Composite positive electrode material for aqueous secondary battery and manufacturing method therefor

Abstract

The present invention relates to: a composite positive electrode material for zinc secondary batteries, the composite positive electrode material comprising a layered MXene sheet and vanadium oxide particles formed in the interlayers or on the surface of the layered MXene sheet; and a method for manufacturing a composite positive electrode material for zinc secondary batteries, the method comprising the steps of mixing a layered MXene sheet and a vanadium particle source in an aqueous carboxylic acid solution such that vanadyl dicarboxylate is composited with the layered MXene sheet, and subsequently performing solvothermal synthesis in a separate solvent.

Description

Composite cathode material for aqueous secondary batteries and method for manufacturing the same

[0001] The present invention relates to a composite cathode material for an aqueous secondary battery and a method for manufacturing the same, and more particularly, to a composite cathode material having improved electrochemical performance and stability compared to a commercial vanadium oxide cathode material and a method for manufacturing the same.

[0002] Aqueous zinc-ion secondary batteries (ZIBs) are attracting attention as next-generation secondary batteries that are environmentally friendly and highly safe. Among these, vanadium-based cathode materials are considered advantageous for long-life characteristics due to their high theoretical capacity and stable structure. Among vanadium-based oxides, V₂O5, in particular, with its layered structure, is being studied as a representative ZIB cathode material due to its high capacity. However, when applied to actual ZIBs, performance degradation during long-term charge and discharge cycles has been reported.

[0003] There are two main reasons for this performance degradation. First, V₂O5 has low electrical conductivity, making it difficult for electrons to move smoothly during the charge and discharge process, delaying the electrochemical reaction within the electrode and increasing the possibility of vanadium ions being eluted. Second, Zn 2+ As V₂O5 is repeatedly inserted and removed, the crystal structure of V₂O5 gradually collapses, which can lead to capacity loss and structural instability of the electrode during charge and discharge. Therefore, strategies to improve electrical conductivity and strengthen structural stability are needed to overcome these limitations.

[0004] One approach to address this issue is to form a composite with a highly conductive material to compensate for the low electrical conductivity of V₂O5 and utilize the nanostructure to promote redox reactions on the surface. Forming the composite enhances electrochemical reactivity, prevents structural collapse, and ensures long-term electrode stability. To address these requirements, the present invention proposes a composite cathode material utilizing vanadium-based MXene (V-MXene). Vanadium-based MXene inherently possesses high conductivity, and its layered structure provides excellent mechanical strength and chemical stability, making it suitable for enhancing the performance of ZIB.

[0005] In the present invention, a method for improving electrical conductivity and maximizing structural stability was introduced by uniformly forming nano-sized vanadium oxide on the surface of vanadium-based MXene by applying a specific synthetic process. Through this, Zn is formed inside the electrode. 2+ This was done to ensure smooth insertion / de-insertion processes and effectively suppress structural collapse of vanadium oxides. In addition, by applying a cathode material based on a tunnel structure that does not require an activation process during the initial charge / discharge process, a high initial capacity was achieved while maintaining long-term stability.

[0006] Therefore, the present invention provides a high-performance ZIB cathode material that simultaneously addresses the low electrical conductivity and structural instability inherent in existing vanadium-based oxide cathode materials, while also exhibiting long-life characteristics. This is expected to enable the implementation of more practical and commercially viable aqueous zinc-ion batteries.

[0007] The present invention has been devised to solve the above-mentioned problem, and one embodiment of the present invention provides a composite cathode material for a zinc secondary battery.

[0008] In addition, another embodiment of the present invention provides a method for manufacturing a composite cathode material for a zinc secondary battery.

[0009] In addition, another embodiment of the present invention provides a zinc secondary battery.

[0010] 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.

[0011] As a technical means for achieving the aforementioned technical task, one aspect of the present invention is,

[0012] Layered MXene sheet; and formed between layers or on the surface of the layered MXene sheet, V x O y A composite cathode material for a zinc secondary battery is provided, comprising vanadium oxide particles represented by; and characterized in that the primary particle diameter of the vanadium oxide particles is 5 to less than 100 nm.

[0013] The above composite cathode material may be obtained by mixing a vanadium oxide source and a layered maxene sheet source in a weight ratio of 0.75 to 3:1.

[0014] The atomic % fluorine content measured by Energy Dispersive X-ray Spectroscopy (EDS) may be less than 10 atomic %.

[0015] The above vanadium oxides are V2O5, VO2, V6O 13 , and may be at least one selected from those consisting of V2O3.

[0016]

[0017] Another aspect of the present invention is:

[0018] A composite cathode material for a zinc secondary battery is provided, comprising: a layered MXene sheet; and vanadium oxide particles formed between layers or on the surface of the layered MXene sheet and containing VO2; wherein the primary particle size of the vanadium oxide particles is 100 to 300 nm.

[0019] The above composite cathode material may be obtained by mixing a vanadium oxide source and a layered maxene sheet source in a weight ratio of 1 to 10:1.

[0020] VO2, V2C, Al by X-ray diffraction analysis 45 At least two peaks selected from the group consisting of V7, and V2AlC may be detected.

[0021] The above layered maxine sheet may be a vanadium-based maxine sheet.

[0022]

[0023] Another aspect of the present invention is:

[0024] A method for producing a composite cathode material for a zinc secondary battery is provided, comprising: a step of ultrasonically dispersing a first mixture containing a layered maxine sheet source exfoliated from the first mixture into an organic solvent; a step of adding a vanadium oxide source to the first mixture to produce a second mixture; and a step of solvothermally synthesizing the second mixture.

[0025] The above vanadium oxide may be V2O5.

[0026] The step of solvothermal synthesis of the second mixture may be performed at 60 to 250°C for 1 to 100 hours.

[0027]

[0028] Another aspect of the present invention is:

[0029] A method for producing a composite cathode material for a zinc secondary battery is provided, comprising: a step of ultrasonically dispersing a first mixture in which a layered MXene sheet is exfoliated; a step of producing a second mixture by introducing vanadium oxide particles into a dicarboxylic acid aqueous solution; a step of mixing the first mixture and the second mixture to obtain a material in which a vanadyl dicarboxylate is complexed with the layered MXene sheet; and a step of solvent-thermal synthesis by introducing the material in which the vanadyl dicarboxylate is complexed with the layered MXene sheet into a second solvent.

[0030] The above vanadium oxide particles may be V2O5, and the above dicarboxylic acid may be oxalic acid.

[0031] The step of solvothermal synthesis by introducing the material in which the above vanadyl dicarboxylate is complexed into a layered maxene sheet into a second solvent may be performed at 60 to 250°C for 1 to 100 hours.

[0032]

[0033] Another aspect of the present invention is:

[0034] A zinc secondary battery is provided, comprising: a positive electrode including the composite positive electrode material; a negative electrode; and an electrolyte.

[0035] According to an embodiment of the present invention, by complexing a vanadium-based MXene (V-MXene) and vanadium oxide, the problems of low electrical conductivity and structural instability of existing vanadium-based oxide cathode materials can be effectively solved, and by introducing a vanadium-based MXene with excellent electrical conductivity, the charge transfer resistance within the electrode can be reduced, and the electrochemical reaction during the charge and discharge process can be smoothly performed, thereby suppressing the elution of vanadium ions. In addition, by uniformly forming nano-sized vanadium oxide through a specific synthesis process, the oxidation-reduction reactivity on the surface can be improved, and repeated Zn 2+ Long-term stability can be ensured by preventing structural collapse due to insertion / detachment.

[0036] Furthermore, according to one embodiment of the present invention, a tunnel-structured cathode material that does not require an initial activation process can be applied to achieve high initial capacity while maintaining long-life characteristics. This overcomes the charge / discharge endurance limitations of existing V₂O5-based cathode materials, providing a practical cathode material for ZIB with high energy storage performance and a long lifespan.

[0037] The effects of the present invention are not limited to the above-described effects, and should be understood to include all effects that can be inferred from the composition of the invention described in the description or claims of the present invention.

[0038] Figure 1 is a schematic diagram showing a manufacturing method according to one embodiment of a composite cathode material according to one embodiment of the present invention.

[0039] Figure 2 shows the results of observing a sample of a composite cathode material according to one embodiment of the present invention using a scanning electron microscope (SEM).

[0040] Figure 3 shows a composite cathode material according to one embodiment of the present invention, in which V-MXene is a single sample (black curve) and V x O y @This is a comparison of the X-ray diffraction (XRD) patterns of the V-MXene composite material (red curve).

[0041] Figure 4 is a schematic diagram showing a cross-sectional configuration of a 2032 coin cell manufactured using a composite cathode material according to one embodiment of the present invention.

[0042] Figure 5 compares the long-term charge / discharge results of two batteries (Zn anode and Zn₃Hg cathode) using a commercial V₂O5 cathode in a composite cathode material according to one embodiment of the present invention. The black curve represents the case where the Zn cathode was used, and the red curve represents the case where the Zn₃Hg cathode was used.

[0043] Figure 6 is a composite cathode material according to one embodiment of the present invention, in which V is used instead of V2O5. x O y@This shows the long-term charge / discharge results when the V-MXene sample was used as the positive electrode.

[0044] FIG. 7 shows a charge / discharge curve of a composite cathode material according to an embodiment of the present invention.

[0045] Figure 8 shows the composite cathode material according to one embodiment of the present invention, V₂O5 (black curve) and V x O y @The impedance spectroscopy (EIS) was measured for the V-MXene(6:4) (red curve) electrode and is represented as a Nyquist plot.

[0046] Figure 9 shows the composite cathode material according to one embodiment of the present invention, V₂O5 (black curve) and V x O y In a coin cell assembled with a V-MXene(6:4) (red curve) electrode and a Zn₃Hg cathode, the current density was 0.1→0.2→0.5→1→2→5→10 A g -1 This shows the capacity retention rate (upper left graph) measured by gradually increasing the capacity.

[0047] Figure 10 shows the results of observing the capacity change during long-term charge / discharge at a current density of 0.1 A / g for a composite cathode material according to one embodiment of the present invention, using commercial V₂O5 (red curve) and synthetic VO₂ (blue curve).

[0048] Figure 11 shows the entire process for synthesizing a VO₂@V-MXene composite material in a composite cathode material according to one embodiment of the present invention.

[0049] FIG. 12 is a result of observing a VO2@V-MXene composite cathode material manufactured by varying the content of V2O5, which is a vanadium source, and V-MXene, which is an exfoliated MXene source, in a composite cathode material according to one embodiment of the present disclosure and another embodiment of the present disclosure, through SEM.

[0050] Figure 13 shows the results of comparing X-ray diffraction (XRD) patterns of VO₂, V-MXene, and VO₂@V-MXene composite materials in a composite cathode material according to one embodiment of the present invention.

[0051] Figure 14 shows a composite cathode material according to one embodiment of the present invention, in which VO₂@V-MXene (1:9, 3:7, 5:5, 7:3, 9:1) samples were tested in a 2 M Zn(OTf)₂ electrolyte at 15 A g -1 The current density was increased to 0.1 A g and then reversed to 0.1 A g. -1 This is a graph that observes the change in discharge capacity while gradually lowering the current density.

[0052] Figure 15 shows the results of comparing capacity changes in composite cathode materials according to one embodiment of the present invention by charging / discharging samples at 1 A g¹ for a long period of time (up to 500 cycles or more).

[0053] Figures 16 to 20 show the composite cathode material according to one embodiment of the present invention, with VO₂@V-MXene (1:9, 3:7, 5:5, 7:3, 9:1) at 0.1 to 15 A g, respectively. -1 It shows the charge / discharge curve recorded while changing the current up to the current density.

[0054] Figure 21 shows the results of long-term charge / discharge (about 1000 cycles or more) of VO₂ (red curve) and VO₂@V-MXene(9:1) (purple curve) electrodes at a current density of 1 A / g in a composite cathode material according to one embodiment of the present invention.

[0055] FIG. 22 shows a comparison of charge / discharge curves measured at key cycle points, such as the 1st, 50th, 100th, 500th, and 700-900th sections, of a composite cathode material according to an embodiment of the present invention, at a current density of 1 A / g for a VO₂ electrode (left) and a VO₂@V-MXene (9:1) electrode (right).

[0056] FIG. 23 shows electrochemical impedance (EIS) data of VO₂ (red curve) and VO₂@V-MXene(9:1) (purple curve) in a composite cathode material according to one embodiment of the present invention, represented as a Nyquist plot.

[0057] Figures 24 and 25 show the composite cathode material according to one embodiment of the present invention at different scan rates (0.1 to 2.0 mV s). -1 ) is a bar graph that calculates the relative contribution of the surface control (capacitive) reaction by performing cyclic voltammetry (CV).

[0058] FIGS. 26 and 27 show how the diffusion coefficient (D) changes in the VO₂ electrode and VO₂@V-MXene (9:1) while Zn² is intercalated and deintercalated into the electrode in a composite cathode material according to one embodiment of the present disclosure.

[0059] Hereinafter, the present invention will be described in more detail. However, the present invention may be implemented in various different forms, and the present invention is not limited to the embodiments described herein, but is defined only by the claims set forth below.

[0060] Additionally, the terminology used herein is solely for the purpose of describing specific embodiments and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. Throughout the specification of the present invention, the term "including" or "comprising" a component does not exclude other components, but rather implies the inclusion of other components, unless specifically stated otherwise.

[0061] Throughout the specification, when a part is said to be "connected (connected, contacted, joined)" to another part, this includes not only cases where the two parts are "directly connected," but also cases where the two parts are "indirectly connected" with other elements in between. Furthermore, when a part is said to "include" a component, this does not mean that the other components are excluded, but rather that the other components may be included, unless otherwise specifically stated.

[0062] As used herein, “%” may mean “weight%” or “wt%” in terms of content, unless otherwise specified.

[0063] In the case of “thermal synthesis” used in this specification, if the solvent in which the synthesis is performed is not water such as deionized water, it may be interpreted in the same way as “solvothermal synthesis.”

[0064] The term “aqueous secondary battery” used herein may refer to a battery in which charging and discharging are performed by utilizing the movement of alkali metal or non-alkali metal-based ions using an aqueous electrolyte, and may preferably be a zinc secondary battery.

[0065] The terminology used in this specification is for the purpose of describing specific embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0066]

[0067] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0068]

[0069] Manufacturing Example 1: General method for manufacturing composite cathode material

[0070] Figure 1 is a schematic diagram showing a manufacturing method according to one embodiment of a composite cathode material according to one embodiment of the present invention.

[0071] Looking at it in order, the first step is a schematic representation of the process of ultrasonically dispersing the exfoliated vanadium-based MXene (V-MXene) in ethanol solvent. The ultrasonic energy separated the V-MXene layers, resulting in uniform dispersion, which was then converted to V₂O 5 It provides a basis for improved reactivity when mixed with .

[0072] The second step is to add commercial V₂O to the ultrasonically dispersed V-MXene solution. 5 This shows the steps of adding powder, stirring, and performing a solvothermal synthesis reaction. The synthesis reaction proceeds for 10 hours at approximately 120°C, and during this process, a complex is created in which nanoparticles of V2O5 are evenly distributed on the surface of V-MXene.

[0073] After the synthetic reaction, the final V was collected through filtration and washing processes. x O y @V-MXene complex powders have different microstructures and particle size distributions of the resulting complexes depending on the reaction conditions and the weight ratio of the input sources (e.g., 6:4 or 9:1), which are directly related to electrical conductivity and structural stability, and can contribute to securing long-life characteristics of zinc-ion batteries.

[0074]

[0075] Example 1-1: Preparation of composite cathode material

[0076] Commercial V₂O 5 An example of a composite (VxOy@V-MXene (6:4)) synthesized by mixing V-MXene and vanadium-based MXene in a weight ratio of 6:4 is described. First, the exfoliated V-MXene powder was ultrasonically dispersed in ethanol and stirred, and then commercial V₂O 5was injected. Then, solvent thermal synthesis was performed at 120°C for 10 hours, and after the reaction was completed, filtration and washing were performed. Finally, it was dried at 60°C for more than 12 hours to obtain V that can be used as a cathode material for AZIB. x O y @V-MXene (6:4) powder was obtained.

[0077] This complex is composed of nanoparticles V₂O 5 To overcome the low electrical conductivity and slow reaction speed (kinetics), it is characterized by the composite incorporation of V-MXene, which has excellent electrical conductivity.

[0078]

[0079] Example 1-2: Preparation of composite cathode material

[0080] Commercial V₂O 5 A composite synthesized by mixing vanadium-based MXene (V-MXene) with a weight ratio of 9:1 (V x O y Hereinafter, an example for V-MXene (9:1)) is described. The overall synthetic process was performed in the same manner as Experimental Example 1, including ultrasonic dispersion in ethanol solvent, stirring, and solvothermal synthesis at 120°C for 10 hours. Afterwards, reaction byproducts were removed through filtration and washing, and the powder was obtained by drying at 60°C for more than 12 hours.

[0081] Since the V₂O5 content in the complex is relatively high, the theoretical capacity itself in the anode reaction can be secured significantly, but since the V-MXene content is low, it may be somewhat disadvantageous compared to Example 1 in terms of improved electrical conductivity and structural stability.

[0082] Commercial V₂O5 generally has low electrical conductivity, which limits the charge / discharge efficiency and capacity retention rate, and Zn 2+It is known that it is difficult to achieve long-life characteristics due to interlayer structural collapse caused by insertion and de-insertion of V₂O5. As in the present examples, by complexing V₂O5 and V-MXene, this problem can be supplemented due to the high electrical conductivity and nanostructure formation effect of V-MXene. In addition, by adopting a solvothermal synthesis method, high-purity, small-particle powder can be easily obtained at a relatively low temperature, thereby increasing the applicability as an actual AZIB cathode material.

[0083]

[0084] Comparative Example 1: Preparation of anode material

[0085] Commercial V₂O5 particles were prepared and used as a comparative example.

[0086]

[0087] Experimental Example 1-1: Composite Material Properties According to Changes in Mixing Ratio

[0088] The left drawing of Fig. 2 shows the results of observation of a single V-MXene sample using a scanning electron microscope (SEM). A structure in which a thin film of several μm in size is well exfoliated into a single layer is observed, which shows a typical exfoliated two-dimensional lamellar morphology unique to MXene. The middle drawing of Fig. 2 shows V₂O5 obtained by mixing V-MXene with V₂O5 in a ratio of 6:4. x O y This is an image of a V-MXene (6:4) sample observed with an SEM. Spherical or hemispherical nanoparticles with a size of 20 to 50 nm are observed to have grown all over the surface, which is presumed to be formed by partial growth of V₂O5 precursor on the surface of V-MXene. The right drawing of Fig. 2 shows V synthesized at a ratio of (9:1) with an increased V₂O5 content. x O y@This is an SEM image of V-MXene(9:1). Compared to the 6:4 ratio, irregularly formed amorphous nanoparticles are more prominent, and it is believed that vanadium oxide did not grow uniformly on the MXene surface because the nanoparticles aggregated together and grew into large particles. This can be interpreted as the result of high-concentration reaction and growth of V₂O5 on the vanadium-based MXene surface.

[0089] Element V-MXene V x O y @V-MXene(6:4)V x O y @V-MXene (9:1)C (at%)41.872.134.2V (at%)15.77.816.0O (at%)24.616.849.4F (at%)17.83.30.3Al (at%)0.10.10.1

[0090] Table 1 above is a table of elemental compositions measured by energy dispersive X-ray spectroscopy (EDS), and is compared to V-MXene. x O y @It can be seen that the oxygen (O) content in the V-MXene composite material has increased significantly. In fact, the O at% in the (9:1) sample has increased significantly to about 49.4% compared to the (6:4) sample (16.8%), indicating that vanadium oxide (V) has been deposited on the V-MXene surface. x O y ) supports the formation of a thick layer.

[0091] Experimental Example 1-2: Analysis of Composite Crystalline Phases Using XRD

[0092] Figure 3 shows the V-MXene single sample (black curve) and V x O y @This is the result of comparing the X-ray diffraction (XRD) patterns of the V-MXene composite material (red curve). In addition to the diffraction peaks characteristic of V-MXene (black triangles), the composite spectrum shows V₂O5 (red circles), VO₂ (blue circles), and V6O. 13It can be confirmed that peaks of various vanadium oxide phases coexist, such as V₂O₃ (purple circle), V₂O₃ (green circle), etc. This means that multiple crystal phases exist simultaneously within the complex formed in the form of nanoparticles.

[0093] In summary, these results suggest that not only V₂O5 but also other vanadium oxide species (V₂O₃, VO₂, V6O) are partially present on the V-MXene surface. 13 It can be seen that ) are also mixed. In the end, rather than simply referring to this composite material as V₂O5@V-MXene, it is called “V” to encompass the complex oxide phase with an unclear molecular formula. x O y It was named “@V-MXene”. This, together with the previous material analysis results such as SEM and EDS, suggests that this composite material can be used as a highly active electrode material containing multiphase vanadium oxide.

[0094]

[0095] Experimental Example 1-3: V x O y @V-MXene Long-term durability comparison by mixing ratio

[0096] Figure 4 is a schematic cross-sectional diagram of the fabricated 2032 coin cell. A Zn or Zn3Hg cathode is placed under the upper case, and a glass fiber filter and a 2 M Zn(OTf)2 electrolyte are sequentially layered, followed by V x O y @This structure uses a V-MXene or V2O5 electrode as the anode. The reason for using Zn3Hg instead of Zn here is to ensure a stable charge / discharge process, and the battery performance was evaluated for a long period of time under conditions of 1 A / g current density with this cathode.

[0097] Figure 5 shows the results of comparison using commercial V2O5 as the anode and Zn or Zn3Hg as the cathode. When Zn3Hg is used as the cathode material, more accurate cathode material performance can be confirmed.

[0098] Figure 6 shows V instead of V2O5 x O y This shows the long-term charge / discharge results when the @V-MXene sample was used as a cathode. In the case of the sample with a mixing ratio (6:4), relatively uniform nanoparticles were formed on the surface, and good durability was shown, maintaining about 80.3% of the maximum capacity even up to 2000 cycles (red curve). On the other hand, it was confirmed that the sample with a mixing ratio (9:1) was formed with a very low initial capacity and the retention degree was also relatively low (blue curve). In addition, while commercial V2O5 maintained 70% of the maximum capacity up to 477 cycles, the red curve shows that the activation process was shortened (black curve). V on the surface x O y V appears to be formed in an uneven and clumped manner x O y For V-MXene (9:1), the activation process that increases the initial capacity of the cycle disappeared, but a relatively low capacity was observed (right figure). It was confirmed that the morphology of the particles formed on the surface changed depending on the synthesis ratio, and thus the electrochemical performance also changed (right figure).

[0099] These results are V x O y @V-MXene(6:4) shows a much higher retention rate than V2O5-based electrodes, and the activation process also occurs relatively quickly, suggesting that it can satisfy both high-power and long-life characteristics. In addition, V is uniformly formed on the surface. x O y It was confirmed that nanoparticles smoothly induce oxidation / reduction of active materials during the charge / discharge process, thereby suppressing electrode deterioration even during long-term cycling.

[0100]

[0101] Experimental Example 1-4: Charge / discharge curve at 1 A / g current density

[0102] Fig. 7 shows charge / discharge curves measured at the 1st, 10th, 50th, 100th, 200th, and 477th cycles under 1 A / g conditions for a V₂O5 electrode. The redox reaction occurs in the range of approximately 0.3 to 1.6 V, and the capacity gradually increases (the activation process described above) through repeated charge / discharge from the beginning of the cycle, and a relatively stable plateau region is confirmed at the 200th cycle, and it can be confirmed that high capacity is expressed at the same time. However, the capacity gradually decreases thereafter, and it is shown that 70% of the maximum capacity is maintained at the 477th cycle.

[0103] Figure 7 middle drawing is V x O y @The charge / discharge curve of the V-MXene(6:4) electrode shows that the redox reaction occurs quickly in a certain voltage range while maintaining a short plateau compared to V₂O5. This is because the V formed on the surface of V-MXene x O y Nanoparticles increase the surface reaction rate, and the V of nanoparticles x O y It is interpreted that the plateau is relatively gentle compared to the V2O5 result due to the rapid oxidation / reduction (redox) reaction on the surface. In fact, it shows relatively stable voltage behavior even up to the 1000th and 2000th cycles, so excellent durability can be expected during high-speed charge / discharge.

[0104] Figure 7 Right drawing is V x O y @This is the charge / discharge curve of the V-MXene(9:1) electrode. During the charging process, a voltage range different from the plateau characteristic of V₂O5 is observed. This is V x O yIt is interpreted that this is because the V-MXene is distributed unevenly on the paper V-MXene substrate and at the same time, the V-MXene itself contributes to the oxidation / reduction reaction. The main contributor to the high capacity is V x O y V on the V-MXene surface on paper x O y V rises unevenly x O y @V-MXene(9:1) showed low capacity.

[0105]

[0106] Experimental Example 1-5: Electrochemical Impedance Spectroscopy (EIS) Analysis

[0107] Figure 8 shows the relationship between V₂O5 (black curve) and V x O y @V-MXene(6:4) (red curve) After measuring the impedance spectroscopy (EIS) for the electrode, it is displayed as a Nyquist plot. The part that appears as a semicircle in the high frequency region is the charge transfer resistance (R ct ) reflects the V₂O5 electrode, while the V₂O5 electrode shows about 7.9 Ω·cm². x O y @V-MXene(6:4) electrode was measured to be approximately 4.6 Ω·cm², which is a 1.7-fold decrease in resistance compared to V₂O5.

[0108] This is a vanadium oxide (V) on the surface of V-MXene, which has excellent electrical conductivity. x O y ) is interpreted as a result of uniform formation of nanoparticles, which accelerates the charge / discharge reaction by shortening the ion and charge transfer path at the electrode / electrolyte interface. As a result, it is judged that the internal resistance of the electrode is maintained relatively low even in a high current density environment, showing excellent life characteristics even in long-term cycles.

[0109]

[0110] Experimental Example 1-6: Rate performance at high current density

[0111] Figure 9 shows the relationship between V₂O5 (black curve) and V x O y In a coin cell assembled with a V-MXene(6:4) (red curve) electrode and a Zn₃Hg cathode, the current density was 0.1→0.2→0.5→1→2→5→10 A g -1 The capacity retention rate (upper left graph) measured by gradually increasing the voltage is shown. V x O y @V-MXene(6:4) electrode is 10 A g -1 Even at high current densities, the discharge capacity is maintained at approximately 75% of the initial capacity, and when the current is lowered again (0.1 A g -1 ) showed excellent reversibility, recovering most of the capacity even when restored.

[0112] These results are consistent with the previously confirmed charge transfer resistance (R ct ) is due to the reduction and improved electrical conductivity of V-MXene. That is, the excellent electron transfer ability of V-MXene and vanadium oxide (V x O y ) combines the active material properties of lithium ion batteries, enabling smooth charge transfer on the electrode surface even during high-speed charging / discharging. As a result, electrode damage is minimized and long-life characteristics are maintained even under high-power driving conditions.

[0113] In summary, by incorporating electrically conductive V-MXene into conventional vanadium oxide, which has low electrical conductivity, we found that surface reaction activity and rate characteristics were significantly improved. This composite structure suggests that it has high potential as a cathode material for high-power, long-life energy storage devices.

[0114]

[0115] Manufacturing Example 2: General method for manufacturing composite cathode material

[0116] Figure 10 shows the results of observing the capacity change during long-term charge / discharge of commercial V₂O5 (red curve) and synthetic VO₂ (blue curve) at a current density of 0.1 A / g. Commercial V₂O5 has a layered structure, so Zn2+ An initial activation period of approximately 20 cycles is required for insertion and detachment. In contrast, synthetic VO₂ achieves a relatively high initial capacity and exhibits stable capacity retention after only a short activation period of approximately 5 cycles.

[0117] These results imply that VO₂ achieves a high theoretical capacity in a layered structure based on excellent structural stability. In particular, VO₂ synthesized in nanoscale size has a large reaction area, which increases the specific surface area, and thus Zn 2+ Insertion and removal of VO₂ particles become much smoother. However, since the interfacial resistance of VO₂ particles is high, which may limit electron mobility, if this part is improved in the future through composites with vanadium-based MXene or other conductive materials, it is expected that it can be utilized as an electrode material with superior long-life / high performance. The second embodiment of the present invention describes matters regarding a tunnel-type VO₂-based composite cathode material.

[0118] Figure 11 shows the overall process for synthesizing VO₂@V-MXene composite materials. First, oxalic acid (C₂H₂O₄) and a reducing agent are added to V₂O5 powder and stirred at 60°C for 1 hour, and the solution changes color from yellow to blue, resulting in V₂@V-MXene. 5+ Ion V 4+ It is confirmed that it is reduced to . At this time, Vanadyl oxalate [VO(C₂O₄)₂] is generated, and at the same time, the V-MXene dispersion is prepared through a peeling and dispersion process using ultrasonic treatment.

[0119] In the next step, the vanadyl oxalate solution and the V-MXene solution are mixed and dried at 75℃ for 48 hours to obtain the 'Vanadyl oxalate@V-MXene' precursor. This precursor is mixed again with methanol and deionized water and subjected to a solvothermal reaction at 200℃ for 6 hours. This removes oxalic acid and generates VO₂, ultimately obtaining the VO₂@V-MXene composite material. Finally, the VO₂@V-MXene powder is obtained through a drying process at 60℃ for 12 hours.

[0120]

[0121] Examples 2-1 to 2-5: Preparation of composite cathode materials

[0122] To achieve long-term characteristics and high-capacity utilization of VO₂@V-MXene, the weight ratio between commercial V₂O5 and V-MXene was varied for synthesis. Synthesis ratios of (1:9), (3:7), (5:5), (7:3), and (9:1) were set, and each was manufactured as Examples 2-1 to 2-5.

[0123] As above, the synthesis ratio can be set differently, and depending on the result, the amount and distribution of VO₂ nanoparticles formed on the surface will change. As will be described later, since a partially exfoliated MXene sheet source was used, the vanadium source must evenly penetrate into the layers. To achieve this, the ratio of V2O5, the vanadium source introduced into the synthesis, must increase to 'V2O5:V-MXene=9:1', in which case VO₂ is evenly distributed between the layers, which can exhibit high capacity and excellent electrochemical performance. This phenomenon is presumed to be because the vanadium source can evenly penetrate into the interlayer interior of the MXene due to the concentration gradient formed as the amount of introduced vanadium source increases.

[0124] By adjusting the optimal ratio in this way, it will be possible to simultaneously achieve high energy density and long-term stability by utilizing the redox properties of VO₂ and the electrical conductivity of V-MXene in a balanced manner.

[0125]

[0126] Experimental Example 2-1: Structural observation of VO₂@V-MXene using SEM

[0127] Fig. 12, left, shows a SEM image of VO₂@V-MXene(1:9), and it can be seen that VO₂ nanoparticles with a size of 100 to 150 nm have grown irregularly on the surface of the V-MXene layered structure. In the case of VO₂@V-MXene(1:9), the SEM observation results showed that VO₂ could not penetrate into the V-MXene layer and that the VO₂ particles were clumped together. This is believed to be because the vanadium source content was low during the mixing process of the vanadyl oxalate dispersion and the V-MXene dispersion, and thus the vanadium source could not sufficiently diffuse into the V-MXene layer.

[0128] Figure 12, middle, is a SEM image of a VO₂@V-MXene (5:5) sample. Since the content of VO₂ is similar to that of V-MXene, VO₂ particles can be observed to be relatively homogeneously dispersed on the surface. In this case, due to the appropriate ratio, VO₂ is evenly formed on the surface of V-MXene, which improves interfacial activity and is expected to increase charge / discharge reactivity when used as an electrode.

[0129] Figure 12, on the right, is a SEM image of the VO₂@V-MXene(9:1) sample, confirming that VO₂ is uniformly distributed on the surface of V-MXene. At the same time, spherical and flower-shaped aggregates are observed to have formed here and there. It is believed that the active material VO₂ is uniformly distributed within the layered structure of V-MXene, and thus, high capacity and excellent rate characteristics can be secured.

[0130]

[0131] Experimental Example 2-2: Analysis of crystal phase confirmed by XRD

[0132] Figure 13 shows the results of comparing the X-ray diffraction (XRD) patterns of V-MXene and VO₂@V-MXene composites. V₂AlC, Al corresponding to V-MXene 45 There are many peaks such as V7, V₂C, and V₂Al₂C, and in addition, peaks unique to VO₂ (e.g., JCPDS 15-0755) are detected, indicating that VO₂ is properly formed within the composite material.

[0133] These XRD results, taken together, confirm that VO₂ nanocrystals formed on the V-MXene layered structure grew in various directions through solvothermal reaction, ensuring crystallinity. In actual electrochemical tests, this composite structure is expected to enhance conductivity and promote highly active redox reactions, demonstrating superior performance in future applications in energy storage devices such as aqueous batteries.

[0134]

[0135] Experimental Example 2-3: Rate capability and long-term performance by content ratio

[0136] Figure 14 shows the VO₂@V-MXene (1:9, 3:7, 5:5, 7:3, 9:1) samples in 2 M Zn(OTf)₂ electrolyte at 0.1 A g -1 From 15 A g -1 This is a graph observing the change in discharge capacity while gradually increasing the current density. The 1:9, 3:7, and 5:5 samples showed relatively large voltage hysteresis (energy loss due to structural deformation) during the charge / discharge process, and the capacity recovery ability also tended to decrease somewhat as the current density increased. On the other hand, the 9:1 sample maintained a stable capacity even in the high current range, and quickly returned to the initial capacity level when the current was lowered again, demonstrating excellent responsiveness.

[0137] Figure 15 shows the same samples at 1 A g -1 As a result of comparing the capacity change through long-term charge / discharge (up to 500 cycles or more), the 9:1 sample achieved the highest capacity retention. This is interpreted as being due to the combination of an appropriate amount of VO₂ on the highly conductive network of MXene, which exhibits stable oxidation / reduction characteristics without structural collapse even during long-term reactions.

[0138]

[0139] Experimental Example 2-4: Charge / Discharge Curves by Current Density

[0140] Figures 16 to 20 show the VO₂@V-MXene (1:9, 3:7, 5:5, 7:3, 9:1) at 0.1 to 15 A g, respectively. -1 This shows the charge / discharge curves recorded while varying the current within the range. The 1:9, 3:7, and 5:5 samples have relatively large curve gaps between the discharge and charge sections, showing prominent structural hysteresis. However, the 9:1 sample has curves that are close together, resulting in minimal energy loss, and the profile remains relatively constant across multiple current sections.

[0141] As a result, it was confirmed that by exfoliating and manufacturing V-MXene in an accordion shape and then depositing / growing VO₂ at a 9:1 ratio, the balance between durability and rate characteristics is optimized, enabling simultaneous implementation of high-capacity and long-life performance. Therefore, in this example, VO₂@V-MXene (9:1) can be selected as the optimal composition.

[0142]

[0143] Experimental Example 2-5: Long-Cycle Life Test

[0144] Figure 21 shows the VO₂ (red curve) and VO₂@V-MXene(9:1) (purple curve) electrodes at 1 A g -1 This shows the results of long-term charge / discharge (more than about 1000 cycles) at a current density. The VO₂ electrode initially had about 280 mAh g -1The discharge capacity of VO₂@V-MXene(9:1) was achieved, but a rapid decrease began around 790 cycles, and a continuous performance degradation was observed thereafter. On the other hand, VO₂@V-MXene(9:1) initially had a discharge capacity of 440 mAh g -1 It showed high capacity, about 310 mAh g even after 950 cycles. -1 It has demonstrated excellent long-life characteristics by maintaining the degree.

[0145] These differences are interpreted as being due to the composite structure inducing more uniform insertion / de-insertion of Zn ions within the electrode and suppressing electrode structural degradation. Furthermore, since the Coulombic efficiency of VO₂@V-MXene(9:1) maintains a value close to 100%, it can be confirmed that electrode surface damage and side reactions are minimized even during repeated charge / discharge.

[0146]

[0147] Experimental Example 2-6: Comparison of Charge / Discharge Curves

[0148] Figure 22 shows the VO₂ electrode (left) and VO₂@V-MXene(9:1) electrode (right) at 1 A g -1 This compares the charge / discharge curves measured at key cycle points, such as the 1st, 50th, 100th, 500th, and 700-900th sections, at current densities. While the VO₂ electrode gradually loses its flat voltage curve due to a significant capacity decrease from the latter half of the 700th cycle, VO₂@V-MXene(9:1) maintains a relatively constant curve shape up to the high voltage section.

[0149] This confirms that VO₂@V-MXene(9:1) maintains structural stability not only in terms of initial capacity but also over long-term cycling, and exhibits minimal voltage loss due to electrode degradation. Consequently, we experimentally demonstrate that the shortcomings of VO₂ can be complemented by an MXene-based composite structure, demonstrating its high potential as a next-generation aqueous battery cathode material.

[0150]

[0151] Experimental Example 2-7: EIS Analysis

[0152] Figure 23 shows the electrochemical impedance (EIS) data of VO₂ (red curve) and VO₂@V-MXene(9:1) (purple curve) as Nyquist plots. Charge transfer resistance (R ct ) are compared, VO₂ is about 7.3 Ω, while VO₂@V-MXene(9:1) is reduced to about 5.4 Ω (about 1.4 times difference), indicating that electron and ion exchange occurs more smoothly on the electrode surface.

[0153] This is interpreted as a key factor that the V-MXene layer provides a highly conductive path, lowering the overall electrode resistance despite the nanoparticle size of VO₂, thereby reducing energy loss during the charge / discharge process and improving current responsiveness.

[0154]

[0155] Experimental Example 2-8: Capacitive Contribution

[0156] Figures 24 and 25 show different scan rates (0.1 to 2.0 mV s -1 ) is a bar graph showing the relative contribution of the surface-controlled (capacitive) reaction by performing cyclic voltammetry (CV). The VO₂ electrode shows a surface reaction contribution ranging from about 62.0% to 87.9% as the scan rate increases, while VO₂@V-MXene(9:1) maintains a higher value from 69.4% to 91.0%.

[0157] This means that the rate at which rapid oxidation-reduction reactions occur on the electrode surface is greater in VO₂@V-MXene (9:1), contributing to rapid recovery without a rapid drop in capacity even under high current conditions.

[0158]

[0159] Experimental Example 2-9: Comparison of Zn² Diffusion Coefficients

[0160] Figures 26 and 27 are Zn 2+ The diffusion coefficient (D) changes during the intercalation and deintercalation of Zn into the electrode in the VO₂ electrode and VO₂@V-MXene(9:1). The Zn² diffusion coefficient when only VO₂ was used was approximately 5.16×10 ¹⁴ ~ 1.86×10 ¹² cm² s -1 level, whereas in VO₂@V-MXene(9:1) it is 1.28×10 ¹³ ~ 1.99×10 ¹² cm² s -1 , which shows higher values ​​overall.

[0161] In this way, Zn is formed due to MXene complexation. 2+ This allows ions to rapidly diffuse within the electrode, significantly improving charge / discharge efficiency and durability. Therefore, the combination of V-MXene's unique high-conductivity network and the redox properties of VO₂ nanoparticles ensures long-term, stable performance without electrode deterioration.

[0162] The first aspect of this article is,

[0163] Layered MXene sheet; and formed between layers or on the surface of the layered MXene sheet, V x O y A composite cathode material for an aqueous zinc secondary battery is provided, comprising vanadium oxide particles represented by; and characterized in that the primary particle size of the vanadium oxide particles is 5 to 100 nm.

[0164]

[0165] Hereinafter, a composite cathode material for a zinc secondary battery according to the first aspect of the present invention will be described in detail.

[0166]

[0167] In one embodiment of the present invention, the layered MXene sheet may be a vanadium-based MXene sheet, which may be a two-dimensional structure containing vanadium as a main metal element. However, the present invention is not limited thereto, and various MXene sheets containing transition metals such as titanium (Ti), niobium (Nb), molybdenum (Mo), and tungsten (W) may be applied, and such MXene sheets are generally M n+1 X n T x It can be expressed by a chemical formula such as . Here, M means a metal element such as Ti, V, Nb, Mo, W, etc., and X means carbon (C) or nitrogen (N), T x represents a terminal group bonded to the surface, such as -OH, =O, -F, etc. The MXene sheet used in the present specification can include such chemical formulas and metal element compositions without limitation, and can be modified into a form in which the M element is partially substituted or contains multiple metals. Since the MXene has a layered structure of transition metal carbide or nitride, it has the advantage of exhibiting both a high surface area and excellent conductivity. Therefore, when it is used as a cathode material of a secondary battery, for example, a Zn ion battery, in the electrode reaction, metal ions (e.g., Zn 2+ ) can effectively diffuse inside the electrode, making it easy to implement high-speed charge / discharge characteristics. In addition, the layered structure of MXene can play a buffering role to some extent against volume changes or physical stress due to external repeated cycling, and it is also possible to implement a more stable high-capacity / long-life electrode by complexing or doping not only vanadium but also other metal-based MXene sheets as needed. In conclusion, the MXene sheet utilized in the present invention is not necessarily limited to vanadium-based MXene, but can be interpreted as encompassing a variety of transition metal-based MXene sheets.

[0168] In one embodiment of the present invention, the layered MXene sheet may be based on an exfoliated MXene sheet, and the exfoliated MXene sheet is a two-dimensional layered structure having a transition metal carbide or nitride skeleton, in which a metal element (M) and carbon or nitrogen (X) are alternately stacked, and terminal groups (T_x) such as hydroxyl (-OH), oxygen (=O), and fluorine (-F) exist on the surface. The MXene having such a layered structure provides high porosity and a large surface area because the orientation between transition metals is spread in a two-dimensional plane direction, and has metallic conductive properties so that charge transfer is smooth. In addition, it can be manufactured in the form of a single layer or a thin sheet having a thickness of several nanometers through a peeling process such as ultrasonic dispersion or chemical etching, so that at least some of the interlayer peeling is achieved, and it can have a structure such as an accordion shape, and it can be advantageous in shortening the diffusion path of metal ions during electrode manufacturing and enhancing the effect of dispersing stress within the material.

[0169] In one embodiment of the present invention, the vanadium oxide particles are V x O y It may be represented as. The above x may be 1 to 6, and y may be 2 to 13. Preferably, the vanadium oxide is V2O5, VO2, V6O 13 , and V2O3. These vanadium oxides can secure a wide range of oxidation / reduction reactions according to the various oxidation states of vanadium ions, which is advantageous in achieving high theoretical capacity and excellent electrochemical durability. In addition, when manufactured in a layered or nano-granular form, there is an advantage in that metal ions can be quickly inserted / deintercalated, making it easy to realize high output and long-cycle performance.

[0170] In one embodiment of the present invention, the primary particle size of the vanadium oxide particles may be 5 nm or more, 6 nm or more, 10 nm or more, 15 nm or more, 18 nm or more, 20 nm or more, or 24 nm or more, and may be 500 nm or less, 300 nm or less, 125 nm or less, 100 nm or less, 75 nm or less, 75 nm or less, 62.5 nm or less, or 50 nm or less. When the primary particle size of the particles is less than the above range, the particle surface area excessively increases, so that the reaction with the electrolyte is rapidly activated, and as a result, the frequency of side reactions increases, which may cause electrode deterioration and reduced lifespan. On the other hand, if the above range is exceeded, the diffusion distance of metal ions into the particle becomes longer and the reaction area decreases, which may cause problems such as reduced charge / discharge efficiency or deteriorated output characteristics.

[0171] In one embodiment of the present invention, the vanadium oxide source and the layered MXene sheet source may be obtained by mixing them in a weight ratio of 0.75 to 3:1. If the weight ratio of the vanadium oxide source and the layered MXene sheet source is less than the above-mentioned range, the amount of active material may be small, resulting in a decrease in capacity. If the weight ratio exceeds the above-mentioned range, the overall performance may be reduced due to particle aggregation and blocking of the active site of the sheet caused by excessive dispersion.

[0172] In one embodiment of the present invention, the atomic % content of fluorine measured by Energy Dispersive X-ray Spectroscopy (EDS) may be 0.0001 atomic % or more, 0.05 atomic % or more, 0.075 atomic % or more, 0.09 atomic % or more, 0.1 atomic % or more, or 0.12 atomic % or more, 25 atomic % or less, 20 atomic % or less, 15 atomic % or less, 15 atomic % or less, 12.5 atomic % or less, or 10 atomic % or less. Preferably, it may be less than 10 atomic %. If the above range is exceeded, structural instability and reduced conductivity of the material may be caused due to excessive fluorine content.

[0173] In one embodiment of the present invention, the atomic% content of vanadium measured by Energy Dispersive X-ray Spectroscopy (EDS) may be 0.03 atomic% or more, 0.05 atomic% or more, 0.075 atomic% or more, 0.09 atomic% or more, 0.1 atomic% or more, or 0.12 atomic% or more, and may be 50 atomic% or less, 40 atomic% or less, 30 atomic% or less, 30 atomic% or less, 25 atomic% or less, or 20 atomic% or less. If it is less than the above range, electrochemical activity and electrochemical activity and stability may not be sufficiently secured due to insufficient vanadium content, and if it exceeds the above range, defects may occur and physical properties may deteriorate due to excessive vanadium content.

[0174] In one embodiment of the present invention, the atomic% content of oxygen measured by Energy Dispersive X-ray Spectroscopy (EDS) may be 3 atomic% or more, 5 atomic% or more, 7.5 atomic% or more, 9 atomic% or more, 10 atomic% or more, or 12 atomic% or more, 122.5 atomic% or less, 98 atomic% or less, 73.5 atomic% or less, 73.5 atomic% or less, 61.25 atomic% or less, or 49 atomic% or less. If it is less than the above range, electrochemical activity and structural stability may not be sufficiently secured due to insufficient oxygen content, and if it exceeds the above range, defects may occur and physical properties may deteriorate due to excessive oxide formation.

[0175]

[0176] The second aspect of the original text is,

[0177] A composite cathode material for a zinc secondary battery is provided, comprising: a layered MXene sheet; and vanadium oxide particles formed between layers or on the surface of the layered MXene sheet and containing VO2; wherein the primary particle size of the vanadium oxide particles is 100 to 300 nm.

[0178]

[0179] Detailed explanations of parts that overlap with the first aspect of the present application have been omitted, but the explanations of the first aspect of the present application may be applied equally even if the explanations are omitted in the second aspect.

[0180]

[0181] Hereinafter, a composite cathode material for a zinc secondary battery according to the second aspect of the present invention will be described in detail.

[0182]

[0183] In one embodiment of the present invention, the layered MXene sheet may include vanadium oxide particles formed between layers or on the surface thereof and including VO2. The vanadium oxide particles formed between layers or on the surface of the layered MXene sheet may preferably be composed only of VO2, and may substantially not include other vanadium oxide phases. By only having a constant oxidation number of VO2, unique properties such as a metal-insulator transition are effectively expressed, thereby enhancing electrochemical reactivity, and the interface properties with the MXene sheet are also optimized, thereby improving electron transfer and ion diffusion paths. In addition, since other oxide phases are not mixed, the material properties are uniformly maintained, thereby enabling highly reproducible physical properties and stable performance to be realized.

[0184] In one embodiment of the present invention, the primary particle size of the vanadium oxide particles may be 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, 30 nm or more, 50 nm or more, 75 nm or more, 90 nm or more, 100 nm or more, or 120 nm or more, and may be 500 nm or less, 300 nm or less, 225 nm or less, 225 nm or less, 187.5 nm or less, or 150 nm or less. When the primary particle size of the particles is less than the above range, the particle surface area excessively increases, so that the reaction with the electrolyte is rapidly activated, and as a result, the frequency of side reactions increases, which may cause electrode deterioration and reduced lifespan. On the other hand, if the above range is exceeded, the diffusion distance of metal ions into the particle becomes longer and the reaction area decreases, which may cause problems such as reduced charge / discharge efficiency or deteriorated output characteristics.

[0185] In one embodiment of the present invention, the composite cathode material may be obtained by mixing a vanadium oxide source and a layered MXene sheet source in a weight ratio of 1 to 10:1. If the weight ratio of the vanadium oxide particles to the layered MXene sheets is less than the above-described range, the amount of active sites that exhibit capacity may be small, making it difficult to secure high capacity. If it exceeds the above-described range, the overall performance may be degraded due to particle agglomeration and active site blocking caused by excessive dispersion.

[0186] In one embodiment of the present invention, VO2, V2C, Al are analyzed by X-ray diffraction. 45 At least two peaks selected from the group consisting of V7, and V2AlC may be detected. Accordingly, at least two peaks corresponding to these phases are detected during X-ray diffraction analysis, which means that vanadium-based oxides and metal carbides (or related phases) coexist inside or on the surface of the MXene sheet. These phases can contribute to the material according to the present invention exhibiting excellent performance and durability by comprehensively improving electrochemical reactivity, electron transfer characteristics, mechanical stability, etc. Preferably, VO2, V2C, Al 45 Peaks of V7 and V2AlC can be detected, Al 45 In the case of V7peak, it can be interpreted as some impurities, so it can be detected in very small amounts, and VO2, V2C, and V2AlC can be detected in large quantities as the main phases.

[0187]

[0188] The third aspect of this foundation is,

[0189] A method for producing a composite cathode material for a zinc secondary battery is provided, comprising: a step of ultrasonically dispersing a first mixture containing a layered maxine sheet source exfoliated from the first mixture into an organic solvent; a step of adding a vanadium oxide source to the first mixture to produce a second mixture; and a step of solvothermally synthesizing the second mixture.

[0190]

[0191] Detailed descriptions of overlapping parts with the first and second aspects of the present application have been omitted, but the contents described with respect to the first and second aspects of the present application may be equally applied even if the description is omitted with respect to the third aspect.

[0192]

[0193] Hereinafter, a method for manufacturing a composite cathode material for a zinc secondary battery according to the third aspect of the present disclosure will be described in detail. This may relate to a method for manufacturing a composite cathode material for a zinc secondary battery according to the first aspect of the present disclosure.

[0194]

[0195] First, in one embodiment of the present invention, a step of ultrasonically dispersing a first mixture containing a delaminated layered MXene sheet source in an organic solvent may be included. This step utilizes ultrasonic energy to effectively separate the cohesive forces between the MXene sheet sources and disperse them into a single layer or a few layers, thereby maximizing the total active area. This step can be viewed as a step that provides an important technical effect of improving reactivity and processing efficiency in subsequent processes.

[0196] In one embodiment of the present invention, a solvent is used as a medium that suppresses aggregation between sheets and effectively disperses them into a single layer or a few layers during the ultrasonic dispersion process of the exfoliated layered MXene sheet source. Various types of solvents can be applied, such as solvents containing water, organic solvents, and inorganic solvents. For example, organic solvents such as water, ethanol, methanol, isopropanol, acetone, acetonitrile, THF, dichloromethane, DMF, and DMSO can be used, and inorganic solvents that can be mixed with water, such as hydrochloric acid, sulfuric acid, and nitric acid, can also be applied. In this step, an organic solvent can preferably be used as a medium, and for example, various organic solvents can be used, including alcohols such as ethanol, methanol, and isopropanol, acetone, acetonitrile, dichloromethane, DMF (dimethylformamide), DMSO (dimethylsulfoxide), THF (tetrahydrofuran), and toluene.

[0197] Next, in one embodiment of the present invention, a step of preparing a second mixture by adding a vanadium oxide source to the first mixture may be included. By adding the vanadium oxide source to the first mixture, uniform interfacial contact between the dispersed layered MXene sheet source and the vanadium oxide source can be promoted, and the synergistic effect resulting from their interaction can be maximized, thereby enhancing electrochemical activity and electrochemical reactivity.

[0198] In one embodiment of the present invention, the vanadium oxide source may be V2O5. Commercial V₂O5 is readily available, which can facilitate process simplification and cost efficiency, and can provide the advantage of securing excellent electrochemical activity and performance due to the oxidation state and electronic structure unique to V₂O5.

[0199] Next, in one embodiment of the present invention, a step of solvothermal synthesis of the second mixture may be included. This step may be a key process for optimizing the interfacial bonding and crystal structure between the vanadium oxide source and the layered MXene sheet source present in the second mixture. Through the solvothermal synthesis process, the materials are uniformly crystallized under relatively low temperature and pressure conditions, thereby stabilizing the microstructure and oxidation state of each component, and enhancing electrochemical activity and performance.

[0200] In one embodiment of the present invention, the temperature of the solvothermal synthesis of the second mixture may be 60° C. or higher, 80° C. or higher, 85° C. or higher, 90° C. or higher, 100° C. or higher, or 120° C. or higher, 450° C. or lower, 360° C. or lower, 270° C. or lower, 270° C. or lower, 250° C. or lower, 225° C. or lower, or 180° C. or lower. If it is less than the above range, the thermal energy required for the reaction may be insufficient, so that sufficient crystallization may not occur or the interfacial bond may not be properly formed, thereby deteriorating the electrochemical performance. If it is more than the above range, structural deterioration may be accelerated by excessive heat or unnecessary oxidation / reduction reactions may occur, thereby deteriorating the material properties.

[0201] In one embodiment of the present invention, the time for performing the solvothermal synthesis of the second mixture may be 1 hour or more, 1.8 hours or more, 3 hours or more, 4.5 hours or more, 5.4 hours or more, 6 hours or more, or 7.2 hours or more, 100 hours or less, 72 hours or less, 48 ​​hours or less, 45 hours or less, 36 hours or less, 27 hours or less, 27 hours or less, 22.5 hours or less, or 18 hours or less. If it is less than the above range, the reaction and crystallization may not occur sufficiently, which may deteriorate the electrochemical performance, and if it is more than the above range, the excessive reaction may cause structural deformation or unnecessary bond formation, which may deteriorate the physical properties.

[0202] In one embodiment of the present invention, the step of solvothermally synthesizing the second mixture; a step of cooling the solvothermally synthesized reaction solution thereafter; a step of washing or removing impurities and residual precursors using, for example, water or an alcohol such as ethanol; and a step of drying to obtain a product in powder form may be further included.

[0203] In one embodiment of the present invention, the temperature for drying the final composite may be set to about 15°C to 180°C, about 30°C to 120°C, specifically 40°C to 100°C, or 60°C to 80°C. If the drying temperature is below the above range, sufficient solvent removal may not occur, which may result in deterioration of the final physical properties, and if it exceeds the above range, there is a concern that thermal deformation or compositional change of the material may occur, which may result in deterioration of electrochemical performance.

[0204] In one embodiment of the present invention, the drying time may be set to be approximately 1 hour to 48 hours, specifically 3 hours to 24 hours, or 6 hours to 12 hours. If the drying time is less than the above range, residual solvent or byproducts may not be sufficiently removed, which may increase defects in the material. If the drying time exceeds the above range, the process efficiency may be reduced and the material may be excessively dried, potentially resulting in structural damage. Preferably, the drying may be performed by vacuum drying.

[0205]

[0206] The fourth aspect of this foundation is,

[0207] A method for producing a composite cathode material for a zinc secondary battery is provided, comprising: a step of ultrasonically dispersing a first mixture containing a layered MXene sheet source in a first solvent; a step of producing a second mixture by introducing a vanadium oxide source in a dicarboxylic acid aqueous solution; a step of mixing the first mixture and the second mixture to obtain a material in which a vanadyl dicarboxylate is complexed with a layered MXene sheet; and a step of solvothermal synthesis by introducing the material in which the vanadyl dicarboxylate is complexed with a layered MXene sheet into a second solvent.

[0208]

[0209] Detailed descriptions of parts overlapping with the first to third aspects of the present application have been omitted, but the contents described for the first to third aspects of the present application may be equally applied even if the description is omitted in the fourth aspect.

[0210]

[0211] Hereinafter, a method for manufacturing a composite cathode material for a zinc secondary battery according to the fourth aspect of the present disclosure will be described in detail. This may relate to a method for manufacturing a composite cathode material for a zinc secondary battery according to the second aspect of the present disclosure.

[0212]

[0213] First, in one embodiment of the present invention, a step of ultrasonically dispersing a first mixture in which an exfoliated layered MXene sheet source is introduced into a first solvent may be included. This step effectively disperses agglomeration between the MXene sheet sources, thereby uniformly dispersing them in a single layer or a few layers, thereby maximizing the surface area and reaction-active sites of the MXene. This allows for securing high electrochemical performance and reproducible physical properties in subsequent synthesis and reaction processes. In other words, this step can be viewed as a step for manufacturing a structure in which a single layer or at least a portion of the layered MXene sheet source is exfoliated to form a multilayer in an accordion shape, and a vanadium oxide, which will be described later, can be inserted between the layers.

[0214] In one embodiment of the present invention, the first solvent may be any of the above-described solvents, but deionized water may preferably be used.

[0215] Next, in one embodiment of the present invention, a step of preparing a second mixture by adding a vanadium oxide source to a dicarboxylic acid aqueous solution may be included. This step may be such that the dicarboxylic acid aqueous solution forms a dicarboxylate salt of the vanadium oxide source, uniformly forms a VO2 phase in a subsequent solvothermal synthesis step, and lays the foundation for optimizing the properties of the composite material, such as strengthening interfacial bonding.

[0216] In one embodiment of the present invention, the vanadium oxide source may be V2O5, and since this overlaps with the above-described advantages, a description thereof will be omitted.

[0217] In one embodiment of the present invention, the dicarboxylic acid may include various types of dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, and fumaric acid. These dicarboxylic acids promote surface activation and uniform dispersion of vanadium oxide particles according to their respective acidity and molecular structures, and may contribute to improving the electrochemical performance and structural stability of the final composite by strengthening the interfacial bonding in the subsequent solvothermal synthesis step. Preferably, the dicarboxylic acid may be oxalic acid. The oxalic acid is an organic acid that is easily soluble in water and is economical, and may promote surface activation of vanadium oxide particles, thereby contributing to uniform dispersion and stabilization of the particles. Additionally, the acidic condition of oxalic acid can promote the interfacial reaction between vanadium oxide and layered MXene sheets, thereby promoting the formation of a more robust bond in the subsequent solvothermal synthesis step and providing the effect of improving the electrochemical performance and structural stability of the final composite.

[0218] Next, in one embodiment of the present invention, a step of mixing the first mixture and the second mixture to obtain a material in which the vanadyl dicarboxylate is complexed with the layered MXene sheet may be included. This step is a process in which the vanadyl dicarboxylate is uniformly complexed with the layered MXene sheet by mixing the first mixture and the second mixture, thereby maximizing the interfacial interaction between the layered MXene sheet and the derived vanadyl dicarboxylate, thereby improving electron transfer efficiency and electrochemical activity and electrochemical performance.

[0219] In one embodiment of the present invention, the step of mixing the first mixture and the second mixture may be performed by stirring for 1 to 10 hours.

[0220] In one embodiment of the present invention, after the step of mixing the first mixture and the second mixture, a step of drying at a temperature of 50 to 150°C for 2 to 72 hours to obtain a material in which vanadyl dicarboxylate is complexed with the layered maxine sheet in a powder form may be additionally included.

[0221] Next, in one embodiment of the present invention, a step of solvothermal synthesis may be included by introducing a material in which the vanadyl dicarboxylate is complexed into a layered MXene sheet into a second solvent. This step may be a process for uniformly synthesizing the vanadyl dicarboxylate into VO2, further strengthening the interfacial bonding and crystal structure within the complex, and forming a uniform microstructure. Through this, the interaction between the layered MXene sheet and vanadium oxide can be optimized, thereby improving electrochemical performance and structural stability.

[0222] In one embodiment of the present invention, the second solvent may freely utilize the above-described solvent, preferably an aqueous mixed solvent or co-solvent, and more preferably, a mixture of alcohol such as methanol and deionized water may be used.

[0223] In one embodiment of the present invention, the vanadium oxide may have a tunnel structure. This is because the oxidation state is uniformly formed into a VO₂ structure. Since VO₂ has a tunnel structure, electron and ion transfer paths are clearly defined, so that high conductivity and electrochemical reactivity can be exhibited. For example, since VO₂ has a tunnel structure, ion transfer can be more efficient than V2O5, which has a narrow interlayer distance and thus has difficulty in ion insertion. Therefore, the VO₂ tunnel-type vanadium oxide adopted in the present embodiment can exhibit superior performance compared to other oxides based on the consistency and stability of the crystal structure due to the uniform oxidation state.

[0224] In one embodiment of the present invention, the step of performing solvothermal synthesis by introducing a material in which the vanadyl dicarboxylate is complexed into a layered maxene sheet into a second solvent; may be performed at a temperature of 45°C or higher, 60°C or higher, 75°C or higher, 112.5°C or higher, 135°C or higher, 150°C or higher, or 180°C or higher, and may be 625°C or lower, 500°C or lower, 375°C or lower, 375°C or lower, 312.5°C or lower, or 250°C or lower. If it is below the above range, the thermal energy required for the reaction is insufficient, resulting in insufficient crystallization into VO2, which may result in a deterioration in electrochemical performance. If it is above the above range, structural deterioration due to excessive temperature or unnecessary oxidation / reduction reactions may occur, which may result in a deterioration in material properties.

[0225] In one embodiment of the present invention, the time for performing the step of solvothermal synthesis by introducing the material in which the vanadyl dicarboxylate is complexed into the layered maxene sheet into a second solvent may be 1 hour or more, 1.5 hours or more, 2.25 hours or more, 2.7 hours or more, 3 hours or more, or 3.6 hours or more, and may be 100 hours or less, 72 hours or less, 48 ​​hours or less, 24 hours or less, 22.5 hours or less, 18 hours or less, 13.5 hours or less, 13.5 hours or less, 11.25 hours or less, or 9 hours or less. If it is below the above range, the reaction time may be insufficient, resulting in insufficient crystallization into VO2, which may result in a deterioration in electrochemical performance. If it is above the above range, structural deterioration due to excessive reaction or unnecessary oxidation / reduction reactions may occur, which may result in a deterioration in material properties.

[0226] In one embodiment of the present invention, the method may further include a step of cooling the solvent-thermally synthesized reaction solution after the solvent-thermal synthesis, a step of washing or removing impurities and residual precursors using, for example, water or an alcohol such as ethanol, and a step of drying to obtain a powdered product. Since the conditions for each step have been described above, a description thereof will be omitted.

[0227]

[0228] The fifth aspect of this foundation is,

[0229] A zinc secondary battery is provided, comprising: a positive electrode including the composite positive electrode material; a negative electrode; and an electrolyte.

[0230]

[0231] Detailed descriptions of overlapping parts with aspects 1 to 4 of the present application have been omitted, but the contents described with respect to aspects 1 to 4 of the present application may be equally applied even if the description is omitted with respect to aspect 5.

[0232]

[0233] Hereinafter, a zinc secondary battery according to the fifth aspect of the present invention will be described in detail.

[0234]

[0235] In one embodiment of the present invention, the positive electrode may include the composite positive electrode material, a conductive material, and a binder as a positive electrode active material. To enhance electron transport within the positive electrode, a carbon-based conductive material (e.g., carbon black, acetylene black, etc.) may be mixed in an appropriate ratio. The positive electrode active material may be implemented in various forms, such as powder, thin film, or nanostructured, and the selection of such forms varies depending on the device characteristics and manufacturing process.

[0236] In one embodiment of the present invention, the cathode mainly uses zinc (Zn) metal or a zinc alloy, and when discharging, Zn → Zn 2+ + 2e -It is believed that an oxidation reaction occurs and a reduction reaction proceeds in the reverse direction during charging. In the zinc anode, there is a possibility that dendrites (metal dendritic structures) may form or a hydrogen evolution reaction may occur during the charge / discharge cycle, so various electrolyte compositions or anode surface treatments can be applied to suppress this. For example, there is a method of suppressing dendrite formation by doping a small amount of aluminum (Al), indium (In), magnesium (Mg), etc. into the anode metal, or applying a protective coating (e.g. nickel plating, carbon coating) to the anode surface to reduce corrosion and side reactions. In addition, current density control or three-dimensionalization of the anode structure (porous structure, etc.) is being studied to uniformly induce zinc peeling and plating, and through these, it is possible to increase the cycle life and efficiency.

[0237] In one embodiment of the present invention, the separator refers to a material selected to physically block contact between the anode and cathode, while allowing ions to move freely. Representative examples include porous membranes made of polyolefins, such as polypropylene (PP) and polyethylene (PE), while cellulose-based paper or glass fiber membranes are also considered. The separator must maintain chemical stability when in contact with the electrolyte, and at the same time, must have uniform pores so as not to impede ion conductivity. Additionally, in some embodiments, an inorganic particle coating (e.g., alumina, zirconia, etc.) is introduced to enhance heat and chemical resistance.

[0238] In one embodiment of the present invention, the electrolyte provides an ion movement path of a zinc secondary battery and can be mainly classified into an aqueous or non-aqueous type. The aqueous electrolyte includes potassium hydroxide (KOH), zinc sulfate (ZnSO₄) solution, and Zn(OTf)2. aqueous solution, Salts such as acetate or phosphate are also used by mixing them at an appropriate concentration. In the case of non-aqueous electrolytes, a form that mixes organic solvents (e.g., carbonate series) and zinc salts (e.g., Zn(CF₃SO₃)₂, etc.) is possible, but generally, aqueous electrolytes are widely used in terms of safety and ease of manufacturing. In addition, technologies using gel-type electrolytes (e.g., polyvinyl alcohol (PVA)-based gels) or solid electrolytes (e.g., ceramic materials) have also been studied recently, and can be applied differently depending on the mounting environment or special purpose.

[0239] In one embodiment of the present invention, the current collector serves to support the positive and negative electrode materials so that current can be uniformly exchanged. In a zinc secondary battery, materials such as titanium (Ti), nickel (Ni), and stainless steel (including special alloys) that have good corrosion resistance and electrical conductivity can be considered as positive electrode collectors. Carbon-based materials (carbon cloth, carbon paper, carbon nanotubes, etc.) can also be utilized. The positive electrode collectors described above can be used on the negative electrode side, and preferably, a zinc plate or a zinc-plated metal foil can be directly utilized, and copper (Cu)-based materials can also be used as an additional support. Since the current collector must not cause corrosion or oxidation problems even during long-term charge and discharge, a metal surface treatment or protective coating (e.g., nickel plating, carbon coating) is sometimes applied.

[0240] In one embodiment of the present invention, a conductive agent is an additive used to improve electrical connection within the electrode. Commonly used materials include carbon black, acetylene black, graphite powder, carbon nanotubes (CNTs), and graphene. These materials have high electron conductivity, which helps the electrode active materials receive electrons evenly, while also maintaining a certain degree of mechanical flexibility in the electrode. Furthermore, since the resistance value within the electrode varies significantly depending on the concentration and dispersion method of the conductive agent, it is important to apply an appropriate composition and pretreatment process to ensure uniform dispersion.

[0241] In one embodiment of the present invention, the binder binds the electrode active material and the conductive material to maintain the electrode structure and mitigate volume changes that may occur during charge and discharge. Representative binders include PVDF (Polyvinylidene fluoride), PTFE (Polytetrafluoroethylene), CMC (Carboxymethyl cellulose), and SBR (Styrene-butadiene rubber). Since the binder affects chemical stability with the electrolyte, adhesion, and pore control within the electrode, the type and mixing ratio are set differently depending on the required cell performance. In addition, when manufacturing through an aqueous process, aqueous binders such as CMC or SBR may be advantageous, while PVDF series are widely used in organic solvent-based processes.

[0242] In one embodiment of the present invention, a zinc secondary battery manufactured by appropriately combining these components can be applied to various energy storage devices due to its low toxicity and high safety. For example, it is widely considered for large-scale energy storage systems (ESS), portable electronic devices, and military power sources. Furthermore, zinc's relative abundance and competitive price suggest its market potential as an alternative secondary battery technology. In the future, nanostructuring technology and surface treatment processes are expected to receive increased attention for research to improve energy density, cycle life, and output characteristics.

[0243]

[0244] 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.

[0245] The scope of the present invention is indicated by the claims set forth 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.

[0246] According to an embodiment of the present invention, by complexing a vanadium-based MXene (V-MXene) and vanadium oxide, the problems of low electrical conductivity and structural instability of existing vanadium-based oxide cathode materials can be effectively solved, and by introducing a vanadium-based MXene with excellent electrical conductivity, the charge transfer resistance within the electrode can be reduced, and the electrochemical reaction during the charge and discharge process can be smoothly performed, thereby suppressing the elution of vanadium ions. In addition, by uniformly forming nano-sized vanadium oxide through a specific synthesis process, the oxidation-reduction reactivity on the surface can be improved, and repeated Zn 2+ By preventing structural collapse due to insertion / de-insertion, long-term stability can be ensured. Furthermore, according to one embodiment of the present invention, a tunnel-structured cathode material that does not require an initial activation process can be applied to achieve high initial capacity while maintaining long-life characteristics. This overcomes the charge / discharge endurance limitations of existing V₂O5-based cathode materials and provides a practical cathode material for ZIB with high energy storage performance and long lifespan, indicating industrial applicability.

Claims

1. Layered MXene sheet; and Formed between layers or on the surface of the above layered maxine sheet, V x O y Vanadium oxide particles represented by ; Including, A composite cathode material for a zinc secondary battery, characterized in that the primary particle size of the vanadium oxide particles is less than 5 to 100 nm. (where x is 1 to 6 and y is 2 to 13) 2. In paragraph 1, A composite cathode material for a zinc secondary battery, characterized in that it is obtained by mixing the vanadium oxide source and the layered maxine sheet source in a weight ratio of 0.75 to 3:

1.

3. In paragraph 1, A composite cathode material for a zinc secondary battery, characterized in that the atomic % content of fluorine measured by energy dispersive X-ray spectroscopy (EDS) is less than 10 atomic %.

4. In paragraph 1, The above vanadium oxides are V2O5, VO2, V6O 13 A composite cathode material for a zinc secondary battery, characterized in that it is at least one selected from those composed of , and V2O3.

5. Layered MXene sheets; and Vanadium oxide particles formed between layers or on the surface of the above layered maxine sheet and containing VO2; Including, A composite cathode material for a zinc secondary battery, characterized in that the primary particle size of the vanadium oxide particles is 100 to 300 nm.

6. In paragraph 5, A composite cathode material for a zinc secondary battery, characterized in that it is obtained by mixing the vanadium oxide source and the layered maxine sheet source in a weight ratio of 1 to 10:

1.

7. In paragraph 5, VO2, V2C, Al by X-ray diffraction analysis 45 A composite cathode material for a zinc secondary battery, characterized in that at least two peaks selected from the group consisting of V7 and V2AlC are detected.

8. In paragraph 1 or paragraph 5, A composite cathode material for a zinc secondary battery, characterized in that the above layered maxine sheet is a vanadium-based maxine sheet.

9. A step of ultrasonically dispersing the first mixture containing the exfoliated layered maxine sheet source in an organic solvent; A step of preparing a second mixture by adding a vanadium oxide particle source to the first mixture; and A step of solvothermal synthesis of the second mixture; A method for manufacturing a composite cathode material for a zinc secondary battery, comprising:

10. In paragraph 9, A method for manufacturing a composite cathode material for a zinc secondary battery, characterized in that the vanadium oxide is V2O5.

11. In paragraph 9, A method for producing a composite cathode material for a zinc secondary battery, characterized in that the step of solvothermal synthesis of the second mixture is performed at 60 to 250°C for 1 to 100 hours.

12. A step of ultrasonically dispersing a first mixture containing a peeled layered maxine sheet source in a first solvent; A step of preparing a second mixture by adding a vanadium oxide source to a dicarboxylic acid aqueous solution; A step of mixing the first mixture and the second mixture to obtain a material in which vanadyl dicarboxylate is complexed into a layered maxine sheet; A step of solvent-thermal synthesis by introducing a material in which the above vanadyl dicarboxylate is complexed into a layered maxene sheet into a second solvent; A method for manufacturing a composite cathode material for a zinc secondary battery, comprising:

13. In paragraph 12, The above vanadium oxide particles are V2O5, The above dicarboxylic acid is characterized in that it is oxalic acid, for use in zinc secondary batteries. Method for manufacturing composite cathode material.

14. In paragraph 12, A method for manufacturing a composite cathode material for a zinc secondary battery, characterized in that the step of introducing a material in which the above vanadyl dicarboxylate is complexed into a layered maxine sheet into a second solvent and performing solvent thermal synthesis is performed at 60 to 250°C for 1 to 100 hours.

15. A cathode comprising the composite cathode material of paragraph 1 or paragraph 5; cathode; and electrolyte; A zinc secondary battery comprising:

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