阅读说明：本技术 一种复合负极材料及其制备方法和二次电池 (Composite negative electrode material, preparation method thereof and secondary battery ) 是由 杨程 汪福明 徐晓东 任建国 于 2019-11-27 设计创作，主要内容包括：本发明提供了一种复合负极材料及其制备方法和二次电池。所述复合负极材料包括碳和金属材料,所述金属材料分散在碳中,所述复合负极材料中,金属材料的质量分数在70wt％以上。所述制备方法包括：1)将金属前驱体、碳前驱体与抑制剂混合,得到混合前驱体；2)将混合前驱体在保护性气氛下碳化,得到所述复合负极材料。本发明提供的制备方法通过在前驱体混合溶液中加入抑制剂成功抑制了在高温碳化过程中低熔点金属及其氧化物的析出,制备出具有高的低熔点金属及其氧化物负载量、高比容量和良好的循环稳定性的复合负极材料。(The invention 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, wherein the metal material is dispersed in the carbon, and the mass fraction of the metal material in the composite negative electrode material is more than 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; 2) and carbonizing the mixed precursor in a protective atmosphere to obtain the composite negative electrode material. The preparation method provided by the invention successfully inhibits the precipitation of low-melting-point metal and oxides thereof in the high-temperature carbonization process by adding the inhibitor into the precursor mixed solution, and prepares the composite negative electrode material with high loading capacity, high specific capacity and good cycling stability of the low-melting-point metal and the oxides thereof.)

1. The composite negative electrode material is characterized by 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 negative electrode material is more than 70 wt%.

2. The composite anode material according to claim 1, wherein the mass fraction of the metal material in the composite anode material is 70-90 wt%;

preferably, the metal material is a metal simple substance and/or a metal oxide;

preferably, the elemental metal comprises any one of tin, antimony or bismuth or a combination of at least two of the tin, antimony and bismuth;

preferably, the metal oxide comprises any one of tin dioxide, tin monoxide, antimony trioxide or bismuth trioxide or a combination of at least two of the foregoing.

3. A method for preparing the composite anode material according to claim 1 or 2, comprising the steps of:

(1) mixing a metal precursor, a carbon precursor and an inhibitor to obtain a mixed precursor;

(2) and (2) carbonizing the mixed precursor in the step (1) in a protective atmosphere to obtain the composite negative electrode material.

4. The method according to claim 3, wherein the metal precursor, the carbon precursor and the inhibitor of step (1) are mixed in a solvent;

preferably, the mass ratio of the metal precursor to the carbon precursor to the solvent is 1:1: 10-10: 1: 10;

preferably, the solvent is any one of water, acid, alcohol, ketone or ether or a combination of at least two of the above;

preferably, the metal precursor in step (1) comprises any one of tin tetrachloride, tin dichloride, antimony trichloride or bismuth trichloride or a combination of at least two of the tin tetrachloride, the tin dichloride, the antimony trichloride or the bismuth trichloride;

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

5. The method according to claim 3 or 4, wherein the inhibitor in step (1) is a nitrogen-and phosphorus-containing inhibitor;

preferably, the nitrogen and phosphorus containing inhibitor comprises melamine phosphate and/or ammonium dihydrogen phosphate;

preferably, the mass ratio of the inhibitor to the carbon precursor in the step (1) is 1: 10-1: 1.

6. The method of any one of claims 3-5, wherein the step (1) of mixing the metal precursor, the carbon precursor, and the inhibitor comprises: the metal precursor and the carbon precursor are mixed, and then the inhibitor is added and mixed.

7. The method according to any one of claims 3 to 6, wherein the protective atmosphere of step (2) comprises any one of a nitrogen atmosphere, a helium atmosphere, a neon atmosphere, an argon atmosphere, a krypton atmosphere, or a xenon atmosphere, or a combination of at least two thereof;

preferably, the carbonization temperature in the step (2) is 500-1200 ℃, preferably 600-1000 ℃;

preferably, the temperature rise rate of the carbonization in the step (2) is 1.0-10.0 ℃/min;

preferably, the carbonization time in the step (2) is 1-3 h.

8. The production method according to any one of claims 3 to 7, wherein in the step (2), the mixed precursor is dried before carbonization.

9. The method for preparing according to any one of claims 3 to 8, characterized in that it comprises the steps of:

(1) mixing a metal precursor and a carbon precursor in a solvent, and adding a nitrogen and phosphorus-containing inhibitor for mixing to obtain a mixed precursor;

the mass ratio of the metal precursor to the carbon precursor to the solvent is 1:1: 10-10: 1:10, and the mass ratio of the inhibitor to the carbon precursor is 1: 10-1: 1;

the metal precursor comprises any one or the combination of at least two of stannic chloride, antimony trichloride or bismuth trichloride;

the carbon precursor comprises any one or the combination of at least two of glucose, sucrose, starch, cellulose, polyacrylonitrile, polyvinylpyrrolidone, polyvinylidene fluoride, polypyrrole, polyaniline or polythiophene;

the nitrogen and phosphorus containing inhibitor comprises melamine phosphate and/or ammonium dihydrogen phosphate;

(2) and (2) drying the mixed precursor in the step (1), heating to 600-1000 ℃ at a heating rate of 1.0-10.0 ℃/min in a protective atmosphere, and carbonizing for 1-3 h to obtain the composite negative electrode material.

10. A secondary battery comprising the composite anode material according to claim 1 or 2;

preferably, the secondary battery is a lithium ion battery or a sodium ion battery.

Technical Field

The invention belongs to the technical field of energy storage materials, and relates to a composite negative electrode material, a preparation method thereof and a secondary battery.

Background

Lithium ion batteries have the advantages of high energy density, wide operating voltage window, good cycling stability, small self-discharge, no memory effect, and the like, and thus are widely used 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 with lithium ion batteries, sodium ion batteries have the advantages of abundant sodium resource reserves, low price and the like, but the energy density of the sodium ion batteries is relatively low. At present, the commercial lithium ion battery cathode material is mainly graphite, but the theoretical specific capacity of the lithium ion battery cathode material is only 372mAh/g, and the lithium ion battery cathode material cannot meet the requirement of developing a lithium ion battery with higher energy density. Meanwhile, since the size of sodium ions is larger than that of lithium ions, graphite is difficult to be used as a negative electrode material of a sodium ion battery to store sodium. The research reports at home and abroad that tin (Sn), antimony (Sb), bismuth (Bi) and stannic oxide (SnO)₂) Tin monoxide (SnO), antimony trioxide (Sb)₂O₃) Bismuth trioxide (Bi)₂O₃) The low-melting point metal and the oxide thereof not only have very high lithium storage specific capacity, but also have very high sodium storage specific capacity. However, these materials, as negative electrode materials for lithium ion batteries and sodium ion batteries, have severe volume expansion during charging and discharging processes, resulting in rapid decay of battery capacity. This severely reduces the cycling stability of the cell and limits the practical application of low melting point metals and their oxide negative electrode materials.

Domestic and foreign researches show that the main reason of the capacity attenuation of the battery is that the large volume expansion of the low-melting-point metal and the oxide negative electrode material thereof causes the material to be crushed when lithium is de-intercalated. Therefore, suppressing the volume expansion of low melting point metals and their oxides is the key to improving the cycle stability. Currently, the volume expansion of low melting point metals and their oxides is mitigated mainly by material nanocrystallization and compounding of materials with active or inactive materials.

For example, CN 104466140a discloses a method for preparing nano tin/carbon composite nanofibers by using an electrostatic spinning technology, in which stannous chloride, polymethyl methacrylate and polyacrylonitrile are prepared into composite nanofibers by the electrostatic spinning technology, and then calcined in a nitrogen atmosphere to decompose stannous chloride into nano tin, so that polymethyl methacrylate is pyrolyzed to form a porous structure, and polyacrylonitrile is carbonized into carbon nanofibers, thereby obtaining the nano tin/carbon composite nanofibers. The obtained material has high sodium storage specific capacity and good cycling stability, but the mass fraction of tin in the composite material prepared by the method is only 60-65%. The key for further improving the specific capacity of the tin/carbon composite negative electrode material is to improve the content of tin in the composite negative electrode material. However, an increase in the tin content causes melting-out of tin during carbonization, which seriously decreases the cycle stability of the negative electrode material.

CN105118966A discloses SnO prepared by hydrothermal method₂/C_xN_ya/GN composite material. The diaminomaleonitrile containing nitrogen element added in the preparation process will form C_xN_y。C_xN_yAs reactive sites with SnO₂Reacting the nano-crystals to obtain SnO₂The nano particles are uniformly dispersed in the carbon and C_xN_yIn (1). The obtained material has high lithium storage specific capacity, but SnO in the composite material prepared by the method₂The mass fraction of (a) is only 38%. Enhanced SnO₂The content of the composite negative electrode material is further increased by SnO₂The specific capacity of the/carbon composite negative electrode material is critical. However, SnO₂The increase in the content results in SnO₂The melting and precipitation of Sn generated through the carbothermic reduction reaction during the carbonization process may seriously degrade the cycle stability of the anode material. Typically, tin (Sn), antimony (Sb), bismuth (Bi), tin dioxide (SnO)₂) Tin monoxide (SnO), antimony trioxide (Sb)₂O₃) Bismuth trioxide (Bi)₂O₃) The low-melting-point metal and the oxide/carbon composite material thereof are melted at high temperature during the preparation process, and the low-melting-point metal oxideAnd (4) precipitating low-melting-point metal generated through carbothermic reduction reaction. This reduces the lithium and sodium storage specific capacity and cycling stability of the low melting point metal and its oxide/carbon composite negative electrode material.

Therefore, the research and development of low-melting-point metal and oxide/carbon composite negative electrode materials thereof with high low-melting-point metal and oxide loading capacity, high specific capacity and good cycling stability are technical problems in the fields of lithium ion batteries and sodium ion batteries.

Disclosure of Invention

In view of the above problems in the prior art, an object of the present invention is to provide a composite anode material, a method for preparing the same, and a secondary battery. The composite negative electrode material provided by the invention has high low-melting-point metal and oxide loading capacity thereof, high specific capacity and good cycling stability.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a composite anode material, which includes 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 70 wt% or more.

In the composite anode material provided by the invention, the mass fraction of the metal material is more than 70 wt%, such as 70 wt%, 75 wt%, 80 wt%, 85 wt% or 90 wt%. The high metal material loading in the composite negative electrode material improves the lithium storage and sodium storage specific capacity and the cycling stability of the composite negative electrode material.

In the present invention, the metal element in the metal material is a low melting point metal, and the low melting point metal is a metal having a melting point of 700 ℃ or lower.

The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.

As a preferable technical scheme of the invention, in the composite negative electrode material, the mass fraction of the metal material is 70-90 wt%.

Preferably, the metal material is a simple metal and/or a metal oxide. In the composite cathode material provided by the invention, the metal material may be a single metal simple substance, or may be a metal oxide, or a mixture of the two, depending on the carbonization temperature, the higher the carbonization temperature is, the more easily the oxygen element is consumed in the carbonization process, and the metal material tends to be a metal simple substance; on the contrary, the lower the carbonization temperature is, the more easily the oxygen element remains in the raw material, and the metal material tends to be a metal oxide, so that the specific temperature node at which the composition of the metal material changes varies from raw material to raw material.

Preferably, the elemental metal comprises any one of tin, antimony or bismuth or a combination of at least two of the two.

Preferably, the metal oxide comprises any one of tin dioxide, tin monoxide, antimony trioxide or bismuth trioxide or a combination of at least two of the foregoing.

In the composite negative electrode material, if a metal oxide is present, the mass fraction of the oxygen element is preferably 5 to 25 wt%, for example, 5 wt%, 10 wt%, 15 wt%, 20 wt%, or 25 wt%.

In a second aspect, the present invention provides a method for preparing a composite anode material according to the first aspect, the method comprising the steps of:

(1) mixing a metal precursor, a carbon precursor and an inhibitor to obtain a mixed precursor;

(2) and (2) carbonizing the mixed precursor in the step (1) in a protective atmosphere to obtain the composite negative electrode material.

In the preparation method provided by the present invention, the metal precursor is a precursor containing a low-melting-point metal, and the definition of the low-melting-point metal is the same as that of the low-melting-point metal in the first aspect.

According to the preparation method provided by the invention, the inhibitor is added, so that the precipitation of the low-melting-point metal and the oxide thereof in the high-temperature carbonization process is successfully inhibited, and the low-melting-point metal and the oxide/carbon composite material thereof with high loading capacity, high specific capacity and good cycle stability are prepared. In the composite negative electrode material obtained by the preparation method provided by the invention, metal materials (metal simple substances and metal oxides) are uniformly dispersed in the carbon material.

As a preferred embodiment of the present invention, the metal precursor, the carbon precursor and the inhibitor in step (1) are mixed in a solvent.

In the preparation method provided by the invention, the inhibitor, the carbon precursor and the solvent can enable the product to contain the metal oxide, namely, in the composite negative electrode material, the oxygen element of the metal oxide is derived from the reaction raw material.

Preferably, the mass ratio of the metal precursor, the carbon precursor and the 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.

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

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

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

As a preferable technical scheme of the invention, the inhibitor in the step (1) is an inhibitor containing nitrogen and phosphorus.

The nitrogen and phosphorus in the inhibitor play a key role in its functioning. Nitrogen and phosphorus in the inhibitor can form pyridine nitrogen, pyrrole nitrogen, quaternary nitrogen, P-C, P-O, P ═ O and other groups with adsorption effect in the carbon material during carbonization. The groups can inhibit the precipitation of low-melting-point metal molten at high temperature and the precipitation of low-melting-point metal generated by low-melting-point metal oxide through carbothermic reduction reaction through adsorption, thereby improving the loading capacity of the low-melting-point metal and the low-melting-point metal oxide in the low-melting-point metal and the low-melting-point metal oxide/carbon composite material, and improving the lithium storage capacity, the sodium storage capacity and the cycling stability of the low-melting-point metal and the low-melting-point metal oxide/carbon composite material.

Preferably, the nitrogen and phosphorus containing inhibitor comprises melamine phosphate and/or ammonium dihydrogen phosphate.

Preferably, the mass ratio of the inhibitor to the carbon precursor in the step (1) is 1:10 to 1:1, such as 1:10, 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, or 1: 1. In the present invention, if the mass ratio of the inhibitor to the carbon precursor is too large (i.e., the inhibitor is too much), uneven dispersion of the low melting point metal and its oxide in the carbon is caused; if the mass ratio of the inhibitor to the carbon precursor is too small (i.e., the inhibitor is too small), precipitation of low melting point metals and oxides thereof at high temperatures may result.

As a preferred embodiment of the present invention, the method for mixing a metal precursor, a carbon precursor and an inhibitor in step (1) comprises: the metal precursor and the carbon precursor are mixed, and then the inhibitor is added and mixed. The advantage of using this mixing sequence is that it facilitates adequate contact of the inhibitor with the metal precursor and the carbon precursor, thereby allowing the inhibition to be fully performed.

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

Preferably, the carbonization temperature in step (2) is 500-1200 ℃, such as 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃ or 1200 ℃, preferably 600-1000 ℃. In the invention, if the carbonization temperature is too high, partial low-melting-point metal and oxide thereof can be precipitated; if the carbonization temperature is too low, nitrogen and phosphorus elements in the inhibitor are difficult to enter the carbon material, and the inhibition effect is reduced. In addition, the existence form of the metal material in the prepared composite anode material is influenced by the carbonization temperature, the higher the carbonization temperature is, the more easily the oxygen element is consumed in the carbonization process, and the metal material tends to be a metal simple substance; on the contrary, the lower the carbonization temperature is, the more easily the oxygen element remains in the raw material, and the metal material tends to be a metal oxide, so that the specific temperature node at which the composition of the metal material changes varies from raw material to raw material.

Preferably, the temperature rise rate of the carbonization in the step (2) is 1.0-10.0 ℃/min, such as 1.0 ℃/min, 2.0 ℃/min, 3.0 ℃/min, 4.0 ℃/min, 5.0 ℃/min, 6.0 ℃/min, 7.0 ℃/min, 8.0 ℃/min, 9.0 ℃/min or 10.0 ℃/min, and the like.

Preferably, the carbonization time in the step (2) is 1-3 h, such as 1h, 1.5h, 2h, 2.5h or 3 h.

As a preferable technical solution of the present invention, in the step (2), the mixed precursor is dried before carbonization. The drying is mainly aimed at removing the solvent.

As a further preferable technical scheme of the preparation method, the method comprises the following steps:

(1) mixing a metal precursor and a carbon precursor in a solvent, and adding a nitrogen and phosphorus-containing inhibitor for mixing to obtain a mixed precursor;

the mass ratio of the metal precursor to the carbon precursor to the solvent is 1:1: 10-10: 1:10, and the mass ratio of the inhibitor to the carbon precursor is 1: 10-1: 1;

the metal precursor comprises any one or the combination of at least two of stannic chloride, antimony trichloride or bismuth trichloride;

the carbon precursor comprises any one or the combination of at least two of glucose, sucrose, starch, cellulose, polyacrylonitrile, polyvinylpyrrolidone, polyvinylidene fluoride, polypyrrole, polyaniline or polythiophene;

the nitrogen and phosphorus containing inhibitor comprises melamine phosphate and/or ammonium dihydrogen phosphate;

(2) and (2) drying the mixed precursor in the step (1), heating to 600-1000 ℃ at a heating rate of 1.0-10.0 ℃/min in a protective atmosphere, and carbonizing for 1-3 h to obtain the composite negative electrode material.

In a third aspect, the present invention provides a secondary battery comprising the composite anode material according to the first aspect.

Preferably, the secondary battery is a lithium ion battery or a sodium ion battery.

Compared with the prior art, the invention has the following beneficial effects:

(1) the preparation method provided by the invention successfully inhibits the precipitation of the low-melting-point metal and the oxide thereof in the high-temperature carbonization process by adding the inhibitor containing nitrogen and phosphorus elements into the precursor mixed solution for preparing the low-melting-point metal and the oxide/carbon composite material thereof, and prepares the low-melting-point metal and the oxide/carbon composite material thereof with high loading capacity, high specific capacity and good cycle stability of the low-melting-point metal and the oxide thereof. Nitrogen and phosphorus in the inhibitor can form pyridine nitrogen, pyrrole nitrogen, quaternary nitrogen, P-C, P-O, P ═ O and other groups with adsorption effect in the carbon material during carbonization. The groups can inhibit the precipitation of low-melting-point metal molten at high temperature and the precipitation of low-melting-point metal generated by low-melting-point metal oxide through carbothermic reduction reaction through adsorption, thereby improving the loading capacity of the low-melting-point metal and the low-melting-point metal oxide in the low-melting-point metal and the low-melting-point metal oxide/carbon composite material, and improving the lithium storage capacity, the sodium storage capacity and the cycling stability of the low-melting-point metal and the low-melting-point metal oxide/carbon composite material.

(2) The composite negative electrode material provided by the invention has high low-melting-point metal and oxide loading capacity thereof, high specific capacity and good cycling stability. The reversible lithium storage specific capacity of 849.5mAh/g and the reversible sodium storage specific capacity of 676.2mAh/g can be achieved under the current density of 0.2A/g. For lithium ion batteries and sodium ion batteries, the capacity retention rate of more than 80 percent can still be achieved after 2000 times of charge-discharge cycles under the current density of 5A/g, and good cycle stability is shown.

Drawings

FIG. 1 is a transmission electron microscope image of tin and its oxide/carbon composite anode material prepared in example 1 of the present invention;

fig. 2 is an XRD pattern of tin and its oxide/carbon composite anode material prepared in example 1 of the present invention;

fig. 3 is a thermal weight loss curve of tin and its oxide/carbon composite anode material prepared in example 1 of the present invention;

FIG. 4 is a graph of rate capability of tin and its oxide/carbon composite anode materials prepared in example 1 of the present invention;

fig. 5 is a graph of the cycle performance of the tin and its oxide/carbon composite anode material prepared in example 1 of the present invention.

Detailed Description

In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.

The following are typical but non-limiting examples of the invention:

example 1

This example prepares a composite anode material as follows:

firstly, mixing stannic chloride pentahydrate, sucrose and pure water according to the mass ratio of 10:1:10, and stirring for 1 h. And then adding melamine phosphate into the mixed precursor solution according to the mass ratio of 1:1 of the melamine phosphate to the sucrose, and stirring for 1 h. And drying the mixed solution in a 120 ℃ drying oven, then placing the dried mixed solution in a box type furnace, introducing nitrogen, heating to 800 ℃ at the heating rate of 2 ℃/min, preserving heat for 1h, and naturally cooling to room temperature to obtain the tin and the oxide/carbon composite cathode material thereof.

The composite negative electrode material prepared in this example includes carbon and metal materials (tin, tin monoxide and tin dioxide), the metal materials are dispersed in the carbon, and in the composite negative electrode material, the mass fraction of the metal materials is 89.9 wt%, and the mass fraction of oxygen in the composite negative electrode material is 19.1 wt%.

The performance test results of the composite anode material prepared in this example are shown in tables 1 and 2.

Fig. 1 is a transmission electron microscope image of the tin and its oxide/carbon composite negative electrode material in this example. As can be seen from fig. 1, the tin and its oxide nanoparticles having an average particle size of about 5nm are uniformly dispersed in the carbon material, and are not melted out due to high-temperature carbonization. This is mainly because nitrogen and phosphorus elements in the inhibitor melamine phosphate form pyridine nitrogen, pyrrole nitrogen, quaternary nitrogen, P-C, P-O, P ═ O and other groups with adsorption effect in the carbon material during carbonization. These groups can suppress precipitation of tin and its oxides melted at high temperatures by adsorption.

Fig. 2 is an XRD pattern of the tin and its oxide/carbon composite anode material in this example. As can be seen from fig. 2, the characteristic peak positions of tin and its oxide/carbon composite anode material correspond to the standard card JCPDS 4-673 of tin. The broad characteristic peak near 24 ° indicates that the carbon material in tin and its oxide/carbon composite anode material is amorphous carbon.

Fig. 3 is a thermal weight loss curve of the tin and its oxide/carbon composite anode material in this example. As can be seen from fig. 3, the mass fraction of tin and its oxide in the tin and its oxide/carbon composite anode material was 89.9%.

Fig. 4 is a graph of rate capability of the tin and its oxide/carbon composite anode material in this example. As can be seen from FIG. 4, the tin and tin oxide/carbon composite negative electrode material has a reversible lithium storage specific capacity of up to 849.5mAh/g and a reversible sodium storage specific capacity of up to 676.2mAh/g at a current density of 0.2A/g, and still has a reversible lithium storage specific capacity of up to 221.6mAh/g and a reversible sodium storage specific capacity of up to 261.0mAh/g at a current density of 5A/g.

Fig. 5 is a graph of the cycle performance of the tin and its oxide/carbon composite anode material in this example. As can be seen from fig. 5, the tin and its oxide/carbon composite anode material still has a capacity retention rate as high as 80% after 2000 times of charge-discharge cycles at a current density of 5A/g, and shows good cycle stability.

Example 2

This example prepares a composite anode material as follows:

firstly, mixing stannic chloride pentahydrate, sucrose and pure water according to the mass ratio of 1:1:10, and stirring for 1 h. And then adding melamine phosphate into the mixed precursor solution according to the mass ratio of 1:1 of the melamine phosphate to the sucrose, and stirring for 1 h. And drying the mixed solution in a 120 ℃ drying oven, then placing the dried mixed solution in a box type furnace, introducing nitrogen, heating to 800 ℃ at the heating rate of 2 ℃/min, preserving heat for 1h, and naturally cooling to room temperature to obtain the tin and the oxide/carbon composite cathode material thereof.

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

The performance test results of the composite anode material prepared in this example are shown in tables 1 and 2.

Example 3

This example prepares a composite anode material as follows:

mixing bismuth trichloride, glucose and pure water according to the mass ratio of 4:1:10, and stirring for 1 h. And then adding ammonium dihydrogen phosphate into the mixed precursor solution according to the mass ratio of the ammonium dihydrogen phosphate to the glucose of 1:5, and stirring for 1 h. And drying the mixed solution in a 120 ℃ drying oven, then placing the dried mixed solution in a box-type furnace, introducing argon, heating to 500 ℃ at the heating rate of 1 ℃/min, preserving heat for 3h, and naturally cooling to room temperature to obtain the bismuth and oxide/carbon composite cathode material thereof.

The composite negative electrode material prepared in this embodiment includes carbon and metal materials (bismuth and bismuth trioxide), the metal materials are dispersed in the carbon, and in the composite negative electrode material, the mass fraction of the metal materials is 73.9 wt%, and the mass fraction of oxygen in the composite negative electrode material is 10.1 wt%.

The performance test results of the composite anode material prepared in this example are shown in tables 1 and 2.

Example 4

This example prepares a composite anode material as follows:

mixing bismuth trichloride, glucose and pure water according to the mass ratio of 6:1:10, and stirring for 2 hours. And then adding ammonium dihydrogen phosphate into the mixed precursor solution according to the mass ratio of the ammonium dihydrogen phosphate to the glucose of 1:10, and stirring for 2 h. And drying the mixed solution in a 120 ℃ drying oven, then placing the dried mixed solution in a box-type furnace, introducing argon, heating to 1200 ℃ at the heating rate of 10 ℃/min, preserving heat for 3h, and naturally cooling to room temperature to obtain the bismuth/carbon composite negative electrode material.

The composite negative electrode material prepared in this example includes carbon and a metal material (bismuth), the metal material is dispersed in the carbon, in the composite negative electrode material, the mass fraction of the metal material is 89.8 wt%, and the mass fraction of oxygen in the composite negative electrode material is 0.

The performance test results of the composite anode material prepared in this example are shown in tables 1 and 2.

Example 5

This example prepares a composite anode material as follows:

antimony trichloride, cellulose and pure water are mixed according to the mass ratio of 8:1:10 and stirred for 1 hour. And then adding ammonium dihydrogen phosphate into the mixed precursor solution according to the mass ratio of the melamine phosphate to the cellulose of 1:6, and stirring for 1 h. And drying the mixed solution in a 120 ℃ drying oven, then placing the dried mixed solution in a box type furnace, introducing argon, heating to 1000 ℃ at the heating rate of 8 ℃/min, preserving heat for 2h, and naturally cooling to room temperature to obtain the antimony/carbon composite negative electrode material.

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

The performance test results of the composite anode material prepared in this example are shown in tables 1 and 2.

Example 6

This example prepares a composite anode material as follows:

antimony trichloride, polyvinylpyrrolidone and ethanol are mixed according to the mass ratio of 3:1:10 and stirred for 1 h. And then adding ammonium dihydrogen phosphate into the mixed precursor solution according to the mass ratio of the melamine phosphate to the cellulose of 1:3, and stirring for 1 h. And drying the mixed solution in a 120 ℃ oven, then placing the dried mixed solution in a box-type furnace, introducing argon, heating to 600 ℃ at the heating rate of 4 ℃/min, preserving the heat for 2 hours, and naturally cooling to room temperature to obtain the antimony and antimony oxide/carbon composite negative electrode material.

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

The performance test results of the composite anode material prepared in this example are shown in tables 1 and 2.

Example 7

The operation conditions and raw materials are the same as those of example 1 except that the mass ratio of the melamine phosphate to the sucrose is 1: 0.8.

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

The performance test results of the composite anode material prepared in this example are shown in tables 1 and 2.

Example 8

The operation conditions and raw materials of this example were the same as those of example 1 except that the mass ratio of melamine phosphate to sucrose was 1: 12.

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

The performance test results of the composite anode material prepared in this example are shown in tables 1 and 2.

Comparative example 1

This comparative example was carried out under the same operating conditions and starting materials as in example 1, except that no melamine phosphate was added.

The composite negative electrode material prepared by the comparative example comprises carbon and metal materials (tin, tin monoxide and tin dioxide), wherein the metal materials are dispersed in the carbon, the mass fraction of the metal materials in the composite negative electrode material is 78.2 wt%, and the mass fraction of oxygen in the composite negative electrode material is 10.2 wt%.

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

Test method

Lithium ion half cell testing:

respectively taking the composite negative electrode materials prepared in the examples and the comparative examples as active substances, taking SBR and CMC as binders, adding conductive carbon black, stirring, pulping, coating on a copper foil, and finally drying and rolling to prepare a pole piece, wherein the active substances are as follows: conductive agent: binder 85:15: 10. Using metal lithium sheet as counter electrode, PP as diaphragm, LiPF₆The electrolyte solution was EC + DEC + DMC (EC, DEC and DMC in a volume ratio of 1:1:1), and the simulated cell was assembled in an argon-filled glove box. And testing the electrochemical performance of the button cell by using a blue 5V/10mA type battery tester.

And (3) charging and discharging under the current density of 0.2A/g, and testing the reversible lithium storage specific capacity.

The capacity retention rate after 2000 cycles of charging and discharging was tested by charging and discharging at a current density of 5A/g.

TABLE 1 lithium ion half cell test results

Sodium ion half cell test:

respectively taking the composite negative electrode materials prepared in the examples and the comparative examples as active substances, taking SBR and CMC as binders, adding conductive carbon black, stirring, pulping, coating on a copper foil, and finally drying and rolling to prepare a negative electrode sheet, wherein the active substances are: conductive agent: binder 85:15: 10. Metal sodium sheet as counter electrode, PP as diaphragm, NaPF₆The electrolyte was EC + DMC (EC and DMC in a volume ratio of 1:1), and the simulated cell was assembled in an argon-filled glove box. And testing the electrochemical performance of the button cell by using a blue 5V/10mA type battery tester.

Charging and discharging are carried out under the current density of 0.2A/g, and the reversible sodium storage specific capacity is tested.

The capacity retention rate after 2000 cycles of charging and discharging was tested by charging and discharging at a current density of 5A/g.

Table 2 sodium ion battery test results

It can be seen from the above examples and comparative examples that examples 1 to 6 successfully suppress the precipitation of low melting point metals and their oxides during high temperature carbonization by adding nitrogen-and phosphorus-containing inhibitors to the precursor mixed solution for preparing low melting point metals and their oxides/carbon composites, and low melting point metals and their oxides/carbon composites having high low melting point metals and their oxide loading, high specific capacity, and good cycle stability were prepared.

The use of the inhibitor of example 7 was too high, resulting in uneven dispersion of the low melting point metal and its oxide in carbon, thereby reducing the specific capacity and cycling stability of the composite negative electrode.

The use amount of the inhibitor in example 8 is low, which causes precipitation of low-melting point metals and oxides thereof at high temperature, thereby reducing the specific capacity and the cycling stability of the composite anode.

Comparative example 1, in which no inhibitor was used, resulted in precipitation of a large amount of low-melting metals and their oxides at high temperatures, thereby reducing the specific capacity and cycling stability of the composite negative electrode.

The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.