Self-repairing adhesive based on metal ion-polymer coordination bond and preparation method thereof

Abstract

The application relates to a self-repairing binder based on a metal ion-polymer coordination bond and a preparation method thereof, and belongs to the technical field of lithium ion batteries. The structural general formula of the binder is: the binder is autonomously broken / forming through a metal-polymer reversible coordination bond in the electrode volume expansion / contraction process, the internal stress generated in the volume change is released, the electrode material is relatively stable in appearance; meanwhile, after the crack is formed, the self-repairing ability of the reversible chemical bond can induce crack healing, and long-term stable circulation of the battery is realized.

Description

TECHNICAL FIELD

[0001] The application relates to a self-repairing binder based on a metal ion-polymer coordination bond and a preparation method thereof, and belongs to the technical field of lithium ion batteries. BACKGROUND

[0002] In recent years, the demand for clean and renewable energy has rapidly increased in order to solve global warming caused by the use of fossil fuels. However, the available energy of renewable energy such as solar energy, wind energy, and geothermal energy varies with time and location, which greatly limits its development prospects. Electrochemical energy storage devices exhibit great advantages due to their high power, high energy density, and low cost. At present, lithium ion batteries dominate in the fields of portable electronic devices, electric vehicles, aerospace, and the like due to their high energy density and mature manufacturing technology. However, the specific capacity of the traditional graphite anode and lithium iron phosphate cathode is low and has approached the theoretical energy density, which cannot meet the rapidly growing technological and market demand, and therefore it is necessary to explore lithium ion battery electrodes that can be used for high energy density.

[0003] Silicon (Si) negative electrodes have a high theoretical capacity of 4200 mAh g -1 -1, are the second most abundant element on earth, are non-toxic, and are environmentally friendly. However, the volume expansion of Si in electrochemical cycling exceeds 300%, and the huge volume change leads to electrode pulverization and the formation of an unstable interface layer, and repeated expansion and contraction further increases the intergranular gap and causes the electrode to break and fall off, thus hindering the commercialization of Si-based material negative electrodes.

[0004] Self-repairing refers to the ability to spontaneously recover from damage by rebuilding the broken interface. Self-repairing binders enable the electrode to maintain a relatively fixed position during volume expansion and contraction, thereby maintaining the integrity of the electrode. After cracks are generated during cycling, the self-repairing polymer can spontaneously pull the cracks back to restore the cycling capacity through dynamic broken / generated chemical bonds. The internal stress generated by the huge volume expansion can be released through the breaking and formation of reversible chemical bonds, and the electrode spontaneously returns to its original position after breaking. However, the weak interaction of the currently reported hydrogen bond self-repairing system and the weak reversibility of the chemical bond-based self-repairing limit the further improvement of the performance of the self-repairing binder. SUMMARY

[0005] Therefore, the self-repairing binder based on dynamic reversible chemical bonds has a wide application prospect due to its perfect adaptability to volume expansion and its binding capacity to active materials. Thus, the self-repairing binder based on dynamic reversible chemical bonds has a wide application prospect due to its perfect adaptability to volume expansion and its binding capacity to active materials.

[0006] To achieve the above object, the technical scheme of the present application is as follows:

[0007] A self-repairing adhesive based on metal ion-polymer coordination bond, the structural general formula of the adhesive is as follows:

[0008]

[0009] Wherein, C n H 2n-2 is a diene monomer structure, n≥4; x and y are both positive integers and represent the number of ungrafted and grafted parts of polydiene respectively, y accounts for 2%-3% of the total sum of (x+y), (x+y) is equal to the number average degree of polymerization of polydiene; R1 is -(CONH)-; R2 is carboxyl (-COOH), which is connected to Si by chemical bond and hydrogen bond; M represents metal ion, m + is the valence state of metal ion, which is connected to M ion by metal-polymer coordination bond.

[0010] Preferably, the polydiene can be one or more of poly-1,3-butadiene, polyisoprene and poly-1,3-hexadiene.

[0011] Preferably, the R3 is one or more of the above.

[0012] Preferably, the M metal ion is Zn 2+ , Mn 2+ , Ni 2+ , Fe 2+ or Al 3+ .

[0013] Preferably, (x+y) is 590-610, and y is 12-18.

[0014] A preparation method of the self-repairing adhesive based on metal ion-polymer coordination bond according to the present application, the method steps include:

[0015] (1) polydiene, maleic anhydride and antioxidant 1 are added to solvent 1 and mixed, first heated at 80-120℃ for 10-20min, then heated at 200-240℃ for 0.5-2h, the obtained mixture is dissolved and then added to a precipitant, the precipitate is collected and washed with the precipitant, and after drying, the intermediate product 1 is obtained;

[0016] (2) the intermediate product 1, amino nitrogen polybasic ring compound and antioxidant 2 are mixed, heated to 60-120℃ and stirred at a speed of 40-80r / min for 50-70min to obtain the intermediate product 2;

[0017] (3) dissolving the intermediate product 2 in solvent 2, then adding a salt of M metal ion, stirring at a speed of 100-300 r / min for 2-4 h, and then removing solvent 2 to obtain a self-repairing adhesive based on metal ion-polymer coordination bond;

[0018] In step (3), the coordination number of the M metal ion is 1-2:1 of the mole ratio of the N atoms in the ring of the amino nitrogen polybasic ring compound in step (2).

[0019] Preferably, in step (1), the mole ratio of the polydiene to maleic anhydride is 10-20:1.

[0020] Preferably, in step (1), the mole ratio of the antioxidant 1 to the polydiene is 1-2:100.

[0021] Preferably, in step (1), the mole ratio of the solvent 1 to the polydiene is 2-3:10.

[0022] Preferably, in step (1), the solvent is one or more of toluene, xylene, C9-C15 naphthene and aromatic hydrocarbon solvent oil.

[0023] Preferably, in step (1), the mixture is dissolved using toluene and / or xylene, and the precipitant is one or more of acetonitrile, propionitrile and ethanedinitrile; and the drying is performed at 40-80°C under vacuum for 6-12 h.

[0024] Preferably, in step (1), the antioxidant 1 is one or more of diphenylamine, p-phenylenediamine, dihydroquinoline compound and derivatives thereof.

[0025] Preferably, in step (2), the antioxidant 2 is one or more of diphenylamine, p-phenylenediamine, dihydroquinoline compound and derivatives thereof.

[0026] Preferably, in step (2), the amino nitrogen polybasic ring compound is one or more of 3-amino-1,2,4-triazole, 4-aminopyridine, 2-aminopyrimidine, 5-aminopyrimidine and 2-amino-1,3,5-triazine.

[0027] Preferably, in step (2), the mole ratio of the amino nitrogen polybasic ring compound to the maleic anhydride in step (1) is 1-2:1.

[0028] Preferably, in step (2), the mass of the antioxidant 2 is 0.2%-0.5% of the mass of the intermediate product 1.

[0029] Preferably, in step (3), the solvent 2 is tetrahydrofuran and / or dimethyl sulfoxide.

[0030] Preferably, in step (3), the M metal ion salt is a chloride salt, a bromide salt or a sulfate salt.

[0031] A lithium ion battery, the battery anode is a silicon-based anode, and the anode binder is a self-repairing binder based on metal ion-polymer coordination bonds according to the present application.

[0032] Advantages

[0033] The present application provides a self-repairing binder based on metal ion-polymer coordination bonds, which can autonomously break / form through metal-polymer reversible coordination bonds during the volume expansion / contraction of the electrode, release the internal stress generated in the volume change, and realize the relatively stable morphology of the electrode material; at the same time, after the crack is formed, the self-repairing ability of the reversible chemical bond can induce crack healing, and realize long-term stable cycling of the battery. The binder also has a chemical bond with the silicon hydroxyl group, which is a carboxyl group generated in the ring-opening process, a part of which reacts with the amino nitrogen heterocycle, and the remaining part serves as a functional group to enhance the interaction with silicon, effectively improving the stability of the electrode during the cycling process. The -COOH from R2 which forms a chemical bond with the Si hydroxyl group forms a hydrogen bond with the lone pair of electrons from N and O in R3; the lone pair of electrons of the multi-nitrogen ring in R3 coordinates with the metal ion to form a dynamic reversible self-repairing metal coordination bond.

[0034] The self-repairing binder based on coordination bonds according to the present application can reduce the damage to the electrode caused by volume change, improve the cycling stability; autonomously induce the repair of damage, improve the cycle life; the introduction of multi-nitrogen heterocycle provides more coordination sites, improves the physical crosslinking degree, and enhances the mechanical properties of the material; at the same time, the functional groups that form interactions with silicon are introduced to enhance the force on the electrode material, and maintain the morphological stability of the electrode sheet during the cycling process. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The capacity versus cycle number plot for the battery assembled in Example 1 and Comparative Example 1.

[0036] Figure 2 The capacity-voltage plot for the battery assembled in Example 1. DETAILED DESCRIPTION

[0037] The present application will be further described in detail below with specific examples.

[0038] Example 1

[0039] (1) 6.1 g of polyisoprene, 0.878 g of maleic anhydride, and 0.061 g of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine were added to a mixed solvent of 0.95 g of xylene and 0.61 g of aromatic oil, and stirred at 100°C and 60 r / min for 15 min, and then heated to 220°C and mixed at 60 r / min for 60 min. The obtained mixture was dissolved in toluene, and then mixed with acetonitrile to obtain a precipitate. The precipitate was washed with acetonitrile and dried at 60°C under vacuum for 8 h to obtain an intermediate product 1.

[0040] (2) 6 g of the intermediate product 1, 0.252 g of 3-amino-1,2,4-triazole, and 0.018 g of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine were stirred at 60 r / min for 60 min at 90°C to obtain an intermediate product 2.

[0041] (3) 40 mL of tetrahydrofuran was added to 6 g of the intermediate product 2, and mixed at a stirring speed of 200 r / min for 3 h to form a uniform solution. 0.102 g of zinc chloride was added to the solution under stirring, and after the zinc chloride was completely dissolved, the solution was placed in a vacuum oven at 30°C and heated for 8 h to obtain a metal ion-polymer coordination bond-based self-repairing adhesive.

[0042] The chemical bonds inside the substance were detected by Fourier transform infrared spectroscopy, and the characteristic peaks of the functional groups were detected by hydrogen nuclear magnetic resonance spectroscopy to determine the structure of the metal coordination polymer as follows:

[0043] wherein (x+y) is 600, and y is 15.

[0044] (4) Silicon carbon, Super P conductive carbon black, and the adhesive were mixed in a mass ratio of 8:1:1, and an appropriate amount of N-methyl pyrrolidone was added to prepare a coating agent slurry by stirring and uniformly coated on a copper foil. After vacuum drying at 80°C overnight, the copper foil was cut into a circular electrode sheet with a diameter of 11 mm. A CR2025 type button cell was assembled in an argon environment glove box, in which the silicon carbon electrode was used as the negative electrode, a lithium metal sheet was used as the positive electrode, polypropylene was used as the separator, and 1M LiPF6 (lithium hexafluorophosphate) / EC:DEC (ethylene carbonate: diethyl carbonate) = 1:1 Vol% was used as the electrolyte. After standing for 12 h, the button cell was tested on a LAND CT2001A tester (purchased from Wuhan Land Electronic Co., Ltd.).

[0045] Example 2

[0046] In this example, the amount of 3-amino-1,2,4-triazole added was 0.168 g, and the rest was the same as in Example 1.

[0047] Example 3

[0048] In this embodiment, 0.252g of 3-amino-1, 2, 4-triazole is replaced by 0.392g of 2-aminopyrimidine, and the amount of zinc chloride added is 0.266g, and the rest is the same as in Example 1.

[0049] The chemical bonds inside the substance are detected by Fourier transform infrared spectroscopy, and the characteristic peaks of the functional groups are detected by hydrogen nuclear magnetic resonance spectroscopy, and the structure of the metal coordination polymer formed is as follows:

[0050] Wherein, (x+y) is 610, and y is 16.

[0051] Example 4

[0052] In this embodiment, step (2) is heated at a speed of 40r / min and 100℃ for 50min, and the rest is the same as in Example 1.

[0053] Example 5

[0054] In this embodiment, 0.102g of zinc chloride is replaced by 0.161g of ZnSO4, and the rest is the same as in Example 1.

[0055] Example 6

[0056] In this embodiment, the mass ratio of silicon carbon, Super P and the binder is 6:2:2, and the rest is the same as in Example 1.

[0057] Example 7

[0058] In this embodiment, the amount of zinc chloride added is 0.051g, and the rest is the same as in Example 1.

[0059] Example 8

[0060] In this embodiment, 0.102g of zinc chloride is replaced by 0.066g of aluminum chloride, and the rest is the same as in Example 1.

[0061] Comparative Example 1

[0062] In this comparative example, polyvinylidene fluoride is used as a binder, and an electrode material is prepared according to a mass ratio of silicon carbon: Super P conductive carbon black: polyvinylidene fluoride of 8:1:1, uniformly coated on a copper foil and cut into an electrode sheet with a diameter of 11mm. A CR2025 type button cell is assembled in an argon environment, the silicon carbon electrode is used as the anode, the lithium metal sheet is used as the cathode, the single-layer PP is used as the separator, and the electrolyte is 1M LiPF6 / EC:DEC=1:1Vol%. After standing for 12h, the test is carried out on a LAND CT2001A tester.

[0063] Comparative Example 2

[0064] In this comparative example, the homogeneous solution obtained in step (3) was directly vacuum dried at 40°C for 12h to obtain the binder, the rest was the same as in Example 1. The obtained electrode did not have self-repairing ability.

[0065] Comparative Example 3

[0066] In this comparative example, the amount of 3-amino-1,2,4-triazole added was 0.336g and the amount of zinc chloride added was 0.136g, the rest was the same as in Example 1. The excess nitrogen-containing polybasic ring consumed the generated carboxyl group, obtaining a self-repairing binder without carboxyl group remaining. This binder could not form chemical bond interaction with silicon.

[0067] Comparative Example 4

[0068] In this comparative example, 3-amino-1,2,4-triazole was replaced by 0.372g of aniline, the rest was the same as in Example 1. Due to the introduction of a branched cyclic compound without lone pair electrons, this polymer did not have the ability to coordinate with cations, and therefore could not be self-repaired.

[0069] Comparative Example 5

[0070] In this comparative example, the reaction temperature of step (2) was 40°C, the rest was the same as in Example 1. Due to the insufficient ring-opening acylation at this reaction temperature, no nitrogen-containing polybasic ring was introduced.

[0071] The electrochemical performance results of each example and comparative example are shown in Table 1; the capacity of the battery assembled in Example 1 and Comparative Example 1 as a function of the number of cycles at a current density of 48mA -1 (0.1C) is shown in Figure 1 The capacity-voltage curve of the battery assembled in Example 1 at a current density of 480mA g -1 is shown in Figure 2 .

[0072] Table 1

[0073] Specific capacity (mAh g -1 )]]> Capacity retention (%) after 50 weeks Example 1 518.2 81.6 Example 2 462.7 73.2 Example 3 502.4 77.2 Example 4 510.6 79.8 Example 5 514.4 79.9 Example 6 512.1 81.2 Example 7 474.6 75.1 Example 8 506.9 78.9 Comparative Example 1 391.3 69.2 Comparative Example 2 355.4 57.6 Comparative Example 3 400.6 70.9 Comparative Example 4 367.2 60.4 Comparative Example 5 362.3 60.3

[0074] From Table 1 and Figure 1 it can be seen that:

[0075] The amount of nitrogen-containing polybasic ring is too low, which results in insufficient number of coordination bonds formed, leading to insufficient coordination strength to maintain the sustained volume change of the electrode, which will have a negative impact on the cycle performance of the battery. The preferred amount of nitrogen-containing polybasic ring is 4.8mol% of polyisoprene. The preferred ring-opening reaction temperature is 90°C.

[0076] When organic materials contain more lone pairs of electrons, self-healing binders form higher density coordination bonds, resulting in more significant self-healing capabilities and better cycling performance. However, as shown in Comparative Example 3, fully coordinated binders have no remaining carboxyl groups and therefore cannot interact with silicon, leading to decreased electrode cycling stability. Furthermore, if coordination cannot be formed, as in Comparative Example 4, the material cannot maintain electrode cycling stability.

[0077] Full-cell test results show that the introduction of the self-healing binder significantly improves the cycle stability of the battery. The silicon-carbon electrode with the binder described in Example 1 has a capacity of 518.2 mAh g after 50 cycles. -1 The capacity retention rate was 81.6%, while the silicon-carbon electrode using PVDF as a binder in Comparative Example 1 only achieved 391.3 mAh g⁻¹. -1 The capacity retention rate was 69.2%. The binder in Comparative Example 2 lacked self-healing properties, and therefore its capacity decayed to below 60% of its initial specific capacity after 50 cycles. When cycling at a 1C rate, as... Figure 2 As shown, the electrode using the self-healing binder exhibited a more stable capacity retention, maintaining 75% capacity retention after 180 cycles. These results demonstrate that the self-healing ability of the binder is achieved by the formation of metal-polymer coordination bonds between polyvalent ions and polydiolefins. Such binders can improve the cycling stability of electrodes, especially for electrodes with severe volume expansion. Furthermore, this self-healing binder possesses functional groups that interact with silicon, increasing the stability of the electrode morphology through chemical bonding with silanol groups, thus making it suitable for applications in silicon-based electrodes.

[0078] Table 2 lists the elongation at break and residual strain after 10 weeks of stretching at 200% deformation for the binders in the examples and comparative examples. As shown in Table 2, the self-healing binder with metal-polymer coordination exhibits high elongation at break and good deformation recovery under repeated strain, thus demonstrating good practicality in alleviating electrode volume expansion. In contrast, PVDF and polymers without coordination bonds cannot be stretched to 200%. Saturated coordination bonds exhibit better tensile properties. Comparative Example 3 shows that the self-healing ability of the fully coordinated binder with no residue is improved, and it has better deformation recovery during tensile cycles. However, due to its lack of carboxyl groups, it does not have the interaction with silanol groups and instead exhibits poor electrochemical performance.

[0079] The introduction of polyvalent ions can form metal-polymer coordination bonds with the lone pair of electrons on the polymer, giving the binder self-repairing ability. When the electrode is broken, it can be restored to the position before the breakage through the self-repairing ability of the reversible chemical bond. However, when the added metal cations are insufficient, as in Example 7, considering factors such as steric hindrance, loss, etc., the coordination strength formed is insufficient, and thus the tensile properties and the cycling performance of the electrode with vegetation are not good. Changing the type of introduced ions, when introducing aluminum ions with a smaller radius, as in Example 8, due to the steric hindrance effect of the branched cyclic structure of the polymer, the coordination cannot be completely saturated, and thus similar rather than more superior performance is exhibited compared to the introduction of zinc ions.

[0080] Table 2

[0081] Elongation at break (%) Residual strain after 10 weeks of 200% stretch (%) Example 1 367 4.6 Example 2 323 8.4 Example 3 342 7.4 Example 4 359 6.8 Example 5 369 5.2 Example 6 367 4.6 Example 7 318 8.5 Example 8 355 4.9 Comparative Example 1 13.5 - Comparative Example 2 174 - Comparative Example 3 378 4.5 Comparative Example 4 201 7.9 Comparative Example 5 202 8.0

[0082] In summary, the invention includes but is not limited to the above examples, any equivalent replacement or partial improvement made within the spirit and principles of the invention will be considered within the protection scope of the invention.

Claims

1. A self-repairing adhesive based on metal ion-polymer coordination bonds, characterized in that: The structure general formula of the adhesive is as follows: wherein C n H 2n-2 is a repeating unit structure of a polydiene, n≥4; x and y are both positive integers and represent the number of ungrafted and grafted portions of the polydiene respectively, (x+y) is equal to the number average degree of polymerization of the polydiene, y is 2%-3% of the total sum of (x+y), (x+y) is 590-610, and y is 12-18; R1 is -(CONH)-; R2 is -COOH; M represents a metal ion, m + is the valence of the metal ion, and the connection to the metal ion is a metal-polymer coordination bond; R3 is one or more of the group consisting of 2. The metal ion-polymer coordination bond based self-healing adhesive according to claim 1, wherein: The polydiene is one or more of poly-1,3-butadiene, polyisoprene and poly-1,3-hexadiene.

3. The self-repairing adhesive based on metal ion-polymer coordination bond according to claim 1, characterized in that: the metal ion is Zn 2+ , Mn 2+ , Ni 2+ , Fe 2+ or Al 3+ .

4. A method for producing the self-repairing adhesive based on metal ion-polymer coordination bond according to any one of claims 1 to 3, characterized by: The method steps include: (1) mixing polydiene, maleic anhydride and antioxidant 1 in solvent 1, first heating at 80-120℃ for 10-20 min, then heating at 200-240℃ for 0.5-2 h, dissolving the obtained mixture and adding a precipitant, collecting the precipitate and washing with the precipitant, drying to obtain intermediate product 1; (2) mixing the intermediate product 1, compound 1 and antioxidant 2, heating to 60-120℃ and stirring at a speed of 40-80 r / min for 50-70 min to obtain intermediate product 2; (3) dissolving the intermediate product 2 in solvent 2, then adding a metal ion salt, stirring at a speed of 100-300 r / min for 2-4 h, then removing the solvent 2 to obtain a self-repairing adhesive based on metal ion-polymer coordination bond; In step (1), the antioxidant 1 is one or more of diphenylamine, p-phenylenediamine, dihydroquinoline compound and derivatives of the above substances; In step (2), the compound 1 is one or more of 3-amino-1,2,4-triazole, 4-aminopyridine, 2-aminopyrimidine, 5-aminopyrimidine and 2-amino-1,3,5-triazine; the antioxidant 2 is one or more of diphenylamine, p-phenylenediamine, dihydroquinoline compound and derivatives of the above substances; In step (3), the molar ratio of the coordination number of the metal ion to the N atom in the compound 1 in step (2) is 1-2:

1.

5. The preparation method of a self-healing adhesive based on metal ion-polymer coordination bonds as described in claim 4, characterized in that: In step (1), the molar ratio of the polydiene to maleic anhydride is 10-20:1; the molar ratio of the antioxidant 1 to the polydiene is 1-2:100; The molar ratio of the solvent 1 to the polydiene is 2-3:10; The solvent 1 is one or more of toluene, xylene, C9-C15 naphthene and aromatic hydrocarbon solvent oil; the mixture is dissolved by toluene and / or xylene, the precipitant is one or more of acetonitrile, propionitrile and ethanedinitrile; during drying, vacuum drying is performed at 40-80℃ for 6-12 h.

6. The preparation method of a self-healing adhesive based on metal ion-polymer coordination bonds as described in claim 4, characterized in that: In step (2), the molar ratio of the compound 1 to the maleic anhydride in step (1) is 1-2:1; The mass of the antioxidant 2 is 0.2%-0.5% of the mass of the intermediate product 1.

7. The preparation method of a self-healing adhesive based on metal ion-polymer coordination bonds as described in claim 4, characterized in that: In step (3), the metal ion salt is a chloride salt, a bromide salt or a sulfate salt; The solvent 2 is tetrahydrofuran and / or dimethyl sulfoxide.

8. A lithium-ion battery, characterized by: The battery negative electrode is a silicon-based negative electrode, and the negative electrode adhesive is a self-repairing adhesive based on metal ion-polymer coordination bond according to any one of claims 1-3.

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