KR102268183B1 - Polymer Electrolyte and Method for Preparing the Same - Google Patents

Abstract

The present invention relates to a polymer electrolyte and a method for preparing the same. More specifically, non-PEO-based polymers; adjuvant; and a phosphate-based cross-linking agent; by polymerizing a raw material comprising: a cross-linked polymer electrolyte having excellent voltage stability and flame retardancy can be prepared.

Description

Polymer Electrolyte and Method for Preparing the Same

The present invention relates to a polymer electrolyte having excellent voltage stability and flame retardancy and a method for manufacturing the same.

Currently, a lithium ion secondary battery having a high energy density is mainly used in portable electronic devices. At this time, the liquid electrolyte mainly used has problems such as leakage and explosion hazard. In order to protect this, a safety circuit device is required, and an increase in weight is inevitable by sealing the battery with a metal outer can to prevent leakage. In addition, since the battery becomes thick, there is a limit in the design of the battery. As electronic devices become thinner and more flexible in the future, lithium ion batteries using liquid as an electrolyte cannot satisfy all requirements such as miniaturization, weight reduction, and flexibility.

On the other hand, lithium polymer batteries have high average voltage and high energy density, and in addition to the characteristics of lithium ion batteries without a memory effect, electrolyte leakage to the outside of the battery can be prevented, which improves battery stability, and the electrode and separator are integrated. Since the surface resistance is reduced, it is advantageous for high-efficiency charging and discharging with relatively low internal resistance. In addition, by thinning the electrolyte film, it can be made into a flexible device and a battery of any shape, and the thickness of the battery can be made thinner by not using a metal outer can. Accordingly, batteries of portable electronic devices such as mobile phones, notebook computers, and digital cameras, which are increasingly required by consumers for stability, miniaturization and high capacity, are expected to be replaced by lithium polymer batteries in large quantities from conventional lithium ion batteries. In addition, the lithium polymer battery is expected to be applied to a high-capacity lithium secondary battery such as a hybrid electric vehicle, etc., and is in the spotlight as a next-generation battery.

The most important difference between a lithium polymer battery and a lithium ion battery using a liquid electrolyte is that the separator between the positive and negative electrodes is made of a polymer, and this polymer separator can even act as an electrolyte. In a lithium polymer battery, ion conduction is achieved by internal ion transport in a stable polymer electrolyte like a solid phase.

The polymer electrolyte used in lithium polymer batteries is an intrinsic solid polymer electrolyte and polymer film in which electrolyte salts are added to polymers containing hetero elements such as O, N, and S, and the ions of the dissociated salt are moved by the segmentation motion of the polymer. A gel-type polymer electrolyte that exhibits ionic conductivity by impregnating a liquid electrolyte inside and immobilizing it with an electrolyte salt is being studied in two major areas.

Of these, gel-type polymer electrolytes still have difficulties in securing battery stability due to leakage, which existing liquid electrolytes have when used, and difficulties in battery manufacturing processes remain a problem. Intrinsic solid polymer electrolytes have been studied continuously since the discovery of conduction of sodium ions in polyethylene oxide (PEO) by P. V. Wright in 1975. The intrinsic solid polymer electrolyte has advantages in that it has high chemical and electrochemical stability and can use a high-capacity lithium metal electrode, but has a problem of very low ionic conductivity at room temperature.

As it was found that the ionic conductivity in the intrinsic solid polymer electrolyte is closely related to the degree of local motion of the polymer chain, various methods were studied to lower the high crystallinity of the PEO-based polymer electrolyte in order to allow the dissociated ions to move freely. .

As one method, studies have been conducted to graft low molecular weight PEO into a flexible polymer main chain with a very low Tg value as a side branch. Siloxane polymer electrolytes having both side branches of PEO of various lengths were synthesized, and when there were 6 repeating chains of PEO that did not show crystallinity, high ionic conductivity of ^{4.5Х10 -4 S/cm at room temperature was exhibited.}

In order to supplement and improve the problems of the conventional electrolyte, various studies have been conducted in terms of electrolyte materials and shapes.

Korea Patent Publication No. 2015-3364763 Japanese Patent Laid-Open No. 1999-240998

The present inventors have conducted various studies to solve the above problems, and as a result, a non-PEO (polyethylene oxide)-based polymer; adjuvant; phosphate-based crosslinking agents; and a solvent; was prepared, and the thus-prepared polymer electrolyte was a non-PEO-based polymer electrolyte showing superior voltage stability and flame retardancy compared to the conventional PEO-based polymer electrolyte, and it was confirmed that it was advantageous for improving battery performance. .

Accordingly, it is an object of the present invention to provide a method for preparing a polymer electrolyte alc having excellent voltage stability and flame retardancy.

Another object of the present invention is to provide a lithium secondary battery including the polymer electrolyte as described above.

In order to achieve the above object, the present invention, a non-PEO-based polymer; adjuvant; phosphate-based crosslinking agents; And sorbate ionic liquid (Solvate Ionic Liquid, SIL); provides a polymer electrolyte comprising.

The non-PEO-based polymer is 2-(2-ethoxyethoxy)ethyl acrylate [2-(2-ethoxyethoxy)ethyl acrylate, EEEA], butyl acrylate, hexyl acrylate, and ethyl It may be at least one selected from the group consisting of ethyl hexyl acrylate.

The reinforcing agent may be at least one selected from the group consisting of styrene, methyl methacrylate (MMA), and methacrylate (MA).

The phosphate-based crosslinking agent is bis [2- (methacryloyloxy) ethyl] phosphate (bis [2- (methacryloyloxy) ethyl] phosphate), triphenyl phosphate, tricresyl phosphate, tri (2,6-dimethylphenyl) It may be at least one selected from the group consisting of phosphate and tri(2,4,6-trimethylphenyl)phosphate.

It may include the sorbate ionic liquid lithium salt and a glyme-based material or an amide-based material.

In the sorbate ionic liquid, the molar ratio of the lithium salt and the glyme-based material may be 1:0.1 to 3, and the molar ratio of the lithium salt and the amide-based material may be 1:1 to 6.

The polymer electrolyte may include 1 to 30% by weight of the non-PEO-based polymer; 1 to 20% by weight of the reinforcing agent; 3 to 10% by weight of the phosphate-based crosslinking agent; and 45 to 75% by weight of the sorbate ionic liquid.

The polymer electrolyte may be a polymer electrolyte membrane in the form of a network.

The present invention also provides (S1) a non-PEO-based polymer; adjuvant; phosphate-based crosslinking agents; and adding an initiator to the mixed solution of the sorbate ionic liquid to form a mixture; (S2) removing oxygen from the mixture formed in step (S1); and (S3) applying the mixture from which oxygen has been removed in step (S2) on a substrate and curing the mixture; It provides a method for producing a polymer electrolyte, comprising a.

The initiator may be added in an amount of 0.1 to 2% by weight based on the total weight of the mixture.

In step (S3), the curing may be thermosetting or photocuring.

The present invention also provides a lithium secondary battery comprising the polymer electrolyte.

According to the present invention, it is possible to provide a polymer electrolyte in the form of a non-PEO-based polymer membrane in a network shape.

In addition, the polymer electrolyte according to the present invention, including a non-PEO (polyethylene oxide)-based polymer, exhibits improved voltage stability with ionic conductivity equivalent to or higher than that of a conventional PEO-based polymer electrolyte.

In addition, since the polymer electrolyte according to the present invention contains a flame retardant phosphate-based crosslinking agent, it can exhibit excellent flame retardancy.

1 is a graph showing the results of measuring voltage stability for coin cells including polymer electrolytes prepared in Examples 1 and 3 and Comparative Example 1. FIG.
FIG. 2 shows photographs of the polymer electrolytes of Examples 1 to 3 before and after combustion.

Hereinafter, the present invention will be described in more detail to help the understanding of the present invention.

The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. It should be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

Polyelectrolyte

The present invention relates to a non-PEO-based cross-linked polymer electrolyte, which exhibits improved voltage stability compared to the conventional PEO-based polymer electrolyte.

Polymer electrolyte according to the present invention, non-PEO-based polymer; adjuvant; phosphate-based crosslinking agents; and sorbate ionic liquid (SIL); may include.

In the present invention, the non-PEO-based polymer may be included in the polymer electrolyte, and voltage stability may be improved while maintaining ions equivalent to or higher than that of the polymer electrolyte including the PEO-based polymer.

The non-PEO-based polymer may be selected from an acrylate-based polymer and an allyl ether-based polymer having a low glass transition temperature (Tg).

Specifically, the non-PEO-based polymer is 2-(2-ethoxyethoxy)ethyl acrylate [2-(2-ethoxyethoxy)ethyl acrylate, EEEA], butyl acrylate, hexyl acrylate ) and ethyl hexyl acrylate (ethyl hexyl acrylate) may be at least one selected from the group consisting of, preferably EEEA.

The non-PEO-based polymer may be 1 to 30% by weight, preferably 10 to 30% by weight, more preferably 20 to 30% by weight based on the total weight of the polymer electrolyte. If it is less than the above range, the voltage stability of the battery including the polymer electrolyte may be reduced, the degree of crosslinking of the polymer electrolyte may be reduced, and if it exceeds the above range, the ionic conductivity of the polymer electrolyte may be reduced.

In the present invention, the reinforcing agent may improve physical properties such as strength of the polymer electrolyte.

The reinforcing agent may be at least one selected from the group consisting of styrene, methyl methacrylate (MMA) and methacrylate (MA), preferably styrene.

In addition, the reinforcing agent may be 1 to 20% by weight, preferably 2 to 16% by weight, more preferably 3 to 12% by weight based on the total weight of the polymer electrolyte. If it is less than the above range, the polymerization process efficiency of the polymer electrolyte may be reduced, and if it exceeds the above range, the ionic conductivity of the polymer electrolyte may be reduced.

In the present invention, the phosphate-based crosslinking agent can improve the flame retardancy and crosslinking properties of the polymer electrolyte.

The phosphate-based crosslinking agent is bis [2- (methacryloyloxy) ethyl] phosphate (bis [2- (methacryloyloxy) ethyl] phosphate), triphenyl phosphate, tricresyl phosphate, tri (2,6-dimethylphenyl) It may be at least one selected from the group consisting of phosphate and tri(2,4,6-trimethylphenyl)phosphate, and preferably bis[2-(methacryloyloxy)ethyl]phosphate.

In addition, the phosphate-based crosslinking agent may be 3 to 10% by weight, preferably 3 to 9% by weight, more preferably 4 to 8% by weight based on the total weight of the polymer electrolyte. If it is less than the above range, non-curing of the polymer electrolyte may occur, and the flame retardancy improvement effect may be insignificant, and if it exceeds the above range, ionic conductivity may be reduced due to high crosslinking density.

The sorbate ionic liquid may be in an amount of 45 to 75% by weight, preferably 50 to 70% by weight, more preferably 55 to 65% by weight based on the total weight of the polymer electrolyte. If it is less than the above range, non-curing of the polymer electrolyte may occur, and the flame retardancy improvement effect may be insignificant, and if it exceeds the above range, ionic conductivity may be reduced due to high crosslinking density.

The SIL may be included in the polymer electrolyte in a swollen or non-swelled state according to a difference in solubility with each component included in the polymer electrolyte.

For example, the SIL is included in a non-swelled form in the reinforcing agent included in the polymer electrolyte, that is, styrene, and may be included in a swollen form for other components other than styrene, that is, non-PEO-based polymers and phosphate-based crosslinking agents. have.

The SIL may include a lithium salt and a glyme-based material or an amide-based material.

When the SIL contains a lithium salt and a glyme-based material, the molar ratio of the lithium salt and the glyme-based material may be 1:0.1 to 3, preferably 1:0.1 to 2, more preferably 1:0.5 to 1.5. . If the molar ratio of the glyme-based material to the lithium salt is less than or greater than the above range, SIL cannot be formed.

The glyme-based material may be at least one selected from the group consisting of monoglyme, diglyme, triglyme, and tetraglyme. The glyme-based material contains oxygen to coordinate lithium salts.

When the SIL contains a lithium salt and an amide-based material, the molar ratio of the lithium salt and the amide-based material may be 1:1 to 6, preferably 1:2 to 6, more preferably 1:3 to 5. . If the molar ratio of the amide-based material to the lithium salt is less than or greater than the above range, SIL cannot be formed.

The lithium salt is LiSCN, LiN(CN) ₂ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiN(SO ₂ F) ₂ , Li(CF ₃ SO ₂ ) ₃ C, LiN(SO) ₂ CF ₃ ) ₂ [LiTFSI], LiN(SO ₂ CF ₂ CF ₃ ) ₂ , LiSbF ₆ and LiPF ₃ (CF ₂ CF ₃ ) ₃ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiPF ₃ (CF ₃ ) ₃ , And LiB(C ₂ O ₄ ) _{2 It} may be at least one selected from the group consisting of. Preferably, the lithium salt is LiN(SO ₂ F) ₂ or LiN(SO ₂ CF ₃ ) ₂ [LiTFSI] In this case, it may be more advantageous to improve the ionic conductivity and mechanical properties of the polymer electrolyte.

The amide-based material is N-methylacetamide (NMAC), acetamide, N-methylpropionamide, N-ethylacetamide, propionamide, formamide, N-methylformamide, N-ethylformamide , may be at least one selected from the group consisting of N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, and N,N-diethylacetamide, preferably N -methylacetamide (NMAC).

The polymer electrolyte according to the present invention is a non-PEO-based cross-linked polymer electrolyte, and specifically, the polymer electrolyte according to the present invention may be a network type polymer electrolyte membrane.

Method for manufacturing a polymer electrolyte

The present invention also relates to a method for producing a polymer electrolyte having improved elasticity while exhibiting an ionic conductivity equivalent to or higher than that of a conventional liquid electrolyte.

The method for producing a polymer electrolyte according to the present invention comprises: (S1) a non-PEO-based polymer; adjuvant; phosphate-based crosslinking agents; and adding an initiator to the mixed solution of the sorbate ionic liquid to form a mixture; (S2) removing oxygen from the mixture formed in step (S1); and (S3) applying the mixture from which oxygen has been removed in step (S2) to the substrate and curing the mixture.

Hereinafter, the method for manufacturing the polymer electrolyte according to the present invention will be described in more detail for each step.

(S1) step

In step (S1), a non-PEO-based polymer; adjuvant; and a phosphate-based crosslinking agent; an initiator may be added to a mixed solution obtained by dissolving the sorbate ionic liquid to form a mixture.

The types and contents of the non-PEO-based polymer, the reinforcing agent, the phosphate-based crosslinking agent, and the solvent are as described above.

The initiator may initiate polymerization of the monomers to initiate a polymerization reaction to form a polymer electrolyte in the form of a random copolymer.

The initiator may be a photoinitiator or a thermal initiator, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide [Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide], azobis(isobutyronitrile) [ AIBN (Azobis(isobutyronitrile)], Benzoyl peroxide, Acetyl peroxide, Dilauryl peroxide, Di-tert-butylperoxide, t- Butyl peroxy-2-ethyl-hexanoate (t-butyl peroxy-2-ethyl-hexanoate), cumyl hydroperoxide (Cumyl hydroperoxide), hydrogen peroxide (Hydrogen peroxide), 2,2-azobis (2-cyano) butane) [2,2-Azobis(2-cyanobutane)], 2,2-Azobis(methylbutyronitrile) [2,2-Azobis(Methylbutyronitrile)] and azobisdimethyl-Valeronitrile [AMVN (Azobisdimethyl-Valeronitrile)] )] may be at least one selected from the group consisting of, and preferably, a photoinitiator phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide [Phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide]. .

The initiator may be more than 0 wt%, less than 2 wt%, preferably 0.3 to 1.8 wt%, more preferably 0.5 to 1.5 wt%, based on the total weight of the mixture. If it is less than the above range, the polymerization reaction for forming a polymer electrolyte in the form of a random copolymer may not be initiated, and even if it exceeds the above range, the polymerization reaction does not start more smoothly, so there is no benefit from exceeding the above range.

(S2) step

In step (S2), oxygen may be removed from the mixture obtained in step (S1). Since the oxygen serves to remove radicals necessary for the polymerization reaction, it is preferable to remove oxygen from the mixed solution.

The method of removing oxygen may be a bubbling method or a freeze-pump-thaw method, and preferably, oxygen may be removed by nitrogen bubbling.

(S3) step

In step (S3), the mixture from which oxygen has been removed in step (S2) may be applied on a substrate to be cured.

A method of applying the oxygen-free mixture on the substrate may be selected from the group consisting of a spray method, screen printing, doctor blade method, and slot die method, but can be used in the art, the solution is applied on the substrate The method is not limited thereto.

After the application, the polymer electrolyte formed on the substrate, specifically, the polymer electrolyte membrane may be peeled off.

The polymer electrolyte formed on the substrate may be preferably a release film.

The release film is not particularly limited as long as it is a release film used in the art. For example, polyester resins such as polyethylene terephthalate, polybutyrene terephthalate, polyethylene naphthalate, and polybutyren naphthalate; polyimide resin; acrylic resin; styrene-based resins such as polystyrene and acrylonitrile-styrene; polycarbonate resin; polylactic acid resin; polyurethane resin; polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymer; vinyl resins such as polyvinyl chloride and polyvinylidene chloride; polyamide resin; sulfone-based resins; polyether-etherketone-based resins; allylate-based resin; Alternatively, a release film formed of a mixture of the above resins may be used.

The curing may be thermal curing or photo curing. The thermal curing may be performed by heating at a temperature of 50 to 80°C, preferably 55 to 75°C, and more preferably 60 to 70°C. If the thermosetting temperature is less than the above range, curing is not made as desired and thus a polymer electrolyte cannot be obtained. The photocuring may be UV curing.

lithium secondary battery

The present invention also relates to a lithium secondary battery comprising the polymer electrolyte as described above.

The lithium secondary battery according to the present invention includes a positive electrode, a negative electrode, and an electrolyte interposed therebetween, and in this case, the polymer electrolyte as described above may be used as the electrolyte.

The polymer electrolyte exhibits high lithium ion conductivity while satisfying both electrochemically excellent voltage stability and cation transport rate, so that it can be preferably used as an electrolyte for a battery to improve battery performance.

In addition, the electrolyte may further include a material used for this purpose in order to further increase lithium ion conductivity.

If necessary, the polymer electrolyte further includes an inorganic solid electrolyte or an organic solid electrolyte. The inorganic solid electrolyte is a ceramic-based material, a crystalline or amorphous and crystalline materials can be _{used, Thio-LISICON (Li 3.} 25 Ge 0 .25 P 0. 75 S 4), Li 2 S-SiS 2, LiI -Li ₂ S-SiS ₂ , LiI-Li ₂ SP ₂ S ₅ , LiI-Li ₂ SP ₂ O ₅ , LiI-Li ₃ PO ₄ -P ₂ S ₅ , Li ₂ SP ₂ S ₅ , Li ₃ PS ₄ , Li ₇ P ₃ S ₁₁ , Li ₂ OB ₂ O ₃ , Li ₂ OB ₂ O ₃ -P ₂ O ₅ , Li ₂ OV ₂ O ₅ -SiO ₂ , Li ₂ OB ₂ O ₃ , Li ₃ PO ₄ , Li ₂ O-Li ₂ WO ₄ -B ₂ O ₃ , LiPON, LiBON, Li ₂ O-SiO ₂ , LiI, Li ₃ N, Li ₅ La ₃ Ta ₂ O12, Li ₇ La ₃ Zr ₂ O ₁₂ , Li ₆ BaLa ₂ Ta ₂ O ₁₂ , Li ₃ PO _(4-3/2w) Nw (w is w<1), Li _{3 .} The inorganic solid electrolyte such as a _{6 Si 0 .6 P 0. 4 O} 4 is possible.

Examples of organic solid electrolytes include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, etc. A mixture of lithium salts may be used. In this case, these may be used alone or in combination of at least one or more.

A specific application method to the polymer electrolyte is not particularly limited in the present invention, and a known method may be selected or applied by a person skilled in the art.

A lithium secondary battery in which a polymer electrolyte can be applied as an electrolyte is not limited by a positive electrode or a negative electrode, and is particularly applicable to lithium-air batteries, lithium oxide batteries, lithium-sulfur batteries, lithium metal batteries, and all-solid-state batteries operating at high temperatures. .

The positive electrode of the lithium secondary battery is _{a layered compound such as lithium cobalt oxide (LiCoO 2} ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Formula _{Li 1 + x Mn 2 - x} O 4 (0≤x≤0.33), LiMnO 3, the lithium manganese oxide such as LiMn ₂ O _3, LiMnO _2; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O _{7 ;} Ni site type lithium nickel oxide represented by the formula LiNi _{1 - x} M _x O ₂ (M = Co, Mn, Al, Cu, Fe, Mg, B or Ga; 0.01≤x≤0.3); Formula LiMn _{2 - x} M _x O ₂ (M = Co, Ni, Fe, Cr, Zn or Ta; 0.01≤x≤0.1) or Li ₂ Mn ₃ MO ₈ (M = Fe, Co, Ni, Cu or Zn) ) represented by lithium manganese composite oxide; LiNi _x Mn _{2 - x} O ₄ A lithium-manganese composite oxide having a spinel structure; _{LiMn 2} O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; disulfide compounds; Chalcogenides such as Fe _{2 (MoO 4} ) ₃ , Cu ₂ Mo ₆ S ₈ , FeS, CoS and MiS, scandium, ruthenium, titanium, vanadium, molybdenum, chromium, manganese, iron, cobalt, nickel, copper, zinc, etc. oxides, sulfides, or halides of may be used, and more specifically, TiS ₂ , ZrS ₂ , RuO ₂ , Co ₃ O ₄ , Mo ₆ S ₈ , V ₂ O ₅ and the like may be used, but are limited thereto no.

Such a positive active material may be formed on a positive electrode current collector. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, for example, stainless steel, aluminum, nickel, titanium, fired carbon, or carbon on the surface of aluminum or stainless steel; Those surface-treated with nickel, titanium, silver, etc. may be used. In this case, the positive electrode current collector may use various forms such as a film, sheet, foil, net, porous body, foam, nonwoven body, etc. having fine irregularities formed on the surface so as to increase adhesion with the positive electrode active material.

In addition, as the negative electrode, a negative electrode mixture layer having a negative electrode active material is formed on the negative electrode current collector, or a negative electrode mixture layer (eg, lithium foil) is used alone.

In this case, the type of the anode current collector or the anode mixture layer is not particularly limited in the present invention, and known materials may be used.

In addition, the negative electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, carbon on the surface of copper or stainless steel , nickel, titanium, silver, etc. surface-treated, aluminum-cadmium alloy, etc. may be used. In addition, the negative electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, non-woven body, etc. having fine irregularities formed on the surface, like the positive electrode current collector.

In addition, the negative active material is one selected from the group consisting of crystalline artificial graphite, crystalline natural graphite, amorphous hard carbon, low crystalline soft carbon, carbon black, acetylene black, Ketjen black, super-P, graphene, and fibrous carbon More than carbon-based material, Si-based material, LixFe ₂ O ₃ (0≤x≤1), Li _x WO ₂ (0≤x≤1), Sn _x Me _{1 - x} Me' _y O _z (Me: Mn, Fe , Pb, Ge; Me': Al, B, P, Si, elements of Groups 1, 2, and 3 of the periodic table, halogen; 0<x≤1;1≤≤y≤3; 1≤z≤8), etc. of metal complex oxides; lithium metal; lithium alloy; silicon-based alloys; tin-based alloys; SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ , metal oxides such as Bi ₂ O _{5 ;} conductive polymers such as polyacetylene; Li-Co-Ni-based materials; titanium oxide; lithium titanium oxide and the like, but is not limited thereto.

In addition, the negative active material is SnxMe _{1 - x} Me' _y O _z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of Groups 1, 2, 3 of the periodic table, metal complex oxides such as halogen;0<x≤1;1≤y≤3;1≤z≤8); SnO, SnO ₂ , PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , GeO, GeO2 ₂ , Bi ₂ O ₃ , Bi ₂ O ₄ and An oxide such as Bi ₂ O ₅ may be used, and a carbon-based negative active material such as crystalline carbon, amorphous carbon, or a carbon composite material may be used alone or in combination of two or more thereof.

In this case, the electrode mixture layer may further include a binder resin, a conductive material, a filler, and other additives.

The binder resin is used for bonding the electrode active material and the conductive material and bonding to the current collector. Examples of such binder resins include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetra fluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

The conductive material is used to further improve the conductivity of the electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, graphite such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; polyphenylene derivatives and the like can be used.

The filler is optionally used as a component for inhibiting the expansion of the electrode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. For example, an olipine-based polymer such as polyethylene or polypropylene; A fibrous material such as glass fiber or carbon fiber is used.

The shape of the lithium secondary battery as described above is not particularly limited, and may be, for example, a jelly-roll type, a stack type, a stack-folding type (including a stack-Z-folding type), or a lamination-stack type, preferably It may be stack-folding.

After manufacturing the electrode assembly in which the negative electrode, the polymer electrolyte and the positive electrode are sequentially stacked, the electrode assembly is placed in a battery case, and then sealed and assembled with a cap plate and gasket to manufacture a lithium secondary battery.

At this time, lithium secondary batteries can be classified into various batteries such as lithium-sulfur batteries, lithium-air batteries, lithium-oxide batteries, and lithium all-solid-state batteries depending on the anode/cathode material used. , pouch type, and the like, and can be divided into bulk type and thin film type according to the size. Since the structure and manufacturing method of these batteries are well known in the art, a detailed description thereof will be omitted.

The lithium secondary battery according to the present invention can be used as a power source for devices requiring high capacity and high rate characteristics. Specific examples of the device include a power tool powered by an omniscient motor; electric vehicles, including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters; electric golf carts; and a power storage system, but is not limited thereto.

Hereinafter, preferred examples are presented to help the understanding of the present invention, but the following examples are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, It goes without saying that changes and modifications fall within the scope of the appended claims.

In the following Examples and Comparative Examples, polymer electrolytes were prepared according to the compositions shown in Table 1 below.

(unit:
weight%) Non-PEO polymer adjuvant Phosphate-based crosslinking agent menstruum
SIL ^{Note 4)} EEEA ^{Note 1)} styrene ^{Note 2)} Bis[2-(methacryloyloxy)ethyl]phosphate ^{Note 3)} NMAC LiTFSI Example 1 28 4 9 30 29 Example 2 28 9 4 30 29 Example 3 24 13 4 30 29 Example 4 20 17 4 30 29 Comparative Example 1 21 (PEGMA ^{Note 5)} ) - 20
(PEGDA ^{Note 6)} ) 30 29 Note 1) EEEA (Sigma-Aldrich)
Note 2) styrene (Sigma-Aldrich)
Note 3) bis[2-(methacryloyloxy)ethyl]phosphate (bis[2-(methacryloyloxy)ethyl]phosphate, Sigma-Aldrich)
Note 4) SIL: According to Preparation Example 1 below, prepared by mixing NMAC (N-methylacetamide, Sigma-Aldrich) and LiTFSI (3M, Sigma-Aldrich).
Note 5) PEGMEA (poly(ethylene glycol) methyl ether acrylate, Sigma-Aldrich, Mn: 480)
Note 6) PEGDA poly(ethylene glycol) diacrylate (PEGDA, Sigma-Aldrich, Mn: 575)

manufacturing example One: sorbate ionic liquids ( SIL ) synthesis

NMAC (Triglyme, G3, Sigma-Aldrich), an amide-based material, and LiTFSI (bis(trifluoromethane)sulfonimide lithium salt, Sigma-Aldrich), a lithium salt vacuum dried at 100° C. for 24 hours, were 50.46 wt% and 49.54 wt%, respectively. % was mixed. Thereafter, SIL (Li[NMAC][TFSI], 1.9M) represented by the following Chemical Formula 1 was synthesized by stirring for 4 hours at room temperature in a glove box.

<Formula 1>

Examples 1 to 4

(1) Raw material mixing

According to the composition described in Table 1, a mixed solution was prepared by measuring in a 20 ml reaction vial so that the total amount of the non-PEO-based polymer, reinforcing agent, phosphate-based crosslinking agent and solvent was 2 g.

Then, a photoinitiator Irgacure-819 (Sigma-Aldrich) was added to the mixed solution and mixed through a vortex for 1 minute to completely dissolve to obtain a mixture. The photoinitiator was made to be 1% by weight based on the total weight of the mixture.

(2) oxygen removal

The mixture was bubbled with nitrogen for 2 minutes to remove residual oxygen from the mixed solution, thereby preparing a polymer electrolyte.

(3) hardening

Using a dropper, the mixture from which the residual oxygen has been removed was applied on a release film (Polyester film (SKC, SH71S, 100 μm)) and photocured.

The photocuring was carried out by placing the release film coated with the mixture in a UV black light chamber and UV curing for 1 h to prepare a polymer electrolyte membrane.

Comparative Example 1

According to the composition of Table 1, it was carried out in the same manner as in Example 1, except that PEGMA was used instead of EEEA, a non-PEO-based polymer, PEGDA was used as a crosslinking agent, and a polymer electrolyte membrane was prepared without using styrene as a reinforcing agent.

Experimental Example 1

For the polymer electrolyte membranes prepared in Examples and Comparative Examples, the ionic conductivity was measured in the following manner, and whether a free-standing film was formed was observed, and the results are shown in Table 2 below.

Ion conductivity is measured using a potentiostat after manufacturing a coin cell in the form of SUS (Steel Use Stainless)/polymer electrolyte/SUS, but 10mV at 25℃, 1Hz to 5MHz The ionic conductivity was measured while applying a voltage of , and the results are shown in Table 2.

The formation of free-standing film was observed with the naked eye, and the case where the polymer electrolyte was formed in the form of a free-standing film was classified by ○, and the case where the polymer electrolyte was not formed in the form of a free-standing film was divided by ×.

Ionic Conductivity (σ, S/cm) Free-standing film formation Example 1 1.2 x 10 ^-5 ○ Example 2 5.4 x 10 ^-4 ○ Example 3 8.0 x 10 ^-4 ○ Example 4 1.6 x 10 ^-4 × Comparative Example 1 4.4 x 10 ^-5 ×

Referring to Table 2, it can be seen that the ionic conductivity of the polymer electrolytes of Examples 1 to 4 prepared using a non-PEO-based polymer and a phosphate-based crosslinking agent is superior to that of Comparative Example 1 without using a phosphate-based crosslinking agent. .

In addition, it was confirmed that Examples 4 and Comparative Example 1 in which the content of styrene as a reinforcing agent was high or not included was not formed in the form of a free-standing film, which is a polymer electrolyte.

Experimental Example 2

For the polymer electrolytes prepared in Examples and Comparative Examples, voltage stability was measured in the following manner.

After the coin cell was fabricated in the form of Li/polymer electrolyte/SUS, voltage stability was measured in the range of 3 to 6 V at a scan rate of 5 mV/s.

1 is a graph showing the results of measuring voltage stability for coin cells including polymer electrolytes prepared in Examples 1 and 3 and Comparative Example 1. FIG.

Referring to FIG. 1 , when using the polymer electrolytes prepared in Examples 1 and 3, it can be seen that the voltage stability is improved compared to the case of using the polymer electrolytes prepared in Comparative Example 1.

Experimental Example 3

For the polymer electrolytes prepared in Examples and Comparative Examples, a flame retardancy evaluation experiment was performed.

Using a torch, the polymer electrolytes of Examples 1 to 3 and Comparative Example 1 were ignited.

2 shows photographs before and after ignition of the polymer electrolytes of Examples 1 to 3;

Referring to FIG. 2 , Example 1 did not ignite, Example 2 burned after 2 to 3 seconds of ignition, and Example 3 showed combustion after 4 to 5 seconds of ignition.

On the other hand, in Comparative Example 1 (not shown), the ignition state was maintained for 5 seconds or more, and it was confirmed that the flame retardant properties of the polymer electrolyte prepared using the flame-retardant phosphate-based crosslinking agent as in Examples 1 to 3 were excellent.

Claims (12)

non-PEO (polyethylene oxide)-based polymers; adjuvant; phosphate-based crosslinking agents; and a sorbate ionic liquid (SIL). According to claim 1,
The non-PEO-based polymer is 2-(2-ethoxyethoxy)ethyl acrylate [2-(2-ethoxyethoxy)ethyl acrylate, EEEA], butyl acrylate, hexyl acrylate, and ethyl At least one selected from the group consisting of hexyl acrylate (ethyl hexyl acrylate), a polymer electrolyte. According to claim 1,
The reinforcing agent is at least one selected from the group consisting of styrene, methyl methacrylate (MMA) and methacrylate (MA), a polymer electrolyte. According to claim 1,
The phosphate-based crosslinking agent is bis [2- (methacryloyloxy) ethyl] phosphate (bis [2- (methacryloyloxy) ethyl] phosphate), triphenyl phosphate, tricresyl phosphate, tri (2,6-dimethylphenyl) At least one selected from the group consisting of phosphate and tri (2,4,6-trimethylphenyl) phosphate, a polymer electrolyte. According to claim 1,
The sorbate ionic liquid is a polymer electrolyte comprising a lithium salt and a glyme-based material or an amide-based material. 6. The method of claim 5,
In the sorbate ionic liquid, the molar ratio of the lithium salt and the glyme-based material is 1: 0.1 to 3, and the molar ratio of the lithium salt and the amide-based material is 1: 1 to 6, the polymer electrolyte. According to claim 1,
The polymer electrolyte is
1 to 30% by weight of the non-PEO-based polymer;
1 to 20% by weight of the reinforcing agent;
3 to 10% by weight of the phosphate-based crosslinking agent; and
45 to 75% by weight of said sorbate ionic liquid;
A polymer electrolyte comprising a. According to claim 1,
The polymer electrolyte is a polymer electrolyte membrane in the form of a network, a polymer electrolyte. (S1) non-PEO polymer; adjuvant; phosphate-based crosslinking agents; and adding an initiator to the mixed solution of the sorbate ionic liquid to form a mixture;
(S2) removing oxygen from the mixture formed in step (S1); and
(S3) applying the mixture from which oxygen has been removed in step (S2) on a substrate and curing the mixture; 10. The method of claim 9,
The method for producing a polymer electrolyte, wherein the initiator is added in an amount of 0.1 to 2% by weight based on the total weight of the mixture. 10. The method of claim 9,
In the step (S3), the curing is thermosetting or photocuring, a method for producing a polymer electrolyte. A lithium secondary battery comprising the polymer electrolyte of any one of claims 1 to 8.

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