Composite negative electrode material, preparation method thereof and secondary battery

Abstract

The application provides a composite negative electrode material, a preparation method thereof and a secondary battery. The composite negative electrode material comprises carbon and a metal material, the metal material is dispersed in the carbon, and the mass fraction of the metal material in the composite negative electrode material is above 70 wt%. The preparation method comprises the following steps: 1) mixing a metal precursor, a carbon precursor and an inhibitor to obtain a mixed precursor; and 2) carbonizing the mixed precursor in a protective atmosphere to obtain the composite negative electrode material. The preparation method provided by the application successfully inhibits the precipitation of low-melting-point metals and oxides thereof in the high-temperature carbonization process by adding an inhibitor into the mixed precursor solution, and a composite negative electrode material with high loading of low-melting-point metals and oxides thereof, high specific capacity and good cycle stability is prepared.

Description

Technical Field

[0001] This invention belongs to the field of energy storage materials technology, and relates to a composite negative electrode material, its preparation method, and a secondary battery. Background Technology

[0002] Lithium-ion batteries possess advantages such as high energy density, wide operating voltage window, good cycle stability, low self-discharge, and no memory effect, leading to their widespread application in electric vehicles and portable electronic devices. However, the development of lithium-ion batteries faces the problem of excessive consumption and shortage of lithium resources. Compared to lithium-ion batteries, sodium-ion batteries have advantages such as abundant sodium resources and low cost, but their energy density is relatively low. Currently, the main anode material for commercially available lithium-ion batteries is graphite, but its theoretical specific capacity is only 372 mAh / g, which cannot meet the demand for developing higher energy density lithium-ion batteries. Furthermore, because sodium ions are larger than lithium ions, graphite is difficult to use as an anode material for storing sodium in sodium-ion batteries. Domestic and international research reports that low-melting-point metals and their oxides, such as tin (Sn), antimony (Sb), bismuth (Bi), tin dioxide (SnO2), tin monoxide (SnO), antimony trioxide (Sb2O3), and bismuth trioxide (Bi2O3), not only have high lithium storage specific capacity but also high sodium storage specific capacity. However, these materials exhibit significant volume expansion during charge and discharge processes when used as anode materials in lithium-ion and sodium-ion batteries, leading to rapid capacity decay. This severely reduces the cycle stability of the battery and limits the practical application of low-melting-point metals and their oxides as anode materials.

[0003] Domestic and international research indicates that the primary cause of battery capacity decay is the significant volume expansion of low-melting-point metals and their oxides during lithium insertion / extraction, leading to material breakage. Therefore, suppressing the volume expansion of low-melting-point metals and their oxides is crucial for improving cycle stability. Currently, the main methods to mitigate this volume expansion are material nanostructuring and combining these materials with active or inactive materials.

[0004] For example, CN 104466140A discloses a method for preparing nano-tin / carbon composite nanofibers using electrospinning technology. This invention prepares composite nanofibers from stannous chloride, polymethyl methacrylate, and polyacrylonitrile using electrospinning technology, then calcines them under a nitrogen atmosphere. This causes the stannous chloride to decompose into nano-tin, the polymethyl methacrylate to pyrolyze to form a porous structure, and the polyacrylonitrile to carbonize into carbon nanofibers, thus obtaining nano-tin / carbon composite nanofibers. The resulting material exhibits high sodium storage specific capacity and good cycle stability, but the tin mass fraction in the composite material prepared by this method is only 60-65%. Increasing the tin content in the composite anode material is key to further improving the specific capacity of the tin / carbon composite anode material. However, increasing the tin content leads to tin melting and precipitation during carbonization, which severely reduces the cycle stability of the anode material.

[0005] CN105118966A discloses a method for preparing SnO2 / C using a hydrothermal method. x N y / GN composite material. The nitrogen-containing diaminomaleitrile added during the preparation process will form C... x N y C x N y As reactive sites, they react with SnO2 nanocrystals, allowing SnO2 nanoparticles to be uniformly dispersed in carbon and C. x N y The resulting material exhibits a high lithium storage specific capacity, but the SnO2 mass fraction in the composite material prepared by this method is only 38%. Increasing the SnO2 content in the composite anode material is key to further improving the specific capacity of the SnO2 / carbon composite anode material. However, increasing the SnO2 content leads to the melting and precipitation of Sn generated by the carbothermic reduction reaction of SnO2 during carbonization, which severely reduces the cycle stability of the anode material. Typically, low-melting-point metals and their oxides, such as tin (Sn), antimony (Sb), bismuth (Bi), tin dioxide (SnO2), tin monoxide (SnO), antimony trioxide (Sb2O3), and bismuth trioxide (Bi2O3), and their oxides / carbon composite materials, all experience high-temperature melting and precipitation of low-melting-point metals during preparation, as well as precipitation of low-melting-point metals generated by the carbothermic reduction reaction of low-melting-point metal oxides. This reduces the lithium and sodium storage specific capacity and cycle stability of low-melting-point metal and their oxide / carbon composite anode materials.

[0006] Therefore, developing low-melting-point metal and oxide / carbon composite anode materials with high loading of low-melting-point metals and their oxides, high specific capacity, and good cycle stability is a technical challenge in the fields of lithium-ion batteries and sodium-ion batteries. Summary of the Invention

[0007] To address the aforementioned problems in the prior art, the present invention aims to provide a composite anode material, its preparation method, and a secondary battery. The composite anode material provided by the invention exhibits high loading of low-melting-point metals and their oxides, high specific capacity, and good cycle stability.

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

[0009] In a first aspect, the present invention provides a composite anode material comprising carbon and a metal material, wherein the metal material is dispersed in the carbon, and the mass fraction of the metal material in the composite anode material is above 70 wt%.

[0010] In the composite anode material provided by this invention, the mass fraction of the metal material is above 70 wt%, for example, 70 wt%, 75 wt%, 80 wt%, 85 wt%, or 90 wt%. The high metal loading in this composite anode material improves its lithium and sodium storage specific capacity and cycle stability.

[0011] In this invention, the metal element in the metal material is a low-melting-point metal, which refers to a metal with a melting point below 700°C.

[0012] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0013] As a preferred embodiment of the present invention, the mass fraction of the metal material in the composite negative electrode material is 70-90 wt%.

[0014] Preferably, the metallic material is an elemental metal and / or a metal oxide. In the composite negative electrode material provided by the present invention, the metallic material may be a single elemental metal, a metal oxide, or a mixture of both, depending on the carbonization temperature. The higher the carbonization temperature, the easier it is for oxygen to be consumed during the carbonization process, and the metallic material tends to be an elemental metal; conversely, the lower the carbonization temperature, the easier it is for oxygen to remain in the raw material, and the metallic material tends to be a metal oxide. The specific temperature point at which the composition of the metallic material changes varies depending on the raw material.

[0015] Preferably, the metallic element includes any one or a combination of at least two of tin, antimony, or bismuth.

[0016] Preferably, the metal oxide includes any one or a combination of at least two of tin dioxide, tin monoxide, antimony trioxide, or bismuth trioxide.

[0017] In the composite negative electrode material, if metal oxides are present, the mass fraction of oxygen is preferably 5 to 25 wt%, such as 5 wt%, 10 wt%, 15 wt%, 20 wt%, or 25 wt%.

[0018] In a second aspect, the present invention provides a method for preparing the composite negative electrode material as described in the first aspect, the method comprising the following steps:

[0019] (1) Mix the metal precursor, carbon precursor and inhibitor to obtain a mixed precursor;

[0020] (2) The mixed precursor described in step (1) is carbonized under a protective atmosphere to obtain the composite anode material.

[0021] In the preparation method provided by the present invention, the metal precursor is a precursor containing a low-melting-point metal, and the low-melting-point metal is defined in the same way as the low-melting-point metal in the first aspect.

[0022] The preparation method provided by this invention successfully suppresses the precipitation of low-melting-point metals and their oxides during high-temperature carbonization by adding inhibitors, thus preparing a low-melting-point metal and oxide / carbon composite material with high loading of low-melting-point metals and their oxides, high specific capacity, and good cycle stability. In the composite anode material obtained by the preparation method provided by this invention, the metal materials (metal elements and metal oxides) are uniformly dispersed in the carbon materials.

[0023] As a preferred technical solution of the present invention, the metal precursor, carbon precursor and inhibitor in step (1) are mixed in a solvent.

[0024] In the preparation method provided by this invention, the inhibitor, carbon precursor and solvent may all contribute to the presence of metal oxides in the product. That is, in the composite anode material, the oxygen element of the metal oxide comes from the reaction raw materials.

[0025] Preferably, the mass ratio of the metal precursor, carbon precursor and solvent is 1:1:10 to 10:1:10, for example 1:1:10, 2:1:10, 3:1:10, 4:1:10, 5:1:10, 6:1:10, 7:1:10, 8:1:10, 9:1:10 or 10:1:10, etc.

[0026] Preferably, the solvent is any one or a combination of at least two of water, acid, alcohol, ketone or ether.

[0027] Preferably, the metal precursor in step (1) includes any one or a combination of at least two of tin tetrachloride, tin dichloride, antimony trichloride, or bismuth trichloride.

[0028] Preferably, the carbon precursor in step (1) includes any one or a combination of at least two of glucose, sucrose, starch, cellulose, polyacrylonitrile, polyvinylpyrrolidone, polyvinylidene fluoride, polypyrrole, polyaniline or polythiophene.

[0029] As a preferred technical solution of the present invention, the inhibitor in step (1) is a nitrogen- and phosphorus-containing inhibitor.

[0030] Nitrogen and phosphorus in the inhibitor play a crucial role in its effectiveness. During carbonization, nitrogen and phosphorus elements in the inhibitor form pyridine nitrogen, pyrrole nitrogen, quaternary nitrogen, PC, PO, P=O, and other groups in the carbon material that have adsorption properties. These groups can inhibit the precipitation of low-melting-point metals at high temperatures and the precipitation of low-melting-point metals generated from the carbothermic reduction reaction of low-melting-point metal oxides through adsorption, thereby increasing the loading of low-melting-point metals and their oxides in the low-melting-point metal and their oxide / carbon composite material, and improving the lithium and sodium storage specific capacity and cycle stability of the low-melting-point metal and their oxide / carbon composite material.

[0031] Preferably, the nitrogen- and phosphorus-containing inhibitors include melamine phosphate and / or ammonium dihydrogen phosphate.

[0032] Preferably, the mass ratio of the inhibitor to the carbon precursor in step (1) is 1:10 to 1:1, for example, 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, or 1:1. In this invention, if the mass ratio of the inhibitor to the carbon precursor is too large (i.e., too much inhibitor), it will lead to uneven dispersion of low-melting-point metals and their oxides in carbon; if the mass ratio of the inhibitor to the carbon precursor is too small (i.e., too little inhibitor), it will lead to the precipitation of some low-melting-point metals and their oxides at high temperatures.

[0033] As a preferred embodiment of the present invention, the method of mixing the metal precursor, carbon precursor, and inhibitor in step (1) includes: first mixing the metal precursor and carbon precursor, and then adding the inhibitor for further mixing. The advantage of this mixing order is that it facilitates sufficient contact between the inhibitor and the metal and carbon precursors, thereby maximizing the inhibitory effect.

[0034] As a preferred technical solution of the present invention, the protective atmosphere in step (2) includes any one or a combination of at least two of nitrogen atmosphere, helium atmosphere, neon atmosphere, argon atmosphere, krypton atmosphere or xenon atmosphere.

[0035] Preferably, the carbonization temperature in step (2) is 500–1200°C, such as 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C, 1100°C, or 1200°C, and more preferably 600–1000°C. In this invention, if the carbonization temperature is too high, some low-melting-point metals and their oxides will precipitate; if the carbonization temperature is too low, nitrogen and phosphorus elements in the inhibitor will have difficulty entering the carbon material, thereby reducing the inhibition effect. In addition, the carbonization temperature also affects the form of the metal material in the prepared composite negative electrode material. The higher the carbonization temperature, the easier it is for oxygen to be consumed during the carbonization process, and the metal material tends to be a metallic element; conversely, the lower the carbonization temperature, the easier it is for oxygen to remain in the raw material, and the metal material tends to be a metal oxide. The specific temperature node that causes the metal material composition to change varies with the raw material.

[0036] Preferably, the heating rate of carbonization in step (2) is 1.0 to 10.0 °C / min, for example, 1.0 °C / min, 2.0 °C / min, 3.0 °C / min, 4.0 °C / min, 5.0 °C / min, 6.0 °C / min, 7.0 °C / min, 8.0 °C / min, 9.0 °C / min or 10.0 °C / min.

[0037] Preferably, the carbonization time in step (2) is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0038] As a preferred technical solution of the present invention, in step (2), the mixed precursor is dried before carbonization. The purpose of drying is mainly to remove the solvent.

[0039] As a further preferred embodiment of the preparation method described in this invention, the method includes the following steps:

[0040] (1) After mixing the metal precursor and carbon precursor in a solvent, nitrogen and phosphorus inhibitors are added and mixed to obtain a mixed precursor.

[0041] The mass ratio of the metal precursor, carbon precursor and solvent is 1:1:10 to 10:1:10, and the mass ratio of the inhibitor to carbon precursor is 1:10 to 1:1.

[0042] The metal precursor includes any one or a combination of at least two of tin tetrachloride, tin dichloride, antimony trichloride, or bismuth trichloride.

[0043] The carbon precursor includes any one or a combination of at least two of glucose, sucrose, starch, cellulose, polyacrylonitrile, polyvinylpyrrolidone, polyvinylidene fluoride, polypyrrole, polyaniline, or polythiophene.

[0044] The nitrogen and phosphorus-containing inhibitors include melamine phosphate and / or ammonium dihydrogen phosphate;

[0045] (2) After drying the mixed precursor described in step (1), carbonize it to 600-1000℃ for 1-3 hours under a protective atmosphere at a heating rate of 1.0-10.0℃ / min to obtain the composite anode material.

[0046] Thirdly, the present invention provides a secondary battery comprising the composite negative electrode material as described in the first aspect.

[0047] Preferably, the secondary battery is a lithium-ion battery or a sodium-ion battery.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] (1) The preparation method provided by this invention successfully inhibits the precipitation of low-melting-point metals and their oxides during high-temperature carbonization by adding nitrogen and phosphorus-containing inhibitors to the precursor mixture solution for preparing low-melting-point metal and their oxide / carbon composite materials. This results in a low-melting-point metal and their oxide / carbon composite material with high loading capacity, high specific capacity, and good cycle stability. During the carbonization process, the nitrogen and phosphorus elements in the inhibitor form pyridine nitrogen, pyrrole nitrogen, quaternary nitrogen, PC, PO, P=O, and other groups with adsorption properties in the carbon material. These groups can inhibit the precipitation of high-temperature molten low-melting-point metals and the precipitation of low-melting-point metals generated by the carbothermic reduction reaction of low-melting-point metal oxides through adsorption, thereby increasing the loading capacity of low-melting-point metals and their oxides in the low-melting-point metal and their oxide / carbon composite material and improving its lithium and sodium storage specific capacity and cycle stability.

[0050] (2) The composite anode material provided by this invention has high loading of low-melting-point metals and their oxides, high specific capacity, and good cycle stability. It achieves a reversible lithium storage specific capacity of 849.5 mAh / g and a reversible sodium storage specific capacity of 676.2 mAh / g at a current density of 0.2 A / g. For both lithium-ion and sodium-ion batteries, it retains more than 80% of its capacity after 2000 charge-discharge cycles at a current density of 5 A / g, demonstrating excellent cycle stability. Attached Figure Description

[0051] Figure 1 Transmission electron microscope (TEM) image of tin and its oxide / carbon composite anode material prepared in Example 1 of this invention;

[0052] Figure 2 The image shows the XRD pattern of the tin and its oxide / carbon composite anode material prepared in Example 1 of this invention.

[0053] Figure 3 Thermogravimetric curves of tin and its oxide / carbon composite anode materials prepared in Example 1 of this invention;

[0054] Figure 4 The rate performance diagram of the tin and its oxide / carbon composite anode material prepared in Example 1 of this invention is shown.

[0055] Figure 5 The diagram shows the cycle performance of the tin and its oxide / carbon composite anode material prepared in Example 1 of this invention. Detailed Implementation

[0056] To better illustrate the present invention and facilitate understanding of its technical solutions, the present invention will be further described in detail below. However, the following embodiments are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0057] The following are typical but non-limiting embodiments of the present invention:

[0058] Example 1

[0059] In this embodiment, the composite anode material is prepared according to the following method:

[0060] First, tin tetrachloride pentahydrate, sucrose, and pure water were mixed at a mass ratio of 10:1:10 and stirred for 1 hour. Then, melamine phosphate was added to the mixed precursor solution at a mass ratio of melamine phosphate to sucrose of 1:1, and stirred for 1 hour. The mixed solution was dried in an oven at 120°C, then placed in a box furnace, nitrogen gas was introduced, and the temperature was increased to 800°C at a rate of 2°C / min, held at that temperature for 1 hour, and then naturally cooled to room temperature to obtain tin and its oxide / carbon composite anode material.

[0061] The composite anode material prepared in this embodiment includes carbon and metal materials (tin, tin monoxide and tin dioxide), wherein the metal materials are dispersed in carbon, and the mass fraction of the metal materials in the composite anode material is 89.9 wt%, and the mass fraction of oxygen in the composite anode material is 19.1 wt%.

[0062] The performance test results of the composite anode material prepared in this embodiment are shown in Tables 1 and 2.

[0063] Figure 1 This is a transmission electron microscope (TEM) image of the tin and its oxide / carbon composite anode material in this embodiment. From... Figure 1As can be seen, tin and its oxide nanoparticles with an average particle size of approximately 5 nm are uniformly dispersed in the carbon material without melting and precipitating due to high-temperature carbonization. This is mainly because during the carbonization process, the nitrogen and phosphorus elements in the inhibitor melamine phosphate form pyridine nitrogen, pyrrole nitrogen, quaternary nitrogen, PC, PO, P=O, and other groups with adsorption properties in the carbon material. These groups can inhibit the precipitation of molten tin and its oxides at high temperatures through adsorption.

[0064] Figure 2 This is the XRD pattern of the tin and its oxide / carbon composite anode material in this embodiment. From... Figure 2 As can be seen, the characteristic peak positions of tin and its oxide / carbon composite anode materials correspond to those of the tin standard card JCPDS 4-673. The broad characteristic peak near 24° indicates that the carbon material in the tin and its oxide / carbon composite anode materials is amorphous carbon.

[0065] Figure 3 This is the thermogravimetric curve of the tin and its oxide / carbon composite anode material in this embodiment. From... Figure 3 As can be seen, the mass fraction of tin and its oxides in the tin and its oxides / carbon composite anode material is 89.9%.

[0066] Figure 4 This is a rate performance diagram of the tin and its oxide / carbon composite anode material in this embodiment. From... Figure 4 As can be seen, tin and its oxide / carbon composite anode materials have a reversible lithium storage capacity of up to 849.5 mAh / g and a reversible sodium storage capacity of up to 676.2 mAh / g at a current density of 0.2 A / g, and still have a reversible lithium storage capacity of up to 221.6 mAh / g and a reversible sodium storage capacity of up to 261.0 mAh / g at a current density of 5 A / g.

[0067] Figure 5 This is a cycle performance diagram of the tin and its oxide / carbon composite anode material in this embodiment. From... Figure 5 As can be seen, tin and its oxide / carbon composite anode materials still have a capacity retention rate of up to 80% after 2000 charge-discharge cycles at a current density of 5A / g, demonstrating good cycle stability.

[0068] Example 2

[0069] In this embodiment, the composite anode material is prepared according to the following method:

[0070] First, tin tetrachloride pentahydrate, sucrose, and pure water were mixed at a mass ratio of 1:1:10 and stirred for 1 hour. Then, melamine phosphate was added to the mixed precursor solution at a mass ratio of melamine phosphate to sucrose of 1:1, and stirred for 1 hour. The mixed solution was dried in an oven at 120°C, then placed in a box furnace, nitrogen gas was introduced, and the temperature was increased to 800°C at a rate of 2°C / min, held at that temperature for 1 hour, and then naturally cooled to room temperature to obtain tin and its oxide / carbon composite anode material.

[0071] The composite anode material prepared in this embodiment includes carbon and metal materials (tin, tin monoxide and tin dioxide), wherein the metal materials are dispersed in carbon, and the mass fraction of the metal materials in the composite anode material is 70.2 wt%, and the mass fraction of oxygen in the composite anode material is 14.9 wt%.

[0072] The performance test results of the composite anode material prepared in this embodiment are shown in Tables 1 and 2.

[0073] Example 3

[0074] In this embodiment, the composite anode material is prepared according to the following method:

[0075] First, bismuth trichloride, glucose, and pure water were mixed at a mass ratio of 4:1:10 and stirred for 1 hour. Then, ammonium dihydrogen phosphate was added to the mixed precursor solution at a mass ratio of 1:5 to ammonium dihydrogen phosphate, and stirred for 1 hour. The mixed solution was dried in an oven at 120°C, then placed in a box furnace, purged with argon gas, and heated to 500°C at a rate of 1°C / min, held at that temperature for 3 hours, and then naturally cooled to room temperature to obtain bismuth and its oxide / carbon composite anode material.

[0076] The composite anode material prepared in this embodiment includes carbon and metal materials (bismuth and bismuth trioxide), wherein the metal materials are dispersed in carbon. In the composite anode material, the mass fraction of the metal materials is 73.9 wt%, and the mass fraction of oxygen in the composite anode material is 10.1 wt%.

[0077] The performance test results of the composite anode material prepared in this embodiment are shown in Tables 1 and 2.

[0078] Example 4

[0079] In this embodiment, the composite anode material is prepared according to the following method:

[0080] First, bismuth trichloride, glucose, and pure water were mixed at a mass ratio of 6:1:10 and stirred for 2 hours. Then, ammonium dihydrogen phosphate was added to the mixed precursor solution at a mass ratio of 1:10 to ammonium dihydrogen phosphate, and stirred for 2 hours. The mixed solution was dried in an oven at 120°C, then placed in a box furnace, purged with argon gas, and heated to 1200°C at a heating rate of 10°C / min, held at that temperature for 3 hours, and then naturally cooled to room temperature to obtain the bismuth / carbon composite anode material.

[0081] The composite anode material prepared in this embodiment includes carbon and a metal material (bismuth), wherein the metal material is dispersed in the carbon, and the mass fraction of the metal material in the composite anode material is 89.8 wt%, and the mass fraction of oxygen in the composite anode material is 0.

[0082] The performance test results of the composite anode material prepared in this embodiment are shown in Tables 1 and 2.

[0083] Example 5

[0084] In this embodiment, the composite anode material is prepared according to the following method:

[0085] First, antimony trichloride, cellulose, and pure water were mixed at a mass ratio of 8:1:10 and stirred for 1 hour. Then, ammonium dihydrogen phosphate was added to the mixed precursor solution at a mass ratio of melamine phosphate to cellulose of 1:6, and stirred for 1 hour. The mixed solution was dried in an oven at 120°C, then placed in a box furnace, purged with argon gas, and heated to 1000°C at a heating rate of 8°C / min, held at that temperature for 2 hours, and then naturally cooled to room temperature to obtain the antimony / carbon composite anode material.

[0086] The composite anode material prepared in this embodiment includes carbon and a metal material (antimony), wherein the metal material is dispersed in the carbon, and the mass fraction of the metal material in the composite anode material is 89.2 wt%, and the mass fraction of oxygen in the composite anode material is 0.

[0087] The performance test results of the composite anode material prepared in this embodiment are shown in Tables 1 and 2.

[0088] Example 6

[0089] In this embodiment, the composite anode material is prepared according to the following method:

[0090] First, antimony trichloride, polyvinylpyrrolidone, and ethanol were mixed at a mass ratio of 3:1:10 and stirred for 1 hour. Then, ammonium dihydrogen phosphate was added to the mixed precursor solution at a mass ratio of melamine phosphate to cellulose of 1:3, and stirred for 1 hour. The mixed solution was dried in an oven at 120°C, then placed in a box furnace, purged with argon gas, and heated to 600°C at a heating rate of 4°C / min, held at that temperature for 2 hours, and then naturally cooled to room temperature to obtain the antimony and its oxide / carbon composite anode material.

[0091] The composite anode material prepared in this embodiment includes carbon and metal materials (antimony and antimony trioxide), wherein the metal materials are dispersed in carbon, and the mass fraction of the metal materials in the composite anode material is 80.3 wt%, and the mass fraction of oxygen in the composite anode material is 13.2 wt%.

[0092] The performance test results of the composite anode material prepared in this embodiment are shown in Tables 1 and 2.

[0093] Example 7

[0094] Except for the mass ratio of melamine phosphate to sucrose of 1:0.8, the operating conditions and raw materials in this embodiment are the same as in Example 1.

[0095] The composite anode material prepared in this embodiment includes carbon and metal materials (tin, tin monoxide, and tin dioxide), wherein the metal materials are dispersed in carbon, and the mass fraction of the metal materials in the composite anode material is 85.6 wt%, and the mass fraction of oxygen in the composite anode material is 15.2 wt%.

[0096] The performance test results of the composite anode material prepared in this embodiment are shown in Tables 1 and 2.

[0097] Example 8

[0098] Except for the mass ratio of melamine phosphate to sucrose of 1:12, the other operating conditions and raw materials in this embodiment are the same as in Example 1.

[0099] The composite anode material prepared in this embodiment includes carbon and metal materials (tin, tin monoxide and tin dioxide), wherein the metal materials are dispersed in carbon, and the mass fraction of the metal materials in the composite anode material is 82.3 wt%, and the mass fraction of oxygen in the composite anode material is 12.5 wt%.

[0100] The performance test results of the composite anode material prepared in this embodiment are shown in Tables 1 and 2.

[0101] Comparative Example 1

[0102] Except for the absence of melamine phosphate, the operating conditions and raw materials in this comparative example are the same as those in Example 1.

[0103] The composite anode material prepared in this comparative example includes carbon and metal materials (tin, tin monoxide, and tin dioxide), wherein the metal materials are dispersed in carbon, and the mass fraction of the metal materials in the composite anode material is 78.2 wt%, and the mass fraction of oxygen in the composite anode material is 10.2 wt%.

[0104] The performance test results of the composite anode material prepared in this comparative example are shown in Tables 1 and 2.

[0105] Test methods

[0106] Lithium-ion half-cell test:

[0107] The composite negative electrode materials prepared in each embodiment and comparative example were used as active materials, SBR+CMC as binders, and conductive carbon black was added. After stirring and slurry preparation, the mixture was coated onto copper foil and finally dried and rolled to obtain electrode sheets. The ratio of active material: conductive agent: binder was 85:15:10. A lithium metal sheet was used as the counter electrode, PP as the separator, and LiPF6 / EC+DEC+DMC (EC, DEC, and DMC volume ratio of 1:1:1) as the electrolyte. Simulated batteries were assembled in an argon-filled glove box. The electrochemical performance of the coin cells was tested using a Blue Electric 5V / 10mA battery tester.

[0108] The reversible lithium storage specific capacity was tested by charging and discharging at a current density of 0.2 A / g.

[0109] The capacity retention rate was tested after 2000 charge-discharge cycles at a current density of 5 A / g.

[0110] Table 1. Test results of lithium-ion half-cells

[0111]

[0112] Sodium-ion half-cell test:

[0113] The composite negative electrode materials prepared in each embodiment and comparative example were used as active materials, SBR+CMC as binders, and conductive carbon black was added. After stirring and slurry preparation, the mixture was coated onto copper foil, and finally dried and rolled to obtain negative electrode sheets. The ratio of active material: conductive agent: binder was 85:15:10. A sodium metal sheet was used as the counter electrode, PP as the separator, and NaPF6 / EC+DMC (EC and DMC volume ratio of 1:1) as the electrolyte. Simulated batteries were assembled in an argon-filled glove box. The electrochemical performance of the coin cells was tested using a Blue Electric 5V / 10mA battery tester.

[0114] The reversible sodium storage specific capacity was tested by charging and discharging at a current density of 0.2 A / g.

[0115] The capacity retention rate was tested after 2000 charge-discharge cycles at a current density of 5 A / g.

[0116] Table 2. Test results of sodium-ion batteries

[0117]

[0118] Based on the above examples and comparative examples, it can be seen that Examples 1-6 successfully suppressed the precipitation of low-melting-point metals and their oxides during high-temperature carbonization by adding nitrogen and phosphorus-containing inhibitors to the precursor mixture solution for preparing low-melting-point metal and their oxide / carbon composite materials, thus preparing low-melting-point metal and their oxide / carbon composite materials with high loading of low-melting-point metals and their oxides, high specific capacity and good cycle stability.

[0119] The excessive amount of inhibitor used in Example 7 resulted in uneven dispersion of low-melting-point metals and their oxides in carbon, thereby reducing the specific capacity and cycle stability of the composite anode.

[0120] The amount of inhibitor used in Example 8 was too low, which led to the precipitation of some low-melting-point metals and their oxides at high temperatures, thereby reducing the specific capacity and cycle stability of the composite anode.

[0121] Comparative Example 1 did not use inhibitors, which led to the precipitation of a large amount of low-melting-point metals and their oxides at high temperatures, thereby reducing the specific capacity and cycle stability of the composite anode.

[0122] The applicant declares that the detailed process equipment and process flow of this invention are illustrated through the above embodiments, but this invention is not limited to the above detailed process equipment and process flow, that is, it does not mean that this invention must rely on the above detailed process equipment and process flow to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the products of this invention, additions of auxiliary components, and selection of specific methods, all fall within the protection scope and disclosure scope of this invention.

Claims

1. A composite negative electrode material, characterized in that, The composite anode material includes carbon and metal materials, wherein the metal materials are dispersed in the carbon, and the mass fraction of the metal materials in the composite anode material is above 70 wt%. The metallic material is a metallic element and / or a metallic oxide, wherein the metallic element includes any one or a combination of at least two of tin, antimony or bismuth, and the metallic oxide includes any one or a combination of at least two of tin dioxide, tin monoxide, antimony trioxide or bismuth trioxide. The composite anode material is prepared by the following method, the method comprising: (1) Mixing a metal precursor, a carbon precursor and an inhibitor to obtain a mixed precursor; wherein the mass ratio of the inhibitor to the carbon precursor is 1:10 to 1:1, and the inhibitor is a nitrogen- and phosphorus-containing inhibitor; the nitrogen- and phosphorus-containing inhibitor includes melamine phosphate and / or ammonium dihydrogen phosphate. (2) Carbonize the mixed precursor described in step (1) under a protective atmosphere to obtain the composite anode material.

2. The composite negative electrode material according to claim 1, characterized in that, In the composite anode material, the mass fraction of the metal material is 70~90 wt%.

3. A method for preparing the composite negative electrode material as described in claim 1 or 2, characterized in that, The method includes the following steps: (1) Mix the metal precursor, carbon precursor and inhibitor to obtain a mixed precursor; wherein the mass ratio of the inhibitor to the carbon precursor is 1:10 to 1:1, and the inhibitor is a nitrogen and phosphorus-containing inhibitor. (2) Carbonize the mixed precursor described in step (1) under a protective atmosphere to obtain the composite anode material.

4. The preparation method according to claim 3, characterized in that, In step (1), the metal precursor, carbon precursor and inhibitor are mixed in a solvent.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the metal precursor, carbon precursor and solvent is 1:1:10 to 10:1:

10.

6. The preparation method according to claim 4, characterized in that, The solvent is any one or a combination of at least two of water, acid, alcohol, ketone or ether.

7. The preparation method according to claim 3, characterized in that, The metal precursor in step (1) includes any one or a combination of at least two of tin tetrachloride, tin dichloride, antimony trichloride, or bismuth trichloride.

8. The preparation method according to claim 3, characterized in that, The carbon precursor in step (1) includes any one or a combination of at least two of glucose, sucrose, starch, cellulose, polyacrylonitrile, polyvinylpyrrolidone, polyvinylidene fluoride, polypyrrole, polyaniline or polythiophene.

9. The method according to claim 3, characterized in that, The method of mixing the metal precursor, carbon precursor and inhibitor in step (1) includes: first mixing the metal precursor and carbon precursor, and then adding the inhibitor for mixing.

10. The method according to claim 3, characterized in that, The protective atmosphere in step (2) includes any one or a combination of at least two of the following: nitrogen atmosphere, helium atmosphere, neon atmosphere, argon atmosphere, krypton atmosphere or xenon atmosphere.

11. The preparation method according to claim 3, characterized in that, The carbonization temperature in step (2) is 500~1200℃.

12. The preparation method according to claim 11, characterized in that, The carbonization temperature in step (2) is 600~1000℃.

13. The preparation method according to claim 3, characterized in that, The heating rate for carbonization in step (2) is 1.0~10.0℃ / min.

14. The preparation method according to claim 3, characterized in that, The carbonization time in step (2) is 1 to 3 hours.

15. The preparation method according to claim 3, characterized in that, In step (2), the mixed precursor is dried before carbonization.

16. The preparation method according to claim 3, characterized in that, The method includes the following steps: (1) After mixing the metal precursor and carbon precursor in a solvent, nitrogen and phosphorus inhibitors are added and mixed to obtain a mixed precursor; The mass ratio of the metal precursor, the carbon precursor and the solvent is 1:1:10 to 10:1:

10. The metal precursor includes any one or a combination of at least two of tin tetrachloride, tin dichloride, antimony trichloride, or bismuth trichloride. The carbon precursor includes any one or a combination of at least two of glucose, sucrose, starch, cellulose, polyacrylonitrile, polyvinylpyrrolidone, polyvinylidene fluoride, polypyrrole, polyaniline, or polythiophene. (2) After drying the mixed precursor described in step (1), the temperature is increased to 600-1000℃ for 1-3 hours under a protective atmosphere at a heating rate of 1.0-10.0℃ / min to obtain the composite anode material.

17. A secondary battery, characterized in that, The secondary battery comprises the composite negative electrode material as described in claim 1 or 2.

18. The secondary battery according to claim 17, characterized in that, The secondary battery is a lithium-ion battery or a sodium-ion battery.

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