Negative electrode protection layer for zinc-ion battery, zinc-ion battery including same, and manufacturing method thereof

Abstract

An embodiment of the present invention provides: a negative electrode protection layer including carbon nanotubes and titanium dioxide nanoparticles; and a zinc-ion battery including same. The negative electrode protection layer according to an embodiment of the present invention can provide a zinc-ion battery which has a high energy power density and a higher volumetric energy storage capacity due to having improved electrochemical behavior, and in which flat and dense dendrite growth is induced and thus a thinner separator can be used.

Description

Anode protective layer for zinc-ion batteries, zinc-ion batteries containing the same, and a method for manufacturing the same

[0001] The present invention relates to a cathode protective layer, and more particularly, to a cathode protective layer for a zinc ion battery that can improve the electrochemical behavior of a zinc ion battery.

[0002] Battery technology based on rechargeable organic electrolytes is indispensable in modern society, but disposal of these batteries today poses serious ecological and environmental challenges.

[0003] In addition, lithium-ion batteries (LIBs) are currently being widely used in various fields such as mobile electronic devices, implantable medical devices, grid-level storage applications, and electric vehicles, but the stability of the batteries is still an issue due to the chemical reactivity of the electrolyte composed of metallic lithium, sodium, and organic carbonate ester.

[0004] Zinc-ion batteries (ZIBs) are being proposed as a viable alternative to replace lithium-ion batteries and secure renewable energy resources. ZIBs offer an attractive alternative due to their high theoretical capacity (820 mAh / g), low redox potential (-0.76 V vs. SHE), low cost, safety, and availability of naturally abundant materials. Zinc-ion batteries consist of a zinc anode, an intercalated cathode, and a porous separator, and their structure allows zinc ions to migrate during the charge / discharge process. The use of an aqueous electrolyte in ZIBs ensures fire and explosion safety, allows for a flexible manufacturing process in air, and allows for low-cost production.

[0005] However, the zinc anode of ZIBs stores energy through the zinc plating / stripping process, but if there is insufficient nucleation for zinc plating on the surface of the zinc anode, the effect is reduced, resulting in an uneven distribution of interfacial charge density and zinc 2+ flux, which causes dendrites to grow in the vertical direction. In addition, the zinc anode has low stability in weakly acidic electrolytes, which causes corrosion and the formation of byproducts such as Zn4SO4(OH)6·5H2O (ZHS) through hydrogen generation. Therefore, an ideal zinc anode has the technical challenges of exhibiting uniform dendrite growth, suppressing corrosion, and suppressing side reactions.

[0006] (Patent Document 0001) Republic of Korea Patent Publication No. 10-2398953

[0007] The present invention provides a zinc ion battery having a protective layer formed on the surface of the negative electrode of the zinc ion battery, which improves electrochemical behavior, induces dense dendrite growth, and has a higher volumetric energy storage capacity by forming a protective layer on the surface of the negative electrode of the zinc ion battery as a method for solving the problems of the prior art described above.

[0008] The technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0009] In order to achieve the above technical task, one embodiment of the present invention provides a negative electrode protective layer for a zinc ion battery.

[0010] According to one embodiment of the present invention, a cathode protective layer for a zinc ion battery is characterized by including carbon nanotubes; and titanium dioxide nanoparticles.

[0011] In an embodiment of the present invention, the carbon nanotube may be a cathode protective layer for a zinc ion battery, characterized in that it has a diameter of 1 to 50 nm.

[0012] In an embodiment of the present invention, the titanium dioxide nanoparticles may be a cathode protective layer for a zinc ion battery, characterized in that they are nanoparticles having a diameter of 1 to 50 nm.

[0013] In an embodiment of the present invention, the cathode protective layer may be a cathode protective layer for a zinc ion battery, characterized in that the thickness of the cathode protective layer is 1 to 20 μm.

[0014] In an embodiment of the present invention, the weight ratio of the carbon nanotubes and the titanium dioxide may be 1:1 to 1:10, which may be a negative electrode protective layer for a zinc ion battery.

[0015] One embodiment of the present invention provides a zinc ion battery.

[0016] A zinc ion battery according to one embodiment of the present invention is characterized by including a positive electrode; a negative electrode; an electrolyte formed between the positive electrode and the negative electrode; and a separator.

[0017] In an embodiment of the present invention, the separator may be a zinc ion battery characterized in that it has a thickness of 300 μm or less.

[0018] One embodiment of the present invention provides a method for manufacturing a cathode protective layer for a zinc ion battery.

[0019] A method for manufacturing a cathode protective layer for a zinc ion battery according to one embodiment of the present invention is characterized by including the steps of adding and mixing titanium dioxide nanopowder into alcohol; adding and mixing carbon nanotubes into the alcohol to prepare a solution; and coating the solution onto a zinc cathode.

[0020] In an embodiment of the present invention, the step of coating the solution on a zinc cathode may be a method for manufacturing a cathode protective layer for a zinc ion battery, characterized in that it uses a spin coating method.

[0021] According to an embodiment of the present invention, a composite protective layer composed of titanium dioxide and carbon nanotubes is introduced onto the negative electrode surface of a zinc ion battery to protect the negative electrode and improve electrochemical behavior, thereby significantly improving the energy storage performance of the zinc ion battery while reducing the cell volume.

[0022] Specifically, the zinc anode having a surface protective layer of the present invention exhibits a high energy power density of 155 to 57 Wh / kg in a power density range of 300 to 2000 W / kg, and has the effect of enabling a higher volumetric energy storage capacity.

[0023] In addition, the cathode protective layer according to the embodiment of the present invention has the effect of inducing flatter and denser dendrite growth, thereby enabling the use of a thinner separator.

[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 detailed description of the present invention or the composition of the invention described in the claims.

[0025] Figure 1 is a flow chart schematically illustrating a method for manufacturing a cathode protective layer for a zinc ion battery according to one embodiment of the present invention.

[0026] Figure 2 is a conceptual diagram illustrating a method for manufacturing a cathode protective layer for a zinc ion battery according to one embodiment of the present invention.

[0027] Figure 3 is a drawing showing SEM images of a negative electrode having a negative electrode protective layer for a zinc ion battery according to an embodiment of the present invention and a comparative example. Figure 3a shows a surface SEM image of bare Zn as a comparative example. Figure 3b shows a surface SEM image of Zn having a TiO2 layer bonded thereto as a comparative example. Figure 3c shows a surface SEM image of Zn having a negative electrode protective layer for a zinc ion battery according to an embodiment of the present invention. Figure 3d shows an elemental analysis through EDX mapping of a negative electrode having a negative electrode protective layer for a zinc ion battery according to an embodiment of the present invention.

[0028] Figure 4 is a diagram showing the XRD results of Zn anode, TiO2 nanoparticles, and carbon nanotubes.

[0029] FIG. 5 is a diagram showing the TGA results showing the chemical composition of a cathode protective layer and a protective layer composed of CNTs according to one embodiment of the present invention.

[0030] FIG. 6 is a drawing showing the results of measuring the electrical conductivity of a cathode protective layer and a protective layer composed of TiO2 according to one embodiment of the present invention.

[0031] Figure 7 is a diagram showing the results of measuring the contact angle to evaluate the wetting properties of (a) bare Zn, (b) TiO2-Zn, and (c) CNT@TiO2-Zn cathodes, respectively.

[0032] Figure 8a is a diagram showing the results of galvanoelectric measurements performed to evaluate the cyclic stability and voltage hysteresis of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0033] Figure 8b shows the 0.5 mA·cm of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes. -2 This is a diagram showing the nucleation overvoltage at a current density of .

[0034] Figure 8c shows the 2 mA·cm of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.-2 This is a diagram showing the nucleation overvoltage at a current density of .

[0035] Figure 8d is a diagram showing the current density LSV test results of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes at a scanning rate of 5 mV / s.

[0036] Figure 8e is a CA curve showing the diffusion behavior of Zn atoms or cations in bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0037] Figure 9a is a diagram showing the Nyquist plots of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0038] Figure 9b shows the calculated impedance coefficient values ​​(σ, ω) of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0039] Figure 9c shows the calculated diffusion coefficient values ​​(D) of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0040] Figure 9d shows CV curves recorded in the potential range of 1.0 to 1.9 V for bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0041] Figure 10a is a diagram showing the rate performance of ZIBs containing bare Zn, TiO2-Zn, and CNT@TiO2 cathodes at current densities ranging from 0.3 to 20 A / g.

[0042] Figure 10b is a diagram showing the energy density and power density values ​​of the CNT@TiO2-Zn cathode.

[0043] Figure 10c is a conceptual diagram showing the role of TiO2 nanoparticles in the cathode protective layer.

[0044] Figure 10d is a conceptual diagram showing the role of CNTs in the cathode protection layer.

[0045] Figure 11 is a drawing showing the results of analysis of the surface of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes fabricated after charging at a high current density of 2.0 A / g using CLSM.

[0046] Figure 12 shows SEM images of the fabricated ZIB cathode after charging at a current density of 0.3 A / g. Figure 12a shows an SEM image of bare Zn. Figure 12b shows an SEM image of TiO2-Zn. Figure 12c shows an SEM image of CNT@TiO2.

[0047] Figure 13 is a conceptual diagram depicting dendrite formation on the surfaces of bare Zn and CNT@TiO2 cathodes.

[0048] Figure 14 is a diagram showing (a) a schematic diagram of a conventional ZIB cell and a CNT@TiO2 cell, (b) thickness measurements of a cell including a cathode, a separator, and an anode, and (c) the speed performance results of a ZIB measured by changing the thickness of the separator.

[0049] Figure 15 is a diagram showing the performance evaluation results after long-term charge / discharge cycles. Figure 15a shows 1.0 Ma·cm -2 Figure 15b is a diagram showing the cycle stability of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes for 300 cycles. Figure 15b is a diagram showing the cross-sectional samples analyzed using SEM after charge / discharge tests of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0050] Figure 16 shows SEM images of corrosion and side reactions observed for (a) bare Zn, (b) TiO2-Zn, and (c) CNT@TiO2 cathodes, respectively.

[0051] Figure 17 is a diagram showing the XRD analysis results of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes after cycle tests.

[0052] Figure 18 is a diagram showing power supply to a microcontroller using a ZIB based on bare Zn and CNT@TiO2 cathodes.

[0053] When a part is said to be "connected (connected, in contact, or joined)" to another part, this includes not only cases where it is "directly connected," but also cases where it is "indirectly connected" with another member in between. Furthermore, when a part is said to "include" a component, this does not exclude other components, but rather implies that it may include other components, unless otherwise specifically stated.

[0054] The terminology used herein is merely used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0055] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

[0056]

[0057] A cathode protective layer for a zinc ion battery according to one embodiment of the present invention is described.

[0058] According to one embodiment of the present invention, a cathode protective layer for a zinc ion battery is characterized by including carbon nanotubes (CNTs); and titanium dioxide (TiO2) nanoparticles.

[0059] In an embodiment of the present invention, the titanium dioxide may be a nanoparticle having a diameter of 1 to 50 nm, and preferably, a nanoparticle having a diameter of 17 to 25 nm.

[0060] The above titanium dioxide can be introduced as a cathode protective layer of a zinc ion battery to suppress zinc corrosion and hydrogen generation due to its excellent chemical stability, and to provide numerous nucleation sites for zinc plating.

[0061] However, in this case, the low electrical conductivity of titanium dioxide may increase the cell interface resistance, impairing electron mobility and hindering improvement of energy storage capacity.

[0062] Meanwhile, carbon nanotubes (CNTs) are a new material that is very small and thin and has a hexagonal lattice structure made of carbon atoms, and has a size in the nanometer range.

[0063] In an embodiment of the present invention, the carbon nanotube may have a diameter of 1 to 50 nm, and preferably a diameter of 20 nm.

[0064] The above carbon nanotubes were introduced to solve the problem of low electrical conductivity of the titanium dioxide described above, and serve to improve the electrical conductivity of the zinc ion cathode protective layer of the present invention and reduce the interface resistance of the ZIB cell.

[0065] At this time, the thickness of the cathode protective layer may be 1 to 20 μm, and the weight ratio of the carbon nanotubes and the titanium dioxide may be 1:1 to 1:10, and preferably 1:4.

[0066]

[0067] Next, one embodiment of the present invention provides a zinc ion battery.

[0068] A zinc ion battery according to one embodiment of the present invention is characterized by including a positive electrode; a negative electrode; an electrolyte formed between the positive electrode and the negative electrode; and a separator.

[0069] At this time, the separator may be 300 μm or less. The present invention has the characteristic of being able to provide a zinc ion battery that can smoothly charge / discharge even with a low separator thickness due to higher energy density and uniform dendrite growth, unlike existing zinc ion batteries.

[0070]

[0071] Finally, one embodiment of the present invention provides a method for manufacturing a cathode protective layer for a zinc ion battery.

[0072] Figure 1 is a flow chart schematically illustrating a method for manufacturing a cathode protective layer for a zinc ion battery according to one embodiment of the present invention.

[0073] A method for manufacturing a cathode protective layer for a zinc ion battery according to one embodiment of the present invention is characterized by including, as illustrated in FIG. 1, a step (S100) of adding and mixing titanium dioxide nanopowder into alcohol; a step (S200) of adding and mixing carbon nanotubes into the alcohol to prepare a solution; and a step (S300) of coating the solution onto a zinc cathode.

[0074] At this time, the step of coating the solution on the zinc cathode may use a coating method generally used in the related technical field, for example, a spin coating method may be used, but is not limited thereto.

[0075]

[0076] Hereinafter, the present invention will be described in more detail through manufacturing examples, comparative examples, and experimental examples. However, the present invention is not limited to the following manufacturing examples and experimental examples.

[0077]

[0078] Manufacturing Example 1: Manufacturing of a cathode including a cathode protective layer for a zinc ion battery

[0079] Figure 2 is a conceptual diagram illustrating a method for manufacturing a cathode protective layer for a zinc ion battery according to one embodiment of the present invention.

[0080] As shown in Fig. 2, a negative electrode protective layer for a zinc-ion battery according to one embodiment of the present invention was manufactured. 20 mg of TiO2 nanopowder was added to 6 mL of ethanol and physically mixed using ultrasonic waves for 5 minutes. Next, 5 mg of CNT was added to the previously mixed TiO2 solution and ultrasonically mixed for 5 minutes. The mixed TiO2 / CNT solution was then dropped onto a zinc foil, and the solution was coated using a spin coater.

[0081] Additionally, as comparative examples, a zinc cathode coated with TiO2 nanoparticles and a bare zinc cathode were also fabricated.

[0082] Hereinafter, a zinc anode coated with a negative electrode protective layer for a zinc ion battery according to an embodiment of the present invention manufactured above is expressed as CNT@TiO2-Zn, a zinc anode coated with TiO2 nanoparticles is expressed as TiO2-Zn, and a bare zinc anode is expressed as Bare Zn.

[0083]

[0084] Manufacturing Example 2: Manufacturing of zinc-ion batteries (ZIBs)

[0085] ZIBs were fabricated using prepared Zn foil cathodes, glass fiber paper separators, manganese oxide (MnO2) cathodes, and 2 M zinc sulfate (ZnSO4) and 0.1 M manganese sulfate (MnSO4) electrolytes. The cathodes were fabricated by coating a slurry mixture containing MnO2 as an active material, Super P carbon as a conductive additive, and polyvinylidene difluoride (PVDF) as a binder onto graphite foils used as current collectors. The mixture was coated on the graphite foils using a coating blade at a ratio of 8:1:1 in N-methyl-2-pyrrolidone (NMP), and the slurry-coated Zn foils were dried at 80 °C.

[0086]

[0087] Experimental Example 1: Morphological and structural characteristics of the cathode surface

[0088] Figure 3 is a drawing showing SEM images of a negative electrode having a negative electrode protective layer for a zinc ion battery according to an embodiment of the present invention and a comparative example. Figure 3a shows a surface SEM image of bare Zn as a comparative example. Figure 3b shows a surface SEM image of Zn having a TiO2 layer bonded thereto as a comparative example. Figure 3c shows a surface SEM image of Zn having a negative electrode protective layer for a zinc ion battery according to an embodiment of the present invention. Figure 3d shows an elemental analysis through EDX mapping of a negative electrode having a negative electrode protective layer for a zinc ion battery according to an embodiment of the present invention.

[0089] As shown in the above Fig. 3, bare Zn (Fig. 3a) showed a smooth surface, and TiO2 nanoparticles with a size of 17 to 25 nm were observed in TiO2-Zn (Fig. 3b). Meanwhile, the SEM image of CNT@TiO2-Zn observed a composite structure in which one-dimensional CNTs with a diameter of 20 nm were combined with TiO2 nanoparticles (Fig. 3c).

[0090] Additionally, the coating of the zinc anode with a CNT@TiO2 protective layer with a thickness of 3.3 μm was confirmed (Fig. 3d), and elemental analysis using EDX mapping confirmed that Zn, O, Ti, and C elements were uniformly distributed within the composite. These SEM analysis results confirmed the successful coating of CNTs and TiO2 nanoparticles on the anode surface for high-performance ZIB.

[0091]

[0092] Experimental Example 2: Crystal structure, chemical composition, and electrical conductivity of the cathode

[0093] Figure 4 is a diagram showing the XRD results of Zn anode, TiO2 nanoparticles, and carbon nanotubes.

[0094] As shown in Fig. 4, diffraction peaks were observed at approximately 36.2, 38.9, and 43.2° in the XRD pattern of the XRD cathode, which correspond to the (002), (100), and (101) planes of Zn, respectively. In addition, as is generally known, it was confirmed that TiO2 has an anatase phase, and CNTs were confirmed to exhibit a graphitic crystal structure. In the XRD patterns of the TiO2-Zn and CNT@TiO2-Zn samples, no diffraction peaks related to TiO2 and CNTs were observed, which seems to be due to the high crystallinity and abundant amount of Zn.

[0095] FIG. 5 is a diagram showing the TGA results showing the chemical composition of a cathode protective layer and a protective layer composed of CNTs according to one embodiment of the present invention.

[0096] As shown in Figure 5, the TGA results showed that the CNTs exhibited a pure carbon composition without impurities and experienced a complete weight loss of 100%. The initial stage of the TGA graph was observed at approximately 300 °C, corresponding to water loss, while the subsequent stage indicates weight loss due to oxidation. When CNT@TiO2 was used as a protective layer, a weight loss rate of 9% was observed due to the presence of CNTs.

[0097] FIG. 6 is a drawing showing the results of measuring the electrical conductivity of a cathode protective layer and a protective layer composed of TiO2 according to one embodiment of the present invention.

[0098] As shown in Fig. 6, the CNT@TiO2 protective layer is TiO2 (3.8 mS·cm -1 ) has an electrical conductivity (36.9 mS·cm) that is 9.7 times higher than that of -1 ) was observed. These results are attributed to the high electrical conductivity of the integrated CNTs and the efficient electron mobility provided by the one-dimensional network structure. In addition, the protective layer of the cathode facilitates electron transfer during the charge / discharge process, thereby enhancing the energy storage performance and electrical conductivity.

[0099]

[0100] Experimental Example 3: Evaluation of wetting properties

[0101] Figure 7 is a diagram showing the results of measuring the contact angle to evaluate the wetting properties of (a) bare Zn, (b) TiO2-Zn, and (c) CNT@TiO2-Zn cathodes, respectively.

[0102] As shown in Fig. 7, the contact angle was measured to evaluate the wettability of the cathodes. The bare Zn cathode exhibited the highest contact angle (101°), suggesting inefficient interaction between the cathode and the aqueous electrolyte. However, after introducing a TiO2 nanoparticle protective layer onto the bare Zn cathode, the wettability performance of the cathode was improved, as evidenced by the contact angle of the TiO2-Zn cathode (73°). This improvement may be due to the increased surface roughness caused by the presence of TiO2 nanoparticles. The CNT@TiO2-Zn cathode exhibited the lowest contact angle (68°), indicating excellent wetting behavior due to the high aspect ratio of the integrated CNTs.

[0103]

[0104] Experimental Example 4: Evaluation of cycling stability and voltage hysteresis

[0105] Figure 8a is a diagram showing the results of galvanoelectric measurements performed to evaluate the cyclic stability and voltage hysteresis of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0106] As shown in Fig. 8a, symmetric Zn||Zn cells were fabricated using the composite cathodes to evaluate the cycling stability and voltage hysteresis of bare Zn, TiO2-Zn, and CNT@TiO2-Zn cathodes, and galvanoelectric measurements were performed at 0.5 and 2.0 mAh cm to monitor the voltage change over time. 2Voltage profiles were recorded during cycling for 150 and 500 h at two current densities. The bare Zn cathode exhibited uncontrolled formation of Zn dendrites on the cathode surface and abrupt voltage spikes and drops during cycling, highlighting the importance of the protective layer. In contrast, TiO2-Zn and CNT@TiO2-Zn showed consistent and minimized voltage polarization throughout the cycling process at both current densities, indicating the controlled growth of Zn dendrites due to the introduction of the protective layer.

[0107] Figure 8b shows the 0.5 mA·cm of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes. -2 This is a diagram showing the nucleation overvoltage at a current density of .

[0108] Figure 8c shows the 2 mA·cm of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes. -2 This is a diagram showing the nucleation overvoltage at a current density of .

[0109] As shown in Fig. 8b, 0.5 mA·cm -2 The nucleation overvoltages of bare Zn, TiO2-Zn, and CNT@TiO2-Zn cathodes at a current density of 76, 68, and 65 mV, respectively. As shown in Fig. 8c, the nucleation overvoltages of TiO2-Zn and CNT@TiO2-Zn cathodes were 2.0 mA cm -2 At the current density of , the ZnO2 / CNT ratio decreased to 56 and 64 mV, respectively. This indicates that the introduction of CNTs and TiO2 nanoparticles as a protective layer promoted uniform Zn growth with a low nucleation barrier.

[0110] Figure 8d is a diagram showing the current density LSV test results of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes at a scanning rate of 5 mV / s.

[0111] As shown in Fig. 8d, a three-electrode system consisting of a prepared Zn cathode (working electrode), a Pt foil (counter electrode), and an Ag / AgCl (reference electrode) was used to evaluate the hydrogen evolution reaction (HER) and corrosion prevention properties of the prepared cathode at 5 mV·s. -1 At a scanning rate of , the cathodic current density of the bare Zn cathode increased rapidly during the LSV test. In contrast, the current densities of the TiO2-Zn and CNT@TiO2-Zn cathodes increased at a considerably slower rate. This result suggests that the HER was suppressed in the TiO2-Zn and CNT@TiO2-Zn cathodes due to the excellent chemical stability of the introduced TiO2 nanoparticles.

[0112] Figure 8e is a CA curve showing the diffusion behavior of Zn atoms or cations in bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0113] As shown in Fig. 8e, the diffusion behavior of the Zn2+ cations or adsorbed Zn atoms on the cathode was investigated using CA curves collected at fixed potentials. The current density of bare Zn was determined by the current density of Zn on the Zn cathode surface. 2+ It did not stabilize for a long time due to the two-dimensional diffusion of Zn. In contrast, CNT@TiO2-Zn showed a stable current density after a short deposition time of about 84 s. This indicates that the CNTs / TiO2 nanoparticle composite protective layer and Zn electrode patterning were effective in stabilizing the Zn 2+ This may be because the random diffusion behavior of cations or adsorbed Zn atoms was suppressed through the three-dimensional diffusion effect.

[0114]

[0115] Experimental Example 5: Nyquist plot

[0116] Figure 9a is a diagram showing the Nyquist plots of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0117] The Nyquist plot of the ZIB fabricated using the prepared cathode in Fig. 9a is shown. The high-frequency region was used to measure the charge transfer resistance (Rct). Compared to the bare Zn and TiO2-Zn cathodes, the CNT@TiO 2- The Zn cathode had high electrical conductivity due to the integration of CNTs, and the interfacial resistance was reduced, resulting in a low Rct value.

[0118]

[0119] (Formula 1)

[0120]

[0121] (Formula 2)

[0122]

[0123]

[0124] Figure 9b shows the calculated impedance coefficient values ​​(σ, ω) of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0125] Figure 9c shows the calculated diffusion coefficient values ​​(D) of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0126] The Warburg impedance coefficient (σw) and Zn-ion diffusion coefficient (D) values ​​were calculated using the above equations (Eq. 1) and (Eq. 2). These equations take into account various variables such as the total electrode resistance (Re), gas constant (R), temperature (T), electrode area (A), number of electrons per molecule (n), Faraday constant (F), and molar concentration of Zn-ions (C). Zreal and ω -1 / 2 The calculated σw values ​​by analyzing the relationship were 23.7, 20.6, and 11.2 for the bare Zn, TiO2-Zn, and CNT@TiO2-Zn cathodes, respectively (Fig. 9b). In addition, the calculated D values ​​for the Zn-ion diffusion in the bare Zn, TiO2-Zn, and CNT@TiO2-Zn cathodes were 0.40, 0.52, and 1.81 × 1015 cm2·s, respectively. -1(Fig. 9c). These findings indicate that the ion diffusion behavior observed in the CNT@TiO2-Zn cathode may be attributed to the enhanced wettability of the cathode due to the presence of TiO2 nanoparticles and CNTs on the cathode surface.

[0127] Figure 9d shows CV curves recorded in the potential range of 1.0 to 1.9 V for bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0128] The above figure 9d is 10 mV·s -1 The CV curves of the samples recorded at injection rates of and in the potential range of 1.0 to 1.9 V are presented. The presence of redox peaks or humps in these CV curves indicates a Faradic process associated with the occurrence of electrochemical reactions. In particular, these peaks represent the plating and stripping of Zn ions at the cathode of the ZIB and are explained by the reaction:

[0129] Zn ↔ 2e + Zn 2+

[0130] These observations confirm the characteristic behavior typically observed in ZIB. Furthermore, compared to the TiO2-Zn and CNT@TiO2-Zn cathodes, the CNT@TiO2-Zn cathode has a larger CV area, indicating that more electrochemically active sites are available for Zn plating.

[0131]

[0132] Experimental Example 6: Speed ​​Performance and Dendrite Growth of ZIB

[0133] Figure 10a is a diagram showing the rate performance of ZIBs containing bare Zn, TiO2-Zn, and CNT@TiO2 cathodes at current densities ranging from 0.3 to 20 A / g.

[0134] As shown in the above figure 10a, from 0.3 to 20 A·g -1 The speed performance of ZIB can be verified at various current densities up to 0.3 A·g. -1At a current density of , the capacities of bare Zn, TiO2-Zn, and CNT@TiO2-Zn were 236, 264, and 297 mAh / g, respectively, indicating that the bare Zn cathode had a lower capacity than the TiO2-Zn and CNT@TiO2-Zn cathodes, highlighting the importance of interfacial engineering between the Zn cathode and the aqueous electrolyte to achieve improved performance. However, despite the improved energy storage performance of the TiO2-Zn cathode compared to the bare Zn cathode, the energy storage performance of the TiO2-Zn cathode was only slightly higher. The unsatisfactory energy storage performance of the TiO2-Zn cathode may be due to the limited nucleation sites for Zn plating and the poor electrical conductivity of TiO2, which limited the energy storage potential of the cathode. To solve this problem, CNTs were introduced into the TiO2-Zn cathode to enhance the nucleation sites for Zn plating and the electrical conductivity of the passivation layer. As a result, the CNT@TiO2-Zn cathode exhibited a high current density of 2.0 A·g -1 102mAh·g in -1 The capacity of bare Zn (65mAh·g) was shown -1 ) and TiO2-Zn cathode (76 mAh·g -1 ) exceeded all of its capacities.

[0135] Figure 10b is a diagram showing the energy density and power density values ​​of the CNT@TiO2-Zn cathode.

[0136] Figure 10c is a conceptual diagram showing the role of TiO2 nanoparticles in the cathode protective layer.

[0137] Figure 10d is a conceptual diagram showing the role of CNTs in the cathode protection layer.

[0138] The above Fig. 10b shows the energy density and power density values ​​of the CNT@TiO2-Zn cathode. From 300 to 2,000 W·kg -1 Within the power density range of , the energy density of CNT@TiO2-Zn cathode ranges from 267 to 91 Wh·kg-1 , and showed higher performance than the previously reported ZIB using MnO2 anode. This improvement in energy storage performance may be due to the composite protective layer composed of TiO2 nanoparticles and CNTs. As shown in Figs. 10c and 10d, TiO2 nanoparticles provided excellent chemical stability and numerous nucleation sites for Zn plating, which improved stable electrochemical reaction and ion diffusion behavior, and CNTs provided high electrical conductivity and facilitated electron transfer through a one-dimensional network structure.

[0139] Figure 11 is a drawing showing the results of analysis of the surface of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes fabricated after charging at a high current density of 2.0 A / g using CLSM.

[0140] As shown in the above figure 11, 2.0 A·g -1The surface of the fabricated cathode after charging at a high current density was analyzed using CLSM, demonstrating the excellent high-rate performance of the cathode. The CLSM images of the bare Zn (Fig. 11(a), (b)) showed an irregular surface with a thickness of about 15.2 μm, which must be suppressed to achieve stable operation in the ZIB, as it can penetrate the separator and contact the cathode, potentially causing an electrical short. In contrast, the TiO2-Zn cathode (Fig. 11(c), (d)) showed a uniform surface due to the numerous nucleation sites provided by the TiO2 nanoparticles. In addition, the CNT@TiO2-Zn (Fig. 11(e), (f)) cathode showed a very flat surface, indicating very stable Zn plating even at high current densities, which can be attributed to the improved wettability and electrical conductivity of the CNT@TiO2-Zn compared to the bare Zn and TiO2-Zn cathodes. These results highlight the importance of optimizing cathode materials to suppress irregular dendrite growth in order to ensure stable operation and high-speed performance of ZIBs.

[0141] Figure 12 shows SEM images of the fabricated ZIB cathode after charging at a current density of 0.3 A / g. Figure 12a shows an SEM image of bare Zn. Figure 12b shows an SEM image of TiO2-Zn. Figure 12c shows an SEM image of CNT@TiO2.

[0142] As shown in the above Figure 12, the Zn plating behavior of the cathode for ZIB is 0.3 A·g -1After charging at a current density of , the prepared cathodes were examined using SEM. The SEM image of the bare Zn (Fig. 12a) cathode showed vertical dendrite growth. The concentration of dendrite growth in these few areas is thought to be due to the lack of sufficient nucleation sites for Zn plating during the charging process. In contrast, the SEM image of the TiO2-Zn (Fig. 12b) cathode showed horizontal dendrite growth due to the numerous nucleation sites provided by TiO2 nanoparticles during Zn plating. The CNT@TiO2-Zn cathode (Fig. 12c) showed denser and flatter Zn plating than the TiO2-Zn, which may be due to the improved electrical properties due to the introduction of CNTs. These achievements of the CNT@TiO2-Zn cathode were realized through two important mechanisms: (i) the provision of numerous nucleation sites for Zn plating by the TiO2 nanoparticles and (ii) the electrically connected CNTs acting as a skillful network for efficient charge collection.

[0143] Figure 13 is a conceptual diagram depicting dendrite formation on the surfaces of bare Zn and CNT@TiO2 cathodes.

[0144] The uniform and horizontal Zn plating depicted in Fig. 13 above contributed to improving the cycle stability of the ZIB by reducing the risk of dendrite penetration through the separator and subsequent electrical short circuit.

[0145]

[0146] Experimental Example 7: ZIB Cell Thickness

[0147] Figure 14 is a diagram showing (a) a schematic diagram of a conventional ZIB cell and a CNT@TiO2 cell, (b) thickness measurements of a cell including a cathode, a separator, and an anode, and (c) the speed performance results of a ZIB measured by changing the thickness of the separator.

[0148] In secondary batteries, a lower cell volume can result in higher energy density, which extends battery life and improves device performance. Furthermore, lightweight designs enhance portability, positively impacting applications such as portable electronics and electric vehicles. However, ZIB requires a separator as thick as 260 µm due to dendrite growth on the cathode, which occupies a significant volume within the cell and reduces the cell's energy density.

[0149] As illustrated in Fig. 14, the CNT@TiO2-Zn cathode enables flat Zn plating during charging, enabling a cell design with lower cell volume capacity compared to the conventional design (Fig. 14(a)).

[0150] In addition, the glass microfibers were used with thicknesses of 70 and 260 micrometers. When the CNT@TiO2-Zn cathode was used, the thickness of the cell including the cathode, separator, and cathode was 0.14 mm, which was four times smaller than the thickness (0.33 mm) when the bare Zn cathode was used.

[0151] The rate performance of ZIB measured by varying the thickness of the separator is presented in (c) of Fig. 14. In the case of the bare Zn anode, the charge / discharge behavior could not be investigated due to an electrical short circuit when the cell was fabricated using a 70 μm separator. However, both the TiO2-Zn and CNT@TiO2-Zn anodes successfully demonstrated charge / discharge behavior even with a low separator thickness of 70 μm. In addition, the current at 0.6 mA cm -2 The capacities of TiO2-Zn and CNT@TiO2-Zn cathodes were 22.9 and 24.0 mAh cm, respectively. -3 , bare Zn (15.3 mAh cm) using a 260 μm membrane -3 ) is about 1.5 times higher than that of 4.0 mA·cm -2 In the CNT@TiO2-Zn cathode, bare Zn (4.2 mAh cm -3) and TiO2-Zn cathode (9.8 mAh·cm -3 ) with superior speed performance (13.2 mAh·cm -3 ) was shown, which may be due to the improved electrical conductivity and ion diffusion behavior by introducing CNTs into the protective layer.

[0152]

[0153] Experimental Example 8: Cycle Test and Corrosion / Bad Reaction Experiment of ZIB

[0154] Figure 15 is a diagram showing the performance evaluation results after long-term charge / discharge cycles. Figure 15a shows 1.0 Ma·cm -2 Figure 15b is a diagram showing the cycle stability of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes for 300 cycles. Figure 15b is a diagram showing the cross-sectional samples analyzed using SEM after charge / discharge tests of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes.

[0155] As illustrated in Fig. 15a, cycle tests were conducted to evaluate the stability, durability, and reliability of secondary batteries for long-term use. The cycle stabilities of Zn, TiO2-Zn, and CNT@TiO2-Zn were 24, 55, and 71%, respectively.

[0156] Furthermore, as illustrated in Fig. 15b, cross-sectional samples were analyzed using SEM after charge-discharge tests to demonstrate the enhanced long-term stability of the CNT@TiO2-Zn. In the case of the bare Zn anode, it was evident that ZHS formed on the Zn surface due to side reactions with the electrolyte during the charge-discharge process. This ZHS contributed to the decreased cycle stability of the bare Zn anode. In addition, EDS mapping confirmed the presence of oxygen in the by-product on the anode surface. In contrast, in the TiO2-Zn and CNT@TiO2-Zn cathodes, Ti was uniformly distributed, indicating the maintenance of a protective layer. This observation confirmed that the TiO2-Zn and CNT@TiO2-Zn cathodes effectively suppressed Zn corrosion and hydrogen evolution, and thus they exhibited enhanced cycle stability.

[0157]

[0158] Figure 16 shows SEM images of corrosion and side reactions observed for (a) bare Zn, (b) TiO2-Zn, and (c) CNT@TiO2 cathodes, respectively.

[0159] In general, corrosion of the Zn cathode and formation of by-products are unavoidable during the charging and discharging processes of ZIB.

[0160] As illustrated in Fig. 16, the SEM image of the bare Zn cathode showed surface erosion and the appearance of flake-shaped by-products after cycling. In contrast, the TiO2-Zn cathode maintained the TiO2 protective layer, and some flake-shaped by-products were present on the surface.

[0161] Surprisingly, CNT@TiO2-Zn maintained its initial morphology without any visible by-products. This suggests that the improved wettability and enhanced electrical conductivity of the cathode protective layer contributed to suppressing by-product formation.

[0162] Figure 17 is a diagram showing the XRD analysis results of bare Zn, TiO2-Zn, and CNT@TiO2 cathodes after cycle tests.

[0163] As shown in Fig. 17, a new peak was observed at 7.8° in the XRD pattern of the cycled bare Zn, which corresponds to the formation of by-products (i.e., ZHS). However, no peak indicating the formation of by-products was observed in the XRD patterns of the cycled TiO2-Zn and CNT@TiO2-Zn cathodes. In particular, in the case of TiO2-Zn, although no by-products were detected in the SEM analysis, a small amount of by-products appeared to have been formed, indicating that the protective layer effectively protected the surface of the Zn cathode, preventing the formation of harmful by-products.

[0164] Experimental Example 9: Operation of a Manufactured Battery

[0165] Figure 18 is a diagram showing power supply to a microcontroller using a ZIB based on bare Zn and CNT@TiO2 cathodes.

[0166] As illustrated in Fig. 18, the practical application of the battery was demonstrated by powering a microcontroller using ZIBs based on bare Zn and CNT@TiO2-Zn cathodes. Both systems successfully operated a drone propeller. Furthermore, voltage measurements confirmed that the CNT@TiO2-Zn cathode was superior to the bare Zn cathode, enabling the drone propeller to operate for a longer time. Furthermore, the CNT@TiO2-Zn cathode stably operated the drone propeller even in a penetrating environment, demonstrating the high stability of the cell and suggesting its wide applicability in various fields.

[0167]

[0168] According to the above-described embodiment of the present invention, by introducing a composite protective layer composed of titanium dioxide and carbon nanotubes onto the negative electrode surface of a zinc ion battery, the negative electrode can be protected and the electrochemical behavior can be improved, and the energy storage performance of the zinc ion battery can be significantly improved while reducing the cell volume.

[0169] Specifically, the cathode protective layer of the zinc ion battery according to the present invention has high electrical conductivity by including CNTs, and can improve energy storage performance and electrical conductivity by facilitating electron transfer.

[0170] In addition, the cathode with the cathode protective layer has improved wettability, shows consistent and minimized voltage polarization throughout the cycling process, can promote uniform Zn growth, and can provide more electrochemically active sites on the cathode.

[0171] This allows for a high energy power density of 155 to 57 Wh / kg in a power density range of 300 to 2000 W / kg, and enables higher volumetric energy storage capacity, resulting in higher energy storage performance than conventional zinc-ion batteries.

[0172] Additionally, the cathode protective layer according to an embodiment of the present invention induces flatter and denser dendrite growth, thereby enabling the use of thinner separators, thereby enabling cell designs with lower cell volume capacity, and also has the effect of suppressing the formation of visible by-products.

[0173]

[0174] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will readily appreciate that the present invention can be readily modified into other specific forms without altering the technical spirit or essential characteristics 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 entity may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0175] The scope of the present invention is indicated by the claims described below, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention.

Claims

1. In the cathode protective layer formed on the surface of the anode of a zinc ion battery, Carbon nanotubes; and A cathode protective layer for a zinc ion battery, characterized in that it comprises titanium dioxide nanoparticles.

2. In paragraph 1, A cathode protective layer for a zinc ion battery, characterized in that the carbon nanotubes have a diameter of 1 to 50 nm.

3. In paragraph 1, A cathode protective layer for a zinc ion battery, characterized in that the titanium dioxide nanoparticles are nanoparticles having a diameter of 1 to 50 nm.

4. In paragraph 1, A cathode protective layer for a zinc ion battery, characterized in that the thickness of the cathode protective layer is 1 to 20 μm.

5. In paragraph 1, A cathode protective layer for a zinc ion battery, characterized in that the weight ratio of the carbon nanotubes and the titanium dioxide is 1:1 to 1:

10.

6. In a zinc ion battery comprising: a positive electrode; a negative electrode; an electrolyte formed between the positive electrode and the negative electrode; and a separator; The above cathode is, A zinc ion battery comprising a metal layer containing zinc; and a cathode protective layer according to claim 1 formed on at least one surface of the metal layer.

7. In paragraph 6, A zinc ion battery, characterized in that the above separator has a thickness of 300 μm or less.

8. Step of adding titanium dioxide nanopowder to alcohol and mixing; A step of preparing a solution by adding carbon nanotubes to the above alcohol and mixing them; and A method for manufacturing a cathode protective layer for a zinc ion battery, characterized in that it comprises a step of coating the above solution on a zinc cathode.

9. In paragraph 8, A method for manufacturing a cathode protective layer for a zinc ion battery, characterized in that the step of coating the above solution on a zinc cathode uses a spin coating method.

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