Multi-component coating-modified single-crystal nickel cobalt manganese oxide lithium cathode material, its manufacturing method, and lithium-ion battery

Abstract

The present invention relates to a modified single-crystal lithium nickel cobalt manganese oxide cathode material, a manufacturing method thereof, and a lithium-ion battery. The modified single-crystal lithium nickel cobalt manganese oxide cathode material includes a matrix and a coating layer coated on the surface of the matrix. The chemical formula of the matrix is ​​Li a Ni x Co y Mn 1-x-y-z M z O2, 0.9≦a≦1.2, 0.5≦x<1, 0

Description

[Technical Field]

[0001] The present invention relates to the technical field of positive electrode materials for lithium ion batteries, and in particular to a single-crystal nickel-cobalt-manganese positive electrode material and a manufacturing method thereof, and a lithium ion battery. [Background technology]

[0002] With the development of new energy vehicles, consumer demand for driving range is constantly increasing, so it is extremely important for lithium-ion battery cathode materials to develop lithium-ion batteries with high energy density, high power density, and low cost. Ternary nickel cobalt manganese oxide cathode materials have the characteristics of low Co content and high capacity, and therefore show significant advantages in capacity and cost compared to lithium cobalt oxide.

[0003] Currently, lithium nickel-cobalt manganese oxide cathode materials have two development directions, distinguished primarily by morphology: secondary spherical particles and single-crystal particles. Mature manufacturing methods have already been developed for these two types of materials. Chinese patent application number 201811382498.7 discloses a method for manufacturing secondary spherical materials, which allows for the production of secondary spherical cathode materials. Secondary spherical cathode materials have high energy density due to their small primary particles, but are limited by factors such as poor high-temperature cycling performance, rapid high-temperature DCR increase, and gas generation. Therefore, they are primarily used in energy storage and have little application in power. Chinese patent application number 201710883429.3 discloses a method for manufacturing single-crystal materials, which allows for the production of single-crystal cathode materials. Single-crystal ternary cathode materials have large primary particles and a perfect structure, which reduces the anisotropy of lattice expansion and contraction between crystal grains during cycling, ensuring structural integrity during repeated cycling and improving cycle stability. In addition, single-crystal materials have both a low specific surface area and excellent structural stability, which improves cycle stability and allows the particles to retain their original shape even after long-term cycling, and they are currently widely used in the new energy industry.

[0004] Generally, single-crystal ternary cathode materials have low energy density and poor output performance due to their large primary particle design. The primary method for improving the energy density of single-crystal materials is to increase their cutoff voltage. However, as the cutoff voltage increases to ≥ 4.35 V, the material surface undergoes structural changes from a layered structure to a spinel structure and then to a NiO rock salt phase. During repeated lithium ion absorption and desorption, the anisotropy of the crystals leads to intracrystalline cracks within the material, which facilitates electrolyte penetration into the material particles and causes various side reactions on the particle surface. All of these factors degrade the capacity, cycle performance, rate performance, gas generation, and other performance characteristics of lithium-ion batteries. Therefore, improving the surface structural stability of single-crystal ternary cathode materials is an important research topic. A common method for modifying single-crystalline ternary cathode materials is to coat them with lithium transition metal oxides (Li2ZrO3, LiCoO2, LiAlO2, Li2WO4, etc.) or non-electrochemically active metal oxides (Al2O3, ZrO3, MgO, TiO2, etc.).

[0005] In general, Al2O3 coating is known to be an effective method for improving the stability of the surface structure of layered lithium transition metal oxide cathode materials and reducing interfacial side reactions between the material and the electrolyte. In a non-patent document (Binghong Han, Baris Key, Saul H. Lapidus, Juan C. Garcia, Hakim Iddir, John T. Vaughey, and Fulya Dogan, Applied Materials & Interfaces (47) 2017:41291-41302), Al elements were found in the transition metal layer of the crystal lattice on the surface after high-temperature sintering. In the case of nickel-cobalt-manganese layered cathode materials, Al2O3 coating significantly weakens the coating effect, ultimately resulting in a deterioration in capacity and cycle performance. This shows that direct Al2O3 coating is not possible. On the other hand, in the case of tungsten-coated layered cathode materials, the only way to improve the capacity and rate performance of the material is to reduce the material's resistance. A non-patent document (Xinhe Yang, Zicheng Zuo, Haiyan Wang, Quanbin Chen, Hui Zhang, Zhenlei Huang, Borong Wu, Henghui Zhuo, Electrochimica Acta (180) 2015: 604-609) demonstrates that layered materials coated with simple tungsten oxide do not form stable tungsten compounds, and therefore tungsten concentrates in the graphite anode during the electrochemical reaction, resulting in deterioration of high-temperature cycle performance and storage performance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Chinese Patent Application Publication No. 109244436 [Patent Document 2] Chinese Patent Application Publication No. 107768619 [Non-patent literature]

[0007] [Non-Patent Document 1] Binghong Han, Baris Key, Saul H. Lapidus, Juan C. Garcia, Hakim Iddir, John T. Vaughey, and Fulya Dogan, Applied Materilas & Interfaces(47)2017:41291-41302 [Non-patent document 2] XinheYang, Zicheng Zuo, Haiyan Wang, Quanbin Chen, Hui Zhang, Zhenlei Huang, Borong Wu, Henghui Zhuo, Electrochimica Acta(180)2015:604-609 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention overcomes the drawbacks and deficiencies described in the background art and aims to provide a multi-component coating-modified monocrystalline lithium nickel cobalt manganese oxide cathode material containing Al and W, a method for producing the same, and its application in the production of lithium-ion batteries. [Means for solving the problem]

[0009] In order to solve the above technical problems, the present invention provides the following technical means.

[0010] A multi-component coating-modified single-crystal lithium nickel cobalt manganese oxide positive electrode material, comprising a matrix and a coating layer coated on the surface of the matrix, the chemical formula of the matrix is: Li a Ni x Co y Mn 1-x-y-z M zIt is O2, where 0.9 ≤ a ≤ 1.2, 0.5 ≤ x < 1, 0 < y ≤ 0.2, 0 ≤ z ≤ 0.1, M contains one or more of Ti, Mg, Y, Al or Zr elements, the coating layer contains tungsten element and aluminum element, the mass of the tungsten element accounts for 0.2% - 1.0% of the mass of the matrix of the cathode material, the aluminum element accounts for 0.03% - 0.2% of the mass of the matrix of the cathode material, and the coating layer contains Al2(WO4)3.

[0011] More preferably, the coating layer further contains one or two of Li2WO4 and Li4WO5.

[0012] The single-crystalline nickel cobalt manganese lithium oxide cathode material with multi-component coating modification according to the present invention is co-coated at high temperature using an Al compound, a W compound and an additional small amount of lithium source. The Al element in the aluminum compound and the W element in the W compound form a stable Al2(WO4)3 substance at high temperature, thereby effectively suppressing the Al element in the aluminum compound, preventing the diffusion of the transition metal layer into the crystal lattice of the material, forming an aluminum tungsten compound coating layer beneficial to the material interface stability on the surface of the material, effectively stabilizing the surface structure of the material. Moreover, the W compound further reacts with the lithium source and the residual lithium in the material to generate a stable lithium tungstate compound, effectively reducing the elution of the tungsten element in the coating into the electrolyte, promoting the tight bonding to the surface of the cathode material, and effectively improving the material capacity and output performance.

[0013] More preferably, the specific surface area of the single-crystalline nickel cobalt manganese lithium oxide cathode material is 0.5 m 2 / g - 0.8 m 2 / g.

[0014] More preferably, the particle size range of the single-crystalline nickel cobalt manganese lithium oxide cathode material means that D V 50 is 3.0 μm - 4.5 μm, and D V 90 is 6.0 μm - 8.0 μm, and D V99% value is <10 μm.

[0015] More preferably, the residual NiO content on the surface of the single crystal lithium nickel cobalt manganese oxide positive electrode material is 300 to 500 ppm of the mass of the single crystal lithium nickel cobalt manganese oxide positive electrode material, the residual Li2CO3 content is 0.08% to 0.15% of the mass of the single crystal lithium nickel cobalt manganese oxide positive electrode material, and the residual LiOH content is 0.04% to 0.10% of the mass of the single crystal lithium nickel cobalt manganese oxide positive electrode material.

[0016] As a general concept of the present invention, the present invention further provides a method for producing the above-mentioned single crystal lithium nickel cobalt manganese oxide positive electrode material, which method comprises the steps of: Step S1: mixing a nickel cobalt manganese hydroxide precursor, a first lithium source, and an M-containing compound, followed by a first sintering to obtain a matrix; and step S2 of mixing the matrix with a second lithium source and a coating agent, the coating agent including an Al compound and a W compound, and sintering the matrix for a second time at a temperature of 750°C to 950°C to obtain a multi-component coated modified single crystal lithium nickel cobalt manganese oxide cathode material.

[0017] The second sintering in the present invention is a process of supplementing a small amount of lithium. After the matrix produced in step S1 is crushed, there is a large amount of fine powder and rock salt phase on the particle surface. Therefore, a high reaction temperature is used in step S2, where the supplemented lithium source and the lithium remaining on the surface after the first sintering can undergo a sufficient chemical reaction. The metal oxide can participate in the chemical reaction as a coating material and is carried out almost simultaneously with the repair process of the fine powder and rock salt phase, which is advantageous for tight bonding to the surface of the positive electrode material.

[0018] In the present invention, the aluminum and tungsten compounds added during the second sintering process produce coating effects that are not ideal when applied at low temperatures (<600°C), resulting in increased internal resistance and electrochemical polarization. On the other hand, when applied to a single aluminum oxide coating at high temperatures (700-900°C), Al diffuses into the crystal lattice of the material, resulting in poor coating effectiveness. Research has shown that mixing Al and W compounds with a positive electrode material and sintering at high temperatures significantly inhibits the diffusion kinetics of Al into the bulk phase of the material, ultimately forming a composite coating containing one or more of Al2(WO4)3, Li2WO4, or Li4WO5 on the surface of the positive electrode material, stabilizing the surface structure of the material and further improving various performance characteristics of the material.

[0019] More preferably, the first lithium source and the second lithium source are one or more selected from lithium carbonate, lithium nitrate, lithium hydroxide, and lithium acetate, the molar ratio of the lithium element in the first lithium source to the nickel cobalt manganese hydroxide precursor is 1.0 to 1.2:1, and the molar ratio of the lithium element in the second lithium source to the W element in the W compound is 2 to 4:1.

[0020] More preferably, the M-containing compound is one or more selected from M-containing carbonates, M-containing hydroxides, M-containing nitrates, M-containing chlorides, M-containing sulfates, and M-containing oxides.

[0021] More preferably, the Al compound contains one or more of aluminum oxide, aluminum hydroxide, and hydroxyaluminum oxide, the W compound contains one or more of tungsten oxide and ammonium tungstate, and the molar ratio of tungsten element in the W compound to Al element in the Al compound is 1.5 to 3:1.

[0022] More preferably, the sintering temperature in the first sintering is 920°C to 1000°C, the sintering time is 6 hours to 14 hours, and the sintering atmosphere in the first sintering is one of oxygen and air.

[0023] More preferably, the second sintering is performed at a temperature of 800 to 850°C for a period of 2 to 12 hours in an atmosphere of oxygen or air. Sintering at a temperature lower than 800°C may reduce the stability of the compound formed by Al and W, limiting the degree of repair of the fine powder and rock salt phase. On the other hand, a sintering temperature that is too high may increase the diffusion kinetics of Al into the bulk phase of the material, affecting the electrochemical performance of the material.

[0024] As a general concept of the present invention, the present invention further provides a lithium-ion battery, which includes a positive electrode current collector, a positive electrode sheet coated on the positive electrode current collector and containing the above-mentioned positive electrode material, a negative electrode current collector, a negative electrode sheet coated on the negative electrode current collector and containing the above-mentioned negative electrode material, a separator interposed between the positive electrode sheet and the negative electrode sheet, and an electrolyte, wherein the positive electrode material is the above-mentioned multi-component coating modified single-crystal lithium nickel cobalt manganese oxide positive electrode material. [Effects of the Invention]

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] (1) The single-crystal nickel-cobalt-manganese lithium cathode material produced by the present invention has several advantages. First, it can improve the initial charge / discharge capacity, rate performance, and low power issues. Second, it can improve the high-temperature cycle capacity retention rate at a high charge cutoff voltage of the material. Third, it can improve the problems of increased internal resistance and gas generation during high-temperature storage at a high charge cutoff voltage of the material. Fourth, it can improve the surface properties of the single-crystal nickel-cobalt-manganese cathode material, reducing the residual NiO content on the surface and reducing side reactions with the electrolyte during the electrochemical process.

[0027] (2) The present invention provides a multi-component coating modified single-crystal nickel-cobalt-manganese oxide positive electrode material by co-coating an Al compound, a W compound, and a small amount of an additional lithium source at high temperatures. The Al element in the Al compound and the W element in the W compound form a stable Al2(WO4)3 substance at high temperatures, which effectively inhibits the Al element in the Al compound and prevents it from diffusing into the transition metal layer in the crystal lattice of the material. This forms an aluminum tungsten compound coating layer on the surface of the material, which is beneficial to the material interface stability and effectively stabilizes the surface structure of the material. The W compound also reacts with the lithium source and residual lithium in the material to form a stable lithium tungstate compound, which effectively reduces the elution of tungsten in the coating into the electrolyte and promotes tight bonding to the surface of the positive electrode material, effectively improving the material capacity and power performance.

[0028] (3) In the manufacturing method of the present invention, by using high-temperature sintering coating and adding a small amount of lithium source (lithium hydroxide, lithium carbonate, or other substances), the fine powder and rock salt phase components on the surface of the matrix obtained in the first sintering react with the residual lithium on the surface and the additional lithium source, and integrate with the single crystal particles, improving the fine powder content of the material, reducing the NiO content, and improving the high-temperature cycle performance of the material.

[0029] (4) In the multi-component coating-modified single-crystal lithium nickel-cobalt-manganese oxide positive electrode material produced by the method of the present invention, the W compound forms a lithium-containing coating, which not only improves its own capacity and rate performance, but also suppresses the diffusion kinetics of the Al element in the coating. Furthermore, the additional lithium source not only promotes the formation of lithium tungsten compounds, but also reduces the content of fine powder and the content of surface NiO. Therefore, in the present invention, the combination of the coating with the W compound, the Al compound, and a small amount of lithium source not only compensates for the deficiencies of a single compound coating, but also creates a synergistic effect among the three, further improving the high capacity, long cycle life, and high rate performance of the positive electrode material.

[0030] In summary, the present invention performs surface modification on a single-crystal lithium nickel cobalt manganese oxide positive electrode material with a multi-component composite coating layer, thereby ultimately ensuring excellent electrochemical performance of the positive electrode material, such as specific capacity, cycle performance, and rate performance. [Brief explanation of the drawings]

[0031] In order to more clearly describe the technical solutions in the embodiments of the present invention or the prior art, the following briefly introduces the drawings necessary for the description of the embodiments or the prior art. It is obvious that the drawings in the following description are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative work.

[0032] [Figure 1] 1 is a scanning electron microscope (SEM) photograph of the single-crystal lithium nickel cobalt manganese oxide positive electrode material prepared in Example 1 of the present invention. [Figure 2] FIG. 2 is a particle size volume distribution diagram of the single-crystal lithium nickel cobalt manganese oxide positive electrode material prepared in Example 1 of the present invention. [Figure 3] FIG. 1 is an XPS diagram of the single-crystal lithium nickel cobalt manganese oxide positive electrode material prepared in Example 1 of the present invention. [Figure 4] 1 is a scanning electron microscope (SEM) photograph of a single-crystal lithium nickel cobalt manganese oxide positive electrode material produced in Comparative Example 1. [Figure 5] FIG. 2 is a particle size volume distribution diagram of the single-crystal lithium nickel cobalt manganese oxide positive electrode material produced in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0033] In order to facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the drawings and preferred embodiments of the specification, but the scope of protection of the present invention is not limited to the following specific examples.

[0034] Unless otherwise defined, all technical terms used below have the same meaning as commonly understood by those skilled in the art. The technical terms used in this specification are only for describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0035] Unless otherwise specified, the various raw materials, reagents, instruments, and devices used in the present invention can all be purchased from the market or prepared by conventional methods.

[0036] Example 1 The multi-component coating modified single crystal nickel cobalt manganese oxide cathode material is a cathode material matrix Li 1.02 Ni 0.666 Co 0.08 Mn 0.25 Zr 0.004 O2, and a tungsten-containing compound coating layer coated on the surface of the matrix: Al2(WO4)3, Li2WO4, Li4WO5, where the tungsten element accounts for 0.5% of the mass of the positive electrode material matrix, and the aluminum element accounts for 0.04% of the mass of the positive electrode material matrix.

[0037] The method for producing the multi-component coating-modified single-crystal lithium nickel cobalt manganese oxide positive electrode material according to this embodiment includes the following steps (1) and (2).

[0038] In step (1), a commercially available nickel cobalt manganese hydroxide precursor, Ni 0.67 Co 0.08 Mn 0.25 (OH)2, LiOH·H2O, and nano-zirconia were uniformly mixed in a molar ratio of 1:1.02:0.004. The mixed material was then sintered at 950°C for 12 hours in an oxygen atmosphere (oxygen concentration > 96%), cooled, crushed, and sieved through a 200-mesh sieve to obtain the lithium transition metal oxide of the positive electrode material matrix. ICP measurement revealed that its molecular formula was Li 1.02 Ni 0.666 Co 0.08 Mn 0.25 Zr 0.004 It is O2.

[0039] In step (2), the positive electrode material matrix obtained in step (1), 0.055 mol of nano-WO3 (the mass ratio of W element to the positive electrode material matrix is ​​0.5%), 0.014 mol of nano-Al2O3 (the mass ratio of Al element to the positive electrode material matrix is ​​0.04%), and 0.22 mol of LiOH·H2O were uniformly mixed to form a mixed material, which was then placed in a calciner and calcined under the conditions of heating to 830°C at a rate of 3°C / min in an air atmosphere and maintaining the temperature for 10 hours. After cooling to room temperature, the resulting material was passed through a 200-mesh sieve to finally obtain a single-crystalline lithium nickel-cobalt-manganese oxide positive electrode material coated with a tungsten-containing composite.

[0040] As can be seen from the scanning electron microscope observation in Figure 1, the surface of the coated sample is smooth, with few fine particles (there is no peak protrusion in the region below Dv1 in the particle size volume distribution in Figure 2), and there is a fine dot-like coating. The specific surface area is 0.658 m 2 / g, Dv50 value is 3.7μm, and D V 90 value is 7.2 μm, and D V The 99 value was 8.6 μm. ICP measurement showed that the residual NiO content on the surface of the sample after composite coating was 300 ppm, which is favorable for mitigating adverse phase transformation during cycling and improving structural stability.

[0041] As can be seen from the XPS diagram in Figure 3, the tungsten-containing compounds on the surface of the coated sample are mainly composed of Al2(WO4)3, Li2WO4, and Li4WO5, forming a stable Al2(WO4)3 material, which effectively inhibits the Al element in the aluminum compound and prevents it from diffusing into the transition metal layer within the crystal lattice of the material. This forms an aluminum tungsten compound coating on the surface of the material, which is beneficial to the material's interface stability and effectively stabilizes the material's surface structure. Furthermore, the W element can react with the lithium source and residual lithium in the material to form a stable lithium tungstate compound, which effectively reduces the elution of tungsten in the coating into the electrolyte and promotes tight bonding to the surface of the positive electrode material, thereby effectively improving the material's capacity and power performance.

[0042] <Example 2> This example differs from Example 1 in that in step (2), 0.0079 mol of ammonium tungstate is weighed, the mass ratio of tungsten element to the positive electrode material matrix is ​​0.5%, and the sintering conditions are to heat the mixture in an air atmosphere at a rate of 3°C / min up to 850°C and keep the temperature for 10 hours; the other process parameters are the same as those in Example 1.

[0043] Example 3 This example differs from Example 1 in that in step (2), 0.028 mol of aluminum hydroxide is weighed out, the mass ratio of aluminum element to the positive electrode material matrix is ​​0.05%, and the sintering conditions are to heat the mixture in an air atmosphere at a rate of 3°C / min up to 800°C and maintain the temperature for 10 hours; the other process parameters are the same as those in Example 1.

[0044] <Comparative Example 1> This comparative example is a cathode material matrix prepared in step (1) of Example 1, which is a lithium transition metal oxide Li 1.02 Ni 0.666 Co 0.08 Mn 0.25 Zr 0.004O2. Fig. 4 is a scanning electron microscope (SEM) photograph of the single crystal lithium nickel cobalt manganese oxide positive electrode material prepared in Comparative Example 1. Fig. 5 is a particle size volume distribution diagram of the single crystal lithium nickel cobalt manganese oxide positive electrode material prepared in Comparative Example 1.

[0045] <Comparative Example 2> Step (1) of this comparative example is completely identical to that of Example 1, except that in step (2), only 0.22 mol of LiOH·H2O is weighed and mixed with the positive electrode material matrix. The other process parameters are the same as those of Example 1.

[0046] <Comparative Example 3> Step (1) of this comparative example is completely identical to that of Example 1, except that in step (2), only 0.055 mol of WO3 (the mass ratio of tungsten element to the positive electrode material matrix is ​​0.5%) is weighed and mixed with the positive electrode material matrix, and other process parameters are the same as those of Example 1.

[0047] <Comparative Example 4> Step (1) of this comparative example is completely consistent with Example 1. The difference is that in step (2), only 0.055 mol of WO3 (the mass ratio of tungsten element to the positive electrode material matrix is ​​0.5%) and 0.014 mol of Al2O3 (the mass ratio of aluminum element to the positive electrode material matrix is ​​0.04%) are weighed and mixed with the positive electrode material matrix; other process parameters are the same as those in Example 1.

[0048] <Comparative Example 5> Step (1) of this comparative example is completely identical to Example 1, except that in step (2), the sintering conditions are to heat the material to 700°C at a rate of 3°C / min in an air atmosphere, keep the temperature for 10 hours, and then naturally cool it to room temperature. The other process parameters are the same as in Example 1.

[0049] The battery cathode materials prepared in the examples and comparative examples were mixed uniformly with conductive carbon black and binder PVDF in a mass ratio of 92:5:3 using NMP as a solvent, and then coated onto Al foil. The mixture was dried at 120°C for 12 hours, rolled, and punched into 12 mm disks. In an argon gas-protected glove box (oxygen content less than 1 ppm, moisture content less than 1 ppm), a CR2032 coin battery was assembled using a metallic lithium sheet as the anode, and electrochemical performance measurements were performed at 25°C over a voltage window of 3.0 to 4.45 V. The specific measurement method was as follows: in the first cycle, charge at 0.1C and discharge at 0.1C; in the second cycle, charge at 0.2C and discharge at 0.2C; in the third cycle, charge at 0.2C and discharge at 0.5C; in the fourth cycle, charge at 0.2C and discharge at 1C; in the fifth cycle, charge at 0.2C and discharge at 0.2C; and in the sixth to fifteenth cycles, charge at 1C and discharge at 1C. The electrochemical data of the button batteries assembled using the materials obtained in the above examples and comparative examples, such as the 0.1C discharge specific capacity, the 2C discharge specific capacity, and the 50-cycle capacity retention (the ratio of the 55th cycle discharge specific capacity to the 6th cycle discharge specific capacity), as well as the surface NiO content, residual lithium, and fine powder content of the materials, are shown in Table 1.

[0050] [Table 1]

[0051] As can be seen from the data in Table 1, comparing Example 1 with Comparative Example 1, the one with the tungsten-containing composite coating layer exhibits better performance, with better electrochemical performance, lower residual lithium, residual NiO, and lower fine powder content. Comparing Example 1 with Comparative Example 5, the coating layer composed of tungsten oxide, aluminum oxide, and a lithium source only works optimally at high temperatures, promoting the formation of tungsten-containing composite materials at high temperatures and inhibiting the incorporation of Al into the material's crystal lattice, further demonstrating the advantages of this composite coating modification method. Comparing Example 1 with Comparative Example 4, it can be seen that tungsten oxide and aluminum oxide can react with residual lithium and significantly reduce it when coated at high temperatures, but no additional lithium is added, resulting in a lithium deficiency and resulting in less lithium tungstate formation, resulting in weak improvements in the capacity and rate performance of the material.

[0052] Comparing Example 1 and Comparative Example 3, it can be seen that when tungsten oxide is coated at high temperatures, it reacts with residual lithium and an external lithium source to produce sufficient lithium tungstate, significantly improving the capacity and rate performance of the material. However, due to the lack of Al2O3, its cycle performance and ability to suppress internal resistance increase are poor. Compared to the primary sintered material of Comparative Example 1, the NiO, Li2CO3, and LiOH contents on the surface of the coated material are significantly reduced, improving sheet processing performance and reducing gas generation in lithium-ion batteries. After being modified by high-temperature composite coating, this single-crystal positive electrode material combines the advantages of a single coating and compensates for the shortcomings of a single coating. Lithium-ion batteries using this material as the active material have high capacity, high rate, long cycle life, and low internal resistance increase.

[0053] The above are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above examples. Improvements and modifications made by those skilled in the art without departing from the technical spirit of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A multi-component coating-modified single-crystal lithium nickel cobalt manganese oxide positive electrode material, comprising a matrix and a coating layer coated on the surface of the matrix, wherein the chemical formula of the matrix is ​​Li ａ Ni ｘ Co ｙ Mn １－ｘ－ｙ－ｚ M ｚ O ２ wherein 0.9≦a≦1.2, 0.5≦x<1, 0<y≦0.2, 0≦z≦0.1, and M comprises one or more of Ti, Mg, Y, Al, or Zr elements; The coating layer contains tungsten and aluminum elements, the mass of the tungsten element accounts for 0.2% to 1.0% of the mass of the matrix of the positive electrode material, and the mass of the aluminum element accounts for 0.03% to 0.2% of the mass of the matrix of the positive electrode material. The coating layer contains Al ２ (W.O. ４ ) ３ Including, A single-crystal nickel cobalt manganese oxide lithium positive electrode material.

2. The coating layer is Li ２ WO ４ and Li ４ WO ５ The single crystal lithium nickel cobalt manganese oxide positive electrode material according to claim 1, further comprising one or two of the following:

3. The specific surface area of ​​the single crystal nickel cobalt manganese oxide lithium cathode material is 0.5 m ２ / g to 0.8m ２ 3. The single crystal lithium nickel cobalt manganese oxide positive electrode material according to claim 1, wherein the ZnO content is 1.0 wt % or more.

4. The particle size range of the single crystal nickel cobalt manganese oxide lithium positive electrode material is D Ｖ 50 is 3.0 μm to 4.5 μm, and D Ｖ 90 is 6.0 μm to 8.0 μm, and D Ｖ 3. The single crystal lithium nickel cobalt manganese oxide positive electrode material according to claim 1, wherein the .99 value is less than 10 μm.

5. The residual NiO content on the surface of the single crystal lithium nickel cobalt manganese oxide positive electrode material is 300-500 ppm based on the mass of the single crystal lithium nickel cobalt manganese oxide positive electrode material, and the residual Li ２ CO ３ 3. The monocrystalline lithium nickel cobalt manganese oxide positive electrode material according to claim 1, wherein the content of LiOH is 0.08% to 0.15% by mass of the monocrystalline lithium nickel cobalt manganese oxide positive electrode material, and the residual LiOH content is 0.04% to 0.10% by mass of the monocrystalline lithium nickel cobalt manganese oxide positive electrode material.

6. A method for producing the single crystal lithium nickel cobalt manganese oxide positive electrode material according to any one of claims 1 to 5, Step S1: mixing a nickel-cobalt-manganese hydroxide precursor, a first lithium source, and an M-containing compound, and then performing a first sintering to obtain a matrix; Step S2: mixing the matrix with a second lithium source and a coating agent, the coating agent including an Al compound and a W compound, and performing a second sintering at a temperature of 750°C to 950°C to obtain a multi-component coating-modified single-crystal lithium nickel cobalt manganese oxide positive electrode material; 1. A method for producing a single crystal lithium nickel cobalt manganese oxide positive electrode material, comprising:

7. 7. The method for producing a single-crystal lithium nickel cobalt manganese oxide positive electrode material according to claim 6, wherein the first lithium source and the second lithium source are one or more selected from the group consisting of lithium carbonate, lithium nitrate, lithium hydroxide, and lithium acetate, the molar ratio of the lithium element in the first lithium source to the nickel cobalt manganese hydroxide precursor is 1.0 to 1.2:1, and the molar ratio of the lithium element in the second lithium source to the W element in the W compound is 2 to 4:

1.

8. 8. The method for producing a single-crystal lithium nickel cobalt manganese oxide positive electrode material according to claim 7, wherein the M-containing compound is one or more compounds selected from the group consisting of an M-containing carbonate, an M-containing hydroxide, an M-containing nitrate, an M-containing chloride, an M-containing sulfate, and an M-containing oxide.

9. 9. The method for producing a single-crystal lithium nickel cobalt manganese oxide positive electrode material according to claim 8, wherein the Al compound comprises one or more of aluminum oxide, aluminum hydroxide, and hydroxyaluminum oxide; the W compound comprises one or more of tungsten oxide and ammonium tungstate; and the molar ratio of tungsten in the W compound to Al in the Al compound is 1.5 to 3:

1.

10. The method for producing a single-crystal lithium nickel cobalt manganese oxide positive electrode material according to any one of claims 6 to 9, characterized in that the sintering temperature of the first sintering is 920°C to 1000°C, the sintering time is 6 hours to 14 hours, and the sintering atmosphere of the first sintering is one of oxygen and air.

11. 11. The method for producing a single-crystal lithium nickel cobalt manganese oxide positive electrode material according to claim 10, wherein the sintering temperature of the second sintering is 800°C to 850°C, the sintering time is 2 hours to 12 hours, and the sintering atmosphere of the second sintering is one of oxygen and air.

12. 12. A lithium ion battery comprising: a positive electrode current collector; a positive electrode sheet coated on the positive electrode current collector and containing a positive electrode material; a negative electrode current collector; a negative electrode sheet coated on the negative electrode current collector and containing a negative electrode material; a separator interposed between the positive electrode sheet and the negative electrode sheet; and an electrolyte, wherein the positive electrode material is the single-crystal lithium nickel cobalt manganese oxide positive electrode material according to any one of claims 1 to 11.

Images