A hybrid high-nickel cathode material and its preparation method

Abstract

This invention provides a hybrid high-nickel cathode material and its preparation method. The hybrid high-nickel cathode material is formed by wet mixing of polycrystalline large particles, polycrystalline small particles, and single crystal particles in a molar ratio of 1:m:n, followed by coating with a coating agent and sintering, wherein 5≤l≤10, 0≤m≤5, 0≤n≤5, and 1+m+n=10. The hybrid high-nickel cathode material of this invention has a wide particle size distribution, high material filling rate, high particle coordination number, and uniform surface coating, thereby increasing the energy density of lithium-ion batteries, improving rate performance, reducing surface residual alkali, and improving cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode materials, and relates to a hybrid high-nickel cathode material and its preparation method. Background Technology

[0002] Lithium-ion rechargeable batteries possess advantages such as high energy density, good cycle performance, low self-discharge, and small size, and have been widely used in mobile communication devices, small electronic products, aerospace, and biomedicine. Currently, the market is mainly dominated by lithium cobalt oxide and lithium iron phosphate, but the high cost of lithium cobalt oxide and the low capacity of lithium iron phosphate cannot meet the demands of the lithium battery consumer market. As the market demands higher energy density for cathode materials, high-nickel ternary materials such as NCM8 series and NCA will gradually become the mainstream.

[0003] High-nickel ternary cathode materials possess high specific capacity but lack high compaction density. Energy density, specific capacity, and compaction density are all positively correlated. Specific capacity is generally increased by raising the nickel content, but higher nickel content leads to more severe nickel-lithium mixing, significantly impacting material performance. Compaction density is typically achieved through a mixing process of large and small particles.

[0004] Currently, the mixing process of large and small particles has been gradually improved. For example, Chinese patent document CN103904310A discloses that precursors of two different particle sizes are separately sintered with lithium, and then mixed in different proportions after being crushed. Another example is Chinese patent document CN110010889A, which discloses that precursors of two different particle sizes are mixed, sintered with lithium, crushed, washed with water, and then sintered again. Yet another example is Chinese patent document CN111384372A, which discloses that a precursor is separately sintered with lithium at different temperatures to obtain polycrystalline and single-crystal products, which are then mixed and sintered after surface coating.

[0005] The above methods have insufficient particle size distribution and low particle filling rate, and all employ mechanical dry mixing. Due to powder agglomeration and electrostatic effects, dry mixing is prone to reverse homogenization, resulting in poor uniformity. Furthermore, the dot-like coating formed by dry mixing cannot provide effective protection and is prone to side reactions during charging and discharging, leading to battery bulging, poor cycle performance, and safety performance.

[0006] Therefore, there is a need in this field for a ternary cathode material with good overall performance and its preparation method. Summary of the Invention

[0007] The purpose of this invention is to provide a high-pressure, high-rate, and high-cycle hybrid ternary cathode material and its preparation method. This material has a wide particle size distribution, high material filling rate, high particle coordination number, and uniform surface coating, thereby increasing the energy density of lithium-ion batteries, improving rate performance, reducing surface residual alkali, and improving cycle performance.

[0008] Specifically, one aspect of the present invention provides a mixed high-nickel cathode material, wherein the mixed high-nickel cathode material is formed by wet mixing of polycrystalline large particles, polycrystalline small particles and single crystal particles in a molar ratio of 1:m:n and coating with a coating agent and then sintering, wherein 5≤l≤10, 0≤m≤5, 0≤n≤5, and 1+m+n=10;

[0009] The polycrystalline large particles are composed of the precursor Ni x M 1-x (OH)2 is sintered with lithium salt, wherein 0.6≤x<1, M is two or three elements selected from Co, Mn and Al, and the D50 particle size of the polycrystalline large particles is 10~15μm;

[0010] The polycrystalline particles are composed of the precursor Ni y M' 1-y (OH)2 is sintered with lithium salt, wherein 0.6≤y<1, M' is two or three elements selected from Co, Mn and Al, and the D50 particle size of the polycrystalline particles is 6~9μm;

[0011] The single crystal particles are composed of the precursor Ni z M” 1-z The single crystal particles are formed by sintering (OH)2 with lithium salt, wherein 0.6≤z<1, M is two or three elements selected from Co, Mn and Al, and the D50 particle size of the single crystal particles is 2~5μm.

[0012] In one or more implementations, 5 ≤ l < 10, 0 < m ≤ 5, 0 < n ≤ 5.

[0013] In one or more implementations, 6.5 ≤ l ≤ 7.5, 1.5 ≤ m ≤ 2.5, and 0.5 ≤ n ≤ 1.5.

[0014] In one or more embodiments, the D50 particle size of the polycrystalline large particles is 12-14 μm, the D50 particle size of the polycrystalline small particles is 6.5-7.5 μm, and the D50 particle size of the single crystal particles is 3.5-4.5 μm.

[0015] In one or more embodiments, the variance σ of the D50 particle size of the mixed high-nickel cathode material is ≤0.04.

[0016] In one or more embodiments, the D50 particle size of the mixed high-nickel cathode material is 8–13 μm, preferably 10–12 μm.

[0017] In one or more implementations, 0.8 ≤ x < 1, 0.8 ≤ y < 1, and 0.8 ≤ z < 1.

[0018] In one or more embodiments, M, M' and M” are all Co, Mn and Al; preferably, the molar ratio of Co, Mn and Al in M, M' and M” is (4-6):(3-5):1.

[0019] In one or more embodiments, the polycrystalline large particles, the polycrystalline small particles, and the single crystal particles are each independently formed by sintering a precursor and a lithium salt in a molar ratio of 1:(1 to 1.08).

[0020] In one or more embodiments, the coating agent is one or more compounds comprising one or more elements selected from lithium, manganese, aluminum, cobalt, magnesium, zirconium, strontium, barium, titanium, fluorine, silicon, boron, and phosphorus; preferably, the coating agent is ZrO2.

[0021] In one or more embodiments, the ratio of the amount of the coating agent to the total amount of the polycrystalline large particles, polycrystalline small particles and single crystal particles is (0.01 to 1):100, preferably (0.05 to 0.5):100.

[0022] Another aspect of the present invention provides a hybrid high-nickel cathode material, wherein the hybrid high-nickel cathode material is composed of polycrystalline large particles, polycrystalline small particles and single crystal particles in a molar ratio of 1:m:n, wherein 1+m+n=10, 6.5≤l≤7.5, 1.5≤m≤2.5, and 0.5≤n≤1.5;

[0023] The polycrystalline large particles are Li a Ni x M 1-x O2, where 1≤a≤1.08, 0.6≤x<1, M is two or three elements selected from Co, Mn and Al, and the D50 particle size of the polycrystalline large particles is 10~15μm;

[0024] The polycrystalline particles are Li b Ni y M' 1-y O2, where 1≤b≤1.08, 0.6≤y<1, M' is two or three elements selected from Co, Mn and Al, and the D50 particle size of the polycrystalline particles is 6~9μm;

[0025] The single crystal particles are Li c Ni z M' 1-z O2, where 1≤c≤1.08, 0.6≤z<1, and M” is two or three elements selected from Co, Mn and Al, and the D50 particle size of the single crystal particles is 2~5μm.

[0026] In one or more embodiments, the D50 particle size of the polycrystalline large particles is 12-14 μm, the D50 particle size of the polycrystalline small particles is 6.5-7.5 μm, and the D50 particle size of the single crystal particles is 3.5-4.5 μm.

[0027] In one or more embodiments, the variance σ of the D50 particle size of the mixed high-nickel cathode material is ≤0.04.

[0028] In one or more embodiments, the D50 particle size of the mixed high-nickel cathode material is 8–13 μm, preferably 10–12 μm.

[0029] In one or more implementations, 0.8 ≤ x < 1, 0.8 ≤ y < 1, and 0.8 ≤ z < 1.

[0030] In one or more embodiments, M, M' and M” are all Co, Mn and Al; preferably, the molar ratio of Co, Mn and Al in M, M' and M” is (4-6):(3-5):1.

[0031] In one or more embodiments, the surfaces of the polycrystalline large particles, polycrystalline small particles, and monocrystalline particles are coated with a coating agent.

[0032] In one or more embodiments, the ratio of the amount of the coating agent to the total amount of the polycrystalline large particles, polycrystalline small particles and single crystal particles is (0.01 to 1):100, preferably (0.05 to 0.5):100.

[0033] In one or more embodiments, the coating agent is one or more compounds comprising one or more elements selected from lithium, manganese, aluminum, cobalt, magnesium, zirconium, strontium, barium, titanium, fluorine, silicon, boron, and phosphorus; preferably, the coating agent is ZrO2.

[0034] This invention also provides a method for preparing the hybrid high-nickel cathode material according to any embodiment of the present invention, the method comprising the following steps:

[0035] (1) Preparation of polycrystalline large particles: The precursor Ni x M 1-x (OH)2 is sintered with lithium salt to form the aforementioned polycrystalline large particles;

[0036] (2) Preparation of polycrystalline small particles: The precursor Ni y M' 1-y (OH)2 is sintered with lithium salt to form the polycrystalline small particles;

[0037] (3) Preparation of single crystal particles: The precursor Ni z M” 1-z(OH)2 is sintered with lithium salt to form the single crystal particles described above;

[0038] (4) Wet mixing and coating, sintering: The polycrystalline large particles, the polycrystalline small particles, the single crystal particles and the coating agent are added to water or alcohol in steps and stirred and mixed. The mixture is dried and then sintered to obtain the mixed high-nickel cathode material.

[0039] In one or more embodiments, the sintering temperature for preparing polycrystalline large particles is 600–900°C, and the sintering time is 8–15 h.

[0040] In one or more embodiments, the sintering temperature for preparing polycrystalline small particles is 600–900°C, and the sintering time is 8–15 h.

[0041] In one or more embodiments, the sintering temperature for preparing single-crystal particles is 800–1000°C, and the sintering time is 8–15 h.

[0042] In one or more embodiments, wet blending and coating includes: adding 30% to 80% of the large polycrystalline particles and part of the coating agent to water or alcohol at a speed of 80 to 130 rpm, stirring for 10 to 60 seconds, then adding 40% to 60% of the small polycrystalline particles and part of the coating agent, stirring for 10 to 60 seconds, then adding all the single crystal particles and part of the coating agent, stirring for 10 to 60 seconds, then adding the remaining small polycrystalline particles and part of the coating agent, stirring for 10 to 60 seconds, then adding the remaining large polycrystalline particles and the remaining coating agent. The molar ratio of the coating agent added in each step is the same as the molar ratio of the particles added in each step. After the addition is completed, the speed is increased to 150 to 200 rpm, and then stirred for 60 to 120 seconds.

[0043] In one or more embodiments, the sintering temperature for preparing the mixed high-nickel cathode material is 200–700°C, and the sintering time is 3–8 h.

[0044] Another aspect of the present invention provides a positive electrode sheet comprising a hybrid high-nickel positive electrode material as described in any embodiment herein.

[0045] Another aspect of the present invention provides a lithium-ion battery comprising a positive electrode as described in any embodiment herein. Attached Figure Description

[0046] Figure 1 This is an electron microscope image of the cathode material prepared in Example 1.

[0047] Figure 2 This is an electron microscope image of the cathode material prepared in Comparative Example 1.

[0048] Figure 3A comparison chart of 0.1C charge-discharge curves of a lithium-ion battery made using the cathode material prepared in Example 1 and a lithium-ion battery made using the cathode material prepared in Comparative Example 1.

[0049] Figure 4 The dQ / dV curves of a lithium-ion battery made using the cathode material prepared in Example 1 after 1 cycle (1th), 30 cycles (30th), 50 cycles (50th), and 70 cycles (70th).

[0050] Figure 5 The dQ / dV curves of a lithium-ion battery made using the cathode material prepared in Comparative Example 1 after 1 cycle (1th), 30 cycles (30th), 50 cycles (50th), and 70 cycles (70th). Detailed Implementation

[0051] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0052] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0053] In this document, the terms “contains,” “includes,” “containing,” and similar terms encompass the meanings of “basically composed of” and “composed of.” For example, when this document discloses “A contains B and C,” “A is basically composed of B and C” and “A is composed of B and C” should be considered as having been disclosed in this document.

[0054] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0055] Unless otherwise specified, percentages refer to mass percentages and proportions refer to mass ratios in this article.

[0056] In this document, when describing embodiments or examples, it should be understood that it is not intended to limit the invention to those embodiments or examples. Rather, all alternatives, modifications, and equivalents of the methods and materials described herein are covered within the scope defined by the claims.

[0057] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0058] The hybrid high-nickel cathode material of this invention is formed by wet mixing of polycrystalline large particles, polycrystalline small particles, and single-crystal particles, followed by coating with a coating agent and sintering. In this article, polycrystalline particles are secondary spherical particles formed by the combination of many single-crystal particles, also known as polycrystalline secondary spherical particles.

[0059] In this invention, the chemical formulas of the polycrystalline large particles, polycrystalline small particles, and single crystal particles can be Li. v Ni w M 1-w O2, where v = 1 to 1.08, 0.6 ≤ w < 1, and M is two or three elements selected from Co, Mn, and Al. For example, the polycrystalline large particles, polycrystalline small particles, and single crystal particles can be ternary cathode materials of nickel cobalt aluminum oxide (NCA), quaternary cathode materials of nickel cobalt manganese aluminum oxide (NCMA), etc. In some embodiments, 0.8 ≤ w < 1, for example, w can be 0.9. In some embodiments, M is Co, Mn, and Al; preferably, the molar ratio of Co, Mn, and Al in M ​​is (4 to 6):(3 to 5):1, for example, 5:4:1. In the mixed high-nickel cathode material of the present invention, the chemical formulas of the polycrystalline large particles, polycrystalline small particles, and single crystal particles can be the same or different.

[0060] This invention improves the energy density by mixing large polycrystalline secondary spheres, small polycrystalline secondary spheres, and single crystal particles to increase the filling rate. The mixing and coating are carried out by mechanical wet mixing and coating with water or alcohol as the medium. Preferably, during the mixing process, additives are added simultaneously in proportion to the amount of the particles added at the same time. This results in a finished material with better uniformity and a layered coating layer, reducing side reactions and improving safety and cycle performance.

[0061] In this invention, the molar ratio of polycrystalline large particles, polycrystalline small particles, and single crystal particles used to prepare the mixed high-nickel cathode material is l:m:n, where 5≤l≤10, 0≤m≤5, 0≤n≤5, and l+m+n=10. In some preferred embodiments, 5≤l<10, 0<m≤5, and 0<n≤5. More preferably, 6.5≤l≤7.5, 1.5≤m≤2.5, and 0.5≤n≤1.5, for example, l:m:n can be 7:2:1. Controlling the particle ratio within the above range is beneficial for improving the overall electrical performance, including discharge specific capacity, rate performance, and cycle performance.

[0062] In this invention, the D50 particle size of the large polycrystalline particles is 10–15 μm, preferably 12–14 μm, for example 13 μm; the D50 particle size of the small polycrystalline particles is 6–9 μm, preferably 6.5–7.5 μm, for example 7 μm; and the D50 particle size of the single crystal particles is 2–5 μm, preferably 3.5–4.5 μm, for example 4 μm. Controlling the particle sizes of the large polycrystalline particles, small polycrystalline particles, and single crystal particles within the above ranges is beneficial for improving the overall electrical performance, including discharge specific capacity, rate performance, and cycle performance.

[0063] In this invention, the D50 particle size of the mixed high-nickel cathode material can be 8–13 μm, for example, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, and 12.5 μm. In some preferred embodiments, the D50 particle size of the mixed high-nickel cathode material is 10–12 μm, for example, 10.5 μm, 10.7 μm, 10.8 μm, 10.9 μm, 11 μm, 11.1 μm, 11.2 μm, and 11.5 μm, which is beneficial for improving the overall electrical performance, including discharge specific capacity, rate performance, and cycle performance. The D50 particle size, also called the median particle size, refers to the particle size corresponding to a cumulative particle size distribution percentage of 50% for a sample.

[0064] In this invention, the variance σ of the D50 particle size of the mixed high-nickel cathode material is preferably ≤0.04, for example 0.01, 0.02, or 0.03, which is beneficial to improving the overall electrical performance, including discharge specific capacity, rate performance, and cycle performance.

[0065] In this invention, the D50 particle size of the cathode material can be measured using a laser particle size analyzer. The variance σ of the D50 particle size of the cathode material is calculated using the following formula: Where n represents the number of samples, S represents the mean D50 particle size. i This represents the D50 particle size value for each sample. In some implementations, the sample size n ≥ 20 is used when calculating the variance σ.

[0066] In this invention, the large polycrystalline particles, small polycrystalline particles, and single-crystal particles can each be formed by sintering a hydroxide precursor and a lithium salt. The chemical formula of the hydroxide precursor is Ni. x M 1-x(OH)₂, where 0.6 ≤ x < 1, and M is two or three elements selected from Co, Mn, and Al. In some embodiments, 0.8 ≤ x < 1, for example, x can be 0.9. In some embodiments, M is Co, Mn, and Al; preferably, the molar ratio of Co, Mn, and Al in M ​​is (4–6):(3–5):1, for example, 5:4:1. The lithium salt can be one or more selected from lithium hydroxide and lithium carbonate. The molar ratio of the hydroxide precursor to the lithium salt can be 1:(1–1.08). The molecular formulas of polycrystalline large particles, polycrystalline small particles, and single crystal particles can be the same or different, and the chemical formulas of the corresponding hydroxide precursors and the molar ratios of the hydroxide precursors to the lithium salts can also be the same or different. In some embodiments, the chemical formulas of the precursors used to prepare polycrystalline large particles, polycrystalline small particles, and single crystal particles are the same, for example, the chemical formula of the precursors of polycrystalline large particles, polycrystalline small particles, and single crystal particles is Ni. x M 1-x (OH)₂, where 0.8 ≤ x < 1, for example, x = 0.9, M is Co, Mn, and Al, and the molar ratio of Co, Mn, and Al in M ​​is (4-6):(3-5):1, for example, 5:4:1. In some embodiments, the molar ratio of hydroxide precursor to lithium salt used to prepare polycrystalline large particles, polycrystalline small particles, and single crystal particles is different. For example, the molar ratio of hydroxide precursor to lithium salt used to prepare polycrystalline large particles, polycrystalline small particles, and single crystal particles can be 1:1.03, 1:1.05, and 1:1.06, respectively.

[0067] The coating agent suitable for use in this invention can be one or more compounds comprising one or more elements selected from lithium, manganese, aluminum, cobalt, magnesium, zirconium, strontium, barium, titanium, fluorine, silicon, boron, and phosphorus, such as ZrO2. The coating agent can be a nanoscale powder. The molar ratio of the coating agent to the total molar ratio of polycrystalline large particles, polycrystalline small particles, and single crystal particles can be (0.01 to 1):100, preferably (0.05 to 0.5):100, for example 0.1:100 or 0.2:100.

[0068] In this invention, the sintering temperature for preparing large and small polycrystalline particles can be 600–900℃, and the sintering time can be 8–15 h. The sintering temperature for preparing single-crystal particles can be 800–1000℃, and the sintering time can be 8–15 h.

[0069] After obtaining polycrystalline large particles, polycrystalline small particles, and monocrystalline particles, this invention employs a wet blending and coating process to mix the polycrystalline large particles, polycrystalline small particles, and monocrystalline particles into an admixture, while simultaneously coating them with a coating agent. Wet blending and coating refers to mixing and coating the materials in a liquid medium (e.g., water, alcohol). The ratio of the mass of the liquid medium to the total mass of the polycrystalline large particles, polycrystalline small particles, and monocrystalline particles can be (0.5–2.0):1.

[0070] The preferred method for mixing and coating is to add materials in batches. More preferably, under stirring, a portion of large polycrystalline particles and a portion of coating agent are added first, and after stirring for a period of time, a portion of small polycrystalline particles and a portion of coating agent are added, and after stirring for a period of time, single crystal particles and a portion of coating agent are added, and after stirring for a period of time, the remaining small polycrystalline particles and a portion of coating agent are added, and after stirring for a period of time, the remaining large polycrystalline particles and the remaining coating agent are added, and finally, the mixture is stirred for a period of time. In a preferred embodiment, during wet blending and coating, at a speed of 80–130 rpm, 30%–80% of the large polycrystalline particles and part of the coating agent are first added to water and stirred for 10–60 seconds. Then, 40%–60% of the small polycrystalline particles and part of the coating agent are added and stirred for 10–60 seconds. After stirring, all the single crystal particles and part of the coating agent are added and stirred for 10–60 seconds. After stirring, the remaining small polycrystalline particles and part of the coating agent are added and stirred for 10–60 seconds. After stirring, the remaining large polycrystalline particles and part of the coating agent are added. After the addition is complete, the speed is increased to 150–200 rpm and stirred for another 60–120 seconds. Preferably, the proportion of the amount of coating agent added in each batch is the same as the proportion of the amount of particles added in each batch. That is, the ratio of the amount of coating agent added in each batch to the amount of particles added in the corresponding batch is equal to the ratio of the total amount of coating agent to the amount of coated particles (including large polycrystalline particles, small polycrystalline particles, and monocrystalline particles). This is beneficial for improving the overall performance, including discharge specific capacity, rate performance, and cycle performance. For example, when the ratio of the amount of coating agent to the total amount of large polycrystalline particles, small polycrystalline particles, and monocrystalline particles is 0.2:100, it is preferable that the ratio of the amount of coating agent added in each batch to the amount of particles added in the corresponding batch is equal to 0.2:100.

[0071] In some embodiments, the method for preparing the hybrid high-nickel cathode material of the present invention includes the following steps:

[0072] (1) Preparation of large-particle secondary spherical high-nickel materials:

[0073] Ni x M y(OH)2 precursor is mixed with a lithium salt and sintered at 600 - 900 °C for 8 - 15 h, then pulverized to obtain large particle high-nickel powder with D50 = 10 - 15 μm, named powder I. The precursor has D50 = 10 - 15 μm, 0.6 ≤ x < 1, 0 < y ≤ 0.4, x + y = 1, and M is selected from two or three of Co, Mn, and Al;

[0074] (2) Preparation of small particle secondary spherical high-nickel material:

[0075] Mix Ni x M y (OH)2 precursor with a lithium salt, sinter at 600 - 900 °C for 8 - 15 h, and pulverize to obtain small particle high-nickel powder with D50 = 6 - 9 μm, named powder II. The precursor has D50 = 6 - 9 μm, 0.6 ≤ x < 1, 0 < y ≤ 0.4, x + y = 1, and M is selected from two or three of Co, Mn, and Al;

[0076] (3) Preparation of single crystal high-nickel material:

[0077] Mix Ni x M y (OH)2 precursor with a lithium salt, sinter at 800 - 1000 °C for 8 - 15 h, and pulverize to obtain single crystal high-nickel powder with D50 = 2 - 5 μm, named powder III. The precursor has D50 = 2 - 5 μm, 0.6 ≤ x < 1, 0 < y ≤ 0.4, x + y = 1, and M is selected from two or three of Co, Mn, and Al;

[0078] (4) Particle blending, coating, and sintering

[0079] Weigh powders I, II, and III with a molar ratio of l:m:n, where 5 ≤ l ≤ 10, 0 ≤ m ≤ 5, 0 ≤ n ≤ 5, and l + m + n = 10. Also weigh a coating agent, and the molar ratio of the coating agent to (powder I + powder II + powder III) is 0.01% - 1.00%. The coating agent is one or more compounds containing one or more elements selected from lithium, manganese, aluminum, cobalt, magnesium, zirconium, strontium, barium, titanium, fluorine, silicon, boron, and phosphorus, and perform wet blending and coating;

[0080] The steps of wet blending and coating are as follows:

[0081] (a) Add a certain amount of deionized water to the reaction kettle, and the mass ratio of deionized water to (powder I + powder II + powder III) is (0.5 - 2.0):1, and adjust the rotation speed to 80 - 130 rpm;

[0082] (b) Add 30%–80% of powder I, then add 40%–60% of powder II after 10–60 seconds, then add 100% of powder III after 10–60 seconds, then add the remaining powder II after 10–60 seconds, and then add the remaining powder I after 10–60 seconds. During this process, each time powder is added, the same amount of coating agent is added.

[0083] (c) Increase the rotation speed of the reactor to 150-200 rpm and stir for 60-180 s;

[0084] After wet blending and coating, the material is dehydrated by suction filtration or centrifugation to achieve a moisture content of 2-8%. The dehydrated material is then placed in an oven at 110-180℃ for 5-10 hours to achieve a moisture content of 0.03-0.2%. The dried material is then subjected to secondary sintering at 200-700℃ for 3-8 hours. After sieving, a uniformly mixed and coated Li is obtained. a (Ni x M y O2P Z The powder is 1≤a≤1.08, 0.01%≤z≤1.00%, and P is the coating element.

[0085] The present invention also includes a positive electrode sheet containing the mixed high-nickel positive electrode material of the present invention, and a lithium-ion battery containing the positive electrode sheet.

[0086] A lithium-ion battery comprises a positive electrode, a negative electrode, a separator, and an electrolyte. The lithium-ion battery of this invention is characterized in that the positive electrode comprises the hybrid high-nickel positive electrode material of this invention.

[0087] The positive electrode sheet includes a positive current collector and a positive electrode material layer formed on the surface of the positive current collector. The positive electrode material layer includes a positive electrode material, a conductive agent, and a binder. The positive electrode material layer is obtained by coating a positive electrode slurry containing the positive electrode material, conductive agent, binder, and solvent onto the positive current collector, followed by rolling and baking. The positive current collector can be copper foil, aluminum foil, titanium foil, nickel foil, iron foil, zinc foil, etc. The solvent of the positive electrode slurry can be N-methylpyrrolidone (NMP). The positive electrode material in the positive electrode sheet of the present invention includes the mixed high-nickel positive electrode material of the present invention. The conductive agent of the positive electrode can be one or more selected from conductive carbon black (SP), carbon fiber (CF), acetylene black, conductive graphite, graphene, carbon nanotubes, and carbon microspheres. The binder of the positive electrode can be one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene, polyvinyl alcohol, polyolefin, styrene-butadiene rubber, fluorinated rubber, polyurethane, and sodium alginate. In some implementations, the conductive agent in the positive electrode material layer is SP, and the binder is PVDF. The content ratio of each component in the positive electrode material layer can be conventional.

[0088] The negative electrode sheet includes a negative current collector and a negative electrode material layer formed on the surface of the negative current collector. The negative electrode material layer includes a negative electrode material, a conductive agent, and a binder. The negative electrode material layer is obtained by coating a negative electrode slurry containing the negative electrode material, conductive agent, binder, and solvent onto the positive electrode current collector, followed by rolling and baking. The negative electrode current collector can be copper foil. The solvent for the negative electrode slurry can be water. The negative electrode material can be one or more selected from carbon materials (e.g., graphite), silicon, silicon compounds, lithium titanate, tin, and tin compounds. The negative electrode conductive agent can be one or more selected from conductive carbon black (SP), acetylene black, carbon nanotubes, carbon nanowires, carbon microspheres, carbon fibers, and graphene. The negative electrode binder can be one or more selected from polyvinylidene fluoride, polytetrafluoroethylene, acrylonitrile copolymers, polybutylene acrylate, polyacrylonitrile, styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose. The mass ratio of the components in the negative electrode material layer can be conventional. The negative electrode sheet can be a lithium sheet.

[0089] The membrane can be a polymer porous membrane, an inorganic porous membrane, or a polymer-inorganic composite porous membrane. Polymer porous membranes include single-layer polymer porous membranes and multi-layer polymer porous membranes.

[0090] The positive electrode, negative electrode, and separator are stacked or wound according to design requirements, encapsulated in a casing, and then dried, injected with electrolyte, encapsulated, left to stand, formed, and sorted to obtain a lithium-ion battery. The form of the lithium-ion battery of this invention is not particularly limited; it can be a cylindrical lithium-ion battery, a pouch lithium-ion battery, or an aluminum-cased lithium-ion battery, etc.

[0091] Lithium-ion battery electrolytes contain organic solvents and lithium salts. Commonly used organic solvents in electrolytes are carbonate solvents. Suitable carbonate solvents include, but are not limited to, one or more selected from ethylene carbonate (EC), propylene carbonate (PC), butenyl carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC), preferably two or more. Preferably, the carbonate solvent contains at least one cyclic carbonate and at least one linear carbonate. Examples of cyclic carbonates include EC, PC, and butenyl carbonate. Examples of linear carbonates include DMC, DEC, and EMC. The mass ratio of cyclic carbonate to linear carbonate can be from 1:4 to 1:1, for example, 1:2. The lithium salt in the electrolyte of this invention can be a commonly used lithium salt in the art, including but not limited to lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalato)borate (LiBOB), lithium difluorooxalatoborate (LiODFB), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), lithium fluoride (LiF), lithium trifluoromethanesulfonate (LiCF3SO3), etc. In some embodiments, the lithium salt is LiPF6. The concentration of the lithium salt in the electrolyte can be 0.5-2 mol / L, for example, 1 mol / L.

[0092] The present invention has the following beneficial effects:

[0093] 1. This invention uses mechanical wet-mixing in stages to mix large and small secondary spherical particles and single-crystal morphology particles, avoiding particle agglomeration, increasing material filling rate and thus obtaining higher compaction density, further improving the energy density of lithium-ion batteries, and increasing particle coordination number, thereby improving rate performance.

[0094] 2. This invention uses a wet, staged coating process to create a layered, uniform coating layer on the surface of the particles, which reduces residual alkali, decreases side reactions with the electrolyte, and reduces gas production, thereby achieving excellent cycle performance and safety performance.

[0095] 3. The method for preparing the mixed high-nickel cathode material of the present invention involves wet-mixing and coating of three particles with different particle sizes in stages to obtain a high-compaction, high-rate, and long-cycle high-nickel cathode material.

[0096] The present invention will be described below by way of specific embodiments. It should be understood that these embodiments are merely illustrative and are not intended to limit the scope of the invention. The methods, reagents, and materials used in the embodiments are conventional methods, reagents, and materials in the art, unless otherwise stated. The raw material compounds in the embodiments are all commercially available.

[0097] Example 1

[0098] According to the particle ratio shown in Table 1, the cathode material of Example 1 was prepared according to the following steps:

[0099] (1) Preparation of polycrystalline secondary spherical large particles: Ni with a D50 of 13μm was mixed in a molar ratio of 1:1.03. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 700℃ for 10h in an oxygen atmosphere and crushed to obtain large polycrystalline secondary spheres with a D50 of 13μm, which is called powder I.

[0100] (2) Preparation of polycrystalline secondary spherical small particles: Ni with a D50 of 7μm was mixed at a molar ratio of 1:1.05. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 720℃ for 10h in an oxygen atmosphere and crushed to obtain polycrystalline secondary spherical small particles with D50 of 7μm, which are called powder II.

[0101] (3) Preparation of single-crystal particles: Ni with a D50 of 4μm is mixed at a molar ratio of 1:1.06. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 900℃ for 15h in an oxygen atmosphere and then pulverized to obtain a single crystal material with D50 of 4μm, which is called powder III.

[0102] (4) Preparation of cathode material by wet mixing and coating: Powder I, powder II, and powder III were weighed according to a mass ratio of 7:2:1. 0.2% of nano-sized ZrO2 (Zr molars equal to the total molars of Ni, Co, Mn, and Al) was weighed. Deionized water (1.5 times the total mass of the powders) was added to the reactor. The mixing speed was adjusted to 100 rpm. 50% of powder I and 35% of ZrO2 were added. After 30 seconds, 50% of powder II and 10% of ZrO2 were added. After 30 seconds, 100% of powder III and 10% of ZrO2 were added. After 30 seconds, 50% of powder II and 10% of ZrO2 were added. After 30 seconds, 50% of powder I and 35% of ZrO2 were added. The mixing speed was adjusted to 150 rpm. The mixture was mixed for 120 seconds. S The solution was then poured into a vacuum filtration flask for dehydration for 1 hour, followed by drying in a 120°C oven for 8 hours. Finally, it was sintered in a box furnace at 400°C for 5 hours to obtain Li with a ZrO2-coated surface. 1.037 (Ni 0.9 Co 0.05 Mn 0.04 Al 0.01O2 cathode material.

[0103] Example 2

[0104] According to the particle ratio shown in Table 1, the cathode material of Example 2 was prepared according to the following steps:

[0105] (1) Preparation of polycrystalline secondary spherical large particles: Ni with a D50 of 13μm was mixed in a molar ratio of 1:1.03. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 700℃ for 10h in an oxygen atmosphere and crushed to obtain large polycrystalline secondary spheres with a D50 of 13μm, which is called powder I.

[0106] (2) Preparation of polycrystalline secondary spherical small particles: Ni with a D50 of 7μm was mixed at a molar ratio of 1:1.05. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 720℃ for 10h in an oxygen atmosphere and crushed to obtain polycrystalline secondary spherical small particles with D50 of 7μm, which are called powder II.

[0107] (3) Wet mixing and coating preparation of cathode material: Powder I and powder II were weighed in a 5:5 mass ratio, and 0.2% of nano-sized ZrO2 (the molar amount of Zr is equal to the total molar amount of Ni, Co, Mn, and Al) was weighed. Deionized water with a mass of 1.5 times the total mass of the powders was added to the reactor. The mixing speed was adjusted to 100 rpm. 50% of powder I and 25% of ZrO2 were added. After 30 s, 100% of powder II and 50% of ZrO2 were added. After another 30 s, 50% of powder I and 25% of ZrO2 were added. The mixing speed was adjusted to 150 rpm. The mixture was mixed for 120 seconds. S The solution was then poured into a vacuum filtration flask for dehydration for 1 hour, followed by drying in a 120°C oven for 8 hours. Finally, it was sintered in a box furnace at 400°C for 5 hours to obtain Li with a ZrO2-coated surface. 1.04 (Ni 0.9 Co 0.05 Mn 0.04 Al 0.01 O2 cathode material.

[0108] Example 3

[0109] According to the particle proportions shown in Table 1, the cathode material of Example 3 was prepared following these steps:

[0110] (1) Preparation of polycrystalline secondary spherical large particles: Ni with a D50 of 13μm was mixed in a molar ratio of 1:1.03. 0.9Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 700℃ for 10h in an oxygen atmosphere and crushed to obtain large polycrystalline secondary spheres with a D50 of 13μm, which is called powder I.

[0111] (2) Preparation of polycrystalline secondary spherical small particles: Ni with a D50 of 7μm was mixed at a molar ratio of 1:1.05. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 720℃ for 10h in an oxygen atmosphere and crushed to obtain polycrystalline secondary spherical small particles with D50 of 7μm, which are called powder II.

[0112] (3) Preparation of single-crystal particles: Ni with a D50 of 4μm is mixed at a molar ratio of 1:1.06. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 900℃ for 15h in an oxygen atmosphere and then pulverized to obtain a single crystal material with D50 of 4μm, which is called powder III.

[0113] (4) Preparation of cathode material by wet mixing and coating: Powder I, powder II, and powder III were weighed according to a mass ratio of 5:4:1. 0.2% of nano-sized ZrO2 (Zr molars equal to the total molars of Ni, Co, Mn, and Al) was weighed. Deionized water (1.5 times the total mass of the powders) was added to the reactor. The mixing speed was adjusted to 100 rpm. 50% of powder I and 25% of ZrO2 were added. After 30 seconds, 50% of powder II and 20% of ZrO2 were added. After 30 seconds, 100% of powder III and 10% of ZrO2 were added. After 30 seconds, 50% of powder II and 20% of ZrO2 were added. After 30 seconds, 50% of powder I and 25% of ZrO2 were added. The mixing speed was adjusted to 150 rpm. The mixture was mixed for 120 seconds. S The solution was then poured into a vacuum filtration flask for dehydration for 1 hour, followed by drying in a 120°C oven for 8 hours. Finally, it was sintered in a box furnace at 400°C for 5 hours to obtain Li with a ZrO2-coated surface. 1.041 (Ni 0.9 Co 0.05 Mn 0.04 Al 0.01 O2 cathode material.

[0114] Example 4-20

[0115] According to the particle proportions shown in Table 1, the cathode materials of Examples 4-20 were prepared following these steps:

[0116] (1) Preparation of polycrystalline secondary spherical large particles: Ni with a D50 of 13μm was mixed in a molar ratio of 1:1.03. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 700℃ for 10h in an oxygen atmosphere and crushed to obtain large polycrystalline secondary spheres with a D50 of 13μm, which is called powder I.

[0117] (2) Preparation of polycrystalline secondary spherical small particles: Ni with a D50 of 7μm was mixed at a molar ratio of 1:1.05. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 720℃ for 10h in an oxygen atmosphere and crushed to obtain polycrystalline secondary spherical small particles with D50 of 7μm, which are called powder II.

[0118] (3) Preparation of single-crystal particles: Ni with a D50 of 4μm is mixed at a molar ratio of 1:1.06. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 900℃ for 15h in an oxygen atmosphere and then pulverized to obtain a single crystal material with D50 of 4μm, which is called powder III.

[0119] (4) Wet mixing and coating preparation of cathode material: Powder I, powder II, and powder III are weighed according to the mass ratio of X:Y:Z (X+Y+Z=10), and 0.2% of nano-sized ZrO2 with a Zr molar number equal to the total molar number of Ni, Co, Mn, and Al is weighed; deionized water with a mass of 1.5 times the total mass of powders is added to the reactor, the mixing speed is adjusted to 100 rpm, 50% of powder I and 5*X% of ZrO2 are added, 50% of powder II and 5*Y% of ZrO2 are added after 30 s, 100% of powder III and 10*Z% of ZrO2 are added after 30 s, 50% of powder II and 5*Y% of ZrO2 are added after 30 s, 50% of powder I and 5*X% of ZrO2 are added after 30 s, the mixing speed is adjusted to 150 rpm, and the mixture is mixed for 120 seconds. S The solution was then poured into a vacuum filtration flask for dehydration for 1 hour, followed by drying in a 120°C oven for 8 hours. Finally, it was sintered in a box furnace at 400°C for 5 hours to obtain Li with a ZrO2-coated surface. (1.03*X+1.05*Y+1.06*Z) / 10 (Ni 0.9 Co 0.05 Mn 0.04 Al 0.01 O2 cathode material.

[0120] Comparative Example 1

[0121] According to the particle proportions shown in Table 1, the cathode material of Comparative Example 1 was prepared following these steps:

[0122] (1) Preparation of polycrystalline secondary spherical large particles: Ni with a D50 of 13μm was mixed in a molar ratio of 1:1.03. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 700℃ for 10h in an oxygen atmosphere and crushed to obtain large polycrystalline secondary spheres with a D50 of 13μm, which is called powder I.

[0123] (2) Preparation of polycrystalline secondary spherical small particles: Ni with a D50 of 7μm was mixed at a molar ratio of 1:1.05. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 720℃ for 10h in an oxygen atmosphere and crushed to obtain polycrystalline secondary spherical small particles with D50 of 7μm, which are called powder II.

[0124] (3) Preparation of single-crystal particles: Ni with a D50 of 4μm is mixed at a molar ratio of 1:1.06. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 900℃ for 15h in an oxygen atmosphere and then pulverized to obtain a single crystal material with D50 of 4μm, which is called powder III.

[0125] (4) Dry mixing and coating preparation of cathode material: Powder I, powder II, and powder III were weighed according to a mass ratio of 7:2:1. 0.2% of nano-sized ZrO2 (the molar amount of Zr equal to the total molar amount of Ni, Co, Mn, and Al) was weighed. All particles were washed and dried with deionized water at a mass of 1.5 times the total mass of the powders. Then, the coating agent ZrO2 was added, and the mixture was poured into a high-speed mixer and mixed evenly. Finally, the mixture was sintered in a box furnace at 400℃ for 5 hours to obtain Li-type cathode material with a ZrO2 surface coating. 1.037 (Ni 0.9 Co 0.05 Mn 0.04 Al 0.01 O2 cathode material.

[0126] Comparative Example 2

[0127] According to the particle proportions shown in Table 1, the cathode material of Comparative Example 2 was prepared following these steps:

[0128] (1) Preparation of polycrystalline secondary spherical large particles: Ni with a D50 of 13μm was mixed in a molar ratio of 1:1.03. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 700℃ for 10h in an oxygen atmosphere and crushed to obtain large polycrystalline secondary spheres with a D50 of 13μm, which is called powder I.

[0129] (2) Preparation of polycrystalline secondary spherical small particles: Ni with a D50 of 7μm was mixed at a molar ratio of 1:1.05. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 720℃ for 10h in an oxygen atmosphere and crushed to obtain polycrystalline secondary spherical small particles with D50 of 7μm, which are called powder II.

[0130] (3) Preparation of single-crystal particles: Ni with a D50 of 4μm is mixed at a molar ratio of 1:1.06. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 900℃ for 15h in an oxygen atmosphere and then pulverized to obtain a single crystal material with D50 of 4μm, which is called powder III.

[0131] (4) Wet mixing and coating preparation of cathode material: Powder I, powder II, and powder III were weighed according to a mass ratio of 7:2:1. 0.2% of nano-sized ZrO2 (the molar amount of Zr equal to the total molar amount of Ni, Co, Mn, and Al) was weighed. Deionized water (1.5 times the total mass of the powders) was added to the reactor. The mixing speed was adjusted to 100 rpm. 50% of powder I and 100% of ZrO2 were added. After 30 seconds, 50% of powder II was added. After 30 seconds, 100% of powder III was added. After 30 seconds, 50% of powder II was added. After 30 seconds, 50% of powder I was added. The mixing speed was adjusted to 150 rpm. The mixture was mixed for 120 seconds. S The solution was then poured into a vacuum filtration flask for dehydration for 1 hour, followed by drying in a 120°C oven for 8 hours. Finally, it was sintered in a box furnace at 400°C for 5 hours to obtain Li with a ZrO2-coated surface. 1.037 (Ni 0.9 Co 0.05 Mn 0.04 Al 0.01 O2 cathode material.

[0132] Comparative Example 3

[0133] According to the particle proportions shown in Table 1, the cathode material of Comparative Example 3 was prepared following these steps:

[0134] (1) Preparation of polycrystalline secondary spherical large particles: Ni with a D50 of 13μm was mixed in a molar ratio of 1:1.03. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 700℃ for 10h in an oxygen atmosphere and crushed to obtain large polycrystalline secondary spheres with a D50 of 13μm, which is called powder I.

[0135] (2) Preparation of polycrystalline secondary spherical small particles: Ni with a D50 of 7μm was mixed at a molar ratio of 1:1.05. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 720℃ for 10h in an oxygen atmosphere and crushed to obtain polycrystalline secondary spherical small particles with D50 of 7μm, which are called powder II.

[0136] (3) Preparation of single-crystal particles: Ni with a D50 of 4μm is mixed at a molar ratio of 1:1.06. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 900℃ for 15h in an oxygen atmosphere and then pulverized to obtain a single crystal material with D50 of 4μm, which is called powder III.

[0137] (4) Wet mixing and coating preparation of cathode material: Powder I, powder II, and powder III were weighed according to a mass ratio of 7:2:1. 0.2% of nano-sized ZrO2 (the molar amount of Zr equal to the total molar amount of Ni, Co, Mn, and Al) was weighed. Deionized water (1.5 times the total mass of the powders) was added to the reactor. The mixing speed was adjusted to 100 rpm. 50% of powder I was added, followed by 50% of powder II after 30 seconds. Then, 100% of powder III and 100% of ZrO2 were added after 30 seconds. Then, 50% of powder II was added after 30 seconds. Finally, 50% of powder I was added after 30 seconds. The mixing speed was adjusted to 150 rpm. The mixture was mixed for 120 seconds. S The solution was then poured into a vacuum filtration flask for dehydration for 1 hour, followed by drying in a 120°C oven for 8 hours. Finally, it was sintered in a box furnace at 400°C for 5 hours to obtain Li with a ZrO2-coated surface. 1.037 (Ni 0.9 Co 0.05 Mn 0.04 Al 0.01 O2 cathode material.

[0138] Comparative Example 4

[0139] According to the particle proportions shown in Table 1, the cathode material of Comparative Example 4 was prepared following these steps:

[0140] (1) Preparation of polycrystalline secondary spherical large particles: Ni with a D50 of 13μm was mixed in a molar ratio of 1:1.03. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 700℃ for 10h in an oxygen atmosphere and crushed to obtain large polycrystalline secondary spheres with a D50 of 13μm, which is called powder I.

[0141] (2) Preparation of polycrystalline secondary spherical small particles: Ni with a D50 of 7μm was mixed at a molar ratio of 1:1.05. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 720℃ for 10h in an oxygen atmosphere and crushed to obtain polycrystalline secondary spherical small particles with D50 of 7μm, which are called powder II.

[0142] (3) Preparation of single-crystal particles: Ni with a D50 of 4μm is mixed at a molar ratio of 1:1.06. 0.9 Co 0.05 Mn 0.04 Al 0.01 (OH)2 precursor and LiOH are sintered at 900℃ for 15h in an oxygen atmosphere and then pulverized to obtain a single crystal material with D50 of 4μm, which is called powder III.

[0143] (4) Wet mixing and coating preparation of cathode material: Powder I, powder II, and powder III were weighed according to a mass ratio of 7:2:1. 0.2% of nano-sized ZrO2 (Zr molars equal to the total molars of Ni, Co, Mn, and Al) was weighed. Deionized water (1.5 times the total mass of the powders) was added to the reactor. The mixing speed was adjusted to 100 rpm. 50% of powder I and 30% of ZrO2 were added. After 30 seconds, 50% of powder II was added. After 30 seconds, 100% of powder III and 40% of ZrO2 were added. After 30 seconds, 50% of powder II was added. After 30 seconds, 50% of powder I and 30% of ZrO2 were added. The mixing speed was adjusted to 150 rpm. The mixture was mixed for 120 seconds. S The solution was then poured into a vacuum filtration flask for dehydration for 1 hour, followed by drying in a 120°C oven for 8 hours. Finally, it was sintered in a box furnace at 400°C for 5 hours to obtain Li with a ZrO2-coated surface. 1.037 (Ni 0.9 Co 0.05 Mn 0.04 Al 0.01 O2 cathode material.

[0144] Table 1: Particle proportions for preparing cathode materials (unit: parts by mass)

[0145] Polycrystalline secondary spheres large particle material Polycrystalline secondary sphere small particles Single crystal granules Example 1 70 20 10 Example 2 50 50 0 Example 3 50 40 10 Example 4 50 30 20 Example 5 50 20 30 Example 6 50 10 40 Example 7 50 0 50 Example 8 60 40 0 Example 9 60 30 10 Example 10 60 20 20 Example 11 60 10 30 Example 12 60 0 40 Example 13 70 30 0 Example 14 70 10 20 Example 15 70 0 30 Example 16 80 20 0 Example 17 80 10 10 Example 18 80 0 20 Example 19 90 10 0 Example 20 90 0 10 Comparative Example 1 70 20 10 Comparative Example 2 70 20 10 Comparative Example 3 70 20 10 Comparative Example 4 70 20 10

[0146] The difference between Example 1 and Comparative Examples 2-4 is that the ratio of powder and coating agent added in each feeding during wet coating is different, as shown in Table 2.

[0147] Table 2: Proportions of powder and coating agent added at each feeding stage in the wet mixing and coating preparation of cathode materials

[0148]

[0149]

[0150] Note: In Table 1, the mass ratio of polycrystalline secondary sphere large particles (powder I): polycrystalline secondary sphere small particles (powder II): monocrystalline particles (powder III) is X:Y:Z, and X+Y+Z=10.

[0151] Test Example 1

[0152] The cathode materials obtained in the examples and comparative examples were used to fabricate lithium-ion batteries using the following methods:

[0153] (1) Preparation of positive electrode sheet: The positive electrode material, conductive carbon black and polyvinylidene fluoride (PVDF) are mixed and ground evenly in a mortar at a mass ratio of 8:1:1. During the grinding process, an appropriate amount of NMP is added dropwise to adjust the viscosity of the slurry. After thorough grinding, the slurry is evenly coated on the current collector aluminum foil and dried at 80℃ for 2 days. After the electrode sheet is dried, it is cut into circular electrode sheets with a diameter of 15mm using a punching machine. The mass of a single electrode sheet is weighed using an electronic balance and placed in a glove box (H2O concentration <1ppm, O concentration <0.2ppm) for later use.

[0154] (2) Button cell assembly: Using lithium sheet as negative electrode, and 1M Li PF6 dissolved in EC-EMC-DMC (volume ratio 1:1:1) as electrolyte, the button cell is assembled in a glove box filled with argon gas. From top to bottom, the components are: positive electrode shell, positive electrode sheet, electrolyte, separator, electrolyte, lithium sheet, and negative electrode shell.

[0155] The cathode materials and corresponding lithium-ion batteries prepared in the examples and comparative examples were subjected to the following tests, and the results are shown in Table 3:

[0156] (1) Discharge specific capacity: The discharge capacity is measured under the test conditions of 2.8-4.3V and 0.1C rate.

[0157] (2) Rate performance: The ratio of discharge specific capacity under 1C rate test condition to discharge specific capacity under 0.1C rate test condition is measured at a test voltage of 2.8-4.3V.

[0158] (3) Compacted density: Apply pressure in the range of 10-200MPa, pressurize at intervals of 10MPa, hold pressure for 10s, release pressure to 3MPa, and hold pressure for 10s.

[0159] (4) Residual lithium: The sample was stirred in pure water using a titration method to dissolve the residual alkali. The OH content was determined using phenolphthalein and methyl red-bromocresol green indicators respectively with standard hydrochloric acid titration solution. - and CO 3- .

[0160] (5) Cyclic capacity retention rate: The test voltage is 2.8-4.3V, 1C rate test, and the ratio of the discharge specific capacity at the 50th cycle to the discharge specific capacity at the 1st cycle.

[0161] Table 3: Performance of cathode materials and corresponding lithium-ion batteries in the examples and comparative examples

[0162]

[0163] The experimental results of Example 1 and Comparative Example 1 show that wet mixing is simpler than dry mixing, has higher compaction density, better rate performance, higher discharge specific capacity, and lower residual lithium.

[0164] The experimental results from Examples 1-20 show that, in terms of discharge specific capacity, rate performance, and cycle performance, the overall performance is optimal when the mass ratio of large polycrystalline particles to small polycrystalline particles to single crystal particles is 7:2:1. In Examples 1-20, the molecular weights of the large polycrystalline particles, small polycrystalline particles, and single crystal particles are basically the same (the differences are negligible), therefore, the molar ratio of large polycrystalline particles to small polycrystalline particles to single crystal particles is also 7:2:1.

[0165] The experimental results of Example 1 and Comparative Examples 2-4 show that, in terms of discharge specific capacity, rate performance, and cycle performance, the best overall performance is achieved when the coating agent is added in batches along with the powder at a fixed molar ratio relative to the powder (e.g., the molar ratio of coating agent to powder is 0.2:100), i.e., the molar ratio of the coating agent added each time is the same as the molar ratio of the particles added each time. Furthermore, the closer the addition ratio of each batch is to the fixed molar ratio, the better the performance.

[0166] In Embodiment 1 of this invention, the D50 values ​​of the polycrystalline large particles, polycrystalline small particles, and single crystal particles are 13 μm, 7 μm, and 4 μm, respectively, and their volumes calculated based on spherical shape are 1150 μm. 3 180μm3 33μm 3 Polycrystalline large particles, polycrystalline small particles, and single crystal particles were mixed in a mass ratio of 7:2:1. Assuming that the densities of the polycrystalline large particles, polycrystalline small particles, and single crystal particles are equal, the theoretical ratio of the number of polycrystalline large particles, polycrystalline small particles, and single crystal particles in a given volume when uniformly mixed is 6:11:30. Based on the above theoretical calculations, the uniformity of the mixing can be verified by observing the SEM images of the cathode material. The SEM images of the cathode materials prepared in Example 1 and Comparative Example 1 are shown below. Figure 1 and Figure 2 As shown in the SEM images, the ratio of the three types of particles in a given volume in Example 1 is closer to the theoretical value of 6:11:30, indicating that the dispersion and uniformity of the cathode material particles in Example 1 are better than those in Comparative Example 1. The 0.1C charge-discharge curves of the lithium-ion battery made using the cathode material of Example 1 and the lithium-ion battery made using the cathode material of Comparative Example 1 in Test Example 1 are shown in the images. Figure 3 As shown, the discharge specific capacity of the lithium-ion battery made using the cathode material of Example 1 is much higher than that of Comparative Example 1.

[0167] The dQ / dV curves of the lithium-ion battery made using the cathode material of Example 1 and the lithium-ion battery made using the cathode material of Comparative Example 1 in Test Example 1 are as follows: Figure 4 and Figure 5 As shown.

[0168] The dQ / dV curve testing method is as follows: Coin cells are fabricated according to the above-described coin cell assembly method, with a voltage of 2.8-4.3V. First, charge and discharge at 0.1C, 0.2C, 0.5C, and 1C rates, then perform a cycle test at 1C rate. "1 cycle," "30 cycles," "50 cycles," and "70 cycles" refer to the 1st, 30th, 50th, and 70th cycles at 1C rate, respectively. The capacity Q and voltage V data obtained during the test are analyzed according to the definition of dQ / dV.

[0169] The data obtained from the dQ / dV curves are shown in Table 4, and the explanations are as follows:

[0170] (1) ΔE is the redox peak change rate. The higher the value, the more irreversible phase transformation of the material increases, leading to increased internal resistance and decreased capacity. The calculation method for ΔE is: ΔE = (oxidation peak voltage - reduction peak voltage) / oxidation peak voltage * 100%;

[0171] (2) From Figure 4 , Figure 5 As can be seen from the data in Table 4, the ΔE of Comparative Example 1 is greater than that of Example 1, indicating that as the number of cycles increases, the irreversible phase transition of Comparative Example 1 is larger than that of Example 1, and the internal resistance is greater.

[0172] (3) The positive electrode material ΔE prepared by the method of the present invention 30 ≤4.0, 4.0<ΔE 50 ≤5.0, ΔE 50 ≤7.0.

[0173] As shown in Table 4, the cathode material of Example 1 has significantly improved capacity and cycle performance compared to Comparative Example 1.

[0174] Table 4: Data derived from the dQ / dV curve

[0175]

[0176] Test Example 2

[0177] The D50 particle size and variance of the cathode materials prepared in the examples and comparative examples were tested using the following methods:

[0178] Twenty samples were taken for each type of cathode material, and the D50 particle size was measured using a Mastersize 3000 particle size analyzer. Test conditions included: water as the medium, stirring speed of 3000 r / min, shading limits of 5%-20%, and both background and sample measurement times of 5 seconds. Each sample group was measured three times, and the average value was taken as the D50 particle size for that group. The σ value (variance) of the D50 particle size for the 20 sample groups was calculated using the following formula: Where n represents the number of sample groups, S represents the mean D50 particle size. i The D50 particle size values ​​represent the values ​​of each group of samples, and the results are shown in Tables 5 and 6.

[0179] Table 5: D50 particle size and variance σ of the cathode materials of Example 1 and Comparative Example 2

[0180]

[0181]

[0182] In Example 1 and Comparative Example 2, polycrystalline large particles, polycrystalline small particles, and single crystal particles were wet-mixed in a mass ratio of 7:2:1. Since the D50 of the polycrystalline large particles is 13 μm, the D50 of the polycrystalline small particles is 7 μm, and the D50 of the single crystal particles is 4 μm, the theoretically calculated D50 after mixing in the above ratio is 13*0.7 + 7*0.2 + 4*0.1 = 10.9 μm. As can be seen from Table 5, the σ value in Example 1 is smaller than that in Comparative Example 2, indicating that the wet mixing method of Example 1 achieves better mixing uniformity. When σ ≤ 0.04, the mixing uniformity can be considered to meet the requirements.

[0183] Table 6: Variance σ of D50 particle size of the cathode material in the examples

[0184]

[0185] 221654 1CNCN

[0186]

[0187] As can be seen from Table 6, when wet mixing is performed using the method of the present invention, the proportion of the amount of coating agent added each time is kept the same as the proportion of the amount of particles added each time, and the cathode material has a very good mixing uniformity, with the variance σ of the D50 particle size ≤ 0.04.

Claims

1. A hybrid high-nickel cathode material, characterized in that, The mixed high-nickel cathode material is formed by wet mixing of polycrystalline large particles, polycrystalline small particles and single crystal particles in a molar ratio of l:m:n, followed by coating with a coating agent and sintering, wherein 6.5≤l≤7.5, 1.5≤m≤2.5, 0.5≤n≤1.5, and l+m+n=10. The polycrystalline large particles are composed of the precursor Ni x M 1-x (OH)2 is sintered with lithium salt, wherein 0.8≤x<1, and the D50 particle size of the polycrystalline large particles is 12~14μm; The polycrystalline particles are composed of the precursor Ni y M' 1-y (OH)2 is sintered with lithium salt, wherein 0.8≤y<1, and the D50 particle size of the polycrystalline particles is 6.5~7.5μm; The single crystal particles are composed of the precursor Ni z M'' 1-z (OH)2 is sintered with lithium salt, wherein 0.8≤z<1, and the D50 particle size of the single crystal particles is 3.5~4.5μm; M, M', and M'' are all Co, Mn, and Al; In M, M' and M'', the molar ratio of Co, Mn and Al is independently (4~6):(3~5):1; the variance σ of the D50 particle size of the mixed high-nickel cathode material is ≤0.04; The D50 particle size of the mixed high-nickel cathode material is 10~12μm; The coating agent is ZrO2, and the ratio of the amount of coating agent to the total amount of polycrystalline large particles, polycrystalline small particles and single crystal particles is (0.1~0.2):

100. The preparation method of the hybrid high-nickel cathode material includes the following steps: (1) Preparation of polycrystalline large particles: The precursor Ni x M 1-x (OH)2 is sintered with lithium salt to form the aforementioned polycrystalline large particles; (2) Preparation of polycrystalline small particles: The precursor Ni y M' 1-y (OH)2 is sintered with lithium salt to form the polycrystalline small particles; (3) Preparation of single crystal particles: The precursor Ni z M'' 1-z (OH)2 is sintered with lithium salt to form the single crystal particles described above; (4) Wet mixing and coating, sintering: The polycrystalline large particles, the polycrystalline small particles, the single crystal particles and the coating agent are added to water or alcohol in steps and stirred and mixed. The mixture is dried and then sintered to obtain the mixed high-nickel cathode material. The wet blending and coating process includes: at a speed of 80-130 rpm, first adding 30%-80% of the large polycrystalline particles and part of the coating agent to water or alcohol, stirring for 10-60 seconds, then adding 40%-60% of the small polycrystalline particles and part of the coating agent, stirring for 10-60 seconds, then adding all the single crystal particles and part of the coating agent, stirring for 10-60 seconds, then adding the remaining small polycrystalline particles and part of the coating agent, stirring for 10-60 seconds, then adding the remaining large polycrystalline particles and the remaining coating agent. The molar ratio of the coating agent added in each step is the same as the molar ratio of the particles added in each step. After the addition is complete, the speed is increased to 150-200 rpm, and then stirred for 60-120 seconds.

2. The mixed high-nickel cathode material as described in claim 1, characterized in that, The polycrystalline large particles, the polycrystalline small particles, and the single crystal particles are each independently formed by sintering a precursor and a lithium salt in a molar ratio of 1:(1~1.08).

3. The mixed high-nickel cathode material as described in claim 1, characterized in that, The method for preparing the hybrid high-nickel cathode material has one or more of the following characteristics: The sintering temperature for preparing polycrystalline large particles is 600~900℃, and the sintering time is 8~15h. The sintering temperature for preparing polycrystalline small particles is 600~900℃, and the sintering time is 8~15h; The sintering temperature for preparing single-crystal particles is 800~1000℃, and the sintering time is 8~15h; The sintering temperature for preparing the mixed high-nickel cathode material is 200~700℃, and the sintering time is 3~8h.

4. A positive electrode sheet, characterized in that, The positive electrode comprises the mixed high-nickel positive electrode material according to any one of claims 1-3.

5. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode sheet as described in claim 4.

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