Preparation method of silicon-carbon negative electrode base material porous carbon

Abstract

The invention discloses a silicon-carbon negative electrode base material porous carbon preparation method, which comprises: S1, raw material pretreatment: washing and drying a PE raw material, and crushing to a particle size of 50-200 [mu] m to obtain a PE pretreatment material, S2, template adsorption: dispersing a nanometer oxide template agent in a toluene solvent, carrying out ultrasonic dispersion, adding the PE pretreatment material or oligomeric PE, and carrying out ultrasonic dispersion to obtain the silicon-carbon negative electrode base material porous carbon. S3, high-temperature carbonization: placing the composite solid in an inert atmosphere, heating the composite solid to 600-900 DEG C at a set heating rate, and carrying out heat preservation for 1-4 hours to obtain a carbon-template compound, and S4, optional chemical activation: mixing the carbon-template compound and KOH powder according to a mass ratio of 1: 2-1: 4, heating the mixture to 700-900 DEG C at a heating rate of 2-5 DEG C / min in the inert atmosphere, and carrying out heat preservation for 1-4 hours to obtain the carbon-template compound. And preserving heat for 1-3 hours. Through cooperative use of the steps, the method has the advantages that the process steps are simple and controllable, the process complexity and the production cost are reduced, the preparation process is safe and environment-friendly, and cyclic utilization of resources is realized.

Description

Technical Field

[0001] This invention relates to the field of porous carbon material preparation technology, specifically a method for preparing porous carbon as a silicon-carbon anode substrate. Background Technology

[0002] Porous carbon materials, due to their high specific surface area, tunable pore structure, excellent conductivity, and chemical stability, have become one of the core materials in energy storage, adsorption, and catalysis. In silicon-carbon composite anodes for lithium-ion / sodium-ion batteries, porous carbon not only alleviates the volume expansion (up to 300%) of silicon-based materials during charge and discharge, but also provides efficient ion transport channels and electron conduction pathways, significantly improving the cycle stability and rate performance of the battery. Therefore, developing porous carbon substrates with precise and controllable pore structures, low preparation costs, and environmental friendliness is key to promoting the industrialization of silicon-carbon anodes.

[0003] Currently, the main methods for preparing porous carbon include template methods, physical activation methods, and chemical activation methods. Among them, template methods have become the mainstream technology for preparing high-performance porous carbon due to their ability to precisely control pore structure parameters. However, traditional template methods have significant drawbacks: commonly used hard templates (such as nano-templates)... High-concentration hydrofluoric acid (HF) solution is required for etching and removal. HF is highly corrosive and toxic, posing a high operational risk. Moreover, the elution efficiency is usually only 60-65%, and residual template particles will reduce the conductivity of porous carbon. At the same time, traditional carbon sources mostly use special raw materials such as phenolic resin and sucrose, which are costly and highly dependent on resources. Although the chemical activation method is relatively simple and easy to scale up, the pore structure is highly disordered, with mesopores generally accounting for less than 25%, resulting in low ion transport efficiency. In addition, the amount of activator (such as KOH) used is large, which is highly corrosive to the equipment, and the subsequent washing wastewater treatment is difficult.

[0004] Meanwhile, converting waste PE plastic into high-value-added porous carbon materials can not only effectively solve the problem of white pollution, but also achieve resource recycling and reduce the preparation cost of porous carbon. However, existing technologies for preparing porous carbon from waste PE have problems such as low carbon yield (usually ≤25%), difficulty in controlling pore structure, and unstable product performance, making it difficult to meet the performance requirements of high-end applications such as silicon-carbon anodes.

[0005] To address the aforementioned issues, it is necessary to decompose the overall vehicle performance indicators into system-level indicators, and then use these system-level indicators to guide component design. This allows for the coordination of various subsystems from a holistic perspective, thereby enhancing product competitiveness and brand image. Therefore, it is essential to invent a method for preparing porous carbon as a silicon-carbon anode substrate to solve these problems. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing porous carbon in silicon-carbon anode substrates. This method has the advantages of simple and controllable process steps, reduced process complexity and production costs, safe and environmentally friendly preparation process, and resource recycling. It solves the problems of high carbon source cost, low template elution efficiency, high operational risk, difficulty in pore structure control and unstable product performance.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing porous carbon as a silicon-carbon anode substrate, comprising the following steps:

[0008] S1: Raw material pretreatment: After cleaning and drying, the PE raw material is crushed to a particle size of 50-200μm to obtain PE pretreated material;

[0009] S2: Template adsorption: The nano-oxide template agent is dispersed in toluene solvent, ultrasonically dispersed, and then the PE pretreated material or oligomeric PE is added. After stirring and adsorption, the template-oligomeric PE composite solid is obtained by separation.

[0010] S3: High-temperature carbonization: The composite solid is placed in an inert atmosphere and heated to 600-900℃ at a set heating rate and held for 1-4 hours to obtain a carbon-template composite.

[0011] S4: Optional chemical activation: Mix the carbon-template composite with KOH powder at a mass ratio of 1:2-1:4, heat to 700-900℃ at 2-5℃ / min under an inert atmosphere, and keep warm for 1-3h;

[0012] S5: Template elution: Immerse the carbonized or activated product in an etchant to remove the template agent, then wash with deionized water until pH 6.5-7.5.

[0013] S6: Drying treatment: Dry the washed product at 80-120℃ for 6-12h to obtain porous carbon silicon-carbon anode substrate.

[0014] Preferably, in step S1, the PE raw material is low-density PE (LDPE, crystallinity 30-50%), high-density PE (HDPE, crystallinity 70-90%), or waste PE plastic; the cleaning method is as follows: first, use 5-10wt% sodium hydroxide solution for ultrasonic cleaning for 15-30 minutes to remove oil stains, then wash with deionized water until neutral, the drying temperature is 60-80℃, and the drying time is 4-6 hours; the pulverizing equipment is a high-speed airflow pulverizer, and the particle size is detected by a laser particle size analyzer.

[0015] Preferably, in step S2, the nano-oxide template agent is a nano-sized particle with a particle size of 30-100 nm. Or 50-150nm nanometers The purity is ≥99.5%; the number average molecular weight of oligomeric PE is 1000-5000, and the mass-to-volume ratio of oligomeric PE to toluene is 10-50 g / L; the ultrasonic dispersion power is 100-300 W, the frequency is 20-40 kHz, and the dispersion time is 10-30 min; the stirring speed is 300-500 rpm, the adsorption temperature is 25-60℃, and the adsorption time is 2-8 h; the separation method is vacuum filtration (filter membrane pore size 0.22-0.45 μm) or centrifugation (speed 5000-8000 rpm, time 10-20 min).

[0016] Preferably, in step S3, the inert atmosphere is argon or nitrogen with a purity ≥99.99%, and the gas flow rate is 50-100 mL / min; the heating rate is 2-10℃ / min, precisely controlled by a programmable temperature controller; the carbonization temperature is 600-900℃, and the holding time is 1-4 h; the carbonization equipment is a tube furnace, and the furnace pressure is controlled at 0.1-0.15 MPa.

[0017] Preferably, in step S4, the KOH powder has a purity of ≥98% and a particle size of ≤100μm; the mixing equipment is a planetary ball mill with a ball-to-material ratio of 5:1-10:1, a rotation speed of 200-300rpm, and a mixing time of 1-2h; the inert gas flow rate during activation is 80-120mL / min.

[0018] Preferably, in step S5, the etching agent is: when the template agent is nano-sized... When etching, a 5-20 wt% HF solution is used, the etching temperature is 25-50℃, and the etching time is 6-12 hours; when the template agent is nano-sized... When etching, a 10-30 wt% KOH solution is used, the etching temperature is 40-80℃, and the etching time is 4-8h. Magnetic stirring is used during the etching process, and the rotation speed is 200-300 rpm. The elution rate is detected by inductively coupled plasma optical emission spectroscopy (ICP-OES), and the residual amount of template agent is required to be ≤0.1 wt%.

[0019] Preferably, in step S6, the drying method is vacuum drying or spray drying, and the drying is carried out for 6-12 hours under the corresponding process conditions to obtain porous carbon silicon-carbon anode substrate with a moisture content of 30%-70%; the moisture content of the dried product is detected by a Karl Fischer moisture analyzer and is required to be ≤0.5%.

[0020] Preferably, the porous carbon has a hierarchical porous structure, with micropores (<2nm) accounting for 35-55%, mesopores (2-50nm) accounting for 30-45%, and macropores (>50nm) accounting for 10-20%; the specific surface area is 1000-3500m² / g (BET method detection), the pore volume is 0.8-2.5cm³ / g (BJH method detection), and the resistivity is... (Detected using the four-probe method), electrolyte contact angle ≤30° (detected using a contact angle measuring instrument).

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. Significant benefits of resource recycling and environmental protection: Using waste PE plastic as a carbon source, it realizes "turning waste into treasure". Every 1 ton of waste PE can produce 0.3-0.4 tons of porous carbon products, with a solid waste reduction rate of ≥60%, effectively solving the white pollution problem caused by PE waste; the cost of carbon source is 70-80% lower than that of traditional phenolic resin, which significantly reduces the preparation cost of porous carbon.

[0023] Template elution process is safe and environmentally friendly, nano The template is etched using KOH solution, avoiding the strong corrosiveness and toxicity of HF solution, significantly reducing operational risks; the washing wastewater, after neutralization and precipitation (neutralizing KOH with acid and precipitating residual metal ions with fluoride), has COD ≤ 50 mg / L and ammonia nitrogen ≤ 5 mg / L, and can be directly discharged in compliance with standards; the etching process generates... The solution can be adjusted to pH 8-9 by adding acid to induce precipitation. The precipitate, after recovery, can be used to prepare nanoparticles. Templates enable resource recycling;

[0024] The process produces no toxic or harmful gases; the carbonization and activation processes are carried out under an inert atmosphere, and the exhaust gas is mainly... , Combustible gases can be collected and burned for reuse, achieving energy recovery; free of dioxins, It produces toxic and harmful gases, but is environmentally friendly.

[0025] 2. Outstanding technological advantages and easy to scale up production: The process steps are simple and controllable. Pretreatment, template adsorption, carbonization, elution, drying and other steps are all mature chemical unit operations, which do not require complex special equipment. Moreover, the parameters of each step can be monitored and controlled in real time by conventional testing instruments (laser particle size analyzer, ICP-OES, Karl Fischer moisture analyzer, etc.), and the product quality is highly stable (the coefficient of variation of specific surface area between batches is ≤5%).

[0026] It can achieve continuous production, using a continuous tubular furnace (10-15m in length, 500-800mm in inner diameter) to achieve continuous carbonization and activation; the washing process uses an automatic plate and frame filter, and the drying process uses a belt vacuum dryer, which can build a complete continuous production line. The annual capacity of a single production line can reach 500-1000 tons, meeting the needs of industrial applications.

[0027] High template elution efficiency, nano The template elution rate is ≥99%, which is much higher than the 60-65% of traditional SiO2 templates. The product purity is ≥99%, eliminating the need for additional purification steps and reducing process complexity and production costs.

[0028] 3. Excellent product performance and wide range of applications: The pore structure is highly controllable. By adjusting the type, particle size, ratio, and carbonization / activation parameters of the template agent, the "micropore-mesopore-macropore" ratio of porous carbon can be precisely customized (micropores 35-55%, mesopores 30-45%, macropores 10-20%) to meet the needs of different application scenarios. The specific surface area can reach 1000-3500m² / g, and the pore volume is 0.8-2.5cm³ / g, which is at the leading level in the industry.

[0029] Excellent core performance, porous carbon resistivity It exhibits good electrical conductivity; the electrolyte contact angle is ≤30°, and it has excellent wettability. When used as a silicon-carbon anode substrate, it can effectively alleviate the volume expansion of silicon after being combined with silicon-based materials, achieving an initial discharge capacity ≥1100mAh / g and a capacity retention rate ≥80% after 500 cycles, meeting the requirements of high-performance lithium-ion batteries; when used as a sodium-ion battery anode, it achieves an initial discharge capacity ≥450mAh / g and a capacity retention rate ≥75% after 300 cycles.

[0030] 4. Diverse application areas: In addition to silicon-carbon anodes, it can also be widely used in supercapacitors (specific capacitance ≥200F / g at a current density of 1A / g), water treatment adsorption (for... (Adsorption capacity ≥120 mg / g, adsorption capacity for methyl orange ≥150 mg / g) It has broad market application prospects in fields such as capture (adsorption capacity ≥4.5mmol / g at 25℃ and 1bar) and catalyst support (metal nanoparticle loading and dispersibility ≥90%). Attached Figure Description

[0031] Figure 1 This is a process flow diagram for preparing porous carbon as the silicon-carbon anode substrate of the present invention. Detailed Implementation

[0032] A method for preparing porous carbon as a silicon-carbon anode substrate includes the following steps:

[0033] S1: Raw material pretreatment: After cleaning and drying, the PE raw material is crushed to a particle size of 50-200μm to obtain PE pretreated material;

[0034] S2: Template adsorption: The nano-oxide template agent is dispersed in toluene solvent, ultrasonically dispersed, and then the PE pretreated material or oligomeric PE is added. After stirring and adsorption, the template-oligomeric PE composite solid is obtained by separation.

[0035] S3: High-temperature carbonization: The composite solid is placed in an inert atmosphere and heated to 600-900℃ at a set heating rate and held for 1-4 hours to obtain a carbon-template composite.

[0036] S4: Optional chemical activation: Mix the carbon-template composite with KOH powder at a mass ratio of 1:2-1:4, heat to 700-900℃ at 2-5℃ / min under an inert atmosphere, and keep warm for 1-3h;

[0037] S5: Template elution: Immerse the carbonized or activated product in an etchant to remove the template agent, then wash with deionized water until pH 6.5-7.5.

[0038] S6: Drying treatment: Dry the washed product at 80-120℃ for 6-12h to obtain porous carbon silicon-carbon anode substrate.

[0039] In step S1, the PE raw material is low-density PE (LDPE, crystallinity 30-50%), high-density PE (HDPE, crystallinity 70-90%), or waste PE plastic;

[0040] The cleaning method is as follows: Take PE raw materials (LDPE, HDPE or waste PE plastic), and select 5-10wt% sodium hydroxide solution as the cleaning agent according to the degree of contamination of the raw materials. Ultrasonic cleaning is carried out at 40-60℃ for 15-30 minutes (ultrasonic power 100-200W). The saponification effect of the alkaline solution removes oil, dust and other organic and inorganic impurities from the surface of the raw materials. Then, it is repeatedly washed with deionized water until neutral (pH 6.5-7.5) to remove residual alkaline solution and avoid the influence of impurities on the pore structure in subsequent processes.

[0041] Drying: Place the cleaned PE raw material in a forced-air drying oven at 60-80℃ and dry for 4-6 hours. Monitor the moisture content in real time using a Karl Fischer moisture analyzer to ensure that the moisture content is ≤1% after drying, so as to avoid moisture causing cracks or closed pores in the carbon skeleton during the carbonization process.

[0042] Pulverization: The dried PE raw material is fed into a high-speed air jet mill and pulverized to a particle size of 50-200μm. The particle size distribution is monitored in real time using a laser particle size analyzer to ensure uniformity (coefficient of variation ≤10%). The pulverized PE particles have an increased specific surface area, which can improve the contact area with the template agent and promote the uniformity of subsequent adsorption and compounding processes. At the same time, the pulverization process can destroy some of the crystalline structure of PE, which is beneficial to the breaking of molecular chains and the formation of carbon skeletons during pyrolysis.

[0043] Core objective: To improve the purity and dispersibility of raw materials, laying the foundation for subsequent compounding and carbonization.

[0044] In step S2, the nano-oxide template agent is a nano-sized particle with a diameter of 30-100 nm. Or 50-150nm nanometers The purity is ≥99.5%; the number average molecular weight of oligomeric PE is 1000-5000, and the mass-to-volume ratio of oligomeric PE to toluene is 10-50 g / L;

[0045] Template dispersion: Nano-oxide template agent was added to toluene solvent to prepare a dispersion with a template concentration of 10-30 g / L. The dispersion was then placed in an ultrasonic cleaner and ultrasonically dispersed for 10-30 min at 100-300 W and 20-40 kHz. The cavitation effect of ultrasound broke the van der Waals forces between template agent particles, ensuring uniform dispersion and preventing agglomeration (TEM observation showed agglomerate particle size ≤500 nm). The particle size selection of the template agent directly determines the pore size of the subsequent porous carbon: nano-... When the particle size is 30-60 nm, the proportion of micropores in porous carbon is higher; when the particle size is 60-100 nm, the proportion of mesopores increases; nano-sized particles... When the particle size is 50-80nm, the proportion of mesopores is optimal; when the particle size is 80-150nm, the proportion of macropores increases.

[0046] Composite adsorption: Oligomeric PE (number average molecular weight 1000-5000) or the above-mentioned PE pretreatment material was added to the template dispersion, and the mass ratio of nano-oxide to PE was strictly controlled at 1:1-1:5 (after optimization, the pore structure was most uniform when the mass ratio was 1:2). The mixture was placed in a constant temperature water bath and stirred at 300-500 rpm for 2-8 hours at 25-60℃. The control logic of temperature and speed was as follows: low temperature (25-30℃) is suitable for the adsorption of oligomeric PE, which can avoid excessive dissolution of PE and agglomeration; medium and high temperature (40-60℃) is suitable for the adsorption of PE pretreatment material, which can promote the dissolution of PE particle surface and adsorption combination with template surface. The changes of functional groups on template surface before and after adsorption (the CH stretching vibration peak of PE appears and is enhanced) were detected by infrared spectroscopy (FT-IR) to confirm the adsorption effect.

[0047] Solid-liquid separation: The mixed system is separated by vacuum filtration (filter membrane pore size 0.22-0.45μm) or centrifugation (5000-8000rpm, time 10-20min), and the solid product is collected; the unadsorbed free PE is removed by washing with a small amount of toluene 2-3 times to obtain a template-oligomeric PE composite solid with high purity;

[0048] Core objective: To achieve uniform compounding of template agent and PE, providing a foundation for subsequent replication of pore structure.

[0049] In step S3, the inert atmosphere is argon or nitrogen with a purity ≥99.99%, and the gas flow rate is 50-100 mL / min; the heating rate is 2-10℃ / min, precisely controlled by a programmed temperature controller; the carbonization temperature is 600-900℃, and the holding time is 1-4 h; the carbonization equipment is a tube furnace, and the furnace pressure is controlled at 0.1-0.15 MPa.

[0050] Furnace loading: Evenly spread the template-oligomeric PE composite solid in the quartz boat, with a material thickness of ≤1cm, to avoid uneven heat transfer during carbonization and resulting in insufficient local carbonization; place the quartz boat in the constant temperature zone of the tube furnace to ensure that the material is completely in a temperature uniform zone.

[0051] Atmosphere control: Introduce argon or nitrogen gas with a purity of ≥99.99% into the tube furnace, and control the gas flow rate at 50-100 mL / min. Replace the air in the furnace 3-5 times (each replacement time ≥5 min). Detect the oxygen content in the furnace using an oxygen content detector to ensure it is ≤0.1% to prevent oxygen from causing PE oxidation and combustion, which would reduce the carbon yield.

[0052] Carbonization reaction: A precise temperature rise program is set using a programmed temperature controller, increasing the temperature to 600-900℃ at a rate of 2-10℃ / min, and holding at that temperature for 1-4 hours. The carbonization process consists of three key stages, and the reaction characteristics and control requirements for each stage are as follows:

[0053] Low temperature stage (300-400℃): PE molecular chains undergo thermally induced breakage, generating small molecule intermediates such as olefins and alkanes. During this stage, the heating rate needs to be controlled to ≤5℃ / min to ensure that the small molecule intermediates volatilize slowly and avoid violent gas production that could lead to the rupture of the carbon skeleton.

[0054] Intermediate temperature stage (400-600℃): Small molecule intermediates further decompose and volatilize. , , Small molecule gases (the components of the exhaust gas were detected by gas chromatography-GC to confirm complete volatilization), and the carbon skeleton was initially formed;

[0055] High temperature stage (above 600℃): The residual carbon skeleton gradually graphitizes, forming a stable carbon-template composite. The degree of graphitization increases with increasing temperature (the degree of graphitization is 30-40% at 700-800℃, and the conductivity and structural stability reach a balance).

[0056] Cooling: After carbonization, keep the inert gas continuously flowing in and allow it to cool naturally to room temperature (cooling rate ≤10℃ / min) to avoid sudden temperature changes that could cause thermal stress concentration in the carbon skeleton and lead to structural collapse or cracks.

[0057] Core objective: To achieve the pyrolysis and carbonization of PE, forming a carbon-template composite, and laying the foundation for a porous carbon skeleton.

[0058] In step S4, the KOH powder has a purity of ≥98% and a particle size of ≤100μm; the mixing equipment is a planetary ball mill with a ball-to-powder ratio of 5:1-10:1, a rotation speed of 200-300rpm, and a mixing time of 1-2h; the inert gas flow rate during activation is 80-120mL / min.

[0059] Mixing: Add the carbon-template composite and KOH powder to a planetary ball mill at a mass ratio of 1:2-1:4, add agate balls, and mix at 200-300 rpm for 1-2 hours to ensure that the KOH powder is uniformly dispersed on the surface and in the pores of the carbon-template composite. The purpose of controlling the KOH particle size is to avoid local over-etching caused by large KOH particles;

[0060] Activation reaction: The mixture is placed in a tube furnace, inert gas is introduced, and the temperature is raised to 700-900℃ at a rate of 2-5℃ / min, and held for 1-3 hours. During the activation process, KOH undergoes a multi-step concerted reaction with carbon: First, KOH decomposes at high temperature to produce… and Subsequently, It reacts with carbon to produce K and CO ( ↑); simultaneously, KOH reacts directly with carbon to produce K, and , Further decomposed into and The gases produced by these reactions ( K will have an "etching" effect on the carbon skeleton, expanding the pore size of existing pores; at the same time, K penetrates into the interior of the carbon skeleton at high temperature, and is removed by washing after cooling, forming new micropores and mesopores, thereby significantly improving the specific surface area and pore volume of porous carbon.

[0061] Cooling: After activation, keep the inert gas flowing in and allow it to cool naturally to room temperature to avoid sudden temperature changes that could damage the pore structure;

[0062] Core objective: To further optimize the pore structure, increase specific surface area and pore volume, and make it suitable for high-performance application scenarios.

[0063] In step S5, etching: Select a suitable etchant based on the template type, and use magnetic stirring (200-300 rpm) to assist etching and improve etching uniformity.

[0064] nanometer For the etching agent: Use a 5-20 wt% HF solution as the etching agent, and etch at 25-50℃ for 6-12 hours. The etching reaction is as follows: Real-time monitoring of the solution using ICP-OES When the concentration change rate is ≤1% / h, the etching is considered complete, ensuring that the template is completely removed.

[0065] nanometer As a template agent: Use a 10-30 wt% KOH solution as the etching agent, and etch at 40-80℃ for 4-8 hours. The etching reaction is as follows: +2KOH→ . It is readily soluble in water, eliminating the need for toxic HF solutions and significantly improving operational safety; simultaneously, its etching efficiency is higher than... With a template thickness of over 35%, the template washing rate can reach 99.2-99.8%.

[0066] Washing: After etching, wash the product with plenty of deionized water until the pH reaches 6.5-7.5 to remove residual etching agent and reaction products. For products activated with KOH, soak them in a 5-10 wt% HCl solution for 1-2 hours to neutralize residual KOH and dissolve the generated potassium salts (such as...). The product is then washed with deionized water until neutral. The residual amount of alkali metal ions in the washed product is detected by atomic absorption spectrometry (AAS), and is required to be ≤0.1wt% to avoid residual ions affecting the conductivity and chemical stability of porous carbon.

[0067] Core objective: To efficiently remove template agents, form the target porous structure, and ensure product purity.

[0068] In step S6, the drying method is vacuum drying or spray drying, and drying is carried out for 6-12 hours under the corresponding process conditions to obtain porous carbon silicon-carbon anode substrate with a moisture content of 30%-70%. The moisture content of the dried product is detected by a Karl Fischer moisture analyzer and is required to be ≤0.5%.

[0069] Vacuum drying: Suitable for small-scale production or applications requiring precise product form. Process conditions are: vacuum degree -0.08~-0.1MPa, drying temperature 80-120℃, drying time 6-12h. The vacuum environment lowers the boiling point of moisture evaporation, prevents slight collapse of the pore structure due to high temperatures, and ensures uniform moisture removal with precise control of the moisture content between 30% and 70%.

[0070] Spray drying: Suitable for large-scale continuous production. Process conditions are: inlet air temperature 120-180℃, outlet air temperature 60-90℃, atomization pressure 0.3-0.6MPa, drying time 2-4h (continuous). Spray drying disperses materials into tiny droplets through an atomizer, allowing them to quickly contact the hot airflow for efficient drying. The product is a uniform powder, and the moisture content can be precisely controlled between 30%-70% by adjusting the inlet air temperature and atomization pressure. Furthermore, its production efficiency is 3-5 times higher than vacuum drying.

[0071] After drying, the moisture content of the product is measured using a Karl Fischer moisture analyzer, and it must be ≤0.5%. The product is then sealed and stored away from light to prevent moisture absorption from affecting its subsequent application performance.

[0072] Core objective: To remove moisture from the product and ensure stable product performance.

[0073] Example 1: Using nanometers Porous carbon was prepared as a template (without activation).

[0074] 1. Raw material pretreatment: Take 10kg of waste PE shopping bags, ultrasonically clean them for 20min at 50℃ with 8wt% NaOH solution (power 150W), wash them with deionized water until pH 7.0, dry them with forced air at 70℃ for 5h (moisture content 0.8%), and pulverize them with high-speed airflow to a particle size of 100μm (detected by laser particle size analyzer, coefficient of variation 8%) to obtain PE pretreated material.

[0075] 2. Template adsorption: Take 5 kg of nanomaterials... (Particle size 50 nm, purity 99.8%) was added to 200 L of toluene to prepare a dispersion with a concentration of 25 g / L; ultrasonic dispersion was performed at 200 W and 30 kHz for 20 min (TEM observation showed no obvious agglomeration); 10 kg of PE pretreated material (template to PE mass ratio 1:2) was added, and the mixture was stirred at 50 °C and 400 rpm for 4 h for adsorption (FT-IR detection confirmed PE adsorption); vacuum filtration (0.45 μm filter membrane) was performed, and the mixture was washed three times with toluene to obtain... -PE composite solid.

[0076] 3. High-temperature carbonization: The composite solid is placed in a tube furnace, and 99.99% nitrogen gas (flow rate 80 mL / min) is introduced to replace the air in the furnace 4 times; the temperature is increased to 750℃ at a rate of 5℃ / min and held for 2 hours; it is then naturally cooled to room temperature (cooling rate 8℃ / min) to obtain carbon- Complex.

[0077] 4. Template elution: The complex was immersed in 10wt% HF solution and etched at 30℃ and 250rpm for 8 hours with stirring (ICP-OES detection). (Concentration stable); wash with deionized water until pH 7.0 to obtain the washing product.

[0078] 5. Drying treatment: Vacuum drying at 100℃ (-0.09MPa) for 8 hours, Karl Fischer analysis showed that the moisture content was 0.3%, and porous carbon product A was obtained.

[0079] Product A performance indicators: specific surface area 2200m² / g, pore volume 1.2cm³ / g, micropore ratio 45%, mesopore ratio 40%, macropore ratio 15%, resistivity The electrolyte contact angle was 28°, the template residue was 0.08 wt%, and the carbon yield was 32%.

[0080] Example 2: Using nanometers Porous carbon was prepared as a template (without activation).

[0081] 1. Raw material pretreatment: Same as in Example 1, to obtain PE pretreated material of the same specifications.

[0082] 2. Template adsorption: Take 5 kg of nanomaterials... (Particle size 80nm, purity 99.5%) was added to 200L of toluene to prepare a dispersion with a concentration of 25g / L; ultrasonic dispersion was performed at 200W and 30kHz for 20min; 10kg of PE pretreated material (template to PE mass ratio 1:2) was added, and the mixture was stirred and adsorbed at 50℃ and 400rpm for 4h; centrifuged at 8000rpm for 15min, and washed three times with toluene to obtain... -PE composite solid.

[0083] 3. High-temperature carbonization: Same as in Example 1, to obtain carbon- Complex.

[0084] 4. Template elution: The complex was immersed in 20wt% KOH solution and etched at 60℃ and 250rpm for 6 hours with stirring (ICP-OES detection). (Concentration stable); wash with deionized water until pH 7.0 to obtain the washing product.

[0085] 5. Drying treatment: Same as in Example 1, to obtain porous carbon product B.

[0086] Product B performance indicators: specific surface area 2350m² / g, pore volume 1.4cm³ / g, micropore ratio 42%, mesopore ratio 43%, macropore ratio 15%, resistivity The electrolyte contact angle is 25°, the template residue is 0.05wt%, and the carbon yield is 33%. The preparation process does not use HF, is safe to operate, and the cost is reduced by 30% compared to product A.

[0087] Example 3: Using nanometers Porous carbon (high specific surface area type) was prepared by template + KOH activation.

[0088] 1. Raw material pretreatment: Same as in Example 1, to obtain PE pretreated material of the same specifications.

[0089] 2. Template adsorption: Same as in Example 2, yielding... -PE composite solid.

[0090] 3. High-temperature carbonization: Same as in Example 1, to obtain carbon- Complex.

[0091] 4. Chemical activation: Carbon- The composite was mixed with KOH powder at a mass ratio of 1:3 (KOH purity 98%, particle size 80μm), and mixed in a planetary ball mill (ball-to-material ratio 8:1, 250rpm) for 1.5h; then placed in a tube furnace, heated to 800℃ at a nitrogen flow rate of 100mL / min and 3℃ / min, and held at that temperature for 2h; and then allowed to cool naturally to room temperature.

[0092] 5. Template elution: The activated product was first soaked in 8wt% HCl solution for 1.5h, and then washed with deionized water until neutral; then soaked in 20wt% KOH solution and etched by stirring at 60℃ and 250rpm for 6h; and washed with deionized water until pH 7.0 to obtain the washed product.

[0093] 6. Drying treatment: Same as in Example 1, to obtain porous carbon product C.

[0094] Product C performance indicators: specific surface area 2850m² / g, pore volume 2.1cm³ / g, micropore ratio 50%, mesopore ratio 38%, macropore ratio 12%, resistivity The electrolyte contact angle is 22°, the template residue is 0.03wt%, and the carbon yield is 35%. When used as a silicon-carbon anode substrate for lithium-ion batteries, it is combined with silicon-based materials at a mass ratio of 1:1, with an initial discharge capacity of 1200mAh / g and a capacity retention rate of 85% after 500 cycles.

[0095] Example 4: Different nanometers Effect of Particle Size on the Properties of Porous Carbon

[0096] 1. Raw material pretreatment: Same as in Example 1, to obtain PE pretreated material of the same specifications.

[0097] 2. Template adsorption: Take 5 kg of nanoparticles of different sizes respectively. (50nm, 80nm, and 120nm, all with a purity of 99.5%) were added to 200L of toluene and ultrasonically dispersed for 20min; 10kg of PE pretreated material (template to PE mass ratio 1:2) was added to each, and the mixture was stirred and adsorbed at 50℃ and 400rpm for 4h; after centrifugation and washing three times with toluene, particles of different sizes were obtained. -PE composite solid.

[0098] 3. High-temperature carbonization-activation-elution-drying: Same as in Example 3, to obtain product D (50nm template), product E (80nm template), and product F (120nm template).

[0099] Product DF performance indicators:

[0100] Product Template particle size (nm) Specific surface area (m2 / g) Pore volume (cm3 / g) Micropore ratio (%) Mesopore ratio (%) Macropore ratio (%) Resistivity (x 10⁻ 4 Ω·m) D 50 3000 2.3 55 35 10 5.5 E 80 2850 2.1 50 38 12 5.0 F 120 2500 1.8 40 42 18 6.0

[0101] Example 5: Effect of different KOH activation ratios on the properties of porous carbon

[0102] 1. Raw material pretreatment: Same as in Example 1, to obtain PE pretreated material of the same specifications.

[0103] 2. Template adsorption: Same as in Example 2, yielding... -PE composite solid, carbonized to obtain carbon- Complex.

[0104] 3. Chemical activation: Carbon- The complex was mixed with KOH powder at mass ratios of 1:2, 1:3, and 1:4, and the remaining activation conditions were the same as in Example 3, resulting in activated products with different activation ratios.

[0105] 4. Template elution-drying: Same as in Example 3, to obtain product G (1:2), product H (1:3), and product I (1:4).

[0106] Product GI performance metrics: Product KOH / carbon mass ratio Specific surface area (m2 / g) Pore volume (cm3 / g) Resistivity (x 10⁻ 4 Ω·m) First discharge capacity (mAh / g) Capacity retention rate after 500 cycles (%) G 1.2 2400 1.7 6.0 1050 82 H 1.3 2850 2.1 5.0 1200 85 I 1.4 2900 2.2 9.0 1100 78 Example 6: Preparation of porous carbon (high conductivity type) using HDPE as a carbon source

[0107] Raw material pretreatment: Take 10 kg of HDPE (80% crystallinity, 150,000 weight average molecular weight), ultrasonically clean it with 8 wt% NaOH solution at 50℃ for 20 min, wash it with deionized water until neutral, dry it with forced air at 70℃ for 5 h, and pulverize it with high-speed airflow to a particle size of 100 μm to obtain HDPE pretreated material.

[0108] Template adsorption-carbonization-activation-elution-drying: Same as in Example 3, to obtain porous carbon product J.

[0109] Product J performance indicators: specific surface area 2700m² / g, pore volume 1.9cm³ / g, micropore ratio 48%, mesopore ratio 39%, macropore ratio 13%, resistivity The electrolyte contact angle is 23°, the template residue is 0.04wt%, and the carbon yield is 38%. When used as a silicon-carbon anode substrate for lithium-ion batteries, the initial discharge capacity is 1180mAh / g, and the capacity retention rate is 88% after 500 cycles.

[0110] Example 7: Preparation of porous carbon (high specific surface area type) using LDPE as a carbon source

[0111] Raw material pretreatment: Take 10 kg of LDPE (40% crystallinity, 100,000 weight average molecular weight) and pretreat it according to the method in Example 6 to obtain LDPE pretreated material.

[0112] Template adsorption-carbonization-activation-elution-drying: Same as in Example 3, to obtain porous carbon product K.

[0113] Product K performance indicators: specific surface area 3000m² / g, pore volume 2.3cm³ / g, micropore ratio 52%, mesopore ratio 36%, macropore ratio 12%, resistivity 6×10⁻ 4 Ω・m, electrolyte contact angle 24°, template residue 0.03wt%, carbon yield 34%; when used as a supercapacitor electrode, specific capacitance is 220F / g at a current density of 1A / g.

[0114] In summary, the method for preparing porous carbon in silicon-carbon anode substrate solves the problems of high carbon source cost, low template elution efficiency, high operational risk, difficulty in pore structure control, and unstable product performance through the above steps.

Claims

1. A method for preparing porous carbon as a silicon-carbon anode substrate, characterized in that: Includes the following steps: S1: Raw material pretreatment: After cleaning and drying, the PE raw material is crushed to a particle size of 50-200μm to obtain PE pretreated material; S2: Template adsorption: The nano-oxide template agent is dispersed in toluene solvent, ultrasonically dispersed, and then the PE pretreated material or oligomeric PE is added. After stirring and adsorption, the template-oligomeric PE composite solid is obtained by separation. S3: High-temperature carbonization: The composite solid is placed in an inert atmosphere and heated to 600-900℃ at a set heating rate and held for 1-4 hours to obtain a carbon-template composite. S4: Optional chemical activation: Mix the carbon-template composite with KOH powder at a mass ratio of 1:2-1:4, heat to 700-900℃ at 2-5℃ / min under an inert atmosphere, and keep warm for 1-3h; S5: Template elution: Immerse the carbonized or activated product in an etchant to remove the template agent, then wash with deionized water until pH 6.5-7.

5. S6: Drying treatment: Dry the washed product at 80-120℃ for 6-12h to obtain porous carbon silicon-carbon anode substrate.

2. The method for preparing porous carbon as a silicon-carbon anode substrate according to claim 1, characterized in that: In step S1, the PE raw material is low-density PE (LDPE, crystallinity 30-50%), high-density PE (HDPE, crystallinity 70-90%), or waste PE plastic; the cleaning method is as follows: first, use 5-10wt% sodium hydroxide solution for ultrasonic cleaning for 15-30 minutes to remove oil stains, then wash with deionized water until neutral, the drying temperature is 60-80℃, and the drying time is 4-6 hours; the pulverizing equipment is a high-speed airflow pulverizer, and the particle size is detected by a laser particle size analyzer.

3. The method for preparing porous carbon as a silicon-carbon anode substrate according to claim 1, characterized in that: In step S2, the nano-oxide template agent is a nano-sized particle with a particle size of 30-100 nm. Or 50-150nm nanometers The purity is ≥99.5%; the number average molecular weight of oligomeric PE is 1000-5000, and the mass-to-volume ratio of oligomeric PE to toluene is 10-50 g / L; the ultrasonic dispersion power is 100-300 W, the frequency is 20-40 kHz, and the dispersion time is 10-30 min; the stirring speed is 300-500 rpm, the adsorption temperature is 25-60℃, and the adsorption time is 2-8 h; the separation method is vacuum filtration (filter membrane pore size 0.22-0.45 μm) or centrifugation (speed 5000-8000 rpm, time 10-20 min).

4. The method for preparing porous carbon as a silicon-carbon anode substrate according to claim 1, characterized in that: In step S3, the inert atmosphere is argon or nitrogen with a purity ≥99.99%, and the gas flow rate is 50-100 mL / min; the heating rate is 2-10℃ / min, precisely controlled by a programmed temperature controller; the carbonization temperature is 600-900℃, and the holding time is 1-4 h; the carbonization equipment is a tube furnace, and the furnace pressure is controlled at 0.1-0.15 MPa.

5. The method for preparing porous carbon as a silicon-carbon anode substrate according to claim 1, characterized in that: In step S4, the KOH powder has a purity of ≥98% and a particle size of ≤100μm; the mixing equipment is a planetary ball mill with a ball-to-material ratio of 5:1-10:1, a rotation speed of 200-300rpm, and a mixing time of 1-2h; the inert gas flow rate during the activation process is 80-120mL / min.

6. The method for preparing porous carbon as a silicon-carbon anode substrate according to claim 1, characterized in that: In step S5, the etching agent is: when the template agent is nano-sized... When etching, a 5-20 wt% HF solution is used, the etching temperature is 25-50℃, and the etching time is 6-12 hours; when the template agent is nano-sized... When etching, a 10-30 wt% KOH solution is used, the etching temperature is 40-80℃, and the etching time is 4-8h. Magnetic stirring is used during the etching process, and the rotation speed is 200-300 rpm. The elution rate is detected by inductively coupled plasma optical emission spectroscopy (ICP-OES), and the residual amount of template agent is required to be ≤0.1 wt%.

7. The method for preparing porous carbon as a silicon-carbon anode substrate according to claim 1, characterized in that: In step S6, the drying method is vacuum drying or spray drying, and the drying is carried out for 6-12 hours under the corresponding process conditions to obtain porous carbon silicon-carbon anode substrate with a moisture content of 30%-70%; the moisture content of the dried product is detected by a Karl Fischer moisture analyzer and is required to be ≤0.5%.

8. The method for preparing porous carbon as a silicon-carbon anode substrate according to claim 1, characterized in that: In step S6, the porous carbon has a hierarchical porous structure, with micropores (<2nm) accounting for 35-55%, mesopores (2-50nm) accounting for 30-45%, and macropores (>50nm) accounting for 10-20%; the specific surface area is 1000-3500m² / g (BET method detection), the pore volume is 0.8-2.5cm³ / g (BJH method detection), and the resistivity is... (Detected using the four-probe method), electrolyte contact angle ≤30° (detected using a contact angle measuring instrument).

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