Preparation method and application of a highly composite tin dioxide / titanium dioxide / carbon composite material

Abstract

The application discloses a preparation method and application of a highly composite tin dioxide / titanium dioxide / carbon composite material and relates to the technical field of lithium ion batteries. Tin source, titanium source and a surfactant are used as raw materials to prepare a tin dioxide / titanium dioxide / carbon precursor through a hydrothermal method, and then the precursor is subjected to heat treatment in an inert atmosphere to obtain the highly composite tin dioxide / titanium dioxide / carbon composite material. The highly composite structure composed of non-porous nanospheres, amorphous titanium dioxide and tin-titanium oxide interface solid solution is constructed, so that the volume expansion effect caused by tin dioxide when lithium ions are deintercalated can be relieved, and the initial coulomb efficiency and specific capacity of the composite material can be improved. Specifically, the initial coulomb efficiency of the tin dioxide / titanium dioxide / carbon composite material is 84.71%, and the reversible specific capacity can be kept at 855.2 mAh / g after 100 cycles when the charge-discharge current density is 0.2 A / g.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a preparation method and application of a highly compounded tin dioxide / titanium dioxide / carbon composite material. BACKGROUND

[0002] Lithium ion batteries have become the mainstream power source for portable electronic devices and electric vehicles due to their high energy density and long cycle life. Currently, the negative electrode material of commercial lithium ion batteries is mainly graphite, which directly restricts the improvement of the energy density of lithium ion batteries due to its low theoretical capacity. Therefore, the research and development of high specific capacity electrode materials that can replace commercial carbon materials have become a hot topic in the research of new electrode materials.

[0003] Tin dioxide has a high theoretical specific capacity (782 mAh·g -1 ), is safe and non-toxic, and has a reasonable lithium potential (0.6 V), making it a research hotspot for commercial lithium battery negative electrode materials. However, as a negative electrode material for lithium ion batteries, tin dioxide has the following defects: first, during the lithium extraction process, tin dioxide negative electrode material has a serious volume expansion, which causes the active material to collapse in structure, fall off from the current collector, and other problems, leading to a sharp decrease in the specific capacity of the battery; second, as a transition metal oxide, tin dioxide has low electrical conductivity and low electron migration rate, which makes its electrochemical kinetics slow, resulting in poor rate performance; in addition, tin dioxide negative electrode material often has low initial coulombic efficiency, which affects its actual commercial application. These shortcomings limit the commercial application of tin dioxide negative electrode material. In recent years, nano materials, doping, or compounding with other materials have been used to improve the electrochemical performance of tin dioxide. Among them, compounding tin dioxide with other transition metal oxides to improve the performance of electrode materials through the synergistic effect between different materials is particularly necessary for the development of high-performance composite negative electrode materials.

[0004] In the prior art, the modification research of SnO2-based anode materials for lithium-ion batteries (Wang Sai, Kunming University of Science and Technology, April 2020) discloses a TiO2@SnO2@C hollow sphere material, in which tin dioxide nanoparticles are confined between stable TiO2nanohollow spheres and a high-conductivity amorphous carbon layer. Although the hollow structure of the TiO2@SnO2@C composite material can effectively alleviate the volume expansion, such a hollow structure will increase the specific surface area of the composite material, thereby reducing the volume specific capacity and the first coulomb efficiency. In the preparation and lithium storage performance research of graphene nanoribbon / nanosnO2 and nanotitanium dioxide composite (Zhang Xinlin, Chongqing University, May 2016), graphene nanoribbon wraps the core-shell structure of tin dioxide@titanium dioxide nanosphere to form a tin dioxide@titanium dioxide / graphene nanoribbon composite. In the composite material, tin dioxide can provide a higher capacity, titanium dioxide can effectively alleviate the volume effect of tin dioxide and maintain the stability of the electrode, and graphene nanoribbon can improve the conductivity of the composite material. However, the introduction of graphene nanoribbon will increase the specific surface area of the composite material, thereby reducing the volume specific capacity and the first coulomb efficiency, and graphene nanoribbon only contacts the surface of titanium dioxide and tin dioxide, which is not conducive to the rapid transfer of electrons inside the composite material.

[0005] Therefore, it is particularly necessary to optimize the structure of the tin dioxide / titanium dioxide / carbon composite material to not only alleviate the volume expansion effect of tin dioxide when lithium ions are deintercalated, but also overcome the problems of low specific capacity and low first coulomb efficiency of the tin dioxide / titanium dioxide / carbon composite material in the prior art. SUMMARY

[0006] In view of the above prior art, the purpose of the present application is to provide a preparation method and application of a highly composite tin dioxide / titanium dioxide / carbon composite material. The present application uses a tin source, a titanium source and a surfactant as raw materials to prepare a tin dioxide / titanium dioxide / carbon composite material in a non-porous nanosphere structure through a hydrothermal method and heat treatment. By constructing a highly composite structure composed of non-porous nanospheres, amorphous titanium dioxide and tin-titanium oxide interfacial solid solution, not only the volume expansion effect of tin dioxide when lithium ions are deintercalated can be alleviated to improve the electrochemical cycle stability of the composite material, but also the first coulomb efficiency and the specific capacity of the composite material can be improved.

[0007] To achieve the above purpose, the present application adopts the following technical solutions:

[0008] In a first aspect of the present application, a preparation method of a highly composite tin dioxide / titanium dioxide / carbon composite material is provided, comprising the following steps:

[0009] (1) tin source and titanium source are mixed and then added into anhydrous ethanol, the mixture is stirred uniformly, and then a surfactant is added to obtain a mixed solution; the mixed solution is heated to perform hydrothermal reaction to obtain a tin dioxide / titanium dioxide / carbon precursor;

[0010] The material liquid ratio of the tin source, the titanium source, the surfactant and the anhydrous ethanol is (2-7) mmol:(3-8) mmol:(0.02-0.1) g:40 mL.

[0011] (2) the tin dioxide / titanium dioxide / carbon precursor is subjected to heat treatment in an inert atmosphere to obtain a highly composite tin dioxide / titanium dioxide / carbon composite material.

[0012] Preferably, in step (1), the tin source is one or more of tin chloride pentahydrate, anhydrous tin chloride, stannous chloride dihydrate and anhydrous stannous chloride.

[0013] Preferably, in step (1), the titanium source is titanium tetrachloride and / or tetrabutyl titanate.

[0014] Preferably, in step (1), the surfactant is cetyltrimethylammonium bromide.

[0015] Preferably, in step (1), the heating temperature is 80-200 DEG C, and the hydrothermal reaction time is 10-18 h.

[0016] Preferably, in step (2), the inert atmosphere is an argon atmosphere.

[0017] Preferably, in step (2), during the heat treatment, the treatment temperature is 400-800 DEG C, and the treatment time is 1-6 h.

[0018] According to a second aspect of the present application, there is provided a highly composite tin dioxide / titanium dioxide / carbon composite material prepared by the above preparation method.

[0019] Preferably, the highly composite tin dioxide / titanium dioxide / carbon composite material is a non-porous nanosphere structure, and the size of the non-porous nanosphere is 300-800 nm.

[0020] Preferably, according to a third aspect of the present application, the above highly composite tin dioxide / titanium dioxide / carbon composite material is provided for use in preparation of a lithium ion battery negative electrode material.

[0021] Preferably, the preparation method of the lithium ion battery negative electrode material is as follows:

[0022] The above highly composite tin dioxide / titanium dioxide / carbon composite material, a conductive agent and a binder are mixed and then added into deionized water to obtain a mixed slurry; the mixed slurry is coated on a substrate and dried to obtain a lithium ion battery composite material.

[0023] Further, the conductive agent is acetylene black, and the binder is sodium carboxymethyl cellulose.

[0024] Further, the mass ratio of the tin dioxide / titanium dioxide / carbon composite material, the conductive agent and the binder is (7-9):(0.5-1):(0.5-1).

[0025] Further, the substrate is a copper foil, and the thickness of the copper foil is 20-30 mu m.

[0026] Further, the coating amount of the mixed slurry is (1.2-2) mg / cm 2 .

[0027] Further, the drying method is vacuum drying, the drying temperature is 70-90 DEG C, and the drying time is 10-14 h.

[0028] Advantages of the present application:

[0029] The present application uses a tin source, a titanium source and a surfactant as raw materials, and a tin dioxide / titanium dioxide / carbon precursor is prepared by a hydrothermal method, and then the precursor is subjected to heat treatment in an inert atmosphere, so that a highly composite tin dioxide / titanium dioxide / carbon composite material is obtained.

[0030] The present application constructs a "trinity" type highly composite structure composed of non-porous nanospheres, amorphous titanium dioxide and tin-titanium oxide interfacial solid solution, so that the volume expansion effect of tin dioxide during the deintercalation of lithium ions is relieved, and good first coulomb efficiency and specific capacity are ensured, and good electrochemical performance is ensured.

[0031] Specifically, the first coulomb efficiency of the tin dioxide / titanium dioxide / carbon composite material prepared by the present application is as high as 84.71%, the reversible specific capacity is maintained at 855.2 mAh / g after 100 cycles at a charge-discharge current density of 0.2 A / g, and the high reversible specific capacity of 595.7 mAh / g is still maintained when the charge-discharge current is increased to 5.0 A / g. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 : XRD pattern of the highly composite tin dioxide / titanium dioxide / carbon composite material prepared in Example 1;

[0033] Figure 2 : Scanning electron microscope pattern of the highly composite tin dioxide / titanium dioxide / carbon composite material prepared in Example 1;

[0034] Figure 3 : Low-resolution transmission electron microscope pattern of the highly composite tin dioxide / titanium dioxide / carbon composite material prepared in Example 1;

[0035] Figure 4 High-resolution transmission electron microscopy image of the highly composite tin dioxide / titanium dioxide / carbon composite material prepared in Example 1;

[0036] Figure 5 Scanning electron microscope image of the tin dioxide / titanium dioxide / carbon composite material prepared in Comparative Example 1;

[0037] Figure 6 Graphs showing the first charge-discharge voltage-to-capacity test results of the tin dioxide / titanium dioxide / carbon composite materials prepared in Example 1 and Comparative Examples 1-2;

[0038] Figure 7 Electrochemical cycle life test graphs of the tin dioxide / titanium dioxide / carbon composite materials prepared in Example 1 and Comparative Examples 1-2;

[0039] Figure 8 Electrochemical rate performance test graphs of the tin dioxide / titanium dioxide / carbon composite materials prepared in Example 1 and Comparative Examples 1-2. Detailed Implementation

[0040] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0041] While existing technologies disclose the use of tin dioxide / titanium dioxide / carbon composite materials for lithium-ion battery anode materials, these composites are mostly porous and hollow. Although this structure can effectively mitigate the volume expansion of tin dioxide during lithium insertion / extraction, the large specific surface area it provides reduces the specific capacity and initial coulombic efficiency of the composite material, thus affecting its electrochemical performance.

[0042] Based on this, this application provides a highly composite tin dioxide / titanium dioxide / carbon composite material, which is prepared by the following method: using tin source, titanium source and surfactant as raw materials, a tin dioxide / titanium dioxide / carbon precursor is prepared by hydrothermal method, and then placed in an inert atmosphere for heat treatment to obtain a highly composite tin dioxide / titanium dioxide / carbon composite material.

[0043] From the reaction principle, in the hydrothermal process, the surface of the titanium dioxide and tin dioxide nanoparticles produced by the hydrolysis of the titanium source and tin source will adsorb the surfactant, and then under the action of the surfactant, the titanium dioxide and tin dioxide nanoparticles will be aggregated and finally form a non-porous nanosphere precursor. The precursor is heat-treated in an inert atmosphere, the surfactant is carbonized to form carbon, and finally a non-porous nanosphere structure of the tin dioxide / titanium dioxide / carbon composite material is formed. Whether it is the tin dioxide / titanium dioxide active material on the surface of the nanosphere or the tin dioxide / titanium dioxide active material inside the nanosphere is closely combined with carbon. This close combination can enable electrons to quickly transfer to the inside of the nanosphere, and the interface formed by titanium dioxide and tin dioxide can enable the rapid migration of lithium ions, and the combination of the two can fully exert the lithium storage performance of the active material inside the nanosphere and improve the rate performance of the composite material.

[0044] The non-porous structure of the tin dioxide / titanium dioxide / carbon composite material can reduce its specific surface area, thereby reducing the occurrence of side reactions of the electrode material during the first discharge, and thereby improving the first coulombic efficiency of the composite material. At the same time, the titanium dioxide in the tin dioxide / titanium dioxide / carbon composite material is in an amorphous structure. The amorphous structure of titanium dioxide has isotropy, and the flexibility characteristics produced can greatly alleviate the volume expansion effect produced by tin dioxide when lithium ions are deintercalated, which is beneficial to improving the electrochemical cycle stability of the composite material. In addition, a tin-titanium oxide interface solid solution can be produced at the interface between tin dioxide and titanium dioxide. This solid solution can firmly combine tin dioxide and titanium dioxide, prevent their separation, and is beneficial to the integrity of the composite material structure, thereby stabilizing the electrochemical cycle stability of the composite material, and the formation of the interface is also beneficial to the rapid migration of lithium ions and thus the electrochemical rate performance of the composite material.

[0045] In addition, the amount of surfactant used in the preparation of the tin dioxide / titanium dioxide / carbon composite material is crucial. Specifically, when too little surfactant is used, it is not possible to form a sufficient and complete adsorption layer on the surface of the titanium dioxide and tin dioxide nanoparticles produced by the hydrolysis of the titanium source and tin source, resulting in the inability to guide the particles to directional aggregation in the form of a predetermined nanosphere structure. At the same time, the surfaces of the bare or semi-bare titanium dioxide and tin dioxide nanoparticles have the same charge, and the particles mainly exhibit strong electrostatic repulsion. This repulsive force hinders the ordered and close arrangement of nanoparticles in the critical initial stage of material growth, resulting in the formation of only nanoparticles and the inability to form a non-porous nanosphere structure. The nanoparticle structure will agglomerate due to its high surface energy, resulting in low first coulombic efficiency. When too much surfactant is used, it results in too large a proportion of carbon in the composite material, thereby reducing the specific capacity of the material composite.

[0046] In order for those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

[0047] The experimental materials used in the embodiments of the present application are all conventional experimental materials in the art and can be purchased through commercial channels.

[0048] Example 1: Preparation of a highly composite tin dioxide / titanium dioxide / carbon composite material

[0049] (1) 5 mmol of anhydrous tin tetrachloride and 5 mmol of tetrabutyl titanate were mixed and then added to 40 mL of anhydrous ethanol, 0.05 g of cetyltrimethylammonium bromide (a surfactant) was added after stirring to uniformity, to obtain a mixed solution; the mixed solution was subjected to hydrothermal treatment at 180°C for 12 h to obtain a tin dioxide / titanium dioxide / carbon precursor;

[0050] (2) The tin dioxide / titanium dioxide / carbon precursor was subjected to heat treatment at 500°C for 2 h in an argon atmosphere to obtain a highly composite tin dioxide / titanium dioxide / carbon composite material.

[0051] Example 2: Preparation of a highly composite tin dioxide / titanium dioxide / carbon composite material

[0052] (1) 7 mmol of anhydrous tin tetrachloride and 3 mmol of tetrabutyl titanate were mixed and then added to 40 mL of anhydrous ethanol, 0.02 g of cetyltrimethylammonium bromide (a surfactant) was added after stirring to uniformity, to obtain a mixed solution; the mixed solution was subjected to hydrothermal treatment at 200°C for 10 h to obtain a tin dioxide / titanium dioxide / carbon precursor;

[0053] (2) The tin dioxide / titanium dioxide / carbon precursor was subjected to heat treatment at 400°C for 6 h in an argon atmosphere to obtain a highly composite tin dioxide / titanium dioxide / carbon composite material.

[0054] Example 3: Preparation of a highly composite tin dioxide / titanium dioxide / carbon composite material

[0055] (1) 2 mmol of anhydrous tin tetrachloride and 8 mmol of tetrabutyl titanate were mixed and then added to 40 mL of anhydrous ethanol, 0.08 g of cetyltrimethylammonium bromide (a surfactant) was added after stirring to uniformity, to obtain a mixed solution; the mixed solution was subjected to hydrothermal treatment at 80°C for 18 h to obtain a tin dioxide / titanium dioxide / carbon precursor;

[0056] (2) The tin dioxide / titanium dioxide / carbon precursor was subjected to heat treatment at 800°C for 1 h in an argon atmosphere to obtain a highly composite tin dioxide / titanium dioxide / carbon composite material.

[0057] Example 4: Preparation of highly compounded tin dioxide / titanium dioxide / carbon composite material

[0058] (1) 5 mmol of anhydrous tin tetrachloride and 5 mmol of tetrabutyl titanate were mixed and then added to 40 mL of anhydrous ethanol, 0.1 g of cetyltrimethylammonium bromide (surfactant) was added after stirring, to obtain a mixed solution; the mixed solution was hydrothermally treated at 180°C for 12 h to obtain a tin dioxide / titanium dioxide / carbon precursor;

[0059] (2) The tin dioxide / titanium dioxide / carbon precursor was placed in an argon atmosphere and heat treated at 600°C for 2 h to obtain a highly compounded tin dioxide / titanium dioxide / carbon composite material.

[0060] Example 5: Preparation of highly compounded tin dioxide / titanium dioxide / carbon composite material

[0061] (1) 5 mmol of anhydrous tin tetrachloride and 5 mmol of tetrabutyl titanate were mixed and then added to 40 mL of anhydrous ethanol, 0.06 g of cetyltrimethylammonium bromide (surfactant) was added after stirring, to obtain a mixed solution; the mixed solution was hydrothermally treated at 140°C for 12 h to obtain a tin dioxide / titanium dioxide / carbon precursor;

[0062] (2) The tin dioxide / titanium dioxide / carbon precursor was placed in an argon atmosphere and heat treated at 500°C for 2 h to obtain a highly compounded tin dioxide / titanium dioxide / carbon composite material.

[0063] Example 6: Preparation of highly compounded tin dioxide / titanium dioxide / carbon composite material

[0064] (1) 5 mmol of anhydrous tin tetrachloride and 5 mmol of tetrabutyl titanate were mixed and then added to 40 mL of anhydrous ethanol, 0.05 g of cetyltrimethylammonium bromide (surfactant) was added after stirring, to obtain a mixed solution; the mixed solution was hydrothermally treated at 140°C for 12 h to obtain a tin dioxide / titanium dioxide / carbon precursor;

[0065] (2) The tin dioxide / titanium dioxide / carbon precursor was placed in an argon atmosphere and heat treated at 700°C for 2 h to obtain a highly compounded tin dioxide / titanium dioxide / carbon composite material.

[0066] Application Example 1: Preparation of lithium ion negative electrode composite material

[0067] The tin dioxide / titanium dioxide / carbon composite material prepared in Example 1, acetylene black and sodium carboxymethyl cellulose were mixed and then added to deionized water to obtain a mixed slurry; wherein the mass ratio of the tin dioxide / titanium dioxide / carbon composite material, acetylene black, sodium carboxymethyl cellulose and deionized water was 8:1:1:80;

[0068] The mixed slurry was coated onto a copper foil with a thickness of 25 μm, and then vacuum dried at 80 °C for 12 h before being removed to obtain the lithium-ion battery anode material.

[0069] Comparative Example 1:

[0070] The difference between this comparative example and Example 1 is that the ratio of anhydrous tin tetrachloride, tetrabutyl titanate, and hexadecyltrimethylammonium bromide (surfactant) added in the preparation of the tin dioxide / titanium dioxide / carbon composite material is 5 mmol:5 mmol:0.01 g. Specifically:

[0071] (1) Mix 5 mmol of anhydrous tin tetrachloride and 5 mmol of tetrabutyl titanate, add to 40 mL of anhydrous ethanol, stir evenly, and then add 0.01 g of cetyltrimethylammonium bromide (surfactant) to obtain a mixed solution; place the mixed solution at 180 °C for hydrothermal treatment for 12 h to obtain tin dioxide / titanium dioxide / carbon precursor;

[0072] (2) The tin dioxide / titanium dioxide / carbon precursor was placed in an argon atmosphere and heat-treated at 500°C for 2 hours to obtain a highly composite tin dioxide / titanium dioxide / carbon composite material.

[0073] The electron microscope image of the tin dioxide / titanium dioxide / carbon composite material prepared in this comparative example is shown below. Figure 5 As shown. By Figure 5 It can be seen that the composite material is in the form of nanoparticles. This is because too little surfactant is used in the preparation process, resulting in too few surfactant molecules adsorbed on the surfaces of titanium dioxide and tin dioxide generated by the titanium and tin sources. This makes it impossible to effectively guide the particles to assemble into nanosphere structures. Furthermore, the titanium dioxide nanoparticles and tin dioxide nanoparticles repel each other, hindering the orderly and compact arrangement of the nanoparticles in the early stage of growth. As a result, only nanoparticles can be generated, but non-porous nanosphere structures cannot be generated.

[0074] Comparative Example 2:

[0075] The difference between this comparative example and Example 1 is that the ratio of anhydrous tin tetrachloride, tetrabutyl titanate, and hexadecyltrimethylammonium bromide (surfactant) added in the preparation of the tin dioxide / titanium dioxide / carbon composite material is 5 mmol:5 mmol:0.12 g. Specifically:

[0076] (1) Mix 5 mmol of anhydrous tin tetrachloride and 5 mmol of tetrabutyl titanate, add to 40 mL of anhydrous ethanol, stir evenly, and then add 0.12 g of cetyltrimethylammonium bromide (surfactant) to obtain a mixed solution; place the mixed solution at 180 °C for hydrothermal treatment for 12 h to obtain tin dioxide / titanium dioxide / carbon precursor;

[0077] (2) The tin dioxide / titanium dioxide / carbon precursor is placed in an argon atmosphere and heat treated at 500°C for 2h to obtain a highly composite tin dioxide / titanium dioxide / carbon composite material.

[0078] Test Example 1:

[0079] The highly composite tin dioxide / titanium dioxide / carbon composite material prepared in Example 1 is subjected to structural characterization, and the results are shown in Figure 1

[0080] As can be seen from Figure 1 , the crystal structure of the highly composite tin dioxide / titanium dioxide / carbon composite material prepared in Example 1 is rutile tin dioxide, and no structure peak of titanium dioxide appears, which indicates that the titanium dioxide in the composite material is in an amorphous structure. This is because when tin dioxide and titanium dioxide are heat treated together, the preferential crystallization growth of tin dioxide inhibits the crystallization growth of titanium dioxide. Due to the flexibility characteristics of the isotropic amorphous titanium dioxide, the volume expansion effect generated when tin dioxide is deintercalated by lithium ions can be alleviated to some extent, which is beneficial to improve the electrochemical cycle stability of the composite material.

[0081] As can be seen from Figure 2 and Figure 3 , the highly composite tin dioxide / titanium dioxide / carbon composite material prepared in Example 1 presents irregular nanospheres with a size of about 600nm, and there are no obvious pores on the surface and inside. The non-porous structure can reduce the specific surface area of the composite material and thus reduce the occurrence of side reactions of the electrode material during the first discharge, which is beneficial to improve the first coulombic efficiency of the composite material.

[0082] As can be seen from Figure 4 , the highly composite tin dioxide / titanium dioxide / carbon composite material prepared in Example 1 presents two regions, one of which is an obvious lattice fringe region, and the other of which has no obvious lattice fringe. The lattice fringe corresponds to the (110) crystal plane of tin dioxide, and the region without obvious lattice fringe corresponds to amorphous titanium dioxide. There is no obvious boundary between the two regions, indicating that a tin-titanium oxide interfacial solid solution is formed between the tin dioxide and titanium dioxide interface, which is caused by the mutual diffusion of tin / titanium atoms during heat treatment. The formation of the tin-titanium oxide interfacial solid solution can firmly combine tin dioxide and titanium dioxide to prevent their separation, which is beneficial to the structural integrity of the composite material and thus stabilizes the electrochemical cycle stability of the composite material.

[0083] Test Example 2: Verification of electrochemical performance

[0084] ​The tin dioxide / titanium dioxide / carbon composite materials prepared in Example 1 and Comparative Examples 1-2 were used as negative electrode materials to construct lithium-ion batteries. The electrochemical performance was then tested, and the results are as follows: Figures 7-8 As shown.

[0085] The specific steps are as follows:

[0086] (1) The tin dioxide / titanium dioxide / carbon composite materials prepared in Example 1 and Comparative Examples 1-2 were mixed with acetylene black and sodium carboxymethyl cellulose at a mass ratio of 8:1:1 and then added to 3 mL of deionized water and stirred evenly to obtain a mixed slurry. The mixed slurry was coated on a copper foil with a thickness of 25 μm, and then placed in a vacuum dryer at 80 °C for 12 h. After drying, the copper foil was cut into round pieces with a diameter of 16 mm using a cutting machine as negative electrode sheets.

[0087] (2) A coin cell was assembled using a negative electrode sheet and lithium metal as the counter electrode, and 1M LiPF6 / EC:DMC (1:1, volume ratio) as the electrolyte, and the electrochemical performance was tested. The cycle stability test was performed with a charge / discharge current density of 0.2 A / g and a cutoff charge / discharge voltage of 0.01-3 V. The rate performance test was performed with charge / discharge current densities of 0.1, 0.2, 0.5, 1, 2, 5, and 0.1 A / g, respectively, and a cutoff charge / discharge voltage of 0.01-3 V.

[0088] Depend on Figure 6 As can be seen, the highly composite tin dioxide / titanium dioxide / carbon composite material prepared in Example 1, when used as a lithium-ion anode material, exhibits an initial charge specific capacity of 934.6 mAh / g, an initial discharge specific capacity of 791.7 mAh / g, and an initial coulombic efficiency of 84.71%. This demonstrates that the non-porous nanosphere structure of the composite material effectively improves its initial coulombic efficiency. However, in Comparative Example 1, due to the insufficient use of surfactant, nanoparticles were formed. The high surface energy of these nanoparticles led to agglomeration, resulting in a low initial coulombic efficiency. Specifically, the composite material obtained in Comparative Example 1 had an initial charge specific capacity of 966.2 mAh / g, an initial discharge specific capacity of 720.2 mAh / g, and an initial coulombic efficiency of 74.5%. The tin dioxide / titanium dioxide / carbon composite material prepared in Comparative Example 2 had an initial charge specific capacity of 814.1 mAh / g, an initial discharge specific capacity of 680.0 mAh / g, and an initial coulombic efficiency of 83.5%. It can be seen that although the composite material prepared in Comparative Example 2 has a high initial coulombic efficiency, its initial charge specific capacity is low. This is because when the tin dioxide / titanium dioxide / carbon precursor is subjected to subsequent heat treatment, the surfactant is carbonized. The more surfactant used, the higher the proportion of carbon in the tin dioxide / titanium dioxide / carbon composite material, thus causing a decrease in the specific capacity of the composite material.

[0089] By Figure 7 And Figure 8 It can be seen that the highly complex tin dioxide / titanium dioxide / carbon composite material prepared in Example 1 exhibits excellent cycle stability and rate performance as a lithium ion negative electrode material. The reversible specific capacity of the electrode remains at 855.2 mAh / g after 100 cycles at a test current of 0.2 A / g, fully demonstrating the structural stability of the composite material. On the one hand, the flexible nature of the isotropic amorphous titanium dioxide greatly alleviates the volume expansion effect of tin dioxide when lithium ions are deintercalated. On the other hand, the tin-titanium oxide interfacial solid solution generated at the interface between tin dioxide and titanium dioxide can firmly bind tin dioxide and titanium dioxide to prevent their separation. As can be seen from the rate performance graph, the electrode can still maintain 595.7 mAh / g at a test current density of 5.0 A / g, indicating that the composite material has excellent lithium ion transmission channels. This is because the high complexity of tin dioxide and titanium dioxide generates a large number of interfaces, which are conducive to the rapid migration of lithium ions. However, Comparative Example 1 uses too little surfactant, and tin-titanium oxide interfacial solid solutions cannot be formed between the tin dioxide and titanium dioxide particles, so the large volume expansion of tin dioxide cannot be effectively alleviated, resulting in poor cycle performance. In addition, the carbon content in the composite material is low, resulting in poor electrical conductivity and thus poor rate performance. Although the composite material prepared in Comparative Example 2 has excellent cycle performance and rate performance, the use of too much surfactant causes the carbon content in the composite material to be too high, resulting in a decrease in the specific capacity of the composite material.

[0090] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Those skilled in the art can make various modifications and changes to the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a highly composite tin dioxide / titanium dioxide / carbon composite material, characterized in that, Includes the following steps: (1) Mix the tin source and titanium source and add them to anhydrous ethanol. Stir well and then add the surfactant to obtain a mixed solution. The mixed solution was heated to carry out a hydrothermal reaction to obtain a tin dioxide / titanium dioxide / carbon precursor; The ratio of tin source, titanium source, surfactant and anhydrous ethanol in the liquid-to-solid mixture is (2-7) mmol: (3-8) mmol: (0.02-0.1) g: 40 mL. The surfactant is hexadecyltrimethylammonium bromide. The heating temperature is 80-200℃ and the hydrothermal reaction time is 10-18 h. (2) The tin dioxide / titanium dioxide / carbon precursor was heat-treated in an inert atmosphere to obtain a highly composite tin dioxide / titanium dioxide / carbon composite material. The inert atmosphere is argon; during the heat treatment process, the treatment temperature is 400-800℃ and the treatment time is 1-6h.

2. The method for preparing the highly composite tin dioxide / titanium dioxide / carbon composite material as described in claim 1, characterized in that, In step (1), the tin source is one or more of tin tetrachloride pentahydrate, anhydrous tin tetrachloride, stannous chloride dihydrate, and anhydrous stannous chloride; the titanium source is titanium tetrachloride and / or tetrabutyl titanate.

3. The highly composite tin dioxide / titanium dioxide / carbon composite material prepared by the preparation method according to claim 1 or 2, characterized in that, The highly composite tin dioxide / titanium dioxide / carbon composite material has a non-porous nanosphere structure with a size of 300-800 nm.

4. The application of the highly composite tin dioxide / titanium dioxide / carbon composite material as described in claim 3 in the preparation of lithium-ion battery anode materials.

5. The application as described in claim 4, characterized in that, The preparation method of lithium-ion battery anode material is as follows: The conductive agent, binder, and the highly composite tin dioxide / titanium dioxide / carbon composite material as described in claim 3 are mixed and added to deionized water to obtain a mixed slurry; the mixed slurry is coated onto a substrate and dried to obtain a lithium-ion battery anode material.

6. The application as described in claim 5, characterized in that, The conductive agent is acetylene black, and the binder is sodium carboxymethyl cellulose; the mass ratio of tin dioxide / titanium dioxide / carbon composite material, conductive agent, and binder is (7-9):(0.5-1):(0.5-1).

7. The application as described in claim 5, characterized in that, The drying method is vacuum drying, with a drying temperature of 70-90℃ and a drying time of 10-14 hours.

Images