CN108987702B

CN108987702B - Integrated electrode material based on composite aerogel and preparation and application thereof

Info

Publication number: CN108987702B
Application number: CN201810778374.4A
Authority: CN
Inventors: 陈咪; 宗平; 张慧; 李维汉; 连崑
Original assignee: XI'AN JIAOTONG UNIVERSITY SUZHOU ACADEMY
Current assignee: XI'AN JIAOTONG UNIVERSITY SUZHOU ACADEMY
Priority date: 2018-07-16
Filing date: 2018-07-16
Publication date: 2021-03-12
Anticipated expiration: 2038-07-16
Also published as: CN108987702A

Abstract

The invention relates to a preparation method of an integrated electrode material based on composite aerogel, which comprises the following steps: uniformly mixing the carbon nano tube, the silicon powder, the metal oxide, the polyvinylpyrrolidone, the sodium alginate and the gluconolactone in water, and obtaining hydrogel after complete reaction; freeze drying the hydrogel to obtain aerogel, and then pressing at 10 deg.C^‑ ⁶And heating at 100-200 ℃ under the vacuum condition of Pa-4Pa to reduce the metal oxide into metal, thereby obtaining the integrated electrode material based on the composite aerogel. The invention also provides an integrated electrode material based on the composite aerogel prepared by the preparation method, which comprises the composite aerogel, wherein the composite aerogel comprises sodium alginate aerogel and metal particles, carbon nano tubes and silicon powder which are uniformly distributed in the sodium alginate aerogel. The composite aerogel-based integrated electrode material is prepared under the conditions of vacuum and low temperature, a binder and a current collector are not needed, and the electrode material has good flexibility, mechanical properties and electrochemical properties.

Description

Integrated electrode material based on composite aerogel and preparation and application thereof

Technical Field

The invention relates to the technical field of electrode material preparation, in particular to an integrated electrode material based on composite aerogel and preparation and application thereof.

Background

As is well known, the energy problem is a big crisis faced by people at present, and an efficient and green energy storage system is an effective means for solving the problem. The battery is irreplaceable in daily portable electronic equipment such as mobile phones, computers, digital cameras and the like, and in electric vehicles and even large-scale energy storage power grids. Particularly since the 90 s of the 20 th century, lithium ion batteries have been widely popularized and widely used on a large scale along with the use of graphite negative electrodes by Sony corporation and Moli corporation, canada. However, with the continuous progress of technology and the continuous increase of demand, it is important to develop a lithium ion battery that is smaller, lighter, thinner and can bear various deformation. However, most of the currently used electrode materials require a binder and a current collector, and an active material is easily separated from the current collector during bending to cause capacity fade, and thus, development of an integrated electrode material becomes particularly important. The Chinese patent with the application number of 201711249261.7 discloses a composite electrode material and a preparation method and application thereof, the sodium alginate hydrogel is used as a framework to prepare the composite electrode material, but the material prepared by the method is powdery, has poor mechanical property, cannot form a film and cannot be applied to a flexible battery.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide an integrated electrode material based on composite aerogel and preparation and application thereof.

In one aspect, the present invention provides a method for preparing a composite aerogel-based integrated electrode material, comprising the following steps:

(1) uniformly mixing a carbon nano tube, silicon powder, metal oxide, polyvinylpyrrolidone, sodium alginate and gluconolactone in water, and reacting completely to obtain hydrogel, wherein the particle size of the silicon powder is nano-scale or micron-scale;

(2) freeze drying the hydrogel to obtain aerogel, and then pressing at 10 deg.C^-6And heating at 100-200 ℃ under the vacuum condition of Pa-4Pa to reduce the metal oxide into metal, thereby obtaining the integrated electrode material based on the composite aerogel.

Further, in the step (1), the carbon nanotube has a diameter of 100-300nm (preferably 300nm) and a length of 5 μm. Further, in the step (1), the metal oxide is one or more of copper oxide, zinc oxide and ferroferric oxide.

Further, in the step (1), the mass ratio of the carbon nanotubes to the metal oxide is 1:1 to 1: 5.

Further, in the step (1), the mass ratio of the silicon powder to the metal oxide is 1:1 to 1: 5.

Further, in the step (1), the mass ratio of the metal oxide to the sodium alginate is 1:2-1: 4.

Further, in the step (1), the mass ratio of the sodium alginate to the gluconolactone is 1:1.5-1: 5.

Further, in the step (1), the mass ratio of the sodium alginate to the polyvinylpyrrolidone is 1:1-6: 1.

Further, in the step (1), the viscosity of sodium alginate is 20cps to 1194 cps.

Further, in the step (1), the carbon nanotube, the silicon powder, the metal oxide and the polyvinylpyrrolidone are uniformly mixed in water by ultrasonic treatment for 30 min. Then adding sodium alginate, stirring for 6h, finally adding glucolactone, and standing for 48h to obtain the hydrogel.

Further, in the step (2), the freeze-drying time is 1 to 2 days.

Further, in the step (2), the temperature is raised from room temperature to 100-200 ℃ for heating, and the temperature raising rate is 1-10 ℃/min.

Further, in the step (2), the heating time is 1h-4 h.

In the above method, the carbon nanotubes function to provide a conductive network and to increase mechanical properties. The function of the silicon powder is to provide capacity. The metal oxide is reduced to metal particles under vacuum conditions during the preparation process, and can play a role of a current collector in the traditional coating process when the electrode material is used. The polyvinylpyrrolidone is used as a dispersing agent and a main reducing agent in the invention, the sodium alginate is used for forming hydrogel and used as a support body and a binding agent of an integrated electrode material, and the gluconolactone is used as a slow release agent.

In the invention, the preparation principle of the integrated electrode material based on the composite aerogel is as follows:

the sodium alginate composite hydrogel is prepared by an in-situ release method, gluconolactone can be hydrolyzed to generate gluconic acid when dissolved in water, the gluconic acid can react with metal oxide to slowly release metal cations when the metal oxide is added, and the sodium alginate has-COO in the molecule^-1Group, Na in sodium alginate when it encounters a metal cation⁺Exchange with the cations to convert the sodium alginate solution into gel, and freeze drying can dry the solvent in the hydrogel and keep the sodium alginate structure from collapsing, so that the sodium alginate aerogel with flexibility can be formed.

In addition, according to a sodium alginate TGA diagram, the breakage of a sodium alginate framework is about 220 ℃, but the metal oxide is difficult to reduce into a metal simple substance below 220 ℃ in an inert gas atmosphere, so that the electrode material cannot be charged and discharged due to poor conductivity, the metal oxide in the electrode material can be reduced into the metal simple substance below 220 ℃ in a vacuum environment, the breakage of the sodium alginate framework can be avoided while the conductivity of the electrode material is increased, the formation of the sodium alginate aerogel with a uniform and complete structure is facilitated, and the connection effect of the carbon nano tube is added to connect metal simple substance particles to replace the effect of a current collector in the traditional coating process.

On the other hand, the invention also provides the composite aerogel-based integrated electrode material prepared by the preparation method, which comprises the composite aerogel, wherein the composite aerogel comprises sodium alginate aerogel and metal particles, carbon nano tubes and silicon powder which are uniformly distributed in the sodium alginate aerogel.

Further, the thickness of the electrode material is 50-1000 μm.

Further, the carbon nanotubes have a diameter of 100-300nm and a length of 5 μm.

Further, the metal particles are one or more of copper, zinc and iron.

Further, the particle size of the silicon powder is nano-scale or micron-scale.

In still another aspect, the invention also claims the application of the composite aerogel-based integrated electrode material in the preparation of a flexible battery.

Flexible battery refers to a battery that can be used by repeated bending. The composite aerogel-based integrated electrode material disclosed by the invention has good mechanical properties, flexibility and electrochemical properties, so that the composite aerogel-based integrated electrode material can be applied to the preparation of flexible batteries.

Further, the composite aerogel-based integrated electrode material can be combined with a diaphragm and electrolyte to form a half cell and a full cell.

By the scheme, the invention at least has the following advantages:

adopting sodium alginate as a template, and preparing the composite aerogel-based integrated electrode material under the non-high temperature (100-; the heat treatment is carried out under the vacuum condition, and the reduction temperature of the metal oxide can be reduced under the vacuum environment, so that the structure of the sodium alginate aerogel is not damaged.

The composite aerogel-based integrated electrode material prepared by the invention has good mechanical property, flexibility and electrochemical property, and is low in cost, simple in preparation process and easy for large-scale preparation.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.

Drawings

FIG. 1 shows XRD test results of composite aerogel-based monolithic electrode materials prepared under different vacuum conditions in example 1 of the present invention;

FIG. 2 shows XRD test results of composite aerogel-based monolithic electrode materials prepared under different temperature-rising rate conditions in example 1 of the present invention;

FIG. 3 is a diagram of an integrated electrode material based on composite aerogel prepared in example 3 of the present invention;

FIG. 4 is an SEM image of a composite aerogel-based monolithic electrode material prepared in example 3 of the present invention;

FIG. 5 is an XRD pattern of a composite aerogel-based monolithic electrode material prepared according to example 3 of the present invention;

fig. 6 is a discharge capacity-cycle number test result of the composite aerogel-based integrated electrode material prepared in example 3 of the present invention.

FIG. 7 is an XRD pattern of a composite aerogel-based monolithic electrode material prepared according to example 4 of the present invention;

fig. 8 is a result of a discharge capacity-cycle number test of the composite aerogel-based integrated electrode material prepared in example 4 of the present invention.

FIG. 9 is an XRD pattern of a composite aerogel-based monolithic electrode material prepared according to example 5 of the present invention;

fig. 10 is a discharge capacity-cycle number test result of the composite aerogel-based integrated electrode material prepared in example 5 of the present invention.

FIG. 11 is an XRD pattern of a composite aerogel-based monolithic electrode material prepared according to example 6 of the present invention;

fig. 12 shows the results of the discharge capacity-cycle number test of the composite aerogel-based integrated electrode material prepared in example 6 of the present invention.

FIG. 13 is an XRD pattern of a composite aerogel-based monolithic electrode material prepared according to example 7 of the present invention;

fig. 14 shows the results of the discharge capacity-cycle number test of the composite aerogel-based integrated electrode material prepared in example 7 of the present invention.

FIG. 15 is an XRD pattern of a composite aerogel-based monolithic electrode material prepared according to example 8 of the present invention;

fig. 16 is a discharge capacity-cycle number test result of the composite aerogel-based integrated electrode material prepared in example 8 of the present invention.

Fig. 17 is an XRD pattern of the composite aerogel-based integrated electrode material prepared in example 9 of the present invention.

Detailed Description

The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

Example 1

Adding 50mg of nano silicon powder (with particle size of 20-60nm), 25mg of carbon nanotube (with diameter of 300nm and length of 5 μm), 25mg of copper oxide and 10mg of polyvinylpyrrolidone into deionized water, and performing ultrasonic treatment for 30 min; slowly adding 62.5mg of low viscosity (20cps) sodium alginate powder into the above solution, mechanically stirring for 6 hr, adding 90mg of gluconolactone, stirring for 5min, standing for 48 hr, and waiting for gelling; putting the hydrogel into a refrigerator with the temperature of-80 ℃ for freezing for 2-6 hours, and then putting the hydrogel into a freeze drier for drying; heating the dried aerogel material from room temperature to 200 ℃ at the heating rate of 1 ℃/min for 2h, then naturally cooling to room temperature to obtain the composite aerogel-based integrated electrode material, wherein the pressure of the heat treatment is normal pressure (N is normal pressure) respectively₂Atmospheric), 1000Pa and 0.4Pa, FIG. 1 is the XRD pattern of the material after heat treatment at different pressures, from which it can be seen that N is₂The diffraction peak of CuO still exists in the atmosphere, the diffraction peak of CuO disappears under the pressure of 1000Pa, but Cu still exists₂Diffraction peak of O, and no CuO and Cu at 0.4Pa pressure₂And the diffraction peak of O shows that under the pressure of 0.4Pa, the copper oxide is completely reduced into a copper simple substance which has conductivity, so that the finally prepared composite aerogel-based integrated electrode material has conductivity.

Example 2

Adding 50mg of nano silicon powder (with particle size of 20-60nm), 25mg of carbon nanotube (with diameter of 300nm and length of 5 μm), 25mg of copper oxide and 10mg of polyvinylpyrrolidone into deionized water, and performing ultrasonic treatment for 30 min; slowly adding 62.5mg of low viscosity (20cps) sodium alginate powder into the above solution, mechanically stirring for 6 hr, adding 90mg of gluconolactone, stirring for 5min, standing for 48 hr, and waiting for gelling; putting the hydrogel into a refrigerator with the temperature of-80 ℃ for freezing for 2-6 hours, and then putting the hydrogel into a freeze drier for drying; and heating the dried aerogel material in a vacuum environment (the pressure is 0.4Pa) from room temperature to 200 ℃ at the speed of 5 ℃/min, respectively preserving the heat for 1h, 2h and 4h, and naturally cooling to room temperature to obtain the integrated electrode material based on the composite aerogel. FIG. 2 is an XRD pattern of the obtained material, and as can be seen from the figure, the diffraction peak of copper oxide still exists when the heat preservation is carried out for 1 hour, but the diffraction peak of cuprous oxide still exists when the heat preservation time is prolonged to 4 hours, so that 2 hours is preferably the heat preservation time of the heat treatment.

Example 3

Adding 50mg of nano silicon powder (with particle size of 20-60nm), 25mg of carbon nanotube (with diameter of 200nm and length of 5 μm), 25mg of copper oxide and 10mg of polyvinylpyrrolidone into deionized water, and performing ultrasonic treatment for 30 min; slowly adding 62.5mg of low viscosity (20cps) sodium alginate powder into the above solution, mechanically stirring for 6 hr, adding 90mg of gluconolactone, stirring for 5min, standing for 48 hr, and waiting for gelling; putting the hydrogel into a refrigerator with the temperature of-80 ℃ for freezing for 2-6 hours, and then putting the hydrogel into a freeze drier for drying; and (3) heating the dried aerogel material to 200 ℃ at the heating rate of 1 ℃/min under the pressure of 0.4Pa, preserving the heat for 2h, and naturally cooling to room temperature to obtain the composite aerogel-based integrated electrode material. As shown in fig. 3, the material of the electrode material prepared in this example is black, and the film-like material can be directly obtained by the above method, and the material has flexibility, can be gripped and bent by forceps, and has good mechanical properties.

Fig. 4 is an SEM image of the electrode material prepared as described above, in which silver white bright regions are copper elements, and the scale length is 8 μm, and a number of silver white particles are generated on the surface of the electrode material after heat treatment (fig. 4b) compared with the electrode material before and after heat treatment (fig. 4 a).

Fig. 5 is an XRD pattern of the electrode material prepared as described above (degree represents diffraction angle and intensity represents intensity in the figure), the diffraction peak of copper oxide completely disappeared after heat treatment, and a weaker cuprous oxide copper was present and appeared, indicating that the silvery white particles in SEM are elementary copper.

The integrated electrode material of the copper/carbon nanotube/silicon composite aerogel and a lithium sheet are respectively used as a positive electrode and a negative electrode, a diaphragm and electrolyte are added to assemble a button half cell, the electrical performance of the button half cell is tested, fig. 6 is a discharge capacity-cycle number diagram of the electrode material, the cycle number represents the cycle number, and the specific capacity represents the specific discharge capacity. Fig. 6 shows that the cell still has a capacity of about 800mAh/g after 20 cycles at a current density of 100 mA/g.

Example 4

An integrated electrode material based on composite aerogel was prepared according to the method of example 3, except that: the sodium alginate is medium-viscous (485 cps).

Fig. 7 is an XRD pattern of the electrode material prepared as described above, and it can be seen from the XRD pattern that diffraction peaks of copper oxide and cuprous oxide completely disappear, and only diffraction peaks of copper exist, and it is presumed that sodium alginate having a higher viscosity has a larger molecular weight, and more secondary hydroxyl groups are present on the molecular chain, and thus has a stronger reducibility.

The integrated electrode material of copper/carbon nanotube/silicon composite aerogel and a lithium plate are respectively used as a positive electrode and a negative electrode, a diaphragm and electrolyte are added to assemble a button half cell, the electrical performance of the button half cell is tested, and fig. 8 is a discharge capacity-cycle number graph of the electrode material. Fig. 8 shows that the cell still has a capacity of about 600mAh/g after 11 cycles at a current density of 100 mA/g.

Example 5

An integrated electrode material based on composite aerogel was prepared according to the method of example 3, except that: the sodium alginate is high viscosity (1194 cps).

Fig. 9 is an XRD pattern of the electrode material prepared as described above, and it can be seen from the XRD pattern that diffraction peaks of copper oxide and cuprous oxide completely disappear, and only diffraction peaks of copper exist, and it is presumed that sodium alginate having a higher viscosity has a larger molecular weight, and more secondary hydroxyl groups are present on the molecular chain, and thus has a stronger reducibility.

The integrated electrode material of copper/carbon nanotube/silicon composite aerogel and a lithium plate are respectively used as a positive electrode and a negative electrode, a diaphragm and electrolyte are added to assemble a button half cell, the electrical performance of the button half cell is tested, and a discharge capacity-cycle number graph of the electrode material is shown in fig. 10. FIG. 10 shows that the cell still has a capacity of about 1800mAh/g after 20 cycles at a current density of 100 mA/g.

Example 6

An integrated electrode material based on composite aerogel was prepared according to the method of example 3, except that: the ratio of the carbon nano tube to the nano silicon powder to the polyvinylpyrrolidone is 2.5: 5: 1.

fig. 11 is an XRD pattern of the electrode material prepared as described above, from which it can be seen that diffraction peaks of copper oxide and cuprous oxide completely disappear, and only diffraction peaks of copper exist, indicating that the reduction of copper oxide is not significantly affected after the amount of carbon nanotubes is increased.

The integrated electrode material of copper/carbon nanotube/silicon composite aerogel and a lithium plate are respectively used as a positive electrode and a negative electrode, a diaphragm and electrolyte are added to assemble a button half cell, the electrical performance of the button half cell is tested, and fig. 12 is a discharge capacity-cycle number graph of the electrode material. FIG. 12 shows that the cell still has a capacity of about 2700mAh/g after 8 cycles at a current density of 100 mA/g.

Example 7

An integrated electrode material based on composite aerogel was prepared according to the method of example 3, except that: the proportion of the carbon nano tube, the nano silicon powder and the polyvinylpyrrolidone is 5: 5: 1.

fig. 13 is an XRD pattern of the electrode material prepared as described above, from which it can be seen that diffraction peaks of copper oxide and cuprous oxide completely disappear, and only diffraction peaks of copper exist, indicating that the reduction of copper oxide is not significantly affected after the amount of carbon nanotubes is increased.

The integrated electrode material of copper/carbon nanotube/silicon composite aerogel and a lithium plate are respectively used as a positive electrode and a negative electrode, a diaphragm and electrolyte are added to assemble a button half cell, the electrical performance of the button half cell is tested, and fig. 14 is a discharge capacity-cycle number graph of the electrode material. Fig. 14 shows that the cell still has a capacity of about 1300mAh/g after 25 cycles at a current density of 100 mA/g.

Example 8

An integrated electrode material based on composite aerogel was prepared according to the method of example 3, except that: the ratio of copper oxide, nano silicon powder and gluconolactone is 5: 5: 9.

fig. 15 is an XRD pattern of the electrode material prepared as described above, and it can be seen from the XRD pattern that diffraction peaks of copper oxide and cuprous oxide completely disappear, and only diffraction peaks of copper exist, indicating that the copper oxide is reduced to copper under the heat treatment condition after the amount of copper oxide increases.

The integrated electrode material of copper/carbon nanotube/silicon composite aerogel and a lithium plate are respectively used as a positive electrode and a negative electrode, a diaphragm and electrolyte are added to assemble a button half cell, the electrical performance of the button half cell is tested, and fig. 16 is a discharge capacity-cycle number graph of the electrode material. FIG. 16 shows that the cell still has a capacity of about 600mAh/g after 34 cycles at a current density of 100 mA/g.

Example 9

An integrated electrode material based on composite aerogel was prepared according to the method of example 3, except that: the particle size of the silicon powder used was 1 μm.

Fig. 17 is an XRD pattern of the electrode material prepared as described above, from which it can be seen that the diffraction peak of copper oxide has disappeared completely, and there is also a very weak diffraction peak of cuprous oxide and a diffraction peak of copper appears, indicating that the micro silicon powder also has the same effect as the nano silicon powder.

Example 10

An integrated electrode material based on composite aerogel was prepared according to the method of example 3, except that: the pressure of the heat treatment is 1X 10^-4Pa。

Example 11

An integrated electrode material based on composite aerogel was prepared according to the method of example 3, except that: the metal oxide used is ferroferric oxide.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of an integrated electrode material based on composite aerogel is characterized by comprising the following steps:

(1) uniformly mixing a carbon nano tube, silicon powder, metal oxide, polyvinylpyrrolidone, sodium alginate and gluconolactone in water, and reacting completely to obtain hydrogel, wherein the particle size of the silicon powder is nano-scale or micron-scale; the metal oxide is one or more of copper oxide, zinc oxide and ferroferric oxide;

(2) freeze-drying the hydrogel to obtain an aerogel, and then carrying out the freeze-drying under the pressure of 10^-6And heating at 100-200 ℃ under the vacuum condition of Pa-4Pa to reduce the metal oxide into metal, thereby obtaining the composite aerogel-based integrated electrode material.

2. The method of claim 1, wherein: in the step (1), the diameter of the carbon nanotube is 100-300nm, and the length is 5 μm.

3. The method of claim 1, wherein: in the step (1), the mass ratio of the carbon nanotubes to the metal oxide is 1:1-1: 5.

4. The method of claim 1, wherein: in the step (1), the mass ratio of the silicon powder to the metal oxide is 1:1-1: 5.

5. The method of claim 1, wherein: in the step (1), the viscosity of the sodium alginate is 20cps to 1194 cps.

6. The method of claim 1, wherein: in the step (2), the heating time is 1-4 h.

7. The composite aerogel-based integrated electrode material prepared by the preparation method of any one of claims 1 to 6, which comprises a composite aerogel, wherein the composite aerogel comprises a sodium alginate aerogel and metal particles, carbon nanotubes and silicon powder which are uniformly distributed in the sodium alginate aerogel.

8. The composite aerogel based monolithic electrode material of claim 7, wherein: the thickness of the electrode material is 50-1000 μm.

9. Use of the composite aerogel based monolithic electrode material of claim 7 in the preparation of a flexible battery.