A negative electrode material capable of regulating silicon dispersion and silicon-carbon interstitial and its preparation method

Abstract

The present invention provides a negative electrode material capable of regulating silicon dispersion and silicon-carbon interstitial and a preparation method thereof, comprising the following steps: Step 1, dispersing nano-silicon in a pore-forming auxiliary agent, adding a certain amount of emulsifier to the pore-forming auxiliary agent, and mixing evenly; Step 2, preparing a resin oligomer solution, mixing phenol or amine substances and aldehyde substances at room temperature to prepare a clear and transparent resin solution; Step 3, adding the resin solution to the pore-forming auxiliary agent solution and rapidly stirring to form an opaque emulsion; waiting for the resin polymerization reaction to be complete after stirring; Step 4, placing the reacted solution in an oven, waiting for the water to evaporate completely to form a block, and performing heat treatment on the block under an inert gas; Step 5, crushing and screening the heat-treated material, solving the technical problems that the existing technology has relatively high requirements for equipment and processes.

Description

Technical Field

[0001] The present invention relates to the technical field of anode material production, and particularly relates to an anode material capable of regulating silicon dispersion and silicon-carbon gap and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are developing rapidly towards high energy density. The selection of anode materials is crucial. As the most commercially mature anode material, graphite can no longer meet higher requirements due to its low capacity. Therefore, silicon anode materials have become a popular research object. As an anode material, silicon has a high theoretical capacity, but during use, due to its severe volume expansion property, problems such as serious attenuation of material capacity will occur. Generally, silicon is usually compounded with carbon materials and used as an anode material in the form of a silicon-carbon composite anode. The composite structure of silicon and carbon is very important. Silicon particles in the form of nanoparticles need to be evenly embedded in the carbon matrix, that is, the carbon layer forms a perfect coating on the silicon particles. Such a structure can enhance the conductivity between silicon and silicon, and at the same time can provide a solid shell for the volume expansion of silicon.

[0003] Usually, such a composite of silicon and carbon can be achieved through surface coating technology. The coating technology is divided into solid-state, liquid-state and gaseous coating, and solid-state coating.

[0004] Chinese Patent Application No. CN201310282713.7 discloses a preparation method of porous Si / C composite microspheres. The process steps include: using an aqueous sodium alginate solution dispersing silicon as the aqueous phase, using an isooctane solution dissolved with an emulsifier as the oil phase, emulsifying the two evenly under stirring, then adding a coagulant to crosslink and gel the sodium alginate droplets, followed by freeze-drying, and finally carbonizing in an inert atmosphere to obtain porous Si / C composite microspheres.

[0005] However, both this technical solution and the prior art still have the following problems:

[0006] For example, using molten coating when asphalt is above the softening point temperature, the coating method is simple, but the uniformity is poor; liquid coating, that is, dissolving other carbon sources such as resin, asphalt, and sugars in a solvent, mixing with silicon in a solid-liquid manner, and after drying and carbonizing, a silicon-carbon composite material with uniform coating can be formed. However, silicon at the nanoscale is prone to agglomeration in the carbon source solution, and the volume expansion of silicon during charge and discharge is likely to cause irreversible cracking of the material, resulting in rapid attenuation of capacity; gaseous coating is to uniformly coat the surface of silicon through the process of pyrolysis-deposition of a gaseous carbon source. The coating effect is good, but the process is complex and expensive. In addition, the method of depositing nanosilicon into porous carbon through a gaseous silicon source, such as silane, can also achieve uniform distribution of silicon and carbon, but this process requires the use of silane gas with safety hazards and has relatively high requirements for equipment and technology. Summary of the Invention

[0007] The object of the present invention is to address the deficiencies of the prior art. Through a special preparation method, during the sintering process, the pore-forming aid phase volatilizes, leaving abundant pores inside the carbon skeleton. These pores contain a large number of micropores and mesopores, which can provide abundant paths for the transmission of lithium ions, and solve the problem that during the production of traditional anode materials, the product is prone to irreversible cracking, resulting in rapid capacity decay.

[0008] To achieve the above object, the present invention provides the following technical solution: A preparation method for an anode material capable of regulating silicon dispersion and silicon-carbon gap, comprising the following steps:

[0009] Step 1: Disperse nano-silicon in a pore-forming aid, and add a certain amount of emulsifier to the pore-forming aid, and mix evenly. Among them, the mass ratio of the emulsifier to the pore-forming aid is 1:4 to 1:10, and the mass ratio of nano-silicon in the pore-forming aid solution is 5% to 40%;

[0010] Step 2: Prepare a resin oligomer solution, and mix phenol or a mixture of phenol, amine substances and aldehyde substances at room temperature to prepare a clear and transparent resin solution;

[0011] Step 3: Add the resin solution to the pore-forming aid solution and stir rapidly to form an opaque emulsion. Among them, the mass ratio of the resin contained in the resin solution to the pore-forming aid is 1:0.5 to 1:2; the stirring rate is 500 to 4000 rpm / min, and after stirring, wait for the resin polymerization reaction to be complete;

[0012] Step 4: Place the reacted solution in an oven, and after the water evaporates completely to form a block, perform heat treatment on the block under an inert gas;

[0013] Step 5: Crush and screen the heat-treated material.

[0014] Preferably, the heat treatment temperature program is:

[0015] S1: Heat up to temperature T1 at a rate of r1 and keep it at a constant temperature for time t1, where r1 is 2 to 10 °C / min, T1 is 120 to 250 °C, and the constant temperature time t1 is 20 to 360 min;

[0016] S2: Then heat up to temperature T2 at a rate of r2 and keep it at a constant temperature for time t2, where r2 is 0.2 to 3 °C / min, T1 is 320 to 450 °C, and the constant temperature time t1 is 60 to 180 min;

[0017] S3: Finally, heat up to temperature T3 at a rate of r3 and keep it at a constant temperature for time t3, where r3 is 2 to 5 °C / min, T1 is 600 to 1000 °C, and the constant temperature time t1 is 60 to 300 min;

[0018] S4. Natural cooling for temperature reduction.

[0019] Preferably, in the first step, the pore-forming aid component can be a long-chain alkane, including one of n-heptane, hexadecane, oleic acid, silicone oil, mineral oil, vegetable oil, or a combination of multiple substances among the above.

[0020] Preferably, in the first step, the emulsifier includes, but is not limited to, one or a combination of polyethylene glycol, cetyltrimethylammonium bromide, octylphenol polyoxyethylene ether, polyol fatty acid ester, polysorbate, sorbitan fatty acid ester, and steareth.

[0021] Preferably, the phenolic substance includes one of phenol, cresol, m-cresol, o-cresol, catechol, resorcinol, hydroquinone, phloroglucinol, naphthol, and polycyclic phenol;

[0022] the amine substance includes one of melamine, dicyandiamide, aniline, and benzoguanamine;

[0023] the aldehyde substance includes one of formaldehyde and furfural.

[0024] Preferably, in the first step, the surface of the nano-silicon is functionalized in advance with one of ammonia water and silane coupling agent.

[0025] Preferably, in the third step, it is carried out at a heating temperature in the range of 40~90°C.

[0026] Preferably, in the third step, a certain amount of catalyst is added, and the catalyst is one of hydrochloric acid solution, sulfuric acid solution, nitric acid solution, acetic acid solution, sodium hydroxide solution, sodium carbonate solution, potassium hydroxide solution, potassium carbonate solution, ammonia water solution, and lithium hydroxide solution.

[0027] A negative electrode material includes a combination of silicon and amorphous carbon. Silicon or silicon aggregates are dispersed in the pores inside the amorphous carbon. Among them, the silicon pore diameter is smaller than the carbon pores, and the silicon is adhered to the inner wall of the carbon pores.

[0028] Preferably, the particle size (D50) of this negative electrode material is 4~30μm, and the silicon is one of nano single particles with a particle size of 1~500nm or nano-silicon aggregates with a particle size of 100~1000nm.

[0029] The beneficial effects of the present invention are as follows:

[0030] (1) In the silicon-carbon composite material of the present invention, between the nano-silicon or the agglomerates of silicon and carbon, since the dispersion of silicon depends on the dispersion of the pore-forming aid phase, during the subsequent heat treatment process, after the pore-forming aid volatilizes, pores are left between silicon and carbon, which can accommodate the volume expansion of silicon, so that the material will not crack easily during charge and discharge in the battery, providing a rich path for the transmission of lithium ions.

[0031] (2) The present invention provides a buffer for the volume expansion of silicon during charge and discharge through the adjustable gap between the nano-silicon or the agglomerates of silicon and carbon. The size of the gap can be adjusted by the content of silicon in the pore-forming aid phase and the ratio of the resin phase to the pore-forming aid phase.

[0032] In summary, the present invention has the advantages of high product quality and relatively simple manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is the morphology diagram before coating in Example 3 of the present invention;

[0034] Figure 2 It is the morphology diagram before coating in Comparative Example 1 of the present invention;

[0035] Figure 3 It is the schematic diagram after carbonization at low speed of the present invention;

[0036] Figure 4 It is the schematic diagram after carbonization at high speed of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0038] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more unless otherwise specifically defined.

[0039] Example 1

[0040] As Figure 1-2 shown, this embodiment provides a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap, including a combination of silicon and amorphous carbon. Silicon or silicon aggregates are dispersed in the pores inside the amorphous carbon, where the pore diameter of silicon is smaller than that of the carbon pores, and the silicon is bonded to the inner wall of the carbon pores.

[0041] Furthermore, the particle size (D50) of the negative electrode material is 4 - 30 μm, and the silicon is one of nano single particles with a particle size of 1 - 500 nm or nano silicon aggregates with a particle size of 100 - 1000 nm.

[0042] In the silicon-carbon composite material in this application, the components are a combination of silicon and amorphous carbon, and the particle size (D50) is 4 - 30 μm. Among them, the silicon can be nano single particles with a particle size of 1 - 500 nm or nano silicon aggregates with a particle size of 100 - 1000 nm. The silicon or silicon aggregates are dispersed in the pores inside the amorphous carbon. The silicon does not completely fill the pores in the carbon but is slightly smaller than the pore diameter, that is, there is a gap between the silicon and the carbon.

[0043] It should be noted that in the silicon-carbon composite material in this application, there is a certain gap between the nano silicon or silicon aggregates and the carbon, and the size of the gap can be adjusted. The existence of these gaps can provide a buffer for the volume expansion of silicon during charge and discharge. The size of the gap can be adjusted by the content of silicon in the pore-forming aid phase and the ratio of the resin phase to the pore-forming aid phase.

[0044] Example 2

[0045] A method for preparing a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap, comprising the following steps:

[0046] Step 1: Disperse nano-silicon in the pore-forming aid, and add a certain amount of emulsifier to the pore-forming aid and mix evenly. Among them, the mass ratio of the emulsifier to the pore-forming aid is 1:4 - 1:10, and the mass ratio of nano-silicon in the pore-forming aid solution is 5% - 40%.

[0047] Step 2: Prepare a resin oligomer solution by mixing phenolic or amine substances and aldehyde substances at room temperature to form a clear and transparent resin solution.

[0048] Step 3: Add the resin solution to the pore-forming aid solution and stir rapidly to form an opaque emulsion. Among them, the mass ratio of the resin contained in the resin solution to the pore-forming aid is 1:0.5 - 1:2; the stirring rate is 500 - 4000 rpm / min. After stirring, wait for the resin polymerization reaction to be complete.

[0049] Step 4: Place the reacted solution in an oven. After the water evaporates completely, a block is formed. Heat-treat the block under an inert gas.

[0050] Step 5: Crush and screen the heat-treated material.

[0051] It is worth mentioning that nano-silicon can be obtained by grinding micro-silicon, and the particle size of micro-silicon is 1 - 50 μm.

[0052] Furthermore, the heat treatment temperature program is as follows:

[0053] S1: Heat up to temperature T1 at a rate of r1 and keep it at a constant temperature for time t1, where r1 is 2 - 10 °C / min, T1 is 120 - 250 °C, and the constant temperature time t1 is 20 - 360 min.

[0054] S2: Then heat up to temperature T2 at a rate of r2 and keep it at a constant temperature for time t2, where r2 is 0.2 - 3 °C / min, T1 is 320 - 450 °C, and the constant temperature time t1 is 60 - 180 min.

[0055] S3: Finally, heat up to temperature T3 at a rate of r3 and keep it at a constant temperature for time t3, where r3 is 2 - 5 °C / min, T1 is 600 - 1000 °C, and the constant temperature time t1 is 60 - 300 min.

[0056] S4: Cool down naturally.

[0057] Furthermore, in the above Step 1, the components of the pore-forming aid can be long-chain alkanes, including one of n-heptane, hexadecane, oleic acid, silicone oil, mineral oil, vegetable oil, or a combination of multiple substances among the above substances.

[0058] Further, in the first step, the emulsifier includes but is not limited to one or a combination of substances such as polyethylene glycol, cetyltrimethylammonium bromide, octylphenol polyoxyethylene ether, polyol fatty acid ester, polysorbate, sorbitan fatty acid ester, and steareth.

[0059] Further, the phenolic substance includes one of phenol, cresol, m-cresol, o-cresol, catechol, resorcinol, hydroquinone, phloroglucinol, naphthol, and polycyclic phenol;

[0060] The aldehyde substance includes one of formaldehyde and furfural.

[0061] Further, in the first step, the nano-silicon is pre-treated with a functional group on the surface of the nano-silicon using one of ammonia water and silane coupling agent, and the purpose is to make the nano-silicon in the pore-forming aid phase disperse faster in the first step.

[0062] Further, in the third step, it is carried out at a heating temperature in the range of 40~90 °C, and the purpose is to accelerate the polymerization reaction. Or, a certain amount of catalyst can also be added in the third step. The catalyst is one of hydrochloric acid solution, sulfuric acid solution, nitric acid solution, acetic acid solution, sodium hydroxide solution, sodium carbonate solution, potassium hydroxide solution, potassium carbonate solution, ammonia water solution, and lithium hydroxide solution.

[0063] Among them, during the production process, according to needs, to further optimize the surface of the material and reduce the specific surface area of the material, the crushed material can be subjected to surface carbon coating, and the carbon coating refers to any one of gas-phase coating, liquid-phase coating, and solid-phase coating.

[0064] In this application, the key point is the controllable dispersion technology of nano-silicon. The nano-silicon is dispersed in the pore-forming aid phase, and through the dispersion of the pore-forming aid phase in the carbon precursor, such as the resin phase, the dispersion effect of silicon in carbon is realized. At the same time, the dispersion of silicon can be regulated. If uniform dispersion of single nano-silicon particles is required, the pore-forming aid phase needs to be dispersed into nano-scale droplets in the resin. By regulating the stirring rate, regulation can be achieved. The faster the stirring rate, the more uniform the dispersion of the pore-forming aid phase, and the more uniform the dispersion of nano-silicon. Similarly, if uniform distribution of silicon clusters in porous carbon is required, the stirring rate can be appropriately slowed down to make the pore-forming aid phase form larger droplets.

[0065] Based on the above discussion, since the dispersion of silicon depends on the dispersion of the pore-forming aid phase, during the subsequent heat treatment process, after the pore-forming aid volatilizes, pores are left between silicon and carbon, which can accommodate the volume expansion of silicon, so that the material will not easily crack during charge and discharge in the battery.

[0066] Meanwhile, an emulsion is used to promote the dispersion of nano-silicon in porous carbon. The dispersion degree of nano-silicon is changed by altering the dispersion of the pore-forming aid phase, and the dispersion of the pore-forming aid phase can be regulated by adjusting the shear rate during mixing. Therefore, the preparation method and structure regulation are simple.

[0067] Furthermore, during the sintering process, due to the volatilization of the pore-forming aid phase, abundant pores are left inside the carbon skeleton. This pore contains a large number of micropores and mesopores, which can provide abundant paths for the transport of lithium ions.

[0068] Therefore, the size of the silicon aggregates in the silicon-carbon composite material in this application, that is, the dispersion degree of silicon in carbon, can be arbitrarily adjusted according to the dispersion of the resin phase and the pore-forming aid phase. The adjustment methods include changing the shear rate during mixing, changing the polymerization rate of the resin, etc.

[0069] Example Three

[0070] The morphology of the material is as Figure 1 shown. A preparation method for a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap includes the following steps:

[0071] Step 1: Disperse 60 g of nano-silicon (D50 = 50 nm) in a mixed pore-forming aid of 300 g of oleic acid and 100 g of cyclohexane, and add 80 g of polyethylene glycol thereto, and mix evenly;

[0072] Step 2: Mix 300 g of phenol and 273 g of formaldehyde at room temperature and stir for 20 min;

[0073] Step 3: Add the solution in Step 2 to the solution in Step 1 and stir rapidly to form an opaque emulsion, where the stirring rate is 1000 rpm / min, and continue stirring for 2 hours until the polymerization reaction is completed;

[0074] Step 4: Place the reacted solution in an oven at 100 °C. After the water evaporates to form a block, carbonize the block under nitrogen. The heating program is as follows:

[0075] S1: Heat up to a temperature of 150 °C at a rate of 5 °C / min and keep it at a constant temperature for 120 min;

[0076] S2: Then heat up to a temperature of 350 °C at a rate of 1 °C / min and keep it at a constant temperature for 120 min;

[0077] S3: Finally, heat up to a temperature of 700 °C at a rate of 2 °C / min and keep it at a constant temperature for 180 min;

[0078] S4: Cool down naturally.

[0079] Step 5: Grind and crush the heat-treated and carbonized material and screen it with a 200-mesh sieve.

[0080] It should be noted that for surface coating of the material: Take 100 grams of the crushed material, add 10 grams of coating asphalt, and perform coating at 250 °C with a melting coating machine. After coating, heat-treat for 2 hours in a nitrogen atmosphere at 1000 °C to obtain the dry-coated material.

[0081] Example 4

[0082] A method for preparing a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap, comprising the following steps:

[0083] Step 1: Disperse 30 g of nano-silicon (D50 = 50 nm) in a mixed pore-forming aid of 400 g of styrene and 100 g of n-heptane, and add 80 g of polyethylene glycol thereto, and mix evenly;

[0084] Step 2: Mix 195 g of phenol and 177 g of formaldehyde at room temperature and stir for 20 min;

[0085] Step 3: Add the solution in Step 2 to the solution in Step 1 and stir rapidly to form an opaque emulsion, wherein the stirring rate is 1200 rpm / min. After stirring for 15 min, add 20 ml of dilute hydrochloric acid with a concentration of 1 M, and continue to stir for 2 hours until the polymerization reaction is complete;

[0086] Step 4: Place the reacted solution in an 80 °C oven. After the water evaporates completely, a block is formed. Carbonize the block under nitrogen, and the heating program is as follows:

[0087] S1: Heat up to a temperature of 120 °C at a rate of 5 °C / min and keep it at a constant temperature for 60 min;

[0088] S2: Then heat up to a temperature of 350 °C at a rate of 1 °C / min and keep it at a constant temperature for 120 min;

[0089] S3: Finally, heat up to a temperature of 800 °C at a rate of 2 °C / min, keep it at a constant temperature for 120 min, and then cool down naturally;

[0090] S4: Cool down naturally.

[0091] Step 5: Grind and crush the carbonized material and screen it with a 200-mesh sieve.

[0092] It should be noted that for surface coating of the material: Take 100 grams of the crushed material, add 30 grams of sucrose, and perform coating at 160 °C with a melting coating machine. After coating, heat-treat for 2 hours in a nitrogen atmosphere at 850 °C to obtain the dry-coated material.

[0093] Example 5

[0094] A preparation method of a negative electrode material capable of regulating silicon dispersion and silicon-carbon interstitial spaces, comprising the following steps:

[0095] Step 1: Disperse 50 g of nano-silicon (D50 = 50 nm) in a mixed solvent of 300 g of oleic acid and 100 g of cyclohexane and a pore-forming aid, and add 100 g of polysorbate thereto, and mix evenly;

[0096] Step 2: Mix 344 g of o-cresol and 273 g of formaldehyde at room temperature and stir for 20 min;

[0097] Step 3: Add the solution in Step 2 to the solution in Step 1 and stir rapidly to form an opaque emulsion, wherein the stirring rate is 2000 rpm / min. After stirring for 15 min, add 20 ml of dilute hydrochloric acid with a concentration of 1 M and continue stirring for 2 hours until the polymerization reaction is complete;

[0098] The heating program is the same as the other steps in Example 4.

[0099] Example 6

[0100] A preparation method of a negative electrode material capable of regulating silicon dispersion and silicon-carbon interstitial spaces, comprising the following steps:

[0101] Step 1: Disperse 40 g of nano-silicon (D50 = 80 nm) in an ethanol solution, add 1.5 ml of ammonia water, ultrasonicate for 1 h, centrifuge to obtain ammonia-treated nano-silicon powder, and then disperse the centrifuged nano-silicon powder in 250 g of dimethyl silicone oil, stir for 30 min. After stirring and mixing, add 50 g of polyvinyl alcohol thereto and mix evenly;

[0102] Step 2: Mix 187 g of phenol and 171 g of formaldehyde at room temperature and stir for 20 min;

[0103] Step 3: Add the solution in Step 2 to the solution in Step 1 and stir rapidly to form an opaque emulsion, with a stirring rate of 1000 rpm / min. After stirring for 20 min, add 20 ml of dilute hydrochloric acid with a concentration of 3 M and continue stirring for 40 min until the polymerization reaction is complete;

[0104] Step 4: Place the reacted solution in an oven at 100 °C. After the water has evaporated to form a block, carbonize the block under nitrogen at 700 °C for 3 h.

[0105] The heating program is the same as the other steps in Example 3.

[0106] Example 7

[0107] A preparation method of a negative electrode material capable of regulating silicon dispersion and silicon-carbon interstitial spaces, comprising the following steps:

[0108] Step 1: Disperse 80g of nano-silicon (D50=110nm) in an ethanol solution, add 5ml of silane coupling agent, ultrasonicate for 1h, centrifuge to obtain nano-silicon powder treated with silane coupling agent, disperse the nano-silicon powder obtained by centrifugation in 150g of dimethyl silicone oil, stir for 30min to mix, then add 30g of sorbitol fatty acid ester and mix evenly;

[0109] Step 2: Mix 187 g of phenol and 191 g of furfural at room temperature and stir for 20 min;

[0110] Step 3: Add the solution in step 2 to the solution in step 1 and stir rapidly to form a non-transparent emulsion at a stirring rate of 1000 rpm / min. After stirring for 20 minutes, add 20 ml of 3M dilute hydrochloric acid and continue stirring for 40 minutes until the polymerization reaction is complete;

[0111] Step 4: Place the reacted solution in an oven at 100°C, and after the water evaporates to dryness, form a block, and carbonize the block under nitrogen. The heating program is as follows:

[0112] S1, heating at 8°C / min to 200°C and keeping the temperature constant for 90min;

[0113] S2, then raise the temperature to 450°C at 0.5°C / min and keep the temperature constant for 90min;

[0114] S3. Finally, the temperature was raised to 900°C at a rate of 2°C / min, and kept constant for 180min before being cooled naturally.

[0115] Step 5: crush the carbonized material by ball milling and sieve with a 200-mesh sieve.

[0116] It should be noted that the material was surface coated by taking 100 grams of the crushed material, adding 20 grams of coating asphalt, and coating it at 200°C using a melt coating machine: after coating, heat treatment was performed at 1000°C for 2 hours in a nitrogen atmosphere to obtain a dry-coated material.

[0117] Embodiment 8

[0118] The stirring rate in step 3 of Example 7 was changed to 1800 rpm / min.

[0119] The remaining steps are the same as those in Example 7.

[0120] Embodiment 9

[0121] The stirring rate in step 3 of Example 7 was changed to 3000 rpm / min. The remaining steps were the same as those in Example 7.

[0122] Embodiment 10

[0123] Change the stirring rate in Step 3 of Example 7 to 650 rpm / min. The remaining steps are the same as those in Example 7.

[0124] Example 11

[0125] A method for preparing a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap, comprising the following steps:

[0126] Step 1: Ultrasonically disperse 20 g of nano-silicon (D50 = 120 nm) in 400 g of hexadecane, and then add 80 g of octylphenol polyoxyethylene ether thereto and mix evenly;

[0127] Step 2: Prepare an aqueous solution of 175 g of resorcinol and 306 g of furfural, mix at room temperature, and stir for 20 min;

[0128] Step 3: Add the solution in Step 2 to the solution in Step 1 and stir rapidly to form an opaque emulsion. The stirring rate is 1800 rpm / min, and continue to stir for 2 hours until the polymerization reaction is complete;

[0129] Step 4: Place the reacted solution in an oven at 100 °C. After the water has evaporated to form a block, carbonize the block under nitrogen at 700 °C for 3 h;

[0130] The heating program and the remaining steps are the same as those in Example 4.

[0131] It should be noted that the material is coated: Take 100 g of the crushed material, in a CVD furnace, introduce acetylene and hydrogen, and use argon as the carrier gas, and perform gas-phase coating at 800 °C for 4 hours to obtain the coated material.

[0132] Example 12

[0133] A method for preparing a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap, comprising the following steps:

[0134] Step 1: Ultrasonically disperse 40 g of nano-silicon (D50 = 120 nm) in 400 g of coconut oil, and then add 20 g of sorbitan fatty acid ester and 50 g of polysorbate thereto and mix evenly.

[0135] Step 2: Prepare an aqueous solution of 175 g of resorcinol, 48 g of melamine and 272 g of formaldehyde, mix at room temperature, and stir for 20 min;

[0136] Step 3: Add the solution in Step 2 to the solution in Step 1 and stir rapidly to form an opaque emulsion. The stirring rate is 1600 rpm / min, and continue to stir for 2 hours until the polymerization reaction is complete;

[0137] Step 4: Place the reacted solution in an oven at 100°C and wait for the water to evaporate to form a block. Carbonize the block under nitrogen at 900°C for 3 hours.

[0138] The heating procedure and other steps are the same as those in Example 7.

[0139] It should be noted that the material is coated: 100 grams of the crushed material is added with 20 grams of sucrose, coated at 140°C using a melt coating machine, and after coating, heat treated at 700°C for 2 hours in a nitrogen atmosphere to obtain a dry-coated material.

[0140] Embodiment 13

[0141] The second step in Example 12 is changed to: 300 g of phenol, 64 g of dicyandiamide and 288 g of formaldehyde are prepared into an aqueous solution, mixed at room temperature, and stirred for 20 minutes. The remaining steps are the same as those in Example 12.

[0142] Embodiment 14

[0143] The second step in Example 12 is changed to: 270 g of phenol, 129 g of benzoguanamine and 260 g of formaldehyde are prepared into an aqueous solution, mixed at room temperature, and stirred for 20 minutes. The remaining steps are the same as those in Example 12.

[0144] Comparative Example 1

[0145] The morphology of the material Figure 2 As shown, a method for preparing a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap comprises the following steps:

[0146] Step 1: Disperse 60g of nano-silicon (D50=50nm) in 400g of ethanol;

[0147] Step 2: 380 g of alcohol-soluble phenolic resin was dissolved in 400 g of ethanol to prepare a solution;

[0148] Step 3: Add the solution in step 2 to the solution in step 1 and stir rapidly to form a non-transparent emulsion, wherein the stirring rate is 1000 rpm / min and the mixture is stirred rapidly for 1 hour to make the silicon evenly distributed in the resin;

[0149] Step 4: Dry the mixture in an oven at 100°C to form a block, and carbonize the block under nitrogen at 700°C for 3 hours;

[0150] The heating procedure and other steps are the same as those in Example 3.

[0151] The alcohol-soluble phenolic resin in this embodiment is in a gel state and is directly purchased from Hebei Zetian Chemical Co., Ltd.

[0152] Comparative Example 2

[0153] A preparation method of a negative electrode material capable of regulating silicon dispersion and silicon-carbon interstitial, comprising the following steps:

[0154] Step 1: Disperse 60 g of nano-silicon (D50 = 50 nm) evenly in a pore-forming auxiliary agent mixture of 300 g of oleic acid and 100 g of cyclohexane;

[0155] The remaining steps are the same as those in Example 3.

[0156] Analyze the physical and chemical characteristic parameters of the silicon-carbon materials in the above examples and comparative examples.

[0157] 1. Determination of silicon content in the material: Obtained by thermogravimetric analysis.

[0158] 2. Specific surface area analysis of the material: Tested by nitrogen adsorption and desorption method.

[0159] 3. Morphology observation of the material: Observed by field emission scanning electron microscope.

[0160] The detection results are as follows:

[0161]

[0162] Battery performance evaluation of the material:

[0163] (1) Make the obtained silicon-carbon material into a slurry, and the formula of the slurry is: silicon-carbon material, binder, and conductive agent are mixed in a ratio of 90:5:5 to prepare an aqueous dispersion slurry; wherein the binder is sodium carboxymethyl cellulose and styrene-butadiene rubber; the conductive agent is conductive carbon black;

[0164] (2) Coat the stirred slurry on the electrolytic copper foil, and the coating thickness of the wet film is 300 μm, and dry it in vacuum at 80 degrees;

[0165] (3) Assemble the prepared electrode into a button battery, where the counter electrode is a lithium metal sheet, the separator is a polypropylene separator, and the electrolyte is an EC / DEC / EMC solution of 1 M LiPF6;

[0166] (4) Perform constant current charge and discharge tests, with a voltage range of 0~1.5 V and a current density of 0.1 C.

[0167] The test results are as follows:

[0168]

[0169] The morphology of the sample obtained in Example 3 is as Figure 1As shown, there are pores with a size of 1 μm or less inside the carbon, and nano-silicon is distributed in the pores. Since the proportion of silicon and pore-forming aids in Example 3 is relatively small, there is a large space around the silicon, which can accommodate the volume change of silicon during charge and discharge. The material will not crack due to the expansion of silicon. As a control, in the sample of Comparative Example 1, the combination of silicon and carbon is tight, and there is no space around the silicon. Therefore, during charge and discharge, the volume expansion of silicon will cause the material to crack.

[0170] From the battery performance test results, it can be seen that the silicon-carbon anode materials obtained by the preparation method provided by the present invention can all enable the raw material silicon to exhibit good initial specific capacity. Among them, Examples 5 and 6 were not coated, and the specific surface area was relatively large because there were many micropores inside the carbon. Correspondingly, the first-cycle Coulombic efficiency of Examples 5 and 6 was relatively low, but the overall structural advantages made them have good cycle stability. The remaining examples were all surface-coated, so the first-cycle Coulombic efficiency was also improved.

[0171] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap, characterized in that: The following steps are involved: Step 1: Disperse 60 g of nano-silicon with a particle size of D50 = 50 nm in a mixed pore-forming agent of 300 g of oleic acid and 100 g of cyclohexane, and add 80 g of polyethylene glycol thereto, and mix well; Step 2: Mix 300 g of phenol and 273 g of formaldehyde at room temperature and stir for 20 min; Step 3: Add the solution in step 2 to the solution in step 1 and stir rapidly to form a non-transparent emulsion, wherein the stirring rate is 1000 rpm / min, and continue stirring for 2 hours until the polymerization reaction is completed; Step 4: Place the reacted solution in an oven at 100°C, and after the water evaporates to dryness, form a block, and carbonize the block under nitrogen. The heating program is as follows: S1, heating at 5°C / min to 150°C and keeping the temperature constant for 120min; S2, then raise the temperature to 350°C at 1°C / min and keep the temperature constant for 120min; S3, finally raising the temperature to 700°C at 2°C / min and maintaining the temperature for 180min; S4, natural cooling; Step 5: crush the heat-treated carbonized material by ball milling and sieve with a 200-mesh sieve; The material obtained in step five is surface coated: 100 grams of the crushed material is taken, 10 grams of coating asphalt is added, and coating is performed at 250°C using a melt coating machine. After coating, heat treatment is performed at 1000°C for 2 hours in a nitrogen atmosphere to obtain a dry-coated material.

2. A method for preparing a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap, characterized in that: The following steps are involved: Step 1: Disperse 30 g of nano-silicon with a particle size of D50 = 50 nm in a mixed pore-forming agent of 400 g of styrene and 100 g of n-heptane, add 80 g of polyethylene glycol thereto, and mix well; Step 2: Mix 195 g of phenol and 177 g of formaldehyde at room temperature and stir for 20 min; Step 3: Add the solution in step 2 to the solution in step 1 and stir rapidly to form a non-transparent emulsion, wherein the stirring rate is 1200 rpm / min. After stirring for 15 minutes, add 20 ml of 1M dilute hydrochloric acid and continue stirring for 2 hours until the polymerization reaction is complete; Step 4: Place the reacted solution in an oven at 80°C to form a block after the water evaporates; carbonize the block under nitrogen, and the heating program is as follows: S1, heating at 5°C / min to 120°C and keeping the temperature constant for 60min; S2, then raise the temperature to 350°C at 1°C / min and keep the temperature constant for 120min; S3, finally raising the temperature to 800°C at 2°C / min, keeping the temperature constant for 120min, and then cooling naturally; S4, natural cooling; Step 5: crush the carbonized material by ball milling and sieve with a 200-mesh sieve; The material obtained in step five is surface coated: 100 g of the crushed material is added with 30 g of sucrose, coated at 160°C using a melt coating machine, and heat treated at 850°C for 2 hours in a nitrogen atmosphere to obtain a dry-coated material.

3. A method for preparing a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap, characterized in that: The following steps are involved: Step 1: Disperse 50 g of nano-silicon with a particle size of D50 = 50 nm in a mixed solvent of 300 g of oleic acid and 100 g of cyclohexane as a pore-forming aid, add 100 g of polysorbate thereto, and mix well; Step 2: Mix 344 g of o-cresol and 273 g of formaldehyde at room temperature and stir for 20 min; Step 3: Add the solution in step 2 to the solution in step 1 and stir rapidly to form a non-transparent emulsion, wherein the stirring rate is 2000 rpm / min. After stirring for 15 minutes, add 20 ml of 1M dilute hydrochloric acid and continue stirring for 2 hours until the polymerization reaction is complete; Step 4: Place the reacted solution in an oven at 80°C to form a block after the water evaporates; carbonize the block under nitrogen, and the heating program is as follows: S1, heating at 5°C / min to 120°C and keeping the temperature constant for 60min; S2, then raise the temperature to 350°C at 1°C / min and keep the temperature constant for 120min; S3, finally raising the temperature to 800°C at 2°C / min, keeping the temperature constant for 120min, and then cooling naturally; S4, natural cooling; Step 5: crush the carbonized material by ball milling and sieve with a 200-mesh sieve; The material obtained in step five is surface coated: 100 g of the crushed material is added with 30 g of sucrose, coated at 160°C using a melt coating machine, and heat treated at 850°C for 2 hours in a nitrogen atmosphere to obtain a dry-coated material.

4. A method for preparing a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap, characterized in that: The following steps are involved: Step 1: Disperse 40g of nano-silicon with a particle size of D50 = 50nm in an ethanol solution, add 1.5ml of ammonia water, ultrasonicate for 1h, centrifuge to obtain nano-silicon powder treated with ammonia water, and then disperse the nano-silicon powder obtained by centrifugation in 250g of dimethyl silicone oil, stir for 30min, stir and mix, then add 50g of polyvinyl alcohol thereto and mix evenly; Step 2: Mix 187 g of phenol and 171 g of formaldehyde at room temperature and stir for 20 min; Step 3: Add the solution in step 2 to the solution in step 1 and stir rapidly to form a non-transparent emulsion at a stirring rate of 1000 rpm / min. After stirring for 20 minutes, add 20 ml of 3M dilute hydrochloric acid and continue stirring for 40 minutes until the polymerization reaction is complete; Step 4: Place the reacted solution in an oven at 100°C, and after the water evaporates to dryness, form a block, and carbonize the block under nitrogen at 700°C for 3 hours; Step 4: Place the reacted solution in an oven at 100°C, and after the water evaporates to dryness, form a block, and carbonize the block under nitrogen. The heating program is as follows: S1, heating at 5°C / min to 150°C and keeping the temperature constant for 120min; S2, then raise the temperature to 350°C at 1°C / min and keep the temperature constant for 120min; S3, finally raising the temperature to 700°C at 2°C / min and maintaining the temperature for 180min; S4, natural cooling; Step 5: crush the heat-treated carbonized material by ball milling and sieve with a 200-mesh sieve; The material obtained in step five is surface coated: 100 grams of the crushed material is taken, 10 grams of coating asphalt is added, and coating is performed at 250°C using a melt coating machine. After coating, heat treatment is performed at 1000°C for 2 hours in a nitrogen atmosphere to obtain a dry-coated material.

5. A method for preparing a negative electrode material capable of regulating silicon dispersion and silicon-carbon gap, characterized in that: The following steps are involved: Step 1: 80 g of nano-silicon with a particle size of D50 = 50 nm is dispersed in an ethanol solution, and 5 ml of a silane coupling agent is added. The solution is ultrasonicated for 1 h, and the nano-silicon powder treated with the silane coupling agent is obtained by centrifugation. The nano-silicon powder obtained by centrifugation is then dispersed in 150 g of dimethyl silicone oil, stirred for 30 min, and then 30 g of sorbitol fatty acid ester is added thereto and mixed evenly. Step 2: Mix 187 g of phenol and 191 g of furfural at room temperature and stir for 20 min; Step 3: Add the solution in step 2 to the solution in step 1 and stir rapidly to form a non-transparent emulsion at a stirring rate of 1000 rpm / min. After stirring for 20 minutes, add 20 ml of 3M dilute hydrochloric acid and continue stirring for 40 minutes until the polymerization reaction is complete; Step 4: Place the reacted solution in an oven at 100°C, and after the water evaporates to dryness, form a block, and carbonize the block under nitrogen. The heating program is as follows: S1, heating at 8°C / min to 200°C and keeping the temperature constant for 90min; S2, then raise the temperature to 450°C at 0.5°C / min and keep the temperature constant for 90min; S3, finally raising the temperature to 900°C at 2°C / min, keeping the temperature constant for 180min, and then cooling naturally; Step 5: crush the carbonized material by ball milling and sieve with a 200-mesh sieve; The material obtained in step five is surface coated by taking 100 g of the crushed material, adding 20 g of coating asphalt, and coating it at 200°C using a melt coating machine: after coating, heat treat it at 1000°C for 2 hours in a nitrogen atmosphere to obtain a dry-coated material.

6. A negative electrode material, prepared based on the negative electrode material preparation method capable of adjusting silicon dispersion and silicon-carbon gap according to any one of claims 1 to 5, characterized in that: The invention comprises a combination of silicon and amorphous carbon, wherein silicon or silicon agglomerates are dispersed in the pores inside the amorphous carbon, wherein the pore diameter of silicon is smaller than that of the pores of carbon, and silicon is bonded to the inner wall of the pores of carbon.

7. A negative electrode material according to claim 6, characterized in that: The particle size D50 of the negative electrode material is 4-30 μm, and silicon adopts one of nanometer single particles with a particle size of 1-500 nm or nanometer silicon agglomerates with a particle size of 100-1000 nm.

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