grain boundary dislocations, poor crystal structure stability, and low cycle stability.

[0136] As can be seen from the measurement data of Example 1 and Example 12, free SO4 in the cathode material 2- The high content of SO4 negatively affects the volume and rate of the material, and also causes excessive SO4 to be released onto the surface. 2- This also affects the stability of the SEI film and reduces its cycle performance.

[0137] As can be seen from the measurement data of Examples 13 to 16, when cathode materials based on ternary materials with different Ni / Co / Mn content satisfy the particle size and distribution rules of Ni and Mn elements of this application, they all exhibit good material structural stability, high cycle performance, and capacity retention.

[0138] The foregoing describes only preferred embodiments of the present invention and is not intended to limit the invention. To those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and principles of the present invention should be understood to be within the scope of protection of this application.

Claims

1. General formula: Li ｎ Ni １－ｘ－ｙ M ｘ Mn ｙ O ２ (However, this is shown as 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 maximum diameter of 1.5 μm or less and second particles having a maximum diameter of 2.5 μm or more, Let the average value of the molar ratio of Ni element to Mn element in the first particle measured by energy dispersive spectroscopy (EDS) be R １ and let the average value of the molar ratio of Ni element to Mn element in the second particle measured by energy dispersive spectroscopy (EDS) be R ２ Then, 0 < R ２ −R １ < 0.5 is satisfied, The cathode material has an average particle diameter of 2.5 μm to 3.5 μm.

2. The positive electrode material according to claim 1, satisfying at least one of the following features (1) to (2). (1) In the positive electrode material, R １ It is >0.

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

6.

3. The aforementioned R ２ -R １ The positive electrode material according to claim 1, wherein the value of satisfies any of the following conditions (1) to (5). (1) The R ２ -R １ The value is either 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5, or a range consisting of both numbers 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 The value is ≤ 0.

41.

4. The positive electrode material according to claim 1, wherein the average particle diameter of the first particles is 0.5 μm to 1.5 μm.

5. The positive electrode material according to claim 1, satisfying at least one of the following features (1) to (2). (1) The positive electrode material is a general formula: Li ｎ Ni １－ｘ－ｙ M ｘ Mn ｙ M2 ｚ O ２ (However, 0 ≤ z < 1, and 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) (2) The positive electrode material is a general formula: Li ｎ Ni １－ｘ－ｙ M ｘ Mn ｙ M2 ｚ M3 ｕ O ２ (However, 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)

6. The positive electrode material according to claim 1, satisfying at least one of the following technical features (1) to (2). (1) 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 a first particle and / or a second particle, and the orientation of all primary particles in at least one of the crystal grains is the same. (2) 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 a first particle and / or a second particle, the orientation of all primary particles in at least one crystal grain being the same, and the average particle diameter of the primary particles being 1 μm to 5 μm.

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

8. The positive electrode material according to claim 1, wherein the sulfate content is 800 ppm or less.

9. The positive electrode material according to claim 1, satisfying at least one of the following features (1) to (3). (1) The pH of the positive electrode material satisfies 11.0 ≤ pH ≤ 12.

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

10. The positive electrode material according to claim 1, satisfying at least one of the following features (1) to (4). (1) The free lithium content (mass) in the positive electrode material is 100 ppm < m Ｌｉ The concentration is ≤2000 ppm. (2) The specific surface area of ​​the positive electrode material is 0.5 m². ２ / g to 1.5m ２ It is / g. (3) The tap density of the positive electrode material is 1.5 g / cm³. ３ ~3.0 g / cm ３ That is the case. (4) The press density of the positive electrode material is 2.5 g / cm³. ３ ~4.0 g / cm ３ That is the case.

11. A battery comprising the positive electrode material according to any one of claims 1 to 10.

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