Green water-based supramolecular binder for battery as well as preparation method and application of green water-based supramolecular binder

Abstract

The invention discloses a green water-based supramolecular binder for a battery as well as a preparation method and application of the green water-based supramolecular binder. The binder comprises polyoxyethylene and organic acid, and has a supramolecular structure formed by the polyoxyethylene and the organic acid through intermolecular hydrogen bond interaction. The preparation method comprises the following steps: (1) dissolving polyoxyethylene (PEO) in deionized water at 80 DEG C; and (2) adding an organic acid into the mixed solution obtained in the step (1), continuously stirring at 80 DEG C for 6 hours, and cooling the mixed solution to room temperature to obtain the water-based supramolecular binder. Compared with the existing binder based on an organic solvent, the water-based supramolecular binder prepared by the invention is greener and low in price. In addition, the supramolecular binder can form strong electron interaction with the electrode material, so that the electrode reaction kinetics is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, and particularly relates to a green water-based supramolecular binder for batteries and its application. Background Technology

[0002] With the continued expansion of the global population and the accelerated pace of industrialization, human society's energy consumption is growing exponentially, leading to a sharp decline in non-renewable resource reserves and causing severe ecological damage. Against this backdrop, developing clean and sustainable energy solutions has become an urgent priority, and recyclable secondary batteries, with their unique advantages, demonstrate enormous application potential in addressing energy shortages and environmental pollution.

[0003] The advent of lithium-ion batteries has significantly alleviated major petroleum fuel pollution and the energy crisis. With its unique advantages, including high power density, no storage requirements, small size, light weight, long cycle life, and low self-discharge rate, lithium-ion batteries are widely used in consumer electronics, medical, electric vehicles, industrial, aerospace and defense, and energy storage industries. Besides lithium-ion batteries, other important energy storage systems also have great application potential, such as aqueous zinc-ion batteries, aqueous magnesium-ion batteries, and lithium-sulfur batteries. Binders, as an indispensable component of various energy storage systems, play a crucial role in realizing the practical application potential of these systems.

[0004] Currently, the most widely used binders are organic systems such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). These binders require the combined use of toxic organic solvents, thus causing numerous pollution problems in practical applications. In addition, there are water-based binders such as sodium carboxymethyl cellulose (CCFC), but existing water-based binders have low bonding strength to electrode materials and lack strong electron interactions with them, thus failing to accelerate electrode reaction kinetics. For example, invention patent CN116004150A discloses a polymer binder, a positive electrode slurry, and its preparation method. This polymer binder is a complex formed by the shared electron pair complexation of carboxyl groups in an acrylate-based multi-component copolymer and the ether oxygen in polyethylene oxide. However, the synthesis process requires complex condensation reactions, making it unsuitable for large-scale industrial production. The polymer binder provided by this invention, as a water-based binder, meets the requirements of green and low-cost production and improves the low-temperature performance of batteries, providing new raw materials, pathways, and methods for the preparation of lithium-ion batteries.

[0005] Therefore, developing green, environmentally friendly, and inexpensive water-based binders is of great significance for reducing the cost of secondary battery applications and achieving sustainable development. Furthermore, accelerating electrode reaction kinetics by enhancing the strong electronic interactions between the binder and electrode materials also has important application value. Summary of the Invention

[0006] To address the technical problems of low bonding strength and weak interaction between existing water-based binders and electrode materials, this invention proposes a green water-based supramolecular binder for batteries, its preparation method, and its application.

[0007] To achieve the above objectives, the technical solution of the present invention is implemented as follows: This invention provides a water-based supramolecular binder comprising polyethylene oxide and organic acid, and having a supramolecular structure formed by the interaction of polyethylene oxide and organic acid through intermolecular hydrogen bonds. Its mechanism of action is as follows: in an aqueous environment, polyethylene oxide acts as a hydrogen bond acceptor, while organic acid acts as a hydrogen bond donor. The two are combined through multiple hydrogen bonds to form a non-covalently cross-linked dynamic network.

[0008] The supramolecular three-dimensional network structure provides strong and universal bonding strength, forming a firm bond with various polar and non-polar materials (such as metals, plastics, wood, paper, and fibers). Using water as the dispersion medium completely avoids the pollution problems of volatile organic compounds (VOCs) associated with traditional solvent-based adhesives, making it non-toxic and harmless, and meeting the requirements of sustainable development. Therefore, this invention provides an environmentally friendly, strong-bonding, high-energy water-based adhesive with broad application prospects in cutting-edge fields such as green packaging and structural materials.

[0009] The mass ratio of polyethylene oxide to organic acid is 1:2-20:1. When the proportion of polyethylene oxide is high (e.g., close to 20:1), the ether oxygen atoms, which act as hydrogen bond acceptors, dominate the system, resulting in a relatively low crosslinking density in the supramolecular network. This makes the adhesive solution have moderate viscosity and good fluidity, and it tends to form flexible films, exhibiting excellent film-forming properties and cohesive strength, suitable for applications requiring high toughness and coating processing. When the proportion of organic acid is high (e.g., close to 1:2), the carboxyl functional groups, which act as hydrogen bond donors, greatly increase in the system, leading to denser crosslinking points in the supramolecular network and a significantly increased crosslinking density. This results in extremely strong initial adhesion of the adhesive, increased solution viscosity, and the formation of a more rigid adhesive layer, suitable for applications requiring rapid positioning and the establishment of high-strength bonds. The specific mass ratio range of 1:2 to 20:1 endows this supramolecular binder system with strong flexibility and adaptability. By simply adjusting the component ratio, a series of products with different properties, ranging from high toughness to high rigidity and from high flowability to high viscosity, can be customized to meet different application needs, greatly expanding its application fields.

[0010] The molecular weight of the polyethylene oxide is 1×10⁻⁶. 5 - 4×10 5Within this molecular weight range, polyethylene oxide (PEO) molecular chains possess sufficient length to serve as a robust "backbone" for supramolecular networks. A long PEO molecular chain can simultaneously interact with multiple organic acid molecules through hydrogen bonds, acting as a "bridge" and "crosslink" link at multiple sites, thereby forming a stable, continuous, and effectively stress-transferring three-dimensional network structure on a macroscopic scale. The molecular weight is at the lower limit of the range (approximately 1 × 10⁻⁶). 5 When the molecular chains are relatively short and the chain entanglement is weak, the binder solution has low viscosity and good fluidity, making it easy to wet porous or complex-shaped substrate surfaces. This makes it particularly suitable for processing techniques requiring good penetration, such as spraying and dipping. The molecular weight is at the upper limit of the range (approximately 4 × 10⁻⁶). 5 At this stage, the molecular chains are longer, and the chain entanglement effect based on polymer physics is significantly enhanced. This, combined with the hydrogen bond network, endows the binder with extremely high cohesive strength and melt strength. This makes its film-forming properties, creep resistance, and toughness particularly outstanding, allowing the prepared adhesive layer to withstand greater long-term loads and impact stresses.

[0011] The polyethylene oxide (PE) content is 0.5%-10% by mass, a concentration range that allows for precise control from low-viscosity solutions to high-strength gels / films. In the low concentration range (e.g., 0.5%-2%), PE molecules are fully extended in water but have not yet formed a permeable network; the system is primarily a low-viscosity, easily flowing liquid. This gives the adhesive excellent permeability and wettability, making it ideal for use as a spray adhesive, impregnating adhesive, or for penetrating bonding of porous materials (such as wood and paper). In the medium concentration range (e.g., 2%-5%), as the concentration increases, PE molecular chains begin to overlap and entangle, forming a preliminary permeable three-dimensional network with the organic acid. The system viscosity increases significantly, exhibiting a typical gel or paste-like consistency. This morphology gives it excellent thixotropic and surface coating properties, making it suitable for use as a "coatable putty" or sealant. In the high concentration range (e.g., 5%-10%), high concentrations of PE and organic acids form an extremely dense three-dimensional supramolecular network; the system can exhibit a highly viscous paste or be directly cast into a film. After coating and drying, it can form a dense and tough solid adhesive film, which is suitable for preparing high-performance pressure-sensitive tapes, flexible electrode bonding layers or structural adhesive films.

[0012] The organic acid is selected from any one of phytic acid, citric acid, gambogeylic acid, tartaric acid, oxalic acid, malic acid, and ascorbic acid.

[0013] The organic acid comprises 0.5%-10% by mass. In the low concentration range (e.g., 0.5%-2%), the number of organic acid "crosslinking points" is relatively small, resulting in a looser three-dimensional network with PEO. This leads to lower hardness and modulus of the adhesive layer, exhibiting higher flexibility and elasticity, suitable for flexible substrates requiring bending or deformation. In the high concentration range (e.g., 5%-10%), the high concentration of organic acid provides a large number of carboxyl functional groups, forming dense hydrogen bond crosslinking points with the ether oxygen bonds on the PEO chains. This significantly increases the crosslinking density of the supramolecular network, resulting in a significant improvement in the hardness, modulus, and cohesive strength of the adhesive layer, making it suitable for structural bonding scenarios requiring high load-bearing capacity. An organic acid concentration in the 0.5%-10% range ensures sufficient organic acid molecules migrate to the interface, achieving strong anchoring for various materials. Too low a concentration may lead to insufficient interfacial adhesion; too high a concentration may sacrifice toughness due to excessive crosslinking.

[0014] This invention provides a method for preparing a water-based supramolecular binder, the specific steps of which are as follows: (1) First, dissolve polyethylene oxide in deionized water to obtain an aqueous solution of polyethylene oxide; (2) Add organic acid to the aqueous solution of polyethylene oxide, stir and cool to room temperature to obtain water-based supramolecular binder.

[0015] The stirring temperature in step (2) is 50-90℃, and the stirring time is 3-8 h.

[0016] This invention also provides the application of a water-based supramolecular binder in the preparation of secondary battery electrode sheets.

[0017] The water-based supramolecular binder is used to bind the electrode active material, the conductive agent, and the current collector; the electrode active material is a positive electrode active material or a negative electrode active material.

[0018] The present invention has the following beneficial effects: 1. This invention utilizes molecular interactions under low-temperature stirring to prepare a binder, which spontaneously assembles into a supramolecular network through intermolecular hydrogen bonds. The preparation process is simple, the conditions are mild, the cost is low, and water is used as a solvent, making it safe and non-toxic. This completely avoids the pollution and risks of volatile organic compounds (VOCs) during the production and use of traditional binders, significantly reducing raw material and production costs, and possessing great potential for large-scale industrial production.

[0019] 2. Supramolecular binders prepared based on intermolecular hydrogen bonding interactions possess a unique supramolecular structure, and multiple functional groups enable the binder to exhibit strong adhesion strength to the electrode material. Among these, the various polar functional groups provided by organic acids (such as carboxyl groups) can form strong multiple interactions (including hydrogen bonds and ionic bonds) with electrode active materials (such as iodine, conductive agents, and current collectors), generating a universal and robust adhesive force. This strong adhesive force effectively inhibits the volume expansion, pulverization, and detachment of the electrode material during cycling, maintaining the integrity of the electrode structure, which is the foundation for achieving a long cycle life.

[0020] 3. Compared to existing binders, the supramolecular binder prepared in this invention exhibits strong electronic interactions with the electrode material. This not only further enhances interfacial bonding, but more importantly, this interaction optimizes the electron transport pathway of iodine species, effectively promoting the redox reaction kinetics of iodine. This results in more rapid electron and ion transport at the electrode interface, thereby improving the utilization rate and rate performance of the active material. The supramolecular binder of this invention achieves high capacity (at 0.5 A g) in aqueous zinc-iodine (Zn-I2) batteries. -1 The following is 326 mAh g -1 ) and long-term cycling stability (at 5 A g) -1 (The capacity retention rate is 75% after 8500 cycles), providing key material support for the development of a new generation of high-performance, low-cost energy storage devices. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of the supramolecular binder prepared in Example 1.

[0023] Figure 2 The Fourier transform infrared (FTIR) spectrum of the supramolecular binder prepared in Example 1 is shown, where a is the infrared spectrum of pure polyethylene oxide, pure phytic acid, and the supramolecular binder; and b is a magnified view of a portion of the infrared spectrum.

[0024] Figure 3 The X-ray photoelectron spectroscopy (XPS) of the supramolecular binder prepared in Example 1 is shown, where a is the P 2p spectrum and b is the O 1s spectrum.

[0025] Figure 4Peel strength test of electrode materials based on the binders prepared in Example 1 and the comparative example on current collectors.

[0026] Figure 5 The rate performance of Zn-I2 batteries based on the binders prepared in Example 1 and the comparative example is shown.

[0027] Figure 6 To assess the long-cycle stability of Zn-I2 batteries based on the binders prepared in Example 1 and the comparative example.

[0028] Figure 7 Zn-I2 batteries based on the binders prepared in Example 1 and the comparative example were tested at 5 A g. -1 Scanning electron microscope (SEM) images of the electrode surface after 5000 cycles, where a is an electrode SEM image of the Zn-I2 battery prepared based on the comparative binder; b is an electrode SEM image of the Zn-I2 battery prepared based on the binder of Example 1. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0030] Unless otherwise specified, the experimental methods used in the following experimental examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0031] Example 1 A method for preparing a green water-based supramolecular binder, comprising the following steps: (1) First, dissolve 0.6 g of polyethylene oxide (PEO) in 30 mL of deionized water to obtain an aqueous solution of polyethylene oxide; (2) Then, 0.6 g of phytic acid (PA) was added to the polyethylene oxide aqueous solution in step (1), and the resulting mixed solution was stirred at 80°C for 6 h. (3) After the above mixed solution is cooled to room temperature, a water-based supramolecular binder is obtained.

[0032] Figure 1 This is a schematic diagram of the phytic acid-based supramolecular binder prepared in this embodiment. Polyethylene oxide and phytic acid form a supramolecular network through intermolecular hydrogen bonding. This structure contains a variety of oxygen-containing functional groups, which gives the binder and electrode material a strong bonding strength.

[0033] Figure 2 The FTIR spectrum of the phytic acid-based supramolecular binder prepared in this embodiment is shown. The FTIR spectrum at 2876.7 cm⁻¹ is also shown. -1 and 1091.3 cm -1 The peaks at 3083 cm⁻¹ are attributed to the stretching vibrations of -CH₂ and COC, respectively. However, the stretching vibration peaks of -CH₂ and COC in the supramolecular binder shift to lower wavenumbers, indicating a strong hydrogen bond between the functional groups of PA and PEO. The peaks at 3083 cm⁻¹ in the FTIR spectrum of PA... -1 1615.6 cm -1 and 987.6 cm -1 The peaks at these locations represent -OH stretching, C=O stretching, and PO stretching, respectively. Similarly, these peaks show a significant shift in the FTIR spectrum of the supramolecular binder, further demonstrating the strong hydrogen bonding interaction between PA and PEO.

[0034] Figure 3 The XPS spectrum of the phytic acid-based supramolecular binder prepared in this embodiment shows that the characteristic peaks at 133.6 and 132.9 eV in the high-resolution XPS P2p spectrum of PA belong to PO and PC bonds, respectively. These characteristic peaks in the supramolecular binder shift to lower binding energies, indicating that PEO transfers charge to PA through strong hydrogen bonds. In the O 1s spectrum, the characteristic peaks of COC and CO / P=O in the supramolecular binder are significantly shifted relative to the characteristic peaks in PEO and PA, indicating a strong chemical interaction between PA and PEO in the supramolecular binder.

[0035] Example 2 A method for preparing a green water-based supramolecular binder, comprising the following steps: (1) First, dissolve 1.0 g of polyethylene oxide (PEO) in 30 mL of deionized water to obtain an aqueous solution of polyethylene oxide; (2) Then, 0.6 g of citric acid was added to the polyethylene oxide aqueous solution in step (1), and the resulting mixed solution was stirred continuously at 60 °C for 6 h. (3) After the above mixture is cooled to room temperature, a water-based supramolecular binder is obtained.

[0036] Example 3 A method for preparing a green water-based supramolecular binder, comprising the following steps: (1) First, dissolve 0.6 g of polyethylene oxide (PEO) in 30 mL of deionized water; (2) Then, 1 g of ascorbic acid was added to the polyethylene oxide aqueous solution in step (1), and the resulting mixed solution was stirred at 60°C for 6 h. (3) After the above mixed solution is cooled to room temperature, a water-based supramolecular binder is obtained.

[0037] Example 4 A method for preparing a green water-based supramolecular binder, comprising the following steps: (1) First, dissolve 0.15 g of polyethylene oxide (PEO) in 30 mL of deionized water; (2) Then, 0.3 g of ascorbic acid was added to the polyethylene oxide aqueous solution in step (1), and the resulting mixed solution was stirred at 50°C for 3 h. (3) After the above mixed solution is cooled to room temperature, a water-based supramolecular binder is obtained.

[0038] Example 5 A method for preparing a green water-based supramolecular binder, comprising the following steps: (1) First, dissolve 3 g of polyethylene oxide (PEO) in 30 mL of deionized water; (2) Then, 0.15 g of ascorbic acid was added to the polyethylene oxide aqueous solution in step (1), and the resulting mixed solution was stirred at 60°C for 8 h. (3) After the above mixed solution is cooled to room temperature, a water-based supramolecular binder is obtained.

[0039] Example 6 A method for preparing a green water-based supramolecular binder, comprising the following steps: (1) First, dissolve 3 g of polyethylene oxide (PEO) in 30 mL of deionized water; (2) Then, 3 g of ascorbic acid was added to the polyethylene oxide aqueous solution in step (1), and the resulting mixed solution was stirred at 90°C for 8 h. (3) After the above mixed solution is cooled to room temperature, a water-based supramolecular binder is obtained.

[0040] Comparative Example Add 0.63 g of polyvinylidene fluoride (PVDF) to 30 mL of N-methylpyrrolidone (NMP) and stir continuously until PVDF is completely dissolved to obtain a 2% (w / w) organic solution of polyvinylidene fluoride, which is the PVDF-based binder.

[0041] Implementation Results Example The bonding properties of electrode materials based on the binders prepared in Example 1 and the comparative example were tested. Two adhesives were mixed with the electrode material to form a slurry, which was then applied to the current collector and dried. A peel test was then performed on the electrode material using a universal testing machine, and the peel strength of the electrode material on the current collector was calculated. The results are as follows: Figure 4 As shown, the electrode material based on the binder prepared in Example 1 exhibits a peel strength as high as 0.75 N / cm. -1 The peel strength of the electrode material based on the binder prepared in the comparative proportion was only 0.12 N / cm. -1 This indicates that supramolecular binders have superior bonding properties.

[0042] Performance testing was conducted on Zn-I2 batteries prepared using the binders from Example 1 and the comparative example. Battery rate performance A zinc-iodine battery was assembled using iodine-carbon nanofiber composite material as the positive electrode, zinc foil as the negative electrode, and ZnSO4 as the electrolyte. The electrolyte concentration was 0.5–5 A g. -1 The following rate performance test was conducted. The results are as follows: Figure 5 As shown, the electrode based on the supramolecular binder at 0.5 A g -1 Achieving up to 326 mAh g -1 The capacity, even when the current density increases to 5 A g. -1 The capacity also remains at 207 mAh g -1 However, PVDF-based electrodes at 0.5 A g... -1 It only reached 203 mAh g -1 The capacity.

[0043] Long-cycle stability A zinc-iodine battery was assembled using iodine-carbon nanofiber composite material as the positive electrode, zinc foil as the negative electrode, and ZnSO4 as the electrolyte. The battery was tested at 5 A g. -1 Long-cycle performance testing was then conducted. The results are as follows: Figure 6 As shown, when the current density is 5 A g -1 At that time, the capacity retention rate of the battery based on supramolecular binder was 75% after 8500 cycles, but the capacity of the battery based on PVDF dropped to 54% after 1400 cycles.

[0044] Figure 7 Based on the comparative example and Example 1, the Zn-I2 battery at 5 A g -1 SEM images of the electrode surface after 5000 cycles. The SEM images of the PVDF-based electrode after cycling show obvious cracking of the active material, but no cracking of the electrode material was observed in the supramolecular binder-based electrode. This further illustrates that the supramolecular binder has a strong bonding ability to the electrode material.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A water-based supramolecular binder, characterized by, The water-based supramolecular binder comprises polyethylene oxide and organic acid, and has a supramolecular structure formed by the intermolecular hydrogen bond interaction between the polyethylene oxide and the organic acid.

2. The water-based supramolecular adhesive according to claim 1, characterized in that: The mass ratio of the polyethylene oxide to the organic acid is 1:2-20:

1.

3. The water-based supramolecular adhesive according to claim 2, wherein: The polyethylene oxide has a molecular weight of 1 x 10 5 - 4 x 10 5 .

4. The water-based supramolecular adhesive according to claim 3, wherein: The mass percentage of the polyethylene oxide in the binder is 0.5%-10%.

5. The water-based supramolecular adhesive according to claim 4, wherein: The organic acid is selected from any one of phytic acid, citric acid, gambogic acid, tartaric acid, oxalic acid, malic acid and ascorbic acid.

6. The water-based supramolecular adhesive according to claim 5, wherein: The mass percentage of the organic acid in the binder is 0.5%-10%.

7. A process for the preparation of the water-based supramolecular adhesive according to any one of claims 1-6, characterized in that, The specific steps are as follows: (1) dissolving the polyethylene oxide in deionized water to obtain a polyethylene oxide aqueous solution; (2) adding the organic acid into the polyethylene oxide aqueous solution, stirring and cooling to room temperature to obtain the water-based supramolecular binder.

8. The method of claim 7, wherein: The stirring temperature in the step (2) is 50-90℃, and the stirring time is 3-8h.

9. Use of the water-based supramolecular binder according to any one of claims 1-6 in the preparation of a secondary battery electrode sheet.

10. Use according to claim 9, characterized in that: The water-based supramolecular binder is used for bonding electrode active material, conductive agent and current collector; the electrode active material is positive electrode active material or negative electrode active material.

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