Vanadium-based composite positive electrode material and preparation and application thereof

Abstract

The application discloses a vanadium-based composite positive electrode material and a preparation and application thereof. The vanadium-based composite positive electrode material comprises microspheres of a micron level which are aggregated by nanoscale primary particles, the primary particles are composed of a Na and Zr doped V2O5 material and a MXene material which is composited on the material, and a heterojunction is formed between the Na and Zr doped V2O5 material and the MXene material. The preparation method comprises the following steps: dissolving a vanadium source, a sodium source, a zirconium source, a surfactant and a complexing agent in a first solvent to obtain a first solution, performing a hydrothermal reaction on the first solution, filtering a reaction product to obtain a precipitate, mixing the precipitate with a MXene material through ball milling to obtain an intermediate substance, dispersing the intermediate substance in water or an alcohol solvent, and performing spray drying to obtain a precursor powder, and calcining the precursor powder to obtain the composite positive electrode material. When the material is applied to a positive electrode, the specific capacity of a water-based zinc ion battery and the cycle stability in a charging and discharging process can be effectively improved.

Description

Technical Field

[0001] This invention relates to a battery cathode material, its preparation and application, and more particularly to a vanadium-based composite cathode material, its preparation and application in the preparation of cathodes for aqueous zinc-ion batteries. Background Technology

[0002] Rechargeable aqueous zinc-ion batteries (AZIBs), as a type of multivalent ion battery, are valued for their safety (compatibility of zinc with non-flammable aqueous electrolytes), low manufacturing cost, and high theoretical capacity of the zinc anode (819 mAh g⁻¹). - ¹) and its relatively low redox potential (-0.76 V relative to the standard hydrogen electrode) have led to its being considered a promising advanced energy storage technology. However, one of the main obstacles to the practical application of AZIBs is the lack of suitable cathode materials to match the high capacity and structural stability of zinc ion storage.

[0003] Various cathode materials have been explored to improve the performance of zinc-ion battery cathodes, such as manganese-based compounds, vanadium-based compounds, and Prussian blue analogues (PBAs). Manganese-based cathodes have high capacity but poor rate performance and cycle performance; PBAs have high voltage but poor capacity, even less than 100 mAh·g. -1 These drawbacks significantly limit their further application in next-generation ZIBs. Vanadium-based materials, on the other hand, possess multiple valence states and different crystal structures, typically exhibiting high theoretical specific capacity and significant cycling stability. In particular, V₂O₅ with its layered structure, due to its open framework, can accommodate large amounts of Zn. 2+ It can be used for storage and can provide high energy density and specific capacity. However, vanadium oxide cathodes have been reported for storing Zn. 2+ The battery's performance is greatly limited by its inherent electrochemical properties. For example, the solubility of vanadium in acidic / neutral electrolytes leads to electrode structure degradation, electrolyte contamination, and zinc anode corrosion. Furthermore, the low intrinsic conductivity and strong electrostatic repulsion of the layered vanadium oxide structure typically contribute to degraded battery performance.

[0004] MXene materials are two-dimensional layered materials composed of transition metal carbides, nitrides, or carbonitrides. MXenes possess high metalloid conductivity, and their layered structure endows them with high strength and flexibility. The rich surface chemistry of MXenes makes them easy to chemically modify, allowing for optimization of material performance through surface property control. The two-dimensional layered structure of MXenes provides a large specific surface area, which is beneficial for improving the redox reaction efficiency of electrode materials. These numerous advantages enable their introduction into electrode materials not only to prevent direct contact between the cathode material and the electrolyte but also to suppress side reactions.

[0005] Currently, studies have reported that doping battery cathode materials with metal elements such as Na can improve the electrical performance of composite materials. However, in the field of aqueous zinc-ion batteries, there are no reports on using metal doping technology and MXene materials to improve the electrochemical performance of vanadium oxide cathode materials. Summary of the Invention

[0006] Purpose of the Invention: The purpose of this invention is to provide a vanadium-based composite cathode material that solves the problems of structural collapse caused by vanadium dissolution during charge and discharge, low electrical conductivity of the material itself, and poor Zn content in existing vanadium-based cathode materials. 2+ The issue of diffusion rate. A second objective of this invention is to propose a method for preparing vanadium-based composite cathode materials, solving the problem of how to prepare vanadium-based composite cathode materials. A third objective of this invention is to propose the application of vanadium-based composite cathode materials in the preparation of cathodes for aqueous zinc-ion batteries, solving the problem of how to prepare cathode sheets for aqueous zinc-ion batteries.

[0007] Technical solution: The vanadium-based composite cathode material of the present invention includes micron-sized microspheres formed by the aggregation of nano-sized primary particles. The primary particles are composed of Na and Zr-doped V2O5 material and MXene material composited on the primary particles. A heterogeneous interface is formed between the Na and Zr-doped V2O5 material and the MXene material.

[0008] This invention introduces a small amount of Na between the V2O5 layers. + It acts as a "column" support to stabilize the structure and increase the interlayer spacing, thus alleviating the Zn... 2+ Embedded / de-embedded structural stresses.

[0009] Meanwhile, the Zr doped in this invention 4+ Partially replaces V 5+ By stabilizing the crystal framework with high-valence ions, the Zn content is reduced. 2+ Electrostatic repulsion with the V₂O₅ lattice suppresses phase transitions during charge-discharge processes, improving reversibility. Furthermore, Zr... 4+ The formed Zr-O bonds have high energy, which is beneficial for enhancing the overall mechanical strength of the material.

[0010] This invention addresses the structural collapse problem of traditional V2O5 materials during charge and discharge by employing Na and Zr co-doping and modification with composite conductive materials (MXene), aiming to improve material structural stability, increase conductivity, and optimize electrochemical performance.

[0011] Preferably, the Na and Zr-doped V₂O₅ material is Na x Zr yV₂O₅, wherein 0.1 ≤ x + y ≤ 0.7; the size of the primary particles is 5-15 nm; the size of the microspheres is 2-25 μm; the MXene material comprises Ti₃C₂T x Nb2CT x Mo2CT x At least one of them.

[0012] The second aspect of this invention discloses a method for preparing the above-mentioned vanadium-based composite cathode material, comprising the following steps: (1) Dissolve vanadium source, sodium source, zirconium source, surfactant and complexing agent in a first solvent to obtain a first solution, subject the first solution to a hydrothermal reaction, and filter the reaction product to obtain a precipitate; (2) The precipitate was ball-milled and mixed with MXene material to obtain an intermediate substance; (3) Disperse the intermediate substance in water or alcohol solvent and spray dry to obtain precursor powder; (4) The precursor powder is calcined to obtain a composite cathode material.

[0013] Preferably, in step (1), the vanadium source includes at least one of vanadium pentoxide, ammonium metavanadate, and vanadium chloride; the sodium source includes at least one of sodium oxalate, sodium nitrate, sodium sulfate, and sodium phosphate; and the zirconium source includes at least one of zirconium oxychloride, zirconium nitrate, zirconium sulfate, and zirconium acetylacetonate.

[0014] Preferably, in step (1), the surfactant includes at least one of polyethylene glycol, polyvinylpyrrolidone, sodium dodecyl sulfate, and hexadecyltrimethylammonium chloride; the complexing agent includes at least one of oxalic acid, tartaric acid, and EDTA; and the first solvent includes at least one of water, ethanol, and ethylene glycol.

[0015] In some embodiments, polyethylene glycol is PEG. 200 -PEG 20000 The first solvent is water, or a 0.5-35.0% aqueous solution of ethanol, or a 0.5-35.0% aqueous solution of ethylene glycol.

[0016] Preferably, in step (1), the mass ratio of the vanadium source, sodium source, zirconium source, surfactant, and complexing agent is 1.5-2.5: 0.09-0.36: 0.2-0.6: 0.05-0.2: 1.0-1.5; The concentration of the vanadium source in the first solution is 0.01-5.0 mol / L; the hydrothermal reaction conditions are 100-250℃ for 6-24 h. This invention utilizes a microwave hydrothermal synthesis method in precursor preparation, rapidly raising the reaction temperature to ensure uniform heating of all components in the reaction system, reducing the temperature gradient, and facilitating the preparation of nanomaterials with uniform particle size. It achieves efficient nanoscale synthesis of intermediate substances under low-temperature conditions and improves the purity of intermediate substances and the uniformity of the composite material.

[0017] Preferably, in step (2), the method for ball milling and mixing the precipitate with the MXene material is as follows: The precipitate was mixed with an alcohol solution of MXene material, and after mixing, a second solution was obtained. The second solution was ball-milled, and the ball-milled product was dried to obtain an intermediate substance.

[0018] This invention uses wet ball milling to mix precipitates with MXene solution. The process is simple and efficient, and does not require complex high-temperature and high-pressure equipment (such as hydrothermal reactors). The raw materials can be mixed, refined and reacted directly by mechanical force, which reduces equipment costs and operation difficulty. In addition, the solvents (such as ethanol) used in wet ball milling are easy to recover, reducing waste liquid pollution.

[0019] Furthermore, the mass ratio of the MXene material to the precipitate is in the range of 5-25:75-95; The ball milling method is as follows: add the grinding balls to the second solution at a mass ratio of 1:10-30 and grind at 300-600 rpm for 2-12 hours.

[0020] Preferably, in step (3), the conditions for spray drying are: feed rate of 1-20 L / h, inlet temperature of 200-300℃, and outlet temperature of 80-140℃; In step (4), the precursor powder is calcined by heating it to 300-800 ℃ at a rate of 1-3℃ / min under an inert atmosphere, holding it at that temperature for 3-5 hours, and then naturally cooling it to room temperature.

[0021] This invention utilizes spray drying to effectively prepare intermediate substances with good dispersibility and uniform size. Finally, after high-temperature calcination, a material with uniform composite structure, stable structure, and regular morphology is obtained.

[0022] The third aspect of this invention discloses the application of the above-mentioned vanadium-based composite cathode material in the preparation of cathodes for aqueous zinc-ion batteries.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The preparation method provided by this invention maintains uniform dispersion of the material throughout the intermediate preparation process, enabling effective Na doping of V₂O₅. + Zr 4+Furthermore, it exhibits uniform composite formation and good crystallization with MXene. Co-doping with Na and Zr can promote the formation of layered Na structures. x Zr y When V₂O₅ is used as a cathode material in aqueous zinc-ion batteries, it maintains a good structure during charge and discharge, and exhibits almost no structural collapse due to vanadium dissolution during cycling. Unlike traditional single-element doping, the co-doping of Na and Zr has a dual effect on phase composition and electrochemical performance: the Na dopant acts as a "pillar ion" embedded in the V₂O₅ interlayer, widening the interlayer spacing and mitigating the effects of Zn doping. 2+ Structural stresses for insertion / extraction; Zr doping can modulate the electronic structure of V₂O₅, creating oxygen defects, thereby lowering the diffusion barrier and facilitating Zn absorption. 2+ The embedding of Zr provides more active sites, promoting ion transfer rates and electron transport kinetics. 4+ Partially replaces V 5+ By stabilizing the crystal framework with high-valence ions, the Zn content is reduced. 2+ The electrostatic repulsion with the V₂O₅ lattice suppresses phase transitions during charging and discharging, improving reversibility. Furthermore, the high energy of the formed Zr-O bonds enhances the overall mechanical strength of the material.

[0024] Furthermore, to address the structural collapse of V2O5 doped materials caused by volume changes due to zinc ion insertion and extraction, appropriate amounts of composite MXene materials alleviated the volume changes in V2O5 doped materials and helped maintain the crystal structure stability of V2O5 doped materials during repeated zinc ion insertion and extraction. + Zr 4+ The MXene layer on the surface of doped V₂O₅ materials can maintain structural integrity and inhibit vanadium (V) dissolution, and Na + Zr 4+ The heterogeneous interface between the doped V₂O₅ and MXene materials improved the electrochemical kinetics of the doped host material, reduced the electrostatic repulsion between the host layers, and promoted the interfacial Zn exchange. 2+ Diffusion. This invention successfully enables aqueous zinc-ion batteries to possess high specific capacity and better cycle stability during charge and discharge processes through the aforementioned modification strategy. Attached Figure Description

[0025] Figure 1 Na prepared in Example 1 at different magnifications x Zr y SEM image of V2O5 / MXene composite material; Figure 2 Rate cycling performance of water-washed zinc-ion batteries made with different composite cathode materials at different current densities; Figure 3Cyclic stability diagram of water-washed zinc-ion batteries made with different composite cathode materials. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0027] Example 1: A method for preparing a vanadium-based composite cathode material is as follows: (1) Accurately weigh 1.81 g vanadium pentoxide, 0.169 g sodium nitrate, 0.337 g zirconium nitrate, 0.09 g polyethylene glycol 2000, and 1.45 g oxalic acid, and add them sequentially to 50 mL of 20% (V / V) ethylene glycol aqueous solution. Stir magnetically at 600 rpm for 2 h to fully dissolve the solutes and obtain a homogeneous first solution. Transfer the first solution to a reaction vessel and place it in a microwave hydrothermal synthesizer at 180℃ for continuous reaction for 8 h. After the reaction is complete, centrifuge the reaction product to collect the precipitate. Wash the precipitate alternately with deionized water and ethanol by centrifugation to obtain the intermediate substance.

[0028] (2) The above intermediate substance was reacted with Ti3C2T at a concentration of 5 mg / mL. x Mixing of MXene anhydrous ethanol dispersion requires Ti3C2T x The mass ratio of MXene material to intermediate was 10:90. The mixed solution was transferred to a 100 mL planetary ball mill with a material-to-ball ratio of 1:25. Anhydrous ethanol was used as the milling medium, and the mixture was continuously milled at 400 rpm for 3 h. The milled product was then dried under vacuum to remove the milling medium, yielding the intermediate material.

[0029] (3) Transfer the above intermediate product to a beaker and add an appropriate amount of deionized water. Stir magnetically at 600 rpm for 40 min. After stirring, spray dry the resulting solution. The inlet temperature of the spray dryer is 220 ℃, the outlet temperature is 90 ℃, and the feed rate is 1.5 L / h to obtain the precursor powder.

[0030] (4) The precursor powder was placed in a crucible and then placed in a tube furnace. The temperature was increased to 400°C at a rate of 2°C / min in an argon atmosphere. The mixture was then calcined at 400°C for 2 h. After naturally cooling to room temperature, Na was obtained. 0.2 Zr 0.1 V2O5 / MXene composite material.

[0031] The obtained Na 0.2 Zr 0.1 The V2O5 / MXene composite material was analyzed by SEM, and the results are as follows: Figure 1 As shown. Figure 1 Show Na 0.2Zr 0.1 The V₂O₅ / MXene composite material consists of micron-sized microspheres formed by the aggregation of small primary particles. The overall morphology of the sample is spherical, with a sphere size of approximately 2-25 μm. These spheres are formed by the aggregation of nano-sized primary particles, with a particle size of 5-15 nm. The nano-sized primary particle structure is due to the presence of MXene influencing the original growth orientation of V₂O₅. Furthermore, the use of a spray-drying method allows the nano-sized primary particles to further aggregate into micron-sized microspheres. This unique structure provides a larger specific surface area and more active sites, resulting in better specific capacity and stronger structural stability during charge and discharge.

[0032] Example 2: A method for preparing a composite cathode material is as follows: (1) 1.81 g vanadium pentoxide, 0.141 g sodium sulfate, 0.281 g zirconium sulfate, 0.108 g polyvinylpyrrolidone, and 1.45 g tartaric acid were added sequentially to 50 mL of deionized water and magnetically stirred at 400 rpm for 1.5 h to fully dissolve the solutes, thus obtaining the first solution. The first solution was transferred to a reaction vessel and placed in a microwave hydrothermal synthesizer at 160 ℃ for continuous reaction for 6 h. The reaction product was centrifuged to collect the precipitate, which was then washed with deionized water and ethanol alternately by centrifugation to obtain the intermediate substance.

[0033] (2) The above intermediate substance was reacted with Ti3C2T at a concentration of 5 mg / mL. x Mixing of MXene anhydrous ethanol dispersion requires Ti3C2T x The mass ratio of MXene material to intermediate was 15:85. The solution was then transferred to a 100 mL planetary ball mill with a material-to-ball ratio of 1:30. Anhydrous ethanol was used as the milling medium, and the mixture was continuously milled at 450 rpm for 2 hours. The milled product was then dried under vacuum to remove the milling medium, yielding the intermediate material.

[0034] (3) Transfer the above intermediate product to a beaker and add an appropriate amount of ethanol. Stir magnetically at 400 rpm for 30 min. After stirring, spray dry the resulting solution. The inlet temperature of the spray dryer is 240 ℃, the outlet temperature is 110 ℃, and the feed rate is 1 L / h to obtain the precursor powder.

[0035] (4) The precursor powder was placed in a corundum crucible and then placed in a tube furnace. Under an argon atmosphere, the temperature was increased to 450°C at a heating rate of 3°C / min. The mixture was then calcined at 450°C for 3 h. After naturally cooling to room temperature, Na was obtained. 0.2 Zr 0.1 V2O5 / MXene composite material.

[0036] Example 3: A method for preparing a composite cathode material is as follows: (1) Accurately weigh 2.172 g ammonium metavanadate, 0.152 g sodium acetate, 0.303 g zirconium acetate, 0.152 g sodium dodecyl sulfate, and 1.30 g EDTA, and add them sequentially to 75 mL of 20% (V / V) ethanol aqueous solution. Heat to 70 °C at 600 rpm and stir magnetically for 5 h to fully dissolve the solutes and obtain the first solution. Transfer the first solution to a reaction vessel and place it in a microwave hydrothermal synthesizer at 200 °C for continuous reaction for 6 h. Centrifuge the reaction product to collect the precipitate. Wash the precipitate with deionized water and ethanol alternately by centrifugation to obtain the intermediate substance.

[0037] (2) The above intermediate substance was reacted with Ti3C2T at a concentration of 5 mg / mL. x Mixing of MXene anhydrous ethanol dispersion requires Ti3C2T x The mass ratio of MXene material to intermediate was 20:80. The mixed solution was then transferred to a 100 mL planetary ball mill with a material-to-ball ratio of 1:40. Anhydrous ethanol was used as the milling medium, and the mixture was continuously milled at 600 rpm for 2 h. The milled product was then dried under vacuum to remove the milling medium, yielding the intermediate material.

[0038] (3) Transfer the above intermediate product to a beaker and add an appropriate amount of ethanol. Stir magnetically at 600 rpm for 30 min. After stirring, spray dry the resulting solution. The inlet temperature of the spray dryer is 260℃, the outlet temperature is 120℃, and the feed rate is 1 L / h to obtain the precursor powder.

[0039] (4) The precursor powder was then placed in a crucible and placed in a tube furnace. Under argon protection, the temperature was increased to 300 °C at a heating rate of 2 °C / min, and calcined at 300 °C for 5 h. After cooling to room temperature, the mixture was thoroughly washed with hydrochloric acid solution and deionized water to remove impurities, and dried overnight at 80 °C to obtain the product Na. 0.2 Zr 0.1 V2O5 / MXene composite material.

[0040] Example 4: A method for preparing a composite cathode material is as follows: (1) Accurately weigh 1.884 g vanadium chloride, 0.0982 g sodium phosphate, 0.388 g zirconium oxychloride, 0.113 g hexadecyltrimethylammonium chloride, and 1.13 g tartaric acid, and add them sequentially to 50 mL of 35% (V / V) ethanol aqueous solution. Stir magnetically at 550 rpm for 1.5 h to fully dissolve the solutes and obtain the first solution. Transfer the first solution to a reaction vessel and place it in a microwave hydrothermal synthesizer at 180 ℃ for continuous reaction for 8 h. Centrifuge the reaction product to collect the precipitate. Wash the precipitate with deionized water and ethanol alternately by centrifugation to obtain the intermediate substance.

[0041] (2) The above intermediate substance was reacted with Ti3C2T at a concentration of 5 mg / mL. x Mixing of MXene anhydrous ethanol dispersion requires Ti3C2T x The mass ratio of MXene material to intermediate was 25:75. The mixed solution was then transferred to a 100 mL planetary ball mill with a material-to-ball ratio of 1:35. Anhydrous ethanol was used as the milling medium, and the mixture was continuously milled at 400 rpm for 2.5 h. The milled product was then dried under vacuum to remove the milling medium, yielding the intermediate material.

[0042] (3) The above intermediate product was transferred to a beaker and an appropriate amount of ethanol was added. The mixture was magnetically stirred at 500 rpm for 45 min. After stirring, the resulting solution was spray-dried. The inlet temperature of the spray drying was 210 ℃, the outlet temperature was 90 ℃, and the feed rate was 2 L / h to obtain the precursor powder.

[0043] (4) Then, the precursor powder was placed in a crucible and placed in a tube furnace. Calcination was carried out in a nitrogen atmosphere at 350 °C for 3 h and 500 °C for 4 h. After cooling naturally to room temperature, the powder was ground through a 0.77 mm sieve using an agate mortar to obtain Na. 0.3 Zr 0.2 V2O5 / MXene composite material.

[0044] Example 5: A method for preparing a composite cathode material is as follows: (1) Accurately weigh 2.172 g ammonium metavanadate, 0.316 g sodium nitrate, 0.527 g zirconium sulfate, 0.172 g sodium dodecyl sulfate, and 1.09 g oxalic acid, and add them sequentially to 75 mL of deionized water. Stir magnetically at 500 rpm for 3 h to fully dissolve the solutes and obtain the first solution. Transfer the first solution to a reaction vessel and place it in a microwave hydrothermal synthesizer at 160 ℃ for continuous reaction for 6 h. Centrifuge the reaction product to collect the precipitate. Wash the precipitate with deionized water and ethanol alternately by centrifugation to obtain the intermediate substance.

[0045] (2) The above intermediate substance was reacted with Ti3C2T at a concentration of 5 mg / mL. x Mixing of MXene anhydrous ethanol dispersion requires Ti3C2T x The mass ratio of MXene material to intermediate was 15:85. The mixed solution was then transferred to a 100 mL planetary ball mill with a material-to-ball ratio of 1:25. Anhydrous ethanol was used as the milling medium, and the mixture was continuously milled at 450 rpm for 3 h. The milled product was then dried under vacuum to remove the milling medium, yielding the intermediate material.

[0046] (3) Transfer the above intermediate product to a beaker and add an appropriate amount of deionized water. Stir magnetically at 400 rpm for 30 min. After stirring, spray dry the resulting solution. The inlet temperature of the spray dryer is 230 ℃, the outlet temperature is 100 ℃, and the feed rate is 2 L / h to obtain the precursor powder.

[0047] (4) Then the precursor powder was placed in a crucible and placed in a tube furnace. Under argon protection, it was heated to 800 °C at a heating rate of 3 °C / min, calcined at 800 °C for 2 h, and then naturally cooled to room temperature to obtain Na. 0.4 Zr 0.2 V2O5 / MXene composite material.

[0048] Example 6: A method for preparing a composite cathode material is as follows: (1) Accurately weigh 1.81 g vanadium pentoxide, 0.353 g sodium sulfate, 0.563 g zirconium sulfate, 0.15 g polyethylene glycol 2000, and 1.13 g tartaric acid, and add them sequentially to 50 mL of deionized water. Stir magnetically at 600 rpm for 2 h to fully dissolve the solutes and obtain the first solution. Transfer the first solution to a reaction vessel and place it in a microwave hydrothermal synthesizer at 180 ℃ for continuous reaction for 10 h. Centrifuge the reaction product to collect the precipitate. Wash the precipitate alternately with deionized water and ethanol by centrifugation to obtain the intermediate substance.

[0049] (2) The above intermediate substance was reacted with Ti3C2T at a concentration of 5 mg / mL. x Mixing of MXene anhydrous ethanol dispersion requires Ti3C2T x The mass ratio of MXene material to intermediate was 5:95. The mixed solution was then transferred to a 100 mL planetary ball mill with a material-to-ball ratio of 1:35. Anhydrous ethanol was used as the milling medium, and the mixture was continuously milled at 300 rpm for 12 hours. The milled product was then dried under vacuum to remove the milling medium, yielding the intermediate material.

[0050] (3) The above intermediate product was transferred to a beaker and an appropriate amount of deionized water was added. The mixture was magnetically stirred at 600 rpm for 2 h. After stirring, the resulting solution was spray-dried. The inlet temperature of the spray drying was 240 ℃, the outlet temperature was 120 ℃, and the feed rate was 1.5 L / h to obtain the precursor powder.

[0051] (4) The precursor powder was then placed in a corundum crucible and placed in a tube furnace. Under an argon atmosphere, the temperature was increased to 550°C at a heating rate of 3°C / min. The mixture was then calcined at 550°C for 3 h. After naturally cooling to room temperature, Na was obtained. 0.5 Zr 0.2 V2O5 / MXene composite material.

[0052] Comparative Example 1: Everything else is the same as in Example 1, except that: Sodium nitrate and zirconium nitrate are not added in step (1), and Ti3C2T is not added in step (2). x MXene solution.

[0053] Undoped V2O5 material was finally obtained.

[0054] Comparative Example 2: Everything else is the same as in Example 1, except that: Ti3C2T is not added in step (2) x MXene solution.

[0055] Na was finally obtained 0.2 Zr 0.1 V2O5 material.

[0056] Comparative Example 3: Everything else is the same as in Example 1, except that: Sodium nitrate and zirconium nitrate are not added in step (1).

[0057] Comparative Example 4: Everything else is the same as in Example 1, except that: Zirconium nitrate is not added in step (1).

[0058] Comparative Example 5: Everything else is the same as in Example 1, except that: Sodium nitrate is not added in step (1).

[0059] Comparative Example 6: Everything else is the same as in Example 1, except that: Replace sodium nitrate with lithium nitrate.

[0060] Comparative Example 7: Everything else is the same as in Example 1, except that: Replace zirconium nitrate with nickel nitrate.

[0061] Comparative Example 8: Everything else is the same as in Example 1, except that: Replace zirconium nitrate with manganese nitrate.

[0062] Comparative Example 9: Everything else is the same as in Example 1, except that: Replace zirconium nitrate with cobalt nitrate.

[0063] Comparative Example 10: Everything else is the same as in Example 1, except that: Replace zirconium nitrate with titanium nitrate.

[0064] Comparative Example 11: Everything else is the same as in Example 1, except that: Ti3C2T x Replace MXene solution with V2CT x MXene solution.

[0065] Comparative Example 12: Everything else is the same as in Example 1, except that: Ti3C2T x MXene was replaced with graphene (purchased from Merck, product number 900561).

[0066] Comparative Example 13: Everything else is the same as in Example 1, except that: Ti3C2T x MXene was replaced with a graphite intercalation compound (purchased from Merck, catalog number 808121).

[0067] The final products obtained in Example 1, Comparative Example 1, and Comparative Example 2 were used as positive electrode material samples. The positive electrode material samples, conductive carbon black, and PVDF were dissolved in NMP at a ratio of 7:2:1 and ground to obtain a uniform slurry. The slurry was uniformly coated on carbon paper, vacuum dried at 65°C for 18 h, pressed into sheets, and cut into 12 mm diameter discs as positive electrode sheets. 80 μm thick high-purity zinc foil (12 mm diameter discs) was used as the negative electrode. The electrolyte was an anhydrous organic electrolyte Zn(OTf)2 / MeOH-PC composed of methanol (80 vol%) as hydrogen bond donor, propylene carbonate (20 vol%) as co-solvent, and 3 mol / L zinc trifluoromethanesulfonate. A 14 mm diameter GF / A glass fiber membrane was used as the separator to better wet the zinc trifluoromethanesulfonate electrolyte. The positive electrode shell, positive electrode sheet, electrolyte-soaked separator, zinc negative electrode, gasket, and negative electrode shell are arranged in sequence, pressurized and sealed to assemble a 2016-type button-type aqueous zinc-ion battery, and then placed in the Blue Electric test system to test the battery performance.

[0068] The assembled aqueous zinc-ion battery was subjected to charge-discharge tests at different rates, and the results are as follows: Figure 3 As shown, the Na prepared in Example 1 0.2Zr 0.1 When the V2O5 / MXene composite material is used as an aqueous zinc ion cathode material, it achieves a specific capacity of approximately 525 mAh / g during the first discharge at 0.1 mA / g, and can also release a specific capacity of approximately 380 mAh / g under a high current of 5.0 A / g. In contrast, the V2O5 material prepared in Comparative Example 1 has a discharge specific capacity of approximately 365 mAh / g at 0.1 A / g and approximately 220 mAh / g at 5.0 A / g. It can be seen that under the same testing conditions, the performance of Comparative Example 1 is significantly lower than that of Example 1. The Na prepared in Comparative Example 2... 0.2 Zr 0.1 When used as an aqueous zinc-ion cathode material, the V₂O₅ composite material achieved a specific capacity of over 410 mAh / g during the first discharge at 0.1 A / g, and also exhibited a specific capacity of approximately 280 mAh / g at a high current of 5.0 A / g. Although the rate performance of the composite material prepared in Comparative Example 2 was not as good as that of the composite material prepared in Example 1, it was still significantly improved compared to the uncomposite V₂O₅ material prepared in Comparative Example 1. This demonstrates that co-doping with Na... + and Zr 4+ It can effectively improve its rate performance, and through further MXene composite, the conductivity and rate performance of the material can be effectively improved.

[0069] The assembled aqueous zinc-ion battery was subjected to cycle stability testing at a high rate of 5.0 A / g, and the results are as follows: Figure 3 As shown, after 2000 long cycles at a high current of 5.0 A / g, the Na prepared in Example 1... 0.2 Zr 0.1 The discharge specific capacity of the V2O5 / MXene composite material decreased from a peak of 330 mAh / g to 265 mAh / g, with a capacity retention of approximately 80.1%. This indicates that the material exhibits stronger structural stability and greater reactivity during cycling.

[0070] The capacity retention and specific capacity of the aqueous zinc-ion batteries assembled using the composite materials prepared in Examples 2-6 and Comparative Examples 1-13 were further tested using the above method after 2000 cycles. The results are as follows: Table 1. Electrochemical performance test results of different composite materials

[0071] The values ​​in Table 1 are all average data obtained from the tests. As can be seen from the results in Table 1, in Comparative Example 2, due to the absence of MXene material, the Na and Zr co-doped vanadium oxide material exhibits the phenomenon of nanoparticle aggregation during charge-discharge cycles, resulting in a decrease in the active surface area. This manifests as a significant reduction in the electrochemical performance of the Na and Zr co-doped vanadium oxide material compared to Example 1, and a relatively limited improvement in performance compared to the undoped V2O5 material in Comparative Example 1.

[0072] In Comparative Examples 3-5, due to the lack of Na and / or Zr doping, even though the introduction of MXene material can prevent the aggregation of V2O5 material, relying solely on the doping of a single metal element or without metal doping cannot support and maintain the layered structure of V2O5, making it difficult to alleviate the Zn²⁺ aggregation. + The structural stress of insertion / extraction causes the composite material to still have the problem of structural collapse caused by vanadium dissolution. Therefore, the electrochemical performance of Comparative Examples 3-5 is significantly worse than that of Example 1, and the performance improvement compared with Comparative Example 1 is extremely limited.

[0073] In Comparative Examples 6-10, replacing Na or Zr with other metal elements significantly reduced the electrochemical performance of the composite materials compared to Example 1. The electrochemical performance of some comparative examples was even lower than that of Comparative Example 1, indicating that co-doping with other metal elements and Na or Zr makes it difficult to expand and maintain the interlayer spacing of V₂O₅, thus hindering the improvement of the electrochemical performance of the V₂O₅ material. Co-doping with some metals (such as Li, Mn, and Ti) may even reduce the electrochemical performance of the V₂O₅ material, which may be related to the poor influence of these metal elements on the formation of the nanocrystalline structure of the primary particles. Therefore, specific combinations of Na and Zr co-doping are necessary conditions for improving the electrochemical performance of the composite materials.

[0074] Comparative Example 11 uses V2CT x As an MXene material introduced into composite materials, but V2CT x Unable to stop Na 0.2 Zr 0.1 The direct contact between V₂O₅ material and electrolyte disrupts the integrity of the main structure and dissolves vanadium (V), leading to increased electrostatic repulsion between the main layers and hindering the interaction of Zn at the interface. 2+ The diffusion of [the substance] ultimately leads to a significant reduction in the electrochemical performance of the composite material.

[0075] Comparative Examples 12 and 13 used sheet-like carbon materials with the same electrical conductivity and Na 0.2 Zr 0.1However, the electrochemical performance of the composite material was even worse than that of Comparative Example 1, indicating that these layered conductive carbon materials could not synergistically improve the electrochemical performance of the composite material with Na and Zr co-doping technology. This is related to the difficulty in forming uniform nanoscale primary particles after the introduction of materials such as graphene and the aggregation of primary particles during cycling.

Claims

1. A vanadium-based composite cathode material, characterized in that, It includes micron-sized microspheres formed by the aggregation of nanoscale primary particles, wherein the primary particles are composed of Na and Zr-doped V2O5 material and MXene material composited on the primary particles, and a heterogeneous interface is formed between the Na and Zr-doped V2O5 material and the MXene material.

2. The vanadium-based composite cathode material according to claim 1, characterized in that, The Na and Zr-doped V₂O₅ material is Na x Zr y V₂O₅, wherein 0.1 ≤ x + y ≤ 0.7; the size of the primary particles is 5-15 nm; the size of the microspheres is 2-25 μm; the MXene material comprises Ti₃C₂T x Nb2CT x Mo2CT x At least one of them.

3. The method for preparing the vanadium-based composite cathode material according to claim 1 or 2, characterized in that, Includes the following steps: (1) Dissolve vanadium source, sodium source, zirconium source, surfactant and complexing agent in a first solvent to obtain a first solution, subject the first solution to a hydrothermal reaction, and filter the reaction product to obtain a precipitate; (2) The precipitate was ball-milled and mixed with MXene material to obtain an intermediate substance; (3) Disperse the intermediate substance in water or alcohol solvent and spray dry to obtain precursor powder; (4) The precursor powder is calcined to obtain a composite cathode material.

4. The method for preparing the vanadium-based composite cathode material according to claim 3, characterized in that, In step (1), the vanadium source includes at least one of vanadium pentoxide, ammonium metavanadate, and vanadium chloride; the sodium source includes at least one of sodium oxalate, sodium nitrate, sodium sulfate, and sodium phosphate; and the zirconium source includes at least one of zirconium oxychloride, zirconium nitrate, zirconium sulfate, and zirconium acetylacetonate.

5. The method for preparing the vanadium-based composite cathode material according to claim 3, characterized in that, In step (1), the surfactant includes at least one of polyethylene glycol, polyvinylpyrrolidone, sodium dodecyl sulfate, and hexadecyltrimethylammonium chloride; the complexing agent includes at least one of oxalic acid, tartaric acid, and EDTA; and the first solvent includes at least one of water, ethanol, and ethylene glycol.

6. The method for preparing the vanadium-based composite cathode material according to claim 3, characterized in that, In step (1), the mass ratio of the vanadium source, sodium source, zirconium source, surfactant, and complexing agent is 1.5-2.5: 0.09-0.36: 0.2-0.6: 0.05-0.2: 1.0-1.5; The concentration of the vanadium source in the first solution is 0.01-5.0 mol / L; the hydrothermal reaction conditions are 100-250℃ for 6-24 h.

7. The method for preparing the vanadium-based composite cathode material according to claim 3, characterized in that, In step (2), the method for ball milling and mixing the precipitate with the MXene material is as follows: The precipitate was mixed with an alcohol solution of MXene material, and after mixing, a second solution was obtained. The second solution was ball-milled, and the ball-milled product was dried to obtain an intermediate substance.

8. The method for preparing the vanadium-based composite cathode material according to claim 7, characterized in that, The mass ratio of the MXene material to the precipitate is 5-25:75-95; The ball milling method is as follows: add the grinding balls to the second solution at a mass ratio of 1:10-30 and grind at 300-600 rpm for 2-12 hours.

9. The method for preparing the vanadium-based composite cathode material according to claim 3, characterized in that, In step (3), the conditions for spray drying are: feed rate of 1-20 L / h, inlet temperature of 200-300℃, and outlet temperature of 80-140℃; In step (4), the precursor powder is calcined by heating it to 300-800 ℃ at a rate of 1-3℃ / min under an inert atmosphere, holding it at that temperature for 3-5 hours, and then naturally cooling it to room temperature.

10. The application of the vanadium-based composite cathode material according to claim 1 or 2 in the preparation of the cathode of an aqueous zinc-ion battery.

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