CN117766725A - Silicon-carbon composite material and preparation method and application thereof - Google Patents
Silicon-carbon composite material and preparation method and application thereof Download PDFInfo
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- 239000002153 silicon-carbon composite material Substances 0.000 title claims abstract description 106
- 238000002360 preparation method Methods 0.000 title abstract description 16
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 194
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 187
- 239000011148 porous material Substances 0.000 claims abstract description 142
- 239000010703 silicon Substances 0.000 claims abstract description 96
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 96
- 230000000149 penetrating effect Effects 0.000 claims abstract description 16
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 94
- 239000002245 particle Substances 0.000 claims description 55
- 238000005229 chemical vapour deposition Methods 0.000 claims description 32
- 239000007789 gas Substances 0.000 claims description 29
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 28
- BLRPTPMANUNPDV-UHFFFAOYSA-N Silane Chemical compound [SiH4] BLRPTPMANUNPDV-UHFFFAOYSA-N 0.000 claims description 20
- 238000000151 deposition Methods 0.000 claims description 20
- 230000008021 deposition Effects 0.000 claims description 20
- 230000035484 reaction time Effects 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 17
- 239000011248 coating agent Substances 0.000 claims description 15
- 238000000576 coating method Methods 0.000 claims description 15
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 claims description 15
- 229910010271 silicon carbide Inorganic materials 0.000 claims description 15
- 229910052757 nitrogen Inorganic materials 0.000 claims description 14
- 238000009826 distribution Methods 0.000 claims description 13
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 10
- 239000001301 oxygen Substances 0.000 claims description 10
- 229910052760 oxygen Inorganic materials 0.000 claims description 10
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims description 8
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 claims description 8
- 239000002243 precursor Substances 0.000 claims description 8
- 239000011247 coating layer Substances 0.000 claims description 7
- 239000000758 substrate Substances 0.000 claims description 6
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- 239000000203 mixture Substances 0.000 claims description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- PZPGRFITIJYNEJ-UHFFFAOYSA-N disilane Chemical compound [SiH3][SiH3] PZPGRFITIJYNEJ-UHFFFAOYSA-N 0.000 claims description 2
- 239000001307 helium Substances 0.000 claims description 2
- 229910052734 helium Inorganic materials 0.000 claims description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 2
- 229910001416 lithium ion Inorganic materials 0.000 claims description 2
- 230000001681 protective effect Effects 0.000 claims description 2
- ZDHXKXAHOVTTAH-UHFFFAOYSA-N trichlorosilane Chemical compound Cl[SiH](Cl)Cl ZDHXKXAHOVTTAH-UHFFFAOYSA-N 0.000 claims description 2
- 239000005052 trichlorosilane Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 3
- 239000011159 matrix material Substances 0.000 abstract description 24
- 238000005253 cladding Methods 0.000 abstract description 12
- 239000000463 material Substances 0.000 abstract description 5
- 229910052744 lithium Inorganic materials 0.000 description 16
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 15
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 8
- 229910052814 silicon oxide Inorganic materials 0.000 description 8
- 239000011856 silicon-based particle Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 6
- 229910002804 graphite Inorganic materials 0.000 description 6
- 239000010439 graphite Substances 0.000 description 6
- 230000002687 intercalation Effects 0.000 description 5
- 238000009830 intercalation Methods 0.000 description 5
- 239000010410 layer Substances 0.000 description 4
- 239000007773 negative electrode material Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000005137 deposition process Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 229920002125 Sokalan® Polymers 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 239000011149 active material Substances 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000007770 graphite material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000004584 polyacrylic acid Substances 0.000 description 1
- -1 polyethylene Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 229910000077 silane Inorganic materials 0.000 description 1
- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Chemical compound [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Silicon Compounds (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a silicon-carbon composite material and a preparation method and application thereof. The silicon-carbon composite material comprises a conductive carbon network penetrating from inside to outside, wherein the conductive carbon network comprises matrix carbon and cladding carbon, the cladding carbon is positioned on the outer side of the silicon-carbon composite material, the matrix carbon is provided with a porous structure, and at least a part of pores of the porous structure are filled with silicon. The silicon-carbon composite material provided by the invention has a conductive carbon network penetrating from inside to outside, so that high conductivity is provided for the material; the silicon is positioned in the pore structure of the matrix carbon, so that the volume expansion is effectively limited, and the silicon-carbon composite material has high capacity, low expansion, high conductivity and good quick-charging performance.
Description
Technical Field
The invention belongs to the technical field of batteries, and relates to a silicon-carbon composite material and a preparation method and application thereof.
Background
The requirements of various industries on the energy density and the quick charge of the lithium battery are higher and higher, and the fact that the energy density and the quick charge cannot meet the requirements of end users becomes the biggest pain point for restricting the quick development of the lithium battery industry.
The negative electrode material is used as one of active materials of the lithium battery, and has great effect on improving the energy density and the quick charge capacity of the lithium battery. The traditional lithium battery cathode is made of graphite material, the theoretical capacity of graphite is 372mAh/g, the capacity of a graphite product in the current market reaches 365mAh/g, the theoretical limit is reached, and the requirement of the lithium battery on high energy density cannot be met subsequently. A new negative electrode with higher capacity and higher quick charge capacity is urgently needed at the market end to replace the traditional graphite negative electrode.
The silicon negative electrode has a theoretical capacity of 4200mAh/g, so that the silicon negative electrode becomes the best alternative to the graphite negative electrode and is the only next-generation negative electrode material at present. Meanwhile, unlike the directional intercalation lithium intercalation mechanism of the graphite cathode, the silicon and lithium can perform alloying reaction, and the lithium intercalation process is not limited by a specific direction, so that the lithium intercalation lithium battery has higher quick charge capacity. In addition, the lithium intercalation potential (0.4V) of the silicon negative electrode is higher than that of graphite (0.1V), the risk of lithium precipitation during charging of the lithium battery is greatly reduced, and the quick charging performance of the lithium battery is further improved.
However, silicon cathodes face a number of challenges. The volume expansion of the silicon negative electrode during charging is as high as 300%, and such high volume expansion may cause breakage of silicon particles to reduce the cycle life of the silicon negative electrode. In addition, silicon is a semiconductor, and has low electronic conductivity, so that the exertion of the quick charge performance of the silicon cathode is restricted.
Currently, a series of solutions are proposed for the problem of silicon negative electrode, wherein one of the effective solutions is to use porous carbon as a substrate, decompose gases such as silane by chemical vapor deposition method to deposit on the carbon substrate, and then coat the surface of the obtained product with carbon. The expansion rate of the material obtained by the method can be controlled by adjusting the silicon content, and meanwhile, the internal carbon substrate provides a good electron conduction channel for the silicon cathode. However, the above-described method has a significant challenge in interface control. CN116936780a is passivated after silicon deposition to form a silicon oxide layer, which is then carbon coated. However, the oxide of silicon is a semiconductor, and blocking the connection of the outer carbon layer and the inner carbon substrate may restrict the quick charge performance of the resulting anode material.
Therefore, it is necessary to provide a silicon-carbon composite material with excellent quick-charging performance, which is a technical problem to be solved at present.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a silicon-carbon composite material and a preparation method and application thereof.
In order to achieve the above purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a silicon-carbon composite material, the silicon-carbon composite material including a conductive carbon network penetrating from inside to outside, the conductive carbon network including a base carbon and a coated carbon, the coated carbon being located on an outer side of the silicon-carbon composite material, the base carbon having a porous structure, at least a portion of pores of the porous structure being filled with silicon.
The silicon-carbon composite material provided by the invention has a conductive carbon network penetrating from inside to outside, so that high conductivity is provided for the material; the silicon is positioned in the pore structure of the matrix carbon, so that the volume expansion is effectively limited, and the silicon-carbon composite material has high capacity, low expansion, high conductivity and good quick-charging performance.
The following preferred technical solutions are used as the present invention, but not as limitations on the technical solutions provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solutions.
Preferably, the matrix carbon and the coated carbon have direct physical contact and the contact area of the two is 5% to 100% of the inner surface area of the coating, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 100%, etc.
Preferably, the silicon is present in an amount of 5% to 80%, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 80% by mass, based on 100% of the total mass of the silicon-carbon composite material.
Preferably, the mass content of the conductive carbon network is 20% -95%, for example 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90% or 95%, etc., based on 100% of the total mass of the silicon carbon composite material.
Preferably, the oxygen content is <20wt%, e.g. 18wt%, 15wt%, 12wt%, 10wt%, 8wt%, 6wt%, 5wt%, 4wt%, 2wt%, 1wt%, 0.5wt%, 0.1wt%, etc., based on the total mass of the silicon carbon composite material being 100%; the silicon carbide content is <20wt%, e.g., 18wt%, 15wt%, 12wt%, 10wt%, 8wt%, 6wt%, 5wt%, 4wt%, 2wt%, 1wt%, 0.5wt%, 0.1wt%, etc. The lower the oxygen and silicon carbide content in the silicon-carbon composite material of the present invention, the better.
In one embodiment, the oxygen is in the form of silicon oxide SiO x (0<x<2) Is present in the form of (c).
Preferably, the particle diameter D50 of the silicon carbon composite material is 1 μm to 20 μm, for example 1 μm, 2 μm, 3 μm, 7 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm, etc.
In a second aspect, the present invention provides a method for preparing a silicon-carbon composite material according to the first aspect, the method comprising the steps of:
(1) Taking porous carbon particles as a substrate, and adopting a mixed gas of a silicon source and a protective gas to perform chemical vapor deposition to obtain a precursor;
(2) Coating carbon on the precursor to form coated carbon, so as to obtain a silicon-carbon composite material;
the porous carbon particles and the coated carbon are communicated to form a conductive carbon network by adjusting the pore distribution of the porous carbon particles and/or the concentration of a silicon source in the mixed gas, and at least part of pores of the porous carbon particles are filled with silicon.
The method can accurately regulate and control the interface, obtain a conductive carbon network penetrating from inside to outside, and effectively limit the silicon to obtain the silicon-carbon composite material with a brand new structure, and has higher capacity and better quick charge performance.
Preferably, the silicon source comprises at least one of monosilane, disilane, and trichlorosilane.
Preferably, the shielding gas includes at least one of nitrogen, helium and argon.
Preferably, the concentration of the silicon source in the gas mixture is 20% -90%, such as 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85% or 90%, etc. at the beginning of the chemical vapor deposition.
Preferably, the temperature of the chemical vapor deposition is 400 ℃ to 700 ℃, for example 400 ℃, 450 ℃, 500 ℃, 550 ℃, 600 ℃, 650 ℃, 700 ℃, or the like.
As a preferred technical scheme of the preparation method of the silicon-carbon composite material, the step (1) is performed according to a first mode, in the first mode, the porous carbon particles have uniform pore distribution, the concentration of a silicon source in the mixed gas is reduced in the later stage of chemical vapor deposition, and the reaction time is controlled so that after the chemical vapor deposition, the silicon fills the pores of the porous carbon particles, a discontinuous silicon coating layer is formed on the surfaces of the porous carbon particles, and the surfaces of the porous carbon particles are at least partially exposed.
According to the first mode, a precursor is prepared, after the subsequent carbon coating, the coated carbon is prevented from being in direct contact with exposed porous carbon particles, a conductive carbon network penetrating from inside to outside is constructed, and the obtained silicon-carbon composite material has a structure schematically shown in fig. 1, wherein 1 represents matrix carbon, 2 represents coated carbon and 3 represents silicon.
In the present invention, "uniform pore distribution" means that the pore diameters of the pores in the porous carbon particles are the same or close, wherein close means that the pore diameters fluctuate up and down within 20%.
Preferably, in one of the modes, the pore diameter in the porous carbon particles is in the range of 0.2nm to 50nm, and the pore diameter may be, for example, 0.2nm, 0.5nm, 1nm, 1.5nm, 2nm, 5nm, 8nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm or the like.
Preferably, in the first aspect, the post chemical vapor deposition accounts for 20% -50% of the total deposition time, for example, 20%, 22%, 25%, 28%, 30%, 35%, 40%, 45% or 50%, etc.; the concentration of the silicon source is reduced to 10% -50%, such as 10%, 12%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50% of the concentration of the silicon source at the beginning of chemical vapor deposition; the reaction time is 1h to 20h, for example 1h, 2h, 3h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, 17h, 18h or 20h, etc.
As a preferred technical scheme of the preparation method of the silicon-carbon composite material, the step (1) is carried out according to a second mode, in the second mode, the porous carbon particles are distributed in multiple stages, the pore diameters of the pores in the porous carbon particles are increased along the direction away from the inner core, the concentration of a silicon source in the mixed gas is constant in the whole process of chemical vapor deposition, and the reaction time is controlled so that the silicon fills the pores of the porous carbon particles after the chemical vapor deposition, and the surfaces of the porous carbon particles are not coated by the silicon.
Preparing a precursor according to a second mode, and after subsequent carbon coating, avoiding direct contact between coated carbon and porous carbon particles, and constructing a conductive carbon network penetrating from inside to outside, wherein the structural schematic diagram of the obtained silicon-carbon composite material is shown in fig. 2, wherein 1 represents matrix carbon, 2 represents coated carbon, and 3 represents silicon.
Preferably, in the second mode, the pores in the porous carbon particles are a primary pore and a secondary pore in this order in a direction away from the core, and the pore diameter of the primary pore is in the range of 0.2nm to 20nm (specific values of the particle diameter may be, for example, 0.2nm, 0.5nm, 1nm, 1.5nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm or 20nm, etc.), the pore diameter of the second-stage pores is in the range of 1nm to 50nm (specific values of the particle diameter may be, for example, 1nm, 1.5nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, 22nm, 24nm, 26nm, 28nm, 30nm, 32nm, 35nm, 37nm, 40nm, 43nm, 45nm or 50nm, etc.), the pore diameter minimum value in the second-stage pores is larger than the pore diameter maximum value in the first-stage pores, and the later stage of chemical vapor deposition accounts for 20% -50%, for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc., of the total deposition time; the reaction time is 1h to 20h, for example 1h, 3h, 5h, 7h, 9h, 11h, 13h, 15h, 17h, 18h or 20h, etc.
As a preferred technical scheme of the preparation method of the silicon-carbon composite material, the step (1) is performed according to a third mode, in the third mode, the porous carbon particles are distributed in multiple stages, the pore diameters of the pores in the porous carbon particles are increased along the direction away from the inner core, the concentration of a silicon source in the mixed gas is reduced at the later stage of chemical vapor deposition, and the reaction time is controlled so that after the chemical vapor deposition, the pores close to the inner core are mainly filled with silicon but the pores close to the outer surface are not filled with silicon.
Preparing a precursor according to a mode III, and after subsequent carbon coating, directly contacting the coated carbon with the exposed porous carbon particles to construct a conductive carbon network penetrating from inside to outside, wherein the structural schematic diagram of the obtained silicon-carbon composite material is shown in fig. 3, wherein 1 represents matrix carbon, 2 represents coated carbon and 3 represents silicon.
Preferably, in the third mode, the pores in the porous carbon particles are a primary pore and a secondary pore in this order in a direction away from the core, and the pore diameter of the primary pore is in the range of 0.2nm to 20nm (specific values of the particle diameter may be, for example, 0.2nm, 0.5nm, 1nm, 1.5nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm or the like), the pore diameter of the second-stage pores is in the range of 1nm to 50nm (specific values of the particle diameter may be, for example, 1nm, 1.5nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, 22nm, 24nm, 26nm, 28nm, 30nm, 32nm, 35nm, 37nm, 40nm, 43nm, 45nm or 50nm, etc.), the pore diameter minimum value in the second-stage pores is larger than the pore diameter maximum value in the first-stage pores, and the concentration of the silicon source is reduced to 10% to 50%, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45% or 50%, etc., of the concentration of the silicon source at the beginning of chemical vapor deposition stage; the later chemical vapor deposition accounts for 20% -50% of the total deposition time, such as 20%, 25%, 30%, 35%, 40%, 45% or 50%, etc.; the reaction time is 1h to 20h, for example 1h, 3h, 5h, 7h, 9h, 11h, 13h, 15h, 17h, 18h or 20h, etc.
Preferably, in the third aspect, the volume of the pores not filled with silicon accounts for 10% to 30% of the total pore volume of the porous carbon, for example, 10%, 12%, 15%, 18%, 20%, 23%, 26%, 28% or 30%, etc. The partial holes are filled with carbon after carbon coating by chemical vapor deposition, which is beneficial to improving the conductivity of the material. In the range, the silicon-carbon composite material can have higher capacity and better quick-charging performance.
Preferably, the carbon is coated by chemical vapor deposition using a carbon source comprising acetylene at a temperature of 400-800 c, such as 400 c, 450 c, 500 c, 550 c, 600 c, 650 c, 700 c, 750 c or 800 c, etc.
In the method adopted in the step (1) for preparing the precursor, the mode two and the mode three are preferred, because the conductive carbon network in the silicon-carbon composite material prepared by adopting the two methods has better penetrability. Compared with the silicon-carbon composite material obtained in the mode three, the silicon-carbon composite material obtained in the mode two has higher silicon content and higher capacity; compared with the silicon-carbon composite material obtained in the mode II, the silicon-carbon composite material obtained in the mode III has better conductivity and better quick charge performance.
In a third aspect, the present invention provides a lithium ion battery comprising the silicon-carbon composite material of the first aspect.
The numerical ranges recited herein include not only the recited point values, but also any point values between the recited numerical ranges that are not recited, and are limited to, and for the sake of brevity, the invention is not intended to be exhaustive of the specific point values that the recited range includes.
Compared with the prior art, the invention has the following beneficial effects:
the silicon-carbon composite material provided by the invention has a conductive carbon network penetrating from inside to outside, so that high conductivity is provided for the material; the silicon is positioned in the pore structure of the matrix carbon, so that the volume expansion is effectively limited, and the silicon-carbon composite material has high capacity, low expansion, high conductivity and good quick-charging performance.
Drawings
Fig. 1 is a schematic structural diagram of a silicon-carbon composite material according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of a silicon-carbon composite material according to an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of a silicon-carbon composite material according to an embodiment of the present invention.
Fig. 4 is a schematic structural diagram of the silicon carbon composite material provided in comparative example 1.
Detailed Description
The technical scheme of the invention is further described below by the specific embodiments with reference to the accompanying drawings.
The specific embodiments described herein are to be considered in an illustrative sense only and are not intended to limit the invention.
Example 1
The embodiment provides a silicon-carbon composite material, which comprises a conductive carbon network penetrating from inside to outside, wherein the conductive carbon network comprises basal body carbon and cladding carbon, the cladding carbon is positioned at the outer side of the silicon-carbon composite material, the basal body carbon is provided with a porous structure, and at least part of pores of the porous structure are filled with silicon;
the matrix carbon and the coated carbon have direct physical contact, and the contact area of the matrix carbon and the coated carbon accounts for 30% of the inner surface area of the coating layer;
the particle size D50 of the silicon-carbon composite material is 5 mu m; the mass content of silicon in the silicon-carbon composite material is 52wt%, and the mass content of the conductive carbon network is 44wt%;
the silicon-carbon composite material also comprises silicon oxide and silicon carbide, wherein the oxygen content is 2wt%, and the silicon carbide content is 2wt%.
The preparation method of the silicon-carbon composite material provided by the embodiment comprises the following steps:
(1) And (3) delivering porous carbon particles with uniform pore distribution (2 nm) into a reactor, introducing nitrogen to remove air, introducing mixed gas of monosilane and nitrogen at 600 ℃, performing silicon deposition, reducing the concentration of monosilane in the mixed gas to 25% in the later deposition period (accounting for 30% of the total deposition time), and controlling the reaction time to 6 hours to obtain the silicon-carbon composite material with deposited silicon particles in pores and partially coated with silicon on the outer surface.
(2) And then introducing acetylene into the reactor, and carrying out carbon coating at 700 ℃ to obtain the silicon-carbon composite material shown in figure 1.
Example 2
The embodiment provides a silicon-carbon composite material, which comprises a conductive carbon network penetrating from inside to outside, wherein the conductive carbon network comprises basal body carbon and cladding carbon, the cladding carbon is positioned at the outer side of the silicon-carbon composite material, the basal body carbon is provided with a porous structure, and at least part of pores of the porous structure are filled with silicon;
the matrix carbon and the coated carbon have direct physical contact, and the contact area of the matrix carbon and the coated carbon accounts for 100% of the inner surface area of the coating layer;
the particle size D50 of the silicon-carbon composite material is 5 mu m; the mass content of silicon in the silicon-carbon composite material is 48wt%, and the mass content of the conductive carbon network is 48wt%;
the silicon-carbon composite material also comprises silicon oxide and silicon carbide, wherein the oxygen content is 2wt%, and the silicon carbide content is 2wt%.
The preparation method of the silicon-carbon composite material provided by the embodiment comprises the following steps:
(1) And (3) delivering porous carbon particles with multistage pore distribution (a first stage pore and a second stage pore are sequentially arranged along the direction far away from the inner core, wherein the pore diameter of the first stage pore is in the range of 0.2-5 nm, the pore diameter of the second stage pore is in the range of 10-50 nm) into a reactor, introducing nitrogen to remove air, introducing mixed gas of monosilane and nitrogen (wherein the concentration of monosilane is 80%) at 600 ℃, carrying out silicon deposition, keeping the concentration of monosilane in the mixed gas constant in the deposition process, and controlling the reaction time to be 4 hours to obtain the silicon-carbon composite material with deposited silicon particles in pores and the outer surface not coated by silicon.
(2) And then introducing acetylene into the reactor, and carrying out carbon coating at 700 ℃ to obtain the silicon-carbon composite material shown in figure 2.
Example 3
The embodiment provides a silicon-carbon composite material, which comprises a conductive carbon network penetrating from inside to outside, wherein the conductive carbon network comprises basal body carbon and cladding carbon, the cladding carbon is positioned at the outer side of the silicon-carbon composite material, the basal body carbon is provided with a porous structure, and at least part of pores of the porous structure are filled with silicon;
the matrix carbon and the coated carbon have direct physical contact, and the contact area of the matrix carbon and the coated carbon accounts for 100% of the inner surface area of the coating layer;
the particle size D50 of the silicon-carbon composite material is 6 mu m; the mass content of silicon in the silicon-carbon composite material is 40wt%, and the mass content of the conductive carbon network is 57wt%;
the silicon-carbon composite material also comprises silicon oxide and silicon carbide, wherein the oxygen content is 2wt%, and the silicon carbide content is 1wt%.
The preparation method of the silicon-carbon composite material provided by the embodiment comprises the following steps:
(1) And (3) delivering porous carbon particles with multi-stage pore distribution (a first stage pore and a second stage pore in sequence along the direction far away from the inner core, wherein the pore diameter of the first stage pore is in the range of 6 nm-20 nm, the pore diameter of the second stage pore is in the range of 30 nm-50 nm) into a reactor, introducing nitrogen to remove air, introducing mixed gas of monosilane and nitrogen (wherein the concentration of monosilane is 30%) at 600 ℃, performing silicon deposition, reducing the concentration of monosilane in the mixed gas to 6% in the later deposition stage (accounting for 45% of the total deposition time), and controlling the reaction time to obtain the silicon-carbon composite material with deposited silicon particles in the inner pores (namely the first stage pores) and non-deposited silicon in the outer pores (namely the second stage pores), wherein the volume of the non-deposited silicon pores accounts for 18% of the total pore volume of the porous carbon.
(2) And then introducing acetylene into the reactor, and carrying out carbon coating at 700 ℃ to obtain the silicon-carbon composite material shown in figure 3.
Example 4
The embodiment provides a silicon-carbon composite material, which comprises a conductive carbon network penetrating from inside to outside, wherein the conductive carbon network comprises basal body carbon and cladding carbon, the cladding carbon is positioned at the outer side of the silicon-carbon composite material, the basal body carbon is provided with a porous structure, and at least part of pores of the porous structure are filled with silicon;
the matrix carbon and the coated carbon have direct physical contact, and the contact area of the matrix carbon and the coated carbon accounts for 100% of the inner surface area of the coating layer;
the particle size D50 of the silicon-carbon composite material is 8 microns; the mass content of silicon in the silicon-carbon composite material is 50wt%, and the mass content of the conductive carbon network is 48wt%;
the silicon-carbon composite material also comprises silicon oxide and silicon carbide, wherein the oxygen content is 1wt%, and the silicon carbide content is 1wt%.
The preparation method of the silicon-carbon composite material provided by the embodiment comprises the following steps:
(1) And (3) delivering porous carbon particles with multistage pore distribution (a first stage pore and a second stage pore are sequentially arranged along the direction far away from the inner core, wherein the pore diameter of the first stage pore is in the range of 1 nm-10 nm, the pore diameter of the second stage pore is in the range of 20 nm-40 nm) into a reactor, introducing nitrogen to remove air, introducing mixed gas of monosilane and nitrogen (wherein the concentration of monosilane is 20%) at 700 ℃, carrying out silicon deposition, keeping the concentration of monosilane in the mixed gas constant in the deposition process, and controlling the reaction time to be 5h to obtain the silicon-carbon composite material with deposited silicon particles in pores and the outer surface not coated by silicon.
(2) And then introducing acetylene into the reactor, and carrying out carbon coating at 500 ℃ to obtain the silicon-carbon composite material shown in figure 2.
Example 5
The embodiment provides a silicon-carbon composite material, which comprises a conductive carbon network penetrating from inside to outside, wherein the conductive carbon network comprises basal body carbon and cladding carbon, the cladding carbon is positioned at the outer side of the silicon-carbon composite material, the basal body carbon is provided with a porous structure, and at least part of pores of the porous structure are filled with silicon;
the matrix carbon and the coated carbon have direct physical contact, and the contact area of the matrix carbon and the coated carbon accounts for 100% of the inner surface area of the coating layer;
the particle size D50 of the silicon-carbon composite material is 7 mu m; the mass content of silicon in the silicon-carbon composite material is 46wt%, and the mass content of the conductive carbon network is 51wt%;
the silicon-carbon composite material also comprises silicon oxide and silicon carbide, wherein the oxygen content is 1wt%, and the silicon carbide content is 2wt%.
The preparation method of the silicon-carbon composite material provided by the embodiment comprises the following steps:
(1) And (3) delivering porous carbon particles with multi-stage pore distribution (a first-stage pore and a second-stage pore in sequence along the direction far away from the inner core, wherein the pore diameter of the first-stage pore is in the range of 3 nm-10 nm, the pore diameter of the second-stage pore is in the range of 20 nm-50 nm) into a reactor, introducing nitrogen to remove air, introducing mixed gas of monosilane and nitrogen (wherein the concentration of the monosilane is 40%) at 600 ℃, performing silicon deposition, reducing the concentration of the monosilane in the mixed gas to 12% in the later deposition stage (accounting for 20% of the total deposition time), and controlling the reaction time to obtain the silicon-carbon composite material with deposited silicon particles in the inner pores (namely the first-stage pores) and non-deposited silicon in the outer pores (namely the second-stage pores), wherein the volume of the non-deposited silicon pores accounts for 12wt% of the total pore volume of the porous carbon.
(2) And then introducing acetylene into the reactor, and carrying out carbon coating at 600 ℃ to obtain the silicon-carbon composite material shown in figure 3.
Example 6
This example provides a silicon carbon composite material whose preparation method is different from that of example 3 in that in step (1), the volume of pores not deposited by silicon accounts for 8% of the total pore volume of the porous carbon.
Example 7
This example provides a silicon carbon composite material whose preparation method is different from that of example 3 in that in step (1), the volume of pores not deposited by silicon accounts for 33% of the total pore volume of the porous carbon.
Comparative example 1
The comparative example provides a silicon-carbon composite material, which comprises a matrix carbon, wherein the matrix carbon is provided with a porous structure, silicon is filled in pores of the porous structure, a silicon layer is coated on the surface of the matrix carbon, and coated carbon is coated on the surface of the silicon layer.
The particle size D50 of the silicon-carbon composite material is 5 mu m; the mass content of silicon in the silicon-carbon composite material is 58wt%, and the mass content of matrix carbon is 37wt%;
the silicon-carbon composite material also comprises silicon oxide and silicon carbide, wherein the oxygen content is 3wt%, and the silicon carbide content is 2wt%.
The preparation method of the silicon-carbon composite material provided by the comparative example comprises the following steps:
(1) Porous carbon particles with uniform pore distribution (same as in example 1) are sent into a reactor, nitrogen is introduced to remove air, mixed gas of monosilane and nitrogen (wherein the concentration of monosilane is 50%) is introduced at 600 ℃ for silicon deposition, the concentration of monosilane in the mixed gas is kept constant during the deposition, and the reaction time is controlled to be 8 hours, so that the silicon-carbon composite material with deposited silicon particles in pores and the outer surface of the silicon-carbon composite material is completely coated with silicon is obtained.
(2) And then introducing acetylene into the reactor, and carrying out carbon coating at 700 ℃ to obtain the silicon-carbon composite material shown in fig. 4, wherein 1 represents matrix carbon, 2 represents coated carbon and 3 represents silicon.
Performance test:
with the silicon carbon composite materials of examples 1 to 7 and comparative example 1 as negative electrode materials, the negative electrode materials, acetylene black and polyacrylic acid were prepared according to a ratio of 90:5:5 mass ratio, and then coating the mixture on a copper foil to obtain an electrode. And after the electrode is dried, testing is carried out on a half battery with the prepared electrode as a positive electrode, lithium metal as a negative electrode and polyethylene as a diaphragm. Electrolyte is 1M LiPF 6 EC/EMC (3:7 vol/vol) solution.
The test conditions were 0.01V-1.5V and the current was 0.2C-2C.
The test results are shown in Table 1.
TABLE 1
As can be seen from table 1, compared with comparative example 1, the silicon carbon composite material of the present invention has a high capacity and a high 2C/0.2C capacity ratio by constructing a conductive carbon network penetrating from inside to outside, indicating that it has better quick charge performance.
As can be seen from a comparison of example 1 and examples 6 to 7, by controlling the ratio of the volume of pores not deposited with silicon to the total pore volume of porous carbon, a silicon-carbon composite material having both high capacity and fast charge performance can be obtained. If the volume ratio is too small, the capacity will increase, but the quick charge performance will decrease; if the volume ratio is large, the quick charge performance will be improved, but the capacity will be reduced.
The applicant states that the detailed method of the present invention is illustrated by the above examples, but the present invention is not limited to the detailed method described above, i.e. it does not mean that the present invention must be practiced in dependence upon the detailed method described above. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of raw materials for the product of the present invention, addition of auxiliary components, selection of specific modes, etc., falls within the scope of the present invention and the scope of disclosure.
Claims (10)
1. The silicon-carbon composite material is characterized by comprising a conductive carbon network penetrating from inside to outside, wherein the conductive carbon network comprises base carbon and coated carbon, the coated carbon is positioned on the outer side of the silicon-carbon composite material, the base carbon has a porous structure, and at least part of pores of the porous structure are filled with silicon.
2. The silicon-carbon composite of claim 1 wherein the base carbon and the coated carbon have direct physical contact and contact areas of between 5% and 100% of the inner surface area of the coating;
preferably, the mass content of the silicon is 5-80% based on 100% of the total mass of the silicon-carbon composite material;
preferably, the mass content of the conductive carbon network is 20% -95% based on 100% of the total mass of the silicon-carbon composite material;
preferably, the oxygen content is <20wt% and the silicon carbide content is <20wt% based on 100% of the total mass of the silicon carbon composite.
3. The silicon-carbon composite material according to claim 1 or 2, wherein the particle diameter D50 of the silicon-carbon composite material is 1 μ 5 to 20 μm.
4. A method of preparing a silicon carbon composite material as claimed in any one of claims 1 to 3, comprising the steps of:
(1) Taking porous carbon particles as a substrate, and adopting a mixed gas of a silicon source and a protective gas to perform chemical vapor deposition to obtain a precursor;
(2) Coating carbon on the precursor to form coated carbon, so as to obtain a silicon-carbon composite material;
the porous carbon particles and the coated carbon are communicated to form a conductive carbon network by adjusting the pore distribution of the porous carbon particles and/or the concentration of a silicon source in the mixed gas, and at least part of pores of the porous carbon particles are filled with silicon.
5. The method of preparing according to claim 4, wherein the silicon source comprises at least one of monosilane, disilane, and trichlorosilane;
preferably, the shielding gas includes at least one of nitrogen, helium and argon;
preferably, in the initial stage of the chemical vapor deposition, the concentration of the silicon source in the mixed gas is 20% -90%;
preferably, the temperature of the chemical vapor deposition is 400-700 ℃.
6. The production method according to claim 4 or 5, wherein step (1) is performed in a first mode in which the porous carbon particles have a uniform pore distribution, the concentration of the silicon source in the mixed gas is reduced in the latter stage of chemical vapor deposition, and the reaction time is controlled so that, after chemical vapor deposition, silicon fills the pores of the porous carbon particles and a discontinuous silicon coating layer is formed on the surfaces of the porous carbon particles, at least partially exposing the surfaces of the porous carbon particles;
preferably, in the first mode, the post chemical vapor deposition period is 20% -50% of the total deposition time, the concentration of the silicon source is reduced to 10% -50% of the concentration of the silicon source in the initial stage of chemical vapor deposition, and the reaction time is 1 h-20 h.
7. The production method according to claim 4 or 5, wherein step (1) is performed in a second mode in which the porous carbon particles have a multi-stage pore distribution, the pore diameters of the pores in the porous carbon particles increase in a direction away from the inner core, the concentration of the silicon source in the mixture gas is constant during the whole process of chemical vapor deposition, and the reaction time is controlled so that, after chemical vapor deposition, the silicon fills the pores of the porous carbon particles, and the surfaces of the porous carbon particles are not coated with silicon;
preferably, in the second mode, the pores in the porous carbon particles are a first-stage pore and a second-stage pore in sequence along the direction far away from the inner core, the pore diameter of the first-stage pore is in the range of 0.2 nm-20 nm, the pore diameter of the second-stage pore is in the range of 1 nm-50 nm, the pore diameter minimum value in the second-stage pore is larger than the pore diameter maximum value in the first-stage pore, the later stage of chemical vapor deposition accounts for 20% -50% of the total deposition time, and the reaction time is 1 h-20 h.
8. The production method according to claim 4 or 5, wherein step (1) is performed in a third mode in which the porous carbon particles have a multi-stage pore distribution, the pore diameters of the pores in the porous carbon particles increase in a direction away from the inner core, the concentration of the silicon source in the mixed gas is reduced in a later stage of chemical vapor deposition, and the reaction time is controlled so that, after chemical vapor deposition, the silicon mainly fills the pores near the inner core but not the pores near the outer surface;
preferably, in the third mode, the pores in the porous carbon particles are a first-stage pore and a second-stage pore in sequence along a direction far away from the inner core, the pore diameter of the first-stage pore is in a range of 0.2 nm-20 nm, the pore diameter of the second-stage pore is in a range of 1 nm-50 nm, the pore diameter minimum value in the second-stage pore is larger than the pore diameter maximum value in the first-stage pore, the concentration of the silicon source is reduced to 10% -50% of the concentration of the silicon source in the initial stage of chemical vapor deposition, the later stage of chemical vapor deposition accounts for 20% -50% of the total deposition time, and the reaction time is 1 h-20 h;
preferably, in the third mode, the volume of the pores not filled with silicon accounts for 10% to 30% of the total pore volume of the porous carbon.
9. The method according to any one of claims 4 to 8, wherein the carbon is coated by chemical vapor deposition using a carbon source comprising acetylene at a temperature of 400 ℃ to 800 ℃.
10. A lithium ion battery comprising the silicon-carbon composite of any one of claims 1-3.
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