Negative electrode for zinc-ion battery, comprising predominant β-phase polymer protective layer, method for manufacturing same, and zinc-ion battery

Abstract

The present invention relates to a negative electrode for a zinc-ion battery, a method for manufacturing same, and a zinc-ion battery, the negative electrode comprising a polymer protective layer comprising a predominant β-phase polar polymer.

Description

A zinc-ion battery negative electrode comprising a polymer protective layer of a dominant β-phase, a method for producing the same, and a zinc-ion battery

[0001] The present invention relates to a negative electrode for a zinc-ion battery. In particular, it relates to a negative electrode for a zinc-ion battery comprising a predominant β-phase polymer protective layer, a method for producing the same, and a zinc-ion battery.

[0002] This application claims priority to Korean Patent Application No. 10-2023-0172644, filed on December 1, 2023, the entire contents of which are disclosed in the specification and drawings of the said application are incorporated herein by reference.

[0003] Meanwhile, the present invention was supported by the following national research and development project.

[0004] Assignment ID: 2710004376

[0005] Assignment Number: RS-2024-00342112

[0006] Ministry of Science and ICT

[0007] Project Management Agency Name: National Research Foundation of Korea

[0008] Research Project Name: Individual Basic Research (Ministry of Science and ICT)

[0009] Research Project Title: Implementation of a High-Energy-Density Fiber-Type Power Source and Investigation of the Correlation Between Faraday Reaction and Inductive Charge Separation for Self-Charging

[0010] Project implementation organization name: Gyeongsang National University

[0011] Research period: May 1, 2024 - April 30, 2025

[0012] Environmental concerns and energy issues surrounding the use of fossil fuels have fueled growing interest in generating electricity using renewable energy sources such as solar and wind. However, the output of solar and wind power is not always stable and consistent due to unexpectedly diverse environmental and geographical conditions. To efficiently utilize variable renewable and clean energy, large-scale electrical energy storage (EES) systems capable of achieving high energy / power densities and excellent cycling stability are required.

[0013] Lithium-ion batteries (LIBs) are the most common energy storage devices and are proposed as a solution. However, the use of lithium has drawbacks such as poor safety, limited supply, uneven distribution, and high cost. In this regard, rechargeable batteries, especially aqueous batteries based on earth-abundant materials such as aluminum (Al), magnesium (Mg), or zinc (Zn), are attracting attention due to their low cost and safe aqueous electrolytes.

[0014] Rechargeable aqueous zinc-ion batteries (AZIBs), in particular, have attracted significant attention as a promising alternative for low-cost and safe energy storage systems. This is due to the natural abundance of zinc, the inherent safety of aqueous electrolytes, the high theoretical capacity of zinc metal, and the low cathode potential. However, zinc is thermodynamically unstable in weakly acidic aqueous electrolytes, and its surface spontaneously undergoes hydrogen evolution reaction (HER) and is prone to forming byproducts within the ZnSO4 electrolyte. Furthermore, uneven diffusion of zinc ions and dendrite growth due to plating can lead to battery short-circuiting. Various methods have been introduced to overcome these issues, among which the introduction of a protective layer is recognized for its convenience and effectiveness.

[0015] Protective layers include carbon, metal oxides, and polymers. Polar polymers are particularly popular. However, research and development is needed to develop more effective polymer protective layers that suppress zinc corrosion and hydrogen production, prevent the uneven diffusion of zinc ions, and thus suppress dendrite formation.

[0016] The present invention was conceived to solve the above-described problem, and aims to provide a zinc-ion battery negative electrode including a polymer protective layer made of a predominant β-phase polar polymer, a method for manufacturing the same, and a zinc-ion battery.

[0017] The technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the description below.

[0018] A negative electrode for a zinc-ion battery according to the present invention comprises a zinc substrate and a predominantly β-phase polymer protective layer formed on the surface of the zinc substrate.

[0019] A method for manufacturing a negative electrode for a zinc-ion battery according to the present invention comprises the steps of preparing a solution in which a polymer is completely dissolved in a solvent, adding one or more cationic additives selected from ZnCl2, Zn(CF3SO3)2, Zn(TFSI)2, ZnO, Zn(NO3)26H2O, Zn(NTF2)2 and ZnSO47H2O to the solution and then completely dissolving them to prepare a coating solution, applying the coating solution to the surface of a zinc substrate washed with ethanol and then drying it to prepare a polymer protective layer, and annealing the zinc substrate on which the polymer protective layer is prepared to generate a predominant β-phase.

[0020] The present invention further includes a negative electrode for a zinc-ion battery manufactured by the above manufacturing method.

[0021] The present invention further includes a zinc-ion battery including the above negative electrode.

[0022] According to the present invention as described above, when a predominant β-phase polymer protective layer is applied to the negative electrode of a zinc-ion battery, corrosion of zinc and hydrogen production reaction are suppressed, and non-uniform diffusion of zinc ions is prevented, so that dendrite formation can be suppressed very effectively.

[0023] In addition, the polymer protective layer of the present invention has a porosity of a certain level or higher, thereby improving wettability with an electrolyte, thereby improving the cycle performance of a zinc-ion battery and enhancing safety.

[0024] The effects of the present invention are not limited to those mentioned above, and also include other effects that are not explicitly mentioned, although they can be clearly understood by those skilled in the art from the description throughout the specification.

[0025] Figure 1 is a schematic diagram showing the manufacturing process and phase change of zinc anodes of comparative examples and examples.

[0026] Figure 2 shows the results of experiments conducted to compare the surface structure and interface characteristics of zinc cathodes (related to Experimental Example 1).

[0027] Figure 3 shows the results of experiments conducted to compare the phase changes of zinc cathodes, particularly the change to the β phase (related to Experimental Example 2).

[0028] Figure 4 shows the results of experiments conducted to compare the chemical stability of zinc cathodes (related to Experimental Example 3).

[0029] Figure 5 shows the results of experiments conducted to compare the dendrite inhibition performance of zinc cathodes (related to Experimental Example 4).

[0030] Figure 6 shows the results of experiments conducted to compare the zinc ion diffusion capacity and energy storage capacity of zinc cathodes (related to Experimental Example 5).

[0031] Figure 7 shows the results of experiments conducted to compare the cycling stability (life characteristics) of zinc cathodes (related to Experimental Example 6).

[0032] Figure 8 shows the results of experiments conducted to compare the performance of batteries through power supply of zinc cathodes (related to Experimental Example 7).

[0033] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. The advantages and features of the present invention, and methods for achieving them, will become clear with reference to the embodiments described in detail below together with the attached drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

[0034] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in a sense commonly understood by those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise. The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise.

[0035] The terms "comprises" and / or "comprising" as used in the specification do not exclude the presence or addition of one or more other components, steps, operations and / or elements.

[0036]

[0037] The present invention relates to a negative electrode for a zinc-ion battery, and the present invention will be described in detail below.

[0038] A negative electrode for a zinc-ion battery according to the present invention comprises a zinc substrate and a predominant β-phase polymer protective layer formed on the surface of the zinc substrate.

[0039] As the zinc substrate, zinc foil, etc. may be used, and without particular limitation, any zinc substrate that contains zinc and can be used as a current collector or negative electrode active material may be used.

[0040] It is preferable that the polymer forming the polymer protective layer be a polar polymer.

[0041] More specifically, polar polymers include polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), polystyrene (PS), polymethyl methacrylate (PMMA), poly(n-butyl acrylate) (PBA), polyacrylonitrile (PAN), polyaniline (PANi), polyacrylic acid (PAA), polyester-amides (PEA), polyethylene (PE), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyurethane, The polymer may be one or more of polyvinylidene fluoride (PVDF), polychloroprene, polyisoprene, and polybutadiene. Among these, polyvinylidene fluoride (PVDF) may be particularly preferred.

[0042] The cathode of the present invention is characterized by a water contact angle of less than 70°, more specifically 10° to 60°, and even more specifically 10° to 55°. Here, the water contact angle specifically refers to the water contact angle targeting the surface of the polymer protective layer.

[0043] This is because the polymer protective layer formed on the surface of the zinc substrate has a porous structure, and can preferably satisfy a porosity of 40 to 80%. More details on the porous structure are explained in Experimental Example 1.

[0044] Meanwhile, the cathode of the present invention is characterized in that the value of F(β) according to the following formula of the polymer protective layer formed on the surface of the zinc substrate is 70% or more. More specifically, it can satisfy 70% to 90%.

[0045]

[0046] In the above formula, X α and X β are the crystal percentages of α and β phases, respectively, and K α and K β are the absorption coefficients at individual wavenumbers, A α and A β are 763cm each -1 and 839 cm -1 Indicates the absorbance values ​​of the α phase and β phase.

[0047] That is, in the present invention, the term 'predominant β-phase' may quantitatively mean that a large amount of β-phase exists within the polymer protective layer formed on the zinc substrate, and more specifically, it may mean that the F(β) value, which is the relative fraction of β-phase within the polymer protective layer, is 70% or more. More detailed information about this is explained through Experimental Example 2.

[0048] This β phase has the highest polarity compared to other phases, such as the α phase, because all the binary molecules are oriented in the same direction. When the β phase is dominant as a polymer protective layer for a zinc anode, and thus has high polarity, zinc ion movement can diffuse uniformly through the polymer protective layer, which can be very effective in suppressing zinc dendrite formation.

[0049] Meanwhile, a method for manufacturing a zinc anode according to an embodiment of the present invention comprises the steps of preparing a solution in which a polymer is completely dissolved in a solvent, and adding ZnCl2, Zn(CF3SO3)2, Zn(TFSI)2, ZnO, Zn(NO3)26H2O, Zn(NTF2) to the solution.2, The method includes a step of preparing a coating solution by adding and completely dissolving one or more cationic additives among ZnBr2, Zn(ClO3)2, Zn(CH3CO2)22H2O and ZnSO47H2O, a step of applying the coating solution to the surface of a zinc substrate washed with ethanol and then drying it to prepare a polymer protective layer, and a step of annealing the zinc substrate on which the polymer protective layer is prepared to generate a predominant β-phase.

[0050] The polymer used is a polar polymer and is the same as the polymer described above, so its description is omitted.

[0051] The solvent used may be a polar solvent, and specifically may include one or more of N-methylformamide (NMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc), dipropylene glycol monomethyl ether (DPM), sulfolane, N-methyl-2-pyrrolidone (NMP), N-ethyl pyrrolidone (N-ethyl pyrrolidone), and dipropylene glycol monoethyl ether (DPE). Among these, N-methyl pyrrolidone (NMP) may be particularly preferred.

[0052] The cationic additive used may preferably be ZnSO47H2O.

[0053] The use of cationic additives plays a role in promoting the formation of β phase, thereby helping to form a predominant β-phase polymer protective layer. To explain this in more detail, for example, when ZnSO47H2O is used as a cationic additive, when ZnSO47H2O is dissolved, zinc cations (Zn 2+ ) and SO4 2-The highly electronegative CF groups of polar polymers such as PVDF rearrange in one direction due to interaction with zinc cations, forming a predominant β-phase with high polarity. In other words, the zinc cations due to the cation additive ultimately induce the formation of a predominant β-phase.

[0054] These cationic additives are preferably added in an amount of 10 to 40 wt% based on the polymer weight. If added in an amount less than 10 wt%, it is difficult to promote the formation of the β phase, and if added in an amount greater than 40 wt%, the problem of zinc precipitation may occur. More preferably, they can be added in an amount of 10 to 30 wt%.

[0055] Meanwhile, drying and annealing can be carried out simultaneously, and can be carried out by maintaining the temperature at 50°C to 70°C for 3 to 9 hours and then slowly cooling. The temperature and holding time of drying and annealing, along with the use of cationic additives, are important factors in the formation of the predominant β phase, and the above range is the optimal condition.

[0056] The manufacturing method of the present invention described so far forms a polymer protective layer of β phase by incorporating a simple ion-dipole interaction mechanism in a traditional heat treatment process, and further induces the formation of a more dominant β phase through the use of a cationic additive and the optimization of drying and annealing conditions. Consequently, the polymer protective layer of predominant β phase can suppress dendrite formation by ensuring uniform zinc ion diffusion, and can suppress zinc corrosion and hydrogen production reactions by acting as a protective layer between the electrode and electrolyte. In addition, the formation of a highly polar β phase and a porous structure enhances the wettability of the electrolyte, thereby improving the cycle performance and stability of the battery.

[0057] The present invention further includes a negative electrode for a zinc-ion battery manufactured by the above-described manufacturing method. The present invention further includes a zinc-ion battery including the above-described negative electrode.

[0058]

[0059] Below, specific embodiments and experimental examples of the present invention are examined.

[0060]

[0061] Example: Preparation of a zinc cathode using a cationic additive

[0062] PVDF, a polar polymer, was added at 2 wt% in 10 ml of NMP (N-methyl 2-pyrolidone) at 210 mg, and stirred overnight to prepare a solution in which PVDF was completely dissolved in NMP. Then, 42 mg of ZnSO47H2O as a cationic additive was added to the solution, and stirred at room temperature for 6 hours to completely dissolve ZnSO47H2O to prepare a coating solution. After that, a zinc foil with a diameter of 13 mm as a zinc substrate was washed with ethanol to remove any oily residue or other contaminants that may be present on the surface. After that, the prepared coating solution was applied to the washed zinc foil by drop coating, and then it was placed in an oven at 60℃ and maintained for 6 hours, and then slowly cooled to dry and anneale at the same time to manufacture the final zinc anode.

[0063]

[0064] Comparative example: Manufacturing a zinc cathode without using cationic additives.

[0065] A zinc anode was manufactured in the same manner as in the previous example, except that a solution in which PVDF was completely dissolved in NMP was used as a coating solution and applied to the zinc foil without using a cationic additive.

[0066]

[0067] In the drawings below, a zinc anode in the form of a zinc foil without forming a polymer protective layer is indicated as Bare Zn, a zinc anode of a comparative example manufactured previously is indicated as MBP@Zn or MBP film, and a zinc anode of an example is indicated as PBP@Zn or PBP film.

[0068]

[0069] Figure 1 (a) is a schematic diagram showing the manufacturing process of a zinc anode in each of the examples and comparative examples, (b) is a schematic diagram showing the phase change of a polymer protective layer formed on the zinc anode of the comparative example, and (c) is a schematic diagram showing the phase change of a polymer protective layer formed on the zinc anode of the examples.

[0070] As shown in (b) of Fig. 1, the PVDF of the comparative example undergoes a phase change from the initial α-phase to the minor β-phase, and as shown in (c) of Fig. 1, the PVDF of the exemplary embodiment undergoes a phase change from the initial α-phase to the predominant β-phase.

[0071]

[0072] In the following experiments, experiments were conducted on a zinc anode in the form of a zinc foil without forming a polymer protective layer, a zinc anode of a comparative example manufactured previously (a zinc anode with a minor β-phase polymer protective layer formed without using a cationic additive), and a zinc anode of an example (a zinc anode with a predominant β-phase polymer protective layer formed using a cationic additive).

[0073]

[0074] Experimental Example 1: Surface Structure and Interface Characteristics

[0075] Figures 2 (a) to (c) show the surface of each zinc anode observed using a scanning electron microscope (SEM), and (d) to (f) show the side views. (a) and (d) show the zinc anode without a polymer protective layer, (b) and (e) show the zinc anode of a comparative example, and (c) and (f) show the zinc anode of an exemplary embodiment.

[0076] As can be seen here, the zinc anode without a polymer protective layer has a smooth surface, and the side view confirms that there is no polymer protective layer. In the case of the zinc anode of the comparative example, interconnected micrometer hemispheres were observed on the surface, and the side view confirms that a polymer protective layer was formed, and its thickness is about 10㎛. In the case of the zinc anode of the embodiment, unlike the previous zinc anodes, it was observed to have a porous structure in which various pores of 0.5 to 4㎛ in size were distributed, and the side view confirms that a polymer protective layer was formed, and its thickness is about 10㎛.

[0077] In conclusion, the zinc anode of the present invention has a polymer protective layer formed on its surface with a thickness of approximately 10 μm, which has a porous structure with various pores of 0.5 to 4 μm in size. The reason why the polymer protective layer according to the present invention has such porosity may be due to the Marangoni effect and the use of a cationic additive. More specifically, the porous structure is formed due to the difference in surface tension with the NMP solvent caused by the H2O present in the cationic additive.

[0078] Figures 2 (g) to (i) show the results of measuring the water contact angle of each zinc cathode. (g) is the result of a zinc cathode without a polymer protective layer, (h) is the result of a zinc cathode of a comparative example, and (i) is the result of a zinc cathode of an example.

[0079] As can be seen, the zinc cathode of the example shows the lowest contact angle, which can be understood to be due to the polymer protective layer having a porous structure.

[0080] In conclusion, the zinc anode of the present invention is characterized by a low contact angle due to the formation of a porous polymer protective layer on the surface, and can satisfy a water contact angle of preferably less than 70°, and more preferably 10° to 60°. This means that the characteristics with respect to the hydrophilic interface are improved, and consequently, when applied to an aqueous zinc ion battery, the interfacial characteristics (wettability) with the aqueous electrolyte can be improved. This has the effect of improving the cycle performance of the battery and enhancing its safety.

[0081]

[0082] Experimental Example 2: Conversion to β phase

[0083] Figure 3 (a) shows the results of measuring X-ray diffraction (XRD) patterns for the zinc anode of the comparative example and the zinc anode of the exemplary embodiment. More specifically, the measurements were performed using an X-ray diffractometer equipped with a Cu Kα radiation source.

[0084] As can be seen, a prominent peak was observed at 20.4° for both zinc cathodes, indicating successful conversion to the β phase.

[0085] Figures 3 (b) and (c) show the results of measuring the crystal phase of the zinc anode of the comparative example and the zinc anode of the example. More specifically, the measurements were performed using Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy.

[0086] As shown in Fig. 3 (b), both zinc cathodes have β-phase characteristics (839 cm -1 ) was observed. However, as shown in (c) of Fig. 3, in the case of the zinc cathode of the comparative example, the characteristics of the α phase (763 cm -1) was observed more than the zinc anode of the example. This means that a greater amount of α phase exists in the polymer protective layer of the zinc anode of the comparative example than in the polymer protective layer of the zinc anode of the example. In other words, it can be seen that the polymer protective layer of the zinc anode of the example achieved a more successful conversion to the β phase.

[0087] Figure 3 (d) shows the results of calculating the relative fraction of β phase, F(β), for the zinc anode of the comparative example and the zinc anode of the embodiment. Specifically, using the Lambert-Beer law, 763 cm -1 and 839cm -1 The α and β phases were quantified from the characteristic absorption peaks. More specifically, they were calculated using the following equation.

[0088]

[0089] In the above formula, X α and X β are the crystal percentages of α and β phases, respectively, and K α and K β are the absorption coefficients at individual wavenumbers, A α and A β are 763cm each -1 and 839 cm -1 Indicates the absorbance values ​​of the α phase and β phase.

[0090] As a result of the calculation, the F(β) of the zinc anode of the comparative example was 61.8%, and the F(β) of the zinc anode of the example was 74.2%. That is, the content of the β phase in the polymer protective layer of the zinc anode of the example is higher, and preferably, the F(β) value of 70% to 90% can be satisfied.

[0091] Figure 3 (e) shows the results of measuring the thermal behavior of the crystal phase for the zinc anode of the comparative example and the zinc anode of the example. More specifically, the results were investigated using differential scanning calorimetry (DSC).

[0092] As can be seen, the melting temperature of the zinc anode of the comparative example was observed to be approximately 170°C, and the melting temperature of the zinc anode of the example was observed to be approximately 167°C, confirming the presence of a β-phase crystal phase in both polymer protective layers. In particular, it was confirmed that the melting temperature of the zinc anode of the example was more biased toward the β-phase crystal phase.

[0093] Figure 3 (f) shows the results of measuring the surface elemental composition and chemical state of the zinc anode of the comparative example and the zinc anode of the exemplary embodiment. More specifically, the analysis was performed using X-ray photoelectron spectroscopy (XPS).

[0094] As can be seen, both zinc cathodes had distinct peaks observed at 285.8 eV and 290.5 eV, indicating the presence of CH2 and CF2 groups, respectively. Unlike the comparative example, the results of the zinc cathode of the example showed that the area of ​​the CF2 species was reduced, and asymmetric lines of CH2 and CF2 were observed. This was due to the zinc cation (Zn 2+ ) and the CH2 / CF2 species of PVDF occurred. This is also supported by Fig. 3(g), where the high-resolution F1s spectrum shows a slight asymmetry at the center at 687.3 eV. In other words, these results indicate that the zinc anode of the example has a polymer protective layer with a predominant β phase.

[0095] In conclusion, the zinc (Zn) ion flux was uniformly dispersed in the polymer protective layer formed on the zinc cathode of the example, which was due to the zinc cations (Zn) introduced by the cationic additive. 2+ ) is promoted by the strong ion-dipole interaction between the electronegative CF functional group. In addition, the diffusion path created by the more ordered F atoms under the influence of the cationic additive can improve the movement of zinc ions (Zn), thereby increasing the overall energy storage capacity.

[0096]

[0097] Experimental Example 3: Chemical Stability

[0098] Figures 4(a) to (c) show the results of observing the surface condition of each zinc anode after immersing it in an electrolyte for 5 days. (a) shows a zinc anode without a polymer protective layer, (b) shows a zinc anode of a comparative example, and (c) shows a zinc anode of an exemplary embodiment.

[0099] As can be seen, the zinc anode of the example exhibits almost no corrosion byproducts caused by the electrolyte. Consequently, the zinc anode of the example exhibits excellent chemical stability in an aqueous electrolyte.

[0100] Figure 4 (d) shows the results of measuring the state of each zinc cathode after immersing it in the electrolyte for 5 days using XRD.

[0101] As can be seen, the peak corresponding to Zn4SO4(OH)65H2O, a by-product of corrosion, was found in the zinc anode without a polymer protective layer and the zinc anode of the comparative example, confirming that significant corrosion occurred due to the electrolyte. On the other hand, the corresponding peak was not found in the zinc anode of the example.

[0102] Figure 4 (e) shows the results of Tafel and Linear Sweep Voltammetry (LSV) tests performed using a three-electrode system configured with each zinc cathode as a working electrode, Pt foil as a counter electrode, and Ag / AgCl as a reference electrode.

[0103] As shown here, the corrosion potential values ​​of each zinc anode were measured as -0.988 V (zinc anode without a polymer protective layer), -0.985 V (zinc anode of the comparative example), and -0.981 V (zinc anode of the example). The corrosion current was reduced when the polymer protective layer was present rather than when it was absent, and in particular, the corrosion current value of the zinc anode of the example was the smallest, confirming that it most effectively suppressed the corrosion reaction. The corrosion current value of each zinc anode was 1.061 mAcm -2 (zinc cathode without polymer protective layer), 0.757 mAcm -2 (zinc cathode for comparison), 0.679 mAcm -2 (zinc cathode of the example) was measured.

[0104] Figure 4(f) shows the results of measuring the HER of each zinc cathode using LSV. The potential required to reach 20 mA was the lowest at -1.104 V for the zinc cathode of the example, indicating a decrease in hydrogen generation.

[0105] Figure 4 (g) shows the results showing that the corrosion resistance of the zinc anode is greatly improved by the introduction of the polymer protective layer, and the corrosion resistance of the zinc anode of the example is shown to be the best in both corrosion current value and HER value.

[0106]

[0107] Experimental Example 4: Inhibition of Dendrites

[0108] Figures 5 (a) to (c) show the surface measurements of zinc anodes of symmetrical cells manufactured using each zinc anode while zinc plating for 30 minutes. The symmetrical cells used a glass fiber separator as a separator and an aqueous electrolyte consisting of 2 M ZnSO4 and 0.1 M MnSO4 as an electrolyte. (a) shows a zinc anode without a polymer protective layer, (b) shows a zinc anode of a comparative example, and (c) shows a zinc anode of an exemplary embodiment.

[0109] As can be seen, unlike the zinc anode of the comparative example and the zinc anode without a polymer protective layer, which has dendrites or protrusions formed on the surface over time, the zinc anode of the embodiment can be seen to have a relatively uniform thickness of plating without visible dendrites or protrusions throughout the entire plating process.

[0110] Through this, it can be seen that the polymer protective layer of the zinc negative electrode of the embodiment most effectively suppresses the growth of dendrites, and by suppressing the growth of dendrites that cause side reactions between the electrode and electrolyte, etc., the safety and lifespan of the battery are improved as a result.

[0111] (d) of Fig. 5 is 2mAcm -2 The stability of the zinc anode was evaluated through long-term galvanostatic cycling of the symmetric cell at a current density of . The symmetric cell using the zinc anode without a polymer protective layer showed an initial overpotential of 82 mV, and the electrode potential was maintained stable for 50 hours before a sudden voltage drop was detected. This can be expected to be due to an internal short circuit caused by the formation of dendrites. The symmetric cell using the zinc anode of the comparative example showed an initial overpotential of 71 mV, maintained a stable potential for 245 hours, and eventually experienced a short circuit. On the other hand, the symmetric cell using the zinc anode of the example showed the smallest initial overpotential of 52 mV, and showed excellent long-term stability without a short circuit even after 400 hours of plating / stripping.

[0112] Figure 5 (e) shows the current density from 0.5 to 4 mAcm for further evaluation. -2This is the result of examining the critical current density of the symmetrical cell by gradually increasing it to . As can be seen from this, in the case of using a zinc anode without a polymer protective layer, a short circuit was experienced after 20 hours due to a rapid change in current density, and in the case of using the zinc anode of the comparative example, the overpotential increased significantly as the current density increased, whereas in the case of using the zinc anode of the example, the overpotential increased to 4 mAcm -2 It also exhibited a small and consistent overpotential at a current density of .

[0113] (f) of Fig. 5 is 2mAcm -2 The results show the nucleation overpotential of zinc deposition at each current density. As shown, the zinc cathode of the example exhibited the lowest nucleation overpotential of approximately 27 mV. This indicates a significantly improved zinc nucleation process, which can be attributed to a significant increase in the number of active nucleation sites.

[0114] Figure 5 (g) is a CA curve obtained at a fixed potential, where zinc cations (Zn) are deposited on the zinc surface. 2+ ) or the diffusion behavior of adsorbed zinc atoms. As shown here, in the case of the zinc anode without a polymer protective layer, when an overpotential of -150 mV was applied, the current density continuously increased for more than 500 seconds, indicating a long-term uncontrolled 2D diffusion process. On the other hand, in the case of the zinc anodes of the comparative examples and the examples, zinc nucleation and 2D diffusion processes occurred within 76 seconds and 55 seconds, respectively, followed by a stable and continuous 3D diffusion process. This indicates that the zinc cations (Zn) adsorbed on the surface by limited 2D surface diffusion 2+ ) is Zn 0 It shows that it is locally reduced to .

[0115] Figures 5 (h) to (j) show the surface of each zinc anode, where (h) is a zinc anode without a polymer protective layer, (i) is a zinc anode of a comparative example, and (j) is a zinc anode of an example. It can be seen that the growth of dendrites is suppressed in the zinc anode of the example.

[0116] FIG. 5(k) is a schematic diagram schematically illustrating the plating / stripping behavior of zinc and schematically showing the detailed modification mechanism achieved by the polymer protective layer according to the present invention.

[0117] As can be seen, the main factor for the inadequate zinc plating / stripping performance comes from the significant interfacial reaction between the uncontrolled electrochemical corrosion reaction of zinc and the chemical corrosion reaction of the electrolyte.

[0118]

[0119] Experimental Example 5: Zinc ion diffusion and energy storage capacity

[0120] A two-electrode system was configured with each zinc anode and MnO2 as the anode. The electrode slurry was prepared by mixing the active material (MnO2), conductive agent (Super-P), and binder (PVDF) in NMP at a weight ratio of 8:1:1, and mixing for 3 hours to ensure homogenization and uniformity. The prepared electrode slurry was applied onto the graphite foil used as the current collector using the doctor blade method, and the current collector was dried and heat-treated in an oven at 80°C for 12 hours. The electrochemical performance of the battery was tested as follows. Electrochemical impedance spectroscopy (EIS) showed a value of 10 5 ~10 -2 It was performed in the frequency range of Hz. Cyclic voltammetry (CV) was performed at 0.2 mVs -1 1.0~1.9V(Zn / Zn) at a scan rate of2+ The rate performance was performed between 0.3 and 2.0Ag for up to 10 cycles. -1 It was evaluated at various current densities in the range.

[0121] Figure 6 (a) shows the results of analyzing the EIS plot. As can be seen, the case of using the zinc anode of the comparative example and the zinc anode of the example has a higher R than the case of the zinc anode without a polymer protective layer. ct It can be seen that the value is small. This can be understood as the polymer protective layer promoted efficient electron transfer by suppressing corrosion of the zinc surface. In particular, R in the case of using the zinc cathode of the example ct You can see that the value is the smallest.

[0122] Figure 6 (b) shows the Warburg impedance coefficient (σ w ) is the result of measurement. Specifically, the Warburg impedance coefficient (σ w ) and Zn ion diffusion coefficients (D) are calculated using the following equations (2) and (3), respectively.

[0123]

[0124]

[0125] Warburg impedance coefficient (σ w ) are 17.7, 15.1 and 9.9 Ωcm in the order of the zinc anode without a polymer protective layer, the zinc anode of the comparative example and the zinc anode of the embodiment. 2 s -1 / 2 The values ​​were shown. Also, as shown in (c) of Fig. 6, the ion diffusion coefficients (D) were 0.71, 0.98, and 2.28x10 in the same order. -17 cm 2 s -1 The values ​​were shown. Through this, it was found that the diffusion of zinc ions was most greatly improved in the case of the zinc cathode of the example.

[0126] (d) of Fig. 6 is 0.2 mVs -1 The results show CV curves of batteries based on each zinc anode. The CV profiles were similar. When the zinc ion of the example was used, the CV curves showed a higher peak current response and a smaller polarization potential, confirming improved reaction activity.

[0127] This is further supported by Fig. 6(e), which shows the galvanostatic charge / discharge (GCD) curve. As shown therein, the capacity when the zinc anode of the embodiment was used was 255.7 mAhg. -1 It was confirmed that it has the highest capacity.

[0128] (f) of Fig. 6 is 0.3~2.0Ag -1 The results show the speed performance at a current density range of 0.3, 0.5, 0.7, 1.0, 1.3, 1.5, 1.7, and 2.0 A g. As can be seen, the case using the zinc anode of the example showed the best energy storage performance. Specifically, the results show that the anodes used in the example showed the best energy storage performance at a current density of 0.3, 0.5, 0.7, 1.0, 1.3, 1.5, 1.7, and 2.0 A g. -1 At current densities of 258.5, 231.0, 205.2, 171.7, 137.3, 119.2, 108.1, and 97.7 mAhg -1 It showed a high cost capacity.

[0129] The reason why the zinc anode of the present invention has an excellent energy storage capacity is largely because (1) the polymer protective layer has a predominant β phase due to the use of a cationic additive, and this phase promotes the alignment of F atoms, thereby establishing a more organized diffusion path that enhances the movement of Zn ions, and (2) the electrode wettability improved by the hydrophilic interface of the polymer protective layer and the formation of a porous surface through the Marangoni effect promote a more efficient electrode / electrolyte interface.

[0130] Furthermore, as shown in (g) of Fig. 6, the case using the zinc cathode of the embodiment (This work) showed the best results in speed performance, specific capacity, power, and energy density.

[0131]

[0132] Experimental Example 6: Cycling Stability (Life Characteristics)

[0133] Figure 7 shows the cycling stability of batteries based on each zinc anode. The batteries are identical to those fabricated in Experimental Example 5.

[0134] Figure 7 (a) is 0.5Ag -1 The results show the cycling stability after completing 250 charge / discharge cycles at a current density of . As can be seen, the case using the zinc anode of the example showed the most improved cycling stability.

[0135] Figures 7 (b) to (d) show the results of observing the surface of each zinc anode after 250 charge / discharge cycles, where (b) is the case of a zinc anode without a polymer protective layer, (c) is the case of a zinc anode of a comparative example, and (d) is the case of a zinc anode of an example.

[0136] As shown in Figures 7 (b) to (d), in the case of the zinc anode without a polymer protective layer, the surface was observed to be covered with excessively large zinc flakes due to the formation of byproducts. On the other hand, in the case of the zinc anodes of the comparative examples and examples, the growth and dissolution of byproducts were observed to be suppressed.

[0137] Figure 7(e) is a schematic diagram showing the appearance of each zinc anode when in direct contact with an acid-based aqueous electrolyte. As shown, in the absence of a polymer protective layer, zinc is gradually eluted during cycling due to direct contact with the acid-based aqueous electrolyte. On the other hand, in the case of including a polymer protective layer, the polymer protective layer has the effect of preventing zinc eluted by blocking direct interaction with the electrolyte. Therefore, it is possible to exhibit improved cycle life characteristics while maintaining low polarization.

[0138]

[0139] Experimental Example 7: Battery Performance Through Power Supply

[0140] Figure 8 shows an experiment in which a pouch-type zinc-ion battery was manufactured using a zinc anode without a polymer protective layer and a zinc anode of an example, and power was supplied to a micro monitor by connecting a microcontroller and a liquid crystal display panel using the manufactured battery, and the result graph thereof.

[0141] As can be seen, both zinc cathodes supplied power, but the case using the zinc cathode of the example maintained a continuous power supply, demonstrating improved battery performance.

[0142]

[0143] In conclusion, the present invention is to form a polymer protective layer having a predominant β-phase and a porous structure by using a cationic additive when forming a polymer protective layer on the surface of a zinc substrate. The zinc anode having a predominant β-phase and a porous polymer protective layer formed thereon has the following characteristics: 1) improved wettability with an aqueous electrolyte, thereby improving battery cycle performance; 2) improved energy storage capacity by creating a diffusion path to improve the movement of zinc ions; 3) excellent chemical stability, such as improved corrosion resistance by suppressing corrosion reactions and reducing hydrogen generation; 4) improved safety and lifespan of the battery by suppressing the growth of dendrites; and 5) excellent zinc ion diffusion capacity, energy storage capacity, and cycling stability.

[0144]

[0145] Although embodiments of the present invention have been described with reference to the attached drawings, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without altering the technical concept or essential features thereof. Therefore, the embodiments described above should be understood to be illustrative in all respects and not restrictive.

Claims

1. Zinc base; and Comprising a predominant β-phase polymer protective layer formed on the surface of the zinc substrate, Cathode for zinc-ion batteries.

2. In paragraph 1, The porosity of the polymer protective layer is characterized by being 40 to 80%. Cathode for zinc-ion batteries.

3. In paragraph 1, Characterized in that the water contact angle of the polymer protective layer is less than 70°. Cathode for zinc-ion batteries.

4. In paragraph 1, The above polymer protective layer is characterized in that the value of F(β) according to the following formula is 70% or more. Cathode for zinc-ion battery; (In the above formula, X α and X β are the crystal percentages of α and β phases, respectively, and K α and K β are the absorption coefficients at individual wavelengths, A α and A β are 763cm each -1 and 839 cm -1 ) shows the absorbance values ​​of the α and β phases.

5. In paragraph 1, The above polymer is characterized in that it is a polar polymer. Cathode for zinc-ion batteries.

6. In paragraph 5, The above polar polymers are polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), polystyrene (PS), polymethyl methacrylate (PMMA), poly(n-butyl acrylate) (PBA), polyacrylonitrile (PAN), polyaniline (PANi), polyacrylic acid (PAA), polyester-amides (PEA), polyethylene (PE), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyurethane (PU), characterized by one or more of polychloroprene, polyisoprene and polybutadiene, Cathode for zinc-ion batteries.

7. A step of preparing a solution in which the polymer is completely dissolved in a solvent; ZnCl in the above solution 2 , Zn(CF 3 SO 3 ) 2 , Zn(TFSI) 2 , ZnO, Zn(NO 3 ) 2 6H 2 O, Zn(NTF 2 ) 2, ZnBr 2 , Zn(ClO 3 ) 2 , Zn(CH 3 CO 2 ) 2 2H 2 O and ZnSO 4 7H 2 A step of preparing a coating solution by adding one or more cationic additives of O and then completely dissolving them; A step of applying the coating solution to the surface of a zinc substrate washed with ethanol and then drying it to produce a polymer protective layer; and A step of annealing the zinc substrate on which the polymer protective layer is manufactured to generate a predominant β-phase, A method for manufacturing a negative electrode for a zinc-ion battery comprising a polymer protective layer.

8. In paragraph 7, The above cationic additive is ZnSO 4 7H 2 characterized by O, A method for manufacturing a negative electrode for a zinc-ion battery comprising a polymer protective layer.

9. In paragraph 7, The cationic additive is characterized in that it is added in an amount of 10 to 40 wt% based on the polymer weight. A method for manufacturing a negative electrode for a zinc-ion battery comprising a polymer protective layer.

10. In paragraph 7, The above polymers are polar polymers, such as polyvinylpyrrolidone (PVP), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), polystyrene (PS), polymethyl methacrylate (PMMA), poly(n-butyl acrylate) (PBA), polyacrylonitrile (PAN), polyaniline (PANi), polyacrylic acid (PAA), polyester-amides (PEA), polyethylene (PE), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), Characterized by one or more of polyurethane (PU), polychloroprene, polyisoprene and polybutadiene. A method for manufacturing a negative electrode for a zinc-ion battery comprising a polymer protective layer.

11. In paragraph 7, The above drying and annealing are carried out simultaneously, and are characterized in that they are carried out by maintaining at a temperature of 50℃ to 70℃ for 3 to 9 hours and then cooling. A method for manufacturing a negative electrode for a zinc-ion battery comprising a polymer protective layer.

12. A negative electrode for a zinc-ion battery, manufactured by any one of the manufacturing methods of clause 7.

13. A zinc-ion battery comprising the negative electrode of claim 1 or 12.

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