KR100508578B1 - Electrochemical cell having an improved safety and method for preparing the same - Google Patents

Abstract

The present invention provides an electrochemical device including an anode, a cathode, and an electrolyte, wherein the cathode is coated with a polymer in which the surface of the active material in the anode is swelled by the electrolyte while the pore structure of the cathode is maintained, and the electrolyte is ionized. It provides an electrochemical device and a method for producing the same, comprising a liquid and a metal salt. The electrochemical device of the present invention is excellent in both performance and safety.

Description

ELECTROCHEMICAL CELL HAVING AN IMPROVED SAFETY AND METHOD FOR PREPARING THE SAME

The present invention relates to an electrochemical device having improved performance and safety and a method of manufacturing the same.

Recently, interest in energy storage technology is increasing. In addition, as the field of application of the energy of mobile phones, camcorders, notebook PCs, and even electric vehicles has been expanded, efforts for research and development of electrochemical devices have been increasingly realized. The electrochemical device is the most attracting field in this respect, and the development of a secondary battery capable of charging and discharging has been the focus of attention. Recently, research and development on the design of new electrodes and batteries have been conducted in order to improve capacity density and specific energy.

Among the secondary batteries currently applied, lithium ion batteries developed in the early 1990s have a higher operating voltage and significantly higher energy density than conventional batteries such as Ni-MH, Ni-Cd, and sulfuric acid-lead batteries that use an aqueous electrolyte solution. It is attracting attention as an advantage. However, such lithium ion batteries have safety problems such as ignition and explosion due to the use of the organic electrolyte, and are difficult to manufacture.

On the other hand, the ionic liquid refers to a salt exhibiting liquid properties at room temperature, also referred to as room temperature molten salt. The structure is composed of organic cations and inorganic anions and has characteristics such as high evaporation temperature, high ionic conductivity, heat resistance and flame retardancy. Application fields include organic synthetic solvents, separation extraction solvents, and the like, and recently, the potential of the electrochemical devices such as capacitors, lithium ion batteries, and fuel cells is emerging. Most of these studies are on electrolytes for capacitors, and researches on electrolytes for lithium ion batteries have been recently conducted in Japan and the United States.

When the ionic liquid is used as an electrolyte of an electrochemical device such as a capacitor or a lithium ion battery, the principle of operation is not specifically disclosed, but it is known to improve the safety of the electrochemical device. However, due to problems such as the reaction between the ionic liquid and the carbon-based negative electrode and the increase in the viscosity of the electrolyte, the situation has not yet been reached.

Japanese Patent Laid-Open Nos. 11-86905 and 11-260400 describe contents of an electrolyte solution for a lithium ion battery containing a material containing an imidazolium cation among ionic liquids. The ionic liquids used in these patents are described. Has the disadvantage of reducing before lithium ions at the negative electrode due to a higher reduction potential than lithium.

In order to solve the high reduction potential problem of the ionic liquid as described above, Japanese Patent Laid-Open No. 11-297355 discloses an ammonium-based ionic liquid having a lower reduction potential than lithium. In this case, however, the reduction potential problem can be overcome, but there is a problem in that the ionic liquid is co-intercalated with lithium ions at the cathode.

In order to solve the problems of the carbon-based negative electrode and the ionic liquid as described above, Japanese Patent Laid-Open No. 2002-110225 discloses a titanium-based negative electrode. However, in this case, due to the high viscosity of the ionic liquid shows a disadvantage that the high efficiency discharge characteristics when applied to the battery.

U.S. Patent No. 2002-0110739 describes that the reaction between an ionic liquid and a carbon-based negative electrode can be suppressed through a two-step electrolyte injection process. However, the two-stage electrolyte injection process is difficult to achieve in reality, and the manufacturing conditions of the ionic liquid in which the reaction with the negative electrode is suppressed are difficult.

Accordingly, the problem caused by using an electrolyte containing an ionic liquid while improving the safety of the battery using an electrolyte containing an ionic liquid, that is, a reaction between the ionic liquid and a carbon-based negative electrode or an increase in the viscosity of the electrolyte There is a demand for the development of technology to solve the problem.

The inventors of the present invention improve the safety of an electrochemical device by an ionic liquid by using a cathode in which the polymer swelled by the electrolyte is coated on the surface of the active material in the negative electrode together with an electrolyte containing an ionic liquid in the electrochemical device. At the same time, it has been found that the polymer coated on the negative electrode active material can suppress the reaction between the ionic liquid and the carbon-based negative electrode so as not to reduce the performance of the electrochemical device. Accordingly, it is an object of the present invention to provide an electrochemical device having improved performance and safety and a method of manufacturing the same based on such facts.

The present invention provides an electrochemical device including an anode, a cathode, and an electrolyte, wherein the cathode is coated with a polymer in which the surface of the active material in the anode is swelled by the electrolyte while the pore structure of the cathode is maintained, and the electrolyte is ionized. An electrochemical device comprising an aqueous liquid and a metal salt is provided.

In addition, the present invention

a) preparing a negative electrode by applying a negative electrode active material slurry to a current collector and drying the slurry solvent;

b) coating the surface of the active material in the negative electrode prepared in step a) with a polymer swollen by an electrolyte solution; And

c) assembling the coated cathode obtained in step b) together with the anode and the separator and injecting an electrolyte solution containing an ionic liquid and a metal salt.

It provides a method for producing an electrochemical device comprising a.

Hereinafter, the present invention will be described in detail.

The present invention improves the safety of a battery by using an electrolyte solution containing an ionic liquid, and at the same time, the surface of the active material in the negative electrode is coated with a polymer swollen by the electrolyte, thereby electrochemically reacting with the ionic liquid and the carbon-based negative electrode. It is characterized by preventing the performance degradation of the device.

First, the manufacturing method of the negative electrode coated with the polymer which swells the surface by electrolyte solution is demonstrated.

In the present invention, the method of coating the surface of the active material in the negative electrode by the polymer swelled by the electrolyte is not particularly limited, but when the method of coating the surface of the negative electrode by using the solution containing the polymer swelled by the electrolyte, the solution The silver can easily penetrate to the inside of the electrode through the pores inherent to the negative electrode, thereby evenly coating the active material located inside the negative electrode while maintaining the basic structure of the negative electrode. 1 shows a cathode reforming process by the same method as described above.

In the present invention, the reaction between the ionic liquid and the negative electrode can be suppressed by the polymer coated on the surface of the active material inside the negative electrode as described above. In other words, when an ionic liquid is conventionally used as an electrolyte, the cathode reacts with the ionic liquid in direct contact, thereby degrading the performance of the electrochemical device. However, in the present invention, since the surface of the active material inside the negative electrode is surrounded by the polymer swelled by the electrolyte by the above method, even if the electrolyte containing ionic liquid is injected after assembly of the electrochemical device, the negative electrode active material is an ionic liquid. In contact with the polymer swelled by the electrolyte rather than in direct contact with the ionic liquid, the reaction between the ionic liquid and the cathode is significantly reduced, thereby preventing the performance of the electrochemical device.

In addition, in the present invention, the polymer coated on the surface of the active material inside the negative electrode does not deteriorate the performance of the battery in other ways. Specifically, it is as follows.

The present invention is different from that of preparing a negative electrode using the coated active material by coating the active material with a conductive polymer or an inorganic material before manufacturing the negative electrode, in that the polymer is coated on the surface after the production of the negative electrode. As a result, unlike the prior art, aggregation of the active material or separation of the polymer coated on the active material does not occur, and the distribution and structure of the constituent materials present in the negative electrode are maintained almost intact. The basic physical properties of the back are maintained.

In addition, since the polymer used in the present invention has a property of swelling by the electrolyte, the electrolyte containing the ionic liquid injected during battery assembly is permeated into the polymer, and the polymer due to the electrolyte containing the ionic liquid soaked into the polymer. Has electrolyte ion conducting ability. Therefore, unlike conductive polymers or inorganic substances that do not have mobility of electrolyte ions, the polymer swelled by the electrolyte solution used in the present invention does not deteriorate the performance of the battery.

In one embodiment for producing a modified negative electrode according to the present invention, by dispersing or dissolving a polymer swelled by an electrolyte in a solvent, coating the solution on the surface of the negative electrode and drying the solvent, the surface of the active material in the negative electrode It may be coated with a polymer that is swollen by the electrolyte solution. As the coating method, dip coating, die coating, roll coating, comma coating, and a mixing method thereof may be used.

The polymer-coated negative electrode should maintain the pore structure of the negative electrode surface, and the coated polymer is preferably present in an independent phase without chemically reacting with the binder.

In the above embodiment, when the polymer swelled by the electrolyte solution is dissolved in the solvent, the content of the polymer in the solvent should be controlled below the concentration that completely fills the surface of the negative electrode. If the content of the polymer in the solution is too high, the solution viscosity rises, whereby the polymer is present on the negative electrode surface rather than penetrating into the negative electrode pores to form a new polymer layer on the negative electrode surface. In such a case, the reaction between the negative electrode active material and the ionic liquid becomes difficult to control, but due to the newly formed polymer layer on the surface of the negative electrode, only battery performance is reduced. On the other hand, when the content of the polymer in the solution is too low, the content of the polymer present on the surface of the active material in the negative electrode is low, the reaction control of the negative electrode and the ionic liquid is insufficient. The content of the polymer in the solvent may be variously adjusted depending on the type of the polymer or solvent to be used, the viscosity of the solution and the negative electrode porosity, but is preferably controlled within the range of 0.1 to 20% by weight.

When the polymer swelled by the electrolyte is coated on the negative electrode, the content of the polymer present in the negative electrode is possible until the pores of the negative electrode are filled with the gel polymer in terms of volume, but the relationship between the performance and safety of the electrochemical device It can be adjusted in various ways. The polymer swelled by the electrolyte is preferably present in the negative electrode in an amount of 0.01% by weight or more, preferably 0.01% by weight to 50% by weight based on the weight of the active material. In addition, the coating layer coated on the surface of the active material in the negative electrode preferably has a thickness of about 0.001 ~ 10 ㎛. When the thickness of the coating layer is thinner than 0.001 μm, the reaction control between the negative electrode active material and the ionic liquid is not sufficient, and when the thickness of the coating layer is thicker than 10 μm, the movement of electrolyte ions is reduced, resulting in deterioration of battery performance. And, the porosity of the negative electrode coated with the polymer is preferably controlled within the range of 0.01 to 50%.

It is preferable that the polymer swelled by the electrolyte solution usable in the present invention has a high degree of swelling of the electrolyte solution. When a polymer having a low electrolyte absorption rate is used, conduction of electrolyte ions is lowered, causing battery performance to be deteriorated. Therefore, in the present invention, it is preferable to select hydrophilic polymers having more polar groups than hydrophobic polymers such as polyolefins. In the present invention, it is preferable that the polymer swelled by the electrolyte has a solubility parameter of 17 [J ^1/2 / cm ^3/2 ] or more. In addition, the polymer swelled by the electrolyte is preferably as high as the dielectric constant. The dielectric constant of the electrolyte-soluble polymer is preferably 3 or more, more preferably 3 to 30 (measurement frequency = 1 kHz).

 Preferred examples of the polymer swelled by the electrolyte are cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, polyethylene oxide, polyvinylidene fluoride-hexafulluoro Propylene, polyvinylidene fluoride-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polystyrene-acrylonitrile copolymer, polyvinylchloride, polyvinylpyrrolidone, polyvinylacetate, polyethylene vinyl acetate Coalesce, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, carboxymethyl cellulose, polyethylene glycol dimethyl ether, gelatin and mixtures thereof, including double cyano groups (cyano, -CN) Polymers are particularly preferred.

The solvent to dissolve the polymer swelled by the electrolyte is not particularly limited, but the solubility index is similar to those of the polymer, and a material having a low boiling point for easy solvent removal is preferable. Specific examples thereof include, but are not limited to, acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, and mixtures thereof.

In the present invention, the negative electrode to be modified by the polymer swelled by the electrolyte is not particularly limited, unlike in the prior art in which various problems occur when the ionic liquid is introduced into the carbon-based negative electrode, for example, lithium metal or lithium alloy, carbon ( A negative electrode active material mainly composed of lithium adsorption material such as carbon, petroleum coke, activated carbon, graphite or other carbons may be a negative electrode current collector such as copper, gold, nickel or copper. Various negative electrodes may be used, such as a negative electrode configured in the form of a binder bound with a foil prepared by an alloy or a combination thereof.

The electrochemical device of the present invention is not particularly limited in manufacturing method, but for example, after assembling a negative electrode coated with a polymer swelled with an electrolyte as described above together with a positive electrode and a separator, an electrolyte including an ionic liquid and a metal salt is prepared. By injection, it can be produced through a conventional assembly process of the electrochemical device.

In the present invention, the battery safety is improved by using the ionic liquid as all or part of the electrolyte solution.

The principle of action by which the ionic liquid improves the safety of the battery has not yet been elucidated. However, due to the high boiling point and nonflammability, which are inherent in ionic liquids as described in the prior art, the fact that ionic liquids can contribute to improved safety of electrochemical devices is known in the art. It is known and such an effect can be confirmed by the Example of this specification.

In addition, since the ionic liquid has a requirement as an electrolyte, it can be used as all or part of the electrolyte. Specifically, in order to be used as an electrolyte, the corresponding ions must be dissociated, and the dissociated ions must have a certain level of mobility. In this respect, the ionic liquid is in a state in which most of the cations and anions are dissociated, and since the dissociated state is the liquid phase, the mobility of the ions is also excellent. Due to these characteristics, ionic liquids are currently used as electrolytes for capacitors.

The ionic liquid which can be used in the present invention is not particularly limited, but by way of non-limiting example the cation of the ionic liquid is imidazolium, pyrazollium, tria unsubstituted or substituted by an alkyl group having 1 to 15 carbon atoms. It can be selected from the group consisting of zoleum, thiazolium, oxazolium, pyridazinium, pyrimidinium, pyrazinium, ammonium, phosphonium, pyridinium, pyrrolidinium, and mixtures thereof, and ethylmethyl-imida. Zolium, butylmethyl-imidazolium, hexylmethyl-imidazolium, octylmethyl-imidazolium, ethyldimethyl-imidazolium, butyldimethyl-imidazolium, hexyldimethyl-imidazolium, octyldimethyl-imidazolium And it is more preferable to select from the group which consists of these mixtures. In addition, the anion of the ionic liquid may be selected from the group consisting of PF6-, BF4-, CF3SO3-, N (CF3SO2) 2-, N (C2F5SO2) 2-, C (CF2SO2) 3- and mixtures thereof. have. In particular, the cation of the ionic liquid is more preferably imidazolium series, the anion of the ionic liquid is more preferably hexafluorophosphate series.

The ionic liquid may include a zwitterion or a derivative thereof in which a cation and an anion are covalently linked to each other to form a negative and positive ion structure.

In the present invention, the ionic liquid in the electrolyte may be mixed with the metal salt in an appropriate composition, and the metal salt, such as a lithium salt, is preferably mixed at a concentration of 0.01 to 3 moles relative to the ionic liquid. In addition, in the present invention, a battery electrolyte solvent commonly used in the electrolyte containing the ionic liquid and the metal salt may be added, and in this case, an improvement in the ionic conductivity can be expected. In the present invention, the ionic liquid content of the electrolyte component is preferably in the range of 1 to 99% by weight.

Examples of the metal salt that can be used in the present invention are salts having a structure such as A + B-, A + is an ion composed of an alkali metal cation such as Li +, Na +, K + or a combination thereof, and B-is PF 6-, BF 4-or Cl -Salts which are ions consisting of anions such as Br-, I-, ClO4-, ASF6-, CH3CO2-, CF3SO3-, N (CF3SO2) 2-, C (CF2SO2) 3-, or a combination thereof. In addition, a conventional battery electrolyte solvent may be used as the electrolyte solvent in the present invention, and for example, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dipropyl carbonate (DPC). ), Dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethyl carbonate (EMC), gamma butyrolactone and the like or mixtures thereof There is an organic solvent selected from the group consisting of.

In the manufacturing process of the electrochemical device of the present invention, the electrolyte injection may be performed at an appropriate stage in the manufacturing process of the electrochemical device according to the manufacturing process and the required physical properties of the final product. That is, before the assembly of the electrochemical device or in the final step of the electrochemical device assembly, and the like.

The positive electrode that can be used in the electrochemical device of the present invention is a lithium adsorption material such as a composite oxide formed by LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , LiFePO ₄ , V ₂ O ₅ , TiS, MoS, and combinations thereof. The positive electrode active material mainly composed of a lithium intercalation material may be a positive electrode composed of a positive electrode current collector, for example, a foil manufactured by aluminum, nickel, or a combination thereof, but is not limited thereto. .

As the separator of the electrochemical device of the present invention, it is preferable to use a porous separator. For example, a polypropylene-based, polyethylene-based, or polyolefin-based porous separator may be used, but is not limited thereto.

The electrochemical device manufactured according to the present invention may be a lithium ion secondary battery capable of charging and discharging.

The present invention will be described in detail through the following examples. However, an Example is for illustrating this invention and this invention is not limited only to these.

Example 1

(Manufacture of Anode)

LiCoO2 as a positive electrode active material, artificial graphite as a conductive material, polyvinylidene fluoride (PVdF) as a binder was mixed at a weight ratio of 94: 3: 3, and N-methyl pyrrolidone (NMP) was added to the resulting mixture to prepare a slurry. do. The prepared slurry was applied to an aluminum foil, dried at 130 ° C. for 2 hours to prepare a positive electrode, and then roll press was performed.

(Manufacture of Cathode)

As a negative electrode, mesocarbon microbeads, artificial graphite, and a binder were mixed in a weight ratio of 93: 1: 1, and N-methyl pyrrolidone (NMP) was added to prepare a slurry. The prepared slurry was applied to a copper foil, dried at 130 ° C. for 2 hours to prepare a negative electrode, and then roll press was performed.

The prepared negative electrode was impregnated with a 3% cyanoethyl pullulan solution dissolved in acetone to prepare a negative electrode modified by a cyanoethyl pullulan layer loaded at 3 g / m ² .

(Battery assembly)

After cutting the positive and negative electrodes prepared as described above to 4 × 5 cm ² and assembled by a stacking (stacking) method, the electrolyte solution (ethylene carbonate (EC) / ethyl methyl carbonate (EMC) = 1/2% by volume, 1 mole of lithium hexafluorophosphate (LiPF6) and BMI-PF6 were injected at a weight ratio of 9: 1 to finally complete the battery.

The charge and discharge characteristics of the prepared battery are shown in Table 1 below. On the other hand, in order to evaluate the thermal stability of the charged positive electrode / electrolyte solution, after charging the battery to 4.2V to decompose to separate the positive electrode only, using a differential scanning calorimeter (DSC) to evaluate the thermal safety up to 350 ℃ The results are shown in Table 2 below.

Example 2

A battery was assembled in the same manner as in Example 1, except that cyanoethyl polyvinylalcohol was used instead of cyanoethyl pullulan as a polymer for negative electrode modification.

The charge and discharge characteristics of the prepared battery are shown in Table 1 below. On the other hand, in order to evaluate the thermal stability of the charged positive electrode / electrolyte solution, after charging the battery up to 4.2 V to decompose the positive electrode only, using a differential scanning calorimeter (DSC) to evaluate the thermal safety up to 350 ℃ The results are shown in Table 2 below.

Comparative Example 1

Without coating the polymer on the negative electrode, a battery was prepared in the same manner as in Example 1, the charge and discharge characteristics were evaluated and the results are shown in Table 1 below. In addition, the thermal stability of the positive electrode / electrolyte solution up to 350 ℃ by differential scanning calorimeter and the results are shown in Table 2 below.

Comparative Example 2

A battery was manufactured in the same manner as in Example 1 except that the polymer was not coated on the negative electrode and BMI-PF6 was not added to the electrolyte, and then the charge and discharge characteristics were evaluated and the results are shown in Table 1 below. In addition, the thermal stability of the positive electrode / electrolyte solution up to 350 ℃ by differential scanning calorimeter and the results are shown in Table 2 below.

Battery charge and discharge characteristics Example 1 Example 2 Comparative Example 1 Comparative Example 2 Initial 0.2C Charge (mAh) 72.5 73.5 69.0 77.4 Initial 0.5C discharge amount (mAh) 69.1 70.3 65.2 74.9 Initial Efficiency (%) 95.3 95.6 94.5 96.9 C-rate (1C / 0.2C) 89.0 92.4 68.9 98.0 C-rate (2C / 0.2C) 52.8 74.7 32.4 90.2

Anode / electrolyte calorific value at 350 ° C using differential scanning calorimeter Example 1 Example 2 Comparative Example 1 Comparative Example 2 Calorific Value (△ H, J / g) 151.1 117.3 145.4 405.9

As shown in Table 1 and Table 2, it can be seen that the batteries of Comparative Examples 1, 1 and 2 using the electrolyte solution to which the ionic liquid is added are significantly reduced in heat generation compared to Comparative Example 2 which is not. In addition, while the charge and discharge characteristics of the batteries of Examples 1 and 2 were significantly improved compared to those of Comparative Example 1 in which the negative electrode was not modified, it can be seen that the heat of reaction between the positive electrode and the electrolyte was not significantly different.

The present invention improves battery safety by using an electrolyte solution containing an ionic liquid, while suppressing the reaction between the ionic liquid and the negative electrode by reducing the battery performance by coating the surface of the negative electrode active material with a polymer swelled by the electrolyte solution. You may not.

1 is a schematic diagram of a cathode reforming process according to the present invention.

Claims (25)

In the electrochemical device including a positive electrode, a negative electrode and an electrolyte, the negative electrode is coated with a polymer in which the surface of the active material in the negative electrode is swelled by the electrolyte while the pore structure of the negative electrode is maintained, the electrolyte is ionic liquid and An electrochemical device comprising a metal salt. The method of claim 1, wherein the negative electrode is prepared by applying a negative electrode active material slurry to a current collector and drying the slurry solvent to prepare a negative electrode, and then coating the surface of the active material in the negative electrode with a polymer swollen by an electrolyte solution. Electrochemical device, characterized in that. The method of claim 1, wherein the content of the polymer swelled by the electrolyte in the coating layer on the surface of the active material in the negative electrode is an electrochemical device, characterized in that 0.01 to 50% by weight based on the weight of the active material. The electrochemical device according to claim 1, wherein the thickness of the coating layer on the surface of the active material in the anode is 0.001 to 10 µm. The electrochemical device according to claim 1, wherein the polymer swelled by the electrolyte has a solubility parameter of 17 [J ^1/2 / cm ^3/2 ] or more. The electrochemical device according to claim 1, wherein the polymer swelled by the electrolyte has a dielectric constant (measurement frequency = 1 kHz) of 3 to 30. The polymer swelled by the electrolyte is cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, polyethylene oxide, polyvinylidene fluoride-. Hexafluorolupropylene, polyvinylidene fluoride-trichloroethylene, polymethyl methacrylate, polyacrylonitrile, polystyrene-acrylonitrile copolymer, polyvinyl chloride (PVC), polyvinylpyrrolidone, poly At least one selected from the group consisting of vinyl acetate, polyethylene vinyl acetate copolymer, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, carboxyl methyl cellulose, polyethylene glycol dimethyl ether, gelatin and mixtures thereof Electrochemical device, characterized in that. The method of claim 1, wherein the porosity of the cathode is an electrochemical device, characterized in that 0.01 to 50%. The electrochemical device according to claim 1, wherein the negative electrode has a lithium adsorption material selected from the group consisting of lithium alloy, carbon, petroleum coke, activated carbon, and graphite and is bound to a negative electrode current collector. The method of claim 1, wherein the anode is a lithium adsorption material selected from the group consisting of a composite oxide formed by LiMn ₂ O ₄ , LiCoO ₂ , LiNi _{O 2} , LiFePO ₄ , V ₂ O ₅ , TiS, MoS and combinations thereof An electrochemical device characterized in that it is configured in the form of a binder with the anode current collector. The electrochemical device according to claim 1, wherein the electrolyte contains 1 to 99% by weight of an ionic liquid. The method of claim 1, wherein the cation of the ionic liquid is imidazolium, pyrazolium, triazium, thiazolium, oxazolium, pyridazinium, pyrimidinium unsubstituted or substituted by an alkyl group having 1 to 15 carbon atoms. , Pyrazinium, ammonium, phosphonium, pyridinium, pyrrolidinium and mixtures thereof. The method of claim 12, wherein the cation of the ionic liquid is ethylmethyl-imidazolium, butylmethyl-imidazolium, hexylmethyl-imidazolium, octylmethyl-imidazolium, ethyldimethyl-imidazolium, butyldimethyl An electrochemical device selected from the group consisting of imidazolium, hexyldimethyl-imidazolium, octyldimethyl-imidazolium and mixtures thereof. The method of claim 1, wherein the anion of the ionic liquid is selected from the group consisting of PF6-, BF4-, CF3SO3-, N (CF3SO2) 2-, N (C2F5SO2) 2-, C (CF2SO2) 3-, and mixtures thereof. An electrochemical device, characterized in that selected. The electrochemical device according to claim 1, wherein the cation of the ionic liquid is imidazolium-based and the anion is hexafluorophosphate-based. The electrochemical device according to claim 1, wherein the ionic liquid comprises a zwitterion or a derivative thereof in which a cation and an anion are covalently linked to each other in a negative ion and a positive ion structure. 2. The metal salt of claim 1, wherein the metal salt is a salt having a structure such as A + B −, wherein A + is an ion consisting of an alkali metal cation or a combination thereof, and B − is PF 6 −, BF 4 −, Cl −, Br −, I -, An electrochemical device characterized in that the salt is an ion selected from the group consisting of ClO4-, ASF6-, CH3CO2-, CF3SO3-, N (CF3SO2) 2-, C (CF2SO2) 3- or an ion consisting of a combination thereof. . The electrochemical device of claim 1, wherein the metal salt is mixed at a concentration of 0.01 to 3 moles relative to the ionic liquid. The method of claim 1, wherein the electrolyte is propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxy And an organic solvent selected from the group consisting of ethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethylmethylcarbonate (EMC), gamma butyrolactone and mixtures thereof Electrochemical device characterized in that. The electrochemical device according to claim 1, wherein the electrochemical device is a lithium ion battery capable of charging and discharging. a) preparing a negative electrode by applying a negative electrode active material slurry to a current collector and drying the slurry solvent; b) coating the surface of the active material in the negative electrode prepared in step a) with a polymer swollen by an electrolyte solution; And c) assembling the coated cathode obtained in step b) together with the anode and the separator and injecting an electrolyte solution containing an ionic liquid and a metal salt. The manufacturing method of the electrochemical element as described in any one of Claims 1-20 containing. The preparation of the electrochemical device according to claim 21, wherein the coating in step b) is performed by a method selected from the group consisting of dip coating, die coating, roll coating, comma coating, and a mixture thereof. Way. The method of claim 21, wherein the coating in step b) is performed by coating a surface of an active material in an electrode with a solution prepared by dissolving or dispersing a polymer swelled by an electrolyte in a solvent and then removing the solvent. The manufacturing method of the electrochemical element made into. The method of claim 23, wherein the polymer content in the solvent is 0.1 to 20% by weight. The method of claim 23, wherein the solvent is selected from the group consisting of acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water and mixtures thereof. Method for producing an electrochemical device, characterized in that.