Gel polymer electrolyte, electrochromic device comprising the same and production method thereof

Abstract

The present application relates to a gel polymer electrolyte, a method for producing a gel polymer electrolyte, and an electrochromic device comprising the same. As the gel polymer electrolyte comprises a block copolymer, the present application can simultaneously satisfy high ionic conductivity, low turbidity and adhesiveness.

Claims

1. A gel polymer electrolyte comprising (i) a block copolymer which comprises a first block comprising a unit of Formula 1 below; and a second block comprising a unit containing an amino group, a hydroxy group or polyalkylene oxide and a unit derived from polymerizing a monomer of Formula 2 below: ##STR00004## wherein, A in Formula 1 is an alkylene group having 1 to 8 carbon atoms, and in Formula 2, Q is hydrogen or an alkyl group having 1 to 20 carbon atoms and B is an alkyl group having 1 to 32 carbon atoms, an aromatic hydrocarbon having 6 to 32 carbon atoms or a carboxyl group, and (ii) a glycolic oligomer, wherein the glycolic oligomer comprises one or more of a polypropylene glycolic oligomer, a polyethylene glycolic oligomer, a polyethylene imine oligomer and an aniline oligomer.

2. The gel polymer electrolyte according to claim 1, wherein B in Formula 2 is an alkyl group having 1 to 32 carbon atoms.

3. The gel polymer electrolyte according to claim 1, wherein the second block comprises a unit represented by Formula 3 below: ##STR00005## wherein, Q is hydrogen or an alkyl group having 1 to 20 carbon atoms, X is an alkylene group having 1 to 8 carbon atoms, Y is —OR.sub.2 or —NR.sub.3R.sub.4, where R.sub.2, R.sub.3 and R.sub.4 are each independently hydrogen, an alkyl group having 1 to 32 carbon atoms, an aromatic hydrocarbon having 6 to 32 carbon atoms or a carboxyl group, and m is an integer of 1 to 20.

4. The gel polymer electrolyte according to claim 1, wherein the second block further comprises a unit derived from polymerizing a monomer having a cross-linkable functional group.

5. The gel polymer electrolyte according to claim 1, wherein the block copolymer comprises 10 to 500 parts by weight of the second block relative to 100 parts by weight of the first block.

6. The gel polymer electrolyte according to claim 1, further comprising one or more lithium salts selected from the group consisting of LiF, LiCl, LiBr, LiI, LiClO.sub.4, LiClO.sub.3, LiAsF.sub.6, LiSbF.sub.6, LiAlO.sub.4, LiAlCl.sub.4, LiNO.sub.3, LiN(CN).sub.2, LiPF.sub.6, Li(CF.sub.3).sub.2PF.sub.4, Li(CF.sub.3).sub.3PF.sub.3, Li(CF.sub.3).sub.4PF.sub.2, Li(CF.sub.3).sub.5PF, Li(CF.sub.3).sub.6P, LiSO.sub.3CF.sub.3, LiSO.sub.3C.sub.4F.sub.9, LiSO.sub.3(CF.sub.2).sub.7CF.sub.3, LiN(SO.sub.2CF.sub.3).sub.2, LiN(SO.sub.2CaF.sub.2a+1)(SO.sub.2C.sub.bF.sub.2b+1) (provided that a and b are each a natural number), LiOC(CF.sub.3).sub.2CF.sub.2CF.sub.3, LiCO.sub.2CF.sub.3, LiCO.sub.2CH.sub.3, LiSCN, LiB(C.sub.2O.sub.4).sub.2, LiBF.sub.2(C.sub.2O.sub.4) and LiBF.sub.4.

7. The gel polymer electrolyte according to claim 1, further comprising a polar solvent.

8. The gel polymer electrolyte according to claim 7, wherein the polar solvent comprises one or more of a carbonate-based compound, an ether-based compound and an ester-based compound.

9. The gel polymer electrolyte according to claim 1, further comprising a unit derived from polymerizing a multifunctional (meth)acrylate.

10. An electrochromic device comprising a first electrode; an electrochromic layer; the gel polymer electrolyte of claim 1; an ion storage layer; and a second electrode.

11. A method for producing a gel polymer electrolyte comprising coating a composition between a plurality of release films, the composition comprising (i) a block copolymer which comprises a first block comprising a unit of Formula 1 below; and a second block comprising a unit containing an amino group, a hydroxyl group or polyalkylene oxide and a unit derived from polymerizing a monomer of Formula 2 below: ##STR00006## wherein, A in Formula 1 is an alkylene group having 1 to 8 carbon atoms, and in Formula 2, Q is hydrogen or an alkyl group having 1 to 20 carbon atoms and B is an alkyl group having 1 to 32 carbon atoms, an aromatic hydrocarbon having 6 to 32 carbon atoms or a carboxyl group, and (ii) a glycolic oligomer, wherein the glycolic oligomer comprises one or more of a polypropylene glycolic oligomer, a polyethylene glycolic oligomer, a polyethylene imine oligomer and an aniline oligomer; and curing the composition.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram of a structure of an electrochromic device comprising a gel polymer electrolyte according to the present application.

(2) FIG. 2 is a color-switching driving image of the electrochromic device according to Examples and Comparative Examples.

MODE FOR INVENTION

(3) Hereinafter, the present application will be described in detail by way of examples, but the scope of the present application is not limited by the following examples.

Preparation Example 1. Preparation of Block Copolymer (GP1)

(4) To prepare an initiator for atom transfer radical polymerization (ATRP), 3 equivalents of triethylamine (TEA) and 2 equivalents of 2-bromoisobutyryl bromide are added relative to 1 equivalent of the terminal hydroxy (mPEG-OH) of polyethylene glycol and reacted. In order to remove impurities, the reaction product was dissolved in a diethyl ether solvent to recover a precipitate, which was repeated twice and then dried.

(5) The prepared initiator has bromine at the end of the polyethylene glycol (PEG) polymer, where 49 parts by weight of the prepared initiator is dissolved in ethanol as a reaction solvent and 43 parts by weight of methyl methacrylate, 2.25 parts by weight of polyethylene glycol-acrylate and 4.75 parts by weight of hydroxypropyl methacrylate are introduced thereto. The flask is sealed with a rubber membrane, and the dissolved oxygen is removed through nitrogen bubbling for 30 minutes while stirring at room temperature. Thereafter, the flask was immersed in an oil bath at 60° C., and a catalyst solution and a catalyst reducing agent were added thereto, and the reaction was carried out for 24 hours. As the ATRP catalyst, 100 ppm of copper bromide (CuBr.sub.2) and 2 equivalents of tris(2-pyridylmethyl)amine (TPMA) relative to copper were dissolved in acetonitrile (CAN) and used. As the catalyst reducing agent, 6 equivalents (relative to Cu) of 2,2′-azobis(2.4-dimethylvaleronitrile) (V-65) was used.

(6) The prepared block polymer is dissolved in ethyl acetate. This was immersed in an oil bath set at 60° C. under an oxygen pressure, and then 1 equivalent of 2-isocyanatoethyl acrylate (AOI) and 0.1 equivalents of dibutyltin dilaurate (DBTDL) relative to the hydroxy functional group of the hydroxypropyl methacrylate were added thereto and stirred for 4 hours, where the hydroxy functional group and the isocyanate group of 2-isocyanatoethyl acrylate were subjected to urethane reaction to introduce the acryloyl group. After completing the reaction, the reactant is precipitated in a cold mixed solution of isopropyl alcohol:hexane=1:1 and purified. The block weight ratio (first block:second block) of the prepared block copolymer (GP1) was confirmed to be 50:50.

Preparation Example 2. Preparation of Block Copolymer (GP2)

(7) An initiator was prepared in the same manner as in Preparation Example 1. A block copolymer was prepared in the same manner as in Preparation Example 1, except that 64 parts by weight of the prepared initiator was dissolved in ethanol and 29.75 parts by weight of methyl methacrylate, 1.75 parts by weight of polyethylene glycol-acrylate and 3.5 parts by weight of hydroxypropyl methacrylate were added. The block weight ratio (first block:second block) of the prepared block copolymer (GP2) was confirmed to be 65:35.

Preparation Example 3. Preparation of Block Copolymer (GP3)

(8) An initiator was prepared in the same manner as in Preparation Example 1. A block copolymer was prepared in the same manner as in Preparation Example 1, except that 79 parts by weight of the prepared initiator was dissolved in ethanol and 17 parts by weight of methyl methacrylate, 1 part by weight of polyethylene glycol-acrylate and 2 parts by weight of hydroxypropyl methacrylate were added. The block weight ratio (first block:second block) of the prepared block copolymer (GP3) was confirmed to be 80:20.

Preparation Example 4. Preparation of Block Copolymer (GP4)

(9) An initiator was prepared in the same manner as in Preparation Example 1. A block copolymer was prepared in the same manner as in Preparation Example 1, except that 49 parts by weight of the prepared initiator was dissolved in ethanol and 43.5 parts by weight of methyl methacrylate, 2.5 parts by weight of N,N-dimethylaminoethyl methacrylate and 4 parts by weight of hydroxypropyl methacrylate were added. The block weight ratio (first block:second block) of the prepared block copolymer (GP4) was confirmed to be 50:50.

Preparation Example 5. Preparation of Block Copolymer (GP5)

(10) An initiator was prepared in the same manner as in Preparation Example 1, and a block copolymer was prepared in the same manner as in Preparation Example 1, except that 49 parts by weight of the prepared initiator was dissolved in ethanol and 46 parts by weight of methyl methacrylate and 4 parts by weight of hydroxypropyl methacrylate were added. The block weight ratio (first block:second block) of the prepared block copolymer (GP5) was confirmed to be 50:50.

Preparation Example 6. Preparation of Random Copolymer (GP6)

(11) 2 parts by weight of polyethylene glycol-acrylate purchased from a reagent manufacturer (Sigma Aldrich), 43.5 parts by weight of methyl methacrylate and 4.5 parts by weight of hydroxypropyl methacrylate are introduced thereto. The flask is sealed with a rubber membrane, and the dissolved oxygen is removed through nitrogen bubbling for 30 minutes while stirring at room temperature. Thereafter, the flask was immersed in an oil bath at 60° C., and a catalyst solution and a catalyst reducing agent were added thereto, and the reaction was carried out for 24 hours. As the ATRP catalyst, 100 ppm of copper bromide (CuBr.sub.2) and 2 equivalents of tris(2-pyridylmethyl)amine (TPMA) relative to copper were dissolved in acetonitrile (CAN) and used. As the catalyst reducing agent, 6 equivalents (relative to Cu) of 2,2′-azobis(2.4-dimethylvaleronitrile) (V-65) was used.

(12) The prepared random polymer is dissolved in ethyl acetate. This is immersed in an oil bath set at 60° C. under an oxygen pressure, and then 1 equivalent of 2-isocyanatoethyl acrylate (AOI) and 0.1 equivalents of dibutyltin dilaurate (DBTDL) relative to the hydroxy functional group of the hydroxypropyl methacrylate were added thereto and stirred for 7 hours. After completing the reaction, the reactant is precipitated in a cold mixed solution of isopropyl alcohol:hexane=1:1 and purified.

Example 1

(13) Preparation of Coating Liquid

(14) A mixed liquid of 1.0 g of the block copolymer (GP1) prepared in Preparation Example 1, 1.0 g of polypropylene glycol, 4 g of LiClO.sub.4 dissolved in propylene carbonate, 0.2 g of pentaerythritol triacrylate and 0.3 g of a radical initiator (Irgacure 819, a product from Ciba) is mixed with the homogenizer at 600 rpm for 3 hours or more to blend well. Then, to remove bubbles generated in the solution, the lid of the container is slightly opened and left for 3 hours. All processes proceed in a yellow room state where UV is blocked.

(15) Preparation of Polymer Electrolyte

(16) A predetermined amount of the coating liquid is applied between release films, and the film is covered. Then, a Bakers applicator is used to make a uniform thickness. If it is placed in a UV curing unit and cured for 1 minute, a polymer electrolyte in a freestanding film state can be obtained. The transmittance, turbidity, ionic conductivity and the like of the formed polymer electrolyte were measured.

(17) Manufacture of Electrochromic Device

(18) An electrochromic layer such as WO.sub.3 and PB was prepared on an ITO film, and then the polymer electrolyte film cured to a uniform thickness on the release film was laminated on the electrochromic layer, where the electrochromic layer was bonded in a sandwich form on both sides. The performance of the device according to the applied voltage was measured.

Examples 2 to 5 and Comparative Examples 1 to 3

(19) A gel polymer electrolyte was prepared in the same manner as in Example 1, except that components and ratios were adjusted as shown in Table 1 upon preparing the coating liquid.

(20) TABLE-US-00001 TABLE 1 Lithium Copolymer Glycolic Multifunctional Radical salt Used polymer (meth)acrylate initiator (LiClO.sub.4) Kind amount (PPG) (PETA) (Irgacure 819) Example 1 4 GP1 1.0 1.0 0.2 0.3 Example 2 4 GP2 1.0 1.0 0.2 0.3 Example 3 4 GP3 1.0 1.0 0.2 0.3 Example 4 4 GP4 1.0 1.0 0.2 0.3 Example 5 4 GP4 0.5 1.5 0.2 0.3 Comparative Example 1 4 GP5 1.0 1.0 0.2 0.3 Comparative Example 2 4 GP6 1.0 1.0 0.2 0.3 Comparative Example 3 4 — 0 0 2.2 0.3 LiClO.sub.4: 1M concentration in propylene carbonate (PC) Ratios of the polymer and PPG are changed in a state fixed with a weight ratio of lithium salt:copolymer/glycolic oligomer:cross-linkable monomer:radical initiator = 4:2:0.2:0.3 PPG: polypropylene glycol PETA: pentaerythritol triacrylate Unit: part by weight

Experimental Example 1. Evaluation of Block Ratio and Molecular Weight of the Prepared Copolymer

(21) The block ratios and molecular weights of the prepared copolymers were evaluated by the following methods and shown in Table 2 below.

(22) Specifically, the polymer solution from which the catalyst was completely removed was solidified through a purification step, and then the block ratio of the block polymer was confirmed through .sup.1H NMR analysis. The purification of the polymer solution was carried out by passing the polymer solution through an alumina column to remove the copper complex catalyst and then dropping it to an excess amount of diethyl ether under stirring to remove the residual monomer, thereby solidifying the polymer. The solidified polymer was dried in a vacuum oven for 24 hours. The block polymer purified by the above method was dissolved in a CDCl.sub.3 solvent and measured by nuclear magnetic resonance (.sup.1H NMR) analysis equipment. As a result of the analysis, 1H peak derived from CH.sub.2═C(CH.sub.3)— of the acrylate monomer double bond end was not confirmed, whereby it was confirmed that the unreacted monomer was not present. Also, the 3H peak derived from —OCH.sub.3 of the ethylene glycol block end was confirmed at around 3.2 ppm, and on the basis of this, the ratio and the molecular weight of each polymer block were calculated. Since peaks of about 450 H derived from —CH.sub.2CH.sub.2O— of ethylene glycol formed into the polymer (4H×113 repeating units) appeared in the region of 3.6 to 3.8 ppm and 3H peaks derived from —CH.sub.3 adjacent to the main chain of methyl methacrylate formed into the polymer appeared in the region of 3.5 to 3.6 ppm, the content of each constituent monomer was calculated as a mass fraction by calculating their area ratios. Since 2H peaks derived from —OCH.sub.2— adjacent to COO— of dimethylaminoethyl methacrylate and 2-isocyanate methyl acrylate formed into the copolymer appeared in the regions of 4.0 to 4.2 ppm and 3.9 to 4.0 ppm, respectively, the content of each constituent monomer was calculated as a mass fraction through their area ratios.

(23) TABLE-US-00002 TABLE 2 Second block Molecular Block weight ratio polymerized weight Dispersion (first block/second unit weight ratio (Mw) degree block) (PMMA/X/AOI) GP1.sup.a 17,000 1.16 50/50 86/4.5/9.5 GP2.sup.a 12,000 1.18 65/35 85/5/10 GP3.sup.a 12,000 1.10 80/20 85/5/10 GP4.sup.b 26,000 1.20 50/50 87/5/8 GP5.sup.a 16,000 1.18 50/50 92/0/8 GP6.sup.a 25,000 1.43 87/4/9 .sup.aX: polyethylene glycol-acrylate (PEG-acrylate) .sup.bX: N,N-dimethylaminoethyl methacrylate (DMAEMA)

Experimental Example 2. Evaluation of Physical Properties of Gel Polymer Electrolyte Film

(24) The gel polymer electrolyte compositions of Examples 1 to 5 and Comparative Examples 1 to 3 were each applied to a release film to a constant thickness and then UV cured to prepare a gel polymer electrolyte film. The physical properties of the prepared polymer electrolyte film were evaluated and shown in Table 3.

(25) The transmittance of the gel polymer electrolyte film was measured based on a 550 nm wavelength of the UV-VIS spectrum and the turbidity was measured using a haze meter, where it means that the smaller the value is, the more the transparency is.

(26) The ionic conductivity was obtained by measuring impedance and then using Equation 1 below. A gel polymer electrolyte film sample having constant width and thickness was prepared for measurement. A stainless steel (SUS) substrate having excellent electronic conductivity as an ion blocking electrode was brought into contact with both sides of the plate-shaped sample, and then an alternating voltage was applied through both side electrodes of the sample. At this time, the applied condition was set as amplitude, and the measurement frequency was set in the range of 0.1 Hz to 10 MHz. The bulk resistance of the electrolyte was obtained from an intersection point (R.sub.h) where the semicircle or line of the measured impedance trajectory meets the real axis, and the ionic conductivity was obtained from the width and thickness of the sample.

(27) $\begin{array}{cc}{\sigma \left(\Omega .Math.\mathrm{Cm}\right)}^{-1}=\frac{1}{R_b}.Math.\frac{t}{A}& \left[\mathrm{Equation}1\right]\end{array}$

(28) σ: ionic conductivity

(29) R.sub.b: intersection point where the impedance trajectory meets the real axis

(30) A: width of sample

(31) t: thickness of the sample

(32) TABLE-US-00003 TABLE 3 Transmittance Turbidity Ionic conductivity Modulus Adhesion (%) (%) (S/cm) (Pa) reliability Example 1 94.6 0.7 1.7 × 10.sup.−3 198,000 ◯ Example 2 94.5 0.6 1.9 × 10.sup.−3 112,000 ◯ Example 3 94.6 0.6 2.0 × 10.sup.−3 103,000 ◯ Example 4 94.7 0.6 1.6 × 10.sup.−3 210,000 ◯ Example 5 94.3 1.0 1.0 × 10.sup.−3 167,000 ◯ Comparative Example 1 no film formation Comparative Example 2 93.7 1.1 1.5 × 10.sup.−3 283,000 ◯ Comparative Example 3 89.5 1.5 4.0 × 10.sup.−3 179,000 X

(33) The modulus was measured by using a universal testing machine (UTM, Zwick Roel, Z005), where the sample specimen of the gel polymer electrolyte film (1×12 cm) was fixed with the upper and lower clamps at room temperature and Young's modulus was measured under the conditions of 5% strain and 1 Hz frequency.

(34) With regard to the adhesion reliability, the polymer electrolyte film was laminated on a WO.sub.3 substrate, and then when a force of 30N was applied thereto after 30 minutes, the adhesion performance was evaluated by X in the case of being detached and by O in the case of not being detached.

(35) 10: substrate

(36) 11: transparent electrode

(37) 12: electrochromic layer

(38) 20: gel polymer electrolyte layer

(39) 30: substrate

(40) 31: transparent electrode

(41) 32: ion storage layer