KR100368438B1 - Polymer electrolyte having multilayer structure, method for preparing the same and lithium secondary battery employing the same - Google Patents

Abstract

A polymer electrolyte having a multilayer structure, a method of manufacturing the same, and a lithium secondary battery using the same are disclosed. The polymer electrolyte of the present invention includes a first electrolyte layer having excellent mechanical strength and ion conductivity and a second electrolyte layer having excellent interfacial stability with lithium metal. By manufacturing a lithium secondary battery using a multi-layered polymer electrolyte composed of a first electrolyte layer having excellent mechanical strength and ion conductivity and a second electrolyte layer having excellent stability of lithium metal, mechanical stability and interfacial stability of the polymer electrolyte are improved. Since it can improve simultaneously, the stable charging / discharging characteristic of the lithium secondary battery using a lithium metal and a carbon negative electrode can be acquired, and the lithium secondary battery which has a high capacity can be manufactured easily.

Description

Polymer electrolyte of multi-layered structure, a method of manufacturing the same and a lithium secondary battery using the same {POLYMER ELECTROLYTE HAVING MULTILAYER STRUCTURE, METHOD FOR PREPARING THE SAME AND LITHIUM SECONDARY BATTERY EMPLOYING THE SAME

The present invention relates to a polymer electrolyte, a method for manufacturing the same, and a lithium secondary battery using the same. More particularly, the present invention relates to a polymer electrolyte having a multilayer structure including an electrolyte layer exhibiting excellent interfacial stability to lithium metal and an electrolyte layer having excellent mechanical strength and ion conductivity. The present invention relates to a polymer electrolyte, a method of manufacturing the same, and a lithium secondary battery using the same.

In general, the polymer lithium secondary battery is composed of a positive electrode, a polymer electrolyte, and a negative electrode. These components are selected to meet the various requirements of the secondary battery, such as battery life, charge and discharge capacity, temperature characteristics, stability.

The anodes used in the conventional secondary batteries include lithium composite oxides (LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ ) which form a layered structure that can be intercalated / deintercalated of lithium (Li) ions, and recently, conductive polymers and disulfides. Polymer anodes using (disulfide) compounds are in the spotlight.

As a negative electrode used in a lithium secondary battery, carbon-based materials such as graphite or coke, such as mesocarbon microbead (MCMB), mesophase carbon fiber (MPCF), or Lithium metal is commonly used.

Among them, polymer electrolytes require excellent ionic conductivity, thermal and electrochemical stability, excellent mechanical strength and adhesion to electrodes, and there is no problem of leakage of electrolyte solution. Component.

The electrolyte is composed of an organic solvent, a lithium salt, and a polymer separator.

The organic solvents generally used in the polymer electrolytes currently used or developed include liquid main organic solvents such as ethylene carbonate and propylene carbonate, and liquid crude organic solvents such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

In addition, lithium hexafluorophosphate (LiPF ₆ ), lithium hexafluorophosphate (LiAsF ₆ ), and the like are used as lithium salts, and polyvinylidene difluoride may be used as an electrolyte that can accommodate such lithium salts. PVdF) series, polyacrylonitrile (PAN) series, polyethylene oxide series or copolymers or mixtures thereof are used, and porous polyethylene and polypropylene separators are mainly used.

However, although the carbon anodes used in the prior art show better stability than lithium metal, the capacity is very low compared to lithium metal, and thus there is a limitation in manufacturing a high density lithium secondary battery.

On the other hand, lithium metal also has a problem in that the activity of the lithium is reduced due to the reaction with the organic electrolyte and the polymer and short circuit due to the generation of dendrites.

Accordingly, a method of manufacturing a polymer electrolyte having a multilayer structure is disclosed in US Pat. No. 5,853,916.

However, the polymer electrolyte has a problem in that interfacial adhesion between the polymer electrolyte, the positive electrode and the negative electrode is deteriorated because the polymer electrolyte having a multilayer structure is composed of a non-gelling layer and a gelling layer, respectively.

In addition, US Pat. Nos. 5,716,421 and 5,834,135 disclose a method for preparing a polymer electrolyte having a multilayer structure of a porous separator and a gel polymer electrolyte, but the polymer electrolyte also has an interface between the polymer electrolyte and the positive electrode and the negative electrode as described above. There is a problem that the adhesion and the adhesion between each polymer electrolyte is lowered.

Therefore, there is an urgent need to develop a polymer electrolyte that has excellent stability with lithium metal and exhibits mechanical strength that is sufficient to prevent a short circuit due to generation of dendrites.

Accordingly, an object of the present invention is to provide a polymer electrolyte having excellent ion conductivity, mechanical strength, and stability with lithium metal, a method for preparing the same, and a lithium secondary battery using the same.

1 is a schematic view for explaining the structure of a lithium secondary battery according to the present invention.

2 shows charge and discharge characteristics of a lithium secondary battery constructed using a polymer electrolyte prepared according to Example 1 of the present invention.

3 shows cycle characteristics at a 0.2C rate of a lithium secondary battery constructed using a polymer electrolyte prepared according to Example 1 of the present invention.

Figure 4 shows the results of examining the voltage shape during the charge and discharge of the conventional lithium secondary battery.

<Explanation of symbols for main parts of the drawings>

2: anode 4: first electrolyte layer

6: cathode 8: second electrolyte layer

In order to achieve the above object of the present invention, the present invention provides a polymer electrolyte comprising a first electrolyte layer excellent in mechanical strength and ionic conductivity and a second electrolyte layer excellent in interfacial stability with lithium metal.

The first electrolyte layer is polyacrylonitrile, polymethyl methacrylate, polyvinyl chloride, polyvinylidene fluoride, polyester, polyamide, polyethylene, polypropylene-based polymers, mixtures thereof and copolymers thereof Any one selected from the polymer and the electrolyte solution in which the lithium salt is dissolved are formed by mixing in a ratio of 1: 2 to 10, wherein the second electrolyte layer is polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride , Polyethylene oxide, a polypropylene oxide-based polymer, a mixture thereof, and a copolymer selected from any one of polymers and a lithium salt-dissolved electrolyte are formed by mixing at a ratio of 1: 2 to 10.

The polyvinylidene fluoride polymer exhibits excellent mechanical strength while containing a large amount of electrolyte and lithium salt, and the polyacrylate polymer has good affinity with the electrolyte, and thus has good adhesion with the electrode and the electrolyte. Indicates. In addition, the polyacrylate-based polymer exhibits a property of uniformly mixing with polyvinylidene fluoride and is effective in improving adhesion between the electrolyte and the electrode without inhibiting the excellent mechanical properties of the polyvinylidene fluoride-based polymer.

In addition, an electrolyte formed using polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, polyethylene oxide, and polypropylene oxide-based polymer has excellent stability with lithium metal using a negative electrode.

Thus, by preparing an electrolyte having a multi-layered structure having each characteristic using the above materials, it is possible to obtain a polymer electrolyte that can satisfy the stability, high ionic conductivity, electrochemical stability and excellent mechanical properties with lithium metal at the same time, By manufacturing a lithium secondary battery using such a polymer electrolyte, a lithium secondary battery having stable charge and discharge characteristics and a high capacity can be obtained.

Hereinafter, the present invention will be described in detail.

The polymer electrolyte of the present invention includes a first electrolyte layer and a second electrolyte layer.

The first electrolyte layer is bonded to the positive electrode, and the second electrolyte layer is attached to the negative electrode.

Since the first electrolyte layer contains a large amount of electrolyte solution and lithium salt and maintains excellent mechanical strength, the first electrolyte layer prevents short circuit caused by dendrites grown at the interface between the second electrolyte layer and the lithium metal, and has excellent ion conductivity. By the reduction of the cell resistance by the excellent mechanical strength is given to the process ease.

In addition, the second electrolyte layer serves to suppress the generation of lithium dendrites while minimizing interfacial peeling during the process of adsorbing and desorbing lithium ions onto the lithium metal cathode while being in contact with the lithium metal.

As the polymer used in the first electrolyte layer, polyacrylonitrile, polymethyl methacrylate, polyvinyl chloride, polyvinylidene fluoride, polyester, polyamide, polyethylene, polypropylene-based polymer, these A mixture, a copolymer thereof, and the like are used. An electrolyte solution in which lithium salt is dissolved in the above-described polymer is added at a ratio of 2 to 10 times the weight of the polymer, and heated to a temperature of about 20 to 200 ° C. to prepare a uniform solution. Thereafter, the film is formed using a doctor blade method to produce the first electrolyte layer.

The electrolyte may be ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), gamma-caprolactone (γ-BL), or a mixture thereof. It is preferably used, and the ratio of the polymer mixture and the electrolyte is preferably about 1: 2 to 10.

Examples of the lithium salts include lithium perchlorate (LiCl0 ₄ ), lithium trifluoromethane sulfonate (LiCF ₃ SO ₃ ), boron lithium fluoride (LiBF ₄ ), and lithium hexafluorophosphate (LiPF ₆ ) each having a concentration of 0.2 to ₄ M. ), Lithium salts such as lithium hexafluoride arsenate (LiAsF ₆ ), or mixtures thereof.

In addition, the first electrolyte layer is a mixture of tetrahydrofuran (THF) and acetone to the mixture of the polymer, the lithium salt, and the electrolyte at a ratio of 1.5 to 3 times the weight of the electrolyte, and at 120 ° C. It can also manufacture by heating in the range and coating by a doctor blade method.

In this case, the polyacrylonitrile, polyvinylidene fluoride, and the like may be used as both the first electrolyte layer and the second electrolyte layer, but in this case, its properties vary depending on the components of the electrolyte solution.

That is, when polyacrylonitrile or polyvinylidene fluoride is used as the polymer component of the first electrolyte layer, propylene carbonate or gamma-caprolactone is used as the electrolyte to improve mechanical strength and ionic conductivity. It is preferable.

In addition, polymethyl methacrylate, polyethylene oxide or polypropylene oxide of less than 20% of the total polymer content of the first electrolyte layer is added to the first electrolyte layer for uniform interfacial adhesion with the second electrolyte layer. You may.

As the polymer used in the second electrolyte layer, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, polyethylene oxide, polypropylene oxide-based polymers, mixtures thereof and copolymers thereof may be used. After adding the electrolyte solution in which the lithium salt is dissolved in the above-mentioned polymer at a ratio of 2 to 10 times the weight of the polymer, and heating it to a temperature of about 20 to 200 ° C. to prepare a uniform solution, a film was formed using a doctor blade method. To prepare the second electrolyte layer.

In this case, the electrolyte solution and the lithium salt used are the same as the electrolyte solution and lithium salt used in the above-mentioned first electrolyte layer, and tetrahydrofuran (THF) and acetone as described in the method for producing the above-mentioned first electrolyte layer. Cosolvents, such as these, may be added at a ratio of 1.5 to 3 times the weight of the electrolyte solution, and heated at room temperature within a range of 120 ° C. to coat the same by a doctor blade method.

In addition, when polyacrylonitrile is used as the polymer component of the second electrolyte layer, ethylene carbonate is preferably used as the electrolyte solution in order to improve interfacial stability with lithium metal. More preferably, dimethyl carbonate or methylethyl carbonate is further added to the electrolyte solution.

At this time, the content of the ethylene carbonate used is preferably contained about 30 to 80% by weight based on the total amount of the electrolyte in order to maintain mechanical strength, the content of dimethyl carbonate or methylethyl carbonate is 20 to 70% by weight It is about.

At this time, when the content of the ethylene carbonate is 40% by weight or less, about 20 to 40% by weight of propylene carbonate or gamma-caprolactone is added based on the total amount of the electrolyte in order to improve mechanical strength and low temperature charge and discharge capacity. In this case, it is advantageous to improve the mechanical strength and to improve the low-temperature charge and discharge capacity.

In addition, in the case of using polymethyl methacrylate as the polymer component of the second electrolyte layer, ethylene carbonate, propylene carbonate, gamma-caprolactone, and the like are used as electrolyte to impart excellent adhesion to the second electrolyte layer. It is desirable to.

In order to improve the performance of the first electrolyte layer and the second electrolyte layer, about 2 to 50% of silicon oxide (SiO ₂ ), zeolite and aluminum oxide (Al ₂ O ₃ ) with respect to each polymer mixture. It is also possible to add.

As described above, after the first electrolyte layer and the second electrolyte layer are formed, the polymer electrolyte is prepared by adhering the second electrolyte layer on the first electrolyte layer.

As such, a method of manufacturing the polymer electrolyte by coating a second electrolyte layer on the first electrolyte layer may be used.

That is, in the method of coating and forming the second electrolyte layer on the first electrolyte layer, the first electrolyte layer is first formed by the aforementioned method, and polyacrylonitrile, polymethyl methacrylate, and polyvinylidene fluoride are formed. , At least one polymer selected from polyethylene oxide, polypropylene oxide-based polymers, mixtures thereof, copolymers thereof, and the like, in which an electrolyte solution in which lithium salt is dissolved is added at a ratio of 2 to 10 times the weight of the polymer. ℃)), the mixed solution was heated at about 80 ℃ for one hour, and then heated at about 120 ℃ for 20 minutes to prepare a homogeneous second electrolyte solution, the solution on the first electrolyte layer Direct coating

The coating method includes a method of forming a second electrolyte layer on the first electrolyte layer by using a doctor blade method, and a second electrolyte layer formed on both surfaces by dip coating the first electrolyte layer on a second electrolyte solution. A method of obtaining a polymer electrolyte can be used.

Table 1 shows the ionic conductivity at room temperature for the polymer electrolyte according to the present invention.

Furtherance thickness Ion conductivity First electrolyte layer Polyacrylonitrile (1 g) 1 M LiPF ₆ EC / PC (2/1) solution (7 g) 100 μm 3.6 × 10 ^-3 S / cm Second electrolyte layer Polymethylmethacrylate (1 g) 1 M LiPF ₆ EC / PC (2/1) solution (4 g) 50 μm 3.6 × 10 ^-3 S / cm

As described above, the polymer electrolyte composed of the first electrolyte layer and the second electrolyte layer exhibited excellent ion conducting properties, and the polymer electrolyte of the first electrolyte layer did not break even when the polymer electrolyte was drawn twice by the excellent mechanical strength. Mechanical strength is shown.

A method of manufacturing a lithium secondary battery using the polymer electrolyte prepared as described above is as follows.

1 is a schematic view for explaining the structure of a lithium secondary battery according to the present invention.

Referring to FIG. 1, the positive electrode 2 formed by mixing an active material, a conductive agent, a binder, and a solvent is attached to one side of the first electrolyte layer 4, and the lithium metal negative electrode 6 is attached to the second electrolyte layer 8. Attach to one side of).

Subsequently, a tab is attached to a surface of the positive electrode 2 and the negative electrode 4 on which a polymer electrolyte composed of the first electrolyte layer 4 and the second electrolyte layer 8 is not formed, and the resulting product is attached. After loading in a case, a predetermined amount of liquid electrolyte is injected into the case to manufacture a lithium secondary battery.

Although the resin composition of this invention is demonstrated concretely as an Example below, the scope of the present invention is not restrict | limited by these Examples.

Example 1

After mixing 1 g of polyacrylonitrile and 7 g of a mixed solution of ethylene carbonate (EC) / propylene carbonate (PC) (weight ratio 2: 1) in which 1 M of lithium hexafluorophosphate (LiPF ₆ ) was dissolved, the mixture was mixed at room temperature. Heated at 80 ° C. for one hour and heated at about 120 ° C. for 20 minutes to prepare a first electrolyte solution. This was formed into a film with a thickness of 100 μm using a doctor blade method to prepare a first electrolyte layer.

After mixing 1 g of polymethyl methacrylate and 7 g of a mixed solution of ethylene carbonate (EC) / propylene carbonate (PC) (weight ratio 2: 1) in which 1 M of lithium hexafluorophosphate (LiPF ₆ ) was dissolved, the mixture was mixed at room temperature. A second electrolyte solution was prepared by heating at 80 ° C. for one hour and heating at about 120 ° C. for 15 minutes. This was directly coated on the first electrolyte layer with a thickness of 50 μm to prepare a polymer electrolyte in which the first electrolyte layer and the second electrolyte layer were sequentially stacked.

Example 2

The first electrolyte layer was prepared in the same manner as in Example 1, the second electrolyte solution was prepared in the same manner as in Example 2, and the second electrolyte solution was formed into a film by using a doctor blade method. 2 prepared an electrolyte layer, and then a polymer electrolyte was prepared by adhering the first electrolyte layer and the second electrolyte layer.

Example 3

A mixed solution of ethylene carbonate (EC) / dimethyl carbonate (DMC) (weight ratio 1: 1) in which 1 M lithium hexafluorophosphate (LiPF ₆ ) is dissolved in a mixture of 0.7 g of polyvinyl chloride and 0.3 g of polymethylmethacrylate. After mixing 5 g and 5 g of THF at room temperature, a first electrolyte layer was prepared in the same manner as in Example 1 above.

Ethylene carbonate (EC) / dimethyl carbonate (DMC) (1: 1 weight ratio) in which 1 M of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixture of 0.3 g of polyvinylidene fluoride and 0.7 g of polyacrylonitrile. After mixing 5 g of the mixed solution at room temperature, the mixture was mixed at 120 ° C. for 30 minutes to obtain a second electrolyte solution having a uniform and high viscosity.

Subsequently, the second electrolyte solution was directly coated on the first electrolyte layer using a doctor blade method to prepare a polymer electrolyte in which the first electrolyte layer and the second electrolyte layer were sequentially stacked.

Example 4

Ethylene carbonate (EC) / dimethyl carbonate (DMC) / in which 1 M of lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixture of 0.3 g of polyvinylidene fluoride 761 (manufactured by Atochem) and 0.7 g of polyacrylonitrile. 7 g of a mixed solution of propylene carbonate (PC) (weight ratio 2: 0.5 / 0.5) was mixed at room temperature, heated to a temperature of 120 ° C. to prepare a homogeneous first electrolyte solution, and the same as in Example 1 described above. The first electrolyte layer was prepared by the method.

A second electrolyte solution was prepared by mixing 3 g of polymethylmethacrylate and 18 g of a mixed solution of ethylene carbonate (EC) / dimethyl carbonate (DMC) (weight ratio 1: 1) in which 1 M of lithium hexafluorophosphate (LiPF ₆ ) was dissolved. After the formation, the first electrolyte layer was dip coated on the second electrolyte solution to prepare a polymer electrolyte coated with a second electrolyte layer on both surfaces of the first electrolyte layer.

Comparative example

According to the conventional method, 4 g of a mixed solution of ethylene carbonate (EC) / propylene carbonate (PC) (weight ratio 2: 1) in which 1 g of polymethyl methacrylate and 1 M of lithium hexafluorophosphate (LiPF ₆ ) are dissolved is added at room temperature. After mixing, the mixture was heated at 80 ° C. for one hour and heated at 120 ° C. for 15 minutes to prepare an electrolyte solution. Subsequently, the electrolyte solution was formed into a film having a thickness of 200 μm using the doctor blade method to prepare an electrolyte.

Performance evaluation

A lithium cobalt (LiCoO ₂ ) positive electrode was attached to the first electrolyte layer of the polymer electrolyte prepared according to Example 1, and a lithium metal negative electrode was attached to the second electrolyte layer at a rate of 0.2%. The results of the investigation of the electrode capacity and cycle life based on the anode are shown in FIGS. 2 and 3.

2 shows charge and discharge characteristics of a lithium secondary battery constructed using a polymer electrolyte prepared according to Example 1 of the present invention.

As shown in Figure 2, it can be seen that when charging and discharging at a 0.2C rate shows a normal charge and discharge characteristics similar to a typical lithium secondary battery.

3 shows cycle characteristics at a 0.2C rate of a lithium secondary battery constructed using a polymer electrolyte prepared according to Example 1 of the present invention.

As shown in Figure 3, it can be seen that a constant discharge capacity.

In addition, a voltage during charge and discharge using a battery prepared by adhering a lithium cobalt (LiCoO ₂ ) positive electrode to one side of the polymer electrolyte prepared according to the comparative example, and by attaching a lithium metal negative electrode to the other side of the polymer electrolyte The result of examining the shape is shown in FIG.

As shown in FIG. 4, it can be seen that the cell voltage decreases as the cycle progresses during constant current charge / discharge.

As described above, according to the present invention, the polymer electrolyte is formed by forming a polymer electrolyte including a second electrolyte layer having excellent mechanical stability and ionic conductivity and a second electrolyte layer having excellent interfacial stability between lithium metal. Since the mechanical stability and the interfacial stability can be improved simultaneously, stable charge and discharge characteristics of the lithium secondary battery using the lithium metal and the carbon negative electrode can be obtained, and a lithium secondary battery having a high capacity can be easily manufactured.

In addition to the lithium secondary battery, the polymer electrolyte may be variously applied as an electrolyte of a capacitor and an electrolyte of a sensor.

Claims (20)

A polymer electrolyte comprising a first electrolyte layer having excellent mechanical strength and ion conductivity and a second electrolyte layer having excellent interfacial stability with lithium metal. The method of claim 1, wherein the first electrolyte layer is polyacrylonitrile, polymethyl methacrylate, polyvinyl chloride, polyvinylidene fluoride, polyester, polyamide, polyethylene, polypropylene-based polymer, these A polymer electrolyte formed by mixing any one polymer selected from a mixture and a copolymer thereof and an electrolyte solution in which lithium salt is dissolved in a ratio of 1: 2 to 10. The method of claim 1, wherein the second electrolyte layer is selected from polyacrylonitrile, polymethylmethacrylate, polyvinylidene fluoride, polyethylene oxide, polypropylene oxide-based polymers, mixtures thereof, and copolymers thereof. A polymer electrolyte, wherein any one of the polymer and the electrolyte in which the lithium salt is dissolved are mixed at a ratio of 1: 2 to 10. The method of claim 2 or 3, wherein the lithium salt is lithium perchlorate (LiCl0 ₄ ), trifluoro methane sulfonate (LiCF ₃ SO ₃ ), boron lithium fluoride (LiBF ₄ ), the concentration of 0.2 to 4M, At least one lithium salt selected from the group consisting of lithium hexafluorophosphate (LiPF ₆ ) and lithium hexafluorophosphate (LiAsF ₆ ). The method of claim 2 or 3, wherein the electrolyte is ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and gamma-caprolactone ( polymer electrolyte, characterized in that at least one solvent selected from the group consisting of γ-BL). The method of claim 2, wherein when the first electrolyte layer comprises a polymer made of polyacrylonitrile or polyvinylidene fluoride, the electrolyte is selected from propylene carbonate and gamma-caprolactone (γ-BL). A polymer electrolyte characterized by the above-mentioned. The method of claim 2, wherein the first electrolyte layer further comprises 1 to 20% by weight of at least one polymer selected from the group consisting of polymethyl methacrylate, polyethylene oxide and polypropylene oxide based on the total amount of the polymer. Polymer electrolyte. The method of claim 3, wherein when the second electrolyte layer contains a polymer made of polyacrylonitrile, the electrolyte solution is composed of 40 to 80% by weight of ethylene carbonate and 20 to 60% by weight of dimethyl carbonate or methylethyl carbonate. Polymer electrolyte. The solvent mixture of claim 3, wherein the electrolyte comprises 30 to 40 wt% of ethylene carbonate, 60 to 70 wt% of dimethyl carbonate or methylethyl carbonate when the second electrolyte layer contains a polymer made of polyacrylonitrile. The polymer electrolyte further comprises 20 to 40% by weight of propylene carbonate or gamma-caprolactone (γ-BL) based on the total amount of the solvent mixture. The method of claim 3, wherein when the second electrolyte layer uses a polymer made of polymethyl methacrylate, the electrolyte includes at least one solvent selected from the group consisting of ethylene carbonate, propylene carbonate, and γ-caprolactone. A polymer electrolyte, characterized in that. Forming a first electrolyte layer having excellent mechanical strength and ion conductivity; And Forming a second electrolyte layer having excellent interfacial stability with lithium metal on the first electrolyte layer. The method of claim 11, wherein the forming of the first electrolyte layer is performed. Iii) any one selected from polyacrylonitrile, polymethylmethacrylate, polyvinylchloride, polyvinylidene fluoride, polyester, polyamide, polyethylene, polypropylene-based polymers, mixtures thereof and copolymers thereof Mixing the polymer and the electrolyte solution in which the lithium salt is dissolved in a ratio of 1: 2 to 10, Ii) heating the mixed solution, and Iii) forming the polymer solution by using a doctor blade method. The method of claim 11, wherein the forming of the second electrolyte layer is performed. a) a polymer in which any one polymer selected from polyacrylonitrile, polymethylmethacrylate, polyvinylidene fluoride, polyethylene oxide, polypropylene oxide-based polymers, mixtures thereof and copolymers thereof is dissolved Mixing the electrolyte in a ratio of 1: 2 to 10, and iii) a method of producing a polymer electrolyte comprising heating the mixed solution. The method according to claim 12 or 13, wherein the steps ii) and b) are performed by heating the respective mixed solutions at a temperature of 20 to 200 ° C. The method of claim 12 or 13, wherein the step (iii) and a) is a step of mixing any solvent selected from tetrahydrofuran (THF) and acetone in a ratio of 1.5 to 3 times based on the electrolyte solution Method for producing a polymer electrolyte, characterized in that it further comprises. The method of claim 15, wherein steps ii) and b) are performed by heating the respective mixed solutions at a temperature of 25 to 120 ° C. The method of claim 13, wherein the step (iii) comprises forming a second electrolyte layer by forming the heated mixed solution using a doctor blade method and adhering the second electrolyte layer on the first electrolyte layer. Method for producing a polymer electrolyte, characterized in that it further comprises. The method of claim 13, wherein the step iii) further comprises coating the heated solution on the first electrolyte layer to form the second electrolyte layer. The method of claim 13, wherein the step iii) further comprises the step of forming the second electrolyte layer on the entire surface of the first electrolyte layer by impregnating the first electrolyte layer in the heated solution for a predetermined time. A method for producing a polymer electrolyte. Lithium secondary battery comprising a polymer electrolyte according to claim 1.