Asymmetric flexible self-supporting composite zinc negative electrode and preparation method thereof, electrochemical energy storage device and flexible electronic device

Abstract

This invention provides an asymmetric flexible self-supporting composite zinc anode and its preparation method, as well as an electrochemical energy storage device and a flexible electronic device. It relates to the technical field of secondary battery anode materials. The zinc anode has an asymmetric composite structure. The first main surface facing the separator is an ion-functional layer, which is an ion-conducting-interface protective layer composed of high-molecular zinc salts, used to guide the uniform transport of zinc ions and isolate side reactions. The second main surface facing the external circuit is an electron-collecting layer, composed of conductive materials, used to establish ohmic contact with the external circuit. The intermediate main layer is a three-dimensional electron-conducting-zinc-storage layer, which is a porous electron-conducting-zinc-storage network composed of a conductive agent and zinc-based active powder. This invention's zinc anode maintains excellent flexibility, high ion conductivity, and dendrite suppression capability while significantly improving electron extraction efficiency and effectively optimizing zinc deposition behavior and interface stability. It is particularly suitable for high-performance flexible zinc-ion batteries requiring high-rate performance.

Description

Technical Field

[0001] This invention relates to the technical field of secondary battery anode materials, and in particular to an asymmetric flexible self-supporting composite zinc anode and its preparation method, electrochemical energy storage devices, and flexible electronic devices. Background Technology

[0002] Aqueous zinc-ion batteries, with their advantages of high theoretical capacity, high safety, environmental friendliness, and low cost, have become a promising next-generation energy storage system, especially suitable for large-scale energy storage and wearable flexible electronic devices. However, metallic zinc anodes face a series of severe challenges in practical applications, which seriously restricts their commercialization process.

[0003] First, uncontrolled zinc dendrite growth is the core issue. During charge-discharge cycles, uneven deposition of zinc ions on the negative electrode surface leads to the formation of dendritic protrusions. The continuous growth of these dendrites can puncture the separator, causing internal short circuits and posing serious safety hazards, significantly shortening the battery's cycle life. Second, severe interfacial side reactions urgently need to be addressed. The zinc negative electrode is thermodynamically unstable in aqueous electrolytes, prone to hydrogen evolution corrosion and surface passivation (such as the formation of byproducts like basic zinc sulfate). This not only leads to irreversible consumption of active zinc and reduced coulombic efficiency but also increases interfacial impedance, deteriorating the battery's rate performance and cycle stability. Furthermore, the significant volume changes of the zinc negative electrode during cycling cannot be ignored. Zinc deposition and stripping cause repeated expansion and contraction of the electrode structure, leading to contact failure between the active material and the current collector, electrode pulverization and detachment, thus accelerating capacity decay.

[0004] To address these challenges, existing technologies primarily focus on improvements in two areas: current collector / host structure design and surface modification / coating. Existing technology CN114975847A proposes a "sandwich structure composite anode," but its design is general-purpose (suitable for lithium, sodium, zinc, etc.), with an inner layer of electrodeposited metal and an outer layer of fluorine-doped carbon. It does not specifically optimize for the dendrite and corrosion problems unique to zinc anodes. This structure, based on a rigid current collector, lacks flexibility and cannot meet the mechanical requirements of flexible electronic devices for bent and foldable electrodes. Existing technology CN108735970B proposes a "sandwich structure metal composite anode sheet" that relies on metal foil for support and current collection. Its rigid structure also limits its application in flexible scenarios, and the metal layer may exacerbate local current concentration, hindering uniform deposition. Surface coating of zinc anodes with zinc-loving polymers such as sodium alginate and sodium carboxymethyl cellulose is another common strategy. While such coatings can isolate the electrolyte and guide ion flow to some extent, they typically exist as additional coatings on traditional zinc foil or three-dimensional host surfaces. The interfacial adhesion between the coating and the substrate is weak, making them prone to peeling failure under long-term cycling and mechanical deformation. This simple surface modification fails to be integrated with the electron conduction network inside the negative electrode, making it difficult to achieve matching and uniform distribution of zinc ion flux and electron flux in three-dimensional space.

[0005] In summary, existing technologies either sacrifice flexibility (such as sandwich structures based on rigid current collectors) or fail to achieve integrated and functionalized synergistic design of ion and electron conduction paths (such as simple surface coatings), making it difficult to meet the requirements of high-performance flexible zinc-ion batteries for the negative electrode.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] One of the objectives of this invention is to provide an asymmetric flexible self-supporting composite zinc anode that can significantly improve electron extraction efficiency while maintaining excellent flexibility, high ionic conductivity and dendrite suppression capability, effectively optimize zinc deposition behavior and interface stability, and is particularly suitable for high-performance flexible zinc-ion batteries that require high rate performance.

[0008] The second objective of this invention is to provide a method for preparing an asymmetric flexible self-supporting composite zinc anode.

[0009] The third objective of this invention is to provide an electrochemical energy storage device.

[0010] The fourth objective of this invention is to provide a flexible electronic device.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: In one aspect, an asymmetric flexible self-supporting composite zinc anode includes a three-dimensional host layer, and an ion functional layer and an electron collection layer located on two sides of the three-dimensional host layer, respectively. The three-dimensional host layer serves as a self-supporting electrode film, comprising a porous electronic conduction-zinc storage network composed of zinc-based active powder and conductive agent. The ion functional layer includes an ion conduction-interface protection layer composed of high molecular weight zinc salt, which is used to guide the uniform transport of zinc ions and isolate side reactions, and is located on the surface of the three-dimensional host layer facing the membrane. The electron collection layer includes a material layer made of conductive material for establishing ohmic contact with the external circuit, and is located on the surface of the three-dimensional main body layer facing the external circuit.

[0012] Furthermore, the conductive material of the electron collection layer includes at least one of conductive carbon paste, metal nanowire paste, conductive polymer paste, and metal mesh; Preferably, the conductive carbon paste includes at least one of carbon black, graphene, and carbon nanotubes; Preferably, the metal nanowires include at least one of silver nanowires and copper nanowires.

[0013] Furthermore, the electron collection layer is attached to the surface of the three-dimensional host layer by means of coating, printing and / or transfer. Preferably, the electron collection layer is embedded in the pores of the three-dimensional main body layer to form a mechanical interlocking structure; Preferably, the electron collecting layer has a patterned structure; Preferably, the patterned structure is a grid, strip, and / or dot matrix; Preferably, the thickness of the electron collecting layer is 1μm-8μm.

[0014] Furthermore, the conductive agent is composed of carbon nanotubes, graphene, and carbon black. Preferably, the mass ratio of the carbon nanotubes, graphene, and carbon black is (3-4):1:(5-6). Preferably, the zinc-based active powder comprises an alloy powder formed from zinc and other metals; Preferably, the other metals include at least one of tin, indium, silver, and copper.

[0015] Furthermore, the polymeric zinc salt is a polymeric zinc salt containing carboxyl groups and / or a polymeric zinc salt containing sulfonic acid groups; Preferably, the high molecular weight zinc salt includes at least one of zinc alginate, zinc carboxymethyl cellulose, zinc carboxylated chitosan, and zinc polyacrylate; Preferably, the thickness of the ion functional layer is 1μm-20μm.

[0016] Secondly, a method for preparing a zinc negative electrode according to any one of the above claims includes the following steps: (a) Disperse the conductive agent, binder and zinc-based active powder in a solvent to obtain a composite slurry, coat the composite slurry onto a substrate and dry it to obtain a self-supporting electrode film; (b) An electron collecting layer is formed by curing on one surface of the self-supporting electrode film, and an ion functional layer is formed by in-situ reaction on the other surface and side. After post-processing, the zinc anode is obtained.

[0017] Further, in step (a), based on the total mass of solid matter in the composite slurry, the mass content of the conductive agent is 10%-20%, the mass content of the binder is 10%-15%, and the remainder is the zinc-based active powder; Preferably, the adhesive comprises at least one of polyvinylidene fluoride, polyacrylonitrile, hydrogenated nitrile rubber, and polyimide; Preferably, the solvent includes at least one of N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide; Preferably, the coating thickness of the composite slurry is 150μm-400μm; Preferably, the drying includes step drying; Preferably, the step drying process includes first drying with forced air at 60℃-80℃ for 4h-6h, and then vacuum drying at 80℃-100℃ for 6h-12h.

[0018] Furthermore, in step (b), the curing temperature is 60℃-120℃ and the time is 10min-60min; Preferably, the in-situ reaction includes the following steps: The electrode film with the electron collection layer is first immersed in a polymer solution containing carboxyl and / or sulfonic acid groups, and then transferred to a zinc salt solution for ion exchange reaction, thereby forming an ion functional layer. Preferably, the mass concentration of the polymer solution is 1%-3%; Preferably, the immersion time is 15 min to 30 min; Preferably, the molar concentration of the zinc salt solution is 0.05 mol / L to 0.8 mol / L; Preferably, the ion exchange reaction takes 5-60 minutes; Preferably, the post-processing includes washing and drying steps.

[0019] Thirdly, an electrochemical energy storage device comprising the zinc negative electrode described in any of the above claims.

[0020] Fourthly, a flexible electronic device comprising the electrochemical energy storage device described above.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects: The asymmetric flexible self-supporting composite zinc anode provided by this invention can be understood as an asymmetric flexible self-supporting zinc anode based on an ion-electron dual conduction network. This network fundamentally optimizes zinc deposition behavior, solves the problem of impeded ion and electron conduction at the interface in flexible devices, and achieves synergistic optimization of ion and electron transport paths in both space and function. Specifically, due to its asymmetric configuration, the zinc anode of this invention conducts ions on one side and electrons on the other, thus achieving physical separation and functional complementarity of the ion-electron dual conduction network at the material level, and meeting the requirements for flexible self-support at the structural level. This simultaneously improves the interface stability, cycle life, rate performance, and mechanical flexibility of the zinc anode. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the asymmetric flexible self-supporting composite zinc anode provided in Embodiment 1 of the present invention; Figure 2 This is a comparison graph showing the long-cycle performance of the zinc anodes of Example 1 and Comparative Examples 1-3 obtained from the experimental examples of the present invention at a current density of 1C. Figure 3 This is a comparison graph showing the rate performance of the zinc anodes of Example 1 and Comparative Examples 1-2 obtained from the experimental examples of the present invention at different current densities. Figure 4 This is a surface morphology diagram of the zinc negative electrode of Example 1 obtained from the experimental examples of the present invention after long cycling; Figure 5 This is a surface morphology diagram of the zinc anode of Comparative Example 1 obtained in the experimental example of the present invention after long cycling. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] According to a first aspect of the present invention, an asymmetric flexible self-supporting composite zinc anode is provided, comprising a three-dimensional host layer, and an ion functional layer and an electron collection layer respectively located on two sides of the three-dimensional host layer; The three-dimensional host layer serves as a self-supporting electrode film, comprising a porous electronic conduction-zinc storage network composed of zinc-based active powder and conductive agent. The ion functional layer includes an ion conduction-interface protection layer composed of high molecular weight zinc salt, which is used to guide the uniform transport of zinc ions and isolate side reactions. It is located on the surface of the three-dimensional host layer facing the membrane. The electron collection layer comprises a material layer made of conductive material for establishing ohmic contact with the external circuit, located on the surface of the three-dimensional main body layer facing the external circuit.

[0026] The zinc anode has an asymmetric composite structure. The first main surface facing the separator is an ion-functional layer, which is an ion-conducting and interface-protecting layer composed of high-molecular zinc salts, used to guide the uniform transport of zinc ions and isolate side reactions. The second main surface facing the external circuit is an electron-collecting layer, which is composed of conductive materials and is used to establish ohmic contact with the external circuit. The middle main layer is a three-dimensional electron-conducting and zinc-storing layer, which serves as a self-supporting electrode film and is a porous electron-conducting and zinc-storing network composed of conductive agents and zinc-based active powders. The first and second main surfaces are two opposite main surfaces of the anode.

[0027] The zinc anode of this invention adopts an asymmetric configuration, with one side of the self-supporting electrode film conducting ions and the other side conducting electrons. Therefore, at the material level, it achieves physical separation and functional complementarity of the "ion-electron" dual conduction network, and at the structural level, it meets the requirements of flexible self-support. Thus, it can simultaneously improve the interface stability, cycle life, rate performance and mechanical flexibility of the zinc anode.

[0028] In a preferred embodiment, the conductive material of the electron collection layer includes, but is not limited to, at least one of conductive carbon paste, metal nanowire paste, conductive polymer paste, and metal mesh.

[0029] In a preferred embodiment, the conductive carbon paste includes, but is not limited to, at least one of carbon black, graphene, and carbon nanotubes.

[0030] In a preferred embodiment, the metal nanowires include, but are not limited to, at least one of silver nanowires and copper nanowires.

[0031] In a preferred embodiment, the electron collection layer can be attached to the surface of the three-dimensional host layer by coating, printing, and / or transfer, with some of its material embedded in the surface pores of the three-dimensional host layer to form a mechanical interlocking structure. The electron collection layer forms a robust mechanical interlocking structure and electrical connection with the three-dimensional host layer, rather than a simple physical bond, which helps ensure efficient electron extraction.

[0032] In this invention, the electron collecting layer can be a patterned structure, which can be a grid, strip, and / or dot matrix. The thickness of the electron collecting layer can be 1μm-8μm, for example, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, but is not limited thereto.

[0033] In a preferred embodiment, the conductive agent can be composed of carbon nanotubes, graphene and carbon black, and the mass ratio of carbon nanotubes, graphene and carbon black can be (3-4):1:(5-6), which is more conducive to improving the electronic conductivity.

[0034] In a preferred embodiment, the zinc-based active powder may be an alloy powder formed by zinc and other metals; the other metals include, but are not limited to, at least one of tin, indium, silver and copper.

[0035] In a preferred embodiment, the polymeric zinc salt can be a carboxyl-containing polymeric zinc salt and / or a sulfonic acid-containing polymeric zinc salt, including but not limited to at least one of zinc alginate, zinc carboxymethyl cellulose, zinc carboxylated chitosan, and zinc polyacrylate.

[0036] In this invention, the thickness of the ion functional layer can be 1μm-20μm, for example, 1μm, 2μm, 3μm, 4μm, 5μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, but is not limited thereto.

[0037] According to a second aspect of the present invention, a method for preparing the zinc negative electrode according to any one of the above claims is provided, comprising the following steps: (a) Disperse the conductive agent, binder and zinc-based active powder in a solvent to obtain a composite slurry, coat the composite slurry onto a substrate, and dry it to obtain a self-supporting electrode film; (b) An electron collecting layer is formed by curing on one surface of the self-supporting electrode film, and an ion functional layer is formed by in-situ reaction on the other surface and side. After post-processing, a zinc anode is obtained.

[0038] The method of the present invention is to construct asymmetric functional layers in steps. First, a self-supporting electrode film is prepared, then an electron collecting layer is constructed on one side of it, and finally an ion functional layer is generated in situ on the other side and the side surface through selective wetting and ion exchange. The process is controllable and easy to scale up.

[0039] In a preferred embodiment, in step (a), the mass content of the conductive agent can be 10%-20% and the mass content of the binder can be 10%-15% based on the total mass of solid matter in the composite slurry, with the remainder being zinc-based active powder.

[0040] In a preferred embodiment, the adhesive includes, but is not limited to, at least one of polyvinylidene fluoride, polyacrylonitrile, hydrogenated nitrile rubber, and polyimide.

[0041] In a preferred embodiment, the solvent includes, but is not limited to, at least one of N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide.

[0042] In a preferred embodiment, the coating thickness of the composite slurry can be 150μm-400μm, and its drying can be step drying. The step drying procedure includes first drying with forced air at 60℃-80℃ for 4h-6h, and then vacuum drying at 80℃-100℃ for 6h-12h, which is more conducive to thorough drying.

[0043] In a preferred embodiment, in step (b), the curing temperature can be 60℃-120℃ and the time can be 10min-60min, which is more conducive to full curing.

[0044] In this invention, the in-situ reaction includes the following steps: An electrode film with an electron collecting layer is first immersed in a polymer solution containing carboxyl and / or sulfonic acid groups, and then transferred to a zinc salt solution for ion exchange reaction, thereby forming an ion-functionalized layer.

[0045] By controlling the immersion depth or by temporarily waterproofing the electron collection layer, it can be ensured that the ion exchange reaction mainly occurs on the electrode surface not covered by the electron collection layer.

[0046] In a preferred embodiment, the mass concentration of the polymer solution can be 1%-3%, and the impregnation time can be 15-30 minutes, which is more conducive to thorough impregnation and thus improves the effect of subsequent ion exchange reaction.

[0047] In a preferred embodiment, the molar concentration of the zinc salt solution can be 0.05 mol / L to 0.8 mol / L, and the ion exchange reaction time can be 5 min to 60 min, which is more conducive to the full reaction and formation of the ion functional layer.

[0048] In a preferred embodiment, the post-treatment includes, but is not limited to, washing and drying steps. Washing may involve rinsing with deionized water at least three times, and drying may involve first drying with forced air at 60°C-80°C for 30-60 minutes, and then drying under vacuum at 80°C-100°C for 3-6 hours.

[0049] According to a third aspect of the present invention, an electrochemical energy storage device is provided, comprising the zinc negative electrode described in any of the preceding claims.

[0050] According to a fourth aspect of the present invention, a flexible electronic device is provided, comprising the electrochemical energy storage device described above.

[0051] The present invention will be further illustrated below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0052] Example 1 An asymmetric flexible self-supporting composite zinc anode, see Figure 1 It includes a three-dimensional main body layer, and an ion functional layer and an electron collection layer located on two sides of the three-dimensional main body layer, respectively; The three-dimensional host layer, namely the three-dimensional electronic conduction zinc storage active layer, is a porous electronic conduction-zinc storage network composed of zinc-based active powder and conductive agent, referred to as a self-supporting electrode film. The three-dimensional main layer is formed by coating a composite slurry onto a PET temporary substrate and drying it. The composite slurry is obtained by dispersing conductive agent, binder and zinc-based active powder in a solvent. The mass ratio of carbon nanotubes, graphene and carbon black in the conductive agent is 3.5:1:5.5, and the zinc-based active powder is zinc-tin alloy powder (zinc-tin ratio is 9:1). The ion functional layer is an ion conduction-interface protection layer composed of high molecular weight zinc salt, which is used to guide the uniform transport of zinc ions and isolate side reactions. It is located on the surface of the three-dimensional main layer facing the membrane. The ion-functional layer is formed through an in-situ reaction, specifically by impregnating the seaweed with an aqueous solution of sodium alginate and then conducting an ion exchange reaction with an aqueous solution of zinc sulfate. The electron collection layer is a material layer made of conductive material, used to establish ohmic contact with the external circuit, and is located on the surface of the aforementioned three-dimensional main layer facing the external circuit; The electron collection layer is specifically formed by coating with conductive carbon paste (mainly composed of carbon black and graphene) and then drying and curing it. The electron collection layer forms a strong mechanical interlocking structure and electrical connection with the three-dimensional host layer, rather than a simple physical bonding, to ensure efficient electron extraction.

[0053] Example 2 The difference between this embodiment and Embodiment 1 is that the electron collection layer is formed by printing a grid pattern of silver nanowire conductive ink using screen printing technology. The ion-functionalized layer is formed by impregnating the layer with sodium carboxymethyl cellulose solution and then reacting it with zinc acetate solution via an ion exchange reaction. The rest is the same as in Example 1.

[0054] Example 3 The difference between this embodiment and Embodiment 1 is that the mass ratio of carbon nanotubes, graphene, and carbon black in the conductive agent used in the three-dimensional main body layer is 3:1:6. The rest is the same as in Example 1.

[0055] Example 4 The difference between this embodiment and Embodiment 1 is that the mass ratio of carbon nanotubes, graphene and carbon black in the conductive agent used in the three-dimensional main body layer is 4:1:5. The rest is the same as in Example 1.

[0056] Example 5 The difference between this embodiment and Embodiment 1 is that the zinc-based active powder used in the three-dimensional main body layer is zinc-indium alloy powder; The rest is the same as in Example 1.

[0057] Example 6 The difference between this embodiment and Embodiment 1 is that the zinc-based active powder used in the three-dimensional main body layer is zinc-silver alloy powder; The rest is the same as in Example 1.

[0058] Example 7 The difference between this embodiment and Embodiment 1 is that the zinc-based active powder used in the three-dimensional main body layer is zinc-copper alloy powder; The rest is the same as in Example 1.

[0059] Example 8 The difference between this embodiment and Embodiment 1 is that the ion functional layer is formed by impregnating the layer with sodium carboxymethyl cellulose solution and then reacting it with zinc ion solution through an ion exchange reaction. The rest is the same as in Example 1.

[0060] Example 9 The difference between this embodiment and Embodiment 1 is that the ion functional layer is formed by impregnating the layer with a sodium carboxylated chitosan solution and then subjecting it to an ion exchange reaction with a zinc ion solution. The rest is the same as in Example 1.

[0061] Example 10 The difference between this embodiment and Embodiment 1 is that the ion functional layer is formed by impregnating with sodium polyacrylate solution and then undergoing an ion exchange reaction with zinc ion solution. The rest is the same as in Example 1.

[0062] Example 11 This embodiment describes the preparation method of the zinc negative electrode of Example 1, including the following steps: (1) Preparation of self-supporting electrode thin film: Based on the total solid mass, 15% of the composite conductive agent (CNT, graphene and carbon black in a mass ratio of 3.5:1:5.5), 10% of the binder (polyvinylidene fluoride, PVDF) and 75% of the zinc-based active powder (zinc-tin alloy powder, zinc-tin ratio of 9:1) were added to N-methylpyrrolidone (NMP) solvent and stirred and dispersed thoroughly to obtain a uniform composite slurry. The composite slurry was coated onto a PET temporary substrate with a wet film thickness of 300 μm. It was first dried at 70°C for 5 hours by forced air drying, and then dried under vacuum at 90°C for 10 hours to completely remove the solvent. After cooling, the self-supporting electrode film was completely peeled off from the substrate to obtain the self-supporting electrode film. (2) Constructing an electron collection layer: On the surface of the electrode film obtained by peeling, a layer of commercial conductive carbon paste (mainly composed of carbon black and graphene) is uniformly coated by coating method, and then placed in an 80°C oven to dry for 30 minutes. During this process, the low viscosity carbon paste partially penetrates into the surface pores on one side of the electrode film. After curing, it forms a strong mechanical interlocking structure, rather than a simple physical bonding. This layer is the electron collection layer facing the external circuit. (3) Constructing an ion functional layer: The electrode film with the electron collecting layer is fixed with the side facing upwards using a clamp, ensuring that the side is completely out of contact with the liquid. The film is then immersed in a 2.0% sodium alginate aqueous solution for 20 minutes to fully wet the surface and sides, while keeping the electron collecting layer dry. After removal, it is immediately transferred to a 0.5 mol / L zinc sulfate aqueous solution for ion exchange reaction for 30 minutes, thereby generating a dense and continuous zinc alginate gel layer in situ on the opposite side of the electron collecting layer. This layer is the ion functional layer facing the diaphragm. (4) Post-processing: Rinse five times with deionized water to thoroughly remove residual salts, then dry in a forced-air dryer at 70°C for 45 minutes, and then vacuum dry at 90°C for 4 hours to finally obtain a structurally complete asymmetric flexible self-supporting composite zinc anode.

[0063] Example 12 This embodiment describes the preparation method of the zinc negative electrode in Example 2, including the following steps: (1) Preparation of self-supporting electrode thin film, same as in Example 11; (2) Constructing a patterned electron collection layer: Using screen printing technology, a grid pattern of silver nanowire conductive ink is precisely printed on a main surface of a self-supporting electrode film. The ink is then heat-treated in an inert atmosphere at 90°C for 20 minutes. This gentle heat treatment process removes volatile solvents from the ink and allows the silver nanowires to form a tighter contact to reduce sheet resistance. At the same time, it avoids oxidation of zinc powder in the main electrode and damage to the polymer binder structure. (3) Constructing an ion functional layer: With the electron collecting layer facing upwards, the film is slowly immersed in a 1.5% sodium carboxymethyl cellulose solution for 25 minutes, followed by an ion exchange reaction in a 0.6 mol / L zinc acetate solution for 15 minutes. Throughout the process, the silver nanowire mesh electron collecting layer is kept out of contact with the solution, thus generating an ion-functionalized layer in situ.

[0064] (4) Post-processing, same as in Example 11.

[0065] Examples 13-14 Examples 13-14 are the preparation methods of zinc anodes of Examples 3-4, respectively. The difference between Examples 13-14 and Example 11 is that the conductive agent ratio used in the three-dimensional main body layer is different. The rest is the same as in Example 11.

[0066] Examples 15-17 Examples 15-17 are the preparation methods of zinc anodes of Examples 5-7, respectively. The difference between Examples 15-17 and Example 11 is that the zinc-based active powder used in the three-dimensional main body layer is different. The rest is the same as in Example 11.

[0067] Examples 18-20 Examples 18-20 are the preparation methods of the zinc anodes of Examples 8-10, respectively. The difference between Examples 18-20 and Example 11 is that the polymer solution used for the ion functional layer is different. The rest is the same as in Example 11.

[0068] Comparative Example 1 The difference between this comparative example and Example 1 is that this comparative example only has a self-supporting electrode film, and does not have an electron collection layer or an ion functional layer. The method for preparing the self-supporting electrode film is the same as in Example 11.

[0069] Comparative Example 2 The difference between this comparative example and Example 1 is that both sides of the self-supporting electrode film are ion functional layers, but there is no electron collection layer. The preparation methods for the self-supporting electrode film and the ion functional layer are the same as in Example 11.

[0070] Comparative Example 3 The difference between this comparative example and Example 1 is that the composite slurry was directly coated onto commercial copper foil and dried. An ion-functional layer was constructed on the electrode surface in the same manner as in Example 11.

[0071] Experimental Example 1 Using the zinc anodes of Examples 1-10 and Comparative Examples 1-3 as anodes, and modified manganese dioxide as cathode material, CR2032 coin cells were assembled using 2M ZnSO4 and 0.1M MnSO4 aqueous solutions as electrolytes for long-cycle and rate performance testing (Examples 1 and Comparative Example 3 were bent 50 times before testing). The cells were fully activated before testing, with 1C = 300 mA / g.

[0072] Table 1

[0073] analyze: As shown in Table 1 and Figure 2 As shown, at a current density of 1C, the asymmetric flexible self-supporting composite zinc anodes of Examples 1-10 exhibited excellent long-cycle stability: the capacity retention rate was greater than 75% after 300 cycles. In contrast, the zinc anode of Comparative Example 1 without functional layer modification showed a rapid decrease in capacity retention rate to 51.2% after 150 cycles and a decrease to 9.6% after 300 cycles. This is mainly because the unprotected zinc-based powder particles are fully exposed to the electrolyte, leading to uncontrolled zinc dendrite growth and electrode failure caused by interfacial side reactions during subsequent cycles. In contrast, the zinc anode of Comparative Example 2, employing a symmetrical coating structure, showed relatively stable capacity retention in the initial cycling phase, but its capacity gradually decreased with each cycle, dropping to 72.9% after 300 cycles. This indicates that the symmetrical structure's obstruction of electron conduction significantly affects the electrode's cycling stability. The zinc anode of Comparative Example 3, relying on a rigid copper foil current collector, only achieved a capacity retention of 41.3% after 300 cycles. This is because the internal structure was severely damaged after 50 folds, resulting in impaired ion and electron conduction, decreased interfacial stability, and a significant decline in cycling performance. This demonstrates the structural instability and performance limitations of traditional rigid current collectors in flexible applications. Therefore, the superior performance of the zinc anodes in Examples 1-10 of this invention benefits from the synergistic design of its "ion-electron" dual conduction network. This structure effectively suppresses dendrite growth, alleviates interfacial corrosion and volume changes, while its inherent flexibility ensures performance stability under mechanical deformation.

[0074] Table 2

[0075] As shown in Table 2 and Figure 3As shown, the asymmetric flexible self-supporting composite zinc anodes of Examples 1-10 exhibited superior rate performance at different current densities. At a low current density of 0.1C, the average specific capacity of the zinc anodes of Examples 1-10 was similar to that of Comparative Examples 1-2. However, as the current density gradually increased to 0.2C, 0.5C, 1C, 3C, and even 5C, the capacity decay of the zinc anodes of Examples 1-10 was significantly less than that of Comparative Examples 1-2. The main reason for the rate performance difference between Examples 1-10 and Comparative Example 1 is that the ion conduction layer of the zinc anodes of Examples 1-10 not only accelerated ion conduction but also provided interface protection, effectively suppressing dendrite growth and side reactions on the zinc anode surface, thereby optimizing the rate performance. The rate performance of the zinc anodes of Examples 1-10 and Comparative Example 1 was significantly better than that of Comparative Example 2. The main reason is that the symmetrical coating structure of Comparative Example 2 significantly inhibited electron conduction, resulting in the inability of ion and electron transport to proceed in tandem. When the current density reaches a high rate of 5C, the zinc anodes of Examples 1-10 can still maintain a stable discharge capacity, while the capacity of Comparative Example 2 has decreased significantly. These results fully demonstrate that the zinc anodes of Examples 1-10 of this invention, through the asymmetric synergistic design of the ion-electron dual conduction network, fundamentally solve the problem of ion and electron transport mismatch in traditional structures. Even in high-rate charge-discharge scenarios, they can achieve rapid and uniform charge transport, significantly improving the rate adaptability of zinc-ion batteries.

[0076] Experimental Example 2 After the long-cycle test of Example 1 was completed, the batteries in Example 1 and Comparative Example 1 were disassembled, the negative electrodes were removed, washed with deionized water, and their surface morphology was characterized. The surface morphology of the zinc negative electrode of Example 1 after long-cycle testing is shown in [Figure 1]. Figure 4 The surface morphology of the zinc anode in Comparative Example 1 after long cycling is shown in [reference needed]. Figure 5 .

[0077] analyze: like Figure 4 and Figure 5 As shown, after the long cycle test, the surface of the zinc anode in Example 1 was relatively smooth, while the zinc anode in Comparative Example 1 showed a large number of zinc dendrites on its surface after cycling, and the corrosion phenomenon was also obvious. This indicates that the ion conduction layer plays an important role in inhibiting zinc dendrites and corrosion.

[0078] In summary, the asymmetric flexible self-supporting composite zinc anode of this invention exhibits significant advantages in terms of cycle stability, rate performance, and interface stability. It exhibits high capacity retention and a stable voltage plateau during long-term cycling, demonstrating its effectiveness in suppressing dendrite growth and mitigating side reactions; It maintains excellent capacity output at different rates, and is particularly stable at high rates, which demonstrates the synergistic promotion of charge transport by the ion-electron dual conduction network. After cycling, the surface of the negative electrode was smooth, with no obvious dendrites or corrosion, further verifying the protective effect of the structure on interface stability.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An asymmetric flexible self-supporting composite zinc anode, characterized in that, It includes a three-dimensional main body layer, and an ion functional layer and an electron collection layer located on two sides of the three-dimensional main body layer, respectively; The three-dimensional host layer serves as a self-supporting electrode film, comprising a porous electronic conduction-zinc storage network composed of zinc-based active powder and conductive agent. The ion functional layer includes an ion conduction-interface protection layer composed of high molecular weight zinc salt, which is used to guide the uniform transport of zinc ions and isolate side reactions, and is located on the surface of the three-dimensional host layer facing the membrane. The electron collection layer includes a material layer made of conductive material for establishing ohmic contact with the external circuit, and is located on the surface of the three-dimensional main body layer facing the external circuit.

2. The zinc negative electrode according to claim 1, characterized in that, The conductive material of the electron collection layer includes at least one of conductive carbon paste, metal nanowire paste, conductive polymer paste, and metal mesh; Preferably, the conductive carbon paste includes at least one of carbon black, graphene, and carbon nanotubes; Preferably, the metal nanowires include at least one of silver nanowires and copper nanowires.

3. The zinc negative electrode according to claim 1, characterized in that, The electron collection layer is attached to the surface of the three-dimensional host layer by means of coating, printing and / or transfer. Preferably, the electron collection layer is embedded in the pores of the three-dimensional main body layer to form a mechanical interlocking structure; Preferably, the electron collecting layer has a patterned structure; Preferably, the patterned structure is a grid, strip, and / or dot matrix; Preferably, the thickness of the electron collecting layer is 1μm-8μm.

4. The zinc negative electrode according to any one of claims 1-3, characterized in that, The conductive agent is composed of carbon nanotubes, graphene, and carbon black. Preferably, the mass ratio of the carbon nanotubes, graphene, and carbon black is (3-4):1:(5-6). Preferably, the zinc-based active powder comprises an alloy powder formed from zinc and other metals; Preferably, the other metals include at least one of tin, indium, silver, and copper.

5. The zinc negative electrode according to any one of claims 1-3, characterized in that, The high molecular weight zinc salt is a high molecular weight zinc salt containing carboxyl groups and / or a high molecular weight zinc salt containing sulfonic acid groups; Preferably, the high molecular weight zinc salt includes at least one of zinc alginate, zinc carboxymethyl cellulose, zinc carboxylated chitosan, and zinc polyacrylate; Preferably, the thickness of the ion functional layer is 1μm-20μm.

6. A method for preparing a zinc negative electrode according to any one of claims 1-5, characterized in that, Includes the following steps: (a) Disperse the conductive agent, binder and zinc-based active powder in a solvent to obtain a composite slurry, coat the composite slurry onto a substrate and dry it to obtain a self-supporting electrode film; (b) An electron collecting layer is formed by curing on one surface of the self-supporting electrode film, and an ion functional layer is formed by in-situ reaction on the other surface and side. After post-processing, the zinc anode is obtained.

7. The preparation method according to claim 6, characterized in that, In step (a), based on the total mass of solid matter in the composite slurry, the mass content of the conductive agent is 10%-20%, the mass content of the binder is 10%-15%, and the remainder is the zinc-based active powder; Preferably, the adhesive comprises at least one of polyvinylidene fluoride, polyacrylonitrile, hydrogenated nitrile rubber, and polyimide; Preferably, the solvent includes at least one of N-methylpyrrolidone, N,N-dimethylformamide, and dimethyl sulfoxide; Preferably, the coating thickness of the composite slurry is 150μm-400μm; Preferably, the drying includes step drying; Preferably, the step drying process includes first drying with forced air at 60℃-80℃ for 4h-6h, and then vacuum drying at 80℃-100℃ for 6h-12h.

8. The preparation method according to claim 6, characterized in that, In step (b), the curing temperature is 60℃-120℃ and the time is 10min-60min; Preferably, the in-situ reaction includes the following steps: An electrode film with an electron collecting layer is first immersed in a polymer solution containing carboxyl and / or sulfonic acid groups, and then transferred to a zinc salt solution for ion exchange reaction, thereby forming an ion-functionalized layer. Preferably, the mass concentration of the polymer solution is 1%-3%; Preferably, the immersion time is 15-30 minutes; Preferably, the molar concentration of the zinc salt solution is 0.05 mol / L to 0.8 mol / L; Preferably, the ion exchange reaction takes 5-60 minutes; Preferably, the post-processing includes washing and drying steps.

9. An electrochemical energy storage device, characterized in that, It includes the zinc anode as described in any one of claims 1-5.

10. A flexible electronic device, characterized in that, It includes the electrochemical energy storage device as described in claim 9.

Images