High-purity cobalt hydroxide with small size, preparation method and application thereof

Abstract

The present application relates to the technical field of lithium battery electrode material preparation, in particular to a kind of high-purity, small size cobalt hydroxide and its preparation method and application, comprising the following steps: after the pre-mixing of solid powder of cobalt salt, amphoteric ligand, protective agent is uniform, then join alkaline solid, subsequently transfer to ball mill jar, ball mill under normal temperature and normal pressure, after ball milling, the ball material mixture is washed, centrifuged, dried to obtain high-purity, small size cobalt hydroxide.The present application ingeniously utilizes the reduction effect of amphoteric ligand construction buffer system and protective agent, effectively controls the rate of Co 2+ React with OH ‑ Co (OH) 2 is further oxidized during synthesis, so the prepared cobalt hydroxide has the characteristics of high purity, small size, etc., and has excellent specific capacity when used to prepare lithium cobaltate positive electrode material.In addition, the synthesis method also has the advantages of simple operation, less three wastes, etc., and has good industrialization application prospect.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery electrode material preparation technology, specifically relating to a high-purity, small-size cobalt hydroxide, its preparation method, and its application. Background Technology

[0002] With the growing global demand for sustainable and clean energy, lithium-ion batteries, as a highly efficient energy storage system, are increasingly widely used in electric vehicles, portable electronic devices, and other fields. This has driven research into battery materials with higher performance, greater safety, and lower cost. Among these, lithium cobalt oxide is one of the commonly used cathode materials in lithium-ion batteries, favored for its high energy density and good cycle stability.

[0003] Cobalt hydroxide is a key precursor in the production of lithium cobalt oxide. Optimizing the synthesis of cobalt hydroxide allows for effective control over the microstructure and performance of the final lithium cobalt oxide product. The purity of cobalt hydroxide is closely related to the specific capacity and stability of lithium cobalt oxide, while the particle size of cobalt hydroxide determines the size of lithium cobalt oxide, thus affecting the sufficient contact between the active sites and the electrolyte solution. Therefore, preparing high-purity, small-size cobalt hydroxide is crucial for producing high-performance lithium cobalt oxide. However, traditional cobalt hydroxide synthesis methods face the following challenges.

[0004] (1) Due to Co 2+ With OH - The reaction to form Co(OH)2 proceeds very easily, which leads to an excessively fast growth rate of Co(OH)2 nanoparticles during the synthesis process, making the synthesis of Co(OH)2 with a particle size of less than 100 nm quite challenging.

[0005] (2) Since Co(OH)2 is chemically unstable and easily oxidized, synthesizing high-purity Co(OH)2 is quite challenging. Summary of the Invention

[0006] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0007] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0008] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing high-purity, small-size cobalt hydroxide.

[0009] To solve the above-mentioned technical problems, the present invention provides the following technical solution: including,

[0010] After cobalt salt solid powder, amphoteric ligand, and protective agent are premixed evenly, an alkaline solid is added, and then the mixture is transferred to a ball mill jar and ball milled at room temperature and pressure. After ball milling, the ball mixture is washed, centrifuged, and dried to obtain high-purity, small-sized cobalt hydroxide.

[0011] The ball milling speed is 200-600 rpm, the ball milling time is 1-120 min, and the molar ratio of cobalt salt solid powder to alkaline solid is 1:2.1-2.3.

[0012] In a preferred embodiment of the method for preparing high-purity, small-size cobalt hydroxide according to the present invention, the mass ratio of the cobalt salt solid powder, the amphoteric ligand, and the protective agent is 1:0.01-0.5:0.001-0.2.

[0013] As a preferred embodiment of the method for preparing high-purity, small-size cobalt hydroxide according to the present invention, the cobalt salt includes one or more of cobalt chloride, cobalt sulfate, cobalt nitrate, or cobalt acetate.

[0014] In a preferred embodiment of the method for preparing high-purity, small-size cobalt hydroxide according to the present invention, the amphoteric ligand includes one or more of aspartic acid or glutamic acid.

[0015] In a preferred embodiment of the method for preparing high-purity, small-size cobalt hydroxide according to the present invention, the protective agent includes one or more of hydrazine hydrate or ascorbic acid.

[0016] In a preferred embodiment of the method for preparing high-purity, small-size cobalt hydroxide according to the present invention, the alkaline solid includes one or more of sodium hydroxide or potassium hydroxide.

[0017] In a preferred embodiment of the method for preparing high-purity, small-size cobalt hydroxide according to the present invention, the ball-to-material ratio is 10 to 20:1.

[0018] As a preferred embodiment of the method for preparing high-purity, small-size cobalt hydroxide according to the present invention, the ball milling speed is 200-300 rpm, the ball milling time is 5-20 min, and the ball-to-material ratio is 10-15:1.

[0019] Another object of the present invention is to overcome the shortcomings of the prior art and provide a high-purity, small-size cobalt hydroxide, wherein the cobalt hydroxide contains Co 2+ The content is greater than 99%, and the average particle size is 10-100 nm.

[0020] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of high-purity, small-size cobalt hydroxide in the preparation of lithium cobalt oxide cathode materials.

[0021] Beneficial effects of this invention:

[0022] (1) Based on solid-phase ball milling, this invention ingeniously utilizes amphoteric ligands to construct a buffer system to effectively mitigate the effects of Co. 2+ With OH - The increased rate of Co(OH)2 formation in the reaction is beneficial for reducing the particle size of Co(OH)2. In addition, the reducing effect of the protective agent alleviates the oxidation of Co(OH)2 formed during the synthesis process. Therefore, the cobalt hydroxide prepared by this invention has the characteristics of high purity and small size.

[0023] (2) The Co(OH)2 preparation method proposed in this invention has the advantages of simple process, simple and controllable operation, and easy industrial scale-up production.

[0024] (3) The Co(OH)2 prepared by the method of the present invention has a high specific capacity when used to prepare lithium cobalt oxide cathode material, which makes it more competitive in the market. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0026] Figure 1 The image shows the XRD pattern of Co(OH)2 prepared in Example 1 of this invention.

[0027] Figure 2 This is a SEM image of Co(OH)2 obtained in Example 1 of the present invention. Detailed Implementation

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0029] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0030] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0031] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0032] The materials prepared in the embodiments of the present invention were subjected to electrochemical performance testing according to the following method:

[0033] After mixing 1 mol of the Co(OH)2 solid powder prepared in the example with 1.003 mol of lithium carbonate solid powder evenly, the mixture was placed in a muffle furnace and heated to 1000°C at a heating rate of 2°C / min for 8 hours. After cooling to room temperature, the mixture was pulverized to obtain the lithium cobalt oxide cathode material.

[0034] The prepared lithium cobalt oxide electrode material was mixed with conductive carbon black and PVDF in a ratio of 8:1:1 to form a slurry, which was then coated onto copper foil to serve as the positive electrode of a lithium-ion battery. Commercial graphite carbon was used as the negative electrode, and 1M LiPF6 was used as the electrolyte solute to fabricate a button cell. The discharge capacity of the battery was tested at a rate of 4C.

[0035] Example 1

[0036] This embodiment provides a method for preparing cobalt hydroxide, specifically as follows:

[0037] 0.2 mol cobalt chloride (25.96 g) solid powder, 2.596 g aspartic acid, and 0.2596 g hydrazine hydrate were premixed, and then 0.42 mol sodium oxide solid powder was added. The mixture was then transferred to a ball mill jar, and small balls were added at a ball-to-material ratio of 10:1. The mixture was ball-milled for 10 min at 200 rpm under normal temperature and pressure. After ball milling, the mixture was washed three times alternately with anhydrous ethanol and ultrapure water. After centrifugation at 8000 rpm, the mixture was dried overnight at 80°C in a vacuum oven to obtain high-purity, small-sized cobalt hydroxide.

[0038] Figure 1 The figure shows the XRD pattern of Co(OH)2 prepared in Example 1 of this invention. As can be seen from the figure, the XRD peaks of the sample perfectly match PFD30-0433, and no other impurity peaks appear, indicating that the method of this invention can successfully prepare high-purity Co(OH)2.

[0039] Figure 2 The image shows a SEM image of Co(OH)2 obtained in Example 1 of this invention. As can be seen from the image, the particle size of the synthesized Co(OH)2 is between 10-100 nm, and its average size is 20 nm.

[0040] Example 2

[0041] 0.2 mol cobalt sulfate (35.4 g) solid powder, 3.54 g glutamic acid, and 0.354 g ascorbic acid were premixed, and then 0.42 mol sodium oxide solid powder was added. The mixture was then transferred to a ball mill jar, and small balls were added at a ball-to-material ratio of 10:1. The mixture was ball-milled at 200 rpm for 5 min at room temperature and pressure. After ball milling, the mixture was washed three times alternately with anhydrous ethanol and ultrapure water. After centrifugation at 8000 rpm, the mixture was dried overnight at 80°C in a vacuum oven to obtain high-purity, small-sized cobalt hydroxide.

[0042] Example 3

[0043] 0.2 mol cobalt chloride (25.96 g) solid powder, 12.98 g aspartic acid, and 10 g hydrazine hydrate were premixed, and then 0.46 mol sodium oxide solid powder was added. The mixture was then transferred to a ball mill jar, and small balls were added at a ball-to-material ratio of 20:1. The mixture was ball-milled at 600 rpm for 120 min at room temperature and pressure. After ball milling, the mixture was washed three times alternately with anhydrous ethanol and ultrapure water. After centrifugation at 8000 rpm, the mixture was dried overnight at 80°C in a vacuum oven to obtain high-purity, small-sized cobalt hydroxide.

[0044] Comparative Example 1

[0045] Commercial cobalt hydroxide: Brand: 9dingchem; Product No.: L-UI299; Purity: 99.9%.

[0046] Performance tests were conducted on the above embodiments and comparative examples, and the comparison with Embodiment 1 is shown in Table 1.

[0047] Table 1

[0048]

[0049]

[0050] Table 1 shows that the method of the present invention can successfully prepare high-purity (high Co) materials. 2+ This invention produces cobalt hydroxide with low content and small size (average particle size less than 100 nm) because it cleverly utilizes amphoteric ligands to construct a buffer system based on solid-phase ball milling to effectively mitigate the degradation of Co. 2+ With OH -The increased rate of Co(OH)₂ formation is beneficial for reducing the particle size of Co(OH)₂. Furthermore, the reducing effect of the protective agent prevents the oxidation of Co(OH)₂ formed during the synthesis process. Moreover, the Co(OH)₂ preparation method proposed in this invention is simple, easy to operate and controllable, and readily scalable for industrial production. In addition, the lithium cobalt oxide prepared from the cobalt oxide prepared in Example 1 exhibits the best performance, with a specific capacity of 134.9 mA·h / g. Further observation reveals that the specific capacity of the lithium cobalt oxide prepared from the cobalt hydroxide of this invention is significantly higher than that of commercially available cobalt hydroxide, making it more competitive in the market.

[0051] Example 4

[0052] The difference between this embodiment and Example 1 is that the ball milling speed is adjusted to 600 rpm, while the rest of the preparation process is the same as in Example 1, to obtain cobalt hydroxide.

[0053] Example 5

[0054] The difference between this embodiment and Example 1 is that the ball milling speed is adjusted to 150 rpm, while the rest of the preparation process is the same as in Example 1, to obtain cobalt hydroxide.

[0055] Comparative Example 2

[0056] The difference between this comparative example and Example 1 is that the ball milling speed was adjusted to 100 rpm, while the rest of the preparation process was the same as in Example 1, and cobalt hydroxide was obtained.

[0057] Performance tests were conducted on the above embodiments and comparative examples, and the comparison with Embodiment 1 is shown in Table 2.

[0058] Table 2

[0059] <![CDATA[Co 2+ Content (%) Average particle size (nm) Lithium cobalt oxide specific capacity (mA·h / g) Example 1 99.9 20 134.9 Example 4 99.9 19 136.2 Example 5 99.9 25 115.1 Comparative Example 2 99.9 132 74.1

[0060] As shown in Table 1, adjusting the ball milling speed affects the performance of cobalt hydroxide. When the ball milling speed increases from 200 rpm to 600 rpm, the average size of the prepared Co(OH)2 particles decreases slightly, and the specific capacity of the lithium cobalt oxide cathode material prepared using it as a precursor increases slightly. However, it should be noted that increasing the speed leads to an increase in the energy consumption required for ball milling, resulting in significantly higher synthesis energy consumption. Furthermore, when the ball milling speed decreases from 200 rpm to 150 rpm, the average size of the prepared Co(OH)2 particles increases significantly, and the specific capacity of the lithium cobalt oxide cathode material prepared using it as a precursor also decreases significantly. This is because excessively low speeds cause the Co(OH)2 generated during the ball milling process to aggregate, leading to an increase in particle size. Therefore, considering particle size, energy consumption, and experimental results, a ball milling speed of 200 rpm in this invention achieves the best technical effect.

[0061] Example 6

[0062] The difference between this embodiment and Example 1 is that the ball milling time is adjusted to 1 minute, while the rest of the preparation process is the same as in Example 1, and cobalt hydroxide is obtained.

[0063] Example 7

[0064] The difference between this embodiment and Example 1 is that the ball milling time is adjusted to 120 min, while the rest of the preparation process is the same as in Example 1, and cobalt hydroxide is obtained.

[0065] Comparative Example 3

[0066] The difference between this comparative example and Example 1 is that the ball milling time was adjusted to 150 min, while the rest of the preparation process was the same as in Example 1, and cobalt hydroxide was obtained.

[0067] Performance tests were conducted on the above embodiments and comparative examples, and the comparison with Embodiment 1 is shown in Table 3.

[0068] Table 3

[0069] <![CDATA[Co 2+ Content (%) Average particle size (nm) Lithium cobalt oxide specific capacity (mA·h / g) Example 1 99.9 20 134.9 Example 6 99.9 26 120.6 Example 7 99.9 29 121.1 Comparative Example 3 91.3 53 58.2

[0070] As shown in the table above, when the ball milling time is increased to 150 min, the purity of the prepared Co(OH)2 and the performance of the corresponding lithium cobalt oxide cathode material both decrease. This is because a longer reaction time increases the contact time between the formed Co(OH)2 and the air, and after the protective agent fails, some of the Co(OH)2 will be oxidized. At the same time, if the reaction time is too short, the raw materials will not react fully, resulting in a very low product yield. Therefore, based on the purity and yield of Co(OH)2 and the experimental results, the ball milling time of 10 min in this invention can achieve the best technical effect.

[0071] Example 8

[0072] The difference between this embodiment and Example 1 is that the amount of sodium oxide solid powder added is adjusted to 0.46 mol, while the rest of the preparation process is the same as in Example 1, and cobalt hydroxide is obtained.

[0073] Example 9

[0074] The difference between this embodiment and Example 1 is that the amount of sodium oxide solid powder added is adjusted to 0.36 mol, while the rest of the preparation process is the same as in Example 1, and cobalt hydroxide is obtained.

[0075] Comparative Example 4

[0076] The difference between this comparative example and Example 1 is that the amount of sodium oxide solid powder added was adjusted to 0.6 mol, while the rest of the preparation process was the same as in Example 1, to obtain cobalt hydroxide.

[0077] Comparative Example 5

[0078] The preparation of Co(OH)₂ using the traditional coprecipitation method follows these steps:

[0079] 0.2 mol cobalt chloride (25.96 g) solid powder was dissolved in 300 mL of water, and then 2.596 g of aspartic acid and 0.2596 g of hydrazine hydrate were added and mixed thoroughly to obtain mixture A. 0.42 mol sodium oxide solid was dissolved in 300 mL to form solution B. Then, under stirring at 500 rpm, solution B was added to mixture A at a rate of 5 mL / min and stirred for 20 min. After the reaction was completed, the precipitate was washed three times alternately with anhydrous ethanol and ultrapure water, centrifuged at 8000 rpm, and dried overnight at 80 °C in a vacuum oven to obtain high-purity, small-sized cobalt hydroxide.

[0080] Performance tests were conducted on the above embodiments and comparative examples, and the comparison with Embodiment 1 is shown in Table 4.

[0081] Table 4

[0082] <![CDATA[Co 2+ Content (%) Average particle size (nm) Lithium cobalt oxide specific capacity (mA·h / g) Example 1 99.9 20 134.9 Example 8 99.9 39 126.8 Example 9 99.9 26 128.7 Comparative Example 4 99.9 366 35.1 Comparative Example 5 85.6 5.2μm 18.2

[0083] As shown in the table above, when the molar ratio of cobalt salt solid powder to alkaline solid increases to 1:3 (Comparative Example 4), the average size of the prepared Co(OH)2 particles and the corresponding performance of the lithium cobalt oxide cathode material are significantly reduced. This is because the increased proportion of alkaline solid increases the formation rate of Co(OH)2 generated during the ball milling process, leading to larger particle aggregation. At the same time, if the ratio of cobalt salt solid powder to alkaline solid is less than 1:2, it will result in the waste of expensive cobalt salt solid. Therefore, based on the reaction rate, raw material cost considerations, and experimental results, the molar ratio of cobalt salt solid powder to alkaline solid in this invention is 1:2.1-2.3.

[0084] As can be seen from Comparative Example 5, even when the same raw materials are used for synthesis, the particle size of Co(OH)2 obtained by the traditional co-precipitation method is in the micrometer range, which is much larger than that obtained by the method of the present invention.

[0085] In summary, this invention relates to the field of lithium battery electrode material preparation technology, specifically to a high-purity, small-size cobalt hydroxide, its preparation method, and its application. The method includes the following steps: pre-mixing cobalt salt solid powder, amphoteric ligands, and a protective agent until homogeneous; then adding an alkaline solid; subsequently transferring the mixture to a ball mill jar; and ball milling at room temperature and pressure. After ball milling, the mixture is washed, centrifuged, and dried to obtain high-purity, small-size cobalt hydroxide. This invention cleverly utilizes the amphoteric ligands to construct a buffer system and the reducing effect of the protective agent to effectively control the cobalt content. 2+ With OH - The reaction process generates Co(OH)₂ at a rapid rate while effectively preventing further oxidation of the Co(OH)₂ produced during synthesis. Therefore, the prepared cobalt hydroxide exhibits high purity and small size, resulting in excellent specific capacity when used to prepare lithium cobalt oxide cathode materials. Furthermore, the synthesis method of this invention is simple to operate and generates less waste, demonstrating promising prospects for industrial application.

[0086] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing high-purity, small-size cobalt hydroxide, characterized in that: include, After cobalt salt solid powder, amphoteric ligand, and protective agent are premixed evenly, an alkaline solid is added, and then the mixture is transferred to a ball mill jar and ball milled at room temperature and pressure. After ball milling, the ball mixture is washed, centrifuged, and dried to obtain high-purity, small-sized cobalt hydroxide. The ball milling speed is 200~600 rpm, the ball milling time is 1~120 min, and the molar ratio of cobalt salt solid powder to alkaline solid is 1:2.1~2.

3. The mass ratio of the cobalt salt solid powder, the amphoteric ligand, and the protective agent is 1:0.01~0.5:0.001~0.2; the amphoteric ligand includes one or more of aspartic acid or glutamic acid; the protective agent is one or more of hydrazine hydrate or ascorbic acid. Co in cobalt hydroxide 2+ The content is greater than 99%, and the average particle size is 10~100 nm.

2. The method for preparing high-purity, small-size cobalt hydroxide as described in claim 1, characterized in that: The cobalt salt is one or more of cobalt chloride, cobalt sulfate, cobalt nitrate, or cobalt acetate.

3. The method for preparing high-purity, small-size cobalt hydroxide as described in claim 1, characterized in that: The alkaline solid is one or more of sodium hydroxide or potassium hydroxide.

4. The method for preparing high-purity, small-size cobalt hydroxide as described in claim 1, characterized in that: The ball-to-material ratio is 10~20:1.

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