CN113611843A - Biomass-based porous silicon-carbon composite material and preparation method thereof - Google Patents

Biomass-based porous silicon-carbon composite material and preparation method thereof Download PDF

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CN113611843A
CN113611843A CN202110862052.XA CN202110862052A CN113611843A CN 113611843 A CN113611843 A CN 113611843A CN 202110862052 A CN202110862052 A CN 202110862052A CN 113611843 A CN113611843 A CN 113611843A
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biomass
carbon composite
porous silicon
composite material
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CN113611843B (en
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侯佼
王兴蔚
侯春平
马勇
杨丹
贺超
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Bolt New Materials Yinchuan Co ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
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    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/20—Graphite
    • C01B32/205—Preparation
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/02—Silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention provides a biomass-based porous silicon-carbon composite material and a preparation method thereof, wherein the preparation process comprises the steps of kudzu root residue pretreatment, spray granulation, high-temperature carbonization, hydrothermal-in-situ polymerization coating, pyrolysis treatment and the like. According to the invention, the kudzu root residue micro powder has excellent cohesiveness and coating performance, and the obtained material has a three-dimensional carbon fiber skeleton structure by controlling the swelling degree and viscosity of the micro powder, so that the structure effectively buffers the volume expansion of the nano silicon material, shortens the diffusion path of lithium ions, improves the diffusion rate of the lithium ions, and improves the capacity and electrochemical performance of the electrode material.

Description

Biomass-based porous silicon-carbon composite material and preparation method thereof
Technical Field
The invention belongs to the field of novel energy materials, relates to a porous silicon-carbon composite material and a preparation method thereof, and particularly relates to a biomass-based porous silicon-carbon composite negative electrode material and a preparation method thereof.
Background
The lithium ion battery has the advantages of high working voltage, high energy density, no pollution, small self-discharge, long cycle life and the like, and is widely applied to the fields of energy storage and power batteries. The theoretical capacity of the conventional graphite negative electrode carbon material is only 372mAh & g-1The lithium iron phosphate lithium battery has low actual capacity and small tap density, so that the volume energy density of the electrode material is small, and the energy density of the commercial battery assembled by matching with the lithium iron phosphate, lithium manganate and other positive electrode materials is difficult to meet the increasing energy density requirement of the energy industry. In addition, it is easy to generate "lithium dendrite" during rapid charging and discharging process, resulting in potential safety hazard of the battery. And silicon-based materials due to their high 4200mAh g-1Theoretical capacity of about 0.4V, low voltage plateau (Li/Li)+) High safety, excellent low-temperature performanceAnd the material has the advantages of abundant natural storage and the like, and becomes a new-generation substitute for commercial negative electrode materials.
However, some problems in the application of silicon-based materials have prevented their commercial application. Firstly, in the process of charging and discharging, the silicon-based material can generate volume expansion and shrinkage as high as 300% during lithium insertion and lithium removal, so that silicon particles can be extruded and pulverized, effective active materials can fall off from a current collector, the electrode structure is damaged, further, the electric contact is lost, the initiation capacity is rapidly attenuated, and the cycling stability of the battery is poor. Secondly, the volume effect causes that a new and unstable SEI film is continuously formed on the fracture surface of the silicon-based material, thereby causing the problems of sudden increase of irreversible capacity, increase of internal resistance of the battery, reduction of coulombic efficiency, deterioration of conductivity and the like. Moreover, silicon is a semiconductor material, and its low conductivity and ionic diffusion coefficient reduce the diffusion kinetics of lithium ions. Therefore, the structure of the silicon-based material needs to be optimally designed to improve and enhance the performance thereof. The common modification method mainly reduces the volume change of silicon by nano-treatment of silicon, and constructs structures such as core-shell, yolk-shell, porous and the like by compounding the silicon and carbon-based materials with different structures to relieve the volume change and increase the conductivity of the materials so as to improve the cycle performance of the silicon-based materials.
In order to solve the problems of the existing silicon-carbon composite negative electrode material, it is necessary to develop a new biomass-based porous silicon-carbon composite material and a preparation method thereof.
Disclosure of Invention
The invention provides a biomass-based porous silicon-carbon composite material and a preparation method thereof aiming at the problems.
The invention adopts the kudzu root residue as the biomass base, aims at the problems of large residual amount, single treatment method, low additional value and the like of residues (epidermis, root hair, residues and the like) in the kudzu root industry, utilizes the characteristic that kudzu root residue powder swells and becomes sticky in water to form a three-dimensional porous carbon-based material, can be used as a binder, a thickening agent and a primary coating agent in the process of preparing a composite material, provides a biomass-based porous silicon-carbon composite negative electrode material prepared by reutilizing kudzu root residue resources and a method thereof, and the prepared silicon-carbon composite negative electrode material has the advantages of high capacity, high-rate charge and discharge performance, long cycle life, low production cost and the like. The method provides a brand new technical route for recycling the pueraria residues and solves the problem of the source of the novel power battery cathode electrode material.
According to the biomass-based porous silicon-carbon composite material, a three-dimensional porous silicon-carbon composite material prepared by uniformly dispersing and coating nano silicon powder on a partially graphitized thin coating carbon layer formed by carbohydrate and bridging a three-dimensional carbon fiber framework formed by plant fibers is used as a precursor, and a pyrolytic carbon layer subjected to hydrothermal in-situ secondary coating is coated outside the precursor. The pore diameter of the porous structure in the precursor is 50 nm-5 μm, the mass of the porous structure accounts for 50-60% of the mass of the precursor, and the mass of the secondary coating layer accounts for 5.0-15.0% of the mass of the precursor.
The biomass-based porous silicon-carbon composite material disclosed by the invention has the following structure: the core is nano silicon powder, a part of graphitized thin coating carbon layer formed by uniformly dispersing and coating carbohydrate outside the nano silicon powder, plant fibers are bridged between the nano silicon powder and the graphitized thin coating carbon layer to form a three-dimensional porous silicon-carbon composite material with a three-dimensional carbon fiber framework, and the outer layer of the three-dimensional porous silicon-carbon composite material is coated with a pyrolytic carbon layer secondarily.
Specifically, the size of the nano silicon particles is 30-100 nm, and the mass of the nano silicon particles accounts for 5-30% of the mass of the three-dimensional porous silicon-carbon composite material;
the pore diameter of the porous structure of the graphitized thin coating carbon layer is 50 nm-5 μm, and the mass of the porous structure accounts for 50% -60% of the mass of the precursor;
the thickness of the secondary coating pyrolytic carbon layer is 5 nm-15 nm, and the mass of the secondary coating pyrolytic carbon layer is 5.0% -15.0% of the mass of the precursor.
The invention provides a method for preparing a porous silicon-carbon composite cathode material by forming a biomass-based porous carbon material from pueraria residues, which is characterized in that epidermis, root hairs and process residues remained during the production of pueraria powder are taken as raw materials, residue micro powder with high purity is obtained by cleaning, crushing, purifying and drying, the residue micro powder and nano silicon powder are uniformly dispersed under the action of an alcohol solvent, stirring and heating are carried out, the swelling degree and viscosity of the pueraria residue micro powder are controlled by regulating and controlling the temperature, then a porous silicon-carbon composite precursor is prepared by spray granulation, high-temperature pyrolysis and crushing screening treatment, and the in-vitro precursor is subjected to hydrothermal in-situ secondary organic coating and pyrolysis treatment to finally obtain the biomass-based porous silicon-carbon composite cathode material.
The invention provides a preparation method of a biomass-based porous silicon-carbon composite material, which comprises the following specific steps:
firstly, preparing biomass-based porous silicon-carbon composite precursor (p-C/Si)
S1 pretreatment of kudzu root residue: cleaning the kudzu root residue at room temperature, crushing the kudzu root residue into micro powder particles with the particle size of 3-5 mu m, further cleaning and purifying the crushed kudzu root residue powder, and fully drying to obtain pure kudzu root residue micro powder;
specifically, at room temperature, the kudzu root residue is stirred and cleaned by using a detergent as a cleaning agent to remove sand on the surface and residual impurities inside, then the kudzu root residue is crushed into micro powder particles with the particle size of 3-5 mu m, the crushed kudzu root residue powder is further cleaned and purified in an aqueous solution by using a purifying device, and under the condition that a certain drying temperature and drying time can be designed by a person skilled in the art, the kudzu root residue micro powder is fully dried, for example, a blast oven at the temperature of 80-100 ℃ is used for drying for 12-24 hours, so that pure kudzu root residue micro powder is obtained;
in the step, the pueraria residue is one or more of epidermis, root hair and production residue which are remained when the pueraria product is produced;
the crushing mode is any one of mechanical crushing, air flow crushing and grinding crushing, and the equipment can be selected from a mechanical crusher, a roller mill, an air flow crusher, a grinder and the like;
the purification mode is one of natural sedimentation, filtration and centrifugation, and the equipment can be selected from a vacuum suction filter, a pressure filter, a centrifuge, a vortex separator, a belt press filter, a dehydrator and the like;
in the step, some surface layers and internal impurities in the pueraria residues are removed so as to prevent the impurities from influencing the performance of the electrode material. The residues are crushed into micro powder particles, so that not only can purification treatment be better carried out to obtain pure raw materials, but also the micro powder particles can be more fully heated, swollen and sticky in the later period, and a stable and effective three-dimensional porous structure carbon-based material is formed. The purification is to remove some suspended impurities in the micro powder in the grinding process to obtain pure residue micro powder particles with the impurity content of less than 1%.
S2 spray granulation: mixing the kudzu root residue micro powder and the nano silicon powder according to the mass ratio of 100: (5.0-30.0) dispersing in an alcohol solvent solution for liquid-phase mechanical mixing, then stirring and heating the mixed slurry in heating equipment, adjusting the temperature to control the swelling performance of the radix puerariae residue powder to adjust the viscosity of the slurry, and then performing spray granulation to obtain a biomass-based porous silicon-carbon composite sample;
in the step, the nano silicon powder is silicon powder particles with the particle size of 30-100 nm;
the alcohol solvent is one or more of methanol, ethanol and isopropanol;
the mass fraction of the mixture in the slurry is 10-40%;
the liquid phase mixing speed is 200-1500 r/min, and the stirring time is 30-120 min;
the stirring and heating equipment is one of a magnetic stirrer, a constant-temperature oil bath kettle and a constant-temperature water bath kettle;
the heating temperature range is 50-120 ℃, and the stirring speed is 500-800 r/min;
heating and stirring the mixed slurry, and obtaining the mixed slurry with the viscosity of 1000-1500cP after the radix puerariae residue micro powder is fully swelled;
the inlet temperature of the spray dryer is 180-260 ℃, and the outlet temperature is 120-160 ℃;
the feeding speed of spray drying is 10 ml/min-50 ml/min;
the three-dimensional porous carbon-based material is formed by utilizing the swelling and viscosity change of the radix puerariae micro powder, the characteristics of the material which can be used as a binder, a thickening agent and a primary coating agent in the process of preparing the composite material are omitted, the nano silicon powder is directly coated and structurally treated by taking the micro powder as the binder and the coating agent, and the biomass-based porous silicon-carbon composite sample with swelling holes is obtained through spray granulation.
S3 high-temperature carbonization: placing the biomass-based porous silicon-carbon composite sample in a high-temperature atmosphere furnace, carrying out pyrolysis treatment in a protective gas atmosphere, after pyrolysis is finished, and crushing the material to obtain a biomass-based porous silicon-carbon composite precursor (p-C/Si); after being crushed, the biomass-based porous silicon-carbon composite precursor is screened by a fine screen, and the uniformity of the obtained biomass-based porous silicon-carbon composite precursor is better, such as a 150-mesh screen, a 200-mesh screen, a 250-mesh screen and the like;
in this step, the protective gas is one or more of nitrogen, helium, neon, argon, krypton, or xenon. The flow rate is 0.5L/min-10L/min;
the pyrolysis treatment is carried out, the temperature rising speed is 2 ℃/min to 5 ℃/min, the pyrolysis temperature is 600 ℃ to 1100 ℃, and the pyrolysis carbonization time is 2h to 5 h;
in the step, under the conditions of protective atmosphere and high temperature, disordered fibers are distributed in the residue micro powder and are connected with each other to form a three-dimensional carbon fiber skeleton structure; and the carbohydrate forms a thin partially graphitized coating layer to dispersedly coat the nano silicon powder and bridge a three-dimensional carbon fiber skeleton structure to form a three-dimensional porous structure biomass silicon carbon composite precursor.
Secondly, preparing the biomass-based porous silicon-carbon composite material (p-C/Si/C)
S4 hydrothermal-in situ polymerization coating: mixing the prepared biomass-based porous silicon-carbon composite precursor and an organic carbon source according to the mass ratio of 1: (1.0-3.0) uniformly mixing, ultrasonically dispersing in water, performing secondary carbon coating in a hydrothermal reaction kettle through hydrothermal-in-situ polymerization, centrifuging, washing and drying the mixture solution to obtain a secondary coated composite material;
in the step, the solid-liquid mass ratio of the mixture of the biomass-based porous silicon-carbon composite precursor and the organic carbon source to water is (1.0-2.0): (20-40);
the organic carbon source is one or more of glucose, sucrose, polyethylene glycol, carboxymethyl cellulose, water-soluble phenolic resin and polyvinyl alcohol;
the temperature of the hydrothermal-in-situ polymerization is 150-200 ℃, and the polymerization time is 12-24 h;
in the step, the organic carbon source is uniformly coated on the surface layer of the precursor for the second time by a hydrothermal-in-situ polymerization method, so that the secondary coated composite material is obtained.
S5 pyrolysis treatment: placing the obtained secondary coating composite material in a high-temperature atmosphere furnace, carrying out pyrolysis carbonization in protective gas atmosphere, and crushing after the material is cooled to obtain a biomass-based porous silicon-carbon composite material (p-C/Si/C); pulverizing, and sieving with fine sieve to obtain material with good uniformity, such as 150 mesh sieve, 200 mesh sieve, 250 mesh sieve, etc.;
in the step, the protective gas is one of nitrogen and argon, and the flow rate is 0.5L/min-10L/min;
carrying out pyrolysis treatment, wherein the heating rate is 2-5 ℃/min, the pyrolysis temperature is 500-1000 ℃, and the constant-temperature pyrolysis time is 2-4 h;
in the step, under the protective atmosphere and high temperature, the organic carbon source coating layer is carbonized into a secondary carbon coating layer which is coated on the surface layer of the precursor, and the final biomass-based porous silicon-carbon composite material is obtained.
Further, the biomass-based porous silicon-carbon composite material is a lithium ion battery cathode material.
The method takes the kudzu root residue and the nano silicon powder which are low in utilization rate, small in added value and low in price as raw materials, utilizes the characteristics that the kudzu root residue powder can swell and become sticky to generate a pore structure along with the rise of temperature in an aqueous solution and has excellent bonding and coating properties to uniformly disperse and coat the nano silicon powder, and prepares the biomass-based porous silicon-carbon composite material after spray granulation and hydrothermal in-situ secondary carbon coating. The three-dimensional carbon fiber skeleton formed by sintering the disorderly distributed plant fibers in the pueraria lobata residue not only provides a buffer space for volume expansion of the nano silicon material in the charge-discharge cycle process to protect the integrity of an electrode, but also shortens the diffusion path of lithium ions to improve the diffusion rate of the lithium ions, and improves the capacity and the electrochemical performance of the material through micropore lithium storage and excellent liquid absorption performance. The carbohydrate forms a thin partially graphitized coating layer to dispersedly coat the nano silicon powder and bridge a three-dimensional carbon fiber skeleton structure to form a three-dimensional porous structure precursor, so that the nano silicon in the precursor material is protected from being in contact with an electrolyte to generate a side reaction, and the conductivity of the electrode material is increased to improve the capacity and the rate cycle performance of the material. The carbon coating layer coated outside the precursor for the second time can not only further buffer the volume effect of the nano silicon material in the charge-discharge cycle process, prevent the stripping and falling of the electrode, but also reduce the electrochemical resistance and the specific surface area of the precursor to improve the electrochemical performance and the machining performance of the electrode material. The method not only provides a brand new technical route for recycling the pueraria residues, but also solves the problem of the source of the novel power battery silicon-carbon cathode electrode material.
The invention has the following beneficial effects:
1) the invention takes the residual epidermis, root hair and process residues in the production of the kudzu root powder as the raw materials for preparing the biomass-based porous silicon-carbon composite material, and the raw materials are low in price. The mechanical processing property and the electrochemical property of the prepared composite material can meet the requirements of electrode materials of power batteries.
2) The invention not only provides a brand new technical route for recycling the pueraria residues, but also explores a new raw material and a preparation method for a novel power battery silicon-carbon composite negative electrode material.
3) The kudzu root residue micro powder has excellent cohesiveness and coating performance, the swelling of the micro powder can be controlled by adjusting the heating temperature, the viscosity of the slurry is further controlled, and finally the nano silicon is dispersed and coated to form a three-dimensional porous structure precursor. In the preparation process, the residue micropowder of radix Puerariae can be used as binder, thickener and primary coating agent, and the addition of related adjuvants is omitted.
4) The method is characterized in that disordered fibers distributed in the pueraria lobata residue micropowder are connected with one another to form a three-dimensional carbon fiber skeleton structure, wherein carbohydrates form a thin partially graphitized coating layer to disperse and coat the nano silicon powder and bridge the three-dimensional carbon fiber skeleton to construct a three-dimensional porous structure. The structure effectively buffers the volume expansion of the nano silicon material, shortens the diffusion path of lithium ions, improves the diffusion rate of the lithium ions, and improves the capacity and the electrochemical performance of the electrode material through microporous lithium storage and excellent liquid absorption performance.
The preparation method provided by the invention is simple, the process is easy to control, and the material cost is low.
Drawings
FIG. 1 is an X-ray diffraction pattern of the composite material p-C/Si/C obtained in example 3,
FIG. 2 is an SEM image (1 μm) of a sample after the fine powder of the kudzu root residue is swollen and carbonized,
FIG. 3 is an SEM image (500nm) of the sample after the fine powder of the kudzu root residue is swelled and carbonized,
FIG. 4 is an SEM photograph of the composite p-C/Si/C prepared in example 3,
FIG. 5 is a TEM image of the composite p-C/Si/C obtained in example 3.
Detailed Description
The above embodiments are further described in detail with reference to the following examples and the accompanying drawings:
for the characterization of the inventive examples, the prepared materials were characterized by their composition and structure by means of an X-ray diffractometer (SmartLab, Japan science) under irradiation with Cu Ka at a scanning speed of 10 °/min. The morphology of the electrode material was observed with a scanning electron microscope (SEM; Verios G4 UC, FEI, USA) and a transmission electron microscope (TEM; Talos 200F, FEI, USA). The specific surface area of the electrode material was determined with a dynamic nitrogen adsorption surface analyzer (JW-DX, microscopical gaobo, china).
The electrode materials obtained in the examples and the comparative examples are used for half-cell tests, the electrode materials, the conductive agent carbon black SP and the binder PVDF are prepared into slurry according to the mass ratio of 85:7:8 to coat pole pieces, a metal lithium piece is used as a comparative electrode, HR-8315 type electrolyte of Shandong Haichong power supply materials GmbH is used as electrolyte, Celgard 2400 is used as a diaphragm, and a CR2025 button experimental cell is prepared in a German Braun MBRAUN glove box protected by high-purity argon. The constant-current charging and discharging test is carried out by using a CT2001A type blue-spot battery test system of blue-electron GmbH in Wuhan City, and the charging and discharging voltage range is 0.003-2.0V (vs. Li)+Li), the first discharge capacity mAh/g of 0.1C is measured, and the first efficiency percent is respectively 0.1C. And (3) performing 1C charge-discharge cycle test after 3 weeks of charge-discharge activation at 0.2C and 0.5C respectively, measuring the discharge capacity mAh/g after 50 weeks of cycle, and calculating the capacity retention rate% after 50 weeks of cycle at 1C high magnification by using the ratio of the 1C discharge capacity at 50 weeks to the 1C discharge capacity at 1 week.
Example 1
The preparation method of the biomass-based porous silicon-carbon composite material comprises the following specific steps:
firstly, preparing biomass-based porous silicon-carbon composite precursor (p-C/Si)
S1 pretreatment of kudzu root residue: at room temperature, the surface of the pueraria lobata residue is stirred and cleaned by using a detergent as a cleaning agent to remove sand on the surface and residual impurities in the pueraria lobata residue, then the pueraria lobata residue is crushed into micropowder particles with the particle size of 3-5 mu m, the crushed pueraria lobata residue powder is further cleaned and purified in aqueous solution by using a purifying device, and the pueraria lobata residue micropowder is dried for 12 hours in a blast oven with the temperature of 100 ℃ to obtain pure pueraria lobata residue micropowder.
S2 spray granulation: 100g of kudzu root residue micro powder and 5g of 30nm silicon powder are weighed and dispersed in an ethanol solution, the mass sum of the kudzu root residue micro powder and the nano silicon powder is 10 percent of the sum of the kudzu root residue micro powder, the nano silicon powder and a solvent, and the mixture is mechanically mixed in a liquid phase for 120min at the rotating speed of 200 r/min. And transferring the mixed solution to a constant-temperature water bath kettle, stirring at the temperature of 50 ℃ and the rotating speed of 800r/min until the radix puerariae micropowder swells to obtain mixed slurry with the viscosity of 1000cP, spraying and granulating the uniformly mixed slurry at the inlet temperature of 260 ℃ and the outlet temperature of 120 ℃ at the feeding speed of 20ml/min to obtain the biomass-based porous silicon-carbon composite sample with swelling holes.
S3 high-temperature carbonization: placing the biomass-based porous silicon-carbon composite sample in a high-temperature atmosphere furnace, heating to 800 ℃ at the nitrogen flow rate of 5L/min at the heating rate of 2 ℃/min, carrying out pyrolysis treatment for 3h, naturally cooling to room temperature, crushing, and then sieving with a 250-mesh screen to obtain a biomass-based porous silicon-carbon composite precursor (p-C/Si), wherein the biomass-based porous silicon-carbon composite precursor (p-C/Si) is a thin partially graphitized coating layer, and is formed by dispersing and coating nano silicon powder and bridging a three-dimensional carbon fiber framework structure to form the three-dimensional porous structure biomass-based silicon-carbon composite precursor.
Secondly, preparing the biomass-based porous silicon-carbon composite material (p-C/Si/C)
S4 hydrothermal coating: mixing a biomass-based porous silicon-carbon composite precursor (p-C/Si) and sucrose according to a mass ratio of 1:1, adding the biomass-based porous silicon-carbon composite precursor (p-C/Si) and sucrose in a solid-liquid mass ratio of 1:20 into water, transferring the mixture into a hydrothermal reaction kettle after ultrasonic dispersion for 30min, polymerizing the mixture for 24h at 150 ℃, centrifuging, washing and drying the polymerized mixture to obtain the secondary coating composite material.
S5 pyrolysis treatment: and (3) placing the obtained secondary coating composite material in a high-temperature atmosphere furnace, heating to 800 ℃ at the heating rate of 2 ℃/min under the condition of nitrogen flow of 5L/min, carrying out pyrolysis treatment for 3h, naturally cooling to room temperature, crushing, and then sieving with a 250-mesh sieve to obtain the biomass-based porous silicon-carbon composite material (p-C/Si/C).
The size of the biomass-based porous silicon-carbon composite material (p-C/Si/C) nano silicon particles obtained in the embodiment is 30nm, and the mass of the nano silicon particles accounts for 5% of the mass of the three-dimensional porous silicon-carbon composite material;
the pore diameter of the porous structure of the graphitized thin coating carbon layer is 50 nm-2 μm, and the mass of the porous structure accounts for 60% of the mass of the precursor;
the thickness of the secondary coating pyrolytic carbon layer is 5-10 nm, and the mass of the secondary coating pyrolytic carbon layer is 5% of that of the precursor.
The composite sample prepared in example 1 was subjected to physical and chemical property tests. The specific surface area of the composite material powder is 37.47m2·g-1The tap density is 0.68g cm-1And the first discharge capacity at 0.1C was 432.1mAh g-1The first efficiency was 77.5%. Capacity retention of 210.5mAh g after 50 weeks of cycling at 1C high rate-1The capacity retention rate was 70.7%. The test results are summarized in Table 1.
Example 2
The preparation method of the biomass-based porous silicon-carbon composite material comprises the following specific steps:
firstly, preparing biomass-based porous silicon-carbon composite precursor (p-C/Si)
S1 pretreatment of kudzu root residue: stirring and cleaning the root hairs of the pueraria residues by using a detergent as a cleaning agent at room temperature to remove surface sand and internal residual impurities, then crushing to obtain micropowder particles with the particle size of 3-5 mu m, further cleaning and purifying the crushed pueraria residues in an aqueous solution by using a purifying device, and physically purifying and drying by using a vacuum pump filter to obtain pure pueraria residues micropowder.
S2 spray granulation: weighing 100g of radix Puerariae residue micropowder and 30g of 100nm silicon powder, dispersing in methanol solution, wherein the mass sum of radix Puerariae residue micropowder and nanometer silicon powder is 40% of the sum of radix Puerariae residue micropowder, nanometer silicon powder and solvent, and performing liquid-phase mechanical mixing at 600r/min for 110 min. And transferring the mixed solution to a constant-temperature water bath kettle, stirring at the temperature of 80 ℃ and the rotating speed of 700r/min until the radix puerariae micropowder swells to obtain mixed slurry with the viscosity of 1300cP, spraying and granulating the uniformly mixed slurry at the inlet temperature of 240 ℃ and the outlet temperature of 130 ℃ at the feeding speed of 30ml/min to obtain the biomass-based porous silicon-carbon composite sample with swelling holes.
S3 high-temperature carbonization: and placing the biomass-based porous silicon-carbon composite sample in a high-temperature atmosphere furnace, heating to 850 ℃ at the argon flow rate of 6L/min and at the heating rate of 3 ℃/min, carrying out pyrolysis treatment for 3.5h, naturally cooling to room temperature, crushing, and then passing through a 150-mesh screen to obtain a biomass-based porous silicon-carbon composite precursor (p-C/Si), wherein the biomass-based porous silicon-carbon composite precursor (p-C/Si) is a thin partially graphitized coating layer, and nano silicon powder is dispersedly coated and is bridged with a three-dimensional carbon fiber skeleton structure to form the three-dimensional porous structure biomass silicon-carbon composite precursor.
Secondly, preparing the biomass-based porous silicon-carbon composite material (p-C/Si/C)
S4 hydrothermal coating: mixing a biomass-based porous silicon-carbon composite precursor (p-C/Si) and glucose according to a mass ratio of 1: 1.5, adding the biomass-based porous silicon-carbon composite precursor (p-C/Si) and glucose into water, wherein the mass ratio of the solid to the liquid of the glucose to the water is 1:30, transferring the mixture into a hydrothermal reaction kettle for ultrasonic dispersion for 30min, polymerizing the mixture for 18h at 160 ℃, and obtaining the secondary coating composite material after centrifugation, washing and drying.
S5 pyrolysis treatment: and (3) placing the obtained secondary coating composite material in a high-temperature atmosphere furnace, heating to 850 ℃ at the argon flow rate of 6L/min at the heating rate of 3 ℃/min, carrying out pyrolysis treatment for 3.5h, naturally cooling to room temperature, crushing, and screening by using a 150-mesh screen to obtain the biomass-based porous silicon-carbon composite material (p-C/Si/C).
The size of the biomass-based porous silicon-carbon composite material (p-C/Si/C) nano silicon particles obtained in the embodiment is 100nm, and the mass of the nano silicon particles accounts for 30% of the mass of the three-dimensional porous silicon-carbon composite material;
the pore diameter of the porous structure of the graphitized thin coating carbon layer is 100 nm-5 μm, and the mass of the porous structure accounts for 50% of the mass of the precursor;
the thickness of the secondary coating pyrolytic carbon layer is 10-15 nm, and the mass of the secondary coating pyrolytic carbon layer is 8% of that of the precursor.
The composite sample prepared in example 2 was subjected to physical and chemical property tests. The specific surface area of the composite material powder is 38.96m2·g-1The tap density is 0.70g cm-1And the first discharge capacity at 0.1C was 1073.2mAh g-1The first efficiency was 73.3%. Capacity retention of 512.5mAh g after 50 weeks of cycling at 1C high rate-1The capacity retention rate was 63.5%. The test results are summarized in Table 1.
Example 3
The preparation method of the biomass-based porous silicon-carbon composite material comprises the following specific steps:
firstly, preparing biomass-based porous silicon-carbon composite precursor (p-C/Si)
S1 pretreatment of kudzu root residue: and at room temperature, stirring and cleaning residues in the process of the pueraria lobata residues by using a detergent as a cleaning agent to remove surface sand and internal residual impurities, then crushing the residues into micropowder particles with the particle size of 3-5 mu m, further cleaning and purifying the crushed pueraria lobata residues in an aqueous solution by using a purifying device, and physically purifying and drying by using a centrifuge to obtain pure pueraria lobata residues micropowder.
S2 spray granulation: 100g of kudzu root residue micro powder and 20g of 100nm silicon powder are weighed and dispersed in isopropanol solution, the mass sum of the kudzu root residue micro powder and the nano silicon powder is 35 percent of the sum of the kudzu root residue micro powder, the nano silicon powder and the solvent, and the mixture is subjected to liquid-phase mechanical mixing for 100min at the rotating speed of 700 r/min. And transferring the mixed solution to a magnetic stirrer, stirring at the temperature of 100 ℃ and the rotating speed of 800r/min until the radix puerariae micropowder swells to obtain mixed slurry with the viscosity of 1350cP, spraying and granulating the uniformly mixed slurry at the inlet temperature of 250 ℃ and the outlet temperature of 140 ℃ at the feeding speed of 40ml/min to obtain the biomass-based porous silicon-carbon composite sample with swelling holes.
S3 high-temperature carbonization: placing the biomass-based porous silicon-carbon composite sample in a high-temperature atmosphere furnace, heating to 900 ℃ at a nitrogen flow rate of 7L/min at a heating rate of 4 ℃/min, carrying out pyrolysis treatment for 4h, naturally cooling to room temperature, crushing, and then sieving with a 200-mesh screen to obtain a biomass-based porous silicon-carbon composite precursor (p-C/Si), wherein the biomass-based porous silicon-carbon composite precursor (p-C/Si) is a thin partially graphitized coating layer, and is formed by dispersing and coating nano silicon powder and bridging a three-dimensional carbon fiber skeleton structure to form the three-dimensional porous structure biomass-based silicon-carbon composite precursor.
Secondly, preparing the biomass-based porous silicon-carbon composite material (p-C/Si/C)
S4 hydrothermal coating: mixing a biomass-based porous silicon-carbon composite precursor (p-C/Si) and water-soluble phenolic resin according to a mass ratio of 1:2, adding the biomass-based porous silicon-carbon composite precursor (p-C/Si) and water-soluble phenolic resin into water, wherein the solid-liquid mass ratio of the water-soluble phenolic resin to the biomass-based porous silicon-carbon composite precursor (p-C/Si) is 1:20, ultrasonically dispersing for 30min, transferring the mixture into a hydrothermal reaction kettle, polymerizing for 16h at 170 ℃, centrifuging, washing and drying to obtain the secondary coating composite material.
S5 pyrolysis treatment: and (3) placing the obtained secondary coating composite material in a high-temperature atmosphere furnace, heating to 900 ℃ at the heating speed of 4 ℃/min under the condition that the flow of nitrogen is 7L/min, carrying out pyrolysis treatment for 4h, naturally cooling to room temperature, crushing, and screening by using a 200-mesh screen to obtain the biomass-based porous silicon-carbon composite material (p-C/Si/C).
The size of the biomass-based porous silicon-carbon composite material (p-C/Si/C) nano silicon particles obtained in the embodiment is 100nm, and the mass of the nano silicon particles accounts for 20% of the mass of the three-dimensional porous silicon-carbon composite material;
the pore diameter of the porous structure of the graphitized thin coating carbon layer is 100 nm-5 μm, and the mass of the porous structure accounts for 60% of the mass of the precursor;
the thickness of the secondary coating pyrolytic carbon layer is 12-14 nm, and the mass of the secondary coating pyrolytic carbon layer is 12% of that of the precursor.
The composite sample prepared in example 3 was subjected to physical and chemical property tests. The specific surface area of the composite material powder is 30.72m2·g-1The tap density is 0.75g cm-1And the first discharge capacity at 0.1C was 739.8mAh g-1The first efficiency was 78.8%. Capacity retention of 411.7mAh g after 50 weeks of cycling at a high rate of 1C-1The capacity retention rate was 75.2%. The test results are summarized in Table 1.
As shown in FIG. 1, the X-ray diffraction pattern of the composite material p-C/Si/C obtained in example 3, by comparison with the corresponding standard PDF card, revealed that the diffraction peaks observed at around 23.2 ℃ and 43.5 ℃ correspond to the (002) and (101) crystal planes of the biomass-based porous carbon material, respectively, and the diffraction peaks observed at 28.4 ℃, 47.3 ℃, 56.1 ℃, 69.1 ℃ and 76.4 ℃ correspond to the (111), (220), (311), (400) and (331) crystal planes of crystalline silicon (PDF card No. 27-1402), respectively.
The main components of the prepared composite material are carbon material and silicon through XRD pattern analysis.
As shown in fig. 2 and fig. 3, in SEM images of the sample after swelling and carbonization of the pueraria lobata residue micropowder, after swelling and high-temperature sintering, the pueraria lobata residue micropowder has a three-dimensional carbon fiber skeleton structure formed by interconnecting randomly distributed fibers, and the carbohydrate forms a thin partially graphitized coating layer to wrap the three-dimensional carbon fiber skeleton in series to form a three-dimensional porous carbon material with a pore size of 100nm to 5 μm.
As shown in fig. 4 and 5, which are SEM images and TEM images of the composite material p-C/Si/C prepared in example 3, the pueraria lobata residue micropowder uniformly disperses and coats the silica nanoparticles and bridges the three-dimensional carbon fiber skeleton formed by the plant fiber by using the excellent swelling property and bonding property of the pueraria lobata residue micropowder to obtain a biomass-based porous silicon-carbon composite precursor, the precursor is uniformly secondarily coated by an amorphous carbon layer formed by an organic carbon source, and the thickness of the coating layer is about 12 to 14 nm. This indicates that it is expected that nano-silicon is dispersed in a porous carbon material and an organic carbon layer is coated well on the surface layer.
Example 4
The preparation method of the biomass-based porous silicon-carbon composite material comprises the following specific steps:
firstly, preparing biomass-based porous silicon-carbon composite precursor (p-C/Si)
S1 pretreatment of kudzu root residue: mixing the epidermis, the root hair and the process residues of the pueraria lobata residues according to the mass ratio of 1:1:1, then using a detergent as a cleaning agent to stir and clean to remove surface sand and internal residual impurities, then crushing into micropowder particles with the particle size of 3-5 mu m, further cleaning and purifying the crushed pueraria lobata residue powder in an aqueous solution by using a purifying device, and obtaining pure pueraria lobata residue micropowder after physical purification and drying treatment by using a centrifuge.
S2 spray granulation: 100g of kudzu root residue micro powder and 20g of 100nm silicon powder are weighed and dispersed in ethanol solution, the mass sum of the kudzu root residue micro powder and the nano silicon powder is 40% of the sum of the kudzu root residue micro powder, the nano silicon powder and the solvent, and the mixture is subjected to liquid-phase mechanical mixing for 80min at the rotating speed of 900 r/min. And transferring the mixed solution to a constant-temperature oil bath, stirring at the temperature of 110 ℃ and the rotating speed of 500r/min until the radix puerariae micropowder swells to obtain mixed slurry with the viscosity of 1300cP, spraying and granulating the uniformly mixed slurry at the inlet temperature of 225 ℃ and the outlet temperature of 160 ℃ at the feeding speed of 45ml/min to obtain the biomass-based porous silicon-carbon composite sample with swelling holes.
S3 high-temperature carbonization: placing the biomass-based porous silicon-carbon composite sample in a high-temperature atmosphere furnace, heating to 950 ℃ at the flow rate of argon of 8L/min and at the heating rate of 5 ℃/min, carrying out pyrolysis treatment for 4.5h, naturally cooling to room temperature, crushing, and then sieving with a 200-mesh screen to obtain a biomass-based porous silicon-carbon composite precursor (p-C/Si), wherein the biomass-based porous silicon-carbon composite precursor (p-C/Si) is a thin partially graphitized coating layer, and nano silicon powder is dispersedly coated and is bridged with a three-dimensional carbon fiber skeleton structure to form the three-dimensional porous structure biomass silicon-carbon composite precursor.
Secondly, preparing the biomass-based porous silicon-carbon composite material (p-C/Si/C)
S4 hydrothermal coating: mixing a biomass-based porous silicon-carbon composite precursor (p-C/Si) and polyvinyl alcohol according to a mass ratio of 1: 2.5 adding the biomass-based porous silicon-carbon composite precursor (p-C/Si) and polyvinyl alcohol into water, wherein the solid-liquid mass ratio of the polyvinyl alcohol to the water is 2:40, transferring the mixture into a hydrothermal reaction kettle for ultrasonic dispersion for 30min, polymerizing for 14h at 180 ℃, centrifuging, washing and drying to obtain the secondary coating composite material.
S5 pyrolysis treatment: and (3) placing the obtained secondary coating composite material in a high-temperature atmosphere furnace, heating to 950 ℃ at the temperature rise speed of 5 ℃/min under the condition that the flow of argon is 8L/min, carrying out pyrolysis treatment for 4.5h, naturally cooling to room temperature, crushing, and screening by using a 200-mesh screen to obtain the biomass-based porous silicon-carbon composite material (p-C/Si/C).
The size of the biomass-based porous silicon-carbon composite material (p-C/Si/C) nano silicon particles obtained in the embodiment is 100nm, and the mass of the nano silicon particles accounts for 20% of the mass of the three-dimensional porous silicon-carbon composite material;
the pore diameter of the porous structure of the graphitized thin coating carbon layer is 80 nm-3.5 μm, and the mass of the porous structure accounts for 55% of the mass of the precursor;
the thickness of the secondary coating pyrolytic carbon layer is 10-12 nm, and the mass of the secondary coating pyrolytic carbon layer is 10% of that of the precursor.
The composite sample prepared in example 4 was subjected to physical and chemical property tests. The specific surface area of the composite material powder is 34.35m2·g-1The tap density is 0.72g cm-1And the first discharge capacity at 0.1C was 728.4mAh g-1The first efficiency was 75.9%. Capacity retention of 406.9mAh g after 50 weeks of cycling at a high rate of 1C-1The capacity retention rate was 72.5%. The test results are summarized in Table 1.
Example 5
The preparation method of the biomass-based porous silicon-carbon composite material comprises the following specific steps:
firstly, preparing biomass-based porous silicon-carbon composite precursor (p-C/Si)
S1 pretreatment of kudzu root residue: mixing the epidermis, the root hair and the process residues of the pueraria lobata residues at room temperature according to the mass ratio of 1:1:1, stirring and cleaning by using a cleaning agent as a cleaning agent to remove sand on the surface and residual impurities inside, then crushing into micro powder particles with the particle size of 3-5 mu m, further cleaning and purifying the crushed pueraria lobata residue powder in an aqueous solution by using a purifying device, and physically purifying and drying by using a centrifuge to obtain pure pueraria lobata residue micro powder.
S2 spray granulation: 100g of kudzu root residue micro powder and 20g of 100nm silicon powder are weighed and dispersed in a mixed solution of methanol and ethanol solution, the mass sum of the kudzu root residue micro powder and the nano silicon powder is 40% of the sum of the kudzu root residue micro powder, the nano silicon powder and the solvent, and the mixture is subjected to liquid-phase mechanical mixing for 60min at the rotating speed of 1000 r/min. And transferring the mixed solution to a magnetic stirrer, stirring at the temperature of 120 ℃ and the rotating speed of 700r/min until the radix puerariae micropowder swells to obtain mixed slurry with the viscosity of 1500cP, spraying and granulating the uniformly mixed slurry at the inlet temperature of 180 ℃ and the outlet temperature of 130 ℃ at the feeding speed of 50ml/min to obtain the biomass-based porous silicon-carbon composite sample with swelling holes.
S3 high-temperature carbonization: placing the biomass carbon-based silicon composite sample in a high-temperature atmosphere furnace, heating to 850 ℃ at a nitrogen flow rate of 9L/min at a heating rate of 5 ℃/min, carrying out pyrolysis treatment for 3.5h, naturally cooling to room temperature, crushing, and then sieving with a 200-mesh screen to obtain a biomass-based porous silicon-carbon composite precursor (p-C/Si), wherein the biomass-based porous silicon-carbon composite precursor (p-C/Si) is a thin partially graphitized coating layer, and is formed by dispersing and coating nano silicon powder and bridging a three-dimensional carbon fiber skeleton structure to form the three-dimensional porous biomass silicon-carbon composite precursor.
Secondly, preparing the biomass-based porous silicon-carbon composite material (p-C/Si/C)
S4 hydrothermal coating: mixing a biomass-based porous silicon-carbon composite precursor (p-C/Si) and polyethylene glycol according to a mass ratio of 1:3, adding the biomass-based porous silicon-carbon composite precursor (p-C/Si) and polyethylene glycol to water in a solid-liquid mass ratio of 2:30, ultrasonically dispersing for 30min, transferring to a hydrothermal reaction kettle, polymerizing for 12h at 190 ℃, centrifuging, washing, and drying to obtain the secondary coating composite material.
S5 pyrolysis treatment: and (3) placing the obtained secondary coating composite material in a high-temperature atmosphere furnace, heating to 850 ℃ at the heating rate of 5 ℃/min under the condition that the flow of nitrogen is 9L/min, carrying out pyrolysis treatment for 3.5h, naturally cooling to room temperature, crushing, and screening by using a 200-mesh screen to obtain the biomass-based porous silicon-carbon composite material (p-C/Si/C).
The size of the biomass-based porous silicon-carbon composite material (p-C/Si/C) nano silicon particles obtained in the embodiment is 100nm, and the mass of the nano silicon particles accounts for 20% of the mass of the three-dimensional porous silicon-carbon composite material;
the pore diameter of the porous structure of the graphitized thin coating carbon layer is 70 nm-3.0 μm, and the mass of the porous structure accounts for 53% of the mass of the precursor;
the thickness of the secondary coating pyrolytic carbon layer is 10-15 nm, and the mass of the secondary coating pyrolytic carbon layer is 15% of that of the precursor.
The composite sample prepared in example 5 was subjected to physical and chemical property tests. The specific surface area of the composite material powder is 36.28m2·g-1The tap density was 0.71g · cm-10.1C first discharge capacity 716.5mAh g-1The first efficiency was 76.8%. The circulating capacity is kept at 397.6mAh g under the large multiplying power of 1C-1The capacity retention rate was 71.2%. The test results are summarized in Table 1.
Comparative example 1
The preparation method of the silicon-carbon composite material by using the common carbon material as the raw material comprises the following specific steps:
firstly, preparing a silicon-carbon composite precursor (C/Si)
S1 spray granulation: 100g of natural spherical graphite with the average particle size D50 of 8.0 and 20g of 100nm silicon powder are weighed and dispersed in isopropanol solution, 50g of coating agent polyethylene glycol and 5g of adhesive carboxymethyl cellulose are added, wherein the mass sum of the natural graphite, the nano silicon powder, the polyethylene glycol and the carboxymethyl cellulose is 35 percent of the sum of all solutes and solvents, and the mixture is mechanically mixed for 100min at the rotation speed of 700r/min by a liquid-phase camera. And obtaining mixed slurry with the viscosity of 1350cP, and spraying and granulating the obtained uniform mixed slurry at the inlet temperature of 250 ℃ and the outlet temperature of 140 ℃ at the feeding speed of 40ml/min to obtain the silicon-carbon composite sample.
S2 high-temperature carbonization: and (3) placing the silicon-carbon composite sample in a high-temperature atmosphere furnace, heating to 900 ℃ at the heating rate of 4 ℃/min under the condition that the flow of nitrogen is 7L/min, carrying out pyrolysis treatment for 4h, naturally cooling to room temperature, crushing, and screening by using a 200-mesh screen to obtain a silicon-carbon composite precursor (C/Si).
Secondly, preparing a silicon-carbon composite material (C/Si/C)
S3 hydrothermal coating: mixing a silicon-carbon composite precursor (C/Si) and water-soluble phenolic resin according to a mass ratio of 1:2, adding the silicon-carbon composite precursor (C/Si) and the water-soluble phenolic resin into water, wherein the solid-liquid mass ratio of the silicon-carbon composite precursor (C/Si) to the water is 1:20, ultrasonically dispersing for 30min, transferring the mixture into a hydrothermal reaction kettle, polymerizing for 16h at 170 ℃, centrifuging, washing and drying to obtain the secondary coating composite material.
S4 pyrolysis treatment: and (3) placing the obtained secondary coating composite material in a high-temperature atmosphere furnace, heating to 900 ℃ at the heating rate of 4 ℃/min under the condition that the flow of nitrogen is 7L/min, carrying out pyrolysis treatment for 4h, naturally cooling to room temperature, crushing, and then sieving with a 200-mesh sieve to obtain the silicon-carbon composite material (C/Si/C).
The size of the silicon-carbon composite material (C/Si/C) nano silicon particles obtained by the comparative example is 100nm, and the mass of the nano silicon particles accounts for 20% of the mass of the silicon-carbon composite material;
no microporous structure was detected on the surface of the composite.
The thickness of the secondary coating pyrolytic carbon layer is 10-12 nm, and the mass of the secondary coating pyrolytic carbon layer is 12% of that of the precursor.
The composite sample prepared in comparative example 1 was subjected to physical and chemical property tests. The specific surface area of the composite material powder is 4.65m2·g-1The tap density was 0.91g · cm-1First discharge capacity at 0.1C of 786.5mAh g-1The first efficiency was 80.6%. The circulating capacity is kept at 340.6mAh g under the large multiplying power of 1C-1The capacity retention rate was 65.3%. The test results are summarized in Table 1.
Comparative example 2
The preparation method selects corncob micropowder as a biomass raw material to prepare the biomass-based porous silicon-carbon composite material, and comprises the following specific steps:
firstly, preparing biomass-based porous silicon-carbon composite precursor (p' -C/Si)
S1 pretreatment of corncobs: at room temperature, the corn cobs after threshing are stirred and cleaned by using a detergent as a cleaning agent to remove surface grits and internal residual impurities, then the corn cobs are crushed into micro powder particles with the particle size of 3-5 mu m, the crushed corn cob powder is further cleaned and purified in aqueous solution by using a purifying device, and the pure corn cob micro powder is obtained after physical purification and drying treatment by a centrifuge.
S2 spray granulation: weighing 100g of corncob micro powder with the particle size of 3-5 mu m and 20g of 100nm silicon powder, dispersing the corncob micro powder and the 100nm silicon powder into an isopropanol solution, wherein the mass sum of the kudzu root residue micro powder and the nano silicon powder is 35% of the sum of the kudzu root residue micro powder, the nano silicon powder and the solvent, and carrying out liquid-phase mechanical mixing for 100min at the rotating speed of 700 r/min. And transferring the mixed solution to a magnetic stirrer, stirring at the temperature of 100 ℃ and the rotating speed of 800r/min, adding a binder carboxymethyl cellulose to adjust the viscosity of the slurry to obtain mixed slurry with the viscosity of 1350cP, and performing spray granulation on the obtained uniformly mixed slurry at the inlet temperature of 250 ℃ and the outlet temperature of 140 ℃ at the feeding speed of 40ml/min to obtain the biomass silicon-carbon composite sample.
S3 high-temperature carbonization: and (2) placing the biomass silicon carbon composite sample in a high-temperature atmosphere furnace, heating to 900 ℃ at the nitrogen flow rate of 7L/min at the heating rate of 4 ℃/min, carrying out pyrolysis treatment for 4h, naturally cooling to room temperature, crushing, and screening by using a 200-mesh screen to obtain a biomass-based porous silicon carbon composite precursor (p' -C/Si).
Secondly, preparing the biomass-based porous silicon-carbon composite material (p' -C/Si/C)
S4 hydrothermal coating: mixing a biomass-based porous silicon-carbon composite precursor (p' -C/Si) and water-soluble phenolic resin according to a mass ratio of 1:2, adding the biomass-based porous silicon-carbon composite precursor (p '-C/Si) and water-soluble phenolic resin into water, wherein the solid-liquid mass ratio of the water-soluble phenolic resin to the biomass-based porous silicon-carbon composite precursor (p' -C/Si) is 1:20, transferring the mixture into a hydrothermal reaction kettle for ultrasonic dispersion for 30min, polymerizing the mixture for 16h at 170 ℃, and obtaining the secondary coating composite material after centrifugation, washing and drying.
S5 pyrolysis treatment: and (3) placing the obtained secondary coating composite material in a high-temperature atmosphere furnace, heating to 900 ℃ at the heating speed of 4 ℃/min under the condition that the flow of nitrogen is 7L/min, carrying out pyrolysis treatment for 4h, naturally cooling to room temperature, crushing, and screening by using a 200-mesh screen to obtain the biomass-based porous silicon-carbon composite material (p' -C/Si/C).
The size of the biomass-based porous silicon-carbon composite material (p' -C/Si/C) nano silicon particles obtained in the comparative example is 100nm, and the mass of the nano silicon particles accounts for 20% of the mass of the porous silicon-carbon composite material;
the pore diameter of the porous structure of the graphitized thin coating carbon layer is 30-200 nm, the pore diameter of the porous structure is smaller, and the mass of the pore diameter accounts for 40% of the mass of the precursor;
the thickness of the secondary coating pyrolytic carbon layer is 10-13 nm, and the mass of the secondary coating pyrolytic carbon layer is 12% of that of the precursor.
The composite sample prepared in comparative example 2 was subjected to physical and chemical property tests. The specific surface area of the composite material powder was 33.54m2·g-1The tap density was 0.65 g/cm-1And the first discharge capacity at 0.1C was 719.7mAh g-1The first efficiency was 70.5%. Capacity retention of 330.9mAh g after 50 weeks of cycling at a high rate of 1C-1The capacity retention rate was 60.1%. The test results are summarized in Table 1.
TABLE 1 results of physical and chemical Properties test of examples and comparative examples
Figure BDA0003186083390000181
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (10)

1. The biomass-based porous silicon-carbon composite material is characterized by comprising the following structures: the core is nano silicon powder, a part of graphitized thin coated carbon layer formed by uniformly dispersing and coating carbohydrate outside the nano silicon powder, plant fibers are bridged between the nano silicon powder and the graphitized thin coated carbon layer to form a three-dimensional porous silicon-carbon composite material with a three-dimensional carbon fiber framework, the outer layer of the three-dimensional porous silicon-carbon composite material is coated with a pyrolytic carbon layer for the second time, and the biomass matrix is kudzu root residue.
2. The biomass-based porous silicon-carbon composite material as claimed in claim 1, wherein the size of the nano silicon particles is 30 nm-100 nm, and the mass of the nano silicon particles accounts for 5% -30% of the mass of the three-dimensional porous silicon-carbon composite material;
the pore diameter of the porous structure of the graphitized thin coating carbon layer is 50 nm-5 μm, and the mass of the porous structure accounts for 50% -60% of the mass of the precursor;
the thickness of the secondary coating pyrolytic carbon layer is 5 nm-15 nm, and the mass of the secondary coating pyrolytic carbon layer is 5.0% -15.0% of the mass of the precursor.
3. A preparation method of a biomass-based porous silicon-carbon composite material comprises the steps of preparing a biomass-based porous silicon-carbon composite precursor (p-C/Si), preparing a biomass-based porous silicon-carbon composite material (p-C/Si/C),
the method is characterized in that the specific steps for preparing the biomass-based porous silicon-carbon composite precursor (p-C/Si) are as follows:
s1 pretreatment of kudzu root residue: cleaning the kudzu root residue at room temperature, then crushing the cleaned kudzu root residue into micro powder particles with the particle size of 3-5 mu m, further cleaning and purifying the crushed kudzu root residue powder, and fully drying to obtain pure kudzu root residue micro powder;
s2 spray granulation: mixing the kudzu root residue micro powder and the nano silicon powder according to the mass ratio of 100: (5.0-30.0) dispersing in an alcohol solvent solution for liquid-phase mechanical mixing, then stirring and heating the mixed slurry in heating equipment, adjusting the temperature to control the swelling performance of the radix puerariae residue powder to adjust the viscosity of the slurry, and then performing spray granulation to obtain a biomass-based porous silicon-carbon composite sample;
s3 high-temperature carbonization: and (2) placing the biomass-based porous silicon-carbon composite sample in a high-temperature atmosphere furnace, carrying out pyrolysis treatment in a protective gas atmosphere, after pyrolysis is finished, and crushing the material to obtain a biomass-based porous silicon-carbon composite precursor (p-C/Si).
4. The preparation method of the biomass-based porous silicon-carbon composite material according to claim 3, wherein the specific steps for preparing the biomass-based porous silicon-carbon composite material (p-C/Si/C) are as follows:
s4 hydrothermal-in situ polymerization coating: mixing the prepared biomass-based porous silicon-carbon composite precursor and an organic carbon source according to the mass ratio of 1: (1.0-3.0) uniformly mixing, ultrasonically dispersing in water, performing secondary carbon coating in a hydrothermal reaction kettle through hydrothermal-in-situ polymerization, centrifuging, washing and drying the mixture solution to obtain a secondary coated composite material;
s5 pyrolysis treatment: and (3) placing the obtained secondary coating composite material in a high-temperature atmosphere furnace, carrying out pyrolysis carbonization in protective gas atmosphere, and crushing after the material is cooled to obtain the biomass-based porous silicon-carbon composite material (p-C/Si/C).
5. The method for preparing the biomass-based porous silicon-carbon composite material as claimed in any one of claims 1, 2 and 3, wherein the biomass base is kudzu root residue, and the kudzu root residue is one or more of epidermis, root hair and process residue remained in the production of kudzu root products.
6. The preparation method of the biomass-based porous silicon-carbon composite material according to claim 3, wherein in the step S2 of spray granulation, the temperature of stirring and heating the mixed slurry in a heating device is 50-120 ℃.
7. The method for preparing the biomass-based porous silicon-carbon composite material according to claim 3, wherein in the step S2 of spray granulation, after the mixed slurry is heated and stirred sufficiently, and the residue micropowder of the radix puerariae swells sufficiently, the viscosity of the obtained mixed slurry is 1000 cP-1500 cP.
8. The preparation method of the biomass-based porous silicon-carbon composite material according to claim 3, wherein the biomass-based porous silicon-carbon composite precursor (p-C/Si) is a three-dimensional porous biomass-based silicon-carbon composite precursor formed by dispersedly coating nano silicon powder with a thin partially graphitized coating layer and bridging a three-dimensional carbon fiber skeleton structure.
9. The method for preparing the biomass-based porous silicon-carbon composite material according to claim 4, wherein the solid-liquid mass ratio of the mixture of the biomass-based porous silicon-carbon composite precursor and the organic carbon source to water in step S4 is (1.0-2.0): (20-40).
10. The porous silicon-carbon composite material is characterized by being used as a negative electrode material of a lithium ion battery.
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CN106935821A (en) * 2017-03-16 2017-07-07 湖南工业大学 A kind of phosphoric acid vanadium lithium composite positive pole with porous foam and preparation method thereof
CN109449423A (en) * 2018-11-13 2019-03-08 东莞市凯金新能源科技股份有限公司 Hollow/porous structure the silicon based composite material of one kind and its preparation method
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