Multifunctional monomer and preparation method thereof, solid electrolyte, lithium ion battery and power-related equipment

Abstract

The invention provides a multifunctional monomer and a preparation method thereof, a solid electrolyte, a lithium ion battery and electric equipment. The polyfunctional monomer has a structure as shown in a formula (1), when the polyfunctional monomer is used as a reactant raw material and is subjected to in-situ curing in electrolyte to form the solid electrolyte, the functionality of the polyfunctional monomer is relatively high, and the polyfunctional monomer can form a highly cross-linked polymer network structure in a polymerization reaction process; the structure endows the polymer with excellent mechanical properties, such as high strength and high modulus, so that the polymer can maintain better structural stability when bearing external stress, the high voltage resistance of the polymer structure is improved, the solid electrolyte is not easy to decompose or crack and lose efficacy, the structural damage of the electrolyte material in the charging and discharging process is inhibited, and the service life of the electrolyte material is prolonged. The electrochemical stability of the electrolyte material is maintained, so that the service life and the safety of the battery are prolonged, and the charge-discharge performance of the battery is maintained.

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and in particular relates to a multifunctional monomer and a preparation method thereof, a solid electrolyte, a lithium-ion battery and electrical equipment. Background Art

[0002] Solid-state batteries, a cutting-edge battery technology, have garnered significant attention in recent years for their high energy density and safety. Using solid electrolytes instead of the liquid electrolytes found in traditional lithium-ion batteries, solid-state batteries significantly reduce the risk of thermal runaway and combustion. The energy density of solid-state batteries is directly proportional to their operating voltage. Therefore, improving a battery's high-voltage tolerance directly increases its energy density, which is crucial for applications requiring high-energy-density batteries, such as electric vehicles and aerospace.

[0003] However, in related technologies, solid electrolytes are prone to decomposition under high voltage conditions, which reduces the overall performance of the battery and needs further improvement. Summary of the Invention

[0004] The embodiments of the present application provide a multifunctional monomer and a preparation method thereof, a solid electrolyte, a lithium-ion battery and electrical equipment, aiming to solve the aforementioned technical problems.

[0005] In a first aspect, an embodiment of the present application provides a multifunctional monomer for use in a solid electrolyte, wherein the multifunctional monomer has a structure as shown in formula (1): Formula (1); Wherein, R1, R2, R3, R4, R5, and R6 are each independently selected from an acrylate group or a hydroxyl group, and at most only one of R1, R2, R3, R4, R5, and R6 is a hydroxyl group, and R7 is selected from an alkyl group or a cycloalkyl group.

[0006] In one embodiment, R7 has a structure as shown in Formula (2) or Formula (3): Formula (2); Formula (3); wherein n1 is selected from an integer of 0-10, n2 is selected from an integer of 0-10, n3 is selected from an integer of 0-3, and the sum of n1 and n2 is between 1-10; n4 is selected from an integer of 0-5, n5 is selected from an integer of 0-5, n6 is selected from an integer of 0-3, n7 is selected from an integer of 0-3, and the sum of n4 and n5 is between 1-10.

[0007] In one embodiment, n1 is selected from an integer between 3 and 10, n2 is selected from an integer between 0 and 2, n3 is selected from an integer between 0 and 1, and the sum of n1 and n2 is between 3 and 10; and / or n4 is selected from an integer of 0-2, n5 is selected from an integer of 0-2, n6 is selected from an integer of 0-1, n7 is selected from an integer of 0-1, and the sum of n4 and n5 is 4.

[0008] In one embodiment, the multifunctional monomer includes at least one of the following compounds: 、 、 、 、 、 、 、 .

[0009] In one embodiment, the functionality of the multifunctional monomer is between 5 and 6; and / or The multifunctional monomer has a symmetrical molecular structure.

[0010] In a second aspect, an embodiment of the present application provides a method for preparing a multifunctional monomer, the preparation method comprising: Provide trifunctional acrylate monomers and diisocyanate compounds; reacting the trifunctional acrylate monomer and the diisocyanate compound to obtain the multifunctional monomer; Wherein, the multifunctional monomer has a structure as shown in formula (1): Formula (1); Wherein, R1, R2, R3, R4, R5, and R6 are each independently selected from an acrylate group or a hydroxyl group, and at most only one of R1, R2, R3, R4, R5, and R6 is a hydroxyl group, and R7 is selected from an alkyl group or a cycloalkyl group.

[0011] In one embodiment, the molar ratio between the trifunctional acrylate monomer and the diisocyanate compound is 2:(1-1.1); and / or The reaction temperature is 20°C-50°C.

[0012] In one embodiment, the preparation method of the trifunctional acrylate monomer includes: Provide pentaerythritol and acrylic acid; The pentaerythritol and the acrylic acid are subjected to an esterification reaction under catalyst conditions to generate the trifunctional acrylate monomer.

[0013] In one embodiment, the molar ratio between the pentaerythritol and the acrylic acid is 1:(3-3.1); and / or The reaction temperature is 20°C-50°C; and / or The structural formula of the diisocyanate compound is shown in formula (4): O=C=N-R7-N=C=O formula (4); Wherein, R7 is selected from alkyl or cycloalkyl.

[0014] In a third aspect, an embodiment of the present application provides a solid electrolyte, wherein the solid electrolyte is formed by solidifying a multifunctional monomer in an electrolyte; The multifunctional monomer is the multifunctional monomer described above or a multifunctional monomer obtained by the preparation method described above.

[0015] In one embodiment, the electrical conductivity of the solid electrolyte is 4 mS / cm-10 mS / cm.

[0016] In a fourth aspect, an embodiment of the present application provides a method for preparing a solid electrolyte, the preparation method comprising: Providing a prepolymer solution, wherein the prepolymer solution includes an electrolyte and a multifunctional monomer; causing the multifunctional monomer in the prepolymer solution to undergo an in-situ curing reaction to obtain the solid electrolyte; Wherein, the multifunctional monomer is the multifunctional monomer as described above or a multifunctional monomer obtained by the preparation method as described above.

[0017] In one embodiment, the curing reaction temperature is 40° C.-80° C., and / or the curing time is 12 h-72 h; and / or The viscosity of the prepolymer liquid at room temperature is 2mPa.s-8mPa.s; and / or The prepolymer solution further includes an initiator.

[0018] In one embodiment, the mass percentage of the multifunctional monomer in the prepolymer solution is 1%-5%; and / or The mass percentage of the electrolyte in the prepolymer solution is 94%-98.997%; and / or The electrolyte comprises a solvent, a lithium salt and / or an additive; and / or The mass percentage of the initiator in the prepolymer solution is 0.003%-0.15%; and / or The initiator includes at least one of an azo initiator and a peroxide initiator.

[0019] In one embodiment, the solvent includes at least one of a carbonate solvent and a carboxylate solvent; and / or The mass percentage of the solvent in the electrolyte is 79%-89%; and / or The lithium salt comprises at least one of lithium hexafluorophosphate, lithium perchlorate, lithium difluorooxalatoborate, lithium trifluoromethanesulfonyl imide, lithium bisfluorosulfonyl imide, lithium diacetate borate, lithium tetrafluoroborate, and lithium difluorophosphate; and / or The mass percentage of the lithium salt in the electrolyte is 10%-20%; and / or The additive comprises at least one of propane sultone, vinyl sulfate, and 1,3,6-hexane trinitrile; and / or The mass percentage of the additive in the electrolyte is 1%-5%.

[0020] In a fifth aspect, an embodiment of the present application provides a lithium-ion battery comprising the solid electrolyte as described above, or a solid electrolyte prepared using the method as described above.

[0021] In a sixth aspect, an embodiment of the present application provides an electrical device, comprising the solid electrolyte as described above, or a solid electrolyte prepared by the method as described above, or comprising the lithium-ion battery as described above.

[0022] Beneficial effects of the embodiments of the present application: The multifunctional monomer of the present application has a structure as shown in formula (1). When the multifunctional monomer is used as a reactant raw material to form a solid electrolyte by in-situ curing in an electrolyte, firstly, the acrylate group is a reactive functional group, the number of acrylate groups is at least 5, and the functionality of the multifunctional monomer is relatively high. The multifunctional monomer can form a highly cross-linked polymer network structure during the polymerization reaction. The highly cross-linked polymer network structure is like a tightly woven large net. The molecular chains are entangled and fixed with each other through a large number of chemical bonds, which greatly restricts the movement of the molecular chains. This structure gives the polymer excellent mechanical properties, such as high strength and high modulus, so that it can maintain good structural stability when subjected to external stress, and also improves the high voltage resistance of the polymer structure. The solid electrolyte is not easy to decompose or rupture and fail, and the structural damage of the electrolyte material during the charge and discharge process is suppressed, and the electrochemical stability of the electrolyte material is maintained, thereby extending the service life and safety of the battery and maintaining the charge and discharge performance of the battery.

[0023] Secondly, the carbamate group in the backbone chain of the multifunctional monomer gives the monomer molecule a strong polarity, allowing the multifunctional monomer to interact with the electrolyte solvent molecules to improve the conductivity. In addition, the carbamate group has a strong chemical bond energy and can enhance the structural stability of the solid electrolyte by forming hydrogen bonds and other interactions. This enhanced structural stability helps the solid electrolyte maintain its shape and integrity under high pressure, preventing performance degradation due to structural damage.

[0024] Thirdly, multifunctional monomers are polymerized to form cross-linked polymers, and the cross-linked polymers are combined with the electrolyte to form a solid electrolyte. The solid electrolyte contains carbamate groups. The nitrogen atoms and carbonyl oxygen atoms in the carbamate groups can form strong interactions with conductive ions. This interaction helps to stabilize the existence form of conductive ions and reduce the migration and aggregation of conductive ions under high voltage, thereby improving the high voltage resistance of the solid electrolyte.

[0025] Fourthly, after the polymerization reaction of the multifunctional monomer, both ends of the carbamate group on the main chain are bonded with larger ester side groups, and the nitrogen atom and carbonyl oxygen atom in the carbamate group have lone pairs of electrons, which makes the carbamate group as a whole carry a negative charge, thereby giving the carbamate group a stronger polarity, so that the carbamate group can enhance the electron cloud density of the ester side group connected to it, lowering the HOMO energy level (highest occupied molecular orbital energy level) of the cross-linked polymer, making it more difficult for the cross-linked polymer to lose electrons, and requiring greater external energy and higher voltage to be oxidized. Therefore, the larger ester side groups at both ends of the carbamate group act like a "protective umbrella", providing protection for the polymer molecular chain, so as to better resist the oxidation under external high voltage, reduce the oxidative decomposition or side reactions of the polymer, reduce the risk of oxidative degradation of the solid electrolyte in a high voltage environment, and thus improve the high voltage resistance of the solid electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] To more clearly illustrate the solutions in the present application or the prior art, a brief introduction to the drawings required for use in the embodiments or descriptions of the prior art is provided below. Obviously, the drawings described below are some embodiments of the present application. A person skilled in the art can derive other drawings based on these drawings without inventive effort. Figure 1 This is the infrared spectrum of the multifunctional monomer of Example 1 of the present application; Figure 2 This is a scanning curve diagram of the electrochemical stability window of the solid electrolyte of Example 1 of the present application; Figure 3 This is a high-voltage cycle curve diagram of the solid-state soft-pack full battery of Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, unless otherwise specified, the directional words used, such as "upper" and "lower", generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; and "inside" and "outside" refer to the outline of the device.

[0028] In related technologies, solid electrolytes are prone to decomposition under high voltage conditions, which reduces the overall performance of the battery and needs further improvement.

[0029] The present application provides a multifunctional monomer for use in solid electrolytes. The multifunctional monomer has a structure as shown in formula (1): Formula (1); Wherein, R1, R2, R3, R4, R5, and R6 are each independently selected from an acrylate group or a hydroxyl group, and at most only one of R1, R2, R3, R4, R5, and R6 is a hydroxyl group, and R7 is selected from an alkyl group or a cycloalkyl group.

[0030] In this embodiment, the multifunctional monomer of the present application has a structure as shown in formula (1). When the multifunctional monomer is used as a reactant raw material to form a solid electrolyte in situ solidification in an electrolyte, firstly, the acrylate group is a reactive functional group, the number of acrylate groups is at least 5, and the functionality of the multifunctional monomer is relatively high. The multifunctional monomer can form a highly cross-linked polymer network structure during the polymerization reaction. The highly cross-linked polymer network structure is like a tightly woven large net. The molecular chains are entangled and fixed with each other through a large number of chemical bonds, which greatly restricts the movement of the molecular chains. This structure gives the polymer excellent mechanical properties, such as high strength and high modulus, so that it can maintain good structural stability when subjected to external stress, and also improves the high voltage resistance of the polymer structure. The solid electrolyte is not easy to decompose or rupture and fail, and the structural damage of the electrolyte material during the charge and discharge process is suppressed, and the electrochemical stability of the electrolyte material is maintained, thereby extending the service life and safety of the battery and maintaining the charge and discharge performance of the battery.

[0031] Secondly, the carbamate group in the backbone chain of the multifunctional monomer gives the monomer molecule a strong polarity, allowing the multifunctional monomer to interact with the electrolyte solvent molecules to improve the conductivity. In addition, the carbamate group has a strong chemical bond energy and can enhance the structural stability of the solid electrolyte by forming hydrogen bonds and other interactions. This enhanced structural stability helps the solid electrolyte maintain its shape and integrity under high pressure, preventing performance degradation due to structural damage.

[0032] Thirdly, multifunctional monomers are polymerized to form cross-linked polymers, and the cross-linked polymers are combined with the electrolyte to form a solid electrolyte. The solid electrolyte contains carbamate groups. The nitrogen atoms and carbonyl oxygen atoms in the carbamate groups can form strong interactions with conductive ions. This interaction helps to stabilize the existence form of conductive ions and reduce the migration and aggregation of conductive ions under high voltage, thereby improving the high voltage resistance of the solid electrolyte.

[0033] Fourthly, after the polymerization reaction of the multifunctional monomer, both ends of the carbamate group on the main chain are bonded with larger ester side groups, and the nitrogen atom and carbonyl oxygen atom in the carbamate group have lone pairs of electrons, which makes the carbamate group as a whole carry a negative charge, thereby giving the carbamate group a stronger polarity, so that the carbamate group can enhance the electron cloud density of the ester side group connected to it, lowering the HOMO energy level (highest occupied molecular orbital energy level) of the cross-linked polymer, making it more difficult for the cross-linked polymer to lose electrons, and requiring greater external energy and higher voltage to be oxidized. Therefore, the larger ester side groups at both ends of the carbamate group act like a "protective umbrella", providing protection for the polymer molecular chain, so as to better resist the oxidation under external high voltage, reduce the oxidative decomposition or side reactions of the polymer, reduce the risk of oxidative degradation of the solid electrolyte in a high voltage environment, and thus improve the high voltage resistance of the solid electrolyte.

[0034] Fifthly, after the multifunctional monomer undergoes polymerization, both ends of the carbamate group on the backbone chain are bonded with larger ester side groups. Specific intermolecular interactions exist between the carbamate group and the larger ester side groups. These interactions prevent the polymer from generating free ionic fragment groups at high voltages (>4.5V). The solid electrolyte can match the high-voltage positive electrode and demonstrate a strong high-voltage resistance advantage. Taking lithium cobalt oxide as an example, during the charging process, lithium cobalt oxide forms high-valent tetravalent cobalt ions after delithiation. These high-valent cobalt ions are highly chemically active and easily react with surrounding substances, such as solvent molecules, resulting in an unstable surface structure of the positive electrode active particles. The substances surrounding the high-valent cobalt ions are easily oxidized and decomposed into ionic fragments. The carbamate and ester side groups in the polymer molecular chain can produce a good synergistic complexation with the tetravalent cobalt ions, "fixing" the cobalt ions on the surface of the positive electrode active particles through coordination chemistry, effectively stabilizing the metal ions on the surface of the positive electrode active particles, reducing the dissolution and migration of the metal ions, and improving the stability of the polymer molecular chain in high voltage fields. In addition, the intermolecular interaction between the carbamate group and the larger ester side groups also significantly improves the polymer molecular chain's ability to complex lithium ions and solvents. Under high voltage, the distribution of lithium ions is easily affected by the electric field and chemical reactions, leading to localized aggregation. By forming stable complexes with lithium ions and solvents, the polymer molecular chain can evenly disperse lithium ions, reduce localized aggregation of lithium ions, and enable lithium ions to be evenly and efficiently transmitted in the polymer electrolyte, thereby improving the high-voltage resistance of the polymer electrolyte and extending the battery's service life.

[0035] In one embodiment, R7 has a structure as shown in Formula (2) or Formula (3): Formula (2); Formula (3); wherein n1 is selected from an integer of 0-10, n2 is selected from an integer of 0-10, n3 is selected from an integer of 0-3, and the sum of n1 and n2 is between 1-10; n4 is selected from an integer of 0-5, n5 is selected from an integer of 0-5, n6 is selected from an integer of 0-3, n7 is selected from an integer of 0-3, and the sum of n4 and n5 is between 1-10.

[0036] In this embodiment, the sum of n1 and n2 is between 1-10, and / or the sum of n4 and n5 is between 1-10, which can ensure that the volume and molecular weight of the multifunctional monomer will not be too large. When the multifunctional monomer is added to the prepolymer solution, the viscosity of the prepolymer solution will not be too large, which is conducive to the wetting of the electrode by the prepolymer solution.

[0037] In one embodiment, n1 is selected from an integer between 3 and 10, n2 is selected from an integer between 0 and 2, n3 is selected from an integer between 0 and 1, and the sum of n1 and n2 is between 3 and 10.

[0038] In one embodiment, n4 is selected from an integer between 0 and 2, n5 is selected from an integer between 0 and 2, n6 is selected from an integer between 0 and 1, n7 is selected from an integer between 0 and 1, and the sum of n4 and n5 is 4.

[0039] In one embodiment, the multifunctional monomer includes at least one of the following compounds: 、 、 、 、 、 、 、 .

[0040] Using the multifunctional monomer of the above structure, R1, R2, R3, R4, R5, and R6 are each independently selected from an acrylate group or a hydroxyl group, and the number of functional groups is between 5 and 6. They can be efficiently cross-linked, thereby improving the structural stability of the polymer, and thus improving the high-voltage stability of the solid electrolyte. Moreover, the high functionality enables the multifunctional monomer to undergo polymerization reaction at a relatively low content to form a polymer network, so that the solid electrolyte can have better conductivity. The alkyl and cycloalkyl structures adopted by the R7 group control the values of the relevant n1 to n6 to ensure that the volume and molecular weight of the multifunctional monomer are not too large. When the multifunctional monomer is added to the prepolymer solution, the viscosity of the prepolymer solution is not too large, which is conducive to the wetting of the prepolymer solution on the electrode. In addition, the above-mentioned multifunctional monomer has a basically symmetrical molecular structure, which helps the multifunctional monomer molecules to approach each other more efficiently and react, thereby promoting the formation of a cross-linked structure and improving the structural stability of the material. Therefore, the above-mentioned multifunctional monomers show better effects in the viscosity of the prepolymer solution, the conductivity of the solid electrolyte, the high voltage resistance of the solid electrolyte and other properties, and perform better in the high voltage cycle performance of the battery.

[0041] In one embodiment, the number of functional groups of the multifunctional monomer is between 5 and 6. Optionally, the number of functional groups of the multifunctional monomer is 5 or 6. Functionality refers to the number of functional groups in a monomer molecule that can participate in the reaction, which is directly related to the reactivity of the reactants and the structural characteristics of the products. Generally speaking, the more functional groups there are, the more active points the monomer molecule has in the reaction, the faster the reaction rate, the greater the probability that the monomer molecule participates in the polymerization reaction, and the higher the degree of cross-linking of the resulting polymer. When the number of functional groups of the multifunctional monomer is less than 5, the structural stability of the polymer is easily reduced, and the solid electrolyte is prone to decomposition. When the number of functional groups of the multifunctional monomer is greater than 6, it is easy to cause the cross-linking points to be too dense, and the molecular pores constructed by the polymer molecular chains are small, which is not conducive to the absorption of electrolytes, nor is it conducive to the shuttling and conduction of conductive ions between the molecular pores, and it seriously hinders the flexible movement of the molecular chains, resulting in a significant decrease in the flexibility of the polymer, becoming stiff and brittle. At the same time, the tightly cross-linked network structure also limits the transmission of ions within the polymer, causing the ion transport performance of the solid electrolyte to deteriorate.

[0042] In this embodiment, the number of functionalities of the multifunctional monomer is set between 5 and 6, which can ensure that the generated polymer has an appropriate degree of cross-linking. At the same time, the carbamate groups on the trunk chain of the multifunctional monomer can give the monomer molecule stronger flexibility. The nitrogen atom and carbonyl oxygen atom in the carbamate group have greater polarity. The carbamate group can bring partial charge and steric hindrance weakening effect, and the carbamate group can produce specific intermolecular interactions with the large-volume ester side groups at both ends. This interaction reduces the energy barrier for the rotation and creep of the main chain of the polymer molecular chain, allowing the polymer molecular chain to rotate and creep to a certain extent when subjected to a small external force, thereby improving the mobility of the polymer molecular chain. This improvement in flexibility injects a "lubricant" into the originally rigid polymer network structure, allowing the polymer molecular chain to move freely to a certain extent, effectively offsetting the problems of decreased flexibility and reduced porosity of the polymer molecular chain caused by the high cross-linking degree of the side groups, and can improve the polymer molecular chain's ability to absorb and dissolve electrolytes and lithium salts. At the same time, the improvement of the mobility of polymer molecular chains by carbamate groups also indirectly improves the ion transmission performance. The enhancement of the mobility of polymer molecular chains opens up a smoother channel for the transmission of ions within the polymer, allowing ions to migrate more freely between polymer molecular chains, thereby improving the ion transmission efficiency of the solid electrolyte.

[0043] In one embodiment, the multifunctional monomer has a symmetrical molecular structure. In this embodiment, the high-functionality and structurally symmetrical multifunctional monomer shows a significant tendency to form a highly cross-linked polymer network structure during the polymerization reaction. High-functionality monomers mean that each monomer molecule has multiple active sites. When the polymerization reaction occurs, these active sites can react chemically with adjacent monomer molecules quickly and in large quantities to form multiple chemical bonds. The symmetrical structure makes the multifunctional monomer molecules have a regular arrangement in space. During the polymerization process, this regularity helps the monomer molecules to approach each other more efficiently and react, thereby promoting the formation of a cross-linked structure.

[0044] The high functionality and structural symmetry of the multifunctional monomers and the carbamate groups in the molecules each play a unique role in the polymer, and work together to give full play to their advantages to prepare solid electrolyte materials with excellent structural stability, high voltage resistance, good flexibility and efficient ion transport performance, meeting the battery's demand for high-performance materials.

[0045] The present application also provides a method for preparing a multifunctional monomer, the preparation method comprising: S1. Providing a trifunctional acrylate monomer and a diisocyanate compound; S2, reacting a trifunctional acrylate monomer with a diisocyanate compound to obtain a multifunctional monomer; The multifunctional monomer has a structure as shown in formula (1): Formula (1); Wherein, R1, R2, R3, R4, R5, and R6 are each independently selected from an acrylate group or a hydroxyl group, and at most only one of R1, R2, R3, R4, R5, and R6 is a hydroxyl group, and R7 is selected from an alkyl group or a cycloalkyl group.

[0046] In this embodiment, the trifunctional acrylate monomer refers to a monomer having a functionality of 3, and all functional groups are acrylate groups.

[0047] In one embodiment, the molar ratio of the trifunctional acrylate monomer to the diisocyanate compound is 2:(1-1.1).

[0048] In one embodiment, the reaction temperature of the trifunctional acrylate monomer and the diisocyanate compound is 20°C-50°C.

[0049] In one embodiment, the structural formula of the diisocyanate compound is shown in Formula (4): O=C=N-R7-N=C=O formula (4); Wherein, R7 is selected from alkyl or cycloalkyl.

[0050] In one embodiment, the preparation method of the trifunctional acrylate monomer includes: S11, providing pentaerythritol and acrylic acid; S12, allowing pentaerythritol and acrylic acid to undergo esterification reaction under catalyst conditions to generate trifunctional acrylate monomers.

[0051] In one embodiment, the molar ratio between pentaerythritol and acrylic acid is 1:(3-3.1).

[0052] In one embodiment, the reaction temperature of the esterification reaction is 75°C-80°C.

[0053] In a specific embodiment, the preparation method of the multifunctional monomer is as follows: S111. Add pentaerythritol, acrylic acid, p-toluenesulfonic acid, copper chloride, and cyclohexane into a flask; S112, while introducing an oxygen-containing gas (oxygen volume percentage of 5%, nitrogen volume percentage of 95%) into the flask, a dehydration esterification reaction was carried out at 75-80° C. for 12 hours, during which the generated water was discharged to the outside of the system using a fractionating tube; After the reaction in step S113 and step S112 is completed, n-propyl acetate and distilled water are added to the reaction solution for dilution, and the mixture is stirred thoroughly. The mixture is allowed to stand for separation into an aqueous phase (lower layer) and an organic solvent phase (upper layer), and the aqueous phase of the lower layer is removed. Subsequently, a 20 wt % aqueous sodium hydroxide solution is added to the organic solvent phase to neutralize the acid component contained in the organic solvent phase. The mixture is allowed to stand for separation into an aqueous phase (lower layer) and an organic solvent phase (upper layer), and the aqueous phase of the lower layer is removed. The organic solvent phase is recovered, and then distilled water is added to the recovered organic solvent phase for washing. The mixture is allowed to stand for separation, the aqueous phase (lower layer) is removed, and the organic solvent phase of the upper layer is recovered. S114, introducing dry air into the organic solvent phase finally recovered in step S113, and heating to 70° C. under reduced pressure to distill off the solvent, thereby obtaining trifunctional acrylate; S115. Take the above trifunctional acrylate, add a diisocyanate compound, first stir and react at room temperature for 5 hours, then stir and react at 50° C. for 2 hours to obtain a multifunctional monomer.

[0054] In this embodiment, the general reaction formula for preparing the multifunctional monomer is: .

[0055] In this embodiment, the preparation method of the multifunctional monomer is efficient and simple, and has the characteristics of low energy consumption, no pollution, and easy production.

[0056] The present application also provides a solid electrolyte, which is formed by solidifying a multifunctional monomer in an electrolyte; the multifunctional monomer is the multifunctional monomer described above or a multifunctional monomer obtained by the preparation method described above.

[0057] In one embodiment, the solid electrolyte has an electrical conductivity of 4mS / cm-10mS / cm. Because the polymer molecules comprising the solid electrolyte contain carbamate groups on their main chains, which have a high dielectric constant, these groups can more effectively conduct charge under an electric field, preventing localized charge accumulation. This efficient ion conduction helps maintain electrolyte stability in high-voltage environments while also improving the conductivity of the solid electrolyte.

[0058] The present application also provides a method for preparing a solid electrolyte, the preparation method comprising: S21, providing a prepolymer solution, wherein the prepolymer solution includes an electrolyte and a multifunctional monomer; S22, causing the multifunctional monomer in the prepolymer solution to undergo an in-situ curing reaction to obtain a solid electrolyte; The multifunctional monomer is the multifunctional monomer as described above or a multifunctional monomer obtained by the preparation method as described above.

[0059] In one embodiment, the viscosity of the prepolymer solution at room temperature is 2mPa.s-8mPa.s. Optionally, the viscosity of the prepolymer solution at room temperature can be any one of 2mPa.s, 3mPa.s, 5mPa.s, 7mPa.s, 8mPa.s, etc., or a range between any two thereof, without limitation herein. In this embodiment, the viscosity of the prepolymer solution at room temperature is relatively low. The low-viscosity prepolymer solution has better flow properties and can better infiltrate the electrode pores and diaphragm pores, making it easier to form a uniform and stable gel structure and continuous ion channels in the battery, thereby improving the high voltage resistance and ion transport performance of the solid electrolyte.

[0060] In one embodiment, the curing temperature of the curing reaction is 40° C.-80° C., and / or the curing time is 12 h-72 h.

[0061] In one embodiment, the prepolymer solution further includes an initiator, which can initiate a polymerization reaction between multifunctional monomers to improve the efficiency of the polymerization reaction.

[0062] In one embodiment, the mass percentage of the initiator in the prepolymer liquid is 0.003%-0.15%; alternatively, the mass percentage of the initiator in the prepolymer liquid can be any one of 0.003%, 0.005%, 0.01%, 0.05%, 0.15%, etc., or a range between any two of them, which is not limited here.

[0063] In one embodiment, the initiator includes at least one of an azo initiator and a peroxide initiator. For example, the initiator may include at least one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, benzoyl peroxide, and tert-butyl peroxybenzoate.

[0064] In one embodiment, the mass percentage of the multifunctional monomer in the prepolymer solution is 1%-5%. Alternatively, the mass percentage of the multifunctional monomer in the prepolymer solution can be any one of 1%, 2%, 3%, 4%, 5%, or any range between two thereof, without limitation herein. In this embodiment, the multifunctional monomer is a high-functionality monomer, each functionality being a reaction site. The dense concentration of reaction sites imparts high reactivity to the multifunctional monomer, enabling polymerization to occur at relatively low concentrations to form a polymer network, resulting in the polymerized molecular chain having good high-voltage resistance.

[0065] In this embodiment, when the mass percentage of the multifunctional monomer in the prepolymer solution is less than 1%, the multifunctional monomer cannot be effectively cured, the structure of the formed solid electrolyte is loose, and the mechanical properties, ion transport properties, and high voltage resistance of the solid electrolyte are reduced. When the mass percentage of the multifunctional monomer in the prepolymer solution is greater than 5%, the viscosity of the prepolymer solution is likely to be too high, which is not conducive to the wetting of the battery electrodes by the prepolymer solution, resulting in a decrease in the electrochemical performance of the battery.

[0066] In one embodiment, the mass percentage of the electrolyte in the prepolymer solution is 94%-98.997%. Alternatively, the mass percentage of the electrolyte in the prepolymer solution can be any one of 94%, 95%, 96%, 97%, 98.997%, etc., or any range between any two thereof, without limitation herein.

[0067] In one embodiment, the electrolyte includes a solvent, a lithium salt and / or an additive.

[0068] In one embodiment, the mass percentage of the solvent in the electrolyte is 79%-89%. Alternatively, the mass percentage of the solvent in the electrolyte can be any one of 79%, 82%, 84%, 86%, 89%, etc., or a range between any two of them, without limitation herein.

[0069] In one embodiment, the solvent includes at least one of a carbonate solvent and a carboxylate solvent. For example, the solvent may include at least one of propyl propionate, dimethyl carbonate, ethyl methyl carbonate, ethyl propionate, ethylene carbonate, and fluoroethylene carbonate. In this embodiment, the multifunctional monomer contains a carbamate group, which can enhance the structural stability of the solid electrolyte by forming hydrogen bonds with the above-mentioned solvent. This enhanced structural stability helps the solid electrolyte maintain its structural integrity at high voltages, reducing battery performance degradation caused by structural damage to the solid electrolyte.

[0070] In one embodiment, the mass percentage of the lithium salt in the electrolyte is 10%-20%; optionally, the mass percentage of the lithium salt in the electrolyte can be any one of 10%, 12%, 14%, 16%, 20%, etc. or a range between any two of them, which is not limited here.

[0071] In one embodiment, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, lithium difluorooxalatoborate, lithium trifluoromethanesulfonyl imide, lithium bisfluorosulfonyl imide, lithium diacetate borate, lithium tetrafluoroborate, and lithium difluorophosphate.

[0072] In one embodiment, the mass percentage of the additive in the electrolyte is 1%-5%. Alternatively, the mass percentage of the additive in the electrolyte can be any one of 1%, 2%, 3%, 4%, 5%, etc., or a range between any two of them, which is not limited here.

[0073] In one embodiment, the additive includes at least one of propane sultone, vinyl sulfate, and 1,3,6-hexanetrinitrile.

[0074] The present application also provides a lithium-ion battery, comprising the solid electrolyte as described above, or a solid electrolyte prepared using the method as described above.

[0075] The present application also provides an electrical device comprising the solid electrolyte described above, or a solid electrolyte prepared using the method described above, or a lithium-ion battery described above. In this embodiment, the type of electrical device is not limited, and the electrical device may be a car, a ship, an unmanned aerial vehicle, a fixed power source, a portable power source, etc.

[0076] The present application is further described below by way of specific examples. The experimental materials used in the following examples, unless otherwise specified, can be purchased from conventional biochemical reagent companies.

[0077] Example 1 A method for preparing a multifunctional monomer comprises the following steps: (1) Add 1 mol of pentaerythritol, 3 mol of acrylic acid, 6 g of p-toluenesulfonic acid, 0.2 g of copper chloride, and 38 g of cyclohexane into a flask; (2) While introducing oxygen-containing gas (oxygen volume percentage is 5%, nitrogen volume percentage is 95%) into the flask, a dehydration esterification reaction is carried out at 75-80 °C for 12 hours. During the reaction, the generated water is discharged to the outside of the system using a fractionating tube; (3) After the reaction of step (2) is completed, 100 g of n-propyl acetate and 8 g of distilled water are added to the reaction solution for dilution, and the mixture is stirred thoroughly. The mixture is allowed to stand for separation into an aqueous phase (lower layer) and an organic solvent phase (upper layer), and the aqueous phase of the lower layer is removed. Subsequently, a 20 wt % aqueous sodium hydroxide solution is added to the organic solvent phase to neutralize the acid component contained in the organic solvent phase. The mixture is allowed to stand for separation into an aqueous phase (lower layer) and an organic solvent phase (upper layer), and the aqueous phase of the lower layer is removed. The organic solvent phase is recovered, and distilled water is added to the recovered organic solvent phase for washing. The mixture is allowed to stand for separation, the aqueous phase (lower layer) is removed, and the organic solvent phase of the upper layer is recovered. (4) introducing dry air into the organic solvent phase finally recovered in step (3), and heating to 70° C. under reduced pressure to distill off the solvent, thereby obtaining a trifunctional acrylate; (5) Take 1 mol of the above trifunctional acrylate, add 0.5 mol of 1,3-propylene diisocyanate, stir and react at room temperature for 5 hours, and then stir and react at 50°C for 2 hours to obtain a multifunctional monomer.

[0078] In this embodiment, the structural formula of the multifunctional monomer is: .

[0079] A method for preparing a lithium ion battery comprises the following steps: (6) 3 g of the multifunctional monomer prepared in this example and 0.03 g of azobisisobutyronitrile were dissolved in 96.97 g of an electrolyte to obtain a prepolymer solution; wherein the electrolyte comprises: 39.97 g of propyl propionate, 12 g of ethyl methyl carbonate, 14 g of ethylene carbonate, 11 g of fluoroethylene carbonate, 1 g of propane sultone, 1 g of vinyl sulfate, 2 g of 1,3,6-hexanetrinitrile, 12 g of lithium hexafluorophosphate, 3 g of lithium bis(fluorosulfonyl)imide, and 1 g of lithium difluorophosphate; (7) In a dry room (relative humidity less than 2%, dew point less than -40 ºC) at room temperature, inject the prepolymer liquid into a dry cell assembled from a positive electrode sheet, a negative electrode sheet and a separator, pre-seal it with a heat-plastic sealing machine, let it stand at room temperature for 24 hours, then put it in a hot oven, slowly heat it to 50 ℃, and react it for 24 hours. During the heating, the prepolymer liquid undergoes a solidification reaction inside the dry cell, and a solid electrolyte is obtained by in-situ thermal curing to prepare a lithium-ion battery.

[0080] Example 2 The main difference between Example 2 and Example 1 is that: The same as in Example 1 except that 1,3-propylene diisocyanate was replaced with hexamethylene diisocyanate; In this embodiment, the structural formula of the multifunctional monomer is: .

[0081] Example 3 The main difference between Example 3 and Example 1 is that: 1,3-propylene diisocyanate was replaced by 1,10-decane diisocyanate, and the rest was the same as in Example 1; In this embodiment, the structural formula of the multifunctional monomer is: .

[0082] Example 4 The main difference between Example 4 and Example 1 is that: 1,3-propylene diisocyanate was replaced with 1-methylbutane-1,4-diisocyanate, and the rest was the same as in Example 1; In this embodiment, the structural formula of the multifunctional monomer is: .

[0083] Example 5 The main difference between Example 5 and Example 1 is that: 1,3-propylene diisocyanate was replaced with 1,2-diethylpentane-1,5-diisocyanate, and the rest was the same as in Example 1; In this embodiment, the structural formula of the multifunctional monomer is: .

[0084] Example 6 The main difference between Example 6 and Example 1 is that: 1,3-propylene diisocyanate was replaced by 1,4-cyclohexane diisocyanate, and the rest was the same as in Example 1; In this embodiment, the structural formula of the multifunctional monomer is: .

[0085] Example 7 The main difference between Example 7 and Example 1 is that: 1,3-propylene diisocyanate was replaced with 1,4-dimethylene cyclohexane diisocyanate, and the rest was the same as in Example 1; In this embodiment, the structural formula of the multifunctional monomer is: .

[0086] Example 8 The main difference between Example 8 and Example 1 is: The ratio of the added raw materials was adjusted, that is, pentaerythritol (1 mol) and acrylic acid (3 mol) were added and heated to react to obtain a trifunctional acrylate, and pentaerythritol (1 mol) and acrylic acid (2 mol) were added and heated to react to obtain a difunctional acrylate. The above two acrylates were then stirred and reacted with 1,3-propylene diisocyanate at room temperature for 5 h and then at 50°C for 2 h to obtain the target product monomer. The rest of the reaction was the same as in Example 1; In this embodiment, the structural formula of the multifunctional monomer is: .

[0087] Example 9 The main difference between Example 9 and Example 1 is that: In the prepolymer solution, the multifunctional monomer is composed of the multifunctional monomer prepared in Example 1 (referred to as monomer 1) and the multifunctional monomer prepared in Example 8 (referred to as monomer 2). The amount of monomer 1 added is 0.5 mol, and the amount of monomer 2 added is 0.5 mol. The rest is the same as in Example 1.

[0088] Example 10 The main difference between Example 10 and Example 1 is that: A method for preparing a prepolymer liquid comprises the following steps: 5 g of the multifunctional monomer prepared in Example 1 and 0.05 g of azobisisobutyronitrile were dissolved in 94.95 g of an electrolyte to obtain a prepolymer solution; wherein the electrolyte comprised: 37.95 g of propyl propionate, 12 g of ethyl methyl carbonate, 14 g of ethylene carbonate, 11 g of fluoroethylene carbonate, 1 g of propane sultone, 1 g of vinyl sulfate, 2 g of 1,3,6-hexanetrinitrile, 12 g of lithium hexafluorophosphate, 3 g of lithium bis(fluorosulfonyl)imide, and 1 g of lithium difluorophosphate; The rest is the same as in Example 1.

[0089] Example 11 The main differences between Example 11 and Example 1 are: A method for preparing a prepolymer liquid comprises the following steps: 3 g of the multifunctional monomer prepared in Example 1 and 0.03 g of azobisisobutyronitrile were dissolved in 96.97 g of an electrolyte to obtain a prepolymer solution; wherein the electrolyte included: 31.97 g of propyl propionate, 10 g of ethyl propionate, 10 g of propylene carbonate, 10 g of ethylene carbonate, 15 g of fluoroethylene carbonate, 0.5 g of vinylene carbonate, 1 g of vinyl sulfate, 2.5 g of 1,3,6-hexanetrinitrile, 13 g of lithium hexafluorophosphate, 2.5 g of lithium bis(fluorosulfonyl)imide, and 0.5 g of lithium dioxalatoborate.

[0090] The rest is the same as in Example 1.

[0091] Example 12 The main difference between Example 12 and Example 1 is that: A method for preparing a prepolymer liquid comprises the following steps: 1 g of the multifunctional monomer prepared in Example 1 and 0.01 g of azobisisobutyronitrile were dissolved in 98.99 g of an electrolyte to obtain a prepolymer solution; wherein the electrolyte comprised: 41.99 g of propyl propionate, 12 g of ethyl methyl carbonate, 14 g of ethylene carbonate, 11 g of fluoroethylene carbonate, 1 g of propane sultone, 1 g of vinyl sulfate, 2 g of 1,3,6-hexanetrinitrile, 12 g of lithium hexafluorophosphate, 3 g of lithium bis(fluorosulfonyl)imide, and 1 g of lithium difluorophosphate; The rest is the same as in Example 1.

[0092] Example 13 The main differences between Example 13 and Example 1 are: A method for preparing a prepolymer liquid comprises the following steps: 0.8 g of the multifunctional monomer prepared in Example 1 and 0.008 g of azobisisobutyronitrile were dissolved in 99.192 g of an electrolyte to obtain a prepolymer solution; wherein the electrolyte comprised: 42.192 g of propyl propionate, 12 g of ethyl methyl carbonate, 14 g of ethylene carbonate, 11 g of fluoroethylene carbonate, 1 g of propane sultone, 1 g of vinyl sulfate, 2 g of 1,3,6-hexanetrinitrile, 12 g of lithium hexafluorophosphate, 3 g of lithium bis(fluorosulfonyl)imide, and 1 g of lithium difluorophosphate; The rest is the same as in Example 1.

[0093] Example 14 The main differences between Example 14 and Example 1 are: A method for preparing a prepolymer liquid comprises the following steps: 7.3 g of the multifunctional monomer prepared in Example 1 and 0.073 g of azobisisobutyronitrile were dissolved in 92.627 g of an electrolyte to obtain a prepolymer solution; wherein the electrolyte comprised: 35.627 g of propyl propionate, 12 g of ethyl methyl carbonate, 14 g of ethylene carbonate, 11 g of fluoroethylene carbonate, 1 g of propane sultone, 1 g of vinyl sulfate, 2 g of 1,3,6-hexanetrinitrile, 12 g of lithium hexafluorophosphate, 3 g of lithium bis(fluorosulfonyl)imide, and 1 g of lithium difluorophosphate; The rest is the same as in Example 1.

[0094] Example 15 The main difference between Example 15 and Example 1 is that: 1,3-propylene diisocyanate was replaced with 1,15-pentadecanediisocyanate, and the rest was the same as in Example 1; In this comparative example, the structural formula of the multifunctional monomer is: .

[0095] Comparative Example 1 The main difference between Comparative Example 1 and Example 1 is: The multifunctional monomer is replaced by a compound represented by the following formula (5): Formula (5); The rest is the same as in Example 1.

[0096] Comparative Example 2 The main difference between Comparative Example 2 and Example 1 is: Step (1) is: adding 1 mol of pentaerythritol, 2 mol of acrylic acid, 6 g of p-toluenesulfonic acid, 0.2 g of copper chloride and 38 g of cyclohexane into a flask; The rest is the same as in Example 1; In this comparative example, the structural formula of the multifunctional monomer is: .

[0097] Comparative Example 3 The main difference between Comparative Example 3 and Example 1 is that: The multifunctional monomer is replaced by a compound represented by the following formula (6): Formula (6); The rest is the same as in Example 1.

[0098] Test method: (1) Infrared spectrum test: The multifunctional monomer sample prepared in Example 1 was placed on the optical platform crystal surface of the infrared spectrometer ATR (model is20). The infrared ATR test software was opened and the test parameters were set to 4 resolution and 32 scans. After starting the test instrument, the knob above the reflector was rotated to press the sample to be tested so that it was in full contact with the emission hole below, and data collection began. After the test was completed, the infrared spectrum information of the sample was obtained as shown below. Figure 1 shown.

[0099] in, Figure 1 The infrared spectrum test results show that at 3343cm -1 The absorption peak that appears is the stretching vibration peak of the nitrogen hydrogen bond in the carbamate group; at 1721cm -1 The absorption peak that appears is the stretching vibration peak of the carbonyl group, which is the characteristic peak of the carbonyl group in acrylate; at 1668cm -1 The absorption peak that appears is the stretching vibration peak of the carbon-oxygen double bond of the carbamate group; 1264 cm -1 The absorption peak that appears is the stretching vibration peak of the carbon-oxygen single bond of the carbamate group; 1172 cm -1 The absorption peaks that appear are the stretching vibrations of the ester group. These infrared absorption peaks all prove the chemical structure of the multifunctional monomer.

[0100] (2) Viscosity test: The viscosity of the prepolymer liquid prepared in Examples 1-15 and Comparative Examples 1-3 was tested using an NDJ-5S digital display rotary viscometer. During the test, the prepolymer liquid sample was poured into a flat-bottomed container with a diameter greater than 60 mm, the prepolymer liquid temperature was maintained at 25°C, and the operating table was stable and vibration-free. The instrument protection frame was screwed back onto the lower end of the instrument, and the L0 rotor was screwed counterclockwise into the instrument universal joint. The lifting knob was rotated to slowly immerse the rotor in the prepolymer liquid until the rotor liquid level mark, i.e., the groove scale, was in the same plane as the liquid surface, and the instrument was adjusted to be level again. Press the rotor selection key, select the speed, and then press the OK key. The rotor starts to rotate, and after the displayed value stabilizes, press the stop key to read the viscosity value. The test results are shown in Table 1 below.

[0101] (III) Electrochemical stability window test: A stainless steel sheet was placed in a 2016-type battery shell, and the prepolymer solution samples prepared in Examples 1-15 and Comparative Examples 1-3 were dripped in. The lithium sheet and battery shell were covered and clamped, and the CR2016-type button battery was assembled in a glove box filled with high-purity argon. Four batteries were prepared for each sample. The sample was heated to 50°C and reacted for 24 hours. A linear voltammetric scan was performed using an electrochemical workstation (BioLogicScience Instruments) to measure the electrochemical stability window. The starting potential was 2.5 V, the maximum potential was 6 V, and the scan rate was 10 mV / s. The voltage corresponding to the intersection of the tangent line of the current slope increase area in the curve and the horizontal axis was read as the high voltage resistance window. The test results are shown in Tables 1 and 2. Figure 2 shown.

[0102] in, Figure 2 This is a scanning curve diagram of the electrochemical stability window of the solid electrolyte of Example 1 of the present application, from Figure 2 It can be seen that the solid electrolyte of Example 1 has a relatively high electrochemical stability window, which reaches 4.71 V. It can withstand a relatively high voltage, which helps to improve the high-voltage resistance of the battery.

[0103] (IV) Conductivity test: Place the electrode ring that fixes the electrolyte container and the polytetrafluoroethylene single ring that serves as the electrolyte container at the bottom of the battery shell, then drip the prepolymer liquid samples prepared in Examples 1-15 and Comparative Examples 1-3 into the electrolyte container, so that the prepolymer liquid completely fills the cavity of the electrolyte container, and cover it with a stainless steel electrode plug to form a blocking electrode; finally, cover the battery shell with the upper cover, tighten the butterfly nut, and complete the assembly of the battery. The assembled blocking battery is directly connected to the electrochemical workstation (VMP-3e, Bio-Logic) and placed in a 50°C constant temperature box. The battery is cured at high temperature, and an AC impedance test is performed at a frequency of 1MHz to 0.03Hz, and an EIS test is performed on the battery. According to The ionic conductivity (σ, mS / cm) of the solid electrolyte was calculated using the above formula: σ is the ionic conductivity, L is the electrolyte thickness, S is the contact area between the electrolyte membrane and the electrode, and R is the impedance measured by the impedance meter. The test results are shown in Table 1 below.

[0104] (V) High voltage cycle test: Preparation of positive electrode sheets: Grind and mix 95%-99% lithium cobalt oxide material and 1%-5% conductive agent acetylene black, add 1%-5% polyvinylidene fluoride by mass, grind and disperse in 1-methyl-2-pyrrolidone (NMP), and mix to obtain a positive electrode slurry, wherein NMP is used for mixing, dispersing and adjusting the viscosity of the slurry. It evaporates during drying and is therefore not included in the mass percentage of the positive electrode material. Coat the positive electrode material on the surface of aluminum foil and dry it to obtain a positive electrode sheet.

[0105] Preparation of negative electrode sheet: Silicon particles and graphite are evenly mixed in a mass ratio of 9:1 to obtain a silicon-carbon composite negative electrode material, and then 80%-95% of the silicon-carbon composite negative electrode material is added to 1%-10% of the conductive carbon black by mass, and the mixture is ground and mixed. 1%-5% of sodium carboxymethyl cellulose by mass, 1%-5% of polystyrene butadiene copolymer by mass and water are added, and the mixture is ground, dispersed and mixed, and coated on the surface of copper foil and dried to obtain a negative electrode sheet.

[0106] The diaphragm is a porous supporting material that isolates the positive and negative electrodes and is made of polyethylene.

[0107] The prepolymer samples prepared in Examples 1-15 and Comparative Examples 1-3 were injected into the battery system of the positive electrode sheet, the separator and the negative electrode sheet, pre-sealed and allowed to stand at room temperature for 24-72 hours, and then heated and cured at 40°C-80°C for 12 hours-72 hours to prepare a solid-state battery.

[0108] Solid-state soft-pack full battery high voltage cycle test: First, the battery was formed, and charged with 0.02C constant current for 60min, 0.05C constant current for 60min, 0.1C constant current for 120min, and 0.2C constant current for 180min. It was heated at 45℃ for 24h, cooled to room temperature, and charged with 0.01C constant current and constant voltage to an upper limit voltage of 4.58V, with a cutoff current of 0.02C. It was left for 10min, and then discharged with a current of 0.1C to 3V, and left for 10min, that is, CC-CV mode was used for room temperature cycle 4 times; then charged with 1C current constant current and constant voltage at room temperature, and discharged with 1C current constant current, with a charge and discharge cutoff voltage of 3V-4.58V, and cycled 500 times to obtain the capacity retention rate (%) after 500 cycles of high voltage cycling. The test results are referenced. Figure 3 and Table 1.

[0109] in, Figure 3 This is a high voltage cycle curve diagram of the solid-state soft-pack full battery of Example 1 and Comparative Example 1 of the present application, wherein: Figure 3 The red curve in FIG is the high voltage cycle curve of the solid-state soft-pack full battery of Example 1. Figure 3 The black curve in FIG is the high voltage cycle curve of the solid-state soft-pack full battery of comparative example 1. Figure 3 It can be seen that the battery capacity of the solid-state battery corresponding to Example 1 decays to 94.6% of the original value after 500 cycles of high-voltage cycling, while the battery capacity of the solid-state battery of Comparative Example 1 decays to 85.0% of the original value after 500 cycles of high-voltage cycling. This shows that the solid-state electrolyte of Example 1 can still maintain normal operation inside the battery during the high-voltage charge and discharge cycle of the full battery. The solid-state electrolyte of Example 1 can withstand higher voltages and has higher voltage stability, thereby improving the battery cycle life.

[0110] Table 1

[0111] The test results in Table 1 show that batteries containing the solid electrolytes of Examples 1 to 15 exhibited high capacity retention and electrochemical stability windows after 500 high-voltage cycles. This demonstrates that using the multifunctional monomers of the examples herein as raw materials to prepare solid electrolytes can improve their high-voltage resistance.

[0112] From the comparison of Examples 1-12, Example 13, and Example 14, it can be seen that controlling the mass percentage of the multifunctional monomer in the prepolymer solution within the range of 1%-5% can further ensure that the battery has better high voltage resistance.

[0113] From the comparison of Examples 1-3, Example 4, Example 5 and Example 8, it can be seen that when R7 in the multifunctional monomer is an alkyl group and the structure of the multifunctional monomer is a symmetrical molecular structure, it can further ensure that the battery has better high voltage resistance and a wider electrochemical stability window.

[0114] From the comparison between Examples 1-7 and Example 15, it can be seen that R7 has a structure as shown in Formula (2) or Formula (3), and the sum of n1 and n2 is between 1 and 10, and / or the sum of n4 and n5 is between 1 and 10, which can further ensure that the battery has better high voltage resistance, a wider electrochemical stability window and higher conductivity.

[0115] The above is a detailed introduction to the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of the present application. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A multifunctional monomer used in solid electrolytes, characterized in that: The multifunctional monomer has a structure as shown in formula (1): Formula (1); Wherein, R1, R2, R3, R4, R5, and R6 are each independently selected from an acrylate group or a hydroxyl group, and at most only one of R1, R2, R3, R4, R5, and R6 is a hydroxyl group, and R7 is selected from an alkyl group or a cycloalkyl group.

2. The multifunctional monomer according to claim 1, characterized in that The R7 has a structure as shown in formula (2) or formula (3): Formula (2); Formula (3); wherein n1 is selected from an integer of 0-10, n2 is selected from an integer of 0-10, n3 is selected from an integer of 0-3, and the sum of n1 and n2 is between 1-10; n4 is selected from an integer of 0-5, n5 is selected from an integer of 0-5, n6 is selected from an integer of 0-3, n7 is selected from an integer of 0-3, and the sum of n4 and n5 is between 1-10.

3. The multifunctional monomer according to claim 2, characterized in that n1 is selected from an integer of 3-10, n2 is selected from an integer of 0-2, n3 is selected from an integer of 0-1, and the sum of n1 and n2 is between 3-10; and / or n4 is selected from an integer of 0-2, n5 is selected from an integer of 0-2, n6 is selected from an integer of 0-1, n7 is selected from an integer of 0-1, and the sum of n4 and n5 is 4.

4. The multifunctional monomer according to claim 3, characterized in that The multifunctional monomer includes at least one of the following compounds: 、 、 、 、 、 、 、 。 5. The multifunctional monomer according to any one of claims 1 to 4, characterized in that: The functionality of the multifunctional monomer is between 5 and 6; and / or The multifunctional monomer has a symmetrical molecular structure.

6. A method for preparing a multifunctional monomer, characterized in that: The preparation method comprises: Provide trifunctional acrylate monomers and diisocyanate compounds; reacting the trifunctional acrylate monomer and the diisocyanate compound to obtain the multifunctional monomer; Wherein, the multifunctional monomer has a structure as shown in formula (1): Formula (1); Wherein, R1, R2, R3, R4, R5, and R6 are each independently selected from an acrylate group or a hydroxyl group, and at most only one of R1, R2, R3, R4, R5, and R6 is a hydroxyl group, and R7 is selected from an alkyl group or a cycloalkyl group.

7. The method for preparing a multifunctional monomer according to claim 6, wherein: The molar ratio between the trifunctional acrylate monomer and the diisocyanate compound is 2:(1-1.1); and / or The reaction temperature is 20°C-50°C; and / or The structural formula of the diisocyanate compound is shown in formula (4): O=C=N-R7-N=C=O formula (4); Wherein, R7 is selected from alkyl or cycloalkyl.

8. The method for preparing a multifunctional monomer according to claim 6 or 7, characterized in that: The preparation method of the trifunctional acrylate monomer comprises: Provide pentaerythritol and acrylic acid; The pentaerythritol and the acrylic acid are subjected to an esterification reaction under catalyst conditions to generate the trifunctional acrylate monomer.

9. The method for preparing a multifunctional monomer according to claim 8, wherein: The molar ratio between the pentaerythritol and the acrylic acid is 1:(3-3.1); and / or The reaction temperature of the esterification reaction is 75°C-80°C.

10. A solid electrolyte, characterized in that The solid electrolyte is formed by solidifying a multifunctional monomer in an electrolyte; The multifunctional monomer is the multifunctional monomer as claimed in any one of claims 1 to 5 or the multifunctional monomer obtained by the preparation method as claimed in any one of claims 6 to 9.

11. The solid electrolyte according to claim 10, characterized in that The electrical conductivity of the solid electrolyte is 4mS / cm-10mS / cm.

12. A method for preparing a solid electrolyte, characterized in that: The preparation method comprises: Providing a prepolymer solution, wherein the prepolymer solution includes an electrolyte and a multifunctional monomer; causing the multifunctional monomer in the prepolymer solution to undergo an in-situ curing reaction to obtain the solid electrolyte; Wherein, the multifunctional monomer is the multifunctional monomer according to any one of claims 1 to 5 or the multifunctional monomer obtained by the preparation method according to any one of claims 6 to 9.

13. The method for preparing a solid electrolyte according to claim 12, wherein: The curing reaction has a curing temperature of 40° C. to 80° C., and / or a curing time of 12 h to 72 h; and / or The viscosity of the prepolymer liquid at room temperature is 2mPa.s-8mPa.s; and / or The prepolymer solution further includes an initiator.

14. The method for preparing a solid electrolyte according to claim 13, wherein: The mass percentage of the multifunctional monomer in the prepolymer solution is 1%-5%; and / or The mass percentage of the electrolyte in the prepolymer solution is 94%-98.997%; and / or The electrolyte comprises a solvent, a lithium salt and / or an additive; and / or The mass percentage of the initiator in the prepolymer solution is 0.003%-0.15%; and / or The initiator includes at least one of an azo initiator and a peroxide initiator.

15. The method for preparing a solid electrolyte according to claim 14, characterized in that: The solvent comprises at least one of a carbonate solvent and a carboxylate solvent; and / or The mass percentage of the solvent in the electrolyte is 79%-89%; and / or The lithium salt comprises at least one of lithium hexafluorophosphate, lithium perchlorate, lithium difluorooxalatoborate, lithium trifluoromethanesulfonyl imide, lithium bisfluorosulfonyl imide, lithium diacetate borate, lithium tetrafluoroborate, and lithium difluorophosphate; and / or The mass percentage of the lithium salt in the electrolyte is 10%-20%; and / or The additive comprises at least one of propane sultone, vinyl sulfate, and 1,3,6-hexane trinitrile; and / or The mass percentage of the additive in the electrolyte is 1%-5%.

16. A lithium ion battery, characterized in that: The solid electrolyte comprises the solid electrolyte according to claim 10 or 11, or a solid electrolyte prepared by the method according to any one of claims 12 to 15.

17. An electrical equipment, characterized in that: It comprises the solid electrolyte according to claim 10 or 11, or the solid electrolyte prepared by the method according to any one of claims 12 to 15, or the lithium ion battery according to claim 16.

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