KR102510291B1 - Solid electrolyte composition for secondary battery and solid electrolyte - Google Patents

Abstract

The present invention relates to an electrolyte composition and a solid electrolyte including a polycarbonate-based polymer, and more particularly, to an electrolyte composition in which polyethylene oxide having a molecular weight of a specific value or more is introduced and a polycarbonate-based linear polymer blended with polyethylene oxide is applied. A solid electrolyte formed of a flexible film having excellent conductivity and capable of free standing at room temperature can be provided.

Description

Solid electrolyte composition for secondary battery and solid electrolyte prepared therefrom

The present invention relates to a solid electrolyte composition for a secondary battery and a solid electrolyte prepared therefrom.

A secondary battery, which is representatively known among electrochemical devices, refers to a device that converts external electrical energy into chemical energy, stores it, and generates electricity when needed. The name "rechargeable battery" is also used to mean that it can be charged multiple times. Commonly used secondary batteries include lead storage batteries, nickel cadmium batteries (NiCd), nickel hydrogen storage batteries (NiMH), lithium ion batteries (Li-ion), and lithium ion polymer batteries (Li-ion polymer). Secondary batteries provide both economic and environmental advantages compared to disposable primary batteries.

On the other hand, as wireless communication technology gradually develops, portable devices or automobile accessories, etc. are required to be lightweight, and demand for secondary batteries used as energy sources for these devices is increasing.

Currently, secondary batteries are used where low power is required, such as devices that help start a car, portable devices such as laptops and mobile phones, and uninterruptible power supplies. In particular, as hybrid vehicles and electric vehicles are put into practical use in terms of preventing environmental pollution, studies to reduce manufacturing cost and weight and extend lifespan by using secondary batteries for next-generation vehicle batteries are emerging.

In general, a secondary battery is manufactured by mounting an electrode assembly composed of a negative electrode, a positive electrode, and a separator inside a pouch-type case of a cylindrical or prismatic metal can or an aluminum laminate sheet, and injecting an electrolyte into the electrode assembly.

However, in the case of a secondary battery, since a cylindrical, prismatic, or pouch-shaped case having a certain space is required, there are limitations in developing various types of portable devices. Accordingly, there is a demand for a new type of secondary battery that can be easily modified. In particular, as an electrolyte included in a secondary battery, an electrolyte having no fear of leakage and excellent ionic conductivity is required.

Conventionally, as an electrolyte for an electrochemical device, a liquid electrolyte obtained by dissolving a salt in a non-aqueous organic solvent has been mainly used. However, such a liquid electrolyte has a high possibility of deterioration of electrode materials and volatilization of organic solvents, as well as occurrence of combustion due to an increase in the ambient temperature and the temperature of the battery itself, and there is a risk of leakage, and thus various types of high safety. It is difficult to implement the electrochemical device of

In order to solve the problem of these liquid electrolytes, research on polymer electrolytes is being actively conducted. Polymer electrolytes are largely classified into gel type and solid type. A gel-type polymer electrolyte is an electrolyte that exhibits conductivity by impregnating a liquid electrolyte with a high boiling point in a polymer film and fixing it together with a lithium salt. It contains a large amount of liquid electrolyte and has similar ionic conductivity to pure liquid electrolyte, but there is still a problem in electrochemical stability. remains

On the other hand, in the case of a solid polymer electrolyte, there is an advantage in that the stability problem related to leakage is improved because a liquid electrolyte is not included, and chemical and electrochemical stability are high. However, the ionic conductivity at room temperature is about 100 times lower than that of the liquid electrolyte, and many studies are being conducted to improve this.

Polyethylene oxide (PEO) is currently the most widely used material for solid polymer electrolytes, and has the ability to conduct lithium ions despite being in a solid state. However, in the case of linear PEO polymer electrolytes, chain fluidity is limited due to high crystallinity, and a large amount of lithium ions cannot be dissociated due to a low dielectric constant (5.0). In addition, it is difficult to apply to lithium secondary batteries due to its very low conductivity at room temperature, and its electrochemically stable voltage range is 4.0 V vs Li+/Li, which is not sufficient as a high-voltage battery material for high-energy batteries.

Accordingly, a method of increasing the flexibility of the polymer main chain by adding a plasticizer to polyethylene oxide, a method of lowering the crystallinity by combining low molecular weight ethylene oxide side branches with a non-rigid polymer main chain, or a method of adding low molecular weight polyethylene oxide to a polymer having a crosslinked structure. A method of improving conductivity by lowering the crystallinity of polyethylene oxide by immobilizing it has been studied, but there are still limitations.

On the other hand, as the liquid carbonate-based electrolyte is modified into a polycarbonate-based material, interest in the polycarbonate-based solid electrolyte is increasing, focusing on forming a stable SEI (Solid Electrolyte Interphase) layer on the electrode. For example, solid electrolytes using poly(carprolactone-co-trimethylene carbonate), poly(propylene carbonate), poly(vinylene carbonate), or poly(ethylene carbonate) have high ionic conductivity and a higher lithium ion transfer number than PEO-based electrolytes. (Li+ transference number) was shown.

According to a recent study, it is known that a polymer containing a carbonate functional group can be applied as a solid electrolyte by introducing an aliphatic chain or an ethylene oxide chain between carbonate groups. However, in this study, there is a problem of using an excessive amount of lithium salt in order to exhibit an ionic conductivity of 10 ⁻⁵ S/cm or more at room temperature, and it is actually applied in a liquid form at room temperature, revealing its limitations. In addition, since the unit of the ethylene oxide chain is short, it is difficult to efficiently chelate lithium ions, and accordingly, the limit of ionic conductivity is also appearing.

Korean Patent Registration No. 10-1527560 (2015.06.03), "Polymer electrolyte for lithium secondary battery, manufacturing method thereof, and lithium secondary battery comprising the same" Korean Patent Registration No. 10-0531724 (November 22, 2005), "Oligomer Viscous Material Impregnated Porous Membrane Solventless Polymer Electrolyte and Secondary Battery Using It"

Accordingly, the present inventors have conducted various studies to solve the above problems, and as a result, when preparing a polycarbonate-based linear polymer into which polyethylene oxide having a molecular weight of a specific value or more is introduced and blending it with polyethylene oxide to prepare a solid electrolyte, the electrolyte The present invention was completed by confirming that the ionic conductivity of is improved and suitable processability capable of forming a flexible film capable of free standing at room temperature can be secured.

Accordingly, an object of the present invention is to provide a solid electrolyte composition for a secondary battery including a polyethylene oxide-containing polycarbonate-based linear polymer and a polyethylene oxide polymer.

In addition, another object of the present invention is to provide a solid electrolyte for a secondary battery formed by crosslinking the composition.

In order to achieve the above object, the present invention,

Provided is a solid electrolyte composition for a secondary battery including a polycarbonate-based polymer having a structure represented by Formula 1 below and polyethylene oxide.

[Formula 1]

(In Formula 1, n and m are each independently an integer of 8≤n≤114 and 2≤m≤500, and R ₁ and R ₂ are each independently hydrogen or independently of each other substituted or unsubstituted C1 to C6 is an alkyl group)

One embodiment of the present invention is that the weight average molecular weight of the polycarbonate-based polymer is 1,000 to 200,000 g / mol.

One specific example of the present invention is that the polyethylene oxide has a number average molecular weight of 20,000 to 2,000,000.

One embodiment of the present invention is that the weight ratio of the polycarbonate-based polymer and polyethylene oxide is 1:99 to 50:50.

One embodiment of the present invention is that the composition further comprises a crosslinking agent.

One specific example of the present invention is that the crosslinking agent is any one selected from the group consisting of an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, and a vinyl-based crosslinking agent.

One embodiment of the present invention is that the crosslinking agent is included in 0.1 to 20 parts by weight based on 100 parts by weight of the total electrolyte composition.

Also, the present invention

Provided is a solid electrolyte for a secondary battery formed by heating or photocuring the above-described solid electrolyte composition for a secondary battery.

One embodiment of the present invention is to include 10 to 90 parts by weight of a lithium salt based on 100 parts by weight of the electrolyte composition.

One embodiment of the present invention is that the lithium salt is LiF, LiCl, LiBr, LiI, LiClO ₄ , LiClO ₃ , LiAsF ₆ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiNO ₃ , LiN(CN) ₂ , LiPF ₆ , Li (CF ₃ ) ₂ PF ₄ , Li(CF ₃ ) ₃ PF ₃ , Li(CF ₃ ) ₄ PF ₂ , Li(CF ₃ ) ₅ PF, Li(CF ₃ ) ₆ P, LiSO ₃ CF ₃ , LiSO ₃ C ₄ F ₉ , LiSO ₃ (CF ₂ ) ₇ CF ₃ , LiN(SO ₂ CF ₃ ) ₂ , LiOC(CF ₃ ) ₂ CF ₂ CF ₃ , LiCO ₂ CF ₃ , LiCO ₂ CH ₃ , LiSCN, LiB(C ₂ It is one or more selected from the group consisting of O ₄ ) ₂ , LiBF ₂ (C ₂ O ₄ ) and LiBF ₄ .

One embodiment of the present invention is that the thickness of the electrolyte is 10 to 1000㎛.

The solid electrolyte composition for a secondary battery according to the present invention includes a polyethylene oxide-containing polycarbonate-based linear polymer and a plasticized polyethylene oxide-based polymer to improve the ionic conductivity and electrochemical stability of the electrolyte of a lithium secondary battery, and is free at room temperature. It is possible to secure suitable fairness capable of forming a flexible film capable of standing (free standing).

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

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

Terms used in the present invention are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In the present invention, terms such as 'include' or 'having' designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other It should be understood that the presence or addition of features, numbers, steps, operations, components, parts, or combinations thereof is not precluded.

The present invention relates to a solid electrolyte composition for a secondary battery and a solid electrolyte prepared therefrom, and relates to an electrolyte composition obtained by blending polycarbonate and polyethylene oxide having improved ion conductivity and free standing properties at room temperature, and a solid electrolyte using the same .

Solid electrolyte composition for secondary batteries

The present invention provides a linear polymer in which a polyethylene oxide unit exists between carbonate groups as a structure capable of suppressing the crystallinity of a polyethylene oxide polymer to improve lithium ion conductivity and simultaneously obtaining high ionic dissociation and voltage stability of a carbonate group do. In addition, an electrolyte composition obtained by blending polyethylene oxide having a molecular weight of a unit having a predetermined value or more as a polymer that can form a flexible film while being free standing and exhibits an additional plasticizing effect is provided.

The polycarbonate-based linear polymer into which polyethylene oxide is introduced according to one embodiment of the present invention may be a compound represented by Formula 1 below.

[Formula 1]

In Formula 1, n and m are each independently an integer of 8≤n≤114 and 2≤m≤500, R ₁ and R ₂ are n and m are each independently hydrogen or each independently substituted or unsubstituted C1 to C6 alkyl group.

The polymer of Formula 1 may have a weight average molecular weight of 1,000 to 200,000 g/mol.

In Formula 1, n is the number of added moles of ethylene oxide. If n is less than 8, effective chelation of lithium salt may be difficult and ionic conductivity may be poor. Preparation of carbonate-based polymers can be difficult. In Formula 1, m is the number of added moles of carbonate, and the molecular weight may be determined by a combination of n and m. If the weight average molecular weight of Chemical Formula 1 is less than 1,000 g / mol, the solid electrolyte membrane is too plasticized and is sticky or unsuitable for handling. It is appropriately adjusted within the above range.

The polycarbonate-based linear polymer introduced with polyethylene oxide of Formula 1 can be prepared through condensation polymerization of polyethylene oxide and dialkyl carbonate. The dialkyl carbonate may have a C1 to C6 alkyl group, and diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), etc. are preferred, but not limited thereto.

The condensation polymerization reaction is preferably carried out under catalytic conditions. Examples of the catalyst include inorganic catalysts such as NaH, K ₂ CO ₃ , NaO t -Bu, and KtO t -Bu, dimethylaminopyridine (DMAP), 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU), and triethylamine Organic catalysts such as (TEA) and 1,3-bis[3,5-bis(trifluoromethyl)phenyl]thiourea may be used, but are not limited thereto.

The condensation reaction can be promoted by effective removal of alkanol generated as a by-product, and for this purpose, the reaction can be performed by heating under vacuum. The heating may proceed at 50 to 250 °C, preferably at 70 to 200 °C, but is not limited thereto.

The molar ratio of polyethylene oxide:dialkylcarbonate according to the present invention may be selected from a ratio of 2:1 to 1:2, but is not limited thereto.

In one embodiment of the present invention, the mixing ratio of the linear polycarbonate-based polymer of Formula 1 and polyethylene oxide may be 1:99 to 50:50. When mixed in the above range, the solid electrolyte membrane exhibits sufficient mechanical strength, so that handling is easy and high ion conductivity can be secured with sufficient plasticity effect.

In one embodiment of the present invention, the polyethylene oxide is preferably selected from the range of 20,000 or more and 2,000,000 or less in number average molecular weight. When the number average molecular weight of polyethylene oxide is 20,000 or less, there is a high probability of dewetting of the film during the curing or drying process, and when it is 2,000,000 or more, the miscibility with the polycarbonate-based linear polymer is rapidly lowered, resulting in the formation of a homogeneous blend film. it can get difficult

In one embodiment of the present invention, the solid electrolyte composition for a secondary battery including the linear polycarbonate-based polymer of Chemical Formula 1 and polyethylene oxide may further include a crosslinking agent to improve mechanical strength or manufacturing processability of the solid electrolyte membrane. The crosslinking agent allows the electrolyte membrane to be crosslinked through a heating and drying process of the electrolyte membrane or an additional exposure process to improve mechanical strength and maintain the shape of the film.

The type of crosslinking agent is not particularly limited, and any one selected from the group consisting of thermal polymerization crosslinking agents such as isocyanate crosslinking agents, epoxy crosslinking agents, and aziridine crosslinking agents, and photopolymerization crosslinking agents such as vinyl-based crosslinking agents may be used. The content of the crosslinking agent may be 0.01 to 20 parts by weight based on the total of 100 parts by weight of the linear polycarbonate-based polymer of Formula 1 and the polymer exhibiting the plasticizing effect, but is not limited thereto. If the content of the crosslinking agent is less than 0.01 parts by weight, curing is not sufficiently performed, and mechanical strength may not be improved. If it is more than 20 parts by weight, the solid electrolyte membrane is too hard and interfacial adhesion with the electrode is insufficient, resulting in increased interfacial resistance or lithium. Since the ionic conductivity may be significantly lowered, it is appropriately adjusted within the above range.

Specific examples of the isocyanate crosslinking agent include diisocyanate compounds such as toluene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isoborone diisocyanate, tetramethylxylene diisocyanate or naphthalene diisocyanate, or the diisocyanate A compound obtained by reacting a compound with a polyol may be used, and trimethylol propane, for example, may be used as the polyol.

In addition, specific examples of the epoxy crosslinking agent include ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N,N,N',N'-tetraglycidyl ethylenediamine and glycerin diglycidyl. At least one selected from the group consisting of dil ether may be mentioned, and specific examples of the aziridine crosslinking agent include N,N'-toluene-2,4-bis(1-aziridinecarboxamide), N,N'-diphenyl consisting of methane-4,4'-bis(1-aziridinecarboxamide), triethylene melamine, bisisoprotaloyl-1-(2-methylaziridine) and tri-1-aziridinylphosphine oxide It may include one or more selected from the group, but is not limited thereto.

Specific examples of the vinyl-based crosslinking agent include ethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, tri(propylene glycol) di(meth)acrylate, and tris(2-(meth)acrylo Ethyl) isocyanurate, trimethylolpropane tri(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol di(meth)acrylate ) acrylate, dipentaerythritol tri (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. It may, but is not limited thereto.

The vinyl-based crosslinking agent forms a crosslinking structure when irradiated with UV together with the photopolymerization initiator, thereby improving physical strength of the film and allowing the solid electrolyte membrane according to the present invention to be formed into a free standing film. As an example of the photopolymerization initiator, at least one compound selected from the group consisting of an acetophenone-based compound, a biimidazole-based compound, a triazine-based compound, and an oxime-based compound may be used.

Examples of acetophenone-based compounds usable as the photopolymerization initiator include 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan- 1-one, 4-(2-hydroxyethoxy)-phenyl-(2-hydroxy-2-propyl)ketone, 1-hydroxycyclohexylphenylketone, benzoinmethyl ether, benzoinethyl ether, benzoin Isobutyl ether, benzoin butyl ether, 2,2-dimethoxy-2-phenylacetophenone, 2-methyl-(4-methylthio)phenyl-2-morpholino-1-propan-1-one, 2- Benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one, 2-(4-bromo-benzyl-2-dimethylamino-1-(4-morpholinophenyl)- It is selected from the group consisting of butan-1-one and 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, and the biimidazole-based compound is 2,2- Bis (2-chlorophenyl) -4,4', 5,5'-tetraphenyl biimidazole, 2,2'-bis (o-chlorophenyl) -4,4', 5,5'-tetrakis ( 3,4,5-trimethoxyphenyl) -1,2'-biimidazole, 2,2'-bis (2,3-dichlorophenyl) -4,4',5,5'-tetraphenyl biimi dazole, and 2,2'-bis(o-chlorophenyl)-4,4,5,5'-tetraphenyl-1,2'-biimidazole, and triazine-based compounds include 3- {4-[2,4-bis(trichloromethyl)-s-triazin-6-yl]phenylthio}propionic acid, 1,1,1,3,3,3-hexafluoroisopropyl-3 -{4-[2,4-bis(trichloromethyl)-s-triazin-6-yl]phenylthio}propionate, ethyl-2-{4-[2,4-bis(trichloromethyl) -s-triazin-6-yl]phenylthio}acetate, 2-epoxyethyl-2-{4-[2,4-bis(trichloromethyl)-s-triazin-6-yl]phenylthio}acetate , Cyclohexyl-2-{4-[2,4-bis(trichloromethyl)-s-triazin-6-yl]phenylthio}acetate, benzyl-2-{4-[2,4-bis(trichloromethyl) Romethyl)-s-triazin-6-yl]phenylthio}acetate, 3-{chloro-4-[2,4-bis(trichloromethyl)-s-triazin-6-yl]phenylthio}propy Onic acid, 3-{4-[2,4-bis(trichloromethyl)-s -triazin-6-yl]phenylthio}propionamide, 2,4-bis(trichloromethyl)-6-p-methoxystyryl-s-triazine, 2,4-bis(trichloromethyl)- 6-(1-p-dimethylaminophenyl)-1,3,-butadienyl-s-triazine, and 2-trichloromethyl-4-amino-6-p-methoxystyryl-s-triazine It is selected from the group consisting of, and the oxime-based compound includes 1,2-octadione-1-(4-phenylthio)phenyl-2-(o-benzoyloxime) (Ciba-Geigy, CGI 124), and ethane One-1-(9-ethyl)-6-(2-methylbenzoyl-3-yl)-1-(o-acetyloxime) (Ciba-Geigy, CGI 242), oxime OX-03 (Ciba-Ga Iggy Company), NCI-831 (Adeka Company), PI-102 (LG Chemical Company), PBG 304, PBG 305, PBG 3057 (Tronney Company), etc.

The amount of the photopolymerization initiator may be 0.01 to 5 parts by weight or 0.1 to 1 part by weight based on the total weight of the polymer and the vinyl-based crosslinking agent, but is not limited thereto.

Manufacturing method of solid electrolyte for secondary battery

The present invention provides a solid electrolyte for a secondary battery formed using the above-described solid electrolyte composition for a secondary battery. The solid electrolyte may exhibit the above-mentioned effects.

The solid electrolyte for a secondary battery may be prepared by using an electrolyte composition containing a blend of a polycarbonate-based polymer having the structure of Chemical Formula 1 and a polymer containing polyethylene oxide, and the above-described crosslinking agent and lithium salt. In one embodiment of the present invention, the solid electrolyte may include 10 to 90 parts by weight of a lithium salt based on 100 parts by weight of the electrolyte composition.

In one embodiment of the present invention, the electrolyte is LiF, LiCl, LiBr, LiI, LiClO ₄ , LiClO ₃ , LiAsF ₆ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiNO ₃ , LiN(CN) ₂ , LiPF ₆ , Li (CF ₃ ) ₂ PF ₄ , Li(CF ₃ ) ₃ PF ₃ , Li(CF ₃ ) ₄ PF ₂ , Li(CF ₃ ) ₅ PF, Li(CF ₃ ) ₆ P, LiSO ₃ CF ₃ , LiSO ₃ C ₄ F ₉ , LiSO ₃ (CF ₂ ) ₇ CF ₃ , LiN(SO ₂ CF ₃ ) ₂ , LiOC(CF ₃ ) ₂ CF ₂ CF ₃ , LiCO ₂ CF ₃ , LiCO ₂ CH ₃ , LiSCN, LiB(C ₂ At least one lithium salt selected from the group consisting of O ₄ ) ₂ , LiBF ₂ (C ₂ O ₄ ) and LiBF ₄ may be included.

The solid electrolyte according to the present invention may be formed by thermally or photocuring the solid electrolyte composition described above. To this end, a step of dissolving the electrolyte composition in a solvent and stirring for 1 to 6 hours may be included. Various solvents known in the art may be used as the solvent in consideration of desired performance and the like. For example, N-methylpyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl Carbonate, diethyl carbonate, gamma-butylolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, formamide, dimethylformamide, acetonitrile, nitro Methane, methyl formate, methyl acetate, phosphoric acid triesters, trimethoxy methane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, propionic acid An organic solvent such as methyl or ethyl propionate may be used, but is not limited thereto.

Thereafter, the solution may be cast on a release-treated PET film or Teflon plate, followed by thermal curing or UV exposure. The coated film may be prepared by drying the coated film at 50 to 150 ° C. under normal pressure and, if necessary, by secondary drying at 50 to 150 ° C. under normal pressure to vacuum so that the solvent content is less than 1%. When the completely dried solid electrolyte film is separated from the support, a free-standing film having lithium ion conductivity can be produced.

According to one embodiment of the present invention, the solid electrolyte may have a thickness of 10 to 1000 μm, preferably 50 to 250 μm. If the thickness of the electrolyte is less than the above range, the mechanical properties of the solid electrolyte may be deteriorated, and if it exceeds the above range, it may be difficult to reduce the electrical short and crossover of the electrolyte material. It is appropriately adjusted within the above range so as to exhibit lithium ion conductivity characteristics.

Hereinafter, the present invention will be described in more detail through examples and the like, but the scope and contents of the present invention are reduced or limited by the examples below and cannot be interpreted. In addition, based on the disclosure of the present invention including the following examples, it is clear that a person skilled in the art can easily practice the present invention for which no experimental results are specifically presented, and the patents to which such variations and modifications are attached. It goes without saying that it falls within the scope of the claims.

Example

The molecular weight of the polymer according to one embodiment of the present invention was measured according to the following conditions.

Number average molecular weight (Mn) and molecular weight distribution (PDI) were measured using Gel Permeation Chromatography (GPC) under the following conditions, and Agilent's standard polystyrene was used to create a calibration curve, and the measurement results were converted. did

<Measurement conditions>

Meter: Waters GPC (Alliance 4)

Column: Connect 2 PL Mixed B

Column temperature: 65 °C

Eluent: DMF/0.05M LiBr

Flow Rate: 1.0 mL/min

Concentration: ~ 1 mg/mL (100 μl injection)

manufacturing example 1. Polyethylene oxide Contained linear polycarbonate-based polymer (A1)

30 g of polyethylene oxide (Mn: 1000) from which moisture was removed in advance, 4.1 g of dimethyl carbonate, and 0.04 g of dimethylaminopyridine (DMAP) as a catalyst were added to a 250 ml two-neck flask. A mechanical stirrer and a distillation device were installed and refluxed at 130 ° C. for 3 hours. Thereafter, the temperature was raised to 170 ° C., and condensation polymerization was performed for 18 hours while removing unreacted dimethyl carbonate and methanol under vacuum. The reactant was purified by precipitation in diethyl ether to obtain Polymer A1 of Preparation Example 1 (Mw 32,000, Mw/Mn 1.56).

manufacturing example 2. Polyethylene oxide Contained linear polycarbonate-based polymer (A2)

40 g of polyethylene oxide (Mn: 2000) from which moisture was previously removed, 2.7 g of dimethyl carbonate, and 0.01 g of NaH as a catalyst were added to a 250 ml two-neck flask. A mechanical stirrer and a distillation device were installed and refluxed at 130 ° C. for 3 hours. Thereafter, the temperature was raised to 170 ° C., and condensation polymerization was performed for 18 hours while removing unreacted dimethyl carbonate and methanol under vacuum. The reaction product was purified by precipitation in diethyl ether to obtain Polymer A2 of Preparation Example 2 (Mw 49,000, Mw/Mn 1.50).

manufacturing example 3. Polyethylene oxide Contained linear polycarbonate-based polymer (A3)

40 g of polyethylene oxide (Mn: 2000) from which moisture was previously removed, 2.2 g of dimethyl carbonate, and 0.01 g of NaH as a catalyst were added to a 250 ml two-neck flask. A mechanical stirrer and a distillation device were installed and refluxed at 130 ° C. for 3 hours. Thereafter, the temperature was raised to 170 ° C., and condensation polymerization was performed for 42 hours while removing unreacted dimethyl carbonate and methanol under vacuum. The reaction product was purified by precipitation in diethyl ether to obtain Polymer A3 of Preparation Example 3 (Mw 85,000, Mw/Mn 1.57).

comparison manufacturing example One. diethylene glycol Contained linear polycarbonate-based polymer (B1)

10 g of polyethylene oxide (Mn: 400) from which moisture was removed in advance, 3.4 g of dimethyl carbonate, and 0.03 g of dimethylaminopyridine (DMAP) as a catalyst were added to a 50 ml Schlenk flask. After inserting a stirring bar, a distillation device was installed and reflux was performed at 130 ° C. for 3 hours. Thereafter, the distillation device was removed, the temperature was raised to 170° C., and condensation polymerization was performed for 18 hours while removing unreacted dimethyl carbonate and methanol under vacuum. The reactant was purified by precipitation in diethyl ether to obtain polymer B1 of Comparative Preparation Example 1 (Mn, _NMR 3100)

comparison manufacturing example 2. aliphatic Chain-containing linear polycarbonate-based polymer (B2)

Add 10 g of 1,12-dodecanediol, 6.7 g of dimethyl carbonate, and 0.06 g of 4-dimethylaminopyridine (DMAP) as a catalyst to a 50 ml Schlenk flask. did After inserting a stirring bar, a distillation device was installed and reflux was performed at 130 ° C. for 3 hours. Thereafter, the distillation device was removed, the temperature was raised to 170° C., and condensation polymerization was performed for 18 hours while removing unreacted dimethyl carbonate and methanol under vacuum. The reactant was purified by precipitation in diethyl ether to obtain polymer B2 of Comparative Preparation Example 2 (Mw 20,000, Mw/Mn 1.55)

Example . Preparation of solid electrolyte

The preparation of the solid electrolyte was carried out in a dry room. The content of lithium bis(trifluoromethanesulfonyl)imide (LiN(SO ₂ CF ₃ ) ₂ , LiTFSI) as the polymer prepared in Preparation Examples 1 and 2 and polyethylene oxide, which is a polymer having a plasticizing effect, and lithium salt Differently as shown in Table 1 below, a solution dissolved in anhydrous tetrahydrofuran (hereinafter referred to as THF) solvent was stirred for 6 hours to prepare a uniform solution.

The solution was coated with a doctor blade on the release-treated PET film with an appropriate gap, dried at 60° C. for 4 hours, and then dried by heating at 80° C. for an additional 2 hours. Thereafter, the solid film was separated from the PET film to obtain a free-standing solid electrolyte for a secondary battery having a thickness of 50 to 200 μm.

comparative example . Preparation of solid electrolyte

The polymer prepared in Comparative Preparation Examples 1 and 2 was blended with polyethylene oxide, which is a polymer that gives a plasticizing effect, alone or with a plasticizing effect, and the content of LiTFSI as a lithium salt was changed as shown in Table 1 below. A solution dissolved in an anhydrous THF solvent was stirred for 6 hours. to prepare a homogeneous solution.

The solution was coated with a doctor blade on a release-treated PET film with an appropriate gap, dried at 60° C. for 4 hours, and dried by heating at 90° C. for an additional 2 hours. Thereafter, the solid film was separated from the PET film to observe the state of the film, and when a free standing film was formed, the ionic conductivity was measured as in the following experimental example.

Examples 1 to 6 and Comparative Examples 1 to 5 according to the above Examples and Comparative Examples are shown in Table 1 below.

Polymer (wt%) Polyethylene oxide Mn (wt%) LiTFSI content
(wt%) Example 1 A1 (10) PEO 100,000 (50) 40 Example 2 A1 (20) PEO 100,000 (40) 40 Example 3 A2 (10) PEO 100,000 (50) 40 Example 4 A2 (20) PEO 100,000 (40) 40 Example 5 A3 (10) PEO 100,000 (50) 40 Example 6 A3 (20) PEO 100,000 (40) 40 Comparative Example 1 - PEO 100,000 (60) 40 Comparative Example 2 B1 (10) PEO 100,000 (50) 40 Comparative Example 3 B1 (20) PEO 100,000 (40) 40 Comparative Example 4 B2 (10) PEO 100,000 (50) 40 Comparative Example 5 B2 (20) PEO 100,000 (40) 40

Experimental example . Ionic Conductivity Measurement of Solid Electrolytes

The ionic conductivity of the solid electrolytes prepared in Examples 1 to 6 and Comparative Examples 1 to 5 was obtained by using Equation 1 below after measuring the impedance.

A film sample of the solid electrolyte having a constant area and thickness was prepared for measurement. An AC voltage was applied through the electrodes on both sides of the sample after contacting a SUS substrate having excellent electronic conductivity with an ion blocking electrode on both sides of the plate-shaped sample. At this time, the amplitude range of the measurement frequency 0.1Hz ~ 10MHz was set as the applied condition. The resistance of the bulk electrolyte was obtained from the intersection (R _b ) where the semicircle or straight line of the measured impedance trajectory meets the real axis, and the ionic conductivity of the polymer solid electrolyte membrane was calculated from the area and thickness of the sample, and is shown in Table 2 below.

[Equation 1]

σ: ionic conductivity

R _b : Intersection of the impedance locus with the real axis

A: the area of the sample

t: thickness of the sample

Ionic conductivity (S/cm, 25 °C) Membrane characteristics Example 1 3.2 x 10 ^-5 Flexible Free standing membrane Example 2 4.7 x 10 ^-5 Flexible Free standing membrane Example 3 4.8 x 10 ^-5 Flexible Free standing membrane Example 4 7.5 x 10 ^-5 Flexible Free standing membrane Example 5 1.3 x 10 ^-5 Flexible Free standing membrane Example 6 3.6 x 10 ^-5 Flexible Free standing membrane Comparative Example 1 8.7 x 10 ^-7 Free standing film that breaks easily Comparative Example 2 1.4 x 10 ^-6 Flexible Free standing membrane Comparative Example 3 2.2 x 10 ^-6 Sticky, waxy film Comparative Example 4 1.1 x 10 ^-6 Flexible Free standing membrane Comparative Example 5 1.8 x 10 ^-6 Flexible Free standing membrane

As shown in Table 2, when a solid electrolyte was prepared by blending a polycarbonate-based linear polymer introduced with polyethylene oxide and polyethylene oxide, it was found that membrane properties were excellent and ionic conductivity was improved.

Claims (11)

As a solid electrolyte for a secondary battery,
The solid electrolyte for a secondary battery is formed by heating or photocuring a solid electrolyte composition for a secondary battery in which a polycarbonate-based polymer having a structure represented by Formula 1 and polyethylene oxide are blended,
The polycarbonate-based polymer and polyethylene oxide are in a weight ratio of 1:5 to 1:2,
Solid electrolyte for secondary batteries:
[Formula 1]

In Formula 1, n and m are each independently an integer of 8≤n≤114 and 2≤m≤500, and R ₁ and R ₂ are each independently hydrogen or independently of each other a substituted or unsubstituted C1 to C6 alkyl group. am. According to claim 1,
The polycarbonate-based polymer is a solid electrolyte for a secondary battery, characterized in that the weight average molecular weight of 1,000 to 200,000 g / mol. According to claim 1,
The polyethylene oxide is a solid electrolyte for a secondary battery, characterized in that the number average molecular weight is 20,000 to 2,000,000. delete According to claim 1,
The solid electrolyte for a secondary battery, characterized in that the composition further comprises a crosslinking agent. According to claim 5,
The crosslinking agent is an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, and a solid electrolyte for a secondary battery, characterized in that any one selected from the group consisting of a vinyl crosslinking agent. According to claim 5,
The crosslinking agent is a solid electrolyte for a secondary battery, characterized in that included in 0.1 to 20 parts by weight based on 100 parts by weight of the total electrolyte composition. delete According to claim 1,
The solid electrolyte for a secondary battery, characterized in that the electrolyte comprises 10 to 90 parts by weight of a lithium salt based on 100 parts by weight of the electrolyte composition. According to claim 9,
The lithium salt is LiF, LiCl, LiBr, LiI, LiClO ₄ , LiClO ₃ , LiAsF ₆ , LiSbF ₆ , LiAlO 4 , LiAlCl _{4 ,} LiNO ₃ , LiN(CN) ₂ , LiPF ₆ , Li(CF ₃ ) ₂ PF ₄ , Li(CF ₃ ) ₃ PF ₃ , Li(CF ₃ ) ₄ PF ₂ , Li(CF ₃ ) ₅ PF, Li(CF ₃ ) ₆ P, LiSO ₃ CF ₃ , LiSO ₃ C ₄ F ₉ , LiSO ₃ ( CF ₂ ) ₇ CF ₃ , LiN(SO ₂ CF ₃ ) ₂ , LiOC(CF ₃ ) ₂ CF ₂ CF ₃ , LiCO ₂ CF ₃ , LiCO ₂ CH ₃ , LiSCN, LiB(C ₂ O ₄ ) ₂ , LiBF ₂ (C ₂ O ₄ ) And LiBF ₄ A solid electrolyte for a secondary battery, characterized in that at least one selected from the group consisting of. According to claim 1,
A solid electrolyte for a secondary battery, characterized in that the thickness of the electrolyte is 10 to 1000㎛.