KR100970400B1 - Polymer electrolyte formed from polymerization of monomer including sulfonyl group and Li battery appling the same - Google Patents

Abstract

The present invention relates to a lithium battery employing a polymer electrolyte obtained by polymerizing a composition for forming a polymer electrolyte comprising a lithium salt containing an sulfonyl group, an organic solvent, a polymerization initiator and a polymerization catalyst in an electrode assembly.

By using the polymer electrolyte of the present invention, it is possible to obtain a lithium battery that does not require a degassing step in the battery manufacturing process and does not have a swelling phenomenon even at high temperature.

Sulfonyl group, polymerization initiator, polymerization catalyst, swelling

Description

Polymer electrolyte formed from polymerization of monomer including sulfonyl group and Li battery appling the same}

The present invention relates to a polymer electrolyte and a lithium battery employing the same, and more particularly to a polymer electrolyte and a lithium battery employing the same, which does not require a gas removal step in the manufacturing process and reduces the degree of swelling at high temperature.

In a lithium battery using a liquid electrolyte, when an organic solvent having a low boiling point is used to enhance low temperature performance as an organic solvent constituting the electrolyte, the electrode assembly or pouch swells due to the low boiling point solvent at high temperature. swelling phenomenon occurs.

In order to improve this problem, a method of using a polymer solid electrolyte instead of an electrolyte solution has been proposed. As such, the use of the polymer solid electrolyte reduces the risk of leakage of the electrolyte to the outside as compared with the case of using the liquid electrolyte, thereby increasing the safety of the battery.

By the way, in the case of using the polymer solid electrolyte, the ionic conductivity is lower than in the case of using the liquid electrolyte. Therefore, in order to put the polymer solid electrolyte into a lithium secondary battery, it is urgent to develop a polymer solid electrolyte having high ion conductivity and excellent electrochemical stability.

As the monomer of the ion conductive polymer for forming a solid polymer electrolyte, a linear polymer or a crosslinked polymer of a homopolymer or copolymer based on ethylene oxide is mainly used. In addition, as the demand for thinner and lighter batteries increases, the necessity for developing a lithium ion battery using a pouch as an exterior material is increasing. However, a lithium ion battery using a pouch as an exterior material shows an advantage of being thin and light. Due to the characteristics of the exterior material, the battery thickness is deformed due to the swelling phenomenon at high temperature, which is a problem in the reliability of battery performance.

In order to solve this problem, a recently developed process is to prepare a gel polymer electrolyte by injecting an electrolyte solution in which a lithium salt and an organic solvent are mixed with a monomer or a prepolymer, instead of using a conventional lithium ion battery manufacturing process. Process comprising the steps. For example, US Pat. No. 4,908,283 discloses a polymer electrolyte made by polymerizing a composition composed of acryloyl-denatured polyalkylene oxide, and US Pat. No. 4,792,504 discloses polyethylene glycol dimethacrylate. A polymer electrolyte composed of polyethylene oxide is described.

As described above, the swelling problem must be solved for practical use of the lithium secondary battery using the pouch as an exterior material.                         

As a result of research efforts to overcome the problems of the prior arts, a polymer prepared by polymerizing a composition for forming a polymer electrolyte comprising a monomer, a lithium salt, an organic solvent, a polymerization initiator and a polymerization catalyst represented by Formula 1 In the case of the electrolyte lithium secondary battery, it was confirmed that the swelling phenomenon was improved and the present invention was completed.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a polymer electrolyte having improved swelling phenomenon and a lithium battery employing the same.

In order to achieve the above technical problem, the present invention provides a polymer electrolyte comprising a polymerization product of a composition for forming a polymer electrolyte comprising a monomer, a lithium salt, an organic solvent, a polymerization initiator, and a polymerization catalyst including a sulfonyl group represented by Formula 1 below. To provide.

Wherein R ₁ is H or —C _n H _{2n + 1} (n is 1 to 10)

(A는 H, -C_nH_2n+1, Cl, F 또는 Br) 또는 -CR₁=CH₂이다.R ₂ is H, -C _n H _{2n + 1} (n = 1-10),

(A is H, —C _n H _{2n + 1} , Cl, F or Br) or —CR ₁ = CH ₂ .

In the polymer electrolyte of the present invention, the polymerization initiator is dibenzoyl peroxide, succinic acid peroxide, dilauroyl peroxide, didecanoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl- 2,5-di- (t-butylperoxy) hexane, α-cumylperoxy neodecanoate, 1,1-dimethyl-3-hydroxybutylperoxy-2-ethylhexanoate, t-amylper Oxybenzoate, t-butylperoxy pivalate, 2,5-dihydroperoxy-2,5-dimethylhexane, cumene hydroperoxide, t-butylhydroperoxide, 1,1-di- (t-amyl Peroxy) -cyclohexane, 2,2-di- (t-butylperoxy) butane, ethyl-3,3-di- (t-butylperoxy) -butylate, di (n-propyl) peroxydicarbonate At least one selected from the group consisting of di (sec-butyl) peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate, and azobisisobutyronitrile.

In the polymer electrolyte of the present invention, the polymerization catalyst may be at least one selected from the group consisting of triethylamine, tributylamine, triethanolamine and N-benzyldimethylamine.

In the polymer electrolyte of the present invention, the organic solvent is propylene carbonate, ethylene carbonate, dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate, tetrahydrofuran, 2-methylhydrofuran, diethoxyethane, methyl formate, ethylform At least one selected from the group consisting of mate, gammabutyrolactone and fluorobenzene.

In the polymer electrolyte of the present invention, the lithium salt is lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium trifluoromethane sulfonate (LiCF ₃ SO ₃ ) and lithium At least one selected from the group consisting of bistrifluoromethanesulfonylamide (LiN (CF ₃ SO ₂ ) ₂ ).

In order to achieve another technical problem of the present invention, the present invention comprises the steps of preparing a composition for forming a polymer electrolyte comprising a monomer, a lithium salt, an organic solvent represented by the formula (1);

Casting the polymer electrolyte forming composition on an electrode assembly; And

It provides a method for producing a polymer electrolyte comprising the step of polymerizing the polymer electrolyte using a polymerization medium containing heat, current or ultraviolet light.

In the polymer electrolyte production method of the present invention, the polymerization temperature of the polymerization step is preferably 25 to 85 ℃.

In order to achieve another technical problem of the present invention, the present invention provides a lithium battery comprising a polymer electrolyte by the polymer electrolyte manufacturing method.

Hereinafter, the present invention will be described in more detail.

The composition for forming a polymer electrolyte of the present invention is prepared by mixing a proper amount of a monomer, an organic solvent, a lithium salt, a polymerization initiator, and a polymerization catalyst containing a sulfonyl group represented by Chemical Formula 1. The organic solvent may be any one commonly used in lithium batteries. In order to improve the mechanical strength of the polymer electrolyte and the interfacial performance with the electrode, various additives such as an adhesion improving agent and a filler may be further added.

The polymerization initiator may also be diacyl peroxides such as dibenzoyl peroxide, succinic acid peroxide, dilauroyl peroxide, didecanoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane and dialkyl peroxides, α-cumyl peroxy-neodecanoate, 1,1-dimethyl- Such as 3-hydroxybutyl peroxy-2-ethyl hexanoate, t-amyl peroxy-benzoate, t-butyl peroxy-pivalate Quaternary alkyl hydroperoxides such as peroxy esters, 2,5-dihydroxyperoxy-2,5-dimethylhexane, cumene hydroperoxide, t-butyl hydroperoxide, 2,2 Peroxy ketals such as di- (t-butyl peroxy) butane, ethyl 3,3-ethyl 3,3-di- (t-butylperoxy) -butylate), di (n-pro) More preferably at least one selected from the group consisting of peroxydicarbonates such as peroxy-dicarbonate, di (sec-butyl) peroxy-dicarbonate, di (2-ethylhexyl) peroxy-dicarbonate However, azos such as azobisisobutyryl are not preferable because a phenomenon in which a gas is generated during polymerization and the surface of the polymer electrolyte formed on the electrode plate is uneven occurs.

The content of the polymerization initiator is preferably 0.0001 to 10 parts by weight based on 100 parts by weight of the monomer including the sulfonyl group represented by Chemical Formula 1.                     

When the content of the polymerization initiator is less than 0.0001 parts by weight, the polymerization does not proceed. When the content of the polymerization initiator exceeds 10 parts by weight, it affects the components of the polymer electrolyte, which decreases electrochemical properties, which is not preferable.

In the polymer electrolyte of the present invention, the polymerization catalyst is preferably at least one selected from the group consisting of triethylamine, tributylamine, triethanolamine and N-benzyldimethylamine.

The content of the polymerization catalyst may be 0.01 to 2 parts by weight based on 100 parts by weight of the monomer including the sulfonyl group represented by Chemical Formula 1.

When the content of the polymerization catalyst is more than 2 parts by weight, the electrochemical properties of the polymer electrolyte are lowered. If the content of the polymerization catalyst is less than 0.01 parts by weight, the polymerization reaction is not smoothly performed, which is not preferable.

The cathode and the anode are each prepared in accordance with conventional methods used in the manufacture of lithium batteries. In this case, a lithium metal composite oxide, a transition metal compound, a sulfur compound, or the like is used as the cathode active material, and a lithium metal, carbon material, graphite material, or the like is used as the anode active material.

A separator made of an insulating resin having a mesh structure is inserted between the cathode and the anode, and the electrode structure is formed by winding or stacking the separator and then placing the separator in a battery case. Wherein the separator is a polyethylene separator, a polypropylene separator, a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator or a polypropylene / polyethylene / polypropylene 3 Use a layer separator.

Then or at the same time to prepare a composition for forming a polymer electrolyte comprising a monomer containing a sulfonyl group, an organic solvent, a lithium salt, a polymerization initiator and a polymerization catalyst.

In the polymer electrolyte of the present invention, the organic solvent is propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate, ethyl methyl carbonate (EMC), diethyl carbonate, tetrahydrofuran, 2-methylhydrofuran, diethoxy At least one selected from the group consisting of ethane, methyl formate, ethyl formate, gamma butyrolactone, and fluorobenzene (FB).

The content of the organic solvent may be 90 to 99.9 parts by weight based on 100 parts by weight of an electrolyte consisting of an organic solvent and a lithium salt.

In the polymer electrolyte of the present invention, the lithium salt is lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium trifluoromethane sulfonate (LiCF ₃ SO ₃ ) and lithium It is preferably at least one selected from the group consisting of bistrifluoromethanesulfonylamide (LiN (CF ₃ SO ₂ ) ₂ ).

The content of the lithium salt may be 0.1 to 10 parts by weight based on 100 parts by weight of an electrolyte consisting of an organic solvent and a lithium salt.

The polymer electrolyte forming composition prepared as described above is injected into a battery case in which an electrode structure is stored, followed by heat treatment to perform an in-cell polymerization reaction, and then polymerization at 75 ° C. for 4 hours to complete a polymer electrolyte lithium secondary battery. do. It is preferable that it is 25-85 degreeC, and, as for the said polymerization temperature, it is more preferable that it is 60-80 degreeC. If the polymerization temperature exceeds 85 ° C, volatilization of the liquid electrolyte or decomposition of lithium salts are caused, and if the polymerization temperature is less than 25 ° C, the polymerization reaction is not smoothly performed, which is not preferable.

The lithium battery of the present invention is not particularly limited in form, and both lithium primary batteries and lithium secondary batteries can be used.

Hereinafter, the present invention will be described in detail with reference to the following examples, but the present invention is not limited only to the following examples.

Example 1

A cathode active material slurry was prepared by dissolving 94 g of LiCoO ₂ , 3 g of Super-P and 3 g of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone. The cathode active material slurry was applied to an Al-foil having a width of 4.9 cm and a thickness of 147 μm, dried, rolled, and cut to a predetermined dimension to prepare a cathode.

 89.8 g of mesocarbon fiber (MCF: Petoca), 0.2 g of oxalic acid, and 10 g of PVDF were dissolved in N-methyl-2-pyrrolidone to prepare an anode active material slurry. The anode active material slurry was applied on a copper foil having a width of 5.1 cm and a thickness of 178 μm, and then dried, rolled, and cut into predetermined dimensions to produce an anode. A separator was placed between the cathode and the anode and wound to make an electrode assembly.

The composition for forming a polymer electrolyte is EC: EMC as an electrolyte solution containing 1 g of phenyl vinyl sulfone as a monomer containing a sulfonyl group, 0.01 g of dilauroyl peroxide as a polymerization initiator, triethylamine as a polymerization catalyst, an organic solvent and a lithium salt. 30 g of a 1.3 M LiPF ₆ solution was prepared by mixing: PC: FB in a volume ratio of 30: 55: 5: 10. 2.3g of the composition for forming the polymer electrolyte was injected into a battery case and then polymerized at 75 ° C. for 4 hours to complete a lithium secondary battery.

Comparative Example 1

Lithium secondary was prepared in the same manner as in Example 1, except that 1.3M LiPF ₆ electrolyte solution containing an EC: EMC: PC: FB mixture in a volume ratio of 30: 55: 5: 10 was used instead of the polymer electrolyte composition. The battery was prepared.

In order to evaluate the swelling characteristics of the battery at high temperature, the lithium secondary battery prepared as described above was charged and then left in a hot air oven at 90 ° C. for 4 hours, and then the thickness change before and after standing was measured.

Table 1 shows the performance of the lithium secondary battery prepared according to Example 1 and Comparative Example 1 and the swelling characteristics of the battery when left at 90 ° C. or higher.

As can be seen in Table 1, when the polymer electrolyte of Example 1 was used as the electrolyte, the battery performance was equal to or higher than that of the electrolyte solution of Comparative Example 1, and the electrolyte solution of Comparative Example 1 was used. Compared to the high temperature swelling properties were found to be significantly improved.

Remarks Standard charge and discharge characteristics
(mAh) Rate discharge characteristics
(mAh) High temperature leaving characteristic charge Discharge efficiency(%) 0.5C 1.0C 2.0C I'm
(mm) after
(mm) Thickness change
(%) Example 1 725 726 100.1 723.2 715.6 683.5 3.6 3.65 1.4 Comparative Example 1 717 716 99.9 708.8 708.0 680.2 3.7 5.0 36.1

Swelling at high temperature when using a polymer electrolyte lithium secondary battery prepared by polymerizing a composition for forming a polymer electrolyte comprising a sulfonyl group-containing monomer, a lithium salt, an organic solvent, a polymerization initiator and a polymerization catalyst as in the present invention It was confirmed that the characteristics were improved.

Claims (8)

A polymer electrolyte comprising a polymerization product of the composition for forming a polymer electrolyte comprising a monomer containing a sulfonyl group represented by the formula (1), a lithium salt, an organic solvent, a polymerization initiator and a polymerization catalyst. <Formula 1>

Wherein R ₁ is H or —C _n H _{2n + 1} (n is 1 to 10) R ₂ is H, -C _n H _{2n + 1} (n = 1-10),

(A is H, —C _n H _{2n + 1} , Cl, F or Br) or —CR ₁ = CH ₂ . The method of claim 1, wherein the polymerization initiator is dibenzoyl peroxide, succinic acid peroxide, dilauroyl peroxide, didecanoyl peroxide, dicumyl peroxide, di-t- butyl peroxide, 2,5-dimethyl-2, 5-di- (t-butylperoxy) hexane, α-cumylperoxy neodecanoate, 1,1-dimethyl-3-hydroxybutylperoxy-2-ethylhexanoate, t-amylperoxybenzo Et, t-butylperoxy pivalate, 2,5-dihydroperoxy-2,5-dimethylhexane, cumene hydroperoxide, t-butylhydroperoxide, 1,1-di- (t-amylperoxy ) -Cyclohexane, 2,2-di- (t-butylperoxy) butane, ethyl-3,3-di- (t-butylperoxy) -butylate, di (n-propyl) peroxydicarbonate, di (sec-butyl) peroxydicarbonate, di (2-ethylhexyl) peroxydicarbonate and azobisisobutyronitrile and at least one selected from the group consisting of Polymer electrolyte, characterized in that 0.0001 to 10 parts by weight based on 100 parts by weight of the monomer containing a sulfonyl group represented by the formula (1). The sulfonyl group according to claim 1, wherein the polymerization catalyst is at least one selected from the group consisting of triethylamine, tributylamine, triethanolamine, and N-benzyldimethylamine, and the content of the polymerization catalyst is a sulfonyl group represented by Chemical Formula 1. A polymer electrolyte, characterized in that 0.01 to 2 parts by weight based on 100 parts by weight of the monomer. The method of claim 1, wherein the organic solvent is propylene carbonate, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, tetrahydrofuran, 2-methylhydrofuran, diethoxyethane, methyl formate, ethyl formate, gamma At least one selected from the group consisting of butyrolactone and fluorobenzene, wherein the content of the organic solvent is 90 to 99.9 parts by weight based on 100 parts by weight of an electrolyte comprising an organic solvent and a lithium salt. The lithium salt of claim 1, wherein the lithium salt is lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), and lithium bistry. At least one selected from the group consisting of fluoromethanesulfonylamide (LiN (CF ₃ SO ₂ ) ₂ ), and the content of the lithium salt is 0.1 to 10 parts by weight based on 100 parts by weight of an electrolyte composed of an organic solvent and a lithium salt. Polymer electrolyte. Preparing a composition for forming a polymer electrolyte by mixing a monomer, a lithium salt, and an organic solvent represented by Formula 1; Casting the polymer electrolyte forming composition on a substrate; And A method of preparing a polymer electrolyte comprising polymerizing an electrolyte using heat, current, or ultraviolet light, and then peeling off the polymer electrolyte from the substrate. <Formula 1>

Wherein R ₁ is H or —C _n H _{2n + 1} (n is 1 to 10) R ₂ is H, -C _n H _{2n + 1} (n = 1-10),

(A is H, —C _n H _{2n + 1} , Cl, F or Br) or —CR ₁ = CH ₂ . The method of claim 6, wherein the temperature of the polymerization step is 25 to 85 ℃ manufacturing method of a polymer electrolyte. A lithium battery comprising the polymer electrolyte of any one of claims 1 to 5.