Long cycle battery zinc negative electrode material and preparation method thereof

Abstract

The application discloses a long-circulation battery zinc negative electrode material and a preparation method thereof, and belongs to the technical field of zinc batteries. The zinc base is pretreated by cleaning, polyethylene glycol modified ZnO dispersion liquid and silane coupling agent modified SiO2 dispersion liquid are respectively prepared, a composite sol is obtained by mixing, the sol film is coated on the surface of the zinc foil by using the dip-coating method, vacuum annealing treatment is carried out, ZnO crystal state recrystallization bridging and cross-linking and amorphous SiO2 rigid support are utilized, and an integrated porous composite protective coating is constructed. The application solves the defects of poor ion conduction of the traditional dense coating, easy pulverization and falling of the loose coating and no synergistic effect of the physical blending coating. The application improves the cycle life and the electrochemical stability of the aqueous zinc negative electrode, and is suitable for large-scale production and application of energy storage type aqueous zinc batteries.

Description

Technical Field

[0001] This invention belongs to the field of zinc battery technology, specifically relating to a zinc anode material for long-cycle batteries and its preparation method. Background Technology

[0002] Aqueous zinc-ion batteries, with their advantages of safety, non-toxicity, low cost, environmental friendliness, and high theoretical capacity, have excellent industrialization prospects in large-scale energy storage, portable power supplies for civilian use, and low-speed energy storage devices. Metallic zinc anodes are abundant, have excellent conductivity, and are easy to process, making them the core anode material for aqueous zinc batteries.

[0003] However, commercial pure zinc anodes have many inherent defects: during repeated charge-discharge cycles, zinc ions tend to preferentially deposit at the tips of the electrode surface, forming sharp zinc dendrites that can easily pierce the separator and cause battery short-circuit failure; at the same time, zinc metal has high chemical activity, and long-term contact with aqueous electrolytes can easily cause severe corrosion, passivation, and hydrogen evolution side reactions, resulting in continuous loss of active zinc and continuous increase in interfacial impedance, ultimately leading to rapid capacity decay and a significant reduction in cycle life, which seriously restricts the large-scale application of aqueous zinc-ion batteries.

[0004] Currently, surface inorganic coating modification is the mainstream technical solution for improving the stability of zinc anodes. While existing dense protective coatings can achieve good electrolyte barrier and corrosion resistance, their overly dense structure and lack of ion transport channels lead to problems such as high interfacial impedance, severe electrode polarization, poor rate performance, and slow zinc deposition kinetics. On the other hand, conventional loose porous coatings can improve ion transport performance, but the weak bonding force between particles and the lack of an effective cross-linking network result in poor overall structural integrity. Under the repeated volume deformation stress of long-term charge and discharge of the battery, particle peeling, coating powdering, and large-area detachment failure are prone to occur. In addition, existing composite modification schemes are mostly simple physical blends and stacks of different functional particles. There is no structural synergy between the two phase components and no phase change differentiation design. It is impossible to simultaneously achieve structural integrity, corrosion resistance, rapid ion conduction, and interfacial electric field homogenization. The overall performance of the modification has obvious bottlenecks, making it difficult to meet the industrial application requirements of long-cycle, high-stability aqueous zinc batteries. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a long-cycle zinc anode material for batteries and its preparation method. By depositing a mixture of SiO2 and ZnO particles on a zinc sheet and then annealing it to obtain an integrated porous composite protective coating, the technical defects of traditional modified coatings are overcome, significantly improving the cycle life and electrochemical stability of the zinc anode.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a zinc anode material for a long-cycle battery includes the following steps:

[0008] S1. Zinc substrate pretreatment: The zinc foil is ultrasonically cleaned with anhydrous ethanol and deionized water, and then dried to obtain a clean zinc substrate;

[0009] S2. Preparation of composite sol:

[0010] Preparation of ZnO dispersion: Dissolve 2.0-2.4 g of zinc acetate dihydrate in 40-60 mL of anhydrous ethanol to obtain solution A. Then dissolve 0.8-1.0 g of potassium hydroxide in 10-12 mL of anhydrous ethanol to obtain solution B. Add solution B to solution A and stir for 5-10 min. Then add 3 times the volume of n-hexane, precipitate, centrifuge, and wash with anhydrous ethanol to obtain ZnO particles. Disperse the particles in 10-15 mL of anhydrous ethanol and add 0.1-0.2 g of polyethylene glycol 600. Stir to obtain ZnO dispersion.

[0011] Preparation of SiO2 dispersion: Mix 3-5 mL of tetraethyl orthosilicate, 40-60 mL of anhydrous ethanol, and 1-2 mL of deionized water evenly, then add 0.4-0.6 mL of 25% ammonia water. Stir at room temperature for 5-6 hours, then centrifuge to obtain SiO2 particles. Disperse the particles in 10-15 mL of anhydrous ethanol, add 0.1-0.2 g of silane coupling agent KH550, and stir to obtain SiO2 dispersion.

[0012] Preparation of composite sol: ZnO dispersion and SiO2 dispersion are mixed evenly to obtain composite sol;

[0013] S3. Sol deposition coating: The zinc foil is immersed in the composite sol using the dip-coating method at a speed of 75-100 mm / min and then naturally dried to form a uniform sol film.

[0014] S4. Vacuum annealing treatment: Place the dried zinc anode in a vacuum annealing furnace and anneal at 500-600℃ for 2-3 hours to obtain the zinc anode material.

[0015] A zinc anode material for long-cycle batteries was obtained according to the above preparation method.

[0016] The beneficial effects of this invention are as follows:

[0017] (1) This invention utilizes the synergistic effect of differential phase transformation between ZnO crystalline recrystallization bridging crosslinking and SiO2 amorphous rigid support to successfully construct a porous composite protective coating with integrated structure and high adhesion. Through vacuum annealing, a grain boundary bonded crosslinking network is formed between ZnO particles, overcoming the shortcomings of traditional simple physical mixing coatings where particle bonding is weak and relies solely on van der Waals forces for stacking. This has been verified through long-term cycling tests.

[0018] (2) The porous structure of the composite coating of the present invention solves the problem of insufficient ion transport in traditional single dense coatings, and at the same time makes up for the shortcomings of poor protection of single loose SiO2 coatings.

[0019] (3) The composite coating prepared by the present invention is undamaged and does not peel off, and has excellent mechanical wear resistance. It transforms the weak van der Waals forces between coating particles into a crystal connection structure, which significantly improves the mechanical strength of the coating. Attached Figure Description

[0020] Figure 1 The XRD diffraction patterns of the ZnO particles and SiO2 particles prepared in Example 1 are shown below.

[0021] Figure 2 The image shows a scanning electron microscope (SEM) image of the surface morphology of the zinc anode material prepared in Example 1.

[0022] Figure 3 Here are scanning electron microscope images of the surface morphology of the zinc anode material prepared in Comparative Example 2;

[0023] Figure 4 Here are scanning electron microscope images of the surface morphology of the zinc anode material prepared in Comparative Example 3;

[0024] Figure 5 Here are scanning electron microscope images of the surface morphology of the zinc anode material prepared in Comparative Example 4.

[0025] Figure 6 For coating abrasion resistance testing, among which Figure 6 (a) in the image shows the 3H pencil mark on the sample from Example 1. Figure 6 (b) in the figure shows the 3H pencil marks on the sample in Comparative Example 4;

[0026] Figure 7 The capacity retention rate of the zinc anode material in Example 1 and Comparative Examples 1-4 is given. Detailed Implementation

[0027] To make the above-mentioned objectives, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to examples. The following content is merely illustrative and explanatory of the concept of the present invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the inventive concept, all of which should fall within the protection scope of the present invention. The preparation method of the present invention will be described below through specific embodiments.

[0028] Example 1

[0029] A method for preparing a zinc anode material for a long-cycle battery includes the following steps:

[0030] S1. Zinc substrate pretreatment: Commercial pure zinc foil was selected and ultrasonically cleaned for 15 minutes each with anhydrous ethanol and deionized water to remove surface oil, oxide layer and impurities. It was then dried in a 60℃ oven to obtain a clean zinc substrate.

[0031] S2. Preparation of composite sol:

[0032] Preparation of ZnO dispersion: Dissolve 2.2 g of zinc acetate dihydrate in 50 mL of anhydrous ethanol and stir until homogeneous to obtain solution A; dissolve 0.9 g of potassium hydroxide in 11 mL of anhydrous ethanol and stir until dissolved to obtain solution B; slowly add solution B dropwise to solution A and stir continuously for 8 min, then add 3 times the volume of n-hexane to carry out precipitation reaction, centrifuge to separate the solid product, wash 3 times with anhydrous ethanol, and collect pure ZnO particles; disperse the obtained ZnO particles in 12 mL of anhydrous ethanol, add 0.15 g of polyethylene glycol 600, and stir magnetically for 30 min to obtain a uniform and stable ZnO dispersion.

[0033] Preparation of SiO2 dispersion: Take 4 mL of tetraethyl orthosilicate, 50 mL of anhydrous ethanol and 1.5 mL of deionized water and mix them evenly. Add 0.5 mL of 25% ammonia water and stir at room temperature for 5.5 h. After the reaction is completed, centrifuge to collect SiO2 particles. Disperse the SiO2 particles in 12 mL of anhydrous ethanol, add 0.15 g of silane coupling agent KH550, and stir for 20 min to modify and disperse, thus obtaining SiO2 dispersion.

[0034] Preparation of composite sol: The above ZnO dispersion and SiO2 dispersion were mixed in equal volumes and magnetically stirred for 20 min to obtain a uniform composite sol system.

[0035] S3. Sol-deposition coating: The pretreated zinc substrate is coated using the dip-coating method. The dipping speed is set to 85 mm / min, and the dip-coating is performed in a single step. The substrate is then air-dried at room temperature to form a uniform and transparent sol film on the zinc foil surface.

[0036] S4. Vacuum annealing treatment: The coated zinc anode is placed in a vacuum annealing furnace and annealed at a constant temperature of 550℃ for 2.5 hours in a vacuum atmosphere, and then cooled naturally with the furnace to finally obtain an integrated porous composite coating modified long-cycle zinc anode material.

[0037] Example 2

[0038] A method for preparing a zinc anode material for a long-cycle battery includes the following steps:

[0039] S1. Zinc matrix pretreatment: completely consistent with Example 1.

[0040] S2. Preparation of composite sol:

[0041] Preparation of ZnO dispersion: Dissolve 2.0 g of zinc acetate dihydrate in 40 mL of anhydrous ethanol and stir until homogeneous to obtain solution A; dissolve 0.8 g of potassium hydroxide in 10 mL of anhydrous ethanol and stir until homogeneous to obtain solution B; add solution B dropwise to solution A, stir for 5 min, add 3 times the volume of n-hexane to precipitate, centrifuge, wash with anhydrous ethanol and collect ZnO particles; disperse ZnO particles in 10 mL of anhydrous ethanol, add 0.1 g of polyethylene glycol 600, stir until homogeneous to obtain ZnO dispersion.

[0042] Preparation of SiO2 dispersion: Take 3 mL of tetraethyl orthosilicate, 40 mL of anhydrous ethanol and 1 mL of deionized water and mix well. Add 0.4 mL of 25% ammonia water and stir at room temperature for 5 h. Collect SiO2 particles by centrifugation. Disperse it in 10 mL of anhydrous ethanol, add 0.1 g of silane coupling agent KH550 and stir evenly to obtain SiO2 dispersion.

[0043] Preparation of composite sol: Mix the two dispersions evenly to obtain composite sol.

[0044] S3. Sol-deposition coating: The dipping and lifting speed is set to 75 mm / min, and the rest of the operation is the same as in Example 1.

[0045] S4. Vacuum annealing: Anneal at 500℃ for 2 hours in a vacuum atmosphere, followed by furnace cooling to obtain modified zinc anode material.

[0046] Example 3

[0047] A method for preparing a zinc anode material for a long-cycle battery includes the following steps:

[0048] S1. Zinc matrix pretreatment: completely consistent with Example 1.

[0049] S2. Preparation of composite sol:

[0050] Preparation of ZnO dispersion: Dissolve 2.4 g of zinc acetate dihydrate in 60 mL of anhydrous ethanol and stir until homogeneous to obtain solution A; dissolve 1.0 g of potassium hydroxide in 12 mL of anhydrous ethanol and stir until homogeneous to obtain solution B; add solution B dropwise to solution A, stir for 10 min, add 3 times the volume of n-hexane to precipitate, centrifuge, wash and collect ZnO particles; disperse ZnO particles in 15 mL of anhydrous ethanol, add 0.2 g of polyethylene glycol 600, stir until homogeneous to obtain ZnO dispersion.

[0051] Preparation of SiO2 dispersion: Take 5 mL of tetraethyl orthosilicate, 60 mL of anhydrous ethanol and 2 mL of deionized water and mix well. Add 0.6 mL of 25% ammonia water and stir at room temperature for 6 h. Collect SiO2 particles by centrifugation. Disperse it in 15 mL of anhydrous ethanol, add 0.2 g of silane coupling agent KH550 and stir evenly to obtain SiO2 dispersion.

[0052] Preparation of composite sol: Mix the two dispersions evenly to obtain composite sol.

[0053] S3. Sol-deposition coating: The dipping and lifting speed is set to 100 mm / min, and the rest of the operation is the same as in Example 1.

[0054] S4. Vacuum annealing: Anneal at 600℃ for 3 hours in a vacuum atmosphere, followed by furnace cooling to obtain modified zinc anode material.

[0055] Comparative Example 1

[0056] Raw pure zinc foil of the same specifications as in the examples was selected and subjected to ultrasonic cleaning and drying with anhydrous ethanol and deionized water, without any sol coating or annealing modification, as a blank pure zinc negative electrode control sample.

[0057] Comparative Example 2

[0058] The traditional single ZnO dense coating modification process was adopted, in which only ZnO sol was prepared to coat zinc foil without adding SiO2 components. After high-temperature annealing, a dense and non-porous ZnO protective coating was formed. The remaining substrate pretreatment, coating and annealing processes were consistent with those in Example 1, and a single dense ZnO coating modified zinc anode was prepared.

[0059] Comparative Example 3

[0060] The traditional single SiO2 porous coating modification process was adopted. Only SiO2 sol was prepared to coat zinc foil without adding ZnO components. The single porous SiO2 coating modified zinc anode was prepared by the same annealing process. The other operating parameters were the same as in Example 1.

[0061] Comparative Example 4

[0062] ZnO and SiO2 dispersions were prepared according to the ratio in Example 1 and mixed to obtain a composite sol. The same dip-coating process was used to coat the zinc foil surface, omitting the vacuum high-temperature annealing process and only allowing it to dry naturally at room temperature, resulting in a ZnO / SiO2 simple physical stacked composite coating modified zinc anode with no crystallization crosslinking structure.

[0063] Application performance test cases

[0064] The zinc anode materials prepared in Examples 1, 2, 3, and Comparative Examples 1-4 were used to assemble symmetrical coin-type aqueous zinc batteries, and the test conditions were uniform: current density 1 mA / cm². 2 Deposition stripping capacity 1mAh / cm 2 The system was tested for long-term cycling stability at room temperature.

[0065] Electrochemical testing was conducted using the Blue Battery Testing System and an electrochemical workstation (CHI660E) for long-cycle constant current charge-discharge testing. The capacity retention rate was calculated as: real-time discharge capacity / initial discharge capacity × 100%.

[0066] Figure 1 XRD diffraction patterns of ZnO particles and SiO2 particles in Example 1. Figure 1 The X-ray diffraction patterns of ZnO particles and SiO2 particles prepared in Example 1 of this invention are shown. One set of diffraction peaks matches the standard PDF card of hexagonal ZnO and shows sharp, high-intensity diffraction peaks, proving that ZnO is a highly crystalline crystalline particle. The other set of peaks has no sharp characteristic peaks, confirming that SiO2 is an amorphous structure.

[0067] This invention deliberately preserves the dual-phase raw material properties of crystalline ZnO and amorphous SiO2, providing a raw material basis for subsequent crystalline bridging crosslinking and amorphous rigid support heterogeneous composite structures after vacuum annealing;

[0068] Figure 2 Example 1: SEM morphology of the modified zinc anode surface. Figure 2 The image shows a scanning electron microscope (SEM) image of the integrated porous composite protective coating prepared in the preferred embodiment 1 of the present invention. The coating is continuous and intact, without cracks or local peeling. ZnO crystal particles overlap each other at the interface to form a three-dimensional cross-linked skeleton, and amorphous SiO2 fills the gaps in the skeleton to construct multi-level interconnected porous channels.

[0069] Vacuum annealing process allows ZnO to recrystallize in situ, forming chemically bonded grain boundary bridges between particles, which solves the problem of traditional physical blend coatings where particles are only bonded by van der Waals forces and are prone to powdering and falling off.

[0070] The SiO2 amorphous phase acts as a rigid framework to fill the voids, which on the one hand constrains the excessive growth of ZnO grains, and on the other hand, it buffers the volumetric deformation stress of zinc deposition / stripping by relying on the mechanical toughness of the amorphous structure.

[0071] Figure 3 : Figure 3 The image shows a scanning electron microscope image of a single coating prepared using only ZnO as a comparative example 2. After high-temperature annealing, the ZnO grains excessively agglomerate and the grain boundaries fuse, forming a film without continuous pores.

[0072] Figure 4Comparative Example 3 (Single loose SiO2 coating) SEM morphology image shows that after annealing, the SiO2 particles are still granular, and the coating exhibits a loosely aggregated particle state.

[0073] Figure 5 Comparative Example 4 (unannealed physical hybrid coating) SEM morphology image. Figure 5 The image shows a SEM image of the ZnO / SiO2 mixed coating obtained by omitting the vacuum annealing process and only drying at room temperature in Comparative Example 4. The ZnO and SiO2 particles are randomly and disorderly stacked, and there is no fusion and cross-linking at the interface between the two phases. The coating has weak adhesion to the zinc substrate and there are a large number of interfacial gaps.

[0074] Figure 6 The image shows a comparative test of the wear resistance and adhesion of the coatings conducted using a pencil hardness tester. The test uniformly used a 3H standard pencil to perform scratch tests on the sample coatings to characterize the structural stability, film adhesion, and wear resistance of the modified coatings.

[0075] in, Figure 6 Image (a) shows the scratch morphology of the integrated porous composite coated zinc anode sample prepared in Example 1 of this invention. The coating surface is intact and smooth, with no obvious scratches or coating peeling. Figure 6 (b) in the figure shows the scratch morphology of the unannealed physically stacked ZnO / SiO2 mixed coating zinc anode sample of Comparative Example 4. Under the same 3H pencil hardness scratch test conditions, obvious deep scratches appeared on the sample surface.

[0076] Figure 7 Example 1, Comparative Examples 1-4: Comparison curves of zinc anode capacity retention rate. Figure 7 The graph shows the capacity retention rate changes of all samples in this invention during long-cycle processing; the horizontal axis represents cycle time, and the vertical axis represents the percentage of remaining capacity. The curve for Example 1 shows a gradual decline throughout the cycle, maintaining a capacity retention rate of 86.2% after 800 hours; while the decline rates of Comparative Examples 1, 2, 3, and 4 are faster than that of Example 1. This indicates that within the process parameter range defined by this invention, the cycle life and capacity stability of the examples are superior to those of the comparative examples, which consist of only single components and are not annealed.

Claims

1. A method for preparing a zinc anode material for a long-cycle battery, characterized in that, Includes the following steps: S1. Zinc substrate pretreatment: The zinc foil is ultrasonically cleaned with anhydrous ethanol and deionized water, and then dried to obtain a clean zinc substrate; S2. Preparation of composite sol: Equal volumes of ZnO dispersion and SiO2 dispersion are mixed evenly to prepare composite sol; S3. Sol deposition coating: The zinc foil is immersed in the composite sol using the dip-coating method at a speed of 75-100 mm / min and then naturally dried to form a uniform sol film. S4. Vacuum annealing treatment: Place the dried zinc anode in a vacuum annealing furnace and anneal at 500-600℃ for 2-3 hours to obtain the zinc anode material.

2. The preparation method according to claim 1, characterized in that, The method for preparing the ZnO dispersion in step S2 includes the following steps: dissolving zinc acetate dihydrate in anhydrous ethanol to obtain solution A, dissolving potassium hydroxide in anhydrous ethanol to obtain solution B, adding solution B to solution A and stirring to react, adding n-hexane to precipitate, centrifuging and washing to obtain ZnO particles, dispersing the ZnO particles in anhydrous ethanol and adding polyethylene glycol 600 and stirring to obtain the ZnO dispersion.

3. The preparation method according to claim 2, characterized in that, The amount of zinc acetate dihydrate used is 2.0-2.4g, and the amount of anhydrous ethanol used for dissolution is 40-60mL; the amount of potassium hydroxide used is 0.8-1.0g, and the amount of anhydrous ethanol used for dissolution is 10-12mL; the amount of polyethylene glycol 600 added is 0.1-0.2g, and the amount of anhydrous ethanol used for ZnO particle dispersion is 10-15mL.

4. The preparation method according to claim 2, characterized in that, The stirring time after adding solution B to solution A is 5-10 minutes, and the volume of n-hexane added is 3 times the volume of the mixed solution.

5. The preparation method according to claim 1, characterized in that, The method for preparing the SiO2 dispersion in step S2 includes the following steps: mixing tetraethyl orthosilicate, anhydrous ethanol, and deionized water, adding ammonia water and stirring at room temperature, centrifuging to obtain SiO2 particles, dispersing the SiO2 particles in anhydrous ethanol and adding silane coupling agent KH550 and stirring to obtain the SiO2 dispersion.

6. The preparation method according to claim 5, characterized in that, The amount of tetraethyl orthosilicate used is 3-5 mL, the amount of anhydrous ethanol used is 40-60 mL, the amount of deionized water used is 1-2 mL, the amount of 25% ammonia water added is 0.4-0.6 mL, the amount of silane coupling agent KH550 added is 0.1-0.2 g, and the amount of anhydrous ethanol used for dispersing SiO2 particles is 10-15 mL.

7. The preparation method according to claim 5, characterized in that, The reaction time at room temperature with stirring is 5-6 hours.

8. A zinc anode material for long-cycle batteries prepared by the preparation method according to any one of claims 1-7.

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