Composite material as well as preparation method and application thereof

Abstract

The embodiment of the invention relates to a composite material as well as a preparation method and application thereof. Uniformly mixing a carbon source material, a surfactant and alcohol in a stirring tank to obtain a mixed solution; placing the mixed solution in a sand mill, adding Prussian blue for sanding treatment to obtain a mixed dispersion liquid, and then drying the mixed dispersion liquid to obtain a porous carbon precursor; placing the porous carbon precursor in a rotary furnace, performing carbonization treatment in an inert gas environment, and then performing grinding, crushing and sieving to obtain a carbonized compound; putting the carbonized compound into a rotary furnace, and activating under the condition of carbon dioxide and / or water vapor to obtain a porous carbon composite material matrix; and introducing gas containing a silicon source into the rotary furnace, and depositing nano silicon in the porous carbon composite material matrix through chemical vapor deposition to obtain the silicon-carbon composite material on which the nano silicon grows.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery materials, and particularly to a composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Silicon materials have attracted great attention from researchers due to their extremely high theoretical lithium intercalation specific capacity (up to 4200 mAh / g at most) and relatively low lithium storage potential, and are one of the ideal candidate materials for high-capacity lithium storage materials. However, during the process of lithium deintercalation and intercalation, silicon materials have serious volume changes, which easily cause pulverization of silicon particles, leading to the detachment of active materials from the current collector and a significant decrease in the cycle stability of the electrode. At the same time, when silicon particles are exposed to the electrolyte, an unstable solid electrolyte interface film (SEI) will form on the surface of silicon, reducing the cycle performance of the electrode material.

[0003] Silicon-carbon materials generally have certain advantages in terms of suppressing volume expansion compared to pure silicon materials. The silicon-carbon composite material combines the characteristics of silicon and carbon materials, and may be able to reduce the overall thermal expansion coefficient and improve the stability of the material. The current synthesis routes for preparing silicon-carbon materials mainly utilize special synthesis processes, such as chemical vapor deposition, liquid-phase impregnation, hydrothermal self-assembly, etc. In order to reduce the expansion rate of the electrode sheet, the existing methods currently include: preparing nano-silicon by reducing the particle size; constructing a core-shell structure and coating silicon materials, etc. However, simply using a coating structure cannot achieve satisfactory results in suppressing silicon expansion, and there are not many obvious outstanding advantages in electrochemical performance, unable to meet the requirements of high-performance applications. Summary of the Invention

[0004] The purpose of the present invention is to solve the problems existing in the existing traditional silicon-carbon materials, such as high expansion rate and poor cycle performance, and to provide a composite material, a preparation method thereof, and an application thereof.

[0005] To this end, in the first aspect, an embodiment of the present invention provides a preparation method of a composite material, and the preparation method includes:

[0006] Mixing a carbon source material, a surfactant, and alcohol evenly in a stirring tank to obtain a mixed solution;

[0007] Placing the mixed solution in a sand mill, adding Prussian blue for sanding treatment to uniformly mix Prussian blue with the carbon source material to obtain a mixed dispersion liquid, and then drying the mixed dispersion liquid to obtain a porous carbon precursor;

[0008] Placing the porous carbon precursor in a rotary furnace, performing carbonization treatment in an inert gas environment, and then grinding, pulverizing, and sieving to obtain a carbonized composite;

[0009] Put the carbonized composite into a rotary kiln again and activate it under the conditions of carbon dioxide and / or water vapor to obtain a porous carbon composite matrix;

[0010] Introduce a gas containing a silicon source into the rotary kiln and deposit nano-silicon inside the porous carbon composite matrix by chemical vapor deposition to obtain a silicon-carbon composite material with nano-silicon grown.

[0011] Preferably, the carbon source material is a thermosetting alcohol-soluble resin, specifically including one or more of phenolic resin, epoxy resin, melamine resin, and acrylic resin;

[0012] The volume percentage concentration of the alcohol is greater than or equal to 99%;

[0013] The mass ratio of the carbon source material, surfactant, and alcohol is [1-7]:[1-4]:[5-40].

[0014] Preferably, the particle size Dv50 of the Prussian blue is 10-100nm; the pore volume is 0.6m 3 / g - 0.9m 3 / g;

[0015] The mass ratio of the carbon source material to the Prussian blue is [100-1000]:[10-70];

[0016] The rotation speed of the sand mill is 1200rpm - 4000rpm, and the sanding time is 1 hour - 4 hours.

[0017] Preferably, the method of the drying treatment includes:

[0018] Oven drying, the drying temperature is 100°C - 150°C, and the drying time is 8 - 16h; or,

[0019] Closed spray drying, and the equipment used is a closed-loop spray dryer;

[0020] The specific conditions of the closed spray drying are: set the inlet air temperature to 150°C - 200°C, the outlet air temperature to 80°C - 150°C, and the frequency of the atomizer to 220Hz - 280Hz.

[0021] Preferably, the inert gas includes nitrogen and / or argon; during the carbonization treatment, the flow rate of the inert gas introduced is 0.5L / min - 4L / min;

[0022] The carbonization treatment specifically includes: heating at a heating rate of 2°C / min - 5°C / min to 400°C - 600°C, holding for 2 hours - 10 hours, and then naturally cooling to room temperature.

[0023] Preferably, putting the carbonized composite into a rotary kiln and activating it under the conditions of carbon dioxide and / or water vapor to obtain a porous carbon composite matrix specifically includes:

[0024] Put the carbonized composite into a rotary kiln again, introduce carbon dioxide gas to keep a carbon dioxide atmosphere in the rotary kiln; after heating to the set temperature, turn on the peristaltic pump, introduce deionized water and generate water vapor by heating, and carry out the activation reaction of the carbonized composite under the carbon dioxide atmosphere and water vapor atmosphere. Then turn off the peristaltic pump, switch the gas introduced into the rotary kiln from carbon dioxide gas to inert gas, and naturally cool it in an inert gas environment to obtain a porous carbon composite matrix;

[0025] Among them, the gas flow rate of the carbon dioxide is 2 L / min - 8 L / min, and the dropping amount of the deionized water is 6 - 14 g / min;

[0026] The heating process specifically includes: heating at a heating rate of 1 °C / min - 3 °C / min to 800 °C - 1000 °C;

[0027] The heat preservation time of the activation reaction is 6 hours - 14 hours.

[0028] Preferably, the gas containing the silicon source is a mixed gas of a protective gas and a silicon source gas; the mixing volume ratio of the protective gas and the silicon source gas is 1:1 - 10:1, and the flow rate of the mixed gas is 8 L / h - 50 L / h; the protective gas is one of hydrogen, nitrogen, and argon; the silicon source gas is one of silane, disilane, trisilane, tetrasilane, chlorosilane, and hexachlorosilane;

[0029] The heating temperature of the chemical vapor deposition is 500 °C - 950 °C, and the heat preservation time is 4 h - 12 h;

[0030] The mass of the nano - silicon accounts for 5% - 45% of the total mass of the silicon - carbon composite material.

[0031] In the second aspect, the embodiments of the present invention provide a composite material prepared by the preparation method described in the first aspect above.

[0032] In the third aspect, the embodiments of the present invention provide a negative electrode plate including the composite material described in the second aspect above.

[0033] In the fourth aspect, the embodiments of the present invention provide a lithium - ion battery including the negative electrode plate described in the third aspect above.

[0034] The preparation method of the composite material provided by the embodiments of the present invention has a simple preparation process, controllable operating conditions, low raw material prices, and the prepared new - type silicon - carbon composite material has a high purity and is easy to realize industrial production. Description of the Drawings

[0035] Figure 1 is a flowchart of the preparation method of the composite material provided by the embodiment of the present invention.

[0036] Figure 2 is a schematic structural diagram of the composite material provided by the embodiment of the present invention;

[0037] Figure 3 is a scanning electron microscope (SEM) image of the novel silicon-carbon composite material provided by Embodiment 1 of the present invention. Detailed Embodiments

[0038] The technical solutions of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0039] The embodiment of the present invention provides a composite material, and the main steps of its preparation method are as Figure 1 shown, including:

[0040] Step 110: Place the carbon source material, surfactant and alcohol in a stirring tank and mix them evenly to obtain a mixed solution.

[0041] Among them, the carbon source material is a thermosetting alcohol-soluble resin, specifically including: one or more of phenolic resin, epoxy resin, melamine resin, and acrylic resin; the surfactant includes: polyvinylpyrrolidone, dialkyl sulfosuccinate, alkyl sulfate, alkyl aryl sulfonate, and fatty alcohol polyoxyethylene ether sulfate;

[0042] The volume percentage concentration of alcohol is greater than or equal to 99%;

[0043] The mass ratio of the carbon source material, surfactant and alcohol is [1-7]:[1-4]:[5-40].

[0044] Step 120: Place the mixed solution in a sand mill, add Prussian blue for sanding treatment to uniformly mix Prussian blue with the carbon source material to obtain a mixed dispersion liquid, and then dry the mixed dispersion liquid to obtain a porous carbon precursor.

[0045] In the present invention, Prussian blue is used as the raw material of the composite material precursor mainly to obtain a high specific surface area and more active sites.

[0046] Metal-organic frameworks (MOFs) are organic-inorganic hybrid materials containing intramolecular voids assembled from metal ions and organic ligands or clusters according to coordination bonds. MOF-derived materials are widely used mainly because they have a high specific surface area, abundant active sites, stable structure, and high degree of adjustability. Among more than 20,000 MOFs with different structures and properties, Prussian blue (PB) belongs to a subcategory with unique characteristics. Prussian blue is a coordination polymer synthesized by co-precipitation of Fe(Ⅲ) salts and 6 4- . PB has a porous three-dimensional structure with voids occupied by water molecules, a relatively high specific surface area, abundant active sites, and a stable structure. Using the unique porous nanobox structure to coat silicon materials will be more conducive to new silicon-carbon materials meeting the requirements of special applications. Moreover, Prussian blue is a relatively inexpensive material because its preparation method is relatively simple and the raw material cost is relatively low. It is an economical and widely used chemical material.

[0047] In the present invention, the particle size Dv50 of Prussian blue is 10 - 100 nm; the pore volume is 0.6 m 3 / g - 0.9 m 3 / g; the pore volume range of Prussian blue represents the total volume of pores inside each gram of Prussian blue material within this range. The value of the pore volume has an important influence on the properties of the material such as adsorption, storage, and transmission. A larger pore volume usually means more pores, which helps to improve the adsorption capacity and storage capacity of the material.

[0048] The mass ratio of the carbon source material to Prussian blue is [100 - 1000]:[10 - 70];

[0049] The rotation speed of the sand mill is 1200 rpm - 4000 rpm, and the sanding time is 1 hour - 4 hours.

[0050] The methods of drying treatment include:

[0051] Oven drying, the drying temperature is 100℃ - 150℃, and the drying time is 8 - 16 h; or,

[0052] Closed spray drying, the equipment used is a closed-loop spray dryer; the specific conditions of closed spray drying are: set the inlet air temperature to 150℃ - 200℃, the outlet air temperature to 80℃ - 150℃, and the frequency of the atomizer to 220 Hz - 280 Hz.

[0053] Step 130, place the porous carbon precursor in a rotary furnace, carry out carbonization treatment in an inert gas environment, and then obtain the carbonized composite through grinding, crushing, and sieving.

[0054] ​Among them, the inert gas includes nitrogen and / or argon; during the carbonization process, the flow rate of the inert gas introduced is 0.5 L / min - 4 L / min;

[0055] The carbonization treatment specifically includes: heating at a heating rate of 2 °C / min - 5 °C / min to 400 °C - 600 °C, holding for 2 hours - 10 hours, and then naturally cooling to room temperature.

[0056] Step 140, put the carbonized composite into a rotary furnace again, and activate it under the condition of carbon dioxide and / or water vapor to obtain a porous carbon composite matrix.

[0057] Specifically, the implementation method of this step can be as follows: put the carbonized composite into a rotary furnace again. Before heating to the set temperature, introduce carbon dioxide gas to keep a carbon dioxide atmosphere in the rotary furnace; after heating to the set temperature, turn on the peristaltic pump, introduce deionized water and generate water vapor by heating, and carry out the activation reaction of the carbonized composite under the carbon dioxide atmosphere and water vapor atmosphere. Then turn off the peristaltic pump, switch the gas introduced into the rotary furnace from carbon dioxide gas to inert gas, and naturally cool under the inert gas environment to obtain a porous carbon composite matrix.

[0058] Among them, the gas flow rate of carbon dioxide is 2 L / min - 8 L / min, and the dropping amount of deionized water is 6 - 14 g / min;

[0059] The heating process specifically includes: heating at a heating rate of 1 °C / min - 3 °C / min to 800 °C - 1000 °C;

[0061] The holding time of the activation reaction is 6 hours - 14 hours.

[0062] The carbon in the carbonized composite will react with carbon dioxide and water vapor, resulting in activation. The presence of water vapor and carbon dioxide promotes the gasification reaction of carbon at high temperature, forming gas products, causing the structure of the carbonized composite to change, forming more micropores and mesoporous structures, thereby increasing the specific surface area of the material. This porous structure is very beneficial for improving the adsorption performance and catalytic activity of the material. The activation process will also form active centers on the carbon skeleton, and these active centers may have a catalytic effect in subsequent reactions.

[0063] Step 150, introduce a gas containing a silicon source into the rotary furnace, and deposit nano-silicon inside the porous carbon composite matrix by chemical vapor deposition to obtain a silicon-carbon composite material growing nano-silicon.

[0064] The silicon source-containing gas is a mixed gas of a protective gas and a silicon source gas; the mixed volume ratio of the protective gas and the silicon source gas is 1:1-10:1, and the mixed gas flow rate is 8L / h-50L / h; the protective gas is one of hydrogen, nitrogen, and argon; the silicon source gas is one of silane, disilane, trisilane, tetrasilane, chlorosilane, and hexachlorosilane;

[0065] The heating temperature of chemical vapor deposition is 500℃-950℃, and the holding time is 4h-12h;

[0066] The mass of nano-silicon accounts for 5%-45% of the total mass of the silicon-carbon composite material.

[0067] The silicon-carbon composite material prepared by the above method of the present invention has a structure as follows Figure 2 As shown, silicon is generated inside the Prussian blue framework by chemical vapor deposition, and the porous carbon composite matrix outside the silicon is the Prussian blue framework structure and the carbon coating layer, so it has a better effect of inhibiting the volume expansion of the silicon material. At the same time, due to the high specific surface area and rich active sites of Prussian blue, the silicon element can be more evenly distributed in the framework structure, which further reduces the probability of excessive local volume expansion of the silicon material, making the material more consistent.

[0068] The silicon-carbon composite material provided in the embodiment of the present invention can be used to prepare a negative electrode plate. Applying the negative electrode plate containing the silicon-carbon composite material to a lithium-ion battery can effectively improve the first-cycle coulombic efficiency and cycle stability of the lithium-ion battery.

[0069] In order to more clearly illustrate the purpose and advantages of the present invention, the present invention is further described below in conjunction with the embodiments. In addition, the embodiments described in the present invention are only partial embodiments. Based on the embodiments described in the present invention, all other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present invention. In addition, it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, that is, they are not intended to limit the protection scope of the present invention.

[0070] Example 1

[0071] This embodiment provides a preparation process and performance test of a novel silicon-carbon composite material, and the specific process is as follows:

[0072] (1) 2 kg of phenolic resin is used as a carbon source material, and the carbon source material, polyvinyl pyrrolidone and alcohol are taken in a stirring tank in a mass ratio of 2:1:12, and mixed evenly to obtain a mixed solution.

[0073] (2) Place the mixed solution in a sand mill. After adding 20 g of Prussian blue, perform sand milling at a rotation speed of 1200 rpm for 2 hours to evenly disperse Prussian blue in the phenolic resin solution, obtaining a mixed dispersion.

[0074] (3) Perform closed - type spray drying on the mixed dispersion. The inlet air temperature is 160 °C, the outlet air temperature is 80 °C, and the atomizer frequency is 240 Hz, obtaining a composite porous carbon precursor.

[0075] (4) Place the composite porous carbon precursor in a rotary furnace for carbonization treatment. Under a nitrogen atmosphere with a gas flow rate of 3 L / min, heat it to 600 °C at a rate of 3 °C / min, hold for 3 hours, naturally cool to room temperature, grind, crush, and sieve (200 mesh) to obtain a carbonized composite.

[0076] (5) First, purge the rotary furnace with nitrogen, then switch the gas introduced into the rotary furnace to carbon dioxide gas to expel nitrogen. After that, heat it to 980 °C at a heating rate of 3 °C / min, start the peristaltic pump to drip deionized water, use carbon dioxide gas and water vapor as the activation atmosphere, the gas flow rate of carbon dioxide is 5 L / min, the deionized water dripping amount is 9 g / min, hold for 14 hours, then close the peristaltic pump, stop supplying water and switch the carbon dioxide gas to nitrogen at the same time, and naturally cool in a nitrogen gas environment to finally obtain a porous carbon composite material.

[0077] (6) Place the porous carbon composite material in a rotary furnace, introduce a mixed gas of a protective gas and a silicon source gas to deposit nano - silicon inside the porous carbon matrix, obtaining a porous carbon matrix with grown nano - silicon; wherein, the volume ratio of the protective gas to the silicon source gas in the mixed gas is 3:1, the mixed gas flow rate is 30 L / h, the heating temperature is 800 °C, the holding time is 4 h, the protective gas is hydrogen, and the silicon source gas is silane.

[0078] Figure 3 It is a scanning electron microscope (SEM) image of the novel silicon - carbon composite material provided in Example 1 of the present invention. Use the silicon - carbon composite material prepared in this example to prepare a negative electrode sheet and assemble it into a CR2032 - type button cell for testing. The specific process is as follows.

[0079] Prepare the negative electrode sheet: Mix graphite, the silicon - carbon composite material, carbon black, and the binder polyvinylidene fluoride (PVDF) in a mass ratio of 55:41:1:3, disperse them in deionized water to form a uniform slurry; then cast the slurry on a copper foil by the doctor - blade method, bake it at 85 °C for 3 hours, perform cold pressing, edge cutting, and slicing, and then dry it in a vacuum at 95 °C for 16 hours to obtain the negative electrode sheet.

[0080] Assemble the CR2032 - type button cell: In a glove box filled with inert gas (where H 2O and O 2 The contents of both are lower than 0.1 ppm. Using a lithium metal sheet as the counter electrode, a double-layer separator of polypropylene (PP) and polyethylene (PE), and 1 mol / L LiPF 6 solution as the electrolyte, where the solvent in the electrolyte is a mixed solution of 97 wt% ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) (where the volume ratio of EC, EMC, and DMC is 1:1:1) + 3 wt% fluoroethylene carbonate (FEC).

[0081] Electrochemical performance test:

[0082] (1) Cycle performance test

[0083] Take 3 pieces from each group of the batteries assembled in this example above, and repeat charging and discharging the batteries through the following steps, and calculate the discharge capacity retention rate of the batteries.

[0084] First, in an environment of 25°C, first charge to 1.5 V at a current density of 0.1 C, then discharge to 5 mV at a current density of 0.5 C, discharge to 5 mV at a density of 0.05 C, discharge to 5 mV at a current density of 0.02 C, discharge to 5 mV at a density of 0.01 C, and record the charging specific capacity of the first cycle. Then perform 400 cycles of discharge and charge, the charging rate during the cycle is 0.5 C, and the discharging rate is 1 C, and record the charging specific capacity of the 400th cycle.

[0085] Calculate the cycle capacity retention rate according to the following formula: Cycle capacity retention rate = specific capacity of the first cycle / specific capacity of the 400th cycle × 100%.

[0086] Calculate the average capacity retention rate of the three groups of batteries after 400 cycles, as shown in Table 1.

[0087] (2) Test on the thickness expansion rate of the negative electrode plate in the fully inserted state

[0088] Measure the thickness of the negative electrode plate before assembling the battery, denoted as D1. The assembled battery is in an environment of 25°C. First, discharge to 5 mV at 0.1 C and discharge to 5 mV at 0.02 C to make the negative electrode plate in the fully inserted state; disassemble the battery and test the thickness of the negative electrode plate in the fully inserted state, denoted as D2. The thickness of the foil used is 9 μm. Calculate the thickness expansion rate according to the following formula: Thickness expansion rate = (D2 - D1) / (D1 - 9) × 100%. The test data are shown in Table 1 for details.

[0089] Example 2

[0090] This example provides a preparation process and performance test of a silicon-carbon composite material. The specific process is as follows:

[0091] (1) Take 2 kg of phenolic resin as the carbon source material, and take the carbon source material, polyvinylpyrrolidone, and alcohol according to a mass ratio of 2:1:12, and place them in a stirring tank to mix evenly to obtain a mixed solution.

[0092] (2) Place the mixed solution in a sand mill, add 15 g of Prussian blue, and perform sanding treatment at a speed of 1200 rpm for 2 hours to evenly disperse Prussian blue in the phenolic resin solution to obtain a mixed dispersion.

[0093] The processes of other steps are the same as those in Example 1, and the test data are shown in Table 1 for details.

[0094] Example 3

[0095] This example provides a preparation process and performance test of a silicon-carbon composite material. The specific process is as follows:

[0096] (1) Take 4 kg of epoxy resin as the carbon source material, and take the carbon source material, polyvinylpyrrolidone, and alcohol according to a mass ratio of 3:1:12, and place them in a stirring tank to mix evenly to obtain a mixed solution.

[0097] (2) Place the mixed solution in a sand mill, add 15 g of Prussian blue, and perform sanding treatment at a speed of 1200 rpm for 2 hours to evenly distribute the phenolic resin in the pores of Prussian blue to obtain a mixed solution.

[0098] The processes of other steps are the same as those in Example 1, and the test data are shown in Table 1 for details.

[0099] Example 4

[0100] This example provides a preparation process and performance test of a silicon-carbon composite material. The specific process is as follows:

[0101] (1) Take 5 kg of melamine resin as the carbon source material, and take the carbon source material, alkyl aryl sulfonate, and alcohol according to a mass ratio of 2:1:14, and place them in a stirring tank to mix evenly to obtain a mixed solution.

[0102] (2) Place the mixed solution in a sand mill, add 25 g of Prussian blue, and perform sanding treatment at a speed of 1200 rpm for 2 hours to evenly distribute the phenolic resin in the pores of Prussian blue to obtain a mixed solution.

[0103] The processes of other steps are the same as those in Example 1, and the test data are shown in Table 1 for details.

[0104] Example 5

[0105] This example provides a preparation process and performance test of a silicon-carbon composite material. The specific process is as follows:

[0106] (1) Take 5 kg of acrylic resin as the carbon source material, and take the carbon source material, fatty alcohol polyoxyethylene ether sulfate, and alcohol according to a mass ratio of 2:1:14, and place them in a stirring tank to mix evenly to obtain a mixed solution.

[0107] (2) Place the mixed solution in a sand mill, add 10 g of Prussian blue, and perform sanding treatment at a speed of 1200 rpm for 2 hours to make the phenolic resin evenly distributed in the pores of Prussian blue, obtaining a mixed solution.

[0108] The processes of other steps are the same as those in Example 1. For the test data, see Table 1 for details.

[0109] To better illustrate the effects of the embodiments of the present invention, Comparative Example 1 is compared with Examples 1-5.

[0110] Comparative Example 1

[0111] This comparative example provides a preparation process and performance test of a traditional silicon-carbon anode material, including the following steps:

[0112] (1) In an ethanol solution, add silicon particles, a carbon source precursor polyvinylpyrrolidone, phenolic resin, and an antioxidant citric acid, and perform sanding according to a mass ratio of 1:1:1:0.1 to obtain a dispersion.

[0113] (2) Spray-dry the dispersion to obtain a precursor material.

[0114] (3) Perform gas-phase coating on the precursor material. Specifically, place 1 kg of the precursor material in a rotary furnace, heat it to 850 °C under a protective atmosphere, and introduce argon and acetylene gases according to a volume ratio of 2:1 for gas-phase coating. Keep the temperature for 1.5 hours, then turn off the organic gas source, and after cooling to room temperature, discharge and classify to obtain the silicon-carbon anode material.

[0115] Use the traditional silicon-carbon anode material prepared in this comparative example to prepare an electrode and assemble a button cell for testing. The specific process is the same as that in Example 1. For the test data, see Table 1 for details.

[0116] Table 1 is a summary of the test data of the button cells assembled in Examples 1-5 and Comparative Example 1:

[0117]

[0118] Table 1

[0119] It can be seen from the test data in Table 1 that the capacity retention rates of the batteries assembled in Examples 1-5 after 400 cycles are all greater than that of Comparative Example 1, and the pole piece expansion rates of Examples 1-5 are all less than that of Comparative Example 1, indicating that the batteries containing the silicon-carbon composite material of the present invention have better performance.

[0120] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only for the specific embodiments of the present invention and is not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a composite material, characterized in that, the preparation method includes: Mixing a carbon source material, a surfactant and alcohol evenly in a stirring tank to obtain a mixed solution; Placing the mixed solution in a sand mill, adding Prussian blue for sanding treatment to uniformly mix the Prussian blue with the carbon source material to obtain a mixed dispersion, and then drying the mixed dispersion to obtain a porous carbon precursor; Placing the porous carbon precursor in a rotary furnace, performing carbonization treatment in an inert gas environment, and then grinding, pulverizing and sieving to obtain a carbonized composite; Putting the carbonized composite into the rotary furnace again, activating it under the conditions of carbon dioxide and / or water vapor to obtain a porous carbon composite matrix; introducing a gas containing a silicon source into the rotary furnace, and depositing nano-silicon inside the porous carbon composite matrix by chemical vapor deposition to obtain a silicon-carbon composite material with grown nano-silicon.

2. The preparation method according to claim 1, characterized in that, the carbon source material is a thermosetting alcohol-soluble resin, specifically including: one or more of phenolic resin, epoxy resin, melamine resin, acrylic resin; the surfactant includes: polyvinylpyrrolidone, dialkyl sulfosuccinate, alkyl sulfate, alkyl aryl sulfonate, fatty alcohol polyoxyethylene ether sulfate; the volume percentage concentration of the alcohol is greater than or equal to 99%; the mass ratio of the carbon source material, the surfactant and the alcohol is [1-7]:[1-4]:[5-40].

3. The preparation method according to claim 1, characterized in that, The particle size Dv50 of the Prussian blue is 10 - 100 nm; the pore volume is 0.6 m 3 / g - 0.9 m 3 / g; the mass ratio of the carbon source material to the Prussian blue is [100-1000]:[10-70]; the rotation speed of the sand mill is 1200 rpm - 4000 rpm, and the sanding time is 1 hour - 4 hours.

4. The preparation method according to claim 1, characterized in that, the drying treatment method includes: oven drying, the drying temperature is 100°C - 150°C, and the drying time is 8 - 16 h; or, closed spray drying, and the equipment used is a closed-loop spray dryer; the specific conditions of the closed spray drying are: setting the inlet air temperature to 150°C - 200°C, the outlet air temperature to 80°C - 150°C, and the frequency of the atomizer to 220 Hz - 280 Hz.

5. The preparation method according to claim 1, characterized in that, the inert gas includes nitrogen and / or argon; during the carbonization treatment, the flow rate of the introduced inert gas is 0.5 L / min - 4 L / min; the carbonization treatment specifically includes: heating at a heating rate of 2°C / min - 5°C / min to 400°C - 600°C, holding for 2 hours - 10 hours, and then naturally cooling to room temperature.

6. The preparation method according to claim 1, characterized in that, the step of putting the carbonized composite into the rotary furnace again and activating it under the conditions of carbon dioxide and / or water vapor to obtain a porous carbon composite matrix specifically includes: Put the carbonized composite into a rotary furnace again, and introduce carbon dioxide gas to maintain a carbon dioxide atmosphere in the rotary furnace; after heating to the set temperature, turn on the peristaltic pump, introduce deionized water and generate water vapor by heating, and carry out the activation reaction of the carbonized composite under the carbon dioxide atmosphere and water vapor atmosphere. Then turn off the peristaltic pump, switch the gas introduced into the rotary furnace from carbon dioxide gas to inert gas, and cool naturally in the inert gas environment to obtain a porous carbon composite matrix; Among them, the gas flow rate of the carbon dioxide is 2 L / min - 8 L / min, and the dropping amount of the deionized water is 6 - 14 g / min; The specific process of the heating includes: heating to 800 °C - 1000 °C at a heating rate of 1 °C / min - 3 °C / min; The heat preservation time of the activation reaction is 6 hours - 14 hours.

7. According to the preparation method described in claim 1, it is characterized in that, the gas containing the silicon source is a mixed gas of a protective gas and a silicon source gas; the mixing volume ratio of the protective gas and the silicon source gas is 1:1 - 10:1, and the flow rate of the mixed gas is 8 L / h - 50 L / h; the protective gas is one of hydrogen, nitrogen, and argon; the silicon source gas is one of silane, disilane, trisilane, tetrasilane, chlorosilane, and hexachlorosilane; the heating temperature of the chemical vapor deposition is 500 °C - 950 °C, and the heat preservation time is 4 h - 12 h; the mass of the nano-silicon accounts for 5% - 45% of the total mass of the silicon-carbon composite.

8. A composite material prepared by the preparation method described in any one of claims 1 - 6 above.

9. A negative electrode plate, it is characterized in that, the negative electrode plate includes the composite material described in claim 8 above.

10. A lithium-ion battery, it is characterized in that, the lithium-ion battery includes the negative electrode plate described in claim 9 above.

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