KR20000045100A - Method for manufacturing a secondary lithium ion battery using a polymer electrolyte - Google Patents

Abstract

PURPOSE: A method for manufacturing a secondary lithium ion battery using a polymer electrolyte is provided to easily regulate the capacity of the battery by regulating the length, the width, and the number of windings. Further, the shape of the battery can be easily changed. CONSTITUTION: A circular secondary lithium ion battery is manufactured by winding four plates. The four plates comprises a cathode plate(1), a composite film(3), an anode plate(4), and a composite film(6). The cathode plate(1) is formed by coating carbon or black lead on both surface of a copper foil(2). The anode plate(4) is formed by coating lithium metal oxide on both surfaces of an aluminum foil.

Description

Manufacturing method of lithium ion secondary battery using polymer electrolyte

The present invention relates to a method for manufacturing a lithium ion secondary battery using a polymer electrolyte, and more specifically, to manufacture a battery of high capacity, without having to manufacture and stack a plurality of single cells, the length and width of the cell structure and the number of windings The present invention relates to a method for manufacturing a lithium ion secondary battery using a polymer electrolyte capable of freely modifying the capacity of a single cell as well as controlling the capacity of the cell.

Recent developments in the information and telecommunications industry have led to the need for batteries that can be miniaturized, lightweight, thin, and portable, and have high energy density. Lithium-based secondary batteries using a lithium metal having a high energy density as a negative electrode and a liquid solvent as an electrolyte have been difficult to prolong the life of the battery and to ensure safety due to the dendrite phenomenon. In order to improve this disadvantage, crystalline or amorphous carbon that can absorb a large amount of lithium ions instead of lithium metal is composed of a gel polymer electrolyte composite in which a solid polymer electrolyte or an organic solvent and a salt are mixed with a polymer instead of a negative electrode or a liquid electrolyte. One is a lithium ion polymer battery. It is free from leakage, and can be manufactured in various forms of batteries such as thin films by using the characteristics of polymers, and there are many advantages in terms of the possibility of innovatively simplifying the manufacturing process according to the improvement of technology and securing the safety of batteries. have.

However, polymer electrolytes that have been used in the manufacture of lithium-ion batteries so far can be classified into two types: lithium salt and plasticizer, polymer gel type including organic solvent and completely solid polymer electrolyte without organic solvent. The latter has the disadvantages of excellent mechanical properties but poor ionic conductivity, which cannot be used at room temperature, while the former exhibits high ionic conductivity similar to the ionic conductivity obtained from organic solvents at room temperature, but the disadvantages of low mechanical properties make the battery manufacturing process difficult. There is this. In particular, the polymer gel has fluidity, which increases the resistance of the electrode during charging and discharging, thereby degrading the life of the battery. Also, due to the lack of mechanical properties, it is difficult to make the polymer gel electrolyte into a film, which makes the assembly process of the battery difficult. have.

Therefore, not only the process of manufacturing a single cell having a certain size of capacity is difficult, but also a process of stacking a plurality of single cells is required when manufacturing a high capacity battery. For example, using a polymer electrolyte composite film using poly (vinylidene fluoride-co-hexafluoropropylene) (poly (vinylidene fluoride-co-hexafluoropropylene) hereinafter referred to as "P (VdF-co-HFP)") In order to manufacture a lithium-ion polymer, 1) insert a net-shaped current collector (X-met) between two sheets of electrode sheets prepared in advance and use a roll presser to maintain a temperature of 100 ° C. or higher. 2) The P (VdF-co-HFP) film is sandwiched between the positive electrode and the negative electrode fused on both sides of the current collector, and sandwiched. 3 cells were prepared, and 3) di-butyl phthalate (DBP), which was already contained in the electrode and polymer membrane manufacturing process, was extracted in an ether solvent to extract porosity, and 4) it was thoroughly dried in a vacuum oven. And then 5) One unit cell is completed through the process of injecting the electrolyte by dipping in a liquid electrolyte composed of a carbonate-based mixed organic solvent to infiltrate the electrode and the polymer separator. In the case of manufacturing a battery through such a process, it is inconvenient to stack a plurality of single cells and additionally involves welding and attaching a tab to each single cell, which not only complicates the manufacturing process of the battery but also requires various batteries. There is a disadvantage that can not flexibly respond to changes in the form and dosage of.

Accordingly, it is an object of the present invention to provide a method for easily manufacturing a battery by improving the disadvantages of the battery manufacturing process described above.

In the manufacturing method of the present invention for achieving the above object, in the method of manufacturing a lithium secondary battery, a negative electrode plate coated with carbon or graphite on both sides of the negative electrode current collector to a predetermined thickness, a first polymer gel electrolyte composite film, a positive electrode current collector Forming a thin film in the form of a film by squeezing a circular or elliptical cell structure obtained by winding a positive electrode plate coated with lithium metal oxides on both sides in a predetermined thickness and four plates arranged in the order of the second polymer gel electrolyte composite film to a desired length. It consists of

1 is a schematic view showing the arrangement of a battery assembly for battery assembly according to the present invention.

2 is a manufacturing process chart of a lithium ion polymer battery using a polymer electrolyte film according to the present invention.

3 is a graph showing charge and discharge characteristics of a lithium ion polymer battery prepared according to the method of the present invention.

4 is a graph showing the cycle life of the lithium ion polymer battery prepared according to the method of the present invention.

※ Explanation of codes for main parts of drawing

1: negative electrode plate 2: negative electrode current collector

3: first polymer electrolyte film 4: positive electrode plate

5: positive electrode current collector 6: second polyelectrolyte film

11 and 13: polymer gel composite electrolyte film 12: anode

14: cathode 15 and 16: polymer gel electrolyte

17: winder 18: pressing process of the electrode assembly

19: battery pressed in thin film 20: tab attach process

21: Vacuum-packed cell in plastic

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

1, the present invention is a negative electrode plate (1), the first polymer gel electrolyte composite film (3), a positive electrode coated with carbon or graphite on both sides of a copper foil (2), which is a negative electrode current collector Circular sheet obtained by winding four plates arranged in order of the positive electrode plate 4 and the second polymer gel electrolyte composite film 6 coated with lithium metal oxide with a constant thickness on both surfaces of the aluminum foil 5 as the current collector, or The present invention relates to a method of manufacturing a thin film in the form of a film by pressing an elliptical battery assembly.

In other words, as shown in Figure 2, a battery composed of a polymer gel composite electrolyte film 11, a double-coated positive electrode film 12, a polymer gel composite electrolyte film 13, a double-coated negative electrode film containing a reinforcing agent After winding the structure in a circular or oval shape using a winder (winder, 17), it is compressed (18) to produce a thin (19), and then attached to the step (20) and put in a plastic packing bag 21 in a vacuum By sealing, a thin lithium ion polymer battery can be produced.

The present invention can easily adjust the capacity of the unit cell as well as freely deform the shape by adjusting the length, width and number of windings of the cell structure without the need to manufacture and stack a plurality of unit cells in order to manufacture a high capacity battery. There is an advantage.

On the other hand, as the polymer used in the preparation of the polymer gel composite electrolyte film of the present invention, polyethylene oxide and its copolymer, polyacrylonitrile (PAN) and its copolymer, poly (vinylidene fluoride) and its copolymer P (VdF- co-HFP), polymethyl methacrylate (PMMA), and polyvinyl chloride (PVC), such as a polar polymer alone or a mixture of two or more components of a carbonate organic solvent, a lithium salt and fumed SiO ₂ by mixing After the gel composition is prepared, it can be easily impregnated or coated with a reinforcing agent in a woven or non-woven form as a reinforcing agent to easily prepare a polymer electrolyte composite on a film. The amount of the polymer compound is preferably 5 to 30% by weight based on the polymer gel electrolyte mixture. In addition, the polymer gel electrolyte mixture is impregnated or coated as much as possible in the porous reinforcing agent, and the amount of such impregnation or coating is determined according to the thickness and porosity of the porous reinforcing agent. The thickness of commercially available reinforcing agents is usually about 20 to 80 μm, but a thinner reinforcing agent may be used. In the present invention, the thinner the reinforcing agent, the better.

Such a composite polymer electrolyte film has sufficient mechanical properties to prevent short circuits between electrodes, and easily laminates in the form of a sandwich of anode / polymer electrolyte / cathode, thereby greatly simplifying a battery assembly process.

As the reinforcing agent used in the present invention, woven or non-woven forms which are electrochemically stable and stable to carbonate organic solvents can be used, but polyester, nylon, polyethylene, polypropylene, polyurethane, and natural Inorganic polymers, such as glass fiber, as well as organic polymers, such as a polypeptide, are especially preferable.

The organic solvent used in the present invention is a linear carbonate such as cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), diethylene carbonate (DEC), dimethyl carbonate (DEC), etc. which can be used as a liquid electrolyte. System or mixtures thereof. In addition, all of the organic solvents that can dissolve lithium salts such as ether and ester and are electrochemically stable can be used. The amount of the carbonate-based organic solvent is preferably 60 to 90% by weight with respect to the polymer gel electrolyte mixture, less than 60% by weight of the ion conductivity is lowered, exceeds 90% by weight increases the interface resistance with the electrode.

As the salt used in the present invention, salts including lithium such as LiClO ₄ , LiPF ₆ , LiAsF ₆ , or Li (CF ₃ SO ₂ ) ₂ N can be used. The amount of the lithium salt is preferably 2 to 10% by weight based on the polymer gel electrolyte mixture, and less than 2% by weight of the ion salt is inferior.

In addition, in the present invention, fumed SiO ₂ is added in an amount of 0.1 to 2.0% by weight based on the polymer gel electrolyte mixture to obtain an effect of preventing the organic solvent from falling out of the polymer film.

The positive electrode material used in the production of a lithium ion battery using the polymer electrolyte composition prepared in the present invention is LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ or LiNi _1-x by adding Co, Ni, Mn to their lithium oxide It is more desirable to improve capacity and lifetime, such as Co _x 0 ₂ . In addition, it is effective to combine electronegativity and atomic weight of elements in the upper left and upper right of the periodic table. As such a compound, oxides, sulfides, selenides, halides and the like can be used.

As the material for the negative electrode, both low crystalline carbon and high crystalline carbon can be used as well as lithium metal. Low crystalline carbon includes soft carbon and hard carbon. Highly crystalline carbon includes natural graphite, Kish graphite, pyrolytic carbon, mesophase pitch based carbon fiber, Meso-carbon microbeads, Mesophase pitches High-temperature calcined carbon, such as petroleum or coal tar pitch derived cokes. In the case of using crystalline graphite, in the present invention, an organic solvent in which diethylene carbonate (DEC) or dimethyl carbonate (DMC) is mixed with ethylene carbonate (EC) having a high dielectric constant is used as a plasticizer of a polymer in order to prolong battery life. Good to do. The organic solvent as a plasticizer of the polymer should be prepared to mix the cyclic carbonate and the linear carbonate organic solvent to suit the properties of the carbon. In particular, it is preferable to combine them in consideration of the state of the carbon surface, the crystallinity, the type of electrolyte and the type of solvent, and their characteristics.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples. The unit "%" means "% by weight" unless otherwise specified.

Example 1

The positive electrode was coated with a sludge prepared by dissolving 85% LiCoO ₂ and 5% KS6 from Switzerland's Timcal Company, acetylene black and graphite-based conductive material, and 10% PVDF in Nmethylpyrrolidone (NMP). After drying, using a roll press was prepared by pressing a thickness of 20 to 30%. The final thickness was prepared at 80-140 μm. In the same manner, the negative electrode was prepared by coating 95% graphite and 5% PVDF on pitch-coated meso-carbon microbeads on a copper plate, and then compressing the electrode thickness using a roll press.

The polymer electrolyte was prepared by impregnating an ion conductive polymer gel in a natural polypeptide-based polymer in the form of a woven or nonwoven fabric. In this case, the polymer gel was prepared by heating a mixture composed of PAN, EC, PC, LiClO ₄ , and fumed SiO ₂ in a weight ratio of 15, 42, 42, 5, and 1, respectively, at 120 ° C. PAN used herein was used by mixing a polymer having a molecular weight distribution of 10,000 ~ 1,000,000 as appropriate, the thickness of the prepared polymer electrolyte composition was 25μm, and the ion conductivity of 2.3 × 10 ^-3 S / cm at 20 ℃ It was stable to 1.0-4.5V with respect to a lithium electrode.

The battery is arranged as shown in FIG. 1 using the polymer electrolyte membrane, the positive electrode, the polymer electrolyte membrane, and the negative electrode prepared as described above, wound into a cylindrical shape having a diameter of 3 cm and a width of 5 cm, and then compressed into a thin card of 3 cm × 5 cm. After preparing in the form of a vacuum-packed using a quadruple paper in the form of a bag coated with a polymer on aluminum. The charging and discharging characteristics of the battery were investigated while applying a constant current of 1 mA / cm ² between 2.8 V and 4.2 V. As shown in FIGS. 3 and 4, the charging and discharging capacity was 100 mAh or more at room temperature, based on the electrode active material. The utilization rate was over 95%, the initial charge and discharge efficiency was over 99%, and the life span was maintained more than 500 times.

Example 2

Same as the manufacturing process of the polymer electrolyte used in the battery prepared in Example 1, except that polyethylene fiber is used as the material of the woven or nonwoven fabric, and has an ion conductivity of 1.3 x 10 ^-3 S / cm and 1.0 to 4.6 for the lithium electrode. It was stable up to V. As a result of using the battery, the charge and discharge capacity was 100 mAh or more, and the utilization rate was 95% or more based on the electrode active material. The initial charge and discharge efficiency was 99% or more and the life was maintained 500 times or more.

Example 3

The same procedure as in the preparation of the polymer electrolyte used in the battery prepared in Example 1, except that the polypropylene fiber is used as a woven or nonwoven fabric, and has an ion conductivity of 1.5 × 10 ⁻³ S / cm and 1.0 to lithium electrode. It was stable up to 4.7V. As a result of using the battery, the charge and discharge capacity was 100 mAh or more, and the utilization rate was 95% or more based on the electrode active material. The initial charge and discharge efficiency was 99% or more and the life was maintained 500 times or more.

Example 4

It is the same as the manufacturing process of the polymer electrolyte used in the battery prepared in Example 1, except that when using the polypubide fiber as a material of woven or non-woven fabric, the ion conductivity of 2.3 × 10 ^-3 S / cm and 1.0 for the lithium electrode It was stable to -4.5V. As a result of using the battery, the charge and discharge capacity was 100 mAh or more, and the utilization rate was 95% or more based on the electrode active material. The initial charge and discharge efficiency was 99% or more and the life was maintained 500 times or more.

Example 5

All procedures were the same as in Example 1, except that DEC was used instead of PC when the polymer gel was used, and the ion conductivity of 5.3 × 10 ⁻³ S / cm was stable to 1.0 to 4.5V for the lithium electrode. As a result of using the battery, the charge and discharge capacity was 100 mAh or more, and the utilization rate was 95% or more based on the electrode active material. The initial charge and discharge efficiency was 99% or more and the life was maintained 500 times or more.

Example 6

All procedures are the same as in Example 1, except that 3 to 5% of the PVdF copolymer (2801) is added to the PAN used when the polymer gel is used, the ion conductivity of 3.3 x 10 ^-3 S / cm and 1.0 for the lithium electrode. It was stable to -4.5V. As a result of using the battery, the charge and discharge capacity was 100 mAh or more, and the utilization rate was 95% or more based on the electrode active material. The initial charge and discharge efficiency was 99% or more and the life was maintained 500 times or more.

Example 7

Example 1 and all process is the same, but the polymer, even if the addition of 3-5% of PVdF copolymer (2801) to use in the manufacture instead of PAN gel 3.2 × 10 ^-3 ionic conductivity in S / cm and the lithium electrode It was stable to 1.0-4.5V with respect to. As a result of using the battery, the charge and discharge capacity was 100 mAh or more, and the utilization rate was 95% or more based on the electrode active material. The initial charge and discharge efficiency was 99% or more and the life was maintained 500 times or more.

Example 8

All procedures were the same as in Example 1, except that PMMA was used instead of the PAN used to prepare the polymer gel, and was stable up to 1.0 to 4.5 V with respect to an ion conductivity of 3.2 × 10 ⁻³ S / cm and a lithium electrode. As a result of using the battery, the charge and discharge capacity was 100 mAh or more, and the utilization rate was 95% or more based on the electrode active material. The initial charge and discharge efficiency was 99% or more and the life was maintained 500 times or more.

9 to implementation

All procedures are the same as in Example 1, except that 3 ~ 5% of PMMA is added to the PAN used to prepare the polymer gel, and the ion conductivity of 5.2 × 10 ⁻³ S / cm and 1.0 to 4.5V for the lithium electrode are used. It was stable. As a result of using the battery, the charge and discharge capacity was 100 mAh or more, and the utilization rate was 95% or more based on the electrode active material. The initial charge and discharge efficiency was 99% or more and the life was maintained 500 times or more.

As described above, the method of the present invention can easily adjust the capacity of the unit cell by adjusting the length, width, and number of windings of the battery construct, without the need to manufacture and stack a plurality of unit cells in order to produce a high capacity battery. But there is an advantage that can freely change the form.

Claims (5)

In the method of manufacturing a lithium secondary battery, a negative electrode plate, a first polymer gel electrolyte composite film, a lithium metal oxide on both sides of the positive electrode current collector is coated with lithium or a carbon active material on both sides in a negative electrode collector Using a polymer electrolyte characterized in that the film is formed in a thin film form by compressing a round or oval battery assembly obtained by winding four plates arranged in the order of the positive electrode plate and the second polymer gel electrolyte composite film coated with a desired length. Method of manufacturing a lithium ion secondary battery. According to claim 1, wherein the polymer gel electrolyte composite film 5-30% by weight of a polymer compound, 60-90% by weight carbonate-based organic solvent, 2-10% by weight of lithium salt and 0.1-2.0% by weight of fumed SiO ₂ After preparing the gel composition, it is impregnated or coated in a woven or non-woven reinforcement of the manufacturing method of a lithium ion secondary battery using a polymer electrolyte, characterized in that the manufacturing. According to claim 2, wherein the polymer compound is polyethylene oxide and copolymers thereof, polypropylene oxide and copolymers thereof, polyacrylonitrile (PAN) and copolymers thereof, poly (vinylidene fluoride) and copolymers thereof P ( VdF-co-HFP), polymethyl methacrylate (PMMA), and polyvinyl chloride (PVC) is a method for producing a lithium ion secondary battery using a polymer electrolyte, characterized in that composed of one or more mixtures selected from the group consisting of . The method of claim 2, wherein the reinforcing agent is a woven or non-woven form of polyester, nylon, polyethylene, polypropylene, polyurethane, natural polypeptide, or glass fiber. Method of manufacturing a lithium ion secondary battery. The method of claim 1, wherein the carbonate-based organic solvent is one or more selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), diethylene carbonate (DEC) and dimethyl carbonate (DEC) Method of manufacturing a lithium ion secondary battery using a polymer electrolyte.