Precursor having radially oriented acicular primary particles, method of making and use

Abstract

The application provides a precursor with radially oriented needle-like primary particles, a preparation method and application. The preparation method of the precursor with radially oriented needle-like primary particles comprises the following steps: under the condition of electromagnetic field assistance, continuously feeding mixed salt solution, precipitant solution and complexing agent solution into a reaction kettle to perform a first coprecipitation reaction; then performing a second coprecipitation reaction under the condition of no electromagnetic field assistance, continuously adding a crystal face directing agent during the second coprecipitation reaction; stopping adding the crystal face directing agent to perform a third coprecipitation reaction; and performing aging, washing, filtering and drying on the obtained slurry to obtain the precursor with radially oriented needle-like primary particles. The preparation method provided by the application realizes the radial orientation arrangement of the primary particles through the cooperation of electromagnetic field assistance and the crystal face directing agent, optimizes the crystal structure and electrochemical performance of the precursor, and improves the rate performance and cycle performance of the positive electrode material prepared from the precursor.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, and relates to a precursor with radially oriented needle-like primary particles, its preparation method and application. Background Technology

[0002] With the increasing demands for energy density in lithium-ion batteries, high-nickel ternary materials (Ni≥0.9) have become a research hotspot due to their high specific capacity. However, during the charge and discharge process, high-nickel materials are prone to microcracks between primary particles due to anisotropic volume changes. This leads to electrolyte penetration along grain boundaries, exacerbating side reactions and ultimately causing rapid capacity decay.

[0003] In existing technologies, researchers have mitigated this problem through core-shell structures and concentration gradient designs, but these approaches primarily focus on controlling elemental distribution. Regarding the morphology and orientation of primary particles, current precursors are generally randomly arranged plate-like or needle-like particles, lacking directional alignment design, and thus failing to fundamentally suppress microcrack propagation. More critically, in existing co-precipitation processes, the growth direction of primary particles is difficult to control, resulting in random grain orientation in the sintered cathode material, tortuous lithium-ion diffusion paths, and limited rate performance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a precursor with radially oriented needle-like primary particles, a preparation method, and an application. This precursor with radially oriented needle-like primary particles controls the primary particles to be arranged radially from the particle center outwards, so that the sintered cathode material grains are preferentially oriented along specific crystal planes, thereby shortening the lithium-ion diffusion path and suppressing the generation of microcracks.

[0005] To achieve this objective, the present invention employs the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a precursor having radially oriented needle-like primary particles, the method comprising the following steps:

[0007] Under electromagnetic field assistance, a mixed salt solution, a precipitant solution, and a complexing agent solution are introduced concurrently into a reactor to carry out a first coprecipitation reaction; then, a second coprecipitation reaction is carried out without electromagnetic field assistance, during which a crystal plane guiding agent is continuously added; the addition of the crystal plane guiding agent is stopped, and a third coprecipitation reaction is carried out; the resulting slurry is aged, washed, filtered, and dried to obtain the precursor with radially oriented needle-like primary particles.

[0008] The electromagnetic field assistance employed in this invention can apply a directional magnetic field during the first coprecipitation reaction, inducing magnetic metal ions (Ni, Co) to align along the magnetic field lines, providing a template for subsequent oriented growth. The crystal plane inducer can selectively adsorb on different crystal planes, controlling the aspect ratio and growth direction of the primary particles to form a radial structure. This invention achieves radial orientation of primary particles through the synergy of electromagnetic field assistance and crystal plane inducer, optimizing the crystal structure and electrochemical performance of the precursor, and improving the rate performance and cycle performance of the cathode material.

[0009] In some embodiments, the magnetic field strength of the electromagnetic field-assisted condition is 0.1T to 0.5T.

[0010] In some embodiments, the temperature of the first coprecipitation reaction is 45°C to 65°C.

[0011] In some embodiments, the pH value of the first coprecipitation reaction is 11-12.

[0012] In some embodiments, the concentration of the complexing agent in the first coprecipitation reaction is 8 g / L to 15 g / L.

[0013] In some embodiments, the first coprecipitation reaction takes 2 to 4 hours.

[0014] In some embodiments, the stirring speed of the first coprecipitation reaction is 200 rpm to 400 rpm.

[0015] In some embodiments, the crystal plane guiding agent includes any one or a combination of at least two of citric acid, tartaric acid, or ethylenediaminetetraacetic acid.

[0016] In some embodiments, the amount of the crystal plane guiding agent is 0.1% to 1% of the total molar amount of metal in the precursor.

[0017] In some embodiments, the temperature of the second coprecipitation reaction is 50°C to 70°C.

[0018] In some embodiments, the pH value of the second coprecipitation reaction is 10.5 to 11.5.

[0019] In some embodiments, the concentration of the complexing agent in the second coprecipitation reaction is 5 g / L to 10 g / L.

[0020] In some embodiments, the stirring speed of the second coprecipitation reaction is 100 rpm to 200 rpm.

[0021] In some embodiments, the median particle size D50 at the endpoint of the second coprecipitation reaction is 3 μm to 15 μm.

[0022] In some embodiments, the temperature of the third coprecipitation reaction is 50°C to 70°C.

[0023] In some embodiments, the pH value of the third coprecipitation reaction is 11.5 to 12.5.

[0024] In some embodiments, the concentration of the complexing agent in the third coprecipitation reaction is 10 g / L to 15 g / L.

[0025] In some embodiments, the stirring speed of the third coprecipitation reaction is 300 rpm to 500 rpm.

[0026] In some embodiments, the third coprecipitation reaction takes 1 to 3 hours.

[0027] In some embodiments, the metal salts in the mixed salt solution include nickel salts, cobalt salts, and manganese salts.

[0028] In some embodiments, the concentration of the metal salt in the mixed salt solution is 100 g / L to 150 g / L.

[0029] In some embodiments, the molar ratio of nickel, cobalt and manganese in the mixed salt solution is (0.94~0.98):(0.01~0.03):(0.01~0.03).

[0030] In some embodiments, the precipitant solution comprises a sodium hydroxide solution with a mass concentration of 25wt% to 35wt%.

[0031] In some embodiments, the complexing agent solution comprises ammonia water with a mass concentration of 15wt% to 25wt%.

[0032] As a preferred embodiment of the preparation method provided by the present invention, the preparation method includes:

[0033] (1) Under electromagnetic field-assisted conditions, a mixed salt solution, a precipitant solution and a complexing agent solution are introduced into the reactor in parallel to carry out the first coprecipitation reaction;

[0034] The magnetic field strength of the electromagnetic field auxiliary conditions is 0.1T~0.5T;

[0035] The temperature of the first coprecipitation reaction is 45℃~65℃, the pH value is 11~12, the concentration of the complexing agent is 8g / L~15g / L, and the time is 2h~4h; the stirring speed of the first coprecipitation reaction is 200rpm~400rpm.

[0036] (2) Then, a second coprecipitation reaction is carried out under conditions without electromagnetic field assistance, during which a crystal plane guiding agent is continuously added;

[0037] The crystal plane guiding agent comprises any one or a combination of at least two of citric acid, tartaric acid, or ethylenediaminetetraacetic acid; the amount of the crystal plane guiding agent is 0.1% to 1% of the total molar amount of the metal in the precursor;

[0038] The temperature of the second coprecipitation reaction is 50℃~70℃, the pH value is 10.5~11.5, the complexing agent concentration is 5g / L~10g / L, the stirring speed is 100rpm~200rpm, and the median particle size D50 at the endpoint is 3μm~15μm.

[0039] (3) Stop adding crystal plane guiding agent and carry out the third coprecipitation reaction; the resulting slurry is aged, washed, filtered and dried to obtain the precursor with radially oriented needle-like primary particles;

[0040] The third coprecipitation reaction was carried out at a temperature of 50℃~70℃, a pH value of 11.5~12.5, a complexing agent concentration of 10g / L~15g / L, a stirring speed of 300rpm~500rpm, and a time of 1h~3h.

[0041] In a second aspect, the present invention provides a precursor having radially oriented needle-like primary particles, the precursor being prepared by the preparation method described in the first aspect.

[0042] Thirdly, the present invention provides a cathode material, which is prepared from the precursor described in the second aspect.

[0043] 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.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention provides a method for preparing a precursor with radially oriented needle-like primary particles. The method employs electromagnetic field assistance, which applies a directional magnetic field during the first co-precipitation reaction to induce magnetic metal ions (Ni, Co) to align along the magnetic field lines, providing a template for subsequent oriented growth. A crystal plane inducer selectively adsorbs on different crystal planes, controlling the aspect ratio and growth direction of the primary particles to form a radial structure. This invention, through the synergy of electromagnetic field assistance and crystal plane inducer, achieves radially oriented alignment of primary particles, optimizing the crystal structure and electrochemical performance of the precursor, and improving the rate performance and cycle performance of the cathode material obtained from the precursor. Attached Figure Description

[0046] Figure 1 This is a SEM image of the precursor obtained in Example 1. Detailed Implementation

[0047] 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.

[0048] 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.

[0049] 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.

[0050] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0051] 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.

[0052] 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.

[0053] 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."

[0054] 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.

[0055] 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.

[0056] In this invention, "optional" means that something is optional, that is, it refers to either "with" or "without". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0057] In a first aspect, the present invention provides a method for preparing a precursor having radially oriented needle-like primary particles, the method comprising the following steps:

[0058] Under electromagnetic field assistance, a mixed salt solution, a precipitant solution, and a complexing agent solution are introduced concurrently into a reactor to carry out a first coprecipitation reaction; then, a second coprecipitation reaction is carried out without electromagnetic field assistance, during which a crystal plane guiding agent is continuously added; the addition of the crystal plane guiding agent is stopped, and a third coprecipitation reaction is carried out; the resulting slurry is aged, washed, filtered, and dried to obtain the precursor with radially oriented needle-like primary particles.

[0059] The electromagnetic field assistance employed in this invention can apply a directional magnetic field during the first coprecipitation reaction, inducing magnetic metal ions (Ni, Co) to align along the magnetic field lines, providing a template for subsequent oriented growth. The crystal plane inducer can selectively adsorb on different crystal planes, controlling the aspect ratio and growth direction of the primary particles to form a radial structure. This invention achieves radial orientation of primary particles through the synergy of electromagnetic field assistance and crystal plane inducer, optimizing the crystal structure and electrochemical performance of the precursor, and improving the rate performance and cycle performance of the cathode material.

[0060] The present invention forms oriented crystal nuclei through a first coprecipitation reaction, and causes primary particles to preferentially grow along a specific crystal plane through a second coprecipitation reaction to form a radially arranged needle-like structure; and forms a dense thin layer on the surface of the radial structure through a third coprecipitation reaction.

[0061] In some embodiments, the magnetic field strength of the electromagnetic field auxiliary condition is 0.1T to 0.5T, for example, it can be 0.1T, 0.2T, 0.3T, 0.4T or 0.5T, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0062] In this invention, the first coprecipitation reaction, the second coprecipitation reaction, and the third coprecipitation reaction are carried out in a reactor, and the direction of the electromagnetic field assisted by the electromagnetic field is perpendicular to the stirring shaft of the reactor.

[0063] In some embodiments, the temperature of the first coprecipitation reaction is 45°C to 65°C, for example, 45°C, 50°C, 55°C, 60°C, 62°C, 64°C or 65°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0064] In some embodiments, the pH value of the first coprecipitation reaction is 11 to 12, for example, it can be 11, 11.2, 11.5, 11.8 or 12, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0065] In some embodiments, the concentration of the complexing agent in the first coprecipitation reaction is 8 g / L to 15 g / L, for example, it can be 8 g / L, 9 g / L, 10 g / L, 12 g / L or 15 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0066] In some embodiments, the time for the first coprecipitation reaction is 2h to 4h, for example, it can be 2h, 2.5h, 3h, 3.5h or 4h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0067] In some embodiments, the stirring speed of the first coprecipitation reaction is 200 rpm to 400 rpm, for example, 200 rpm, 250 rpm, 300 rpm, 350 rpm or 400 rpm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0068] In some embodiments, the crystal plane guiding agent comprises any one or a combination of at least two of citric acid, tartaric acid, or ethylenediaminetetraacetic acid. Typical but non-limiting combinations include combinations of citric acid and tartaric acid, combinations of citric acid and ethylenediaminetetraacetic acid, combinations of tartaric acid and ethylenediaminetetraacetic acid, or combinations of citric acid, tartaric acid, and ethylenediaminetetraacetic acid.

[0069] In some embodiments, the amount of the crystal plane guiding agent is 0.1% to 1% of the total molar amount of metal in the precursor, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8% or 1%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] In some embodiments, the temperature of the second coprecipitation reaction is 50°C to 70°C, for example, 50°C, 55°C, 60°C, 65°C or 70°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0071] In some embodiments, the pH value of the second coprecipitation reaction is 10.5 to 11.5, for example, it can be 10.5, 10.8, 11, 11.2 or 11.5, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0072] In some embodiments, the concentration of the complexing agent in the second coprecipitation reaction is 5 g / L to 10 g / L, for example, it can be 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0073] In some embodiments, the stirring speed of the second coprecipitation reaction is 100 rpm to 200 rpm, for example, 100 rpm, 120 rpm, 150 rpm, 160 rpm, 180 rpm or 200 rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0074] In some embodiments, the median particle size D50 at the endpoint of the second coprecipitation reaction is 3 μm to 15 μm, for example, it can be 3 μm, 5 μm, 6 μm, 8 μm, 10 μm, 12 μm or 15 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0075] In some embodiments, the temperature of the third coprecipitation reaction is 50°C to 70°C, for example, 50°C, 55°C, 60°C, 65°C or 70°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0076] In some embodiments, the pH value of the third coprecipitation reaction is 11.5 to 12.5, for example, it can be 11.5, 11.8, 12, 12.2 or 12.5, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0077] In some embodiments, the concentration of the complexing agent in the third coprecipitation reaction is 10 g / L to 15 g / L, for example, it can be 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L or 15 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0078] In some embodiments, the stirring speed of the third coprecipitation reaction is 300 rpm to 500 rpm, for example, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0079] In some embodiments, the time for the third coprecipitation reaction is 1h to 3h, for example, it can be 1h, 1.5h, 2h, 2.5h or 3h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0080] In some embodiments, the metal salts in the mixed salt solution include nickel salts, cobalt salts, and manganese salts.

[0081] Optionally, 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; and the manganese salt includes any one or a combination of at least two of manganese sulfate, manganese chloride, or manganese nitrate.

[0082] In some embodiments, the concentration of the metal salt in the mixed salt solution is 100 g / L to 150 g / L, for example, it can be 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0083] In some embodiments, the molar ratio of nickel, cobalt and manganese in the mixed salt solution is (0.94~0.98):(0.01~0.03):(0.01~0.03).

[0084] In some embodiments, the precipitant solution comprises a sodium hydroxide solution with a mass concentration of 25wt% to 35wt%, for example, 25wt%, 27wt%, 28wt%, 30wt%, 32wt%, 33wt%, or 35wt%, but is not limited to the listed values; other unlisted values ​​within the range are also applicable.

[0085] In some embodiments, the complexing agent solution comprises ammonia water with a mass concentration of 15wt% to 25wt%, for example, it may be 15wt%, 16wt%, 18wt%, 20wt%, 21wt%, 24wt%, or 25wt%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0086] As a preferred embodiment of the preparation method provided by the present invention, the preparation method includes:

[0087] (1) Under electromagnetic field-assisted conditions, a mixed salt solution, a precipitant solution and a complexing agent solution are introduced into the reactor in parallel to carry out the first coprecipitation reaction;

[0088] The magnetic field strength of the electromagnetic field auxiliary conditions is 0.1T~0.5T;

[0089] The temperature of the first coprecipitation reaction is 45℃~65℃, the pH value is 11~12, the concentration of the complexing agent is 8g / L~15g / L, and the time is 2h~4h; the stirring speed of the first coprecipitation reaction is 200rpm~400rpm.

[0090] (2) Then, a second coprecipitation reaction is carried out under conditions without electromagnetic field assistance, during which a crystal plane guiding agent is continuously added;

[0091] The crystal plane guiding agent comprises any one or a combination of at least two of citric acid, tartaric acid, or ethylenediaminetetraacetic acid; the amount of the crystal plane guiding agent is 0.1% to 1% of the total molar amount of metal in the precursor;

[0092] The temperature of the second coprecipitation reaction is 50℃~70℃, the pH value is 10.5~11.5, the complexing agent concentration is 5g / L~10g / L, the stirring speed is 100rpm~200rpm, and the median particle size D50 at the endpoint is 3μm~15μm.

[0093] (3) Stop adding crystal plane guiding agent and carry out the third coprecipitation reaction; the resulting slurry is aged, washed, filtered and dried to obtain the precursor with radially oriented needle-like primary particles;

[0094] The third coprecipitation reaction was carried out at a temperature of 50℃~70℃, a pH value of 11.5~12.5, a complexing agent concentration of 10g / L~15g / L, a stirring speed of 300rpm~500rpm, and a time of 1h~3h.

[0095] In a second aspect, the present invention provides a precursor having radially oriented needle-like primary particles, the precursor being prepared by the preparation method described in the first aspect.

[0096] Thirdly, the present invention provides a cathode material, which is prepared from the precursor described in the second aspect.

[0097] Example 1

[0098] This embodiment provides a method for preparing a precursor with radially oriented needle-like primary particles, including:

[0099] (1) Under electromagnetic field-assisted conditions, a mixed salt solution, a precipitant solution (30wt% NaOH solution) and a complexing agent solution (20wt% ammonia water) are introduced into the reactor in parallel to carry out the first coprecipitation reaction;

[0100] The magnetic field strength of the electromagnetic field auxiliary condition is 0.3T, and the direction of the magnetic field is perpendicular to the stirring shaft of the reactor.

[0101] The temperature of the first coprecipitation reaction was 55℃, the pH value was 11.5, the complexing agent concentration was 12g / L, and the time was 3h; the stirring speed of the first coprecipitation reaction was 300rpm.

[0102] The mixed salt solution is prepared from nickel sulfate, cobalt sulfate and manganese sulfate, with a molar ratio of nickel, cobalt and manganese of 0.95:0.02:0.03 and a total metal ion concentration of 120 g / L.

[0103] (2) Then, a second coprecipitation reaction is carried out under conditions without electromagnetic field assistance, during which a crystal plane guiding agent is continuously added;

[0104] The crystal plane guiding agent is citric acid; the amount of crystal plane guiding agent used is 0.3% of the total molar amount of metal in the precursor;

[0105] The second coprecipitation reaction was carried out at a temperature of 60°C, a pH of 11, a complexing agent concentration of 8 g / L, a stirring speed of 150 rpm, and a median particle size D50 of 8 μm at the endpoint.

[0106] (3) Stop adding crystal plane guiding agent and carry out the third coprecipitation reaction; the resulting slurry is aged for 12 hours, washed, filtered and dried at 120°C for 2 hours to obtain the precursor with radially oriented needle-like primary particles;

[0107] The third coprecipitation reaction was carried out at a temperature of 60°C, a pH of 12, a complexing agent concentration of 12 g / L, a stirring speed of 400 rpm, and a time of 2 h.

[0108] The SEM image of the precursor obtained in this embodiment is as follows: Figure 1 As shown.

[0109] Example 2

[0110] This embodiment provides a method for preparing a precursor with radially oriented needle-like primary particles, including:

[0111] (1) Under electromagnetic field-assisted conditions, a mixed salt solution, a precipitant solution (25wt% NaOH solution) and a complexing agent solution (15wt% ammonia water) are introduced into the reactor in parallel to carry out the first coprecipitation reaction;

[0112] The magnetic field strength of the electromagnetic field auxiliary condition is 0.1T, and the direction of the magnetic field is perpendicular to the stirring shaft of the reactor.

[0113] The temperature of the first coprecipitation reaction was 45℃, the pH value was 11, the concentration of the complexing agent was 8g / L, and the time was 2h; the stirring speed of the first coprecipitation reaction was 200rpm.

[0114] The mixed salt solution is prepared from nickel sulfate, cobalt sulfate and manganese sulfate, with a molar ratio of nickel, cobalt and manganese of 0.95:0.02:0.03 and a total metal ion concentration of 100 g / L.

[0115] (2) Then, a second coprecipitation reaction is carried out under conditions without electromagnetic field assistance, during which a crystal plane guiding agent is continuously added;

[0116] The crystal plane guiding agent is citric acid; the amount of crystal plane guiding agent used is 0.1% of the total molar amount of metal in the precursor;

[0117] The second coprecipitation reaction was carried out at a temperature of 50°C, a pH of 10.5, a complexing agent concentration of 5 g / L, a stirring speed of 100 rpm, and a final median particle size D50 of 3 μm.

[0118] (3) Stop adding crystal plane guiding agent and carry out the third coprecipitation reaction; the resulting slurry is aged for 12 hours, washed, filtered and dried at 120°C for 2 hours to obtain the precursor with radially oriented needle-like primary particles;

[0119] The third coprecipitation reaction was carried out at a temperature of 50°C, a pH of 11.5, a complexing agent concentration of 10 g / L, a stirring speed of 300 rpm, and a time of 1 h.

[0120] Example 3

[0121] This embodiment provides a method for preparing a precursor with radially oriented needle-like primary particles, including:

[0122] (1) Under electromagnetic field-assisted conditions, a mixed salt solution, a precipitant solution (35wt% NaOH solution) and a complexing agent solution (25wt% ammonia water) are introduced into the reactor in parallel to carry out the first coprecipitation reaction;

[0123] The magnetic field strength of the electromagnetic field auxiliary condition is 0.5T, and the direction of the magnetic field is perpendicular to the stirring shaft of the reactor.

[0124] The temperature of the first coprecipitation reaction was 65℃, the pH value was 12, the concentration of the complexing agent was 15g / L, and the time was 4h; the stirring speed of the first coprecipitation reaction was 400rpm.

[0125] The mixed salt solution is prepared from nickel sulfate, cobalt sulfate and manganese sulfate, with a molar ratio of nickel, cobalt and manganese of 0.95:0.02:0.03 and a total metal ion concentration of 150 g / L.

[0126] (2) Then, a second coprecipitation reaction is carried out under conditions without electromagnetic field assistance, during which a crystal plane guiding agent is continuously added;

[0127] The crystal plane guiding agent is citric acid; the amount of crystal plane guiding agent used is 1% of the total molar amount of metal in the precursor;

[0128] The second coprecipitation reaction was carried out at a temperature of 70°C, a pH of 11.5, a complexing agent concentration of 10 g / L, a stirring speed of 200 rpm, and a final median particle size D50 of 15 μm.

[0129] (3) Stop adding crystal plane guiding agent and carry out the third coprecipitation reaction; the resulting slurry is aged for 12 hours, washed, filtered and dried at 120°C for 2 hours to obtain the precursor with radially oriented needle-like primary particles;

[0130] The third coprecipitation reaction was carried out at a temperature of 70°C, a pH of 12.5, a complexing agent concentration of 15 g / L, a stirring speed of 500 rpm, and a time of 3 h.

[0131] Example 4

[0132] This embodiment provides a method for preparing a precursor with radially oriented needle-like primary particles. Except for the magnetic field strength of 0.05T, it is the same as that in Example 1.

[0133] Example 5

[0134] This embodiment provides a method for preparing a precursor with radially oriented needle-like primary particles. Except for the magnetic field strength of 0.8T, it is the same as that in Example 1.

[0135] Example 6

[0136] This embodiment provides a method for preparing a precursor with radially oriented needle-like primary particles. Except that the amount of crystal plane guiding agent is 0.05% of the total molar amount of metal in the precursor, the rest is the same as in Example 1.

[0137] Example 7

[0138] This embodiment provides a method for preparing a precursor with radially oriented needle-like primary particles. Except that the amount of crystal plane guiding agent is 1.2% of the total molar amount of metal in the precursor, the rest is the same as in Example 1.

[0139] Example 8

[0140] This embodiment provides a method for preparing a precursor with radially oriented needle-like primary particles. Except that the crystal plane guiding agent is tartaric acid, the rest is the same as in Example 1.

[0141] Example 9

[0142] This embodiment provides a method for preparing a precursor with radially oriented needle-like primary particles. Except for the crystal plane guiding agent being ethylenediaminetetraacetic acid, the rest is the same as in Example 1.

[0143] Comparative Example 1

[0144] This comparative example provides a method for preparing a precursor, which is the same as in Example 1 except that electromagnetic field assistance is not used, including:

[0145] (1) A mixed salt solution, a precipitant solution (30wt% NaOH solution) and a complexing agent solution (20wt% ammonia water) are introduced into the reactor in parallel to carry out the first coprecipitation reaction;

[0146] The temperature of the first coprecipitation reaction was 55℃, the pH value was 11.5, the complexing agent concentration was 12g / L, and the time was 3h; the stirring speed of the first coprecipitation reaction was 300rpm.

[0147] The mixed salt solution is prepared from nickel sulfate, cobalt sulfate and manganese sulfate, with a molar ratio of nickel, cobalt and manganese of 0.95:0.02:0.03 and a total metal ion concentration of 120 g / L.

[0148] (2) Then a second coprecipitation reaction is carried out, during which a crystal plane guiding agent is continuously added;

[0149] The crystal plane guiding agent is citric acid; the amount of crystal plane guiding agent used is 0.3% of the total molar amount of metal in the precursor;

[0150] The second coprecipitation reaction was carried out at a temperature of 60°C, a pH of 11, a complexing agent concentration of 8 g / L, a stirring speed of 150 rpm, and a median particle size D50 of 8 μm at the endpoint.

[0151] (3) Stop adding crystal plane guiding agent and carry out the third coprecipitation reaction; the resulting slurry is aged for 12 hours, washed, filtered and dried at 120°C for 2 hours to obtain the precursor with radially oriented needle-like primary particles;

[0152] The third coprecipitation reaction was carried out at a temperature of 60°C, a pH of 12, a complexing agent concentration of 12 g / L, a stirring speed of 400 rpm, and a time of 2 h.

[0153] Comparative Example 2

[0154] This comparative example provides a method for preparing a precursor, which is the same as in Example 1 except that no crystal plane guiding agent is added, including:

[0155] (1) Under electromagnetic field-assisted conditions, a mixed salt solution, a precipitant solution (30wt% NaOH solution) and a complexing agent solution (20wt% ammonia water) are introduced into the reactor in parallel to carry out the first coprecipitation reaction;

[0156] The magnetic field strength of the electromagnetic field auxiliary condition is 0.3T, and the direction of the magnetic field is perpendicular to the stirring shaft of the reactor.

[0157] The temperature of the first coprecipitation reaction was 55℃, the pH value was 11.5, the complexing agent concentration was 12g / L, and the time was 3h; the stirring speed of the first coprecipitation reaction was 300rpm.

[0158] The mixed salt solution is prepared from nickel sulfate, cobalt sulfate and manganese sulfate, with a molar ratio of nickel, cobalt and manganese of 0.95:0.02:0.03 and a total metal ion concentration of 120 g / L.

[0159] (2) Then, the second coprecipitation reaction is carried out under conditions without electromagnetic field assistance;

[0160] The second coprecipitation reaction was carried out at a temperature of 60°C, a pH of 11, a complexing agent concentration of 8 g / L, a stirring speed of 150 rpm, and a median particle size D50 of 8 μm at the endpoint.

[0161] (3) A third coprecipitation reaction was carried out; the resulting slurry was aged for 12 hours, washed, filtered and dried at 120°C for 2 hours to obtain the precursor with radially oriented needle-like primary particles;

[0162] The third coprecipitation reaction was carried out at a temperature of 60°C, a pH of 12, a complexing agent concentration of 12 g / L, a stirring speed of 400 rpm, and a time of 2 h.

[0163] Performance Characterization

[0164] The precursors obtained in the above embodiments and comparative examples were used to prepare cathode materials: the precursors and lithium hydroxide were mixed at a molar ratio of 1.04:1, and the mixture was first kept at 500°C for 5 hours under an oxygen atmosphere, and then kept at 720°C for 12 hours. After cooling, pulverizing, and sieving, the cathode material was obtained.

[0165] The rate performance corresponding to the shortened lithium-ion diffusion path was characterized using a CR2025 coin cell. The prepared positive electrode material, polyvinylidene fluoride binder, and acetylene black conductive agent were mixed uniformly at a mass ratio of 80:10:10. N-methylpyrrolidone was added to form a uniform slurry, which was then coated onto an aluminum foil current collector. After drying, rolling, and punching, the slurry was cut into positive electrode sheets with a diameter of 14 mm. A lithium metal sheet was used as the negative electrode. A battery was assembled in an argon-protected glove box using a 2400-porous membrane as the separator and 1 mol / L LiPF6 / EC+DMC+EMC (volume ratio 1:1:1) as the electrolyte. After standing for 12 hours, constant current charge-discharge tests were performed in the voltage range of 2.8V to 4.3V. First, the battery was activated by charging and discharging three times at a 0.1C rate. The discharge specific capacity of the third charge-discharge was recorded as the 0.1C discharge capacity (referred to as the first discharge specific capacity). Subsequently, the battery was charged and discharged sequentially at 0.2C, 0.5C, 1C, 2C, 5C, and 10C rates. The ratio of the discharge specific capacity at 10C rate to the discharge capacity at 0.1C rate was calculated, which is the 10C rate discharge capacity retention rate.

[0166] The microcrack suppression effect was comprehensively evaluated by combining long-cycle performance testing with microstructure characterization before and after cycling. The long-cycle performance test used CR2025 coin cells assembled with the same process as the rate test. Within the voltage range of 2.8V to 4.3V, activation was completed by three constant current charge-discharge cycles at a rate of 0.1C. Subsequently, 1000 consecutive constant current charge-discharge cycles at a rate of 1C were performed. The ratio of the specific capacity of the 1000th discharge cycle to the specific capacity of the 2nd discharge cycle was calculated, which is the capacity retention rate after 1000 cycles at 1C.

[0167] The improvement in thermal stability was characterized by differential scanning calorimetry (DSC) combined with thermogravimetric analysis (TG). The positive electrode was charged to 4.3V and kept at a constant voltage until the current dropped to 0.05C. The positive electrode was then disassembled in an argon-protected glove box. The positive electrode material was taken out and rinsed three times with dimethyl carbonate (DMC) to completely remove residual electrolyte. After vacuum drying for 24 hours, 5-10 mg of sample was placed in a sealed aluminum crucible and heated from room temperature to 600℃ at a heating rate of 10℃ / min under a high-purity argon atmosphere. The heat flow change and mass loss curve of the sample were recorded simultaneously to determine the thermal decomposition temperature.

[0168] The characterization results are shown in Table 1.

[0169] Table 1

[0170]

[0171] As shown in Table 1, the preparation methods of the precursor with radially oriented needle-like primary particles provided in Examples 1 to 3 of the present invention can effectively optimize the crystal structure and electrochemical performance of the precursor by combining electromagnetic field assistance with crystal facet inducers, thereby improving the rate performance and cycle performance of the cathode material obtained from the precursor.

[0172] Comparison of Comparative Examples 1 and 2 with Example 1 shows that when only electromagnetic field assistance is used without adding a crystal facet inducer (Comparative Example 1), although magnetic metal ions can initially align along the direction of magnetic field lines, there is a lack of crystal facet selectivity control. The primary particle growth direction is disordered, and a continuous radial structure cannot be formed. The lithium ion diffusion path is long and the microcrack suppression effect is poor. When only a crystal facet inducer is added without using electromagnetic field assistance (Comparative Example 2), the crystal facet inducer cannot play a role on the oriented template. The primary particles grow randomly, the internal density of the particles is low, and the structural uniformity is poor. All performance characteristics show a significant decline.

[0173] A comparison of Examples 4 and 5 with Example 1 shows that when the magnetic field strength is too low (Example 4), it cannot effectively induce Ni. 2+ Co 2+ When magnetic metal ions are arranged in an orderly manner along the direction of magnetic field lines, they cannot provide a clear template for the orientation growth of subsequent particles. The radial structure is not fully developed, resulting in reduced lithium-ion transport efficiency and significant stress concentration during charging and discharging. When the magnetic field strength is too high (Example 5), magnetic metal ions will over-aggregate, forming local clusters, which will destroy the uniformity of the precursor particles. After calcination, the structural defects of the cathode material will increase, which will accelerate capacity decay and voltage decay.

[0174] A comparison of Examples 6 and 7 with Example 1 shows that when the amount of crystal facet inducer is too small (Example 6), it is impossible to form sufficient adsorption coverage on a specific crystal facet, making it difficult to effectively control the aspect ratio and growth direction of the primary particles. The radial orientation of the radial structure is low, and the effect of shortening the lithium-ion diffusion path is limited. When the amount of crystal facet inducer is too large (Example 7), the crystal facet inducer will be adsorbed on all crystal faces of the particles, inhibiting the directional growth of the primary particles. This results in an excessively small aspect ratio of the primary particles and overly dense particle packing, which in turn hinders the bulk transport of lithium ions. At the same time, the stress release channels inside the particles are reduced, making it easier for microcracks to be generated during cycling.

[0175] As can be seen from the comparison between Examples 8 and 9 and Example 1, tartaric acid and ethylenediaminetetraacetic acid both contain multiple carboxyl and hydroxyl functional groups, which can form coordination bonds with transition metal ions and selectively adsorb on specific crystal planes, thereby regulating the growth direction of primary particles. In conjunction with electromagnetic field assistance, they form a radial structure, ensuring that the cathode material has high rate performance, cycle stability and thermal stability.

[0176] In summary, the electromagnetic field assistance employed in this invention applies a directional magnetic field during the first co-precipitation reaction, inducing magnetic metal ions (Ni, Co) to align along the magnetic field lines, providing a template for subsequent oriented growth. The crystal plane inducer selectively adsorbs onto different crystal planes, controlling the aspect ratio and growth direction of the primary particles to form a radial structure. The method proposed in this invention, through the synergy of electromagnetic field assistance and the crystal plane inducer, achieves radial orientation of the primary particles, optimizing the crystal structure and electrochemical performance of the precursor, and improving the rate performance and cycle performance of the cathode material obtained from the precursor.

[0177] 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 precursor having radially oriented needle-like primary particles, characterized in that, The preparation method includes the following steps: Under electromagnetic field assistance, a mixed salt solution, a precipitant solution, and a complexing agent solution are introduced concurrently into a reactor to carry out a first coprecipitation reaction; then, a second coprecipitation reaction is carried out without electromagnetic field assistance, during which a crystal plane guiding agent is continuously added; the addition of the crystal plane guiding agent is stopped, and a third coprecipitation reaction is carried out; the resulting slurry is aged, washed, filtered, and dried to obtain the precursor with radially oriented needle-like primary particles.

2. The preparation method according to claim 1, characterized in that, The magnetic field strength of the electromagnetic field auxiliary conditions is 0.1T~0.5T.

3. The preparation method according to claim 1, characterized in that, The temperature of the first coprecipitation reaction is 45℃~65℃; And / or, the pH value of the first coprecipitation reaction is 11~12; And / or, the concentration of the complexing agent in the first coprecipitation reaction is 8 g / L to 15 g / L; And / or, the time for the first coprecipitation reaction is 2h~4h; And / or, the stirring speed of the first coprecipitation reaction is 200 rpm to 400 rpm.

4. The preparation method according to claim 1, characterized in that, The crystal plane guiding agent includes any one or a combination of at least two of citric acid, tartaric acid, or ethylenediaminetetraacetic acid. And / or, the amount of the crystal plane guiding agent is 0.1% to 1% of the total molar amount of metal in the precursor.

5. The preparation method according to claim 4, characterized in that, The temperature for the second coprecipitation reaction is 50℃~70℃; And / or, the pH value of the second coprecipitation reaction is 10.5~11.5; And / or, the concentration of the complexing agent in the second coprecipitation reaction is 5 g / L to 10 g / L; And / or, the stirring speed for the second coprecipitation reaction is 100 rpm to 200 rpm; And / or, the median particle size D50 at the endpoint of the second coprecipitation reaction is 3 μm to 15 μm.

6. The preparation method according to claim 1, characterized in that, The temperature for the third coprecipitation reaction is 50℃~70℃; And / or, the pH value of the third coprecipitation reaction is 11.5~12.5; And / or, the concentration of the complexing agent in the third coprecipitation reaction is 10 g / L to 15 g / L; And / or, the stirring speed for the third coprecipitation reaction is 300 rpm to 500 rpm; And / or, the time for the third coprecipitation reaction is 1h to 3h.

7. The preparation method according to claim 1, characterized in that, The metal salts in the mixed salt solution include nickel salts, cobalt salts, and manganese salts; And / or, the concentration of the metal salt in the mixed salt solution is 100 g / L to 150 g / L; And / or, the molar ratio of nickel, cobalt and manganese in the mixed salt solution is (0.94~0.98):(0.01~0.03):(0.01~0.03); And / or, the precipitant solution comprises a sodium hydroxide solution with a mass concentration of 25wt% to 35wt%; And / or, the complexing agent solution comprises ammonia water with a mass concentration of 15wt% to 25wt%.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The preparation method includes: (1) Under electromagnetic field-assisted conditions, a mixed salt solution, a precipitant solution and a complexing agent solution are introduced into the reactor in parallel to carry out the first coprecipitation reaction; The magnetic field strength of the electromagnetic field auxiliary conditions is 0.1T~0.5T; The temperature of the first coprecipitation reaction is 45℃~65℃, the pH value is 11~12, the concentration of the complexing agent is 8g / L~15g / L, and the time is 2h~4h; the stirring speed of the first coprecipitation reaction is 200rpm~400rpm. (2) Then, a second coprecipitation reaction is carried out under conditions without electromagnetic field assistance, during which a crystal plane guiding agent is continuously added; The crystal plane guiding agent comprises any one or a combination of at least two of citric acid, tartaric acid, or ethylenediaminetetraacetic acid; the amount of the crystal plane guiding agent is 0.1% to 1% of the total molar amount of the metal in the precursor; The temperature of the second coprecipitation reaction is 50℃~70℃, the pH value is 10.5~11.5, the complexing agent concentration is 5g / L~10g / L, the stirring speed is 100rpm~200rpm, and the median particle size D50 at the endpoint is 3μm~15μm. (3) Stop adding crystal plane guiding agent and carry out the third coprecipitation reaction; the resulting slurry is aged, washed, filtered and dried to obtain the precursor with radially oriented needle-like primary particles; The third coprecipitation reaction was carried out at a temperature of 50℃~70℃, a pH value of 11.5~12.5, a complexing agent concentration of 10g / L~15g / L, a stirring speed of 300rpm~500rpm, and a time of 1h~3h.

9. A precursor having radially oriented needle-like primary particles, characterized in that, The precursor is prepared by the preparation method according to any one of claims 1 to 8.

10. A positive electrode material, characterized in that, The cathode material is prepared from the precursor described in claim 9.

Images