A cobalt-based bimetallic oxide, its preparation method and application, and electrode materials.

Abstract

This invention provides a method for preparing cobalt-based bimetallic oxides, belonging to the field of materials preparation technology. The method includes: mixing a non-cobalt metal source with cobalt trioxide and then ball milling the mixture under supercritical carbon dioxide conditions to obtain the cobalt-based bimetallic oxide. This invention uses cobalt trioxide and non-cobalt metal sources as raw materials, and ball mills them under supercritical carbon dioxide conditions. Under the collision, compression, impact, and shearing action of the ball milling jar and grinding beads, the ionic bonds of the raw materials break and recombine, resulting in the cobalt-based bimetallic oxide. The pressure and temperature of supercritical carbon dioxide can be used to change the properties of the reaction system, such as density, preventing reactant agglomeration, improving the energy efficiency of the reaction, reducing impurities in the crystal structure of the product, increasing product purity, and thus improving the electrochemical performance of the product.

Description

Technical Field

[0001] This invention relates to the field of materials preparation technology, and in particular to a cobalt-based bimetallic oxide, its preparation method, and its application. Background Technology

[0002] Cobalt-based bimetallic oxides, such as nickel cobaltate, magnesium cobaltate, zinc cobaltate, and copper cobaltate, are spinel-type binary oxides with a cubic crystal system. In this structure, cobalt ions occupy tetrahedral lattice sites, while the other divalent metal occupies octahedral sites. Due to their high conductivity, wide bandgap, and high theoretical capacitance, cobalt-based bimetallic oxides have broad application prospects in energy storage and conversion fields such as supercapacitors, magnesium-ion batteries, photoelectric water splitting, electrocatalytic oxygen evolution reaction, and fuel cells.

[0003] However, existing methods for preparing cobalt-based bimetallic oxides are complex, have low yields, high costs, and produce products with poor performance, making it difficult to meet the needs of industrial applications. For example, Chinese patent CN112939097A discloses a nickel cobalt oxide nanomaterial, its preparation method, and its application. This method prepares nickel cobalt oxide nanomaterials through a high-temperature solvothermal reaction and subsequent high-temperature calcination, but the batch yield is low, less than 0.05g, making it difficult to achieve large-scale preparation of cobalt-based bimetallic oxides. Wang et al. (Journal of Nanoparticle Research 2015, 13, 339-349) prepared magnesium cobalt oxide nanowires through hydrothermal deposition and high-temperature calcination. This method not only requires high-temperature calcination but also uses flammable and harmful hexamethylenetetramine as a structural agent, which limits the large-scale application of cobalt-based bimetallic oxides. In addition, Wang et al. (JAlloys Compd 2015, 688, 933-938) prepared magnesium cobalt oxide electrode material using a solvothermal method. Its electrochemical performance was low, only 340 F / g, and the supercapacitors prepared based on this material could not meet the needs of practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide a cobalt-based bimetallic oxide, its preparation method, and its applications. The preparation method provided by this invention is simple, and the resulting cobalt-based bimetallic oxide, when used to prepare electrodes, can give the electrodes a high specific capacity.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a cobalt-based bimetallic oxide, comprising: mixing a non-cobalt metal source with cobalt trioxide and then ball milling the mixture under supercritical carbon dioxide conditions to obtain a cobalt-based bimetallic oxide; wherein the non-cobalt metal source is an alkali or salt containing a non-cobalt metal; and the ball milling time is 8 hours or more.

[0007] Preferably, the salt containing non-cobalt metal is a carbonate.

[0008] Preferably, the molar ratio of the non-cobalt metal source to cobalt trioxide is 1:1.

[0009] Preferably, the temperature of the supercritical carbon dioxide condition is 35–80°C, and the pressure of the supercritical carbon dioxide condition is 8–20 MPa.

[0010] Preferably, the ball milling time is 8 to 48 hours.

[0011] Preferably, the rotational speed of the ball mill is 100 to 800 rpm.

[0012] Preferably, the ball-to-material ratio in the ball mill is (5-20):1.

[0013] The present invention also provides a cobalt-based bimetallic oxide prepared by the preparation method described above, wherein the cobalt-based bimetallic oxide is a single spinel phase.

[0014] The present invention also provides the application of the cobalt-based bimetallic oxide described in the above technical solution.

[0015] The present invention also provides an electrode material comprising the cobalt-based bimetallic oxide described in the above technical solution.

[0016] This invention provides a method for preparing cobalt-based bimetallic oxides, comprising: mixing a non-cobalt metal source with cobalt trioxide and then ball milling under supercritical carbon dioxide conditions to obtain cobalt-based bimetallic oxides; wherein the non-cobalt metal source is an alkali or salt containing a non-cobalt metal; and the ball milling time is 8 hours or more. This invention uses an alkali or salt containing a non-cobalt metal and cobalt trioxide as raw materials. Through ball milling under supercritical carbon dioxide conditions, the ionic bonds of the raw materials are broken and recombined under the collision, compression, impact, and shearing action of the ball milling jar and the ball milling beads, resulting in cobalt-based bimetallic oxides. By changing the pressure and temperature of supercritical carbon dioxide, the properties of the reaction system can be adjusted, such as changing the density, to avoid reactant agglomeration, thereby improving the energy efficiency of the reaction. This, in turn, reduces impurities in the crystal structure of the product, improves product purity, and further enhances the electrochemical performance of the product. Example results show that the preparation method provided by this invention only requires one ball milling reaction step, without post-processing steps such as calcination; and it prepares a cobalt-based bimetallic oxide with a single spinel phase, which, when used to prepare electrodes, achieves a specific capacity of 963 F / g. Attached Figure Description

[0017] Figure 1 Macroscopic photograph of the cobalt-based bimetallic oxide prepared in Example 1;

[0018] Figure 2 X-ray diffraction pattern of the cobalt-based bimetallic oxide prepared in Example 1;

[0019] Figure 3 The graph shows the charge-discharge test results of the electrode, which includes the cobalt-based bimetallic oxide prepared in Example 1.

[0020] Figure 4 X-ray diffraction pattern of the cobalt-based bimetallic oxide prepared in Example 2;

[0021] Figure 5 X-ray diffraction pattern of the cobalt-based bimetallic oxide prepared in Example 3;

[0022] Figure 6 A macroscopic photograph of the cobalt-based bimetallic oxide prepared for Comparative Example 1;

[0023] Figure 7 X-ray diffraction pattern of the powder prepared in Comparative Example 1;

[0024] Figure 8 X-ray diffraction pattern of the powder prepared in Comparative Example 2;

[0025] Figure 9 The X-ray diffraction pattern of the powder prepared in Comparative Example 3 is shown. Detailed Implementation

[0026] All raw materials used in this invention are not particularly restricted in their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0027] There are no particular restrictions on the purity of any raw materials used in this invention. However, it is preferred to use analytical grade or materials of conventional purity in the field of materials preparation.

[0028] This invention provides a method for preparing cobalt-based bimetallic oxide, comprising: mixing a non-cobalt metal source with cobalt trioxide and then ball milling the mixture under supercritical carbon dioxide conditions to obtain cobalt-based bimetallic oxide.

[0029] In this invention, the non-cobalt metal source is an alkali or salt containing a non-cobalt metal, preferably an alkali containing a non-cobalt metal; the non-cobalt metal salt is preferably a carbonate. In embodiments of this invention, the non-cobalt metal source can be magnesium hydroxide, nickel hydroxide, zinc hydroxide, copper hydroxide, magnesium carbonate, nickel carbonate, zinc carbonate, or copper carbonate. The molecular structures of the above-mentioned non-cobalt metal sources all contain ionic bonds, which can be broken by ball milling, reacting with cobalt trioxide to obtain a cobalt-based bimetallic oxide.

[0030] In this invention, the molar ratio of the non-cobalt metal source to cobalt trioxide is preferably 1:1. A suitable molar ratio is beneficial for synthesizing magnesium cobaltate material with a purity of 100%.

[0031] In this invention, as one embodiment, the temperature of the supercritical carbon dioxide condition can be 35–80°C or 35–50°C; in specific embodiments of this invention, the temperature of the supercritical carbon dioxide condition can be 35°C, 37°C, 40°C, 42°C, 45°C, 47°C, or 50°C. The temperature of the supercritical carbon dioxide condition within the above range ensures that the carbon dioxide is in a supercritical state without requiring excessive energy consumption.

[0032] In this invention, as one embodiment, the pressure of the supercritical carbon dioxide condition can be 8–20 MPa or 8–15 MPa; in specific embodiments of this invention, the pressure of the supercritical carbon dioxide condition can be 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, or 15 MPa. The pressure of the supercritical carbon dioxide condition within the above range ensures that the carbon dioxide is in a supercritical state and also reduces the requirements for equipment.

[0033] In this invention, the ball milling time is 8 hours or more. As one embodiment, the ball milling time can be 8–48 hours or 8–24 hours. Specifically, in embodiments of this invention, the ball milling time can be 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, or 24 hours. The ball milling time directly affects the reaction progress. Too short a milling time results in incomplete reaction, wasting resources and affecting product quality; too long a milling time prolongs the production cycle and affects production efficiency. The ball milling time within the above range ensures complete reaction while maintaining good production efficiency.

[0034] In this invention, as one embodiment, the ball mill's rotational speed can be 100–800 rpm or 250–350 rpm. The ball mill's rotational speed affects its effect and efficiency. If the speed is too low, the ball mill will not achieve the desired effect or will require a longer milling time; if the speed is too high, it may cause uneven grinding of the material and increase equipment wear. When the ball mill's rotational speed is within the above range, it can effectively grind the material, which is beneficial for improving reaction efficiency.

[0035] In this invention, as one embodiment, the grinding balls used in the ball mill can be one or more of stainless steel balls, zirconium oxide, alumina, and agate; the diameter of the grinding balls can be 1–5 mm; and the ball-to-material ratio can be (5–20):1 or (8–15):1. The ball-to-material ratio affects the reaction efficiency; too few grinding balls will lead to incomplete reaction, while too many will reduce energy efficiency. Within the above-mentioned range, the ball milling can be effectively carried out, allowing the reaction to proceed normally.

[0036] After ball milling, the present invention preferably releases and recovers the carbon dioxide in the ball milling vessel, and then separates the material and the ball milling beads to obtain cobalt-based bimetallic oxide.

[0037] In this invention, the separation is preferably carried out by sieve separation, and the mesh size of the sieve is preferably 20 to 100 mesh.

[0038] This invention uses cobalt trioxide and non-cobalt metal sources as raw materials and ball mills them under supercritical carbon dioxide conditions. Under the collision, compression, impact and shearing action of the ball milling jar and the ball milling beads, the ionic bonds of the raw materials are broken and recombined to obtain cobalt-based bimetallic oxides. By utilizing the pressure and temperature of supercritical carbon dioxide, the properties of the reaction system can be adjusted, such as changing the density, to avoid reactant agglomeration, improve the energy efficiency of the reaction, reduce impurities in the crystal structure of the product, and improve the purity of the product.

[0039] The present invention also provides a cobalt-based bimetallic oxide prepared by the preparation method described above, wherein the cobalt-based bimetallic oxide is a single spinel phase.

[0040] This invention also provides applications of the cobalt-based bimetallic oxide described in the above technical solution. This invention does not impose any particular limitation on the method of application; any application method of cobalt-based bimetallic oxides well-known to those skilled in the art can be used.

[0041] The present invention also provides an electrode material comprising the cobalt-based bimetallic oxide described in the above-described technical solution. As one embodiment of the present invention, the cobalt-based bimetallic oxide, as the active component of the electrode material, is mixed with a conductive agent, a binder, and a solvent, and then coated onto an electrode sheet to prepare an electrode.

[0042] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0043] Example 1

[0044] A cobalt-based bimetallic oxide is prepared as follows:

[0045] Add 74g of cobalt trioxide and 26g of magnesium hydroxide (molar ratio 1:1) to a 1L stainless steel ball mill flask, then add 1000g of zirconia grinding beads (1mm in diameter). Tighten the flask lid until sealed, then fill with 350g of carbon dioxide and place the flask into the ball mill. Adjust the ball milling speed to 350rpm, the flask temperature to 35℃, and the flask pressure to 10MPa. After milling for 8 hours, release the carbon dioxide gas, open the flask lid, and observe the product state. Figure 1 As shown, according to Figure 1 The product can be seen to be a fluffy black powder. The reaction product and the ball milling beads were removed and separated through a sieve (50 mesh) to obtain a cobalt-based bimetallic oxide, totaling 99g, with a yield of 99% (mass of powder after reaction / mass of powder before reaction).

[0046] The cobalt-based bimetallic oxide was characterized by X-ray diffraction using a Rigaku Mini Flex 600 instrument. The analytical conditions were a scan rate of 10° / min. The results are as follows: Figure 2 As shown, from Figure 2 It can be seen that the cobalt-based bimetallic oxide prepared in Example 1 is magnesium cobaltate with a single spinel phase, indicating that the non-cobalt metal source reacts completely and the reaction conversion rate (100% - mass of non-cobalt metal source after reaction / mass of non-cobalt metal source before reaction) reaches 100%.

[0047] The cobalt-based bimetallic oxide prepared in Example 1 was subjected to electrochemical performance testing. The specific method is as follows: The prepared cobalt-based bimetallic oxide, conductive agent, and binder were mixed in N-methylpyrrolidone at a ratio of 80:15:5, coated onto cleaned nickel foam, and dried to serve as the working electrode. A three-electrode system was used for electrochemical performance testing, with a mercury oxide electrode as the reference electrode and a platinum wire as the counter electrode; the electrolyte solution was a 3 mol / L potassium hydroxide solution; the charge / discharge voltage range was 0.1–0.5 V, and the current density was 0.1 A / g. The results are as follows: Figure 3 As shown. From Figure 3It can be seen that the electrode has a specific capacitance of up to 963 F / g and good electrochemical performance, indicating that the cobalt-based bimetallic oxide prepared in this invention can be used as an electrode material in supercapacitors.

[0048] Example 2

[0049] A cobalt-based bimetallic oxide is prepared as follows:

[0050] 64g of cobalt trioxide and 36g of nickel hydroxide (molar ratio 1:1) were added to a 1L stainless steel ball mill flask, along with 1000g of zirconia grinding beads (1mm in diameter). The flask lid was tightened until sealed, and 350g of carbon dioxide was introduced before placing the flask into a ball mill. The milling speed was adjusted to 350rpm, the temperature in the flask to 35℃, and the pressure to 10MPa. After milling for 24 hours, carbon dioxide gas was released, the flask lid was opened, and the product was observed to be a fluffy black powder. The reaction product and grinding beads were removed and separated through a 50-mesh sieve to obtain 99g of cobalt-based bimetallic oxide, with a yield of 99%.

[0051] The cobalt-based bimetallic oxide was characterized by X-ray diffraction using a Rigaku Mini Flex 600 instrument. The analytical conditions were a scan rate of 10° / min. The results are as follows: Figure 4 As shown, from Figure 4 It can be seen that the cobalt-based bimetallic oxide obtained in Example 2 is nickel cobalt oxide with a single spinel phase, indicating that the reaction conversion rate reached 100%.

[0052] Example 3

[0053] A cobalt-based bimetallic oxide is prepared as follows:

[0054] 66g of cobalt trioxide and 34g of magnesium carbonate (molar ratio 1:1) were added to a 1L stainless steel ball mill flask, along with 1000g of zirconia grinding beads (1mm in diameter). The flask lid was tightened until sealed, and 150g of carbon dioxide was introduced before placing the flask into a ball mill. The milling speed was adjusted to 350rpm, the temperature in the flask to 35℃, and the pressure to 8MPa. After milling for 24 hours, carbon dioxide gas was released, the flask lid was opened, and the product was observed to be a fluffy black powder. The reaction product and grinding beads were removed and separated through a 50-mesh sieve to obtain 99g of cobalt-based bimetallic oxide, with a yield of 99%.

[0055] The cobalt-based bimetallic oxide was characterized by X-ray diffraction using a Rigaku Mini Flex 600 instrument. The analytical conditions were a scan rate of 10° / min. The results are as follows: Figure 5 As shown, from Figure 5It can be seen that the cobalt-based bimetallic oxide prepared in Example 3 is magnesium cobaltate with a single spinel phase, indicating that the reaction conversion rate is as high as 100%.

[0056] Comparative Example 1

[0057] The preparation was carried out in accordance with the method of Example 1, except that carbon dioxide was not added during the ball milling process. Specifically:

[0058] Add 74g of cobalt trioxide and 26g of magnesium hydroxide (molar ratio 1:1) to a 1L stainless steel ball mill flask, then add 1000g of zirconia grinding beads (1mm in diameter). Tighten the flask lid until sealed, then place the flask into the ball mill. Adjust the milling speed to 350rpm and the flask temperature to 35℃. After milling for 8 hours, open the flask lid and observe the product condition. Figure 6 As shown, from Figure 6 It can be seen that the product undergoes significant solidification at the bottom of the ball mill. After separating the unsolidified powder from the milling beads through a sieve (50 mesh), a total of 15g of product was obtained, with a yield of only 15%. The significant solidification of the material severely affected the product yield.

[0059] The products were characterized using X-ray diffraction (XRD) with a Rigaku Mini Flex 600 instrument and a scan rate of 10° / min. The results are as follows: Figure 7 As shown, from Figure 7 It can be seen that the product obtained in Comparative Example 1 has a significant impurity phase, which is magnesium hydroxide, a reactant, and the content of magnesium hydroxide reaches 16.5 wt%. Based on this, the reaction conversion rate is only 63.5%. By comparing Example 1 with Comparative Example 1, it can be shown that the present invention not only has a high conversion rate and yields a product with a single spinel phase, but also has a high yield, which is beneficial for industrial promotion.

[0060] Comparative Example 2

[0061] The preparation was carried out according to the method of Example 1, except that the ball milling time was reduced to 4 hours, specifically:

[0062] 74g of cobalt trioxide and 26g of magnesium hydroxide (molar ratio 1:1) were added to a 1L stainless steel ball mill flask, along with 1000g of zirconia grinding beads (1mm in diameter). The flask lid was tightened until sealed, and 350g of carbon dioxide was introduced before placing the flask into a ball mill. The ball milling speed was adjusted to 350rpm, the temperature in the flask to 35℃, and the pressure in the flask to 10MPa. After milling for 4 hours, carbon dioxide gas was released, and the product was observed to be a fluffy black powder. The reaction product and grinding beads were removed and separated through a 50-mesh sieve to obtain the final product.

[0063] The products were characterized using X-ray diffraction (XRD) with a Rigaku Mini Flex 600 instrument and a scan rate of 10° / min. The results are as follows: Figure 8 As shown, from Figure 8 It can be seen that the product obtained in Comparative Example 2 has obvious impurity phases. The impurity is magnesium hydroxide, a reactant, with a content of 3.8 wt%. Based on this, the conversion rate of the reaction is calculated to be 85.4%.

[0064] Comparative Example 3

[0065] The preparation was carried out according to the method of Example 1, except that the reactants were changed from hydroxides to oxides, specifically:

[0066] Take 80g of cobalt trioxide and 20g of magnesium oxide (molar ratio of 1:1) and add them to a 1L stainless steel ball mill flask. Add 1000g of zirconia grinding beads (1mm in diameter). Tighten the screws to seal the flask lid. After filling with 350g of carbon dioxide, place the ball mill flask into a ball mill. Adjust the ball milling speed to 350rpm, the temperature in the ball mill flask to 35℃, and the pressure in the ball mill flask to 10MPa. After ball milling for 8 hours, release carbon dioxide gas. The product is observed to be a fluffy black powder. Take out the reaction product and the grinding beads, and separate them through a sieve (50 mesh) to obtain the product after the reaction.

[0067] The products were characterized using X-ray diffraction (XRD) with a Rigaku Mini Flex 600 instrument and a scan rate of 10° / min. The results are as follows: Figure 9 As shown, from Figure 9 It can be seen that the product obtained in Comparative Example 3 has obvious impurity phases, the impurity being magnesium oxide, with a content of 19.0 wt%, and the reaction conversion rate only reaches 5%. This is because the Mg-O bond in magnesium oxide is a covalent bond, while the Mg-(OH) bond in magnesium hydroxide is an ionic bond; in the ball milling reaction, covalent bonds are more difficult to break than ionic bonds, indicating that the type of reactant metal raw material has a significant impact on the reaction process.

[0068] As can be seen from the above embodiments and comparative examples, the present invention uses cobalt trioxide and non-cobalt metal sources as raw materials, and ball mills them under supercritical carbon dioxide conditions. By limiting the types of raw materials and controlling the ball milling time, a cobalt-based bimetallic oxide with a single spinel phase can be obtained for preparing electrodes. The specific capacitance of the electrodes reaches 963 F / g, which can be applied to supercapacitors.

[0069] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing a cobalt-based double metal oxide, characterized by, Comprising: mixing a non-cobalt metal source with cobalt sesquioxide under supercritical carbon dioxide conditions to obtain a cobalt-based double metal oxide; the non-cobalt metal source is an alkali or salt containing a non-cobalt metal; the ball milling time is 8 hours or more; the non-cobalt metal is magnesium or nickel; the temperature of the supercritical carbon dioxide conditions is 35-80℃, and the pressure of the supercritical carbon dioxide conditions is 8-20 MPa.

2. The production method according to claim 1, characterized by, The salt containing a non-cobalt metal is a carbonate salt.

3. The production method according to claim 1 or 2, characterized by, The molar ratio of the non-cobalt metal source to cobalt sesquioxide is 1:

1.

4. The production method according to claim 1, characterized by, The ball milling time is 8-48 hours.

5. The preparation method according to claim 1, characterized in that, The ball milling speed is 100-800 rpm.

6. The production method according to claim 1, 4 or 5, characterized by, The ball milling ball-to-material ratio is (5-20):

1.

7. The cobalt-based double metal oxide prepared by the preparation method of any one of claims 1-6, wherein the cobalt-based double metal oxide is a single spinel phase.

8. The use of the cobalt-based double metal oxide of claim 7 in supercapacitors.

9. An electrode material comprising the cobalt-based double metal oxide of claim 7.

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