CN112420993A - Lithium battery SiOC @ nitrogen-doped carbon fiber composite negative electrode and preparation method thereof - Google Patents

Lithium battery SiOC @ nitrogen-doped carbon fiber composite negative electrode and preparation method thereof Download PDF

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CN112420993A
CN112420993A CN202011300011.3A CN202011300011A CN112420993A CN 112420993 A CN112420993 A CN 112420993A CN 202011300011 A CN202011300011 A CN 202011300011A CN 112420993 A CN112420993 A CN 112420993A
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sioc
negative electrode
carbon fiber
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陈庆
廖健淞
司文彬
白涛
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Chengdu New Keli Chemical Science Co Ltd
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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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    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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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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Abstract

The invention relates to the technical field of lithium battery cathode materials, in particular to a SiOC @ nitrogen-doped carbon fiber composite cathode of a lithium battery and a preparation method thereof, wherein the SiOC @ nitrogen-doped carbon fiber composite cathode comprises the following steps: s1 preparation of Al2O3Polysiloxane composite particles; s2, preparing a spinning film; s3, preparing the nitrogen-doped carbon fiber/SiOC composite negative electrode material. The invention solves the problem of high process difficulty of the SiOC negative electrode material in the prior art. The SiOC @ nitrogen-doped carbon fiber composite negative electrode can be formed into a lithium battery negative electrode material in one step by loading polysiloxane on alumina, spinning with polyacrylonitrile and then sintering, and compared with the SiOC @ nitrogen-doped carbon fiber composite negative electrode materialThe traditional production process and the sintering process are greatly simplified. Meanwhile, in the negative electrode material prepared by the spinning process, more SiOC is embedded in the carbon fiber, so that the conductivity and the cycle performance of the SiOC can be effectively improved.

Description

Lithium battery SiOC @ nitrogen-doped carbon fiber composite negative electrode and preparation method thereof
Technical Field
The invention relates to the technical field of lithium battery cathode materials, in particular to a SiOC @ nitrogen-doped carbon fiber composite cathode of a lithium battery and a preparation method thereof.
Background
As a new type of high-energy battery, lithium ion batteries have been widely used in people's daily life. The negative electrode material is used as a main component of the lithium battery, and the performance of the negative electrode material directly influences the performance of the lithium battery. The negative electrode refers to the end of the power supply with the lower potential. In galvanic cells, which refer to the electrode that functions as the oxidizing electrode, the cell reaction is written to the left. From a physical point of view, it is the one pole of the electron flow in the circuit. The cathode material refers to a raw material for forming a cathode in a battery, and currently common cathode materials include a carbon cathode material, a tin-based cathode material, a lithium-containing transition metal nitride cathode material, an alloy cathode material and a nano-scale cathode material.
At present, the commercial lithium ion battery mainly adopts graphite carbon materials as negative electrode materials. However, with the rapid development and application of lithium ion batteries as power batteries in hybrid electric vehicles and portable electronic devices, the disadvantage of lower theoretical specific capacity of graphite-based negative electrode materials is increasingly prominent.
The silicon-based negative electrode material has high theoretical capacity (4200 mAh-1) And a more suitable de-intercalation potential (<0.5V) is the most promising high capacity anode material. However, the silicon material has large volume expansion (volume expansion 100% -300%) during lithium extraction/insertion. The structural expansion and contraction change destroys the stability of the electrode structure, leads to the breakage and pulverization of silicon particles, causes the collapse and the peeling of the electrode material structure, leads the electrode material to lose electric contact, finally leads to the rapid attenuation of the specific capacity of the negative electrode, and leads to the deterioration of the cycle performance of the lithium battery.
SiOC is a porous framework structure that also contains free carbon dispersed in the framework. SiOC is a porous skeleton structure composed of C-Si-O bonds and C-C bonds, and contains free carbon dispersed in the skeleton. SiOC has high electrical conductivity and thermal stability in addition to high tap density. The polymer derived SiOC ceramic has obvious advantages as a negative electrode material, such as high reversible specific capacity, high charging rate, simple synthesis, low cost, designable physical and chemical properties and the like. Although the reversible specific capacity of the SiOC negative electrode material is obviously higher than that of graphite, the irreversible capacity generated by the first charge and discharge of the material is higher, so that the first coulombic efficiency is lower; in subsequent cycles, the material exhibits a voltage hysteresis, i.e. higher voltages are required for delithiation than for intercalation, which limits the widespread use of SiOC anode materials.
The invention patent CN102637864A in China provides a preparation method of a lithium ion battery composite negative electrode material, which discloses that an intercalation type SiOC/graphene composite material is prepared by one step through an in-situ reduction method, the electrochemical performance of the SiOC negative electrode material can be effectively improved by doping graphene, but the method has high first irreversible capacity and cycle stability which needs to be improved, and the method uses a large amount of graphene, has high cost and is difficult to industrially popularize.
The patent CN107910554A provides an SiOC composite negative electrode material for a lithium ion battery and a preparation method thereof, porous SiOC ceramic powder is prepared by wood powder and solid polysiloxane, then the porous SiOC ceramic powder is compounded with graphene oxide, and a thermal reduction method is adopted to prepare the porous SiOC/graphene composite material. However, obtaining graphene oxide by thermal reduction in a gas phase is very difficult, which results in a very difficult process and difficult application to industrial production.
Patent CN104752691B proposes a silicon/carbon composite negative electrode material for lithium ion batteries and a preparation method thereof, the material is composed of a graphite skeleton material, an intermediate buffer layer SiOC material, carbon fibers and a surface carbon-coated silicon-containing material, and the surface carbon-coated silicon-containing material is combined with the graphite skeleton material through the buffer layer SiOC and the carbon fibers, however, the synthesis process is complex, repeated sintering is required, the bonding force between layers is relatively poor, and the problem of material disintegration caused by uneven expansion between layers is easy to occur.
Therefore, the performance optimization and the process improvement of the SiOC negative electrode material have very important practical significance.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide an SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery and a preparation method thereof, which are used for solving the problem of high process difficulty of an SiOC negative electrode material in the prior art; the SiOC @ nitrogen doped carbon fiber composite negative electrode is prepared by loading polysiloxane on alumina, spinning the obtained product with polyacrylonitrile and then sintering the obtained product, and can be formed into a lithium battery negative electrode material in one step. Meanwhile, in the negative electrode material prepared by the spinning process, more SiOC is embedded in the carbon fiber, so that the conductivity and the cycle performance of the SiOC can be effectively improved.
In order to attain the above and other related objects,
the invention provides a preparation method of a SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery, which comprises the following steps of:
s1 preparation of Al2O3Polysiloxane composite particles:
s11, adding aminosiloxane into an organic solvent, adding a dilute hydrochloric acid aqueous solution, and stirring for reaction to obtain sol;
s12, adjusting the pH value of the sol to 6.5-7.5, adding porous alumina microspheres to adsorb the sol, filtering, and carrying out heat treatment at 100-110 ℃ for 30-90 min to obtain Al2O3Polysiloxane composite particles;
s2, preparing a spinning film:
s21, adding polyacrylonitrile into the polar aprotic solvent to form a suspension, heating in a water bath, and stirring until the polyacrylonitrile is completely dissolved to obtain a spinning solution;
s22, adding Al into the spinning solution2O3The/polysiloxane composite particles are evenly mixed and then subjected to electrostatic spinning to obtain a spinning membrane;
s3, preparing a nitrogen-doped carbon fiber/SiOC composite negative electrode material: and (3) placing the spinning film in a vacuum furnace, preheating for 1-3 h at 400-600 ℃ in an ammonia atmosphere, heating to 800-1000 ℃, sintering for 6-8 h, and soaking the powder in dilute hydrochloric acid and purified water in sequence to obtain the nitrogen-doped carbon fiber/SiOC composite negative electrode material.
The preparation method is to prepare Al in advance2O3Polysiloxane composite particles, Al2O3During the preparation process of the/polysiloxane composite particles, dilute hydrochloric acid is adopted to catalyze siloxane to hydrolyze and perform polycondensation to form sol in advance, and then porous alumina microspheres are added, so that silicon hydroxyl generated by hydrolysis preferentially reacts with aluminum oxide to generate Si-O-Al which is attached to the interior and the surface of the porous alumina microspheres. After thatHeating polyacrylonitrile to form spinning solution, and adding Al into the spinning solution2O3Polysiloxane composite particles, Al2O3Coating the/polysiloxane composite particles in the spinning solution, and spinning to form a film to obtain Al2O3The/polysiloxane composite particles are more supported inside the tow. And finally carbonizing to prepare the nitrogen-doped carbon fiber/SiOC composite negative electrode material, introducing ammonia gas in the preheating process to ensure that polyacrylonitrile fibers are subjected to nitrogen doping in an ammonia gas environment, then sintering and carbonizing to ensure that polysiloxane is pyrolyzed and carbonized to form SiOC, washing out porous alumina microspheres after carbonization, and forming holes in the carbonized fibers to ensure that SiOC particles cannot deform and break due to volume expansion.
The SiOC @ nitrogen doped carbon fiber composite negative electrode is prepared by loading polysiloxane on alumina, spinning the obtained product with polyacrylonitrile and then sintering the obtained product, and can be formed into a lithium battery negative electrode material in one step. Meanwhile, in the negative electrode material prepared by the spinning process, more SiOC is embedded in the carbon fiber, so that the conductivity and the cycle performance of the SiOC can be effectively improved.
In an embodiment of the invention, the organic solvent is absolute ethyl alcohol, the molar concentration of hydrochloric acid in the dilute hydrochloric acid aqueous solution is 0.05-0.5 mol/L, and the aminosiloxane is a KH550 silane coupling agent; the size of the porous alumina microspheres is 1-20 mu m, and the pore diameter is 50-500 nm.
The organic solvent is absolute ethyl alcohol which has good solubility and can be mixed with dilute hydrochloric acid aqueous solution, so that the hydrolysis and polycondensation of siloxane are not influenced to form sol.
The size of the porous alumina microspheres is 1-20 mu m, the pore diameter is 50-500 nm, and the porous alumina microspheres are controlled at the micron level, so that the situation that the porosity of the SiOC @ nitrogen-doped carbon fiber composite anode material is too large due to the fact that holes in the carbon fibers are large after the porous alumina microspheres are washed away is avoided, and the conductivity and the cycle performance of the SiOC @ nitrogen-doped carbon fiber composite anode material are not improved. The pore diameter of the porous alumina microspheres is controlled at a nanometer level, and the porosity and the specific surface area of the porous alumina microspheres are high, so that the silicon hydroxyl generated by hydrolysis preferentially reacts with aluminum oxide to generate Si-O-Al which is attached to the inside and the surface of the porous alumina microspheres.
In an embodiment of the invention, the amino siloxane, the organic solvent, the dilute hydrochloric acid aqueous solution, and the porous alumina microspheres in the S1 are, in sequence, 100 to 150 parts, 50 to 200 parts, 10 to 30 parts, and 30 to 50 parts by weight.
Al2O3During the preparation process of the/polysiloxane composite particles, dilute hydrochloric acid is adopted to catalyze siloxane to hydrolyze and perform polycondensation to form sol in advance, and then porous alumina microspheres are added, so that silicon hydroxyl generated by hydrolysis preferentially reacts with aluminum oxide to generate Si-O-Al which is attached to the interior and the surface of the porous alumina microspheres.
In an embodiment of the invention, the amino siloxane, the organic solvent, the dilute hydrochloric acid aqueous solution, and the porous alumina microspheres in the S1 are, in sequence, 100 to 150 parts, 80 to 150 parts, 15 to 25 parts, and 35 to 50 parts by weight.
In an embodiment of the invention, the weight average molecular weight of the polyacrylonitrile is 10 to 30 ten thousand, the polar aprotic solvent is N, N-dimethylformamide, and the mass concentration of the polyacrylonitrile in the suspension is 5 to 20%.
Heating polyacrylonitrile to form spinning solution, and adding Al into the spinning solution2O3Polysiloxane composite particles, Al2O3Coating the/polysiloxane composite particles in the spinning solution, and spinning to form a film to obtain Al2O3The/polysiloxane composite particles are more supported inside the tow.
In an embodiment of the invention, the mass concentration of polyacrylonitrile in the suspension is 10-12%.
In an embodiment of the present invention, the spinning solution and Al2O3The weight ratio of the/polysiloxane composite particles is (90-98): (2-10).
In an embodiment of the present invention, the spinning solution and Al2O3The weight ratio of the/polysiloxane composite particles is (95-97): (3-5).
The water bath heating temperature in the S21 is 70-90 ℃;
the voltage of electrostatic spinning in the S22 is 15-20 kV;
the preheating temperature in the S3 is 550 ℃, and the preheating time is 1.5-2.5 h;
and in the S3, the sintering temperature is 900 ℃, and the sintering time is 6.5-7.5 h.
The purpose of preheating is to carry out nitrogen doping on polyacrylonitrile fibers in an ammonia environment. The purpose of sintering is to carbonize polyacrylonitrile and pyrolytically carbonize polysiloxanes to form SiOC.
In a second aspect of the invention, a SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery is provided.
In the negative electrode material prepared by the SiOC @ nitrogen-doped carbon fiber composite negative electrode through the spinning process, more SiOC is embedded in the carbon fiber, so that the conductivity and the cycle performance of the SiOC can be effectively improved.
As described above, the SiOC @ nitrogen-doped carbon fiber composite negative electrode for the lithium battery and the preparation method thereof have the following beneficial effects:
1. the preparation method is to prepare Al in advance2O3Polysiloxane composite particles, Al2O3During the preparation process of the/polysiloxane composite particles, dilute hydrochloric acid is adopted to catalyze siloxane to hydrolyze and perform polycondensation to form sol in advance, and then porous alumina microspheres are added, so that silicon hydroxyl generated by hydrolysis preferentially reacts with aluminum oxide to generate Si-O-Al which is attached to the interior and the surface of the porous alumina microspheres. Heating polyacrylonitrile to form spinning solution, and adding Al into the spinning solution2O3Polysiloxane composite particles, Al2O3Coating the/polysiloxane composite particles in the spinning solution, and spinning to form a film to obtain Al2O3The/polysiloxane composite particles are more supported inside the tow. And finally carbonizing to prepare the nitrogen-doped carbon fiber/SiOC composite negative electrode material, introducing ammonia gas in the preheating process to ensure that polyacrylonitrile fibers are subjected to nitrogen doping in an ammonia gas environment, then sintering and carbonizing to ensure that polysiloxane is pyrolyzed and carbonized to form SiOC, washing out porous alumina microspheres after carbonization, and forming holes in the carbonized fibers to ensure that SiOC particles cannot deform and break due to volume expansion.
2. The SiOC @ nitrogen doped carbon fiber composite negative electrode is prepared by loading polysiloxane on alumina, spinning the obtained product with polyacrylonitrile and then sintering the obtained product, and can be formed into a lithium battery negative electrode material in one step. Meanwhile, in the negative electrode material prepared by the spinning process, more SiOC is embedded in the carbon fiber, so that the conductivity and the cycle performance of the SiOC can be effectively improved.
Detailed Description
The present invention will be described in further detail with reference to specific embodiments, but it should not be construed that the scope of the present invention is limited to the following examples. Various substitutions and alterations can be made by those skilled in the art and by conventional means without departing from the spirit of the method of the invention described above.
Example 1
A preparation method of a SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery comprises the following steps:
s1 preparation of Al2O3Polysiloxane composite particles: the KH550 silane coupling agent, the absolute ethyl alcohol, the dilute hydrochloric acid aqueous solution and the porous alumina microspheres are 100 parts, 10 parts and 30 parts in sequence;
s11, adding the KH550 silane coupling agent into absolute ethyl alcohol, adding a dilute hydrochloric acid aqueous solution (the molar concentration of hydrochloric acid is 0.5 mol/L), and keeping mechanically stirring for reaction for 30min to obtain sol;
s12, adding ammonia water into the sol to adjust the pH of the sol to be neutral, adding porous alumina microspheres (the size is 1-20 mu m, and the pore diameter is 50-500 nm) to fully adsorb the sol, filtering, and carrying out heat treatment at 100 ℃ for 90min to obtain Al2O3Polysiloxane composite particles;
s2, preparing a spinning film: the weight ratio of the spinning solution to the Al2O 3/polysiloxane composite particles is 94: 6;
s21, adding polyacrylonitrile (with the weight-average molecular weight of 10-30 ten thousand) into N, N-dimethylformamide to form a suspension (the mass concentration of the polyacrylonitrile in the suspension is 6%), then heating in a water bath (at the temperature of 75 ℃) while keeping mechanical stirring until the polyacrylonitrile is completely dissolved, and thus obtaining a spinning solution;
s22, adding Al into the spinning solution2O3The/polysiloxane composite particles are uniformly mixed and then subjected to electrostatic spinning (the voltage is 15 kV), so that a spinning membrane is obtained;
s3, preparing a nitrogen-doped carbon fiber/SiOC composite negative electrode material: and (3) placing the spinning membrane in a vacuum furnace, preheating for 3h at 400 ℃ in an ammonia atmosphere, heating to 800 ℃ for sintering for 8h (in the sintering process, in an argon atmosphere), and soaking the sintered powder in dilute hydrochloric acid and purified water in sequence to obtain the nitrogen-doped carbon fiber/SiOC composite negative electrode material.
Example 2
A preparation method of a SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery comprises the following steps:
s1 preparation of Al2O3Polysiloxane composite particles: 150 parts, 200 parts, 30 parts and 50 parts of KH550 silane coupling agent, absolute ethyl alcohol, dilute hydrochloric acid aqueous solution and porous alumina microspheres in sequence;
s11, adding the KH550 silane coupling agent into absolute ethyl alcohol, adding a dilute hydrochloric acid aqueous solution (the molar concentration of hydrochloric acid is 0.1 mol/L), and keeping mechanically stirring for reaction for 30min to obtain sol;
s12, adding ammonia water into the sol to adjust the pH of the sol to be neutral, adding porous alumina microspheres (the size is 1-20 mu m, and the pore diameter is 50-500 nm) to fully adsorb the sol, filtering, and carrying out heat treatment at 110 ℃ for 30min to obtain Al2O3Polysiloxane composite particles;
s2, preparing a spinning film: the weight ratio of the spinning solution to the Al2O 3/polysiloxane composite particles is 98: 2;
s21, adding polyacrylonitrile (with the weight-average molecular weight of 10-30 ten thousand) into N, N-dimethylformamide to form a suspension (the mass concentration of the polyacrylonitrile in the suspension is 18%), then heating in a water bath (at the temperature of 90 ℃) while keeping mechanical stirring until the polyacrylonitrile is completely dissolved, and thus obtaining a spinning solution;
s22, adding Al into the spinning solution2O3The/polysiloxane composite particles are uniformly mixed and then subjected to electrostatic spinning (the voltage is 20 kV), so that a spinning membrane is obtained;
s3, preparing a nitrogen-doped carbon fiber/SiOC composite negative electrode material: and (3) placing the spinning membrane in a vacuum furnace, preheating for 1h at 600 ℃ in an ammonia atmosphere, heating to 1000 ℃ for sintering for 6h (in the sintering process, in an argon atmosphere), and soaking the sintered powder in dilute hydrochloric acid and purified water in sequence to obtain the nitrogen-doped carbon fiber/SiOC composite negative electrode material.
Example 3
A preparation method of a SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery comprises the following steps:
s1 preparation of Al2O3Polysiloxane composite particles: the weight parts of the KH550 silane coupling agent, the absolute ethyl alcohol, the dilute hydrochloric acid aqueous solution and the porous alumina microspheres are 120 parts, 140 parts, 15 parts and 35 parts in sequence.
S11, adding the KH550 silane coupling agent into absolute ethyl alcohol, adding a dilute hydrochloric acid aqueous solution (the molar concentration of hydrochloric acid is 0.2 mol/L), and keeping mechanically stirring for reaction for 30min to obtain sol;
s12, adding ammonia water into the sol to adjust the pH of the sol to be neutral, adding porous alumina microspheres (the size is 1-20 mu m, and the pore diameter is 50-500 nm) to fully adsorb the sol, filtering, and carrying out heat treatment at 110 ℃ for 60min to obtain Al2O3Polysiloxane composite particles;
s2, preparing a spinning film: the weight ratio of the spinning solution to the Al2O 3/polysiloxane composite particles was 95: 5;
s21, adding polyacrylonitrile (with the weight-average molecular weight of 10-30 ten thousand) into N, N-dimethylformamide to form a suspension (the mass concentration of the polyacrylonitrile in the suspension is 10%), then heating in a water bath (at the temperature of 80 ℃) while keeping mechanical stirring until the polyacrylonitrile is completely dissolved, and thus obtaining a spinning solution;
s22, adding Al into the spinning solution2O3The/polysiloxane composite particles are uniformly mixed and then subjected to electrostatic spinning (the voltage is 18 kV), so that a spinning membrane is obtained;
s3, preparing a nitrogen-doped carbon fiber/SiOC composite negative electrode material: and (3) placing the spinning membrane in a vacuum furnace, preheating for 2h at 500 ℃ in an ammonia atmosphere, heating to 900 ℃ and sintering for 7h (in the sintering process, in an argon atmosphere), and soaking the sintered powder in dilute hydrochloric acid and purified water in sequence to obtain the nitrogen-doped carbon fiber/SiOC composite negative electrode material.
Example 4
A preparation method of a SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery comprises the following steps:
s1 preparation of Al2O3Polysiloxane composite particles: 130 parts, 150 parts, 25 parts and 50 parts of KH550 silane coupling agent, absolute ethyl alcohol, dilute hydrochloric acid aqueous solution and porous alumina microspheres in sequence;
s11, adding the KH550 silane coupling agent into absolute ethyl alcohol, adding a dilute hydrochloric acid aqueous solution (the molar concentration of hydrochloric acid is 0.3 mol/L), and keeping mechanically stirring for reaction for 30min to obtain sol;
s12, adding ammonia water into the sol to adjust the pH of the sol to be neutral, adding porous alumina microspheres (the size is 1-20 mu m, and the pore diameter is 50-500 nm) to fully adsorb the sol, filtering, and carrying out heat treatment at 110 ℃ for 60min to obtain Al2O3Polysiloxane composite particles;
s2, preparing a spinning film: the weight ratio of the spinning solution to the Al2O 3/polysiloxane composite particles was 97: 3;
s21, adding polyacrylonitrile (with the weight-average molecular weight of 10-30 ten thousand) into N, N-dimethylformamide to form a suspension (the mass concentration of the polyacrylonitrile in the suspension is 12%), then heating in a water bath (at the temperature of 80 ℃) while keeping mechanical stirring until the polyacrylonitrile is completely dissolved, and thus obtaining a spinning solution;
s22, adding Al into the spinning solution2O3The/polysiloxane composite particles are uniformly mixed and then subjected to electrostatic spinning (the voltage is 18 kV), so that a spinning membrane is obtained;
s3, preparing a nitrogen-doped carbon fiber/SiOC composite negative electrode material: and (3) placing the spinning membrane in a vacuum furnace, preheating for 2h at 550 ℃ in an ammonia atmosphere, heating to 900 ℃ and sintering for 7h (in the sintering process, in an argon atmosphere), and soaking the sintered powder in dilute hydrochloric acid and purified water in sequence to obtain the nitrogen-doped carbon fiber/SiOC composite negative electrode material.
Example 5
A preparation method of a SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery comprises the following steps:
s1 preparation of Al2O3Polysiloxane composite particles: 140 parts, 130 parts, 20 parts and 40 parts of KH550 silane coupling agent, absolute ethyl alcohol, dilute hydrochloric acid aqueous solution and porous alumina microspheres in sequence;
s11, adding the KH550 silane coupling agent into absolute ethyl alcohol, adding a dilute hydrochloric acid aqueous solution (the molar concentration of hydrochloric acid is 0.2 mol/L), and keeping mechanically stirring for reaction for 30min to obtain sol;
s12, adding ammonia water into the sol to adjust the pH of the sol to be neutral, adding porous alumina microspheres (the size is 1-20 mu m, and the pore diameter is 50-500 nm) to fully adsorb the sol, filtering, and carrying out heat treatment at 110 ℃ for 60min to obtain Al2O3Polysiloxane composite particles;
s2, preparing a spinning film: the weight ratio of the spinning solution to the Al2O 3/polysiloxane composite particles was 97: 3;
s21, adding polyacrylonitrile (with the weight-average molecular weight of 10-30 ten thousand) into N, N-dimethylformamide to form a suspension (the mass concentration of the polyacrylonitrile in the suspension is 11%), then heating in a water bath (at the temperature of 80 ℃) while keeping mechanical stirring until the polyacrylonitrile is completely dissolved, and thus obtaining a spinning solution;
s22, adding Al into the spinning solution2O3The/polysiloxane composite particles are uniformly mixed and then subjected to electrostatic spinning (the voltage is 18 kV), so that a spinning membrane is obtained;
s3, preparing a nitrogen-doped carbon fiber/SiOC composite negative electrode material: and (3) placing the spinning membrane in a vacuum furnace, preheating for 2h at 550 ℃ in an ammonia atmosphere, heating to 900 ℃ and sintering for 7h (in the sintering process, in an argon atmosphere), and soaking the sintered powder in dilute hydrochloric acid and purified water in sequence to obtain the nitrogen-doped carbon fiber/SiOC composite negative electrode material.
Example 6
A preparation method of a SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery comprises the following steps:
s1 preparation of Al2O3Polysiloxane composite particles: 130 parts, 20 parts and 45 parts of KH550 silane coupling agent, absolute ethyl alcohol, dilute hydrochloric acid aqueous solution and porous alumina microspheres in sequence;
s11, adding the KH550 silane coupling agent into absolute ethyl alcohol, adding a dilute hydrochloric acid aqueous solution (the molar concentration of hydrochloric acid is 0.2 mol/L), and keeping mechanically stirring for reaction for 30min to obtain sol;
s12, adding ammonia water into the sol to adjust the pH of the sol to be neutral, adding porous alumina microspheres (the size is 1-20 mu m, and the pore diameter is 50-500 nm) to fully adsorb the sol, filtering, and carrying out heat treatment at 110 ℃ for 60min to obtain Al2O3Polysiloxane composite particles;
s2, preparing a spinning film: the weight ratio of the spinning solution to the Al2O 3/polysiloxane composite particles was 97: 3;
s21, adding polyacrylonitrile (with the weight-average molecular weight of 10-30 ten thousand) into N, N-dimethylformamide to form a suspension (the mass concentration of the polyacrylonitrile in the suspension is 12%), then heating in a water bath (at the temperature of 80 ℃) while keeping mechanical stirring until the polyacrylonitrile is completely dissolved, and thus obtaining a spinning solution;
s22, adding Al into the spinning solution2O3The/polysiloxane composite particles are uniformly mixed and then subjected to electrostatic spinning (the voltage is 18 kV), so that a spinning membrane is obtained;
s3, preparing a nitrogen-doped carbon fiber/SiOC composite negative electrode material: and (3) placing the spinning membrane in a vacuum furnace, preheating for 2h at 550 ℃ in an ammonia atmosphere, heating to 900 ℃ and sintering for 7h (in the sintering process, in an argon atmosphere), and soaking the sintered powder in dilute hydrochloric acid and purified water in sequence to obtain the nitrogen-doped carbon fiber/SiOC composite negative electrode material.
Comparative example 1
A preparation method of a SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery comprises the following steps:
s1 preparation of Al2O3Polysiloxane composite particles: KH550 siliconThe weight parts of the alkane coupling agent, the absolute ethyl alcohol, the dilute hydrochloric acid aqueous solution and the porous alumina microspheres are 100 parts, 10 parts and 10 parts in sequence;
s11, adding the KH550 silane coupling agent into absolute ethyl alcohol, adding a dilute hydrochloric acid aqueous solution (the molar concentration of hydrochloric acid is 0.5 mol/L), and keeping mechanically stirring for reaction for 30min to obtain sol;
s12, adding ammonia water into the sol to adjust the pH of the sol to be neutral, adding porous alumina microspheres (the size is 1-20 mu m, and the pore diameter is 50-500 nm) to fully adsorb the sol, filtering, and carrying out heat treatment at 100 ℃ for 90min to obtain Al2O3Polysiloxane composite particles;
s2, preparing a spinning film: the weight ratio of the spinning solution to the Al2O 3/polysiloxane composite particles is 94: 6;
s21, adding polyacrylonitrile (with the weight-average molecular weight of 10-30 ten thousand) into N, N-dimethylformamide to form a suspension (the mass concentration of the polyacrylonitrile in the suspension is 6%), then heating in a water bath (at the temperature of 75 ℃) while keeping mechanical stirring until the polyacrylonitrile is completely dissolved, and thus obtaining a spinning solution;
s22, adding Al into the spinning solution2O3The/polysiloxane composite particles are uniformly mixed and then subjected to electrostatic spinning (the voltage is 15 kV), so that a spinning membrane is obtained;
s3, preparing a nitrogen-doped carbon fiber/SiOC composite negative electrode material: and (3) placing the spinning membrane in a vacuum furnace, preheating for 3h at 400 ℃ in an ammonia atmosphere, heating to 800 ℃ for sintering for 8h (in the sintering process, in an argon atmosphere), and soaking the sintered powder in dilute hydrochloric acid and purified water in sequence to obtain the nitrogen-doped carbon fiber/SiOC composite negative electrode material.
Comparative example 1 is a control example of example 1, and in comparative example 1, the amount of porous alumina microspheres was greatly reduced.
Comparative example 2
A preparation method of a SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery comprises the following steps:
s1 preparation of Al2O3Polysiloxane composite particles: KH550 silane coupling agent, absolute ethyl alcohol, dilute hydrochloric acid aqueous solution and porousThe weight parts of the alumina microspheres are 130 parts, 20 parts and 45 parts in sequence;
s11, adding the KH550 silane coupling agent into absolute ethyl alcohol, adding a dilute hydrochloric acid aqueous solution (the molar concentration of hydrochloric acid is 0.2 mol/L), and keeping mechanically stirring for reaction for 30min to obtain sol;
s12, adding ammonia water into the sol to adjust the pH of the sol to be neutral, adding porous alumina microspheres (the size is 1-20 mu m, and the pore diameter is 50-500 nm) to fully adsorb the sol, filtering, and carrying out heat treatment at 110 ℃ for 60min to obtain Al2O3Polysiloxane composite particles;
s2, preparing a precursor solution: the weight ratio of the spinning solution to the Al2O 3/polysiloxane composite particles was 97: 3;
s21, adding polyacrylonitrile (with the weight-average molecular weight of 10-30 ten thousand) into N, N-dimethylformamide to form a suspension (the mass concentration of the polyacrylonitrile in the suspension is 12%), then heating in a water bath (at the temperature of 80 ℃) while keeping mechanical stirring until the polyacrylonitrile is completely dissolved, and thus obtaining a spinning solution;
s22, adding Al into the spinning solution2O3Mixing the polysiloxane composite particles uniformly to obtain a precursor solution;
and S3, placing the precursor solution in a vacuum furnace, preheating for 2h at 550 ℃ under the ammonia atmosphere, heating to 900 ℃, sintering for 7h (argon atmosphere in the sintering process), and soaking the sintered powder in dilute hydrochloric acid and purified water in sequence to obtain the composite negative electrode material.
Comparative example 2 is a comparative example of example 6, and in comparative example 2, the spinning solution and Al were not used2O3/polysiloxane composite particles are mixed and subjected to electrostatic spinning.
The performance tests of examples 1 to 6 and comparative examples 1 to 2 were performed, and the test results are shown in table 1:
the negative electrode materials of examples 1 to 6 and comparative examples 1 to 3, PVDF and Super-P are added into an NMP solvent according to a mass ratio of 8:1:1 to prepare a slurry, the slurry is coated on the surface of copper foil to serve as a positive electrode, a lithium sheet is taken as a negative electrode, 1mol/L lithium hexafluorophosphate and EC/DMC are taken as electrolyte, celgard2400 is taken as a diaphragm, a CR2032 button cell is assembled, the rate performance of the cell is tested under a current of 0.4ma/g, and the results are shown in Table 1: a
Table form
Figure 565908DEST_PATH_IMAGE001
Figure 23434DEST_PATH_IMAGE002
As can be seen from the data in Table 1, the cycle performance of examples 1-6 is significantly better than that of comparative examples 1-2, which is because the SiOC particles of examples 1-6 expand without causing deformation of the whole material, so that the whole structure is more stable. During sintering and carbonization, polysiloxane is pyrolyzed and carbonized to form SiOC, porous alumina microspheres are washed away after carbonization, and pores are formed in the carbonized fibers, so that SiOC particles cannot deform and break due to volume expansion.
Comparative example 1 since porous alumina was added less as a support, the change in lithium intercalation volume thereof easily causes deformation of the fiber.
Comparative example 2 does not use the spinning solution and Al2O3/polysiloxane composite particles are mixed and subjected to electrostatic spinning. Since comparative example 2 did not perform electrospinning to form a spinning film, the porous alumina was not partially uniform in the sol, resulting in poor cycle performance thereof. Because during the circulation process, the volume expansion of SiOC particles can cause local fiber deformation and fracture, thereby influencing the stability of the whole structure.
In conclusion, the SiOC @ nitrogen-doped carbon fiber composite negative electrode can be formed into a lithium battery negative electrode material in one step by loading polysiloxane on alumina and then spinning the polysiloxane and polyacrylonitrile and then sintering, and compared with the traditional production process, the sintering process is greatly simplified. Meanwhile, in the negative electrode material prepared by the spinning process, more SiOC is embedded in the carbon fiber, so that the conductivity and the cycle performance of the SiOC can be effectively improved. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. 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 spirit of the present invention be covered by the claims of the present invention.

Claims (9)

1. A preparation method of a SiOC @ nitrogen-doped carbon fiber composite negative electrode of a lithium battery is characterized by comprising the following steps of:
s1 preparation of Al2O3Polysiloxane composite particles:
s11, adding aminosiloxane into an organic solvent, adding a dilute hydrochloric acid aqueous solution, and stirring for reaction to obtain sol;
s12, adjusting the pH value of the sol to 6.5-7.5, adding porous alumina microspheres to adsorb the sol, filtering, and carrying out heat treatment at 100-110 ℃ for 30-90 min to obtain Al2O3Polysiloxane composite particles;
s2, preparing a spinning film:
s21, adding polyacrylonitrile into the polar aprotic solvent to form a suspension, heating in a water bath, and stirring until the polyacrylonitrile is completely dissolved to obtain a spinning solution;
s22, adding Al into the spinning solution2O3The/polysiloxane composite particles are evenly mixed and then subjected to electrostatic spinning to obtain a spinning membrane;
s3, preparing a nitrogen-doped carbon fiber/SiOC composite negative electrode material: and (3) placing the spinning film in a vacuum furnace, preheating for 1-3 h at 400-600 ℃ in an ammonia atmosphere, heating to 800-1000 ℃, sintering for 6-8 h, and soaking the powder in dilute hydrochloric acid and purified water in sequence to obtain the nitrogen-doped carbon fiber/SiOC composite negative electrode material.
2. The preparation method of the SiOC @ nitrogen-doped carbon fiber composite negative electrode of the lithium battery as claimed in claim 1, wherein the preparation method comprises the following steps: the organic solvent is absolute ethyl alcohol, the molar concentration of hydrochloric acid in the dilute hydrochloric acid aqueous solution is 0.05-0.5 mol/L, and the aminosiloxane is a KH550 silane coupling agent; the size of the porous alumina microspheres is 1-20 mu m, and the pore diameter is 50-500 nm.
3. The preparation method of the SiOC @ nitrogen-doped carbon fiber composite negative electrode of the lithium battery as claimed in claim 1, wherein the preparation method comprises the following steps: the amino siloxane, the organic solvent, the dilute hydrochloric acid aqueous solution and the porous alumina microspheres in the S1 are 100-150 parts, 50-200 parts, 10-30 parts and 30-50 parts in sequence.
4. The preparation method of the SiOC @ nitrogen-doped carbon fiber composite negative electrode of the lithium battery as claimed in claim 1, wherein the preparation method comprises the following steps: the weight average molecular weight of the polyacrylonitrile is 10-30 ten thousand, the polar aprotic solvent is N, N-dimethylformamide, and the mass concentration of the polyacrylonitrile in the suspension is 5-20%.
5. The preparation method of the SiOC @ nitrogen-doped carbon fiber composite negative electrode of the lithium battery as claimed in claim 1, wherein the preparation method comprises the following steps: the spinning solution and Al2O3The weight ratio of the/polysiloxane composite particles is (90-98): (2-10).
6. The preparation method of the SiOC @ nitrogen-doped carbon fiber composite negative electrode of the lithium battery as claimed in claim 1, wherein the preparation method comprises the following steps: and the heating temperature of the water bath in the S21 is 70-90 ℃.
7. The preparation method of the SiOC @ nitrogen-doped carbon fiber composite negative electrode of the lithium battery as claimed in claim 1, wherein the preparation method comprises the following steps: the voltage of electrostatic spinning in the S22 is 15-20 kV.
8. The preparation method of the SiOC @ nitrogen-doped carbon fiber composite negative electrode of the lithium battery as claimed in claim 1, wherein the preparation method comprises the following steps: the preheating temperature in the S3 is 550 ℃, and the preheating time is 1.5-2.5 h; the sintering temperature is 900 ℃, and the sintering time is 6.5-7.5 h.
9. The utility model provides a lithium cell SiOC @ nitrogen doping carbon fiber composite negative pole which characterized in that: the SiOC @ nitrogen-doped carbon fiber composite negative electrode for the lithium battery as claimed in any one of claims 1 to 8.
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Publication number Priority date Publication date Assignee Title
CN114975997A (en) * 2022-05-09 2022-08-30 东莞理工学院 Lithium ion battery cathode material and preparation method thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114975997A (en) * 2022-05-09 2022-08-30 东莞理工学院 Lithium ion battery cathode material and preparation method thereof
CN114975997B (en) * 2022-05-09 2024-04-30 东莞理工学院 Lithium ion battery negative electrode material and preparation method thereof

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