Oxygen-vacancy-rich Nb2O5 material and preparation method thereof, negative pole piece and zinc ion battery

Abstract

The invention discloses an oxygen-vacancy-rich Nb2O5 material and a preparation method thereof, a negative pole piece and a zinc ion battery, and belongs to the technical field of batteries. The preparation method comprises the following steps: S1, mixing a niobium source, quaternary ammonium base and a solvent to obtain initial gel; s2, heating the initial gel, and carrying out a reaction so as to obtain an Nb2O5 precursor; and S3, calcining the Nb2O5 precursor and hypophosphite in an inactive atmosphere to obtain the oxygen vacancy-enriched Nb2O5 material. The Nb2O5 negative electrode material for the zinc ion battery is developed for the first time, and the oxygen-vacancy-rich Nb2O5 material prepared by adopting a solvothermal and reduction dual-regulation mode has high oxygen vacancy density and good structural stability; the prepared rocking chair type battery structure avoids the problems of dendritic crystals, rusting, hydrogen precipitation and the like caused by a traditional metal zinc negative electrode, and is high in safety and long in cycle life.

Description

Technical Field

[0001] This application relates to the field of zinc battery technology, specifically to an oxygen-rich vacancy Nb2O5 material and its preparation method, a negative electrode sheet, and a zinc-ion battery. Background Technology

[0002] Zinc-ion batteries have attracted much attention due to their advantages such as fast charging, high energy density, good cycle performance, and low cost. However, most aqueous zinc-ion batteries still use metallic zinc as the negative electrode. During the charging and discharging process, zinc deposition and dissolution repeatedly occur on the surface of the zinc negative electrode, inevitably forming zinc dendrites. Zinc dendrites can easily puncture the separator, causing a short circuit. Furthermore, zinc negative electrodes in aqueous electrolytes also pose risks of side reactions such as corrosion, hydrogen evolution, and passivation, seriously affecting battery safety and shortening cycle life. In addition, the energy storage mechanism of metallic zinc negative electrodes is a conversion reaction of deposition / galvanization, while common positive electrodes are ion intercalation reactions. The different reaction mechanisms result in low utilization of active ions, limiting the improvement of battery energy density.

[0003] To address the aforementioned issues, researchers proposed the concept of a rocking chair zinc-ion battery. This battery uses a material capable of intercalating zinc ions instead of metallic zinc as the negative electrode. Energy is stored through the intercalation / deintercalation of zinc ions at both the positive and negative electrodes, fundamentally avoiding the formation of zinc dendrites. Furthermore, the rocking chair zinc-ion battery avoids the use of metal electrodes, belonging to a metal-free battery system, which helps to reduce battery costs. The key to the rocking chair zinc-ion battery lies in the preparation of a suitable intercalation-type negative electrode material to replace the zinc metal negative electrode.

[0004] Although some intercalation-type anode materials have been explored for use in zinc-ion batteries, the overall research is still in its early stages, with limited options. For example, VO2-based pre-intercalated zinc anodes require pre-intercalation of zinc ions into the material, making the manufacturing process complex. MoO3 and similar materials exhibit poor cycle stability as anodes, failing to fully meet the demands for high energy density (e.g., MoO3 anode materials have far fewer than 1000 cycles, with significant capacity decay after around 200 cycles). MoO2 anodes have low capacity, less than 100 mAh / g. Nb2O5 materials suffer from poor stability during zinc ion intercalation, resulting in poor battery cycle stability and difficulty in achieving stable charge-discharge. Furthermore, the long-term structural stability and cycle performance of these materials require further verification and improvement. While existing technologies have researched intercalation-type anode materials, they lack a matching rocking chair battery fabrication technique; after constructing the anode material, a suitable rocking chair battery construction strategy is needed to realize its application. Therefore, current technologies have not yet provided a zinc-ion battery anode solution that combines high specific capacity, excellent cycle life, and simple fabrication. Summary of the Invention

[0005] The main objective of this application is to provide an oxygen-vacancy-rich Nb2O5 material and its preparation method, a negative electrode sheet, and a zinc-ion battery, in order to solve the problems of dendrite growth and side reactions in the existing zinc anode, which lead to poor safety, poor specific capacity, and short cycle life of zinc-ion batteries.

[0006] To achieve the above objectives, according to one aspect of this application, a method for preparing oxygen-rich vacancy Nb2O5 material is provided, comprising the following steps:

[0007] Step S1: Mix the niobium source, quaternary ammonium base, and solvent to obtain the initial gel;

[0008] Step S2: The initial gel is heated and reacted to obtain the Nb2O5 precursor;

[0009] Step S3: Calcine the Nb2O5 precursor and hypophosphite in an inactive atmosphere to obtain oxygen-rich vacancy Nb2O5 material.

[0010] Further, in step S1, the weight ratio of niobium source to quaternary ammonium base is 1:(0.125-2.0); preferably 1:(0.125-1.5).

[0011] Furthermore, in step S3, the weight ratio of Nb2O5 precursor to hypophosphite is 1:(3-7); preferably 1:(3-5).

[0012] Furthermore, the hypophosphite is sodium hypophosphite and / or potassium hypophosphite.

[0013] Furthermore, in step S2, the reaction is a solvothermal reaction.

[0014] Furthermore, the conditions for the solvothermal reaction include: a reaction temperature of 150–200°C and a reaction time of 15–24 h; preferably, the reaction temperature is 170–190°C and the reaction time is 22–24 h.

[0015] Furthermore, in step S3, the calcination conditions include: a calcination temperature of 100–200°C and a calcination time of 1–2 h; preferably, the calcination temperature is 130–180°C and the calcination time is 1–1.5 h.

[0016] Further, the inactive atmosphere is argon; preferably, the flow rate of argon is 100-150 mL / min; more preferably, it is 100-130 mL / min.

[0017] Furthermore, the calcination is carried out in a tubular furnace; preferably, the hypophosphite is located at the upstream end of the tubular furnace, and the Nb2O5 precursor is located at the downstream end of the tubular furnace.

[0018] Further, in step S1, the four substituents of the quaternary ammonium ion of the quaternary ammonium base are either substituted C1-C8 straight-chain alkyl or branched-chain alkyl groups, or unsubstituted C1-C8 straight-chain alkyl or branched-chain alkyl groups.

[0019] Furthermore, the four substituents of the quaternary ammonium ion in the quaternary ammonium base are either substituted C1-C6 straight-chain alkyl or branched-chain alkyl groups, or unsubstituted C1-C6 straight-chain alkyl or branched-chain alkyl groups.

[0020] Furthermore, the quaternary ammonium base is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide.

[0021] Further, in step S1, the niobium source is selected from at least one of niobium pentachloride, niobium oxalate, ammonium niobium oxalate, niobium pentafluoride, potassium heptafluoroniobate, and sodium heptafluoroniobate; preferably at least one of niobium pentachloride, niobium oxalate, and ammonium niobium oxalate.

[0022] Furthermore, the initial gel has a pH of 9–11.

[0023] Furthermore, the solvent is a mixture of alcohol and water.

[0024] Furthermore, the quaternary ammonium base is added in the form of an aqueous solution of quaternary ammonium base; the ratio of niobium source, aqueous solution of quaternary ammonium base and solvent is (1-2)g:(1-5)mL:(50-100)mL; preferably (1-1.8)g:(1-4)mL:(50-100)mL; wherein, the concentration of the aqueous solution of quaternary ammonium base is 20-30wt%.

[0025] According to a second aspect of this application, an oxygen-rich vacancy Nb2O5 material is provided, which is prepared by the above-described preparation method.

[0026] Furthermore, the particle size of the oxygen-vacancy-rich Nb2O5 material is 100–200 nm.

[0027] According to a third aspect of this application, a negative electrode sheet is provided, comprising a negative current collector and a negative active layer attached to the surface of the negative current collector; the slurry of the negative active layer comprises a negative active material, a conductive agent, a binder, and a solvent; the negative active material is an oxygen-vacancy-rich Nb2O5 material obtained by the above preparation method or the above-mentioned oxygen-vacancy-rich Nb2O5 material.

[0028] Furthermore, the thickness of the negative electrode active layer is 60–80 μm.

[0029] Furthermore, the negative electrode current collector is titanium foil.

[0030] Furthermore, the weight ratio of the oxygen-vacancy-rich Nb2O5 material, the conductive agent, and the binder is (7-9):(1-1.5):1.

[0031] Furthermore, the solid content of the negative electrode slurry is 60–80 wt%.

[0032] Furthermore, the conductive agent is acetylene black.

[0033] Furthermore, the adhesive is polyvinylidene fluoride.

[0034] Furthermore, the solvent is N-methylpyrrolidone.

[0035] According to a fourth aspect of this application, a zinc-ion battery is provided, comprising a positive electrode, a negative electrode, a separator, and an electrolyte; the negative electrode is the aforementioned negative electrode.

[0036] Furthermore, the positive electrode sheet includes a positive current collector and a positive active layer attached to the surface of the positive current collector; the positive active layer includes a positive active material; preferably, the positive current collector is a titanium foil; the positive active material is MnO2.

[0037] Furthermore, the weight ratio of oxygen-vacancy-rich Nb2O5 material to MnO2 is (1.1–1.5):1.

[0038] Furthermore, the electrolyte is an aqueous solution of zinc sulfate.

[0039] Furthermore, the diaphragm is a glass fiber diaphragm.

[0040] Compared with the prior art, this application has the following beneficial effects:

[0041] This application is the first to develop Nb2O5 anode material for zinc-ion batteries. The oxygen-rich Nb2O5 material prepared by the solvothermal and reduction dual-regulation method has high oxygen vacancy density and good structural stability. The prepared rocking chair battery structure avoids the problems of dendrites, rusting and hydrogen evolution caused by traditional metallic zinc anodes, and has high safety and long cycle life. The overall battery system can use industrially available materials, the preparation process is simple, and it is easy to carry out large-scale preparation and application. Attached Figure Description

[0042] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0043] Figure 1 A scanning electron microscope image (SEM, magnification 50000) of the oxygen-rich vacancy Nb2O5 anode material prepared in Example 1 of this application;

[0044] Figure 2 The O1s orbital pattern shown by X-ray photoelectron spectroscopy (XPS) of the oxygen-rich vacancy Nb2O5 anode material prepared in Example 1 of this application;

[0045] Figure 3 Cyclic performance testing of the zinc-ion half-cell prepared in Example 1 of this application;

[0046] Figure 4 Cyclic performance testing of the rocking chair-type zinc-ion battery prepared in Example 2 of this application;

[0047] Figure 5 Cyclic performance testing of the zinc-ion half-cell prepared in Comparative Application Example 1 of this application;

[0048] Figure 6 Cycle performance testing of the rocking chair zinc-ion battery prepared in Comparative Application Example 2 of this application. Detailed Implementation

[0049] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present application will now be described in detail with reference to the embodiments.

[0050] As mentioned in the background technology, the zinc anode of zinc-ion batteries suffers from dendrite growth and side reactions, which leads to poor safety, poor specific capacity, and short cycle life of zinc-ion batteries. Furthermore, the novel material Nb2O5 has poor stability during zinc ion intercalation, resulting in poor battery cycle stability and difficulty in achieving stable charge and discharge.

[0051] According to a first aspect of this application, a method for preparing an oxygen-vacancy-rich Nb2O5 material is provided, comprising the following steps:

[0052] Step S1: Mix the niobium source, quaternary ammonium base, and solvent to obtain the initial gel;

[0053] Step S2: The initial gel is heated and reacted to obtain the Nb2O5 precursor;

[0054] Step S3: Calcine the Nb2O5 precursor and hypophosphite in an inactive atmosphere to obtain oxygen-rich vacancy Nb2O5 material.

[0055] This application utilizes the aforementioned quaternary ammonium base to complex with niobium ions under hydrothermal conditions to form various hydroxyl / oxygen bridge complexes, which is beneficial to the morphology and crystal phase of Nb2O5 products. For example, it synthesizes T-phase Nb2O5, which has good open ion channels and excellent rate performance, making it very suitable for use in zinc-ion batteries. In contrast, most Nb2O5 synthesized by traditional methods is in TT or H phase, which cannot be used well as Nb2O5 anode materials, let alone as a matrix for oxygen-vacancy-rich Nb2O5.

[0056] In the calcination process described in this application, the unique advantage of using hypophosphite (e.g., sodium hypophosphite NaH2PO2 and / or potassium hypophosphite KH2PO2) as a reducing agent lies in its ability to decompose and release PH3 and H2, forming a uniform and mild local reducing atmosphere on the material surface. This effectively induces the formation of oxygen vacancies without causing excessive reduction of Nb or the generation of impurity phases. Simultaneously, its byproducts (such as NaPO3) are easily washed away without introducing additional cationic impurities. This controllable and easy-to-clean characteristic is difficult to achieve simultaneously with other reducing agents, while traditional methods using hydrogen or similar reducing agents struggle to provide the aforementioned mild atmosphere.

[0057] This application addresses the poor cycle stability of Nb₂O₅ during zinc ion intercalation by introducing oxygen vacancy defects to regulate its performance, significantly improving Nb₂O₅ capacity and effectively enhancing zinc storage performance. It also solves dendrite and safety issues by designing a novel intercalation-type anode material to replace zinc metal. For the first time, a niobium pentoxide anode material for zinc-ion batteries is prepared, overcoming the limitations of alternative anode solutions. The structure of the niobium pentoxide material is optimized by introducing oxygen vacancies (point defects in metal oxide crystals where lattice sites that should be occupied by oxygen ions are vacant), addressing the poor stability of niobium pentoxide during zinc ion intercalation. Furthermore, a novel rocking chair zinc-ion battery strategy is proposed, using oxygen-vacancy-rich Nb₂O₅ as the anode, combined with a commercially available MnO₂ cathode and an appropriate electrolyte, to create a high-safety, high-performance rocking chair zinc-ion battery.

[0058] In some embodiments, in step S1, the weight ratio of the niobium source to the quaternary ammonium base is 1:(0.125 to 2.0); for example, any value or a range between any two of 1:0.125, 1:0.15, 1:0.20, 1:0.25, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:16, 1:1.7, 1:1.8, 1:1.9, and 1:2.0; another example is 1:(0.125 to 1.5). The aforementioned quaternary ammonium base is a pure solid powder. For ease of acquisition, dissolution, and mixing with other components, the quaternary ammonium base can be prepared as an aqueous solution with a concentration of 20–30 wt%, commonly 25 wt%. This concentration can be purchased commercially or prepared in-house. The ratio of niobium source, quaternary ammonium base aqueous solution, and solvent is (1–2) g:(1–5) mL:(50–100) mL; further, (1–1.8) g:(1–4) mL:(50–100) mL; even further, (1–1.5) g:(1–3) mL:(50–100) mL; and still further, (1.2–1.5) g:(2–3) mL:(50–100) mL. Controlling the ratio of niobium source and quaternary ammonium base within the above range is beneficial for controlling the crystal size, morphology, and crystallinity of Nb₂O₅ particles.

[0059] In some embodiments, the niobium source is first dispersed in a solvent to form a niobium source solution before mixing, and then a quaternary ammonium base or an aqueous solution of a quaternary ammonium base is added to the solution; wherein the solvent is a mixture of alcohol and water; for example, ethanol; the volume ratio of water to ethanol is (3-5):1; for example, 4:1.

[0060] In some embodiments, the niobium source is selected from at least one of niobium oxalate, ammonium niobium oxalate, niobium pentafluoride, potassium heptafluoroniobate, and sodium heptafluoroniobate. Niobium pentachloride, niobium oxalate, and ammonium niobium oxalate are particularly preferred; niobium pentachloride is the most effective.

[0061] In some embodiments, in step S1, the four substituents of the quaternary ammonium ion of the quaternary ammonium base are either substituted C1-C8 straight-chain alkyl or branched-chain alkyl groups, or unsubstituted C1-C8 straight-chain alkyl or branched-chain alkyl groups; further, the four substituents of the quaternary ammonium ion of the quaternary ammonium base are either substituted C1-C6 straight-chain alkyl or branched-chain alkyl groups, or unsubstituted C1-C6 straight-chain alkyl or branched-chain alkyl groups. In practical applications, the quaternary ammonium base is preferably selected from at least one of tetramethylammonium hydroxide (TMAOH), tetraethylammonium hydroxide (TEAOH), tetrapropylammonium hydroxide (TPAOH), and tetrabutylammonium hydroxide (TBAOH). The above-mentioned quaternary ammonium base can not only provide a suitable alkaline environment for the reaction system, such as adjusting the pH of the initial gel system to 9-11, for example, pH = 9.5-10.5, and further pH = 10; the above-mentioned quaternary ammonium base also has a template agent function, participating in or promoting the formation of Nb2O5 precursors with small crystallites and large specific surface area.

[0062] For the hydrothermal reaction of the initial gel described above, in addition to selecting a suitable quaternary ammonium base, niobium source, and their ratio, the temperature and time of the hydrothermal reaction also have a significant impact on the synthesis of the Nb2O5 precursor. In some embodiments, the hydrothermal reaction is carried out in a polytetrafluoroethylene-lined reactor, and the hydrothermal reaction conditions include: a reaction temperature of 150–200°C and a reaction time of 15–24 h; the reaction temperature can be any value or a range between 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C; the reaction time can be any value or a range between 15, 16, 17, 18, 19, 20, 21, 22, 23, and 24 h; for example, the hydrothermal reaction temperature is 170–190°C, and the reaction time is 22–24 h. Using the above reaction temperature helps to activate the reactants, promote the formation of Nb2O5 crystals, and avoid high-temperature side reactions; the above reaction time helps to control the crystallinity of the Nb2O5 precursor, ensuring that the material has enough time to form a stable crystal form while maintaining a small grain size.

[0063] After the above hydrothermal reaction is completed, the mixed product is filtered and separated to obtain the Nb2O5 precursor solid product, which is a niobium-containing hydroxide, hydrated oxide (Nb2O5·xH2O) or amorphous niobate gel; the not completely purified niobium pentoxide needs to be further calcined to become crystallized niobium pentoxide.

[0064] In some embodiments, the calcination is carried out in a non-reactive atmosphere such as argon in a tubular furnace; wherein, sodium hypophosphite is placed at the upstream end of the tubular furnace, and the Nb₂O₅ precursor is placed at the downstream end; the calcination temperature is set to 100–200°C, the calcination time to 1–2 h, and the argon flow rate to 100–150 mL / min. The calcination temperature can be any value or a range between 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, and 200°C; the calcination time can be any value or a range between 1, 1.5, and 2 h. The argon flow rate can be 100, 110, 120, 130, 140, or 150 mL / min. For example, the calcination temperature is 130–180℃, and the calcination time is 1–1.5 h; the argon flow rate is 100–130 mL / min; further, the calcination temperature is 140–160℃, and the calcination time is 1–1.2 h; the argon flow rate is 100–110 mL / min; even further, the calcination temperature is 145–155℃, and the calcination time is 1–1.1 h; the argon flow rate is 100–105 mL / min; still further, the calcination temperature is 150℃, and the calcination time is 1 h; the argon flow rate is 100 mL / min. This argon flow rate ensures the stability of the atmosphere protection and oxygen vacancy formation. Simultaneously, the weight ratio of Nb₂O₅ precursor to sodium hypophosphite is controlled to be 1:(3–7); for example, any value from 3:1, 4:1, 5:1, 6:1, 7:1, or any range between two; another example is 1:(3–5). Controlling the Nb₂O₅ precursor and sodium hypophosphite ratio within the aforementioned range helps promote the stable formation of oxygen vacancies in Nb₂O₅. Calcination temperature and time within this range facilitate the full reaction between the Nb₂O₅ precursor and the PH₃ gas from hypophosphite decomposition, introducing stable and sufficient oxygen vacancies into the Nb₂O₅ crystal. An inert atmosphere promotes effective contact and reaction between PH₃ gas and Nb₂O₅, and a suitable argon flow rate helps maintain the inert atmosphere within the furnace. The synergistic effect of these conditions helps optimize the microstructure of the material, including lattice parameters, grain size, specific surface area, and the number of oxygen vacancies, thereby affecting the material's electrochemical performance.

[0065] For example, sodium hypophosphite, as a reducing agent, reacts as follows:

[0066] 2Na2H2PO2·H2O (s) → PH3 (g) + Na2HPO4 (s) + 2H2O (g);

[0067] Nb₂O₅(s) + PH₃(g) → Nb₂O 5-x (s)+x / 4H3PO4(g).

[0068] According to a second aspect of this application, an oxygen-rich vacancy Nb2O5 material is obtained by the above preparation method; the material is grayish-blue, and its morphology is a blocky structure with stacked particles and a particle size of 100-200 nm.

[0069] According to a third aspect of this application, a negative electrode sheet is provided, comprising a negative electrode current collector and a negative electrode active layer attached to the surface of the negative electrode current collector; the slurry of the negative electrode active layer comprises a negative electrode active material, a conductive agent, a binder, and a solvent; the negative electrode active material is an oxygen-vacancy-rich Nb2O5 material obtained by the above preparation method or the above-mentioned oxygen-vacancy-rich Nb2O5 material. The thickness of the negative electrode active layer is 60–80 μm; the negative electrode current collector is titanium foil; the weight ratio of the oxygen-vacancy-rich Nb2O5 material, the conductive agent, and the binder is (7–9):(1–1.5):1; the solid content of the negative electrode slurry is 60–80 wt%; the conductive agent is acetylene black; the binder is polyvinylidene fluoride; and the solvent is N-methylpyrrolidone.

[0070] A specific method for preparing the aforementioned negative electrode sheet of this application includes:

[0071] Step 1: Weigh the oxygen-enriched Nb2O5 material powder, acetylene black conductive agent and PVDF binder at a mass ratio of 8:1:1, add an appropriate amount of N-methylpyrrolidone solvent, and stir to form a uniform slurry.

[0072] Step 2: Coat the obtained slurry evenly onto the titanium foil with a thickness of 70μm, dry it under vacuum at 80℃ for 10 hours, and after cooling, cut it into a 12mm diameter disc for use as the negative electrode.

[0073] In the above method, the titanium foil thickness is 10-15 μm; acetylene black with a particle size of 30-50 nm is selected to enhance conductivity; the amount of N-methylpyrrolidone solvent used is 5 mL, and the total solid mass is 1 g.

[0074] According to a fourth aspect of this application, a rocking chair type zinc-ion battery is provided, comprising a positive electrode, a negative electrode, a separator, and an electrolyte; the negative electrode is the aforementioned negative electrode.

[0075] In some embodiments, the positive electrode includes a positive current collector and a positive active layer attached to the surface of the positive current collector; the positive active layer includes a positive active material; the positive current collector is titanium foil; the positive active material is MnO2; the weight ratio of oxygen-vacancy-rich Nb2O5 material to MnO2 is (1.1-1.5):1; the electrolyte is an aqueous solution of zinc sulfate with a concentration of 1-3 mol / L and a dosage of 0.1-0.5 mL; and the separator is a glass fiber separator.

[0076] Replacement of cathode materials: Although the embodiments use MnO2 as the cathode, the rocking chair battery structure of this application is not limited to this. Other cathode materials capable of reversibly inserting / extracting zinc ions can be used in conjunction with Nb2O5 anodes, such as V2O5 and its derivatives, and Prussian Blue-type materials (such as zinc ferrocyanide). Choosing different cathode materials can achieve adjustments to the battery voltage and capacity, but all follow the rocking chair zinc intercalation energy storage principle.

[0077] Electrolyte and other component changes: The battery of this application can be adapted to electrolyte systems with different compositions, such as using other soluble zinc salts (Zn(CF3SO3)2, Zn(ClO4)2, etc.).

[0078] In the rocking chair-type zinc-ion battery provided in this application, zinc ions are deintercalated from the Nb₂O₅ negative electrode and intercalated into the MnO₂ lattice during charging; during discharging, zinc ions are released from MnO₂ and reintercalated into the Nb₂O₅ negative electrode. The entire process is an intercalation / deintercalation process, and no zinc deposition or stripping reaction occurs in the system, exhibiting a typical rocking chair operating mechanism. Therefore, zinc dendrites do not form on the surface of the battery negative electrode, giving zinc-ion batteries using this negative electrode the advantage of excellent stability. The rocking chair-type zinc-ion battery provided in this application exhibits excellent electrochemical performance; at a current density of 0.5 A / g, the battery specific capacity can reach 162 mAh / g, and after 1000 cycles, the capacity retention rate is as high as 85.6%.

[0079] The Nb2O5 anode material and the rocking chair zinc-ion battery prepared therefrom have the following advantages:

[0080] Dendrite-free for enhanced safety: Utilizing an intercalated Nb2O5 anode without metallic zinc, the generation of zinc dendrites during charging and discharging is eliminated. Therefore, the battery eliminates the risk of dendrites piercing the separator and causing short circuits, and also avoids issues such as zinc anode corrosion and passivation, resulting in significantly improved overall safety and a markedly extended cycle life.

[0081] Structural stability: Oxygen-vacancy Nb₂O₅ exhibits high theoretical capacity and excellent structural stability. The O-Nb₂O₅ anode optimized with oxygen vacancies achieves a higher actual specific capacity than zinc-intercalated anodes such as VO₂ (the anode of this application can reach over 160 mAh / g), and the material structure remains stable and does not collapse during cycling. Compared with existing intercalated anode materials such as VO₂, the anode of this invention has significant advantages in both capacity and long-term cycle stability.

[0082] Reasonable matching and long lifespan: The selected Nb2O5 negative electrode has a low and stable potential, which can form a good potential match with the MnO2 positive electrode, reducing the occurrence of side reactions. The zinc intercalation mechanism between the positive and negative electrodes is the same, and the reaction kinetics are highly coordinated, so the battery has small capacity decay during long cycles, exhibiting an ultra-long cycle life and excellent stability.

[0083] Rocking chair zinc-ion battery: This refers to a zinc-ion battery technology that uses an intercalated, reversible zinc-storing negative electrode, rather than a metallic zinc negative electrode. During charging and discharging, zinc ions shuttle back and forth between the positive and negative electrodes, intercalating and deintercalating (similar to the rocking chair principle), thus avoiding problems such as dendrite short circuits on the surface of the metallic zinc negative electrode.

[0084] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0085] The raw materials used in the embodiments of this application are all existing technologies and are commercially available.

[0086] Example 1

[0087] Step S1: Weigh 1.5g of niobium pentachloride powder and disperse it in a 70mL mixture of ethanol and water, wherein the volume ratio of water to ethanol is 8:2, and stir for 30 minutes; then add 2.5mL of 25wt% TMAOH solution to the mixture and stir continuously at 25℃ for 30 minutes. The pH of the solution system is 10.

[0088] Step S2: Transfer the solution obtained in step S1 to a 100 mL polytetrafluoroethylene-lined reactor and carry out a hydrothermal reaction at 180 °C for 24 h. After the reaction is completed, filter and separate the mixture to obtain the Nb2O5 precursor solid product.

[0089] Step S3: 1.5g of the solid product obtained in Step S2 and 6g of sodium hypophosphite powder (weight ratio 1:4) were placed separately in a quartz boat of a tube furnace, with the sodium hypophosphite at the upstream end and the solid product at the downstream end. The mixture was calcined in an argon atmosphere at 150℃ for 1 hour at an argon flow rate of 100mL / min. Calcination and reduction yielded a grayish-blue oxygen-vacancy-rich Nb₂O₅ anode material; its microstructure is as follows. Figure 1 and Figure 2 As shown.

[0090] Example 2

[0091] Step S1: Weigh 1.0 g of niobium pentachloride powder and disperse it in a 50 mL mixture of ethanol and water, wherein the volume ratio of water to ethanol is 8:2, and stir for 30 minutes; then add 1.0 mL of 25 wt% TMAOH solution to the mixture and stir continuously at 25 °C for 30 minutes. The pH of the solution system is 9.

[0092] Step S2: Transfer the solution obtained in step S1 to a 100 mL polytetrafluoroethylene-lined reactor and carry out a hydrothermal reaction at 150 °C for 15 h. After the reaction is completed, filter and separate the mixture to obtain the Nb2O5 precursor solid product.

[0093] Step S3: 0.86g of the solid product obtained in step S2 and 6g of sodium hypophosphite powder (weight ratio 1:7) are placed separately in a quartz boat of a tube furnace, with the sodium hypophosphite placed at the upstream end and the solid product at the downstream end. The mixture is calcined in an argon atmosphere at a temperature of 100℃ for 2 hours at an argon flow rate of 130mL / min. The calcination and reduction process yields a grayish-blue oxygen-vacancy-rich Nb2O5 anode material.

[0094] Example 3

[0095] Step S1: Weigh 2.0g of niobium pentachloride powder and disperse it in a 100mL mixture of ethanol and water, wherein the volume ratio of water to ethanol is 8:2, and stir for 30 minutes; then add 5.0mL of 25wt% TMAOH solution to the mixture and stir continuously at 25℃ for 30 minutes. The pH of the solution system is 11.

[0096] Step S2: Transfer the solution obtained in step S1 to a 100 mL polytetrafluoroethylene-lined reactor and carry out a hydrothermal reaction at 200 °C for 20 h. After the reaction is completed, filter and separate the mixture to obtain the Nb2O5 precursor solid product.

[0097] Step S3: 2g of the solid product obtained in step S2 and 6g of sodium hypophosphite powder (weight ratio 1:3) are placed separately in a quartz boat of a tube furnace, with the sodium hypophosphite placed at the upstream end and the solid product at the downstream end. The mixture is calcined in an argon atmosphere at a temperature of 200℃ for 1 hour at an argon flow rate of 150mL / min. The calcination and reduction process yields a grayish-blue oxygen-vacancy-rich Nb2O5 anode material.

[0098] Example 4

[0099] Example 4 differs from Example 1 in that the ratio of niobium pentachloride powder, 25wt% TMAOH solution, and ethanol / water mixed solvent in step S1 is replaced with 1.2g:2mL:75mL; the other steps are the same.

[0100] Example 5

[0101] Example 5 differs from Example 1 in that the ratio of niobium pentachloride powder, 25wt% TMAOH solution, and ethanol / water mixed solvent in step S1 is replaced with 1.8g:3mL:75mL; the other steps are the same.

[0102] Example 6

[0103] The difference between Example 6 and Example 1 is that the hydrothermal reaction temperature in step S2 is replaced with 170°C and the reaction time is 24 hours; the other steps are the same.

[0104] Example 7

[0105] The difference between Example 7 and Example 1 is that the hydrothermal reaction temperature in step S2 is replaced with 190°C and the reaction time is 22 hours; the other steps are the same.

[0106] Example 8

[0107] The difference between Example 8 and Example 1 is that the weight ratio of the solid product to sodium hypophosphite powder in step S3 is replaced with 1.2g:6g (1:5); the other steps are the same.

[0108] Example 9

[0109] The difference between Example 9 and Example 1 is that the weight ratio of the solid product to sodium hypophosphite powder in step S3 is replaced with 1g:6g (1:6); the other steps are the same.

[0110] Example 10

[0111] The difference between Example 10 and Example 1 is that the calcination temperature in step S3 is replaced with 130°C and the calcination time is 1.5h; the other steps are the same.

[0112] Example 11

[0113] The difference between Example 11 and Example 1 is that the calcination temperature in step S3 is replaced with 180°C and the calcination time is 1.2h; the other steps are the same.

[0114] Example 12

[0115] The difference between Example 12 and Example 1 is that tetramethylammonium hydroxide in step S1 is replaced with tetraethylammonium hydroxide; the other steps are the same.

[0116] Example 13

[0117] The difference between Example 13 and Example 1 is that tetramethylammonium hydroxide in step S1 is replaced with tetrapropylammonium hydroxide; the other steps are the same.

[0118] Example 14

[0119] The difference between Example 14 and Example 1 is that tetramethylammonium hydroxide in step S1 is replaced with tetrabutylammonium hydroxide; the other steps are the same.

[0120] Example 15

[0121] The difference between Example 15 and Example 1 is that niobium pentachloride in step S1 is replaced with niobium oxalate.

[0122] Example 16

[0123] The difference between Example 16 and Example 1 is that niobium pentachloride in step S1 is replaced with ammonium niobium oxalate.

[0124] Example 17

[0125] The difference between Example 17 and Example 1 is that sodium hypophosphite in step S3 is replaced with potassium hypophosphite.

[0126] Comparative Example 1

[0127] The difference between Comparative Example 1 and Example 1 is that sodium hypophosphite is not included in step S3;

[0128] Step S3 is as follows: The obtained solid product is placed in a quartz boat in a tube furnace and calcined in an argon atmosphere at a temperature of 150°C for 1 hour. The argon flow rate is 100 mL / min. The Nb2O5 anode material is obtained by calcination. Other steps are the same.

[0129] Comparative Example 2

[0130] The preparation of Nb₂O₅ anode materials using the hydrogen reduction method includes:

[0131] Procedure: Spread the dry Nb2O5 powder evenly on a quartz boat (layer thickness ≤3mm), place it in a tube furnace, purge with H2 / Ar mixed gas (10% H2) at a flow rate of 200sccm, pre-purge for 30min; raise the temperature to 320℃ at 3℃ / min, and hold for 1h; maintain the same H2 / Ar ratio throughout the process, and stop the gas flow and take samples after the furnace cools to <80℃.

[0132] Comparative Example 3

[0133] The preparation of Nb₂O₅ anode materials using a plasma surface reduction method includes:

[0134] Steps: Spread Nb2O5 thin film or powder thin layer on an inert substrate and place it in a cavity; fill with Ar or Ar / H2 (H2≤10%), cavity pressure 1.0mbar; radio frequency power 100W, process for 150min; after processing, cool and remove in inert gas or vacuum.

[0135] Comparative Example 4

[0136] The preparation of Nb₂O₅ anode materials using photo-irradiation reduction includes:

[0137] Procedure: Place the sample on a quartz substrate and insert it into an Ar-filled cavity or pump it to ≤10. -2 mbar. Deep ultraviolet: 254nm, sample temperature ≤100℃, irradiation for 60min; or pulsed light: energy density 1.0J / cm². 2 30 pulses; after processing, it is cooled with inert gas and removed.

[0138] Comparative Example 5

[0139] Nb₂O₅ anode materials were prepared using an electroreduction method, including:

[0140] The Nb₂O₅ electrode was used as the working electrode, the Pt sheet as the counter electrode, and Ag / AgCl as the reference. The electrolyte was the same as the target system (e.g., 3M ZnSO₄ aqueous solution). The electrode was polarized at a constant potential of -0.8V (vs. Ag / AgCl) for 10 min; then removed, gently washed with deionized water, and vacuum dried at 80℃ for 2 h.

[0141] Application Example 1

[0142] The oxygen-rich vacancy Nb2O5 anode materials prepared in each embodiment were used to prepare anode sheets and assembled into zinc-ion half-cells, and their performance was tested.

[0143] The zinc-ion half-cell assembly method includes the following steps:

[0144] (1) The prepared oxygen-rich vacancy Nb2O5 sample, acetylene black and PVDF were mixed in proportions of 0.8g, 0.1g and 0.1g by mass, respectively. 5mL of N-methylpyrrolidone solvent was added and stirred to form a uniform slurry. After the mixture was evenly mixed, it was coated on Ti foil current collector and dried under vacuum at 80℃ for 10 hours. After cooling, it was cut into a circular piece with a diameter of 12mm and used as a working electrode.

[0145] (2) The above working electrode and zinc foil negative electrode were used to form a button half cell in a 3M zinc sulfate aqueous solution, and the electrode performance was tested; the test results are shown in Table 1.

[0146] Application Example 2

[0147] The oxygen-rich vacancy Nb2O5 anode materials prepared in each embodiment were used to prepare anode sheets and assembled into rocking chair zinc-ion batteries, and their performance was tested.

[0148] The assembly method for a rocking chair-style zinc-ion battery includes the following steps:

[0149] (1) Using the method of Application Example 1(1), oxygen-rich vacancy Nb2O5 electrode sheets were prepared as negative electrode sheets and MnO2 positive electrode sheets (commercial MnO2, acetylene black, and PVDF in a weight ratio of 9.6g:0.1g:0.1g) and assembled in a coin cell, wherein the mass ratio of Nb2O5 to MnO2 was 1:1.2.

[0150] (2) A glass fiber separator was placed between the positive and negative electrodes, and 0.1 mL of 3 mol / L ZnSO4 aqueous solution was added to form a rocking chair zinc-ion battery; the electrochemical performance was tested, and the test results are shown in Table 1.

[0151] Comparative Application Example 1

[0152] The difference between Comparative Example 1 and Application Example 2 is that the negative electrode material is the Nb2O5 negative electrode material of Comparative Example 1.

[0153] Comparative Application Example 2

[0154] The difference between Comparative Example 2 and Comparative Example 2 is that the negative electrode material is the Nb2O5 negative electrode material of Comparative Example 1.

[0155] Test method:

[0156] (1) Battery specific capacity: under constant current charging and discharging in a voltage window of 0.2-1.8V, the specific capacity obtained by discharging is used as the standard, based on the mass of the positive electrode active material.

[0157] (2) Cycle capacity retention: Test the battery capacity; charge to 1.6V with a constant current density of 0.5A / g and discharge to 0.2V with a constant current density of 0.5A / g, which is recorded as one cycle; record the discharge specific capacity of the 1st cycle and the 1000th cycle (or the actual number of the final cycle), and use the percentage of the latter relative to the former as the cycle capacity retention.

[0158] Table 1

[0159]

[0160]

[0161] Table 1 shows that the materials prepared by the integrated process of niobium source + quaternary ammonium base template + hypophosphite mild reduction proposed in this application are generally superior to the comparative examples in terms of core indicators such as capacity and long-cycle stability, with Example 1 showing the most outstanding performance. The raw materials used are common and the cost is controllable. The process conditions are mild and the process is simple, avoiding harsh methods such as high-temperature hydrogen. It has good repeatability and is easy to scale up.

[0162] Figure 1 The Nb2O5 anode material has a morphology of stacked blocks with a particle size of 100–200 nm.

[0163] Figure 2 XPS detection conditions: Acquire O1s high-resolution (pass energy ≤ 20 eV) spectra, calibrated with C1s = 284.8 eV, Shirley background, GL mixed peak fitting; samples were dried at low temperature under vacuum before testing to remove adsorbed water / hydroxyl groups; from Figure 2 XPS analysis of oxygen shows that O1s is split into two components: lattice oxygen and defect oxygen. The defect oxygen is located on the side of the high binding energy of lattice oxygen (commonly around 531 eV). The distinguishable presence of the defect oxygen sub-peak confirms the presence of oxygen vacancies in the material. Figure 2 The O1s spectrum shown in the figure, after fitting, revealed an independent defective oxygen component, proving that the synthesized sample does indeed contain oxygen vacancies.

[0164] The performance test results of the zinc-ion half-cell assembled with the Nb2O5 anode material prepared in Example 1 are as follows: Figure 3 As shown; from Figure 3 It can be seen that the obtained half-cell can achieve a specific capacity of about 165 mAh / g at a current density of 0.5 A / g, and the capacity does not decrease significantly after 1000 cycles, indicating good stability.

[0165] The performance test results of the rocking chair zinc-ion battery assembled with the Nb2O5 anode material prepared in Example 1 are as follows: Figure 4 As shown; from Figure 4 It can be seen that the obtained rocking chair battery can achieve a specific capacity of 162 mAh / g at a current density of 0.5 A / g, and after 1000 charge-discharge cycles, the specific capacity remains at 85.6%, showing good stability and battery performance.

[0166] The performance test results of the zinc-ion half-cell assembled with the Nb2O5 anode material prepared in Comparative Example 1 are as follows: Figure 5 As shown in the figure; the cycling test data shows that, since the material obtained in Comparative Example 1 was not reduced by sodium hypophosphite, no oxygen vacancies were generated, resulting in reduced ion transport performance and significantly weaker cycling stability than the electrode in Example 1; this illustrates the importance of oxygen vacancies in the embodiments of this application.

[0167] The performance test results of the rocking chair zinc-ion battery assembled with the Nb2O5 anode material prepared in Comparative Example 1 are as follows: Figure 6 As shown, this battery achieves a specific capacity of 108 mAh / g at a current density of 0.5 A / g, which is significantly lower than that of the rocking chair zinc-ion battery in Example 1. The lack of oxygen vacancies in the negative electrode material used in Comparative Example 1 significantly reduces its battery performance, highlighting the importance of oxygen vacancies.

[0168] The batteries assembled with Nb2O5 anode materials prepared by conventional methods in Comparative Examples 2 to 5 showed significantly lower performance than the batteries assembled with Nb2O5 anode materials rich in oxygen vacancies in the embodiments of this application.

[0169] This application is the first to apply Nb2O5 to the negative electrode of a zinc-ion battery, creatively selecting Nb2O5, a transition metal oxide, as an intercalation-type zinc-ion negative electrode material.

[0170] Oxygen vacancy modulation enhances zinc intercalation performance: By introducing oxygen-vacancy-rich defect structures into Nb₂O₅ crystals through a unique material processing method, the stability of the material is significantly improved. This oxygen vacancy modulation strategy greatly improves the zinc intercalation capacity and cycle stability of Nb₂O₅, and is an important technical means to achieve high-capacity anode materials.

[0171] Rocking Chair Full Battery Structure Design: A rocking chair zinc-ion battery system was constructed, using oxygen-rich vacancy Nb₂O₅ as the negative electrode, MnO₂ as the positive electrode, and ZnSO₄ aqueous solution as the electrolyte. This design allows zinc ions to move back and forth between the positive and negative electrodes through insertion / extraction, avoiding the precipitation of metallic zinc and dendrite growth, thus achieving a full battery solution with high safety and long cycle life.

[0172] In summary, this application addresses dendrite and safety issues by designing a novel intercalation-type anode material to replace zinc metal; it also presents the first preparation of a niobium pentoxide anode material for zinc-ion batteries, overcoming the limitations of alternative anode solutions; it optimizes the structure of the niobium pentoxide material through oxygen vacancies, solving the problem of poor stability of the niobium pentoxide material during zinc ion intercalation; and it proposes a novel rocking chair zinc-ion battery design strategy, using oxygen-vacancy-rich Nb2O5 as the anode, combined with a commercially available MnO2 cathode, and a suitable electrolyte to form a high-safety, high-performance rocking chair zinc-ion battery.

[0173] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0174] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing an oxygen-vacancy-rich Nb2Os material, characterized in that, The preparation method comprises the following steps: Step S1: mixing a niobium source, a quaternary ammonium base and a solvent to obtain an initial gel; Step S2: heating and reacting the initial gel to obtain an Nb2O5 precursor; Step S3: calcining the Nb2O5 precursor and a hypophosphite in a non-active atmosphere to obtain the oxygen vacancy-rich Nb2O5 material.

2. The method of claim 1, wherein the oxygen-rich-vacancy Nb205 material is prepared by the method comprising: In the step S1, the weight ratio of the niobium source to the quaternary ammonium base is 1:(0.125-2.0); preferably 1:(0.125-1.5); In the step S3, the weight ratio of the Nb2O5 precursor to the hypophosphite is 1:(3-7); preferably 1:(3-5); The hypophosphite is sodium hypophosphite and / or potassium hypophosphite.

3. The method of claim 1 or 2, wherein the method is characterized by, In the step S2, the reaction is a solvothermal reaction. Preferably, the solvothermal reaction is carried out under the following conditions: a reaction temperature of 150-200℃ and a reaction time of 15-24h; further preferably, the reaction temperature is 170-190℃ and the reaction time is 22-24h.

4. The method of producing an oxygen-vacancy-rich Nb2Os material according to any one of claims 1 to 3, characterized by, In the step S3, the calcination is carried out under the following conditions: a calcination temperature of 100-200℃ and a calcination time of 1-2h; preferably, the calcination temperature is 130-180℃ and the calcination time is 1-1.5h. The non-active atmosphere is argon; preferably, the flow rate of the argon is 100-150mL / min; further preferably 100-130mL / min. The calcination is carried out in a tube furnace; preferably, the hypophosphite is located at the upstream end of the tube furnace and the Nb2O5 precursor is located at the downstream end of the tube furnace.

5. The method of producing an oxygen-vacancy-rich Nb2Os material according to any one of claims 1 to 4, characterized by, In the step S1, the four substituents of the quaternary ammonium ion of the quaternary ammonium base are substituted C1-C8 linear or branched alkyl groups or unsubstituted C1-C8 linear or branched alkyl groups; Preferably, the four substituents of the quaternary ammonium ion of the quaternary ammonium base are substituted C1-C6 linear or branched alkyl groups or unsubstituted C1-C6 linear or branched alkyl groups; Further preferably, the quaternary ammonium base is selected from at least one of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide.

6. The method of producing an oxygen-vacancy-rich Nb2Os material according to any one of claims 1 to 5, characterized by, In the step S1, the niobium source is selected from at least one of niobium pentachloride, niobium oxalate, ammonium niobium oxalate, niobium pentafluoride, potassium heptafluoro-niobate and sodium heptafluoro-niobate; preferably at least one of niobium pentachloride, niobium oxalate and ammonium niobium oxalate; The pH of the initial gel is 9-11; The solvent is a mixture of alcohol and water; Preferably, the quaternary ammonium base is added in the form of a quaternary ammonium base aqueous solution; the ratio of the niobium source, the quaternary ammonium base aqueous solution and the solvent is (1-2)g:(1-5)mL:(50-100)mL; further preferably (1-1.8)g:(1-4)mL:(50-100)mL; wherein the concentration of the quaternary ammonium base aqueous solution is 20-30wt%.

7. An oxygen-vacancy-rich Nb2Os material, characterized in that, The oxygen-vacancy-rich Nb2O5 material is prepared by the preparation method of the oxygen-vacancy-rich Nb2O5 material in any one of claims 1 to 6. Preferably, the particle size of the oxygen-vacancy-rich Nb2O5 material is 100-200 nm.

8. A negative electrode sheet comprising a negative electrode current collector and a negative electrode active layer attached to a surface of the negative electrode current collector; a slurry of the negative electrode active layer comprising a negative electrode active material, a conductive agent, a binder, and a solvent; characterized in that, The negative electrode active material is the oxygen-vacancy-rich Nb2O5 material prepared by the preparation method in any one of claims 1 to 6 or the oxygen-vacancy-rich Nb2O5 material in claim 7.

9. The negative electrode sheet according to claim 8, characterized by, The thickness of the negative electrode active layer is 60-80 μm. Preferably, the negative electrode current collector is a titanium foil. Preferably, the weight ratio of the oxygen-vacancy-rich Nb2O5 material, the conductive agent and the binder is (7-9): (1-3): (0.1-0.3). (1～1.5):1； Preferably, the solid content of the negative electrode slurry is 60-80 wt%. Preferably, the conductive agent is acetylene black. Preferably, the binder is polyvinylidene fluoride. Preferably, the solvent is N-methyl pyrrolidone.

10. A zinc-ion battery comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte; characterized in that, The negative electrode tab is the negative electrode tab in claim 8 or 9. Preferably, the positive electrode tab comprises a positive electrode current collector and a positive electrode active layer attached to the surface of the positive electrode current collector; the positive electrode active layer comprises a positive electrode active material; further preferably, the positive electrode current collector is a titanium foil; and the positive electrode active material is MnO2. Preferably, the weight ratio of the oxygen-vacancy-rich Nb2O5 material and the MnO2 is (1.1-1.5):

1. Preferably, the electrolyte is an aqueous zinc sulfate solution. Preferably, the separator is a glass fiber separator.

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