Preparation Method and Application of a Fast Self-Healing Polymer Electrolyte Interface Layer

Abstract

A preparation method and application of a fast self-healing polymer electrolyte interface layer, belonging to the technical field of lithium-ion batteries. The specific scheme includes: Step 1, dissolve 2-amino-4-hydroxy-6-substituted pyrimidine in dimethyl sulfoxide under heating conditions, then add isocyanate to the reaction system, stir and react. After the product is precipitated, filtered by suction and dried, UPyMA is obtained, where the substituent is ethyl or methoxy; Step 2, uniformly mix UPyMA, polyethylene glycol methyl ether methacrylate, pentaerythritol tetra(3-mercaptopropionate) and lithium salt in a solvent, and carry out a thiol-Michael addition reaction under the action of a catalyst. Cast the reaction mixture into a film and dry to obtain a polymer electrolyte interface layer. The present invention provides a new perspective for solving the problem of poor interface stability between NASICON-type solid electrolytes and lithium electrodes.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a preparation method and application of a fast self-healing polymer electrolyte interface layer. Background Art

[0002] Solid-state lithium batteries have become an important direction for the development of next-generation lithium-ion batteries due to their high energy density and excellent safety performance. At present, important progress has been made in the research and development of electrolytes with high ionic conductivity. NASICON-type solid electrolytes have attracted much attention due to their high ionic conductivity, mechanical strength, wide electrochemical window, and good cathode compatibility at room temperature. [1] However, NASICON-type solid electrolytes / lithium have interface stability problems such as poor interface contact, poor interface chemical / electrochemical stability, etc., which seriously hinder the interfacial lithium-ion transport, resulting in uneven lithium-ion deposition, forming lithium dendrites at the interface, and restricting the rate performance and cycling performance of solid-state lithium batteries. [2,3] Therefore, solving the problem of poor interface stability of NASICON-type solid electrolytes / lithium is the key to promoting the wide application of NASICON-type solid electrolytes in solid-state lithium batteries.

[0003] Constructing a polymer electrolyte with certain flexibility as the interface layer between the solid electrolyte and lithium has been proven to effectively improve the interface stability. [4,5] In addition, to solve the problem of interface layer failure caused by volume changes during repeated deposition / stripping of metallic lithium during long cycling, constructing an interface layer with a "self-healing" function can repair the damaged interface layer, maintain a firm and complete interface contact and continuous lithium-ion transport during cycling, and at the same time prevent side reactions between metallic lithium and the solid electrolyte interface, relieve stress caused by volume expansion of electrode materials, and other interface problems, enhance the stability of the interface layer itself, and thus improve the interface stability between the solid electrolyte and lithium, achieving the purpose of improving the cycling stability of solid-state lithium batteries. [6,7] The purpose.

[0004] Hydrogen bonds have the characteristics of strong orientation, saturation, selectivity, and dynamic reversibility. Without external stimulation, they can automatically recombine to form a cross-linked dynamic supramolecular network, realizing the self-healing of polymers. Based on the self-healing of hydrogen bonds, polymer electrolytes can automatically repair the damage caused by lithium volume expansion without external stimulation, which has attracted much attention. However, at present, the research on self-healing polymer electrolytes as self-healing interface layers between solid electrolytes and lithium is very limited. The currently constructed self-healing polymer materials usually require 1-2 hours to heal after cutting. [8-10] This is far from meeting the requirements of high rate and long cycling stability of the battery, greatly limiting its application as an interface layer in energy storage devices. [11,12]Therefore, there is an urgent need to construct a self-healing interface layer with a fast self-healing rate. However, the structure-activity relationships between the molecular structure of the self-healing interface layer and its self-healing performance and electrochemical performance are not clear at present. In addition, the influence rules of the self-composition and structure evolution of the self-healing interface layer on its self-healing performance during high-rate and long-cycle processes, as well as the influence mechanism of the introduction of the self-healing interface layer on the composition change, structure evolution, and lithium-ion transport at the solid electrolyte / lithium interface during the cycling process, are also not clear. As a result, there is a lack of clear theoretical basis and technical support for how to design and construct the molecular structure of the self-healing interface layer to improve its self-healing rate.

[0005] Theoretically, when multiple hydrogen bonds crosslink simultaneously, a large binding energy and stability will be generated [13,14] , which can significantly improve the self-healing rate. The 2-ureido-4[1H]-pyrimidinone (UPy) unit has attracted extensive attention from scholars at home and abroad due to its quadruple hydrogen bonds. Currently, the self-healing polymers containing UPy units constructed by scholars at home and abroad are all based on the 3-(6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl)ureido self-healing unit. Although the quadruple hydrogen bond-ureidopyrimidinone polymer electrolyte can improve the cycling stability of solid-state lithium batteries, compared with single hydrogen bonds, the existing self-healing polymer electrolytes based on the quadruple hydrogen bond-ureidopyrimidinone unit do not fully utilize the advantage of fast self-healing of quadruple hydrogen bonds. This is mainly related to the structure of the UPy unit. In the currently constructed self-healing polymer electrolytes based on UPy, the 6-position substituent group on the UPy structure is methyl, which is a weak electron-donating group, restricting the density of the delocalized π electron cloud of the UPy structure, weakening the quadruple hydrogen bond binding energy, and reducing the hydrogen bond interaction [15-17] , slowing down the self-healing rate of the self-healing polymer electrolyte. Therefore, there is an urgent need to construct a self-healing polymer electrolyte with fast self-healing performance.

[0006] References:

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[17] Kan Lei, Ma Ning, Wei Hao. Influence of Substituents on the Aggregation Behavior of 2-Ureido-4(1H)-pyrimidinone Derivatives[J]. Chemistry Bulletin, 2019, 82(4): 359-364. Summary of the Invention

[0024] In order to solve the problem of slow self-healing rate of the polymer electrolyte interface layer constructed based on ureidopyrimidinone in the prior art, the present invention provides a preparation method and application of a rapidly self-healing polymer electrolyte interface layer. Based on the advantages of thiol-Michael addition reaction and quadruple hydrogen bond, a novel cross-linked network rapidly self-healing polymer is designed and synthesized. The present invention can improve the reaction rate and conversion rate, which is beneficial to solving the problems of complex production process and harsh reaction conditions of polymer electrolytes. It can improve the self-healing rate of the self-healing polymer interface layer and make it applicable to high-rate devices. Studying the molecular composition and structural evolution law of the self-healing interface layer during high-rate and long-cycle processes is the key scientific issue to reveal the long-term stability mechanism of the self-healing interface layer.

[0025] In order to achieve the above object, the present invention adopts the following technical solutions:

[0026] A preparation method of a rapidly self-healing polymer electrolyte interface layer, comprising the following steps:

[0027] Based on density functional theory to calculate the hydrogen bond binding energy of strongly electron-donating substituent ureidopyrimidinone, screen out suitable 6-position substituents, synthesize 2-amino-4-hydroxy-6-substituted pyrimidine by solution reaction method, and then react with isocyanate to prepare ureidopyrimidinone monomer (UPyMA), and the reaction equation is as Figure 2 shown. By thiol-Michael addition method, cross-link flexible oligomers of UPyMA containing different 6-position substituents. Since the shorter the chain segment, the faster the lithium ion transport, polyethylene glycol methyl ether methacrylate with a molecular weight of 300-600 is selected for polymerization, and pentaerythritol tetra(3-mercaptopropionate) containing four-terminal thiols is added at the same time. By changing parameters such as solvent, catalyst and temperature, control the synthesis of a polymer matrix with a cross-linked network, and obtain a rapidly self-healing polymer electrolyte after drying. Characterize the self-healing performance and electrochemical performance of the constructed self-healing polymer electrolyte, etc., and compare and analyze to obtain the optimal reaction parameters. The overall route of the present invention is as Figure 3 shown.

[0028] The specific preparation scheme includes the following steps:

[0029] Step 1. Synthesis of the quadruple hydrogen bond system UPy unit: Dissolve 2-amino-4-hydroxy-6-substituted pyrimidine in dimethyl sulfoxide under heating conditions, then add isocyanate to the reaction system, stir the reaction, and obtain UPyMA after precipitation, suction filtration, and drying, where the substituent is ethyl or methoxy, preferably ethyl;

[0030] Step 2. Preparation of the self-healing polymer electrolyte with a crosslinked network: Mix UPyMA, polyethylene glycol methyl ether methacrylate PEGMA, pentaerythritol tetra(3-mercaptopropionate) PETMP, and a lithium salt uniformly in a solvent under air and room temperature conditions, and carry out a thiol-Michael addition reaction under the action of a catalyst. Cast the reaction mixture on polytetrafluoroethylene and obtain a polymer electrolyte interface layer after drying.

[0031] The fast self-healing polymer with a crosslinked network in the present invention is formed by a crosslinked network polymer through the thiol-Michael addition polymerization of the quadruple hydrogen bond structure UPyMA, polyethylene glycol methyl ether methacrylate PEGMA, and pentaerythritol tetra(3-mercaptopropionate) PETMP. The synthesis route is as Figure 4 shown, and the crosslinked network polymer is as Figure 5 shown.

[0032] Furthermore, in Step 1, the mass ratio of the 2-amino-4-hydroxy-6-substituted pyrimidine to the isocyanate is 1:1 to 1:1.2.

[0033] Furthermore, in Step 2, the molar ratio of the lithium salt to the ethoxy group in polyethylene glycol methyl ether methacrylate is 1:15 to 1:20; the molar ratio of the thiol group in pentaerythritol tetra(3-mercaptopropionate) to the double bond in polyethylene glycol methyl ether methacrylate and UPyMA is 0.5:1 to 1:1.

[0034] Furthermore, in Step 1, the isocyanate includes isocyanatoethyl methacrylate or 2-isocyanatoethyl acrylate.

[0035] Furthermore, in Step 2, the molecular weight of the polyethylene glycol methyl ether methacrylate is 300 - 600.

[0036] Furthermore, in Step 2, the lithium salt includes any one of lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide, and lithium trifluoromethanesulfonate.

[0037] Furthermore, in Step 2, the solvent is any one of dimethyl sulfoxide, N,N-dimethylformamide, and acetonitrile.

[0038] Furthermore, in Step 2, the catalyst is n-hexylamine, diethylamine, triethylamine, or tetramethylguanidine.

[0039] Further, in Step 2, the reaction time of the thiol-Michael addition reaction is not less than 5 minutes. Preferably, the reaction time is 5 - 30 minutes.

[0040] Application of a polymer electrolyte interface layer prepared by the method described above, where the polymer electrolyte interface layer is used as a self-healing interface layer between a NASICON-type solid electrolyte and lithium.

[0041] Compared with the prior art, the beneficial effects of the present invention are:

[0042] The present invention proposes a new strategy of using the thiol-Michael addition method to construct a multifunctional interface layer based on a modified ureidopyrimidinone polymer electrolyte as the NASICON-type solid electrolyte / lithium to improve its interface stability. Aiming at the problem of slow self-healing rate of polymer electrolytes based on ureidopyrimidinone in the prior art, the structure of ureidopyrimidinone is modified by a strong electron-donating group at the 6-position for the first time. A green and environmentally friendly cross-linking agent is used to cross-link low-flexibility oligomer molecular chains through the thiol-Michael addition method to increase the reaction rate and construct a new self-healing polymer electrolyte as the interface layer between the solid electrolyte and lithium in a lithium battery, giving full play to its multiple functions of improving interface stability, inducing uniform lithium deposition, and rapidly repairing structural damage, providing a new perspective for solving the problem of poor interface stability between the NASICON-type solid electrolyte and the lithium electrode.

[0043] The present invention reveals the long-term stability mechanism of the NASICON-type solid electrolyte / lithium interface based on a strong hydrogen bond self-healing interface layer. The present invention studies the changes in the molecular composition and structural evolution laws of the self-healing interface layer itself during high-rate and long-cycle processes and their influence laws on the self-healing function, interface stability, and battery cycle stability, revealing the long-term stability mechanism of the self-healing interface layer for the NASICON-type solid electrolyte / metal lithium interface, providing a theoretical basis for designing and constructing a high-stability interface layer structure and improving the interface stability of solid-state lithium batteries. Description of the Drawings

[0044] Figure 1 It is a chemical structural formula and a schematic diagram of the self-healing mechanism of the UPy unit, where R is a substituent at the 6-position, and the wavy line represents a flexible polymer side chain;

[0045] Figure 2 It is the synthesis route of the UPy unit, where R is a substituent containing an electron-donating group at the 6-position;

[0046] Figure 3 It is the overall technical roadmap of the present invention;

[0047] Figure 4 It is the synthesis route of the fast self-healing polymer with a cross-linked network prepared by the present invention, where x:y = 1:5 and n = 3 - 20;

[0048] Figure 5 It is a schematic diagram of the crosslinked network polymer prepared by the present invention;

[0049] Figure 6 It is the FT-IR spectrum of the polymer electrolyte interface layer prepared in Example 1;

[0050] Figure 7 It is the FT-IR spectrum of the polymer electrolyte interface layer prepared in Comparative Example 1;

[0051] Figure 8 It is the process diagram of the self-healing of the polymer electrolyte interface layers prepared in Example 1 and Comparative Example 1;

[0052] Figure 9 It is the first charge-discharge curve diagram of the batteries in Example 1 and Comparative Example 1;

[0053] Figure 10 It is the cycle performance diagram of the batteries in Example 1 and Comparative Example 1;

[0054] Figure 11 It is the impedance spectrum diagram of the batteries in Example 1 and Comparative Example 1;

[0055] Figure 12 It is the time-voltage curve diagram of the symmetric batteries in Example 1 and Comparative Example 1. Detailed implementation manners

[0056] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0057] The self-healing rate of the polymer mainly depends on "the dynamics of intermolecular forces" and "the mobility of polymer segments". By structurally modifying the UPy unit with a 6-position strong electron-donating group, the density of the π electron cloud can be increased, the quadruple hydrogen bond binding energy can be enhanced, the hydrogen bond interaction of the UPy unit can be improved, and thus the self-healing rate can be increased. As Figure 1 shown, this technology has not been applied in batteries at present. Introducing flexible oligomers can lower the glass transition temperature of the polymer matrix, improve the molecular chain segment mobility, accelerate the migration and diffusion rate, and can increase the self-healing rate. Therefore, by regulating the 6-position substituents of the UPy unit and the crosslinked flexible oligomers, the healing rate of the self-healing interface layer can be increased.

[0058] Click chemistry refers to a class of highly efficient and highly selective chemical reaction strategies, usually specifically referring to those reactions that can occur under mild conditions, without the use of toxic catalysts, and produce high-yield products. Considerable research has been conducted on organic synthesis using click chemical reactions, but relatively few studies have focused on the synthesis of polymers using click chemical reactions. The thiol-ene reaction is an important type of click chemical reaction, and there are usually two pathways for the thiol-ene reaction: (1) a radical-mediated addition reaction, commonly referred to as the thiol-ene reaction; (2) a thiol-Michael addition reaction catalyzed by a base catalyst or a nucleophile. Although the radical-mediated thiol-ene reaction is an efficient click reaction, this reaction usually requires the selection of specific light sources and conditions, which limits the reaction process. The Michael addition reaction catalyzed by a base usually occurs at room temperature and has high functional group compatibility with many different types of functional groups. Therefore, it can effectively react thiols with alkenes to form the structural units of the target polymer.

[0059] Selecting monomers containing thiols as crosslinkers has relatively high environmental friendliness and sustainability compared to other crosslinkers. They can usually be obtained from natural sources or easily accessible chemical synthesis routes, meeting the requirements of modern electrochemical devices for environmental protection and sustainable development.

[0060] In summary, by modifying the ureidopyrimidinone structure with 6-position substituents, and constructing a fast self-healing polymer electrolyte based on strong hydrogen bonds as a self-healing interface layer between NASICON-type solid electrolyte and lithium through a highly efficient and highly selective click chemical reaction between the modified ureidopyrimidinone structure and thiol monomers, it can play a multifunctional role in improving poor interface stability, inhibiting dendrite growth, and repairing damaged interface layers, maintaining interface contact and continuous lithium ion transport during cycling. This is of great significance for solving the problem of poor interface stability between NASICON-type solid electrolyte and lithium and improving the cycling performance of solid-state lithium batteries.

[0061] Example 1

[0062] 2.0 g of 2-amino-4-hydroxy-6-ethylpyrimidine was added to 80 mL of dimethyl sulfoxide and heated to 150 °C for dissolution. Then, 2.64 g of isocyanatoethyl methacrylate was added. After stirring at 25 °C for 24 hours, the reaction solution was cooled with water to obtain a white solid precipitate. The white solid obtained after suction filtration and vacuum drying was UPyMA with an ethyl group as the 6-position substituent. 0.72 g of methoxypolyethylene glycol methacrylate with a molecular weight of 475, 0.08 g of UPyMA, and 0.11 g of pentaerythritol tetra(3-mercaptopropionate) were added with lithium bis(trifluoromethanesulfonyl)imide in a ratio of 16:1 of the ethoxy group in methoxypolyethylene glycol methacrylate to Li mole ratio, 5 mL of dimethyl sulfoxide. After stirring at room temperature for 3 hours, 1 wt% of triethylamine was added. After vigorously stirring for ten minutes, the solution was poured into a mold. First, it was dried at room temperature for 12 hours, and then vacuum dried at 80 °C for 24 hours. After completely removing the solvent in the electrolyte, a polymer electrolyte with rapid self-healing function was obtained.

[0063] Example 2

[0064] 1.0 g of 2-amino-4-hydroxy-6-ethylpyrimidine was added to 40 mL of dimethyl sulfoxide and heated to 150 °C for dissolution. Then, 1.32 g of isocyanatoethyl methacrylate was added. After stirring at 25 °C for 12 hours, the reaction solution was cooled with water to obtain a white solid precipitate. The white solid obtained after suction filtration and vacuum drying was UPyMA with an ethyl group as the 6-position substituent. 0.75 g of methoxypolyethylene glycol methacrylate with a molecular weight of 500, 0.08 g of UPyMA, and 0.11 g of pentaerythritol tetra(3-mercaptopropionate) were added with lithium bis(trifluoromethanesulfonyl)imide in a ratio of 18:1 of the ethoxy group in methoxypolyethylene glycol methacrylate to Li mole ratio, 5 mL of N,N-dimethylformamide. After stirring at room temperature for 3 hours, 1 wt% of triethylamine was added. After vigorously stirring for ten minutes, the solution was poured into a mold. First, it was dried at room temperature for 12 hours, and then vacuum dried at 80 °C for 24 hours. After completely removing the solvent in the electrolyte, a polymer electrolyte with rapid self-healing function was obtained.

[0065] Example 3

[0066] Dissolve 1.0 g of 2-amino-4-hydroxy-6-methoxypyrimidine in 40 mL of dimethyl sulfoxide and heat to 150 °C for dissolution. Then add 1.32 g of isocyanatoethyl methacrylate and stir at 25 °C for 24 hours. Cool the reaction solution with water to obtain a white solid precipitate. The white solid obtained after suction filtration and vacuum drying is UPyMA with a methoxy group at the 6-position substituent. Add 0.72 g of polyethylene glycol methyl ether methacrylate with a molecular weight of 475, 0.08 g of UPyMA, and 0.11 g of pentaerythritol tetrakis(3-mercaptopropionate). Add lithium bis(trifluoromethanesulfonyl)imide in a ratio of 18:1 of ethoxy groups in polyethylene glycol methyl ether methacrylate to Li mole ratio, 5 mL of dimethyl sulfoxide. Stir at room temperature for 3 hours, then add 1 wt% of triethylamine. After stirring vigorously for fifteen minutes, pour the solution into a mold. First, dry at room temperature for 12 hours, then dry under vacuum at 80 °C for 24 hours. After completely removing the solvent in the electrolyte, a polymer electrolyte with rapid self-healing function is obtained.

[0067] Comparative Example 1

[0068] Dissolve 2.0 g of 2-amino-4-hydroxy-6-methylpyrimidine in 80 mL of dimethyl sulfoxide and heat to 150 °C for dissolution. Then add 2.64 g of isocyanatoethyl methacrylate and stir at 25 °C for 24 hours. Cool the reaction solution with water to obtain a white solid precipitate. The white solid obtained after suction filtration and vacuum drying is UPyMA with a methyl group at the 6-position substituent. Add 0.72 g of polyethylene glycol methyl ether methacrylate with a molecular weight of 475, 0.08 g of UPyMA, and 0.11 g of pentaerythritol tetrakis(3-mercaptopropionate). Add lithium bis(trifluoromethanesulfonyl)imide in a ratio of 16:1 of ethoxy groups in polyethylene glycol methyl ether methacrylate to Li mole ratio, 5 mL of dimethyl sulfoxide. Stir at room temperature for 3 hours, then add 1 wt% of triethylamine. After stirring vigorously for ten minutes, pour the solution into a mold. First, dry at room temperature for 12 hours, then dry under vacuum at 80 °C for 24 hours. After completely removing the solvent in the electrolyte, a polymer electrolyte with self-healing function is obtained.

[0069] The polymer electrolytes obtained in Example 1 and Comparative Example 1 were further characterized for the polymer structure by FT-IR testing. The FT-IR spectra corresponding to Example 1 and Comparative Example 1 are as Figure 6 and Figure 7 shown. The signal peaks at 1589 cm -1 and 1661 cm -1 in the FT-IR spectrum are the stretching vibration peaks of the C═C and C═O groups in the UPyMA structure in the polymer. The signal peak at 1650 cm -1 is the stretching vibration peak of C═C in the PEGMA structure, and at 2553 cm -1The absorption peak at [the specific position] corresponds to the stretching vibration peak of S-H in the PETMP structure. These absorption peaks disappear in the synthesized polymer electrolyte, indicating the successful preparation of the polymer electrolyte.

[0070] After the polymer electrolytes obtained in Comparative Example 1 and Example 1 were cut with a dry scalpel at room temperature, self-healing was achieved respectively. The polymer electrolyte prepared when the substituent of UPyMA was methyl self-healed at room temperature in 1 hour, and the polymer electrolyte prepared when the substituent was ethyl self-healed at room temperature in 30 minutes. The healing time of the polymer with ethyl substituent of UPyMA in Example 1 was shorter, as Figure 8 shown.

[0071] In the glove box, the polymer electrolytes (SHPE) prepared in Example 1 and Comparative Example 1 were respectively used as the self-healing interfacial layer between the NASICON-type solid electrolyte (ss) and metallic lithium to assemble CR2025 coin cells. The first charge-discharge curves at 30 °C were as Figure 9 shown. The plateau of the cell in Example 1 was lower than that in Comparative Example 1, and it was more stable during the charge-discharge process. Its discharge specific capacity was also higher than that in Comparative Example 1. The cycle performance was as Figure 10 shown. The cell in Comparative Example 1 short-circuited after 26 cycles, while the cell in Example 1 was still cycling stably. The capacity retention rate of the cell in Comparative Example 1 after 26 cycles was 80.98%, and the capacity retention rate of the cell in Example 1 after 30 cycles was 87.96%, indicating that the cell in Example 1 had better cycle performance and was expected to have long-term stable cycling.

[0072] The cells in Example 1 and Comparative Example 1 were tested by electrochemical impedance spectroscopy, as Figure 11 shown. The impedance of the cell in Comparative Example 1 was greater than that of the cell in Example 1. Impedance is inversely proportional to ionic conductivity, which is consistent with the comparison results in Table 1. That is, at 30 °C, the ionic conductivity of Example 1 was greater than that of Comparative Example 1. The greater the ionic conductivity, the more conducive to the + insertion and extraction of Li. Therefore, the self-healing electrolyte interfacial layer prepared when the substituent of UPyMA was ethyl had better performance.

[0073] Table 1 Ionic conductivities of Example 1 and Comparative Example 1 at 30 °C

[0074]

[0075] Among them, δ is the ionic conductivity of the polymer electrolyte interfacial layer; L is the thickness of the polymer electrolyte interfacial layer; S is the actual contact area of the tested polymer electrolyte interfacial layer with the stainless steel sheet; R is the bulk impedance of the polymer electrolyte interfacial layer obtained experimentally.

[0076] Li / SHPE / ss / SHPE / Li symmetric batteries were assembled using the polymer electrolytes prepared in Example 1 and Comparative Example 1, and the polarization curves are compared as Figure 12 shown. The polarization voltage of the symmetric battery in Comparative Example 1 was stabilized at 0.1 V, and the polarization voltage of the symmetric battery in Example 1 was stabilized at 0.03 V. The lower the polarization voltage, the more electrochemically stable it is, and there are fewer side reactions at the interface layer. Therefore, using the polymer with an ethyl substituent in UPyMA in Example 1 as the self-healing interface layer is more beneficial to the cycling stability of lithium-ion batteries.

[0077] In summary, by combining the changes in self-healing performance and electrochemical performance, the relationship between the molecular structure of the self-healing interface layer, self-healing performance, interface stability, and electrochemical performance was established, and finally, the long-term stability mechanism of the self-healing interface layer prepared with an ethyl substituent in UPyMA at the negative electrode interface of solid-state lithium batteries was revealed. It provides key support for further in-depth research on this mechanism and the long-term reliability development of solid-state lithium batteries.

[0078] In addition, it should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a fast self-healing polymer electrolyte interface layer, characterized in that: The following steps are involved: Step 1, dissolving 2-amino-4-hydroxy-6-substituted pyrimidine in dimethyl sulfoxide under heating conditions, then adding isocyanate to the reaction system, stirring the reaction, and obtaining UPyMA after precipitation, suction filtration and drying, wherein the substituent is ethyl or methoxy; Step 2: UPyMA, polyethylene glycol methyl ether methacrylate, pentaerythritol tetrakis(3-mercaptopropionic acid) ester and lithium salt are uniformly mixed in a solvent, a thiol-Michael addition reaction occurs under the action of a catalyst, the reaction mixture is cast into a film, and a polymer electrolyte interface layer is obtained after drying; The molar ratio of the lithium salt to the ethoxy group in polyethylene glycol methyl ether methacrylate is 1:15 to 1:20; the molar ratio of the mercapto group in pentaerythritol tetrakis(3-mercaptopropionic acid) to the double bond in polyethylene glycol methyl ether methacrylate and UPyMA is 0.5:1 to 1:

1.

2. The preparation method according to claim 1, characterized in that: In step 1, the mass ratio of the 2-amino-4-hydroxy-6-substituted pyrimidine to the isocyanate is 1:1 to 1:1.

2.

3. The preparation method according to claim 1, characterized in that: In step 1, the isocyanate includes isocyanoethyl methacrylate or 2-isocyanoethyl acrylate.

4. The preparation method according to claim 1, characterized in that: In step 2, the molecular weight of the polyethylene glycol methyl ether methacrylate is 300-600.

5. The preparation method according to claim 1, characterized in that: In step 2, the lithium salt includes any one of lithium perchlorate, lithium bis(trifluoromethanesulfonyl)imide and lithium trifluoromethanesulfonate.

6. The preparation method according to claim 1, characterized in that: In step 2, the solvent is any one of dimethyl sulfoxide, N,N-dimethylformamide, and acetonitrile.

7. The preparation method according to claim 1, characterized in that: In step 2, the catalyst is n-hexylamine, diethylamine, triethylamine or tetramethylguanidine.

8. The preparation method according to claim 1, characterized in that: In step 2, the reaction time of the mercapto-Michael addition reaction is not less than 5 minutes.

9. An application of a polymer electrolyte interface layer prepared by the method according to any one of claims 1 to 8, characterized in that: The polymer electrolyte interface layer is applied as a self-healing interface layer between the NASICON type solid electrolyte and lithium.

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