JP3510488B2 - Lithium ion secondary battery and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium ion secondary battery that can be repeatedly charged and discharged and uses a lithium-containing compound for a positive electrode and a method for manufacturing the same.

[0002]

_2. Description of the Related Art Conventionally, a lithium-ion secondary battery having a large charge capacity is prepared by mixing LiCoO ₂ (lithium cobalt oxide) powder as a positive electrode with a binder and a solvent to form a paste, and using aluminum having a thickness of about 20 μm. The foil was applied on both sides and dried.
Similarly, the negative electrode was also formed by applying paste-like carbon to both surfaces of a copper foil having a thickness of about 10 μm and drying it.

After that, together with the separator for separating the positive electrode and the negative electrode, the negative electrode, the separator, the positive electrode, and the separator are stacked in this order with the negative electrode and the positive electrode protruding to the opposite sides by a predetermined width, and formed into a cylindrical shape. Rolling up, the laminated electrode body 1 is formed as shown in FIG. The protruding electrode portions form the positive electrode current collector 2 and the negative electrode current collector 3, respectively.

Here, when forming a battery, the positive electrode current collector 2 and the negative electrode current collector 3 are connected to external electrodes, respectively.
The electrodes need to be pulled outside the battery. Conventionally, when the storage capacity of the battery is small or the operating current is small, the electrode can be pulled out to the outside only by making contact between the current collectors 2 and 3 and the metal case of the battery. .

Further, in a lithium ion secondary battery having a large storage capacity, as a method of pulling out an electrode to the outside, after forming the positive electrode and the negative electrode as described above, the positive electrode is formed on the positive electrode at regular intervals on one side edge. A plurality of strip-shaped aluminum foils or nickel foils are welded, and similarly, a plurality of strip-shaped copper foils are welded to the negative electrode. Then, the negative electrode, the separator, the positive electrode, and the separator are superposed in this order such that the portions where the strip-shaped metal foils are provided are projected to the outside to form the laminated electrode body 1 and are provided on the respective electrode current collectors 2 and 3. The electrode was drawn out through the strip-shaped metal foil.

A method of joining a strip-shaped copper foil to the one side edge of the negative electrode with solder is also conceivable, but solder cannot be used in this portion because it is attacked by the electrolytic solution.

The laminated electrode body 1 thus formed
Is housed in a metal container 4 having a bottomed cylindrical shape and forming an external positive electrode so that the strip of the positive electrode current collector 2 is in contact with the bottom surface. A metal plate 5 made of the same metal as the metal foil is placed. At this time, an insulator 6 is provided on a portion of the inner surface of the metal container 4 which is in contact with the negative electrode current collector 3 and the metal plate 5 to insulate the both.

Further, an electrode shaft 8 having an external negative electrode 7 is provided around the side surface at the center of the laminated electrode body 1 at a position in contact with the negative electrode current collector 3 and the metal plate 5, and is fixed together with the laminated electrode body 1. There is.

An electrolytic solution is injected into the metal container 4,
An insulating sealing body 9 is attached to the upper part of the metal plate 5, and an O-ring 10 is provided between the sealing body 9 and the electrode shaft 8 and the metal container 4.
It is provided to prevent the electrolyte from leaking to the outside.

[0010]

In the case of the above-mentioned conventional technique, when the electrode current collectors 2 and 3 are brought into direct contact with the metal container 4 and the electrodes are pulled out to the outside, power loss due to contact resistance occurs and the battery is discharged. Adversely affect the output of. Therefore, as the battery has a larger storage capacity, the power loss due to contact increases, making it difficult to take out a large current, and charging with a large current also becomes difficult.

On the other hand, when strip-shaped metal foils are provided on each of the electrode current collectors 2 and 3 by welding, the number of welded spots is small when the storage capacity is small, but the number of strip-shaped metal foils increases when the storage capacity is large. Therefore, it was necessary to weld to many places. As a result, there is a problem that the time required for the welding process becomes long, and the process becomes complicated in addition to the work of bundling the welded strip-shaped metal foils and pulling out the electrodes to the outside.

The present invention has been made in view of the above conventional problems, and provides a lithium ion secondary battery having an electrode capable of efficiently charging and discharging electricity and a simple manufacturing process, and a manufacturing method thereof. The purpose is to provide.

[0013]

The lithium ion secondary battery of the present invention has a laminated electrode body formed by laminating a sheet-shaped positive electrode, a negative electrode, and a separator in a metal container and winding them in a cylindrical shape. The positive and negative electrodes of this laminated electrode assembly are separated by
Cylindrical shape so that it does not overlap with the pole and the other pole
It is overlapped on the end side of
The above-mentioned positive electrode and negative electrode in the part not overlapping the separator
Each of the current collectors is made up of the metal container
A conductive paint containing nickel powder is applied between the current collector on the side connected with the metal container and the metal container, and the conductive paint electrically connects one of the current collectors to the metal container. It is what Further, the conductive paint is a mixture of an epoxy resin with nickel powder and an organic fatty acid such as oleic acid. The conductive paint may connect the collectors on both ends of the laminated electrode body to the positive and negative electrode members, respectively.

Next, in the method for manufacturing the lithium ion secondary battery, the positive electrode material made of a compound containing lithium is used as a gold material.
It is provided on the surface of the metal sheet to form the positive electrode, and in the same manner as other metal shields.
The negative electrode material is provided on the cathode surface to form the negative electrode.
If the pole overlaps the separator of the insulating sheet and the other pole,
So that each end is offset by a specified width
Was, together with a separator to the positive electrode and the negative electrode were laminated a negative electrode, a separator, a positive electrode, in the order of the separator, these circles
It is wound in a tubular shape to form a laminated electrode body, and
The above-mentioned positive electrode and negative electrode of the non-forming part respectively constitute current collectors.
The bottom of the metal container that houses this laminated electrode assembly.
Layered electrode body after applying a conductive paint containing powder
The current collector at one end of the sheet contacts the conductive paint
This laminated electrode body is housed in the metal container as
After 50 to 100 and temperature to cure the conductive ° C., electrically connected to a bottom surface of the current collector and the metal container, this
After that, apply conductive paint to the other current collector and cover it with a metal plate.
After the conductive paint is cured, electrolysis is performed in the metal container.
It is for filling the liquid .

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a lithium ion secondary battery according to an embodiment of the present invention. This lithium-ion secondary battery has a cylindrical laminated electrode body 14 formed by laminating a plurality of sheets in a metal container 12 serving as an external positive electrode.
Is provided.

The laminated electrode body 14 is formed by stacking a metal sheet-shaped positive electrode and negative electrode, and a resin film-shaped separator in the order of the negative electrode, the separator, the positive electrode, and the separator, and rolling them up into a cylindrical shape. When formed into a cylindrical shape, they are superposed on the lower part and the upper part with a predetermined width offset so as not to overlap the separator and the respective electrodes. A positive electrode collector 16 and a negative electrode collector 18 are formed on the positive electrode and the negative electrode, respectively, which do not overlap the separator.

Here, the positive electrode is LiCoO ₂ or LiNiO ₂ .
₂ , a powder of lithium composite oxide such as LiMn ₂ O _{4 is} mixed with a binder / solvent to form a paste, which is applied to both sides of a metal foil such as aluminum and dried, and the negative electrode is graphite or carbon. A negative electrode material such as the above is applied to both surfaces of a metal foil such as copper and dried. The separator is an insulating sheet made of a polyolefin microporous film such as polyethylene or polypropylene, and prevents the positive electrode and the negative electrode from coming into contact with each other and preventing a failure due to a short circuit or the like.

Further, a highly conductive conductive paint 20 is applied to the bottom of the metal container 12 which is the external positive electrode on which the positive electrode current collector 16 is located before housing the laminated electrode body 14.
The conductive paint 20 is a mixture of an epoxy resin with nickel powder, and an organic fatty acid such as oleic acid for the purpose of obtaining good conductivity.

Here, when general silver is used as the metal powder used for the conductive paint 20, there is a problem that the life of the battery is shortened because ion migration is likely to occur, and when copper is used. Then, there was a problem such as corrosion of copper, which was not suitable. Further, it is difficult to keep the cost down because gold and platinum are expensive, and for these reasons, usable metal powders are limited to nickel.

As the conductive coating material 20, there is conventionally a thermosetting resin mixed with metal powder, but the conventional coating material has to be baked and cured at a high temperature of 100 ° C. or higher, and the separator is made of polyethylene. Therefore, the heat-resistant temperature was relatively low and was not suitable. In addition, when a metal powder is mixed with an acrylic resin, the metal powder is applied to the positive electrode current collector 16 and dried at room temperature, the acrylic resin is dissolved in the electrolytic solution, resulting in poor conductivity. . Therefore, the epoxy resin is suitable as the resin of the conductive paint 20.

A ring-shaped metal plate 22 made of copper or the like is placed on the upper portion of the laminated electrode body 14 so as to come into contact with the negative electrode current collector 18, and a cylindrical shape at the center of the laminated electrode body 14 is placed. In the space of, the metal foil 2 serving as an external negative electrode is provided on the outer peripheral portion.
4 is provided with an electrode shaft 26.

The metal plate 22 and the metal foil 24 are made of the same metal as the metal foil forming the negative electrode.
4 is provided at a position in contact with the negative electrode current collector 18 and the metal plate 22. Further, an insulator 28 is provided at a position where the negative electrode current collector 18 and the metal plate 22 are in contact with the metal container 12. The conductive paint 20 is also applied to the negative electrode current collector 18 so as to be electrically connected to the metal plate 22 and the metal foil 24 with certainty.

The metal container 12 having these electrode bodies and the like is filled with an electrolytic solution, the laminated electrode body 14 and the electrode shaft 26 are fixed, and further the metal plate 22 is provided to prevent leakage of the electrolytic solution.
On the upper side, a ring-shaped sealing body 30 corresponding to the shape between the electrode shaft 26 and the metal container 12 is placed, and between the sealing body 30 and the electrode shaft 26 and the metal container 12 is made of rubber. The O-ring 32 is sandwiched, and the sealing body 3 is thereby provided.
0 is fixed. Further, here, the sealing body 30 and the O-ring 32 are made of an insulating material. As the electrolytic solution, a nonaqueous electrolytic solution prepared by dissolving a supporting electrolyte in a high dielectric constant solvent is generally used. Since the high dielectric constant solvent has a large degree of ion dissociation and a high solvation power, many lithium ions can be stably present, but it has a drawback that it has a high viscosity and a large ion migration resistance. Therefore, the viscosity of the electrolytic solution is lowered by adding a low-viscosity solvent.

Propylene carbonate, ethylene carbonate, dimethyl sulfoxide, γ-butyl lactone, sulfolane and the like are used as the high dielectric constant solvent, and 1,2-dimethoxyethane, tetrahydrofuran, dioxolane and diethyl carbonate are used as the low viscosity solvent. Etc. are used, and the compounding ratio is appropriately selected. Further, as a supporting electrolyte serving as a lithium ion source, LiCF ₃ SO
₃ , LiAsF ₆ , LiClO ₄ , LiBF ₄ , LiP
F ₆ or the like is used.

In the method for manufacturing a lithium ion secondary battery according to this embodiment, a conductive coating material 20 is applied to the bottom of the metal container 12, the electrode shaft 26 is housed in the laminated electrode body 14, and the negative electrode current collector 18 is further provided. Also, after applying the conductive paint 20, the metal plate 22 is covered, and the conductive paint 20 is cured at a low temperature of about 60 ° C. After that, the electrolytic solution is filled in the metal container 12 through the gap formed in the metal plate 22. After this,
In order to prevent leakage of the electrolytic solution, the sealing body 30 is placed on the metal plate 22 and the O-ring 32 is fitted.

In the lithium ion secondary battery thus formed, the conductive paint 20 using Ni has a conductivity of 5%.
× 10 ⁻⁴ Ω · cm, the conductivity of the electrolytic solution is 10
It is about 10 ² Ω · cm, and has sufficient conductivity, and a metal foil or the like forming the laminated electrode body 14 does not dissolve in the electrolytic solution, and a battery having good performance can be obtained.

[0027]

EXAMPLE As an example of the lithium ion secondary battery of the present invention, the metal powder of the conductive paint 20 has an average particle size of 2
Direct contact between a lithium ion secondary battery formed by using nickel powder of about 0 μm and a bisphenol A type resin (Epicoat 828 made of oiled shell epoxy) as an epoxy resin, and the conventional current collectors 2 and 3 The lithium-ion secondary batteries in which the electrodes are drawn outside by comparison with each other were compared.

Here, in the conductive paint 20, triethylenetetramine (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) as a curing agent for epoxy resin and oleic acid (a reagent manufactured by Wako Pure Chemical Industries) as an organic fatty acid are used.
The nickel powder is 82w.
t%, epoxy resin 14.4 wt%, oleic acid 3.6 wt%, and the mixing ratio of these materials was 100 parts by weight, triethylenetetramine was further added by 1.4 parts by weight. Each of these materials is sufficiently kneaded to form a nickel conductive coating material 20, which is applied to the bottom of the metal container 12 in which the positive electrode current collector 16 is located, and then the laminated electrode body 14 is housed, and the negative electrode current collector 18 is further stored. Conductive paint 20 was also applied. Then, after the metal plate 22 was attached, it was cured at a low temperature of around 60 ° C. In addition, ethylene glycol monobutyl ether (a reagent manufactured by Wako Pure Chemical Industries, Ltd.) was appropriately added to the conductive coating material 20 as a low viscosity modifier.

The positive electrode of the lithium ion secondary battery is
An aluminum foil coated with lithium cobaltate on both sides, a copper foil coated with amorphous carbon on both sides was used for the negative electrode, and propylene carbonate plus lithium perchlorate was used as an electrolytic solution. .

When the capacity of the lithium ion secondary battery formed in this way is set to 70 Ah as the calculated discharge capacity at an average voltage of 3.6 V and 4.4 V to 3.0 V, the battery is charged and discharged. The charge current capacity and the discharge current capacity after 5 cycles from the start of charge / discharge were compared. The results are shown in Table 1.

[0031]

[Table 1]

As a result, when comparing the lithium ion secondary battery in which the electrode is pulled out to the outside through the conductive paint 20 and the lithium ion secondary battery in which the electrode is pulled out to the outside only by the contact of the positive electrode current collector, 1 A is charged. When discharged, no significant difference was observed between the two, but as the charging / discharging current increased, the difference between the two became more pronounced, and the lithium ion secondary battery via the conductive paint 20 was more , It has been shown that it has excellent characteristics for extracting the electrode to the outside.

The lithium-ion secondary battery of this embodiment is not limited to the above-mentioned examples, and the metal and other materials forming each electrode and the like can be appropriately selected.

[0034]

INDUSTRIAL APPLICABILITY The lithium-ion secondary battery and the method for manufacturing the same according to the present invention have an easy and reliable connection between the laminated electrode body and the external electrode, and have high safety and durability even when a large current flows. . Therefore, cars, electric wheelchairs for the disabled,
Alternatively, it can be widely used for storage of high power. Furthermore, since the manufacturing process is simple, a low-cost lithium ion secondary battery can be provided.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a lithium ion secondary battery according to an embodiment of the present invention.

FIG. 2 shows a vertical sectional view of a conventional lithium-ion secondary battery.

[Explanation of symbols]

12 metal containers 14 laminated electrode body 16 Positive electrode current collector 18 Negative electrode current collector 20 Conductive paint 22 Metal plate 24 metal foil 26 electrode shaft 28 Insulator 30 sealed body 32 O-ring

─────────────────────────────────────────────────── ─── Continuation of the front page (73) Patent holder 000152675 Nihei Toyama Co., Ltd. 6-26-2 Minamioi, Shinagawa-ku, Tokyo (72) Inventor Katsumi Yano 150 Nikami-cho, Takaoka-shi, Toyama Toyama Industrial Technology Center Planning and Administration Department (72) Inventor Akira Nakagawa 383 Takada, Toyama City, Toyama Prefecture In-house Mechanical and Electronics Research Laboratory, Toyama Industrial Technology Center (72) Inventor Toshifumi Fujishiro, 383 Takada, Toyama City, Toyama Prefecture In-machine Research and Engineering Center, Toyama Prefecture (72) Inventor Masahiro Kadosaki 383 Takada, Toyama City, Toyama Prefecture Toyama Prefecture Industrial Technology Center Mechanical and Electronic Research Laboratory (72) Inventor Toshihiro Matsuda 383 Takada, Toyama City, Toyama Prefecture Toyama City Industrial Technology Center Mechanical and Electronic Research Laboratory (72) Inventor Yoshikawa Hirokawa 1-643 Kamiakae-cho, Toyama City, Toyama Prefecture Cosel Co., Ltd. (72) Inventor Osamu Iino Toyama No. 838 Uejima, Namekawa City, Todo Industrial Co., Ltd. (72) Inventor Yasushi Takako 635 Sasakura, Fuchu-cho, Nenju-gun, Toyama Prefecture Nissan Chemical Co., Ltd.Toyama Plant (72) Inventor Michihiro Takada Higashitonami-gun, Toyama Prefecture Fukuno-cho 100, Ltd. NIPPON TOYAMA Toyama Factory (56) References JP-A-4-206275 (JP, A) JP-A 5-13089 (JP, A) (58) Fields investigated (Int.Cl. ⁷⁾ , DB name) H01M 10/40 H01M 2/22 H01M 2/22-2/26

Claims (4)

(57) [Claims] 1. A laminated electrode body formed by laminating a sheet-shaped positive electrode, a negative electrode, and a separator in a metal container and winding them in a cylindrical shape. The positive electrode and the negative electrode of the laminated electrode body are separated by a separator.
Cylindrical shape so that it does not overlap with the pole and the other pole
It is overlapped on the end side of
The above-mentioned positive electrode and negative electrode in the part not overlapping the separator
Each of the current collectors is made up of the metal container
A conductive paint containing nickel powder is applied between the current collector on the side connected with the metal container and the metal container, and the conductive paint electrically connects one of the current collectors to the metal container. The lithium-ion secondary battery is characterized by 2. The lithium ion secondary battery according to claim 1, wherein the conductive paint is a mixture of an epoxy resin with nickel powder and an organic fatty acid. 3. The lithium according to claim 1, wherein the conductive paint is obtained by connecting the current collectors at both ends of the laminated electrode body to the positive and negative electrode members, respectively. Ion secondary battery. Wherein the positive electrode material composed of a compound containing lithium is provided on the surface of the metal sheet to form a positive electrode, similarly to the anode material is provided to form a cathode to other metal sheet surface, this
The positive electrode and the negative electrode are the separator of the insulating sheet and the other electrode.
So that they do not overlap
Overlap, the positive electrode and the negative electrode together with the separator ,
By laminating the negative electrode, the separator, the positive electrode, in the order of the separator, this
The stacked electrode body formed by winding a these in a cylindrical shape, the separator
The positive electrode and the negative electrode in the parts that do not overlap each other are collected.
The bottom of a metal container that constitutes an electric body and houses this laminated electrode body
After applying the conductive coating material containing nickel powder, the product
The current collector at the one end of the layer electrode body becomes the conductive paint.
This laminated electrode body is housed in the metal container so that it contacts.
After that, the conductive paint is hardened at a temperature of 50 to 100 ° C. to electrically connect the current collector and the bottom surface of the metal container, and then the other current collector. Also apply conductive paint
Then, cover the metal plate to cure the conductive paint, and then
Method for producing a lithium ion secondary battery, characterized by filling the electrolytic solution to the genus vessel.