CN115117317A - Carbon-silicon composite material and preparation method and application thereof - Google Patents
Carbon-silicon composite material and preparation method and application thereof Download PDFInfo
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- 239000002153 silicon-carbon composite material Substances 0.000 title claims abstract description 72
- 238000002360 preparation method Methods 0.000 title claims abstract description 32
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 42
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- 238000003763 carbonization Methods 0.000 claims abstract description 9
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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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
- 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
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/386—Silicon or alloys based on silicon
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—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
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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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
- H01M2220/00—Batteries for particular applications
- H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
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Abstract
The invention relates to a carbon-silicon composite material and a preparation method and application thereof. The carbon-silicon composite material comprises activated carbon, wherein a silicon material layer is loaded on the inner wall and the surface of a hole of the activated carbon, and a carbon coating layer covers the surface of the silicon material layer. The invention also provides a preparation method of the carbon-silicon composite material, which comprises the following steps: performing activation treatment on the activated carbon; dispersing activated carbon subjected to activation treatment in a weak polar solvent, and adding a silane coupling agent for coupling reaction to obtain a silicon precursor; mixing the silicon precursor with a reducing agent and then carrying out heat treatment to obtain silicon-loaded activated carbon; and mixing silicon-loaded active carbon with a carbon source, and carrying out carbonization treatment twice to obtain the carbon-silicon composite material. The invention also provides application of the carbon-silicon composite material as a negative electrode material in a lithium ion battery. The invention solves the problem that the capacity of the cathode is too fast to be attenuated and the performance of the battery can not be effectively ensured because the volume change of the existing silicon cathode material is large.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a carbon-silicon composite material and a preparation method and application thereof.
Background
With the rapid development of the field of electric automobiles, people have higher and higher requirements on the quality, capacity and density of power batteries. Lithium ion batteries have attracted much attention because of their advantages of high specific energy, high operating voltage, high safety, and little environmental pollution. In the prior art, most of commercial lithium ion secondary batteries adopt graphite as a negative electrode material, the theoretical capacity of the graphite negative electrode is lower and is only 372mAh/g, the specific capacity of the commercial graphite negative electrode material is generally 360mAh/g and is difficult to greatly improve the capacity density of the battery through the improvement of the process. Therefore, the development of a negative electrode material for a battery having a high energy density is an urgent requirement in the lithium battery industry.
Research shows that the silicon negative electrode material has high specific capacity (3579mAh/g, and is lithiated to Li by Si 15 Si 4 ) Suitable discharge plateau (0.4V Vs Li/Li) + The formation of lithium dendrite can be prevented, and the battery can be ensured to have high working voltage), the reserves are abundant, the environment is friendly, and the like, and the lithium-ion battery becomes one of the next generation high-energy-density anode material candidates which are hopeful to replace the current graphite anode. However, the silicon-based materials have a large volume change during the insertion and extraction of lithium (for Li) 15 Si 4 The volume change is about 360% for SiO x Volume change of about 200%), which causes pulverization of the material, collapse of electrode structure, loss of electronic contact between active materials, active materials and current collectors, and continuous cracking and regeneration of a solid electrolyte interface film (SEI). Resulting in a rapid decay of the capacity of the silicon-based anode.
A self-filling coated silicon-based composite material, a preparation method and applications thereof as disclosed in CN 113193201 a. The self-filling coated silicon-based composite material is composed of a nano silicon layer, a filling layer and a surface modification layer; the granularity D50 of the nano silicon in the nano silicon layer is less than 200 nm; the filling layer is a carbon filling layer and is filled between the nano silicon; the composite material has the advantages of high first efficiency, low expansion, long circulation and the like; the invention also provides a preparation method and application of the self-filling coated silicon-based composite material, and the preparation method is simple and feasible in process, stable in product performance and good in application prospect. Although the silicon-based composite material has higher specific capacity (the highest specific capacity can reach 1856mAh/g), the lowest expansion rate after 50-week circulation is 49%, so the silicon-based composite material still has larger volume change and cannot meet the use requirement of an actual lithium battery.
The current research shows that the cycle stability of the silicon-based material can be successfully improved through the core-shell structure design of the carbon-coated silicon-based material with reserved expansion gaps inside. Currently, the preparation of the silicon-carbon composite material with reserved expansion gaps inside is mainly through the formation of porous silicon to absorb expansion, however, the method utilizing the internal gaps of the porous silicon is generally based on a sacrificial template method of a Si alloy and a chemical vapor deposition method, and both methods have the defects of complex operation, harsh conditions and high cost, so that the method is not suitable for large-scale commercial application.
Disclosure of Invention
One of the purposes of the invention is to provide a carbon-silicon composite material to solve the problems that the capacity of a negative electrode is too fast to be attenuated and the performance of a battery cannot be effectively ensured due to large volume change of the conventional silicon negative electrode material; the second purpose is to provide a preparation method of the carbon-silicon composite material, which is used for solving the problems of complex operation, harsh conditions and high cost of the existing silicon-carbon composite material, and the third purpose is to provide an application of the carbon-silicon composite material in the field of lithium batteries.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
the carbon-silicon composite material comprises activated carbon, wherein a silicon material layer is loaded on the inner wall and the surface of a hole of the activated carbon, and a carbon coating layer covers the surface of the silicon material layer.
According to the technical means, the active carbon with pores inside is used as the framework, the silicon material layer is formed on the inner wall and the surface of the hole of the active carbon, the surface of the silicon material layer is covered with the carbon coating layer, the number of inner holes of the active carbon is large, the silicon loaded on the inner wall of the hole is hundreds of times of that of the surface, the silicon material layer expands towards the inner part of the hole of the active carbon due to most volume changes in the lithium intercalation process, and the volume expansion of the composite material is greatly reduced outwards.
Preferably, the average pore diameter of the activated carbon is D, the thickness of the silicon material layer is S, and the thickness of the carbon coating layer covered on the surface of the silicon material layer is H, so that 4S + H is less than or equal to 0.5D.
According to the technical means, the porosity inside the composite material is effectively ensured by limiting the relation among the average pore diameter of the activated carbon, the thickness of the silicon material layer and the thickness of the carbon coating layer, and a sufficient space is provided for the volume change of the silicon material layer.
Preferably, the carbon accounts for 70-95 wt% of the composite negative electrode material, and the silicon accounts for 5-30 wt%; wherein the activated carbon is powder, and the silicon material layer is nano silicon.
According to the technical means, by controlling the ratio of carbon to silicon in the composite material, adopting the powdered activated carbon as a framework and the nanoscale silicon as a loaded silicon layer, the electrochemical performance of the composite material is ensured, and the volume change of the silicon material serving as a lithium negative electrode material in the charging and discharging process can be ensured by ensuring the gaps of the activated carbon.
Preferably, the particle size of the carbon-silicon composite material is 4-30 um;
the specific surface area of the activated carbon is 300-2000 m 2 An average pore diameter of 0.8 to 10nm and a pore volume of 0.2 to 1.0cm 3 /g；
The specific surface area of the activated carbon loaded with the silicon material layer is 75-1500m 2 Average pore diameter of 0.15-7.5nm and pore volume of 0.10-0.69cm 3 /g。
Wherein, the particle size analysis shows that the particle size of the carbon-silicon composite material is 4-30 umAnd (3) removing the solvent. And experimental research proves that the specific surface area of the activated carbon powder needs to be controlled to be 300-2000 m 2 The average pore diameter is between 0.8 and 10nm, and the pore volume is between 0.2 and 1.0cm 3 The load of the silicon material layer can be ensured, and after the carbon coating layer is formed, enough expansion space can be reserved for the volume change of the silicon material, and the required power performance is considered.
The invention also provides a preparation method of the carbon-silicon composite material, which comprises the following steps:
s1, performing activation treatment on the activated carbon;
s2, dispersing the activated carbon in a weak polar solvent, and adding a silane coupling agent for coupling reaction to obtain a silicon precursor;
s3, mixing the silicon precursor with a reducing agent and then carrying out heat treatment to obtain silicon-loaded activated carbon;
and S4, mixing the silicon-loaded activated carbon with a carbon source, and carrying out carbonization treatment twice to obtain the carbon-silicon composite material.
Preferably, in S1, the activated carbon is activated by nitric acid, and the concentration of nitric acid is 5wt% to 60 wt%.
According to the technical means, the silicon-based composite anode material with the expansion gap reserved inside is prepared by adopting a wet chemical treatment method. Wherein, the thickness and the uniformity of the silicon material layer can be better controlled only by carrying out coupling reaction on the activated carbon powder and grafting the silane coupling agent in situ, thereby effectively improving the cycle performance and the power performance of the silicon-based negative electrode material and avoiding using SiO 2 The template sacrificing method, chemical vapor deposition and the like have the problems of complex operation, strict condition requirement and high cost. Therefore, the preparation method of the carbon-silicon composite material has the advantages of simple process, low cost and contribution to large-scale industrial preparation.
According to the technical means, the quantity of the activated groups formed inside and on the surface of the pores of the activated carbon is effectively ensured by controlling the concentration of the nitric acid, so that the loading capacity of the silicon material layer is effectively ensured.
Experiments prove that when the concentration of the nitric acid is lower than 5wt%, the amount of activated groups-C-OH formed by the activated carbon is small, the subsequent silicon loading is low, and the capacity of the prepared composite negative electrode material is low; when the concentration of the nitric acid is higher than 60wt%, the activated carbon can form-COOH groups, and the subsequent silicon loading is low, so that the capacity of the prepared carbon-silicon composite material is low, and therefore, the concentration of the nitric acid needs to be controlled within a certain range.
In S1, the activation treatment is preferably performed by heating and refluxing a suspension obtained by mixing nitric acid and activated carbon;
the heating reflux temperature is 75-85 ℃, and the time is 2-5 h.
According to the technical means, the effective activation of the activated carbon is further ensured by controlling the heating reflux temperature and time of the nitric acid and the activated carbon powder, so that the load capacity of the later-stage silicon material layer reaches the specified requirement, and the electrochemical performance of the carbon-silicon composite material as a negative electrode material is effectively ensured.
Experiments prove that in the heating reflux treatment process of the turbid liquid, the heating time is too short, the activated carbon cannot be effectively activated, the loading capacity of silicon is low, the prepared carbon-silicon composite material is low in capacity, after the turbid liquid is heated for a certain time, heating is continued, the amount of activated groups is hardly increased, the raw material cost is increased, and therefore the heating time is not too long.
Preferably, in the S2, the silane coupling agent is selected from one or more of 3-aminopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane and chlorobenzyltrichlorosilane.
The surface of the activated carbon powder and the inner wall surface of the hole are activated to have hydrophilic-C-OH groups, so that the selection of the silane coupling agent with the high-hydrophilicity groups can reduce the steric hindrance of the reaction to ensure the full reaction with the-C-OH groups formed by the activated surface of the activated carbon, thereby effectively ensuring the loading capacity of the silicon material.
The weakly polar solvent is selected from one or more of toluene, isopropanol, acetonitrile and dimethyl sulfoxide.
Because the polarity/dielectric constant of the reaction medium is reduced, the solvation degree of the solute is reduced, the energy barrier to be overcome by the grafting reaction is lower, the reaction is easier, and the silane grafting amount is reduced along with the reduction of the polarity/dielectric constant, so that the loading amount of the silicon material is effectively ensured.
Preferably, in the step S3, the heat treatment is carried out for 4-8 hours in an inert atmosphere at a temperature of 600-750 ℃.
Experiments prove that in S2, a silane coupling agent is grafted only through coupling reaction, so that a silicon material loading layer can be controlled to be thin, and the stability and the power performance of a product can be effectively guaranteed.
Preferably, the reducing agent is Zn, Mg or Al.
Wherein, the reducing agent is gasified at high temperature and contacts with the silane coupling agent through diffusion to deprive oxygen atoms therein to generate oxide, and the oxide can be removed by HCl acid cleaning.
Preferably, in S4, specifically, the method includes: dispersing and soaking silicon-loaded activated carbon in an aqueous solution containing a carbon source, and then carrying out primary carbonization treatment in an inert atmosphere; and then mechanically mixing the carbon source with the carbon source, and then carrying out secondary carbonization treatment in an inert atmosphere to obtain the carbon-coated composite negative electrode material.
The method comprises the steps of dispersing silicon-loaded activated carbon in an aqueous solution containing a carbon source, soaking, performing primary carbonization treatment to cover the surface of a silicon material layer loaded on the inner wall of an activated carbon hole with a carbon coating layer, mechanically mixing the carbon source with the activated carbon, and performing secondary carbonization treatment to cover the surface of the silicon material layer loaded on the surface of the activated carbon with the carbon coating layer.
Preferably, the carbon source is an organic carbon source. Wherein the organic carbon source is selected from one or more of saccharides, oils and fats, organic acids, organic acid esters and small molecular alcohols.
The invention also provides an application of the carbon-silicon composite material, and the carbon-silicon composite material is used as a negative electrode material of a lithium ion battery.
The invention has the beneficial effects that:
1) according to the carbon-silicon composite material, the activated carbon with pores inside is used as a framework, the silicon material layers are formed on the inner wall and the surface of the pores of the activated carbon, and the surface of the silicon material layer is covered with the carbon coating layer, so that the silicon loaded on the inner wall of the pores is hundreds of times of the surface due to more inner pores of the activated carbon, most of volume changes of the silicon material layer are expanded towards the inner parts of the pores of the activated carbon in the lithium intercalation and deintercalation process, the outward volume expansion of the composite material is greatly reduced, and the problems of material pulverization, electrode structure collapse, loss of electronic contact among active substances, active substances and current collectors and continuous cracking and regeneration of a solid electrolyte interface film (SEI) caused by the volume change of a negative electrode material are solved. The cycling stability of the silicon-based cathode capacity is effectively ensured, and the method has the advantages of rich raw material reserves and environmental friendliness;
2) according to the preparation method of the carbon-silicon composite material, the silicon-based composite negative electrode material with the expansion gap reserved inside is prepared by adopting a wet chemical treatment method, expensive methods such as etching and vapor deposition are avoided, the preparation method has the advantages of simple process, low cost and contribution to large-scale commercial application, and the silane coupling agent is grafted in situ only through coupling reaction, so that the thickness and uniformity of a silicon material layer can be well controlled, and the cycle performance and the power performance of the silicon-based negative electrode material are effectively improved;
3) the carbon-silicon composite material is used for preparing a negative electrode material of a lithium battery, and the gram capacity of the carbon-silicon composite material as a negative electrode is over 600mAh/g, the first effect of the battery is over 80 percent, the expansion rate of a pole piece is lower than 30 percent, the retention rate of 3C discharge capacity is over 70 percent, the cycle life of 0.5C 150cycles is over 80 percent under the condition of 0.005-1.5V at 25 ℃, and the carbon-silicon composite material has excellent electrochemical performance and popularization and application values in the technical field of lithium ion batteries.
Drawings
Fig. 1 is a schematic structural view of the carbon-silicon composite materials prepared in examples 1 to 8.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the disclosure herein, wherein the embodiments of the present invention are described in detail with reference to the accompanying drawings and preferred embodiments. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be understood that the preferred embodiments are illustrative of the invention only and are not limiting upon the scope of the invention.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
In the following description, numerous details are set forth to provide a more thorough explanation of the embodiments of the present application, however, it will be apparent to one skilled in the art that the embodiments of the present application may be practiced without these specific details.
Example 1
A preparation method of a carbon-silicon composite material comprises the following steps:
s1, mixing 100g of activated carbon (D504 um, specific surface area 1000 m) 2 /g) adding 500mL of 30wt% nitric acid, mixing to obtain a suspension, heating and refluxing for 4 hours in a water bath at the heating temperature of 80 ℃, washing a product after the heating is finished, and drying for 24 hours at the temperature of 105 ℃;
s2, dispersing the dried product in S1 in a DMSO solution, adding 3-aminopropyl trimethoxy silane for coupling reaction, washing the product after the coupling reaction is finished, and drying the product for 12 hours at the temperature of 80 ℃;
s3, mixing the dried product in the S2 with 10 wt% of Mg powder, and then carrying out heat treatment for 6 hours at 650 ℃ in an inert atmosphere;
s4, adding 500mL of 10 wt% sucrose solution into the heat-treated product of S3 for soaking, filtering and drying the product, and reacting for 2 hours at 800 ℃ in an inert atmosphere to cover the surface of the silicon material layer with a carbon coating layer; and performing spray granulation on 300g of product and 50g of citric acid, and reacting for 5 hours at 1000 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the activated carbon to obtain the carbon-silicon composite material.
Example 2
A preparation method of a carbon-silicon composite material comprises the following steps:
s1, mixing 100g of activated carbon (D5030 um, specific surface area 1000 m) 2 /g) adding 500mL of 30wt% nitric acid, mixing to obtain a suspension, heating and refluxing for 4 hours in a water bath at the heating temperature of 80 ℃, washing a product after the heating is finished, and drying for 24 hours at the temperature of 105 ℃;
s2, dispersing the dried product in S1 in a DMSO solution, adding 3-aminopropyl trimethoxy silane for coupling reaction, washing the product after the coupling reaction is finished, and drying the product for 12 hours at the temperature of 80 ℃;
s3, mixing the dried product in S2 with 10 wt% of Mg powder, and then carrying out heat treatment for 6h at 650 ℃ in an inert atmosphere;
s4, adding 500mL of 10 wt% sucrose solution into the heat-treated product of S3, soaking, filtering and drying the product, and reacting for 2 hours at 800 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the silicon material layer; and performing spray granulation on 300g of product and 50g of citric acid, and reacting for 5 hours at 1000 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the activated carbon to obtain the carbon-silicon composite material.
Example 3
A preparation method of a carbon-silicon composite material comprises the following steps:
s1, 100g of activated carbon (D5010 um, specific surface area 300 m) 2 /g) adding 500mL of 30wt% nitric acid, mixing to obtain a suspension, heating and refluxing for 4 hours in a water bath at the heating temperature of 80 ℃, washing a product after the heating is finished, and drying for 24 hours at the temperature of 105 ℃;
s2, dispersing the dried product in S1 in a DMSO solution, adding 3-aminopropyl trimethoxy silane for coupling reaction, washing the product after the coupling reaction is finished, and drying the product for 12 hours at the temperature of 80 ℃;
s3, mixing the dried product in S2 with 10 wt% of Mg powder, and then carrying out heat treatment for 6h at 650 ℃ in an inert atmosphere;
s4, adding 500mL of 10 wt% sucrose solution into the heat-treated product of S3, soaking, filtering and drying the product, and reacting for 2 hours at 800 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the silicon material layer; and performing spray granulation on 300g of product and 50g of citric acid, and reacting for 5 hours at 1000 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the activated carbon to obtain the carbon-silicon composite material.
Example 4
A preparation method of a carbon-silicon composite material comprises the following steps:
s1, mixing 100g of activated carbon (D5010 um, specific surface area 2000 m) 2 /g) adding 500mL of 30wt% nitric acid, mixing to obtain a suspension, heating and refluxing for 4 hours in a water bath at the heating temperature of 80 ℃, washing a product after the heating is finished, and drying for 24 hours at the temperature of 105 ℃;
s2, dispersing the dried product in S1 in a DMSO solution, adding 3-aminopropyl trimethoxy silane for coupling reaction, washing the product after the coupling reaction is finished, and drying the product for 12 hours at the temperature of 80 ℃;
s3, mixing the dried product in the S2 with 10 wt% of Mg powder, and then carrying out heat treatment for 6 hours at 650 ℃ in an inert atmosphere;
s4, adding 500mL of 10 wt% sucrose solution into the heat-treated product of S3, soaking, filtering and drying the product, and reacting for 2 hours at 800 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the silicon material layer; and performing spray granulation on 300g of product and 50g of citric acid, and reacting for 5 hours at 1000 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the activated carbon to obtain the carbon-silicon composite material.
Example 5
A preparation method of a carbon-silicon composite material comprises the following steps:
s1, mixing 100g of activated carbon (D5010 um, specific surface area 1000 m) 2 Per g) 500mL of 30wt% nitric acid was addedMixing to obtain suspension, heating and refluxing for 4h in water bath at 80 deg.C, washing the product, and drying at 105 deg.C for 24 h;
s2, dispersing the dried product of S1 in a DMSO solution, adding 3-aminopropyl trimethoxy silane for coupling reaction, washing the product after the coupling reaction is finished, and drying the product for 12 hours at the temperature of 80 ℃;
s3, mixing the dried product in the S2 with 10 wt% of Mg powder, and then carrying out heat treatment for 6 hours at 650 ℃ in an inert atmosphere;
s4, adding 500mL of 10 wt% sucrose solution into the heat-treated product of S3, soaking, filtering and drying the product, and reacting for 2 hours at 800 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the silicon material layer; and performing spray granulation on 300g of product and 50g of citric acid, and reacting for 5 hours at 1000 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the activated carbon to obtain the carbon-silicon composite material.
Example 6
A preparation method of a carbon-silicon composite material comprises the following steps:
s1, mixing 100g of activated carbon (D5010 um, specific surface area 1000 m) 2 /g) adding 500mL of 30wt% nitric acid, mixing to obtain a suspension, heating and refluxing for 4 hours in a water bath at the heating temperature of 80 ℃, washing a product after the heating is finished, and drying for 24 hours at the temperature of 105 ℃;
s2, dispersing the dried product in S1 in a DMSO solution, adding 3-aminopropyl trimethoxy silane for coupling reaction, washing the product after the coupling reaction is finished, and drying the product for 12 hours at the temperature of 80 ℃;
s3, mixing the dried product in the S2 with 10 wt% of Mg powder, and then carrying out heat treatment for 6 hours at 650 ℃ in an inert atmosphere;
s4, adding 500mL of 10 wt% sucrose solution into the heat-treated product of S3, soaking, filtering and drying the product, and reacting for 2 hours at 800 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the silicon material layer; and performing spray granulation on 300g of product and 50g of citric acid, and reacting for 5 hours at 1000 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the activated carbon to obtain the carbon-silicon composite material.
Example 7
A preparation method of a carbon-silicon composite material comprises the following steps:
s1, mixing 100g of activated carbon (D5010 um, specific surface area 1000 m) 2 /g) adding 500mL of 5wt% nitric acid, mixing to obtain a suspension, heating and refluxing for 4h in a water bath at 80 ℃, washing a product after the heating is finished, and drying for 24h at 105 ℃;
s2, dispersing the dried product in S1 in a DMSO solution, adding 3-aminopropyl trimethoxy silane for coupling reaction, washing the product after the coupling reaction is finished, and drying the product for 12 hours at the temperature of 80 ℃;
s3, mixing the dried product in the S2 with 10 wt% of Mg powder, and then carrying out heat treatment for 6 hours at 650 ℃ in an inert atmosphere;
s4, adding 500mL of 10 wt% sucrose solution into the heat-treated product of S3, soaking, filtering and drying the product, and reacting for 2 hours at 800 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the silicon material layer; and performing spray granulation on 300g of product and 50g of citric acid, and reacting for 5 hours at 1000 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the activated carbon to obtain the carbon-silicon composite material.
Example 8
A preparation method of a carbon-silicon composite material comprises the following steps:
s1, mixing 100g of activated carbon (D5010 um, specific surface area 1000 m) 2 /g) adding 500mL of 60wt% nitric acid, mixing to obtain a suspension, heating and refluxing for 4 hours in a water bath at the heating temperature of 80 ℃, washing a product after the heating is finished, and drying for 24 hours at the temperature of 105 ℃;
s2, dispersing the dried product in S1 in a DMSO solution, adding 3-aminopropyl trimethoxy silane for coupling reaction, washing the product after the coupling reaction is finished, and drying the product for 12 hours at the temperature of 80 ℃;
s3, mixing the dried product in S2 with 10 wt% of Mg powder, and then carrying out heat treatment for 6h at 650 ℃ in an inert atmosphere;
s4, adding 500mL of 10 wt% sucrose solution into the heat-treated product of S3, soaking, filtering and drying the product, and reacting for 2 hours at 800 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the silicon material layer; and performing spray granulation on 300g of product and 50g of citric acid, and reacting for 5 hours at 1000 ℃ in an inert atmosphere to cover a carbon coating layer on the surface of the activated carbon to obtain the carbon-silicon composite material.
Comparative example 1
A preparation method of a lithium battery negative electrode material comprises the following steps:
s1, mixing SiO X Mixing the raw materials with a mixed material of an artificial stone mill, hard carbon, graphene and polyacrylate in a mass ratio of 93.3:5:0.5:1.2, and stirring the mixture with N-methyl pyrrolidone at a stirring speed of 80m/min for 30min to obtain mixed slurry with a solid content of 45%;
and S2, drying the mixed slurry in the S1 at 60 ℃ for 8h to obtain the lithium battery negative electrode material.
Comparative example 2
A preparation method of a self-filling coated silicon-based composite material comprises the following steps:
s1, mixing and dispersing 1000g of nano silicon with the granularity D50 of 100nm and 100g of citric acid in alcohol uniformly, and performing spray drying treatment to obtain a precursor A1;
s2, mixing and fusing the precursor A1 and asphalt according to the mass ratio of 10:3 to obtain a precursor B1;
s3, then placing the precursor B1 in a vacuum furnace, sintering under vacuum conditions, keeping the temperature at 1000 ℃ for 5h, cooling to obtain a precursor C1, and crushing and screening the C1 to obtain a precursor D1;
s4, mixing and fusing the precursor D1 and the asphalt according to the mass ratio of 10:1, then sintering under the condition of nitrogen protection atmosphere, wherein the heating rate is 1 ℃/min, the heat treatment temperature is 1000 ℃, preserving heat for 5 hours, and screening after cooling to obtain the self-filling coated silicon-based composite material.
Comparative example 3
A preparation method of a carbon-silicon anode material comprises the following steps:
adding 30 g of activated carbon with the particle size of 0.1 micron into 500 g of deionized water, adding 10 g of sodium silicate, stirring for 10min, dropping 0.3mol/L hydrochloric acid solution by utilizing the principle of weak acid preparation by using strong acid until the pH value of the solution reaches 4, stirring for 5 hours in the whole process, then adding deionized water to wash until the solution is neutral, drying to obtain a silicon dioxide/carbon composite material, then placing the obtained composite material into a closed container, introducing hydrogen at the speed of 2mL/s to perform reduction reaction, heating to 300 ℃ at the heating rate of 5 ℃/min, performing heat preservation reaction for 5 hours, and then taking out to obtain the carbon-silicon cathode material.
Detection assay
1) The schematic structural diagrams of the carbon-silicon composite materials prepared in examples 1 to 8 are shown in fig. 1 through cross-sectional SEM-EDS detection.
As can be seen from the observation in FIG. 1, the structure of the carbon-silicon composite material comprises a framework of activated carbon 1, the inner wall and the surface of the pores of the activated carbon 1 are covered with a silicon material layer 2, the surface of the silicon material layer 2 is covered with a carbon coating layer 3, and the expansion gap 4 is reserved in the hole of the active carbon 1, because the number of the inner holes of the active carbon is large, the silicon loaded on the inner wall of the hole is hundreds of times of the surface, so that most volume changes of the silicon material layer expand towards the inside of the pores of the activated carbon in the process of lithium intercalation and deintercalation, and further, the volume change of the silicon material layer in the process of lithium intercalation and deintercalation is effectively met, the outward volume expansion of the composite material is greatly reduced, and the problems of material pulverization, electrode structure collapse, loss of electronic contact between active substances, between the active substances and a current collector and continuous fracture and regeneration of a solid electrolyte interface film (SEI) caused by the volume change of the negative electrode material are solved. Thereby ensuring the cycling stability of the silicon-based cathode capacity.
2) XRD (X-ray diffraction) detection and analysis are carried out on the carbon-silicon composite materials prepared in the examples 1 to 8, and the C diffraction peak intensity I is known through XRD spectrum analysis 002 Diffraction Peak intensity with Si Peak I 111 The ratio of (A) to (B) is more than or equal to 0.1.
3) The materials obtained in examples 1 to 8, and comparative examples 1 to 3 were subjected to performance tests
The test method specifically comprises the following steps: taking the materials prepared in examples 1 to 8 and comparative examples 1 to 3 as negative electrode materials of lithium batteries, mixing the materials with polyvinylidene fluoride (PVDF) as a binder and a conductive agent (Super-P) according to a mass ratio of 80:10:10, adding a proper amount of N-methyl pyrrolidone (NMP) as a solvent to prepare slurry, coating the slurry on a copper foil, performing vacuum drying and rolling to prepare a negative electrode sheet, and measuring the rolling thickness of a fresh negative electrode sheet by using a micrometer; a metallic lithium plate is used as a counter electrode, and 1mol/L LiPF is used 6 The three-component mixed solvent is an electrolyte mixed according to EC: DMC: EMC 1:1:1(v/v), a polypropylene microporous membrane is used as a diaphragm, and the three-component mixed solvent is assembled into a paired lithium button cell in a glove box filled with inert gas.
The prepared lithium button cell is subjected to lithium removal gram capacity (namely charge gram capacity), first effect, 3C discharge and cycle life test at the normal temperature of 25 ℃, and the test voltage interval is 0.005-1.5V. In addition, the lithium is embedded into the lithium by electricity until the voltage is 0.005V, the negative pole piece is disassembled, the full charge thickness of the pole piece is tested by a micrometer, and the full charge expansion rate (full charge thickness/rolling thickness) is calculated, and the result is shown in Table 1;
TABLE 1 test results for lithium cell performance
As can be seen from the analysis in table 1, the full charge expansion rates of the electrode sheets prepared by using the silicon-based composite negative electrode materials in examples 1 to 8 are better than those of the silicon particle-doped hard carbon material (comparative example 1) and the hard carbon-coated silicon nanoparticles (comparative example 2), and are equivalent to those of the graphite negative electrode (about 30%). Among them, the energy density of the carbon-silicon composite material prepared in example 1 is 1300mAh/g, which is about 3.7 times of that of graphite (1300mAh/g Vs 350mAh/g), and the expansion rate is equivalent to that of graphite, so the carbon-silicon composite material prepared in the present application has excellent expansion characteristics, and thus has excellent electrochemical performance. Meanwhile, the carbon-silicon composite materials in the embodiments 1 to 8 are used for preparing the negative electrode material of the lithium battery to prepare a pair of lithium button type half batteries, and a charge and discharge test is carried out, so that the cycle life of more than 150cycles is over 80%, the cycle life is improved by more than 50% compared with that of a comparative example, the 3C discharge capacity retention rate is over 70%, and the carbon-silicon composite material has the characteristic of quick charge and has popularization and application values in the technical field of lithium batteries.
Compared with the carbon-silicon composite material, the carbon-silicon composite material similar to the carbon-silicon composite material can be evaluated for the full-life-cycle watt-hour Cost by using Cost (Cost: the full-life-cycle watt-hour Cost, P: the price of a single battery cell, Cap: the capacity of the battery cell, V: the average voltage of the battery cell, and C: the number of cycles attenuated to 80%). Through the structural design of the reserved expansion space, the particle breakage of the carbon-silicon material and the collapse of the electrode structure can be reduced, and the cycle life of the material is greatly prolonged. Practical experiment verifies that the cycle life is prolonged by more than 50%, and the full life cycle watt-hour cost of the carbon-silicon composite material is reduced by more than 50%. Meanwhile, due to the improvement of the cycle life, the large-scale use of the negative electrode material in square and soft packages is promoted, and the method has a good market application prospect.
In summary, according to the carbon-silicon composite material of the present invention, the activated carbon powder having pores inside is used as the skeleton, the silicon material layer is loaded on the inner wall and the surface of the pores of the activated carbon, and the carbon coating layer is covered on the surface of the silicon material layer, so that the number of inner pores of the activated carbon powder is large, and the silicon material loaded on the inner wall of the pores of the activated carbon is hundreds of times that of the surface of the activated carbon, so that most of the volume change of the silicon material layer expands towards the inside of the pores of the activated carbon during the lithium intercalation and deintercalation process, thereby greatly reducing the rate of volume expansion of the composite material, and avoiding the problems of material pulverization, electrode structure collapse, loss of electronic contact between active materials, between the active materials and a current collector, and continuous cracking and regeneration of a solid electrolyte interface film (SEI). Effectively ensuring the cycling stability of the silicon-based cathode capacity.
According to the preparation method of the carbon-silicon composite material, the silicon-based composite negative electrode material with the expansion gap reserved inside is prepared by adopting a wet chemical treatment method, expensive methods such as etching and vapor deposition are avoided, the preparation method has the advantages of simple process, low cost and contribution to large-scale commercial application, and the silane coupling agent is grafted in situ only through coupling reaction, so that the thickness and uniformity of the silicon material layer can be well controlled, and the cycle performance and the power performance of the silicon-based negative electrode material are effectively improved.
By using the carbon-silicon composite material disclosed by the invention for preparing a negative electrode material of a lithium battery, through button cell charge-discharge tests, the gram capacity of the carbon-silicon composite material as a negative electrode is over 600mAh/g, the first effect of the battery is over 80%, the expansion rate of a pole piece is lower than 30%, the discharge capacity retention rate of 3C is over 70%, and the cycle life of the carbon-silicon composite material under the condition of 0.5C 150cycles 0.005-1.5V 25 ℃ is over 80%, so that the carbon-silicon composite material has excellent electrochemical performance and has popularization and application values in the technical field of lithium ion batteries.
The above embodiments are merely illustrative of the principles of the present invention and its efficacy, and are not intended to limit the present application. Any person skilled in the art can modify or change the above-described embodiments without departing from the spirit and scope of the present application. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical concepts disclosed in the present application shall be covered by the claims of the present application.
Claims (13)
1. The carbon-silicon composite material is characterized by comprising activated carbon, wherein a silicon material layer is loaded on the inner wall and the surface of a hole of the activated carbon, and a carbon coating layer covers the surface of the silicon material layer.
2. The carbon-silicon composite material as claimed in claim 1, wherein the average pore diameter of the activated carbon is D, the thickness of the silicon material layer is S, and the thickness of the carbon coating layer covering the surface of the silicon material layer is H, so that 4S + H is less than or equal to 0.5D.
3. The carbon-silicon composite material as claimed in claim 1, wherein the carbon accounts for 70-95 wt% of the composite negative electrode material, and the silicon accounts for 5-30 wt%; wherein the activated carbon is powder, and the silicon material layer is nano silicon.
4. The carbon-silicon composite material according to claim 3, wherein the particle size of the carbon-silicon composite material is 4-30 um;
the specific surface area of the activated carbon is 300-2000 m 2 An average pore diameter of 0.8 to 10nm and a pore volume of 0.2 to 1.0cm 3 /g；
The specific surface area of the activated carbon loaded with the silicon material layer is 75-1500m 2 Average pore diameter of 0.15-7.5nm and pore volume of 0.10-0.69cm 3 /g。
5. A method of producing a carbon-silicon composite material as claimed in any one of claims 1 to 4, comprising the steps of:
s1, performing activation treatment on the activated carbon;
s2, dispersing activated carbon in a weak polar solvent, adding a silane coupling agent for coupling reaction, and then washing and drying to obtain a silicon precursor;
s3, mixing the silicon precursor with a reducing agent and then carrying out heat treatment to obtain silicon-loaded activated carbon;
and S4, mixing the silicon-loaded activated carbon with a carbon source, and carrying out carbonization treatment twice to obtain the carbon-silicon composite material.
6. The preparation method of claim 5, wherein in the S1, the activated carbon is activated by nitric acid, and the concentration of the nitric acid is 5wt% to 60 wt%.
7. The method according to claim 6, wherein in S1, the activation treatment is performed by heating and refluxing a suspension obtained by mixing nitric acid and activated carbon;
the heating reflux temperature is 75-85 ℃, and the time is 2-5 h.
8. The method according to claim 5, wherein in S2, the silane coupling agent is selected from one or more of 3-aminopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane and chlorobenzyltrichlorosilane;
the weakly polar solvent is selected from one or more of toluene, isopropanol, acetonitrile and dimethyl sulfoxide.
9. The preparation method of claim 5, wherein in the S3, the heat treatment is carried out at a temperature of 600 ℃ to 750 ℃ for 4 to 8 hours in an inert atmosphere.
10. The method according to claim 5, wherein the reducing agent is Zn, Mg or Al.
11. The preparation method according to claim 5, wherein in S4, specifically: dispersing and soaking silicon-loaded activated carbon in an aqueous solution containing a carbon source, and then carrying out primary carbonization treatment in an inert atmosphere; and then mechanically mixing the carbon source with the carbon source, and then carrying out secondary carbonization treatment in an inert atmosphere to obtain the carbon-coated composite negative electrode material.
12. The method according to claim 11, wherein the carbon source is an organic carbon source.
13. Use of the carbon silicon composite material according to any one of claims 1 to 4 as a negative electrode material for lithium ion batteries.
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| CN104466141A (en) * | 2013-09-17 | 2015-03-25 | 北京有色金属研究总院 | Preparation method of Si / graphite / C composite material for lithium ion battery |
| CN110224125A (en) * | 2019-06-13 | 2019-09-10 | 长沙矿冶研究院有限责任公司 | A kind of porous carbon-nanometer silico-carbo Core-shell structure material and preparation method thereof |
| CN112054171A (en) * | 2020-08-13 | 2020-12-08 | 利普同呈(江苏)新能源科技有限公司 | Carbon-silicon negative electrode material and preparation method thereof |
| CN114068901A (en) * | 2021-11-15 | 2022-02-18 | 陕西煤业化工技术研究院有限责任公司 | Silicon-carbon composite negative electrode material, preparation method and application |
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