KR20190086148A - Solvent for solid electrolytes synthesis including onium composite and solid electrolytes synthesis method using the same - Google Patents

Abstract

The present invention relates to a solvent for synthesizing a solid electrolyte including an onium salt compound and a method for synthesizing a solid electrolyte using the same, wherein the solvent includes an onium salt compound represented by chemical formula 1, Q^+·A^-, and thus, the solid electrolyte can be manufactured through a wet method. In the chemical formula 1, Q^+ represents an onium ion, and A^− is at least one selected from the group consisting of bis(trifluoromethanesulfonyl)imide anion (TFSI^−), NO3^−, PF6^−, and AsF6^−. According to the present invention, it is possible to improve output characteristics according to an increase in the ion conductivity of the solid electrolytes.

Description

TECHNICAL FIELD [0001] The present invention relates to a solvent for synthesizing a solid electrolyte including an onium salt compound using a pyrrolidinium cation, and a method for synthesizing a solid electrolyte using the same. BACKGROUND ART < RTI ID = 0.0 >

The present invention relates to a solvent for synthesizing a solid electrolyte comprising an onium salt compound using a pyrrolidinium cation so that a solid electrolyte can be produced by a wet process.

BACKGROUND ART [0002] Today, rechargeable secondary batteries are widely used as large-capacity power storage batteries used in electric vehicles and power storage systems, and portable high-performance energy sources in portable electronic devices such as mobile phones, camcorders, and notebook computers.

The lithium ion battery as a secondary battery has a larger capacity per unit area, a lower self-discharge rate than the nickel-manganese battery or the nickel-cadmium battery, and has advantages in ease of use because there is no memory effect.

The lithium ion battery is composed of a carbon-based cathode, an electrolyte containing an organic solvent, and a lithium-oxide cathode. The lithium-ion battery uses a chemical reaction occurring in the anode and the cathode to discharge lithium ions from the anode, And proceeds to the reverse of the charging process at the time of discharging. That is, it is a representative secondary battery which can perform charging and discharging several times by using the principle that lithium ions come and going between the positive electrode and the negative electrode.

However, since the lithium ion battery uses a liquid electrolyte containing an organic solvent, there are various problems in the stability of the battery due to leak, impact, etc. due to use of highly volatile organic solvent.

Therefore, in order to secure the safety of a lithium ion battery, all solid batteries using solid electrolytes instead of liquid electrolytes have been actively studied.

Since the pre-solid battery uses a solid electrolyte, there is no problem of ignition or the like generated in the liquid electrolyte, and it can be manufactured in a bipolar structure, so that it has many advantages such that the volume energy density can be improved.

A conventional all-solid-state cell is manufactured by a dry process, which is a process of forming a cell by stacking a solid electrolyte powder, a cathode active material powder and an anode active material powder. The dry process has a merit that it is possible to manufacture a pre-solid battery very simply, but it has a limitation in that it is difficult to increase the size because it is a method of producing powder by pressurizing.

Korean Patent Laid-Open Publication No. 10-2013-0130820 discloses a method for producing a solid electrolyte sheet by coating a slurry containing a solvent, a binder and a solid electrolyte on a substrate to form a solid electrolyte sheet and then coating a slurry containing the electrode active material on the substrate to form an electrode However, since it is a method of coating a slurry containing a solid electrolyte on a substrate, it is difficult to manufacture the thin film, and since it is formed only by a wet process, the process is complicated and the contact between the solid electrolyte and the electrode is not uniform Battery capacity and the like are not so good.

Korean Patent No. 10-1684074 Korean Patent Publication No. 10-2013-0130820

An object of the present invention is to provide a solvent for synthesizing a solid electrolyte containing an onium salt compound using a pyrrolidinium cation so that a solid electrolyte can be produced by a wet process.

Another object of the present invention is to provide a method for synthesizing a solid electrolyte using a solvent for synthesizing a solid electrolyte containing an onium salt compound using a pyrrolidinium cation.

It is still another object of the present invention to provide a solid electrolyte synthesized by a method of synthesizing the solid electrolyte.

It is still another object of the present invention to provide a lithium secondary battery including the solid electrolyte.

In order to achieve the above object, the solvent for synthesizing a solid electrolyte of the present invention may include an onium salt compound represented by the following formula (1);

[Chemical Formula 1]

Q ⁺ A ^-

In the above formula (1), Q ⁺ represents an onium ion, and A ^- is one or more selected from the group consisting of TFSI ^- (bis (trifluoromethanesulfonyl) imide anion), NO 3 ^- , PF 6 ^- and AsF 6 ^- .

The Q ⁺ is a quaternary ammonium cation, and A ^- may be TFSI ^- (bis (trifluoromethanesulfonyl) imide anion).

Wherein Q ⁺ is a pyrrolidinium cation, and A < ^- > is TFSI ^- (bis (trifluoromethanesulfonyl) imide anion).

The solvent for synthesizing the solid electrolyte may be subjected to the synthesis reaction of the solid electrolyte in a wet state at a temperature of 300 ° C or lower.

Since the solvent for synthesizing the solid electrolyte exhibits a viscosity of 5 to 8 cP based on 100 ° C, the synthesis reaction of the solid electrolyte can be carried out in a wet state.

According to another aspect of the present invention, there is provided a method of synthesizing a solid electrolyte according to the present invention, which comprises performing a reaction at a reaction temperature of 300 ° C or lower in a solvent containing an onium salt compound represented by the general formula (1).

When the above Q ⁺ is a pyrrolidinium cation, the salt compound of Formula 3 and the lithium salt compound of Formula 4 are reacted at 20 to 27 ° C for 20 to 30 hours according to Reaction Scheme 1 below, 2] can be prepared;

[Reaction Scheme 1]

[Chemical Formula 3] < EMI ID =

In the above Reaction Scheme 1, R is a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, and X ^- is one selected from the group consisting of Cl ^- , Br ^- and I ^- .

R is an alkyl group having 1 to 40 carbon atoms, an alkylamino group having 1 to 40 carbon atoms, an arylamino group having 6 to 40 carbon atoms, an alkylamino group having 3 to 3 carbon atoms, a halogen atom, a cyano group, a halogen atom, An aryloxy group having 6 to 40 carbon atoms, an aryloxy group having 3 to 40 carbon atoms, a heteroaryl group having 3 to 40 carbon atoms, an aryloxy group having 3 to 40 carbon atoms, an aryloxy group having 6 to 40 carbon atoms, , Germanium groups, phosphorus, and boron.

The salt compound of formula (3) may be prepared by stirring the compound of formula (5) and the compound of formula (6) at -3 to 1 ° C for 48 to 72 hours according to the following scheme 2:

[Reaction Scheme 2]

[Chemical Formula 5] < EMI ID = 6.1 >

According to another aspect of the present invention, there is provided a method of synthesizing a solid electrolyte according to the present invention.

 According to another aspect of the present invention, there is provided a lithium secondary battery including the solid electrolyte.

The solid electrolyte prepared using the solid electrolyte synthesis solvent containing the onium salt compound of the present invention can widen the use temperature range compared with the conventional molten salt electrolyte and can prevent the active material from overflowing when the liquid electrolyte electrode active material is melted. And it has an effect of solving problems such as electrolyte leakage and short-circuit which occurred when using the existing molten salt electrolyte.

In addition, since the solid electrolyte can be used at a relatively higher temperature than the conventional aqueous electrolyte or the organic electrolyte, the output characteristics of the solid electrolyte can be improved as the ion conductivity of the solid electrolyte increases.

1 is a diagram showing a process of preparing a compound according to one step of an embodiment of the present invention.
2 is a view illustrating a process of preparing a compound according to two steps of an embodiment of the present invention.
FIG. 3 is a graph showing the 1 H NMR measurement of the compound of formula (7) as a starting material and the compound of formula (9) prepared according to an embodiment of the present invention.
FIG. 4 is a graph showing 1 H NMR measurement of a compound represented by Formula 9 before and after synthesis of a solid electrolyte using a compound of Formula 9 prepared according to an embodiment of the present invention as a solvent. FIG.
FIG. 5 is a graph showing 19 F NMR measurement of a compound of the formula (9) before and after synthesis of a solid electrolyte using a compound of the formula (9) prepared according to an embodiment of the present invention as a solvent.
FIG. 6 is a graph of 31 P NMR measurement of a compound of the formula (9) before and after synthesis of a solid electrolyte using a compound of the formula (9) prepared according to an embodiment of the present invention as a solvent.

The present invention relates to a solvent for synthesizing a solid electrolyte comprising an onium salt compound using a pyrrolidinium cation so that a solid electrolyte can be produced by a wet process.

Hereinafter, the present invention will be described in detail.

The solvent for synthesizing a solid electrolyte of the present invention includes an onium salt compound (ionic liquid) represented by the following formula (1).

[Chemical Formula 1]

Q ⁺ A ^-

In the above formula (1), Q ⁺ is an onium ion, preferably an ammonium cation, more preferably a pyrrolidinium cation. In addition, the A ^- is TFSI ^- a (bis (trifluoromethanesulfonyl) imide anion) - (bis (trifluoromethanesulfonyl) imide anion), NO3 -, PF6 - and AsF6 ^- 1 or more, preferably selected from the group consisting of TFSI.

The solvent for synthesizing the solid electrolyte of the present invention can be subjected to the synthesis reaction of the solid electrolyte by a wet process at a temperature of 300 ° C or less, preferably 100 to 300 ° C. When the reaction temperature is lower than the above lower limit, the viscosity of the solvent is increased and it is difficult to use as a solvent because it is difficult to disperse. When the reaction temperature is higher than the upper limit, pyrolysis proceeds and the solid electrolyte can not be synthesized.

In addition, since the solvent for synthesizing a solid electrolyte of the present invention exhibits a viscosity of 5 to 8 cP based on 100 ° C, it is easy to disperse and thus a solid electrolyte can be synthesized. If a cation and an anion other than the cation and anion are used as the onium salt compound, the viscosity may be increased to 30 cP or lower or the yield may be lowered at 100 ° C.

The present invention also provides a method for synthesizing a solid electrolyte at a reaction temperature of 350 DEG C or lower in a solvent containing an onium salt compound represented by the above formula (1).

In the case where Q ⁺ is a pyrrolidinium cation in the onium salt compound represented by the above formula (1), it is synthesized by the synthesis process of the following reaction formulas (1) and (2).

[Reaction Scheme 2]

[Chemical Formula 5] < EMI ID =

The above Reaction Scheme 2 is a process for synthesizing the salt compound of Formula 3, wherein the compound of Formula 5 and the compound of Formula 6 are prepared by stirring at -3 to 1 ° C for 48 to 72 hours. In this case, X ^- is one selected from the group consisting of Cl ^- , Br ^- and I ^- .

[Reaction Scheme 1]

[Chemical Formula 3] < EMI ID =

[Reaction Scheme 1] is a process for producing a lithium salt represented by the following Chemical Formula 2, wherein the salt compound of Chemical Formula 3 and the lithium salt compound of Chemical Formula 4 are stirred at 20 to 27 ° C for 20 to 30 hours to perform an anion exchange reaction, To prepare a pyrrolidine salt compound. At this time, the Li ⁺ A ^- is preferably synthesized using water as a solvent. When water is used as a solvent, the intermediate and Li ⁺ A ^- form a one-phase solution due to its high solubility in water, but the pyrrolidine ionic The liquid is separated into a liquid state at the bottom due to the hydrophobic property of A ^- , so that it is easy to separate the pyrrolidine ionic liquid represented by the formula (2).

In the above Reaction Scheme 1, R is a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, and X ^- is one selected from the group consisting of Cl ^- , Br ^- and I ^- . R represents an alkyl group having 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbon atoms, an alkylamino group having 1 to 40 carbon atoms, an arylamino group having 6 to 40 carbon atoms, a carbonyl group having a carbon number of 1 to 40, a halogen atom, An arylsilyl group having 6 to 40 carbon atoms, an aryl group having 6 to 40 carbon atoms, an aryloxy group having 3 to 40 carbon atoms, a heteroaryl group having 3 to 40 carbon atoms, a heteroaryl group having 3 to 40 carbon atoms, an alkylaryl group having 1 to 40 carbon atoms, Group, a germanium group, phosphorus, and boron.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention. Such variations and modifications are intended to be within the scope of the appended claims.

Example 1 Synthesis of Onium Salt Compound Represented by Formula 9

1 step: alkylation

1, 1 equivalent of the compound of the formula (7) and 1.1 equivalents of bromobutane were dissolved in acetonitrile, and the mixture was stirred at 0 ° C for 48 hours to carry out an alkylation reaction. When the reaction is completed, the product is precipitated to obtain a solid state. To increase the purity of the solid product, the product is washed twice with ethyl acetate and diethyl ether to remove residual reactants and side products, thereby obtaining a compound of the formula Was purified and separated.

2 step: anion exchange reaction

The anion exchange reaction was carried out by mixing 1 equivalent of the compound of the formula 8 with 1 equivalent of LiTFSI and stirring at room temperature for 24 hours. The LiTFSI was synthesized by using water as a solvent. In this case, the intermediate and LiTFSI form a single phase solution due to high solubility in water, but the pyrrolidine ionic liquid (BMPyrr TFSI) of formula (9) was obtained by separating into a liquid state at the bottom due to the hydrophobic property of LiTFSI.

[Chemical Formula 9]

<Test Example>

Test Example 1. Yield Measurement

The yields of the onium salt compounds (ionic liquids) prepared according to Examples and Comparative Examples were measured. The yield was obtained by extracting the ionic liquid with dichloromethane (DCM) and further extraction with water twice to remove the residual reactants. The extracted product was then separated by column chromatography using Al ₂ O ₃ Followed by vacuum distillation to obtain an onium-TFSI-based material from which residual DCM was removed. The product was then dried in a vacuum oven to ensure final product and yield was determined.

division Example 1
The compound of the formula [9] yield(%) 52.0

As shown in Table 1, the yield of the onium salt compound prepared according to Example 1 of the present invention was 52%, and thus the yield was high.

Test Example 2. 1H NMR measurement

3 and Table 2 are graphs showing 1 H NMR measurement of the compound of Formula 7 as a starting material and the compound of Formula 9 prepared in Example 1.

Classification (Unit: ppm) Starting material
The compound of formula (7) Example 1
The compound of the formula [9] C1 1.69 2.29 C2 2.35 3.68 C3 2.24 3.21 C4 - 3.50 C5 - 1.88 C6 - 1.41 C7 - 0.96

As shown in FIG. 3 and Table 2, it was confirmed that a large change in the chemical shift value was observed by ¹ H NMR analysis according to the alkylation and anion exchange reaction. When the alkylation occurs in one step, the chemical shift value of H present at the C1 position of pyrrolidinium tends to increase to the downfield region. Generally, when the absence of electrons occurs in the surrounding chemical environment, the synthesis shifts successfully, considering that the chemical shift value changes in the downfield direction.

Test Example  3. Confirm thermal stability _ TGA , DSC  analysis

As a result of TGA analysis, it was confirmed that the compound of formula (9), which is a pyrrolidinium ionic liquid, has a high T _d value. Specifically, the compound of formula (9) confirmed the progress of pyrolysis at about 300 ° C, and it was confirmed that the solid electrolyte can be synthesized wet at a temperature of 300 ° C or less.

Further, DSC analysis showed that the compound of formula (9) stably exists in a liquid state at a measurable temperature range (-50 to 100 ° C), and when it is considered that there is no boiling point in the case of an ionic liquid, (T _d ) at the above-mentioned temperature range.

Test Example  4. Viscosity measurement

The viscosity of the compound was measured to be 43.1 cP at room temperature and 5.6 cP at 100 ° C, indicating that the viscosity tended to decrease with increasing temperature. It is expected that it will be difficult to disperse in the synthesis of the solid electrolyte at room temperature. However, when it is synthesized at a high temperature of 100 ° C or higher, the viscosity of the solvent is low and it is considered that the dispersion will not be greatly affected.

Test Example 5. A solid electrolyte (Li ₃ PS ₄ ) NMR measurement for solvent before / after synthesis

(Li ₃ S ₄ ) was synthesized by mixing Li ₂ S and P ₂ S ₅ with the compound as a solvent and then applying heat to the compound to synthesize a solid electrolyte (Li ₃ PS ₄ ) Elements corresponding to 31P were analyzed.

4 and Table 3 are graphs showing 1 H NMR measurement of the compound of Formula 9 before and after the synthesis of the solid electrolyte using the compound of Formula 9 prepared in Example 1 as a solvent.

Classification (Unit: ppm) Before solid electrolyte synthesis
The compound of the formula [9] After solid electrolyte synthesis
The compound of the formula [9] C1 2.29 2.29 C2 3.68 3.70 C3 3.21 3.22 C4 3.50 3.50 C5 1.88 1.88 C6 1.41 1.42 C7 0.96 0.96

As shown in FIG. 4 and Table 3, in the case of 1H NMR, no specific change was observed between the peak before and after the synthesis in the synthesis of the solid electrolyte using the compound of the formula (9) as a solvent.

5 and Table 4 are graphs of 19 F NMR measurement of the compound of the formula (9) before and after the synthesis of the solid electrolyte using the compound of the formula (9) prepared in Example 1 as a solvent.

Classification (Unit: ppm) Before solid electrolyte synthesis
The compound of the formula [10] After solid electrolyte synthesis
The compound of the formula [10] F1 -79.9 -80.0

As shown in Fig. 5 and Table 4, in the case of 19F NMR, no specific change was observed between the peak and the synthesized peak before synthesis of the solid electrolyte using the compound of the formula (9) as a solvent.

6 and Table 5 are graphs of 31P NMR measurement of the compound of Formula 9 before and after synthesis of the solid electrolyte using the compound of Formula 9 prepared in Example 1 as a solvent.

Classification (Unit: ppm) Before solid electrolyte synthesis
The compound of the formula [10] After solid electrolyte synthesis
The compound of the formula [10] P1 - 100.6

As shown in Fig. 6 and Table 5, a new peak was observed in the case of 31P NMR, and a peak corresponding to Li ₃ PS ₄ , which is expected to come from the P ₂ S ₅ reactant for solid electrolyte synthesis and the solid electrolyte, is observed Respectively.

The solid electrolyte synthesized in the solvent containing the onium salt compound of the present invention can improve the output characteristic by simultaneously reducing the interface contact resistance and the internal resistance of the electrode, and it is possible to reduce the lithium ion A secondary battery can be provided.

Claims (12)

1. A solid electrolyte synthesis solvent comprising an onium salt compound represented by the following formula (1):
[Chemical Formula 1]
Q ⁺ A ^-
In the above formula (1), Q ⁺ represents an onium ion, and A ^- is one or more selected from the group consisting of TFSI ^- (bis (trifluoromethanesulfonyl) imide anion), NO 3 ^- , PF 6 ^- and AsF 6 ^- . 2. The method of claim 1, wherein Q ⁺ is a quaternary ammonium cation, wherein A ^- is ^{TFSI - (bis (trifluoromethanesulfonyl) imide} anion) of the solid electrolyte, characterized in that a solvent for synthesis. 2. The method of claim 1, wherein Q ⁺ is a blood Raleigh pyridinium cation, wherein A ^- is ^{TFSI - (bis (trifluoromethanesulfonyl) imide} anion) a solid electrolyte, characterized in that a solvent for synthesis. The solvent for synthesizing a solid electrolyte according to claim 1, wherein the solvent for synthesizing the solid electrolyte is subjected to a synthesis reaction of the solid electrolyte in a wet state at a temperature of 300 ° C or less. The solvent for synthesizing a solid electrolyte according to claim 1, wherein the solvent for synthesizing the solid electrolyte exhibits a viscosity of 5 to 8 cP based on 100 캜, so that the synthesis reaction of the solid electrolyte is performed in a wet state. A method of synthesizing a solid electrolyte at a reaction temperature of 300 ° C or less in a solvent containing an onium salt compound represented by the following formula (1);
[Chemical Formula 1]
Q ⁺ A ^-
In the above formula (1), Q ⁺ represents an onium ion, and A ^- is one or more selected from the group consisting of TFSI ^- (bis (trifluoromethanesulfonyl) imide anion), NO 3 ^- , PF 6 ^- and AsF 6 ^- . The method of synthesizing a solid electrolyte according to claim 6, wherein the Q ⁺ is a pyrrolidinium cation. 8. The method of claim 7, wherein when Q ⁺ is a pyrrolidinium cation, the salt compound of Formula 3 and the lithium salt compound of Formula 4 are reacted at 20 to 27 ° C for 20 to 30 hours Followed by stirring to produce a pyrrolidine salt compound represented by the following formula (2): &lt; EMI ID = 1.0 &gt;
[Reaction Scheme 1]

[Chemical Formula 3] &lt; EMI ID =
In the above Reaction Scheme 1, R is a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, and X ^- is one selected from the group consisting of Cl ^- , Br ^- and I ^- . And R is an alkyl group having 1 to 40 carbon atoms, an alkoxy group having 1 to 40 carbon atoms, an alkylamino group having 1 to 40 carbon atoms, an alkyl group having 6 to 40 carbon atoms An aryloxy group having 3 to 40 carbon atoms, an arylamino group having 3 to 40 carbon atoms, an alkylsilyl group having 1 to 40 carbon atoms, an arylsilyl group having 6 to 40 carbon atoms, an aryl group having 6 to 40 carbon atoms, an aryloxy group having 3 to 40 carbon atoms, Wherein said solid electrolyte is substituted with at least one member selected from the group consisting of a heteroaryl group, a germanium group, phosphorus, and boron. The process according to claim 8, wherein the salt compound of formula (3) is prepared by stirring the compound of formula (5) and the compound of formula (6) at -3-1 ° C for 48-72 hours according to the following scheme A method of synthesizing a solid electrolyte characterized by:
[Reaction Scheme 2]

[Chemical Formula 5] &lt; EMI ID = 6.1 &gt; A solid electrolyte synthesized by the method of synthesizing the solid electrolyte of claim 6. A lithium secondary battery comprising the solid electrolyte of claim 11.

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