Flame-retardant epoxy resin electrolyte prepolymer and solid electrolyte membrane comprising the same

Abstract

The application discloses a flame-retardant epoxy resin electrolyte prepolymer and a solid electrolyte membrane containing the same, the flame-retardant epoxy resin electrolyte prepolymer is an oligomer obtained through ring-opening addition reaction of phosphonate diol, diglycidyl ether and polyether amine; the terminal of the 1,4-butanediol oligomer contains unreacted epoxy groups and / or amine groups; the chemical formula of the 1,4-butanediol phosphonate diol is shown as formula (I): formula (I); wherein, R1 and R2 are alkyl or aryl; the flame-retardant epoxy resin electrolyte prepolymer of the application improves the flame retardance of the epoxy resin electrolyte prepolymer by introducing the phosphonate diol, improves the compatibility with lithium salt by providing lithium ion coordination sites through ether bonds P-O-C bonds and P=O, guarantees the smooth progress of subsequent curing reaction by retaining unreacted active groups (epoxy groups and / or amine groups), and finally improves the flame retardance and ionic conductivity of the epoxy resin solid electrolyte membrane formed after the epoxy resin electrolyte prepolymer and lithium salt are cured.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more particularly to a flame-retardant epoxy resin electrolyte prepolymer and a solid electrolyte membrane containing the same. Background Technology

[0002] Developing high-energy-density lithium-ion batteries is a key measure to solve the range anxiety problem of power batteries. Replacing traditional graphite anodes with lithium metal anodes promises to achieve higher energy densities in lithium-ion batteries; however, the growth of lithium dendrites can puncture the electrolyte membrane, leading to electrolyte leakage and short circuits between the positive and negative electrodes, posing a significant safety hazard. Solid-state polymer electrolytes, through targeted structural design, can balance the mechanical strength and flexibility of materials, construct rapid lithium-ion transport channels, and suppress lithium dendrite growth, thereby achieving a better balance in terms of electrolyte mechanical properties, electrochemical performance, and safety performance.

[0003] The epoxy groups in epoxy resin structures can effectively dissolve and complex lithium salts. Furthermore, the cross-linked epoxy resin system has low crystallinity, minimal state transitions, and relatively low temperature-dependent ionic conductivity, exhibiting good structural stability at high temperatures. This makes it a potential candidate for future all-solid-state polymer electrolyte substrates. However, epoxy resin itself is highly flammable, with a limiting oxygen index of only 17%-19%. If the assembled lithium battery experiences thermal runaway, the potential safety hazards cannot be ignored. In addition, epoxy resin has a low room-temperature ionic conductivity, typically only around 10. -6 -10 -8 S cm -1 Epoxy resins that have not undergone electrochemical modification are difficult to meet the needs of practical applications.

[0004] Therefore, there is a need to provide a modified epoxy resin prepolymer for preparing epoxy resin electrolytes, so as to improve the flame retardancy and ionic conductivity of epoxy resin electrolyte membranes. Summary of the Invention

[0005] In view of this, this application provides a flame-retardant epoxy resin electrolyte prepolymer and a solid electrolyte membrane containing the prepolymer, in order to solve the problem of how to improve the flame retardancy and ionic conductivity of epoxy resin electrolyte membranes.

[0006] To achieve the above technical objectives, this application adopts the following technical solution:

[0007] In a first aspect, this application provides a flame-retardant epoxy resin electrolyte prepolymer, which is an oligomer obtained by ring-opening addition reaction of phosphonate diol, diglycidyl ether and polyetheramine; the oligomer ends with unreacted epoxy groups and / or amine groups;

[0008] The chemical formula of phosphonate diol is shown in formula (I):

[0009] Formula (I); wherein R1 and R2 are both alkyl or aryl groups.

[0010] Secondly, this application provides a method for preparing a flame-retardant epoxy resin electrolyte prepolymer, comprising the following steps:

[0011] S1. Obtain phosphonate diol;

[0012] S2. Under an inert gas atmosphere, a ring-opening addition reaction is carried out using phosphonate diol, diglycidyl ether, and polyetheramine as raw materials to obtain a flame-retardant epoxy resin prepolymer.

[0013] Preferably, the ring-opening addition reaction temperature is 50-100℃.

[0014] Preferably, the method for obtaining phosphonate diols is as follows:

[0015] S11. Under an inert atmosphere, a ring-opening alcoholysis reaction is carried out using cyclic phosphoric anhydride and diol / diphenol as raw materials to obtain methylpropionic acid ester phosphonic acid;

[0016] S12. Under inert atmosphere and catalyst conditions, esterification reaction is carried out using methylpropionic acid ester phosphonic acid and diol / diphenol as raw materials to obtain phosphonate diol.

[0017] Thirdly, this application provides a flame-retardant epoxy resin solid electrolyte membrane, which includes a flame-retardant epoxy resin electrolyte prepolymer, a lithium salt, and hydroxylated boron nitride; the hydroxylated boron nitride has a three-dimensional chain-like structure.

[0018] Preferably, hydroxylated boron nitride is obtained by modifying nano-boron nitride with an inorganic base.

[0019] Fourthly, this application provides a method for preparing a flame-retardant epoxy resin solid electrolyte membrane, comprising the following steps:

[0020] K1. Lithium salt and hydroxylated boron nitride are added to flame-retardant epoxy resin electrolyte prepolymer to obtain a blend;

[0021] K2. Inject the blend into a conductive mold, arrange the alternating electric field, then heat-cur and demold to obtain a flame-retardant epoxy resin solid electrolyte membrane.

[0022] Preferably, the AC electric field frequency is 10-1000 Hz, the voltage is 100-1000 V, the heat curing temperature is 100-160℃, and the heat curing time is 2-6h.

[0023] Preferably, the lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium dioxalate borate.

[0024] Fifthly, this application provides a lithium battery comprising a flame-retardant epoxy resin solid electrolyte membrane.

[0025] The beneficial effects of this application are as follows:

[0026] The flame-retardant epoxy resin electrolyte prepolymer of this application improves the flame retardancy of the epoxy resin electrolyte prepolymer by introducing phosphonate diol, improves the compatibility with lithium salt by providing lithium ion coordination sites through ether bond POC bond and P=O, and ensures the smooth progress of subsequent curing reaction by retaining unreacted active groups (epoxy groups and / or amine groups), ultimately improving the flame retardancy and ionic conductivity of the epoxy resin solid electrolyte film formed after the epoxy resin electrolyte prepolymer and lithium salt are cured.

[0027] This application utilizes a flame-retardant epoxy resin solid electrolyte membrane prepared from a phosphonate diol-based flame-retardant epoxy resin electrolyte prepolymer and nano-boron nitride. This membrane exhibits a high limiting oxygen index, achieving a superior multi-element synergistic flame-retardant mechanism within PBN and significantly improving the electrolyte's safety performance. Furthermore, this application employs a flame-retardant epoxy resin solid electrolyte prepared by hydroxylating boron nitride with an alkali. The oxygen vacancies on the boron nitride surface effectively immobilize TFSI. - This creates a lithium-rich region at the electrolyte and electrode interface, promoting the migration and conduction of lithium ions in the epoxy resin. By arranging nano-boron nitride in an orderly manner under an alternating electric field, a three-dimensional chain-like lithium ion transport channel is constructed, effectively improving the electrochemical performance of the epoxy resin solid electrolyte. Attached Figure Description

[0028] Figure 1 Infrared spectrum of the flame-retardant epoxy resin solid polymer electrolyte prepared in Example 9;

[0029] Figure 2 Here is a SEM image of the epoxy resin electrolyte membrane from Example 9;

[0030] Figure 3 This is a SEM image of the epoxy resin electrolyte membrane in Comparative Example 4. Detailed Implementation

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

[0032] This application provides a flame-retardant epoxy resin electrolyte prepolymer, which is an oligomer obtained by ring-opening addition reaction of phosphonate diol, diglycidyl ether and polyetheramine; the oligomer contains unreacted epoxy groups and / or amine groups at the end;

[0033] The chemical formula of phosphonate diol is shown in formula (I):

[0034] Formula (I); wherein R1 and R2 are both alkyl or aryl groups.

[0035] The flame-retardant epoxy resin electrolyte prepolymer of this application contains POC bonds formed by the P=O group of phosphonate diol and epoxy groups, and CN bonds formed by the amino group of polyetheramine and epoxy groups. The epoxy groups are derived from the ring-opening of diglycidyl ether. It is worth noting that the flame-retardant epoxy resin electrolyte prepolymer of this application is a raw material for preparing flame-retardant epoxy resin solid electrolyte membranes. The prepolymer undergoes a cross-linking and curing reaction to finally form epoxy resin, which serves as the continuous phase network matrix of the flame-retardant epoxy resin solid electrolyte membrane.

[0036] In this application, the flame-retardant epoxy resin electrolyte prepolymer improves the flame retardancy of the epoxy resin electrolyte prepolymer by introducing phosphonate diol, improves the compatibility with lithium salt by providing lithium ion coordination sites through ether bond POC bond and P=O, and ensures the smooth progress of subsequent curing reaction by retaining unreacted active groups (epoxy groups and / or amine groups), ultimately improving the flame retardancy and ionic conductivity of the epoxy resin solid electrolyte film formed after the epoxy resin electrolyte prepolymer and lithium salt are cured.

[0037] In some embodiments, phosphonate diols include one or more of ethylene glycol methylpropionate phosphonate ester, ethylene glycol methylpropionate phosphonate ester, and butylene glycol methylpropionate ester.

[0038] Preferably, the phosphonate diol is ethylene glycol methylpropionate phosphonate.

[0039] In some embodiments, the mass ratio of phosphonate diol, diglycidyl ether, and polyetheramine is 1:(1-1.2):(3-3.2).

[0040] This application provides a method for preparing a flame-retardant epoxy resin electrolyte prepolymer, comprising the following steps:

[0041] S1. Obtain phosphonate diol;

[0042] S2. Under an inert atmosphere, a ring-opening addition reaction is carried out using phosphonate diol, diglycidyl ether, and polyetheramine as raw materials to obtain a flame-retardant epoxy resin prepolymer.

[0043] In some embodiments, the ring-opening addition reaction is carried out at a temperature of 50-100°C.

[0044] In some embodiments, the diglycidyl ether is one or more of polyethylene glycol diglycidyl ether (PEGDGE), polypropylene glycol diglycidyl ether (PPGDGE), 1,4-butanediol diglycidyl ether (BDDE), and poly(dimethylsiloxane) diglycidyl ether (PDMSDE).

[0045] In some embodiments, the polyetheramine is one or more of polyetheramine D230, polyetheramine D400, polyetheramine D2000 and polyetheramine T5000.

[0046] In some embodiments, the method for obtaining phosphonate diols to prepare flame-retardant epoxy resin electrolyte prepolymers is as follows:

[0047] S11. Under an inert atmosphere, a ring-opening alcoholysis reaction is carried out using cyclic phosphoric anhydride and diol / diphenol as raw materials to obtain methylpropionic acid ester phosphonic acid;

[0048] S12. Under inert atmosphere and catalyst conditions, esterification reaction is carried out using methylpropionic acid ester phosphonic acid and diol / diphenol as raw materials to obtain phosphonate diol.

[0049] The temperature for the ring-opening alcoholysis reaction in step S11 is 120-160℃, and the molar ratio of cyclic phosphoric anhydride, diol / diphenol is 1:1-1.2.

[0050] The molecular formula of cyclic phosphoric anhydrides is shown in formula (II):

[0051] Formula (II);

[0052] The reaction formula for step S11 is as follows:

[0053]

[0054] In some embodiments, the catalyst in step S12 is 4A molecular sieve.

[0055] The temperature of the esterification reaction in step S12 is 150-200℃, and the molar ratio of methylpropionic acid ester phosphonic acid and diol / diphenol is 1:1-1.2.

[0056] The reaction formula for step S12 is as follows:

[0057]

[0058] R1 and R2 are any one of ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, isopentyl, n-hexyl, isohexyl, n-octyl, isooctyl, 1-decyl, cyclohexyl, cyclopentyl, cycloheptyl, and phenyl.

[0059] Preferably, the diol is ethylene glycol.

[0060] This application provides a flame-retardant epoxy resin solid electrolyte membrane, which includes a flame-retardant epoxy resin electrolyte prepolymer, a lithium salt, and hydroxylated boron nitride; the hydroxylated boron nitride has a three-dimensional chain-like structure.

[0061] The flame-retardant epoxy resin solid electrolyte membrane of this application uses phosphonate diol as an intrinsic flame retardant. At the same time, the introduced nano-boron nitride is used to construct a three-dimensional chain-like lithium-ion transport channel under the drive of an AC electric field. The prepared flame-retardant epoxy resin solid electrolyte membrane has a good PBN multi-element synergistic flame-retardant mechanism, and achieves improved electrochemical performance while obtaining high safety performance.

[0062] This application utilizes a flame-retardant epoxy resin solid electrolyte membrane prepared from a phosphonate diol-based flame-retardant epoxy resin electrolyte prepolymer and nano-boron nitride. This membrane exhibits a high limiting oxygen index, achieving a superior multi-element synergistic flame-retardant mechanism within PBN and significantly improving the electrolyte's safety performance. Furthermore, this application employs a flame-retardant epoxy resin solid electrolyte prepared by hydroxylating boron nitride with an alkali. The oxygen vacancies on the boron nitride surface effectively immobilize TFSI. - This creates a lithium-rich region at the electrolyte and electrode interface, promoting the migration and conduction of lithium ions in the epoxy resin. By arranging nano-boron nitride in an orderly manner under an alternating electric field, a three-dimensional chain-like lithium ion transport channel is constructed, effectively improving the electrochemical performance of the epoxy resin solid electrolyte.

[0063] In some embodiments, hydroxylated boron nitride is obtained by modifying nano-boron nitride with an inorganic base; the inorganic base includes one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, and lithium hydroxide.

[0064] This application provides a method for preparing a flame-retardant epoxy resin solid electrolyte membrane, comprising the following steps:

[0065] K1. Lithium salt and hydroxylated boron nitride are added to flame-retardant epoxy resin electrolyte prepolymer to obtain a blend;

[0066] K2. Inject the blend into a conductive mold, arrange the alternating electric field, then heat-cur and demold to obtain a flame-retardant epoxy resin solid electrolyte membrane.

[0067] In some embodiments, the conductive mold is made of ITO glass and conductive adhesive; after the blended liquid is arranged in an alternating electric field, the electric field is removed, and then the conductive mold is placed on a hot plate for heat curing and demolding.

[0068] In some embodiments, the AC electric field frequency is 10-1000 Hz, the voltage is 100-1000 V, the thermosetting temperature is 100-160℃, and the thermosetting time is 2-6 h.

[0069] In some embodiments, the lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium dioxalate borate.

[0070] This application provides a lithium battery comprising a flame-retardant epoxy resin solid electrolyte membrane.

[0071] The following specific embodiments further illustrate this solution.

[0072] Raw material preparation:

[0073] The preparation method of ethylene glycol methylpropionate phosphonate ester is as follows:

[0074] Under a nitrogen atmosphere, 1.0 mol of cyclic phosphoric anhydride and 1.0 mol of ethylene glycol were placed in a three-necked flask and mechanically stirred at 120 °C for 3 h. After stirring, the mixture was allowed to stand and cool to room temperature to obtain a bright yellow clear liquid, which is ethylene glycol methylpropionate phosphonic acid.

[0075] Under a nitrogen atmosphere, 1.0 mol of ethylene glycol methylpropionate phosphonic acid, 1.03 mol of ethylene glycol, and 100 g of 4A molecular sieve were placed in a three-necked flask and reacted with mechanical stirring at 150 °C for 4 h. The mixture was then filtered while hot, and the filtrate was allowed to stand and cool to room temperature to obtain a brownish-yellow gel-like viscous solid, which is the ethylene glycol methylpropionate phosphonate flame retardant.

[0076] The preparation method of ethylene glycol methylpropionate phosphonate butyl glycol ester is the same as that of ethylene glycol methylpropionate phosphonate ester, except that ethylene glycol is replaced with 1,4-butanediol.

[0077] Example 1

[0078] A flame-retardant epoxy resin electrolyte prepolymer is an oligomer obtained by ring-opening addition reaction of ethylene glycol methylpropionate, ethylene glycol phosphonate, diglycidyl ether, and polyetheramine; the oligomer ends contain unreacted epoxy groups and / or amine groups.

[0079] A method for preparing a flame-retardant epoxy resin electrolyte prepolymer includes the following steps:

[0080] S1. Under a nitrogen atmosphere, 1.0 mol of cyclic phosphoric anhydride and 1.0 mol of ethylene glycol were placed in a three-necked flask and mechanically stirred at 120°C for 3 h. After stirring, the mixture was allowed to stand and cool to room temperature to obtain a bright yellow clear liquid, which is ethylene glycol methylpropionate phosphonic acid. Under a nitrogen atmosphere, 1.0 mol of ethylene glycol methylpropionate phosphonic acid, 1.03 mol of ethylene glycol, and 100 g of 4A molecular sieve were placed in a three-necked flask and mechanically stirred at 150°C for 4 h. The mixture was then filtered while hot, and the filtrate was allowed to stand and cool to room temperature to obtain a brownish-yellow gelatinous viscous solid, which is ethylene glycol methylpropionate phosphonate ethylene glycol ester.

[0081] S2. Under an inert gas atmosphere, 2.0 g of ethylene glycol methylpropionate phosphonate, 2.21 g of polyethylene glycol diglycidyl ether, and 6.06 g of polyetheramine D230, which have been vacuum dehydrated and dried, are added to a three-necked flask and stirred at 60 °C for 2 h to carry out a ring-opening addition reaction, thereby obtaining a flame-retardant epoxy resin prepolymer.

[0082] Example 2

[0083] A flame-retardant epoxy resin electrolyte prepolymer is identical to that in Example 1, except that in step S2, 2.0g of ethylene glycol methylpropionate phosphonate, 2.29g of polypropylene glycol diglycidyl ether, and 6.06g of polyetheramine D230, which have been vacuum dehydrated and dried, are added to a three-necked flask.

[0084] Example 3

[0085] A flame-retardant epoxy resin electrolyte prepolymer is identical to that in Example 1, except that in step S2, 2.0g of ethylene glycol methylpropionate phosphonate, 2.37g of 1,4-butanediol diglycidyl ether, and 6.25g of polyetheramine D400, which have been vacuum dehydrated and dried, are added to a three-necked flask.

[0086] Example 4

[0087] A flame-retardant epoxy resin electrolyte prepolymer is identical to that in Example 1, except that in step S2, 2.0g of ethylene glycol methylpropionate phosphonate, 2.21g of polyethylene glycol diglycidyl ether, and 6.25g of polyetheramine D400, which have been vacuum dehydrated and dried, are added to a three-necked flask.

[0088] Example 5

[0089] A flame-retardant epoxy resin electrolyte prepolymer is identical to that in Example 1, except that in step S2, 2.0g of ethylene glycol methylpropionate phosphonate, 2.29g of polypropylene glycol diglycidyl ether, and 6.33g of polyetheramine D2000, which have been vacuum dehydrated and dried, are added to a three-necked flask.

[0090] Example 6

[0091] A flame-retardant epoxy resin electrolyte prepolymer is identical to that in Example 1, except that in step S2, 2.0g of ethylene glycol methylpropionate phosphonate, 2.37g of 1,4-butanediol diglycidyl ether, and 6.39g of polyetheramine T5000, which have undergone vacuum dehydration and drying, are added to a three-necked flask.

[0092] Example 7

[0093] A flame-retardant epoxy resin electrolyte prepolymer is an oligomer obtained by ring-opening addition reaction of ethylene glycol methyl methacrylate, butylene phosphonate, diglycidyl ether, and polyether amine; the oligomer ends contain unreacted epoxy groups and / or amine groups.

[0094] A method for preparing a flame-retardant epoxy resin electrolyte prepolymer includes the following steps:

[0095] S1. Under a nitrogen atmosphere, 1.0 mol of cyclic phosphoric anhydride and 1.0 mol of 1,4-butanediol were placed in a three-necked flask and mechanically stirred at 120°C for 3 h. After stirring, the mixture was allowed to stand and cool to room temperature to obtain a bright yellow clear liquid, which is methylpropionic acid phosphonic acid. Under a nitrogen atmosphere, 1.0 mol of methylpropionic acid phosphonic acid, 1.03 mol of 1,4-butanediol and 100 g of 4A molecular sieve were placed in a three-necked flask and mechanically stirred at 150°C for 4 h. The mixture was then filtered while hot, and the filtrate was allowed to stand and cool to room temperature to obtain a brownish-yellow gel-like viscous solid, which is ethylene glycol methylpropionate phosphonate butylene glycol ester.

[0096] S2. Under an inert gas atmosphere, 2.0 g of ethylene glycol methylpropionate phosphonate butylene glycol ester, 2.21 g of polyethylene glycol diglycidyl ether, and 6.06 g of polyetheramine D400, which have been vacuum dehydrated and dried, are added to a three-necked flask and stirred at 60 °C for 2 h to carry out a ring-opening addition reaction, thereby obtaining a flame-retardant epoxy resin prepolymer.

[0097] Example 8

[0098] A flame-retardant epoxy resin electrolyte prepolymer is identical to that in Example 7, except that in step S2, 2.0g of ethylene glycol methylpropionate phosphonate butylene glycol ester, 2.29g of polypropylene glycol diglycidyl ether, and 6.06g of polyetheramine D400, after being vacuum dehydrated and dried, are added to a three-necked flask.

[0099] Example 9

[0100] A flame-retardant epoxy resin solid electrolyte membrane includes a flame-retardant epoxy resin electrolyte prepolymer, a lithium salt, and hydroxylated boron nitride; the hydroxylated boron nitride has a three-dimensional chain-like structure.

[0101] A method for preparing a flame-retardant epoxy resin solid electrolyte membrane includes the following steps:

[0102] K1. 2.06 g of lithium bis(trifluoromethanesulfonylimide) and 0.51 g of nano boron nitride (soaked in 3 mol / L sodium hydroxide for 24 h, washed and dried with deionized water) were added to the flame-retardant epoxy resin electrolyte prepolymer prepared in Example 1 and stirred thoroughly to form a blend.

[0103] K2. Inject the blend into a mold made of ITO glass and conductive adhesive, then place it in a 100Hz, 500V AC electric field for 10 minutes. After the arrangement is completed, remove the electric field and place the mold on a hot plate for heat curing at 120℃ for 4 hours. After demolding, a flame-retardant epoxy resin solid electrolyte membrane with a thickness of 192μm can be obtained.

[0104] Figure 1 The infrared spectrum results for flame-retardant epoxy resin solid electrolytes are shown below. The peaks in the figure are assigned as follows: 3436 cm⁻¹ -1 The peak at 2919 cm⁻¹ is the stretching vibration peak of BN-OH on the surface of nano-boron nitride in flame-retardant epoxy resin solid electrolyte. -1 and 2854cm -1 The peaks at 1716 cm⁻¹ correspond to the asymmetric and symmetric stretching vibration peaks of -CH₂-, respectively. -1 The peak at 1509 cm⁻¹ is a characteristic peak of the carbonyl group (C=O). -1 The absorption peak corresponding to PO-CH2 is 1473 cm⁻¹. -1 The peak is a deformed form of -CH2-, at 1403 cm⁻¹. -1 The peak at 1327 cm⁻¹ corresponds to the BN bond. -1 The peak at 1251 cm⁻¹ coincides with the absorption peak of -C-SO₂-N in lithium salt. -1 The peak at 1137 cm⁻¹ corresponds to the absorption peak of P-CH₃. -1 The peak at 1062 cm⁻¹ belongs to P=O. -1 The peak at 1015 cm⁻¹ belongs to SNS.-1 and 827cm -1 The peaks at the specified locations are attributed to the stretching vibration peaks of PO and BNB, respectively. The above analysis confirms that the flame-retardant epoxy resin solid electrolyte membrane has been successfully prepared.

[0105] Example 10

[0106] A flame-retardant epoxy resin solid electrolyte membrane is described, with the other contents being the same as in Example 9. The difference is that in step K1, 2.07g of lithium bis(trifluoromethanesulfonylimide) and 0.52g of nano-boron nitride (soaked in 3mol / L sodium hydroxide for 24h, washed and dried with deionized water) are added to the flame-retardant epoxy resin prepolymer obtained in Example 2 and stirred thoroughly to form a blend. Finally, a flame-retardant epoxy resin solid electrolyte membrane with a thickness of 177μm is obtained.

[0107] Example 11

[0108] A flame-retardant epoxy resin solid electrolyte membrane is described, with the other contents being the same as in Example 9, except that in step K1, 2.12g of lithium bis(trifluoromethanesulfonylimide) and 0.53g of nano-boron nitride (soaked in 3mol / L sodium hydroxide for 24h, washed and dried with deionized water) are added to the flame-retardant epoxy resin prepolymer obtained in Example 3 and stirred thoroughly to form a blend, ultimately yielding a flame-retardant epoxy resin solid electrolyte membrane with a thickness of 185μm.

[0109] Example 12

[0110] A flame-retardant epoxy resin solid electrolyte membrane is described, with the other contents being the same as in Example 9. The difference is that in step K1, 2.09 g of lithium cobalt oxide and 0.52 g of nano boron nitride (soaked in 3 mol / L sodium hydroxide for 24 h, washed and dried with deionized water) are added to the flame-retardant epoxy resin prepolymer obtained in Example 4 and stirred thoroughly to form a blend, ultimately yielding a flame-retardant epoxy resin solid electrolyte membrane with a thickness of 181 μm.

[0111] Example 13

[0112] A flame-retardant epoxy resin solid electrolyte membrane is described, with the other contents being the same as in Example 9, except that in step K1, 2.12g of lithium bis(trifluoromethanesulfonylimide) and 0.53g of nano-boron nitride (soaked in 3mol / L sodium hydroxide for 24h, washed and dried with deionized water) are added to the flame-retardant epoxy resin prepolymer obtained in Example 5 and stirred thoroughly to form a blend, ultimately yielding a flame-retardant epoxy resin solid electrolyte membrane with a thickness of 194μm.

[0113] Example 14

[0114] A flame-retardant epoxy resin solid electrolyte membrane is described, with the other contents being the same as in Example 9, except that in step K1, 2.15g of lithium bis(trifluoromethanesulfonylimide) and 0.54g of nano-boron nitride (soaked in 3mol / L sodium hydroxide for 24h, washed and dried with deionized water) are added to the flame-retardant epoxy resin prepolymer obtained in Example 6 and stirred thoroughly to form a blend, ultimately yielding a flame-retardant epoxy resin solid electrolyte membrane with a thickness of 179μm.

[0115] Example 15

[0116] A flame-retardant epoxy resin solid electrolyte membrane is described, with the other contents being the same as in Example 9, except that in step K1, 2.06 g of lithium bis(trifluoromethanesulfonylimide) and 0.51 g of nano-boron nitride (soaked in 3 mol / L sodium hydroxide for 24 h, washed and dried with deionized water) are added to the flame-retardant epoxy resin prepolymer obtained in Example 7 and stirred thoroughly to form a blend, ultimately yielding a flame-retardant epoxy resin solid electrolyte membrane with a thickness of 197 μm.

[0117] Example 16

[0118] A flame-retardant epoxy resin solid electrolyte membrane is described, with the other contents being the same as in Example 9. The difference is that in step K1, 2.06 g of lithium bis(trifluoromethanesulfonylimide) and 0.51 g of nano-boron nitride (soaked in 3 mol / L sodium hydroxide for 24 h, washed and dried with deionized water) are added to the flame-retardant epoxy resin prepolymer obtained in Example 8 and stirred thoroughly to form a blend. Finally, a flame-retardant epoxy resin solid electrolyte membrane with a thickness of 197 μm is obtained.

[0119] Comparative Example 1

[0120] An epoxy resin solid electrolyte membrane is prepared by the following method:

[0121] 2.0 g of ethylene glycol, 2.21 g of polyethylene glycol diglycidyl ether, and 6.06 g of polyetheramine D230, which have been vacuum dehydrated and dried, were added to a three-necked flask and stirred at 60 °C for 2 h under nitrogen protection to obtain epoxy resin prepolymer.

[0122] 2.06g of lithium bis(trifluoromethanesulfonylimide) was added to the epoxy resin prepolymer and stirred thoroughly to form a blend. The blend was then injected into a mold made of ITO glass and conductive adhesive, and placed in a 100Hz, 500V AC electric field. After 10 minutes, the electric field was removed, and the mold was placed on a hot plate and heat-cured at 120℃ for 4 hours before demolding to obtain an epoxy resin solid electrolyte membrane with a thickness of 186μm.

[0123] Comparative Example 2

[0124] An epoxy resin solid electrolyte membrane is prepared by the following method:

[0125] 2.0 g of ethylene glycol, 2.21 g of polyethylene glycol diglycidyl ether, and 6.06 g of polyetheramine D230, which have been vacuum dehydrated and dried, were added to a three-necked flask and stirred at 60 °C for 2 h under nitrogen protection to obtain epoxy resin prepolymer.

[0126] 2.06g of lithium bis(trifluoromethanesulfonylimide) and 0.51g of nano-boron nitride (soaked in 3mol / L sodium hydroxide for 24h, washed and dried with deionized water) were added to the epoxy resin prepolymer and stirred thoroughly to form a blend. The blend was then injected into a mold made of ITO glass and conductive adhesive, and then placed in a 100Hz, 500V AC electric field for 10min. After the arrangement was completed, the electric field was removed, and the mold was placed on a hot plate and heat-cured at 120℃ for 4h before demolding to obtain an epoxy resin solid electrolyte membrane with a thickness of 199μm.

[0127] Comparative Example 3

[0128] An epoxy resin solid electrolyte membrane is prepared by the following method:

[0129] 2.0g of ethylene glycol methyl propionate phosphonate, 2.21g of polyethylene glycol diglycidyl ether, and 6.06g of polyetheramine D230, which have been vacuum dehydrated and dried, were added to a three-necked flask and stirred at 60°C for 2 hours under nitrogen protection to obtain a flame-retardant epoxy resin prepolymer.

[0130] 2.06g of lithium bis(trifluoromethanesulfonylimide) was added to the flame-retardant epoxy resin prepolymer and stirred thoroughly to form a blend. The blend was then injected into a mold made of ITO glass and conductive adhesive, and placed in a 100Hz, 500V AC electric field. After 10 minutes, the electric field was removed, and the mold was placed on a hot plate and heat-cured at 120℃ for 4 hours before demolding to obtain a flame-retardant epoxy resin solid electrolyte membrane with a thickness of 205μm.

[0131] Comparative Example 4

[0132] An epoxy resin solid electrolyte membrane is prepared by the following method:

[0133] 2.0g of ethylene glycol methyl propionate phosphonate, 2.21g of polyethylene glycol diglycidyl ether, and 6.06g of polyetheramine D230, which have been vacuum dehydrated and dried, were added to a three-necked flask and stirred at 60°C for 2 hours under nitrogen protection to obtain a flame-retardant epoxy resin prepolymer.

[0134] 2.06g of lithium bis(trifluoromethanesulfonylimide) and 0.51g of nano-boron nitride (soaked in 3mol / L sodium hydroxide for 24h, washed and dried with deionized water) were added to the flame-retardant epoxy resin prepolymer and stirred thoroughly to form a blend. The blend was then injected into a mold made of ITO glass and conductive adhesive. Without electric field arrangement, the mold was placed directly on a hot plate and heat-cured at 120℃ for 4h before demolding to obtain a flame-retardant epoxy resin solid electrolyte membrane with a thickness of 187μm.

[0135] Testing and Evaluation

[0136] The flame retardant properties and conductivity of the epoxy resin solid electrolyte membranes obtained in different embodiments or comparative examples were tested using the following methods:

[0137] Flame retardant performance testing: Limiting oxygen index (LOI) test: The limiting oxygen index of the sample was tested using the HC-2 digital display oxygen index tester of Beijing Xinsheng Zhuorui Technology Co., Ltd. (refer to national standard: ASTM D2863); Self-extinguishing time (SET) test: The electrolyte membrane was cut into strips with a length of 80±3 mm, a width of 10±0.5 mm, and a thickness of 190±15 μm, and fixed on a vertical fixture. The electrolyte membrane was ignited with an igniter for 5 seconds, and then the igniter was removed. The stopwatch recorded the time from when the electrolyte membrane burned until it extinguished after the flame source was removed. The results are shown in Table 1.

[0138] Conductivity test: Electrochemical impedance spectroscopy (EIS) was performed on the samples at 30 °C using a Metrohm PGSTAT302N electrochemical workstation. The ionic conductivity of each electrolyte was calculated using the formula σ=L / (R*S) (σ is the ionic conductivity, L is the thickness of the electrolyte membrane, R is the bulk impedance, and S is the area of ​​the solid electrolyte membrane). The results are shown in Table 1.

[0139] Table 1. Test results of flame retardant properties and electrical conductivity

[0140]

[0141] As shown in Table 1, the flame-retardant epoxy resin solid electrolyte membranes prepared in Examples 9-16 exhibit good flame-retardant properties. Compared to Comparative Examples 1-3, the limiting oxygen index (LOI) of the flame-retardant epoxy resin solid electrolytes in the examples is significantly higher than that in the comparative examples, while the self-extinguishing time (SET) is significantly lower. Furthermore, the LOI values ​​of the electrolytes in Comparative Examples 2 and 3 are higher than those in Comparative Example 1, indicating that both phosphonate diol and nano-boron nitride have a certain flame-retardant effect on epoxy resin when used alone. However, the composite flame-retardant epoxy resin using phosphonate diol and nano-boron nitride achieves a good synergistic flame-retardant effect of PBN, which can greatly improve the safety performance of solid polymer electrolytes. The high LOI value of 32.6% in Comparative Example 4 indicates that whether or not the nano-boron nitride is arranged in an AC electric field has no significant impact on the flame-retardant properties of the electrolyte.

[0142] Furthermore, ESI test results showed that, compared with Comparative Example 1, the flame-retardant epoxy resin solid electrolyte membranes prepared in Examples 9-16 exhibited an order of magnitude improvement in ionic conductivity at 30 °C. This is attributed in two ways: firstly, the P=O and PO groups in the phosphonate diol structure provide more lone pairs of electrons, enhancing the dissolution and complexation capabilities of lithium ions and improving the lithium ion transport channels; secondly, the introduction of nano-boron nitride disrupts the polymer's crystal phase structure, reducing its crystallinity and regularity. Simultaneously, the oxygen vacancies on the surface of the boron nitride modified with alkali can effectively fix TFSI. - This creates a lithium-rich region at the electrolyte and electrode interface, promoting the migration and conduction of lithium ions in the epoxy resin. Figure 2 This is a SEM image of the epoxy resin electrolyte membrane from Example 9. Figure 3 The image shows a SEM image of the epoxy resin electrolyte membrane in Comparative Example 4. Compared with Comparative Example 4, the ionic conductivity of the electrolyte in Example 9 is more than doubled. This indicates that the three-dimensional chain-like lithium-ion transport channels constructed by orderly arranging the nano-boron nitride in the epoxy resin under the drive of an AC electric field can effectively improve the ion transport performance of the electrolyte.

[0143] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A flame-retardant epoxy resin solid electrolyte membrane, characterized in that, It includes a flame-retardant epoxy resin electrolyte prepolymer, a lithium salt, and hydroxylated boron nitride; the hydroxylated boron nitride has a three-dimensional chain structure; the flame-retardant epoxy resin electrolyte prepolymer is an oligomer obtained by ring-opening addition reaction of phosphonate diol, diglycidyl ether, and polyether amine; the oligomer contains unreacted epoxy groups and / or amine groups at its ends; The chemical formula of the phosphonate diol is shown in formula (I): Equation (I); Wherein, R1 and R2 are both alkyl or aryl groups; A method for preparing a flame-retardant epoxy resin electrolyte prepolymer includes the following steps: Obtain phosphonate diols; Under an inert gas atmosphere, a ring-opening addition reaction is carried out using phosphonate diol, diglycidyl ether, and polyetheramine as raw materials to obtain the flame-retardant epoxy resin electrolyte prepolymer; the temperature of the ring-opening addition reaction is 50-100℃. The method for obtaining phosphonate diols is as follows: Under an inert atmosphere, cyclic phosphoric anhydride and diol / diphenol were used as raw materials to carry out a ring-opening alcoholysis reaction to obtain methylpropionic acid ester phosphonic acid. Under inert atmosphere and catalyst conditions, the methylpropionic acid ester phosphonic acid and diol / diphenol are used as raw materials for esterification reaction to obtain the phosphonate diol.

2. The flame-retardant epoxy resin solid electrolyte membrane according to claim 1, characterized in that, The hydroxylated boron nitride was obtained by modifying nano-boron nitride with an inorganic base.

3. A method for preparing a flame-retardant epoxy resin solid electrolyte membrane as described in any one of claims 1-2, characterized in that, Includes the following steps: Lithium salt and hydroxylated boron nitride were added to the flame-retardant epoxy resin electrolyte prepolymer to obtain a blend. The blend liquid is injected into a conductive mold, an alternating electric field is arranged, and then it is thermo-cured and demolded to obtain the flame-retardant epoxy resin solid electrolyte membrane.

4. The preparation method according to claim 3, characterized in that, The frequency of the alternating electric field is 10-1000 Hz, and the voltage is 100-1000 V; the temperature for heat curing is 100-160℃, and the heat curing time is 2-6 hours.

5. The preparation method according to claim 3, characterized in that, The lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium dioxalate borate.

6. A lithium battery comprising a flame-retardant epoxy resin solid electrolyte membrane as described in any one of claims 1-2.

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