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CN-122000611-A - Polyimide diaphragm and preparation method and application thereof

CN122000611ACN 122000611 ACN122000611 ACN 122000611ACN-122000611-A

Abstract

The polyimide membrane is characterized in that the polyimide membrane is introduced by a BMIM structural unit, the thermal stability, the electrolyte wettability and the lithium ion conductivity of the membrane are improved, meanwhile, the original mechanical strength of polyimide is kept, the membrane can keep a stable structure in a high-temperature environment and is further applied to lithium ion battery manufacturing, the safety of a battery is ensured, the preparation method is simple to operate, the requirement on experimental environment is low, the polyimide nanofiber membrane obtained by an electrostatic spinning process has a high-porosity and three-dimensional tortuous pore diameter structure, the infiltration of electrolyte and the direct perforation of lithium dendrites are facilitated, the permeation speed and the retention of the electrolyte in the membrane can be improved, the transmission efficiency of lithium ions is improved, the charge and discharge efficiency and the power density of the battery are improved, the expansion and the contraction of electrode materials can be born in the long-term circulation process of the battery, and the cycle life of the battery is ensured.

Inventors

  • CONG BING
  • LI HAITING
  • LI YE
  • DING MEICHAO
  • LIU KAIKAI
  • ZHAO ZONGLIANG
  • LIU LIZHEN

Assignees

  • 中汽新能电池科技有限公司

Dates

Publication Date
20260508
Application Date
20260109

Claims (10)

  1. 1. A polyimide diaphragm is characterized by having a structure shown in a formula I: The compound of the formula I, Wherein Ar is: 。
  2. 2. the polyimide separator as recited in claim 1 wherein Ar is: 。
  3. 3. The polyimide separator as recited in claim 1 wherein Ar is: 。
  4. 4. the polyimide diaphragm according to claim 1, wherein the diaphragm has a three-dimensional meandering pore structure, and the porosity is not less than 75%.
  5. 5. A process for producing a polyimide separator according to any one of claims 1 to 4, characterized in that a polyimide separator is obtained by synthesizing a diamine monomer having 1-butyl-3-methylimidazole, polymerizing the resultant at a low temperature to obtain a polyamic acid solution, and further electrospinning the resultant solution.
  6. 6. The method for preparing a polyimide diaphragm according to claim 5, comprising the following specific steps: (1) Nucleophilic substitution reaction Dripping acetonitrile solution of 1, 4-dibromobutane into mixed solution of 4,4' -di (N, N-dimethylamino) diphenyl methanol, K 2 CO 3 and acetonitrile, using the mixed solution as solvent, adding 1-5ml solvent for every millimole monomer, making reaction for 6-10 hr at 80-85 deg.C, using dichloromethane and water to make extraction, combining organic phases, drying with anhydrous sodium sulfate, rotary-steaming and purifying product by means of column chromatography technology so as to obtain the invented product containing bromodiamine monomer; (2) Ionization reaction and anion exchange reaction Adding a bromine-containing diamine monomer and 1-butyl imidazole into a round-bottom flask, adding DMF (dimethyl formamide) as a solvent, reacting for 5-15h under the nitrogen atmosphere at 140-160 ℃, adding a lithium perchlorate aqueous solution with the solubility of 0.5-1M after the reaction is finished, extracting with dichloromethane after the reaction is finished, and drying with magnesium sulfate; (3) Low temperature polycondensation Fully dissolving the prepared diamine monomer in a three-neck flask filled with DMF solvent under the action of mechanical stirring, placing a reaction system in an ice-water bath for reaction, and adding dianhydride monomer into the reaction system in batches, fully stirring for 3-6 hours to obtain a yellowish transparent viscous PAA spinning solution; (4) Electrospinning and thermal imidization PAA spinning solution placed in a 20-30ml syringe is prepared into a PAA nanofiber membrane by utilizing an electrostatic spinning technology, the specific parameters are set as follows, the environment temperature is 22-25 ℃, the environment humidity is 20-40%, the spinning voltage is 20-22kV, the syringe propulsion speed is 0.6-0.8ml/h, an aluminum foil is used as a receiving substrate and is tightly attached to a receiving roller, the distance between the receiving roller and the syringe is 15-18cm, the rotating speed of the roller is 430-450r/min, after continuous spinning is carried out for 10-12h, a white PAA nanofiber membrane is obtained, the PAA nanofiber membrane is subjected to thermal imidization through programmed temperature control under the action of drafting force at two ends, the specific temperature control flow is as follows, the total removal of the solvent is ensured through temperature rising from room temperature to 100-110 ℃ for 2-3h, the temperature rising is further carried out through 1-2h to 300-320 ℃ and the heat preservation is carried out for 1-2h, and the imidization is ensured to be completely completed, and finally the yellow PI nanofiber membrane is prepared.
  7. 7. The method of producing a polyimide separator according to claim 6, wherein the molar ratio of 4,4' -bis (N, N-dimethylamino) diphenylmethanol to 1, 4-dibromobutane to K 2 CO 3 in the step (1) is 1:1 to 1.2:3 to 4.
  8. 8. The method for producing a polyimide separator according to claim 6, wherein 3 to 5ml of DMF solvent is added per millimole of diamine monomer in the step (3).
  9. 9. The method of producing a polyimide separator according to claim 6, wherein the molar ratio of the dianhydride monomer to the diamine monomer in the step (3) is 1:1.
  10. 10. Use of the polyimide separator of any of claims 1-4 in the manufacture of lithium ion batteries.

Description

Polyimide diaphragm and preparation method and application thereof Technical Field The invention relates to the technical field of battery manufacturing, in particular to a polyimide diaphragm and a preparation method and application thereof. Background In practical application of lithium ion batteries, the performance of the separator, which is a key component, has a critical influence on the safety, charge-discharge efficiency and cycle life of the battery. Currently, conventional polyolefin separators (e.g., polypropylene, polyethylene separators) suffer from a number of significant drawbacks. Firstly, the thermal stability is poor, shrinkage deformation is easy to occur under a high-temperature environment, direct contact of positive and negative electrodes is often caused, short circuit is caused, and the safety performance of a battery is seriously threatened. Secondly, the electrolyte wettability of the traditional diaphragm is poor, so that the electrolyte is difficult to fully permeate into the diaphragm, thereby influencing the transmission efficiency of lithium ions and reducing the charge-discharge efficiency and the power density of the battery. In addition, the conventional separator has limited mechanical strength, and the separator is easily damaged due to expansion and contraction of electrode materials during charge and discharge of the battery, thereby affecting the cycle life of the battery. However, although the common polyimide diaphragm has better thermal stability and mechanical strength, the lithium ion conductivity is still to be improved, the chemical property of the surface of the polyimide diaphragm is that the compatibility of the polyimide diaphragm and electrolyte is not ideal enough, and after the polyimide diaphragm contacts with the electrolyte, interface reaction is easy to occur, so that the migration of lithium ions in the diaphragm is blocked to a certain extent, and the overall performance of the battery is limited. Therefore, developing a separator with good thermal stability, high electrolyte wettability, high lithium ion conductivity and mechanical strength is a technical problem to be solved in the current lithium ion battery field. Disclosure of Invention The invention aims to provide a polyimide diaphragm. Another technical problem to be solved by the present invention is to provide a method for preparing the polyimide diaphragm. Another technical problem to be solved by the present invention is to provide an application of the polyimide separator. In order to solve the technical problems, the technical scheme of the invention is as follows: a polyimide diaphragm is a polyimide nanofiber membrane based on BMIM, and has a structure shown in a formula I: The compound of the formula I, Wherein Ar is: 。 preferably, the polyimide separator above, wherein Ar is: 。 preferably, the polyimide separator above, wherein Ar is: 。 preferably, the polyimide diaphragm has a three-dimensional zigzag pore structure, and the porosity is more than or equal to 75%. The preparation method of the polyimide diaphragm comprises the steps of synthesizing diamine monomer with 1-butyl-3-methylimidazole (BMIM), polymerizing at low temperature to obtain polyamic acid solution, and further carrying out electrostatic spinning to obtain the polyimide diaphragm. The reaction equation is as follows: 。 Preferably, the preparation method of the polyimide diaphragm comprises the following specific steps: (1) Nucleophilic substitution reaction Dripping acetonitrile solution of 1, 4-dibromobutane into mixed solution of 4,4' -di (N, N-dimethylamino) diphenyl methanol, K 2CO3 and acetonitrile, using the mixed solution as solvent, adding 1-5ml solvent for every millimole monomer, making reaction for 6-10 hr at 80-85 deg.C, using dichloromethane and water to make extraction, combining organic phases, drying with anhydrous sodium sulfate, rotary-steaming and purifying product by means of column chromatography technology so as to obtain the invented product containing bromodiamine monomer; (2) Ionization reaction and anion exchange reaction Adding bromine-containing diamine monomer and 1-butyl imidazole into a 100ml round bottom flask, adding DMF (N, N-dimethylformamide) as a solvent, reacting for 5-15h under the nitrogen atmosphere at 140-160 ℃, adding lithium perchlorate water solution with the solubility of 0.5-1M after the reaction is finished, extracting with dichloromethane after the reaction is finished, drying with magnesium sulfate, and finally, steaming the dichloromethane to remove the dichloromethane to obtain diamine monomer with 1-butyl-3-methylimidazole (BMIM); (3) Low temperature polycondensation Fully dissolving the prepared diamine monomer in a three-neck flask filled with DMF solvent under the action of mechanical stirring, placing a reaction system in an ice-water bath for reaction, and adding dianhydride monomer into the reaction system in batches, fully stirring for 3-6 hours to obtain