Vapor deposition silicon carbon material and preparation method and application thereof

Abstract

The invention discloses a vapor deposition silicon carbon material and a preparation method and application thereof, and relates to the technical field of lithium ion battery negative electrode materials, and the preparation method comprises the following steps: dissolving phenolic resin in a solvent, then adding boric acid, heating and stirring until the solution is clear, pouring the obtained aqueous phase solution into an oil phase, adding an emulsion stabilizer, and uniformly stirring; a solution of a water-in-oil system is obtained; heating the obtained solution of the water-in-oil system, continuously stirring, adding a curing agent, continuously stirring, removing an oil phase on the surface, and drying to obtain a phenolic resin microsphere precursor; carrying out heat treatment in an oxidizing atmosphere, cooling, calcining in an inert atmosphere, cooling, washing and drying to obtain a carbonized precursor; and mixing and grinding the carbonized precursor and potassium hydroxide, calcining, cooling, washing, drying, and introducing silane gas for deposition to obtain the vapor deposition silicon-carbon material. The preparation process is simple, the cost is low, and the first efficiency of the prepared vapor deposition silicon carbon material is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion battery negative electrode materials, and particularly relates to a gas deposition silicon-carbon material and a preparation method and application thereof. BACKGROUND

[0002] As the current mainstream energy storage device, the performance improvement of lithium ion batteries highly depends on the innovation of electrode materials. As an important component of lithium ion batteries, the performance of negative electrode materials directly affects the key indicators of the batteries, such as energy density, cycle life and rate performance. The traditional graphite negative electrode material has a low theoretical specific capacity (372 mAh / g), which has been difficult to meet the increasing demand for high energy density. Therefore, the development of new negative electrode materials with higher specific capacity, longer cycle life and better rate performance has become a research hotspot in the field of lithium ion batteries. Silicon-based negative electrode materials are considered as the most promising candidate for the next generation of high energy density lithium ion battery negative electrode materials due to their advantages of ultra-high theoretical specific capacity (4200 mAh / g, about 10 times that of graphite), abundant reserves, low cost and environmental friendliness. However, silicon-based negative electrode materials have a huge volume expansion (~300%) during the charging and discharging process, which leads to electrode pulverization, active material shedding, repeated rupture and regeneration of the solid electrolyte interface film (SEI), and other problems, which seriously limits their cycle stability and practical application.

[0003] The current commercial silicon-carbon negative electrode material mainly includes the first generation of ground silicon-carbon negative electrode. The silicon-carbon negative electrode prepared by the grinding method or the sand milling method can effectively reduce the powder particle size, adjust the size distribution, and help to relieve the stress and deformation generated by silicon during the deintercalation of lithium ions. However, this method is difficult to grind the particles to below 100 nm, the particle size of the material is still large, the particle size distribution cannot be effectively controlled, and the particle agglomeration phenomenon is obvious. In addition, impurities are easily introduced during the grinding process, and the purity is low. The larger nano-silicon particles will quickly attenuate the capacity with the cycle of the battery, resulting in a cycle of less than 500 times. Therefore, the ground silicon-carbon can only be applied to some rate type batteries with low cycle requirements.

[0004] The second generation of silicon-oxygen material, silicon monoxide (SiO), has a smaller volume expansion (220%) during lithium intercalation, and therefore, compared with pure silicon negative electrode, the cycle stability is obviously improved. However, the silicon-oxygen negative electrode has a low first coulombic efficiency, which is due to the reaction of lithium ions with silicon-oxygen material to generate lithium oxide and lithium silicate, which irreversibly consumes lithium ions. Therefore, the silicon-oxygen material generally needs to be pre-lithiated or pre-magnesium.

[0005] The third generation of silicon-oxygen materials, pre-lithium / pre-magnesium silicon-oxygen, a large number of lithium ions are lost in the process of lithium extraction of silicon-oxygen to form lithium oxide and lithium silicate, not only the cost rises, but also the material has a low first efficiency, which cannot meet the requirements of the full battery for the negative electrode material. In order to improve the first efficiency, pre-lithium and pre-magnesium doping technologies are mainly used. However, the pre-lithium and pre-magnesium silicon-oxygen materials still face many problems.

[0006] Therefore, the existing preparation method of the silicon-carbon material has the problems of complex process and high cost, and the material has a low first efficiency, which cannot meet the requirements of the full battery for the negative electrode material. SUMMARY

[0007] Based on the existing preparation method of the silicon-carbon material, the process is complex, the cost is high, and the material has a low first efficiency, which cannot meet the requirements of the full battery for the negative electrode material. The purpose of the present application is to provide a gas-phase deposition silicon-carbon material, a preparation method and application thereof. Phenolic resin and boric acid are obtained by reverse microemulsion method to obtain phenolic resin microspheres. After carbonization and activation treatment of the phenolic resin microspheres, spherical resin precursor porous carbon is obtained. The preparation process is simple, the cost is low, the material has a high first efficiency, the surface of the microspheres is smooth, and the microspheres have high strength. The application has a very broad application prospect in lithium ion battery silicon-carbon negative electrode materials.

[0008] The present application is realized by the following technical solutions:

[0009] In a first aspect, the present application provides a preparation method of porous spherical carbon for gas-phase deposition silicon-carbon, comprising the following steps:

[0010] Dissolve the phenolic resin in the solvent, then add boric acid, heat and stir until the solution is clear, and obtain an aqueous solution;

[0011] Pour the aqueous solution into the oil phase, and add an emulsion stabilizer to obtain a water-in-oil system solution;

[0012] Heat the obtained water-in-oil system solution and continuously stir, then add a solidifying agent and continue to stir to obtain a solid-liquid mixture;

[0013] After removing the oil phase on the surface of the solid-liquid mixture, dry it to obtain phenolic resin microsphere precursors;

[0014] Heat treat the phenolic resin microsphere precursors in an oxidizing atmosphere, and obtain pre-oxidized precursors after cooling;

[0015] After calcining, cooling, washing and drying the pre-oxidized precursors in an inert atmosphere, obtain carbonized precursors;

[0016] After mixing and grinding the carbonized precursors with potassium hydroxide, calcine, cool, wash and dry to obtain spherical resin precursor porous carbon;

[0017] The silane gas is introduced into the spherical resin precursor porous carbon to deposit, so as to obtain a gas phase deposition silicon-carbon material.

[0018] The oil phase includes any one or a combination of multiple of machine oil, heat conducting oil, mineral oil, and vegetable oil; the emulsion stabilizer includes any one or a combination of multiple of Span 20, Span 40, Span 60, and Span 80; the curing agent includes any one or a combination of multiple of methenamine, ammonia water, and formaldehyde, and the adding amount of the curing agent is about 10% of the mass of the phenolic resin; the washing agent used for washing the carbonization precursor and the spherical resin precursor porous carbon includes any one or a combination of multiple of methanol, ethanol, and propanol; and the drying time of the carbonization precursor and the spherical resin precursor is 12-24 hours.

[0019] In the preparation of the aqueous phase solution, the temperature is heated to 40-60℃ after the addition of boric acid; the volume ratio of the mixed solution of ethylene glycol and ethanol to the oil phase is 1:(5-8); the volume ratio of the emulsion stabilizer to the oil phase is 1:(5-6); and the solution of the water-in-oil system is heated to 100-150℃ before the addition of the curing agent, wherein the stirring rate is 1000-2000 r / min.

[0020] Further, the solvent is a mixed solution of ethylene glycol and ethanol, and the volume ratio of the ethylene glycol to the ethanol is 1:(3-4).

[0021] Further, the adding amount of the boric acid is 20-40% of the mass of the phenolic resin.

[0022] Further, in the preparation of the aqueous phase solution, the temperature is heated to 40-60℃ after the addition of boric acid.

[0023] Further, the volume ratio of the mixed solution of ethylene glycol and ethanol to the oil phase is 1:(5-8).

[0024] Further, the volume ratio of the emulsion stabilizer to the oil phase is 1:(5-6).

[0025] Further, the solution of the water-in-oil system is heated to 100-150℃ before the addition of the curing agent, wherein the stirring rate is 1000-2000 r / min.

[0026] Further, in the preparation of the pre-oxidation precursor, the temperature is first increased to 250-450℃ at a rate of 2-5℃ / min, and the temperature is maintained for 2-5 hours.

[0027] Further, in the preparation of the carbonized precursor, the temperature is raised to 700-1000 DEG C at a rate of 5-10 DEG C / min, and the temperature is kept for 1-5 hours.

[0028] Further, the mass ratio of the carbonized precursor to the potassium hydroxide is 1:(1-2), wherein in the grinding process, the temperature is raised to 500-800 DEG C at a rate of 3-10 DEG C / min, and the temperature is kept for 1-5 hours.

[0029] Further, the deposition temperature of the spherical resin precursor porous carbon is 300-500 DEG C, wherein the flow rate of the silane gas is 80-120 sccm, and the deposition time is 1-3 hours.

[0030] In the second aspect, the application provides a porous spherical carbon for vapor deposition of silicon carbon, which is prepared by the above method.

[0031] In the third aspect, the application provides a silicon carbon negative electrode material, which comprises the above porous spherical carbon for vapor deposition of silicon carbon.

[0032] In the fourth aspect, the application provides a lithium ion battery, which comprises the above silicon carbon negative electrode material.

[0033] Compared with the prior art, the application has the following advantages and beneficial effects:

[0034] (1) In the application, the phenolic resin and boric acid are used to obtain phenolic resin microspheres by the reverse microemulsion method, and then the phenolic resin microspheres are carbonized and activated to obtain spherical resin precursor porous carbon, so that the preparation process is simple, the cost is low, the first effect of the material is high, the surface of the microspheres is smooth, and the microspheres have high strength, and the application has a very broad application prospect in lithium ion battery silicon carbon negative electrode materials.

[0035] (2) In the application, the spherical precursor material has uniform spherical morphology and smooth surface, and the introduction of boron atoms in the polymerization stage of the phenolic resin improves the mechanical properties of the microspheres, and the precursor material with good mechanical properties can effectively alleviate the volume expansion of the silicon carbon negative electrode in the cycle process. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the example embodiments of the application, the following will briefly introduce the drawings needed to be used in the examples. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be considered as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings:

[0037] Figure 1Microstructure of the gas-phase deposited silicon-carbon material prepared in Example 1 of the present application;

[0038] Figure 2 Microstructure of the gas-phase deposited silicon-carbon material prepared in Example 1 of the present application;

[0039] Figure 3 Nitrogen adsorption-desorption curve of the gas-phase deposited silicon-carbon material prepared in Example 1 of the present application;

[0040] Figure 4 Nanoindentation test of the phenolic resin microsphere precursor before activation of Example 1 and Comparative Example 1 of the present application;

[0041] Figure 5 Microstructure of the silicon-carbon negative electrode material prepared in Example 1 of the present application;

[0042] Figure 6 First charge-discharge curve of the silicon-carbon negative electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0043] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with embodiments. The illustrative embodiments of the present application and their descriptions are only used to explain the present application and not as a limitation of the present application.

[0044] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, it will be apparent to one ordinarily skilled in the art that the present application can be practiced without these specific details. In other instances, well-known materials or methods have not been described in detail in order to avoid obscuring the present application.

[0045] Throughout the specification, reference to "one embodiment", "an embodiment", "one example" or "an example" means that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present application. The appearances of the phrases "in one embodiment", "an embodiment", "in one example" or "an example" in various places in the specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics can be combined in any suitable manner in one or more embodiments or examples. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. In addition, those skilled in the art will be able to make the different embodiments or examples described in the specification, as well as the features of the different embodiments or examples, in combination and combination, without mutual contradiction.

[0046] The ranges disclosed herein are defined by their lower and upper limits. Ranges that are given by selecting a lower limit and an upper limit define the range between the particular lower and upper limits. Ranges defined by these methods can be inclusive or exclusive of the end values, and are combinable to form additional ranges. For example, if a range of 60-120 and a range of 80-110 are listed, it is understood that a range of 60-110 and a range of 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 are listed, and a maximum range value of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise indicated, a numerical range "a-b" is intended to mean any and all subcombinations of the values between a and b, in which a and b are both real numbers. For example, the numerical range "0-5" is intended to mean that all real numbers between 0 and 5, inclusive of 0 and 5, have been listed herein. In addition, when a parameter is stated to be an integer > 2, it is equivalent to state that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise specified, all steps of the methods of the present application can be performed in any order, preferably in the order specified. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in the order specified, or the method can comprise steps (b) and (a) in the order specified. For example, the method comprising step (c) means that step (c) can be added to the method in any order. For example, the method can comprise steps (a), (b), and (c), or the method can comprise steps (a), (c), and (b), or the method can comprise steps (c), (a), and (b), etc.

[0048] Example 1

[0049] The present embodiment provides a method for preparing a silicon-carbon material by vapor deposition. The specific steps are as follows:

[0050] S1. 50 g of phenolic resin was dissolved in a mixed solution of 125 ml of ethylene glycol and 375 ml of ethanol, 10 g of boric acid was added, and the solution was stirred at 1000 r / min at 40°C until it became clear, obtaining a clear light yellow solution.

[0051] S2. The clear light yellow solution was poured into 2500 ml of heat-conducting oil, and 500 ml of Span 20 was added as an emulsion stabilizer, obtaining a water-in-oil system solution.

[0052] S3, the water-in-oil system solution is heated to 120°C with stirring at a speed of 1000 r / min, and 5 g of curing agent hexamethylenetetramine is added after the temperature is raised to 120°C.

[0053] S4, keep stirring at 120°C for 30 min to obtain a solid-liquid mixture, filter and wash the solid-liquid mixture with anhydrous ethanol three times, and then place it in a vacuum drying oven and dry at 120°C for 12 h to obtain a phenolic resin microsphere precursor.

[0054] S5, the phenolic resin microsphere precursor is placed in a tube furnace, pre-oxidized at 350°C for 3 h under an air atmosphere at a heating rate of 2°C / min, and naturally cooled to room temperature to obtain a pre-oxidized precursor.

[0055] S6, the pre-oxidized precursor is placed in a tube furnace, carbonized at 850°C for 3 h under an inert gas atmosphere at a heating rate of 5°C / min, and naturally cooled to room temperature to obtain a carbonized precursor.

[0056] S7, the carbonized precursor and KOH are ground at a mass ratio of 1:2, placed in a tube furnace, and heated to 800°C for 2 h under an inert gas atmosphere at a heating rate of 5°C / min, and then naturally cooled to room temperature, washed and dried to obtain a spherical resin precursor porous carbon.

[0057] S8, the obtained spherical resin precursor porous carbon is deposited with silane argon mixed gas at 400°C for 1.5 h to obtain a gas phase deposition silicon carbon (the flow rate of silane gas is 100 sccm).

[0058] Example 2

[0059] The embodiment provides a preparation method of a gas phase deposition silicon carbon material, and the difference between the embodiment and example 1 is that the volume ratio of ethylene glycol to the ethanol in the embodiment is about 1:3.5. The specific steps are as follows:

[0060] S1, 50 g of phenolic resin is dissolved in a mixed solution of 107 ml of ethylene glycol and 375 ml of ethanol, 10 g of boric acid is added, and the solution is stirred at a speed of 1000 r / min at 40°C until the solution is clear to obtain a clear light yellow solution.

[0061] S2, pour the clear light yellow solution into 2500 ml of heat-conducting oil, and add 500 ml of Span 20 as an emulsion stabilizer to obtain a water-in-oil system solution.

[0062] S3, the water-in-oil system solution is heated to 120°C with stirring at a speed of 1000 r / min, and 5 g of curing agent hexamethylenetetramine is added after the temperature is raised to 120°C.

[0063] S4, keep stirring at 120℃ for 30min, get solid-liquid mixture, filter and wash the solid-liquid mixture with anhydrous ethanol for three times, put into vacuum drying oven, dry at 120℃ for 12h, get phenolic resin microsphere precursor.

[0064] S5, put the phenolic resin microsphere precursor into tube furnace, pre-oxidize at 350℃ for 3h under air atmosphere with the heating rate of 2℃ / min, naturally cool to room temperature, get pre-oxidized precursor.

[0065] S6, put the pre-oxidized precursor into tube furnace, carbonize at 850℃ for 3h under inert gas atmosphere with the heating rate of 5℃ / min, naturally cool to room temperature, get carbonized precursor.

[0066] S7, grind the carbonized precursor and KOH with the mass ratio of 1:2, put into tube furnace, heat to 800℃ under inert gas atmosphere with the heating rate of 5℃ / min, keep for 2h, naturally cool to room temperature, wash and dry, get spherical resin precursor porous carbon.

[0067] S8, get the spherical resin precursor porous carbon, at 400℃, pass in silane argon mixed gas for 1.5h, get gas deposition silicon carbon (the flow rate of silane gas is 100sccm).

[0068] Example 3

[0069] The embodiment provides a preparation method of gas deposition silicon carbon material, and the difference between the embodiment and example 1 is that the volume ratio of ethylene glycol to the ethanol is about 1:4 in the embodiment. The specific steps are as follows:

[0070] S1, dissolve 50g of phenolic resin in a mixed solution of 94ml of ethylene glycol and 375ml of ethanol, add 10g of boric acid, and stir at 1000r / min at 40℃ until the solution is clear, to get a clear light yellow solution.

[0071] S2, pour the clear light yellow solution into 2500ml of heat conducting oil, and add 500ml of Span20 as emulsion stabilizer, to get a water-in-oil system solution.

[0072] S3, heat the water-in-oil system solution to 120℃ under stirring, and the stirring speed is 1000r / min, after the temperature is heated to 120℃, add 5g of curing agent hexamethylene tetramine.

[0073] S4, keep stirring at 120℃ for 30min, get solid-liquid mixture, filter and wash the solid-liquid mixture with anhydrous ethanol for three times, put into vacuum drying oven, dry at 120℃ for 12h, get phenolic resin microsphere precursor.

[0074] S5, the phenolic resin microsphere precursor was placed in a tube furnace, and was pre-oxidized at 350°C for 3h under an air atmosphere at a temperature increasing rate of 2°C / min, and was naturally cooled to room temperature to obtain a pre-oxidized precursor.

[0075] S6, the pre-oxidized precursor was placed in a tube furnace, and was carbonized at 850°C for 3h under an inert gas atmosphere at a temperature increasing rate of 5°C / min, and was naturally cooled to room temperature to obtain a carbonized precursor.

[0076] S7, the carbonized precursor and KOH were ground at a mass ratio of 1:2, and were placed in a tube furnace, and were heated to 800°C for 2h under an inert gas atmosphere at a temperature increasing rate of 5°C / min, and were naturally cooled to room temperature, and were washed and dried to obtain a spherical resin precursor porous carbon.

[0077] S8, the obtained spherical resin precursor porous carbon was subjected to deposition of silane argon mixed gas at 400°C for 1.5h to obtain a gas phase deposition silicon carbon (the flow rate of the silane gas was 100sccm).

[0078] Example 4

[0079] The embodiment provides a preparation method of a gas phase deposition silicon carbon material, and the difference between the embodiment and example 1 is that the amount of boric acid added in the embodiment is 30% of the mass of the phenolic resin. The specific steps are as follows:

[0080] S1, 50g of phenolic resin was dissolved in a mixed solution of 125ml of ethylene glycol and 375ml of ethanol, 15g of boric acid was added, and the solution was stirred at 1000r / min at 40°C until the solution was clear to obtain a clear light yellow solution.

[0081] S2, the clear light yellow solution was poured into 2500ml of heat conducting oil, and 500ml of Span20 was added as an emulsion stabilizer to obtain a water-in-oil system solution.

[0082] S3, the water-in-oil system solution was heated and stirred to 120°C, and 5g of curing agent hexamethylene tetramine was added after the temperature was increased to 120°C.

[0083] S4, the stirring was maintained at 120°C for 30min to obtain a solid-liquid mixture, the solid-liquid mixture was filtered and washed with anhydrous ethanol three times, and was placed in a vacuum drying oven and dried at 120°C for 12h to obtain a phenolic resin microsphere precursor.

[0084] S5, the phenolic resin microsphere precursor was placed in a tube furnace, and was pre-oxidized at 350°C for 3h under an air atmosphere at a temperature increasing rate of 2°C / min, and was naturally cooled to room temperature to obtain a pre-oxidized precursor.

[0085] S6, the pre-oxidized precursor is placed into a tube furnace, carbonized at 850°C for 3h under inert gas atmosphere at a heating rate of 5°C / min, and naturally cooled to room temperature to obtain a carbonized precursor.

[0086] S7, the carbonized precursor and KOH are ground at a mass ratio of 1:2, placed into a tube furnace, and heated to 800°C for 2h under inert gas atmosphere at a heating rate of 5°C / min, and naturally cooled to room temperature, washed and dried to obtain a spherical resin precursor porous carbon.

[0087] S8, the obtained spherical resin precursor porous carbon is subjected to deposition of silane argon mixed gas at 400°C for 1.5h to obtain a gas phase deposition silicon carbon (the flow rate of silane gas is 100sccm).

[0088] Example 5

[0089] The embodiment provides a preparation method of a gas phase deposition silicon carbon material, and the difference between the embodiment and example 1 is that the amount of boric acid added in the embodiment is 40% of the mass of the phenolic resin. The specific steps are as follows:

[0090] S1, 50g of phenolic resin is dissolved in a mixed solution of 125ml of ethylene glycol and 375ml of ethanol, 20g of boric acid is added, and the solution is stirred at 40°C at a speed of 1000r / min until the solution is clear to obtain a clear light yellow solution.

[0091] S2, the clear light yellow solution is poured into 2500ml of heat conducting oil, and 500ml of Span20 is added as an emulsion stabilizer to obtain a water-in-oil system solution.

[0092] S3, the water-in-oil system solution is heated and stirred to 120°C, and the stirring speed is 1000r / min. After the temperature is raised to 120°C, 5g of curing agent hexamethylene tetramine is added.

[0093] S4, the stirring is maintained at 120°C for 30min to obtain a solid-liquid mixture, the solid-liquid mixture is filtered and washed with anhydrous ethanol for three times, and is placed into a vacuum drying oven and dried at 120°C for 12h to obtain a phenolic resin microsphere precursor.

[0094] S5, the phenolic resin microsphere precursor is placed into a tube furnace, pre-oxidized at 350°C for 3h under air atmosphere at a heating rate of 2°C / min, and naturally cooled to room temperature to obtain a pre-oxidized precursor.

[0095] S6, the pre-oxidized precursor is placed into a tube furnace, carbonized at 850°C for 3h under inert gas atmosphere at a heating rate of 5°C / min, and naturally cooled to room temperature to obtain a carbonized precursor.

[0096] S7, grind the carbonized precursor and KOH at a mass ratio of 1:2, put into a tube furnace, heat to 800℃ at a heating rate of 5℃ / min under inert gas atmosphere, keep for 2h, naturally cool to room temperature, wash and dry to obtain spherical resin precursor porous carbon.

[0097] S8, pass silane argon mixed gas into the obtained spherical resin precursor porous carbon at 400℃ for 1.5h to obtain gas phase deposition silicon carbon (the flow rate of silane gas is 100sccm).

[0098] Example 6

[0099] The embodiment provides a preparation method of gas phase deposition silicon carbon material, and the difference between the embodiment and example 1 is that, in the preparation of the pre-oxidized precursor, the temperature is first increased to 250℃ at a heating rate of 3℃ / min, and the temperature is kept for 2h. The specific steps are as follows:

[0100] S1, dissolve 50g of phenolic resin in a mixed solution of 125ml of ethylene glycol and 375ml of ethanol, add 10g of boric acid, stir at 1000r / min at 40℃ until the solution is clear, and obtain a clear light yellow solution.

[0101] S2, pour the clear light yellow solution into 2500ml of heat conducting oil, and add 500ml of Span20 as emulsion stabilizer to obtain a water-in-oil system solution.

[0102] S3, heat and stir the water-in-oil system solution to 120℃, and the stirring speed is 1000r / min. After the temperature is increased to 120℃, add 5g of curing agent hexamethylene tetramine.

[0103] S4, keep stirring at 120℃ for 30min to obtain a solid-liquid mixture, filter and wash the solid-liquid mixture with anhydrous ethanol for three times, and put into a vacuum drying oven to dry at 120℃ for 12h to obtain phenolic resin microsphere precursor.

[0104] S5, put the phenolic resin microsphere precursor into a tube furnace, pre-oxidize at a heating rate of 3℃ / min to 250℃ under air atmosphere for 2h, and naturally cool to room temperature to obtain a pre-oxidized precursor.

[0105] S6, put the pre-oxidized precursor into a tube furnace, carbonize at a heating rate of 5℃ / min to 850℃ under inert gas atmosphere for 3h, and naturally cool to room temperature to obtain a carbonized precursor.

[0106] S7, the carbonized precursor and KOH were ground in a mass ratio of 1:2, put into a tube furnace, and heated to 800°C at a heating rate of 5°C / min under an inert gas atmosphere for 2h, and then naturally cooled to room temperature. After washing and drying, spherical resin precursor porous carbon was obtained.

[0107] S8, the obtained spherical resin precursor porous carbon was deposited with silane argon mixed gas at 400°C for 1.5h to obtain gas phase deposition silicon carbon (the flow rate of silane gas was 100sccm).

[0108] Example 7

[0109] The embodiment provides a preparation method of gas phase deposition silicon carbon material, and the difference between the embodiment and example 1 is that, in the preparation of the pre-oxidized precursor, the temperature is first increased to 450°C at a heating rate of 5°C / min, and then kept for 5h. The specific steps are as follows:

[0110] S1, 50g of phenolic resin was dissolved in a mixed solution of 125ml of ethylene glycol and 375ml of ethanol, 10g of boric acid was added, and the solution was stirred at 40°C at a speed of 1000r / min until the solution was clear, to obtain a clear light yellow solution.

[0111] S2, pour the clear light yellow solution into 2500ml of heat conducting oil, and add 500ml of Span20 as emulsion stabilizer to obtain a water-in-oil system solution.

[0112] S3, the water-in-oil system solution is heated and stirred to 120°C, and the stirring speed is 1000r / min. After the temperature is increased to 120°C, 5g of curing agent hexamethylene tetramine is added.

[0113] S4, keep stirring at 120°C for 30min to obtain a solid-liquid mixture, filter and wash the solid-liquid mixture with anhydrous ethanol for three times, and then put it into a vacuum drying oven and dry at 120°C for 12h to obtain phenolic resin microsphere precursor.

[0114] S5, the phenolic resin microsphere precursor is put into a tube furnace, pre-oxidized at 450°C for 5h under an air atmosphere at a heating rate of 5°C / min, and then naturally cooled to room temperature to obtain a pre-oxidized precursor.

[0115] S6, the pre-oxidized precursor is put into a tube furnace, carbonized at 850°C for 3h under an inert gas atmosphere at a heating rate of 5°C / min, and then naturally cooled to room temperature to obtain a carbonized precursor.

[0116] S7, the carbonized precursor and KOH were ground at a mass ratio of 1:2, put into a tube furnace, and heated to 800°C at a heating rate of 5°C / min under an inert gas atmosphere for 2h, and then naturally cooled to room temperature. After washing and drying, spherical resin precursor porous carbon was obtained.

[0117] S8, the obtained spherical resin precursor porous carbon was deposited with silane argon mixed gas at 400°C for 1.5h to obtain gas phase deposition silicon carbon (the flow rate of silane gas was 100sccm).

[0118] Example 8

[0119] The embodiment provides a preparation method of gas phase deposition silicon carbon material, and the difference between the embodiment and example 1 is that the carbonized precursor is prepared by first heating at a heating rate of 7°C / min to 700°C and holding for 1h. The specific steps are as follows:

[0120] S1, 50g of phenolic resin was dissolved in a mixed solution of 125ml of ethylene glycol and 375ml of ethanol, 10g of boric acid was added, and the solution was stirred at 1000r / min at 40°C until the solution was clear, to obtain a clear light yellow solution.

[0121] S2, pour the clear light yellow solution into 2500ml of heat conducting oil, and add 500ml of Span20 as emulsion stabilizer to obtain a water-in-oil system solution.

[0122] S3, heat the water-in-oil system solution to 120°C with stirring at a speed of 1000r / min, and then add 5g of curing agent hexamethylene tetramine after the temperature is raised to 120°C.

[0123] S4, keep stirring at 120°C for 30min to obtain a solid-liquid mixture, filter and wash the solid-liquid mixture with anhydrous ethanol three times, and then put it into a vacuum drying oven and dry at 120°C for 12h to obtain phenolic resin microsphere precursor.

[0124] S5, put the phenolic resin microsphere precursor into a tube furnace, pre-oxidize the precursor at a heating rate of 2°C / min to 350°C under air atmosphere for 3h, and then naturally cool to room temperature to obtain a pre-oxidized precursor.

[0125] S6, put the pre-oxidized precursor into a tube furnace, carbonize the precursor at a heating rate of 7°C / min to 700°C under an inert gas atmosphere for 1h, and then naturally cool to room temperature to obtain a carbonized precursor.

[0126] S7, the carbonized precursor and KOH were ground at a mass ratio of 1:2, put into a tube furnace, and heated to 800°C at a heating rate of 5°C / min under an inert gas atmosphere for 2h, and then naturally cooled to room temperature. After washing and drying, spherical resin precursor porous carbon was obtained.

[0127] S8, the obtained spherical resin precursor porous carbon was deposited with silane argon mixed gas at 400°C for 1.5h to obtain gas phase deposition silicon carbon (the flow rate of silane gas was 100sccm).

[0128] Example 9

[0129] The embodiment provides a preparation method of gas phase deposition silicon carbon material, and the difference between the embodiment and example 1 is that the carbonized precursor is prepared by first heating at a heating rate of 10°C / min to 1000°C and maintaining for 5h. The specific steps are as follows:

[0130] S1, 50g of phenolic resin was dissolved in a mixed solution of 125ml of ethylene glycol and 375ml of ethanol, 10g of boric acid was added, and the solution was stirred at 1000r / min at 40°C until the solution was clear. A clear light yellow solution was obtained.

[0131] S2, pour the clear light yellow solution into 2500ml of heat conducting oil, and add 500ml of Span20 as emulsion stabilizer to obtain a water-in-oil system solution.

[0132] S3, heat the water-in-oil system solution to 120°C with stirring at a speed of 1000r / min. After the temperature is raised to 120°C, add 5g of curing agent hexamethylene tetramine.

[0133] S4, keep stirring at 120°C for 30min to obtain a solid-liquid mixture. The solid-liquid mixture is filtered and washed with anhydrous ethanol three times, and then put into a vacuum drying oven and dried at 120°C for 12h to obtain phenolic resin microsphere precursor.

[0134] S5, the phenolic resin microsphere precursor was put into a tube furnace and pre-oxidized at a heating rate of 2°C / min to 350°C under air atmosphere for 3h, and then naturally cooled to room temperature to obtain a pre-oxidized precursor.

[0135] S6, the pre-oxidized precursor was put into a tube furnace and carbonized at a heating rate of 10°C / min to 1000°C under an inert gas atmosphere for 5h, and then naturally cooled to room temperature to obtain a carbonized precursor.

[0136] S7, the carbonized precursor and KOH were ground in a mass ratio of 1:2, placed in a tube furnace, and heated to 800°C at a heating rate of 5°C / min under an inert gas atmosphere for 2h, naturally cooled to room temperature, washed and dried to obtain spherical resin precursor porous carbon.

[0137] S8, the obtained spherical resin precursor porous carbon was deposited with silane argon mixed gas at 400°C for 1.5h to obtain gas phase deposition silicon carbon (the flow rate of silane gas was 100sccm).

[0138] Example 10

[0139] The embodiment provides a preparation method of gas phase deposition silicon carbon material, and the difference between the embodiment and example 1 is that the mass ratio of carbonized precursor to potassium hydroxide in the embodiment is 1:1, and the specific steps are as follows:

[0140] S1, 50g of phenolic resin was dissolved in a mixed solution of 125ml of ethylene glycol and 375ml of ethanol, 10g of boric acid was added, and the solution was stirred at 1000r / min at 40°C until the solution was clear, to obtain a clear light yellow solution.

[0141] S2, pour the clear light yellow solution into 2500ml of heat conducting oil, and add 500ml of Span20 as emulsion stabilizer to obtain a water-in-oil system solution.

[0142] S3, heat the water-in-oil system solution to 120°C with stirring at a speed of 1000r / min, and add 5g of curing agent hexamethylene tetramine after the temperature is raised to 120°C.

[0143] S4, keep stirring at 120°C for 30min to obtain a solid-liquid mixture, filter and wash the solid-liquid mixture with anhydrous ethanol three times, and place it in a vacuum drying oven for drying at 120°C for 12h to obtain phenolic resin microsphere precursor.

[0144] S5, place the phenolic resin microsphere precursor into a tube furnace, pre-oxidize the precursor at a heating rate of 2°C / min to 350°C under air atmosphere for 3h, and naturally cool to room temperature to obtain a pre-oxidized precursor.

[0145] S6, place the pre-oxidized precursor into a tube furnace, carbonize the precursor at a heating rate of 5°C / min to 850°C under an inert gas atmosphere for 3h, and naturally cool to room temperature to obtain a carbonized precursor.

[0146] S7, the carbonized precursor and KOH were ground in a mass ratio of 1:2, placed in a tube furnace, and heated to 800°C at a heating rate of 5°C / min under an inert gas atmosphere for 2h, naturally cooled to room temperature, washed and dried to obtain spherical resin precursor porous carbon.

[0147] S8, the obtained spherical resin precursor porous carbon is subjected to silane argon mixed gas deposition at 400°C for 1.5h to obtain gas phase deposition silicon carbon (the flow rate of silane gas is 100sccm).

[0148] Example 11

[0149] The embodiment provides a preparation method of a gas phase deposition silicon carbon material, and the difference between the embodiment and example 1 is that the mass ratio of the carbonization precursor to potassium hydroxide in the embodiment is 1:1.5, and the specific steps are as follows:

[0150] S1, 50g of phenolic resin is dissolved in a mixed solution of 125ml of ethylene glycol and 375ml of ethanol, 10g of boric acid is added, and the solution is stirred at 1000r / min at 40°C until the solution is clear, to obtain a clear light yellow solution.

[0151] S2, pour the clear light yellow solution into 2500ml of heat conducting oil, and add 500ml of Span20 as an emulsion stabilizer to obtain a water-in-oil system solution.

[0152] S3, the water-in-oil system solution is heated and stirred to 120°C, and the stirring speed is 1000r / min. After the temperature is raised to 120°C, 5g of curing agent hexamethylenetetramine is added.

[0153] S4, keep stirring at 120°C for 30min to obtain a solid-liquid mixture, filter and wash the solid-liquid mixture with anhydrous ethanol three times, and place it in a vacuum drying oven for drying at 120°C for 12h to obtain a phenolic resin microsphere precursor.

[0154] S5, the phenolic resin microsphere precursor is placed in a tube furnace, pre-oxidized at 350°C for 3h under an air atmosphere at a temperature rising rate of 2°C / min, and naturally cooled to room temperature to obtain a pre-oxidized precursor.

[0155] S6, the pre-oxidized precursor is placed in a tube furnace, carbonized at 850°C for 3h under an inert gas atmosphere at a temperature rising rate of 5°C / min, and naturally cooled to room temperature to obtain a carbonized precursor.

[0156] S7, the carbonized precursor and KOH are ground at a mass ratio of 1:1.5, placed in a tube furnace, and heated to 800°C under an inert gas atmosphere at a temperature rising rate of 5°C / min for 2h, and naturally cooled to room temperature, washed and dried to obtain a spherical resin precursor porous carbon.

[0157] S8, the obtained spherical resin precursor porous carbon is subjected to silane argon mixed gas deposition at 400°C for 1.5h to obtain gas phase deposition silicon carbon (the flow rate of silane gas is 100sccm).

[0158] Example 12

[0159] The embodiment provides a preparation method of a gas-phase deposition silicon-carbon material, and the difference between the embodiment and example 1 is that, in the embodiment, the carbonized precursor is ground with potassium hydroxide at a temperature rising rate of 3 ℃ / min to 500 ℃, and kept for 1 h. The specific steps are as follows:

[0160] S1, 50 g of phenolic resin is dissolved in a mixed solution of 125 ml of ethylene glycol and 375 ml of ethanol, 10 g of boric acid is added, and the solution is stirred at a speed of 1000 r / min at 40 ℃ until the solution is clear, to obtain a clear light yellow solution.

[0161] S2, pour the clear light yellow solution into 2500 ml of heat-conducting oil, and add 500 ml of Span 20 as an emulsion stabilizer to obtain a water-in-oil system solution.

[0162] S3, heat the water-in-oil system solution to 120 ℃ under stirring at a speed of 1000 r / min, and add 5 g of curing agent hexamethylenetetramine after the temperature rises to 120 ℃.

[0163] S4, keep stirring at 120 ℃ for 30 min to obtain a solid-liquid mixture, filter and wash the solid-liquid mixture with anhydrous ethanol three times, and place it in a vacuum drying oven to dry at 120 ℃ for 12 h to obtain a phenolic resin microsphere precursor.

[0164] S5, place the phenolic resin microsphere precursor into a tube furnace, pre-oxidize it at 350 ℃ for 3 h under an air atmosphere at a temperature rising rate of 2 ℃ / min, and naturally cool it to room temperature to obtain a pre-oxidized precursor.

[0165] S6, place the pre-oxidized precursor into a tube furnace, carbonize it at 850 ℃ for 3 h under an inert gas atmosphere at a temperature rising rate of 5 ℃ / min, and naturally cool it to room temperature to obtain a carbonized precursor.

[0166] S7, grind the carbonized precursor and KOH at a mass ratio of 1:2, place them into a tube furnace, and keep them at 500 ℃ for 1 h under an inert gas atmosphere at a temperature rising rate of 3 ℃ / min, and naturally cool them to room temperature, wash and dry them to obtain a spherical resin precursor porous carbon.

[0167] S8, deposit the obtained spherical resin precursor porous carbon at 400 ℃ by passing in a silane-argon mixed gas for 1.5 h to obtain a gas-phase deposition silicon-carbon (the flow rate of the silane gas is 100 sccm).

[0168] Example 13

[0169] The embodiment provides a preparation method of a gas-phase deposited silicon-carbon material, and different from the embodiment 1, in the embodiment, the carbonized precursor and potassium hydroxide are ground at a temperature increasing rate of 10 ℃ / min to 600 ℃, and are kept for 5 h. The specific steps are as follows:

[0170] S1, 50 g of phenolic resin is dissolved in a mixed solution of 125 ml of ethylene glycol and 375 ml of ethanol, 10 g of boric acid is added, and the solution is stirred at a speed of 1000 r / min at 40 ℃ until the solution is clear, to obtain a clear light yellow solution.

[0171] S2, the clear light yellow solution is poured into 2500 ml of heat-conducting oil, and 500 ml of Span 20 is added as an emulsion stabilizer to obtain a water-in-oil system solution.

[0172] S3, the water-in-oil system solution is heated and stirred to 120 ℃, and the stirring speed is 1000 r / min. After the temperature is increased to 120 ℃, 5 g of curing agent hexamethylenetetramine is added.

[0173] S4, the stirring is kept at 120 ℃ for 30 min to obtain a solid-liquid mixture, the solid-liquid mixture is filtered and washed with anhydrous ethanol for three times, and is placed in a vacuum drying oven and dried at 120 ℃ for 12 h to obtain a phenolic resin microsphere precursor.

[0174] S5, the phenolic resin microsphere precursor is placed in a tube furnace, is pre-oxidized at 350 ℃ for 3 h under an air atmosphere at a temperature increasing rate of 2 ℃ / min, is naturally cooled to room temperature, and a pre-oxidized precursor is obtained.

[0175] S6, the pre-oxidized precursor is placed in a tube furnace, is carbonized at 850 ℃ for 3 h under an inert gas atmosphere at a temperature increasing rate of 5 ℃ / min, is naturally cooled to room temperature, and a carbonized precursor is obtained.

[0176] S7, the carbonized precursor and KOH are ground sufficiently at a mass ratio of 1:2, are placed in a tube furnace, are kept at 600 ℃ for 5 h under an inert gas atmosphere at a temperature increasing rate of 10 ℃ / min, are naturally cooled to room temperature, are washed and dried, and a spherical resin precursor porous carbon is obtained.

[0177] S8, the obtained spherical resin precursor porous carbon is subjected to deposition at 400 ℃ for 1.5 h by passing in a silane-argon mixed gas to obtain a gas-phase deposited silicon-carbon (the flow rate of the silane gas is 100 sccm).

[0178] Embodiment 14

[0179] The embodiment provides a preparation method of a gas-phase deposited silicon-carbon material, and different from the embodiment 1, in the embodiment, the deposition temperature of the spherical resin precursor porous carbon is 300 DEG C, the flow rate of the silane gas is 80 sccm, and the deposition time is 1 h. The specific steps are as follows:

[0180] S1, 50g of phenolic resin is dissolved in a mixed solution of 125ml of ethylene glycol and 375ml of ethanol, 10g of boric acid is added, stirring is carried out at 40 DEG C and at a speed of 1000r / min until the solution is clear, and a clear light yellow solution is obtained.

[0181] S2, the clear light yellow solution is poured into 2500ml of heat-conducting oil, and 500ml of Span 20 is added as an emulsion stabilizer to obtain a water-in-oil system solution.

[0182] S3, the water-in-oil system solution is heated and stirred to 120 DEG C, wherein the stirring speed is 1000r / min, and after the temperature is raised to 120 DEG C, 5g of curing agent hexamethylenetetramine is added.

[0183] S4, the stirring is maintained at 120 DEG C for 30min to obtain a solid-liquid mixture, the solid-liquid mixture is filtered and washed with anhydrous ethanol for three times, and is placed in a vacuum drying oven and dried at 120 DEG C for 12h to obtain phenolic resin microsphere precursor.

[0184] S5, the phenolic resin microsphere precursor is placed in a tube furnace, pre-oxidized at 350 DEG C for 3h under an air atmosphere at a temperature rising rate of 2 DEG C / min, and naturally cooled to room temperature to obtain a pre-oxidized precursor.

[0185] S6, the pre-oxidized precursor is placed in a tube furnace, carbonized at 850 DEG C for 3h under an inert gas atmosphere at a temperature rising rate of 5 DEG C / min, and naturally cooled to room temperature to obtain a carbonized precursor.

[0186] S7, the carbonized precursor and KOH are ground sufficiently at a mass ratio of 1:2, placed in a tube furnace, and heated to 800 DEG C under an inert gas atmosphere at a temperature rising rate of 5 DEG C / min for 2h, and naturally cooled to room temperature, washed and dried to obtain a spherical resin precursor porous carbon.

[0187] S8, the obtained spherical resin precursor porous carbon is deposited for 1h at 300 DEG C by passing in a silane argon mixed gas to obtain a gas-phase deposited silicon-carbon (the flow rate of the silane gas is 80sccm).

[0188] Embodiment 15

[0189] The embodiment provides a preparation method of a gas-phase deposited silicon-carbon material, and different from the embodiment 1, in the embodiment, the deposition temperature of the spherical resin precursor porous carbon is 500 DEG C, the flow rate of the silane gas input is 120 sccm, and the deposition time is 3 h. The specific steps are as follows:

[0190] S1, 50g of phenolic resin is dissolved in a mixed solution of 125ml of ethylene glycol and 375ml of ethanol, 10g of boric acid is added, and the solution is stirred at 40 DEG C at a speed of 1000r / min until the solution is clear, to obtain a clear light yellow solution.

[0191] S2, the clear light yellow solution is poured into 2500ml of heat-conducting oil, and 500ml of Span 20 is added as an emulsion stabilizer to obtain a water-in-oil system solution.

[0192] S3, the water-in-oil system solution is heated and stirred to 120 DEG C, wherein the stirring speed is 1000r / min, and 5g of curing agent hexamethylenetetramine is added after the temperature is raised to 120 DEG C.

[0193] S4, the stirring is maintained at 120 DEG C for 30min to obtain a solid-liquid mixture, the solid-liquid mixture is filtered and washed with anhydrous ethanol for three times, and is placed in a vacuum drying oven and dried at 120 DEG C for 12h to obtain a phenolic resin microsphere precursor.

[0194] S5, the phenolic resin microsphere precursor is placed in a tube furnace, pre-oxidized at 350 DEG C for 3h under an air atmosphere at a temperature rising rate of 2 DEG C / min, and naturally cooled to room temperature to obtain a pre-oxidized precursor.

[0195] S6, the pre-oxidized precursor is placed in a tube furnace, carbonized at 850 DEG C for 3h under an inert gas atmosphere at a temperature rising rate of 5 DEG C / min, and naturally cooled to room temperature to obtain a carbonized precursor.

[0196] S7, the carbonized precursor and KOH are ground sufficiently at a mass ratio of 1:2, placed in a tube furnace, and heated to 800 DEG C under an inert gas atmosphere at a temperature rising rate of 5 DEG C / min for 2h, and naturally cooled to room temperature, washed and dried to obtain a spherical resin precursor porous carbon.

[0197] S8, the obtained spherical resin precursor porous carbon is deposited at 500 DEG C by inputting a silane argon mixed gas for 3h to obtain a gas-phase deposited silicon-carbon (the flow rate of the silane gas input is 120 sccm).

[0198] Comparative example 1

[0199] The comparative example provides a preparation method of a gas-phase deposited silicon-carbon material, and different from the embodiment 1, in the comparative example, no boric acid is added, and the specific steps are as follows:

[0200] S1, 50 g of phenolic resin was dissolved in a mixed solution of 125 ml of ethylene glycol and 375 ml of ethanol, stirred at 40°C at a speed of 1000 r / min until the solution was clear, to obtain a clear light yellow solution.

[0201] S2, the clear light yellow solution was poured into 2500 ml of heat conducting oil, and 500 ml of Span 20 was added as emulsion stabilizer to obtain a water-in-oil system solution.

[0202] S3, the water-in-oil system solution was heated and stirred to 120°C, the stirring speed was 1000 r / min, after the temperature was raised to 120°C, 5 g of curing agent hexamethylenetetramine was added.

[0203] S4, keep stirring at 120°C for 30 min, obtain a solid-liquid mixture, filter and wash the solid-liquid mixture with anhydrous ethanol three times, put it into a vacuum drying oven, dry at 120°C for 12 h, to obtain phenolic resin microsphere precursor.

[0204] S5, the phenolic resin microsphere precursor was put into a tube furnace, pre-oxidized at 350°C for 3 h under air atmosphere at a heating rate of 2°C / min, naturally cooled to room temperature, to obtain a pre-oxidized precursor.

[0205] S6, the pre-oxidized precursor was put into a tube furnace, carbonized at 850°C for 3 h under inert gas atmosphere at a heating rate of 5°C / min, naturally cooled to room temperature, to obtain a carbonized precursor.

[0206] S7, the carbonized precursor and KOH were ground in a mass ratio of 1:2, put into a tube furnace, heated to 800°C for 2 h under inert gas atmosphere at a heating rate of 5°C / min, naturally cooled to room temperature, washed and dried, to obtain spherical resin precursor porous carbon.

[0207] S8, the obtained spherical resin precursor porous carbon was deposited with silane argon mixed gas at 400°C for 1.5 h, to obtain gas phase deposition silicon carbon (the flow rate of silane gas was 100 sccm).

[0208] Comparative Example 2

[0209] The comparative example provides a preparation method of gas phase deposition silicon carbon material, which is different from example 1 in that the comparative example does not contain the content of grinding the carbonized precursor and KOH in a mass ratio of 1:2 in step S7, the specific steps are as follows:

[0210] S1. Dissolve 50 g of phenolic resin in a mixed solution of 125 ml of ethylene glycol and 375 ml of ethanol, add 10 g of boric acid, and stir at 40°C and 1000 r / min until the solution becomes clear to obtain a clear light yellow solution.

[0211] S2. Pour the clear light yellow solution into 2500 ml of heat transfer oil and add 500 ml of Span 20 as an emulsion stabilizer to obtain a water-in-oil system solution.

[0212] S3. The water-in-oil system solution was heated to 120° C. with stirring at a stirring speed of 1000 r / min. After the temperature reached 120° C., 5 g of hexamethylenetetramine as a curing agent was added.

[0213] S4. Stirring was continued at 120° C. for 30 min to obtain a solid-liquid mixture. The solid-liquid mixture was filtered and washed three times with anhydrous ethanol, placed in a vacuum drying oven, and dried at 120° C. for 12 h to obtain a phenolic resin microsphere precursor.

[0214] S5. Place the phenolic resin microsphere precursor in a tube furnace, heat it to 350°C at a heating rate of 2°C / min in an air atmosphere, and pre-oxidize it for 3 hours. Then naturally cool it to room temperature to obtain a pre-oxidized precursor.

[0215] S6. Place the pre-oxidized precursor in a tube furnace, heat it to 850° C. at a heating rate of 5° C. / min under an inert gas atmosphere, and carbonize it for 3 h. Then naturally cool it to room temperature to obtain a carbonized precursor.

[0216] S8. The obtained carbonized precursor is introduced into a silane-argon mixed gas at 400° C. for deposition for 1.5 hours to obtain vapor-deposited silicon carbon (the flow rate of the silane gas is 100 sccm).

[0217] Comparative Example 3

[0218] This comparative example provides a method for preparing a vapor-deposited silicon-carbon material. The difference from Example 1 is that this comparative example does not contain the grinding of the carbonized precursor and KOH at a mass ratio of 1:2 in step S7, and no boric acid is added in step S1. The specific steps are:

[0219] S1. Dissolve 50 g of phenolic resin in a mixed solution of 125 ml of ethylene glycol and 375 ml of ethanol. Stir at 40°C and 1000 r / min until the solution becomes clear to obtain a clear light yellow solution.

[0220] S2. Pour the clear light yellow solution into 2500 ml of heat transfer oil and add 500 ml of Span 20 as an emulsion stabilizer to obtain a water-in-oil system solution.

[0221] S3, the water-in-oil system solution is heated to 120℃ with stirring at a speed of 1000 r / min, and 5 g of solidification agent hexamethylenetetramine is added after the temperature is raised to 120℃.

[0222] S4, the stirring is maintained at 120℃ for 30 min to obtain a solid-liquid mixture, the solid-liquid mixture is filtered and washed with anhydrous ethanol three times, and then placed in a vacuum drying oven and dried at 120℃ for 12 h to obtain a phenolic resin microsphere precursor.

[0223] S5, the phenolic resin microsphere precursor is placed in a tube furnace, pre-oxidized at 350℃ for 3 h under an air atmosphere at a heating rate of 2℃ / min, and naturally cooled to room temperature to obtain a pre-oxidized precursor.

[0224] S6, the pre-oxidized precursor is placed in a tube furnace, carbonized at 850℃ for 3 h under an inert gas atmosphere at a heating rate of 5℃ / min, and naturally cooled to room temperature to obtain a carbonized precursor.

[0225] S8, the obtained carbonized precursor is subjected to deposition of silane argon mixed gas at 400℃ for 1.5 h to obtain a gas-phase deposited silicon carbon (the flow rate of silane gas is 100 sccm).

[0226] The gas-phase deposited silicon carbon material prepared by the method of Example 1 is subjected to scanning electron microscope analysis, and the results are shown in Figure 1 , Figure 2 The scanning electron microscope pictures are further enlarged, and it can be seen from Figure 1 and Figure 2 that the gas-phase deposited silicon carbon material prepared by the preparation method of the application is spherical, and the morphology and size distribution are uniform.

[0227] The gas-phase deposited silicon carbon material prepared in Example 1 is subjected to specific surface area and porosity analysis, and the nitrogen adsorption / desorption curve is shown in Figure 3 , the specific surface area is measured to be 1583 m 2 / g, the pore volume is 0.78 cm 3 / g, the average pore size is 1.98 nm, and the micropore volume is 0.61 cm 3 / g.

[0228] The silicon-carbon materials prepared in Examples 1-15 and Comparative Examples 1-3 were tested for assembling half-cells, including testing the specific surface area, pore volume, and pore size of the spherical porous carbon and the charge-discharge performance and first coulombic efficiency of the silicon-carbon negative electrode material prepared accordingly. The negative electrode active material was prepared into a slurry with a ratio of active material:CNTs (containing dispersant):CMC:SBR = 89%:4.5%:1.5%:5%, wherein the CMC was a 1.5% aqueous solution, and then the slurry was coated on a copper foil and vacuum dried for 12 h to prepare a negative electrode sheet. The electrolyte was commercially purchased, the separator was a PP film, and lithium was used as the counter electrode to assemble a half-cell in a glove box. The 0.1C constant current charge-discharge test was carried out at room temperature, and the voltage range was 0.005V-3V. The test results are shown in Table 1.

[0229] Table 1

[0230]

[0231] As can be seen from the data in Table 1, the addition of boric acid in the examples improved the crosslinking degree of the material, and the overall mechanical properties were high. Good mechanical properties effectively alleviated the problem of volume expansion in the silicon-carbon negative electrode. At the same time, the addition of a relatively high amount of KOH resulted in a larger specific surface area and pore volume of the examples. For Examples 10 and 11, the amount of KOH was reduced, resulting in a decrease in the specific surface area and pore volume. Due to these two factors, the deposition of silane was not uniform during silane deposition, so the electrochemical performance was relatively lower than that of other examples. Comparative Example 1 did not add boric acid, so the mechanical properties of the obtained silicon-carbon negative electrode material were reduced, and thus the electrochemical performance was also reduced. Comparative Example 2 added boric acid but not KOH, so the specific surface area of the activated spherical porous carbon was very small, only 2.93m2 / g, and there were no pores, which resulted in the inability of silane to deposit into the material and only deposit on the surface. Therefore, the specific capacity of the prepared silicon-carbon negative electrode material was low. Comparative Example 3 did not add boric acid or KOH, so the capacity was also relatively low. Overall, the capacity of Examples 1-15 was relatively higher than that of Comparative Examples 1, 2, and 3, and the first coulombic efficiency was also relatively higher. The discharge specific capacity of Example 1 was 2308.9mAh / g, the charge specific capacity was 2100mAh / g, and the first coulombic efficiency was 90.9%.

[0232] Nanoindentation tests were performed on the phenolic resin precursors prepared in Example 1 and Comparative Example 1 to study their mechanical properties, and the results are shown in Table 2. Figure 4 Figure 4 ​It can be seen that the displacement of Example 1 is less than that of Comparative Example 1 under the same load, indicating that the mechanical properties of Example 1 are more excellent. The hardness of Example 1 is 4.1 Gpa, and the elastic modulus is 20.3 Gpa. The hardness of Comparative Example 1 is 3.2 Gpa, and the elastic modulus is 15.7 Gpa. The hardness and elastic modulus are increased, which also indicates that the obtained precursor material has good mechanical properties.

[0233] Figure 5 is the SEM image after material chemical vapor deposition, which still maintains a spherical morphology after deposition.

[0234] Figure 6 is the image after the first cycle of the material, the specific discharge capacity is 2308.9 mAh / g, the specific charge capacity is 2100 mAh / g, and the first coulombic efficiency is 90.9%.

[0235] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the specification of the present application.

Claims

1. A method for preparing porous spherical carbon for vapor-deposited silicon carbon, characterized in that: The following steps are involved: The phenolic resin is dissolved in a solvent, and then boric acid is added, and the mixture is heated and stirred until the solution becomes clear to obtain an aqueous solution; Pour the aqueous phase solution into the oil phase and add an emulsion stabilizer to obtain a water-in-oil system solution; The obtained water-in-oil system solution is heated and continuously stirred, and a curing agent is added and continuously stirred to obtain a solid-liquid mixture; removing the oil phase on the surface of the solid-liquid mixture and then drying it to obtain a phenolic resin microsphere precursor; The phenolic resin microsphere precursor is heat-treated in an oxidizing atmosphere and then cooled to obtain a pre-oxidized precursor; The pre-oxidized precursor is calcined under an inert atmosphere, cooled, washed, and dried to obtain a carbonized precursor; The carbonized precursor is mixed with potassium hydroxide, ground, calcined, cooled, washed, and dried to obtain spherical resin precursor porous carbon; Silane gas is introduced into the spherical resin precursor porous carbon for deposition to obtain vapor-deposited silicon-carbon material.

2. The method for preparing porous spherical carbon for vapor-deposited silicon carbon according to claim 1, characterized in that: The solvent is a mixed solution of ethylene glycol and ethanol, and the volume ratio of the ethylene glycol to the ethanol is 1:(3-4).

3. The method for preparing porous spherical carbon for vapor-deposited silicon carbon according to claim 1, characterized in that: The added amount of the boric acid is 20% to 40% of the mass of the phenolic resin.

4. The method for preparing porous spherical carbon for vapor-deposited silicon carbon according to claim 1, characterized in that: When preparing the pre-oxidation precursor, first increase the temperature to 250° C. to 450° C. at a heating rate of 2° C. / min to 5° C. / min and keep the temperature for 2 h to 5 h.

5. The method for preparing porous spherical carbon for vapor-deposited silicon carbon according to claim 1, characterized in that: When preparing the carbonized precursor, first heat the temperature to 700° C. to 1000° C. at a heating rate of 5° C. / min to 10° C. / min and keep the temperature for 1 h to 5 h.

6. The method for preparing porous spherical carbon for vapor-deposited silicon carbon according to claim 1, characterized in that: The mass ratio of the carbonized precursor to the potassium hydroxide is 1:(1-2). During the grinding process, the temperature is increased to 500-800° C. at a heating rate of 3-10° C. / min and kept warm for 1-5 hours.

7. The method for preparing porous spherical carbon for vapor-deposited silicon carbon according to claim 1, characterized in that: The deposition temperature of the spherical resin precursor porous carbon is 300° C. to 500° C., the flow rate of the silane gas is 80 sccm to 120 sccm, and the deposition time is 1 hour to 3 hours.

8. A porous spherical carbon for vapor-deposited silicon carbon, characterized in that: The preparation method is described in any one of claims 1 to 7.

9. A silicon-carbon negative electrode material, characterized in that: The porous spherical carbon for vapor-deposited silicon carbon according to claim 8 is included.

10. A lithium ion battery, characterized in that: Including the silicon-carbon negative electrode material according to claim 9.

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