A branched polyimide-based polymer useful in electrolytes

Abstract

The application discloses a branched-chain polyimide-based polymer which can be used in electrolyte, and a structural general formula of the branched-chain polyimide-based polymer is shown in the following formula: wherein R1 is selected from one of an alkyl group, an aromatic chain group, an aromatic chain group with an alicyclic group or an aromatic condensed ring group; R2 is selected from one of an alkyl group, an aromatic chain group, an aromatic chain group with an alicyclic group or an alkyl group with an ether group substituent branched chain; R3 and R4 are each independently selected from one of an ionic liquid substituent group, an ester group, H and an ether group, and R3 and R4 are not H at the same time; R5 is selected from one of an ionic liquid substituent group, an ester group, H and an ether group; n is a polymerization degree, and the range of n is 1000-10000; wherein the number of carbon atoms in R1 is C1-C20; the number of carbon atoms in R2 is C1-C30; and the number of carbon atoms in R3, R4 and R5 is independently C1-C15. The introduction of the branched chain in the polyimide-based polymer reduces the mechanical hardness of the polyimide-based polymer electrolyte.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery manufacturing, and more specifically to a branched polyimide polymer that can be used as an electrolyte. Background Technology

[0002] With the development of energy storage technology, lithium batteries are gradually moving towards higher specific energy and better safety performance. However, commercial electrolytes use organic solvents with low flash points, posing risks of volatility and leakage, and even serious consequences such as combustion and explosion. This has spurred accelerated research into solid-state electrolytes and increased the urgent demand for all-solid-state lithium batteries. All-solid-state polymer electrolytes, in particular, offer advantages such as high safety, low cost, and lightweight properties. The excellent processing performance of polymer solid-state electrolytes has attracted even more attention. Polyimide is a commonly used specialty material, but its high mechanical strength limits its application in lithium battery electrolytes. Because the peristalsis of polymer molecular chains drives lithium-ion transport in the electrolyte, high polymer mechanical strength reduces the lithium-ion transport rate, affecting the charge and discharge performance of lithium batteries. Summary of the Invention

[0003] This invention addresses the problems in the prior art by disclosing a branched polyimide-based polymer that can be used in electrolytes. The branched polyimide-based polymer is formed by introducing branches into the polyimide main chain. Introducing branches reduces the mechanical hardness and density of the polyimide-based polymer, thereby improving the transport of lithium ions in the battery and the ionic conductivity of the battery.

[0004] This invention is achieved through the following technical solution:

[0005] A branched polyimide polymer that can be used in electrolytes, the general structural formula of the branched polyimide polymer is:

[0006]

[0007] In the formula:

[0008] R1 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or aromatic fused ring groups;

[0009] R2 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or alkyl groups with ether substituents.

[0010] R3 and R4 are each independently selected from one of the substituent groups of ionic liquid, ester group, H, ether group, and R3 and R4 are not both H;

[0011] R5 is selected from one of the substituent groups of ionic liquids, ester groups, H, and ether groups;

[0012] n represents the degree of aggregation, and the range of n is 1000-10000;

[0013] Among them, R1 has a carbon atom count of C1-C20; R2 has a carbon atom count of C1-C30; and R3, R4 and R5 each have a carbon atom count of C1-C15.

[0014] The above-described design of the present invention increases the free volume of the polymer and increases the peristalsis of the molecular chains by introducing branches into the polyimide-based polymer, thereby obtaining a branched polyimide polymer electrolyte material with high ionic conductivity and reducing the mechanical strength of the polyimide polymer electrolyte.

[0015] As a further embodiment, the substituent groups of the ionic liquid include imidazole cationic ionic liquid substituent groups, pyridine cationic ionic liquid substituent groups, quaternary ammonium salt cationic ionic liquid substituent groups, and sulfonic acid anionic ionic liquid substituent groups.

[0016] As a further embodiment, the substituted anions of the substituent groups in the cationic ionic liquid include Cl... - ,Br - TFSI - FSI - PF6 - DFOB - The substituted cations of the substituent groups in the anionic ionic liquid include Li. + Na + Mg + .

[0017] As a further option, R1 is selected from one of an aromatic chain group, an alicyclic aromatic chain group, or an aromatic fused-ring group. The aromatic chain group, the alicyclic aromatic chain group, or the aromatic fused-ring group have better electrophilicity than alkyl groups and can react with Li in the battery. + To foster positive interaction and thus promote Li + The transmission.

[0018] As a further embodiment, the chemical formula (1) has the structure of the following chemical formula (2):

[0019]

[0020] In the formula:

[0021] R2 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or alkyl groups with ether substituents.

[0022] R3 and R4 are each independently selected from one of the substituent groups of ionic liquid, ester group, H, ether group, and R3 and R4 are not both H;

[0023] At least one of R5 and R10 is H, and either R5 or R10 is selected from H, ionic liquid substituents, ester groups, and ether groups;

[0024] n represents the degree of aggregation, which ranges from 1000 to 10000.

[0025] Because aromatic chain groups and dianhydride compounds have higher structural freedom, they are more conducive to reducing the mechanical strength of branched polyimide polymers.

[0026] As a further option, both R5 and R10 are H. Having non-H groups in R5 or R10 will affect the interaction between R5 or R10 and the main chain, thus affecting the structure and stability of the branched polyimide polymer.

[0027] As a further option, R2 is selected from one of C1-C8 alkyl groups, C12-C15 aromatic chain groups, C16-C18 aromatic chain groups with alicyclic rings, or C3-C8 alkyl groups with ether substituent branches.

[0028] As a further option, the ionic liquid substituent is selected from imidazole cationic ionic liquid substituents and pyridine cationic ionic liquid substituents, wherein the imidazole cationic ionic liquid substituent has the structure of chemical formula (3) and the pyridine cationic ionic liquid substituent has the structure of chemical formula (4).

[0029]

[0030] In the formula,

[0031] R6, R7, R8 and R9 are each independently selected from one of the following: C1-C8 alkyl, C1-C8 ether, C1-C8 ester, C1-C8 haloalkyl, C1-C8 haloether, C1-C8 haloester, and C1-C8 sulfonic acid groups.

[0032] B - One of the substituted anions selected from the substituent groups of cationic ionic liquids, selected from Cl... - ,Br - TFSI - FSI - PF6 - DFOB - One of them.

[0033] As a further option, the chemical formula (1) is selected from one of the following i-iii preferred options:

[0034] Scheme i: The chemical formula (1) has the general structure of the following chemical formula (5):

[0035]

[0036] In the formula:

[0037] R2 is selected from one of C1-C5 alkyl groups, C12-C15 aromatic chain groups, C16-C18 aromatic chain groups with alicyclic rings, or C3-C5 alkyl groups with ether substituents.

[0038] R3 and R4 are each independently selected from ionic liquid substituents or H, and R3 and R4 are not both H at the same time;

[0039] Scheme ii: The chemical formula (1) has the general structure of the following chemical formula (5):

[0040]

[0041] R2 is selected from one of C1-C5 alkyl groups, C12-C15 aromatic chain groups, C16-C18 aromatic chain groups with alicyclic rings, or C3-C5 alkyl groups with ether substituents.

[0042] R3 and R4 are each independently selected from ester, ether, or H groups, and R3 and R4 are not both H groups.

[0043] Scheme iii: The chemical formula (1) has the general structure of the following chemical formula (5):

[0044]

[0045] R2 is selected from one of C1-C5 alkyl groups, C12-C15 aromatic chain groups, C16-C18 aromatic chain groups with alicyclic rings, or C3-C5 alkyl groups with ether substituents.

[0046] R3 and R4 are ester groups.

[0047] As a further option, in option i, R3 is a substituent group of a pyridine cationic ionic liquid; as an even further option, in option ii, R3 is an ether group of multiple ether branches; as an even further option, the chemical formula (1) is option iii.

[0048] As a further embodiment, the method for preparing the branched polyimide polymer includes the following steps:

[0049] S1: Under an inert atmosphere, reactant 4 (dianhydride compound), reactant 2 (tetracarboxylic acid compound), reactant 5 (diacarboxylic acid diester compound), or reactant 3 (tetracarboxylic acid compound) reacts with reactant 1 to prepare a polyimide polymer with functional groups. The chemical equation is as follows:

[0050]

[0051] In the formula,

[0052] A, D, and E are each independently selected from hydroxyl, carboxyl, or H; and D and E are not both H.

[0053] R1 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or aromatic fused ring groups;

[0054] R2 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or alkyl groups with ether substituents.

[0055] n represents the degree of aggregation, and the range of n is 1000-10000;

[0056] Among them, the number of carbon atoms in R1 is C1-C20; the number of carbon atoms in R2 is C1-C30.

[0057] S2: Reactant 6 is grafted onto the main chain of a polyimide polymer containing functional groups to prepare a branched polyimide polymer. The chemical equation is as follows:

[0058]

[0059] In the formula,

[0060] G-R1 / R2 / R3 are organic reagents with active groups, wherein G is an active group that can undergo group exchange reaction with A group or hydroxyl or carboxyl group. As a further preferred option, G is selected from halogen group or hydroxyl group.

[0061] A is selected from one of hydroxyl, carboxyl, or H;

[0062] R1 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or aromatic fused ring groups;

[0063] R2 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or alkyl groups with ether substituents.

[0064] R3 and R4 are each independently selected from one of the substituent groups of ionic liquid, ester group, H, ether group, and R3 and R4 are not both H;

[0065] R5 is selected from one of the substituent groups of ionic liquids, ester groups, H, and ether groups;

[0066] n represents the degree of aggregation, and the range of n is 1000-10000;

[0067] Among them, R1 has a carbon atom count of C1-C20; R2 has a carbon atom count of C1-C30; and R3, R4 and R5 each have a carbon atom count of C1-C15.

[0068] As a further approach, the specific preparation method of the branched polyimide polymer includes the following steps:

[0069] S11: Under an inert atmosphere, reactant 4 (dianhydride compound), reactant 2 (tetracarboxylic acid compound), reactant 5 (diacarboxylic acid diester compound), or reactant 3 (tetracarboxylic acid compound) are dissolved in an organic solvent, reactant 1 is added to react, and the mixture is stirred at room temperature. Then, a methanol / water solution is added to the solution, filtered, and vacuum dried. Then, under vacuum, the mixture is heated at different temperature gradients to prepare a polyimide polymer with functional groups.

[0070] S12: Dissolve the functionalized polyimide polymer in an organic solvent, add reactant 6, stir at room temperature, add water to the solution to produce a precipitate, filter, and then dry under vacuum to obtain a branched polyimide polymer.

[0071] As a further embodiment, the molar ratio of the amount of reactant 4 (dianhydride compound), reactant 2 (tetracarboxylic acid compound), reactant 5 (diacarboxylic acid diester compound), or reactant 3 (tetracarboxylic acid compound) to the amount of reactant 1 is 1:1.

[0072] As a further embodiment, the molar ratio of the amount of the functionalized polyimide polymer added to the amount of reactant 6 added is 1:1.1 to 1.5.

[0073] As a further embodiment, in step S11 of the specific preparation method of the branched polyimide polymer, the stirring time is 48 hours; the volume ratio of the methanol / aqueous solution is V. 甲醇 V 水 =1:1; the vacuum drying time is 12h, and the vacuum drying temperature is 60℃; the different temperature gradients are 100℃, 150℃, 200℃ and 250℃, and the heating time is 1h at each gradient temperature; as a further embodiment, in S12 of the specific preparation method of the branched polyimide polymer, the stirring time is 24-48h; the vacuum drying time is 12h, and the vacuum drying temperature is 60℃.

[0074] As a further option, the electrolyte also includes lithium salt and additives.

[0075] As a further option, the lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), and lithium bis(oxalateborate) (LiDFOB).

[0076] As a further embodiment, the additives include film-forming additives and inward flow aids; as an even further embodiment, the film-forming additives include lithium halides, lithium nitrates, and halogenated carbonates; the inward flow aids include low-molecular-weight compounds, branched polymers with similar polarity, highly branched polymers with similar polarity, dendritic polyesters, polyamides, polyesteramides, polyethers, or polyurethanes.

[0077] As a further embodiment, the preparation method of the branched polyimide polymer electrolyte includes the following steps: under an argon atmosphere, a branched polyimide polymer is weighed and dissolved in an organic solvent, then a lithium salt is added, and the mixture is stirred at room temperature to obtain the branched polyimide polymer electrolyte; as an even further embodiment, the stirring time is 30 minutes.

[0078] As a further embodiment, the mass ratio of the amount of branched polyimide polymer added to the amount of lithium salt added to the amount of additive added is 50-95:5-50:0.1-10.

[0079] As a further option, the organic solvent is selected from N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), or a mixture thereof.

[0080] The features and beneficial effects of this invention are as follows: by introducing branches into the polyimide-based polymer, the free volume of the polymer is increased, the peristalsis of the molecular chains is increased, and a branched polyimide polymer electrolyte material with high ionic conductivity is obtained, while the mechanical hardness of the polyimide-based polymer electrolyte is reduced. Detailed Implementation

[0081] To facilitate understanding of the branched polyimide-based polymer that can be used as an electrolyte according to the present invention, the preparation method of the branched polyimide-based polymer electrolyte of the present invention will be described more comprehensively below, and embodiments of the present invention will be given, but this does not limit the scope of the present invention.

[0082] (1) Preparation method of branched polyimide polymer electrolyte:

[0083] Step 1: Under an inert atmosphere, dissolve reactant 4 (dianhydride compound), reactant 2 (tetracarboxylic acid compound), reactant 5 (diacarboxylic acid diester compound), or reactant 3 (tetracarboxylic acid compound) in an organic solvent. Add reactant 1 to the solution to initiate the reaction. Stir at room temperature for 48 hours. Then add methanol / water solution (V) to the solution.甲醇 V 水 The 1:1 mixture solution was filtered and vacuum dried at 60°C for 12 hours. Then, under vacuum, it was heated at 100°C, 150°C, 200°C, and 250°C for 1 hour each to prepare a polyimide polymer with functional groups. The reaction equation is shown below:

[0084]

[0085] In the formula,

[0086] A, D, and E are each independently selected from hydroxyl, carboxyl, or H groups; and A, D, and E are not all H groups simultaneously.

[0087] R1 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or aromatic fused ring groups;

[0088] R2 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or alkyl groups with ether substituents.

[0089] n represents the degree of aggregation, and the range of n is 1000-10000;

[0090] In R1, the number of carbon atoms ranges from C1 to C20; in R2, the number of carbon atoms ranges from C1 to C20.

[0091] Step 2: Dissolve the functionalized polyimide polymer in an organic solvent, add reactant 6, stir at room temperature for 24-48 hours, then add water to the solution to produce a precipitate, filter, and then vacuum dry at 60°C for 12 hours to obtain the branched polyimide polymer. The reaction equation is shown below:

[0092]

[0093] G-R1 / R2 / R3 are organic solvents with exchangeable active groups, wherein G is an active group that can undergo group exchange reaction with A group or hydroxyl or carboxyl group. As a further preferred option, G is selected from halogen group or hydroxyl group.

[0094] A is selected from one of hydroxyl, carboxyl, or H;

[0095] R1 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or aromatic fused ring groups;

[0096] R2 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or alkyl groups with ether substituents.

[0097] R3 and R4 are each independently selected from one of the substituent groups of ionic liquid, ester group, H, ether group, and R3 and R4 are not both H;

[0098] R5 is selected from one of the substituent groups of ionic liquids, ester groups, H, and ether groups;

[0099] n represents the degree of aggregation, and the range of n is 1000-10000;

[0100] Among them, R1 has a carbon atom count of C1-C20; R2 has a carbon atom count of C1-C30; and R3, R4 and R5 each have a carbon atom count of C1-C15.

[0101] (2) Preparation of branched polyimide polymer electrolytes

[0102] Under an argon atmosphere, 2g of branched polyimide polymer was dissolved in 4mL of organic solvent, and then 0.6g of lithium salt was added and stirred at room temperature for 30min to obtain a branched polyimide polymer electrolyte solution.

[0103] (3) Fabrication of all-solid-state batteries

[0104] A stainless steel-stainless steel symmetric cell was assembled using a branched polyimide-based polymer electrolyte film as the electrolyte material.

[0105] In addition, the Shore hardness of the branched polyimide polymer electrolyte was tested. The specific test method was as follows: the obtained branched polyimide polymer electrolyte solution was uniformly coated on a glass plate and vacuum dried at 60°C for 12 hours to obtain a branched polyimide polymer electrolyte film, and its Shore hardness was tested.

[0106] The ionic conductivity of the battery with branched polyimide polymer electrolyte was tested at 25°C.

[0107] Example 1

[0108] 1) Preparation of branched polyimide polymers

[0109] Under a nitrogen atmosphere, pyromellitic dianhydride (2 g, 9.17 mmol) was dissolved in 10 mL of N,N-dimethylacetamide (DMAc), followed by the addition of 1,3-diamino-2-hydroxypropane (0.8264 g, 9.17 mmol). The mixture was stirred at room temperature for 48 hours to produce a poly(carbamate) (PAA) solution. Then, methanol / water solution (V) was slowly added dropwise to the PAA solution. 甲醇 V 水 A precipitate was formed by mixing 1:1, and after filtering the precipitate, it was vacuum dried at 60°C for 12 hours to obtain polyamino acid PAA.

[0110]

[0111] Under continuous vacuum, poly(carbamate) (PAA) was heated at 100℃, 150℃, 200℃ and 250℃ for 1 hour each to obtain polyimide (PI).

[0112]

[0113] 2 g (7.32 mmol) of polyimide (PI) was dissolved in 10 mL of N-methylpyrrolidone (NMP), and 1.72 g (8.82 mmol) of lithium 2-bromoethanesulfonate was added, followed by 0.03 g of lithium hydroxide (LiOH). The mixture was stirred at room temperature for 48 hours to produce a branched polyimide (B-PI) solution. Water was then slowly added dropwise to the branched polyimide (B-PI) solution to produce a precipitate. The precipitate was filtered and dried under vacuum at 60 °C for 12 h to obtain branched polyimide (B-PI).

[0114]

[0115] 2) Preparation of branched polyimide polymer electrolytes

[0116] Under an argon atmosphere, 2g of branched polyimide (B-PI) was dissolved in 4mL of NMP, and then 0.6g of LiTFSI was added and stirred at room temperature for 30min to obtain a branched polyimide-based polymer electrolyte solution.

[0117] Example 2

[0118] 1) Preparation of branched polyimide polymers

[0119] Under a nitrogen atmosphere, the p-dioxanide raw material (2.46 g, 9.17 mmol) was dissolved in 10 mL of N,N-dimethylacetamide (DMAc), followed by the addition of 1,5-diamino-3-hydroxypropane (1.08 g, 9.17 mmol). The mixture was stirred at room temperature for 48 hours to produce a poly(carbamate) (PAA) solution. Then, methanol / water solution (V) was slowly added dropwise to the PAA solution. 甲醇 V 水 A precipitate was formed by mixing 1:1, and after filtering the precipitate, it was vacuum dried at 60°C for 12 hours to obtain polyamino acid PAA.

[0120]

[0121] Under continuous vacuum, poly(carbamate) (PAA) was heated at 100℃, 150℃, 200℃ and 250℃ for 1 hour each to obtain polyimide (PI).

[0122]

[0123] Polyimide (PI) (2.78 g, 7.32 mmol) was dissolved in 10 mL of N-methylpyrrolidone (NMP), and 1-(2-chloroethyl)imidazolium (1.15 g, 8.82 mmol) was added. Then, 0.03 g of lithium hydroxide (LiOH) was added, and the mixture was stirred at room temperature for 24 hours. Bromoethane (1.16 g, 10.6 mmol) was then added, and the mixture was stirred at room temperature for another 24 hours to produce a branched polyimide (B-PI) solution. Water was then slowly added dropwise to the branched polyimide (B-PI) solution to produce a precipitate. The precipitate was filtered and dried under vacuum at 60 °C for 12 hours to obtain branched polyimide (B-PI).

[0124]

[0125] 2) Preparation of branched polyimide polymer electrolytes

[0126] Under an argon atmosphere, 2g of branched polyimide (B-PI) was dissolved in 4mL of NMP, and then 0.6g of LiTFSI was added and stirred at room temperature for 30min to obtain a branched polyimide-based polymer electrolyte solution.

[0127] Example 3

[0128] 1) Preparation of branched polyimide polymers

[0129] Under a nitrogen atmosphere, the p-dioxanide raw material (2.46 g, 9.17 mmol) was dissolved in 10 mL of N,N-dimethylacetamide (DMAc), followed by the addition of 1,5-diamino-3-hydroxypropane (1.08 g, 9.17 mmol). The mixture was stirred at room temperature for 48 hours to produce a poly(carbamate) (PAA) solution. Then, methanol / water solution (V) was slowly added dropwise to the PAA solution. 甲醇 V 水 A precipitate was formed by mixing 1:1, and after filtering the precipitate, it was vacuum dried at 60°C for 12 hours to obtain polyamino acid PAA.

[0130]

[0131] Under continuous vacuum, poly(carbamate) (PAA) was heated at 100℃, 150℃, 200℃ and 250℃ for 1 hour each to obtain polyimide (PI).

[0132]

[0133] Polyimide (PI) (2.78 g, 7.32 mmol) was dissolved in 10 mL of N-methylpyrrolidone (NMP), and 4-(3-chloroethyl)pyridine (1.25 g, 8.82 mmol) was added. Then, 0.03 g of lithium hydroxide (LiOH) was added, and the mixture was stirred at room temperature for 24 hours. 1-Bromobutane (1.45 g, 10.6 mmol) was then added, and the mixture was stirred at room temperature for 24 hours. LiTFSI (3.65 g, 12.72 mmol) was then added, and the mixture was stirred at room temperature for 24 hours to generate a branched polyimide (B-PI) solution. Water was then slowly added dropwise to the branched polyimide (B-PI) solution to produce a precipitate. The precipitate was filtered and dried under vacuum at 60 °C for 12 hours to obtain branched polyimide (B-PI).

[0134]

[0135] 2) Preparation of branched polyimide polymer electrolytes

[0136] Under an argon atmosphere, 2g of branched polyimide (B-PI) was dissolved in 4mL of NMP, and then 0.6g of LiTFSI was added and stirred at room temperature for 30min to obtain a branched polyimide-based polymer electrolyte solution.

[0137] Example 4

[0138] 1) Preparation of branched polyimide polymers

[0139] Under a nitrogen atmosphere, the p-dioxanide raw material (2.46 g, 9.17 mmol) was dissolved in 10 mL of N,N-dimethylacetamide (DMAc), followed by the addition of 1,5-diamino-3-hydroxypropane (1.08 g, 9.17 mmol). The mixture was stirred at room temperature for 48 hours to produce a poly(carbamate) (PAA) solution. Then, methanol / water solution (V) was slowly added dropwise to the PAA solution. 甲醇 V 水 A precipitate was formed by mixing 1:1, and after filtering the precipitate, it was vacuum dried at 60°C for 12 hours to obtain polyamino acid PAA.

[0140]

[0141] Under continuous vacuum, poly(carbamate) (PAA) was heated at 100℃, 150℃, 200℃ and 250℃ for 1 hour each to obtain polyimide (PI).

[0142]

[0143] Polyimide (PI) (2.78 g, 7.32 mmol) was dissolved in 10 mL of N-methylpyrrolidone (NMP), and 1-bromo-2-(methoxymethoxy)ethane (1.49 g, 8.82 mmol) was added. The mixture was stirred at room temperature for 24 hours to generate a branched polyimide (B-PI) solution. Water was then slowly added dropwise to the branched polyimide (B-PI) solution to produce a precipitate. The precipitate was filtered and dried under vacuum at 60 °C for 12 h to obtain branched polyimide (B-PI).

[0144]

[0145] 2) Preparation of branched polyimide polymer electrolytes

[0146] Under an argon atmosphere, 2g of branched polyimide (B-PI) was dissolved in 4mL of NMP, and then 0.6g of LiTFSI was added and stirred at room temperature for 30min to obtain a branched polyimide-based polymer electrolyte solution.

[0147] Example 5

[0148] 1) Preparation of branched polyimide polymers

[0149] Under a nitrogen atmosphere, the p-dioxanide raw material (2.46 g, 9.17 mmol) was dissolved in 10 mL of N,N-dimethylacetamide (DMAc), followed by the addition of 1,5-diamino-3-hydroxypropane (1.08 g, 9.17 mmol). The mixture was stirred at room temperature for 48 hours to produce a poly(carbamate) (PAA) solution. Then, methanol / water solution (V) was slowly added dropwise to the PAA solution. 甲醇 V 水 A precipitate was formed by mixing 1:1, and after filtering the precipitate, it was vacuum dried at 60°C for 12 hours to obtain polyamino acid PAA.

[0150]

[0151] Under continuous vacuum, poly(carbamate) (PAA) was heated at 100℃, 150℃, 200℃ and 250℃ for 1 hour each to obtain polyimide (PI).

[0152]

[0153] Polyimide (PI) (2.78 g, 7.32 mmol) was dissolved in 10 mL of N-methylpyrrolidone (NMP), and 2-chloro-1,1,1-trimethoxyethane (1.36 g, 8.82 mmol) was added. The mixture was stirred at room temperature for 24 hours to generate a branched polyimide (B-PI) solution. Water was then slowly added dropwise to the branched polyimide (B-PI) solution to produce a precipitate. The precipitate was filtered and dried under vacuum at 60 °C for 12 h to obtain branched polyimide (B-PI).

[0154]

[0155] 2) Preparation of branched polyimide polymer electrolytes

[0156] Under an argon atmosphere, 2g of branched polyimide (B-PI) was dissolved in 4mL of NMP, and then 0.6g of LiTFSI was added and stirred at room temperature for 30min to obtain a branched polyimide-based polymer electrolyte solution.

[0157] Example 6

[0158] 1) Preparation of branched polyimide polymers

[0159] Under a nitrogen atmosphere, the p-dioxanide raw material (2.46 g, 9.17 mmol) was dissolved in 10 mL of N,N-dimethylacetamide (DMAc), followed by the addition of 1,5-diamino-3-hydroxypropane (1.08 g, 9.17 mmol). The mixture was stirred at room temperature for 48 hours to produce a poly(carbamate) (PAA) solution. Then, methanol / water solution (V) was slowly added dropwise to the PAA solution. 甲醇 V 水 A precipitate was formed by mixing 1:1, and after filtering the precipitate, it was vacuum dried at 60°C for 12 hours to obtain polyamino acid PAA.

[0160]

[0161] Under continuous vacuum, poly(carbamate) (PAA) was heated at 100℃, 150℃, 200℃ and 250℃ for 1 hour each to obtain polyimide (PI).

[0162]

[0163] Polyimide (PI) (2.78 g, 7.32 mmol) was dissolved in 10 mL of N-methylpyrrolidone (NMP), and isopropyl bromoacetate (1.60 g, 8.82 mmol) was added. The mixture was stirred at room temperature for 24 hours to generate a branched polyimide (B-PI) solution. Water was then slowly added dropwise to the branched polyimide (B-PI) solution to produce a precipitate. The precipitate was filtered and dried under vacuum at 60 °C for 12 h to obtain branched polyimide (B-PI).

[0164]

[0165] 2) Preparation of branched polyimide polymer electrolytes

[0166] Under an argon atmosphere, 2g of branched polyimide (B-PI) was dissolved in 4mL of NMP, and then 0.6g of LiTFSI was added and stirred at room temperature for 30min to obtain a branched polyimide-based polymer electrolyte solution.

[0167] Example 7

[0168] 1) Preparation of branched polyimide polymers

[0169] Under a nitrogen atmosphere, a tetracarboxylic acid (3.03 g, 9.17 mmol) feedstock was dissolved in 10 mL of N,N-dimethylacetamide (DMAc), followed by the addition of a diamine feedstock (2.99 g, 9.17 mmol). The mixture was stirred at room temperature for 48 hours to produce a poly(carbamate) (PAA) solution. Then, methanol / water solution (V) was slowly added dropwise to the PAA solution. 甲醇 V 水 A precipitate was formed by mixing 1:1, and after filtering the precipitate, it was vacuum dried at 60°C for 12 hours to obtain polyamino acid PAA.

[0170]

[0171] Under continuous vacuum, poly(carbamate) (PAA) was heated at 100℃, 150℃, 200℃ and 250℃ for 1 hour each to obtain polyimide (PI).

[0172]

[0173] Polyimide (PI) (4.65 g, 7.32 mmol) was dissolved in 10 mL of N-methylpyrrolidone (NMP), and n-butanol (1.30 g, 17.6 mmol) and concentrated sulfuric acid (0.06 g) were added. The mixture was refluxed at 110 °C for 24 hours to generate a branched polyimide (B-PI) solution. Water was then slowly added dropwise to the branched polyimide (B-PI) solution to produce a precipitate. The precipitate was filtered and dried under vacuum at 60 °C for 12 hours to obtain branched polyimide (B-PI).

[0174]

[0175] 2) Preparation of branched polyimide polymer electrolytes

[0176] Under an argon atmosphere, 2g of branched polyimide (B-PI) was dissolved in 4mL of NMP, and then 0.6g of LiTFSI was added and stirred at room temperature for 30min to obtain a branched polyimide-based polymer electrolyte solution.

[0177] Comparative Example 1

[0178] 1) Preparation of branched polyimide polymers

[0179] Under a nitrogen atmosphere, pyromellitic dianhydride (2 g, 9.17 mmol) was dissolved in 10 mL of N,N-dimethylacetamide (DMAc), followed by the addition of 1,3-diamino-2-hydroxypropane (0.8264 g, 9.17 mmol). The mixture was stirred at room temperature for 48 hours to produce a poly(carbamate) (PAA) solution. Then, methanol / water solution (V) was slowly added dropwise to the PAA solution. 甲醇 V 水 A precipitate was formed by mixing 1:1, and after filtering the precipitate, it was vacuum dried at 60°C for 12 hours to obtain polyamino acid PAA.

[0180]

[0181] Under continuous vacuum, poly(carbamate) (PAA) was heated at 100℃, 150℃, 200℃ and 250℃ for 1 hour each to obtain polyimide (PI).

[0182]

[0183] 2) Preparation of branched polyimide polymer electrolytes

[0184] Under an argon atmosphere, 2g of branched polyimide (PI) was dissolved in 4mL of NMP, and then 0.6g of LiTFSI was added and stirred at room temperature for 30min to obtain a branched polyimide-based polymer electrolyte solution.

[0185] Verification Result Analysis:

[0186] Table 1. Ionic conductivity and Shore hardness of each embodiment

[0187]

[0188]

[0189] We selected seven representative branched polyimide polymers for experiments and performance tests, and the results are shown in Table 1. Comparing Examples 1-7 with Comparative Example 1, the ionic conductivity of Examples 1-7 was on the order of three times that of the Comparative Example, and the Shore hardness of the electrolytes in Examples 1-7 was lower than that in Comparative Example 1. We found that by introducing branches into the polyimide polymer backbone, the polyimide polymer acquires the excellent properties of branched chains, thereby improving the ionic conductivity of the polyimide polymer electrolyte and reducing the mechanical strength of the polyimide polymer.

[0190] The main chain, as the host of the cross-linked structure, plays a more important structural role in forming the ion transport interconnection network. Retaining aromatic rings in R1 is beneficial for efficient ion conduction. We found that Examples 2-6 contain the same number of aromatic rings in R1 of the main chain as Example 7, and the ionic conductivity differences between Examples 2-6 are not significant. However, the ionic conductivity of Example 7 is better than that of Examples 2-6. We believe this may be because the aromatic chain groups have lower polarity, resulting in higher stability of the branched polyimide polymer. Furthermore, the greater flexibility in the combination of aromatic chain groups and dianhydrides reduces the mechanical strength of the branched polyimide polymer, which is more conducive to ion transport. The above analysis can be further verified by Example 1. Compared to Examples 2-7, Example 1 contains only one aromatic ring in R1, and the ionic conductivity of Example 1 is at a lower level. The introduction of branches gives the polyimide polymer excellent properties. The more branches there are, the better the performance of the branched polyimide polymer. Example 7 has two branches. Compared with Examples 2-6, the Shore hardness of Example 7 is lower than that of Examples 1-6. It can be seen that the introduction of multiple branches is beneficial to further reduce the mechanical strength of the branched polyimide polymer.

[0191] We also studied different branched polyimide polymers with the same type of branched R3. When the branched R3 is an ionic liquid substituent, different types of ionic liquid substituents also showed certain differences in the improvement effect. For example, in Examples 2-3, the ionic conductivity and Shore hardness of the branched polyimide polymer electrolyte in Example 3 were higher than those in Example 2. We believe this may be because the pyridine cationic liquid substituent contains aromatic heterocycles. The combination of the aromatic heterocycles in the pyridine cationic liquid substituent with the aromatic rings of the main chain of the branched polyimide polymer enhances the ion transport capacity of the branch while improving the flexibility of the branch. Furthermore, the pyridine cationic liquid substituent has higher flexibility, thus making the improvement of the ionic conductivity and the reduction of the mechanical hardness of the branched polyimide polymer by the pyridine cationic liquid substituent more significant.

[0192] We further investigated different branched polyimide polymers with ether or ester groups as the branching group. When the branching group is ether, the ether bond with lone pair electrons can react with Li. + Interactions can promote Li + It is easier to transfer, as in Examples 4 and 6, where the ionic conductivity of the two branched polyimide polymers is not significantly different; when the ether group structure is different, it will also affect the lone pair electron pair and Li. + The interaction between the ether group and Li, when there are multiple ether branches on the ether group (as in the structure of Example 5), can increase the interaction between the lone pair of electrons and Li. + The space for interaction is more conducive to promoting Li + The above analysis can be verified by Example 5, which shows that the ionic conductivity of Example 5 is higher than that of Examples 4 and 6.

[0193] In summary, introducing branched chains into polyimide-based polymers can reduce the mechanical strength of polyimide-based polymer electrolytes and increase their ionic conductivity.

[0194] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electrolyte, characterized in that, It includes branched polyimide polymers, and the general structural formula of branched polyimide polymers is: Chemical formula (2) In the formula: R2 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or alkyl groups with ether substituents. R3 and R4 are each independently selected from one of the substituent groups of ionic liquid, ester group, H, ether group, and R3 and R4 are not both H; At least one of R5 and R10 is H, and either R5 or R10 is selected from H, ionic liquid substituents, ester groups, and ether groups; n represents the degree of aggregation, which ranges from 1000 to 10000.

2. The electrolyte according to claim 1, characterized in that, The substituent groups of the ionic liquid include imidazole cationic ionic liquid substituent groups, pyridine cationic ionic liquid substituent groups, quaternary ammonium salt cationic ionic liquid substituent groups, and sulfonic acid anionic ionic liquid substituent groups.

3. The electrolyte according to claim 2, characterized in that, The substituted anions of the substituent groups in the cationic ionic liquid include Cl. - ,Br - TFSI - FSI - PF6 - DFOB - The substituted cations of the substituent groups in the anionic ionic liquid include Li. + Na + Mg + .

4. The electrolyte according to claim 1, characterized in that, Both R5 and R10 are H.

5. The electrolyte according to claim 1, characterized in that, R2 is selected from one of C1-C8 alkyl groups, C12-C15 aromatic chain groups, C16-C18 aromatic chain groups with alicyclic rings, or C3-C8 alkyl groups with ether substituents.

6. The electrolyte according to claim 1, characterized in that, The substituent groups of the ionic liquid are selected from imidazole cationic ionic liquid substituent groups and pyridine cationic ionic liquid substituent groups. The imidazole cationic ionic liquid substituent groups have the structure of chemical formula (3), and the pyridine cationic ionic liquid substituent groups have the structure of chemical formula (4). Chemical formula (3) Chemical formula (4) In the formula, R6, R7, R8 and R9 are each independently selected from one of the following: C1-C8 alkyl, C1-C8 ether, C1-C8 ester, C1-C8 haloalkyl, C1-C8 haloether, C1-C8 haloester, and C1-C8 sulfonic acid groups. B - One of the substituted anions selected from the substituent groups of cationic ionic liquids, selected from Cl... - ,Br - TFSI - FSI - PF6 - DFOB - One of them.

7. The electrolyte according to claim 1, characterized in that, The chemical formula (1) is selected from one of the following schemes i-iii: Scheme i: The chemical formula (1) has the general structure of the following chemical formula (5): Chemical formula (5) In the formula: R2 is selected from one of C1-C5 alkyl groups, C12-C15 aromatic chain groups, C16-C18 aromatic chain groups with alicyclic rings, or C3-C5 alkyl groups with ether substituents. R3 and R4 are each independently selected from ionic liquid substituents or H, and R3 and R4 are not both H at the same time; Scheme ii: The chemical formula (1) has the general structure of the following chemical formula (5): Chemical formula (5) R2 is selected from one of C1-C5 alkyl groups, C12-C15 aromatic chain groups, C16-C18 aromatic chain groups with alicyclic rings, or C3-C5 alkyl groups with ether substituents. R3 and R4 are each independently selected from ester group, ether group or H, and R3 and R4 are not both H at the same time; Scheme iii: The chemical formula (1) has the general structure of the following chemical formula (5): Chemical formula (5) R2 is selected from one of C1-C5 alkyl groups, C12-C15 aromatic chain groups, C16-C18 aromatic chain groups with alicyclic rings, or C3-C5 alkyl groups with ether substituents. R3 and R4 are ester groups.

8. The electrolyte according to claim 7, characterized in that, In scheme i, R3 is a substituent group for a pyridine-based cationic ionic liquid.

9. The electrolyte according to claim 7, characterized in that, In scheme ii, R3 is an ether group with multiple ether branches.

10. The electrolyte according to claim 1, characterized in that, The electrolyte also includes additives and lithium salts. The lithium salt is selected from one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), and lithium bis(oxalateborate) (LiDFOB); the additives include film-forming additives and inward flow aids.

11. The electrolyte according to claim 10, characterized in that, The film-forming additives include lithium halides, lithium nitrates, and halogenated carbonates; the inflow aids include dendritic polyesters, polyamides, polyesteramides, polyethers, or polyurethanes.

12. The electrolyte according to claim 10, characterized in that, The mass ratio of branched polyimide polymer addition: lithium salt addition: additive addition is 50~95:5~50:0.1~10.

13. A method for preparing the branched polyimide polymer in the electrolyte according to any one of claims 1-12, characterized in that, Includes the following steps: S1: Under an inert atmosphere, reactant 4 (dianhydride compound), reactant 2 (tetracarboxylic acid compound), reactant 5 (diacarboxylic acid diester compound), or reactant 3 (tetracarboxylic acid compound) reacts with reactant 1 to prepare a polyimide polymer with functional groups. The chemical equation is as follows: ； In the formula, A, D, and E are each independently selected from hydroxyl, carboxyl, or H; and D and E are not both H. R1 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or aromatic fused ring groups; R2 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or alkyl groups with ether substituents. n represents the degree of aggregation, and the range of n is 1000-10000; Among them, the number of carbon atoms in R1 is between C1 and C20; the number of carbon atoms in R2 is between C1 and C30. S2: Reactant 6 is grafted onto the main chain of a polyimide polymer containing functional groups to prepare a branched polyimide polymer. The chemical equation is as follows: ； In the formula, G-R1 / R2 / R3 are organic reagents with active groups, where G is an active group that can undergo group exchange reactions with A groups or hydroxyl and carboxyl groups. A is selected from one of hydroxyl, carboxyl, or H; R1 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or aromatic fused ring groups; R2 is selected from one of alkyl groups, aromatic chain groups, aromatic chain groups with alicyclic rings, or alkyl groups with ether substituents. R3 and R4 are each independently selected from one of the substituent groups of ionic liquid, ester group, H, ether group, and R3 and R4 are not both H; R5 is selected from one of the substituent groups of ionic liquids, ester groups, H, and ether groups; n represents the degree of aggregation, and the range of n is 1000-10000; Among them, R1 has a carbon atom count of C1-C20; R2 has a carbon atom count of C1-C30; and R3, R4 and R5 each have a carbon atom count of C1-C15.

14. The preparation method according to claim 13, characterized in that, G is selected from halogen groups or hydroxyl groups.

15. The preparation method according to claim 13, characterized in that, Includes the following steps: S11: Under an inert atmosphere, reactant 4 (dianhydride compound), reactant 2 (tetracarboxylic acid compound), reactant 5 (diacarboxylic acid diester compound), or reactant 3 (tetracarboxylic acid compound) are dissolved in an organic solvent, reactant 1 is added to react, and the mixture is stirred at room temperature. Then, a methanol / water solution is added to the solution, filtered, and vacuum dried. Then, under vacuum, the mixture is heated at different temperature gradients to prepare a polyimide polymer with functional groups. S12: Dissolve the functionalized polyimide polymer in an organic solvent, add reactant 6, stir at room temperature, add water to the solution to produce a precipitate, filter, and then dry under vacuum to obtain a branched polyimide polymer.

16. The preparation method according to claim 15, characterized in that, The molar ratio of reactant 4 (dianhydride compound), reactant 2 (tetracarboxylic acid compound), reactant 5 (diacarboxylic acid diester compound), or reactant 3 (tetracarboxylic acid compound) to reactant 1 is 1:1; the organic solvent is selected from N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), or a mixture thereof.

17. The preparation method according to claim 15, characterized in that, The molar ratio of the amount of the functionalized polyimide polymer added to the amount of reactant 6 is 1:1.1~1.

5.

18. The preparation method according to claim 15, characterized in that, In step S11 of the method for preparing a branched polyimide polymer that can be used as an electrolyte, the stirring time is 48 hours; the volume ratio of the methanol / aqueous solution is V. 甲醇 V 水 =1:1; the vacuum drying time is 12h, and the vacuum drying temperature is 60℃; the different temperature gradients are 100℃, 150℃, 200℃ and 250℃, and the heating time is 1h at each gradient temperature.

19. The preparation method according to claim 15, characterized in that, In step S12 of the method for preparing a branched polyimide polymer that can be used in electrolytes, the stirring time is 24-48 h; the vacuum drying time is 12 h, and the vacuum drying temperature is 60 °C.

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