High-performance fiber electrode and its manufacturing method, and Ni-Fe fiber battery using the same

Abstract

A fiber electrode is provided. The fiber electrode may include carbon nanotube fibers formed by rolling and stacking carbon nanotube sheets, an active material provided between the rolled and stacked carbon nanotube sheets, and a buffer layer that surrounds the outer surface of the carbon nanotube fibers and prevents the active material from falling off the carbon nanotube fibers.

Description

Technology Field

[0001] The present invention relates to a high-performance fiber electrode, a method for manufacturing the same, and a Ni-Fe fiber battery applying the same. More specifically, it relates to a high-performance fiber electrode in which an active material is provided on carbon nanotube fibers, a method for manufacturing the same, and a Ni-Fe fiber battery applying the same. Background Technology

[0002] As the field of flexible and wearable electronic devices—such as personal health monitoring devices, intelligent clothing, roll-up displays, and implantable medical devices—advances, the field of batteries applicable to these devices is also advancing. In particular, fiber batteries are attracting attention as batteries applicable to flexible and wearable electronic devices, and research on this topic is actively underway.

[0003] For example, Korean Patent Publication No. 10-2266637 (March 24, 2021) discloses a fiber fabric-based structural battery comprising a fiber fabric-based first electrode, a second electrode spaced apart from the first electrode, and an electrolyte between the first electrode and the second electrode, wherein the first electrode comprises a fiber fabric substrate, a metal nanoparticle layer comprising an Fe and Al alloy provided on the fiber fabric substrate, a carbon nanotube layer provided on the metal nanoparticle layer; a Ni nanoparticle layer provided between the metal nanoparticle layer and the fiber fabric substrate, and a graphene layer provided between the Ni nanoparticle layer and the metal nanoparticle layer.

[0004] In addition to this, various studies on fiber batteries are continuously being conducted. Prior art literature

[0005] Korean Patent Publication No. 10-2266637 (March 24, 2021) The problem to be solved

[0006] The technical problem that the present invention aims to solve is to provide a high-performance fiber electrode, a method for manufacturing the same, and a Ni-Fe fiber battery applying the same.

[0007] Another technical problem that the present invention aims to solve is to provide a high-reliability fiber electrode, a method for manufacturing the same, and a Ni-Fe fiber battery applying the same.

[0008] Another technical problem that the present invention aims to solve is to provide a fiber electrode with high mechanical flexibility, a method for manufacturing the same, and a Ni-Fe fiber battery applying the same.

[0009] Another technical problem that the present invention aims to solve is to provide a fiber electrode with improved stability, a method for manufacturing the same, and a Ni-Fe fiber battery applying the same.

[0010] The technical problems that the present invention aims to solve are not limited to those described above. means of solving the problem

[0011] To solve the above technical problems, the present invention provides a fiber electrode.

[0012] According to one embodiment, the fiber electrode may include carbon nanotube fibers formed by rolling and stacking carbon nanotube sheets, an active material provided between the rolled and stacked carbon nanotube sheets, and a buffer layer that surrounds the outer surface of the carbon nanotube fibers and prevents the active material from falling off from the carbon nanotube fibers.

[0013] According to one embodiment, the active material may include either nickel hydroxide (Ni(OH)2) or iron oxide (Fe3O4).

[0014] According to one embodiment, the active material may be provided in the form of particles between the rolled and stacked carbon nanotube sheets.

[0015] According to one embodiment, the buffer layer may comprise a plurality of carbon nanotube sheets stacked together.

[0016] According to one embodiment, the mass percentage of the active material in the carbon nanotube fiber may be 97 wt% or more.

[0017] According to one embodiment, the carbon nanotube fiber may be extended in a first direction, and in a cross-section cut along a first plane having the first direction as a normal, the cross-section of the carbon nanotube fiber may be provided in a spiral shape.

[0019] To solve the above technical problems, the present invention provides a fiber battery.

[0020] According to one embodiment, the fiber battery may include a cathode comprising a fiber electrode according to the embodiment, wherein the active material is nickel hydroxide (Ni(OH)2), an anode comprising a fiber electrode according to the embodiment, wherein the active material is iron oxide (Fe3O4), and an aqueous electrolyte in which the cathode and the anode are immersed.

[0021] According to one embodiment, the fiber battery has 422 mWh / cm² 3 The maximum energy density above and 7535 mW / cm² 3 It can have a maximum power density of the above.

[0023] To solve the above technical problems, the present invention provides a method for manufacturing a fiber electrode.

[0024] According to one embodiment, the method for manufacturing the fiber electrode may include the steps of preparing a carbon nanotube sheet, providing an active material on the carbon nanotube sheet, manufacturing a preliminary fiber electrode in which the active material is provided between the carbon nanotube sheets that are twisted, rolled, and stacked with the carbon nanotube sheet on which the active material is provided, and wrapping the outer surface of the preliminary fiber electrode with a buffer sheet containing the carbon nanotube sheet.

[0025] According to one embodiment, the step of wrapping the outer surface of the prefabricated fiber electrode with a buffer sheet including the carbon nanotube sheet may include: preparing the buffer sheet including a carbon nanotube sheet in which a plurality of carbon nanotubes extending in one direction are arranged side by side; rolling the buffer sheet to have a cylinder shape with a hollow formed inside, and placing the prefabricated fiber electrode within the hollow inside; applying a twist to one end of the buffer sheet having the cylinder shape to deform it into an hourglass shape so that a central part located between one end and the other end of the buffer sheet comes into contact with the prefabricated fiber electrode; and applying a twist to one end of the buffer sheet having the hourglass shape to press the buffer sheet against the outer surface of the prefabricated fiber electrode.

[0026] According to one embodiment, the step of providing an active material on the carbon nanotube sheet may include the step of preparing a source solution in which the active material is dispersed in ethanol, and the step of drop-casting the source solution onto the carbon nanotube sheet.

[0027] According to one embodiment, the mass percentage of the active material in the prefabric electrode may be controlled by controlling the concentration of the active material in the source solution.

[0028] According to one embodiment, as the concentration of the active material in the source solution increases, the mass percentage of the active material in the prefabric electrode may increase. Effects of the invention

[0029] A fiber electrode according to an embodiment of the present invention may comprise carbon nanotube fibers formed by rolling and stacking carbon nanotube sheets, an active material (Ni(OH)2 or Fe3O4) provided between the rolled and stacked carbon nanotube sheets, and a buffer layer that surrounds the outer surface of the carbon nanotube fibers and prevents the active material from detaching from the carbon nanotube fibers. Accordingly, a fiber electrode having high performance and high reliability can be provided.

[0030] In addition, the method for manufacturing the fiber electrode may include the steps of preparing a carbon nanotube sheet, providing an active material on the carbon nanotube sheet, manufacturing a preliminary fiber electrode in which the active material is provided between the carbon nanotube sheets that are twisted, rolled, and stacked by the carbon nanotube sheet provided with the active material, and wrapping the outer surface of the preliminary fiber electrode with a buffer sheet containing the carbon nanotube sheet. Accordingly, since the loading amount of the active material can be easily improved, a fiber electrode having high performance and high reliability can be manufactured. Brief explanation of the drawing

[0031] FIG. 1 is a flowchart illustrating a method for manufacturing a fiber electrode according to an embodiment of the present invention. FIGS. 2 and FIGS. 3 are drawings for explaining a fiber electrode and the manufacturing process thereof according to an embodiment of the present invention. FIG. 4 is a diagram illustrating the effect of the buffer layer of a fiber electrode according to an embodiment of the present invention. FIG. 5 is a drawing for explaining a fiber battery according to an embodiment of the present invention. Figure 6 is a photograph of a fiber electrode according to Experimental Example 1 and Experimental Example 3 of the present invention. FIG. 7 is a diagram illustrating the resistance of fiber electrodes according to Experimental Example 1 and Experimental Example 3 of the present invention. FIG. 8 is a diagram for verifying the electrical conductivity of a fiber electrode according to Experimental Example 1 of the present invention. FIG. 9 is a diagram for verifying the mechanical flexibility of a fiber electrode according to Experimental Example 1 of the present invention. FIG. 10 is a photograph of a fiber electrode according to Experimental Example 1 and Experimental Example 2 of the present invention. FIG. 11 is a diagram illustrating the CV curve of a fiber battery according to Experimental Example 2 of the present invention. FIGS. 12 to 14 are drawings comparing the electrochemical characteristics of fiber batteries according to Experimental Example 1 and Experimental Example 2 of the present invention. Figure 15 is a diagram illustrating the capacity characteristics according to the number of stacked buffer sheets. Figure 16 is a diagram illustrating the change in characteristics of a fiber battery according to the amount of active material loaded. FIG. 17 is a diagram illustrating a galvanostatic discharge curve for a fiber battery according to Experimental Example 2 of the present invention. FIG. 18 is a diagram illustrating the capacity retention performance and Coulomb efficiency of a fiber battery according to Experimental Example 2 of the present invention. FIG. 19 is a diagram illustrating the power density and energy density of a fiber battery according to Experimental Example 2 of the present invention. FIG. 20 is a photograph of a fabric woven through fiber electrodes according to Experimental Example 2 and Experimental Example 4 of the present invention. FIG. 21 is a diagram comparing the performance according to the arrangement of fiber electrodes according to Experimental Example 2 of the present invention. FIG. 22 is a diagram comparing the performance according to the buffer layer thickness of the fiber electrode according to Experimental Example 2 of the present invention. Specific details for implementing the invention

[0032] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. However, the technical concept of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed content is thorough and complete, and to ensure that the concept of the present invention is sufficiently conveyed to those skilled in the art.

[0033] In this specification, when a component is described as being on another component, it means that it may be formed directly on the other component or that a third component may be interposed between them. Additionally, in the drawings, the thicknesses of the films and regions are exaggerated for the effective description of the technical content.

[0034] Additionally, although terms such as first, second, third, etc. have been used to describe various components in various embodiments of this specification, these components should not be limited by such terms. Accordingly, what is referred to as the first component in one embodiment may be referred to as the second component in another embodiment.

[0035] Each embodiment described and exemplified herein also includes its complementary embodiment. Additionally, the term 'and / or' in this specification is used to mean including at least one of the components listed before and after it.

[0036] In the specification, singular expressions include plural expressions unless the context clearly indicates otherwise. Furthermore, terms such as "include" or "have" are intended to specify the existence of the features, numbers, steps, components, or combinations thereof described in the specification, and should not be understood as excluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0037] In addition, in describing the present invention below, if it is determined that a detailed description of related known functions or configurations could unnecessarily obscure the essence of the invention, such detailed description will be omitted.

[0039] fiber electrode

[0040] FIG. 1 is a flowchart for explaining a method for manufacturing a fiber electrode according to an embodiment of the present invention, FIG. 2 and FIG. 3 are drawings for explaining a fiber electrode and the manufacturing process according to an embodiment of the present invention, and FIG. 4 is a drawing for explaining the effect of a buffer layer of a fiber electrode according to an embodiment of the present invention.

[0041] Additionally, FIG. 2(a) shows the process of a carbon nanotube sheet (110) provided with an active material (AM) being twisted, FIG. 2(b) shows a carbon nanotube fiber (200) that is rolled and stacked from the carbon nanotube sheet (110), FIG. 2(c) shows a preliminary fiber electrode (300), and FIG. 2(d) shows a fiber electrode (400).

[0042] Referring to FIGS. 1 to 4, a carbon nanotube sheet (110) is prepared (S100). According to one embodiment, the carbon nanotube sheet (110) may be prepared on a substrate (100). Additionally, according to one embodiment, the carbon nanotube sheet (110) may be manufactured from a carbon nanotube forest (CNT forest).

[0043] An active material (AM) may be provided on the carbon nanotube sheet (110) (S200). According to one embodiment, the step of providing the active material (AM) on the carbon nanotube sheet (110) may include the step of preparing a source solution in which the active material (AM) is dispersed in ethanol, and the step of drop-casting the source solution onto the carbon nanotube sheet (110). For example, the active material (AM) may be nickel hydroxide (Ni(OH)2). Alternatively, as another example, the active material (AM) may be iron oxide (Fe3O4). Also, according to one embodiment, the active material (AM) may have a particle form.

[0044] As illustrated in FIG. 2, the carbon nanotube sheet (110) provided with the active material (AM) can be twisted to produce a preliminary fiber electrode (300) (S300). When the carbon nanotube sheet (110) is twisted, the carbon nanotube sheet (110) can be rolled and stacked. Accordingly, the carbon nanotube sheet (110) can be transformed into a carbon nanotube fiber (200).

[0045] That is, the above-described preliminary fiber electrode (300) may have a structure comprising the carbon nanotube fiber (200) formed by rolling and stacking the carbon nanotube sheet (110), and the active material (AM) provided between the rolled and stacked carbon nanotube sheets (110). Additionally, the carbon nanotube fiber (200) may be provided with a spiral cross-section cut along a first plane having a first direction (extending direction) as the normal.

[0046] According to one embodiment, the mass percentage of the active material (AM) in the preliminary fiber electrode (300) can be controlled by controlling the concentration of the active material (AM) in the source solution. For example, by increasing the concentration of the active material (AM) in the source solution, the mass percentage of the active material (AM) in the preliminary fiber electrode (300) can be improved. Specifically, the mass percentage of the active material (AM) in the preliminary fiber electrode (300) may be 97 wt% or more. The mass percentage of the active material (AM) in the preliminary fiber electrode (300) can be calculated using the following <Equation 1>.

[0047] <Mathematical Formula 1>

[0048]

[0049] (wt%: mass percentage of active material in the prefabric electrode, W total : Mass of the preliminary fiber electrode, W CNT : Mass of carbon nanotube fiber)

[0050] Conventional fiber electrodes had the problem that it was difficult to improve electrochemical properties because it was difficult to increase the loading amount (mass percentage) of the active material within the fiber electrode. However, the method for manufacturing a fiber electrode according to an embodiment of the present invention has the advantage of being able to manufacture a high loading amount (mass percentage) of the active material (AM) by providing the active material (AM) on the carbon nanotube sheet (110) and then twisting it, as described above.

[0051] After manufacturing the above-mentioned preliminary fiber electrode (300), the outer surface of the preliminary fiber electrode (300) can be wrapped with a buffer sheet (310) (S400). Accordingly, the fiber electrode (400) can be manufactured. According to one embodiment, the buffer sheet (310) may be a plurality of carbon nanotube sheets stacked together. Additionally, the carbon nanotube sheets may be a plurality of carbon nanotubes extending in one direction arranged side by side. According to one embodiment, the buffer sheet (310) wrapped around the outer surface of the preliminary fiber electrode (300) may be defined as a buffer layer.

[0052] As illustrated in FIG. 3, the step of wrapping the outer surface of the prefabric electrode (300) with the buffer sheet (310) may include the step of preparing the buffer sheet (310) (S410), the step of rolling the buffer sheet (310) to have a hollow cylinder shape with a hollow formed inside and placing the prefabric electrode (300) inside the hollow (S420), the step of applying a twist to one end of the buffer sheet (310) having the cylinder shape to deform it into an hourglass shape so that the central part located between one end and the other end of the buffer sheet (310) comes into contact with the prefabric electrode (300) (S430), and the step of applying a twist to one end of the buffer sheet (310) having the hourglass shape to press the buffer sheet (310) against the outer surface of the prefabric electrode (300) (S440).

[0053] As shown in FIG. 4(a), if the buffer sheet (310) is not wrapped around the outer surface of the prefabricated fiber electrode (300), the active material (AM) may detach from the carbon nanotube fiber (200) during the electrochemical reaction process, which may result in a problem of degraded electrochemical properties.

[0054] However, as shown in FIG. 4(b), when the buffer sheet (310) is wrapped around the outer surface of the prefabricated fiber electrode (300), the phenomenon of the active material (AM) detaching from the carbon nanotube fiber (200) during the electrochemical reaction process can be prevented by the buffer sheet (310). Accordingly, the fiber electrode (400) can have high electrochemical properties.

[0056] The fiber electrode and the method for manufacturing the same according to an embodiment of the present invention have been described above. Hereinafter, a fiber battery to which the fiber electrode according to an embodiment of the present invention is applied is described.

[0057] fiber battery

[0058] FIG. 5 is a drawing for explaining a fiber battery according to an embodiment of the present invention.

[0059] Referring to FIG. 5, a fiber battery according to an embodiment of the present invention may include a cathode (10), an anode (20), an electrolyte (30), and a wire (40).

[0060] The cathode (10) comprises a fiber electrode according to the embodiment described with reference to FIGS. 1 to 4, wherein the active material (AM) may include nickel hydroxide (Ni(OH)2). Alternatively, the anode (20) comprises a fiber electrode according to the embodiment described with reference to FIGS. 1 to 4, wherein the active material (AM) may include iron oxide (Fe3O4).

[0061] The cathode (10) and the anode (20) are positioned to be immersed in an aqueous electrolyte (30), but may be positioned to face each other while spaced apart. According to one embodiment, the electrolyte (30) may be an aqueous solution of potassium hydroxide (KOH) with a concentration of 6 M.

[0062] The above wire (40) can connect the cathode (10) and the anode (20). According to one embodiment, the wire (40) may be a copper wire.

[0063] The redox reaction within the fiber battery above can occur as shown in <Chemical Formula 1> below.

[0064] <Chemical Formula 1>

[0065]

[0066] According to one embodiment, as described above, since the fiber electrode can have high electrochemical properties, the fiber battery can also have high electrochemical properties. Specifically, the fiber battery has 422 mWh / cm² 3 The maximum energy density above and 7535 mW / cm² 3 It can have a maximum power density of the above.

[0068] The fiber battery according to the embodiment of the present invention has been described above. Specific experimental examples and characteristic evaluation results of the fiber electrode and fiber battery according to the embodiment of the present invention are described below.

[0069] Fabrication of fiber electrode according to Experimental Example 1

[0070] A carbon nanotube sheet measuring 10 mm (width) x 75 mm (length) was prepared on a glass substrate. A source solution was prepared in which nickel hydroxide (Ni(OH)2) powder was dispersed in ethanol.

[0071] A source solution was drop-casted onto a prepared carbon nanotube sheet, and the carbon nanotube sheet was twisted at a speed of 1200 turns / m to prepare a fiber electrode according to Experimental Example 1. The fiber electrode according to Experimental Example 1 is the same as the preliminary fiber electrode described with reference to FIGS. 1 to 4. In addition, in the description of the characteristic evaluation results that follows, the fiber electrode according to Experimental Example 1 is defined as a biscrolled yarn.

[0073] Fabrication of fiber electrode according to Experimental Example 2

[0074] A buffer sheet was wrapped around the outer surface of the fiber electrode according to Experimental Example 1 to prepare the fiber electrode according to Experimental Example 2. A carbon nanotube sheet measuring 10 mm (width) x 75 mm (length) was used as the buffer sheet. The fiber electrode according to Experimental Example 2 is the same as the fiber electrode described with reference to FIGS. 1 to 4. In addition, in the description of the characteristic evaluation results that follows, the fiber electrode according to Experimental Example 2 is defined as B-biscrolled yarn.

[0076] Fabrication of fiber electrode according to Experimental Example 3

[0077] A fiber electrode according to Experimental Example 1 above was prepared using a source solution in which iron oxide (Fe3O4) powder was dispersed in ethanol.

[0079] Fabrication of fiber electrode according to Experimental Example 4

[0080] A fiber electrode according to Experimental Example 4 was prepared by wrapping a buffer sheet around the outer surface of the fiber electrode according to Experimental Example 3. A carbon nanotube sheet measuring 10 mm (width) x 75 mm (length) was used as the buffer sheet.

[0082] division active material Whether to apply buffer sheet Experiment Example 1 Ni(OH)2 X Experiment Example 2 Ni(OH)2 O Experiment Example 3 Fe3O4 X Experiment Example 4 Fe3O4 O

[0083] Figure 6 is a photograph of a fiber electrode according to Experimental Example 1 and Experimental Example 3 of the present invention.

[0084] Referring to Fig. 6(a), a Scanning Electron Microscope (SEM) image of the fiber electrode according to Experimental Example 1 is shown, and referring to Fig. 6(b), a Scanning Electron Microscope (SEM) image of the fiber electrode according to Experimental Example 3 is shown.

[0085] As can be seen in Figures 6 (a) and (b), the fiber electrode according to Experimental Example 1 and the fiber electrode according to Experimental Example 3 were found to have a structure in which an active material (Ni(OH)2 or Fe3O4) was provided to carbon nanotube fibers.

[0086] FIG. 7 is a diagram illustrating the resistance of fiber electrodes according to Experimental Example 1 and Experimental Example 3 of the present invention.

[0087] Referring to Fig. 7, the resistance (Ω / cm) of the fiber electrodes according to Experimental Example 1 and Experimental Example 3 is measured and shown. As can be seen in Fig. 7, it was confirmed that both Experimental Example 1 and Experimental Example 3 exhibited a stable resistance of approximately 90 Ω / cm.

[0088] FIG. 8 is a diagram for verifying the electrical conductivity of a fiber electrode according to Experimental Example 1 of the present invention.

[0089] Referring to Fig. 8, the fiber electrode (biscrolled yarn) according to Experimental Example 1 was attached to a conductive film and used in an electrical circuit for lighting an LED. In addition, to verify the durability of the fiber electrode according to Experimental Example 1, 30g of water was suspended from the end of the fiber electrode. As can be seen in Fig. 8, it was confirmed that a blue LED was lit through the fiber electrode according to Experimental Example 1. Furthermore, it was confirmed that the fiber electrode has high durability as it did not break even when a load (30g of water) was applied to it.

[0090] FIG. 9 is a diagram for verifying the mechanical flexibility of a fiber electrode according to Experimental Example 1 of the present invention.

[0091] Referring to FIGS. 9(a) to (c), various mechanical deformations are applied to the fiber electrode according to Experimental Example 1. Specifically, FIGS. 9(a) shows a straightened state, FIGS. 9(b) shows a pleated state, and FIGS. 9(c) shows a wound state. As can be seen in FIGS. 9(a) to (c), it was confirmed that the fiber electrode according to Experimental Example 1 can undergo various mechanical deformations.

[0092] FIG. 10 is a photograph of a fiber electrode according to Experimental Example 1 and Experimental Example 2 of the present invention.

[0093] Referring to FIG. 10 (a), an optical photograph of a fiber electrode according to Experimental Example 1 (Biscrolled Ni / CNT yarn) is shown, and referring to FIG. 10 (b), an optical photograph of a fiber electrode according to Experimental Example 2 (B-biscrolled Ni / CNT yarn) is shown.

[0094] As can be seen in Figures 10 (a) and (b), in the fiber electrode according to Experimental Example 1, a large amount of active material particles were found on the surface of the carbon nanotube fiber, whereas in the fiber electrode according to Experimental Example 2, a large amount of active material particles were found wrapped by a buffer sheet and were not exposed to the outside.

[0096] Fiber battery manufacturing according to Experimental Example 1

[0097] A fiber battery according to Experimental Example 1 was manufactured by placing a cathode and an anode in an aqueous solution of potassium hydroxide (KOH) at a concentration of 6 M and then connecting the cathode and anode with a copper wire. Specifically, the fiber electrode according to Experimental Example 1 was used as the cathode, and the fiber electrode according to Experimental Example 3 was used as the anode.

[0099] Fiber battery manufacturing according to Experimental Example 2

[0100] A fiber battery according to Experimental Example 1 was manufactured by placing a cathode and an anode in an aqueous solution of potassium hydroxide (KOH) at a concentration of 6 M and then connecting the cathode and anode with a copper wire. Specifically, the fiber electrode according to Experimental Example 2 was used as the cathode, and the fiber electrode according to Experimental Example 4 was used as the anode.

[0102] division cathode Anode Experiment Example 1 Experimental Example 1 (Ni(OH)2 without buffer sheet) Experimental Example 3 (Fe3O4 without buffer sheet) Experiment Example 2 Experimental Example 2 (Ni(OH)2 with buffer sheet) Experimental Example 4 (Fe3O4 with buffer sheet)

[0103] FIG. 11 is a diagram illustrating the CV curve of a fiber battery according to Experimental Example 2 of the present invention.

[0104] Referring to Fig. 11, the CV curves measured at various scan speeds (5 mV / s, 10 mV / s, 20 mV / s, 30 mV / s, and 40 mV / s) for the fiber battery according to Experimental Example 2 are shown. As can be seen in Fig. 11, the CV curve area increases as the scan speed increases, but the shape of the CV curve area is formed similarly.

[0105] FIGS. 12 to 14 are drawings comparing the electrochemical characteristics of fiber batteries according to Experimental Example 1 and Experimental Example 2 of the present invention.

[0106] Referring to FIG. 12(a), the change in capacity (specific capacity, mAh / g) according to the scan rate (scan rate, mV / s) is measured and shown for the fiber battery (biscrolled yarn) according to Experimental Example 1 and the fiber battery (B-biscrolled yarn) according to Experimental Example 2, respectively. As can be seen in FIG. 12(a), it was confirmed that the fiber battery according to Experimental Example 1 and the fiber battery according to Experimental Example 2 exhibited similar capacity changes.

[0107] Referring to FIG. 12(b), the change in potential (V) according to discharge time (Time, s) is measured and shown for the fiber battery (Biscrolled yarn) according to Experimental Example 1 and the fiber battery (B-biscrolled yarn) according to Experimental Example 2, respectively. As can be seen in FIG. 12(b), it was confirmed that the fiber battery according to Experimental Example 1 and the fiber battery according to Experimental Example 2 exhibited similar changes in potential.

[0108] That is, as can be seen in Figures 12 (a) and (b), it was found that no change in electrochemical properties due to the buffer sheet actually occurred.

[0109] Referring to FIG. 13, Nyquist plots (frequency range of 10 Hz to 100 kHz) are shown for the fiber battery (biscrolled yarn) according to Experimental Example 1 and the fiber battery (B-biscrolled yarn) according to Experimental Example 2, respectively. As can be seen in FIG. 13, it was confirmed that the fiber battery according to Experimental Example 1 and the fiber battery according to Experimental Example 2 exhibit similar Nyquist plots. In addition, since they exhibit low impedance at low frequencies (10 Hz, <200 Ω), it was found that the aqueous electrolyte can easily penetrate even when wrapped with a buffer sheet.

[0110] Referring to Fig. 14, the change in linear capacity (mAh / cm) according to the number of charge / discharge cycles is measured and shown for each of the fiber battery (biscrolled yarn) according to Experimental Example 1 and the fiber battery (B-biscrolled yarn) according to Experimental Example 2.

[0111] As can be seen in Fig. 14, the fiber battery according to Experimental Example 1 showed a capacity retention of approximately 20.2% after 300 charge-discharge cycles, whereas the fiber battery according to Experimental Example 2 showed a capacity retention of approximately 60.1% after 300 charge-discharge cycles. Accordingly, it can be seen that the cycle stability is improved by the buffer sheet.

[0112] Figure 15 is a diagram illustrating the capacity characteristics according to the number of stacked buffer sheets.

[0113] Referring to Fig. 15, fiber batteries according to Experimental Example 1 and Experimental Example 2 were prepared to verify capacity characteristics (Linear capacity, Capacity retention) according to the number of stacked buffer sheets. The electrodes (cathode and anode) of the fiber battery according to Experimental Example 1 were used as a sample without a buffer sheet (Outer CNT buffer 0), and the electrodes (cathode and anode) of the fiber battery according to Experimental Example 2 were used as a sample with a buffer sheet, but the number of stacked carbon nanotube sheets constituting the buffer sheet was configured differently (Outer CNT buffer 1, 2, 3).

[0114] As can be seen in Fig. 15, it was confirmed that the linear capacity (mAh / cm) remained practically constant regardless of the presence or absence of the buffer sheet and the number of stacked buffer sheets. However, the capacity retention performance (%) was significantly improved when the buffer sheet was present compared to when it was absent, and it was confirmed that the capacity retention performance continued to improve as the number of stacked carbon nanotube sheets constituting the buffer sheet increased (1->2->3).

[0115] Figure 16 is a diagram illustrating the change in characteristics of a fiber battery according to the amount of active material loaded.

[0116] Referring to Fig. 16, the loading density (g / cm²) according to the loading amount of active material (Ni loading in cathode, wt%) is shown. 3 Changes in ) and linear capacity (mAh / cm) are measured and expressed. Specifically, the cathode of the fiber battery according to Experimental Example 2 above was prepared as a target for changing the loading amount of the active material.

[0117] As can be seen in Fig. 16, as the loading amount of active material (Ni loading in cathode, wt%) increases, the loading density (Loading density, g / cm³) 3 It was also confirmed that ) and linear capacity (mAh / cm) were continuously improving.

[0118] FIG. 17 is a diagram illustrating a galvanostatic discharge curve for a fiber battery according to Experimental Example 2 of the present invention.

[0119] Referring to Fig. 17, the galvanostatic discharge curve for the fiber battery according to Experimental Example 2 is shown, and the galvanostatic discharge curve at different current densities (0.1 mA / cm, 0.2 mA / cm, 0.3 mA / cm, 0.5 mA / cm, 1.0 mA / cm). As can be seen in Fig. 17, it was confirmed that the galvanostatic discharge curve exhibited similar behavior despite changes in current density.

[0120] FIG. 18 is a diagram illustrating the capacity retention performance and Coulomb efficiency of a fiber battery according to Experimental Example 2 of the present invention.

[0121] Referring to FIG. 18, the capacity retention (%) and Coulombic efficiency (%) of the fiber battery according to Experimental Example 2 are measured and shown as the number of charge-discharge cycles increases. As can be seen in FIG. 18, the fiber battery according to Experimental Example 2 exhibits excellent capacity retention performance and a Coulombic efficiency of 100% despite the increase in the number of charge-discharge cycles.

[0122] FIG. 19 is a diagram illustrating the power density and energy density of a fiber battery according to Experimental Example 2 of the present invention.

[0123] Referring to FIG. 19, the power density (mW / cm²) of the fiber battery (This work) according to Experimental Example 2 above 3 ) and energy density (mWh / cm² 3 ) is measured and expressed. As can be seen in Fig. 19, the fiber battery according to Experimental Example 2 above is 422 mWh / cm². 3 The maximum energy density of and 7535 mW / cm² 3 It was confirmed that it represents the maximum power density.

[0124] FIG. 20 is a photograph of a fabric woven through fiber electrodes according to Experimental Example 2 and Experimental Example 4 of the present invention.

[0125] Referring to FIG. 20, a cathode and an anode are woven in parallel onto a commercial fabric, and the fabric is coated with a PVA-based gel electrolyte. Specifically, the fiber electrode according to Experimental Example 2 was used as the cathode, and the fiber electrode according to Experimental Example 4 was used as the anode. As can be seen in FIG. 20, it was confirmed that the fiber electrodes according to Experimental Example 2 and Experimental Example 4 have high mechanical flexibility and can be easily woven onto the fabric.

[0126] FIG. 21 is a diagram comparing the performance according to the arrangement of fiber electrodes according to Experimental Example 2 of the present invention.

[0127] Referring to Figure 21, the galvanostatic discharge curves for the case where the fiber electrode battery according to Experimental Example 2 is placed alone (Single battery), the case where three batteries are connected in series (Three batteries connected in series), and the case where three batteries are connected in parallel (Three batteries connected in series) are each shown.

[0128] As can be seen in Fig. 21, it was confirmed that the voltage and capacity were tripled for both series and parallel connections, resulting in increased power and energy output. Additionally, due to the high power and energy density, it was confirmed that seven blue LEDs and six green LEDs lit up simultaneously.

[0129] FIG. 22 is a diagram comparing the performance according to the buffer layer thickness of the fiber electrode according to Experimental Example 2 of the present invention.

[0130] Referring to FIG. 22, a fiber electrode according to Experimental Example 2 is prepared, and multiple samples are prepared by varying the number of layers of carbon nanotube sheets used as buffer layers (Outer CNT buffer, layer), and then the linear capacity (mAh / cm) and capacity retention (%) are measured and shown for each.

[0131] As can be seen in Fig. 22, when the number of carbon nanotube sheets stacked is three or more layers, the capacity retention performance continuously increases, but the linear capacity gradually decreases. Accordingly, it was found that the number of carbon nanotube sheets stacked to ensure a certain level of capacity retention performance without a decrease in linear capacity is three layers.

[0133] Although the present invention has been described in detail using preferred embodiments, the scope of the invention is not limited to specific embodiments and should be interpreted by the appended claims. Furthermore, those skilled in the art will understand that many modifications and variations are possible without departing from the scope of the invention. Explanation of the symbols

[0134] 100: Substrate 110: Carbon nanotube sheet 200: Carbon nanotube fiber 300: Preliminary fiber electrode 310: Buffer sheet (buffer layer) 400: Fiber electrode

Claims

Claim 1 A fiber electrode comprising: carbon nanotube fibers formed by rolling and stacking carbon nanotube sheets; an active material provided between the rolled and stacked carbon nanotube sheets; and a buffer layer covering the outer surface of the carbon nanotube fibers and preventing the active material from falling off from the carbon nanotube fibers, wherein the active material comprises either nickel hydroxide (Ni(OH)2) or iron oxide (Fe3O4), and the active material is provided in the form of particles between the rolled and stacked carbon nanotube sheets, and the buffer layer comprises a plurality of carbon nanotube sheets stacked. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A fiber electrode according to claim 1, wherein the mass percentage of the active material in the carbon nanotube fiber is 97 wt% or more. Claim 6 A fiber electrode according to claim 1, wherein the carbon nanotube fiber extends in a first direction, and in a cross-section cut with a first plane having the first direction as normal, the cross-section of the carbon nanotube fiber is provided in a spiral. Claim 7 A fiber battery comprising: a cathode comprising a fiber electrode according to claim 1, wherein the active material is nickel hydroxide (Ni(OH)2); an anode comprising a fiber electrode according to claim 1, wherein the active material is iron oxide (Fe3O4); and an aqueous electrolyte in which the cathode and the anode are immersed. Claim 8 In Paragraph 7, 422 mWh / cm² 3 The maximum energy density above and 7535 mW / cm² 3 Fiber battery having a maximum power density of the above. Claim 9 The method comprises the steps of: preparing a carbon nanotube sheet; providing an active material on the carbon nanotube sheet; manufacturing a prefiber electrode provided with the active material between the carbon nanotube sheets that are twisted, rolled, and stacked with the carbon nanotube sheet provided with the active material; and wrapping the outer surface of the prefiber electrode with a buffer sheet comprising a carbon nanotube sheet, wherein the step of wrapping the outer surface of the prefiber electrode with a buffer sheet comprising a carbon nanotube sheet comprises the steps of: preparing the buffer sheet comprising a carbon nanotube sheet in which a plurality of carbon nanotubes extending in one direction are arranged side by side; rolling the buffer sheet to have a cylinder shape with a hollow formed inside, and placing the prefiber electrode within the internal hollow; and applying a twist to one end of the buffer sheet having a cylinder shape to deform it into an hourglass shape such that the central portion located between the one end and the other end of the buffer sheet comes into contact with the prefiber electrode. A method for manufacturing a fiber electrode comprising the step of applying a twist to one end of the buffer sheet having an hourglass shape and pressing the buffer sheet against the outer surface of the prefabricated fiber electrode. Claim 10 delete Claim 11 A method for manufacturing a fiber electrode according to claim 9, wherein the step of providing an active material on the carbon nanotube sheet comprises: preparing a source solution in which the active material is dispersed in ethanol; and drop-casting the source solution onto the carbon nanotube sheet. Claim 12 A method for manufacturing a fiber electrode according to claim 11, wherein the mass percentage of the active material in the prefabricated fiber electrode is controlled by controlling the concentration of the active material in the source solution. Claim 13 A method for manufacturing a fiber electrode according to claim 12, wherein as the concentration of the active material in the source solution increases, the mass percentage of the active material in the prefabricated fiber electrode increases.

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