Polyurethane-based composite solid electrolyte and its preparation method and application

Abstract

The present invention relates to a polyurethane-based composite solid electrolyte and its preparation method and application. The electrolyte comprises a polyurethane-modified inorganic solid electrolyte and a lithium salt dispersed in the polyurethane-modified inorganic solid electrolyte. Among them, the expression of the polyurethane-modified inorganic solid electrolyte is shown in formula (1); in formula (1), R<subgt;3< / subgt> is Among them, R<subgt;1< / subgt> is selected from alkyl groups, R<subgt;2< / subgt> is selected from aliphatic hydrocarbons, alicyclic hydrocarbons or aromatic hydrocarbons, m and n are both integers, m = 5 - 30, n = 5 - 50; R<subgt;4< / subgt>, R<subgt;5< / subgt>, R<subgt;6< / subgt>, R<subgt;7 are each independently selected from alkyl groups; R<subgt;8 is selected from perfluoroalkyl groups; M represents a modified inorganic solid electrolyte, which comprises an inorganic solid electrolyte and a polydopamine layer coating the inorganic solid electrolyte; X- is selected from or y and z are both integers, y = 5 - 50, z = 5 - 50. This electrolyte can improve the contact with the electrode interface, reduce the interface impedance and improve the battery electrical performance when used in solid-state lithium batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolytes, and particularly to a polyurethane-based composite solid electrolyte, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries are widely used in the fields of drones, energy storage, and new energy vehicles due to their high energy density, high power density, and long service life. However, at present, commercially available lithium-ion batteries usually use liquid electrolytes as electrolytes, and there are safety problems such as easy combustion and explosion during use, which seriously limit the development of lithium-ion batteries in special fields such as high energy density and high power.

[0003] Since solid-state lithium batteries do not contain electrolytes, they can effectively avoid problems such as electrolyte leakage, fire, and explosion, thereby improving the safety of the batteries and at the same time increasing the energy density of the batteries. The solid electrolytes used in solid-state lithium batteries include inorganic solid electrolytes and polymer solid electrolytes. Among them, polymer solid electrolytes mainly include polyurethane-based solid electrolytes. However, traditional polyurethane-based solid electrolytes have problems such as poor solid-solid interface contact with the electrode sheet, resulting in high interface impedance. At the same time, the ionic conductivity and mechanical strength of the electrolyte membrane are also difficult to meet the requirements of solid-state lithium batteries. Summary of the Invention

[0004] Based on this, in view of the above problems, it is necessary to provide a polyurethane-based composite solid electrolyte, a preparation method thereof, and an application thereof; the polyurethane-based composite solid electrolyte has excellent ionic conductivity and mechanical strength, and can effectively improve the solid-solid interface contact effect with the electrode sheet when used in solid-state lithium batteries, reduce the interface impedance, and improve the electrical performance of solid-state lithium batteries.

[0005] A polyurethane-based composite solid electrolyte includes a polyurethane-modified inorganic solid electrolyte and a lithium salt dispersed in the polyurethane-modified inorganic solid electrolyte. Among them, the expression of the polyurethane-modified inorganic solid electrolyte is shown in the following formula (1),

[0006]

[0007] In formula (1), R3 is wherein, R1 is selected from alkyl groups, R2 is selected from aliphatic hydrocarbons, alicyclic hydrocarbons or aromatic hydrocarbons, m and n are both integers, m = 5 - 30, and n = 5 - 50;

[0008] R4, R5, R6, and R7 are each independently selected from alkyl groups;

[0009] R8 is selected from perfluoroalkyl groups;

[0010] M represents a modified inorganic solid electrolyte, which includes an inorganic solid electrolyte and a polydopamine layer coating the inorganic solid electrolyte;

[0011] X - selected from

[0012] Both y and z are integers, where y = 5 - 50 and z = 5 - 50.

[0013] In one embodiment, R1 is selected from alkyl groups having 2 to 4 carbon atoms;

[0014] And / or, R2 is selected from at least one of;

[0015] And / or, R4 is selected from alkyl groups having 2 to 5 carbon atoms;

[0016] And / or, R5 is selected from alkyl groups having 2 to 5 carbon atoms;

[0017] And / or, R6 is selected from alkyl groups having 2 or 3 carbon atoms;

[0018] And / or, R7 is selected from alkyl groups having 1 to 3 carbon atoms;

[0019] And / or, R8 is selected from at least one of trifluoromethyl, pentafluoroethyl, and heptafluoropropyl.

[0020] In one embodiment, the inorganic solid electrolyte is selected from Li 6.4 La3Zr 1.4 Ta 0.6 O 12 、Li 3.3 La 0.56 TiO3、Li7La3Zr2O 12 、Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li 14 ZnGe4O 16 at least one of;

[0021] In one embodiment, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium hexafluorophosphate.

[0022] In one embodiment, the mass fraction of the lithium salt in the polyurethane-based composite solid electrolyte is 10% - 30%.

[0023] A preparation method of the polyurethane-based composite solid electrolyte as described above, comprising the following steps:

[0024] Perform a Michael addition reaction on the ionic liquid and the diolamine to obtain a dihydroxy ionic liquid, wherein the structural formula of the ionic liquid is selected from wherein, R7 is selected from alkyl groups, R8 is selected from perfluoroalkyl groups, R9 is selected from olefin groups, and X - is selected from

[0025] Mix the polyol and the diisocyanate and perform a prepolymerization reaction to obtain a polyurethane prepolymer with isocyanate end groups;

[0026] Perform a first polymerization reaction on the polyurethane prepolymer and the modified inorganic solid electrolyte to obtain a prepolymer, and perform a second polymerization reaction on the prepolymer and the dihydroxy ionic liquid to obtain a polyurethane-modified inorganic solid electrolyte; and

[0027] Mix the polyurethane-modified inorganic solid electrolyte and the lithium salt to obtain a polyurethane-based composite solid electrolyte.

[0028] In one embodiment, an organic base, dopamine and an inorganic solid electrolyte are mixed for in-situ oxidative polymerization to obtain the modified inorganic solid electrolyte.

[0029] In one embodiment, the ionic liquid is selected from at least one of;

[0030] and / or, the diolamine is selected from at least one of diethanolamine, diisopropanolamine, dibutanolamine, 2-(hydroxymethylamino)ethanol, N-ethanolpropanolamine, N-(5-hydroxypentyl)ethanolamine;

[0031] and / or, the polyol is selected from at least one of polyethylene glycol, polypropylene glycol, polybutylene glycol;

[0032] and / or, the diisocyanate is selected from at least one of diphenylmethane diisocyanate, toluene-2,3-diisocyanate, p-phenylene diisocyanate, cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, 1,6-hexamethylene diisocyanate.

[0033] In one embodiment, the molar ratio of the ionic liquid to the diolamine is 0.7:1 - 1:1;

[0034] and / or, the mass ratio of the polyol to the diisocyanate is 1:2 - 2:1;

[0035] And / or, the molar ratio of the isocyanate in the polyurethane prepolymer to the sum of the hydroxyl groups in the modified inorganic solid electrolyte and the dihydroxy ionic liquid is 0.7:1 - 0.95:1.

[0036] In one embodiment, the temperature of the Michael addition reaction is 25°C - 40°C, and the time is 1 h - 5 h;

[0037] And / or, the temperature of the prepolymerization reaction is 60°C - 100°C, and the time is 2 h - 8 h;

[0038] And / or, the temperature of the primary polymerization reaction is 60°C - 100°C, and the time is 2 h - 8 h;

[0039] And / or, the temperature of the secondary polymerization reaction is 60°C - 100°C, and the time is 2 h - 8 h.

[0040] Application of the polyurethane-based composite solid electrolyte as described above in a solid-state lithium battery.

[0041] In one embodiment, the polyurethane-based composite solid electrolyte is processed into an electrolyte membrane for use in a solid-state lithium battery, and the thickness of the electrolyte membrane is 10 μm - 100 μm.

[0042] In the present invention, a polydopamine layer and polyurethane are sequentially formed in-situ on the inorganic solid electrolyte, and a dihydroxy ionic liquid is used as a chain extender for the polyurethane to form a polyurethane-modified inorganic solid electrolyte with a diversified molecular structure. Then, it is compounded with a lithium salt to form a polyurethane-based composite solid electrolyte, which can not only improve the mechanical strength, heat resistance, ion mobility, and electrochemical window of the polyurethane-based composite solid electrolyte, but also can improve the dissociation degree of the lithium salt to a certain extent, thereby facilitating the improvement of the ionic conductivity of the polyurethane-based composite solid electrolyte.

[0043] Furthermore, when the polyurethane-based composite solid electrolyte is used in a solid-state lithium battery, it can not only improve the solid-solid interface contact effect with the electrode sheet, reduce the interface impedance, and improve the electrical performance of the solid-state lithium battery, but also when contacting with the lithium metal negative electrode, the perfluoroalkyl structure in the polyurethane-modified inorganic solid electrolyte can undergo a passivation reaction with the surface of the lithium metal negative electrode, and the formed lithium fluoride can effectively improve the cycling performance of the solid-state lithium battery with the lithium metal negative electrode. Description of the Drawings

[0044] Figure 1This is a cyclic performance test chart of the polyurethane-based composite solid electrolyte membrane prepared in Example 1 and Comparative Example 1 of the present invention at 25°C. Among them, A is the cyclic performance curve of the polyurethane-based composite solid electrolyte membrane prepared in Example 1 at 25°C; B is the cyclic performance curve of the polyurethane-based composite solid electrolyte membrane prepared in Comparative Example 1 at 25°C. Detailed implementation mode

[0045] To facilitate the understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention.

[0047] The present invention provides a polyurethane-based composite solid electrolyte, which includes a polyurethane-modified inorganic solid electrolyte and a lithium salt dispersed in the polyurethane-modified inorganic solid electrolyte. Among them, the expression of the polyurethane-modified inorganic solid electrolyte is shown in the following formula (1).

[0048]

[0049] In formula (1), R3 is Among them, R1 is selected from alkyl groups, R2 is selected from aliphatic hydrocarbons, alicyclic hydrocarbons or aromatic hydrocarbons, m and n are both integers, m = 5 - 30, and n = 5 - 50;

[0050] R4, R5, R6, and R7 are each independently selected from alkyl groups;

[0051] R8 is selected from perfluoroalkyl groups;

[0052] M represents a modified inorganic solid electrolyte, and the modified inorganic solid electrolyte includes an inorganic solid electrolyte and a polydopamine layer coating the inorganic solid electrolyte;

[0053] X - is selected from

[0054] y and z are both integers, y = 5 - 50, and z = 5 - 50.

[0055] It should be noted that the R3 structural unit is obtained by opening the carbon-nitrogen double bond of the isocyanate-terminated polymer during the polymerization reaction; the R6 structural unit is obtained by opening the carbon-carbon double bond of the olefin group during the Michael addition reaction.

[0056] In the polyurethane-based composite solid electrolyte of the present invention, it includes a polyurethane-modified inorganic solid electrolyte and a lithium salt. Among them, in the polyurethane-modified inorganic solid electrolyte, the polyurethane is bonded to the surface of the modified inorganic solid electrolyte through chemical bonds to form an integral whole.

[0057] Specifically, after the surface of the inorganic solid electrolyte is coated with a polydopamine layer, it has rich active functional groups such as hydroxyl groups, amino groups, and catechol. The polyurethane can be in-situ polymerized on the surface of the modified inorganic solid electrolyte through these active functional groups to form an integral whole, thereby significantly improving the mechanical strength and heat resistance of the polyurethane-based composite solid electrolyte of the present invention. Moreover, the polydopamine layer has excellent adhesiveness, so that when the polyurethane-based composite solid electrolyte of the present invention is used in a solid-state lithium battery, it can effectively improve the solid-solid interface contact effect with the electrode sheet, reduce the interface impedance, and thus improve the electrical performance of the solid-state lithium battery.

[0058] It should be noted that in the modified inorganic solid electrolyte, the polydopamine layer can coat a part of the surface of the inorganic solid electrolyte or completely coat the surface of the inorganic solid electrolyte, and this scheme does not limit this. Further, the thickness of the polydopamine layer is preferably nanoscale.

[0059] In some embodiments, the inorganic solid electrolyte is selected from Li 6.4 La3Zr 1.4 Ta 0.6 O 12 、Li 3.3 La 0.56 TiO3、Li7La3Zr2O 12 、Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li 14 ZnGe4O 16 and at least one of them, preferably Li 6.4 La3Zr 1.4 Ta 0.6 O 12 .

[0060] In addition, the chain extender structure used in the polyurethane of the present invention can effectively improve the ion mobility and electrochemical window of the polyurethane-based composite solid electrolyte of the present invention. At the same time, the chain extender structure has a perfluoroalkyl group (R8). First, it can enhance the dissociation degree of the lithium salt and improve the ionic conductivity of the polyurethane-based composite solid electrolyte of the present invention. Second, when the polyurethane-based composite solid electrolyte of the present invention is used in a solid-state lithium battery, the perfluoroalkyl structure can undergo a passivation reaction with the surface of the lithium metal anode, and the formed lithium fluoride can effectively improve the cycling performance of the solid-state lithium battery with the lithium metal anode. Third, when the polyurethane-based composite solid electrolyte of the present invention is used in a solid-state lithium battery, the abundant fluorine elements in the perfluoroalkyl structure can achieve a flame-retardant effect and improve the safety of the battery.

[0061] Specifically, R8 is selected from at least one of trifluoromethyl, pentafluoroethyl, and heptafluoropropyl, and is preferably pentafluoroethyl.

[0062] In some embodiments, R1 in the polyurethane structure is selected from alkyl groups having 2 to 4 carbon atoms, and is preferably ethyl.

[0063] In some embodiments, R2 in the polyurethane structure is selected from at least one of, and is preferably

[0064] In some embodiments, R4 in the polyurethane structure is selected from alkyl groups having 2 to 5 carbon atoms, and is preferably ethyl.

[0065] In some embodiments, R5 in the polyurethane structure is selected from alkyl groups having 2 to 5 carbon atoms, and is preferably ethyl.

[0066] It should be noted that R4 and R5 can be selected from alkyl groups having the same number of carbon atoms or alkyl groups having different numbers of carbon atoms, and the present solution does not limit this. Further, in order to make R4 and R5 form a symmetric structure, R4 and R5 are preferably alkyl groups having the same number of carbon atoms.

[0067] In some embodiments, R6 in the polyurethane structure is selected from alkyl groups having 2 or 3 carbon atoms, and is preferably ethyl.

[0068] In some embodiments, R7 in the polyurethane structure is selected from alkyl groups having 1 to 3 carbon atoms, and is preferably ethyl.

[0069] In the polyurethane-based composite solid electrolyte of the present invention, the polyurethane is bonded to the surface of the modified inorganic solid electrolyte through chemical bonds to form an integral body, and the lithium salt is dispersed in the polyurethane of the inorganic solid electrolyte modified by the polyurethane.

[0070] In some embodiments, the mass fraction of the lithium salt in the polyurethane-based composite solid electrolyte is 10%-30%.

[0071] In some embodiments, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium hexafluorophosphate, and is preferably lithium bis(trifluoromethanesulfonyl)imide or lithium bis(fluorosulfonyl)imide.

[0072] In some embodiments, the structural formula of the polyurethane-modified inorganic solid electrolyte is preferably as shown in the following formulas (1-1) and (1-2).

[0073]

[0074] wherein, R3 is M represents a modified inorganic solid electrolyte, and the modified inorganic solid electrolyte includes an inorganic solid electrolyte and a polydopamine layer coating the inorganic solid electrolyte.

[0075]

[0076] wherein, R3 is M represents a modified inorganic solid electrolyte, and the modified inorganic solid electrolyte includes an inorganic solid electrolyte and a polydopamine layer coating the inorganic solid electrolyte.

[0077] The present invention also provides a method for preparing a polyurethane-based composite solid electrolyte, which includes the following steps:

[0078] S1, performing a Michael addition reaction on an ionic liquid and a diolamine to obtain a dihydroxy ionic liquid, wherein the structural formula of the ionic liquid is selected from wherein, R7 is selected from alkyl groups, R8 is selected from perfluoroalkyl groups, R9 is selected from olefin groups, and X - is selected from

[0079] S2, mixing a polyglycol and a diisocyanate to perform a prepolymerization reaction to obtain a polyurethane prepolymer with isocyanate end groups;

[0080] S3, performing a primary polymerization reaction on the polyurethane prepolymer and a modified inorganic solid electrolyte to obtain a prepolymer, and performing a secondary polymerization reaction on the prepolymer and the dihydroxy ionic liquid to obtain a polyurethane-modified inorganic solid electrolyte; and

[0081] S4, mixing the polyurethane-modified inorganic solid electrolyte and a lithium salt to obtain a polyurethane-based composite solid electrolyte.

[0082] In step S1, by using the Michael addition reaction, the ionic liquid can be made to have dihydroxy active groups, which is conducive to chain extension of the polyurethane by the dihydroxy ionic liquid.

[0083] In some embodiments, the molar ratio of the ionic liquid to the diolamine is 0.7:1 - 1:1, preferably 0.7:1 - 0.95:1.

[0084] Specifically, the ionic liquid is selected from at least one of, and preferably The diolamine is selected from at least one of diethanolamine, diisopropanolamine, dibutanolamine, 2-(hydroxymethylamino)ethanol, N-ethanolpropanolamine, N-(5-hydroxypentyl)ethanolamine, and is preferably diethanolamine.

[0085] In some embodiments, the temperature of the Michael addition reaction is 25°C - 40°C and the time is 1 h - 5 h.

[0086] To further illustrate the reaction process of step S1, taking diethanolamine and X - as of as an example, the reaction equation of step S1 is shown as the following formula (2):

[0087]

[0088] It should be noted that the preparation steps of the ionic liquid used in the present invention include: reacting an olefin-based imidazole with a perfluoroiodoalkane under a protective atmosphere to obtain an iodine-containing ionic liquid, and then performing anion exchange on the iodine-containing ionic liquid with bis(fluorosulfonyl)imide (FSI) or bis(trifluoromethanesulfonyl)imide (TFSI) to obtain the ionic liquid.

[0089] Specifically, the olefin-based imidazole is selected from at least one of vinylimidazole and allylimidazole, and the perfluoroiodoalkane is selected from at least one of trifluoroiodoethane, trifluoroiodopropane, trifluoroiodobutane, pentafluoroiodoethane, pentafluoroiodopropane, pentafluoroiodobutane, heptafluoroiodoethane, heptafluoroiodopropane, and heptafluoroiodobutane.

[0090] In step S2, to prepare a polyurethane prepolymer with isocyanate end groups, the polyurethane prepolymer can be used as a bridge to chemically bond the isocyanate active group at one end of the polyurethane prepolymer to the modified inorganic solid electrolyte, and the isocyanate active group at the other end to the dihydroxy ionic liquid, thereby constructing a polyurethane-modified inorganic solid electrolyte with a diversified molecular structure.

[0091] Specifically, the mass ratio of the polyol to the diisocyanate is 1:2 - 2:1, preferably 4:5 - 2:1.

[0092] Furthermore, the polyol is selected from at least one of polyethylene glycol, polypropylene glycol, and polybutylene glycol, preferably polyethylene glycol. Among them, the molecular weight of polyethylene glycol is 1000 g / mol - 5000 g / mol, preferably 1000 g / mol - 4000 g / mol.

[0093] The diisocyanate is selected from at least one of diphenylmethane diisocyanate, toluene - 2,3 - diisocyanate, p - phenylene diisocyanate, cyclohexane - 1,4 - diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and 1,6 - hexamethylene diisocyanate, preferably diphenylmethane diisocyanate and toluene - 2,3 - diisocyanate.

[0094] In some embodiments, in the step of the prepolymerization reaction, a catalyst is further included, and the catalyst is selected from dibutyltin dilaurate.

[0095] In some embodiments, the temperature of the prepolymerization reaction is 60°C - 100°C, and the time is 2 h - 8 h.

[0096] In step S3, first, a modified inorganic solid electrolyte is added to the polyurethane prepolymer for a first polymerization to enable the polyurethane prepolymer to be bonded to the surface of the modified inorganic solid electrolyte through chemical bonds, and then a dihydroxy ionic liquid is added for a second polymerization to enable the dihydroxy ionic liquid to be bonded to the polyurethane prepolymer through chemical bonds, thereby obtaining a polyurethane - modified inorganic solid electrolyte.

[0097] In some embodiments, the molar ratio of the isocyanate in the polyurethane prepolymer to the sum of the hydroxyl groups in the modified inorganic solid electrolyte and the dihydroxy ionic liquid is 0.7:1 - 0.95:1.

[0098] In some embodiments, the temperature of the first polymerization reaction is 60°C - 100°C, and the time is 2 h - 8 h; the temperature of the second polymerization reaction is 60°C - 100°C, and the time is 2 h - 8 h.

[0099] To further illustrate the reaction processes of steps S2 and S3, taking polyethylene glycol, toluene - 2,3 - diisocyanate, the dihydroxy ionic liquid obtained from formula (2), and the modified inorganic solid electrolyte as examples, the reaction equations of steps S2 and S3 are shown as the following formula (3):

[0100]

[0101] In formula (3), R3 is M represents a modified inorganic solid electrolyte, which includes an inorganic solid electrolyte and a polydopamine layer coating the inorganic solid electrolyte.

[0102] It should be noted that the preparation steps of the modified inorganic solid electrolyte used in the present invention include: under a protective atmosphere, dopamine is in-situ oxidized and polymerized on the surface of the inorganic solid electrolyte in an organic base, so that a polydopamine layer is formed on the surface of the inorganic solid electrolyte.

[0103] Specifically, the organic base is selected from piperidine organic bases; the dopamine is selected from dopamine hydrochloride; the solvent for the mixing reaction of dopamine and the inorganic solid electrolyte is selected from chlorobenzene solution; the protective atmosphere is selected from argon.

[0104] In step S4, when the lithium salt is dispersed in the polyurethane-modified inorganic solid electrolyte, the mass ratio of the polyurethane-modified inorganic solid electrolyte to the lithium salt is 7:3 - 9:1.

[0105] The present invention also provides an application of the polyurethane-based composite solid electrolyte in a solid-state lithium battery.

[0106] Using the polyurethane-based composite solid electrolyte provided by the present invention in a solid-state lithium battery can improve the solid-solid interface contact effect with the electrode sheet, reduce the interface impedance, thereby improving the electrical performance of the solid-state lithium battery. At the same time, it can increase the ionic conductivity, improve the cycle performance and safety of the solid-state lithium battery, and further meet the market demand for high-performance solid-state lithium batteries.

[0107] In some embodiments, the polyurethane-based composite solid electrolyte is processed into an electrolyte membrane for use in a solid-state lithium battery. The thickness of the electrolyte membrane is 10 μm - 100 μm, preferably 20 μm - 80 μm.

[0108] Hereinafter, the polyurethane-based composite solid electrolyte, its preparation method and application will be further described through the following specific examples.

[0109] Example 1

[0110] 1 mol of ionic liquid and 1.1 mol of diethanolamine were added to a reaction vessel, and a dihydroxy ionic liquid was prepared through a Michael addition reaction at 25°C. Among them, the structural formula of the ionic liquid is selected from Among them, X - is

[0111] 80 g of polyethylene glycol with a molecular weight of 4000 g / mol and 25 g of diphenylmethane diisocyanate were placed in a reaction vessel, and a trace amount of dibutyltin dilaurate was added. The temperature was raised to 85 °C and the reaction was carried out for 3 h to obtain a polyurethane prepolymer with isocyanate end groups.

[0112] 0.05 g of dopamine hydrochloride and 1 g of Li 6.4 La3Zr 1.4 Ta 0.6 O 12 were uniformly dispersed in a chlorobenzene solution, and a piperidine organic base was added. Under argon protection, continuous oxidative polymerization was carried out at 25 °C for 3 h. After filtration, washing, and drying, modified Li 6.4 La3Zr 1.4 Ta 0.6 O 12 was prepared.

[0113] 15.5 g of the modified Li 6.4 La3Zr 1.4 Ta 0.6 O 12 was added to the polyurethane prepolymer and in-situ polymerization was carried out at 85 °C for 2 h. After the reaction was completed, 50 g of the above-prepared dihydroxy ionic liquid was added and further polymerization was carried out at 85 °C for 3 h to prepare a polyurethane-modified inorganic solid electrolyte, the structural formula of which is shown in formula (1-1).

[0114]

[0115] Among them, R3 is M is modified Li 6.4 La3Zr 1.4 Ta 0.6 O 12 .

[0116] 90 parts by mass of the polyurethane-modified inorganic solid electrolyte and 10 parts by mass of lithium bis(trifluoromethanesulfonyl)imide were mixed evenly to obtain a polyurethane-based composite solid electrolyte.

[0117] Example 2

[0118] 1 mol of ionic liquid and 1.1 mol of diethanolamine were added to a reaction vessel, and under the condition of 25 °C, a dihydroxy ionic liquid was prepared through a Michael addition reaction. Among them, the structural formula of the ionic liquid is selected from Among them, X - is

[0119] 80 g of polyethylene glycol with a molecular weight of 4000 g / mol and 25 g of toluene-2,3-diisocyanate were placed in a reaction vessel, and a trace amount of dibutyltin dilaurate was added. The temperature was raised to 85 °C and the reaction was carried out for 3 h to obtain a polyurethane prepolymer with isocyanate end groups.

[0120] 0.05 g of dopamine hydrochloride and 1 g of Li 3.3 La 0.56 TiO3 were uniformly dispersed in a chlorobenzene solution, and piperidine organic base was added. Under the protection of argon, continuous oxidative polymerization was carried out at 25 °C for 3 h. After filtration, washing, and drying, modified Li 3.3 La 0.56 TiO3 was prepared.

[0121] 15.5 g of modified Li 3.3 La 0.56 TiO3 was added to the polyurethane prepolymer and in-situ polymerization was carried out at 85 °C for 2 h. After the reaction was completed, 50 g of the above-prepared dihydroxy ionic liquid was added and further polymerization was carried out at 90 °C for 2 h to prepare a polyurethane-modified inorganic solid electrolyte, the structural formula of which is shown in formula (1-2),

[0122]

[0123] wherein, R3 is M is modified Li 3.3 La 0.56 TiO3.

[0124] 80 parts by mass of the polyurethane-modified inorganic solid electrolyte and 20 parts by mass of lithium bis(fluorosulfonyl)imide were mixed evenly to obtain a polyurethane-based composite solid electrolyte.

[0125] Example 3

[0126] 0.9 mol of ionic liquid and 1.1 mol of diethanolamine were added to a reaction vessel. Under the condition of 25 °C, a dihydroxy ionic liquid was prepared by Michael addition reaction. Among them, the structural formula of the ionic liquid is selected from wherein, X - is

[0127] 80 g of polyethylene glycol with a molecular weight of 4000 g / mol and 25 g of diphenylmethane diisocyanate were placed in a reaction vessel, and a trace amount of dibutyltin dilaurate was added. The temperature was raised to 85 °C and the reaction was carried out for 3 h to obtain a polyurethane prepolymer with isocyanate end groups.

[0128] The preparation method of the modified inorganic solid electrolyte is the same as that in Example 1.

[0129] 15.5 g of modified Li6.4 La3Zr 1.4 Ta 0.6 O 12 It was added to the polyurethane prepolymer and in-situ polymerized at 80 °C for 4 h. After the reaction was completed, 50 g of the above-prepared dihydroxy ionic liquid was added, and further polymerized at 85 °C for 3 h to prepare a polyurethane-modified inorganic solid electrolyte.

[0130] 70 parts by mass of the polyurethane-modified inorganic solid electrolyte was mixed uniformly with 30 parts by mass of lithium bis(oxalato)borate to obtain a polyurethane-based composite solid electrolyte.

[0131] Example 4

[0132] 1 mol of the ionic liquid and 1.1 mol of dipropanolamine were added to a reaction vessel, and a dihydroxy ionic liquid was prepared by Michael addition reaction at 25 °C. Among them, the structural formula of the ionic liquid was selected from wherein, X - is

[0133] 80 g of polyethylene glycol with a molecular weight of 4000 g / mol and 40 g of toluene-2,3-diisocyanate were placed in a reaction vessel, and a trace amount of dibutyltin dilaurate was added. The temperature was raised to 85 °C and the reaction was carried out for 3 h to obtain a polyurethane prepolymer with isocyanate end groups.

[0134] The preparation method of the modified inorganic solid electrolyte was the same as that in Example 1.

[0135] 15.5 g of the modified Li 6.4 La3Zr 1.4 Ta 0.6 O 12 was added to the polyurethane prepolymer and in-situ polymerized at 85 °C for 2 h. After the reaction was completed, 90 g of the above-prepared dihydroxy ionic liquid was added, and further polymerized at 85 °C for 3 h to prepare a polyurethane-modified inorganic solid electrolyte.

[0136] 80 parts by mass of the polyurethane-modified inorganic solid electrolyte was mixed uniformly with 20 parts by mass of lithium difluoroborate oxalate to obtain a polyurethane-based composite solid electrolyte.

[0137] Example 5

[0138] 1 mol of the ionic liquid and 1.1 mol of diethanolamine were added to a reaction vessel, and a dihydroxy ionic liquid was prepared by Michael addition reaction at 30 °C. Among them, the structural formula of the ionic liquid was selected from wherein, X - is

[0139] 80 g of polyethylene glycol with a molecular weight of 4000 g / mol and 40 g of toluene - 2,3 - diisocyanate were placed in a reaction vessel, and a small amount of dibutyltin dilaurate was added. The temperature was raised to 85 °C and the reaction was carried out for 3 h to obtain a polyurethane prepolymer with isocyanate - terminated ends.

[0140] The preparation method of the modified inorganic solid electrolyte is the same as that in Example 1.

[0141] 23 g of modified Li 6.4 La3Zr 1.4 Ta 0.6 O 12 were added to the polyurethane prepolymer and in - situ polymerization was carried out at 85 °C for 2 h. After the reaction was completed, 90 g of the above - prepared dihydroxy ionic liquid was added and further polymerization was carried out at 85 °C for 3 h to prepare a polyurethane - modified inorganic solid electrolyte.

[0142] 80 parts by mass of the polyurethane - modified inorganic solid electrolyte and 20 parts by mass of lithium bis(fluorosulfonyl)imide were mixed evenly to obtain a polyurethane - type composite solid electrolyte.

[0143] Example 6

[0144] 1 mol of ionic liquid and 1.1 mol of diethanolamine were added to a reaction vessel, and a dihydroxy ionic liquid was prepared by Michael addition reaction at 25 °C. Among them, the structural formula of the ionic liquid is selected from wherein, X - is

[0145] 80 g of polyethylene glycol with a molecular weight of 4000 g / mol and 25 g of diphenylmethane diisocyanate were placed in a reaction vessel, and a small amount of dibutyltin dilaurate was added. The temperature was raised to 85 °C and the reaction was carried out for 3 h to obtain a polyurethane prepolymer with isocyanate - terminated ends.

[0146] The preparation method of the modified inorganic solid electrolyte is the same as that in Example 1.

[0147] 7.75 g of modified Li 6.4 La3Zr 1.4 Ta 0.6 O 12 were added to the polyurethane prepolymer and in - situ polymerization was carried out at 85 °C for 2 h. After the reaction was completed, 50 g of the above - prepared dihydroxy ionic liquid was added and further polymerization was carried out at 85 °C for 3 h to prepare a polyurethane - modified inorganic solid electrolyte.

[0148] 80 parts by mass of the polyurethane - modified inorganic solid electrolyte and 20 parts by mass of lithium bis(oxalato)borate were mixed evenly to obtain a polyurethane - type composite solid electrolyte.

[0149] Example 7

[0150] 1 mol of ionic liquid and 1.1 mol of diethanolamine were added to a reaction vessel, and at 35 °C, through a Michael addition reaction, a dihydroxy ionic liquid was prepared, wherein the structural formula of the ionic liquid was selected from wherein, X - is

[0151] 20 g of polyethylene glycol with a molecular weight of 1000 g / mol and 25 g of diphenylmethane diisocyanate were placed in a reaction vessel, and a trace amount of dibutyltin dilaurate was added. The temperature was raised to 85 °C and the reaction was carried out for 3 h to obtain a polyurethane prepolymer with isocyanate end groups.

[0152] The preparation method of the modified inorganic solid electrolyte was the same as that in Example 1.

[0153] 15.5 g of modified Li 6.4 La3Zr 1.4 Ta 0.6 O 12 was added to the polyurethane prepolymer and in-situ polymerized at 85 °C for 2 h. After the reaction was completed, 50 g of the above-prepared dihydroxy ionic liquid was added and further polymerized at 85 °C for 3 h to prepare a polyurethane-modified inorganic solid electrolyte.

[0154] 80 parts by mass of the polyurethane-modified inorganic solid electrolyte and 20 parts by mass of lithium bis(trifluoromethanesulfonyl)imide were mixed evenly to obtain a polyurethane-based composite solid electrolyte.

[0155] Comparative Example 1

[0156] 80 g of polyethylene glycol with a molecular weight of 4000 g / mol and 25 g of diphenylmethane diisocyanate were placed in a reaction vessel, and a trace amount of dibutyltin dilaurate was added. The temperature was raised to 85 °C and the reaction was carried out for 3 h to obtain a polyurethane prepolymer with isocyanate end groups. Then 8 g of 1,4-butanediol was added and further polymerized at 85 °C for 3 h to prepare a polyurethane.

[0157] 15.5 g of Li 6.4 La3Zr 1.4 Ta 0.6 O 12 was mixed with the polyurethane to obtain a mixture, and then 80 parts by mass of the mixture and 20 parts by mass of lithium bis(trifluoromethanesulfonyl)imide were mixed evenly to obtain a polyurethane-based composite solid electrolyte.

[0158] Comparative Example 2

[0159] The difference between Comparative Example 2 and Example 1 is that 1,4-butanediol is used instead of the dihydroxy ionic liquid.

[0160] Comparative Example 3

[0161] The difference between Comparative Example 3 and Example 1 is that Li 6.4 La3Zr 1.4 Ta 0.6 O 12 has not been modified and has no polydopamine layer on its surface.

[0162] Application Example

[0163] The polyurethane-based composite solid electrolytes prepared in Examples 1-7 were respectively processed into electrolyte membrane samples 1-7 with a thickness of 80 μm.

[0164] Application Comparative Example

[0165] The polyurethane-based composite solid electrolytes prepared in Comparative Examples 1-3 were respectively processed into electrolyte membrane samples 8-10 with a thickness of 80 μm.

[0166] Samples 1-10 were respectively subjected to ionic conductivity tests and mechanical strength tests at 25 °C and 60 °C. Ionic conductivity test method: In the glove box, the above electrolyte membrane samples (Φ18 mm) were assembled with the positive electrode sheet (Φ15 mm) and the lithium sheet (Φ15 mm) into a solid-state battery. Electrochemical impedance tests were respectively carried out at 25 °C and 60 °C in the frequency range of 1 Hz to 8 MHz. According to the measured electrolyte impedance and formula (1), the ionic conductivity of the electrolyte was calculated.

[0167] σ = l / RS Formula (1);

[0168] where σ is the ionic conductivity of the electrolyte; l is the thickness of the electrolyte membrane; R is the bulk impedance of the electrolyte measured by the electrochemical impedance method; S is the contact area between the electrolyte and the lithium sheet.

[0169] The test results are shown in Table 1.

[0170] Table 1

[0171]

[0172]

[0173] As can be seen from Table 1, the electrolyte membranes prepared in Examples 1-7 have higher ionic conductivities at 25 °C and 60 °C than those in Comparative Examples 1-4, and excellent mechanical strength. In the electrolyte membrane prepared in Comparative Example 1, since it does not contain perfluoroalkyl groups, the dissociation degree of the lithium salt is weak. Therefore, its ionic conductivity at 25 °C and 60 °C is much lower than that of the electrolyte membranes prepared in the examples. Moreover, the inorganic solid electrolyte was not modified. After mixing polyurethane, inorganic solid electrolyte and lithium salt, the obtained polyurethane-based composite solid electrolyte is only a physical combination of the components without chemical bonding, resulting in poor mechanical strength of the electrolyte membrane. In the electrolyte membrane prepared in Comparative Example 2, 1,4-butanediol was used as the chain extender, and the dissociation degree of the lithium salt is far less than that in Example 1. Therefore, its ionic conductivity at 25 °C and 60 °C is low. In the electrolyte membrane prepared in Comparative Example 3, since the inorganic solid electrolyte was not modified, the chemical bonding with other components is weak, resulting in low mechanical strength of the electrolyte membrane and its ionic conductivity is also lower than that in the examples.

[0174] The cyclic performance tests were carried out on Sample 1 and Sample 8. Cyclic performance test method: Under the condition of 25 °C, the solid-state battery was charged at a constant current of 0.33C from 3.0V to 4.2V, then left standing for 5 minutes, and then charged at a constant voltage of 4.2V until the cut-off current of 0.02C, and finally discharged at a rate of 0.33C to 3.0V, and finally left standing for 5 minutes. Cycle 50 - 200 times in this way, and the test results are as Figure 1 shown.

[0175] According to Figure 1 it can be seen that the electrolyte membrane prepared in Example 1 has excellent cyclic stability. It can still maintain about 97% of the capacitance after about 100 cycles of cyclic testing, about 94% of the capacitance after about 150 cycles of cyclic testing, and the capacitance only begins to decrease slowly after more than 150 cycles of cyclic testing. In the cyclic testing of the electrolyte membrane prepared in Comparative Example 1, the capacitance decreased significantly. The capacitance dropped to about 80% after about 50 cycles of cyclic testing, and the cyclic stability is poor.

[0176] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0177] The above-described embodiments merely represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A polyurethane-based composite solid electrolyte, characterized in that, It includes a polyurethane-modified inorganic solid electrolyte and a lithium salt dispersed in the polyurethane-modified inorganic solid electrolyte. Among them, the expression of the polyurethane-modified inorganic solid electrolyte is shown as the following formula (1). ； In formula (1), R3 is , where R1 is selected from alkyl groups, R2 is selected from aliphatic hydrocarbons, alicyclic hydrocarbons or aromatic hydrocarbons, m and n are both integers, m = 5 - 30, and n = 5 - 50; R4, R5, R6, and R7 are each independently selected from alkyl groups; R8 is selected from perfluoroalkyl groups; M represents a modified inorganic solid electrolyte, and the modified inorganic solid electrolyte includes an inorganic solid electrolyte and a polydopamine layer coating the inorganic solid electrolyte; X - selected from or ; y and z are both integers, y = 5 - 50, z = 5 - 50; The preparation method of the polyurethane-based composite solid electrolyte includes the following steps: The Michael addition reaction is carried out between an ionic liquid and a diolamine to obtain a dihydroxy ionic liquid, wherein the structural formula of the ionic liquid is selected from , wherein R9 is selected from an olefin group; Mix a polyglycol with a diisocyanate and carry out a prepolymerization reaction to obtain a polyurethane prepolymer with isocyanate end groups; Carry out a primary polymerization reaction on the polyurethane prepolymer and the modified inorganic solid electrolyte to obtain a prepolymer, and carry out a secondary polymerization reaction on the prepolymer and the dihydroxy ionic liquid to obtain a polyurethane-modified inorganic solid electrolyte; Mix the polyurethane-modified inorganic solid electrolyte with a lithium salt to obtain a polyurethane-based composite solid electrolyte.

2. The polyurethane-based composite solid electrolyte according to claim 1, characterized in that, R1 is selected from alkyl groups having 2 to 4 carbon atoms; And / or, R2 is selected from , , , , , , at least one of; And / or, R4 is selected from alkyl groups having 2 to 5 carbon atoms; And / or, R5 is selected from alkyl groups having 2 to 5 carbon atoms; And / or, R6 is selected from alkyl groups having 2 or 3 carbon atoms; And / or, R7 is selected from alkyl groups having 1 to 3 carbon atoms; And / or, R8 is selected from at least one of trifluoromethyl, pentafluoroethyl, and heptafluoropropyl.

3. The polyurethane-based composite solid electrolyte according to claim 1, wherein The inorganic solid electrolyte is selected from Li 6.4 La3Zr 1.4 Ta 0.6 O 12 、Li 3.3 La 0.56 TiO3, Li7La3Zr2O 12 、Li 1.3 Al 0.3 Ti 1.7 (PO4)3, Li 14 ZnGe4O 16 or at least one of them.

4. The polyurethane-based composite solid electrolyte according to claim 1, characterized in that, The lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium tetrafluoroborate, and lithium hexafluorophosphate.

5. The polyurethane-based composite solid electrolyte according to claim 1, characterized in that, The mass fraction of the lithium salt in the polyurethane-based composite solid electrolyte is 10% - 30%.

6. A method for preparing the polyurethane-based composite solid electrolyte according to any one of claims 1 to 5, characterized in that, It includes the following steps: The Michael addition reaction is carried out between an ionic liquid and a diolamine to obtain a dihydroxy ionic liquid, wherein the structural formula of the ionic liquid is selected from , wherein R7 is selected from alkyl groups, R8 is selected from perfluoroalkyl groups, R9 is selected from olefin groups, and X - is selected from or ; Mix a polyglycol with a diisocyanate and carry out a prepolymerization reaction to obtain a polyurethane prepolymer with isocyanate end groups; Carry out a primary polymerization reaction on the polyurethane prepolymer and the modified inorganic solid electrolyte to obtain a prepolymer, and carry out a secondary polymerization reaction on the prepolymer and the dihydroxy ionic liquid to obtain a polyurethane-modified inorganic solid electrolyte; and Mix the polyurethane-modified inorganic solid electrolyte with a lithium salt to obtain a polyurethane-based composite solid electrolyte.

7. The preparation method of the polyurethane-based composite solid electrolyte according to claim 6, characterized in that, Mix an organic base, dopamine, and an inorganic solid electrolyte and carry out in-situ oxidative polymerization to obtain the modified inorganic solid electrolyte.

8. The preparation method of the polyurethane-based composite solid electrolyte according to claim 6, characterized in that The ionic liquid is selected from , , , , , , , , , , , , , , , , , , , , , , , , , , ; and at least one of them And / or, the diolamine is selected from at least one of diethanolamine, diisopropanolamine, dibutanolamine, 2-(hydroxymethylamino)ethanol, N-ethanolpropanolamine, and N-(5-hydroxypentyl)ethanolamine; And / or, the polyglycol is selected from at least one of polyethylene glycol, polypropylene glycol, and polybutylene glycol; And / or, the diisocyanate is selected from at least one of diphenylmethane diisocyanate, toluene-2,3-diisocyanate, p-phenylene diisocyanate, cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and 1,6-hexamethylene diisocyanate.

9. The preparation method of the polyurethane-based composite solid electrolyte according to claim 6, wherein The molar ratio of the ionic liquid to the diolamine is 0.7:1 - 1:1; and / or, the mass ratio of the polyglycol to the diisocyanate is 1:2 - 2:1; and / or, the molar ratio of the isocyanate in the polyurethane prepolymer to the sum of the hydroxyl groups in the modified inorganic solid electrolyte and the dihydroxy ionic liquid is 0.7:1 - 0.95:

1.

10. The preparation method of the polyurethane-based composite solid electrolyte according to claim 6, characterized in that, The temperature of the Michael addition reaction is 25°C - 40°C, and the time is 1 h - 5 h; and / or, the temperature of the prepolymerization reaction is 60°C - 100°C, and the time is 2 h - 8 h; and / or, the temperature of the primary polymerization reaction is 60°C - 100°C, and the time is 2 h - 8 h; and / or, the temperature of the secondary polymerization reaction is 60°C - 100°C, and the time is 2 h - 8 h.

11. Use of a polyurethane-based composite solid electrolyte according to any one of claims 1 - 5 in a solid-state lithium battery.

12. Use of the polyurethane-based composite solid electrolyte according to claim 11 in a solid-state lithium battery, characterized in that, The polyurethane-based composite solid electrolyte is processed into an electrolyte membrane for use in a solid-state lithium battery, and the thickness of the electrolyte membrane is 10 µm - 100 µm.

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