TW201724632A - Solid electrolyte, solid electrolyte membrane and manufacturing method therefor, and secondary battery - Google Patents

Abstract

A solid electrolyte, a solid electrolyte membrane and a manufacturing method therefor, and a secondary battery. The solid electrolyte contains an ionic liquid polymer, a nitrile compound and a lithium salt. The battery containing the solid electrolyte has a very good specific discharge capacity and an excellent cycle performance at high charge and discharge rates (for example, 0.5C and 1.0C), and is suitable for use as a battery, and particularly suitable for use as a secondary lithium battery.

Description

Solid electrolyte, solid electrolyte membrane, method of manufacturing the same, and secondary battery

The present invention relates to a solid electrolyte, a solid electrolyte membrane, a method of manufacturing the same, and a secondary battery.

The present application claims priority to Chinese Patent Application No. 201510955695.3, filed on Jan. 17, 2015, in

Electrolytes are an important part of electrochemical devices. At present, the electrolyte of a lithium secondary battery is mainly composed of an organic solvent and a lithium salt, and the organic solvent has a low boiling point, a low flash point, is flammable and volatile, and greatly affects the safety of the lithium secondary battery; With the expansion of battery applications, the power density and energy density of batteries are also increasing, and the safety hazards caused by organic electrolytes are becoming increasingly prominent.

The safety hazards such as fire, explosion and liquid leakage caused by organic electrolytes seriously restrict the development of high specific energy lithium ion batteries. Therefore, solid electrolytes with strong safety, good flexibility, and inhibition of lithium dendrite growth have received extensive attention. However, at present, solid electrolytes generally have problems such as low room temperature ionic conductivity and excessive electrode/solid electrolyte interface impedance, which limits their practical application in lithium ion batteries.

The solid electrolyte for lithium secondary batteries has attracted attention due to its good mechanical properties and high safety, which can prevent electrolyte leakage and eliminate the need for a separator. However, most solid electrolytes have low room temperature ionic conductivity (10 ^-5 ~ 10 ^-6 S cm ^-1 ), which limits their practical application. To date, some strategies have been taken to enhance their ionic conductivity, such as doping fillers, polymer blending, copolymerization, and cross-linking. However, ionic conductivity is still not ideal.

The ionic liquid has a series of excellent characteristics such as substantially non-volatile, high heat resistance, non-flammability, and good electrochemical stability, and is combined with a lithium salt as an electrolyte for use in a lithium secondary battery, which can improve the safety of the battery. To date, prior art ionic liquids have existed single-site cationic ionic liquids and dual-center cationic ionic liquids. However, this type of electrolyte is still present in the liquid phase in the lithium secondary battery, which does not solve the problem of leakage of the battery, and it is difficult to ensure the safety and stability of the battery.

The nitrile compound has high polarity and has a good ability to dissolve a plurality of lithium salts.

For example, the study found that the electrolyte of the succinonitrile/bis(trifluoromethylsulfonyl)imide lithium system has an ionic conductivity of 10 ^-3 S cm ^-1 at room temperature (Nature materials, 2004, ³ , 476-481). ).

There is also an electrolyte in which succinonitrile is introduced into the polymer matrix, for example, an electrolyte including polyacrylonitrile (Electrochemistry Communications, 2008, 10, 1912-1515) and succinonitrile; including chitin (Journal of Membrane Science) , 2014, 468, 149-154) and electrolytes of succinonitrile and the like.

Recently, researchers have also developed in-situ synthesis techniques to prepare a nitrile solid electrolyte (Advanced Energy Materials, 2015, 5, 1500353). The solid electrolyte is formed by dissolving a nitrile ethylated polyvinyl alcohol (PVA-CN) monomer in a solid electrolyte of succinonitrile. The precursor is prepared by immersing the precursor in a polyacrylonitrile electrospun fiber membrane network for in situ polymerization. However, when it is applied to a lithium secondary battery, the discharge specific capacity of the battery at room temperature and a low charge and discharge rate (0.1 C) is ok, but as the charge and discharge rate (for example, 0.5 C and 1.0 C) is increased, The discharge specific capacity is greatly reduced.

Therefore, it has been demanded to develop an electrolyte having a high discharge specific capacity and a good cycle performance at a high charge and discharge rate without lowering the discharge specific capacity at a high charge and discharge rate.

For the electrolyte of a lithium secondary battery, it is essential to ensure that the battery has a high discharge specific capacity and excellent cycle performance at a high charge and discharge rate.

The inventors of the present invention have intensively studied the combination of an ionic liquid polymer and a nitrile compound, and developed a solid state containing the ionic liquid polymer, the nitrile compound, and the lithium salt of the present invention in view of the above-described drawbacks of the prior art. An electrolyte, a solid electrolyte membrane, a method for producing the same, and a secondary battery.

The present invention provides a solid electrolyte containing an ionic liquid polymer, a nitrile compound, and a lithium salt.

In the solid electrolyte of the present invention, the ionic liquid polymer is one selected from the group consisting of a polymer of the following formula (1) and a polymer of the following formula (2): In the formula (1), n is 300. n 4000; where in formula (2), m is 50 m 2000; R ₁ is a hydrogen atom or a C1-C10 linear aliphatic alkyl group; and R ₂ is a C1-C10 linear aliphatic alkyl group or an ether group.

Formula (1) and (2) B ^- is _{^{BF 4 -, PF 6 -,}} (CF 3 SO 2) 2 N -, (FSO 2) 2 N - _{﹉, [C (SO 2 F)} 3] - , CF ₃ BF ₃ ^- , C ₂ F ₅ BF ₃ ^- , C ₃ F ₇ BF ₃ ^- , C ₄ F ₉ BF ₃ ^- , [C(SO ₂ CF ₃ ) ₃ ] ^- , CF ₃ SO ₃ ^- , CF ₃ Any of COO ^- and CH ₃ COO ^- .

In the above formula (2), the ether group of R ₂ may be: -CH ₂ OCH ₃ , -CH ₂ CH ₂ OCH ₃ , -CH ₂ CH ₂ OCH ₂ CH ₃ , -CH ₂ CH ₂ OCH ₂ CH ₂ CH ₃ or -CH ₂ CH ₂ CH ₂ OCH ₃ .

In the solid electrolyte of the present invention, the nitrile compound is selected from the group consisting of malononitrile, succinonitrile, ethoxymethylene malononitrile, terephthalonitrile, isophthalonitrile, and phthalic acid. One of diacetonitrile and 4-fluorophthalonitrile.

The nitrile compound is preferably ethoxymethylenemalononitrile or succinonitrile.

In the solid electrolyte of the present invention, the lithium salt is LiY; wherein Y is BF ₄ ^- , PF ₆ ^- , (FSO ₂ ) ₂ N ^- fluorene, [C(SO ₂ F) ₃ ] ^- or ( CF ₃ SO ₂ ) ₂ N ^- .

In the solid electrolyte of the present invention, the mass ratio of the ionic liquid polymer to the nitrile compound is from 1:0.1 to 1:2.0.

Further, the mass ratio of the above ionic liquid polymer to the above lithium salt is from 1:0.1 to 1:1.0.

The present invention also provides a solid electrolyte membrane containing the aforementioned solid electrolyte.

The present invention also provides a secondary battery comprising the above solid state electrolysis Plasma membrane.

The present invention also provides a secondary battery comprising the above solid electrolyte.

Further, the present invention also provides a solid electrolyte membrane using a solid electrolyte having an amorphous state and a glass transition temperature of less than or equal to -80 ° C, and a secondary battery using the solid electrolyte membrane.

The secondary battery of the present invention may be a lithium ion battery.

The present invention also provides a method for producing the aforementioned solid electrolyte membrane, the method comprising the steps of: (1) according to a mass ratio of an ionic liquid polymer to a nitrile compound of 1:0.1 to 1:2.0, and an ionic liquid polymer and Dissolving the ionic liquid polymer, the nitrile compound, and the lithium salt in a solvent at a mass ratio of lithium salt of 1:0.1 to 1:1.0, and mixing to obtain a mixed solution; (2) The mixed liquid obtained in the step (1) was coated on a template to prepare a solid electrolyte membrane.

Technical effect

In the present invention, not only a combination of new components of a solid electrolyte but also a specific ratio of these new components is provided, and the solid electrolyte of the present invention is used as compared with the prior art and its conventional polymer matrix. The battery has a very good discharge specific capacity and excellent cycle performance at a high charge and discharge rate of 0.5 C and 1.0 C.

Furthermore, the solid electrolyte of the present invention has an amorphous state, has a low glass transition temperature (<-80 ° C), is favorable for the movement of lithium ions in the battery, and also enables the battery of the present invention to have a high charge and discharge at 0.5 C and 1.0 C. It has very good discharge specific capacity and excellent cycle performance at the rate.

1 is a ¹ H NMR spectrum (deuterated solvent: deuterated acetone) of the ionic liquid polymer obtained in Example 1.

2 is a graph showing discharge specific capacity and cycle performance of Li/LiFePO ₄ batteries formed by the solid electrolyte prepared in Example 1 at different charge and discharge rates (0.1 C, 0.5 C, and 1.0 C).

3 is a ¹ H NMR spectrum (deuterated solvent: deuterated dimethyl hydrazine) of the ionic liquid polymer obtained in Example 2.

4 is a graph showing discharge specific capacity and cycle performance of Li/LiFePO ₄ batteries formed by the solid electrolyte prepared in Example 2 at different charge and discharge rates (0.1 C, 0.5 C, and 1.0 C).

Fig. 5 is a ¹ H NMR spectrum (deuterated solvent: deuterated dimethyl hydrazine) of the ionic liquid polymer obtained in Example 3.

Fig. 6 is a graph showing discharge specific capacity and cycle performance of a Li/LiFePO ₄ battery formed by the solid electrolyte obtained in Example 3 at different charge and discharge rates (0.1 C, 0.5 C, and 1.0 C).

Fig. 7 is a graph showing discharge specific capacity and cycle performance of a Li/LiFePO ₄ battery formed by the solid electrolyte obtained in Example 4 at different charge and discharge rates (0.1 C, 0.5 C, and 1.0 C).

8 is a schematic cross-sectional view showing an example of a lithium secondary battery.

Hereinafter, embodiments of the present invention will be described. However, the invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including the element steps and the like) are not essential unless otherwise specified. The same is true for values and their scope. Limit the invention.

In the present specification, the numerical range indicated by "~" includes the numerical values described before and after "~" as the minimum value and the maximum value, respectively.

In the numerical range recited in the specification, the upper limit or the lower limit described in the numerical range of one step can be replaced with the upper or lower limit of the numerical range described in other stages. Further, in the numerical ranges described in the specification, the upper or lower limit of the numerical range may be replaced with the value shown in the examples.

In the present specification, the term "layer" or "film" includes a case where only a part of the region is formed in addition to the case where the region in which the layer or the film is present is formed in the entire region.

In the present specification, the term "stacking" means that layers are stacked, two or more layers may be combined, or two or more layers may be detachable.

The present invention provides a solid electrolyte containing an ionic liquid polymer, a nitrile compound, and a lithium salt.

<Ionic Liquid Polymer>

The aforementioned ionic liquid polymer is one selected from the group consisting of a polymer of the following formula (1) and a polymer of the following formula (2). In the present invention, the ionic liquid polymer refers to a polymer obtained by introducing a polymerizable unsaturated group into a cationic species or an anionic species constituting the ionic liquid and polymerizing them.

In the formula (1), n is 300. n 4000.

In the formula (2), m is 50. m 2000; R ₁ is a hydrogen atom or a C1-C10 linear aliphatic alkyl group; and R ₂ is a C1-C10 linear aliphatic alkyl group or an ether group.

Specifically, in the formula (1), n represents an integer of from 300 to 4,000, preferably from 500 to 3,900, more preferably from 1,000 to 3,700, still more preferably from 1,500 to 3,500, still more preferably from 2,000 to 3,000. In the formula (2), m represents an integer of from 50 to 2,000, preferably from 200 to 1800, more preferably from 500 to 1,500.

Formula (1) and (2) B ^{- _{include: BF 4 -, PF 6 -}} , (CF 3 SO 2) 2 N -, (FSO 2) 2 N - ﹉, [C (SO ₂ F) ₃ ] ^- , CF ₃ BF ₃ ^- , C ₂ F ₅ BF ₃ ^- , C ₃ F ₇ BF ₃ ^- , C ₄ F ₉ BF ₃ ^- , [C(SO ₂ CF ₃ ) ₃ ] ^- , CF ₃ SO ₃ ^- Any of CF ₃ COO ^- and CH ₃ COO ^- .

The aforementioned linear aliphatic alkyl group of C1-C10 is, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a decyl group or a fluorenyl group.

The linear aliphatic alkyl group is preferably a C1-C5 linear aliphatic alkyl group, and is exemplified by a methyl group, an ethyl group, a propyl group, a butyl group and a pentyl group.

The ether group of the above R ₂ is, for example, -CH ₂ OCH ₃ , -CH ₂ CH ₂ OCH ₃ , -CH ₂ CH ₂ OCH ₂ CH ₃ , -CH ₂ CH ₂ OCH ₂ CH ₂ CH ₃ , or -CH ₂ CH ₂ CH ₂ OCH ₃ , preferably -CH ₂ CH ₂ OCH ₃ or -CH ₂ CH ₂ OCH ₂ CH ₃ .

R _{1 is} preferably a hydrogen atom or a methyl group.

R _{2 is} preferably an ether group of a methyl group, an ethyl group or -CH ₂ CH ₂ OCH ₃ .

<Method for Producing Ionic Liquid Polymer>

The method for preparing the ionic liquid polymer is not particularly limited, and may be the following production method.

A method for producing an ionic liquid polymer of the formula (1) can be used, for example, in the literature. A.-L. Pont, R. Marcilla, I. De Meatza, H. Grande, D. Mecerreyes, Journal of Power Sources (2009, 188, 558-563).

The ionic liquid polymer of the formula (1) can be obtained by a method of producing a polydimethyldiallylammonium chloride aqueous solution (concentration: 20.00% by mass) dissolved in deionized water and stirred to form a polydimethyl group. A solution of diallyl ammonium chloride.

Further, the lithium salt was dissolved in deionized water and stirred to form a solution containing a lithium salt.

The two solutions prepared according to the molar ratio of polydimethyldiallylammonium chloride and lithium salt are 1:1.2~1:2.0, and the mixture is stirred for 2-8 hours, and solids are formed. The solid was collected by filtration. The mixture was washed with deionized water until the eluted material was free from halogen anions, and finally vacuum dried for 12 to 48 hours to obtain an ionic liquid polymer of the formula (1).

As the lithium salt, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate or the like can be used.

The viscosity average molecular weight M _v of the ionic liquid polymer of the formula (1) of the present invention is preferably 1.0 × 10 ⁵ to 5.0 × 10 ⁶ g mol ^-1 , more preferably 3.0 × 10 ⁵ to 5.0 × 10 ⁶ g mol ^{- 1} (polymethyl methacrylate as a standard). If the viscosity average molecular weight M _v of the ionic liquid polymer of the formula (1) is greater than or equal to 1.0 × 10 ⁵ g mol ^-1 , the ion formed by dissolving the ionic liquid polymer in a solvent and dried by coating drying can be sufficiently secured. When the sheet strength of the liquid polymer is less than or equal to 5.0 × 10 ⁶ g mol ^-1 , the ionic liquid polymer is easily dissolved in the solvent, and further, the workability of coating formation can be improved.

The method for confirming the ionic liquid polymer (1) is a ¹ H NMR spectrum.

The method for producing the ionic liquid polymer of the formula (2) can be used, for example, in the literature. K.Yin, Z.X. Zhang, L. Yang, S.-i. Hirano, Journal of Power Sources (2014, 258, 150-154).

The ionic liquid polymer of the formula (2) can be obtained by the following production method: First step: dissolving an olefin-containing unsaturated group imidazole monomer in a solvent, and an initiator comprising the olefin-containing unsaturated group imidazole The initiator is added in a ratio of 0.2 to 1.0% by mass of the monomer to carry out radical polymerization. Under the protection of a protective gas such as argon, the reaction is stirred at 60 to 90 ° C for 6 to 12 hours under reflux. The polymer precipitated after solids is formed. After filtration, the polymer is washed with a solvent at 60 to 90 ° C. The polymer containing the imidazole structure was obtained by vacuum drying for 12 to 48 hours.

The imidazole-containing monomer having an olefin-unsaturated group may be 1-vinylimidazole, 1-propenylimidazole or the like.

The polymerization initiator may be azobisisobutyronitrile, azobisisoheptanenitrile or dimethyl azobisisobutyrate.

The solvent may be: toluene, benzene, tetrahydrofuran, acetone, γ-butyrolactone, N-methylpyrrolidone or the like. Among them, acetone is preferred.

These solvents may be used alone or in combination of two or more.

The molecular weight of the obtained polymer: its viscosity average molecular weight M _v was 1.0 × 10 ⁴ - 5.0 × 10 ⁵ g mol ^-1 (polymethyl methacrylate as a standard).

The second step: the imidazole structure-containing polymer obtained in the first step is dissolved in a solvent with a halogenated hydrocarbon or a halogenated ether at a molar ratio of 1:1.5 to 1:2.0, and stirred at 40 to 80 ° C. The solvent was distilled off under reduced pressure for 24 to 72 hours. The solid precipitated polymer was collected, and the solid was washed three times with anhydrous diethyl ether. The ether was removed by rotary evaporation and dried in vacuo for 12 to 48 hours to give a halogen. Anionic ionic liquid polymer.

The solvent thereof may, for example, be N,N-dimethylformamide or methanol.

The halogenated hydrocarbon may be: ethyl bromide, bromopropane, bromobutane or the like.

The halogenated ether may be 2-bromoethyl methyl ether, bromomethyl methyl ether, 2-bromoethyl ethyl ether or the like.

The molecular weight of the obtained halogen-containing anionic ionic liquid polymer: its viscosity average molecular weight M _v is preferably 1.0 × 10 ⁵ to 5.0 × 10 ⁶ g mol ^-1 (polymethyl methacrylate as a standard).

The third step: the halogen-containing anion ionic liquid polymer obtained in the second step and the lithium salt are dissolved in deionized water at a molar ratio of 1:1.2 to 1:2.0, and the reaction is stirred for 2 to 8 hours, and solids are formed and collected by filtration. The solid (precipitated polymer) was washed with deionized water until the eluate was detected with silver nitrate without halogen anions. Finally, the ionic liquid polymer of the formula (2) is obtained by vacuum drying for 12 to 48 hours.

The lithium salt may be lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium tetrafluoroborate or the like.

The viscosity average molecular weight M _v of the ionic liquid polymer of the formula (2) of the present invention is preferably 1.0 × 10 ⁵ to 5.0 × 10 ⁶ g mol ^-1 (polymethyl methacrylate as a standard), more preferably 1.0. ×10 ⁵ ~1.0×10 ⁶ g mol ^-1 . If the viscosity average molecular weight M _v of the ionic liquid polymer of the formula (2) is greater than or equal to 1.0 × 10 ⁵ g mol ^-1 , the ion formed by dissolving the ionic liquid polymer in a solvent and dried by coating drying can be sufficiently secured. When the sheet strength of the liquid polymer is less than or equal to 5.0 × 10 ⁶ g mol ^-1 , the ionic liquid polymer is easily dissolved in the solvent, and the workability of coating formation can be improved.

The method for confirming the ionic liquid polymer is a ¹ H NMR spectrum.

The nitrile compound used in the present invention is selected from the group consisting of malononitrile, succinonitrile, ethoxymethylenemalononitrile, terephthalonitrile, isophthalonitrile, phthalonitrile and 4- One of fluorine phthalonitriles is preferably ethoxymethylenemalononitrile or succinonitrile.

The aforementioned nitrile compound can be obtained by a conventional production method or can be directly purchased from the market.

For example, succinonitrile produced by Fujian Chuangxin Technology Development Co., Ltd. can be used as the succinonitrile in the nitrile compound used in the present invention. The malononitrile, ethoxymethylenemalononitrile, terephthalonitrile, isophthalonitrile, phthalonitrile, and 4-fluorophthalonitrile can also be used by Aladdin. The produced nitrile compound is purchased directly as a commodity. In addition, succinonitrile, malononitrile, ethoxymethylenemalononitrile, terephthalonitrile, isophthalonitrile, phthalonitrile, and tetrafluorocarbon manufactured by Tokyo Chemical Industry Co., Ltd. can also be used. O-phthalonitrile and 4-fluorophthalonitrile.

The lithium salt used in the solid electrolyte of the present invention is not particularly limited as long as it can be used as an electrolyte for an electrolyte solution for a lithium ion battery, and examples thereof include inorganic lithium salts and fluorine-containing organic lithium salts described below. , oxalate borate, etc.

Examples of the inorganic lithium salt include inorganic fluoride salts such as LiPF ₆ , LiBF ₄ , LiAsF ₆ and LiSbF ₆ , perhalogen salts such as LiClO ₄ , LiBrO ₄ and LiIO ₄ , and inorganic chlorides such as LiAlCl ₄ .

Examples of the fluorine-containing organic lithium salt include perfluoroalkylsulfonates such as LiCF ₃ SO ₃ , LiN(CF ₃ SO ₂ ) ₂ , LiN(FSO ₂ ) ₂ , and LiN(CF ₃ CF ₂ SO ₂ ) ₂ . Perfluoroalkylsulfonamide salt such as LiN(CF ₃ SO ₂ )(C ₄ F ₉ SO ₉ ), perfluoroalkylsulfonyl group such as LiC(CF ₃ SO ₂ ) ₃ or LiC(SO ₂ F) ₃ A base salt, Li[PF ₅ (CF ₂ CF ₂ CF ₃ )], Li[PF ₄ (CF ₂ CF ₂ CF ₃ ) ₂ ], Li[PF ₃ (CF ₂ CF ₂ CF ₃ ) ₃ ], Li [ PF ₅ (CF ₂ CF ₂ CF ₂ CF ₃ )], Li[PF ₄ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₃ ], etc. Radical phosphates and the like.

Examples of the oxalic acid borate include lithium dioxalate borate and lithium difluorooxalate borate.

The lithium salt used in the solid electrolyte of the present invention is preferably lithium tetrafluoroborate, lithium hexafluorophosphate or lithium bis(trifluoromethylsulfonyl)imide, and a lithium salt produced by Morita Chemical (Zhangjiagang) Co., Ltd. can be used as a commercial product. Buy directly. Further, a lithium salt sold by Tokyo Chemical Industry Co., Ltd. can also be used.

In the present invention, the mass ratio of the ionic liquid polymer to the nitrile compound is preferably from 1:0.1 to 1:2.0, more preferably from 1:0.2 to 1:1.8, still more preferably from 1:0.3 to 1:1.5. . If the mass ratio of the nitrile compound is more than 0.1, the electrochemical characteristics of the solid electrolyte membrane are improved, and if it is greater than or equal to 0.3, the electrochemical characteristics are further improved. If the mass ratio of the nitrile compound is less than 2.0, the solid electrolyte membrane is inhibited from sticking and is easily peeled off from the mold, and if it is less than or equal to 1.5, it is more preferable.

In the present invention, the mass ratio of the ionic liquid polymer to the lithium salt is from 1:0.1 to 1:1.0, more preferably from 1:0.2 to 1:0.9, still more preferably from 1:0.3 to 1:0.8. If the mass ratio of the lithium salt is less than 0.1, the concentration of the lithium ion carrier in the solid electrolyte becomes low, the ionic conductivity tends to decrease, and if the mass ratio of the lithium salt exceeds 1.0, the solid electrolyte membrane tends to become brittle.

The present invention also provides a solid electrolyte membrane containing the aforementioned solid electrolyte.

The present invention also provides a method of manufacturing the aforementioned solid electrolyte membrane, the method comprising the steps of: (1) The mass ratio of the ionic liquid polymer to the nitrile compound is preferably from 1:0.1 to 1:2.0, more preferably from 1:0.2 to 1:1.8, still more preferably from 1:0.3 to 1:1.5. and, The mass ratio of the ionic liquid polymer to the lithium salt is preferably from 1:0.1 to 1:1.0, more preferably from 1:0.2 to 1:0.9, still more preferably from 1:0.3 to 1:0.8. Dissolving the ionic liquid polymer, the nitrile compound, and the lithium salt in a solvent in the above ratio, uniformly mixing to prepare a mixed solution; (2) coating the mixed solution obtained in the step (1) on a template A solid electrolyte membrane is produced.

The thickness of the solid electrolyte membrane varies greatly depending on the configuration of the battery, and is not particularly limited.

The solid electrolyte of the present invention is applied to a secondary battery, that is, the present invention also provides a secondary battery comprising the aforementioned ionic liquid polymer solid electrolyte membrane.

The solid electrolyte of the present invention is preferably used in a Li/LiFePO ₄ battery.

Further, the solid electrolyte of the present invention can contribute to an improvement in the safety of a lithium secondary battery because of its flame retardancy. Further, since the electrolyte of the present invention is in a solid state, a bipolar electrode can be used. By using a bipolar electrode, it is possible to manufacture a battery having a high energy density that cannot be realized by a conventional lithium secondary battery.

<Preparation and assembly method of lithium secondary battery>

The configuration example of the lithium secondary battery of the present embodiment will be described with reference to FIG. 8 , but the lithium secondary battery is not limited to the configuration of FIG. 8 .

In the lithium secondary battery shown in FIG. 8, the solid electrolyte membrane 3 is disposed between the anode active material layer 2 and the cathode active material layer 4. The anode active material layer 2 is formed on the anode current collector 1 and the cathode active material layer 4 is formed on the cathode current collector 5. (Hereinafter, the negative electrode active material layer 2 formed on the negative electrode current collector 1 is also referred to as a negative electrode sheet, and the positive electrode active material layer 4 including the positive electrode current collector 5 is also referred to as a positive electrode sheet.)

Hereinafter, each configuration of the lithium secondary battery of the present invention will be described.

1. Solid electrolyte layer

The solid electrolyte layer in the lithium secondary battery of the present invention is a layer formed between the positive electrode active material layer and the negative electrode active material layer. The solid electrolyte layer contains a solid electrolyte membrane, and may be, for example, a form in which a solid electrolyte is applied to an electrode. In the present invention, the thickness of the solid electrolyte layer varies greatly depending on the configuration of the battery, and is not particularly limited.

2. Positive electrode

The positive electrode sheet in the lithium secondary battery of the present invention is a layer containing at least a positive electrode active material (that is, a positive electrode active material layer). Further, the positive electrode active material layer may further contain at least one of a conductive material and a binder in addition to the positive electrode active material.

The type of the positive electrode active material is not particularly limited, and examples thereof include an oxide active material, and examples of the oxide active material include LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , LiVO ₂ , and LiNi _1/3 Co _1/3 Mn _{1 . /3} O ₂ and other rock salt layered active materials; spinel-type active materials such as LiMn ₂ O ₄ and Li(Ni _0.5 Mn _1.5 )O ₄ ; olivine-type actives such as LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ and LiCuPO ₄ Substance and so on. From the viewpoint of thermal stability, lithium iron phosphate (LiFePO ₄ ) is preferably used.

The conductive material is not particularly limited as long as it has a desired electron conductivity, and examples thereof include a carbon material. Examples of the carbon material include carbon black such as acetylene black, ketjen black, furnace black, and thermal black.

On the other hand, the binder is not particularly limited as long as it is a chemically stable and electrically stable binder, and examples thereof include fluorine-based binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE). Further, from the viewpoint of the capacity, the content of the positive electrode active material in the positive electrode active material layer is preferably as large as possible. Further, the thickness of the positive electrode active material layer varies greatly depending on the configuration of the battery, and is not particularly limited.

Further, examples of the material of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, carbon, and the like.

3. Negative electrode sheet

The negative electrode sheet in the lithium secondary battery of the present invention is a layer containing at least a negative electrode active material (that is, a negative electrode active material layer). Further, the negative electrode active material layer may further contain at least one of a conductive material and a binder in addition to the negative electrode active material.

The type of the negative electrode active material is not particularly limited, and examples thereof include a metal active material and a carbon active material. Examples of the metal active material include a simple metal, an alloy, a metal oxide, and the like. Examples of the metal element contained in the metal active material include Li, Al, Mg, In, Si, and Sn. As the negative electrode active material, Li metal, carbon, or Li ₄ Ti ₅ O ₁₂ is preferably used.

As the conductive material and the binder, the same material as that described in the above-mentioned positive electrode active material layer can be used. Further, from the viewpoint of capacity, the content of the negative electrode active material in the negative electrode active material layer is preferably as large as possible. Further, the thickness of the negative electrode active material layer varies greatly depending on the configuration of the battery, and is not particularly limited.

Further, examples of the material of the negative electrode current collector include SUS, copper, nickel, carbon, and the like.

4. Other composition

The material of the battery case is not particularly limited as long as it is a general material, and examples thereof include a SUS or Al laminate film. The shape of the lithium secondary battery of the present invention may, for example, be a coin type, a laminate type, a cylindrical type, or a square type.

The assembling method of the lithium secondary battery of the present invention may be: The positive electrode cover and the positive electrode of the battery are prepared in an argon-protected glove box. The solid electrolyte membrane, the negative electrode sheet, and the negative electrode cover are stacked in a stack from bottom to top to form a laminate, and then the laminate is placed on a punch to press, so that the positive and negative shell covers of the battery are tightly locked to each other, and thus the present invention Lithium secondary battery preparation and assembly is completed. Specifically, the negative electrode sheet was cut into a circular shape having a diameter of 1.6 cm, the positive electrode sheet was cut into a circular shape having a diameter of 1.4 cm, and the solid electrolyte membrane was cut into a circular shape having a diameter of 1.9 cm. Next, a positive electrode sheet, a solid electrolyte membrane, a negative electrode sheet, and (cut diameter as a separator) were sequentially stacked in a stainless steel coin outer container (positive electrode cover) having a diameter of 2.0 cm and a thickness of 0.3 cm (CR2032 type). 1.4cm round copper foil). Next, a stainless steel cap (negative electrode cap) was placed on the container through a gasket made of polypropylene, and the container was sealed by pressing. Thus, a lithium secondary battery (button battery) was produced.

The battery member other than the solid electrolyte membrane of the present invention, which is used in the above, may be a battery member obtained by a known method, or may be obtained from various sellers.

Further, a bipolar type in which a plurality of unit cells in which a negative electrode mixture layer, a solid electrolyte, and a positive electrode mixture layer are stacked may be laminated.

<Measurement of molecular weight>

Viscosity-average molecular weight test method: Using polymethyl methacrylate as a standard, the viscosity [η] of the polymer at 25 ° C was measured using a Ubbelohde viscometer, and then the formula [η]=KM _v (where K represents the expansion factor) The value is related to temperature, polymer, solvent properties, M _v represents the viscosity average molecular weight, [η] represents the viscosity of the polymer) to obtain the viscosity average molecular weight M _v .

<Measurement of Glass Transfer Temperature T _g of Solid Electrolyte of the Present Invention>

Differential Scanning Calorimetry (DSC) and TA Instruments The Q2000 type differential calorimeter was used for the measurement. Usually, a second cycle is performed, and the DSC curve data of the second cycle is used to obtain a glass transition temperature: first, the solid electrolyte sample is cooled from room temperature to -80 ° C, kept at a constant temperature for 10 minutes, and then heated to 200 at a rate of 10 ° C / minute. °C, constant temperature for 5 minutes, and then cooled to -80 ° C at a rate of 10 ° C / minute, as the first cycle. The above operation was repeated once as the second cycle.

<Measurement of Ionic Conductivity of Solid Electrolyte of the Present Invention>

The ionic conductivity of the solid electrolyte was measured by the AC impedance method, and the instrument used was a CHI600D electrochemical workstation. The sample to be tested was composed of a stainless steel electrode/solid electrolyte/stainless steel electrode in the order of composition, and the simulated battery was subjected to an AC impedance test at 25 °C. Before the test, the simulated battery was allowed to stand at a constant temperature for 1 h at each temperature point, the frequency range was 1 Hz to 100 KHz, and the AC amplitude was 5 mV. The conductivity calculation formula is as follows:

In the formula, R is the solid electrolyte bulk resistance (Ω), L represents the thickness (cm) of the solid electrolyte membrane, and S represents the effective area (cm ² ) of the solid electrolyte membrane.

<Measurement of discharge specific capacity>

The discharge specific capacity of the battery is measured as follows: The obtained solid electrolyte was made into a battery, and the battery was placed at a temperature of 25 ° C, and charged and discharged at a voltage range of 2.5-4.0 V and a constant current of 0.1 C, 0.5 C or 1.0 C, using CT2001A (Wuhan City) The charging and discharging device of Lanbo Test Equipment Co., Ltd., LAND Battery Test System-CT2001A) measures the first discharge capacity of the battery and the discharge capacity up to 10 times.

Calculation formula of discharge specific capacity: discharge specific capacity (mAh g ^-1 ) = actual discharge capacity (mAh) / mass (g) of active material in the positive electrode sheet.

Further, the data of the cycle performance map in the drawing was obtained by taking the data of the discharge specific capacity obtained above as the ordinate and the cycle number as the abscissa.

<Example>

The following examples are intended to further illustrate the invention but are not intended to limit the scope of the invention.

<Example 1>

[1] Preparation of poly(dimethyldiallylammonium bis(trifluoromethylsulfonyl)imide) based solid electrolyte

[1-1] Preparation of poly(dimethyldiallylammonium bis(trifluoromethylsulfonyl)imide) ionic liquid polymer:

Add 20.00 g of polydimethyldiallyl ammonium chloride in a 250.00 mL beaker ( An aqueous solution (20% by mass) (product of Aldrich Co., Ltd.) and 100.00 mL of deionized water were magnetically stirred for 1 hour to form a solution containing polydimethyldiallyl ammonium chloride.

In a separate 50.00 mL beaker, 8.52 g (29.68 mmol) of lithium bis(trifluoromethylsulfonate) imide (product of Morita Chemical (Zhangjiagang) Co., Ltd.) and 10.00 mL of deionized water were added in sequence, and magnetic stirring was completed to complete Dissolved to form a solution containing lithium bis(trifluoromethylsulfonate)imide.

The above two solutions were mixed, ion exchanged for 2 hours, solid (precipitated polymer) was formed, and the solid was collected by filtration, and then washed with water until the elution was detected with silver nitrate, and chloride ions were not detected, and finally dried at 105 ° C under vacuum. 72 hours. The structural formula of the obtained ionic liquid polymer poly(dimethyldiallylammonium bis(trifluoromethylsulfonyl)imide) is:

The ionic liquid polymer has a viscosity average molecular weight of 2.11 × 10 ⁶ g mol ^-1 .

The chemical structure of the ionic liquid polymer is characterized by a ¹ H NMR spectrum as shown in FIG.

The ¹ H NMR spectrum of the solid electrolyte produced in Example 1 was measured by the following method using AVANCE III HD 400 manufactured by Bruker BioSpin.

Deuterated solvent: deuterated acetone

Resonance frequency: 6~440MHz

Resolution: <0.005Hz

Pulse width: 1H 9μsec

Chemical shift value reference: tetramethyl decane (TMS) 0 ppm

It can be seen that the results of the spectrum correspond to the desired structure.

[1-2] Preparation of solid electrolyte:

1.00 g of the obtained poly(dimethyldiallylammonium bis(trifluoromethylsulfonyl)imide) was added to a one-neck round bottom flask, and 20.00 g of acetone as a solvent was added, dissolved by magnetic stirring, and then added. 1.00g of succinonitrile as a nitrile compound (product of Fujian Chuangxin Technology Development Co., Ltd.) And 0.50 g of lithium bis(trifluoromethylsulfonyl)imide (product of Morita Chemical (Zhangjiagang) Co., Ltd.) as a lithium salt, and magnetically stirred at 25 ° C for 12 hours to obtain a transparent mixture of poly(dimethyl Allyl diallyl ammonium bis(trifluoromethylsulfonyl)imide) solid electrolyte.

[1-3] Preparation of solid electrolyte membrane:

The obtained mixed liquid poly(dimethyldiallylammonium bis(trifluoromethylsulfonyl)imide) solid electrolyte was coated on a polytetrafluoroethylene template, and then vacuum dried at 30 ° C for 48 hours. A solid electrolyte membrane was obtained. The solid electrolyte membrane had a glass transition temperature T _g of less than -80 ° C and an ion conductivity of 5.74 × 10 ^-4 S cm ^-1 at 25 °C.

[1-4] Preparation of lithium secondary battery:

A positive electrode sheet containing lithium iron phosphate (LiFePO ₄ ) as a positive electrode active material, a prepared solid electrolyte membrane, and a negative electrode sheet containing lithium (Li) as a negative electrode active material are stacked in order from bottom to top to form a laminated electrode. Then, the laminated electrode was placed on a press and punched to obtain a Li/LiFePO ₄ battery.

The prepared Li/LiFePO ₄ battery was subjected to a constant current charge and discharge test at a voltage range of 2.5 to 4.0 V at 25 ° C, and each test was carried out for 10 cycles at a charge and discharge rate of 0.1 C, 0.5 C and 1.0 C.

The results of the measurement data of Example 1 are summarized in Tables 2 to 3 and Figures 1 and 2.

<Example 2>

[2] Preparation of poly(1-(2-methoxyethyl)-3-vinylimidazolium bis(trifluoromethylsulfonyl)imide) solid electrolyte

[2-1] Preparation of poly(1-(2-methoxyethyl)-3-vinylimidazolium bis(trifluoromethylsulfonyl)imide) ionic liquid polymer:

(1) A radical polymerization reaction is carried out using 1-vinylimidazole as a reaction monomer, azobisisobutyronitrile as an initiator, and toluene as a reaction solvent, wherein the initiator accounts for 0.5% by mass of the monomer. The reaction was refluxed under an Ar atmosphere at 65 ° C for 8 hours. The solid was formed, washed with acetone, and dried under vacuum at 75 ° C for 24 hours to give a polyvinyl imidazole.

The viscosity average molecular weight M _v of the polyvinylimidazole is 3.39 × 10 ⁵ g mol ^-1 .

(2) 4.00 g of the obtained polyvinyl imidazole and 8.90 g of 2-bromoethyl methyl ether (63.83 mmol) were dissolved in 60.00 mL of N,N-dimethylformamide at 60 ° C The reaction was stirred for 48 hours, and the solvent was evaporated evaporated evaporated evaporated evaporated, evaporated,jjjjjjjjjjjjjjjjjjjjjjj Imidazolium bromide).

The viscosity average molecular weight M _v of poly(1-(2-methoxyethyl)-3-vinylimidazolium bromide) was 5.62 × 10 ⁵ g mol ^-1 .

(3) 3.50 g of the obtained poly(1-(2-methoxyethyl)-3-vinylimidazolium bromide) and 5.17 g (18.02 mmol) of lithium bis(trifluoromethylsulfonyl)imide (Products of Morita Chemical (Zhangjiagang) Co., Ltd.) were dissolved in 20.00 mL of deionized water and magnetically stirred at room temperature for 6 hours. Solids were formed and the solid was collected by filtration. It was washed with deionized water until the eluate was detected with silver nitrate without halogen anion, and finally dried under vacuum at 75 ° C for 24 hours to obtain an ionic liquid polymer poly(1-(2-methoxyethyl)-3-ethylene. A base imidazole bis(trifluoromethylsulfonyl)imide) having the structural formula:

The chemical structure of the ionic liquid polymer was characterized by ¹ H NMR spectroscopy, as shown in FIG. The ¹ H NMR spectrum of the solid electrolyte produced in Example 2 was measured by the following method using AVANCE III HD 400 manufactured by Bruker BioSpin.

Deuterated solvent: deuterated dimethyl hydrazine

Resonance frequency: 6~440MHz

Resolution: <0.005Hz

Pulse width: 1H 9μsec

Chemical shift value reference: tetramethyl decane (TMS) 0 ppm

It can be seen that the spectral results are consistent with the desired structure.

The ionic liquid polymer has a viscosity average molecular weight M _v of 7.32 × 10 ⁵ g mol ^-1 .

[2-2] Preparation of solid electrolyte:

1.00 g of the obtained poly(1-(2-methoxyethyl)-3-vinylimidazolium di(trifluoromethylsulfonyl)imide) was added to a one-neck round bottom flask, and 20.00 as a solvent was added. g acetone, dissolved by magnetic stirring, and further added 0.60 g of ethoxymethylenemalononitrile (Aladdin product) as a nitrile compound and 0.50 g of lithium bis(trifluoromethylsulfonate) imide as a lithium salt (Product of Morita Chemical (Zhangjiagang) Co., Ltd.), after magnetic stirring at 25 ° C for 12 hours, a transparent mixture of poly(1-(2-methoxyethyl)-3-vinylimidazolium di(trifluoro) was obtained. Methylsulfonyl)imide) solid electrolyte.

[2-3] Preparation of solid electrolyte membrane:

The obtained mixed liquid poly(1-(2-methoxyethyl)-3-vinylimidazolium bis(trifluoromethylsulfonyl)imide) solid electrolyte was coated on a polytetrafluoroethylene template, and then The film was dried under vacuum at 25 ° C for 48 hours to obtain a solid electrolyte membrane. The solid electrolyte membrane had a glass transition temperature T _g of less than -80 ° C and an ion conductivity of 2.98 × 10 ^-4 S cm ^-1 at 25 °C.

[2-4] Preparation of lithium secondary battery:

A positive electrode sheet containing lithium iron phosphate (LiFePO ₄ ) as a positive electrode active material, a prepared solid electrolyte membrane, and a negative electrode sheet containing lithium (Li) as a negative electrode active material are stacked in order from bottom to top to form a laminated electrode. Then, the laminated electrode was placed on a press and punched to obtain a Li/LiFePO ₄ battery.

The prepared Li/LiFePO ₄ battery was subjected to a constant current charge and discharge test at a voltage range of 2.5 to 4.0 V at 25 ° C, and each test was carried out for 10 cycles at a charge and discharge rate of 0.1 C, 0.5 C and 1.0 C.

The results of the measurement data of Example 2 are summarized in Tables 2 to 3 and Figures 3 to 4.

<Example 3>

[3] Preparation of poly(1-(2-methoxyethyl)-3-vinylimidazolium hexafluorophosphate) based solid electrolyte

[3-1] Preparation of poly(1-(2-methoxyethyl)-3-vinylimidazolium hexafluorophosphate) ionic liquid polymer:

(1) A radical polymerization reaction is carried out using 1-vinylimidazole as a reaction monomer, azobisisobutyronitrile as an initiator, and toluene as a reaction solvent, wherein the initiator accounts for 0.5% by mass of the monomer. The reaction was refluxed under an Ar atmosphere at 65 ° C for 8 hours. The solid was formed, washed with acetone, and dried under vacuum at 75 ° C for 24 hours to give a polyvinyl imidazole.

The viscosity average molecular weight M _v of the polyvinylimidazole is 3.39 × 10 ⁵ g mol ^-1 .

(2) 4.00 g of the obtained polyvinyl imidazole and 8.90 g of 2-bromoethyl methyl ether (63.83 mmol) were dissolved in 60.00 mL of N,N-dimethylformamide at 60 ° C under The reaction was stirred for 48 hours, and the solvent was evaporated evaporated evaporated evaporated, evaporated,jjjjjjjjjjjjjjjjjjjjj Imidazolium bromide).

The viscosity average molecular weight M _v of poly(1-(2-methoxyethyl)-3-vinylimidazolium bromide) was 5.62 × 10 ⁵ g mol ^-1 .

(3) Dissolving 3.50 g of the obtained poly(1-(2-methoxyethyl)-3-vinylimidazolium bromide) and 2.74 g (18.02 mmol) of lithium hexafluorophosphate (product of Morita Chemical (Zhangjiagang) Co., Ltd.) Magnetic stirring was carried out in 20.00 mL of deionized water at room temperature for 6 hours at room temperature to form a solid which was collected by filtration. Then, it was washed with deionized water until the washings were detected with silver nitrate without halogen anions, and finally dried under vacuum at 75 ° C for 24 hours to obtain an ionic liquid polymer poly(1-(2-methoxyethyl)-3- Vinyl imidazolium hexafluorophosphate), its structural formula is:

The chemical structure of the ionic liquid polymer was characterized by ¹ H NMR spectroscopy, as shown in FIG. The ¹ H NMR spectrum of the solid electrolyte produced in Example 3 was measured by the following method using AVANCE III HD 400 manufactured by Bruker BioSpin.

Deuterated solvent: deuterated dimethyl hydrazine

Resonance frequency: 6~440MHz

Resolution: <0.005Hz

Pulse width: 1H 9μsec

Chemical shift value reference: tetramethyl decane (TMS) 0 ppm

It can be seen that the spectral results are consistent with the desired structure.

The ionic liquid polymer has a viscosity average molecular weight M _v of 6.35 × 10 ⁵ g mol ^-1 .

[3-2] Preparation of solid electrolyte:

1.00 g of the obtained poly(1-(2-methoxyethyl)-3-vinylimidazolium hexafluorophosphate) was added to a one-neck round bottom flask, and 20.00 g of acetone was added as a solvent, and the mixture was dissolved by magnetic stirring. 0.60 g of ethoxymethylenemalononitrile (product of Aladdin) and 0.40 g of lithium hexafluorophosphate (product of Morita Chemical (Zhangjiagang) Co., Ltd.) as a nitrile compound were added, and magnetic stirring was carried out at 25 ° C for 12 After a while, a clear mixture of poly(1-(2-methoxyethyl)-3-vinylimidazolium hexafluorophosphate) solid electrolyte was obtained.

[3-3] Preparation of solid electrolyte membrane:

The obtained mixed liquid poly(1-(2-methoxyethyl)-3-vinylimidazolium hexafluorophosphate) solid electrolyte was coated on a polytetrafluoroethylene template, and then vacuum dried at 30 ° C for 48 hours. A solid electrolyte membrane is obtained. The solid electrolyte membrane had a glass transition temperature T _g of less than -80 ° C and an ion conductivity of 1.08 × 10 ^-4 S cm ^-1 at 25 °C.

[3-4] Preparation of lithium secondary battery:

A positive electrode sheet containing lithium iron phosphate (LiFePO ₄ ) as a positive electrode active material, a prepared solid electrolyte membrane, and a negative electrode sheet containing lithium (Li) as a negative electrode active material are stacked in order from bottom to top to form a laminated electrode. Then, the laminated electrode was placed on a press and punched to obtain a Li/LiFePO ₄ battery.

The results of the measurement data of Example 3 are summarized in Tables 2 to 3 and Figs. 5 to 6.

<Example 4>

A solid electrolyte and a solid electrolyte membrane and a lithium secondary battery were formed as in Example 1 except that the weight ratio of the ionic liquid polymer and succinonitrile of Example 1 was changed to 1:1.5.

The solid electrolyte membrane had a glass transition temperature T _g of less than -80 ° C and an ion conductivity of 3.56 × 10 ^-4 S cm ^-1 at 25 °C.

The results of the measurement data of Example 4 are summarized in Tables 2 to 3 and FIG.

<Example 5>

A solid electrolyte and a solid electrolyte membrane were formed as in Example 2 except that the weight ratio of the ionic liquid polymer and ethoxymethylenemalononitrile of Example 2 was changed to 1:0.3.

The glass transition temperature T _g of the solid electrolyte membrane of less than -80 ℃, ionic conductivity at 25 deg.] C was 1.01 × 10 ^-4 S cm ^-1.

The results of the measurement data of Example 5 are summarized in Table 2.

<Comparative example>

The composition and related fabrication of the solid electrolyte of the comparative example can be referred to the cited article "Advanced Energy Materials" (2015, 5, 1500353).

The solid electrolyte composition is: polyacrylonitrile (product of J&KS Scientific Ltd.), nitrile ethylated polyvinyl alcohol (product of Shin-Etsu Chemical), succinonitrile (product of Aladdin), and LiTFSI lithium salt (product of TCI Corporation). Nitrile ethylated polyvinyl alcohol: succinonitrile: LiTFSI = 5:83:10 (mass ratio). The ionic liquid polymer of the present invention was not used and contained in Comparative Example 1.

A solid electrolyte was prepared by using polyacrylonitrile as a matrix and nitrile ethylated polyvinyl alcohol as a crosslinking component in combination with succinonitrile and a lithium salt, and the obtained solid electrolyte was applied to a Li/LiFePO ₄ battery.

At 25 ° C, with a voltage range of 2.4 ~ 4.2V, the first discharge specific capacity of the battery was 155mAh g ^-1 with 0.1C constant current charge and discharge, and the discharge specific capacity after 150 cycles was 150mAh g ^-1 , and at 0.5 discharge capacity was 125mAh g ^-1 and were 98mAh g ^-1, and after 10 cycles the discharge capacity was 120mAh g ^-1 and were 85mAh g ^-1 and C under 1.0C.

They were compounded to prepare a solid electrolyte having an ionic conductivity of 4.49 × 10 ^-4 S cm ^-1 at 25 °C.

The results are shown in Tables 2 to 3.

2 is a graph showing discharge specific capacity and cycle performance of Li/LiFePO ₄ batteries formed by the solid electrolyte prepared in Example 1 at different charge and discharge rates (0.1 C, 0.5 C, and 1.0 C).

Battery respectively 0.1C, 0.5C and 1.0C of constant current charge and discharge rate at 25 ℃, initial discharge capacity of 150mAh g ^-1, respectively, 132mAh g ^-1 and 121mAh g ^-1, discharge ratio after 10 cycles capacities are 152mAh g ^-1, 130mAh g ^-1 and 116mAh g ^-1.

4 is a graph showing discharge specific capacity and cycle performance of Li/LiFePO ₄ batteries formed by the solid electrolyte prepared in Example 2 at different charge and discharge rates (0.1 C, 0.5 C, and 1.0 C).

The battery was subjected to constant current charge and discharge at a rate of 0.1 C, 0.5 C and 1.0 C at 25 ° C, respectively. The discharge specific capacities were 135 mAh g ^-1 (0.1 C), 129 mAh g ^-1 (0.5 C) and 119 mAh g ^{-1 , respectively.} (1.0C), the discharge specific capacities after 10 cycles were 143 mAh g ^-1 (0.1 C), 128 mAh g ^-1 (0.5 C), and 113 mAh g ^-1 (1.0 C), respectively.

Fig. 6 is a graph showing discharge specific capacity and cycle performance of a Li/LiFePO ₄ battery formed by the solid electrolyte obtained in Example 3 at different charge and discharge rates (0.1 C, 0.5 C, and 1.0 C).

The battery was subjected to constant current charge and discharge at a rate of 0.1 C, 0.5 C and 1.0 C at 25 ° C, respectively. The discharge specific capacities were 132 mAh g ^-1 (0.1 C), 128 mAh g ^-1 (0.5 C) and 112 mAh g ^{-1 , respectively.} (1.0C), after 10 cycles, discharge capacities were ^{138mAh g -1 (0.1C), 126mAh} g -1 (0.5C) and 110mAh g ^-1 (1.0C).

Fig. 7 is a graph showing discharge specific capacity and cycle performance of a Li/LiFePO ₄ battery formed by the solid electrolyte obtained in Example 4 at different charge and discharge rates (0.1 C, 0.5 C, and 1.0 C).

Battery respectively 0.1C, 0.5C and 1.0C of constant current charge and discharge rate at 25 ℃, discharge capacity were ^{145mAh g -1 (0.1C), 127mAh} g -1 (0.5C) and 116mAh g ^-1 (1.0C), the discharge specific capacities after 10 cycles were 146 mAh g ^-1 (0.1 C), 126 mAh g ^-1 (0.5 C), and 111 mAh g ^-1 (1.0 C), respectively.

The foregoing information is summarized in Tables 2 and 3 below.

The solid electrolyte membranes of Examples 1 to 5 were in an amorphous state, and had only a glass transition temperature and no melting point.

The solid electrolyte membrane of the comparative example is a crystalline polymer having a melting point.

As is clear from Table 3, in the batteries formed of the solid electrolytes of Example 1, Example 2, Example 3, and Example 4 of the present invention, the first discharge specific capacity at a charge and discharge rate of 0.5 C was greater than or equal to 125mAh g ^-1 is a high discharge specific capacity. Even at a high charge and discharge rate of 1.0 C, the first discharge specific capacities of the batteries of Examples 1 to 4 were both greater than or equal to 112 mAh g ^-1 .

In the comparative example, although the first discharge specific capacity is 125 mAh g ^-1 at a charge and discharge rate of 0.5 C, the first discharge specific capacity is reduced to less than or equal to 100 mAh g ^-1 at a high charge and discharge rate of 1.0 C. , for 98mAh g ^-1 , does not work properly.

Further, for the cycle performance, the discharge was evaluated by the attenuation of the discharge capacity after 10 cycles.

At a charge and discharge rate of 0.5 C, the attenuation ratio of Example 1 of the present invention was 1.51%, that of Example 2 was 0.78%, that of Example 3 was 1.56%, and that of Example 4 was 0.79%. From this, it is understood that the average attenuation ratio of Examples 1 to 4 is 1.16%, indicating that the attenuation is extremely small even after 10 cycles.

For the comparative example, the ratio of the discharge specific capacity attenuation after the 10 cycles at a charge and discharge rate of 0.5 C was 4.00%, the attenuation was more pronounced, and the cycle performance was poor.

Further, with respect to the attenuation of the discharge specific capacity after 10 cycles at a charge and discharge rate of 1.0 C, the attenuation ratio of Example 1 of the present invention was 4.13%, that of Example 2 was 5.04%, and that of Example 3 was 1.79%. Example 4 was 4.31%. From this, it can be seen that even after 10 cycles, the average attenuation ratio is 3.82%, which is only about 4%.

For the comparative example, the ratio of the specific capacity of the discharge after the 10 cycles of the charge-discharge rate of 1.0 C was 13.27%, the attenuation was very remarkable, and the cycle performance was poor.

From the above attenuation data analysis, we can know the following:

(1) At a charge-discharge rate of 0.5 C, the average value of the discharge specific capacity attenuation ratio of the batteries of Examples 1 to 4 of the present invention after 10 cycles was only 1.16%, which was much less than 4.00% of the comparative example.

(2) The average value of the ratio of the decay ratio of the discharge specific capacity after 10 cycles of the battery formed by the solid electrolytes of Examples 1 to 4 of the present invention at a charge and discharge rate of 1.0 C at a charge and discharge rate of 1.0 C was 3.82% is only equivalent to the attenuation ratio (4.00%) of the discharge specific capacity after 10 cycles of the charge and discharge rate of Comparative Example 0.5C.

On the other hand, in the comparative example, the ratio of the discharge specific capacity after 10 cycles of the charge-discharge rate of 1.0 C was 13.27%, which was the charge-discharge ratio of 1.0 C of the battery formed by the solid electrolytes of Examples 1 to 4 of the present invention. After 10 cycles, the ratio of the discharge to the capacity is 3.5 times, the attenuation is very high, the cycle performance of the battery is very poor, and the battery has poor cycleability.

That is, after 10 cycles of the battery formed of the solid electrolytes of Examples 1 to 4 of the present invention, the discharge specific capacity attenuation was small even after 10 cycles at a high charge and discharge rate of 1.0 C, after 10 cycles. It also maintains a very stable discharge specific capacity, which is very important as a battery.

From the foregoing analysis of the first discharge specific capacity data and the attenuation ratio of the first discharge specific capacity and the discharge specific capacity after 10 cycles, it is understood that the solid electrolyte of the present invention and its battery have high charge and discharge rates (0.5 C and 1.0 C). It has very good discharge specific capacity and excellent cycle performance, and is very suitable for use as a battery, and is particularly suitable for use in a lithium secondary battery.

That is, in the present invention, not only a combination of new components of a solid electrolyte but also a specific ratio of these new components is provided, compared with the prior art and its conventional polymer matrix, so that its battery is at 0.5. C and 1.0C have very good discharge specific capacity and excellent cycle performance at high charge and discharge rates.

Furthermore, the solid electrolyte of the present invention has an amorphous state, has a very low glass transition temperature (<-80 ° C), is favorable for the movement of lithium ions in the battery, and also enables the battery of the present invention to have a high charge and discharge rate (0.5C). And 1.0C), it has very good discharge specific capacity and excellent cycle performance.

Industrial use possibilities

By applying the solid electrolyte of the present invention to a lithium secondary battery, particularly in a Li/LiFePO ₄ lithium secondary battery, excellent discharge specific capacity and cycle performance can be obtained at a high charge and discharge rate.

Claims (16)

A solid electrolyte containing an ionic liquid polymer, a nitrile compound, and a lithium salt. The solid electrolyte according to claim 1, wherein the ionic liquid polymer is one selected from the group consisting of a polymer of the following formula (1) and a polymer of the following formula (2): In the formula (1), n is 300. n 4000; where in formula (2), m is 50 m 2000; R ₁ is a hydrogen atom or a C1-C10 linear aliphatic alkyl group; and R ₂ is a C1-C10 linear aliphatic alkyl group or an ether group. A solid electrolyte according to claim 2, wherein B ^- in the formulas (1) and (2) is BF ₄ ^- , PF ₆ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- ̅, [C(SO ₂ F) ₃ ] ^- , CF ₃ BF ₃ ^- , C ₂ F ₅ BF ₃ ^- , C ₃ F ₇ BF ₃ ^- , C ₄ F ₉ BF ₃ ^- , [C(SO ₂ CF ₃ ) Any of ₃ ] ^- , CF ₃ SO ₃ ^- , CF ₃ COO ^- , and CH ₃ COO ^- . The solid electrolyte of claim 2, wherein the ether group of R ₂ is: -CH ₂ OCH ₃ , -CH ₂ CH ₂ OCH ₃ , -CH ₂ CH ₂ OCH ₂ CH ₃ , -CH ₂ CH ₂ OCH ₂ CH ₂ CH ₃ or -CH ₂ CH ₂ CH ₂ OCH ₃ . The solid electrolyte of claim 1, wherein the nitrile compound is selected from the group consisting of malononitrile, succinonitrile, ethoxymethylene malononitrile, terephthalonitrile, isophthalonitrile, and adjacent One of phthalonitrile and 4-fluorophthalonitrile. The solid electrolyte of claim 5, wherein the nitrile compound is ethoxymethylenemalononitrile or succinonitrile. The solid electrolyte of claim 1, wherein the lithium salt is LiY; wherein Y is BF ₄ ^- , PF ₆ ^- , (FSO ₂ ) ₂ N ^- ̅, [C(SO ₂ F) ₃ ] ^- or (CF ₃ SO ₂ ) ₂ N ^- . The solid electrolyte according to claim 1, wherein the mass ratio of the ionic liquid polymer to the nitrile compound is 1:0.1 to 1:2.0. The solid electrolyte according to claim 1, wherein the mass ratio of the ionic liquid polymer to the lithium salt is 1:0.1 to 1:1.0. A solid electrolyte membrane comprising the solid electrolyte according to any one of claims 1 to 8. A secondary battery comprising the solid electrolyte membrane of claim 10 of the patent application. A secondary battery comprising the solid electrolyte according to any one of claims 1 to 9. A solid electrolyte membrane using a solid electrolyte in an amorphous state and having a glass transition temperature of less than or equal to -80 °C. A secondary battery using the solid electrolyte membrane of claim 13 of the patent application. A secondary battery according to claim 11, 12 or 14, wherein the secondary battery is a lithium ion battery. A method for producing a solid electrolyte membrane, comprising the steps of: (1) a mass ratio of an ionic liquid polymer to a nitrile compound of 1:0.1 to 1:2.0, and a mass ratio of an ionic liquid polymer to a lithium salt of 1: a ratio of 0.1 to 1:1.0: the ionic liquid polymer, the nitrile compound, and the lithium salt are dissolved in a solvent and mixed to obtain a mixed solution; (2) the mixed solution obtained in the step (1) is applied to the template. On top, a solid electrolyte membrane is produced.