Wide-span lithium cobalt oxide precursor material as well as preparation method and application thereof

Abstract

The invention provides a wide-span lithium cobalt oxide precursor material as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) adding a first cobalt-aluminum salt solution, a first villiaumite solution and a first precipitant solution in a parallel flow manner, and carrying out a first co-precipitation reaction to obtain to-be-reacted first seed crystal slurry and residual first seed crystal slurry; adding a second cobalt aluminum salt solution, a second villiaumite solution and a second precipitant solution into the first seed crystal slurry to be reacted in a parallel flow manner, and carrying out a second coprecipitation reaction to obtain second seed crystal slurry; a third cobalt aluminum salt solution, a third villiaumite solution, a third precipitator solution and the remaining first seed crystal slurry are added into the second seed crystal slurry in a parallel flow mode, a third co-precipitation reaction is conducted, and cobalt carbonate is obtained; and (2) calcining cobalt carbonate to obtain the lithium cobalt oxide precursor material. According to the invention, uniform doping of aluminum and fluorine is realized, and the span of the lithium cobalt oxide precursor material is increased, so that the compaction density of an electrode coating and the capacity and cycling stability of a positive electrode material are improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and relates to a wide-spacing lithium cobalt oxide precursor material, its preparation method, and its applications. Background Technology

[0002] Lithium cobalt oxide (LCO) cathode materials have become the most promising cathode materials for lithium-ion batteries used in digital 3C electronic products due to their high specific capacity and compaction density. In recent years, with the increasing demands for electronic product functionality, more components have been incorporated into these products, severely squeezing the space available for lithium-ion batteries. Simultaneously, the energy requirements of these products are also constantly increasing, leading to the need for the development of lithium-ion batteries with larger volume, greater capacity, and higher gravimetric energy density for digital 3C electronic products. Therefore, for LCO cathodes, greater specific capacity, higher compaction density, and improved high-voltage cycle stability are important development directions.

[0003] Current research indicates that the compaction density of the electrode coating and the volumetric energy density can be increased by utilizing the wide-spacing particle gradation effect, where small particles fill the gaps between large particles. However, wide-spacing lithium cobalt oxide is currently often achieved by separately preparing large-particle lithium cobalt oxide and small-particle lithium cobalt oxide and then mixing them in a gradation manner. This increases the number of preparation steps, and simple particle gradation cannot improve the material's reversible specific capacity while simultaneously enhancing high-voltage cycling stability.

[0004] Therefore, how to obtain wide-aperture lithium cobalt oxide cathode materials while improving the reversible capacity and high-voltage cycle stability of the materials is an urgent technical problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a wide-spacing lithium cobalt oxide precursor material, its preparation method, and its applications. The preparation method provided by this invention achieves uniform doping of aluminum and fluorine, and by controlling the precursor preparation process, increases the pitch of the lithium cobalt oxide precursor material. This results in a well-balanced particle size distribution when preparing the lithium cobalt oxide cathode material from the precursor, improving the compaction density of the electrode coating, and enhancing capacity and cycle stability under high voltage.

[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 wide-spacing lithium cobalt oxide precursor material, the method comprising the following steps:

[0008] (1) The first cobalt-aluminum mixed salt solution, the first fluoride salt solution and the first precipitant solution are added in parallel to carry out the first coprecipitation reaction to obtain the first seed slurry. The first seed slurry is divided into the first seed slurry to be reacted and the remaining first seed slurry.

[0009] The second cobalt-aluminum mixed salt solution, the second fluoride salt solution, and the second precipitant solution are added concurrently to the first seed slurry to be reacted, and a second coprecipitation reaction is carried out to obtain the second seed slurry.

[0010] The third cobalt-aluminum mixed salt solution, the third fluoride salt solution, the third precipitant solution and the remaining first seed slurry are added to the second seed slurry in a co-flow manner to carry out the third co-precipitation reaction, thereby obtaining the cobalt carbonate precursor material.

[0011] (2) The cobalt carbonate precursor material is calcined to obtain the wide-spacing lithium cobalt oxide precursor material.

[0012] This invention, based on aluminum and fluorine co-doping, further employs a staged co-precipitation reaction process. Through the phased use of the first seed crystal, not only is a lithium cobalt carbonate precursor material with a wide particle size distribution (wide pitch), but it also facilitates the uniform distribution of aluminum and fluorine within the lithium cobalt oxide precursor material. This ensures that during subsequent calcination, the particle size distribution of the obtained lithium cobalt oxide precursor material (cobalt tetroxide) is maintained while simultaneously ensuring the uniform distribution of aluminum and fluorine, avoiding elemental segregation problems caused by high-temperature calcination. Furthermore, it exhibits high structural stability and mechanical strength. The lithium cobalt oxide cathode material obtained from the lithium cobalt oxide precursor material of this invention simultaneously… With a wide-spacing structure, it achieves a graded distribution of large and small particles in the electrode sheet, mitigating volume changes during charge and discharge, increasing the compaction density of the electrode sheet, and thus increasing the volumetric energy density of the electrode sheet. Simultaneously, it facilitates the formation of a porous structure during subsequent positive electrode sintering, reducing the loss of active sites caused by densification and improving the utilization rate of cobalt ions. It can balance porosity and tap density to adapt to different electrode requirements; it can provide buffer space, reduce stress concentration, suppress electrode pulverization, and extend cycle life; furthermore, it demonstrates that the uniform doping of aluminum and fluorine utilizes charge compensation, lattice stability, and surface chemical regulation to produce a significant synergistic effect. 3+ The doping of F enhances the structural rigidity of the lithium cobalt oxide cathode material and suppresses cycle volume expansion; while F - This stabilizes the surface chemical stability of the lithium cobalt oxide precursor material, which helps reduce electrolyte side reactions and gives the lithium cobalt oxide cathode material high capacity and high voltage cycle stability.

[0013] For the technical solution of this invention, simple staged co-precipitation may not be able to precisely control the balance of nucleation, growth and aggregation processes. 3+ It may suppress lattice expansion, while F -It may alter surface energy, but without coordinated control, it can easily lead to problems such as excessively narrow or disordered radial spacing distribution.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0015] Preferably, in step (1), the concentration of cobalt ions in the first cobalt-aluminum mixed salt solution, the second cobalt-aluminum mixed salt solution, and the third cobalt-aluminum mixed salt solution is independently 110 g / L to 160 g / L, for example, 110 g / L, 120 g / L, 130 g / L, 140 g / L, 150 g / L, or 160 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0016] Preferably, in step (1), based on the cobalt, the doping mass of aluminum ions in the first cobalt-aluminum mixed salt solution, the second cobalt-aluminum mixed salt solution, and the third cobalt-aluminum mixed salt solution is independently 2000ppm to 8000ppm, for example, 2000ppm, 2500ppm, 3000ppm, 3500ppm, 4000ppm, 4500ppm, 5000ppm, 5500ppm, 6000ppm, 6500ppm, 7000ppm, 7500ppm, or 8000ppm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0017] Preferably, in step (1), based on the cobalt, the doping mass of fluoride ions in the first fluoride salt solution, the second fluoride salt solution, and the third fluoride salt solution is independently 700ppm to 2000ppm, for example, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm, or 2000ppm, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0018] It is understood that the cobalt reference for the doping quality of aluminum and fluorine is used in different stages. For example, in the first co-precipitation reaction stage, the aluminum and fluorine in the first cobalt-aluminum mixed salt and the first fluorine salt are based on the cobalt in the first cobalt-aluminum mixed salt. Correspondingly, the aluminum in the second cobalt-aluminum and the fluorine in the second fluorine salt are based on the cobalt in the second cobalt-aluminum salt. The aluminum in the third cobalt-aluminum and the fluorine in the second fluorine salt are based on the cobalt in the third cobalt-aluminum salt.

[0019] Preferably, in step (1), the concentrations of the first precipitant solution, the second precipitant solution, and the third precipitant solution are each independently 200 g / L to 230 g / L, for example, 200 g / L, 210 g / L, 220 g / L, or 230 g / L, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] It is understood that the present invention does not impose specific limitations on the specific salt types and substance types of cobalt-aluminum mixed salts, fluoride salts and precipitants. In principle, all substances that can be used in coprecipitation reactions are applicable to the present invention without departing from the inventive concept.

[0021] Optionally, the cobalt salt in the cobalt-aluminum mixed salt solution includes, but is not limited to, at least one of cobalt chloride, cobalt nitrate, or cobalt sulfate.

[0022] Optionally, the aluminum salt in the cobalt-aluminum mixed salt solution includes, but is not limited to, aluminum sulfate and / or aluminum chloride.

[0023] Optionally, the fluoride salt in the fluoride solution includes, but is not limited to, sodium fluoride and / or ammonium fluoride.

[0024] Optionally, the precipitant in the precipitant solution includes, but is not limited to, ammonium bicarbonate and / or ammonium carbonate.

[0025] Furthermore, the solvent in the solution system of this invention is water.

[0026] Preferably, in step (1), the first coprecipitation reaction, the second coprecipitation reaction, and the third coprecipitation reaction are each carried out independently using a concentration method.

[0027] It is understood that the specific operation process of the concentration method in this invention is a conventional technical solution. Without violating the inventive concept of this invention, the concentration method in any known coprecipitation reaction process is applicable in principle.

[0028] For example, the present invention provides a specific operation process of the thickening method: the raw materials are added in parallel to carry out the reaction. When the reaction solution reaches the overflow port in the reaction vessel, the precision filter is turned on to allow the solution in the vessel to circulate and react with the thickener. At the same time, the clearing function of the thickener is turned on to return the material to the vessel and the supernatant is discharged from the reaction system.

[0029] Preferably, in step (1), the reaction temperatures of the first coprecipitation reaction, the second coprecipitation reaction, and the third coprecipitation reaction are each independently 40℃~60℃, for example 40℃, 45℃, 50℃, 55℃ or 60℃, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Preferably, in step (1), the stirring speed of the first coprecipitation reaction, the second coprecipitation reaction and the third coprecipitation reaction are each independently 60 r / min to 400 r / min, for example 60 r / min, 100 r / min, 130 r / min, 150 r / min, 180 r / min, 200 r / min, 230 r / min, 250 r / min, 280 r / min, 300 r / min, 330 r / min, 350 r / min, 380 r / min or 400 r / min, but not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0031] It should be noted that the "independent" in this invention means that they can be completely the same, completely different, or not completely the same, and can be adapted and adjusted according to actual needs.

[0032] Preferably, in step (1), the pH value of the first coprecipitation reaction is 7.7 to 8.4, such as 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3 or 8.4, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, in step (1), the pH value of the second coprecipitation reaction is 7.2 to 7.6, such as 7.2, 7.3, 7.4, 7.5 or 7.6, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, in step (1), the pH value of the third coprecipitation reaction is 7.2 to 7.6, such as 7.2, 7.3, 7.4, 7.5 or 7.6, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] In the preparation process of this invention, the pH value in the reaction system can be controlled by adjusting the feed amount of each raw material. The specific feed amount can be adaptively selected and adjusted by those skilled in the art according to actual needs.

[0036] Furthermore, in the preparation process of this invention, the first coprecipitation reaction uses a relatively high pH, ​​which is more conducive to rapid nucleation, while the subsequent coprecipitation reaction uses a relatively low pH, which is conducive to particle growth. Further, the pH value of the first coprecipitation reaction is adjusted to 7.7-8.4, which is more conducive to nucleation, and the pH value of 7.2-7.6 in the later stage is more conducive to particle growth and less likely to cause particle agglomeration.

[0037] Preferably, in step (1), the median particle size D50 of the first seed crystal is 5μm to 8μm, such as 5μm, 5.3μm, 5.5μm, 5.8μm, 6μm, 6.3μm, 6.5μm, 6.8μm, 7μm, 7.3μm, 7.5μm or 8μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, in step (1), the median particle size D50 of the second seed crystal is 12μm to 14μm, such as 12μm, 12.3μm, 12.5μm, 12.8μm, 13μm, 13.3μm, 13.5μm, 13.8μm or 14μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0039] Preferably, in step (1), the median particle size D50 of the cobalt carbonate precursor material is 18 μm to 21 μm, such as 18 μm, 18.3 μm, 18.5 μm, 18.8 μm, 19 μm, 20 μm, 20.3 μm, 20.5 μm, 20.8 μm or 21 μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] In the technical solution of this invention, based on the staged coprecipitation reaction, the median particle size D50 of the first seed crystal is controlled to be 5μm to 8μm to ensure that the first seed crystal has a high specific surface area and promotes subsequent reactions; the median particle size D50 of the second seed crystal is controlled to be 12μm to 14μm to better achieve uniform particle growth and avoid agglomeration; and the median particle size D50 of the cobalt carbonate precursor material is controlled to be 18μm to 21μm to make the particles as round as possible during the third coprecipitation reaction, so as to achieve the particle size and morphology required by the final product.

[0041] It is understood that other specific details in the preparation process not specifically defined in this invention are all conventional technical solutions, and those skilled in the art can use any known preparation process to prepare the product without departing from the inventive concept of this invention.

[0042] Optionally, before any initial reaction, the present invention may pre-add a reaction base liquid to the reaction vessel. The reaction base liquid includes a solvent and a precipitant. The concentration of the precipitant solution in the reaction base liquid is 30 g / L to 70 g / L, for example, 30 g / L, 40 g / L, 50 g / L, 60 g / L, or 70 g / L. The volume percentage of the reaction base liquid in the reaction vessel is 30% to 70%, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Optionally, after the third coprecipitation reaction is completed, the reaction slurry is subjected to conventional washing and drying treatment.

[0044] The washing process includes washing with pure water or an alkaline solution (the alkaline solution includes ammonium bicarbonate and / or ammonium carbonate), and drying after the impurity content is tested and found to be within acceptable limits.

[0045] Preferably, the heating rate of calcination in step (2) is 5℃ / min to 12℃ / min, such as 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min or 12℃ / min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the calcination holding temperature in step (2) is 550℃~800℃, such as 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the holding time for calcination in step (2) is 60 min to 120 min, such as 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] In addition, the calcination in step (2) of the present invention can be carried out in multiple stages, such as three stages, in addition to one stage.

[0049] Preferably, the three-stage calcination includes sequentially performing a first-stage calcination, a second-stage calcination, and a third-stage calcination.

[0050] Preferably, the heating rates of the first, second, and third calcination stages are each independently 1℃ / min to 10℃ / min, for example, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, or 10℃ / min, but are not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0051] Preferably, the calcination and heat preservation temperature of the first stage is 180℃~250℃, such as 180℃, 200℃, 225℃ or 300℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, the holding temperature of the second calcination stage is 300℃~500℃, such as 300℃, 350℃, 400℃, 450℃ or 500℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] Preferably, the holding temperature for the third calcination stage is 650℃ to 800℃, such as 650℃, 700℃, 750℃ or 800℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0054] Preferably, the sintering atmosphere can be an oxygen-containing atmosphere (such as pure oxygen or air) or a protective atmosphere (such as nitrogen, argon or helium). Those skilled in the art can make adaptive selections and adjustments according to actual needs.

[0055] In a second aspect, the present invention provides a wide-spacing lithium cobalt oxide precursor material, which is prepared by the preparation method described in the first aspect.

[0056] The lithium cobalt oxide precursor material provided by this invention is a cobalt tetroxide material simultaneously doped with uniformly distributed aluminum and fluorine, which has a wide diameter-gap structure and a wide particle size distribution range.

[0057] Thirdly, the present invention provides a lithium cobalt oxide cathode material, which is obtained by mixing and sintering a wide-spacing lithium cobalt oxide precursor material as described in the second aspect with a substance containing at least a lithium source.

[0058] The lithium cobalt oxide cathode material of this invention has both large and small particles, which can achieve particle size distribution in the subsequent electrode preparation process. It is also doped with aluminum and fluorine, thereby achieving the goal of high capacity and high voltage cycle stability.

[0059] Preferably, in the preparation process of the lithium cobalt oxide cathode material, in addition to the essential addition of a lithium source for lithium enrichment, conventional doping or coating processes can also be performed.

[0060] Preferably, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, or lithium acetate.

[0061] Preferably, the molar ratio of the total amount of metal elements in the wide-axis-spacing lithium cobalt oxide precursor material to the molar ratio of lithium in the lithium source is 1:(1 to 1.3), such as 1:1, 1:1.1, 1:1.2 or 1:1.3, but it is not limited to the listed values. Other unlisted values ​​within this range are also suitable.

[0062] Preferably, the sintering process includes a heating section and a heat-holding section.

[0063] Preferably, the heating section is carried out under a protective atmosphere, and the heating rate of the heating section is 7℃ / min to 10℃ / min, such as 7℃ / min, 8℃ / min, 9℃ / min or 10℃ / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0064] Preferably, the heat preservation section includes heat preservation treatment after heating to the target temperature.

[0065] Preferably, the heat preservation treatment at the target temperature is carried out in an oxygen-containing atmosphere.

[0066] Preferably, the target temperature is 700℃ to 1000℃, such as 700℃, 750℃, 800℃, 850℃, 900℃, 950℃ or 1000℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0067] Preferably, the heat preservation treatment time at the target temperature is 10h to 20h, such as 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0068] In this invention, during the preparation of lithium cobalt oxide cathode material from lithium cobalt oxide precursor, the sintering process is carried out in stages, and the heating stage is conducted under an oxygen-free protective atmosphere. This oxygen-free protection helps maintain cobalt ions in a Co-O-free state. 2+ / Co 3+The presence of mixed valence states ensures uniform reaction with the lithium source to form pure-phase LiCoO2, while preventing premature oxidation of the precursor that could lead to localized compositional inhomogeneity. The heat preservation stage is conducted in an oxygen-containing atmosphere because, during the high-temperature heat preservation phase, oxygen can fill oxygen vacancies in the LiCoO2 lattice, suppressing lattice distortion caused by oxygen deficiency and improving structural stability.

[0069] Fourthly, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising the lithium cobalt oxide cathode material as described in the third aspect.

[0070] In this invention, apart from the technical features specified above, the other raw materials, structures, and preparation processes of the lithium-ion battery are all conventional technical solutions. Without departing from the inventive concept of this invention, this invention is applicable in principle to any known lithium-ion battery that is compatible with lithium cobalt oxide cathode material.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] This application, based on aluminum and fluorine co-doping, also employs a staged co-precipitation reaction process. Through the staged use of the first seed crystal, not only is a wide-spacing lithium cobalt carbonate precursor material obtained, but it also facilitates the uniform distribution of aluminum and fluorine within the lithium cobalt oxide precursor material. This ensures that during subsequent calcination, the resulting lithium cobalt oxide precursor material maintains the same spacing as cobalt tetroxide while ensuring the uniform distribution of aluminum and fluorine, avoiding elemental segregation problems caused by high-temperature calcination. Furthermore, it exhibits high structural stability and mechanical strength. The lithium cobalt oxide cathode material obtained from this precursor material possesses a wide-spacing structure, achieving particle size distribution within the electrode sheet, mitigating volume changes during charge and discharge, and increasing the compaction density of the electrode sheet, thereby increasing its volumetric energy density. Furthermore, the uniform doping of aluminum and fluorine demonstrates a significant synergistic effect through charge compensation, lattice stability, and surface chemical regulation. 3+ The doping of F enhances the structural rigidity of the lithium cobalt oxide cathode material and suppresses cycle volume expansion; while F - This stabilizes the surface chemical stability of the lithium cobalt oxide precursor material, which helps reduce electrolyte side reactions and gives the lithium cobalt oxide cathode material high capacity and high voltage cycle stability. Attached Figure Description

[0073] Figure 1 The image shows a SEM image of the lithium cobalt oxide precursor material provided in Example 1. Detailed Implementation

[0074] 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.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application; the terms “comprising” and “having” and any variations thereof in this application are intended to cover non-exclusive inclusion.

[0076] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary or secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0077] Example 1

[0078] This embodiment provides a method for preparing a wide-spacing lithium cobalt oxide precursor material, the preparation method being as follows:

[0079] (1) Prepare a cobalt-aluminum mixture of cobalt salt solution and aluminum salt solution, with the mass of cobalt ions as the basis, wherein the concentration of cobalt ions is 110 g / L, and the doping ratio of aluminum ions in the mixed salt solution is 5000 ppm; the doping mass of fluoride ions in the ammonium fluoride fluoride solution is 1500 ppm; prepare an ammonium bicarbonate precipitant solution with a concentration of 200 g / L.

[0080] (2) The reactor is 200L in size, and ammonium bicarbonate is added to it as a base liquid. The concentration of ammonium bicarbonate solution in the base liquid is 50g / L, and the volume ratio of the base liquid in the reactor is 45%.

[0081] A cobalt-aluminum mixed salt solution, a fluoride salt solution, and a precipitant solution were added in parallel. The feed rate of the fluoride salt solution was set at 3 L / h, and the flow rate of the cobalt-aluminum mixed salt solution was set at 8 L / h. The first coprecipitation reaction was carried out at a reaction temperature of 45℃. The pH value was controlled to 7.8 during the reaction by adjusting the flow rate of the precipitant. The stirring speed was 230 r / min to obtain the first seed slurry. The median particle size D50 of the first seed was 8 μm.

[0082] A portion of the first seed slurry was retained in the reactor as the first seed slurry to be reacted, and a portion was taken out as the remaining first seed slurry. The cobalt-aluminum mixed salt solution, fluoride salt solution, and precipitant solution were then added to the first seed slurry in a co-flow manner to carry out the second coprecipitation reaction. During the second coprecipitation reaction, the feed rates of the fluoride salt solution and the cobalt-aluminum mixed salt solution were halved, the reaction temperature was 45℃, and the pH value was controlled to 7.4 by adjusting the flow rate of the precipitant during the reaction. The stirring speed was 230 r / min to obtain the second seed slurry. The median particle size D50 of the second seed was 12 μm.

[0083] Without stopping the reactor, cobalt-aluminum mixed salt solution, fluoride salt solution and precipitant solution are added in parallel stream, and first seed slurry (a portion of the remaining first seed slurry is removed) is added at a feed rate of 3L / h to carry out the third coprecipitation reaction. During the third coprecipitation reaction, the reaction temperature is 45℃. The pH value is controlled to 7.4 by adjusting the flow rate of the precipitant during the reaction. The stirring speed is 230r / min. When the median particle size D50 of the cobalt carbonate precursor material is 18μm, the reactor is stopped to obtain the cobalt carbonate precursor material slurry.

[0084] (3) The obtained cobalt carbonate precursor slurry was washed with a dilute ammonium carbonate solution with a concentration of 30 g / L, and then dried in an oven at a drying temperature of 105 °C to obtain cobalt carbonate precursor material.

[0085] (4) The cobalt carbonate precursor material is placed in a rotary kiln and calcined. The calcination holding temperature is set at 750°C, the heating rate is 7°C / min, and the holding time is 60min to obtain the wide-diameter distance lithium cobalt oxide precursor material. The lithium cobalt oxide precursor material is a co-doped cobalt tetroxide material (lithium cobalt oxide precursor material) with aluminum and fluorine.

[0086] This embodiment also provides a lithium cobalt oxide cathode material, the preparation method of which is as follows:

[0087] (5) The lithium cobalt oxide precursor material obtained in step (4) is thoroughly mixed with Li2CO3 at a total molar ratio of metal elements to lithium elements of 1:1.3. The mixed material is heated from room temperature to the target temperature of 850°C at a heating rate of 7°C / min under an argon atmosphere. Then, the argon gas is changed to oxygen gas and the mixture is kept at 850°C for 13 hours. Finally, the mixture is crushed, screened and iron removed to obtain the lithium cobalt oxide cathode material.

[0088] Figure 1 SEM images of the lithium cobalt oxide precursor material provided in Example 1 are shown. Figure 1It can be seen that the particles have a wide particle size distribution, and the rough surface and porous structure increase the number of active sites and improve the charge storage capacity.

[0089] Example 2

[0090] This embodiment provides a method for preparing a wide-spacing lithium cobalt oxide precursor material, the preparation method being as follows:

[0091] (1) Prepare a cobalt-aluminum mixture of cobalt salt solution and aluminum salt solution, with the mass of cobalt ions as the basis, wherein the concentration of cobalt ions is 160 g / L, the doping mass of aluminum ions in the mixed salt solution is 8000 ppm; the doping mass of fluoride ions in the ammonium fluoride fluoride solution is 7000 ppm; prepare an ammonium bicarbonate precipitant solution with a concentration of 230 g / L.

[0092] (2) The reactor is 200L in size, and ammonium bicarbonate is added to it as a base liquid. The concentration of ammonium bicarbonate solution in the base liquid is 30g / L, and the volume ratio of the base liquid in the reactor is 70%.

[0093] A cobalt-aluminum mixed salt solution, a fluoride salt solution, and a precipitant solution were added in parallel. The feed rate of the fluoride salt solution was set at 10 L / h, and the flow rate of the cobalt-aluminum mixed salt solution was set at 15 L / h. The first coprecipitation reaction was carried out at a temperature of 50°C. The pH value was controlled to 8.4 during the reaction by adjusting the flow rate of the precipitant. The stirring speed was 380 r / min to obtain the first seed slurry. The median particle size D50 of the first seed crystal was 5 μm.

[0094] A portion of the first seed slurry was retained in the reactor. Cobalt-aluminum mixed salt solution, fluoride salt solution, and precipitant solution were then added to the first seed slurry in a co-current flow to carry out the second coprecipitation reaction. During the second coprecipitation reaction, the feed rates of the fluoride salt solution and the cobalt-aluminum mixed salt solution were halved. The reaction temperature was 50°C. The pH value was controlled to 7.2 during the reaction by adjusting the flow rate of the precipitant. The stirring speed was 3800 r / min to obtain the second seed slurry. The median particle size D50 of the second seed was 14 μm.

[0095] Without stopping the reactor, cobalt-aluminum mixed salt solution, fluoride salt solution and precipitant solution were added in parallel streams, along with the first seed slurry with a feed rate of 3 L / h, to carry out the third coprecipitation reaction. During the third coprecipitation reaction, the reaction temperature was 50℃. The pH value was controlled to 7.2 by adjusting the flow rate of the precipitant during the reaction, and the stirring speed was 380 r / min. When the median particle size D50 of the cobalt carbonate precursor material was 21 μm, the reactor was stopped, and the cobalt carbonate precursor material slurry was obtained.

[0096] (3) The obtained cobalt carbonate precursor slurry was washed with a dilute ammonium carbonate solution with a concentration of 30 g / L, and then dried in an oven at a drying temperature of 105 °C to obtain cobalt carbonate precursor material.

[0097] (4) The cobalt carbonate precursor material is placed in a rotary kiln and calcined. The calcination holding temperature is set at 550°C, the heating rate is 5°C / min, and the holding time is 210min to obtain the wide-diameter distance lithium cobalt oxide precursor material. The lithium cobalt oxide precursor material is co-doped cobalt tetroxide material with aluminum and fluorine.

[0098] This embodiment also provides a lithium cobalt oxide cathode material, the preparation method of which is as follows:

[0099] (5) The lithium cobalt oxide precursor material obtained in step (4) is thoroughly mixed with Li2CO3 at a total molar ratio of metal elements to lithium elements of 1:1.3. The mixed material is heated from room temperature to the target temperature of 1000℃ at a heating rate of 10℃ / min under an argon atmosphere. Then, the argon gas is changed to oxygen gas and the mixture is kept at 1000℃ for 10h. Then, the mixture is crushed, screened and iron removed to obtain the lithium cobalt oxide cathode material.

[0100] Example 3

[0101] This embodiment provides a method for preparing a wide-spacing lithium cobalt oxide precursor material, the preparation method being as follows:

[0102] (1) Prepare a cobalt-aluminum mixture of cobalt salt solution and aluminum salt solution, with the mass of cobalt ions as the basis, wherein the concentration of cobalt ions is 130 g / L, the doping mass of aluminum ions in the mixed salt solution is 2000 ppm; the doping mass of fluoride ions in the ammonium fluoride fluoride solution is 700 ppm; prepare an ammonium bicarbonate precipitant solution with a concentration of 210 g / L.

[0103] (2) The reactor is 200L in size, and ammonium bicarbonate is added to it as a base liquid. The concentration of ammonium bicarbonate solution in the base liquid is 50g / L, and the volume ratio of the base liquid in the reactor is 45%.

[0104] A cobalt-aluminum mixed salt solution, a fluoride salt solution, and a precipitant solution were added in parallel. The feed rate of the fluoride salt solution was set at 1.5 L / h, and the flow rate of the cobalt-aluminum mixed salt solution was set at 6 L / h. The first coprecipitation reaction was carried out at a temperature of 45°C. The pH value was controlled to 8 by adjusting the flow rate of the precipitant during the reaction. The stirring speed was 300 r / min to obtain the first seed slurry. The median particle size D50 of the first seed crystal was 6.5 μm.

[0105] A portion of the first seed slurry was retained in the reactor. Cobalt-aluminum mixed salt solution, fluoride salt solution, and precipitant solution were then added to the first seed slurry in a co-current flow to carry out the second coprecipitation reaction. During the second coprecipitation reaction, the feed rates of the fluoride salt solution and the cobalt-aluminum mixed salt solution were halved. The reaction temperature was 45°C. The pH value was controlled to 7.6 during the reaction by adjusting the flow rate of the precipitant. The stirring speed was 300 r / min to obtain the second seed slurry. The median particle size D50 of the second seed was 13 μm.

[0106] Without stopping the reactor, cobalt-aluminum mixed salt solution, fluoride salt solution and precipitant solution were added in parallel streams, and first seed slurry with a feed rate of 3L / h was added at the same time to carry out the third coprecipitation reaction. During the third coprecipitation reaction, the reaction temperature was 45℃. The pH value was controlled to 7.6 by adjusting the flow rate of precipitant during the reaction. The stirring speed was 300r / min. When the median particle size D50 of the cobalt carbonate precursor material was 20μm, the reactor was stopped to obtain cobalt carbonate precursor material slurry.

[0107] (3) The obtained cobalt carbonate precursor slurry was washed with a dilute ammonium carbonate solution with a concentration of 30 g / L, and then dried in an oven at a drying temperature of 105 °C to obtain cobalt carbonate precursor material.

[0108] (4) The cobalt carbonate precursor material is placed in a rotary kiln and calcined. The calcination holding temperature is set at 800℃, the heating rate is 10℃ / min, and the holding time is 70min to obtain the wide-diameter distance lithium cobalt oxide precursor material. The lithium cobalt oxide precursor material is co-doped cobalt tetroxide material with aluminum and fluorine.

[0109] This embodiment also provides a lithium cobalt oxide cathode material, the preparation method of which is as follows:

[0110] (5) The lithium cobalt oxide precursor material obtained in step (4) is thoroughly mixed with Li2CO3 at a total molar ratio of metal elements to lithium elements of 1:1.3. The mixed material is heated from room temperature to the target temperature of 700°C at a heating rate of 8°C / min under an argon atmosphere. Then, the argon gas is changed to oxygen gas and the mixture is kept at 700°C for 20 hours. Finally, the mixture is crushed, screened and iron removed to obtain the lithium cobalt oxide cathode material.

[0111] Example 4

[0112] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the mass percentage of aluminum ions is 9000 ppm.

[0113] The remaining preparation methods and parameters are consistent with those in Example 1.

[0114] Example 5

[0115] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the mass percentage of aluminum ions is 1000 ppm.

[0116] The remaining preparation methods and parameters are consistent with those in Example 1.

[0117] Example 6

[0118] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the mass percentage of fluoride ions is 500 ppm.

[0119] The remaining preparation methods and parameters are consistent with those in Example 1.

[0120] Example 7

[0121] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the mass percentage of fluoride ions is 2500 ppm.

[0122] The remaining preparation methods and parameters are consistent with those in Example 1.

[0123] Example 8

[0124] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the pH value of the first coprecipitation reaction is 7.5.

[0125] The remaining preparation methods and parameters are consistent with those in Example 1.

[0126] Example 9

[0127] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the pH value of the second coprecipitation reaction and the third coprecipitation reaction is 8.4.

[0128] The remaining preparation methods and parameters are consistent with those in Example 1.

[0129] Example 10

[0130] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the median particle size D50 of the first seed crystal is 3 μm.

[0131] The remaining preparation methods and parameters are consistent with those in Example 1.

[0132] Example 11

[0133] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the median particle size D50 of the first seed crystal is 10 μm.

[0134] The remaining preparation methods and parameters are consistent with those in Example 1.

[0135] Example 12

[0136] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the median particle size D50 of the second seed is 10 μm.

[0137] The remaining preparation methods and parameters are consistent with those in Example 1.

[0138] Example 13

[0139] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the median particle size D50 of the first seed crystal is 16 μm.

[0140] The remaining preparation methods and parameters are consistent with those in Example 1.

[0141] Example 14

[0142] The difference between this embodiment and embodiment 1 is that oxygen is introduced throughout the sintering process of step (5) in this embodiment, including the heating stage, instead of argon.

[0143] The remaining preparation methods and parameters are consistent with those in Example 1.

[0144] Example 15

[0145] The difference between this embodiment and embodiment 1 is that in the sintering process of step (5) of this embodiment, the heating rate of the heating section is 12℃ / min.

[0146] The remaining preparation methods and parameters are consistent with those in Example 1.

[0147] Comparative Example 1

[0148] The difference between this comparative example and Example 1 is that no aluminum salt is added during the preparation process of step (1) of this comparative example, that is, no aluminum doping is performed.

[0149] The remaining preparation methods and parameters are consistent with those in Example 1.

[0150] Comparative Example 2

[0151] The difference between this comparative example and Example 1 is that in the preparation process of step (1) of this comparative example, the preparation of fluoride salt solution is not carried out, that is, fluorine doping is not carried out.

[0152] The remaining preparation methods and parameters are consistent with those in Example 1.

[0153] Comparative Example 3

[0154] The difference between this comparative example and Example 1 is that in the preparation process of step (1) of this comparative example, neither aluminum salt nor fluoride salt solution is added, that is, neither aluminum nor fluoride is doped at the same time.

[0155] The remaining preparation methods and parameters are consistent with those in Example 1.

[0156] Comparative Example 4

[0157] The difference between this comparative example and Example 1 is that in step (2) of this comparative example, the first seed slurry is not added after the second coprecipitation reaction is completed. Instead, the raw materials added and the reaction process of the second coprecipitation reaction and the third coprecipitation reaction are completely the same. That is, the first seed slurry is not retained and all subsequent particle growth reactions are carried out.

[0158] The remaining preparation methods and parameters are consistent with those in the examples.

[0159] The lithium cobalt oxide precursor materials prepared in Examples 1-15 and Comparative Examples 1-4 were subjected to pitch measurement. The particle size was measured in accordance with GB / T 19077-2016 (laser diffraction method for particle size analysis), and the pitch (D90-D10) / D50 was calculated. The test results are shown in Table 1.

[0160] Table 1

[0161]

[0162]

[0163] [Battery fabrication and electrochemical performance testing]

[0164] I. Battery Manufacturing

[0165] An electrode slurry was prepared by dispersing 80 wt% of the positive electrode active material provided in the examples and comparative examples, 10 wt% of Super-P and 10 wt% of polyvinylidene fluoride (PVDF) in an N-methylpyrrolidone (NMP) solution, coating it on an aluminum foil, and drying it to obtain the positive electrode.

[0166] The lithium sheet is the negative electrode.

[0167] The diaphragm is a Φ19 PP microporous membrane (Celgard2400).

[0168] The electrolyte is composed of a mixture of 1M LiPF6 and EC, DMC and EMC (EC:DMC:EMC volume ratio = 1:1:1).

[0169] The above-mentioned positive electrode, separator, negative electrode and electrolyte are assembled to obtain a coin cell.

[0170] II Performance Testing

[0171] ① Discharge specific capacity: At room temperature, the initial discharge specific capacity was tested in the voltage range of 3V-4.5V using a current density of 0.3C.

[0172] ② Cyclic performance: At room temperature, the voltage range of 3V-4.5V was tested using a current density of 1C. After 200 cycles, the test was stopped and the capacity retention rate was calculated.

[0173] The test results are shown in Table 2.

[0174] Table 2

[0175]

[0176]

[0177] In summary, the preparation method provided by this invention achieves uniform doping of aluminum and fluorine, and by controlling the preparation process of the precursor, the radial distance of the lithium cobalt oxide precursor material is increased. Thus, when preparing the lithium cobalt oxide cathode material from the lithium cobalt oxide precursor, a particle size distribution is achieved, the compaction density of the electrode coating is improved, and the capacity and cycle stability under high voltage are enhanced.

[0178] 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 wide-spacing lithium cobalt oxide precursor material, characterized in that, The preparation method includes the following steps: (1) The first cobalt-aluminum mixed salt solution, the first fluoride salt solution and the first precipitant solution are added in parallel to carry out the first coprecipitation reaction to obtain the first seed slurry to be reacted and the remaining first seed slurry; The second cobalt-aluminum mixed salt solution, the second fluoride salt solution, and the second precipitant solution are added concurrently to the first seed slurry to be reacted, and a second coprecipitation reaction is carried out to obtain the second seed slurry. The third cobalt-aluminum mixed salt solution, the third fluoride salt solution, the third precipitant solution and the remaining first seed slurry are added to the second seed slurry in a co-flow manner to carry out the third co-precipitation reaction, thereby obtaining the cobalt carbonate precursor material. (2) The cobalt carbonate precursor material is calcined to obtain the wide-spacing lithium cobalt oxide precursor material.

2. The preparation method according to claim 1, characterized in that, In step (1), the concentration of cobalt ions in the first cobalt-aluminum mixed salt solution, the second cobalt-aluminum mixed salt solution, and the third cobalt-aluminum mixed salt solution is independently 110 g / L to 160 g / L; Preferably, in step (1), based on the mass of the cobalt, the doping mass of aluminum ions in the first cobalt-aluminum mixed salt solution, the second cobalt-aluminum mixed salt solution, and the third cobalt-aluminum mixed salt solution is independently 2000ppm to 8000ppm. Preferably, in step (1), based on the mass of the cobalt, the fluoride ion doping mass in the first fluoride salt solution, the second fluoride salt solution, and the third fluoride salt solution is 700ppm to 2000ppm; Preferably, in step (1), the concentrations of the first precipitant solution, the second precipitant solution, and the third precipitant solution are each independently 200 g / L to 230 g / L.

3. The preparation method according to claim 1, characterized in that, In step (1), the first coprecipitation reaction, the second coprecipitation reaction, and the third coprecipitation reaction are each carried out independently using a concentration method; Preferably, in step (1), the reaction temperatures of the first coprecipitation reaction, the second coprecipitation reaction, and the third coprecipitation reaction are each independently 40°C to 60°C; Preferably, in step (1), the stirring speed of the first coprecipitation reaction, the second coprecipitation reaction and the third coprecipitation reaction is independently 60 r / min to 400 r / min.

4. The preparation method according to claim 1 or 3, characterized in that, In step (1), the pH value of the first coprecipitation reaction is 7.7 to 8.4; Preferably, in step (1), the pH value of the second coprecipitation reaction is 7.2 to 7.6; Preferably, in step (1), the pH value of the third coprecipitation reaction is 7.2 to 7.

6.

5. The preparation method according to claim 1, characterized in that, In step (1), the median particle size D50 of the first seed crystal is 5 μm to 8 μm; Preferably, in step (1), the median grain size D50 of the second seed crystal is 12 μm to 14 μm; Preferably, in step (1), the median particle size D50 of the cobalt carbonate precursor material is 18 μm to 21 μm.

6. The preparation method according to claim 1, characterized in that, The heating rate of calcination in step (2) is 5℃ / min to 12℃ / min, the holding temperature of calcination is 550℃ to 800℃, and the holding time of calcination is 60min to 120min.

7. A wide-spacing lithium cobalt oxide precursor material, characterized in that, The wide-spacing lithium cobalt oxide precursor material is prepared by the preparation method according to any one of claims 1-6.

8. A lithium cobalt oxide cathode material, characterized in that, The lithium cobalt oxide cathode material is obtained by mixing and sintering the wide-spacing lithium cobalt oxide precursor material as described in claim 7 with a substance containing at least a lithium source.

9. The lithium cobalt oxide cathode material according to claim 8, characterized in that, The sintering process includes a heating section and a heat-holding section; Preferably, the heating section is carried out under a protective atmosphere, and the heating rate of the heating section is 7℃ / min to 10℃ / min; Preferably, the heat preservation section includes a heat preservation treatment after heating to the target temperature; Preferably, the heat preservation treatment at the target temperature is carried out in an oxygen-containing atmosphere, the target temperature is 700℃~1000℃, and the heat preservation treatment time is 10h~20h.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the lithium cobalt oxide cathode material as described in claim 8 or 9.

Images