Octadecahedron cerium-cobalt composite oxide lithium battery negative electrode material and preparation method thereof

Abstract

The invention discloses an octadecahedral cerium-cobalt composite oxide lithium battery negative electrode material and a preparation method thereof, and the preparation method comprises the following steps: dissolving cerium salt in absolute ethyl alcohol to prepare a cerium salt alcoholic solution; the preparation method comprises the following steps: dissolving cobalt potassium cyanide in water to prepare a cobalt salt solution, and sequentially adding glucose and sodium carboxymethyl cellulose to obtain a mixed aqueous solution containing glucose, sodium carboxymethyl cellulose and cobalt salt; mixing the two solutions, stirring to obtain white precipitate, centrifugally separating, washing with ethanol for three times, and drying to obtain a white cerium-cobalt precursor; and placing the obtained cerium-cobalt precursor in a crucible with a cover, wrapping the cerium-cobalt precursor with a thin foil, carrying out high-temperature calcination in a muffle furnace, and naturally cooling to obtain the octadecahedral cerium-cobalt composite oxide. The octadecahedral cerium-cobalt composite oxide negative electrode material disclosed by the invention has a special microstructure, relatively good charge-discharge capacity and good cyclicity.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic functional materials, and in particular relates to an octahedral cerium-cobalt composite oxide lithium battery negative electrode material and a preparation method thereof. Background Art

[0002] Metal-organic frameworks (MOFs), a new class of crystalline porous coordination polymers composed of organic linkers and metal nodes, have attracted increasing attention for electrochemical energy storage due to their rigidity, extensibility, and insolubility in organic electrolytes. Prussian blue analogs (PBAs) with MOF structures have become templates for the development of high-performance functional materials in recent years due to their abundant raw material reserves, simple synthesis process, and unique structure. Therefore, the preparation of cerium-cobalt composite metal oxides with specialized structures using PBAs as precursors to enhance their electrochemical performance is a challenging research topic. Summary of the Invention

[0003] In view of this, the present invention provides an octahedral cerium-cobalt composite oxide negative electrode material for a lithium battery and a preparation method thereof. The octahedral cerium-cobalt composite oxide negative electrode material of the present invention has a special microstructure, good charge and discharge capacity and good cyclability.

[0004] In order to solve the above technical problems, the present application discloses an octahedral cerium-cobalt composite oxide lithium battery negative electrode material and a preparation method thereof, comprising the following steps: Step 1: dissolving cerium salt in anhydrous ethanol to prepare a cerium salt alcohol solution.

[0005] Step 2: dissolving potassium cobalt cyanide in water, and sequentially adding glucose and sodium carboxymethyl cellulose to obtain a mixed aqueous solution containing glucose, sodium carboxymethyl cellulose and cobalt salt.

[0006] Step 3, the two solutions were mixed and stirred for 30 minutes; the precipitate was centrifuged, washed three times with ethanol, and dried to obtain a white cerium-cobalt precursor; Step 4: placing the obtained cerium-cobalt precursor in a crucible with a lid, wrapping it with thin foil, calcining it at a high temperature in a muffle furnace, and naturally cooling it to obtain an octahedral cerium-cobalt composite oxide lithium battery negative electrode material.

[0007] Furthermore, the concentration of the cerium salt alcohol solution in step 1 is 0.3-0.6 mol / L.

[0008] Furthermore, the cerium salt alcohol solution in step 1 is a cerium chloride alcohol solution, a cerium nitrate alcohol solution or a cerium acetylacetonate alcohol solution.

[0009] Furthermore, the concentration of the potassium cobalt cyanide solution in step 2 is 0.6-1.2 mol / L, the molar ratio of cerium salt to potassium cobalt cyanide is 0.8:1-1:1.2, the molar ratio of cerium salt to glucose is 1:1-1:3, and the molar ratio of cerium salt to sodium carboxymethyl cellulose is 0.8:1-1:1.2.

[0010] Furthermore, in the stirring conditions in step 3, the temperature is 20-25° C. and the rotation speed is 180-220 r / min.

[0011] Furthermore, the drying temperature in step 3 is 50-70°C.

[0012] Furthermore, the calcination temperature in step 4 is 450-600° C., the time is 1-3 hours, and the heating rate is 1-5° C. / min.

[0013] The invention also discloses an octahedral cerium-cobalt composite oxide lithium battery negative electrode material prepared by the above preparation method.

[0014] Compared with the existing technology, this application can achieve the following technical effects: 1) The preparation process of the present invention is simple, and a cerium-cobalt precursor is obtained by a one-step method, and then the product is sintered at a high temperature.

[0015] 2) The precursor of the present invention is prepared at room temperature without heating.

[0016] 3) The preparation method of the present invention is a normal pressure liquid phase method, which does not require complex processes such as hydrothermal processes.

[0017] Of course, any product implementing the present invention does not necessarily need to achieve all of the above-mentioned technical effects at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 This is a scanning electron microscope photograph of the octahedral cerium-cobalt composite oxide lithium battery negative electrode material of the present application; Figure 2 This is the XRD spectrum of the octahedral cerium-cobalt composite oxide lithium battery negative electrode material of the present application; Figure 3 This is the cycle performance of the octahedral cerium-cobalt composite oxide lithium battery negative electrode material of the present application. DETAILED DESCRIPTION

[0019] The following will describe the embodiments of the present invention in detail with reference to examples, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0020] The present invention discloses an octahedral cerium-cobalt composite oxide lithium battery negative electrode material and a preparation method thereof, comprising the following steps: Step 1: dissolve the cerium salt in anhydrous ethanol to prepare a 0.3-0.6 mol / L cerium salt alcohol solution.

[0021] Step 2: Dissolve potassium cobalt cyanide in water to prepare a 0.6-1.2 mol / L potassium cobalt cyanide aqueous solution, and sequentially add glucose and sodium carboxymethyl cellulose. The molar ratio of cerium salt to potassium cobalt cyanide is 0.8:1-1:1.2, the molar ratio of cerium salt to glucose is 1:1-1:3, and the molar ratio of cerium salt to sodium carboxymethyl cellulose is 0.8:1-1:1.2. A mixed aqueous solution containing glucose, sodium carboxymethyl cellulose, and cobalt salt is obtained.

[0022] Step 3: Mix the two solutions at room temperature (20-25°C) and a stirring speed of 180-220 r / min for 30 minutes; centrifuge the precipitate, wash three times with ethanol, and dry at 50-70°C to obtain a white cobalt-cerium precursor; Step 4: Place the obtained cerium-cobalt precursor in a covered crucible, wrap it with thin foil, and calcine it at high temperature in a muffle furnace at a temperature of 450-600°C for 1-3 hours at a heating rate of 1-5°C / min. After natural cooling, obtain an octahedral cerium-cobalt composite oxide lithium battery negative electrode material.

[0023] In this preparation method, 1. The cobalt source used is potassium cobalt cyanide, not free cobalt ions. Cobalt cyanate ions react with cerium ions to form a metal-organic framework precursor. During high-temperature calcination, some cyanide decomposes to form gas, leaving behind a porous structure. Some cyanide can carbonize in the absence of oxygen, forming a carbon layer that improves the material's conductivity. The metal ions convert the oxides to retain the ordered metal skeleton structure, thereby enhancing its electrochemical performance.

[0024] 2. Glucose can serve as a good carbon source. Glucose molecules can enter the pore structure of the metal-organic framework precursor through adsorption, forming a carbon layer with good conductivity during high-temperature calcination, thereby improving its electrochemical performance.

[0025] 3. Adding the surfactant sodium carboxymethyl cellulose can serve as a crystal growth regulator to obtain octahedral nanoparticles with a more uniform structure.

[0026] 4. During the calcination process, a covered crucible wrapped with thin foil is used to provide an oxygen-deficient environment, which is conducive to the formation of carbon coating on the surface of cerium cobalt oxide nanoparticles by some organic matter such as glucose without complete decomposition.

[0027] Example 1 Cerium nitrate was dissolved in anhydrous ethanol to prepare a 0.5 mol / L cerium nitrate alcohol solution; potassium cobalt cyanide was dissolved in water to prepare a 1.0 mol / L potassium cobalt cyanide aqueous solution, and glucose and sodium carboxymethyl cellulose were added in sequence, with the molar ratio of cerium nitrate to glucose being 1:1, and the molar ratio of cerium nitrate to sodium carboxymethyl cellulose being 1:1.2. A mixed aqueous solution containing glucose, sodium carboxymethyl cellulose and cobalt salt was obtained. The two solutions were mixed and stirred for 30 minutes at a temperature of 20°C and a speed of 200 r / min; the precipitate was centrifuged, washed three times with ethanol, and dried at 60°C to obtain a white cerium cobalt precursor; the obtained product was placed in a crucible with a lid, wrapped with thin foil, and calcined at high temperature in a muffle furnace at a calcination temperature of 500°C for 1 hour at a heating rate of 2°C / min. After natural cooling, an octahedral cerium cobalt composite oxide lithium battery negative electrode material was obtained. The scanning electron microscope photograph of the obtained product is shown as follows: Figure 1 As shown in the figure, and the XRD spectrum is as shown in the figure Figure 2 The cycle performance of button cells assembled with the prepared octahedral cerium-cobalt composite oxide is shown in Figure 3 As shown, the capacity remains at 490 mAh g after 200 cycles. -1 .

[0028] Example 2 Cerium chloride was dissolved in anhydrous ethanol to prepare a 0.4 mol / L cerium chloride alcohol solution. Potassium cobalt cyanide was dissolved in water to prepare a 0.8 mol / L potassium cobalt cyanide aqueous solution. Glucose and sodium carboxymethyl cellulose were then added sequentially, with a molar ratio of cerium chloride to glucose of 1:2 and a molar ratio of cerium chloride to sodium carboxymethyl cellulose of 0.8:1. This resulted in a mixed aqueous solution containing glucose, sodium carboxymethyl cellulose, and cobalt salt. The two solutions were mixed and stirred at 23°C and 220 r / min for 30 minutes. The precipitate was centrifuged, washed three times with ethanol, and dried at 60°C to obtain a white cerium-cobalt precursor. The resulting product was placed in a covered crucible, wrapped with thin foil, and calcined in a muffle furnace at 450°C for 2 hours at a heating rate of 1°C / min. After natural cooling, the resulting octahedral cerium-cobalt composite oxide was obtained as a negative electrode material for lithium batteries.

[0029] Example 3 Cerium acetylacetonate was dissolved in anhydrous ethanol to prepare a 0.6 mol / L cerium acetylacetonate alcohol solution. Potassium cobalt cyanide was dissolved in water to prepare a 1.2 mol / L potassium cobalt cyanide aqueous solution. Glucose and sodium carboxymethyl cellulose were then added sequentially, with a molar ratio of cerium acetylacetonate to glucose of 1:1 and a molar ratio of cerium acetylacetonate to sodium carboxymethyl cellulose of 1:1.2. This resulted in a mixed aqueous solution containing glucose, sodium carboxymethyl cellulose, and cobalt salt. The two solutions were mixed and stirred at 25°C and 180 r / min for 30 minutes. The precipitate was centrifuged, washed three times with ethanol, and dried at 70°C to obtain a white cerium-cobalt precursor. The resulting product was placed in a covered crucible, wrapped with thin foil, and calcined in a muffle furnace at 600°C for 3 hours at a heating rate of 4°C / min. After natural cooling, the resulting octahedral cerium-cobalt composite oxide was obtained as a negative electrode material for lithium batteries.

[0030] The foregoing description shows and describes several preferred embodiments of the invention. However, as previously stated, it should be understood that the invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the invention is applicable to various other combinations, modifications, and environments and is capable of modification within the scope of the inventive concept described herein, through the teachings above, or through techniques or knowledge in the relevant art. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the invention are intended to be within the scope of the appended claims.

Claims

1. A method for preparing an octahedral cerium-cobalt composite oxide negative electrode material for a lithium battery, characterized in that: The following steps are involved: Step 1, dissolving the cerium salt in anhydrous ethanol to prepare a cerium salt alcohol solution; Step 2, dissolving potassium cobalt cyanide in water, and sequentially adding glucose and sodium carboxymethyl cellulose to obtain a mixed aqueous solution containing glucose, sodium carboxymethyl cellulose and cobalt salt; Step 3, the two solutions were mixed and stirred for 30 minutes; the precipitate was centrifuged, washed three times with ethanol, and dried to obtain a white cerium-cobalt precursor; Step 4: placing the obtained cerium-cobalt precursor in a crucible with a lid, wrapping it with thin foil, calcining it at a high temperature in a muffle furnace, and naturally cooling it to obtain an octahedral cerium-cobalt composite oxide lithium battery negative electrode material.

2. The method for preparing the negative electrode material of an octahedral cerium-cobalt composite oxide lithium battery according to claim 1, characterized in that: The concentration of the cerium salt alcohol solution in step 1 is 0.3-0.6 mol / L.

3. The method for preparing the negative electrode material of an octahedral cerium-cobalt composite oxide lithium battery according to claim 1, characterized in that: The cerium salt alcohol solution in step 1 is cerium chloride solution, cerium nitrate solution or cerium acetylacetonate alcohol solution.

4. The method for preparing the negative electrode material of an octahedral cerium-cobalt composite oxide lithium battery according to claim 1, characterized in that: The concentration of the potassium cobalt cyanide solution in step 2 is 0.6-1.2 mol / L, the molar ratio of cerium salt to potassium cobalt cyanide is 0.8:1-1:1.2, the molar ratio of cerium salt to glucose is 1:1-1:3, and the molar ratio of cerium salt to sodium carboxymethyl cellulose is 0.8:1-1:1.

2.

5. The method for preparing the negative electrode material of an octahedral cerium-cobalt composite oxide lithium battery according to claim 1, characterized in that: The stirring conditions in step 3 are a temperature of 20-25° C. and a rotation speed of 180-220 r / min.

6. The method for preparing the negative electrode material of an octahedral cerium-cobalt composite oxide lithium battery according to claim 1, characterized in that: The drying temperature in step 3 is 50-70°C.

7. The method for preparing the negative electrode material of an octahedral cerium-cobalt composite oxide lithium battery according to claim 1, characterized in that: The calcination temperature in step 4 is 450-600°C, the time is 1-3 hours, and the heating rate is 1-5°C / min.

8. An octahedral cerium-cobalt composite oxide negative electrode material for a lithium battery prepared by the preparation method according to any one of claims 1 to 7.

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