KR100365392B1 - Ion-conductive polymer electrolyte and electrochemical element using the same - Google Patents

Abstract

PURPOSE: Provided are a polymer electrolyte excellent in ionic conductivity, which has excellent film formability and physical properties when producing a solid electrolyte by adding a liquid electrolyte to the polymer electrolyte, and an electrochemical element using the polymer electrolyte. CONSTITUTION: The polymer electrolyte is represented by the formula (I), wherein R1 is H or CH3, R2 and R3 are identically or differently C1-C5 alkyl or 3-acryloxypropylmethyl, k is an integer of 1-40, l is an integer of 1-40, and m is an integer of 0-100. And the solid electrolyte is produced by curing a mixture containing 10-90pts.wt. of the polymer electrolyte, 3-30pts.wt. of a lithium salt, 10-90pts.wt. of the liquid electrolyte, and an initiator. And the electrochemical element contains the polymer electrolyte.

Description

Ion Conductive Polymer Electrolyte and Electrochemical Devices Using the Same

The present invention relates to a polymer electrolyte having a high ionic conductivity and an electrochemical device using the same, and more particularly, to an electrochemical device such as a battery, a storage battery, a fuel cell, etc., due to its excellent ionic conductivity and flexibility in manufacturing a film. It relates to a compound comprising a siloxane group that can be usefully used as an electrochemical device using the same as an electrolyte.

Typically, the electrolyte used in the cell is a non-water-soluble liquid electrolyte that allows charge to be transferred between the cell's positive electrode and negative electrode. However, liquid electrolytes are difficult to handle due to strong corrosiveness and toxicity, and leaks occur easily.

To solve this problem, a polymer electrolyte has been developed that can transfer ions better. Representative examples include polyethylene oxide (PEO), which has a high dissociation degree to lithium salts, but has a disadvantage in that ionic conductivity is reduced due to crystallization at room temperature. Therefore, as a method for reducing the degree of crystallinity, a method of inserting a flexible functional group into a linear polymer or making a branched polymer is studied. Among these polymers, a polymer having a siloxane group inserted between ethylene oxide (EO) groups (UK Patent GB2164047 A) was found to have the highest ionic conductivity. However, since the polymer is made into a film under pressure after adding Al ₂ O ₃ to make the liquid solid, there is a disadvantage in that the workability is poor and the produced film is not flexible.

US Pat. No. 5,229,225 (Schackle et al.) Discloses polyethylene glycol diacrylate (PEGDA) in which both ends of polyethylene glycol are substituted with acrylates, such as lithium salts such as LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF _6, and the like. A liquid electrolyte capable of dissociating lithium salts, such as propylene carbonate and polyethylene glycol dimethyl ether, was mixed and cured by electron light to prepare a solid electrolyte having an ionic conductivity of up to 2 × 10 ⁻³ s / cm. Since the electrolyte film thus prepared breaks well when it is bent, 10 parts by weight of polyethylene oxide (PEO) is added during manufacture to improve physical properties. However, the addition of PEO causes a problem that the processability is lowered due to the formation of a gel having a high viscosity during film forming.

Accordingly, the present inventors have repeatedly studied to solve the above problems and to develop a pure polymer electrolyte having high ionic conductivity, and based on the fact that the siloxane groups lower the glass transition temperature and crystallinity of the PEO, Polymers inserted and substituted at both ends with acrylates have excellent ionic conductivity, and when liquid electrolyte is added and cured to form a gel solid electrolyte, the film formability and physical properties are excellent without adding PEO. The present invention was completed.

Accordingly, an object of the present invention is to provide a polymer compound having high ionic conductivity and excellent film formability and physical properties when manufactured from a solid electrolyte, and an electrochemical device using the same as an electrolyte.

In order to achieve the above object, the present invention provides a compound of the general formula (I):

In the above formula,

R ₁ is H or CH ₃ ,

R ₂ and R ₃ are the same or different and are C ₁ -C ₅ alkyl or 3-acryloxypropylmethyl,

k is an integer from 1 to 40,

l is an integer from 1 to 40,

m is an integer of 0-100.

The present invention also provides an electrochemical device comprising the compound of general formula (I) together with an anode and a cathode.

Hereinafter, the present invention will be described in detail.

Compounds of formula (I) of the present invention may be prepared according to the following schemes:

Wherein R ₁ , R ₂ , R ₃ , k, 1 and m are as defined above.

According to the above reaction scheme, polyethylene glycol, polyethylene glycol substituted at one end with acrylate, and dichlorosilane may be reacted at a temperature of -20 to 60 ° C in the presence of pyridine to obtain a compound of formula (I). The polymer thus prepared is amorphous. At this time, the length of the polymer chain is determined by the reaction ratio of dichlorosilane, polyethylene glycol, polyethylene glycol monoacrylate. For example, in order to obtain a compound whose m is 1, it is possible to make x: y: z ratio 1: 1: 2. In addition, the reaction temperature affects the molecular weight distribution. In other words, when the reaction temperature is high, a wide molecular weight distribution is shown, and at a low temperature, the opposite aspect is shown.

The compound of general formula (I) of the present invention is mixed with a lithium salt and a liquid electrolyte, and cured by ultraviolet rays, electron beams, radiation, etc. in the presence of an initiator to prepare a gel solid electrolyte film. At this time, the compound of formula (I) is preferably used in an amount of 10 to 90 parts by weight, 10 to 90 parts by weight of the liquid electrolyte, and 3 to 30 parts by weight of the lithium salt.

Lithium salt used in the present invention is lithium perchlorate (LiClO ₄ ), lithium hexafluoro arsenate (LiAsF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium trifluor Relatively large anions such as lithium salts such as rosulfonate (LiCF ₃ SO ₃ ) are included. Using large anions can increase the number of cations' migration.

As the liquid electrolyte, any organic solvent capable of dissociating the lithium salt may be used, and examples thereof include propylene carbonate, ethylene carbonate, dimethyl carbonate, tetrahydrofuran, and the like. The initiator may use a compound used in the curing process, for example, using Darocure 1173 in an amount of 0.1 to 5 parts by weight.

Among the compounds of the general formula (I), 8 parts by weight of LiClO ₄ is mixed with a compound of the general formula (I) in which R ₁ , R ₂ and R ₃ are methyl, k is 8 and m is 0, and cured by ultraviolet rays. In this case, the ionic conductivity of 3.2 × 10 ⁻⁶ s / cm was shown. Ionic conductivity depends on k, l, m and R ₁ to R ₃ , where k = 8, l = 8, m = 5, R ₁ = H, and R ₂ = R ₃ = CH ₃ The highest value was 6 × 10 ⁻⁵ s / cm. In addition, when R ₁ is hydrogen and R ₂ is 3-acryloxypropylmethyl group, a more rigid film could be formed when made into a gel.

The electrolyte prepared from the compound of formula (I) of the present invention can make an electrochemical device such as a battery together with the positive electrode material and the negative electrode material.

Hereinafter, the present invention will be described in more detail based on the following examples. However, these Examples are only for illustrating the present invention, the present invention is not limited to these.

Example 1

30 g of polyethylene glycol (molecular weight 400), 31.8 g of polyethylene glycol monoacrylate (molecular weight 424) and 6 g of pyridine were added to 200 ml of dry THF under nitrogen gas. 8.93 g of dimethylchlorosilane was slowly added dropwise at room temperature for about 1 hour. At this time a white precipitate of pyridinium salt was produced. After the reaction was performed at room temperature for 6 hours, the pyridinium salt precipitate was filtered off, and THF was removed from the remaining solution under reduced pressure. The substance obtained here is a compound of formula (I) wherein R ₁ , R ₂ and R ₃ are each methyl, k is 1, 1 is 8 and m is 1. The resulting reaction was heated to 50-150 ° C. to remove moisture and impurities by high vacuum. When the moisture was less than 100 ppm, the reaction was transferred to a glove box and dissolved by adding 4.8 g of LiClO ₄ . 0.3g of photoinitiator Darocure 1173 was added to the resulting solution, poured into a quartz plate maintaining a constant thickness, and cured with ultraviolet rays to prepare a film. The thickness of the produced film was 200 μm, and the ionic conductivity was 6.3 × 10 ⁻⁶ s / cm.

Example 2

30 g of pyridine polyethylene glycol (molecular weight 400) and 12.7 g of polyethylene glycol monoacrylate (molecular weight 424) were added to 200 ml of dry THF under nitrogen gas. 10.7 g of dimethylchlorosilane was slowly added dropwise at 0 ° C. for about 2 hours. At this time a white precipitate of pyridinium salt was produced. After the reaction was conducted at 0 ° C. for 24 hours, the pyridinium salt precipitate was removed by filtration, and the remaining solution was dried to a moisture content of 100 ppm or less under high vacuum. The material thus obtained is a compound of formula (I) wherein R ₁ , R ₂ and R ₃ are each methyl, k is 1, 1 is 8 and m is 4. The dried reaction was transferred to a glove box and dissolved by adding ₄ g of LiClO ₄ . 0.3g of the photoinitiator Darocure 1173 was added to the resulting solution and cured in the same manner as in Example 1 to prepare a film. The ionic conductivity of the prepared film was 6 × 10 ⁻⁶ s / cm.

Example 3

To 3 g of the pre-cured reactant obtained in Example 1, 7 g of propylene carbonate and 0.8 g of LiClO ₄ were added and mixed well until there was no precipitate. 0.5 parts by weight of the photoinitiator Darocure 1173 was added to the resulting mixture, poured into a quartz plate having a constant thickness, and cured with ultraviolet rays to prepare a film. The film thus produced was very flexible and had an ion conductivity of 3 × 10 ⁻³ s / cmi.

As described above, the polymer in which the siloxane group is inserted in the middle of the PEO structure and the both ends are substituted with the acrylate has excellent ionic conductivity and the film formability and physical properties when the liquid electrolyte is added to form the gel solid electrolyte. It is excellent and can be usefully used as an electrolyte in electrochemical devices such as batteries.

Claims (7)

A polymer electrolyte of the general formula (I) In the above formula, R ₁ is H or CH ₃ , R ₂ and R ₃ are the same or different and are C ₁ -C ₅ alkyl or 3-acryloxypropylmethyl, k is an integer from 1 to 40, l is an integer from 1 to 40, m is an integer of 0-100. A process for producing a compound of formula (I) according to claim 1 comprising reacting polyethylene glycol, polyethylene glycol substituted at one end with an acrylate, and dichlorosilane at a temperature of -20 to 60 ° C in the presence of pyridine. A method of preparing a solid electrolyte by curing a mixture comprising 10 to 90 parts by weight of the polymer electrolyte of claim 1, 3 to 30 parts by weight of a lithium salt, 10 to 90 parts by weight of a liquid electrolyte and an initiator. The method of claim 3, wherein The lithium salt is LiClO ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ or LiBF ₄ characterized in that Way. The method of claim 3, wherein The liquid electrolyte is propylene carbonate, ethylene carbonate, dimethyl carbonate or tetrahydrofuran Way. The method of claim 3, wherein Characterized in that the mixture is cured by ultraviolet light, electron beam or radiation. Way. An electrochemical device comprising the electrolyte of claim 1.