High-nickel positive electrode precursor, high-nickel positive electrode material, preparation method and lithium ion battery

Abstract

The application provides a high-nickel positive electrode precursor, a high-nickel positive electrode material, a preparation method and a lithium ion battery. The preparation method of the high-nickel positive electrode precursor comprises the following steps: parallelly passing mixed salt solution, precipitant solution, complexing agent solution and additive solution into a bottom liquid to perform a coprecipitation reaction, so that the high-nickel positive electrode precursor is obtained; and the additive in the additive solution comprises polyvinyl alcohol and polyacrylic acid with a mass ratio of 1:3 to 3:1. The preparation method of the high-nickel positive electrode precursor provided by the application utilizes the hydrogen bond, ion-dipole interaction and molecular chain entanglement between PVA and PAA to form a composite adsorption system, so that nucleation and crystal growth are synergistically controlled, which is beneficial to preparing a high-nickel ternary precursor with smaller primary particle size, higher aspect ratio and more uniform distribution; and the corresponding positive electrode material can inhibit the generation and expansion of microcracks in the cycle process, and meanwhile, excellent rate performance is also exhibited.

Description

Technical Field

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

[0002] The rapid development of new energy vehicles and portable electronic devices has placed increasingly higher demands on the energy density, cycle life, and safety performance of lithium-ion batteries. High-nickel ternary cathode materials (Ni...) x Co y Mn z O2 (x≥0.6) has advantages in high specific capacity, low cobalt content, and cost. However, with the continuous increase of nickel content, the structural stability and thermal stability of the material decrease.

[0003] High-nickel ternary cathode materials suffer from particle cracking and structural degradation during preparation and charge-discharge cycling. During charge-discharge, the insertion and extraction of lithium ions cause anisotropic volume changes in the crystal lattice. This repeated expansion and contraction generates significant internal stress within the primary particles, leading to the generation and propagation of microcracks. The appearance of microcracks not only disrupts the material's conductive network but also exposes grain boundaries to the electrolyte, accelerating the dissolution of transition metal ions and electrolyte decomposition. This ultimately results in rapid capacity decay and even thermal runaway, posing safety hazards. The cycle stability of high-nickel cathode materials is closely related to the microstructure of their primary particles. The size, aspect ratio, number of grain boundaries, and growth orientation of the primary particles directly determine the material's ability to resist volume changes and suppress microcrack propagation.

[0004] To address the aforementioned issues, existing technologies have attempted to control the morphology of primary particles in high-nickel ternary precursors through various methods, with the addition of template agents for confined growth being a commonly used approach. For instance, some techniques utilize the one-dimensional confined space of molecular sieve channels to prepare oriented nanoscale primary particles, achieving a degree of control over the precursor morphology. However, these inorganic template agents suffer from drawbacks such as difficulty in removal, easy introduction of impurities, and limited controllability, making it difficult to simultaneously achieve ultrafine particle size, high aspect ratio, and controlled growth orientation. Existing technologies cannot obtain large-size cathode primary particles with fewer grain boundaries and higher crystallinity without increasing the sintering temperature, making it difficult to simultaneously and significantly improve the material's cycle stability and rate performance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a high-nickel cathode precursor, a high-nickel cathode material, a preparation method, and a lithium-ion battery. The preparation method provided by the present invention can utilize the synergistic regulation of nucleation and crystal growth by the composite adsorption system formed by hydrogen bonds, ion-dipole interactions, and molecular chain entanglement between PVA and PAA, which is beneficial for preparing a high-nickel ternary precursor with smaller primary particle size, higher aspect ratio, and more uniform distribution. The corresponding cathode material can suppress the generation and propagation of microcracks during cycling and also exhibits excellent rate performance.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a high-nickel cathode precursor, the method comprising:

[0008] A mixed salt solution, a precipitant solution, a complexing agent solution, and an additive solution are simultaneously introduced into the bottom solution to carry out a co-precipitation reaction, thereby obtaining the high-nickel cathode precursor.

[0009] The additives in the additive solution include polyvinyl alcohol (PVA) and polyacrylic acid (PAA) in a mass ratio of 1:3 to 3:1.

[0010] This invention employs a combination of PVA and PAA as a synergistic regulator. Without being constrained by specific theories, the hydroxyl groups of PVA and the carboxyl / carboxylic acid groups of PAA can form a composite adsorption system through hydrogen bonding, ion-dipole interactions, and molecular chain entanglement. This system synergistically regulates nucleation, crystal growth, and particle assembly, which is beneficial for obtaining high-nickel ternary precursors with smaller primary particle size, higher aspect ratio, and more uniform distribution. The more uniform primary particle morphology is conducive to uniform reaction and crystallization during subsequent lithium-ion sintering, reducing local stress concentration, thereby improving the cycle stability and rate performance of high-nickel ternary cathode materials.

[0011] In some embodiments, the mass concentration of the additive in the additive solution is 0.5wt% to 5wt%.

[0012] In some embodiments, the amount of the additive solution is such that the mass of the additive is 0.2wt% to 3wt% of the total mass of the metal salt in the mixed salt solution.

[0013] In some embodiments, the weight-average molecular weight of the polyvinyl alcohol is 50,000 Da to 150,000 Da.

[0014] In some embodiments, the weight-average molecular weight of the polyacrylic acid is 5000 Da to 50000 Da.

[0015] In some embodiments, the metal salts in the mixed salt solution include nickel salts, cobalt salts, and manganese salts;

[0016] The nickel salt includes any one or a combination of at least two of nickel sulfate, nickel chloride, or nickel nitrate.

[0017] The cobalt salt includes any one or a combination of at least two of cobalt sulfate, cobalt chloride, or cobalt nitrate.

[0018] The manganese salt includes any one or a combination of at least two of manganese sulfate, manganese chloride, or manganese nitrate.

[0019] In some embodiments, the molar ratio of nickel, cobalt and manganese in the mixed salt solution is x:y:z, where x ≥ 0.6 and x + y + z = 1.

[0020] In some embodiments, the total concentration of metal ions in the mixed salt solution is 1.5 mol / L to 2.5 mol / L.

[0021] In some embodiments, the concentration of the precipitant solution is 4 mol / L to 10 mol / L.

[0022] In some embodiments, the precipitant in the precipitant solution includes sodium hydroxide and / or potassium hydroxide.

[0023] In some embodiments, the concentration of the complexing agent solution is 2 mol / L to 8 mol / L.

[0024] In some embodiments, the complexing agent in the complexing agent solution includes ammonia.

[0025] In some embodiments, the temperature of the coprecipitation reaction is 40°C to 85°C.

[0026] In some embodiments, the pH value of the coprecipitation reaction is 9 to 12.5.

[0027] In some embodiments, the stirring speed of the coprecipitation reaction is 300 rpm to 800 rpm.

[0028] In some embodiments, the concentration of the complexing agent in the coprecipitation reaction is 0.1 mol / L to 0.5 mol / L.

[0029] In some embodiments, the average primary particle size of the high-nickel cathode precursor is 80 nm to 210 nm.

[0030] In some embodiments, the median particle size D50 of the high-nickel cathode precursor is 2 μm to 3 μm.

[0031] In a second aspect, the present invention provides a high-nickel cathode precursor, which is prepared by the preparation method described in the first aspect.

[0032] Thirdly, the present invention provides a high-nickel cathode material, which is obtained by sintering a mixture of lithium salt and a high-nickel cathode precursor.

[0033] The high-nickel cathode precursor is either the high-nickel cathode precursor prepared by the preparation method described in the first aspect, or the high-nickel cathode precursor described in the second aspect.

[0034] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the high-nickel cathode material described in the third aspect.

[0035] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The method for preparing high-nickel cathode precursor provided by this invention uses a combination of PVA and PAA as a synergistic regulator. Without being limited by specific theories, the hydroxyl groups of PVA and the carboxyl / carboxylic acid groups of PAA can form a composite adsorption system through hydrogen bonding, ion-dipole interactions, and molecular chain entanglement. This system synergistically regulates nucleation, crystal growth, and particle assembly, which is beneficial for obtaining high-nickel ternary precursors with smaller primary particle size, higher aspect ratio, and more uniform distribution. The more uniform primary particle morphology is conducive to uniform reaction and crystallization in the subsequent lithium-ion sintering process, reducing local stress concentration, thereby improving the cycle stability and rate performance of the high-nickel ternary cathode material. Attached Figure Description

[0038] Figure 1 Here is a SEM image of the high-nickel cathode precursor obtained in Example 1;

[0039] Figure 2 The image shows a SEM image of the high-nickel cathode precursor obtained in Comparative Example 1. Detailed Implementation

[0040] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0041] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0042] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0043] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0044] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0045] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0046] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0047] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0048] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0049] An embodiment of the present invention provides a method for preparing a high-nickel cathode precursor, the method comprising:

[0050] A mixed salt solution, a precipitant solution, a complexing agent solution, and an additive solution are simultaneously introduced into the bottom solution to carry out a co-precipitation reaction, thereby obtaining the high-nickel cathode precursor.

[0051] The additives in the additive solution include polyvinyl alcohol (PVA) and polyacrylic acid (PAA) in a mass ratio of 1:3 to 3:1.

[0052] This invention employs a combination of PVA and PAA as a synergistic regulator. Without being constrained by specific theories, the hydroxyl groups of PVA and the carboxyl / carboxylic acid groups of PAA can form a composite adsorption system through hydrogen bonding, ion-dipole interactions, and molecular chain entanglement. This system synergistically regulates nucleation, crystal growth, and particle assembly, which is beneficial for obtaining high-nickel ternary precursors with smaller primary particle size, higher aspect ratio, and more uniform distribution. The more uniform primary particle morphology is conducive to uniform reaction and crystallization during subsequent lithium-ion sintering, reducing local stress concentration, thereby improving the cycle stability and rate performance of high-nickel ternary cathode materials.

[0053] The mass ratio of polyvinyl alcohol to polyacrylic acid is 1:3 to 3:1, for example, it can be 1:3, 1:1 or 3:1, but it is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0054] In some embodiments, the mass concentration of the additive in the additive solution is 0.5wt% to 5wt%, for example, it can be 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0055] In some embodiments, the amount of the additive solution is such that the mass of the additive is 0.2wt% to 3wt% of the total mass of the metal salt in the mixed salt solution, for example, it can be 0.2wt%, 0.4wt%, 0.5wt%, 0.8wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt% or 3wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] In some embodiments, the weight-average molecular weight of the polyvinyl alcohol is 50,000 Da to 150,000 Da, for example, it can be 50,000 Da, 60,000 Da, 80,000 Da, 90,000 Da, 100,000 Da, 120,000 Da, 140,000 Da or 150,000 Da, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] In some embodiments, the weight-average molecular weight of the polyacrylic acid is 5000 Da to 50000 Da, for example, it can be 5000 Da, 10000 Da, 15000 Da, 20000 Da, 25000 Da, 30000 Da, 35000 Da, 40000 Da, 45000 Da or 50000 Da, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0058] In some embodiments, the metal salts in the mixed salt solution include nickel salts, cobalt salts, and manganese salts;

[0059] The nickel salt includes any one or a combination of at least two of nickel sulfate, nickel chloride, or nickel nitrate.

[0060] The cobalt salt includes any one or a combination of at least two of cobalt sulfate, cobalt chloride, or cobalt nitrate.

[0061] The manganese salt includes any one or a combination of at least two of manganese sulfate, manganese chloride, or manganese nitrate.

[0062] In some embodiments, the molar ratio of nickel, cobalt and manganese in the mixed salt solution is x:y:z, where x ≥ 0.6 and x + y + z = 1.

[0063] In some embodiments, the total concentration of metal ions in the mixed salt solution is 1.5 mol / L to 2.5 mol / L, for example, it can be 1.5 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, 2.1 mol / L, 2.4 mol / L or 2.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] In some embodiments, the concentration of the precipitant solution is 4 mol / L to 10 mol / L, for example, it can be 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0065] In some embodiments, the precipitant in the precipitant solution includes sodium hydroxide and / or potassium hydroxide.

[0066] In some embodiments, the concentration of the complexing agent solution is 2 mol / L to 8 mol / L, for example, it can be 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L or 8 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0067] In some embodiments, the complexing agent in the complexing agent solution includes ammonia.

[0068] In some embodiments, the temperature of the coprecipitation reaction is 40°C to 85°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or 85°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0069] In some embodiments, the pH value of the coprecipitation reaction is 9 to 12.5, for example, it can be 9, 9.5, 10, 10.5, 11, 11.5, 12 or 12.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] In some embodiments, the stirring speed of the coprecipitation reaction is 300 rpm to 800 rpm, for example, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm or 800 rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0071] In some embodiments, the concentration of the complexing agent in the coprecipitation reaction is 0.1 mol / L to 0.5 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0072] In some embodiments, the coprecipitation reaction is carried out in a protective atmosphere, the gas used in which the protective atmosphere includes nitrogen and / or an inert gas.

[0073] In some embodiments, the average primary particle size of the high-nickel cathode precursor is 80 nm to 210 nm.

[0074] In some embodiments, the median particle size D50 of the high-nickel cathode precursor is 2 μm to 3 μm.

[0075] In this invention, under the premise that other process parameters remain unchanged, the average primary particle size of the high-nickel cathode precursor is related to the time of the co-precipitation reaction. By controlling the reaction time and process parameters, this invention makes the average primary particle size 80nm~210nm and the median particle size D50 2μm~3μm.

[0076] In some embodiments, the preparation method further includes aging, filtration, washing and vacuum drying after the coprecipitation reaction, wherein the vacuum drying temperature is 100℃~150℃, for example, 100℃, 110℃, 120℃, 130℃, 140℃ or 150℃, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0077] As a preferred embodiment of the method provided by the present invention, the preparation method includes the following steps:

[0078] S1. Pure water, precipitant solution and complexing agent solution are mixed in a reaction vessel to obtain a solution with a temperature of 40℃~85℃, a pH value of 9~12.5 and a complexing agent concentration of 0.1mol / L~0.5mol / L.

[0079] S2. A mixed salt solution, precipitant solution, complexing agent solution and additive solution are introduced concurrently into the bottom liquid to carry out a co-precipitation reaction. Then, after aging, filtration, washing and vacuum drying at a temperature of 100℃~150℃, the high-nickel cathode precursor is obtained.

[0080] The additive in the additive solution comprises polyvinyl alcohol and polyacrylic acid in a mass ratio of 1:3 to 3:1; the mass concentration of the additive in the additive solution is 0.5wt% to 5wt%; the amount of the additive solution used satisfies the following condition: the mass of the additive is 0.2wt% to 3wt% of the total mass of the metal salt in the mixed salt solution.

[0081] The weight-average molecular weight of the polyvinyl alcohol is 50,000 Da to 150,000 Da;

[0082] The weight-average molecular weight of the polyacrylic acid is 5000 Da to 50000 Da;

[0083] The metal salts in the mixed salt solution include nickel salts, cobalt salts, and manganese salts, with a molar ratio of nickel, cobalt, and manganese of x:y:z, where x ≥ 0.6 and x + y + z = 1; the total concentration of metal ions in the mixed salt solution is 1.5 mol / L to 2.5 mol / L.

[0084] The concentration of the precipitant solution is 4 mol / L to 10 mol / L, and the precipitant in the precipitant solution includes sodium hydroxide and / or potassium hydroxide; the concentration of the complexing agent solution is 2 mol / L to 8 mol / L, and the complexing agent includes ammonia.

[0085] The coprecipitation reaction was carried out in a nitrogen atmosphere at a temperature of 40℃~85℃, a pH of 9~12.5, a stirring speed of 300rpm~800rpm, and a complexing agent concentration of 0.1mol / L~0.5mol / L. The resulting high-nickel cathode precursor had an average primary particle size of 80nm~210nm and a median particle size D50 of 2μm~3μm.

[0086] One embodiment of the present invention provides a high-nickel cathode precursor, which is prepared by the preparation method described in any embodiment.

[0087] One embodiment of the present invention provides a high-nickel cathode material, which is obtained by sintering a mixture of lithium salt and a high-nickel cathode precursor.

[0088] In some embodiments, the mixed sintering includes: holding at 250°C to 400°C (e.g., 250°C, 270°C, 280°C, 300°C, 320°C, 350°C, 380°C, or 400°C, etc.) in an oxygen atmosphere for 2 hours to 4 hours (e.g., 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours, etc.), and then holding at 740°C to 800°C (e.g., 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, or 800°C, etc.) for 8 hours to 16 hours (e.g., 8 hours, 10 hours, 12 hours, 14 hours, 15 hours, or 16 hours, etc.).

[0089] In some embodiments, the lithium salt may be lithium hydroxide, and the molar ratio of lithium to the high-nickel cathode precursor in the lithium salt is 1.05:1 to 1.08:1, for example, it may be 1.05:1, 1.06:1, 1.07:1 or 1.08:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0090] One embodiment of the present invention provides a lithium-ion battery, the lithium-ion battery comprising the high-nickel cathode material described in any embodiment.

[0091] Example 1

[0092] This embodiment provides a method for preparing a high-nickel cathode precursor, the method comprising:

[0093] S1. Pure water, precipitant solution (6 mol / L sodium hydroxide solution), and complexing agent solution (5 mol / L ammonia solution) are mixed in a reaction vessel to obtain a solution with a temperature of 60℃, a pH value of 11, and a complexing agent concentration of 0.3 mol / L.

[0094] S2. A mixed salt solution, precipitant solution, complexing agent solution and additive solution are introduced concurrently into the bottom liquid to carry out a co-precipitation reaction. Then, after aging, filtration, washing and vacuum drying at 120°C, the high-nickel cathode precursor is obtained.

[0095] The additive in the additive solution comprises polyvinyl alcohol and polyacrylic acid in a mass ratio of 1:1; the mass concentration of the additive in the additive solution is 3 wt%; the amount of the additive solution used satisfies the following condition: the mass of the additive is 1 wt% of the total mass of the metal salt in the mixed salt solution.

[0096] The weight-average molecular weight of the polyvinyl alcohol is 100,000 Da;

[0097] The weight-average molecular weight of the polyacrylic acid is 30,000 Da;

[0098] The metal salts in the mixed salt solution include nickel sulfate, cobalt sulfate, and manganese sulfate, with a molar ratio of nickel, cobalt, and manganese of 0.8:0.1:0.1; the total concentration of metal ions in the mixed salt solution is 2 mol / L.

[0099] The precipitant solution is a 6 mol / L sodium hydroxide solution; the complexing agent solution is a 5 mol / L ammonia solution.

[0100] The coprecipitation reaction was carried out in a nitrogen atmosphere at a temperature of 60°C, a pH of 11, a stirring speed of 500 rpm, and a complexing agent concentration of 0.3 mol / L. The average primary particle size of the resulting high-nickel cathode precursor was 110 nm.

[0101] The SEM image of the high-nickel cathode precursor obtained in this embodiment is as follows: Figure 1 As shown.

[0102] Example 2

[0103] This embodiment provides a method for preparing a high-nickel cathode precursor, the method comprising:

[0104] S1. Pure water, precipitant solution (4 mol / L sodium hydroxide solution), and complexing agent solution (2 mol / L ammonia solution) are mixed in a reaction vessel to obtain a solution with a temperature of 40℃, a pH value of 9, and a complexing agent concentration of 0.1 mol / L.

[0105] S2. A mixed salt solution, precipitant solution, complexing agent solution and additive solution are introduced concurrently into the bottom liquid to carry out a co-precipitation reaction. Then, after aging, filtration, washing and vacuum drying at 100°C, the high-nickel cathode precursor is obtained.

[0106] The additive in the additive solution comprises polyvinyl alcohol and polyacrylic acid in a mass ratio of 1:3; the mass concentration of the additive in the additive solution is 0.5 wt%; the amount of the additive solution used satisfies the following condition: the mass of the additive is 0.2 wt% of the total mass of the metal salt in the mixed salt solution;

[0107] The weight-average molecular weight of the polyvinyl alcohol is 50,000 Da;

[0108] The weight-average molecular weight of the polyacrylic acid is 5000 Da;

[0109] The metal salts in the mixed salt solution include nickel sulfate, cobalt sulfate, and manganese sulfate, with a molar ratio of nickel, cobalt, and manganese of 0.8:0.1:0.1; the total concentration of metal ions in the mixed salt solution is 1.5 mol / L.

[0110] The precipitant solution is a 4 mol / L sodium hydroxide solution; the complexing agent solution is a 2 mol / L ammonia solution.

[0111] The coprecipitation reaction was carried out in a nitrogen atmosphere at a temperature of 40°C, a pH of 9, a stirring speed of 300 rpm, and a complexing agent concentration of 0.1 mol / L. The average primary particle size of the resulting high-nickel cathode precursor was 80 nm.

[0112] Example 3

[0113] This embodiment provides a method for preparing a high-nickel cathode precursor, the method comprising:

[0114] S1. Pure water, precipitant solution (10 mol / L sodium hydroxide solution) and complexing agent solution (8 mol / L ammonia solution) are mixed in a reaction vessel to obtain a solution with a temperature of 85℃, a pH value of 12.5 and a complexing agent concentration of 0.5 mol / L.

[0115] S2. A mixed salt solution, precipitant solution, complexing agent solution and additive solution are introduced concurrently into the bottom liquid to carry out a co-precipitation reaction. Then, after aging, filtration, washing and vacuum drying at 150°C, the high-nickel cathode precursor is obtained.

[0116] The additive in the additive solution comprises polyvinyl alcohol and polyacrylic acid in a mass ratio of 3:1; the mass concentration of the additive in the additive solution is 5 wt%; the amount of the additive solution used satisfies the following condition: the mass of the additive is 3 wt% of the total mass of the metal salt in the mixed salt solution.

[0117] The weight-average molecular weight of the polyvinyl alcohol is 150,000 Da;

[0118] The weight-average molecular weight of the polyacrylic acid is 50,000 Da;

[0119] The metal salts in the mixed salt solution include nickel sulfate, cobalt sulfate, and manganese sulfate, with a molar ratio of nickel, cobalt, and manganese of 0.8:0.1:0.1; the total concentration of metal ions in the mixed salt solution is 2.5 mol / L.

[0120] The precipitant solution is a 10 mol / L sodium hydroxide solution; the complexing agent solution is an 8 mol / L ammonia solution.

[0121] The coprecipitation reaction was carried out in a nitrogen atmosphere at a temperature of 85°C, a pH of 12.5, a stirring speed of 800 rpm, and a complexing agent concentration of 0.5 mol / L. The average primary particle size of the resulting high-nickel cathode precursor was 210 nm.

[0122] Example 4

[0123] This embodiment provides a method for preparing a high-nickel cathode precursor. Except for adjusting the amount of additive solution so that the mass of the additive is 0.1 wt% of the total mass of the metal salt in the mixed salt solution, the rest is the same as in Example 1.

[0124] Example 5

[0125] This embodiment provides a method for preparing a high-nickel cathode precursor. Except for adjusting the amount of additive solution so that the mass of the additive is 4 wt% of the total mass of the metal salt in the mixed salt solution, the rest is the same as in Example 1.

[0126] Example 6

[0127] This embodiment provides a method for preparing a high-nickel cathode precursor, which is the same as in Example 1 except that the weight-average molecular weight of polyvinyl alcohol is 40,000 Da.

[0128] Example 7

[0129] This embodiment provides a method for preparing a high-nickel cathode precursor, which is the same as in Example 1 except that the weight-average molecular weight of polyvinyl alcohol is 180,000 Da.

[0130] Example 8

[0131] This embodiment provides a method for preparing a high-nickel cathode precursor, which is the same as in Example 1 except that the weight-average molecular weight of polyacrylic acid is 3000 Da.

[0132] Example 9

[0133] This embodiment provides a method for preparing a high-nickel cathode precursor, which is the same as in Example 1 except that the weight-average molecular weight of polyacrylic acid is 80,000 Da.

[0134] Comparative Example 1

[0135] This comparative example provides a method for preparing a high-nickel cathode precursor, which is the same as in Example 1 except that the mass ratio of polyvinyl alcohol to polyacrylic acid in the additive solution is 1:5.

[0136] The SEM image of the high-nickel cathode precursor obtained in this comparative example is shown below. Figure 2 As shown.

[0137] Comparative Example 2

[0138] This comparative example provides a method for preparing a high-nickel cathode precursor, which is the same as in Example 1 except that the mass ratio of polyvinyl alcohol to polyacrylic acid in the additive solution is 5:1.

[0139] Comparative Example 3

[0140] This comparative example provides a method for preparing a high-nickel cathode precursor. Except that the additive in the additive solution is only polyvinyl alcohol, everything else is the same as in Example 1.

[0141] Comparative Example 4

[0142] This comparative example provides a method for preparing a high-nickel cathode precursor. Except that the additive in the additive solution is only polyacrylic acid, everything else is the same as in Example 1.

[0143] Performance Characterization

[0144] The average aspect ratio, average primary particle size, BET specific surface area, and median particle size D50 of the high-nickel cathode precursors obtained in the above examples and comparative examples were measured, and the results are shown in Table 1.

[0145] Specifically, the method for determining the average primary particle size is as follows: the precursor sample is characterized by field emission scanning electron microscopy. At least five different non-overlapping and non-agglomerated fields of view are randomly selected at 10,000x magnification. At least 50 primary particles with clear boundaries are counted in each field of view. The equivalent projected diameter of each particle (i.e., the diameter of a circle with the same projected area as the particle) is measured using ImageJ image analysis software. The arithmetic mean of the equivalent projected diameters of all the counted particles is calculated, which is the average primary particle size of the sample.

[0146] The method for determining the average aspect ratio is as follows: Based on the same set of images taken by the field emission scanning electron microscope, for each particle with a statistically equivalent projected diameter, the length of its longest axis (L) and the length of its shortest axis perpendicular to the longest axis (W) are measured respectively. The aspect ratio L / W of each particle is calculated, and then the arithmetic mean of the aspect ratios of all statistically measured particles is calculated, which is the average aspect ratio of the sample.

[0147] The method for determining the BET specific surface area is as follows: Before the test, the precursor sample is vacuum degassed at 120℃ for 6h to remove the surface adsorbed moisture and gas. Then, a nitrogen adsorption-desorption experiment is carried out at 77K liquid nitrogen temperature. The specific surface area of ​​the sample is calculated using the BET multi-point method.

[0148] The method for determining the median particle size D50 is as follows: the precursor sample is ultrasonically dispersed in deionized water and tested using a laser particle size analyzer. D50 is the particle size corresponding to a volume cumulative distribution of 50%.

[0149] Table 1

[0150]

[0151] To prepare high-nickel cathode materials from the high-nickel cathode precursors obtained in the above examples and comparative examples: lithium hydroxide and high-nickel cathode precursors were mixed and sintered in an oxygen atmosphere to obtain high-nickel cathode materials; wherein, the molar ratio of lithium hydroxide to high-nickel cathode precursors was 1.06:1; the sintering included: holding at 350°C for 3 hours, and then holding at 760°C for 12 hours.

[0152] The high-nickel ternary cathode material, conductive agent (Super P), and binder (polyvinylidene fluoride) were uniformly mixed at a mass ratio of 90:5:5. N-methylpyrrolidone (NMP) was added to form a uniform slurry, which was coated on one side of an aluminum foil current collector. After vacuum drying at 120°C for 12 hours, the slurry was rolled and punched into cathode sheets with a diameter of 14 mm. The active material loading of the cathode was 8 mg / cm2~10 mg / cm2. Using lithium metal sheets as the anode, Celgard 2400 as the separator, and 1 mol / L LiPF6 / EC+DMC+EMC (volume ratio 1:1:1) as the electrolyte, the CR2032 coin cell was assembled in an argon-atmospheric glove box. After standing for 12 hours, the battery was charged at a constant current of 0.1C to 4.3V within a voltage range of 2.8V to 4.3V using the Blue Battery Testing System. Then, it was charged at a constant voltage until the current decreased to 0.05C, followed by constant current discharge at 0.1C to 2.8V. The initial discharge specific capacity was recorded. In this invention, 1C is calculated as 200mA / g.

[0153] After assembling the coin cells using the same method described above and allowing them to stand for 12 hours, they were first activated by three charge-discharge cycles at 0.1C. Then, they were cycled at 1C within a voltage range of 2.8V to 4.3V. Constant current-constant voltage charging was used during charging, and constant current discharging was used during discharging, for a total of 100 cycles. The discharge specific capacity of the first 1C cycle and the discharge specific capacity of the 100th 1C cycle were recorded. The capacity retention rate of the sample after 100 1C cycles was calculated according to the formula "Capacity retention rate (%) = (100th 1C discharge specific capacity / 1st 1C discharge specific capacity) × 100%".

[0154] After assembling the coin cells using the same method described above and allowing them to stand for 12 hours, they were first activated by constant current charge and discharge at a rate of 0.1C three times. Then, the charging rate was fixed at 0.2C, and the discharge rates were set sequentially to 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C. Each rate was cycled three times, and the specific capacity of the third discharge was taken as the discharge specific capacity at that rate. The discharge specific capacity at the 10C rate is the 10C discharge specific capacity of the sample.

[0155] The results are shown in Table 2.

[0156] Table 2

[0157]

[0158] As can be seen from Examples 1 to 3 in Tables 1 and 2, the PVA and PAA synergistic regulation method provided by the present invention can effectively prepare high-nickel cathode precursors with small primary particle size, high aspect ratio, and large specific surface area, thereby improving the first discharge specific capacity, cycle stability, and rate performance of the cathode material after sintering.

[0159] A comparison of Examples 4 and 5 with Example 1 shows that when the total mass of PVA and PAA is 0.2% to 3.0% of the total mass of the metal salt in the mixed salt solution, the comprehensive regulation effect on morphology and electrochemical performance is better. When the additive dosage is less than 0.2%, the degree of composite adsorption on the crystal nucleus surface is insufficient, weakening the synergistic regulation effect on nucleation and crystal growth, resulting in a larger primary particle size and a lower aspect ratio of the precursor. When the additive dosage is greater than 3.0%, the viscosity of the reaction system and the molecular chain bridging effect are enhanced, affecting mass transfer and causing particle agglomeration. Excessive organic matter may also increase the risk of residual carbon and porosity during sintering, thereby leading to a decrease in electrochemical performance.

[0160] A comparison of Examples 6-9 with Example 1 shows that a better balance can be achieved between composite adsorption, molecular chain entanglement, and system dispersibility when the weight-average molecular weight of PVA is 50,000 Da to 150,000 Da and the weight-average molecular weight of PAA is 5,000 Da to 50,000 Da. When the molecular weight is too low, the molecular chains are too short, resulting in insufficient surface adsorption and steric hindrance; when the molecular weight is too high, the solution viscosity, chain entanglement, and bridging effects are enhanced, which is detrimental to uniform mass transfer and particle dispersion. Both situations reduce the overall control effect of primary particle size, aspect ratio, and orientation packing, thereby affecting the electrochemical performance of the cathode material.

[0161] A comparison of Comparative Examples 1 and 2 with Example 1 shows that a better balance between composite adsorption and dispersion stability is achieved when the mass ratio of PVA to PAA is 1:3 to 3:1. When the mass ratio of PVA to PAA is less than 1:3, the PAA content is too high, and the interaction between carboxyl / carboxylate groups and metal ions or crystal nuclei is too strong, easily leading to bridging and agglomeration. When the mass ratio is higher than 3:1, the PVA content is too high, and the coordination / adsorption effect of PAA on the crystal nuclei surface is insufficient, making it difficult to fully utilize the synergistic regulatory effect of the two. Both situations result in a decrease in the aspect ratio, uniformity, and ordered packing degree of the primary particles.

[0162] A comparison of Comparative Examples 3 and 4 with Example 1 shows that the synergistic effect of PVA and PAA is key to achieving precise control of the precursor microstructure; neither component alone can achieve the technical effect of this invention. When using only PVA, its adsorption and coordination with the crystal nucleus surface are limited, making it impossible to simultaneously control crystal growth, particle orientation, and dispersion stability. When using only PAA, the interaction between its carboxyl / carboxylate groups and metal ions or the crystal nucleus surface is strong, which can excessively inhibit crystal growth. Although the average particle size of the primary particles is small and the BET is high, the aspect ratio is low, the orientation and packing are poor, and agglomeration is severe, resulting in the worst electrochemical performance. This indicates that simply reducing the size of the primary particles does not necessarily lead to performance improvement; the synergistic effect of PVA and PAA is more crucial for controlling the aspect ratio, uniformity, and ordered packing of the primary particles.

[0163] In summary, the method for preparing the high-nickel cathode precursor provided by this invention uses a combination of PVA and PAA as synergistic regulators. Without being constrained by specific theories, the hydroxyl groups of PVA and the carboxyl / carboxylate groups of PAA can form a composite adsorption system through hydrogen bonding, ion-dipole interactions, and molecular chain entanglement. This system synergistically regulates nucleation, crystal growth, and particle assembly, which is beneficial for obtaining high-nickel ternary precursors with smaller primary particle size, higher aspect ratio, and more uniform distribution. The more uniform primary particle morphology facilitates uniform reaction and crystallization during subsequent lithium-ion sintering, reduces local stress concentration, and thus improves the cycle stability and rate performance of the high-nickel ternary cathode material.

[0164] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a high-nickel cathode precursor, characterized in that, The preparation method includes: A mixed salt solution, a precipitant solution, a complexing agent solution, and an additive solution are simultaneously introduced into the bottom solution to carry out a co-precipitation reaction, thereby obtaining the high-nickel cathode precursor. The additives in the additive solution include polyvinyl alcohol and polyacrylic acid in a mass ratio of 1:3 to 3:

1.

2. The preparation method according to claim 1, characterized in that, The additive solution contains an additive concentration of 0.5 wt% to 5 wt%.

3. The preparation method according to claim 1 or 2, characterized in that, The amount of the additive solution used satisfies the following condition: the mass of the additive is 0.2wt% to 3wt% of the total mass of the metal salt in the mixed salt solution.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The weight-average molecular weight of the polyvinyl alcohol is 50,000 Da to 150,000 Da; And / or, the weight-average molecular weight of the polyacrylic acid is 5000 Da to 50000 Da.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The metal salts in the mixed salt solution include nickel salts, cobalt salts, and manganese salts; The nickel salt includes any one or a combination of at least two of nickel sulfate, nickel chloride, or nickel nitrate. The cobalt salt includes any one or a combination of at least two of cobalt sulfate, cobalt chloride, or cobalt nitrate. The manganese salt includes any one or a combination of at least two of manganese sulfate, manganese chloride, or manganese nitrate. And / or, in the mixed salt solution, the molar ratio of nickel, cobalt and manganese is x:y:z, where x≥0.6 and x+y+z=1; And / or, the total concentration of metal ions in the mixed salt solution is 1.5 mol / L to 2.5 mol / L.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The concentration of the precipitant solution is 4 mol / L to 10 mol / L; And / or, the precipitant in the precipitant solution includes sodium hydroxide and / or potassium hydroxide; And / or, the concentration of the complexing agent solution is 2 mol / L to 8 mol / L; And / or, the complexing agent in the complexing agent solution includes ammonia.

7. The preparation method according to any one of claims 1 to 6, characterized in that, The temperature for the coprecipitation reaction is 40℃~85℃; And / or, the pH value of the coprecipitation reaction is 9~12.5; And / or, the stirring speed of the coprecipitation reaction is 300 rpm to 800 rpm; And / or, the concentration of the complexing agent in the coprecipitation reaction is 0.1 mol / L to 0.5 mol / L; And / or, the average primary particle size of the high-nickel cathode precursor is 80 nm to 210 nm; And / or, the median particle size D50 of the high-nickel cathode precursor is 2 μm to 3 μm.

8. A high-nickel cathode precursor, characterized in that, The high-nickel cathode precursor is prepared by the preparation method described in any one of claims 1 to 7.

9. A high-nickel cathode material, characterized in that, The high-nickel cathode material is obtained by sintering a mixture of lithium salt and a high-nickel cathode precursor. The high-nickel cathode precursor is the high-nickel cathode precursor prepared by the preparation method according to any one of claims 1 to 7, or the high-nickel cathode precursor according to claim 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the high-nickel cathode material as described in claim 9.

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