CN116344918A

CN116344918A - Ammonium salt-added porous polymer electrolyte membrane, preparation method and application

Info

Publication number: CN116344918A
Application number: CN202310440873.3A
Authority: CN
Inventors: 王佳运; 刘明义; 徐若晨; 孙周婷; 白盼星; 张江涛; 贾志全; 曹传钊; 刘大为; 曹曦; 朱勇; 裴杰; 黄茹玲
Original assignee: Huaneng Clean Energy Research Institute
Current assignee: Huaneng Clean Energy Research Institute
Priority date: 2023-04-21
Filing date: 2023-04-21
Publication date: 2023-06-27

Abstract

The invention discloses a porous polymer electrolyte membrane added with ammonium salt, a preparation method and application thereof. The preparation method of the porous polymer electrolyte membrane is simple, the porous polymer electrolyte membrane is prepared in air without being limited by environment, and meanwhile, the viscosity of injection molding liquid is improved by adding ammonium salt, the process difficulty is reduced, and the cost is further reduced. The inside of the porous polymer electrolyte membrane can form a compact micropore structure, so that the liquid retention rate of the polymer electrolyte membrane is improved. The battery prepared from the porous polymer electrolyte membrane has better cycle performance and multiplying power performance.

Description

Ammonium salt-added porous polymer electrolyte membrane, preparation method and application

Technical Field

The invention relates to the technical field of energy storage, in particular to a porous polymer electrolyte membrane added with ammonium salt, a preparation method and application thereof.

Background

The lithium ion battery for energy storage has the advantages that both the electrical performance and the safety performance are guaranteed, most of the current electrochemical energy storage batteries are liquid lithium ion batteries, the leakage risk exists, the battery can be required to operate at low temperature in a low power mode in order to improve the service efficiency of a power station, lithium is easy to separate out due to the fact that the battery is charged at low temperature, and the safety performance of the battery is affected. At present, matrix materials of gel electrolyte comprise polyether system, polymethacrylic acid, methyl ester system, polyacrylonitrile system and polyvinylidene fluoride system, the electrolyte matrix material is required to have higher electrochemical stability, and lithium salt can be uniformly dispersed and ionized in a solvent or a polymer, so that the electrolyte matrix material has higher ionic conductivity. The polymer electrolyte which has been developed includes PEO base, PMMA base, PVDF base, PVC (polyvinyl chloride) base and the like, and some polymers have high crystallinity, low ionic conductivity, poor mechanical properties, harsh synthesis conditions and poor interfaces, so that the wide popularization of the polymer electrolyte is restricted.

The development of polymer electrolytes has undergone three stages, all solid, gel and microporous. The polymer matrix for the all-solid polymer electrolyte is used as a solvent of the electrolyte, does not contain any liquid component, mainly uses PEO-based polymer electrolyte, but has high crystallinity, can only play a role at high temperature, has low ion conductivity at room temperature, has high energy consumption in practical application, and cannot be used on a large scale.

The gel polymer electrolyte contains a certain amount of organic solvent as plasticizer, the plasticizer and the lithium salt are solidified in the grid structure of the polymer matrix, and the preparation process needs to provide an anhydrous environment, so that the preparation conditions are harsh, and the industrialization development is not facilitated.

The microporous polymer electrolyte is a special example of gel polymer electrolyte, the microporous polymer electrolyte adopts a porous polymer membrane as a base material, and then adopts a leaching electrolyte activation method, the pores in the membrane absorb liquid electrolyte, and meanwhile, amorphous areas in a polymer matrix can be swelled by the liquid electrolyte, so that compared with a method for directly preparing the gel polymer electrolyte, the microporous polymer electrolyte has no severe requirements on environment in membrane preparation. In addition, polymer with good film forming property is selected as a base material, so that microporous films with uniform thickness and no defects can be manufactured, and the guarantee is provided for the industrial preparation of polymer electrolyte with excellent performance.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems in the related art to some extent.

To this end, embodiments of the present invention provide a porous polymer electrolyte membrane to which an ammonium salt is added, a method of preparing the same, and applications thereof.

In one aspect, the present invention provides a method for preparing a porous polymer electrolyte membrane to which an ammonium salt is added, comprising the steps of:

(1) The mass ratio is 1: adding the polymer and the organic solvent in the steps (3-7) into a container, and stirring in a water bath to obtain a polymer solution;

(2) Adding ammonium salt into the polymer solution in the step (1), and stirring to obtain injection molding liquid, wherein the mass of the ammonium salt is 1% -10% of that of the polymer;

(3) Coating the injection molding liquid on a matrix by using a coater, standing the base material coated with the injection molding liquid in air for 10-60 s, and then standing in deionized water to realize phase separation so as to obtain a porous polymer electrolyte membrane;

(4) And sucking deionized water on the surface of the porous polymer electrolyte membrane, and vacuum drying to obtain the porous polymer electrolyte membrane, wherein the inside of the porous polymer electrolyte membrane is of a honeycomb porous structure.

Wherein the container may be, but is not limited to, a glass container.

In some embodiments, the polymer is one or more of PVDF-HFP, PMMA, PAN, PVDF, PEO.

Wherein PVDF-HFP is polyvinylidene fluoride-hexafluoropropylene, PMMA is polymethyl methacrylate, PAN is polyacrylonitrile, PVDF is polyvinylidene fluoride, and PEO is polyethylene oxide.

In some embodiments, the organic solvent is one or more of DMF, NMP, DMC, acetonitrile, acetone.

Wherein DMF is N, N-dimethylformamide, NMP is N-methylpyrrolidone, and DMC is dimethyl carbonate.

In some embodiments, the ammonium salt is one or more of ammonium carbonate, ammonium fluoride, urea, ammonium bicarbonate.

In some embodiments, the applicator is a 250 μm four-sided applicator, a 300 μm four-sided applicator, or a 400 μm four-sided applicator.

In some embodiments, the temperature of the water bath in step (1) is 50 ℃ to 70 ℃ and the temperature of the vacuum drying in step (4) is 50 ℃ to 70 ℃.

In some embodiments, the water bath stirring time in the step (1) is 1-3 h, the stirring time in the step (2) is 4-6 h, the vacuum drying time in the step (4) is 12-24 h, and the standing time in the step (4) is 4-24 h.

In some embodiments, the substrate is a glass material.

In another aspect, the present invention provides a porous polymer electrolyte membrane with an ammonium salt added.

In another aspect, the present invention provides an application of a porous polymer electrolyte membrane added with ammonium salt, wherein the porous polymer electrolyte membrane is applied to a preparation process of a lithium ion battery, a sodium ion battery or a soft package battery.

It is understood that the porous polymer electrolyte membrane may be applied to the preparation of lithium ion batteries, sodium ion batteries, or pouch batteries, but is not limited to the above-mentioned types of batteries.

Compared with the prior art, the invention has the beneficial effects that:

the preparation method of the porous polymer electrolyte membrane is simple, the porous polymer electrolyte membrane is prepared in air without being limited by environment, and meanwhile, the viscosity of injection molding liquid is improved by adding ammonium salt, the process difficulty is reduced, and the cost is further reduced.

The inside of the porous polymer electrolyte membrane added with the ammonium salt can form a compact micropore structure, and the liquid retention rate of the polymer electrolyte membrane is improved by adding the ammonium salt.

The battery prepared from the porous polymer electrolyte membrane has better cycle performance and multiplying power performance.

Drawings

The foregoing and/or additional aspects and advantages of the invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a process for preparing a porous polymer electrolyte membrane;

FIG. 2 is a scanning electron microscope image of the surface of the porous polymer electrolyte membrane produced in example 1;

FIG. 3 is a scanning electron microscope image of a cross section of the porous polymer electrolyte membrane produced in example 1;

FIG. 4 is a graph showing the results of mechanical property tests of porous polymer electrolyte membranes with different ammonium bicarbonate addition levels prepared in example 1;

FIG. 5 is a schematic diagram showing the results of the first charge and discharge tests of the lithium ion batteries prepared by the porous polymer electrolyte membranes and the commercial separators with different ammonium bicarbonate addition amounts prepared in example 1;

FIG. 6 is a graph showing the results of the cycle performance test of the lithium ion battery prepared by the electrolyte membrane and the commercial separator, in which the addition amount of ammonium bicarbonate is 3% of the mass of the polymer, prepared in example 1;

FIG. 7 is a schematic diagram showing the results of the rate performance test of a lithium ion full cell prepared by an electrolyte membrane in which the addition amount of ammonium bicarbonate is 3% of the mass of the polymer prepared in example 1;

fig. 8 is a schematic diagram showing the results of the first charge and discharge performance test of the flexible battery fabricated by the porous polymer electrolyte membrane prepared in example 1.

Detailed Description

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.

Example 1:

weighing PVDF-HFP with certain mass, and pouring into a beaker; weighing PVDF-HFP in mass ratio: DMF was 1:5, pouring DMF into a beaker, heating and stirring in a water bath at 50 ℃ for 1h, wherein the stirring speed is 200r/min; adding ammonium bicarbonate accounting for 3% of the mass of the polymer PVDF-HFP, stirring for 6 hours at a stirring speed of 200r/min to obtain injection molding liquid; coating injection molding liquid on glass by adopting a 250 mu m four-side coater, standing for 20s in air, then putting into deionized water, and standing for 5h to realize phase separation so as to obtain a porous polymer electrolyte membrane; and sucking the residual deionized water on the surface of the porous polymer electrolyte membrane by using dust-free paper, and drying the residual deionized water in a vacuum drying oven at 50 ℃ for 24 hours to obtain the porous polymer electrolyte membrane.

The process for preparing the porous polymer electrolyte membrane is shown in fig. 1, and it is understood that the mass of ammonium bicarbonate can be 5%, 6%, 7%, 8%, 10% of the mass of the polymer, and other suitable values.

Example 2:

weighing a certain amount of materials according to the mass ratio of 9:1, pouring PVDF-HFP and PMMA into a beaker; weigh mass ratio (PVDF-hfp+pmma): NMP is 1:6, pouring NMP into a beaker, heating and stirring in a water bath at 60 ℃ for 2 hours, wherein the stirring speed is 300r/min; adding ammonium bicarbonate accounting for 1% of the mass of the polymer (a mixture of PVDF-HFP and PMMA), and stirring for 4 hours at a stirring speed of 300r/min to obtain injection molding liquid; coating injection molding liquid on glass by adopting a 300 mu m four-side coater, standing for 15s in air, then putting into deionized water, and standing for 4h to realize phase separation so as to obtain a porous polymer electrolyte membrane; and sucking the residual deionized water on the surface of the porous polymer electrolyte membrane by using dust-free paper, and drying the residual deionized water in a vacuum drying oven at the temperature of 60 ℃ for 12 hours to obtain the porous polymer electrolyte membrane.

Example 3:

weighing a certain amount of materials according to the mass ratio of 8:1:1 PVDF-HFP, PMMA and PAN, poured into a beaker; weigh mass ratio (PVDF-hfp+pmma+pan): DMP is 1:7, pouring the DMP into a beaker, heating and stirring in a water bath at 65 ℃ for 1h, wherein the stirring speed is 350r/min; adding ammonium fluoride accounting for 2% of the mass of the polymer (a mixture of PVDF-HFP, PMMA and PAN), stirring for 4 hours at a stirring speed of 350r/min to obtain injection molding liquid; coating injection molding liquid on glass by adopting a 250 mu m four-side coater, standing for 20s in air, then putting into deionized water, and standing for 6h to realize phase separation so as to obtain a porous polymer electrolyte membrane; and sucking the residual deionized water on the surface of the porous polymer electrolyte membrane by using dust-free paper, and drying the residual deionized water in a vacuum drying oven at 50 ℃ for 18 hours to obtain the porous polymer electrolyte membrane.

Example 4:

taking the porous polymer electrolyte membrane prepared in example 1 as an example, a scanning electron microscope is used for characterizing the surface and the section of the porous polymer electrolyte membrane, the characterization results are shown in fig. 2 and 3, and as can be seen from fig. 2 and 3, the inside of the porous polymer electrolyte membrane is in a honeycomb micropore structure.

Taking the preparation process of example 1 as an example, the mechanical performance of the porous polymer electrolyte membrane under the condition of different ammonium bicarbonate addition amounts is tested, and the test results are shown in fig. 4, and it can be seen from fig. 4 that the ammonium bicarbonate addition amounts are respectively 3%, 5%, 8% and 10% of the mass of the polymer, and the mechanical performance of the porous polymer electrolyte membrane is poor along with the increase of the ammonium bicarbonate addition ratio, which is caused by the fact that the flexibility is poor along with the increase of the ammonium bicarbonate and the ammonium salt addition ratio is required to be comprehensively considered according to the requirement in practical application.

Comparative example 1:

weighing PVDF-HFP with certain mass, and pouring into a beaker; weighing PVDF-HFP in mass ratio: DMF was 1:5, pouring DMF into a beaker, heating and stirring in a water bath at 50 ℃ for 1h, and obtaining injection molding liquid at a stirring speed of 200r/min; coating injection molding liquid on glass by adopting a 250 mu m four-side coater, standing for 20s in air, then putting into deionized water, and standing for 5h to realize phase separation so as to obtain a porous polymer electrolyte membrane; and sucking the residual deionized water on the surface of the porous polymer electrolyte membrane by using dust-free paper, and drying the residual deionized water in a vacuum drying oven at 50 ℃ for 24 hours to obtain the porous polymer electrolyte membrane.

The injection molding solutions prepared in example 1 and comparative example 1 were each subjected to a viscosity test by taking 3 samples, and the test results are shown in table 1. As can be seen from table 1, the viscosity of the injection molding liquid of example 1 is lower than that of the injection molding liquid of comparative example 1, and it is understood that the viscosity of the injection molding liquid is reduced after the ammonium salt is added, the low viscosity of the injection molding liquid is beneficial to coating, the process difficulty is reduced, the use amount of the organic solvent is reduced, and the cost of the organic solvent is saved.

Table 1. Table for viscosity test of injection molding solutions of comparative example 1 and example 1.

Sample preparation	viscosity/mPa.s
		Example 1-1	536
Examples 1 to 2	534
		Examples 1 to 3	542
Comparative examples 1 to 1	724
		Comparative examples 1 to 2	716
Comparative examples 1 to 3	720

The liquid absorption test was performed using the porous polymer electrolyte membranes prepared in example 1 and comparative example 1 as an example, and the test results are shown in table 2. The testing process is that a small piece of dry film is soaked in the volume ratio PC after being weighed: DEC: EMC is 1:1:1, soaking for 2 hours, taking out the polymer film after fully absorbing the electrolyte, sucking the redundant electrolyte on the surface of the polymer film by using filter paper, and weighing. The liquid absorption was calculated by the following formula:

wherein w is the weight (g) of the wet film containing the saturated electrolyte, w ₀ Dry film weight (g). As can be seen from table 2, the liquid absorption rate of the porous polymer electrolyte membrane prepared in example 1 was greater than that of the porous polymer electrolyte membrane prepared in comparative example 1, and it was found that the liquid absorption rate of the porous polymer electrolyte membrane was increased after the ammonium salt was added, thereby improving the liquid retention rate of the polymer electrolyte membrane.

Table 2. Table for liquid absorption test of porous polymer electrolyte membranes of comparative example 1 and example 1.

Example 5:

taking the porous polymer electrolyte membrane produced in example 1 as an example, the porous polymer electrolyte membrane was punched into small discs having a diameter of 16mm by a microtome, and the small discs were put into a volume ratio PC in a glove box: DEC: EMC is 1:1:1, leaching the lithium hexafluorophosphate electrolyte for 30 to 180 minutes; and wiping off the surface electrolyte to prepare the button type lithium ion full battery. The lithium ion full battery prepared by the electrolyte membrane with the addition amount of ammonium bicarbonate being 3% and 5% of the mass of the polymer and the lithium ion full battery prepared by the commercial diaphragm (PP diaphragm) are subjected to a first charge and discharge test, and the test results are shown in figure 5. As can be seen from fig. 5, the polymer electrolyte membranes with different ammonium salt addition amounts have little difference from the lithium ion full cell prepared by the commercial separator, and the electrochemical performance of the porous polymer electrolyte membranes prepared by the method of the invention is stable and better.

The lithium ion full cell prepared by the electrolyte membrane with the addition amount of ammonium bicarbonate being 3% of the mass of the polymer and the lithium ion full cell prepared by the commercial diaphragm (PP diaphragm) were subjected to a cycle test, and the test results are shown in FIG. 6. As can be seen from fig. 6, the polymer electrolyte membrane assembled by the ammonium bicarbonate prepared by the present invention, which has an additive amount of 3% of the mass of the polymer, has better cycle performance than the commercial separator, and the retention rate after 250 cycles is still 98%, thus the polymer electrolyte membrane prepared by the present invention has excellent stability.

The lithium ion full cell prepared by the electrolyte membrane with the addition amount of ammonium bicarbonate being 3% of the mass of the polymer is subjected to rate performance test under the conditions of 0.5C, 0.1C and 1C, and the test result is shown in figure 7. As can be seen from fig. 7, the lithium ion full cell prepared from the electrolyte membrane, in which the ammonium bicarbonate is added in an amount of 3% of the mass of the polymer, has excellent rate capability, and can still exhibit 73% capacity at 1C.

Example 6:

and (3) selecting a lithium ion battery system, wherein the positive electrode adopts lithium iron phosphate, the negative electrode adopts graphite, the battery is assembled in a lamination mode, the porous polymer electrolyte membrane prepared in the embodiment 1 after electrolyte activation is stacked between the positive electrode and the negative electrode, and the battery is subjected to plastic package by using an aluminum plastic film to complete the preparation of the soft package battery. The first charge and discharge test was performed on the soft pack battery, and the test results are shown in fig. 8. As can be seen from fig. 8, the soft-pack battery assembled by the porous polymer electrolyte membrane, which has the ammonium bicarbonate added in an amount of 3% of the mass of the polymer, still can exert performance, and the soft-pack battery is less in pressure than the button battery, so that the polymer electrolyte membrane is slightly worse in contact with the positive and negative pole pieces, has larger polarization, and can subsequently pass a pressurization test to change the performance of the soft-pack battery.

In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms may be directed to different embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a porous polymer electrolyte membrane to which an ammonium salt is added, comprising the steps of:

2. The method of manufacture of claim 1, wherein the polymer is one or more of PVDF-HFP, PMMA, PAN, PVDF, PEO.

3. The preparation method of claim 1, wherein the organic solvent is one or more of DMF, NMP, DMC, acetonitrile and acetone.

4. The method of claim 1, wherein the ammonium salt is one or more of ammonium carbonate, ammonium fluoride, urea, ammonium bicarbonate.

5. The method of claim 1, wherein the applicator is a 250 μm four-sided applicator, a 300 μm four-sided applicator, or a 400 μm four-sided applicator.

6. The process according to claim 1, wherein the water bath in step (1) is at a temperature of 50 to 70 ℃ and the vacuum drying in step (4) is at a temperature of 50 to 70 ℃.

7. The method according to claim 1, wherein the water bath stirring time in the step (1) is 1 to 3 hours, the stirring time in the step (2) is 4 to 6 hours, the vacuum drying time in the step (4) is 12 to 24 hours, and the standing time in the step (4) is 4 to 24 hours.

8. The method of claim 1, wherein the substrate is a glass material.

9. A porous polymer electrolyte membrane to which an ammonium salt is added, characterized in that the porous polymer electrolyte membrane is produced by the production method according to any one of claims 1 to 8.

10. The use of a porous polymer electrolyte membrane with an ammonium salt, wherein the porous polymer electrolyte membrane is prepared by the preparation method according to any one of claims 1 to 8, and the porous polymer electrolyte membrane is used in the preparation process of a lithium ion battery, a sodium ion battery or a soft-pack battery.