Zinc Anode with Polyamide-Based Ionic Conductor Coating, Preparation Method and Application Thereof

Abstract

The present invention relates to a zinc negative electrode with a polyamide-based coating having the characteristics of large-scale production, environmental protection, rapid preparation, and integration, belonging to the field of energy materials technology. It is characterized in that a polyamide gel is coated on the zinc surface, and then a rapid preparation of the integration of the coating and metallic zinc is achieved through a coagulation bath to realize the rapid transformation of the gel into a solid phase. During phase transformation, partial recovery of the electrolyte salt can be achieved and a rapid preparation of a coating with a differentiated internal and external structure can be realized; the residual metal salt can reduce the crystallinity of the polyamide-based polymer coating and play a role in accelerating the transport of lithium ions / zinc ions inside the polymer coating. The special ant nest-like structure and a large number of polar functional groups on the surface of the coating regulate the Zn<supgt;2+< / supgt; flux on the electrode surface, slow down zinc dendrites, and can also assist the desolvation process and reduce the initial zinc nucleation energy; the coating physically prevents direct contact between the zinc negative electrode and the electrolyte, thereby inhibiting adverse factors such as hydrogen evolution and side reactions during battery use, so as to extend the service life of the zinc negative electrode.

Description

Technical Field

[0001] The present invention belongs to the technical field of energy materials, and particularly relates to a preparation method and application of a zinc negative electrode with a polyamide-based ionic conductor coating having the characteristics of large-scale, environmental protection, rapid preparation, and integration. Background Art

[0002] Energy storage devices with metallic zinc as the negative electrode have been considered by researchers as one of the ideal energy storage systems to supplement organic lithium-ion batteries due to the advantages of rich zinc reserves, high safety, non-toxicity, high theoretical specific capacity (820 mAh / g, 5851 mAh / cm 3 ), relatively high hydrogen evolution potential (~1.2 V), and relatively low equilibrium potential (-0.763 V vs. standard hydrogen electrode (SHE)). However, due to the fact that the metallic zinc negative electrode is not completely flat during the processing, with sharp protrusions on the surface, during the discharge process, zinc ions will preferentially gain electrons and deposit on these protrusions and then cause dendrite growth. Dendrite growth will exacerbate the hydrogen evolution reaction, resulting in serious corrosion and passivation of the zinc negative electrode surface, greatly reducing the Coulombic efficiency and causing the energy storage device to fail. Researchers have proposed organic-inorganic coating strategies, which effectively extend the life of the zinc negative electrode. Regarding the inorganic coating strategy, the inorganic materials used have poor mechanical properties and cannot buffer the growth of dendrites. Additionally, binders need to be added, and some also require expensive instruments, which are not conducive to the large-scale application of zinc-ion batteries. Regarding organic coatings, researchers have proven that some organic polymer materials with a large number of polar functional groups on the surface have broad application prospects in the protection of zinc negative electrodes. However, some coatings are not suitable for large-scale, environmental protection, and rapid preparation due to factors such as the use of strongly corrosive chemical agents during the preparation process. Therefore, for the promotion of the commercial application of zinc-ion batteries, organic polymer coatings that can be prepared on a large scale, environmentally friendly, efficiently, and rapidly are of great significance for the protection of zinc negative electrodes. Inspired by deep eutectic materials, the present invention uses a high-concentration metal salt as a hydrogen bond donor and a polyamide material as a hydrogen bond acceptor. The intermolecular hydrogen bonds of the polyamide are dissociated by highly Lewis acidic high-concentration cations to promote its eutectic gelation. Then, through a water-infiltrated gel conversion method, a special ant-nest-like structure, a polyamide-based ionic conductor coating containing a trace amount of electrolyte salt, is successfully constructed on the surface of the zinc negative electrode, regulating the zinc ion flow on the surface of the zinc negative electrode, slowing down dendrite growth. At the same time, the solvated water of zinc ions is filtered out layer by layer, achieving the effect of reducing the initial nucleation energy of zinc; it can physically block the direct contact between the electrode and the electrolyte, inhibit hydrogen evolution, effectively extend the life of the zinc negative electrode, and specifically solve the key problems of dendrites and side reactions existing in the current energy storage system with metallic zinc as the negative electrode, having great significance for promoting the commercial application of zinc-based energy storage devices. Summary of the Invention

[0003] The object of the present invention is to physically block the direct contact between the electrode and the electrolyte, thereby achieving the ideal effect of inhibiting the side reaction between the zinc negative electrode and the electrolyte; by regulating the zinc ion flow, the problem of zinc dendrite growth is solved; and the solvated water is filtered layer by layer to reduce the initial zinc nucleation energy. To achieve the above object, the technical solution adopted by the present invention is as follows:

[0004] A zinc negative electrode with a polyamide-based ion conductor coating having large-scale, environmental protection, rapid preparation, and integration characteristics, the zinc negative electrode comprising an active material layer and a polyamide-based ion conductor coating.

[0005] For the zinc negative electrode with the polyamide-based ion conductor coating, the main components of the polyamide coating are polyamide-based materials (such as PA-6, PA-66, etc.) and trace lithium salts or zinc salts that can interact with the polymer. The mass fraction of polyamide in the coating is up to 60-90% at most, and the mass fraction of the lithium salt or zinc salt combined with the polyamide-based polymer in the coating is at least 10%.

[0006] The polymer coating contains at least one polyamide, and the polyamide includes aliphatic polyamide, aromatic polyimide. The salts combined with the polyamide-based polymer coating in a polyamide-based ion conductor coating having large-scale, environmental protection, rapid preparation, and integration characteristics include one or more of lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonate), lithium chloride, lithium bromide, zinc trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonate), zinc chloride, and zinc bromide.

[0007] The thickness of the polyamide-based polymer coating is 5-50 μm.

[0008] The metal zinc negative electrode active material includes one or more of pure zinc foil, pure zinc sheet, zinc alloy sheet, and flexible zinc negative electrode prepared from pure zinc powder and zinc alloy powder.

[0009] The formation of the polymer gel does not require the assistance of an organic solvent, and it can directly achieve gel sol-gelation in a salt solution.

[0010] The formation of the gel and the process of gel phase transformation into a film do not require heating or a coagulation bath of an organic solvent. Water acts as both a solvent and a coagulation bath carrier in this process.

[0011] A method for preparing a zinc negative electrode with a polyamide-based ion conductor coating having large-scale, environmental protection, rapid preparation, and integration characteristics according to claim 1, the steps are as follows:

[0012] One or more of the above lithium salts or zinc salts and one or more polyamide materials, or only one polyamide is dissolved in the aqueous solution of the above salt, placed at room temperature or heated in a forced-air oven at no higher than 80 °C until the mixture becomes a uniform gel; the prepared gel is coated on the surface of the above zinc negative electrode by a doctor blade method, a spraying method or a spin coating method; finally, through a water infiltration gel phase conversion method, with a fixed infiltration time for infiltration, a large amount of salt is dissolved into water during the infiltration process for recovery, and the polymer gel is successfully converted into a solid polymer coating with a low crystallinity and high ion conduction property containing a trace amount of salt, obtaining a polymer-integrated zinc negative electrode.

[0013] Application of a zinc negative electrode with a polyamide-based ion conductor coating having the characteristics of large-scale, environmental protection, rapid preparation, and integration. The zinc negative electrode with a polyamide-based ion conductor coating is used in zinc-based batteries including: lithium-zinc hybrid batteries, zinc-manganese batteries, secondary zinc-ion batteries, zinc-ion capacitors, lithium-zinc hybrid ion capacitors, and zinc-air batteries.

[0014] Advantages of the present invention:

[0015] The zinc negative electrode with a polyamide-based ion conductor coating of the present invention has the advantages of being capable of large-scale, environmental protection, rapid preparation, integration, high thermodynamic and chemical stability, and being able to achieve zinc ion transport. The biggest feature of the present invention is to use a high-concentration salt to reconstruct a polyamide gel with excellent ion conductivity. Water is both a solvent and a coagulation bath carrier, realizing a large proportion of salt recovery and using a polyamide coating containing a trace amount of salt for the protection of the aqueous zinc negative electrode, constructing a stable electrode interface, physically isolating the direct contact between the electrode and the electrolyte, thereby inhibiting hydrogen evolution, reducing the concentration of hydroxide ions in the electrolyte, reducing the generation of by-products on the electrode surface, and improving the Coulomb efficiency of the battery. At the same time, during the phase conversion process of the polyamide gel, the formation of a special ant nest-like structure has spatial penetration and a layer-by-layer filtering effect on solvated water, achieving the ideal effect of reducing the initial nucleation energy barrier of zinc. This coating can effectively extend the cycle life of the zinc negative electrode, and has great practical application value in terms of green, low-cost, and large-scale preparation. Brief Description of the Drawings

[0016] Appendix Figure 1 It is a long cycle curve graph of a Zn / Zn symmetric battery assembled with an uncoated zinc sheet and a Zn / Zn symmetric battery assembled with a zinc sheet with a polyamide-based ion conductor coating provided in Example 1 of the present invention in a 2M zinc sulfate aqueous electrolyte.

[0017] Appendix Figure 2 It is a cyclic voltammogram obtained by performing cyclic voltammetry testing on a zinc-stainless steel half-cell assembled with a zinc sheet with a polyamide-based ion conductor coating provided in Example 1 of the present invention at a scanning speed of 0.2 mV / s.

[0018] AppendixFigure 3 Tafel curve corrosion test diagrams of the Zn / Zn symmetric cell assembled with uncoated zinc sheets and the Zn / Zn symmetric cell assembled with zinc sheets having a polyamide-based ion conductor coating provided in Example 1 of the present invention in a 2M zinc sulfate aqueous electrolyte.

[0019] Attachment Figure 4 X-ray diffraction spectra (XRD) of the Zn / Zn symmetric cell assembled with uncoated zinc sheets and the Zn / Zn symmetric cell assembled with zinc sheets having a polyamide-based ion conductor coating provided in Example 1 of the present invention after 760 hours of cycling in a 2M zinc sulfate aqueous electrolyte.

[0020] Attachment Figure 5 Charge-discharge curve diagram of the Zn / AC hybrid capacitor assembled with zinc sheets having a polyamide-based ion conductor coating provided in Example 1 of the present invention.

[0021] Attachment Figure 6 Charge-discharge curve diagram of the Zn / MnO₂ battery assembled with zinc sheets having a polyamide-based ion conductor coating provided in Example 1 of the present invention.

[0022] Attachment Figure 7 Capacity-voltage diagram of the Zn / S battery assembled with zinc sheets having a polyamide-based ion conductor coating provided in Example 1 of the present invention.

[0023] Attachment Figure 8 SEM diagram of the zinc sheet having a polyamide-based ion conductor coating provided in Example 1 of the present invention.

[0024] Attachment Figure 9 Surface state of the Zn / Zn symmetric cell assembled with zinc sheets having a polyamide-based ion conductor coating provided in Example 1 of the present invention after 760 hours of cycling.

[0025] Attachment Figure 10 Coulombic efficiency of the half-cell assembled with a zinc sheet having a polyamide-based ion conductor coating and a copper foil with a polyamide-based ion conductor coating provided in Example 1 of the present invention tested on LAND.

[0026] Attachment Figure 11 And attachment Figure 12 The preparation process of the zinc sheet with a polyamide-based ion conductor coating provided in Example 1 of the present invention and the zinc sheet with a polyamide-based ion conductor coating after the transformation of the water-wetted gel.

[0027] Attachment Figure 13 Schematic diagram of dendrite inhibition by the polyamide-based ion conductor coating provided in Example 1 of the present invention.

[0028] Attachment Figure 14SEM image of the polyamide membrane provided in Example 2 of the present invention.

[0029] Appendix Figure 15 Polyamide states at different mass ratios provided in Example 5 of the present invention. Detailed description of specific implementation

[0030] The present invention will be further described in detail below through specific examples. The following examples are only used to illustrate the present invention, but not to limit the scope of implementation of the present invention. All technical solutions obtained by equivalent replacement or equivalent transformation fall within the protection scope of the present invention.

[0031] Example 1

[0032] Weigh polyamide, lithium trifluoromethanesulfonate, and water in a mass ratio of 0.5:1:0.3 into a 10 mL transparent vial, and let it stand to gel naturally. Gelation can be promoted by auxiliary heating, but ensure that the temperature does not exceed 80 °C. The zinc sheet can be used after ultrasonic cleaning with ethanol only. Then, use a wet film applicator with adjustable thickness to scrape the prepared gel on the surface of the zinc sheet. After coating, the zinc negative electrode is placed in distilled water, and the fixed infiltration time is 30 seconds. Finally, completely remove the moisture in a blast drying oven at 80 °C. After drying, a zinc sheet with a polyamide-based ion conductor coating is obtained. Using a 2M zinc sulfate aqueous solution as the electrolyte and ordinary filter paper as the separator, a Zn / Zn symmetric battery and a Zn / SS half-cell are assembled with this zinc sheet with a polyamide-based ion conductor coating and an uncoated zinc sheet as the electrodes respectively; at a current density of 0.5 mA / cm 2 Perform charge and discharge cycling, and the long-cycle curve is as shown in Figure 1 As shown, it is found that the symmetric battery assembled with the uncoated zinc sheet fails after 50 hours of cycling, while the symmetric battery assembled with the zinc sheet with a polyamide-based ion conductor coating stably cycles for 1500 hours, effectively increasing the life of the zinc negative electrode by 30 times; the assembled zinc-stainless steel (SS) half-cell is subjected to cyclic voltammetry testing at a scanning rate of 0.2 mV / s, and the cyclic voltammogram is as shown in Figure 2 As shown, the presence of the polyamide-based ion conductor coating does not affect the oxidation and reduction of zinc. Corrosion tests are carried out on the uncoated zinc sheet and the zinc sheet with a polyamide-based ion conductor coating in this example in a 2M zinc sulfate solution, and the results are as shown in Figure 3 As shown, the results show that. The corrosion potential of the zinc sheet with a polyamide-based ion conductor coating in this example is increased by 6.91 mV compared with the uncoated zinc sheet, indicating that the protection effect is significant. Figure 4XRD patterns of zinc foils of the Zn / Zn symmetric cells assembled with uncoated zinc foils and zinc foils with polyamide-based ion conductor coatings after cycling for 50 h and 760 h in 2 M zinc sulfate electrolyte, respectively. By comparison, there are two by-products of basic zinc sulfate on the surface of the uncoated zinc foil after cycling for 50 h, while there is only one by-product on the surface of the zinc foil with polyamide-based ion conductor coating in the example after cycling for 760 h. Using 2 M aqueous solution as the electrolyte and ordinary filter paper as the separator, Zn / AC hybrid capacitors and zinc-manganese batteries were assembled with the zinc foil with polyamide-based ion conductor coating in the example as the negative electrode. At a current density of 0.5 mA / cm 2 the charge-discharge curves of the Zn / AC hybrid capacitors and zinc-manganese batteries are as shown in Figure 5 and 6 , indicating that the polyamide-based ion conductor coating effectively extends the service life of the Zn / AC hybrid capacitors and zinc-manganese batteries. Using 2 M zinc sulfate added with 5% mass ratio of iodine as the electrolyte, filter paper as the separator, the zinc foil with polyamide-based ion conductor coating as the negative electrode, and elemental sulfur (S) as the positive electrode, a Zn / S battery was assembled. At a current density of 0.5 mA / cm 2 the charge-discharge curves of the Zn / S battery are as shown in Figure 7 .

[0033] Example 2

[0034] Weigh polyamide and anhydrous formic acid with a mass ratio of 0.5:0.3 into a transparent vial and let it stand to gel. Gelation can be promoted by auxiliary heating, but the temperature should not exceed 80 °C. Using a flat glass plate to simulate the zinc foil as the substrate, use a wet film applicator with adjustable thickness to scrape the prepared gel on the surface of the glass plate. After coating, place the glass plate in distilled water and fix the soaking time at 30 s. Finally, completely remove the moisture in an oven at 80 °C. After drying, a comparative polyamide film was obtained.

[0035] Example 3

[0036] Weigh polyamide 6 and lithium bis(trifluoromethanesulfonyl)imide with a mass ratio of 1:1 into a 10 mL transparent vial, add an appropriate amount of water, and then let it stand to gel naturally. Gelation can be promoted by auxiliary heating, but the temperature should not exceed 80 °C. Then use a wet film applicator with adjustable thickness to scrape the prepared gel on the surface of the treated zinc foil. After coating, place the negative electrode of the zinc foil in a coagulation bath of distilled water and fix the soaking time at 30 s. Finally, completely remove the moisture in an oven at 80 °C. After drying, a zinc foil with a polyamide-based ion conductor coating was obtained. Using 2 M aqueous zinc sulfate solution as the electrolyte and ordinary filter paper as the separator, AC capacitors were assembled with the zinc foil with polyamide-based ion conductor coating and the uncoated zinc foil as the electrodes respectively

[0037] Example 4

[0038] Weigh polyamide, lithium trifluoromethanesulfonate and water according to the mass ratios of 1:1:0.3, 0.5:1.5:0.3 and 1:0.5:0.3 respectively, place them in a vial, and let it stand to gel naturally. The gelation process can be promoted by auxiliary heating, but make sure the temperature does not exceed 80 °C.

[0039] Example 5

[0040] Weigh lithium trifluoromethanesulfonate, zinc trifluoromethanesulfonate, polyamide and water according to the mass ratio of 1:0.5:0.5:0.3, place them in a vial, and let it stand to gel naturally. The gelation process can be promoted by auxiliary heating, but make sure the temperature does not exceed 80 °C. Finally, a double-salt gel is obtained.

Claims

1. A zinc negative electrode with a polyamide-based ion conductor coating, characterized in that: The zinc negative electrode consists of a metallic zinc active material and a polyamide-based coating containing one or more lithium salts or zinc salts, wherein the polyamide-based coating is formed from a gel formed by an aqueous solution of one or more lithium salts or zinc salts and one or more polyamide materials, and is obtained by converting it into a solid polymer coating through a water-infiltrated gel phase inversion method.

2. The zinc negative electrode with a polyamide-based ion conductor coating according to claim 1, characterized in that, The main components of the polyamide-based coating are polyamide materials and lithium salts or zinc salts that can interact with the polymer; the mass fraction of the polyamide material in the coating is up to 60-90%, and the mass fraction of the lithium salt or zinc salt in the coating is at least 10%.

3. The zinc negative electrode with a polyamide-based ionic conductor coating according to claim 1, wherein, The metallic zinc active material includes one or several of pure zinc foil, pure zinc sheet, zinc alloy sheet, and flexible zinc negative electrodes prepared from pure zinc powder and zinc alloy powder.

4. A zinc negative electrode with a polyamide-based ionic conductor coating according to claim 1, characterized in that, The lithium salts or zinc salts contained in the polyamide-based coating are one or several of lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonate), lithium chloride, lithium bromide, zinc trifluoromethanesulfonate, zinc bis(trifluoromethanesulfonate), zinc chloride, and zinc bromide.

5. A zinc negative electrode having a polyamide-based ion conductor coating according to claim 1, wherein The polyamide-based coating contains at least one polyamide, and the polyamide includes aliphatic polyamide, aromatic polyamide, and aliphatic-aromatic polyamide.

6. The zinc negative electrode with a polyamide-based ionic conductor coating according to claim 1, characterized in that, The formation of the gel does not require the assistance of an organic solvent, and it directly achieves gel sol-gelation in a salt solution.

7. The zinc negative electrode with a polyamide-based ionic conductor coating according to claim 1, characterized in that, The processes of forming the gel and converting it into a solid polymer coating do not require heating nor a coagulation bath of an organic solvent. Water serves as both a solvent and a coagulation bath in this process.

8. A method for preparing a zinc negative electrode with a polyamide-based ion conductor coating according to claim 1, the steps are as follows: forming an aqueous solution of one or more of the above-mentioned lithium salts or zinc salts, one or more polyamide materials, and water, placing it in a room temperature environment or heating it in a blast drying oven at no higher than 80 °C until the mixture becomes a uniform gel; coating the prepared gel on the surface of the metallic zinc active material by a doctor blade method, spraying method, or spin coating method; finally, through a water-infiltrated gel phase inversion method, fixing the infiltration time for infiltration, during which a large amount of salt dissolves into the water for recovery, and the polymer gel is successfully converted into a solid polymer coating with a low crystallinity and high ion conductivity containing a trace amount of salt, obtaining a zinc negative electrode with a polyamide-based ion conductor coating.

9. Use of a zinc negative electrode with a polyamide-based ion conductor coating according to claim 1, characterized in that, Application of a zinc negative electrode with a polyamide-based ion conductor coating in a zinc-based battery, the zinc-based battery includes: a lithium-zinc hybrid battery, a zinc-manganese battery, a secondary zinc ion battery, a zinc ion capacitor, a lithium-zinc hybrid ion capacitor, and a zinc-sulfur battery, a zinc-air battery.

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