CN109053976B

CN109053976B - Multifunctional polymer, preparation method and application thereof

Info

Publication number: CN109053976B
Application number: CN201810648703.3A
Authority: CN
Inventors: 薛志刚; 肖逐流; 周炳华; 左偲; 周兴平; 解孝林
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2018-06-22
Filing date: 2018-06-22
Publication date: 2020-05-19
Anticipated expiration: 2038-06-22
Also published as: CN109053976A

Abstract

The invention belongs to the field of polymer electrolyte materials, and particularly relates to a multifunctional polymer, a preparation method thereof and application thereof in preparing electrolyte. The polymer comprises a crosslinked polymer core containing a ring-shaped polyethylene oxide and chain arms containing a linear polyethylene oxide, the chain arms are connected to the crosslinked polymer core through covalent bonds, and the chain arms are radially arranged in a star shape. The multifunctional polymer is applied to preparing electrolyte, and because the annular structure in the polymer can contain more lithium ions, sodium ions or potassium ions, and the interlaced chain arms of the star polymer enable the conduction of ions to be more efficient, the electrolyte material with multi-path ion transmission channels is obtained. The annular PEO structure, the cross-linked structure and the star-shaped structure in the electrolyte material can reduce the crystallinity of PEO, so that the problems of difficult lithium ion migration and low ionic conductivity at room temperature are expected to be solved.

Description

Multifunctional polymer, preparation method and application thereof

Technical Field

The invention belongs to the field of polymer electrolyte materials, and particularly relates to a multifunctional polymer capable of promoting lithium, sodium and potassium ion conduction, a preparation method thereof and application thereof in an electrolyte.

Background

Energy has been an indispensable part in human social production and life. The limited earth resource forces people to continuously find various methods to improve the utilization rate of energy, and the adoption of an economical and practical rechargeable battery with thousands of times to tens of thousands of times of charging and discharging is one of effective ways. Compared with the traditional lead-acid battery and nickel-cadmium battery, the lithium ion battery is more and more widely applied to the life of people due to the advantages of high energy density, low self-discharge rate, no memory effect and the like. Electrolytes are key materials in lithium ion batteries. At present, liquid electrolyte is generally adopted in large-scale commercialized lithium batteries, and further application of the electrolyte is restricted by safety problems of easy leakage, easy combustion, easy explosion and the like. The solid polymer electrolyte has the advantages of good safety performance, high energy density, wide working temperature range, long cycle life and the like, and has very important application prospect.

The polyoxyethylene-based solid polymer electrolyte is the earliest and most studied polymer electrolyte material, but the problems of difficult lithium ion migration, low ionic conductivity and the like at room temperature caused by high crystallinity of the polyoxyethylene-based solid polymer electrolyte need to be solved. In previous researches, physical methods such as blending and adding nanoparticles and chemical methods such as synthesizing block polymers and cross-linked polymers are available for reducing the crystallinity of PEO, but the method has an unsatisfactory effect on solving the problems of difficult lithium ion migration, low ionic conductivity and the like caused by high crystallinity of the polyethylene oxide-based polymer.

Disclosure of Invention

In view of the above drawbacks or needs for improvement of the prior art, the present invention provides a multifunctional polymer, a method for preparing the same, and an application thereof in an electrolyte, which aim to solve the technical problems of difficulty in lithium ion migration, low ionic conductivity, and the like caused by high crystallinity of a polyoxyethylene-based polymer of the prior art by designing a star polymer composed of a crosslinked polymer core containing a ring-shaped polyethylene oxide (PEO) structure and a chain arm containing a linear polyethylene oxide, to be used for preparing an electrolyte.

To achieve the above object, according to one aspect of the present invention, there is provided a multi-functionalized polymer comprising a crosslinked polymer core containing a ring-shaped polyethylene oxide and chain arms containing a linear polyethylene oxide, the chain arms being linked to the crosslinked polymer core by covalent bonds, the crosslinked polymer core containing a ring-shaped polyethylene oxide constituting a star polymer with the peripherally linked chain arms.

Preferably, the molecular structural general formula of the polymer is shown as the formula (I):

wherein x, y is 1: 4-1: 5, z is an integer of 1-11, R₁、R₂……R_mM is an integer not less than 30, and the structural general formula of the chain arm is shown as a formula (II):

wherein n is an integer of 22 to 113.

Preferably, the crosslinked polymer core containing the ring-shaped polyethylene oxide is obtained by crosslinking an acrylate monomer with double bonds at two ends and a crosslinking agent, wherein the acrylate monomer with double bonds at two ends is polyethylene glycol dimethacrylate, and the molecular structure is shown as the formula (III):

wherein z is an integer of 1-11, and the molecular weight of the polyethylene glycol dimethacrylate is 330-750;

preferably, the crosslinking agent is ethylene glycol dimethacrylate, and the molecular structure is shown as the formula (IV):

according to another aspect of the present invention, there is provided a method for preparing a multifunctional polymer, comprising the steps of:

(1) dispersing polyethylene glycol monoether and an acid-binding agent in an organic solvent to obtain a polyethylene glycol monoether solution; under the ice bath condition, dropwise adding a bromization reagent into the obtained polyethylene glycol monoether solution, stirring and dispersing, removing the ice bath, reacting at room temperature for 12-24 hours, carrying out solid-liquid separation to obtain a precipitate, and washing and drying the precipitate to obtain a macroinitiator;

(2) dissolving polyethylene glycol dimethacrylate and alkali metal salt in an organic solvent to obtain polyethylene glycol dimethacrylate organic solution;

(3) dispersing the macroinitiator obtained in the step (1), a low-valence metal catalyst and a ligand in an organic solvent under the anhydrous and oxygen-free conditions, then adding ethylene glycol dimethacrylate and the polyethylene glycol dimethacrylate organic solution obtained in the step (2), and carrying out atom transfer radical polymerization reaction at the temperature of 60-80 ℃ for 12-24 hours to obtain the multifunctional polymer.

Preferably, the polyethylene glycol monoether is one or more of polyethylene glycol monomethyl ether, polyethylene glycol monobutyl ether and polyethylene glycol monooctyl ether; the relative molecular mass of the polyethylene glycol monoether is 1000-5000; the acid-binding agent is one or more of triethylamine, pyridine and dimethylformamide; the dosage of the acid-binding agent is 200-300 mol% of the polyethylene glycol monoether; the organic solvent is tetrahydrofuran and/or dichloromethane; the bromization reagent is 2-bromine isobutyryl bromide and/or 2-bromine propionyl bromide, and the dosage of the bromization reagent is 200-300 mol% of the polyethylene glycol monoether.

Preferably, in the step (2), the alkali metal salt is one or more of lithium iodide, sodium iodide and potassium iodide; the dosage of the alkali metal salt is 100-200 mol% of the polyethylene glycol dimethacrylate; the molecular weight of the polyethylene glycol dimethacrylate is 330-750; the organic solvent is toluene and/or acetonitrile.

Preferably, in the step (3), the amount of the macroinitiator is 25-45 mol% of the polyethylene glycol dimethacrylate; the low-valence metal catalyst is one or more of cuprous chloride, ferrous chloride, cuprous bromide and ferrous bromide, and the amount of the low-valence metal catalyst is 5-20 mol% of the polyethylene glycol dimethacrylate; the ligand is pentamethyldiethylenetriamine and/or 2, 2-bipyridyl, and the dosage of the ligand is 10-40 mol% of the polyethylene glycol dimethacrylate; the using amount of the ethylene glycol dimethacrylate is 400-500 mol% of the polyethylene glycol dimethacrylate; the organic solvent is toluene and/or acetonitrile.

According to another aspect of the invention, there is provided a use of the multifunctional polymer for the preparation of an electrolyte.

Preferably, the application of the multifunctional polymer to the preparation of an electrolyte comprises the following steps:

(1) mixing the multifunctional polymer with a polyethylene oxide-containing polymer in a ratio of 1: 1 to 1: 3 is dissolved in an organic solvent to prepare a solution with the concentration of 5 to 15 weight percent;

(2) adding alkali metal salt into the solution obtained in the step (1), and mixing to obtain a mixed system, wherein the molar ratio of ethoxy groups to cations of the alkali metal salt in the mixed system is 8: 1-20: 1, uniformly stirring, casting to form a film, and drying to obtain the polymer electrolyte film with the thickness of 100-300 microns.

Preferably, the polyoxyethylene-containing polymer is polyoxyethylene, and the relative molecular mass of the polyoxyethylene-containing polymer is 300000-7000000; the organic solvent is acetonitrile or/and tetrahydrofuran; the alkali metal salt is lithium salt, sodium salt or potassium salt, the lithium salt is one or more of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate and bis-trifluoromethyl imine sulfonyl lithium, the sodium salt is one or more of sodium perchlorate, sodium hexafluorophosphate and bis-trifluoromethyl imine sulfonyl sodium, and the potassium salt is one or more of potassium perchlorate, potassium hexafluorophosphate and bis-trifluoromethyl imine sulfonyl potassium. .

In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:

(1) the multifunctional polymer provided by the invention is a star-shaped polymer consisting of a cross-linked polymer core containing a ring-shaped polyethylene oxide (PEO) structure and chain arms containing linear polyethylene oxide, wherein the ring-shaped cross-linked molecular core obtained by changing the PEO linear structure can reduce the crystallinity of PEO, and can accommodate more lithium ions, sodium ions or potassium ions, thereby providing more ion transmission channels and ion transmission paths; in addition, the star polymer has the advantages of difficult crystallization and fast molecular chain movement, and the conduction of lithium ions, sodium ions or potassium ions is more efficient through the mutually staggered chain arm structures in the star polymer;

(2) when the method is applied to electrolytes containing cations of different alkali metal salts, for lithium ions, sodium ions and potassium ions with different ionic radii, the size of a PEO ring in a crosslinked polymer core can be regulated and controlled by regulating and controlling the molecular weight of a monomer and the addition amounts of the monomer and a crosslinking agent, so that the method can adapt to the complexation and dissociation of alkali metal cations with different ionic radii;

(3) the multifunctional polymer provided by the invention is applied to the preparation of electrolyte, the star polymer containing the annular cross-linked molecular core is blended with the flexible polyoxyethylene polymer, the star polymer has certain mechanical property strength, the polyoxyethylene polymer provides more polyoxyethylene chain segments, and the solid polymer electrolyte with high ionic conductivity and good mechanical property is comprehensively obtained;

(4) the preparation method of the polymer electrolyte has the advantages of mild reaction conditions, simple and convenient operation method and high conversion rate, and the structure of the polymer can be regulated and controlled by selecting PEGDMA with different molecular weights, so that the conductivity and the mechanical property of the polymer can be controlled.

Drawings

FIG. 1 is a nuclear magnetic resonance spectrum of a multifunctional star polymer prepared in example 1 of the present invention using potassium ions as a template, with the abscissa representing chemical shift;

FIG. 2 is a UV spectrum of a multifunctional star polymer prepared in example 2 of the present invention using lithium ions as a template, with the abscissa being the wavelength (nm);

FIG. 3 is DSC data of a multifunctional star polymer prepared using sodium ions as a template in example 5 of the present invention as a multifunctional polymer electrolyte membrane, with the abscissa being temperature (. degree. C.);

fig. 4 is a graph showing the change of conductivity with temperature of the polymer electrolyte prepared in example 6 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

The invention provides a multifunctional polymer, which comprises a crosslinked polymer core containing annular polyethylene oxide and chain arms containing linear polyethylene oxide, wherein the chain arms are connected to the crosslinked polymer core through covalent bonds, the chain arms are arranged on the periphery of the crosslinked polymer core in a radial mode (the radial mode is not limited to the diameter direction in a strict sense), and the chain arms arranged on the periphery in the radial mode form a star-shaped polymer. The molecular structural general formula of the polymer is preferably shown as the formula (I):

the crosslinked polymer core in the star polymer comprises an annular PEO structure, wherein x: y is 1: 4-1: 5, the ratio can be regulated by controlling the ratio of a monomer to a crosslinking agent, the control of the ratio of x to y is very critical for maintaining the PEO ring structure in the crosslinked polymer core, and if the ratio of the x to y is not properly controlled, the PEO ring in the core can collapse; z is an integer of 1-11, and the value of z determines the size of a PEO ring in a core, further determines whether an alkali metal cation is easy to complex and dissociate, and finally determines the conductivity of an electrolyte prepared by the star polymer; r₁、R₂……R_mThe monomer and the macroinitiator are chain arms containing linear polyoxyethylene, m is an integer not less than 30, the numerical value of m is determined by reaction time and the using amount of the macroinitiator, and can be obtained by GPC molecular weight test specifically, and the conversion rate of the monomer and the macroinitiator after the reaction is finished can be obtained according to the content percentage of parts with different molecular weights in the GPC test, so that the percentage of the core and the arms in the star polymer is determined; calculating to obtain the number m of chain arms of the star polymer through the number average molecular weight and absolute weight average molecular weight values; the chain arm has a preferable structural general formula as shown in the formula (A)Two) and then carrying out the following steps of,

wherein n is an integer of 22-113, and the size of the annular crosslinked polymer core is not greatly different from the length of the chain arm, so that z, n and the size of the ring of the crosslinked polymer core need to be controlled within a certain range to ensure the maintenance of the star structure and further ensure higher conductivity.

Preferably, the crosslinked polymer core can be obtained by crosslinking an acrylate monomer with double bonds at two ends and a crosslinking agent, wherein the acrylate monomer with double bonds at two ends is polyethylene glycol dimethacrylate, and the molecular structure is shown as the formula (III):

preferably, the molecular weight of the polyethylene glycol dimethacrylate is 330 to 750, wherein z is the same as z in the formula (I), and is an integer of 1 to 11. This molecular weight range, in which the PEO rings are moderately sized and the ring structures are stable, also actually determines the size of the PEO rings within the crosslinked polymer core. The cross-linking agent is preferably ethylene glycol dimethacrylate, and the molecular structure is shown as the formula (IV):

in the design of the star polymer, the crosslinked polymer core is obtained by polymerizing the monomer and the crosslinking agent, and as a preferable scheme, the monomer and the crosslinking agent are specially designed to comprise the same structural unit ethylene glycol dimethacrylate, so that the compatibility of the monomer and the crosslinking agent and the stability of the crosslinked polymer are more favorable.

The invention provides a preparation method of the multifunctional polymer, which comprises the following steps:

(1) uniformly dispersing polyethylene glycol monoether and an acid-binding agent in an organic solvent to obtain a polyethylene glycol monoether solution; under the ice bath condition, adding a bromization reagent dropwise into the obtained polyethylene glycol monoether solution, stirring and dispersing, removing the ice bath, reacting at room temperature for 12-24 hours, carrying out solid-liquid separation to obtain a precipitate, and washing and drying the precipitate to obtain a macroinitiator, namely the linear chain polyoxyethylene-containing chain arm. The polyethylene glycol monoether is one or more of polyethylene glycol monomethyl ether, polyethylene glycol monobutyl ether and polyethylene glycol monooctyl ether, preferably polyethylene glycol monomethyl ether, and the relative molecular mass of the polyethylene glycol monoether is 1000-5000; the acid-binding agent is one or more of triethylamine, pyridine and dimethylformamide, preferably triethylamine, and the dosage of the acid-binding agent is 200-300 mol% of the polyethylene glycol monoether; the organic solvent is tetrahydrofuran and/or dichloromethane, preferably tetrahydrofuran; the bromination reagent is 2-bromine isobutyryl bromide and/or 2-bromine propionyl bromide, preferably 2-bromine isobutyryl bromide, and the dosage of the bromination reagent is 200-300 mol% of the polyethylene glycol monoether.

(2) Dissolving polyethylene glycol dimethacrylate and alkali metal salt in an organic solvent to obtain polyethylene glycol dimethacrylate organic solution; thus obtaining the structure of the crosslinked polymer core containing the PEO small ring structure. The alkali metal salt is one or more of lithium iodide, sodium iodide and potassium iodide; the dosage of the alkali metal salt is 100-200 mol% of the polyethylene glycol dimethacrylate; the molecular weight of the polyethylene glycol dimethacrylate is 330-750; the organic solvent is toluene and/or acetonitrile.

(3) And (2) uniformly dispersing the macroinitiator obtained in the step (1), a low-valence metal catalyst and a ligand in an organic solvent under the anhydrous and oxygen-free conditions, then adding the polyethylene glycol dimethacrylate organic solution and ethylene glycol dimethacrylate obtained in the step (2), carrying out atom transfer radical polymerization reaction at the temperature of 60-80 ℃, wherein the reaction time is 12-24 hours, and reacting to ensure that the chain arm and the cross-linked polymer are connected by a covalent bond so as to obtain the multifunctional polymer. The using amount of the macromolecular initiator is 25-45 mol% of the polyethylene glycol dimethacrylate; the low-valence metal catalyst is one or more of cuprous chloride, ferrous chloride, cuprous bromide and ferrous bromide, and the amount of the low-valence metal catalyst is 5-20 mol% of the polyethylene glycol dimethacrylate; the ligand is pentamethyldiethylenetriamine and/or 2, 2-bipyridyl, and the dosage of the ligand is 10-40 mol% of the polyethylene glycol dimethacrylate; the using amount of the ethylene glycol dimethacrylate is 400-500 mol% of the polyethylene glycol dimethacrylate; the organic solvent is toluene and/or acetonitrile.

The multifunctional polymer can be applied to the preparation of electrolyte. The multifunctional polymer is applied to the preparation of electrolyte, and comprises the following steps:

(1) mixing the multifunctional polymer with a polyethylene oxide-containing polymer in a ratio of 1: 1 to 1: 3 is dissolved in an organic solvent to prepare a solution with the concentration of 5 to 15 weight percent; the polyethylene oxide-containing polymer is preferably polyethylene oxide, and the relative molecular mass of the polyethylene oxide-containing polymer is 300000-7000000; the organic solvent is acetonitrile or/and tetrahydrofuran.

(2) Adding electrolyte lithium salt, electrolyte sodium salt or electrolyte potassium salt into the solution obtained in the step (1), and mixing to obtain a mixed system, wherein the molar ratio of ethoxy to Li, Na or K in the mixed system is 8: 1-20: 1, uniformly stirring, casting to form a film, and drying to obtain the polymer electrolyte film with the thickness of 100-300 microns. The lithium salt is one or more of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate and bis-trifluoromethyl imine sulfonyl lithium, the sodium salt is one or more of sodium perchlorate, sodium hexafluorophosphate and bis-trifluoromethyl imine sulfonyl sodium, and the potassium salt is one or more of potassium perchlorate, potassium hexafluorophosphate and bis-trifluoromethyl imine sulfonyl potassium.

The multifunctional polymer provided by the invention is applied to preparing electrolyte, and because the annular structure in the polymer can contain more lithium ions, sodium ions or potassium ions, and the interlaced chain arms of the star polymer enable the ion conduction to be more efficient, the electrolyte material with multi-path ion transmission channels is obtained. The cross-linked structure and the star-shaped structure in the electrolyte material can reduce the crystallinity of PEO, so that the problems of difficult lithium ion migration and low ionic conductivity at room temperature can be hopefully solved. The multifunctional electrolyte has high room-temperature ionic conductivity and can maintain considerable conductivity under low-temperature conditions.

The following are examples:

the multifunctional polymer prepared in the examples 1 to 4 has the structure shown as the formula (I):

example 1

A multifunctional polymer is composed of a crosslinked polymer core containing a ring-shaped structure molecule and polyethylene oxide-containing chain arms which are connected to the crosslinked polymer core through covalent bonds, wherein the chain arms are radially arranged in a star shape, and the structure is shown in the figure, wherein x, y, z, 11, and n, 113.

The preparation method of the multifunctional polymer provided by the invention comprises the following steps:

(1) 25 g of polyethylene glycol monooctyl ether with the molecular weight of 5000 is dissolved in 45 ml of tetrahydrofuran, and 0.92 g of dimethylformamide is added into the tetrahydrofuran and stirred to obtain polyethylene glycol monooctyl ether solution.

(2) Under the ice bath condition, 1.6mL of 2-bromine isobutyryl bromide is dropwise added into the polyethylene glycol mono-octyl ether solution obtained in the step (1), the stirring is continuously carried out until the dropwise addition is finished, after the reaction is carried out for 12 hours at room temperature, the reaction product is filtered, the filtrate is dropwise added into excessive ethyl glacial ether, and the macromolecular initiator is prepared after precipitation separation, washing and drying.

(3) Weighing 14g of macroinitiator obtained in the step (2) and 40mg of cuprous chloride in a glove box, putting 0.16mL of pentamethyldiethylenetriamine ligand into a reaction bottle, dissolving in acetonitrile obtained by distillation in advance under anhydrous and oxygen-free conditions, adding 6g of polyethylene glycol dimethacrylate monomer (Mn & gt 750) dissolved with 1.99g of potassium iodide, adding 6.4g of ethylene glycol dimethacrylate cross-linking agent, freezing, vacuumizing, filling argon, carrying out atom transfer radical polymerization at 80 ℃, reacting for 24 hours, and separating and drying the reaction product to obtain the multifunctional polymer.

FIG. 1 is a nuclear magnetic resonance spectrum of a star polymer prepared in this example using potassium ions as a template (the polymer in FIG. 1 is the star polymer prepared in this example), with the abscissa representing the chemical shift; as can be seen from FIG. 1, when potassium iodide was added to the polymer, a new small peak appeared in the chemical shift interval of 3.5 to 4, which corresponds to the ethoxy segment in the polymer, due to the coordination between potassium iodide and the ring structure in the polymer, confirming that the ring structure is indeed present in the star polymer with rings.

Example 2

A multifunctional polymer is composed of a crosslinked polymer core containing a ring-structured molecule and polyethylene oxide-containing chain arms which are connected to the crosslinked polymer core through covalent bonds, wherein the chain arms are radially arranged in a star shape, the structure is shown in the figure, wherein x, y, z, n, 45 and m are more than 30.

(1) 20 g of polyethylene glycol monomethyl ether with molecular weight of 2000 are dissolved in 45 ml of tetrahydrofuran, and 2.02 g of triethylamine is added into the solution and stirred to obtain polyethylene glycol monomethyl ether solution.

(2) Under the ice bath condition, 2.56mL of 2-bromine isobutyryl bromide is dropwise added into the polyethylene glycol monomethyl ether solution obtained in the step (1), the stirring is continuously carried out until the dropwise addition is finished, after the reaction is carried out for 18 hours at room temperature, the reaction product is filtered, the filtrate is dropwise added into excessive ethyl glacial ether, and the macromolecular initiator is prepared after precipitation separation, washing and drying.

(3) Weighing 4g of macroinitiator obtained in the step (2) and 114mg of cuprous bromide in a glove box, putting 0.32mL of pentamethyldiethylenetriamine ligand in a reaction bottle, dissolving the pentamethyldiethylenetriamine ligand in acetonitrile obtained by distillation in advance under anhydrous and oxygen-free conditions, adding 4.4g of polyethylene glycol dimethacrylate monomer (Mn 550) dissolved with 1.07g of lithium iodide, adding 7.2g of ethylene glycol dimethacrylate cross-linking agent, freezing, vacuumizing, filling argon, carrying out atom transfer radical polymerization reaction at 70 ℃, reacting for 24 hours, and separating and drying a reaction product to obtain the multifunctional polymer.

FIG. 2 is a UV spectrum of a (multi-functionalized polymer) star polymer prepared in this example using lithium ions as a template, with the abscissa being the wavelength (nm); it can be seen that the ultraviolet absorption peak is weak only in the presence of lithium iodide and almost no in the presence of the polymer only, and is strong when lithium iodide and the polymer are present at the same time, and it can be confirmed that the ring structure coordinates with lithium cation and thus the absorption peak is enhanced.

Example 3

A multifunctional polymer is composed of a crosslinked polymer core containing a ring-structured molecule and polyethylene oxide-containing chain arms which are connected to the crosslinked polymer core through covalent bonds, wherein the chain arms are radially arranged in a star shape, the structure is shown in the figure, wherein x, y, z, n, 45 and m is more than 30.

(1) 20 g of polyethylene glycol monobutyl ether with molecular weight of 2000 is dissolved in 45 ml of dichloromethane, 2.37 g of pyridine is added into the dichloromethane and stirred, and polyethylene glycol monobutyl ether solution is obtained.

(2) Under the ice bath condition, 3.15mL of 2-bromopropionyl bromide is dropwise added into the polyethylene glycol monobutyl ether solution obtained in the step (1), the stirring is continuously carried out until the dropwise addition is finished, after the reaction is carried out for 24 hours at room temperature, reaction products are filtered, filtrate is dropwise added into excessive ethyl glacial ether, precipitation separation is carried out, and the macromolecule initiator is prepared after washing and drying.

(3) Weighing 8g of macroinitiator obtained in the step (2), 345mg of ferrous bromide and 250mg of 2, 2-bipyridine ligand in a reaction bottle in a glove box, dissolving the macroinitiator, the ferrous bromide and the 2, 2-bipyridine ligand in an organic solvent toluene which is distilled under reduced pressure in advance under anhydrous and oxygen-free conditions, then adding 2.64g of polyethylene glycol dimethacrylate monomer (Mn 330) dissolved with 2.4g of sodium iodide, adding 8g of ethylene glycol dimethacrylate cross-linking agent, freezing, vacuumizing, filling argon, carrying out atom transfer radical polymerization reaction at 60 ℃, wherein the reaction time is 18 hours, and separating and drying the reaction product to obtain the multifunctional polymer.

Example 4

A multifunctional polymer is composed of a crosslinked polymer core containing a ring-structured molecule and polyethylene oxide-containing chain arms which are connected to the crosslinked polymer core through covalent bonds, wherein the chain arms are radially arranged in a star shape, the structure is shown in the figure, wherein x, y, z, n, 22 and m are more than 30.

(1) 10 g of polyethylene glycol monomethyl ether with molecular weight of 1000 is dissolved in 45 ml of tetrahydrofuran, and 2.02 g of triethylamine is added into the solution and stirred to obtain polyethylene glycol monomethyl ether solution.

(3) Weighing 0.2g of macroinitiator obtained in the step (2) and 20.3mg of ferrous chloride in a glove box, putting 32 mu L of pentamethyldiethylenetriamine ligand in a reaction bottle, dissolving in acetonitrile obtained by pre-distillation under anhydrous and oxygen-free conditions, then adding 0.44g of polyethylene glycol dimethacrylate monomer (Mn is 550) dissolved with 0.107g of lithium iodide, adding 0.72g of ethylene glycol dimethacrylate cross-linking agent, freezing, vacuumizing, filling argon, carrying out atom transfer radical polymerization reaction at 70 ℃, wherein the reaction time is 24 hours, and separating and drying the reaction product to obtain the multifunctional polymer.

Example 5

The multifunctional polymer can be applied to the preparation of electrolyte. The preparation method comprises the following steps:

the multifunctional polymer prepared in example 3 and 600000 molecular weight polyethylene oxide were mixed in a mass ratio of 1: 1 is dissolved in organic solvent tetrahydrofuran to prepare 10 weight percent solution, sodium perchlorate is added according to the mole ratio of ethoxy to Na in the polymer of 16:1, the solution is evenly stirred and then cast into a film, and the film is fully dried to obtain the polymer electrolyte film with the thickness of 180 micrometers.

FIG. 3 is a DSC chart of the multi-functionalized polymer electrolyte membrane and the pure polyethylene oxide electrolyte membrane prepared in this example, and it can be seen that the glass transition temperature of the multi-functionalized polymer electrolyte membrane is-45 ℃ and the glass transition temperature of the pure polyethylene oxide electrolyte membrane is-33 ℃, and the decrease of the glass transition temperature of the multi-functionalized polymer electrolyte membrane compared to the pure polyethylene oxide electrolyte membrane and the disappearance of the melting peak in the multi-functionalized polymer electrolyte membrane indicate that the preparation of the multi-functionalized polymer electrolyte membrane can decrease the crystallinity and promote the ion migration.

Example 6

the multifunctional polymer prepared in example 2 and 600000 molecular weight polyethylene oxide were mixed in a mass ratio of 1: 1 is dissolved in organic solvent acetonitrile to prepare a 10 wt% solution, lithium perchlorate is added according to the mole ratio of ethoxy/Li in the polymer of 16:1, the solution is evenly stirred and then cast into a film, and the film is fully dried to obtain the polymer electrolyte film with the thickness of 150 microns.

Other steps are the same, the star polymer with rings is prepared without adding metal salt in the polymerization process of the polymer, and the ring-containing crosslinked polymer is obtained by replacing the macroinitiator with a common initiator such as ethyl 2-bromoisobutyrate. The curve of the change of the conductivity of the prepared electrolyte along with the temperature is shown in figure 4, and it can be seen that the conductivity of the star polymer with rings of the invention is higher than that of the star polymer without rings and the cross-linked polymer with rings, which indicates that the star structure and the ring structure in the design structure of the patent are really beneficial to the lithium ion conduction, so that the conductivity is improved to a certain extent.

Example 7

the multifunctional polymer prepared in example 1 and 7000000 molecular weight polyethylene oxide are mixed according to the mass ratio of 1: 3 dissolving in organic solvent acetonitrile to prepare a 10 wt% solution, adding potassium bistrifluoromethanesulfonylimide according to the mole ratio of ethoxy to K in the polymer of 12:1, uniformly stirring, casting to form a film, and fully drying to obtain the polymer electrolyte film with the thickness of 220 microns.

Example 8

the multifunctional polymer prepared in example 4 and 300000 molecular weight polyethylene oxide were mixed in a mass ratio of 1: 1 is dissolved in organic solvent tetrahydrofuran to prepare 10 weight percent solution, lithium tetrafluoroborate is added according to the mole ratio of ethoxy/Li in the polymer of 20:1, the mixture is evenly stirred and cast into a film, and the polymer electrolyte film with the thickness of 200 microns is obtained after full drying.

The polymer electrolyte membranes prepared by the examples have improved mechanical properties and room temperature conductivity compared to the electrolyte membranes prepared from pure polyethylene oxide.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. The preparation method of the multifunctional star-shaped polymer is characterized by comprising the following steps:

(1) dispersing polyethylene glycol monoether and an acid-binding agent in an organic solvent to obtain a polyethylene glycol monoether solution; under the ice bath condition, dropwise adding a bromization reagent into the obtained polyethylene glycol monoether solution, stirring and dispersing, removing the ice bath, reacting at room temperature for 12-24 hours, carrying out solid-liquid separation to obtain a precipitate, and washing and drying the precipitate to obtain a macroinitiator; the polyethylene glycol monoether is one or more of polyethylene glycol monomethyl ether, polyethylene glycol monobutyl ether and polyethylene glycol monooctyl ether; the structural general formula of the macroinitiator is shown as the formula (II):

wherein n is an integer of 22-113;

(2) dissolving polyethylene glycol dimethacrylate and alkali metal salt in an organic solvent to obtain polyethylene glycol dimethacrylate organic solution; the molecular weight of the polyethylene glycol dimethacrylate is 330-750; the alkali metal salt is one or more of lithium iodide, sodium iodide and potassium iodide; the dosage of the alkali metal salt is 100-200 mol% of the polyethylene glycol dimethacrylate;

(3) dispersing the macroinitiator obtained in the step (1), a low-valence metal catalyst and a ligand in an organic solvent under the anhydrous and oxygen-free conditions, then adding ethylene glycol dimethacrylate and the polyethylene glycol dimethacrylate organic solution obtained in the step (2), and carrying out atom transfer radical polymerization reaction at the temperature of 60-80 ℃ for 12-24 hours to obtain a multifunctional star polymer; the using amount of the macromolecular initiator is 25-45 mol% of the polyethylene glycol dimethacrylate; the dosage of the ethylene glycol dimethacrylate is 400-500 mol% of the polyethylene glycol dimethacrylate.

2. The preparation method according to claim 1, wherein in the step (1), the acid-binding agent is one or more of triethylamine, pyridine and dimethylformamide; the dosage of the acid-binding agent is 200-300 mol% of the polyethylene glycol monoether; the bromination reagent is 2-bromine isobutyryl bromide, and the dosage of the bromination reagent is 200-300 mol% of the polyethylene glycol monoether.

3. The method according to claim 1, wherein in the step (2), the organic solvent is toluene and/or acetonitrile.

4. The preparation method according to claim 1, wherein in the step (3), the low-valence metal catalyst is one or more of cuprous chloride, ferrous chloride, cuprous bromide and ferrous bromide, and the amount of the low-valence metal catalyst is 5-20 mol% of the polyethylene glycol dimethacrylate; the ligand is pentamethyldiethylenetriamine and/or 2, 2-bipyridyl, and the dosage of the ligand is 10-40 mol% of the polyethylene glycol dimethacrylate; the organic solvent is toluene and/or acetonitrile.

5. The multi-functionalized star-shaped polymer prepared by the preparation method according to any one of claims 1 to 4.

6. The polymer of claim 5, wherein the molecular structure of the polyethylene glycol dimethacrylate is according to formula (III):

wherein z is an integer of 1-11; the molecular structure of the ethylene glycol dimethacrylate is shown as a formula (IV):

7. the use of the multi-functionalized star polymer of claim 5 or 6, wherein the multi-functionalized star polymer is used to prepare an electrolyte.

8. The use of claim 7, wherein the application of the multi-functionalized star polymer to the preparation of an electrolyte comprises the steps of:

(1) reacting the multi-functionalized star polymer of claim 5 or 6 with polyethylene oxide in a ratio of 1: 1 to 1: 3 is dissolved in an organic solvent to prepare a solution with the concentration of 5 to 15 weight percent;

(2) adding alkali metal salt into the solution obtained in the step (1), mixing to obtain a mixed system, wherein the molar ratio of the ethylene oxide structural unit to the cation of the alkali metal salt in the mixed system is 8: 1-20: 1, uniformly stirring, casting to form a film, and drying to obtain the polymer electrolyte film with the thickness of 100-300 microns.

9. The use according to claim 8, wherein the polyethylene oxide has a relative molecular mass of 300000 to 7000000; the organic solvent is acetonitrile or/and tetrahydrofuran; the alkali metal salt is lithium salt, sodium salt or potassium salt, the lithium salt is one or more of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate and bis-trifluoromethyl imine sulfonyl lithium, the sodium salt is one or more of sodium perchlorate, sodium hexafluorophosphate and bis-trifluoromethyl imine sulfonyl sodium, and the potassium salt is one or more of potassium perchlorate, potassium hexafluorophosphate and bis-trifluoromethyl imine sulfonyl potassium.