Silicon-carbon negative electrode material, preparation method thereof, negative electrode sheet and battery

Abstract

The application provides a silicon-carbon negative electrode material, a preparation method thereof, a negative electrode sheet and a battery. The preparation method of the silicon-carbon negative electrode material comprises the following steps: adding silicon powder and carbon powder into an acidic hydrolysis solution of a gel precursor, stirring to obtain a wet gel under an alkaline condition; performing post-treatment on the wet gel to obtain a dry gel; mixing the dry gel with grinding balls in a container, and performing vibration compaction folding to obtain the silicon-carbon negative electrode material; the diameter of the grinding balls is 5mm-50mm; the deviation rate of the diameter of the grinding balls is 30%-60%; the rotation speed n of the vibration compaction folding satisfies 25.44*D 0.5 ≤n≤36.02*D 0.5 ; wherein D is the inner diameter of the container. The method adopts the dry gel as a framework to coat the silicon powder and the carbon powder, and combines the vibration compaction folding to form a gradient density structure in the dry gel, so that the structural stability of the silicon-carbon negative electrode material is improved, the lithium ion transmission path is reserved, and the rate performance and the cycle performance of the battery are improved.

Description

Technical Field

[0001] This application relates to the field of battery materials, and in particular to a silicon-carbon anode material and its preparation method, anode sheet and battery. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics, electric vehicles, and energy storage systems due to their high energy density, long cycle life, and environmental friendliness. The anode material, as a core component of lithium-ion batteries, directly affects battery performance indicators such as capacity, cycle life, and rate performance. Silicon (Si) is favored due to its extremely high theoretical specific capacity (4200 mAh / g, approximately 10 times that of graphite) and suitable lithium intercalation potential (0.2 V vs. Li / Li). + It is considered an ideal choice for the next generation of high energy density anode materials.

[0003] However, silicon materials face several key challenges during charge and discharge: volume expansion rates can reach up to 300% during battery cycling, leading to electrode structure collapse; repeated volume changes cause continuous rupture and regeneration of the electrolyte interphase (SEI) film, consuming electrolyte and increasing internal resistance. Furthermore, silicon itself is a semiconductor material with very low conductivity, further hindering its large-scale application in lithium-ion batteries. Therefore, some researchers have proposed preparing silicon-carbon materials by carbon coating nano-silicon, which can improve battery specific capacity while maintaining the structural stability of the anode material. However, existing silicon-carbon materials suffer from a decrease in rate performance and cycle performance as the silicon content increases.

[0004] To ensure the structural stability of silicon anodes during battery cycling, researchers have deposited nano-silicon on porous carbon as an anode material to reduce the expansion rate of silicon anodes. For example, patent CN119812247A discloses a silicon-carbon composite material and its preparation method, as well as a lithium-ion battery. Utilizing the property of porous carbon to adsorb silane gas, the silane gas is adsorbed onto porous carbon and then decomposed. The silane gas adsorbed within the pores and on the surface is decomposed into elemental silicon, which is then deposited in situ at the adsorption sites. This method reduces the proportion of silicon deposited on the surface of the silicon-carbon composite material, thereby reducing the direct contact between silicon and the electrolyte, which is beneficial for the formation and stability of the SEI film, and thus improves the initial discharge specific capacity, initial efficiency, and capacity retention of the silicon-carbon anode material. Patent CN120413647A discloses a silicon-carbon anode material, its preparation method, and a lithium-ion battery. By coating an amorphous carbon layer onto the surface of a porous carbon framework filled with silicon nanoparticles, and then vertically growing a carbon material array structure on the surface of the amorphous carbon layer, the compressive strength and conductivity of the resulting silicon-carbon anode material are improved, thereby enhancing cycle performance and rate performance while reducing cycle expansion rate. However, the porous carbon framework in the aforementioned patent belongs to graphitized foam carbon and resin-based porous carbon. The compressive strength of the silicon material prepared from this type of porous carbon framework can only reach 10MPa-20MPa, and the silicon content is low, resulting in a low energy density of the resulting silicon-carbon composite material.

[0005] Therefore, there is an urgent need to study a silicon-carbon anode material that utilizes the high compressive strength of dry gel to prevent the expansion of the silicon-carbon anode material, so that the lithium battery can have excellent structural stability while having a high silicon content, thereby obtaining a high initial coulombic efficiency and capacity retention rate. Summary of the Invention

[0006] This application provides a silicon-carbon anode material and its preparation method, anode sheet, and battery, which aim to improve the structural stability of the silicon-carbon anode material at high silicon content, thereby improving the rate performance and cycle performance of the silicon-carbon anode material.

[0007] In a first aspect, embodiments of this application provide a method for preparing a silicon-carbon anode material, comprising:

[0008] Silicon powder and carbon powder were added to the acidic hydrolysate of the gel precursor, and the mixture was stirred under alkaline conditions to obtain a wet gel.

[0009] The wet gel is post-processed to obtain a dry gel;

[0010] The dry gel is mixed with the grinding balls in a container and then vibrated and folded to obtain the silicon-carbon anode material.

[0011] The diameter of the grinding ball is 5mm-50mm;

[0012] The diameter deviation rate of the grinding balls is 30%-60%;

[0013] The rotational speed n of the vibratory folding satisfies 25.44*D. 0.5 ≤n≤36.02*D 0.5 Where D is the inner diameter of the container.

[0014] In one possible implementation, the grinding balls comprise 2-8 different diameter grinding balls;

[0015] And / or, the grinding balls constitute 10%-50% of the volume fraction of the dry gel;

[0016] And / or, the rotational speed n of the vibratory folding satisfies 27.56*D 0.5 ≤n≤31.8*D 0.5 .

[0017] In one possible implementation, the grinding balls include 3 to 4 different types of grinding balls with different diameters;

[0018] And / or, the gel precursor includes at least one of silicate, titanate, zirconate, and aluminum sec-butoxide;

[0019] And / or, the D50 particle size of the silicon powder is 0.02μm-5μm;

[0020] And / or, the D50 particle size of the toner is 20nm-50nm;

[0021] And / or, the toner includes at least one of carbon nanotubes and graphene;

[0022] And / or, the volume-to-mass ratio of the gel precursor hydrolysate, silicon powder, and carbon powder is (700-1000) ml: (20-75) g: (5-25) g;

[0023] And / or, the pH of the acidic hydrolysate is 2-4, and the pH of the alkaline conditions is 7-10.

[0024] In one possible implementation, the method for preparing the silicon-carbon anode material further includes:

[0025] Prior to the post-treatment, the wet gel was mixed with the capping agent and soaked for 3-12 hours;

[0026] The end-capping agent includes at least one of hexamethylsilazane, chloroform, and methyltriethoxysilane;

[0027] The volume ratio of the wet gel to the capping agent is 100:(20-70).

[0028] And / or, carbon coating the surface of the dry gel after the tapping fold, including:

[0029] The dry gel was carbon-coated at 650°C-950°C in an atmosphere containing a mixture of acetylene and an inert gas.

[0030] The mass-to-volume ratio of the dry gel to the mixed gas is (10-30) g: 100 ml.

[0031] In one possible implementation, the post-processing includes aging, solvent replacement, and drying.

[0032] Secondly, embodiments of this application provide a silicon-carbon anode material prepared by the above-described preparation method.

[0033] In one possible implementation, the silicon-carbon anode material comprises, by mass fraction: 10%-80% silicon powder, 5%-30% carbon powder, and the balance being a dry gel; the end-capping groups of the dry gel include hydroxyl and / or carbonyl groups.

[0034] In one possible implementation, the silicon powder has a mass fraction of 20%-70%.

[0035] And / or, the toner has a mass percentage of 5%-25%;

[0036] And / or, the D50 particle size of the silicon-carbon anode material is 3μm-20μm;

[0037] And / or, the tap density of the silicon-carbon anode material is 0.30 g / m³. 3 -0.95g / m 3 ;

[0038] And / or, the specific surface area of ​​the silicon-carbon anode material is 2m² / g-7m² / g.

[0039] Thirdly, embodiments of this application provide a negative electrode sheet, including the silicon-carbon negative electrode material prepared by the above preparation method or the above silicon-carbon negative electrode material.

[0040] Fourthly, embodiments of this application provide a battery comprising a silicon-carbon anode material prepared by the above-described preparation method, or the above-described silicon-carbon anode material, or the above-described anode sheet.

[0041] This application provides a silicon-carbon anode material, its preparation method, anode sheet, and battery. By using dry gel as a framework to coat silicon powder and carbon powder and then vibrating and folding it, the structural stability of the silicon-carbon anode material is improved, thereby enabling the silicon-carbon anode material to have excellent rate performance and cycle performance under the premise of high silicon content. Attached Figure Description

[0042] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0043] Figure 1 Scanning electron microscope image of the silicon-carbon anode material provided in this application;

[0044] Figure 2 Transmission electron microscope (TEM) image of the silicon-carbon anode material provided in this application.

[0045] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0046] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0047] In existing technologies, there is a technical problem that the large volume change rate of the negative electrode material leads to electrode deactivation.

[0048] The method for preparing silicon-carbon anode materials provided in this application solves the technical problem of large volume change rate of materials caused by high silicon content by using dry gel as a skeleton to coat silicon powder and carbon powder, and combining it with the tapping and folding technique.

[0049] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0050] This application provides a method for preparing a silicon-carbon anode material, the method comprising:

[0051] Silicon powder and carbon powder were added to the hydrolysate of the gel precursor, and the mixture was stirred under alkaline conditions to obtain a wet gel.

[0052] The wet gel was post-processed to obtain the dry gel;

[0053] The dry gel is mixed with the grinding balls in a container and then vibrated and folded to obtain the silicon-carbon anode material.

[0054] The diameter of the grinding balls is 5mm-50mm;

[0055] The diameter deviation rate of the grinding balls is 30%-60%;

[0056] The rotational speed n of the vibratory folding satisfies 25.44*D. 0.5 ≤n≤36.02*D 0.5 Where D is the inner diameter of the container.

[0057] In this application, the hydrolysate of the gel precursor can be prepared by conventional methods in the art. For example, the gel precursor is dissolved in water, and at least one acidic solution selected from acetic acid, hydrofluoric acid, hydrochloric acid, and sulfuric acid is added dropwise to adjust the pH value of the solution to 2-4. The solution is stirred for more than 10 minutes to obtain the hydrolysate of the gel precursor.

[0058] When the pH is adjusted, the gel precursor rapidly hydrolyzes in water to generate a large number of monomers with -OH groups, but the condensation polymerization of these monomers to form a network is relatively slow. Therefore, the sol system of the gel precursor remains in a low-viscosity state, filled with active -OH monomers, for a considerable period. Adding silica powder and carbon powder at this time provides them with sufficient time and fluidity to ensure uniform dispersion in the system and prevent agglomeration due to rapid gelation. In the acidic hydrolysate of the gel precursor, the surfaces of silica powder and carbon powder (especially silica powder, whose natural oxide layer has -Si-OH groups) can serve as "nucleation sites" for subsequent condensation polymerization reactions.

[0059] An alkaline reagent with a concentration of 0.05 mol / L to 1.0 mol / L, such as at least one of ammonium hydroxide, potassium hydroxide, and sodium hydroxide, is added dropwise to the hydrolysate of the gel precursor containing silicon powder and carbon powder to adjust the pH of the system to 6-8. Preferably, the concentration of the alkaline reagent can be 0.1 mol / L to 0.2 mol / L. Under alkaline conditions, the alkoxide monomers (-OH) slowly generated in the solution surrounding the silicon powder and carbon powder will gradually undergo a condensation reaction on the surface of these particles, forming a uniform and dense silica gel coating layer in situ. The chemical bonds in the silica gel coating layer greatly enhance the bonding force between the coating layer and the silicon powder. The formed coating layer can also constrain and buffer the volume expansion of the silicon powder during battery charging and discharging, preventing the electrode structure from shattering. In addition, the uniform coating layer can avoid direct and large-area contact between the silicon core and the electrolyte, thereby forming a more stable solid electrolyte interphase (SEI) film, improving coulombic efficiency and cycle life. While toner surfaces are chemically inert with few hydroxyl groups, defects or oxygen-containing functional groups on the toner surface can be activated in acidic environments, facilitating bonding with the gel network through hydrogen bonds and other forces, thus improving interfacial compatibility. More importantly, the slow polymerization in acidic environments allows the gel sufficient time to wrap around and cover the toner surface through physical forces. The toner is uniformly embedded in the gel network, providing excellent channels for electron transport.

[0060] Tap-folding is a processing technique that alternates between tapping (to increase density) and folding (to ensure uniformity). This application utilizes tap-folding on a dry gel containing silicon powder and carbon powder, and selects grinding balls with different diameters for the tap-folding process to maximize the overall tap density of the silicon-carbon composite material. This means that more active material can be filled within the limited volume of the battery, significantly improving the battery's volumetric energy density. Furthermore, it ensures that each silicon particle is uniformly surrounded and supported by carbon material, forming a uniform conductive network and buffer matrix.

[0061] Through the inventor's research, by selecting grinding balls with a diameter deviation rate of 30%-60%, multi-scale filling can be achieved, complex shear forces can be provided, delamination can be effectively suppressed, and ultimately silicon-carbon anode materials with high tap density and good mixing uniformity can be obtained.

[0062] By selecting grinding balls with a diameter between 5mm and 50mm, the relatively larger diameter grinding balls provide the main impact energy, effectively breaking up large agglomerates and providing the main vibration force. This forces the silicon and carbon powders inside the dry gel to rearrange, reducing large voids. Simultaneously, the relatively smaller diameter grinding balls not only fill the large gaps between larger balls and between the larger balls and the can wall, achieving a tighter geometric filling and eliminating "compaction dead zones," pushing the compaction density to its limit, but also provide a significant amount of shear and friction. This effectively prevents the segregation of powder components of different densities or particle sizes (such as heavy silicon powder and light carbon powder) during vibration, thereby achieving a superior compaction effect and obtaining silicon-carbon anode materials with higher mechanical strength. In some optional embodiments, based on the ball diameter deviation rate of the above-mentioned grinding balls being 30%-60%, the particle size of the grinding balls may include at least two particle sizes selected from 5mm, 10mm, 15mm, 20mm, 25mm, 30mm, 35mm, 40mm, 45mm and 50mm, preferably, it may include 3 to 4 particle sizes.

[0063] More importantly, in order to achieve effective tap-folding, the rotational speed n for tap-folding the dry gel needs to satisfy 25.44*D. 0.5 ≤n≤36.02*D 0.5 Where D is the inner diameter of the container. When the rotational speed n satisfies 25.44 * D... 0.5 ≤n≤36.02*D 0.5 In this inequality, both the dry gel and the grinding balls are in a "slipping state." The balls can fall from a height, generating sufficient impact force to compact the dry gel powder. During the slipping process, the balls also generate shear and mixing, turning the dry gel powder at the bottom to the top, achieving uniform mixing. Preferably, to obtain better folding and compaction effects, the rotational speed n satisfies 27.56*D. 0.5 ≤n≤31.8*D 0.5 Specifically, during the vibratory folding process, the dry gel containing silicon powder and carbon powder is placed in a container along with grinding balls. The container is then subjected to three-dimensional rotation, vertical rotation, or up-and-down vibration at the specified speeds for 3-72 hours, preferably 12-24 hours, to obtain the silicon-carbon anode material. During up-and-down vibration, the vibration speed is 30-60 times / min. The grinding balls used can be steel balls, etc.

[0064] For example, the diameter deviation rate of the grinding ball can be a range of 30%, 33%, 35%, 40%, 45%, 50%, 55%, 60%, or any combination thereof.

[0065] In some specific implementations, the grinding balls include 2 to 8 different types of grinding balls with different diameters.

[0066] By selecting grinding balls with 2-8 different diameters to perform tap folding in synergy, it is possible to achieve tap folding with "high tap density" and "high uniformity", thereby obtaining silicon-carbon anode materials with higher mechanical strength, which is beneficial to improving the rate performance and cycle performance of the battery.

[0067] In some specific embodiments, the grinding balls account for 10%-50% of the volume fraction of the dry gel.

[0068] By selecting a grinding ball volume fraction of 10%-50% for the dry gel, sufficient space is maintained within the container to allow for adequate ball movement. The balls can be carried to a certain height and then effectively accelerated downwards, generating sufficient impact kinetic energy to compact the dry gel powder (vibration compaction). Simultaneously, the balls exert good shear force on the dry gel powder during rolling and sliding, resulting in higher energy transfer efficiency and thus achieving more uniform mixing (folding).

[0069] For example, the volume fraction of the grinding balls in the dry gel can be 10%, 20%, 30%, 40%, 50%, or any combination thereof.

[0070] In some specific embodiments, the gel precursor includes at least one of silicate, titanate, zirconate, and aluminum sec-butoxide.

[0071] These metal alkoxides readily undergo hydrolysis to generate metal hydroxyl compounds (M-OH). Subsequently, these hydroxyl groups undergo condensation reactions with each other or with the remaining alkoxy groups, forming a strong MOM (metal-oxygen bond) network. By adjusting the pH value, the rates of hydrolysis and condensation in the system can be precisely controlled, allowing them to penetrate into every gap of the silicon and carbon powders, achieving molecular-level contact and subsequent in-situ, uniform coating. The resulting amorphous metal oxide network buffer layer effectively absorbs the stress on silicon during charging and discharging, preventing electrode structure shattering. Moreover, these metal oxides form a more stable interface with the electrolyte, suppressing side reactions and improving the battery's initial efficiency and cycle life.

[0072] It should be noted that other gel precursors that can achieve the same technical effects as described above can also be used in this application, and no further limitation is made on the types of gel precursors.

[0073] In some specific implementations, the D50 particle size of the silicon powder is 0.02μm-5μm.

[0074] By selecting silicon powder with a D50 particle size within the range of 0.02 μm to 5 μm, it is not only beneficial for uniform wetting and encapsulation by the hydrolysate of the gel precursor to form a complete and dense coating layer, but also shortens the path of lithium ions diffusing from the surface to the interior of the particles, thus improving the rate performance of the material. Furthermore, it provides more inter-particle contact points, which is conducive to constructing a more uniform and efficient conductive network in the electrode. Preferably, the D50 particle size of the silicon powder can be 0.02 μm to 5 μm, more preferably, it can be 0.05 μm to 0.6 μm.

[0075] For example, the D50 particle size of the silicon powder can be a range of 0.02 μm, 0.05 μm, 0.08 μm, 0.10 μm, 0.15 μm, 0.20 μm, 0.30 μm, 0.40 μm, 0.50 μm, 0.60 μm, 0.70 μm, 0.80 μm, 0.90 μm, 1.0 μm, 2.0 μm, 3.0 μm, 4.0 μm, 5.0 μm, or any combination thereof.

[0076] In some specific implementations, the D50 particle size of the toner is 20nm-50nm.

[0077] In this application, the core task of the toner is to establish efficient electronic conduction pathways between active materials (such as silicon) and between the active materials and the current collector. By selecting a D50 particle size of 20nm-50nm for the toner, the densest packing of the particle size distribution can be achieved, allowing more active material to be packed into the same volume, thereby further improving the compaction density of the electrode and the volumetric energy density of the battery.

[0078] For example, the D50 particle size of the toner can be a range of 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, or any combination thereof.

[0079] In some specific embodiments, the toner includes at least one of carbon nanotubes and graphene.

[0080] Carbon nanotubes possess extremely high aspect ratios and toughness. In the hydrolysate of the gel precursor, they intertwine to form a porous, elastic three-dimensional network capable of encapsulating silicon particles. This provides a larger buffer zone for volume expansion, which is beneficial for improving battery cycle life. Furthermore, carbon nanotubes provide defect-free, fast pathways for electrons, helping to reduce electrode internal resistance and improve battery rate performance. Graphene, a two-dimensional sheet structure, can wrap around the surface of each silicon particle like a "blanket," providing excellent surface contact conductive pathways for silicon-carbon anode materials. In other alternative embodiments, the carbon powder can also be conductive carbon black, carbon fiber, etc.

[0081] In some specific implementations, the volume-to-mass ratio of the gel precursor hydrolysate, silicon powder, and carbon powder is (700-1000) ml: (20-75) g: (5-25) g.

[0082] The primary purpose of the sol-gel method employed in this application is to allow the hydrolyzed precursor (such as silanol Si-OH) to uniformly condense on the surface of silicon powder and carbon powder, forming a complete coating layer. By selecting a volume-to-mass ratio of (700-1000) ml: (20-75) g: (5-25) g for the hydrolysate of the gel precursor, silicon powder, and carbon powder, it is possible to ensure that the hydrolysate effectively wets and disperses the silicon powder and carbon powder, allowing them to be fully dispersed. This enables the hydrolysis and condensation reactions to proceed in a homogeneous phase, facilitating the formation of a more uniform coating support framework. Furthermore, it optimizes the pore structure of the dry gel, thereby providing a larger specific surface area for charge storage and rapid ion transport, which is beneficial for improving the battery's initial efficiency and cycle performance.

[0083] For example, the volume-to-mass ratio of the gel precursor hydrolysate, silicon powder, and carbon powder can be 700ml:20g:25g, 800ml:50g:15g, 880ml:60g:15g, 1000ml:20g:5g, 1000ml:30g:10g, 1000ml:40g:13g, 1000ml:50g:15g, 1000ml:60g:15g, 1000ml:60g:20g, 1000ml:70g:25g, 1000ml:75g:20g, or any combination thereof.

[0084] In some specific embodiments, before post-treatment, the wet gel is mixed with a capping agent and soaked for 3-12 hours; the capping agent includes at least one of hexamethylsilazane, chloroform, and methyltriethoxysilane; the volume ratio of the wet gel to the capping agent is 100:(20-70).

[0085] In this application, to improve the hydrophobicity of the silicon-carbon anode material and enhance its dispersion stability in water-based anode slurries, carbonyl end-capping of the gel is also performed. Specifically, a wet gel containing silicon powder and carbon powder is mixed with an end-capping agent and soaked for 3-12 hours to achieve hydrolytic cross-linking between the silanol groups in the wet gel and the end-capping agent, thereby introducing carbonyl groups onto the gel molecules. The end-capping agent may include at least one of hexamethylsilazane, trichloromethane, and methyltriethoxysilane. The introduction of carbonyl groups improves the flowability and stability of the anode slurry, resulting in electrode sheets with more uniform thickness and smoother surfaces. Furthermore, the presence of carbonyl groups can improve the electronic conductivity of the silicon-carbon anode material and promote the formation of more favorable Li-... + A conductive, thinner, and more stable SEI film improves the battery's initial coulombic efficiency and cycle stability.

[0086] Since the molecular structure of the capping agent preferentially reflects the ends of the polymer in the growing gel precursor, preventing further cross-linking, it is necessary to control the amount of capping agent added to avoid affecting the formation of the three-dimensional network inside the gel. By selecting a mixing volume ratio of wet gel to capping agent of 100:(20-70), while taking into account the nanoporous structure, degree of cross-linking, and impurity content in the final dry gel, a silicon-carbon anode material that is more conducive to electrolyte wetting and lithium-ion transport can be obtained.

[0087] For example, the mixing volume ratio of wet gel to capping agent can be 100:20, 100:30, 100:40, 100:50, 100:60, 100:70, or any combination thereof.

[0088] In some specific embodiments, after the dry gel is vibrated and folded, it can also be carbon coated, including: heating the dry gel to 650℃-950℃ in an atmosphere of mixed gas including acetylene and inert gas for carbon coating; the mass-volume ratio of the dry gel to the mixed gas is (10-30) g: 100 ml.

[0089] To improve the conductivity of silicon-carbon anode materials, carbon coating can be applied to the dry gel. Specifically, the dry gel is heated at 650℃-950℃ in a mixed atmosphere containing acetylene and an inert gas. The inert gas can be argon and / or nitrogen.

[0090] In some specific implementations, post-treatment includes aging, solvent replacement, and drying.

[0091] Wet gels require aging to allow unreacted active groups (such as hydroxyl and alkoxy groups) to continue condensation reactions (e.g., silanol condensation to form Si-O-Si bonds), increasing the crosslinking point density and transforming the gel skeleton from a "fragile network" to a "dense and stable structure." Solvent replacement is performed using a solvent with lower surface tension to reduce capillary forces in the gel and prevent damage to the dry gel skeleton. Solvents with lower surface tension can include n-hexane, n-heptane, hexamethylsiloxane, and dichloromethane. Drying removes the solvent portion from the wet gel while preserving its porous structure. Specifically, aging time can be 1-6 hours; solvent replacement can involve immersing the wet gel in a solvent 2-4 times, each time for 30-180 minutes; drying can include at least one of vacuum drying, supercritical drying, or atmospheric pressure drying. Reduced pressure drying can be carried out at 50℃ and 200kPa for 12 hours; supercritical drying can be carried out at 34℃ and 9MPa using CO2 supercritical drying; atmospheric pressure drying can be carried out at 120℃ for 24 hours.

[0092] In some specific embodiments, the silicon-carbon anode material can also be ground and / or sorted to obtain silicon-carbon anode material with a particle size of 3μm-20μm. Specifically, grinding includes at least one of pressure grinding, air jet milling, and ball milling; sorting includes oscillating screening or air jet sorting, with a sorting accuracy of 10μm or 20μm, preferably 10μm.

[0093] The method for preparing silicon-carbon anode materials provided in this application involves using a sol-gel method to prepare a dry gel support framework and combining it with a vibratory folding process with specific grinding ball diameters and rotation speeds to obtain silicon-carbon anode materials with high silicon content. This method suppresses the volume expansion of silicon-carbon anode materials, thereby improving the first-efficiency and cycle performance of the battery.

[0094] This application also provides a silicon-carbon anode material prepared by the above-described preparation method. Figure 1 This is a scanning electron microscope image of the silicon-carbon anode material provided in this application. Figure 2 This is a transmission electron microscope (TEM) image of the silicon-carbon anode material provided in this application. It can be seen that the preparation method provided in this application successfully prepared the silicon-carbon anode material. Figure 1 As can be seen from the embodiments, the particle size of the silicon-carbon anode material provided in this application includes 6.573 μm, 8.012 μm, 8.134 μm, 12.53 μm, and 12.90 μm.

[0095] like Figure 1 As shown, the silicon-carbon anode material provided in this application embodiment comprises, by mass fraction: 10%-80% silicon, 5%-30% carbon, and the balance being a dry gel; the end capping groups of the dry gel include hydroxyl and / or carbonyl groups.

[0096] Using the above preparation method, the silicon content in the silicon-carbon anode material provided in this application can reach up to 80%, achieving higher specific capacity and cycle performance than traditional silicon-carbon materials. Moreover, even with a high silicon content, the volume expansion rate of this silicon-carbon anode material remains below 30% after 100 cycles, demonstrating its excellent ability to suppress volume expansion.

[0097] In some specific implementations, the mass percentage of silicon in the silicon-carbon anode material is 20%-70%.

[0098] To achieve both lower volume expansion and better first-efficiency and cycle performance, the mass percentage of silicon in silicon-carbon anode materials can be controlled between 20% and 70%.

[0099] For example, the mass percentage of silicon can be a range of 20%, 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or any combination thereof.

[0100] In some specific implementations, the mass percentage of carbon in the silicon-carbon anode material is 5%-25%.

[0101] In order to balance the electronic conductivity and specific capacity of silicon-carbon anode materials, the mass percentage of carbon in silicon-carbon anode materials can be controlled between 5% and 25%.

[0102] For example, the mass percentage of carbon can be a range of 5%, 10%, 15%, 20%, 25%, or any combination thereof.

[0103] In some specific embodiments, the particle size of the silicon-carbon anode material prepared by the above preparation method can be 3μm-50μm. Specifically, it can be a range of 3μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, or any combination thereof.

[0104] In some specific embodiments, the tap density of the silicon-carbon anode material prepared by the above preparation method is 0.30 g / m³. 3 -0.95g / m 3 Specifically, it can be 0.30 g / m³. 3 0.40g / m 3 0.50g / m 3 0.60g / m 3 0.70g / m 3 0.75g / m 3 0.80g / m 3 0.85g / m 3 0.90g / m 3 0.95g / m 3 Or a range consisting of any two of them.

[0105] In some specific embodiments, the specific surface area of ​​the silicon-carbon anode material prepared by the above preparation method is 2 m² / g to 7 m² / g. Specifically, it can be a range of 2 m² / g, 3 m² / g, 4 m² / g, 5 m² / g, 6 m² / g, 7 m² / g, or any combination thereof.

[0106] The silicon-carbon anode material provided in this application uses dry gel as a supporting framework for silicon powder and carbon powder, which achieves a good suppression effect on the volume expansion of silicon during cycling, resulting in a silicon-carbon anode material with excellent structural stability, good rate performance, and excellent cycle performance.

[0107] This application also provides a negative electrode sheet, comprising the silicon-carbon negative electrode material prepared by the above-described preparation method or the silicon-carbon negative electrode material described above. This negative electrode sheet exhibits good rate performance and excellent cycle performance.

[0108] This application also provides a battery comprising a silicon-carbon anode material prepared by the above preparation method, or the above silicon-carbon anode material, or the above anode sheet.

[0109] The negative electrode sheet and / or battery provided in this embodiment can perform the method provided in the above method embodiment. The implementation principle and technical effect are similar, and will not be described in detail here.

[0110] The following specific embodiments will be used to further illustrate the technical solution of this application.

[0111] Example 1

[0112] Precursor hydrolysate for gel formation: Dissolve 120g of tetraethyl orthosilicate in 880ml of a mixed solution of ethanol and water (V 乙醇 V 水 In a mixture of 1:3, 0.1 mol / L hydrochloric acid was added dropwise and stirred for 15 min. The pH of the mixed solution was adjusted to 3 to obtain the hydrolysate of the gel precursor.

[0113] Formation of wet gel: Silicon powder (D50=0.05μm, MESA-50) and carbon powder (carbon nanotubes, D50=10nm, YACNT-10) were added in batches to the hydrolysate of the obtained gel precursor, and the mixture was ultrasonically dispersed for 30 min. The mass-volume ratio of silicon powder, carbon powder and hydrolysate of gel precursor was 60 g:15 g:750 ml. Ammonia solution with a concentration of 0.15 mol / L was added dropwise to adjust the pH of the system to 7.2, and the mixture was stirred for 30 min to obtain wet gel.

[0114] Formation of dry gel: After aging the obtained wet gel at room temperature for 4 hours, it was soaked in n-hexane 3 times for 120 minutes each time to perform solvent replacement, and then dried under reduced pressure at 50℃ and 150KPa for 12 hours to obtain dry gel;

[0115] Vibration-compacted folding: The dry gel was placed in a container with a diameter of D=0.4m, and three types of steel balls with diameters of 10mm, 20mm, and 30mm were added. The gel was rotated in three dimensions at a speed of 47rpm (40rpm≤n≤57rpm) for 18h. The total volume of the steel balls accounted for 35% of the volume fraction of the dry gel.

[0116] Grinding and sorting: The obtained dry gel is subjected to air jet milling and air jet sorting (accuracy ±50μm). Particles with a diameter of 5μm-15μm are taken and transferred to a rotary kiln. The kiln is heated to 850℃ in a mixed atmosphere of acetylene and nitrogen to perform carbon coating (the mass-volume ratio of dry gel to mixed gas is 30g:100ml), which is the obtained silicon-carbon anode material.

[0117] The resulting silicon-carbon anode material, by mass percentage, comprises 60% silicon, 20% carbon, and 20% dry gel, with a tap density of 0.87 g / cm³. 3 Its specific surface area is 3.5 m² / g.

[0118] Example 2

[0119] Similar to Example 1, except that the rotational speed of the vibratory folding is 40 rpm.

[0120] Example 3

[0121] Similar to Example 1, the difference is that the vibration folding speed is 44 rpm (n=27.56*D). 0.5 ).

[0122] Example 4

[0123] Similar to Example 1, except that the vibration folding speed is 50 rpm (n=31.8*D). 0.5 ).

[0124] Example 5

[0125] Similar to Example 1, except that the rotational speed of the vibratory folding is 57 rpm.

[0126] Example 6

[0127] Similar to Example 1, except that the steel balls account for 10% of the volume fraction of the dry gel.

[0128] Example 7

[0129] Similar to Example 1, except that the steel balls account for 50% of the volume fraction of the dry gel.

[0130] Example 8

[0131] Hydrolysate for forming gel precursor: Dissolve 80g tetrabutyl titanate and 40g propyl zirconate in 900ml of a mixed solution of ethanol and water (V 乙醇 V 水 The mixture was prepared by adding sulfuric acid (0.1 mol / L) to a solution with a ratio of 1:4 and stirring for 15 minutes. The pH of the mixture was then adjusted to 3.5 to obtain the hydrolysate of the gel precursor.

[0132] Formation of wet gel: Silicon powder (D50=1μm, MESA-1000) and carbon powder (carbon nanotubes, D50=15nm, YACNT-15) were added in batches to the hydrolysate of the obtained gel precursor and ultrasonically dispersed for 30 min. The mass-volume ratio of silicon powder, carbon powder and hydrolysate of gel precursor was 66g:20g:750ml. A 0.1mol / L sodium hydroxide solution was added dropwise to adjust the pH of the system to 7.0 and stirred for 30 min to obtain wet gel.

[0133] Formation of dry gel: After aging the obtained wet gel at room temperature for 3 hours, it was soaked in n-hexane 3 times for 120 minutes each time to perform solvent replacement, and then dried in an oven at 110°C for 24 hours to obtain dry gel;

[0134] Vibration-compacted folding: The dry gel was placed in a container with a diameter of D=0.4m, and three types of steel balls with diameters of 5mm, 15mm, and 25mm were added. The gel was vibrated up and down at a speed of 50rpm (40rpm≤n≤57rpm) for 24h (vibration frequency of 60 times / min). The total volume of the steel balls accounted for 40% of the volume fraction of the dry gel.

[0135] Grinding and sorting: The obtained dry gel is subjected to air jet milling and air jet sorting (accuracy ±10μm). Particles with a diameter of 8μm-18μm are taken and transferred to a rotary kiln. The kiln is heated to 750℃ in an atmosphere of acetylene and nitrogen mixture for carbon coating (the mass-volume ratio of dry gel to mixed gas is 25:100), which is the obtained silicon-carbon anode material.

[0136] The resulting silicon-carbon anode material comprises, by mass percentage, 60% silicon, 10% carbon, and 30% carbon-coated dry gel.

[0137] Example 9

[0138] Similar to Example 1, except that the silicon powder has a D50 of 1 μm and the carbon powder has a D50 of 30 nm; the mass-to-volume ratio of silicon powder, carbon powder and gel precursor hydrolysate is 60 g: 18 g: 800 ml; the drying conditions are an oven at 80 °C; the tapping and folding speed is n = 45 rpm; and the volume fraction of the dry gel in the total volume of the steel balls is 30%.

[0139] The resulting silicon-carbon anode material contains 55% silicon, 20% carbon, and the remainder is dry gel. Its tap density is 0.80 g / cm³ and its specific surface area is 3.8 m² / g.

[0140] Example 10

[0141] Similar to Example 1, except that the silicon powder has a D50 of 2 μm and the carbon powder has a D50 of 30 nm; the mass-to-volume ratio of silicon powder, carbon powder and gel precursor hydrolysate is 70 g: 15 g: 750 ml; the drying conditions are an oven at 80 °C; and the diameters of the steel balls are 15 mm, 25 mm and 40 mm.

[0142] The resulting silicon-carbon anode material contains 60% silicon, 15% carbon, and the remainder is dry gel. Its tap density is 0.85 g / cm³, and its specific surface area is 3.2 m² / g.

[0143] Example 11

[0144] Similar to Example 1, except that the D50 of the silicon powder is 4.6 μm and the D50 of the carbon powder is 30 nm; the mass-volume ratio of silicon powder, carbon powder and gel precursor hydrolysate is 70 g: 20 g: 700 ml; the tapping and folding speed is n = 45 rpm; and the particle size obtained by sorting is 10 μm-20 μm.

[0145] The resulting silicon-carbon anode material contains 65% silicon, 20% carbon, and the remainder is dry gel. Its tap density is 0.88 g / cm³, and its specific surface area is 2.9 m² / g.

[0146] Example 12

[0147] Similar to Example 11, except that the silicon powder has a D50 of 5 μm.

[0148] Example 13

[0149] Similar to Example 1, except that the silicon powder has a D50 of 0.02 μm.

[0150] Example 14

[0151] To form the gel precursor hydrolysate: Dissolve 100g of aluminum sec-butoxide in a 30% ethanol aqueous solution, and add 0.1mol / L acetic acid dropwise. Stir for 15min, adjust the pH of the mixed solution to 2.5, and obtain the gel precursor hydrolysate.

[0152] Formation of wet gel: Silicon powder (D50=100nm, Brofos-Si-100) and carbon powder (graphene, D50=10m, YACNT-10) were added in batches to the obtained gel precursor hydrolysate, and the mixture was ultrasonically dispersed for 30 min. The mass-volume ratio of silicon powder, carbon powder and gel precursor hydrolysate was 70g:23g:700ml. Ammonia solution with a concentration of 0.1mol / L was added dropwise to adjust the pH of the system to 7.5, and the mixture was stirred for 30 min to obtain wet gel.

[0153] End-capping agent treatment: The obtained wet gel was placed in 900 ml of hexamethylsilazane (HMDS) at a volume ratio of 100:45 and soaked for 8 h. The waste liquid was then discharged to obtain carbonyl-terminated wet gel.

[0154] Formation of dry gel: After aging the obtained carbonyl-terminated wet gel at room temperature for 5 hours, it was soaked in n-hexane 3 times for 120 minutes each time to perform solvent replacement, and then dried in an oven at 80°C for 24 hours to obtain dry gel;

[0155] Vibration-compacted folding: The dry gel was placed in a container with a diameter of D=0.35m, and three types of steel balls with diameters of 15mm, 25mm, and 40mm were added. The gel was vertically vibrated at a speed of 47rpm (40rpm≤n≤57rpm) for 24h (vibration frequency of 50 times / min). The total volume of the steel balls accounted for 30% of the volume fraction of the dry gel.

[0156] Grinding and sorting: The obtained dry gel is subjected to air jet milling and air jet sorting (accuracy ±10μm). Particles with a diameter of 3μm-15μm are taken and transferred to a rotary kiln. The kiln is heated to 750℃ in an atmosphere of acetylene and nitrogen mixture for carbon coating (the mass-volume ratio of dry gel to mixed gas is 20g:100ml), which is the obtained silicon-carbon anode material.

[0157] The resulting silicon-carbon anode material, by mass percentage, comprises 65% silicon, 20% carbon, and 15% dry gel, with a tap density of 0.82 g / cm³. 3 Its specific surface area is 3.2 m² / g.

[0158] Example 15

[0159] Similar to Example 14, except that the volume ratio of the wet gel to the capping agent hexamethylsilazane (HMDS) used was 100:20.

[0160] Example 16

[0161] Similar to Example 14, except that the volume ratio of the wet gel to the capping agent hexamethylsilazane (HMDS) used was 100:70.

[0162] Example 17

[0163] Similar to Example 14, except that the capping agent used is chloroform.

[0164] Example 18

[0165] Similar to Example 14, except that the capping agent used is methyltrimethylsilane.

[0166] Example 19

[0167] Similar to Example 14, except that the capping agent used was a mixture of hexamethylsilazane and chloroform in a volume ratio of 1:1.

[0168] Example 20

[0169] Similar to Example 14, the difference is that the gel precursor is 150g of tetraethyl orthosilicate; the mass-to-volume ratio of silicon powder (D50=0.2μm), carbon powder, and gel precursor hydrolysate is 54g:17g:850ml; during the tapping and folding, the steel balls used include three types with diameters of 10mm, 20mm, and 35mm, and the rotation speed is 50rpm; the sorted particles are transferred to a rotary kiln and heated to 750℃ in a mixed atmosphere of acetylene and nitrogen for carbon coating (the mass-to-volume ratio of dry gel to acetylene is 30:1), resulting in silicon-carbon anode material with a particle size of 8μm-18μm.

[0170] Example 21

[0171] Similar to Example 14, the difference is that supercritical CO2 drying is used; during the compaction and folding, four types of steel balls with diameters of 8mm, 15mm, 25mm and 40mm are used, and the steel balls account for 40% of the volume of the dry gel; the rotation speed is 54 rpm.

[0172] Comparative Example 1

[0173] Similar to Example 1, except that no vibration folding is performed.

[0174] Comparative Example 2

[0175] Similar to Example 2, except that the rotational speed is 35 rpm.

[0176] Comparative Example 3

[0177] Similar to Example 5, except that the rotational speed is 60 rpm.

[0178] Comparative Example 4

[0179] Similar to Example 1, the difference is that the steel balls include three types of steel balls with diameters of 10mm, 29mm, and 83mm.

[0180] Comparative Example 5

[0181] Commercially available silicon-carbon materials, by weight percentage, consist of 30% silicon and 70% carbon.

[0182] Application examples

[0183] Preparation of the negative electrode sheet: The silicon-carbon negative electrode materials obtained in Examples 1-21 and Comparative Examples 1-5 were used to prepare the negative electrode slurry according to the following method: The silicon-carbon negative electrode material was mixed with carboxymethyl cellulose and polyacrylic acid at a mass percentage of 96:1.5:2.5, dissolved in 100 parts of deionized water, and stirred for 8 hours to obtain a negative electrode slurry with a solid content of 40%. The obtained slurry was coated onto aluminum foil at a coating amount of 12 mg / cm², vacuum dried at 120°C, and rolled until the porosity of the active layer was 35% to obtain the negative electrode sheet.

[0184] Half-cell preparation: Take a CR2032 battery lower shell, place the negative electrode in the center of the lower shell with the active material coated side facing up; add 1-2 drops of electrolyte to the electrode, just enough to wet the electrode; cover the electrode with the separator, ensuring complete coverage; add an appropriate amount of electrolyte (200μL) to the separator, ensuring the separator is also fully wetted; place the lithium sheet (15.8mm in diameter) in the center of the separator; place the spring sheet on the lithium sheet, with the convex side of the spring sheet facing up; take the CR2032 battery upper shell (negative electrode shell, shallower), cover it with the spring sheet, move the assembled battery to the center of the sealing machine mold, and seal to obtain the half-cell.

[0185] Performance testing

[0186] Compressive strength: 20g of silicon-carbon anode material was prepared into a preform. A universal testing machine was used to apply compressive force to the specimen at a constant loading rate (1mm / min) until it fractured. The maximum crushing load (F) was recorded. max / N) and the cross-sectional area of ​​the sample (A / mm²) 2 ) Calculate: σ c (MPa) = F max / A.

[0187] Carbon coating thickness: Sample preparation: Disperse a small amount of powder sample in anhydrous ethanol, drop it onto a copper grid with a carbon support film, let it dry, and observe it under a transmission electron microscope; select an edge location with a clear and contrasting interface between the core and the coating. Measure the distance from the edge of the core material to the outer edge of the carbon coating using the image processing software provided with the electron microscope, perpendicular to the interface; select 5-10 different areas on the surface of a particle for measurement to obtain the range of carbon coating thickness.

[0188] Initial Coulomb Efficiency: The half-cell containing the above-mentioned negative electrode was tested using a Xinwei CT-4000 battery tester: It was first charged at 0.8C and 1.5C currents to a lower voltage cutoff point (0.01V vs. Li). + / Li), then keep the voltage constant until the current decays to a very small value (e.g., 0.01C) to obtain the initial charge capacity; then let it rest for 15 minutes, and discharge at a current of 0.8C to a higher voltage cutoff point (1.5V vs. Li). + / Li), to obtain the first discharge capacity; the first coulombic efficiency ICR = (first charge capacity / first discharge capacity) × 100%.

[0189] Initial specific capacity: First discharge specific capacity = First discharge capacity (mAh) / Mass of active material (g).

[0190] Capacity retention rate: Under 1C rate and voltage window, continuous constant current charge-discharge cycles are performed, and the initial discharge capacity and the discharge capacity after 500, 1000 and 1500 cycles are recorded. The capacity retention rate is the ratio of the discharge capacity after 500, 1000 and 1500 cycles to the initial discharge capacity.

[0191] Expansion rate: Before battery assembly, the thickness of the original electrode is measured at multiple points and the average value (T0) is taken; the battery is disassembled after 1000 cycles at 1C; the electrode is carefully removed, the residual electrolyte is cleaned and dried, and the electrode thickness is measured again and the average value (T1) is taken. Expansion rate = ((T1-T0) / T0)×100%.

[0192] The test results are detailed in Table 1:

[0193] Table 1

[0194]

[0195] As shown in Table 1, the silicon-carbon anode material provided in this application can still have an expansion rate of less than 50% after 1500 cycles while having a high silicon content, and the resulting anode sheet has excellent initial coulombic efficiency, high initial specific capacity and excellent cycle performance.

[0196] Data from Examples 2-5 shows that when the rotational speed n of the vibration folding is within the preferred range of 27.56*D... 0.5 ≤n≤31.8*D 0.5 The resulting silicon-carbon anode material has higher compressive strength, and the resulting battery has better initial coulombic efficiency, higher initial specific capacity, and better cycle performance.

[0197] Data from Examples 14-19 show that the silicon-carbon anode material prepared by carbonyl end capping has higher compressive strength, and the battery prepared by this silicon-carbon anode material also has better initial coulombic efficiency and higher initial specific capacity.

[0198] Compared with Comparative Example 1, the silicon-carbon anode material obtained in Example 1 has higher compressive strength and better battery performance. This shows that the use of tap folding plays a key role in improving the compressive strength of silicon-carbon anode material and battery performance.

[0199] Compared with Comparative Examples 2-3, the silicon-carbon anode material obtained in Example 1 has higher compressive strength and better battery performance. This indicates that the rotation speed of the tap folding plays a key role in improving the compressive strength of the silicon-carbon anode material and the performance of the battery.

[0200] Compared with Comparative Example 4, the silicon-carbon anode material obtained in Example 1 has higher compressive strength and better battery performance. This indicates that the diameter difference of the steel balls used in the tapping folding plays a key role in improving the compressive strength of the silicon-carbon anode material and the performance of the battery.

[0201] Compared with Comparative Example 5, the silicon-carbon anode material obtained in Example 1 has higher compressive strength and better battery performance. This shows that the silicon-carbon anode material prepared by the method provided in this application has superior mechanical properties compared with ordinary silicon-carbon anode materials, and the battery performance is better when it is used to prepare batteries.

[0202] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for preparing a silicon-carbon anode material, characterized in that, include: Silicon powder and carbon powder are added to the hydrolysate of the gel precursor and stirred under alkaline conditions to obtain a wet gel; the gel precursor includes at least one of silicate ester, titanate ester, zirconate ester, and aluminum sec-butoxide; the volume-to-mass ratio of the hydrolysate of the gel precursor, silicon powder, and carbon powder is (700-1000) ml: (20-75) g: (5-25) g. The wet gel is post-processed to obtain a dry gel; The dry gel is mixed with the grinding balls in a container and then vibrated and folded to obtain the silicon-carbon anode material. The diameter of the grinding ball is 5mm-50mm; The diameter deviation rate of the grinding balls is 30%-60%; The rotational speed n of the vibratory folding satisfies 25.

44. D 0.5 ≤n≤36.02 D 0.5 Where D is the inner diameter of the container.

2. The method for preparing the silicon-carbon anode material according to claim 1, characterized in that, The grinding balls include 2 to 8 different types of grinding balls with different diameters; And / or, the grinding balls constitute 10%-50% of the volume fraction of the dry gel; And / or, the rotational speed n of the vibratory folding satisfies 27.

56. D 0.5 ≤n≤31.8 D 0.5 .

3. The method for preparing the silicon-carbon anode material according to claim 1 or 2, characterized in that, The grinding balls include 3 to 4 different types of grinding balls with different diameters; And / or, the D50 particle size of the silicon powder is 0.02μm-5μm; And / or, the D50 particle size of the toner is 20nm-50nm; And / or, the toner includes at least one of carbon nanotubes, graphene, conductive carbon black, and conductive graphite; And / or, the pH of the hydrolysate of the gel precursor is 2-4, and the pH of the alkaline conditions is 7-10.

4. The method for preparing the silicon-carbon anode material according to claim 1, characterized in that, Also includes: Prior to the post-treatment, the wet gel was mixed with the capping agent and soaked for 3-12 hours; The end-capping agent includes at least one of hexamethylsilazane, chloroform, and methyltriethoxysilane; The volume ratio of the wet gel to the capping agent is 100:(20-70). And / or, carbon coating the surface of the dry gel after the tapping fold, including: The dry gel was heated to 650°C-950°C in an atmosphere containing a mixture of acetylene and an inert gas. The mass-to-volume ratio of the dry gel to the mixed gas is (10-30) g: 100 ml.

5. The method for preparing the silicon-carbon anode material according to claim 4, characterized in that, The post-processing includes aging, solvent replacement, and drying.

6. A silicon-carbon anode material, characterized in that, Prepared by the preparation method according to any one of claims 1-5.

7. The silicon-carbon anode material according to claim 6, characterized in that, By mass percentage, it comprises: 10%-80% silicon powder, 5%-30% carbon powder, and the balance being a dry gel; the end-capping groups of the dry gel include hydroxyl and / or carbonyl groups.

8. The silicon-carbon anode material according to claim 7, characterized in that, The silicon powder has a mass percentage of 20%-70%; And / or, the toner has a mass percentage of 5%-25%; And / or, the particle size of the silicon-carbon anode material is 3μm-50μm; And / or, the tap density of the silicon-carbon anode material is 0.30 g / m³. 3 -0.95g / m 3 ; And / or, the specific surface area of ​​the silicon-carbon anode material is 2m² / g-7m² / g.

9. A negative electrode sheet, characterized in that, The silicon-carbon anode material prepared by the preparation method according to any one of claims 1-5 or the silicon-carbon anode material according to any one of claims 6-8.

10. A battery, characterized in that, The silicon-carbon anode material prepared by the preparation method according to any one of claims 1-5, or the silicon-carbon anode material according to any one of claims 6-8, or the anode sheet according to claim 9.

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