KR20030093051A - Method Of Fabricating Lithium Ion Battery - Google Patents

Abstract

PURPOSE: A method for preparing a lithium ion battery is provided, to obtain a lithium ion battery employing a gel electrolyte having a high voltage, a high energy, an excellent cycle characteristic and physical properties to be controlled easily. CONSTITUTION: The method comprises the steps of inserting a precursor containing an electrolyte solution into an electrode laminated structure comprising a positive electrode layer(2) and a negative electrode layer(4) which contain an active material capable inserting or taking out a lithium ion and are placed on a positive electrode current collector(1) and a negative electrode current collector(5), respectively and a separator(3) placed between the positive electrode layer and the negative electrode layer; and thermal polymerizing the precursor to prepare a gel-phase electrolyte. Preferably the electrode laminated structure is inserted into an aluminum laminate film(6), a precursor containing any one between a reactive monomer and a macromer and an electrolyte solution are inserted, and the precursor is thermally polymerized.

Description

Manufacturing method of lithium ion battery {Method Of Fabricating Lithium Ion Battery}

The present invention relates to a method for manufacturing a lithium ion battery, and more particularly, to a method for manufacturing a lithium ion battery using a gel polymer electrolyte.

In recent years, there has been a demand for higher performance of batteries due to miniaturization and weight reduction of devices such as mobile phones and notebook computers. In particular, in order to cope with the miniaturization of the main body of the apparatus, miniaturization of the battery and securing of capacity at the same time, that is, high energy density are required. Lithium ion batteries have high energy density and have high voltage, so that research and development has been actively conducted. In particular, the gel polymer battery is a secondary battery having high energy density as well as no electrolyte leakage, and can be used as an energy source in various portable devices.

The lithium ion battery is composed of a positive electrode, a negative electrode, a lithium salt and a non-aqueous electrolyte capable of inserting and removing lithium ions. The reason why non-aqueous electrolyte is used is that lithium cannot be stably present because of its high reactivity with water. Therefore, a non-aqueous electrolyte is used for a lithium battery. However, most of the non-aqueous electrolytes are organic compound liquids, which are flammable and odorous, and have a risk of leakage and ignition. For this reason, in recent years, in order to improve safety, a battery in which a non-aqueous electrolyte is replaced with a gel electrolyte has been developed. In a gel electrolyte, fluidity | liquidity falls remarkably and maintains shape, maintaining electrolyte solution characteristics, such as ionic conductivity. In addition, the volatilization rate is also suppressed. Therefore, the risk of leakage or fire is lowered.

In general, in a lithium ion battery, a positive electrode or a negative electrode is prepared by applying a mixture containing a positive electrode active material or a negative electrode active material, an electrolyte, a conductive material, and a binder on a current collector such as aluminum foil (Al foil) or copper foil (Cu Foil). . As the gel electrolyte, a method of preparing a gel polymer film, laminating with an electrode, injecting a liquid electrolyte solution, and laminating an electrode group, and then injecting and thermally polymerizing a precursor mixed with a reactive monomer, a polymerization initiator, and an electrolyte solution are used.

However, in the above method, when the reactive monomer is used alone when preparing the gel electrolyte, it is not easy to control the physical properties of the gel.

The present invention has been made to solve the above-described problems, to provide a method for producing a lithium ion battery using a gel polymer electrolyte having a high voltage and high energy, excellent cycle characteristics and easy control of the physical properties of the gel Its purpose is.

The inventors of the present invention intensively studied to obtain a lithium ion battery using a gel polymer electrolyte having a high voltage, a high energy density, excellent cycle characteristics, and minimizing problems such as leakage, as a result of reactive monomers or macromonomers ( It has been found that various properties can be obtained by changing the mixing ratio using a macromonomer and a reactive modifier.

Specifically, the positive electrode and the negative electrode are coated and pressed on the collector with a layer containing an active material capable of inserting and removing lithium ions, and laminated in the order of the positive electrode, the separator, and the negative electrode, and then inserted into an aluminum laminate film. do. Thereafter, a precursor mixed with a liquid electrolyte solution, a reactive monomer or macromonomer, a reactive modifier, a polymerization initiator, and the like is injected and vacuum-sealed. Thereafter, the gel polymer electrolyte is prepared by maintaining the polymerization in a constant temperature chamber at 60-80 ° C. for up to 1 hour 30 minutes.

1A to 1C are cross-sectional views illustrating a manufacturing process of a lithium ion battery according to the present invention;

2 is a view showing a state in which the laminated structure of Figure 1c is inserted into an aluminum laminate film,

3 is a diagram illustrating a cyclic voltammogram of a polyurethane acrylate gel polymer electrolyte,

4 is a view measuring the change in ion conductivity according to the temperature of the gel polymer electrolyte,

5 is a view measuring the change in the ionic conductivity according to the addition amount of the reactive modifier,

6 is a view measuring the capacity of each discharge rate of a lithium ion battery using a gel polymer electrolyte,

7 is a view of measuring the capacity according to the temperature of the lithium ion battery using the gel polymer electrolyte.

※ Explanation of code for main part of drawing

1: positive electrode current collector 2: positive electrode

3: separator 4: cathode

5: negative electrode current collector 6: exterior material (aluminum laminate film)

Hereinafter, a lithium ion battery according to an embodiment of the present invention and a manufacturing method thereof will be described with reference to the accompanying drawings.

First, as illustrated in FIG. 1A, LiCoO ₂ as a cathode active material, Super P black as a conductive material, and PVdF as a dispersant are mixed at a ratio of 91: 6: 3 (wt%) to form an aluminum foil. Or after coating on a copper foil (Cu foil) collector (1), and dried, compressed to prepare a positive electrode (2). The positive electrode active material may be a transition metal oxide capable of inserting and deintercalating lithium ions, a composite oxide of lithium and a transition metal, and the like.

In addition, as shown in Figure 1b, by mixing MCF (Milled Carbon Fiber) as a negative electrode active material, Super P black as a conductive material, PVdF as a dispersant in a ratio of 90: 2: 8 (wt%), copper foil (Cu foil) After coating on the current collector (5), and dried, compressed to prepare a negative electrode (4). As the negative electrode active material, graphite or carbon-based material capable of inserting and removing lithium ions is used.

After that, the positive electrode portions of the positive electrode current collector 1 and the positive electrode 2 prepared above, and the negative electrode portions of the negative electrode current collector 5 and the positive electrode 4 prepared above, are shown in FIG. 1C. After the cathode 4 and the cathode 4 face each other and are laminated in such a manner as to sandwich a separator (Polyethylene or Polypropylene) 3 therebetween, the laminated structure is used as an exterior material of a battery as shown in FIG. 2. Al laminate film) (6). Here, the aluminum laminate film 6 is composed of a plastic layer made of PET, Nylon, and the like, an aluminum layer, and an adhesive layer.

Precursors for preparing a gel polymer electrolyte consisted of a liquid electrolyte, a reactive macromer, a reactive modifier, and a polymerization initiator. Specifically, 1M LiPF ₆ / EC + DEC (5 + 5 vol%) as an electrolyte, urethaneacrylate having a trifunctional group as a macromer, HDDA (Hexanediol diacrylate) as a reactive modifier, and BPO (as polymerization initiator). Benzoyl Peroxide) was used. The mixing ratio of the liquid electrolyte and the curable mixture (macromer + reactive modifier + polymerization initiator) in the precursor was set to 95: 5 (vol%).

After the precursor is injected into the aluminum laminate film 6 into which the electrode is inserted, a predetermined pressure and heat are applied to the sealing portion 7 of the aluminum laminate film 6 under vacuum. After that, the mixture is stored at room temperature for about 3 days, and the polymerization is performed after the precursor is sufficiently impregnated into the separator and the electrode. The polymerization was performed using a constant temperature chamber in which the temperature was kept constant, and the temperature was performed at 80 ° C. for 60 minutes.

FIG. 3 shows the results of Cyclic Voltammetry of a Gel Polymer Electrolyte in which the content of polyurethane acrylate and HDDA is 1: 1 vol% and 5 vol% is added to the liquid electrolyte. . As can be seen from the figure, 4.5 V vs. No current peak is observed in the voltage range up to Li / Li ⁺ . This indicates that it is electrochemically stable.

4 shows the ion conductivity according to the temperature of the gel polymer electrolyte. In the case of the liquid electrolyte, the ion conductivity at room temperature is about 8 × 10 ⁻³ S / cm, and in the polyurethane acrylate gel polymer electrolyte, it is about 4 × 10 ⁻³ S / cm. This value is higher than the conventional gel polymer electrolyte, and is expected to have excellent discharge characteristics at high and low temperatures.

Figure 5 shows the room temperature ion conductivity when the content of HDDA in the gel polymer electrolyte. If the HDDA content is high, the mechanical strength is expected to increase further. The ion conductivity increased up to 200 phr of HDDA, but slightly decreased at 300 phr.

Figure 6 shows the capacity characteristics according to the discharge rate of the lithium ion battery using a gel polymer electrolyte. The capacity at 0.2 C of a lithium ion battery containing about 5 vol% of a reactive mixture is about 70 mAh. Based on this, the capacity at the 1.0C discharge rate was about 55 mAh, representing about 80%.

Figure 7 shows the capacity characteristics according to the discharge rate of a lithium ion battery using a gel polymer electrolyte. The capacity at 20 ° C. of a lithium secondary battery containing about 5 vol% of a reactive mixture is about 650 mAh. Based on this, the capacity at -10 ° C was about 550mAh, representing about 85%.

On the other hand, the present invention is not limited to the above-described typical preferred embodiments, but can be carried out in various ways without departing from the gist of the present invention, various modifications, alterations, substitutions or additions are common in the art Those who have knowledge will easily understand. If the implementation by such improvement, change, replacement or addition falls within the scope of the appended claims, the technical idea should also be regarded as belonging to the present invention.

As described in detail above, according to the present invention, the ion conductivity of the gel polymer electrolyte is as high as about 10 ⁻³ S / cm, and the electrolyte solution is formed in a gel form, so that there is no fear of leakage. In addition, by adjusting the mixing ratio of the reactive macromer and the reactive modifier, physical properties such as ion conductivity and mechanical properties can be changed. In addition, the productivity is high due to the simplification of the production process.

Claims (6)

An electrolyte solution in an electrode laminated structure in which a positive electrode layer and a negative electrode layer containing an active material capable of inserting and removing lithium ions are placed on a positive electrode current collector and a negative electrode current collector, respectively, and a separator is interposed between the positive electrode layer and the negative electrode layer. Method of producing a lithium ion battery, characterized in that the precursor is injected into a gel electrolyte after thermal polymerization. The method of claim 1, The electrode laminated structure is inserted into an aluminum laminate film, and any one of a reactive monomer, a macromer, and a precursor including an electrolyte solution are injected, followed by heating, polymerization to polymerize to produce a gel polymer electrolyte. Way. The method of claim 2, Reactive monomers or macromers, and reactive modifiers are added to the precursor to change the composition ratio thereof to change the physical properties of the gel polymer electrolyte. The method of claim 3, The macromer is a polyurethane acrylate (Polyurethaneacrylate) having two or more double bonds, and the reactive modifiers are HDDA (Hexanediol diacrylate) and triethylene glycol dimethacrylate (Triethyleneglycoldimehta-crylate), tetraethylene glycol di Method for producing a lithium ion battery, characterized in that using any one of acrylate (Tetraethyleneglycoldiacrylate). The method of claim 3, The precursor is composed of a liquid electrolyte and a curable mixture, the ratio of the lithium ion battery, characterized in that the ratio is in the range from 85:15 (vol%) to 97: 3 (vol%). The method of claim 5, The curable mixture comprises a macromer, a reactive modifier and a polymerization initiator.