Metal ion doped conductive polymer-coated carbon nanotubes composite material and anode protective layer for zinc-ion battery including the same

Abstract

One embodiment of the present invention provides a zinc ion battery negative electrode comprising a negative electrode protective layer. According to an embodiment of the present invention, by coating polypyrrole on the surface of a carbon nanotube, the interfacial adhesion between the zinc negative electrode body and the protective layer is improved to enhance stability, and by doping zinc into the polypyrrole-coated carbon nanotube, electrical conductivity and ion diffusion ability are improved, thereby providing a zinc ion battery with excellent performance.

Description

Technology Field

[0001] The present invention relates to a negative electrode for a zinc ion battery, and more specifically, to a negative electrode comprising a carbon nanotube composite negative electrode protective layer for a zinc ion battery that can improve the electrochemical behavior of the zinc ion battery. Background Technology

[0002] Energy Storage Systems (ESS) have emerged as a solution to improve energy efficiency and facilitate the storage of generated power for use when needed. The need for high-capacity, low-cost ESS systems is increasing due to environmental changes, such as the surge in power demand caused by rapid climate change, large-scale power outages, and the proliferation of renewable energy sources.

[0003] Conventional lithium-ion batteries (LIBs) currently used in ESS are expensive due to the use of lithium and present significant safety issues. Zinc-ion batteries (ZIBs) have emerged as an alternative for ESS applications where safety and lifespan are critical. As batteries tailored for ESS, ZIBs are optimized by using aqueous electrolytes to eliminate the risk of explosion and demonstrate excellent capacity per unit volume.

[0004] However, cathode corrosion caused by acidic aqueous electrolytes, gas generation due to inevitable hydrogen production, passivation of byproducts, and the formation of non-uniform dendritic crystals on the Zn surface adversely affect the performance and lifespan of ZIBs. There has been a demand for means to resolve these problems of zinc-ion batteries, and a representative strategy proposed involves forming a protective layer at the interface of the Zn metal cathode. Prior art literature

[0005] Republic of Korea Published Patent Application 10-2024-0157325 The problem to be solved

[0006] The present invention aims to provide a zinc ion battery having excellent performance and stability by forming a novel carbon nanotube composite protective layer on the negative electrode surface of a zinc ion battery as a method to solve the problems of the aforementioned prior art.

[0007] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention belongs from the description below. means of solving the problem

[0008] To achieve the above technical problem, one embodiment of the present invention provides a zinc ion battery negative electrode.

[0009] A zinc ion battery negative electrode according to one embodiment of the present invention comprises: a zinc negative electrode body; and a negative electrode protective layer formed on the zinc negative electrode body; wherein the negative electrode protective layer comprises a polypyrrole-coated carbon nanotube.

[0010] In an embodiment of the present invention, the polypyrrole-coated carbon nanotube may be a zinc ion battery negative electrode characterized by being doped with zinc metal.

[0011] In an embodiment of the present invention, the zinc ion battery negative electrode may be characterized in that the thickness of the negative electrode protective layer is 5 μm to 20 μm.

[0012] Another embodiment of the present invention for achieving the technical problem described above provides a zinc ion battery.

[0013] A zinc ion battery according to one embodiment of the present invention comprises a negative electrode; a positive electrode spaced apart from the negative electrode; and an electrolyte disposed in the space between the positive electrode and the negative electrode, wherein the negative electrode comprises a zinc negative electrode body; and a negative electrode protective layer formed on at least one surface of the zinc negative electrode body, and wherein the negative electrode protective layer comprises a polypyrrole-coated carbon nanotube.

[0014] In an embodiment of the present invention, the positive electrode may be a zinc ion battery comprising a positive electrode active material, a conductive material, and a binder, wherein the positive electrode active material is one or more selected from the group consisting of a manganese-based compound, a Prussian blue-based compound, and a vanadium-based compound.

[0015] In an embodiment of the present invention, the electrolyte may be a zinc ion battery characterized by being an aqueous electrolyte.

[0016] In an embodiment of the present invention, the polypyrrole-coated carbon nanotube may be a zinc ion battery characterized by being doped with zinc metal.

[0017] Another embodiment of the present invention for achieving the above-described technical problem provides a method for manufacturing a zinc ion battery negative electrode.

[0018] A method for manufacturing a zinc ion battery negative electrode according to one embodiment of the present invention comprises: a step of oxidizing carbon nanotubes; a step of adding the oxidized carbon nanotubes to a pyrrole monomer dispersion and stirring; a step of polymerizing the pyrrole monomer to obtain polypyrrole-coated carbon nanotubes; a step of mixing the polypyrrole-coated carbon nanotubes with a binder to prepare a slurry; and a step of applying the slurry onto a zinc negative electrode body.

[0019] In an embodiment of the present invention, the method for manufacturing a zinc ion battery negative electrode may further include the step of doping a zinc element into the polypyrrole-coated carbon nanotubes in the step of obtaining the polypyrrole-coated carbon nanotubes. Effects of the invention

[0020] According to an embodiment of the present invention, it has the following effects.

[0021] (i) The polypyrrole coating on the surface of carbon nanotubes can improve interfacial adhesion between the zinc metal cathode and the protective layer, allowing the layer to adhere firmly to the cathode even after repeated cycling.

[0022] (ii) In one embodiment, doping zinc into a polypyrrole-coated carbon nanotube material improves the ion diffusion ability and electrical conductivity of the protective material, thereby improving the resistance characteristics of the electrode interface and facilitating the generation of a uniform electric field across the entire interface.

[0023] (iii) Doped zinc acts as a nucleation site for the Zn cathode, increasing the uniformity of zinc plating during charging and promoting the formation of a uniform zinc layer, which can improve the long-term stability of the cell.

[0024] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description of the invention or the claims. Brief explanation of the drawing

[0025] Figure 1 shows the manufacturing process of Zn-PPy-CNT that can be used as a protective layer for a cathode according to one embodiment of the present invention. Figure 2a is a diagram showing a low-magnification SEM image of a bare Zn cathode. Figure 2b is a diagram showing a low-magnification SEM image of a cathode including a CNT protective layer. Figure 2c is a diagram showing a low-magnification SEM image of a cathode including a PPy-CNT protective layer. Figure 2d is a diagram showing a low-magnification SEM image of a cathode including a Zn-PPy-CNT protective layer. Figure 2e is a diagram showing a high-magnification SEM image of a bare Zn cathode. Figure 2f is a diagram showing a high-magnification SEM image of a cathode including a CNT protective layer. Figure 2g is a diagram showing a high-magnification SEM image of a cathode including a PPy-CNT protective layer. Figure 2h is a diagram showing a high-magnification SEM image of a cathode including a Zn-PPy-CNT protective layer. Figure 3 is a diagram showing the results of an adhesion test between a Zn metal foil of a cathode and a protective layer according to one embodiment and a comparative example of the present invention. Figure 4a is a TEM image of a CNT. Figure 4b is a TEM image of PPy-CNT. Figure 4c is a TEM image of Zn-PPy-CNT. Figure 4d is a TEM image and EDS mapping result diagram of Zn-PPy-CNT. Figure 4e is an FT-IR analysis diagram of PPy, PPy-CNT, and Zn-PPy-CNT. Figure 4f is the N 1s XPS spectrum of PPy-CNT. Figure 4g is the N 1s XPS spectrum of Zn-PPy-CNT. Figure 4h is the Zn 2p XPS spectrum of Zn-PPy-CNT. Figure 4i shows the ICP-MS analysis results of PPy-CNT and Zn-PPy-CNT. Figure 4j shows the results of the electrical conductivity analysis of PPy-CNT and Zn-PPy-CNT. Figure 4k shows the EPR analysis results confirming the presence and distribution of radicals in PPy-CNT and Zn-PPy-CNT. Figure 41 is a diagram visually illustrating the doping of zinc and the improvement of electrical conductivity. FIG. 5a is a diagram showing the voltage profile of a symmetric cell including an embodiment and a comparative example of the present invention. Figure 5b shows a voltage profile illustrating the nucleation overpotential during the initial cycle of a bare Zn cathode. Figure 5c shows a voltage profile showing the nucleation overpotential during the initial cycle of a cathode containing a CNT protective layer. Figure 5d shows a voltage profile showing the nucleation overpotential during the initial cycle of a cathode containing a PPy-CNT protective layer. Figure 5e shows a voltage profile showing the nucleation overpotential during the initial cycle of a cathode containing a Zn-PPy-CNT protective layer. FIG. 5f is a diagram showing the LSV curve of a cathode according to one embodiment and a comparative example of the present invention. FIG. 5g is a diagram showing a Tafel plot of a cathode according to one embodiment and a comparative example of the present invention. Figure 6a shows an SEM image of a bare Zn cathode after charging. Figure 6b is a diagram showing an SEM image of a cathode containing a CNT protective layer after charging. Figure 6c is a diagram showing an SEM image of a cathode containing a PPy-CNT protective layer after charging. Figure 6d is a diagram showing an SEM image of a cathode containing a Zn-PPy-CNT protective layer after charging. FIG. 6e is a schematic diagram showing the surface Zn plating behavior of a bare Zn cathode and a Zn cathode with a protective layer applied according to an embodiment of the present invention. FIG. 7a is a figure showing the Nyquist plot of an embodiment and a comparative example of the present invention. FIG. 7b shows Z of an embodiment and a comparative example of the present invention. real and ω -1 / 2This is a diagram showing the relationship between them. FIG. 7c is a figure showing the Zn ion diffusion coefficients of an embodiment and a comparative example of the present invention. FIG. 7d is a diagram showing the CV curves of an embodiment and a comparative example of the present invention. FIG. 7e is a diagram showing the charge and discharge curves of an embodiment and a comparative example of the present invention. FIG. 7f is a diagram showing the rate-limiting performance of an embodiment and a comparative example of the present invention. FIG. 7g is a comparison diagram of the rate capability performance of a zinc ion battery according to one embodiment of the present invention and the previously reported rate capability performance. FIG. 7h is a comparison diagram of power and energy density using Ragone plots of a zinc ion battery according to one embodiment of the present invention and a previously reported zinc ion battery. Figure 7i is a figure showing the rate capability performance over time for various C-rates of a bare Zn cathode. Figure 7j is a diagram showing the rate capability performance over time for various C-rates of a cathode including a CNT protective layer. Figure 7k is a figure showing the rate capability performance over time for various C-rates of a cathode including a PPy-CNT protective layer. Figure 71 is a diagram showing the rate capability performance over time for various C-rates of a cathode including a Zn-PPy-CNT protective layer. FIG. 8a is a diagram showing the cycle stability of a zinc ion battery according to an embodiment and a comparative example of the present invention. FIG. 8b is a comparative XRD curve diagram for confirming discharge byproducts after a cycling test of a zinc ion battery according to an embodiment and a comparative example of the present invention. Figure 8c is an SEM image of a zinc-ion battery containing a bare Zn cathode after cycling. Figure 8d is an SEM image of a zinc-ion battery after cycling that includes a cathode containing a CNT protective layer. Figure 8e is an SEM image of a zinc-ion battery after cycling that includes a cathode containing a PPy-CNT protective layer. Figure 8f is an SEM image of a zinc-ion battery after cycling that includes a cathode containing a Zn-PPy-CNT protective layer. FIG. 9 is a schematic diagram illustrating the advantages of a cathode according to one embodiment of the present invention, including high adhesion, electrical conductivity, and many nucleation sites. Specific details for implementing the invention

[0026] The present invention will be described below with reference to the attached drawings. However, the present invention may be implemented in various different forms and is therefore not limited to the embodiments described herein. Furthermore, in order to clearly explain the present invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification have been given similar reference numerals.

[0027] Throughout the specification, when it is stated that a part is "connected (connected, in contact, combined)" with another part, this includes not only cases where they are "directly connected," but also cases where they are "indirectly connected" with other members interposed between them. Furthermore, when it is stated that a part "includes" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but rather allows for the inclusion of additional components.

[0028] The terms used herein are merely for describing specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising” or “having” are intended to indicate the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0029] Embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0030] In the following specifications, PPy means polypyrrole and CNT means carbon nanotube.

[0032] A zinc ion battery negative electrode according to one embodiment of the present invention is described.

[0033] Zinc-ion batteries use abundant zinc metal as the negative electrode, and zinc metal has a high theoretical capacity per unit weight (820 mAh·g -1 ) and high theoretical capacity per area (5,855mAh·cm²) -2 It is evaluated as a promising technology to replace existing lithium batteries by providing ).

[0034] Much research has been conducted to improve the performance of existing zinc-ion batteries, and zinc-ion batteries are expected to play a very important role as a future energy storage technology.

[0035] However, there are challenges that need to be solved for the use of zinc cathodes.

[0036] First, zinc forms non-uniform dendrites during the cycling process of zinc-ion batteries. If these formed dendrites penetrate the separator, it can lead to an internal short circuit, which adversely affects the battery's performance and lifespan.

[0037] Accordingly, in order to fully utilize the potential of the zinc anode, the present invention aims to solve the aforementioned problems by forming a cathode protection layer containing a carbon composite material, namely carbon nanotubes, on the surface of the anode of a zinc ion battery.

[0038] However, although it is known that using conventional carbon nanotubes as a cathode protective layer can effectively prevent the generation of non-uniform electric fields at the Zn cathode and suppress dendritic crystal growth, carbon-based materials have a problem in that they have weak adhesion to the Zn metal cathode, are easily damaged even under low pressure, and tend to detach from the Zn cathode after charge-discharge cycles.

[0039] Accordingly, the present invention solves the problems of the existing technology by coating the surface of the aforementioned carbon nanotube cathode protective layer with polypyrrole, known as a conductive polymer.

[0040] That is, a zinc ion battery negative electrode according to one embodiment of the present invention comprises a zinc negative electrode body (20) and a negative electrode protective layer (10) formed on the surface of the zinc negative electrode body, and the negative electrode protective layer (10) is characterized by comprising a carbon nanotube with a surface coated with polypyrrole.

[0041] Unlike other conventional organic polymers, conductive polymers represented by polypyrrole possess electrical, magnetic, and optical properties similar to metals and semiconductors; in particular, polypyrrole is a promising polymer due to its excellent conductivity, electrochemical reversibility, high polarizability, and easy synthesis.

[0042] In addition, polypyrrole enables a coating chemically bonded to carbon nanotubes, which improves the corrosion resistance of carbon nanotubes and enhances the chemical-mechanical stability of the zinc ion battery anode.

[0043] In an embodiment of the present invention, the polypyrrole-coated carbon nanotubes of the cathode protection layer (10) may be metal-doped. Preferably, the metal doping is zinc ions (Zn 2+ It may refer to metal doping of ). In addition, not only zinc metal doping but also additionally other metals, e.g., Fe 2+ , Al 3+ It may also include additional dopings such as those mentioned above. Metal doping can increase the electrical conductivity of the cathode protective layer, and in particular, Zn metal-doped polypyrrole-coated carbon nanotubes (Zn-PPy-CNT) can act as nucleation sites for Zn during the charging and discharging process of zinc-ion batteries, thereby promoting the uniform deposition of Zn at the cathode. Consequently, large nucleation sites are formed within the cathode, which can improve the performance of the zinc cathode.

[0044] The above zinc metal doping can be formed, for example, by zinc ions adsorbing onto the polypyrrole and binding with the nitrogen of the polypyrrole to form N-Zn-OH bonds, or by binding with portions of oxidized CNTs. In this case, doping the polypyrrole with Zn causes electron redistribution and strengthens the polaron state of the polypyrrole, which consequently improves the electrical conductivity of the polypyrrole.

[0045] In an embodiment of the present invention, the zinc cathode body (20) may have a plate shape having one side and another side opposite to the one side, but is not limited thereto. Such a zinc cathode body (10) may be a zinc metal plate or a metal plate on which a zinc metal thin film is formed on a cathode current collector. At this time, the method of forming the zinc metal thin film is not particularly limited, and known metal thin film forming methods such as lamination and sputtering may be used. In addition, the zinc metal plate of the present invention includes cases where a zinc metal thin film is formed on a metal plate by initial charging after assembling a battery in a state where there is no zinc thin film on the cathode current collector.

[0046] In an embodiment of the present invention, the cathode protection layer (10) is formed on at least one surface of the zinc cathode body (20). At this time, the cathode protection layer (10) may be formed as a single-sided structure formed only on one surface or the other surface of the zinc cathode body (20). Additionally, the cathode protection layer (10) may be formed as a double-sided structure formed on one surface and the other surface of the zinc cathode body (20), respectively.

[0047] The thickness of the above cathode protection layer (10) may be, for example, about 5 μm to 20 μm, and preferably 10 μm.

[0049] Next, a zinc ion battery according to another embodiment of the present invention will be described.

[0050] A zinc ion battery according to one embodiment of the present invention comprises: a negative electrode (100); a positive electrode (200) spaced apart from the negative electrode; and an electrolyte (300) disposed in the space between the positive electrode and the negative electrode.

[0051] At this time, the cathode (100) comprises a zinc cathode body; and a cathode protective layer formed on at least one surface of the zinc cathode body, wherein the cathode protective layer comprises a polypyrrole-coated carbon nanotube.

[0052] The above-mentioned cathode (100) corresponds to a cathode according to one embodiment of the present invention, as described above. That is, it includes a zinc cathode body and a cathode protective layer. Regarding the cathode, the same description as above is omitted.

[0053] The zinc cathode body may have a plate shape having one side and another side opposite to the one side, but is not limited thereto. Such a zinc cathode body may be a zinc metal plate or a metal plate on which a zinc metal thin film is formed on a cathode current collector. In this case, the method of forming the zinc metal thin film is not particularly limited, and known metal thin film forming methods such as lamination or sputtering may be used. Furthermore, the zinc metal plate of the present invention includes cases where a zinc metal thin film is formed on a metal plate by initial charging after the battery is assembled without a zinc thin film on the cathode current collector.

[0054] A cathode protection layer is formed on at least one surface of a zinc cathode body. At this time, the cathode protection layer may be formed as a single-sided structure formed only on one surface or the other surface of the zinc cathode body. Additionally, the cathode protection layer may be formed as a double-sided structure formed on one surface and the other surface of the zinc cathode body (110), respectively.

[0055] The anode (200) is spaced apart from the zinc cathode (100) to face it.

[0056] The positive electrode (200) may have a positive electrode active material layer comprising a positive electrode active material, a conductive material, and a binder.

[0057] The above-mentioned positive active material may include one or more selected from the group consisting of manganese-based compounds, Prussian blue-based compounds and vanadium-based compounds, and may include at least one selected from the group consisting of, for example, MnO2, Mn3O4, Mn2O3 and V2O5, preferably MnO2, but is not limited thereto.

[0058] The above conductive material may include one or more selected from the group consisting of carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotube, and graphene.

[0059] The above binder may include one or more selected from the group consisting of polyethylene oxide, polyethyleneglycol, polyacrylonitrile, polyvinyl chloride, polymethyl methacrylate, polypropylene oxide, polydimethylsiloxane, polyvinylidenefluoride, polyvinylidenecarbonate, and polyvinyl pyrrolidinone.

[0060] The electrolyte (300) may be an aqueous electrolyte containing an aqueous solvent. In this case, the aqueous solvent may be water (H2O), and the metal salt may include one or more selected from zinc sulfate (ZnSO4), Zn(NO3)2, Zn(CF3SO3)2, manganese sulfate (MnSO4), vanadium sulfate (VOSO4), phosphoric acid (H3PO4), sulfuric acid (H2SO4), sodium hydroxide (NaOH), potassium hydroxide (KOH), calcium hydroxide (Ca(OH)2) and magnesium hydroxide (Mg(OH)2), and preferably may include ZnSO4.

[0061] In addition, the zinc-ion battery may further include a separator (400) in the space between the negative electrode (100) and the positive electrode (200).

[0062] This separator (400) is placed in the space between the zinc cathode (100) and the anode (200) to prevent a short circuit between the zinc cathode (100) and the anode (200). The separator can be used without special limitations as long as it functions to physically separate the zinc cathode (100) and the anode (200), and it is particularly desirable to use one that has low resistance to electrolyte ion movement and excellent electrolyte moisture retention capacity.

[0063] At this time, the separator (400) may include at least one selected from the group consisting of a porous film made of a material such as polyethylene, polypropylene or other polyolefin resins, fluoropolymers, nitrogen-containing aromatic polymers, nonwoven fabrics, woven fabrics, filter papers, and glass fibers.

[0064] At this time, the thickness of the separator (400) is preferably thinner as long as mechanical strength is maintained, in that the volume energy density of the battery increases and the internal resistance decreases.

[0065] Specifically, the thickness of the separator (400) may be, for example, about 5 μm to 200 μm, and preferably, 5 μm to 40 μm.

[0067] Next, a method for manufacturing a negative electrode for a zinc ion battery according to another embodiment of the present invention will be described.

[0068] Figure 1 shows the manufacturing process of Zn-PPy-CNT that can be used as a protective layer for a cathode according to one embodiment of the present invention.

[0069] A method for manufacturing a negative electrode for a zinc ion battery according to one embodiment of the present invention comprises: a step of oxidizing carbon nanotubes (S100); a step of adding the oxidized carbon nanotubes to a pyrrole monomer dispersion and stirring (S200); a step of polymerizing the pyrrole monomer to obtain polypyrrole-coated carbon nanotubes (S300); a step of mixing the polypyrrole-coated carbon nanotubes with a binder to prepare a slurry (S400); and a step of applying the slurry onto a zinc negative electrode body (S500).

[0070] First, carbon nanotubes are oxidized (S100). Oxidation of the carbon nanotube surface facilitates effective bonding between CNTs and PPy through the bonding of defects on the oxidized carbon nanotube surface and pyrrole monomers. The S100 step can be performed, for example, by adding nitric acid to the carbon nanotubes.

[0071] Next, oxidized carbon nanotubes are added to the pyrrole monomer dispersion and stirred (S200), and then polymerized (S300). At this time, the polymerization can be performed by adding ammonium persulfate.

[0072] When ammonium persulfate is added, SO4 in the aqueous medium 2- and NH4 + Ions such as SO4 are generated. 2- It acts as a counterion to promote the polymerization of pyrrole into PPy. During the polymerization process, pyrrole is oxidized, inducing electron redistribution and the formation of cationic radicals (polarons) within the polymer chain structure. These cationic radicals (polarons) act as charge carriers, converting PPy into a conductive polymer with high electrical conductivity.

[0073] In an embodiment of the present invention, zinc doping may preferably be performed by adding a zinc precursor, for example, zinc nitrate, during the polymerization. That is, step S300 may include a step (S310) of doping zinc elements into the polypyrrole-coated carbon nanotube composite. The doped Zn ions act as nucleation sites and can promote uniform Zn deposition.

[0074] Finally, the manufactured carbon nanotube material is mixed with a binder to prepare a slurry, and this is applied onto the cathode body.

[0075] The above slurry may be prepared, for example, by adding the polypyrrole-coated carbon nanotubes to a solvent and stirring. The solvent may be NMP (N-Methyl-2-pyrrolidinone).

[0076] In addition, as an example, the binder may be PVDF (Polyvinylidene Fluoride).

[0078] The present invention will be explained in more detail below through manufacturing examples, comparative examples, and experimental examples. However, the present invention is not limited to the following manufacturing examples and experimental examples.

[0080] <Example 1> Cathode including a Zn-PPy-CNT cathode protection layer

[0081] (Step 1: Preparation of Zn-doped PPy-coated CNTs)

[0082] First, the CNTs were oxidized before polymerizing PPy onto the CNTs. To do this, 0.05 g of CNTs were added to 1 ml of nitric acid (Sigma-Aldrich, 70%) and activated by stirring for 30 minutes. The resulting solution was washed several times with distilled water and filtered to obtain oxidized CNTs.

[0083] To obtain PPy-coated CNTs (PPy-CNTs), 0.05 g of oxidized CNT powder was dispersed in 0.1 M hydrochloric acid (Sigma-Aldrich) for 30 minutes to activate the CNTs. Then, 0.75 ml of pyrrole monomer (Sigma-Aldrich, 98.0%) was added to the dispersion, and the resulting dispersion was sonicated for 5 minutes and then vigorously stirred for 10 minutes.

[0084] Next, 0.75 g of ammonium persulfate (Sigma-Aldrich, ≥98.0%) was dissolved in 18.75 ml of deionized water. For polymerization, the ammonium persulfate solution was slowly added to the pyrrole mixture, and the resulting solution was stirred for 5 hours. The stirred solution was washed with ethanol and distilled water to obtain PPy-CNT powder. To obtain Zn-PPy-CNT, 1.2 M zinc nitrate (Sigma-Aldrich, 98.0%) was added during PPy-CNT polymerization.

[0086] (Step 2: Preparation of Zn cathode protective layer)

[0087] To form a protective layer on the Zn cathode, each coating material (CNT, PPy-CNT, Zn-PPy-CNT, 80%) was mixed with N-methyl-2-pyrrolidone (NMP; Sigma-Aldrich, 99%) and poly(vinylidene fluoride) (PVDF; 20%) to obtain a paste. This paste was coated onto a Zn foil to form a 10 μm thick layer and dried at 60°C for 3 hours.

[0089] <Example 2> Preparation of a Zinc Ion Battery

[0090] An MnO2 anode was prepared using the blade coating method. The slurry was prepared by mixing an active material (MnO2; ≥ 90%, Sigma-Aldrich), a conductive material (Super P; IMERYS), and a polyvinylidene difluoride (PVDF) binder (Solef 5130, Solvay) in an 80:10:10 ratio in an N-methylpyrrolidone (NMP) solvent (99%, Sigma-Aldrich).

[0091] Next, the slurry was uniformly coated onto a 30 μm thick graphite foil and dried overnight in a 60 °C oven. For the electrolyte, a solution of ZnSO4 2M and MnSO4 0.1M mixed in DI water was used. A zinc-ion battery containing the prepared MnO2 cathode was assembled.

[0093] <Experimental Example 1> Analysis of Cathode Characteristics

[0095] (Cathode structure, shape)

[0096] FIG. 2 is a drawing showing an SEM image of a cathode according to one embodiment of the present invention.

[0097] Specifically, FIGS. 2a and 2e show low-magnification and high-magnification SEM images of a bare Zn cathode, FIGS. 2b and 2f show a cathode including a CNT protective layer, FIGS. 2c and 2g show a cathode including a PPy-CNT protective layer, and FIGS. 2d and 2h show a cathode including a Zn-PPy-CNT protective layer, respectively.

[0098] SEM images of cathode examples and comparative examples prepared as shown in Figure 2 above were obtained to investigate the morphology of the Zn cathode.

[0099] While the bare Zn cathode exhibited a typical smooth surface, the CNT, PPy-CNT, and Zn-PPy-CNT on the cathode surface showed a one-dimensional (1D) network structure.

[0100] On a smooth bare Zn surface, the growth of dendrites and byproducts is accelerated due to the scarcity of nucleation sites and the presence of a non-uniform electric field.

[0101] In contrast, the 1D network structure has the advantage of providing more nucleation sites for Zn plating during ZIB filling. The fact that the thickness of PPy-CNT and Zn-PPy-CNT is greater than that of CNT confirms that PPy was polymerized on the CNT surface. Notably, no morphological change was observed after Zn doping (Figs. 2d, 2h).

[0103] (Cathode Adhesion Test)

[0104] Figure 3 is a diagram showing the results of an adhesion test between a Zn metal foil of a cathode and a protective layer according to one embodiment and a comparative example of the present invention.

[0105] In ZIB, it is important to provide a protective layer that is strongly bonded to the cathode surface. Strong adhesion provides mechanical stability to the protective layer during charge-discharge cycles, prevents damage to the layer, minimizes direct contact between the Zn cathode and the electrolyte, thereby reducing corrosion of the Zn cathode and dendritic crystal formation, and improves the overall performance and lifespan of the battery. An adhesion analysis was performed to investigate whether polymerizing PPy on the CNT surface improves the adhesion between the Zn metal electrode and the protective layer.

[0106] As can be seen in Fig. 3, a force of 260.40 mN was required to peel off the CNT protective layer from the Zn cathode surface (part a), but a much larger force was required for the PPy-CNT (564.11 mN) and Zn-PPy-CNT (566.40 mN) layers (parts b, c).

[0107] These results suggest that coating PPy on the CNT surface improves interfacial adhesion between the metal surface to be protected and the CNT protective layer.

[0108] In addition, the cell was disassembled after cycling to check the condition of the protective layer on the cathode. It was found that the CNT protective layer without PPy was detached from the Zn metal, and the underlying Zn foil reacted with the electrolyte, causing the surface of the Zn foil to become rough. In contrast, the protective PPy-CNT layer was much more strongly bonded to the Zn cathode. This can be explained by the fact that the adhesion between the Zn cathode and the protective layer was enhanced by introducing CP PPy into the CNTs.

[0110] (Analysis of the presence or absence of PPy and Zn dopants)

[0111] Various analyses were performed to confirm whether PPy and Zn dopants were present on the CNT surface.

[0112] FIG. 4 is a diagram showing the results of structural characteristic analysis and chemical analysis of a cathode according to one embodiment and a comparative example of the present invention.

[0113] Specifically, Fig. 4a shows a TEM image of a CNT, Fig. 4b shows a PPy-CNT, Fig. 4c shows a Zn-PPy-CNT, and Fig. 4d shows a TEM image of a Zn-PPy-CNT and a diagram of the EDS mapping results.

[0114] The presence of a PPy coating and Zn elements on the CNT surface was confirmed through TEM images and EDS mapping. TEM images confirmed that the diameter of the multilayer CNTs used in this study was approximately 10 nm (Fig. 4a). The PPy-CNT and Zn-PPy-CNT layers had a core-shell structure with a diameter of 20 nm, as PPy coated the CNT surface (Figs. 4b, 4c). The presence of Zn in the Zn-PPy-CNT was confirmed through the EDS analysis shown in Fig. 4d. Figs. 4b and 4c show that a 20 nm thick layer was formed on the CNT surface, and the presence of Zn elements in this layer was confirmed through EDS analysis (Fig. 4d).

[0116] Figure 4e is an FT-IR analysis diagram of PPy, PPy-CNT, and Zn-PPy-CNT.

[0117] Next, FT-IR analysis was performed to confirm whether this layer contains PPy as shown in Fig. 4e above. The analysis result was 3436.75 cm⁻¹ -1 NH, 1702.43 and 1549.43 cm -1 C=C, 1467.20 cm -1 of CN, 1313.07 cm -1 CH in-plane deformation, 1042 cm -1 NH in-plane deformation, and 913 and 794 cm -1 It showed the wavenumbers of various peaks, such as the =CH out-of-plane strain. Since PPy-CNT and Zn-CNT-PPy exhibited peaks almost identical to PPy, it could be inferred that the layer formed on the CNT surface was a PPy layer.

[0119] Figure 4f is the N 1s XPS spectrum of PPy-CNT, and Figure 4g is the N 1s XPS spectrum of Zn-PPy-CNT.

[0120] The bonding states of PPy-CNT and Zn-PPy-CNT were characterized using XPS, and the obtained results are shown in Figures 4f and 4g. In Figure 4f, the N 1s XPS spectrum of PPy-CNT shows the bonding state between the CNT and PPy, and -N + ( 401.2 eV), -NH - ( The existence of C=N (399.7 eV) and C=N (398.3 eV) can be confirmed. -N + The presence of indicates that PPy is in a polaron state. Zn-PPy-CNT exhibits an additional Zn-N bonding peak at 399.6 eV, which indicates that Zn is bonded to N of the PPy structure (Fig. 4g).

[0121] Figure 4h is the Zn 2p XPS spectrum of Zn-PPy-CNT.

[0122] Zn bonded to the CNT surface can be in the form of CO-Zn, because the CO groups on the CNT surface can bind to the Zn-N of PPy, acting as a bridge connecting the CNT and PPy. Zn can also bind to oxygen functional groups on the CNT surface and be adsorbed onto the PPy surface, or bind to the nitrogen of PPy in the form of Zn-OH. The formation of bonds between Zn and O is indicated by two symmetry peaks (△E) appearing at 1021.36 eV and 1044.36 eV in the Zn 2p spectrum (Fig. 4h). It was confirmed through 23 eV.

[0124] i) Confirmation of the presence of PPy and Zn doping on the CNT surface based on ICP-MS analysis results and j) electrical conductivity measurement results. k) EPR analysis. l) Schematic diagram showing the enhanced electrical conductivity of the fabricated Zn-PPy-CNT.

[0125] ICP-MS analysis was performed to quantitatively measure the Zn content. Figure 4i shows the results of ICP-MS analysis of PPy-CNT and Zn-PPy-CNT. As expected, the analysis results showed that Zn was absent in PPy-CNT, but Zn-PPy-CNT contained 3.815 mg / L of Zn.

[0126] Figure 4j shows the results of the electrical conductivity analysis of PPy-CNT and Zn-PPy-CNT, and the presented analysis results show that Zn doping increases the conductivity by 1.67 × 10⁻⁶ -3 8.07 × 10 at S / m -3 It showed once again that it was increased to S / m.

[0127] Figure 4k shows the results of EPR analysis confirming the presence and distribution of radicals in PPy-CNT and Zn-PPy-CNT. The presence of radicals was confirmed by the appearance of the EPR signal, which indicates that PPy is a conductive polymer. A shift of the peak to the left in the magnetic field was observed, which indicates that the g-factor increased from 2.0054 to 2.0066.

[0128] In addition, an increase in EPR signal intensity was observed. These results are related to Zn 2+ This suggests that the electronic structure of PPy was altered by this, leading to stronger electronic interactions.

[0129] Therefore, Zn doping generates more radicals in PPy, enhancing the polaron state and ultimately improving electrical conductivity. As seen in TEM-EDS, XPS, ICP, and EPR analyses, the electrical conductivity of PPy was successfully enhanced by Zn doping.

[0130] This improvement is very important for the cathode protection layer because it promotes a uniform electric field distribution, thereby increasing the efficiency of the Zn adsorption and desorption processes.

[0131] The enhanced electrical conductivity of Zn-doped PPy and the resulting electron transport are visually represented in Fig. 4l.

[0133] (Evaluation of cell stability and corrosion characteristics)

[0134] To evaluate cell stability and corrosion characteristics after the introduction of the protective layer, symmetrical cells and linear scanning voltammetry (LSV) tests were performed.

[0135] FIG. 5a is a diagram showing the voltage profile of a symmetric cell including an embodiment and a comparative example of the present invention. FIG. 5b, 5c, 5d, and 5e each show voltage profiles showing the nucleation overpotential during the initial cycle of a cathode including a bare Zn cathode, CNT, PPy-CNT, and a Zn-PPy-CNT protective layer.

[0136] As shown in FIG. 5a above, symmetric cells with different configurations are 2 mA cm -2 It was tested at current densities. The symmetric cell configurations were bare Zn / bare Zn, CNT / CNT, PPy-CNT / PPy-CNT, and Zn-PPy-CNT / Zn-PPy-CNT.

[0137] The bare Zn cell exhibited a high overvoltage of 79 mV and showed a sudden voltage drop after about 70 hours, which is presumed to be due to a short circuit caused by dendritic growth within the cell (Fig. 5b).

[0138] The CNT-based symmetric cell exhibited a low overpotential of 35 mV compared to bare Zn and was short-circuited after 120 hours (Fig. 5c). Given the high electrical conductivity of CNTs, these results suggest low interfacial adhesion between the Zn metal cathode and the CNT protective layer, which may cause delamination of the protective layer during cycling.

[0139] In contrast, the PPy-CNT / PPy-CNT cell remained stable for up to 360 hours with a lower overpotential of 29 mV compared to the CNT-based symmetric cell (Fig. 5d), which means that the interfacial adhesion between the Zn metal and the protective layer is improved, resulting in a stable overpotential.

[0140] The Zn-PPy-CNT / Zn-PPy-CNT cell stably maintained a low overpotential of 23 mV for 500 hours during the plating / demetallization process (Fig. 5e), which indicates an enhanced Zn transfer rate. This suggests that doped Zn ions acted as nucleation sites in the PPy-CNTs, promoting uniform Zn deposition and inhibiting dendritic growth, thereby improving cell stability.

[0141] Figure 5f is a diagram showing the LSV curves of a cathode with various protective layers applied.

[0142] A three-electrode system was used for a detailed analysis of the HER reaction and the corrosion resistance properties of the cathode. The system consisted of a prepared Zn cathode or a comparative example Zn cathode (working electrode), a Pt foil (counter electrode), and an Ag / AgCl (reference electrode). The LSV was 5 mVs. -1 It was performed at a scan speed. If the interfacial adhesion between the protective layer and the Zn cathode is insufficient, the protective layer may easily peel off due to hydrogen generation.

[0143] Referring to Figure 5f above, the LSV results showed that the slowest increase in current density was observed at the cathode with the Zn-PPy-CNT protective layer.

[0144] In addition, Figure 5g shows Tafel plots of cathodes with various protective layers applied, where the corrosion potential of the Zn cathode gradually increased from -0.991 V of bare Zn to -0.988 V of the CNT layer, -0.987 V of the PPy-CNT layer, and -0.979 V of the Zn-PPy-CNT layer. This indicates that the protective layer effectively suppressed the corrosion reaction of the Zn cathode (Figure 5g). Therefore, it can be seen that the introduction of the Zn-PPy-CNT protective layer improved cell stability, corrosion performance, and HER.

[0146] (Observation of Zn dendritic crystal growth)

[0147] Figure 6 shows SEM images of the cathode after charging according to the embodiments and comparative examples of the present invention.

[0148] SEM analysis was performed to investigate Zn dendritic crystal growth at the cathode.

[0149] Figure 6a shows an SEM image of the bare Zn cathode after charging, where the bare Zn exhibited very large and irregularly shaped Zn dendrites.

[0150] Figure 6b shows an SEM image of a cathode containing a CNT protective layer after charging. In the case of CNT, the observed dendrites were smaller than those of bare Zn due to the high charge transfer ability of CNT, even though the CNT growth was non-uniform and in the vertical direction.

[0151] In the case of PPy-CNT (Fig. 6c), dendritic growth was significantly less compared to CNT, but mismatched plating occurred due to reduced electrical conductivity.

[0152] In contrast, the overall dendritic growth of Zn-PPy-CNT was less and more uniform due to the abundant nucleation sites on the surface of the protective layer and higher electrical conductivity (Fig. 6d).

[0153] FIG. 6e is a schematic diagram showing the surface Zn plating behavior of a bare Zn cathode and a Zn cathode with a protective layer applied according to an embodiment of the present invention.

[0154] Based on the results described above, a schematic diagram illustrating the Zn plating / demetallization behavior of bare Zn and Zn-PPy-CNT is shown in Fig. 6e. The main cause of the poor chemical and electrochemical performance of bare Zn is interfacial reactions resulting from the direct interaction between the Zn surface morphology and the electrolyte. A smooth Zn surface hinders the uniform deposition of Zn due to a limited number of nucleation sites and an irregular electric field distribution. Additionally, H2O and dissolved O2 in the aqueous electrolyte can cause chemical corrosion reactions on the Zn surface, hindering uniform Zn deposition and leading to the formation of dendrites, H2, and byproducts.

[0155] However, chemical and electrochemical performance degradation can be effectively prevented by introducing a Zn-doped polymer into the CNT used as a protective layer. i) Enhanced adhesion prevents direct contact between the zinc anode and the electrolyte, thereby effectively suppressing side reactions that cause Zn anode corrosion and H2 generation, and ii) Zn contained in the polymer acts as a nucleation site, increasing the adsorption energy and conductivity of zinc ions, thereby preventing localized Zn accumulation on the zinc anode.

[0157] <Experimental Example 2> Analysis of Electrochemical Characteristics of the Cathode

[0159] (Evaluation of charge transport and ion transport capabilities)

[0160] FIG. 7 is a diagram showing the electrochemical performance of a battery using a negative electrode according to one embodiment of the present invention.

[0161] Specifically, FIG. 7a is a figure showing the Nyquist plots of an embodiment and a comparative example of the present invention.

[0162] EIS was performed to investigate the charge transport and ion transport capabilities of the prepared cathode. EIS analysis helps evaluate the electrode's transport rates, which are important for understanding cathode behavior. The results showed that the bare Zn cathode has a high charge transfer impedance (R ct It was shown that it exhibits ) and relatively low ion transport capacity. In contrast, the CNT cathode showed a significantly lower R due to high electrical conductivity. ct It indicated low R ct It is advantageous because it reduces resistance to charge transport at the electrode interface, thereby preventing dendritic crystal growth and improving cell performance.

[0163] Both PPy-CNT and Zn-PPy-CNT cathodes have higher R than CNT cathodes ct The values ​​indicate that electrical conductivity decreased due to the PPy coating. Surprisingly, Zn-PPy-CNT exhibited higher electrical conductivity than PPy-CNT, R ct It reduced [the value] and promoted efficient charge transfer on the Zn surface.

[0164] FIG. 7b shows Z of an embodiment and a comparative example of the present invention. real and ω -1 / 2 This is a diagram showing the relationship between them.

[0165] FIG. 7c is a figure showing the Zn ion diffusion coefficients of an embodiment and a comparative example of the present invention.

[0166] The Warburg impedance coefficient (σw) and the Zn ion diffusion coefficient (D) were calculated using the following Equations 1 and 2.

[0167] Equation (1)

[0168]

[0170] Equation (2)

[0171]

[0172] Here, R eR represents the total resistance of the electrode, and D represents the diffusion coefficient of Zn ions. R is the gas constant, T is the temperature, A is the area of ​​the electrode, n is the number of electrons per molecule, F is the Faraday constant, and C is the molar concentration of Zn ions.

[0173] The Warburg impedance coefficient (σw) values ​​for bare Zn, CNT, PPy-CNT, and Zn-PPy-CNT cathodes were 17.9, 9.89, 11.1, and 8.23 ​​Ω cm² s⁻¹, respectively. -1 / 2 It was (Fig. 7b). In addition, the diffusion coefficient values ​​of the fabricated ZIBs were 0.72, 2.28, 1.81, and 3.30 × 10⁻¹³ cm⁻¹ for bare Zn, CNT, PPy-CNT, and Zn-PPy-CNT, respectively. 2 s -1 It was calculated as (Fig. 7c).

[0175] (CV curve / Charge / Discharge curve)

[0176] FIG. 7d is a diagram showing the CV curves of an embodiment and a comparative example of the present invention.

[0177] In addition, the CV curves indicated that the active surface area increased from bare Zn to Zn-PPy-CNT (Fig. 7d). This increase is thought to be due to enhanced electrical conductivity and a larger number of nucleation sites provided by the protective layer.

[0179] FIG. 7e is a figure showing the charge / discharge curves of an embodiment and a comparative example of the present invention. In FIG. 7e, the constant current charge / discharge curve is for Zn-PPy-CNT bare Zn (227.2 mAh g -1 255.7 mAh g, which has a higher capacity compared to ) -1 It shows that it represents.

[0181] (Rate performance)

[0182] FIG. 7f is a diagram showing the rate-limiting performance of an embodiment and a comparative example of the present invention.

[0183] FIG. 7g is a comparison diagram of the rate capability performance of a zinc ion battery according to one embodiment of the present invention and the previously reported rate capability performance.

[0184] FIG. 7h is a comparison diagram of power and energy density using Ragone plots of a zinc ion battery according to one embodiment of the present invention and a previously reported zinc ion battery.

[0185] The rate capability performance of the four samples was evaluated by stepwise increasing the current density from 0.3 C to 2.0 C in the voltage range of 1.0 to 1.9 V. The results demonstrated the excellent energy storage capacity of Zn-PPy-CNT (Fig. 7f). In particular, Zn-PPy-CNT exhibited 199.2, 170.7, 151.3, 131.9, 118.8, 109.7, 102.9, and 94.2 mAh g⁻¹ at current densities of 0.3, 0.5, 0.7, 1.0, 1.3, 1.5, 1.7, and 2.0 C, respectively. -1 It exhibited impressive capacity characteristics.

[0186] The enhanced rate capability of the Zn-PPy-CNT cathode exhibited a higher energy storage capacity than previously reported in ZIB studies, as shown in Fig. 7g. In particular, the Zn-PPy-CNT showed 240 W kg⁻¹ as shown in Fig. 7h. -1 159.4 Wh kg at a power density -1 The energy density of, 1,600 W kg -1 75.4 Wh kg at a power density -1 It had an energy density.

[0187] The enhanced energy storage capacity of Zn-PPy-CNT can be explained as follows. First, the nanoscale 1D network structure increases the number of nucleation sites for Zn plating. Second, Zn doping of PPy improves Zn ion diffusion behavior, facilitating a stable charge-discharge process even at high current densities.

[0189] FIGS. 7i to 7l are drawings showing the rate-limiting performance over time for various C-rates of an embodiment and a comparative example of the present invention.

[0190] To further investigate the effect of the Zn-PPy-CNT protective layer, full cells were assembled and rate capability performance was measured after 1, 10, 20, and 30 days, and the results are shown in Figures 7i to 7l above. Figures 7i and 7j show that bare Zn and CNT with the protective layer exhibited a significant decrease in capacity at 20 and 30 days, respectively. Although the CNT protective layer initially performed a protective function, the capacity decreased over time, which is thought to be due to low adhesion.

[0191] In contrast, PPy-CNT and Zn-PPy-CNT, which have improved interfacial adhesion compared to CNT, continuously performed a protective role and maintained a nearly constant capacity for up to 30 days, demonstrating an effect as a Zn cathode protective layer (Figs. 7k, 7l).

[0193] (Long-term cycle performance)

[0194] FIG. 8a is a diagram showing the cycle stability of a zinc ion battery according to an embodiment and a comparative example of the present invention. FIG. 8b is a diagram comparing the XRD curves of a zinc ion battery according to an embodiment and a comparative example of the present invention.

[0195] As shown in Figure 8a above, the long-term cycle performance of a full cell using the prepared cathode was evaluated at a current density of 1.0 C.

[0196] After 250 charge-discharge cycles, Zn-PPy-CNT was compared to three other samples (bare Zn: 42.4 mAh g -1 , CNT: 43.7 mAh g -1 , PPy-CNT: 54.2 mAh g -1 Specific capacity higher than ), i.e., 67.7 mAh g -1 It represented.

[0197] In particular, Zn-PPy-CNT exhibited higher cycle stability than bare Zn. The formation of byproducts on the Zn cathode was confirmed through X-ray diffraction (XRD) analysis (Fig. 8b). A peak corresponding to the byproduct Zn4SO4(OH)65H2O (ZHS) was observed around 13° for bare Zn, CNT, and PPy-CNT, whereas it did not appear for Zn-PPy-CNT.

[0198] This indicates that corrosion reactions related to the electrolyte occurred at the Zn cathode. In the case of the Zn-PPy-CNT protective layer, the absence of such byproducts confirmed that this layer is effective in preventing corrosion.

[0199] Figures 8c to 8f are SEM images after cycling of zinc ion batteries containing a cathode including bare Zn and CNT, PPy-CNT, and Zn-PPy-CNT protective layers, respectively.

[0200] Figures 8c to 8f show SEM images illustrating the morphology of the Zn cathode surface after discharge. The surface of bare Zn in direct contact with a weakly acidic electrolyte exhibited a significant corrosion reaction, as can be seen in Figure 8c. This corrosion reaction leads to Zn depletion, ultimately impairing the structural integrity of the Zn metal cathode. Consequently, these changes make Zn plating more difficult and reduce the reversibility of ZIB.

[0201] The surface of the protective CNT layer showed less corrosion response, but the layer delaminated and exhibited low cycle stability due to poor interfacial adhesion between the Zn metal cathode and the protective layer (Fig. 8d).

[0202] In contrast, the surface with the protective PPy-CNT and Zn-PPy-CNT layers remained clean without byproduct formation or leaching. The protective Zn-PPy-CNT layer appears to provide conditions conducive to reversible Zn plating / st in a weakly acidic electrolyte (Fig. 8f).

[0204] FIG. 9 is a schematic diagram illustrating the advantages of a cathode according to one embodiment of the present invention, including high adhesion, electrical conductivity, and many nucleation sites.

[0205] As schematically illustrated in Figure 9 above, the introduction of a Zn-PPy-CNT protective layer to the zinc ion battery negative electrode provides three characteristic effects as follows.

[0206] First, (i) the PPy coating on the surface of the CNT can improve the interfacial adhesion between the Zn metal cathode and the protective PPy-CNT layer, allowing the layer to adhere firmly to the cathode even after repeated cycling.

[0207] In addition, (ii) doping PPy-CNT with Zn improves the ion diffusion ability and electrical conductivity of the protective material, thereby improving the resistance characteristics of the electrode interface and facilitating the generation of a uniform electric field across the entire interface.

[0208] In addition, (iii) doped Zn acts as a nucleation site for the Zn cathode, increasing the uniformity of Zn plating during charging and promoting the formation of a uniform Zn layer, which can improve the long-term stability of the cell.

[0210] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without altering the technical spirit or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form.

[0211] The scope of the present invention is defined by the claims set forth below, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention. Explanation of the symbols

[0213] 10: Cathode protection layer 20 : Zinc cathode body 100 : Cathode 200 : Anode 300 : Electrolyte 400 : Separator

Claims

Claim 1 A zinc ion battery cathode comprising: a zinc cathode body; and a cathode protective layer formed on the zinc cathode body; wherein the cathode protective layer comprises polypyrrole-coated carbon nanotubes. Claim 2 A zinc ion battery negative electrode according to claim 1, wherein the polyphenol-coated carbon nanotube is zinc metal-doped. Claim 3 A zinc ion battery negative electrode according to claim 1, characterized in that the thickness of the negative electrode protective layer is 5 μm to 20 μm. Claim 4 A zinc ion battery comprising: a cathode; an anode spaced apart from the cathode and positioned opposite to the cathode; and an electrolyte disposed in the space between the anode and the cathode, wherein the cathode comprises: a zinc cathode body; and a cathode protective layer formed on at least one surface of the zinc cathode body, and wherein the cathode protective layer comprises a polypyrrole-coated carbon nanotube. Claim 5 A zinc ion battery according to claim 4, wherein the positive electrode comprises a positive electrode active material, a conductive material, and a binder, and the positive electrode active material is one or more selected from the group consisting of manganese-based compounds, Prussian blue-based compounds, and vanadium-based compounds. Claim 6 A zinc ion battery according to claim 4, wherein the above electrolyte is an aqueous electrolyte. Claim 7 In paragraph 4, A zinc ion battery characterized by the above-mentioned polypyrrole-coated carbon nanotubes being doped with zinc metal. Claim 8 A method for manufacturing a zinc ion battery negative electrode, characterized by comprising: a step of oxidizing carbon nanotubes; a step of adding the oxidized carbon nanotubes to a pyrrole monomer dispersion and stirring; a step of polymerizing the pyrrole monomer to obtain polypyrrole-coated carbon nanotubes; a step of mixing the polypyrrole-coated carbon nanotubes with a binder to prepare a slurry; and a step of applying the slurry onto a zinc negative electrode body. Claim 9 A method for manufacturing a zinc ion battery negative electrode according to claim 8, characterized in that zinc nitrate is added during the polymerization step of obtaining the polypyrrole-coated carbon nanotube. Claim 10 A method for manufacturing a zinc ion battery negative electrode according to claim 8, characterized in that, in the step of obtaining the polypyrrole-coated carbon nanotube, the step of doping the polypyrrole-coated carbon nanotube with a zinc element is further included. Claim 11 A negative electrode for a zinc ion battery manufactured by the manufacturing method of claim 8.

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