Modified electrolyte for aqueous zinc-ion battery and preparation method thereof

Abstract

The application discloses a modified electrolyte of a water-based zinc ion battery and a preparation method thereof, and belongs to the field of electrochemistry. The application provides a strategy for modifying the electrolyte of the water-based zinc ion battery by using sulfur-defect-containing molybdenum disulfide quantum dots as electrolyte additives of the water-based zinc ion battery. The sulfur-defect-containing molybdenum disulfide quantum dots have the advantages of high specific surface area and high active site of quantum dots and low Zn 2+ migration energy barrier and strong zincophilic property. By using the sulfur-defect-containing molybdenum disulfide quantum dots as electrolyte additives, the synergistic effect of interface adsorption regulation, crystal face orientation induction and ion transmission acceleration can synchronously solve the problems of zinc dendrite growth and side reactions, and a new technical path is provided for breaking through the bottleneck of the prior art.

Description

Technical Field

[0001] This invention belongs to the field of electrochemistry, specifically relating to a modified electrolyte for aqueous zinc-ion batteries and its preparation method. Background Technology

[0002] Aqueous zinc-ion batteries are considered one of the most promising next-generation low-cost and high-safety energy storage technologies due to their significant advantages, such as abundant zinc resources (abundance of about 70 mg / kg in the Earth's crust), low cost, non-toxic and non-flammable electrolyte, and high theoretical capacity (the theoretical specific capacity of zinc is 820 mAh / g). They have shown broad application prospects in portable electronic devices, large-scale energy storage power stations, and other fields.

[0003] However, the inherent instability of zinc anodes has become a core bottleneck restricting the industrialization of aqueous zinc-ion batteries. During charge-discharge cycles, two key problems easily occur on the surface of the zinc anode: firstly, zinc ions (Zn²⁺) tend to dissolve... + First, the deposition / stripping process on the electrode surface exhibits spatially uneven distribution, leading to localized electric field concentration and preferential formation of dendritic zinc dendrites in high-curvature regions. Second, in a weakly acidic aqueous electrolyte environment, the zinc anode is prone to self-corrosion and hydrogen evolution reactions, generating inert byproducts such as zinc hydroxide and basic zinc sulfate. To address these stability issues of the zinc anode, researchers have developed various technical strategies, primarily focusing on three main directions: electrode structure optimization, construction of artificial solid electrolyte interphase (SEI) layers, and electrolyte modification. The core idea of ​​electrolyte modification is to reconstruct Zn²⁺ by introducing functional additives or adjusting the electrolyte composition. + The solvation structure modulates the charge distribution and reaction kinetics at the electrode / electrolyte interface, thereby suppressing zinc dendrite growth and reducing side reactions. Existing electrolyte additives mainly include hydrogen-bonded types (such as Tween-80) and electrostatic types (such as Na...). + Reactive (such as sodium maleate) and surfactant (such as sodium dodecylbenzene sulfonate) types improve the stability of zinc anodes through mechanisms such as adsorption regulation, crystal orientation induction, and solvation structure reconstruction.

[0004] Meanwhile, molybdenum disulfide (MoS2), as a typical layered transition metal sulfide, has attracted widespread attention in the field of aqueous zinc-ion batteries due to its unique layered structure, excellent electronic conductivity, and good zinc affinity. Current applications of molybdenum disulfide-based materials in aqueous zinc-ion batteries mainly focus on cathode material modification, improving the Zn² content of the cathode through interlayer expansion and phase structure regulation (such as 1T phase induction). +Regarding storage and transport properties, there are no reports of its use as an electrolyte additive for zinc anode protection. Some studies have used molybdenum disulfide as an electrode coating material, but it suffers from similar problems to artificial SEI layers: the coating preparation process is complex, and molybdenum disulfide nanosheets are prone to stacking and agglomeration, leading to increased interfacial impedance; furthermore, pure molybdenum disulfide without sulfur defects has a negative impact on Zn²⁺. + Its adsorption and transport regulation capabilities are limited, making it impossible to fully utilize its zinc-affinity properties. In addition, traditional molybdenum disulfide materials are relatively large in size (micrometer-scale or ordinary nanometer-scale), with limited specific surface area and low contact efficiency with the electrolyte, making it difficult to achieve efficient regulation of the zinc anode interface.

[0005] Therefore, there are currently no reports on the use of molybdenum disulfide quantum dots with sulfur defects as additives in aqueous zinc-ion battery electrolytes to regulate the interfacial reaction of zinc anodes and protect zinc anodes. Their unique potential in improving the stability of zinc anodes needs to be explored. Summary of the Invention

[0006] To address the challenge of existing technologies simultaneously meeting the industrialization demands for high safety, long cycle life, and excellent kinetic performance, this invention provides a strategy for modifying aqueous zinc-ion battery electrolytes using sulfur-defect-containing molybdenum disulfide quantum dots as additives. These sulfur-defect-containing molybdenum disulfide quantum dots combine the advantages of high specific surface area and high active sites of quantum dots with the low Zn² content of sulfur-defect-containing molybdenum disulfide. + Due to its migration energy barrier and strong affinity for zinc, it can be used as an electrolyte additive. Through the synergistic effect of interfacial adsorption regulation, crystal orientation induction, and ion transport acceleration, it can simultaneously solve the problems of zinc dendrite growth and side reactions, providing a new technical path to overcome existing technical bottlenecks.

[0007] To achieve the above objectives, the following technical solution is adopted:

[0008] A modified electrolyte for aqueous zinc-ion batteries, the modified electrolyte comprising a base electrolyte and an additive, wherein the additive is molybdenum disulfide quantum dots with sulfur defects.

[0009] Preferably, the diameter of the sulfur-containing defective molybdenum disulfide quantum dots is 3~10 nm.

[0010] Preferably, the mass fraction of the additive in the modified electrolyte is 0.1% to 0.5%.

[0011] More preferably, the mass fraction of the additive in the modified electrolyte is 0.3% to 0.5%.

[0012] Preferably, the preparation steps of the sulfur-defective molybdenum disulfide quantum dots are as follows: 1) Raw material selection: Sodium molybdate is used as the molybdenum source, thiourea as the sulfur source, citric acid monohydrate as the complexing / morphology control agent, deionized water as the solvent, and hydrochloric acid as the pH adjuster. 2) Precursor preparation: Dissolve sodium molybdate and thiourea in deionized water and stir until completely dissolved. Then add citric acid monohydrate and add hydrochloric acid dropwise to adjust the pH of the solution to 2-3. Continue stirring to obtain a homogeneous precursor solution. 3) Hydrothermal reaction preparation: Heat the precursor solution to 180~240℃ and keep it at that temperature for 20~24 hours; 4) Post-processing purification: After the reaction is completed, the product is naturally cooled to room temperature, centrifuged and washed with deionized water and anhydrous ethanol in sequence to remove unreacted raw materials and impurities. After drying, the product is obtained as sulfur-defective molybdenum disulfide quantum dot powder.

[0013] Preferably, in step 2), the molar ratio of sodium molybdate to thiourea and citric acid monohydrate is 1:1.2:1.

[0014] Preferably, in step 4), the centrifugation speed is 8000~10000 r / min and the time is 10~15 minutes; the drying is carried out in a vacuum drying oven at a temperature of 60~80℃ for 12 hours.

[0015] Preferably, the base electrolyte in the modified electrolyte is zinc sulfate electrolyte with a concentration of 2 mol / L.

[0016] A method for preparing a modified electrolyte for aqueous zinc-ion batteries involves ultrasonically mixing molybdenum disulfide quantum dots with sulfur defects with a basic electrolyte.

[0017] Preferably, the ultrasonic dispersion power is 150~200 W and the time is 30~60 minutes.

[0018] The beneficial effects of this invention are: The zinc anode provides thorough protection, and the core bottleneck has been effectively addressed: Leveraging the synergistic effect of the high specific surface area of ​​quantum dots and sulfur defects, a dynamically adaptive interface adsorption layer can be formed, and Zn²⁺ can be precisely reconstructed. + The solvated structure effectively inhibits zinc dendrite growth, ensuring no short-circuit risk, while also isolating free water molecules and significantly reducing self-corrosion and hydrogen evolution side reactions. Actual testing shows that the battery's coulombic efficiency can be stably maintained at 99.6%, the cycle life is 8 times longer than the blank electrolyte system, and the highest specific capacity of the full cell is 220 mAh·g. -1 Far exceeding the comparison group (160mmAh·g) -1 Its protective effect far surpasses that of traditional artificial SEI layers and single-function additives. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the preparation process of a modified electrolyte for an aqueous zinc-ion battery according to the present invention. Figure 2 Characterization of MoS2 and electrolyte in Example 1; wherein, (a) XRD test of MoS2 material; (b) SEM surface morphology analysis of MoS2; (c) EPR / ESR spectrum of MoS2; (d) TEM of electrolyte modified with sulfur-containing defective molybdenum disulfide quantum dots; Figure 3 Example 1: Performance testing of Zn||Zn symmetric battery and Zn||Cu asymmetric battery; (a) Cycle life of zinc||Zn symmetric battery; (b) Comparison of coulombic efficiency of zinc-copper battery.

[0020] Figure 4 The contact angle of MoS2@ZnSO4 and ZnSO4 electrolyte on the zinc anode is given.

[0021] Figure 5 Cycle life of zinc||zinc symmetric cells prepared by adding different mass percentages of molybdenum disulfide quantum dots containing sulfur defects. Specific implementation methods The present invention is further illustrated below with reference to specific embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions in the art or as recommended by the manufacturer; the raw materials and reagents used, unless otherwise specified, are all commercially available from the conventional market. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention are within the scope of protection claimed by the present invention.

[0022] Example 1 1.1 Experimental Materials Titanium foil (99.9% purity), zinc foil (99.99% purity), and copper foil (99.9% purity) were all purchased from Alfa Aesar. Coumarin (CMA, analytical grade), zinc sulfate (ZnSO4, analytical grade), N-methylpyrrolidone (NMP, analytical grade), commercial vanadium pentoxide (analytical grade), acetylene black (ACET), and polyvinylidene fluoride (PVDF) sodium molybdate [Na2MoO4], thiourea [CS(NH2)2], citric acid monohydrate [C6H8O7·H2O] were all purchased directly from Shanghai Maclean Biochemical Technology Co., Ltd. All chemical reagents used in this experiment were used directly without further purification.

[0023] 1.2 Preparation of Electrolyte I. Preparation of molybdenum disulfide quantum dots with sulfur defects 1. Raw material selection: Sodium molybdate [Na2MoO4] was used as the molybdenum source, thiourea [CS(NH2)2] as the sulfur source, citric acid monohydrate [C6H8O7·H2O] (complexing / morphology control agent), deionized water as the solvent, and hydrochloric acid as the pH adjuster; 2. Precursor preparation: Dissolve sodium molybdate and thiourea in deionized water at a molar ratio of 1:1.2 and stir magnetically for 40 minutes until completely dissolved. Then add citric acid in water at a molar ratio of 1:1 to sodium molybdate. Add hydrochloric acid to adjust the pH of the solution to 2 and continue stirring for 20 minutes to obtain a homogeneous precursor solution. 3. Hydrothermal reaction preparation: The precursor solution was transferred to a polytetrafluoroethylene-lined reactor, sealed, and placed in an oven. It was kept at 200°C for 24 hours. The sulfur defect content was controlled by adjusting the hydrothermal temperature and time. 4. Post-processing purification: After the reaction is completed, the product is naturally cooled to room temperature and centrifuged (9000 r / min, 15 minutes). It is then washed four times with deionized water and anhydrous ethanol to remove unreacted raw materials and impurities. Subsequently, it is dried in a vacuum drying oven at 80℃ for 12 hours to obtain molybdenum disulfide quantum dot powder with sulfur defects, the size of which is controlled at 3~10 nm.

[0024] II. Preparation of Modified Aqueous Zinc Ion Electrolyte 1. Preparation of basic electrolyte: Using zinc sulfate (ZnSO4) as the zinc source and deionized water as the solvent, prepare a 2 mol / L ZnSO4 basic electrolyte and stir magnetically for 30 minutes until completely dissolved; 2. Additive dispersion: Take the above-mentioned sulfur-defective molybdenum disulfide quantum dot powder and add it to the basic electrolyte at a ratio of 0.3% by mass of the electrolyte. Use ultrasonic dispersion (power 200 W, time 60 minutes) to ensure that the quantum dots are uniformly dispersed and there is no agglomeration. The modified aqueous zinc ion electrolyte is obtained and is denoted as MoS2@ZnSO4.

[0025] As a control group, a pure 2 mol / L zinc sulfate electrolyte was obtained by using the same preparation process but without adding molybdenum disulfide quantum dot material.

[0026] 1.3 Electrode Preparation Anode preparation The zinc foil is first polished, then ultrasonically cleaned with anhydrous ethanol to remove the passivation layer on its surface. The treated zinc foil is then cut into circular zinc sheets with a diameter of 15mm to serve as the negative electrode of the battery.

[0027] Positive electrode preparation Vanadium pentoxide, polyvinylidene fluoride, and acetylene black were added to N-methylpyrrolidone solvent at a mass ratio of 8:1:1 and thoroughly mixed to form a homogeneous slurry. This slurry was then uniformly coated onto the surface of a titanium foil using a doctor blade coating method, and subsequently dried in a vacuum drying oven at 80°C for 12 hours. The dried titanium foil was then cut into circular electrode sheets with a diameter of 12 mm to serve as the positive electrode of the battery.

[0028] 1.4 Material Characterization The morphological evolution of the zinc anode during the electrochemical reaction was observed using a Hitachi SU8230 in-situ electron microscope. The microstructure of the zinc anode was characterized using a Thermo Fisher Scientific AperoS scanning electron microscope. The interaction mechanism between the electrolyte components and zinc ions was analyzed using a Bruker AV-400 nuclear magnetic resonance spectrometer and a Horiba LabRAMSoleil Raman spectrometer. The zinc affinity of the electrolyte was tested using a Shanghai Zhongchen Digital Technology Equipment Co., Ltd. (China).

[0029] 1.5 Battery Assembly In an air atmosphere, CR2032 coin cells (including Zn||Zn symmetric cells, Zn||Cu asymmetric cells, and Zn||V2O5 full cells) were assembled. Approximately 120 μL of the corresponding electrolyte was injected into each cell system, and Whatman glass fiber was used as the separator. Specifically, the Zn||Zn symmetric cells were assembled from two 12 mm diameter circular zinc sheets and a 16 mm diameter glass fiber separator; the Zn||Cu asymmetric cells used a 12 mm diameter copper sheet as the positive electrode and a zinc sheet of the same size as the negative electrode; and the Zn|||V2O5 full cells were assembled using the aforementioned vanadium pentoxide positive electrode and zinc negative electrode.

[0030] 1.6 Electrochemical Performance Testing A CHI-760E electrochemical workstation from Shanghai Chenhua Instruments Co., Ltd. was used to perform a series of electrochemical characterizations on the assembled battery, including linear sweep voltammetry (LSV), chronoamperometry (CA), Tafel polarization curves, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Chronoamperometry was performed under a constant overpotential of -150 mV relative to the open circuit potential; the Tafel polarization curves were measured at a scan rate of 10 mV / s, with the electrode assembly consistent with the battery testing; cyclic voltammetry was performed at a scan rate of 100 mV / s, and the differential capacitance of the electrodes was calculated.

[0031] The hydrogen evolution reaction (HER) behavior of the electrolyte was evaluated using a standard three-electrode system, with a graphite electrode as the working electrode, a silver / silver chloride electrode saturated with potassium chloride as the reference electrode, and a zinc sheet as the counter electrode. Linear sweep voltammetry was performed at a scan rate of 5 mV / s. Electrochemical impedance spectroscopy (EIS) was conducted in the frequency range of 0.01 Hz to 100 kHz, with an AC voltage amplitude set to 5 mV, to analyze the electrochemical impedance characteristics of the battery system.

[0032] The CT4008 battery testing system from Shenzhen Xinwei Electronics Co., Ltd. was used to conduct constant current charge-discharge cycle tests on Zn||Zn symmetric cells, Zn||Cu asymmetric cells, and Zn / / V2O5 full cells. All electrochemical tests in this experiment were performed at room temperature.

[0033] 1.7 Results Characterization of molybdenum disulfide quantum dot electrolytes with sulfur defects 1. The molybdenum disulfide powder was analyzed by XRD test, and the test results showed that the molybdenum disulfide material was successfully prepared.

[0034] 2. The surface morphology of molybdenum disulfide material was analyzed using SEM. The results showed that the surface of molybdenum disulfide material has a nanoscale morphology.

[0035] 3. Sulfur defects were detected in molybdenum disulfide materials, and EPR results showed the presence of sulfur vacancies within the molybdenum disulfide materials.

[0036] 4. The presence of quantum dots in the sulfur-vacancy molybdenum disulfide electrolyte was detected using TEM. The results shown in the figure indicate the presence of a large number of small spheres, indicating the successful preparation of sulfur-defect molybdenum disulfide quantum dots in the electrolyte.

[0037] 5. By comparing the cycle stability of Zn||Zn symmetric cells, it was found that the molybdenum disulfide quantum dot additive containing sulfur defects can significantly improve the cycle life of the cells. The zinc-copper half-cell can stably cycle for 1200 cycles with an average coulombic efficiency of 99.6%. Finally, the analysis of Zn / / V2O5 full cells showed that the molybdenum disulfide quantum dot additive containing sulfur defects can effectively improve the specific capacity of the full cells.

[0038] 6. Electrolytes were prepared by adding different mass percentages of molybdenum disulfide quantum dots with sulfur defects prepared in Example 1. The most suitable mass percentage of molybdenum disulfide quantum dots with sulfur defects was selected by zinc-zinc cycling time.

Claims

1. A modified electrolyte for aqueous zinc-ion batteries, characterized in that, The modified electrolyte includes a base electrolyte and an additive, wherein the additive is a sulfur-defective molybdenum disulfide quantum dot.

2. The aqueous zinc-ion battery modified electrolyte according to claim 1, characterized in that, The diameter of the sulfur-containing defective molybdenum disulfide quantum dots is 3~10 nm.

3. The aqueous zinc-ion battery modified electrolyte according to claim 1, characterized in that, The mass fraction of the additive in the modified electrolyte is 0.1% to 0.5%.

4. The aqueous zinc-ion battery modified electrolyte according to any one of claims 1 to 3, characterized in that, The preparation steps of the sulfur-defective molybdenum disulfide quantum dots are as follows: 1) Raw material selection: Sodium molybdate is used as the molybdenum source, thiourea as the sulfur source, citric acid monohydrate as the complexing / morphology control agent, deionized water as the solvent, and hydrochloric acid as the pH adjuster. 2) Precursor preparation: Dissolve sodium molybdate and thiourea in deionized water and stir until completely dissolved. Then add citric acid monohydrate and add hydrochloric acid dropwise to adjust the pH of the solution to 2-3. Continue stirring to obtain a homogeneous precursor solution. 3) Hydrothermal reaction preparation: Heat the precursor solution to 180~240℃ and keep it at that temperature for 20~24 hours; 4) Post-processing purification: After the reaction is completed, the product is naturally cooled to room temperature, centrifuged and washed with deionized water and anhydrous ethanol in sequence to remove unreacted raw materials and impurities. After drying, the product is obtained as sulfur-defective molybdenum disulfide quantum dot powder.

5. The aqueous zinc-ion battery modified electrolyte according to claim 4, characterized in that, In step 2), the molar ratio of sodium molybdate to thiourea and citric acid monohydrate is 1:1.2:

1.

6. The aqueous zinc-ion battery modified electrolyte according to claim 4, characterized in that, In step 4), the centrifugation speed is 8000~10000 r / min and the time is 10~15 minutes; the drying is carried out in a vacuum drying oven at 60~80℃ for 12 hours.

7. The aqueous zinc-ion battery modified electrolyte according to claim 4, characterized in that, The base electrolyte in the modified electrolyte is zinc sulfate electrolyte with a concentration of 2 mol / L.

8. A method for preparing an aqueous zinc-ion battery modified electrolyte according to any one of claims 1 to 7, characterized in that, The solution can be ultrasonically mixed with the basic electrolyte by molybdenum disulfide quantum dots containing sulfur defects.

9. The method for preparing an aqueous zinc-ion battery modified electrolyte according to claim 8, characterized in that, Ultrasonic dispersion power 150~200 W, time 30~60 minutes.

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