CN117613231A - Silicon-carbon negative electrode material, preparation method and lithium battery using silicon-carbon negative electrode material - Google Patents
Silicon-carbon negative electrode material, preparation method and lithium battery using silicon-carbon negative electrode material Download PDFInfo
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- 238000010438 heat treatment Methods 0.000 claims description 8
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- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 5
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Classifications
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- 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 application relates to the field of silicon-carbon negative electrode materials, in particular to a silicon-carbon negative electrode material, a preparation method and a lithium battery using the silicon-carbon negative electrode material. A silicon-carbon negative electrode material comprises a nano silicon inner core and a porous graphene coating layer coated on the surface of the nano silicon inner core. According to the method, the porous graphene coating layer is selected to carry out effective coating modification on the nano silicon core material, so that the volume change phenomenon of the nano silicon core material in the lithium removal and intercalation processes is improved, and the structural change of the nano silicon core material is reduced; secondly, the coating layer of the porous graphene material selected by the application can effectively improve the rate of lithium ion extraction and intercalation in the nano silicon core, so that the charge and discharge efficiency performance of the material for the lithium battery material is further improved.
Description
Technical Field
The application relates to the field of silicon-carbon negative electrode materials, in particular to a silicon-carbon negative electrode material, a preparation method and a lithium battery using the silicon-carbon negative electrode material.
Background
The lithium ion battery is used as an advanced energy storage device, has the advantages of high working voltage, environmental friendliness, no memory effect and the like, and has been widely applied to the fields of electric automobiles, rail transit, aerospace and the like. However, the energy density of the lithium ion battery at the present stage cannot meet the requirement of the electronic equipment on the endurance, so the development of the lithium ion battery with high energy density is an urgent pursuit target in the current energy field.
The silicon negative electrode material has the advantages of high theoretical capacity which is more than 10 times of that of a graphite negative electrode, environment friendliness, abundant crust content, low price, low discharge potential and the like, and is a lithium ion battery negative electrode material with great development prospect.
In view of the above-mentioned related art, the inventors found that the existing silicon-based negative electrode material causes volume expansion and shrinkage exceeding 300% in the process of lithium removal and lithium intercalation, which greatly shortens the cycle life of the battery.
Disclosure of Invention
In order to overcome the defect that the cycle life of a lithium battery is poor due to volume expansion in the use process of the traditional silicon-carbon negative electrode material, the application provides the silicon-carbon negative electrode material, a preparation method and the lithium battery using the silicon-carbon negative electrode material.
The application provides a silicon-carbon anode material, which adopts the following technical scheme:
a silicon-carbon negative electrode material comprises a nano silicon inner core and a porous graphene coating layer coated on the surface of the nano silicon inner core.
According to the technical scheme, the porous graphene coating layer is selected for effective coating modification of the nano silicon core material, and due to effective coating of the porous graphene coating layer, the volume change phenomenon of the nano silicon core material in the lithium removal and intercalation processes is improved, so that the structural change of the nano silicon core material is reduced; secondly, the coating layer of the porous graphene material selected by the application can effectively improve the rate of lithium ion extraction and intercalation in the nano silicon core, so that the charge and discharge efficiency performance of the material for the lithium battery material is further improved.
Preferably, the silicon-carbon anode material further comprises a carbon coating layer, and the carbon coating layer is arranged between the porous graphene coating layer and the nano silicon core.
Through above-mentioned technical scheme, this application has further optimized the structure of silicon carbon negative pole material, because graphite alkene is sheet structure generally, at the in-process that combines with nanometer silicon kernel, easily appears the problem that drops, and this application passes through the carbon coating layer that sets up between porous graphite alkene material and the nanometer silicon kernel, further improves silicon carbon negative pole material's bonding strength.
Meanwhile, compared with the porous graphene coating layer, the carbon coating layer has better coating performance, and has good volume control effect, and meanwhile, the rate of lithium ion extraction and intercalation in the nano silicon core is further improved, so that the electrical performance of the lithium battery material is also effectively improved.
Preferably, the nano silicon core is a porous nano silicon particle with a core-shell structure.
Preferably, the porous nano silicon particles with the core-shell structure are prepared by adopting the following scheme:
and placing the silicon dioxide particles, sodium dodecyl benzene sulfonate and urea into deionized water, performing ultrasonic dispersion, adding isopropanol, toluene and ethyl orthosilicate, continuously stirring, mixing, heating, performing heat preservation reaction, performing water bath heating treatment, separating a product, washing, drying, and calcining to obtain the porous nano silicon particles with the core-shell structure.
Through the technical scheme, the nano silicon core structure is optimized, nano silicon particles with a porous structure are prepared, nano silicon is selected as a core material, and the surface of the nano silicon particles is coated with the nano silicon core material to form the nano silicon core material with the composite core-shell structure with the porous silicon structure.
On the one hand, the prepared porous shell structure can be effectively combined with the porous graphene coating layer or the carbon coating layer, and a part of graphene or carbon layer particles are embedded into the nano silicon core material to serve as a skeleton supporting structure of the nano silicon material, so that stress generated by expansion of the nano silicon core material is restrained in the actual use process, and the use stability of the silicon-carbon anode material is further improved.
On the other hand, the nano silicon core material with the core-shell structure is prepared by using sodium dodecyl benzene sulfonate as a template agent, so that the shell structure of the nano silicon core material forms a good three-dimensional pore structure, the permeation of electrolyte and the diffusion effect of lithium ions can be effectively accelerated through the design of the structure, and meanwhile, the structure of the three-dimensional pore can be effectively applicable to the phenomenon of volume change of the silicon core material in the lithium removing-inserting process, thereby further improving the charge and discharge efficiency performance of the material for lithium battery materials.
In a second aspect, the present application provides a method for preparing a silicon-carbon anode material, including the following preparation steps:
s1, dispersing nano silicon cores into absolute ethyl alcohol, stirring, mixing, performing ultrasonic dispersion, and collecting dispersion slurry;
s2, adding graphene oxide particles into the dispersion slurry, performing ultrasonic dispersion, and then performing spray drying to collect dry particles;
s3, taking dry particles, placing the dry particles under inert gas for calcination treatment, standing and cooling to room temperature, and obtaining the silicon-carbon anode material.
Through the technical scheme, after spray drying is carried out on the dispersion slurry formed by the graphene oxide and the nano silicon core material, the silicon-carbon anode material is prepared by calcining and activating, and the graphene oxide material can form a uniform and stable load structure on the surface of the nano silicon core material by adopting the scheme, and the preparation process is simple.
Preferably, step S1 further comprises a carbon coating layer preparation step comprising:
and (3) taking a carbon source material, placing the carbon source material in a pyrolysis device, carrying out pyrolysis treatment, carrying out carbon coating treatment on the surface of the nano silicon core, standing and cooling to room temperature, and thus completing the preparation of the carbon coating.
Through the technical scheme, the preparation of the carbon coating layer is carried out through the scheme of vapor deposition, and the defect of poor uniformity performance in the traditional carbonization preparation scheme after coating is overcome because the carbon coating layer prepared through vapor deposition is compact and uniform in structure.
Preferably, the thickness of the carbon coating layer is 10-20 nm.
Preferably, the carbon source material includes at least one of a high molecular carbon source or a gas phase carbon source.
Preferably, the nano-silicon core comprises at least one of nano-silicon particles or nano-silicon oxide particles.
In a third aspect, the present application provides a lithium battery comprising a silicon carbon anode material as described in any one of the above.
Through the technical scheme, the structure and the preparation process of the silicon-carbon anode material are optimized, so that the prepared lithium battery has good cycle service life and charge-discharge efficiency.
In summary, the present application has the following beneficial effects:
firstly, the porous graphene coating layer is selected for effective coating modification of the nano silicon core material, and due to effective coating of the porous graphene coating layer, the volume change phenomenon of the nano silicon core material in the lithium removal and intercalation processes is improved, so that the structural change of the nano silicon core material is reduced; secondly, the coating layer of the porous graphene material selected by the application can effectively improve the rate of lithium ion extraction and intercalation in the nano silicon core, so that the charge and discharge efficiency performance of the material for the lithium battery material is further improved.
Secondly, this application has further optimized the structure of silicon carbon negative pole material, because graphite alkene is sheet structure generally, at the in-process that combines with nanometer silicon kernel, easily appears the problem that drops, and this application passes through the carbon coating layer that sets up between porous graphite alkene material and the nanometer silicon kernel, further improves the bonding strength of silicon carbon negative pole material.
Meanwhile, compared with the porous graphene coating layer, the carbon coating layer has better coating performance, and has good volume control effect, and meanwhile, the rate of lithium ion extraction and intercalation in the nano silicon core is further improved, so that the electrical performance of the lithium battery material is also effectively improved.
Thirdly, the nano silicon core structure is optimized, nano silicon is selected as a core material by preparing nano silicon particles with a porous structure, and the nano silicon core material with a composite core-shell structure with the porous silicon structure is coated on the surface of the nano silicon core material.
On the one hand, the prepared porous shell structure can be effectively combined with the porous graphene coating layer or the carbon coating layer, and a part of graphene or carbon layer particles are embedded into the nano silicon core material to serve as a skeleton supporting structure of the nano silicon material, so that stress generated by expansion of the nano silicon core material is restrained in the actual use process, and the use stability of the silicon-carbon anode material is further improved.
On the other hand, the nano silicon core material with the core-shell structure is prepared by using sodium dodecyl benzene sulfonate as a template agent, so that the shell structure of the nano silicon core material forms a good three-dimensional pore structure, the permeation of electrolyte and the diffusion effect of lithium ions can be effectively accelerated through the design of the structure, and meanwhile, the structure of the three-dimensional pore can be effectively applicable to the phenomenon of volume change of the silicon core material in the lithium removing-inserting process, thereby further improving the charge and discharge efficiency performance of the material for lithium battery materials.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate a certain embodiment of the present invention and therefore should not be considered as limiting the scope, and that other related drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a silicon-carbon anode material prepared in this example 1;
fig. 2 is a schematic structural diagram of the silicon-carbon negative electrode material prepared in this example 5;
fig. 3 is a schematic structural diagram of the silicon carbon negative electrode material prepared in this example 8.
Wherein, in the figure;
1. a nano silicon core; 2. a porous graphene coating layer; 3. and (3) a carbon coating layer.
Detailed Description
For a further understanding of the present invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further features and advantages of the invention and are not limiting of the invention claims.
All the raw materials of the present invention are not particularly limited in their sources, and may be purchased on the market or prepared according to conventional methods well known to those skilled in the art.
All raw materials of the invention, the brands and abbreviations of which belong to the conventional brands and abbreviations in the field of the related application are clear and definite, and the person skilled in the art can purchase from the market or prepare by the conventional method according to the brands, abbreviations and the corresponding application.
All processes of the present invention, the abbreviations of which are conventional in the art, are each well-defined in the art of their relevant use, and the skilled artisan will be able to understand the conventional process steps thereof based on the abbreviations.
Preparation example
Preparation example 1: porous nano silicon particles 1 with core-shell structure
300g of silicon dioxide particles with the particle size of 10-100 nm, 300g of sodium dodecyl benzene sulfonate and 150g of urea are placed in 9kg of deionized water, after ultrasonic dispersion under 200W, 250g of isopropanol, 85g of toluene and 300g of ethyl orthosilicate are continuously added, stirring and mixing are continuously carried out under the room temperature environment, the temperature is raised and heated to 65 ℃, after water bath heat preservation and heating reaction, centrifugation and lower-layer precipitation are collected, absolute ethyl alcohol washing and drying are carried out, and then the mixture is placed in 500 ℃ air atmosphere for calcination treatment for 2 hours, so that the porous nano silicon particles 1 with the core-shell structure can be prepared.
Preparation example 2: porous nano silicon particles 2 with core-shell structure
400g of silicon dioxide particles with the particle size of 10-100 nm, 400g of sodium dodecyl benzene sulfonate and 175g of urea are placed in 9.5kg of deionized water, after ultrasonic dispersion under 200W, 275g of isopropanol, 92g of toluene and 400g of ethyl orthosilicate are continuously added, stirring and mixing are continuously carried out under the room temperature environment, the temperature is raised and heated to 70 ℃, water bath heat preservation and heating reaction are carried out, centrifugation is carried out, the lower-layer sediment is collected, absolute ethyl alcohol is washed and dried, and calcination treatment is carried out for 2 hours under the air atmosphere at 550 ℃, so that the porous nano silicon particles 2 with the core-shell structure can be prepared.
Preparation example 3: porous nano-silicon particles 3 of core-shell structure.
Putting 500g of silicon dioxide particles with the particle size of 10-100 nm, 500g of sodium dodecyl benzene sulfonate and 200g of urea into 10kg of deionized water, after ultrasonic dispersion under 200W, continuously adding 300g of isopropanol, 100g of toluene and 500g of ethyl orthosilicate, continuously stirring and mixing under room temperature environment, heating to 75 ℃, carrying out water bath heat preservation and heating reaction, centrifuging, collecting the lower-layer precipitate, washing with absolute ethyl alcohol, drying, and calcining for 2 hours under 600 ℃ air atmosphere to obtain the porous nano silicon particles 3 with the core-shell structure.
Examples
Example 1
A silicon-carbon negative electrode material comprises a nano silicon inner core and a porous graphene coating layer coated on the surface of the nano silicon inner core.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
s1, taking 200g of 10-100 nm nano silicon particles as nano silicon cores to be dispersed into 5kg of absolute ethyl alcohol, stirring, mixing, placing under 200W for ultrasonic dispersion, and collecting dispersion slurry;
s2, adding 15g of graphene oxide particles into 3kg of dispersion slurry, continuing 200W ultrasonic dispersion, placing the dispersion slurry in a spray drying device for spray drying, controlling the air inlet temperature of the spray drying to be 135 ℃ and the air outlet temperature to be 110 ℃, and collecting dry particles;
s3, taking dry particles, placing the dry particles in a nitrogen atmosphere for calcination treatment, adjusting the calcination temperature to 500 ℃, calcining for 4 hours, and standing and cooling to room temperature to prepare the silicon-carbon negative electrode material.
Example 2
A silicon-carbon negative electrode material comprises a nano silicon inner core and a porous graphene coating layer coated on the surface of the nano silicon inner core.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
s1, taking 250g of 10-100 nm nano silicon particles as nano silicon cores to be dispersed into 5.5kg of absolute ethyl alcohol, stirring, mixing, placing under 200W for ultrasonic dispersion, and collecting dispersion slurry;
s2, adding 22g of graphene oxide particles into 4kg of dispersion slurry, continuing 200W ultrasonic dispersion, placing the dispersion slurry in a spray drying device for spray drying, controlling the air inlet temperature of the spray drying to be 135 ℃ and the air outlet temperature to be 110 ℃, and collecting dry particles;
s3, taking dry particles, placing the dry particles in a nitrogen atmosphere for calcination treatment, adjusting the calcination temperature to 750 ℃, calcining for 3 hours, and standing and cooling to room temperature to prepare the silicon-carbon negative electrode material.
Example 3
A silicon-carbon negative electrode material comprises a nano silicon inner core and a porous graphene coating layer coated on the surface of the nano silicon inner core.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
s1, taking 300g of 10-100 nm nano silicon particles as nano silicon cores to be dispersed into 6kg of absolute ethyl alcohol, stirring, mixing, placing under 200W for ultrasonic dispersion, and collecting dispersion slurry;
s2, adding 30g of graphene oxide particles into 5kg of dispersion slurry, continuing 200W ultrasonic dispersion, placing the dispersion slurry in a spray drying device for spray drying, controlling the air inlet temperature of the spray drying to be 135 ℃ and the air outlet temperature to be 110 ℃, and collecting dry particles;
s3, taking dry particles, placing the dry particles in a nitrogen atmosphere for calcination treatment, adjusting the calcination temperature to 1000 ℃, calcining for 3 hours, and standing and cooling to room temperature to prepare the silicon-carbon negative electrode material.
Example 4
A silicon-carbon negative electrode material comprises a nano silicon inner core and a porous graphene coating layer coated on the surface of the nano silicon inner core.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
s1, taking 250g of 10-100 nm nano silicon oxide particles as nano silicon cores to be dispersed into 5.5kg of absolute ethyl alcohol, stirring, mixing, placing under 200W for ultrasonic dispersion, and collecting dispersion slurry;
s2, adding 22g of graphene oxide particles into 4kg of dispersion slurry, continuing 200W ultrasonic dispersion, placing the dispersion slurry in a spray drying device for spray drying, controlling the air inlet temperature of the spray drying to be 135 ℃ and the air outlet temperature to be 110 ℃, and collecting dry particles;
s3, taking dry particles, placing the dry particles in a nitrogen atmosphere for calcination treatment, adjusting the calcination temperature to 750 ℃, calcining for 3 hours, and standing and cooling to room temperature to prepare the silicon-carbon negative electrode material.
Example 5
A silicon-carbon negative electrode material comprises a nano silicon inner core and a porous graphene coating layer coated on the surface of the nano silicon inner core.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
s1, taking 250g of 10-100 nm core-shell porous nano silicon particles 1 as nano silicon cores to be dispersed into 5.5kg of absolute ethyl alcohol, stirring, mixing, placing into 200W for ultrasonic dispersion, and collecting dispersion slurry;
s2, adding 22g of graphene oxide particles into 4kg of dispersion slurry, continuing 200W ultrasonic dispersion, placing the dispersion slurry in a spray drying device for spray drying, controlling the air inlet temperature of the spray drying to be 135 ℃ and the air outlet temperature to be 110 ℃, and collecting dry particles;
s3, taking dry particles, placing the dry particles in a nitrogen atmosphere for calcination treatment, adjusting the calcination temperature to 750 ℃, calcining for 3 hours, and standing and cooling to room temperature to prepare the silicon-carbon negative electrode material.
Example 6
A silicon-carbon negative electrode material comprises a nano silicon inner core and a porous graphene coating layer coated on the surface of the nano silicon inner core.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
s1, taking 250g of 10-100 nm core-shell porous nano silicon particles 2 as nano silicon cores to be dispersed into 5.5kg of absolute ethyl alcohol, stirring, mixing, placing into 200W for ultrasonic dispersion, and collecting dispersion slurry;
s2, adding 22g of graphene oxide particles into 4kg of dispersion slurry, continuing 200W ultrasonic dispersion, placing the dispersion slurry in a spray drying device for spray drying, controlling the air inlet temperature of the spray drying to be 135 ℃ and the air outlet temperature to be 110 ℃, and collecting dry particles;
s3, taking dry particles, placing the dry particles in a nitrogen atmosphere for calcination treatment, adjusting the calcination temperature to 750 ℃, calcining for 3 hours, and standing and cooling to room temperature to prepare the silicon-carbon negative electrode material.
Example 7
A silicon-carbon negative electrode material comprises a nano silicon inner core and a porous graphene coating layer coated on the surface of the nano silicon inner core.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
s1, taking 250g of 10-100 nm core-shell porous nano silicon particles 3 as nano silicon cores to be dispersed into 5.5kg of absolute ethyl alcohol, stirring, mixing, placing into 200W for ultrasonic dispersion, and collecting dispersion slurry;
s2, adding 22g of graphene oxide particles into 4kg of dispersion slurry, continuing 200W ultrasonic dispersion, placing the dispersion slurry in a spray drying device for spray drying, controlling the air inlet temperature of the spray drying to be 135 ℃ and the air outlet temperature to be 110 ℃, and collecting dry particles;
s3, taking dry particles, placing the dry particles in a nitrogen atmosphere for calcination treatment, adjusting the calcination temperature to 750 ℃, calcining for 3 hours, and standing and cooling to room temperature to prepare the silicon-carbon negative electrode material.
Example 8
The silicon-carbon anode material sequentially comprises a nano silicon core, a carbon coating layer and a porous graphene coating layer from inside to outside.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
s1, taking sucrose as a high molecular carbon source, placing the high molecular carbon source into a pyrolysis device, carrying out pyrolysis treatment under nitrogen atmosphere at 900 ℃, collecting pyrolysis products, carrying out carbon coating treatment on the surfaces of porous nano silicon particles 2 with a core-shell structure by taking argon as a loading gas, controlling the argon introducing rate to be 6.5mL/min, and standing and cooling to room temperature after the argon introducing rate is controlled to be 20nm, thus completing the preparation of the carbon coating.
S2, taking 250g of porous nano silicon particles 2 with a core-shell structure of which the carbon coating layer is finished as nano silicon cores, dispersing the nano silicon particles into 5.5kg of absolute ethyl alcohol, stirring, mixing, placing the mixture into 200W for ultrasonic dispersion, and collecting dispersion slurry;
s3, adding 22g of graphene oxide particles into 4kg of dispersion slurry, continuing 200W ultrasonic dispersion, placing the dispersion slurry in a spray drying device for spray drying, controlling the air inlet temperature of the spray drying to be 135 ℃ and the air outlet temperature to be 110 ℃, and collecting dry particles;
s4, taking the dry particles, placing the dry particles in a nitrogen atmosphere for calcination treatment, adjusting the calcination temperature to 750 ℃, calcining for 3 hours, and standing and cooling to room temperature to prepare the silicon-carbon anode material.
Example 9
The silicon-carbon anode material sequentially comprises a nano silicon core, a carbon coating layer and a porous graphene coating layer from inside to outside.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
s1, taking glucose as a high molecular carbon source, placing the glucose into a pyrolysis device, carrying out pyrolysis treatment under nitrogen atmosphere at 900 ℃, collecting pyrolysis products, carrying out carbon coating treatment on the surfaces of porous nano silicon particles 2 with a core-shell structure by taking argon as a loading gas, controlling the argon introducing rate to be 6.5mL/min, and standing and cooling to room temperature after introducing the carbon coating layer to the thickness of 15nm to finish the preparation of the carbon coating layer.
S2, taking 250g of porous nano silicon particles 2 with a core-shell structure of which the carbon coating layer is finished as nano silicon cores, dispersing the nano silicon particles into 5.5kg of absolute ethyl alcohol, stirring, mixing, placing the mixture into 200W for ultrasonic dispersion, and collecting dispersion slurry;
s3, adding 22g of graphene oxide particles into 4kg of dispersion slurry, continuing 200W ultrasonic dispersion, placing the dispersion slurry in a spray drying device for spray drying, controlling the air inlet temperature of the spray drying to be 135 ℃ and the air outlet temperature to be 110 ℃, and collecting dry particles;
s4, taking the dry particles, placing the dry particles in a nitrogen atmosphere for calcination treatment, adjusting the calcination temperature to 750 ℃, calcining for 3 hours, and standing and cooling to room temperature to prepare the silicon-carbon anode material.
Example 10
The silicon-carbon anode material sequentially comprises a nano silicon core, a carbon coating layer and a porous graphene coating layer from inside to outside.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
s1, introducing acetylene as a gas carbon source, placing the carbon source into a pyrolysis device, carrying out pyrolysis treatment under a nitrogen atmosphere at 900 ℃, collecting pyrolysis products, carrying out carbon coating treatment on the surfaces of porous nano silicon particles 2 with a core-shell structure by taking argon as a load gas, controlling the introducing rate of the argon to be 6.5mL/min, and standing and cooling to room temperature after the introducing rate of the argon is 10nm, thus completing the preparation of the carbon coating.
S2, taking 250g of porous nano silicon particles 2 with a core-shell structure of which the carbon coating layer is finished as nano silicon cores, dispersing the nano silicon particles into 5.5kg of absolute ethyl alcohol, stirring, mixing, placing the mixture into 200W for ultrasonic dispersion, and collecting dispersion slurry;
s3, adding 22g of graphene oxide particles into 4kg of dispersion slurry, continuing 200W ultrasonic dispersion, placing the dispersion slurry in a spray drying device for spray drying, controlling the air inlet temperature of the spray drying to be 135 ℃ and the air outlet temperature to be 110 ℃, and collecting dry particles;
s4, taking the dry particles, placing the dry particles in a nitrogen atmosphere for calcination treatment, adjusting the calcination temperature to 750 ℃, calcining for 3 hours, and standing and cooling to room temperature to prepare the silicon-carbon anode material.
Comparative example
Comparative example 1
A silicon-carbon negative electrode material comprises a nano silicon inner core and a porous graphite coating layer coated on the surface of the nano silicon inner core.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
s1, taking 250g of 10-100 nm nano silicon particles as nano silicon cores to be dispersed into 5.5kg of absolute ethyl alcohol, stirring, mixing, placing under 200W for ultrasonic dispersion, and collecting dispersion slurry;
s2, adding 22g of nano graphite particles into 4kg of dispersion slurry, continuing 200W ultrasonic dispersion, placing the dispersion slurry in a spray drying device for spray drying, controlling the air inlet temperature of the spray drying to be 135 ℃ and the air outlet temperature to be 110 ℃, and collecting dry particles;
s3, taking dry particles, placing the dry particles in a nitrogen atmosphere for calcination treatment, adjusting the calcination temperature to 750 ℃, calcining for 3 hours, and standing and cooling to room temperature to prepare the silicon-carbon negative electrode material.
Comparative example 2
The silicon-carbon negative electrode material sequentially comprises a nano silicon core and a carbon coating layer from inside to outside.
The preparation method of the silicon-carbon anode material comprises the following preparation steps:
introducing acetylene as a gas carbon source, placing the carbon source into a pyrolysis device, carrying out pyrolysis treatment in a nitrogen atmosphere at 900 ℃, collecting pyrolysis products, carrying out carbon coating treatment on the surfaces of porous nano silicon particles 2 with a core-shell structure by taking argon as a loading gas, controlling the introducing rate of the argon to be 6.5mL/min, introducing the argon to the carbon coating layer with the thickness of 20nm, standing and cooling to room temperature, and thus obtaining the silicon-carbon anode material.
Performance detection and characterization
Taking the silicon-carbon anode materials prepared in examples 1-10 and comparative examples 1-2, setting the total solid mass according to the requirement, and mixing the silicon-carbon anode materials, the carbon nano tube and the PVDF according to the formula mass ratio
And PVA according to qualityThe resulting slurry was applied to copper as a working electrode by doctor blade after mixing and grinding in a ratio of 6.0:2.0:1.9:0.1 by weight, and then poured into NMP solution to disperse uniformly. Silicon-carbon negative electrode material is used as a working electrode, a lithium sheet is used as a counter electrode, microporous polypropylene is used as a diaphragm, and 1M LiPF 6 +EC/DEC (1:1) +10% FEC is the electrolyte. The lithium ion half-cell was assembled in an argon filled glove box. The performance of the battery is tested by adopting a constant current charge-discharge instrument, the current density is 0.1C, and the voltage is 0.01-1.50V.
Electrochemical performance test:
and (3) testing the cycle performance: and (3) carrying out cyclic charge and discharge test on the material at the rate of 0.1C.
Table 1 performance test table
Analysis was performed in combination with the technical schemes of examples 1 to 10 and comparative examples 1 to 2 and the data in table 1 as follows:
the comparison of the technical schemes of comparative examples 1-2 and the technical schemes of examples 1-4 and the analysis of the electrode appearance after 150 times of circulation are combined, show that the technical scheme of the application effectively coats and modifies the nano silicon core material by selecting the porous graphene coating layer, improves the volume change phenomenon of the nano silicon core material in the process of lithium removal and lithium intercalation, and further reduces the structural change of the nano silicon core material.
Comparing examples 5-7 with examples 1-4, it is further illustrated that by optimizing the nano silicon core structure, the porous shell structure can form effective combination with the porous graphene coating layer or the carbon coating layer, and the stress generated by expansion of the nano silicon core material is inhibited, so that the use stability of the silicon-carbon anode material is further improved. Meanwhile, the nano silicon core material with the core-shell structure is prepared by taking sodium dodecyl benzene sulfonate as a template agent, so that the shell structure of the nano silicon core material forms a good three-dimensional pore structure, the permeation of electrolyte and the diffusion effect of lithium ions can be effectively accelerated through the design of the structure, and meanwhile, the structure of the three-dimensional pore can be effectively applicable to the phenomenon of volume change of the silicon core material in the lithium removal-intercalation process, so that the charge and discharge efficiency performance of the material for a lithium battery material is further improved.
Comparing examples 8-10 with examples 5-7, it is illustrated that the structure of the silicon-carbon negative electrode material is further optimized according to the technical scheme, and as graphene is generally of a lamellar structure, in the process of combining with the nano silicon core, the problem of falling easily occurs.
Meanwhile, compared with the porous graphene coating layer, the carbon coating layer has better coating performance, and has good volume control effect, and meanwhile, the rate of lithium ion extraction and intercalation in the nano silicon core is further improved, so that the electrical performance of the lithium battery material is also effectively improved.
The present embodiment is merely illustrative of the present application and is not intended to be limiting, and those skilled in the art, after having read the present specification, may make modifications to the present embodiment without creative contribution as required, but is protected by patent laws within the scope of the claims of the present application.
Claims (10)
1. The silicon-carbon anode material is characterized by comprising a nano silicon inner core and a porous graphene coating layer coated on the surface of the nano silicon inner core.
2. The silicon-carbon negative electrode material of claim 1, further comprising a carbon coating layer disposed between the porous graphene coating layer and the nano-silicon core.
3. The silicon-carbon negative electrode material according to claim 1, wherein the nano-silicon core is a porous nano-silicon particle with a core-shell structure.
4. A silicon-carbon negative electrode material according to claim 3, wherein the porous nano silicon particles of the core-shell structure are prepared by the following scheme:
and placing the silicon dioxide particles, sodium dodecyl benzene sulfonate and urea into deionized water, performing ultrasonic dispersion, adding isopropanol, toluene and ethyl orthosilicate, continuously stirring, mixing, heating, performing heat preservation reaction, performing water bath heating treatment, separating a product, washing, drying, and calcining to obtain the porous nano silicon particles with the core-shell structure.
5. The method for producing a silicon-carbon negative electrode material according to any one of claims 1 to 4, comprising the steps of:
s1, dispersing nano silicon cores into absolute ethyl alcohol, stirring, mixing, performing ultrasonic dispersion, and collecting dispersion slurry;
s2, adding graphene oxide particles into the dispersion slurry, performing ultrasonic dispersion, and then performing spray drying to collect dry particles;
s3, taking dry particles, placing the dry particles under inert gas for calcination treatment, standing and cooling to room temperature, and obtaining the silicon-carbon anode material.
6. The method for producing a silicon-carbon negative electrode material according to claim 5, wherein step S1 further comprises the preparation of a carbon coating layer, the carbon coating layer preparation step comprising:
and (3) taking a carbon source material, placing the carbon source material in a pyrolysis device, carrying out pyrolysis treatment, carrying out carbon coating treatment on the surface of the nano silicon core, standing and cooling to room temperature, and thus completing the preparation of the carbon coating.
7. The method for producing a silicon-carbon negative electrode material according to claim 6, wherein the carbon coating layer has a thickness of 10 to 20nm.
8. The method of claim 6, wherein the carbon source material comprises at least one of a polymeric carbon source or a gas phase carbon source.
9. The method of claim 5, wherein the nano-silicon core comprises at least one of nano-silicon particles or nano-silicon oxide particles.
10. A lithium battery comprising the silicon-carbon negative electrode material according to any one of claims 1 to 4.
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