A method for preparing a polymer layer-nanocellulose composite separator with a dense nanoporous structure and applications thereof

Abstract

The application provides a preparation method and application of a polymer layer-nanocellulose composite diaphragm with a compact nanopore structure, and belongs to the technical field of new energy batteries. The preparation method comprises the following steps: S1, vacuum self-assembly forming a substrate; S2, bidirectional solution construction: S2.1, alkaline-induced monomer ionization construction; S3, soaking; S4, heterogeneous molecule self-assembly dynamic crosslinking film formation; and S5, annealing treatment. The application uses one of 2,5-diaminobenzenesulfonic acid, o-phenylenediamine, p-xylene diamine, 2,5-dimethyl-1,4-benzenediamine and 1,4-cyclohexanediamine and 1,3,5-benzene triformyl chloride as raw materials to prepare a diaphragm applied in an aqueous zinc ion battery pack. The composite diaphragm optimizes the performance of the aqueous zinc ion battery in many aspects such as inhibiting zinc dendrite growth, improving zinc ion migration number and prolonging battery cycle life through the unique nanopore structure and functional group design.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology and relates to a method for preparing a polymer-nanocellulose composite membrane with a dense nanoporous structure and its application. Background Technology

[0002] Aqueous zinc-ion batteries use zinc metal as the negative electrode and materials such as manganese dioxide and vanadium pentoxide as the positive electrode. Thanks to the high hydrogen evolution overpotential (-0.76V vs SHE) of the zinc negative electrode, zinc-ion batteries can directly use aqueous solutions as the electrolyte, greatly improving their safety. In addition, zinc metal negative electrodes have advantages that lithium metal negative electrodes cannot match, such as: high zinc resource abundance in the Earth's crust, low difficulty in zinc ore mining, and low storage costs. Furthermore, the production of aqueous zinc-ion batteries does not rely on a highly anhydrous and oxygen-free environment. These advantages make aqueous zinc-ion batteries far superior to lithium-ion batteries in both production cost and safety. However, there are currently many problems hindering the large-scale application of directly using zinc metal negative electrodes: 1. Uneven zinc ion deposition leading to dendrite growth: During electrodeposition, zinc ions tend to grow in a dendritic or moss-like form. This uneven deposition behavior leads to the formation of zinc dendrites. The growth of zinc dendrites can puncture the battery separator, causing internal short circuits, which not only seriously affects the cycle stability of the battery but may also lead to battery failure or safety issues. 2. Side reactions between aqueous electrolyte and zinc anode: When water molecules in the aqueous electrolyte come into contact with the zinc anode, hydrogen evolution and corrosion reactions easily occur. These side reactions not only consume the water in the electrolyte but also reduce battery energy efficiency and may trigger hydrogen release, increasing battery safety risks.

[0003] The aforementioned problems severely restrict the practical application performance of aqueous zinc-ion batteries. Therefore, there is an urgent need to develop a membrane material that can suppress zinc dendrite growth and prevent side reactions at the zinc anode, in order to improve the cycle stability, energy efficiency, and safety of aqueous zinc-ion batteries. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems in existing technologies by proposing a method for preparing and applying a polymer layer-nanocellulose composite membrane with a dense nanoporous structure.

[0005] The objective of this invention can be achieved through the following technical solution: a method for preparing a polymer layer-nanocellulose composite membrane with a dense nanoporous structure, the method comprising the following steps:

[0006] S1 Vacuum Self-Assembly Molding Substrate: Nanocellulose is uniformly dispersed in pure water to obtain a nanocellulose solution. The nanocellulose solution is then subjected to vacuum filtration to obtain a composite membrane substrate.

[0007] The purposes of vacuum filtration are as follows: 1. Oriented alignment and dense structure construction of nanocellulose: Nanocellulose has the characteristics of high aspect ratio and enriched surface hydroxyl groups, but it is prone to disordered aggregation in aqueous solution due to hydrogen bonding. Shear force-induced orientation: During vacuum filtration, nanocellulose is subjected to shear force under negative pressure, and is oriented along the filter membrane surface to form a layered stacked structure. Layer-by-layer densification: When water passes through the filter membrane, nanocellulose particles are gradually compressed and self-assemble into a dense network through hydrogen bonding and van der Waals forces, reducing pore defects. Controllable porosity: By adjusting the filtration time, vacuum degree, or solution concentration, the substrate porosity can be precisely controlled, providing a uniform interface for subsequent interfacial polymerization. 2. Efficient solvent removal and rapid film formation: Rapid water removal: Vacuum negative pressure accelerates water passage through the filter membrane, avoiding redispersion or structural relaxation of nanocellulose caused by prolonged natural drying. Inhibition of capillary shrinkage: Compared with natural drying, vacuum filtration drives liquid discharge by external force, reducing capillary stress during the drying process and reducing the risk of substrate cracking or curling. 3. Balancing Laboratory Research and Industrial Production: Vacuum filtration equipment is simple, low-cost, and can achieve large-area continuous preparation through porous filter membranes (such as roll-to-roll processes), making it suitable for industrial production. The core value of vacuum filtration in step S1 lies in: achieving rapid directional self-assembly of nanocellulose through physical drive; constructing a uniform substrate with high porosity and high mechanical strength; and providing a chemically active surface and structural stability for subsequent interfacial reactions.

[0008] S2 Two-way Solution Construction: S2.1 Alkaline-Induced Monomer Ionization Construction: After adding the polymer precursor to pure water and stirring evenly, the pH value was adjusted to 12-15 using an alkaline solution, and then the precursor liquid was dispersed to obtain the precursor liquid. S2.2: Dispersion of Acyl Chloride Organic Phase Microenvironment: 1,3,5-Benzotricarboxylic acid chloride was added to an organic solvent and the acyl chloride was dispersed to obtain a 1,3,5-Benzotricarboxylic acid chloride dispersion.

[0009] The polymer precursor is one of 2,5-diaminobenzenesulfonic acid, o-phenylenediamine, p-dimethylbenzenediamine, 2,5-dimethyl-1,4-phenylenediamine, and 1,4-cyclohexanediamine; the organic solvent is n-heptane or n-hexane.

[0010] S3 Immersion: The composite membrane substrate is immersed in the precursor fluid for immersion. After the immersion is completed, the interfacial liquid phase desorption is controlled to obtain the nanocellulose heterogeneous interfacial substrate.

[0011] S4 heterogeneous molecular self-assembly dynamic crosslinking film formation: 1,3,5-benzenetricarboxyl chloride dispersion was added dropwise to the upper surface of the nanocellulose heterogeneous interface substrate to carry out interfacial polymerization reaction. After the reaction was completed, the 1,3,5-benzenetricarboxyl chloride dispersion on the surface was removed to obtain the initial composite membrane.

[0012] S5 Annealing: The initial composite membrane is annealed to obtain a polymer layer-nanocellulose composite membrane.

[0013] Alkaline activation mechanism: The alkaline environment induces the ionization of polymer precursors, endows the substrate surface with charge properties, and enhances the activity of subsequent interfacial polymerization reactions.

[0014] The reasons for choosing 1,3,5-benzenetricarboxylic chloride and n-heptane / n-hexane are as follows: Functional advantages of 1,3,5-benzenetricarboxylic chloride: High crosslinking density: The three acyl chloride groups can react with multiple amino groups to form a three-dimensional crosslinking network, significantly improving the mechanical strength and chemical stability of the polymer layer (superior resistance to electrolyte corrosion compared to linear polymers). Symmetrical structure: The triple symmetry of the benzene ring promotes uniform crosslinking, reduces stress concentration within the film, and avoids microcrack formation. Low hydrolysis rate: Compared to aliphatic acyl chlorides (such as oxaloyl chloride), aromatic acyl chlorides have a lower hydrolysis rate in the organic phase, ensuring sufficient interfacial polymerization. Characteristics of n-heptane / n-hexane: Low polarity forms a stable liquid-liquid interface with the aqueous phase (high polarity), limiting the monomer diffusion area and achieving nanoscale thickness polymer layers; Optimized solvent compatibility: For example, the low surface tension of n-heptane promotes the spreading of acyl chloride monomers on the surface of the nanocellulose substrate, forming a continuous liquid film, providing a uniform reaction interface for interfacial polymerization.

[0015] Synergistic effect: The alkaline aqueous phase and the organic phase form a pH gradient, and the local pH of acyl chloride in the organic phase is close to neutral, which greatly reduces the side reaction of acyl chloride hydrolysis.

[0016] Immersion process: Immersion in alkaline precursor fluid causes the nanocellulose substrate to swell, exposing more hydroxyl groups to form hydrogen bonds with amino groups, thereby enhancing interfacial bonding.

[0017] Interfacial liquid phase desorption control: The purpose is to remove excess liquid from the substrate surface through physical means, thereby providing uniform reaction sites for subsequent interfacial polymerization.

[0018] The purposes of annealing are as follows: Promoting polymer layer densification: In the initial composite membrane generated by the interfacial polymerization reaction (step S4), the polymer layer may contain incompletely cross-linked regions or loosely arranged molecular chains. Annealing, through thermal excitation of molecular chain movement, promotes further cross-linking and rearrangement of the polymer chains, thereby forming a denser nanoporous structure and reducing defects (such as pinholes or cracks). Eliminating internal stress and residual solvent: During interfacial polymerization, residual mechanical stress or trace amounts of organic solvent remain inside the material. Annealing releases internal stress through thermal relaxation and accelerates solvent evaporation, preventing structural failure due to solvent residue or stress concentration in subsequent applications. Enhancing the interfacial bonding between the polymer layer and the substrate: There are physical adsorption or weak interactions (such as hydrogen bonds) at the interface between the nanocellulose substrate and the polymer layer. Annealing promotes intermolecular interactions through thermal energy, strengthening the interfacial bonding between the two phases and improving the mechanical strength and thermal stability of the composite membrane. Optimizing the nanoporous structure and distribution: The porous structure of the nanocellulose substrate is partially covered or blocked during interfacial polymerization. Annealing, through gentle heating, adjusts the shrinkage behavior of the polymer layer, optimizes pore distribution, and forms a uniform and well-connected nanoporous network, thereby balancing ionic conductivity and mechanical strength. It also improves the thermal stability of the separator: annealing increases the glass transition temperature and thermal decomposition temperature of the polymer layer, ensuring the composite separator maintains structural stability at battery operating temperatures and preventing deformation or shrinkage caused by high temperatures. The core purpose of annealing is to regulate the microstructure of the composite separator through thermal densification, achieving the following objectives: enhanced density (reducing defects); optimized pores and interfaces (improving ionic conductivity and mechanical strength); and improved thermal stability (ensuring battery application safety). This step is crucial for the transformation of the composite separator from its initial state to its functional state, ensuring the final product meets the stringent performance requirements of high-energy-density batteries (resistance to dendrite penetration, high ionic conductivity, and high-temperature resistance).

[0019] Preferably, by weight ratio, the ratio of nanocellulose to pure water is 0.6:1000-3000, the ratio of polymer precursor to pure water is 1:50-100, and the ratio of 1,3,5-benzenetricarboxyl chloride to organic solvent is 2:90-100.

[0020] The reasons for the nanocellulose:pure water ratio are as follows: Dispersion and structure control: The concentration of nanocellulose directly affects its dispersion state in solution. If the concentration is too high, it will agglomerate due to hydrogen bonding, resulting in uneven pores in the substrate formed by vacuum filtration; if the concentration is too low, it is difficult to form a continuous nanofiber network, resulting in insufficient mechanical strength of the substrate. Film thickness and porosity: This ratio range can balance dispersion and film formation efficiency. At low concentrations, a uniform nanoporous structure is formed through self-assembly via vacuum filtration, providing high specific surface area and interfacial bonding sites for subsequent polymer layers. At this ratio, the substrate pore size and mechanical properties are balanced, suitable for subsequent interfacial polymerization reactions.

[0021] Preferably, in step S2.1, the alkaline solution is a sodium hydroxide solution.

[0022] Preferably, in step S2.1, the precursor liquid dispersion operation adopts ultrasonic dispersion method; in step S2.2, the acyl chloride dispersion operation adopts low temperature ultrasonic-mechanical synergistic dispersion method.

[0023] The precursor liquid is dispersed using ultrasonic dispersion to avoid nanoscale agglomeration;

[0024] Low-temperature ultrasonic-mechanical synergistic dispersion method: Ultrasonic-induced solvent micro-perturbation breaks up molecular clusters, while mechanical stirring maintains dynamic equilibrium and prevents sedimentation.

[0025] Preferably, in step S3, the soaking time is 10-20 minutes; in the interfacial liquid phase desorption control operation, excess liquid on the surface is adsorbed by gently pressing filter paper. The reasons for using gentle pressing with filter paper are as follows: No residue: The filter paper fibers do not chemically react with the reaction system, ensuring a clean interface. Gentle operation: Gently pressing the filter paper avoids damage to the substrate structure and maintains the integrity of the nanopores. Nitrogen purging or centrifugation may introduce mechanical stress or damage the substrate morphology, while filter paper adsorption is more controllable and gentle. Industrial production: Using filter paper adsorption is simple to operate and helps improve production efficiency.

[0026] Preferably, in step S4, the reaction time of the interfacial polymerization reaction is 1-5 minutes.

[0027] Preferably, in step S5, the annealing parameters are as follows: annealing temperature is 40-80℃; annealing time is 10-20 minutes. 10-20 minutes is sufficient to complete molecular chain rearrangement and pore structure closure, while avoiding film embrittlement caused by prolonged heat treatment.

[0028] An application of a polymer layer-nanocellulose composite separator with a dense nanoporous structure is disclosed. The polymer layer-nanocellulose composite separator with a dense nanoporous structure is prepared using the aforementioned preparation method. The application of the polymer layer-nanocellulose composite separator with a dense nanoporous structure is in an aqueous zinc-ion battery pack. In the assembly structure of the aqueous zinc-ion battery pack, from top to bottom, the components are: negative electrode shell, spring sheet, gasket, zinc negative electrode, polymer layer-nanocellulose composite separator, glass fiber separator, polymer layer-nanocellulose composite separator, positive electrode, and positive electrode shell.

[0029] The symmetrical bilayer composite membrane (zinc anode → composite membrane → glass fiber → composite membrane → cathode) employs a core mechanism that: the nanocellulose substrate provides excellent mechanical strength, inhibiting zinc dendrite formation; the polymer layer facilitates better desolvation of zinc ions before deposition at the anode, increasing the zinc ion transference number and effectively reducing the overpotential of the zinc anode; simultaneously, the porous framework provides more active sites, promoting uniform zinc ion deposition and reducing side reactions at the zinc anode. The glass fiber layer acts as a buffer layer, absorbing local stress, while its high porosity reduces ion transport resistance; interface consistency: the bilayer composite membrane ensures the symmetry of the positive and negative electrode interface reactions, maintaining high coulombic efficiency even after multiple cycles.

[0030] Preferably, the aqueous zinc-ion battery pack is a Zn-Zn symmetrical battery pack or a Zn-V2O5 full battery pack.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. Significantly inhibits zinc dendrite growth and improves battery cycle life: The composite separator promotes uniform deposition of zinc ions on the negative electrode surface, effectively inhibiting zinc dendrite growth. (At 25℃ and 1mA / cm²) 2 0.5mAh / cm 2 At current densities of [specific values ​​not specified], symmetrical cells using the separator of this invention achieved an ultra-long cycle life exceeding 3000 hours, far surpassing the cycle performance of traditional glass fiber separators. This demonstrates that the separator of this invention has significant advantages in solving the zinc dendrite problem.

[0033] 2. Improved zinc ion transport number and battery efficiency: The polymer layer promotes the desolvation process of zinc ions, optimizes the migration path of zinc ions in the electrolyte, and significantly increases the zinc ion transport number. This improvement not only reduces the occurrence of side reactions but also significantly improves the energy efficiency and coulombic efficiency of the battery.

[0034] 3. Excellent mechanical strength and battery stability: The nanocellulose layer provides the separator with good mechanical strength and flexibility, ensuring that the separator maintains structural stability during battery cycling, effectively preventing separator deformation or rupture, thereby improving battery safety and reliability.

[0035] 4. Excellent thermal and chemical stability: The synergistic effect of the polymer layer and the nanocellulose layer endows the separator with excellent thermal and chemical stability, enabling it to exhibit good corrosion resistance and degradation resistance in aqueous electrolytes, thus extending the overall service life of the battery.

[0036] 5. Precise pore size control to meet the needs of different electrochemical systems: By selecting organic monomers, the pore size of the covalent organic framework can be precisely controlled, thereby meeting the requirements of different electrochemical systems. This pore size control capability not only enhances the versatility of the separator but also enables it to adapt to the characteristics of different battery systems, further expanding its application range.

[0037] 6. Green and sustainable: Nanocellulose is an abundant source of renewable materials, and the polymer layer adopts a green preparation process. The entire membrane preparation process is environmentally friendly and sustainable, which is in line with the current trend of green development of energy storage devices.

[0038] In summary, the composite separator of this invention, through its unique nanoporous structure and functional group design, optimizes the performance of aqueous zinc-ion batteries in many aspects, such as inhibiting zinc dendrite growth, increasing zinc ion migration number, and extending battery cycle life, providing important technical support for the development of high-performance, high-safety, and low-cost aqueous zinc-ion batteries. Attached Figure Description

[0039] Figure 1 This is an electron microscope image of the polymer-cellulose composite membrane prepared in Example 1 of the present invention.

[0040] Figure 2 This is an electron microscope image of the polymer-glass fiber composite membrane prepared in Comparative Example 4 of this invention.

[0041] Figure 3 This is a scanning electron microscope image of the zinc anode surface after 60 hours of cycling of the zinc-zinc (Zn-Zn) symmetric battery assembled in Embodiment 1 of the present invention.

[0042] Figure 4 This is a scanning electron microscope image of the zinc anode surface after 60 hours of cycling of the zinc-zinc (Zn-Zn) symmetric battery assembled in Embodiment 2 of the present invention.

[0043] Figure 5 This is a scanning electron microscope image of the zinc anode surface after 60 hours of cycling of the zinc-zinc (Zn-Zn) symmetric battery assembled in Embodiment 3 of the present invention.

[0044] Figure 6 This is a comparative graph showing the cycle performance analysis of zinc-zinc (Zn-Zn) symmetric batteries assembled in Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3 of the present invention.

[0045] Figure 7 This is a cycle performance analysis diagram of the zinc vanadium pentoxide full battery assembled in Example 1 of the present invention.

[0046] Figure 8 This is a scanning electron microscope image of the zinc anode surface after 60 hours of cycling of the zinc-zinc (Zn-Zn) symmetric battery assembled in Comparative Example 1 of this invention. Detailed Implementation

[0047] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0048] Example 1:

[0049] A method for preparing a polymer layer-cellulose nanocomposite membrane with a dense nanoporous structure includes the following steps:

[0050] S1 Vacuum Self-Assembly Molding Substrate: Nanocellulose is uniformly dispersed in pure water to obtain a nanocellulose solution. The nanocellulose solution is then subjected to vacuum filtration to obtain a composite membrane substrate.

[0051] S2 Two-way Solution Construction: S2.1 Alkaline-Induced Monomer Ionization Construction: The polymer precursor was added to pure water and stirred evenly. The pH value was adjusted to 13 using an alkaline solution, and then the precursor liquid was dispersed to obtain the precursor liquid. S2.2 Acyl Chloride Organic Phase Microenvironment Dispersion: 1,3,5-Benzotricarboxylic acid chloride was added to an organic solvent and dispersed to obtain a 1,3,5-Benzotricarboxylic acid chloride dispersion. The alkaline solution was sodium hydroxide solution.

[0052] The polymer precursor is 2,5-diaminobenzenesulfonic acid, and the organic solvent is n-heptane; the precursor liquid is dispersed by ultrasonic dispersion; the acyl chloride is dispersed by low-temperature ultrasonic-mechanical synergistic dispersion.

[0053] S3 Immersion: The composite membrane substrate is immersed in the precursor fluid for immersion. After immersion, interfacial liquid phase desorption is controlled to obtain a nanocellulose heterogeneous interfacial substrate. The immersion time is 20 minutes. In the interfacial liquid phase desorption control, excess liquid on the surface is adsorbed by gently pressing filter paper.

[0054] S4 heterogeneous molecular self-assembly dynamic crosslinking film formation: 1,3,5-benzenetriformyl chloride dispersion was added dropwise to the upper surface of the nanocellulose heterogeneous interface substrate to carry out interfacial polymerization reaction. After the reaction was completed, the excess 1,3,5-benzenetriformyl chloride dispersion on the surface was removed to obtain the initial composite membrane; the interfacial polymerization reaction time was 2 minutes.

[0055] S5 Annealing: The initial composite membrane is annealed to obtain a polymer layer-nanocellulose composite membrane. The annealing parameters are as follows: annealing temperature is 60℃; annealing time is 10 minutes.

[0056] By weight ratio, the ratio of nanocellulose to pure water is 0.6:1000, the ratio of polymer precursor to pure water is 1:50, and the ratio of 1,3,5-benzenetricarboxyl chloride to organic solvent is 2:98.

[0057] The polymer-cellulose nanocomposite membrane with a dense nanoporous structure prepared above was cut into circles with a diameter of 15 mm, and assembled into zinc-zinc (Zn-Zn) symmetric cells and zinc-vanadium pentoxide full cells respectively using 2032 battery cases.

[0058] In the zinc-zinc (Zn-Zn) symmetrical battery assembly structure, from top to bottom, the components are: negative electrode shell, spring sheet, gasket, zinc negative electrode, polymer layer-nanocellulose composite separator, glass fiber separator, polymer layer-nanocellulose composite separator, zinc positive electrode, and positive electrode shell.

[0059] The assembly process of a zinc-vanadium pentoxide full cell is as follows: negative electrode shell, spring sheet, gasket, zinc negative electrode, polymer layer-nanocellulose composite membrane, glass fiber membrane, polymer layer-nanocellulose composite membrane, and vanadium pentoxide (active material loading of 0.68 mg / cm³). 2 ), positive electrode shell.

[0060] Example 2

[0061] A method for preparing a polymer layer-cellulose nanocomposite membrane with a dense nanoporous structure includes the following steps:

[0062] S1 Vacuum Self-Assembly Molding Substrate: Nanocellulose is uniformly dispersed in pure water to obtain a nanocellulose solution. The nanocellulose solution is then subjected to vacuum filtration to obtain a composite membrane substrate.

[0063] S2 Two-way Solution Construction: S2.1 Alkaline-Induced Monomer Ionization Construction: The polymer precursor was added to pure water and stirred evenly. The pH value was adjusted to 13 using an alkaline solution, and then the precursor liquid was dispersed to obtain the precursor liquid. S2.2 Acyl Chloride Organic Phase Microenvironment Dispersion: 1,3,5-Benzotricarboxylic acid chloride was added to an organic solvent and dispersed to obtain a 1,3,5-Benzotricarboxylic acid chloride dispersion. The alkaline solution was sodium hydroxide solution.

[0064] The polymer precursor is o-phenylenediamine, and the organic solvent is n-heptane; the precursor liquid is dispersed by ultrasonic dispersion; the acyl chloride is dispersed by low-temperature ultrasonic-mechanical synergistic dispersion.

[0065] S3 Immersion: The composite membrane substrate is immersed in the precursor fluid for immersion. After immersion, interfacial liquid phase desorption is controlled to obtain a nanocellulose heterogeneous interfacial substrate. The immersion time is 20 minutes. In the interfacial liquid phase desorption control, excess liquid on the surface is adsorbed by gently pressing filter paper.

[0066] S4 heterogeneous molecular self-assembly dynamic crosslinking film formation: 1,3,5-benzenetriformyl chloride dispersion was added dropwise to the upper surface of the nanocellulose heterogeneous interface substrate to carry out interfacial polymerization reaction. After the reaction was completed, the excess 1,3,5-benzenetriformyl chloride dispersion on the surface was removed to obtain the initial composite membrane; the interfacial polymerization reaction time was 2 minutes.

[0067] S5 Annealing Treatment: The initial composite membrane is annealed to obtain a polymer layer-nanocellulose composite membrane.

[0068] By weight ratio, the ratio of nanocellulose to pure water is 0.6:1000, the ratio of polymer precursor to pure water is 1:50, and the ratio of 1,3,5-benzenetricarboxyl chloride to organic solvent is 2:98.

[0069] The polymer-cellulose nanocomposite membrane with a dense nanoporous structure prepared above was cut into circles with a diameter of 15 mm and assembled into a zinc-zinc (Zn-Zn) symmetric battery using a 2032 battery case.

[0070] In the assembly structure of a zinc-zinc (Zn-Zn) symmetrical battery, from top to bottom, the components are: negative electrode shell, spring sheet, gasket, zinc negative electrode, polymer layer-nanocellulose composite separator, glass fiber separator, polymer layer-nanocellulose composite separator, zinc positive electrode, and positive electrode shell.

[0071] The assembled zinc-zinc (Zn-Zn) symmetric cell was tested at 25℃ and 1 mA / cm². 2 (0.5mAh / cm 2 Its cycle performance was tested under certain conditions, and after 3000 cycles, its symmetric cell remained stable.

[0072] Example 3

[0073] A method for preparing a polymer layer-cellulose nanocomposite membrane with a dense nanoporous structure includes the following steps:

[0074] S1 Vacuum Self-Assembly Molding Substrate: Nanocellulose is uniformly dispersed in pure water to obtain a nanocellulose solution. The nanocellulose solution is then subjected to vacuum filtration to obtain a composite membrane substrate.

[0075] S2 Two-way Solution Construction: S2.1 Alkaline-Induced Monomer Ionization Construction: The polymer precursor was added to pure water and stirred evenly. The pH value was adjusted to 13 using an alkaline solution, and then the precursor liquid was dispersed to obtain the precursor liquid. S2.2 Acyl Chloride Organic Phase Microenvironment Dispersion: 1,3,5-Benzotricarboxylic acid chloride was added to an organic solvent and dispersed to obtain a 1,3,5-Benzotricarboxylic acid chloride dispersion. The alkaline solution was sodium hydroxide solution.

[0076] The polymer precursor was p-dimethylamine, and the organic solvent was n-heptane; the precursor liquid was dispersed using ultrasonic dispersion; and the acyl chloride was dispersed using a low-temperature ultrasonic-mechanical synergistic dispersion method.

[0077] S3 Immersion: The composite membrane substrate is immersed in the precursor fluid for immersion. After immersion, interfacial liquid phase desorption is controlled to obtain a nanocellulose heterogeneous interfacial substrate. The immersion time is 20 minutes. In the interfacial liquid phase desorption control, excess liquid on the surface is adsorbed by gently pressing filter paper.

[0078] S4 heterogeneous molecular self-assembly dynamic crosslinking film formation: 1,3,5-benzenetriformyl chloride dispersion was added dropwise to the upper surface of the nanocellulose heterogeneous interface substrate to carry out interfacial polymerization reaction. After the reaction was completed, the excess 1,3,5-benzenetriformyl chloride dispersion on the surface was removed to obtain the initial composite membrane; the interfacial polymerization reaction time was 2 minutes.

[0079] S5 Annealing Treatment: The initial composite membrane is annealed to obtain a polymer layer-nanocellulose composite membrane.

[0080] By weight ratio, the ratio of nanocellulose to pure water is 0.6:1000, the ratio of polymer precursor to pure water is 1:50, and the ratio of 1,3,5-benzenetricarboxyl chloride to organic solvent is 2:98.

[0081] The polymer-cellulose nanocomposite membrane with a dense nanoporous structure prepared above was cut into a circle with a diameter of 15 mm and assembled into a zinc-zinc (Zn-Zn) symmetric battery using a 2032 battery case.

[0082] The assembly process of a zinc-zinc (Zn-Zn) symmetrical battery consists of, in sequence, a negative electrode shell, a spring, a gasket, a zinc negative electrode, a polymer-nanocellulose composite separator, a glass fiber separator, a polymer-nanocellulose composite separator, a zinc positive electrode, and a positive electrode shell.

[0083] Comparative Example 1

[0084] A zinc-zinc (Zn-Zn) symmetrical battery is assembled using a 2032 battery case and directly using a glass fiber separator as the battery separator. The zinc-zinc (Zn-Zn) symmetrical battery assembly structure consists of, from top to bottom, a negative electrode case, a spring, a gasket, a zinc negative electrode, a glass fiber separator, a zinc positive electrode, and a positive electrode case.

[0085] Comparative Example 2

[0086] A method for preparing a polymer layer-cellulose nanocomposite membrane with a dense nanoporous structure includes the following steps:

[0087] S1 Vacuum Self-Assembly Molding Substrate: Nanocellulose is uniformly dispersed in pure water to obtain a nanocellulose solution. The nanocellulose solution is then subjected to vacuum filtration to obtain a composite membrane substrate.

[0088] S2 Two-way Solution Construction: S2.1 Alkaline-Induced Monomer Ionization Construction: The polymer precursor was added to pure water and stirred evenly. The pH value was adjusted to 13 using an alkaline solution, and then the precursor liquid was dispersed to obtain the precursor liquid. S2.2 Acyl Chloride Organic Phase Microenvironment Dispersion: 1,3,5-Benzotricarboxylic acid chloride was added to an organic solvent and dispersed to obtain a 1,3,5-Benzotricarboxylic acid chloride dispersion. The alkaline solution was sodium hydroxide solution.

[0089] The polymer precursor was p-phenylenediamine, and the organic solvent was n-heptane; the precursor liquid was dispersed using ultrasonic dispersion; and the acyl chloride was dispersed using a low-temperature ultrasonic-mechanical synergistic dispersion method.

[0090] S3 Immersion: The composite membrane substrate is immersed in the precursor fluid for immersion. After immersion, interfacial liquid phase desorption is controlled to obtain a nanocellulose heterogeneous interfacial substrate. The immersion time is 20 minutes. In the interfacial liquid phase desorption control, excess liquid on the surface is adsorbed by gently pressing filter paper.

[0091] S4 heterogeneous molecular self-assembly dynamic crosslinking film formation: 1,3,5-benzenetriformyl chloride dispersion was added dropwise to the upper surface of the nanocellulose heterogeneous interface substrate to carry out interfacial polymerization reaction. After the reaction was completed, the excess 1,3,5-benzenetriformyl chloride dispersion on the surface was removed to obtain the initial composite membrane; the interfacial polymerization reaction time was 2 minutes.

[0092] S5 Annealing Treatment: The initial composite membrane is annealed to obtain a polymer layer-nanocellulose composite membrane.

[0093] By weight ratio, the ratio of nanocellulose to pure water is 0.6:1000, the ratio of polymer precursor to pure water is 1:50, and the ratio of 1,3,5-benzenetricarboxyl chloride to organic solvent is 2:98.

[0094] The polymer-cellulose nanocomposite membrane with a dense nanoporous structure prepared above was cut into a circle with a diameter of 15 mm and assembled into a zinc-zinc (Zn-Zn) symmetric battery using a 2032 battery case.

[0095] The assembly process of a zinc-zinc (Zn-Zn) symmetrical battery consists of, in sequence, a negative electrode shell, a spring, a gasket, a zinc negative electrode, a polymer-nanocellulose composite separator, a glass fiber separator, a polymer-nanocellulose composite separator, a zinc positive electrode, and a positive electrode shell.

[0096] Comparative Example 3

[0097] Nanocellulose was uniformly dispersed in pure water at a mass ratio of 0.6:1000, and a nanocellulose membrane was obtained by filtration. The nanocellulose membrane with a dense nanoporous structure was cut into circles with a diameter of 15 mm and assembled into a zinc-zinc (Zn-Zn) symmetric battery using a 2032 battery case.

[0098] The assembly process of a zinc-zinc (Zn-Zn) symmetrical battery is as follows: negative electrode shell, spring sheet, gasket, zinc negative electrode, nanocellulose membrane, glass fiber membrane, nanocellulose membrane, zinc positive electrode, and positive electrode shell.

[0099] Comparative Example 4

[0100] 2,5-Diaminobenzenesulfonic acid was dispersed in pure water at a mass ratio of 1:50 and the pH of the solution was adjusted to 13. 1,3,5-Benzotricarboxylic acid chloride was dispersed in n-heptane at a mass ratio of 2:98. The glass fiber membrane substrate was directly immersed in the 2,5-diaminobenzenesulfonic acid solution for 20 min, and then the 1,3,5-Benzotricarboxylic acid chloride solution was dropped onto the membrane surface for interfacial polymerization reaction for 2 min. The resulting composite membrane was removed from the n-heptane solution and annealed in an oven for 10 min to obtain the polymer-glass fiber composite membrane.

[0101] Performance testing and analysis:

[0102] like Figure 1 As shown, the polymer-cellulose nanocomposite membrane with a dense nanoporous structure prepared in Example 1 of this invention exhibits a flat, uniform, and dense polymer layer, and the nanocellulose contains porous channels that facilitate ion transport. Figure 3 As shown, the assembled zinc-zinc (Zn-Zn) symmetric battery, at 25℃ and 1 mA / cm², 2 (0.5mAh / cm 2 After cycling for 60 hours under the following conditions, if Figure 3 As shown, the protective layer remained intact after cycling, indicating that it facilitates uniform zinc ion deposition and effectively inhibits zinc dendrite formation. Figure 7 As shown, the zinc vanadium pentoxide full cell has an initial discharge capacity of up to 240 mAh / g, and after more than 1,000 cycles, the capacity is maintained at 90%, and the coulombic efficiency remains above 60%.

[0103] The polymer-cellulose nanofiber composite membranes with dense nanoporous structures prepared in Examples 2 and 3 of this invention, assembled into zinc-zinc (Zn-Zn) symmetric batteries, performed at 25°C and 1 mA / cm². 2 (0.5mAh / cm 2 After cycling for 60 hours under the specified conditions, the results were as follows: Figure 4 and 5As shown, the protective layer remained intact after cycling, indicating that the protective layer facilitates the uniform deposition of zinc ions and effectively inhibits the formation of zinc dendrites.

[0104] like Figure 8 As shown, Comparative Example 1 was assembled into a zinc-zinc (Zn-Zn) symmetric cell, and tested at 25℃ and 1 mA / cm². 2 (0.5mAh / cm 2 Under these conditions, after 60 hours of cycling, it can be observed that zinc dendrites formed in the Zn-Zn symmetric cell after only 60 hours of cycling. If cycling continues, micron-sized dendrites will form, which can pierce the glass fiber separator and cause a short circuit in the cell.

[0105] like Figure 2 As shown in Comparative Example 4, the interfacial polymerization reaction of 2,5-diaminobenzenesulfonic acid and 1,3,5-benzenetricarboxyl chloride was carried out directly on the surface of glass fiber. Then, the results were observed directly by scanning electron microscopy. No smooth, uniform and dense polymer layer was observed, which indicates that the interfacial polymerization reaction of diamino monomer and 1,3,5-benzenetricarboxyl chloride requires nanocellulose as a substrate.

[0106] like Figure 6 As shown, the cycle performance of zinc-zinc (Zn-Zn) symmetric batteries assembled in Examples 1, 2, and 3 and Comparative Examples 1, 2, and 3 was compared. It was found that the batteries in Comparative Example 1 and Comparative Example 2 were prone to short circuits during operation.

[0107] In summary, the separator prepared by this invention achieves desolvation of zinc ions through a polymer layer with a dense nanoporous structure and a porous framework, thereby increasing the zinc ion transference number, effectively reducing the overpotential of the zinc anode, facilitating uniform zinc ion deposition, and reducing side reactions at the zinc anode. Simultaneously, the cellulose layer provides good mechanical strength and inhibits the formation of zinc dendrites. The polymer with a dense nanoporous structure can improve the cycle life of aqueous zinc-ion batteries.

[0108] The specific embodiments described herein are merely illustrative examples of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the defined scope.

Claims

1. A method for preparing a polymer layer-cellulose nanofiber composite separator with a dense nanoporous structure for use in aqueous zinc-ion battery packs, characterized in that, The preparation method of the polymer layer-nanocellulose composite membrane includes the following steps: S1 Vacuum Self-Assembly Molding Substrate: Nanocellulose is uniformly dispersed in pure water to obtain a nanocellulose solution. The nanocellulose solution is then subjected to vacuum filtration to obtain a composite membrane substrate. S2 Two-way Solution Construction: S2.1 Alkaline-Induced Monomer Ionization Construction: After adding the polymer precursor to pure water and stirring evenly, the pH value was adjusted to 12-15 using an alkaline solution, and then the precursor liquid was dispersed to obtain the precursor liquid. S2.2 Acyl Chloride Organic Phase Microenvironment Dispersion: 1,3,5-Benzotricarboxylic acid chloride was added to an organic solvent and acyl chloride dispersion was carried out to obtain a 1,3,5-Benzotricarboxylic acid chloride dispersion. The polymer precursor is one of 2,5-diaminobenzenesulfonic acid, o-phenylenediamine, p-dimethylbenzenediamine, 2,5-dimethyl-1,4-phenylenediamine, and 1,4-cyclohexanediamine; the organic solvent is n-heptane or n-hexane. S3 Immersion: The composite membrane substrate is immersed in the precursor liquid for 10-20 minutes. After immersion, the interfacial liquid phase desorption is controlled by using filter paper to gently press and adsorb excess liquid on the surface to obtain the nanocellulose heterogeneous interfacial substrate. S4 heterogeneous molecular self-assembly dynamic crosslinking film formation: 1,3,5-benzenetricarboxylic acid chloride dispersion was added dropwise to the upper surface of the nanocellulose heterogeneous interface substrate to carry out interfacial polymerization reaction. After the reaction was completed, the excess liquid on the surface was removed to obtain the initial composite membrane. S5 Annealing: The initial composite membrane is annealed to obtain a polymer layer-nanocellulose composite membrane.

2. The method for preparing a polymer layer-cellulose nanocomposite membrane with a dense nanoporous structure for use in aqueous zinc-ion battery packs as described in claim 1, characterized in that, According to the weight ratio, the ratio of nanocellulose to pure water is 0.6:1000-3000, the ratio of polymer precursor to pure water is 1:50-100, and the ratio of 1,3,5-benzenetricarboxyl chloride to organic solvent is 2:90-100.

3. The method for preparing a polymer layer-cellulose nanofiber composite separator with a dense nanoporous structure for use in aqueous zinc-ion battery packs as described in claim 1, characterized in that, In step S2.1, the alkaline solution is a sodium hydroxide solution.

4. The method for preparing a polymer layer-cellulose nanocomposite membrane with a dense nanoporous structure for use in aqueous zinc-ion battery packs as described in claim 1, characterized in that, In step S2.1, the precursor liquid dispersion operation adopts ultrasonic dispersion method; in step S2.2, the acyl chloride dispersion operation adopts low temperature ultrasonic-mechanical synergistic dispersion method.

5. The method for preparing a polymer layer-cellulose nanocomposite membrane with a dense nanoporous structure for use in aqueous zinc-ion battery packs as described in claim 1, characterized in that, In step S4, the reaction time for the interfacial polymerization reaction is 1-5 minutes.

6. The method for preparing a polymer layer-cellulose nanofiber composite separator with a dense nanoporous structure for use in aqueous zinc-ion battery packs as described in claim 1, characterized in that, In step S5, the annealing process parameters are as follows: annealing temperature is 40-80℃; annealing time is 10-20 minutes.

7. An aqueous zinc-ion battery pack, wherein the aqueous zinc-ion battery pack comprises a polymer layer-cellulose nanocomposite membrane with a dense nanoporous structure prepared by the method according to any one of claims 1-6, characterized in that, In the assembly structure of an aqueous zinc-ion battery pack, from top to bottom, the components are: negative electrode shell, spring sheet, gasket, zinc negative electrode, polymer layer-nanocellulose composite separator, glass fiber separator, polymer layer-nanocellulose composite separator, positive electrode, and positive electrode shell.

8. The aqueous zinc-ion battery pack as described in claim 7, characterized in that, The aqueous zinc-ion battery pack is specifically a Zn-Zn symmetrical battery pack or a Zn-V2O5 full battery pack.

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