CN112500519B - Terpolymer based on polyvinylidene fluoride and preparation method thereof - Google Patents
Terpolymer based on polyvinylidene fluoride and preparation method thereof Download PDFInfo
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Abstract
The terpolymer based on the polyvinylidene fluoride comprises a polyvinylidene fluoride structural unit, a acrylamide structural unit and a perfluoro vinyl ether sulfonic acid lithium structural unit; the preparation method comprises the following steps: in a reaction device, a vinylidene fluoride monomer, an acrylamide monomer, a perfluoro vinyl ether lithium sulfonate monomer and an initiator are respectively added, and the polymerization is carried out by one-step copolymerization through a polymerization reaction method. The invention reserves the advantageous structure of polyvinylidene fluoride, ensures that the copolymer has enough mechanical strength and thermal stability, overcomes the defects of the existing PVDF as the polymer lithium ion battery material by introducing a lithium ion high-efficiency transmission structural unit, a polar group and a large number of ultrastable structural units, optimizes the transmission efficiency of lithium ions, improves the ionic conductivity of the lithium battery, reduces the polarization of the battery in the charging process, improves the charge and discharge performance of the battery, and provides a new material and a new method for further development and application of the lithium battery.
Description
Technical Field
The invention relates to a lithium ion polymer and a preparation method thereof, in particular to a polyvinylidene fluoride-based terpolymer and a preparation method thereof, belonging to the technical field of production and manufacturing of lithium ion polymer batteries.
Background
The polymer lithium ion battery has the characteristics of small volume, light weight, high energy density, small self-discharge, no memory effect, good safety performance, capability of being made into any shape and the like, becomes the most advanced rechargeable battery at present, and is researched and developed vigorously by major scientific and technological strong countries in the world at present.
Lithium polymer batteries are mainly composed of a positive electrode, a negative electrode, separator paper, and the like, and in lithium polymer batteries developed at present, polymer materials are mainly applied to the positive electrode and an electrolyte.
Polyvinylidene fluoride (English) as polymer materialFor short: PVDF) is vinylidene fluoride (english abbreviation: VDF) is a thermoplastic fluoropolymer having repeating units of the molecular chain of-CH2-CF2The PVDF fluororesin has the characteristics of both fluorine-containing resin and general resin due to the special molecular structure, has good chemical stability and thermal stability, and has excellent electrochemical performance which is widely applied to lithium batteries as a positive electrode material, a binder, a negative electrode material, a battery diaphragm and the like.
Since the operation process of the lithium battery can be regarded as the "reciprocating motion" of lithium ions between two electrodes, along with the cyclic intercalation and deintercalation of the lithium ions, the polymer used in the lithium battery has higher requirements on the conductivity, lithium ion mobility and electrochemical stability of the material.
However, because polyvinylidene fluoride is a crystalline polymer, the crystallinity is between 60% and 80%, the dielectric constant and the ohmic resistance are high, and the crystal melting temperature is about 140 ℃, under the normal use temperature of the battery, the PVDF polymer is purely used as a battery material, and the crystalline unit of the PVDF polymer can obstruct the transmission of ions in the electrolytic liquid, thereby greatly reducing the transmission efficiency of the ions and seriously influencing the charge and discharge performance of the lithium battery.
In addition, the stronger acting force among the PVDF molecules enables the internal free volume of the polymer to be smaller, so that the number of internal ion transfer channels is reduced;
more seriously, the smaller internal free volume of PVDF polymer can reduce the adsorption capacity of the electrolyte and reduce the "back-and-forth" mobility of lithium ions.
At present, aiming at the defects of PVDF in lithium batteries, the prior art mainly introduces a conductive agent containing a lithium sulfonate component in a blending mode to improve the ion transmission performance of materials, such as:
the invention patent application (application number: 201611173765.0) provides a single ion gel polymer electrolyte and a preparation method thereof;
the invention patent application (application number: 201611145093.2) provides a lithium single-ion conductive solid polymer electrolyte, and the like.
However, although the addition of a conductive agent is effective in improving the electrochemical performance of the material, it reduces the compatibility of PVDF with other materials, weakens the adhesive force of the polymer material itself and the durability of the adhesive force, and causes problems such as easy partial or complete peeling of the electrode binder layer from the current collector, deterioration of load characteristics, and capacity deterioration.
In addition, there is also a related art that introduces a lithium sulfonate structure into a PVDF structure by way of copolymerization to improve ion conductivity, such as:
the invention provides a manufacturing process of an electrolyte membrane special for a solid lithium ion battery (application number: 02138204.2).
However, the copolymer obtained in this way has lower chemical stability and other properties than those of the corresponding PVDF homopolymer because of the introduction of a large number of carbon-hydrogen bonds (C-H) in the copolymerization process and the stability of the copolymer is not as high as that of the carbon-fluorine bonds (C-F) in the PVDF structure.
Therefore, the chemical structure of the PVDF homopolymer is optimized so as to obtain the vinylidene fluoride multipolymer with more excellent performance, the lithium ion mobility of the PVDF copolymer is effectively improved, and the method has important significance for the development and application of lithium ion batteries.
Disclosure of Invention
In order to overcome the defects of the related technology, the invention provides a terpolymer based on polyvinylidene fluoride and a preparation method thereof, aiming at:
while the advantages of the existing PVDF structure are maintained, a copolymerization mode is adopted to introduce a high-efficiency transmission structural unit of lithium ions into a copolymer structure, a high-speed transmission channel of the lithium ions is constructed in the copolymer structure, the transmission efficiency of the lithium ions is optimized, the ionic conductivity of a lithium battery is improved, the polarization of the battery in the charging process is reduced, and the charge and discharge performance of the battery is improved;
in addition, by introducing polar groups into the copolymer structure, the free volume in the copolymer is regulated and controlled, and the adsorption capacity of the copolymer on electrolyte and the migration rate of lithium ions are effectively increased;
in addition, a large number of ultrastable structural units are introduced into the copolymer structure, so that the chemical stability of the copolymer is greatly improved, and an important polymer material is provided for further research and application of lithium batteries.
To achieve the above object, the present invention provides a polyvinylidene fluoride-based terpolymer comprising:
the copolymer consists of three compound structural units, namely a polyvinylidene fluoride structural unit (A) consisting of x molar parts of vinylidene fluoride monomers, a acrylamide structural unit (B) consisting of y molar parts of acrylamide monomers and a perfluoro vinyl ether lithium sulfonate structural unit (C) consisting of z molar parts of perfluoro vinyl ether lithium sulfonate monomers; and is
The copolymer has the following structural general formula:
and further:
in the acrylamide structural unit, the following:
r is-H, -CH3、-CH(CH3)2、-CH2CH3、-(CH2)3-OCH3、-CH2-OH、-(CH2)11-CH3、 -(CH2)3-N(CH3)2、-C(CH3)3、-CH(CH3)2、-CH2C6H5、-C6H5Any one of the above;
in the lithium perfluorovinyl ether sulfonate structural unit, the weight ratio of:
m is an integer of 0 to 10, and n is an integer of 0 to 6;
the respective mole fractions of the polyvinylidene fluoride structural unit, the acrylamide structural unit and the perfluorinated vinyl ether lithium sulfonate structural unit are respectively as follows:
x/(x+y+z)＝0.50～0.80，y/(x+y+z)＝0.10～0.40，z/(x+y+z)＝0.10～0.40。
further, the method comprises the following steps:
in the acrylamide structural unit, the following:
r is-H, - (CH)2)3-N(CH3)2、-CH3、-CH(CH3)2Any one of the above;
in the lithium perfluorovinyl ether sulfonate structural unit, the weight ratio of:
m is an integer of 1 to 3, and n is an integer of 0 to 3;
the polyvinylidene fluoride structural unit, the acrylamide unit and the lithium perfluorovinyl ether sulfonate structural unit respectively have the following molar parts:
x/(x+y+z)＝0.60～0.80，y/(x+y+z)＝0.10～0.30，z/(x+y+z)＝0.10～0.30。
further, the invention also provides a preparation method of the polyvinylidene fluoride-based terpolymer, which comprises the following steps:
in a reaction device, adding a vinylidene fluoride monomer, an acrylamide monomer, a perfluoro vinyl ether lithium sulfonate monomer and an initiator according to respective mole fractions of a polyvinylidene fluoride structural unit, a acrylamide structural unit and a perfluoro vinyl ether lithium sulfonate structural unit, and copolymerizing by adopting a polymerization reaction method to prepare the polyvinylidene fluoride-based terpolymer, wherein the reaction formula is as follows:
further, in the above preparation method:
the reaction device is a high-pressure reaction kettle;
the step of respectively adding the vinylidene fluoride monomer, the acrylamide monomer, the perfluoro vinyl ether lithium sulfonate monomer and the initiator specifically comprises the following steps:
firstly, adding an acrylamide monomer, a perfluorinated vinyl ether lithium sulfonate monomer and an initiator into the high-pressure reaction kettle, repeatedly evacuating to remove oxygen, then filling vinylidene fluoride monomer gas into the high-pressure reaction kettle in a nitrogen atmosphere, and keeping the pressure in the high-pressure reaction kettle between 1.25 and 1.85 MPa;
the step of preparing the polyvinylidene fluoride-based terpolymer by copolymerization through a polymerization reaction method specifically comprises the following steps:
slowly heating the materials in the high-pressure reaction kettle to 75-135 ℃, reacting for 12-36 hours by a polymerization reaction method under mechanical stirring, cooling to room temperature, releasing unreacted gas to obtain a polyvinylidene fluoride-based terpolymer emulsion, demulsifying the emulsion by ethanol to obtain a broken emulsion, washing the broken emulsion to remove an emulsifier and unreacted vinylidene fluoride monomer, acrylamide monomer and perfluoro vinyl ether lithium sulfonate monomer, and drying to obtain the polyvinylidene fluoride-based terpolymer.
Further:
the initiator is one of benzoyl peroxide, azo compounds or persulfate;
the polymerization reaction method is any one of emulsion polymerization, suspension polymerization or aqueous solution polymerization.
And further:
the emulsion polymerization method further comprises an emulsifier, wherein the emulsifier is ammonium perfluorooctanoate.
And further:
the aqueous phase solution polymerization method further comprises a dispersion medium, wherein the dispersion medium is trifluorotrichloroethane.
Further, the method comprises the following steps:
and after the emulsion is demulsified by ethanol to obtain a demulsified solution, dissolving the demulsified solution in an organic solvent to be subjected to subsequent washing and drying operation steps, wherein the organic solvent is one or a mixture of more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, ethanol, isopropanol, dimethyl sulfoxide or ethyl acetate.
Compared with the prior art, the invention has the beneficial effects and remarkable progresses that:
1) according to the polyvinylidene fluoride-based terpolymer provided by the invention, a perfluorinated vinyl ether sulfonic acid lithium conduction unit is introduced into a PVDF structure in a ternary polymerization manner, so that a new method is provided for applying a PVDF material to the field of lithium batteries;
2) the polyvinylidene fluoride-based terpolymer provided by the invention is copolymerized by a one-step method to prepare the vinylidene fluoride-acrylamide-perfluoro vinyl ether lithium sulfonate terpolymer, a subsequent alkali treatment process is not needed, and the chemical degradation of a PVDF structure is avoided;
3) according to the polyvinylidene fluoride-based terpolymer provided by the invention, the polymerized monomer lithium perfluorovinyl ether sulfonate has a self-emulsifying function, and an emulsifier is avoided in the emulsion polymerization process;
4) according to the polyvinylidene fluoride-based terpolymer provided by the invention, the acrylamide structural unit can regulate and control the hydrophilicity of the PVDF copolymer, so that the adsorption capacity of an electrolyte and the migration rate of lithium ions are effectively increased;
5) the polyvinylidene fluoride-based terpolymer provided by the invention has the advantages of the PVDF structure and simultaneously introduces a large amount of super-stable perfluoro structural units (-CF)2CF2-) can effectively improve the chemical stability;
6) according to the polyvinylidene fluoride-based terpolymer provided by the invention, the lithium sulfonate structural unit in the copolymer is connected with the controllable chain segment, so that the crystallinity and the ionic conductivity of the copolymer can be effectively controlled;
7) according to the preparation method of the polyvinylidene fluoride-based terpolymer, the perfluoro vinyl ether lithium sulfonate in the comonomer has a self-emulsifying function, so that an emulsifier is not needed or is not needed in the polymerization reaction process, the production can be ensured, the production cost can be reduced, and the waste discharge is reduced, so that the preparation method has great popularization and application values.
Detailed Description
In order to make the objects, technical solutions, advantages and significant progress of the present invention clearer, the following will clearly and completely describe embodiments and examples provided by the present invention, and obviously, all the described embodiments and examples are only part of the embodiments and examples of the present invention, but not all of them;
all other embodiments or examples, which can be derived by a person skilled in the art from the embodiments presented herein without making any inventive step, are within the scope of the claimed invention.
It should be noted that:
the terms "first," "second," "again," and the like in the description and in the claims of the present invention are used for distinguishing between different objects and not for describing a particular order;
furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to the listed steps or elements, but may alternatively include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus;
in addition, in the description and claims of the present invention:
the copolymer consists of three compound structural units, namely a polyvinylidene fluoride structural unit (A) consisting of x molar parts of vinylidene fluoride monomers, a acrylamide structural unit (B) consisting of y molar parts of acrylamide monomers and a perfluoro vinyl ether lithium sulfonate structural unit (C) consisting of z molar parts of perfluoro vinyl ether lithium sulfonate monomers; and is
The copolymer has the following structural general formula:
further, in the above structural formula:
x, y and z are respectively the respective mole fractions of a polyvinylidene fluoride structural unit, a acrylamide structural unit and a lithium perfluorovinyl ether sulfonate structural unit; and is
The polyvinylidene fluoride structural unit, the acrylamide structural unit and the perfluoro vinyl ether lithium sulfonate structural unit respectively account for the following molar parts in the polyvinylidene fluoride-based terpolymer structure:
x/(x + y + z), y/(x + y + z), and z/(x + y + z).
It should also be noted that:
the following embodiments and examples may be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments and examples; and is
The reaction apparatus, monomer compounds, initiators, emulsifiers, demulsifiers, organic solvents, and the like, referred to in the following examples and examples, are commercially available.
The technical solution of the present invention will be described in detail below with specific examples and examples.
Example one
This example provides a polyvinylidene fluoride-based terpolymer.
The polyvinylidene fluoride-based terpolymer provided by the embodiment comprises:
the copolymer consists of three compound structural units, namely a polyvinylidene fluoride structural unit (A) consisting of x molar parts of vinylidene fluoride monomers, a acrylamide structural unit (B) consisting of y molar parts of acrylamide monomers and a perfluoro vinyl ether sulfonic acid lithium structural unit (C) consisting of z molar parts of perfluoro vinyl ether sulfonic acid lithium monomers; and is
The copolymer has the following structural general formula:
wherein:
in the acrylamide structural unit, the following:
r is-H, -CH3、-CH(CH3)2、-CH2CH3、-(CH2)3-OCH3、-CH2-OH、-(CH2)11-CH3、 -(CH2)3-N(CH3)2、-C(CH3)3、-CH(CH3)2、-CH2C6H5、-C6H5Any one of the above;
in the lithium perfluorovinyl ether sulfonate structural unit, the weight ratio of:
m is an integer of 0 to 10, and n is an integer of 0 to 6;
the respective mole fractions of the polyvinylidene fluoride structural unit, the acrylamide structural unit and the perfluorinated vinyl ether lithium sulfonate structural unit are respectively as follows:
x/(x+y+z)＝0.50～0.80，y/(x+y+z)＝0.10～0.40，z/(x+y+z)＝0.10～0.40。
as a preferred technical solution, further:
in the acrylamide structural unit, the following:
r is-H, - (CH)2)3-N(CH3)2、-CH3、-CH(CH3)2Any one of the above;
in the lithium perfluorovinyl ether sulfonate structural unit, the weight ratio of:
m is an integer of 1 to 3, and n is an integer of 0 to 3;
the polyvinylidene fluoride structural unit, the acrylamide unit and the lithium perfluorovinyl ether sulfonate structural unit respectively have the following molar parts:
x/(x+y+z)＝0.60～0.80，y/(x+y+z)＝0.10～0.30，z/(x+y+z)＝0.10～0.30。
from the above description and the general structural formulae, it can be found that:
firstly, according to the polyvinylidene fluoride-based terpolymer provided by the embodiment, while the advantages of the existing PVDF structure are maintained, a copolymerization mode is adopted to introduce a high-efficiency transmission structural unit of lithium ions into the copolymer structure, a high-speed transmission channel of the lithium ions is constructed in the copolymer structure, the transmission efficiency of the lithium ions is optimized, the ionic conductivity of a lithium battery is improved, the polarization of the battery in the charging process is reduced, and the charge-discharge performance of the battery is improved;
in addition, by introducing polar groups into the copolymer structure, the free volume in the copolymer is regulated and controlled, and the adsorption capacity of the copolymer on electrolyte and the migration rate of lithium ions are effectively increased;
in addition, a large number of ultra-stable structural units are introduced into the copolymer structure, so that the chemical stability of the copolymer is greatly improved, and an important polymer material is provided for further research and application of lithium batteries.
Example two
The embodiment provides a preparation method of a terpolymer based on polyvinylidene fluoride.
The preparation method of the polyvinylidene fluoride-based terpolymer provided by the embodiment comprises the following steps:
in a reaction device, adding a vinylidene fluoride monomer, an acrylamide monomer, a perfluoro vinyl ether lithium sulfonate monomer and an initiator according to respective mole fractions of a polyvinylidene fluoride structural unit, a acrylamide structural unit and a perfluoro vinyl ether lithium sulfonate structural unit, and copolymerizing by adopting a polymerization reaction method to prepare the polyvinylidene fluoride-based terpolymer, wherein the reaction formula is as follows:
further, in the above preparation method:
the reaction device is a high-pressure reaction kettle;
the step of respectively adding the vinylidene fluoride monomer, the acrylamide monomer, the perfluoro vinyl ether lithium sulfonate monomer and the initiator specifically comprises the following steps:
firstly, adding an acrylamide monomer, a perfluorinated vinyl ether lithium sulfonate monomer and an initiator into the high-pressure reaction kettle, repeatedly evacuating to remove oxygen, then filling vinylidene fluoride monomer gas into the high-pressure reaction kettle in a nitrogen atmosphere, and keeping the pressure in the high-pressure reaction kettle between 1.25 and 1.85 MPa;
the step of preparing the polyvinylidene fluoride-based terpolymer by copolymerization through a polymerization reaction method specifically comprises the following steps:
slowly heating the materials in the high-pressure reaction kettle to 75-135 ℃, reacting for 12-36 hours by a polymerization reaction method under mechanical stirring, cooling to room temperature, releasing unreacted gas to obtain a polyvinylidene fluoride-based terpolymer emulsion, demulsifying the emulsion by ethanol to obtain a broken emulsion, washing the broken emulsion to remove an emulsifier and unreacted vinylidene fluoride monomer, acrylamide monomer and perfluoro vinyl ether lithium sulfonate monomer, and drying to obtain the polyvinylidene fluoride-based terpolymer.
In this embodiment:
the initiator can be one of benzoyl peroxide, azo compounds or persulfate;
the polymerization method may be any of emulsion polymerization, suspension polymerization, or aqueous solution polymerization.
In the preparation process by using an emulsion polymerization method, an emulsifier can be further included, and the emulsifier is ammonium perfluorooctanoate.
In the preparation process by using the aqueous phase solution polymerization method, the aqueous phase solution polymerization method also comprises a dispersion medium, and the dispersion medium can be trifluorotrichloroethane.
In addition, after the emulsion is demulsified by ethanol to obtain a demulsified emulsion, the demulsified liquid can be dissolved in an organic solvent for subsequent washing and drying operation steps;
the organic solvent may be one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, ethanol, isopropanol, dimethylsulfoxide, or ethyl acetate.
From the above description, it can be found that:
first, in the preparation method of the polyvinylidene fluoride-based terpolymer provided by this embodiment, a copolymerization mode is adopted to introduce a structural unit (lithium sulfonate structural unit) with high ion transmission efficiency into a structure, so that a high-speed lithium ion transmission channel can be constructed in a material, and finally, the purposes of optimizing the transmission efficiency of PVDF ions and improving the ionic conductivity of a lithium battery are achieved, and the polarization of the battery in a charging process can be reduced, so that the charge and discharge performance of the battery is improved, and further research and application of the lithium battery are providedImportant polymeric materials. In addition, acrylamide units in the terpolymer structure can improve the hydrophilicity of the PVDF copolymer, and effectively increase the adsorption capacity of the electrolyte and the migration rate of lithium ions. More importantly, a large amount of ultrastable perfluorinated structural units (-CF) are introduced into the ternary structure2CF2-) with chemical stability much higher than that of PVDF structural unit (-CH)2CF2-) and the chemical stability of the vinylidene fluoride-acrylamide-perfluorovinyl ether sulfonic acid lithium terpolymer is greatly improved.
In addition, the preparation method of the polyvinylidene fluoride-based terpolymer provided by this embodiment may include:
by regulating and controlling acrylamide monomer, perfluoro vinyl ether sulfonic acid lithium monomer and vinylidene fluoride (CH)2＝CF2) The feeding ratio of the gas monomer adopts the multiple CH addition according to the pressure change of the reaction kettle in the feeding process2＝CF2Feeding by means of gas monomers.
The crystallinity of the terpolymer is further regulated and controlled by regulating and controlling the length of a linking group in the perfluorinated vinyl ether lithium sulfonate monomer, the crystallization melting temperature of the PVDF is reduced, and the problems of low ion transmission efficiency, poor charge and discharge capacity, poor load characteristics and the like when the PVDF is singly used as a binder at present are solved;
when emulsion polymerization is adopted, ammonium Perfluorooctanoate (PFOA) is used as an emulsifier of a reaction system. In addition, the perfluoro vinyl ether sulfonic acid lithium monomer has self-emulsifying function, and can also carry out emulsion polymerization without adding an emulsifier.
According to the above description, it can be seen that the polyvinylidene fluoride-based terpolymer and the preparation method thereof provided by the invention have at least the following advantages:
1) the invention provides a terpolymer based on polyvinylidene fluoride and a preparation method thereof.A perfluorinated vinyl ether sulfonic acid lithium conduction unit is introduced into a PVDF structure in a ternary polymerization mode, so that a new method is provided for applying a PVDF material to the field of lithium batteries;
2) according to the polyvinylidene fluoride-based terpolymer and the preparation method thereof, the one-step copolymerization is adopted to prepare the vinylidene fluoride-acrylamide-perfluoro vinyl ether lithium sulfonate terpolymer, the subsequent alkali treatment process is not needed, and the chemical degradation of a PVDF structure is avoided;
3) in the terpolymer based on polyvinylidene fluoride and the preparation method thereof provided by the invention, the comonomer lithium perfluorovinyl ether sulfonate has a self-emulsifying function, and when the terpolymer is prepared by an emulsion polymerization method, an emulsifier can be not used or used less;
4) in the polyvinylidene fluoride-based terpolymer and the preparation method thereof, the hydrophilicity of the PVDF copolymer can be regulated and controlled through the acrylamide structural unit, and the adsorption capacity of electrolyte and the migration rate of lithium ions are effectively increased;
5) in the polyvinylidene fluoride-based terpolymer and the preparation method thereof provided by the invention, the copolymer introduces a large amount of ultrastable perfluoro structural units (-CF) while retaining the structural advantages of PVDF (polyvinylidene fluoride)2CF2-) can effectively improve the chemical stability;
6) in the polyvinylidene fluoride-based terpolymer and the preparation method thereof, the lithium sulfonate structural unit in the copolymer comprises an adjustable chain segment, so that the crystallinity and the ionic conductivity of the copolymer can be effectively adjusted and controlled.
In summary, it can be seen that:
the terpolymer based on polyvinylidene fluoride and the preparation method thereof provided by the invention are novel and creative, and have extremely high popularization and application values.
To further assist understanding of the technical aspects of the present invention, the technical aspects of the present invention will be described in more detail below by providing several specific implementation examples.
Examples 1, 1,
Adding CH with the structural formula into a high-pressure reaction kettle which can endure 10MPa2＝CH-CONH2Acrylamide monomer and structural formula
The perfluoro vinyl ether sulfonic acid lithium monomer and the benzoyl peroxide initiator are repeatedly pumped out to remove oxygen, and then the perfluoro vinyl ether sulfonic acid lithium monomer and the benzoyl peroxide initiator are filled with the structural formula CH in the nitrogen atmosphere2＝CF2Vinylidene fluoride gas of (a);
wherein:
is represented by the structural formula CH2＝CF2The polyvinylidene fluoride structural unit formed by the vinylidene fluoride gas has a structural formula of CH2＝CH-CONH2Acrylamide structural unit composed of acrylamide monomer, and acrylamide structural unit represented by the structural formula F2C＝CF-OCF2CF(CF3)-OCF2CF2-SO3Li+The mol fraction ratio of the perfluorinated vinyl ether sulfonic acid lithium structural unit formed by the perfluorinated vinyl ether sulfonic acid lithium monomer is as follows:
vinylidene fluoride structural units, acrylamide structural units and perfluoro vinyl ether sulfonic acid lithium structural units are 0.50: 0.25;
keeping the pressure of the reaction kettle between 1.25MPa, slowly heating to 100 ℃, adding ammonium perfluorooctanoate as an emulsifier under mechanical stirring, and carrying out polymerization reaction for 24 hours by adopting an emulsion polymerization method;
after the reaction is finished, cooling the feed liquid to room temperature, releasing unreacted gas to obtain a uniform terpolymer emulsion, demulsifying the emulsion by using an ethanol solution, washing, removing an emulsifier, unreacted vinylidene fluoride monomer, acrylamide monomer and perfluoro vinyl ether lithium sulfonate monomer, and drying to obtain the target product, namely the polyvinylidene fluoride-based terpolymer.
Examples 2,
The operation process and method of the present example are substantially the same as those of example 1, except that:
the added acrylamide monomer has a structural formula: CH (CH)2＝CH-CONHCH3；
The structural formula of the added lithium perfluorovinyl ether sulfonate monomer is as follows:
further:
is represented by the structural formula CH2＝CF2The polyvinylidene fluoride structural unit formed by the vinylidene fluoride gas has a structural formula of CH2＝CH-CONHCH3Acrylamide structural unit composed of acrylamide monomer, and acrylamide structural unit represented by the structural formula F2C＝CF-OCF2CF(CF3)-OCF2CF2-SO3Li+The mol fraction ratio of the perfluorinated vinyl ether sulfonic acid lithium structural unit formed by the perfluorinated vinyl ether sulfonic acid lithium monomer is as follows:
vinylidene fluoride structural units, acrylamide structural units and perfluoro vinyl ether sulfonic acid lithium structural units are 0.80: 0.10;
the pressure of the reaction kettle is kept at 1.50MPa, and the materials are slowly heated and kept at about 95 ℃;
in addition, the polymerization reaction still adopts emulsion polymerization method without adding emulsifier, and takes the perfluoro vinyl ether sulfonic acid lithium structural unit as the emulsifier to carry out the polymerization reaction.
Examples 3,
The operation process and method of the present example are substantially the same as those of example 1, except that:
the initiator adopts azo compound; the added acrylamide monomer has the structural formula: CH (CH)2＝CH-CONHCH3(ii) a The structural formula of the added lithium perfluorovinyl ether sulfonate monomer is as follows:
is represented by the structural formula CH2＝CF2The polyvinylidene fluoride structural unit formed by the vinylidene fluoride gas has a structural formula of CH2＝CH-CONHCH3Acrylamide structural unit composed of acrylamide monomer, and acrylamide structural unit represented by the structural formula F2C＝CF-OCF2CF(CF3)-OCF2CF2-SO3Li+The molar parts of the perfluorinated vinyl ether sulfonic acid lithium structural unit consisting of the perfluorinated vinyl ether sulfonic acid lithium monomerThe fraction ratio is as follows:
vinylidene fluoride structural units, acrylamide structural units and perfluoro vinyl ether sulfonic acid lithium structural units are 0.60: 0.15: 0.25;
the pressure of the reaction kettle is kept at 1.85MPa, and the materials are slowly heated and kept at about 75 ℃;
in addition, the polymerization reaction adopts a suspension polymerization method and does not add an emulsifier.
Examples 4,
The operation process and method of the present example are substantially the same as those of example 3, except that:
the added acrylamide monomer has a structural formula: CH (CH)2＝CH-CONHCH3(ii) a The structural formula of the added lithium perfluorovinyl ether sulfonate monomer is as follows:
further: is represented by the structural formula CH2＝CF2The polyvinylidene fluoride structural unit formed by the vinylidene fluoride gas has a structural formula of CH2＝CH-CONHCH3Acrylamide structural unit composed of acrylamide monomer, and acrylamide structural unit represented by the structural formula F2C＝CF-OCF2CF(CF3)-OCF2CF2-SO3Li+The mol fraction ratio of the perfluorinated vinyl ether sulfonic acid lithium structural unit formed by the perfluorinated vinyl ether sulfonic acid lithium monomer is as follows:
vinylidene fluoride structural units, acrylamide structural units and perfluoro vinyl ether sulfonic acid lithium structural units are 0.70: 0.15;
the pressure of the reaction kettle is kept at 1.60MPa, and the materials are slowly heated and kept at about 135 ℃.
Examples 5,
The operation process and method of the present example are substantially the same as those of example 1, except that:
the initiator adopts sulfate; the added acrylamide monomer has a structural formula: CH (CH)2＝CHCONH-(CH3)3OCH3；
Added lithium perfluorovinyl ether sulfonate monomer and structure thereofThe formula is as follows:
further:
is represented by the structural formula CH2＝CF2The polyvinylidene fluoride structural unit formed by the vinylidene fluoride gas has a structural formula of CH2＝CHCONH-(CH3)3OCH3Acrylamide structural unit composed of acrylamide monomer, and acrylamide structural unit represented by the structural formula F2C＝CF-OCF2CF(CF3)-OCF2CF2-SO3Li+The mol fraction ratio of the perfluorinated vinyl ether sulfonic acid lithium structural unit formed by the perfluorinated vinyl ether sulfonic acid lithium monomer is as follows:
vinylidene fluoride structural units, acrylamide structural units and perfluoro vinyl ether sulfonic acid lithium structural units are 0.60: 0.20;
the pressure of the reaction kettle is kept at 1.75MPa, and the materials are slowly heated and kept at about 85 ℃;
in addition, the polymerization reaction adopts an aqueous phase solution polymerization method, and trifluorotrichloroethane is added without adding an emulsifier to be used as a dispersion medium to carry out polymerization reaction to obtain a terpolymer emulsion of polyvinylidene fluoride, acrylamide and perfluorovinyl ether in polyvinylidene fluoride;
and after emulsion breaking by an ethanol solution, dissolving the emulsion in one or more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, ethanol, isopropanol, dimethyl sulfoxide or ethyl acetate for storage, washing when needed, removing an emulsifier, an organic solvent and unreacted vinylidene fluoride gas, acrylamide and a lithium perfluorovinyl ether sulfonate structural unit, and drying to obtain the target product, namely the terpolymer based on the polyvinylidene fluoride.
Examples 6,
The operation process and method of the present example are substantially the same as those of example 3, except that:
the structural formula of the added lithium perfluorovinyl ether sulfonate monomer is as follows:
F2C＝CF-(OCF2CF(CF3))2-(OCF2CF2)2-SO3Li+
further:
is represented by the structural formula CH2＝CF2The polyvinylidene fluoride structural unit formed by the vinylidene fluoride gas has a structural formula of CH2＝CHCONH-CH3Acrylamide structural unit composed of acrylamide monomer, and acrylamide monomer represented by the formula F2C＝CF-(OCF2CF(CF3))2-(OCF2CF2)2-SO3Li+The mol fraction ratio of the perfluorinated vinyl ether sulfonic acid lithium structural unit formed by the perfluorinated vinyl ether sulfonic acid lithium monomer is as follows:
vinylidene fluoride structural units, acrylamide structural units and perfluoro vinyl ether sulfonic acid lithium structural units are 0.80: 0.10;
in addition, the pressure of the reaction kettle is kept at 1.55MPa, and the materials are slowly heated and maintained at about 105 ℃.
The following are specifically mentioned:
the above examples are provided only as partial examples for illustrating the technical aspects of the present invention, and as the acrylamide structural unit, in addition to the monomers of the specific structural formulae exemplified in the above examples, the structural units thereof are:
r is-H, -CH3、-CH(CH3)2、-CH2CH3、-(CH2)3-OCH3、-CH2-OH、-(CH2)11-CH3、 -(CH2)3-N(CH3)2、-C(CH3)3、-CH(CH3)2、-CH2C6H5、-C6H5The various monomeric compounds formed when they are copolymerized, the corresponding products obtained after they are copolymerized, all have the same or similar functions and effects as the products obtained in the above examples, and the copolymerization methods and control conditions are the same or similar to those listed in the above examples and are included in the examples listed aboveTherefore, the description is not repeated and only the general description is made;
similarly, for the lithium perfluorovinylether sulfonate structural unit, in addition to the monomers of the specific structural formula exemplified in the above examples, the structural formula of the monomer is as follows:
all the monomers indicated that m is an integer of 0 to 10 and n is an integer of 0 to 6, especially all the monomers where m is an integer of 1 to 3 and n is an integer of 0 to 3, which are involved in copolymerization, have the same or similar functions and effects as those of the products obtained in the above examples, and the copolymerization method and control conditions are the same or similar to those of the methods and conditions listed in the above examples and are included in the ranges listed in the above examples, so that the description is omitted and only the summary description is made.
To further illustrate the embodiments of the present invention and the advantages achieved by the various cases, the following description will be made with reference to specific effect embodiments.
It should be noted that:
the detection instrument and the detection reagent according to the following effect examples are commercially available, and the detection method used is a conventional technique that can be searched.
Effect embodiment:
1) determination of the average molecular weight of the copolymer:
the average molecular weight is obtained by measuring the weight average relative molecular weight of the copolymer by a PL-22 type high temperature gel permeation chromatograph.
In the detection process, N-dimethylformamide is taken as a solvent, the detection is carried out at 160 ℃, and data are processed by a universal correction method with narrow distribution vinylidene fluoride as a standard sample.
The average molecular weight values of the copolymers of cases 1 to 6 obtained by the test are shown in Table 1.
2) Determination of the crystallinity of the copolymer:
the crystallinity of the copolymer was measured by DSC2910 Differential Scanning Calorimeter (British name: Differential Scanning Calorimeter) manufactured by TA of America, and the copolymer was tested under nitrogen protection according to the method specified in GB/T19466.3-2004.
During detection, the sample is heated from room temperature to 150 ℃ at the speed of 10 ℃/min, is kept warm for 5min, is naturally cooled to room temperature, is subjected to temperature rise scanning at the speed of 10 ℃/min (from room temperature to 150 ℃), and is recorded with a corresponding DSC curve to obtain the corresponding melting enthalpy delta HfThen, the percent crystallinity of each copolymer was calculated according to the following formula:
Xi＝(ΔHf÷293)×100％
in the formula:
ΔHfis the enthalpy of fusion of the sample polymer, given in units of J.g-1；
293 is the enthalpy of fusion at 100% crystallinity of polyethylene, in J.g-1。
The percent crystallinity of the copolymers obtained in cases 1 to 6 was examined and is shown in Table 1.
3) Determination of the free volume of the copolymer:
the free volume of the copolymer is measured by soaking the copolymer in 80 ℃ propylene carbonate serving as an electrolyte of a lithium battery for 10 hours, measuring the volume of the copolymer before and after soaking, and determining the difference value of the volume before and after soaking as the free volume of the copolymer, namely:
Vf＝V－Vo
in the formula:
Vois the volume of the initial copolymer sample;
v is the volume of the copolymer sample after soaking.
The free volume of each copolymer of cases 1 to 6 obtained by the examination is shown in Table 1.
4) Determination of the ionic conductivity of the copolymer:
the determination of the ionic conductivity of the copolymer is to thermally press each copolymer into a film at 150 ℃, then test the film resistance R of the film after swelling propylene carbonate on the film by adopting a two-electrode method, the adopted detection instrument is an electrochemical workstation Autolab PGSTA302, the frequency interval is 106-10 Hz, and the conductivity is calculated by the following calculation formula:
σ＝L/RS
in the formula:
σ is the conductivity (s/cm) of the sample after swelling;
l is the thickness (cm) of the swollen membrane;
r is the resistance (omega) of the membrane after swelling;
s is the area (cm) of the test portion of the sample after swelling2)。
The ionic conductivity of the copolymers obtained in cases 1 to 6 was measured and is shown in Table 1.
TABLE 1
| Molecular weight | Crystallinity (%) | Ion conductivity (S/cm) | |
| Example 1 | 420000 | 35 | 3.9×10-4 |
| Example 2 | 430000 | 33 | 4.5×10-4 |
| Example 3 | 460000 | 38 | 3.9×10-3 |
| Example 4 | 440000 | 36 | 1.1×10-3 |
| Example 5 | 430000 | 32 | 5.6×10-4 |
| Example 6 | 450000 | 27 | 0.2×10-3 |
The test results are as follows: examples 1 to 6 had a molecular weight of 420000-460000, crystallinity of 27 to 38%, and an ionic conductivity of 3.9X 10-4-3.9×10-3. The results prove that the polymeric material provided by the invention has better stability, crystallinity and ionic conductivity.
During the description of the above description:
the description of the terms "present embodiment," "present example," "further," 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 invention;
in this specification, the schematic representations of the terms used above are not necessarily for the same embodiment or example, and the particular features, structures, materials, or characteristics described, etc., may be combined or brought together in any suitable manner in any one or more embodiments or examples;
furthermore, those of ordinary skill in the art may combine or combine features of different embodiments or examples and features of different embodiments or examples described in this specification without undue conflict.
Finally, it should be noted that:
although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made on the technical solutions described in the foregoing embodiments, or some or all of the technical features of the embodiments can be equivalently replaced, and the corresponding technical solutions do not depart from the technical solutions of the embodiments of the present invention.
Claims (9)
1. A polyvinylidene fluoride-based terpolymer comprising:
the copolymer consists of three compound structural units, namely a polyvinylidene fluoride structural unit (A) consisting of x molar parts of vinylidene fluoride monomers, a acrylamide structural unit (B) consisting of y molar parts of acrylamide monomers and a perfluoro vinyl ether lithium sulfonate structural unit (C) consisting of z molar parts of perfluoro vinyl ether lithium sulfonate monomers; and is
The copolymer has the following structural general formula:
in the acrylamide structural unit, the following:
r is-H, -CH3、-CH(CH3)2、-CH2CH3、-(CH2)3-OCH3、-CH2-OH、-(CH2)11-CH3、-(CH2)3-N(CH3)2、-C(CH3)3、-CH(CH3)2、-CH2C6H5、-C6H5Any one of the above;
in the lithium perfluorovinyl ether sulfonate structural unit, the weight ratio of:
m is an integer of 0 to 10, and n is an integer of 0 to 6;
the respective mole fractions of the polyvinylidene fluoride structural unit, the acrylamide structural unit and the perfluorinated vinyl ether lithium sulfonate structural unit are respectively as follows:
x/(x+y+z)＝0.50～0.80，y/(x+y+z)＝0.10～0.40，z/(x+y+z)＝0.10～0.40。
2. the polyvinylidene fluoride-based terpolymer of claim 1, characterized by:
in the acrylamide structural unit, the following:
r is-H, - (CH)2)3-N(CH3)2、-CH3、-CH(CH3)2Any one of the above;
in the lithium perfluorovinyl ether sulfonate structural unit, the weight ratio of:
m is an integer of 1 to 3, and n is an integer of 0 to 3;
the polyvinylidene fluoride structural unit, the acrylamide unit and the lithium perfluorovinyl ether sulfonate structural unit respectively have the following molar parts:
x/(x+y+z)＝0.60～0.80，y/(x+y+z)＝0.10～0.30，z/(x+y+z)＝0.10～0.30。
3. a method for preparing a polyvinylidene fluoride-based terpolymer according to claim 1 or 2, comprising the steps of:
in a reaction device, adding a vinylidene fluoride monomer, an acrylamide monomer, a perfluoro vinyl ether lithium sulfonate monomer and an initiator according to respective mole fractions of a polyvinylidene fluoride structural unit, a acrylamide structural unit and a perfluoro vinyl ether lithium sulfonate structural unit, and copolymerizing by adopting a polymerization reaction method to prepare the polyvinylidene fluoride-based terpolymer, wherein the reaction formula is as follows:
4. the method of claim 3, wherein the at least one monomer is selected from the group consisting of:
the reaction device is a high-pressure reaction kettle;
the step of respectively adding the vinylidene fluoride monomer, the acrylamide monomer, the perfluoro vinyl ether lithium sulfonate monomer and the initiator specifically comprises the following steps:
firstly, adding an acrylamide monomer, a perfluorinated vinyl ether lithium sulfonate monomer and an initiator into the high-pressure reaction kettle, repeatedly evacuating to remove oxygen, then filling vinylidene fluoride monomer gas into the high-pressure reaction kettle in a nitrogen atmosphere, and keeping the pressure in the high-pressure reaction kettle between 1.25 and 1.85 MPa;
the step of preparing the polyvinylidene fluoride-based terpolymer by copolymerization through a polymerization reaction method specifically comprises the following steps:
slowly heating the materials in the high-pressure reaction kettle to 75-135 ℃, reacting for 12-36 hours by a polymerization reaction method under mechanical stirring, cooling to room temperature, releasing unreacted gas to obtain a polyvinylidene fluoride-based terpolymer emulsion, demulsifying the emulsion by ethanol to obtain a broken emulsion, washing the broken emulsion to remove an emulsifier and unreacted vinylidene fluoride monomer, acrylamide monomer and perfluoro vinyl ether lithium sulfonate monomer, and drying to obtain the polyvinylidene fluoride-based terpolymer.
5. The method of claim 4, wherein the polyvinylidene fluoride-based terpolymer comprises: the initiator is one of benzoyl peroxide, azo compounds or persulfate.
6. The method of claim 4, wherein the polyvinylidene fluoride-based terpolymer comprises: the polymerization reaction method is any one of emulsion polymerization, suspension polymerization or aqueous solution polymerization.
7. The method of claim 6, wherein the polyvinylidene fluoride-based terpolymer comprises: the emulsion polymerization method further comprises an emulsifier, wherein the emulsifier is ammonium perfluorooctanoate.
8. The method of claim 6, wherein the polyvinylidene fluoride-based terpolymer comprises: the aqueous phase solution polymerization method further comprises a dispersion medium, wherein the dispersion medium is trifluorotrichloroethane.
9. The method of claim 4, wherein the polyvinylidene fluoride-based terpolymer comprises:
and after the emulsion is demulsified by an ethanol solution to obtain a demulsified emulsion, dissolving the demulsified solution in an organic solvent to wait for the subsequent washing and drying operation steps, wherein the organic solvent is one or a mixture of more of N, N-dimethylformamide, N-dimethylacetamide, N-methylpyrrolidone, ethanol, isopropanol, dimethyl sulfoxide or ethyl acetate.
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