CN110854379A - Silicon-carbon composite negative electrode material and preparation method thereof, negative electrode plate and lithium ion battery - Google Patents
Silicon-carbon composite negative electrode material and preparation method thereof, negative electrode plate and lithium ion battery Download PDFInfo
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- CN110854379A CN110854379A CN201911176604.0A CN201911176604A CN110854379A CN 110854379 A CN110854379 A CN 110854379A CN 201911176604 A CN201911176604 A CN 201911176604A CN 110854379 A CN110854379 A CN 110854379A
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- 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
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
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Abstract
The invention relates to a silicon-carbon composite negative electrode material and a preparation method thereof, a negative electrode plate and a lithium ion battery, and belongs to the technical field of preparation of lithium ion battery materials. According to the invention, a silane polymer is deposited on the surface of a template agent by a chemical bath method, wherein thioacetamide and silicon acetate form a silane compound with a stable structure, carbon nano tubes are doped among the materials to form a network structure, then the template is dissolved away by a solvent to obtain a porous silane compound, namely a silicon dioxide/carbon composite material, and then the silicon monoxide/carbon composite material is obtained by magnesiothermic reduction. The material has high conductivity and specific surface area; and the preparation process is simple, the consistency is high, and the industrialization is easy. The pole piece prepared by the method has strong liquid absorption and retention capacity and low rebound rate; the battery prepared from the lithium ion battery has high initial discharge capacity, high initial efficiency and good cycle performance.
Description
Technical Field
The invention relates to a silicon-carbon composite negative electrode material and a preparation method thereof, a negative electrode plate and a lithium ion battery, and belongs to the technical field of preparation of lithium ion battery materials.
Background
The silicon-carbon cathode material is a novel cathode material developed in recent years, becomes a research hotspot due to the advantages of high specific capacity, wide source and the like, and is applied to the lithium ion battery with high specific energy density. However, the poor conductivity of the silicon material itself and the severe volume effect generated during the electrochemical lithium intercalation and deintercalation cause the damage and mechanical pulverization of the material structure, which leads to the separation between the electrode materials and the electrode material and the current collector, and further the loss of electric contact, thus causing the rapid decrease of the cycle performance of the electrode. One of the measures for reducing the expansion of the silicon carbon material is to manufacture the porous silicon carbon material and compound the porous silicon carbon material with the carbon material with low expansion rate and stable structure and the polymer material thereof so as to reduce the expansion of the material in the charging and discharging process and improve the conductivity.
For example, chinese patent application with application publication No. CN 105226285 a discloses a porous silicon-carbon composite material and a preparation method thereof, wherein the preparation process comprises: firstly, providing a silicon-active metal alloy and reacting with a pore-forming agent through a liquid phase method to remove the active metal, then cleaning the porous silicon nano material with hydrofluoric acid solution to remove silicon oxide, then carrying out ball milling, coating a polymer and carbonizing to finally obtain the porous silicon-carbon composite material, wherein although the expansion rate of the material is reduced and the specific capacity is improved, the preparation process is complex by adopting the method, the hydrofluoric acid has strong corrosivity to equipment and easily causes safety hidden danger, and the prepared material has low initial efficiency and influences the application and popularization of the material in the field of lithium ion batteries.
Disclosure of Invention
The invention aims to provide a silicon-carbon composite negative electrode material which is high in conductivity and specific surface area.
The invention also provides a preparation method of the silicon-carbon composite negative electrode material, which is simple and convenient, and the raw materials have no corrosivity on equipment.
The invention also provides a negative pole piece using the silicon-carbon composite negative pole material as a negative active material.
The invention also provides a lithium ion battery using the silicon-carbon composite negative electrode material as a negative electrode active material.
In order to achieve the purpose, the invention adopts the technical scheme that:
a silicon-carbon composite negative electrode material is prepared by the following steps:
1) preparing a template agent, a dispersing agent, a carbon nano tube and thioacetamide into a mixed solution;
2) mixing the mixed solution in the step 1) with a silicon acetate solution, reacting at 50-90 ℃, and then filtering to obtain a solid to obtain a filtered substance;
3) and removing the template agent in the filtrate to obtain a precursor material, mixing the precursor material with magnesium powder to perform magnesium thermal reaction, washing and drying to obtain the magnesium-doped aluminum-magnesium alloy.
The silicon-carbon composite negative electrode material is prepared by depositing a silane polymer on the surface of a template agent by a chemical bath method, wherein thioacetamide and silicon acetate form a silane compound with a stable structure, carbon nano tubes are doped among the materials to form a network structure, then removing the template agent to obtain a porous silane compound, namely a silicon dioxide/carbon composite material, and then performing magnesium thermal reduction to obtain the silicon monoxide/carbon composite material.
In the process of charging and discharging the silicon materials, the expansion rate is high, the failure of a conductive network is easily caused, and the carbon nano tubes have strong conductivity and form a network structure, so that the failure of electric contact caused by the expansion between the silicon materials is avoided.
The silicon-carbon composite negative electrode material is prepared by a chemical bath method, and has high conductivity and specific surface area; and the preparation process is simple, the consistency is high, and the industrialization is easy. Meanwhile, sulfur is doped in the silicon compound, and the specific capacity of the material can be improved by utilizing the specific capacity of the sulfur.
Preferably, the mass ratio of the template agent, the dispersing agent, the carbon nano tube and the thioacetamide in the step 1) is (10-20): (1-3): (1-5): (10-20).
Preferably, the dispersant is polyvinylpyrrolidone. The dispersing agent has good dispersing effect, strong stability and wide sources.
Preferably, the mass ratio of the thioacetamide to the silicon acetate is (10-20): (50-100).
Preferably, the solvent of the mixed solution in the step 1) is ethanol, and the mass ratio of the ethanol to the template agent is 500: (10-20).
Preferably, the mass fraction of the silicon acetate in the silicon acetate solution in the step 2) is 8-12%. Preferably, the solvent in the silicon acetate solution is diethyl ether.
Preferably, the step 3) is to remove the template agent in the filtrate by using a dissolution method. Specifically, mixing the filtrate obtained in the step 2) with a solvent to dissolve a template agent, filtering to remove the template agent, and drying the solid to obtain the precursor material. Preferably, the template agent is polystyrene microspheres (diameter 300-600nm), and the solvent in step 3) is tetrahydrofuran. Tetrahydrofuran serves to dissolve away the polystyrene template core microspheres, so it can be used in excess.
The method for dissolving the polystyrene by adopting the tetrahydrofuran has the advantages of good effect, simple process and low cost.
Preferably, the reaction time in the step 2) is 1-6 h. The reaction of the step generates silicon compounds containing sulfur (SiOx, wherein 2 is more than or equal to X and more than or equal to 1, and contains silicon monoxide, silicon dioxide or a composite body formed by the silicon monoxide and the silicon dioxide).
Silicon acetate (C)8H12O8Si) in diethyl ether to form a compound having a-COOH group, and an organic base which is thioacetamide (CH)3CSNH2) In which contains-NH2A group. The two react to form NH3·H2O+C8H12O-Si-S-CH3。
Preferably, the drying in step 3) is vacuum drying at 70-90 ℃.
Preferably, the mass ratio of the magnesium powder to the precursor material in the step 3) is 1: (1-2). Magnesium reacts with silica to form silicon monoxide.
Preferably, the magnesium thermal reaction in the step 3) is specifically: and (3) preserving the heat for 1-6 h at 700-800 ℃ under the inert atmosphere.
More preferably, the magnesium thermal reaction in the step 3) is carried out under the condition that the temperature is raised to 700-800 ℃ at the temperature raising rate of 1-10 ℃/min under the inert atmosphere, and the temperature is kept for 1-6 h.
A preparation method of a silicon-carbon composite negative electrode material comprises the following steps:
1) preparing a template agent, a dispersing agent, a carbon nano tube and thioacetamide into a mixed solution;
2) mixing the mixed solution in the step 1) with a silicon acetate solution, reacting at 50-90 ℃, and then filtering to obtain a solid to obtain a filtered substance;
3) and removing the template agent in the filtrate to obtain a precursor material, mixing the precursor material with magnesium powder to perform magnesium thermal reaction, washing and drying to obtain the magnesium-doped aluminum-magnesium alloy.
The operation and technical parameters of the preparation method of the silicon-carbon composite negative electrode material are the same as the above.
The silicon-carbon composite negative electrode material is used as a negative electrode active material of a lithium ion battery.
A negative electrode plate of a lithium ion battery is characterized in that a negative active material used in the negative electrode plate is the silicon-carbon composite negative electrode material. The negative pole piece adopts the silicon-carbon composite material as a negative active material, and has strong liquid absorption and retention capacity and low rebound rate.
A lithium ion battery comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm, wherein a negative active material used in the negative pole piece is the silicon-carbon composite negative pole material. The lithium ion battery adopts the silicon-carbon composite material as a negative active material, and has high first discharge capacity and high first efficiency; the cycle performance is good.
Drawings
Fig. 1 is an SEM image of a silicon-carbon composite anode material prepared in example 1 of the present invention;
FIG. 2 is a graph showing the reaction equation of silicon acetate and thioacetamide in example 1 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples. The equipment and reagents used in the examples and the experimental examples were commercially available except as specifically indicated.
Example 1
The silicon-carbon composite negative electrode material in the embodiment is prepared by the method comprising the following steps of:
1) weighing 500mL of ethanol, 15g of polystyrene microspheres (500nm), 2g of polyvinylpyrrolidone, 3g of carbon nanotubes and 15g of thioacetamide, adding into a conical flask, and stirring uniformly to obtain an organic alkali solution A;
2) dissolving 75g of silicon acetate in 750g of diethyl ether to prepare a 10% solution, slowly and dropwise adding the solution into the organic alkali solution A, uniformly stirring, stirring and heating in a water bath at 60 ℃ for 2 hours, and filtering to obtain a solid; the reaction equation of this step is shown in FIG. 2;
3) then adding the solid obtained by filtering into an excessive tetrahydrofuran solution, soaking for 6 hours, filtering, taking the solid, and drying in vacuum at 80 ℃ to obtain a precursor material B;
4) then, 10g of magnesium powder and 15g of precursor material B were weighed, mixed uniformly, transferred to a tube furnace, and then subjected to a magnesium thermal reaction (reaction conditions: heating to 750 ℃ at a heating rate of 5 ℃/min under an argon atmosphere, and preserving heat for 3h) to reduce silicon dioxide into silicon monoxide, then washing with 1mol/L dilute hydrochloric acid, and vacuum drying at 80 ℃ to obtain the porous silicon monoxide/carbon composite negative electrode material.
Firstly preparing polystyrene emulsion, then adding thioacetamide and an additive to prepare an organic alkali liquor, then dropwise adding silicon acetate through a separating funnel, transferring the mixture into a water bath at 50-90 ℃, stirring and heating, filtering, soaking in tetrahydrofuran, drying and reducing to obtain the porous silicon-carbon composite material. The prepared silicon-carbon composite material has the advantages of simple preparation process, high efficiency, low cost and the like by adopting a chemical bath method, and the prepared silicon-carbon composite material has the characteristics of high specific capacity, good cycle performance and the like when being applied to a lithium ion battery. Fig. 1 is an SEM image of the silicon-carbon composite anode material prepared in this example, and it can be seen from the SEM image that the silicon-carbon composite anode material has uniform particle size and reasonable distribution, and the particle size is between (5-12) μm.
Example 2
The silicon-carbon composite negative electrode material in the embodiment is prepared by the method comprising the following steps of:
1) weighing 500mL of ethanol, 10g of polystyrene microspheres (300nm), 1g of polyvinylpyrrolidone, 1g of carbon nanotubes and 10g of thioacetamide thereof, adding into a conical flask, and stirring uniformly to obtain an organic alkali solution A;
2) then weighing 50g of silicon acetate, dissolving the silicon acetate in 500mL of diethyl ether to prepare a 10% solution, slowly and dropwise adding the solution into the organic alkali solution A, stirring the solution uniformly, heating the solution for 6 hours in a water bath at 50 ℃, and filtering the solution to obtain a solid;
3) then adding an excessive tetrahydrofuran solution, soaking for 6 hours, filtering, taking solid, and drying in vacuum at 80 ℃ to obtain a precursor material B;
4) then, 10g of magnesium powder and 10g of precursor material B were weighed, mixed uniformly, transferred to a tube furnace, and then subjected to a magnesium thermal reaction (reaction conditions: heating to 700 ℃ at a heating rate of 1 ℃/min under the argon atmosphere, and preserving heat for 6h) to reduce the silicon dioxide into silicon monoxide, then washing by adopting 1mol/L dilute hydrochloric acid, and drying in vacuum at 80 ℃ to obtain the porous silicon monoxide/carbon composite negative electrode material.
Example 3
The silicon-carbon composite negative electrode material in the embodiment is prepared by the method comprising the following steps of:
1) in a conical flask, weighing 500ml of ethanol, 20g of polystyrene microspheres (600nm), 3g of polyvinylpyrrolidone, 5g of carbon nanotubes and 20g of thioacetamide thereof, adding into the conical flask, and stirring uniformly to obtain an organic alkali solution A;
2) dissolving 100g of silicon acetate in 1000mL of diethyl ether to prepare a 10% solution, slowly and dropwise adding the solution into the organic alkali solution A, uniformly stirring, stirring and heating in a water bath at 90 ℃ for 1h, and filtering to obtain a solid;
3) then adding an excessive tetrahydrofuran solution, soaking for 6 hours, filtering, taking solid, and drying in vacuum at 80 ℃ to obtain a precursor material B;
4) then, 10g of magnesium powder and 20g of precursor material B were weighed, mixed uniformly, transferred to a tube furnace, and then subjected to a magnesium thermal reaction (reaction conditions: heating to 800 ℃ at a heating rate of 10 ℃/min under an argon inert atmosphere, and keeping the temperature for 1h) to reduce silicon dioxide into silicon monoxide, then washing with 1mol/L dilute hydrochloric acid, and vacuum drying at 80 ℃ to obtain the porous silicon monoxide/carbon composite negative electrode material.
Example 4
The negative electrode plate in the embodiment is prepared by the method comprising the following steps:
the silicon-carbon composite material obtained in example 1 was added with a binder, a conductive agent and a solvent, stirred to prepare a slurry, coated on a copper foil, dried and rolled to obtain the silicon-carbon composite material. The binder is LA132 binder, conductive agent SP, solvent is secondary distilled water, and the proportion is: silicon-carbon composite material: SP: LA 132: 95g of secondary distilled water: 1 g: 4 g: 220 mL.
Example 5
The negative electrode plate in the embodiment is prepared by the method comprising the following steps:
the silicon-carbon composite material obtained in example 2 was added with a binder, a conductive agent and a solvent, stirred to prepare a slurry, coated on a copper foil, dried and rolled to obtain the silicon-carbon composite material. The rest is the same as in example 4.
Example 6
The negative electrode plate in the embodiment is prepared by the method comprising the following steps:
and adding a binder, a conductive agent and a solvent into the silicon-carbon composite material obtained in the embodiment 3, stirring and pulping, coating the mixture on a copper foil, and drying and rolling the copper foil to obtain the silicon-carbon composite material. The rest is the same as in example 4.
Example 7
The lithium ion button cell in the embodiment comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm, wherein the positive pole piece is a metal lithium piece, the negative pole piece is the negative pole piece in embodiment 4, and the electrolyte is LiPF6EC + DEC, volume ratio of Ethylene Carbonate (EC) to diethyl carbonate (DEC) 1:1, LiPF6The concentration was 1.3 mol/L. The separator was Polyethylene (PE).
In other embodiments, the separator may also use a polypropylene (PP) or polyethylene propylene (PEP) composite film.
Example 8
The lithium ion button cell in the embodiment comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm, wherein the positive pole piece is a metal lithium piece, and the negative pole piece is the negative pole piece in the embodiment 5; the electrolyte and separator were the same as in example 7.
Example 9
The lithium ion button cell in the embodiment comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm, wherein the positive pole piece is a metal lithium piece, and the negative pole piece is the negative pole piece in the embodiment 6; the electrolyte and separator were the same as in example 7.
Example 10
The lithium ion soft package battery in the embodiment comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm.
The silicon-carbon composite material in example 1 was used as a negative electrode active material for the negative electrode sheet; wherein, the active substance: CMC: SBR: SP: deionized water 96 g: 1.2 g: 1.8 g: 1 g: 120 mL.
The positive electrode material on the positive electrode piece is lithium iron phosphate. Wherein, the active substance: PVDF: SP: and 93g of deionized water: 3.5 g: 3.5 g: 80 mL.
The electrolyte is as follows: LiPF6EC + DEC, volume ratio of Ethylene Carbonate (EC) to diethyl carbonate (DEC) 1:1, LiPF6The concentration was 1.3 mol/L.
The septum was Celgard 2400 membrane.
Example 11
The lithium ion soft package battery in the embodiment comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm.
The negative electrode sheet used the silicon-carbon composite material of example 2 as a negative active material.
The rest is the same as in example 10.
Example 12
The lithium ion soft package battery in the embodiment comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm.
The negative electrode sheet used the silicon-carbon composite material of example 3 as a negative active material.
The rest is the same as in example 10.
Comparative example 1
The commercially available silica composite material was used as comparative example 1, type: S500-2A; the manufacturer: shenzhen city beibei new energy materials stockings limited.
Comparative example 2
The negative pole piece in the comparative example is prepared by the method comprising the following steps:
and adding a binder, a conductive agent and a solvent into the silicon-carbon composite material obtained in the comparative example 1, stirring and pulping, coating the mixture on a copper foil, and drying and rolling the copper foil to obtain the silicon-carbon composite material. The rest is the same as in example 4.
Comparative example 3
The lithium ion button cell in the embodiment comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm, wherein the positive pole piece is a metal lithium piece, and the negative pole piece is the negative pole piece in the comparative example 2; the electrolyte and separator were the same as in example 7.
Comparative example 4
The lithium ion soft package battery in the embodiment comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm.
The negative electrode sheet used the silicon-carbon composite material in comparative example 1 as a negative active material.
The rest is the same as in example 10.
Test example 1 test of physical and chemical properties of silicon-carbon composite Material
The testing method of the silicon-carbon composite material comprises the following steps: the resistance, tap density and specific surface area of the silicon-carbon composite materials obtained in examples 1-3 and comparative example 1 are tested according to the national standard GB/T-2433and 2009 graphite cathode material for lithium ion batteries. The test results are detailed in table 1.
TABLE 1 physicochemical Properties of the composites in examples 1-3 and comparative example 1
| Negative electrode active material | Example 1 | Example 2 | Example 3 | Comparative example 1 |
| Conductivity (cm/S) | 3.4*10-9 | 1.9*10-9 | 1.2*10-9 | 1*10-10 |
| Tap density (g/cm)3) | 0.98 | 0.97 | 0.94 | 0.95 |
| Specific surface area (m)2/g) | 4.2 | 4.1 | 3.8 | 1.3 |
As can be seen from table 1, the electrical conductivity of the silicon-carbon composite materials prepared in examples 1-3 is significantly higher than that of comparative example 1, because the carbon nanotube material with high electrical conductivity is doped in the silicon-carbon composite materials, so that the electrical conductivity of the materials is improved. The material prepared by the chemical bath method has the characteristic of high density, so that the tap density of the material is improved; meanwhile, the material is of a hollow core structure, so that the tap density of the material is reduced, and the tap density of the material is not changed greatly.
Test example 2 button cell performance test
Examples 7-9 and comparative example 3 the simulated cells were assembled in a hydrogen-charged glove box and the electrochemical performance was carried out on a Wuhan blue New Wien 5V/10mA cell tester with a charge-discharge voltage range of 0.005V to 2.0V and a charge-discharge rate of 0.1C. The results of the power-off test are shown in table 2.
TABLE 2 physicochemical Properties of silicon-carbon composite Material obtained in examples 7 to 9 and comparative example 3
| Example 7 | Example 8 | Example 9 | Comparative example 3 | |
| First discharge capacity (mAh/g) | 1312.4 | 1300.1 | 1281.7 | 539.5 |
| First efficiency (%) | 87.1 | 86.8 | 85.3 | 84.4 |
As can be seen from Table 2, the discharge capacity and efficiency of the rechargeable battery using the negative active materials obtained in examples 1 to 3 were significantly higher than those of the comparative examples. The experimental result shows that the cathode active material of the invention can lead the battery to have good discharge capacity and efficiency; the reason is that: the silane compound material prepared by the chemical bath method has a stable structure, improves the conductivity of the silane compound material by utilizing the high conductivity of the carbon nano tube, promotes the exertion of the gram volume of the silicon monoxide, and finally improves the first efficiency of the silicon monoxide/carbon negative electrode material.
Test example 3 pouch battery performance test
In examples 10 to 12 and comparative example 4, a 5Ah pouch battery and a corresponding negative electrode plate thereof were prepared, and the negative electrode plate was tested for liquid absorption and retention capacity and electrode plate rebound, with the results shown in tables 3 to 4, and the pouch battery was tested for cycle performance, with the results shown in table 5. The test methods are shown below, and the test results are shown in tables 3 to 5:
liquid absorption capacity:
and (3) adopting a 1mL burette, sucking the electrolyte VmL, dripping a drop on the surface of the pole piece, timing until the electrolyte is completely absorbed, recording the time t, and calculating the liquid absorption speed V/t of the pole piece. The test results are shown in table 2.
And (4) testing the liquid retention rate:
calculating the theoretical liquid absorption amount m1 of the pole piece according to the pole piece parameters, weighing the weight m2 of the pole piece, then placing the pole piece into electrolyte to be soaked for 24 hours, weighing the weight m3 of the pole piece, calculating the liquid absorption amount m3-m2 of the pole piece, and calculating according to the following formula: the liquid retention rate was (m3-m2) × 100%/m 1.
Cycle performance: testing the cycle performance of the battery at the temperature of 25 +/-3 ℃ with the charge-discharge multiplying power of 1C/1C and the voltage range of 2.8V-4.2V;
the rebound rate of the pole piece is as follows: firstly, testing the average thickness of the pole piece to be D1 by using a thickness gauge, then placing the pole piece in a vacuum drying oven at 80 ℃ for drying for 48h, testing the thickness of the pole piece to be D2, and calculating according to the following formula: the rebound rate was (D2-D1) × 100%/D1.
TABLE 3 comparison table of liquid absorption and retention capacities of pole pieces of different materials
As can be seen from Table 3, the liquid and liquid absorbing abilities of the silicon carbon composites obtained in examples 1 to 3 are significantly higher than those of the comparative example. The experimental results show that the negative active material of the invention has higher liquid absorption and retention capacity because: the materials prepared in the examples 1-3 are porous structures, so that the electrolyte can more easily enter the interior of the materials, and the liquid absorption and retention capacity of the materials is improved.
TABLE 4 rebound Rate comparison Table of Pole pieces
As can be seen from table 4, the rebound rate of the negative electrode sheet prepared by using the negative electrode active materials obtained in examples 1 to 3 is significantly lower than that of the comparative example. Experimental results show that the negative pole piece obtained by adopting the negative pole material has lower rebound rate, and the reason is as follows: the porous structure prepared by the chemical bath method improves the buffer space for the expansion of the material, thereby reducing the rebound of the pole piece.
TABLE 5 comparison of the cycling behavior of different materials
| Battery with a battery cell | Negative electrode active material | Capacity retention (%) after 500 cycles |
| Example 10 | Example 1 | 90.62 |
| Example 11 | Example 2 | 89.78 |
| Example 12 | Example 3 | 86.39 |
| Comparative example 4 | Comparative example 1 | 81.55 |
The table 5 shows that the cycle performance curve of the pouch cell prepared from the negative electrode material is obviously the same as that of the comparative example, the reason why the cycle performance of the cell in the examples is that the porous silicon carbon material has a porous structure and provides a buffer space for the insertion of lithium ions during the charging and discharging processes of the material, so that the expansion of the material is reduced, and meanwhile, the material is doped with a carbon nanotube material with high mechanical strength so that the expansion is reduced, and the expansion rate of the material is reduced, so that the cycle performance of the material is also improved.
Claims (10)
1. A silicon-carbon composite negative electrode material is characterized in that: is prepared by the method comprising the following steps:
1) preparing a template agent, a dispersing agent, a carbon nano tube and thioacetamide into a mixed solution;
2) mixing the mixed solution in the step 1) with a silicon acetate solution, reacting at 50-90 ℃, and then filtering to obtain a solid to obtain a filtered substance;
3) and removing the template agent in the filtrate to obtain a precursor material, mixing the precursor material with magnesium powder to perform magnesium thermal reaction, washing and drying to obtain the magnesium-doped aluminum-magnesium alloy.
2. The silicon-carbon composite anode material according to claim 1, characterized in that: the mass ratio of the template agent, the dispersing agent, the carbon nano tube and the thioacetamide in the step 1) is (10-20): (1-3): (1-5): (10-20).
3. The silicon-carbon composite anode material according to claim 1 or 2, characterized in that: the mass ratio of the thioacetamide to the silicon acetate is (10-20): (50-100).
4. The silicon-carbon composite anode material according to claim 1, characterized in that: the solvent of the mixed solution in the step 1) is ethanol, and the mass ratio of the ethanol to the template agent is 500: (10-20).
5. The silicon-carbon composite anode material according to claim 1, characterized in that: the mass fraction of the silicon acetate in the silicon acetate solution in the step 2) is 8-12%.
6. The silicon-carbon composite anode material according to claim 1 or 2, characterized in that: in the step 3), the template agent in the filtrate is removed by using a dissolving method.
7. The silicon-carbon composite anode material according to claim 6, wherein: the template agent is polystyrene microspheres, and the solvent used by the dissolution method is tetrahydrofuran.
8. A preparation method of a silicon-carbon composite negative electrode material is characterized by comprising the following steps: the method comprises the following steps:
1) preparing a template agent, a dispersing agent, a carbon nano tube and thioacetamide into a mixed solution;
2) mixing the mixed solution in the step 1) with a silicon acetate solution, reacting at 50-90 ℃, and then filtering to obtain a solid to obtain a filtered substance;
3) and removing the template agent in the filtrate to obtain a precursor material, mixing the precursor material with magnesium powder to perform magnesium thermal reaction, washing and drying to obtain the magnesium-doped aluminum-magnesium alloy.
9. A negative pole piece is characterized in that: the negative active material used in the negative pole piece is the silicon-carbon composite negative pole material in any one of claims 1 to 7.
10. The utility model provides a lithium ion battery, includes positive pole piece, negative pole piece, electrolyte and diaphragm, its characterized in that: the negative active material used in the negative pole piece is the silicon-carbon composite negative pole material in any one of claims 1 to 7.
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