Boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium ion battery energy storage materials, and particularly relates to a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, jointly dissolving fluoroalcohol, allyl isocyanate, polycaprolactone glycol and a first initiator in an electrolyte, carrying out nucleophilic addition reaction to obtain an intermediate solution containing a carbamate group, then adding lithium salt into the intermediate solution containing the carbamate group, and carrying out polymerization reaction to obtain the lithium ion battery. The preparation method comprises the following steps: adding a boron ester monomer and a first initiator, uniformly mixing, adding a boric acid ester monomer and a second initiator, carrying out an addition reaction to form a self-repairing precursor solution, heating the self-repairing precursor solution, and carrying out in-situ polymerization to obtain the boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte. The boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte prepared by the invention can repair cracks or electrode deformation generated in a circulation process, contains rich fluorine elements, and can improve an electrochemical window of a self-repairing solid electrolyte.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery energy storage materials, and specifically relates to a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte and a preparation method and application thereof. Background Art

[0002] With the rapid development of electronic devices and electric vehicles, the demand for high-performance and high-safety energy storage systems is increasing. Lithium-ion batteries have become one of the mainstream energy storage technologies due to their high energy density and long cycle life. However, traditional lithium-ion batteries mostly use organic carbonate liquid electrolytes, which are flammable and easily form lithium dendrites during the use of lithium-ion batteries, causing lithium-ion batteries to short-circuit and even cause fires, posing serious safety hazards. To solve this problem, solid-state electrolytes have gradually attracted attention. Solid-state electrolytes have the advantages of being non-flammable, leak-free, and having good thermal stability, and are considered an important way to improve battery safety. However, existing solid-state electrolytes still face some challenges, such as deficiencies in mechanical strength, interfacial stability, and electrochemical performance. Especially in wearable electronic devices and electric vehicle applications, solid-state electrolytes may be damaged by bending, torsion, or impact, which in turn affects the performance and life of lithium-ion batteries.

[0003] In recent years, the development of self-healing functional materials has provided a new approach to solving this problem. Self-healing solid electrolytes can automatically repair themselves after damage, restoring their original physical and electrochemical properties, thereby significantly improving the safety and reliability of lithium-ion batteries. However, recent studies have found that the introduction of self-healing functionality can also negatively impact the electrolyte's antioxidant and ion transport properties. Furthermore, self-healing groups are sensitive to the complex chemical and electrochemical reaction mechanisms within lithium-ion batteries, as well as to external physical and mechanical changes, making it difficult to guarantee the cycling stability of lithium-ion batteries. These issues have severely hindered the development of self-healing solid electrolytes. Summary of the Invention

[0004] In response to the deficiencies in the above-mentioned prior art, the present invention provides a boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte and its preparation method and application. The present invention first uses fluoroalcohol, isocyanate, polycaprolactone diol and a first initiator as raw materials to carry out a nucleophilic addition reaction to obtain an intermediate solution containing carbamate groups; then the intermediate solution containing carbamate groups is mixed with a lithium salt, a borate ester monomer and a second initiator, and an addition reaction is carried out to obtain a self-healing precursor solution; finally, the self-healing precursor solution is heated and in situ polymerized to obtain a boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte. The boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte prepared by the method of the present invention has excellent mechanical strength, interfacial stability, electrochemical performance, antioxidant properties, ion transport performance and cyclic stability, and solves the technical defects of existing solid electrolytes and self-healing functional materials.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: The first object of the present invention is to provide a method for preparing a boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte, comprising the following steps: Fluoroalcohol, isocyanate, polycaprolactone diol and a first initiator are dissolved together in an electrolyte and subjected to a nucleophilic addition reaction to obtain an intermediate solution containing carbamate groups; the hydroxyl groups in the fluoroalcohol and polycaprolactone diol react together with the isocyanate groups in the isocyanate, and carbamate is easily generated. As the most important group in the intermediate solution containing carbamate groups, carbamate can also form intermolecular hydrogen bonds with each other, so that the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte prepared using the intermediate solution containing carbamate groups has good mechanical properties and self-healing properties. At the same time, the introduction of fluorine can also improve the redox potential of the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte, so that it can match high-voltage positive electrode materials.

[0006] Adding lithium salt to the intermediate solution containing carbamate groups, stirring and dissolving the solution, and obtaining a functionalized electrolyte.

[0007] A borate monomer and a second initiator are added to a functionalized electrolyte to carry out an addition reaction. The double bond of the functionalized electrolyte undergoes electrophilic addition with the thiol group or double bond of the borate monomer. The second initiator is cleaved under heating conditions to generate free radicals. The free radicals capture the thiol hydrogen atoms or carbon-carbon double bond hydrogen atoms on the borate monomer to generate thiol radicals or alkyl radicals. The generated thiol radicals or alkyl radicals attack the carbon-carbon double bond on the isocyanate, causing the active center to transfer and generate alkyl radicals. The alkyl radicals attack the borate monomer again, thus entering a cycle. Finally, the free radicals are annihilated and the free radical reaction is completed to obtain a self-healing precursor solution.

[0008] The self-repairing precursor solution is heated and in-situ polymerized to obtain a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte, and the boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte is a solid-state electrolyte.

[0009] In a preferred embodiment of the present application, the fluoroalcohol is selected from one of 1H, 1H, 2H, 2H-perfluoro-1-octanol, 1H, 1H, 2H, 2H-perfluoro-1-hexanol, 1H, 1H, 2H, 2H-perfluoro-1-dodecanol, 1H, 1H, 2H, 2H-perfluoro-1-decanol; wherein the mass of the fluoroalcohol accounts for 5% to 30% of the mass of the electrolyte.

[0010] In a preferred embodiment of the present application, the isocyanate ester is selected from one of isocyanatoethyl methacrylate, isocyanatoallyl, isocyanatoethyl acrylate; wherein the mass ratio of the fluoroalcohol to the isocyanate ester is 1 to 10:1.

[0011] In a preferred embodiment of the present application, the polycaprolactone diol is selected from one of polycaprolactone diol-1000, polycaprolactone diol-2000, polycaprolactone diol-3000, polycaprolactone diol-6000, polycaprolactone diol-10000; wherein the mass ratio of the polycaprolactone diol to the isocyanate ester is 1 to 10:1.

[0012] In a preferred embodiment of the present application, the first initiator is selected from one of dibutyltin dilaurate, triethylamine, N,N-dimethylbenzylamine, stannous octoate, triphenylphosphine, 2-methylimidazole; wherein the mass ratio of the fluoroalcohol to the first initiator is 50 to 500:1.

[0013] In a preferred embodiment of the present application, the electrolyte is selected from one of KLD-1230C electrolyte, LB301 electrolyte, LB302 electrolyte, LB303 electrolyte, LB313 electrolyte.

[0014] In a preferred embodiment of the present application, the conditions of the nucleophilic addition reaction are heating at 40°C to 100°C for 1h.

[0015] In a preferred embodiment of the present application, the lithium salt is selected from one or more of lithium nitrate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, lithium bistrifluoromethylsulfonylimide, lithium bisfluorosulfonylimide; wherein the mass of the lithium salt accounts for 0.1% to 10% of the total amount of the functional electrolyte.

[0016] In a preferred embodiment of the present application, the borate monomer is selected from one of 2,2'-(1,4-phenylene)-bis[4-thiol-1,3,2-dioxaborolane], 2,2'-(1,4-phenylene)-bis(4-allyloxy-1,3,2-dioxaborolane), 4-((allyloxy)methyl)-2-(4-vinylphenyl)-1,3,2-dioxaborolane; wherein the molar ratio of the borate monomer to the isocyanate is 1:1-4.

[0017] In a preferred embodiment of the present application, the second initiator is selected from one of azobisisobutyronitrile, azobisisoheptyl nitrile, di-tert-butyl peroxide, diisopropylbenzene peroxide, benzoyl peroxide, triphenylphosphine; wherein the mass of the second initiator is 0.05%-1% of the mass of the fluoroalcohol.

[0018] In a preferred embodiment of the present application, the conditions of the addition reaction are heating at 40-100℃ for 0.5-1h.

[0019] A second object of the present application is to provide a boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte prepared by the above preparation method.

[0020] A third object of the present application is to provide the use of the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte in the preparation of a high-voltage lithium metal battery, wherein the voltage range of the high-voltage lithium metal battery is 4.2-4.7V.

[0021] In a preferred embodiment of the present application, the self-healing precursor solution is added dropwise between the positive electrode and the negative electrode, and then heated and in-situ polymerized to obtain a high-voltage lithium metal battery.

[0022] In a preferred embodiment of the present application, the positive electrode is a lithium cobaltate positive electrode, and the negative electrode is a lithium metal negative electrode.

[0023] In a preferred embodiment of the present application, the heating conditions of the in-situ polymerization are heating at 40-100℃ for 0.5-24h.

[0024] Compared with the prior art, the present application has the beneficial effects that: 1、The application first takes fluorinated alcohol, isocyanate, polycaprolactone diol and first initiator as raw materials to carry out nucleophilic addition reaction to obtain intermediate solution containing urethane groups; then the intermediate solution containing urethane groups is mixed with lithium salt, borate monomer and second initiator to carry out addition reaction to obtain self-repairing precursor solution; finally, the self-repairing precursor solution is heated and in-situ polymerization is carried out to obtain boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte. The boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte prepared by the application can form a solid CEI film rich in F elements and B elements on the positive electrode side, the CEI film is a positive electrolyte interface film, effectively inhibiting the interface side reaction of the positive electrode side, preventing the generation of cracks and the generation of phase change; forming a SEI film rich in LiF and Li3N on the negative electrode side, the SEI is a solid-state electrolyte interface layer rich in LiF, the solid SEI film prevents further reaction of metal lithium and electrolyte, inhibits dendrite growth and lithium metal pulverization, and can also quickly conduct lithium ions, greatly improving the cycle life and safety performance of high-voltage lithium metal batteries.

[0025] The boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte is a self-repairing solid-state electrolyte applied to high-voltage lithium metal batteries. The application takes borate monomer as raw material, the borate monomer contains boron ester bond, and the boron ester bond contained in the self-repairing solid-state electrolyte realizes dynamic crosslinking and self-healing through ester exchange reaction, so as to repair the interface damage generated in the cycle process of high-voltage lithium metal batteries and restore the original physical performance and electrochemical performance, thereby significantly improving the safety and reliability of high-voltage lithium metal batteries. The Lewis acidity of the boron ester bond can also interact with the lithium salt anion, promote the uniform deposition of lithium ions, and improve the interface stability and electrochemical performance of high-voltage lithium metal batteries. At the same time, the self-repairing solid-state electrolyte also contains a large number of hydrogen bonds formed between the urethane groups, and these hydrogen bonds have the characteristics of reversibility, directionality and high sensitivity, so that the boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte can first break the weak hydrogen bond after being damaged by external force, and the new interface generated contains many uncombined hydrogen bond donors or acceptors. These groups form active sites on the fracture surface, and when the fracture surfaces contact, these active sites will re-form hydrogen bonds, gradually restoring the integrity and function of the boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte. Through the joint action of hydrogen bonds and boron ester bonds, the boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte has excellent self-healing performance.

[0026] 2、The fluorinated alcohol has rich fluorine elements in the molecular structure, strong electronegativity and high oxidation stability, can significantly improve the electrochemical stability of the self-repairing solid electrolyte, so that the self-repairing solid electrolyte can match the high-voltage positive electrode material, at the same time, the fluorine element also promotes the formation of SEI film, can effectively inhibit the growth of lithium dendrites, and prevent the side reaction between the electrode and the electrolyte, significantly improve the cycle life of the high-voltage lithium metal battery, and improve the electrochemical window of the self-repairing solid electrolyte.

[0027] 3、The polycaprolactone diol is a flexible polymer segment, which can be used as a supporting skeleton of the self-repairing solid electrolyte, and can also effectively alleviate the volume change of the positive electrode and the negative electrode generated in the charging and discharging process, release stress, so as to maintain the stability of the electrode structure. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a film physical map; wherein, (a) is a borate ester bond / hydrogen bond synergistic self-repairing polymer film physical map prepared by replacing the KLD-1230C electrolyte of example 1 with dimethylacetamide, (b) is a hydrogen bond self-repairing polymer film physical map prepared by replacing the KLD-1230C electrolyte of comparative example 1 with dimethylacetamide.

[0029] Figure 2 It is a scanning electron microscope image; wherein, a graph and b graph are scanning electron microscope images of the surface of the borate ester bond / hydrogen bond synergistic self-repairing polymer film under different magnifications, c graph and d graph are scanning electron microscope images of the surface of the hydrogen bond self-repairing polymer film under different magnifications.

[0030] Figure 3 It is a scanning electron microscope image and an element distribution graph; wherein, a graph~b graph in A graph are surface scanning electron microscope images of the lithium metal negative electrode of the high-voltage lithium metal battery after cycling of example 1 under different magnifications; B graph is a cross-section scanning electron microscope image of the lithium metal negative electrode of the high-voltage lithium metal battery after cycling of example 1 and C, N, O, F element distribution graphs.

[0031] Figure 4 It is a self-healing performance graph of the borate ester bond / hydrogen bond synergistic self-repairing polymer film.

[0032] Figure 5 It is a cycle performance graph; wherein, (a) is a cycle performance graph of a button high-voltage lithium metal battery assembled by using the borate ester bond / hydrogen bond synergistic self-repairing polymer electrolyte of example 1; (b) is a cycle performance graph of a button high-voltage lithium metal battery assembled by using the hydrogen bond self-repairing polymer electrolyte of comparative example 1.

[0033] Figure 6Figure (a) is a rate performance graph of a button high-voltage lithium metal battery assembled using the boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte of Example 1; and Figure (b) is a rate performance graph of a button high-voltage lithium metal battery assembled using the hydrogen bond self-repairing polymer electrolyte of Comparative Example 1.

[0034] Figure 7 Figure (a) is a self-repairing precursor solution, and Figure (b) is a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the preferred embodiments and the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0036] In view of the problems that in the prior art self-healing solid-state electrolyte, due to the introduction of self-healing functional materials, the oxidation resistance and ion transport performance of the electrolyte are negatively affected, and the self-healing groups are sensitive to the complex chemical and electrochemical reaction mechanisms inside the lithium ion battery and external physical and mechanical changes, causing the cycle stability of the lithium ion battery to be unable to be guaranteed, the present application provides a brand-new boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte. The boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte has high ionic conductivity, solving the problem of ion transport performance; the high-voltage lithium metal battery prepared by using the boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte has excellent electrochemical performance, solving the problem of sensitivity; and the present application uses a fluorinated alcohol as a raw material, and the fluorine element of the fluorinated alcohol has a strong electron-withdrawing effect, improving the oxidation resistance, solving the problem of oxidation resistance.

[0037] The technical solutions of the present application are studied by using the following examples and comparative examples, and the specific research methods and results are shown as follows: Example 1 The preparation method of the boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte comprises the following steps: S1, 0.58 g of polycaprolactone diol-2000 was weighed and dissolved in 2 mL of KLD-1230C electrolyte to obtain a mixture, then 0.21 mL of isocyanatoethyl methacrylate and 0.22 mL of 1H, 1H, 2H, 2H-perfluoro-1-octanol were added to the mixture, and a uniform transparent solution was obtained after stirring, then 10 μL of the first initiator dibutyltin dilaurate was added, and the solution was fully stirred at 50°C for 1 h to obtain an intermediate solution containing urethane groups.

[0038] S2, 20 mg of lithium nitrate was added to the intermediate solution containing urethane groups, and then fully stirred at 50°C for 3 h to obtain a functional electrolyte.

[0039] S3, 0.09 g of 2,2'-(1,4-phenylene)-bis[4-thiol-1,3,2-dioxaborinane] and 5 mg of the second initiator azobisisobutyronitrile were added to the functional electrolyte, and the solution was clear after stirring at 50°C for 0.5 h to obtain a self-repairing precursor solution.

[0040] S4, the self-repairing precursor solution was heated in an oven at 55°C for 1 h to obtain a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte.

[0041] A method for preparing a high-voltage lithium metal battery, comprising the following steps: The self-repairing precursor solution was added dropwise between the lithium cobalt oxide positive electrode and the lithium metal negative electrode, and then heated in an oven at 55°C for 1 h to obtain a high-voltage lithium metal battery.

[0042] Example 2 A method for preparing a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte, comprising the following steps: S1, 0.6 g of polycaprolactone diol-3000 was weighed and dissolved in 2 mL of LB301 electrolyte to obtain a mixture, then 0.18 mL of isocyanate and 0.3 mL of 1H, 1H, 2H, 2H-perfluoro-1-hexanol were added to the mixture, and a uniform transparent solution was obtained after stirring, then 10 μL of the first initiator triethylamine was added, and the solution was fully stirred at 50°C for 1 h to obtain an intermediate solution containing urethane groups.

[0043] S2, 40 mg of lithium difluorophosphate and 20 mg of lithium nitrate were added to the intermediate solution containing urethane groups, and then fully stirred at 50°C for 3 h to obtain a functional electrolyte.

[0044] S3, 0.06 g of 4-((allyloxy)methyl)-2-(4-vinylphenyl)-1,3,2-dioxaborolane and 7 mg of the second initiator azobisisoheptane nitrile were added to the functional electrolyte, stirred at 50°C for 1 h, to obtain a self-repairing precursor solution.

[0045] S4, the self-repairing precursor solution was heated in a 50°C oven for 1 h to obtain a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte.

[0046] A method for preparing a high-voltage lithium metal battery, comprising the following steps: The self-repairing precursor solution was added dropwise between the lithium cobaltate positive electrode and the lithium metal negative electrode, and then heated in a 50°C oven for 1 h to obtain a high-voltage lithium metal battery.

[0047] Example 3 A method for preparing a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte, comprising the following steps: S1, 1.0 g of polycaprolactone diol-10000 was weighed and dissolved in 4 mL of LB302 electrolyte to obtain a mixture, then 0.35 mL of isocyanatoethyl acrylate and 0.54 mL of 1H,1H,2H,2H-perfluoro-1-dodecanol were added to the mixture, and after stirring, a uniform transparent solution was obtained, then 20 μL of the first initiator N,N-dimethylbenzylamine was added, and the mixture was fully stirred at 50°C for 1 h to obtain an intermediate solution containing urethane groups.

[0048] S2, 60 mg of lithium bis(trifluoromethylsulfonyl)imide and 40 mg of lithium tetrafluoroborate were added to the intermediate solution containing urethane groups, and then the mixture was fully stirred at 50°C for 2 h to obtain a functional electrolyte.

[0049] S3, 0.34 g of 2,2'-(1,4-phenylene)-bis(4-allyloxy-1,3,2-dioxaborolane) and 15 mg of the second initiator dicumyl peroxide were added to the functional electrolyte, and the mixture was stirred at 50°C for 1 h to obtain a self-repairing precursor solution.

[0050] S4, the self-repairing precursor solution was heated in a 60°C oven for 0.5 h to obtain a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte.

[0051] A method for preparing a high-voltage lithium metal battery, comprising the following steps: The self-repairing precursor solution was added dropwise between the lithium cobaltate positive electrode and the lithium metal negative electrode, and then heated in a 60°C oven for 0.5 h to obtain a high-voltage lithium metal battery.

[0052] Example 4 A method for preparing a boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte, comprising the following steps: S1, 0.74 g of polycaprolactone diol-6000 was weighed and dissolved in 4 mL of LB303 electrolyte to obtain a mixture, then 0.3 mL of isocyanatoethyl methacrylate and 0.48 mL of 1H, 1H, 2H, 2H-perfluoro-1-decanol were added to the mixture, and a uniform transparent solution was obtained after stirring, then 20 μL of the first initiator stannous octoate was added, and the mixture was stirred at 50°C for 1 h to obtain an intermediate solution containing urethane groups.

[0053] S2, 40 mg of lithium difluoroborates was added to the intermediate solution containing urethane groups, and then the mixture was stirred at 50°C for 1 h to obtain a functional electrolyte.

[0054] S3, 0.25 g of 4-((allyloxy)methyl)-2-(4-vinylphenyl)-1,3,2-dioxaborolane and 12 mg of the second initiator benzoyl peroxide were added to the functional electrolyte, and the mixture was stirred at 50°C for 1 h to obtain a self-healing precursor solution.

[0055] S4, the self-healing precursor solution was heated in an oven at 60°C for 4 h to obtain a boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte.

[0056] A method for preparing a high-voltage lithium metal battery, comprising the following steps: The self-healing precursor solution was added dropwise between the lithium cobaltate positive electrode and the lithium metal negative electrode, and then heated in an oven at 60°C for 4 h to obtain a high-voltage lithium metal battery.

[0057] Example 5 A method for preparing a boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte, comprising the following steps: S1, 0.4 g of polycaprolactone diol-1000 was weighed and dissolved in 4 mL of LB313 electrolyte to obtain a mixture, then 0.2 mL of isocyanatoethyl acrylate and 0.25 mL of 1H, 1H, 2H, 2H-perfluoro-1-octanol were added to the mixture, and a uniform transparent solution was obtained after stirring, then 10 μL of the first initiator 2-methylimidazole was added, and the mixture was stirred at 50°C for 1 h to obtain an intermediate solution containing urethane groups.

[0058] S2, 20 mg of lithium nitrate and 80 mg of lithium bisfluorosulfonylimide were added to the intermediate solution containing urethane groups, and then the mixture was stirred at 50°C for 3 h to obtain a functional electrolyte.

[0059] S3, 0.25 g of 2,2'-(1,4-phenylene)-bis[4-thiol-1,3,2-dioxaborinane] and 5 mg of the second initiator triphenylphosphine were added to the functional electrolyte, stirred at 50 °C for 1 h, to obtain a self-repairing precursor solution.

[0060] S4, the self-repairing precursor solution was heated in an oven at 55 °C for 2 h to obtain a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte.

[0061] The preparation method of the high-voltage lithium metal battery comprises the following steps: The self-repairing precursor solution was added dropwise between the lithium cobaltate positive electrode and the lithium metal negative electrode, and then heated in an oven at 55 °C for 2 h to obtain a high-voltage lithium metal battery.

[0062] Example 6 The preparation method of the boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte comprises the following steps: S1, 0.1 g of polycaprolactone diol-2000 was weighed and dissolved in 2 mL of KLD-1230C electrolyte to obtain a mixed solution, then 0.1 mL of isocyanatoethyl methacrylate and 0.1 mL of 1H,1H,2H,2H-perfluoro-1-octanol were added to the mixed solution, and after stirring, a uniform transparent solution was obtained, then 5 μL of the first initiator dibutyltin dilaurate was added, and the mixture was fully stirred at 40 °C for 1 h to obtain an intermediate solution containing urethane groups.

[0063] S2, 2.3 mg of lithium nitrate was added to the intermediate solution containing urethane groups, and then fully stirred at 50 °C for 3 h to obtain a functional electrolyte.

[0064] S3, 0.2 g of 2,2'-(1,4-phenylene)-bis[4-thiol-1,3,2-dioxaborinane] and 2 mg of the second initiator azobisisobutyronitrile were added to the functional electrolyte, and stirred at 100 °C for 0.5 h to obtain a self-repairing precursor solution.

[0065] S4, the self-repairing precursor solution was heated in an oven at 100 °C for 0.5 h to obtain a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte.

[0066] The preparation method of the high-voltage lithium metal battery comprises the following steps: The self-repairing precursor solution was added dropwise between the lithium cobaltate positive electrode and the lithium metal negative electrode, and then heated in an oven at 100 °C for 0.5 h to obtain a high-voltage lithium metal battery.

[0067] Example 7 The preparation method of the boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte comprises the following steps: S1. Weigh 0.2 g of polycaprolactone diol-2000 and dissolve it in 6 mL of KLD-1230C electrolyte to obtain a mixed solution. Then, add 0.02 mL of isocyanatoethyl methacrylate and 0.2 mL of 1H,1H,2H,2H-perfluoro-1-octanol to the mixed solution, stir to obtain a uniform and transparent solution, then add 5 μL of the first initiator dibutyltin dilaurate, and stir thoroughly at 100°C for 1 h to obtain an intermediate solution containing a carbamate group.

[0068] S2. Add 64 mg of lithium nitrate to the intermediate solution containing the carbamate group, and then stir thoroughly at 50° C. for 3 h to obtain a functionalized electrolyte.

[0069] S3. Add 0.04 g of 2,2′-(1,4-phenylene)-bis[4-thiol-1,3,2-dioxaborolane] and 5 mg of the second initiator azobisisobutyronitrile to the functionalized electrolyte, stir at 10°C for 1 hour, and obtain a self-healing precursor solution.

[0070] S4. Heat the self-healing precursor solution in an oven at 40° C. for 24 h to obtain a boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte.

[0071] A method for preparing a high-voltage lithium metal battery comprises the following steps: The self-healing precursor solution was added dropwise between the lithium cobalt oxide positive electrode and the lithium metal negative electrode, and then heated in an oven at 40°C for 24 hours to obtain a high-voltage lithium metal battery.

[0072] Comparative Example 1 A method for preparing a hydrogen bond self-repairing polymer electrolyte, which has the same preparation steps as Example 1, except that no borate monomer is added in step S3, comprises the following steps: S1. Weigh 0.58 g of polycaprolactone diol-2000 and dissolve it in 2 mL of KLD-1230C electrolyte to obtain a mixed solution. Then, add 0.21 mL of isocyanatoethyl methacrylate and 0.22 mL of 1H,1H,2H,2H-perfluoro-1-octanol to the mixed solution, and stir to obtain a uniform and transparent solution. Then, add 10 μL of the first initiator dibutyltin dilaurate, and stir thoroughly at 50°C for 1 hour to obtain an intermediate solution containing a carbamate group.

[0073] S2. Add 20 mg of lithium nitrate to the intermediate solution containing the carbamate group, and then stir thoroughly at 50° C. for 3 h to obtain a functionalized electrolyte.

[0074] S3. Add 5 mg of the second initiator azobisisobutyronitrile to the functionalized electrolyte and stir until the solution is clear to obtain a self-healing precursor solution.

[0075] S4, heating the self-repairing precursor solution in a 55℃ oven for 1h to obtain a hydrogen bond self-repairing polymer electrolyte.

[0076] A method for preparing a high-voltage lithium metal battery, comprising the following steps: A high-voltage lithium metal battery is prepared by dropping the self-repairing precursor solution between the lithium cobaltate positive electrode and the lithium metal negative electrode, and then heating in a 55℃ oven for 1h.

[0077] Result analysis: Examples 1-7 of the present application all produce hydrogen bond self-repairing polymer electrolytes with excellent self-healing performance and electrochemical performance. The following takes the hydrogen bond self-repairing polymer electrolyte and high-voltage lithium metal battery of Example 1 as an example, and compares them with the hydrogen bond self-repairing polymer electrolyte and high-voltage lithium metal battery of Comparative Example 1. The specific research methods and results are shown below: 1. Morphology test: (1) Macroscopic morphology test: In order to facilitate film formation, the KLD-1230C electrolyte of Example 1 and Comparative Example 1 was replaced with dimethylacetamide, respectively, and then the same operation was performed until the self-repairing precursor solution was obtained. Finally, the self-repairing precursor solution was dried at 60℃ for 24h under an inert atmosphere to obtain a borate ester bond / hydrogen bond synergistic self-repairing polymer film and a hydrogen bond self-repairing polymer film, respectively. The macroscopic morphology of the two was tested, and the test results are shown in Figure 1 . Figure 1 The results show that under the macroscopic state, the surface of the borate ester bond / hydrogen bond synergistic self-repairing polymer film and the hydrogen bond self-repairing polymer film is very smooth and flat, but the borate ester bond / hydrogen bond synergistic self-repairing polymer film is more flexible and elastic than the hydrogen bond self-repairing polymer film. The hydrogen bond self-repairing polymer film only contains hydrogen bonds, and due to the directionality of the hydrogen bonds, the hydrogen bond self-repairing polymer film has a higher crystallinity and a harder texture, so the self-healing performance is poor, almost no self-healing performance.

[0078] (2) Microscopic morphology test: The microscopic morphology of the surface of the borate ester bond / hydrogen bond synergistic self-repairing polymer film and the hydrogen bond self-repairing polymer film was tested, and the test results are shown in Figure 2 . It can be seen from Figure 2 that the introduction of borate ester monomers makes the surface of the borate ester bond / hydrogen bond synergistic self-repairing polymer film smoother and flatter, while the surface of the hydrogen bond self-repairing polymer film has more fine cracks and wrinkles.

[0079] The lithium metal negative electrode of the high-voltage lithium metal battery of Example 1 after cycling was taken as an example for research, Figure 3A figure in the middle is a lithium metal negative electrode surface diagram, B is a lithium metal negative electrode cross-sectional diagram and element distribution diagram, from A, it can be seen that the surface of the lithium metal negative electrode is smooth after cycling, and no lithium dendrite is generated, which indicates that a solid SEI film has been formed on the surface of the lithium metal negative electrode; from B, it can be seen that the C, N, O and F elements in the SEI film are uniformly distributed, which indicates that the borate bond / hydrogen bond synergistic self-healing polymer electrolyte has good compatibility with the lithium metal negative electrode interface, and a uniform SEI film is formed on the surface of the lithium metal negative electrode after cycling.

[0080] 2. Self-healing performance: Figure 4 The test figure of the self-healing performance of the borate bond / hydrogen bond synergistic self-healing polymer film. From Figure 4 It can be seen that under the dual action of dynamic borate bond and hydrogen bond, the polymer network has excellent self-healing performance, which can complete self-healing within 3h at 30℃.

[0081] 3. Cycle performance test: The borate bond / hydrogen bond synergistic self-healing polymer electrolyte of Example 1 and the hydrogen bond self-healing polymer electrolyte of Comparative Example 1 were respectively assembled into high-voltage lithium metal batteries, and the cycle performance of the two high-voltage lithium metal batteries was tested according to the following test method, and the test results are shown in Figure 5 .

[0082] Test method: take a lithium sheet with a diameter of 16mm as the negative electrode, take a lithium cobaltate sheet with a diameter of 8mm as the positive electrode, load the lithium cobaltate on the aluminum foil to obtain the lithium cobaltate sheet, and the loading amount of lithium cobaltate on the lithium cobaltate sheet is 5.5mg cm -2 ; take a Whatman® filter as a separator, the Whatman® filter is 100% borosilicate glass fiber, model GF / A, 1.6µm pore size, diameter 16mm, evenly drop 150μL of self-healing precursor solution on the Whatman® filter, clamp the Whatman® filter between the positive electrode and the negative electrode, then heat in a 55℃ oven for 1h to obtain a high-voltage lithium metal battery, and the battery shell type is CR2032.

[0083] Test conditions: the first two circles use 0.1C rate for charging and discharging, so as to activate the high-voltage lithium metal battery, and then use 0.5C rate for charging and discharging cycle test, and the charging and discharging voltage interval is 3.0V~4.6V.

[0084] From Figure 5The test results show that after 180 cycles, the high-voltage lithium metal battery assembled by using the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte of Example 1 still has a specific capacity retention rate of 83%, which is greatly improved compared to the 44% specific capacity retention rate of the high-voltage lithium metal battery assembled by using the hydrogen bond self-healing polymer electrolyte of Comparative Example 1, indicating that the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte can improve the cycle stability of the high-voltage lithium metal battery.

[0085] 4. Rate performance test: According to the following method, the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte of Example 1 and the hydrogen bond self-healing polymer electrolyte of Comparative Example 1 were respectively assembled with lithium metal negative electrode and lithium cobaltate positive electrode to form button cells, and the rate performance of each was tested, and the test results are shown in Figure 6 .

[0086] Test method: lithium sheet with a diameter of 16 mm was used as the negative electrode, lithium cobaltate sheet with a diameter of 8 mm was used as the positive electrode, and lithium cobaltate was loaded on aluminum foil to obtain lithium cobaltate sheet, the loading amount of lithium cobaltate on the lithium cobaltate sheet was 5.5 mg cm -2 ; Whatman® filter was used as the separator, Whatman® filter was 100% borosilicate glass fiber, model GF / A, 1.6 µm pore size, diameter 16 mm, 150 µL of self-healing precursor solution was uniformly drop-coated on the Whatman® filter, the Whatman® filter was clamped between the positive electrode and the negative electrode, and then heated in a 55°C oven for 1 h to obtain a high-voltage lithium metal battery, and the battery shell type was CR2032.

[0087] Test conditions: under the conditions of 0.2C, 0.5C, 1C, 1.5C, 2C, and 4C, the charge and discharge test was carried out according to the current density of first increasing and then decreasing, 1C = 180 mAh / g, and the charge and discharge voltage interval was 3.0V~4.3V.

[0088] From the test results of Figure 6 , it can be seen that the high-voltage lithium metal battery assembled by using the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte of Example 1 has good rate performance, which greatly alleviates the specific capacity decay of the high-voltage lithium metal battery under high-rate charge and discharge.

[0089] Figure 7 The results show that the self-healing precursor solution can be solidified to form a boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte after heating.

[0090] In summary, the application provides a self-repairing solid electrolyte applied to high-voltage positive electrode and lithium metal negative electrode, i.e., borate bond / hydrogen bond synergistic self-repairing polymer electrolyte, the self-repairing solid electrolyte is a flexible cross-linked polymer, the fluorine functional group in the molecule can improve the electrochemical window of the self-repairing solid electrolyte, the flexible polymer chain effectively buffers the volume change generated in the charging and discharging process of the positive electrode and the negative electrode, and releases the reaction stress. The borate structure in the polymer skeleton can realize dynamic cross-linking and self-healing through ester exchange reaction, combined with the reversible transformation of a large number of hydrogen bonds in the skeleton, the two synergistically repair the interface damage generated in the cycle process of the high-voltage lithium metal battery, restore its original physical properties and electrochemical properties, thereby significantly improve the safety and reliability of the high-voltage lithium metal battery; at the same time, it can also form a CEI film rich in F and B on the positive electrode side, and form a SEI film rich in LiF and Li3N on the negative electrode side, significantly improve the cycle stability of the high-voltage lithium metal battery.

[0091] It should be noted that when the numerical range is involved in the present application, both endpoints of each numerical range and any number between the two endpoints can be selected. Since the same steps and examples are used, the preferred embodiments are described in the present application to prevent redundancy. Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to the embodiments once they know the basic creative concept. Therefore, the appended claims are intended to include the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0092] Obviously, those skilled in the art can make various modifications and changes to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and changes of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and changes.

Claims

1. A method for preparing a boron ester bond / hydrogen bond synergistic self-repairing polymer electrolyte, characterized in that: The steps include: Dissolving a fluoroalcohol, olefinic isocyanate, polycaprolactone diol, and a first initiator in an electrolyte to undergo a nucleophilic addition reaction, wherein the hydroxyl groups in the fluoroalcohol and polycaprolactone diol react with the isocyanate groups in the olefinic isocyanate to obtain an intermediate solution containing a carbamate group; adding lithium salt to the intermediate solution containing carbamate groups and stirring and dissolving the mixture to obtain a functionalized electrolyte; adding a borate monomer and a second initiator to the functionalized electrolyte to carry out an addition reaction to obtain a self-healing precursor solution; The self-healing precursor solution is heated and in-situ polymerized to obtain a boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte.

2. The method for preparing the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte according to claim 1, characterized in that: The mass of fluoroalcohol accounts for 5% to 30% of the mass of the electrolyte.

3. The method for preparing the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte according to claim 1, characterized in that: The mass ratio of fluoroalcohol, isocyanate and polycaprolactone diol is 1-10:1:1-10.

4. The method for preparing the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte according to claim 1, characterized in that: The conditions for the nucleophilic addition reaction are: heating at 40℃~100℃ for 1h.

5. The method for preparing the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte according to claim 1, characterized in that: The mass of lithium salt accounts for 0.1%~10% of the total amount of functionalized electrolyte.

6. The method for preparing the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte according to claim 1, characterized in that: The molar ratio of the borate monomer to the isocyanate is 1:1-4.

7. The method for preparing the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte according to claim 1, characterized in that: The conditions for the addition reaction are: heating at 40°C~100°C for 0.5h~1h.

8. A boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the boron ester bond / hydrogen bond synergistic self-healing polymer electrolyte according to claim 8 in the preparation of a high-voltage lithium metal battery, characterized in that: The voltage range of high voltage lithium metal batteries is 4.2V~4.7V.

10. The use according to claim 9, characterized in that The self-repairing precursor solution is dropped between the positive electrode and the negative electrode, and heated to cause the self-repairing precursor solution to polymerize in situ to obtain a high-voltage lithium metal battery.

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