A precursor for preparing cathode materials and its preparation method, and cathode materials.

Abstract

This invention provides a precursor for preparing a cathode material, a method for preparing the same, and the cathode material itself. The precursor is designed to provide a sufficiently pre-oxidized precursor that offers a sufficient number of diffusion channels for lithium ions. The precursor comprises a hydroxyl oxide and a hydroxide; the molar amount f of the hydroxyl oxide per mole of the precursor is in the range of 0.7 < f ≤ 1; wherein the molecular formula of the hydroxyl oxide is Ni. x Co y Mn z M k OOH, the molecular formula of the hydroxide is Ni x Co y Mn z M k (OH)2, 0 < x < 1, 0 ≤ y < 0.3, 0 < z < 1, 0 ≤ k < 0.05, and x + y + z + k = 1, M is selected from at least one of Al, Mg, Cr, V, Mg, Zr, W, Ti, Ga, Se, Eu, Zn and B.

Description

Technical Field

[0001] This application relates to the field of secondary battery cathode material technology, and in particular to a precursor for preparing cathode materials, a preparation method thereof, and cathode materials. Background Technology

[0002] Currently, nickel-cobalt-manganese ternary cathode materials remain the mainstream cathode materials for lithium-ion batteries. The main preparation method for this ternary cathode material is the co-precipitation-calcination method: the precursor material obtained by co-precipitation is calcined under high temperature conditions to obtain the aforementioned ternary cathode material.

[0003] However, the precursor material obtained by the co-precipitation reaction lacks a sufficient number of uniformly distributed channels, which leads to uneven lithium-ion diffusion and low diffusion efficiency during high-temperature calcination. This affects the performance of the calcined product—the ternary cathode material.

[0004] To alleviate the aforementioned problems of uneven lithium-ion diffusion and low diffusion efficiency, high temperature control is required during calcination, such as sintering at 800-1000℃ for a relatively long time to allow sufficient time for lithium ions to diffuse into the material. However, prolonged sintering at excessively high temperatures inevitably leads to problems such as high residual alkali and severe lithium-nickel mixing in the ternary cathode material, making it difficult for the ternary cathode material to achieve the expected performance. Therefore, existing technologies often pre-oxidize the precursor after obtaining it to prepare for the high-temperature calcination step to obtain the cathode material, allowing lithium-ion diffusion channels to form at high temperatures. However, even after pre-oxidation, the oxide materials still suffer from insufficient bulk lithium-ion diffusion channels due to inadequate oxidation. Summary of the Invention

[0005] This invention provides a precursor for preparing a cathode material, a method for preparing the same, and a cathode material, which provides a precursor that is sufficiently pre-oxidized and can provide a sufficient number of diffusion channels for lithium-ion diffusion.

[0006] In a first aspect, embodiments of this application provide a precursor for preparing a cathode material, comprising a hydroxyl oxide and a hydroxide; the molar amount f of the hydroxyl oxide per mole of the precursor is in the range of: 0.7 < f ≤ 1; wherein,

[0007] The molecular formula of the hydroxyl oxide is Ni x Co y Mn z M k OOH, the molecular formula of the hydroxide is Ni x Co y Mn z M k(OH)2, 0 < x < 1, 0 ≤ y < 0.3, 0 < z < 1, 0 ≤ k < 0.05, and x + y + z + k = 1, M is selected from at least one of Al, Mg, Cr, V, Mg, Zr, W, Ti, Ga, Se, Eu, Zn and B.

[0008] In one possible implementation, the oxide is a secondary particle with a median particle size of 1-30 μm.

[0009] One possible implementation is that the secondary particles contain Ni 3+ Molar quantity and Ni 2+ and Ni 3+ The first ratio between the total molar amounts is greater than or equal to 80%, Co 3+ With Co 2+ and Co 3+ The second ratio between the total molar amounts is greater than or equal to 80%, Mn 4+ With Mn 4+ and Mn 2+ The third ratio among the total molar amounts is greater than or equal to 80%.

[0010] In one possible implementation, the secondary particles are quasi-spherical particles composed of rod-shaped primary particles, wherein the maximum axial length of the primary particles is 500 nm to 3 μm, and the aspect ratio of the primary particles is 10:1 to 20:1; wherein the aspect ratio is the ratio of the maximum axial length to the maximum radial width.

[0011] In one possible implementation, the secondary particle includes cracks, and the ratio of the length of the cracks distributed on the cross-section of the secondary particle to the radius of the secondary particle is greater than or equal to 5%, and the ratio of the length of the cracks to the maximum width of the cracks is less than or equal to 30:1.

[0012] Wherein, the cross section is a section passing through the geometric center of the secondary particle, and the radius of the secondary particle is the radius of the circumcircle corresponding to the longest line segment passing through the geometric center and connecting any two points on the surface of the secondary particle.

[0013] In one possible implementation, the number of cracks is less than or equal to 30.

[0014] In one possible implementation, the ratio of the weighted average α of the first, second, and third proportions in each region of the cross-section to the ratio k of the outer diameter of the region and the radius of the secondary particle is... The values ​​are: 0.8-1.2; among which,

[0015] The weights of the first ratio, the second ratio, and the third ratio are respectively the atomic indices of Ni, Co, and Mn in the molecular expression of the hydroxyl oxide, and the region is a ring of a predetermined width centered at the geometric center.

[0016] Secondly, embodiments of this application provide a method for preparing the oxide described in the first aspect and any possible implementation, comprising:

[0017] The oxidizing solution containing the oxidant is divided into N portions and passed into a reaction device containing a base liquid, so that the oxidant and the precursor in the base liquid continuously undergo an oxidation reaction in a liquid phase environment with a pH greater than or equal to 9.

[0018] Wherein, the cation in the precursor corresponds to the cation in the precursor; the total molar amount of oxidant introduced into the reaction device in the Nth time is a preset value, the molar amount of the oxidant introduced in the Nth time is greater than or equal to the molar amount of the oxidant introduced into the reaction device in the (N-1)th time, and the amount of the oxidant introduced in the Nth time is less than or equal to 2 / 3 of the preset value; the preset value is 0.5-1.5 times the molar amount of the precursor; N is an integer greater than 1.

[0019] In one possible implementation, the oxidant includes at least one selected from Na2S2O8, K2S2O8, (NH4)2S2O8, O3, H2O2, NaClO, NaClO4, and KMnO4; the concentration of the oxidizing solution is 0.5-5 mol / L.

[0020] In one possible implementation, the pH adjusting solution corresponding to a pH greater than or equal to 9 includes at least one of KOH, NaOH, and LiOH; the concentration of the pH adjusting solution is 1-15 mol / L.

[0021] In one possible implementation, the oxidation reaction conditions include a temperature of less than or equal to 100°C and a time of 4-16 hours.

[0022] Thirdly, embodiments of this application provide a method for preparing the oxide described in the first aspect and any possible implementation, comprising:

[0023] The oxidizing solution containing the oxidant is continuously passed into the reaction equipment containing the base liquid until the precursor is obtained, so that the oxidant and the precursor of the base liquid continuously undergo an oxidation reaction in a liquid phase environment with a pH greater than or equal to 9.

[0024] Wherein, the cation in the precursor corresponds to the cation in the precursor; the rate at which the oxidant is introduced into the reaction device is greater than or equal to (8 / 3V) mol / min, and the rate is not greater than (15 / 4V) mol / min; where V is the volume of the bottom liquid, and the unit of V is L.

[0025] In one possible implementation, the oxidant is continuously introduced into the reaction apparatus at a constant rate.

[0026] In one possible implementation, the oxidant includes at least one selected from Na2S2O8, K2S2O8, (NH4)2S2O8, O3, H2O2, NaClO, NaClO4, and KMnO4; the concentration of the oxidizing solution is 0.5-5 mol / L.

[0027] In one possible implementation, the pH adjusting solution corresponding to a pH greater than or equal to 9 includes at least one of KOH, NaOH, and LiOH; the concentration of the pH adjusting solution is 1-15 mol / L.

[0028] In one possible implementation, the interval between the Nth time the oxidant solution is introduced into the reaction device and the (N-1)th time the oxidant solution is introduced into the reaction device is no greater than 4 hours.

[0029] In one possible implementation, the oxidation reaction conditions include a temperature of less than or equal to 100°C and a time of 4-16 hours.

[0030] In one possible implementation, the precursor comprises a hydroxide containing at least one element selected from Ni, Co, Mn, and M.

[0031] Fourthly, embodiments of this application also provide a cathode material, which generates lithium metal oxide Li by an ion exchange reaction between the precursor described in the first aspect and any possible embodiment and a lithium salt-containing solution. h Ni x Co y Mn z M k ; and the lithium metal oxide is co-sintered with a lithium source to obtain the following; wherein, 0 < h ≤ 1.1.

[0032] One or more technical solutions provided in the embodiments of this application have at least the following features:

[0033] Beneficial effects:

[0034] 1. By increasing the pre-oxidation degree in the precursor, the content of hydroxyl oxides in the precursor is greater than or equal to 0.7%. In particular, for individual secondary particles in the precursor, the increased pre-oxidation degree means that the channels for uniform and sufficient diffusion of lithium ions are increased. This ensures that lithium ions diffuse fully and uniformly during the subsequent high-temperature calcination stage for the preparation of cathode materials, avoiding the problem of poor electrochemical performance such as rate performance of cathode materials due to insufficient lithium ion diffusion during the preparation stage in the existing technology.

[0035] 2. In preparing the aforementioned precursor, the precursor is fully oxidized through staged oxidation or continuous addition of the oxidant. This allows the oxidant to enter the bulk phase through cracks in the secondary particles during the oxidation reaction, oxidizing the interior of the secondary particles. Furthermore, this method avoids the problem of insufficient oxidant usage caused by a one-time addition of the oxidant, where the self-decomposition rate exceeds the oxidation reaction rate, thus conserving raw materials. Attached Figure Description

[0036] Figure 1 A schematic diagram of the cross-sectional area of ​​the secondary particles provided in the embodiments of this application;

[0037] Figure 2a SEM images of the precursor used in Embodiment 1 provided in this application;

[0038] Figure 2b SEM images of the precursor used in Embodiment 1 provided in this application;

[0039] Figure 3a SEM image of the precursor in Embodiment 1 provided in this application;

[0040] Figure 3b SEM image of the precursor in Embodiment 1 provided in this application;

[0041] Figure 4 A cross-sectional view of the secondary particles of the precursor used in Example 1, which is provided as an embodiment of this application;

[0042] Figure 5 A cross-sectional view of the secondary particles of the precursor in Embodiment 1 provided in this application;

[0043] Figure 6 The XRD pattern of Example 1 provided in this application is shown. Detailed Implementation

[0044] To address the problem of insufficient pre-oxidation of precursors in existing technologies, this application provides a precursor for preparing cathode materials. The molar amount f of oxides—hydroxy oxides—in the precursor per mole is in the range of 0.7 < f ≤ 1. This ensures that the hydroxy oxides in the precursor are no longer limited to their surface (for a single secondary particle) but are also distributed within the bulk phase. This significantly increases the oxide content in the precursor, thereby increasing the number of channels for high-temperature diffusion of lithium ions. In other words, it promotes more complete and uniform diffusion of lithium ions during the subsequent high-temperature calcination of the precursor to prepare lithium-ion battery cathode materials.

[0045] The following provides a detailed description of a precursor for preparing a cathode material, its preparation method, and the cathode material itself, based on embodiments of this application. It should be noted that the embodiments described below are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0046] This application provides a precursor for preparing a cathode material, the pre-oxidation degree of which is higher than that of prior art precursors. The precursor comprises hydroxyl oxide and hydroxide. The molar amount f of hydroxyl oxide per mole of the precursor ranges from 0.7 to f ≤ 1.

[0047] The molecular formula for this hydroxyoxide is Ni. x Co y Mn z M k OOH. The molecular formula for hydroxides is Ni. x Co y Mn z M k (OH)2.

[0048] 0 < x < 1, 0 ≤ y < 0.3, 0 < z < 1, 0 ≤ k < 0.05, and x + y + z + k = 1, M is selected from at least one of Al, Mg, Cr, V, Mg, Zr, W, Ti, Ga, Se, Eu, Zn and B.

[0049] In some embodiments, the content of hydroxyl oxide per mole of precursor is 0.8-0.9 mol.

[0050] Furthermore, the aforementioned precursor is a mixture of secondary particles, meaning that the relative content of hydroxyl oxides between any two secondary particles in the precursor can be the same or different.

[0051] In each secondary particle, the content of hydroxy oxide is 0.7-1 relative to that of hydroxide. When the relative content of hydroxy oxide is <100%, the secondary particles composed of hydroxy oxide and hydroxide form a solid solution.

[0052] The aforementioned precursor can then be represented as eNi x Co y Mn z M k OOH·Ni x Co y Mn z M k (OH)₂; d is 0.7-1. Furthermore, the median particle size D of the secondary particles... 50 The range is 1-30 μm.

[0053] The aforementioned secondary particles are polycrystalline spherical particles composed of rod-shaped primary particles.

[0054] The rod-shaped primary particle can be a regular cylinder or an irregular quasi-cylindrical shape. The maximum axial length of the primary particle is 500 nm to 3 μm, and the aspect ratio is 10:1 to 20:1.

[0055] The aspect ratio is the ratio of the maximum axial length to the maximum radial width.

[0056] It should be noted that in the molecular expressions of this application, the subscripts are atomic indices, used to represent the relative molar content between corresponding atoms in the molecule. For example, Ni x Co y Mn z M k In (OH)₂, x, y, z, and k are atomic indices, representing the relative molar amounts of Ni, Co, Mn, and dopant M in the molecule. For example, x represents the molar proportion of Ni in the hydroxide.

[0057] The relative contents of Ni, Co, Mn elements and dopant element M in the aforementioned hydroxyl oxides and hydroxides are the same.

[0058] Furthermore, the aforementioned secondary particles contain internal cracks. These cracks are particularly noticeable when the cross-section of the secondary particles is observed using SEM images. (See reference...) Figure 5 The cracks that resemble fissures on the cross-section are the aforementioned fissures. These fissures can be distributed radially or non-radially near or through the geometric center.

[0059] Unless otherwise specified, the cross-sections described in the embodiments of this application are all sections passing through the geometric center of the secondary particles.

[0060] The number of cracks distributed on the above cross section is less than or equal to 30, the ratio of crack length to the radius of secondary particles is greater than or equal to 5%, and the ratio of crack length to maximum crack width is less than or equal to 30:1.

[0061] Cracks are defined by their discontinuity or interruption on the cross-section. That is, each crack is continuous from its starting point to its ending point. Cracks can be curved or straight, their length is the straight-line distance from their starting point to their ending point, and their maximum width is the farthest distance between the two sides of any crack on the cross-section. The radius of a secondary particle is the radius of the circumcircle corresponding to the longest line segment passing through its geometric center and connecting any two points on its surface.

[0062] The number and shape parameters of the cracks were obtained by high-magnification SEM testing of the cross-section.

[0063] Furthermore, Ni in the aforementioned secondary particles 3+ Molar quantity and Ni 2+ and Ni 3+ The first ratio between the total molar amounts is greater than or equal to 80%, Co 3+ With Co 2+ and Co 3+ The second ratio between the total molar amounts is greater than or equal to 80%, Mn 4+ With Mn 4+ and Mn 2+ The third ratio among the total molar amounts is greater than or equal to 80%.

[0064] The ratio of the weighted average α of the first, second, and third proportions in each region of the cross-section to the ratio k of the outer diameter and the radius of the secondary particles in the corresponding region is... The value is 0.8-1.2. Preferably, The value is: 0.9-1.1.

[0065] Wherein, the weights of the first, second, and third ratios are respectively the atomic indices (x, y, z) of Ni, Co, and Mn in the aforementioned molecular expression of hydroxyl oxides. For any region of the cross-section belonging to a secondary particle, the molecular expression of the hydroxyl oxide contained in the corresponding secondary particle is Ni. x Co y Mn z M k In OOH, the atomic indices x, y, and z are constants. Correspondingly, the weighted average α of the first, second, and third proportions in any region of the cross-section can be calculated based on the following formula:

[0066]

[0067] Each region in the above cross-section is a ring of predetermined width centered at the geometric center. For example... Figure 1 The region shown in the cross-section is the shaded area. The outer diameter of this region is the distance between any point on the circumference of the annulus and the center of the annulus.

[0068] Furthermore, the XRD pattern of the above precursor includes characteristic peaks of hydroxyl oxides: (001) characteristic peak with a diffraction angle of 17.8-18.5°; (002) characteristic peak with a diffraction angle of 36.7-37.6°; and (110) characteristic peak with a diffraction angle of 66.0-67.5°; wherein the peak intensity of (001) characteristic peak is 1100-3000; the peak intensity of (002) characteristic peak is 900-2500; and the peak intensity of (110) characteristic peak is 700-2000.

[0069] Based on the same inventive concept, embodiments of this application provide a method for preparing the precursor as described above, used to fully pre-oxidize the precursor before obtaining the cathode material in the high-temperature calcination stage, so as to form channels for lithium-ion diffusion in the oxide in advance, thereby promoting the full and uniform diffusion of lithium ions in the lithium source in the cathode material during high-temperature calcination, and also achieving the purpose of reducing sintering energy consumption. The method includes:

[0070] The oxidizing solution containing the oxidant is divided into N portions and passed into a reaction apparatus containing a base liquid, so that the oxidant and the precursor in the base liquid continuously undergo an oxidation reaction in a liquid phase environment with a pH greater than or equal to 9.

[0071] When the oxidizing solution is intermittently introduced into the reaction device N times, the total molar amount of the oxidant introduced into the reaction device N times is a preset value. The molar amount of the oxidant introduced in the Nth time is greater than or equal to the molar amount of the oxidant introduced into the reaction device in the (N-1)th time, and the amount of the oxidant introduced in the Nth time is less than or equal to 2 / 3 of the preset value; N is an integer greater than 1.

[0072] When the oxidizing solution is introduced into the reaction apparatus N times, the amount of oxidant introduced into the reaction apparatus in any two adjacent cycles can be the same or different. The time interval between any two adjacent cycles of introducing the oxidizing solution into the reaction apparatus can be the same or different.

[0073] The above preset values ​​are determined based on the stoichiometric coefficients in the chemical equation for the oxidation reaction.

[0074] In some embodiments, the interval between the Nth time the oxidizing solution is introduced into the reaction device and the (N-1)th time the oxidizing solution is introduced into the reaction device is no greater than 4 hours.

[0075] The standard electrode potential of the above-mentioned oxidant is 0.5-3.0V; preferably 1.5-2.5V.

[0076] The reaction conditions for the above oxidation reaction are atmospheric pressure, temperature of 10-100℃, and time of 0.5-24h.

[0077] The precursor in the aforementioned substrate can be a hydroxide containing at least one of Ni, Co, Mn, and dopant element M. One or more of these hydroxides can also be replaced by their corresponding oxides. For example, it can be Ni. a Co b Mn c M d (OH)2, Ni a Co b Mn c M d O, Co3O4, or Ni(OH)2, etc. Where 0 < a < 1, 0 ≤ b < 0.3, 0 < c < 1, 0 ≤ d < 0.05, and x + y + z + k = 1.

[0078] The liquid phase environment with a pH greater than or equal to 9 can be set based on an alkaline solution (i.e., a pH adjustment solution). The alkaline solution corresponding to a pH greater than or equal to 9 includes at least one of KOH, NaOH, and LiOH. The concentration of the pH adjustment solution is 1-15 mol / L.

[0079] The oxidizing agents mentioned above include at least one of Na2S2O8, K2S2O8, (NH4)2S2O8, O3, H2O2, NaClO, NaClO4, and KMnO4.

[0080] The concentration of the above-mentioned oxidizing solution is 0.5-5 mol / L. That is, the molar amount of oxidant contained in each liter of oxidizing solution is 0.5-5 mol.

[0081] This application also provides a method for preparing the above-mentioned precursor, which is used to fully oxidize the precursor in the substrate to obtain a precursor with a hydroxyl oxide content f of 0.7 < f ≤ 1. The method includes:

[0082] The oxidizing solution containing the oxidant is continuously passed into a reaction apparatus containing a base liquid until the precursor is obtained, allowing the oxidant and the precursor in the base liquid to continuously undergo an oxidation reaction in a liquid phase environment with a pH greater than or equal to 9. Similarly, the base liquid contains the precursor from the base liquid.

[0083] That is, before the material is discharged (i.e., before the precursor is obtained), an oxidation solution is continuously or repeatedly introduced into the reaction equipment to ensure that the oxidation reaction continues before the precursor is obtained.

[0084] The precursor includes a hydroxide containing at least one of the elements Ni, Co, Mn, and M in the precursor; the rate at which the oxidant is introduced into the reaction apparatus is greater than or equal to (8 / 3V) mol / min, and the rate is not greater than (15 / 4V) mol / min; where V is the volume of the base liquid, and the unit of V is L.

[0085] For example, when the volume of the reaction substrate is 1m 3 When the oxidizing solution is continuously introduced into the reaction equipment, the rate at which the oxidant is introduced into the reaction equipment is 0.375-3.75 mol / min.

[0086] In some embodiments, when the oxidant is continuously introduced into the reaction apparatus, the introduction rate is kept constant. That is, the amount of oxidant introduced into the reaction apparatus per minute remains constant.

[0087] The standard electrode potential of the above-mentioned oxidant is 0.5-3.0V; preferably 1.5-2.5V.

[0088] The reaction conditions for the above oxidation reaction are atmospheric pressure, temperature of 10-100℃, and time of 0.5-24h.

[0089] The cations in the precursor in the aforementioned substrate correspond to the cations in the pre-form precursor. This precursor can be a hydroxide containing at least one of Ni, Co, Mn, and dopant element M. One or more of these hydroxides can also be replaced by corresponding oxides. For example, it can include Ni. a Co b Mn c M d (OH)2, Ni a Co b Mn c M d O, Co3O4, or Ni(OH)2, etc. Where 0 < a < 1, 0 ≤ b < 0.3, 0 < c < 1, 0 ≤ d < 0.05, and x + y + z + k = 1.

[0090] The liquid phase environment with a pH greater than or equal to 9 can be set based on an alkaline solution (i.e., a pH adjustment solution). The alkaline solution corresponding to a pH greater than or equal to 9 includes at least one of KOH, NaOH, and LiOH. The concentration of the pH adjustment solution is 1-15 mol / L.

[0091] The oxidizing agents mentioned above include at least one of Na2S2O8, K2S2O8, (NH4)2S2O8, O3, H2O2, NaClO, NaClO4, and KMnO4.

[0092] The concentration of the above-mentioned oxidizing solution is 0.5-5 mol / L. That is, the molar amount of oxidant contained in each liter of oxidizing solution is 0.5-5 mol.

[0093] Regardless of whether the flow is continuous or repeated, the flow rate of the oxidizing solution into the reaction equipment must be greater than or equal to 3 ml / min.

[0094] In some embodiments, the oxidation solution is introduced into the reaction apparatus containing the base liquid N times, or when the oxidation solution is continuously introduced, the temperature of the liquid phase environment is maintained at 80-100°C, the oxidation reaction time is 6-16 hours, and the oxidant is persulfate, to ensure that the Ni content in the secondary particles of the final precursor is high. 3+ Molar quantity and Ni 2+ and Ni 3+ The first ratio between the total molar amounts is greater than or equal to 80%, Co 3+ With Co 2+ and Co 3+ The second ratio between the total molar amounts is greater than or equal to 80%, Mn 4+ With Mn 4+ and Mn 2 + The third ratio among the total molar amounts is greater than or equal to 80%.

[0095] In some embodiments, the oxidation solution and the pH adjustment solution are continuously fed into the reaction apparatus during the preparation of the precursor. In this case, the flow rate of the oxidation solution into the reaction apparatus is 0.05-20 times the flow rate of the pH adjustment solution, preferably 0.1-10 times.

[0096] Since the precursors provided in the embodiments of this application are obtained by wet reaction, after obtaining the precursors in the reaction equipment, the reaction equipment contains a slurry containing the precursors. Therefore, it is necessary to filter and wash the slurry to extract the precursors.

[0097] Washing can be done using deionized water at 30-70°C; and drying can be done at 80-120°C for 6-24 hours to obtain the precursor.

[0098] Based on the same inventive concept, embodiments of this application also provide a cathode material, which generates lithium metal oxide Li through an ion exchange reaction between the aforementioned precursor and a lithium salt-containing solution. h Ni x Co y Mn z M k The lithium metal oxide is obtained by co-sintering with a lithium source.

[0099] Where 0 < h ≤ 1.1.

[0100] Specifically, the lithium salt mentioned above can be at least one of soluble lithium salts such as lithium hydroxide, lithium carbonate, lithium sulfate, lithium chloride, and lithium acetate.

[0101] The above-mentioned ion exchange reaction mainly refers to the reaction of Ni hydroxide in the precursor. x Co y Mn z M k OOH of OH - With Li in lithium salt + An ion exchange reaction occurs. Furthermore, to promote this reaction, the molar ratio of lithium salt to hydroxyoxide must be greater than or equal to 2.

[0102] The lithium source can be selected from lithium carbonate and / or lithium hydroxide; the lithium metal oxide and lithium source can be sintered in one stage or in multiple stages; the sintering temperature is less than or equal to 900℃, and the sintering time can be, for example, 3-24h.

[0103] Because the precursor contains a high content of oxides (i.e. hydroxy oxides) and the oxides are distributed on the surface and in the internal cracks of the precursor, the lithium metal oxide obtained through ion exchange has a sufficient number of lithium ion diffusion channels when it participates in co-sintering. Therefore, the cathode material prepared has high stability and rate performance.

[0104] The following detailed description is provided through examples:

[0105] Example 1

[0106] S1, Add 100g of precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 50 °C, and stirring was started at a rate of 200 r / min. At the same time as stirring, the pH adjustment solution and the oxidation solution were simultaneously introduced into the reactor at a flow rate of 3 mL / min, so that the oxidation reaction was carried out at pH 13 for 8 h to obtain a slurry containing the precursor.

[0107] The pH adjustment solution was a NaOH solution. This NaOH solution was obtained by dissolving 2.5 times the molar amount of sodium hydroxide solid (mol) of the aforementioned precursor in 500 ml of deionized water. The oxidation solution was an H₂O₂ solution. This H₂O₂ solution was obtained by dissolving 1.3 times the theoretical amount of hydrogen peroxide solid in 500 ml of deionized water. SEM images of the secondary particles of this precursor are shown below. Figures 2a-2b See the cross-sectional diagram of its secondary particles. Figure 4 .

[0108] S2. After filtering the slurry containing the precursor, wash it with water at 50°C and then dry it at 100°C for 12 hours to obtain the precursor.

[0109] See the SEM image of the precursor secondary particles. Figures 3a-3b See the cross-sectional diagram of its secondary particles. Figure 5 The phase composition of this precursor can be found in [reference needed]. Figure 6 .

[0110] XPS (X-ray Photoelectron Spectroscopy) analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.75:0.25. Therefore, the molecular formula of the precursor is 0.85Ni. 0.8 Co 0.1 Mn 0.1 OOH·0.15Ni 0.8 Co 0.1 Mn 0.1 (OH)2.

[0111] Example 2

[0112] S1, Add 100g of precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 60 °C, and stirring was started at a rate of 200 r / min. At the same time as stirring started, the pH adjustment solution and the oxidation solution were introduced into the reactor at flow rates of 3 ml / min and 5 ml / min, respectively, so that the oxidation reaction was carried out at pH 13 for 10 h to obtain a slurry containing the precursor.

[0113] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving twice the molar amount of the aforementioned precursor (in mol) of solid sodium hydroxide in 500 ml of deionized water. The oxidation solution is a potassium permanganate solution. This potassium permanganate solution is obtained by dissolving 1.2 times the theoretical amount of solid potassium permanganate in 800 ml of deionized water.

[0114] S2. After filtering the slurry containing the precursor, wash it with water at 50°C and then dry it at 100°C for 12 hours to obtain the precursor.

[0115] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.92:0.08. Therefore, the molecular formula of the precursor is 0.92Ni. 0.8 Co 0.1 Mn 0.1 OOH·0.08Ni 0.8 Co0.1 Mn 0.1 (OH)2.

[0116] Example 3

[0117] S1, Add 100g of precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 70 °C, and stirring was started at a rate of 150 r / min. At the same time as stirring started, the pH adjustment solution and the oxidation solution were introduced into the reactor at flow rates of 5 ml / min and 10 ml / min, respectively, so that the oxidation reaction was carried out at a pH of 13.5 for 8 h to obtain a slurry containing the precursor.

[0118] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving 2.5 times the molar amount of sodium hydroxide solid (mol) of the aforementioned precursor in 500 ml of deionized water. The oxidation solution is a potassium permanganate solution. This potassium permanganate solution is obtained by dissolving 1.3 times the theoretical amount of potassium permanganate solid in 1000 ml of deionized water.

[0119] S2. After filtering the slurry containing the precursor, wash it with water at 50°C and then dry it at 100°C for 12 hours to obtain the precursor.

[0120] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.77:0.23. Therefore, the molecular formula of the precursor is 0.95Ni. 0.9 Co 0.05 Mn 0.05 OOH·0.05Ni 0.9 Co 0.05 Mn 0.05 (OH)2.

[0121] Example 3

[0122] S1, Add 100g of precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 70 °C, and stirring was started at a rate of 150 r / min. At the same time as stirring started, the pH adjustment solution and the oxidation solution were introduced into the reactor at flow rates of 5 ml / min and 10 ml / min, respectively, so that the oxidation reaction was carried out at a pH of 13.5 for 8 h to obtain a slurry containing the precursor.

[0123] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving 2.5 times the molar amount of sodium hydroxide solid (mol) of the aforementioned precursor in 500 ml of deionized water. The oxidation solution is a potassium permanganate solution. This potassium permanganate solution is obtained by dissolving 1.3 times the theoretical amount of potassium permanganate solid in 1000 ml of deionized water.

[0124] S2. After filtering the slurry containing the precursor, wash it with water at 50°C and then dry it at 100°C for 12 hours to obtain the precursor.

[0125] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.85:0.15. Therefore, the molecular formula of the precursor is 0.85Ni. 0.9 Co 0.05 Mn 0.05 OOH·0.15Ni 0.9 Co 0.05 Mn 0.05 (OH)2.

[0126] Example 4

[0127] S1, Add 100g of precursor Ni 0.9 Co 0.05 Mn 0.05 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 80℃, and stirring was started at a rate of 150 r / min. The pH adjustment solution and the oxidation solution were added in three portions, with the pH adjustment solution and the oxidation solution being introduced simultaneously each time. The amounts introduced into the reactor were 1 / 6, 1 / 3, and 1 / 2 of the total volume of their respective solutions, respectively. The oxidation reaction was carried out at a pH of 13.5 for 8 hours to obtain a slurry containing the precursor.

[0128] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving 2.5 times the molar amount of sodium hydroxide solid (mol) of the aforementioned precursor in 800 ml of deionized water. The oxidation solution is a sodium perchlorate solution. This sodium perchlorate solution is obtained by dissolving 1.3 times the theoretical amount of sodium perchlorate solid in 800 ml of deionized water.

[0129] S2. After filtering the slurry containing the precursor, wash it with water at 50°C and then dry it at 100°C for 12 hours to obtain the precursor.

[0130] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.93:0.07. Therefore, the molecular formula of the precursor is 0.93Ni. 0.9 Co 0.05 Mn 0.05OOH·0.07Ni 0.9 Co 0.05 Mn 0.05 (OH)2.

[0131] Example 5

[0132] S1, Add 100g of precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 60 °C, and stirring was started at a rate of 150 r / min. The pH adjustment solution and the oxidation solution were added in two portions, with the pH adjustment solution and the oxidation solution being introduced simultaneously each time. The amounts introduced into the reactor were 1 / 3 and 2 / 3 of the total volume of their respective solutions, respectively. The oxidation reaction was carried out at a pH of 11.5 for 8 hours to obtain a slurry containing the precursor.

[0133] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving 2.5 times the molar amount of sodium hydroxide solid (mol) of the aforementioned precursor in 600 ml of deionized water. The oxidation solution is a sodium persulfate solution. This sodium persulfate solution is obtained by dissolving 1.3 times the theoretical amount of sodium persulfate solid in 800 ml of deionized water.

[0134] S2. After filtering the slurry containing the precursor, wash it with water at 50°C and then dry it at 100°C for 12 hours to obtain the precursor.

[0135] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.89:0.11. Therefore, the molecular formula of the precursor is 0.89Ni. 0.6 Co 0.1 Mn 0.3 OOH·0.11Ni 0.6 Co 0.1 Mn 0.3 (OH)2.

[0136] Example 6

[0137] S1, Add 100g of precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 95℃, and stirring was started at a rate of 150 r / min. The pH adjustment solution and the oxidation solution were added in four portions, with the pH adjustment solution and the oxidation solution being introduced simultaneously each time. The amounts introduced into the reactor were 1 / 9, 2 / 9, 2 / 9, and 4 / 9 of the total volume of their respective solutions, respectively. The oxidation reaction was carried out at a pH of 11.5 for 4 hours to obtain a slurry containing the precursor.

[0138] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving twice the molar amount of sodium hydroxide solid (mol) of the aforementioned precursor in 700 ml of deionized water. The oxidation solution is a sodium hypochlorite solution. This sodium hypochlorite solution is obtained by dissolving 1.2 times the theoretical amount of sodium hypochlorite solid in 800 ml of deionized water.

[0139] S2. After filtering the slurry containing the precursor, wash it with water at 55°C and then dry it at 80°C for 7 hours to obtain the precursor.

[0140] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.82:0.18. Therefore, the molecular formula of the precursor is 0.82Ni. 0.6 Co 0.1 Mn 0.3 OOH·0.18Ni 0.6 Co 0.1 Mn 0.3 (OH)2.

[0141] Example 7

[0142] S1, Add 100g of precursor Ni 0.33 Co 0.33 Mn 0.33 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 55℃, and stirring was started at a rate of 150 r / min. The pH adjustment solution and the oxidation solution were added in four portions, with the pH adjustment solution and the oxidation solution being introduced simultaneously each time. The amounts introduced into the reactor were 1 / 9, 2 / 9, 2 / 9, and 4 / 9 of the total volume of their respective solutions, respectively. The oxidation reaction was carried out at pH 11 for 7 hours to obtain a slurry containing the precursor.

[0143] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving 1.5 times the molar amount of sodium hydroxide solid (mol) of the aforementioned precursor in 500 ml of deionized water. The oxidation solution is a sodium persulfate solution. This sodium persulfate solution is obtained by dissolving 1.1 times the theoretical amount of sodium persulfate solid in 500 ml of deionized water.

[0144] S2. After filtering the slurry containing the precursor, wash it with water at 55°C and then dry it at 90°C for 5 hours to obtain the precursor.

[0145] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.76:0.24. Therefore, the molecular formula of the precursor is 0.88Ni. 0.33 Co 0.33 Mn 0.33OOH·0.12Ni 0.33 Co 0.33 Mn 0.33 (OH)2.

[0146] Example 8

[0147] S1, Add 100g of precursor Ni 0.33 Co 0.33 Mn 0.33 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 60℃, and stirring was started at a rate of 600 r / min. The pH adjustment solution and the oxidation solution were added in 5 portions, with the pH adjustment solution and the oxidation solution being introduced simultaneously each time. The amount of each solution introduced into the reactor was 1 / 5, 1 / 5, 1 / 5, 1 / 5 of the total volume of the corresponding solution, respectively. The oxidation reaction was carried out at pH 11 for 12 h to obtain a slurry containing the precursor.

[0148] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving 1.5 times the molar amount of sodium hydroxide solid (mol) of the aforementioned precursor in 600 ml of deionized water. The oxidation solution is a sodium persulfate solution. This sodium persulfate solution is obtained by dissolving 1.1 times the theoretical amount of sodium persulfate solid in 500 ml of deionized water.

[0149] S2. After filtering the slurry containing the precursor, wash it with water at 60°C and then dry it at 90°C for 5 hours to obtain the precursor.

[0150] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.91:0.09. Therefore, the molecular formula of the precursor is 0.91Ni. 0.33 Co 0.33 Mn 0.33 OOH·0.09Ni 0.33 Co 0.33 Mn 0.33 (OH)2.

[0151] Example 9

[0152] S1, Add 100g of precursor Ni 0.25 Mn 0.75 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 70℃, and stirring was started at a rate of 500 r / min. The pH adjustment solution and the oxidation solution were added in 6 portions, with the pH adjustment solution and the oxidation solution being introduced simultaneously each time. The amount of each solution introduced into the reactor was 1 / 6, 1 / 6, 1 / 6, 1 / 6, 1 / 6 of the total volume of the corresponding solution, respectively. The oxidation reaction was carried out at pH 10 for 12 h to obtain a slurry containing the precursor.

[0153] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving twice the molar amount of the aforementioned precursor in 1000 ml of deionized water. The oxidation solution is a hydrogen peroxide solution. This hydrogen peroxide solution is obtained by dissolving 1.3 times the theoretical amount of hydrogen peroxide in 500 ml of deionized water.

[0154] S2. After filtering the slurry containing the precursor, wash it with water at 60°C and then dry it at 90°C for 5 hours to obtain the precursor.

[0155] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.78:0.22. Therefore, the molecular formula of the precursor is 0.89Ni. 0.25 Mn 0.75 OOH·0.11Ni 0.25 Mn 0.75 (OH)2.

[0156] Example 10

[0157] S1, Add 100g of precursor Ni 0.2 Co 0.2 Mn 0.6 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 70 °C, and stirring was started at a rate of 500 r / min. The pH adjustment solution and the oxidation solution were added in 6 portions, with the pH adjustment solution and the oxidation solution being introduced simultaneously each time. The amount of each solution introduced into the reactor was 1 / 6, 1 / 6, 1 / 6, 1 / 6, 1 / 6 of the total volume of the corresponding solution, respectively. The oxidation reaction was carried out at pH 9 for 12 h to obtain a slurry containing the precursor.

[0158] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving 1.5 times the molar amount of sodium hydroxide solid (mol) of the aforementioned precursor in 850 ml of deionized water. The oxidation solution is a sodium persulfate solution. This sodium persulfate solution is obtained by dissolving 1.1 times the theoretical amount of sodium persulfate in 500 ml of deionized water.

[0159] S2. After filtering the slurry containing the precursor, wash it with water at 60°C and then dry it at 90°C for 7 hours to obtain the precursor.

[0160] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.86:0.14. Therefore, the molecular formula of the precursor is 0.86Ni. 0.2 Co 0.2 Mn 0.6 OOH·0.14Ni 0.2 Co0.2 Mn 0.6 (OH)2.

[0161] Example 11

[0162] S1, Add 100g of precursor Ni 0.3 Co 0.2 Mn 0.5 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 60℃, and stirring was started at a rate of 200 r / min. The pH adjustment solution and the oxidation solution were added in 7 portions, with the pH adjustment solution and the oxidation solution being introduced simultaneously each time. The amount of each solution introduced into the reactor was 1 / 7, 1 / 7, 1 / 7, 1 / 7, 1 / 7, and 1 / 7 of the total volume of their respective solutions. The oxidation reaction was carried out at pH 11 for 12 hours to obtain a slurry containing the precursor.

[0163] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving 1.5 times the molar amount of the aforementioned precursor in 650 ml of deionized water. The oxidation solution is a potassium permanganate solution. This potassium permanganate solution is obtained by dissolving 1.05 times the theoretical amount of potassium permanganate in 500 ml of deionized water.

[0164] S2. After filtering the slurry containing the precursor, wash it with water at 60°C and then dry it at 90°C for 7 hours to obtain the precursor.

[0165] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.87:0.13. Therefore, the molecular formula of the precursor is 0.87Ni. 0.3 Co 0.2 Mn 0.5 OOH·0.13Ni 0.3 Co 0.2 Mn 0.5 (OH)2.

[0166] Comparative Example 1

[0167] S1, Add 100g of precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 50 °C, and stirring was started at a rate of 200 r / min. At the same time as stirring, the pH adjustment solution and the oxidation solution were simultaneously introduced into the reactor at a flow rate of 3 mL / min, so that the oxidation reaction was carried out at pH 10 for 8 h to obtain a slurry containing the precursor.

[0168] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving 2.5 times the molar amount of sodium hydroxide solid (mol) of the aforementioned precursor in 700 ml of deionized water. The oxidation solution is a hydrogen peroxide (H₂O₂) solution. This hydrogen peroxide solution is obtained by dissolving 1.5 times the theoretical amount of hydrogen peroxide in 700 ml of deionized water.

[0169] S2. After filtering the slurry containing the precursor, wash it with water at 50°C and then dry it at 100°C for 12 hours to obtain the precursor.

[0170] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.70:0.30. Therefore, the molecular formula of the precursor is 0.70Ni. 0.8 Co 0.1 Mn 0.1 OOH·0.30Ni 0.8 Co 0.1 Mn 0.1 (OH)2.

[0171] Comparative Example 2

[0172] S1, Add 100g of precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ was dispersed in 1000 mL of deionized water to prepare a slurry, which was used as the base solution. The temperature was raised to 50 °C, and stirring was started at a rate of 200 r / min. At the same time as stirring began, the pH adjustment solution was added into the reactor in a single step, and the pH of the liquid phase environment in the reactor was maintained at 9 by controlling the flow rate of the pH adjustment solution into the reaction equipment. The oxidation reaction was carried out continuously for 5 hours to obtain a slurry containing the precursor.

[0173] The pH adjustment solution is a NaOH solution. This NaOH solution is obtained by dissolving 2.5 times the molar amount of the aforementioned precursor in 500 ml of deionized water. The oxidation solution is a hydrogen peroxide (H₂O₂) solution. This hydrogen peroxide solution is obtained by dissolving 1.6 times the theoretical amount of hydrogen peroxide in 700 ml of deionized water.

[0174] S2. After filtering the slurry containing the precursor, wash it with water at 50°C and then dry it at 100°C for 12 hours to obtain the precursor.

[0175] XPS analysis of the precursor determined the relative molar ratio of hydroxyl oxide to hydroxide to be 0.65:0.35. Therefore, the molecular formula of the precursor is 0.65Ni. 0.8 Co 0.1 Mn 0.1OOH·0.35Ni 0.8 Co 0.1 Mn 0.1 (OH)2.

[0176] It should be noted that the theoretical amount of oxidant in the above examples and comparative examples is calculated based on the stoichiometric ratio of oxidant to precursor in the corresponding chemical reaction equations, with 100g of precursor as the matrix.

[0177] Furthermore, using XPS testing of the different valence states of Ni, Co, and Mn ions on the surface of a single secondary particle of the precursor in the examples and comparative examples, the average value of any five particles was calculated as the Ni valence state on the surface of a single secondary particle. 3+ Co 3+ Mn 4+ Ion content. See Table 1 for details.

[0178] The secondary particles of the precursor were sectioned using an ion milling apparatus to obtain a cross-section containing its geometric center. XPS was then used to measure the valence states of different metals Ni, Co, and Mn ions in the cross-sections of any five secondary particles, and the average value was calculated as the content of Ni, Co, and Mn ions in different valence states on the cross-section. Furthermore, it was determined that when k = 0.5, and k = 0.1, the content of Ni, Co, and Mn ions in the region of the cross-section was... In this section, the region is a 10nm wide annulus. α is obtained by subtracting the corresponding proportion in the inner circle of the annulus from the proportions (first proportion, second proportion, and third proportion) in the outer circle (including the geometric center of the secondary particles). For example, the first proportion = Ni in the outer circle of the annulus. 3+ Molar quantity and Ni 2+ and Ni 3+ The ratio of the inner circle Ni 3+ Molar quantity and Ni 2+ and Ni 3+ The ratio. The calculation methods for the second and third ratios are the same as those for the first ratio. Specific test calculation data is shown in Table 1.

[0179] Table 1

[0180]

[0181]

[0182] Furthermore, using the particle size analysis software UV-G, the surfaces of the examples and comparative examples were tested under an electron microscope at 15K magnification. The minimum ratio of crack length to secondary particle radius in each section was obtained, and the average value A of the minimum values ​​among the 20 secondary particle sections was calculated. The maximum ratio of crack length to crack width in each section was also calculated, and the average value H of the maximum values ​​among the 20 secondary particle sections was calculated. The maximum number of cracks in each of the 20 secondary particle sections was also calculated. The content of hydroxyl oxides on the surface of the secondary particles (uncut) was tested using XPS. Specific test results are shown in Table 2.

[0183] Table 2

[0184]

[0185] Table 1 shows that the oxidation degree of the outer layer of the secondary particles is higher than that of the inner cross-section. Further comparison is made with the SEM images of the precursor secondary particles from Example 1. Figures 2a-2b , Figure 4 ) and precursors ( Figures 3a-3b , Figure 5 As can be seen, the precursor secondary particles provided in this application cause cracks to appear in the bulk phase due to local stress concentration (especially at the geometric center) during the transformation of the precursor to the precursor. This allows oxidation energy to continue to penetrate the secondary particles along the cracks, thereby increasing the degree of oxidation of the secondary particles of the precursor and thus increasing the content of hydroxyl oxides in the precursor.

[0186] Further reference to Table 2 shows that the hydroxyl oxide content in Examples 1-11 is higher than that in Comparative Examples 1-2.

[0187] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A precursor for preparing a cathode material, characterized in that, Including hydroxyl oxides and hydroxides; the molar amount f of the hydroxyl oxide per mole of the precursor is in the range of: 0.7 < f ≤ 1; wherein, The molecular formula of the hydroxyl oxide is Ni x Co y Mn z M k OOH, the molecular formula of the hydroxide is Ni x Co y Mn z M k (OH)2, 0 < x < 1, 0 ≤ y < 0.3, 0 < z < 1, 0 ≤ k < 0.05, and x + y + z + k = 1, M is selected from at least one of Al, Mg, Cr, V, Mg, Zr, W, Ti, Ga, Se, Eu, Zn and B; The precursor is a secondary particle, which includes cracks. The ratio of the length of the cracks distributed on the cross-section of the secondary particle to the radius of the secondary particle is greater than or equal to 5%, and the ratio of the length of the crack to the maximum width of the crack is less than or equal to 30:

1.

2. The precursor as described in claim 1, characterized in that, The median particle size of the secondary particles is 1-30 μm.

3. The precursor as described in claim 1 or 2, characterized in that, Ni in secondary particles 3+ Molar quantity and Ni 2+ and Ni 3 + The first ratio between the total molar amounts is greater than or equal to 80%, Co 3+ With Co 2+ and Co 3+ The second ratio between the total molar amounts is greater than or equal to 80%, Mn 4+ With Mn 4+ and Mn 2+ The third ratio among the total molar amounts is greater than or equal to 80%.

4. The precursor as described in claim 3, characterized in that, The secondary particles are quasi-spherical particles composed of rod-shaped primary particles. The maximum axial length of the primary particles is 500 nm to 3 μm, and the aspect ratio of the primary particles is 10:1 to 20:

1.

5. The precursor as described in claim 1, characterized in that, The number of cracks is less than or equal to 30.

6. The precursor as described in claim 3, characterized in that, The weighted average of the first, second, and third proportions in each region of the cross section. α The ratio of the outer diameter of the region to the radius of the secondary particle. k ratio The value is 0.8-1.2; wherein the cross-section is a section passing through the geometric center of the secondary particle; The weights of the first ratio, the second ratio, and the third ratio are respectively the atomic indices of Ni, Co, and Mn in the molecular expression of the hydroxyl oxide, and the region is a ring of a predetermined width centered at the geometric center.

7. A method for preparing the precursor according to any one of claims 1-6, characterized in that, include: The oxidizing solution containing the oxidant is divided into N portions and passed into a reaction device containing a base liquid, so that the oxidant and the precursor in the base liquid continuously undergo an oxidation reaction in a liquid phase environment with a pH greater than or equal to 9. Wherein, the cation in the precursor corresponds to the cation in the precursor; the total molar amount of oxidant introduced into the reaction device in the Nth time is a preset value, the molar amount of the oxidant introduced in the Nth time is greater than or equal to the molar amount of the oxidant introduced into the reaction device in the (N-1)th time, and the amount of the oxidant introduced in the Nth time is less than or equal to 2 / 3 of the preset value; the preset value is 0.5-1.5 times the molar amount of the precursor; N is an integer greater than 1.

8. A method for preparing the precursor according to any one of claims 1-6, characterized in that, include: An oxidizing solution containing an oxidant is continuously passed into a reaction apparatus containing a base liquid until the precursor is obtained, so that the oxidant and the precursor in the base liquid continuously undergo an oxidation reaction in a liquid phase environment with a pH greater than or equal to 9. Wherein, the cation in the precursor corresponds to the cation in the precursor; the rate at which the oxidant is introduced into the reaction apparatus is greater than or equal to (3 / 8V) mol / min, and the rate is not greater than (15 / 4V) mol / min; where V is the volume of the base liquid, and the unit of V is m³. 3 .

9. A positive electrode material, characterized in that, The cathode material undergoes an ion exchange reaction with a lithium-containing salt solution via the precursor described in any one of claims 1-6 to generate lithium metal oxide Li. h Ni x Co y Mn z M k ; and the lithium metal oxide is co-sintered with a lithium source to obtain the following; wherein, 0 < h ≤ 1.1.

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