Composite silicon-carbon material as well as preparation method and application thereof

Abstract

The invention discloses a composite silicon-carbon material as well as a preparation method and application thereof. The composite silicon-carbon material comprises a substrate material and nano silicon-based particles, the substrate material is a porous hard carbon material with through holes inside; the nano silicon-based particles are uniformly distributed on the hole walls of the through holes; the diameter size of the pore diameter of each continuous pore channel of the through hole is uniform, and the diameter size of the pore diameter is 1 nm to 500 nm; the through holes are obtained by uniformly mixing and curing starch fibers containing nano silicon-based particles and liquid-phase resin and then carrying out enzymolysis reaction with amylase; when the composite silicon carbon material is applied to the lithium ion battery, the cycle performance of the lithium ion battery can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and particularly relates to a composite silicon-carbon material, a preparation method thereof, and an application thereof. Background Art

[0002] Due to its theoretical specific capacity of 4200 mAh / g, silicon has great application prospects as an ideal anode material for high-capacity lithium-ion batteries. However, the high capacity of lithium-ion batteries is also accompanied by a 300% volume expansion of the silicon anode during the lithium insertion process, resulting in a large number of cracks in the electrode and attenuation of the battery capacity.

[0003] At present, nanosizing silicon particles or preparing silicon-carbon composite materials can effectively alleviate the influence caused by the volume effect. By adopting a combination of the two methods, the silicon-carbon composite material can give full play to its advantages. Most silicon-carbon composite methods, such as ball milling, liquid-phase mixing, gas-phase coating, etc., achieve uniform distribution of silicon-based materials in the hard carbon matrix to reduce the concentration of expansion stress of the silicon-based materials and prevent the carbon matrix from cracking and pulverizing, thereby affecting the cycle stability.

[0004] A potential new solution has been proposed in the prior art to solve the above problems. This solution is to use different residual carbon polymers for compounding and utilize the residual carbon gap to construct pores as a buffer space for silicon-based materials. However, in the carbonization process, the low-residual carbon polymers in the high-residual carbon polymers generate a large amount of gas due to cracking, which easily destroys the overall structure of the carbon matrix and has an adverse effect on the stability of the silicon-carbon material during the cycling process. Summary of the Invention

[0005] Embodiments of the present invention provide a composite silicon-carbon material, a preparation method thereof, and an application thereof. Compared with the prior art, in this composite silicon-carbon material, starch fibers are used to form a uniform distribution of nano-silicon-based particles in the resin matrix material, and the starch-based fiber filaments form uniform through-holes after enzymatic dissolution. On the one hand, it can limit the growth of nano-silicon-based materials during carbonization, limit the size, and reduce the expansion effect. At the same time, it is removed in advance by enzymatic hydrolysis. On the other hand, it provides a certain buffer space for the volume expansion of silicon-based nano-materials during the subsequent charge and discharge process, avoiding the problem of poor electrical contact caused by silicon pulverization, enabling the composite silicon-carbon to fully perform the lithium deintercalation and insertion reaction and maintain the structure unchanged, thereby improving the electrochemical performance of the battery.

[0006] To achieve the above object, in a first aspect, embodiments of the present invention provide a composite silicon-carbon material, which includes: a substrate material and nano-silicon-based particles;

[0007] The substrate material is a porous hard carbon material with through-holes inside;

[0008] The nano-silicon-based particles are uniformly distributed on the pore walls of the through-holes; the nano-silicon-based particles include nano-silicon particles or nano-silicon monoxide particles;

[0009] The diameter size of the aperture of each continuous pore channel of the through-hole is uniform; the diameter size of the aperture is 1 nm - 500 nm; the through-hole is obtained after the amylolytic reaction by uniformly curing a starch-based fiber containing nano-silicon-based particles and a liquid-phase resin.

[0010] Preferably, the particle size of the nano-silicon-based particles is 0.1 nm - 100 nm; the percentage of the mass of the nano-silicon-based particles in the total mass of the composite silicon-carbon material is 1% - 50%;

[0011] The porosity of the through-holes in the composite silicon-carbon material is 10% - 60%;

[0012] The particle size D of the composite silicon-carbon material 50 is 2 μm - 80 μm.

[0013] In a second aspect, an embodiment of the present invention provides a preparation method of the composite silicon-carbon material described in the first aspect above. The preparation method includes:

[0014] Step S1: Dissolve the starch raw material in deionized water, heat it at 53°C - 95°C until the starch raw material becomes pasty, and then stir to form a uniform colloidal solution with a concentration of 5 wt% - 30 wt%;

[0015] Step S2: Add the nano-silicon-based particles to the uniform colloidal solution, stir well for 12 hours - 24 hours to obtain a spinning precursor;

[0016] Step S3: Spin the spinning precursor through an electrospinning device with 25 kV to obtain starch-based fibers containing nano-silicon-based particles;

[0017] Step S4: Mix the starch-based fibers containing nano-silicon-based particles and the liquid-phase resin uniformly to obtain a mixed solution;

[0018] Step S5: Add a curing agent to the mixed solution for curing, keep the mixed solution flowing during the curing process, and keep the stirring rate at 20 r / min - 50 r / min. After complete curing, obtain a solid-phase material of starch-based fibers containing nano-silicon-based particles and resin;

[0019] Step S6: Place the solid-phase material in a pulverizer for pulverization treatment to obtain solid-phase particles with a particle size of 2 μm - 80 μm;

[0020] Step S7: Put the solid-phase particles into an aqueous solution containing amylase for enzymatic hydrolysis reaction. After filtration, dry the solid matter to obtain a resin matrix material with nano-silicon-based particles attached in the through-holes.

[0021] Step S8: Put the resin matrix material into a high-temperature furnace and perform high-temperature carbonization treatment under a protective atmosphere to obtain a composite silicon-carbon material.

[0022] Preferably, the starch raw material includes one or more of corn starch, cassava starch, and wheat starch.

[0023] The nano-silicon-based particles include nano-silicon particles or nano-silicon monoxide particles.

[0024] The liquid-phase resin is an ethanol solution formed by one or more of phenolic resin, epoxy resin, and furfural resin; the solid content of the liquid-phase resin is 70wt%-83wt%.

[0025] Preferably, the curing agent includes one or more of trimethylhexamethylenediamine, ethylenediamine, and m-xylenediamine.

[0026] The mass percentage of the curing agent in the mass of the solute of the liquid-phase resin is 20%-25%.

[0027] Preferably, the concentration of the aqueous solution containing amylase is 3wt%-10wt%; the temperature of the enzymatic hydrolysis reaction is 50°C-80°C, and the holding time is 24 hours-120 hours.

[0028] Preferably, the protective atmosphere is a nitrogen atmosphere or an argon atmosphere; the temperature of the high-temperature carbonization treatment is 600°C-1300°C, and the holding time is 0.5 hours-24 hours.

[0029] In a third aspect, an embodiment of the present invention provides a negative electrode plate, which includes the composite silicon-carbon material described in the first aspect above.

[0030] In a fourth aspect, an embodiment of the present invention provides a lithium-ion battery, which includes the negative electrode plate described in the third aspect above.

[0031] Preferably, the lithium-ion battery includes any one of a liquid lithium-ion battery, a semi-solid lithium-ion battery, a quasi-solid lithium-ion battery, and a all-solid-state electrolyte lithium-ion battery.

[0032] An embodiment of the present invention provides a composite silicon-carbon material, its preparation method and application. Starch-based fibers containing nano-silicon-based particles are prepared by electrospinning, and then mixed with a liquid-phase resin. A solid-phase material of starch-based fibers and resin containing nano-silicon particles is constructed by using the resin curing process. Then, an aqueous solution containing amylase is added to cause the starch-based fibers to undergo an enzymatic hydrolysis reaction to form continuous and uniform through pores. At the same time, the nano-silicon-based particles are retained in the pores of the through pores, and then through high-temperature carbonization treatment, a composite silicon-carbon material is finally obtained. During the preparation process of the present invention, through enzymatic hydrolysis, the gas expansion generated by the decomposition of starch-based fibers during the later carbonization process is reduced, which has a destructive effect on the resin carbonization matrix, and is beneficial to the structural stability. Since the cured resin carbonization system is not prone to melting, during the carbonization process, the uniform through pores will still be retained. The continuous and uniform through pores can provide a buffer space for the volume expansion of nano-silicon-based particles during the lithium-ion insertion / extraction process. At the same time, compared with most porous structures formed by etching to create pores, the pores formed by this method are uniformly controllable and the preparation process is simple and environmentally friendly. The uniform through pore structure can ensure the thickness of the SEI film during the electrolyte infiltration process, thereby improving the cycle stability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The technical solutions of the embodiments of the present invention will be further described in detail below with reference to the drawings and embodiments.

[0034] Figure 1 is a flowchart of the preparation method of the composite silicon-carbon material provided by the embodiment of the present invention;

[0035] Figure 2 are a schematic structural diagram and a partial enlarged view of the composite silicon-carbon material prepared by the preparation method provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The present invention will be further described in detail below with reference to the drawings and specific embodiments, but it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any form, that is, it is not intended to limit the protection scope of the present invention.

[0037] An embodiment of the present invention provides a composite silicon-carbon material, including: a substrate material and nano-silicon-based particles; wherein, the substrate material is a porous hard carbon material with through pores inside; the nano-silicon-based particles are uniformly distributed on the pore walls of the through pores, including nano-silicon particles or nano-silicon monoxide particles; the diameter size of the aperture of each continuous pore channel of the through pores is uniform, and the diameter size of the aperture of the through pores is 1 nm - 500 nm; the particle size D of the composite silicon-carbon material 50 is 2 μm - 80 μm.

[0038] The above-mentioned through-holes are obtained by uniformly curing a mixture of starch-based fibers containing nano-silicon-based particles and a liquid-phase resin, followed by an enzymatic hydrolysis reaction with amylase.

[0039] Specifically, the particle size D of the nano-silicon-based particles 50 is 0.1 nm - 100 nm; the percentage of the mass of the nano-silicon-based particles in the total mass of the composite silicon-carbon material is 1% - 50%; the porosity of the through-holes in the composite silicon-carbon material is 10% - 60%.

[0040] An embodiment of the present invention provides a method for preparing the above-mentioned composite silicon-carbon material, as Figure 1 shown, which specifically includes the following steps:

[0041] Step S1, dissolve the starch raw material in deionized water, heat it at 53°C - 95°C until the starch raw material becomes pasty, and then stir to form a uniform colloidal solution with a concentration of 5 wt% - 30 wt%;

[0042] Among them, the starch raw material includes one or more of corn starch, cassava starch, and wheat starch;

[0043] The starch dissolved in deionized water will form a pasty colloidal solution after heating, and the small molecules formed by the breaking of hydrogen bonds between starch molecules are dispersed in water.

[0044] Step S2, add the nano-silicon-based particles to the uniform colloidal solution, and stir well for 12 hours - 24 hours to obtain a spinning precursor;

[0045] Specifically, the nano-silicon-based particles of the present invention are nano-silicon-based particles with a particle size D 50 of 0.1 nm - 100 nm prepared in advance by a conventional method, including nano-silicon particles or nano-silicon monoxide particles.

[0046] Step S3, spin the spinning precursor through an electrospinning device with 25 kV to obtain starch-based fibers containing nano-silicon-based particles;

[0047] Step S4, mix the starch-based fibers containing nano-silicon-based particles with the liquid-phase resin uniformly to obtain a mixed solution;

[0048] Among them, the liquid-phase resin is an ethanol solution formed by one or more of phenolic resin, epoxy resin, and furfural resin; the solid content of the liquid-phase resin is 70 wt% - 83 wt%.

[0049] Step S5, add a curing agent to the mixed solution for curing, keep the mixed solution flowing during the curing process, and the stirring rate is maintained at 20 r / min - 50 r / min. After complete curing, a solid-phase material of starch-based fibers containing nano-silicon-based particles and resin is obtained;

[0050] Among them, the curing agent includes one or more of trimethylhexamethylenediamine, ethylenediamine, and m-xylenediamine; the mass percentage of the curing agent in the solute of the liquid resin is 20%-25%.

[0051] Step S6: Place the solid-phase material in a pulverizer for pulverization treatment to obtain solid-phase particles with a particle size of 2 μm to 80 μm.

[0052] Step S7: Put the solid-phase particles into an aqueous solution containing amylase for enzymatic hydrolysis reaction. After filtration, dry the solid matter to obtain a resin matrix material with nano-silicon-based particles attached in the through-holes.

[0053] Among them, the concentration of the aqueous solution containing amylase is 3 wt%-10 wt%; the temperature of the enzymatic hydrolysis reaction is 50°C - 80°C, and the holding time is 24 hours - 120 hours.

[0054] Step S8: Put the resin matrix material into a high-temperature furnace and perform high-temperature carbonization treatment under a protective atmosphere to obtain a composite silicon-carbon material.

[0055] Among them, the protective atmosphere is a nitrogen atmosphere or an argon atmosphere; the temperature of the high-temperature carbonization treatment is 600°C - 1300°C, and the holding time is 0.5 hours - 24 hours.

[0056] For the composite silicon-carbon material of the present invention, the diameter size of each continuous pore of the through-hole is uniform, and the diameter size of the through-hole is 1 nm - 500 nm, which can be any value within the above range, such as: 1 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable. The diameter size of each continuous pore of the through-hole is related to the fiber diameter spun by electrospinning. The cross-sectional diameter of each electrospun starch-based fiber containing nano-silicon-based particles is the same, that is, the thickness of the starch-based fiber is the same along its length. After the enzymatic hydrolysis reaction, the position of the starch fiber forms a through-hole with a uniform pore diameter size. After sintering, due to the shrinkage of the resin matrix and the residual starch carbon residue, the pore diameter of the through-hole will shrink to 1 nm - 500 nm.

[0057] The structural schematic diagram and partial enlarged view of the composite silicon-carbon material prepared by the present invention through the above preparation method are as follows Figure 2As shown, it can be seen that the hard carbon material with through holes in the composite silicon-carbon material provided by the present invention is attached with a nano-silicon-based material, and the nano-silicon-based particles include nano-silicon particles or nano-silicon monoxide particles. The above composite silicon-carbon material provided by the embodiments of the present invention can be used as a negative electrode active material for the preparation of a negative electrode sheet.

[0058] The above negative electrode sheet can be used in a lithium-ion battery, and the lithium-ion battery includes any one of a liquid lithium-ion battery, a semi-solid lithium-ion battery, a quasi-solid lithium-ion battery, and a solid-state electrolyte lithium-ion battery.

[0059] To better understand the technical solution provided by the present invention, the following uses multiple specific examples to separately illustrate the preparation process and characteristics of the composite silicon-carbon material of the present invention.

[0060] Example 1

[0061] This example provides a preparation process and performance test of a composite silicon-carbon material, and the specific process is as follows:

[0062] (1) Dissolve 10 g of cassava starch raw material in 200 g of deionized water, heat it to 60 °C to make the cassava starch become paste-like, and then stir to form a uniform colloidal solution with a concentration of 5 wt%.

[0063] (2) Add 3 g of pre-prepared nano-silicon particles with a particle size D 50 of 0.1 nm to the uniform colloidal solution, stir well for 12 hours to obtain a spinning precursor.

[0064] (3) Spin the spinning precursor through an electrospinning device with 25 kV to obtain 12 g of starch-based fibers containing nano-silicon particles.

[0065] (4) Mix 12 g of starch-based fibers containing nano-silicon particles with 100 g of liquid phenolic resin evenly to obtain a mixed solution; wherein, the solid content of the liquid phenolic resin is 70 wt%.

[0066] (5) Add 14 g of trimethylhexamethylenediamine to the mixed solution for curing, keep the mixed solution flowing during the curing process, and keep the stirring rate at 20 r / min. After complete curing, obtain a solid-phase material of starch-based fibers containing nano-silicon particles and resin.

[0067] (6) Place the solid-phase material in a pulverizer for pulverization treatment to obtain solid-phase particles with a particle size of 20 μm.

[0068] (7) Put the solid-phase particles into 200 g of an aqueous solution containing amylase, carry out an enzymatic hydrolysis reaction at 60 °C, keep warm for 120 hours, filter and dry the solid substance to obtain a resin matrix material with nano-silicon particles attached in the through holes; wherein, the concentration of the aqueous solution containing amylase is 3 wt%.

[0069] (8) Put the resin matrix material into a high-temperature furnace, heat it to 1300 °C under a nitrogen atmosphere, keep it warm for 0.5 hours, and carry out high-temperature carbonization treatment to obtain a composite silicon-carbon material with a particle size D 50 of 18 μm, wherein the diameter size of the internal through-holes of the composite silicon-carbon material is between 1 nm and 300 nm.

[0070] Use the composite silicon-carbon material of this example to prepare an electrode sheet and assemble it into a CR2032 type button half-cell for testing. The specific process is as follows.

[0071] The specific process of battery assembly is as follows: Weigh the composite silicon-carbon material, the conductive additive carbon black, and the binder (the binder is sodium carboxymethyl cellulose and styrene-butadiene rubber in a ratio of 1:1) according to a mass ratio of 95:2:3. Place them in a pulper at room temperature to prepare a slurry. Coat the prepared slurry evenly on the copper foil. After drying in a forced-air drying oven at 50 °C for 2 hours, cut it into electrode sheets of 8×8 mm, and then vacuum-dry them in a vacuum drying oven at 100 °C for 10 hours. Immediately transfer the dried electrode sheets into a glove box for standby to assemble the battery.

[0072] The assembly of the simulated battery is carried out in a glove box containing a high-purity Ar atmosphere. Use metallic lithium as the counter electrode, a polypropylene film as the separator, and a solution of 1 mol / L LiPF 6 in ethylene carbonate (EC) / dimethyl carbonate (DMC) (the volume ratio of EC to DMC is 1:1) as the electrolyte to assemble a CR2032 type button half-cell.

[0073] The test process is as follows: Use a charge-discharge instrument to conduct a constant-current charge-discharge mode test. The discharge cut-off voltage is 0.005 V, the charge cut-off voltage is 1.5 V, and the charge-discharge test is carried out at a current density of C / 10.

[0074] Test the charge specific capacity, the first-cycle Coulombic efficiency of the battery, and the cycle capacity retention rates at 50 weeks, 100 weeks, 200 weeks, 300 weeks, and 500 weeks respectively. The test data are shown in Table 1.

[0075] Example 2

[0076] This example provides a preparation process and performance test of a composite silicon-carbon material. The specific process is as follows:

[0077] (1) Dissolve 60 g of cassava starch raw material in 200 g of deionized water, heat it at 53 °C until the cassava starch becomes pasty, and then stir to form a uniform colloidal solution with a concentration of 30 wt%.

[0078] (2) Put 10 g of the pre-prepared particle size D 505 nm nano-silicon particles were added to a homogeneous colloidal solution and stirred thoroughly for 12 hours to obtain a spinning precursor.

[0079] (3) The spinning precursor was electrospun through an electrospinning device with 25 kV to obtain 65 g of starch-based fibers containing nano-silicon particles.

[0080] (4) 65 g of starch-based fibers containing nano-silicon particles were mixed uniformly with 120 g of liquid phenolic resin to obtain a mixed solution; among them, the solid content of the liquid phenolic resin was 70 wt%.

[0081] (5) 20 g of trimethylhexamethylenediamine was added to the mixed solution for curing. During the curing process, the flow of the mixed solution was maintained, and the stirring rate was kept at 30 r / min. After complete curing, a solid-phase material of starch-based fibers containing nano-silicon particles and resin was obtained.

[0082] (6) The solid-phase material was placed in a pulverizer for pulverization to obtain solid-phase particles with a particle size of 20 μm.

[0083] (7) The solid-phase particles were put into 300 g of an aqueous solution containing amylase and subjected to an enzymatic hydrolysis reaction at 80 °C for 24 hours of heat preservation. After filtration, the solid substance was dried to obtain a resin matrix material with nano-silicon particles attached in the through-holes; among them, the concentration of the aqueous solution containing amylase was 10 wt%.

[0084] (8) The resin matrix material was placed in a high-temperature furnace and heated to 600 °C under a nitrogen atmosphere for 24 hours of heat preservation for high-temperature carbonization treatment to obtain a composite silicon-carbon material with a particle size D 50 of 80 μm, where the diameter size of the through-holes inside the composite silicon-carbon material was between 1 nm and 400 nm.

[0085] The composite silicon-carbon material of this example was used to prepare an electrode sheet and assembled into a CR2032 type button half-cell for testing. The battery assembly process and testing process were the same as those in the example. The test data are shown in Table 1.

[0086] Example 3

[0087] This example provides a preparation process and performance test of a composite silicon-carbon material. The specific process is as follows:

[0088] (1) 5 g of corn starch raw material was dissolved in 100 g of deionized water and heated at 55 °C until the corn starch became paste-like, and then stirred to form a homogeneous colloidal solution with a concentration of 5 wt%.

[0089] (2) 3 g of pre-prepared nano-silicon oxide particles with a particle size D 50 of 5 nm were added to the homogeneous colloidal solution and stirred thoroughly for 12 hours to obtain a spinning precursor.

[0090] (3) The spinning precursor is spun through an electrospinning device with 25 kV to obtain 65 g of starch-based fibers containing nano-sized silicon monoxide particles.

[0091] (4) 65 g of starch-based fibers containing nano-sized silicon monoxide particles are mixed evenly with 120 g of liquid phenolic resin to obtain a mixed solution; among them, the solid content of the liquid phenolic resin is 70 wt%.

[0092] (5) 20 g of trimethylhexamethylenediamine is added to the mixed solution for curing. During the curing process, the flow of the mixed solution is maintained, and the stirring rate is kept at 20 r / min. After complete curing, a solid-phase material of starch-based fibers containing nano-sized silicon monoxide particles and resin is obtained.

[0093] (6) The solid-phase material is placed in a pulverizer for pulverization treatment to obtain solid-phase particles with a particle size of 20 μm.

[0094] (7) The solid-phase particles are put into 200 g of an aqueous solution containing amylase, and an enzymatic hydrolysis reaction is carried out at 60 °C for 120 hours. After filtration, the solid substance is dried to obtain a resin matrix material with nano-sized silicon monoxide particles attached in the through-holes; among them, the concentration of the aqueous solution containing amylase is 3 wt%.

[0095] (8) The resin matrix material is placed in a high-temperature furnace and heated to 1300 °C under a nitrogen atmosphere and held for 0.5 hours for high-temperature carbonization treatment to obtain a composite silicon-carbon material with a particle size D 50 of 18 μm, where the diameter size of the through-holes inside the composite silicon-carbon material is between 1 nm and 500 nm.

[0096] The composite silicon-carbon material of this example is used to prepare an electrode sheet and assembled into a CR2032 type button half-cell for testing. The assembly process and testing process of the battery are the same as those in the example. The test data are shown in Table 1 in detail.

[0097] Example 4

[0098] This example provides a preparation process and performance test of a composite silicon-carbon material. The specific process is as follows:

[0099] (1) 20 g of corn starch raw material is dissolved in 200 g of deionized water. After heating at 60 °C to make the corn starch become paste-like, it is stirred to form a uniform colloidal solution with a concentration of 10 wt%.

[0100] (2) 5 g of pre-prepared nano-sized silicon particles with a particle size D 50 of 4 nm are added to the uniform colloidal solution and stirred thoroughly for 12 hours to obtain a spinning precursor.

[0101] (3) The spinning precursor is spun through an electrospinning device with 25 kV to obtain 65 g of starch-based fibers containing nano-silicon-based particles.

[0102] (4) 25 g of starch-based fibers containing nano-silicon particles are mixed evenly with 100 g of liquid phenolic resin to obtain a mixed solution; among them, the solid content of the liquid phenolic resin is 75 wt%.

[0103] (5) 18 g of trimethylhexamethylenediamine is added to the mixed solution for curing. During the curing process, the flow of the mixed solution is maintained, and the stirring rate is kept at 20 r / min. After complete curing, a solid-phase material of starch-based fibers containing nano-silicon-based particles and resin is obtained.

[0104] (6) The solid-phase material is placed in a crusher for crushing treatment to obtain solid-phase particles with a particle size of 15 μm.

[0105] (7) The solid-phase particles are put into 200 g of an aqueous solution containing amylase, and an enzymatic hydrolysis reaction is carried out at 60 °C for 120 hours. After filtration, the solid substance is dried to obtain a resin matrix material with nano-silicon particles attached in the through-holes; among them, the concentration of the aqueous solution containing amylase is 3 wt%.

[0106] (8) The resin matrix material is placed in a high-temperature furnace, heated to 1300 °C under a nitrogen atmosphere, and kept warm for 0.5 hours for high-temperature carbonization treatment to obtain a composite silicon-carbon material with a particle size D 50 of 12 μm, where the diameter size of the through-holes inside the composite silicon-carbon material is between 1 nm and 300 nm.

[0107] The composite silicon-carbon material of this example is used to prepare an electrode sheet and assembled into a CR2032 type button half-cell for testing. The assembly process and testing process of the battery are the same as those in the example. The test data are shown in Table 1 for details.

[0108] Example 5

[0109] This example provides a preparation process and performance test of a composite silicon-carbon material. The specific process is as follows:

[0110] (1) 30 g of cassava starch raw material is dissolved in 200 g of deionized water. After heating at 65 °C to make the cassava starch become paste-like, it is stirred to form a uniform colloidal solution with a concentration of 15 wt%.

[0111] (2) 3 g of pre-prepared nano-silicon particles with a particle size D 50 of 3 nm are added to the uniform colloidal solution and stirred thoroughly for 24 hours to obtain a spinning precursor.

[0112] (3) The spinning precursor was spun through a 25 kV electrospinning device to obtain 32 g of starch fibers containing nano-silicon particles.

[0113] (4) 12 g of starch fibers containing nano-silicon-based particles and 100 g of liquid phenolic resin are uniformly mixed to obtain a mixed solution, wherein the solid content of the liquid phenolic resin is 75 wt %.

[0114] (5) 18 g of trimethylhexamethylenediamine was added to the mixed solution for curing. During the curing process, the mixed solution was kept flowing and the stirring rate was maintained at 20 r / min. After complete curing, a solid phase material of starch fibers containing nano-silicon particles and resin was obtained.

[0115] (6) The solid phase material is placed in a pulverizer for pulverization to obtain solid phase particles with a particle size of 32 μm.

[0116] (7) placing the solid particles into 200 g of an aqueous solution containing amylase, performing an enzymatic hydrolysis reaction at 60° C., keeping the temperature for 120 hours, filtering and drying the solid matter to obtain a resin matrix material with nano-silicon particles attached in the through-holes; wherein the concentration of the aqueous solution containing amylase is 3 wt %.

[0117] (8) The resin matrix material is placed in a high temperature furnace, heated to 1300°C in a nitrogen atmosphere, and kept at this temperature for 0.5 hours for high temperature carbonization treatment to obtain a particle size D 50 The composite silicon-carbon material has a diameter of 28 μm, wherein the diameter of the through holes inside the composite silicon-carbon material is between 1 nm and 300 nm.

[0118] The composite silicon-carbon material of this embodiment was used to prepare the pole piece and assembled into a CR2032 button half-cell for testing. The assembly process and test process of the battery were the same as those in the embodiment. The test data are detailed in Table 1.

[0119] Example 6

[0120] This embodiment provides a preparation process and performance test of a composite silicon-carbon material, and the specific process is as follows:

[0121] (1) 20 g of cassava starch raw material was dissolved in 200 g of deionized water, heated to 75° C. to make the cassava starch paste-like, and then stirred to form a uniform colloidal solution with a concentration of 10 wt %.

[0122] (2) 6 g of pre-prepared particles of size D 50 Nano-silicon particles with a diameter of 5 nm are added to the uniform colloidal solution and stirred for 18 hours to obtain a spinning precursor.

[0123] (3) The spinning precursor is spun through an electrospinning device with 25 kV to obtain 25 g of starch-based fibers containing nano-silicon particles.

[0124] (4) 12 g of starch-based fibers containing nano-silicon particles are mixed evenly with 100 g of liquid phenolic resin to obtain a mixed solution; among them, the solid content of the liquid phenolic resin is 80 wt%.

[0125] (5) 20 g of trimethylhexamethylenediamine is added to the mixed solution for curing. During the curing process, the flow of the mixed solution is maintained, and the stirring rate is kept at 20 r / min. After complete curing, a solid-phase material of starch-based fibers containing nano-silicon particles and resin is obtained.

[0126] (6) The solid-phase material is placed in a pulverizer for pulverization treatment to obtain solid-phase particles with a particle size of 15 μm.

[0127] (7) The solid-phase particles are put into 200 g of an aqueous solution containing amylase, and an enzymatic hydrolysis reaction is carried out at 60 °C for 120 hours. After filtration, the solid substance is dried to obtain a resin matrix material with nano-silicon particles attached in the through-holes; among them, the concentration of the aqueous solution containing amylase is 3 wt%.

[0128] (8) The resin matrix material is placed in a high-temperature furnace and heated to 1200 °C in a nitrogen atmosphere, and kept warm for 0.5 hours for high-temperature carbonization treatment to obtain a composite silicon-carbon material with a particle size D 50 of 12 μm, where the diameter size of the through-holes inside the composite silicon-carbon material is between 1 nm and 500 nm.

[0129] The composite silicon-carbon material of this example is used to prepare a pole piece and assembled into a CR2032 type button half-cell for testing. The assembly process and testing process of the battery are the same as those in the example. The test data are shown in Table 1 in detail.

[0130] Example 7

[0131] This example provides a preparation process and performance test of a composite silicon-carbon material. The specific process is as follows:

[0132] (1) 30 g of pea starch raw material is dissolved in 200 g of deionized water, heated to 75 °C to make the pea starch become paste-like, and then stirred to form a uniform colloidal solution with a concentration of 15 wt%.

[0133] (2) 3 g of pre-prepared nano-silicon particles with a particle size D 50 of 7 nm are added to the uniform colloidal solution, and stirred thoroughly for 17 hours to obtain a spinning precursor.

[0134] (3) The spinning precursor is spun through an electrospinning device with 25 kV to obtain 12 g of starch-based fibers containing nano-silicon particles.

[0135] (4) 12 g of starch-based fibers containing nano-silicon particles are mixed evenly with 100 g of liquid-phase furfural resin to obtain a mixed solution; among them, the solid content of the liquid-phase phenolic resin is 70 wt%.

[0136] (5) 14 g of trimethylhexamethylenediamine is added to the mixed solution for curing. During the curing process, the flow of the mixed solution is maintained, and the stirring rate is kept at 20 r / min. After complete curing, a solid-phase material of starch-based fibers containing nano-silicon particles and resin is obtained.

[0137] (6) The solid-phase material is placed in a pulverizer for pulverization treatment to obtain solid-phase particles with a particle size of 12 μm.

[0138] (7) The solid-phase particles are put into 200 g of an aqueous solution containing amylase, and an enzymatic hydrolysis reaction is carried out at 60 °C for 120 hours. After filtration, the solid substance is dried to obtain a resin matrix material with nano-silicon particles attached in the through-holes; among them, the concentration of the aqueous solution containing amylase is 3 wt%.

[0139] (8) The resin matrix material is placed in a high-temperature furnace and heated to 1300 °C in a nitrogen atmosphere, and kept warm for 0.5 hours for high-temperature carbonization treatment to obtain a composite silicon-carbon material with a particle size D 50 of 10 μm, where the diameter size of the through-holes inside the composite silicon-carbon material is between 1 nm and 300 nm.

[0140] The composite silicon-carbon material of this example is used to prepare an electrode sheet and assembled into a CR2032 type button half-cell for testing. The battery assembly process and testing process are the same as those in the example. The test data are shown in Table 1 for details.

[0141] Example 8

[0142] This example provides a preparation process and performance test of a composite silicon-carbon material. The specific process is as follows:

[0143] (1) 10 g of cassava starch raw material is dissolved in 200 g of deionized water, heated to 80 °C to make the cassava starch become paste-like, and then stirred to form a uniform colloidal solution with a concentration of 5 wt%.

[0144] (2) 3 g of pre-prepared nano-silicon particles with a particle size D 50 of 5 nm are added to the uniform colloidal solution and stirred thoroughly for 12 hours to obtain a spinning precursor.

[0145] (3) The spinning precursor is spun through an electrospinning device with 25 kV to obtain 12 g of starch-based fibers containing nano-silicon particles.

[0146] (4) 12 g of starch-based fibers containing nano-silicon particles are mixed evenly with 100 g of liquid phenolic resin to obtain a mixed solution; among them, the solid content of the liquid phenolic resin is 70 wt%.

[0147] (5) 14 g of trimethylhexamethylenediamine is added to the mixed solution for curing. During the curing process, the flow of the mixed solution is maintained, and the stirring rate is kept at 20 r / min. After complete curing, a solid-phase material of starch-based fibers containing nano-silicon particles and resin is obtained.

[0148] (6) The solid-phase material is placed in a crusher for crushing treatment to obtain solid-phase particles with a particle size of 20 μm.

[0149] (7) The solid-phase particles are put into 200 g of an aqueous solution containing amylase, and an enzymatic hydrolysis reaction is carried out at 60 °C for 120 hours. After filtration, the solid substance is dried to obtain a resin matrix material with nano-silicon particles attached in the through-holes; among them, the concentration of the aqueous solution containing amylase is 3 wt%.

[0150] (8) The resin matrix material is placed in a high-temperature furnace, heated to 1300 °C in a nitrogen atmosphere, and kept warm for 0.5 hours for high-temperature carbonization treatment to obtain a composite silicon-carbon material with a particle size D 50 of 18 μm, where the diameter size of the through-holes inside the composite silicon-carbon material is between 1 nm and 500 nm.

[0151] The composite silicon-carbon material of this example is used to prepare an electrode sheet and assembled into a CR2032 type button half-cell for testing. The battery assembly process and testing process are the same as those in the example. The test data are shown in Table 1 for details.

[0152] Example 9

[0153] This example provides a preparation process and performance test of a composite silicon-carbon material. The specific process is as follows:

[0154] (1) 10 g of sweet potato starch raw material is dissolved in 200 g of deionized water, heated to 95 °C to make the sweet potato starch become pasty, and then stirred to form a uniform colloidal solution with a concentration of 5 wt%.

[0155] (2) 3 g of pre-prepared nano-silicon particles with a particle size D 50 of 5 nm are added to the uniform colloidal solution, and stirred thoroughly for 12 hours to obtain a spinning precursor.

[0156] (3) The spinning precursor is spun through an electrospinning device with 25 kV to obtain 12 g of starch-based fibers containing nano-silicon particles.

[0157] (4) 12 g of starch-based fibers containing nano-silicon particles are mixed evenly with 100 g of liquid phenolic resin to obtain a mixed solution; among them, the solid content of the liquid phenolic resin is 70 wt%.

[0158] (5) 14 g of trimethylhexamethylenediamine is added to the mixed solution for curing. During the curing process, the flow of the mixed solution is maintained, and the stirring rate is kept at 20 r / min. After complete curing, a solid-phase material of starch-based fibers containing nano-silicon particles and resin is obtained.

[0159] (6) The solid-phase material is placed in a pulverizer for pulverization treatment to obtain solid-phase particles with a particle size of 20 μm.

[0160] (7) The solid-phase particles are put into 200 g of an aqueous solution containing amylase, and an enzymatic hydrolysis reaction is carried out at 60 °C for 120 hours. After filtration, the solid substance is dried to obtain a resin matrix material with nano-silicon particles attached in the through-holes; among them, the concentration of the aqueous solution containing amylase is 3 wt%.

[0161] (8) The resin matrix material is placed in a high-temperature furnace, heated to 1300 °C under a nitrogen atmosphere, and kept warm for 0.5 hours for high-temperature carbonization treatment to obtain a composite silicon-carbon material with a particle size D 50 of 18 μm, where the diameter size of the through-holes inside the composite silicon-carbon material is between 1 nm and 300 nm.

[0162] The composite silicon-carbon material of this example is used to prepare an electrode sheet and assembled into a CR2032 type button half-cell for testing. The assembly process and testing process of the battery are the same as those in the example. The test data are shown in Table 1 for details.

[0163] Example 10

[0164] This example provides a preparation process and performance test of a composite silicon-carbon material. The specific process is as follows:

[0165] (1) 20 g of wheat starch raw material is dissolved in 200 g of deionized water, heated to 60 °C to make the wheat starch become paste-like, and then stirred to form a uniform colloidal solution with a concentration of 10 wt%.

[0166] (2) 3 g of pre-prepared nano-silicon particles with a particle size D 50 of 3 nm are added to the uniform colloidal solution, and stirred thoroughly for 12 hours to obtain a spinning precursor.

[0167] (3) The spinning precursor is spun through an electrospinning device with 25 kV to obtain 12 g of starch-based fibers containing nano-silicon particles.

[0168] (4) 12 g of starch-based fibers containing nano-silicon particles are mixed evenly with 100 g of liquid phenolic resin to obtain a mixed solution; among them, the solid content of the liquid phenolic resin is 70 wt%.

[0169] (5) 15 g of m-xylenediamine is added to the mixed solution for curing. During the curing process, the flow of the mixed solution is maintained, and the stirring rate is kept at 30 r / min. After complete curing, a solid-phase material of starch-based fibers and resin containing nano-silicon particles is obtained.

[0170] (6) The solid-phase material is placed in a pulverizer for pulverization treatment to obtain solid-phase particles with a particle size of 15 μm.

[0171] (7) The solid-phase particles are put into 200 g of an aqueous solution containing amylase, and an enzymatic hydrolysis reaction is carried out at 60 °C for 120 hours. After filtration, the solid substance is dried to obtain a resin matrix material with nano-silicon particles attached in the through-holes; among them, the concentration of the aqueous solution containing amylase is 3 wt%.

[0172] (8) The resin matrix material is placed in a high-temperature furnace, and the temperature is raised to 1300 °C under a nitrogen atmosphere and held for 0.5 hours for high-temperature carbonization treatment to obtain a composite silicon-carbon material with a particle size D 50 of 12 μm, wherein the diameter size of the through-holes inside the composite silicon-carbon material is between 1 nm and 300 nm.

[0173] The composite silicon-carbon material of this example is used to prepare an electrode sheet and assembled into a CR2032 type button half-cell for testing. The battery assembly process and testing process are the same as those of the example. The test data are shown in Table 1 in detail.

[0174] To better illustrate the effects of the embodiments of the present invention, Comparative Examples 1-2 are compared with the above embodiments.

[0175] Comparative Example 1

[0176] This comparative example provides a preparation process and performance test of a silicon-carbon material. Different from Example 1, Comparative Example 1 does not undergo the enzymatic hydrolysis reaction in step (7) of Example 1, and other preparation processes are the same as those of Example 1. The specific process is as follows.

[0177] (1) 10 g of cassava starch raw material is dissolved in 200 g of deionized water, heated to 60 °C to make the cassava starch become pasty, and then stirred to form a uniform colloidal solution with a concentration of 5 wt%.

[0178] (2) 3 g of pre-prepared particle size D 505 nm nano-silicon-based particles were added to a homogeneous colloidal solution and stirred thoroughly for 12 hours to obtain a spinning precursor.

[0179] (3) The spinning precursor was electrospun through an electrospinning device with 25 kV to obtain 12 g of starch-based fibers containing nano-silicon-based particles.

[0180] (4) 3 g of the starch-based fibers containing nano-silicon-based particles were mixed evenly with 100 g of liquid phenolic resin to obtain a mixed solution; among them, the solid content of the liquid phenolic resin was 70 wt%.

[0181] (5) 15 g of trimethylhexamethylenediamine was added to the mixed solution for curing. During the curing process, the flow of the mixed solution was maintained, and the stirring rate was kept at 20 r / min. After complete curing, a solid-phase material of starch-based fibers containing nano-silicon-based particles and resin was obtained.

[0182] (6) The solid-phase material was placed in a pulverizer for pulverization to obtain solid-phase particles with a particle size of 22 μm.

[0183] (8) The solid-phase particles were placed in a high-temperature furnace and heated to 1300 °C under a nitrogen atmosphere and kept for 0.5 hours for high-temperature carbonization treatment to obtain a silicon-carbon material with a non-through internal pore and a particle size D 50 of 19 μm.

[0184] The silicon-carbon material of this comparative example was used to prepare an electrode sheet and assembled into a CR2032 type button half-cell for testing. The assembly process and testing process of the battery were the same as those in the example. The test data are shown in Table 1 for details.

[0185] Comparative Example 2

[0186] This comparative example provides a process for preparing silicon-carbon materials using an existing method. Different from Example 1, it did not go through the electrospinning and enzymatic hydrolysis reaction processes. The internal pores of the material obtained in this comparative example were formed by the different residual carbons after high-temperature sintering of starch and phenolic resin under a protective atmosphere, forming a non-uniform and non-through pore structure;

[0187] (1) 10 g of cassava starch raw material was dissolved in 200 g of deionized water and heated to 60 °C to make the starch pasty and then stirred to form a homogeneous solution with a concentration of 5 wt%.

[0188] (2) 3 g of pre-prepared nano-silicon-based particles with a particle size D 50 of 5 nm were added to the homogeneous solution, stirred thoroughly for 12 hours, then dried, and pulverized after drying to obtain starch particles containing nano-silicon-based particles.

[0189] (3) Mix 13 g of starch particles containing nano-silicon-based particles evenly with 100 g of liquid phenolic resin to obtain a mixed solution; wherein, the solid content of the liquid phenolic resin is 70 wt%.

[0190] (4) Add 15 g of trimethylhexamethylenediamine to the mixed solution for curing, and keep the mixed solution flowing during the curing process. The stirring rate is kept at 20 r / min. After complete curing, a solid-phase material containing starch-based fibers with nano-silicon-based particles and resin is obtained.

[0191] (5) Place the solid-phase material in a pulverizer for pulverization treatment to obtain solid-phase particles with a particle size of 22 μm.

[0192] (6) Put the solid-phase particles into a high-temperature furnace, heat them up to 1300 °C under a nitrogen atmosphere, and keep them at this temperature for 0.5 hours for high-temperature carbonization treatment to obtain silicon-carbon materials with a particle size D 50 of 19 μm.

[0193] Use the silicon-carbon material of this comparative example to prepare a pole piece and assemble it into a CR2032-type button half-cell for testing. The battery assembly process and testing process are the same as those in the examples. The test data are shown in Table 1 for details.

[0194] Table 1 is a summary of the electrochemical performance test data of the batteries assembled in Examples 1-10 and Comparative Examples 1-2.

[0195]

[0196] Table 1

[0197] It can be seen from the comparison of the test data in Table 1 that the initial Coulomb efficiency and capacity retention rate at different cycle numbers of the batteries in Examples 1-10 are higher than those in Comparative Example 1 and Comparative Example 2. This is because in Comparative Example 1, the starch-based material did not use enzymatic decomposition to remove starch fibers, and its phenolic carbon matrix was damaged by the expansion stress of the gas decomposed from the starch fibers during the carbonization process, resulting in poor cycling performance. In Comparative Example 2, the non-uniform pores formed led to the easy enrichment of nano-silicon-based particles, causing local stress concentration and more serious damage to the carbon matrix during the cycling process, resulting in even worse cycling performance. While in the negative electrode materials of the batteries in Examples 1-10 of the present invention, there is the composite silicon-carbon material of the present invention, and this composite silicon-carbon material has a continuous and uniform through-hole pore structure. The nano-silicon-based particles are distributed in the pores of the through-holes. The continuous and uniform through-holes can provide a buffer space for the volume expansion of the nano-silicon-based particles during the lithium-ion insertion and extraction process. At the same time, the uniform through-hole pore structure can ensure the thickness of the SEI film formed during the electrolyte infiltration process, thereby improving the cycling stability of the battery.

[0198] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above description is only the specific embodiments of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A composite silicon carbide material, characterized in that, the composite silicon carbide material comprises: a substrate material and nano silicon-based particles; the substrate material is a porous hard carbon material with through holes inside; the nano silicon-based particles are uniformly distributed on the pore walls of the through holes; the nano silicon-based particles include nano silicon particles or nano silicon monoxide particles; the diameter size of the aperture of each continuous pore channel of the through holes is uniform; the diameter size of the aperture is 1nm - 500nm; the through holes are obtained after the starch-based fibers containing nano silicon-based particles are mixed uniformly with a liquid-phase resin and cured, and then subjected to an amylase enzymatic hydrolysis reaction.

2. The composite silicon carbide material according to claim 1, characterized in that, the particle size of the nano silicon-based particles is 0.1nm - 100nm; the percentage of the mass of the nano silicon-based particles in the total mass of the composite silicon carbide material is 1% - 50%; the porosity of the through holes in the composite silicon carbide material is 10% - 60%; The particle size D of the composite silicon carbide material 50 is 2 μm - 80 μm.

3. A preparation method of the composite silicon carbide material according to any one of claims 1 - 2 above, characterized in that, the preparation method comprises: Step S1, dissolving the starch raw material in deionized water, heating at 53°C - 95°C until the starch raw material becomes pasty, and then stirring to form a uniform colloidal solution with a concentration of 5wt% - 30wt%; Step S2, adding the nano silicon-based particles into the uniform colloidal solution, stirring thoroughly for 12 hours - 24 hours to obtain a spinning precursor; Step S3, spinning the spinning precursor through an electrospinning device with 25kV to obtain starch-based fibers containing nano silicon-based particles; Step S4, mixing the starch-based fibers containing nano silicon-based particles uniformly with a liquid-phase resin to obtain a mixture; Step S5, adding a curing agent to the mixture for curing, keeping the mixture flowing during the curing process, with the stirring rate maintained at 20r / min - 50r / min. After complete curing, a solid-phase material of starch-based fibers containing nano silicon-based particles and resin is obtained; Step S6, placing the solid-phase material in a pulverizer for pulverization treatment to obtain solid-phase particles with a particle size of 2μm - 80μm; Step S7, putting the solid-phase particles into an aqueous solution containing amylase for enzymatic hydrolysis reaction, filtering and then drying the solid substance to obtain a resin matrix material with nano silicon-based particles attached in the through holes; Step S8, putting the resin matrix material into a high-temperature furnace and performing high-temperature carbonization treatment under a protective atmosphere to obtain the composite silicon carbide material.

4. The preparation method according to claim 3, characterized in that, the starch raw material includes one or more of corn starch, tapioca starch, and wheat starch; the nano silicon-based particles include nano silicon particles or nano silicon monoxide particles; the liquid-phase resin is an ethanol solution formed by one or more of phenolic resin, epoxy resin, and furfural resin; the solid content of the liquid-phase resin is 70wt% - 83wt%.

5. The preparation method according to claim 3, characterized in that, the curing agent includes: one or more of trimethylhexamethylenediamine, ethylenediamine, and m-xylenediamine; The mass percentage of the curing agent in the solute of the liquid resin is 20%-25%.

6. According to the preparation method described in claim 3, it is characterized in that the concentration of the aqueous solution containing amylase is 3wt%-10wt%; the temperature of the enzymatic hydrolysis reaction is 50°C-80°C, and the holding time is 24 hours-120 hours.

7. According to the preparation method described in claim 3, it is characterized in that the protective atmosphere is a nitrogen atmosphere or an argon atmosphere; the temperature of the high-temperature carbonization treatment is 600°C-1300°C, and the holding time is 0.5 hours-24 hours.

8. A negative electrode sheet, it is characterized in that the negative electrode sheet comprises the composite silicon-carbon material described in any one of claims 1-2 above.

9. A lithium-ion battery, it is characterized in that the lithium-ion battery comprises the negative electrode sheet described in claim 8 above.

10. According to the lithium-ion battery described in claim 9, it is characterized in that the lithium-ion battery comprises any one of a liquid lithium-ion battery, a semi-solid lithium-ion battery, a quasi-solid lithium-ion battery, and a all-solid-state electrolyte lithium-ion battery.

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