CN113299896B

CN113299896B - Preparation method and application of hollow porous silicon-carbon @ lignin-carbon nanospheres

Info

Publication number: CN113299896B
Application number: CN202110581383.6A
Authority: CN
Inventors: 席跃宾; 刘雪; 孔凡功; 王守娟; 熊文龙; 杨牧原; 刘淇; 崔航; 张振涛
Original assignee: Qilu University of Technology
Current assignee: Qilu University of Technology
Priority date: 2021-05-27
Filing date: 2021-05-27
Publication date: 2022-05-31
Anticipated expiration: 2041-05-27
Also published as: CN113299896A

Abstract

The invention relates to a preparation method and application of hollow porous silicon-carbon @ lignin-carbon nanospheres, and belongs to the field of preparation of carbon composite materials. The preparation method comprises the following steps of S1, preparing quaternized lignin; s2, forming lignin-silicon dioxide nanospheres by combining the electrostatic effect between quaternized lignin and silicon dioxide generated by continuous hydrolysis of a silicon source through a hydrothermal reaction; s3, carbonizing the lignin-silicon dioxide nanospheres, carrying out magnesiothermic reduction and acid washing to obtain the spherical silicon carbon @ lignin carbon nanospheres which are regular in shape and hollow inside. Compared with the prior art, the silicon carbon @ lignin carbon nanosphere composite material prepared by the method disclosed by the invention is good in mechanical property and more stable in performance, and can be applied to a lithium ion battery cathode material, so that the specific capacity, the cycle performance, the rate capability and the like of a lithium ion battery can be effectively improved.

Description

Preparation method and application of hollow porous silicon-carbon @ lignin-carbon nanospheres

Technical Field

The invention discloses a preparation method and application of hollow porous silicon-carbon @ lignin-carbon nanospheres, and belongs to the technical field of carbon composite materials.

Background

The lithium ion power battery partially replaces the traditional battery to be used in the aspects of mobile phones, portable computers, video cameras, cameras and the like, and particularly, the high-capacity lithium ion battery is applied to the aspects of electric automobiles, artificial satellites, aerospace, energy storage devices and the like. However, with the rapid development of scientific technology, the capacity and energy density of lithium ion batteries are increasingly required. At present, graphite materials are widely commercialized as lithium ion negative electrodes, but the theoretical specific capacity of the graphite materials is only 372mAh g^-1The demand of electronic energy equipment is far from being met, so that a cathode material with higher energy density needs to be developed to be widely applied to a lithium ion battery.

The highest specific mass capacity of the silicon material can reach 4200mAh g^-1The material is far larger than graphite material, and is the material which is known to be used for negative electrode material and has the highest theoretical specific volume. And the silicon material is environment-friendly, abundant in reserves and low in cost. However, the simple substance of silicon is very easy to swell, so that the simple substance of silicon has the problems of low cycle life, continuous generation of SEI film and the like. Researchers turn their attention to the field of composite materials, in which carbon materials have the advantages of stable chemical properties, excellent electron transport capability and low cost, and carbon materials (graphite, graphene, carbon nanotubes and porous carbon) with easily-controlled micro-morphology are compounded with silicon materials, so that the expansion of the silicon materials can be inhibited, and the lithium intercalation capacity, the cycling stability and the coulombic efficiency can be improved.

Lignin is an aromatic high polymer widely present in plants, and the global industrial lignin yield reaches 5000 million tons every year. The lignin has a 3D network structure, is rich in functional groups, has high heat value, has the carbon content of 50-60 percent, and is an ideal precursor for preparing the silicon-carbon composite material. Most of lignin in the industry exists in papermaking waste liquid, is mainly combusted and is not reasonably utilized, so that the lignin serving as a carbon source of the lithium ion battery cathode material has the advantages of being cheap and easy to obtain, can be changed into valuables, and is beneficial to environmental protection and resource utilization.

The lignin as a carbon source can be converted into hard carbon or porous carbon material after being directly carbonized or carbonized and activated and can be used as a lithium ion battery cathode material. Among them, the hard template method is a more common carbonization activation method, especially using nano SiO with better mechanical strength and mechanical stress₂The lignin carbon skeleton hard template agent can support a lignin carbon skeleton to prevent polycondensation and collapse of the lignin carbon skeleton, and can also be used as a silicon source to provide high specific capacity. However, the use of silica as a template agent for lignin has the problems of easy aggregation and difficult dispersion due to the hydrogen bonding on the surface, which leads to the problems of difficult uniform dispersion and easy agglomeration, thereby hindering the rapid transmission of lithium ions and reducing lithium intercalation active sites.

The lignin has rich functional groups, can be effectively compounded with silicon dioxide after being modified, and can obtain the lignin carbon or silicon carbon material with uniform structure and stable performance after being carbonized and activated. Chinese invention patent ZL201810617043.2 discloses a lignin porous carbon with uniform pore channels, a preparation method thereof and application thereof in lithium ion battery cathode materials, wherein the lignin porous carbon is prepared by directly uniformly dispersing gas phase nano-silica in lignin solution, obtaining lignin-silica compound through hydrothermal reaction, and then obtaining the lignin porous carbon material through carbonization and acid pickling, wherein the lignin porous carbon material is prepared at 200 mA.g^-1The current density of the alloy still keeps 513mAh g after 100 cycles^-1Specific discharge capacity of (2). ZL201911176604.0 discloses a silicon-carbon composite negative electrode material and a preparation method thereof, a negative electrode plate and a lithium ion battery, wherein a silane polymer is deposited on the surface of a template agent through a chemical bath method, thioacetamide and silicon acetate form a silane compound with a stable structure, carbon nano tubes are doped among the materials to form a network structure, then the template is dissolved away through a solvent to obtain a carbon dioxide composite material, and finally the carbon monoxide composite material is obtained through magnesium thermal reductionIs easy to be industrialized. The pole piece prepared by the method has strong liquid absorption and retention capacity and low rebound rate; the battery prepared from the lithium ion battery has high initial discharge capacity, high initial efficiency and good cycle performance. Secondary granulation of ZL201810654489.2 to obtain SiO_xThe metal oxide compound is mixed with a carbon material after being calcined, and the mixture is continuously calcined to obtain the silicon-carbon cathode material, wherein the first coulombic efficiency of the silicon-carbon cathode material can reach more than 80 percent. The comprehensive patent shows that a plurality of preparation processes of the lignin carbon/silicon dioxide composite material exist at present, but the preparation processes are complex, toxic reagents such as tetrahydrofuran and the like are contained in the experiment, the particle size of the prepared carbon oxide composite material is large (between 5 and 12 micrometers), the coulomb efficiency is improved for one pursuit, the particle size of the particles reaches 3 to 20 micrometers, and the cycle performance is reduced.

The hierarchical porous carbon nanosphere dioxide composite material is obtained by using silicon dioxide as a silicon source and lignin as a carbon source through a self-assembly process by Tao et al of Kentuki university in the United states, does not need a traditional conductive agent, has excellent electrochemical performance and is 200 mA-g^-1The rate of the catalyst is still 900mAh g after 250 cycles^-1. Li Wen jumping et al, university of hong Kong City, first prepared a foam sheet carbon film supported core-shell carbon composite material by using sodium chloride (NaCl) as a template and adopting a magnesiothermic reduction/glucose carbonization process. At 1 A.g^-1After 200 cycles, the capacity remained 93.6% (about 1018mAh g)^-1). Zhang Lei of Wulungong university adopts improved template method and CVD method, with CaCO₃The material is a sacrificial layer, acetylene is a carbon precursor to prepare the silicon-carbon anode material with the yolk shell structure, and the material has higher initial specific capacity (1643.9 mA.g)^-1) After 200 cycles, the current density was 250mA · g^-1About 1100mAh g is provided in the case of^-1The reversible capacity and the structural integrity of the composite material are relatively good. In summary, although silicon-carbon materials have been greatly developed, silicon dioxide is easy to aggregate, and the obtained materials as lithium ion battery negative electrode materials have low reversible specific capacity retention rate, poor cycle performance, low coulombic efficiency (80%) and the like due to serious aggregation of silicon dioxide and poor cohesiveness with lignin carbonAnd (5) problems are solved.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a preparation method of hollow porous silicon-carbon @ lignin-carbon nanospheres. The silicon carbon @ lignin carbon nanospheres prepared by the method are a hollow silicon carbon composite material with silicon carbon wrapped by a firm spherical carbon shell, silicon and carbon are tightly combined, the spherical particles are uniform in size, and the mechanical property of the material can be improved; the hollow structure and the silicon carbon layer reduce the strain force caused by volume change of the electrode in the cyclic charge-discharge process, and the performance is more stable.

In the present invention, the lignin comprises at least one of poplar alkali lignin, wheat straw alkali lignin, bamboo pulp alkali lignin, reed alkali lignin, cotton pulp alkali lignin and bagasse alkali lignin.

The technical task of the invention is realized by the following modes: a preparation method of hollow porous silicon carbon @ lignin carbon nanospheres is characterized in that industrial lignin is used as a raw material, the electrostatic action of quaternized lignin and silicon dioxide generated by continuous hydrolysis of a silicon source is combined through a hydrothermal reaction to form highly dispersed and regularly shaped lignin-silicon dioxide nanospheres, and then carbonization, magnesium thermal reduction and acid washing are carried out to obtain a regularly shaped and internally hollow spherical silicon carbon @ lignin carbon composite material.

The specific method comprises the following steps:

s1, preparing quaternized lignin;

s2, forming lignin-silicon dioxide nanospheres by combining the electrostatic effect between quaternized lignin and silicon dioxide generated by continuous hydrolysis of a silicon source through a hydrothermal reaction;

s3, carbonizing the lignin-silicon dioxide nanospheres to obtain lignin porous carbon/silicon dioxide nanospheres;

s4, carrying out magnesiothermic reduction on the lignin porous carbon/silicon dioxide nanospheres to obtain a silicon carbon @ lignin carbon nanosphere precursor;

and S5, acid washing the silicon carbon @ lignin carbon nanosphere precursor to obtain the spherical silicon carbon @ lignin carbon nanospheres which are regular in shape and hollow inside.

Preferably, step S1 prepares the quaternized lignin as: dissolving lignin in an alkaline aqueous solution to prepare a solution with a solid content of 20-30 wt%, heating the solution to 80-90 ℃, then dropwise adding a certain amount of intermediate (30-60% of the total amount of the intermediate), supplementing a proper amount of alkali into the solution (keeping the pH of a reaction system within a range of 11-12), dropwise adding the rest of intermediate, reacting for 2-6 hours, cooling, dialyzing, and freeze-drying to obtain the quaternized lignin.

The dissolution process of lignin is a swelling process, and functional groups such as carboxyl, hydroxyl, phenolic hydroxyl and the like in lignin molecules are gradually ionized in the dissolution process. Here, an alkaline aqueous solution must be used for dissolution, in order to facilitate the reaction thereof with the intermediates to give the quaternized lignin. The weight ratio of the lignin to the intermediate in the step is preferably 50 (15-22.5), and particularly preferably 50 (16.5-19.5). If the weight ratio is too low, the quaternization degree of lignin is reduced, which results in a decrease in the specific gravity of lignin in the lignin-silica nanospheres obtained in step S2, and the performance of the composite is affected.

The intermediate is 3-chloro-2-hydroxypropyl trimethyl ammonium chloride, preferably in the form of aqueous solution, and is dripped into the lignin solution at the speed of 1-1.5 ml/min by a peristaltic pump.

The aqueous alkaline solution used to dissolve the lignin is preferably an aqueous solution of NaOH. The mass ratio of NaOH to water in the initial NaOH aqueous solution is 9 (150-200).

The mass ratio of the supplemented NaOH to the NaOH in the original solution is preferably (4-4.5): 9, and the mass fraction of the supplemented NaOH is preferably 40-60 wt%.

Preferably, the specific method for preparing the lignin-silica nanosphere in step S2 is as follows: dissolving quaternized lignin in an ethanol-water solution with the pH value of 2-5, adding a surfactant, then adding a silicon source, reacting to obtain a lignin/silicon source mixed solution, carrying out hydrothermal reaction on the mixed solution, and purifying and drying to obtain the lignin-silicon dioxide nanospheres.

The mass-volume ratio of the quaternized lignin to the ethanol-water solution is 3 (20-160), and particularly preferably 3 (25-50). If the proportion is too low, the occupied equipment space is large, the yield is low, and if the proportion is too high, the shape of the obtained lignin-silicon dioxide nanospheres is irregular. The volume ratio of ethanol to water in the ethanol-water solution is 10 (5-100), particularly preferably 10 (10-60), and the ratio is influenced by a silicon source. The pH of the ethanol-water solution can be adjusted by using dilute sulfuric acid or the like.

The surfactant may be cetyltrimethylammonium bromide (CTAB), polyethylene glycol and/or sodium dodecylbenzene sulphonate (SDBS), preferably sodium dodecylbenzene sulphonate. The mass ratio of the surfactant to the quaternized lignin is 1: (15-60), preferably 1 (20-40).

The silicon source can adopt any raw material which can be hydrolyzed into silicon dioxide, and preferably ethyl orthosilicate, sodium silicate, tetramethoxysilane, silicon tetrachloride and the like. In the reaction process, firstly dispersing a silicon source into an ethanol-water solution, then dropwise adding the ethanol-water solution into a quaternized lignin solution at a rate of 0.1-0.5 ml/min (preferably 0.2-0.3 ml), stirring and reacting for 1-4 h to obtain a lignin/silicon source mixed solution, and then carrying out hydrothermal reaction for 2-24 h at 120-200 ℃ (preferably 150-200 ℃). The mass-to-volume ratio of the silicon source to the ethanol-water solution is preferably 0.7 (10-100), and particularly preferably 0.7 (10-60). If the ratio is too low, the spherical surface of the composite is too rough, and if the ratio is too high, silica is easily agglomerated during the reaction, and the size of the resulting composite is too large. The volume ratio of ethanol to water in the ethanol-water solution is 100 (0-150), and particularly preferably 100 (0-100).

The weight ratio of the quaternized lignin to the silicon source is preferably 100:20 to 100, and particularly preferably 100:40 to 100.

After the hydrothermal reaction, the reactant is centrifuged, washed, centrifuged again and freeze-dried to obtain the lignin-silicon dioxide nanospheres.

Preferably, the carbonization temperature of the lignin-silica nanospheres in the step S3 is preferably 650-850 ℃.

The carbonization process is preferably carried out under inert gas conditions. The carbonization temperature rise process is preferably as follows: heating to 650-850 ℃ at the speed of 5-15 ℃/min (particularly preferably 7-12 ℃/min), preserving the heat for 1-4 h, and cooling to room temperature to obtain the lignin porous carbon/silicon dioxide nanospheres.

Preferably, the specific method of the magnesiothermic reduction in step S4 is: mixing the lignin porous carbon/silicon dioxide nanospheres and magnesium powder according to the mass ratio of 1: 0.6-3 (particularly preferably 1: 0.6-2.5) to obtain a mixture, heating the mixture to 650-850 ℃, and performing magnesiothermic reduction for 2-8 hours to obtain the silicon-carbon @ lignin carbon nanosphere precursor. The amount of magnesium powder must not be too low, otherwise incomplete reduction of the silica will result.

The magnesium thermal reduction is preferably carried out under the condition of argon-hydrogen mixed gas, and the temperature rise process is preferably as follows: heating the mixture of the porous carbon/silicon dioxide nanospheres of the lignin and the magnesium powder to 200-400 ℃, then heating to 650-850 ℃ at a speed of 2-10 ℃/min (preferably 2-6 ℃/min), keeping for 2-8 h, and cooling to room temperature to obtain the precursor of the silicon-carbon @ lignin carbon nanospheres.

Preferably, in step S5, the silicon carbon @ lignin carbon nanosphere precursor is acid-washed by using a hydrochloric acid solution with a concentration of 0.1-2 mol/L to wash away impurities such as magnesium and magnesium oxide in the silicon carbon @ lignin carbon nanosphere precursor, and then the silicon carbon @ lignin carbon nanosphere is centrifuged and dried to obtain a hollow porous silicon carbon @ lignin carbon nanosphere.

The pickling time is controlled to be more than 4h, if the acid liquor concentration is too low or the pickling time is too short, the magnesium oxide residue is too much, the pore structure is less, the cycle performance and the rate performance are greatly reduced, and the pickling concentration is too high, so that the reaction is violent, even open fire is generated, and the silicon-carbon composite material structure is damaged.

Further, the invention provides an application of the silicon-carbon @ lignin-carbon nanosphere.

The method takes industrial lignin as a raw material, and the silicon carbon @ lignin carbon nanosphere composite material prepared by the in-situ self-assembly method is highly dispersed and regular in shape, wherein the hollow structure and the silicon carbon layer reduce the strain force caused by volume change of an electrode in the cyclic charge-discharge process, and inhibit the cracking and pulverization of silicon, and the shell is the carbon layer, so that the conductivity can be effectively improved, the continuous formation of SEI (solid electrolyte interphase) can be prevented, the performance is more stable, and the method can be used for preparing a lithium ion battery to improve the specific capacity, the cycle performance, the multiplying power performance and the like of the lithium ion battery.

The hollow porous silicon carbon @ lignin carbon nanospheres are used for preparing the lithium ion battery negative plate, and the preparation method is preferably as follows:

preparing slurry from silicon carbon @ lignin carbon nanospheres (active materials), conductive carbon black and PVDF according to the mass ratio of 8 (0.5-1.5) to (0.5-1.5), coating the slurry by using a scraper with copper foil as a current collector, drying, and rolling by using a roll-in machine to obtain the pole piece.

The mass of the active material is preferably 160-400 mg.

The height of the scraper is preferably 10-30 mu m.

The drying process is preferably drying at 80-100 ℃ for 10-30 min, and then transferring to a vacuum drying oven for drying at 110-130 ℃ for 6-24 h.

A lithium ion battery can adopt the pole piece prepared by the invention as an anode, a lithium piece as a counter electrode and LiPF₆The electrolyte is assembled by adopting a battery with the model number of CR2032, and a cyclic voltammetry test, a constant current charge and discharge test, a multiplying power performance test and an alternating current impedance test are carried out.

The assembly of the cell was performed in a high argon glove box. The Neware battery performance test system can be used for testing the battery performance within the voltage range of 0.001V-3.0V at 200 mA.g^-1The constant current charging/discharging performance test of the battery is carried out under the current density, and the multiplying power performance test is carried out at 50 mA.g^-1、100mA·g^-1、200mA·g^-1、500mA·g^-1And 1000mA · g^-1And is completed at current density.

Compared with the prior art, the preparation method and the application of the hollow porous silicon-carbon @ lignin-carbon nanospheres have the following outstanding beneficial effects:

in the preparation method, the uniformly dispersed and uniformly sized spherical lignin-silica composite (lignin-silica nanospheres) can be obtained by an in-situ self-assembly method, the lignin and the silica are combined more tightly by virtue of an esterification reaction between the lignin and the silica after hydrothermal treatment, the firm composite is subjected to high-temperature magnesiothermic reduction to form a hollow composite material (silicon carbon @ lignin carbon nanospheres) with a silicon carbon-coated carbon layer, the original spherical structure and particle size are still maintained, the composite material has the characteristics of high dispersion, uniform distribution, regular shape and hollow interior, and has higher reversible capacity, good cycle performance and rate capability as a lithium ion negative electrode material, and the application prospect is wide.

The silicon-carbon composite material is prepared by taking industrial lignin as a carbon source, and the in-situ self-assembly and template methods are adopted to synchronously generate the synergistic preparation method.

Drawings

FIG. 1 is a scanning electron micrograph of the lignin-silica nanospheres obtained in example 1;

FIG. 2 is a transmission electron micrograph of the lignin-silica nanospheres obtained in example 1;

FIG. 3 is a scanning electron microscope image of the silicon-carbon @ lignin-carbon nanosphere obtained in example 1;

FIG. 4 is a transmission electron micrograph of the silicon-carbon @ lignin-carbon nanosphere obtained in example 1;

FIG. 5 is the XRD pattern of the Si-C @ ligno-C nanospheres obtained in example 1;

FIG. 6 is the Raman spectrum of the Si-C @ ligno-carbon nanosphere obtained in example 1.

Detailed Description

The invention is further described with reference to the following figures and specific examples, which are not intended to be limiting.

The materials involved in all the examples of the present invention are commercially available.

Unless otherwise specified, the contents of the respective components used below are mass% contents.

Example 1

Weighing 9g of NaOH and dissolving in 170g of deionized water, then dissolving 50g of poplar alkali lignin in NaOH solution to prepare solution with the solid content of 25 wt%, and transferring to a three-neck flask after the solution is completely dissolved. The stirring paddle was placed vertically with the flask, without reaching the thermometer, the condenser tube was fixed with a clamp, the condenser tube was taken in and out with water, the oil bath pot temperature was set to 85 ℃, after the temperature reached 85 ℃, 20g of 3-chloro-2-hydroxypropyltrimethylammonium chloride (10 g of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added dropwise to the above lignin solution at a rate of 1mL/min by a peristaltic pump, 8g of 50% sodium hydroxide solution was added to the solution in order to maintain the reaction system ph in the range of 11 to 12, and then the remaining 3-chloro-2-hydroxypropyltrimethylammonium chloride was all added dropwise to the lignin solution). The time at which the addition of the intermediate was completed was recorded, followed by incubation for 4 h. And after the reaction is finished, closing the condensed water, cooling the reaction liquid to room temperature, and dialyzing, filtering, and freeze-drying to obtain the quaternized lignin (QAL).

2g of QAL was added to 80ml of an ethanol-water (1:1) solution, 0.1g of SDBS (sodium dodecylbenzenesulfonate) was added thereto, the pH was maintained at 3 and the mixture was stirred continuously, 1.0g of ethyl orthosilicate dispersed in 20ml of an ethanol solution was added dropwise to the QAL solution at a rate of 0.25ml/min, and stirring was continued for 1 hour after completion of the dropwise addition to obtain a mixed dispersion. And (3) placing the mixed dispersion liquid into a 200ml polytetrafluoroethylene reaction kettle, and carrying out hydrothermal reaction for 6h at 150 ℃. After the reaction kettle is cooled to room temperature, centrifuging, washing, re-centrifuging and freeze-drying the solution to obtain QAL/SiO₂And (c) a complex.

1gQAL/SiO₂The composite is placed in a porcelain square boat in a corundum porcelain square boat with the specification of 30 x 90 x 60mm, and carbonization is carried out by using a carbonization furnace. The carbonization conditions are as follows: raising the temperature to 650 ℃ after 65min from room temperature under the protection of nitrogen, keeping the temperature for 2h, and then naturally cooling. Grinding to obtain lignin carbon/silicon dioxide (LC/SiO)₂) And (3) a compound.

0.5g of LC/SiO was taken₂The compound and 0.6g of magnesium powder are mixed uniformly and placed in a corundum porcelain ark with 30 x 90 x 60mm, and the carbonization conditions are as follows: raising the temperature from room temperature to 300 ℃ after 30min under the condition of argon-hydrogen mixed gas, raising the temperature to 650 ℃ at the speed of 5 ℃/min, preserving the temperature for 4h, and then naturally cooling. And (3) pickling the carbonized product for 4h by using 0.5mol/L hydrochloric acid, centrifuging, drying and grinding to obtain the hollow porous silicon-carbon @ lignin-carbon nanospheres.

The QAL/SiO films were aligned using transmission electron microscopy (TEM, JEOL-2100, Hokkaido, Japan) and scanning electron microscopy (FESEM, Regulus8220, Japan)₂Composite and silicon carbon @ lignin carbon nanosphere appearanceAnd (5) observing the appearance and the structure.

As shown in FIG. 1, the lignin-silica complex obtained by the hydrothermal reaction was uniformly dispersed, and had a regular spherical shape and a diameter of about 500 nm. As shown in fig. 2, the lignin-silica complex is spherical and hollow inside. As shown in fig. 3 and 4, after the magnesiothermic reduction of the lignin-silica composite, the original structure is not damaged, the diameter is still about 500nm, and the inside of the prepared silicon carbon @ lignin carbon nanospheres is of a hollow structure, so that the strain force generated during charge and discharge can be buffered in a certain space of the nanospheres, and the service life of the material is prolonged.

XRD analysis was performed on silicon carbon composites (silicon carbon @ lignin carbon nanospheres) using an x-ray diffractometer (Bruker, Rheinstetten, Germany). As shown in figure 5, the XRD diffraction peak of the product of the example is consistent with the diffraction peak of the silicon-carbon material, which shows that the embodiment can obtain the hollow and porous silicon-carbon @ lignin-carbon nanosphere.

Raman spectroscopy was performed on the silicon-carbon @ lignin-carbon nanospheres using a Raman spectrometer (renishawinnvia, London, UK), as shown in fig. 6, the diffraction peak was consistent with that reported in the literature, indicating that we successfully obtained silicon by thermal reduction of silica magnesium in the silicon-carbon @ lignin-carbon nanospheres.

Example 2

Weighing 9g of NaOH and dissolving in 180g of deionized water, then dissolving 50g of wheat straw alkali lignin in NaOH solution to prepare solution with solid content of 25 wt%, and transferring to a three-neck flask after the solution is dissolved. The stirring paddle was placed vertically with the flask, without reaching the thermometer, the condenser tube was fixed with a clamp, the condenser tube was taken in and out, the oil bath pot temperature was set to 85 ℃, after the temperature reached 85 ℃, 18g of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added dropwise to the above lignin solution at a rate of 1.3mL/min by a peristaltic pump (8 g of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added dropwise first, 8g of 50% sodium hydroxide solution was added to the solution in order to keep the reaction system ph in the range of 11 to 12), and then the remaining 3-chloro-2-hydroxypropyltrimethylammonium chloride was all added dropwise to the lignin solution). The time at which the addition of the intermediate was completed was recorded, followed by incubation for 4 h. And after the reaction is finished, closing the condensed water, cooling the reaction liquid to room temperature, and dialyzing, filtering, freezing and drying to obtain the quaternized lignin (QAL).

2g of QAL was added to 50ml of an ethanol-water (1:6) solution, 0.1g of SDBS (sodium dodecylbenzenesulfonate) was added thereto, the pH was maintained at 3 and the mixture was stirred continuously, 1.2g of sodium silicate dispersed in 60ml of an ethanol-water (1:6) solution was added dropwise to the QAL solution at a rate of 0.25ml/min, and stirring was continued for 2 hours after completion of the dropwise addition to obtain a mixed dispersion. And (3) placing the mixed dispersion liquid into a 200ml polytetrafluoroethylene reaction kettle, and carrying out hydrothermal reaction at 160 ℃ for 12 h. After the reaction kettle is cooled to room temperature, centrifuging, washing, re-centrifuging and freeze-drying the solution to obtain QAL/SiO₂And (c) a complex.

1g QAL/SiO₂The composite was placed in a porcelain ark of a 30 x 90 x 60mm corundum porcelain ark. Carbonizing by using a carbonization furnace, wherein the carbonizing conditions are as follows: raising the temperature to 750 ℃ after 75min from room temperature under the protection of nitrogen, keeping the temperature for 2h, and then naturally cooling. Grinding to obtain lignin porous carbon/silicon dioxide (LC/SiO)₂) And (c) a complex.

1g of LC/SiO was taken₂The compound and 1g of magnesium powder are mixed uniformly and placed in a corundum porcelain ark with 30 x 90 x 60mm, and the carbonization conditions are as follows: raising the temperature from room temperature to 400 ℃ after 40min under the condition of argon-hydrogen mixed gas, raising the temperature to 750 ℃ at the speed of 2 ℃/min, preserving the temperature for 4h, and then naturally cooling. And (3) carrying out acid washing on the carbonized product for 4h by using 1mol/L hydrochloric acid, centrifuging, drying and grinding to obtain the hollow porous silicon-carbon @ lignin-carbon nanospheres.

Example 3

Weighing 9g of NaOH and dissolving in 190g of deionized water, then dissolving 50g of bamboo pulp alkali lignin in NaOH solution, preparing the solution with the solid content of 25 wt%, and transferring the solution to a three-neck flask after the solution is completely dissolved. The stirring paddle was placed vertically with the flask, without reaching the thermometer, the condenser tube was fixed with a clamp, the condenser tube was taken in and out, the oil bath pot temperature was set to 85 ℃, after the temperature reached 85 ℃, 13g of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added dropwise to the above lignin solution at a rate of 1.4mL/min with a peristaltic pump (6 g of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added dropwise first, 10g of 50% sodium hydroxide solution was added to the solution in order to maintain the reaction system ph in the range of 11 to 12), and then the remaining 3-chloro-2-hydroxypropyltrimethylammonium chloride was all added dropwise to the lignin solution). The time at which the addition of the intermediate was complete was recorded and the reaction was then allowed to incubate for 4 h. And after the reaction is finished, closing the condensed water, cooling the reaction liquid to room temperature, and dialyzing, filtering, and freeze-drying to obtain the quaternized lignin (QAL).

2g of QAL was added to 100ml of an ethanol-water (1:1) solution, 0.1g of SDBS (sodium dodecylbenzenesulfonate) was added thereto, the pH was maintained at 4 while stirring, 1.0g of ethyl orthosilicate dispersed in 40ml of an ethanol solution was added dropwise to the QAL solution at a rate of 0.25ml/min, and after completion of the dropwise addition, stirring was continued for 1 hour to obtain a mixed dispersion. And (3) placing the mixed dispersion liquid into a 200ml polytetrafluoroethylene reaction kettle, and carrying out hydrothermal reaction for 8h at the temperature of 200 ℃. After the reaction kettle is cooled to room temperature, centrifuging, washing, re-centrifuging and freeze-drying the solution to obtain QAL/SiO₂And (3) a compound.

2gQAL/SiO₂The composite was placed in a porcelain ark of a 30 x 90 x 60mm corundum porcelain ark. Carbonizing by using a carbonization furnace, wherein the carbonizing conditions are as follows: raising the temperature from room temperature to 800 ℃ after 80min under the protection of nitrogen, preserving the temperature for 2h, and then naturally cooling. Grinding to obtain lignin porous carbon/silicon dioxide (LC/SiO)₂) And (c) a complex.

1g of LC/SiO was taken₂The compound and 2g of magnesium powder are mixed uniformly and placed in a corundum porcelain ark with 30 x 90 x 60mm, and the carbonization conditions are as follows: raising the temperature from room temperature to 400 ℃ after 40min under the condition of argon-hydrogen mixed gas, raising the temperature to 850 ℃ at the speed of 4 ℃/min, preserving the temperature for 2h, and then naturally cooling. And (3) carrying out acid washing on the carbonized product for 12h by using 1mol/L hydrochloric acid, centrifuging, drying and grinding to obtain the hollow porous silicon-carbon @ lignin-carbon nanospheres.

Example 4

Weighing 9g of NaOH and dissolving in 200g of deionized water, then dissolving 50g of reed alkali lignin in NaOH solution to prepare solution with the solid content of 25 wt%, and transferring to a three-neck flask after the solution is dissolved. The stirring paddle was placed vertically with the flask, without reaching the thermometer, the condenser tube was fixed with a clamp, the condenser tube was taken in and out, the oil bath pot temperature was set to 85 ℃, after the temperature reached 85 ℃, 18g of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added dropwise to the above lignin solution at a rate of 1.2mL/min with a peristaltic pump (9 g of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added dropwise first, 9g of 50% sodium hydroxide solution was added to the solution in order to maintain the reaction system ph in the range of 11 to 12), and then the remaining 3-chloro-2-hydroxypropyltrimethylammonium chloride was all added dropwise to the lignin solution). The time at which the addition of the intermediate was completed was recorded, followed by incubation for 4 h. And after the reaction is finished, closing the condensed water, cooling the reaction liquid to room temperature, and dialyzing, filtering, and freeze-drying to obtain the quaternized lignin (QAL).

3g of QAL is taken and added into 80ml of ethanol-water (1:6) solution, 0.1g of SDBS (sodium dodecyl benzene sulfonate) is added, the pH value is kept at 5 and stirring is continuously carried out, 1.5g of silicon tetrachloride dispersed into 80ml of ethanol-water (1:6) solution is dripped into the QAL solution at the speed of 0.25ml/min, and stirring is continuously carried out for 3h after dripping is finished, so that mixed dispersion liquid is obtained. And (3) placing the mixed dispersion liquid into a 200ml polytetrafluoroethylene reaction kettle, and carrying out hydrothermal reaction at 180 ℃ for 6 h. After the reaction kettle is cooled to room temperature, centrifuging, washing, re-centrifuging and freeze-drying the solution to obtain QAL/SiO₂And (c) a complex.

2gQAL/SiO₂The composite was placed in a porcelain ark of a 30 x 90 x 60mm corundum porcelain ark. Carbonizing by using a carbonization furnace, wherein the carbonizing conditions are as follows: raising the temperature from room temperature to 700 ℃ after 70min under the protection of nitrogen, keeping the temperature for 2h, and then naturally cooling. Grinding to obtain lignin porous carbon/silicon dioxide (LC/SiO)₂) And (c) a complex.

1g of LC/SiO was taken₂The compound and 2.5g of magnesium powder are mixed uniformly and placed in a corundum porcelain square boat with the size of 30 x 90 x 60mm, and the carbonization conditions are as follows: raising the temperature from room temperature to 350 ℃ after 35min under the condition of argon-hydrogen mixed gas, raising the temperature to 700 ℃ at the speed of 5 ℃/min, preserving the temperature for 4h, and then naturally cooling. And (3) pickling the carbonized product for 2h by using 2mol/L hydrochloric acid, centrifuging, drying and grinding to obtain the hollow porous silicon-carbon @ lignin-carbon nanospheres.

Example 5

Weighing 9g of NaOH and dissolving in 190g of deionized water, then dissolving 50g of cotton pulp alkali lignin in NaOH solution, preparing the solution with the solid content of 25 wt%, and transferring the solution to a three-neck flask after the dissolution is finished. The stirring paddle was placed vertically with the flask, without reaching the thermometer, the condenser tube was fixed with a clamp, the condenser tube was taken in and out, the oil bath pot temperature was set to 85 ℃, after the temperature reached 85 ℃, 23g of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added dropwise to the above lignin solution at a rate of 1.5mL/min with a peristaltic pump (10 g of 3-chloro-2-hydroxypropyltrimethylammonium chloride was added dropwise first, 8g of 50% sodium hydroxide solution was added to the solution in order to maintain the reaction system ph in the range of 11 to 12), and then the remaining 3-chloro-2-hydroxypropyltrimethylammonium chloride was all added dropwise to the lignin solution). The time at which the addition of the intermediate was completed was recorded, followed by incubation for 4 h. And after the reaction is finished, closing the condensed water, cooling the reaction liquid to room temperature, and dialyzing, filtering, and freeze-drying to obtain the quaternized lignin (QAL).

3g of QAL was dissolved in 120ml of an ethanol-water (1:1) solution, 0.1g of SDBS (sodium dodecylbenzenesulfonate) was added thereto, and while keeping pH 3 under stirring, 2.0g of tetramethoxysilane dispersed in 20ml of an ethanol solution was added dropwise to the QAL solution at a rate of 0.25ml/min, and after completion of the dropwise addition, stirring was continued for 2 hours to obtain a mixed dispersion. And (3) placing the mixed dispersion liquid into a 200ml polytetrafluoroethylene reaction kettle, and carrying out hydrothermal reaction for 2h at 200 ℃. And after the reaction kettle is cooled to room temperature, centrifuging, washing, centrifuging again, and freeze-drying the solution to obtain the QAL/SiO2 compound.

2gQAL/SiO₂The composite was placed in a porcelain ark of a 30 x 90 x 60mm corundum porcelain ark. Carbonizing by using a carbonization furnace, wherein the carbonizing conditions are as follows: raising the temperature from room temperature to 850 ℃ after 85min under the protection of nitrogen, keeping the temperature for 2h, and then naturally cooling. Grinding to obtain lignin porous carbon/silicon dioxide (LC/SiO)₂) And (c) a complex.

1g of LC/SiO was taken₂The compound and 0.6g of magnesium powder are mixed uniformly and placed in a corundum porcelain ark with 30 x 90 x 60mm, and the carbonization conditions are as follows: heating to 250 deg.C after 25min from room temperature under the condition of argon-hydrogen mixed gas, heating to 850 deg.C at a speed of 3 deg.C/min, maintaining for 6h, and naturally cooling. And (3) carrying out acid washing on the carbonized product for 4h by using 1.5mol/L hydrochloric acid, centrifuging, drying and grinding to obtain the hollow porous silicon-carbon @ lignin-carbon nanospheres.

Example 6

The hollow porous silicon carbon @ lignin carbon nanosphere composite material prepared in examples 1-5 was used as an anode active material.

Preparing slurry from silicon carbon @ lignin carbon nanospheres, conductive carbon black and PVDF according to the mass ratio of 8:1:1, coating the slurry by using a copper foil as a current collector and a scraper with the height of 20 mu m, drying at 90 ℃ for 20min, transferring into a vacuum drying oven, drying at 120 ℃ for 12h, and rolling by a roll-to-roll machine to obtain the pole piece. The mass of active material in each pole piece was 300 mg.

The pole piece is used as an anode, the lithium piece is used as a counter electrode, and LiPF₆The electrolyte is assembled by adopting a battery with the model number of CR2032, and a cyclic voltammetry test, a constant current charge and discharge test, a multiplying power performance test and an alternating current impedance test are carried out. The assembly of the cell was performed in a high argon glove box.

The results of the constant current charge and discharge test performed by the nova battery test system are shown in table 1.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. The preparation method of the hollow porous silicon-carbon @ lignin-carbon nanospheres is characterized by comprising the following steps of:

s1, preparing quaternized lignin;

s2, dissolving quaternized lignin in a first ethanol-water solution with the pH = 2-5, adding a surfactant, dispersing a silicon source into a second ethanol-water solution, dropwise adding the second ethanol-water solution into the quaternized lignin solution at the speed of 0.1-0.5 ml/min, stirring and reacting for 1-4 h to obtain a lignin/silicon source mixed solution, performing hydrothermal reaction on the lignin/silicon source mixed solution by utilizing the electrostatic interaction between the quaternized lignin and silicon dioxide generated by continuous hydrolysis of the silicon source to form lignin-silicon dioxide nanospheres,

the surfactant is cetyl trimethyl ammonium bromide, polyethylene glycol or sodium dodecyl benzene sulfonate;

the silicon source is tetraethoxysilane, sodium silicate, tetramethoxysilane or silicon tetrachloride, and the mass volume ratio of the silicon source to the second ethanol-water solution is 0.7 (10-100);

s4, carrying out magnesiothermic reduction on the lignin porous carbon/silicon dioxide nanospheres to obtain a silicon carbon @ lignin carbon nanosphere precursor,

the magnesiothermic reduction process comprises: heating the mixture of the lignin porous carbon/silicon dioxide nanospheres and the magnesium powder to 200-400 ℃, heating to 650-850 ℃ at a speed of 2-10 ℃/min, keeping for 2-6 h, and cooling to room temperature to obtain a silicon carbon @ lignin carbon nanosphere precursor;

and S5, acid washing the silicon carbon @ lignin carbon nanosphere precursor to obtain the silicon carbon @ lignin carbon nanospheres which are regular in shape and hollow and porous in the interior.

2. The method for preparing hollow porous silicon-carbon @ lignin-carbon nanospheres according to claim 1,

the mass volume ratio of the quaternized lignin to the first ethanol-water solution is 3 (20-160), and the volume ratio of ethanol to water in the first ethanol-water solution is 10 (5-100);

the hydrothermal reaction is carried out for 2-24 h at 120-200 ℃, and the volume ratio of ethanol to water in the second ethanol-water solution is 100 (0-150);

the weight ratio of the quaternized lignin to the silicon source is 100: 20-100.

3. The method for preparing hollow porous silicon-carbon @ lignin-carbon nanospheres according to claim 1,

s3, the carbonization temperature of the lignin-silicon dioxide nanospheres is 650-850 ℃.

4. The method for preparing hollow porous silicon-carbon @ lignin-carbon nanospheres according to claim 1,

the carbonization process is carried out under the condition of inert gas;

heating the lignin-silicon dioxide nanospheres to 650-850 ℃ at the speed of 5-15 ℃/min, preserving the heat for 1-4 h, and cooling to room temperature to obtain the lignin porous carbon/silicon dioxide nanospheres.

5. The preparation method of the hollow porous silicon-carbon @ lignin-carbon nanosphere according to claim 1, wherein the specific method of magnesiothermic reduction in step S4 is: mixing the lignin porous carbon/silicon dioxide nanospheres and magnesium powder according to the mass ratio of 1: 0.8-3 to obtain a mixture.

6. The method for preparing hollow porous silicon-carbon @ lignin-carbon nanospheres according to claim 5,

the magnesium thermal reduction process is carried out under the condition of argon-hydrogen mixed gas.

7. The preparation method of the hollow porous silicon carbon @ ligno-carbon nanosphere according to claim 1, wherein step S5 is performed by acid washing the precursor of the silicon carbon @ ligno-carbon nanosphere with hydrochloric acid solution with concentration of 0.1-2 mol/L.

8. Use of the hollow porous silicon carbon @ ligno-carbon nanospheres of any of claims 1-7 in the preparation of a lithium ion battery.

9. The application of the hollow porous silicon carbon @ lignin carbon nanosphere according to claim 8 is used for preparing a lithium ion battery negative plate, and the specific preparation method comprises the following steps:

preparing slurry from silicon carbon @ lignin carbon nanospheres, conductive carbon black and PVDF according to the mass ratio of 8 (0.5-1.5) to (0.5-1.5), coating the slurry by using a scraper with copper foil as a current collector, drying, and rolling by using a roll-to-roll machine to obtain the pole piece.