Aqueous composite electrolyte, zinc ion battery and preparation method of zinc ion battery

Abstract

The invention discloses a composite electrolyte for an aqueous zinc ion battery and application of the composite electrolyte, and belongs to the technical field of electrochemical energy storage. The composite electrolyte comprises water, zinc salt and a composite additive; the composite additive includes group III metal ions as a first additive and group V metallate ions as a second additive. The invention also provides a group III metal cation doped vanadium oxide positive electrode material matched with the first additive element in the electrolyte. The composite electrolyte provided by the invention is combined with a correspondingly doped positive electrode material, so that the composite electrolyte can synergistically act on positive and negative electrode interfaces of the battery: V-group metal acid radical ions preferentially regulate and control a zinc negative electrode interface, guide zinc to be uniformly deposited and inhibit side reaction; group III metal ions are mainly used for stabilizing the bulk phase and interface structure of the positive electrode material and inhibiting the dissolution of active substances. According to the technical scheme, the rate capability, the cycling stability and the service life of the water-based zinc ion battery are remarkably improved, and the water-based zinc ion battery has important application value.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy storage technology, specifically to a composite electrolyte for aqueous zinc-ion batteries, and a battery system comprising the composite electrolyte. Background Technology

[0002] Rechargeable aqueous zinc-ion batteries have shown great promise for large-scale energy storage due to their high safety, low cost, and environmental friendliness. However, their commercialization is mainly limited by two factors: 1) Zinc anodes are prone to dendrite growth, hydrogen evolution reaction, and surface passivation during cycling, leading to rapid capacity decay and shortened cycle life; 2) High-capacity vanadium-based oxide cathodes (such as VO2) suffer from structural instability and active material dissolution, which also limit the overall performance of the battery.

[0003] To improve the stability of zinc anodes, existing technologies typically employ electrolyte additive strategies, such as introducing Li... + Na + Metal cations, such as cations, are used to guide the uniform deposition of zinc through their electrostatic shielding effect. However, this strategy has shown inconsistent results and a complex mechanism, with traditional descriptors (such as cation valence state and water exchange rate constant) often contradicting each other in predicting and explaining the performance of different additives. More importantly, most of these studies focus on the improvement of the anode by a single type of additive (mostly cations), lacking a systematic approach.

[0004] To address the issue of cathode instability, bulk doping (such as Zn) is used. 2+ Mg 2+ Doping with VO2 is one of the effective strategies. However, existing technologies often treat electrolyte additives and cathode material modification as two separate steps. How to systematically combine and functionalize these two processes so that different components in the electrolyte can act differently and synergistically at the cathode and anode interfaces, thereby simultaneously solving the stability problems at both ends, is still lacking in-depth research and effective technical solutions.

[0005] Therefore, there is an urgent need in this field to develop a novel electrolyte system and supporting battery technology with a clear design concept that can synergistically stabilize zinc anode and vanadium-based cathode. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a composite electrolyte that can synergistically improve the reversibility of zinc anode deposition and the structural stability of vanadium-based cathode, a matching cathode material, and an aqueous zinc-ion battery with excellent comprehensive performance.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a composite electrolyte for an aqueous zinc-ion battery, comprising a zinc salt, water, and a composite additive; the composite additive comprises a first additive and a second additive. The first additive is a group III metal ion selected from at least one of aluminum (Al), gallium (Ga), indium (In), scandium (Sc), yttrium (Y), lanthanum (La), samarium (Sm), and ytterbium (Yb).

[0008] The second additive is a group V metal anion, selected from antimony ions (SbO3). ˉ ), bismuthate (BiO3) ˉ ), vanadate (VO3) ˉ / VO4 3- ), niobate (NbO3) ˉ ) and tantalate (TaO3) ˉ At least one of the following.

[0009] This invention creatively proposes a design concept for functionalized ion classification and synergy: The second additive (Group V anions) preferentially acts on the negative electrode interface. Due to their larger ionic radius and specific geometry, these polyatomic anionic groups can more strongly and selectively adsorb onto active growth sites (such as dendrite tips) on the zinc negative electrode surface. Through steric hindrance and alteration of the local electric field distribution, they effectively guide Zn... 2+ Ions deposit in flatter regions, thereby significantly suppressing dendrite growth and reducing side reactions such as hydrogen evolution.

[0010] The primary additives (Group III metal ions) mainly function at the cathode interface. On one hand, they can be pre-doped into the lattice of vanadium-based oxides (such as VO2) as structural stabilizers, enhancing the metal-oxygen bond strength and introducing beneficial defects (such as oxygen vacancies), thereby stabilizing the bulk structure of the cathode material and promoting Zn production. 2+ On the other hand, the Group III metal ions remaining in the electrolyte can dynamically adsorb onto the surface of the cathode material during cycling, forming a protective layer and further inhibiting the dissolution of vanadium. Simultaneously, these Group III metal cations can also utilize their electrostatic shielding effect to guide the uniform deposition of zinc, further suppressing dendrite growth.

[0011] When this composite electrolyte is used in conjunction with vanadium oxide cathode materials pre-doped with the same group III metal ions, it can achieve a multi-level stabilization effect from "bulk phase doping stabilization" to "cathode interface adsorption protection", and then through electrolyte conduction, it can synergistically optimize "negative interface induced deposition", thus constructing a highly synergistic and functionally defined complete stabilization system.

[0012] Preferably, the group III metal ion is Al. 3+or In 3+ The group V metal anion is SbO3. - or BiO3 ˉ .

[0013] Preferably, the zinc salt is zinc sulfate, zinc trifluoromethanesulfonate, zinc perchlorate, or zinc acetate, and its concentration in the electrolyte is 1 M to 4 M.

[0014] Preferably, the concentration of the first additive in the electrolyte is from 0.01 mM to 100 mM; and the concentration of the second additive in the electrolyte is from 0.1 mM to 50 mM.

[0015] Secondly, the present invention provides an electrode material, which is a vanadium oxide doped with the same Group III metal cation as the first additive in the electrolyte, preferably vanadium dioxide (VO2). The atomic doping concentration (III / (III+V)) of the doped Group III metal cation in the vanadium oxide is from 0.1 at.% to 5.0 at.%. Within this range, it can effectively stabilize the crystal lattice, introduce an appropriate amount of active defects, and avoid excessively damaging the intrinsic electrochemical properties of the host material.

[0016] Thirdly, the present invention provides an aqueous zinc-ion battery comprising a positive electrode, a negative electrode, a separator, and a composite electrolyte as described above; the positive electrode comprises a vanadium oxide electrode material doped with a group III metal cation as described above.

[0017] Furthermore, the negative electrode is metallic zinc (Zn) or a zinc alloy. More preferably, the surface of the negative electrode is provided with a zinc fluoride (ZnF2) modification layer, the thickness of which is 5 nm to 100 nm. This artificial interface layer can produce a stronger synergistic effect with the second additive in the electrolyte, providing a superior negative electrode protection effect.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Pioneering functional synergistic design: Breaking through the traditional single-type additive approach (especially relying solely on cations), a composite additive design paradigm of “Group III metal cations (mainly stabilizing the positive electrode) + Group V metal anions (mainly attracting the negative electrode)” was proposed, achieving a targeted synergistic solution to the positive and negative electrode interface problem.

[0019] (2) Significantly improved electrochemical performance: The zinc-ion battery constructed using the above synergistic system exhibits high specific capacity, excellent rate performance, and ultra-long cycle life. The full cell of the optimal embodiment achieves a cycle life of 10 A g. -1 After cycling more than 10,000 times at high rates, the capacity retention rate can still reach about 70%.

[0020] (3) Provides rational design guidance: The classification and functional matching ideas based on element groups provided by this invention provide a clear and operable theoretical framework for the rational design and high-throughput screening of electrolytes and electrode materials for aqueous batteries.

[0021] (4) Mature and easy to implement: The processes involved, such as electrolyte preparation, hydrothermal doping of positive electrode material, and physical coating of negative electrode surface, are all mature technologies with mild conditions, making them easy to scale up and apply. Attached Figure Description

[0022] Figure 1 Comparative Example 1 and Example 3 (In only) 3+ Example 21 (In) 3+ +SbO3 ˉ +In-VO2) and Example 27 (In 3+ +SbO3 ˉ A Zn||Zn symmetric cell assembled with (+In-VO2+ZnF2 / Zn) at 1 mA cm⁻¹ -2 Comparison of cycle life under current density.

[0023] Figure 2 Zn||In-VO2 full cells assembled for Comparative Example 1 (basic system) and Example 27 (optimal system) at 10 A g -1 Comparison of long-cycle performance under current density.

[0024] Figure 3 This is a SEM image of the zinc anode surface after cycling in Comparative Example 1 (basic system).

[0025] Figure 4 This is a SEM image of the zinc anode surface after cycling in Example 27 (optimal system). Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to all the embodiments and comparative examples listed in the appendices (Tables 1 and 2). It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0028] 1) General preparation method of composite electrolyte for each example and comparative example: A 2M soluble zinc salt aqueous solution (comparative examples 2, 3, and 4 in Table 2 use other zinc salts, while other comparative examples and examples use ZnSO4) is used as the base electrolyte. According to the formulations in Tables 1 and 2 below, accurately weigh the corresponding mass of the first additive (a group III metal soluble salt, unless otherwise specified, is a sulfate, such as Al2(SO4)3, In2(SO4)3, Sc2(SO4)3, etc.) and the second additive (unless otherwise specified, is a group V metal anion sodium salt, such as NaSbO3, NaBiO3, etc.), and add them to the base electrolyte. Stir magnetically and ultrasonically disperse at room temperature for 1 hour until all additives are uniformly dispersed, thus obtaining the aqueous composite electrolyte. The concentration of the first additive is controlled in the range of 0.01 mM to 100 mM, and the concentration of the second additive is controlled in the range of 0.1 mM to 50 mM. In the examples, the preferred concentrations are 10 mM and 5 mM, respectively.

[0029] 2). General preparation method of cathode materials in various embodiments and comparative examples (taking group III metal doped VO2 as an example): Hydrothermal method is used. 0.2 g V2O5 powder is dispersed in 25 mL of anhydrous ethanol and ultrasonically treated for 30 minutes to form a uniform suspension (solution A). According to the target doping concentration (atomic ratio III / (III+V) of 0.1% to 5.0%), the corresponding amount of group III metal nitrate (such as Al(NO3)3·9H2O, In(NO3)3·xH2O, or Sc(NO3)3·xH2O, etc.) is weighed and dissolved in 10 mL of deionized water (solution B). Under vigorous stirring, solution B is slowly added dropwise to solution A, and stirring is continued for 30 minutes to mix evenly. Then the mixture is transferred to a 50 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene, sealed, and placed in an oven to react at 160°C for 24 hours. After the reaction is completed, it is naturally cooled to room temperature, the obtained precipitate is centrifuged, and washed three times each with deionized water and anhydrous ethanol. Finally, the product was dried in a vacuum drying oven at 70°C for 12 hours, and then ground to obtain the corresponding Group III metal-doped VO2 powder (denoted as M-VO2, such as Al-VO2). The preparation method for undoped pure VO2 is the same, but without the addition of any metal nitrates.

[0030] 3) General treatment method for the negative electrode in each embodiment and comparative example (ZnF2 coating preparation): For embodiments requiring a ZnF2 coating, radio frequency magnetron sputtering was used. Commercial zinc foil (0.1 mm thick) was cut, cleaned, and dried as a substrate. High-purity zinc fluoride (ZnF2) was used as the target material, and the working pressure was set to 2.0 Pa under an argon (Ar) atmosphere. At room temperature, the radio frequency power supply was turned on, and sputtering was performed on the zinc foil surface for 5 minutes to obtain a dense and uniform ZnF2 film. By controlling the sputtering time, the film thickness could be controlled within the range of 5 nm to 100 nm; in the embodiments, a thickness of approximately 20 nm was preferred. The Zn negative electrode containing the ZnF2 coating is designated as ZnF2 / Zn.

[0031] 4) General battery assembly method for each embodiment and comparative example: The above-prepared positive electrode active material, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) binder are mixed evenly in N-methylpyrrolidone (NMP) solvent at a mass ratio of 7:2:1 to form a slurry. This slurry is coated onto a current collector (titanium foil is used unless otherwise specified), vacuum dried at 80°C for 10 hours, and then rolled and punched into discs with a diameter of 12 mm (active material loading of approximately 1.5 mg cm⁻¹). -2 Using unmodified zinc foil or ZnF2-modified zinc foil as the negative electrode, glass fiber (Whatman GF / D) as the separator, and injecting an appropriate amount of corresponding electrolyte, CR2032 coin cells were assembled in air and sealed using a sealing machine. All cells were allowed to stand for 10 hours after assembly before testing.

[0032] Table 1 Example electrolytes First Additive Second additive positive electrode negative electrode Specific capacity Cycle life (70% retention) Example 1 Zinc sulfate <![CDATA[Al 3+ ]]> / <![CDATA[VO2]]> Zn foil ~350 ~800 Example 2 Zinc sulfate <![CDATA[Ga 3+ ]]> / <![CDATA[VO2]]> Zn foil ~345 ~750 Example 3 Zinc sulfate <![CDATA[In 3+ ]]> / <![CDATA[VO2]]> Zn foil ~360 ~1200 Example 4 Zinc sulfate <![CDATA[Sc 3+ ]]> / <![CDATA[VO2]]> Zn foil ~355 ~900 Example 5 Zinc sulfate <![CDATA[Y 3+ ]]> / <![CDATA[VO2]]> Zn foil ~350 ~850 Example 6 Zinc sulfate <![CDATA[La 3+ ]]> / <![CDATA[VO2]]> Zn foil ~348 ~800 Example 7 Zinc sulfate <![CDATA[Sm 3+ ]]> / <![CDATA[VO2]]> Zn foil ~345 ~780 Example 8 Zinc sulfate <![CDATA[Yb 3+ ]]> / <![CDATA[VO2]]> Zn foil ~342 ~750 Example 9 Zinc sulfate / <![CDATA[SbO3 ˉ ]]> <![CDATA[VO2]]> Zn foil ~365 ~1500 Example 10 Zinc sulfate / <![CDATA[BiO3 ˉ ]]> <![CDATA[VO2]]> Zn foil ~360 ~1400 Example 11 Zinc sulfate / <![CDATA[VO3 ˉ / VO4 3- ]]> <![CDATA[VO2]]> Zn foil ~340 ~1000 Example 12 Zinc sulfate / <![CDATA[NbO3 ˉ ]]> <![CDATA[VO2]]> Zn foil ~338 ~950 Example 13 Zinc sulfate / <![CDATA[TaO3 ˉ ]]> <![CDATA[VO2]]> Zn foil ~335 ~900 Example 14 Zinc sulfate <![CDATA[Al 3+ ]]> <![CDATA[SbO3 ˉ ]]> <![CDATA[VO2]]> Zn foil ~390 ~3000 Example 15 Zinc sulfate <![CDATA[In 3+ ]]> <![CDATA[SbO3 ˉ ]]> <![CDATA[VO2]]> Zn foil ~400 ~3500 Example 16 Zinc sulfate <![CDATA[Sc 3+ ]]> <![CDATA[SbO3 ˉ ]]> <![CDATA[VO2]]> Zn foil ~385 ~2800 Example 17 Zinc sulfate <![CDATA[Al 3+ ]]> <![CDATA[BiO3 ˉ ]]> <![CDATA[VO2]]> Zn foil ~388 ~2900 Example 18 Zinc sulfate <![CDATA[In 3+ ]]> <![CDATA[BiO3 ˉ ]]> <![CDATA[VO2]]> Zn foil ~395 ~3200 Example 19 Zinc sulfate <![CDATA[Sc 3+ ]]> <![CDATA[BiO3 ˉ ]]> <![CDATA[VO2]]> Zn foil ~382 ~2700 Example 20 Zinc sulfate <![CDATA[Al 3+ ]]> <![CDATA[SbO3 ˉ ]]> <![CDATA[Al-VO2]]> Zn foil ~425 ~6000 Example 21 Zinc sulfate <![CDATA[In 3+ ]]> <![CDATA[SbO3 ˉ ]]> <![CDATA[In-VO2]]> Zn foil ~430 ~6500 Example 22 Zinc sulfate <![CDATA[Sc 3+ ]]> <![CDATA[SbO3 ˉ ]]> <![CDATA[Sc-VO2]]> Zn foil ~418 ~5500 Example 23 Zinc sulfate <![CDATA[Al 3+ ]]> <![CDATA[BiO3 ˉ ]]> <![CDATA[Al-VO2]]> Zn foil ~422 ~6200 Example 24 Zinc sulfate <![CDATA[In 3+ ]]> <![CDATA[BiO3 ˉ ]]> <![CDATA[In-VO2]]> Zn foil ~428 ~6500 Example 25 Zinc sulfate <![CDATA[Sc 3+ ]]> <![CDATA[BiO3 ˉ ]]> <![CDATA[Sc-VO2]]> Zn foil ~415 ~5200 Example 26 Zinc sulfate <![CDATA[Al 3+ ]]> <![CDATA[SbO3 ˉ ]]> <![CDATA[Al-VO2]]> <![CDATA[ZnF2 / Zn foil]]> ~448 ~9500 Example 27 Zinc sulfate <![CDATA[In 3+ ]]> <![CDATA[SbO3 ˉ ]]> <![CDATA[In-VO2]]> <![CDATA[ZnF2 / Zn foil]]> ~452 >10000 Example 28 Zinc sulfate <![CDATA[Sc 3+ ]]> <![CDATA[SbO3 ˉ ]]> <![CDATA[Sc-VO2]]> <![CDATA[ZnF2 / Zn foil]]> ~440 ~9000 Example 29 Zinc sulfate <![CDATA[Al 3+ ]]> <![CDATA[BiO3 ˉ ]]> <![CDATA[Al-VO2]]> <![CDATA[ZnF2 / Zn foil]]> ~445 ~8500 Example 30 Zinc sulfate <![CDATA[In 3+ ]]> <![CDATA[BiO3 ˉ ]]> <![CDATA[In-VO2]]> <![CDATA[ZnF2 / Zn foil]]> ~450 ~9200 Example 31 Zinc sulfate <![CDATA[Sc 3+ ]]> <![CDATA[BiO3 ˉ ]]> <![CDATA[Sc-VO2]]> <![CDATA[ZnF2 / Zn foil]]> ~438 ~8800 Table 2 Comparative Example electrolytes First Additive Second additive positive electrode negative electrode Specific capacity Cycle life (70% retention) Comparative Example 1 Zinc sulfate / / <![CDATA[VO2]]> Zn foil 300-330 <700 Comparative Example 2 Zinc trifluoromethylsulfonate / / <![CDATA[VO2]]> Zn foil 280-310 <800 Comparative Example 3 Zinc perchlorate / / <![CDATA[VO2]]> Zn foil 290-320 <600 Comparative Example 4 Zinc acetate / / <![CDATA[VO2]]> Zn foil 250-280 <400 Comparative Example 5 Zinc sulfate / / <![CDATA[V2O5]]> Zn foil 260-290 <300 Comparative Example 6 Zinc sulfate / / <![CDATA[MnO2]]> Zn foil 240-270 <600 Comparative Example 7 Zinc sulfate / / <![CDATA[VO2]]> Zn powder 290-320 <400 Comparative Example 8 Zinc sulfate / / <![CDATA[VO2]]> Zn-Sn alloy powder 295-325 <450 Based on the above preparation method description and Tables 1 and 2 above, the electrolytes, positive and negative electrodes, and battery assembly of each embodiment and comparative example will be further described below.

[0033] Table 1 shows the main process parameters and key electrochemical performance indicators of Examples 1-31, with Example 27 being the optimal system among the examples. Table 2 shows the main process parameters and key electrochemical performance indicators of Comparative Examples 1-8, with Comparative Example 1 as the basic system.

[0034] Electrolyte: Add Al to a 2M ZnSO4 base solution 3+ As the first additive, its concentration was set at 10 mM (added in the form of Al2(SO4)3). No second additive was added.

[0035] Positive electrode: Undoped pure VO2 material.

[0036] Negative electrode: Ordinary zinc foil.

[0037] Battery assembly: Assembled using standard methods.

[0038] Example 2: The only difference from Example 1 is that the first additive is Ga. 3+ (Added in the form of Ga2(SO4)3).

[0039] Example 3: The only difference from Example 1 is that the first additive is In. 3+ (Added in the form of In2(SO4)3).

[0040] Example 4: The only difference from Example 1 is that the first additive is Sc. 3+ (Added in the form of Sc2(SO4)3).

[0041] Example 5: The only difference from Example 1 is that the first additive is Y. 3+ (Added in the form of Y2(SO4)3).

[0042] Example 6: The only difference from Example 1 is that the first additive is La. 3+ (Added in the form of La2(SO4)3).

[0043] Example 7: The only difference from Example 1 is that the first additive is Sm 3+ (Added in the form of Sm2(SO4)3).

[0044] Example 8: The only difference from Example 1 is that the first additive is Yb. 3+ (Added in the form of Yb2(SO4)3).

[0045] Example 9: Electrolyte: Add SbO3 to a 2M ZnSO4 base solution - As a second additive, its concentration is set to 5 mM (added in the form of NaSbO3). The first additive is not added.

[0046] Positive electrode: Undoped pure VO2 material.

[0047] Negative electrode: Ordinary zinc foil.

[0048] Battery assembly: Assembled using standard methods.

[0049] Example 10: The only difference from Example 9 is that the second additive is BiO3. ˉ (Added in the form of NaBiO3).

[0050] Example 11: The only difference from Example 9 is that the second additive is VO3. ˉ / VO4 3- (Added in the form of Na3VO4).

[0051] Example 12: The only difference from Example 9 is that the second additive is NbO3. ˉ (Added in the form of NaNbO3).

[0052] Example 13: The only difference from Example 9 is that the second additive is TaO3. ˉ (Added in the form of NaTaO3).

[0053] Example 14: Electrolyte: Al was added simultaneously to a 2M ZnSO4 base solution. 3+ (10 mM) as the first additive and SbO3 - (5 mM) was used as a second additive.

[0054] Positive electrode: Undoped pure VO2 material.

[0055] Negative electrode: Ordinary zinc foil.

[0056] Battery assembly: Assembled using standard methods.

[0057] Example 15: The only difference from Example 14 is that the first additive is In. 3+ .

[0058] Example 16: The only difference from Example 14 is that the first additive is Sc. 3+ .

[0059] Example 17: The only difference from Example 14 is that the second additive is BiO3. ˉ .

[0060] Example 18: The difference from Example 14 is that the first additive is In. 3+ The second additive is BiO3. ˉ .

[0061] Example 19: The difference from Example 14 is that the first additive is Sc.3+ The second additive is BiO3. ˉ .

[0062] Example 20: Electrolyte: Same as in Example 14 (containing Al) 3+ and SbO3 ˉ ).

[0063] Positive electrode: using the same Al as the first additive in the electrolyte. 3+ The doped VO2 material (Al-VO2) has a doping concentration of approximately 1.5 at.%.

[0064] Negative electrode: Ordinary zinc foil.

[0065] Battery assembly: Assembled using standard methods.

[0066] Example 21: The difference from Example 20 is that the first additive in the electrolyte is In. 3+ , is extremely In 3+ Doped VO2 (In-VO2).

[0067] Example 22: The difference from Example 20 is that the first additive in the electrolyte is Sc. 3+ , positively Sc 3+ Doped VO2 (Sc-VO2).

[0068] Example 23: Electrolyte: Same as in Example 17 (containing Al) 3+ and BiO3 ˉ ).

[0069] Anode: Al-VO2 (doping concentration approximately 1.5 at.%).

[0070] Negative electrode: Ordinary zinc foil.

[0071] Battery assembly: Assembled using standard methods.

[0072] Example 24: The difference from Example 23 is that the first additive in the electrolyte is In. 3+ , is positively In-VO2.

[0073] Example 25: The difference from Example 23 is that the first additive in the electrolyte is Sc. 3+ The positive pole is Sc-VO2.

[0074] Example 26: Electrolyte: Same as in Example 14 (containing Al) 3+and SbO3 ˉ ).

[0075] Anode: Al-VO2 (doping concentration approximately 1.5 at.%).

[0076] Negative electrode: A ZnF2 coating with a thickness of about 20 nm was deposited on the zinc foil surface using a common method.

[0077] Battery assembly: Assembled using standard methods.

[0078] Example 27: The difference from Example 26 is that the first additive in the electrolyte is In. 3+ , is positively In-VO2.

[0079] Example 28: The difference from Example 26 is that the first additive in the electrolyte is Sc. 3+ The positive pole is Sc-VO2.

[0080] Example 29: Electrolyte: Same as in Example 17 (containing Al) 3+ and BiO3 ˉ ).

[0081] Anode: Al-VO2 (doping concentration approximately 1.5 at.%).

[0082] Negative electrode: A ZnF2 coating with a thickness of about 20 nm was deposited on the zinc foil surface using a common method.

[0083] Battery assembly: Assembled using standard methods.

[0084] Example 30: The difference from Example 29 is that the first additive in the electrolyte is In. 3+ , is positively In-VO2.

[0085] Example 31: The difference from Example 29 is that the first additive in the electrolyte is Sc. 3+ The positive pole is Sc-VO2.

[0086] Electrolyte: 2M ZnSO4 aqueous solution, without any first or second additives.

[0087] Positive electrode: Undoped pure VO2 material.

[0088] Negative electrode: Ordinary zinc foil.

[0089] Battery assembly: Assembled using standard methods.

[0090] Comparative Example 2: The only difference from Comparative Example 1 is that the electrolyte is a 2M aqueous solution of zinc trifluoromethanesulfonate (Zn(OTf)2).

[0091] Comparative Example 3: The only difference from Comparative Example 1 is that the electrolyte is a 2M aqueous solution of zinc perchlorate (Zn(ClO4)2).

[0092] Comparative Example 4: The only difference from Comparative Example 1 is that the electrolyte is a 2M aqueous solution of zinc acetate (Zn(Ac)2).

[0093] Comparative Example 5: The only difference from Comparative Example 1 is that the positive electrode active material is V2O5.

[0094] Comparative Example 6: The only difference from Comparative Example 1 is that the positive electrode active material is δ-MnO2.

[0095] Comparative Example 7: The only difference from Comparative Example 1 is that the negative electrode is an electrode sheet pressed from zinc powder.

[0096] Comparative Example 8: The only difference from Comparative Example 1 is that the negative electrode is a Zn-Sn alloy foil.

[0097] Symmetrical battery cycle stability test: Figure 1 The Zn||Zn symmetric cell system, which exhibits some key features, was demonstrated at 1 mAcm. -2 The long-cycle performance is shown. It can be seen that, compared to Comparative Example 1 (no additives) and Example 3 (only In), the performance is significantly better. 3+ ) to Example 21 (In 3+ +SbO3 ˉ +In-VO2), the cycle life and voltage stability of the battery are gradually improved. The optimal example 27 (In 3+ +SbO3 ˉ The +In-VO2+ZnF2 / Zn) exhibits extremely good stability, maintaining a very low polarization voltage even after cycling for more than 4000 hours, demonstrating the excellent zinc deposition / dissolution reversibility brought about by the synergy between the composite additive and the modified electrode.

[0098] Full battery long-cycle performance test: Figure 2 A comparison was made between the full cells of Comparative Example 1 (basic 2M ZnSO4 electrolyte + pure VO2 cathode + bare zinc anode) and Example 27 (optimal system) at 10 A g. -1 Cycling performance at high rates. The battery in Example 27 has an initial specific capacity of up to 452 mAh g⁻¹. -1Furthermore, after 10,000 cycles, the capacity retention rate remains at approximately 70%, with an extremely low decay rate. In contrast, the battery in Comparative Example 1 experiences rapid capacity decay and a short cycle life. This fully demonstrates that the composite electrolyte system of this invention, together with the matched positive and negative electrode materials, can significantly improve the long-term cycle stability of the full battery.

[0099] Negative electrode deposition morphology analysis: The morphology of the zinc negative electrode after cycling was observed using scanning electron microscopy (SEM). For example... Figure 3 As shown, in Comparative Example 1, the zinc anode surface exhibits a large number of loose, sharp dendrites and "dead zinc." In stark contrast, Figure 4 The zinc anode surface deposit of Example 27 is dense and flat, exhibiting a regular lamellar stacked structure with almost no dendrite formation. This directly demonstrates the significant effect of the composite electrolyte (especially the second additive) and ZnF2 coating of the present invention on guiding uniform zinc deposition and inhibiting dendrite growth.

[0100] Parameter Optimization Range and Mechanism Explanation: The extensive example data in Table 1 demonstrate that the technical effects of this invention are robust and excellent within the specified parameter range (first additive concentration 0.01-100 mM, second additive concentration 0.1-50 mM, positive electrode doping concentration 0.1-5.0 at.%, ZnF2 thickness 5-100 nm). This range was obtained through systematic experimental optimization: 1) If the additive concentration is too low, an effective adsorption layer cannot be formed at the electrode / electrolyte interface, or the required doping level cannot be achieved, resulting in insufficient stabilization. 2) If the additive concentration is too high, it may lead to a decrease in ionic conductivity, an increase in interfacial impedance, or excessive doping may damage the main crystal structure of the positive electrode material, thereby impairing electrochemical performance. 3) If the ZnF2 layer is too thin, its protective effect is limited; if it is too thick, it will severely hinder the growth of Zn. 2+ The transmission of these parameters leads to increased battery polarization and decreased rate performance. Therefore, the aforementioned parameter range is a key window for achieving the optimal synergistic effect of this invention.

[0101] In summary, this invention, through careful design and combination of group III metal cations and group V metal anions with specific functions as composite additives, and matching with corresponding positive electrode doping materials and negative electrode interface modifications, successfully constructed a multi-level synergistically stable high-performance aqueous zinc-ion battery system, providing an efficient and feasible solution to the long-standing stability bottleneck in this field.

[0102] It should be particularly noted that the present invention includes an aqueous composite electrolyte (containing a first additive and / or a second additive), a positive electrode material (mainly a doped positive electrode), and a negative electrode material (including a modified negative electrode), etc., and the above arrangements and combinations are diverse and not limited to those described in the embodiments. For example, the first additive may be Al. 3+The cathode material can also achieve similar or near-similar effects by using VO2 doped with In or Sc.

[0103] Although the above embodiments have described the present invention in detail, the scope of protection of the present invention is not limited thereto. Any improvements, equivalent substitutions, etc., made by those skilled in the art without departing from the principles of the present invention should be considered as included within the scope of protection of the present invention.

Claims

1. A composite electrolyte for aqueous zinc-ion batteries, characterized in that, The composite electrolyte comprises an electrolyte zinc salt, a solvent water, and a composite additive; the composite additive includes a first additive and a second additive; the first additive is a group III metal ion; and the second additive is a group V metal anion.

2. The composite electrolyte as described in claim 1, characterized in that, The group III metal ions are selected from at least one of aluminum (Al), gallium (Ga), indium (In), scandium (Sc), yttrium (Y), lanthanum (La), samarium (Sm), and ytterbium (Yb); the group V metal anions are selected from antimonate (SbO3). ˉ ), bismuthate (BiO3) ˉ ), vanadate (VO3) ˉ / VO4 3ˉ ), niobate (NbO3) ˉ ) and tantalate (TaO3) ˉ At least one of the following.

3. The composite electrolyte as described in claim 2, characterized in that, The group III metal ion is Al. 3+ or In 3+ The group V metal anion is SbO3. ˉ or BiO3 ˉ .

4. The composite electrolyte as described in claim 1, characterized in that, The concentration of the zinc salt in the electrolyte is 1M to 4M; the concentration of the first additive in the electrolyte is 0.01mM to 100mM; and the concentration of the second additive in the electrolyte is 0.1mM to 50mM.

5. An electrode material, characterized in that, It is a vanadium oxide doped with a group III metal cation, wherein the group III metal cation is the same group III metal ion as the first additive in any one of claims 1-3.

6. The electrode material as described in claim 5, characterized in that, The vanadium oxide is vanadium dioxide (VO2); the doping concentration of the group III metal cation is from 0.1 at.% to 5.0 at.%.

7. An aqueous zinc-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and a composite electrolyte as described in any one of claims 1-4.

8. The aqueous zinc-ion battery as described in claim 7, characterized in that, The positive electrode comprises the electrode material as described in any one of claims 5 or 6.

9. The aqueous zinc-ion battery as described in claim 7 or 8, characterized in that, The negative electrode is metallic zinc or a zinc alloy, and the surface of the negative electrode is provided with a zinc fluoride (ZnF2) modification layer, the thickness of which is 5 nm to 100 nm.

10. A method for preparing an aqueous zinc-ion battery as described in claim 9, characterized in that, Includes the following steps: Preparation of composite electrolyte: Dissolve zinc salt, first additive and second additive in water, stir and ultrasonically disperse evenly; Preparation of cathode materials: Vanadium oxides doped with group III metal cations were synthesized by hydrothermal method; Preparation of negative electrode material: Zinc fluoride (ZnF2) thin film is deposited on the surface of metallic zinc (Zn) or zinc alloy using physical vapor deposition; Battery assembly: Assembling the positive electrode, negative electrode, separator, and composite electrolyte into a battery.

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