KR100722834B1 - Preparation method of solid polymer electrolytic composite and lithium polymer cell employing solid polymer electrolytic composite - Google Patents

Abstract

The present invention is a solid polymer electrolyte composite material for a lithium polymer battery prepared in the form of a film using a solution prepared by dissolving polyethylene oxide and lithium salt in an organic solvent, the mixture is prepared by further mixing medium-porous nanosilica The present invention relates to a solid polymer electrolyte composite material, a manufacturing method thereof, and a lithium polymer battery using the same.

In the solid polymer electrolyte composite material of the present invention, the mechanical properties are improved by using medium porosity nanosilica as a filler, and the electrical properties are improved because the medium porosity nanosilica decreases the crystalline region of the polyethylene oxide polymer to increase the ionic conductivity. Is improved. Therefore, the solid polymer electrolyte composite material is environmentally friendly and there is no risk of explosion and leakage, which can be usefully used in the lithium polymer battery business.

Secondary battery, polymer electrolyte composite material, polyethylene oxide, filler, lithium salt

Description

TECHNICAL FIELD OF THE INVENTION A method for producing a solid polymer electrolyte composite material and a lithium polymer battery having a solid polymer electrolyte composite material manufactured thereon {PREPARATION METHOD OF SOLID POLYMER ELECTROLYTIC COMPOSITE AND LITHIUM POLYMER CELL EMPLOYING SOLID POLYMER ELECTROLYTIC COMPOSITE}

1 shows the structure of the medium-porous nanosilica (MCM-41) of the present invention,

2 is a measurement result of a differential scanning calorimeter (DSC) according to the amount of MCM-41 added in the solid polymer electrolyte composite material of the present invention,

3 is an X-ray diffraction analysis (XRD) according to the amount of MCM-41 added in the solid polymer electrolyte composite material of the present invention,

Figure 4a is a surface photograph of a solid polymer electrolyte composite material prepared in Comparative Example 1 of the present invention,

Figure 4b is a surface photograph of the solid polymer electrolyte composite material prepared in Comparative Example 2 of the present invention,

Figure 4c is a photograph of the surface of the solid polymer electrolyte composite material prepared in Example 1 of the present invention,

Figure 4d is a surface photograph of the solid polymer electrolyte composite material prepared in Example 2 of the present invention,

Figure 4e is a photograph of the surface of the solid polymer electrolyte composite material prepared in Example 3 of the present invention,

Figure 4f is a surface photograph of the solid polymer electrolyte composite material prepared in Example 4 of the present invention,

5 is a result of measuring ion conductivity according to the amount of MCM-41 added in the solid polymer electrolyte composite material of the present invention.

The present invention relates to a solid polymer electrolyte composite material, a method for preparing the same, and a lithium polymer battery using the same. More specifically, lithium salt and medium-sized porous nanosilica are mixed with polyethylene oxide as a filler and dissolved in an organic solvent to prepare a solution. The present invention relates to a solid polymer electrolyte composite material having improved mechanical and electrical properties, a method of preparing the same, and a lithium polymer battery using the same by coating the solution on one surface and drying the film to prepare a film.

In order to cope with the rapidly increasing energy consumption and to change to an environment-friendly form of consumption, a lot of research is being conducted focusing on alternative energy and alternative power sources, namely electrochemical energy production methods. The storage and conversion of electrochemical energy includes secondary batteries, fuel cells, and capacitors, and many studies on lithium secondary batteries, which are known to have the best discharge performance, are being conducted.

Rechargeable batteries are the three key strategic products that will lead the domestic electronic information equipment industry along with semiconductors and displays. They determine the performance of future mobile IT products closely related to the 21st century human life such as mobile phones, laptops, computers, camcorders, MP3s, and PDAs. Of course, the importance of electric vehicles is increasing.

Among them, lithium polymer batteries are the most studied due to high energy density and discharge voltage, and are currently commercialized in mobile phones and camcorders. In general, the lithium polymer battery mainly uses a PEO-LiX-based electrolyte. The PEO-LiX-based polymer electrolyte may be manufactured in a thin film form, and has advantages in various aspects, such as excellent mechanical properties, excellent adhesion between the electrode and the electrolyte, and no fear of leakage.

However, it has a relatively low ionic conductivity at room temperature compared to an aqueous solution or an electrolyte in a gel state, and is difficult to use as a high energy source because its interface with the electrode is inferior.

In order to solve the problems of the PEO-LiX-based polymer electrolyte, many researchers have added inorganic particles and nanoparticles such as TiO ₂ , Al ₂ O ₃ , SiO ₂ , activated silica and ceramic powder as fillers to improve the mechanical properties of the electrolyte. I'm trying to improve.

In order to solve the problems of PEO-LiX-based polymer electrolytes, the present inventors have tried to obtain a solid polymer electrolyte composite material having improved mechanical properties as well as electrical properties. As a result, lithium salt and medium-sized porosity nanosilica are used as a filler in polyethylene oxide. The mixture was dissolved in an organic solvent to prepare a solution. The solution was applied on one surface and dried to prepare a solid polymer electrolyte composite material on a film. The solid polymer electrolyte composite material had improved mechanical properties, and medium porosity. The present invention was completed by confirming that the ionic nanosilica reduced the crystalline region of polyethylene oxide, thereby increasing the electrical properties, thereby improving the electrical properties.

An object of the present invention is to provide a PEO-LiX-based electrolyte composite material with improved electrical and mechanical properties.

It is another object of the present invention to provide a method for preparing a solid polymer electrolyte composite material for a lithium polymer battery, which prepares a solution prepared by dissolving lithium salt and medium-sized porous nanosilica in an organic solvent in a film form.

Still another object of the present invention is to provide a lithium polymer battery comprising the solid polymer electrolyte composite material.

In order to achieve the above object of the present invention, the present invention is a solid polymer electrolyte composite material for a lithium polymer battery prepared in a film using a solution prepared by dissolving polyethylene oxide and lithium salt in an organic solvent, the solution It provides a solid polymer electrolyte composite material prepared by further mixing the medium-sized porous nanosilica.

The medium porosity nanosilica has a pore size of 2 to 30 nm, and has an average diameter of 50 to 500 nm.

According to the present invention, a solution is prepared by dissolving 1 to 200 parts by weight of lithium salt and 1 to 30 parts by weight of medium porosity nanosilica in an organic solvent based on 100 parts by weight of polyethylene oxide polymer, and applying the solution onto one surface. It provides a method for producing the solid polymer electrolyte composite material which is dried at 30 to 60 ℃ for 24 to 48 hours to form a film.

In the above lithium salts are lithium perchlorate (LiClO ₄ ), lithium triplate (LiCF ₃ SO ₃ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ) and lithium trifluoromethanesulfonyl Mid (LiN (CF ₃ SO ₂ ) ₂ ) It is at least one selected from the group consisting of.

The organic solvent is used alone or in combination of two or more selected from the group consisting of ethanol, methanol, isopropyl alcohol, acetonitrile, acetone, dimethylformamide, dimethylsulfoxide and N-methylpyrrolidone.

In addition, the present invention provides a lithium polymer battery having the solid polymer electrolyte composite material.

Hereinafter, the present invention will be described in detail.

The present invention is a solid polymer electrolyte composite material for a lithium polymer battery prepared in the form of a film using a solution prepared by dissolving polyethylene oxide and lithium salt in an organic solvent, the mixture is prepared by further mixing medium-porous nanosilica It provides a solid polymer electrolyte composite material for a lithium polymer battery.

The medium porous nanosilica is prepared through hydrothermal reaction and has a mesoporous structure. More preferably, the pore size of the medium porosity nanosilica is 2 to 30 nm, and its average diameter is 50 to 500 nm. At this time, if the pore size and the average diameter is less than the range, the passage through which the ions can be transferred is too narrow to reduce the ion conduction phenomenon, while if the pore size and the average diameter are exceeded, the ion transfer passage is too large to cause the ion The effect as a filler to secure the passage is lowered so that the ionic conductivity is reduced.

In particular, the medium-porous nanosilica used in the present invention is one of the M41S-based material, which is a material developed by Mobil, USA, and is preferably a mobil crystalline material-41 (hereinafter referred to as "MCM-"). 41 "). Figure 1 shows the structure of the medium-sized porosity nanosilica (MCM-41) of the present invention, a mesoporous structure of the pore size of most of the prepared nanosilica 39.6Å. The M41S material includes MCM-41 having regular pores in one-dimensional arrangement and hexagonal shape, MCM-48 having pores in three-dimensional arrangement and cube shape, and MCM-51 having lamellar structure.

The medium-porous nanosilica is used as a filler of the solid polymer electrolyte composite material for a lithium polymer battery of the present invention, thereby contributing to the reduction of the crystalline region and the increase of the ionic conductivity of the polyethylene oxide polymer, thereby increasing the mechanical and electrical properties of the solid polymer electrolyte composite material. Physical properties can be improved.

2 is a measurement result of differential scanning calorimetry (DSC) according to the amount of MCM-41 added in the solid polymer electrolyte composite material of the present invention, and FIG. 3 shows the results of X-ray diffraction analysis (XRD), and MCM-41. As the amount of is increased, since the melting point temperature of the solid polymer electrolyte composite material is lowered, such a change in melting point means a decrease in the crystalline region of polyethylene oxide. In addition, the XRD measurement results show that the crystalline region decreases as the amount of MCM-41 added increases.

According to the present invention, a solution is prepared by dissolving 1 to 200 parts by weight of lithium salt and 1 to 30 parts by weight of medium porosity nanosilica in an organic solvent based on 100 parts by weight of polyethylene oxide polymer, and applying the solution onto one surface. It provides a method for producing the solid polymer electrolyte composite material which is dried at 30 to 60 ℃ for 24 to 48 hours to form a film.

The lithium salt is lithium perchlorate (LiClO ₄ ), lithium triplate (LiCF ₃ SO ₃ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ) and lithium trifluoromethanesulfonylimide At least one selected from the group consisting of (LiN (CF ₃ SO ₂ ) ₂ ). More preferably, lithium perchlorate (LiClO ₄ ) is used. At this time, 1 to 200 parts by weight of the lithium salt is used with respect to 100 parts by weight of the polyethylene oxide polymer, more preferably 1 to 100 parts by weight, most preferably 1 to 15 parts by weight. If the lithium salt is less than 1 part by weight, the lithium ion concentration is too low to lower the ion conductivity, which is undesirable. If the content exceeds 200 parts by weight, the viscosity increases due to the use of excessive lithium salt, resulting in a decrease in ion conductivity and a problem of cost increase. do.

It is preferable to use 1-30 weight part with respect to 100 weight part of polyethylene oxide polymers, and, as for the said medium-sized porous nanosilica, More preferably, 2-10 weight part is used. In this case, when the medium-porous nanosilica is used in less than 1 part by weight, the effect of reducing the degree of crystallinity is small, when used in excess of 30 parts by weight, the crystallinity effect is reduced and is not preferable due to the problem of material cost increase.

The organic solvent may be used alone or in combination of two or more selected from the group consisting of ethanol, methanol, isopropyl alcohol, acetonitrile, acetone, dimethylformamide, dimethyl sulfoxide and N-methylpyrrolidone. At this time, in the embodiment of the present invention it was carried out by selecting acetonitrile as a preferred organic solvent.

4A to 4F are photographs showing the surface of the solid polymer electrolyte composite material according to the amount of MCM-41 added in the solid polymer electrolyte composite material of the present invention. From the surface results, the solid polymer electrolyte composite material prepared without adding LiClO ₄ or LiClO ₄ and MCM-41, which are lithium salts, is semi-crystalline of the polyethylene oxide polymer itself. On the surface, it shows a crystal region in which several plate phases are connected to each other ( FIGS. 4A and 4B ).

On the other hand, LiClO ₄ and MCM-41 are added to the polyethylene oxide polymer, but as the amount of the MCM-41 is increased, the boundary between the plates is blurred, resulting in a decrease in the crystalline region of the polyethylene oxide polymer. ( FIG. 4C- 4F ).

In addition, the addition of the medium porosity nanosilica (MCM-41) of the present invention, the result that the crystalline region of the polyethylene oxide polymer is reduced can be confirmed from the result that the ion conductivity increases with the addition amount of MCM-41 ( FIG. 5 ).

Accordingly, the present invention is a solid polymer electrolyte by additionally mixing medium-porous nanosilica as a filler in a conventional PEO-LiX-based electrolyte composite material prepared by dissolving lithium salt in polyethylene oxide in an organic solvent in the form of a film. By producing the composite material, the effect of reducing the crystalline region of the polyethylene oxide and increasing the ionic conductivity is given. From this, it can be expected to improve the mechanical properties only by using the filler, it is possible to improve the electrical properties of increasing the ionic conductivity.

In addition, the polymer electrolyte composite material of the present invention is provided in a simple and easy process.

The present invention provides a lithium polymer battery having the solid polymer electrolyte composite material.

Since the solid polymer electrolyte composite material of the present invention has enhanced physical properties of the polymer membrane and improved electrical properties due to an increase in ionic conductivity, it is expected to reduce the amount, weight, and thickness of electronic devices. For example, it may be usefully used in portable electronic devices such as camcorders and mobile phones.

Hereinafter, the present invention will be described in more detail with reference to Examples.

This embodiment is intended to illustrate the present invention in more detail, and the scope of the present invention is not limited to these examples.

<Example 1>

Step 1: Preparation of the filler MCM-41 (mobil crystalline material-41)

To prepare MCM-41, 14.3 g of colloidal silica, Ludox H40 (manufactured by Unichem), and 46.9 g of an aqueous 1 M NaOH solution were stirred at 80 ° C. (353K) for 2 hours. The solution was prepared.

Sodium silicate solution prepared above was slowly added dropwise to a mixture of 20 g of CTMACl (cetyltrimethylammonium chloride, Aldrich) and 0.29 g of 28 wt% aqueous ammonia solution which was used as a surfactant for 1 hour at room temperature, and further 1 hour at room temperature. The gel mixture was prepared by stirring. Thereafter, the gel mixture was heated at 97 ° C. (370 K) for 24 hours, then cooled at room temperature and adjusted to pH 10.2 using 30 wt% acetic acid. After pH adjustment, the process of heating at 97 ° C. (370 K) for 24 hours was repeated two more times, and the precipitated product was dried at 97 ° C. (370 K) through filtration and washing. Thereafter, MCM-41 was prepared by baking for 5 hours at 550 ° C. (823K) in air to remove the organic template from the obtained product.

Step 2: Preparation of Solid Polymer Electrolyte Composite

As a polymer, polyethylene oxide (manufactured by Aldrich) having a molecular weight of 2.0 × 10 ⁵ was prepared by drying at 50 ° C. for 24 hours, and LiClO ₄ (manufactured by Aldrich), which is a lithium salt, and MCM-41 prepared in the step were 130 ° C. Dried for 24 hours and used. 2 parts by weight of the filler prepared in the above step, MCM-41, based on 100 parts by weight of polyethylene oxide was added to the mixed solution of 1 g of polyethylene oxide, 0.15 g of lithium salt, and 6 ml of acetonitrile, and stirred for 24 hours. To prepare a solid polymer electrolyte composite material (SPE), it was cast in a glass container to prepare a film, and dried in a vacuum oven at 40 ° C. for 24 hours.

<Example 2>

A solid polymer electrolyte composite material (SPE) was prepared in the same manner as in Example 1 except that 5 parts by weight of the filler prepared in Step 1 of Example 1, MCM-41, was added based on 100 parts by weight of polyethylene oxide. Prepared.

<Example 3>

A solid polymer electrolyte composite material (SPE) was prepared in the same manner as in Example 1 except that 8 parts by weight of the filler prepared in Step 1 of Example 1, MCM-41, was added to 100 parts by weight of polyethylene oxide. Prepared.

<Example 4>

A solid polymer electrolyte composite material (SPE) was prepared in the same manner as in Example 1, except that 10 parts by weight of the filler prepared in Step 1 of Example 1, MCM-41, was added based on 100 parts by weight of polyethylene oxide. Prepared.

Comparative Example 1

In the preparation of the polymer electrolyte composite material of Step 2 of Example 1, after drying at 50 ° C. for 24 hours, 1 g of polyethylene oxide and 6 ml of acetonitrile were mixed, stirred for 24 hours, and then cast into a glass container ( casting to prepare a film form and dried for 24 hours in a vacuum oven at 40 ℃ to prepare a solid polymer electrolyte composite material (SPE).

Comparative Example 2

0.15 g of LiClO ₄ , which is a lithium salt in Comparative Example 1, was dried at 130 ° C. for 24 hours, except that 1 g of polyethylene oxide was added to 6 ml of acetonitrile.

Experimental Example 1 Confirmation of Structure of MCM-41

In order to examine the structure of the MCM-41 prepared in Step 1 of Example 1, X-ray diffraction analysis was performed. The results are shown in FIG.

As shown in Figure 1, the structure of the MCM-41 has a mesoporous structure of the most pore size of 39.6Å, Miller index (hkl) of the crystal plane [100].

Experimental Example 2 Measurement of Change in Crystallinity

The change in crystallinity was observed for the solid polymer electrolyte composite materials (SPE) prepared in Examples 1 to 4 and Comparative Examples 1 and 2.

1. DSC measurement results

Differential scanning calorimetry (DSC, Perkin) set at a temperature increase rate of 5 ° C./min under N ₂ atmosphere from room temperature to 125 ° C. for the solid polymer electrolyte composite materials (SPE) prepared in Examples 1 to 4 and Comparative Examples 1 to 2. The melting point change of the solid polymer electrolyte was measured using Elmer DSC6). The results are shown in Table 1 and FIG.

As a result of DSC measurement, as the amount of MCM-41 increased, the melting point temperature of the solid polymer electrolyte composite material was confirmed to be low. The change in the melting point means a decrease in the crystalline region of the polyethylene oxide, the decrease in the crystalline region between the polyethylene jade can be confirmed through the crystallinity (χ) of the following equation (1).

In the above, ΔH _f ^o and melting point (T _m ) of the polyethylene oxide is 189 J / g and 65 ℃, respectively, ΔH _f according to the addition of LiClO ₄ and MCM-41 can be obtained through DSC measurement.

2. XRD measurement result

For the solid polymer electrolyte composite materials (SPE) prepared in Examples 1 to 4 and Comparative Examples 1 to 2, the degree of crystallinity of polyethylene oxide (PEO) according to the addition of MCM-41 was determined through X-ray diffraction analysis (XRD). We looked at the impact. The results are shown in Table 1 and FIG. 3.

Melting Point (Tm) and Crystallinity (χ) Results of the Prepared Solid Polymer Electrolyte Composites division Si / Li Melting Point, T _m (℃) Crystallinity, χ (%) Comparative Example 2 - 59.82 43.4 Example 1 0.16  59.32 32.9 Example 2 0.40 58.24 32.1 Example 3 0.66 56.82 26.3 Example 4 0.85 56.98 28.3

From the XRD measurement results of Table 1 and FIG. 3, it was confirmed that the change in crystallinity (χ) of the polyethylene oxide (PEO) polymer decreased as the amount of MCM-41 increased. This change in crystallinity (χ) means a decrease in intensity, that is, a decrease in crystallinity, as MCM-41 is added. These results suggest that the addition of MCM-41 with mesoporous structure affects the crystallinity growth of polyethylene oxide. This does not happen, because the electrolyte is inserted between the well-ordered SiO ₂ channels of the MCM-41. This phenomenon could also be observed through surface morphology changes.

Experimental Example 3 Measurement of Morphology Change

Changes in morphology were observed for the solid polymer electrolyte composite materials (SPE) prepared in Examples 1-4 and Comparative Examples 1-2.

In other words, the surface change of the polymer electrolyte according to the addition of LiClO ₄ and MCM-41 to the polyethylene oxide polymer was observed by using a scanning electron microscope (SEM, Hitachi S-2400). The results are shown in Figures 4a to 4f.

Figure 4a is a comparative example 1, showing the surface of the solid polymer electrolyte composite material prepared without adding LiClO ₄ and MCM-41 to the polyethylene oxide polymer.

4B is a comparative example 2 showing the surface of the prepared solid polymer electrolyte composite material without adding LiClO ₄ to the polyethylene oxide polymer and without adding MCM-41. From the results of FIGS. 4A and 4B, the semi-crystalline polymer polyethylene oxide showed a rough surface due to the presence of crystal regions, that is, a shape in which several plate phases were connected to each other.

On the other hand, FIGS. 4C to 4F illustrate the change of the surface of the solid polymer electrolyte composite material by adding LiClO ₄ and MCM-41 to the polyethylene oxide polymer, but increasing the amount of MCM-41. .

From the results of the scanning electron microscope of FIGS. 4C to 4F, it was confirmed that the boundary on the plate became ambiguous as lithium salt (LiClO ₄ ) and MCM-41 were added. This result is due to the decrease in crystalline region of ethylene oxide as MCM-41 is dispersed in the polyethylene oxide polymer matrix.

Experimental Example 4 Measurement of Electrochemical Properties

Electrochemical properties of the solid polymer electrolyte composite materials (SPE) prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were measured.

In order to measure the ionic conductivity of the solid polymer electrolyte composite materials (SPE) prepared in Examples 1 to 4 and Comparative Examples 1 to 2, AC impedance was measured. Impedance measurement is produced by sandwiching the prepared solid polymer electrolyte composite material (SPE) on two inactive electrodes, stainless steel electrodes (SS), in the frequency range of 10 Hz to 10 kHz (frequency response analyzer, FRA) was measured using AUTOLAB 30 (potentiostat / galvanostat) (Eco Chemie, Netherlands). In this case, the resistance R _{b of the} bulk phase was measured by equivalent circuit analysis using FRA software, and the conductivity σ was calculated based on Equation 2 below.

In the above, t is the thickness of the solid polymer electrolyte composite material, and A is the area of the solid polymer electrolyte composite material.

From the results of FIG. 5, the ion conductivity measurement results were shown. As the amount of MCM-41 added increased, the ion conductivity increased. This change in ion conductivity is due to the fact that the filler MCM-41 is bonded to the polyethylene oxide segment, thereby reducing the bond between the polymer chains, affecting the overall structure of the polymer, thereby reducing the crystallinity of the polymer electrolyte composite material.

As described above, the present invention

First, a solid polymer electrolyte composite prepared by additionally mixing medium-porous nanosilica as a filler in a conventional PEO-LiX electrolyte composite material prepared by dissolving lithium salt in polyethylene oxide in an organic solvent in a film form. Materials and methods for their preparation,

Second, the manufacturing method was performed in a simple and easy process to provide a solid polymer electrolyte composite material,

Third, the solid polymer electrolyte composite material reduces the crystalline region of polyethylene oxide and increases the ionic conductivity, thereby improving mechanical and electrical properties to solve the problems of the conventional PEO-LiX-based electrolyte composite material, environmentally friendly and explosion And there is no risk of leakage is very useful for lithium polymer battery business.

Although the present invention has been described in detail only with respect to the embodiments described, it will be apparent to those skilled in the art that various modifications and variations are possible within the technical spirit of the present invention, and such modifications and variations belong to the appended claims. .

Claims (7)

delete delete delete To 100 parts by weight of polyethylene oxide polymer, 1 to 200 parts by weight of lithium salt, 2 to 6 parts by weight of medium-sized porous nanosilica having a pore size of 2 to 30 nm and an average diameter of 50 to 500 nm were dissolved in an organic solvent. To prepare, and apply the solution on one surface, it is dried for 24 to 48 hours at 30 to 60 ℃ to produce a solid polymer electrolyte composite material for a lithium polymer battery, characterized in that it is produced in a film form. The lithium salt of claim 4, wherein the lithium salt is lithium perchlorate (LiClO ₄ ), lithium triflate (LiCF ₃ SO ₃ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), and lithium trifluoro A method for producing the solid polymer electrolyte composite material, characterized in that at least one selected from the group consisting of romethanesulfonylimide (LiN (CF ₃ SO ₂ ) ₂ ). The method of claim 4, wherein the organic solvent is selected from the group consisting of ethanol, methanol, isopropyl alcohol, acetonitrile, acetone, dimethylformamide, dimethyl sulfoxide and N-methylpyrrolidone, or a mixture of two or more thereof. The method of producing a solid polymer electrolyte composite material, characterized in that the form. A lithium polymer battery comprising a solid polymer electrolyte composite material prepared by the method for producing a solid polymer electrolyte composite material of claim 4.

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