Disclosure of Invention
In view of the above, the present invention provides a copper nanowire-wrapped silicon carbon composite material, and a preparation method and an application thereof.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a silicon-carbon composite material wound by copper nanowires, which comprises silicon-in-carbon particles and copper nanowires wound on the surfaces of the silicon-in-carbon particles;
the carbon-coated silicon particles comprise submicron silicon and a carbon layer coated on the surface of the submicron silicon; the carbon layer has metal nanoparticles dispersed therein.
Preferably, the particle size of the carbon-coated silicon particles is 0.7-2 μm.
Preferably, the carbon layer has a thickness of 100 to 500 nm.
Preferably, the material of the metal nanoparticles comprises one or more of metals including Cu, Ni, Mn, Zn, Co and Fe;
the particle size of the metal nanoparticles is 20-100 nm;
the mass of the metal nano particles is 3-10% of that of the carbon-coated silicon particles.
Preferably, the diameter of the copper nanowire is 20-10 nm, and the length of the copper nanowire is 1-60 mu m;
the content of the copper nanowire in the copper nanowire wound silicon-carbon composite material is 15-40 wt%.
The invention provides a preparation method of a copper nanowire wound silicon-carbon composite material, which comprises the following steps:
mixing a carbon source, a first water-soluble copper source, submicron silicon and water, and sequentially carrying out hydrothermal reaction and annealing treatment to obtain carbon-coated silicon particles;
and mixing the carbon-coated silicon particles, a second water-soluble copper source, a surfactant, a polyhydroxy compound and water, and winding and growing copper nanowires on the surfaces of the carbon-coated silicon particles in situ to obtain the copper nanowire-wound silicon-carbon composite material.
Preferably, the carbon source comprises one or more of glucose, starch, cellulose, polysaccharide, cyclodextrin, lignin and cyclic hydrocarbon.
Preferably, the mass ratio of the carbon source, the submicron silicon and the first water-soluble copper source is 10: (1-20): (1-5);
the temperature of the hydrothermal reaction is 170-300 ℃, and the heat preservation time is 2-24 h.
Preferably, the mass ratio of the silicon-on-carbon particles, the second water-soluble copper source, the surfactant and the polyol is 1: (2-10): (45-100): (25-80);
the temperature of the in-situ winding growth is 80-150 ℃, and the heat preservation time is 2-24 h.
The invention provides an application of the copper nanowire-wound silicon-carbon composite material or the copper nanowire-wound silicon-carbon composite material obtained by the preparation method in the technical scheme in a lithium ion battery.
The invention provides a silicon-carbon composite material wound by copper nanowires, which comprises silicon-in-carbon particles and copper nanowires wound on the surfaces of the silicon-in-carbon particles; the carbon-coated silicon particles comprise submicron silicon and a carbon layer coated on the surface of the submicron silicon; metal nano particles are dispersed in the carbon layer; the carbon layer has metal nanoparticles dispersed therein. In the copper nanowire wound silicon-carbon composite material provided by the invention, the metal nanoparticles and the copper nanowires form a conductive network from inside to outside, and the good conductivity of the metal and the copper are utilized to greatly improve the conductivity of the material. Meanwhile, the carbon layer has high strength and limits the volume expansion of silicon, so that the conductivity between the composite material and the current collector is greatly improved, and the electrochemical performance is effectively improved. In addition, the particle size and the particle diameter of the copper nanowire wound silicon-carbon composite material provided by the invention are uniform, the metal nanoparticles are uniformly distributed in the carbon layer, the purity is high, the coating is complete and uniform, the diameter distribution of the copper nanowires is uniform, and the copper nanowire wound silicon-carbon composite material is obviously wound on the surface of the carbon-coated silicon particles.
The invention provides a preparation method of the copper nanowire wound silicon-carbon composite material in the technical scheme. The preparation method provided by the invention has the characteristics of simple and convenient operation, low cost of raw materials, low energy consumption and low pollution, and is suitable for industrial production.
Detailed Description
The invention provides a silicon-carbon composite material wound by copper nanowires, which comprises silicon-in-carbon particles and copper nanowires wound on the surfaces of the silicon-in-carbon particles.
In the invention, the carbon-coated silicon particles comprise submicron silicon and a carbon layer coated on the surface of the submicron silicon; the particle size of the carbon-coated silicon particles is preferably 0.7-2 μm, more preferably 0.8-1.5 μm, and most preferably 1-1.3 μm. In the invention, the particle size of the submicron silicon is preferably 100 to 1000nm, more preferably 300 to 800nm, and most preferably 400 to 600 nm.
In the present invention, the thickness of the carbon layer is preferably 100 to 500nm, more preferably 200 to 400nm, and still more preferably 200 to 300 nm.
In the present invention, metal nanoparticles are dispersed in the carbon layer; the particle size of the metal nanoparticles is preferably 20-100 nm, more preferably 30-80 nm, and most preferably 45-60 nm; the metal nanoparticles preferably account for 3-10%, more preferably 4-8%, and most preferably 5-7% of the mass of the silicon-on-carbon particles.
In the invention, the diameter of the copper nanowire is preferably 20-10 nm, more preferably 30-80 nm, and most preferably 45-60 nm; the length of the copper nanowire is 1-60 mu m, more preferably 10-50 mu m, and most preferably 20-40 mu m; the content of the copper nanowire in the copper nanowire wound silicon-carbon composite material is preferably 15-40 wt%, more preferably 20-35 wt%, and most preferably 25-30 wt%.
The invention provides a preparation method of a copper nanowire wound silicon-carbon composite material, which comprises the following steps:
mixing a carbon source, a first water-soluble copper source, submicron silicon and water, and sequentially carrying out hydrothermal reaction and annealing treatment to obtain carbon-coated silicon particles;
and mixing the carbon-coated silicon particles, a second water-soluble copper source, a surfactant, a polyhydroxy compound and water, and carrying out in-situ winding growth to obtain the copper nanowire wound silicon-carbon composite material.
In the present invention, all the raw material components are commercially available products well known to those skilled in the art unless otherwise specified.
According to the invention, a carbon source, a first water-soluble copper source, submicron silicon and water are mixed, and hydrothermal reaction and annealing treatment are sequentially carried out to obtain the carbon-coated silicon particles.
In the invention, the carbon source preferably comprises one or more of glucose, starch, cellulose, polysaccharide, cyclodextrin, lignin and cyclic hydrocarbon; when the carbon source is a mixture of two or more carbon sources, the mass ratio of the different carbon sources is not particularly limited, and any ratio may be used.
In the invention, the first water-soluble copper source is preferably a water-soluble salt, and the water-soluble copper salt preferably comprises one or more of copper chloride, copper acetate, copper nitrate and copper sulfate; when the first water-soluble copper source is a mixture, the mass ratio of different first water-soluble copper sources is not particularly limited, and any ratio can be adopted in the invention.
In the invention, the particle size of the submicron silicon is preferably 100-1000 nm, more preferably 300-800 nm, and most preferably 400-600 nm; the submicron silicon is preferably one or more of commercial silicon, photovoltaic silicon and waste silicon; the shape of the submicron silicon preferably includes a granular shape, a flake shape or a needle shape; the scrap silicon is preferably sourced from the photovoltaic industry; when the submicron silicon is a mixture of commercially available silicon and waste silicon, the mass ratio of the commercially available silicon to the waste silicon is not particularly limited in the present invention, and may be any ratio.
In the present invention, the mass ratio of the carbon source, the submicron silicon and the first water-soluble copper source is preferably 10: (1-20): (1-5), more preferably 10: (2-15): (2-4), most preferably 10: (5-10): (2-3).
The mixing mode is not particularly limited, and the raw materials can be uniformly mixed, specifically, ultrasonic mixing is adopted. In the invention, the concentration of the carbon source in the hydrothermal reaction solution obtained by mixing is preferably 0.1-5 mol/L, more preferably 0.3-3 mol/L, and most preferably 0.5-2 mol/L.
In the invention, the temperature of the hydrothermal reaction is preferably 170-300 ℃, more preferably 190-250 ℃, and most preferably 220-230 ℃; the time for heating the temperature from room temperature to the hydrothermal reaction temperature is preferably 1-6 h, and more preferably 2-4 h; starting timing when the temperature is increased to the temperature of the hydrothermal reaction, wherein the heat preservation time of the hydrothermal reaction is preferably 2-24 h, more preferably 5-20 h, and most preferably 10-15 h; the hydrothermal reaction is preferably carried out under stirring conditions, and the stirring speed is not particularly limited in the present invention, and the hydrothermal reaction can be smoothly carried out.
The invention preferably carries out post-treatment on a product system after the hydrothermal reaction; the post-treatment preferably comprises solid-liquid separation, and the obtained solid product is washed with water, dried and then annealed. The solid-liquid separation method of the present invention is not particularly limited, and those skilled in the art can use a solid-liquid separation method. In the present invention, the washing with water is not particularly limited, and the unreacted carbon source and the first water-soluble copper source may be removed. In the invention, the drying temperature is preferably 50-90 ℃, and more preferably 60-80 ℃; the drying time is preferably 5-48 h, and more preferably 12-36 h. In the invention, the annealing temperature is preferably 600-1100 ℃, and more preferably 700-1000 ℃; the time of the annealing treatment is preferably 0.5 to 2 hours, and more preferably 1 to 1.5 hours.
In the invention, in the hydrothermal reaction process, a carbon source is subjected to polymerization reaction and coated on the surface of the submicron silicon; meanwhile, the carbon simple substance with reducibility generated after annealing treatment can reduce copper metal ions to form copper metal nano particles which are uniformly dispersed in the carbon layer to form carbon-coated silicon particles, so that the controllable synthesis of the carbon-coated silicon particles is realized.
After the silicon-on-carbon particles are obtained, the silicon-on-carbon particles, a second water-soluble copper source, a surfactant, a polyhydroxy compound and water are mixed and subjected to in-situ winding growth to obtain the copper nanowire wound silicon-carbon composite material.
In the present invention, the polyol preferably comprises one or more of cellulose, sugar, alcohol and starch; the sugar preferably comprises one or more of glucose, sucrose and fructose; the alcohol preferably comprises glycerol and/or ethylene glycol; when the polyol is a mixture of polyols, the mass ratio of the different polyols in the present invention is not particularly limited, and may be any ratio.
In the invention, the surfactant is preferably organic amine, and the organic amine preferably comprises one or more of hexadecylamine, octadecylamine and oleylamine; when the surfactant is a mixture of organic amines, the mass ratio of different organic amines is not particularly limited, and any ratio can be adopted.
In the present invention, the mass ratio of the silicon-on-carbon particles, the second water-soluble copper source, the surfactant, and the polyol is preferably 1: (2-10): (45-100): (25-80), more preferably 1: (3-8): (50-80): (30-60), and most preferably 1: (4-6): (55-70): (40-55).
The mixing method of the invention is not particularly limited, and the raw materials can be uniformly mixed. In the invention, the concentration of the silicon-in-carbon particles in the winding fluid obtained by mixing is preferably 0.5-5 g/L, more preferably 1-4 g/L, and most preferably 2-3 g/L.
In the invention, the temperature of the in-situ winding growth is preferably 80-150 ℃, more preferably 90-130 ℃, and most preferably 100-120 ℃; the time for raising the temperature from room temperature to the temperature for in-situ winding growth is preferably 0.5-2 h, and more preferably 1-1.5 h; starting timing when the temperature is increased to the temperature of the in-situ winding growth, wherein the heat preservation time of the in-situ winding growth is preferably 2-24 h, more preferably 5-20 h, and most preferably 10-15 h; the in-situ winding growth is preferably carried out under the stirring condition, the stirring speed is not specially limited, and the in-situ winding growth can be ensured to be carried out smoothly; in the in-situ winding growth process, the polyhydroxy compound reduces copper ions to form a copper simple substance, and in the process, the surfactant limits the growth direction of copper crystals, so that copper nanowires are formed and wound on the surfaces of the silicon-in-carbon particles.
After the in-situ winding growth, the method preferably further comprises the step of carrying out post-treatment on a product system after the in-situ winding growth, wherein the post-treatment preferably comprises solid-liquid separation, and the obtained solid product is washed and dried to obtain the copper nanowire wound silicon-carbon composite material. The solid-liquid separation method of the present invention is not particularly limited, and those skilled in the art can use a solid-liquid separation method. The water washing is not particularly limited in the present invention, and the unreacted second water-soluble copper source, the surfactant and the polyhydroxy compound may be removed. In the invention, the drying temperature is preferably 30-70 ℃, and more preferably 40-55 ℃; the drying time is preferably 5-48 h, and more preferably 12-36 h.
The invention also provides an application of the copper nanowire-wound silicon-carbon composite material in the technical scheme or the copper nanowire-wound silicon-carbon composite material prepared by the preparation method of any one of claims 7 to 9 in a lithium ion battery. In the invention, the copper nanowire wound silicon-carbon composite material is preferably used as a negative electrode material of a lithium ion battery.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
Mixing 5g of glucose, 3g of photovoltaic industrial waste silicon with the particle size of 500nm, 0.5g of anhydrous copper acetate and 50mL of water, carrying out hydrothermal reaction for 6h under the conditions of stirring and 190 ℃, carrying out solid-liquid separation, washing the obtained solid product with water, drying for 12h under the condition of 85 +/-5 ℃, and then carrying out annealing treatment for 1.5h under the condition of 800 +/-5 ℃ to obtain carbon-coated silicon particles; wherein the temperature is increased from room temperature to 190 ℃ for 10 min;
mixing 0.05g of carbon-coated silicon particles, 1.2g of hexadecylamine, 0.3g of copper chloride dihydrate, 0.8g of glucose and 55mL of water, and carrying out in-situ winding growth for 16h under the conditions of stirring and 95 ℃, wherein the time for heating the temperature from room temperature to 95 ℃ is 30 min; then carrying out solid-liquid separation, washing the obtained solid product with water, and drying for 24h at the temperature of 60 +/-5 ℃ to obtain the copper nanowire wound silicon-carbon composite material; the grain diameter of the copper nanowire wound silicon-carbon composite material is 1.2 mu m; the thickness of the carbon layer is 250 nm; the copper nano-particles are uniformly dispersed in the carbon layer and the particle size is 30 nm; the diameter of the copper nanowire is 30nm, and the length of the copper nanowire is 50 μm.
Example 2
Mixing 10g of cellulose, 6g of photovoltaic industrial waste silicon with the particle size of 450nm, 0.3g of copper chloride and 50mL of water, carrying out hydrothermal reaction for 6h under the conditions of stirring and 250 ℃, carrying out solid-liquid separation, washing the obtained solid product with water, drying for 24h under the condition of 70 +/-5 ℃, and then carrying out annealing treatment for 1h under the condition of 1000 +/-5 ℃ to obtain carbon-coated silicon particles; wherein the temperature is increased from room temperature to 250 ℃ for 10 min;
mixing 1g of carbon-coated silicon particles, 4g of octadecylamine, 2g of copper nitrate hexahydrate, 2g of starch and 50mL of water, and carrying out in-situ winding growth for 8h under the conditions of stirring and 120 ℃, wherein the time for heating the temperature from room temperature to 120 ℃ is 1 h; then carrying out solid-liquid separation, washing the obtained solid product with water, and drying for 2h at the temperature of 55 +/-5 ℃ to obtain the copper nanowire wound silicon-carbon composite material; the grain diameter of the copper nanowire wound silicon-carbon composite material is 1.7 mu m; the thickness of the carbon layer is 500 nm; the copper nano-particles are uniformly dispersed in the carbon layer and the particle size is 15 nm; the diameter of the copper nanowire is 80nm, and the length of the copper nanowire is 45 μm.
Example 3
Mixing 10g of cyclodextrin, 5g of photovoltaic industrial waste silicon with the particle size of 700nm, 0.5g of copper sulfate pentahydrate and 50mL of water, carrying out hydrothermal reaction for 20h under the conditions of stirring and 180 ℃, carrying out solid-liquid separation, washing the obtained solid product with water, drying for 36h under the condition of 60 +/-5 ℃, and then carrying out annealing treatment for 2h under the condition of 700 +/-5 ℃ to obtain carbon-coated silicon particles; wherein the temperature is increased from room temperature to 180 ℃ for 30 min;
mixing 0.04g of carbon-coated silicon particles, 1g of oleylamine, 0.5g of copper sulfate pentahydrate, 1g of glycerol and 100mL of water, and carrying out in-situ winding growth for 18h under the conditions of stirring and 80 ℃, wherein the temperature is increased from room temperature to 80 ℃ for 20 min; then carrying out solid-liquid separation, washing the obtained solid product with water, and drying for 48h at the temperature of 40 +/-5 ℃ to obtain the copper nanowire wound silicon-carbon composite material; the grain diameter of the copper nanowire wound silicon-carbon composite material is 1.9 mu m; the thickness of the carbon layer is 600 nm; the copper nano-particles are uniformly dispersed in the carbon layer and the particle size is 30 nm; the diameter of the copper nanowire is 25nm, the length of the copper nanowire is 15 mu m, and the copper nanowire is in a branch shape.
Example 4
Mixing 5g of fructose, 3g of photovoltaic industrial waste silicon with the particle size of 550nm, 0.5g of copper nitrate and 50mL of water, carrying out hydrothermal reaction for 8h under the conditions of stirring and 200 ℃, carrying out solid-liquid separation, washing the obtained solid product with water, drying for 24h under the conditions of 75 +/-5 ℃, and then carrying out annealing treatment for 2h under the conditions of 800 +/-5 ℃ to obtain carbon-coated silicon particles; wherein the temperature is increased from room temperature to 200 ℃ for 10 min;
mixing 0.05g of carbon-coated silicon particles, 1.2g of hexadecylamine, 0.3g of copper chloride dihydrate, 0.8g of cane sugar and 55mL of water, and carrying out in-situ winding growth for 16h under the conditions of stirring and 95 ℃, wherein the time for heating the temperature from room temperature to 95 ℃ is 30 min; then carrying out solid-liquid separation, washing the obtained solid product with water, and drying for 5 hours at the temperature of 60 +/-5 ℃ to obtain the copper nanowire wound silicon-carbon composite material; the grain diameter of the copper nanowire wound silicon-carbon composite material is 1.3 mu m; the thickness of the carbon layer is 300 nm; the copper nano-particles are uniformly dispersed in the carbon layer and the particle size is 30 nm; the diameter of the copper nanowire is 30nm, the length of the copper nanowire is 50 mu m, and the copper nanowire is in a spider web shape.
FIG. 1 is an SEM image of a copper nanowire-wrapped silicon-carbon composite material prepared in examples 1-4, wherein (a) is example 1 and (b) is example 2; (c) example 3 was used, and (d) was example 4. As can be seen from FIG. 1, the carbon source wraps the silicon and forms spherical carbon-coated silicon particles; the copper nano-wires realize the winding of the spherical carbon-coated silicon particles.
Example 5
Mixing the copper nanowire wound silicon-carbon composite material prepared in the example 1, conductive carbon black and sodium alginate in a mass ratio of 8:1:1, adding 50mL of water, stirring for 8 hours to obtain mixed slurry, coating the mixed slurry on a copper foil to obtain a coating with the thickness of 100 micrometers, and performing vacuum drying at 100 ℃ for 6 hours to obtain a negative electrode of a lithium ion battery;
installing a button-type half cell with the specification of CR 2032 in a glove box filled with argon (electrolyte: 2.0 wt% of vinylene carbonate is added into a mixed solution of ethylene carbonate, dimethyl carbonate and diethyl carbonate with the volume ratio of 1:1: 1; counter electrode: a metal lithium sheet; diaphragm: Celgard 2500), and standing for 24 hours to obtain the button-type half cell with the specification of CR 2032;
comparative example 1
The silicon powder (the particle size is 500-1000 nm) is replaced by the copper nanowire wound silicon-carbon composite material in the embodiment 5, and other preparation conditions of the button-type half battery with the specification of CR 2032 are the same as those in the embodiment 5.
Test example 1
Constant current charge and discharge test
Electrochemical tests were carried out on the CR 2032-sized button-type half-cells prepared in example 5 and comparative example 1 at a test voltage ranging from 0.01V to 1.2V and a current density of 4200mA g-1Under the conditions (1) to perform constant current charge and discharge test. As shown in FIG. 2, it can be seen from FIG. 2 that the first-cycle capacity of the battery prepared in comparative example 1 using pure silicon as the negative electrode material is 3342.2mAh g-1The coulombic efficiency is 78 percent, and the residual capacity is 775.3mA after 100 circles of circulationh·g-1(ii) a The first-turn capacity of the battery prepared in example 5 and using the copper nanowire-wound silicon-carbon composite material as the negative electrode material was 4144.3mAh g-1The coulombic efficiency is 80.8 percent, and the residual capacity is 2059.7mAh g after 100 circles of circulation-1The copper nano winding silicon-carbon composite material prepared by the invention has excellent constant current charge and discharge performance.
Test example 2
Test of charge and discharge multiplying power
Electrochemical tests were carried out on the CR 2032-sized button-type half-cells prepared in example 5 and comparative example 1 at a test voltage ranging from 0.01V to 1.2V and at current densities of 420mA · g, respectively-1, 840mA·g-1,1680mA·g-1,2520mA·g-1,3360mA·g-1,4200mA·g-1The constant current charge and discharge rate test was performed under the conditions of (1), the result of the 10-cycle charge and discharge rate test for each current density test is shown in fig. 3, and it can be seen from fig. 3 that the residual capacity of the battery prepared in comparative example 1 was 1869.2mA · g, respectively, for each current density-1、1356.6mA·g-1、1217mA·g-1、997.4mA·g-1833.1mAh/g and 664.4mAh/g, return to 420mA g-1The post capacity can still be maintained at about 1873.9mAh g-1The remaining capacity of the battery prepared in example 5 was 2329mA · g, respectively, at each current density-1、1821 mA·g-1、1533.3mA·g-1、1448.9mA·g-11375mAh/g and 1412.2mAh/g, recovered to 420mA g-1The post capacity can still be maintained at about 2795.9mAh g-1It is demonstrated that the copper nano-winding silicon-carbon composite material prepared by the invention has excellent rate performance.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.