A low-alkali residual cathode material, its preparation method, and its application.

Abstract

This invention provides a cathode material with low residual alkali. The invention utilizes the synergistic effect of an aluminum source and a metal-containing fluoride to consume residual lithium on the cathode material surface. This fluoride has the same lattice constant as the cathode material matrix, allowing for excellent solid solution formation with the layered bulk structure of the lithium-ion material. This results in the formation of an M-O-F surface film on the metal surface [M being the metal element of the aforementioned fluoride]. This fluoride, as an excellent friction-reducing material, exhibits superior lubrication and film-forming properties. The coated material demonstrates good pressure resistance. Furthermore, the synergistic effect of the fluoride and aluminum source in consuming residual alkali on the surface and generating a stable composite coating layer effectively reduces residual alkali on the cathode material surface and minimizes direct contact between the electrolyte and the cathode material. This effectively prevents the dissolution of metal ions in the cathode material, suppresses side reactions, and improves the material's lifespan and gas generation performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, specifically relating to a low-alkali-residue cathode material, its preparation method, and its application. Background Technology

[0002] With the widespread application of portable electronic products and the development of electric vehicles such as EVs and HEVs, lithium-ion battery cathode materials are constantly breaking through their bottlenecks and developing towards higher capacity, longer lifespan, and greater safety and stability. High-nickel cathode materials, such as Li(Ni) x M 1-x O2, with its low cost, high capacity, and environmental friendliness, has attracted increasing attention. However, there are some pressing issues to be addressed in its practical applications: high-nickel materials have high surface pH and residual alkali content, making processing and storage difficult, and resulting in severe gas expansion in the prepared batteries; with the cycling process, the material's microstructure changes, ultimately leading to capacity decay and poor cycle performance. Therefore, reducing residual alkali on the surface of high-nickel materials has become a key research focus.

[0003] Currently, water washing followed by secondary sintering is commonly used to reduce residual alkali on the surface of high-nickel materials. While this method can significantly reduce surface alkali, it also increases the specific surface area of ​​the treated high-nickel materials and exacerbates side reactions between the material and the electrolyte, leading to a decrease in battery capacity and cycle performance. Therefore, it is necessary to provide a modified lithium-ion battery cathode material, its preparation method, and a lithium-ion battery that can significantly reduce surface alkali while avoiding an increase in specific surface area.

[0004] Chinese patent CN 110054226 A discloses a method for preparing a low-surface-residue nickel-cobalt-manganese ternary cathode material. This method includes specific steps and implementation methods, involving dissolving boric acid or citric acid in ethanol and then adding the nickel-cobalt-manganese ternary cathode material, utilizing H... + An acid-base neutralization reaction occurs between the material and residual alkali on the surface. The reaction intensity is controlled by stirring time, which effectively reduces residual alkali on the material surface and lowers the pH value. Afterwards, ethanol solution is used for rinsing to ensure that no residual borate or citrate ions remain on the material surface. Finally, a secondary calcination method is used to remove any remaining ethanol molecules, thereby improving the material's consistency and stability. However, this method is cumbersome and uses a large amount of ethanol solution for rinsing, causing waste and safety issues, which is detrimental to production. Chinese patent CN107732199 B discloses a fluorinated lithium-ion battery cathode material and its preparation method. This method includes specific steps and implementation methods, involving reacting the high-nickel cathode material with a polyfluorinated compound (NH4) raw material. a MF b (H3O) a MFb Or (CSO3) a MF b A salt solution is mixed with polyfluorinated compound raw materials, and the mixture is stirred until homogeneous, forming an aqueous solution, suspension, or sol. High-nickel cathode material is then added to this aqueous solution, suspension, or sol to form a paste-like solid-liquid mixture. This mixture is then sintered under an inert atmosphere to obtain a polyfluorinated compound coating layer covering the high-nickel cathode material. This coating layer is distributed on the surface of the high-nickel cathode material, or the polyfluorinated compound material is both distributed on the surface forming a coating layer and partially penetrates into the interior of the high-nickel cathode material. This effectively reduces the residual alkali content on the surface of the high-nickel cathode material in lithium-ion batteries and improves its processing and electrochemical performance. However, this method involves sintering under an inert atmosphere, making it impossible to repair surface defects in the high-nickel material. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a cathode material with low residual alkali, its preparation method and application. The cathode material provided by the present invention has low and stable residual alkali content on the surface, and the resulting battery has good cycle and safety performance.

[0006] This invention provides a cathode material with low residual alkali, having the following chemical formula:

[0007] Li (1+n) Ni (1-a-b-c) Co a M b Q c O2

[0008] Where, 0 < a + b ≤ 0.4, 0 ≤ b ≤ 0.2, 0 < c < 0.04, 0 < n ≤ 0.060;

[0009] M is one or more elements selected from Mn, Al, Zr, Sr, Mg, Cr, Zr, Y, Ta, Zn, V, W, and B;

[0010] Q is the coating material on the surface of the cathode material matrix. The coating material is prepared from an aluminum source compound and a fluoride, and the fluoride has the same lattice constant as the cathode material matrix.

[0011] Preferably, the aluminum source compound is selected from at least one of aluminum hydroxide, aluminum nitrate, nano-alumina, and aluminum phosphate; the fluoride is selected from at least one of strontium fluoride, lanthanum fluoride, nickel fluoride, cobalt fluoride, magnesium fluoride, aluminum fluoride, calcium fluoride, cerium fluoride, yttrium fluoride, and zirconium fluoride.

[0012] Preferably, the cathode material has a layered crystal structure belonging to space group R-3m; the coating on the surface of the cathode material has a discrete island structure.

[0013] Preferably, the median particle size D50 of the cathode material ranges from 3.0 μm to 15.0 μm, and the specific surface area is 0.65 ± 0.3 m². 2 / g, compacted density is 3.4±0.4g / cm³ 3 .

[0014] Preferably, in the ternary cathode material, the aluminum source compound accounts for (0.2-0.8) wt% of the ternary cathode material by mass percentage: 1; and the fluoride accounts for (0.3-0.8) wt% of the ternary cathode material by mass percentage: 1.

[0015] Preferably, the residual alkali content on the surface of the positive electrode material is <0.15%.

[0016] The present invention also provides a method for preparing the above-mentioned cathode material, comprising the following steps:

[0017] A) The lithium source compound, nickel-cobalt-containing compound and doped element compound are mixed and then ball-milled, sintered and pulverized in sequence to obtain the cathode material matrix;

[0018] B) After mixing the aluminum source compound, the fluorine-containing compound and the cathode material matrix, the mixture is sintered to obtain the cathode material.

[0019] Preferably, the lithium source compound is selected from lithium hydroxide and lithium carbonate;

[0020] The nickel-cobalt compound is selected from one or more of the three types of materials: NCA, NCM, and NC.

[0021] The doping element in the doped compound is selected from one or more elements selected from Mn, Al, Zr, Sr, Mg, Cr, Zr, Y, Ta, Zn, V, W, and B;

[0022] The aluminum source compound is selected from at least one of aluminum hydroxide, aluminum nitrate, nano-alumina, and aluminum phosphate;

[0023] The metal fluoride is selected from at least one of strontium fluoride, lanthanum fluoride, nickel fluoride, cobalt fluoride, magnesium fluoride, aluminum fluoride, calcium fluoride, cerium fluoride, yttrium fluoride, and zirconium fluoride.

[0024] Preferably, in step A), the sintering temperature is 700–950°C and the time is 5–15 hours;

[0025] In step B), the sintering temperature is between 300 and 800°C, and the holding time is between 5 and 15 hours.

[0026] The present invention also provides a lithium-ion battery comprising the above-mentioned positive electrode material.

[0027] Compared with the prior art, the present invention provides a cathode material with low residual alkali, having the following chemical formula: Li (1+n) Ni (1-a-b-c) Co a M b Q c O2, where 0 < a + b ≤ 0.4, 0 ≤ b ≤ 0.2, 0 < c < 0.04, 0 < n ≤ 0.060; M is one or more elements selected from Mn, Al, Zr, Sr, Mg, Cr, Zr, Y, Ta, Zn, V, W, and B; Q is the coating material on the surface of the cathode material matrix, wherein the coating material is an aluminum source compound and a fluoride, and the fluoride has the same lattice constant as the cathode material matrix.

[0028] This invention utilizes the synergistic effect of an aluminum source and a metal-containing fluoride to consume residual lithium on the surface of the cathode material. The fluoride has the same lattice constant as the cathode material matrix, allowing for excellent solid solution formation with the layered bulk structure of the lithium-ion material. This results in the formation of a MOF surface film on the metal surface [M being the metal element of the aforementioned fluoride]. As an excellent friction-reducing material, the fluoride exhibits superior lubrication and film-forming properties. The coated material demonstrates good pressure resistance. Furthermore, the synergistic effect of the fluoride and aluminum source consumes residual alkali on the surface, generating a stable composite coating layer. This effectively reduces residual alkali on the cathode material surface and minimizes direct contact between the electrolyte and the cathode material, effectively preventing the dissolution of metal ions in the cathode material, suppressing side reactions, and improving the material's lifespan and gas generation performance. Attached Figure Description

[0029] Figure 1 SEM image of magnesium fluoride provided in Example 1;

[0030] Figure 2 XRD patterns of the materials used in the comparative example and Example 1;

[0031] Figure 3 SEM images of the material surface for comparison with Example 1;

[0032] Figure 4 This is a cumulative volumetric particle size distribution diagram for the comparative example and Example 1 under different pressures. Detailed Implementation

[0033] This invention provides a cathode material with low residual alkali, having the following chemical formula:

[0034] Li (1+n) Ni (1-a-b-c) Co a M b Q c O2

[0035] Where, 0 < a + b ≤ 0.4, 0 ≤ b ≤ 0.2, 0 < c < 0.04;

[0036] M is one or more elements selected from Mn, Al, Zr, Sr, Mg, Cr, Zr, Y, Ta, Zn, V, W, and B;

[0037] Q is the coating material on the surface of the cathode material matrix, which is an aluminum source compound and a fluoride, and the fluoride has the same lattice constant as the cathode material matrix.

[0038] In the chemical formula, 0 < n ≤ 0.060, 0 < a + b ≤ 0.4, 0 ≤ b ≤ 0.2, and 0 < c < 0.04.

[0039] M is one or more elements selected from Mn, Al, Zr, Sr, Mg, Cr, Zr, Y, Ta, Zn, V, W, and B, with Mn being the preferred element.

[0040] Q represents the coating material on the surface of the positive electrode material, which is prepared from an aluminum source compound and a fluoride. The aluminum source compound is selected from at least one of aluminum hydroxide, aluminum nitrate, nano-alumina, and aluminum phosphate. The fluoride has a particulate structure and is selected from at least one of strontium fluoride, lanthanum fluoride, nickel fluoride, cobalt fluoride, magnesium fluoride, aluminum fluoride, calcium fluoride, cerium fluoride, yttrium fluoride, and zirconium fluoride. The fluoride has the same lattice constant as the positive electrode material matrix: lattice constant a = lattice constant b ≠ lattice constant c, α = β = 90℃, γ = 120℃, allowing for excellent solid solution formation with the lithium-ion positive electrode material matrix.

[0041] The cathode material has a layered crystal structure belonging to space group R-3m; the median particle size D50 of the cathode material ranges from 3.0 μm to 15.0 μm, preferably 3, 5, 7, 9, 10, 12, 15, or any value between 3.0 μm and 15.0 μm, and the specific surface area is 0.65 ± 0.3 m². 2 / g, compacted density is 3.4±0.4g / cm³ 3 .

[0042] In the ternary cathode material, the mass percentage of the aluminum source compound is 0.2wt% to 0.8wt%, preferably 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, or any value between 0.2wt% and 0.8wt%; the mass percentage of the fluoride is 0.3wt% to 0.8wt%, preferably 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, or any value between 0.3wt% and 0.8wt%.

[0043] In this invention, the coating on the surface of the positive electrode material has a discrete island structure, and the residual alkali content on the surface of the positive electrode material is <0.15%.

[0044] The present invention also provides a method for preparing the above-mentioned cathode material, comprising the following steps:

[0045] A) The lithium source compound, nickel-cobalt-containing compound and doped element compound are mixed and then ball-milled, sintered and pulverized in sequence to obtain the cathode material matrix;

[0046] B) After mixing the aluminum source compound, the fluorine-containing compound and the cathode material matrix, the mixture is sintered to obtain the cathode material.

[0047] Specifically, the present invention first mixes a lithium source compound, a nickel-cobalt compound, and a dopant compound to obtain a mixture. The lithium source compound is selected from lithium hydroxide and lithium carbonate; the nickel-cobalt compound is selected from one or more of NCA, NCM, and NC materials; and the dopant compound contains one or more elements selected from Mn, Al, Zr, Sr, Mg, Cr, Zr, Y, Ta, Zn, V, W, and B.

[0048] The mixture is sequentially ball-milled, sintered, and pulverized to obtain a positive electrode material matrix. The sintering temperature is 700–950°C, preferably 700, 750, 800, 850, 900, or 950°C, or any value between 700 and 950°C, and the sintering time is 5–15 hours, preferably 5, 8, 10, 12, or 15 hours, or any value between 5 and 15 hours. This invention does not impose any particular limitation on the ball-milling and pulverizing methods; methods known to those skilled in the art are acceptable.

[0049] After obtaining the cathode material matrix, the cathode material matrix is ​​mixed with an aluminum source compound and a metal fluorine compound.

[0050] The aluminum source compound is selected from at least one of aluminum hydroxide, aluminum nitrate, nano-alumina, and aluminum phosphate; the metal fluoride is selected from at least one of strontium fluoride, lanthanum fluoride, nickel fluoride, cobalt fluoride, magnesium fluoride, aluminum fluoride, calcium fluoride, cerium fluoride, yttrium fluoride, and zirconium fluoride.

[0051] Then, the material is placed in a box furnace for sintering. The sintering temperature is 300-800℃, preferably 300, 400, 500, 600, 700, 800℃, or any value between 300-800℃. The holding time is 5-15h, preferably 5, 8, 10, 12, 15h, or any value between 5-15h.

[0052] The present invention also provides a lithium-ion battery comprising the above-mentioned positive electrode material.

[0053] In the cathode material provided by this invention, the fluoride has the same lattice constant as the cathode material matrix, which can form a good solid solution effect with the layered bulk structure of the lithium-ion material, and generate an MOF surface film on the metal surface [M is the metal element of the above fluoride], which is stable. The fluoride is a good anti-friction material and has excellent lubrication and film-forming properties. The coated material has good pressure resistance and the coated surface is resistant to acid corrosion. It works synergistically with the aluminum source to consume residual alkali on the surface and generate a stable composite coating layer. This can effectively reduce residual alkali on the cathode material surface and reduce direct contact between the electrolyte and the cathode material, effectively prevent the dissolution of metal ions in the cathode material, inhibit the generation of side reactions, and improve the lifespan and gas production performance of the material.

[0054] In addition, the preparation method provided by the present invention is simple in steps, low in cost, easy to operate, and short in preparation time, which is conducive to large-scale stable production.

[0055] This invention constructs a positive electrode material with an island-like structure and a wear-resistant coating, which effectively consumes residual alkali on the surface and generates a layer of wear-resistant and lubricating positive electrode material on the material surface. It is not prone to cracking during the electrode rolling process, enhances the particle compressive strength of the material, and has good cycle and safety performance.

[0056] To further understand the present invention, the following embodiments illustrate the low residual alkali cathode material, its preparation method, and its application. The scope of protection of the present invention is not limited by the following embodiments.

[0057] Comparative Example 1:

[0058] (1) Ni prepared by co-precipitation method 0.8 Co 0.1 Mn 0.1 (OH)₂ and lithium hydroxide were mixed uniformly at a molar ratio of Li / Me = 1.03, and 0.03 mol% ZrO₂ was added. The mixture was then sintered at 750°C for 15 hours in an oxygen atmosphere to obtain the final composition Li. 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2 cathode material;

[0059] (2) The cathode material obtained in step (1) is added at 30°C with a mass percentage of 0.3% Al2O3 and 0.1% boric acid relative to the cathode material. After the additives are stirred evenly, the cathode material is placed at 300°C in an oxygen atmosphere and sintered for 10 hours to obtain a surface-modified high-nickel multi-element cathode material.

[0060] (3) The surface-modified high-nickel multi-element cathode material was used to make a coin cell battery with lithium metal sheet as negative electrode for evaluation and testing. The first charge and discharge capacity at 0.2C under voltage of 3.0-4.25V is shown in Table 1. The surface-modified high-nickel multi-element cathode material was used to make a soft pack battery with graphite as negative electrode for evaluation and testing of its gas production performance. The test conditions were 70℃ for 7 days and 28 days, and its volume change rate was tested. The storage performance of the battery is shown in Table 1.

[0061] Example 1:

[0062] (1) Ni prepared by co-precipitation method 0.8 Co 0.1 Mn 0.1 (OH)₂ and lithium hydroxide were mixed uniformly at a molar ratio of Li / Me = 1.03, along with 0.03 mol% ZrO₂. The mixture was then sintered at 750°C for 15 hours in an oxygen atmosphere to obtain a final composition of Li. 1.02 Ni 0.8 Co 0.1 Mn 0.1 O2 cathode material;

[0063] (2) Take the positive electrode material, aluminum source, and fluoride obtained in step (1), wherein the aluminum salt is aluminum hydroxide, with a mass percentage of 0.4% relative to the positive electrode material, and the fluoride is magnesium fluoride (see...). Figure 1 , Figure 1 The image shows the SEM image of magnesium fluoride provided in Example 1, wherein the magnesium fluoride has a spherical granular structure (particle size 250±30 nm) and a mass percentage of 0.35%. After being stirred evenly at 30°C, it was sintered at 500°C in an oxygen atmosphere for 10 hours to obtain a surface-modified high-nickel multi-element cathode material. The XRD pattern of the comparative example is shown in Example 1. Figure 2 Both have similar structures, and the coating did not affect the structure; the XRD refinement results are shown in Table 1. The material cell parameter c / a > 4.9, and it has a good layered structure with space group R-3m. 006 +I 102 ) / I 101 The value is often used to determine the orderliness of hexagonal close-packed structures. This value indicates the orderliness of hexagonal crystal structures, and both have similar crystal structures.

[0064] (3) The positive electrode material obtained in Example 1 was coated with an active material ratio of 96.5% and a coating surface density of 0.018 g / cm³. 2The negative electrode is made of artificial graphite, the separator is a PP / PE / PP three-layer separator, and the electrolyte is a 1.0M LiPF6 EC / DMC / EMC (1:1:1 volume ratio) electrolyte solution. A coin cell with a lithium metal sheet as the negative electrode was fabricated using the surface-modified high-nickel multi-element positive electrode material for evaluation and testing. The initial charge-discharge capacity at 0.2C under 3.0-4.3V voltage is shown in Table 1. SEM images of the control group and the materials in Example 1 are shown below. Figure 3 As shown, by Figure 3 It can be seen that from Figure 3 Compared with Example 1, the control group was coated with Al2O3 and boric acid. Boric acid melts at a lower temperature and can coat the grain boundaries, providing good protection. A small amount of coating remained on the material surface. Example 1 was coated with aluminum fluoride and aluminum hydroxide, resulting in a greater distribution of white dots on the surface, located on the primary particle surface and at the interface, exhibiting a discrete island-like distribution. The positive electrode material obtained in Example 1 was coated with an active material ratio of 94.5% and a coating surface density of 0.016 g / cm³. 2 The negative electrode uses artificial graphite, the separator is a PP / PE / PP three-layer separator, and the electrolyte is a 1.0M LiPF6 EC / DMC / EMC (1:1:1 volume ratio) electrolyte solution. An 800mAh soft-pack battery was assembled, and its performance at room temperature and high temperature, as well as its DCR, were tested under 3.0-4.25V conditions. The results are shown in Table 1. In the comparative group, the double coating initially provided strong protection to the surface of the positive electrode material, but this protection weakened after long-term high-temperature storage, resulting in poor gas generation. The fluoride double-coated material formed a stable and highly protective coating layer on the surface. Compared to the comparative group, the battery's storage performance was significantly improved after the coating modification of this invention. From the data in Table 1 of the comparative and example samples, it can be concluded that after this coating improvement, the initial efficiency of the three positive electrode materials (NCM, NCA, and NC) was improved, and their long-term high-temperature storage performance was effectively enhanced.

[0065] (4) Characterization method of particle compressive strength of control group and Example 1 materials: After applying pressure of 0 / 150 / 250 / 300 MPa on a powder compactor, the external oversize was tested to obtain the cumulative volumetric particle size distribution map, as shown in the figure. Figure 4 .Depend on Figure 4 It can be seen that, in the control group, the proportion of small particles in the cumulative volume particle size distribution increases with increasing pressure, indicating that as the pressure increases, the particles in the control group are crushed, the overall particle size distribution shifts towards smaller particles, and the number of small particles increases, indicating that the particles in the control group have poor compressive strength. In Example 1, as the pressure increases, there is no significant change in the cumulative volume particle size distribution, indicating that although there are small particles, the number of small particles does not increase with increasing pressure, indicating that the particles in Example 1 have high compressive strength.

[0066] Example 2:

[0067] (1) Ni prepared by co-precipitation method 0.9 Co 0.05 Mn 0.05 (OH)₂ and lithium hydroxide were mixed uniformly at a molar ratio of Li / Me = 1.03, along with 0.04 mol% ZrO₂. The mixture was then sintered at 720°C for 10 hours in an oxygen atmosphere to obtain a final composition of Li. 1.02 Ni 0.9 Co 0.05 Mn 0.05 O2 cathode material;

[0068] (2) The cathode material, aluminum source and fluoride obtained in step (1), wherein the aluminum salt is nano-alumina with a mass percentage of 0.3% and the fluoride is lanthanum fluoride with a mass percentage of 0.5%, are stirred evenly at 30°C and then placed in an oxygen atmosphere at 600°C for 10 hours to obtain a surface-modified high-nickel multi-element cathode material.

[0069] (3) The surface-modified high-nickel multi-element cathode material was used to make a coin cell battery with lithium metal sheet as negative electrode for evaluation and testing. The first charge and discharge capacity at 0.2C under voltage of 3.0-4.25V is shown in Table 1. The surface-modified high-nickel multi-element cathode material was used to make a soft pack battery with graphite as negative electrode for evaluation and testing. After the coating modification of the present invention, the storage performance of the battery was greatly improved.

[0070] Example 3:

[0071] (1) Ni prepared by co-precipitation method 0.8 Co 0.1 Mn 0.1 (OH)₂ and lithium hydroxide were mixed uniformly at a molar ratio of Li / Me = 1.04, along with 0.025 mol% YO₃. The mixture was then sintered at 820°C for 12 hours in an oxygen atmosphere to obtain a final composition of Li. 1.03 Ni 0.8 Co 0.1 Mn 0.1 O2 cathode material;

[0072] (2) The cathode material, aluminum source and fluoride obtained in step (1), wherein the aluminum salt is nano alumina with a mass percentage of 0.4% and the fluoride is yttrium fluoride with a mass percentage of 0.35%, are stirred evenly at 30°C and then placed in an oxygen atmosphere at 550°C for 10 hours to obtain a surface-modified high-nickel multi-element cathode material.

[0073] (3) The surface-modified high-nickel multi-element cathode material was used to make a coin cell battery with lithium metal sheet as negative electrode for evaluation and testing. The first charge and discharge capacity at 0.2C under voltage of 3.0-4.25V is shown in Table 1. The surface-modified high-nickel multi-element cathode material was used to make a soft pack battery with graphite as negative electrode for evaluation and testing. After the coating modification of the present invention, the storage performance of the battery was greatly improved.

[0074] Example 4:

[0075] (1) Ni prepared by co-precipitation method 0.7 Co 0.1 Mn 0.2 (OH)₂ and lithium hydroxide were mixed uniformly at a molar ratio of Li / Me = 1.03, along with 0.025 mol% SrO. The mixture was then sintered at high temperature for 15 hours in an oxygen atmosphere to obtain the final composition of Li. 1.02 Ni 0.7 Co 0.1 Mn 0.2 O2 cathode material;

[0076] (2) The cathode material, aluminum source and fluoride obtained in step (1), wherein the aluminum salt is nano alumina with a mass percentage of 0.4% and the fluoride is cerium fluoride with a mass percentage of 0.35%, are stirred evenly at 30°C and then placed in an oxygen atmosphere at 300°C for sintering for 10 hours to obtain a surface-modified high-nickel multi-element cathode material.

[0077] (3) The surface-modified high-nickel multi-element cathode material was used to make a coin cell battery with lithium metal sheet as negative electrode for evaluation and testing. The first charge and discharge capacity at 0.2C under voltage of 3.0-4.25V is shown in Table 1. The surface-modified high-nickel multi-element cathode material was used to make a soft pack battery with graphite as negative electrode for evaluation and testing. After the coating modification of the present invention, the storage performance of the battery was greatly improved.

[0078] Example 5:

[0079] (1) Ni prepared by co-precipitation method 0.6 Co 0.1 Mn 0.3 (OH)₂ and lithium hydroxide were mixed uniformly at a molar ratio of Li / Me = 1.03, along with 0.035 mol% ZrO₂. The mixture was then sintered at 850°C for 10 hours in an oxygen atmosphere to obtain a final composition of Li. 1.02 Ni 0.6 Co 0.1 Mn 0.3 O2 cathode material;

[0080] (2) The cathode material, aluminum source and fluoride obtained in step (1), wherein the aluminum salt is aluminum oxide with a mass percentage of 0.3% and the fluoride is cerium fluoride with a mass percentage of 0.4% relative to the cathode material, are stirred evenly at 30°C and then placed in an oxygen atmosphere at 400°C for 10 hours to obtain a surface-modified high-nickel multi-element cathode material.

[0081] (3) The surface-modified high-nickel multi-element cathode material was used to make a coin cell battery with lithium metal sheet as negative electrode for evaluation and testing. The first charge and discharge capacity at 0.2C under voltage of 3.0-4.25V is shown in Table 1. The surface-modified high-nickel multi-element cathode material was used to make a soft pack battery with graphite as negative electrode for evaluation and testing. After the coating modification of the present invention, the storage performance of the battery was greatly improved.

[0082] Example 6:

[0083] (1) Ni prepared by co-precipitation method 0.6 Co 0.2 Mn 0.2 (OH)₂ and lithium hydroxide were mixed uniformly at a molar ratio of Li / Me = 1.03, along with 0.035 mol% ZrO₂. The mixture was then sintered at 840 °C for 10 h in an oxygen atmosphere to obtain a final composition of Li. 1.02 Ni 0.6 Co 0.1 Mn 0.3 O2 cathode material;

[0084] (2) The cathode material, aluminum source and fluoride obtained in step (1), wherein the aluminum salt is alumina with a mass percentage of 0.3% and the fluoride is zirconium fluoride with a mass percentage of 0.4% relative to the cathode material, are stirred evenly at 30°C and then placed in an oxygen atmosphere at 600°C for 10 hours to obtain a surface-modified high-nickel multi-element cathode material.

[0085] (3) The surface-modified high-nickel multi-element cathode material was used to make a coin cell battery with lithium metal sheet as negative electrode for evaluation and testing. The first charge and discharge capacity at 0.2C under voltage of 3.0-4.25V is shown in Table 1. The surface-modified high-nickel multi-element cathode material was used to make a soft pack battery with graphite as negative electrode for evaluation and testing. After the coating modification of the present invention, the storage performance of the battery was greatly improved.

[0086] NCA Comparative Example 2:

[0087] (1) Ni prepared by co-precipitation method 0.9 Co 0.05 Al 0.05(OH)₂ and lithium hydroxide were mixed uniformly at a molar ratio of Li / Me = 1.03, along with 0.035 mol% ZrO₂. The mixture was then sintered at 835 °C for 10 h in an oxygen atmosphere to obtain a final composition of Li. 1.02 Ni 0.9 Co 0.05 Al 0.05 O2 cathode material;

[0088] (2) The cathode material and aluminum source obtained in step (1), wherein the aluminum salt is aluminum oxide and the mass percentage of the cathode material is 0.3%, are stirred evenly at 30°C and then placed in an oxygen atmosphere at 500°C for 10 hours to obtain a surface-modified high-nickel multi-element cathode material.

[0089] (3) The surface-modified high-nickel multi-element cathode material was used to make a coin cell battery with lithium metal sheet as negative electrode for evaluation and testing. The first charge and discharge capacity at 0.2C under voltage of 3.0-4.25V is shown in Table 1. The surface-modified high-nickel multi-element cathode material was used to make a soft pack battery with graphite as negative electrode for evaluation and testing. After the coating modification of the present invention, the storage performance of the battery was greatly improved.

[0090] NCA Example 7:

[0091] (1) Ni prepared by co-precipitation method 0.9 Co 0.05 Al 0.05 (OH)₂ and lithium hydroxide were mixed uniformly at a molar ratio of Li / Me = 1.03, along with 0.035 mol% ZrO₂. The mixture was then sintered at 840 °C for 10 h in an oxygen atmosphere to obtain a final composition of Li. 1.02 Ni 0.9 Co 0.05 Al 0.05 O2 cathode material;

[0092] (2) The cathode material, aluminum source and fluoride obtained in step (1), wherein the aluminum salt is aluminum oxide with a mass percentage of 0.2% and the fluoride is cerium fluoride with a mass percentage of 0.4% relative to the cathode material, are stirred evenly at 30°C and then placed in an oxygen atmosphere at 500°C for 10 hours to obtain a surface-modified high-nickel multi-element cathode material.

[0093] (3) The surface-modified high-nickel multi-element cathode material was used to make a coin cell battery with lithium metal sheet as negative electrode for evaluation and testing. The first charge and discharge capacity at 0.2C under voltage of 3.0-4.25V is shown in Table 1. The surface-modified high-nickel multi-element cathode material was used to make a soft pack battery with graphite as negative electrode for evaluation and testing. After the coating modification of the present invention, the storage performance of the battery was greatly improved.

[0094] NC Comparative Example 3:

[0095] (1) Ni prepared by co-precipitation method 0.85 Co 0.15 (OH)₂ and lithium hydroxide were mixed uniformly at a molar ratio of Li / Me = 1.03, along with 0.035 mol% ZrO₂. The mixture was then sintered at 850°C for 10 hours in an oxygen atmosphere to obtain a final composition of Li. 1.02 Ni 0.85 Co 0.15 O2 cathode material;

[0096] (2) The cathode material and aluminum source obtained in step (1), wherein the aluminum salt is aluminum oxide and the mass percentage of the cathode material is 0.3%, are stirred evenly at 30°C and then placed in an oxygen atmosphere at 500°C for 10 hours to obtain a surface-modified high-nickel multi-element cathode material.

[0097] (3) The surface-modified high-nickel multi-element cathode material was used to make a coin cell battery with lithium metal sheet as negative electrode for evaluation and testing. The first charge and discharge capacity at 0.2C under voltage of 3.0-4.25V is shown in Table 1. The surface-modified high-nickel multi-element cathode material was used to make a soft pack battery with graphite as negative electrode for evaluation and testing. After the coating modification of the present invention, the storage performance of the battery was greatly improved.

[0098] NC Example 8:

[0099] (1) Ni prepared by co-precipitation method 0.85 Co 0.15 (OH)₂ and lithium hydroxide were mixed uniformly at a molar ratio of Li / Me = 1.03, along with 0.035 mol% ZrO₂. The mixture was then sintered at 840 °C for 10 h in an oxygen atmosphere to obtain a final composition of Li. 1.02 Ni 0.85 Co 0.15 O2 cathode material;

[0100] (2) The cathode material, aluminum source and fluoride obtained in step (1), wherein the aluminum salt is alumina with a mass percentage of 0.3% and the fluoride is cobalt fluoride with a mass percentage of 0.4% relative to the cathode material, are stirred evenly at 30°C and then placed in an oxygen atmosphere at 450°C for 10 hours to obtain a surface-modified high-nickel multi-element cathode material.

[0101] (3) The surface-modified high-nickel multi-element cathode material was used to make a coin cell battery with lithium metal sheet as negative electrode for evaluation and testing. The first charge and discharge capacity at 0.2C under voltage of 3.0-4.25V is shown in Table 1. The surface-modified high-nickel multi-element cathode material was used to make a soft pack battery with graphite as negative electrode for evaluation and testing. After the coating modification of the present invention, the storage performance of the battery was greatly improved.

[0102] Table 1. RieTveld refinement results of Example 1 and the control group.

[0103]

[0104] Table 2. Physicochemical and electrical performance data of the comparative group and the example.

[0105]

[0106]

[0107] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A cathode material with low residual alkali, characterized in that, having the following chemical formula: Li （1+n） Ni （1-a-b-c） Co a M b Q c O2 wherein 0 M is one or more elements selected from Mn, Al, Zr, Sr, Mg, Cr, Y, Ta, Zn, V, W, B; Q is a coating on the surface of the positive electrode material matrix, the coating being prepared from an aluminum source compound and a fluoride, the fluoride having the same lattice constant as the positive electrode material matrix; the fluoride being selected from at least one of strontium fluoride, lanthanum fluoride, nickel fluoride, cobalt fluoride, magnesium fluoride, aluminum fluoride, calcium fluoride, cerium fluoride, yttrium fluoride, and zirconium fluoride; In the positive electrode material, the aluminum source compound accounts for (0.2~0.8)wt%:1 of the mass percentage of the positive electrode material; the fluoride accounts for (0.3~0.8)wt%:1 of the mass percentage of the positive electrode material; The positive electrode material has a layered crystal structure belonging to space group R-3m.

2. The positive electrode material of claim 1, wherein, The aluminum source compound is selected from at least one of aluminum hydroxide, aluminum nitrate, nano-aluminum oxide, and aluminum phosphate.

3. The cathode material of claim 1, wherein, The coating on the surface of the positive electrode material is in a discrete island structure.

4. The cathode material of claim 1, wherein, The median particle size D50 of the positive electrode material ranges from 3.0 μm to 15.0 μm, the specific surface area is 0.65±0.3 m 2 / g, and the compacted density is 3.4±0.4 g / cm 3 .

5. The cathode material of claim 1, wherein, The residual alkali content on the surface of the positive electrode material is <0.15%.

6. A method for producing the positive electrode material according to any one of claims 1 to 5, characterized by, The method comprises the following steps: A) mixing a lithium source compound, a nickel-containing compound, and a doping element compound, and then sequentially performing ball milling, sintering, and crushing to obtain a positive electrode material matrix; B) mixing an aluminum source compound, a metal-containing fluoride compound, and the positive electrode material matrix, and then sintering to obtain a positive electrode material.

7. The preparation method according to claim 6, characterized in that, The lithium source compound is selected from one of lithium hydroxide and lithium carbonate; The nickel-containing compound is selected from a nickel-containing cobalt compound, the nickel-containing cobalt compound being selected from one or more of NCA, NCM, and NC; The doping element in the doping element compound is selected from one or more elements selected from Mn, Al, Zr, Sr, Mg, Cr, Y, Ta, Zn, V, W, and B; The aluminum source compound is selected from at least one of aluminum hydroxide, aluminum nitrate, nano-aluminum oxide, and aluminum phosphate; The metal-containing fluoride is selected from at least one of strontium fluoride, lanthanum fluoride, nickel fluoride, cobalt fluoride, magnesium fluoride, aluminum fluoride, calcium fluoride, cerium fluoride, yttrium fluoride, and zirconium fluoride.

8. The preparation method according to claim 6, characterized in that, In step A), the sintering temperature is 700~950℃, and the time is 5~15h; In step B), the sintering temperature is between 300~800℃, and the holding time is 5~15h.

9. A lithium-ion battery, characterized by The positive electrode material as claimed in any one of claims 1~5.

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