WO2019059705A2 - Polymer electrolyte and preparation method therefor - Google Patents

Abstract

The present invention relates to a polymer electrolyte comprising a polymer of poly (ethylene oxide) (PEO); and a lithium salt, one end of the polyethylene oxide polymer being substituted with a functional group of a nitrogen compound or a functional group of a phosphorus compound, and its method of preparation.

Description

POLYMER ELECTROLYTE AND METHOD FOR MANUFACTURING THE SAME

This application claims the benefit of priority based on Korean Patent Application No. 10-2017-0121709 dated September 21, 2017 and No. 10-2018-0093721 dated August 10, 2018, and all contents disclosed in the Korean patent application document Are incorporated herein by reference.

The present invention relates to a polymer electrolyte and a method for producing the same, and more particularly, to a polymer electrolyte improved in the number of lithium cation transport and a method for producing the same.

2. Description of the Related Art [0002] The application fields of rechargeable secondary batteries ranging from portable devices such as mobile phones, notebooks, and camcorders to electric vehicles are increasingly being developed, and secondary batteries are being actively developed. In addition, research and development on battery design for improving capacity density and specific energy in the development of secondary batteries are under way.

Generally, the safety of a battery is improved in the order of liquid electrolyte < gel polymer electrolyte &gt; solid electrolyte, while battery performance is known to decrease.

Background Art [0002] Electrolytes for electrochemical devices such as batteries and electric double layer capacitors using electrochemical reactions have been mainly used as liquid electrolytes, especially ion conductive organic liquid electrolytes in which salts are dissolved in non-aqueous organic solvents. However, when such a liquid electrolyte is used, there is a possibility that the electrode material is degenerated and the organic solvent is volatilized, and there is a problem in safety such as combustion due to the ambient temperature and the temperature rise of the battery itself.

Particularly, the electrolyte used in the lithium secondary battery is in a liquid state, and there is a risk of flammability in a high temperature environment, which may be a considerable burden to the application of electric vehicles. In addition, since organic electrolytic solutions whose solvents are flammable are used, problems of not only leakage but also ignition and combustion accidents are always accompanied. For this reason, it has been studied to use an ionic liquid, a gel-like electrolyte, or a polymer electrolyte in the electrolytic solution. Therefore, this problem can be solved by replacing the liquid lithium electrolyte with a solid electrolyte. So far, various solid electrolytes have been researched and developed.

Solid electrolytes are mainly made of flame retardant materials, and are stable at high temperatures because they are made of nonvolatile materials with high stability. In addition, since the solid electrolyte serves as a separator, a conventional separator is not necessary and a thin film process may be possible.

The most ideal form is a secondary battery which is not only safe but also excellent in stability and reliability as a high-solid type using an inorganic solid in an electrolyte. In order to obtain a large capacity (energy density), it is also possible to adopt a laminated structure. In addition, like the conventional electrolytic solution, there is no need for desolvation of the solvated lithium, and only the lithium ion migrates into the ion conductor solid electrolyte, so unnecessary side reactions do not occur and the cycle life can be greatly extended.

Although the ionic conductivity of the solid electrolyte, which is the biggest problem to be solved in realizing the solid secondary battery, has not been much larger than that of the organic electrolytic solution in the past, various techniques for improving the ionic conductivity have been reported recently. Studies on the practical use of secondary batteries are continuing.

The composite electrolyte of polyethylene oxide (PEO) and lithium salt, which is one of the electrolytes used in the lithium ion battery, is advantageous in that it has higher stability than the conventional liquid electrolyte.

However, PEO used in this electrolyte is a polymer having a high crystallinity, and therefore, there is a problem that when the polymer is crystallized at a melting point (about 50 ° C) of the polymer, the ion conductivity becomes extremely low. Conventionally, a polymer having a liquid state at room temperature is frequently used because the molecular weight of PEO is extremely low. However, this is not a fundamental study for relaxing crystallization characteristics of PEO.

(Non-Patent Document 1) Ito, K .; Nishina, N .; Ohno, H. J. Mater. Chem. 1997, 7, 1357-1362.

(Non-Patent Document 2) Jo, G .; Anh, H .; Park, M. J. ACS Macro Lett. 2013, 2, 990-995.

As described above, when PEO is used in an electrolyte, ionic conductivity is extremely lowered when the polymer is crystallized at a temperature of about 50 캜 or less due to a low melting point of the polymer. The inventors of the present invention conducted various studies and found a method for solving the problem by synthesizing a new polymer capable of reducing the intrinsic crystallinity of the PEO chain and completed the present invention.

Accordingly, it is an object of the present invention to provide an electrolyte for a lithium battery, wherein a PEO-based polymer electrolyte including a lithium salt has excellent room temperature ionic conductivity at room temperature and a lithium cation transport number is improved through a polymer having a new functional group.

In order to accomplish the above object, the present invention provides a polymer electrolyte membrane comprising: a poly (ethylene oxide) (PEO) polymer; And lithium salts; Wherein the end of the polyethylene oxide polymer is substituted with a sulfur compound functional group, a nitrogen compound functional group or a phosphorus compound functional group.

The present invention also provides a method for preparing a polyethylene oxide polymer, comprising the steps of: (a) adding a sulfur compound, a nitrogen compound or a phosphorus compound to a poly (ethylene oxide) (PEO) polymer to modify the terminal of the polyethylene oxide polymer; And (b) adding a lithium salt to the polymer electrolyte.

The present invention also relates to a solid electrolyte comprising an anode, a cathode and a solid polymer electrolyte interposed therebetween, wherein the solid polymer electrolyte is selected from the group consisting of polyethylene oxide (PEO) -based polymer; And a lithium salt, wherein the end of the polyethylene oxide polymer is a polymer electrolyte substituted with a nitrogen compound functional group or a phosphorus compound functional group.

When the polymer electrolyte of the present invention is applied to an all solid-state cell, the crystallinity of the polymer can be reduced by synthesizing a polymer having various terminal functional groups introduced therein without changing the molecular weight of the PEO. Therefore, And can have excellent ionic conductivity. In addition, the number of lithium cation transport can be improved by controlling the molecular attraction between the terminal functional group and the lithium salt, thereby improving the discharge capacity and the charge / discharge rate.

1 is a graph showing the results of NMR data measurement of Examples 1 to 3 and Comparative Example 1 of the present invention.

FIG. 2 is a graph showing ³¹ P NMR results of measuring the hydrolysis efficiency of Examples 2 to 3 of the present invention. FIG.

3 is a graph showing the results of gel permeation chromatography analysis of Examples 1 to 3 and Comparative Example 1 of the present invention.

4 is a graph showing the results of differential scanning calorimetry (DSC) analysis of Examples 1 to 3 and Comparative Examples 1 and 2 of the present invention.

5 is a graph showing the results of analyzing ionic conductivities of Examples 1 to 3 and Comparative Example 1 of the present invention.

Fig. 6 is a graph showing correction of the results of analyzing ionic conductivities of Examples 1 to 3 and Comparative Example 1 of the present invention. Fig.

7 is a graph showing the results of measurement of electrode polarization in Examples 1 to 3 and Comparative Example 1 of the present invention.

8 is a graph showing FT-IR measurement results of Examples 1 to 3 and Comparative Example 1 of the present invention.

9 is a graph showing FT-IR measurement results of Examples 1 to 3 and Comparative Example 1 of the present invention.

10 is a graph showing FT-IR measurement results of Examples 1 to 3 and Comparative Example 1 of the present invention.

11 is a graph showing FT-IR measurement results obtained by doping a polymer with LiTFSI salt in Example 1 and Example 1 of the present invention.

12 is a graph showing FT-IR measurement results obtained after doping LiTFSI salt into the polymer of Example 3 and Example 3 of the present invention.

13 is a graph showing Examples 1 to 3 and Comparative Example 1 of the present invention and FT-IR measurement results obtained after doping with LiTFSI salt thereof.

Figure 14 shows the synthesis route of the PS-b-PEO block copolymer with terminal substitution via thiol-ene click chemistry.

FIG. 15 shows the results of the analysis of (a) ¹ H NMR spectrum of SEO-ene, SEO-c, SEO-2h and SEO-2c (b) SEC data (c) SEO- FT-IR, OH stretching and C = O stretching of 2c are shown in (c).

q ^*,

q ^*,

q ^*,

q ^*,

q ^*, 그리고

q ^* 를 나타낸다. 말단 그룹에 의한 계면 변화를 그림으로 나타내었다. 말단을 치환한 SEO 시료들의 결정화도를 나타내는 DSC 데이터를 삽입하였다.Figure 16 shows SAXS data at 60 占 폚 for SEO-h, SEO-c, SEO-2h, and SEO-2c. The filled inverse triangle represents bragg peaks q ^* , 2 q ^* of SEO-c. The open inverted triangles are bragg peaks in SEO-2h and SEO-2c

q ^* ,

q ^* ,

q ^* ,

q ^* ,

q ^* , and

q ^* . Interfacial changes by end groups are shown in the figure. DSC data showing the degree of crystallinity of the SEO samples with terminal substitutions were inserted.

17 shows (a) storage (G ', filled symbol) and loss (G, open symbol) modulus. The cooling (blue) and temperature (red) experiments were performed at a constant rate of 1 ° C / min at a strain of 0.1% at 0.5 rad / s. The plateau modulus of each sample with terminal substitution is indicated by a dotted line. (B) G ', G "measured by the frequency of SEO-2c and PEO-2c at 50 ° C.

18 is a graph showing ion conduction characteristics by doping a lithium salt-doped sample into a terminal group-substituted sample.

19 is a graph showing the ion conduction characteristics of an SEO electrolyte membrane substituted with a terminal group doped with a lithium salt at r = 0.02 (b) ion conduction characteristics at a temperature of T = 60 DEG C and DV = 0.1 V, Typical data observing the flow of the lithium transference number current is inserted. (c) Ion conduction characteristics of SEO electrolyte membrane substituted with terminal group doped with lithium salt at r = 0.06 according to temperature. Vogel-Tammann-Fulcher (VTF) equation. (d) Data not doped with lithium salt of PEO-2h ( r = 0.06). TFSI-anion, and lithium ion, respectively. A range peak between 3700-2500 cm ^-1 was magnified and inserted.

20 shows (a) intermolecular interactions of PEO chains substituted with terminal groups. (b) the intermolecular interaction of PEO-2c and PEO-2h under the lithium salt. In both samples, the terminal was hydrogen bonded to TFSI-anion, and lithium ion coordinated with ether oxygen. The formation of dimer that can be observed in PEO-2c is also shown.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the drawings, the same reference numerals are used for similar parts throughout the specification. Also, the size and relative size of the components shown in the figures are independent of the actual scale and may be reduced or exaggerated for clarity of description.

Polymer electrolyte

The present invention relates to a novel polymer capable of reducing the crystallinity of a polymer by synthesizing a polymer having various terminal functional groups introduced therein without changing the molecular weight of PEO, and includes a polymer such as polyethylene oxide (PEO) -based polymer; And a lithium salt,

Wherein the end of the polyethylene oxide polymer is substituted with a sulfur compound functional group, a nitrogen compound or a phosphorus compound.

The polymer electrolyte of the present invention can induce various interactions between a functional group introduced into a polymer and a lithium salt by introducing a sulfur compound, a nitrogen compound or a phosphorus compound as a functional group at the terminal of the polyethylene oxide polymer, .

Specifically, in the present invention, the nitrogen compound functional group to be introduced into the terminal of the polyethylene oxide polymer includes nitrile, amine, pyridine, imidazole and the like. Diethyl phosphonate, or phosphonic acid.

In the present invention, specific examples of the polymer in which a nitrogen compound or a phosphorus compound is introduced as a functional group at the terminal of the polyethylene oxide polymer may be represented by any one of the following Chemical Formulas 1 to 3.

[Chemical Formula 1]

(2)

(3)

Wherein n is an integer of from 10 to 120, and R is an alkyl chain having from 1 to 4 carbon atoms.

As described above, the polymer electrolyte of the present invention can be produced by synthesizing a polymer having various terminal functional groups introduced therein without changing the molecular weight of polyethylene oxide (PEO) To about 80%.

Specifically, as the sulfur compound functional group introduced into the terminal of the polyethylene oxide polymer in the present invention, those having a functional group represented by the following general formula (4) can be used.

[Chemical Formula 4]

-S-R

(Wherein R is a carboxyl group having 1 to 4 carbon atoms, a diol group, or a dicarbonyl group)

In the formula (4), -R may be selected from one or more functional groups represented by the following formulas (5) to (5).

(5)

(5)

In the present invention, when the terminal of the polyethylene oxide polymer is substituted with a sulfur compound, the polyethylene oxide polymer may be a block copolymer composed of a polyethylene oxide block and a hydrophobic block, for example, a polystyrene block.

In the practice of the present invention, the block copolymer may be represented by the following formula (6)

(6)

(6)

Here, R is a carboxyl group, a diol group, or a dicarboxyl group having 1 to 4 carbon atoms,

R1 is alkyl of 1-8 carbon atoms,

b means a block copolymer,

0 <n <200, 0 <m <100, 1.5 m <n <2.5 m,

The molecular weight of the block copolymer is 20 kg / mol or less, preferably 2 to 20 kg / mol, and the molecular weight of each block is 1 to 10 kg / mol.

In a preferred embodiment of the present invention, the block copolymer is represented by the following chemical formula (7), and the functional group -R may be represented by the chemical formula (5).

(7)

(7)

(5)

(5)

Here, b means a block copolymer,

0 <n <200, 0 <m <100, 1.5 m <n <2.5 m,

The molecular weight of the block copolymer is 2 to 20 kg / mol.

In the present invention, the block copolymer may be doped with a metal salt, preferably a lithium salt.

In the present invention, the block copolymer may have a gyroid, a lamellar, or an amorphous structure.

In addition, the polymer electrolyte of the present invention can be used as a solid electrolyte for all solid-state batteries.

Solid electrolytes are mainly made of flame retardant materials, and are stable at high temperatures because they are made of nonvolatile materials with high stability. In addition, since the solid electrolyte serves as a separator, a conventional separator is not necessary and a thin film process may be possible.

The most ideal form is a secondary battery which is not only safe but also excellent in stability and reliability as a high-solid type using an inorganic solid in an electrolyte. In order to obtain a large capacity (energy density), it is also possible to adopt a laminated structure. In addition, like the conventional electrolytic solution, there is no need for desolvation of the solvated lithium, and only the lithium ion migrates into the ion conductor solid electrolyte, so unnecessary side reactions do not occur and the cycle life can be greatly extended.

Further, since the polymer electrolyte of the present invention has improved ionic conductivity as described later, it is preferable to be applied to all solid ion batteries.

In addition, the present invention intends to improve the ionic conductivity and lithium cation transport property by introducing a lithium salt into the polymer as described above to prepare a composite electrolyte.

To this end, the present invention dope a lithium salt to a polyethylene oxide-based polymer.

The lithium salt is not particularly limited but preferably LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl _{4, CH 3 SO 3 Li,} CF 3 SO 3 Li, LiSCN, LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, (FSO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium , Lithium 4-phenylborate, imide, and bis (trifluoromethane sulfonyl) imide (LiTFSI).

The polymer electrolyte of the present invention can reduce the crystallinity of a polymer by synthesizing a polymer having various terminal functional groups introduced therein without changing the molecular weight of polyethylene oxide (PEO), so that the molecular weight of the polymer electrolyte is preferably 1 to 20 kg / mol .

The polymer electrolyte of the present invention may have a value of [Li +] / [EO] of 0.02 to 0.08, which is a ratio of [Li +] of the lithium salt to that of the polymer [EO] in order to ensure practical performance of the lithium battery. have. When the concentration of [EO] of the polymer and the [Li +] concentration of the lithium salt are within the above range, the electrolyte has appropriate conductivity and viscosity, and therefore, excellent electrolyte performance can be exhibited and lithium ions can be effectively transferred.

Further, the polymer electrolyte of the present invention has an excellent ion transport property with a number of lithium cation transporting number of 0.5 or more.

Method for producing polymer electrolyte

Also, in order to produce the polymer electrolyte as described above,

 (a) modifying the end of the polyethylene oxide polymer by adding a sulfur compound, a nitrogen compound or a phosphorus compound to a poly (ethylene oxide) (PEO) based polymer; And (b) adding a lithium salt to the polymer electrolyte.

In the step (a) of the present invention, a sulfur compound, a nitrogen compound or a phosphorus compound is added to a poly (ethylene oxide) (PEO) polymer to modify the terminal of the polyethylene oxide polymer, The end of the oxide polymer may be substituted with a sulfur compound functional group, a nitrogen compound functional group or a phosphorus compound functional group.

The polymer electrolyte of the present invention can induce various interactions between a functional group introduced into a polymer and a lithium salt by introducing a sulfur compound, a nitrogen compound or a phosphorus compound as a functional group at the terminal of the polyethylene oxide polymer, .

The method of adding the sulfur compound, the nitrogen compound or the phosphorus compound can be added in a manner conventionally used in the industry without particular limitation.

Specifically, in the present invention, the nitrogen compound functional group to be introduced into the terminal of the polyethylene oxide polymer includes nitrile, amine, pyridine, imidazole and the like. Diethyl phosphonate, or phosphonic acid.

In the step (a), specific examples of the polymer in which a nitrogen compound or a phosphorus compound is introduced as a functional group at the terminal of the polyethylene oxide polymer may be represented by any one of the following Chemical Formulas 1 to 3.

[Chemical Formula 1]

(2)

(3)

Wherein n is an integer of from 10 to 120, and R is an alkyl chain having from 1 to 4 carbon atoms.

Also, in the present invention, when the terminal of the polyethylene oxide polymer is substituted with a sulfur compound, the polyethylene oxide polymer may be a block copolymer composed of a polyethylene oxide block and a hydrophobic block, for example, a polystyrene block.

In this case, in the block copolymer comprising a polyethylene oxide block, the end of the polyethylene oxide block is modified by the following formula (8); And

-R ₂ -CH ₂ = CH ₂ (8)

(Wherein R &lt; ₂ &gt; is alkyl having 1 to 6 carbon atoms)

Subjecting the compound of formula (8) to a zeol-entitled reaction with a compound of formula (9);

HS-R (9)

(Wherein R is a carboxyl group, a diol group or a dicarboxyl group having 1 to 4 carbon atoms)

, The terminal of the polyethylene oxide polymer may be substituted with a sulfur compound.

As described above, the polymer electrolyte of the present invention can be produced by synthesizing a polymer having various terminal functional groups introduced therein without changing the molecular weight of polyethylene oxide (PEO) To about 80%.

The present invention also provides a method for preparing a composite electrolyte by introducing a lithium salt into the polymer modified in the step (a) through a step of adding a lithium salt in step (b) to improve ionic conductivity and lithium cation transport property do.

For this purpose, the present invention can be doped with a lithium salt to a polyethylene oxide-based polymer.

The lithium salt is not particularly limited but preferably LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl _{4, CH 3 SO 3 Li,} CF 3 SO 3 Li, LiSCN, LiC (CF 3 SO 2) 3, (CF 3 SO 2) 2 NLi, (FSO 2) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium , Lithium 4-phenylborate, imide, and bis (trifluoromethane sulfonyl) imide (LiTFSI).

The polymer electrolyte of the present invention can reduce the crystallinity of a polymer by synthesizing a polymer having various terminal functional groups introduced therein without changing the molecular weight of polyethylene oxide (PEO), so that the molecular weight of the polymer electrolyte is preferably 1 to 20 kg / mol .

The polymer electrolyte of the present invention may have a value of [Li +] / [EO] of 0.02 to 0.08, which is a ratio of [Li +] of the lithium salt to that of the polymer [EO] in order to ensure practical performance of the lithium battery. have. When the concentration of [EO] of the polymer and the [Li +] concentration of the lithium salt are within the above range, the electrolyte has appropriate conductivity and viscosity, and therefore, excellent electrolyte performance can be exhibited and lithium ions can be effectively transferred.

Further, the polymer electrolyte of the present invention has an excellent ion transport property with a number of lithium cation transporting number of 0.5 or more.

All solid-state cells

The present invention also relates to a solid electrolyte comprising an anode, a cathode and a solid polymer electrolyte interposed therebetween, wherein the solid polymer electrolyte is selected from the group consisting of polyethylene oxide (PEO) -based polymer; And a lithium salt, wherein the end of the polyethylene oxide polymer is a polymer electrolyte substituted with a nitrogen compound functional group or a phosphorus compound functional group.

In the present invention, the electrode active material may be a cathode active material when the electrode is a positive electrode, or a negative active material when it is a negative electrode. At this time, each of the electrode active materials can be any active material applied to conventional electrodes, and is not particularly limited in the present invention.

The cathode active material may be varied depending on the use of the lithium secondary battery, and a known material is used for the specific composition. For example, any one selected from the group consisting of a lithium-phosphoric acid-iron compound, a lithium cobalt oxide, a lithium manganese oxide, a lithium copper oxide, a lithium nickel oxide and a lithium manganese composite oxide, and a lithium-nickel-manganese- Of lithium transition metal oxides. More specifically, among the lithium metal phosphates represented by Li _{1 + a} M (PO _4-b ) X _b , M is at least one selected from metals of Groups 2 to 12, X is at least one selected from the group consisting of F, S and N, it is preferable that -0.5 = a = +0.5 and 0 = b? = 0.1.

At this time, the negative electrode active material may be selected from the group consisting of lithium metal, lithium alloy, lithium metal composite oxide, lithium-containing titanium composite oxide (LTO), and combinations thereof. The lithium alloy may be an alloy of lithium and at least one metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Ba, Ra, Al and Sn. In addition, lithium metal composite oxide is lithium and Si, Sn, Zn, Mg, Cd, Ce, Ni, and is one of a metal (Me) oxide (MeO _x) selected from the group consisting of Fe, for example in Li _x Fe ₂ O ₃ (0 <x = 1) or Li _x WO ₂ (0 <x = 1).

At this time, if necessary, a conductive material or a polymer electrolyte may be further added to the active material, and examples of the conductive material include nickel powder, cobalt oxide, titanium oxide, carbon, and the like. Examples of the carbon include any one selected from the group consisting of Ketjen black, acetylene black, furnace black, graphite, carbon fiber and fullerene, or one or more of them.

The preparation of the entire solid battery is carried out by a dry compression process in which an electrode and a solid electrolyte are prepared in a powder state and then put into a predetermined mold and pressed, or a slurry composition including an active material, a solvent and a binder, &Lt; / RTI &gt; slurry coating process. The production of the all solid battery having the above-mentioned constitution is not particularly limited in the present invention, and a known method can be used.

For example, a solid electrolyte is disposed between an anode and a cathode, and the cell is assembled by compression molding. After the assembled cells are installed in the casing, they are sealed by heat compression or the like. Laminate packs made of aluminum, stainless steel or the like, and cylindrical or square metal containers are very suitable for the exterior material.

The method of coating the electrode slurry on the current collector includes a method of uniformly dispersing the electrode slurry on the current collector using a doctor blade or the like, a method of die casting, a comma coating, , Screen printing, and the like. Alternatively, the electrode slurry may be bonded to the current collector by pressing on a separate substrate and then laminating. At this time, the thickness of the coating to be finally coated can be controlled by adjusting the concentration of the slurry solution, the number of times of coating, and the like.

The drying process is a process for removing the solvent and moisture in the slurry to dry the slurry coated on the metal current collector, and may be changed depending on the solvent used. For example, it is carried out in a vacuum oven at 50 to 200 ° C. Examples of the drying method include a drying method by hot air, hot air, low-humidity air, vacuum drying, and irradiation with (circle) infrared rays or electron beams. The drying time is not particularly limited, but is usually in the range of 30 seconds to 24 hours.

After the drying process, the process may further include a cooling process, and the cooling process may be slow cooling to room temperature so that the recrystallized structure of the binder is well formed.

If necessary, a rolling process may be performed to increase the capacity density of the electrode after the drying process and to increase the adhesion between the current collector and the active materials, thereby compressing the electrode to a desired thickness by passing the electrode between the two heated rolls. The rolling process is not particularly limited in the present invention, and a known rolling process is possible. For example, between rotating rolls or using a flat press machine.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example: Preparation of terminally substituted polyethylene oxide

Experimental conditions

Experimental condition 1: Preparation of polymer doped with salt

The calculated amount of LiTFSI is mixed with the polymer using a methanol / benzene cosolvent and then stirred at room temperature for one day. The solvent in the argon environment is slowly evaporated to dryness and then completely dried in vacuum for one week. All sample preparation and drying procedures were performed in a glove box in an argon environment equipped with an oxygen and moisture sensor, vacuum oven to avoid water absorption by the sample.

Experimental Condition 2: X-ray Small Scattering Experiment (Small Angle X-Ray Scattering, SAXS)

All synthesized polymer samples were run on Pohang Light Source (PLS) 4C and 9A beam lines. Wavelength (l) of the incident X-ray is 0.118 nm (Dλ / λ = 10 -4). In order to prevent the samples from absorbing oxygen and moisture during the measurement process, a sealed cell was fabricated using Capton film. The scattering wave vector ( q = 4psin (q / 2) / l, q: scattering angle) was broadened by the distance from the sample to the detector using 0.5m and 1.5m.

Experimental Condition 3: Differential Scanning Calorimetry (DSC)

The DSC thermogram of all synthesized polymer samples was measured using TA Instruments (model Q20). About 5 mg of the sample was placed in an aluminum pan in a glove box filled with argon, and an empty aluminum pan was used as a reference. Thermodynamic properties of between -65 ^° C and 120 ^° C were measured for 5 ^° C / min and 10 ^° C / min temperature rise / cooling rates.

Experimental Condition 4: Rheology

The dynamic storage modulus and loss modulus were measured using an Anton Paar MCR 302 rheometer. The rheometer was fitted with an 8 mm parallel plate and the sample was adjusted to 0.5 mm. All measurements were taken at a strain of 0.1% in a linear viscoelastic regime. Experiments were carried out at a frequency ranging from 0.1 to 100 rad / s at a temperature of 50 ° C. The temperature and the cooling rate were fixed at 0.5 rad / s and 1 ^o C / min.

Test condition 5: Conductivity measurement

The salt-doped samples were measured for through-plane conductivity using a potentiostat (VersaSTAT 3, Princeton Applied Research) in a glove box in an argon environment. Two electrode cells (consisting of a stainless steel blocking electrode and a 1 cm x 1 cm platinum working / counter electrode) were used and the sample thickness was 200 mm.

Experimental Condition 6: Polarization Experiment

Samples doped with salt were placed between two lithium electrodes to conduct polarization experiments. The temperature of the sample was set at 60 ° C, and the polarization current (DV) was observed at 1 V while maintaining the voltage at 0.1 V. All procedures were performed in a glove box in an argon environment.

Experimental Condition 7: Fourier Transform Infrared Spectroscopy (FT-IR)

Infrared spectroscopy was performed using a Bruker Vertex 70 FT-IR spectrophotometer at a constant temperature of 22 ° C. Powder samples (high molecular weight) were averaged 32 times in reflection mode (frequency resolution 1 cm ^-1 ) and liquid samples (low molecular weight) were averaged 16 times in transmission mode. (Frequency resolution 4 cm ^-1 )

[ Example  One]: Nightly ( nitrile ) Substituted polyethylene Oxide  synthesis( PEO  (Synthesis of CN)

Polyethylene glycol methyl ether (Mn = 2000 g / mol, 4.0 g, 2.0 mmol) and acrylonitrile (20 mL) were stirred at 0 ° C for 30 minutes and KOH (10 mg, 0.18 mmol) was added thereto. When the reaction product turned yellow, 5 mL of HCl was added to terminate the reaction. The obtained reaction product was extracted with dichloromethane and the solvent was removed using a rotary evaporator. The obtained polymer was purified using ether. NMR data of the prepared material was measured and shown in PEO-CN of FIG.

^{1 H NMR (300 MHz, CDCl} 3) δ ppm: 3.99-3.43 (n Х 4H, -OCH 2 CH 2 O-), 3.37 (3H, -OCH 3), 2.59 (2H, -OCH 2 CH 2 CN) ,

[ Example  2]: Diethyl Phosphate (diethyl 포스톤 ) Synthesis of Substituted Polyethylene Oxide (Synthesis of PEO (PE)

(Ethylene glycol) methyl ether (Mw = 1) was added to the 50 mL round bottom flask (RBF), and the mixture was stirred at 90 ° C. for 30 minutes. 2000 g / mol, 5 g, 2.5 mmol) was dissolved in 24 mL of acetonitrile and dropped. After three days of reaction, HCl was added to terminate the reaction. The obtained reaction product was extracted with dichloromethane and the solvent was removed using a rotary evaporator. The obtained polymer was purified using ether. The NMR data of the prepared material was measured and shown in the PEO-PE of FIG.

¹ H NMR (300 MHz, D ₂ O)? Ppm: 4.15 (4H, -P═O (OCH ₂ CH ₃ ) ₂ ), 3.99-3.43 (n Х 4H, -OCH ₂ CH ₂ O-), 3.37 _{3H, -OCH 3), 2.26 (} 2H, -PCH 2 CH 2 O-), 1.33 (4H, -P = O (OCH 2 CH 3) 2)

[ Example  3]: Phosphonic acid  Substituted polyethylene Oxide  Synthesis (Synthesis of PEO (PA)

Poly (ethylene glycol) methyl ether (1 g, 0.46 mmol), whose terminal was substituted with phosphonate, was dissolved in 25 mL of chloroform at 0 ° C. Bromotrimethylsilane (0.1 mL, 0.75 mmol) is slowly added dropwise. After reaction at 40 ° C for 15 hours, MeOH was added to terminate the reaction. After completion of the reaction, the solvent was removed using a rotary evaporator. NMR data of the prepared material was measured and shown in the PEO-PA of FIG.

^{1 H NMR (300 MHz, D} 2 O) δ ppm: 3.99-3.43 (n Х 4H, -OCH 2 CH 2 O-), 3.37 (3H, -OCH 3), 1.99 (2H, -PCH 2 CH 2 O -).

[Comparative Example 1]: Synthesis of polyethylene oxide

Ethylene oxide monomer was refined by CaH ₂ for one day and n-butyllithium for 30 minutes with stirring repeatedly twice. Methanol was purified using magnesium and THF to be used as a solvent was purified using benzophenone kethyl. Methanol (0.04 mL, 1 mmol) and t-Bu-P ₄ (1 mL, 1 mmol) are added to purified 100 mL THF and degassed to give a vacuum. The distilled ethylene oxide (5 mL, 100 mmol) is distilled and the reaction is carried out at room temperature for 3 days. The reaction is terminated by adding 0.1 mL of acetic acid. After completion of the reaction, purification was carried out using hexane.

The NMR data of the prepared material was measured and shown in PEO in Fig.

^{1 H NMR (300 MHz, D} 2 O) δ ppm: 3.99-3.43 (n Х 4H, -OCH 2 CH 2 O-), 3.37 (3H, -OCH 3), 1.99

[Comparative Example 2] Synthesis of Polyethylene Oxide Substituted with Two Hydroxyl Groups

A solution of poly (ethylene glycol) methyl ether (Mw = 2000 g / mol, 5 g, 2.5 mmol) in 100 mL of anhydrous benzene was prepared in a 250 mL round bottom flask. Sodium hydride g, 25 mmol). The mixture is reacted at room temperature for 3 hours, then allyl bromide (15 g, 125 mmol) is added dropwise. After reacting for a day, unreacted sodium hydride (NaH) is removed by filtration. The obtained reaction product is dried for 2 days and then reacted. The reaction product (4 g, 2 mmol) was dissolved in 80 mL of anhydrous toluene, thioglycerol (8.6 g, 80 mmol) and AIBN (1.3 mg, 8 mmol) The reaction proceeds at 80 DEG C for 1.5 hours. The solvent was removed from the reaction mixture using a rotary evaporator, and the residue was purified using ether

Experimental Example 1: NMR measurement results

It was confirmed that the PEO-CN polymer of Example 1, in which the nitrile functional group was introduced, had an extremely high substitution efficiency of 99% or more as a result of ¹ H NMR measurement (using AV300, Bruker) of Examples 1 to 3 and Comparative Example 1 there was. The PEO-PE polymer of Example 2 having diethylphosphonate functional group had a high substitution efficiency of 87%, and the phosphonic acid functional group of Example 3 synthesized by hydrolysis thereof was PEO having a hydrolysis efficiency of 100% -PA &lt; / RTI &gt; polymer was synthesized. In the case of such a hydrolysis efficiency, it was also confirmed by the ³¹ P NMR in FIG. 2 that it was 100%.

Experimental Example 2: GPC measurement result (confirmation of crosslinking formation)

The Polydispersity Index (PDI) of each of the polymers synthesized in Examples 1 to 3 and Comparative Example 1 was analyzed by Gel Permeation Chromatography (GPC) analysis (Waters Breeze 2 HPLC , Using Waters). As a result, as shown in Fig. 3, PDI of the polymer of Example 1 (PEO-CN), Example 2 (PEO-PA) and Example 3 (PEO-PE) was 1.03, 1 (PEO). That is, it was confirmed that no crosslinking was formed during the substitution reaction of terminal functional groups.

Experimental Example 3: Results of DSC Measurement (Determination of Effect of Functional Group on Crystallinity of Polymer)

Differential scanning calorimeter (DSC) analysis was performed to analyze the effect of the functional groups on the crystallinity of the polymer. As a result, as shown in Fig. 4 and Table 1, PEO- (OH) ₂ (polymer used in our earlier patent, 10-2017-0029527) of Comparative Example 2 in which two hydroxyl functional groups were introduced and nitrile functional group In the case of the PEO-CN of Example 1 introduced, a further decrease of crystallinity of about 9% was observed compared to PEO of Comparative Example 1. On the other hand, the PEO-PE of Example 2, in which the diethylphosphonate functional group was introduced, had a crystallinity of 53% compared to PEO. In Example 3, which hydrolyzed the phosphonic acid functional group to form PEO, the crystallinity was only 42% I could see that I had. It was found that introduction of terminal functional groups has a great influence on the crystallinity of PEO and it can be a method of improving the room temperature conductivity of the polymer electrolyte.

Sample T _m (° C) ΔH _m (J / g) T _c (° C) ΔH _c (J / g) T _g (° C) Comparative Example 1 PEO 55.2 178.3 33.6 161.7 -65 Comparative Example 2 PEO- (OH) ₂ 54.4 161.4 21.6 136.7 -44 Example 1 PEO-CN 54.1 156.9 28.7 145.8 -19 Example 2 PEO-PE 47.3 91.9 20.8 74.3 -22 Example 3 PEO-PA 53.2 78.8 18.4 66.5 -33

Experimental Example  4: Ion conductivity measurement result

Lithium salt (LiTFSI) was doped with 6% in each of the polymers synthesized in Example 1 (PEO-CN), Example 2 (PEO-PE), Example 3 (PEO-PA) and Comparative Example 1 (r = 0.06), and ionic conductivity was analyzed using Potentiostat (VersaSTAT 3, Princeton Applied Research). As shown in FIG. 5, the conductivity of the polymer of Example 3 (PEO-PA) in which phosphonic acid was bonded at room temperature was increased about 7 times.

When the temperature of the x axis is corrected to T ₀ (= Tg-50K) in consideration of the fact that the glass transition temperature (Tg) of the terminally substituted polymer is improved, as shown in FIG. 6, It was found that the end chemistry effectively increases the ion transport efficiency of the salt doping polymer.

Experimental Example 5: Electrode Polarization Measurement Result

(PEO-CN), Example 3 (PEO-PA) and Comparative Example 1 (PEO) in order to analyze the effect of the interaction between the lithium salt and the functional group on ion diffusion in the electrolyte. Polarization experiments were performed at 46 ° C for samples doped with LiTFSI in each polymer. The potential difference of 0.1 V was applied to the two lithium electrodes to measure the change of the current for 0.5 hour, and the result is shown in FIG. As a result, it was confirmed that the PEO-CN of Example 1 and the PEO-PA of Example 3 had a higher final current value than the general PEO. This is thought to be due to the fact that nitrile and phosphonic acid functional groups present at the end of the polymer effectively dissociate the lithium salt and diffuse lithium despite the slow relaxation of the polymer (increase in Tg).

Sample I _0.5 / I ₀ Comparative Example 1 PEO 0.442 Example 1 PEO-CN 0.619 Example 3 PEO-PA 0.522

Experimental Example  6: Infrared spectroscopy (FT-IR) measurement results

In order to analyze the cause of decrease in crystallinity as in Experimental Example 3, the interaction between the functional group and the polymer and the lithium salt was analyzed through infrared spectroscopy (FT-IR, Fourier transform infrared spectroscopy). The FT-IR measurement results of Examples 1 to 3 and Comparative Example 1 are shown in FIG. 8 to FIG.

As shown in FIG. 8, PA shows hydrogen bond between strong OH functional groups when compared with PEO. This is because the absolute number of OH is about 1.7 times more, and the hydrogen bonding network between phosphonic acids is formed more efficiently.

In the spectrum between 1500 and 800 cm ^{-1 shown in} FIG. 9, the characteristic peaks of the PEO chain represented by vibration (δ), wagging (ω), twisting (τ) and rocking (ρ) And in the case of PA, the intensity decreases remarkably. This is because the crystallinity of the PEO chain is decreased due to the introduction of the diethylphosphonate functional group and the phosphonic acid functional group. This is in good agreement with the DSC results described above.

Also, as shown in FIG. 10, it was confirmed that the IR peak was redshifted by the strong inter- and intra-hydrogen bonding between the terminal OH groups in the case of the phosphorous-bonded PEO.

Also, in order to analyze the effect of the lithium salt, FT-IR spectra of CN, PE, and PA polymers and polyelectrolytes doped with 2% LiTFSI salt were compared with each other as shown in FIGS. 11 to 13.

First, when a lithium salt-doped, as shown in Figure 11, by the nitrile functional group to form a new interaction with the lithium salt is reduced due to the intensity of the peak appearing at 2248 cm ^-1, nitrile at the same time in combination with Li cations in the 2276 cm ^-1 Peaks are newly emerged.

On the other hand, in the case of PA, as shown in FIG. 12, the phosphonic acid functional group forms a strong hydrogen bond with the TFSI anion, and the OH peak at about 3400 cm ^-1 shifts to about 3200 cm ^-1 .

Each polymer synthesized in Example 1 (PEO-CN), Example 2 (PEO-PE), Example 3 (PEO-PA) and Comparative Example 1 (PEO) was doped with 2% LiTFSI salt The FT-IR spectrum of the polymer electrolyte is shown in Fig. Comparing the 1354 and 1146 cm ^-1 peaks attributed to the stretching (ν) of the TFSI anion O = S = O bond, the intensity of the peak in the case of PA increased significantly from 1146 to 1136 cm ^-1 The peak shift can be observed. This result also shows strong hydrogen bonding between PA and anions.

Experimental Example 7: Molecular weight analysis

All the synthesized polymers were precipitated several times by ether, purified and dried for one week at room temperature and vacuum. Experiments were carried out using nuclear magnetic resonance (1H-NMR), and CDCl ₃ and MeOD were used as internal standards. The molecular weight distribution of polymers synthesized on the basis of PS standard was analyzed by gel permeation chromatography (GPC, Waters Breeze 2 HPLC) using THF as a solvent. As a result, the molecular weight of the polymers prepared in Examples 1 to 3 and Comparative Examples 1 and 2 was 1 to 20 kg / mol.

[ Manufacturing example  1]: the terminal is an allyl group ( allyl  group) to  Substituted polyethylene Oxide  Synthesis (synthesis of SEO-ene)

Prepare a solution of PS- b- PEO (200 mg, 0.014 mmol) using 4 mL anhydrous benzene in a 50 mL round bottom flask and add sodium hydride (NaH, 3.4 mg, 0.14 mmol) to the solution. The mixture is reacted at room temperature for 3 hours and then allyl bromide (87 mg, 0.72 mmol) is added dropwise. After reacting for a day, unreacted sodium hydride (NaH) is removed by filtration.

^{1 H NMR (500 MHz, CDCl} 3) δ ppm: 7.10-6.40 (b, n Х 5H, CH 2 CH (C 6 H 5)), 5.95-5.87 (m, 1H, CH = CH 2), 5.29- 5.16 (m, 2H, CH = CH 2), 4.0 (d, 2H, OCH 2 CH = CH 2), 3.64 (b, n Х 4H, -OCH 2 CH 2 O-), 2.21-1.20 (b, n 3H, CH ₂ CH (C ₆ H ₅ )).

[ Example  4]: Thioglycolic acid  ( thioglycolic  acid) (Synthesis of SEO-c)

SEO-ene (80 mg, 0.0057 mmol), thioglycolic acid (10.57 mg, 0.1147 mmol) and AIBN (1.9 mg, 0.0114 mmol) prepared in Preparation Example 1 were added to a 50 mL round- And dissolved in 1.6 mL anhydrous toluene. The reaction proceeds at 80 DEG C for 2.5 hours.

¹ H NMR (500 MHz, CDCl ₃ )? Ppm: 7.10-6.30 (b, n Х 5H, CH ₂ CH (C ₆ H ₅ )), 3.56 (b, n Х 4H, -OCH ₂ CH ₂ O-) , 3.23 (s, 2H, -SCH 2 COOH), 2.78-2.75 (t, 2H, -CH 2 SCH 2 COOH), 2.21-1.20 (b, n ХХ 3H, CH 2 CH (C 6 H 5)).

[ Example  5]: Mercapto  Succinic acid ( mercaptosuccinic  acid) (Synthesis of SEO-2c)

SEO-ene (85 mg, 0.0061 mmol), mercaptosuccinic acid (36.6 mg, 0.244 mmol) and AIBN (4 mg, 0.0244 mmol) prepared in Preparation Example 1 were placed in a 50 mL round- In 1.7 mL of anhydrous dioxane. The reaction proceeds at 80 DEG C for 1.5 hours.

¹ H NMR (500 MHz, CDCl ₃ and MeOD (5: 1)) δ ppm: 7.10-6.30 (b, n Х 5H, CH ₂ CH (C ₆ H ₅ )), 3.56 OCH ₂ CH ₂ O- and 1H of -C (H) COOH), 2.88-2.56 (m, 2H of -CH ₂ COOH and 2H of -CH ₂ S-), 2.20-1.20 _{2 CH (C 6 H 5)} ).

[ Example  6]: Thioglycerol  ( thioglycerol ) Polyethylene &lt; RTI ID = 0.0 &gt; Oxide  Synthesis (synthesis of SEO-2h)

SEO-ene (85 mg, 0.0061 mmol), thioglycerol (26.4 mg, 0.244 mmol), and AIBN (4 mg, 0.0244 mmol) prepared in Preparation Example 1 were added to a 50 mL round bottom flask under an argon atmosphere It is dissolved in 1.7 mL of anhydrous toluene. The reaction proceeds at 80 ° C for 1.5 hours.

¹ H NMR (500 MHz, CDCl ₃ )? Ppm: 7.10-6.30 (b, n Х 5H, CH ₂ CH (C ₆ H ₅ )), 3.64 (b, n Х 4H of -OCH ₂ CH ₂ O- and 3H of thioglycerol), 2.66-2.63 (m , 4H, -CH 2 SCH 2 -), 2.20-1.20 (b, n ХХ 3H, CH 2 CH (C 6 H 5))

Experimental Example 8 Synthesis of End-Substituted PS-b-PEO Block Copolymer

As in Examples 4 to 6, PS-b-PEO block copolymers substituted with different kinds and numbers of end groups were synthesized. As can be seen from Fig. 14, PS-b-PEO (7.4-6.5 kg / mol) in which the end of PEO was the -OH group was first replaced with an allyl bromide group under sodium hydride (NaH). Then, different terminal groups can be introduced through a thiol-ene coupling reaction using thiolating agents (thioglycolic acid, mercaptosuccinic acid, thioglycerol). SEO, SEO-c, SEO-2h, SEO, SEO, SEO, SEO, SEO, SEO, SEO, -2c. PEO-h, PEO-ene, PEO-c PEO-2h and PEO-2c were synthesized by a similar reaction to the PEO homopolymer (5.0 kg / mol). All samples with terminal substitutions for PEO have an increase in molecular weight of less than 0.19 kg / mol.

15A shows the &lt; 1 &gt; H-NMR spectra of SEO-ene, SEO-c, SEO-2h and SEO-2c. We confirmed that SEO-c, SEO-2h, and SEO-2c were successfully synthesized by the disappearance of peaks at 5.94-5.88 ppm and 5.29-5.16 ppm in the spectrum and the creation of new peaks at 3.30-2.50 ppm. Based on NMR data, it was confirmed that the degree of terminal substitution was 95% or more. It was confirmed by gel permeation chromatography (GPC) of Fig. 15B that no side reaction or cross linking occurred.

From the FT-IR spectrum of FIG. 15C, it can be seen that the OH stretching peak appearing between 3700-3100 cm ^-1 is approximately proportional to the number of terminal groups. Also, it can be seen that the C = O peak at 1750-1700 cm ^-1 in the spectrum of SEO-c and SEO-2c is related to the number of terminal -COOH groups. Terminal substitution FT-IR analysis was further discussed in the analysis of intermolecular interactions.

Experimental Example  9: SEO  The structure of the block copolymer (Morphology) and Viscoelastic  (Viscoelastic) analysis

Next, we examined the structure of SEO block copolymers with terminal substitution. FIG. 16 shows SAXS data at 60 DEG C of the prepared samples. SEO-h samples with one -OH showed only one bragg peak at q ^* = 0.363 nm ^-1 . The SEO-c sample with -COOH at the end is similar in q ^* (domain spacing, d ₁₀₀ = 17.3 nm) 1 q ^* : bragg of 2 q ^* respectively. This result implies the formation of an ordered lamellar structure. Compared with SEO-h, it can be seen that the scattering intensity increases markedly at low q values, which is considered to be the effect of the formation of the structure by the introduction of -COOH at the terminal.

q ^*,

q ^*,

q ^*,

q ^*,

q ^*, 그리고

q ^* bragg peak을 관찰 할 수 있었으며, 이는 잘 정렬된 자이로이드 (gyroid) 구조를 의미한다. Domain spacing (d ₂₁₁) 은 SEO-2h 가 18.4 nm, SEO-2c 가 18.8 nm 로 눈에 띄게 증가한 것을 관찰할 수 있었는데, 이는 말단의 다이올 (diol), 디카르복시산 (dicarboxylic acid)에 의해 free volume이 증가한 결과라고 생각된다. 전체적으로, 이 결과를 통해 말단 작용기를 PEO 사슬에 도입하면 결정성이 감소하여 free volume이 증가하는 것이라 해석할 수 있다. 결정성 PEO의 밀도는 1.21 g/cm³ 인 반면 무정형 PEO의 밀도는 1.12 g/cm³ 이다. Both SEO-2h and SEO-2c, when attaching two ends to the PEO chain of SEO

q ^* ,

q ^* ,

q ^* ,

q ^* ,

q ^* , and

The q ^* bragg peak was observed, which means a well-ordered gyroid structure. Domain spacing ( d ₂₁₁ ) showed a remarkable increase in SEO-2h of 18.4 nm and SEO-2c of 18.8 nm, which was attributed to the free diol, dicarboxylic acid, and free volume Is expected to increase. Overall, it can be interpreted that the incorporation of terminal functional groups into the PEO chain results in a decrease in crystallinity and an increase in free volume. The density of crystalline PEO is 1.21 g / cm ³ while the density of amorphous PEO is 1.12 g / cm ³ .

In the DSC data inserted in FIG. 16, SEO samples (SEO-c, SEO-2c, and SEO-2h) which introduced the end showed lower heat of fusion (ΔH _m ) than SEO-h. The crystallinity calculated using 100% crystallinity when the heat of fusion (ΔH _m ) = 215.6 J / g (PEO homopolymer) was 60.3% for SEO-h, SEO-c, SEO-2h and SEO- , 36.0%, 27.9%, and 31.8%, respectively. It is interesting to note that the concentration of the group introduced at the end is less than 1 mol% and thus shows a decrease in crystallinity.

The introduction of end groups to SEO also has an important effect on linear viscoelastic properties. The storage stability (storage, G ') and loss (G ") elastic modulus of the samples substituted at the end of Figure 17a were measured at a rate of 1 ° C / min from 80 ° C. The modulus of the stable state (indicated by the dotted line) is significantly increased when the terminal group is introduced (G '= 0, 17-MPa (SEO-h), 35 MPa (SEO-c), 122 MPa (SEO-2h), and 121 MPa (SEO-2c). SEO-2h and SEO-2c have a cubic symmetry In the case of PEO homopolymer, the modulus was decreased regardless of the end group, and the number of the end groups Has a big impact on the mechanical strength of SEO Conclusions can be built.

Figure 17b directly compares the modulus and viscoelastic properties of SEO-2c and PEO-2c. As a result of observing the frequency change at a specific temperature (323 K), PEO-2c showed a reaction of viscoelastic solid (G '(w) ~ G "(w) ~ w ^1/4 ) -2c is PEO-2c more showed a higher modulus greater than or equal to 10 ³ times, dependent on the frequency was about (G '(w) ~ w 0.12, G "(w) ~ w 0.03). The results show that the characteristics of the cube and elastic behavior are exhibited by the glassy state of the PS block.

Ion Conduction Properties of Polymer Electrolyte Membranes with Terminal Functional Groups

Next, samples with terminal group substitution were doped with lithium salt to investigate ion conduction characteristics. 18A shows the results of measurement of ion conduction characteristics of samples doped with r = 0.02 ( r = [Li ⁺ ] / [EO]) salt using AC impedance spectroscopy. As a result, it was clearly observed that conductivity at room temperature was much improved when terminal was substituted, and the substance having carboxylic acid introduced most significantly lowered the crystallinity of PEO. The similar ion conduction characteristics were obtained when the temperature was raised for all the samples. If the introduction of the end-groups the glass transition temperature (glass transition temperature) is ^{-65 o C (SEO-h)} , -45 o C (SEO-c), -44 o C (SEO-2h), and -37 ^o C (SEO-2c), the improvement in conductivity is a very interesting result. In particular, SEO-2h and SEO-2c are three to seven times more robust than SEO-h. When the lithium salt is doped with r = 0.02, the structure of SEO-c, SEO-2h, and SEO-2c is maintained, and SEO-h increases the segregation strength between PS and PEO including salt to form a lamellar structure .

Although all the samples converge to similar conductivities at high temperatures, we observed a significant improvement in the lithium transference number ( T _Li ⁺ ) with the diol group. Figure 18b shows the T _Li ⁺ value at 60 ° C. The samples doped with lithium salt at r = 0.02 were analyzed by polarization experiment and the polarization voltage ( DV ) was maintained at 0.1 V, and the current was measured between two lithium electrodes. SEO-h showed a T _Li ⁺ value of 0.25, which is consistent with the values of typical PEO and lithium salt composite electrolyte membranes reported in the literature. The introduction of carboxylic acid into the terminal group did not improve T _Li ⁺ , but when a diol group was introduced T _Li ⁺ was nearly doubled (0.48). FIG. 18B shows results of sample polarization experiments in which -OH and - (OH) ₂ were introduced at the terminals. The mechanism of such a result will be discussed in the next chapter.

FIG. 18C shows the conduction characteristics when the salt is doped at r = 0.06, and shows a lamellar structure regardless of the terminal group. DSC data confirmed that all samples were amorphous. Samples with carboxylic acid termini exhibited the lowest conduction characteristics, which are believed to be due to slow segmental motion due to internal dipole-dipole interactions. The notable point is that SEO-2h has higher conductivity than SEO-h at higher temperatures. Even if the salt concentration was increased, T _Li ⁺ was improved by a factor of two in the case of the diol group, and the other samples were very high at about 0.2. Potential barriers obtained by fitting the conductivity data to the Vogel-Tammann-Fulcher (VTF) equation are 974 K, 1181 K, 1380 K for SEO-h, SEO-c, SEO- , And 1227K.

Inter- and Intramolecular Interactions by End Groups on PEO

FT-IR spectroscopy was used for in-depth study of inter- and intramolecular interactions in PEO. Samples were prepared by replacing terminal groups with low molecular weight PEO (0.55 kg / mol) to emphasize the end group signals. This increased the concentration of the terminal group to 8 mol%. The synthesized polymers were liquid phase, filled between CaF ₂ window and observed FT-IR spectrum. The CH stretching peak near 2900 cm ^-1 was used as the internal standard.

We first analyzed PEO samples not doped with lithium salt to examine the effect of end group number and type. Figure 19a, the FT-IR obtained in 22 ℃, 3700-2600 cm ^-1 region Spectrum. Comparing the spectra of PEO-h and PEO-2h, the red-shift (41 cm ^-1 ) was observed and the intensity of the band by OH stretching was increased. This can be thought of as coming from intra-chain hydrogen bonding, as it is usually less shifted than the band of hydrogen bonds seen in the inter-chain. This result implies that simply increasing the number of -OH terminal groups can dramatically change the chain form. These changes eventually play an important role in the crystallinity of PEO, which can be confirmed by DSC and rheology measurements.

PEO-c and PEO-2c samples also showed peaks due to OH stretching. However, a very broad, low-intensity peak was observed in the region of 3000-3700-cm ^-1 , which means that the carboxylic acid at the terminal is actively hydrogen bonding with the ether oxygen in the chain.

Notably, PEO-c and PEO-2c are visible at 1850-1600 cm ^-1 The C = O stretching peak is very different. PEO-c showed three peaks while PEO-2c showed one peak. This difference was due to the hydrogen bonding and the quadrupole formation by forming a dimer with the fact that -COOH at the terminal of PEO-c was adjacent to the PEO- (Quadrupole interactions). In contrast, PEO-2c did not interact well with steric hindrance.

In the presence of lithium salt, hydrogen bond interaction between TFSI-anion and PEO terminal group was observed at the same time as COC vibration. These interactions are more pronounced when introducing hydroxyl groups. FIG. 19d shows the data of PEO-2h, and a broad and red-shifted band due to OH stretching can be observed. When the background is removed by using the PEO-2h spectrum, OH stretching can be observed at 3332 cm ^-1 and 3542 cm ^-1 . These results are attributed to the contribution of the hydrogen bond between the OH group and the TFSI-anion and the coordination between the OH group and the lithium ion, respectively. The blue shifting while coordinating with lithium ions is based on the B3LYP exchange-correlation functional and is based on a net theoretical calculation using the density functional theory ( Ab Intio calculation) was used.

These results show that SEO with a diol group at the terminal shows high T _Li ⁺ because it has the effect of stabilizing the anion with the hydrogen bond between terminal and anion. This led us to conclude that increasing the number of terminal groups is an effective way to increase the conduction characteristics and the lithium ion transport rate.

In the case of PEO-c and PEO-2c doped with lithium salt, a new peak due to C = O stretching was observed in the low frequency region, which means that the terminal -COOH group interacts with lithium ion . Therefore, when the terminal is -COOH, it is explained that the lithium ion is bound by the interaction with the terminal and exhibits a low conduction characteristic. (Fig. 18C).

20A shows PEO-h having crystallinity and PEO-c forming dimer and PEO-2h having intramolecular hydrogen bonding. In the presence of lithium (Fig. 20b), lithium ion primarily coordinates with ether oxygen in the main chain of PEO, and the terminal group and the anion of the lithium salt undergo hydrogen bonding. Samples with diol groups at the ends showed higher conduction characteristics and lithium ion transport rates than samples with dicarboxylic acid at the ends, since they did not undergo quadrupole interactions.

The self-assembly, linear viscoelastic properties and ion conduction properties of PS-b-PEO block copolymers were investigated through end groups. To summarize the two important results of this study, the introduction of several groups at the PEO end of the PE-b-PEO block copolymer increases the free volume of the PEO and changes the chain conformation of the PEO, continuous or amorphous PEO phase can be obtained. These changes had a profound effect on the room temperature conductivity (~ 30-fold increase) and linear viscoelastic properties (3-7 fold increase). Particularly, when a diol group was used as a terminal, high ion conduction efficiency was observed over the entire operating temperature range, which is considered to be useful as a dry polymer electrolyte membrane. Secondly, regardless of the end group, the lithium ion transport rate was greatly improved by hydrogen bonding with the anion of the lithium salt. The method of controlling the density of the end groups proposed in this study can solve the low lithium ion transport rate which is a fundamental disadvantage of the electrolyte membrane doped with PEO and can be utilized in the production of the solid polymer electrolyte membrane to develop the next generation energy storage device Is expected to make a major contribution to

Claims (15)

Poly (ethylene oxide) (PEO) -based polymer; And Lithium salts; &Lt; / RTI &gt; Wherein the terminal of the polyethylene oxide polymer is substituted by a sulfur compound functional group, a nitrogen compound functional group or a phosphorus compound functional group. The method according to claim 1, Wherein the nitrogen compound functionality is nitrile, amine, pyridine or imidazole and the phosphorus compound functionality is diethyl phosphonate or phosphonic acid, Polymer electrolyte. The method according to claim 1, Wherein the polyethylene oxide polymer is represented by any one of the following Chemical Formulas (1) to (3). [Chemical Formula 1]

(2)

(3)

Wherein n is an integer of from 10 to 120, and R is an alkyl chain having from 1 to 4 carbon atoms. The method according to claim 1, Wherein the sulfur compound functional group has a functional group represented by the following general formula (4). [Chemical Formula 4] -S-R (Wherein R is a carboxyl group having 1 to 4 carbon atoms, a diol group, or a dicarbonyl group) 5. The method of claim 4, And -R is at least one selected from the functional groups represented by the following formulas (5) (a) to (5c).

(5) The method according to claim 1, The polyethylene oxide polymer is a block copolymer containing a polyethylene oxide block, Wherein the end of the polyethylene oxide block is substituted with a sulfur compound functional group. The method according to claim 1, The lithium salt is _{LiCl, LiBr, LiI, LiClO 4} , LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF 6, LiSbF 6, LiAlCl 4, CH 3 SO 3 Li, CF ₃ SO ₃ Li, LiSCN, LiC (CF ₃ SO ₂ ) ₃ , (CF ₃ SO ₂ ) ₂ NLi, (FSO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic carboxylate lithium, And bis (trifluoromethanesulfonyl) imide (LiTFSI). The method according to claim 1, Wherein the polymer has a molecular weight of 1 to 20 kg / mol. The method according to claim 1, Wherein a ratio of [Li +] / [EO] of the polymer [EO] and the lithium salt in the polymer electrolyte is between 0.02 and 0.08. The method according to claim 1, Wherein the polymer electrolyte has an ion transporting property of 10 ^-5 to 10 ^-3 S / cm. The method according to claim 1, The polymer electrolyte is a solid electrolyte for all solid-state batteries,  (a) modifying the end of the polyethylene oxide polymer by adding a sulfur compound, a nitrogen compound or a phosphorus compound to a poly (ethylene oxide) (PEO) based polymer; And (b) adding a lithium salt. 13. The method of claim 12, In the step (a), the nitrogen compound may be a nitrile compound, an amine compound, a pyridine compound, or an imidazole compound, and the phosphorus compound may be diethyl phosphate diethyl phosphonate-based compound or a phosphonic acid-based compound. 13. The method of claim 12, In the step (a), the sulfur compound is thionyl glycolic acid, mercapto succinic acid, or thioglycerol. A solid-state battery comprising a positive electrode, a negative electrode, and a solid polymer electrolyte interposed therebetween, Wherein the solid polymer electrolyte is a polymer electrolyte according to any one of claims 1 to 11.

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