CN113224383A

CN113224383A - Composite solid electrolyte membrane based on metal-organic framework material and preparation method and application thereof

Info

Publication number: CN113224383A
Application number: CN202110331191.XA
Authority: CN
Inventors: 欧星; 罗弼; 白笑宇; 张佳峰; 张宝
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2021-03-29
Filing date: 2021-03-29
Publication date: 2021-08-06
Anticipated expiration: 2041-03-29
Also published as: CN113224383B

Abstract

The invention discloses a composite solid electrolyte membrane based on a metal-organic framework material, and a preparation method and application thereof. The composite solid electrolyte membrane comprises a polymer network formed by polymerizing polyethylene oxide (PEO) and a metal-organic framework Material (MOF) modified by Toluene Diisocyanate (TDI) and lithium salt dispersed in the polymer network. According to the invention, the benzene diisocyanate is used as an intermediate, the MOF and the PEO are connected through a chemical bond, the ionic conductivity of lithium ions can be greatly enhanced, meanwhile, the oxidative decomposition of hydroxyl groups of the PEO under high voltage can be avoided, and the high-voltage electrochemical stability is remarkably improved. The preparation method is simple, easy to control, low in cost and easy to industrialize, and has wide application prospects in the fields of high specific energy solid-state battery systems and flexible electronic energy storage devices.

Description

Composite solid electrolyte membrane based on metal-organic framework material and preparation method and application thereof

Technical Field

The invention relates to the technical field of solid electrolyte materials, in particular to a composite solid electrolyte membrane based on a metal-organic framework material and a preparation method and application thereof.

Background

Due to the environmental problems of increasingly exhausted fossil fuels, global warming and the like, the development of new energy materials and technologies which are green, environment-friendly and sustainable in development becomes an important strategic problem in countries in the world. Lithium ion batteries have been widely used in the fields of mobile phones, electric vehicles and the like, but further application of lithium ion batteries is limited by frequent accidents such as fire, combustion, explosion and the like caused by leakage of combustible organic electrolyte. Meanwhile, with social development and technological progress, people have increasingly increased energy requirements, and the energy density of the existing lithium ion battery technology is difficult to meet the requirements. The all-solid-state lithium battery has high energy density and extremely high safety, the solid electrolyte has the advantages of incombustibility, no corrosion, no volatilization, no liquid leakage and the like, and the dendritic phenomenon of lithium is overcome, so that the spontaneous combustion probability of the battery is greatly reduced, and the attention of extensive researchers and related enterprises is paid. However, the industrial production of lithium ion solid electrolyte still has many challenges, such as: low ionic conductivity, narrow electrochemical window, poor interface stability, large interface resistance and the like. Therefore, the development of a solid electrolyte having high ionic conductivity, excellent interface stability, and a wide electrochemical window is of great importance for the advancement of the industrialization of solid lithium batteries.

Current solid electrolytes can be largely classified into organic polymer electrolytes and inorganic electrolytes. Considering the simple preparation process of the polymer electrolyte and the stable interface contact, the polymer electrolyte is the solid electrolyte with the most application potential. PEO polymers are widely used in solid electrolytes due to their strong complexing ability to lithium salts. However, since PEO has a certain crystallinity at room temperature, which hinders the transfer of lithium ions, the room temperature conductivity is low. In addition, because PEO molecules contain-OH groups, the PEO molecules are easily oxidized into-COOH groups under high pressure, so that the voltage stability window of the PEO is narrow, and the PEO molecules are easily subjected to interface side reaction with a positive electrode material when matched with the high-pressure positive electrode material, thereby limiting the further application of the electrolyte. Therefore, development of a PEO-based solid electrolyte with high ionic conductivity and strong electrochemical stability is required to improve the specific capacity, the cycle performance and the rate capability of the solid lithium battery.

The metal-organic framework Material (MOF) has various structural characteristics, higher specific surface area and porous characteristic, and has higher application potential in the fields of catalysis, energy storage and the like. Meanwhile, the chemical environment of the pore channel of the MOFs material can influence the transmission of lithium ions in the solid electrolyte. Chinese patent CN 112002938A discloses a composite solid electrolyte membrane based on cu (bdc) MOF multilevel structure and a preparation method thereof. The Cu (BDC) MOF in the composite solid electrolyte membrane only provides active sites for absorbing free lithium ions and serves as a lithium ion conduction path for lithium ion transmission, but does not generate cross-linking polymerization with a polymer and only exists in a physical mixing mode, so that an obvious physical interface exists between the polymer and the MOF, the interface conduction efficiency of the lithium ions among MOF particles and between the MOF and the polymer is not high, and the problems of insufficient conductivity of solid electrolyte ions and limited high-voltage electrochemical stability still exist.

Therefore, aiming at the problems in the prior art, the solid electrolyte for realizing chemical crosslinking of the MOFs and the PEO polymer is provided, so that the migration and transmission of lithium ions can be promoted, and the high-voltage electrochemical stability can be improved, thereby promoting the development and industrial application of the solid battery.

Disclosure of Invention

The technical problem solved by the invention is as follows: a composite solid electrolyte membrane based on metal-organic framework material, its preparation method and application are provided. The composite solid electrolyte membrane of the metal-organic framework material can realize chemical crosslinking of MOFs and PEO polymer, improve high-voltage electrochemical stability, promote migration and transmission of lithium ions, and has good cycle performance and rate capability in the aspect of solid batteries.

A first aspect of the present invention provides a composite solid electrolyte membrane based on a metal-organic framework material comprising:

a polymer network formed by cross-linking and polymerizing polyethylene oxide (PEO) and a metal-organic framework Material (MOF) modified by Toluene Diisocyanate (TDI); a lithium salt dispersed in the polymer network.

Wherein, the toluene diisocyanate is used as an intermediate, and the two ends of the toluene diisocyanate are respectively connected with the metal-organic framework material and the polyethylene oxide to form a network structure.

The cross-linking polymerization mode of the polymer network structure is represented by a structural formula as follows:

wherein B and A are connected with each other through a C-O chemical bond;

wherein A represents a group of a metal-organic framework material, B represents a group of toluene diisocyanate, and C represents a group of polyethylene oxide, each of which has the following structural formula:

A:

B：

C：

a1 represents a metal-organic framework material, B1 represents toluene diisocyanate, and C1 represents polyethylene oxide, each of which has the following structural formula:

A1：

B1：

C1:

the cross-linked polymeric structure of the above polymers is merely illustrative of the manner of polymerization thereof, and when the ligands of a do not have the same number of-OH functional groups, the structures formed by the reaction thereof are also different.

Preferably, in the structural formula of the polymer, the molecular weight of the polyethylene oxide material is 100000-4000000; the metal-organic framework material is selected from Mg-MOF-74, Co-MOF-74, Ni-MOF-74, Cu-MOF-74 or Zn-MOF-74. The MOF material can be purchased or synthesized by any known method.

Preferably, the lithium salt is selected from the group consisting of LiTFSI, LiFSI or LiClO₄At least one of

Preferably, the solid electrolyte membrane has a thickness of 20 to 150 um.

Preferably, in the solid electrolyte membrane, the content of the toluene diisocyanate-modified metal-organic framework material is 1 to 10 wt%, based on the total mass of the polymer solid electrolyte membrane.

The second aspect of the present invention provides a method for preparing a composite solid electrolyte membrane based on a metal-organic framework material, comprising the steps of:

step (1): dispersing TDI and MOF materials in an organic solvent according to a mass ratio in a glove box filled with argon, heating and stirring to perform a crosslinking reaction to obtain a toluene diisocyanate modified metal-organic framework material (TDI-MOF), washing and drying;

step (2): dissolving the TDI-MOF material obtained in the step (1) and lithium salt in anhydrous acetonitrile in a glove box filled with argon, and performing ultrasonic dispersion to obtain a first slurry;

and (3): adding polyethylene oxide into the first slurry obtained in the step (2), heating and stirring to enable the TDI-MOF material and PEO to perform a cross-linking reaction to obtain a second slurry.

And (4): and (4) pouring the second slurry obtained in the step (3) on a polytetrafluoroethylene template, and drying to obtain the treated PEO-TDI-MOF/LiTFSI composite solid electrolyte membrane.

Preferably, the solvent in the step (1) is one of anhydrous acetonitrile, toluene, diethyl ether, acetone and carbon tetrachloride; the mass ratio of TDI to MOF is (2-8): 1; the MOF accounts for 5-15% of the mass of the solvent; the stirring temperature is 50-110 ℃; the time is 6-12 h.

Preferably, the stirring temperature in the step (3) is 40-80 ℃; stirring for 6-12 h; the drying temperature is 40-60 ℃; the drying time is 8-12 h.

In a third aspect of the invention, there is provided a use of the composite solid electrolyte membrane as described in the first aspect in a high performance solid state battery system and a flexible electronic energy storage device.

The composite solid electrolyte membrane has the following advantages:

1. aiming at the problems of low conductivity and poor high-voltage electrochemical stability of the PEO-based solid electrolyte, the invention skillfully utilizes the reaction of isocyanate functional groups of Toluene Diisocyanate (TDI) and hydroxyl functional groups in MOF and PEO to polymerize PEO on the MOF modified by TDI, thereby realizing a chemical cross-linking polymerization network among PEO polymer, TDI and MOF, enhancing the interface conduction of lithium ions among MOF particles and between MOF and polymer, and improving the ionic conductivity of the PEO-based solid electrolyte. Meanwhile, after the hydroxyl functional group in the PEO is polymerized with TDI, oxidative decomposition of-OH under high voltage is avoided, interface side reaction when the PEO-based electrolyte is matched with a high-voltage positive electrode is reduced, and the problem of poor high-voltage electrochemical stability of the PEO-based solid electrolyte is solved.

2. The preparation method for realizing chemical crosslinking polymerization is simple, easy to control, low in cost and easy to industrialize.

Drawings

FIG. 1 is a scanning electron micrograph of toluene diisocyanate modified Cu-MOF-74 prepared in example 2 of the present invention.

FIG. 2 is a scanning electron micrograph of a composite solid electrolyte membrane prepared in example 3 of the present invention.

Fig. 3 is a graph of the ionic conductivity at different temperatures of the composite solid electrolyte membrane prepared in example 4 of the present invention.

Fig. 4 is a first-turn charge-discharge curve diagram of a lithium ion battery with a composite solid electrolyte membrane prepared in example 4 of the present invention.

Fig. 5 is a graph of cycle performance of lithium ion batteries of the solid electrolyte membranes prepared in example 4 of the present invention and comparative example 1.

Detailed Description

The present invention will be further described with reference to the following examples and the accompanying drawings.

Example 1

A composite solid electrolyte membrane based on a metal-organic framework material comprising:

Preferably, the cross-linking polymerization mode of the polymer network structure is represented by a structural formula as follows:

wherein B and A are connected through a C-O chemical bond;

A:

B：

C：

A1：

B1：

C1:

in the structural formula of the polymer, the molecular weight of the polyethylene oxide material is 600000; the metal-organic framework material is Cu-MOF-74.

The thickness of the solid electrolyte membrane is 150 um.

In the solid electrolyte membrane, the content of the toluene diisocyanate-modified metal-organic framework material is 5 wt%, based on the total mass of the polymer solid electrolyte membrane.

Example 2

A method for preparing a toluene diisocyanate-modified metal-organic framework material (TDI-MOF), comprising the steps of:

(1) adding 8mmol of Cu (NO)₃)₂And 4mmol of 2, 5-dihydroxy terephthalic acid is dissolved in 80ml of mixed liquid of N, N-dimethylformamide and absolute ethyl alcohol, and the volume ratio is 20: 1. the mixed liquid was then heated at 80 ℃ overnight, the resulting powder was separated by centrifugation and washed with DMF, and finally the product was dried under vacuum at 150 ℃ overnight to obtain Cu-MOF-74 material.

(2) In a glove box filled with argon, the TDI and Cu-MOF-74 materials were mixed in a ratio of 3: 1, the MOF is 10 percent of the mass of the solvent; heating and stirring the mixture at 50 ℃ for 6h to perform a crosslinking reaction to obtain a toluene diisocyanate modified metal-organic framework material (TDI-MOF), and washing and drying the TDI-MOF;

the resulting toluene diisocyanate-modified metal-organic framework material (TDI-MOF) was characterized. The scanning electron micrograph is shown in figure 1, and TDI-MOF is a rod-shaped material.

Example 3

A method for preparing a solid electrolyte membrane for use at room temperature, comprising the steps of:

(1) dissolving the TDI-MOF material prepared in the example 2 and the LiTFSI lithium salt in anhydrous acetonitrile in a glove box filled with argon, and performing ultrasonic dispersion to obtain a first slurry;

(2) adding polyethylene oxide into the first slurry obtained in the step (1), heating and stirring at 50 ℃ for 5h, and carrying out a crosslinking reaction on the TDI-MOF material and PEO to obtain a second slurry.

(3) Pouring the second slurry obtained in the step (2) on a polytetrafluoroethylene template, and drying at 50 ℃ for 12h to obtain the treated PEO-TDI-MOF/LiTFSI composite solid electrolyte membrane.

Wherein the lithium salt is added in an amount of n (EO)/n (Li)⁺) The mass of the TDI-MOF material accounts for 2.5 percent of the mass of the composite solid electrolyte membrane calculated as 20 percent.

The composite solid electrolyte membrane is characterized, and a scanning electron micrograph is shown in figure 2, which shows that: the prepared PEO-TDI-MOF/LiTFSI composite solid electrolyte membrane has a smooth surface and does not have the phenomenon of PEO agglomeration.

Example 4

The PEO-TDI-MOF/LiTFSI composite solid electrolyte prepared in example 3 was assembled into a solid electrolyte lithium battery, and the ionic conductivity thereof at different temperatures, the first-turn discharge capacity in a high-voltage interval when matched with the NCM811 positive electrode, and the battery cycle performance were tested, as shown in fig. 3, fig. 4, and fig. 5 in sequence.

FIG. 3 shows: the ion conductivity of the solid electrolyte membrane is as high as 1.5X 10 at room temperature (25 ℃ C.)^-4S cm^-1And shows higher ionic conductivity.

FIG. 4 shows that: the discharge capacity of the first ring of the NCM811 solid-state lithium battery reaches 201.5mAh g at 25 ℃ and under the multiplying power of 0.1C and within the voltage range of 2.75-4.3V^-1。

FIG. 5 shows that: at 25 deg.C, under 0.1C rate, in 2.75-4.3V voltage range, after circulating 150 circles, the discharge capacity is still up to 160mAh g^-1The capacity retention rate reaches 85.1 percent, and the product is evenThe coulombic efficiency reaches about 99 percent, and the high-voltage cyclic stability and the capacity retention rate are good.

Comparative example 1

The method described in example 3 was used to convert a TDI-MOF material to a MOF material without TDI modification, and the other conditions were kept consistent to prepare a physically mixed PEO/MOF/LiTFSI composite solid electrolyte membrane. The physically mixed electrolyte membrane was assembled into a solid electrolyte lithium battery as described in example 4, and tested for cycle performance in a high voltage range matching the NCM811 positive electrode, see fig. 5.

FIG. 5 shows that: at 25 deg.C, under the multiplying power of 0.1C, in the voltage range of 2.75-4.3V, after circulating 150 circles, the discharge capacity is only 73.5mAh g^-1The capacity retention rate is only 51%, the coulombic efficiency fluctuation is large, and the high-pressure cycle stability and the capacity retention rate are poor.

Claims

1. A composite solid-state electrolyte membrane based on a metal-organic framework material, characterized in that: the composite solid-state electrolyte membrane comprises:

A polymer network composed of polyethylene oxide (PEO) polymerized with a metal-organic framework (MOF) modified with toluene diisocyanate (TDI); a lithium salt dispersed in the polymer network.

2 . The solid electrolyte membrane according to claim 1 , wherein the polymerization method is as follows: toluene diisocyanate is used as an intermediate, and the two ends are respectively connected with a metal-organic framework material and polyethylene oxide to form a network structure. 3 .

3. The solid electrolyte membrane according to claim 1, wherein the polymerization mode of the polymer network structure is represented by a structural formula, as shown below:

Wherein, the B and A, B and C are connected by a C-O chemical bond.

A represents a metal-organic framework material, B represents a group of toluene diisocyanate, and C represents a group of polyethylene oxide, and their respective structural formulas are as follows:

A:

B:

C:

4 . The solid electrolyte membrane according to claim 1 , wherein the molecular weight of the polyethylene oxide material is 100,000-4,000,000; the metal-organic framework material is selected from Mg-MOF-74, Co-MOF-74 , Ni-MOF-74, Cu-MOF-74 or Zn-MOF-74; the toluene diisocyanate is selected from 2,4-toluene diisocyanate or 2,6-toluene diisocyanate; the lithium salt is selected from LiTFSI, _At least one of LiFSI or LiClO.

5 . The solid electrolyte membrane according to claim 1 , wherein in the solid electrolyte membrane, the content of the metal-organic framework material modified with toluene diisocyanate is 1-10 wt %, based on the polymer The total mass of the solid electrolyte membrane is the benchmark.

6. a preparation method of the composite solid electrolyte membrane of claim 1, is characterized in that: comprises the following steps:

Step (1): in a glove box filled with argon, the TDI and MOF materials are dispersed in an organic solvent according to the mass ratio, and heated and stirred to generate a polymerization reaction to obtain a metal-organic framework material modified by toluene diisocyanate (TDI- MOF) and washed and dried;

Step (2): in a glove box filled with argon, dissolve the TDI-MOF material and lithium salt obtained in step (1) in anhydrous acetonitrile, and ultrasonically disperse to obtain a first slurry;

Step (3): in a glove box filled with argon, add polyethylene oxide to the first slurry obtained in step (2), and heat and stir to polymerize the TDI-MOF material and PEO to obtain a second slurry material.

Step (4): in a glove box filled with argon, pour the second slurry obtained in step (3) on a polytetrafluoroethylene template, and dry to obtain a treated PEO-TDI-MOF composite solid electrolyte membrane .

7. preparation method according to claim 6 is characterized in that: in described step (1), solvent is a kind of in anhydrous acetonitrile, toluene, ether, acetone, carbon tetrachloride; Wherein, the quality of TDI and MOF The ratio is (2-8):1; the MOF is 5%-15% of the solvent mass; the stirring temperature is 50-110° C.; the time is 6-12h.

8. The preparation method according to claim 6, characterized in that: in the step (3), the stirring temperature is 40～80°C; the stirring time is 6～12h; the drying temperature is 40～60°C; 8～12h.

9 . An application of the composite solid-state electrolyte membrane according to claim 1 , wherein the composite solid-state electrolyte membrane according to claim 1 is used in high-performance solid-state battery systems and flexible electronic energy storage devices. 10 .