Doped cobalt carbonate as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion batteries, and relates to doped cobalt carbonate as well as a preparation method and application thereof. The preparation method comprises the following steps: adding a cobalt-aluminum mixed salt solution, a zinc salt solution and a precipitant solution in a parallel flow manner, and sequentially carrying out a nucleation period coprecipitation reaction and a particle growth period coprecipitation reaction to obtain doped cobalt carbonate; the cobalt-aluminum mixed salt solution comprises cobalt salt, aluminum salt, a complexing agent and a solvent; the reaction temperature of the coprecipitation reaction in the nucleation period is lower than that of the coprecipitation reaction in the particle growth period. According to the invention, aluminum and zinc are adopted for bulk phase doping of cobalt carbonate, a complexing agent is additionally added, and the reaction temperatures of different co-precipitation reaction stages are regulated and controlled, so that uniform distribution of aluminum and zinc in cobalt carbonate is realized, and in the lithium cobalt oxide positive electrode material finally obtained from cobalt carbonate, aluminum and zinc cooperate with each other, so that the lithium cobalt oxide positive electrode material has good electrochemical performance. The lattice stability of the material is stabilized, the layered structure of lithium cobalt oxide is stabilized, lattice slippage is inhibited, and the capacity and cycle performance of the battery are improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and relates to a doped cobalt carbonate, its preparation method and uses. Background Technology

[0002] Among the current mainstream types of rechargeable batteries, lithium-ion batteries exhibit excellent energy density and cycle stability. As the donor of active lithium ions, the performance of the cathode material largely determines the overall electrochemical performance of the lithium-ion battery. Currently, mainstream lithium-ion battery cathode materials include lithium manganese oxide, lithium iron phosphate, lithium nickel manganese oxide, lithium cobalt oxide, and ternary materials such as lithium nickel cobalt manganese oxide, each with its own characteristics. Polyanionic cathode materials, represented by lithium iron phosphate, have high cycle stability, but their low electronic conductivity results in poor rate performance. Spinel-type cathode materials, represented by lithium manganese oxide, have excellent rate performance, but lower energy density. In contrast, lithium cobalt oxide, as a layered cathode material, provides rapid ion diffusion and electron conduction channels, thus combining high energy density and high rate performance, making it one of the mainstream cathode materials for lithium-ion batteries.

[0003] Lithium cobalt oxide (LiCoO2) has shown great promise in the field of lithium-ion batteries due to its excellent performance. Its theoretical specific capacity is as high as 274 mAh / g. However, in practical commercial applications, due to the limiting material structure, the operating voltage reaches 4.5V (vs. LiCoO2). + At the Li / Li ratio, only 180 mAh / g of capacity can be released. Although increasing the cutoff voltage can promote the release of more Li... + Reversible insertion and extraction can improve the energy density of batteries, but it is also accompanied by the irreversibility of the phase transition of the LiCoO2 crystal structure and rapid capacity decay. Heterogeneous doping of the bulk phase can enhance the structural stability of the material and reduce structural failure during cycling.

[0004] Cobalt tetroxide is mainly used in the preparation of lithium cobalt oxide, the cathode material for lithium-ion batteries. With the increasing demand for lithium-ion rechargeable batteries, the market demand for cobalt tetroxide powder is also growing exponentially. Simultaneously, with the continuous development of 3C product functions, high-voltage lithium-ion batteries are gaining market favor. To produce high-voltage lithium-ion batteries, the quality requirements of cobalt tetroxide need to be strictly controlled. Battery-grade cobalt tetroxide requires high purity and stringent requirements for its physical properties, such as tap density, particle size distribution, crystal morphology, electrochemical stability, and thermal stability.

[0005] To improve battery charge-discharge life, doping is often used to enhance the lattice stability of lithium cobalt oxide. Aluminum is considered an effective dopant element for improving the stability of lithium cobalt oxide, its mechanism being to increase the binding energy of oxygen in the lattice, thereby suppressing oxygen escape. However, since the radius of aluminum ions is comparable to that of cobalt ions, its effect on suppressing lattice slip is not significant.

[0006] Therefore, how to improve the lattice stability of lithium cobalt oxide and suppress its lattice slip is an urgent technical problem to be solved. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a doped cobalt carbonate, its preparation method, and its applications. In the preparation stage of the cobalt carbonate precursor, aluminum and zinc are used for bulk doping of cobalt carbonate, and a complexing agent is added. The reaction temperatures at different co-precipitation reaction stages are controlled to achieve a uniform distribution of aluminum and zinc in the cobalt carbonate. This results in a synergistic effect between aluminum and zinc in the final lithium cobalt oxide cathode material obtained from cobalt carbonate. This stabilizes the lattice stability of the material, as well as the layered structure of lithium cobalt oxide and inhibits lattice slip, thereby improving the battery's capacity and cycle performance.

[0008] To achieve this objective, the present invention employs the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing doped cobalt carbonate, the method comprising the following steps:

[0010] Cobalt-aluminum mixed salt solution, zinc salt solution and precipitant solution were added in parallel streams to carry out co-precipitation reaction during the nucleation period and co-precipitation reaction during the particle growth period in sequence to obtain doped cobalt carbonate.

[0011] The cobalt-aluminum mixed salt solution includes cobalt salt, aluminum salt, complexing agent, and solvent; the reaction temperature of the nucleation period coprecipitation reaction is lower than the reaction temperature of the particle growth period coprecipitation reaction.

[0012] Cobalt tetroxide is mainly used in the preparation of lithium cobalt oxide, a cathode material for lithium-ion batteries. Cobalt tetroxide is usually prepared by co-precipitation reaction to obtain cobalt carbonate, which is then sintered and calcined. Although bulk doping of doping elements can be achieved in the conventional co-precipitation reaction to prepare cobalt carbonate, the difference between the ionic radius of the doping element and the radius of the cobalt ion, as well as the large difference in the ion concentration product during the co-precipitation reaction, will lead to asynchronous ion precipitation and uneven element distribution.

[0013] In the preparation method of this invention, aluminum and zinc doping are simultaneously carried out during the co-precipitation preparation of cobalt carbonate. This process avoids the problem of severe aluminum segregation caused by aluminum doping, especially large-particle aluminum doping, by co-feeding the cobalt-aluminum mixed salt and adding a complexing agent to the mixed salt solution, along with the separate addition of the zinc salt solution and the adjustment of the reaction temperature during the nucleation and particle growth stages. It also ensures that zinc can be uniformly distributed in the bulk phase of cobalt carbonate, resulting in excellent synergistic effects from the co-doping of aluminum and zinc in the bulk phase. This yields aluminum-zinc co-doped cobalt carbonate material, which is then used in lithium cobalt oxide cathode materials. The aluminum element enhances the lattice oxygen binding energy to suppress oxygen loss, while the large ionic radius zinc anchors the layered structure, thereby stabilizing the layered structure of lithium cobalt oxide and suppressing lattice slip. This improves the battery capacity and cycle performance. Furthermore, the preparation method is simple and can be industrialized for large-scale production.

[0014] The co-precipitation reaction of this invention is carried out in two stages, with the reaction temperature during the particle growth stage being higher than that during the nucleation stage, in order to achieve rapid, synchronous, and uniform nucleation. The purpose of low-temperature nucleation is to suppress crystal growth, promote a large number of nuclei, and ensure the synchronicity of nucleation. For the doping reaction, during the nucleation stage, all atoms (including host metal ions and dopant ions) are co-precipitated from the solution together, which can ensure the uniform distribution of dopant elements in each crystal nucleus at the atomic level. If nucleation is not synchronous, the doping ratio of the later-formed crystal nuclei may change. At the high-temperature stage, the dissolution rate of small particles and the growth rate of large particles are both accelerated. The higher temperature is conducive to atoms finding the lowest energy position in the crystal lattice and arranging themselves, thereby reducing crystal defects, improving the crystallinity of the precursor material, and thus exerting the synergistic effect of aluminum and zinc, rather than the direct additive effect of their individual effects.

[0015] Preferably, the total concentration of metal ions in the cobalt-aluminum mixed salt solution is 110 g / L to 150 g / L, for example, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L.

[0016] In the cobalt-aluminum mixed salt solution of the present invention, the specific types of cobalt salt and aluminum salt are selected using conventional techniques, such as at least one of chloride salt, nitrate salt or sulfate salt.

[0017] Preferably, the concentration of aluminum ions in the cobalt-aluminum mixed salt solution is 3000ppm to 5000ppm, such as 3000ppm, 3250ppm, 3500ppm, 3750ppm, 4000ppm, 4250ppm, 4500ppm, 4750ppm or 5000ppm.

[0018] Preferably, in the cobalt-aluminum mixed salt solution, the molar ratio of the complexing agent to aluminum is (1~2):8, for example, 1:8, 1.3:8, 1.5:8, 1.8:8 or 2:8, etc.

[0019] It is understood that the present invention also adds a complexing agent to the cobalt-aluminum mixed salt solution to avoid aluminum segregation during the preparation process. The specific type of complexing agent is not limited in the present invention. Conventional complexing agent types are applicable in the present invention as long as they do not affect the normal progress of the coprecipitation reaction. For example, the complexing agent includes, but is not limited to, at least one of citric acid, oxalic acid or tartaric acid. The molar ratio of complexing agent to aluminum is limited to (1~2):8, which is more conducive to promoting the uniform growth of dopant elements in the particles and inhibiting the agglomeration of particles.

[0020] Preferably, the concentration of zinc ions in the zinc salt solution is 2000ppm to 3000ppm, such as 2000ppm, 2100ppm, 2200ppm, 2300ppm, 2400ppm, 2500ppm, 2600ppm, 2700ppm, 2800ppm, 2900ppm, or 3000ppm.

[0021] The zinc salts include, but are not limited to, at least one of zinc sulfate, zinc chloride, or zinc acetate.

[0022] This invention, during the preparation of cobalt carbonate, achieves controlled doping levels of aluminum and zinc in cobalt carbonate by adjusting the concentration of aluminum ions in the cobalt-aluminum mixed salt solution to 3000 ppm–5000 ppm and / or the concentration of zinc ions in the zinc salt solution to 2000 ppm–3000 ppm. This limits the doping quality of aluminum and zinc in cobalt carbonate, allowing for better synergistic effects and prioritizing the stability of the material framework (Al-dominated) while supplementing with sufficient Zn to optimize conductivity and surface activity. This specific concentration window enables Al and Zn to be uniformly distributed at the atomic level, avoiding segregation. Through electronic and structural interactions, it creates superior overall properties not found in single doping, significantly enhancing cycle life, rate performance, and catalytic activity. This is the ultimate goal of multi-element doping design.

[0023] Preferably, the concentration of the precipitant solution is 160 g / L to 220 g / L, such as 160 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, 210 g / L, or 220 g / L.

[0024] Similarly, this invention does not limit the specific material selection of the precipitant in the preparation of cobalt carbonate. Conventional co-precipitant types that can be used to obtain cobalt carbonate, such as ammonium carbonate and / or ammonium bicarbonate, are acceptable.

[0025] Preferably, the reaction temperature of the nucleation period coprecipitation reaction is 36℃~40℃, for example, 36℃, 37℃, 38℃, 39℃ or 40℃.

[0026] Preferably, the stirring speed of the coprecipitation reaction during the nucleation period is 220 r / min to 450 r / min, such as 220 r / min, 230 r / min, 250 r / min, 280 r / min, 300 r / min, 330 r / min, 350 r / min, 380 r / min, 400 r / min, 430 r / min or 450 r / min.

[0027] Preferably, the pH value of the coprecipitation reaction during the nucleation period is 7.4 to 8.6, such as 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5 or 8.6.

[0028] Preferably, the median particle size D50 of the crystal nuclei obtained by the co-precipitation reaction during the nucleation period is 2.5μm to 4.5μm, for example, 2.5μm, 2.8μm, 3μm, 3.3μm, 3.5μm, 3.8μm, 4μm, 4.3μm or 4.5μm.

[0029] Preferably, during the co-precipitation reaction in the nucleation period, the feed flow rate of the cobalt-aluminum mixed salt solution is 8 L / h to 20 L / h, such as 8 L / h, 9 L / h, 10 L / h, 11 L / h, 12 L / h, 13 L / h, 14 L / h, 15 L / h, 16 L / h, 17 L / h, 18 L / h, 19 L / h, or 20 L / h.

[0030] Preferably, during the co-precipitation reaction in the nucleation period, the feed flow rate of the zinc salt solution is 1L / h to 5L / h, such as 1L / h, 2L / h, 3L / h, 4L / h, or 5L / h.

[0031] Preferably, the reaction temperature of the co-precipitation reaction during the particle growth period is 41℃~44℃, for example, 41℃, 42℃, 43℃ or 44℃.

[0032] In this invention, the reaction temperature of the coprecipitation reaction during the nucleation period is 36℃~40℃ and the reaction temperature of the coprecipitation reaction during the particle growth period is 41℃~44℃, which further achieves the effect of reducing crystal defects and improving the crystallinity of the precursor material.

[0033] Preferably, the pH value of the co-precipitation reaction during the particle growth period is 7.2 to 7.5, such as 7.2, 7.3, 7.4 or 7.5.

[0034] In the co-precipitation reaction process, the present invention eliminates the need to limit the feed flow rate of the precipitant solution. Once the pH value and the feed flow rates of other raw materials are determined during the reaction, the flow rate of the precipitant solution can be adjusted adaptively.

[0035] Preferably, during the co-precipitation reaction in the particle growth period, the stirring speed is reduced as the particle size increases. For every 1.5μm to 2μm increase in the median particle size D50, such as 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, or 2μm, the stirring speed is reduced by 30r / min to 50r / min, such as 30r / min, 35r / min, 40r / min, 45r / min, or 50r / min.

[0036] During the co-precipitation reaction in the particle growth period, the stirring speed decreases as the particle size increases, further reducing the occurrence of small particles erupting during the reaction. Correspondingly, for every 1.5μm~2μm increase in particle size, the stirring speed decreases by 30r / min~50r / min, which further contributes to uniform doping during the reaction process.

[0037] Preferably, during the co-precipitation reaction of the particle growth period, when the growth rate of the median particle size D50 does not meet the target rate, the feed flow rate of the cobalt-aluminum mixed salt solution and the feed flow rate of the zinc salt solution are both increased.

[0038] Preferably, during the co-precipitation reaction in the particle growth period, the target velocity is 0.05 μm / h to 0.08 μm / h, for example, 0.05 μm / h, 0.06 μm / h, 0.07 μm / h, or 0.08 μm / h, and the feed flow rate of the cobalt-aluminum mixed salt solution is increased by 2 L / h to 6 L / h, for example, 2 L / h, 3 L / h, 4 L / h, 5 L / h, or 6 L / h.

[0039] Preferably, during the co-precipitation reaction in the particle growth period, the target velocity is 0.05 μm / h to 0.08 μm / h, for example, 0.05 μm / h, 0.06 μm / h, 0.07 μm / h, or 0.08 μm / h, and the feed flow rate of the zinc salt solution is increased by 0.5 L / h to 1 L / h, for example, 0.5 L / h, 0.6 L / h, 0.7 L / h, 0.8 L / h, 0.9 L / h, or 1 L / h.

[0040] In the co-precipitation reaction during the particle growth period, if the particle size growth rate is too fast or too slow, it will affect the sphericity of the particles and the occurrence of small particles breaking out during the reaction. However, by controlling the feed flow rate of the raw materials, the particle size growth rate can be controlled, thereby ensuring uniform particle growth.

[0041] Furthermore, it can be understood that during the co-precipitation reaction in the particle growth stage, the initial stirring speed and the initial feed flow rate of each raw material are the values ​​of the co-precipitation reaction in the nucleation stage.

[0042] Preferably, the target particle size D50 of the co-precipitation reaction during the particle growth period is 15μm~20μm, such as 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm, 18.5μm, 19μm, 19.5μm or 20μm.

[0043] Preferably, after the co-precipitation reaction during the particle growth period is completed, the slurry after the reaction is washed and dried.

[0044] In the coprecipitation reaction process, the present invention allows for the addition of a reaction base liquid to the reaction vessel (such as a reaction kettle) beforehand.

[0045] Optionally, the reaction base liquid includes a solvent and a precipitant, and the volume percentage of the reaction base liquid in the reaction vessel is 40% to 45%, such as 40%, 41%, 42%, 43%, 44%, or 45%, etc. The pH value of the reaction base liquid is 7.4 to 8.6, such as 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8, 8.1, 8.2, 8.3, 8.4, 8.5, or 8.6, etc.

[0046] Optionally, the entire reaction process of the coprecipitation reaction, including the addition of the base liquid, is carried out under a protective atmosphere, wherein the gas in the protective atmosphere includes nitrogen, argon, or helium.

[0047] Optionally, the solvent used in the entire preparation process includes water.

[0048] In a second aspect, the present invention provides a doped cobalt carbonate, which is prepared by the preparation method described in the first aspect; the doped cobalt carbonate is doped with aluminum and zinc.

[0049] Thirdly, the present invention provides cobalt tetroxide, which is obtained by calcining doped cobalt carbonate as described in the second aspect.

[0050] In this invention, the specific method for obtaining cobalt tetroxide from doped cobalt carbonate in the second aspect is a conventional technical solution. Within a reasonable range, any solution known to those skilled in the art is applicable to this invention.

[0051] By way of example, the present invention provides a method for obtaining cobalt tetroxide from doped cobalt carbonate as described in the second aspect, the method comprising:

[0052] The doped cobalt carbonate described in the second aspect is calcined in an oxygen-containing atmosphere.

[0053] Preferably, the oxygen-containing atmosphere includes an oxygen atmosphere or an air atmosphere, etc.

[0054] Preferably, the calcination includes single-stage calcination or multi-stage calcination, which can be adapted and adjusted according to actual needs.

[0055] Preferably, the heating rate of the one-stage calcination is 8℃ / min to 12℃ / min, for example, 8℃ / min, 10℃ / min or 12℃ / min, etc.; the holding temperature after the one-stage calcination heating is 600℃ to 750℃, for example, 600℃, 650℃, 700℃ or 750℃, etc.; and the holding time after the one-stage calcination heating is 90min to 200min, for example, 90min, 100min, 130min, 150min, 180min or 200min, etc.

[0056] Fourthly, the present invention provides a lithium cobalt oxide cathode material, which is obtained by sintering cobalt tetroxide as described in the third aspect with a material containing at least a lithium source.

[0057] This invention does not specifically limit the preparation method of lithium cobalt oxide. For example, it can be a lithium-based sintering method. Exemplarily, the lithium-based sintering method includes the following steps:

[0058] Lithium cobalt oxide is obtained by mixing cobalt tetroxide with lithium salt and then sintering.

[0059] Preferably, the mixing includes dry mixing and / or wet mixing, wherein the solvent for wet mixing includes anhydrous ethanol.

[0060] Preferably, the sintering includes pre-sintering and main sintering in sequence.

[0061] Preferably, the sintering temperature of the pre-sintering is 300℃~450℃, such as 300℃, 350℃, 400℃ or 450℃, and the sintering time of the pre-sintering is 3h~5h, such as 3h, 4h or 5h.

[0062] Preferably, the sintering temperature of the main sinter is 850℃~1050℃, such as 850℃, 900℃, 950℃, 1000℃ or 1050℃, and the sintering time of the main sinter is 18h~25h, such as 18h, 19h, 20h, 21h, 22h, 23h, 24h or 25h.

[0063] Fifthly, the present invention also provides a lithium-ion battery comprising the lithium cobalt oxide cathode material as described in the fourth aspect.

[0064] 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.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] In the preparation method of this invention, aluminum and zinc doping are simultaneously carried out during the co-precipitation preparation of cobalt carbonate. This process avoids the problem of severe aluminum segregation caused by aluminum doping, especially large-particle aluminum doping, by co-feeding the cobalt-aluminum mixed salt and adding a complexing agent to the mixed salt solution, along with the separate addition of the zinc salt solution and the adjustment of the reaction temperature during the nucleation and particle growth stages. It also ensures that zinc can be uniformly distributed in the bulk phase of cobalt carbonate, resulting in excellent synergistic effects from the co-doping of aluminum and zinc in the bulk phase. This yields aluminum-zinc co-doped cobalt carbonate material, which is then used in lithium cobalt oxide cathode materials. The aluminum element enhances the lattice oxygen binding energy to suppress oxygen loss, while the large ionic radius zinc anchors the layered structure, thereby stabilizing the layered structure of lithium cobalt oxide and suppressing lattice slip. This improves the battery capacity and cycle performance. Furthermore, the preparation method is simple and can be industrialized for large-scale production. Detailed Implementation

[0067] 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.

[0068] 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.

[0069] 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.

[0070] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0071] 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.

[0072] 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.

[0073] 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."

[0074] 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.

[0075] 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.

[0076] In this invention, "optional" means that something is optional, that is, it refers to any one of the two parallel solutions of "having" or "not having". 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.

[0077] In this invention, "room temperature" generally refers to 4℃~35℃, and can refer to 20℃±5℃. In some embodiments of this invention, room temperature refers to 20℃~30℃.

[0078] Example 1

[0079] This embodiment provides a doped cobalt carbonate, and the preparation method of the doped cobalt carbonate is as follows:

[0080] (1) Prepare a cobalt-aluminum mixed salt solution of cobalt chloride aqueous solution and aluminum chloride aqueous solution. Tartaric acid is added to the mixed salt solution as a complexing agent. The molar ratio of the complexing agent to aluminum is 1:8. The total ion concentration in the mixed salt solution is 110 g / L. The concentration of aluminum ions in the aluminum salt aqueous solution is 4600 ppm. Prepare a zinc salt solution of zinc chloride with a zinc ion concentration of 2300 ppm. Prepare an ammonium bicarbonate solution with a concentration of 200 g / L as a precipitant solution. Prepare a solution of ammonium bicarbonate and water with a pH of 7.4 as the reaction base liquid.

[0081] (2) In a nitrogen atmosphere and a pressure of 0.3 MPa, the reactor has a size of 0.2 L and a bottom liquid is added to it. The bottom liquid accounts for 40% of the volume of the reactor and has a pH of 7.4.

[0082] Cobalt-aluminum mixed salt solution, zinc salt solution, and precipitant solution were added concurrently to the reaction substrate to initiate a nucleation co-precipitation reaction. During the nucleation stage, the feed flow rate of the cobalt-aluminum mixed salt solution was 9 L / h, the feed flow rate of the zinc salt solution was 2 L / h, the reaction pH was 7.6, and the feed flow rate of the precipitant solution was adjusted accordingly. The reaction temperature was 40℃, and the stirring speed was 220 r / min. After obtaining a median particle size D50 of 3.8 μm for the crystal nuclei, the nucleation co-precipitation reaction was stopped.

[0083] Continue to add the cobalt-aluminum mixed salt solution, zinc salt solution, and precipitant solution in parallel to carry out the co-precipitation reaction during the particle growth period. During the particle growth period, for every 2 μm increase in the median particle size D50, the stirring speed is reduced by 50 r / min. The reaction pH is 7.5, and the reaction temperature is 44℃. During the reaction, when the growth rate of the median particle size D50 does not meet the target rate of 0.08 μm / h, the feed flow rate of the cobalt-aluminum mixed salt solution is increased by 4 L / h, and the feed flow rate of the zinc salt solution is increased by 0.7 L / h. Maintaining the above pattern, directly reach the stop particle size D50 = 20 μm, and the co-precipitation reaction stage ends.

[0084] After the reaction is complete, post-processing such as washing, drying and calcination are carried out to obtain aluminum-zinc co-doped cobalt carbonate precursor.

[0085] Example 2

[0086] This embodiment provides a doped cobalt carbonate, and the preparation method of the doped cobalt carbonate is as follows:

[0087] (1) Prepare a cobalt-aluminum mixed salt solution of cobalt chloride aqueous solution and aluminum chloride aqueous solution, and add tartaric acid as a complexing agent to the mixed salt solution. The molar ratio of complexing agent to aluminum is 2:8. The total ion concentration in the mixed salt solution is 150 g / L, and the concentration of aluminum ions in the aluminum salt aqueous solution is 3000 ppm. Prepare a zinc salt solution of zinc chloride with a zinc ion concentration of 3000 ppm. Prepare an ammonium bicarbonate solution with a concentration of 160 g / L as a precipitant solution. Prepare a solution of ammonium bicarbonate and water with a pH of 7.8 as the reaction base liquid.

[0088] (2) In a nitrogen atmosphere and a pressure of 0.3 MPa, the reactor has a size of 0.2 L and a bottom liquid is added to it. The bottom liquid accounts for 45% of the volume of the reactor and has a pH of 7.8.

[0089] Cobalt-aluminum mixed salt solution, zinc salt solution, and precipitant solution were added concurrently to the reaction substrate to initiate a nucleation co-precipitation reaction. During the nucleation stage, the feed flow rate of the cobalt-aluminum mixed salt solution was 20 L / h, the feed flow rate of the zinc salt solution was 1 L / h, the reaction pH was 8.6, and the feed flow rate of the precipitant solution was adjusted accordingly. The stirring speed was 300 r / min, and the reaction temperature was 36℃. After obtaining a median particle size D50 of 4 μm for the crystal nuclei, the nucleation co-precipitation reaction was stopped.

[0090] Continue to add the cobalt-aluminum mixed salt solution, zinc salt solution, and precipitant solution in parallel to carry out the co-precipitation reaction during the particle growth period. During the particle growth period, for every 1.5 μm increase in the median particle size D50, the stirring speed is reduced by 30 r / min. The reaction pH is 7.4, and the reaction temperature is 41℃. During the reaction, when the growth rate of the median particle size D50 does not meet the target rate of 0.05 μm / h, the feed flow rate of the cobalt-aluminum mixed salt solution is increased by 2 L / h, and the feed flow rate of the zinc salt solution is increased by 0.5 L / h. Maintaining the above pattern, the process continues until the stop particle size D50 = 15 μm is reached, at which point the co-precipitation reaction stage ends.

[0091] After the reaction is complete, post-processing such as washing, drying and calcination are carried out to obtain aluminum-zinc co-doped cobalt carbonate precursor.

[0092] Example 3

[0093] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the concentration of aluminum ions in the cobalt-aluminum mixed salt solution is 3000 ppm, and the concentration of zinc ions in the zinc salt solution is 3000 ppm.

[0094] All other conditions remain the same as in Example 1.

[0095] Example 4

[0096] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the concentration of aluminum ions in the cobalt-aluminum mixed salt solution is 5000 ppm, and the concentration of zinc ions in the zinc salt solution is 2000 ppm.

[0097] All other conditions remain the same as in Example 1.

[0098] Example 5

[0099] The difference between this embodiment and embodiment 1 is that in the co-precipitation reaction during the nucleation period in step (2) of this embodiment, the feed flow rate of the cobalt-aluminum mixed salt solution is 20 L / h, and the feed flow rate of the zinc salt solution is 5 L / h.

[0100] All other conditions remain the same as in Example 1.

[0101] Example 6

[0102] The difference between this embodiment and embodiment 1 is that the concentration of aluminum ions in the cobalt-aluminum mixed salt solution in step (1) of this embodiment is 2000 ppm.

[0103] All other conditions remain the same as in Example 1.

[0104] Example 7

[0105] The difference between this embodiment and embodiment 1 is that the concentration of aluminum ions in the cobalt-aluminum mixed salt solution in step (1) of this embodiment is 6000 ppm.

[0106] All other conditions remain the same as in Example 1.

[0107] Example 8

[0108] The difference between this embodiment and embodiment 1 is that the concentration of zinc ions in the zinc salt solution in step (1) of this embodiment is 1000 ppm.

[0109] All other conditions remain the same as in Example 1.

[0110] Example 9

[0111] The difference between this embodiment and embodiment 1 is that the concentration of zinc ions in the zinc salt solution in step (1) of this embodiment is 1000 ppm.

[0112] All other conditions remain the same as in Example 1.

[0113] Example 10

[0114] The difference between this embodiment and embodiment 1 is that the feed flow rate of the cobalt-aluminum mixed salt solution during the nucleation period co-precipitation reaction in step (2) of this embodiment is 25 L / h.

[0115] All other conditions remain the same as in Example 1.

[0116] Example 11

[0117] The difference between this embodiment and embodiment 1 is that the feed flow rate of the cobalt-aluminum mixed salt solution during the nucleation period co-precipitation reaction in step (2) of this embodiment is 5L / h.

[0118] All other conditions remain the same as in Example 1.

[0119] Example 12

[0120] The difference between this embodiment and embodiment 1 is that the feed flow rate of the zinc salt solution during the co-precipitation reaction in step (2) of this embodiment is 0.5 L / h.

[0121] All other conditions remain the same as in Example 1.

[0122] Example 13

[0123] The difference between this embodiment and embodiment 1 is that the feed flow rate of the zinc salt solution during the co-precipitation reaction of the nucleation period in step (2) of this embodiment is 6L / h.

[0124] All other conditions remain the same as in Example 1.

[0125] Example 14

[0126] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the stirring speed during the particle growth period co-precipitation reaction is kept consistent with that during the nucleation period and is not changed.

[0127] All other conditions remain the same as in Example 1.

[0128] Example 15

[0129] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, during the co-precipitation reaction of the particle growth period, the stirring speed decreases by 10 r / min as the median particle size D50 increases.

[0130] All other conditions remain the same as in Example 1.

[0131] Example 16

[0132] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, during the co-precipitation reaction of the particle growth period, the stirring speed decreases by 60 r / min as the median particle size D50 increases.

[0133] All other conditions remain the same as in Example 1.

[0134] Comparative Example 1

[0135] The difference between this comparative example and Example 1 is that in step (1) of this comparative example, the zinc salt solution is not prepared, which is the preparation process of aluminum-doped cobalt carbonate.

[0136] All other conditions remain the same as in Example 1.

[0137] Comparative Example 2

[0138] The difference between this comparative example and Example 1 is that in step (1), no aluminum salt and complexing agent are added in this comparative example, which is the preparation process of zinc-doped cobalt carbonate.

[0139] All other conditions remain the same as in Example 1.

[0140] Comparative Example 3

[0141] The difference between this comparative example and Example 1 is that in step (2) of this comparative example, the reaction temperature of the coprecipitation reaction during the nucleation period and the coprecipitation reaction during the particle growth period is 40°C.

[0142] All other conditions remain the same as in Example 1.

[0143] Specific applications and performance testing

[0144] Battery manufacturing

[0145] a) Cobalt tetroxide and lithium cobalt oxide cathode materials: Cobalt carbonate provided in the examples and comparative examples were respectively put into a calcining furnace and heated to 750°C for 90 min in an oxygen atmosphere at a heating rate of 8°C / min to obtain cobalt tetroxide.

[0146] The cobalt tetroxide precursor material and lithium carbonate prepared in the examples and comparative examples were weighed out according to a lithium-cobalt molar ratio of 1.025. After wet ball milling with anhydrous ethanol as the solvent, they were mixed and pre-sintered in a box furnace at 350°C for 4 hours. The pre-sintered powder was then placed in a muffle furnace and calcined at 950°C for 20 hours in an oxygen atmosphere. The powder was then cooled to room temperature at a rate of 5°C / min to obtain the lithium cobalt oxide cathode material.

[0147] b) Positive electrode: 80 wt% of positive electrode active material (lithium cobalt oxide prepared in the examples and comparative examples respectively), 10 wt% of Super-P and 10 wt% of polyvinylidene fluoride (PVDF) are dispersed in N-methylpyrrolidone (NMP) solution to prepare an electrode slurry, which is then coated on aluminum foil and dried to obtain the positive electrode.

[0148] The lithium sheet is the negative electrode.

[0149] The diaphragm is a Φ19 PP microporous membrane (Celgard2400).

[0150] The electrolyte is composed of a mixture of 1M LiPF6 and EC, DMC and EMC (EC:DMC:EMC volume ratio = 1:1:1).

[0151] The above-mentioned positive electrode, separator, negative electrode and electrolyte are assembled to obtain a coin cell.

[0152] Performance testing

[0153] The lithium-ion batteries provided in Examples 1-16 and Comparative Examples 1-3 were subjected to performance tests under the following conditions: 3.0-4.48V, current density 1C=180mAh / g, and test temperature 25±1℃. The initial discharge capacity and cycle performance of the lithium-ion batteries were tested, and the test results are shown in Table 1.

[0154] Table 1

[0155]

[0156] Based on the data in Table 1, it can be concluded that in the co-precipitation preparation process of cobalt carbonate, the present invention simultaneously incorporates aluminum and zinc doping. This process, through the co-feeding of cobalt-aluminum mixed salts and the addition of a complexing agent to the mixed salt solution, along with the separate addition of zinc salt solution and the adjustment of reaction temperatures during the nucleation and particle growth phases, ensures a precursor material with uniform aluminum and zinc distribution and few crystal defects, achieving a synergistic effect of aluminum and zinc doping. Furthermore, Examples 1 and 6-13 demonstrate that controlling the concentration of raw materials and the feed flow rate during the preparation process allows for the control of both aluminum and zinc doping levels. This results in a homogeneous and highly stable large-particle cobalt carbonate precursor material, further enhancing the effectiveness of both doping methods. The synergistic effect of these elements significantly improves capacity and cycle performance. Examples 1 and 14-16 show that, during the growth stage, adjusting the particle size increase and stirring speed avoids the explosion of small particles during the reaction, resulting in large particles with uniform particle size. This also benefits the uniform doping of aluminum and zinc, leading to superior battery capacity and cycle performance. Examples 1 and Comparative Examples 1-3 show that the combination of aluminum, zinc, and reaction temperature during the reaction stage is crucial. Only through synergy can a cobalt carbonate precursor material with uniform doping element distribution, uniform particle size, and stable structure be obtained, while also leveraging the synergistic effect of aluminum and zinc doping elements to significantly improve battery capacity and cycle performance.

[0157] 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 doped cobalt carbonate, characterized in that, The preparation method includes the following steps: Cobalt-aluminum mixed salt solution, zinc salt solution and precipitant solution were added in parallel streams to carry out co-precipitation reaction during the nucleation period and co-precipitation reaction during the particle growth period in sequence to obtain doped cobalt carbonate. The cobalt-aluminum mixed salt solution includes cobalt salt, aluminum salt, complexing agent, and solvent; the reaction temperature of the nucleation period coprecipitation reaction is lower than the reaction temperature of the particle growth period coprecipitation reaction.

2. The preparation method according to claim 1, characterized in that, The total concentration of metal ions in the cobalt-aluminum mixed salt solution is 110 g / L to 150 g / L, and the concentration of aluminum ions in the cobalt-aluminum mixed salt solution is 3000 ppm to 5000 ppm. Preferably, in the cobalt-aluminum mixed salt solution, the molar ratio of the complexing agent to aluminum is (1~2):8; Preferably, the concentration of zinc ions in the zinc salt solution is 2000ppm to 3000ppm; Preferably, the concentration of the precipitant solution is 160 g / L to 220 g / L.

3. The preparation method according to claim 1, characterized in that, The reaction temperature for the coprecipitation reaction during the nucleation period is 36℃~40℃; Preferably, the stirring speed of the coprecipitation reaction during the nucleation period is 220 r / min to 450 r / min; Preferably, the pH value of the coprecipitation reaction during the nucleation period is 7.4~8.6; Preferably, the median particle size D50 of the crystal nuclei obtained by the co-precipitation reaction during the nucleation period is 2.5 μm to 4.5 μm.

4. The preparation method according to claim 1 or 3, characterized in that, During the co-precipitation reaction in the nucleation period, the feed flow rate of the cobalt-aluminum mixed salt solution is 8 L / h to 20 L / h. Preferably, during the co-precipitation reaction in the nucleation period, the feed flow rate of the zinc salt solution is 1 L / h to 5 L / h.

5. The preparation method according to claim 1, characterized in that, The reaction temperature for the co-precipitation reaction during the particle growth period is 41℃~44℃; Preferably, the pH value of the co-precipitation reaction during the particle growth period is 7.2~7.5; Preferably, during the co-precipitation reaction of the particles during the growth period, the stirring speed is reduced as the particle size increases. For every 1.5 μm to 2 μm increase in the median particle size D50, the stirring speed is reduced by 30 r / min to 50 r / min. Preferably, during the co-precipitation reaction of the particle growth period, when the growth rate of the median particle size D50 does not meet the target rate, the feed flow rate of the cobalt-aluminum mixed salt solution and the feed flow rate of the zinc salt solution are both increased. Preferably, during the co-precipitation reaction in the particle growth period, the target velocity is 0.05 μm / h to 0.08 μm / h, the feed flow rate of the cobalt-aluminum mixed salt solution is increased by 2 L / h to 6 L / h, and the feed flow rate of the zinc salt solution is increased by 0.5 L / h to 1 L / h.

6. The preparation method according to claim 1, characterized in that, The target particle size D50 for the co-precipitation reaction during the particle growth period is 15μm~20μm; Preferably, after the co-precipitation reaction during the particle growth period is completed, the slurry after the reaction is washed and dried.

7. A doped cobalt carbonate, characterized in that, The doped cobalt carbonate is prepared by the preparation method according to any one of claims 1-6; the doped cobalt carbonate is doped with aluminum and zinc.

8. A cobalt tetroxide, characterized in that, The cobalt tetroxide is obtained by calcining the doped cobalt carbonate as described in claim 7.

9. A lithium cobalt oxide cathode material, characterized in that, The lithium cobalt oxide cathode material is obtained by sintering cobalt tetroxide as described in claim 8 with a material containing at least a lithium source.

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

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