A Si-Sn-TiC / C / asphalt composite material, its preparation method and application

Abstract

The present invention discloses a Si-Sn-TiC / C / asphalt composite material, as well as a preparation method and application thereof. By introducing TiC and asphalt on the basis of silicon-based and tin-based materials, the problems of severe volume expansion and pulverization of silicon-based and tin-based anode materials are well improved, the cycle performance and rate performance of the materials are both improved to a certain extent, and the electrochemical performance of the silicon-based and tin-based composite materials is enhanced. Moreover, the preparation process of the present invention is simple and the cost is low.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy battery materials, and particularly relates to a Si-Sn-TiC / C / pitch composite material, a preparation method thereof, and an application thereof in a negative electrode material of a lithium ion battery. Background Art

[0002] At present, due to the advantages of high energy density, long cycle life, recyclable secondary utilization, cleanliness and environmental protection, lithium ion batteries are widely used in new energy electric vehicles, 3C portable electronic devices, terminal energy storage devices and other fields. With the increasingly fierce market development, new requirements are put forward for the performance of lithium ion batteries. For example, it is required that lithium ion batteries have high cycle life, high energy density and excellent safety characteristics. Among them, the energy density of lithium ion batteries has always been a hot issue concerned by all walks of life. The principle of a lithium ion battery is based on the extraction of lithium ions from the positive electrode material and the insertion into the negative electrode material, which is the charging process of the lithium battery. Vice versa, it is the discharging process. Therefore, in order to improve the energy density of the lithium battery, it is possible to start from improving the density of the positive and negative electrode materials of the lithium battery and increasing the specific capacity of the positive and negative electrode materials.

[0003] At present, the main positive electrode materials in the lithium battery industry are two types: ternary materials and lithium iron phosphate, while the negative electrode material is mainly graphite. At present, the improvement of the positive electrode material mainly involves doping metal elements into the material, and the change in the intrinsic energy density of the material is not large. Therefore, researchers mainly focus on the development of negative electrode materials. Since the development of lithium batteries, carbon (372 mAh / g) negative electrodes have always been the main players in lithium battery negative electrode materials. However, in recent years, researchers have discovered a series of new negative electrode materials such as Si-based (4200 mAh / g) and Sn-based (959 mAh / g). Therefore, the research on new negative electrode materials has entered a new stage of rapid development.

[0004] Although silicon negative electrodes have a high theoretical specific capacity, there are also many defects in the actual application process. As a semiconductor material, silicon has a very low intrinsic conductivity (2.52*10 -4 S / m), and the poor conductivity will result in poor rate performance of the material. But the most important problem is that the volume of silicon expands by up to 400% after being fully lithiated. The volume expansion brings a series of problems: (1) The silicon material cannot overcome the great internal stress generated by the volume expansion during the charge and discharge process, resulting in self-pulverization or even shedding, and losing electrochemical activity; (2) The volume of the silicon material changes greatly during the charge and discharge process, and the electrode plate will continuously expand and contract, resulting in serious damage to the electrode structure and loss of electrical contact, and the battery capacity decays extremely fast; (3) The silicon material is continuously pulverized during the charge and discharge process, continuously exposing new surfaces, and the SEI film is repeatedly regenerated, and the SEI film continuously thickens, resulting in an increase in the internal resistance of the battery and a gradual decrease in the cycle stability of the battery.

[0005] Tin-based anode materials have good electrical conductivity and spatial ductility. Although the theoretical specific capacity of Sn-based anode materials is about 2.5 times higher than that of carbon anode materials, however, during the process of lithium ion extraction and insertion, the phase change evolution of the material depends on the sacrifice of the previous phase change, and Li-Sn will experience 3 phase change processes during the entire charge-discharge process. Therefore, during the phase change process, the reorganization of the SEI film and the stress change between the active materials will cause the material to crack and pulverize. Secondly, the recrystallization agglomeration and growth of tin particles will cause the decline of the kinetic performance of the material. Finally, the existence of the oxide layer on the surface of the tin anode increases the irreversible capacity, reduces the initial Coulomb efficiency of the battery, makes the cycle stability and rate performance of the electrode poor, and hinders its practical application.

[0006] In order to improve the electrochemical performance of silicon-based anode materials, researchers have carried out a large number of modification studies focusing on reducing the volume expansion effect of silicon materials and improving the electrical conductivity of silicon materials. The main modification methods include: nano-Si can effectively improve the pulverization problem caused by the volume expansion of silicon, but the lithium ion diffusion resistance of nano-silicon materials is still relatively large, and the electrochemical performance is still poor; in the Si / C composite material, the C layer can improve the electrical conductivity of the Si material, reduce the direct contact between Si and the electrolyte, and can inhibit the volume expansion of Si to a certain extent, but the cycle performance of the silicon-carbon composite material is also relatively poor, and the applicable range is narrow; the inside of the silicon suboxide material can be understood as amorphous Si and SiO2, which has good cycle performance, small volume expansion, and a wide applicable range, but as the O content increases in the silicon suboxide material, the specific capacity of the silicon suboxide material will decrease; the Si in the Si alloy material is amorphous, which can help relieve the volume expansion, maintain the structural stability, and has good cycle performance, but the process preparation conditions of the Si alloy material are harsh and the cost is high.

[0007] In order to develop tin-based anode materials, researchers have improved their electrochemical performance by methods such as changing the structure of elemental Sn and its oxides and carbon coating. However, tin-based oxides still have problems such as large volume changes, easy agglomeration and pulverization, low electrical conductivity, and high irreversible capacity loss during the lithiation / delithiation process, which limits their commercial application.

[0008] The patent with the authorization number CN105489854B uses asphalt as a carbon source to stir, heat up and polycondense, and heat up and carbonize with Sn-based and / or Si-based to obtain a (mixture of one or several of nano-silicon, tin, germanium, silicon dioxide, tin dioxide, silicon monoxide, tin monoxide particles) / carbon composite material, which overcomes the disadvantages of low yield and difficulty in industrialization using the chemical vapor deposition method in the past, large pollution and high cost using the solvent method, and poor coating effect using the ball milling method, and prepares a new type of anode material with a core-shell structure with a specific capacity reaching 400 mAh / g to 2400 mAh / g, but its cycle performance still needs to be further improved. Summary of the Invention

[0009] In view of the deficiencies of the prior art, the purpose of the present invention is to provide a Si-Sn-TiC / C / asphalt composite material, its preparation method and application to solve the above problems. Among them, TiC has high mechanical strength, high thermal conductivity and electrical conductivity, and is an excellent inert matrix for silicon-based and tin-based anode materials, which can effectively improve the electrical conductivity of the anode active material and buffer the volume expansion of the active material; asphalt is easy to soften at high temperatures and has good electrical conductivity and spatial ductility at room temperature, which can relieve the fracture and pulverization of the anode active material.

[0010] To achieve the above purpose, the present invention provides a Si-Sn-TiC / C / asphalt composite material, wherein the molar ratio of silicon, tin, and titanium in Si-Sn-TiC is 1:0.15-0.25:0.15-0.25.

[0011] Adopting the above technical solution, by introducing TiC on the basis of silicon-based and tin-based materials, TiC, as an inert substance, does not participate in the electrochemical reaction, and because of its electrical conductivity and high thermal conductivity, it can enhance the electrical and thermal conductivity of silicon and tin, and because of its strong mechanical properties, it can restrain the expansion of silicon and tin and play a role in stabilizing the material structure. The C layer further enhances the electrical conductivity of silicon and tin. Asphalt is easy to soften at higher temperatures and has good electrical conductivity and spatial ductility at room temperature, which can relieve the fracture and pulverization of silicon and tin active materials.

[0012] Preferably, the molar ratio of silicon, tin, and titanium in the Si-Sn-TiC is 1:0.20:0.20.

[0013] Preferably, the molar ratio of silicon, tin, and titanium in the Si-Sn-TiC is 1:0.20:0.19.

[0014] The present invention also provides a preparation method of the above Si-Sn-TiC / C / asphalt composite material, which specifically includes the following steps:

[0015] S1. Mix silicon source, stannous oxalate, and titanium hydroxide, and use the thermal reduction method to prepare the precursor Si-SnO-TiO2;

[0016] S2. Mix the precursor Si-SnO-TiO2 with a carbon source, ball mill it, and then carry out two carbothermal reductions to prepare the intermediate Si-Sn-TiC / C;

[0017] S3. Mix the intermediate Si-Sn-TiC / C with asphalt and carry out two calcinations to prepare the Si-Sn-TiC / C / asphalt composite material;

[0018] In step S1, the molar ratio of silicon, tin, and titanium in the silicon source, stannous oxalate, and titanium hydroxide is 1: 0.15 - 0.25: 0.15 - 0.25.

[0019] With the above technical solution, a tin-based material is prepared by reduction using stannous oxalate, avoiding the difficulty of pulverizing elemental tin and the difficulty of uniform mixing with Si, etc. The Si source, stannous oxalate, and titanium hydroxide are mixed together and then pyrolyzed, so that both stannous oxalate and titanium hydroxide are oxidized into oxides, and the three are compounded together, avoiding the cumbersome operation and high time cost of step-by-step compounding; then two carbon thermal reductions are carried out, so that stannous oxide and titanium dioxide are reduced at different temperatures respectively. The first carbon thermal reduction is to reduce SnO to Sn, and the second carbon thermal reduction is to reduce TiO2 to TiC. The two carbon thermal reductions utilize one heating process, which not only shortens the synthesis process, simplifies the synthesis steps of the material, but also saves high-temperature costs during the carbon thermal reduction process, and makes the obtained material have a hierarchical structure; finally, a Si-Sn-TiC / C / asphalt composite material is prepared through two calcinations. The first calcination is to soften the asphalt so that it uniformly coats the surface of the material, and the second calcination is to carbonize the asphalt to enhance its conductivity. In addition, the carbon source that is not completely used during carbonization, during the two high-temperature calcination processes, after high-temperature treatment, part of it is converted into substances such as carbon monoxide and carbon dioxide, and part of it will be graphitized to form graphite, which combines with the softened asphalt to finally form a ductile carbon layer, and the carbon layer can also enhance the conductivity of the material.

[0020] Further, in step S1, the silicon source is nano-Si particles or porous silicon. Among them, the porous silicon can also be nano-sized, and the nano-Si particles can also be porous.

[0021] Further, in step S1, the particle size of the silicon source is 50.0 - 200.0 nm (such as 50.0 nm, 70.0 nm, 90.0 nm, 110.0 nm, 130.0 nm, 150.0 nm, 170.0 nm, 190.0 nm, 200.0 nm), and the shape is spherical particles. Silicon has better electrochemical performance under nano and spherical conditions.

[0022] Further, in step S1, the reduction temperature in the thermal reduction method is 300 - 400 °C (such as 300 °C, 350 °C, 400 °C), and the reduction time is 2 - 4 h (such as 2 h, 3 h, 4 h).

[0023] Further, in step S2, the mass ratio of the precursor Si-SnO-TiO2 to the carbon source is 4 - 6:1 (such as 4:1, 5:1, 6:1).

[0024] Further, in step S2, the carbon source is one or more of pitch, graphite, carbon black, needle coke, and Superp. Preferably, it is any one of them.

[0025] Further, in step S2, in the two carbothermal reductions, the temperature of the first carbothermal reduction is 750 - 850°C (such as 750°C, 800°C, 850°C), and the holding time is 1 - 3 h (such as 1 h, 2 h, 3 h); the temperature of the second carbothermal reduction is 1150 - 1250°C (such as 1150°C, 1200°C, 1250°C), and the holding time is 1.5 - 3 h (such as 1.5 h, 2 h, 2.5 h, 3 h).

[0026] Further, in step S3, the mass ratio of the intermediate Si - Sn - TiC / C to pitch is 1:0.1 - 0.3 (such as 1:0.1, 1:0.2, 1:0.3).

[0027] Further, in step S3, in the two calcinations, the temperature of the first calcination is 250 - 350°C (such as 250°C, 300°C, 350°C), and the calcination time is 1 - 2 h (such as 1 h, 1.5 h, 2 h); the temperature of the second calcination is 500 - 700°C (such as 500°C, 600°C, 700°C), and the calcination time is 1 - 2 h (such as 1 h, 1.5 h, 2 h).

[0028] The present invention also provides an application of the above Si - Sn - TiC / C / pitch composite material, and the Si - Sn - TiC / C / pitch composite material is used as a negative electrode active material for lithium - ion batteries.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. By introducing TiC and pitch on the basis of silicon - based and tin - based materials, the present application effectively improves the problems of severe volume expansion and pulverization of silicon - based and tin - based negative electrode materials, and to a certain extent improves the cycle performance and rate performance of the materials, thus enhancing the electrochemical performance of the silicon - based and tin - based composite materials.

[0031] 2. The preparation process of the present application is simple and the cost is low. Specific Embodiments

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0033] Embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. For the process parameters without specific conditions noted in the following embodiments, they are usually in accordance with conventional conditions.

[0034] In the present invention, for the endpoints and any values within the disclosed ranges, they are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in the present invention.

[0035] In the present invention, unless otherwise specified and / or described, throughout, all numerical values related to the dosage of components are in "parts by weight". For the process parameters without specific conditions noted in the following embodiments, they are usually in accordance with conventional conditions.

[0036] Example 1

[0037] A Si-Sn-TiC / C / asphalt composite material, in which the molar ratio of silicon, tin, and titanium in Si-Sn-TiC is 1:0.20:0.19.

[0038] It is prepared by the following method, which specifically includes the following steps:

[0039] S1. Take 1.0 g of nano-silicon particles with a particle size of 50.0 - 200.0 nm, add 1.5 g of stannous oxalate and 0.8 g of titanium hydroxide thereto and mix until there are no obvious large granular crystals;

[0040] Transfer the mixed material to a high-temperature tube furnace, with a heating rate of 5 °C / min, stay at a temperature of 350 °C in an argon atmosphere for 3 h, and after completion, naturally cool to room temperature to obtain a Si-SnO-TiO2 precursor;

[0041] S2. Mix the Si-SnO-TiO2 precursor obtained in step S1 with asphalt according to a mass ratio of 5:1, then transfer it to a ball milling tank and perform dry ball milling for 2 h; transfer the mixed material after dry ball milling to a high-temperature tube furnace, and carry out carbothermal reduction under the protection of argon. Perform the first carbothermal reduction at 800 °C for 1 h, then raise the temperature to 1200 °C and keep it warm for 2 h for the second carbothermal reduction. The heating rate for both carbothermal reductions is 5 °C / min. After completion, naturally cool to room temperature to obtain an intermediate Si-Sn-TiC / C;

[0042] S3. Mix the Si-Sn-TiC / C intermediate obtained in step S2 with asphalt at a mass ratio of 1:0.2, and use dry ball milling for 1 h to make the two evenly mixed. Then transfer the mixed material to a high-temperature tube furnace and calcine it under the protection of argon. Conduct the first calcination at 300 °C for 1 h, then raise the temperature to 600 °C for the second calcination for 1 h. The heating rate for both calcinations is 5 °C / min. After completion, naturally cool it to room temperature to obtain the Si-Sn-TiC / C / asphalt anode composite material.

[0043] Comparative Example 1

[0044] A Si-Sn-TiC / C / asphalt composite material, in which the molar ratio of silicon, tin, and titanium in Si-Sn-TiC is 1:0.1:0.12.

[0045] It is prepared by the following method, specifically including the following steps:

[0046] S1. Take 1.0 g of nano-silicon particles with a particle size of 50.0 - 200.0 nm, add 0.75 g of stannous oxalate and 0.5 g of titanium hydroxide to it, and mix until there are no obvious large granular crystals;

[0047] Transfer the mixed material to a high-temperature tube furnace, with a heating rate of 5 °C / min, stay at a temperature of 350 °C in an argon atmosphere for 3 h, and after completion, naturally cool it to room temperature to obtain the Si-SnO-TiO2 precursor;

[0048] S2. Mix the Si-SnO-TiO2 precursor obtained in step S1 with asphalt at a mass ratio of 5:1, then transfer it to a ball milling tank and conduct dry ball milling for 2 h; transfer the mixed material after dry ball milling to a high-temperature tube furnace and conduct carbothermal reduction under the protection of argon. Conduct the first carbothermal reduction at 800 °C for 1 h, then raise the temperature to 1200 °C and hold for 2 h for the second carbothermal reduction. The heating rate for both carbothermal reductions is 5 °C / min. After completion, naturally cool it to room temperature to obtain the intermediate Si-Sn-TiC / C;

[0049] S3. Mix the Si-Sn-TiC / C intermediate obtained in step S2 with asphalt at a mass ratio of 1:0.2, and use dry ball milling for 1 h to make the two evenly mixed. Then transfer the mixed material to a high-temperature tube furnace and calcine it under the protection of argon. Conduct the first calcination at 300 °C for 1 h, then raise the temperature to 600 °C for the second calcination for 1 h. The heating rate for both calcinations is 5 °C / min. After completion, naturally cool it to room temperature to obtain the Si-Sn-TiC / C / asphalt anode composite material.

[0050] Comparative Example 2

[0051] A Si-Sn-TiC / C / asphalt composite material, in which the molar ratio of silicon, tin, and titanium in Si-Sn-TiC is 1:0.51:0.48.

[0052] It is prepared by the following method, specifically including the following steps:

[0053] S1. Take 1.0 g of nano-silicon particles with a particle size of 50.0 - 200.0 nm, add 3.8 g of stannous oxalate and 2.0 g of titanium hydroxide to it, and mix until there are no obvious large granular crystals;

[0054] Transfer the mixed material to a high-temperature tube furnace, with a heating rate of 5 °C / min, stay at a temperature of 350 °C in an argon atmosphere for 3 h, and then naturally cool to room temperature to obtain a Si-SnO-TiO2 precursor;

[0055] S2. Mix the Si-SnO-TiO2 precursor obtained in step S1 with asphalt according to a mass ratio of 5:1, then transfer it to a ball milling tank and perform dry ball milling for 2 h; transfer the mixed material after dry ball milling to a high-temperature tube furnace, and carry out carbothermal reduction under the protection of argon. Carry out the first carbothermal reduction at 800 °C for 1 h, then raise the temperature to 1200 °C and keep it warm for 2 h for the second carbothermal reduction. The heating rates of both carbothermal reductions are 5 °C / min, and after completion, naturally cool to room temperature to obtain an intermediate Si-Sn-TiC / C;

[0056] S3. Mix the Si-Sn-TiC / C intermediate obtained in step S2 with asphalt according to a mass ratio of 1:0.2, use dry ball milling for 1 h to mix them evenly, then transfer the mixed material to a high-temperature tube furnace, and carry out calcination under the protection of argon. Carry out the first calcination at 300 °C for 1 h, then raise the temperature to 600 °C and carry out the second calcination for 1 h. The heating rates of both calcinations are 5 °C / min, and after completion, naturally cool to room temperature to obtain a Si-Sn-TiC / C / asphalt negative electrode composite material.

[0057] Comparative Example 3

[0058] A Si-Sn-TiC / C / asphalt composite material, in which the molar ratio of silicon, tin, and titanium in Si-Sn-TiC is 1:0.20:0.19.

[0059] It is prepared by the following method, specifically including the following steps:

[0060] S1. Take 1.0 g of nano-silicon particles with a particle size of 50.0 - 200.0 nm, add 1.5 g of stannous oxalate and 0.8 g of titanium hydroxide to it, and mix until there are no obvious large granular crystals;

[0061] Transfer the mixed materials into a high-temperature tube furnace with a heating rate of 5 °C / min. Keep them at 350 °C in an argon atmosphere for 3 h, and then naturally cool to room temperature to obtain the Si-SnO-TiO2 precursor;

[0062] S2. Mix the Si-SnO-TiO2 precursor obtained in step S1 with pitch at a mass ratio of 5:1, and then transfer them into a ball milling tank for dry ball milling for 2 h. Transfer the mixed materials after dry ball milling into a high-temperature tube furnace and carry out carbothermal reduction under the protection of argon. Keep it at 700 °C for 1 h for the first carbothermal reduction, and then heat up to 1100 °C and keep it for 2 h for the second carbothermal reduction. The heating rate for both carbothermal reductions is 5 °C / min. After that, naturally cool to room temperature to obtain the intermediate Si-Sn-TiC / C;

[0063] S3. Mix the Si-Sn-TiC / C intermediate obtained in step S2 with pitch at a mass ratio of 1:0.2, and use dry ball milling for 1 h to mix them evenly. Then transfer the mixed materials into a high-temperature tube furnace and carry out calcination under the protection of argon. Carry out the first calcination at 300 °C for 1 h, and then heat up to 600 °C for the second calcination for 1 h. The heating rate for both calcinations is 5 °C / min. After that, naturally cool to room temperature to obtain the Si-Sn-TiC / C / pitch anode composite material.

[0064] Comparative Example 4

[0065] A Si-Sn-TiC / C / pitch composite material, in which the molar ratio of silicon, tin, and titanium in Si-Sn-TiC is 1:0.20:0.19.

[0066] It is prepared by the following method, which specifically includes the following steps:

[0067] S1. Take 1.0 g of nano-silicon particles with a particle size of 50.0 - 200.0 nm, add 1.5 g of stannous oxalate and 0.8 g of titanium hydroxide to it, and mix until there are no obvious large granular crystals;

[0068] Transfer the mixed materials into a high-temperature tube furnace with a heating rate of 5 °C / min. Keep them at 350 °C in an argon atmosphere for 3 h, and then naturally cool to room temperature to obtain the Si-SnO-TiO2 precursor;

[0069] S2. Mix the Si-SnO-TiO₂ precursor obtained in step S1 with asphalt at a mass ratio of 5:1, then transfer it to a ball milling jar and perform dry ball milling for 2 h. Transfer the mixed material after dry ball milling to a high-temperature tube furnace and carry out carbothermal reduction under the protection of argon. Keep it at 900 °C for 1 h for the first carbothermal reduction, then raise the temperature to 1500 °C and keep it for 2 h for the second carbothermal reduction. The heating rate for both carbothermal reductions is 5 °C / min. After completion, cool it naturally to room temperature to obtain the intermediate Si-Sn-TiC / C.

[0070] S3. Mix the Si-Sn-TiC / C intermediate obtained in step S2 with asphalt at a mass ratio of 1:0.2, and use dry ball milling for 1 h to make them evenly mixed. Then transfer the mixed material to a high-temperature tube furnace and carry out calcination under the protection of argon. Carry out the first calcination at 300 °C for 1 h, then raise the temperature to 600 °C for the second calcination for 1 h. The heating rate for both calcinations is 5 °C / min. After completion, cool it naturally to room temperature to obtain the Si-Sn-TiC / C / asphalt anode composite material.

[0071] Comparative Example 5

[0072] A Si / C composite material is prepared by the following method, which specifically includes the following steps:

[0073] S1. Take 1.0 g of nano-silicon particles with a particle size of 50.0 - 200.0 nm, add 0.2 g of asphalt to it for mixing, and then perform mechanical dry ball milling for 2 h. Transfer the mixed material after dry ball milling to a high-temperature tube furnace and calcine it at 800 °C in an argon atmosphere for 2 h, with a heating rate of 5 °C / min, to obtain the Si / C material.

[0074] Comparative Example 6

[0075] A Si-Sn / C composite material is prepared by the following method, which specifically includes the following steps:

[0076] S1. Take 1.0 g of nano-silicon particles with a particle size of 50.0 - 200.0 nm, add 1.5 g of stannous oxalate to it for mixing until there are no obvious large granular crystals.

[0077] Transfer the mixed material to a high-temperature tube furnace, with a heating rate of 5 °C / min, stay at 350 °C in an argon atmosphere for 3 h, and after completion, cool it naturally to room temperature to obtain the Si-SnO precursor.

[0078] S2. Mix the Si-SnO precursor obtained in step S1 with asphalt at a mass ratio of 5:1, then transfer it to a ball mill jar and ball mill dry for 2 h; transfer the mixed material after dry ball milling to a high-temperature tube furnace, calcine it at 800 °C under an argon atmosphere for 2 h, with a heating rate of 5 °C / min, and naturally cool it to room temperature after completion to obtain Si-Sn / C.

[0079] Comparative Example 7

[0080] A Si-TiC / C composite material is prepared by the following method, which specifically includes the following steps:

[0081] S1. Take 1.0 g of nano-silicon particles with a particle size of 50.0 - 200.0 nm, add 0.8 g of titanium hydroxide to it and mix until there are no obvious large granular crystals;

[0082] Transfer the mixed material to a high-temperature tube furnace, with a heating rate of 5 °C / min, stay at a temperature of 350 °C and an argon atmosphere for 3 h, and naturally cool it to room temperature after completion to obtain a Si-TiO2 precursor;

[0083] S2. Mix the Si-TiO2 precursor obtained in step S1 with asphalt at a mass ratio of 5:1, then transfer it to a ball mill jar and ball mill dry for 2 h; transfer the mixed material after dry ball milling to a high-temperature tube furnace, calcine it at 1200 °C under an argon atmosphere for 2 h, with a heating rate of 5 °C / min, and naturally cool it to room temperature after completion to obtain Si-TiC / C.

[0084] Comparative Example 8

[0085] A Si-Sn-TiC / C composite material is prepared by the following method, which specifically includes the following steps:

[0086] S1. Take 1.0 g of nano-silicon particles with a particle size of 50.0 - 200.0 nm, add 1.5 g of stannous oxalate and 0.8 g of titanium hydroxide to it and mix until there are no obvious large granular crystals;

[0087] Transfer the mixed material to a high-temperature tube furnace, with a heating rate of 5 °C / min, stay at a temperature of 350 °C and an argon atmosphere for 3 h, and naturally cool it to room temperature after completion to obtain a Si-SnO-TiO2 precursor;

[0088] S2. Mix the Si-SnO-TiO₂ precursor obtained in step S1 with asphalt at a mass ratio of 5:1, then transfer it to a ball milling jar and perform dry ball milling for 2 h; transfer the mixed material after dry ball milling to a high-temperature tube furnace, and carry out carbothermal reduction under the protection of argon. Calcinate at 800 °C for 1 h for the first carbothermal reduction, then raise the temperature to 1200 °C and calcinate for 2 h for the second carbothermal reduction. The heating rate for both carbothermal reductions is 5 °C / min. After completion, cool it naturally to room temperature to obtain Si-Sn-TiC / C.

[0089] Comparative Example 9

[0090] A Si-Sn / C / asphalt composite material is prepared by the following method, which specifically includes the following steps:

[0091] S1. Take 1.0 g of nano-silicon particles with a particle size of 50.0 - 200.0 nm, add 1.5 g of stannous oxalate to it and mix until there are no obvious large granular crystals;

[0092] Transfer the mixed material to a high-temperature tube furnace, with a heating rate of 5 °C / min, stay at a temperature of 350 °C and in an argon atmosphere for 3 h, and after completion, cool it naturally to room temperature to obtain a Si-SnO precursor;

[0093] S2. Mix the Si-SnO precursor obtained in step S1 with asphalt at a mass ratio of 5:1, then transfer it to a ball milling jar and perform dry ball milling for 2 h; transfer the mixed material after dry ball milling to a high-temperature tube furnace, and calcinate at 800 °C in an argon atmosphere for 2 h, with a heating rate of 5 °C / min. After completion, cool it naturally to room temperature to obtain Si-Sn / C.

[0094] S3. Mix the Si-Sn / C intermediate obtained in step S2 with asphalt at a mass ratio of 1:0.2, use dry ball milling for 1 h to make the two evenly mixed, then transfer the mixed material to a high-temperature tube furnace, and carry out calcination under the protection of argon. Perform the first calcination at 300 °C for 1 h, then raise the temperature to 600 °C for the second calcination for 1 h. The heating rate for both calcinations is 5 °C / min. After completion, cool it naturally to room temperature to obtain the Si-Sn / C / asphalt anode composite material.

[0095] Test Example

[0096] The composite materials prepared in Example 1 and Comparative Examples 1-9 were weighed separately, and mixed according to the mass ratio of composite material:SBR:SuperP of 8:1:1. An appropriate amount of water was added for slurry adjustment and then evenly coated on the copper foil. Then it was placed in an oven at 120 °C for 12 h to remove the moisture contained in the electrode, which was used as the negative electrode of the button battery assembled below. At the same time, the battery case, gasket and washer of the button battery (CR2430) were put into absolute ethanol and ultrasonically treated for half an hour, and then dried in a blast drying oven at 60 °C. Then the electrode was taken out and weighed, and transferred to a glove box filled with argon together with the battery materials for battery assembly. Among them, the water concentration was controlled <2 ppm and the oxygen concentration was <2 ppm in the glove box. The assembly sequence was negative electrode, electrode, separator (Celgard 2300 polypropylene porous membrane), lithium sheet, gasket, washer. After assembly, it was sealed with a sealer and left for 24 h for electrochemical testing. The testing conditions were charge and discharge at 25 °C and 0.5C. The test results are shown in Table 1.

[0097] Table 1 Test data table of Example 1 and Comparative Examples 1-9

[0098]

[0099]

[0100] It can be seen from the test data in Table 1 that the battery made of the material obtained in the embodiment of the present invention has the best cycle performance and first charge performance. This is because TiC increases the structural stability and conductivity of the composite material, and at the same time, the asphalt expands the spatial ductility of the material, alleviating the expansion of Si and Sn materials during charge and discharge. And the material ratio in material synthesis is an important factor affecting the final performance of the material. Therefore, an appropriate material ratio should be selected to synthesize the composite material, too much or too little will weaken the electrochemical performance of the material.

Claims

1. A preparation method of Si-Sn-TiC / C / asphalt composite material, characterized in that, Specifically, the steps are as follows: S1. Mix a silicon source, stannous oxalate, and titanium hydroxide, and prepare a precursor Si-SnO-TiO2 by a thermal reduction method; S2. Mix the precursor Si-SnO-TiO2 with a carbon source, ball mill, and then perform two carbothermal reductions to prepare an intermediate Si-Sn-TiC / C; S3. Mix the intermediate Si-Sn-TiC / C with pitch, and after two calcinations, prepare a Si-Sn-TiC / C / pitch composite material; In the Si-Sn-TiC / C / pitch composite material, the molar ratio of the three elements of silicon, tin, and titanium in Si-Sn-TiC is 1:0.15-0.20:0.15-0.

25.

2. The preparation method according to claim 1, characterized in that, In step S1, the silicon source is nano-Si particles or porous silicon.

3. The preparation method according to claim 1, characterized in that In step S1, the particle size of the silicon source is 50.0-200.0 nm, and the shape is spherical particles.

4. The preparation method according to claim 1, characterized in that, In step S1, the reduction temperature in the thermal reduction method is 300-400 °C, and the reduction time is 2-4 h.

5. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of the precursor Si-SnO-TiO2 to the carbon source is 4-6:

1.

6. The preparation method according to claim 1, characterized in that, In step S2, in the two carbothermal reductions, the first carbothermal reduction temperature is 750-850 °C, the holding time is 1-3 h, the second carbothermal reduction temperature is 1150-1250 °C, and the holding time is 1.5-3 h.

7. The preparation method according to claim 1, characterized in that, In step S3, the mass ratio of the intermediate Si-Sn-TiC / C to pitch is 1:0.1-0.

3.

8. The preparation method according to claim 1, wherein In step S3, in the two calcinations, the first calcination temperature is 250-350 °C, the calcination time is 1-2 h, the second calcination temperature is 500-700 °C, and the calcination time is 1-2 h.

9. A Si-Sn-TiC / C / asphalt composite material, characterized in that, Prepared by the preparation method according to any one of claims 1-8.

10. Application of the Si-Sn-TiC / C / pitch composite material described in claim 9, or the Si-Sn-TiC / C / pitch composite material prepared by the preparation method described in any one of claims 1-8 as a negative electrode material in a lithium-ion battery.

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