JP2001236945A - Lithium battery electrode, its manufacturing method, and battery using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium battery electrode having improved battery characteristics and reduced quality variation from the improvement of the permeation of an electrolyte into a battery in a battery using a membrane-like electrode manufactured by applying electrode mixture onto a metal foil, a lithium battery using the same, and a method of manufacturing the electrode. SOLUTION: An electrode (12) is manufactured by applying electrode mixture (13) containing a material for allowing a lithium ion to be electrochemically absorbed into and discharged to one side or both sides of a metal foil (14). A lithium battery uses a lithium battery electrode having partially or wholly at least one or more linear or needle-hole-like holes (16) less than 100 μm in maximum line width or maximum diameter, within 20 mm in diameter on the metal foil with the electrode mixture applied thereto and its manufacturing method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium primary battery or a secondary battery in which at least one of a positive electrode and a negative electrode comprises an electrode containing a substance capable of occluding and releasing lithium ions electrochemically, and more specifically, an organic electrolyte. The present invention relates to a lithium ion secondary battery in which a negative electrode is made of a carbon material capable of inserting and extracting lithium ions.

[0002]

2. Description of the Related Art In recent years, storage batteries with higher energy density have been demanded for miniaturization and portability of portable telephones, video cameras, notebook personal computers, and the like, or for practical use of electric vehicles. Organic electrolyte batteries capable of the above outputs are expected. A typical example is a lithium-ion secondary battery that is already on the market. For the positive electrode of these organic electrolyte batteries, a spinel structure compound such as LiMn ₂ O ₄ or a lithium transition metal composite oxide generally having an α-NaFeO ₂ structure represented by LiMO ₂ can be used. Here, M is a single metal element or two or more metal elements selected from Co, Ni, Al, Mn, Ti, Fe and the like. Further, metal oxides such as MnO ₂ and V ₂ O ₅ into which lithium can be inserted, and T
Use of metal sulfides such as iS ₂ and ZnS ₂ , π-conjugated polymers such as polyaniline and polypyrrole having electrochemical redox activity, and disulfide compounds utilizing formation and cleavage of sulfur-sulfur bonds in the molecule Is also possible. On the other hand, as the negative electrode, metallic lithium or various lithium alloys, or a metal oxide or a carbon material capable of inserting and extracting lithium can be used. In particular, in a lithium ion secondary battery capable of repeatedly charging and discharging, it is common to use a carbon material for the negative electrode. As the carbon material, naturally produced graphite or an organic raw material is used.
Baking at a high temperature of ℃ or higher, graphite-based carbon material with developed graphite structure and flat potential characteristics, or baking an organic material at a relatively low temperature of 1000 ℃ or less, expected to have higher charge / discharge capacity than graphite-based material A coke-based carbon material that can be used is used.

In some cases, powder, fibrous metal or carbon powder is added to the above-mentioned electrode in order to improve the electron conductivity of the electrode. As the metal, copper, silver, aluminum or the like can be used, and as the carbon, graphite, carbon black, acetylene black, Ketjen black or the like can be used. As a method of manufacturing an electrode, a small amount of a polymer material serving as a binder, for example, polyvinylidene fluoride (PV
DF) is dissolved in a solvent such as 1-methyl-2-pyrrolidone, and an electrode mixture is prepared by dispersing various active materials and a conductive assistant made of fine powder of carbon or metal as appropriate into a paste. After applying it on both sides or one side of a metal foil having a thickness of several tens of μm as an electrode core material, a method of forming an electrode mixture layer containing an active material on the metal foil by removing an organic solvent is generally used. It is. Examples of other binders include:
Various fluorine rubbers such as ethylene propylene-dienter polymer (EP rubber), vinylidene fluoride-propylene copolymer and vinylidene fluoride-hexafluoropropylene copolymer are exemplified. Others include sodium polyacrylate and carboxymethylcellulose (CMC) in latexes and dispersions of polymers such as polytetrafluoroethylene (PTFE), SBR, and NBR.
A method in which a water-soluble polymer such as the above is added as a thickener is used as a binder. The electrode core material is also called a current collector, and an aluminum foil is often used on the positive electrode side and a copper foil is often used on the negative electrode side. In the electrode immediately after coating and drying, voids are generated in the electrode due to the removal of the solvent during the drying process,
The filling rate may be too low. In that case, the electrode mixture is easily peeled off due to the low mechanical strength of the electrode,
Since the contact between the particles in the electrode mixture is weak, there are disadvantages such as insufficient electron conductivity of the electrode. Therefore, pressure molding such as a roll press is often performed. In this pressure molding, processing is performed once or a plurality of times to a desired thickness to increase the filling rate of the electrode. The electrode for a lithium ion battery manufactured in this manner is a very smooth porous electrode in which the thickness of the electrode mixture portion on the metal foil is about 100 μm, and the thickness error is within several μm. . The positive and negative electrodes are opposed to each other, and are wound tightly into a high-density layer through a polymer microporous film that serves as a diaphragm. After the battery is inserted into the battery can and finally injected with the electrolytic solution, the battery is manufactured by caulking with a mechanical method or completely sealing by a method such as laser welding. In addition, a battery having a structure in which one or a plurality of layers obtained by laminating electrodes cut in a strip shape via a diaphragm or a film in which a polymer sheet is laminated on the surface of an aluminum foil or the like was processed into a bag shape. In some cases, a metal battery can be used instead of a metal battery can. Here, a polypropylene or polyethylene microporous membrane having a thickness of 100 μm or less having pores of 1 μm or less is often used as the diaphragm.
It is also possible to use a microporous membrane made of DF or PTFE.

On the other hand, as the electrolytic solution, a solution obtained by dissolving a lithium salt in an organic solvent is usually used. Lithium salts mainly include LiClO ₄ , LiPF ₆ , LiBF ₄ , Li
CF ₃ SO _{3 and the} like are used, and as an organic solvent, ethylene carbonate, propylene carbonate, γ-butyrolactone, sulfolane, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, dimethoxyethane, diethoxyethane, 2-methyl-tetrahydrofuran, various glymes And the like may be used alone or in combination of two or more. The injection of the electrolyte is generally performed under reduced pressure. Specifically, the pressure inside the battery is reduced,
After the electrolyte is injected into the battery, the pressure is returned to normal pressure to allow the electrolyte to penetrate into the battery. However, in the lithium ion battery, as described above, the battery can is filled with a thin and smooth electrode and a diaphragm at a considerably high density, and the permeation of the electrolytic solution is not always sufficient even under such reduced pressure injection. In order to reduce variations in the final battery performance, a process called aging for heating the battery at about 40 ° C. to 80 ° C. for a certain time is often performed. Such a step of injecting the electrolytic solution and the resulting permeation state of the electrolytic solution in the battery have a very large effect on variations in battery characteristics and quality, yield, and the like.

[0005]

SUMMARY OF THE INVENTION In the present invention, a battery using a thin-film electrode manufactured by applying an electrode mixture on a metal foil, such as a lithium ion battery, is used. It is an object of the present invention to provide a lithium battery electrode having improved battery characteristics and reduced variation in quality by improving the state of penetration into an electrolytic solution, a lithium battery using the same, and a method of manufacturing the electrode.

[0006]

The above objects of the present invention can be attained by the following inventions. That is, the present invention relates to (1) an electrode manufactured by applying an electrode mixture containing a substance capable of electrochemically absorbing and releasing lithium ions to one or both surfaces of a metal foil; The maximum line width or the maximum diameter is 1 mm or less on the metal foil
An electrode for a lithium battery, wherein at least one or all of a linear or needle-shaped through hole having a diameter of less than 00 μm is provided, and (2) a mass of a metal foil portion before and after providing the through hole. (1) The electrode for a lithium battery according to (1), wherein the change is 1% or less, and (3) the electrode on which the electrode mixture is applied in advance on the metal foil is applied to the metal foil through the electrode mixture. The method for manufacturing an electrode according to (1) or (2), wherein the through hole is provided on the metal foil by providing a cut or a needle hole.
(4) The method for producing an electrode according to (3), wherein after forming a through hole on the metal foil, pressure molding is performed.
(5) A lithium battery using the electrode according to any one of (1) to (3) for at least one of a positive electrode and a negative electrode, and (6) a positive electrode, a diaphragm, and a negative electrode of a battery. (5) The battery element according to (5), wherein the battery elements are laminated and integrated.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The lithium battery electrode of the present invention is provided with a linear or needle-shaped through hole having a maximum line width or a maximum diameter of less than 100 μm. A metal foil having the above-described through holes such as needle holes and cuts may be used from the beginning, but if such through holes such as the needle holes and cuts are used, the electrode mixture is coated on the metal foil. It can be provided even after processing, and it is more preferable after coating. Specifically, a through hole can be provided by making a cut or a needle hole in a metal foil as an electrode core material including an electrode mixture portion with a sharp blade or a needle point. In other words, if there is almost no portion to be cut off such as making a needle hole or making a cut, the likelihood of the electrode mixture falling off or peeling off in the manufacturing process of providing a through hole is low, Very little damage to the electrodes. It is desirable that the portion to be cut off in the step of providing the through-hole is as close to zero as possible, but if the mass of the metal foil portion is 1% or less, damage to the electrode can be kept within an acceptable range. In the production of the electrode for a lithium battery of the present invention, the electrodes immediately after the opening step and after pressure molding are shown in sectional views in FIGS. 1 and 2, respectively. In the figure, reference numeral 12 denotes an electrode;
3 is applied on the metal foil 14. Reference numerals 15 and 16 denote openings formed on the electrodes. The step of providing the through-hole on the metal foil may be performed immediately after coating and drying, after the pressure molding, or at any stage during the pressure molding in a plurality of times. As shown in FIG. 1, there is a case where the opening portion 15 is too open and the electrode has irregularities. In this case, by performing pressure molding by a roll press or the like after the hole forming step, as shown in FIG.
And the surface can be returned to a flat state. Thereby, the surface of the electrode mixture portion can be flattened. In a lithium ion battery, the flatness of the electrodes is extremely important. In the case of electrodes with poor flatness, it is natural that the filling rate of the battery as a whole will decrease, but other electrodes will break through the diaphragm, the way the electrodes are pressed in the battery cell, and the distance between the electrodes will decrease. Becomes uneven,
The internal resistance of the battery may vary, eventually affecting the battery characteristics, and in the worst case, metallic lithium on the dendritic tree may be deposited. In other words, it can be said that it is fatal that the electrode has poor flatness in the lithium ion battery.

In the production of an electrode for a lithium battery according to the present invention, the opening can be narrowed by the pressure molding step after the opening step, and at the same time, the open electrode mixture can be returned to a smooth state. For example, in the case of a linear through hole, both ends of the cut surface of the metal foil that has been opened once come into contact by pressure molding, and gas can pass through even if the through hole is apparently closed. Specifically, the maximum line width when the through-hole is linear or the maximum diameter when the through-hole is needle-shaped is preferably 100 μm or less, more preferably 50 μm or less, and further preferably 10 μm or less.
m or less is more desirable. The lower limit is not particularly limited, but is about 0.1 μm. By the way, conventionally, there has been an electrode using an electrode core material having some kind of through-hole. For example, a method of manufacturing an electrode using a metal net, a woven fabric, a nonwoven fabric, a punched metal, a lath-like metal sheet, or the like having a through hole as an electrode core material from the beginning. However, the conventional one utilizes a through hole having a very large hole diameter. An electrode core material having such a through-hole is more expensive than a metal foil, and when an electrode is actually manufactured, a paste-like electrode mixture is metallized by a normal barcode method, a doctor blade method, or the like. A manufacturing method of directly applying on a foil cannot be applied, and it has been necessary to drastically change the manufacturing method and the manufacturing apparatus of the electrode. The particle size of a general powdered active material used for a lithium ion battery in the present invention is several μm.
~ Several tens μm, so when the opening is in the above range,
At the same time, there is an effect that the possibility that the active material falls off the electrode is reduced.

In the present invention, the effect of the fine through-holes on the electrode is presumed as follows. As described above, the lithium ion battery is difficult to penetrate the electrolyte because the thin-film electrodes and the diaphragm are densely packed. On the other hand, the electrode material used in lithium-ion batteries is a porous material, and PVDF, which is contained as a binder, also has a high affinity for the polar solvent used as an electrolytic solution. The permeability of the liquid is very good. In addition, various surface treatments and the like are applied to the diaphragm, and the wettability to the electrolytic solution is often improved. However, the electrolyte does not easily penetrate into the electrodes when inserted into the battery cells. It is presumed that this is because bubbles remaining in the battery cells do not escape. That is, there is a limit in the pre-decompression process, and it is impossible to completely remove bubbles. After the injection of the electrolytic solution, in the lithium ion battery filled at a high density, there is no escape path for bubbles, and a portion of the lithium ion battery which is not filled with the electrolytic solution is formed between the electrode and the diaphragm. This is likely to eventually cause battery performance and its variation. On the electrode of the present invention, there is a through hole in a circle of a certain size at an arbitrary place on the surface where the electrode mixture is applied, so that bubbles can escape so that the electrolyte can sufficiently penetrate. It is thought to be done. In this case, for example, a diameter of 20 mm
In the case where one or more of the through holes are present in one or more circles, the bubbles reach the through holes after being moved by 10 mm, and are discharged from the battery cells.

When a hole is formed by using a machine such as a sewing machine, a continuous needle-hole-shaped through hole can be easily provided. On the other hand, as for the linear through-holes, the linear through-holes are continuously formed by using a circular rotary cutter 23 having a bladed portion 20 and a blade-removed portion 21 as shown in FIG. Can be provided. However, the shape of the linear through hole is not limited to a linear shape, but may be any shape such as a curved shape, an S shape, a key shape, a cross shape, a radial shape, or a combination of a plurality of these. May be regular or irregular. In the present invention, the through holes are formed over the entire surface or the main part of the battery electrode, and the former is preferable. On the other hand, as described above, for efficient degassing from the inside of the battery cell and injection of the electrolytic solution, which is the main object of the present invention, the distribution of the pores on the electrodes is important as described above. It is desirable that at least one or all of the through-holes be present in a circle of a certain size at any position on the electrode to which the chargeable and dischargeable electrode mixture is applied. The diameter of the circle is desirably 20 mm or less, more desirably 15 mm or less, and more desirably 1 mm or less.
0 mm or less is more desirable. However, even if the electrode mixture is applied, for example, the vicinity of the end of the electrode where the electrolyte can easily penetrate, or the outermost part of the battery having the swirl structure, or the part facing the electrode tab, etc. Naturally, it is not necessary for a portion that is hardly related to the charge and discharge of the battery to have the above characteristics. The method of manufacturing an electrode or an electrode having the features of the present invention is effective for a battery having a general swirl structure, but in particular, a positive electrode, a diaphragm, and a battery element of a negative electrode are bonded to each other in advance,
This is effective for improving the performance and stabilizing the quality of the battery using the integrated cells. For the manufacture of such an integrated battery cell, a normal heat fusion method using a polymer powder can be used. That is, between 1 and 100 between the electrode and the diaphragm.
A polymer powder of about μm is disposed in advance, and the polymer powder is melted by heating at a temperature equal to or higher than the melting point of the polymer powder in a state where the electrode and the diaphragm are overlapped, and the two are porous bodies. The electrode and the diaphragm can be bonded together. Finally, a battery can be manufactured by infiltrating the above-mentioned various organic electrolytes into the inside of the battery cell under an ultra-dry atmosphere and then enclosing the battery in a metal battery can or an aluminum laminate sheet bag.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. In addition, comparative examples for further clarifying the effects of the present invention are also shown. In Examples and Comparative Examples, an integrated battery cell in which a positive electrode and a negative electrode were attached to both surfaces of the above-described diaphragm was used. In such an integrated battery cell, the entry and exit of the electrolytic solution and bubbles usually occur only from the end face of the cell, and the effect of the through-hole provided on the electrode can be easily determined. Preparation of LiCoO ₂ cathode 90 g of LiCoO ₂ (manufactured by Nikko Fine Products) as a cathode active material, 7 g of graphite powder (manufactured by Lonza, trade name: SFG-7) as a conductive agent, and PVD as a binder
An electrode mixture paste was prepared by kneading 3 g of F and 42 g of 1-methyl-2-pyrrolidone. This paste was applied to one side of a 30-μm-thick aluminum foil such that the mass of the electrode mixture after drying was about 20 mg / cm ² ,
Heating at 0 ° C. allowed 1-methyl-2-pyrrolidone to dissipate. Thereafter, a LiCoO ₂ electrode was produced by compression molding using a roll press machine. The LiCoO ₂ electrode produced by this method is simply referred to as a positive electrode in the following examples. In actual battery cell production,
100 × 10 with tab removed by partially removing electrode mixture
An electrode having a size of 0 mm was used. Preparation of carbon negative electrode Graphite-based carbon active material (trade name B, manufactured by Petka Co., Ltd.)
L924) 94 g and 6 g of PVDF as a binder
An electrode mixture paste was prepared by kneading 70 g of -methyl-2-pyrrolidone. This paste is 20μ thick
The mass of the electrode mixture after drying on one side of
/ Cm ² and heated at 100 ° C. to dissipate 1-methyl-2-pyrrolidone. Then, a carbon electrode was produced by press molding with a roll press machine. The carbon electrode produced by this method is simply referred to as a negative electrode in the following examples. In actual battery cell fabrication, the electrode mixture was partially peeled off and a tab was removed.
An electrode having a size of 01 × 101 mm was used. Opening of linear through-hole A linear through-hole was formed on the copper foil by making a cut using a cutter on the coated negative electrode with the electrode mixture produced by the above method. This is shown in FIGS. 4 (a) and 4 (b). FIG. 4B is an enlarged view of a portion A in FIG. As shown in the figure, a perforated cut 2 is formed in a straight line at intervals of 10 mm by 5 mm so as to penetrate both the electrode mixture and the copper foil.
Cuts 2 were formed at intervals of 5 mm. In addition, 1 is an electrode tab. The line width of the through-hole immediately after opening is up to about 30
It was about 0 μm. Also, in this opening step, it was clear that the mass change of the entire electrode was 0.1% or less and the mass change of the copper foil portion was 1% or less. Finally, pressure molding was again performed by a roll press to return the electrode surface to a smooth state as shown in FIG. Due to this pressure molding, the surface of the electrode mixture returned to an almost smooth state although slight scratches remained, and the opening of the through-hole on the copper foil opened in the opening step was almost completely closed to the naked eye. However, when observed with an optical microscope, it was partially
An opening of about 0 μm was observed.

Opening of needle-hole-shaped through holes Similarly, using a needle for a negative electrode coated with an electrode mixture,
A through hole was provided on the copper foil. FIG. 5B is an enlarged view of a portion B in FIG. Specifically, as shown in FIG. 5, 7 mm in length and width, so as to penetrate both the electrode mixture portion and the copper foil.
Needle-hole-shaped through holes 3 were provided at intervals. Also in this case, the line width of the through-hole immediately after the opening was about 500 μm at the maximum. Further, it was clear that the change in mass of the entire electrode was 0.1% or less and the change in mass of the copper foil portion was 1% or less in the opening step. Finally, pressure molding was again performed by a roll press to return the electrode surface to a smooth state as shown in FIG. In this case also, the pressure mixture returns to an almost smooth state although the surface of the electrode mixture is slightly scratched, and the opening of the through hole on the copper foil opened in the opening step is almost closed to the naked eye. However, when observed with an optical microscope, an opening having a maximum size of about 10 μm was partially observed. The diagonal distance of the grid of through-holes of this electrode is about 10 m.
m, one or more through holes always exist in a circle having a diameter of 10 mm at an arbitrary position on the electrode. In addition, regarding the needle-hole-shaped through-hole, for the purpose of optimizing the distribution of the through-hole,
A lattice-shaped hole having a different vertical and horizontal distance was also manufactured. Preparation of Integrated Battery Cell In a glass bottle, 2.5 g of PVDF powder having an average particle diameter of 6 μm and 47.5 g of ethanol were mixed, and the mixture was irradiated with ultrasonic waves in an ultrasonic cleaner to disperse the PVDF powder. This PVDF powder dispersion was transferred to a glass Petri dish, and a microporous membrane made of hydrophilic PTFE (trade name: J, manufactured by Nippon Millipore Co., Ltd.)
After depositing the PVDF powder wet both sides of the GWP membrane filter) soak those cut into 105 × 105 mm, a glass plate by sandwiching a membrane between the positive electrode (LiCoO ₂ positive electrode) and the negative electrode (carbon negative electrode) is taken out And fixed from both sides. After heating and vacuum drying at 60 ° C to dissipate the ethanol, it is heated in a nitrogen stream at 200 ° C for 10 minutes to melt the PVDF powder, thereby bonding the hydrophilic PTFE microporous membrane to the positive and negative electrodes. As a result, a battery cell in which the positive electrode 4 / diaphragm 6 / negative electrode 5 was completely integrated as shown in the sectional view of FIG. 7 described later was produced. Charge / discharge cycle test method In the charge / discharge test of the battery, the battery was charged at a maximum current of 125 mA for 3 hours in a constant temperature bath at 25 ° C. with a charging upper limit voltage of 4.1 V. On the other hand, discharging was performed until the battery voltage reached 2.5 V at a constant current of 100 mA. In addition, a pause of 15 minutes was provided between charging and discharging. Hereinafter, Examples and Comparative Examples relating to a charge / discharge cycle test of a battery in which an electrolyte is injected into the integrated battery cell manufactured by the above method will be described.

EXAMPLE 1 In a dry air having a dew point of -60 ° C. or less, a linear through hole was formed in a copper foil.
The above-mentioned integrated battery cell using the negative electrode provided
The whole is about 100 kPa using a dry vacuum pump.
Until the battery is completely immersed in it,
1M LiPF ₆Ethylene carb containing 1: 1 by volume
And an electrolyte solution consisting of diethyl carbonate and diethyl carbonate.
Was. Reduced pressure for 3 minutes and return to normal pressure for 3 minutes
After that, the pressure was reduced for 1 minute using a dry vacuum pump.
Made sense. After leaving the battery at normal pressure for 10 minutes,
From the electrolytic solution, and finally, as shown in FIGS.
Encapsulation under reduced pressure in the exterior material 7 made of a laminate sheet
To produce a film-shaped lithium-ion battery 11
Was. In the figure, 8 is a positive electrode tab, 9 is a negative electrode tab, and 10 is heat sealing.
Mouth. Six such batteries were fabricated and charged and discharged.
Kul test was performed. The following examples were made with this battery as battery group A.
Table 1 summarizes the results of the charge / discharge test along with the comparative examples.
Confuse. Comparative Example 1 For an integrated battery cell using a negative electrode having no pores on a copper foil
On the other hand, the battery was previously depressurized in the same manner as in Example 1.
The electrolyte was infiltrated using the method described above. about this
In the same manner as in Example 1, an aluminum laminate sheet
Lithium ion film
A battery was manufactured. A total of six batteries were also manufactured and charged.
A discharge cycle test was performed. Hereinafter, these are referred to as battery group B.
You.

Example 2 An integrated battery cell using a negative electrode provided with a linear through hole in a copper foil was immersed in an electrolytic solution at normal pressure for 5 minutes, and then subjected to a pressure reduction treatment for 2 minutes using a dry vacuum pump. went. After leaving the battery at normal pressure for 10 minutes, the battery cell was taken out of the electrolytic solution, and sealed in an aluminum laminate sheet packaging material under reduced pressure in the same manner as in Example 1 to produce a film-shaped lithium ion battery. A total of six batteries were also manufactured and subjected to a charge / discharge cycle test. Hereinafter, these are referred to as a battery C group. Comparative Example 2 An electrolytic solution was permeated into a cell using a method similar to that of Example 2 for an integrated battery cell using a negative electrode having no holes in the copper foil. Also in this case, a film-like lithium-ion battery was produced by encapsulation under reduced pressure in an aluminum laminate sheet exterior material in the same manner as in Example 1. A total of six batteries were also manufactured and subjected to a charge / discharge cycle test. Hereinafter, these are referred to as a battery D group.

Example 3 For an integrated battery cell using a negative electrode in which a needle-hole-shaped through hole is provided in a grid pattern at intervals of 7 mm on a copper foil, the battery cell was previously decompressed in the same manner as in Example 1. The electrolyte solution was permeated using the method described in (1). Also in this case, a film-like lithium-ion battery was produced by encapsulation under reduced pressure in an exterior material made of an aluminum laminated sheet in the same manner as in Example 1. A total of six batteries were also manufactured and subjected to a charge / discharge cycle test. Hereinafter, these are referred to as a battery E1 group, and the results of the charge / discharge cycle test are summarized in Table 2. Example 4 Six batteries were produced in the same manner as in Example 3 except that a negative electrode having a needle-hole-shaped through hole formed in a grid pattern at intervals of 10 mm in length and width on a copper foil was used, and a charge / discharge cycle test was performed. Was done. Hereinafter, these are referred to as a battery E2 group. Since the diagonal distance of the grid of through-holes of this electrode is about 15 mm, one or more through-holes always exist in a circle having a diameter of 15 mm at any place on the electrode. Example 5 Six batteries were prepared in the same manner as in Example 3 except that a negative electrode having a needle-hole-shaped through-hole formed in a lattice at intervals of 14 mm in length and width on a copper foil was used, and a charge / discharge cycle test was performed. Was done. Hereinafter, these are referred to as a battery E3 group. Since the diagonal distance of the grid of through-holes of this electrode is about 20 mm, one or more through-holes always exist in a circle having a diameter of 20 mm at any place on the electrode.

Comparative Example 3 Six batteries were prepared in the same manner as in Example 3 except that a negative electrode having a needle-like through hole formed in a lattice pattern at intervals of 18 mm in length and width on a copper foil was used. A discharge cycle test was performed. Hereinafter, these are referred to as a battery E4 group. Since the diagonal distance of the grid of through-holes of this electrode is about 25 mm, one or more through-holes always exist within a circle having a radius of 25 mm at any place on the electrode.

Charge / discharge cycle test results Table 1 shows the results of the charge / discharge test for the batteries A to E. As can be seen from Tables 1 and 2, the performance is clearly higher from the battery having a linear or needle-shaped through hole in the copper foil of the negative electrode. Specifically, in the batteries A, C, and E1 to E3,
The discharge capacity at the initial 5th cycle is large and the variation is small. Further, the discharge capacity is maintained at about 90% even after 200 cycles. On the other hand, although it seems that the characteristics of the battery group A, which was previously reduced in pressure and immersed in the electrolytic solution, were slightly better than those of the battery group C, this was a very small difference. When it is used, it can be said that it is not always necessary to perform the decompression treatment before injection. This can be said to lead to simplification of the electrolyte injection step and the injection apparatus. Subsequently, looking at the batteries B and D having no holes in the copper foil of the negative electrode, the batteries B in which the electrolytic solution was introduced under reduced pressure showed moderate characteristics. However, compared to the batteries A, C, and E1 to E4 having the copper foil, the discharge capacity is small and the variation is large. After 200 cycles, the discharge capacity was reduced to about 70%. On the other hand, the battery group D, which does not have a through-hole in the copper foil and is not injected under reduced pressure, has extremely poor performance and large variation compared to the others. This is presumed to be because it is very difficult to remove air bubbles remaining in the battery after the electrolyte has penetrated to some extent from the end of the battery cell when the electrode current collector foil has no through hole. On the other hand, with respect to the influence of the distribution of the through-holes on the metal foil, it is clear that all of the batteries E1 to E4 shown in Table 2 have better characteristics than the battery B having no through-hole. However, a battery having a dense through-hole has a larger discharge capacity and smaller variation. Specifically, up to the battery E3 group in which the through-hole was always present in a circle having a diameter of 20 mm, the test results showed considerably good characteristics.
In the group of batteries E4 in which the through holes are always present in a circle having a diameter of 25 mm, the battery performance and its stability seem to be slightly inferior.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

From the above Examples and Comparative Examples,
It is clear that providing the metal foil as the electrode core material with a hole facilitates the introduction of the electrolytic solution into the cell, leading to an improvement in battery performance and a stabilization of quality. In addition, in the through-holes on the metal foil, the aperture ratio and the like are not important, and as shown in the present specification, at least the through-holes having the characteristics of the present invention through which bubbles can pass exist in a constant distribution state. It should just be. By using the method of the present invention, such through-holes can be provided while maintaining the electrode mixture surface in a smooth state, even for an electrode after applying the electrode mixture on a normal metal foil. It is possible. Therefore, the usefulness of the present invention can be said to be extremely universal and widespread. In this specification, mainly the case where the present invention is applied to a battery cell in which the positive electrode / diaphragm / negative electrode is completely integrated is shown. However, the present invention is applied to a lithium ion battery using a metal battery can having a normal swirling internal structure. It is also useful. In other words, in the case of such a revolving type battery, the escape path of air bubbles is only in the direction of the end face of the revolving structure. However, by providing a through hole having the method and features of the present invention on the metal foil of the electrode core material, the revolving structure is provided. Bubbles can also move in the diametric direction. In addition, even for large batteries where it is difficult to inject the electrolyte, the through-holes with a fixed pattern make the pouring process extremely easy regardless of the size of the battery cells, resulting in the production of batteries of stable quality. It is easy to guess that is possible.

[Brief description of the drawings]

FIG. 1 is a sectional view of an electrode immediately after an opening step.

FIG. 2 is a sectional view of an electrode after pressure molding.

FIG. 3 is a front view of a rotary cutter used for opening holes.

FIG. 4 is an explanatory view showing the formation of a linear through hole on a copper foil of a negative electrode.

FIG. 5 is an explanatory view showing formation of a needle-hole-shaped through hole on a copper foil of a negative electrode.

FIG. 6 shows a perspective view of the lithium battery of the present invention.

FIG. 7 is an explanatory view showing a cross-sectional structure of the lithium battery of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 electrode tab 2 linear through hole 3 needle hole through hole 4 LiCoO ₂ positive electrode 5 carbon negative electrode 6 battery diaphragm 7 aluminum laminate film exterior material 8 positive electrode tab 9 negative electrode tab 10 heat sealing sealing part

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Claims (6)

[Claims] 1. An electrode manufactured by applying an electrode mixture containing a substance capable of occluding and releasing lithium ions electrochemically to one or both surfaces of a metal foil, wherein the electrode mixture is applied. An electrode for a lithium battery, wherein at least one or all or a part of a linear or needle-shaped through hole having a maximum line width or a maximum diameter of less than 100 μm is provided within a diameter of 20 mm on a metal foil. . 2. The electrode for a lithium battery according to claim 1, wherein a change in mass of the metal foil portion before and after providing the through hole is 1% or less. 3. An electrode, in which an electrode mixture is previously applied on a metal foil, is provided with a cutout or a needle hole in the metal foil through the electrode mixture to provide the through-hole on the metal foil. The method for manufacturing an electrode according to claim 1 or 2, wherein 4. The method for producing an electrode according to claim 3, wherein after forming a through hole on the metal foil, pressure molding is performed. 5. The method according to claim 1, wherein at least one of the positive electrode and the negative electrode is provided.
A lithium battery using the electrode according to any one of claims 1 to 3. 6. The lithium battery according to claim 5, wherein the battery elements of the positive electrode, the diaphragm, and the negative electrode are laminated and integrated.