阅读说明：本技术 聚合物电解质及其制造方法 (Polymer electrolyte and method for producing same ) 是由 李齐埙 露西娅·金 韩东夹 蔡宗铉 张完洙 于 2019-07-03 设计创作，主要内容包括：本发明涉及聚合物电解质及其制造方法。更具体地,可以使用可交联的可逆加成断裂链转移(RAFT)聚合剂制造具有优异的离子传导率和低交联度的聚合物电解质膜。(The present invention relates to a polymer electrolyte and a method for producing the same. More specifically, a polymer electrolyte membrane having excellent ionic conductivity and a low degree of crosslinking can be manufactured using a crosslinkable reversible addition fragmentation chain transfer (RAFT) polymerization agent.)

1. A polymer electrolyte comprising:

a polymer comprising a monomer comprising Ethylene Oxide (EO) repeat units;

a reversible addition fragmentation chain transfer polymerizer (RAFT agent) containing a styrene group at both ends; and

a Solvating Ionic Liquid (SIL) comprising a lithium salt and a glyme-type material or amide-type material.

2. The polymer electrolyte of claim 1 wherein the polymer electrolyte comprises

From 40 to 60 weight percent of the polymer comprising ethylene oxide repeat unit containing monomers;

3 to 10 wt% of the RAFT agent; and

30 to 50 weight percent of the solvated ionic liquid comprising a lithium salt and a glyme-type material or amide-type material.

3. The polymer electrolyte of claim 1 wherein the ethylene oxide repeat unit-containing monomer is at least one selected from the group consisting of poly (ethylene glycol) methyl ether acrylate (PEGMEA) and poly (ethylene glycol) methyl methacrylate (PEGMEMA).

4. The polymer electrolyte according to claim 1, wherein the RAFT agent comprises a styrene functional group with a C ═ C double bond at both ends.

5. The polymer electrolyte according to claim 1, wherein the RAFT agent is at least one selected from the group consisting of 3, 4-divinylbenzyl trithiocarbonate (DVBTC) represented by the following formula 1 and trithiocarbonate represented by the following formula 2:

< formula 1>

And

< formula 2>

6. The polymer electrolyte according to claim 1, wherein the RAFT agent is cross-linked with the polymer.

7. The polymer electrolyte according to claim 1, wherein

When the solvating ionic liquid contains lithium salt and glyme materials, the molar ratio of the lithium salt to the glyme materials is 1: 0.1-3,

when the solvating ionic liquid contains lithium salt and amide-based material, the molar ratio of the lithium salt to the amide-based material is 1:1 to 6.

8. The polymer electrolyte according to claim 7, wherein the glyme-based material is at least one selected from the group consisting of monoglyme, diglyme, triglyme, and tetraglyme.

9. The polymer electrolyte according to claim 7, wherein the amide-based material is at least one selected from the group consisting of N-methylacetamide (NMAC), acetamide, N-methylpropanamide, N-ethylacetamide, propionamide, formamide, N-methylformamide, N-ethylformamide, N-dimethylformamide, N-diethylformamide, N-dimethylacetamide, and N, N-diethylacetamide.

10. The polymer electrolyte according to claim 7, wherein the lithium salt is selected from the group consisting of LiSCN, LiN (CN)₂、LiClO₄、LiBF₄、LiAsF₆、LiPF₆、LiCF₃SO₃、LiN(SO₂F)₂、Li(CF₃SO₂)₃C、LiN(SO₂CF₃)₂、LiN(SO₂CF₂CF₃)₂、LiSbF₆、LiPF₃(CF₂CF₃)₃、LiPF₃(C₂F₅)₃、LiPF₃(CF₃)₃And LiB (C)₂O₄)₂At least one of the group consisting of.

11. The polymer electrolyte according to claim 1, wherein the solvated ionic liquid is impregnated or contained in a swollen form inside chains of the polymer.

12. The polymer electrolyte according to claim 1, wherein the polymer electrolyte is a polymer electrolyte membrane in a network form.

13. A method of making a polymer electrolyte comprising the steps of:

(S1) mixing a monomer containing Ethylene Oxide (EO) repeating units, a RAFT agent, a Solvated Ionic Liquid (SIL) containing a lithium salt and a glyme-based material or amide-based material, and an initiator;

(S2) removing oxygen from the mixed solution obtained in the above step (S1); and

(S3) applying the mixed solution from which oxygen has been removed in the above step (S2) to a substrate and curing.

14. The method of manufacturing a polymer electrolyte according to claim 13, wherein in step (S1), 40 to 60% by weight of the monomer containing an ethylene oxide repeating unit; 3 to 10 wt% of the RAFT agent; 30 to 50 weight percent of the solvated ionic liquid comprising a lithium salt and a glyme-type material or amide-type material; and 0.1 to 1% by weight of the initiator.

15. The method of manufacturing a polymer electrolyte according to claim 13, wherein in step (S3), the curing is thermal curing or photo-curing.

16. A lithium secondary battery comprising the polymer electrolyte according to any one of claims 1 to 12.

Technical Field

The present application claims priority from korean patent application No. 10-2018-0086460, filed on 25/7/2018, the entire contents of which are incorporated herein by reference in their entirety.

The present invention relates to a polymer electrolyte having excellent fluidity and ionic conductivity and a method for manufacturing the same.

Background

For current portable electronic devices, lithium ion secondary batteries having high energy density are generally used. The liquid electrolyte mainly used in this case has problems such as leakage and risk of explosion. To protect them, a safety circuit device is required, and since it is sealed with a metal sheath can to prevent leakage, the weight of the battery is inevitably increased. In addition, since the thickness of the battery becomes thick, there is a limitation in the design of the battery. As electronic devices become thinner and more flexible in the future, lithium ion secondary batteries currently using liquid as an electrolyte cannot satisfy all requirements such as miniaturization, weight reduction, and flexibility.

On the other hand, lithium polymer batteries have a high average voltage and a high energy density. In addition, the lithium polymer battery can prevent the leakage of an electrolyte to the outside of the battery on the basis of the performance of the lithium ion secondary battery without a memory effect, thereby improving the stability of the battery. Further, in the case of a lithium polymer battery, since electrodes and separators are integrated, surface resistance is reduced, thereby facilitating high-efficiency charge and discharge with relatively low internal resistance. In addition, the electrolyte membrane can be thinned to manufacture flexible devices and batteries of any shape, and since a metal sheath can is not used, the thickness of the battery can be thinner. Accordingly, batteries for portable electronic devices such as mobile phones, notebook computers, and digital cameras, which are expected to have increasing consumer demands for stability, miniaturization, and high capacity, will be largely replaced with lithium polymer batteries from existing lithium ion batteries. Further, the lithium polymer battery is expected to be applied to a high-capacity lithium secondary battery for a hybrid electric vehicle or the like, and is thus gaining popularity as a next-generation battery.

The most important difference of the lithium polymer battery compared with the lithium ion secondary battery using a liquid electrolyte is that a separator between a positive electrode and a negative electrode is made of a polymer, and the polymer separator can also be used as an electrolyte. In a lithium polymer battery, ion conduction is achieved by internal ion transfer of a polymer electrolyte that is stable as a solid phase.

Polymer electrolytes used in lithium polymer batteries are being roughly studied in two parts, namely, intrinsic solid polymer electrolytes, in which ions of salts dissociated by adding electrolyte salts to polymers containing hetero atoms such as O, N and S move by segmental motion of the polymers, and gel-type polymer electrolytes, in which ion conductivity is obtained by impregnating liquid electrolytes into polymer films and immobilizing them together with electrolyte salts.

Among them, in the case of a gel-type polymer electrolyte, it is still difficult to secure the stability of a battery because a liquid electrolyte existing during use leaks, and there is also a problem in that a battery manufacturing process is difficult. Intrinsic solid polymer electrolytes have been investigated since 1975 when p.v. wright discovered that sodium ions are conducted in poly (ethylene oxide) (PEO). The intrinsic solid polymer electrolyte has high chemical and electrochemical stability and has an advantage of being able to use a high-capacity lithium metal electrode, but it has a problem of very low ionic conductivity at room temperature.

It has been found that the ionic conductivity in intrinsic solid polymer electrolytes is closely related to the degree of local movement of the chains of the polymers, and therefore several methods have been investigated to reduce the high crystallinity of PEO-based polymer electrolytes, allowing the dissociated ions to move freely.

As one of the approaches, studies have been conducted to graft low molecular weight PEO as side chains onto flexible polymer backbones with very low Tg values. With synthesis of PEO as branches with different lengths on both sidesA silicone polymer electrolyte, and when the silicone polymer has six PEO repeat chains (which do not exhibit crystallinity), 4.5X 10 at room temperature^-4High ion conductivity of S/cm.

In order to overcome and improve the problems of the conventional electrolyte, various studies have been made on the material and shape of the electrolyte.

Korean patent No. 1232607 relates to a polymer electrolyte membrane for a lithium secondary battery, which comprises an organic-inorganic hybrid copolymer, wherein the organic-inorganic hybrid copolymer can be polymerized by reversible addition fragmentation chain transfer polymerization (RAFT) to form a polymer electrolyte membrane.

Further, korean patent publication No. 2017-0083387 relates to an electrolyte comprising a block copolymer, wherein the block copolymer can also be obtained by a RAFT reaction.

The block copolymer is obtained by reversible addition fragmentation chain transfer polymerization (RAFT) reaction, and the use of a monomer, a chain transfer agent, an ionic liquid, a lithium salt and an initiator as raw materials is disclosed.

As described above, in recent years, attempts have been made to improve the physical properties of polymer electrolyte membranes using reversible addition fragmentation chain transfer polymerization (RAFT). However, low ionic conductivity, which is a problem of the polymer electrolyte membrane, and fluidity of the electrolyte membrane itself remain to be improved.

[ Prior art documents ]

(patent document 1) Korean patent No. 1232607

(patent document 2) Korean patent laid-open publication No. 2017-0083387

Disclosure of Invention

[ problem ] to provide a method for producing a semiconductor device

As a result of various studies to solve the above problems, the inventors of the present invention manufactured a polymer electrolyte membrane using reversible addition fragmentation chain transfer polymerization (RAFT), wherein the polymer electrolyte membrane was manufactured by using a RAFT agent containing a styrene functional group having a C ═ C double bond together with a solvated ionic liquid. The polymer electrolyte membrane thus manufactured has excellent ionic conductivity and excellent fluidity of the electrolyte membrane itself, and thus it has been found to be advantageous in improving the cell performance.

Accordingly, it is an object of the present invention to provide a polymer electrolyte membrane having excellent fluidity and ionic conductivity.

In addition, another object of the present invention is to provide a method of manufacturing a polymer electrolyte membrane as described above.

[ technical solution ] A

In order to achieve the above object, the present invention provides a polymer electrolyte comprising: a polymer comprising a monomer comprising Ethylene Oxide (EO) repeat units; a reversible addition fragmentation chain transfer polymerizer (RAFT agent) containing a styrene group at both ends; and a Solvating Ionic Liquid (SIL) comprising a lithium salt and a glyme-type material or amide-type material.

The polymer electrolyte may contain 40 to 60% by weight of the polymer including a monomer including an ethylene oxide repeating unit; 3 to 10 wt% of the RAFT agent; and 30 to 50 weight percent of the solvated ionic liquid comprising a lithium salt and a glyme-type material or amide-type material.

The ethylene oxide repeat unit-containing monomer may be at least one selected from the group consisting of poly (ethylene glycol) methyl ether acrylate (PEGMEA) and poly (ethylene glycol) methyl ether methacrylate (pegema).

The RAFT agent may comprise a styrene functional group having a C ═ C double bond at both ends.

The RAFT agent may be cross-linked with the polymer.

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

The glyme-based material may be at least one selected from the group consisting of monoglyme, diglyme, triglyme, and tetraglyme.

The lithium salt may be selected from the group consisting of LiSCN, LiN (CN)₂、LiClO₄、LiBF₄、LiAsF₆、LiPF₆、LiCF₃SO₃、LiN(SO₂F)₂、Li(CF₃SO₂)₃C、LiN(SO₂CF₃)₂、LiN(SO₂CF₂CF₃)₂、LiSbF₆、LiPF₃(CF₂CF₃)₃、LiPF₃(C₂F₅)₃、LiPF₃(CF₃)₃And LiB (C)₂O₄)₂At least one of the group consisting of.

The solvated ionic liquid may be impregnated within the chains of the polymer or contained in swollen form within the chains of the polymer.

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

The present invention also provides a method of manufacturing a polymer electrolyte, comprising the steps of: (S1) mixing a monomer containing ethylene oxide repeating units, a RAFT agent, a Solvated Ionic Liquid (SIL) containing a lithium salt and a glyme-type material or amide-type material, and an initiator; (S2) removing oxygen from the mixed solution obtained in the above step (S1); and (S3) applying and curing the mixed solution from which oxygen has been removed in the above step (S2) onto a substrate.

In the above step (S1), 40 to 60% by weight of the ethylene oxide repeating unit-containing monomer; 3 to 10 wt% of the RAFT agent; 30 to 50 wt% of the Solvated Ionic Liquid (SIL) comprising a lithium salt and a glyme-based material or amide-based material; and 0.1 to 1% by weight of an initiator.

In the above step (S3), the above curing may be thermal curing or photo curing.

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

[ PROBLEMS ] the present invention

The polymer electrolyte according to the present invention may be manufactured in the form of a polymer film having a network morphology, which has a uniform and low degree of crosslinking through RAFT polymerization using a RAFT agent, whereby a phenomenon of a decrease in fluidity of polymer chains can be improved, and a problem of leakage occurring when a battery is assembled using a conventional polymer electrolyte can be solved.

In addition, in the production of a polymer electrolyte, a RAFT agent having a styrene functional group having a C ═ C double bond introduced at both ends can function as a crosslinking agent and a chain transfer agent at the same time.

Further, in the production of a polymer electrolyte, the ionic conductivity can be improved by using a solvated ionic liquid.

Drawings

Fig. 1 is a schematic illustration of a solvated ionic liquid according to one embodiment of the present invention.

FIG. 2 shows a process for preparing a reversible addition fragmentation chain transfer polymerizer (RAFT agent) synthesized in preparation example 1 of the present invention¹H-NMR spectrum.

FIG. 3a is a Differential Scanning Calorimetry (DSC) chart of Solvated Ionic Liquid (SIL) synthesized in preparation example 2 of the present invention, and

fig. 3b is a photograph showing the results of an ignition test on the solvated ionic liquid synthesized in preparative example 2 of the present invention.

Fig. 4 is a photograph showing the results of visual inspection of the morphology of the polymer electrolytes manufactured in examples 1 and 3 of the present invention and comparative examples 1 and 2.

Fig. 5 is a graph showing the measurement results of the voltage stability of the polymer electrolyte manufactured in example 3 of the present invention.

Detailed Description

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

The terms and words used in the present specification and claims should not be construed as being limited to general terms or terms in dictionaries, but interpreted as having meanings and concepts consistent with the technical idea of the present invention based on the principle that the inventor can appropriately define the concept of the term to describe his invention in the best way.

Polymer electrolyte

The present invention relates to a polymer electrolyte prepared by reversible addition fragmentation chain transfer polymerization (RAFT), which has a network morphology with a uniform and low degree of crosslinking, and has high ionic conductivity.

The polymer electrolyte of the present invention comprises: a polymer comprising a monomer comprising ethylene oxide repeat units; a reversible addition-fragmentation chain transfer polymerizer (RAFT agent) having styrene groups introduced at both ends; and a Solvating Ionic Liquid (SIL) comprising a lithium salt and a glyme-type material or amide-type material.

Specifically, the polymer electrolyte may include SIL and a random copolymer including a repeating unit having ethylene oxide and styrene.

The content of the polymer including the monomer including the ethylene oxide repeating unit may be 40 to 60% by weight, preferably 43 to 57% by weight, and more preferably 45 to 55% by weight, based on the total weight of the polymer electrolyte. If the amount is less than the above range, leakage may occur. If the amount is more than the above range, the ionic conductivity of the polymer electrolyte may be decreased.

In the present invention, the RAFT agent may be used as a cross-linking agent and a chain transfer agent in the production of a polymer electrolyte, thereby enabling the formation of a polymer electrolyte membrane having a network morphology with a uniform and low degree of cross-linking.

Specifically, the RAFT agent may be included in the polymer electrolyte in a state of being crosslinked with the ethylene oxide monomer-containing polymer, thereby enabling formation of a polymer electrolyte membrane having a network morphology with a uniform and low degree of crosslinking.

The RAFT agent may be present in an amount of 3 to 10 wt%, preferably 4 to 9 wt%, more preferably 5 to 8 wt%, based on the total weight of the polymer electrolyte. If the amount is less than the above range, leakage may occur. If the amount is more than the above range, the ionic conductivity of the polymer electrolyte may be decreased.

Furthermore, the RAFT agent may have a styrene functional group having a C ═ C double bond introduced at both ends. For example, the RAFT agent is at least one selected from the group consisting of 3, 4-divinylbenzyl trithiocarbonate (DVBTC) represented by formula 1 and trithiocarbonate represented by formula 2:

< formula 1>

And

< formula 2>

In the present invention, the Solvated Ionic Liquid (SIL) can function to improve ionic conductivity of the polymer electrolyte.

The solvated ionic liquid may be impregnated within the chains of the polymer comprising ethylene oxide repeat units, or contained in swollen form within the chains of the polymer.

The solvated ionic liquid may be present in an amount of 30 to 50 wt%, preferably 25 to 45 wt%, more preferably 30 to 40 wt%, based on the total weight of the polymer electrolyte. If the amount is less than the above range, leakage may occur. If the amount is more than the above range, the ionic conductivity of the polymer electrolyte may be decreased.

In addition, the solvating ionic liquid may contain a lithium salt and a glyme-type material, or may contain a lithium salt and an amide-type material.

If the solvating ionic liquid contains a lithium salt and a glyme-type material, the molar ratio of the lithium salt to the glyme-type material is 1:0.1 to 3, preferably 1:0.1 to 2, more preferably 1:0.5 to 1.5. If the molar ratio of the lithium salt to the glyme-based material is less than or greater than the above range, no solvating ionic liquid can be formed.

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

The lithium salt may be selected from the group consisting of LiSCN, LiN (CN)₂、LiClO₄、LiBF₄、LiAsF₆、LiPF₆、LiCF₃SO₃、LiN(SO₂F)₂、Li(CF₃SO₂)₃C、LiN(SO₂CF₃)₂、LiN(SO₂CF₂CF₃)₂、LiSbF₆、LiPF₃(CF₂CF₃)₃、LiPF₃(C₂F₅)₃、LiPF₃(CF₃)₃And LiB (C)₂O₄)₂At least one of the group consisting of. Preferably, the lithium salt may be LiN (SO)₂F)₂Or LiN (SO)₂CF₃)₂It may be more advantageous in improving ionic conductivity and mechanical properties of the polymer electrolyte.

Fig. 1 is a schematic illustration of a solvated ionic liquid according to one embodiment of the present invention.

Referring to FIG. 1, a solvated ionic liquid is formed by having an anion X in which lithium (11) of a lithium salt coordinates with oxygen of a glyme-based material (10) and a lithium salt is present^-(12) The fluidity of lithium ions is improved. At this time, X^-May be, for example, Fluorosulfonylimide (FSI)^-) Or (trifluoromethane) sulfonimide (TFSI)^-)。

In addition, fig. 1 illustrates tetraglyme as an example of the glyme-based material. If such a solvated ionic liquid is contained, it is possible to effectively prevent the hindrance to lithium movement due to the excessive formation of coordinate bonds between the monomer polymer containing ethylene oxide repeating units and lithium ions, as compared with the case where the electrolyte does not contain a solvated ionic liquid. As a result, as shown in fig. 1, electrochemical stability is excellent due to a coordinate bond between lithium and a glyme-based material, and fluidity of lithium ions on the surface of the lithium negative electrode can be improved, thereby obtaining an electrolyte having excellent ion conductivity. In addition, the solvated ionic liquid is one of lewis bases, and has excellent effects in stabilizing the surface of lithium metal and suppressing the formation of lithium dendrites on the surface of a lithium metal negative electrode.

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

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

The polymer electrolyte according to the present invention may be a polymer electrolyte membrane in a network form.

Specifically, since the radical formation is slow and the RAFT polymerization is performed uniformly as compared with the radical polymerization, a polymer electrolyte membrane having a network morphology with a uniform and low degree of crosslinking can be formed.

Method for producing polymer electrolyte

The present invention also relates to a method of manufacturing a polymer electrolyte having a network morphology with a uniform and low degree of crosslinking and having high ionic conductivity using RAFT polymerization.

The method of manufacturing a polymer electrolyte according to the present invention may include the steps of: (S1) mixing a monomer containing ethylene oxide repeating units, a RAFT agent, a Solvated Ionic Liquid (SIL) containing a lithium salt and a glyme-type material or amide-type material, and an initiator; (S2) removing oxygen from the mixed solution obtained in the above step (S1); and (S3) applying and curing the mixed solution from which oxygen has been removed in the above step (S2) onto a substrate.

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

Step (S1)

In the step (S1), a monomer containing an ethylene oxide repeating unit may be mixed; a RAFT agent; a Solvating Ionic Liquid (SIL) containing a lithium salt and a glyme-type material or an amide-type material; and an initiator.

The ethylene oxide repeating unit-containing monomer may be at least one selected from the group consisting of poly (ethylene glycol) methyl ether acrylate (PEGMEA) and poly (ethylene glycol) methyl ether methacrylate (pegema), and preferably may be PEGMEA.

The monomer containing an ethylene oxide repeating unit may be mixed in an amount of 40 to 60 wt%, preferably 43 to 57 wt%, more preferably 45 to 55 wt%, based on the total weight of the four mixed materials (i.e., the monomer containing an ethylene oxide repeating unit, the RAFT agent, the solvated ionic liquid containing a lithium salt and a glyme-based material or amide-based material, and the initiator). If the amount is less than the above range, leakage may occur. If the amount is more than the above range, the ionic conductivity of the polymer electrolyte may be decreased.

The function, specific type, appropriate weight for use in mixing, critical significance and characteristics of the RAFT agent and solvated ionic liquid are as described above.

The initiator may initiate RAFT polymerisation.

The initiator may be at least one selected from the group consisting of azobis (isobutyronitrile) (AIBN), benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-t-butyl peroxide, t-butyl peroxy-2-ethylhexanoate, cumyl hydroperoxide, hydrogen peroxide, 2-azobis (2-cyanobutane), 2-azobis (methylbutyronitrile), and Azobisdimethylvaleronitrile (AMVN), and preferably may be azobis (isobutyronitrile) (AIBN).

The initiator may be mixed in an amount of 0.1 to 1 wt%, preferably 0.1 to 0.8 wt%, more preferably 0.1 to 0.5 wt%, based on the total weight of the four mixed materials (i.e., the monomer containing ethylene oxide repeating units, the RAFT agent, the solvated ionic liquid containing a lithium salt and a glyme-based material or amide-based material, and the initiator). If the amount is less than the above range, the RAFT polymerization may not be initiated, and even if the amount exceeds the above range, the RAFT polymerization is not initiated more smoothly, so that there is no benefit to exceeding the above range.

Step (S2)

In the step (S2), oxygen can be removed from the mixed solution obtained in the step (S1). Since oxygen functions to eliminate radicals required for polymerization, it is preferable to remove oxygen from the mixed solution.

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

Step (S3)

In the step (S3), the mixed solution from which oxygen is removed in the step (S2) may be applied on a substrate and cured.

The method of applying the mixed solution from which oxygen has been removed to the 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. There is no particular limitation thereto as long as a method of applying the solution to a substrate, which can be used in the art, is available.

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

The substrate may preferably be a release film.

The release film is not particularly limited as long as it is a release film used in the prior art, and for example, a release film formed of: polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate; a polyimide resin; an acrylic resin; styrene resins such as polystyrene and acrylonitrile-styrene; a polycarbonate resin; a polylactic acid resin; a polyurethane resin; polyolefin resins such as polyethylene, polypropylene and ethylene-propylene copolymers; vinyl resins such as polyvinyl chloride and polyvinylidene chloride; a polyamide resin; a sulfonic acid resin; polyether ether ketone resin; an allylic resin; or mixtures thereof.

The curing may be thermal curing or photo curing. The heat curing may be carried out by heating to a temperature of 50 ℃ to 80 ℃, preferably 55 ℃ to 75 ℃, more preferably 60 ℃ to 70 ℃. If the above-mentioned heat curing temperature is lower than the above-mentioned range, a polymer electrolyte cannot be obtained because curing does not proceed as desired. If the heat curing temperature is higher than the above range, the physical properties of the polymer electrolyte itself may be denatured. The photo-curing may be UV curing.

Lithium secondary battery

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

The lithium secondary battery according to the present invention comprises a positive electrode, a negative electrode and an electrolyte interposed therebetween, wherein the electrolyte may be a polymer electrolyte as described above.

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

In addition, in order to further increase lithium ion conductivity, the electrolyte may further contain a substance for this purpose.

The polymer electrolyte further contains an inorganic solid electrolyte or an organic solid electrolyte, as required. The inorganic solid electrolyte may be a ceramic material, which is a crystalline material or an amorphous material, and may be an inorganic solid electrolyte, such as thio-LISICON (Li)_3.25Ge_0.25P_0.75S₄)、Li₂S-SiS₂、LiI-Li₂S-SiS₂、LiI-Li₂S-P₂S₅、LiI-Li₂S-P₂O₅、LiI-Li₃PO₄-P₂S₅、Li₂S-P₂S₅、Li₃PS₄、Li₇P₃S₁₁、Li₂O-B₂O₃、Li₂O-B₂O₃-P₂O₅、Li₂O-V₂O₅-SiO₂、Li₂O-B₂O₃、Li₃PO₄、Li₂O-Li₂WO₄-B₂O₃、LiPON、LiBON、Li₂O-SiO₂、LiI、Li₃N、Li₅La₃Ta₂O₁₂、Li₇La₃Zr₂O₁₂、Li₆BaLa₂Ta₂O₁₂、Li₃PO_(4-3/2w)N_w(wherein w < 1), Li_3.6Si_0.6P_0.4O₄。

Examples of the organic solid electrolyte may be an organic solid electrolyte prepared by mixing a lithium salt into a polymer material such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate polymer, a polyalginate lysine, a polyester sulfide, a polyvinyl alcohol, and polyvinylidene fluoride. In this case, these may be used alone or in a combination of at least two.

In the present invention, a specific application method of the polymer electrolyte is not particularly limited, and may be selected from methods known to those skilled in the art.

The lithium secondary battery to which the polymer electrolyte can be applied as an electrolyte is not limited to a positive electrode or a negative electrode, and is particularly suitable for a lithium-air battery, a lithium oxide battery, a lithium-sulfur battery, a lithium metal battery, and an all-solid battery that operate at high temperatures.

The positive electrode of the lithium secondary battery may include, but is not limited to, a layered compound, such as lithium cobalt oxide (LiCoO)₂) And lithium nickel oxide (LiNiO)₂) Or a compound substituted with one or more transition metals; lithium manganese oxides, e.g. LiMnO₃、LiMn₂O₃、LiMnO₂Of the formula Li_1+xMn_2-xO₄(0. ltoreq. x. ltoreq.0.33); lithium copper oxide (Li)₂CuO₂) (ii) a Vanadium oxides, e.g. LiV₃O₈、LiFe₃O₄、V₂O₅、Cu₂V₂O₇(ii) a From the formula LiNi_1-xM_xO₂Ni-site type lithium nickel oxide represented by (M ═ Co, Mn, Al, Cu, Fe, Mg, B or Ga; 0.01. ltoreq. x.ltoreq.0.3); represented by the chemical formula LiMn_2-xM_xO₂(M ═ Co, Ni, Fe, Cr, Zn or Ta; 0.01. ltoreq. x.ltoreq.0.1) or Li₂Mn₃MO₈Lithium manganese complex oxides represented by (M ═ Fe, Co, Ni, Cu, or Zn); from LiNi_xMn_2-xO₄A spinel-structured lithium manganese composite oxide represented by; LiMn₂O₄Wherein a part of Li in the chemical formula is replaced by an alkaline earth metal ion; a disulfide compound; chalcogenides, e.g. Fe₂(MoO₄)₃、Cu₂Mo₆S₈FeS, CoS and MiS, oxides, sulfides or halides of scandium, ruthenium, titanium, vanadium, molybdenum, chromium, manganese, iron, cobalt, nickel, copper, zinc, etc., more specifically, TiS may be included₂、ZrS₂、RuO₂、Co₃O₄、Mo₆S₈、V₂O₅And the like.

The positive electrode active material may be formed on a positive electrode current collector. The positive electrode current collector is not particularly restricted so long as it has high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, sintered carbon; aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like is used as the positive electrode current collector. At this time, the cathode current collector may be formed in various forms, such as a film, a sheet, a foil, a mesh, a porous body, a foam, or a non-woven fabric having minute protrusions and depressions on the surface thereof, to enhance the binding force with the cathode active material.

In addition, the anode is manufactured by forming an anode mixture layer with an anode active material on an anode current collector, or may be a separate anode mixture layer (e.g., lithium foil).

At this time, in the present invention, the types of the anode current collector and the anode mixture layer are not particularly limited, and known materials may be used.

In addition, the anode 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, sintered carbon; copper or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like; an aluminum-cadmium alloy or the like is used as the negative electrode current collector. In addition, the shape of the negative electrode current collector may be various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven fabric, etc. having minute irregularities on the surface, as in the positive electrode current collector.

In addition, the negative active material may include, but is not limited to, at least one carbon-based material 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; a Si-based material; metal complex oxides, e.g. Li_xFe₂O₃(0≤x≤1)、Li_xWO₂(0≤x≤1)、Sn_xMe_1-xMe'_yO_z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of groups 1, 2 and 3 of the periodic table, halogen; x is more than 0 and less than or equal to 1; y is more than or equal to 1 and less than or equal to 3; and z is more than or equal to 1 and less than or equal to 8); lithium metal; a lithium alloy; a silicon-based alloy; a tin-based alloy; metal oxides, e.g. SnO, SnO₂、PbO、PbO₂、Pb₂O₃、Pb₃O₄、Sb₂O₃、Sb₂O₄、Sb₂O₅、GeO、GeO₂、Bi₂O₃、Bi₂O₄And Bi₂O₅(ii) a Conductive polymers such as polyacetylene; a Li-Co-Ni-based material; titanium oxide; lithium titanium oxide.

In addition, the negative active material may be a metal composite oxide, such as Sn_xMe_1-xMe'_yO_z(Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of groups 1, 2 and 3 of the periodic table, halogen; x is more than 0 and less than or equal to 1; y is more than or equal to 1 and less than or equal to 3; and z is more than or equal to 1 and less than or equal to 8); oxides, e.g. SnO, SnO₂、PbO、PbO₂、Pb₂O₃、Pb₃O₄、Sb₂O₃、Sb₂O₄、Sb₂O₅、GeO、GeO2₂、Bi₂O₃、Bi₂O₄And Bi₂O₅And a carbon-based anode 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 material mixture layer may further include a binder resin, a conductive material, a filler, and other additives.

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

The conductive material serves 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 chemical changes in the battery, and 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 thermal black; conductive fibers such as carbon fibers and metal fibers; metal powders such as fluorocarbon, aluminum, and nickel powders; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; a polyphenylene derivative.

The filler is selectively used as a component for suppressing the expansion of the electrode, and is not particularly limited as long as it is a fibrous material without causing chemical changes in the battery, and includes, for example, olefin-based polymers such as polyethylene and polypropylene; and fibrous materials such as glass fibers and carbon fibers.

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

An electrode assembly in which a negative electrode, a polymer electrolyte, and a positive electrode were sequentially stacked was prepared, and the electrode assembly was inserted into a battery case and then sealed with a cap plate and a gasket to obtain a lithium secondary battery.

In this case, the lithium secondary battery may be classified into various types of batteries such as a lithium-sulfur battery, a lithium-air battery, a lithium-oxide battery, and a lithium all-solid battery according to the type of cathode/anode material used, into a cylindrical shape, a rectangular shape, a coin shape, a pouch shape according to the form, and into a block shape and a thin film shape according to the size. The structure and preparation method of these batteries are well known in the art, and thus a detailed description thereof is omitted.

The lithium secondary battery according to the present invention may be used as a power source for devices requiring high capacity, high rate characteristics, and the like. Specific examples of the device may include, but are not limited to, a power tool powered by a battery-powered motor; electric vehicles, including Electric Vehicles (EVs), Hybrid Electric Vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; electric motorcycles including electric bicycles (E-bike) and electric scooters (Escooter); an electric golf cart; and an electrical storage system.

Hereinafter, preferred embodiments of the present invention will be described to facilitate understanding of the present invention. However, it will be apparent to those skilled in the art that the following embodiments are only examples of the present invention, and various changes and modifications can be made within the scope and spirit of the present invention. Such changes and modifications are intended to be within the scope of the appended claims.

In the following examples and comparative examples, polymer electrolytes were manufactured according to the compositions listed in table 1 below.

Table 1:

preparation example 1: synthesis of RAFT Agents

(1) Synthesis of RAFT Agents

The RAFT agent 3, 4-divinylbenzyl trithiocarbonate (DVBTC) was synthesized according to reaction scheme 1 below.

< reaction scheme 1>

In a 250mL round bottom flask, carbon disulfide (CS)₂Sigma Aldrich (Sigma-Aldrich), 3.81g) and potassium carbonate (K)₂CO₃Daejungwhatgeum, 7.26g) was dissolved in 100mL of dimethylformamide (DMF, sigma aldrich, 100mL), and stirring was continued for 30 minutes to obtain a solution.

To the resulting solution was added dropwise 3, 4-vinylbenzyl chloride (VBC, sigma aldrich, 7.63g), and the reaction was allowed to proceed at 40 ℃ for 24 hours with stirring.

The solution undergoing the reaction was put into an excess amount of deionized water (DI water) stored in a refrigerator to terminate the reaction.

The reaction-terminated solution was mixed with 300mL of ethyl acetate (EtAC, sigma aldrich), and then the yellow reaction of the EtAC layer was collected using a separatory funnel and magnesium sulfate (MgSO)₄) The residual water was removed.

Then, the reaction was separated by filtration, EtAc was removed using a rotary evaporator, and then the residual solvent was removed by vacuum drying (room temperature, 24 hours).

Additional purification was performed by silica gel column to obtain 3, 4-divinylbenzyl trithiocarbonate (DVBTC) as a yellow oil (RAFT agent).

(2) Identification of synthetic substances

FIG. 2 shows a process for preparing a reversible addition fragmentation chain transfer polymerizer (RAFT agent) synthesized in preparation example 1 of the present invention¹H-NMR spectrum.

Referring to fig. 2, it can be seen that, in preparation example 1, DVBTC as shown in reaction scheme 1 was synthesized as a RAFT agent.

Preparation example 2: synthesis of Solvate Ionic Liquids (SILs)

(1) Synthesis of SIL (Li [ NMAC ] [ TFSI ])

After N-methylacetamide (NMAC, sigma aldrich) and lithium bis (trifluoromethane) sulfonimide (LiTFSI, sigma aldrich) dried under vacuum at 100 ℃ for 24 hours were mixed at a ratio of 50.46% by weight and 49.54% by weight, respectively, the mixture was stirred in a glove box at room temperature for 4 hours, thereby synthesizing a solvated ionic liquid represented by the following formula 3 (Li [ NMAC ] [ TFSI ], 1.9M).

< formula 3>

Li[NMAC][7FSI]

(2) Confirmation of physical Properties of synthesized SIL (Li [ NMAC ] [ TFSI ])

(2-1) phase identification of SIL (Li [ NMAC ] [ TFSI ])

As a result of visual observation of the synthesized SIL (Li [ NMAC ] [ TFSI ]), it was confirmed that NMAC existing in a crystal form at 25 ℃ exists in the form of LiTFSI and an ionic liquid, and that SIL becomes a liquid phase.

(2-2) confirmation of thermal stability

Differential Scanning Calorimetry (DSC) was measured to confirm the thermal stability of the synthesized SIL (Li [ NMAC ] [ TFSI ]).

FIG. 3a is a DSC of Solvated Ionic Liquid (SIL) synthesized in preparative example 2 of the present invention.

Referring to fig. 3a, the synthesized SIL (Li NMAC) (TFSI) did not undergo a phase transition during DSC measurements across-50 ℃ to 100 ℃, thus confirming that thermal stability is excellent.

(2-3) confirmation of flame retardancy

Experiments were performed to confirm the flame retardancy of the synthesized SIL (Li [ NMAC ] [ TFSI ]).

Fig. 3b is a photograph showing the results of an ignition test on the solvated ionic liquid synthesized in preparative example 2 of the present invention.

Referring to fig. 3b, during the ignition experiment using a torch, the synthesized SIL (Li NMAC ] [ TFSI ]) was not ignited, thereby confirming that the flame retardancy was excellent.