Preparation method of aqueous zinc-vanadium battery electrolyte and battery

Abstract

The invention discloses an aqueous zinc-vanadium battery electrolyte preparation method and a battery, and belongs to the technical field of aqueous zinc ion batteries. The preparation method comprises the following steps: preparing a polyquaternium aqueous solution; and adding soluble zinc salt into the polyquaternium aqueous solution, stirring and dissolving to obtain the composite electrolyte. According to the electrolyte, through the synergistic effect of the polyquaternary ammonium salt and the zinc salt, the acidity and water activity of a system are effectively reduced, dendritic crystal growth and hydrogen evolution reaction of a zinc negative electrode are inhibited, meanwhile, a nitrogen-containing protective layer is formed on the surface of a vanadium positive electrode, and vanadium dissolution is reduced. The battery containing the electrolyte shows excellent cycle stability in a wide temperature range of-20 to 80 DEG C, the cycle life of the zinc symmetric battery exceeds 3000 hours, the capacity retention rate of the whole battery after 4000 cycles reaches 87.6%, and the technical problems of aggravation of interface side reaction and fast degradation of battery performance under high-temperature and high-acidity conditions are solved.

Description

Technical Field

[0001] This invention belongs to the field of aqueous zinc-vanadium battery technology, specifically relating to a method for preparing an aqueous zinc-vanadium battery electrolyte and the battery itself. Background Technology

[0002] Aqueous zinc-ion batteries have become an ideal choice for large-scale energy storage due to their inherent safety, high theoretical capacity, abundant resources, and environmental advantages. Aqueous zinc-vanadium batteries, with their high specific capacity and energy density, are considered one of the commercially promising aqueous zinc-ion battery systems. However, zinc-vanadium batteries face multiple challenges due to the instability of the electrode / electrolyte interface (EEI). The zinc anode is not only plagued by hydrogen evolution reaction and corrosion but also suffers from dendrite formation. Furthermore, the complex reactions between the vanadium oxide cathode active material and water molecules lead to irreversible dissolution and electrode structure evolution, ultimately causing battery failure.

[0003] Considering the compatibility and operability of various methods with existing battery fabrication in practical applications, electrolyte modification with additives, which is simple in process and low in cost, has gradually become the preferred strategy for optimizing zinc-vanadium batteries. However, traditional electrolyte modification methods mainly use dilute solution systems (zinc sulfate, zinc trifluoromethanesulfonate, etc.), which are often limited by the activity of water solvents, resulting in poor tolerance of EEI to temperature changes. Especially under high temperature conditions, the increase of active water molecules not only accelerates the hydrogen evolution reaction of the zinc anode but also promotes the dissolution of vanadium species, thereby worsening EEI.

[0004] Water-in-salt (WISE) electrolytes are a promising solution, capable of modulating the zinc solvation structure and enhancing the electrolyte's temperature adaptability. However, this method still fails to completely solve the aforementioned problems, primarily due to residual active water within the system and interfacial side reactions induced by significantly increased high-concentration electrolyte acidity. Therefore, optimizing WISE-type electrolytes to simultaneously enhance the synergistic stability of the zinc anode and vanadium cathode interface in acidic environments to meet the all-weather stable application requirements of zinc-vanadium batteries remains a significant challenge.

[0005] While aqueous zinc-vanadium batteries hold commercial promise in existing technologies, the zinc anode suffers from hydrogen evolution reaction, corrosion, and dendrite formation, while the vanadium cathode exhibits irreversible dissolution of active materials and structural evolution, ultimately leading to battery failure. Electrolyte modification with additives is the preferred optimization strategy, but traditional dilute solution systems are limited by the activity of water solvents, resulting in poor tolerance to temperature changes and accelerated side reactions by active water molecules at high temperatures. Although water-in-salt (WISE) electrolytes can enhance temperature adaptability, residual active water and significantly increased acidity in high-concentration systems still cannot completely resolve the interfacial side reactions between the zinc anode and vanadium cathode, making it difficult to meet the requirements for stable all-weather battery applications. This invention proposes a solution to address these core technical pain points. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a method for preparing an aqueous zinc-vanadium battery electrolyte and a battery, which effectively alleviates the acidity of the high-concentration system, suppresses side reactions such as hydrogen evolution reaction of the zinc anode and dissolution of the vanadium cathode, and solves the technical problems of performance degradation and shortened lifespan of aqueous zinc-vanadium batteries caused by electrode / electrolyte interface instability, and the difficulty of existing electrolyte modification schemes in achieving both wide temperature range adaptability and interface synergistic stability.

[0007] The present invention adopts the following technical solution: A method for preparing an aqueous zinc-vanadium battery electrolyte includes the following steps: Prepare an aqueous solution of a polyquaternary ammonium salt, wherein the polyquaternary ammonium salt is polydimethyldiallylammonium chloride, and its concentration range is 0% to 20%, based on the total weight of the electrolyte solvent; Soluble zinc salt is added to the prepared polyquaternary ammonium salt aqueous solution, and the zinc salt is completely dissolved by high-temperature stirring to obtain WISE-type composite aqueous zinc-vanadium battery electrolyte containing polyquaternary ammonium salt. The addition of the soluble zinc salt can synergistically regulate the acidity of the electrolyte with the polyquaternary ammonium salt, inhibit the hydrogen evolution reaction of zinc negative electrode and the dissolution side reaction of vanadium positive electrode, and promote the preferred orientation of zinc (002) crystal plane.

[0008] Preferably, the concentration of polyquaternium salt added is 15%.

[0009] Preferably, the soluble zinc salt is selected from one or more of zinc chloride, zinc acetate, and zinc tetrafluoroborate.

[0010] Preferably, the soluble zinc salts include zinc chloride and zinc acetate.

[0011] Preferably, the concentration of zinc chloride is 15-25 mol / L, and the concentration of zinc acetate is 1-3 mol / L.

[0012] Preferably, the stirring conditions are: stirring at 50~100℃ for 10~60 minutes.

[0013] Another technical solution of the present invention is an aqueous zinc-vanadium battery, comprising the aqueous zinc-vanadium battery electrolyte, wherein the battery is a symmetrical battery, a half-cell, or a full-cell; The symmetrical battery includes a zinc foil negative electrode, a zinc foil positive electrode, a separator, and the electrolyte; The half-cell includes a zinc foil negative electrode, a current collector, a separator, and the electrolyte; The full battery includes a zinc foil negative electrode, a vanadium-based positive electrode material, a separator, and the electrolyte.

[0014] Preferably, the diaphragm is selected from any one of glass fiber, filter paper, bamboo cellulose, or aqueous polyethylene diaphragm.

[0015] Preferably, the current collector is selected from any one of copper foil, copper mesh, copper foam, stainless steel mesh, titanium foil, or nickel foam.

[0016] Preferably, the vanadium-based cathode material is at least one of vanadium pentoxide or potassium-intercalated hydrated vanadium pentoxide.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: A method for preparing an aqueous zinc-vanadium battery electrolyte is presented, which precisely addresses the core defects of existing WISE-type electrolytes through a core combination of polyquaternary ammonium salt and soluble zinc salt. The synergistic effect of polydimethyldiallyl ammonium chloride and zinc salt inhibits hydrogen evolution at the zinc anode by adjusting the electrolyte acidity, solving the corrosion and dendrite problems of the zinc anode in traditional systems; on the other hand, it reduces vanadium cathode dissolution, mitigating electrode structural evolution and failure. A concentration range of 0% to 20% provides flexibility for adapting to different application scenarios, and high-temperature stirring ensures system uniformity and stability. The resulting composite electrolyte allows for controlled preferential orientation of the zinc (002) crystal face, laying the foundation for stable operation of the battery over a wide temperature range. It is perfectly compatible with existing battery manufacturing processes, combining practicality and innovation.

[0018] Furthermore, by integrating a specially formulated electrolyte, comprehensive stability of the electrode / electrolyte interface (EEI) is achieved. The classic combination of zinc foil anode and vanadium-based cathode, under the action of the composite electrolyte, not only solves the problems of dendrite growth and hydrogen evolution in the zinc anode, but also inhibits vanadium shuttle through the action of the electrolyte on the cathode surface. Multiple designs, including symmetrical cells, half-cells, and full-cells, cover all scenarios from material testing to practical applications. The insulating porous structure of the separator ensures a balance between ion conduction and electrode isolation. The electrolyte fills the gap between the positive and negative electrodes and the separator, constructing a highly efficient ion transport channel, enabling the battery to maintain excellent electrochemical performance over a wide temperature range of -20 to 80°C, breaking through the bottlenecks of high-temperature failure and low-temperature performance degradation in traditional batteries.

[0019] Furthermore, the introduction of ultrasonic treatment accelerates the mixing of commercial aqueous solutions and deionized water, reduces the concentration gradient, and ensures that the polyquaternary ammonium salt is uniformly distributed in the solvent, providing a stable foundation for subsequent synergistic effects with zinc salts. This limitation, by optimizing the physical properties and preparation process of the polyquaternary ammonium salt, ensures that it can fully exert its functions of regulating acidity and stabilizing the interface, avoids electrolyte performance fluctuations caused by uneven material dispersion, and improves the repeatability and reliability of the preparation method.

[0020] Furthermore, the optimal addition amount of polyquaternium salt is 15%, a parameter selection based on extensive experimental verification. At this concentration, the electrolyte achieves a perfect balance between suppressing water activity and reducing system acidity, increasing the Hammett acidity (H0) value to 0.63 and maintaining stability at high temperatures, effectively suppressing interfacial side reactions. Experiments show that the electrolyte at this concentration enables zinc-zinc symmetric cells to operate at 1 mA cm⁻¹.-2 After more than 3000 hours of cycling, 20 mAcm -2 It can stably cycle for 1300 hours under high current, demonstrating its tolerance to harsh conditions such as high current and high temperature, which is significantly better than other concentration ratios. It controls material costs while ensuring performance, achieving a balance between performance and economy.

[0021] Furthermore, zinc chloride, zinc acetate, and zinc tetrafluoroborate are all commonly used zinc sources in aqueous batteries, with wide availability and good electrochemical compatibility, meeting different cost and performance requirements. The optimized magnetic stirring parameters of 90℃ for 30 minutes ensure complete dissolution of the high-concentration zinc salt, forming a stable "water-in-salt" (WISE) structure, while avoiding energy waste or polyquaternium salt decomposition due to excessively high stirring temperature or time. Magnetic stirring provides gentle and uniform shear force, preventing localized overheating, ensuring electrolyte composition stability, and improving the controllability of the preparation process and product yield.

[0022] Furthermore, high-concentration zinc chloride forms the basis of the WISE system, modulating the zinc solvation structure and reducing water activity. The addition of zinc acetate further optimizes the electrolyte ionic strength, enhances the zinc ion migration rate, and, together with polyquaternary ammonium salt, regulates the system acidity. At this concentration combination, the electrolyte exhibits both good conductivity and effectively inhibits hydrogen evolution and vanadium dissolution, maintaining the coulombic efficiency of the zinc-copper asymmetric battery at 99.6% with no significant degradation after more than 1200 cycles, providing core support for the battery's high reversibility and long lifespan.

[0023] Furthermore, the zinc foil thickness is limited to 80 μm, balancing electrode mechanical strength and electrochemical activity, avoiding electrode deformation due to excessive thinness or material waste due to excessive thickness. Specific separator options are clearly defined, all being commercially mature materials. Glass fiber and filter paper possess high porosity and good wettability, enabling them to fully adsorb electrolyte and ensure ion transport efficiency; aqueous polyethylene separators exhibit excellent chemical stability, making them suitable for acidic electrolyte environments. This standardization of electrode and separator parameters reduces battery assembly difficulty, improves the consistency of performance across different batches of batteries, and ensures that the separator achieves efficient ion conduction while isolating the positive and negative electrodes, guaranteeing stable battery operation.

[0024] Furthermore, the vanadium-based cathode material is limited to vanadium pentoxide or potassium-intercalated hydrated vanadium pentoxide, both of which possess high specific capacity and good zinc ion insertion / extraction performance, making them preferred cathode materials for aqueous zinc-vanadium batteries. The composite electrolyte synergistically interacts with this type of cathode material to generate an approximately 6 nm nitrogen-containing protective layer in situ on the cathode surface. Inductively coupled plasma atomic emission spectrometry (ICP-AES) analysis shows that the vanadium dissolution content after cycling is only 9.42 mg / L. -1 This is far lower than the 17.40 mg / L of traditional electrolytes. -1This protective layer effectively blocks the dissolution of vanadium active species, suppresses the vanadium shuttle effect, and protects the structural integrity of the cathode, enabling the zinc-vanadium full cell to operate at 2Ag. -1 After 4000 cycles, the capacity retention rate reaches 87.6%, significantly improving battery cycle life.

[0025] Furthermore, the batteries are subdivided into symmetrical batteries, half-cells, and full-cells to precisely match different testing and application needs: symmetrical batteries are used to evaluate the stability of the negative electrode interface, half-cells focus on the reversibility of zinc deposition / stripping, and full-cells reflect practical application performance. The electrode composition of each type of battery is clearly defined, with zinc foil serving as a unified negative electrode to ensure consistent testing standards, and differentiated configurations of the positive electrode / current collector to meet diverse evaluation needs. This classification design allows the technical effects of this invention to be verified comprehensively from the material basis to system applications, facilitating performance analysis in the research stage and providing direct reference for industrial applications, thus enhancing the practicality and promotional value of the invention.

[0026] In summary, this invention achieves multiple technological breakthroughs through a synergistic electrolyte preparation method using polyquaternary ammonium salt and zinc salt, along with a corresponding battery design. The specially formulated electrolyte effectively reduces the acidity of high-concentration systems, inhibits hydrogen evolution and dendrite growth at the zinc anode, promotes (002) crystal orientation, and simultaneously forms a nitrogen-containing protective layer at the vanadium cathode to inhibit vanadium dissolution. The battery covers multiple structural types, is suitable for a wide temperature range (-20 to 80°C) and high-current scenarios, and significantly improves cycle life and coulombic efficiency. The preparation process is compatible with existing procedures, uses low-cost materials, and solves the core problems of interface failure and poor temperature adaptability in traditional zinc-vanadium batteries, combining performance advantages with industrialization potential.

[0027] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the following description of the relative embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The zinc-zinc symmetric cells assembled using the electrolytes of Examples 1-4 and Comparative Example 1 were tested at 1 mA / cm². -2 Time-voltage curve at 30℃; Figure 2 The zinc-zinc symmetric battery assembled using the electrolytes of Example 3 and Comparative Example 1 of this invention was tested at 20 mA / cm². -2 Time-voltage curve at 30℃.

[0030] Figure 3 The zinc-zinc symmetric battery assembled using the electrolytes of Example 3 and Comparative Example 1 of this invention was tested at 1 mA / cm². -2 Time-voltage curve at -20℃.

[0031] Figure 4 The zinc-zinc symmetric battery assembled using the electrolytes of Example 3 and Comparative Example 1 of this invention was tested at 1 mA / cm². -2 Time-voltage curve at 60℃.

[0032] Figure 5 The zinc-zinc symmetric battery assembled using the electrolytes of Example 3 and Comparative Example 1 of this invention was tested at 1 mA / cm². -2 Time-voltage curve at 80℃.

[0033] Figure 6 The zinc-zinc symmetric battery assembled using the electrolyte of Comparative Example 2 of this invention was tested at 1 mA / cm². -2 The time-voltage curve is shown below.

[0034] Figure 7 The image shows a scanning electron microscope (SEM) image of a zinc-zinc symmetric battery assembled with the electrolytes of Example 3 and Comparative Example 1 after 50 cycles.

[0035] Figure 8 The image shows the X-ray diffraction pattern of the zinc-zinc symmetric battery assembled with the electrolytes of Example 3 and Comparative Example 1 after 8 hours of electrochemical deposition.

[0036] Figure 9 The ultraviolet absorption spectra of the Hammett acidity indicator in the electrolytes of Examples 3 and Comparative Example 1 of the present invention are shown.

[0037] Figure 10 The water molecules in the electrolytes of Example 3 and Comparative Example 1 of this invention 1 H NMR spectrum.

[0038] Figure 11 The zinc-copper asymmetric battery assembled using the electrolytes of Examples 1-4 and Comparative Example 1 of this invention was tested at 2 mA / cm². -2 Coulomb efficiency diagram at 30℃.

[0039] Figure 12 The zinc-copper asymmetric battery assembled using the electrolytes of Example 3 and Comparative Example 1 of this invention was tested at 2 mA / cm². -2 Coulomb efficiency diagram at 60℃.

[0040] Figure 13 The symmetric cells assembled using the electrolytes of Example 3 and Comparative Example 1 of this invention are zinc-vanadium full cells in 2Ag. -1 The cycle life curve.

[0041] Figure 14 The rate curves of the zinc-vanadium full cells assembled with the electrolytes of Example 3 and Comparative Example 1 at different current densities at high temperatures are shown.

[0042] Figure 15 This is a comparison chart of the vanadium dissolution content after cycling and immersion in Example 3 and Comparative Example 1 of the present invention.

[0043] Figure 16 This is a transmission electron microscope image of the vanadium cathode after cycling in Example 3 of the present invention. Detailed Implementation

[0044] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0046] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0047] In this invention, unless otherwise specified, percentage (%) or parts refer to weight percentage or parts relative to the composition.

[0048] Unless otherwise specified, the components or preferred components involved in this invention can be combined with each other to form new technical solutions.

[0049] In this invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is simply an abbreviation of these numerical combinations.

[0050] The "scope" disclosed in this invention can be in the form of a lower limit and an upper limit, and can be one or more lower limits and one or more upper limits, respectively.

[0051] In this invention, the term "and / or" as used herein refers to any combination of one or more of the associated listed items, as well as all possible combinations, and includes such combinations.

[0052] In this invention, unless otherwise stated, the various reactions or operation steps may be performed sequentially or in a particular order. Preferably, the reaction methods described herein are performed sequentially.

[0053] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0054] This invention provides a method for preparing an aqueous zinc-vanadium battery electrolyte and a battery in general. This method promotes the preferential orientation control of the (002) crystal plane of zinc metal, facilitates uniform zinc deposition, and avoids random dendrite growth. Simultaneously, the nitrogen-containing in-situ protective layer formed on the vanadium cathode surface further reduces the dissolution of vanadium active species, thereby inhibiting vanadium shuttle and protecting the stability of the electrode structure. This strategy of regulating electrolyte acidity and synergistically protecting the electrode interface enables the assembled zinc-vanadium battery to exhibit excellent electrochemical performance in a temperature range of -20 to 80°C.

[0055] This invention discloses a method for preparing an aqueous zinc-vanadium battery electrolyte, comprising the following steps: Step 1: Prepare PQ aqueous solutions of different concentrations, wherein the PQ additive is polydimethyldiallylammonium chloride (M... w <100,000), etc.; the concentration range of the regulator is 0%~20%, based on the total weight of the electrolyte solvent.

[0056] The specific structural formula is shown in Equation 1:

[0057] Preferably, the amount of the additive added to the electrolyte is 15%.

[0058] Step 2: Add a large amount of soluble zinc salt to the above PQ aqueous solution and stir continuously at high temperature for 30 minutes under magnetic stirrer until the zinc salt is completely dissolved to obtain WISE type composite aqueous zinc-vanadium battery electrolyte containing PQ.

[0059] The zinc salt is one or more of zinc chloride, zinc acetate, and zinc tetrafluoroborate.

[0060] The preferred soluble zinc salts are zinc chloride and zinc acetate, with concentrations of 20 mol / L and 2 mol / L, respectively.

[0061] The present invention also provides an aqueous zinc-vanadium battery, comprising the aqueous zinc-vanadium battery electrolyte, wherein the battery is a symmetrical battery, a half-cell, or a full-cell; the symmetrical battery comprises a zinc foil negative electrode, a zinc foil positive electrode, a separator, and the electrolyte; the half-cell comprises a zinc foil negative electrode, a current collector, a separator, and the electrolyte; and the full-cell comprises a zinc foil negative electrode, a vanadium-based positive electrode material, a separator, and the electrolyte.

[0062] Among them, a symmetrical cell is composed of commercially available 80μm thick zinc foil, a separator, and an aqueous zinc-ion battery electrolyte; a half-cell is composed of commercially available 80μm thick zinc foil, a commercial current collector, and an aqueous zinc-ion battery electrolyte; and an aqueous zinc-vanadium full cell is composed of commercially available 80μm thick zinc foil as the negative electrode, vanadium-based layered material as the positive electrode, and an aqueous zinc-ion battery electrolyte as the electrolyte.

[0063] The diaphragm can be any one of glass fiber, filter paper, bamboo cellulose, or aqueous polyethylene diaphragm.

[0064] The current collector can be any one of copper foil, copper mesh, copper foam, stainless steel mesh, titanium foil, or nickel foam.

[0065] Furthermore, the positive electrode active material of the zinc-ion battery is a vanadium-based layered material, preferably at least one of vanadium pentoxide or potassium-intercalated hydrated vanadium pentoxide (abbreviated as potassium vanadium oxide).

[0066] A method for preparing an aqueous zinc-vanadium battery electrolyte and a battery thereof, which are prepared by the above method.

[0067] This invention discloses a method for preparing a zinc-vanadium battery electrolyte based on a gold-based solution, and the battery itself is applicable in various fields.

[0068] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0069] Example 1 At room temperature, 1 mL of a commercial 35% polydimethyldiallylammonium chloride aqueous solution was added to 6 mL of deionized water and sonicated until homogeneous to obtain a 5% PQ aqueous solution. 2 mL of this 5% PQ aqueous solution was then added to 5.45 g of zinc chloride and 0.73 g of zinc acetate, respectively. The mixture was magnetically stirred at 90°C for 30 minutes and then allowed to stand to obtain a stable PQ-containing composite electrolyte (abbreviated as ZL-5P).

[0070] Example 2 At room temperature, 1 mL of a commercial 35% polydimethyldiallylammonium chloride aqueous solution was added to 2.5 mL of deionized water and sonicated until homogeneous to obtain a 10% PQ aqueous solution. 2 mL of this 10% PQ aqueous solution was then added to 5.45 g of zinc chloride and 0.73 g of zinc acetate, respectively. The mixture was magnetically stirred at 90 °C for 30 minutes and then allowed to stand to obtain a stable PQ-containing composite electrolyte (abbreviated as ZL-10P).

[0071] Example 3 At room temperature, 3 mL of a commercial 35% polydimethyldiallylammonium chloride aqueous solution was added to 4 mL of deionized water and sonicated until homogeneous to obtain a 15% PQ aqueous solution. 2 mL of this 15% PQ aqueous solution was then added to 5.45 g of zinc chloride and 0.73 g of zinc acetate, respectively. The mixture was magnetically stirred at 90 °C for 30 minutes and then allowed to stand to obtain a stable PQ-containing composite electrolyte (abbreviated as ZL-15P).

[0072] Example 4 At room temperature, 2 mL of a commercial 35% polydimethyldiallylammonium chloride aqueous solution was added to 1.5 mL of deionized water and sonicated until homogeneous to obtain a 20% PQ aqueous solution. 2 mL of this 20% PQ aqueous solution was then added to 5.45 g of zinc chloride and 0.73 g of zinc acetate, respectively. The mixture was magnetically stirred at 90 °C for 30 minutes and then allowed to stand to obtain a stable PQ-containing composite electrolyte (abbreviated as ZL-20P).

[0073] Comparative Example 1 At room temperature, 5.45 g of zinc chloride and 0.73 g of zinc acetate were added to 2 mL of deionized water and sonicated until the solution was clear to obtain WISE-type composite aqueous zinc-vanadium battery electrolyte (abbreviated as ZL).

[0074] Comparative Example 2 At room temperature, 3 mL of a commercial 65% dimethyl diallyl ammonium chloride aqueous solution was added to 10 mL of deionized water and sonicated until homogeneous to obtain a 15% quaternary ammonium salt monomer aqueous solution. Figure 2 As shown.

[0075] Take 2 mL of the 15% quaternary ammonium salt monomer aqueous solution prepared above and add 5.45 g of zinc chloride and 0.73 g of zinc acetate respectively. After stirring magnetically at 90 °C for 30 minutes, let it stand to obtain a composite electrolyte containing quaternary ammonium salt monomer (abbreviated as ZL-15Q).

[0076]

[0077] Example 5 Assemble zinc-zinc symmetrical button cells: A water-based zinc-ion zinc-zinc symmetric battery was assembled using zinc foil as the positive and negative electrodes, glass fiber as the separator, and the electrolytes prepared in Examples 1-3 and Comparative Examples 1-2 were added. A 2032 type battery case was used, and the battery was assembled in the following order: negative electrode case, zinc foil, separator, electrolyte, zinc foil, gasket, spring sheet, and positive electrode case.

[0078] experiment: Electrochemical tests were performed on the zinc-zinc symmetric coin cells assembled in each embodiment and comparative example at 1 mA cm⁻¹. -2 Constant current charge-discharge tests were conducted at various current densities. These tests were performed on the Newway Battery testing system, with the test temperature maintained between -20°C and 80°C.

[0079] 1. Cycle life Figure 1 Symmetric cells assembled using the electrolytes in Examples 1-4 and Comparative Example 1 were tested at 1 mA / cm². -2 The current density and 0.5 mA per hour cm -2 The time-voltage curve at room temperature (30°C) under the specified capacity.

[0080] As shown in the figure, a short circuit occurred in the zinc-zinc symmetric battery after 240 hours of cycling without PQ electrolyte. However, when using an electrolyte containing PQ, the reversible long-cycle stability of the symmetric battery was significantly improved. In particular, when the PQ content was appropriate (Example 3), the battery could cycle for more than 3000 hours. This indicates that the introduction of an appropriate amount of PQ significantly improves the cycle life of the symmetric battery.

[0081] In addition, such as Figure 2 As shown, when using an electrolyte with a preferred PQ content (Example 3), the assembled zinc-zinc symmetric cell achieves a voltage of 20 mA / cm². -2 Larger current density and 20mAh / cm -2 The ability to cycle for 1300 hours at a larger fixed capacity indicates that the PQ-containing composite electrolyte can withstand test conditions with a larger current, demonstrating its superior ability to stabilize the zinc anode.

[0082] 2. High-temperature performance The reversible long-cycle performance of the zinc-zinc symmetric cells assembled in Example 3 and Comparative Example 1 at -20°C, 60°C, and 80°C, respectively, is shown in [reference needed]. Figure 3-5 .

[0083] The ZL-15P assembled battery can cycle stably for 500 hours at low temperatures, and even at 60℃ and 80℃, it can cycle stably for more than 2000 and 1200 hours, respectively. This result further demonstrates the stabilizing and protective effect of the PQ-containing composite electrolyte on the EEI, which also ensures the long life of the zinc anode over a wide temperature range.

[0084] 3. Investigation into the polymer segment interaction of PQ: The reversible long-cycle performance of the zinc-zinc symmetric battery assembled in Comparative Example 2 at 30°C and 60°C is shown in [reference needed]. Figure 6 .

[0085] Compared with the above figure, it can be seen that the performance of ZL-15Q containing quaternary ammonium salt monomers is not significantly improved, which further highlights the important role of PQ polymer segments in batteries.

[0086] 4. Microstructure of zinc negative electrode Figure 7 Images of the zinc anode after 50 cycles of the symmetrical batteries assembled in Example 3 and Comparative Example 1.

[0087] As can be seen from the figure, when using the electrolyte of Comparative Example 1, a large number of rough zinc dendrites form on the surface of the zinc negative electrode, making the surface very uneven. In contrast, when using the electrolyte of Example 2, zinc is deposited in a uniform lamellar shape, and no obvious zinc dendrites are generated on the electrode surface. Figure 8 It also reveals that Example 3 effectively protects the zinc anode / electrolyte interface and regulates the preferential orientation of the zinc (002) deposition crystal plane.

[0088] Example 6 Investigation into the reduction of acidity in PQ-containing WISE-type composite aqueous zinc-vanadium battery electrolyte: The Hammett acidity (H0) of Examples 3 and Comparative Example 1 was tested using ultraviolet absorption spectroscopy.

[0089] from Figure 9 As can be seen, PQ, acting as a weak Lewis acid, transforms the electrolyte into a weaker proton donor, thereby lowering its H0 value. Calculations show that the H0 value of ZL is 0.47, while in the ZL-15P system it rises to 0.63. At a high temperature of 60℃, the H0 value of ZL decreases to 0.39, but no significant change is observed in the ZL-15P system, indicating that the acidity of the PQ-containing composite electrolyte is effectively reduced. Figure 10 Water molecules in Example 3 1 The low-field shift in the H NMR spectrum peaks indicates that water protons are more shielded in a higher electron density environment, exhibiting weak water activity.

[0090] Example 7 Assemble zinc-copper asymmetric button cells: A water-based zinc-copper asymmetric battery was assembled using copper foil as the positive electrode, zinc foil as the negative electrode, glass fiber as the separator, and the electrolyte prepared in Examples 1-4 and Comparative Example 1. A 2032 battery case was used, and the battery was assembled in the following order: negative electrode case, zinc foil, separator, electrolyte, copper foil, gasket, spring sheet, and positive electrode case.

[0091] experiment: Coulombic efficiency tests were performed on the zinc-copper asymmetric coin cells assembled in Examples 1-3 and Comparative Example 1. The tests were conducted on a Newway battery testing system at temperatures ranging from 30 to 60°C.

[0092] Figure 11 The zinc-copper asymmetric cells assembled using the electrolytes in Examples 1-4 and Comparative Example 1 were tested at 2 mA / cm². -2 The current density and 0.5 mAh / cm² -2 Cyclic testing at the specified capacity showed that the battery containing the electrolyte of Example 3 could stably cycle for over 1200 cycles, maintaining a coulombic efficiency of 99.6%; while the battery assembled with the electrolyte of Comparative Example 1 only operated normally for 300 cycles before rapidly failing. This indicates that the composite electrolyte containing PQ can significantly improve the stability of zinc-ion batteries and the reversibility of zinc deposition / stripping. Figure 12 This further highlights the significant improvement in high-temperature tolerance of the ZL-15P electrolyte.

[0093] Example 8: Assemble zinc-vanadium full cells: A water-based zinc-vanadium ion battery was assembled using potassium vanadium oxide as the positive electrode active material, zinc foil as the negative electrode, glass fiber as the separator, and the electrolyte prepared in Example 3 and Comparative Example 1. A 2032 battery case was used, and the battery was assembled in the following order: negative electrode case, zinc foil, separator, electrolyte, positive electrode active material, gasket, spring sheet, and positive electrode case.

[0094] experiment: Electrochemical tests were performed on the zinc-vanadium full cells assembled in Example 3 and Comparative Example 1. The tests were conducted on a Newway battery testing system, with a battery voltage range of 0.2–1.6 V and a test temperature of 30–80 °C.

[0095] 1. Cycle life from Figure 13 It can be seen from 2Ag -1 At the specified current density, the battery containing the electrolyte of Example 3 could stably cycle for 4000 cycles, maintaining a capacity of 87.6%, while the battery assembled with the electrolyte of Comparative Example 1 experienced rapid capacity decay. This demonstrates the successful application of the PQ-containing composite electrolyte in aqueous zinc-vanadium batteries.

[0096] 2. High-temperature rate performance Figure 14 Zinc-vanadium full cells assembled using the electrolytes in Example 3 and Comparative Example 1 were tested at different current densities (0.5-1-2-4-2-1-0.5Ag) under high temperature conditions. -1 The rate performance curve of ).

[0097] As can be seen from the figure, the zinc-vanadium full cell assembled with ZL-15P electrolyte can also exhibit excellent capacity and rate performance at high temperatures.

[0098] Example 9: Investigation on the inhibitory effect of PQ-containing composite electrolyte on vanadium dissolution: Vanadium dissolution in the electrolyte was detected by inductively coupled plasma atomic emission spectrometry: the vanadium content in the ZL electrolyte after cycling was only 9.42 mg / L. -1 However, the vanadium content in ZL is significantly higher, at 17.40 mg / L. -1 ( Figure 15 Even after soaking for 3 days, a strong vanadium signal (2.14 mg / L at 30°C) could still be detected in the ZL electrolyte. -1 3.51 mg / L at 60℃ -1 Its concentration is approximately 130% higher than that of ZL-15P. Furthermore, from... Figure 16 As can be seen, an N-containing protective layer of approximately 6 nm was formed on the surface of the vanadium cathode after cycling in the ZL-15P electrolyte. These results indicate that the PQ-containing composite electrolyte can effectively inhibit the dissolution of active materials and maintain the stability of the vanadium cathode / electrolyte interface by generating a vanadium cathode protective layer in situ.

[0099] This invention has the following significant advantages: First, by introducing polyquaternary ammonium salt (PQ) additives and compounding them with specific zinc salts (such as zinc chloride and zinc acetate), a novel "water-in-salt" (WISE) composite electrolyte system was constructed. Example data shows that this combination synergistically reduces the overall acidity of the electrolyte—Hammett acidity tests show that the H0 value of the electrolyte containing 15% PQ (ZL-15P) increased from 0.47 in the control group to 0.63, and remained stable at a high temperature of 60°C, while the H0 value of the control group decreased to 0.39. Simultaneously, water molecules... 1 The low-field shift in the H NMR peak confirms the effective suppression of water molecule activity.

[0100] Secondly, this electrolyte can induce zinc metal to be deposited along the (002) crystal plane with a preferred orientation. X-ray diffraction pattern ( Figure 8 The results showed that zinc deposition exhibited a strong (002) crystal plane orientation when using ZL-15P electrolyte, as indicated by scanning electron microscopy (SEM). Figure 7 This further confirmed the formation of a uniform and dense zinc deposition layer, effectively suppressing dendrite growth. This enabled the zinc-zinc symmetric cell to achieve a 1 mA cm⁻¹ polarity. -2 It achieved an ultra-long cycle life of over 3000 hours, even at 20mA cm⁻¹. -2 It can also cycle stably for 1300 hours under high current density.

[0101] Third, this strategy can form a nitrogen-containing protective layer of approximately 6 nm in situ on the positive electrode side. (Transmission electron microscopy) Figure 16 Inductively coupled plasma (ICP) tests confirmed that the protective layer effectively prevents vanadium species from directly contacting the electrolyte. The vanadium dissolved in the ZL-15P group electrolyte was 9.42 mg / L. -1 The level was significantly lower than that of the control group (17.40 mg / L). -1 The effect of suppressing the vanadium shuttle effect is obvious.

[0102] Ultimately, based on the aforementioned synergistic effect, the battery using this electrolyte exhibits excellent wide-temperature adaptability. Test data shows that it can cycle stably for 500 hours at a low temperature of -20℃, and for over 2000 hours and 1200 hours at high temperatures of 60℃ and 80℃, respectively. The full cell operates at 2A g... -1 After 4000 cycles at current density, the capacity retention rate still reaches 87.6%. It also has the advantages of simple process and low cost, and solves the core problems of existing zinc vanadium batteries such as interface instability and short life under harsh conditions such as high acidity and high temperature. In summary, this invention provides a method for preparing an aqueous zinc-vanadium battery electrolyte and a battery itself. Through a synergistic electrolyte preparation method using polyquaternary ammonium salt and zinc salt, along with a corresponding battery design, multiple technological breakthroughs are achieved. The specially formulated electrolyte effectively reduces the acidity of high-concentration systems, inhibits hydrogen evolution and dendrite growth at the zinc anode, promotes (002) crystal plane orientation, and simultaneously forms a nitrogen-containing protective layer at the vanadium cathode to inhibit vanadium dissolution. The battery covers multiple structural types, is suitable for a wide temperature range (-20 to 80°C) and high-current scenarios, and significantly improves cycle life and coulombic efficiency. The preparation process is compatible with existing processes, uses low-cost materials, and solves the core problems of interface failure and poor temperature adaptability in traditional zinc-vanadium batteries, combining performance advantages with industrialization potential.

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an aqueous zinc vanadium battery electrolyte, characterized in that, The method comprises the following steps: configuring a polyquaternary ammonium salt aqueous solution, the polyquaternary ammonium salt being polydimethyl diallyl ammonium chloride, the addition concentration of the polyquaternary ammonium salt being in the range of 0% to 20% based on the total weight of the electrolyte solvent; adding a soluble zinc salt into the prepared polyquaternary ammonium salt aqueous solution, and stirring at high temperature to completely dissolve the zinc salt, so as to obtain a WISE type composite aqueous electrolyte for zinc-vanadium batteries containing polyquaternary ammonium salt; the addition of the soluble zinc salt can synergistically regulate the electrolyte acidity with the polyquaternary ammonium salt, inhibit the zinc negative electrode hydrogen evolution reaction and the vanadium positive electrode dissolution side reaction, and promote the zinc (002) crystal plane preferred orientation.

2. The aqueous zinc vanadium cell electrolyte preparation method according to claim 1, characterized in that, The addition concentration of the polyquaternary ammonium salt is 15%.

3. The aqueous zinc vanadium cell electrolyte preparation method according to claim 1, characterized in that, The soluble zinc salt is selected from one or more of zinc chloride, zinc acetate and zinc tetrafluoroborate.

4. The aqueous zinc vanadium cell electrolyte preparation method according to claim 3, characterized in that, The soluble zinc salt comprises zinc chloride and zinc acetate.

5. The aqueous zinc vanadium cell electrolyte preparation method according to claim 4, characterized in that, The concentration of the zinc chloride is 15 to 25 mol / L, and the concentration of the zinc acetate is 1 to 3 mol / L.

6. The aqueous zinc vanadium cell electrolyte preparation method according to claim 1, characterized in that, The stirring condition is that the stirring is performed at 50 to 100℃ for 10 to 60 minutes.

7. An aqueous zinc vanadium battery, characterized in that, The aqueous electrolyte for zinc-vanadium batteries comprises the aqueous electrolyte for zinc-vanadium batteries according to any one of claims 1 to 6, and the battery is a symmetric battery, a half battery or a full battery. The symmetric battery comprises a zinc foil negative electrode, a zinc foil positive electrode, a separator and the electrolyte. The half battery comprises a zinc foil negative electrode, a current collector, a separator and the electrolyte. The full battery comprises a zinc foil negative electrode, a vanadium-based positive electrode material, a separator and the electrolyte.

8. The aqueous zinc vanadium cell of claim 7, wherein, The separator is selected from any one of glass fiber, filter paper, bamboo cellulose or an aqueous polyethylene separator.

9. The aqueous zinc vanadium cell of claim 7, wherein, The current collector is selected from any one of copper foil, copper mesh, foamed copper, stainless steel mesh, titanium foil or foamed nickel.

10. The aqueous zinc vanadium cell of claim 7, wherein, The vanadium-based positive electrode material is at least one of vanadium pentoxide or potassium ion intercalated hydrated vanadium pentoxide.

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