KR100424256B1 - Process for preparing an polymer electolyte by electrochemical polymerization and lithium battery employing such process - Google Patents

Abstract

The present invention relates to a method for producing a polymer electrolyte and a lithium battery employing the same, and more particularly, to a method for producing a polymer electrolyte by an electrochemical polymerization method and a lithium battery obtained using the method.

The present invention provides a method for producing a lithium battery comprising the step of polymerizing a monomer, a prepolymer or a mixture thereof in an battery by an electrochemical method to produce a polymer electrolyte.

According to the present invention, the process of the conventional ion battery can be used as it is by electrochemically polymerizing a monomer, a prepolymer or a mixture thereof in a battery by applying a constant current without a heating process, which is a problem of the thermal curing method used in the conventional method. That has the advantage. Using such a manufacturing method, it is possible to manufacture a lithium battery more efficiently and economically.

Description

Process for preparing an polymer electolyte by electrochemical polymerization and lithium battery employing such process}

The present invention relates to a method for preparing a polymer electrolyte and a lithium battery employing the same, and more particularly, to a method for manufacturing a lithium battery by an electrochemical polymerization method and a lithium battery employing the same.

Recently, with the rapid development of the electric, electronic, communication and computer industries, the demand for high performance and high safety secondary batteries is gradually increasing. In particular, as the miniaturization, thinning and lightening of electronic devices are rapidly spreading, The demand for miniaturization and thinning of secondary batteries as components is increasing day by day. In order to meet these demands, a lithium ion polymer battery has been most interested in recent years.

Lithium ion polymer battery is a next generation advanced battery that can control size and shape as desired, high energy density per unit weight, and high voltage and large capacity by lamination.

However, the reason why the lithium ion polymer electrons have not been commercialized yet is that the manufacturing cost is too high compared to the lithium ion battery, which is a conventional lithium battery, and a polymer electrolyte material applicable to the lithium polymer battery has not been developed.

The manufacturing process of the lithium ion polymer battery developed to date has been prepared by laminating a cathode, a polymer electrolyte, and an anode, or by manufacturing a battery assembly by directly coating and laminating a polymer electrolyte on the cathode or the anode, After extracting the contained plasticizer to form pores, it comprises a step of injecting an organic solvent containing a lithium salt (that is, electrolyte). However, all the processes of the manufacturing process has a problem that the manufacturing cost of the lithium ion polymer battery is high because it must be carried out in dry conditions.

In order to solve this problem, a recently developed process is to prepare a gel polymer electrolyte by injecting an electrolyte solution containing a monomer or a prepolymer into a lithium salt and an organic solvent, instead of using a conventional lithium ion battery manufacturing process. Process comprising the steps. For example, US Pat. No. 4,908,283 discloses a polymer electrolyte made by curing a composition composed of acryloyl-denatured polyalkylene oxide, and US Pat. No. 4,792,504 discloses polyethylene glycol dimethacrylate. A polymer electrolyte composed of polyethylene oxide is described.

However, such a method of applying heat for the polymerization in the battery has to add a heating process to the existing manufacturing method of the lithium ion battery in order to manufacture a lithium polymer battery, which increases the manufacturing cost, which is a problem that the economic efficiency is lowered It has

The technical problem to be achieved by the present invention is to provide a method for producing a polymer electrolyte through the electrochemical polymerization method in the battery without an additional heating process to solve the above problems.

Another object of the present invention is to provide a lithium battery employing the polymer electrolyte obtained by the above production method.

1 is a graph showing standard charge and discharge characteristics of a lithium battery according to the present invention and the prior art.

Figure 2 is a graph showing the discharge characteristics according to the rate of the lithium battery according to the present invention and the prior art.

3 is a graph showing low-temperature discharge characteristics of a lithium battery according to the present invention and the prior art.

4 is a graph showing the life characteristics of the lithium battery according to the present invention and the prior art.

In order to achieve the first technical problem, in the present invention, a method for producing a polymer electrolyte comprising the step of preparing a polymer electrolyte by polymerizing the composition for forming a polymer electrolyte comprising a monomer, a prepolymer or a mixture thereof in the battery by an electrochemical method to provide.

The electrochemical method used in the manufacturing method is characterized in that performed by applying a current of 1 to 1000mA.

The current used in the manufacturing method is preferably added for 0.5 to 48 hours, and if the current application time is less than 0.5 hours, there is a problem that the electrochemical polymerization does not occur, and if it exceeds 48 hours, the composition may be decomposed. It is not desirable because there is a problem that there is.

The monomer or prepolymer used in the production method is not particularly limited as long as it has a double bond and forms a radical.

In order to solve the second technical problem, the present invention provides a lithium battery manufactured by employing a polymer electrolyte obtained through the polymerization method in the electrochemical battery.

More specifically, the manufacturing method of the lithium battery of the present invention,

(A) receiving an electrode structure consisting of an anode / separator / cathode in a battery case;

(B) an electrolyte containing a lithium salt and an organic solvent; Injecting a composition for forming a polymer electrolyte comprising a monomer, a prepolymer, or a mixture thereof into a battery case obtained in step (A);

(C) polymerizing the polymer electrolyte forming composition in a battery by an electrochemical method.

In step (C) of the manufacturing method, the electrochemical method for polymerizing the composition for forming a polymer electrolyte is carried out by applying a current of 1 to 1000mA, there is a problem that electrochemical polymerization is difficult when the amount of current is less than 1mA. If the amount of current exceeds 1000 mA, there is a problem that the composition is likely to decompose.

The monomer or prepolymer, which is a material for forming a polymer matrix in the polymer electrolyte formation composition, is not particularly limited as long as it has a double bond and forms a radical. For example, as a monomer, a vinyl acetate monomer, a (meth) acrylate monomer, or a sty It is preferably at least one selected from the group consisting of ene and acrylonitrile, and is selected from the group consisting of polyethylene glycol di (meth) acrylate, polyethylene glycol divinyl ether, pentaerythritol tetraacrylate and pentaerythritol triacrylate as prepolymers. It is preferably one or more selected.

It is preferable that the mixed weight ratio of the monomer, the prepolymer or a mixture thereof and the electrolyte as the material for forming the polymer matrix is 1: 0.1 to 1:50. If the material for forming the polymer matrix exceeds the above range with respect to the content of the electrolyte, the ion conductivity decreases due to the increase in the fluidity of the polymer electrolyte, and if it is below the above range, the electrochemical polymerization of the monomer or the prepolymer is not easy, which is not preferable. .

In addition, the weight average molecular weight of the prepolymer usable in the present invention is preferably 100 to 10,000. If the weight average molecular weight is out of the above range, the polymerization is not easy, which is not preferable.

In the present invention, the composition for forming a polymer electrolyte may further include a curing initiator and a curing catalyst. At this time, the curing initiator is at least one selected from the group consisting of benzoyl peroxide, acetyl peroxide, azobisisobutyronitrile, the content of which is preferably 0.0001 to 10 parts by weight based on 100 parts by weight of the monomer, prepolymer or a mixture thereof. . In addition, the curing catalyst is used as a material for improving the curing rate, at least one selected from amines such as triethylamine, tributylamine, triethanolamine and N-benzyldimethylamine, the content of which is monomers, prepolymers or mixtures thereof It is preferable that it is 0.1-10 weight part with respect to 100 weight part of.

In the composition for forming a polymer electrolyte, any organic solvent constituting the electrolyte may be used as long as it is commonly used in the production of a lithium battery. Specific examples thereof include propylene carbonate, ethylene carbonate, dimethyl carbonate, methylethyl carbonate, diethyl carbonate, tetrahydrofuran, 2-methylhydrofuran, diethoxyethane, methyl formate, ethyl formate and gamma butyrotactone. Use one or more selected from the group. The content of the organic solvent is 10 to 5,000 parts by weight based on 100 parts by weight of the monomer, prepolymer or a mixture thereof. "

In addition, the lithium salts constituting the electrolyte include lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium trifluoride methanesulfonate (LiCF ₃ SO ₃ ), and lithium bistrifluoro One or more selected from the group consisting of methanesulfonylamide (LiN (CF ₃ SO ₂ ) ₂ ) is used. And the content of the lithium salt is 0.1 to 10 parts by weight based on 100 parts by weight of the electrolyte.

The mixed solution of step (B) of the manufacturing method may further add various additives such as adhesion improving agent, filler, etc. to improve the mechanical strength of the polymer electrolyte and the interface performance with the electrode.

The cathode and the anode used in the present invention may be prepared according to a conventional method used in the manufacture of a lithium battery, wherein the cathode active material is a lithium metal composite oxide, transition metal compound, sulfur compound, etc., the anode active material As the furnace, lithium metal, carbon material, graphite material and the like are used.

The separator used in the present invention is not particularly limited as long as it is commonly used in the manufacture of lithium batteries, and among these, it is preferable to use a separator composed of polyethylene or polypropylene having a network structure, or a combination thereof.

Lithium battery manufacturing method using the electrochemical in-cell polymerization method as described above can be used as a conventional ion cell process by applying a constant current to the polymerization without the addition of a heating step, which is a problem with the thermosetting method used in the conventional method. Has the advantage that it can.

In addition, in using the electrochemical polymerization method of the present invention, a method for accommodating the electrode structure obtained by electropolymerization after coating and drying the composition for forming a polymer electrolyte on the separator in the step before storing the electrode structure in the battery case. It is also possible.

The lithium battery of the present invention is not particularly limited in type and configuration, and can be used in any of forms such as a lithium primary battery and a lithium secondary battery.

Hereinafter, the present invention will be described in detail with reference to the following examples, but the present invention is not limited to the following examples.

Example 1

94 parts by weight of LiCoO ₂ , 3 parts by weight of Super-P (MMM Carbon Co.) and 3 parts by weight of polyvinylidene fluoride (PVDF) were dissolved in 67 parts by weight of N-methyl-2-pyrrolidone to prepare a cathode active material slurry. It was. The cathode active material slurry was applied to an Al-foil having a width of 4.9 cm and a thickness of 147 μm, dried, rolled, and cut to a predetermined dimension to prepare a cathode.

An anode active material slurry was prepared by dissolving 89.8 parts by weight of mesocarbon fiber (MCF: Petoca Co., Ltd.), 0.2 parts by weight of oxalic acid, and 10 parts by weight of PVDF in N-methyl-2-pyrrolidone. The anode active material slurry was applied on a copper foil having a width of 5.1 cm and a thickness of 178 μm, and then dried, rolled, and cut into predetermined dimensions to produce an anode.

An electrode structure was formed between the cathode and the anode through a polyethylene separator, and the electrode structure was wound and then placed in a battery case.

9.08 parts by weight of polyethylene glycol dimethacrylate, 0.05 part by weight of azobisisobutyronitrile as a polymerization initiator, 0.01 part by weight of triethylamine as a curing catalyst, and 1.3 M LiPF ₆ ethylene carbonate: diethyl carbonate (3: 7 parts by weight) A mixed solution containing 90.86 parts by weight of a solution was injected into the battery case under reduced pressure. Next, after vacuum sealing, the mixed solution was aged at room temperature for 16 hours to uniformly distribute into the battery case. Next, a 100 mA current was applied for 5 hours to electrically polymerize polyethylene glycol dimethacrylate to obtain a lithium battery.

The standard charge / discharge characteristics (FIG. 1), the discharge characteristics for each rate (FIG. 2), the low temperature discharge characteristics (FIG. 3), and the life characteristics (FIG. 4) of the obtained lithium battery were evaluated and described in Table 1 below.

Comparative example

94 parts by weight of LiCoO ₂ , 3 parts by weight of Super-P and 3 parts by weight of polyvinylidene fluoride (PVDF) were dissolved in 67 parts by weight of N-methyl-2-pyrrolidone to prepare a cathode active material slurry. The cathode active material slurry was applied to an Al-foil having a width of 4.9 cm and a thickness of 147 μm, dried, rolled, and cut to a predetermined dimension to prepare a cathode.

An anode active material slurry was prepared by dissolving 89.8 parts by weight of mesocarbon fiber (MCF: Petoca Co., Ltd.), 0.2 parts by weight of oxalic acid, and 10 parts by weight of PVDF in N-methyl-2-pyrrolidone. The anode active material slurry was applied on a copper foil having a width of 5.1 cm and a thickness of 178 μm, and then dried, rolled, and cut into predetermined dimensions to produce an anode.

An electrode structure was formed between the cathode and the anode through a polyethylene separator, and the electrode structure was wound and then placed in a battery case.

9.08 parts by weight of polyethylene glycol dimethacrylate, 0.05 part by weight of azobisisobutyronitrile as a polymerization initiator, 0.01 part by weight of triethylamine as a curing catalyst, and 1.3 M LiPF ₆ ethylene carbonate: diethyl carbonate (3: 7 parts by weight) A mixed solution containing 90.86 parts by weight of a solution was injected into the battery case under reduced pressure. Next, after vacuum sealing, the mixed solution was aged at room temperature for 16 hours to uniformly distribute into the battery case. Next, the lithium battery was obtained by heat-polymerizing at 80 degreeC and superposing | polymerizing polyethyleneglycol dimethacrylate.

The standard charge / discharge characteristics (FIG. 1), the discharge characteristics for each rate (FIG. 2), the low temperature discharge characteristics (FIG. 3), and the life characteristics (FIG. 4) of the obtained lithium battery were evaluated and described in Table 1 below.

In order to evaluate the standard charging and discharging characteristics, charging was performed using a constant current / constant voltage (CC / CV) method of charging with a constant current of 0.5 C and then applying a constant voltage of 4.2 V. The discharge was made with a constant current of 0.2 C. A constant current (CC) method of discharging was used, and 2.75 V was used as a discharge cut off condition.

In addition, in order to evaluate the characteristics of each battery's rate, charging was performed using the same method as the standard charging and discharging method, and discharge characteristics were evaluated using the constant current (CC) method, but different current magnitudes (0.5C, 1C, 2C) were used. Measured at

To evaluate the lifetime characteristics, the charging characteristics were evaluated by applying a constant current of 1C and then applying a constant voltage of 4.2V. The discharge characteristics were obtained by discharging at a constant current of 1C and cutting off at 2.75V. .

Battery Performance Comparison by Polymerization Method Remarks Polymerization Method Standard Charge / Discharge Characteristics (mAh) Rate discharge characteristics (mAh) Low Temperature Discharge Characteristics (mAh) life span charge Discharge efficiency(%) 0.5C 1.0C 2.0C -10 ℃ -20 ℃ 1 time (mAh) 50 times (mAh) 100 times (mAh) Example Electrochemical polymerization 811.1 799.0 98.4 663.9 489.4 295.8 449.9 238.1 649.4 648.5 586.0 Comparative example Thermal polymerization 809.6 800.4 98.9 693.5 485.2 299.0 457.8 255.8 646.7 617.1 591.9

As shown in Table 1 or Figures 1 to 4, the lithium battery according to the polymerization method in the electrochemical battery of the present invention is not required for the heating process compared to the lithium battery obtained by the conventional thermal polymerization method, but various battery characteristics It can be seen that this is similar or rather higher.

According to the present invention, the process of the conventional ion battery can be used as it is by electrochemical polymerization in a battery by applying a constant current without the addition of a heating step, which is a problem with the thermosetting method used in the conventional method. Using this manufacturing method, it is possible to manufacture a lithium battery more efficiently and economically.

Although the present invention has been described with reference to the above embodiments, it is merely illustrative, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. . Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (16)

A method for producing a lithium battery comprising the step of polymerizing polyethylene glycol dimethacrylate in a battery by an electrochemical method. The method of claim 1, wherein the electrochemical method is performed by applying a current of 1 to 1000mA. The method of manufacturing a lithium battery according to claim 2, wherein a current is applied for 0.1 to 48 hours. delete (A) placing an electrode structure consisting of an anode / separator / cathode into a battery case; (B) an electrolyte containing a lithium salt and an organic solvent; Injecting a composition for forming a polymer electrolyte containing polyethylene glycol dimethacrylate into the battery case obtained in step (A); (C) a method of manufacturing a lithium battery, comprising the step of polymerizing the polymer electrolyte forming composition in a battery by an electrochemical method. The method of claim 5, wherein the electrochemical method is performed by applying a current of 1 to 1000 mA. The method of manufacturing a lithium battery according to claim 5, wherein a current is applied for 0.5 to 48 hours. delete The method of manufacturing a lithium battery according to claim 5, wherein a mixed weight ratio of the polyethylene glycol dimethacrylate and the electrolyte is 1: 0.1 to 1:50. The method for manufacturing a lithium battery according to claim 5, wherein the composition for forming a polymer electrolyte further comprises a curing initiator and a curing catalyst. The method of claim 10, wherein the curing initiator is at least one selected from the group consisting of benzoyl peroxide, acetyl peroxide, azobisisobutyronitrile, the content of which is from 0.0001 to 100 parts by weight based on 100 parts by weight of the monomer, prepolymer or a mixture thereof Method for producing a lithium battery, characterized in that 10 parts by weight. The method of claim 10, wherein the curing catalyst is at least one selected from the group consisting of triethylamine, tributylamine, triethanolamine and N-benzyldimethylamine, the content of which is 100 parts by weight of the monomer, prepolymer or a mixture thereof Method for producing a lithium battery, characterized in that 0.1 to 10 parts by weight with respect to. The method for producing a lithium battery according to claim 5, wherein the weight average molecular weight of the polyethylene glycol dimethacrylate is 100 to 10,000. The lithium salt of claim 5, wherein the lithium salt is lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), and lithium bistry. Fluoromethanesulfonylamide (LiN (CF ₃ SO ₂ ) ₂ ) One or more selected from the group consisting of, the content of the lithium battery, characterized in that 0.1 to 10 parts by weight based on 100 parts by weight of the electrolyte. The method of claim 5, wherein the organic solvent is propylene carbonate, ethylene carbonate, dimethyl carbonate, methylethyl carbonate, diethyl carbonate, tetrahydrofuran, 2-methylhydrofuran, diethoxyethane, methyl formate, ethyl formate and gamma At least one selected from the group consisting of butyrotactone, and a content thereof is 10 to 5,000 parts by weight based on the weight of the monomer or prepolymer. The lithium battery obtained by the manufacturing method of any one of Claims 1-15.