KR20200077803A - 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, a crosslinked polymer electrolyte having excellent voltage stability and flame retardancy can be prepared by polymerizing a raw material including a non-PEO-based polymer, a reinforcement, and a phosphate-based crosslinking agent.

Description

Polymer electrolyte and its preparation method {Polymer Electrolyte and Method for Preparing the Same}

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

Lithium ion secondary batteries having high energy density are mainly used in current portable electronic devices. At this time, the mainly used liquid electrolyte has problems such as leakage and explosion risk. 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 for preventing leakage. In addition, since the battery is thick, there are limitations in battery design. In the future, as electronic devices become thinner and more flexible, lithium ion batteries using liquid as an electrolyte cannot satisfy all of the 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 that do not have a memory effect, they can prevent electrolyte leakage to the outside of the battery, thereby improving the stability of the battery, and the electrode and separator are integrated. Because of the reduced surface resistance, it is advantageous for high efficiency charging and discharging with relatively low internal resistance. In addition, the electrolyte film can be thinned to form 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. Therefore, batteries of portable electronic devices such as mobile phones, notebook computers, and digital cameras, which are increasing in demand for stability, miniaturization, and high capacity, are expected to be largely replaced with lithium polymer batteries in existing lithium ion batteries. In addition, lithium polymer batteries are expected to be applied to high-capacity lithium secondary batteries, such as hybrid electric vehicles, and are in the spotlight as next-generation batteries.

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 electrode and the negative electrode is made of a polymer, and this polymer separator can even act as an electrolyte. In a lithium polymer battery, ion conduction is performed by internal ion transfer of a stable polymer electrolyte like a solid phase.

The polymer electrolyte used in the lithium polymer battery is an intrinsic solid polymer electrolyte and a polymer film in which ions of dissociated salts are moved by the segmentation motion of the polymer by adding an electrolytic salt to a polymer containing hetero elements such as O, N, and S. The liquid electrolyte is impregnated therein and immobilized like an electrolytic salt to study the gel-type polymer electrolyte that exhibits ion conductivity.

Of these, when using the gel polymer electrolyte, it is still difficult to secure the stability of the battery due to leakage of the existing liquid electrolyte, and the manufacturing process of the battery also remains a problem. Intrinsic solid polymer electrolytes have been studied since 1975, when P. V. Wright discovered the conduction of sodium ions in polyethylene oxide (PEO). Intrinsic solid polymer electrolytes have the advantages of high chemical and electrochemical stability and the ability to use high-capacity lithium metal electrodes, but they have 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 local motion degree of the polymer chain, various methods of lowering the high crystallinity of the PEO-based polymer electrolyte to study the dissociated ions to move freely have been studied. .

As one of the methods, studies have been conducted to graft low molecular weight PEO onto a flexible polymer backbone having a very low Tg value. Siloxane polymer electrolytes having PEOs of various lengths as side branches were synthesized, and when the repeating chains of PEO were six that did not exhibit crystallinity, they exhibited high ionic conductivity of 4.5Х10 ^-4 S/cm at room temperature.

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

Korean Patent Publication No. 2015-3364763 Japanese Patent Publication No. 1999-240998

The present inventors conducted a multi-faceted study to solve the above problems, as a result, non-PEO (polyethylene oxide) polymer; Adjuvant; Phosphate-based crosslinking agents; And a solvent; a non-PEO-based polymer electrolyte was prepared, and the prepared polymer electrolyte was a non-PEO-based polymer electrolyte that exhibited excellent voltage stability and flame retardancy compared to a conventional PEO-based polymer electrolyte, and was confirmed to be advantageous in improving battery performance. .

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

In addition, another object of the present invention is to provide a lithium secondary battery comprising a polymer electrolyte as described above.

In order to achieve the above object, the present invention, non-PEO-based polymer; Adjuvant; Phosphate-based crosslinking agents; And a solvent ionic liquid (SIL).

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 one or more selected from the group consisting of hexyl acrylate (ethyl hexyl acrylate).

The reinforcing agent may be one or more 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), triphenylphosphate, tricresylphosphate, tri(2,6-dimethylphenyl) It may be one or more selected from the group consisting of phosphate and tri(2,4,6-trimethylphenyl)phosphate.

The solvent may include an ionic liquid lithium salt and a glyme-based material or an amide-based material.

In the solvent 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, the non-PEO-based polymer 1 to 30% by weight; 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 solvent ionic liquid.

The polymer electrolyte may be a network type polymer electrolyte membrane.

The present invention also, (S1) non-PEO-based polymer; Adjuvant; Phosphate-based crosslinking agents; And a solvent ionic liquid; adding an initiator to the mixed solution to form a mixture; (S2) removing oxygen from the mixture formed in step (S1); And (S3) applying the mixture from which the oxygen was removed in the step (S2) to the substrate to cure it. It provides a method for producing a polymer electrolyte, including.

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

In the 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 network-shaped non-PEO-based polymer membrane.

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

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

1 is a graph showing the results of measuring the voltage stability of the coin cell containing the polymer electrolyte prepared in Examples 1, 3 and Comparative Example 1.
FIG. 2 shows photographs before and after ignition of the polymer electrolytes of Examples 1 to 3.

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

The terms or words used in the specification and claims should not be interpreted as being limited to ordinary or dictionary meanings, and the inventor can appropriately define the concept of terms to describe his or her invention in the best way. Based on the principle that it should be interpreted as a meaning and a concept consistent with the technical idea of the present invention.

Polymer electrolyte

The present invention relates to a non-PEO-based crosslinked polymer electrolyte that exhibits improved voltage stability compared to a conventional PEO-based polymer electrolyte.

The polymer electrolyte according to the present invention includes a non-PEO polymer; Adjuvant; Phosphate-based crosslinking agents; And Solvate Ionic Liquid (SIL).

In the present invention, the non-PEO-based polymer is included in the polymer electrolyte, and can improve the voltage stability while maintaining ions equal to or higher than the polymer electrolyte containing the PEO-based polymer.

The non-PEO polymer may be selected from acrylate polymers and allyl ether polymers 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, and may be one or more selected from the group consisting of ethyl hexyl acrylate, 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 containing the polymer electrolyte may decrease, and the crosslinking degree of the polymer electrolyte may decrease, and if it is above the range, the ionic conductivity of the polymer electrolyte may decrease.

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

The reinforcing agent may be one or more selected from the group consisting of styrene, methyl methacrylate (MMA), and methacrylate (MA), and 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 efficiency of the polymer electrolyte may be lowered, and if it is above the above range, ionic conductivity of the polymer electrolyte may be lowered.

In the present invention, as the phosphate-based crosslinking agent, flame retardancy and crosslinkability of the polymer electrolyte can be improved.

The phosphate-based crosslinking agent is bis[2-(methacryloyloxy)ethyl]phosphate (bis[2-(methacryloyloxy)ethyl] phosphate), triphenylphosphate, tricresylphosphate, 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, the polymer electrolyte may be uncured, and the flame retardant improving effect may be insignificant, and if it is above the above range, ionic conductivity may be reduced due to high crosslinking density.

The solvent ionic liquid may be 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, the polymer electrolyte may be uncured, and the flame retardant improving effect may be insignificant, and if it is above the above range, ionic conductivity may be reduced due to high crosslinking density.

The SIL may be swelled or not included in the polymer electrolyte according to a difference in solubility with each component included in the polymer electrolyte.

For example, the SIL is included in the non-swelled form of the reinforcing agent included in the polymer electrolyte, that is, styrene, and other components other than styrene, that is, may be included in a swelled form for the non-PEO-based polymer and the phosphate-based crosslinking agent. 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, and 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 equal to 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 the lithium salt.

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, and more preferably 1: 3 to 5 . If the molar ratio of the amide-based material to the lithium salt is less than or equal to 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 . Preferably, the lithium salt is LiN(SO ₂ F) ₂ Or LiN(SO ₂ CF ₃ ) ₂ [LiTFSI] It may be, 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 , N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, and N,N-diethylacetamide. -Methylacetamide (NMAC).

The polymer electrolyte according to the present invention is a non-PEO-based crosslinked polymer electrolyte. Specifically, the polymer electrolyte according to the present invention may be a network-type polymer electrolyte membrane.

Manufacturing method of polymer electrolyte

The present invention also relates to a method for preparing a polymer electrolyte having improved elasticity while exhibiting ionic conductivity equal to or higher than a conventional liquid electrolyte.

Method for producing a polymer electrolyte according to the present invention, (S1) non-PEO-based polymer; Adjuvant; Phosphate-based crosslinking agents; And a solvent ionic liquid; adding an initiator to the mixed solution to form a mixture; (S2) removing oxygen from the mixture formed in step (S1); And (S3) applying the mixture from which the oxygen is removed in the step (S2) to the substrate to cure it.

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

(S1) step

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

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

The initiator may initiate polymerization of the monomers so that a polymerization reaction can be initiated so that a polymer electrolyte in the form of a random copolymer is formed.

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, Cumyl hydroperoxide, 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 )], a phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, which is preferably a photoinitiator. .

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

(S2) step

In the step (S2), oxygen may be removed from the mixture obtained in the 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 the oxygen may be a bubbling method or a freeze-pump-thaw method, and oxygen may be removed by bubbling nitrogen.

(S3) step

In the step (S3), the mixture from which oxygen is removed in the step (S2) may be applied to the substrate to cure.

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

After the coating, 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 terephthalide, polyethylene naphthalate, and polybutyrene naphthalate; Polyimide resin; Acrylic resin; Styrene resins such as polystyrene and acrylonitrile-styrene; Polycarbonate resin; Polylactic acid resin; Polyurethane resins; Polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; Vinyl resins such as polyvinyl chloride and polyvinylidene chloride; Polyamide resins; Sulfone resins; Polyether-etherketone-based resins; Allylate-based resins; Alternatively, a release film formed of a mixture of the resins may be used.

The curing may be thermosetting or photocuring. The thermal curing may be to be cured by heating to a temperature of 50 to 80 ℃, preferably 55 to 75 ℃, more preferably 60 to 70 ℃. If the heat curing temperature is less than the above range, curing may not be achieved as desired, so that 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 a polymer electrolyte as described above.

The lithium secondary battery according to the present invention includes an anode, a cathode, and an electrolyte interposed therebetween, and at this time, a 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, and can be preferably used as an electrolyte of the battery to improve the performance of the battery.

In addition, the electrolyte may further include a material used for this purpose in order to further increase the 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 polymer derivatives such as polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, and polyvinylidene fluoride. A mixture of lithium salts can be used. At this time, these may be used alone or in combination of at least one or more.

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

The lithium secondary battery to which the polymer electrolyte is applicable as an electrolyte is not limited to the positive electrode or the 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 may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ) or a compound substituted with one or more transition metals; Lithium manganese oxides such as the formula Li _{1 + x} Mn _{2 - x} O ₄ (0≤x≤0.33), LiMnO ₃ , 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 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 Lithium manganese composite oxide represented by); A spinel-structure lithium manganese composite oxide represented by LiNi _x Mn _{2 - x} O ₄ ; LiMn ₂ O _{4 in} which part of Li in the formula is substituted with alkaline earth metal ions; 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. Oxide, sulfide or halide 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, etc. may be used, but is not limited thereto. no.

The positive electrode active material may be formed on the positive electrode current collector. The positive electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel, Surface treatment with nickel, titanium, silver, or the like can be used. At this time, the positive electrode current collector may be used in various forms, such as films, sheets, foils, nets, porous bodies, foams, and non-woven fabrics, on which fine irregularities are formed on the surface, so as to increase adhesion with the positive electrode active material.

In addition, 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 (for example, lithium foil) is used alone.

At this time, the type of the negative electrode current collector or the negative electrode mixture layer is not particularly limited in the present invention, and a known material can be used.

In addition, the negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery, for example, copper, stainless steel, aluminum, nickel, titanium, fired carbon, carbon on the surface of copper or stainless steel. , Surface treatment with nickel, titanium, silver, etc., aluminum-cadmium alloy, and the like can be used. In addition, the cathode current collector, like the anode current collector, various forms such as a film, sheet, foil, net, porous body, foam, and non-woven fabric with fine irregularities on the surface may be used.

In addition, the negative electrode 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. 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, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0<x≤1;1≤≤y≤3; 1≤z≤8), etc. Metal composite oxide; Lithium metal; Lithium alloys; 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 are not limited to these.

In addition, the negative electrode active material is SnxMe _{1 - x} Me' _y O _z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen; metal composite oxides such as 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 carbon composite may be used alone or in combination of two or more.

At this time, 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 a binder resin include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetra And fluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, fluorine rubber, and various copolymers thereof.

The conductive material is used to further improve the conductivity of the electrode active material. The 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 blacks 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 powder, aluminum powder, 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 selectively used as a component that suppresses 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, olefinic polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are 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 a stack-folding type.

After manufacturing the electrode assembly in which the negative electrode, the polymer electrolyte, and the positive electrode are sequentially stacked, they are placed in a battery case, and then sealed by a cap plate and a gasket to assemble to produce a lithium secondary battery.

At this time, the lithium secondary battery can be classified into various batteries such as lithium-sulfur batteries, lithium-air batteries, lithium-oxide batteries, and lithium solid-state batteries according to the anode/cathode materials used. Cylindrical, square, and coin types depending on the shape , It can be classified as a pouch type, and can be divided into a bulk type and a thin film type according to the size. The structure and manufacturing method of these batteries are well known in the art, so detailed descriptions thereof are 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. As a specific example of the device, a power tool that is driven by an electric motor and moves; Electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); An electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (Escooter); Electric golf carts; And a power storage system, but is not limited thereto.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely illustrative of the present invention, and it is apparent to those skilled in the art that various changes and modifications are possible within the scope and technical thought scope of the present invention. It is natural that changes and modifications fall within the scope of the appended claims.

In the following Examples and Comparative Examples, a polymer electrolyte was prepared according to the composition as 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, it was 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: Solvate Ionic liquid( SIL ) synthesis

The amide-based materials NMAC (Triglyme, G3, Sigma-Aldrich) and 50.46 wt% and 49.54 wt. %. Then, in a glove box (glove box), SIL (Li [NMAC] [TFSI], 1.9 M) represented by the following Chemical Formula 1 was synthesized by stirring for 4 hours at room temperature.

<Formula 1>

Examples 1 to 4

(1) Mixing raw materials

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

Thereafter, Irgacure-819 (Sigma-Aldrich), a photoinitiator, was added to the mixed solution to obtain a mixture mixed through vortex for 1 minute so as to be completely dissolved. The photoinitiator was set to 1% by weight based on the total weight of the mixture.

(2) Oxygen removal

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

(3) Curing

Using the eyedropper, the residual oxygen-removed mixture was applied onto a release film (Polyester film (SKC, SH71S, 100 μm)) and photocured.

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

Comparative Example 1

According to the composition of Table 1, a polymer electrolyte membrane was prepared in the same manner as in Example 1, using PEGMA instead of EEEA, which is a non-PEO-based polymer, PEGDA as a crosslinking agent, and not using styrene, which is a reinforcing agent.

Experimental Example 1

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

The ion conductivity is measured using a potentiostat after producing a coin cell in the form of steel use stainless (SUS)/polymer electrolyte/SUS, but 10mV in the range of 25℃ and 1Hz to 5MHz. Ion conductivity was measured by applying a voltage of, and the results are shown in Table 2.

Whether the free-standing film was formed was observed with the naked eye, and when the polymer electrolyte was formed in the form of a free-standing film, it was classified as ○, and when it was not formed as a free-standing film, it was classified as ×.

Ion conductivity (σ, S/cm) Whether free-standing film is formed 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 Comparative Example 1 without using a phosphate-based crosslinking agent. .

In addition, it was confirmed that the content of styrene, which is a reinforcing agent, was not high, and Example 4 and Comparative Example 1, which did not contain, were 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 manufacturing coin cells in the form of Li/polymer electrolyte/SUS, voltage stability was measured at a scan rate of 5 mV/s in a range of 3 to 6 V.

1 is a graph showing the results of measuring the voltage stability of the coin cell containing the polymer electrolyte prepared in Examples 1, 3 and Comparative Example 1.

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

Experimental Example 3

For the polymer electrolytes prepared in Examples and Comparative Examples, flame retardancy evaluation experiments were conducted.

The polymer electrolytes of Examples 1 to 3 and Comparative Example 1 were ignited using a torch.

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

2, Example 1 was not ignited, Example 2 was burned after 2-3 seconds of ignition, and Example 3 was burned after 4-5 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) polymers; Adjuvant; Phosphate-based crosslinking agents; And a solvent 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 A polymer electrolyte of at least one member selected from the group consisting of hexyl acrylate. 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), triphenylphosphate, tricresylphosphate, tri(2,6-dimethylphenyl) A polymer electrolyte of at least one member selected from the group consisting of phosphate and tri(2,4,6-trimethylphenyl)phosphate. According to claim 1,
The solvent ionic liquid is a lithium salt and a polymer electrolyte comprising a glyme-based material or an amide-based material. The method of claim 5,
In the solvent 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, a polymer electrolyte. According to claim 1,
The polymer electrolyte,
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 solvent ionic liquid;
That is, a polymer electrolyte. According to claim 1,
The polymer electrolyte is a polymer electrolyte membrane in the form of a network. (S1) non-PEO polymer; Adjuvant; Phosphate-based crosslinking agents; And a solvent ionic liquid; adding an initiator to the mixed solution to form a mixture;
(S2) removing oxygen from the mixture formed in step (S1); And
(S3) the step of applying a mixture on which the oxygen is removed in the step (S2) is cured by applying on a substrate; containing, a method of producing a polymer electrolyte. The method of claim 9,
The initiator is to be added in an amount of 0.1 to 2% by weight based on the total weight of the mixture, a method for producing a polymer electrolyte. 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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