KR20210001108A - Polymer electrolyte film for lithium metal electrode, electrode structure and electrochemical device including the same, and manufacturing method of the polymer electrolyte film - Google Patents

Abstract

Disclosed are a polymer electrolyte film, an electrode structure and an electrochemical device including the same, and a method for manufacturing the polymer electrolyte film. The polymer electrolyte film includes a copolymer of a crosslinkable precursor including a urethane group-containing polyfunctional acrylic monomer and a polyfunctional block copolymer, and a lithium salt, thereby producing high elasticity and high strength characteristics, such that a dendrite is stably protected when the dendrite is grown on the surface of a lithium metal electrode according to a charging operation and a discharging operation, and a protective film can be prevented from being damaged. Accordingly, cell performance can be improved. The polymer electrolyte film can be directly coated on a free standing film or a lithium metal electrode and then formed in the form of a protective film to be used in an electrochemical device such as a high-density high-energy lithium metal battery.

Description

A polymer electrolyte membrane, an electrode structure and an electrochemical device including the same, and a method of manufacturing the polymer electrolyte membrane, including the same, and manufacturing method of the polymer electrolyte film.

It relates to a polymer electrolyte membrane, an electrode structure and an electrochemical device including the same, and a method of manufacturing the polymer electrolyte membrane.

In accordance with the trend of light, thin, short and portable electric and electronic products, secondary batteries, which are core components, are also required to be lightweight and miniaturized, and development of batteries having high output and high energy density is required. In response to such demands, one of the high-performance, next-generation, high-tech new batteries that are receiving the most attention in recent years is a lithium metal secondary battery.

However, the lithium metal electrode used as an electrode has high reactivity with the electrolyte component, and forms a passivation film by reaction with the organic electrolyte, and oxidation (dissolution, dissolution) and reduction (precipitation) of lithium on the lithium metal surface during charge and discharge. , deposition) reaction is repeated non-uniformly, the formation and growth of the passive film is severe. Accordingly, not only causes a decrease in the capacity of the battery during charging and discharging, and as the charging/discharging process is repeated, a dendrite in which lithium ions grow in the form of needles is formed on the lithium metal surface, thereby reducing the charge/discharge cycle of the lithium secondary battery. It is shortened and causes a safety problem of the battery, such as causing a short between electrodes.

In order to solve this problem, Korean Patent Registration No. 10-0425585 proposes a technology for forming a protective film by crosslinking a general chain polymer on the surface of a lithium electrode and coating it on the lithium surface. However, due to the nature of the polymer, when it comes into contact with a small amount of electrolyte, Problems such as being damaged occurred. In the case of PEO or PVDF and a copolymer or mixture containing it, for example, PEO or PVDF and a copolymer or mixture containing it, which are generally well known ether polymers or polyvinylidene fluoride (PVDF), do not effectively block needle-shaped dendrite due to the low mechanical strength of the polymer. The protective film is damaged due to the precipitation of dry matter, so it cannot function properly as a protective film.

Korean Patent Publication No. 2014-0083181 proposes a lithium negative electrode that forms a protective film containing inorganic particles on the surface of the lithium metal, stabilizing the lithium metal and lowering the interfacial resistance between the lithium electrode and the electrolyte. However, the inorganic particles in the protective layer are spherical particles, and there is a problem in that lithium dendrites grow along the interface of the spherical particles, and thus there is still a risk of a battery short circuit.

In order to solve this problem, a method of introducing a polymer protective film that suppresses the growth of dendrites to a lithium metal electrode can be used. In general, a protective film is formed by directly applying a protective film composition to a lithium metal plate forming a negative electrode. However, in the case of direct coating on lithium metal using a general material, it is difficult to select a solvent due to the high reactivity of the lithium metal, and a residue may remain after application, which may affect the performance of a battery including the negative electrode.

Therefore, there is a need for research on a new polymer material and method for forming a protective film on a lithium electrode.

One aspect of the present invention is to provide a polymer electrolyte membrane capable of preventing damage to a protective layer due to growth of dendrite on a surface of a lithium metal electrode due to charge and discharge of a battery.

Another aspect of the present invention is to provide an electrode structure to which the polymer electrolyte membrane is applied.

Another aspect of the present invention is to provide an electrochemical device to which the polymer electrolyte membrane is applied.

Another aspect of the present invention is to provide a method of manufacturing the polymer electrolyte membrane.

In one aspect of the present invention,

A copolymer of a crosslinkable precursor including a urethane group-containing polyfunctional acrylic monomer and a polyfunctional block copolymer; And

Lithium salt;

A polymer electrolyte membrane comprising a is provided.

In another aspect of the invention,

Lithium metal electrodes; And a protective film disposed on the lithium metal electrode and including the polymer electrolyte membrane.

In another aspect of the invention,

An electrochemical device including the electrode structure is provided.

In another aspect of the invention,

Preparing a crosslinkable precursor comprising a urethane group-containing polyfunctional acrylic monomer and a polyfunctional block copolymer, and a precursor mixture comprising a lithium salt; And

Applying and curing the precursor mixture in a film form;

A method of manufacturing a polymer electrolyte membrane according to claim 1 is provided.

The polymer electrolyte membrane according to an embodiment has high elasticity and high strength characteristics, so that when dendrite grows on the surface of a lithium metal electrode during charging and discharging of a battery, it can reliably protect it and prevent damage to the protective film, and improve battery performance. Can be improved.

1 is a graph showing the result of measuring the ionic conductivity of the polymer electrolyte membrane prepared in Example 6.
2 is a cross-sectional SEM image of a lithium metal electrode on which a protective film of a polymer electrolyte membrane obtained in Example 7 is formed before charging and discharging.
3 is a cross-sectional SEM image of a lithium metal electrode having a protective film of a polymer electrolyte membrane obtained in Example 7 after charging and discharging.

The present inventive concept described below may apply various transformations and may have various embodiments. Specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. However, this is not intended to limit the present creative idea to a specific embodiment, it is to be understood as including all transformations, equivalents or substitutes included in the technical scope of the present creative idea.

The terms used below are only used to describe specific embodiments, and are not intended to limit the present inventive idea. Singular expressions include plural expressions unless the context clearly indicates otherwise. Hereinafter, terms such as "comprises" or "have" are intended to indicate the existence of features, numbers, steps, actions, components, parts, components, materials, or a combination thereof described in the specification. It is to be understood that the above other features, or the possibility of the presence or addition of numbers, steps, actions, components, parts, components, materials, or combinations thereof, are not excluded in advance. "/" used below may be interpreted as "and" or "or" depending on the situation.

In the drawings, the diameter, length, and thickness are enlarged or reduced in order to clearly express various elements, layers, and regions. The same reference numerals are assigned to similar parts throughout the specification. Throughout the specification, when a part such as a layer, film, region, plate, etc. is said to be "on" or "on" another part, this includes not only the case directly above the other part, but also the case where there is another part in the middle. . Throughout the specification, terms such as first and second may be used to describe various components, but the components should not be limited by terms. The terms are used only for the purpose of distinguishing one component from another. In the drawings, some of the components may be omitted, but this is to help understanding the features of the invention and is not intended to exclude the omitted components.

Unless otherwise specified in the specification, "substituted" means that at least one hydrogen atom is a halogen atom (F, Cl, Br, I), a C1 to C20 alkoxy group, a nitro group, a cyano group, an amino group, an imino group, an azido group, Amidino group, hydrazino group, hydrazono group, carbonyl group, carbamyl group, thiol group, ester group, carboxyl group or salt thereof, sulfonic acid group or salt thereof, phosphoric acid or salt thereof, C1 to C20 alkyl group, C2 to C20 alkenyl group, C2 to C20 alkynyl group, C6 to C20 aryl group, C3 to C20 cycloalkyl group, C3 to C20 cycloalkenyl group, C3 to C20 cycloalkynyl group, C2 to C20 heterocycloalkyl group, C2 to C20 heterocycloalkenyl group , A C2 to C20 heterocycloalkynyl group, a C3 to C20 heteroaryl group, or a substituent of a combination thereof.

In addition, unless otherwise specified in the specification, "hetero" means that at least one hetero atom of at least one of N, O, S and P is included in the formula.

In addition, unless otherwise specified in the specification, "(meth)acrylate" means that both "acrylate" and "methacrylate" are possible, and "(meth)acrylic acid" refers to "acrylic acid" and "methacrylic acid. "It means both are possible.

Hereinafter, an exemplary polymer electrolyte membrane, an electrode structure and an electrochemical device including the same, and a method of manufacturing the polymer electrolyte membrane will be described in more detail with reference to the accompanying drawings.

The polymer electrolyte membrane according to one embodiment,

A copolymer of a crosslinkable precursor including a urethane group-containing polyfunctional acrylic monomer and a polyfunctional block copolymer; And

Lithium salt; includes.

The polymer electrolyte membrane includes a copolymer of a crosslinkable precursor including a urethane group-containing polyfunctional acrylic monomer and a polyfunctional block copolymer and a lithium salt, thereby controlling the crystallinity of the polymer to maintain an amorphous state, and ionic conductivity and It can improve electrochemical properties. The crosslinked matrix prepared by using urethane-containing polyfunctional acrylic monomers and polyfunctional block copolymers as the main skeleton has very low crystallization of the polymer itself and free movement of lithium ions due to the segmental motion of the polymer in the amorphous region inside. Conductivity can be improved. In addition, a polymer electrolyte membrane having a free standing level can be prepared by improving the high mechanical properties of the copolymer itself with a crosslinked polymer structure.

As a crosslinkable precursor, the urethane group-containing polyfunctional acrylic monomer may include diurethane dimethacrylate, diurethane diacrylate, or a combination thereof.

According to an embodiment, the urethane group-containing polyfunctional acrylic monomer may include a diurethane dimethacrylate represented by Formula 1 below.

[Formula 1]

In the above formula, each R is independently a hydrogen atom or a C1-C3 alkyl group.

Polyfunctional acrylic monomer containing urethane group has high mechanical strength and elasticity including urethane moieties, so when forming a copolymer structure with a polyfunctional block copolymer, it maintains high mechanical strength and has elasticity. The membrane can be prepared.

In addition to the urethane group-containing polyfunctional acrylic monomer, other monomers including a polyfunctional functional group having a similar structure may be further mixed and used. Other monomers containing such a multifunctional functional group include, for example, urethane acrylate methacrylate, urethane epoxy methacrylate, Arkema's product names Satomer N3DE180, N3DF230, etc. You can use one or more selected.

As a crosslinkable precursor, the multifunctional block copolymer includes a (meth)acrylate group at both ends, and may include a diblock copolymer or a triblock copolymer including a polyethylene oxide repeat unit and a polypropylene oxide repeat unit. .

According to an embodiment, the multifunctional block copolymer includes a (meth)acrylate group at both ends, and a triblock copolymer consisting of a polyethylene oxide first block, a polypropylene oxide second block, and a polyethylene oxide third block It may include.

According to an embodiment, the multifunctional block copolymer may be represented by Formula 2 below.

[Formula 2]

In the above formula, x, y, and z are each independently an integer of 1 to 50.

The multifunctional block copolymer of the above structure is similar in structure to polyethylene glycol dimethacrylate (PEGDMA), which is widely known in the past, but in the case of PEGDMA, the crystallinity is high due to a single linear structure, and it is broken depending on the degree of crosslinking after crosslinking polymerization. May occur, but the polyfunctional block copolymer breaks the crystallinity that appears in the ethylene oxide single structure due to the structure of a block copolymer of propylene oxide and ethylene oxide, and adds flexibility to the polymer electrolyte membrane due to two different polymer blocks. can do.

The weight average molecular weight (Mw) of the multifunctional block copolymer may range from 500 to 20,000. For example, the weight average molecular weight (Mw) of the multifunctional block copolymer may be in the range of 1,000 to 20,000, or in the range of 1,000 to 10,000. When the weight average molecular weight (Mw) of the polyfunctional block copolymer is within the above range, the length of the block copolymer itself is appropriate so that the polymer may not change to brittle after crosslinking, and a lithium metal electrode that does not use a solvent It can be easy to control viscosity and thickness during coating.

The weight ratio of the urethane group-containing polyfunctional acrylic monomer and the polyfunctional block copolymer may range from 1:100 to 100:1. For example, the weight ratio of the urethane group-containing polyfunctional acrylic monomer and the polyfunctional block copolymer may range from 1:10 to 10:1. For example, the weight ratio of the urethane group-containing polyfunctional acrylic monomer and the polyfunctional block copolymer may range from 1:5 to 5:1. In the above range, the crystallinity of the polymer is controlled to maintain an amorphous state, and ionic conductivity and electrochemical properties may be improved.

In addition to the multifunctional block copolymer, other monomers or polymers having a similar structure may be additionally mixed and used. Such other monomers or polymers include, for example, dipentaerythritol penta-/hexa-acrylate, glycerol propoxylate triacrylate, di(trimethylolpropane). ) Tetraacrylate (Di(trimethylolpropane) tetraacrylate), trimethylolpropane ethoxylate triacrylate, and poly(ethylene glycol) methyl ether acrylate, etc. One or more can be used from this, but is not limited thereto.

According to an embodiment, the polymer electrolyte membrane may further add and copolymerize an oligomer together with the crosslinkable precursor to improve segmental motion of the copolymer and to smoothly move lithium ions. When an oligomer is added, the flexibility of the polymer chain is improved and the interaction between ions and the polymer is facilitated by the oligomer having a low molecular weight compared to the polymer, so that the movement of lithium ions can be accelerated, thereby increasing the ionic conductivity of the polymer electrolyte membrane. It can be further improved.

The oligomer usable with the crosslinkable precursor may have a weight average molecular weight (Mw) in the range of 200 to 600. The oligomer may include an ether type, an acrylate type, a ketone type, or a combination thereof. Further, the oligomer may include an alkyl group, an allyl group, a carboxyl group, or a combination thereof as a functional group. This is because these functional groups are not reactive with lithium metal and are electrochemically stable. On the other hand, a structure including -OH, -COOH, or -SO ₃ H in the terminal group is not suitable. This is because these end groups are reactive with lithium metal and are not electrochemically stable.

As the oligomer, for example, PEG-based diglyme (di-ethylelen glycol), triglyme (tri-ethylelen glycol), tetraglyme (tetra ethylene glycol), and the like can be used.

The added amount of the oligomer may be 1 to 100 parts by weight, based on 100 parts by weight of the total weight of the urethane group-containing polyfunctional acrylic monomer and the polyfunctional block copolymer. Within the above range, the physical properties of the copolymer itself and the crosslinked matrix are not loosened, the mechanical strength, heat resistance, and chemical stability of the copolymer can be maintained, and the shape of the polymer electrolyte membrane can be stably maintained even at high temperatures.

The lithium salt serves to secure the ion conduction path of the polymer electrolyte membrane. The lithium salt may be used without limitation as long as it is commonly used in the art. For example, lithium salts include LiSCN, LiN(CN) ₂ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN(SO ₂ CF ₃ ) ₂ , LiN(SO ₂ F) ₂ , LiSbF ₆ , LiPF ₃ (CF ₂ CF ₃ ) ₃ , LiPF ₃ (CF ₃ ) ₃ and LiB(C ₂ O ₄ ) ₂ It may include one or more selected, but is not limited thereto.

The content of the lithium salt contained in the polymer electrolyte membrane is not particularly limited, but may be, for example, 1% to 50% by weight of the total weight of the copolymer and the lithium salt. For example, the content of the lithium salt may be 5% by weight to 50% by weight of the total weight of the copolymer and the lithium salt, and specifically, may be 10% by weight to 30% by weight. Lithium ion mobility and ion conductivity may be excellent in the above range.

The polymer electrolyte membrane may further include at least one selected from a liquid electrolyte, a solid electrolyte, a gel electrolyte, a polymer ionic liquid, and a separator, and as a result, the ionic conductivity and mechanical properties of the electrolyte may be further improved. .

According to an embodiment, the polymer electrolyte membrane may further include a liquid electrolyte to further form an ion conductive path through the polymer electrolyte membrane.

The liquid electrolyte further includes at least one selected from an organic solvent, an ionic liquid, an alkali metal salt and an alkaline earth metal salt. Organic solvents include carbonate compounds, glyme compounds, dioxolane compounds, dimethyl ether, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether, and the like.

The polymer electrolyte membrane may be very stable with respect to an organic solvent such as a carbonate compound or an electrolyte containing the same when a liquid electrolyte containing an organic solvent such as a carbonate compound is used together.

The polymer electrolyte membrane contains a copolymer of a crosslinkable precursor including a urethane group-containing polyfunctional acrylic monomer and a polyfunctional block copolymer and a lithium salt, thereby controlling the crystallinity of the polymer to maintain an amorphous state, and ionic conductivity and electricity. Chemical properties can be improved. In addition, a polymer electrolyte membrane having a free standing level can be prepared by improving the mechanical properties and elastomeric properties of the copolymer itself with a crosslinked polymer structure. The polymer electrolyte membrane may maintain a free standing film at 25 to 60°C.

The ion conductivity (σ) of the polymer electrolyte membrane may be 1 x 10 ^-5 S/cm to 1 x 10 ^-3 S/cm at room temperature and in a temperature range of 25°C to 60°C.

The polymer electrolyte membrane is formed in the form of a protective film by directly coating a free standing film or a lithium metal electrode, thereby minimizing the interface between the lithium metal electrode and the protective film.

As described above, the polymer electrolyte membrane has excellent ionic conductivity and mechanical strength, and can implement an electrolyte membrane that can be used in an electrochemical device such as a high-density, high-energy lithium secondary battery using a lithium metal electrode. In addition, there is no leakage using the polymer electrolyte membrane, and electrochemical side reactions occurring in the cathode and anode are eliminated, and unlike an electrolyte using a liquid electrolyte, there is no electrolyte decomposition reaction, and battery characteristics and stability can be improved.

An electrode structure according to one embodiment,

Lithium metal electrodes; And

It includes; a protective film disposed on the lithium metal electrode, including the polymer electrolyte membrane described above.

The thickness of the lithium metal electrode may be 100 μm or less, for example, 80 μm or less, or 50 μm or less, or 30 μm or less, or 20 μm or less. According to another embodiment, the thickness of the lithium metal electrode may be 0.1 to 60 μm. Specifically, the thickness of the lithium metal electrode may be 1 to 25 μm, for example 5 to 20 μm.

The protective film disposed on the lithium metal electrode includes the polymer electrolyte membrane described above. Since the protective film including the polymer electrolyte membrane has high ionic conductivity and mechanical strength even at room temperature and high temperature, it is possible to effectively form an electrode structure applicable to a battery while suppressing dendrite on the surface of the lithium metal electrode.

In the case of a protective film made of a previously known material, dendrites accumulate on the lithium metal electrode during charging and discharging and grow through the protective film, causing an internal short circuit or shortening the battery life.However, the polymer electrolyte membrane has very good elasticity and dendrites precipitate. Even if the volume of the lithium metal electrode surface is expanded, the protective film may be stretched with the elastomeric properties of the polymer electrolyte membrane, so that the protective film itself may not be torn or pierced, and the dendrite may be covered. As a result, the polymer electrolyte membrane can continuously maintain its shape even when charging and discharging proceeds, and it can safely cover the dendrite even when the dendrite grows, thereby preventing internal short circuits caused by the dendrite, thereby improving battery life and securing stability. .

An electrochemical device according to an embodiment includes the electrode structure.

이상의 온도에서도 전지의 특성을 유지하며, 이와 같은 고온에 있어서도 모는 전자 제품의 작동을 가능하게 할 수 있다.The telephony device has excellent safety and high energy density by using the polymer electrolyte membrane as a protective film.

It maintains the characteristics of the battery even at the above temperature, and it is possible to operate all electronic products even at such a high temperature.

The electrochemical device may be a lithium secondary battery such as a lithium ion battery, a lithium polymer battery, a lithium air battery, and a lithium solid state battery.

The electrochemical device to which the solid polymer electrolyte is applied is suitable for applications that require high capacity, high output and high temperature driving such as electric vehicles, in addition to conventional mobile phones and portable computers, and conventional internal combustion engines and fuel cells. , Supercapacitors, etc. can be used in hybrid vehicles. In addition, the electrochemical device can be used in all other applications requiring high power, high voltage and high temperature driving.

Hereinafter, a method of manufacturing a polymer electrolyte membrane according to an embodiment will be described.

A method of manufacturing a polymer electrolyte membrane according to an embodiment,

Preparing a crosslinkable precursor comprising a urethane group-containing polyfunctional acrylic monomer and a polyfunctional block copolymer, and a precursor mixture comprising a lithium salt; And

And applying and curing the precursor mixture in a film form.

The crosslinkable precursor and lithium salt including the urethane group-containing polyfunctional acrylic monomer and the polyfunctional block copolymer are as described above.

The precursor mixture may further include a crosslinking agent, a photoinitiator, and the like to assist crosslinking of the crosslinkable precursor. The content of the crosslinking agent, photoinitiator, and the like may be in a conventional range, and for example, may be used in a range of 1 to 5 parts by weight based on 100 parts by weight of the crosslinkable precursor.

According to an embodiment, the precursor mixture may further include an initiator to form a copolymer having a crosslinked structure with a crosslinking agent. As an initiator, for example, peroxide (-OO-) series of benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, cumyl hydroperoxide, etc., or an azo compound (-N=N Thermal initiators such as -) series azobisisobutyronitrile and azobisisovaleronitrile may be used.

When a precursor mixture including a crosslinkable precursor and a lithium salt is prepared, the precursor mixture is applied in a film form and cured to form a polymer electrolyte membrane. The precursor mixture may be applied in the form of a film without using a solvent and including the crosslinkable precursor, an optional initiator, and a lithium salt.

A method of applying the precursor mixture in a film form is various and is not particularly limited. For example, a precursor mixture may be injected between two glass plates, and a predetermined pressure may be applied to the glass plate using a clamp so that the thickness of the electrolyte membrane can be adjusted. As another example, the precursor mixture may be coated directly on the lithium metal electrode using a coating device such as spin coating to form a thin film having a predetermined thickness.

In the process of applying the precursor mixture, the coating process is a gravure coater, a reverse roll coater, a slit die coater, a screen coater, a spin coater, a doctor blade. ), etc., can be used to perform coating.

The coating thickness can range from 1 μm to 10 μm. If the thickness is less than 1 μm, there is a risk that the polymer electrolyte membrane may be torn during dendrite growth, and if the thickness exceeds 10 μm, the properties of the polymer electrolyte membrane may be deteriorated as the resistance according to the thickness increases.

A method of curing the precursor mixture may include a curing method using UV, heat or high energy radiation (electron beam, γ-ray). According to an embodiment, the precursor mixture may be directly irradiated with UV (365 nm) or heat treated at about 60° C. to prepare a polymer electrolyte membrane.

Exemplary embodiments are described in more detail through the following examples and comparative examples. However, the embodiments are for illustrative purposes only, and the scope of the present invention is not limited thereto.

Example 1

Diurethane dimethacrylate (DUDMA) (Sigma-Aldrich, 470.56/mol) 5 g of Formula 1 and Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) diacrylate (PPG-b) of Formula 2 -PEG) (Sigma-Aldrich, average Mn ~ 1200) 2g was mixed in a vial and stirred for 10 minutes, and then 0.7 g of lithium salt LiFSI (lithium bis(fluorosulfonyl)imide) was added to the vial and mixed again. To the mixed mixture, an initiator BEE (Benzoin ethyl ether, Sigma-Aldrich, 240.30 g/mol) was added in an amount of 1% based on the total weight of the mixture, followed by stirring and mixing again to prepare a gel precursor mixture.

0.2 g of the gel precursor mixture was placed on a glass plate, covered with another prepared glass plate, and irradiated with 365 nm UV for 50 seconds to prepare a 20 μm thick transparent polymer electrolyte membrane.

Example 2

A polymer electrolyte membrane was prepared in the same manner as in Example 2, except that the contents of DUDMA and PPG-b-PEG were adjusted to 3g and 3g, respectively.

Example 3

A polymer electrolyte membrane was prepared in the same manner as in Example 2, except that the contents of DUDMA and PPG-b-PEG were adjusted to 2g and 5g, respectively.

Example 4

In Example 1, except that 5 g of an ether oligomer Triethylene glycol dimethyl ether (TEGDME) was additionally mixed with the mixture, and 0.5 g of lithium salt LiFSI (lithium bis (fluorosulfonyl) imide) was mixed. A polymer electrolyte membrane was manufactured by performing the same process as in Example 1.

Example 5

In Example 4, a polymer electrolyte membrane was prepared in the same manner as in Example 4, except that an Ethylene carbonate (EC) electrolyte containing 1M LiFSI salt was used instead of the ether oligomer.

Example 6

In Example 5, the addition amount of the electrolyte solution was changed to 0g, 0.7g, 2.1g, 3.5g, 4.9g, 6.4g, 7.0g, and the same procedure as in Example 5 was performed to prepare a polymer electrolyte membrane and the ionic conductivity was measured. Evaluated. The amount of each electrolyte added is an amount corresponding to 0, 10, 30, 50, 70, 90 and 100 parts by weight based on 100 parts by weight of the total weight of DUDMA and PPG-b-PEG.

Example 7

The gel precursor mixture prepared in Example 1 was applied on a Cu film having a thickness of about ~2 μm vacuum-deposited on the surface of a Si wafer by spin coating rather than pressing between glass plates, and irradiated with 365 nm UV for 50 seconds to a thickness of about 2 to 5 μm. A transparent polymer electrolyte membrane was prepared.

Comparative Example 1

A polymer electrolyte membrane was prepared in the same manner as in Example 2, except that the contents of DUDMA and PPG-b-PEG were adjusted to 0g and 5g, respectively.

Evaluation Example 1: Evaluation of ion conductivity

The ionic conductivity of the polymer electrolyte membrane prepared in Examples 1-4 and Comparative Example 1 was measured, and the results are shown in Table 1 below. Ion conductivity is measured between 1Hz and 1MHz frequency using Solatron 1260A Impedance / Gain-Phase Analyzer with constant pressure applied with springs from both sides after placing the sample between the sus disks using two 1cm ² sus disks. I did.

Example 1 Example 2 Example 3 Example 4 DUDMA / PPG-b-PEG 5g/2g 3g/3g 2g/5g 5g/2g TEGDME - - - 5g Room temperature ion conductivity 7.40E-05 8.30E-05 8.8E-05 8.23E-05

As shown in Table 1, the polymer electrolyte membranes prepared in Example 1-4 and Comparative Example 1 have a difference in ionic conductivity depending on the content ratio of DUDMA and PPG-b-PEG, but the state of the electrolyte membrane after measuring the ion conductivity Was good without significant change. The manufactured electrolyte membrane tends to be somewhat brittle depending on the content of DUDMA, and in the case of Example 1 containing the most DUDMA and Comparative Example 1 (Example 4) not including DUDMA, the flexibility aspect of the membrane There was a lot of difference in. The film produced by crosslinking the composition of PPG-b-PEG without DUDMA was very soft and was not suitable for free standing. This is thought to be a difference depending on the density and structure of the polymer after crosslinking and the structure of its own DUDMA. In the case of Example 2, DUDMA has a linear structure due to the structure of the polymer, whereas PPG-b-PEG has a more flexible characteristic due to its block copolymer structure. .

Meanwhile, in order to confirm the characteristics of the polymer electrolyte membrane prepared by adding EC containing 1M LiFSI salt of the liquid electrolyte for ion batteries instead of TEGDME, the ionic conductivity of the polymer electrolyte membrane prepared in Example 6 was measured, and the results are shown in FIG. Indicated.

As shown in FIG. 1, it can be seen that the ionic conductivity is improved as the content of the electrolyte is increased as in the general polymer electrolyte, but unlike the general gel polymer, the polymer electrolyte membrane prepared according to the present invention is impregnated in a large amount of electrolyte or Even when added, it was confirmed that the shape of the polymer electrolyte membrane did not damage the membrane due to excessive swelling. From this, it is thought that the same effect can be expected when the polymer electrolyte membrane is applied as a protective layer to a lithium metal electrode.

Evaluation Example 2: Film state evaluation before and after charging and discharging

In order to confirm the function of the polymer electrolyte membrane prepared in Example 7 as a protective membrane, a PE separator (Celgard, Celgard 3501) and a positive electrode were sequentially stacked on the polymer electrolyte membrane obtained in Example 7, and then vacuum-packed in an aluminum pouch. The cell was prepared. Here, the positive electrode was prepared as follows, and prepared by sufficiently impregnating an EC electrolytic solution in which 1.3M LiPF ₆ was dissolved in advance was used. To prepare a positive electrode, first, LiCoO ₂ , a conductive agent (Super-P; Timcal Ltd.), polyvinylidene fluoride (PVdF), and N-pyrrolidone were mixed to obtain a positive electrode composition. In the positive electrode composition, the mixing weight ratio of LiCoO ₂ , the conductive agent and PVDF was 97:1.5:1.5. The positive electrode composition was coated on an aluminum foil (thickness: about 15 μm) and dried at 25° C., and the dried result was dried at about 110° C. in vacuum to prepare a positive electrode.

With respect to the cell, after two formation cycles at a current of 0.05C rate, CC-CV charge/discharge 50 times at a current of 0.5C rate, and a cross-sectional SEM photograph of a negative electrode including a polymer electrolyte membrane before and after charge and discharge Are shown in FIGS. 2 and 3 respectively.

As shown in FIG. 2, it can be seen that a Cu metal electrode is coated on a Si wafer, and a polymer electrolyte protective film is formed thereon to a thickness of about 5 μm.

As shown in Figure 3, after 50 times of charging and discharging of the cell, Li ⁺ derived from the positive electrode active material is plated on the surface of the Cu metal electrode to form a lithium metal electrode, and lithium dendrites are deposited thereon to be located under the polymer electrolyte membrane. Can be seen. However, it can be seen that even if the volume of the electrode surface is expanded due to the precipitation of the dendrites, the polymer electrolyte membrane is not torn or punctured due to its elasticity, and its shape is continuously maintained, and the dendrites are safely covered.

From the above results, the polymer electrolyte membrane according to an embodiment has superior ionic conductivity at room temperature and high temperature compared to a generally well-known polymer electrolyte that uses PEO, PVDF, or PEGDMA as a main chain, and in particular, degradation or volume expansion of the membrane due to excessive electrolyte impregnation. It can be seen that it exhibits excellent mechanical and stable properties that maintain the shape and characteristics of the polymer electrolyte membrane without any damage caused by it.

In the above, preferred embodiments according to the present invention have been described with reference to the drawings and embodiments, but these are only exemplary, and various modifications and other equivalent embodiments are possible from those of ordinary skill in the art. You will be able to understand. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims (22)

A copolymer of a crosslinkable precursor including a urethane group-containing polyfunctional acrylic monomer and a polyfunctional block copolymer; And
Lithium salt;
Polymer electrolyte membrane for a lithium metal electrode comprising a. The method of claim 1,
The urethane group-containing polyfunctional acrylic monomer is a polymer electrolyte membrane comprising diurethane dimethacrylate, diurethane diacrylate, or a combination thereof. The method of claim 1,
The urethane group-containing polyfunctional acrylic monomer is a polymer electrolyte membrane comprising a diurethane dimethacrylate represented by the following formula (1):
[Formula 1]

In the above formulas, each R is independently a hydrogen atom or a C1-C3 alkyl group. The method of claim 1,
The polyfunctional block copolymer includes a (meth) acrylate group at both ends, and a polymer electrolyte membrane comprising a diblock copolymer or a triblock copolymer including a polyethylene oxide repeat unit and a polypropylene oxide repeat unit. The method of claim 1,
The polyfunctional block copolymer is a polymer electrolyte membrane comprising a polymer represented by the following formula (2):
[Formula 2]

In the above formula, x, y, and z are each independently an integer of 1 to 50. The method of claim 1,
A polymer electrolyte membrane having a weight average molecular weight (Mw) of the multifunctional block copolymer in the range of 500 to 20,000. The method of claim 1,
A polymer electrolyte membrane in which a weight ratio of the urethane group-containing polyfunctional acrylic monomer and the polyfunctional block copolymer is in the range of 1:100 to 100:1. The method of claim 1,
A polymer electrolyte membrane in which the weight ratio of the urethane group-containing polyfunctional acrylic monomer and the polyfunctional block copolymer is in the range of 1:10 to 10:1. The method of claim 1,
The copolymer is a polymer electrolyte membrane that is copolymerized by further comprising an oligomer having a weight average molecular weight (Mw) of 200 to 600 in the crosslinkable precursor. The method of claim 8,
The oligomer is an ether-based, acrylate-based, ketone-based, or a combination thereof, and a polymer electrolyte membrane comprising an alkyl group, an allyl group, a carboxyl group, or a combination thereof as a functional group. The method of claim 1,
The lithium salt is LiSCN, LiN(CN) ₂ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiCF ₃ SO ₃ , LiC(CF ₃ SO ₂ ) ₃ , LiN(SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) ₂ , LiN(SO ₂ F) ₂ , LiSbF ₆ , LiPF ₃ (CF ₂ CF ₃ ) ₃ , LiPF ₃ (CF ₃ ) ₃ and LiB(C ₂ O ₄ ) ₂ A polymer electrolyte membrane containing. The method of claim 1,
The polymer electrolyte membrane in which the content of the lithium salt is 1% by weight to 50% by weight of the total weight of the copolymer and the lithium salt. The method of claim 1,
The polymer electrolyte membrane is a polymer electrolyte membrane that maintains a free standing film at 25 to 60°C. The method of claim 1,
A polymer electrolyte membrane further comprising at least one selected from a liquid electrolyte, a solid electrolyte, a gel electrolyte, a polymer ionic liquid, and a separator. Lithium metal electrodes; And
A protective film disposed on the lithium metal electrode and including a polymer electrolyte film according to any one of claims 1 to 14;
Electrode structure comprising a. An electrochemical device comprising the electrode structure according to claim 15. Preparing a crosslinkable precursor including a urethane group-containing polyfunctional acrylic monomer and a polyfunctional block copolymer and a precursor mixture including a lithium salt; And
Applying and curing the precursor mixture in a film form;
The method of manufacturing a polymer electrolyte membrane according to claim 1 comprising a. The method of claim 17,
The urethane group-containing polyfunctional acrylic monomer is a method for producing a polymer electrolyte membrane comprising diurethane dimethacrylate, diurethane diacrylate, or a combination thereof. The method of claim 17,
The urethane group-containing polyfunctional acrylic monomer is a method for producing a polymer electrolyte membrane containing a diurethane dimethacrylate represented by the following formula (1):
[Formula 1]

In the above formulas, each R is independently a hydrogen atom or a C1-C3 alkyl group. The method of claim 17,
The multifunctional block copolymer includes an acrylate group at both ends, and a method for producing a polymer electrolyte membrane comprising a diblock copolymer or a triblock copolymer including a polyethylene oxide repeating unit and a polypropylene oxide repeating unit. The method of claim 17,
The multifunctional block copolymer is a method of manufacturing a polymer electrolyte membrane containing a polymer represented by the following formula (2):
[Formula 2]

In the above formula, x, y, and z are each independently an integer of 1 to 50. The method of claim 17,
The curing is a method of manufacturing a polymer electrolyte membrane performed using UV, heat or high energy radiation.

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