Porous carbon-silicon composite material and preparation method and application thereof

Abstract

The invention discloses a porous carbon-silicon composite material as well as a preparation method and application thereof, and belongs to the technical field of battery materials. The preparation method of the porous carbon-silicon composite material comprises the following steps: carrying out ball-milling mixing on porous carbon, silicon powder and a cross-linking agent according to a mass ratio of (20-60): (25-55): (0.5-30), and then carrying out pyrolysis. According to the method, a cross-linking agent is used in the ball milling process, the cross-linking agent forms a covalent bond between porous carbon and silicon powder through a chemical reaction, and a pyrolysis process is combined, so that the interface bonding force between materials is enhanced, the damage of volume expansion of silicon to an electrode structure is effectively inhibited, and the cycling stability of the composite material is improved. The preparation process is simple to operate, easy in condition control, suitable for large-scale industrial production, and beneficial to reducing the equipment cost and improving the production efficiency.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a porous carbon-silicon composite material, its preparation method, and its application. Background Technology

[0002] With the rapid development of electric vehicles and portable electronic devices, the demand for lithium-ion batteries with high energy density and long cycle life is increasing. Silicon, due to its ultra-high theoretical specific capacity (approximately 4200 mAh / g), has become a highly promising anode material. However, during charge and discharge, silicon undergoes a volume expansion of up to approximately 300%, which leads to electrode structure damage and active material shedding, severely affecting the battery's cycle stability and lifespan. Therefore, combining silicon with carbon materials is one of the effective strategies to mitigate silicon volume expansion.

[0003] Traditionally prepared silicon-carbon composite materials have many problems, such as weak interfacial bonding between porous carbon and silicon, which makes them prone to separation during battery charge-discharge cycles, leading to reduced utilization of active materials.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a porous carbon-silicon composite material, its preparation method, and its application, so as to solve or improve the above-mentioned technical problems.

[0006] This invention can be implemented as follows:

[0007] In a first aspect, the present invention provides a method for preparing a porous carbon-silicon composite material, comprising the following steps: ball milling and mixing porous carbon, silicon powder and crosslinking agent in a mass ratio of (20-60):(25-55):(0.5-30), followed by pyrolysis.

[0008] In an optional embodiment, the porous carbon has at least one of the following characteristics:

[0009] Feature 1: The specific surface area of ​​porous carbon is 260 m². 2 / g~2200m 2 / g;

[0010] Feature 2: The pore size of porous carbon is 2nm to 3nm.

[0011] In an optional embodiment, the preparation of porous carbon includes carbonizing the distiller's grains.

[0012] In an optional implementation, the lees are waste lees.

[0013] In an optional implementation, carbonization is carried out in an inert atmosphere.

[0014] In an optional embodiment, the carbonization temperature is 300℃~1800℃, and the carbonization time is 1h~24h.

[0015] In an optional embodiment, the process includes pretreatment of the lees before carbonization; the pretreatment includes crushing the lees, soaking them in an acid solution, washing them until neutral, and drying them.

[0016] In an optional embodiment, the particles are crushed to a size of 1 μm to 100 μm.

[0017] In an optional embodiment, the acid solution is an HCl solution with a concentration of 0.1 mol / L to 20 mol / L.

[0018] In an optional implementation, the soaking time is 6 hours to 48 hours.

[0019] In an optional embodiment, the particle size of the silicon powder is 0.015 μm to 500 μm.

[0020] In an optional embodiment, the crosslinking agent includes at least one selected from polyacrylic acid, polyvinyl alcohol, polyethylene glycol, polyimide, polyaniline, polypyrrole, polyvinylpyrrolidone, phenolic resin, chitosan, gelatin, and sodium alginate.

[0021] In an optional embodiment, the ball mill includes at least one of the following features:

[0022] Feature 3: The grinding media used in the ball mill include zirconia balls or agate balls;

[0023] Feature 4: The diameter of the grinding media used in the ball mill is 2mm to 20mm;

[0024] Feature 5: The ball-to-material ratio used in ball milling is 1:1 to 30:1;

[0025] Feature 6: The ball mill speed is 200 r / min to 1000 r / min;

[0026] Feature 7: The ball milling time is 0.5h to 36h.

[0027] In an optional embodiment, pyrolysis includes: holding at 160°C to 500°C for 0.5h to 8h in an inert gas atmosphere, and then holding at 300°C to 1500°C for 0.5h to 24h.

[0028] In an optional embodiment, the heating rate during the pyrolysis process is 1°C / min to 20°C / min.

[0029] In an optional embodiment, the inert gas includes at least one of argon, nitrogen, hydrogen, and helium.

[0030] Secondly, the present invention provides a porous carbon-silicon composite material, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0031] Thirdly, the present invention provides a battery in which the negative electrode material comprises the porous carbon-silicon composite material of the aforementioned embodiments.

[0032] The beneficial effects of this invention include:

[0033] This invention involves ball milling porous carbon obtained from distiller's grains with silicon powder and a crosslinking agent in a specific ratio, followed by pyrolysis. The crosslinking agent forms covalent bonds between the porous carbon and silicon powder through a chemical reaction, which enhances the interfacial bonding between them. This effectively suppresses the damage to the electrode structure caused by silicon volume expansion, improves the cycle stability of the composite material, and increases the battery capacity and coulombic efficiency. Furthermore, the preparation process provided by this invention is simple to operate, with easily controllable conditions, making it suitable for large-scale industrial production, which helps reduce equipment costs and improve production efficiency. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 The first charge-discharge curve of the porous carbon-silicon composite material prepared in Example 6 of this invention;

[0036] Figure 2 The capacity retention curve of the porous carbon-silicon composite material prepared in Example 6 of this invention is shown. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0038] The porous carbon-silicon composite material, its preparation method, and its application provided by this invention will be described in detail below.

[0039] The present invention provides a method for preparing a porous carbon-silicon composite material, which may include the following steps: ball milling and mixing porous carbon, silicon powder and crosslinking agent in a mass ratio of (20-60):(25-55):(0.5-30), followed by pyrolysis.

[0040] The ball milling process described above uses a crosslinking agent, which forms covalent bonds between porous carbon and silicon powder through a chemical reaction. Combined with the subsequent pyrolysis process, this helps to enhance the interfacial bonding force between materials, thereby effectively suppressing the damage to the electrode structure caused by the volume expansion of silicon and improving the cycle stability of the composite material.

[0041] In some optional embodiments, the mass of porous carbon is 20% to 60% of the raw materials (i.e., porous carbon + silicon powder + crosslinking agent), such as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, or 60%, or other values ​​within the range of 20% to 60%. In some more typical embodiments, the mass of porous carbon can be 36.5% to 55% of the raw materials.

[0042] The mass of silicon powder can be 25% to 55% of the raw materials used in the preparation, such as 25%, 30%, 35%, 40%, 45%, 50%, or 55%, or other values ​​within the range of 25% to 55%. In some more typical embodiments, the mass of silicon powder can be 35% to 47.6% of the raw materials used in the preparation.

[0043] The mass of the crosslinking agent can be 0.5% to 30% of the raw materials, such as 0.5%, 1%, 2%, 5%, 10%, 15%, 20%, 25%, or 30%, or other values ​​within the range of 0.5% to 30%. In some typical embodiments, the mass of the crosslinking agent can be 2.5% to 26.5% of the raw materials.

[0044] It should be noted that if the mass of the crosslinking agent is less than 0.5% of the raw materials, it is difficult to improve the interfacial bonding force between porous carbon and silicon powder; if the mass of the crosslinking agent is more than 30% of the raw materials, it will reduce the capacity of the battery obtained by further preparation of porous carbon-silicon composite material.

[0045] In some alternative embodiments, the specific surface area of ​​porous carbon can be 260 m². 2 / g~2200m 2 / g. In some typical embodiments, the specific surface area of ​​porous carbon is 570m². 2 / g~890m 2 / g.

[0046] In some alternative implementations, the pore size of the porous carbon can be 2 nm to 3 nm.

[0047] In some alternative embodiments, the preparation of porous carbon may include carbonizing distillers' grains; in other embodiments, porous carbon may also be prepared using other substances, but distillers' grains are preferred.

[0048] In some alternative implementations, the lees are waste lees.

[0049] By using waste distiller's grains to prepare porous carbon, we can reduce costs and reuse waste distiller's grains. On the other hand, the porous carbon prepared from distiller's grains has a rich pore structure, which is conducive to loading silicon and thus inhibiting silicon expansion.

[0050] In some alternative implementations, the carbonization process of the distiller's grains is carried out in an inert atmosphere.

[0051] In some alternative embodiments, the carbonization temperature can be between 300°C and 1800°C, such as 300°C, 500°C, 800°C, 1000°C, 1200°C, 1500°C, or 1800°C, or other values ​​within the range of 300°C to 1800°C. In some more typical embodiments, the carbonization temperature is between 800°C and 1200°C.

[0052] If the temperature is below 300℃, carbonization cannot be achieved or may result in incomplete carbonization; if the temperature is above 1800℃, graphitization may easily occur.

[0053] The carbonization time can be from 1 hour to 24 hours, such as 1 hour, 2 hours, 4 hours, 8 hours, 12 hours, 16 hours, 20 hours, or 24 hours, or other values ​​within the range of 1 hour to 24 hours. In some typical embodiments, the carbonization time is 2 hours to 6 hours.

[0054] In some alternative embodiments, pretreatment of the lees may be included prior to carbonization. Pretreatment includes crushing the lees, soaking them in an acidic solution, washing them until neutral, and drying them.

[0055] The crushing process can involve crushing the lees to a particle size of 1μm to 100μm. In some typical implementations, the particle size of the crushed lees is 10μm to 40μm.

[0056] Crushing the distiller's grains beforehand improves carbonization and pyrolysis.

[0057] The acid solution can be an HCl solution with a concentration of 0.1 mol / L to 20 mol / L (e.g., 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 5 mol / L, 10 mol / L, 15 mol / L, or 20 mol / L). In some typical embodiments, the concentration of the acid solution is 3 mol / L to 6 mol / L.

[0058] The soaking time can be from 6 hours to 48 hours, such as 6 hours, 12 hours, 24 hours, 36 hours, or 48 hours, or other values ​​within the range of 6 hours to 48 hours. In some typical embodiments, the soaking time is 24 hours.

[0059] Soaking in an acidic solution helps remove ash and impurities from the lees.

[0060] In some optional embodiments, the particle size of the silicon powder can be from 0.015 μm to 500 μm, such as 0.015 μm, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, or 500 μm, or other values ​​within the range of 0.015 μm to 500 μm. In some more typical embodiments, the particle size of the silicon powder is from 150 nm to 1 μm.

[0061] In some alternative embodiments, the crosslinking agent may, by way of example but not limitation, include at least one of polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyimide (PI), polyaniline (PANI), polypyrrole (PPy), polyvinylpyrrolidone (PVP), phenolic resin, chitosan, gelatin, and sodium alginate.

[0062] In some alternative embodiments, the milling media used in the ball mill may include zirconia balls or agate balls.

[0063] The diameter of the grinding media used in ball milling can be 2mm to 20mm, such as 2mm, 5mm, 10mm, 15mm, or 20mm, or other values ​​within the range of 2mm to 20mm. In some typical embodiments, the diameter of the grinding media is 3mm to 10mm.

[0064] The ball-to-material ratio used in ball milling can be from 1:1 to 30:1, such as 1:1, 5:1, 10:1, 15:1, 20:1, 25:1, or 30:1, or other values ​​within the range of 1:1 to 30:1. In some typical embodiments, the ball-to-material ratio is from 10:1 to 30:1.

[0065] The ball milling speed can be from 200 r / min to 1000 r / min, such as 200 r / min, 400 r / min, 600 r / min, 800 r / min, or 1000 r / min, or other values ​​within the range of 200 r / min to 1000 r / min. In some typical embodiments, the ball milling speed is from 300 rpm / min to 600 r / min.

[0066] The ball milling time can be from 0.5h to 36h, such as 0.5h, 1h, 4h, 8h, 12h, 24h, or 36h, or other values ​​within the range of 0.5h to 36h. In some typical implementations, the ball milling time is 6h to 20h.

[0067] In some alternative embodiments, pyrolysis may include: holding at 160°C to 500°C for 0.5h to 8h in an inert gas atmosphere, and then holding at 300°C to 1500°C for 0.5h to 24h.

[0068] That is, the above-mentioned pyrolysis includes two stages, which can control the decomposition rate of the crosslinking agent. The temperature of the first stage can be 160℃, 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, or 500℃, or other values ​​within the range of 160℃ to 500℃, preferably 220℃ to 400℃. The duration of the first stage can be 0.5h, 1h, 2h, 3h, 4h, 5h, 6h, 7h, or 8h, or other values ​​within the range of 0.5h to 8h, preferably 0.5h to 2h. The temperature of the second stage can be 300℃, 500℃, 800℃, 1000℃, 1200℃, or 1500℃, or other values ​​within the range of 300℃ to 1500℃, preferably 850℃ to 1000℃. The duration of the second stage can be 0.5h, 1h, 2h, 4h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h or 24h, or other values ​​within the range of 0.5h to 24h, preferably 2h to 6h.

[0069] The first stage mentioned above is a low-temperature stage, in which the crosslinking agent slowly solidifies to form a preliminary crosslinked "network skeleton"; the second stage is a high-temperature stage, in which the crosslinking agent is deeply carbonized to form a "transition carbon layer" at the silicon-carbon interface, tightly connecting the two into a whole, thereby enabling the porous carbon-silicon composite material to form a stable structure.

[0070] In some optional embodiments, the heating rate during the above pyrolysis process can be from 1℃ / min to 20℃ / min, such as 1℃ / min, 2℃ / min, 4℃ / min, 6℃ / min, 8℃ / min, 10℃ / min, 12℃ / min, 14℃ / min, 16℃ / min, 18℃ / min or 20℃ / min, or other values ​​within the range of 1℃ / min to 20℃ / min, preferably 1℃ / min to 5℃ / min.

[0071] The aforementioned inert gas may, by way of example, include at least one of argon, nitrogen, hydrogen, and helium.

[0072] Building upon the above, the preparation process of the porous carbon-silicon composite material provided by this invention is simple to operate, with easily controllable conditions, making it suitable for large-scale industrial production. This method helps reduce equipment costs and improve production efficiency. The method prepares the porous carbon-silicon composite material by co-preparing porous carbon obtained from waste distiller's grains with silicon powder and a crosslinking agent. On the one hand, the crosslinking agent improves the interfacial compatibility between the porous carbon and silicon powder, enhancing their bonding force; on the other hand, it realizes the resource utilization of waste distiller's grains.

[0073] Accordingly, the present invention also provides a porous carbon-silicon composite material, which is prepared by the above-described preparation method.

[0074] In addition, the present invention also provides a battery in which the negative electrode material comprises the above-mentioned porous carbon-silicon composite material.

[0075] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0076] The specific surface area and pore size results of porous carbon in Examples 1-11 and Comparative Examples 1-8 are shown in Table 1.

[0077] Table 1 Specific surface area and pore size of porous carbon

[0078]

[0079]

[0080] Example 1

[0081] This embodiment provides a porous carbon-silicon composite material, the preparation method of which includes the following steps:

[0082] S1: Preparation of porous carbon.

[0083] Waste distiller's grains were crushed to 20 μm and then soaked in a 4 mol / L HCl solution for 24 h. After washing with deionized water until neutral, the grains were transferred to a 100°C oven and dried for 12 h to obtain dried distiller's grains. The dried distiller's grains were then carbonized at 800°C for 2 h in an argon atmosphere to obtain a specific surface area of ​​572 m². 2 / g of porous carbon.

[0084] S2: Ball mill and mix porous carbon with silicon powder and crosslinking agent.

[0085] The raw materials were prepared by placing 50g of porous carbon (50wt% of the raw materials), 47.5g of silicon powder (600nm particle size, 47.5wt% of the raw materials), and 2.5g of PVA (2.5wt% of the raw materials) in a ball mill jar. The raw materials were then ball-milled in a planetary ball mill to obtain the milled material. The milling media were zirconia balls with a diameter of 3mm, the ball-to-material ratio was 15:1, the rotation speed was 400rpm, and the milling time was 20h.

[0086] S3: Pyrolysis.

[0087] Under argon protection, the ball mill was heated to 240°C in a carbonization furnace at a rate of 1°C / min and held for 0.5 h; then heated to 900°C at a rate of 1°C / min and held for 3 h; and cooled to obtain a porous carbon-silicon composite material.

[0088] Example 2

[0089] This embodiment provides a porous carbon-silicon composite material, the preparation method of which includes the following steps:

[0090] S1: Preparation of porous carbon.

[0091] Waste distiller's grains were crushed to 40 μm and then soaked in a 4 mol / L HCl solution for 24 h. After washing with deionized water until neutral, the grains were transferred to a 100°C oven and dried for 12 h to obtain dried distiller's grains. The dried distiller's grains were then carbonized at 1000°C for 4 h in an argon atmosphere to obtain a specific surface area of ​​736 m². 2 / g of porous carbon.

[0092] S2: Ball mill and mix porous carbon with silicon powder and crosslinking agent.

[0093] The raw materials were prepared by placing 50g of porous carbon (50wt% of the raw materials), 40g of silicon powder (1μm particle size, 40wt% of the raw materials), and crosslinking agents (5g of PVA and 5g of PAA, 10wt% of the raw materials) in a ball mill jar. The raw materials were then ball-milled in a planetary ball mill to obtain milled material. The milling media were zirconia balls with a diameter of 5mm, the ball-to-material ratio was 20:1, the rotation speed was 300rpm, and the milling time was 12h.

[0094] S3: Pyrolysis.

[0095] Under argon protection, the ball mill was heated to 235°C in a carbonization furnace at a rate of 2°C / min and held for 1 hour; then heated to 850°C at a rate of 2°C / min and held for 2 hours; and cooled to obtain a porous carbon-silicon composite material.

[0096] Example 3

[0097] This embodiment provides a porous carbon-silicon composite material, the preparation method of which includes the following steps:

[0098] S1: Preparation of porous carbon.

[0099] Waste distiller's grains were crushed to 15 μm and then soaked in a 3 mol / L HCl solution for 24 h. After washing with deionized water until neutral, the grains were transferred to a 100°C oven and dried for 12 h to obtain dried distiller's grains. The dried distiller's grains were then carbonized at 1100°C for 4 h in an argon atmosphere to obtain a specific surface area of ​​682 m². 2 / g of porous carbon.

[0100] S2: Ball mill and mix porous carbon with silicon powder and crosslinking agent.

[0101] The raw materials were prepared by placing 40g of porous carbon (40wt% of the raw materials), 40g of silicon powder (350nm particle size, 40wt% of the raw materials), and 20g of PEG (20wt% of the raw materials) in a ball mill jar. The raw materials were then ball-milled in a planetary ball mill to obtain the milled material. The milling media consisted of zirconia balls with a diameter of 10mm, the ball-to-material ratio was 10:1, the rotation speed was 500rpm, and the milling time was 15h.

[0102] S3: Pyrolysis.

[0103] Under argon protection, the ball mill was heated to 265°C in a carbonization furnace at a rate of 2°C / min and held for 1 hour; then heated to 900°C at a rate of 2°C / min and held for 3 hours; and then cooled to obtain a porous carbon-silicon composite material.

[0104] Example 4

[0105] This embodiment provides a porous carbon-silicon composite material, the preparation method of which includes the following steps:

[0106] S1: Preparation of porous carbon.

[0107] Waste distiller's grains were crushed to 10 μm and then soaked in a 5 mol / L HCl solution for 24 h. After washing with deionized water until neutral, the grains were transferred to a 100°C oven and dried for 12 h to obtain dried distiller's grains. The dried distiller's grains were then carbonized at 1000°C for 3 h in an argon atmosphere to obtain a specific surface area of ​​842 m². 2 / g of porous carbon.

[0108] S2: Ball mill and mix porous carbon with silicon powder and crosslinking agent.

[0109] The raw materials were prepared by placing 55g of porous carbon (55wt% of the raw materials), 35g of silicon powder (400nm particle size, 35wt% of the raw materials), and crosslinking agents (5g of PEG and 5g of PVA, 10wt% of the raw materials) in a ball mill jar. The raw materials were then ball-milled in a planetary ball mill to obtain milled material. The milling media were agate balls with a diameter of 5mm, the ball-to-material ratio was 10:1, the rotation speed was 600rpm, and the milling time was 15h.

[0110] S3: Pyrolysis.

[0111] Under argon protection, the ball mill was heated to 265°C in a carbonization furnace at a rate of 3°C / min and held for 1 hour; then heated to 1000°C at a rate of 3°C / min and held for 2 hours; and then cooled to obtain a porous carbon-silicon composite material.

[0112] Example 5

[0113] This embodiment provides a porous carbon-silicon composite material, the preparation method of which includes the following steps:

[0114] S1: Preparation of porous carbon.

[0115] Waste distiller's grains were crushed to 25 μm and then soaked in a 3 mol / L HCl solution for 24 h. After washing with deionized water until neutral, the grains were transferred to a 100°C oven and dried for 12 h to obtain dried distiller's grains. The dried distiller's grains were then carbonized at 1200°C for 2 h in an argon atmosphere to obtain a specific surface area of ​​803 m². 2 / g of porous carbon.

[0116] S2: Ball mill and mix porous carbon with silicon powder and crosslinking agent.

[0117] The raw materials were prepared by placing 45.6 g of porous carbon (45.6 wt% of the raw materials), 35.6 g of silicon powder (500 nm particle size, 35.6 wt% of the raw materials), and 18.8 g of PPy (18.8 wt% of the raw materials) in a ball mill jar. The raw materials were then ball-milled in a planetary ball mill to obtain the milled material. The milling media were agate balls with a diameter of 10 mm, the ball-to-material ratio was 20:1, the rotation speed was 450 rpm, and the milling time was 10 h.

[0118] S3: Pyrolysis.

[0119] Under argon protection, the ball mill was heated to 300°C in a carbonization furnace at a rate of 5°C / min and held for 1 hour; then heated to 950°C at a rate of 5°C / min and held for 6 hours; and then cooled to obtain a porous carbon-silicon composite material.

[0120] Example 6

[0121] This embodiment provides a porous carbon-silicon composite material, the preparation method of which includes the following steps:

[0122] S1: Preparation of porous carbon.

[0123] Waste distiller's grains were crushed to 10 μm and then soaked in a 3.5 mol / L HCl solution for 24 h. After washing with deionized water until neutral, the grains were transferred to a 100°C oven and dried for 12 h to obtain dried distiller's grains. The dried distiller's grains were then carbonized at 950°C for 6 h in an argon atmosphere to obtain a specific surface area of ​​714 m². 2 / g of porous carbon.

[0124] S2: Ball mill and mix porous carbon with silicon powder and crosslinking agent.

[0125] The raw materials were prepared by placing 48.2 g of porous carbon (48.2 wt% of the raw materials), 47.6 g of silicon powder (particle size 150 nm, 47.6 wt% of the raw materials), and 4.2 g of PPy (4.2 wt% of the raw materials) in a ball mill jar. The raw materials were then ball-milled in a planetary ball mill to obtain the milled material. The milling media were agate balls with a diameter of 5 mm, the ball-to-material ratio was 10:1, the rotation speed was 600 rpm, and the milling time was 8 hours.

[0126] S3: Pyrolysis.

[0127] Under argon protection, the ball mill was heated to 400℃ in a carbonization furnace at a rate of 5℃ / min and held for 2 hours; then heated to 1000℃ at a rate of 5℃ / min and held for 3 hours; and then cooled to obtain a porous carbon-silicon composite material.

[0128] Example 7

[0129] This embodiment provides a porous carbon-silicon composite material, the preparation method of which includes the following steps:

[0130] S1: Preparation of porous carbon.

[0131] Waste distiller's grains were crushed to 30 μm and then soaked in a 4.5 mol / L HCl solution for 24 h. After washing with deionized water until neutral, the grains were dried in a 100°C oven for 12 h to obtain dried distiller's grains. The dried distiller's grains were then carbonized at 850°C for 6 h in an argon atmosphere to obtain a specific surface area of ​​769 m². 2 / g of porous carbon.

[0132] S2: Ball mill and mix porous carbon with silicon powder and crosslinking agent.

[0133] The raw materials were prepared by placing 52.4 g of porous carbon (52.4 wt% of the raw materials), 40.6 g of silicon powder (particle size 150 nm, 40.6 wt% of the raw materials), and 7 g of chitosan (7 wt% of the raw materials) in a ball mill jar. The raw materials were then ball-milled in a planetary ball mill to obtain the milled material. The milling media were zirconia balls with a diameter of 2 mm, the ball-to-material ratio was 30:1, the rotation speed was 400 rpm, and the milling time was 6 hours.

[0134] S3: Pyrolysis.

[0135] Under argon protection, the ball mill was heated to 220°C in a carbonization furnace at a rate of 5°C / min and held for 2 hours; then heated to 900°C at a rate of 5°C / min and held for 4 hours; and then cooled to obtain a porous carbon-silicon composite material.

[0136] Example 8

[0137] This embodiment provides a porous carbon-silicon composite material, the preparation method of which includes the following steps:

[0138] S1: Preparation of porous carbon.

[0139] Waste distiller's grains were crushed to 25 μm and then soaked in a 5.5 mol / L HCl solution for 24 h. After washing with deionized water until neutral, the grains were transferred to a 100°C oven and dried for 12 h to obtain dried distiller's grains. The dried distiller's grains were then carbonized at 900°C for 6 h in an argon atmosphere to obtain a specific surface area of ​​889 m². 2 / g of porous carbon.

[0140] S2: Ball mill and mix porous carbon with silicon powder and crosslinking agent.

[0141] The raw materials were prepared by placing 39.2 g of porous carbon (39.2 wt% of the raw materials), 38.6 g of silicon powder (particle size 280 nm, 38.6 wt% of the raw materials), and crosslinking agents (11.1 g of sodium alginate and 11.1 g of chitosan, 22.2 wt% of the raw materials) in a ball mill jar. The raw materials were then ball-milled in a planetary ball mill to obtain the milled material. The milling media were zirconia balls with a diameter of 5 mm, the ball-to-material ratio was 15:1, the rotation speed was 500 rpm, and the milling time was 10 h.

[0142] S3: Pyrolysis.

[0143] Under argon protection, the ball mill was heated to 220°C in a carbonization furnace at a rate of 3°C / min and held for 1 hour; then heated to 950°C at a rate of 3°C / min and held for 6 hours; and cooled to obtain a porous carbon-silicon composite material.

[0144] Example 9

[0145] This embodiment provides a porous carbon-silicon composite material, the preparation method of which includes the following steps:

[0146] S1: Preparation of porous carbon.

[0147] Waste distiller's grains were crushed to 12 μm and then soaked in a 6 mol / L HCl solution for 24 h. After washing with deionized water until neutral, the grains were transferred to a 100°C oven and dried for 12 h to obtain dried distiller's grains. The dried distiller's grains were then carbonized at 700°C for 6 h in an argon atmosphere to obtain a specific surface area of ​​619 m². 2 / g of porous carbon.

[0148] S2: Ball mill and mix porous carbon with silicon powder and crosslinking agent.

[0149] The raw materials were prepared by placing 42.4 g of porous carbon (42.4 wt% of the raw materials), 39 g of silicon powder (360 nm particle size, 39 wt% of the raw materials), and 18.6 g of sodium alginate (18.6 wt% of the raw materials) in a ball mill jar. The raw materials were then ball-milled in a planetary ball mill to obtain the milled material. The milling media were zirconia balls with a diameter of 3 mm, the ball-to-material ratio was 20:1, the rotation speed was 450 rpm, and the milling time was 8 hours.

[0150] S3: Pyrolysis.

[0151] Under argon protection, the ball mill was heated to 235°C in a carbonization furnace at a rate of 3°C / min and held for 2 hours; then heated to 900°C at a rate of 3°C / min and held for 6 hours; and cooled to obtain a porous carbon-silicon composite material.

[0152] Example 10

[0153] This embodiment provides a porous carbon-silicon composite material, the preparation method of which includes the following steps:

[0154] S1: Preparation of porous carbon.

[0155] Waste distiller's grains were crushed to 10 μm and then soaked in a 4 mol / L HCl solution for 24 h. After washing with deionized water until neutral, the grains were dried in a 100°C oven for 12 h to obtain dried distiller's grains. The dried distiller's grains were then carbonized at 950°C for 6 h in an argon atmosphere to obtain a specific surface area of ​​793 m². 2 / g of porous carbon.

[0156] S2: Ball mill and mix porous carbon with silicon powder and crosslinking agent.

[0157] The raw materials were prepared by placing 36.8 g of porous carbon (36.8 wt% of the raw materials), 36.8 g of silicon powder (420 nm particle size, 36.8 wt% of the raw materials), and 26.4 g of PVP (26.4 wt% of the raw materials) in a ball mill jar. The raw materials were then ball-milled in a planetary ball mill to obtain the milled material. The milling media were zirconia balls with a diameter of 5 mm, the ball-to-material ratio was 10:1, the rotation speed was 600 rpm, and the milling time was 6 hours.

[0158] S3: Pyrolysis.

[0159] Under argon protection, the ball mill was heated to 300℃ in a carbonization furnace at a rate of 3℃ / min and held for 2 hours; then heated to 950℃ at a rate of 3℃ / min and held for 6 hours; and then cooled to obtain a porous carbon-silicon composite material.

[0160] Example 11

[0161] The difference between this embodiment and Embodiment 1 is that: an equal amount of crushed raw melon seed shell powder is used to replace waste distiller's grains to prepare porous carbon, and the specific surface area of ​​this porous carbon is 578 m². 2 / g.

[0162] Comparative Example 1

[0163] The difference between this comparative example and Example 1 is that no crosslinking agent was added and the pyrolysis only had one stage, that is, the pyrolysis was carried out by raising the temperature to 900°C at a rate of 1°C / min and holding it at that temperature for 3 hours.

[0164] Comparative Example 2

[0165] The difference between this comparative example and Example 1 is that the pyrolysis has only one stage, that is, the pyrolysis is to raise the temperature to 900°C at a rate of 1°C / min and hold it at that temperature for 3 hours.

[0166] Comparative Example 3

[0167] The difference between this comparative example and Example 2 is that the pyrolysis has only one stage, that is, the pyrolysis is carried out by raising the temperature to 850°C at a rate of 2°C / min and holding it at that temperature for 2 hours.

[0168] Comparative Example 4

[0169] The difference between this comparative example and Example 6 is that the pyrolysis has only one stage, that is, the pyrolysis is carried out by raising the temperature to 1000°C at a rate of 5°C / min and holding it at that temperature for 3 hours.

[0170] Comparative Example 5

[0171] The difference between this comparative example and Example 1 is that in S1, the carbonization temperature is 250°C.

[0172] Comparative Example 6

[0173] The difference between this comparative example and Example 1 is that in S1, the carbonization temperature is 2000°C.

[0174] Comparative Example 7

[0175] The difference between this comparative example and Example 1 is that in S3, the pyrolysis has only one stage, and the specific pyrolysis is to raise the temperature to 500°C at a rate of 1°C / min and hold it at that temperature for 3.5 hours.

[0176] Comparative Example 8

[0177] The difference between this comparative example and Example 1 is that in S3, the pyrolysis includes: under argon protection, the ball milling material is heated to 150°C at a rate of 1°C / min in a carbonization furnace and held at that temperature for 0.5h; then heated to 900°C at a rate of 1°C / min and held at that temperature for 3h.

[0178] Test case

[0179] The porous carbon-silicon composite materials prepared in Examples 1-11 and Comparative Examples 1-8 were assembled into button cells and their electrochemical performance was tested in the following manner.

[0180] Electrode preparation and battery assembly: After the material preparation is completed, the material, conductive agent and binder are added to a mixer for homogenization. The solvent is N-methylpyrrolidone. The slurry is coated on copper foil and the electrode is transferred to a vacuum oven for drying. The dried electrode is punched into a disc and transferred to a glove box. Lithium metal sheet is used as the counter electrode. LiPF6 is dissolved in an electrolyte of EC+DEC+5%FEC. Button battery assembly is carried out. The assembly sequence is: positive electrode shell → electrolyte → electrode → electrolyte → separator → electrolyte → lithium metal sheet → gasket → spring sheet → negative electrode shell.

[0181] The test conditions are as follows: the assembled battery is left to stand for 12 hours before testing, activated at 0.1 A / g, and subjected to long-cycle charge-discharge test at 1 A / g.

[0182] The test results are shown in Table 2. Figure 1 and Figure 2 As shown.

[0183] Table 2 Electrochemical performance test results

[0184] As can be seen from Table 2, the porous carbon-silicon composite materials prepared in Examples 1 to 11 of this invention are more conducive to improving the capacity and coulombic efficiency of batteries than the porous carbon-silicon composite materials prepared in Comparative Examples 1 to 8.

[0185] In summary, this invention ball-mills porous carbon obtained from distiller's grains with silicon powder and a crosslinking agent in a specific ratio, followed by staged pyrolysis to control the decomposition rate of the crosslinking agent. The crosslinking agent forms covalent bonds between the porous carbon and silicon powder through a chemical reaction, which enhances the interfacial bonding between them. This effectively suppresses the damage to the electrode structure caused by silicon volume expansion, improves the cycle stability of the composite material, and increases the battery's capacity and coulombic efficiency. Furthermore, the preparation process provided by this invention is simple to operate, with easily controllable conditions, suitable for large-scale industrial production, and helps reduce equipment costs and improve production efficiency.

[0186] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a porous carbon-silicon composite material, characterized in that, Includes the following steps: Porous carbon, silicon powder, and crosslinking agent are ball-milled and mixed in a mass ratio of (20-60):(25-55):(0.5-30), and then pyrolyzed.

2. The preparation method according to claim 1, characterized in that, The porous carbon has at least one of the following characteristics: Feature 1: The specific surface area of ​​the porous carbon is 260 m². 2 / g~2200m 2 / g; Feature 2: The porous carbon has a pore size of 2nm to 3nm.

3. The preparation method according to claim 1 or 2, characterized in that, The preparation of the porous carbon includes: carbonizing the distiller's grains; Preferably, the lees are waste lees; Preferably, carbonization is carried out in an inert atmosphere; Preferably, the carbonization temperature is 300℃~1800℃, and the carbonization time is 1h~24h.

4. The preparation method according to claim 3, characterized in that, Before carbonization, the process also includes pretreatment of the lees; the pretreatment includes: crushing the lees, then soaking them in an acid solution, then washing them until neutral and drying them; Preferably, the particles are crushed to a particle size of 1μm to 100μm; Preferably, the acid solution is an HCl solution with a concentration of 0.1 mol / L to 20 mol / L; Preferably, the soaking time is 6h to 48h.

5. The preparation method according to claim 1, characterized in that, The particle size of the silicon powder is 0.015μm to 500μm.

6. The preparation method according to claim 1, characterized in that, The crosslinking agent includes at least one of polyacrylic acid, polyvinyl alcohol, polyethylene glycol, polyimide, polyaniline, polypyrrole, polyvinylpyrrolidone, phenolic resin, chitosan, gelatin, and sodium alginate.

7. The preparation method according to claim 1, characterized in that, Ball milling includes at least one of the following characteristics: Feature 3: The grinding media used in the ball mill include zirconia balls or agate balls; Feature 4: The diameter of the grinding media used in the ball mill is 2mm to 20mm; Feature 5: The ball-to-material ratio used in ball milling is 1:1 to 30:1; Feature 6: The ball mill speed is 200 r / min to 1000 r / min; Feature 7: The ball milling time is 0.5h to 36h.

8. The preparation method according to claim 1, characterized in that, The pyrolysis process includes: holding at 160℃~500℃ for 0.5h~8h in an inert gas atmosphere, and then holding at 300℃~1500℃ for 0.5h~24h. Preferably, the heating rate during the pyrolysis process is 1℃ / min to 20℃ / min; Preferably, the inert gas includes at least one of argon, nitrogen, hydrogen, and helium.

9. A porous carbon-silicon composite material, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 8.

10. A battery, characterized in that, The negative electrode material of the battery includes the porous carbon-silicon composite material as described in claim 9.

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