KR100404884B1 - Secondary battery using non-aqueous electrolyte - Google Patents

Abstract

PURPOSE: A secondary battery using a non-aqueous electrolyte is provided to reduce the time needed for injecting an electrolyte and water content in the electrolyte, thereby increasing the battery life. CONSTITUTION: The secondary battery using a non-aqueous electrolyte comprises: (a) a polyolefin separator having hydrophilic property by irradiation of ion particles, or ion particles and a reactive gas; (b) an electrolyte in a non-aqueous organic solvent; (c) an anode comprising a carbonaceous material capable of lithium intercalation/deintercalation as an anode active material; and (d) a cathode comprising a lithium-containing transition metal composite oxide as a cathode active material.

Description

Non-aqueous electrolyte secondary battery

The present invention relates to a non-aqueous electrolyte secondary battery. In particular, the present invention provides a method for absorbing lithium and a separator having hydrophilic properties by irradiating an ion particle or a mixture of ion particles with energy and a reactive gas such as argon, oxygen, air, krypton, N ₂ O, and mixtures thereof. A negative electrode having a carbon material capable of being released as a negative electrode active material and a nonaqueous electrolyte secondary battery using a lithium-containing transition metal composite oxide as a positive electrode active material.

If a non-aqueous electrolyte secondary battery using a carbon material capable of occluding and releasing lithium as an active material of a negative electrode and using a lithium-containing transition metal composite oxide as a positive electrode active material is injected with an electrolytic solution using a hydrophilic separator, the time required for absorbing the electrolyte solution is increased. By reducing the manufacturing process is shortened, the moisture content in the electrolyte is reduced to improve the life of the battery.

Recently, rechargeable batteries (secondary batteries), which provide power according to the miniaturization of electronic devices such as portable telephones, notebook computers, and video cameras, are becoming key components for determining the size, weight, and performance of the entire electronic device. In accordance with the trend of miniaturization of such electronic devices, non-aqueous electrolyte lithium secondary batteries having a higher energy storage density than nickel, nickel hydrogen, and lead storage batteries are widely used as rechargeable secondary batteries of small electronic devices.

However, as miniaturization and high performance of small electronic devices are further demanded, non-aqueous electrolyte lithium secondary batteries are becoming smaller and higher in performance. In particular, the life of the battery determines the usable time of the electronic device, and if the time required for recharging after discharge of the battery is long, the energy storage density of the battery decreases and the use time of the electronic device is shortened. It is an important factor in determining performance.

The life of the non-aqueous electrolyte lithium secondary battery depends on the degree (deterioration rate) of the performance of the active materials constituting the positive electrode and the negative electrode of the battery as the charge and discharge are repeated. In addition, impurities entering the battery manufacturing process may accelerate the deterioration rate, which may significantly shorten the life expectancy. In particular, moisture in the air is dissolved in the electrolyte, which is a component of the battery, which greatly shortens the life of the battery. Therefore, the battery is manufactured in a dry atmosphere environment (dry room) in which moisture in the air is reduced.

In general, moisture in the atmosphere until the battery is sealed continues to penetrate the electrolyte and remain in the electrolyte even after being sealed. The remaining water in the electrolyte reacts with the electrolyte to produce a highly corrosive gas, and the gas reacts with the active material of the positive electrode and the negative electrode to decrease performance. Therefore, the life of the battery is improved by shortening the time required for injecting the electrolyte into the battery and the exposure time after the injection as much as possible.

In the prior art, a method used to shorten the electrolyte injection time (including the time required for the electrolyte to be absorbed by the electrode) is to use a vacuum injection type to inject and evacuate the battery container, a pressurization type to pressurize after electrolyte injection, and centrifugal force Although various methods are used, such as centrifugal injection in a centrifuge or a mixture of two or more of these methods, the manufacturing process is complicated and expensive equipment requires the use of expensive equipment. .

Fundamentally, the rate at which the electrolyte is absorbed depends on the nature of the separator, which serves to carry electrolyte and support ions while preventing short circuits between the positive and negative electrodes, which are internal components of the battery. When the separator is hydrophilic, absorption of the electrolyte becomes easy, and when the separator is hydrophobic, absorption of the electrolyte becomes difficult. Rather than improving the injection method, using a hydrophilic separator is a fundamental solution to shorten the electrolyte injection time. That is, the battery using the hydrophilic separator is shortened the injection time of the electrolyte solution, the water content of the electrolyte is reduced, thereby improving the life of the battery.

The present invention irradiates the separator used in the non-aqueous electrolyte lithium secondary battery with ion particles or a mixture gas of the ion particles and a reactive gas to impart hydrophilicity to the surface of the separator to shorten the injection time of the electrolyte, and to reduce the moisture content of the electrolyte. It is intended to increase the life of the battery by reducing it. Ion particles or a mixture of ionic particles and reactive gases are irradiated during or after completion of the manufacturing process of the separator, and because the ion particles are very small, several hundred nanometers (nm = 10 ^-9 m), irradiation In the separator, spherical or elliptical micropores having a size of 0.05 μm to 1 μm are formed to impart hydrophilicity.

1 is a curve comparing the lifespan of a battery using a conventional separator and the battery of the present invention, and is a curve showing the ratio of the initial capacity of the battery according to the number of recharge cycles.

Separation membrane of the non-aqueous electrolyte secondary battery of the present invention is a polyolefin, in particular polypropylene, polyethylene or ion particles or ion particles having an energy of 0.01 to 10 keV during or during the production process of the polymer membrane composed of two or more of these multiple structures and A mixed gas of reactive gases (argon, oxygen, air, krypton, N ₂ O, and mixtures thereof) is irradiated to become hydrophilic.

The positive electrode of the battery of the present invention is a general formula Li _x M _1-y N _y O _z (M is Co, Ni, Mn; N is Al, In, Sn, Ga, Ge, Si, and transition metals, or mixtures thereof; 0.05 ≤ x ≤ 1.10, 0 ≤ y ≤ 0.5, 1.8 ≤ z ≤ 2.2), and the carbon as the conductive current collector powder is made by using a transition metal composite oxide containing lithium as a positive electrode active material and a fluorine resin compound as a binder. It is an electrode mixed and apply | coated to the aluminum current collector board | substrate.

The negative electrode of the battery of the present invention is an electrode in which a carbon-based material capable of occluding and releasing lithium is used as an active material, and a fluorine-based resin compound is mixed with a binder and coated on a copper current collector substrate.

The non-aqueous organic solvent electrolyte of the battery of the present invention is propylene carbonate (PC), ethylene carbonate (EC), butyl carbonate (BC), vinylene carbonate (VC), gamma- Butyl lactone (γ-butyl l actone), dimethyl carbonate (DMC), diethyl carbonate (DEC), dimethoxy ethane (DME), diethoxy ethane (DEE), etc. Can be used

As the electrolytic solute of the battery of the present invention, LiClO ₄ , LiPF ₆ , LiAlCl _4, LiAsF ₆ , LiBF ₄ and the like can be used.

The battery of the present invention is characterized by using an electrolyte solution in which the electrolytic solute is dissolved in an organic solvent and using a hydrophilic separator to reduce water content so that the water content is 300 ppm or less.

Next, the present invention will be described in detail with reference to Examples. However, the scope of the present invention is not limited by the following examples.

Example 1

The battery produced in Example 1 of the present invention is referred to as battery A.

[Production of Separator]

A polypropylene (PP) pore membrane (32% porosity) film having a thickness of 25 μm was introduced into a vessel having a vacuum degree of 10 ⁻³ to 10 ⁻⁶ torr, and argon particles (Ar +) were irradiated on both sides of the film using an ion gun. At the same time, a reactive gas (oxygen) was flowed to form micropores and hydrophilic treatment. At this time, the energy of the ion particles was 1 keV, the ion irradiation amount was 10 ¹⁶ ions / cm ² and the oxygen flow rate was 4 ml / min. In order to measure the hydrophilic property of the separator thus prepared, the rate of water absorption was measured. The measurement measured the speed of absorption by dropping water droplets into the separator and then time until the contact angle became zero while water was absorbed. As a result, the hydrophilicity was increased from 5.6 sec before treatment to 2.2 sec after treatment. The separator thus prepared was cut into a width of 58 mm and a length of 1300 mm.

[Manufacture of Anode]

Lithium cobalt oxide having a composition of LiCoO ₂ , acetylene black as a conductive current collector powder, and fluorinated resin compound (PVdF) as a binder are mixed in a weight ratio of 90: 5: 5, and the mixture is added to 100 parts by weight of an organic solvent NMP in weight ratio 35 A slurry was prepared by kneading at a ratio of and then applied to one side of the aluminum current collector to dry, and then the other side was applied as above and then dried. Then, pressure rolling was performed to prepare an electrode having a thickness of 180 um, a length of 470 mm, and a width of 54 mm. The aluminum tab to be connected to the outer conductor at one end was fused with a spot welder.

[Production of Cathode]

A crystalline carbon powder and a fluorine resin compound (PVdF) are mixed in a weight ratio of 90:10, and the mixture is kneaded in 100 parts by weight of an organic solvent NMP in a ratio of 70 by weight to prepare a slurry, and applied to one side of a copper current collector substrate. After drying, the other side was dried as above. Then, pressure rolling was performed to prepare an electrode having a thickness of 180 um, a length of 520 mm, and a width of 56 mm. The copper tab to be connected to the outer conductor at one end was welded with a spot welder.

[Lamination of Anode, Cathode and Separator]

The prepared cathode, cathode, and separator were laminated in a coil shape having an outer diameter of 17.1 mm using a winding device. At this time, the separator is wound in a coil shape between the anode and the cathode, and the aluminum tab fused to the anode is located upwardly toward the center of the jelly-roll, and the copper tab fused to the cathode is located outwardly downward.

[Charging of Jelly Roll]

The prepared jelly-roll was charged into a battery outer container having an outer diameter of 17.8 mm, and a negative electrode nickel tab positioned toward the bottom of the container was fused with a spot welder at the bottom of the cell outer container, and then a groove was formed in the upper part of the cell outer container. We have made a part of this.

[Electrolyte injection]

Electrolyte solution in which LiPF ₆ was dissolved at a concentration of 1M in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a 1: 1 (volume ratio) was added to a battery external container in a dry atmosphere having a dew point of -30 ^o C. Dropped and injected. In addition, as described above, the battery was prepared before sealing and assembling the battery, and the electrolyte absorbed amount and the water content of the electrolyte were measured according to the time elapsed after the electrolyte was injected. Specified in

[Sealed assembly of batteries]

After welding the aluminum foil of the positive electrode to the center of the battery lid insulated with the aluminum core in the center and insulated with polypropylene in the outside and putting the battery lid on the groove made in the jelly roll charging process and pressurizing The remaining upper part of the container was bent inward to seal it. The time required for sealing after the injection of the electrolyte solution was set to a time at which the absorption rate of the electrolyte solution was 90% or more, and the battery A of Example 1 was sealed from the result of the measurement of the electrolyte absorption rate and moisture content of the present invention. The time required to control was controlled to 10 minutes.

Example 2

The battery produced in Example 2 of the present invention is referred to as battery B.

The separator is the same as Example 1 described above, and the anode electrode is a lithium nickel cobalt composite oxide having a composition of LiNi _0.8 Co _0.17 Al _0.03 O ₂ , an acetylene black as a conductive current collector powder, and a fluorinated resin compound as a binder. : 5, and the mixture was kneaded in an organic solvent NMP at a weight ratio of 100: 40 to prepare a positive electrode in the same manner as in the manufacturing method of the positive electrode described in Example 1. In addition, the battery B of the present invention was prepared in the same manner as in Example 1 described above. The time required for sealing after the injection of the electrolyte solution was set to a time at which the absorption rate of the electrolyte solution was 90% or more, and the battery B of Example 2 was sealed from the result of the measurement of the electrolyte absorption rate and moisture content of the present invention. The time required to control was controlled to 10 minutes.

Example 3

The battery produced in Example 3 of the present invention is referred to as battery C.

The separator is the same as Example 1 described above, and the anode electrode is a lithium nickel cobalt composite oxide having a LiMn ₂ O ₄ composition, acetylene black as a conductive current collector powder, and a fluorine-based resin compound as a binder in a weight ratio of 82:10:10: The mixture was kneaded in an organic solvent NMP at a weight ratio of 100: 50 to prepare a positive electrode in the same manner as in the manufacturing method of the positive electrode described in Example 1. In addition, the battery C of the present invention was prepared in the same manner as in Example 1 described above. The time required for sealing after the injection of the electrolyte was set to a time at which the absorption rate of the electrolyte was more than 90%, and from the result of the embodiment of the measurement of the electrolyte absorption rate and water content of the present invention, the battery C of Example 3 was sealed with the electrolyte injection water. The time required to control was controlled to 10 minutes.

Comparative Example 1

As the separator, a conventional separator without hydrophilic treatment before irradiating the ion particles and the reactive gas was used as in Example 1, and the preparation of the anode and the cathode was made in the same manner as in Example 1 described above. In addition, the comparative battery D of the present invention was manufactured in the same manner as in Example 1 described above. The time required for sealing after the injection of the electrolyte was set to a time at which the absorption rate of the electrolyte was more than 90%, and the cell D of Comparative Example 1 was sealed after the injection of the electrolyte from the results of the examples of the measurement of the electrolyte absorption and the moisture content of the present invention. The time required to control was controlled to 30 minutes.

Example of Measurement of Electrolyte Absorption Ratio and Water Content

For the batteries A, B, C, and D prepared in Examples 1 to 3 and Comparative Examples described above, the same solution was prepared separately for the batteries before sealing assembling, and the electrolyte solution absorbed into the jelly roll over time after the injection of the electrolyte solution. To measure the amount, remove the remaining electrolyte solution without absorbing it at intervals of 5 to 10 minutes, and measure the mass to calculate the amount of electrolyte absorbed by the jelly roll from the difference with the injected amount. Calculated by absorbance. In addition, the water content in the electrolyte was measured and compared with Karl-Fischer moisture meter over time. The results are illustrated in the table of FIG. 1. The cells A, B, and C of the present invention absorb 90% or more of the electrolyte in the jellyroll within 10 minutes, while the comparative battery D has an absorption rate of 60% or more after 10 minutes, but after 30 minutes, the 90% or more It has an absorption rate. However, when the time elapsed after the injection of the electrolyte (that is, the atmosphere exposure time of the electrolyte) was within 10 minutes, the water content in the electrolyte was within 100 ppm, and after 30 minutes, the water content was about 300 ppm. Therefore, the batteries A, B, and C of the present invention can be manufactured with a time required to absorb at least 90% of the electrolyte to 10 minutes, so that the moisture content of the electrolyte is controlled to 100 ppm or less, but the battery D of Comparative Example 1 The time required is more than 30 minutes and the water content exceeds 300 ppm.

Example of life evaluation of a battery

For the batteries A, B, C, and D prepared in Examples 1 to 3 and Comparative Examples described above, the battery capacities according to the recharge cycles were measured to compare the lifetimes of the batteries A, B, and C of the present invention and the comparative battery D. Evaluated. Charge and discharge conditions are as follows. The non-aqueous solution was prepared by discharging in a constant current method under a condition of a constant charging current of 1.0 A, a constant voltage of 4.1 V, and a charging time of 2.5 h, and a discharge constant current of 1.0 A and a termination voltage of 3.0 V. The electrolyte cell was charged and discharged. The lifespan was evaluated by the percentage of each cycle based on the discharge capacity of the first cycle, and the result shows the battery capacity ratio according to the number of cycles. Compared with the battery D of Comparative Example 1 of the present invention, the batteries A, B, and C of the present invention, in which the atmospheric exposure time of the electrolyte solution was reduced from 30 minutes to 10 minutes and the electrolyte moisture content was controlled to within 100 ppm, have a superior battery life. Improved.

The amount of electrolyte absorption and the water content of the electrolyte according to the time elapsed after the injection of the electrolyte Electrolyte absorption amount ratio according to elapsed time after electrolyte injection Moisture content in electrolyte according to elapsed time after electrolyte injection (ppm) 5 minutes 10 minutes 20 minutes 30 minutes 0 min 5 minutes 10 minutes 20 minutes 30 minutes Battery A 81.9 96.3 99.5 100 12 30 85 160 300 Battery B 78.5 94.7 98.5 100 12 35 82 158 305 Battery C 74.5 92.3 97.5 100 12 32 84 160 300 Battery D 36.7 58.8 80.9 90.3 12 35 85 165 310

From the above results, as described in Examples 1 to 3 of the non-aqueous electrolyte secondary battery, the production time of the battery is shortened by using an ion particle or a separator in which the ion particles and the reactive gas are irradiated and imparted hydrophilic property As a result, the battery life can be improved by reducing the electrolyte moisture content by reducing the electrolyte exposure time.

Claims (8)

In a non-aqueous electrolyte secondary battery, a) a polyolefin separator having ion hydrophilic property by irradiating ion particles or reactive particles with a reactive gas; b) non-aqueous organic solvent electrolyte; c) a negative electrode comprising a carbon material capable of occluding and releasing lithium as a negative electrode active material; And d) A non-aqueous electrolyte secondary battery comprising a positive electrode with a lithium-containing transition metal composite oxide as a positive electrode active material. The method of claim 1, A non-aqueous electrolyte secondary battery, wherein the polyolefin isolation membrane is a polypropylene polymer membrane, a polyethylene polymer membrane, or a polymer membrane having a multilayer structure composed of two or more of these polymer membranes. The method of claim 1, The positive electrode active material is a general formula Li _x M _1-y N _y O _z (M is Co, Ni, Mn, N is Al, In, Sn, Ga, Ge, Si, and transition metals, or mixtures thereof; 0.05≤x A non-aqueous electrolyte secondary battery, wherein the lithium-containing transition metal composite oxide is ≦ 1.10, 0 ≦ y ≦ 0.5, 1.8 ≦ z ≦ 2.2). The method of claim 1, Electrolytes include propylene carbonate (PC), ethylene carbonate (EC), butyl carbonate (BC), vinylene carbonate (VC), gamma-butyl lactone, A non-aqueous electrolyte secondary battery which is dimethyl carbonate (DMC), diethyl carbonate (DEC), dimethoxy ethane (DME), and diethoxy ethane (DEE). The method of claim 4, wherein A non-aqueous electrolyte secondary battery in which the electrolytic solutes are LiClO ₄ , LiPF ₆ , LiAlCl ₄ , LiAsF ₆ , LiBF ₄ . The nonaqueous electrolyte secondary battery according to claim 1, wherein the content of the electrolyte solution moisture is 300 ppm or less. a) a polyolefin separator having ion hydrophilic property by irradiating ion particles or reactive particles with a reactive gas; b) non-aqueous organic solvent electrolyte; c) a negative electrode comprising a carbon material capable of occluding and releasing lithium as a negative electrode active material; And d) a positive electrode using a lithium-containing transition metal composite oxide as a positive electrode active material In manufacturing a secondary battery comprising a non-aqueous electrolyte secondary battery, characterized in that to prepare a separator by irradiating a polyethylene polymer membrane with ion particles having a energy of 0.01-10 KeV or a mixture of ion particles and a reactive gas. Manufacturing method. The method of claim 7, wherein A method for producing a non-aqueous electrolyte secondary battery, wherein the reactive gas is early and is selected from oxygen, air, krypton, N ₂ O and mixtures thereof.