A water-based binder based on coordination cross-linking of polyvalent metal ions, and a preparation method and application thereof
By using a water-based binder with multivalent metal ion coordination crosslinking, the problem of volume expansion of polysaccharide polymer binders in silicon anode materials was solved, thereby improving the stability and performance of lithium-ion batteries. Moreover, the preparation process is environmentally friendly and low-cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA UNIV OF GEOSCIENCES (WUHAN)
- Filing Date
- 2026-01-26
- Publication Date
- 2026-05-15
AI Technical Summary
Existing polysaccharide polymer binders are difficult to effectively buffer volume expansion during the charging and discharging of silicon anode materials, leading to the shedding of electrode active materials and battery capacity decay.
A water-based binder with multivalent metal ion coordination crosslinking is used. Sodium carboxymethyl cellulose and multivalent metal ions form a three-dimensional network structure. The coordination effect and electrostatic interaction between metal ions and polymer chains enhance the stability and stress buffering capacity of the bonded network.
It significantly improves the volume expansion problem of silicon-based anode materials, enhances the cycle stability and rate performance of lithium-ion batteries, reduces manufacturing costs, and the preparation process is environmentally friendly and safe.
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Figure CN121555109B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of adhesive technology, and in particular to an aqueous adhesive based on the coordination crosslinking of multivalent metal ions, its preparation method, and its application. Background Technology
[0002] With the booming development of the electric vehicle and portable electronic device markets, the demand for high-energy-density lithium-ion batteries (LIBs) has increased dramatically. Among many materials, silicon anodes have attracted much attention due to their ultra-high theoretical specific capacity of 4200 mAh / g and low operating voltage approaching that of metallic lithium. In addition, silicon accounts for up to 27.7% of the Earth's crust, making it abundant and inexpensive. This not only significantly reduces the cost of electrode manufacturing but also effectively alleviates dependence on graphite resources.
[0003] However, during charging and discharging, silicon anode materials undergo drastic volume changes. During lithiation, the volume expansion rate can reach 300% to 400%, and after delithiation, it shrinks. This volume change impairs the integrity of the electrode, leading to a sharp increase in internal resistance and rapid capacity decay, severely limiting its practical application performance. Binders can firmly bond silicon particles to conductive agent particles and tightly bind them to the current collector, forming a stable electrode structure. This can withstand the stress generated by the expansion and contraction of silicon particles, reducing electrode material detachment and pulverization, and maintaining electrode integrity.
[0004] Polysaccharide polymers generally possess good water solubility and strong mechanical properties, making them suitable as base materials for water-based multifunctional binders. Furthermore, the polar heteroatom groups on their molecular chains can enable the binder to acquire self-repairing / self-healing functions through dynamic hydrogen bonding. However, when facing the volume expansion problem during the charging and discharging process of silicon anodes, the lack of a strong and resilient spatial constraint network makes it difficult to effectively buffer stress, leading to the shedding of electrode active materials and rapid capacity decay. Summary of the Invention
[0005] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing an aqueous adhesive based on the coordination crosslinking of multivalent metal ions, its preparation method, and its application.
[0006] The first objective of this invention is to provide a method for preparing an aqueous adhesive based on the coordination crosslinking of multivalent metal ions, specifically including the following steps:
[0007] S1. Dissolve sodium carboxymethyl cellulose in water, heat and stir to form an aqueous solution of sodium carboxymethyl cellulose;
[0008] S2. Dissolve the metal ion compound in deionized water to obtain an aqueous solution of the metal ion compound; the metal ions include divalent metal ions and trivalent metal ions;
[0009] S3. A certain amount of aqueous solution of metal ion compound is slowly added dropwise to aqueous solution of sodium carboxymethyl cellulose, and the mixture is heated and stirred for a period of time to obtain the aqueous binder.
[0010] Furthermore, the divalent metal ions include nickel, zinc, calcium, copper, magnesium, and cobalt; the trivalent metal ions include iron and aluminum.
[0011] Furthermore, the molar ratio of the divalent metal ions to the trivalent metal ions is 1:1-2.
[0012] Furthermore, the molar ratio of the metal ion compound to sodium carboxymethyl cellulose is 1% to 10%.
[0013] Furthermore, the anion of the metal ion compound is one or more combinations of chloride ion, sulfate ion, nitrate ion, citrate ion, acetate ion, and salicylate ion.
[0014] Furthermore, in step S1, the concentration of the sodium carboxymethyl cellulose aqueous solution is 2% to 10%.
[0015] Furthermore, in step S2, the mass concentration of the metal ion compound is 0.5% to 20%.
[0016] Furthermore, in step S1, the stirring time is 1 h ~ 6 h, and the stirring temperature is 20℃ ~ 80℃;
[0017] In step S2, the stirring time is 0.1 h ~ 0.5 h, and the stirring temperature is 20℃ ~ 50℃;
[0018] In step S3, the stirring time is 2 h ~ 24 h, and the stirring temperature is 40℃ ~ 90℃.
[0019] A second objective of this invention is to provide an aqueous binder based on coordination crosslinking of multivalent metal ions prepared by the above-described preparation method.
[0020] The third objective of this invention is to provide an application of the aqueous binder based on the coordination crosslinking of multivalent metal ions as described above in the preparation of silicon-based anode materials for lithium-ion batteries. Before use, the pH value of the aqueous binder is adjusted to 6-8, and the silicon anode material is nano-silicon, micron-silicon, silicon-carbon, or silicon-oxygen.
[0021] This invention provides an aqueous adhesive based on the coordination crosslinking of multivalent metal ions. The aqueous adhesive achieves a stronger bonding network through the interaction of multivalent metal ion compounds with sodium carboxymethyl cellulose (CMC). Sodium carboxymethyl cellulose (CMC) contains a large number of ionized carboxyl groups (-COO groups) on its molecular chains. -It can coordinate and electrostatically interact with positively charged metal ions. This coordination connects different polymer chains, allowing linear CMC molecules to form a three-dimensional network structure through the cross-linking sites of metal ions. This system has dynamic and reversible characteristics and can complement hydrogen bonds. Compared with chemical cross-linking, it has better regulation of stress dispersion, can constrain silicon particles, and can greatly improve a series of problems caused by volume expansion during the charging and discharging process of silicon-based anodes, ensuring efficient lithium-ion transport and improving the cycle stability of silicon anode batteries.
[0022] The bimetallic salt in this invention exhibits a more subtle cross-linking mechanism between divalent and trivalent metal ions, becoming key to improving the performance of silicon-based secondary batteries. Divalent metal ions, such as magnesium ions (Mg²⁺), are involved. + ), calcium ions (Ca²) + These ions, such as ferric ions (Fe³⁺), possess specific electronic configurations and ionic radii, enabling them to coordinate with active groups like hydroxyl and carboxyl groups on polysaccharide polymer chains. + ), aluminum ions (Al³) + Besides participating in coordination, trivalent metal ions, with their high charge number and small ionic radius, can also generate significant electrostatic interactions in the system. The strong electric field formed around trivalent metal ions can attract negatively charged active groups on polymer chains, further reducing the distance between polymer chains and making the three-dimensional network structure more compact and stable. Simultaneously, electrostatic interactions can enhance the interaction between binder chains, inhibiting the binder from detaching from the surface of active group particles during charging and discharging, thus ensuring the durability of the three-dimensional network structure. This synergistic effect of coordination and electrostatic interactions is of great significance for buffering the volume effect of silicon-based anodes. Compared to divalent metal ions added alone, trivalent metal ions, due to their higher valence state, form a more stable cross-linked network, and their smaller ionic radius enables rapid lithium ion transport, improving rate performance. The addition of divalent metal ions significantly improves the adhesion of the electrode, indicating that the addition of divalent metal ions improves the degree of cross-linking. The addition of divalent metal ions alleviates the problem of excessively high cross-linking density leading to a decrease in material mechanical properties caused by the introduction of trivalent metal ions alone. Therefore, the addition of polyvalent metal ions can improve the cross-linking degree of the binder, and the prepared battery has better cycle stability.
[0023] The water-based binder of this invention has significantly improved mechanical properties, resulting in batteries with better rate capability and more stable cycling performance.
[0024] The method for preparing a metal ion crosslinking aqueous binder provided by this invention involves a simple and readily available preparation process with low cost, effectively reducing the manufacturing cost of lithium-ion battery anodes. Simultaneously, the required experimental reagents are mild, environmentally friendly, green, non-toxic, and highly safe. Attached Figure Description
[0025] Figure 1 This is a schematic diagram of the structure of the aqueous adhesive based on coordination crosslinking of multivalent metal ions, as shown in the embodiment.
[0026] Figure 2 The figure shows a comparison of the peeling properties of electrodes prepared using the aqueous crosslinking binders obtained in Example 1 and Comparative Examples 2, 8, and 9.
[0027] Figure 3 The surface morphology of the electrode in a silicon-based secondary battery assembled using the aqueous crosslinking binders obtained in Example 1 and Comparative Examples 2, 8, and 9 after 50 cycles is shown. Detailed Implementation
[0028] 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.
[0029] Unless otherwise specified, the experimental methods described in the following implementation plan are conventional methods, and the reagents and materials described are commercially available unless otherwise specified.
[0030] Example 1
[0031] A method for preparing an aqueous adhesive based on the coordination crosslinking of multivalent metal ions, specifically including the following steps:
[0032] S1. Sodium carboxymethyl cellulose (CMC(II)) was dissolved in deionized water by heating and stirring at 60°C for 6 h to form a uniform and transparent sodium carboxymethyl cellulose aqueous solution.
[0033] S2, a metal ion compound, is dissolved in deionized water by heating and stirring at 50°C for 0.5 h;
[0034] S3. A certain amount of metal ion solution is slowly added dropwise to an aqueous solution of sodium carboxymethyl cellulose, and the mixture is heated and stirred at 80°C for 12 h to obtain a metal ion crosslinked aqueous binder.
[0035] The types of metal ions and their proportions to polysaccharide polymers are as follows: Al: 2%, Ni: 1%.
[0036] Preparation of slurry: Adjust the pH value of the metal ion crosslinking aqueous binder to 6-8 (adjusting the pH value of the binder solution avoids precipitation in acidic or alkaline environments, ensuring better dispersibility of the aqueous solution, and providing basic conditions for maintaining uniform mixing between the binder, active material, and conductive agent particles during the subsequent preparation of the negative electrode slurry). Weigh the active material and conductive agent and add them to the aqueous solution containing the binder to obtain a uniformly dispersed slurry.
[0037] The mass ratio of active material, conductive agent, and binder is 60:20:20.
[0038] Electrode preparation: The slurry was stirred evenly and coated onto the surface of copper foil using a coating machine to a thickness of 12 μm. It was then vacuum dried at 120℃ for 12 h and cut into circular electrode sheets with a radius of 7.5 mm for later use.
[0039] Example 2-10
[0040] The process parameters are shown in Table 1, and the others are the same as in Example 1.
[0041] Comparative Examples 1-7
[0042] No metal ions were added, and the process parameters are shown in Table 1. The rest is the same as in Example 1.
[0043] Comparative Examples 8-13
[0044] Monovalent metal ions were added, and the process parameters are shown in Table 1. Other parameters are the same as in Example 1.
[0045] Performance testing
[0046] Preparation of slurry: Adjust the pH value of the metal ion crosslinking aqueous binder to 6-8, weigh the active material and conductive agent and add them to the aqueous solution containing the binder to obtain a uniformly dispersed slurry.
[0047] Electrode preparation: The slurry was stirred evenly and coated onto the surface of copper foil using a coating machine to a thickness of 12 μm. It was then vacuum dried at 120℃ for 12 h and cut into circular electrode sheets with a radius of 7.5 mm for later use.
[0048] Table 1 shows the binders and electrode preparation parameters for the examples and comparative examples.
[0049] The water-based adhesive of the embodiments of the present invention has significantly improved mechanical properties compared with the comparative example.
[0050] The results of battery testing using coin cells show, as presented in Table 2, the electrochemical performance parameters of the examples and comparative examples. Batteries using the aqueous binder of this invention exhibit better rate capability and more stable cycling performance.
[0051] Table 1
[0052]
[0053] *CMC(I) (MW700000, DS=0.9), CMC(II) (MW250000, DS=1.2), CMC(III) (MW250000, DS=0.9), CMC(IV) (MW250000, DS=0.7), CMC(V) (MW90000, DS=0.7). MW is the weight-average molecular weight, and DS represents the degree of carboxymethyl substitution.
[0054] Table 2
[0055]
[0056] Figure 1 This refers to the cross-linking effect between metal ions and sodium carboxymethyl cellulose;
[0057] Figure 2 The figure shows a comparison of the bonding ability between the electrodes prepared in Example 1 and Comparative Examples 2, 8 and 9. It can be clearly seen from the figure that the incorporation of bimetallic ions significantly improves the bonding performance of the electrodes.
[0058] Figure 3 The figure shows the surface morphology of the electrode after 50 cycles of silicon-based secondary batteries assembled using the aqueous crosslinking binders obtained in Example 1 and Comparative Examples 2, 8, and 9. As can be seen from the figure, the incorporation of bimetallic ions can significantly improve the structural integrity of the electrode, thereby giving the battery better cycle stability.
[0059] For any points not covered above, existing technologies shall apply.
[0060] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing an aqueous adhesive based on the coordination crosslinking of multivalent metal ions, characterized in that, Specifically, the following steps are included: S1. Dissolve sodium carboxymethyl cellulose in water, heat and stir to form an aqueous solution of sodium carboxymethyl cellulose; S2. Dissolve the metal ion compound in deionized water to obtain an aqueous solution of the metal ion compound; the metal ions include divalent metal ions and trivalent metal ions; S3. A certain amount of aqueous solution of metal ion compound is slowly added dropwise to aqueous solution of sodium carboxymethyl cellulose, and the mixture is heated and stirred for a period of time to obtain the aqueous binder. The divalent metal ions include one or more of nickel, copper, and magnesium; the trivalent metal ions include one or more of iron and aluminum.
2. The preparation method according to claim 1, characterized in that: The molar ratio of the divalent metal ions to the trivalent metal ions is 1:1-2.
3. The preparation method according to claim 1, characterized in that: The molar ratio of the metal ion compound to sodium carboxymethyl cellulose is 1% to 10%.
4. The preparation method according to claim 1, characterized in that, The anion of the metal ion compound is one or more combinations of chloride, sulfate, nitrate, citrate, acetate, and salicylate.
5. The preparation method according to claim 1, characterized in that, In step S1, the concentration of the sodium carboxymethyl cellulose aqueous solution is 2% to 10%.
6. The preparation method according to claim 1, characterized in that, In step S2, the mass concentration of the metal ion compound is 0.5% to 20%.
7. The preparation method according to claim 1, characterized in that, In step S1, the stirring time is 1 h ~ 6 h, and the stirring temperature is 20℃ ~ 80℃; In step S2, the stirring time is 0.1 h ~ 0.5 h, and the stirring temperature is 20℃ ~ 50℃; In step S3, the stirring time is 2 h ~ 24 h, and the stirring temperature is 40℃ ~ 90℃.
8. An aqueous adhesive based on coordination crosslinking of multivalent metal ions, prepared by the preparation method according to any one of claims 1-7.
9. The application of the aqueous binder based on multivalent metal ion coordination crosslinking as described in claim 8 in the preparation of silicon-based anode materials for lithium-ion batteries, characterized in that: Before use, adjust the pH value of the aqueous binder to 6-8. The silicon anode material is nano-silicon, micron-silicon, silicon-carbon, or silicon-oxygen.