Polymer electrolyte, in-situ preparation method and application thereof

Abstract

The application belongs to the technical field of polymer electrolyte, and more particularly relates to a polymer electrolyte, an in-situ preparation method and application thereof. The in-situ preparation of the electrolyte is realized by catalyzing a mercapto-double bond Michael addition reaction by means of a deep eutectic solvent, wherein a metal salt and an amine compound of the deep eutectic solvent play a catalytic role in the mercapto-double bond Michael addition reaction, the metal salt and a sulfone compound play a role in adjusting the reaction rate, the interaction force between the metal salt, the amine compound and the sulfone compound reduces the melting point of the mixture composed of the solid components, the mixture is liquid at room temperature, no additional solvent is needed in the system, the reaction rate can be adjusted by the composition of the deep eutectic solvent, the problem that the mercapto-double bond Michael addition reaction is difficult to use the in-situ polymerization method is solved, and the deep eutectic solvent is used as a liquid component to improve the safety performance of the alkali metal ion battery, simplify the preparation process and reduce the cost.

Description

Technical Field

[0001] This invention belongs to the field of polymer electrolyte technology, and more specifically, relates to a polymer electrolyte, its in-situ preparation method, and its application. Background Technology

[0002] Lithium-ion batteries play a vital role in human production and daily life. However, traditional lithium-ion batteries use volatile, flammable, and leak-prone organic liquid electrolytes, posing significant safety hazards. Gel polymer electrolytes can avoid the leakage risks of liquid electrolytes, improving safety performance, and possess excellent processing and electrochemical properties, which is beneficial for the production and use of current energy storage devices.

[0003] Currently, there are two main methods for preparing gel polymer electrolytes: non-ex-situ physical methods and in-situ chemical methods. In-situ chemical methods are simpler in process than non-ex-situ physical methods, do not use organic solvents, and produce a more stable interface between the electrolyte and the electrode. The Michael addition reaction of thiol-double bonds is a type of click chemistry reaction that can efficiently build polymer networks, but it generally involves the introduction of catalysts such as triethylamine, which makes the reaction rate too fast, or the addition of initiators to initiate polymerization under light or heat conditions, making in-situ preparation difficult. Using light conditions requires an external light source and cannot be assembled in situ (it can only be assembled after light curing), while heating generally decomposes the initiator, leaving a small amount of initiator residue in the electrolyte. This residue will react with the electrode during battery operation, reducing battery capacity or causing the electrolyte to lack ion-conducting capabilities, resulting in reduced ion transport capacity and other adverse effects. (Macromolecules, 2020, 53, 17, 7450–7459) Furthermore, the addition of non-electrolyte components such as alkalis or initiators can also affect the performance of the electrolyte, hindering practical applications. Summary of the Invention

[0004] The purpose of this invention is to provide a polymer electrolyte, its in-situ preparation method and application, to solve the technical problems of existing technologies that require harsh reaction conditions for in-situ preparation of electrolytes via Michael addition of mercapto-double bonds, and that require the introduction of non-electrolyte components, which affects the performance of the electrolyte.

[0005] To achieve the above objectives, the present invention provides an in-situ preparation method for polymer electrolytes, comprising the following steps:

[0006] (1) A sulfone compound, an alkali metal salt and an amine compound are mixed and stirred to obtain a deep eutectic solvent; wherein the amine compound contains at least one of hydroxyl, urea and amide groups, and the amino group of the amine compound in the deep eutectic solvent obtained after stirring is an imino or a subamino group;

[0007] (2) Mix the first reactant containing a thiol end with the second reactant containing acrylate or methacrylate ends to obtain a mixed reactant solution;

[0008] (3) Mix the reactant mixture solution described in step (2) with the deep eutectic solvent described in step (1) to obtain the reaction precursor solution;

[0009] (4) The reaction precursor liquid described in step (3) is transferred to the surface of the membrane to obtain a membrane loaded with the reaction precursor liquid, and then assembled in situ into an alkali metal battery. The first reactant and the second reactant undergo a thiol-double bond Michael addition reaction in situ on the membrane under the catalysis of the deep eutectic solvent to form a cross-linked network, thereby obtaining a polymer electrolyte loaded on the membrane.

[0010] Preferably, the sulfone compound is sulfolane and / or divinyl sulfone; the alkali metal salt is a lithium salt, a sodium salt, or a potassium salt.

[0011] Preferably, when the amine compound in step (1) is a secondary or tertiary amine compound, it is further preferred to be one or more of 3-dimethylamino-1-propanol, N,N-diethylhydroxylamine, N-methylacetamide, N,N-dimethylformamide, 2-(methylamino)ethanol and bis(2-hydroxyethyl)amino(trihydroxymethyl)methane, the sulfone compound, the alkali metal salt and the secondary or tertiary amine compound are mixed and stirred to obtain a deep eutectic solvent, and the amino group of the amine compound in the deep eutectic solvent is an imino or subamino group;

[0012] When the amine compound in step (1) is a primary amine compound, and more preferably 1,3-diamino-2-hydroxypropane, a sulfone compound, an alkali metal salt, the primary amine compound, and an acrylate compound are mixed, stirred, and reacted to obtain a deep eutectic solvent. During the stirring process, the primary amine compound and the acrylate compound react to convert the amino group in the primary amine compound into an imino or subamino group, so that the amino group in the amine compound in the deep eutectic solvent is an imino or subamino group.

[0013] Preferably, in step (2), the first reactant is one or more of pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), and octamercaptopolyhedral oligomeric silsesquioxane; the second reactant is one or more of polyethylene glycol (diol) diacrylate and polyethylene glycol dimethacrylate; and the relative molecular mass of the polyethylene glycol (diol) diacrylate and polyethylene glycol dimethacrylate is 300 to 1000.

[0014] Preferably, the molar ratio of the thiol group in the first reactant containing the thiol terminal in step (2) to the double bond in the second reactant is 3:1 to 1:3.

[0015] Preferably, in step (1), the molar ratio of the amine compound, alkali metal salt and sulfolane in the deep eutectic solvent is 0.01-1:1:3-10, and more preferably 0.1-1:1:3-10.

[0016] Preferably, the mass ratio of the reactant mixture solution to the deep eutectic solvent in step (3) is 1:1 to 1:6.

[0017] Preferably, the diaphragm in step (4) is a cellulose diaphragm, a polyethylene diaphragm, or a polypropylene diaphragm.

[0018] Preferably, the Michael addition reaction time of the mercapto-double bond is not less than 1 minute.

[0019] According to another aspect of the present invention, a polymer electrolyte prepared by the in-situ preparation method described above is provided.

[0020] According to another aspect of the invention, an alkali metal battery is provided, comprising the polymer electrolyte described above.

[0021] This invention provides an in-situ preparation method for polymer electrolytes, which relies on the Michael addition reaction of thiol-double bonds catalyzed by a deep eutectic solvent. The alkali metal salt and amine compounds in the deep eutectic solvent act as catalysts in the Michael addition reaction, while the alkali metal salt and sulfone compounds regulate the reaction rate. Through the interaction forces (mainly hydrogen bonding and Lewis acid-base interactions) between the alkali metal salt and the amine and sulfone compounds, the melting point of the mixture of solid components is lowered, resulting in a liquid state at room temperature. No external solvent is required in the system, and the reaction rate can be adjusted by the composition of the deep eutectic solvent. This solves the problem that in-situ polymerization methods are difficult to use for the Michael addition reaction of thiol-double bonds. Furthermore, using a deep eutectic solvent as the liquid component improves the safety performance of lithium-ion batteries, simplifies the preparation process, and reduces costs, providing an efficient method for preparing high-performance alkali metal-ion battery gel polymer electrolytes.

[0022] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0023] (1) This invention provides a method for in-situ polymerization of a gel electrolyte by catalyzing a Michael addition reaction of a mercapto-double bond in a deep eutectic solvent. An amine compound, a sulfone compound and a metal salt that are solid at room temperature are mixed to obtain a deep eutectic solvent that is liquid at room temperature. This solvent can be directly used to catalyze the Michael addition reaction of a mercapto-double bond and improve the electrochemical performance of the gel polymer electrolyte in lithium-ion batteries.

[0024] (2) The reaction system of the present invention does not require the addition of catalysts, polar solvents or other compounds. It can prepare gel polymer electrolytes in situ by mixing monomers and deep eutectic solvents as raw materials. On the one hand, the reaction system uses deep eutectic solvents as catalysts and does not require the addition of external solvents. This avoids the use of parts unrelated to ion conduction in polymer gel electrolytes and avoids the disadvantages of complex post-processing, high price and easy volatility of catalysts and organic solvents. On the other hand, deep eutectic solvents are greener and safer than other liquid solvents, have low cost and good conductivity, which improves the safety and performance of lithium-ion batteries and reduces costs.

[0025] (3) This invention uses a deep eutectic solvent to catalyze the Michael addition reaction of thiol-double bond to prepare polymer electrolyte in situ, which solves the problem that the Michael addition reaction of thiol-double bond can only be carried out by non-in situ methods. This can shorten the preparation cycle of traditional electrolytes, simplify the preparation process, inhibit the growth of lithium dendrites, and enable the polymer gel electrolyte to form a uniform and stable interface layer between the electrodes of the lithium-ion battery, thereby improving the cycle stability of the battery.

[0026] (4) The deep eutectic solvent used in this invention contains lithium salt components, which alters the coordination environment of lithium ions, making them easier to dissociate and transport. This results in an increase in the ionic conductivity and lithium ion transference number of the electrolyte, as well as an improvement in the rate performance of the battery. The composition of the deep eutectic solvent used in this invention is adjustable, allowing the reaction rate to be controlled according to actual needs. Furthermore, the battery performance can be adjusted by changing the type of metal salt, making it flexible in use. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the in-situ preparation method of the polymer electrolyte of the present invention.

[0028] Figure 2 The images show the 1H NMR spectra of the monomer and the deep eutectic solvent before and after preparation of the deep eutectic solvent containing the 1,3-diamino-2-hydroxypropane derivative prepared in Example 1.

[0029] Figure 3 This is a graph showing the change in conductivity of the polymer electrolyte prepared in Example 4 of the present invention as a function of temperature.

[0030] Figure 4 This is a diagram showing the electrochemical stability window of the polymer electrolyte prepared in Example 4. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] This invention provides an in-situ preparation method for polymer electrolytes, such as... Figure 1 As shown, it includes the following steps:

[0033] (1) A sulfone compound, an alkali metal salt and an amine compound are mixed and stirred to obtain a deep eutectic solvent; wherein the amine compound contains at least one of hydroxyl, urea and amide groups, and the amino group in the amine compound in the deep eutectic solvent obtained after stirring is an imino or a subamino group;

[0034] (2) Mix and stir the first reactant containing thiol ends with the second reactant containing acrylate or methacrylate ends at both ends to obtain a mixed solution of reactants;

[0035] (3) Mix the reactant mixture solution described in step (2) with the deep eutectic solvent described in step (1) to obtain the reaction precursor solution;

[0036] (4) The reaction precursor liquid described in step (3) is transferred to the surface of the membrane to obtain a membrane loaded with the reaction precursor liquid, and then assembled in situ into an alkali metal battery. The first reactant and the second reactant undergo a thiol-double bond Michael addition reaction in situ on the membrane under the catalysis of the deep eutectic solvent to form a cross-linked network, thereby obtaining a polymer electrolyte loaded on the membrane.

[0037] In the above preparation method, this invention prepares a deep eutectic solvent by mixing solid sulfone compounds, metal salts, and amine compounds, and through the interaction between the components. The deep eutectic solvent catalyzes the Michael addition reaction of the thiol-double bond and regulates the reaction rate, allowing for convenient in-situ preparation of gel polymer electrolytes at room temperature. Taking lithium salt as an example, on the one hand, the amine compounds and lithium salt in this system act as catalyst and co-catalyst for the Michael addition reaction of the thiol-double bond, respectively, giving the deep eutectic solvent itself a catalytic effect, eliminating the need for external initiators or catalysts. Furthermore, the formation of the deep eutectic solvent eliminates the need for external solvents, avoiding the introduction of non-electrolyte components and simplifying the preparation process. On the other hand, the sulfone compounds in the deep eutectic solvent provide good ion conductivity for the electrolyte without participating in the reaction; therefore, the reaction rate can be controlled and the electrolyte's ion conductivity improved by adjusting the composition of the deep eutectic solvent.

[0038] During the experiment, it was discovered that alkali metal salts and sulfone compounds can also form a deep eutectic solvent when mixed in a certain proportion. Sulfone compounds do not affect the reaction and can enhance ion conductivity. However, alkali metal salts, such as lithium salts, cannot directly enable the reaction of mercaptoenes at room temperature. It is necessary to introduce amine components that can form a deep eutectic solvent with them in order to enable the reaction of mercaptoenes at room temperature.

[0039] In some embodiments, the sulfone compound is one or more of sulfolane and divinyl sulfone; the alkali metal salt is a lithium salt, a sodium salt, or a potassium salt; in some embodiments, the lithium salt includes, but is not limited to, at least one of lithium perchlorate, lithium hexafluorophosphate, lithium difluorooxalate borate, lithium trifluoromethanesulfonate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, and lithium iodide; the sodium salt includes, but is not limited to, at least one of sodium (trifluoromethane)sulfonylimide, sodium hexafluorophosphate, sodium perchlorate, sodium bisulfate, sodium nitrate, and sodium fluoroborate; the potassium salt includes, but is not limited to, at least one of potassium bis(fluorosulfonyl)imide, potassium phosphate, potassium fluorophosphate, and potassium fluorosulfate.

[0040] This invention utilizes a mixture of sulfone compounds, alkali metal salts, and amine compounds to prepare a deep eutectic solvent. The hydroxyl, urea, or amide groups in the amine compounds enable strong hydrogen bonding between them and the sulfone compounds and alkali metal salts, which is beneficial for the formation of the deep eutectic solvent. Furthermore, experiments in this invention have shown that while gel polymer electrolytes can be prepared in situ using primary amine compounds, the presence of primary amines in the prepared gel polymer electrolytes leads to side reactions and causes the polymer network to disintegrate after a certain period, causing the gel to revert to a liquid state. Therefore, this invention requires that the amine compounds in the prepared deep eutectic solvent be tertiary or secondary amines.

[0041] In some embodiments, when the amine compound in step (1) is a secondary or tertiary amine compound, preferably one or more of 3-dimethylamino-1-propanol, N,N-diethylhydroxylamine, N-methylacetamide, N,N-dimethylformamide, 2-(methylamino)ethanol, and bis(2-hydroxyethyl)amino(tris(hydroxymethyl)methane), a sulfone compound, an alkali metal salt, and the secondary or tertiary amine compound are mixed and stirred to obtain a deep eutectic solvent, wherein the amino group of the amine compound in the deep eutectic solvent is an imino or subamino group. The stirring is performed using magnetic or mechanical stirring for 10-30 minutes.

[0042] In other embodiments, when the amine compound in step (1) is a primary amine compound, preferably 1,3-diamino-2-hydroxypropane, a sulfone compound, an alkali metal salt, the primary amine compound, and an acrylate compound are mixed and stirred to obtain a deep eutectic solvent. During stirring, the primary amine compound and the acrylate compound react to convert the amino group in the primary amine compound into an imino or sub-amino group, so that the amino group in the amine compound in the deep eutectic solvent is an imino or sub-amino group. The stirring is magnetic or mechanical, and the stirring and reaction time is 2-8 hours. The molar ratio of the amino group to the acrylate double bond in the primary amine compound and the acrylate compound can be 1:1-1:2. Considering the influence of steric hindrance on catalytic performance, the ratio can be controlled at 1:1-1:1.5. The acrylate compound used is preferably a small molecule, such as methyl acrylate. Experiments revealed that directly mixing primary amine compounds with acrylate compounds to react and convert the primary amine compound into a secondary or tertiary amine compound resulted in the formation of a white precipitate, requiring the addition of an external solvent to prevent this. However, when primary amine compounds, acrylate compounds, metal salts, and sulfone compounds were simultaneously mixed and stirred, the interaction between the amine compounds, metal salts, and sulfone compounds dissolved the reaction products, forming a deep eutectic solvent, eliminating the need for external solvents. Furthermore, the metal salts could react with the carbonyl groups of the acrylates, reducing the electron cloud density of the double bonds and further facilitating the reaction. This invention involves mixing acrylate compounds with sulfone compounds, alkali metal salts, and primary amine compounds in a single pot. This process prepares a deep eutectic solvent while simultaneously converting the amino group of the primary amine compound into a secondary or imino group. This avoids reactions between the primary amine and the electrode and prevents interference with the Michael addition reaction of the mercapto group. The use of a reaction between acrylate compounds and primary amine compounds, rather than other methods to convert the primary amine into a secondary or imino group, aims to avoid introducing other solvents or impurities. Preferred acrylate compounds are methyl acrylate or N-isoacrylamide, as shown in formula (I), which is the synthesis of 1,3-diamino-2-hydroxypropane derivatives containing imino groups and their deep eutectic solvents by reacting primary amine 1,3-diamino-2-hydroxypropane with methyl acrylate in the presence of sulfolane and metal salt, wherein n = 2 to 4, and the formula shows the reaction when n = 2.

[0043]

[0044] In some embodiments, in step (2), the first reactant is one or more of pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), and octamercaptopolyhedral oligomeric silsesquioxane; the second reactant is one or more of polyethylene glycol (diol) diacrylate and polyethylene glycol dimethacrylate; the relative molecular mass of the polyethylene glycol (diol) diacrylate and polyethylene glycol dimethacrylate is 300 to 1000.

[0045] In some embodiments, the molar ratio of the thiol group in the first reactant containing the thiol terminal in step (2) to the double bond in the second reactant is 3:1 to 1:3.

[0046] In some embodiments, in step (1), the molar ratio of the amine compound, alkali metal salt, and sulfolane in the deep eutectic solvent is 0.01–1:1:3–10, more preferably 0.1–1:1:3–10. By controlling the proportions of the components in the deep eutectic solvent, the reaction rate and the electrochemical performance of the prepared polymer electrolyte can be adjusted. Step (1) involves stirring for 10–30 min to form the deep eutectic solvent; Step (3) involves mixing the reactant mixture with the deep eutectic solvent from step (1) and stirring for 30 s–30 min to obtain the reaction precursor solution.

[0047] In some embodiments, the mass ratio of the reactant mixture solution to the deep eutectic solvent in step (3) is 1:1 to 1:6.

[0048] In some embodiments, the diaphragm in step (4) is a cellulose diaphragm, a polyethylene diaphragm, or a polypropylene diaphragm.

[0049] This invention involves an in-situ thiol-Michael addition reaction on a membrane. The Michael addition reaction time for the thiol-double bond should not be less than 1 minute, and in this invention, the reaction time ranges from 1 minute to 12 hours. If the reaction time is too short, or if the reaction occurs before the electrolyte has transferred to the membrane surface, a uniform polymer electrolyte cannot be formed on the membrane surface. This results in insufficient contact between the electrolyte and the electrode, preventing in-situ battery assembly and increasing the impedance between the electrolyte and the electrode, ultimately affecting battery performance. However, if the Michael addition reaction time for the thiol-double bond is too long, it is also detrimental to improving the electrolyte preparation efficiency. Traditional thiol-double bond Michael addition reactions generally employ triethylamine Lewis base catalysis or free radical initiation polymerization, which results in excessively fast reaction rates or requires polymerization under light or heat conditions. These methods are unsuitable for the in-situ preparation of the polymer electrolyte of this invention, and all of these methods leave non-electrolyte components in the electrolyte, affecting electrolyte performance. This invention, through the specific selection of the components of the deep eutectic solvent, enables a moderate reaction rate for the in-situ preparation of the polymer electrolyte, resulting in a stable electrolyte structure and excellent performance.

[0050] The polymer electrolyte prepared by the in-situ preparation method of this invention is expected to be used in any alkali metal battery, including lithium-ion batteries, potassium-ion batteries, and sodium-ion batteries. In this invention, the reaction precursor liquid described in step (3) is transferred to the surface of a separator to obtain a separator loaded with the reaction precursor liquid, which is then assembled in situ into an alkali metal battery. Taking the assembly of a lithium-ion battery as an example, the positive electrode uses lithium iron phosphate, lithium cobalt oxide, or lithium nickel cobalt manganese oxide (LiNi). x Coy Mn 1-x-y O2) Ternary cathode material or lithium nickel cobalt aluminum oxide ternary cathode material, with metallic lithium as the anode.

[0051] Deep eutectic solvents are a class of highly promising, green, non-toxic, low-cost liquid solvents with high ionic conductivity. A key characteristic of deep eutectic solvents is that the melting point of the mixture is significantly lower than that of the pure components. Mixing several solid components to form a deep eutectic solvent can better improve the compatibility of each component and ensure its uniform dispersion. Furthermore, its designability offers significant advantages in the in-situ preparation of electrolytes, and it holds great potential for improving electrolyte performance. Therefore, the development of deep eutectic solvents suitable for lithium-ion batteries has become a research hotspot.

[0052] This invention discloses an in-situ preparation method for polymer electrolytes, which relies on the Michael addition reaction of thiol-double bonds catalyzed by a deep eutectic solvent. The metal salts and amine compounds in the deep eutectic solvent act as catalysts in the Michael addition reaction, while the metal salts and sulfone compounds regulate the reaction rate. Through hydrogen bonding between the metal salts and the amine and sulfone compounds, the melting point of the mixture of solid components is lowered, resulting in a liquid at room temperature. No external solvent is required in the system. Compared with existing technologies, this method solves the problem of the difficulty in using in-situ polymerization for the Michael addition reaction of thiol-double bonds. Furthermore, the use of a deep eutectic solvent as the liquid component improves the safety performance of lithium-ion batteries, simplifies the preparation process, and reduces costs, providing an efficient method for preparing high-performance gel polymer electrolyte lithium-ion batteries.

[0053] This invention first constructs a deep eutectic solvent capable of catalyzing the Michael addition reaction of thiol-double bonds. The reaction rate is controlled by adjusting the composition of the deep eutectic solvent and its proportion in the electrolyte. For example, increasing the concentration of amine compounds in the deep eutectic solvent increases the reaction rate while keeping other conditions constant. Similarly, adjusting the concentration of the deep eutectic solvent in the precursor solution (i.e., decreasing or increasing the monomer concentration (first reactant or second reactant)) while keeping the deep eutectic solvent composition constant also affects the reaction rate; a higher concentration of the deep eutectic solvent results in a slower reaction rate. This invention constructs a gel polymer electrolyte by in-situ Michael addition reaction of thiol-double bonds on a membrane. The reaction time ranges from 1 minute to 12 hours, preferably from 2 minutes to 2 hours. The gel polymer electrolyte prepared according to this method has been experimentally proven to be suitable for use as an electrolyte in lithium-ion batteries, exhibiting high ionic conductivity, reaching 1.69 × 10⁻⁶ at 30°C. -4 S cm -1 This facilitates the conduction of ions in the electrolyte.

[0054] The following is an example:

[0055] The conductivity tests in the following examples are performed using the following methods: two steel sheets are used as symmetrical electrodes, and the ionic conductivity is calculated by impedance testing; the full battery capacity and cycle stability are tested using a lithium anode-lithium iron phosphate cathode; and the oxidation voltage of the electrolyte is tested using a lithium anode-stainless steel sheet electrode by linear sweep voltammetry.

[0056] Example 1:

[0057] An in-situ preparation method for a polymer electrolyte, the preparation method is as follows:

[0058] (1) Weigh 8.112 g of sulfolane, 1.938 g of lithium bis(trifluoromethanesulfonyl)imide, 0.06 g of 1,3-diamino-2-hydroxypropane and 0.116 g of methyl acrylate and place them in a round-bottom flask. After stirring magnetically for 2 hours, a deep eutectic solvent of 1,3-diamino-2-hydroxypropane is obtained; wherein the molar ratio of sulfolane, lithium bis(trifluoromethanesulfonyl)imide, 1,3-diamino-2-hydroxypropane and methyl acrylate is 10:1:0.1:0.2. Figure 2 The NMR spectra before and after preparation with a deep eutectic solvent containing 1,3-diamino-2-hydroxypropane derivatives show that the double bond characteristic peaks have completely disappeared, proving that the reaction is complete.

[0059] (2) The first reactant containing thiol-terminated pentaerythritol tetra(3-mercaptopropionate) and the second reactant containing acrylate-terminated polyethylene glycol diacrylate with a relative molecular mass of 600 are mixed to obtain a mixed solution of the reactants; wherein the molar ratio of the thiol-terminated first reactant to the double bond of the second reactant is 1:1. The specific preparation process is as follows: Weigh 0.728g of polyethylene glycol diacrylate with a relative molecular mass of 600 and 0.272g of pentaerythritol tetra(3-mercaptopropionate), put them into a 10ml glass bottle and stir to mix evenly to obtain a mixed solution of the reactants;

[0060] (3) Add 6g of the deep eutectic solvent in step (1) to the mixed solution of the reactants in step (2), mix evenly to obtain the reaction precursor solution, wherein the mass ratio of the mixed solution of the reactants to the deep eutectic solvent is 1:6;

[0061] (4) After magnetically stirring the reaction precursor solution in step (3) for 60 seconds, take it out and transfer it onto a cellulose membrane. Using lithium metal as the negative electrode and lithium iron phosphate as the positive electrode, assemble a lithium-ion button battery. The monomer forms a polymer gel electrolyte in situ after 1 hour under the catalysis of a deep eutectic solvent. Its ionic conductivity at 30°C is 1.54 × 10⁻⁶. -4 S cm -1The lithium-iron phosphate full battery exhibits a capacity of 142 mAh / g at 60°C and a 1C rate. Furthermore, experimental observations show that the polymer gel electrolyte remains in a well-preserved gel state after 72 hours, indicating that the gel polymer electrolyte prepared in this embodiment has good stability.

[0062] Comparative Example 1

[0063] Comparative Example 1 was identical to Example 1 under all other conditions except that the proportion of the deep eutectic solvent in the precursor solution was reduced, increasing the mass ratio of the mixed solution of reactants to the deep eutectic solvent to 2:1. This accelerated the reaction rate, and the monomers could form a polymer gel in situ within 1 minute under the catalysis of the deep eutectic solvent. The polymer gel electrolyte remained in a good gel state after 72 hours.

[0064] Comparative Example 2

[0065] Comparative Example 2 was identical to Example 1 under all other conditions except that the proportion of the deep eutectic solvent in the precursor solution was increased, reducing the mass ratio of the mixed solution of the reactants to the deep eutectic solvent to 1:8. This reduced the reaction rate, and because the monomer component was too small, it was impossible to fix all the deep eutectic solvents. In addition to the polymer gel, a flowable liquid was found.

[0066] Comparative Example 3

[0067] Other conditions are the same as in Example 1. The difference is that methyl acrylate was not introduced into the eutectic solvent prepared in Example 1. The experiment found that the obtained eutectic solvent could also catalyze the monomers in the precursor solution to form a gel polymer network. However, after 12 hours, it was observed that the polymer electrolyte was in a flowable liquid state and was no longer in a gel state. The reason for this may be that the polymer electrolyte network reacted with the primary amine in it, causing the polymer network to degrade and making it impossible to prepare a stable gel polymer electrolyte in situ.

[0068] Patent CN114853621A discloses a method for catalyzing the double addition reaction of primary amines and acrylates. An aminoene polymer network is prepared using lithium difluorooxalate borate catalyst and sulfolane small molecule plasticizer solvent. However, the solvent composed of this salt and plasticizer cannot allow the thiol group to react with the double bond at room temperature. Moreover, its aminoene network is more likely to react with the lithium anode than thiolene, resulting in rapid capacity decay of the battery. The thiolene network catalyzed by the deep eutectic solvent has a stronger interaction force between the components and a stable thiolene polymer network, which greatly improves the oxidation stability and cycle stability of the electrolyte and realizes the in-situ preparation of the electrolyte.

[0069] Comparative Example 4

[0070] With other conditions unchanged, the proportion of the amine compound 1,3-diamino-2-hydroxypropane derivative from Example 1 was increased. A deep eutectic solvent was prepared by mixing sulfolane, lithium bis(trifluoromethanesulfonyl)imide, and the 1,3-diamino-2-hydroxypropane derivative in a molar ratio of 5:1:2. The preparation process was as follows: 4.326 g of sulfolane, 2.067 g of lithium bis(trifluoromethanesulfonyl)imide, 1.299 g of 1,3-diamino-2-hydroxypropane, and 2.481 g of methyl acrylate were weighed and placed in a round-bottom flask. After magnetic stirring for 2 hours, a deep eutectic solvent of 1,3-diamino-2-hydroxypropane was obtained. Then, the polymer electrolyte was prepared using the same method as in Example 1. Experiments showed that when the 1,3-diamino-2-hydroxypropane derivative was in significant excess, the capacity of the lithium-iron phosphate full battery decreased to 102.18 mAh / g, indicating that the content of the amine catalytic component should not be excessive.

[0071] Example 2

[0072] An in-situ preparation method for a polymer electrolyte, the preparation method is as follows:

[0073] (1) Weigh 4.867 g of sulfolane, 3.876 g of lithium bis(trifluoromethanesulfonyl)imide, 0.122 g of 1,3-diamino-2-hydroxypropane and 0.233 g of methyl acrylate and place them in a round-bottom flask. After stirring magnetically for 2 hours, a deep eutectic solvent of 1,3-diamino-2-hydroxypropane is obtained; wherein the molar ratio of sulfolane, lithium bis(trifluoromethanesulfonyl)imide, 1,3-diamino-2-hydroxypropane and methyl acrylate is 3:1:0.1:0.2.

[0074] (2) The first reactant containing thiol-terminated pentaerythritol tetra(3-mercaptopropionate) and the second reactant containing methacrylate-terminated polyethylene glycol dimethacrylate with a relative molecular mass of 550 are mixed to obtain a mixed solution of the reactants; wherein the molar ratio of the thiol-terminated first reactant to the double bond of the second reactant is 1:1. The specific preparation process is as follows: Weigh 0.728g of polyethylene glycol dimethacrylate with a relative molecular mass of 550 and 0.272g of pentaerythritol tetra(3-mercaptopropionate), put them into a 10ml glass bottle and stir to mix evenly to obtain a mixed solution of the reactants;

[0075] (3) Add 5g of the deep eutectic solvent in step (1) to the mixed solution of the reactants in step (2), mix evenly to obtain the reaction precursor solution, wherein the mass ratio of the mixed solution of the reactants to the deep eutectic solvent is 1:5;

[0076] (4) After magnetically stirring the reaction precursor solution from step (3) for 60 seconds, it was taken out and transferred to a cellulose membrane to assemble a lithium-ion button battery. The monomer formed a polymer gel electrolyte in situ after 12 hours under the catalysis of a deep eutectic solvent. The extended reaction time may be due to the electron-donating effect of the methyl group connected to the double bond and the decrease in catalyst content, which led to a significant decrease in the Michael addition reaction rate of the thiol-double bond. Experimental observation showed that the polymer gel electrolyte remained in a good gel state after 72 hours, indicating that the gel polymer electrolyte prepared in this example has good stability.

[0077] Example 3

[0078] An in-situ preparation method for a polymer electrolyte, the preparation method is as follows:

[0079] (1) Weigh 4.326 g of sulfolane, 1.378 g of lithium bis(trifluoromethanesulfonyl)imide, 0.345 g of lithium difluorooxalate borate, 0.065 g of 1,3-diamino-2-hydroxypropane and 0.124 g of methyl acrylate and place them in a round-bottom flask. After stirring magnetically for 2 hours, a deep eutectic solvent of 1,3-diamino-2-hydroxypropane is obtained; wherein the molar ratio of sulfolane, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, 1,3-diamino-2-hydroxypropane and methyl acrylate is 15:2:1:0.3:0.6;

[0080] (2) The first reactant containing thiol-terminated pentaerythritol tetra(3-mercaptopropionate) and the second reactant containing acrylate-terminated polyethylene glycol diacrylate with a relative molecular mass of 600 are mixed to obtain a mixed solution of the reactants; wherein the molar ratio of the thiol-terminated first reactant to the double bond of the second reactant is 1:1. The specific preparation process is as follows: Weigh 0.728g of polyethylene glycol diacrylate with a relative molecular mass of 600 and 0.272g of pentaerythritol tetra(3-mercaptopropionate), put them into a 10ml glass bottle and stir to mix evenly to obtain a mixed solution of the reactants;

[0081] (3) Add 3g of the deep eutectic solvent in step (1) to the mixed solution of the reactants in step (2), mix evenly to obtain the reaction precursor solution, wherein the mass ratio of the mixed solution of the reactants to the deep eutectic solvent is 1:3;

[0082] (4) After magnetically stirring the reaction precursor solution in step (3) for 60 seconds, take it out and transfer it onto a cellulose membrane to assemble a lithium-ion button battery. The monomers form a polymer gel electrolyte in situ after 10 minutes under the catalysis of a deep eutectic solvent, and its ionic conductivity at 30°C is 8.04 × 10⁻⁶. -5 S cm -1Experimental observation showed that the polymer gel electrolyte remained in a well-preserved gel state after 72 hours, indicating that the gel polymer electrolyte prepared in this example has good stability.

[0083] Example 4

[0084] An in-situ preparation method for a polymer electrolyte, the preparation method is as follows:

[0085] (1) Weigh 4.326 g of sulfolane, 1.378 g of lithium bis(trifluoromethanesulfonyl)imide, 0.345 g of difluorooxalate boric acid, 0.065 g of 1,3-diamino-2-hydroxypropane and 0.124 g of methyl acrylate and place them in a round-bottom flask. After stirring magnetically for 40 minutes, a deep eutectic solvent is obtained; wherein, the molar ratio of sulfolane, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate boric acid, 1,3-diamino-2-hydroxypropane and methyl acrylate is 15:2:1:0.3:0.6;

[0086] (2) The first reactant containing thiol-terminated pentaerythritol tetra(3-mercaptopropionate) and the second reactant containing acrylate-terminated polyethylene glycol diacrylate with a relative molecular mass of 600 are mixed to obtain a mixed solution of the reactants; wherein the molar ratio of the thiol-terminated first reactant to the double bond of the second reactant is 1:1. The specific preparation process is as follows: Weigh 0.728g of polyethylene glycol diacrylate with a relative molecular mass of 600 and 0.272g of pentaerythritol tetra(3-mercaptopropionate), put them into a 10ml glass bottle and stir to mix evenly to obtain a mixed solution of the reactants;

[0087] (3) Add 5g of the deep eutectic solvent A in step (1) to the mixed solution of the reactants in step (2), mix evenly to obtain the reaction precursor solution, wherein the mass ratio of the mixed solution of the reactants to the deep eutectic solvent is 1:5;

[0088] (4) After magnetically stirring the reaction precursor solution in step (3) for 60 seconds, take it out and transfer it onto a cellulose membrane to assemble a lithium-ion button battery. The monomer forms a polymer gel electrolyte in situ after 1 hour under the catalysis of a deep eutectic solvent, and its ionic conductivity at 30°C is 1.69 × 10⁻⁶. -4 S cm -1 Experimental observation showed that the polymer gel electrolyte remained in a well-preserved gel state after 72 hours, indicating that the gel polymer electrolyte prepared in this example has good stability. Figure 3 The graph shows the change in conductivity of the gel polymer electrolyte prepared in this embodiment with temperature. It can be seen that the ionic conductivity of the gel polymer electrolyte increases continuously with increasing temperature. Figure 4 This is an electrochemical stability window diagram of the polymer electrolyte prepared in this embodiment, with an oxidation voltage of 4.8V.

[0089] Example 5

[0090] An in-situ preparation method for a polymer electrolyte, the preparation method is as follows:

[0091] (1) Weigh 4.326 g of sulfolane, 1.378 g of lithium bis(trifluoromethanesulfonyl)imide, 0.345 g of difluorooxalate boric acid, 0.065 g of 1,3-diamino-2-hydroxypropane and 0.124 g of methyl acrylate and place them in a round-bottom flask. After stirring magnetically for 40 minutes, a deep eutectic solvent is obtained; wherein, the molar ratio of sulfolane, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate boric acid, 1,3-diamino-2-hydroxypropane and methyl acrylate is 15:2:1:0.3:0.6;

[0092] (2) The first reactant containing thiol-terminated pentaerythritol tetra(3-mercaptopropionate) and the second reactant containing acrylate-terminated polyethylene glycol diacrylate with a relative molecular mass of 600 are mixed to obtain a mixed solution of the reactants; wherein the molar ratio of the thiol-terminated first reactant to the double bond of the second reactant is 3:1. The specific preparation process is as follows: Weigh 0.88g of polyethylene glycol diacrylate with a relative molecular mass of 600 and 0.12g of pentaerythritol tetra(3-mercaptopropionate), put them into a 10ml glass bottle and stir to mix evenly to obtain a mixed solution of the reactants;

[0093] (3) Add 1g of the deep eutectic solvent in step (1) to the mixed solution of the reactants in step (2), mix evenly to obtain the reaction precursor solution, wherein the mass ratio of the mixed solution of the reactants to the deep eutectic solvent is 1:1;

[0094] (4) After magnetically stirring the reaction precursor solution in step (3) for 30 seconds, the solution was transferred to a cellulose membrane and used to assemble a lithium-ion button battery. The monomers formed a polymer gel electrolyte in situ under the catalysis of a deep eutectic solvent. Experimental observation showed that the polymer gel electrolyte remained in a good gel state after 72 hours, indicating that the gel polymer electrolyte prepared in this example had good stability.

[0095] Example 6

[0096] An in-situ preparation method for a polymer electrolyte, the preparation method is as follows:

[0097] (1) Weigh 4.326 g of sulfolane, 1.378 g of lithium bis(trifluoromethanesulfonyl)imide, 0.345 g of difluorooxalate boric acid, 0.065 g of 1,3-diamino-2-hydroxypropane and 0.124 g of methyl acrylate and place them in a round-bottom flask. After stirring magnetically for 40 minutes, a deep eutectic solvent is obtained; wherein, the molar ratio of sulfolane, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate boric acid, 1,3-diamino-2-hydroxypropane and methyl acrylate is 15:2:1:0.3:0.6;

[0098] (2) The first reactant containing thiol-terminated pentaerythritol tetra(3-mercaptopropionate) and the second reactant containing acrylate-terminated polyethylene glycol diacrylate with a relative molecular mass of 600 are mixed to obtain a mixed solution of the reactants; wherein the molar ratio of the thiol-terminated first reactant to the double bond of the second reactant is 1:3. The specific preparation process is as follows: Weigh 0.485g of polyethylene glycol diacrylate with a relative molecular mass of 600 and 0.515g of pentaerythritol tetra(3-mercaptopropionate), put them into a 10ml glass bottle and stir to mix evenly to obtain a mixed solution of the reactants;

[0099] (3) Add 1g of the deep eutectic solvent in step (1) to the mixed solution of the reactants in step (2), mix evenly to obtain the reaction precursor solution, wherein the mass ratio of the mixed solution of the reactants to the deep eutectic solvent is 1:1;

[0100] (4) After magnetically stirring the reaction precursor solution in step (3) for 30 seconds, the solution was transferred to a cellulose membrane and used to assemble a lithium-ion button battery. The monomers formed a polymer gel electrolyte in situ under the catalysis of a deep eutectic solvent. Experimental observation showed that the polymer gel electrolyte remained in a good gel state after 72 hours, indicating that the gel polymer electrolyte prepared in this example had good stability.

[0101] Example 7

[0102] An in-situ preparation method for a polymer electrolyte, the preparation method is as follows:

[0103] (1) Weigh 4.326 g of sulfolane, 1.378 g of lithium bis(trifluoromethanesulfonyl)imide, 0.345 g of lithium difluorooxalate borate and 0.193 g of N,N-diethylhydroxylamine and place them in a round-bottom flask. After stirring magnetically for 40 minutes, a deep eutectic solvent is obtained; wherein, the molar ratio of sulfolane, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate and N,N-diethylhydroxylamine is 15:2:1:0.9;

[0104] (2) The first reactant containing thiol-terminated pentaerythritol tetra(3-mercaptopropionate) and the second reactant containing acrylate-terminated polyethylene glycol diacrylate with a relative molecular mass of 600 are mixed to obtain a mixed solution of the reactants; wherein the molar ratio of the thiol-terminated first reactant to the double bond of the second reactant is 1:1. The specific preparation process is as follows: Weigh 0.728g of polyethylene glycol diacrylate with a relative molecular mass of 600 and 0.272g of pentaerythritol tetra(3-mercaptopropionate), put them into a 10ml glass bottle and stir to mix evenly to obtain a mixed solution of the reactants;

[0105] (3) Add 4g of the deep eutectic solvent in step (1) to the mixed solution of the reactants in step (2), mix evenly to obtain the reaction precursor solution, wherein the mass ratio of the mixed solution of the reactants to the deep eutectic solvent is 1:4;

[0106] (4) After magnetically stirring the reaction precursor solution from step (3) for 60 seconds, the solution was transferred to a cellulose membrane and used to assemble a lithium-ion button battery. The monomers formed a polymer gel electrolyte in situ after 10 minutes under the catalysis of a deep eutectic solvent. Experimental observation showed that the polymer gel electrolyte remained in a good gel state after 72 hours, indicating that the gel polymer electrolyte prepared in this example had good stability.

[0107] In addition to the specific types of polyethylene glycol diacrylate and polyethylene glycol dimethacrylate used in the above embodiments, the polyethylene glycol diacrylate and polyethylene glycol dimethacrylate applicable to the preparation method of the gel polymer electrolyte proposed in this invention can also be any one of those with a relative molecular mass of 300 to 1000. In addition to the specific types of reactants containing thiol terminals used in the above embodiments, the reactants containing thiol terminals applicable to the preparation method of the polymer electrolyte proposed in this invention can also be any one of trimethylolpropane tris(3-mercaptopropionate) and octamercaptopolyhedral oligomeric silsesquioxane. In addition to the cellulose membranes specifically used in the above embodiments, the preparation method of the polymer electrolyte proposed in this invention is also applicable to any one of polyethylene membranes and polypropylene membranes.

[0108] The deep eutectic solvent used in this invention lowers the melting point of the mixture compared to the pure substance due to the interactions between amine compounds and metal salts, and between sulfone compounds and metal salts, causing it to become liquid at room temperature. Therefore, the amine compounds, sulfone compounds, and metal salts in the deep eutectic solvent are not limited to one or more of the above embodiments. Furthermore, since amine compounds and metal salts are widely used as Lewis base catalysts and co-catalysts for the Michael addition reaction of mercapto-double bonds, they can be flexibly selected according to the specific mercapto-double bond Michael addition reaction. Moreover, the gel polymer electrolyte in this invention can be applied to lithium-ion batteries, sodium-ion batteries, and potassium-ion batteries; therefore, the added metal salt can be one or more of the lithium salts, sodium salts, and potassium salts commonly used in various alkali metal batteries in the prior art.

[0109] The deep eutectic solvents used in this invention include both deep eutectic solvents formed by amine compounds and metal salts to catalyze the Michael addition reaction of mercapto-double bonds and deep eutectic solvents formed by sulfone compounds and metal salts to regulate the reaction rate. Therefore, the reaction rate of the Michael addition reaction of mercapto-double bonds can be controlled by adjusting the composition of the deep eutectic solvent, and the time for the monomer to form a gel polymer electrolyte in situ can be controlled according to actual needs.

[0110] This invention provides an in-situ preparation method for polymer electrolytes and its application. It relies on a deep eutectic solvent-catalyzed Michael addition reaction of thiol-double bonds. Through hydrogen bonding between metal salts and amine and sulfone compounds, the melting point of the mixture of solid components is lowered, resulting in a liquid state at room temperature. No external solvent is required, solving the problem that in-situ polymerization of thiol-double bond Michael addition reactions is not possible. Furthermore, using a deep eutectic solvent as the liquid component improves the safety performance of lithium-ion batteries, simplifies the preparation process, and reduces costs. The time for in-situ formation of the gel polymer electrolyte from the monomer reaction can be controlled by adjusting the composition of the deep eutectic solvent, and the performance of the lithium-ion gel polymer electrolyte battery can be modulated by changing the types of amine, sulfone, and metal salts.

[0111] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An in-situ preparation method of a polymer electrolyte, characterized by, Includes the following steps: (1) A sulfone compound, an alkali metal salt, and an amine compound are mixed and stirred to obtain a deep eutectic solvent; the amine compound contains at least one of hydroxyl, urea, and amide groups, and the amino group of the amine compound in the deep eutectic solvent obtained after stirring is an imino or subamino group; the sulfone compound is sulfolane and / or divinyl sulfone; the molar ratio of the amine compound, the alkali metal salt, and the sulfone compound is 0.1~1:1:3~10; When the amine compound is a secondary or tertiary amine compound, such as 3-dimethylamino-1-propanol, N,N-diethylhydroxylamine, N-methylacetamide, N,N-dimethylformamide, 2-(methylamino)ethanol, and bis(2-hydroxyethyl)amino(trihydroxymethyl)methane, a sulfone compound, an alkali metal salt, and the secondary or tertiary amine compound are mixed and stirred to obtain a deep eutectic solvent, wherein the amino group of the amine compound in the deep eutectic solvent is an imino or subamino group; When the amine compound is the primary amine compound 1,3-diamino-2-hydroxypropane, a sulfone compound, an alkali metal salt, the primary amine compound, and an acrylate compound are mixed, stirred, and reacted to obtain a deep eutectic solvent. During the stirring process, the primary amine compound and the acrylate compound react to convert the amino group in the primary amine compound into an imino or subamino group, so that the amino group in the amine compound in the deep eutectic solvent is an imino or subamino group. (2) Mix the first reactant containing thiol ends with the second reactant containing acrylate or methacrylate ends at both ends to obtain a mixed solution of reactants; (3) Mix the reactant mixture solution described in step (2) with the eutectic solvent described in step (1) to obtain a reaction precursor solution; the mass ratio of the reactant mixture solution to the eutectic solvent is 1:1 to 1:

6. (4) The reaction precursor liquid described in step (3) is transferred to the surface of the membrane to obtain a membrane loaded with the reaction precursor liquid, and assembled in situ into an alkali metal battery; the first reactant and the second reactant undergo a thiol-double bond Michael addition reaction in situ on the membrane under the catalysis of the deep eutectic solvent to form a cross-linked network, thereby obtaining a polymer electrolyte loaded on the membrane.

2. The in-situ production method of claim 1, wherein, The alkali metal salt is a lithium salt, a sodium salt, or a potassium salt.

3. The in-situ production method of claim 1, wherein, Step (2) The first reactant is one or more of pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), and octamercaptopolyhedral oligomeric silsesquioxane; the second reactant is one or more of polyethylene glycol diacrylate and polyethylene glycol dimethacrylate; the relative molecular mass of the polyethylene glycol diacrylate and polyethylene glycol dimethacrylate is 300~1000.

4. The in-situ preparation method as described in claim 1, characterized in that, In step (2), the molar ratio of the thiol group in the first reactant containing the thiol terminal to the double bond in the second reactant is 3:1 to 1:

3.

5. The in-situ preparation method as described in claim 1, characterized in that, The diaphragm in step (4) is a cellulose diaphragm, a polyethylene diaphragm, or a polypropylene diaphragm.

6. The in-situ production method of claim 1, wherein, The Michael addition reaction of the mercapto-double bond takes no less than 1 minute.

7. A polymer electrolyte prepared by the in-situ preparation method according to any one of claims 1 to 6.

8. An alkali metal battery, characterized in that, A polymer electrolyte comprising the polymer electrolyte according to claim 7.

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