KR100740548B1 - Gel polymer electrolyte composition for lithium polymer battery and lithium polymer battery using the same - Google Patents

Abstract

A gel polymer electrolyte composition for a lithium polymer battery is provided to maintain mechanical strength of a polymer matrix, to increase ion conductivity inside a battery, and to improve charge and discharge characteristics of a lithium polymer battery. The gel polymer electrolyte composition for a lithium polymer battery comprises a lithium ion-containing non-aqueous electrolyte solution and a PVDF-HFP copolymer-containing polymer matrix. The PVDF-HFP copolymer consists of a first PVDF-HFP copolymer having an HFP content of 6wt% and a second PVDF-HFP copolymer having an HFP content of 8wt%. The first PVDF-HFP copolymer and the second PVDF-HFP copolymer are mixed in a weight ratio of 10:90. The first PVDF-HFP copolymer has a molecular weight of 200,000 and the second PVDF-HFP copolymer has a molecular weight of 450,000.

Description

Gel polymer electrolyte composition for lithium polymer battery and lithium polymer battery using same {Gel Polymer Electrolyte Composition for Lithium Polymer Battery and Lithium Polymer Battery using the same}

1 is a perspective view showing the internal cross-section of a lithium polymer battery according to the present invention.

2 is a view showing the structural formula of the PVDF-HFP copolymer according to the present invention.

3 is a view showing the internal structure of a lithium polymer battery according to the present invention.

4 is a curve showing the discharge capacity according to the charge and discharge cycle of the lithium polymer battery and the comparative example according to the present invention.

※ Explanation of Codes on Major Parts of Drawings

1: Cathode 2: Anode

3: Separator 4: Gel Polymer Electrolyte

5: aluminum pouch 6: Ni-tab

7: Al Tab

The present invention provides a gel polymer electrolyte composition comprising a non-aqueous electrolyte containing lithium salt and a copolymer of poly vinylidene fluoride-hexaxa propylene (hereinafter referred to as “PVDF-HFP”) and a lithium polymer battery using the same It is about. More specifically, the present invention provides a gel polymer electrolyte composition comprising a heterogeneous PVDF-HFP copolymer having a different content of hexafluoropropylene (hereinafter referred to as “HFP”) in a gel polymer electrolyte composition and a lithium polymer battery using the same. It is about.

Recently, research and development of thinning, miniaturization and lightening of electronic devices have been actively progressed, and such thinning, miniaturization and lightening requirements are continuously required for portable electronic devices such as mobile phones, camcorders, and portable computers. As power sources for driving these electronic devices, aqueous secondary batteries and lithium ion secondary batteries such as lead-acid batteries, Ni / Cd batteries, and Ni / MH batteries are known. In particular, the lithium ion secondary battery has an excellent advantage in that the energy density and output is higher than the conventional aqueous solution secondary battery.

Granted to Godzd, et al., Bell Communications Research, Inc. U.S. Patent UP5,296,318, assigned to Bell Communications Research Inc., discloses a gel polymer electrolyte type lithium polymer battery using PVDF-HFP copolymer. Gel polymer electrolyte type lithium polymer battery, also called Plastic Lithium Ion (PLI) battery, includes a positive electrode layer composed of a current collector, an aluminum mesh, a positive electrode active material, and a PVDF-HFP copolymer; A negative electrode layer composed of a current collector copper mesh, a negative electrode active material and a PVDF-HFP copolymer; And a separator composed of a PVDF-HFP copolymer wrapped around these two electrode layers (anode layer and cathode layer). However, the gel polymer electrolyte type lithium polymer battery uses a metal mesh as a current collector, but the metal mesh has a weak mechanical strength as compared to foils, thereby limiting the production speed. In addition, long-term use of the PVDF-HFP-based separator impregnated with the liquid electrolyte occurs swelling by the solvent to deteriorate the characteristics of the battery has not reached the mass production until now.

In another conventional technique, Japanese Patent Laid-Open No. 2002-8723 describes a gel polymer electrolyte composition comprising a non-aqueous electrolyte containing a lithium salt and a PVDF-HFP copolymer and a lithium polymer battery using the same, in particular, HFP as a polymer matrix. It is disclosed to use only PVDF-HFP copolymer having a content of 7% by weight. Therefore, in the case of using a gel polymer electrolyte containing a PVDF-HFP copolymer having an HFP content of 7% by weight described in Japanese Patent Laid-Open No. 2002-8723, it is possible to maintain the mechanical strength of the gel polymer electrolyte and at the same time improve the ionic conductivity. Has certain limitations.

The present invention is to maintain the mechanical strength in the PVDF-HFP copolymer of the polymer matrix material of the gel polymer electrolyte while improving the ionic conductivity, the content of the PVDF-HFP copolymer and HFP content of 7% by weight or less as the polymer matrix By using the gel polymer electrolyte containing the heterogeneous PVDF-HFP copolymer which mixed this PVDF-HFP copolymer which is 7 weight% or more by a fixed ratio, it solves the above-mentioned problem of the prior art.

According to a first aspect of the present invention, in a gel polymer electrolyte composition for a lithium polymer battery, the gel polymer electrolyte composition comprises a polymer matrix containing a non-aqueous electrolyte containing lithium ions and a PVDF-HFP copolymer, wherein the PVDF- The HFP copolymer consists of a first PVDF-HFP copolymer having an HFP content of 7 wt% or less and a second PVDF-HFP copolymer having an HFP content of 7 wt% or more, wherein the first PVDF-HFP copolymer and the second PVDF are The present invention provides a gel polymer electrolyte composition for a lithium polymer battery, wherein the -HFP copolymer is mixed at a predetermined ratio.

According to a second aspect of the present invention, in the gel polymer electrolyte composition for a lithium polymer battery according to the first aspect, a predetermined ratio of the first PVDF-HFP copolymer and the second PVDF-HFP copolymer is 5 to 40% by weight, respectively. It is to provide a gel polymer electrolyte composition for a lithium polymer battery, characterized in that the range of% and 95 to 60% by weight.

According to a third aspect of the present invention, in the gel polymer electrolyte composition for a lithium polymer battery according to the first aspect, the average HFP of the first PVDF-HFP copolymer and the second PVDF-HFP copolymer used as the polymer matrix The present invention provides a gel polymer electrolyte composition for a lithium polymer battery, wherein the content is in the range of 6.5 to 7.5% by weight and the average molecular weight is in the range of 200,000 to 300,000.

According to a fourth aspect of the present invention, in the gel polymer electrolyte composition for a lithium polymer battery according to the first aspect, the first PVDF-HFP copolymer has an HFP content of 6 to 7 wt% and a molecular weight of 100,000 to 250,000. 2 PVDF-HFP copolymer is to provide a gel polymer electrolyte composition for a lithium polymer battery, characterized in that the HFP content is 7 to 12% by weight and the molecular weight is 200,000 to 470,000.

According to a fifth aspect of the present invention, in the gel polymer electrolyte composition for a lithium polymer battery according to the first aspect, the first PVDF-HFP copolymer has an HFP content of 7% by weight, a molecular weight of 600,000, and the second PVDF The -HFP copolymer has an HFP content of 11% by weight, a molecular weight of 350,000, and a predetermined ratio of the first PVDF-HFP copolymer and the second PVDF-HFP copolymer is 10% by weight and 90% by weight, respectively. To provide a gel polymer electrolyte composition for a lithium polymer battery, characterized in that the mixture.

According to a sixth aspect of the present invention, a lithium polymer battery, comprising: a positive electrode; cathode; A separator to isolate the anode and the cathode; And a gel polymer electrolyte composition applied to the electrode surfaces of the positive electrode and the negative electrode, respectively, and comprising a polymer matrix containing a lithium ion-containing nonaqueous electrolyte and a PVDF-HFP copolymer, wherein the PVDF-HFP copolymer comprises: A first PVDF-HFP copolymer having an HFP content of 7 wt% or less and a second PVDF-HFP copolymer having an HFP content of 7 wt% or more, wherein the first PVDF-HFP copolymer and the second PVDF-HFP copolymer To provide a lithium polymer battery, characterized in that the mixture at a predetermined ratio.

According to a seventh aspect of the present invention, in the lithium polymer battery according to the sixth aspect, the polymer matrix may include 5 to 40 wt% of the first PVDF-HFP copolymer and 95 to 95 wt% of the second PVDF-HFP copolymer. It is to provide a lithium polymer battery comprising a PVDF-HFP copolymer in the range of 60% by weight.

According to an eighth aspect of the present invention, in the lithium polymer battery according to the sixth aspect, the average HFP content of the first PVDF-HFP copolymer and the second PVDF-HFP copolymer used as the polymer matrix is 6.5 to It is in the range of 7.5 weight%, and at the same time, it is providing the lithium polymer battery characterized by the average molecular weight in the range of 200,000-300,000.

According to a ninth aspect of the present invention, in the lithium polymer battery according to the sixth aspect, the first PVDF-HFP copolymer has an HFP content of 6 to 7 wt%, a molecular weight of 100,000 to 250,000, and a second PVDF-HFP The copolymer is to provide a lithium polymer battery having a HFP content of 7 to 12% by weight and a molecular weight of 200,000 to 470,000.

According to a tenth aspect of the present invention, in the lithium polymer battery according to the sixth aspect, the first PVDF-HFP copolymer has an HFP content of 7% by weight, a molecular weight of 600,000, and the second PVDF-HFP copolymer. The HFP content is 11% by weight, the molecular weight is 350,000, and the predetermined ratio of the first PVDF-HFP copolymer and the second PVDF-HFP copolymer is mixed in a composition ratio of 10% by weight and 90% by weight, respectively. It is to provide a lithium polymer battery characterized by.

The gel polymer electrolyte and the lithium polymer battery using the same according to the present invention include heterogeneous PVDF-HFP copolymers, while maintaining its mechanical strength and increasing ion conductivity inside the battery, thereby providing excellent charge and discharge characteristics.

Further advantages of the present invention will become apparent from the following description with reference to the accompanying drawings in which like or like reference numerals designate like elements.

Hereinafter, the present invention will be described with reference to embodiments of the present invention.

1 is a perspective view showing the internal cross-section of a lithium polymer battery according to the present invention, Figure 3 is a view showing the internal structure of a lithium polymer battery according to the present invention. 1 and 3, the lithium polymer battery of the present invention is a positive electrode (1); Cathode 2; A separator (3) that isolates the positive electrode (1) and the negative electrode (2); And a gel polymer electrolyte applied to the electrode surfaces of the positive electrode 1 and the negative electrode 2 and composed of a nonaqueous electrolyte and a polymer matrix.

More specifically, LiMeO ₂ (Me = Co, Ni, Mn), which is a lithium metal oxide, is used as the cathode active material used for the anode 1, and a carbon material is used as the cathode active material used for the anode 2, respectively. . In addition, aluminum foil (Al Foil) is used as the positive electrode current collector, copper foil (Cu Foil) is used as the negative electrode current collector, and polyethylene (hereinafter referred to as “PE”) is used as a separator. As the gel polymer electrolyte 4, a lithium salt, an organic solvent and a PVDF-HFP copolymer are used. The gel polymer electrolyte 4 is applied and impregnated on the surfaces of the positive electrode 1 and the negative electrode 2, and then the separator is sandwiched between the positive electrode 1 and the negative electrode 2 to be wound up. Obtained. After the obtained jelly roll is embedded in the aluminum pouch 5 and sealed, the positive electrode 1, the negative electrode 2 and the separator 3 are integrated by thermocompression to complete the lithium polymer battery according to the present invention.

As the polymer matrix of the gel polymer electrolyte 4 used in the present invention, PVDF-HFP copolymer is used, and as electrolyte, ethylene carbonate (hereinafter referred to as "EC") and propylene carbonate (hereinafter referred to as "PC") are used. 2 or more types of organic solvents, such as "," dissolved in a lithium salt are used.

The positive electrode 1 is composed of a mixture layer composed of a positive electrode active material, a conductive material and a binder, and a positive electrode current collector on which the mixture layer is immersed. LiMeO ₂ (Me = Co, Ni, Mn), which is the above-described lithium metal oxide, is used as the cathode active material, carbon black is used as the conductive material to increase the electronic conductivity of the electrode, and polyvinylidene fluoride (Poly) is used as the binder. Vinylidene Fluoride (hereinafter referred to as "PVDF") is used, and these cathode active materials, conductive materials and binders are used in a solvent of N-methyl-2-pyrrolidone (hereinafter referred to as "NMP"). Stirring produces a slurry. The slurry thus prepared is coated on an aluminum foil and dried to prepare an anode (1) electrode.

On the other hand, as the material constituting the negative electrode 2, a carbon-based material capable of occluding / desorbing lithium ions is used. Specifically, carbon materials such as pitch-based carbon, vapor-grown carbon body, carbon fiber, natural graphite, artificial graphite, and the like are used. Can be used. The negative electrode 2 is prepared by applying and drying a slurry prepared by stirring a negative electrode active material, carbon black as a conductive material, and PVDF as a binder in an NMP solvent, onto a copper foil.

The separator 3 is impregnated with a nonaqueous electrolyte, and any material capable of electrically isolating the positive electrode 1 and the negative electrode 2 may be used. Specifically, it is possible to use a film formed of a high molecular compound or a derivative thereof mainly composed of polyethylene (PE), polypropylene (hereinafter referred to as "PP"), or the like.

The gel polymer electrolyte 4 used in the present invention is composed of a lithium salt, an organic solvent and a polymer matrix. Lithium salts include lithium hexafluorophosphate (LiPF ₆ ), lithium perchlorate (LiClO ₄ ), lithium tetrafluoroborate (LiBF ₄ ), lithium trifluoromethanesulfate (LiCF ₃ SO ₃ ) and lithium hexafluoroacenate (LiAsF ₆₎ ) And these lithium salts are used alone or in combination of two or more thereof.

Examples of the organic solvent include cyclic carbonates such as ethylene carbonate (EC) and propylene carbonate (PC), cyclic esters such as gamma-butyrolactone (γ-Butyrolactone: hereinafter referred to as "GBL"), and dimethyl carbonate (dimethyl carbonate): DMC ”), chain carbonates such as ethyl methyl carbonate (hereinafter referred to as“ EMC ”) and diethylene carbonate (hereinafter referred to as“ DEC ”) are used, and these organic solvents may be used alone. Can be. However, when the organic solvent is used alone, the performance of the organic solvent may be limited. In a preferred embodiment of the present invention, two or more organic solvents are mixed and used.

As the polymer matrix, for example, polyethers such as polyethylene oxide (hereinafter referred to as "PEO") and polypropylene, polytetrafluoroethylene (hereinafter referred to as "PTFE") and PVDF Halogen element containing high molecular compounds, such as these, derivatives, copolymers, or mixtures thereof can be used.

Figure 2 is a view showing the structural formula of the PVDF-HFP copolymer according to the present invention. On the left side of Fig. 2, the unit VDF is shown, and a plurality (m) of them are combined to form PVDF. PVDF-HFP copolymer shown in Figure 2 is a copolymer of PVDF and HFP due to the combination of PVDF and HFP can control the mechanical strength and flexibility of the polymer material. That is, the polymer material having one composition is limited to the control of mechanical strength and flexibility, but the copolymer composed of two polymer materials, such as the PVDF-HFP copolymer of the present invention, is the amount of these two polymer materials. It is possible to control the mechanical strength and flexibility of the entire polymer by controlling the. In addition, in the PVDF-HFP copolymer, changing the combination ratio of PVDF and HFP changes the average molecular weight of the PVDF-HFP copolymer, thereby sufficiently characterizing the properties (mechanical strength and flexibility) of the PVDF-HFP copolymer as a polymer material. Since it can be changed, the PVDF-HFP copolymer of this invention can fully collect the electrolyte solution containing an organic solvent according to the combination ratio. Such PVDF-HFP copolymer itself is a known composition, but the present invention provides a gel polymer electrolyte composition comprising a PVDF-HFP copolymer having a specific combination ratio of PVDF and HFP and thus a specific molecular weight.

Referring to FIGS. 1 and 3 again, the positive electrode 1, the negative electrode 2 and the separator 3 in the lithium polymer battery of the present invention described above are connected in a chain by a PVDF-HFP copolymer to form an integrated structure. It can be seen that.

Hereinafter, specific examples of the present invention will be described in detail according to experimental results compared with the comparative examples.

Comparative Example

<Anode manufacturing>

The positive electrode is composed of a positive electrode active material consisting of 94% by weight of lithium cobalt oxide (LiCoO ₂ ), a conductive material consisting of 3% by weight of carbon black, a binder consisting of 3% by weight of PVDF, these positive electrode active materials, conductive material, and binding Each component of the agent is dispersed in an NMP solvent to prepare a positive electrode slurry. The prepared positive electrode slurry is applied in an intermittent pattern on an aluminum foil having a thickness of 15 μm. The NMP solution is then evaporated to dryness while passing the aluminum foil coated with the positive electrode slurry into the drying furnace. After pressing the dried aluminum foil with a roll press to produce a positive electrode sheet, it is cut to a width of 51.5mm. An anode electrode was fabricated by welding an aluminum terminal having a width of 4 mm and a thickness of 80 μm to an uncoated portion of the aluminum foil of the intermittent pattern method.

<Cathode manufacturing>

The negative electrode is composed of a negative electrode active material consisting of 90% by weight graphite powder, a conductive material consisting of 2% by weight carbon black, and a binder consisting of 8% by weight PVDF, and the graphite powder, conductive material, and binder are contained in an NMP solvent. Dispersion produces a negative electrode slurry. The prepared negative electrode slurry is applied to an copper foil having a thickness of 10 μm in an intermittent pattern. Thereafter, the NMP solution is evaporated to dryness while passing the copper foil coated with the negative electrode slurry into the drying furnace. The dried copper foil is pressed with a roll press to prepare a negative electrode sheet, and then cut to a width of 53.0 mm. A negative electrode was produced by welding a nickel terminal having a width of 4 mm and a thickness of 80 μm to a portion where the negative electrode slurry was not coated in the copper foil of the intermittent pattern method.

Preparation of Gel Polymer Electrolyte

The gel polymer electrolyte of the comparative example is prepared as follows. First, each component of the plasticizer constituting the gel polymer electrolyte, each component of the plasticizer constituting the gel polymer electrolyte, a lithium salt consisting of 10% by weight of lithium hexafluorophosphate (LiPF ₆ ), and 45% by weight of ethylene carbonate (EC ) And 45% by weight of propylene carbonate (PC) are taken, and these components are mixed with each of the lithium young and the organic solvent to prepare a nonaqueous electrolyte. Thereafter, a gel polymer electrolyte is prepared by mixing and dissolving a 35 wt% nonaqueous electrolyte, a polymer matrix composed of 5 wt% PVDF-HFP copolymer, and a diluting solvent composed of 60 wt% dimethyl carbonate (DMC). Here, the PVDF-HFP copolymer used as the polymer matrix comprises PVDF-HFP copolymer A (7 wt% HFP, molecular weight 200,000) and PVDF-HFP copolymer B (7 wt% HFP, molecular weight 600,000) each 10 wt% and Mix with a composition ratio of 90% by weight is used.

<Battery manufacturing>

The battery of the comparative example is manufactured as follows. First, the gel polymer electrolyte is applied onto the positive and negative electrode surfaces using a doctor blade and placed in a hot air circulating oven to remove dimethyl carbonate (DMC) by vaporizing at high temperature. In this way, a gel polymer electrolyte layer is formed on the surfaces of the anode and cathode electrodes. Thereafter, the polyethylene separator is sandwiched between the positive electrode and the negative electrode on which the gel electrolyte layer is formed and wound in the longitudinal direction. Subsequently, a finishing tape is attached to prevent the electrode roll from loosening to prepare a jelly roll. The jelly roll thus prepared is compressed to be easily stored in the aluminum pouch. Thereafter, the jelly roll is placed in an aluminum pouch, and the upper end of the aluminum pouch with the terminal is heat-sealed. Subsequently, the bubbles present in the jelly roll are removed by vacuum reduction, and then the side (side) portion of the aluminum pouch is heat-sealed and completely sealed. When the cell is thermally compressed at a high temperature for several minutes, the gel polymer electrolyte penetrates into the positive electrode, the negative electrode, and the separator, and the electrode and the separator are completely integrated. Thereafter, a lithium polymer battery having a thickness of 3.8 mm, a width of 35 mm, and a height of 62 m is obtained through a formation process.

Example 1

Example 1 according to the present invention is to prepare a lithium polymer battery in the same manner as the comparative example, PVDF-HFP copolymer C (HFP 11% by weight, molecular weight 350,000) and PVDF-HFP air as a polymer matrix of the gel polymer electrolyte A mixture of Copolymer B (7 wt% HFP, molecular weight 600,000) with a composition ratio of 10 wt% and 90 wt%, respectively, is used.

Example 2

Example 2 according to the present invention is to prepare a lithium polymer battery in the same manner as the comparative example, PVDF-HFP copolymer D (HFP 12% by weight, molecular weight 150,000) and PVDF-HFP air as a polymer matrix of the gel polymer electrolyte A mixture of Copolymer E (6 wt% HFP, 200,000 molecular weight) in a composition ratio of 30 wt% and 70 wt%, respectively, is used.

Example 3

Example 3 according to the present invention is to prepare a lithium polymer battery in the same manner as the comparative example, PVDF-HFP copolymer D (HFP 12% by weight, molecular weight 150,000) and PVDF-HFP air as a polymer matrix of the gel polymer electrolyte A mixture of copolymer E (6 wt% HFP, 200,000 molecular weight) in a composition ratio of 20 wt% and 80 wt%, respectively, is used.

Example 4

Example 2 according to the present invention is to prepare a lithium polymer battery in the same manner as the comparative example, PVDF-HFP copolymer D (HFP 12% by weight, molecular weight 150,000) and PVDF-HFP air as a polymer matrix of the gel polymer electrolyte A mixture of Copolymer E (6 wt% HFP, 200,000 molecular weight) in a composition ratio of 10 wt% and 90 wt%, respectively, is used.

Example 5

Example 5 according to the present invention is to prepare a lithium polymer battery in the same manner as the comparative example, PVDF-HFP copolymer E (HFP 6% by weight, molecular weight 200,000) and PVDF-HFP air as a polymer matrix of the gel polymer electrolyte A mixture of Copolymer C (11 wt% HFP, 350,000 molecular weight) in a composition ratio of 20 wt% and 80 wt%, respectively, is used.

Example 6

Example 6 according to the present invention is to prepare a lithium polymer battery in the same manner as in the comparative example, PVDF-HFP copolymer E (HFP 6% by weight, molecular weight 200,000) and PVDF-HFP air as a polymer matrix of the gel polymer electrolyte The mixture F (12 weight% of HFP, 470,000 molecular weight) was mixed in the composition ratio of 20 weight% and 80 weight%, respectively.

Example 7

Example 7 according to the present invention is to prepare a lithium polymer battery in the same manner as the comparative example, PVDF-HFP copolymer F (HFP 12% by weight, molecular weight 470,000) and PVDF-HFP air as a polymer matrix of the gel polymer electrolyte A mixture of copolymer G (8 wt% HFP, molecular weight 450,000) in composition ratios of 10 wt% and 90 wt%, respectively, is used as the polymer matrix.

Example 8

Example 8 according to the present invention is to prepare a lithium polymer battery in the same manner as in the comparative example, PVDF-HFP copolymer E (HFP 6% by weight, molecular weight 200,000) and PVDF-HFP air as a polymer matrix of the gel polymer electrolyte The mixture G (8 weight% of HFP, molecular weight 450,000) was mixed in the composition ratio of 10 weight% and 90 weight%, respectively.

-Charge / discharge life evaluation experiment

First, for the lithium polymer battery according to the comparative example and the embodiments of the present invention, the constant current up to 3.15V with a constant-current charge of 0.05C in one step with respect to the battery design capacity at the initial charge (initial charge) The battery was charged, and the constant current-constant voltage charging was performed by setting the constant current at 0.2C and the charge upper limit voltage at 4.2V in two steps. Then, after the stabilization process of the battery was discharged to a discharge lower limit voltage 3.0V at a constant current of 0.2C. Thereafter, charging was performed for 3 hours at a constant current of 0.5C and a charge upper limit voltage of 4.2V, and discharge was performed up to a constant current of 0.5C and a discharge lower limit voltage of 3.0V to evaluate charge and discharge life characteristics of the lithium polymer battery. Its evaluation results are shown in Figure 4, which is shown in Table 1.

Table 1

battery impedance Initial discharge capacity Discharge capacity at 300 cycles Comparative Example ≒ 34mΩ 803 mAh 700 mAh Example 1 Ω 33mΩ 786 mAh 686 mAh Example 2 Ω 33mΩ 795 mAh 709 mAh Example 3 Ω 33mΩ 801 mAh 724 mAh Example 4 3.533.5mΩ 803 mAh 703 mAh Example 5 Ω 33mΩ 821 mAh 753 mAh Example 6 Ω 33mΩ 815 mAh 743 mAh Example 7 Ω 33mΩ 777 mAh 675 mAh Example 8 Ω 33mΩ 820 mAh 763 mAh

As can be seen from Table 1, in the embodiment of the lithium polymer battery according to the present invention, as the polymer matrix for gel polymer electrolyte, the PVDF-HFP copolymer having HFP content of 7-12 wt% and the HFP content of 6-7 wt% It can be seen that the charge and discharge characteristics of the lithium polymer battery can be greatly improved by using a mixture of% PVDF-HFP copolymer. In particular, in the case where two kinds of PVDF-HFP copolymers having different HFP contents are mixed and used, as in Examples 5 and 8, the average HFP content is 6.5 to 7.5% by weight and the average molecular weight is 200,000 to 300,000. It is clearly shown that the effect of the discharge characteristics is excellent. These results indicate that the PVDF-HFP copolymer having an HFP content of 7 wt% or less plays a role in maintaining the mechanical strength of the polymer matrix, and that the PVDF-HFP copolymer having an HFP content of 7 wt% or more contributes to the improvement of ion conductivity. do.

As described above, the lithium polymer battery according to the present invention is a polymer matrix for gel polymer electrolyte by using a PVDF-HFP copolymer having a HFP content of 7 wt% or less and a PVDF-HFP copolymer having a HFP content of 7 wt% or more, The effect of greatly improving the discharge capacity and the charge / discharge life characteristics of the lithium polymer battery is achieved. In particular, an excellent effect is achieved when the average HFP content is 6.5 to 7.5% by weight and the average molecular weight is 200,000 to 300,000 in the mixed use of PVDF-HFP copolymer.

As various modifications may be made to the constructions and methods described and illustrated herein without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings be exemplary, and not intended to limit the invention. It is not. Therefore, the scope of the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims (10)

 In the gel polymer electrolyte composition for a lithium polymer battery, The gel polymer electrolyte composition includes a non-aqueous electrolyte containing lithium ions and a polymer matrix containing a PVDF-HFP copolymer, The PVDF-HFP copolymer is composed of a first PVDF-HFP copolymer having an HFP content of 6% by weight and a second PVDF-HFP copolymer having an HFP content of 8% by weight, The first PVDF-HFP copolymer and the second PVDF-HFP copolymer are mixed in a ratio of 10% by weight to 90% by weight, The molecular weight of the first PVDF-HFP copolymer is 200,000, and the molecular weight of the second PVDF-HFP copolymer is 450,000. Gel polymer electrolyte composition for lithium polymer batteries. delete delete delete delete In a lithium polymer battery, anode; cathode; A separator to isolate the anode and the cathode; And Gel polymer electrolyte composition is applied to the electrode surface of the positive electrode and the negative electrode, respectively, consisting of a polymer matrix containing a non-aqueous electrolyte containing lithium ions and a PVDF-HFP copolymer Including, The PVDF-HFP copolymer is composed of a first PVDF-HFP copolymer having an HFP content of 6% by weight and a second PVDF-HFP copolymer having an HFP content of 8% by weight, The first PVDF-HFP copolymer and the second PVDF-HFP copolymer are mixed in a ratio of 10% by weight to 90% by weight, The molecular weight of the first PVDF-HFP copolymer is 200,000, and the molecular weight of the second PVDF-HFP copolymer is 450,000. Lithium polymer battery. delete delete delete delete

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