CN116435109A - A self-supporting dry-laid film roll with high strength and high conductivity and its application - Google Patents

Abstract

The invention belongs to the technical field of electrochemical energy storage materials, and particularly relates to a self-supporting dry film roll with high strength and high conductivity and application thereof. The invention adopts a whisker carbon tube material with surface modification as an additive, and generates a network structure with strong interface bonding by constructing strong hydrogen bond action at the interface of the whisker carbon tube and an adhesive, thereby preparing a self-supporting dry film roll with high strength and high conductivity. The invention utilizes the characteristic of high graphitization degree of the whisker carbon tube, compared with the carbon nano tube, the strength is higher, compared with the conventional carbon fiber material, the conductivity is higher, and the strength and the conductivity of the self-supporting dry film roll are improved simultaneously. The conductivity of the dry electrode prepared by the invention is improved by 30-40% compared with that of a dry electrode prepared by taking Super P carbon black as a conductive agent; the volume specific capacity is improved by 3 to 8 percent compared with that of a dry electrode prepared by taking Super P carbon black as a conductive agent.

Description

A self-supporting dry-laid film roll with high strength and high conductivity and its application

technical field

The invention belongs to the technical field of electrochemical energy storage materials, in particular to a self-supporting dry-process film roll with high strength and high conductivity and its application.

Background technique

With the rapid development of new energy vehicles, people have put forward higher requirements on the energy density, rate, life, and environmental protection of electrochemical energy storage devices (such as lithium-ion batteries, sodium-ion batteries, supercapacitors, etc.). As an important part of electrochemical energy storage devices, electrodes profoundly affect the performance of energy storage devices. At present, the industrial preparation of positive and negative electrodes in lithium and sodium batteries mostly adopts wet coating process. The wet coating process is mainly to mix the negative electrode or positive electrode powder with a solvent to make a slurry, and then apply it to the current collector, dry it, and compact it to prepare it. The main solvent used in the wet coating process is N-methyl-2-pyrrolidone (NMP), which has high solvent toxicity, fast moisture absorption, large investment in solvent recovery equipment, large floor space, and high energy consumption. The electrode sheet density is limited and other issues.

The opposite of the wet coating process is the dry electrode preparation technology. The dry electrode preparation rarely introduces or even does not introduce solvents. The formed film has a high compaction density, less impurities, and low requirements on the production environment. It can greatly simplify the production process of the pole piece and improve the bulk density of the electrode. However, since the key step in the preparation of dry-process electrodes is to prepare high-density, self-supporting dry-process film rolls, there are problems such as easy to break strips, easy to produce holes, drop grains, and uneven edge cracks in the continuous production process, which seriously affects The cost and product qualification rate of dry electrode continuous preparation. On the basis of ensuring the overall conductivity and bulk density of the electrode, increasing the strength of the self-supporting dry film is the key to the development of dry electrode preparation technology.

The Chinese patent with the publication number CN107895794A discloses a high specific energy lithium carbon fluoride battery. The positive electrode material of the battery includes fluorinated carbon modified by elemental sulfur, a conductive agent, and a binder; the solute in the electrolyte of the battery is not Lithium bistrifluoromethanesulfonimide and lithium nitrate in 1,3-dioxolane and ethylene glycol dimethyl ether as solvents. The battery uses elemental sulfur-modified fluorinated carbon to increase the active specific capacity of the material, but the patent does not disclose the specific increase in the specific capacity.

Based on this, the present invention uses the surface-modified whisker carbon tube material as an additive to prepare a high-strength self-supporting dry-process film roll through the strong hydrogen bond at the interface between the whisker carbon tube and the adhesive, and is used to prepare dry-process electrode, in order to increase the volume specific capacity of the electrode.

Contents of the invention

The purpose of the present invention is to address the shortcomings of the dry electrode preparation technology in the prior art, using a surface-modified whisker carbon tube material as an additive, through the construction of strong hydrogen bonding at the interface between the whisker carbon tube and the adhesive , resulting in a strongly interfacially bonded network structure, leading to the fabrication of a self-supporting dry-laid film roll with high strength and high conductivity. The present invention utilizes the characteristics of high graphitization degree of whisker carbon tubes, higher strength than carbon nanotubes, and higher conductivity than conventional carbon fiber materials, which is conducive to simultaneously improving the strength of self-supporting dry-process film rolls and conductivity.

The invention also provides a preparation method of the self-supporting dry-laid film roll with high strength and high conductivity.

Further, the application of the self-supporting dry-process film roll in the preparation of high-volume-specific capacity supercapacitor dry-process electrodes is also provided.

In order to achieve the above technical purpose, the present invention adopts the following technical solutions:

A self-supporting dry-laid film roll with high strength and high conductivity prepared from surface-modified whisker carbon tubes, binders, conductive agents and active substances.

Specifically, the mass ratio of the surface-modified carbon whisker tube, binder, conductive agent and active material is (0.01-0.1):(0.03-0.08):(0-0.08):(0.82-0.97).

Preferably, the mass ratio of the surface-modified carbon whisker tube, binder, conductive agent and active material is (0.01-0.03):(0.04-0.08):(0-0.03):(0.85-0.95).

Specifically, the carbon whisker tube has a fibrous structure and a high degree of graphitization, the transverse dimension of the fiber is 50-100 nanometers, the longitudinal dimension is 3-10 microns, and the graphitization range is 60-80%.

Specifically, in the surface-modified carbon whisker tubes, the surface-modifying groups include, but are not limited to, one or more of hydroxyl, carboxyl, and amino groups.

Specifically, the binder includes but is not limited to one or more of polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber, and carboxymethyl cellulose.

Specifically, the conductive agent includes, but is not limited to, one or more of acetylene carbon black, Super P carbon black, and graphite powder.

Specifically, the active material includes, but is not limited to, one or more of supercapacitor activated carbon, nickel-cobalt lithium manganese oxide, lithium iron phosphate, graphite, carbon-silicon composite, sodium-ion battery positive electrode material, hard carbon, and fluorinated graphite. kind.

Further, the present invention also provides a method for preparing the above-mentioned self-supporting dry film roll by a pure dry method, comprising the following steps:

1) The surface-modified carbon whisker tubes, binders, conductive agents and active materials are mixed according to the ratio and subjected to fiberization treatment to obtain a dry powder of the fibrous mixture;

2) The fibrous mixture obtained in step 1) is continuously rolled, and then wound up to obtain the high-strength and high-conductivity self-supporting dry-laid film roll.

Specifically, in step 1), the mass ratio of the surface-modified carbon whisker tube, binder, conductive agent and active material is (0.01-0.03): (0.04-0.08): (0-0.03): ( 0.85～0.95).

Specifically, in step 1), the surface-modified carbon whisker tubes, binder, conductive agent and active material are all in powder form.

Specifically, the airflow fiberization preferably adopts an airflow mill, the airflow velocity is 0.5-5 L/min, and the airflow fiberization time is 10min-2h, preferably 10-30min, or preferably 30-2h.

Specifically, in step 2), the continuous rolling temperature is 20-200°C.

Specifically, the continuous rolling is preferably three times of rolling, rolling the fibrous mixture to a thickness of 300-350 microns, 200-250 microns and 100-120 microns in sequence, or rolling the fibrous mixture to a thickness of 300-300 microns in sequence. 350 microns, 100-120 microns and 40-60 microns thick films.

Further, the present invention also provides a method for preparing the above-mentioned self-supporting dry film roll by a dry-wet combination method, comprising the following steps:

The surface-modified whisker carbon tubes, binder and active material are mixed according to the ratio, and placed in a solvent, and then ball milled to achieve pre-fibrillation, followed by medium-temperature banburying and continuous rolling, and finally a self-supporting dry process film rolls.

Specifically, the mass ratio of the surface-modified carbon whisker tube, the binder and the active material is (0.01-0.03):(0.04-0.08):(0.85-0.95).

Further, the method for preparing the above-mentioned self-supporting dry film roll by the dry-wet combination method includes the following steps:

(1) Kneading powder: disperse the surface-modified hydroxyl carbon whisker tubes, binders and active substances in a mixed solvent of water and ethanol according to the proportion, and perform ball milling to obtain a pre-fiberized paste;

(2) Banbury mixing: put the paste obtained in step (1) in a banbury mixer for 30 to 40 minutes and banbury at a temperature of 60 to 120°C to obtain a fibrous mixture;

(3) Rolling: The fibrous mixture obtained in step (2) is continuously rolled, and then wound up to obtain the self-supporting dry-laid film roll.

Specifically, the binder in step (1) is a polytetrafluoroethylene emulsion, preferably an aqueous polytetrafluoroethylene emulsion with a mass fraction of 50-70%.

Specifically, step (1) in the mixed solvent of water and ethanol, the volume ratio of ethanol and water is 1:1 to 1.5:1; three raw materials (whisker carbon tubes with surface-modified hydroxyl groups, binders and active substances) The mass ratio of the sum to the mixed solvent is 1:2 to 1:4.

Specifically, in step (1), shear force is used to uniformly mix the materials during ball milling; the ball milling speed is preferably 350-450 r/min, and the ball milling time is preferably 30-60 min.

Specifically, in step (3), the continuous rolling temperature is 20-200°C.

Specifically, in step (3), the continuous rolling is preferably three times, rolling the fibrous mixture to a thickness of 300-350 microns, 200-250 microns and 100-120 microns in turn, or rolling the fibrous mixture Sequential rolling to 300-350 microns, 100-120 microns and 40-60 microns thick film.

Further, based on a general inventive concept, the present invention also provides the application of the self-supporting dry-process film roll in the preparation of high-volume specific capacity supercapacitor dry-process electrodes.

Further, based on a general inventive concept, the present invention also provides a dry-process electrode for a supercapacitor with high volume specific capacity prepared by using the self-supporting dry-process film roll.

Specifically, the preparation method of the high volume specific capacity supercapacitor dry electrode comprises the following steps:

First, the prepared self-supporting dry-process film roll and the current collector are rolled and combined at high temperature on a rolling machine, then sliced, dried, and positive and negative electrode sheets are obtained;

Then clamp the diaphragm (mainly polyolefin diaphragm based on polyethylene and polypropylene, cellulose diaphragm and ceramic composite diaphragm, preferably a composite diaphragm of polyethylene and polypropylene) between the positive and negative electrode sheets, and inject carbonic acid The propylene ester (PC) electrolyte is finally assembled to prepare the high volume specific capacity supercapacitor dry electrode.

Specifically, the mass ratio of the self-supporting dry film roll to the current collector is 1-1.5:1.

Specifically, the current collector is preferably one or more of aluminum foil, copper foil, and lithium foil, and the thickness of the current collector is 8-20 microns.

Specifically, the temperature of the high-temperature rolling compounding is 60-250°C, preferably 150-250°C.

Specifically, the high-temperature rolling composite rate is 1-60 minutes per meter.

Specifically, the propylene carbonate (PC) electrolyte is 1˜1.5 mol/L tetraethylammonium tetrafluoroborate (TEABF ₄ ) propylene carbonate (PC).

Specifically, the dosage of the propylene carbonate (PC) electrolyte is 0.01g-0.8g/F, wherein F is a capacitance unit.

Compared with the prior art, the present invention has the advantages of:

1) the present invention adopts a kind of surface-modified whisker carbon tube as the reinforcing agent of self-supporting dry-process film roll, through the strong hydrogen bond action of whisker carbon tube surface group and binder group at interface, produces strong Interfacially bonded network structure for preparation of high-strength and highly conductive self-supporting dry-laid film rolls.

2) The preparation method of the present invention improves the self-supporting dry-laid film rolls during the preparation process due to low strength caused by film roll breaks, holes in the middle, edge powder drop, cracking, unevenness and other problems. At the same time, carbon whisker tubes have the characteristics of a high degree of graphitization. Compared with carbon nanotubes, they have stronger strength and higher conductivity than conventional carbon fiber materials, which is conducive to simultaneously improving the strength and conductivity.

3) In the present invention, the strength of the self-supporting dry-process film roll prepared by the whisker carbon tubes modified by surface hydroxyl groups is improved by 25%～ 38%; The volume density of the self-supporting dry-process film roll prepared by the whisker carbon tube modified by surface hydroxyl in the present invention is more than the volume density of the self-support dry-process film roll prepared by Super P carbon black as the conductive agent. 1% to 5%.

4) The present invention makes it possible to prepare self-supporting dry-laid film rolls with a thickness less than 60 microns by improving the strength of the prepared self-supporting dry-laid film rolls.

5) The conductivity of the dry electrode prepared by the present invention is 30% to 40% higher than that of the dry electrode prepared by Super P carbon black as the conductive agent; the volume of the dry electrode prepared by the present invention is The specific capacity is increased by 3% to 8% compared with the volume specific capacity of the dry electrode prepared with Super P carbon black as the conductive agent.

6) A surface-modified carbon whisker tube conductive agent in the present invention has high cost performance, can completely replace the currently used high Super P carbon black, reduce the production cost of the enterprise, and improve the overall performance of the electrode at the same time.

Description of drawings

Fig. 1 is the microstructure schematic diagram of self-supporting dry-laid film roll of the present invention;

Fig. 2 is the electron micrograph of the microstructure of the self-supporting dry film roll prepared in Example 1 of the present invention;

Fig. 3 is the electron microscope topography figure of the whisker carbon tube (conductive agent) of surface-modified hydroxyl used in Example 1 of the present invention;

Fig. 4 is the infrared characterization comparison diagram of the surface groups of the surface-modified whisker carbon tube used in Example 1 of the present invention and the non-surface-modified whisker carbon tube used in Example 2;

Figure 5 is a comparison of the capacitance performance test results of the high volume specific capacity supercapacitor dry electrode prepared in Examples 4, 5, and 6 of the present invention;

Fig. 6 is the comparison of the capacitance DC resistance performance test results of the high volume specific capacity supercapacitor dry method electrodes prepared in Examples 4, 5, and 6 of the present invention;

Fig. 7 is a comparison of the capacitance cycle performance test results of the high-volume-specific-capacity supercapacitor dry-process electrodes prepared in Examples 4, 5, and 6 of the present invention.

Detailed ways

The following examples will further illustrate the present invention in conjunction with the accompanying drawings. This embodiment is carried out on the premise of the technical solution of the present invention, and detailed implementation methods and processes are given, but the protection scope of the present invention is not limited to the following embodiments.

The experimental methods without specific conditions indicated in the following examples are generally in accordance with conventional conditions, and the raw materials and reagents used are conventional commercially available products unless otherwise specified.

Example 1

A self-supporting dry film roll with high strength and high conductivity, composed of carbon whisker tubes (as shown in Figure 3) of surface-modified hydroxyl Topography, as can be clearly seen from Figure 3 that the surface of the whisker carbon tube has hydroxyl functional groups), polytetrafluoroethylene (PTFE) powder and supercapacitor activated carbon powder are prepared, during preparation, the whisker carbon of surface modification hydroxyl The mass ratio of tube, polytetrafluoroethylene powder and supercapacitor activated carbon powder is 0.02:0.07:0.91.

As shown in Figure 1, the preparation method of the above-mentioned self-supporting dry film roll with high strength and high conductivity, the specific steps are as follows:

1) The carbon whisker tubes (i.e. BH carbon whisker tubes) with surface-modified hydroxyl groups, which are prepared with reference to the carbon nanotubes in the patent document (CN101027434A method for preparing vapor-phase grown carbon fibers and device thereof) , and the inventor carried out hydroxyl modification on this basis and finally obtained a surface-modified hydroxyl whisker carbon tube with a diameter of 150nm. Activated carbon powder (YP50F, purchased from Kuraray Co., Japan) was placed in the airflow mill according to the above ratio for airflow mixing and fiberization treatment. The airflow speed was 3L/min, and the airflow fiberization time was 20min to obtain a fibrous mixture dry powder. Powder; the carbon whisker tube has a fibrous structure and a high degree of graphitization, the transverse dimension of the fiber is 50-100 nanometers, the longitudinal dimension is 3-10 microns, and the graphitization range is 60-80%;

2) The fibrous mixture obtained in step 1) is continuously rolled three times at a rolling temperature of 120° C., and rolled successively to films with a thickness of 300 to 350 microns, 200 to 250 microns and 100 to 120 microns in thickness. In the process, through the strong hydrogen bond interaction between the hydroxyl group on the surface of the whisker carbon tube and the fluorine-containing group of polytetrafluoroethylene at the interface, a network structure with strong interfacial bonding is generated, and then rolled up to obtain the high strength and high conductivity. Self-supporting dry-laid film roll, the electron micrograph of the microstructure of the self-supporting dry-laid film roll prepared in Example 1 is as shown in Figure 2, as can be seen from Figure 2, the fibrous network structure entangles the surface modified hydroxyl Whisker carbon tubes surround and radially shoot out from the carbon tip, demonstrating the strong interaction between the surface-modified hydroxyl carbon whisker tubes and PTFE and its key role in the fiberization of PTFE.

Example 2

Embodiment 2 provides a kind of preparation method of conventional self-supporting dry-process film roll, and the difference between embodiment 2 and embodiment 1 is that described self-supporting dry-process film roll is made of whisker carbon without surface-modified hydroxyl tube (i.e. AH whisker carbon tube, the whisker carbon tube is prepared by referring to the carbon nanotube in the patent document (CN101027434A method for preparing vapor-phase grown carbon fiber and its device), without hydroxyl modification, with a tube diameter of 75nm, Described material comes from Henan Keiwei Nano Carbon Material Co., Ltd., as shown in Figure 4, and Figure 4 is the comparison of BH and AH, it can be seen that the surface of BH has been modified with hydroxyl, and the surface of AH has no hydroxyl), polytetrafluoroethylene powder and The supercapacitor activated carbon powder is prepared; the ratio of raw materials and the preparation method in embodiment 2 are the same as in embodiment 1.

Example 3

Embodiment 3 provides a kind of preparation method of conventional self-supporting dry-laid film roll, and the difference between embodiment 3 and embodiment 1 is that described self-supporting dry-laid film roll is made of Super P carbon black (Super P Li, Swiss Temi high conductivity carbon black), polytetrafluoroethylene powder and supercapacitor activated carbon powder are prepared; the ratio of raw materials and the preparation method in embodiment 3 are the same as in embodiment 1.

See Table 1 for comparison of performance test results of self-supporting dry-process film rolls prepared in Example 1, Example 2, and Example 3 (test with reference to the national standard "GB1040 "Test Method for Tensile Properties of Plastics")." See Table 1 for the comparison of film strength values measured after rolling for the first, second and third time.

Table 1 Comparison results of the strength test values of the self-supporting dry-process films prepared in Examples 1-3.

Table 1 is the test result of three kinds of self-supporting dry-laid film rolls of embodiment 1 to embodiment 3, as can be seen from the table, the strength of the self-supporting dry-laid film roll that adds surface hydroxyl modified whisker carbon tube to make increases increased by 25% to 38%, and the body density increased by 1% to 5%.

Example 4

Embodiment 4 provides a high-volume-specific-capacity supercapacitor dry-process electrode, which is formed by laminating the self-supporting dry-process film roll prepared in Example 1 on an aluminum foil current collector. Generally, the thinner the aluminum foil, the overall performance The higher the thickness, the more difficult it will be to prepare electrodes continuously if the aluminum foil is too thin. In this example, the thickness of the aluminum foil is 8-20 microns, and the ratio of the weight of the self-supporting dry film roll prepared in Example 1 to the weight of the aluminum foil is 1.5:1.

The preparation method of the high volume specific capacity supercapacitor dry method electrode, the specific steps are:

First, the self-supporting dry-process film roll prepared in Example 1 and the aluminum foil (current collector) are rolled and combined directly on a rolling mill at a temperature of 200° C. at a rate of 30 minutes per meter to realize the rolling of the self-supporting dry-process film. Covered on the aluminum foil current collector, then sliced and dried to obtain positive and negative electrode sheets;

Then clamp the diaphragm (mainly polyethylene, polypropylene-based polyolefin diaphragm, cellulose diaphragm and ceramic composite diaphragm, in this embodiment, a composite diaphragm of polyethylene and polypropylene) in the middle of the positive and negative electrode sheets, Inject 1mol/L tetraethylammonium tetrafluoroborate (TEABF ₄ ) of propylene carbonate (PC) electrolyte (the amount of electrolyte is 0.6g/F, where F is the capacitance unit), and finally install the button capacitor through the tablet machine , preparing the high volume specific capacity supercapacitor dry electrode.

Example 5

Embodiment 5 provides a kind of preparation method of supercapacitor dry-process electrode with high volume specific capacity, and described electrode is that the self-supporting dry-process film roll that embodiment 2 prepares is laminated on the aluminum foil current collector and compounded (this embodiment The thickness of the aluminum foil is 8-16 microns), and the preparation method of the dry electrode in Example 5 is the same as that in Example 4.

Example 6

Embodiment 6 provides a method for preparing a dry-process electrode for a supercapacitor with a high volume specific capacity, and the electrode is formed by laminating the self-supporting dry-process film roll prepared in Example 3 on an aluminum foil current collector (this embodiment The thickness of the aluminum foil is 8-16 microns), and the preparation method of the dry electrode in Example 6 is the same as that in Example 4.

Refer to Table 2 for comparison of performance test results of dry electrodes prepared in Example 4, Example 5, and Example 6. (Refer to international standards: IEC 62576-2009 and IEC 62391-1-2006)

Table 2 Comparison of capacitance performance test results of dry-process electrodes prepared in Examples 4-6.

Table 2 is the performance test results of three kinds of supercapacitor dry-process electrodes in embodiment 4 to embodiment 6. As can be seen from the results, the resistance of the supercapacitor dry-process electrode added with surface hydroxyl-modified whisker carbon tubes is reduced by 30- 50%, and the volume ratio capacity has increased by 3% to 8%.

Figure 5 is a comparison of the capacitance performance test results of the high volume specific capacity supercapacitor dry process electrodes prepared in Examples 4, 5, and 6 of the present invention; The comparison of the capacitance DC resistance performance test results of the capacitor dry electrode; Fig. 7 is the comparison of the capacitance cycle performance test results of the high volume specific capacity supercapacitor dry electrode prepared by the embodiment of the present invention 4, 5, 6, from Fig. 5, 6, 7, it can be concluded that the supercapacitor dry electrode prepared by surface hydroxyl-modified whisker carbon tubes has better Larger capacity, lower DC resistance, and better cycle life.

Example 7

Embodiment 7 provides a self-supporting dry film roll with high strength and high conductivity, which is prepared from whisker carbon tubes, polytetrafluoroethylene emulsions and supercapacitor activated carbon powders with surface-modified hydroxyl groups. During preparation, surface modification The mass ratio of the hydroxyl whisker carbon tube, the polytetrafluoroethylene emulsion and the supercapacitor activated carbon powder is 0.02:0.07:0.91, and the mass fraction of the polytetrafluoroethylene (PTFE) emulsion is 60%.

The preparation method of the above-mentioned self-supporting dry film roll with high strength and high conductivity, the specific steps are as follows:

(1) and powder: the whisker carbon tube (being BH whisker carbon tube of surface modification hydroxyl, described whisker carbon tube is the carbon nanotube in the reference patent document (CN101027434A preparation method and device thereof of vapor phase growth carbon fiber) Prepared, and the inventor carried out hydroxyl modification on this basis to finally obtain the surface-modified hydroxyl whisker carbon tube, the material comes from Henan Clive Nano Carbon Material Co., Ltd.), polytetrafluoroethylene emulsion and supercapacitor Activated carbon powder (YP50F, purchased from Kuraray, Japan) was dispersed in a mixed solvent of water and ethanol with a volume ratio of 1:1 according to the above ratio, and ball milled, wherein three raw materials (whisker carbon tubes with hydroxyl groups on the surface) , polytetrafluoroethylene emulsion and supercapacitor activated carbon powder) and the mass ratio of the mixed solvent is 1:3; the ball milling speed is 400r/min, and the ball milling time is 60min, so that polytetrafluoroethylene is prefibrillated and prefibrillated paste;

(2) Banbury mixing: put the paste obtained in step (1) in a banbury mixer for 30 to 40 minutes and banbury at a temperature of 60°C to obtain a fibrous mixture;

(3) Rolling: The fibrous mixture obtained in step (2) is continuously rolled three times at a rolling temperature of 120°C, and rolled successively to 300-350 microns, 200-250 microns and 100-120 microns thick film , and then rolled to obtain the self-supporting dry-laid film roll.

Example 8

Embodiment 8 provides a self-supporting dry-laid film roll with high strength and high conductivity. The difference between embodiment 8 and embodiment 1 is that in step 2), the fiberized mixture obtained in step 1) is continuously rolled Rolling three times, rolling it successively to 300-350 microns, 100-120 microns and 40-60 microns thick films; the ratio of raw materials in embodiment 8 is the same as that in embodiment 1.

Example 9

Embodiment 9 provides a self-supporting dry-laid film roll with high strength and high conductivity. The difference between embodiment 9 and embodiment 1 is that the self-supporting dry-laid film roll is modified by the whiskers of hydroxyl groups on the surface. Carbon tubes, Super P carbon black (Super P Li, Swiss Temi high-conductivity carbon black), polytetrafluoroethylene powder and supercapacitor activated carbon powder are prepared. During preparation, whisker carbon tubes and Super P carbons with hydroxyl groups The mass ratio of black, polytetrafluoroethylene powder and super capacitor activated carbon powder is 0.02:0.07:0.02:0.89. The preparation method in Example 9 is the same as that in Example 1.

Example 10

Embodiment 10 provides a self-supporting dry-laid film roll with high strength and high conductivity. The difference between embodiment 10 and embodiment 1 is that the self-supporting dry-laid film roll is made of whiskers with hydroxyl groups modified on the surface. Carbon tube, polytetrafluoroethylene powder and nickel-cobalt-lithium manganese oxide powder are prepared. During preparation, the mass ratio of surface-modified hydroxyl whisker carbon tube, polytetrafluoroethylene powder and nickel-cobalt lithium manganate powder is 0.02:0.06 :0.92. The preparation method in Example 10 is the same as that in Example 1.

After testing, the self-supporting dry-laid film rolls obtained in Examples 7, 8, 9, and 10 also have good strength and bulk density, and their performance is equivalent to that of Examples 1, 2, and 3.

The preparation method adopted by the self-supporting dry-process film roll with high strength and high conductivity in the present invention not only simplifies the preparation method of the dry-process electrode in the prior art but also improves its overall performance, has good application value, and is suitable for Technology promotion and application.

The basic principles and main features of the present invention and the advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (10)

1. A self-supporting dry film roll with high strength and high conductivity is characterized by being prepared from whisker carbon tubes with surface modification, a binder, a conductive agent and an active substance; the mass ratio of the whisker carbon tube with the surface modified, the binder, the conductive agent and the active substance is (0.01-0.1): (0.03-0.08): (0-0.08): (0.82-0.97).

2. The self-supporting dry film roll with high strength and high conductivity according to claim 1, wherein in said surface-modified whisker carbon tube, surface-modifying groups include, but are not limited to, one or more of hydroxyl, carboxyl, amino;

the binder comprises one or more of polytetrafluoroethylene, polyvinylidene fluoride, styrene-butadiene rubber and carboxymethyl cellulose;

the conductive agent comprises one or more of acetylene black, super P carbon black and graphite powder;

the active substances include, but are not limited to, one or more of super capacitor active carbon, nickel cobalt lithium manganate, lithium iron phosphate, graphite, carbon-silicon composite, sodium ion battery positive electrode material, hard carbon and graphite fluoride.

3. A method of purely dry preparing a free-standing dry film roll according to claim 1 or 2, comprising the steps of:

1) Carrying out air flow mixing and fiberizing treatment on the whisker carbon tube with the surface modified, the binder, the conductive agent and the active substance according to the proportion to obtain fiberized mixture dry powder;

2) Continuously rolling the fiberizing mixture obtained in the step 1), and then rolling to obtain the high-strength and high-conductivity self-supporting dry film roll.

4. A method according to claim 3, wherein in step 1), the mass ratio of the surface-modified whisker carbon tube, the binder, the conductive agent and the active material is (0.01 to 0.03): (0.04-0.08): (0-0.03): (0.85-0.95);

the air flow speed of the air flow fiberization is 0.5-5L/min, and the air flow fiberization time is 10 min-2 h.

5. A method according to claim 3, wherein in step 2) the continuous rolling temperature is 20 to 200 ℃.

6. A method of preparing the self-supporting dry film roll of claim 1 or 2 by a dry-wet bonding process, comprising the steps of:

mixing the whisker carbon tube with the surface modified, the binder and the active substance according to the proportion, placing the mixture in a solvent, ball milling the mixture to realize pre-fiberization, and then carrying out medium-temperature banburying and continuous rolling to finally obtain the self-supporting dry film roll.

7. The method of claim 6, comprising the steps of:

(1) And powder: dispersing whisker carbon tubes with surface modified hydroxyl groups, a binder and active substances in a mixed solvent of water and ethanol according to a proportion, and performing ball milling to obtain a pre-fiberized paste;

(2) Banburying: placing the paste obtained in the step (1) into an internal mixer for banburying for 30-40 min at the banburying temperature of 60-120 ℃ to obtain a fiberized mixture;

(3) Rolling: continuously rolling the fiberizing mixture obtained in the step (2), and then rolling to obtain the self-supporting dry film roll.

8. The method of claim 7, wherein in the step (1), the mass ratio of the whisker carbon tube with surface modification, the binder and the active substance is (0.01-0.03): (0.04-0.08): (0.85-0.95);

the adhesive in the step (1) is polytetrafluoroethylene aqueous emulsion with the mass fraction of 50-70%;

in the mixed solvent of the water and the ethanol in the step (1), the volume ratio of the ethanol to the water is 1:1-1.5:1; the mass ratio of the sum of the whisker carbon tube with the surface modified hydroxyl, the binder and the active substance to the mixed solvent is 1: 2-1: 4.

9. the method of claim 7, wherein in the step (3), the continuous rolling temperature is 20 to 200 ℃.

10. Use of a self-supporting dry film roll with high strength and high conductivity according to claim 1 or 2 for the preparation of a high volume specific capacity supercapacitor dry electrode.

Images