KR20170078461A - Fiber-type secondary battery and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a fiber type secondary battery and a manufacturing method thereof, wherein a fiber type secondary battery according to an embodiment of the present invention includes a core fiber, a first electrode formed to surround the core fiber, And a second electrode formed to surround the separator, wherein the core fiber is formed using at least one of cotton, wool fiber, silk, and cotton.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a secondary battery,

The present invention relates to a fiber type secondary battery and a manufacturing method thereof.

Flexibility of the device is required due to the integration of clothes in small electronic devices, body attachment bio-implantation, etc., and a flexible battery is indispensably required for this.

In the prior art, studies have been made to fabricate a fiber-type battery applicable to a wearable device using carbon nanotubes having high electrical conductivity, large capacity, and low density characteristics. However, , There was a limit in manufacturing a fibrous battery.

Therefore, there is a need for a new technology for fabricated batteries and fabrication methods that are flexible and capable of high capacity and light weight.

In this connection, Korean Patent Laid-Open No. 10-2013-0045218 (entitled Cable Type Rechargeable Battery) discloses an internal electrode having an internal current collector and an internal electrode active material layer formed around the external surface of the internal current collector; A separation layer formed surrounding the outer surface of the inner electrode to prevent shorting of the electrode; And an outer electrode formed around the outer surface of the separation layer and including an outer electrode active material layer and an outer current collector including at least one of conductive paste and carbon fiber.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fiber type secondary battery which can be used in various electronic devices and a manufacturing method which do not require a current collector.

It is to be understood, however, that the technical scope of the present invention is not limited to the above-described technical problems, and other technical problems may exist.

According to one aspect of the present invention, there is provided a fiber secondary cell comprising a core fiber, a first electrode formed to surround the core fiber, a separator formed to surround the first electrode, And a second electrode formed to surround the separator, wherein the core fiber is formed using at least one of cotton, wool fiber, silk, and brim.

According to another aspect of the present invention, there is provided a method of fabricating a fibrous secondary cell, including: forming a first electrode and a second electrode; Supporting the electrolyte on the core fiber; A method of manufacturing a secondary battery comprising the steps of forming a first electrode, a separator, and a second electrode on a core fiber sequentially to produce a fibrous secondary battery, wherein the core fiber is formed of a fabric such as cotton, wool fiber, silk and hemp.

According to any one of the above-mentioned objects of the present invention, it is possible to reduce the amount of the metal current collector and the fibrous secondary battery and the weight of the electronic device in manufacturing the fibrous secondary battery.

Further, according to any one of the means for solving the problems of the present invention, the risk of leakage of the electrolyte can be reduced by using the cotton fiber as the core fiber in the production of the fibrous secondary battery.

In addition, according to any one of the means for solving the problems of the present invention, the performance of the fibrous secondary battery can be improved by improving the contact between the electrodes due to swelling in the radial direction of the core fibers.

1 illustrates a structure of a fibrous secondary battery according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a method of manufacturing a fibrous secondary battery according to an embodiment of the present invention. Referring to FIG.
3 is an electron micrograph of a carbon nanotube film according to an embodiment of the present invention.
FIG. 4 is a graph showing charge-discharge characteristics of a fibrous secondary battery produced by using polypropylene fibers as core fibers according to an embodiment of the present invention.
5 is a graph showing impedance characteristics of a fibrous secondary battery produced by using polypropylene fibers as core fibers according to an embodiment of the present invention.
FIG. 6 is a graph showing charge-discharge characteristics of a fiber-type secondary battery manufactured by using cotton fibers as core fibers according to an embodiment of the present invention.
7 is a graph showing the discharge capacity and coulon efficiency of a fibrous secondary battery produced by using cotton fibers as core fibers.
FIG. 8 is a graph showing impedance characteristics of a fiber-type secondary battery manufactured by using cotton fibers as core fibers according to an embodiment of the present invention.
FIG. 9 is a photograph showing a state before and after electrolyte absorption of a cotton fiber considered as core fibers in a method of manufacturing a fiber-type secondary battery according to an embodiment of the present invention.
FIG. 10 illustrates the flexibility of a fibrous secondary cell fabricated using cotton fibers as core fibers according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another part in between . Also, when an element is referred to as "comprising ", it means that it can include other elements as well, without departing from the other elements unless specifically stated otherwise.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fiber secondary cell and a manufacturing method thereof according to an embodiment of the present invention will now be described in detail with reference to the drawings.

1 illustrates a structure of a fibrous secondary battery according to an embodiment of the present invention.

Referring to FIG. 1, a fiber type secondary battery according to an embodiment of the present invention includes a core fiber 100, a first electrode 200, a separation membrane 300, and a second electrode 400.

The core fiber 100 may be formed of a material in the form of a fiber, which is flexible and excellent in electrolyte absorption and electrochemical stability. In particular, in one embodiment of the present invention, the core fibers 100 may be cotton fibers, but are not limited thereto. For example, the core fibers may be formed using wool fibers, silks, hemp, and the like.

The core fiber may be used as it is, but it may be coated with a super absorbent polymer such as polyacrylic acid in order to maximize the swelling.

The first electrode 200 is formed to surround the core fiber 100. The first electrode 200 is a film having a composite structure in which a carbon nanotube film includes a cathode active material or an anode active material, and does not require a polymer adhesive and a current collector.

The cathode active material may be, for example, lithium manganese oxide (LiMnO ₂ ), lithium cobalt oxide (LiCoO ₂ ), iron phosphate, or the like, but is not limited thereto.

The negative electrode active material may be, for example, graphite, graphene, silicon, silicon oxide, metal oxide, or the like, but is not limited thereto.

When the carbon nanotube film forming the first electrode 200 includes the cathode active material, the first electrode 200 acts as an anode and the anode active material is included in the carbon nanotube film forming the first electrode 200 The first electrode 200 acts as a cathode.

The separator 300 is formed to surround the first electrode 200, and a nanoweb formed of polyvinylidene fluoride (PVDF) may be used. However, the present invention is not limited thereto, and the nano web may be made of other polymers such as polyester, nylon and the like.

The separator 300 is formed between the first electrode 200 and the second electrode 400 to physically and chemically separate the first electrode 200 and the second electrode 400.

The second electrode 400 is formed to surround the core fiber 100, the first electrode 200, and the separator 300. Like the first electrode 200, the second electrode 400 may include a cathode active material or an anode active material in a carbon nanotube film. When the first electrode 200 includes the cathode active material, the second electrode 400 includes the anode active material. When the first electrode 200 includes the anode active material, And may include a cathode active material.

In other words, when the first electrode 200 is the anode including the cathode active material, the second electrode 400 is the cathode including the anode active material, and when the first electrode 200 is the cathode including the anode active material And the second electrode 400 may be an anode including a cathode active material.

In addition, although not shown, a fiber type secondary battery according to an embodiment of the present invention includes a first electrode 200 and a second electrode 400 connected to conductors at both ends of the first electrode 200 and the second electrode 400, The second electrode 400 can be electrically connected to an external electronic device.

The fiber type secondary battery according to an embodiment of the present invention may further include a protection layer formed to surround the core fiber 100, the first electrode 200, the separation layer 300, and the second electrode 400 . At this time, the protective film may be formed of an insulating material. In addition, the protective film can protect the fibrous secondary battery against moisture in the air and external impact. Therefore, a conventional polymer resin can be used as the protective film. For example, polyvinyl chloride (PVC), high density polyethylene (HDPE) or epoxy resin can be used.

FIG. 2 is a flowchart illustrating a method of manufacturing a fibrous secondary battery according to an embodiment of the present invention. Referring to FIG.

A method of fabricating a fibrous secondary cell according to an embodiment of the present invention includes forming a first electrode and a second electrode (S100); Absorbing the electrolyte into the core fibers (S200); Forming a fiber-type secondary battery by sequentially winding a first electrode, a separator, and a second electrode on the core fiber (S300).

First, in step S100 of forming the first electrode and the second electrode, a first electrode 200 or a second electrode 400 having a composite structure having a composite structure by applying a cathode active material or a negative electrode active material to a carbon nanotube film ). At this time, the cathode active material and the anode active material are prepared in the form of a slurry and coated on the carbon nanotube film. For example, a positive electrode slurry or a negative electrode slurry is prepared by dispersing a cathode active material or an anode active material in a solvent of N-methylpyrrolidone (NMP) together with powdered carbon nanotubes and PVCF, coating the slurry on the carbon nanotube film , And the first electrode 200 or the second electrode 400 can be manufactured by vacuum drying. At this time, the cathode active material (or the anode active material), the powdered carbon nanotube, and the PVDF may be mixed in a weight ratio of about 88: 2: 10, but are not limited thereto.

Meanwhile, in the carbon nanotube film according to an embodiment of the present invention, a quartz tube placed in a vertical direction is heated, high purity hydrogen gas is flowed into the quartz tube, and a small amount of the carbon nanotube synthesis solution is introduced into a vertical synthesis furnace And the like. At this time, the carbon nanotube synthesis solution contains acetone (Acetone), which is used as a carbon source, and ferrocene, which is a catalyst precursor. Thiophene, which is an activator, and Polysorbate-20, which is used to prevent catalyst aggregation.

When the synthesis solution is fed to the synthesis furnace, the thermal energy separates the iron from the catalyst precursor, ferrocene, and separates the sulfur from the active thiophene, which forms a liquid iron-sulfide. Thereafter, decomposition of acetone causes the supplied carbon to diffuse into the iron sulfide and saturate, so that the carbon nanotubes start to grow. At this time, when the solution is continuously injected, the carbon nanotubes are formed into an aggregate, which can be wound on a roller to produce a carbon nanotube film.

Meanwhile, a method of manufacturing a carbon nanotube film according to an embodiment of the present invention is described in detail in Korean Patent (10-2013-0044173) and PCT (PCT / KR2013 / 010289) invented by the inventors of the present patent application A detailed description thereof will be omitted.

3 is an electron micrograph of a carbon nanotube film according to an embodiment of the present invention.

According to an embodiment of the present invention, a carbon nanotube film having a network structure of a long carbon nanotube bundle as shown in FIG. 3 can be manufactured by the above-described method. In addition, the carbon nanotube film according to an embodiment of the present invention is flexible enough to bend or fold, and can maintain flexibility even in a liquid nitrogen of -196 ° C.

Meanwhile, the carbon nanotube film manufactured according to an embodiment of the present invention may be formed by directly spinning the negative electrode active material or the positive electrode active material when the aggregate of carbon nanotubes is wound on the roller, and the first electrode 200 or the second electrode (400) can be formed.

At this time, if the first electrode 200 is formed to include the cathode active material, the second electrode 400 may be formed to include the anode active material. Alternatively, when the first electrode 200 is formed to include a negative electrode active material, the second electrode 400 may be formed to include a positive electrode active material. Therefore, according to an embodiment of the present invention, the first electrode 200 or the second electrode 400 may act as an anode or a cathode in a fibrous secondary battery.

Referring again to FIG. 2, the core fibers 100 can absorb the electrolyte. At this time, the electrolyte may be prepared by mixing 1 mol of LiPF6 in a solvent prepared by mixing EC (Ethyl carbonate) and DEC (Diethyl carbonate) at a ratio of 1: 1. In one embodiment of the present invention, the core fibers 100 may be cotton fibers, but are not limited thereto (S200).

At this time, steps S100 and S200 of FIG. 2 are not limited to the order, and steps S100 and S200 may be performed in parallel.

Finally, the fibrous secondary battery can be formed by sequentially winding the first electrode 200, the separation membrane 300, and the second electrode 400 on the core fiber 100. Specifically, the first electrode 200 is formed to surround the core fiber 100 absorbing the electrolyte, the separation membrane 300 is formed to surround the core fiber 100 and the first electrode 200, The second electrode 400 may be formed to surround the core fiber 100, the first electrode 200, and the separator 300 (S300).

Meanwhile, a method of fabricating a fiber-type secondary battery according to an embodiment of the present invention includes connecting wires to the ends of the first electrode 200 and the second electrode 400 after the step S300, And then wrapping the connected fiber type secondary battery with a protective film. In this case, the conductive wire may be formed of a conductive metal such as gold, silver, aluminum, nickel, or the like, but is not limited thereto.

In addition, in the step of wrapping the connected fibrous secondary cell with the protective film, the fibrous secondary cell to which the lead is connected is sandwiched between the tube-shaped protective film and the protective film is heated and shrunk, and then the electrolyte is filled in the protective film, . Therefore, the fibrous secondary battery fabricated according to one embodiment of the present invention can be protected from moisture and external impacts in the air.

At this time, the protective film may be formed of a polymer resin, and may be a secondary battery, for example, a polymer resin.

[Example]

The slurry was prepared by dispersing a cathode active material (LCO), a 200-um powdered multi-walled CNT, and PVDF in a weight ratio of 88: 2: 10 to NMP solvent, To form a first electrode.

Similarly, an anode active material (graphite), 200 μm of powdered multi-walled CNT, and PVDF were dispersed in NMP solvent in a weight ratio of 88: 2: 10, respectively, And coated on a tube film to form a second electrode.

PVDF nanoweb was used as the separation membrane and 1 mol of LiPF6 was added to the electrolyte prepared by mixing 1: 1 of ethyl carbonate (EC) and diethyl carbonate (DEC).

Thereafter, cotton fibers and polypropylene fibers were prepared, and fiber type secondary batteries including cotton fibers and polypropylene fibers as core fibers were respectively prepared.

Hereinafter, characteristics of the fabricated secondary battery manufactured according to one embodiment of the present invention will be described in detail with reference to FIGS. 4 to 8. FIG.

The fiber type secondary battery according to an embodiment of the present invention may include cotton fibers as core fibers, thereby improving the overall performance of the secondary battery.

Therefore, in one embodiment of the present invention, in order to confirm the performance of the fiber-type secondary battery that varies depending on the type of core fiber, a fibrous secondary battery was fabricated using polypropylene fibers and cotton fibers.

FIG. 4 is a graph showing the charging and discharging characteristics of a fibrous secondary battery produced by using polypropylene fibers as core fibers according to an embodiment of the present invention. FIG. 5 is a graph showing the charging / Is a graph showing the impedance characteristics of a fiber-type secondary battery manufactured using core fibers.

FIG. 6 is a graph showing the charging and discharging characteristics of a fiber type secondary battery produced by using cotton fibers as core fibers according to an embodiment of the present invention. FIG. 7 is a graph showing the charging / A discharge capacity and a coulomb efficiency of the battery.

8 is a graph showing impedance characteristics of a fiber-type secondary battery fabricated using cotton fibers as core fibers according to an embodiment of the present invention.

Although the polypropylene fibers form a fibrous structure, they fail to exhibit their performance as secondary batteries because they have little ability to absorb electrolytes.

Referring to FIG. 4, in the case of a fibrous secondary battery produced by using polypropylene fiber as the core fiber, the first discharging capacity was about 10 mAh / g, and it was confirmed that the capacity was continuously decreased during the cycle have. In addition, it can be confirmed that charge and discharge are not performed after the third cycle. This is because, in the case of polypropylene fiber, it is not possible to carry the electrolyte, and the performance as a battery can not be exhibited properly.

The above results can be deduced from the impedance measurement results of FIG. Referring to FIG. 5, the interfacial resistance of a fibrous battery using polypropylene fibers is 966 OMEGA, which is significantly higher than the interfacial resistance of a cable type battery as reported generally. This high interfacial resistance is caused by a shortage of the absolute amount of the electrolyte and a reduction in contact between the electrolyte and the electrode. Therefore, in order to solve this problem, a large amount of electrolyte should be injected into the fiber-type secondary battery, which is undesirable because the electrolyte may leak out.

On the other hand, in the case of cotton fibers, it is composed of electrochemically stable cellulose. Therefore, it is excellent in the structure formation of a fibrous secondary cell, and the cotton fiber can absorb and carry about 10 times as much electrolyte as its own mass.

Referring to FIGS. 6 and 7, according to an embodiment of the present invention, a fibrous secondary battery produced by using cotton fibers as core fibers exhibits a stable discharge capacity of about 96 mAh / g during 40 cycles of charging / discharging, 95 % ≪ / RTI >

The impedance measurement result of the fiber type secondary battery fabricated by using the cotton fiber of FIG. 8 as the core fiber was about 20 times lower than the interface resistance of the fiber type secondary battery produced by using the polypropylene fiber as the core fiber Can be confirmed. Also, the result of the low impedance shown in Fig. 8 is that the contact between the electrodes is improved due to the swelling of the cotton fibers.

FIG. 9 is a photograph showing a state before and after electrolyte absorption of a cotton fiber considered as core fibers in a method of manufacturing a fiber-type secondary battery according to an embodiment of the present invention.

Referring to FIG. 9, it can be seen that, in the method of manufacturing a fibrous secondary cell according to an embodiment of the present invention, the cotton fibers considered as core fibers are swollen by about 14% in the radial direction due to the absorption of the electrolyte.

FIG. 10 illustrates the flexibility of a fibrous secondary cell fabricated using cotton fibers as core fibers according to an embodiment of the present invention.

Referring to FIG. 10, a fiber type secondary battery using fibers as core fibers according to an embodiment of the present invention is stable to repetitive bending and knotting. Therefore, the blue LED lamp can be normally operated even when the knot is turned on.

As described above, in the case of a fibrous secondary battery using fibers as core fibers according to an embodiment of the present invention, the performance as a battery can be improved and the risk of electrolyte leakage can be reduced.

In addition, according to any one of the means for solving the problems of the present invention, the performance of the fibrous secondary battery can be improved by improving the contact between the electrodes due to swelling in the radial direction of the core fibers.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

100: core fiber
200: first electrode
300: membrane
400: second electrode

Claims (11)

In the fibrous secondary battery,
Core fibers,
A first electrode formed to surround the core fiber, a separator formed to surround the first electrode,
And a second electrode formed to surround the separator,
Wherein the core fiber is formed using at least one of cotton, wool fiber, silk, and hemp. The method according to claim 1,
Wherein the first electrode and the second electrode are formed of a carbon nanotube film including a cathode active material or an anode active material,
Wherein the first electrode and the second electrode comprise an active material having an opposite polarity to each other. 3. The method of claim 2,
Wherein the positive electrode active material includes any one of lithium manganese oxide (LiMnO ₂ ), lithium cobalt oxide (LiCoO ₂ ), and iron phosphate,
Wherein the negative electrode active material comprises any one of graphite, graphene, silicon, silicon oxide and gold oxide. The method according to claim 1,
Wherein the core fiber is supported on an electrolyte. The method according to claim 1,
Further comprising a first conductor coupled to an end of the first electrode and a second conductor coupled to an end of the second electrode. The method according to claim 1,
And a protection film surrounding the core fiber, the first electrode, the separation membrane, and the second electrode. In the method of manufacturing a fibrous secondary battery,
Forming a first electrode and a second electrode;
Supporting the electrolyte on the core fiber;
And forming the first electrode, the separator, and the second electrode sequentially on the core fiber to produce a fibrous secondary battery,
Wherein the core fibers are formed using at least one fabric selected from the group consisting of cotton, wool fibers, silk, and hemp. 8. The method of claim 7,
Wherein the first electrode and the second electrode are each formed of a carbon nanotube film,
Wherein forming the first electrode and the second electrode comprises:
A carbon nanotube film is coated with a cathode active material or an anode active material,
Wherein the first electrode and the second electrode are formed to include an active material having an opposite polarity to each other. 9. The method of claim 8,
Wherein the cathode active material comprises any one of lithium manganese oxide (LiMnO ₂ ), lithium cobalt oxide (LiCoO ₂ ), and iron phosphate,
Wherein the negative electrode active material comprises any one of graphite, graphene, silicon, silicon oxide, and gold oxide. 8. The method of claim 7,
Forming a first conductor coupled to an end of the first electrode and a second conductor coupled to an end of the second electrode. 8. The method of claim 7,
And forming a protective film surrounding the core fiber, the first electrode, the separation membrane, and the second electrode.

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