阅读说明：本技术 一种高离子迁移数的不可燃聚合物电解质及其制备方法 (Non-combustible polymer electrolyte with high ion transport number and preparation method thereof ) 是由 陈茂 马明钰 赵宇澄 于 2020-03-19 设计创作，主要内容包括：本发明属于聚合物电解质技术领域,具体为一种高离子迁移数的不可燃聚合物电解质及其制备方法。本发明的聚合物电解质以氟乙烯与乙烯基醚及其衍生物作为聚合单体,其中氟乙烯可以是三氟氯乙烯、四氟乙烯、六氟丙烯,乙烯基醚类单体可为侧链含有多种不同数目的含氧官能团的衍生物。在加热或光照的条件下进行聚合反应得到聚合物。本发明得到的聚合物电解质具有高的离子电导率和高的锂离子迁移数,具有不可燃性和优异的化学稳定性。本发明方法单体原料成本低廉、反应条件温和、且适合工业量化生产。(The invention belongs to the technical field of polymer electrolytes, and particularly relates to a non-combustible polymer electrolyte with high ion migration number and a preparation method thereof. The polymer electrolyte of the invention takes vinyl fluoride and vinyl ether and derivatives thereof as polymerization monomers, wherein the vinyl fluoride can be chlorotrifluoroethylene, tetrafluoroethylene and hexafluoropropylene, and the vinyl ether monomers can be derivatives with a plurality of oxygen-containing functional groups with different numbers on side chains. The polymerization reaction is carried out under the condition of heating or illumination to obtain the polymer. The polymer electrolyte obtained by the invention has high ionic conductivity and high lithium ion transference number, and has incombustibility and excellent chemical stability. The method has the advantages of low monomer raw material cost, mild reaction conditions and suitability for industrial quantitative production.)

1. A polymer electrolyte having a structure represented by the following formula (I):

(I)

Wherein R is ₁Is a chlorine atom, a fluorine atom or a trifluoromethyl group; x is alkyl with 2-12 carbon atoms or polyethylene glycol with 1-12 repeating units; r ₂Is hydrogen atom, chlorine atom, iodine atom, methyl, ethyl, isopropyl, isobutyl, tert-butyldimethylsilyl, tert-butyldiphenylsilyl, trimethylsilyl, triethylsilyl, triisopropylsilyl or 1, 3-dioxanyl-2-one.

2. The method for preparing the polymer electrolyte according to claim 1, comprising the steps of:

Step (1), alternating copolymerization of monomers;

The method A comprises the following steps: mixing a fluorine-containing ethylene monomer, a vinyl ether monomer, an initiator and a solvent by a heating method, and adding into a reaction bottle; the molar ratio of the monomers: initiator = 1000 (1-100);

The method B comprises the following steps: mixing a fluorine-containing ethylene monomer, a vinyl ether monomer, a chain transfer agent, a photocatalyst and a solvent by a light irradiation method, and adding into a reaction bottle; the molar ratio of the monomers: the chain transfer agent = 1000 (1-100), and the photocatalyst used in the reaction process is 0.001-10 mol% of the monomer; the reaction formula is as follows:

(II)

Step (2), after the reaction is finished, removing the solvent to obtain poly (vinyl fluoride- Alternating -vinyl ether) copolymers;

And (3) adding metal salt and an additive into the copolymer obtained in the step (2), and completely mixing to obtain a solid fluorine-containing copolymer which can be used as an electrolyte.

3. The method according to claim 2, wherein the solvent is dimethyl carbonate, diethyl carbonate, dipropyl carbonate, anisole, or a mixture thereof, N,N-dimethylformamide, N,N-dimethylacetamide, N-one or more of methyl pyrrolidone, 5-fluoropropane, 5-fluorobutane, acetonitrile, dimethyl sulfoxide, ethyl acetate, toluene, xylene, supercritical carbon dioxide.

4. The method for preparing a polymer electrolyte according to claim 2, wherein in the step (1), the initiator is one or more of an azo compound and an organic peroxide.

5. The method for preparing a polymer electrolyte according to claim 2, wherein in the step (1), the method B, the chain transfer agent is one or more of a thioreagent, an organic nitrogen oxide, an alkyl halide or a perfluoroalkyl halide.

6. The method for preparing a polymer electrolyte according to claim 2, wherein in the step (1), in the method B, the photocatalyst is one or more of organic small molecular compounds with perylene, pyrene, porphyrin, thiophene, phenothiazine and phenoxazine as a skeleton, or one or more of metal organic complexes with copper, ruthenium and iridium as cores.

7. The method for producing a polymer electrolyte according to claim 2, wherein in the step (3), the metal salt is one or more of a bistrifluoromethylsulfonyl imide metal salt, a bisdifluorosulfonyl imide metal salt, a bistrifluoroethylsulfonyl imide metal salt, a tritrifluoromethylsulfonyl imide metal salt, a trifluoromethanesulfonic acid metal salt, a difluorooxalato borate metal salt, a bisoxalato borate metal salt, a perchlorato borate metal salt, a tetrafluoroborato borate metal salt, a hexafluoroarsenate metal salt, and a hexafluorophosphate metal salt, wherein the metal salt is lithium, sodium, or potassium.

8. The method of claim 2, wherein in the step (3), the additive is one or more selected from the group consisting of dimethylformamide, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, γ -butyrolactone, methyl formate, methyl acetate, 1, 2-dimethoxyethane, polyethylene glycol, and polypropylene glycol.

9. The method for preparing a polymer electrolyte according to claim 2, wherein in the step (1), the heating temperature is minus 20 to 200 ℃; the illumination wavelength of the illumination method is 200-850 nm.

10. Use of a polymer electrolyte as claimed in claim 1 in a metal-ion battery.

11. Use of the polymer electrolyte according to claim 10 in a metal-ion battery which is a lithium-ion battery, a sodium-ion battery or a potassium-ion battery.

Technical Field

The invention belongs to the technical field of polymer electrolytes, and particularly relates to a novel non-combustible polymer electrolyte with high ion migration number and a preparation method thereof.

Background

Metal ion batteries (such as lithium ion batteries) have the advantages of high energy density, long cycle life, high power density, no memory effect and the like, and are considered to be an energy storage device with the most application prospect. Currently, conventional metal-ion batteries use organic liquid electrolytes. However, the liquid electrolyte has safety problems of easy leakage, easy volatilization, flammability and the like, and the application of the battery in the fields of automobile power sources, electric vehicle energy sources and the like is seriously hindered. Compared with the traditional liquid electrolyte, the solid polymer electrolyte can fundamentally avoid the dangers of electrolyte leakage, combustion explosion and the like, has better safety and machinability, and can effectively inhibit the generation of metal dendrite. With the increasing demand for new energy in the fields of electric vehicles, unmanned aerial vehicles, personal portable devices, and the like, the research and development of high-performance solid polymer electrolytes have become a focus of attention of global researchers.

Research on polymer electrolytes dates back to 1973 for the first time, and Fenton et al found that mixing polyethylene oxide (PEO) with an alkali metal sodium salt can form an electrolyte with ionic conductivity (publication: Polymer.1973, 14,589). In 1992, the Armand project group has conducted intensive research on the ion transport mechanism of polymer electrolytes (journal: Electrochim. Acta.1992, 37, 1699-1701), however, PEO has low room temperature conductivity and poor machinability, which limits its application. The Feuillade group uses a cross-linked copolymer of vinylidene fluoride-hexafluoropropylene copolymer and polyacrylonitrile for a polymer electrolyte, and improves the electrochemical performance of the polymer electrolyte by doping propylene carbonate and electrolyte salt. Subsequently, Bellcore, USA, uses a polymer electrolyte membrane as a commercial lithium ion battery electrolyte (U.S. Pat. No. US6268088B 1), which provides a solution to the problems of leakage and burning of lithium ion batteries, and attracts much attention. However, solid polymer electrolytes have so far presented a number of problems to be solved, including: ionic conductivity at room temperature Low ion mobility, low processability of low molecular weight polymers, insufficient thermal stability of polymers, harsh polymerization conditions, and the like. In addition, the solid polymer electrolyte has poor interfacial compatibility, and in practical application, small molecules such as solvents, plasticizers and the like are often required to be added, so that the electrolyte still has the possibility of being flammable.

Fluoropolymers generally have excellent heat resistance, chemical resistance, durability, weatherability, and the like, and are indispensable key materials in the fields of military, aerospace, medical, electrical and electronics, and the like. The control of polymer crystallinity, solubility and electrochemical performance can be realized by controlling the main chain and side chain structure of the fluorine polymer (patent No. CN 103456909). Recent research results show that the fluoropolymer electrolyte has the advantages of non-flammability, high ion migration number and the like, and can reduce the concentration polarization of the electrolyte and increase the specific energy and specific power of the battery in the charging and discharging processes of the battery. Therefore, the fluoropolymer electrolyte shows wide application prospects in the field of new energy (publication: ACS Appl. Energy Mater.2018,1, 2, 483-494; patent numbers: CN 105914397A). However, the fluoropolymers currently available for use in electrolytes are not only very few in type, but also have low molecular weight, and have problems such as leakage and difficulty in processing into films. In addition, in order to improve the electrochemical performance, it is generally necessary to add organic small molecules such as a solvent and a plasticizer to the fluorine electrolyte, which poses a danger of flammability to the battery.

The fluorine-containing olefin monomer is a common industrial raw material and is used for producing fluoropolymer materials such as chlorotrifluoroethylene-ethylene copolymer (Halar) (patent number: CN 109722175A), tetrafluoroethylene-ethylene copolymer (Tefzel) (patent number: CN 110204969A; CN 110066610A) and the like on a large scale. The product is an alternating copolymer formed by starting from a fluorine-containing olefin monomer which is cheap and easy to obtain and an alkenyl ether. The polymer has the advantages of non-flammability, high ion migration number, high ion conductivity, processability and the like, and can be used as a high-performance solid polymer electrolyte. The fluorine polymer electrolyte meets the requirements of high capacity and high safety of the battery, and is suitable for mass production. With the increasing global demand of batteries, the invention has important significance in the fields related to new energy resources, such as portable electronic devices, electric vehicles, unmanned aerial vehicles and the like.

Disclosure of Invention

The invention aims to provide a novel non-flammable polymer electrolyte with high ion migration number and a preparation method thereof, the polymer is non-flammable, and the polymer electrolyte has high metal ion migration number, excellent electrochemical stability and thermal stability and higher conductivity under room temperature and heating conditions.

The invention adopts a free radical polymerization method, takes fluorine-containing ethylene, vinyl ether and derivatives thereof as polymerization monomers, and realizes the alternating copolymerization of the monomers in the presence of a solvent by a heating or illumination mode, wherein the vinyl ether monomers can have oxygen-containing flexible groups, and the polymer electrolyte with incombustible property and high metal ion migration number is prepared after adding a certain proportion of metal salt, and has the following structure formula (I):

Formula (I)

Wherein R1 is a chlorine atom, a fluorine atom or a trifluoromethyl group; x is alkyl with 2-12 carbon atoms or polyethylene glycol with 1-12 repeating units; r2 is hydrogen atom, chlorine atom, iodine atom, methyl group, ethyl group, isopropyl group, isobutyl group, tert-butyldimethylsilyl group, tert-butyldiphenylsilyl group, trimethylsilyl group, triethylsilyl group, triisopropylsilyl group or 1, 3-dioxan-2-one.

The invention provides a preparation method of a non-flammable polymer electrolyte with high ion migration number, which comprises the following specific steps:

Step (1), alternating copolymerization of monomers;

The method A comprises the following steps: mixing a fluorine-containing ethylene monomer, a vinyl ether monomer, an initiator and a solvent by a heating method, and adding into a reaction bottle; calculated according to molar ratio, the monomer is initiator =1000 (1-100);

The method B comprises the following steps: mixing a fluorine-containing ethylene monomer, a vinyl ether monomer, a chain transfer agent, a photocatalyst and a solvent by a light irradiation method, and adding into a reaction bottle; according to the molar ratio, the monomer is chain transfer agent =1000 (1-100), and the photocatalyst used in the reaction process is 0.0001-10 mol% of the monomer; the reaction formula is as follows:

Formula (II)

Step (2), after the reaction is finished, removing the solvent to obtain poly (vinyl fluoride- Alternating -vinyl ether) copolymers;

And (3) adding the copolymer obtained in the step (2) into metal salt and an additive, and completely mixing to obtain the solid polymer electrolyte.

In the step (1), the reaction solvent is dimethyl carbonate, diethyl carbonate, dipropyl carbonate, anisole, N,N-dimethylformamide, N,N-dimethylacetamide, N-one or more of methyl pyrrolidone, 5-fluoropropane, 5-fluorobutane, acetonitrile, dimethyl sulfoxide, ethyl acetate, toluene, xylene, supercritical carbon dioxide.

In step (1) of the present invention, the initiator in method a is one or more of azo compounds and organic peroxides. The chain transfer agent in the method B is one or more of a thioreagent, an organic nitrogen oxide, alkyl halide or perfluoroalkyl halide; the photocatalyst is one or more of organic micromolecular compounds taking perylene, pyrene, porphyrin, thiophene, phenothiazine and phenoxazine as frameworks, or one or more of metal organic complexes taking copper, ruthenium and iridium as cores.

In step (3) of the present invention, the metal salt is one or more of bis (trifluoromethyl) sulfonyl imide metal salt, bis (trifluoromethyl) sulfonic acid metal salt, bis (difluoro) sulfonyl imide metal salt, bis (pentafluoroethyl) sulfonyl imide metal salt, tris (trifluoromethyl) sulfonyl methyl metal salt, trifluoro-methanesulfonic acid metal salt, difluoro-oxalic acid metal salt, bis-oxalic acid metal salt, perchloric acid metal salt, tetrafluoro-boric acid metal salt, hexafluoro-arsenic metal salt and hexafluoro-phosphoric acid metal salt, wherein the metal salt may be lithium, sodium or potassium.

In the step (3), the additive is one or more of dimethylformamide, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, methyl formate, methyl acetate, 1, 2-dimethoxyethane, polyethylene glycol and polypropylene glycol.

In the step (1), the heating temperature of the heating method is minus 20-200 ℃; the illumination wavelength of the illumination method is 200-850 nm.

The fluorine-containing copolymer of the present invention can be applied to a metal ion battery as a polymer electrolyte. The metal ion battery comprises a lithium ion battery, a sodium ion battery and a potassium ion battery.

Experimental results show that the polymer electrolyte is successfully obtained by the method, and the polymer electrolyte is high in ion transference number, good in electrochemical stability and non-flammable after being used for the electrolyte of the metal ion battery. The monomer raw materials of the method are low in price and easy to obtain, and the synthesis method is simple and easy for mass production.

Drawings

FIG. 1 is a schematic diagram of a polymer electrolyte.

FIG. 2 is a schematic diagram of an EIS impedance spectrum of a polymer electrolyte at 100 degrees Celsius.

FIG. 3 is a graph showing the results of electrochemical performance tests on the transference number of lithium ions in example 3.

Fig. 4 is a graph showing the results of the conductivity test performed in example 3 at room temperature to 100 degrees celsius.

Detailed Description

The present invention is described in detail below with reference to some specific embodiments, which are only used for illustrating the present invention and are not used for limiting the scope of the present invention, and the preparation schemes in the examples are only preferred schemes, but the present invention is not limited to the preferred preparation schemes. For the same reaction, the reaction time or the reaction device is adjusted to realize the synthesis of polymers with different scales without changing the parameters of reaction conditions.

A first part: a poly (vinyl fluoride-vinyl ether) copolymer was synthesized.