CN114023924B - Preparation method of silicon-based negative electrode without current collector and fiber lithium ion battery - Google Patents

Preparation method of silicon-based negative electrode without current collector and fiber lithium ion battery Download PDF

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CN114023924B
CN114023924B CN202111284288.6A CN202111284288A CN114023924B CN 114023924 B CN114023924 B CN 114023924B CN 202111284288 A CN202111284288 A CN 202111284288A CN 114023924 B CN114023924 B CN 114023924B
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current collector
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CN114023924A (en
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帅波
徐雄文
王志斌
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Hunan Lifang New Energy Science and Technology Co Ltd
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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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Abstract

The invention provides a preparation method of a silicon-based negative electrode without a current collector and a fiber lithium ion battery, wherein the method comprises the following steps: and sequentially immersing the spinnable carbon nanotubes arranged in an array into an acid solution and a silicon-based nano material dispersion liquid while adopting array film drawing, spraying a polymer dispersion liquid, twisting, and collecting to obtain the silicon-based negative electrode without a current collector. The active silicon-based nano material is uniformly loaded among pores formed by overlapping the carbon nano tubes by taking the array carbon nano tube film as a substrate through an interface self-assembly method, so that the gram capacity of the negative electrode is improved. The twisted carbon nano tube three-dimensional network structure can effectively relieve the expansion of silicon, and avoids the use of a current collector, thereby obviously improving the energy density and the cycle performance of the lithium ion battery, and the gram capacity of the silicon-based negative electrode without the current collector is 987-2753 mAh/g; the energy density of the battery is 380-420 Wh/Kg, and the capacity retention rate is 73-93% after the battery circulates for 200 times.

Description

Preparation method of silicon-based negative electrode without current collector and fiber lithium ion battery
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of a silicon-based negative electrode without a current collector and a fiber lithium ion battery.
Background
With the development of social economy, textile batteries are widely used in portable and wearable electronic products, and the current main direction is to manufacture fiber lithium ion batteries with diameters of tens to hundreds of micrometers, so that the fiber lithium ion batteries can be easily woven into wearable and breathable textiles, thereby meeting the power requirements of various wearable electronic products.
The current collector of the cathode is a copper wire, and the loaded active substances are usually graphite, hard carbon, silicon-based materials and the like. When graphite (gram capacity 370 mAh/g) is used as the active material, the energy density of the battery is low due to the lower gram capacity of graphite and the current collector occupying a part of the volume and mass; when silicon (gram capacity 3600 mAh/g) and a silicon-based material are used as active substances, the cycle performance of the battery is poor due to the fact that the volume expansion of the silicon material is too large in the charging and discharging processes.
Disclosure of Invention
In view of the above, the present invention aims to provide a method for preparing a silicon-based negative electrode without a current collector and a fiber lithium ion battery, wherein the silicon-based negative electrode can effectively improve the energy density of the lithium ion battery without using a current collector.
The invention provides a preparation method of a silicon-based negative electrode without a current collector, which comprises the following steps:
sequentially immersing spinnable carbon nanotubes arranged in an array in an acid solution and a silicon-based nano material dispersion liquid while adopting array film drawing, spraying a polymer dispersion liquid, twisting, and collecting to obtain a silicon-based negative electrode without a current collector;
the acid solution is a mixed solution of concentrated sulfuric acid and concentrated nitric acid with the volume ratio of 2.5-3.2:1;
the silicon nanomaterial in the silicon-based nanomaterial dispersion is selected from one or more of silicon, silicon oxide, silicon alloy and silicon-based materials;
the polymer in the polymer dispersion liquid is one or more of polyacrylic acid, polyvinylidene fluoride, polyvinyl alcohol, polyethylene glycol, styrene-butadiene rubber, polyethylene and polypropylene.
In the invention, the acid solution is a mixed solution of concentrated sulfuric acid and concentrated nitric acid in a volume ratio of 3:1.
In the present invention, the concentration of the silicon-based nanomaterial dispersion is 0.01 to 5wt%.
In the present invention, the concentration of the polymer dispersion is 0.01 to 6wt%.
In the invention, the diameter of the silicon-based nano material is 5-50 nm. In a specific embodiment, the silicon-based nanomaterial dispersion is selected from a nano silicon oxide dispersion with a particle size of 10nm and a concentration of 2 wt%; or nano silicon dispersion liquid with the particle size of 15nm and the concentration of 0.8 weight percent; or nano ferrosilicon alloy dispersion liquid with the particle size of 20nm and the concentration of 1.0 weight percent; or nano silicon dispersion liquid with the particle size of 5nm and the concentration of 4 wt%; or nano silicon dispersion liquid with the particle size of 5nm and the concentration of 2 weight percent.
In the invention, the array width of the spinnable carbon nanotubes arranged in an array is 5-300 mm. In particular embodiments, the width is 50mm, 40mm, 100mm or 70mm.
In the present invention, the dispersant in the silicon nanomaterial dispersion is selected from cationic surfactants;
the cationic surfactant is selected from one or more of amine salts, heterocyclic compounds and benzoates;
the solvent in the silicon-based nanomaterial dispersion is selected from ethanol.
In the present invention, the solvent in the polymer dispersion is selected from water or a volatile organic solvent.
In the present invention, the rotational speed of the twisting motor is 50 to 200rpm. In specific embodiments, the twisting motor speed is 50rpm, 80rpm, 60rpm or 100rpm.
In the invention, the diameter of the silicon-based negative electrode without the current collector is 50-300 mu m. In specific embodiments, the diameter of the current collector-free silicon-based negative electrode is 150 μm, 50 μm, 95 μm, 55 μm, or 80 μm.
FIG. 1 is a schematic flow chart of the preparation of a silicon-based negative electrode without a current collector according to the present invention; as can be seen from fig. 1, a spinnable carbon nanotube array is fixed on a sample stage 1, a carbon nanotube film 2 is pulled out from the sample stage to a twisting device 6, the width of a film layer is 10-100 μm, and the spinnable carbon nanotube film sequentially passes through a soaking device 3, a soaking device 4 and a spraying device 5 in the film pulling process; the twisting device 6 is a device for winding raw material wires into wires, and the carbon nanotube film is twisted by the twisting device 6 to obtain a collector-free cathode 7, and is collected into a roll by a collecting roller 8.
In the invention, the silicon-based negative electrode without the current collector can be continuously twisted to obtain rope-shaped fibers, and the liquid can be woven into composite fibers with a net-shaped structure, so that the application of the composite fibers in the fields of lithium ion batteries and the like is expanded.
The invention provides a fiber lithium ion battery, which comprises a silicon-based negative electrode without a current collector, wherein the silicon-based negative electrode is prepared by the preparation method.
A fiber lithium ion battery comprises a positive electrode, a diaphragm, electrolyte, a packaging body and the negative electrode, wherein the diaphragm is used for separating the positive electrode from the negative electrode, and the packaging body is used for mounting the positive electrode, the negative electrode, the diaphragm and the electrolyte.
The invention provides a preparation method of a silicon-based negative electrode without a current collector, which comprises the following steps: and sequentially immersing the spinnable carbon nanotubes arranged in an array into an acid solution and a silicon-based nano material dispersion liquid while adopting array film drawing, spraying a polymer dispersion liquid, twisting, and collecting to obtain the silicon-based negative electrode without a current collector. According to the invention, the array carbon nanotube film is used as a substrate, and the active silicon nano material is uniformly loaded among pores formed by overlapping the carbon nanotubes by an interface self-assembly method, so that the gram capacity of a negative electrode is improved, and the twisted carbon nanotube three-dimensional net structure can effectively relieve the expansion of silicon, so that the energy density and the cycle performance of the lithium ion battery are obviously improved; the twisted and orderly crosslinked carbon nanotubes can form a high-conductivity heat-conduction network, have higher modulus and toughness, and are favorable for forming good interface contact with the active silicon-based nano material, and are not easy to fall off, so that the rate capability of the lithium ion battery is improved. The experimental results show that: the gram capacity of the silicon-based negative electrode without the current collector is 987-2753 mAh/g; the energy density of the lithium ion battery is 380-420 Wh/Kg, and the capacity retention rate is 73-93% after the battery circulates for 200 times.
Drawings
FIG. 1 is a schematic flow chart of a preparation method of a silicon-based negative electrode without a current collector, wherein 1 is a sample stage, 2 is a carbon nanotube film, 3 is an acid solution soaking device, 4 is a silicon nanomaterial dispersion soaking device, 5 is a spraying device, 6 is a twisting device, 7 is a silicon-based negative electrode without a current collector, and 8 is a collecting roller;
fig. 2 is a graph showing the cycle performance test of the lithium ion battery prepared in example 1 of the present invention.
Detailed Description
In order to further illustrate the present invention, the following examples are provided to describe in detail a method for preparing a silicon-based negative electrode without a current collector and a fiber lithium ion battery, but they should not be construed as limiting the scope of the present invention.
Preparation examples
The spinnable carbon nano tube array is prepared by the following steps:
introducing mixed gas (Ar+ 6%H) into a quartz tube furnace 2 ) And pure ethylene, both of which have a flow rate of 100sccm, wherein the mixed gas is a carrier gas, the pure ethylene is a carbon source, and Al is used as a carbon source 2 O 3 The (10 nm)/Fe (1.0 nm) film is used as a catalyst, the temperature is kept at 750 ℃, and the reaction is carried out for 15min, so as to obtain the spinnable carbon nanotube array.
Example 1
A spinnable carbon nano tube array with the array width of 50mm is adopted, a carbon nano tube film is obtained through array film drawing, the film is immersed into concentrated sulfuric acid/concentrated nitric acid solution with the proportion of 3:1 while the film is drawn, then the film is immersed into nano silicon oxide dispersion liquid with the particle size of 10nm and the concentration of 2wt%, finally polyacrylic acid dispersion liquid with the particle size of 0.1wt% is sprayed, and twisting is carried out at the rotating speed of a rotating motor of 50rpm, so that the anode without current collector with the diameter of 80 mu m can be obtained.
And (3) drying the obtained cathode without the current collector, and assembling the cathode with a metal lithium wire to form the fiber lithium ion half battery, wherein the gram capacity of the fiber lithium ion half battery is 987mAh/g.
92.5wt% of lithium cobaltate, 2.5wt% of Super-P,5wt% of polyvinylidene fluoride and N-methylpyrrolidone were mixed to form a slurry, aluminum wires having a diameter of 60 μm were immersed in the slurry, and were uniformly pulled out, and were dried in an air atmosphere at 120℃and vacuum at 80℃for 24 hours in order to be used as a positive electrode.
Preparation of electrolyte: 1.1mol/L lithium hexafluorophosphate (LiPF) 6 ) Dissolved in dimethyl carbonate (DMC), ethylene carbonate (EC) And (3) methyl ethyl carbonate (EMC) and diethyl carbonate (DEC) in a mixed solvent (the mass ratio of DMC to EC to EMC to DEC is 3:5:1:2) to obtain the electrolyte.
After ensuring the capacity allowance of the negative electrode to be 15%, the positive electrode and the negative electrode are subjected to coating (Celgard 2325) diaphragm, twisting, electrolyte injection and packaging to obtain the fiber lithium ion battery. The energy density was 380Wh/kg. After 200 cycles of the battery, the capacity retention rate was 93%.
Example 2
A spinnable carbon nano tube array with the array width of 40mm is adopted, a carbon nano tube film is obtained through array film drawing, the film is immersed into concentrated sulfuric acid/concentrated nitric acid solution with the proportion of 3:1 while the film is drawn, then the film is immersed into nano silicon dispersion liquid with the particle size of 15nm and the concentration of 0.8wt%, finally polyacrylic acid dispersion liquid with the particle size of 0.2wt% is sprayed, and twisting is carried out at the rotating speed of a rotating motor of 80rpm, so that the cathode without a current collector with the diameter of 55 mu m can be obtained.
And (3) drying the obtained cathode without the current collector, and assembling the cathode with a metal lithium wire to form the fiber lithium ion half battery, wherein the gram capacity of the fiber lithium ion half battery is 2125mAh/g.
The preparation process of the positive electrode and the electrolyte is the same as that of the example 1 (the loading amount of the positive electrode active material is 85% of the capacity of the negative electrode), and the fiber lithium ion battery obtained by twisting, liquid injection and encapsulation has the energy density of 405Wh/kg. After 200 cycles of the battery, the capacity retention rate was 77%.
Example 3
A spinnable carbon nano tube array with the array width of 100mm is adopted, a carbon nano tube film is obtained through array film drawing, the film is immersed into concentrated sulfuric acid/concentrated nitric acid solution with the proportion of 3:1 while the film is drawn, then the film is immersed into nano ferrosilicon alloy dispersion liquid with the particle size of 20nm and the concentration of 1.0wt%, finally polyacrylic acid dispersion liquid with the particle size of 1.0wt% is sprayed, and twisting is carried out at the rotating speed of a rotating motor of 60rpm, so that the non-current collector anode with the diameter of 95 mu m can be obtained.
And (3) drying the obtained cathode without the current collector, and assembling the cathode with a metal lithium wire to form the fiber lithium ion half battery, wherein the gram capacity of the fiber lithium ion half battery is 1535mAh/g.
The preparation process of the positive electrode and the electrolyte is the same as that of the example 1 (the loading amount of the positive electrode active material is 85% of the capacity of the negative electrode), and the fiber lithium ion battery obtained by twisting, liquid injection and encapsulation has the energy density of 390Wh/kg. After 200 cycles of the battery, the capacity retention was 76%.
Example 4
A spinnable carbon nano tube array with the array width of 70mm is adopted, a carbon nano tube film is obtained through array film drawing, the film is immersed into concentrated sulfuric acid/concentrated nitric acid solution with the proportion of 3:1 while the film is drawn, then the film is immersed into nano silicon dispersion liquid with the particle size of 5nm and the concentration of 4wt%, finally polyacrylic acid dispersion liquid with the particle size of 1.5wt% is sprayed, and twisting is carried out at the rotating speed of a rotating motor of 50rpm, so that the cathode without current collector with the diameter of 150 mu m can be obtained.
The obtained cathode without current collector is assembled with a metal lithium wire to form a fiber lithium ion battery, the gram capacity of the fiber lithium ion battery is 2753mAh/g,
the procedure of example 1 (the loading of the positive electrode active material was 85% of the negative electrode capacity) was followed to prepare a fibrous lithium ion battery having an energy density of 420Wh/kg. After 200 cycles of the battery, the capacity retention rate was 73%.
Example 5
A spinnable carbon nano tube array with the array width of 70mm is adopted, a carbon nano tube film is obtained through array film drawing, the film is immersed into concentrated sulfuric acid/concentrated nitric acid solution with the proportion of 3:1 while the film is drawn, then the film is immersed into nano silicon dispersion liquid with the particle size of 5nm and the concentration of 2wt%, finally polyacrylic acid dispersion liquid with the particle size of 1.0wt% is sprayed, and twisting is carried out at the rotating speed of a rotating motor of 100rpm, so that the cathode without current collector with the diameter of 50 mu m can be obtained.
And (3) drying the obtained cathode without the current collector, and assembling the cathode with a metal lithium wire to form the fiber lithium ion half battery, wherein the gram capacity of the fiber lithium ion half battery is 1618mAh/g.
The preparation process of the positive electrode and the electrolyte is the same as that of the example 1 (the loading amount of the positive electrode active material is 85% of the capacity of the negative electrode), and the fiber lithium ion battery obtained by twisting, liquid injection and encapsulation has the energy density of 400Wh/kg. After 200 cycles of the battery, the capacity retention was 88%.
As can be seen from the above examples, the present invention provides a method for preparing a silicon-based negative electrode without a current collector, comprising the following steps: and sequentially immersing the spinnable carbon nanotubes arranged in an array into an acid solution and a silicon-based nano material dispersion liquid while adopting array film drawing, spraying a polymer dispersion liquid, twisting, and collecting to obtain the silicon-based negative electrode without a current collector. According to the invention, the array carbon nanotube film is used as a substrate, and the active silicon nano material is uniformly loaded among pores formed by overlapping the carbon nanotubes by an interface self-assembly method, so that the gram capacity of a negative electrode is improved, and the twisted carbon nanotube three-dimensional net structure can effectively relieve the expansion of silicon, so that the energy density and the cycle performance of the lithium ion battery are obviously improved; according to the preparation method, the twisted and orderly crosslinked carbon nanotubes can form a high-conductivity heat-conduction network, have higher modulus and toughness, and are favorable for forming good interface contact with the active silicon nanomaterial, so that the active silicon nanomaterial is not easy to fall off, and the rate capability of the lithium ion battery is improved. The experimental results show that: the gram capacity of the silicon negative electrode without the current collector is 987-2753 mAh/g; the energy density of the lithium ion battery is 380-420 Wh/Kg, and the capacity retention rate is 73-93% after the battery circulates for 200 times.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims (8)

1. The preparation method of the silicon-based negative electrode without the current collector comprises the following steps:
sequentially immersing spinnable carbon nanotubes arranged in an array in an acid solution and a silicon-based nano material dispersion liquid while adopting array film drawing, spraying a polymer dispersion liquid, twisting, and collecting to obtain a silicon-based negative electrode without a current collector;
the volume ratio of the acid solution is 2.5-3.2: 1, a mixed solution of concentrated sulfuric acid and concentrated nitric acid;
the silicon-based nanomaterial in the silicon-based nanomaterial dispersion is selected from one or more of silicon, silicon oxide, silicon alloy and silicon-based materials; the concentration of the silicon-based nano material dispersion liquid is 0.01-5wt%;
the polymer in the polymer dispersion liquid is one or more of polyacrylic acid, polyvinylidene fluoride, polyvinyl alcohol, polyethylene glycol, styrene-butadiene rubber, polyethylene and polypropylene; the concentration of the polymer dispersion liquid is 0.01-6wt%.
2. The method of claim 1, wherein the silicon-based nanomaterial has a diameter of 5-50 nm.
3. The method of claim 1, wherein the array width of the spinnable carbon nanotubes in the array arrangement is 5-300 mm.
4. The method of claim 1, wherein the dispersant in the dispersion of silicon-based nanomaterial is selected from cationic surfactants;
the cationic surfactant is selected from one or more of amine salts, heterocyclic compounds and benzoates;
the solvent in the silicon-based nanomaterial dispersion is selected from ethanol.
5. The method of claim 1, wherein the solvent in the polymer dispersion is selected from water and volatile organic solvents.
6. The method according to claim 1, wherein the rotational speed of the twisting motor is 50 to 200rpm.
7. The method according to claim 1, wherein the diameter of the silicon-based negative electrode without current collector is 50-300 μm.
8. A fibrous lithium ion battery comprising a collector-free silicon-based negative electrode made by the method of any one of claims 1-7.
CN202111284288.6A 2021-11-01 2021-11-01 Preparation method of silicon-based negative electrode without current collector and fiber lithium ion battery Active CN114023924B (en)

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