KR100547085B1 - Manufacturing method of polymer porous separator and lithium ion polymer battery - Google Patents

Abstract

The present invention relates to a polymer porous separator for a lithium ion polymer battery and a method for manufacturing a lithium ion polymer battery including the same. In the method for preparing a polymer porous separator for a lithium ion polymer battery, lithium salt is included at a temperature of 10 to 40 ° C. Preparing a polymer solution of 1-20% by weight and a porous polyolefin-based membrane which are stable to the prepared electrolyte solution and an organic solvent is added to the polymer compound capable of gelling the electrolyte solution; The method of manufacturing a polymer porous separator comprising coating the polymer solution on the porous polyolefin-based membrane to make a polymer porous separator.

The method for producing a lithium ion polymer battery using the polymer porous separator of the present invention is capable of gelation even at low pressure, and the lithium ion polymer battery prepared by the present invention has excellent high rate characteristics, cycle characteristics, high temperature storage characteristics, and the like.

Description

Manufacturing method of polymer porous separator and lithium ion polymer battery {METHOD OF MAKING POROUS POLYMERIC SEPARATOR AND LITHIUM ION POLYMER BATTERY}

1 (a) is a cross-sectional view of the porous polymer membrane according to the present invention,

1 (b) is a cross-sectional view in which the polymer porous separator, the negative electrode plate, and the positive electrode plate are stacked;

1 (c) is a cross-sectional view of a polymer porous separator, a coated negative electrode plate and a coated positive electrode plate laminated,

2 is a process diagram schematically showing a manufacturing process of a lithium ion polymer battery according to the present invention;

Figure 3 is a SEM photograph of the porous polyolefin-based membrane used in the present invention,

Figure 4 (a) is a SEM photograph of the porous polymer membrane prepared by 3.5% by weight polymer solution,

Figure 4 (b) is a SEM photograph of the porous polymer membrane prepared by 2% by weight polymer solution,

Figure 4 (c) is a SEM photograph of the porous polymer membrane prepared by 5% by weight polymer solution,

5 is a SEM photograph of a porous polymer membrane prepared by adding microsilica as an inorganic material to a polymer solution;

6 is a SEM photograph of a polymer membrane coated on a polymer porous separator using a polymer solution prepared at 50 ° C .;

7 is a graph showing a high rate discharge characteristic for a battery prepared according to Example 5 of the present invention;

8 (a) is a graph showing the cycle characteristics of the battery according to the concentration of the polymer solution,

8 (b) is a graph showing the capacity characteristics of the battery according to the concentration of the polymer solution,

9 is a graph showing the cycle characteristics of the battery with or without the gelation process,

10 is a graph showing the cycle characteristics of the battery with and without the addition of minerals,

11 is a graph showing the cycle characteristics of the battery according to the presence or absence of a polymer coating on the electrode,

12 is a graph showing the cycle characteristics of the battery according to Example 5 and Comparative Examples 4, 5, 6.

The present invention relates to a separator for a lithium ion polymer battery and a method for manufacturing a lithium ion polymer battery including the same, and more specifically, a polymer porous membrane coated with a polymer or a polymer and an inorganic material on a porous polyolefin-based membrane, and cycle characteristics, The present invention relates to a method of manufacturing a lithium ion polymer battery having excellent high rate characteristics and safety.

Recently, with the rapid development of the electric, electronic, communication and computer industries, the demand for high performance and high safety secondary batteries has gradually increased. In particular, according to the trend of miniaturization, light weight, and portability of electric and electronic products, thinning and miniaturization of secondary batteries, which are key components in this field, are required.

Lithium ion batteries are currently used in mobile devices and electronic products, but lithium ion batteries use porous films made of polyethylene (PE) or polypropylene (PP) as separators to manufacture batteries by laminating electrodes and separators in the form of flat plates. Since it is difficult to roll, it is rolled and manufactured in cylindrical and square barrels. The rectangular lithium ion battery manufactured in a roll type is currently commercialized, but the manufacturing process of the battery is difficult, it is restricted by the shape of the battery, and it shows a limitation in thinning and high capacity. In contrast, the lithium polymer battery may solve the above problem. It is expected to be. Lithium polymer battery has two kinds of membrane and electrolyte It is very advantageous in terms of productivity because it can be manufactured by stacking electrodes and solid polymer electrolyte on a flat plate according to the type of electrolyte using a solid polymer electrolyte having a function at the same time, or rolling it in a roll form. Do.

Conventional methods for preparing a solid polymer electrolyte are mainly polyethylene oxide (PEO) -based, but at a room temperature of 10 ^-8 S (Siemens, Siemens) / cm very low conductivity is not suitable for use alone. In order to solve this problem, a gel-type polymer electrolyte was developed to achieve a conductivity of 10 ^-3 S / cm, and a representative gel-type polymer electrolyte is a polyacrylonitrile (Polyacrylonitile, PAN) solid polymer of US Patent No. 5,219,679. It is an electrolyte. However, the electrolyte disclosed in U.S. Patent No. 5,219,679 has a problem in that it is difficult to be used as a battery because of its excellent conductivity and adhesive strength with the electrode while having low mechanical strength.

The hybrid polyvinylidene fluoride (PvdF) polymer compound described in U.S. Patent Nos. 5,296,319 and 5,460,904 to A. S. Gozdz et al. Has been developed to attempt mass production of hybrid lithium polymer batteries. However, this battery system has a difficulty in manufacturing process in which the plasticizer must be extracted later, since the plasticizer is added during the manufacture of the solid polymer electrolyte and the negative and positive electrodes. In addition, the PvdF-based electrolyte has excellent mechanical strength but poor adhesion, which requires a heat thinning process at a high temperature in manufacturing electrodes and batteries, and has a disadvantage in that battery performance is degraded due to peeling between the electrode and the solid polymer electrolyte during the extraction process.

Therefore, it is necessary to configure a battery using a gel electrolyte, but the gel electrolyte itself has a limit in mechanical strength. In order to solve this problem, there is a method of coating a gel electrolyte on an electrode as in Korean Patent No. 2000-7004714, but a method of coating a gel electrolyte on an electrode is difficult to generalize, and the manufacturing process must be performed in a controlled inert atmosphere. Have

In addition, in the methods described in US Pat. Nos. 5,681,357, 5,688,293, and 5,834,135, a solution in which a polymer such as PvdF is dissolved in a solvent or a polymer in which a polymer such as PvdF is dissolved in an organic solvent electrolyte is used in a lithium ion battery Alternatively, there is a method of manufacturing a battery by applying a PE separator and drying the separator and an electrode using a dried separator to integrate the electrode and the separator and injecting an organic solvent electrolyte thereto. Disadvantages of this method include casting a high concentration of polymer solution onto the PP or PE membrane, resulting in deformation of the PP or PE membrane or clogging the pores of the membrane, and inadequate contact due to the integration of the electrode and the membrane in a heat thinning process. There is a disadvantage that the interface resistance is increased. Due to these problems, high rate charge / discharge characteristics are poor and cycle life characteristics are deteriorated.

In order to solve this problem, US Pat. No. 5,853,916 discloses a process of gelling at a constant pressure and temperature after forming a cell by coating a polymer on a polyolefin porous separator. In the battery manufacturing process, when the battery is manufactured in a wound type, a large pressure must be applied at high temperatures up and down, so that the pressure in the horizontal direction becomes relatively low, which may cause problems such as local electrodeposition near the edges. Since the route is limited to the gel electrolyte, the high rate charge and discharge characteristics and cycle characteristics of the battery are deteriorated, which is not currently used in industry.

Accordingly, it is an object of the present invention to provide a method for preparing a gel ion polymer battery capable of gelation at low pressure.

The above object, according to the present invention, in the method for producing a polymer porous separator for lithium ion polymer battery, at a temperature of 10 to 40 ℃, the organic solvent in a polymer compound that is stable to the electrolyte containing lithium salts and gelling in the electrolyte Preparing 1-20% by weight of a polymer solution and a porous polyolefin-based membrane; Coating the polymer solution on the porous polyolefin-based membrane is achieved by a method for producing a polymer porous separator, characterized in that it comprises a step of making a polymer porous separator.

       It is preferable that the polymer coated on the polymer porous separator has a pore of 0.1 to 20 μm.

The polyolefin-based film is preferably any one selected from the group consisting of polyethylene film, polypropylene film, and multilayer film of polyethylene film and polypropylene film.

In the polymer solution preparing step, it is preferable to further add an inorganic substance to the polymer solution.

The inorganic material is preferably at least one selected from the group consisting of SiO ₂ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ , BaTiO ₃ , Bi ₂ O ₃ , Fe ₂ O ₃ , CaSiO ₃ , and PbTiO ₃ .

       The inorganic material is preferably mixed with 0.1 to 15% by weight of the polymer solution.

In addition, an object of the present invention is a method of manufacturing a lithium ion polymer battery, comprising the steps of preparing a positive electrode plate and a negative electrode plate; Preparing a porous polyolefin-based membrane and a polymer solution of 1-20% by weight, which is stable to an electrolyte solution containing lithium salt at a temperature of 10 to 40 ° C. and an organic solvent is added to the polymer compound capable of gelling the electrolyte solution; Forming a polymer porous separator by coating the polymer solution on the porous polyolefin-based membrane; Manufacturing a battery structure using the positive electrode plate, the polymer porous separator, and the negative electrode plate; Impregnating the battery structure in a liquid electrolyte containing a lithium salt to provide an impregnated material; After sealing the impregnation, at a temperature of 70 to 100 ° C. under atmospheric pressure to 10 lbs / cm ² It can also be achieved by a method for producing a lithium ion polymer battery comprising the step of gelling for at least 1 hour.

       It is preferable that the polymer coated on the polymer porous separator has a pore of 0.1 to 20 μm.

In addition, an object of the present invention, a method for producing a lithium ion polymer battery, comprising the steps of preparing a positive electrode plate and a negative electrode plate; Preparing a polymer solution of 1-20% by weight and a porous polyolefin-based film, which are stable to an electrolyte solution containing lithium salt at a temperature of 10 to 40 ° C., and an organic solvent is added to the polymer compound capable of gelling the electrolyte solution; Forming a coated positive electrode plate by coating the polymer solution on the positive electrode plate; Forming a coated negative electrode plate by coating the polymer solution on the negative electrode plate; Manufacturing a battery structure using the coated positive electrode plate, the porous polyolefin-based membrane, and the coated negative electrode plate; Impregnating the battery structure in a liquid electrolyte containing a lithium salt to provide an impregnated material; After sealing the impregnation, at a temperature of 70 to 100 ° C. under atmospheric pressure to 10 lbs / cm ² It can also be achieved by a method for producing a lithium ion polymer battery comprising the step of gelling for 1 to 48 hours.

The negative electrode plate and the polymer coated on the positive electrode plate preferably has a pore of 0.1 to 20㎛.

      The polyolefin-based film is preferably any one selected from the group consisting of polyethylene film, polypropylene film, and multilayer film of polyethylene film and polypropylene film.

In the preparing of the polymer solution, it is preferable to further add an inorganic substance to the polymer solution.

The inorganic material is preferably at least one selected from the group consisting of SiO ₂ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ , BaTiO ₃ , Bi ₂ O ₃ , Fe ₂ O ₃ , CaSiO ₃ , and PbTiO ₃ .

       The inorganic material is preferably mixed with 0.1 to 15% by weight of the polymer solution.

      The solvent of the liquid electrolyte is ethylene carbonate (propylene carbonate), propylene carbonate (propylene carbonate), dimethyl carbonate (dimethyl carbonate), diethyl carbonate (diethyl carbonate), ethyl methyl carbonate (diethylmethyl carbonate), gamma-butyrolactone (γ) Butyrolactone, dimethylsulfoxide (dimethylsulfoxide), tetrahydrofuran (tetrahydrofuran) is preferably any one or more selected from the group consisting of.

The lithium salt is at least one selected from the group consisting of LiPF ₆ , LiAsF ₆ , LiClO ₄ , LiSbF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiCF ₃ SO ₃ It is preferable.

       Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 (a) shows a cross-sectional view of the polymer porous separator according to the present invention, the gel-forming polymer layer 10 has a pore 11 and a gel-forming polymer matrix 12 of 0.1 to 20㎛ size. The polyolefin membrane 20 is also porous and has a void 21 and a matrix 22. Here, the gel-forming polymer matrix 12 can be gelled, but the matrix 22 of the polyolefin film is not gelled. If the gel-forming polymer layer is pore-free or the pore 11 is smaller than 0.1 μm, the effect of ion conductivity through the liquid phase is reduced. In addition, the adhesion with the electrode is possible only under high pressure, so that the adhesion with the electrode is degraded under atmospheric or low pressure. On the other hand, if the void is larger than 20 μm, the contact area with the electrode is too small, resulting in poor adhesion. The pore size varies depending on the coating conditions. When the gel-forming polymer matrix 12 is prepared at a low temperature of 10 to 40 ° C., the gel-forming polymer matrix 12 has an excellent adhesion to the electrode while increasing the content of the electrolyte during high temperature gelation. If the manufacturing temperature of the polymer solution is lower than 10 ℃, it takes too much time to manufacture. On the other hand, if the manufacturing temperature is higher than 40 ℃, the history remains in the coated polymer chain as it contains the electrolyte and the adhesive strength decreases during the high temperature gelation. This becomes weak.

Hereinafter, the manufacturing process of the lithium ion polymer battery will be described in more detail.

First step: manufacturing positive and negative plates

The positive electrode plate is prepared by dissolving a mixture consisting of 5% by weight of acetylene black and 3% by weight of PvdF in 92% by weight of the positive electrode active material at 20-60 ° C. in N-methylpyrrolidone.

The positive electrode active material may be composed of one or more selected from the group consisting of LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _1-x Co _x O ₂ , V ₂ O ₅ . As the conductive agent, graphite can be used in addition to acetylene black to exhibit an appropriate effect.

The negative electrode plate is prepared by dissolving 2% by weight of acetylene black and 8% by weight of PvdF in N-methylpyrrolidone at a temperature of 20 to 60 ° C in 90% by weight of the negative electrode active material.

The negative electrode active material is composed of one or more selected from graphite, coke, hard carbon and tin oxide. As the conductive agent, graphite can be used in addition to acetylene black to exhibit an appropriate effect.

The positive electrode plate and the negative electrode plate prepared as described above may be used by themselves, or a porous polymer layer may be formed and used on these electrode plates. At this time, the formation of the porous polymer layer is the same as the method of manufacturing a polymer porous separator to be described below.

Second Step: Preparation of Polymer Porous Membrane

The polymer is placed in an organic solvent to prepare a polymer solution of 1 to 20% by weight at a temperature of 10 to 40 ° C., and then a porous polyolefin membrane is passed through the solution. When the concentration of the polymer solution is less than 1% by weight, the amount of the polymer to be coated is very small, and thus the binding property is reduced. On the other hand, when the concentration of the polymer solution is more than 20% by weight, the coating thickness becomes too thick, making it difficult to apply to a battery. The porous polyolefin membrane including the polymer solution loses the solvent while passing through the drying stand and is coated with a polymer having a thickness of 1 to 20 μm.

It is also possible to further add an inorganic substance to the polymer solution. Inorganic materials have the ability to adsorb electrolytes, improving battery characteristics such as binding capacity. If the inorganic material is less than 0.1% by weight in the polymer solution, the effect is not shown, and if more than 15% by weight, the polymer porous separator may be cured.

The polymer component is a polymer compound that is stable in an electrolyte solution containing lithium salts and is gelable to the electrolyte solution. In addition to the copolymer of vinyldenfluoride and hexafluopropylene, polyvinylidene fluoride, One or two or more polymers selected from the group consisting of polyviny chloride, polymethylmethacrylate, polymethacrylate, polyvinylalcohol, and polyethylene oxide Blends are preferred.

The organic solvent is composed of tetrahydrofuran, acetone, acetonitrile, N-methylpyrrolidone, cyclohexanone, and chloroform. One or more mixtures selected from the group are preferred.

The porous polyolefin membrane may be composed of a polyethylene membrane, a polypropylene membrane or a multilayer membrane of a polyethylene membrane and a polypropylene membrane, and may have a mechanical strength that can be wound.

As the inorganic material, SiO ₂ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ , BaTiO ₃ , Bi ₂ O ₃ , Fe ₂ O ₃ , CaSiO ₃ , PbTiO _3, etc. may be used.

Third Step: Fabrication of Lithium-ion Polymer Battery

FIG. 1 (b) shows a laminated cross-sectional view of the foil 31 to which the negative electrode plate is applied, the negative electrode plate 35, the polymer porous separator 100, the positive electrode plate 45, and the foil 41 to which the positive electrode plate is applied.

1 (c) shows a foil 31 coated with a negative electrode plate, a negative electrode plate 38 having a polymer porous layer 32 formed thereon, a polymer porous separator 100, a positive electrode plate 48 having a polymer porous layer formed thereon, and a foil coated with a positive electrode plate The laminated cross section of 41 is shown.

2 is a process diagram schematically showing a manufacturing process of a lithium ion polymer battery according to the present invention.

The positive electrode plate, the polymer porous separator, and the negative electrode plate are sequentially stacked. Here, the positive electrode plate and the negative electrode plate may be further formed of a polymer porous layer, and when the polymer porous layer is formed on the positive electrode plate and the negative electrode plate, a porous polyolefin membrane may be used instead of the polymer porous separator. The laminate is stacked in the stacking direction or the wound wound around the stack is put in an aluminum foil and impregnated in the electrolyte prepared above for 24 hours. Next, the impregnated winding was sealed, and the sealed cell formation was placed in an oven, followed by gelation under atmospheric pressure to 10 lbs / cm ² for 1 to 48 hours at 70 to 100 ° C. to manufacture a lithium ion polymer battery. do. If the gelation temperature is lower than 70 ?? gelation progress is slow, if the gelation temperature is more than 100 ℃ can be closed pores of the porous polyethylene membrane. If the gelation pressure is 10 lbs / cm ² or more, non-uniform gelation and deformation of the separator may occur.

When the wound is impregnated with the electrolyte, the electrolyte flows into the porous polymer membrane and the electrode plate. In the porous membrane, the polymer is absorbed into the pores of the gel-forming polymer and the porous polyolefin membrane, and is absorbed into the pores of the porous gel-forming polymer layer when the porous polymer layer is coated on the electrode plate. In the gelation process, the gel-forming polymer of the electrolyte and the electrode layer is gelled together with the electrolyte solution. If the gelation process is not performed, the electrolyte in the pore present in the polyolefin or gel-forming polymer may leak to the outside, but after gelling, the gel-forming polymer adheres to the electrode. Plays the role of. The gelation time in the gelation process It is about 500-600mAh class battery. If it is less than 1 hour, it does not complete gelation and lacks adhesiveness and separates liquid and polymer phases. If the gelation time is longer than 48 hours, the energy consumption is high, and the time needs to be properly adjusted according to the battery system. Therefore, the preferred gelation time in the present invention was 5 to 12 hours.

The present invention will be described in detail by the following examples, but these examples are merely illustrative of the present invention and the present invention is not limited thereto.

First, the present invention will be described in detail as an experimental example for producing a polymer porous separator.

Example 1

Polyvinylidene fluoride as a polymer component and 3.5 g of hexafluoropropylene copolymer (PvdF-HFP) were mixed with 96.5 g of tetrahydrofuran as an organic solvent at 30 ° C. for 12 hours. A porous polyethylene membrane having a thickness of 9 μm was passed through the mixed solution. The SEM photograph of the porous polyethylene membrane used in this experiment is shown in FIG. 3. The porous polyethylene membrane passed through the polymer solution was dried at 30 ° C. to prepare a polymer porous separator. The polymer porous membrane thus prepared was 20 μm thick. Figure 4 (a) is a SEM photograph of the polymer porous separator can be seen that the polymer is covered with pores of about 10㎛ size. The polymer porous separator was cut into an area of 2 × 2 cm ² , impregnated into a liquid electrolyte containing lithium salt, and gelled at 80 ° C. for 5 hours. The ion conductivity measured at this time was 1.2 × 10 ⁻³ S / cm.

Example 2

Prepared in the same manner as in Example 1, but the amount of the polymer was 2% by weight. The thickness of the separator was 12㎛. Figure 4 (b) is a SEM photograph of the polymer porous separator can be seen that the polymer layer is partially scattered. Ionic conductivity was 1.23 × 10 ^-3 S / cm

Example 3

Prepared in the same manner as in Example 1, but the amount of the polymer was 5% by weight. The thickness of the separator was 25㎛. Figure 4 (c) is a SEM photograph of the polymer porous membrane, the pores are slightly smaller than in Example 1, it can be seen that the multilayer is formed. Ionic conductivity was 1.17 × 10 ⁻³ S / cm.

 Example 4

Prepared in the same manner as in Example 1, but added 0.35 g of fine silica (fumed silica) having a 7 nm particle size to the polymer solution. The total thickness of the prepared separator was 20 μm. 5 is a SEM image of the polymer porous separator 5-10㎛ It can be seen that it is covered with pores of size and microsilica is distributed in the pores. Ionic conductivity was 1.25 × 10 ⁻³ S / cm.

Comparative Example 1

Prepared in the same manner as in Example 1, but the polymer solution was mixed at 50 ℃. The ion conductivity was 1.1 × 10 ⁻³ S / cm and the SEM photograph is shown in FIG. 6.

Comparative Example 2

Prepared in the same manner as in Example 1, but the polymer solution was mixed at 50 ℃ for 12 hours. In addition, the tension of the porous polyethylene membrane was strengthened to pass the polymer solution. The pores were formed in nanosize, and the ionic conductivity was 1.05 × 10 ⁻³ S / cm.

Table 1 summarizes the above experiments on the preparation of the polymer porous separator.

<Table 1> Polymer porous membrane manufacturing experiment

From Table 1, it can be seen that the polymer solution is prepared at 30 ° C. and the binding capacity and conductivity with the electrode are excellent when the pores of the porous polymer membrane are large. However, in Example 2 having a concentration of 2% of the polymer solution, pores were not clearly generated and the binding force was weak. However, when the battery was made using Example 2, the battery characteristics were good. It can also be seen that the conductivity is improved by adding silica in the preparation of the polymer solution. The binding force with the electrode was measured visually by cutting the negative electrode plate and the positive electrode plate into 1.5 x 1.5 cm ² and inserting a porous polymer separator of 2 x 2 cm ² therebetween and gelating them as in Example 5.

Next, the present invention will be described in detail as an experimental example for manufacturing a lithium ion polymer battery.

Example 5

A polymer solution was prepared by mixing polyvinylidene fluoride as a polymer component and 3.5 g of hexafluoropropylene copolymer (PvdF-HFP) at 30 ° C. for 12 hours in 96.5 g of an organic solvent, tetrahydrofuran. A 9 μm porous polyethylene membrane was passed through the prepared polymer solution. The porous polyethylene separator passed through the polymer solution was dried at 30 ° C. to prepare a polymer porous separator. Thereafter, the polymer porous separator, the positive electrode plate, the polymer porous separator, and the negative electrode plate were laminated and wound in this order. The wound was put in aluminum foil and impregnated with the electrolyte for 24 hours. The electrolyte solution is a solution of LiPF ₆ dissolved in 1 M concentration in a solvent composed of 60% by weight of ethylene carbonate and 40% by weight of dimethyl carbonate. Thereafter, the impregnated wound was sealed, and the sealed battery formation was placed in an oven, and then a lithium ion polymer battery was manufactured by gelling at 80 ° C. and atmospheric pressure for 5 hours.

Example 6

Prepared in the same manner as in Example 5, but the amount of the polymer was 2% by weight

Example 7

Prepared in the same manner as in Example 5, but the amount of the polymer was 5% by weight

Example 8

Prepared in the same manner as in Example 5, but 0.35g of fumed silica of 7 nm particle size was further added to the polymer solution.

Example 9

Manufactured in the same manner as in Example 5 except that the porous polymer layer was formed on the positive electrode plate and the negative electrode plate. The thicknesses of the porous polymer layers coated on the negative electrode plate and the positive electrode plate were 3 μm and 5 μm, respectively.

Example 10

Prepared in the same manner as in Example 5, but gelation conditions were set to 90 ℃, 0.4 lbs / cm ² .

Comparative Example 3

A lithium ion polymer battery was prepared in the same manner as in Example 5, but without gelation.

Comparative Example 4

Prepared in the same manner as in Example 5, the polymer solution was mixed at 50 ℃ for 12 hours. In addition, the tension of the porous polyethylene membrane was strengthened to pass the polymer solution. Pores of the porous polymer membrane was formed in a nano-sized, gelation conditions were 90 ℃, 0.4 lbs / cm ² to be.

Comparative Example 5

Prepared in the same manner as in Example 5, but the gelling conditions at 90 ℃ 50 lbs / cm ² to be about 2 minutes.

Comparative Example 6

Prepared in the same manner as in Comparative Example 4, but the gelation conditions were to be about 2 minutes to 50 lbs / cm ² at 90 ℃.

The above experimental results are summarized in Table 2.

<Table 2> Lithium ion polymer battery manufacturing conditions

Table 3 shows the relationship between pore size, pressure, gelation time and cycle life characteristics, and binding force with the electrode.

<Table 3> Cycle Life Characteristics and Binding Force with Electrodes

In Table 3, it can be seen that the cycle life characteristics and the binding force with the electrode are good when the pore size of the polymer porous membrane is appropriate and the gelation time is long while the gelation pressure is low.

Next will be described in detail the present invention with reference to the performance test data for the battery obtained in this experiment.

7 shows high-rate discharge characteristics of the battery prepared in Example 5, wherein the high-rate discharge characteristics are charged at a constant current / constant voltage at 0.5C, the discharge capacity for each discharge rate is measured, and as a ratio with respect to the 0.2C discharge capacity. Indicated. It can be seen that when the discharge at 3C has a capacity of 95% of the 0.2C discharge. The high rate discharge characteristics are excellent because the ion conductivity of the electrolyte is good and the adhesion to the electrode of the gelling polymer is good, thereby reducing the internal resistance.

8 (a) and 8 (b) show cycle characteristics and discharge capacity characteristics of the batteries of Examples 5, 6, and 7. FIG. At the test temperature of 25 ° C., the discharge capacity was measured with a cycle characteristic of 1C and a capacity characteristic of 0.2C. In the discharge capacity characteristics, the discharge capacity is expressed as the capacity per positive electrode active material, and the discharge capacity in the cycle characteristic is expressed as a ratio with respect to the discharge capacity in the first cycle. The more the polymer component is included, the better the cycle characteristics, but the discharge capacity is slightly smaller.

9 is a lithium ion polymer battery using a polymer electrolyte of Comparative Example 3 and Example 5 Cell cycle characteristics of the lithium ion polymer battery according to the present invention, the discharge capacity is expressed as a ratio of the discharge capacity in the first cycle. It can be seen that the lithium ion polymer battery prepared by the polymer electrolyte of Comparative Example 3, which is not gelled, exhibits significantly poor cycle characteristics compared to the gelled lithium ion polymer battery.

FIG. 10 compares Example 5 with Example 8 and compares the addition of the inorganic material with the addition of the inorganic material. Cycle characteristics were measured by repeatedly charging and discharging at 25 ° C. at 1C. It can be seen that the cycle is improved when the inorganic material is added, which increases the electrolytic solution containing capacity and retention ability of the gelled polymer due to the addition of inorganic material. help Because of giving.

FIG. 11 compares Example 5 with Example 9 in which the polymer porous layer is coated on the positive electrode plate and the negative electrode plate, and the cycle characteristics are improved by coating the polymer porous layer on the electrode.

12 is a comparison of the cycle characteristics of Example 5 and Comparative Examples 4, 5, 6, showing that the cycle characteristics are excellent as 90% under the conditions proposed by the present invention.

As described above, the porous separator for a lithium ion polymer battery of the present invention is manufactured using a polymer solution mixed at a low temperature of 10 to 40 ° C., and the pore size of the coating is adjusted to an appropriate size, so that the electrolyte retention capacity and ion conductivity great. It also enables gelation at low pressures and excellent adhesion to the electrode after gelation. The lithium ion polymer battery including the porous separator resolves problems such as uneven gelation of the battery, deformation of the separator, and weakening of the binder caused by gelation for a few hours under high pressure and pressure by performing gelation at atmospheric pressure or pressure. There is a number. Moreover, it becomes stable at high temperature, and is excellent in high rate discharge, cycle life, high temperature safety, etc.

Claims (16)

In the manufacturing method of the polymer porous separator for lithium ion polymer battery, At a temperature of 10 to 40 ℃, providing a polymer solution of 1-20% by weight and a porous polyolefin-based film that is stable to the electrolyte solution containing lithium salt and added an organic solvent to the polymer compound capable of gelling the electrolyte solution; Coating the polymer solution on the porous polyolefin-based membrane to make a polymer porous separator; The polymer coated on the porous polyolefin-based membrane is a method for producing a polymer porous separator, characterized in that it has a pore of 0.1 to 20㎛. delete The method of claim 1, The polyolefin-based membrane is a method for producing a polymer porous membrane, characterized in that any one selected from the group consisting of polyethylene film, polypropylene film, and a multilayer film of polyethylene film and polypropylene film. The method of claim 1, The polymer solution manufacturing step is a method of producing a polymer porous separator, characterized in that further adding an inorganic material to the polymer solution. The method of claim 4, wherein The inorganic material is any one or more selected from the group consisting of SiO ₂ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ , BaTiO ₃ , Bi ₂ O ₃ , Fe ₂ O ₃ , CaSiO ₃ , and PbTiO ₃ Method for producing a separator.        The method of claim 4, wherein        The inorganic material is a method for producing a polymer porous separator, characterized in that the mixture of 0.1 to 15% by weight of the polymer solution. In the manufacturing method of a lithium ion polymer battery, Manufacturing a positive plate and a negative plate; Preparing a polymer solution of 1-20% by weight and a porous polyolefin-based film, which are stable to an electrolyte solution containing lithium salt at a temperature of 10 to 40 ° C., and an organic solvent is added to the polymer compound capable of gelling the electrolyte solution; Forming a polymer porous separator by coating the polymer solution on the porous polyolefin-based membrane; Manufacturing a battery structure using the positive electrode plate, the polymer porous separator, and the negative electrode plate;        Impregnating the battery structure in a liquid electrolyte containing a lithium salt to provide an impregnated material; After sealing the impregnation, at a temperature of 70 to 100 ° C. under atmospheric pressure to 10 lbs / cm ² Gelling for 1 to 48 hours, The polymer coated on the porous polyolefin-based membrane is a method of manufacturing a lithium ion polymer battery, characterized in that it has a pore of 0.1 to 20㎛. delete In the manufacturing method of a lithium ion polymer battery, Manufacturing a positive plate and a negative plate; Preparing a polymer solution of 1-20% by weight and a porous polyolefin-based film, which are stable to an electrolyte solution containing lithium salt at a temperature of 10 to 40 ° C., and an organic solvent is added to the polymer compound capable of gelling the electrolyte solution; Forming a coated positive electrode plate by coating the polymer solution on the positive electrode plate; Forming a coated negative electrode plate by coating the polymer solution on the negative electrode plate; Manufacturing a battery structure using the coated positive electrode plate, the porous polyolefin-based membrane, and the coated negative electrode plate;        Impregnating the battery structure in a liquid electrolyte containing a lithium salt to provide an impregnated material; After sealing the impregnation, at a temperature of 70 to 100 ° C. under atmospheric pressure to 10 lbs / cm ² Gelling for 1 to 48 hours, The negative electrode plate and the polymer coated on the positive electrode plate has a method of manufacturing a lithium ion polymer battery, characterized in that it has a pore of 0.1 to 20㎛. delete The method according to claim 7 or 9, The polyolefin-based film is any one selected from the group consisting of polyethylene film, polypropylene film, and a multilayer film of polyethylene film and polypropylene film. The method according to claim 7 or 9, The polymer solution manufacturing step is a method of manufacturing a lithium ion polymer battery, characterized in that further adding an inorganic material to the polymer solution. The method of claim 12, The inorganic material is any one or more selected from the group consisting of SiO ₂ , TiO ₂ , ZrO ₂ , Al ₂ O ₃ , BaTiO ₃ , Bi ₂ O ₃ , Fe ₂ O ₃ , CaSiO ₃ , and PbTiO ₃ Method for producing a polymer battery.        The method of claim 13,        The inorganic material is a method for producing a lithium ion polymer battery, characterized in that the mixture of 0.1 to 15% by weight of the polymer solution. The method according to claim 7 or 9,       The solvent of the liquid electrolyte is ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, diethylmethyl carbonate, gamma-butyrolactone (γ). Butyrolactone), dimethyl sulfoxide (dimethylsulfoxide), tetrahydrofuran (tetrahydrofuran) is any one or more selected from the group consisting of lithium ion polymer battery manufacturing method. The method according to claim 7 or 9, The lithium salt is at least one selected from the group consisting of LiPF ₆ , LiAsF ₆ , LiClO ₄ , LiSbF ₆ , LiBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiCF ₃ SO ₃ Method for producing a lithium ion polymer battery, characterized in that.

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