TWI593849B - Improve the hydrophilicity and conductivity of carbon fiber cloth - Google Patents

Description

Method for improving hydrophilicity and electrical conductivity of carbon fiber cloth

The present invention relates to a method for improving the hydrophilicity and electrical conductivity of a carbon fiber cloth, and more particularly to a method for improving the hydrophilicity and electrical conductivity of a carbon fiber cloth by plasma treatment.

Taiwan Patent No. I318243 discloses a method for preparing a hydrophobic carbonaceous material in order to obtain a gas diffusion layer of a thin film electrode and further application in a fuel cell, so that the activated carbon fiber is modified with plasma to increase its hydrophobicity. The activated carbon fiber modified by the plasma has excellent hydrophobicity and can maintain good porosity for gas diffusion, and can effectively improve the power output of the fuel cell.

However, the hydrophobic carbonaceous material has limited application and cannot be applied to various fields. For example, in the field of lead-acid capacitor batteries, since the electrode of the lead-acid capacitor battery is directly in contact with the sulfuric acid electrolyte, the hydrophobic carbonaceous material is used. Not suitable for use in lead acid battery capacitors.

Based on the above, it is still necessary to propose a novel modification method of carbon fiber cloth.

Accordingly, it is an object of the present invention to provide a method of improving the hydrophilicity and electrical conductivity of a carbon fiber cloth.

Therefore, the method for improving the hydrophilicity and conductivity of the carbon fiber cloth comprises the following steps: applying a plasma treatment to the carbon fiber cloth, reacting the carbon fiber cloth with a hydrophilic substance to form a hydrophilic functional group on the carbon fiber cloth. The pellet and the carbon fiber in the carbon fiber cloth are broken to form a loose structure, and the hydrophilicity and conductivity of the carbon fiber cloth after the plasma treatment are greater than the hydrophilicity and conductivity before the plasma treatment of the carbon fiber cloth.

The effect of the present invention is that the carbon fiber cloth is reacted with the hydrophilic substance to form a hydrophilic functional group on the carbon fiber cloth by the plasma treatment, thereby improving the hydrophilicity of the carbon fiber cloth and the plasma treatment. The carbon fibers in the carbon fiber cloth are broken to form a loose structure, thereby improving the electrical conductivity of the carbon fiber cloth.

The contents of the present invention will be described in detail below:

Herein, the hydrophilic functional group is, for example but not limited to, C=O, O-C-O, COOH, OH, and the like. The type of the carbon fiber cloth is not particularly limited as long as a plurality of carbon fibers in the carbon fiber cloth are activated by the plasma treatment and reacted with the hydrophilic substance to bond the hydrophilic functional groups to the carbon fibers, and the plasma is plasma-treated. A carbon fiber cloth which can break the carbon fibers to produce a loose structure is suitable. Preferably, the carbon fiber cloth is activated carbon fiber. The hydrophilic substance is not particularly limited as long as it can be reacted with a hydrophilic substance which reacts with activated carbon fibers in the carbon fiber cloth after the plasma treatment to form a hydrophilic functional group. Preferably, the hydrophilic substance is an oxygen-containing substance. Preferably, the oxygen containing material is derived from the atmosphere, oxygen plasma, or a combination thereof.

Preferably, the plasma treatment is a normal piezoelectric slurry treatment, and when the normal piezoelectric slurry is used, it is easier to control the operating conditions and to facilitate the plasma treatment of the large-area carbon fiber cloth. Preferably, the plasma treated plasma is selected from the group consisting of nitrogen plasma, oxygen plasma, helium gas plasma, argon plasma, or a combination thereof. The condition parameters of the plasma treatment, such as the power range, the flow rate range, the moving speed, and the working distance, are not particularly limited as long as the hydrophilic functional groups are formed on the carbon fiber cloth and the carbon fibers are broken to form a loose structure. can. Preferably, the plasma treatment power ranges from 50 watts to 700 watts, which can further improve the hydrophilicity and electrical conductivity of the carbon fiber cloth after plasma treatment. Preferably, the plasma treatment area of the carbon fiber cloth per unit time is in the range of 222 mm ² /sec to 318 mm ² /sec, which can further improve the hydrophilicity and electrical conductivity of the carbon fiber cloth after the plasma treatment. Preferably, the plasma treatment power per unit area of the carbon fiber cloth ranges from 3.18 W/mm ² to 63.6 W/mm ² , which can further improve the hydrophilicity and conductivity of the carbon fiber cloth after the plasma treatment. Preferably, when the plasma treatment is performed, the plasma treatment causes the surface temperature of the carbon fiber cloth to range from 50 to 90 ° C, which can further improve the hydrophilicity and conductivity of the carbon fiber cloth after the plasma treatment. The plasma treated plasma flow rate range is, for example but not limited to, 5 to 70 ml/min. The plasma treatment has a working range of 5 to 25 mm. The range of plasma movement rates of the plasma treatment is, for example but not limited to, 1 to 700 mm/s.

Preferably, the method of enhancing the hydrophilicity and electrical conductivity of the carbon fiber cloth further comprises a heat treatment after the plasma treatment. The carbon fiber cloth treated by the plasma can have long-term conductivity by the heat treatment. The operating environment of the heat treatment is not particularly limited and may or may not be carried out in a vacuum or in a specific atmosphere. Preferably, the heat treatment has a temperature in the range of from 120 to 170 °C. When the temperature of the heat treatment is in the range of 120 to 170 ° C, the carbon fiber cloth treated by the plasma can be made to have longer-term conductivity. The time of the heat treatment is not particularly limited, and is, for example, but not limited to, 2 to 3 hours.

Compared with the carbon fiber cloth which is not treated by the plasma, the carbon fiber cloth treated by the plasma has high hydrophilicity and electrical conductivity, and its application fields are, for example, but not limited to, lead-acid capacitor batteries. When the plasma-treated carbon fiber cloth is used in a lead-acid capacitor battery, since the carbon fiber in the plasma-treated carbon fiber cloth breaks and forms a loose structure, it has high conductivity and can adsorb more electric charge in the electrolyte. And because the hydrophilic functional group formed on the plasma-treated carbon fiber cloth enables the electrolyte to be more wetted into the carbon fiber cloth, so that the lead-acid capacitor battery has a higher capacitance value.

The invention is further illustrated by the following examples, which are to be construed as illustrative only and not to be construed as limiting.

[Example 1]

Plasma treatment: a reactive carbon fiber cloth (manufacturer: Taiwan Carbon Technology Co., Ltd., model: AW-1114, average specific surface area of 1100 m ² /g, size 1030 × 1000 × 0.4 mm ³ ), at a normal pressure A nitrogen plasma apparatus [pen-like, nitrogen purity of 99.99%] was subjected to a plasma treatment of the activated carbon fiber cloth, and the movement of the normal piezoelectric material device was manipulated using a control device capable of XY two-axis movement. After the activated carbon fiber cloth is placed on the platform of the control device, the nitrogen plasma of the normal piezoelectric device is swept through the activated carbon fiber cloth in the weft direction of the activated carbon fiber cloth, and then the activity is followed. The direction of the warp direction of the carbon fiber cloth is swept through the activated carbon fiber cloth once, and this is used as the number of scanning circles "1 circle" (the power per unit area when the "one circle" is 3.18 W/mm ² , for each additional circle, the unit The amount of area processing power is doubled.). Wherein, the power of the plasma treatment is 100 watts, the flow rate of the nitrogen plasma is 15 ml/min, the diameter of the nitrogen plasma is 4 mm, and the working distance between the nitrogen plasma and the activated carbon fiber cloth is 1.5 cm. The normal piezoelectric slurry device has a moving speed of 30 mm/s.

Heat treatment: Next, the plasma-treated activated carbon fiber cloth was placed on a stainless steel pan and placed in a circulating oven, and the temperature of the circulating oven was controlled at 150 ° C for 2 hours to obtain a modified activated carbon fiber cloth. .

[Examples 2 to 4]

The manner of plasma treatment and heat treatment in Examples 2 to 4 was the same as in Example 1, except that the number of turns of the plasma treatment was changed. The number of cycles of the plasma treatment in Examples 1 to 4 is shown in Table 1.

[Comparative Example 1]

A commercially available and unmodified activated carbon fiber cloth (manufacturer: Taiwan Carbon Technology Co., Ltd., model: AW-1114, average specific surface area: 1,100 m ^ 2 /g) was used as Comparative Example 1.

[Application of modified activated carbon fiber cloth] button type rechargeable battery

The modified carbon fiber cloth of Examples 1 and 2 was separately prepared into a CR2032 button type battery according to a conventional method, wherein the structure of the button type rechargeable battery was from bottom to top in order: stainless steel lower cover, stainless steel sheet, high hydrophilicity A conductive carbon fiber cloth, a PP separator, a highly hydrophilic conductive carbon fiber cloth, a spring piece, and a stainless steel upper cover, and a concentration of 1 M H ₂ SO ₄ as an electrolyte.

A CR2032 button type battery was prepared in the same manner using Comparative Example 1 unmodified activated carbon fiber cloth.

[evaluation project]

Water contact angle

The modified activated carbon fiber cloths of Examples 1 to 4 and the water contact angle of Comparative Example 1 unmodified activated carbon fiber cloth were measured using a Sessile Drop method. The results of the water contact angle are shown in Table 1.

2. X-ray photoelectron spectroscopy (XPS)

The modified activated carbon fiber cloths of Examples 1 to 4 and the unmodified activated carbon fiber cloth of Comparative Example 1 were measured by X-ray photoelectron spectrometer (manufacturer: ULVAC-PHI, model: PHI 5000 Versaprobe II). The results of the X-ray photoelectron spectroscopy are shown in Tables 2 and 3.

3. Fourier transform infrared spectroscopy (FTIR)

The modified activated carbon fiber cloths of Examples 1 to 4 were measured by a Fourier transform infrared spectrum analyzer (manufactured by Thermo Scientific, model: Nicilet 6700). The results of Fourier transform infrared spectroscopy are shown in Figures 1 and 2.

4. AC Impedance Spectrum Test (EIS)

The button type battery obtained in the above Example 1 and Comparative Example 1 was subjected to an AC impedance spectrum test using a potentiostat (manufactured by Autolab, model: PGSTAT30), and buttons obtained in Example 1 and Comparative Example 1 were obtained. The interface contact resistance (Rc) of the battery was as shown in Table 1.

5. Charge and discharge test

The coin-type battery prepared in the above Examples 1 and 2 and Comparative Example 1 was subjected to charge and discharge tests by a potentiostat (manufactured by Autolab, model: PGSTAT30). In the case where the charge/discharge current density was 1.5 mA/cm ² , the specific capacitance values of the button type batteries of Examples 1 and 2 and Comparative Example 1 were as shown in Table 1, and the button types of Example 1 and Comparative Example 1 were used. The relationship between the specific capacitance of the battery and the charge-discharge current density is shown in Fig. 3.

Table 1         <TABLE border="1" borderColor="#000000" width="_0001"><TBODY><tr><td> </td><td> Example 1 </td><td> Example 2 </ Td><td> Example 3 </td><td> Example 4 </td><td> Comparative Example 1 </td></tr><tr><td> Number of cycles of plasma treatment (circle ) </td><td> 1 </td><td> 5 </td><td> 10 </td><td> 20 </td><td> 0 </td></tr>< Tr><td> The amount of power per unit area of the carbon fiber cloth treated by the plasma treatment (unit: W/mm²) </td><td> 3.18 </td><td> 15.9 </ Td><td> 31.8 </td><td> 63.6 </td><td> 0 </td></tr><tr><td> The amount of time per unit time of treatment of carbon fiber cloth by plasma treatment (unit :mm²/sec) </td><td> 318 </td><td> 318 </td><td> 318 </td><td> 318 </td>< Td> 0 </td></tr><tr><td> Water contact angle (unit: degree) </td><td> 0 </td><td> 0 </td><td> 0 < /td><td> 0 </td><td> 120 </td></tr><tr><td> Interface Contact Impedance of Button Cell (R_c) (Unit: Ohm/cm²) </td><td> 0.22 </td><td> --- </td><td> --- </td><td> --- </td><td> 5.26 </td></tr><tr><td> Button battery has a charge and discharge current density of 1.5mA/cm<sup>2</ Sup> specific capacitance value (unit: F/g) </td><td> 102 </td><td> 87 </td><td> --- </td><td> --- < /td><td> 75 </td></tr></TBODY></TABLE> Note: "---" means unmeasured.       

Table 2         <TABLE border="1" borderColor="#000000" width="_0002"><TBODY><tr><td> Region </td><td> Relative content (%) </td ></tr><tr><td> Example 1 </td><td> Example 2 </td><td> Example 3 </td><td> Example 4 </td><td > Comparative Example 1 </td></tr><tr><td> C1s </td><td> 76.2 </td><td> 63.4 </td><td> 64 </td><td> 66.8 </td><td> 87.4 </td></tr><tr><td> O1s </td><td> 22.4 </td><td> 34.6 </td><td> 33.6 </ Td><td> 31.1 </td><td> 11.3 </td></tr><tr><td> N1s </td><td> 1.4 </td><td> 2.0 </td>< Td> 2.4 </td><td> 2.1 </td><td> 1.3 </td></tr></TBODY></TABLE>

table 3         <TABLE border="1" borderColor="#000000" width="_0003"><TBODY><tr><td> Region </td><td> Peak </td><td> Position </td><td> Relative content (%) </td></tr><tr><td> Example 1 </td><td> Example 2 </td> <td> Example 3 </td><td> Example 4 </td><td> Comparative Example 1 </td></tr><tr><td> O1s </td><td> I( a) </td><td> 534.3 eV </td><td> 15 </td><td> 17 </td><td> 29 </td><td> 32 </td><td> 14 </td></tr><tr><td> II(a) </td><td> 532.5 eV </td><td> 67 </td><td> 62 </td><td > 60 </td><td> 63 </td><td> 57 </td></tr><tr><td> III(a) </td><td> 530.8 eV </td>< Td> 18 </td><td> 21 </td><td> 11 </td><td> 5 </td><td> 29 </td></tr><tr><td> C1s </td><td> I(b) </td><td> 289.3 eV </td><td> 16 </td><td> 16 </td><td> 12 </td><td > 18 </td><td> 23 </td></tr><tr><td> II(b) </td><td> 287.2 eV </td><td> 27 </td>< Td> 27 </td><td> 30 </td><td> 31 </td><td> 5 </td></tr><tr><td> III(b) </td>< Td> 285.8 eV </td><td> 14 </td><td> 11 </td><td> 11 </td><td> 10 </td><td> 13 </td></ Tr><tr><td> IV(b) </td><td> 284.7 eV </td><td> 23 </td><td> 26 </td><td> 27 </td><td> 24 </td><td> 26 < /td></tr><tr><td> V(b) </td><td> 284.1 eV </td><td> 20 </td><td> 20 </td><td> 20 </td><td> 17 </td><td> 33 </td></tr></TBODY></TABLE>[Note]: I(a): adsorbed water; II (a): CO, an oxygen atom in a hydroxyl group; III(a): C=O in a carbonyl group, a carboxyl group, an oxygen in a quinone; I(b): a carboxyl group and an ester group carbon; II(b) Carbon of a carbonyl group, a mercapto group and a ketone group; III (b): an alcohol group and an ether group; IV (b): graphite; V (b): a carbide.       

From the results of the water contact angles in Table 1, it is understood that the modified contact carbon fiber cloths of Examples 1 to 4 have a water contact angle of 0 degrees, indicating that the modified activated carbon fiber cloths of Examples 1 to 4 have high hydrophilicity. . The water contact angle of the unmodified activated carbon fiber cloth of Comparative Example 1 was 120 degrees, which represented that the hydrophilicity of the unmodified activated carbon fiber cloth of Example 1 was poor. It is proved that the hydrophilicity of the carbon fiber cloth after the plasma treatment can be made higher than that of the carbon fiber cloth before the plasma treatment by the plasma treatment.

From the results of Table 2, it is understood that the "O1s" peak of the modified activated carbon fiber cloths of Examples 1 to 4 represents a relative content of 22.4% to 34.6%, and the "O1s of the unmodified activated carbon fiber cloth of Comparative Example 1". The peak indicates a relative content of 11.3%, which proves that the plasma treatment does allow most of the carbon fibers in the carbon fiber cloth to be activated and react with oxygen to increase the oxygen on the carbon fiber cloth. 1 and 2, the modified activated carbon fiber cloths of Examples 1 to 4 have hydrophilic functional groups (OH, C=O, CO, -COOH), which proves that the treatment by the plasma can indeed make the carbon fiber cloth Most of the carbon fibers are activated and react with hydrophilic materials to attach hydrophilic functional groups to the carbon fibers.

According to the relative content of I(a) of the peak position of O1s in Tables 2 and 3, the relative content of water vapor adsorbed by the modified activated carbon fiber cloth of Example 1 was 3.36% (0.15×0.224×100%). The relative content of water vapor adsorbed by the modified activated carbon fiber cloth of Example 2 was 5.88% (0.17×0.346×100%), and the relative content of water vapor adsorbed by the modified activated carbon fiber cloth of Example 3 was 9.74% (0.29×). 0.336×100%), the relative content of water vapor adsorbed by the modified activated carbon fiber cloth of Example 4 was 9.95% (0.32×0.311×100%), which was higher than that of the unmodified activated carbon fiber cloth of Comparative Example 1. The relative content of gas is 1.58% (0.15×1.13×100%), which proves that the hydrophilicity of the carbon fiber cloth after the plasma treatment can be made greater than the hydrophilicity of the carbon fiber cloth before the plasma treatment.

From the results of the interface contact resistance in Table 1, it is understood that the button type battery obtained in Example 1 has a low interface contact resistance, and the button type battery obtained in Comparative Example 1 has a high interface contact resistance. As can be seen from the results of the charge and discharge tests in Table 1, the button type batteries produced in Example 1 and Example 2 can withstand a faster charging rate, and the button type electric power produced in Comparative Example 1 can only withstand slower speeds. Charging rate. As can be seen from FIG. 3, the button type battery produced in Example 1 has a higher specific capacitance, and the button type battery obtained in Comparative Example 1 has a lower specific capacitance. It is proved that the electrical conductivity of the carbon fiber cloth after the plasma treatment can be made greater than the conductivity of the carbon fiber cloth before the plasma treatment, so that the button type battery has better performance.

It is demonstrated by Figs. 4 to 7 that the plasma treatment does cause the carbon fibers in the carbon fiber cloth to be broken to form a loose structure.

In summary, the carbon fiber cloth can react with the hydrophilic substance to form a hydrophilic functional group on the carbon fiber cloth by the plasma treatment, thereby improving the hydrophilicity of the carbon fiber cloth and the plasma treatment. Since the carbon fibers in the carbon fiber cloth are broken to form a loose structure, the conductivity of the carbon fiber cloth is improved, and the object of the present invention can be achieved.

However, the above is only the embodiment of the present invention, and the scope of the invention is not limited thereto, and all the equivalent equivalent changes and modifications according to the scope of the patent application and the patent specification of the present invention are still The scope of the invention is covered.

Other features and effects of the present invention will be apparent from the following description of the drawings, wherein: FIG. 1 is a Fourier-transition infrared spectrum of Examples 1 to 4 in a nitrogen (N ₂ ) environment. [Fig. 2] is a Fourier-transition infrared spectrum of Examples 1 to 4 in an atmospheric environment; and [Fig. 3] is a charge and discharge test result of the button type battery of Example 1 and Comparative Example 1, in charge and discharge Fig. 4 is a photograph of a scanning electron microscope of Example 1 when the current density is 1.5 mA/cm ² ; [Fig. 5] is a scanning electron of the embodiment 2 Photograph of the microscope; [Fig. 6] is a photograph of the scanning electron microscope of Example 3; and Fig. 7 is a photograph of the scanning electron microscope of Example 4.

Claims (9)

A method for improving the hydrophilicity and electrical conductivity of a carbon fiber cloth comprises the steps of: applying a plasma treatment to a carbon fiber cloth, reacting the carbon fiber cloth with a hydrophilic substance to form a hydrophilic functional group on the carbon fiber cloth, And breaking the carbon fiber in the carbon fiber cloth to form a loose structure, and the hydrophilicity and conductivity of the carbon fiber cloth after the plasma treatment are greater than the hydrophilicity and conductivity before the plasma treatment of the carbon fiber cloth; and one in the plasma Heat treatment after treatment. The method of improving the hydrophilicity and electrical conductivity of a carbon fiber cloth according to claim 1, wherein the heat treatment has a temperature in the range of 120 to 170 °C. The method for improving the hydrophilicity and electrical conductivity of a carbon fiber cloth according to claim 1, wherein the plasma treatment has a unit time treatment area of the carbon fiber cloth of 222 mm ² /sec to 318 mm ² /sec. The method for improving the hydrophilicity and electrical conductivity of a carbon fiber cloth according to claim 1, wherein the power treatment amount per unit area of the plasma treatment to the carbon fiber cloth ranges from 3.18 W/mm ² to 63.6 W/mm ² . A method of improving the hydrophilicity and electrical conductivity of a carbon fiber cloth according to claim 1, wherein the plasma treatment causes the surface of the carbon fiber cloth to have a temperature in the range of 50 to 90 ° C when the plasma treatment is performed. The method of improving the hydrophilicity and electrical conductivity of a carbon fiber cloth according to claim 1, wherein the hydrophilic substance is an oxygen-containing substance. The method of improving the hydrophilicity and electrical conductivity of a carbon fiber cloth according to claim 1, wherein the oxygen-containing substance is derived from the atmosphere, oxygen plasma, or a combination thereof. The method for improving the hydrophilicity and electrical conductivity of a carbon fiber cloth according to claim 1, wherein the plasma-treated plasma is selected from the group consisting of nitrogen plasma, oxygen plasma, helium gas plasma, and argon plasma. Or a combination of these. The method of improving the hydrophilicity and electrical conductivity of a carbon fiber cloth according to claim 1, wherein the plasma treatment power ranges from 50 watts to 700 watts.