WO2020062826A1

WO2020062826A1 - Preparation method for fluorine-containing capped structure polycarbonate and polyimide composite fiber membrane

Info

Publication number: WO2020062826A1
Application number: PCT/CN2019/081021
Authority: WO
Inventors: 杜辉; 段雅静; 陈照军
Original assignee: 青岛大学
Priority date: 2018-09-28
Filing date: 2019-04-02
Publication date: 2020-04-02
Also published as: CN109295512B; CN109295512A

Abstract

A preparation method for a fluorine-containing capped structure polycarbonate and polyimide composite fiber membrane, comprising: first preparing a polyamic acid solution using 4,4'-diaminodiphenyl ether and pyromellitic dianhydride; performing electrospinning on the polyamic acid solution to obtain a polyamic acid fiber membrane; then performing imidization to obtain a polyimide fiber membrane, and finally dipping the polyimide fiber membrane in a polycarbonate DMF solution and vacuum-drying same, so as to obtain a fluorine-containing capped structure polycarbonate and polyimide composite fiber membrane. The polycarbonate has a fluorine-containing capped structure, effectively improving the thermal stability and affinity for electrolyte of the composite fiber membrane, improving the safety of a lithium ion battery. The preparation method is easy to operate and convenient for industrial production, achieving air permeability and affinity while improving the thermal stability performance of a separator, achieving excellent overall performance, and being applicable to the preparation for a lithium ion battery separator to satisfy high demand of use.

Description

Preparation method of polycarbonate / polyimide composite fiber membrane containing fluorine-terminated structure

Technical field

The invention belongs to the technical field of lithium-ion batteries, and in particular relates to a method for preparing a polycarbonate / polyimide composite fiber membrane with a fluorine-containing end-capping structure.

Background technique

Lithium-ion batteries (LIBs) have the advantages of high voltage, high specific energy, long life, no memory effect, environmental friendliness, fast charging speed, and low self-discharge rate. They have now become the most concerned and highest-yield consumer battery varieties. Lithium-ion battery separators have the important functions of avoiding contact between the positive and negative electrodes of the battery, retaining the electrolyte, and allowing lithium ions to pass through, and their performance will have a huge impact on the electrochemical performance of the lithium-ion battery. Therefore, research and development of battery separators and improvement of separator performance will be an important part of the development of lithium-ion batteries in the future.

The separator used in lithium ion batteries should have both the characteristics of electronic insulation and electrolyte ionic conductors, and must have good mechanical properties, chemical and electrochemical stability, and be able to maintain good electrolyte performance during repeated cycles of charge and discharge. Wettability and so on. Although the separator does not affect the energy storage and output of the battery, the separator plays a vital role in the interface structure, internal resistance, capacity, circulation and safety of the battery. At present, commercial lithium battery separators are widely used in polyolefin microporous membranes, such as polyethylene and polypropylene separators. However, this separator has poor thermal stability, wettability, porosity, and electrolyte absorption. Low, there are hidden dangers, which is not enough to meet people's requirements.

Chinese invention patent 201410147627.X discloses a method for preparing a polyimide nano-lithium ion battery separator, which includes preparing a polyamic acid solution and a melt thereof, and then subjecting the obtained melt to melt spinning, recrystallization, cold and heat Products obtained through a series of processes such as stretching and heat setting have excellent electrochemical stability and heat shrinkage properties. However, the invention needs to strictly control the process parameters and conditions of diaphragm preparation-melt stretching, which brings difficulties in practical operation.

Chinese invention patent 200980111875.6 discloses a battery separator, the battery separator comprising: a porous substrate; and a layer of a crosslinked polymer supported on at least one surface of the porous substrate, wherein the crosslinked polymer The product is obtained by reacting (a) a reactive polymer having an active hydrogen-containing reactive group in the molecule with (b) an isocyanate-terminated polycarbonate urethane prepolymer, and the purpose is to provide A battery separator having excellent oxidation resistance and also having adhesion to electrodes.

Chinese invention patent 201610363502.X discloses a method for preparing a lithium ion battery separator. Polyethylene, polycarbonate, maleic anhydride resin, hydroxyethyl methacrylate, titanium dioxide, polylactic acid, and polylactone Heat and stir with a plasticizer, extrude into a film to obtain a substrate film; then immerse it in a mixed solution consisting of hypromellose, polyethylene glycol, white carbon black, and zirconia; obtain a separator for a lithium ion battery; the The method requires a wide range of raw materials and additives, but only improves the mechanical and electrical properties of the product.

technical problem

The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a polycarbonate / polyimide composite fiber membrane with a fluorine-containing end-capped structure, which can achieve high thermal stability of the separator while having high performance. The air permeability, wettability, and liquid absorption of the electrolyte have excellent comprehensive performance, and can be widely used in lithium ion batteries to meet higher usage requirements. The method is simple to operate and convenient for industrial production.

Technical solutions

The invention provides a method for preparing a polycarbonate / polyimide composite fiber membrane with a fluorine-containing end structure. The polycarbonate is a polycarbonate having a fluorine-containing end structure and is prepared by the following steps. :

(1) Weigh 4,4'-diaminodiphenyl ether and pyromellitic dianhydride in a molar ratio of 1: 1.01, and stir to dissolve 4,4'-diaminodiphenyl ether in a certain amount in an ice water bath. In the amount of N, N-dimethylformamide (DMF), keep the ice-water bath and add pyromellitic dianhydride to the reaction system three times, and mechanically stir the reaction in the ice-water bath for 12-24 hours to obtain polyamic acid. Solution

(2) Electrospinning the polyamic acid solution, the electrostatic spinning parameters are as follows: the spinning voltage is 15kV, the advance rate is 0.01mL / min, the spinning receiving distance is 20cm, the syringe needle is 8 #, and it is spun at room temperature Silk 2-8h to obtain polyamic acid fiber membrane;

(3) Put the polyamic acid fiber membrane into an oven, and dry them at 150 ° C, 200 ° C, 250 ° C, and 300 ° C for 30 minutes to perform imidization to obtain a polyimide fiber membrane;

(4) Prepare a polycarbonate DMF solution with a mass concentration of 2% to 6%, soak the polyimide fiber membrane in it for 2-8h, then take it out and dry it in a vacuum drying box at 120 ° C for 24h, that is, A polyimide / polycarbonate composite fiber membrane was obtained.

In the present invention, the polycarbonate having a fluorine-containing capping structure includes the following main chain structure and capping structure:

The main chain structure of the following formula (1),

Wherein n is 100 to 550, and the R ₁ group is a C ₈ -C ₃₆ group, including at least one benzene ring, and may further include a heteroatom of a cycloalkyl structure, halogen, oxygen, nitrogen, sulfur, silicon, or phosphorus. ;

The capping structure of the following formula (2),

The R ₂ group may be located in the ortho or para position of the oxygen atom connected to the benzene ring, and the R ₂ group is a C ₄ -C ₁₆ saturated group, which may be cyclic or non-cyclic, and 50% ～ 100% of the hydrogen atoms are replaced by fluorine atoms.

In the present invention, the composite fiber membrane has a sheath-core structure, wherein polyimide is a core and polycarbonate is a sheath.

In the present invention, the composite fiber film contains 70% to 90% of polyimide and 10% to 30% of polycarbonate in terms of mass fraction.

The invention also provides the application of the above method in preparing a battery separator.

Beneficial effect

In the present invention, polyimide and polycarbonate are used to prepare a battery separator. Polyimide has the advantage of good thermal stability. Polycarbonate has a high affinity with the lithium ion battery electrolyte. Dipping on the surface of the polyimide separator fiber, while maintaining the thermal stability of the separator, greatly reducing the contact angle of the electrolyte on the surface of the separator, significantly improving the affinity between the separator and the electrolyte of the lithium ion battery, and Effectively improves the liquid retention rate of the separator to the electrolyte. At the same time, the polycarbonate used has fluorine-containing end-capping groups, which further effectively improves the thermal stability of the composite fiber membrane. In addition, polycarbonate has a flame retardant effect.

The invention prepares a polyimide fiber membrane through an electrostatic spinning method and thermal imidization, which has a rich pore structure and a high porosity, has good air permeability, is beneficial to the absorption and maintenance of the electrolyte, and is beneficial to The transport of ions in the separator improves the charge and discharge efficiency of the lithium ion battery.

Compared with the prior art, the technical solution of the present invention has the following advantages and improvements:

The battery separator of the present invention exhibits excellent air permeability, affinity with the electrolyte and thermal stability, and significantly improves the affinity between the traditional separator and the lithium ion battery electrolyte, and the contact angle and absorption of the electrolyte The liquid rate is better. The lithium-ion battery assembled using the polyimide / polycarbonate composite fiber membrane provided by the present invention as a separator has the advantages of high battery capacity, good cycle stability, and high safety.

Embodiments of the invention

The following describes the embodiments of the present invention in detail with reference to the examples. Those who do not indicate specific conditions in the examples are performed according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are conventional products that are commercially available.

Example 1

Weigh 2.00g of 4,4'-diaminodiphenyl ether and dissolve it in 50g of DMF in an ice-water bath. Keep the ice-water bath and add 2.20g of pyromellitic dianhydride to the reaction system in three portions. Mechanically stir the reaction in the ice-water bath for 24h Then, a polyamic acid solution is obtained; an appropriate amount of the polyamic acid solution is subjected to electrostatic spinning under the conditions of a spinning voltage of 15 kV, an advance rate of 0.01 mL / min, a spinning receiving distance of 20 cm, and a syringe needle of 8 #. Spinning at room temperature for 8 hours to obtain a polyamic acid fiber membrane; put the polyamic acid fiber membrane in an oven, and dry at 150 ° C, 200 ° C, 250 ° C, and 300 ° C for 30 minutes to perform imidization to obtain polyimide Amine fiber membrane; using a polycarbonate having a main chain structure described in the following formula (3) and a capped structure described in the following formula (4), a 6% polycarbonate DMF solution was prepared, and the polyimide The fiber membrane was immersed in it for 4 hours, and then taken out and dried in a vacuum drying box at 120 ° C. for 24 hours to obtain a polyimide / polycarbonate composite fiber film. It was determined that the mass fraction of polyimide was 74% and the mass fraction of polycarbonate was 26%.

Example 2

Weigh 2.40 g of 4,4'-diaminodiphenyl ether in 50 g DMF while stirring in an ice water bath. Keep the ice water bath and add 2.62 g of pyromellitic dianhydride to the reaction system in three portions. Mechanically stir the reaction in the ice water bath for 12 h. Then, a polyamic acid solution is obtained; an appropriate amount of the polyamic acid solution is subjected to electrostatic spinning under the conditions of a spinning voltage of 15 kV, an advance rate of 0.01 mL / min, a spinning receiving distance of 20 cm, and a syringe needle of 8 #. Spin at room temperature for 2 h to obtain a polyamic acid fiber membrane; put the polyamic acid fiber membrane in an oven, and dry at 150 ° C, 200 ° C, 250 ° C, and 300 ° C for 30 minutes to perform imidization to obtain polyimide Amine fiber membrane; using a polycarbonate having a main chain structure described in the following formula (5) and a capped structure described in the following formula (6), a 4% mass concentration polycarbonate DMF solution was prepared, and polyimide The fiber membrane was immersed in it for 8 hours, then taken out and dried in a vacuum drying box at 120 ° C. for 24 hours to obtain a polyimide / polycarbonate composite fiber film. It was determined that the mass fraction of polyimide was 90% and the mass fraction of polycarbonate was 10%.

Example 3

Weigh 1.60g of 4,4'-diaminodiphenyl ether in 30 g of DMF while stirring in an ice water bath. Keep the ice water bath and add 1.76 g of pyromellitic dianhydride to the reaction system in three times. The reaction is stirred in the ice water bath for 18 hours Then, a polyamic acid solution is obtained; an appropriate amount of the polyamic acid solution is subjected to electrostatic spinning under the conditions of a spinning voltage of 15 kV, an advance rate of 0.01 mL / min, a spinning receiving distance of 20 cm, and a syringe needle of 8 #. Spinning at room temperature for 6h to obtain a polyamic acid fiber membrane; put the polyamic acid fiber membrane into an oven, and dry at 150 ° C, 200 ° C, 250 ° C, and 300 ° C for 30 minutes to perform imidization to obtain polyimide Amine fiber membrane; using a polycarbonate having a main chain structure described in the following formula (7) and a capped structure described in the following formula (8), a 2% mass concentration polycarbonate DMF solution was prepared, and polyimide The fiber membrane was immersed in it for 2 hours, and then taken out and dried in a vacuum drying box at 120 ° C. for 24 hours to obtain a polyimide / polycarbonate composite fiber film. It was determined that the mass fraction of polyimide was 71% and the mass fraction of polycarbonate was 29%.

Example 4

1.25g of 4,4'-diaminodiphenyl ether was weighed and dissolved in 30g of DMF in an ice-water bath. While maintaining the ice-water bath, 1.37g of pyromellitic dianhydride was added to the reaction system in three portions. The reaction was mechanically stirred in the ice-water bath for 20h. Then, a polyamic acid solution is obtained; an appropriate amount of the polyamic acid solution is subjected to electrostatic spinning under the conditions of a spinning voltage of 15 kV, an advance rate of 0.01 mL / min, a spinning receiving distance of 20 cm, and a syringe needle of 8 #. Spin at room temperature for 4 h to obtain a polyamic acid fiber membrane; put the polyamic acid fiber membrane in an oven, and dry at 150 ° C, 200 ° C, 250 ° C, and 300 ° C for 30 minutes to perform imidization to obtain polyimide Amine fiber membrane; a polycarbonate having a 5% mass concentration of a bisphenol A polycarbonate DMF solution was prepared using a polycarbonate having a main chain structure described in the following formula (9) and a capped structure described in the following formula (10), The imide fiber membrane was immersed in it for 6 hours, and then taken out and dried in a vacuum drying box at 120 ° C. for 24 hours to obtain a polyimide / polycarbonate composite fiber film. It was determined that the mass fraction of polyimide was 84% and the mass fraction of polycarbonate was 16%.

Comparative Example 1

Weigh 2.00g of 4,4'-diaminodiphenyl ether and dissolve it in 50g of DMF in an ice-water bath. Keep the ice-water bath and add 2.20g of pyromellitic dianhydride to the reaction system in three portions. Mechanically stir the reaction in the ice-water bath for 24h Then, a polyamic acid solution is obtained; an appropriate amount of the polyamic acid solution is subjected to electrostatic spinning under the conditions of a spinning voltage of 15 kV, an advance rate of 0.01 mL / min, a spinning receiving distance of 20 cm, and a syringe needle of 8 #. Spinning at room temperature for 8 hours to obtain a polyamic acid fiber membrane; put the polyamic acid fiber membrane in an oven, and dry at 150 ° C, 200 ° C, 250 ° C, and 300 ° C for 30 minutes to perform imidization to obtain polyimide Amine fiber membrane; prepare a 6% bisphenol A polycarbonate DMF solution, soak the polyimide fiber membrane in it for 4h, then take it out and dry it in a vacuum drying box at 120 ° C for 24h. Polyimide / polycarbonate composite fiber membrane. It was determined that the mass fraction of polyimide was 73% and the mass fraction of bisphenol A polycarbonate was 27%.

Diaphragm performance test

Performance tests were performed on the Celgard 2400 commercial separator in the United States, the separator provided in Comparative Example 1, and the separators provided in Examples 1 to 4, including air permeability, contact angle, liquid absorption, and heat shrinkage. The results are shown in Table 1. The electrolyte used in the contact angle and liquid absorption tests was a lithium hexafluorophosphate electrolyte, and its composition was a volume ratio of vinyl carbonate to diethyl carbonate of 1: 1, in which 1 mol / L of lithium hexafluorophosphate was dissolved. The heat shrinkage test was performed at 250 ° C for 30 minutes.

From the results in Table 1, it can be seen that the battery separator prepared by the present invention exhibits excellent air permeability, affinity with the electrolytic solution, and thermal stability. Compared with the polyimide battery separator provided in Comparative Example 1, the polyimide / polycarbonate composite fiber membrane provided by the present invention significantly improves the affinity with the lithium ion battery electrolyte because it contains polycarbonate. , The contact angle and the liquid absorption rate of the electrolyte are more excellent; moreover, the polycarbonate used in the present invention has a fluorine-containing end cap structure, which further effectively improves the thermal stability of the composite fiber membrane.

Table 1 diaphragm performance test results

Claims

A method for preparing a polycarbonate / polyimide composite fiber membrane with a fluorine-containing end structure, wherein the polycarbonate is a polycarbonate having a fluorine-containing end structure, and the composite fiber membrane Prepared by the following steps:

(1) Weigh 4,4'-diaminodiphenyl ether and pyromellitic dianhydride in a molar ratio of 1: 1.01, and stir to dissolve 4,4'-diaminodiphenyl ether in a certain amount in an ice water bath. In the amount of DMF, keep the ice-water bath and add pyromellitic dianhydride to the reaction system in three portions, and mechanically stir the reaction in the ice-water bath for 12-24 hours to obtain a polyamic acid solution;

(2) Electrospinning the polyamic acid solution, the electrostatic spinning parameters are as follows: the spinning voltage is 15kV, the advance rate is 0.01mL / min, the spinning receiving distance is 20cm, the syringe needle is 8 #, and it is spun at room temperature Silk 2-8h to obtain polyamic acid fiber membrane;

(3) Put the polyamic acid fiber membrane into an oven, and dry them at 150 ° C, 200 ° C, 250 ° C, and 300 ° C for 30 minutes to perform imidization to obtain a polyimide fiber membrane;

(4) Prepare a polycarbonate DMF solution with a mass concentration of 3% to 10%, soak the polyimide fiber membrane in it for 2-4 hours, then take it out and dry it in a vacuum drying box at 100-130 ° C. 8 -12h, the composite fiber membrane is obtained.
The method of claim 1, wherein the polycarbonate / polyimide composite fiber membrane with a fluorine-containing end-cap structure comprises the following main chain Structure and capping structure:

The main chain structure of the following formula (1),

Wherein n is 100 to 550, and the R 1 group is a C 8 -C 36 group, including at least one benzene ring, and may further include a heteroatom of a cycloalkyl structure, halogen, oxygen, nitrogen, sulfur, silicon, or phosphorus. ;

The capping structure of the following formula (2),

The R 2 group may be located in the ortho or para position of the oxygen atom connected to the benzene ring, and the R 2 group is a C 4 -C 16 saturated group, which may be cyclic or non-cyclic, and 50% ～ 100% of the hydrogen atoms are replaced by fluorine atoms.
The method for preparing a polycarbonate / polyimide composite fiber membrane with a fluorine-containing end structure according to claims 1-2, wherein the composite fiber membrane has a sheath-core structure, wherein Imide is the core and polycarbonate is the sheath.
The method for preparing a polycarbonate / polyimide composite fiber membrane with a fluorine-containing end structure according to any one of claims 1 to 3, wherein, in terms of mass fraction, the composite fiber membrane 70% to 90% of polyimide, 10% to 30% of polycarbonate.
Use of the method according to any one of claims 1 to 4 for preparing a battery separator.