Silicon-carbon composite material, preparation method thereof, negative electrode and battery
By depositing graphyne and silicon in the pores of the porous carbon matrix, and introducing nanosilver particles and carbon cladding layers to form a silicon-carbon composite material with high conductivity and stable structure, the problem of large volume changes in the existing silicon-carbon materials during charging and discharging is solved, and the circulation and rate performance of the material are improved.
Patent Information
- Application Number
- CN202311824026.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-27
- Publication Date
- 2025-06-27
AI Technical Summary
The existing silicon carbon materials have large volume changes during charging and discharging, and their high temperature and long cycle performance are insufficient, which cannot meet the practical application requirements.
By depositing graphyne and silicon in the pores of the porous carbon matrix, the mass ratio of graphyne and the porous carbon matrix is controlled to be 5 to 10:100, and the mass ratio of silicon to the porous carbon matrix is 45 to 70:100, and nanosilver particles and carbon cladding are introduced during the preparation process to form a silicon-carbon composite material with high conductivity and stable structure.
It effectively suppresses the volume expansion of nano-silicon, improves the circulation and rate performance of the material, and improves the fast charging capability and electrochemical performance of the battery.
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Figure CN120221606A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of battery materials, and in particular, to a silicon-carbon composite material, a preparation method thereof, a negative electrode, and a battery. Background Art
[0002] As an alternative product to graphite, the new silicon-carbon material combines the advantages of both carbon and silicon. Its theoretical specific capacity is higher than 370 mAh / g of graphite, and at the same time, the volume change is also much smaller than that of silicon-based products. However, during the actual charge and discharge process, limited by the size change of nano-silicon in the silicon-carbon product, the high-temperature and long-cycle performance of the material still cannot meet the requirements.
[0003] In view of this, the present invention is specifically proposed. Summary of the Invention
[0004] The purpose of the present invention is to provide a silicon-carbon composite material, a preparation method thereof, a negative electrode, and a battery.
[0005] The present invention is implemented as follows:
[0006] In a first aspect, the present invention provides a silicon-carbon composite material, including a porous carbon matrix and graphdiyne and silicon deposited in the pores of the porous carbon matrix. The mass ratio of graphdiyne to the porous carbon matrix is 5-10:100; the mass ratio of silicon to the porous carbon matrix is 45-70:100.
[0007] In an optional embodiment, in at least a part of the pores of the porous carbon matrix, graphdiyne and silicon are deposited from the inside to the outside.
[0008] In an optional embodiment, the mass ratio of graphdiyne to the porous carbon matrix is 7-10:100.
[0009] In an optional embodiment, nano-silver particles are also deposited in the area where graphdiyne is deposited in the pores of the porous carbon matrix;
[0010] Optionally, the mass ratio of nano-silver particles to the porous carbon matrix is 3-7:100.
[0011] In an optional embodiment, the silicon-carbon composite material further includes a carbon coating layer coated on the surface of the porous carbon matrix.
[0012] In a second aspect, the present invention provides a preparation method of a silicon-carbon composite material according to any one of the foregoing embodiments, including:
[0013] Making catalyst particles enter into the pores of the porous carbon matrix to obtain an intermediate material;
[0014] Placing the intermediate material in a reactor, introducing the vapor of hexaethynylbenzene into the reactor, and making the hexaethynylbenzene enter into the pores of the porous carbon matrix to react with the catalyst particles as the center to form stacked multi-layer graphdiyne;
[0015] Silane is introduced into the reactor, and the silane enters the pores of the porous carbon matrix and decomposes, causing the silicon produced by the decomposition to be deposited in the pores of the porous carbon matrix.
[0016] In an alternative embodiment, the temperature in the reactor is controlled to be 150 - 170 °C to cause hexaethynylbenzene to react to form multilayer graphdiyne.
[0017] Optionally, the reactor is a fluidized bed.
[0018] Optionally, the flow rate of the vapor of hexaethynylbenzene is 0.2 - 0.4 L / min per liter of the reactor, and the reaction time is 2 - 3 h.
[0019] In an alternative embodiment, the temperature in the reactor is controlled to be 480 - 550 °C to cause silane to decompose into silicon.
[0020] Optionally, the flow rate of silane is 0.2 - 0.3 L / min per liter of the reactor, and the reaction time is 3 - 5 h.
[0021] Optionally, after the silicon deposition is completed, surface carbon coating of the porous carbon matrix is further included.
[0022] Optionally, the catalyst particles are nano silver particles.
[0023] In a third aspect, the present invention provides a negative electrode, which is made by using the silicon-carbon composite material according to any one of the foregoing embodiments or the silicon-carbon composite material prepared by the preparation method according to any one of the foregoing embodiments as the active material.
[0024] In a fourth aspect, the present invention provides a battery, including the negative electrode according to the foregoing embodiment.
[0025] The present invention has the following beneficial effects:
[0026] The silicon-carbon composite material provided by the embodiment of the present invention has the following characteristics because graphdiyne with high conductivity and an interlayer structure is introduced into the pores of the porous carbon:
[0027] 1. Due to the buffering of graphdiyne in the carbon substrate, the volume change of the material during charge and discharge is small, and the cycle performance is stronger.
[0028] 2. Graphdiyne inside the pore channels serves as a good adsorption surface, which can promote the deposition of silane inside the pore channels of the porous carbon.
[0029] 3. Graphdiyne has excellent electrical conductivity and a two-dimensional conjugated planar structure, and its interlayer can anchor a certain amount of Li + , compensating for the capacity loss caused by the pursuit of low expansion.
[0030] 4. Graphdiyne allows Li + to move freely inside it parallel or perpendicular to its two-dimensional surface simultaneously, bringing good rate performance and improving the fast charging performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use 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 limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.
[0032] Figure 1 For the electron microscope comparison of the products of Example 1 and Comparative Example 1;
[0033] Figure 2 For the XRD comparison of the products of Example 1 and Comparative Example 1;
[0034] Figure 3 For the Raman spectrum comparison of the products of Example 1 and Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0035] 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. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase.
[0036] The features and performance of the present invention will be further described in detail below with reference to the embodiments.
[0037] The embodiments of the present invention provide a silicon-carbon composite material, its preparation method, a negative electrode, and a battery.
[0038] A silicon-carbon composite material provided by the embodiments of the present invention includes a porous carbon matrix and graphdiyne and silicon deposited in the pores of the porous carbon matrix. The mass ratio of graphdiyne to the porous carbon matrix is 5-10:100 (for example, 5:100, 8:100, or 10:100); the mass ratio of silicon to the porous carbon matrix is 45-70:100 (for example, 45:100, 50:100, 60:100, or 70:100).
[0039] The silicon-carbon composite material provided by the present application introduces graphdiyne with high conductivity and an interlayer structure as a buffer in the pores of the porous carbon, which can effectively inhibit the volume expansion of nano-silicon; at the same time, due to the stable two-dimensional structure of graphdiyne, Li +It can be stored inside its space and can also move along the parallel and vertical directions of the two-dimensional plane. It can not only partially compensate for the capacity reduction caused by reducing the silicon deposition amount, but also improve the rate performance of the novel silicon-carbon material, thereby enhancing the fast charging ability of the product.
[0040] It should be noted that the deposition amount of graphdiyne should be within the above-defined range. If there is too much deposition, the pores of the porous carbon will be blocked, resulting in a large amount of silicon particles deposited outside the carbon support. During the charge and discharge process of the material, the expansion intensifies, weakening the electrochemical performance.
[0041] Optionally, in at least a part of the pores of the porous carbon matrix, graphdiyne and silicon are deposited from the inside to the outside. This part of the pores mainly refers to the larger pores such as micropores of the porous carbon matrix. Based on the preparation method of this silicon-carbon negative electrode material, the silver nanoparticles used to catalyze the growth of graphdiyne generally enter the micropores, and it is generally difficult for silver nanoparticles to enter the smaller pores such as mesopores. Therefore, the growth of graphdiyne mainly occurs in the larger pores.
[0042] During the manufacturing process, graphdiyne is first grown in the pores of the porous carbon matrix. The graphdiyne in the interlayer form, as a good adsorption surface, can promote the deposition of silane inside the pores of the porous carbon, prevent a large amount of silicon crystals from depositing on the surface of the carbon substrate, and further reduce the volume change of the material during the charge and discharge process.
[0043] Preferably, to obtain better electrochemical performance, the mass ratio of graphdiyne to the porous carbon matrix is 6-8:100 (for example, 6:100, 7:100, or 8:100).
[0044] Furthermore, silver nanoparticles are also deposited in the area of the pores of the porous carbon matrix where graphdiyne is deposited; the silver nanoparticles exist in the pores as catalysts for the growth of graphdiyne. An appropriate amount of silver particles will not have an obvious impact on the electrochemical performance of the silicon-carbon composite material. Optionally, the mass ratio of silver nanoparticles to the porous carbon matrix is 3-7:100 (for example, 3:100, 5:100, or 7:100).
[0045] Preferably, to ensure that the silicon-carbon composite material has better electrochemical performance, the silicon-carbon composite material also includes a carbon coating layer coated on the surface of the porous carbon matrix.
[0046] The embodiment of the present invention also provides a preparation method of the above silicon-carbon composite material, including:
[0047] Making catalyst particles enter the pores of the porous carbon matrix to obtain an intermediate material;
[0048] Placing the intermediate material in a reactor, introducing the vapor of hexaethynylbenzene into the reactor, and making the hexaethynylbenzene enter the pores of the porous carbon matrix to react with the catalyst particles as the center to form stacked multi-layer graphdiyne;
[0049] Silane is introduced into the reactor, and the silane enters the pores of the porous carbon matrix and decomposes, so that the silicon produced by the decomposition is deposited in the pores of the porous carbon matrix.
[0050] The preparation method provided by the present invention can obtain the silicon-carbon composite material provided by the embodiments of the present invention.
[0051] Specifically, the preparation method is as follows:
[0052] S1. Prepare an intermediate material
[0053] The catalyst is mixed with the porous carbon matrix. During the mixing process, some catalyst particles enter the larger pores of the porous carbon matrix. For example, some nanoparticles in the catalyst enter the micropores of the porous carbon matrix to obtain the intermediate material.
[0054] The preparation method can be direct mixing or metal sputtering, etc., as long as it can achieve the way that the catalyst particles enter the pores of the porous carbon matrix.
[0055] Preferably, the catalyst is silver nanoparticles.
[0056] S2. Growth and deposition of graphdiyne
[0057] The intermediate material is placed in the reactor, and the vapor of hexaethynylbenzene is introduced into the reactor, so that the hexaethynylbenzene enters the pores of the porous carbon matrix and reacts with the catalyst particles as the center to form multilayer graphdiyne stacked layer by layer.
[0058] Specifically, the reactor is a fluidized bed. Using a fluidized bed to prepare the silicon-carbon composite material can ensure the uniformity of deposition and can blow off the silver particles loaded on the surface of the intermediate material, effectively avoiding the growth of graphdiyne on the surface of the porous carbon matrix.
[0059] Further, the temperature in the reactor is set to 150-170 °C (for example, 150 °C, 160 °C or 170 °C) to realize the reaction of hexaethynylbenzene with silver particles as the center to form multilayer graphdiyne stacked layer by layer.
[0060] Further, to ensure an appropriate deposition amount, the flow rate of the vapor of hexaethynylbenzene is 0.2-0.4 L / min (for example, 0.2 L / min, 0.3 L / min or 0.4 L / min) corresponding to each liter of the reactor, and the reaction time is 2-3 h (for example, 2 h, 2.5 h or 3 h).
[0061] S2. Deposit silicon
[0062] Silane is introduced into the reactor, and the silane enters the pores of the porous carbon matrix and decomposes, so that the silicon produced by the decomposition is deposited in the pores of the porous carbon matrix.
[0063] Further, the temperature in the reactor is controlled to be 480 - 550 °C (480 °C, 500 °C, 530 °C or 550 °C) to decompose silane into silicon.
[0064] Optionally, to ensure proper silicon deposition and minimize silicon deposition on the surface of the porous carbon matrix, the flow rate of silane is 0.2 - 0.3 L / min (0.2 L / min, 2.5 L / min or 3 L / min) per liter of the reactor, and the reaction time is 3 - 5 h (such as 3 h, 4 h or 5 h).
[0065] It should be noted that first allowing the catalyst particles to enter the pores of the porous carbon matrix to grow graphdiyne and then depositing silicon is only the preferred embodiment of the present invention. The main reasons for this setting are as follows: 1. Facilitating production; 2. The prior deposition of graphdiyne can promote better entry of silicon into the pores for deposition, preventing a large amount of silicon crystals from depositing on the surface of the carbon substrate. In other embodiments of the present invention, it is also possible to first deposit silicon, then mix the intermediate product after silicon deposition with the catalyst to allow the catalyst particles to enter the pores, and then grow graphdiyne. This method has slightly worse effects compared to the method of first depositing graphdiyne and then depositing silicon. However, due to the presence of graphdiyne deposited in the pores, it still has better effects compared to the prior art.
[0066] S3. Carbon Coating
[0067] After the silicon deposition is completed, the surface of the porous carbon matrix is carbon-coated.
[0068] Specifically, the carbon coating process is the same as that of existing silicon-carbon materials. For example, a carbon source alone or in mixture is decomposed by chemical vapor deposition into carbon nuclei, and a carbon film is grown on the particle surface to prevent the material from being oxidized by air.
[0069] The embodiment of the present invention also provides a negative electrode, which is prepared using the silicon-carbon composite material provided by the embodiment of the present invention or the silicon-carbon composite material prepared by the preparation method provided by the embodiment of the present invention as the active material.
[0070] The embodiment of the present invention also provides a battery, including the negative electrode provided by the embodiment of the present invention.
[0071] Example 1
[0072] Mix nano-silver powder with a porous carbon matrix (specific surface area 1680 m 2 / g) in a mass ratio of 5:100. During the mixing process, some nano-silver particles enter some of the pores of the porous carbon matrix to obtain a mixture containing the intermediate material.
[0073] Place the intermediate material in a fluidized bed with a volume of 100 L, control the temperature of the fluidized bed at 160 °C, and introduce the vapor of hexaethynylbenzene into the fluidized bed at a flow rate of 28 L / min. Argon is used as the carrier gas with a flow rate of 122 L / min. React for 2.5 h to allow the hexaethynylbenzene to enter the pores of the porous carbon matrix and react with the catalyst particles to form stacked multi-layered graphdiyne, obtaining a porous carbon-graphdiyne composite precursor. At this time, the specific surface area drops to about 1450 m 2 / g.
[0074] Control the temperature of the fluidized bed at 500 °C, introduce silane into the fluidized bed at a flow rate of 25 L / min. Argon is used as the carrier gas with an argon flow rate of 133 L / min. React for 5 h to allow the silane to enter the pores of the porous carbon matrix and decompose, and deposit the silicon produced by the decomposition in the pores of the porous carbon matrix, obtaining a preliminary silicon-carbon composite material.
[0075] Perform carbon coating on the preliminary silicon-carbon composite material. The specific operation method of carbon coating is to keep the temperature unchanged, with the carrier gas (argon) flow rate of 135 L / min, and introduce acetylene with a flow rate of 15 L / min to react for 2 h, obtaining the finished silicon-carbon composite material.
[0076] In the finished silicon-carbon negative electrode material, the mass ratio of the graphdiyne content to the porous carbon matrix is about 7:100, the mass ratio of the silver that enters the pores of the porous carbon matrix to the porous carbon matrix is about 5:100, and the mass ratio of the deposited silicon to the porous carbon matrix is about 63:100.
[0077] Example 2
[0078] Mix the nano-silver powder and the porous carbon matrix (specific surface area 1680 m 2 / g) according to a mass ratio of 10:100. During the mixing process, some nano-silver particles enter some of the pores of the porous carbon matrix to obtain a mixture containing the intermediate material.
[0079] Place the intermediate material in a fluidized bed with a volume of 100 L, control the temperature of the fluidized bed at 170 °C, and introduce the vapor of hexaethynylbenzene into the fluidized bed at a flow rate of 40 L / min. Argon is used as the carrier gas with a flow rate of 110 L / min. React for 2 h to allow the hexaethynylbenzene to enter the pores of the porous carbon matrix and react with the catalyst particles to form stacked multi-layered graphdiyne, obtaining a porous carbon-graphdiyne composite precursor. At this time, the specific surface area drops to about 1362 m 2 / g.
[0080] Control the temperature of the fluidized bed at 550 °C, introduce silane into the fluidized bed at a flow rate of 20 L / min. Argon is used as the carrier gas with an argon flow rate of 140 L / min. React for 5.5 h to allow the silane to enter the pores of the porous carbon matrix and decompose, and deposit the silicon produced by the decomposition in the pores of the porous carbon matrix, obtaining a preliminary silicon-carbon composite material.
[0081] The virgin silicon-carbon composite material is carbon-coated. The specific operation method of carbon coating is that the temperature remains unchanged, the flow rate of the carrier gas (argon) is 135 L / min, acetylene with a flow rate of 15 L / min is introduced and reacts for 2 h to obtain the finished silicon-carbon composite material.
[0082] In the finished silicon-carbon negative electrode material, the mass ratio of the content of graphdiyne to the porous carbon matrix is about 8:100, the mass ratio of silver entering the pores of the porous carbon matrix to the porous carbon matrix is about 7:100, and the mass ratio of deposited silicon to the porous carbon matrix is about 45:100.
[0083] Example 3
[0084] The nano silver powder and the porous carbon matrix (specific surface area 1680 m 2 / g) are mixed at a mass ratio of 10:100. During the mixing process, some nano silver particles enter some pores of the porous carbon matrix to obtain a mixture containing the intermediate material.
[0085] The intermediate material is placed in a fluidized bed with a volume of 100 L. The temperature of the fluidized bed is controlled at 150 °C. Vapor of hexaethynylbenzene is introduced into the fluidized bed at a flow rate of 20 L / min, with argon as the carrier gas and a flow rate of 100 L / min. The reaction lasts for 2.5 h, so that hexaethynylbenzene enters the pores of the porous carbon matrix and reacts around the catalyst particles to form stacked multi-layer graphdiyne, obtaining a porous carbon-graphdiyne composite precursor. At this time, the specific surface area drops to about 1502 m 2 / g.
[0086] The temperature of the fluidized bed is controlled at 480 °C. Silane is introduced into the fluidized bed at a flow rate of 30 L / min, and the argon flow rate remains unchanged. The reaction lasts for 4.5 h, so that the silane enters the pores of the porous carbon matrix and decomposes, and the decomposed silicon is deposited in the pores of the porous carbon matrix to obtain the virgin silicon-carbon composite material.
[0087] The virgin silicon-carbon composite material is carbon-coated. The specific operation method of carbon coating is that the temperature remains unchanged, the flow rate of the carrier gas (argon) is 135 L / min, acetylene with a flow rate of 15 L / min is introduced and reacts for 2 h to obtain the finished silicon-carbon composite material.
[0088] In the finished silicon-carbon negative electrode material, the mass ratio of the content of graphdiyne to the porous carbon matrix is about 6:100, the mass ratio of silver entering the pores of the porous carbon matrix to the porous carbon matrix is about 7:100, and the mass ratio of deposited silicon to the porous carbon matrix is about 70:100.
[0089] Example 4
[0090] This example is basically the same as Example 2, except that: the reaction time for introducing the hexaethynylbenzene vapor is 3 h;
[0091] There is more graphdiyne deposited, and in the prepared silicon-carbon composite material, the mass ratio of graphdiyne to the porous carbon matrix is about 10:100.
[0092] Example 5
[0093] This example is basically the same as Example 3, except that: the reaction time for introducing hexaphenylacetylene vapor is 2 h;
[0094] There is less graphdiyne deposited, and in the prepared silicon-carbon composite material, the mass ratio of graphdiyne to the porous carbon matrix is about 5:100.
[0095] Comparative Example 1
[0096] This comparative example is basically the same as Example 1, except that: the steps of mixing with silver nanoparticles and growing graphdiyne by introducing hexaphenylacetylene vapor are not carried out, and silane is directly introduced for reaction for 5 h.
[0097] Comparative Example 2
[0098] This comparative example is basically the same as Example 1, except that: hexaphenylacetylene vapor is not introduced for growing graphdiyne; the temperature in the fluidized bed is directly controlled at 500 °C, and silane is introduced for reaction for 5 h. This comparative example is equivalent to replacing the graphdiyne growth step with silicon deposition in the previous stage.
[0099] Comparative Example 3
[0100] This comparative example is basically the same as Example 1, except that: the time for growing graphdiyne by introducing hexaphenylacetylene vapor is 6 h; in the prepared silicon-carbon composite material, the mass ratio of graphdiyne to the porous carbon matrix is 16:100.
[0101] Comparative Example 4
[0102] This comparative example is basically the same as Example 1, except that: the time for growing graphdiyne by introducing hexaphenylacetylene vapor is 6 h, and the silicon deposition time is 2 h; in the prepared silicon-carbon composite material, the mass ratio of graphdiyne to the porous carbon matrix is 16:100, and the silicon deposition amount is 26:100.
[0103] Experimental Example 1
[0104] The silicon-carbon composite materials prepared in Example 1 and Comparative Example 1 are subjected to electron microscopy and XRD tests. As Figure 1 , 2 shown, it can be seen from the figure that the graphdiyne deposited in the pores in Example 1 can induce the deposition of silane in the pores of the porous carbon substrate, and a silicon crystal layer appears on the surface in Comparative Example 1 under the same deposition conditions.
[0105] Figure 3Raman spectra of the samples of Example 1 and Comparative Example 1. It can be seen that in Example 1, due to the addition of graphdiyne, the vibration peak of sp2 hybridized carbon on the benzene ring around 1592 cm -1 is higher, and weak alkyne bond peaks caused by sp hybridized carbon appear at 2024 cm -1 and 2290 cm -1 . In Comparative Example, a weak silicon crystal peak appears at 535 cm -1 . This is because the induction of graphdiyne for silane deposition is lacking, resulting in the deposition and crystallization of silane outside the porous carbon. The volume change of this part of silicon is not inhibited, further leading to an excessively high expansion rate of the material and having a negative impact on the electrochemical performance.
[0106] Experimental Example 2
[0107] The prepared silicon-carbon composite materials of each example and comparative example were made into coin-type half-cells and full-cells, and their electrochemical performances were tested;
[0108] Coin-type half-cell: For the coin-type half-cell, in the voltage window of 0 - 2V, the first charge-discharge test conditions: control the temperature at 25°C, the cut-off voltage is 0 - 2V, and the current density is 0.1C. The charge capacity is the specific capacity of the material, and the ratio of the charge capacity to the discharge capacity is the first efficiency of the material.
[0109] Full-cell: The silicon-carbon product and graphite were mixed in a ratio of 1:4 to make the negative electrode material, which was paired with NMC811 to make a soft-pack battery cell. The 1C / 1C charge-discharge test cycle was carried out at 25°C, and the full-charge rebound was measured by calculating the change in the thickness of the charging electrode sheet in the first cycle. The charge-discharge test rates of 0.1C / 0.33C, 1C / 0.33C, 2C / 0.33C, and 3C / 0.33C were measured.
[0110] The test results are shown in Table 1:
[0111] Table 1 Electrochemical performances of the silicon-carbon composite materials prepared in each example and comparative example
[0112]
[0113] It can be seen from the above table that the silicon-carbon composite materials prepared in each example of the present invention have significantly better cycle performance and rate retention rate compared with Comparative Example 1 (the prior art);
[0114] Comparing Example 4 and Example 5 with Example 3 and Example 2 respectively, the cycle performance and rate retention rate of Example 4 and 5 are significantly reduced, indicating that the electrochemical performance of the silicon-carbon negative electrode material obtained when the deposition amount of graphdiyne in the pores is preferably within 6 - 8:100 is better;
[0115] Comparing Comparative Example 2 with Comparative Example 1, the full charge expansion of Comparative Example 2 is similar to that of Comparative Example 1. Nano silver particles are incorporated into the pores of the silicon-carbon composite material in Comparative Example 2. The comparison results with Comparative Example 1 show that the incorporation of silver particles has no obvious effect on the volume change during charge and discharge of the silicon-carbon composite material;
[0116] Comparing Comparative Example 3 with Example 1, and Comparative Example 4 with Example 1, the full charge rebound of Comparative Examples 3 and 4 is significantly worse. Comparative Example 3 is worse than Comparative Example 1. In Comparative Example 4, due to a significant reduction in the amount of deposited silicon, the volume change is smaller, but the loss of specific capacity of the material is very obvious. This shows that when the deposition amount of graphdiyne in the pores is excessive and exceeds the range required by the present invention, good effects cannot be achieved, but instead the electrochemical performance of the silicon-carbon material will be reduced.
[0117] In summary, for the silicon-carbon composite material provided in the embodiments of the present invention, due to the introduction of graphdiyne with high conductivity and an interlayer structure as a buffer in the pores of the porous carbon, the volume expansion of nano silicon can be effectively inhibited; at the same time, due to the stable two-dimensional structure of graphdiyne, Li + can be stored inside its space and can also move along the parallel and vertical directions of the two-dimensional plane. It can not only partially make up for the capacity reduction caused by reducing the silicon deposition amount, but also improve the rate performance of the novel silicon-carbon material, thereby enhancing the fast charging ability of the product. Therefore, the silicon-carbon composite material provided in the embodiments of the present invention is used to manufacture the negative electrode of a battery, which can endow the battery with good electrochemical performance.
[0118] In a preferred embodiment, in at least a part of the pores of the porous carbon matrix, graphdiyne and silicon are deposited from the inside to the outside. During the manufacturing process, graphdiyne is first grown in the pores of the porous carbon matrix. The graphdiyne in the interlayer form serves as a good adsorption surface, which can promote the deposition of silane inside the porous carbon pores, prevent a large amount of silicon crystals from depositing on the surface of the carbon substrate, and further reduce the volume change of the material during charge and discharge.
[0119] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A silicon-carbon composite material, characterized in that, It includes a porous carbon matrix, graphdiyne and silicon deposited in the pores of the porous carbon matrix, and the mass ratio of the graphdiyne to the porous carbon matrix is 5-10:100; the mass ratio of the silicon to the porous carbon matrix is 45-70:
100.
2. The silicon-carbon composite material according to claim 1, characterized in that, In at least a part of the pores of the porous carbon matrix, the graphdiyne and the silicon are deposited from the inside to the outside.
3. The silicon-carbon composite material according to claim 1 or 2, wherein The mass ratio of the graphdiyne to the porous carbon matrix is 6-8:
100.
4. The silicon-carbon composite material according to claim 3, characterized in that, In the region where the graphdiyne is deposited in the pores of the porous carbon matrix, nano silver particles are also deposited; Optionally, the mass ratio of the nano silver particles to the porous carbon matrix is 3-7:
100.
5. The silicon-carbon composite material according to claim 1 or 2, characterized in that The silicon-carbon composite material further includes a carbon coating layer coated on the surface of the porous carbon matrix.
6. A method for preparing a silicon-carbon composite material according to any one of claims 1 to 3, characterized in that, It includes: Making catalyst particles enter into the pores of the porous carbon matrix to obtain an intermediate material; Placing the intermediate material in a reactor, introducing vapor of hexaethynylbenzene into the reactor, and making the hexaethynylbenzene enter into the pores of the porous carbon matrix to react with the catalyst particles as the center to form stacked multi-layer graphdiyne; Introducing silane into the reactor, making the silane enter into the pores of the porous carbon matrix and decompose, and depositing the decomposed silicon in the pores of the porous carbon matrix.
7. The preparation method according to claim 6, characterized in that, Controlling the temperature in the reactor to be 150-170 °C so that the hexaethynylbenzene reacts to form the multi-layer graphdiyne; Optionally, the reactor is a fluidized bed; Optionally, the introduction amount of the vapor of hexaethynylbenzene is 0.2-0.4 L / min corresponding to each liter of the reactor, and the reaction time is 2-3 h.
8. The preparation method according to claim 7, characterized in that, Controlling the temperature in the reactor to be 480-550 °C so that the silane decomposes into silicon; Optionally, the introduction amount of the silane is 0.2-0.3 L / min corresponding to each liter of the reactor, and the reaction time is 3-5 h; Optionally, after the silicon deposition is completed, it further includes surface carbon coating of the porous carbon matrix; Optionally, the catalyst particles are nano silver particles.
9. A negative electrode, characterized in that, It is made by using the silicon-carbon composite material described in any one of claims 1-5 or the silicon-carbon composite material prepared by the preparation method described in any one of claims 6-8 as the active material.
10. A battery, characterized in that, It includes a negative electrode as described in claim 9.