Three-dimensional hierarchical net-like metal oxide / carbon composite, method for preparing same, and use thereof

Abstract

This invention discloses a three-dimensional hierarchical network metal oxide / carbon composite material, its preparation method, and its application. The three-dimensional hierarchical network metal oxide / carbon composite material comprises: a metal oxide active material coated with a carbon shell and a highly conductive carbon skeleton, wherein the metal oxide active material coated with the carbon shell and the highly conductive carbon skeleton are interwoven to form a three-dimensional hierarchical conductive network structure. The three-dimensional hierarchical network metal oxide / carbon composite material provided by this invention, when used as a positive electrode active material in zinc-ion batteries, can significantly improve battery performance. Firstly, the formation of a three-dimensional conductive network improves the overall conductivity of the material and increases the reaction area between the electrolyte and the electrode, while also giving it a higher ion diffusion rate, thus increasing battery capacity. Secondly, the layered structure allows the carbon layer to encapsulate the metal oxide, inhibiting the dissolution of transition metal ions, thereby significantly reducing battery capacity decay and extending cycle life.

Description

Technical Field

[0001] This invention relates to a metal oxide / carbon composite material, and more particularly to a three-dimensional hierarchical network metal oxide / carbon composite material, its preparation method, and its applications, belonging to the field of nanomaterials technology. Background Technology

[0002] With the increasing demand for energy, low-cost and highly safe zinc-ion batteries are expected to be used in various large-scale energy storage facilities such as microgrids, solar power, and wind power due to their enormous development potential. Zinc metal, with its exceptionally high global average production of 502,000 tons and extremely low price of $0.2 per kilogram, possesses an undisputed cost advantage among various ion batteries. Therefore, there is an urgent need to find ideal cathode materials to match and form high-capacity, long-cycle zinc-ion batteries.

[0003] Currently, zinc-ion battery cathode materials on the market are divided into four main categories: vanadium-based, manganese-based, Prussian blue analogues, and organic cathodes. Among these, manganese-based and Prussian blue analogues are difficult to apply industrially due to poor rate performance and low specific capacity, respectively. Research on organic cathodes is still in its early stages and the technology is not yet mature. However, vanadium-based cathodes, with their ultra-high theoretical specific capacity of 589 mAh / g, have attracted widespread attention. Vanadium ions exhibit multi-electron reactions during charge-discharge cycles. 5+ / V 3+ While vanadium pentoxide exhibits stable crystal structures regardless of its valence state, subsequent research has revealed several troubling issues, such as poor conductivity, insufficient cycle life, and severe capacity decay. To address these problems, researchers both domestically and internationally have made several advancements. These include improving capacity by introducing metal ions to enhance the interlayer spacing of vanadium pentoxide; however, altering the crystal structure negatively impacts thermal stability, resulting in unsatisfactory battery life. Another approach involves composites with carbon materials to improve the conductivity of metal oxides; however, the increased surface area of ​​the composite material leads to greater contact between the electrolyte and vanadium pentoxide, failing to suppress vanadium ion dissolution. Furthermore, current research on vanadium-based cathode materials often involves doping with metal cations, but this negatively impacts the formation of the inherent vanadium-oxygen bond crystal structure. Even with a slight increase in capacity, the unbalanced thermal stability compromises cycle life, and cathode dissolution remains uncontrolled. Therefore, designing a suitable three-dimensional hierarchical conductive composite material remains a significant challenge. Summary of the Invention

[0004] The main objective of this invention is to provide a three-dimensional hierarchical network metal oxide / carbon composite material and its preparation method, so as to overcome the shortcomings of the prior art.

[0005] Another object of the present invention is to provide the application of the three-dimensional hierarchical network metal oxide / carbon composite material in the preparation of electrode materials.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] This invention provides a three-dimensional hierarchical network metal oxide / carbon composite material, comprising: a metal oxide active material coated with a carbon shell and a highly conductive carbon skeleton, wherein the metal oxide active material coated with a carbon shell and the highly conductive carbon skeleton are interwoven to form a three-dimensional hierarchical conductive network structure.

[0008] This invention also provides a method for preparing a three-dimensional hierarchical network metal oxide / carbon composite material, comprising:

[0009] Provide a first solution containing a highly conductive carbon framework material;

[0010] A second solution is provided, comprising a transition metal oxide precursor, an organic solvent, and a carbon source (including carbon framework and carbon shell sources);

[0011] The first and second solutions are mixed and subjected to a hydrothermal reaction, followed by freeze-drying to obtain a three-dimensional carbon framework, thus yielding the precursor material.

[0012] The precursor material was calcined to obtain a three-dimensional hierarchical network metal oxide / carbon composite material.

[0013] This invention also provides the application of the aforementioned three-dimensional hierarchical network metal oxide / carbon composite material in the preparation of electrode materials.

[0014] Accordingly, embodiments of the present invention also provide a zinc-ion battery positive electrode, comprising a positive electrode active material, a conductive agent and a binder, wherein the positive electrode active material is the aforementioned three-dimensional hierarchical network metal oxide / carbon composite material.

[0015] This invention also provides a zinc-ion battery, including a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode is the aforementioned zinc-ion battery positive electrode.

[0016] Compared with the prior art, the beneficial effects of the present invention are at least as follows:

[0017] The three-dimensional hierarchical network metal oxide / carbon composite material provided by this invention can be used as a positive electrode active material in zinc-ion batteries, which can significantly improve battery performance. First, by forming a three-dimensional conductive network, the conductivity of the overall material is improved and the reaction area between the electrolyte and the electrode is increased, and it also has a higher ion diffusion rate, which improves the battery capacity. Then, the layered structure allows the carbon layer to encapsulate the metal oxide, which inhibits the dissolution of transition metal ions, thereby greatly reducing the battery capacity decay and extending the cycle life. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1a and Figure 1b This is a SEM image of vanadium pentoxide (V2O5) prepared in Comparative Example 1;

[0020] Figure 1c and Figure 1d This is a SEM image of the three-dimensional hierarchical network structure of the vanadium pentoxide@carbon nanotube / graphene composite (V2O5@G-CNTs) prepared in Example 1 of this invention;

[0021] Figure 2a and Figure 2b This is a TEM image of the carbon-coated structure of the vanadium pentoxide@carbon nanotube / graphene composite (V2O5@G-CNTs) prepared in Example 1 of this invention.

[0022] Figure 3 The XRD patterns are of the materials obtained in Comparative Examples 1-3 and the vanadium pentoxide@carbon nanotube / graphene composite (V2O5@G-CNTs) prepared in Example 1.

[0023] Figure 4a , Figure 4b The graphs show the diffusion coefficient and cycle performance of zinc ions in a battery composed of vanadium pentoxide@carbon nanotube / graphene composite (V2O5@G-CNTs) prepared in Example 1 of this invention as the positive electrode active material of a zinc-ion battery.

[0024] Figure 5 The graph shows the cycle performance of a battery composed of vanadium pentoxide (V2O5) prepared in Comparative Example 1 as the positive electrode active material of a zinc-ion battery.

[0025] Figure 6 This is a SEM image of the material prepared in Comparative Example 2;

[0026] Figure 7 This is a graph showing the cycle performance of a battery composed of the material prepared in Comparative Example 2 as the positive electrode active material of a zinc-ion battery.

[0027] Figure 8 This is a SEM image of the material prepared in Comparative Example 3;

[0028] Figure 9 This is a cycle performance diagram of a battery composed of the material prepared in Comparative Example 3 as the positive electrode active material of a zinc-ion battery. Detailed Implementation

[0029] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The main focus is on studying a three-dimensional conductive carbon network and its composite to obtain a hierarchical network material, thereby achieving efficient electron conduction and rapid ion diffusion, and thus improving its electrochemical performance. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0030] One aspect of the present invention provides a three-dimensional hierarchical network metal oxide / carbon composite material comprising: a metal oxide active material coated with a carbon shell and a highly conductive carbon skeleton material, wherein the metal oxide active material coated with a carbon shell and the highly conductive carbon skeleton material are interwoven to form a three-dimensional hierarchical conductive network structure.

[0031] As a preferred embodiment, the metal oxide active material includes transition metal oxides, which include any one or a combination of two of vanadium-based oxides, manganese-based oxides, niobium-based oxides, molybdenum oxide, etc., but are not limited thereto.

[0032] Furthermore, the vanadium-based oxide may include vanadium pentoxide (V₂O₅), vanadium trioxide (V₂O₃), vanadium dioxide (VO₂), vanadium heptaoxide (V₃O₇), and vanadium hexadecoxide (V₆O₅). 13 The metal ion intercalated vanadium oxide (VNO) is selected from any one or more of the following: vanadium oxide containing metal ions, and a combination of two or more of them, wherein the metal ion intercalated vanadium oxide includes M-VO, Cs, etc. n V2O5, Al n V2O5, Fe n V2O5, Ca n Any one or more combinations of V2O5, etc., where M is selected from any one of the metals such as Li, Na, K, Ag, Ca, Mn, Co, Zn, Fe, Cr, etc., but not limited to these.

[0033] Furthermore, the manganese-based oxide may include manganese dioxide (MnO2, α, β, γ, δ, λ, etc.) of different crystal forms, manganese monoxide (MnO), manganese trioxide (Mn2O3), and metal ion-doped manganese oxides M-MO, such as Na. n MnO2, where M can be any one or more of the following metals: Li, Na, K, V, Ag, Ca, Co, Pb, Zn, Fe, Cr, etc., but is not limited to these.

[0034] Furthermore, the niobium-based oxide includes, but is not limited to, niobium pentoxide (Nb₂O₅).

[0035] As a preferred embodiment, the thickness of the carbon shell is 5–10 nm.

[0036] As a preferred embodiment, the highly conductive carbon framework material may include carbon nanotubes, graphene, graphene oxide, and C. 60 The graphene can be any one or a combination of two or more of the following, but is not limited to: graphdiyne, graphene quantum dots, heteroatom-doped graphene (doping elements include N, P, S, etc.), carbon nanofibers, carbon aerogels, carbon nanotube arrays, etc.

[0037] Furthermore, the carbon nanotubes may be at least one of multi-walled carbon nanotubes, single-walled carbon nanotubes, etc., and the graphene may be at least one of multilayer graphene, single-layer graphene, etc., but is not limited thereto.

[0038] As a preferred embodiment, the content of highly conductive carbon material in the three-dimensional hierarchical network metal oxide / carbon composite material is 10–60 wt%.

[0039] In summary, this invention provides a hierarchical conductive carbon network that facilitates electron conduction and ion diffusion. This structure can achieve multi-level and multi-dimensional coupling and synergistic effects. The multi-level refers to the presence of a carbon shell structure covering the metal oxide active material, while the multi-dimensional refers to the three-dimensional network structure formed. The metal oxide active material with the carbon shell structure and the highly conductive carbon framework material (such as carbon nanotubes, graphene, etc.) intertwine to form a three-dimensional conductive network. This ensures sufficient contact between the electrode and the electrolyte while inhibiting the dissolution of vanadium ions, jointly promoting electron conduction and ion diffusion, resulting in the composite material exhibiting extremely superior cycle stability and ultra-long lifespan.

[0040] Another aspect of the present invention provides a method for preparing a three-dimensional hierarchical network metal oxide / carbon composite material, comprising:

[0041] Provide a first solution containing a highly conductive carbon framework material;

[0042] A second solution is provided, comprising a transition metal oxide precursor, an organic solvent, and a carbon source (including carbon framework and carbon shell sources);

[0043] The first and second solutions are mixed and subjected to a hydrothermal reaction, followed by freeze-drying to obtain a three-dimensional carbon framework, thus yielding the precursor material.

[0044] The precursor material was calcined to obtain a three-dimensional hierarchical network metal oxide / carbon composite material.

[0045] The types of highly conductive carbon materials mentioned above are as described previously and will not be repeated here.

[0046] In one specific embodiment, the preparation method includes: dispersing a highly conductive carbon framework material in water to form the first solution.

[0047] Furthermore, the concentration of the highly conductive carbon framework material in the first solution is 0.8–2.0 mg / mL.

[0048] In one specific embodiment, the mass ratio of the transition metal oxide precursor to the carbon source is 1 to 5:1.

[0049] Furthermore, the mass ratio of the organic solvent to the combination (solute) of the transition metal oxide precursor and the carbon source is 20 to 60:1.

[0050] In one specific implementation, the transition metal oxide precursor includes any one or a combination of two or more of the following: vanadium source, manganese source, niobium source, molybdenum source, etc., but is not limited thereto.

[0051] Furthermore, the vanadium source includes any one or a combination of two or more of vanadates, metavanadates (such as ammonium metavanadate), pyrovanadates, orthovanadates, but is not limited thereto.

[0052] Furthermore, the manganese source includes any one or a combination of two or more of potassium permanganate, manganese sulfate (such as hydrated manganese sulfate), manganese perchlorate (such as hydrated manganese perchlorate), and manganese nitrate (such as hydrated manganese nitrate), but is not limited thereto.

[0053] Furthermore, the niobium source includes any one or a combination of two or more of niobium pentachloride, ammonium niobate, niobium chlorate, etc., but is not limited thereto.

[0054] Furthermore, the molybdenum source includes any one or a combination of two or more of sodium molybdate, cobalt molybdate, molybdenum sulfide, and molybdenum oxide, but is not limited thereto.

[0055] In one specific embodiment, the carbon shell source includes any one or a combination of two or more of the following: oxalic acid, glucose, melamine, dopamine, polydopamine, resorcinol-formaldehyde resin, polyvinylpyrrolidone, tannic acid, citric acid, polyvinyl alcohol, polypyrrole, vitamin C, polyethylene glycol, aniline, anthracene, etc., but is not limited thereto.

[0056] Furthermore, when the carbon shell source is oxalic acid, tannic acid, citric acid, etc., the pH value of the second solution can be adjusted to 2-6. These types of substances have a unique function here, as they can both adjust the pH value and act as a carbon shell coating layer.

[0057] Furthermore, the organic solvent includes any one or a combination of two or more of ethylene glycol, isopropanol, n-butanol, glycerol, propylene glycol, glycerol, polyethylene glycol, ethyl acetate, acetone, etc., but is not limited thereto.

[0058] Furthermore, the preparation method may further include: adding a surfactant to the first solution or the second solution to prevent the highly conductive carbon skeleton material or carbon shell source material from agglomerating in the solution. The surfactant may include any one or a combination of two or more of anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants, but is not limited thereto.

[0059] The anionic surfactant includes any one or a combination of two or more of sodium linear alkylbenzene sulfonate, sodium α-alkenyl sulfonate, and sodium dodecyl sulfate; the cationic surfactant includes any one or a combination of two or more of hexadecyl dimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium chloride, and dodecyl dimethyl ammonium oxide; preferably, the nonionic surfactant includes alkylolamide, fatty alcohol polyvinyl ether, etc., and the amphoteric surfactant includes at least one of dodecyl dimethyl betaine, carboxylate imidazoline, etc., but is not limited thereto.

[0060] In one specific embodiment, the hydrothermal reaction temperature is 100–200°C, and the reaction time is 6–28 h. The preparation mechanism of the hydrothermal reaction in this invention is as follows: First, under a high-temperature, high-pressure reducing atmosphere, carbon-containing functional groups from a carbon shell source (such as oxalic acid-based substances) preferentially adsorb onto the generated transition metal oxides (such as vanadium pentoxide nanoparticles), forming a pre-coated, uncrystallized precursor, which is then uniformly dispersed on the carbon framework in the solution. The three-dimensional structure can be obtained by freeze-drying.

[0061] In one specific embodiment, the preparation method includes: calcining the precursor material in an air atmosphere at a heating rate of 1–10 °C / min to 200–600 °C for 1–4 h to obtain the three-dimensional hierarchical network metal oxide / carbon composite material. The calcination in this invention serves two purposes: 1. to form a complete carbon coating layer during the calcination process; 2. to remove residual solvent from the precursor material and to allow it to crystallize into transition metal oxides.

[0062] In summary, this invention achieves a highly conductive and fast ion diffusion rate metal oxide@carbon composite electrode through a simple one-step hydrothermal in-situ synthesis of a three-dimensional hierarchical conductive network structure. This hierarchical conductive network utilizes carbon material as a carrier, upon which metal oxides are generated in situ, resulting in uniform encapsulation of the active metal oxide material by the carbon material. This multi-layered and multi-dimensional hierarchical structure design achieves a multiplier effect. The carbon layer encapsulating the metal oxide provides excellent conductivity while reducing its contact area with the weakly acidic electrolyte, thus inhibiting the dissolution of transition metal ions. Furthermore, the formed three-dimensional conductive network provides more reactive sites, accelerating the diffusion rate of ions within the electrode.

[0063] Another aspect of the present invention provides a three-dimensional hierarchical network metal oxide / carbon composite material prepared by the aforementioned preparation method.

[0064] Another aspect of the present invention provides the application of any of the aforementioned three-dimensional hierarchical network metal oxide / carbon composite materials in the preparation of electrode materials.

[0065] Specifically, another aspect of the present invention provides a zinc-ion battery positive electrode, comprising a positive electrode active material, a conductive agent, and a binder, wherein the positive electrode active material is the aforementioned three-dimensional hierarchical network metal oxide / carbon composite material.

[0066] Accordingly, another aspect of the present invention provides a zinc-ion battery, including a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode is the aforementioned zinc-ion battery positive electrode.

[0067] The zinc-ion battery assembled in this invention has a high ion diffusion rate (D). Zn 2+ =10 -8 ~10 -10 It features excellent rate performance and an ultra-high specific capacity of 480 mA h / g at a current density of 5 A / g, with 84% capacity retention and nearly 100% coulombic efficiency after 1200 stable cycles.

[0068] The invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0069] The following examples use vanadium pentoxide electrode material with high theoretical specific capacity (589 mAh / g) as an example, and all reagents used are of analytical grade.

[0070] Comparative Example 1

[0071] 1.0 g of ammonium metavanadate was dissolved in 60 mL of ethylene glycol and magnetically stirred for half an hour at 1600 rpm. Dilute hydrochloric acid was added to adjust the pH to approximately 2-3. The solution was then poured into a hydrothermal reactor and reacted at 180 °C for 24 h. After filtration and washing with deionized water until neutral, the solution was freeze-dried overnight to obtain a loose precursor material. The precursor was transferred to a tube furnace and calcined at 450 °C for 2 h in air at a heating rate of 4 °C / min to obtain the electrode material. This material was mixed uniformly with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was uniformly coated onto a graphene film and vacuum-dried at 60 °C for 24 h. The slurry was then cut into electrode sheets with a diameter of 10 mm. A zinc sheet was used as the negative electrode, and a 3 mol / L zinc trifluoromethanesulfonate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery casing.

[0072] Example 1

[0073] First, 80 mg of carbon nanotube powder and 16 mL of graphene aqueous solution (5 mg / mL) were ultrasonically dispersed in 200 mL of deionized water using a 45% power cell disruptor to obtain solution one. Ammonium metavanadate was dissolved in 40 mL of ethylene glycol, and oxalic acid was added to adjust the pH to approximately 2-6 to obtain solution two. The mass ratio of ammonium metavanadate to oxalic acid was 1:1, and the mass ratio of ethylene glycol to the combined ammonium metavanadate and oxalic acid was 20:1. Solution two was slowly added dropwise to the thoroughly stirred solution one. The mixture was then poured into a hydrothermal reactor and reacted at 100 °C for 28 h. Afterward, it was filtered and washed with deionized water until neutral, then freeze-dried overnight to obtain a loose precursor material. The precursor was transferred to a tube furnace and calcined at 350 °C for 2 h at a heating rate of 4 °C / min under air atmosphere to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode, and a 3 mol / L zinc trifluoromethanesulfonate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0074] Example 2

[0075] First, 250 mg of carbon nanofiber powder, 50 mL of nitrogen-doped graphene aqueous solution (5 mg / mL), and 10 mg of N-vinylpyrrolidone were ultrasonically dispersed in 250 mL of deionized water using a cell disruptor with a power of 45%. Solution 1 was prepared by dissolving 1.7 g of ammonium metavanadate in 45 mL of ethylene glycol, adding 1.35 g of oxalic acid and 0.5 g of hexadecyltrimethylammonium bromide, and stirring magnetically at 1600 rpm. Solution 2 was then slowly added dropwise to the uniformly stirred solution 1. The mixture was then poured into a hydrothermal reactor and reacted at 200 °C for 6 h. Afterward, the mixture was filtered and washed with deionized water until neutral, then freeze-dried overnight to obtain a loose precursor material. The precursor material was transferred to a tube furnace and calcined at 450 °C for 2 h under air atmosphere at a heating rate of 4 °C / min to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode, and a 3 mol / L zinc trifluoromethanesulfonate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0076] Example 3

[0077] First, 200 mg of carbon aerogel, 60 mL of graphene quantum dot aqueous solution (5 mg / mL), and 10 mg of sodium dodecyl sulfate were ultrasonically dispersed in 500 mL of deionized water using a cell disruptor with a power of 45% to obtain solution one. 1.45 g of ammonium metavanadate was dissolved in 60 mL of propylene glycol, and 1.15 g of citric acid and 0.5 g of hexadecyltrimethylammonium bromide were added. The mixture was magnetically stirred at 1600 rpm to obtain solution two. Solution two was slowly added dropwise to the uniformly stirred solution one. The mixture was then poured into a hydrothermal reactor and reacted at 180 °C for 24 h. Afterward, it was filtered and washed with deionized water until neutral, then freeze-dried overnight to obtain a loose precursor material. The precursor material was transferred to a tube furnace and calcined at 200 °C for 4 h at a heating rate of 1 °C / min under air atmosphere to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode, and a 3 mol / L zinc trifluoromethanesulfonate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0078] Example 4

[0079] First, 200 mg of carbon nanotube array powder, 60 mL of graphene quantum dot aqueous solution (5 mg / mL), and 10 mg of N-vinylpyrrolidone were ultrasonically dispersed in 500 mL of deionized water using a cell disruptor with a power of 45%. Solution 1 was prepared by dissolving 1.0 g of ammonium metavanadate in 60 mL of ethyl acetate, adding 1.35 g of citric acid and 0.5 g of hexadecyltrimethylammonium bromide, and stirring magnetically at 1600 rpm. Solution 2 was then slowly added dropwise to the uniformly stirred solution 1. The mixture was then poured into a hydrothermal reactor and reacted at 100 °C for 28 h. Afterward, the mixture was filtered and washed with deionized water until neutral, then freeze-dried overnight to obtain a loose precursor material. The precursor material was transferred to a tube furnace and calcined at 600 °C for 1 h under air atmosphere at a heating rate of 10 °C / min to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode, and a 3 mol / L zinc trifluoromethanesulfonate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0080] Example 5

[0081] First, 200 mg of graphdiene powder, 60 mL of nitrogen-doped graphene aqueous solution (5 mg / mL), and 10 mg of N-vinylpyrrolidone were ultrasonically dispersed in 500 mL of deionized water using a cell disruptor with a power of 45%. Solution 1 was prepared by dissolving 1.0 g of ammonium metavanadate in 60 mL of ethyl acetate, adding 1.35 g of citric acid and 0.5 g of hexadecyltrimethylammonium bromide, and stirring magnetically at 1600 rpm to prepare Solution 2. Solution 2 was slowly added dropwise to the uniformly stirred Solution 1. The mixture was then poured into a hydrothermal reactor and reacted at 160 °C for 18 h. Afterward, the mixture was filtered and washed with deionized water until neutral, then freeze-dried overnight to obtain a loose precursor material. The precursor material was transferred to a tube furnace and calcined at 400 °C for 2 h at a heating rate of 5 °C / min in air to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode, and a 3 mol / L zinc trifluoromethanesulfonate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0082] Example 6

[0083] First, 80 mg of carbon nanotube powder, 16 mL of graphene oxide aqueous solution (5 mg / mL), and 10 mg of N-vinylpyrrolidone were ultrasonically dispersed in 200 mL of deionized water using a cell disruptor with a power of 45% to obtain solution one. 0.732 g of hydrated manganese sulfate was dissolved in 40 mL of ethylene glycol, and 0.76 g of oxalic acid and 0.1 g of hexadecyltrimethylammonium bromide were added. The mixture was magnetically stirred at 1600 rpm to obtain solution two. Solution two was slowly added dropwise to the uniformly stirred solution one. The mixture was then poured into a hydrothermal reactor and reacted at 200 °C for 18 h. Afterward, it was filtered and washed with deionized water until neutral, then freeze-dried overnight to obtain a loose precursor material. The precursor material was transferred to a tube furnace and calcined at 400 °C for 4 h in air at a heating rate of 4 °C / min to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode. A 2 mol / L zinc sulfate and 0.2 mol / L manganese sulfate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0084] Example 7

[0085] First, 80 mg of carbon nanotube powder, 16 mL of graphene oxide aqueous solution (5 mg / mL), and 10 mg of N-vinylpyrrolidone were ultrasonically dispersed in 200 mL of deionized water using a cell disruptor with a power of 45%. Solution 1 was prepared by dissolving 0.886 g of niobium chloride in 60 mL of n-butanol, adding 0.89 g of oxalic acid and 0.1 g of hexadecyltrimethylammonium bromide, and stirring magnetically at 1600 rpm. Solution 2 was then slowly added dropwise to the uniformly stirred solution 1. The mixture was then poured into a hydrothermal reactor and reacted at 120 °C for 28 h. Afterward, the mixture was filtered and washed with deionized water until neutral, then freeze-dried overnight to obtain a loose precursor material. The precursor material was transferred to a tube furnace and calcined at 450 °C for 2 h at a heating rate of 5 °C / min in air to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode, and a 2 mol / L zinc sulfate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0086] Example 8

[0087] First, 80 mg of carbon nanotube powder was ultrasonically dispersed in 200 mL of deionized water with 16 mL of graphene oxide aqueous solution (5 mg / mL) and 10 mg of N-vinylpyrrolidone using a 45% power cell disruptor to obtain solution one. 1.36 g of molybdenum oxide was dissolved in 60 mL of glycerol, and 1.5 g of citric acid and 0.1 g of hexadecyltrimethylammonium bromide were added. The mixture was magnetically stirred at 1600 rpm to obtain solution two. Solution two was slowly added dropwise to the uniformly stirred solution one. The mixture was then poured into a hydrothermal reactor and reacted at 180 °C for 18 h. Afterward, it was filtered and washed with deionized water until neutral, then freeze-dried overnight to obtain a loose precursor material. The precursor material was transferred to a tube furnace and calcined at 500 °C for 4 h in air at a heating rate of 5 °C / min to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode, and a 2 mol / L zinc sulfate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0088] Example 9

[0089] First, 300 mg of carbon nanotube powder and 10 mg of N-vinylpyrrolidone were ultrasonically dispersed in 200 mL of deionized water using a 45% power cell disruptor to obtain solution one. 1.0 g of ammonium metavanadate was dissolved in 80 mL of n-butanol, and 1.35 g of glucose and 0.5 g of hexadecyltrimethylammonium bromide were added. The mixture was magnetically stirred at 1600 rpm for half an hour, and the pH was adjusted to approximately 2-3 with dilute hydrochloric acid to obtain solution two. Solution two was slowly added dropwise to the thoroughly stirred solution one. The mixture was then poured into a hydrothermal reactor and reacted at 160 °C for 18 h. Afterward, it was filtered and washed with deionized water until neutral, then freeze-dried overnight to obtain a loose precursor material. The precursor material was transferred to a tube furnace and calcined at 450 °C for 2 h under air atmosphere at a heating rate of 4 °C / min to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode, and a 3 mol / L zinc trifluoromethanesulfonate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0090] Example 10

[0091] First, 60 mL of graphene aqueous solution (5 mg / mL) and 10 mg of N-vinylpyrrolidone were ultrasonically dispersed in 200 mL of deionized water using a 45% power cell disruptor to obtain solution one. 1.0 g of ammonium metavanadate was dissolved in n-butanol, and 5 g of glucose and 0.5 g of hexadecyltrimethylammonium bromide were added. The mixture was magnetically stirred at 1600 rpm for half an hour, and the pH was adjusted to approximately 2-3 with dilute hydrochloric acid to obtain solution two. The mass ratio of n-butanol to ammonium metavanadate and glucose was 60:1. Solution two was slowly added dropwise to the thoroughly stirred solution one. The mixed solution was then poured into a hydrothermal reactor and reacted at 200 °C for 12 h. After filtration, the mixture was washed with deionized water until neutral and freeze-dried overnight to obtain a loose precursor material. The precursor material was transferred to a tube furnace and calcined at 350 °C for 4 h at a heating rate of 4 °C / min under air atmosphere to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode, and a 3 mol / L zinc trifluoromethanesulfonate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0092] Comparative Example 2

[0093] First, 200 mg of carbon nanotube powder and 40 mL of graphene aqueous solution (5 mg / mL) were ultrasonically dispersed in 300 mL of deionized water using a 45% power cell disruptor to obtain solution one. 0.5 g of ammonium metavanadate was dissolved in 40 mL of ethylene glycol, and dilute hydrochloric acid was added to adjust the pH to approximately 2-3 to obtain solution two. Solution two was slowly added dropwise to the thoroughly stirred solution one. The mixture was then poured into a hydrothermal reactor and reacted at 180 °C for 24 h. Afterward, it was filtered and washed with deionized water until neutral, then freeze-dried overnight to obtain a loose precursor material. The precursor was transferred to a tube furnace and calcined at 350 °C for 2 h at a heating rate of 4 °C / min in air to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode, and a 3 mol / L zinc trifluoromethanesulfonate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0094] Comparative Example 3

[0095] Dissolve 0.5 g of ammonium metavanadate in 40 mL of ethylene glycol, add 1.35 g of oxalic acid and 0.5 g of hexadecyltrimethylammonium bromide, and magnetically stir at 1600 rpm for half an hour. Slowly add solution two to the well-stirred solution one. Then pour the mixture into a hydrothermal reactor and react at 180 °C for 24 h. After filtration, wash with deionized water until neutral, and freeze-dry overnight to obtain a loose precursor material. Transfer the precursor to a tube furnace and calcine at 350 °C for 2 h at a heating rate of 4 °C / min in air to obtain the electrode material. The material was mixed with carbon black (Super P) and binder (5% PVDF) at a mass ratio of 7:2:1 to prepare a slurry. The slurry was then uniformly coated onto a graphene film and vacuum dried at 60°C for 24 hours. The slurry was then cut into electrode sheets with a diameter of 10 mm. Zinc sheets were used as the negative electrode, and a 3 mol / L zinc trifluoromethanesulfonate solution was used as the electrolyte. A coin cell was assembled using a 2025 battery case.

[0096] The inventors of this case also conducted various characterization and performance tests on vanadium pentoxide (V2O5) obtained in Comparative Example 1, vanadium pentoxide without carbon coating obtained in Comparative Example 2, the material obtained in Comparative Example 3, and the vanadium pentoxide@carbon nanotube / graphene composite (V2O5@G-CN Ts) obtained in Example 1. The results are as follows:

[0097] Please see Figure 1a and Figure 1b The data are SEM images of vanadium pentoxide (V₂O₅). Figure 1c and Figure 1dSEM data of the three-dimensional hierarchical network structure of vanadium pentoxide@carbon nanotube / graphene composites (V₂O₅@G-CNTs) are shown. Please refer to [link / reference]. Figure 2a and Figure 2b TEM data of the carbon-coated structure of vanadium pentoxide@carbon nanotube / graphene composite (V2O5@G-CNTs) are shown.

[0098] Please see Figure 3 XRD data for vanadium pentoxide (V2O5), vanadium pentoxide without carbon coating, the material obtained in Comparative Example 3, and vanadium pentoxide@carbon nanotube / graphene composite (V2O5@G-CNTs).

[0099] Figure 4a The diffusion coefficient of zinc ions in a battery composed of V2O5@G-CNTs as the positive electrode active material of a zinc-ion battery is shown. Figure 4b The graph shows the cycle performance data of batteries composed of vanadium pentoxide (V2O5) and vanadium pentoxide@carbon nanotube / graphene composite (V2O5@G-CNTs) as positive electrode active materials for zinc-ion batteries.

[0100] Figure 5 The cycling performance of a battery composed of vanadium pentoxide (V2O5) prepared in Comparative Example 1 as the positive electrode active material of a zinc-ion battery is shown.

[0101] Figure 6 The image shows a SEM image of vanadium pentoxide without a carbon coating prepared in Comparative Example 2. This material was used as the positive electrode active material in a zinc-ion battery. The cycle performance of the battery is as follows: Figure 7 As shown.

[0102] Figure 8 This is a SEM image of the material prepared in Comparative Example 3 (coated with a carbon layer, but without cross-linked carbon nanotubes and graphene). This material was used as the positive electrode active material in a zinc-ion battery. The battery's cycle performance is as follows: Figure 9 As shown.

[0103] In addition, the inventors of this case also used other raw materials and process conditions listed in this specification, and referred to the foregoing embodiments to prepare a series of three-dimensional hierarchical network metal oxide / carbon composite materials, all of which have the excellent properties described in this specification.

[0104] In summary, the three-dimensional hierarchical network metal oxide / carbon composite material provided by this invention, when used as a positive electrode active material in zinc-ion batteries, can significantly improve battery performance. Firstly, by forming a three-dimensional conductive network, the overall conductivity of the material is improved, the reaction area between the electrolyte and the electrode is increased, and it also has a higher ion diffusion rate, resulting in an increase in battery capacity. Secondly, the layered structure allows the carbon layer to encapsulate the metal oxide, inhibiting the dissolution of vanadium ions, thereby significantly reducing battery capacity decay and extending cycle life.

[0105] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims.

Claims

1. A method for preparing a three-dimensional hierarchical network metal oxide / carbon composite material, characterized in that, include: Provide a first solution containing a highly conductive carbon framework material; A second solution comprising a transition metal oxide precursor, an organic solvent, and a carbon source is provided; The first and second solutions are mixed and subjected to a hydrothermal reaction, followed by freeze-drying to obtain a three-dimensional carbon framework, thus yielding the precursor material. The precursor material was calcined to obtain a three-dimensional hierarchical network metal oxide / carbon composite material; The three-dimensional hierarchical network metal oxide / carbon composite material includes: a metal oxide active material coated with a carbon shell and a highly conductive carbon skeleton, wherein the metal oxide active material coated with a carbon shell and the highly conductive carbon skeleton are interwoven to form a three-dimensional hierarchical conductive network structure.

2. The preparation method according to claim 1, characterized in that: The active metal oxide material is a transition metal oxide, which is selected from any one or a combination of two or more of vanadium-based oxides, manganese-based oxides, niobium-based oxides, and molybdenum oxide.

3. The preparation method according to claim 2, characterized in that: The vanadium-based oxide is selected from any one or a combination of two or more of vanadium pentoxide, vanadium trioxide, vanadium dioxide, vanadium heptaoxide, vanadium trideoxy, and metal ion intercalated vanadium oxide.

4. The preparation method according to claim 2, characterized in that: The manganese-based oxide is selected from any one or a combination of two or more of manganese dioxide, manganese monoxide, manganese trioxide, and manganese oxides doped with metal ions.

5. The preparation method according to claim 2, characterized in that: The niobium-based oxide is niobium pentoxide.

6. The preparation method according to claim 1, characterized in that: The thickness of the carbon shell is 5~10 nm.

7. The preparation method according to claim 1, characterized in that: The highly conductive carbon framework is composed of carbon nanotubes, graphene, graphene oxide, and C. 60 The graphene contains any one or more of the following: graphdiyne, graphene quantum dots, heteroatom-doped graphene, carbon nanofibers, carbon aerogels, and carbon nanotube arrays, wherein the doping element in the heteroatom-doped graphene includes at least one of N, P, and S.

8. The preparation method according to claim 7, characterized in that: The carbon nanotubes are multi-walled carbon nanotubes and / or single-walled carbon nanotubes.

9. The preparation method according to claim 7, characterized in that: The graphene is multilayer graphene and / or single-layer graphene.

10. The preparation method according to claim 1, characterized in that: The content of highly conductive carbon material in the three-dimensional hierarchical network metal oxide / carbon composite material is 10~60wt%.

11. The preparation method according to claim 1, characterized in that, include: A highly conductive carbon framework material is dispersed in water to form the first solution, wherein the concentration of the highly conductive carbon framework material in the first solution is 0.8~2.0 mg / mL.

12. The preparation method according to claim 1, characterized in that: The mass ratio of the transition metal oxide precursor to the carbon source is 1 to 5:

1.

13. The preparation method according to claim 1, characterized in that: The mass ratio of the organic solvent to the transition metal oxide precursor and the carbon source is 20~60:

1.

14. The preparation method according to claim 1, characterized in that: The transition metal oxide precursor includes any one or a combination of two or more of vanadium, manganese, niobium, and molybdenum sources. The vanadium source includes any one or a combination of two or more of vanadate, metavanadate, pyrovanadate, and orthovanadate. The manganese source includes any one or a combination of two or more of potassium permanganate, manganese sulfate, manganese perchlorate, and manganese nitrate. The niobium source includes any one or a combination of two or more of niobium pentachloride, ammonium niobate, and niobium chlorate. The molybdenum source includes any one or a combination of two or more of sodium molybdate, cobalt molybdate, molybdenum sulfide, and molybdenum oxide.

15. The preparation method according to claim 1, characterized in that: The carbon source includes any one or a combination of two or more of the following: oxalic acid, glucose, melamine, dopamine, polydopamine, resorcinol-formaldehyde resin, polyvinylpyrrolidone, tannic acid, citric acid, polyvinyl alcohol, polypyrrole, vitamin C, polyethylene glycol, aniline, and anthracene.

16. The preparation method according to claim 15, characterized in that: When the carbon source is oxalic acid, citric acid, or tannic acid, the pH of the second solution is adjusted to 2-6.

17. The preparation method according to claim 1, characterized in that: The organic solvent includes any one or a combination of two or more of ethylene glycol, isopropanol, n-butanol, glycerol, propylene glycol, glycerol, polyethylene glycol, ethyl acetate, and acetone.

18. The preparation method according to claim 1, characterized in that, The preparation method further includes: adding a surfactant to the first solution or the second solution, wherein the surfactant includes any one or a combination of two or more of anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants; the anionic surfactant includes any one or a combination of two or more of sodium linear alkylbenzene sulfonate, sodium α-alkenyl sulfonate, and sodium dodecyl sulfate; the cationic surfactant includes any one or a combination of two or more of hexadecyl dimethyl ammonium bromide, hexadecyl trimethyl ammonium bromide, octadecyl trimethyl ammonium chloride, and dodecyl dimethyl ammonium oxide; the nonionic surfactant includes alkylolamides and / or fatty alcohol polyvinyl ethers; and the amphoteric surfactant includes dodecyl dimethyl betaine and / or carboxylate imidazoline.

19. The preparation method according to claim 1, characterized in that: The hydrothermal reaction is carried out at a temperature of 100-200℃ for 6-28 hours.

20. The preparation method according to claim 1, characterized in that, The preparation method includes: calcining the precursor material at a heating rate of 1~10 ℃ / min to 200~600 ℃ for 1~4 h in an air atmosphere to obtain the three-dimensional hierarchical network metal oxide / carbon composite material.

21. The application of the three-dimensional hierarchical network metal oxide / carbon composite material prepared by any one of claims 1-20 in the preparation of electrode materials.

22. A zinc-ion battery positive electrode, comprising a positive electrode active material, a conductive agent, and a binder, characterized in that, The positive electrode active material is a three-dimensional hierarchical network metal oxide / carbon composite material prepared by the preparation method of any one of claims 1-20.

23. A zinc-ion battery, comprising a positive electrode, a negative electrode, and an electrolyte, characterized in that: The positive electrode is the zinc-ion battery positive electrode as described in claim 22.

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