CN117293316A

CN117293316A - Silicon-carbon particles and preparation method thereof, silicon-carbon composite material and preparation method thereof

Info

Publication number: CN117293316A
Application number: CN202311256177.3A
Authority: CN
Inventors: 尹敬锋; 郑安华; 余德馨; 傅儒生; 仰韻霖
Original assignee: Guangdong Kaijin New Energy Technology Co Ltd
Current assignee: Guangdong Kaijin New Energy Technology Co Ltd
Priority date: 2023-09-26
Filing date: 2023-09-26
Publication date: 2023-12-26
Anticipated expiration: 2043-09-26
Also published as: CN117293316B

Abstract

The invention relates to the technical field of material preparation, and provides silicon-carbon particles and a preparation method thereof, and a silicon-carbon composite material and a preparation method thereof. The silicon-carbon particles comprise a silicon-based core and a carbon coating layer coating the silicon-based core, and a gap layer is arranged between the silicon-based core and the carbon coating layer. The carbon coating layer is formed by carbonizing light-cured light-sensitive resin, and the gap layer is formed by removing uncured light-sensitive resin. T (T) ₂ ＝T ₁ ‑D _p *ln(E ₀ /E _c )，E ₀ ＝W*h，T ₁ T is the thickness of the photosensitive resin before photo-curing ₂ Thickness of gap layer, D _p Is the transmission depth of the photosensitive resin, E _c Is critical exposure of photosensitive resin, E ₀ The exposure amount of the incident light for photocuring is W, the light intensity for photocuring is W, and the time for photocuring is h. The silicon carbon particles are provided with a gap layer which can provide buffer space for the expansion of silicon, so that the electrochemical performance of the material can be improved.

Description

Silicon-carbon particles and preparation method thereof, silicon-carbon composite material and preparation method thereof

Technical Field

The invention relates to the technical field of material preparation, in particular to silicon-carbon particles and a preparation method thereof, a silicon-carbon composite material and a preparation method thereof.

Background

The lithium ion battery is widely applied to portable electronic products due to high output voltage, high energy density, small self-discharge, long cycle life and no memory effect, and gradually extends to the fields of electric automobiles, large-scale energy storage equipment and the like. In the aspect of the cathode material, the lithium ion battery is the graphite material with the widest application at present, but the theoretical capacity of the lithium ion battery is lower (372 mAh/g), so that the requirement of the lithium ion battery on high energy density is difficult to meet. Among the many alternative anode materials, silicon is known as one of the most promising anode materials of the next generation because of its higher theoretical specific capacity (4200 mAh/g). However, the silicon negative electrode material is easy to crack and pulverize due to serious volume expansion (the volume expansion rate can reach about 300%) in the charge and discharge process, so that contact with a current collector is lost, and the cycle performance of the lithium ion battery is drastically reduced.

In order to solve the problems, researchers provide buffer space for the volume expansion of silicon by introducing gaps into the silicon-carbon anode material, so as to obtain the silicon-carbon composite anode material with a novel structure. The carbon layer of the shell can prevent silicon from directly contacting with electrolyte to form a stable SEI film, and the introduction of gaps can provide space to relieve huge volume expansion caused by silicon in the charge and discharge process, so that the circulation stability is effectively improved. However, most gaps of silicon-carbon cathode materials are realized by an etching method, wherein hydrofluoric acid is used for etching a silicon dioxide interlayer most commonly, but the hydrofluoric acid belongs to acid with toxicity and strong corrosiveness, and causes great harm to the environment and physical and psychological health of operators in the use process. Meanwhile, hydrofluoric acid is adopted for acid etching, and some active components containing Si in the material are inevitably washed away, so that the performance of the material is reduced.

Therefore, how to design a silicon-carbon anode material which is environment-friendly and simple to operate so as to reduce the volume expansion of silicon and improve the cycle performance has great significance for the application of the silicon-based material in lithium ion batteries.

Disclosure of Invention

In view of the above problems, an object of the present invention is to provide a silicon-carbon particle and a preparation method thereof, a silicon-carbon composite material and a preparation method thereof, wherein the prepared material can provide a buffer space for expansion of silicon to improve electrochemical performance of the material.

To achieve the above object, a first aspect of the present invention provides silicon carbon particles. The silicon-carbon particles comprise a silicon-based core and a carbon coating layer coating the silicon-based core, and a gap layer is arranged between the silicon-based core and the carbon coating layer. The carbon coating layer is formed by carbonizing light-cured light-sensitive resin, and the gap layer is formed by removing uncured light-sensitive resin. T (T) ₂ ＝T ₁ -D _p *ln(E ₀ /E _c )，E ₀ ＝W*h，T ₁ T is the thickness of the photosensitive resin before photo-curing ₂ Thickness of gap layer, D _p Is the transmission depth of the photosensitive resin, E _c Is critical exposure of photosensitive resin, E ₀ The exposure amount of the incident light for photocuring is W, the light intensity for photocuring is W, and the time for photocuring is h.

The silicon-based core peripheral gap layer of the silicon-carbon particles can provide buffer space for expansion of the silicon-based core so as to avoid cracking and pulverization of materials, thereby effectively improving the circulation stability of the materials. The carbon coating layer can prevent the silicon-based inner core from being in direct contact with the electrolyte to form a stable SEI film, so that the electrochemical performance of the lithium ion battery is improved. The thickness of the gap layer can be controlled by the coating thickness of the photosensitive resin, the light intensity and the time of photo-curing, so that the proper thickness of the gap layer can be selected on the premise of taking into consideration the expansion of the buffer silicon and the maintenance of the mechanical properties such as the hardness, the particle size and the like of the silicon-carbon particles.

In some embodiments, the Dv50 of the silicon-based core is 0.005 μm to 5.000 μm.

In some embodiments, the silicon-based core comprises nano-silicon and/or nano-SiO _x X is greater than 0 and less than or equal to 0.8.

In some embodiments, the silicon-based core is nano-silicon, including polycrystalline nano-silicon and/or amorphous nano-silicon.

In some embodiments, the silicon-based core is polycrystalline nano-silicon having a grain size of 1nm to 40nm.

In some embodiments, the carbon coating layer has a thickness of 10nm to 1000nm.

In some embodiments, the thickness of the gap layer is 10nm to 300nm.

In some embodiments, the gap layer is filled with carbon nanotubes.

In some embodiments, the surface of the silicon-based core is provided with a porous carbon layer, and a gap layer is provided between the porous carbon layer and the carbon cladding layer. Further, the thickness of the porous carbon layer is 50nm to 500nm. The thickness of the carbon coating layer is 10nm to 1000nm. The thickness of the gap layer is 10nm to 300nm.

In some embodiments, the plurality of gap layers and the plurality of carbon coating layers are combined into a coating body by a single gap layer and a single carbon coating layer, and a plurality of coating bodies are arranged on the surface of the silicon-based inner core. Further, each gap layer is filled with carbon nanotubes. The thickness of each gap layer is the same, or the thickness of each gap layer is different, and the thickness of each gap layer is smaller as the gap layer is far away from the silicon-based core. The thickness of each carbon coating layer is the same, or the thickness of each carbon coating layer is different, and the thickness is larger as the distance from the silicon-based core is larger.

In a second aspect, the present invention provides a method for preparing silicon carbon particles, comprising the steps of:

(I) Mixing and dispersing a silicon source, liquid photosensitive resin and a photoinitiator, and then sequentially carrying out atomization and photo-curing treatment to obtain a first precursor;

(II) washing the first precursor with a solvent to remove the uncured photosensitive resin to obtain a second precursor;

(III) carbonizing the second precursor.

The preparation method of the silicon carbon particles has at least the following technical effects.

(1) The present invention utilizes photo-curing to fabricate the gap layer. The silicon source, the liquid photosensitive resin and the photoinitiator are mixed and dispersed, and then atomized to form fogdrops, and the photoinitiator in the fogdrops absorbs the light source with specific wavelength so as to trigger the photosensitive resin to perform polymerization reaction to form a solid photosensitive resin layer. The photoinitiator at the outermost layer of the fog drops firstly absorbs energy to initiate reaction, and the energy is gradually absorbed along the direction from the outer layer resin to the silicon source inner core, so that the deep photoinitiator cannot absorb enough energy to initiate polymerization reaction, finally the photosensitive resin at the outer layer is solidified, the photosensitive resin at the inner layer still maintains a liquid state, and then the solvent is adopted to wash away the liquid photosensitive resin to form a gap layer. The invention utilizes the characteristic that the light curing technology is difficult to deeply cure, the curing depth of the photosensitive resin can be controlled by controlling the light curing parameters, and the uncured photosensitive resin in the inner layer can be washed by adopting a solvent to form a gap layer. The preparation method is simple to operate, short in preparation time, low in cost, suitable for large-scale production, free of corrosive strong acid and strong alkali such as HF, naOH and the like, and environment-friendly in the whole preparation process, and does not need complex post-treatment.

(2) The preparation method of the invention uses the photo-curing technology, and can be uniformly cured, so that the carbon coating layer and the gap layer with uniform thickness can be formed after carbonization treatment. The thickness of the gap layer is controllable, so that the buffer silicon expansion and the maintenance of the mechanical properties such as the hardness, the particle size and the like of the silicon-carbon particles can be simultaneously considered.

In some embodiments, the silicon source is nano silicon and/or nano SiO _x X is greater than 0 and less than or equal to 0.8.

In some embodiments, the silicon source is porous carbon layer coated silicon-based particles, the silicon-based particles being nano-silicon and/or nano-SiO _x X is greater than 0 and less than or equal to 0.8.

In some embodiments, the silicon source is a porous carbon layer coated silicon-based particle, and the method of preparing the silicon source includes mixing the silicon-based particle and the porous carbon source in a solvent, drying and carbonizing.

In some embodiments, carbon nanotubes are added in the step (I) for mixing and dispersing, and the mass ratio of the carbon nanotubes to the silicon source is 1:50-200.

In some embodiments, the first precursor has a pore structure comprising micropores with a pore diameter of <2nm and mesopores with a pore diameter of 2nm to 5nm, the proportion of micropores in the pore structure being >80%.

In some embodiments, the photosensitive resin includes one or more of an acrylate resin, an epoxy acrylate resin, a urethane acrylate resin, a polyester acrylate resin, and a photo-curable silicone resin.

In some embodiments, the mass ratio of the silicon source to the photosensitive resin is 1 to 100:1.

In some embodiments, the photoinitiator comprises one or more of 2-hydroxy-2-methyl-1-phenylpropion, 1-hydroxycyclohexylphenyl ketone, 2,4, 6-trimethylbenzoyl-diphenyl phosphine oxide, benzophenone, 2-isopropylthioxanthone, benzoin dimethyl ether, and 2-hydroxy-2-methyl-1- [4- (2-hydroxyethoxy) phenyl ] -1-propanone.

In some embodiments, the mass ratio of photosensitive resin to photoinitiator is 20 to 1000:1.

In some embodiments, the photocuring employs a lamp having a spectral wavelength of 300nm to 600 nm.

In some embodiments, the light intensity of the photo-curing is W, W is 1mW/cm ² To 200mW/cm ² 。

In some embodiments, the photosensitive resin is photo-cured to a depth T ₃ ，T ₃ ＝D _p *ln(E ₀ /E _c )，E ₀ ＝W*h，D _p Is the transmission depth of the photosensitive resin, E _c Is critical exposure of photosensitive resin, E ₀ The exposure amount of the incident light for photocuring is W, the light intensity for photocuring is W, and the time for photocuring is h.

In some embodiments, the photosensitive resin is photo-cured to a depth T ₃ ，T ₃ From 10nm to 1000nm.

In some embodiments, the time of photocuring is h, h being from 0.1s to 1.0s.

In some embodiments, the nebulization is performed using a nebulizer, and the light-curing device is secured to the outlet end of the nebulizer.

In some embodiments, the solvent comprises one or more of ethanol, isopropanol, acetone, butanone, dichloromethane, dichloroethane, dichloropropane, tetrahydrofuran, diethyl ether, and chloroform.

In some embodiments, the temperature of the carbonization treatment is 500 ℃ to 1200 ℃.

In some embodiments, the carbonization treatment is for a period of 2 hours to 5 hours.

In some embodiments, the carbonization treatment is performed under an inert atmosphere comprising one or more of helium, neon, and nitrogen.

In some embodiments, the carbonization process has a ramp rate of 0.1 ℃/min to 10.0 ℃/min.

In some embodiments, the carbonization treatment is followed by cooling to room temperature and then breaking up and sieving.

In some embodiments, steps (I) through (III) are sequentially cycled multiple times to produce a silicon carbon composite.

A third aspect of the invention provides a silicon carbon composite. The silicon-carbon composite material comprises a silicon-carbon core and an outer coating carbon layer coating the silicon-carbon core, wherein the silicon-carbon core is the silicon-carbon particles or the silicon-carbon particles prepared by the preparation method of the silicon-carbon particles.

In the silicon-carbon composite material, the silicon-carbon inner core can provide a buffer space for silicon expansion so as to improve the electrochemical performance of the material. Meanwhile, the outer carbon coating layer can prevent the electrolyte from directly contacting the silicon carbon inner core, so that the electrochemical performance of the silicon carbon composite material is further improved.

With reference to the third aspect, the silicon-carbon composite material includes a silicon-based core, a gap layer, a carbon cladding layer, and an outer cladding carbon layer. Optionally, the carbon overcoat layer may be one layer, two layers, three layers, and so forth.

In some embodiments, the first charge capacity of the silicon-carbon composite is greater than or equal to 2200mAh/g;

in some embodiments, the first discharge capacity of the silicon-carbon composite is greater than or equal to 2000mAh/g;

in some embodiments, the first coulombic efficiency of the silicon-carbon composite is greater than or equal to 90.0%;

in some embodiments, the first week reversible capacity of the silicon-carbon composite is greater than or equal to 500.0mAh/g.

In some embodiments, the 50 week reversible capacity retention of the silicon carbon composite is greater than or equal to 91.0%.

In some embodiments, the silicon-based composite material has an electrical expansion rate of 38.0% or less over 50 cycles.

In some embodiments, the total amount of carbon in the silicon-based composite is 25wt.% to 50wt.%.

The fourth aspect of the invention provides a method for preparing a silicon-carbon composite material, comprising carbon coating a silicon-carbon core. The silicon-carbon core is the silicon-carbon particles or the silicon-carbon particles prepared by the preparation method of the silicon-carbon particles. Optionally, at least one (e.g., one, two, three, etc.) carbon layer may be coated on the surface of the silicon carbon core by means of a carbon coating.

In some embodiments, the carbon coating is a gas phase coating, a solid phase coating, or a liquid phase coating.

In some embodiments, the carbon coating may be followed by cooling, breaking up, and sieving.

Drawings

Fig. 1 is a schematic structural view of a first embodiment of the silicon carbon particles of the present invention.

Fig. 2 is a schematic structural view of a second embodiment of the silicon carbon particles of the present invention.

Fig. 3 is a schematic structural view of a third embodiment of the silicon carbon particles of the present invention.

Fig. 4 is a schematic structural view of a fourth embodiment of the silicon carbon particles of the present invention.

Fig. 5 is a schematic structural view of a fifth embodiment of the silicon carbon particles of the present invention.

Fig. 6 is a schematic structural view of a sixth embodiment of the silicon carbon particles of the present invention.

Fig. 7 is a schematic view of a photo-curing apparatus used in the present invention.

Fig. 8 is an SEM image of the silicon carbon composite material obtained by coating the silicon carbon particles of example 1 with carbon.

Detailed Description

The silicon-carbon particles can be directly used as a negative electrode active material, and can also be used as a precursor to prepare a silicon-carbon composite material after being coated with carbon so as to be used as the negative electrode active material. The silicon carbon particles or the silicon carbon composite material can be used alone or in combination with other negative electrode active materials (e.g., natural graphite, artificial graphite, soft carbon, hard carbon, etc.). The silicon-carbon composite material can be used as a negative electrode active material in a secondary battery. The secondary battery includes a positive electrode material and a negative electrode material. The positive electrode material comprises at least one of a lithium cobalt oxide positive electrode material, a lithium iron phosphate positive electrode material, a nickel cobalt lithium manganate positive electrode material and a nickel cobalt lithium aluminate positive electrode material.

The first charge capacity of the silicon-carbon composite material is more than or equal to 2200mAh/g, and can be, but is not limited to, more than or equal to 2200mAh/g, more than or equal to 2210mAh/g, more than or equal to 2220mAh/g, more than or equal to 2230mAh/g, more than or equal to 2240mAh/g,

≥2250mAh/g、≥2260mAh/g、≥2270mAh/g、≥2280mAh/g、≥2290mAh/g、

Not less than 2300mAh/g. The first discharge capacity of the silicon-carbon composite material is more than or equal to 2000mAh/g, and can be, but is not limited to, more than or equal to 2000mAh/g, more than or equal to 2010mAh/g, more than or equal to 2020mAh/g, more than or equal to 2030mAh/g, more than or equal to 2040mAh/g, and the like,

≥2050mAh/g、≥2060mAh/g、≥2070mAh/g、≥2080mAh/g、≥2090mAh/g、

And is more than or equal to 2100mAh/g. The first coulomb efficiency of the silicon-carbon composite material is more than or equal to 90.0 percent, can be more than or equal to 90.0 percent, more than or equal to 90.2 percent, more than or equal to 90.4 percent, more than or equal to 90.6 percent, more than or equal to 90.8 percent, more than or equal to 91.0 percent, more than or equal to 91.2 percent, more than or equal to 91.4 percent, more than or equal to 91.6 percent, more than or equal to 91.8 percent, and more than or equal to 92.0 percent. The first week reversible capacity of the silicon-carbon composite material is more than or equal to 500.0mAh/g, and can be more than or equal to 500.0mAh/g, more than or equal to 500.5mAh/g, more than or equal to 501.0mAh/g, more than or equal to 501.5mAh/g, and can be, but is not limited to,

Not less than 502.0mAh/g, not less than 502.5mAh/g, not less than 503.0mAh/g, not less than 503.5mAh/g, not less than 540.0mAh/g, not less than 504.5mAh/g, not less than 505.0mAh/g. The 50-week reversible capacity retention rate of the silicon-carbon composite material is more than or equal to 91.0 percent, can be more than or equal to 91.5 percent, more than or equal to 92.0 percent, more than or equal to 92.5 percent, more than or equal to 93.0 percent, more than or equal to 93.5 percent, more than or equal to 94.0 percent, and can be, but is not limited to,

More than or equal to 94.5 percent and more than or equal to 95.0 percent. The silicon-based composite material has a full electrical expansion rate of less than or equal to 38.0 percent for 50 weeks and can be, but is not limited to, less than or equal to 38.0 percent, less than or equal to 37.5 percent, less than or equal to 37.0 percent, less than or equal to 36.5 percent, less than or equal to 36.0 percent, less than or equal to 35.5 percent, less than or equal to 35.0 percent, less than or equal to,

34.5% or less and 34.0% or less. The total carbon amount in the silicon-based composite is 25wt.% to 50wt.%, and may be, but is not limited to, 25wt.%, 26wt.%, 27wt.%, 28wt.%, 29wt.%, 30wt.%, 31wt.%, 32wt.%, 33wt.%, 34wt.%, 35wt.%, 37wt.%, 40wt.%, 42wt.%, 44wt.%, 46wt.%, 48wt.%, 50wt.%, and/or the like.

The silicon-carbon composite material comprises silicon-carbon particles and an outer coating carbon layer coating the silicon-carbon particles. The outer carbon coating layer may be one, two, three, or the like carbon layers formed by carbon coating.

The carbon coating may be a gas phase coating, a solid phase coating, or a liquid phase coating. Of course, other coating methods such as plasma may be used as long as the coating forms an overcoated carbon layer. The outer carbon coating layer formed by the method can be one layer, two layers, three layers and the like. The silicon-carbon composite material is not limited by the mode of carbon coating, and is also not limited by the number of layers of the carbon coating.

Wherein the vapor phase cladding is a chemical vapor deposition method, which can comprise the steps of: adding silicon carbon particles into a CVD furnace, and introducing a gas phase carbon source to react under a protective atmosphere to obtain the silicon carbon composite material. In this gas phase cladding, the protective atmosphere may be, but is not limited to, at least one of argon, nitrogen, and helium. The air flow of the protective atmosphere is 4L/min to 10L/min, and as an example, the air flow of the protective atmosphere can be, but not limited to, 4L/min, 5L/min, 6L/min, 7L/min, 8L/min, 9L/min, 10L/min. The temperature of the reaction is 700 to 1100 ℃, and as an example, the reaction temperature may be, but not limited to, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃. The heating rate is 5 ℃/min to 10 ℃/min, and as an example, the heating rate may be, but is not limited to, 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, 10 ℃/min. The gaseous carbon source comprises methane, ethane, propane, ethylene, propylene, acetylene or propyne. The gas flow rate of the gas phase carbon source is 0.5L/min to 3.0L/min, and as an example, the gas flow rate of the gas phase carbon source may be, but not limited to, 0.5L/min, 1.0L/min, 1.5L/min, 2.0L/min, 2.5L/min, 3.0L/min. The gas phase carbon source is introduced for 4 to 8 hours, and as an example, the gas phase carbon source may be introduced for 4 hours, 5 hours, 6 hours, 7 hours, 8 hours.

The liquid phase coating may comprise the steps of: and uniformly mixing an organic carbon source, a solvent and silicon carbon particles to obtain a mixed solution, and carbonizing the mixed solution after spray drying to obtain the silicon carbon composite material. In this liquid phase coating, the organic carbon source may be, but is not limited to, at least one of polyvinyl alcohol, glucose, and sucrose. The solvent may be, but is not limited to, at least one of water, ethanol, acetone, and isopropanol. The temperature at which the organic carbon source is dissolved in the solvent is 25℃to 70℃and, as an example, the temperature at the time of dissolution may be, but not limited to, 25 ℃, 27 ℃, 30 ℃, 33 ℃, 35 ℃, 37 ℃, 40 ℃, 43 ℃, 46 ℃, 48 ℃, 50 ℃, 52 ℃, 55 ℃, 58 ℃, 60 ℃, 62 ℃, 65 ℃, 68 ℃, 70 ℃. The reaction may be accelerated with stirring while dissolving, and the stirring time may be 0.5h to 2.0h, and as an example, the stirring time may be, but not limited to, 0.5h, 0.7h, 0.9h, 1.1h, 1.3h, 1.5h, 1.7h, 1.9h, 2.0h. The carbonization is performed under a protective atmosphere comprising at least one of nitrogen, argon and helium. The carbonization is performed at a temperature of 700 to 1100 ℃, and as an example, the carbonization temperature may be, but not limited to, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃. The carbonization time is 2h to 6h, and as an example, the carbonization time may be, but is not limited to, 2h, 3h, 4h, 5h, 6h. The heating rate of carbonization is 1 ℃/min to 5 ℃/min, and as an example, the heating rate may be, but not limited to, 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min.

The solid phase coating may comprise the steps of: and mixing and dispersing the solid-phase carbon source and the silicon-carbon particles, and carbonizing in a protective atmosphere to obtain the silicon-carbon composite material. In this solid phase coating, the solid phase carbon source may be, but is not limited to, solid phase pitch, glucose, sucrose, phenolic resin. The mixing and dispersing may be performed using general-purpose equipment, and the parameters used for mixing may be conventional parameters. The temperature used in carbonization is 700 to 1100 ℃, and as an example, the temperature of carbonization may be, but not limited to, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃. The carbonization time is 2h to 6h, and as an example, the carbonization time may be, but is not limited to, 2h, 3h, 4h, 5h, 6h. The heating rate of carbonization is 1 ℃/min to 5 ℃/min, and as an example, the heating rate may be, but not limited to, 1 ℃/min, 2 ℃/min, 3 ℃/min, 4 ℃/min, 5 ℃/min.

The carbon can be cooled, scattered and screened in sequence after being coated. The cooling can be naturally cooled to room temperature. The break up may be, but is not limited to, VC break up. The speed of the scattering is 500r/min to 3000r/min, and the speed of the scattering can be, but is not limited to, 500r/min, 600r/min, 700r/min, 800r/min, 900r/min, 1000r/min, 1100r/min, 1200r/min, 1300r/min, 1400r/min, 1500r/min, 2000r/min, 2500r/min, 3000r/min. The time taken for the break-up is 30min to 120min, and as an example, the break-up time may be, but is not limited to, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min. The screen mesh used for screening is 100 mesh to 500 mesh, and as examples, the screen mesh may be, but is not limited to, 100 mesh, 130 mesh, 150 mesh, 170 mesh, 200 mesh, 230 mesh, 250 mesh, 300 mesh, 350 mesh, 400 mesh, 450 mesh, 500 mesh.

The silicon-carbon particles comprise a silicon-based core and a carbon coating layer coating the silicon-based core, and a gap layer is arranged between the silicon-based core and the carbon coating layer.

The Dv50 of the silicon-based core is 0.005 μm to 5.000 μm and may be, but is not limited to, 0.005 μm, 0.010 μm, 0.050 μm, 0.100 μm, 0.500 μm, 1.000 μm, 2.000 μm, 3.000 μm, 4.000 μm, 5.000 μm. The silicon-based core comprises nano silicon and/or nano SiO _x X is greater than 0 and less than or equal to 0.8, and x may be, but is not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8. I.e. the silicon-based core can be single nano silicon, single nano SiO _x Or nano silicon and nano SiO _x Is a mixture of (a) and (b). In addition, the nano-silicon includes polycrystalline nano-silicon and/or amorphous nano-silicon. The grain size of the polycrystalline nano-silicon is 1nm to 40nm, and may be, but not limited to, 1nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm.

The carbon coating layer is formed by carbonizing a photosensitive resin after photo-curing. The light source intensity is changed in the same illumination time, so that the photosensitive resin with different depths is solidified, and the carbon coating layers with different thicknesses can be obtained through carbonization treatment.

The gap layer is removed by uncured photosensitive resin. Since the cured layer formed after the photosensitive resin is cured has a pore structure comprising micropores and mesopores, the uncured photosensitive resin is still in a liquid state, and the solvent can be removed by being miscible with the photosensitive resin positioned inside through the pore structure. The thickness of the gap layer is T ₂ ，T ₂ ＝T ₁ -D _p *ln(E ₀ /E _c )，E ₀ ＝W*h，T ₁ D is the thickness of the photosensitive resin before photo-curing _p Is the transmission depth of the photosensitive resin, E _c Is critical exposure of photosensitive resin, E ₀ The exposure amount of the incident light for photocuring is W, the light intensity for photocuring is W, and the time for photocuring is h.

The silicon carbon particles of the present invention may have various structures, and the present invention will be described in detail by taking the structures of fig. 1 to 6 as examples.

As shown in fig. 1, the silicon-carbon particles 100 include a silicon-based core 10 and a carbon coating layer 50 coating the silicon-based core 10. A gap layer 30 is provided between the silicon-based core 10 and the carbon cladding 50. The surface of the silicon-based core 10 is completely free of carbon or carbon layers, with the gap layer 30 between it and the carbon cladding 50. The thickness of the carbon coating layer is 10nm to 1000nm, and may be, but not limited to, 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm. The thickness of the gap layer is 10nm to 300nm, and may be, but not limited to, 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm. Further, as shown in fig. 2, the gap layer 30 may be filled with carbon nanotubes 70, and the filled carbon nanotubes may improve the conductivity of the material and facilitate the deintercalation of lithium ions.

Alternatively, as shown in fig. 3, the silicon-carbon particles 100 may include a silicon-based core 10 and a carbon coating layer 50 coating the silicon-based core 10. The surface of the silicon-based core 10 is provided with a porous carbon layer 90, and a gap layer 30 is arranged between the porous carbon layer 90 and the carbon coating layer 50. The thickness of the porous carbon layer is 50nm to 500nm, and may be, but is not limited to, 50nm, 75nm, 100nm, 125nm, 150nm, 175nm, 200nm, 225nm, 250nm, 275nm, 300nm, 325nm, 350nm, 375nm, 400nm, 425nm, 450nm, 475nm, 500nm. The thickness of the carbon coating layer is 10nm to 1000nm, and may be, but not limited to, 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm. The thickness of the gap layer is 10nm to 300nm, and may be, but not limited to, 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm. Further, as shown in fig. 4, the gap layer 30 may be filled with carbon nanotubes 70, and the filled carbon nanotubes may improve the conductivity of the material and facilitate the deintercalation of lithium ions.

Alternatively, as shown in fig. 5, the silicon-carbon particles 100 may include a silicon-based core 10 and a carbon coating layer 50 coating the silicon-based core 10. A gap layer 30 is provided between the silicon-based core 10 and the carbon cladding 50. The gap layer 30 and the carbon cladding 50 are two. Specifically, the silicon carbon particles 100 include the silicon-based core 10, the first gap layer 30a, the first carbon cladding layer 50a, the second gap layer 30b, and the second carbon cladding layer 50b from inside to outside. The thickness of the first gap layer 30a and the second gap layer 30b may be the same, and may be 10nm to 300nm, and may be, but not limited to, 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, 300nm. Alternatively, the thicknesses of the first and second gap layers 30a and 30b may be different and each independently 10nm to 300nm, while the thickness is greater the farther from the silicon-based core 10. The thickness of the first carbon coating layer 50a and the second carbon coating layer 50b may be the same and may be 10nm to 1000nm, and may be, but not limited to, 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm. Alternatively, the thicknesses of the first carbon cladding 50a and the second carbon cladding 50b may be different, and the further from the silicon-based core 10, the greater the thickness. The thickness of the first carbon coating layer 50a may be 10nm to 500nm, and may be, but not limited to, 10nm, 30nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm. The thickness of the second carbon coating layer 50b may be 50nm to 1000nm, and may be, but not limited to, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm. Further, as shown in fig. 6, the gap layer 30 may be filled with carbon nanotubes 70, and the filled carbon nanotubes may improve the conductivity of the material and facilitate the deintercalation of lithium ions.

The preparation method of the silicon carbon particles of the present invention may include the following steps.

(III) carbonizing the second precursor.

In the preparation method of the silicon-carbon particles, a silicon source refers to a material containing silicon, and different silicon sources are selected to prepare different silicon-carbon particles.

If the silicon source is nano silicon and/or nano SiO _x X is greater than 0 and less than or equal to 0.8, and x may be, but is not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8. By selecting such a silicon source, silicon carbon particles having the structure shown in fig. 1 or 2 can be produced. In addition, the nano-silicon includes polycrystalline nano-silicon and/or amorphous nano-silicon, and the grain size of the polycrystalline nano-silicon is 1nm to 40nm, which may be, but is not limited to, 1nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm.

If the silicon source is a porous carbon layer coated silicon-based particle, a silicon-carbon particle having a structure as shown in fig. 3 or 4 can be prepared. The silicon-based particles are nano silicon and/or nano SiO _x X is greater than 0 and less than or equal to 0.8, and x may be, but is not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8. The nano-silicon includes polycrystalline nano-silicon and/or amorphous nano-silicon, and the grain size of the polycrystalline nano-silicon is 1nm to 40nm, which can be but not limited to 1nm, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm. The preparation method of the porous carbon layer coated silicon-based particle serving as a silicon source comprises the steps of mixing the silicon-based particle and the porous carbon source in a solvent, drying and carbonizing. The porous carbon source comprises one or more of phenolic resin, starch, urea-formaldehyde resin, polyurethane, polyacrylate, amino resin, polystyrene, polyacrylamide, polycarbonate and alkyd resin. The solvent comprises one or more of deionized water, ethanol, isopropanol, toluene, xylene, acetone, butanone, cyclohexane, dichloromethane, butyronitrile and tetrahydrofuran. Carbonization temperature of 500 ℃ to 1200 ℃, can be, but not limited to, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃, 1200 ℃. The carbonization time is 2h to 5h, and can be, but is not limited to, 2h, 3h, 4h, 5h.

The photosensitive resin includes one or more of acrylate resin, epoxy acrylate resin, urethane acrylate resin, polyester acrylate resin, and photo-curable silicone resin. The liquid photosensitive resin refers to a resin itself in a liquid state or a liquid state prepared by dissolving the resin in a solvent, and after the liquid photosensitive resin is cured, a micropore or mesoporous structure is usually present in a cured layer, so that a subsequent solvent can penetrate the cured layer through the micropore and the mesoporous to remove the uncured photosensitive resin. The mass ratio of the silicon source to the photosensitive resin is 1-100:1, and can be, but is not limited to, 1:1, 5:1, 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1.

The photoinitiator includes one or more of 2-hydroxy-2-methyl-1-phenylpropion (1173), 1-hydroxycyclohexylphenyl ketone (184), 2,4, 6-trimethylbenzoyl-diphenyl phosphine oxide (TPO), benzophenone (BP), 2-Isopropylthioxanthone (ITX), benzoin dimethyl ether (651), and 2-hydroxy-2-methyl-1- [4- (2-hydroxyethoxy) phenyl ] -1-propanone. The mass ratio of the photosensitive resin to the photoinitiator is 20-1000:1, and can be, but is not limited to, 20:1, 60:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1, 500:1, 550:1, 600:1, 650:1, 700:1, 750:1, 800:1, 850:1, 900:1, 950:1, 1000:1.

In order to improve the conductivity of the material and facilitate the deintercalation of lithium ions, carbon nanotubes can be added on the basis of a silicon source, liquid photosensitive resin and a photoinitiator for mixing and dispersing, and the mass ratio of the carbon nanotubes to the silicon source is 1:50-200, and can be but is not limited to 1:50, 1:70, 1:100, 1:120, 1:140, 1:160, 1:180 and 1:200.

The equipment which can be used for the mixing and dispersing in the step (I) comprises a mechanical fusion machine, a VC high-speed mixer, a planetary mixer or a high-shear mixer. Atomization can be performed by using an atomizer, and the light curing device is fixed at the outlet end of the atomizer. As shown in fig. 7, after atomization, the raw material flows out from the outlet end 21 of the atomizer 20 to form mist droplets M, the mist droplets M are radiated by the light source 60 while falling down in the charging barrel 40, and the photoinitiator in the outer layer of the mist droplets M absorbs the light source with a specific wavelength to initiate polymerization of the photosensitive resin in the outer layer to form a solid photosensitive resin layer, and finally flows out through the discharge port 41 of the charging barrel 40. The time from the mist droplet M to the discharge port 41 through the outlet port 21 is the photo-curing time of the photosensitive resin, and if the same device is used for photo-curing, the photo-curing time is a fixed value. The light source 60 is a lamp having a spectral wavelength of 300nm to 600nm, and may be, but not limited to, a high pressure mercury lamp, a medium pressure mercury lamp, a halogen lamp, an LED lamp.

The depth of the photo-cured photosensitive resin is T ₃ ，T ₃ ＝D _p *ln(E ₀ /E _c )，E ₀ ＝W*h，D _p Is the transmission depth of the photosensitive resin, E _c Is critical exposure of photosensitive resin, E ₀ The exposure amount of the incident light for photocuring is W, the light intensity for photocuring is W, and the time for photocuring is h. Wherein D is _p 、E _c D for each photosensitive resin being an inherent property of the photosensitive resin _p 、E _c The light-cured photosensitive resin can be obtained through detection, and the detection method can be referred to ' Huang Biwu and the like ', the test research of the critical exposure and the transmission depth of the light-cured rapid prototyping photosensitive resin, the information recording material, 2007,8 (1): 59-62 '. By controlling the light intensity and time of the photo-curing, the photo-sensitive resin curing layers with different depths, in other words, the gap layers with different thicknesses can be obtained. T for the purpose of combining the buffer silicon expansion and the maintenance of the mechanical properties such as hardness, particle size and the like of the silicon-carbon particles ₃ From 10nm to 1000nm, it may be, but is not limited to, 10nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm. The time of photo curing is h, which is 0.1s to 1.0s, and may be, but is not limited to, 0.1s, 0.2s, 0.3s, 0.4s, 0.5s, 0.6s, 0.7s, 0.8s, 0.9s, 1.0s. If the same curing device is adopted, the photo-curing time is a fixed value, and different T can be obtained by adopting different light intensities ₃ . The light intensity of the photo-curing is W, W is 1mW/cm ² To 200mW/cm ² Can be, but is not limited to, 1mW/cm ² 、10mW/cm ² 、50mW/cm ² 、100mW/cm ² 、120mW/cm ² 、140mW/cm ² 、160mW/cm ² 、180mW/cm ² 、200mW/cm ² 。

As described above, since a microporous or mesoporous structure is generally present in the cured layer after the liquid photosensitive resin is cured, the first precursor has a pore structure including micropores with a pore diameter of <2nm and mesopores with a pore diameter of 2nm to 5nm, and the ratio of the micropores in the pore structure is >80%. The microwell may have a ratio of, but is not limited to, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%.

The solvent in the step (II) comprises one or more of ethanol, isopropanol, acetone, butanone, methylene dichloride, dichloroethane, dichloropropane, tetrahydrofuran, diethyl ether and chloroform. Such solvents can be used to miscibility and remove the uncured liquid photosensitive resin. The solvent may be selected according to the particular photosensitive resin so as to thoroughly remove the liquid photosensitive resin from the first precursor to obtain the second precursor.

The temperature of the carbonization treatment in the step (III) is 500 to 1200 ℃, and may be, but not limited to, 500 ℃, 600 ℃, 700 ℃, 800 ℃, 900 ℃, 1000 ℃, 1100 ℃, 1200 ℃. The carbonization treatment time is 2h to 5h, and can be, but not limited to, 2h, 3h, 4h, 5h. The carbonization treatment is performed under an inert atmosphere including one or more of helium, neon, and nitrogen. The heating rate of the carbonization treatment is 0.1 to 10.0 ℃ per minute, and may be, but not limited to, 0.1, 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0 ℃/min. Cooling to room temperature after carbonization treatment, and scattering and sieving. The break up may be, but is not limited to, VC break up. The speed of the scattering is 500r/min to 3000r/min, and the speed of the scattering can be, but is not limited to, 500r/min, 600r/min, 700r/min, 800r/min, 900r/min, 1000r/min, 1100r/min, 1200r/min, 1300r/min, 1400r/min, 1500r/min, 2000r/min, 2500r/min, 3000r/min. The time taken for the break-up is 30min to 120min, and as an example, the break-up time may be, but is not limited to, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min, 120min. The screen mesh used for screening is 100 mesh to 500 mesh, and as examples, the screen mesh may be, but is not limited to, 100 mesh, 130 mesh, 150 mesh, 170 mesh, 200 mesh, 230 mesh, 250 mesh, 300 mesh, 350 mesh, 400 mesh, 450 mesh, 500 mesh.

Steps (I) through (III) may be sequentially cycled multiple times to produce a silicon carbon composite material with the resulting silicon carbon particles having a structure as shown in fig. 5 or 6. The light intensity of the photo-curing in the step (I) can be different for a plurality of times, so that the gap layer and the carbon coating layer with different thicknesses are obtained.

For a better description of the objects, technical solutions and advantageous effects of the present invention, the present invention will be further described with reference to specific examples. It should be noted that the following implementation of the method is a further explanation of the present invention and should not be taken as limiting the present invention.

Example 1

The embodiment is a preparation method of silicon carbon particles, which comprises the following steps.

(I) Mixing and dispersing nano silicon, liquid acrylate resin and a photoinitiator 1173 in a mass ratio of 100:10:0.1 by adopting a VC high-speed mixer, atomizing into fogdrops by utilizing an atomizer, and performing photo-curing treatment to obtain a first precursor. Photocuring with high pressure mercury lamp with spectral wavelength of 300-600 nm at light intensity of 30mW/cm ² The illumination time is 0.3s, and the exposure quantity E of the incident light ₀ 9mJ/cm ² The depth of the photo-cured photosensitive resin is calculated as T through a formula ₃ 800nm. The first precursor has a pore structure including a pore size, as tested <Micropores with the diameter of 2nm and mesopores with the diameter of 2nm to 5nm, and the proportion of micropores in the pore structure is 85%.

(II) washing the first precursor with ethanol a plurality of times to remove the uncured acrylate resin and drying to obtain a second precursor.

And (III) sintering the second precursor under the protection of nitrogen, wherein the temperature rising rate of sintering is 1 ℃/min, the sintering temperature is 1000 ℃, the sintering is carried out for 3 hours, the second precursor is naturally cooled to room temperature, and the second precursor is scattered for 60 minutes at the rotating speed VC of 600r/min and then is sieved by a 300-mesh sieve to obtain the silicon-carbon particles.

The structure of the silicon carbon particles prepared in example 1 is schematically shown in fig. 1, and the silicon carbon particles prepared in example 1 were subjected to SEM test, and the results are shown in fig. 8. As can be seen from fig. 8, the silicon-carbon particles include a silicon-based core and a carbon coating layer coating the silicon-based core, and a gap layer is provided between the silicon-based core and the carbon coating layer. The Dv50 of the silicon-based core is 2.000 mu m, the silicon-based core is polycrystalline nano silicon, the grain size is 20nm, and the surface of the silicon-based core is completely free of carbon. The thickness of the carbon coating layer was 800nm, and the thickness of the gap layer was 200nm.

Example 2

(I) Mixing and dispersing nano silicon, liquid acrylate resin and a photoinitiator 1173 in a mass ratio of 100:10:0.1 by adopting a VC high-speed mixer, atomizing into fogdrops by utilizing an atomizer, and performing photo-curing treatment to obtain a first precursor. Photocuring with high pressure mercury lamp with spectral wavelength of 300-600 nm at light intensity of 50mW/cm ² The illumination time is 0.3s, and the exposure quantity E of the incident light ₀ 15mJ/cm ² The depth of the photo-cured photosensitive resin is calculated as T through a formula ₃ 860nm. The first precursor has a pore structure including a pore size, as tested<Micropores with the diameter of 2nm and mesopores with the diameter of 2nm to 5nm, and the proportion of micropores in the pore structure is 88%.

A schematic structure of the silicon carbon particles obtained in example 2 is shown in FIG. 1. According to detection, in the silicon-carbon particles prepared in the example 2, the Dv50 of the silicon-based core is 2.000 mu m, the silicon-based core is polycrystalline nano silicon, the grain size is 20nm, and the surface of the silicon-based core is completely free of carbon. The thickness of the carbon coating layer was 860nm, and the thickness of the gap layer was 140nm.

Example 3

(I) Mixing and dispersing nano silicon, liquid acrylate resin and a photoinitiator 1173 in a mass ratio of 100:15:0.15 by adopting a VC high-speed mixer, atomizing into fogdrops by utilizing an atomizer, and performing photo-curing treatment to obtain a first precursor. Photocuring with high pressure mercury lamp with spectral wavelength of 300-600 nm at light intensity of 30mW/cm ² The illumination time is 0.3s, and the exposure quantity E of the incident light ₀ 9mJ/cm ² The depth of the photo-cured photosensitive resin is calculated as T through a formula ₃ 800nm. The first precursor has a pore structure including a pore size, as tested<Micropores with the diameter of 2nm and mesopores with the diameter of 2nm to 5nm, and the proportion of micropores in the pore structure is 87%.

(II) washing the first precursor with ethanol to remove the uncured acrylate resin and drying to obtain a second precursor.

A schematic structure of the silicon carbon particles obtained in example 3 is shown in FIG. 1. According to detection, in the silicon-carbon particles prepared in the example 3, the Dv50 of the silicon-based core is 1.980 mu m, the silicon-based core is polycrystalline nano silicon, the grain size is 20nm, and the surface of the silicon-based core is completely free of carbon. The thickness of the carbon coating layer was 800nm, and the thickness of the gap layer was 220nm.

Example 4

(I) Uniformly mixing and dispersing nano silicon and phenolic resin in ethanol according to the mass ratio of 100:20, spray drying, carbonizing at the heating rate of 1 ℃/min and the carbonizing temperature of 900 ℃ for 3 hours, naturally cooling to room temperature after carbonizing, scattering at the rotating speed of 500r/min VC for 30 minutes, and sieving the silicon-based particles coated by the porous carbon layer through a 300-mesh sieve. Silicon-based particles coated with porous carbon layer and liquid propylene The acid ester resin and the photoinitiator 1173 are mixed and dispersed by a VC high-speed mixer according to the mass ratio of 100:25:0.25, atomized into fog drops by an atomizer, and subjected to photo-curing treatment to obtain the first precursor. Photocuring with high pressure mercury lamp with spectral wavelength of 300-600 nm at light intensity of 100mW/cm ² The illumination time is 0.3s, and the exposure quantity E of the incident light ₀ 30mJ/cm ² The depth of the photo-cured photosensitive resin is calculated as T through a formula ₃ 920nm. The first precursor has a pore structure including a pore size, as tested<2nm micropores and mesoporous pores with the pore diameter of 2nm to 5nm, wherein the proportion of micropores in the pore structure is 93%.

A schematic structure of the silicon carbon particles obtained in example 4 is shown in FIG. 3. According to detection, in the silicon-carbon particles prepared in example 4, the Dv50 of the silicon-based core is 1.700 μm, the silicon-based core is polycrystalline nano silicon with the grain size of 15nm, and a porous carbon layer with the thickness of 200nm is arranged on the surface of the silicon-based core. The thickness of the carbon coating layer was 920nm, and the thickness of the gap layer was 180nm.

Example 5

(I) Mixing and dispersing nano silicon, liquid acrylate resin, a photoinitiator 1173 and carbon nanotubes in a mass ratio of 100:25:0.25:1 by adopting a VC high-speed mixer, atomizing into mist drops by utilizing an atomizer, and performing photo-curing treatment to obtain a first precursor. Photocuring with high pressure mercury lamp with spectral wavelength of 300-600 nm at light intensity of 80mW/cm ² The illumination time is 0.3s, and the exposure quantity E of the incident light ₀ 24mJ/cm ² The depth of the photo-cured photosensitive resin is calculated as T through a formula ₃ 900nm. The first precursor has holesStructure, tested, the pore structure included pore size<Micropores with the diameter of 2nm and mesopores with the diameter of 2nm to 5nm, and the proportion of micropores in the pore structure is 90 percent.

And (III) sintering the second precursor under the protection of nitrogen, wherein the sintering temperature rising rate is 1 ℃/min, the sintering temperature is 1000 ℃, the sintering is carried out for 3 hours, the second precursor is naturally cooled to room temperature, and the third precursor is obtained by scattering the second precursor for 60 minutes at the rotating speed VC of 600r/min and then sieving the third precursor with a 300-mesh sieve.

(IV) mixing and dispersing the third precursor, the liquid acrylate resin, the photoinitiator 1173 and the carbon nano tubes in a mass ratio of 100:25:0.25:1 by adopting a VC high-speed mixer, atomizing the mixture into mist drops by utilizing an atomizer, and performing photo-curing treatment to obtain a fourth precursor. Photocuring with high pressure mercury lamp with spectral wavelength of 300-600 nm at light intensity of 120mW/cm ² The illumination time is 0.3s, and the exposure quantity E of the incident light ₀ 36mJ/cm ² The depth of the photo-cured photosensitive resin is calculated as T through a formula ₃ 950nm. The fourth precursor has a pore structure, which, as tested, includes pore size<Micropores with the diameter of 2nm and mesopores with the diameter of 2nm to 5nm, and the proportion of micropores in the pore structure is 95%.

(V) washing the fourth precursor with ethanol to remove the uncured acrylate resin and drying to obtain a fifth precursor.

And (VI) sintering the fifth precursor under the protection of nitrogen, wherein the sintering temperature rising rate is 1 ℃/min, the sintering temperature is 1000 ℃, the sintering is carried out for 3 hours, the natural cooling is carried out to the room temperature, the powder is scattered for 60 minutes at the rotating speed of 600r/min, and the powder is sieved by a 300-mesh sieve to obtain the silicon-carbon particles.

A schematic of the structure of the silicon carbon particles produced in example 5 is shown in FIG. 6. The silicon-carbon particles prepared in example 5 were examined to include a silicon-based core, a first interstitial layer, a first carbon coating layer, a second interstitial layer, and a second carbon coating layer from inside to outside. The first gap layer and the second gap layer are filled with carbon nanotubes. The Dv50 of the silicon-based core is 1.900 mu m, the silicon-based core is polycrystalline nano silicon and the grain size is 22nm. The thickness of the first carbon coating layer is 900nm, the thickness of the first gap layer is 200nm, the thickness of the second carbon coating layer is 950nm, and the thickness of the second gap layer is 150nm.

Example 6

(I) Mixing and dispersing nano silicon, liquid epoxy acrylate resin and a photoinitiator TPO by a VC high-speed mixer according to a mass ratio of 100:10:0.1, atomizing into fog drops by an atomizer, and performing photo-curing treatment to obtain a first precursor. Photocuring with high pressure mercury lamp with spectral wavelength of 300-600 nm at light intensity of 30mW/cm ² The illumination time is 0.3s, and the exposure quantity E of the incident light ₀ 9mJ/cm ² The depth of the photo-cured photosensitive resin is calculated as T through a formula ₃ 720nm. The first precursor has a pore structure including a pore size, as tested<Micropores with the diameter of 2nm and mesopores with the diameter of 2nm to 5nm, and the proportion of micropores in the pore structure is 81 percent.

(II) washing the first precursor with acetone for a plurality of times to remove the uncured epoxy acrylate resin and drying to obtain a second precursor.

A schematic structure of the silicon carbon particles obtained in example 6 is shown in FIG. 1. According to detection, in the silicon-carbon particles prepared in the example 6, the Dv50 of the silicon-based core is 2.000 mu m, the silicon-based core is polycrystalline nano silicon, the grain size is 20nm, and the surface of the silicon-based core is completely free of carbon. The thickness of the carbon coating layer was 720nm, and the thickness of the gap layer was 280nm.

Example 7

(I) Mixing and dispersing nano silicon, liquid acrylate resin and a photoinitiator 1173 in a mass ratio of 100:10:0.1 by using a mechanical fusion machine, and atomizing into fogdrops by using an atomizerAnd then photo-curing to obtain the first precursor. Photocuring with high pressure mercury lamp with spectral wavelength of 300-600 nm at light intensity of 30mW/cm ² The illumination time is 0.3s, and the exposure quantity E of the incident light ₀ 9mJ/cm ² The depth of the photo-cured photosensitive resin is calculated as T through a formula ₃ 800nm. The first precursor has a pore structure including a pore size, as tested<Micropores with the diameter of 2nm and mesopores with the diameter of 2nm to 5nm, and the proportion of micropores in the pore structure is 84 percent.

(II) washing the first precursor with isopropanol a plurality of times to remove the uncured acrylate resin and drying to obtain a second precursor.

And (III) sintering the second precursor under the protection of neon, wherein the temperature rising rate of sintering is 3 ℃/min, the sintering temperature is 900 ℃, the sintering is carried out for 5 hours, the second precursor is naturally cooled to room temperature, and the second precursor is scattered for 40 minutes at the rotating speed VC of 500r/min and then is sieved by a 300-mesh sieve to obtain the silicon-carbon particles.

A schematic structure of the silicon carbon particles obtained in example 7 is shown in FIG. 1. According to detection, in the silicon-carbon particles prepared in the example 7, the Dv50 of the silicon-based core is 2.000 mu m, the silicon-based core is polycrystalline nano silicon, the grain size is 30nm, and the surface of the silicon-based core is completely free of carbon. The thickness of the carbon coating layer was 800nm, and the thickness of the gap layer was 200nm.

Comparative example 1

The comparative example is a method for preparing silicon carbon particles, comprising the following steps.

(I) The nano silicon and sucrose solution (concentration 80 wt.%) are mixed and dispersed by a VC high-speed mixer according to a mass ratio of 100:10 to form suspension A1.

(II) spray drying the suspension A1 to obtain a precursor B1.

And (III) sintering the precursor B1 in a nitrogen protection atmosphere, wherein the sintering temperature rising rate is 1 ℃/min, the sintering temperature is 1000 ℃, the sintering is carried out for 3 hours, the natural cooling is carried out to room temperature, the precursor is scattered for 60 minutes at the rotating speed VC of 600r/min, and then the silicon carbon particles are obtained through a 300-mesh sieve.

According to detection, in the silicon-carbon particles prepared in the comparative example 2, a silicon-based inner core is coated with a carbon layer, and a gap layer does not exist between the silicon-based inner core and the carbon layer.

Taking silicon carbon particles prepared in examples 1 to 7 and comparative example 1 as precursors, respectively taking 1kg of asphalt and 250g of asphalt, mechanically mixing uniformly, performing carbonization treatment, wherein the heating rate of carbonization is 1 ℃/min, the carbonization temperature is 1000 ℃, the carbonization time is 3 hours, naturally cooling to room temperature after carbonization, and then scattering at the rotating speed VC of 400r/min for 30min and sieving through a 300-mesh sieve to obtain the silicon carbon composite materials 1 to 8.

The silicon-carbon composite materials 1 to 8 were respectively fabricated into button cells 1 to 8 for electrochemical performance test under the following conditions, and the test results are shown in table 1.

First charge and discharge performance test: and respectively taking the silicon-carbon composite materials 1 to 8 as active substances, mixing with a binder polyvinylidene fluoride and a conductive agent (Super-P) according to the mass ratio of 70:15:15, adding a proper amount of N-methyl pyrrolidone (NMP) as a solvent to prepare slurry, coating the slurry on a copper foil, and carrying out vacuum drying and rolling to prepare the negative plate. A1 mol/L LiPF was used as a counter electrode using a metallic lithium sheet ₆ And mixing the three components of mixed solvents according to the ratio of EC to DMC to emc=1:1:1 (v/v/v) to form an electrolyte, and adopting a polypropylene microporous membrane as a diaphragm to assemble the CR2032 button cell in a glove box filled with inert gas. The charge and discharge test of the button cell was performed on the LANHE cell test system of blue electronics inc. Under normal temperature conditions, the constant current of 0.1C is used for discharging to reach the voltage of 0.01V, the constant current of 0.02C is used for discharging to reach the voltage of 0.005V, the constant current of 0.1C is used for charging to reach the voltage of 1.5V, the capacities of charging and discharging to reach 1.5V are respectively the first charge capacity and the first discharge capacity, and the ratio of the first charge capacity to the first discharge capacity is the first coulombic efficiency.

And (3) testing the cycle performance: the silicon-carbon composite materials 1 to 8 are respectively and uniformly mixed with graphite to be used as active substances, and are mixed with an aqueous dispersion liquid (LA 132, solid content 15%) of an acrylonitrile multipolymer binder and a conductive agent (SuperP) according to the mass ratio of 70:10:20, and then a proper amount of water is added as a solvent to be prepared into slurry, coated on a copper foil, and the slurry is subjected to vacuum drying and rolling to prepare the negative plate. Lithium metal was used as a counter electrode, and 1mol/L LiPF was used ₆ The three-component mixed solvent is prepared by the following components of DMC (methyl methacrylate) and EMC (electro-magnetic compatibility)The electrolyte solution of the combination of =1:1:1 (volume ratio) adopts a polypropylene microporous membrane as a diaphragm, and a CR2032 type button cell with the capacity of 500mAh/g is assembled in a glove box filled with inert gas. The charge and discharge test of the button cell is carried out on a cell test system of blue electronic Co., ltd, and the charge and discharge voltage is limited to 0.005-1.5V under the constant current charge and discharge of 0.2C at normal temperature. The initial and 50-week-after-cycle thicknesses of the negative electrode were measured after 50 weeks of the cycle, and the full-charge expansion rate at 50 weeks of the cycle and the reversible capacity retention rate after 50 weeks of the cycle were calculated.

TABLE 1 electrochemical Performance test results

As can be seen from examples 1 to 7, the silicon-carbon particles having the gap layer were obtained by photo-curing and solvent washing, and the gap layer and the carbon coating layer having different thicknesses were obtained by adjusting the content of the photosensitive resin and the light intensity under a certain light irradiation time by photo-curing with a lamp having a spectral wavelength of 300nm to 600 nm. As shown in the results of table 1, the silicon-carbon composite material prepared by using the silicon-carbon particles as the precursor and coating the carbon has better electrochemical performance, and is beneficial to popularization and application on high-energy-density lithium ion batteries as the negative electrode active material.

Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the present invention can be modified or substituted without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. The silicon-carbon particle is characterized by comprising a silicon-based core and a carbon coating layer coating the silicon-based core, wherein a gap layer is arranged between the silicon-based core and the carbon coating layer, and the carbon coating layer is prepared by the steps of passing through photosensitive resinAnd carbonizing after photo-curing, wherein the gap layer is formed by removing uncured photosensitive resin, T ₂ ＝T ₁ -D _p *ln(E ₀ /E _c )，E ₀ ＝W*h，T ₁ T is the thickness of the photosensitive resin before photo-curing ₂ D is the thickness of the gap layer _p For the transmission depth, E, of the photosensitive resin _c E is the critical exposure of the photosensitive resin ₀ And W is the light intensity of the photo-curing, and h is the time of the photo-curing.

2. The silicon-carbon particles of claim 1 comprising at least one of the following features (1) to (7):

(1) The Dv50 of the silicon-based core is 0.005 μm to 5.000 μm;

(2) the silicon-based core comprises nano silicon and/or nano SiO _x X is more than 0 and less than or equal to 0.8;

(3) the silicon-based inner core is nano silicon, and the nano silicon comprises polycrystalline nano silicon and/or amorphous nano silicon;

(4) the silicon-based inner core is polycrystalline nano silicon, and the grain size of the polycrystalline nano silicon is 1nm to 40nm;

(5) the thickness of the carbon coating layer is 10nm to 1000nm;

(6) the thickness of the gap layer is 10nm to 300nm;

(7) and filling the carbon nano tube in the gap layer.

3. The silicon-carbon particles of claim 1, wherein a porous carbon layer is provided on the surface of the silicon-based core, and the gap layer is provided between the porous carbon layer and the carbon coating layer.

4. A silicon-carbon particle according to claim 3, comprising at least one of the following features (i) to (iii):

(i) The thickness of the porous carbon layer is 50nm to 500nm;

(ii) The thickness of the carbon coating layer is 10nm to 1000nm;

(iii) The thickness of the gap layer is 10nm to 300nm.

5. The silicon-carbon particles according to claim 1, wherein the plurality of gap layers and the plurality of carbon coating layers are formed, wherein a single gap layer and a single carbon coating layer are combined into a coating body, and wherein a plurality of coating bodies are arranged on the surface of the silicon-based core.

6. The silicon-carbon particles of claim 5 comprising at least one of the following features a to E:

A. filling carbon nanotubes in each gap layer;

B. the thickness of each gap layer is the same;

C. the thickness of each gap layer is different, and the thickness of the gap layer which is far away from the silicon-based inner core is smaller;

D. the thickness of each carbon coating layer is the same;

E. the thickness of each carbon coating layer is different, and the thickness is larger as the carbon coating layer is far away from the silicon-based inner core.

7. The preparation method of the silicon-carbon particles is characterized by comprising the following steps:

(II) washing the first precursor with a solvent to remove uncured photosensitive resin to obtain a second precursor;

(III) carbonizing the second precursor.

8. The method of producing silicon-carbon particles as defined in claim 7, comprising at least one of the following features (1) to (22):

(1) The silicon source is nano silicon and/or nano SiO _x X is more than 0 and less than or equal to 0.8;

(2) The silicon source is silicon-based particles coated by a porous carbon layer, the The silicon-based particles are nano silicon and/or nano SiO _x X is more than 0 and less than or equal to 0.8;

(3) The silicon source is silicon-based particles coated by a porous carbon layer, and the preparation method of the silicon source comprises the steps of mixing the silicon-based particles and the porous carbon source in a solvent, drying and carbonizing;

(4) Adding carbon nanotubes in the step (I) for mixing and dispersing, wherein the mass ratio of the carbon nanotubes to the silicon source is 1:50-200;

(5) The first precursor has a pore structure, the pore structure comprises micropores with the aperture of <2nm and mesopores with the aperture of 2nm to 5nm, and the proportion of the micropores in the pore structure is more than 80%;

(6) The photosensitive resin comprises one or more of acrylate resin, epoxy acrylate resin, polyurethane acrylate resin, polyester acrylate resin and photo-curing organic silicon resin;

(7) The mass ratio of the silicon source to the photosensitive resin is 1-100:1;

(8) The photoinitiator comprises one or more of 2-hydroxy-2-methyl-1-phenylpropion, 1-hydroxycyclohexylphenyl ketone, 2,4, 6-trimethylbenzoyl-diphenyl phosphine oxide, benzophenone, 2-isopropylthioxanthone, benzoin dimethyl ether and 2-hydroxy-2-methyl-1- [4- (2-hydroxyethoxy) phenyl ] -1-propanone;

(9) The mass ratio of the photosensitive resin to the photoinitiator is 20-1000:1;

(10) The light curing adopts a lamp with a spectral wavelength of 300nm to 600 nm;

(11) The light intensity of the photo-curing is W, and W is 1mW/cm ² To 200mW/cm ² ；

(12) The depth of the photo-cured photosensitive resin is T ₃ ，T ₃ ＝D _p *ln(E ₀ /E _c )，E ₀ ＝W*h，D _p For the transmission depth, E, of the photosensitive resin _c E is the critical exposure of the photosensitive resin ₀ W is the light intensity of the light curing, and h is the time of the light curing;

(13) The photosensitive treeThe depth of the photo-cured fat is T ₃ ，T ₃ 10nm to 1000nm;

(14) The time of the photo-curing is h, and h is 0.1s to 1.0s;

(15) The atomization is carried out by adopting an atomizer, and the light curing device is fixed at the outlet end of the atomizer;

(16) The solvent comprises one or more of ethanol, isopropanol, acetone, butanone, dichloromethane, dichloroethane, dichloropropane, tetrahydrofuran, diethyl ether and chloroform;

(17) The carbonization treatment temperature is 500-1200 ℃;

(18) The carbonization treatment time is 2 to 5 hours;

(19) The carbonization treatment is performed under an inert atmosphere comprising one or more of helium, neon, and nitrogen;

(20) The heating rate of the carbonization treatment is 0.1 ℃/min to 10.0 ℃/min;

(21) Cooling to room temperature after carbonization treatment, and scattering and screening;

(22) And (3) sequentially cycling the steps (I) to (III) for a plurality of times to obtain the silicon-carbon composite material.

9. A silicon-carbon composite material comprising a silicon-carbon core and an outer carbon-coated layer coating the silicon-carbon core, wherein the silicon-carbon core is a silicon-carbon particle as claimed in any one of claims 1 to 6 or a silicon-carbon particle as produced by the method for producing a silicon-carbon particle as claimed in any one of claims 7 to 8.

10. A method for producing a silicon-carbon composite material, characterized in that a silicon-carbon core is carbon-coated, the silicon-carbon core being the silicon-carbon particles as defined in any one of claims 1 to 6 or the silicon-carbon particles produced by the method for producing a silicon-carbon particle as defined in any one of claims 7 to 8.