CN113178562B - Fabric-like carbon-coated silicon dioxide composite material and application thereof - Google Patents
Fabric-like carbon-coated silicon dioxide composite material and application thereof Download PDFInfo
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- H01M4/00—Electrodes
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
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- 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
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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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
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- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract
The invention discloses a preparation method of a fabric-shaped carbon-coated silicon dioxide composite material, which comprises the following preparation steps: adding cellulose nanofibrils into deionized water, performing ultrasonic treatment to obtain cellulose nanofibrils suspension, uniformly mixing the cellulose nanofibrils suspension with silicon dioxide nanoparticles, freezing the mixture, and performing freeze-drying treatment to obtain silicon dioxide/cellulose nanofibrils composite aerogel; and carrying out carbonization treatment under the protection of inert gas to obtain the fabric-shaped carbon-coated silicon dioxide composite material. The preparation process is simple, harsh conditions such as high temperature and high pressure are not needed, and when the fabric-shaped carbon-coated silicon dioxide composite material is used as a lithium ion negative electrode material, the fabric-shaped carbon-coated silicon dioxide composite material has a good surface structure, a large specific surface area and a high specific capacity.
Description
Technical Field
The invention belongs to the technical field of materials, and particularly relates to a fabric-shaped carbon-coated silicon dioxide composite material and application thereof.
Background
Lithium ion batteries are widely used in the fields of electronic devices, electric vehicles, and the like because of their advantages of high energy density, long cycle life, and the like. The graphite is used as a main negative electrode material of a commercial lithium ion battery, the theoretical specific capacity of the graphite is only 372mAh/g, and the demand of modern production and life is difficult to meet. In order to meet the requirements of social development, it is very important to develop a novel material with higher energy density to replace graphite materials. SiO 2 2 The negative electrode material is widely concerned due to the characteristics of high theoretical specific capacity (1965mAh/g), good cycling stability and the like. However, SiO 2 The further application of the material is limited by the defects of low conductivity and easy volume expansion in the charging and discharging process. Thus, SiO 2 When used as the cathode material of the lithium ion battery, the material is mainly usedThe method aims to solve the problems of large volume change, poor conductivity and the like of an active material in the charging and discharging process. To solve these problems, SiO is mainly used at present 2 Material nanocrystallization and compounding with carbon materials to mitigate SiO 2 The volume expansion of the material in the charge and discharge process and the improvement of the conductivity of the material improve the electrochemical performance of the material.
The carbon material has the characteristics of stable structure, higher electronic conductivity and the like, and can be made into SiO 2 One of the ideal materials for compounding. Cellulose has many advantages as well as the potential to synthesize porous carbon, which is one of the ideal raw materials for synthetic carbon-based materials. The cellulose material is placed in an inert gas or vacuum environment to carry out preliminary decomposition and high-temperature carbonization treatment on the carbon compound with rich content per se, so that the cellulose carbon nano material with better conductivity and a multi-stage structure can be obtained. Besides abundant hydroxyl groups carried by the cellulose, a large amount of carboxyl groups can be introduced into the surface of the modified cellulose, and the cellulose can be converted into carbon oxides, water and porous carbonaceous materials after further high-temperature carbonization treatment. Because the cellulose nano-fibril has the characteristics of high thermal stability, good mechanical property, low expansion coefficient, high length-diameter ratio, biodegradability and the like, the cellulose nano-fibril can be used as a carbon source in the energy field and can also be used for preparing nano materials. The cellulose nanofibrils have a large length-diameter ratio, and are easy to form a porous three-dimensional carbon network structure by mutual weaving when combined with an active substance, the gaps can provide space for the active material with serious volume expansion in the charging and discharging process, and meanwhile, the three-dimensional carbon network can improve the conductivity of the material, so that the material becomes a good base material for constructing a composite material.
Through searching, the following two patent publications related to the patent application of the invention are found:
1. a silicon oxide coated nano carbon composite material and a preparation method (CN101215431B) thereof, which discloses a silicon oxide coated nano carbon composite material and a preparation method thereof, wherein a nano carbon matrix and organosiloxane are used as raw materials, the coated silicon oxide is deposited on the nano carbon matrix by pyrolyzing the organosiloxane in a gas phase, and the thickness of the silicon oxide layer on a single carbon nano tube can be controlled to be 5-300nm by controlling reaction conditions; the carbon matrix is nano carbon and comprises nano carbon fibers and nano carbon tubes, and the diameter of the nano carbon tubes is 1-500 nm; the preparation method comprises the steps of generating nano-carbon in airflow, and rapidly pyrolyzing the organic siloxane in the airflow containing the nano-carbon at the pyrolysis temperature of 600-1500 ℃. The invention is a method for rapidly and controllably synthesizing a large number of coaxial nanofibers with uniform structures, and has the characteristics of simplicity, convenience, high efficiency, high yield and the like.
2. The invention discloses a carbon-coated nano silicon composite material and a preparation method and application thereof (CN106784732B), and aims to solve the technical problems of complex preparation process and high cost of the existing method for reducing the volume effect of a silicon-based negative electrode material by utilizing nanocrystallization, alloying or porosity. The carbon-coated nano silicon composite material is powder with a core-shell structure, wherein nano silicon particles are used as contents, and carbon is used as a shell. The preparation method comprises the following steps: and (3) carrying out oxygen diffusion on the micron-sized silicon powder with the oxidized layer on the surface, then carrying out carbon coating treatment, and then soaking the micron-sized silicon powder with the oxidized layer by using a hydrofluoric acid solution to remove silicon oxide components to obtain the carbon-coated nano-silicon composite material. The capacity of the carbon-coated nano silicon composite material reaches over 900mAh/g, the attenuation after 150 cycles is less than 4%, and the carbon-coated nano silicon composite material can be used as a silicon negative electrode material of a lithium battery.
By contrast, the present patent application is substantially different from the above patent publications.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a fabric-shaped carbon-coated silicon dioxide composite material and application thereof.
The technical scheme adopted by the invention for solving the technical problem is as follows:
a fabric-like carbon-coated silicon dioxide composite material is prepared by the following steps:
uniformly dispersing nano silicon dioxide in deionized water through ultrasonic stirring for 20-50 min to obtain uniformly dispersed silicon dioxide suspension liquid;
the method comprises the following steps of adding cellulose nanofibrils into deionized water, and then carrying out ultrasonic stirring to prepare a gel-like cellulose nanofibril suspension with the concentration of 0.1-5 wt%, wherein the mass ratio is 1: slowly adding the silicon dioxide suspension liquid obtained in the step into a cellulose nanofibril suspension liquid in a proportion of 1-30, and performing ultrasonic dispersion for 20-90 min to prepare a silicon dioxide/cellulose nanofibril mixed solution;
thirdly, freezing the mixed solution prepared in the second step at-80 to-60 ℃ for 4 to 36 hours, and then quickly taking out the mixed solution for freeze-drying treatment to obtain the silicon dioxide/cellulose nanofibril composite aerogel;
fourthly, placing the silicon dioxide/cellulose nanofibril composite aerogel in the step three in a tube furnace for carbonization treatment, wherein the temperature rise process is as follows: heating to 200-300 ℃ in the air atmosphere, preserving heat for 1-4 h, heating to 500-1200 ℃ under the protection of inert gas, preserving heat for 1-5 h, and cooling to room temperature to obtain the fabric-like carbon-coated silicon dioxide composite material.
In the first step, the concentration of the nano silicon dioxide is 0.5-10 wt%, and the particle size of the nano silicon dioxide is 10-300 nm.
Further, in the second step, the diameter of the cellulose nano-fibrils is 2-60 nm, the length of the cellulose nano-fibrils is 0.5-60 microns, and the length-diameter ratio of the cellulose nano-fibrils is larger than 100.
Further, the step three of quickly taking out the product to be subjected to freeze-drying treatment specifically comprises the following steps: taking out and placing in an ultra-low temperature quick freezing refrigerator for freezing for 4-36 h at-80 to-60 ℃, and then quickly taking out and carrying out freeze-drying treatment for 12-48 h at-70 to-50 ℃ in a freeze drying box.
Further, the inert gas in step fourth is one of nitrogen, argon, and helium.
Furthermore, in the step four, the temperature is raised to 200-300 ℃ at a rate of 1-5 ℃/min in an air atmosphere, the temperature is maintained for 1.5-3.5 hours, then the temperature is raised to 600-1200 ℃ at a rate of 5-15 ℃/min under the protection of inert gas, and the temperature is maintained for 2-5 hours.
The use of a textile carbon-coated silica composite as described above in a battery.
The method for assembling the half cell by using the fabric-shaped carbon-coated silicon dioxide composite material comprises the following steps:
the method comprises the following steps of coating a silicon dioxide composite material by fabric-shaped carbon: acetylene black: weighing and mixing polyvinylidene fluoride according to the mass ratio of 8:1:1, and grinding in a mortar for 10-70 min to obtain black powder; then, according to the solid-liquid ratio of 1: 2-10, dropwise adding N-methyl-1-pyrrolidone into the powder, and uniformly stirring to prepare the powder into a slurry state;
rapidly coating the obtained uniform slurry on a dried copper foil, then putting the copper foil coated with the slurry into a vacuum drying oven, and carrying out vacuum drying for 3-30 h at the temperature of 30-100 ℃;
thirdly, compacting the coated and dried copper foil by using a tablet press, cutting the copper foil coated with the composite material into electrode slices with the diameter of 10-20 mm by using a tablet press, and drying the electrode slices at 30-150 ℃ for 0.5-8 h for later use;
and fourthly, assembling the half-cell in the glove box according to the sequence of the negative electrode shell, the electrode slice, the electrolyte, the diaphragm, the electrolyte, the lithium sheet, the gasket, the spring sheet and the positive electrode shell, and packaging the half-cell by using a packaging machine after the half-cell is successfully assembled to obtain the half-cell.
Furthermore, the electrolyte in step fourth is an organic solution mixed solution of lithium hexafluorophosphate, wherein the concentration of lithium hexafluorophosphate in the organic solution mixed solution is 1.0M, the organic mixed solution is ethylene carbonate, dimethyl carbonate and methylethyl carbonate in a volume ratio of 1:1:1, and the diaphragm in step fourth is a polypropylene microporous membrane. And the packaged half cell can be subjected to electrochemical test after being placed for 6-48 hours at room temperature.
The invention has the advantages and positive effects that:
1. according to the invention, the cellulose nano-fibrils are used as a base material for constructing a three-dimensional carbon network structure, and the base material is compounded with silicon dioxide nanoparticles and then subjected to freeze drying and carbonization treatment to obtain the fabric-like carbon-coated silicon dioxide composite material derived from the cellulose nano-fibrils. The silicon dioxide is embedded into a three-dimensional porous carbon network structure formed by mutually interweaving cellulose nano fibrils, wherein a large number of gaps can fully accommodate volume expansion of the silicon dioxide in the charging and discharging processes, and meanwhile, the carbon network can provide a channel for charge transmission to improve the conductivity of the material, so that the rate capability and the cycling stability of the material are improved.
2. The preparation method of the composite material is simple and efficient, harsh conditions such as high temperature and high pressure are not needed, and when the fabric-shaped carbon-coated silicon dioxide composite material is used as a lithium ion negative electrode material, the fabric-shaped carbon-coated silicon dioxide composite material has a good surface structure, a large specific surface area and a high specific capacity.
3. The cellulose nano-fibril adopted by the invention is an environment-friendly biomass resource with low expansion coefficient, high length-diameter ratio and biodegradability, and the derived carbon nano-fiber has obvious advantages compared with the traditional carbon material, and can be applied to the field of energy sources, thus expanding the application range and realizing high-value utilization.
4. For SiO in the prior art 2 The invention provides a preparation method of a fabric-shaped carbon-coated silicon dioxide composite material. The material is used for preparing the lithium ion battery negative plate and has the advantages of good rate capability and high safety performance. The method uses the biodegradable cellulose nano-fibrils which are environment-friendly, low in expansion coefficient, high in length-diameter ratio and capable of being degraded as the base materials for constructing the carbon network structure, so that the application range of the plant fibers is expanded, and the plant fibers are utilized in a high-value mode.
Drawings
FIG. 1 is an SEM photograph of a fabric-like carbon-coated silica composite material prepared in example 1 of the present invention;
FIG. 2 is a nitrogen adsorption-desorption curve and a pore size distribution diagram of the fabric-like carbon-coated silica composite material prepared in example 1 of the present invention;
FIG. 3 is a graph showing the cycle performance of the fabric-like carbon-coated silica composite obtained in example 1 of the present invention;
fig. 4 is a nitrogen adsorption-desorption curve and a pore size distribution diagram of the fabric-like carbon-coated silica composite material prepared in example 2 of the present invention;
FIG. 5 is a graph of the cycle performance of the fabric-like carbon-coated silica composite prepared in example 2 of the present invention;
fig. 6 is a nitrogen adsorption-desorption curve and a pore size distribution diagram of the fabric-like carbon-coated silica composite material prepared in example 3 of the present invention;
fig. 7 is a graph showing cycle performance of the fabric-like carbon-coated silica composite prepared in example 3 of the present invention.
Detailed Description
The present invention is further illustrated by the following examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
The raw materials used in the invention are all conventional commercial products if no special description is provided, the method used in the invention is all conventional methods in the field if no special description is provided, and the mass of all the materials used in the invention is the conventional use mass.
A fabric-like carbon-coated silicon dioxide composite material is prepared by the following steps:
uniformly dispersing nano silicon dioxide in deionized water through ultrasonic stirring for 20-50 min to obtain uniformly dispersed silicon dioxide suspension liquid;
the method comprises the following steps of adding cellulose nanofibrils into deionized water, and then carrying out ultrasonic stirring to prepare a gel-like cellulose nanofibril suspension with the concentration of 0.1-5 wt%, wherein the mass ratio is 1: slowly adding the silicon dioxide suspension liquid obtained in the step I into a cellulose nano-fibril suspension liquid in a proportion of 1-30, and performing ultrasonic dispersion for 20-90 min to prepare a silicon dioxide/cellulose nano-fibril mixed solution;
freezing the mixed solution prepared in the step II at-80 to-60 ℃ for 4-36 h, and then quickly taking out the mixed solution for freeze-drying treatment to obtain the silicon dioxide/cellulose nanofibril composite aerogel;
fourthly, placing the silicon dioxide/cellulose nanofibril composite aerogel in the step three in a tube furnace for carbonization treatment, wherein the temperature rise process is as follows: heating to 200-300 ℃ in the air atmosphere, preserving heat for 1-4 h, heating to 500-1200 ℃ under the protection of inert gas, preserving heat for 1-5 h, and cooling to room temperature to obtain the fabric-like carbon-coated silicon dioxide composite material.
Preferably, in the first step, the concentration of the nano silicon dioxide is 0.5 to 10 wt%, and the particle size of the nano silicon dioxide is 10 to 300 nm.
Preferably, the diameter of the cellulose nanofibrils in the step II is 2-60 nm, the length is 0.5-60 microns, and the length-diameter ratio is larger than 100.
Preferably, the step three of quickly taking out the product for freeze-drying treatment specifically comprises the following steps: taking out and placing in an ultra-low temperature quick freezing refrigerator for freezing for 4-36 h at-80 to-60 ℃, and then quickly taking out and carrying out freeze-drying treatment for 12-48 h at-70 to-50 ℃ in a freeze drying box.
Preferably, the inert gas in step fourth is one of nitrogen, argon and helium.
Preferably, in the step fourth, the temperature is raised to 200-300 ℃ at a rate of 1-5 ℃/min in an air atmosphere, the temperature is preserved for 1.5-3.5 hours, then the temperature is raised to 600-1200 ℃ at a rate of 5-15 ℃/min under the protection of inert gas, and the temperature is preserved for 2-5 hours.
The use of a textile carbon-coated silica composite as described above in a battery.
The method for assembling the half cell by using the fabric-shaped carbon-coated silicon dioxide composite material comprises the following steps:
the method comprises the following steps of coating a silicon dioxide composite material by fabric-shaped carbon: acetylene black: weighing and mixing polyvinylidene fluoride according to the mass ratio of 8:1:1, and grinding in a mortar for 10-70 min to obtain black powder; then, according to the solid-liquid ratio of 1: 2-10, dropwise adding N-methyl-1-pyrrolidone into the powder, and uniformly stirring to prepare the powder into a slurry state;
rapidly coating the obtained uniform slurry on a dried copper foil, then putting the copper foil coated with the slurry into a vacuum drying oven, and carrying out vacuum drying for 3-30 h at the temperature of 30-100 ℃;
thirdly, compacting the coated and dried copper foil by using a tablet press, cutting the copper foil coated with the composite material into electrode slices with the diameter of 10-20 mm by using a tablet press, and drying the electrode slices at 30-150 ℃ for 0.5-8 h for later use;
and fourthly, assembling the half-cell in the glove box according to the sequence of the negative electrode shell, the electrode slice, the electrolyte, the diaphragm, the electrolyte, the lithium slice, the gasket, the spring piece and the positive electrode shell, and packaging the half-cell by using a packaging machine after the half-cell is successfully assembled to obtain the half-cell.
Preferably, the electrolyte in step fourth is an organic solution mixed solution of lithium hexafluorophosphate, wherein the concentration of lithium hexafluorophosphate in the organic solution mixed solution is 1.0M, the organic mixed solution is ethylene carbonate, dimethyl carbonate and methylethyl carbonate in a volume ratio of 1:1:1, and the separator in step fourth is a polypropylene microporous membrane. And the packaged half cell can be subjected to electrochemical test after being placed for 6-48 hours at room temperature.
Specifically, the preparation and detection are as follows:
example 1
A fabric-like carbon-coated silica composite material is prepared by the following steps:
(1) uniformly dispersing 0.1g of silicon dioxide nano particles into 10ml of deionized water by ultrasonic stirring for 30min to obtain a uniformly dispersed silicon dioxide suspension.
(2) Adding cellulose nanofibrils into deionized water, and then carrying out ultrasonic stirring for 30min to prepare a gel-like cellulose nanofibril suspension with the concentration of 0.5 wt%, wherein the mass ratio of the gel-like cellulose nanofibril suspension to the deionized water is 1: 8, slowly adding the silicon dioxide suspension obtained in the step (1) into the cellulose nano-fibril suspension, and then carrying out ultrasonic dispersion for 30min to prepare a silicon dioxide/cellulose nano-fibril mixed solution;
(3) freezing the mixed solution prepared in the step (2) at-80 ℃ for 8h, and then quickly taking out the mixed solution for freeze-drying treatment for 36h to obtain silicon dioxide/cellulose nanofibril composite aerogel;
(4) and (4) putting the silicon dioxide/cellulose nanofibril composite aerogel obtained in the step (3) into a tube furnace for carbonization treatment, wherein the temperature rise process comprises the following steps: and heating to 250 ℃ in the air atmosphere, preserving heat for 2h, heating to 900 ℃ under the protection of inert gas, preserving heat for 3h, and cooling to room temperature to obtain the fabric-shaped carbon-coated silicon dioxide composite material.
SEM pictures, nitrogen adsorption-desorption curves, and electrochemical performance tests of the fabric-like carbon-coated silica composite are shown in fig. 1 to 3.
The material obtained in example 1 was assembled into a half cell as follows:
[1] according to the fabric-like carbon-coated silica composite material: acetylene black: weighing and mixing polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, and grinding in a mortar for 25min to obtain black powder; then, a proper amount of N-methyl-1-pyrrolidone is added dropwise into the powder, and the mixture is stirred uniformly to be prepared into a slurry state.
[2] And quickly coating the obtained uniform slurry on a dried copper foil, putting the copper foil coated with the slurry into a vacuum drying oven, and drying for 12 hours in vacuum at 80 ℃.
[3] And compacting the coated and dried copper foil by using a tablet press, cutting the copper foil coated with the composite material into electrode slices with the diameter of 14mm by using a tablet press, and drying the electrode slices at 120 ℃ for 3h for later use.
[4] And assembling the half-cell in the glove box according to the sequence of the negative electrode shell, the electrode plate, the electrolyte, the diaphragm, the electrolyte, the lithium plate, the gasket, the spring piece and the positive electrode shell, and packaging the half-cell by using a packaging machine after the half-cell is successfully assembled. The electrolyte is an organic solution mixed solution of lithium hexafluorophosphate, wherein the concentration of lithium hexafluorophosphate in the organic solution mixed solution is 1.0M, the organic mixed solution is ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate in a volume ratio of 1:1:1, and the diaphragm is a polypropylene microporous membrane. The packaged half-cells can be tested electrochemically after being left for 24 hours at room temperature. The method adopts a constant current charging and discharging method for testing, a testing instrument is a Wuhan blue CT2001A testing system, the testing current density is 0.1A/g, the voltage range is 0.01-3.0V, and 100-cycle performance tests are performed on the manufactured half cell.
The results show that:
the prepared fabric-shaped carbon-coated silicon dioxide composite material is three-dimensional porous; the specific surface area is 661.1m 2 (g) total pore volume of 0.42cm 3 (iv) g; the specific capacity can reach 645mAh/g after 100 times of circulation under the current density of 0.1A/g.
Example 2
A fabric-like carbon-coated silica composite material is prepared by the following steps:
(1) 0.1g of silicon dioxide nano particles are uniformly dispersed into 10ml of deionized water by ultrasonic stirring for 30min to obtain uniformly dispersed silicon dioxide suspension.
(2) Adding cellulose nanofibrils into deionized water, carrying out ultrasonic stirring for 20min, preparing a gel-like cellulose nanofibril suspension with the concentration of 0.5 wt%, and mixing the cellulose nanofibrils with the water according to the mass ratio of 1: 3, slowly adding the silicon dioxide suspension obtained in the step (1) into the cellulose nano fibril suspension, and then carrying out ultrasonic dispersion for 20min to prepare a silicon dioxide/cellulose nano fibril mixed solution;
(3) freezing the mixed solution prepared in the step (2) at-80 ℃ for 6h, then quickly taking out the mixed solution and carrying out freeze-drying treatment for 32h to obtain the silicon dioxide/cellulose nanofibril composite aerogel;
(4) and (4) putting the silicon dioxide/cellulose nanofibril composite aerogel obtained in the step (3) into a tube furnace for carbonization treatment, wherein the temperature rise process comprises the following steps: and heating to 250 ℃ in the air atmosphere, preserving heat for 2 hours, heating to 900 ℃ under the protection of inert gas, preserving heat for 3 hours, and cooling to room temperature to obtain the fabric-shaped carbon-coated silicon dioxide composite material.
The nitrogen adsorption-desorption curves and electrochemical performance tests of the fabric-like carbon-coated silica composite material are shown in fig. 4 to 5.
Half cells were assembled as described in example 1 for cell assembly and tested using the same electrochemical test method.
The results show that:
the prepared fabric-shaped carbon-coated silicon dioxide composite material is three-dimensional porous; specific surface area of 199.9m 2 Per g, total pore volume of 0.17cm 3 (iv) g; the specific capacity can reach 453mAh/g after 100 times of circulation under the current density of 0.1A/g.
Example 3
A fabric-like carbon-coated silica composite material is prepared by the following steps:
(1) 0.1g of silicon dioxide nano particles are uniformly dispersed into 10ml of deionized water by ultrasonic stirring for 30min to obtain uniformly dispersed silicon dioxide suspension.
(2) Adding cellulose nanofibrils into deionized water, and then carrying out ultrasonic stirring for 60min to prepare a gel-like cellulose nanofibril suspension with the concentration of 0.5 wt%, wherein the mass ratio of the gel-like cellulose nanofibril suspension to the deionized water is 1: 18, slowly adding the silica suspension obtained in the step (1) into the cellulose nano fibril suspension, and performing ultrasonic dispersion for 60min to prepare a silica/cellulose nano fibril mixed solution;
(3) freezing the mixed solution prepared in the step (2) at-80 ℃ for 10h, and then quickly taking out the mixed solution for freeze-drying treatment for 48h to obtain silicon dioxide/cellulose nanofibril composite aerogel;
(4) and (4) putting the silicon dioxide/cellulose nanofibril composite aerogel obtained in the step (3) into a tube furnace for carbonization treatment, wherein the temperature rise process comprises the following steps: and heating to 250 ℃ in the air atmosphere, preserving heat for 2 hours, heating to 900 ℃ under the protection of inert gas, preserving heat for 3 hours, and cooling to room temperature to obtain the fabric-shaped carbon-coated silicon dioxide composite material.
The nitrogen adsorption-desorption curves and electrochemical performance tests of the fabric-like carbon-coated silica composite material are shown in fig. 6 to 7.
Half cells were assembled according to the cell assembly method described in example 1 and tested using the same electrochemical test method.
The results show that:
the prepared fabric-shaped carbon-coated silicon dioxide composite material is three-dimensional porous; specific surface area of 1189.3m 2 Per g, total pore volume of 0.92cm 3 (ii)/g; the specific capacity can reach 358mAh/g after 100 times of circulation under the current density of 0.1A/g.
Although the embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, alterations and modifications are possible without departing from the spirit and scope of this disclosure and appended claims, and accordingly, the scope of this disclosure is not limited to the embodiments disclosed.
Claims (4)
1. A fabric-like carbon-coated silica composite characterized in that: the preparation steps are as follows:
uniformly dispersing nano silicon dioxide in deionized water through ultrasonic stirring for 20-50 min to obtain uniformly dispersed silicon dioxide suspension liquid;
the method comprises the following steps of adding cellulose nanofibrils into deionized water, and then carrying out ultrasonic stirring to prepare a gel-like cellulose nanofibril suspension with the concentration of 0.1-5 wt%, wherein the mass ratio is 1: slowly adding the silicon dioxide suspension liquid obtained in the step into a cellulose nanofibril suspension liquid in a proportion of 1-30, and performing ultrasonic dispersion for 20-90 min to prepare a silicon dioxide/cellulose nanofibril mixed solution;
thirdly, freezing the mixed solution prepared in the second step at-80 to-60 ℃ for 4 to 36 hours, and then quickly taking out the mixed solution for freeze-drying treatment to obtain the silicon dioxide/cellulose nanofibril composite aerogel;
fourth, placing the silica/cellulose nanofibril composite aerogel obtained in the third step into a tube furnace for carbonization treatment, wherein the temperature rising process is as follows: heating to 200-300 ℃ in the air atmosphere, preserving heat for 1-4 h, heating to 500-1200 ℃ under the protection of inert gas, preserving heat for 1-5 h, and cooling to room temperature to obtain a fabric-like carbon-coated silicon dioxide composite material;
the concentration of the nano silicon dioxide in the steps is 0.5-10 wt%, and the particle size of the nano silicon dioxide is 10-300 nm;
in the second step, the cellulose nano-fibrils have the diameters of 2-60 nm, the lengths of 0.5-60 microns and the length-diameter ratio of more than 100;
the step three of quickly taking out the product for freeze-drying treatment specifically comprises the following steps: taking out, freezing for 4-36 h at-80 to-60 ℃ in an ultralow-temperature quick freezing refrigerator, and then quickly taking out, and carrying out freeze-drying treatment for 12-48 h at-70 to-50 ℃ in a freeze drying box;
the inert gas in step four is one of argon and helium;
in the step four, in an air atmosphere, the temperature is increased to 200-300 ℃ at a rate of 1-5 ℃/min, the temperature is maintained for 1.5-3.5 hours, then the temperature is increased to 600-1200 ℃ at a rate of 5-15 ℃/min under the protection of inert gas, and the temperature is maintained for 2-5 hours.
2. Use of the textile carbon-coated silica composite material according to claim 1 in batteries.
3. A method of assembling a half-cell using the fabric-like carbon-coated silica composite of claim 1, wherein: the method comprises the following steps:
the technical scheme includes that the silicon dioxide composite material is coated by fabric-like carbon: acetylene black: weighing and mixing polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1, and grinding in a mortar for 10-70 min to obtain black powder; then, according to the solid-liquid ratio of 1: 2-10, dropwise adding N-methyl-1-pyrrolidone into the powder, and uniformly stirring to prepare the powder into a slurry state;
rapidly coating the obtained uniform slurry on a dried copper foil, then putting the copper foil coated with the slurry into a vacuum drying oven, and carrying out vacuum drying for 3-30 h at the temperature of 30-100 ℃;
thirdly, compacting the coated and dried copper foil by using a tablet press, cutting the copper foil coated with the composite material into electrode plates with the diameter of 10-20 mm by using a tablet press, and drying the electrode plates at 30-150 ℃ for 0.5-8 h for later use;
and fourthly, assembling the half-cell in the glove box according to the sequence of the negative electrode shell, the electrode slice, the electrolyte, the diaphragm, the electrolyte, the lithium sheet, the gasket, the spring sheet and the positive electrode shell, and packaging the half-cell by using a packaging machine after the half-cell is successfully assembled to obtain the half-cell.
4. The method of assembling a half-cell of the fabric-like carbon-coated silica composite of claim 3, wherein: the electrolyte in step four is an organic solution mixed solution of lithium hexafluorophosphate, the concentration of lithium hexafluorophosphate in the organic solution mixed solution is 1.0M, the organic mixed solution is ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate in a volume ratio of 1:1:1, and the diaphragm in step four is a polypropylene microporous membrane.
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