A multifunctional monomer, a preparation method thereof, a solid-state electrolyte, a lithium ion battery and an electrical device

Abstract

The application provides a multifunctional monomer, a preparation method thereof, a solid-state electrolyte, a lithium ion battery and an electrical device. The multifunctional monomer has a structure as shown in formula (1). When the multifunctional monomer is used as a reactant raw material to form a solid-state electrolyte in situ in an electrolyte, the multifunctional monomer has high functionality, and the multifunctional monomer can form a highly cross-linked polymer network structure in a polymerization process. The structure endows the polymer with excellent mechanical properties, such as high strength and high modulus, so that the polymer can maintain good structural stability when bearing external stress, and also makes the polymer structure have improved high-voltage resistance, so that the solid-state electrolyte is not prone to decomposition or rupture failure, the structural damage of the electrolyte material in the charging and discharging process is inhibited, the electrochemical stability of the electrolyte material is maintained, and therefore the service life and safety of the battery are prolonged, and the charging and discharging performance of the battery is maintained.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a multifunctional monomer and a preparation method thereof, a solid-state electrolyte, a lithium ion battery and an electrical equipment. BACKGROUND

[0002] As a cutting-edge battery technology, solid-state batteries have attracted much attention in recent years due to their high energy density and high safety. Solid-state batteries use solid-state electrolytes to replace the liquid electrolytes in traditional lithium ion batteries, which can greatly reduce the risk of thermal runaway and combustion of the battery. The energy density of a solid-state battery is directly proportional to the working voltage, so improving the high-voltage resistance of the battery can directly improve the energy density of the battery, which is of great significance to application fields such as electric vehicles and aerospace that require high energy density batteries.

[0003] However, in the related art, the solid-state electrolyte is prone to decomposition under high voltage conditions, which reduces the overall performance of the battery, and needs to be further improved. SUMMARY

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

[0005] In a first aspect, embodiments of the present application provide a multifunctional monomer applied to a solid-state electrolyte, the multifunctional monomer having a structure as shown in formula (1):

[0006] Formula (1);

[0007] wherein R1, R2, R3, R4, R5, R6 are each independently selected from an acrylate group or a hydroxyl group, and at most one of R1, R2, R3, R4, R5, R6 is a hydroxyl group, and R7 is selected from an alkyl group or a cycloalkyl group.

[0008] In an embodiment, R7 has a structure as shown in formula (2) or formula (3):

[0009] Formula (2);

[0010] Formula (3);

[0011] wherein n1 is an integer selected from 0-10, n2 is an integer selected from 0-10, n3 is an integer selected from 0-3, and the sum of n1 and n2 is between 1-10;

[0012] n4 is an integer selected from 0-5, n5 is an integer selected from 0-5, n6 is an integer selected from 0-3, n7 is an integer selected from 0-3, and the sum of n4 and n5 is between 1-10.

[0013] In an embodiment, n1 is selected from an integer from 3 to 10, n2 is selected from an integer from 0 to 2, n3 is selected from an integer from 0 to 1, the sum of n1 and n2 is between 3 and 10; and / or

[0014] n4 is selected from an integer from 0 to 2, n5 is selected from an integer from 0 to 2, n6 is selected from an integer from 0 to 1, n7 is selected from an integer from 0 to 1, the sum of n4 and n5 is 4.

[0015] In an embodiment, the multifunctional monomer comprises at least one of the following compounds:

[0016] 、 、 、 、 、 、 、 .

[0017] In an embodiment, the multifunctional monomer has a functionality number between 5 and 6; and / or

[0018] The multifunctional monomer has a symmetrical molecular structure.

[0019] In a second aspect, embodiments of the present application provide a preparation method of a multifunctional monomer, the preparation method comprising:

[0020] providing a tri-functional acrylate monomer and a diisocyanate compound;

[0021] reacting the tri-functional acrylate monomer and the diisocyanate compound to obtain the multifunctional monomer;

[0022] wherein the multifunctional monomer has a structure as shown in formula (1):

[0023] formula (1);

[0024] wherein R1, R2, R3, R4, R5, R6 are each independently selected from an acrylate group or a hydroxyl group, and at most only one of R1, R2, R3, R4, R5, R6 is a hydroxyl group, and R7 is selected from an alkyl group or a cycloalkyl group.

[0025] In an embodiment, the molar ratio between the tri-functional acrylate monomer and the diisocyanate compound is 2: (1-1.1); and / or

[0026] The temperature of the reaction is 20-50°C.

[0027] In an embodiment, the preparation method of the tri-functional acrylate monomer comprises:

[0028] providing pentaerythritol and acrylic acid;

[0029] subjecting the pentaerythritol and the acrylic acid to an esterification reaction under catalyst conditions to generate the trifunctional acrylic ester monomer.

[0030] In an embodiment, the molar ratio between the pentaerythritol and the acrylic acid is 1: (3-3.1); and / or

[0031] the temperature of the reaction is 20-50℃; and / or

[0032] The structure of the diisocyanate compound is shown in formula (4):

[0033] O=C=N-R7-N=C=O Formula (4);

[0034] wherein R7 is selected from alkyl or cycloalkyl.

[0035] In a third aspect, embodiments of the present application provide a solid-state electrolyte formed by solidifying a multifunctional monomer in an electrolyte solution;

[0036] The multifunctional monomer is obtained by using the multifunctional monomer described above or by using the preparation method described above.

[0037] In an embodiment, the solid-state electrolyte has an electrical conductivity of 4-10 mS / cm.

[0038] In a fourth aspect, embodiments of the present application provide a preparation method of a solid-state electrolyte, the preparation method comprising:

[0039] providing a pre-polymer solution comprising an electrolyte solution and a multifunctional monomer;

[0040] subjecting the multifunctional monomer in the pre-polymer solution to an in-situ solidification reaction to obtain the solid-state electrolyte;

[0041] wherein the multifunctional monomer is obtained by using the multifunctional monomer described above or by using the preparation method described above.

[0042] In an embodiment, the solidification temperature of the solidification reaction is 40-80℃, and / or the solidification time is 12-72h; and / or

[0043] The viscosity of the pre-polymer solution at room temperature is 2-8 mPa.s; and / or

[0044] The pre-polymer solution further comprises an initiator.

[0045] In an embodiment, the mass percentage of the multifunctional monomer in the prepolymer solution is 1%-5%; and / or

[0046] The mass percentage of the electrolyte in the prepolymer solution is 94%-98.997%; and / or

[0047] The electrolyte comprises a solvent, a lithium salt, and / or an additive; and / or

[0048] The mass percentage of the initiator in the prepolymer solution is 0.003%-0.15%; and / or

[0049] The initiator comprises at least one of an azo initiator and a peroxide initiator.

[0050] In an embodiment, the solvent comprises at least one of a carbonate solvent and a carboxylate solvent; and / or

[0051] The mass percentage of the solvent in the electrolyte is 79%-89%; and / or

[0052] The lithium salt comprises at least one of lithium hexafluorophosphate, lithium perchlorate, lithium difluoro(oxalato)borate, lithium trifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium bis(oxalato)borate, lithium tetrafluoroborate, lithium difluorophosphate; and / or

[0053] The mass percentage of the lithium salt in the electrolyte is 10%-20%; and / or

[0054] The additive comprises at least one of propanesultone, ethylene sulfate, 1,3,6-hexanetricarbonitrile; and / or

[0055] The mass percentage of the additive in the electrolyte is 1%-5%.

[0056] In a fifth aspect, embodiments of the present application provide a lithium ion battery comprising the solid-state electrolyte as described above or prepared by the method as described above.

[0057] In a sixth aspect, embodiments of the present application provide an electrical equipment comprising the solid-state electrolyte as described above or prepared by the method as described above, or comprising the lithium ion battery as described above.

[0058] Advantages of embodiments of the present application:

[0059] The multifunctional monomer of the present application has a structure as shown in formula (1), and when the multifunctional monomer is used as a reactant raw material to in-situ solidify in an electrolyte to form a solid-state electrolyte, in a first aspect, the acrylate groups are reactive functional groups, and the number of acrylate groups is at least 5, so that the multifunctional monomer has a high functionality, and the multifunctional monomer can form a highly cross-linked polymer network structure during polymerization. The highly cross-linked polymer network structure is like a tightly woven large net, in which the molecular chains are intertwined and fixed through a large number of chemical bonds, greatly limiting the movement of the molecular chains. This structure endows the polymer with excellent mechanical properties, such as high strength and high modulus, so that the polymer can maintain good structural stability when subjected to external stress, and also improves the high-voltage resistance of the polymer structure, so that the solid-state electrolyte is less likely to decompose or rupture and fail, inhibits structural damage of the electrolyte material during charging and discharging, maintains the electrochemical stability of the electrolyte material, thereby prolonging the service life and safety of the battery, and maintaining the charging and discharging performance of the battery.

[0060] In a second aspect, the urethane groups of the main chain of the multifunctional monomer endow the monomer molecule with strong polarity, so that the multifunctional monomer can interact with the solvent molecules of the electrolyte to improve the conductivity, and the urethane groups have strong chemical bond energy, which can form hydrogen bonds and other interactions to enhance the structural stability of the solid-state electrolyte. This enhanced structural stability helps the solid-state electrolyte to maintain its form and integrity under high voltage, preventing performance degradation due to structural damage.

[0061] In a third aspect, the multifunctional monomer is polymerized to form a cross-linked polymer, which is combined with the electrolyte to form a solid-state electrolyte containing urethane groups. The nitrogen atoms and carbonyl oxygen atoms in the urethane groups can form strong interactions with conductive ions, which helps to stabilize the existence form of the conductive ions and reduces the migration and aggregation of the conductive ions under high voltage, thereby improving the high-voltage resistance of the solid-state electrolyte.

[0062] In the fourth aspect, after the polyfunctional monomer is polymerized, the two ends of the urethane groups on the backbone chain are both bonded with the bulky ester side groups, and the nitrogen atom and the carbonyl oxygen atom in the urethane group have lone pair electrons, so that the whole urethane group has a negative charge, thereby giving the urethane group strong polarity, so that the urethane group can enhance the electron cloud density of the ester side group connected thereto, lower the HOMO energy level (highest occupied molecular orbital energy level) of the crosslinked polymer, so that the crosslinked polymer is more difficult to lose electrons, and a larger energy and a higher voltage is required to oxidize the crosslinked polymer, therefore, the bulky ester side groups at the two ends of the urethane group have the effect of a "protective umbrella", which protects the polymer molecular chain to better resist oxidation under high voltage, reduces the oxidative decomposition or side reaction of the polymer, reduces the risk of oxidative degradation of the solid-state electrolyte in a high-voltage environment, and thus improves the high-voltage resistance of the solid-state electrolyte. BRIEF DESCRIPTION OF DRAWINGS

[0063] In order to more clearly illustrate the solutions in the present application or prior art, the drawings required to be used in the following embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0064] Figure 1 The infrared spectrum of the polyfunctional monomer of Example 1 of the present application;

[0065] Figure 2 The electrochemical stability window scanning curve of the solid-state electrolyte of Example 1 of the present application;

[0066] Figure 3 The high-voltage cycle curve of the solid-state soft-pack full battery of Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0067] The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. In addition, it should be understood that the specific embodiments 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, the orientation words such as "upper" and "lower" generally refer to the upper and lower of the device in the actual use or working state, and specifically refer to the direction of the drawing surface in the drawings; and "inner" and "outer" refer to the outline of the device.

[0068] In the related art, the solid-state electrolyte is prone to decomposition under high voltage conditions, reducing the overall performance of the battery, which needs to be further improved.

[0069] The present application provides a multifunctional monomer for a solid-state electrolyte, which has a structure as shown in formula (1):

[0070] Formula (1);

[0071] wherein R1, R2, R3, R4, R5, R6 are each independently selected from an acrylate group or a hydroxyl group, and at most one of R1, R2, R3, R4, R5, R6 is a hydroxyl group, and R7 is selected from an alkyl group or a cycloalkyl group.

[0072] In this embodiment, the multifunctional monomer of the present application has a structure as shown in formula (1), and when the multifunctional monomer is used as a reactant raw material to form a solid-state electrolyte in situ in the electrolyte, first, the acrylate group is a reactive functional group, and the number of acrylate groups is at least 5, so the multifunctional monomer has a high degree of functionality, and 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, with molecular chains intertwined and fixed by a large number of chemical bonds, greatly limiting the movement of the molecular chains. This structure gives the polymer excellent mechanical properties, such as high strength and high modulus, allowing it to maintain good structural stability when subjected to external stress, and also improves the high-voltage resistance of the polymer structure, so that the solid-state electrolyte is not prone to decomposition or failure, inhibits structural damage to the electrolyte material during charging and discharging, maintains the electrochemical stability of the electrolyte material, thereby prolonging the service life and safety of the battery, and maintaining the charging and discharging performance of the battery.

[0073] Second, the urethane group of the main chain of the multifunctional monomer gives the monomer molecule a strong polarity, allowing the multifunctional monomer to interact with the solvent molecules of the electrolyte, improving the electrical conductivity, and the urethane group has a strong chemical bond energy, which can form hydrogen bonds and other interactions to enhance the structural stability of the solid-state electrolyte. This enhanced structural stability helps the solid-state electrolyte to maintain its form and integrity under high voltage, preventing performance degradation due to structural damage.

[0074] Third, the multifunctional monomer polymerizes to form a cross-linked polymer, which combines with the electrolyte to form a solid-state electrolyte containing a urethane group. The nitrogen atom and the carbonyl oxygen atom in the urethane group can form a strong interaction with the conducting ions, which helps to stabilize the form of the conducting ions and reduces the migration and aggregation of the conducting ions under high voltage, thereby improving the high-voltage resistance of the solid-state electrolyte.

[0075] In a fourth aspect, after the polyfunctional monomer is polymerized, the two ends of the urethane group on the backbone chain are both bonded with bulky ester side groups, and the nitrogen atom and the carbonyl oxygen atom in the urethane group have lone pair electrons, so that the overall urethane group has a negative charge, thereby giving the urethane group strong polarity, so that the urethane group can enhance the electron cloud density of the ester side group connected thereto, lower the HOMO energy level (highest occupied molecular orbital energy level) of the cross-linked polymer, so that the cross-linked polymer is more difficult to lose electrons, and requires a larger energy and a higher voltage to be oxidized. Therefore, the two ends of the bulky ester side groups of the urethane group act like a "protective umbrella" to protect the polymer molecular chain, better resist oxidation under high voltage, reduce the risk of oxidative degradation of the solid-state electrolyte in a high-voltage environment, and thus improve the high-voltage resistance of the solid-state electrolyte.

[0076] In a fifth aspect, after the polyfunctional monomer is polymerized, the two ends of the urethane group on the backbone chain are both bonded with bulky ester side groups, and there is a specific intermolecular interaction between the urethane group and the bulky ester side group. These interactions make the polymer not produce free ionic fragment groups under high voltage (> 4.5V), and the solid-state electrolyte can match the high-voltage positive electrode, showing strong high-voltage resistance advantage. Taking lithium cobaltate as an example, during the charging process, lithium cobaltate will form tetravalent cobalt ions after lithium is removed. These high-valence cobalt ions have high chemical activity and are easy to react with surrounding substances such as solvent molecules, causing the surface structure of the positive active particles to be unstable, and the substances around the high-valence cobalt ions are easy to be oxidized and decomposed into ionic fragments. The urethane and ester side groups in the polymer molecular chain can produce good synergistic complexation with tetravalent cobalt ions, and through coordination chemical action, the cobalt ions are "fixed" on the surface of the positive active particles, effectively stabilizing the metal ions on the surface of the positive active particles, reducing the dissolution and migration of the metal ions, and improving the stability of the polymer molecular chain in a high-voltage field. In addition, the intermolecular interaction between the urethane group and the bulky ester side group also significantly improves the complexing ability of the polymer molecular chain to lithium ions and solvents. Under high voltage, the distribution of lithium ions is easily affected by the electric field and chemical reaction, causing local aggregation. The polymer molecular chain forms stable complexes with lithium ions and solvents, which can uniformly disperse lithium ions and reduce local aggregation of lithium ions, so that lithium ions can be uniformly and efficiently transported in the polymer electrolyte, thereby improving the high-voltage resistance of the polymer electrolyte and prolonging the service life of the battery.

[0077] In an embodiment, R7 has a structure as shown in formula (2) or formula (3):

[0078] Formula (2);

[0079] Formula (3);

[0080] wherein, n1 is an integer selected from 0-10, n2 is an integer selected from 0-10, n3 is an integer selected from 0-3, the sum of n1 and n2 is between 1-10;

[0081] n4 is an integer selected from 0-5, n5 is an integer selected from 0-5, n6 is an integer selected from 0-3, n7 is an integer selected from 0-3, the sum of n4 and n5 is between 1-10.

[0082] In the present 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 is not too large, and 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 infiltration of the prepolymer solution to the electrode.

[0083] In one embodiment, n1 is an integer selected from 3-10, n2 is an integer selected from 0-2, n3 is an integer selected from 0-1, the sum of n1 and n2 is between 3-10.

[0084] In one embodiment, n4 is an integer selected from 0-2, n5 is an integer selected from 0-2, n6 is an integer selected from 0-1, n7 is an integer selected from 0-1, the sum of n4 and n5 is 4.

[0085] In one embodiment, the multifunctional monomer comprises at least one of the following compounds:

[0086] , , , , , , , .

[0087] The multi-functionality monomer with the above structure, R1, R2, R3, R4, R5, R6 are each independently selected from an acrylate group or a hydroxyl group, the functionality number is between 5-6, can be efficiently cross-linked, improve the structural stability of the polymer, and further improve the high-voltage stability of the solid-state electrolyte. Moreover, the high functionality can make the multi-functionality monomer polymerize to form a polymer network at a lower content, so that the solid-state electrolyte has better electrical conductivity. The alkyl and cycloalkyl structures of the R7 group control the values of n1 to n6, ensuring that the volume and molecular weight of the multi-functionality monomer are not too large. When the multi-functionality monomer is added to the prepolymer solution, the viscosity of the prepolymer solution will not be too large, which is beneficial to the infiltration of the prepolymer solution to the electrode. In addition, the above multi-functionality monomer has a basically symmetrical molecular structure, which helps the multi-functionality monomer molecules to more efficiently approach each other and react, thereby promoting the formation of cross-linked structures and improving the structural stability of the material. Therefore, the above multi-functionality monomer has better effects on the viscosity of the prepolymer solution, the electrical conductivity of the solid-state electrolyte, and the high-voltage resistance of the solid-state electrolyte, and performs better in the high-voltage cycle performance of the battery.

[0088] In an embodiment, the functionality number of the multi-functionality monomer is between 5-6. Alternatively, the functionality number of the multi-functionality monomer is 5 or 6. Functionality refers to the number of functional groups in a monomer molecule that can participate in a reaction, which is directly related to the reactivity of the reactants and the structural properties of the product. Generally speaking, the more the functionality number, the more active sites the monomer molecule has in the reaction, the faster the reaction rate, the greater the probability of the monomer molecule participating in the polymerization reaction, and the higher the cross-linking degree of the generated polymer. When the functionality number of the multi-functionality monomer is less than 5, the structural stability of the polymer is easily reduced, and the solid-state electrolyte is easily decomposed. When the functionality number of the multi-functionality monomer is greater than 6, it is easy to cause the cross-linking points to be too dense, the molecular pores of the polymer molecular chain structure to be small, which is not conducive to the absorption of electrolyte and the shuttling and conduction of conductive ions in the molecular pores, and also seriously hinders the flexible movement of the molecular chain, resulting in a significant decrease in the flexibility of the polymer and becoming rigid and brittle. At the same time, the dense network structure also limits the transmission of ions in the polymer interior, making the ion transmission performance of the solid-state electrolyte worse.

[0089] In the present embodiment, the number of functionalities of the multifunctional monomer is set between 5 and 6, which can ensure that the generated polymer has a suitable crosslinking degree; at the same time, the urethane groups on the dry chain of the multifunctional monomer can endow the monomer molecule with strong flexibility. The nitrogen atom and the carbonyl oxygen atom in the urethane group have great polarity, and the urethane group can bring partial charge and space steric hindrance weakening effect, and the urethane group can produce specific intermolecular interaction with the bulky ester group side groups at both ends. This interaction reduces the energy barrier of the rotation and peristalsis of the polymer molecular chain backbone, so that the polymer molecular chain can rotate and peristalsis to a certain extent when subjected to a small external force, thereby improving the movement ability of the polymer molecular chain. The improvement of flexibility injects a "lubricant" into the originally rigid polymer network structure, so that the polymer molecular chain can move freely to a certain extent, effectively offsetting the problem of decreased flexibility and reduced polymer molecular chain porosity caused by high crosslinking degree of the side groups, and improving the absorption and solubility of the polymer molecular chain to the electrolyte and lithium salt. At the same time, the improvement of the movement ability of the polymer molecular chain by the urethane group also indirectly improves the ion transmission performance. The enhancement of the movement ability of the polymer molecular chain opens up a more unobstructed channel for the transmission of ions in the polymer, so that the ions can migrate more freely between the polymer molecular chains, thereby improving the ion transmission efficiency of the solid electrolyte.

[0090] In an embodiment, the multifunctional monomer has a symmetrical molecular structure. In the present embodiment, the multifunctional monomer with high functionality and symmetrical structure has a significant tendency to form a highly crosslinked polymer network structure during the polymerization reaction. High functionality means that each monomer molecule has multiple active sites, which can rapidly and massively react with adjacent monomer molecules to form multiple chemical bonds during the polymerization reaction. The symmetrical structure enables the multifunctional monomer molecules to have a regular arrangement in space, which facilitates more efficient approach and reaction between monomer molecules during polymerization, thereby promoting the formation of crosslinked structures.

[0091] The high functionality, symmetrical structure, and urethane groups in the multifunctional monomer each play a unique role in the polymer and synergize with each other to fully utilize their advantages, thereby preparing a solid electrolyte material that has excellent structural stability and high-voltage resistance, good flexibility, and efficient ion transmission performance, and meets the demand for high-performance materials in batteries.

[0092] The present application also provides a preparation method of the multifunctional monomer, which comprises:

[0093] S1, providing a trifunctional acrylate monomer and a diisocyanate compound;

[0094] S2, reacting the tri-functional acrylate monomer and the diisocyanate compound to obtain the multi-functional monomer;

[0095] wherein the multi-functional monomer has a structure as shown in formula (1):

[0096] formula (1);

[0097] wherein R1, R2, R3, R4, R5, R6 are each independently selected from an acrylate group or a hydroxyl group, and at most one of R1, R2, R3, R4, R5, R6 is a hydroxyl group, and R7 is selected from an alkyl group or a cycloalkyl group.

[0098] In the present embodiment, the tri-functional acrylate monomer refers to a monomer with a functionality number of 3, and the functionality groups are all acrylate groups.

[0099] In one embodiment, the molar ratio between the tri-functional acrylate monomer and the diisocyanate compound is 2: (1-1.1).

[0100] In one embodiment, the reaction temperature of the tri-functional acrylate monomer and the diisocyanate compound is 20-50°C.

[0101] In one embodiment, the diisocyanate compound has a structure as shown in formula (4):

[0102] O=C=N-R7-N=C=O formula (4);

[0103] wherein R7 is selected from an alkyl group or a cycloalkyl group.

[0104] In one embodiment, the preparation method of the tri-functional acrylate monomer comprises:

[0105] S11, providing pentaerythritol and acrylic acid;

[0106] S12, esterifying the pentaerythritol and the acrylic acid under the condition of a catalyst to generate the tri-functional acrylate monomer.

[0107] In one embodiment, the molar ratio between the pentaerythritol and the acrylic acid is 1: (3-3.1).

[0108] In one embodiment, the reaction temperature of the esterification is 75-80°C.

[0109] In a specific embodiment, the preparation method of the multi-functional monomer is as follows:

[0110] S111, adding pentaerythritol, acrylic acid, p-toluenesulfonic acid, copper chloride and cyclohexane in a flask;

[0111] S112, while passing oxygen-containing gas (5% by volume of oxygen and 95% by volume of nitrogen) into the flask, dehydration esterification is carried out at 75-80℃ for 12 hours, and water generated during the reaction is discharged to the outside of the system through a fractionating tube;

[0112] S113, after the reaction of step S112 is completed, n-propyl acetate and distilled water are added to the reaction solution for dilution, and the solution is stirred thoroughly and allowed to separate into an aqueous phase (lower layer) and an organic solvent phase (upper layer), the aqueous phase (lower layer) is removed, then 20wt% sodium hydroxide aqueous solution is added to the organic solvent phase to neutralize the acid component contained in the organic solvent phase, the solution is allowed to separate into an aqueous phase (lower layer) and an organic solvent phase (upper layer), the aqueous phase (lower layer) is removed, the organic solvent phase is recovered, then distilled water is added to the recovered organic solvent phase for water washing, the solution is allowed to separate, the separated aqueous phase (lower layer) is removed, and the organic solvent phase (upper layer) is recovered;

[0113] S114, dry air is passed into the organic solvent phase recovered in step S113, and the solution is heated to 70℃ under reduced pressure to distill and remove the solvent, thereby obtaining a trifunctional acrylate;

[0114] S115, the trifunctional acrylate is taken, a diisocyanate compound is added, the solution is stirred at room temperature for 5h, and then stirred at 50℃ for 2h, thereby obtaining a multifunctional monomer.

[0115] In this embodiment, the reaction formula for preparing the multifunctional monomer is as follows:

[0116] .

[0117] 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.

[0118] The application further provides a solid-state electrolyte, which is formed by solidifying the multifunctional monomer in an electrolyte; the multifunctional monomer is obtained by using the multifunctional monomer or the preparation method described above.

[0119] In an embodiment, the conductivity of the solid-state electrolyte is 4mS / cm-10mS / cm. Since the polymer molecule constituting the solid-state electrolyte contains a urethane group in the main chain, the urethane group has a high dielectric constant, which means that under the action of an electric field, the group can more effectively conduct charges, avoiding the local aggregation of charges. In a high-voltage environment, this efficient ion conduction helps to maintain the stability of the electrolyte and improve the conductivity of the solid-state electrolyte.

[0120] The application further provides a preparation method of a solid-state electrolyte, which comprises:

[0121] S21, providing a pre-polymer solution, the pre-polymer solution comprising an electrolyte and a multi-functional monomer;

[0122] S22, causing the multi-functional monomer in the pre-polymer solution to undergo an in-situ solidification reaction to obtain a solid-state electrolyte;

[0123] The multi-functional monomer is the multi-functional monomer described above or obtained by the preparation method described above.

[0124] In an embodiment, the viscosity of the pre-polymer solution at room temperature is 2 mPa.s-8 mPa.s. Alternatively, the viscosity of the pre-polymer solution at room temperature can be any one of 2 mPa.s, 3 mPa.s, 5 mPa.s, 7 mPa.s, 8 mPa.s or a range between any two of them, which is not limited herein. In the present embodiment, the pre-polymer solution has a low viscosity at room temperature. The pre-polymer solution with low viscosity has better flow performance, can better infiltrate the electrode pores and the separator holes, and more easily 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-state electrolyte.

[0125] In an embodiment, the solidification temperature of the solidification reaction is 40℃-80℃, and / or the solidification time is 12h-72h.

[0126] In an embodiment, the pre-polymer solution further comprises an initiator. The initiator can initiate the polymerization reaction between the multi-functional monomers and improve the efficiency of the polymerization reaction.

[0127] In an embodiment, the mass percentage of the initiator in the pre-polymer solution is 0.003%-0.15%. Alternatively, the mass percentage of the initiator in the pre-polymer solution can be any one of 0.003%, 0.005%, 0.01%, 0.05%, 0.15% or a range between any two of them, which is not limited herein.

[0128] In an embodiment, the initiator comprises at least one of an azo initiator and a peroxide initiator. For example, the initiator can comprise at least one of azobisisobutyronitrile, azobisisoheptyl nitrile, dimethyl azobisbutyrate, benzoyl peroxide, and tert-butyl benzoyl peroxide.

[0129] In an embodiment, the mass percentage of the multifunctional monomer in the pre-polymer solution is 1%-5%. Alternatively, the mass percentage of the multifunctional monomer in the pre-polymer solution can be any one of 1%, 2%, 3%, 4%, 5%, or a range between any two of them, without limitation. In this embodiment, the multifunctional monomer is a high-functionality monomer, each functionality is a reaction site, and the dense reaction sites give the multifunctional monomer a high reactivity, enabling the polymerization reaction to occur at a lower content to form a polymer network, so that the molecular chain after polymerization can have good high-voltage resistance.

[0130] In this embodiment, when the mass percentage of the multifunctional monomer in the pre-polymer solution is less than 1%, the multifunctional monomer cannot be effectively cured, the structure of the formed solid-state electrolyte is loose, and the mechanical properties, ion transport properties, and high-voltage resistance of the solid-state electrolyte are reduced. When the mass percentage of the multifunctional monomer in the pre-polymer solution is greater than 5%, it is easy to cause the viscosity of the pre-polymer solution to be too high, which is not conducive to the infiltration of the pre-polymer solution into the battery electrode, resulting in a decrease in the electrochemical performance of the battery.

[0131] In an embodiment, the mass percentage of the electrolyte in the pre-polymer solution is 94%-98.997%. Alternatively, the mass percentage of the electrolyte in the pre-polymer solution can be any one of 94%, 95%, 96%, 97%, 98.997%, or a range between any two of them, without limitation.

[0132] In an embodiment, the electrolyte includes a solvent, a lithium salt, and / or an additive.

[0133] In an 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%, or a range between any two of them, without limitation.

[0134] In an embodiment, the solvent includes at least one of a carbonate-based solvent and a carboxylate-based solvent. For example, the solvent can include at least one of propyl propionate, dimethyl carbonate, methyl ethyl carbonate, ethyl propionate, ethylene carbonate, and fluoroethylene carbonate. In this embodiment, the multifunctional monomer contains a urethane group, and the urethane group is capable of forming a hydrogen bond with the above-mentioned solvent, thereby enhancing the structural stability of the solid-state electrolyte. This enhanced structural stability helps the solid-state electrolyte to maintain its structural integrity at high voltage, reducing the performance degradation of the battery due to the destruction of the structure of the solid-state electrolyte.

[0135] In an embodiment, the mass percentage of the lithium salt in the electrolyte is 10%-20%. Alternatively, the mass percentage of the lithium salt in the electrolyte can be any one of 10%, 12%, 14%, 16%, 20%, or a range between any two of them, which is not limited herein.

[0136] In an embodiment, the lithium salt comprises at least one of lithium hexafluorophosphate, lithium perchlorate, lithium difluoro(oxalato)borate, lithium trifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium bis(oxalato)borate, lithium tetrafluoroborate, lithium difluorophosphate.

[0137] In an 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%, or a range between any two of them, which is not limited herein.

[0138] In an embodiment, the additive comprises at least one of propane sultone, ethylene sulfate, 1,3,6-hexanetricarbonitrile.

[0139] The present application also provides a lithium ion battery comprising the solid-state electrolyte as described above, or the solid-state electrolyte prepared by the method as described above.

[0140] The present application also provides an electrical equipment comprising the solid-state electrolyte as described above, or the solid-state electrolyte prepared by the method as described above, or comprising the lithium ion battery as described above. In the present embodiment, the type of the electrical equipment is not limited, and the electrical equipment can be a car, a ship, a drone, a fixed power supply, a portable power supply, etc.

[0141] The present application will be further described below through specific embodiments. In the following embodiments, the experimental materials used are commercially available from conventional biochemical reagent companies, unless otherwise specified.

[0142] Embodiment 1

[0143] A method for preparing a multifunctional monomer, comprising the following steps:

[0144] (1) adding 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;

[0145] (2) passing an oxygen-containing gas (5% by volume of oxygen and 95% by volume of nitrogen) into the flask while performing a dehydration esterification reaction at 75-80 ℃ for 12 hours, and discharging the generated water out of the system by a fractionating tube during the reaction;

[0146] (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 to dilute it, it is stirred thoroughly, and it is left to separate into an aqueous phase (lower layer) and an organic solvent phase (upper layer), the aqueous phase of the lower layer is removed, then, 20 wt% sodium hydroxide aqueous solution is added to the organic solvent phase to neutralize the acid component contained in the organic solvent phase, it is left to separate into an aqueous phase (lower layer) and an organic solvent phase (upper layer), the aqueous phase of the lower layer is removed, the organic solvent phase is recovered, then, distilled water is added to the recovered organic solvent phase to perform water washing, it is left to separate, the aqueous phase (lower layer) is removed, and the organic solvent phase of the upper layer is recovered;

[0147] (4) Dry air is introduced into the organic solvent phase recovered in step (3), and the solvent is distilled off by heating to 70°C under reduced pressure, thereby obtaining a tri-functional acrylate;

[0148] (5) 1 mol of the above tri-functional acrylate is taken, 0.5 mol of 1,3-propanediisocyanate is added, it is stirred at normal temperature for 5 h, and then it is stirred at 50°C for 2 h, thereby obtaining a multi-functional monomer.

[0149] In this embodiment, the structural formula of the multi-functional monomer is:

[0150] .

[0151] A method for manufacturing a lithium ion battery, comprising the following steps:

[0152] (6) 3 g of the multi-functional monomer prepared in this embodiment and 0.03 g of azobisisobutyronitrile are dissolved in 96.97 g of an electrolyte, thereby obtaining a prepolymer solution; the electrolyte comprises 39.97 g of propyl propionate, 12 g of methyl ethyl carbonate, 14 g of ethylene carbonate, 11 g of fluoroethylene carbonate, 1 g of propanesultone, 1 g of ethylene sulfate, 2 g of 1,3,6-hexanetricarbonitrile, 12 g of lithium hexafluorophosphate, 3 g of lithium bisfluorosulfonylimide, and 1 g of lithium difluorophosphate;

[0153] (7) In a dry room (relative humidity is less than 2%, and dew point is less than -40°C), the prepolymer solution is injected into a dry cell formed by assembling a positive electrode sheet, a negative electrode sheet, and a separator, it is pre-sealed by a heat sealing machine, it is left to stand at room temperature for 24 h, it is then placed in a heat oven, and it is slowly heated to 50°C, and it is reacted for 24 h; during the heating, the prepolymer solution undergoes a curing reaction inside the dry cell, thereby obtaining a solid electrolyte by in-situ thermal curing, and a lithium ion battery is prepared.

[0154] Example 2

[0155] The main difference between Example 2 and Example 1 is that:

[0156] The same as Example 1 except that 1,3-propanediisocyanate is replaced by hexane diisocyanate.

[0157] In this example, the structure of the multifunctional monomer is:

[0158] .

[0159] Example 3

[0160] The main difference between Example 3 and Example 1 is that:

[0161] The same as Example 1 except that 1,3-propanediisocyanate is replaced by 1,10-decane diisocyanate.

[0162] In this example, the structure of the multifunctional monomer is:

[0163] .

[0164] Example 4

[0165] The main difference between Example 4 and Example 1 is that:

[0166] The same as Example 1 except that 1,3-propanediisocyanate is replaced by 1-methylbutane-1,4-diisocyanate.

[0167] In this example, the structure of the multifunctional monomer is:

[0168] .

[0169] Example 5

[0170] The main difference between Example 5 and Example 1 is that:

[0171] The same as Example 1 except that 1,3-propanediisocyanate is replaced by 1,2-diethylpentane-1,5-diisocyanate.

[0172] In this example, the structure of the multifunctional monomer is:

[0173] .

[0174] Example 6

[0175] The main difference between Example 6 and Example 1 is that:

[0176] The same as Example 1 except that 1,3-propanediisocyanate is replaced by 1,4-cyclohexane diisocyanate.

[0177] In this example, the structure of the multifunctional monomer is:

[0178] .

[0179] Example 7

[0180] The main difference between Example 7 and Example 1 is that:

[0181] 1,3-propanediisocyanate is replaced by 1,4-dimethylenecyclohexane diisocyanate, and the rest is the same as Example 1;

[0182] In this example, the structure of the multifunctional monomer is:

[0183] .

[0184] Example 8

[0185] The main difference between Example 8 and Example 1 is that:

[0186] The proportion of raw materials added is adjusted, that is, pentaerythritol (1 mol) and acrylic acid (3 mol) are added and heated to obtain a trifunctional acrylic ester, and pentaerythritol (1 mol) and acrylic acid (2 mol) are added and heated to obtain a difunctional acrylic ester. Then, the above two kinds of acrylic esters are stirred at room temperature for 5 h and then stirred at 50°C for 2 h to obtain the target product monomer, and the rest is the same as Example 1;

[0187] In this example, the structure of the multifunctional monomer is:

[0188] .

[0189] Example 9

[0190] The main difference between Example 9 and Example 1 is that:

[0191] 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;

[0192] The rest is the same as Example 1.

[0193] Example 10

[0194] The main difference between Example 10 and Example 1 is that:

[0195] A method for preparing a prepolymer solution, comprising the following steps:

[0196] A pre-polymer solution was prepared by dissolving 5 g of the multi-functional monomer prepared in Example 1 and 0.05 g of azobisisobutyronitrile in 94.95 g of electrolyte solution. The electrolyte solution included 37.95 g of propyl propionate, 12 g of methyl ethyl 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-hexanetricarbonitrile, 12 g of lithium hexafluorophosphate, 3 g of lithium bisfluorosulfonylimide, and 1 g of lithium difluorophosphate.

[0197] The remainder was the same as in Example 1.

[0198] Example 11

[0199] The main difference between Example 11 and Example 1 is that:

[0200] A method of preparing a pre-polymer solution includes the steps of:

[0201] A pre-polymer solution was prepared by dissolving 3 g of the multi-functional monomer prepared in Example 1 and 0.03 g of azobisisobutyronitrile in 96.97 g of electrolyte solution. The electrolyte solution 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-hexanetricarbonitrile, 13 g of lithium hexafluorophosphate, 2.5 g of lithium bisfluorosulfonylimide, and 0.5 g of lithium bis(oxalato)borate.

[0202] The remainder was the same as in Example 1.

[0203] Example 12

[0204] The main difference between Example 12 and Example 1 is that:

[0205] A method of preparing a pre-polymer solution includes the steps of:

[0206] A pre-polymer solution was prepared by dissolving 1 g of the multi-functional monomer prepared in Example 1 and 0.01 g of azobisisobutyronitrile in 98.99 g of electrolyte solution. The electrolyte solution included 41.99 g of propyl propionate, 12 g of methyl ethyl 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-hexanetricarbonitrile, 12 g of lithium hexafluorophosphate, 3 g of lithium bisfluorosulfonylimide, and 1 g of lithium difluorophosphate.

[0207] The remainder was the same as in Example 1.

[0208] Example 13

[0209] The main difference between Example 13 and Example 1 is that:

[0210] A method for preparing a pre-polymer solution, comprising the steps of:

[0211] 0.8 g of the multi-functional monomer prepared in Example 1 was dissolved in 99.192 g of electrolyte solution with 0.008 g of azobisisobutyronitrile to obtain a pre-polymer solution; wherein the electrolyte solution comprises: 42.192 g of propyl propionate, 12 g of methyl ethyl carbonate, 14 g of ethylene carbonate, 11 g of fluoroethylene carbonate, 1 g of propane sultone, 1 g of ethylene sulfate, 2 g of 1,3,6-hexanetricarbonitrile, 12 g of lithium hexafluorophosphate, 3 g of lithium bisfluorosulfonylimide, and 1 g of lithium difluorophosphate;

[0212] The rest is the same as Example 1.

[0213] Example 14

[0214] The main difference between Example 14 and Example 1 is that:

[0215] A method for preparing a pre-polymer solution, comprising the steps of:

[0216] 7.3 g of the multi-functional monomer prepared in Example 1 was dissolved in 92.627 g of electrolyte solution with 0.073 g of azobisisobutyronitrile to obtain a pre-polymer solution; wherein the electrolyte solution comprises: 35.627 g of propyl propionate, 12 g of methyl ethyl carbonate, 14 g of ethylene carbonate, 11 g of fluoroethylene carbonate, 1 g of propane sultone, 1 g of ethylene sulfate, 2 g of 1,3,6-hexanetricarbonitrile, 12 g of lithium hexafluorophosphate, 3 g of lithium bisfluorosulfonylimide, and 1 g of lithium difluorophosphate;

[0217] The rest is the same as Example 1.

[0218] Example 15

[0219] The main difference between Example 15 and Example 1 is that:

[0220] 1,3-propylene diisocyanate is replaced by 1,15-pentadecane diisocyanate, and the rest is the same as Example 1;

[0221] In the present comparative example, the structural formula of the multi-functional monomer is:

[0222] .

[0223] Comparative Example 1

[0224] The main difference between Comparative Example 1 and Example 1 is that:

[0225] The multi-functional monomer is replaced by a compound represented by the following formula (5):

[0226] Formula (5);

[0227] The rest is the same as Example 1.

[0228] Comparative Example 2

[0229] The main difference between Comparative Example 2 and Example 1 is that:

[0230] Step (1) is: add 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 in a flask;

[0231] The rest is the same as Example 1.

[0232] In this comparative example, the structure formula of the multifunctional monomer is:

[0233] .

[0234] Comparative Example 3

[0235] The main difference between Comparative Example 3 and Example 1 is that:

[0236] The multifunctional monomer is replaced by a compound as shown in the following formula (6):

[0237] Formula (6);

[0238] The rest is the same as Example 1.

[0239] Test method:

[0240] (I) Infrared spectrum test:

[0241] The multifunctional monomer sample prepared in Example 1 is placed on the optical platform crystal surface of the infrared spectrometer ATR (model is20) element, the infrared ATR test software is opened, and the test parameters are set, the resolution is 4, and the scanning times are set to 32. After starting the test instrument, rotate the knob above the reflection plate, press the sample to be tested to make it fully contact with the lower emission hole, and start collecting data. After the test is completed, the infrared spectrum information of the sample is as shown in Figure 1 .

[0242] The infrared spectrum test result of Figure 1 shows that the absorption peak appearing at 3343 cm -1 is the stretching vibration peak of the nitrogen-hydrogen bond in the urethane group; the absorption peak appearing at 1721 cm -1 is the stretching vibration peak of the carbonyl group, which is the characteristic peak of the carbonyl group in the acrylate; the absorption peak appearing at 1668 cm -1 is the stretching vibration peak of the carbon-oxygen double bond of the urethane group; the absorption peak appearing at 1264 cm -1The appearing absorption peak is the stretching vibration peak of carbon-oxygen single bond of urethane group; 1172 cm -1 The appearing absorption peaks are the stretching vibration of ester groups, which prove the chemical structure of the multifunctional monomer.

[0243] (II) Viscosity test:

[0244] The viscosity of the prepolymer liquid prepared in Examples 1-15 and Comparative Examples 1-3 was tested by using NDJ-5S digital rotary viscometer. During the test, the prepolymer liquid sample was poured into a flat-bottom container with a diameter of more than 60 mm, the temperature of the prepolymer liquid was maintained at 25°C, and the operation table was stable without vibration. The instrument protection frame was reversely screwed into the lower end of the instrument, the L0 rotor was reversely screwed into the universal joint of the instrument, the rotation lifting knob was adjusted, and the rotor was slowly immersed in the prepolymer liquid until the rotor liquid level mark, i.e. the groove scale, was in the same plane as the liquid level, and the instrument was adjusted again. The rotor selection key was pressed to select the rotation speed, and then the confirm key was pressed. The rotor started to rotate, and after the display value was stable, the viscosity value was read by pressing the stop key. The test results are shown in Table 1 below.

[0245] (III) Electrochemical stability window test:

[0246] A stainless steel sheet was placed in a 2016 type battery shell, and the prepolymer liquid sample prepared in Examples 1-15 and Comparative Examples 1-3 was dropped into it, and then a lithium sheet and a battery shell were covered and clamped. The assembly of CR2016 type button cell was completed in a glove box filled with high-purity argon, and four batteries were prepared for each sample. The sample was heated to 50°C and reacted for 24 h. The electrochemical stability window was measured by linear voltammetry scanning using an electrochemical workstation (BioLogic Science Instruments), the initial potential was 2.5 V, the highest potential was 6 V, the scanning speed was 10 mV / s, and the voltage value corresponding to the intersection of the tangent line of the current slope increase region and the horizontal horizontal axis in the curve was read as the high voltage window. The test results are shown in Table 1 and Figure 2 .

[0247] wherein, Figure 2 is the electrochemical stability window scanning curve of the solid-state electrolyte of Example 1 of the present application, from Figure 2 It can be seen that the solid-state electrolyte of Example 1 has a high electrochemical stability window, the electrochemical stability window reaches 4.71 V, and can withstand a high voltage, which helps to improve the high voltage resistance performance of the battery.

[0248] (IV) Conductivity test:

[0249] The electrode ring of the fixed electrolyte container, the polytetrafluoroethylene single ring serving as the electrolyte container, and the pre-polymer liquid sample prepared in Examples 1-15 and Comparative Examples 1-3 were placed on the bottom of the battery shell, the pre-polymer liquid was dropped into the electrolyte container to fill the cavity of the electrolyte container, a stainless steel electrode plug was covered, and a pair of blocking electrodes was formed. Finally, the upper cover of the battery shell was covered, the butterfly nut was tightened, and the assembly of the battery was completed. The assembled pair of blocking batteries were directly connected to an electrochemical workstation (VMP-3e, Bio-Logic), and placed in a 50°C constant temperature box. The batteries were subjected to high-temperature curing, and the EIS test was performed at a frequency of 1MHz-0.03Hz. According to the formula σ = L / S(R-1), σ is the ionic conductivity, L is the thickness of the electrolyte, S is the area of the electrolyte film in contact with the electrode, and R is the impedance measured by the impedance meter. The ionic conductivity (σ, mS / cm) of the solid electrolyte was calculated using the above formula. The test results are shown in Table 1.

[0250] (V) High-voltage cycle test

[0251] Preparation of positive electrode sheet: 95%-99% by mass of lithium cobaltate material, 1%-5% by mass of conductive agent acetylene black, 1%-5% by mass of polyvinylidene fluoride were mixed and ground, and 1- methyl-2-pyrrolidone (NMP) was used for grinding and dispersing and adjusting the viscosity of the slurry. NMP is volatile during drying and is not included in the mass percentage of the positive electrode material. The positive electrode material was coated on the surface of an aluminum foil, and the positive electrode sheet was obtained after drying.

[0252] Preparation of negative electrode sheet: silicon particles and graphite were mixed in a mass ratio of 9:1 to obtain a silicon-carbon composite negative electrode material. The silicon-carbon composite negative electrode material accounted for 80%-95% by mass, the conductive carbon black accounted for 1%-10% by mass, the sodium carboxymethyl cellulose accounted for 1%-5% by mass, the polystyrene butadiene copolymer accounted for 1%-5% by mass, and water was added for grinding and dispersing. The mixture was coated on the surface of a copper foil and dried to obtain a negative electrode sheet.

[0253] The separator is a porous support material for separating the positive and negative electrodes, and a polyethylene separator is used.

[0254] The pre-polymer liquid 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 placed at room temperature for 24-72h, and then soaked for 24-72h. The solid-state battery was prepared by heating and curing at 40°C-80°C for 12h-72h.

[0255] High-voltage cycle test of solid-state soft-pack full battery

[0256] ​First, the battery is formed, and charged at 0.02C for 60 min, 0.05C for 60 min, 0.1C for 120 min, 0.2C for 180 min, heated at 45°C for 24h, cooled to room temperature, 0.01C constant current and constant voltage, charged to the upper limit voltage 4.58V, the cutoff current is 0.02C, stand for 10 min, then discharged at 0.1C current to 3V, stand for 10 min, that is, CC-CV mode at room temperature for 4 times; then charged at 1C current constant current and constant voltage at room temperature, 1C current constant current discharge, the charge and discharge cutoff voltage is 3V-4.58V, cycle 500 times, get the high voltage cycle 500 times capacity retention rate (%), test results refer to Figure 3 and Table 1.

[0257] wherein, Figure 3 is the high voltage cycle curve of the solid-state soft package battery of Example 1 and Comparative Example 1, wherein, Figure 3 the red curve in is the high voltage cycle curve of the solid-state soft package battery of Example 1, Figure 3 the black curve in is the high voltage cycle curve of the solid-state soft package battery of Comparative Example 1. From Figure 3 it can be seen that the battery capacity of Example 1 corresponding to the solid-state battery attenuates to 94.6% of the original value after 500 cycles of high voltage cycle, while the battery capacity of Comparative Example 1 attenuates to 85.0% of the original value after 500 cycles of high voltage cycle, which shows that the solid-state electrolyte of Example 1 can still maintain the normal operation of the battery during the cycle process of high voltage charge and discharge of the battery, and the solid-state electrolyte of Example 1 can withstand higher voltage and has higher voltage stability, thereby improving the cycle life of the battery.

[0258] Table 1

[0259]

[0260] According to the test results of Table 1, the battery containing the solid-state electrolyte of Examples 1 to 15 has a higher capacity retention rate after 500 cycles of high voltage cycle and an electrochemical stability window. It is shown that the solid-state electrolyte prepared from the multifunctional monomer of the application can improve the high voltage resistance performance of the solid-state electrolyte.

[0261] It can be known from the comparison of Examples 1-12, Example 13 and Example 14 that controlling the mass percentage of the multifunctional monomer in the prepolymer liquid in the range of 1%-5% can further ensure that the battery has good high voltage resistance performance.

[0262] It can be known from the comparison of the embodiment 1-3, the embodiment 4, the embodiment 5 and the embodiment 8 that when R7 in the multifunctional monomer is an alkyl group and the structure of the multifunctional monomer is a symmetrical molecular structure, the battery can further have better high-voltage resistance and a wider electrochemical stability window.

[0263] It can be known from the comparison of the embodiment 1-7 and the embodiment 15 that when R7 has a structure as shown in the formula (2) or the 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, the battery can further have better high-voltage resistance, a wider electrochemical stability window and higher conductivity.

[0264] The above describes the embodiments of the present application in detail, and the principle and implementation mode of the present application are described by applying specific examples; the above embodiment descriptions are only used to help understand the method of the present application and the core idea thereof; meanwhile, according to the principle of the present application, the specific implementation mode and the application range can be changed by the person skilled in the art, and the above description of the present application should not be understood as a limitation.

Claims

1. A solid state electrolyte, characterized by, The solid-state electrolyte is formed by solidification of a multifunctional monomer in an electrolyte solution; The multifunctional monomer has a structure as shown in formula (1): Formula (1); wherein R1, R2, R3, R4, R5, R6 are each independently selected from an acrylate group or a hydroxyl group, and at most only one of R1, R2, R3, R4, R5, R6 is a hydroxyl group, and R7 is selected from an alkyl group or a cycloalkyl group; The R7 has a structure as shown in formula (2) or formula (3): Formula (2); Formula (3); wherein n1 is an integer selected from 0-10, n2 is an integer selected from 0-10, n3 is an integer selected from 0-3, the sum of n1 and n2 is between 1-10; n4 is an integer selected from 0-5, n5 is an integer selected from 0-5, n6 is 0, n7 is 0, the sum of n4 and n5 is between 1-10.

2. The solid-state electrolyte of claim 1, wherein n1 is an integer selected from 3-10, n2 is an integer selected from 0-2, n3 is an integer selected from 0-1, the sum of n1 and n2 is between 3-10.

3. The solid-state electrolyte of claim 1, wherein, n4 is an integer selected from 0-2, n5 is an integer selected from 0-2, the sum of n4 and n5 is 4.

4. The solid-state electrolyte of claim 1, wherein, The multifunctional monomer includes at least one of the following compounds: 、 、 、 、 、 、 。 5. The solid-state electrolyte according to any one of claims 1-4, wherein, The number of functionalities of the multifunctional monomer is between 5-6.

6. The solid-state electrolyte according to any one of claims 1 to 4, wherein The multifunctional monomer has a symmetrical molecular structure.

7. The solid-state electrolyte of claim 1, wherein, The solid-state electrolyte has an electrical conductivity of 4 mS / cm-10 mS / cm.

8. A method of producing a solid-state electrolyte as claimed in any one of claims 1 to 7, characterized in that, The preparation method comprises: providing a pre-polymer solution, the pre-polymer solution comprising an electrolyte solution and a multifunctional monomer; causing in-situ solidification reaction of the multifunctional monomer in the pre-polymer solution to obtain the solid-state electrolyte.

9. The method of claim 8, wherein the solid-state electrolyte is prepared by a method comprising: The preparation method satisfies at least one of the following conditions: (1) the solidification temperature of the solidification reaction is 40℃-80℃; (2) the solidification time of the solidification reaction is 12h-72h; (3) the viscosity of the pre-polymer solution at room temperature is 2mPa.s-8mPa.s; (4) the pre-polymer solution further comprises an initiator.

10. The method of claim 9, wherein the solid-state electrolyte is prepared by a method comprising: The preparation method satisfies at least one of the following conditions: (1) the mass percentage of the multifunctional monomer in the pre-polymer solution is 1%-5%; (2) the mass percentage of the electrolyte solution in the pre-polymer solution is 94%-98.997%; (3) the electrolyte solution comprises a solvent and a lithium salt (4) the electrolyte solution comprises a solvent and an additive; (5) the mass percentage of the initiator in the pre-polymer solution is 0.003%-0.15%; (6) the initiator comprises at least one of an azo initiator, a peroxide initiator.

11. The method of claim 10, wherein the solid-state electrolyte is prepared by a process comprising: The preparation method satisfies at least one of the following conditions: (1) the solvent comprises at least one of a carbonate solvent and a carboxylate solvent; (2) the mass percentage of the solvent in the electrolyte solution is 79%-89%; (3) the lithium salt comprises at least one of lithium hexafluorophosphate, lithium perchlorate, lithium difluoro(oxalato)borate, lithium trifluoromethanesulfonimide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, lithium tetrafluoroborate, lithium difluorophosphate; (4) the mass percentage of the lithium salt in the electrolyte solution is 10%-20%. (5) the additive comprises at least one of propanesultone, ethylene sulfate, 1,3,6-hexanetricarbonitrile; (6) the mass percentage of the additive in the electrolyte is 1%-5%.

12. A lithium-ion battery, characterized by, A lithium ion battery comprising the solid-state electrolyte according to any one of claims 1 to 7, or the solid-state electrolyte prepared by the method according to any one of claims 8 to 11.

13. An electrical device, comprising: A lithium ion battery comprising the solid-state electrolyte according to any one of claims 1 to 7, or the solid-state electrolyte prepared by the method according to any one of claims 8 to 11, or the lithium ion battery according to claim 12.

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