Negative electrode material, preparation method and application thereof

Abstract

The present invention relates to the field of battery technology, and more specifically, to a negative electrode material, its preparation method, and application. The method for preparing the negative electrode material of the present invention comprises the following steps: subjecting a mixed system of an iron salt, a molybdenum source, an amino ligand, and a first solvent to a hydrothermal reaction to obtain a first precursor; mixing the first precursor with a sulfur source, an alkali, an aldehyde compound, and a second solvent, followed by a first heat treatment to obtain a sulfide precursor; and then mixing the sulfide precursor with a selenium source and subjecting the mixture to a second heat treatment. The negative electrode material obtained by the method of the present invention exhibits excellent conductivity, cycle stability, and rate performance.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a negative electrode material and a preparation method and application thereof. Background Art

[0002] At present, the widespread use of lithium-ion batteries has led to a global shortage of lithium resources, further increasing the cost of lithium-ion batteries, which has limited their large-scale application. Sodium not only has similar physical and chemical properties to lithium, but also has an energy storage principle similar to that of lithium-ion batteries, but the sodium reserves are more than 400 times that of lithium resources. More reserves lead to lower sodium resource prices, so sodium-ion batteries have more advantages in the application of large-scale energy storage devices. However, the difference in radius between sodium ions and lithium ions means that sodium ions cannot be inserted into the graphite layer. The excellent performance of graphite negative electrode materials in lithium-ion batteries cannot be fully utilized, and it is necessary to develop suitable sodium-ion battery negative electrode materials.

[0003] In recent years, transition metal selenides and sulfides are promising negative electrode materials for sodium ion batteries due to their + The conversion reaction has attracted widespread attention due to its advantages of low cost, high specific capacity and weak metal selenide bond. Among them, iron selenide (FeSe2) has a high theoretical capacity (500mAh g -1 ) has been widely studied. However, the use of iron selenide in sodium ion batteries also has its shortcomings. On the one hand, its low conductivity and Na + The diffusion rate leads to poor rate performance; on the other hand, the Na + When the conversion reaction occurs, the volume expands greatly, resulting in rapid capacity decay.

[0004] Therefore, how to improve the electronic conductivity and cycle stability of selenide materials is the key to the research on selenide sodium-ion battery negative electrode materials.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] An object of the present invention is to provide a method for preparing a negative electrode material to solve the technical problems of low electrical conductivity of iron selenide, poor rate performance and poor cycle stability when used in sodium ion batteries; the negative electrode material obtained by the method of the present invention has excellent electrical conductivity, cycle stability and rate performance.

[0007] Another object of the present invention is to provide a negative electrode material.

[0008] Another object of the present invention is to provide a negative electrode sheet.

[0009] Another object of the present invention is to provide a battery.

[0010] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0011] A method for preparing a negative electrode material comprises the following steps:

[0012] A mixed system of an iron salt, a molybdenum source, an amino ligand and a first solvent is subjected to a hydrothermal reaction to obtain a first precursor; the first precursor is mixed with a sulfur source, an alkali, formaldehyde and a second solvent and then subjected to a first heat treatment to obtain a sulfide precursor; and the sulfide precursor is then mixed with a selenium source and then subjected to a second heat treatment.

[0013] In one embodiment, the usage ratio of the iron salt, the molybdenum source, the amino ligand and the first solvent is (0.1-10) g: (0.1-10) g: (0.1-10) g: (30-90) mL.

[0014] In one embodiment, the first solvent includes water, alcohol and N,N-dimethylformamide; the volume ratio of water, alcohol and N,N-dimethylformamide is (1-3):(1-3):(1-3).

[0015] In one embodiment, the iron salt includes at least one of ferric chloride, ferric nitrate, and ferric sulfate.

[0016] In one embodiment, the amino ligand comprises at least one of aminoterephthalic acid and aminotrimesic acid;

[0017] In one embodiment, the molybdenum source comprises phosphomolybdic acid.

[0018] In one embodiment, the mixed system is obtained by stirring the iron salt, molybdenum source, amino ligand and solvent, and the stirring time is 0.5 to 2 hours; the stirring speed is 500 to 1000 r / min.

[0019] In one embodiment, the temperature of the hydrothermal reaction is 80 to 220° C., and the time of the hydrothermal reaction is 6 to 18 hours.

[0020] In one embodiment, the system after the hydrothermal reaction is cooled, and the solids are collected and subjected to a first washing and a first drying.

[0021] In one embodiment, the usage ratio of the first precursor, the sulfur source, the base, the formaldehyde and the second solvent is (0.1-2) g: (0.1-20 g): (0-2) g: (10-20) mL: (110-220) mL.

[0022] In one embodiment, the second solvent comprises toluene and N,N-dimethylformamide; the volume ratio of toluene to N,N-dimethylformamide is (1-2): (10-20).

[0023] In one embodiment, the sulfur source includes at least one of mercaptoacetic acid, thiourea, 2-mercaptoimidazole, 2-mercaptobenzimidazole, and 2,5-dimercapto-1,3,4-thiadiazole.

[0024] In one embodiment, the base comprises sodium carbonate.

[0025] In one embodiment, the aldehyde compound comprises formaldehyde.

[0026] In one embodiment, the first precursor is mixed with the sulfur source, alkali, formaldehyde and the second solvent by ultrasonic treatment; the ultrasonic treatment time is 20 to 40 minutes.

[0027] In one embodiment, the temperature of the first heat treatment is 75 to 120° C., and the time of the first heat treatment is 8 to 24 hours.

[0028] In one embodiment, the system after the first heat treatment is subjected to solid-liquid separation, and the solids are collected and subjected to a second washing and a second drying.

[0029] In one embodiment, the mass ratio of the sulfide precursor to the selenium source is (1-5): (1-10).

[0030] In one embodiment, the selenium source comprises elemental selenium.

[0031] In one embodiment, the temperature of the second heat treatment is 300-600° C., and the time of the second heat treatment is 1-4 hours.

[0032] In one embodiment, the heating rate of the second heat treatment is 1-10° C. / min.

[0033] In one embodiment, the second heat treatment is performed under protective gas conditions.

[0034] A negative electrode material is prepared by the negative electrode material preparation method.

[0035] A negative electrode material has a shape including at least one of a rod-like structure and an octahedral structure.

[0036] A negative electrode material having a specific surface area of ​​50 to 500 m 2 / g, and the specific capacity is 400~600mAh / g.

[0037] A negative electrode material and a negative electrode sheet comprising the negative electrode material.

[0038] A battery comprises the negative electrode sheet.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] (1) In the preparation method of the present invention, the introduction of Mo can produce a layered structure with a larger interlayer spacing, which is beneficial to the Na + Diffusion and transmission; organic ligands and metal ions form bonds, and after calcination, an amorphous carbon skeleton is formed, which not only improves the conductivity of the material, but also effectively alleviates the volume expansion of the material and improves the electrode stability; amino groups are introduced in situ into the MOF matrix by using amino ligands to aminize the MOF; sulfur is introduced into the reaction system by covalent bonds, and the thiol groups in the sulfur source are bonded with the amino groups to dope the MOF with sulfur. Sulfur doping can not only provide more active sites and increase the sodium storage capacity of the material, but also improve the conductivity of the material and improve the rate performance. The defects caused by the introduction of sulfur are in the adsorption / storage of Na + At the same time, the reaction energy barrier can be lowered by reducing the stress and electrostatic repulsion between adjacent layers within the material, thereby improving charge transfer and Na + Diffusion; The negative electrode material of the present invention contains a special Fe x Mo y Se m S n Heterostructure, Fe x Mo y Se m S n It has a typical layered structure and a large interlayer distance (0.646nm), which is beneficial to Na + diffusion and transmission.

[0041] (2) The battery prepared from the negative electrode material of the present invention has high energy density and excellent cycle stability, has excellent rate performance, can still maintain a high capacity at high current density, and has excellent fast charging capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0043] Figure 1 This is a scanning electron microscope image of the negative electrode material of Example 1 of the present invention;

[0044] Figure 2 This is a scanning electron microscope image of the negative electrode material of Example 2 of the present invention. DETAILED DESCRIPTION

[0045] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products.

[0046] According to one aspect of the present invention, the present invention relates to a method for preparing a negative electrode material, comprising the following steps:

[0047] A mixed system of an iron salt, a molybdenum source, an amino ligand and a first solvent is subjected to a hydrothermal reaction to obtain a first precursor; the first precursor is mixed with a sulfur source, an alkali, formaldehyde and a second solvent and then subjected to a first heat treatment to obtain a sulfide precursor; and the sulfide precursor is then mixed with a selenium source and then subjected to a second heat treatment.

[0048] In the preparation method of the present invention, the introduction of Mo can produce a layered structure with a larger interlayer spacing (0.646nm), which is beneficial to the Na + Diffusion and transmission; organic ligands and metal ions form bonds, and after calcination, an amorphous carbon skeleton is formed, which not only improves the conductivity of the material, but also effectively alleviates the volume expansion of the material and improves the electrode stability; amino groups are introduced in situ into the MOF matrix by using amino ligands to aminize the MOF; sulfur is introduced into the reaction system by covalent bonds, and the thiol groups in the sulfur source are bonded with the amino groups to dope the MOF with sulfur. Sulfur doping can not only provide more active sites and increase the sodium storage capacity of the material, but also improve the conductivity of the material and improve the rate performance. In addition, the defects generated by the introduction of sulfur have a great influence on the adsorption / storage of Na + At the same time, the reaction energy barrier can be lowered by reducing the stress and electrostatic repulsion between adjacent layers within the material, thereby improving charge transfer and Na + Diffusion; The negative electrode material of the present invention contains a special Fe x Mo y Se m S n Heterostructure, Mo y Se m S n It has a typical layered structure and a large interlayer distance (0.646nm), which is beneficial to Na + diffusion and transmission.

[0049] In one embodiment, the usage ratio of the iron salt, molybdenum source, amino ligand and first solvent is (0.1-10) g: (0.1-10) g: (0.1-10) g: (30-90) mL, for example 0.1 g: 0.1 g: 0.1 g: 30 mL, 0.1 g: 0.2 g: 0.1 g: 40 mL, 1 g: 1 g: 1 g: 50 mL, 10 g: 10 g: 10 g: 90 mL, etc. In one embodiment, the first solvent comprises water, alcohol and N, N-dimethylformamide; the volume ratio of the water, alcohol and N, N-dimethylformamide is (1-3): (1-3): (1-3). In one embodiment, the iron salt comprises at least one of ferric chloride, ferric nitrate and ferric sulfate. In one embodiment, the amino ligand comprises at least one of aminoterephthalic acid and aminotrimesic acid. The molybdenum source comprises phosphomolybdic acid (PMo 12 ).

[0050] In one embodiment, the amount ratio of the iron salt, molybdenum source, amino ligand, water, alcohol and N,N-dimethylformamide is (0.1-10) g: (0.1-10) g: (0.1-10) g: (10-30) mL: (10-30) mL: (10-30) mL.

[0051] In one embodiment, a mixture of amino ligand, alcohol and N,N-dimethylformamide is added to a mixture of iron salt, molybdenum source and water.

[0052] In one embodiment, the mixed system is obtained by stirring the iron salt, molybdenum source, amino ligand, and solvent. The stirring time is 0.5 to 2 hours, such as 0.5 hours, 1 hour, 1.5 hours, or 2 hours. The stirring speed is 500 to 1000 r / min, such as 500 r / min, 600 r / min, 800 r / min, 900 r / min, 1000 r / min, etc. By adopting appropriate stirring conditions, the above raw materials are mixed uniformly.

[0053] In one embodiment, the hydrothermal reaction temperature is 80 to 220° C., for example, 80° C., 100° C., 150° C., 180° C., 220° C., etc.; and the hydrothermal reaction time is 6 to 18 hours, for example, 6 hours, 10 hours, 12 hours, or 18 hours. The present invention ensures the formation of an amino-functionalized MOF precursor (NH2-Mo / Fe-MOF) by ensuring appropriate hydrothermal reaction conditions.

[0054] In one embodiment, the prepared amino-modified MOF precursor has a nanorod or nanooctahedron structure, wherein the C, N, O, Fe, and Mo elements are evenly distributed in the precursor, and the nanorods and nanooctahedrons have a length of 100 nm to 2 μm and a diameter of 200 nm to 500 nm.

[0055] In one embodiment, the system after the hydrothermal reaction is cooled to room temperature, and the solids are collected and subjected to a first washing and a first drying. The first washing is performed by alternating washing with water and ethanol. The temperature of the first drying is 50 to 70°C.

[0056] In one embodiment, the ratio of the first precursor, sulfur source, base, formaldehyde, and second solvent is (0.1-2) g: (0.1-20 g): (0-2) g: (10-20) mL: (110-220) mL, for example, 0.1 g: 0.1 g: 0.01 g: 10 mL: 110 mL, 1 g: 1 g: 0.8 g: 15 mL: 150 mL, 2 g: 20 g: 2 g: 20 mL: 220 mL, etc. In one embodiment, the second solvent includes toluene and N,N-dimethylformamide; the volume ratio of toluene and N,N-dimethylformamide is (1-2): (10-20). By adopting the above appropriate ratio, a more complete reaction is ensured.

[0057] In one embodiment, the sulfur source comprises at least one of mercaptoacetic acid, thiourea, 2-mercaptoimidazole, 2-mercaptobenzimidazole, and 2,5-dimercapto-1,3,4-thiadiazole. Examples include a combination of mercaptoacetic acid and thiourea, or a combination of 2-mercaptobenzimidazole and 2,5-dimercapto-1,3,4-thiadiazole. In one embodiment, the base comprises sodium carbonate. In one embodiment, the aldehyde compound comprises formaldehyde.

[0058] In one embodiment, the first precursor is mixed with the sulfur source, alkali, formaldehyde and the second solvent by ultrasonic treatment; the ultrasonic treatment time is 20 to 40 minutes, such as 20 minutes, 30 minutes, 40 minutes, etc.

[0059] In one embodiment, the temperature of the first heat treatment is 75 to 120°C, for example, 75°C, 80°C, 90°C, 100°C, 110°C, or 120°C; the time of the first heat treatment is 8 to 24 hours, for example, 8 hours, 10 hours, 15 hours, 20 hours, or 24 hours. The first heat treatment is performed in an oil bath, and stirring is performed during the heat treatment. The present invention uses the first heat treatment under appropriate conditions to achieve a more complete reaction of the materials.

[0060] In one embodiment, the system after the first heat treatment is subjected to solid-liquid separation, and the solids are collected and subjected to a second washing and a second drying. The second washing is performed using ethanol and N,N-dimethylformamide for 2 to 4 times, respectively. The temperature of the second drying is 50 to 70°C.

[0061] In one embodiment, the mass ratio of the sulfide precursor to the selenium source is (1-5):(1-10), for example, 1:1, 2:1, 1:3, 1:5, 3:7, 5:9, 5:10, etc.

[0062] In one embodiment, the selenium source comprises elemental selenium.

[0063] In one embodiment, the temperature of the second heat treatment is 300-600°C, for example, 300°C, 350°C, 400°C, 500°C, 550°C, 600°C, etc.; the time of the second heat treatment is 1-4 hours, for example, 1 hour, 2 hours, 3 hours or 4 hours. The heating rate of the second heat treatment is 1-10°C / min, for example, 1°C / min, 3°C / min, 5°C / min, etc. The second heat treatment is carried out under protective gas conditions, for example, at least one of nitrogen and argon. In one embodiment, the second heat treatment is carried out in a tube furnace.

[0064] In a preferred embodiment, the method for preparing the negative electrode material comprises the following steps:

[0065] (a) mixing an iron salt, a molybdenum source and water to obtain a solution A, and mixing an amino ligand, an alcohol and N,N-dimethylformamide to obtain a solution B; wherein the amount ratio of the iron salt, the molybdenum source, the amino ligand, the water, the alcohol and the N,N-dimethylformamide is (0.1-10) g: (0.1-10) g: (0.1-10) g: (10-30) mL: (10-30) mL: (10-30) mL; the iron salt comprises at least one of ferric chloride, ferric nitrate and ferric sulfate; the amino ligand comprises amino At least one of terephthalic acid and aminotrimesic acid; the molybdenum source includes phosphomolybdic acid; adding solution B to solution A, stirring at a speed of 500-1000 r / min for 0.5-2 hours, and then transferring to a hydrothermal reactor for hydrothermal reaction, wherein the temperature of the hydrothermal reaction is 80-220° C., and the time of the hydrothermal reaction is 6-18 hours; cooling the system after the hydrothermal reaction to room temperature, collecting the solids and washing them alternately with deionized water and ethanol, and then drying them at 50-70° C. to obtain a first precursor;

[0066] (b) mixing the first precursor with a sulfur source, an alkali, formaldehyde, toluene, and N,N-dimethylformamide and then performing ultrasonic treatment for 20 to 40 minutes, wherein the amount ratio of the first precursor, the sulfur source, the alkali, formaldehyde, toluene, and N,N-dimethylformamide is (0.1 to 2) g: (0.1 to 20 g): (0.01 to 2) g: (10 to 20) mL: (10 to 20) mL: (10 to 200) mL, and the sulfur source includes mercaptoethyl at least one of acid, thiourea, 2-mercaptoimidazole, 2-mercaptobenzimidazole and 2,5-dimercapto-1,3,4-thiadiazole; then transferring to an oil bath for a first heat treatment, wherein the temperature of the first heat treatment is 75 to 120° C., and the time of the first heat treatment is 8 to 24 hours, performing solid-liquid separation on the system after the first heat treatment, collecting the solids and washing them with ethanol and N,N-dimethylformamide for 2 to 4 times respectively, and then drying overnight to obtain a sulfide precursor;

[0067] (3) placing the sulfide precursor into a tubular furnace, placing selenium powder upstream of the tubular furnace, and heating the temperature to 300-600°C at a rate of 1-10°C / min in an inert atmosphere for a second heat treatment, and maintaining the temperature for 1-4 hours; the mass ratio of the sulfide precursor to the selenium powder is (1-5): (1-10), thereby obtaining a negative electrode material.

[0068] According to another aspect of the present invention, the present invention also relates to a negative electrode material, the negative electrode material prepared by the negative electrode material preparation method. The shape of the negative electrode material includes at least one of a rod-shaped structure and an octahedral structure; the specific surface area of ​​the negative electrode material is 50 to 500 m 2 / g, and the specific capacity is 400~600mAh / g.

[0069] The negative electrode material of the present invention has a special structure such as a nanorod and a nanooctahedron, which can effectively alleviate its own expansion during the charge and discharge process and improve the stability of the electrode; on the other hand, the structure can shorten the Na + The transmission path accelerates ion transmission and improves rate performance.

[0070] According to another aspect of the present invention, the present invention also relates to a negative electrode sheet, comprising the negative electrode material.

[0071] In one embodiment, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode material layer contains the above-mentioned negative electrode material, a binder, and a conductive agent.

[0072] According to another aspect of the present invention, the present invention also relates to a battery comprising the negative electrode sheet.

[0073] In one embodiment, a battery includes the above-mentioned negative electrode sheet, positive electrode sheet, separator and electrolyte.

[0074] The battery of the present invention has excellent energy density and excellent cycle stability, and has excellent fast charging capability.

[0075] According to another aspect of the present invention, the present invention also relates to an electrical device including the battery, such as an electric car.

[0076] The following is further explained with reference to specific embodiments.

[0077] Example 1

[0078] A method for preparing a negative electrode material comprises the following steps:

[0079] (1) 0.27 g of ferric chloride hexahydrate, 0.2 g of phosphomolybdic acid, and 40 mL of deionized water were mixed to form solution A, and 0.1 g of aminoterephthalic acid, 20 mL of ethanol, and 20 mL of N,N-dimethylformamide were mixed to form a solution, which was then added to solution A and stirred at room temperature for 1 h to obtain a mixed system;

[0080] (2) The mixed system was transferred to a hydrothermal reactor and subjected to hydrothermal reaction at 150°C for 10 h. After cooling to room temperature, the precipitate was washed alternately with deionized water and ethanol and dried at 60°C overnight to obtain an amino-functionalized MOF precursor.

[0081] (3) 2 g of the above precursor was transferred to a flask, and 15 g of mercaptoacetic acid, 15 mL of toluene, 15 mL of formaldehyde, and 150 mL of N,N-dimethylformamide were added respectively. After ultrasonic stirring for 30 min, the mixture was transferred to an oil bath and refluxed at 90 °C for 15 h. The product was washed three times with ethanol and N,N-dimethylformamide respectively, and then dried overnight to obtain a nitrogen-doped sulfurized MOF precursor.

[0082] (4) 2 g of the nitrogen-doped sulfurized MOF precursor obtained in the above step (3) was placed in a tubular furnace, 5 g of selenium powder was placed upstream of the tubular furnace, and the temperature was raised to 400 ° C at a rate of 5 ° C / min in an inert atmosphere and maintained for 3 h. After naturally cooling to room temperature, a nanorod composite negative electrode material was obtained.

[0083] Example 2

[0084] A method for preparing a negative electrode material comprises the following steps:

[0085] (1) 0.27 g of ferric chloride hexahydrate, 0.2 g of phosphomolybdic acid, and 40 mL of deionized water were mixed to form solution A, and 0.1 g of aminotrimesic acid, 20 mL of ethanol, and 20 mL of N,N-dimethylformamide were mixed to form a solution, which was then added to solution A and stirred at room temperature for 1 h to obtain a mixed system;

[0086] (2) The mixed system was transferred to a hydrothermal reactor and subjected to hydrothermal reaction at 200°C for 6 h. After cooling to room temperature, the precipitate was washed alternately with deionized water and ethanol and dried at 60°C overnight to obtain an amino-functionalized MOF precursor;

[0087] (3) 1.5 g of the above precursor was transferred to a flask, and 20 g of thiourea, 15 mL of toluene, 15 mL of formaldehyde, and 150 mL of N,N-dimethylformamide were added respectively. After ultrasonic stirring for 30 min, the mixture was transferred to an oil bath and refluxed at 100 °C for 8 h. The product was washed three times with ethanol and N,N-dimethylformamide respectively, and then dried overnight to obtain a nitrogen-doped sulfurized MOF precursor.

[0088] (4) 2 g of the nitrogen-doped sulfide MOF precursor obtained in step (3) was placed in a tubular furnace, 5 g of selenium powder was placed upstream of the tubular furnace, and the temperature was raised to 500 ° C at a rate of 5 ° C / min in an inert atmosphere and maintained for 3 h. After naturally cooling to room temperature, an octahedral composite negative electrode material was obtained.

[0089] Example 3

[0090] A method for preparing a negative electrode material comprises the following steps:

[0091] (1) 0.27 g of ferric chloride hexahydrate, 0.2 g of phosphomolybdic acid, and 40 mL of deionized water were mixed to form solution A, and 0.1 g of aminotrimesic acid, 20 mL of ethanol, and 20 mL of N,N-dimethylformamide were mixed to form a solution, which was then added to solution A and stirred at room temperature for 1 h to obtain a mixed system;

[0092] (2) The mixed system was transferred to a hydrothermal reactor and subjected to hydrothermal reaction at 180°C for 15 h. After cooling to room temperature, the precipitate was washed alternately with deionized water and ethanol and dried at 60°C overnight to obtain an amino-functionalized MOF precursor.

[0093] (3) 1.5 g of the above precursor was transferred to a flask, and 2 g of 2,5-dimercapto-1,3,4-thiadiazole, 2 g of sodium carbonate, 15 mL of toluene, 15 mL of formaldehyde, and 150 mL of N,N-dimethylformamide were added respectively. After ultrasonic stirring for 30 min, the mixture was transferred to an oil bath and refluxed at 120 °C for 12 h. The product was washed three times with ethanol and N,N-dimethylformamide respectively and then dried overnight to obtain a nitrogen-doped sulfurized MOF precursor.

[0094] (4) 2 g of the nitrogen-doped sulfide MOF precursor obtained in step (3) was placed in a tubular furnace, 5 g of selenium powder was placed upstream of the tubular furnace, and the temperature was raised to 400 ° C at a rate of 5 ° C / min in an inert atmosphere and maintained for 6 h. After naturally cooling to room temperature, an octahedral composite negative electrode material was obtained.

[0095] Example 4

[0096] A method for preparing a negative electrode material comprises the following steps:

[0097] (1) 0.27 g of ferric chloride hexahydrate, 0.2 g of phosphomolybdic acid, and 40 mL of deionized water were mixed to form solution A, and 0.1 g of aminoterephthalic acid, 20 mL of ethanol, and 20 mL of N,N-dimethylformamide were mixed to form a solution, and then added to solution A and stirred at room temperature for 1 h to obtain a mixed system;

[0098] (2) The mixed system was transferred to a hydrothermal reactor and subjected to hydrothermal reaction at 120°C for 24 h. After cooling to room temperature, the precipitate was washed alternately with deionized water and ethanol and dried at 60°C overnight to obtain an amino-functionalized MOF precursor.

[0099] (3) 1 g of the above precursor was transferred to a flask, and 3 g of 2-mercaptoimidazole, 15 mL of toluene, 15 mL of formaldehyde, and 150 mL of N,N-dimethylformamide were added respectively. After ultrasonic stirring for 30 min, the mixture was transferred to an oil bath and refluxed at 80 °C for 24 h. The product was washed three times with ethanol and N,N-dimethylformamide respectively, and then dried overnight to obtain a nitrogen-doped sulfurized MOF precursor.

[0100] (4) 2 g of the nitrogen-doped sulfide MOF precursor obtained in step (3) was placed in a tubular furnace, 5 g of selenium powder was placed upstream of the tubular furnace, and the temperature was raised to 450 ° C at a rate of 5 ° C / min in an inert atmosphere and maintained for 3 h. After naturally cooling to room temperature, a nanorod composite negative electrode material was obtained.

[0101] Example 5

[0102] A method for preparing a negative electrode material, except that the mass of the nitrogen-doped sulfurized MOF precursor in step (4) is 1 g, other conditions are the same as those in Example 1.

[0103] Example 6

[0104] A method for preparing a negative electrode material, except that the mass of the nitrogen-doped sulfurized MOF precursor in step (4) is 4 g, and other conditions are the same as those in Example 1.

[0105] Comparative Example 1

[0106] A method for preparing a negative electrode material comprises the following steps:

[0107] (1) 0.27 g of ferric chloride hexahydrate and 40 mL of deionized water were mixed to prepare solution A, and 0.1 g of terephthalic acid, 20 mL of ethanol, and 20 mL of N,N-dimethylformamide were mixed to prepare a solution, and then added to solution A and stirred at room temperature for 1 h;

[0108] (2) The mixture was transferred to a hydrothermal reactor and subjected to hydrothermal reaction at 120°C for 24 h. After cooling to room temperature, the precipitate was washed alternately with deionized water and ethanol and dried at 60°C overnight to obtain a Fe-MOF precursor.

[0109] (3) 2 g of the above precursor was placed in a tubular furnace, and 5 g of selenium powder was placed upstream of the tubular furnace. The temperature was raised to 450 °C at a rate of 2 °C / min in an inert atmosphere and maintained for 3 h. After naturally cooling to room temperature, a FeSe2 / C nanorod composite negative electrode material was obtained.

[0110] Comparative Example 2

[0111] A method for preparing a negative electrode material, wherein the steps are the same as those in Example 1 except that phosphomolybdic acid is not added in step (1), and FeSe is obtained. x S 2-x / C nanorod composite negative electrode material.

[0112] Comparative Example 3

[0113] A method for preparing a negative electrode material, comprising the following steps: adding 0.2 g of phosphomolybdic acid in step 1, and performing the other steps in the same manner as in comparative example 1 to obtain a FeMoSe2 / C nanorod composite negative electrode material.

[0114] Experimental example

[0115] 1. Scanning electron microscope image

[0116] The negative electrode materials of Examples 1 and 2 were examined by scanning electron microscopy. The scanning electron microscopy images of the negative electrode material of Example 1 are as follows: Figure 1 shown; from Figure 1 It can be seen that the material is a nanorod structure, with the nanotubes being about 1.2 μm long and 400 nm in diameter. Figure 2 The scanning electron microscope image of the negative electrode material of Example 2 is shown in FIG. Figure 2 It can be seen that the material has an octahedral structure with an average size of about 1 μm.

[0117] 2. Battery performance test

[0118] The negative electrode materials of each embodiment and comparative example were prepared into batteries according to the following methods, and performance tests were performed.

[0119] The battery preparation method includes: mixing a negative electrode material, a conductive agent Ketjen black, and a binder polyvinylidene fluoride in a mass ratio of 8:1:1 to obtain a mixture; mixing the mixture with N-methylpyrrolidone in a mass ratio of 25:75 and stirring evenly to obtain a slurry; coating the slurry on copper foil, drying, and rolling to obtain a sodium ion battery electrode sheet with a thickness of 90-100 μm; assembling a CR2032 button-type sodium ion battery in an argon-filled glove box using the sodium ion battery electrode sheet as the negative electrode sheet, the sodium sheet as the positive electrode sheet, glass fiber as the separator, and a diethylene glycol dimethyl ether solution containing 1M NaCF3SO3 as the electrolyte. The negative electrode material is obtained from each embodiment and comparative example.

[0120] The CR2032 button sodium ion battery was tested for charge and discharge cycles at different current densities within the voltage range of 0 to 2 V. -1 The capacities and capacity retention rates obtained after the first and 500th cycles of charge-discharge tests at different current densities are shown in Table 1. The average charge capacities of 10 charge-discharge tests at different current densities are shown in Table 2. The negative electrode materials prepared in each embodiment and comparative example were applied to sodium-ion battery negative electrodes, and the electrode expansion results after 500 cycles are shown in Table 3.

[0121] Table 1 at 200mA·g -1 Results of charge and discharge tests at current density

[0122]

[0123]

[0124] Table 2 Average charge capacity retention rate after 10 charge and discharge tests at different current densities

[0125] Rate (A / g) 0.1 0.2 0.5 1 2 3 0.2 Example 1 100％ 99.32％ 98.32％ 96.86％ 95.18％ 92.95％ 98.76％ Example 2 100％ 99.16％ 97.57％ 96.44％ 94.29％ 91.39％ 98.78％ Example 3 100％ 98.88％ 97.57％ 95.75％ 93.80％ 91.96％ 98.37％ Example 4 100％ 99.13％ 97.98％ 97.19％ 95.69％ 93.63％ 99.13％ Example 5 100％ 98.98％ 97.61％ 95.78％ 93.40％ 92.06％ 98.57％ Example 6 100％ 99.01％ 97.83％ 97.04％ 95.58％ 93.49％ 98.96％ Comparative Example 1 100％ 95.30％ 88.59％ 85.81％ 78.82％ 74.15％ 80.62％ Comparative Example 2 100％ 96.02％ 93.50％ 88.70％ 82.03％ 79.79％ 86.36％ Comparative Example 3 100％ 96.34％ 116.52％ 88.69％ 83.15％ 79.92％ 85.05％

[0126] Table 3 Electrode expansion results of each battery after 500 cycles

[0127]

[0128]

[0129] As can be seen from Table 1, the negative electrode material prepared by the present invention is applied to sodium ion batteries. -1 After 500 cycles at the same current density, the charge capacity is 440 mAh g -1 Above, the capacity retention rate is ≥97%, with high energy density and excellent cycle stability.

[0130] As can be seen from Table 2, the negative electrode material prepared by the present invention has excellent rate performance and can still maintain a high capacity even at a current density of 3 A / g, indicating that the material has excellent fast charging capability.

[0131] As can be seen from Table 3, the negative electrode material prepared by the present invention has low expansion when fully charged, and the electrode sheet expands less after 500 cycles, and the surface material has excellent structural stability.

[0132] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a negative electrode material, characterized in that: The following steps are involved: A mixed system of an iron salt, a molybdenum source, an amino ligand, and a first solvent is subjected to a hydrothermal reaction to obtain a first precursor; the first precursor is mixed with a sulfur source, an alkali, an aldehyde compound, and a second solvent, and then subjected to a first heat treatment to obtain a sulfide precursor; the sulfide precursor is then mixed with a selenium source and then subjected to a second heat treatment; The mass ratio of the sulfide precursor to the selenium source is (1-5): (1-10).

2. The method for preparing the negative electrode material according to claim 1, wherein: Contains at least one of the following features (1) to (5): (1) The ratio of the iron salt, molybdenum source, amino ligand and first solvent is (0.1-10) g: (0.1-10) g: (0.1-10) g: (30-90) mL; (2) The first solvent includes water, alcohol and N,N-dimethylformamide; the volume ratio of water, alcohol and N,N-dimethylformamide is (1-3): (1-3): (1-3); (3) The iron salt includes at least one of ferric chloride, ferric nitrate and ferric sulfate; (4) The amino ligand includes at least one of aminoterephthalic acid and aminotrimesic acid; (5) The molybdenum source includes phosphomolybdic acid.

3. The method for preparing the negative electrode material according to claim 1, wherein: Contains at least one of the following features (1) to (3): (1) The mixed system is obtained by stirring the iron salt, molybdenum source, amino ligand and solvent, the stirring time is 0.5~2h; the stirring speed is 500~1000r / min; (2) The temperature of the hydrothermal reaction is 80-220°C, and the time of the hydrothermal reaction is 6-18 hours; (3) Cooling the system after the hydrothermal reaction, collecting the solids and performing a first washing and a first drying.

4. The method for preparing the negative electrode material according to claim 1, wherein: Contains at least one of the following features (1) to (5): (1) The ratio of the amount of the first precursor, the sulfur source, the base, the formaldehyde and the second solvent is (0.1-2) g: (0.1-20 g): (0-2) g: (10-20) mL: (110-220) mL; (2) The second solvent includes toluene and N,N-dimethylformamide; the volume ratio of toluene and N,N-dimethylformamide is (1-2): (10-20); (3) The sulfur source includes at least one of mercaptoacetic acid, thiourea, 2-mercaptoimidazole, 2-mercaptobenzimidazole and 2,5-dimercapto-1,3,4-thiadiazole; (4) The base includes sodium carbonate; (5) The aldehyde compound includes formaldehyde.

5. The method for preparing the negative electrode material according to claim 1, wherein: Contains at least one of the following features (1) to (3): (1) The first precursor is mixed with the sulfur source, alkali, formaldehyde and the second solvent by ultrasonic treatment; the ultrasonic treatment time is 20 to 40 minutes; (2) The temperature of the first heat treatment is 75-120°C, and the time of the first heat treatment is 8-24 hours; (3) Performing solid-liquid separation on the system after the first heat treatment, collecting the solids and performing a second washing and a second drying.

6. The method for preparing the negative electrode material according to claim 1, wherein: Contains at least one of the following features (1) to (4): (1) The selenium source includes elemental selenium; (2) The temperature of the second heat treatment is 300-600°C, and the time of the second heat treatment is 1-4 hours; (3) The heating rate of the second heat treatment is 1-10°C / min; (4) The second heat treatment is carried out under protective gas conditions.

7. A negative electrode material, characterized in that A negative electrode material prepared by the method for preparing a negative electrode material according to any one of claims 1 to 6.

8. The negative electrode material according to claim 7, characterized in that Contains at least one of the following features (1) to (2): (1) The shape of the negative electrode material includes at least one of a rod-like structure and an octahedral structure; (2) The specific surface area of ​​the negative electrode material is 50~500m 2 / g, and the specific capacity is 400~600mAh / g.

9. A negative electrode sheet, characterized in that: Comprising the negative electrode material according to claim 7 or 8.

10. A battery, characterized in that: Including the negative electrode sheet according to claim 9.

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