A preparation method of composite porous carbon conducive to silicon deposition and silicon-carbon composite negative electrode

Abstract

The present invention relates to a preparation method of composite porous carbon that is conducive to silicon deposition and a silicon-carbon composite negative electrode. The method comprises the following steps: (P1) surface oxidation treatment of porous carbon fine powder obtains oxidized porous carbon fine powder; (P2) oxidized porous carbon fine powder and ether polycarboxylic acid silanol are added to a solvent to obtain porous carbon fine powder modified by ether polycarboxylic acid silanol; the ether polycarboxylic acid silanol is prepared by copolymerization of polyether macromonomer, acrylic monomer and alkenyl silane coupling agent in water; (P3) immersing porous carbon fine powder modified by ether polycarboxylic acid silanol in a salt aqueous solution to obtain porous carbon loaded with catalyst; (P4) mixing the porous carbon loaded with catalyst with a carbon source precursor solution and spray drying to obtain a composite carbon precursor; (P5) carbonizing and activating the composite carbon precursor to obtain composite porous carbon that is conducive to silicon deposition. The composite porous carbon prepared by the present invention is conducive to more uniform deposition of silicon in the pores of the inner core porous carbon fine powder.

Description

Technical Field

[0001] The invention belongs to the technical field of batteries, and in particular relates to a preparation method of composite porous carbon that is conducive to silicon deposition and a silicon-carbon composite negative electrode. Background Art

[0002] Porous carbon materials are widely used in lithium-ion batteries due to their excellent electrical conductivity, chemical stability and adjustable pore structure. The pore structure of porous carbon materials plays a decisive role in their performance. The preparation methods of porous carbon materials in the prior art mainly include physical activation and chemical activation. Physical activation generally uses high-temperature gas (such as carbon dioxide or water vapor) to react with carbon materials; while chemical activation generally uses activators (such as KOH, ZnCl 2 or H 3 PO 4 ) react with a carbon source under high temperature conditions. Although these technologies have achieved remarkable results in expanding specific surface area and regulating pore distribution, they still face technical bottlenecks such as high energy consumption, long processing time, and uneven pore structure. In addition, the surface chemical properties, internal pore distribution and conductivity of the prepared porous carbon materials still need to be optimized in the further application process to better meet the needs of high-performance electrodes. In recent years, with the development of lithium silicon anode technology, vapor deposition silicon carbon technology is a new method for preparing silicon-carbon anodes, which uses a vapor deposition process to deposit silicon on porous carbon materials to form silicon-carbon composite materials. This method can effectively improve the electrochemical properties of silicon-carbon anodes, such as cycle stability and capacity retention; at the same time, porous carbon can alleviate the structural damage caused by the volume expansion of silicon during charging and discharging, and provide a framework support for the uniform distribution of silicon. However, the pore structure of porous carbon plays a vital role in the deposition efficiency and final performance of silicon.

[0003] At present, there are still several problems to be solved in the deposition of porous carbon on silicon:

[0004] Insufficient surface floating silicon and deposition uniformity: Traditional porous carbon materials have the problem of "gradual decrease in the development of internal pores" during the etching process, that is, the pore structure inside the porous carbon material is usually not as developed as the outside. This pore structure limits the deposition position of silicon, making it easier for silane molecules to deposit in the external macroporous area, forming silicon aggregates or floating silicon. These uneven silicon depositions will lead to unstable growth and interface failure of the SEI film in subsequent electrochemical cycles, ultimately reducing the capacity retention rate and long cycle performance of the battery. Uneven silicon deposition will also cause the structural stability of the silicon-carbon negative electrode material to deteriorate, resulting in gas production during the preparation of the negative electrode slurry.

[0005] Kinetic issues of silane deposition: As silane molecules diffuse into the interior of porous carbon materials, their deposition is significantly hindered, which is manifested as a significantly lower internal deposition rate than external deposition. The main reasons include: (1) Limited gas phase diffusion: The smaller and deeper the pores of the porous carbon material, the longer the diffusion path of the silane molecules, the greater the resistance, and the diffusion flux decreases with depth. (2) Pore size shrinkage caused by deposition: In the early stage of deposition, silicon is preferentially deposited in larger pores and short diffusion paths, resulting in further reduction of pores, thereby increasing diffusion resistance. (3) Chemical reaction kinetic limitations: Silane cracking reactions may be limited inside the pores due to the non-uniform distribution of the temperature field or the reaction atmosphere. The above factors together lead to an increase in the unevenness of silicon deposition, making the internal silicon loading lower than the external, further limiting the silicon storage efficiency and performance stability of porous carbon materials. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing composite porous carbon which is conducive to silicon deposition so as to solve the problems of floating silicon and uneven deposition of porous carbon during silicon deposition.

[0007] The present invention achieves the above object through the following technical solutions:

[0008] A method for preparing composite porous carbon that is conducive to silicon deposition comprises the following steps:

[0009] (P1) subjecting the porous carbon fine powder to surface oxidation treatment, and then rinsing and drying to obtain oxidized porous carbon fine powder;

[0010] (P2) adding oxidized porous carbon fine powder and ether polycarboxylic acid silanol into a non-polar organic solvent, stirring and reacting to obtain ether polycarboxylic acid silanol-modified porous carbon fine powder;

[0011] The ether polycarboxylic acid silanol is prepared by copolymerizing a polyether macromonomer, an acrylic monomer, and an alkenyl silane coupling agent in a molar ratio of 1: (4-6): (0.1-0.3) in water under the action of an initiator;

[0012] (P3) soaking the porous carbon fine powder modified with ether polycarboxylic acid silanol in an aqueous salt solution of catalytic metal ions to obtain a porous carbon loaded with a catalyst;

[0013] (P4) mixing the catalyst-loaded porous carbon with a carbon source precursor solution, and then spray drying to obtain a composite carbon precursor;

[0014] (P5) The composite carbon precursor is carbonized and activated to obtain a composite porous carbon that is conducive to silicon deposition.

[0015] After the porous carbon fine powder is subjected to surface oxidation treatment, oxygen-containing functional groups such as -OH and -COOH are generated on its surface. The present invention uses homemade ether polycarboxylic acid silanol to modify the surface of the oxidized porous carbon fine powder. The silanol in the polycarboxylic acid silanol reacts with the -OH on the surface of the oxidized porous carbon fine powder to condense, thereby introducing the ether polycarboxylic acid silanol into the surface of the porous carbon fine powder by chemical bonds. The rich carboxylic acid groups in the ether polycarboxylic acid silanol have a complexing effect on the catalytic metal ions; at the same time, the long polyether side chain in the ether polycarboxylic acid silanol not only has good flexibility and segment activity, but also can play a steric hindrance role, preventing the agglomeration between the porous carbon fine powders, which is more beneficial to the complexing catalytic metal ions; therefore, in the subsequent process of loading the catalytic metal ions, the catalytic metal ions are evenly and firmly "adsorbed" in the pores of the porous carbon fine powder. After the porous carbon fine powder loaded with catalytic metal ions is compounded, carbonized, and activated with the carbon source precursor, the carbon source precursor forms an amorphous carbon coated on the surface of the porous carbon fine powder, i.e., a composite porous carbon is formed. Since the pores of the porous carbon fine powder in the inner core contain catalytic metal ions that are evenly and firmly "adsorbed" by the abundant carboxyl groups of ether polycarboxylic acid silanols, and the catalytic metal ions have a catalytic effect on silicon deposition, silicon is deposited more evenly in the pores of the porous carbon fine powder in the inner core, rather than concentrated on the surface of the outer carbon layer; at the same time, the surface of the porous carbon in the inner core contains a large number of active groups due to the modification of ether polycarboxylic acid silanols and surface oxidation treatment, and these active groups can generate hydrogen bonds and π-π interactions with the carbon source precursors in the outer layer, thereby stabilizing the inner and outer layer structures of the composite porous carbon, which is more beneficial to the long-term cycle performance of the battery. In addition, since polycarboxylic acid silanols also contain silicon elements, a layer of organic silicon mesh is formed in the structure of the composite porous carbon, and the Si-O bond has high bond energy and good stability, which can further improve the electrochemical stability of the battery.

[0016] Furthermore, in step (P1), the porous carbon fine powder has a particle size D50 of 1-3 μm, a specific surface area of ​​1800-2500 m² / g, and a total pore volume of 0.8-1.2 cm³ / g.

[0017] Furthermore, in step (P1), the surface oxidation treatment is chemical oxidation, gas phase oxidation or electrochemical oxidation.

[0018] Furthermore, the conditions of the chemical oxidation are: placing the porous carbon fine powder in a liquid-phase oxidant and soaking it at 40-60° C. for 2-6 hours, and the amount ratio of the porous carbon fine powder to the liquid-phase oxidant is 100 g: (1000-3000) mL; the liquid-phase oxidant is at least one of 3-5 mol / L nitric acid, 4-8 mol / L sulfuric acid, 0.1-0.5 mol / L potassium permanganate aqueous solution, and 10-30 wt% hydrogen peroxide. The conditions for gas phase oxidation are: placing porous carbon fine powder in a tubular reactor, and introducing an oxidizing gas to react at 100-300°C for 1-3 hours; the oxidizing gas is oxygen, ozone or air; when the oxidizing gas is oxygen or ozone, the amount of porous carbon and oxidizing gas is 100g: (0.05-0.1) L, and oxygen or ozone must be mixed with nitrogen to form a mixed gas, and the volume concentration of oxygen or ozone in the mixed gas is 0.1% to 5%; when the oxidizing gas is air, the amount of porous carbon and oxidizing gas is 100g: (1-10) L. The conditions for electrochemical oxidation are: dispersing porous carbon fine powder in sulfuric acid or phosphoric acid electrolyte, and electrolyzing for 30-90 minutes at a constant voltage of 1-3V. After surface oxidation treatment, the porous carbon fine powder produces oxygen-containing functional groups such as -OH and -COOH on its surface and reduces the surface isoelectric point, which is beneficial to the subsequent surface modification and loading of metal ions, and is also beneficial to its dispersion in the solvent.

[0019] Furthermore, in step (P1), the rinsing is performed by rinsing with water until the mixture becomes neutral; and the drying is performed by drying the mixture to a constant weight.

[0020] Furthermore, in step (P2), the usage ratio of the oxidized porous carbon fine powder, the ether polycarboxylic acid silanol, and the non-polar organic solvent is 100 g: (4-7) g: (800-1500) mL.

[0021] Furthermore, in step (P2), the non-polar organic solvent is at least one of toluene and xylene; and the stirring reaction conditions are: heating to 50-65° C. and reflux reaction for 3-6 hours.

[0022] Furthermore, in step (P2), the polyether macromonomer is selected from at least one of methyl allyl polyethylene glycol ether, methyl allyl polyethylene glycol ether, and ethylene glycol monovinyl polyethylene glycol ether, wherein the number average molecular weight of the polyethylene glycol segment is 200-600; the acrylic monomer is at least one of acrylic acid, methacrylic acid, and 3,3-dimethylacrylic acid; and the alkenyl silane coupling agent is at least one of γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, vinyltriethoxysilane, and vinyltrimethoxysilane.

[0023] Furthermore, in step (P2), the initiator is at least one of hydrogen peroxide, potassium persulfate, and ammonium persulfate; the amount of the initiator is 6-8% of the total mass of the polyether macromonomer and the acrylic monomer. The amount of the initiator affects the molecular weight of the ether polycarboxylic acid silanol. In the present invention, the amount of the initiator is controlled within the above range in order to prevent the molecular weight of the ether polycarboxylic acid silanol from being too high. Too high a molecular weight will reduce its solubility and activity during surface modification.

[0024] Preferably, in step (P2), the ether polycarboxylic acid silanol is prepared by a preparation method comprising the following steps: dissolving a polyether macromonomer, an acrylic monomer, an alkenyl silane coupling agent, and an initiator in water to form a mixed solution, and then copolymerizing at 40-60° C. for 1-3 hours, and cooling to obtain a suspension; and then filtering and drying the suspension to obtain the ether polycarboxylic acid silanol.

[0025] Taking ethylene glycol monovinyl polyethylene glycol ether (EPEG-400), acrylic acid (AA), and γ-methacryloxypropyltrimethoxysilane as an example, the reaction formula for preparing ether polycarboxylic acid silanol is as follows:

[0026] .

[0027] Furthermore, in step (P3), the catalytic metal ion is Ni 2+ , Cu 2+ 、Mo 2+ , Pd 2+ At least one of, preferably Ni 2+ ; The salt is a chloride salt or a halide salt.

[0028] Furthermore, in step (P3), the ratio of the amount of the polycarboxylic acid silanol-modified porous carbon fine powder to the salt of the catalytic metal ion is 100 g: (1-4) g, the concentration of the salt aqueous solution is 0.1-0.5 wt %; the soaking conditions are: temperature 20-50° C., time 2-4 h, pH 5.5-6.5.

[0029] Furthermore, in step (P4), the carbon source precursor is thermoplastic phenolic resin, starch or polyvinyl alcohol, preferably thermoplastic phenolic resin; the mass ratio of the catalyst-loaded porous carbon to the carbon source precursor is 1:(1~3); and the concentration of the carbon source precursor solution is 10~20wt%.

[0030] Furthermore, in step (P4), the spray drying conditions are as follows: the inlet temperature of the spray dryer is 150-250° C., the outlet temperature is 70-110° C., and the rotation speed is 1500-2000 rpm.

[0031] Furthermore, in step (P5), the carbonization conditions are: keeping at 700-900° C. for 3-8 hours under an inert atmosphere, and the inert atmosphere is nitrogen and / or argon.

[0032] Furthermore, in step (P5), the activation conditions are: using at least one of water vapor, carbon dioxide, ammonia, and hydrogen sulfide as an activating agent, the temperature is 800~1000°C, the time is 3~6h, and the amount ratio of the carbonized composite carbon material to the activating agent is 1g:(1~10)L.

[0033] Furthermore, the particle size D50 of the composite porous carbon that is conducive to silicon deposition is 4-8 μm.

[0034] In a second aspect, the present invention provides a composite porous carbon that is conducive to silicon deposition, which is prepared by the aforementioned preparation method.

[0035] In the third aspect, the present invention also provides a silicon-carbon composite negative electrode, which is prepared by vapor-depositing silicon and carbon coating the composite porous carbon obtained by the above-mentioned preparation method. The processes of vapor-depositing silicon and carbon coating are well known to those skilled in the art, such as using an organic silicon source gas for vapor-depositing silicon, the organic silicon source gas is selected from at least one of silane, dichlorodihydrosilane, trichlorosilane, silicon tetrachloride, silicon tetrafluoride, disilane, etc.; if a carbon source gas is used for carbon coating, the carbon source gas is selected from at least one of C1-4 alkanes, C2-4 alkenes, and C2-4 alkynes.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention modifies the surface of porous carbon fine powder after oxidation treatment by ether polycarboxylic acid silanol, and then loads catalytic metal ions, so that the catalytic metal ions are evenly and firmly "adsorbed" in the pores of the porous carbon fine powder; the catalytic metal ions have a catalytic effect on silicon deposition, thereby achieving more uniform deposition of silicon in the pores of the inner core porous carbon fine powder, rather than concentrating on the surface of the outer carbon. The composite porous carbon formed by the porous carbon fine powder loaded with catalytic metal ions and carbon source precursors after carbonization and activation has a stable structure.

[0038] (2) The composite porous carbon that is conducive to silicon deposition obtained by the preparation method of the present invention is subjected to silicon deposition and carbon coating to obtain a silicon-carbon composite negative electrode material. When the silicon-carbon composite negative electrode material is used as the negative electrode of a lithium battery, its first reversible specific capacity reaches 1900 mAh / g, the first coulombic efficiency reaches more than 93%, and the capacity retention rate after 100 cycles reaches more than 95%; in the process of preparing the negative electrode slurry, the gas production of the slurry is low, all less than 0.2 mL / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1The SEM images of the porous carbon fine powder used in the examples and comparative examples;

[0040] Figure 2 is a SEM image of the porous carbon fine powder modified with ether polycarboxylic acid silanol prepared in step (P2) of Example 1;

[0041] Figure 3 This is the EDS element mapping image of the catalyst-loaded porous carbon prepared in step (P3) of Example 1. DETAILED DESCRIPTION

[0042] In order to better explain the present invention, the following description will be given in detail with reference to the embodiments of the present invention, and the main contents of the present invention will be further clarified in conjunction with specific examples. However, the contents of the present invention are not limited to the following examples.

[0043] Unless otherwise specified, the "parts" in the examples of the present invention are all parts by weight. All reagents used are commercially available reagents in the art.

[0044] Ethylene glycol monovinyl polyethylene glycol ether (EPEG-400) is selected from Aladdin, wherein the number average molecular weight of the polyethylene glycol segment is 400.

[0045] The porous carbon fine powder was selected from Shandong Shengquan New Energy Technology Co., Ltd., with a particle size D50 of 2.2 μm and a specific surface area of ​​1957 m 2 / g, total pore volume 0.988cm 3 / g.

[0046] Preparation of ether polycarboxylic acid silanol

[0047] Preparation Example 1

[0048] Ethylene glycol monovinyl polyethylene glycol ether (EPEG-400), acrylic acid (AA), and γ-methacryloxypropyltrimethoxysilane (KH550) are prepared into a mixture with a total mass of 100 g in a molar ratio of 1:4:0.1, and then the mixture and 6 g of initiator ammonium persulfate are dissolved in pure water to form a mixed solution; then the mixture is reacted at 45°C for 1.5 hours, and a suspension is obtained after cooling to room temperature; the suspension is dried and filtered, washed with pure water twice, and dried in an oven at 80°C for 12 hours to obtain ether polycarboxylic acid silanol a.

[0049] Preparation Example 2

[0050] The rest is the same as Preparation Example 1, except that the molar ratio of ethylene glycol monovinyl polyethylene glycol ether (EPEG-400), acrylic acid (AA), and γ-methacryloxypropyltrimethoxysilane (KH550) is 1:5:0.2, and ether polycarboxylic acid silanol b is finally obtained.

[0051] Preparation Example 3

[0052] The rest is the same as Preparation Example 1, except that the molar ratio of ethylene glycol monovinyl polyethylene glycol ether (EPEG-400), acrylic acid (AA), and γ-methacryloxypropyltrimethoxysilane (KH550) is 1:6:0.3, and ether polycarboxylic acid silanol c is finally obtained.

[0053] Comparative Preparation Example 1

[0054] The rest is the same as Preparation Example 1, except that the molar ratio of ethylene glycol monovinyl polyethylene glycol ether (EPEG-400), acrylic acid (AA), and γ-methacryloxypropyltrimethoxysilane (KH550) is 1:3:0.5, and ether polycarboxylic acid silanol d is finally obtained.

[0055] Comparative Preparation Example 2

[0056] The rest is the same as Preparation Example 1, except that the molar ratio of ethylene glycol monovinyl polyethylene glycol ether (EPEG-400), acrylic acid (AA), and γ-methacryloxypropyltrimethoxysilane (KH550) is 1:7:0.05, and ether polycarboxylic acid silanol e is finally obtained.

[0057] Example 1

[0058] (P1) 200 g of porous carbon fine powder (SEM image of which is shown in Figure 1 The mixture was added into 3000 mL of 5 mol / L nitric acid and stirred at 55°C for 4 h. After soaking, it was rinsed with pure water until neutral and dried in an oven at 80°C to constant weight to obtain oxidized porous carbon fine powder.

[0059] (P2) 100 g of oxidized porous carbon fine powder was dispersed in a mixture of 4 g of ether polycarboxylic acid silanol a and 1000 mL of toluene, and the mixture was heated to 55 °C and refluxed for 5 h. The mixture was then cooled, filtered, and washed with pure water until the filtrate was colorless. The mixture was dried in an oven at 70 °C for 24 h to obtain porous carbon fine powder modified with ether polycarboxylic acid silanol. The SEM image of the powder is shown in FIG. Figure 2 As shown;

[0060] (P3) 2 g of nickel chloride was dissolved in 500 g of pure water to form a nickel chloride aqueous solution, and its pH was adjusted to 6.0 with citric acid; 80 g of ether polycarboxylic acid silanol-modified porous carbon fine powder was then immersed in the above nickel chloride aqueous solution at room temperature (25°C) for 2 h. After the immersion was completed, the porous carbon loaded with catalyst was obtained by filtration and drying at 80°C for 24 h. Its EDS element mapping diagram is shown in FIG. Figure 3 As shown;

[0061] (P4) 60 g of the catalyst-loaded porous carbon was mixed with 600 g of an isopropanol solution of a thermoplastic phenolic resin (with a concentration of 15 wt%), and then spray-dried. The inlet temperature of the spray dryer was 180 ° C, the outlet temperature was 80 ° C, and the rotation speed was 1800 rpm. The spray-dried material was collected and placed in a rotary kiln at 160 ° C for 2 h for cross-linking and curing. After cooling, a composite carbon precursor was obtained.

[0062] (P5) Carbonize 50 g of composite carbon precursor at 800 °C for 5 h in a nitrogen atmosphere; continue to raise the temperature to 900 °C, switch nitrogen to carbon dioxide, activate at a flow rate of 1.5 L / min for 4 h, switch carbon dioxide to nitrogen after activation, stop heating and naturally cool to room temperature to obtain composite porous carbon that is conducive to silicon deposition.

[0063] The particle size D50 of the composite porous carbon that is conducive to silicon deposition is 4.6 μm according to the particle size test. The specific surface area is 2012.4 m 2 / g.

[0064] Example 2

[0065] The rest is the same as Example 1, except that in step (P2), the ether polycarboxylic acid silanol b prepared in Preparation Example 2 is used instead of the ether polycarboxylic acid silanol a.

[0066] Example 3

[0067] The rest is the same as Example 1, except that in step (P2), the ether polycarboxylic acid silanol c prepared in Preparation Example 3 is used instead of the ether polycarboxylic acid silanol a.

[0068] Example 4

[0069] The rest is the same as Example 1, except that in step (P2), the amount of ether polycarboxylic acid silanol a is 7 g, and the mixture is heated to 80° C. and refluxed for 15 h.

[0070] Example 5

[0071] The rest is the same as Example 1, except that: in step (P3), palladium chloride is used instead of nickel chloride; in step (P4), polyvinyl alcohol is used instead of phenolic formaldehyde.

[0072] Comparative Example 1

[0073] The rest is the same as Example 1, except that step (P2) is omitted, and in step (P3), oxidized porous carbon fine powder is used instead of ether-based polycarboxylic acid silanol-modified porous carbon fine powder.

[0074] Comparative Example 2

[0075] The rest is the same as Example 1, except that, in step (P2), the ether polycarboxylic acid silanol d prepared in Comparative Preparation Example 1 is used instead of the ether polycarboxylic acid silanol a.

[0076] Comparative Example 3

[0077] The rest is the same as Example 1, except that, in step (P2), the ether polycarboxylic acid silanol e prepared in Comparative Preparation Example 2 is used instead of the ether polycarboxylic acid silanol a.

[0078] Application Example 1

[0079] 30 g of the composite porous carbon that is conducive to silicon deposition obtained in Example 1 was placed in a rotary kiln with a rotation speed of 50 r / min. Nitrogen was introduced at a flow rate of 5 L / min. After the temperature was raised to 500°C at a heating rate of 8°C / min in a nitrogen environment, the nitrogen flow rate was maintained and monosilane gas was introduced at a flow rate of 0.2 L / min to carry out chemical vapor deposition for 1 hour. After the silane deposition was completed, the monosilane gas was stopped, and helium was continuously introduced at a flow rate of 5 L / min to remove excess monosilane gas. Acetylene gas was then introduced at a flow rate of 0.2 L / min and maintained at 600°C for vapor deposition for 1 hour. The carbon formed after the decomposition of the acetylene gas formed a carbon coating layer to obtain a silicon-carbon composite negative electrode material.

[0080] Application Example 2-5

[0081] Other conditions are the same as those in Application Example 1, except that the composite porous carbon that is conducive to silicon deposition is prepared in Example 2-5.

[0082] Comparative Application Examples 1-3

[0083] Other conditions are the same as those in Application Example 1, except that the composite porous carbon that is conducive to silicon deposition is prepared in Comparative Examples 1-3.

[0084] Testing and analysis

[0085] 1) Performance test of composite porous carbon for silicon deposition

[0086] Specific surface area and particle size distribution: The composite porous carbon prepared in the embodiment and the comparative example was subjected to nitrogen adsorption and desorption experiments using an ipore 620 three-station full-function multi-purpose gas adsorption instrument produced by Lihua Lianke to determine its specific surface area.

[0087] The specific surface area of ​​the composite porous carbon prepared in each embodiment is 1900~2050 m 2 / g, and the specific surface area of ​​the porous carbon fine powder in the inner core is 1957m 2 / g is close, indicating that the preparation method of the present invention will not have an adverse effect on the pore structure and specific surface area.

[0088] In addition, from Figure 1 and Figure 2 It can be clearly seen from the comparison that the porous carbon fine powder after surface oxidation treatment and ether polycarboxylic acid silanol modification is easier to disperse and there is no obvious agglomeration of small particles.

[0089] from Figure 3 From the mapping diagram, it can be seen that the nickel element is evenly distributed in the porous carbon fine powder, indicating that the nickel ions are successfully loaded in the porous carbon fine powder.

[0090] 2) Performance test of silicon-carbon negative electrode materials prepared in application examples and comparative application examples

[0091] Charge and discharge test: The silicon-carbon negative electrode material prepared in the above application examples and comparative application examples is used in the negative electrode of the lithium-ion battery, assembled into a lithium battery and tested for its electrochemical performance. The specific method is as follows: The silicon-carbon composite negative electrode material, polyacrylic acid (PAA) and conductive carbon black Super P are mixed in a mass ratio of 8:1:1, and fully ground with deionized water as a dispersant, and then made into an electrode slurry in a homogenizer. The slurry is evenly coated on the copper foil, and the slurry thickness is controlled to 200μm. Then the coated copper foil is placed in a vacuum oven and dried at 80°C for 12 hours. The dried material was cut into electrode sheets with a diameter of 12 mm using a punching machine, and then the electrode sheets were transferred to a glove box, where they were used as counter electrodes with 16 mm metal lithium sheets, Celgard 2600 was used as a diaphragm, 1M LiPF6 solution was selected as the electrolyte, and the solvent was prepared in a volume ratio of ethylene carbonate (EC): diethyl carbonate (DEC) = 1:1, and 25% fluoroethylene carbonate (FEC) was added as an additive, and finally assembled into a CR2032 button cell. The button cell was electrochemically tested using the Blue Electric CT2001 A battery test system, with a voltage range of 0.01-1.5 V and a current density of 100 mA / g.

[0092] Gas production test: The silicon-carbon negative electrode material, carbon black, sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) composite binder prepared in the application example and the comparative application example were mixed into a slurry at a mass ratio of 90:5:5 (where the mass ratio of CMC to SBR was 2:3), and the air was removed by using an aluminum-plastic bag for packaging. The initial slurry density was tested using a solid density meter, which was recorded as ρ 0 Then store at 45℃ for 24h and test the density again, recorded as ρ 1 , gas production = , where m is the mass of the slurry. The more gas produced, the more serious the material damage and the worse the material stability.

[0093] The above test results are shown in Table 1:

[0094] Table 1 Performance test

[0095] .

[0096] It can be seen from Table 1 that when the silicon-carbon composite negative electrode material prepared by silicon deposition and carbon coating of the composite porous carbon conducive to silicon deposition in the embodiment of the present invention is used as the negative electrode of a lithium battery, its first reversible specific capacity reaches 1900 mAh / g, the first coulombic efficiency reaches more than 93%, and the capacity retention rate after 100 cycles reaches more than 95%; in the process of preparing the negative electrode slurry, the gas production of the slurry is low, all less than 0.2 mL / g.

[0097] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A method for preparing composite porous carbon that is conducive to silicon deposition, characterized in that: The following steps are involved: (P1) subjecting the porous carbon fine powder to surface oxidation treatment, and then rinsing and drying to obtain oxidized porous carbon fine powder; (P2) adding oxidized porous carbon fine powder and ether polycarboxylic acid silanol into a non-polar organic solvent, stirring and reacting to obtain ether polycarboxylic acid silanol-modified porous carbon fine powder; The ether polycarboxylic acid silanol is prepared by copolymerizing a polyether macromonomer, an acrylic monomer, and an alkenyl silane coupling agent in a molar ratio of 1: (4-6): (0.1-0.3) in water under the action of an initiator; (P3) soaking the porous carbon fine powder modified with ether polycarboxylic acid silanol in an aqueous salt solution of catalytic metal ions to obtain a porous carbon loaded with a catalyst; (P4) mixing the catalyst-loaded porous carbon with a carbon source precursor solution, and then spray drying to obtain a composite carbon precursor; (P5) The composite carbon precursor is carbonized and activated to obtain a composite porous carbon that is conducive to silicon deposition.

2. The preparation method according to claim 1, characterized in that: In step (P1), the particle size D50 of the porous carbon fine powder is 1-3 μm, the specific surface area is 1800-2500 m² / g, and the total pore volume is 0.8-1.2 cm³ / g; the surface oxidation treatment is chemical oxidation, gas phase oxidation or electrochemical oxidation.

3. The preparation method according to claim 1, characterized in that: In step (P2), the amount ratio of the oxidized porous carbon fine powder, ether polycarboxylic acid silanol, and non-polar organic solvent is 100 g: (4-7) g: (800-1500) mL; and / or The non-polar organic solvent is at least one of toluene and xylene; the stirring reaction conditions are: heating to 50-65° C. and reflux reaction for 3-6 hours.

4. The preparation method according to claim 1, characterized in that: In step (P2), the polyether macromonomer is selected from at least one of methyl allyl polyethylene glycol ether, methyl allyl polyethylene glycol ether, and ethylene glycol monovinyl polyethylene glycol ether, wherein the number average molecular weight of the polyethylene glycol segment is 200-600; the acrylic monomer is at least one of acrylic acid, methacrylic acid, and 3,3-dimethylacrylic acid; the alkenyl silane coupling agent is at least one of γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, vinyltriethoxysilane, and vinyltrimethoxysilane; the initiator is at least one of hydrogen peroxide, potassium persulfate, and ammonium persulfate; and the amount of the initiator used is 6-8% of the total mass of the polyether macromonomer and the acrylic monomer.

5. The preparation method according to claim 1, characterized in that: In step (P2), the ether polycarboxylic acid silanol is prepared by a preparation method comprising the following steps: dissolving a polyether macromonomer, an acrylic monomer, an alkenyl silane coupling agent, and an initiator in water to form a mixed solution, and then copolymerizing at 40-60° C. for 1-3 hours, and cooling to obtain a suspension; and then filtering and drying the suspension to obtain the ether polycarboxylic acid silanol.

6. The preparation method according to claim 1, characterized in that: In step (P3), the catalytic metal ion is Ni 2 + , Cu 2+ 、Mo 2+ , Pd 2+ At least one of; the salt is a halide salt.

7. The preparation method according to claim 1, characterized in that: In step (P3), the ratio of the polycarboxylic acid silanol-modified porous carbon fine powder to the salt of the catalytic metal ion is 100 g: (1-4) g, the concentration of the salt aqueous solution is 0.1-0.5 wt %; the soaking conditions are: temperature 20-50° C., time 2-4 h, pH 5.5-6.

5.

8. The preparation method according to claim 1, characterized in that: In step (P4), the carbon source precursor is thermoplastic phenolic resin, starch or polyvinyl alcohol; the mass ratio of the catalyst-loaded porous carbon to the carbon source precursor is 1:(1-3); the concentration of the carbon source precursor solution is 10-20wt%; and / or The spray drying conditions are as follows: the inlet temperature of the spray dryer is 150-250° C., the outlet temperature is 70-110° C., and the rotation speed is 1500-2000 rpm.

9. The preparation method according to claim 1, characterized in that: In step (P5), the carbonization conditions are: 700-900°C for 3-8h under an inert atmosphere, wherein the inert atmosphere is nitrogen and / or argon; and / or The activation conditions are: using at least one of water vapor, carbon dioxide, ammonia, and hydrogen sulfide as an activator, the temperature is 800-1000°C, the time is 3-6 hours, and the amount ratio of the carbonized composite carbon material to the activator is 1g: (1-10)L.

10. A silicon-carbon composite negative electrode, prepared by coating the composite porous carbon obtained by the preparation method according to any one of claims 1 to 9 with silicon vapor deposited and carbon coated.

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