A femtosecond laser preparation method of a zinc negative electrode PVA-porous carbon array protective layer and application thereof

Abstract

The application discloses a kind of zinc negative electrode PVA / porous carbon array protective layer femtosecond laser preparation method, zinc negative electrode material and its application, to solve zinc negative electrode dendrite growth, corrosion passivation, hydrogen evolution side reaction highlights and the problems such as existing protective layer preparation process is complex, structure regulation precision is low.The preparation method includes three steps: S1 PVA is mixed with deionized water, heated and stirred to form a semi-thick solution;S2 the solution is uniformly coated on the surface of zinc foil, and a PVA protective layer is formed after drying;S3 PVA protective layer is decomposed by femtosecond laser, and a porous PVA / porous carbon array composite protective layer is prepared.The composite protective layer enhances the interface stability through PVA, and the synergistic effect of porous carbon guiding zinc ion uniform deposition effectively inhibits dendrite growth and corrosion reaction.The application process is simple, raw materials are environmentally friendly and cost is relatively low, suitable for mass production, and provides key technical support for commercialization of aqueous zinc ion battery.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion battery technology, specifically to a method for preparing a composite protective layer on the surface of a zinc metal negative electrode and its application in zinc-ion batteries. Background Technology

[0002] Under the sustainable energy development strategy, large-scale energy storage technology has become crucial for supporting the grid connection and consumption of renewable energy. Aqueous zinc-ion batteries (ZIBs), with their advantages of high safety, low cost, environmental friendliness, and high theoretical capacity, are considered one of the most promising large-scale energy storage technologies. However, zinc-ion batteries face numerous technical bottlenecks in practical applications, severely hindering their commercialization process, with the performance degradation problem of the zinc anode being particularly prominent.

[0003] The core problems of zinc anodes mainly manifest in three aspects: First, dendrite growth. During charging, zinc ions migrate to and deposit on the anode under the influence of an electric field. Due to the uneven distribution of the electric field on the electrode surface and defects inherent in the anode itself, zinc ions tend to accumulate in areas with strong electric fields and active nucleation sites, forming protrusions that gradually grow into dendrites after multiple cycles. Dendrite growth not only punctures the battery separator, causing internal short circuits, but also forms "dead zinc," significantly reducing the battery's coulombic efficiency and severely affecting the battery's cycle life and safety. Second, corrosion and passivation. In alkaline electrolyte systems, zinc metal undergoes spontaneous corrosion, leading to roughening of the electrode surface and further accelerating dendrite growth. Simultaneously, corrosion byproducts increase the battery's internal resistance. In neutral or acidic electrolytes, the zinc anode undergoes electrochemical corrosion, forming a passivation layer covering the electrode surface, hindering the transport channels of zinc ions, resulting in rapid capacity degradation and decreased charging efficiency. Third, hydrogen evolution reaction. The water in the electrolyte undergoes a hydrogen evolution reaction on the surface of the zinc electrode. This not only consumes the water in the electrolyte and affects the normal deposition process of zinc ions, but also corrodes the electrode material. The hydrogen gas produced increases the internal pressure of the battery, causing the battery to expand or even leak. At the same time, the byproducts of the hydrogen evolution reaction can also induce dendrite growth and increase the battery impedance.

[0004] To address these issues, researchers have conducted extensive studies and proposed various improvement strategies. Regarding anode modification, using a three-dimensional substrate can promote dendrite-free zinc plating, but this method suffers from complex processes, high production costs, and significant electrode weight gain. Alloying modification can improve zinc deposition behavior, but it easily introduces impurities that affect battery performance. Adding electrolyte additives can regulate the zinc ion deposition process, but precise control of the amount added is required, and the additives are prone to failure during cycling. In terms of electrolyte optimization, the inherent defects of traditional aqueous electrolytes are difficult to overcome, while non-aqueous electrolytes such as ionic liquids and deep eutectic solvents have limitations such as high cost and low ionic conductivity.

[0005] Introducing a protective layer on the surface of the zinc anode is considered an efficient and feasible solution. This layer isolates zinc metal from direct contact with corrosive electrolytes, fundamentally inhibiting dendrite growth and side reactions. Polyvinyl alcohol (PVA), as a green and environmentally friendly polymer material, possesses good biocompatibility and tunable mechanical properties. The hydroxyl groups in its molecular chain interact with zinc ions through hydrogen bonds, enhancing the electrode's conductivity and structural stability. Simultaneously, the interstitial structure formed between PVA molecules facilitates the insertion and extraction of zinc ions. Previous studies have shown that a PVA@SR-ZnMoO4 protective layer with an SEI-like structure enables the zinc anode to achieve stable cycling for 1700 hours with a coulombic efficiency of 99.42%. Porous carbon materials possess an ultra-large specific surface area, providing abundant zinc ion deposition sites, guiding uniform zinc ion deposition, and their excellent conductivity reduces battery internal resistance, improving charge and discharge efficiency. Combining PVA with porous carbon arrays to form a protective layer can balance interfacial stability and optimized deposition behavior, potentially offering a synergistic solution to the key technical challenges of zinc anodes in zinc-ion batteries.

[0006] However, existing methods for preparing PVA / carbon composite protective layers often suffer from complex processes, low precision in controlling the porous structure, and weak bonding at the composite interface, limiting their practical applications. Femtosecond lasers, as a novel micro / nano fabrication technology, offer advantages such as narrow pulse width, high peak power, and a small heat-affected zone, enabling precise point-to-point processing of materials and providing a new technological pathway for preparing structurally controllable composite protective layers. Summary of the Invention

[0007] To address the problems of dendrite growth, corrosion passivation, and severe side reactions in existing zinc anodes of zinc-ion batteries, as well as the shortcomings of existing protective layer preparation methods such as complex processes and low structural control precision, this invention provides a femtosecond laser preparation method for a PVA-porous carbon array protective layer for zinc anodes. The method achieves precise preparation of the PVA-porous carbon array composite protective layer through femtosecond laser-guided thermal decomposition. This protective layer can effectively inhibit zinc dendrite growth and corrosion reactions, optimize zinc ion deposition behavior, and improve the electrochemical performance of the battery.

[0008] To achieve the above objectives, this invention provides a femtosecond laser fabrication method for a zinc anode PVA / porous carbon array protective layer, comprising the following steps:

[0009] S1, PVA pretreatment: PVA is mixed with deionized water, heated and stirred to dissolve and form a semi-viscous solution;

[0010] S2, Coating to form a film: The semi-viscous solution is uniformly coated onto the surface of zinc foil to form a PVA protective layer;

[0011] S3, Femtosecond laser processing: The PVA protective layer is thermally decomposed at specific points using a femtosecond laser pulse, causing the PVA to undergo a pyrolysis reaction to form a porous carbon structure, ultimately obtaining a PVA / porous carbon array composite protective layer embedded with a porous carbon array.

[0012] Furthermore, the mass-to-volume ratio of PVA to deionized water in step S1 is (5-15) g: 100 mL.

[0013] Furthermore, the heating temperature in step S1 is 60-90℃, and the stirring rate is 200-400 rad / s.

[0014] Furthermore, the heating temperature is 80°C, the stirring rate is 300 rad / s, and the heating and stirring time is 1.5-2.5 h.

[0015] Furthermore, the zinc foil in step S2 has a purity of ≥99.9%, a thickness of 80-120μm, and is ultrasonically cleaned with ethanol and dried before coating.

[0016] Furthermore, the thickness of the PVA protective layer in step S2 is 50-150 μm, and the coating method is scraping, spin coating or dip coating. After coating, it is left to dry at room temperature for 8-16 hours.

[0017] Furthermore, the thickness of the PVA protective layer is 50-100μm, and the coating method is blade coating with a coating speed of 3-7mm / s.

[0018] Furthermore, in step S3, the femtosecond laser has a wavelength of 700-900nm, a pulse width of 50-200fs, a repetition frequency of 0.5-2kHz, and a scanning speed of 5-15μm / s; the porous carbon array has a pore size of 5-15μm and a spacing of 1-5μm between the porous carbon particles.

[0019] In another aspect, the present invention provides a zinc anode material prepared by the above-described preparation method. The zinc anode material includes a zinc foil substrate and a PVA / porous carbon array composite protective layer covering the surface of the zinc foil substrate.

[0020] The present invention also provides an application of the zinc anode material described above in an aqueous zinc-ion battery.

[0021] The beneficial effects of this invention are:

[0022] (1) This invention uses femtosecond laser point-to-point thermal decomposition technology to prepare a PVA / porous carbon array composite protective layer. The process is simple and precise, and it can realize the directional design of the porous carbon array structure, which solves the problems of complex process and poor structural controllability of traditional composite protective layer preparation. The heat-affected zone of the femtosecond laser is small, which can avoid damage to the zinc foil substrate, while ensuring that a strong composite interface is formed between PVA and porous carbon.

[0023] (2) The PVA / porous carbon array composite protective layer has a synergistic effect: the PVA matrix enhances the interfacial stability and inhibits the corrosion reaction through the hydrogen bonding between hydroxyl groups and zinc ions; the porous carbon array provides abundant nucleation sites, reduces the local current density, makes the electric field distribution uniform, guides the directional and uniform deposition of zinc ions, and inhibits dendrite growth from the source; the porous structure can also accelerate zinc ion transport and reduce the internal resistance of the battery.

[0024] (3) The zinc anode material prepared using this invention exhibits excellent electrochemical performance in aqueous zinc-ion batteries: it can effectively inhibit corrosion and contamination of the zinc metal surface and reduce the occurrence of side reactions such as hydrogen evolution; the battery cycle stability is significantly improved, reaching 2 mA / cm 2 It can achieve stable cycling for a long time at current densities; the coulombic efficiency is over 99%, the polarization voltage is significantly reduced, and it also has good storage performance and reversibility.

[0025] (4) The preparation method of the present invention uses readily available raw materials, has low cost and is environmentally friendly, and is suitable for large-scale production. The prepared zinc anode material can be widely used in large-scale energy storage water-based zinc-ion batteries, providing key technical support for the commercial promotion of zinc-ion batteries. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating the preparation principle and dendrite growth suppression of the zinc anode PVA / porous carbon array protective layer of the present invention; wherein (a) is a schematic diagram of dendrite growth of the zinc anode without a protective layer, and (b) is a schematic diagram of the preparation of the PVA / porous carbon array protective layer and dendrite suppression by femtosecond laser.

[0027] Figure 2 This is a SEM characterization image of the LPVA-Zn anode prepared in Example 1 of the present invention.

[0028] Figure 3 This is a schematic diagram of the structure of the aqueous zinc-ion battery involved in this invention.

[0029] Figure 4 The voltage-time cycling stability curves are for the zinc anode assembled batteries prepared in Example 1 and Comparative Examples 1 and 2.

[0030] Figure 5The graph shows a comparison of the coulombic efficiency of the zinc anode assembled batteries prepared in Example 1 and Comparative Examples 1 and 2.

[0031] Figure 6 The graph shows a comparison of the cycle stability of the zinc anode assembled batteries prepared in Example 1 and Comparative Examples 1 and 2. Detailed Implementation

[0032] The specific embodiments of the present invention will be described in further detail below with reference to specific examples. These examples are used to illustrate the present invention, but are not intended to limit the scope of the invention.

[0033] To keep the embodiments concise, only the parts related to the present invention are schematically shown in the embodiments, and they do not represent the actual structure of the product. In addition, to make the embodiments concise and easy to understand, only one of the components with the same structure or function in the embodiments is schematically drawn, or only one of them is marked.

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, specific implementation methods of the present invention will be described below. Obviously, those skilled in the art can obtain other similar structural products and other implementation methods based on this embodiment without any creative effort.

[0035] Example 1

[0036] A femtosecond laser fabrication method for a zinc anode PVA / porous carbon array protective layer, the specific steps of which are as follows:

[0037] PVA pretreatment: Weigh 10g of PVA powder and mix it with 100mL of deionized water. Place the mixture in a constant temperature water bath and control the heating temperature at 80℃. Stir at a stirring rate of 300 rad / s for 2 hours until the PVA is completely dissolved and a uniform, transparent, semi-viscous solution is formed.

[0038] Coating film formation: The pretreated zinc foil with a thickness of 100μm and a purity of 99.99% is cut into 2cm×2cm sheets. The semi-viscous solution prepared in step 1 is uniformly coated onto the surface of the zinc foil using a scraping method at a scraping speed of 5mm / s. The sheets are then allowed to stand and dry at room temperature for 12h to form a PVA protective layer with a thickness of 100μm.

[0039] Femtosecond laser processing: A Ti:sapphire femtosecond laser was used to scan and process the PVA protective layer. The laser wavelength was 800 nm, the pulse width was 100 fs, the repetition rate was 1 kHz, the laser power was 50 mW, and the scanning speed was 10 μm / s. The laser scanning path was controlled by computer programming to achieve point-to-point thermal decomposition, ultimately obtaining a zinc anode material (denoted as LPVA-Zn) with a porous carbon pore size of 10 μm and a porous carbon spacing of 2 μm.

[0040] Comparative Example 1

[0041] Bare zinc negative electrode without protective layer (denoted as Bare Zn): The same zinc foil as in Example 1 is used directly, cut into 2cm×2cm sheets, without any protective coating treatment.

[0042] Comparative Example 2

[0043] Pure PVA protective zinc anode (denoted as PVA-Zn): PVA protective zinc foil was prepared according to steps 1 and 2 of Example 1 without femtosecond laser treatment, i.e. the protective layer was only a PVA film with a thickness of 100 μm.

[0044] Performance testing

[0045] The zinc anode materials prepared in Example 1 and Comparative Examples 1 and 2 were assembled into CR2032 button batteries with MnO2 cathode, 2 mol / L ZnSO4 electrolyte, and glass fiber separator, respectively, and their electrochemical performance was tested.

[0046] Polarization voltage stability test: at 2mA / cm 2 Charge-discharge cycle tests were performed at current densities, and the results are as follows: Figure 4 As shown, Bare Zn exhibited significant voltage fluctuations after 500 hours of cycling, indicating poor cycling stability; PVA-Zn showed improved cycling stability, but capacity decay occurred after 1200 hours; while LPVA-Zn maintained a stable voltage curve after 2000 hours of cycling, without significant decay, demonstrating excellent cycling stability.

[0047] Coulomb efficiency test: at 2mA / cm 2 The coulombic efficiency of the battery was tested at a current density, and the results are as follows: Figure 5 As shown, BareZn's coulombic efficiency is only around 80% and fluctuates significantly; PVA-Zn's coulombic efficiency is improved to over 90%, but decreases slightly in the later stages of cycling; LPVA-Zn's coulombic efficiency remains stable at over 99.4%, demonstrating excellent charge transfer efficiency.

[0048] Cyclic stability test: The polarization voltage was tested at different numbers of cycles, and the results are as follows. Figure 6 As shown, Bare Zn exhibits the fastest capacity decay, decreasing significantly after approximately 200 cycles, and its coulombic efficiency also drops rapidly. This indicates that the bare zinc anode suffers severe capacity loss and extremely low charge transfer efficiency due to dendrite formation, corrosion, and other issues. PVA-Zn experiences a slower capacity decay rate than bare zinc, but it still gradually decreases with the number of cycles, and its coulombic efficiency also shows a decaying trend, only partially alleviating the capacity and efficiency loss problems of the anode. LPVA-Zn shows minimal capacity decay and optimal retention during 1600 cycles, while its coulombic efficiency remains at a high level close to 100% for an extended period. This demonstrates that this composite protective layer effectively suppresses capacity loss and improves charge transfer efficiency, exhibiting significantly better performance than the previous two anode types.

[0049] Microstructure characterization: Scanning electron microscopy (SEM) was used to observe the surface of the negative electrode after cycling. BareZn surface showed a large number of randomly growing dendrites; PVA-Zn surface did not show obvious dendrites, but there were traces of corrosion; while LPVA-Zn surface remained flat, the porous carbon array structure was intact, zinc ions were uniformly deposited on the porous carbon sites, and no dendrite growth was observed.

[0050] The above test results show that the PVA / porous carbon array composite protective layer prepared by the present invention can effectively inhibit zinc dendrite growth and corrosion reaction, significantly improve the electrochemical performance of zinc-ion batteries, and has important practical application value.

[0051] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. 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.

Claims

1. A femtosecond laser fabrication method for a zinc anode PVA / porous carbon array protective layer, characterized in that, Includes the following steps: S1, PVA pretreatment: PVA is mixed with deionized water, heated and stirred to dissolve and form a semi-viscous solution; S2, Coating to form a film: The semi-viscous solution is uniformly coated onto the surface of zinc foil to form a PVA protective layer; S3, Femtosecond laser processing: The PVA protective layer is thermally decomposed at specific points using a femtosecond laser pulse, causing the PVA to undergo a pyrolysis reaction to form a porous carbon structure, ultimately obtaining a PVA / porous carbon array composite protective layer embedded with a porous carbon array.

2. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of PVA to deionized water in step S1 is (5-15) g: 100 mL.

3. The preparation method according to claim 1, characterized in that, The heating temperature in step S1 is 60-90℃, and the stirring rate is 200-400 rad / s.

4. The preparation method according to claim 3, characterized in that, The heating temperature is 80℃, the stirring rate is 300 rad / s, and the heating and stirring time is 1.5-2.5h.

5. The preparation method according to claim 1, characterized in that, The zinc foil mentioned in step S2 has a purity of ≥99.9% and a thickness of 80-120μm. Before coating, the zinc foil is ultrasonically cleaned with ethanol and dried.

6. The preparation method according to claim 1, characterized in that, The thickness of the PVA protective layer in step S2 is 50-150 μm, and the coating method is scraping, spin coating or dip coating. After coating, it is left to dry at room temperature for 8-16 hours.

7. The preparation method according to claim 6, characterized in that, The thickness of the PVA protective layer is 50-100μm, and the coating method is blade coating with a coating speed of 3-7mm / s.

8. The preparation method according to claim 1, characterized in that, The femtosecond laser in step S3 has a wavelength of 700-900nm, a pulse width of 50-200fs, a repetition frequency of 0.5-2kHz, and a scanning speed of 5-15μm / s; the porous carbon array has a porous carbon pore size of 5-15μm and a pore spacing of 1-5μm.

9. A zinc anode material, characterized in that, The zinc anode material is prepared by any one of the preparation methods described in claims 1-8, and includes a zinc foil substrate and a PVA / porous carbon array composite protective layer covering the surface of the zinc foil substrate.

10. The application of the zinc anode material according to claim 9 in an aqueous zinc-ion battery.

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