JPH117961A - Electrode for non-aqueous electrolyte secondary battery, and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the coating workability, prevent the occurrence of peeling of the negative electrode material from a collector foil, while lowering the material machining cost by coating a collector foil provided with holes having a reversible part with the mixture which consists of the negative electrode active material and the resin binder, so as to form an electrode. SOLUTION: A collector foil of a negative electrode 7, which is moved on a carrying belt 34 or a carrying roller 33, is pinched between drilling rollers 28, 39, of which surfaces are formed with pin-shapes, and holes are drilled by pins 40a provided in the roller 28, from over. The collector foil surface is formed with holes having a reversible part in a lower side. The roller 39 supplies the resisting force to the roller 28, and while forming recessed parts for escape of the pins 40a so as to prevent the breakdown of the pins 40a. The collector foil 7 formed with the holes is carried to a negative electrode coating unit 35 by a carrying belt 32, to which a urethane sponge is stuck, and the collector foil 7 formed with the holes is coated with the slurry, which includes the negative electrode material, the resin binder and the solvent. The slurry is filled inside the holes, and arranged so as to surround the reversible part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to an electrode and a method for manufacturing an electrode.

[0002]

2. Description of the Related Art As a non-aqueous electrolyte secondary battery, there is a Li-ion secondary battery. This is an insulation between a positive electrode in which a positive electrode material composed of a positive electrode active material, a conductive material and a resin binder is applied on an Al foil, and a negative electrode in which a negative electrode material composed of a negative electrode active material and a resin binder is applied on a Cu foil. The electrodes are placed so as to face each other with the conductive film interposed therebetween, and the electrolyte is allowed to permeate between the electrodes, and the electrodes are in a sheet shape.

[0003] The reason why the electrodes are formed into a thin sheet is that the organic electrolyte used as the electrolyte has a low ionic conductivity, so that it is necessary to increase the electrode area.

The negative electrode is formed by applying a mixture of a carbon material and a resin binder (for example, PVDF: polyvinylidene fluoride) as a negative electrode active material to a sheet-shaped current collector to form an electrode. Since the binder is an insulator, if the mixing ratio is set to a large value, the binder covers the surface of the carbon material, lowering the electrical conductivity in the electrode, or hindering the insertion and removal of Li ions. Therefore, the mixing ratio of the resin binder to the negative electrode material is usually set to about 5%.

Since a mixture of a carbon material and a resin binder (for example, PVDF) has low fluidity, a volatile organic solvent (for example, NMP: N-methylpyrrolidone) is added to the negative electrode material in the coating step to have fluidity. Then, it is applied to a copper foil as a negative electrode current collector. After coating and drying and pressing to adjust the electrode thickness, a negative electrode is obtained.

In the case of a positive electrode material, during this pressing step, a positive electrode active material (eg, LiCoO ₂ , LiNiO ₂ , LiMn)
₂ O ₄ ) bites into the Al foil, which is the current collector, and enhances the binding force with the current collector due to the hooking effect. However, in the case of the negative electrode, the graphite, which is the active material of the negative electrode, has a crystal structure by pressing. Cannot be pressurized to a level at which the graphite is bitten into the Cu foil as the negative electrode current collector. Therefore, in the case of a negative electrode material using graphite, the binding force of the electrode material to the negative electrode current collector is exclusively
Cu, a resin binder used as a binder for active materials
It depends on the binding force to the foil.

[0007] However, resin binders such as PVDF originally have low adhesive strength to metal, and resin binders which can be mixed for the above-mentioned reason are not generally higher than 5%.
The binding force of the negative electrode material to the current collector foil was very weak, and there was a problem that the negative electrode material was easily peeled off after application.

To solve this problem, Japanese Patent Application Laid-Open No. 8-250109 proposes a method of providing a plurality of holes in a negative electrode current collector foil.

According to this method, the negative electrode active material comprises a first negative electrode active material layer formed on one side of the foil and a second negative electrode active material layer formed on the other side of the foil. Since the structure is connected through the provided holes, the negative electrode active material can be held in the current collector foil.

However, in the above method, it is necessary to apply a current collector foil with a foil in which holes have been processed in advance, and this method is disadvantageous in that the cost is high. Also, when the pore diameter is large, there is a problem that the negative electrode material drips from the pores when coating the first surface.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrode having good workability at the time of coating, preventing peeling of a negative electrode material from a current collector foil, and reducing material processing costs. An object of the present invention is to provide a non-aqueous electrolyte secondary battery electrode having a structure, and a method for manufacturing the same.

[0012]

According to a first aspect of the present invention, there is provided a non-aqueous electrolyte secondary battery comprising an electrode and an electrolyte, The electrode, characterized in that it is created by applying a mixture of a negative electrode active material and a resin binder on a current collector foil provided with a hole having an inverted portion around the hole on the foil surface. I do.

[0013] The non-aqueous electrolyte secondary battery according to claim 2 is
The hole diameter (d mm) of the hole is 0.02 ≦ d ≦ 2, the gap (L m) of the hole is 0.1 ≦ L ≦ 10, and the hole surrounding portion from the foil surface of the inverted portion around the hole is Height (h mm) is 0.01 ≦ h
.Ltoreq.0.1, wherein at least two or more holes are provided on the foil surface.

A non-aqueous electrolyte secondary battery according to claim 3 is
The hole shape of the hole set in the electrode battery according to claim 1 is an ellipse,
It has a current collector foil having a long rectangular shape and a rhombic shape.

A non-aqueous electrolyte secondary battery according to claim 4 is
The mixture comprising the negative electrode active material and the resin binder is applied to the current collector foil according to claim 1, 2 or 3, dried, and then pressurized by a press device (1-2 ton / cm ^2). )
The reversing part is deformed by the pressing force.

A non-aqueous electrolyte secondary battery according to claim 5 is
A pin shape in which the first surface of the battery electrode is coated, dried, and then inverted, and the hole is drilled from the second surface facing the first surface via a foil. A roller having a surface, and pierced by passing between the opposing rollers that provide a reaction force via the electrode, and further dried after applying the electrode material to the second surface so as to fill the same hole, 1-2 to
It is characterized by compression under pressure of n / cm ² .

According to the non-aqueous electrolyte secondary battery of the first aspect, the inversion portion formed around the hole provided in the current collector foil collects an active material and a resin binder by the effect of hooking. It can be held on the body side to prevent the negative electrode material from peeling off from the current collector foil.

According to the non-aqueous electrolyte secondary battery of the present invention, the pore diameter (d mm) is 0.02 ≦ d ≦ 2, and the gap (L m) between the pores is 0.1 ≦ L ≦ 10. And the height (h mm) of the inverted portion around the hole from the foil surface is 0.01 ≦ h ≦
Since it is 0.1, the active material and the resin binder can be easily and appropriately captured by the inverted shape to be formed.

According to the non-aqueous electrolyte secondary battery according to the third aspect, the inverted shape of the foil which is optimal for gripping the electrode material can be formed by making the hole shape of the foil an ellipse, an oblong rectangle, and a rhombus.

According to the non-aqueous electrolyte secondary battery according to the fourth aspect, after the mixture comprising the negative electrode active material and the resin binder is applied to the current collector foil, the inversion portion is inverted by a pressing step. Is strengthened and firmly adhered to the active material and the resin binder, so that the holding of the negative electrode material is ensured.

According to the non-aqueous electrolyte secondary battery according to the fifth aspect, the first surface of the battery electrode is applied to the battery electrode, dried and then inverted, and the first surface is interposed with a foil. From the opposing second surface, a hole is formed by passing between a roller having a pin shape on the surface for piercing the hole and an opposing roller providing a reaction force via an electrode, and further filling the hole. After coating the electrode material on the second surface and drying and compressing under pressure, it is possible to pierce the foil in the coating process,
The processing cost of the foil can be reduced.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail.

FIGS. 1 and 2 show a nonaqueous electrolyte secondary battery 1 according to an embodiment of the present invention.

FIG. 1 shows an example in which a negative electrode according to the present invention is used in a small non-aqueous electrolyte secondary battery. In FIG. 1, reference numeral 1 denotes a battery main body, which has a diameter of 18 mm and a length of 6
5 mm.

Reference numeral 2 denotes a battery can, and reference numeral 3 denotes a battery lid having a built-in safety valve. The material of the battery can 2 is 0.4 mm thick Fe
A material plated with Ni was used. Other materials such as Al, Cu, and SUS may be used as the material of the can 2. 3
The safety valve is provided to release gas in the can before the can 2 is ruptured in response to an increase in the internal pressure of the can. The internal pressure of the can usually rises to 気 圧 2 atm due to the gas generated when the nonaqueous electrolyte is electrolyzed at the time of the first charge, but thereafter remains almost constant.

Reference numeral 4 denotes a positive electrode tab having a thickness of 0.1 mm and a width of 3
mm. Reference numeral 5 denotes an insulating sheet, which is provided to prevent a short-circuit of the electrode due to the tab 4. This is the thickness
It is made of 0.2mm polyimide sheet.

Reference numeral 6 denotes a center pin, which is a SUS circular tube having a diameter of 2.0 mm and a thickness of 0.3 mm. It is installed to prevent the shaft from bending when winding the electrode sheet.

Reference numeral 7 denotes a negative electrode, in which a 80 μm negative electrode material 8 is applied on the surface of a 15 μm copper foil. The negative electrode material 8 is manufactured by mixing a resin binder with a graphite material. The resin binder is
PVDF (polyvinylidene fluoride) is used and 5 W% is mixed. 9 is a separator having a thickness of 25 μm having fine holes.
Is a polyethylene film. The porosity of the fine pores in the film volume is 35 to 60%.

Reference numeral 10 denotes a positive electrode, and a positive electrode material 11 having a thickness of 80 μm is applied to both sides of a 20 μm Al foil. The positive electrode material 11 is made of a positive electrode active material (for example, LiCoO ₂ , LiNi
O ₂ , LiMn ₂ O ₄ ) and a conductive material (eg, graphite) and a resin binder (eg, PVDF) in a weight ratio of 90: 7: 3, respectively.
%. Reference numeral 13 denotes a can bottom insulating film, which is provided to prevent the electrode of the electrode winding body from short-circuiting with the can. The material is made of polyimide and has a thickness of 0.3 mm. Reference numeral 12 denotes a negative electrode tab, which is made of Ni having a width of 4 mm and a thickness of 0.1 mm. Alternatively, a tab made of Pt or Cu may be used.

The non-aqueous electrolyte secondary battery 1 shown in FIG. 1 is a system in which an electrode sheet is wound in a roll shape and then stored in a can 2. Alternatively, as shown in FIG. Can be formed into a rectangular shape, and these can be overlapped to form a rectangular battery.

FIG. 3 is an expanded view of the negative electrode 7 wound into a roll of the nonaqueous electrolyte secondary battery 1 of FIG. When developed, the negative electrode 7 has a size of 55 mm in width and 550 mm in length.

The area of 5 mm from one end of the negative electrode 7 is an uncoated part on both sides, and one side of this area has a thickness of 0.1 mm and a width of 4.0 mm.
The Ni tab 5 mm is welded by ultrasonic welding.

The current collector 7 of the negative electrode is a copper foil having a thickness of 15 μm. This copper foil is provided with a plurality of holes 23 which are opened by a φ0.7 sharp tip pin and have an inverted portion around the hole.

FIG. 4 shows a method of forming the holes 23, and FIG. 5 shows the appearance of the holes 23 formed as a result. The hole 23 provided in the current collector 7 is formed by piercing a sharp pin 29 into the current collector 7 at an angle θ ° (30 ° ≦ θ ≦ 90 °). The pin shape is a conical or pyramidal shape of φ0.7. When this pin has a sharp tip like 29, the inverted shape 26 of the hole 24 formed in the current collector 7 in the traveling direction of the pin 29 has its inverted side broken as shown in FIG. The turning angle a becomes smaller. When the tip shape is a round shape like the shape 30, the inverted portion shape 27 of the hole 25 does not break at the inverted side as shown in FIG. 5, and the turning angle a tends to increase. The shape of the inverted portion is not only the shape shown in this example, but also the shape of the pin, the diameter of the pin,
The shape, the turning angle, and the turning height can be variously set depending on the angle at which the pin is struck, and it goes without saying that the present invention is not limited to the example shown in this example.

The holes 24, 2 having the shape of the inverted portion as described above
When a mixed slurry 8 of a negative electrode material, a resin binder, and a solvent (NMP) is applied on the copper foil on which the
Is filled in the hole 24 as shown in FIG.

At this time, the diameter d of the hole 24 formed in the current collector 7 is set to be 0.02 mm ≦ d ≦ 2.
The slurry 8 does not leak out of 4.

Similarly, the opposite surface is coated and dried, and then pressed and compressed at a pressure of 1 to ² ton / cm ^{2 by} a press device. When compressed, the reversal angle a in FIG. 6 satisfies a ≦ 90 °. Therefore, as shown in FIG. 7, the reversal part 26 is greatly curved, and the graphite and the resin binder existing on the outer periphery of the reversal part are reversed. It is captured by a piece and closely fixed to the current collector foil 7. As a result, the electrode layer 8 is mechanically fixed to the current collector foil 7 by the reversing portion 26, and peeling from the foil 7 is prevented.

FIG. 8 shows a method for producing an electrode sheet according to the present invention. The current collector foil 38, which has been moved on the belt 34 or the roller 33, is sandwiched between the rollers 28 and 39 provided with the pin shapes 40 forming the holes 24 on the surface. A hole is made in the sandwiched current collector foil 38 by a pin 40 a provided on the roller 28 from above. As a result, the current collector foil 38 has a reversing portion 2 on the lower side.
A hole 42 having 6 is formed. At this time, the roller 39 supplies a drag to the roller 28 from below, and
0a is formed on the surface of the recess 41a, and the pin 4
0a is prevented from being damaged.

Further, the rollers 28 and 39 are synchronized in the reverse rotation direction by gears 42 and 43 mounted on the shaft. The hole 42 having the reversing part 26 on the upper side is punched by a pin 40b provided on the roller 28,
The relief shape of the pin 41b is formed on the roller 41a.

The density and distribution of the holes 24 formed in the insulator 7 can be freely set by the arrangement of the pins 40a and the pin reliefs 40b.

The current collector foil 7 having the holes 24 is conveyed by the conveyor belt 32 to the negative electrode material coating section 35.

At this time, a urethane sheet having a thickness of 1 to 5 mm is attached to the surface of the transport belt 32 so as not to damage the inverted portion 26 of the hole 24 formed on the lower side.

In the case of the electrode according to the fifth aspect, unlike the method described above, the collector foil 7 is coated on one side with the negative electrode material 36 in a state where no processing is performed on the foil surface. After that, it is dried.

In this state, the roller 28 shown in FIG. 9 does not have the relief 41a, and the roller 39 is passed between rollers which are flat rollers without the relief 40b.

Thus, the piercing pin 40 on the roller 28
The pressure of the pin 40a when the a is pierced from above the current collector 7 coated with the negative electrode material 37 is offset by the reaction force of the opposing roller 39, and does not form a swelling shape on the coating surface. The boring process can be formed while maintaining the degree.

In this manner, the electrode sheet having a hole having an inverted portion from one side is formed such that the recess formed in the hole by the pin 40a penetrates into the electrode material layer on the opposite side.

The electrode material sheet is placed on the electrode material 36 from above.
After coating and drying, the electrode material of the upper layer is pressed into the concave shape formed in the lower layer electrode material when pressurized by the pressing force according to claim 4, and is connected to the lower electrode layer. At the same time, the reversal portion formed around the hole is strengthened in warpage, and the force of biting into the lower electrode layer is enhanced.

By the connection of the electrode layers and the engagement of the inversion portion, the negative electrode active material layer is mechanically fixed to the current collector foil 7, and peeling from the foil 7 is prevented.

[0049]

According to the electrode structure constituted by the present invention, it is possible to prevent the negative electrode material from peeling off from the current collector foil, to provide a stable electrode structure having excellent conductivity and to improve the handling efficiency of the negative electrode. A good non-aqueous electrolyte secondary battery can be provided.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a cross section of a small non-aqueous electrolyte secondary battery according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view illustrating a non-aqueous electrolyte secondary battery according to an embodiment of the present invention.

FIG. 3 is a developed partial cross-sectional view of a negative electrode.

FIG. 4 is a view showing a method of forming a hole in a negative electrode foil.

FIG. 5 is a perspective view showing an opening state of a hole.

FIG. 6 is an electrode cross-sectional view showing a state where an electrode material is applied to a negative electrode foil having holes.

FIG. 7 is a cross-sectional view of an electrode pressed after applying an electrode material to both surfaces of a foil.

FIG. 8 is a view showing a process of making a hole in the current collector foil.

FIG. 9 is an enlarged view of the hole forming roller unit of FIG. 8;

FIG. 10 is a diagram showing a process in which an electrode is perforated between a roller having a pin having a hole only on one surface and a roller having a flat surface.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Small nonaqueous electrolyte secondary battery main body, 2 ... Battery can, 3 ... Safety valve, 4 ... Positive electrode tab, 5 ... Insulating sheet, 6 ... Center pin, 7, 16 ... Negative electrode, 8, 9, 15, 17 ... Separator Reference Signs List 10, 10, 18 Positive electrode, 11 Positive electrode material, 12 Negative electrode tab, 13 Can bottom insulating film, 14 Square nonaqueous electrolyte secondary battery, 19 Battery case, 20 Negative electrode tab, 21 Negative electrode terminal, 22 ... Positive electrode terminals, 23, 24, 25 ... holes, 26,
27 ... reversing part, 28, 39 ... punching roller, 29, 40
a, 41a: punching pin, 32: conveyor belt with urethane sponge affixed, 33: conveyor roller, 34: conveyor belt, 35: negative electrode material coating section, 36, 37 ... negative electrode material, 40
b, 41b: pin escape hole, 42, 43: roller rotation synchronous gear, a: reversal angle, θ: piercing angle.

Claims (5)

[Claims] 1. A secondary battery comprising an electrode and an electrolytic solution, wherein the electrode is formed by bonding a negative electrode active material and a resin on a current collector foil provided with a hole having an inverted portion around the hole. A non-aqueous electrolyte secondary battery electrode characterized by being prepared by applying a mixture comprising an agent. 2. The hole diameter (d mm) of the hole is 0.02 ≦ d ≦ 2.
And the gap (Lm) of the hole is 0.1 ≦ L ≦ 10, and the height (h mm) of the inversion portion around the hole from the foil surface
Wherein 0.01 ≦ h ≦ 0.1, and two or more nonaqueous electrolyte secondary battery electrodes are provided. 3. The non-aqueous secondary battery electrode according to claim 1, wherein the shape of the hole set in the electrode battery has an elliptical, oblong, or rhombic shape. 4. A mixture comprising an electrode active material and a resin binder is applied to the current collector foil according to claim 1, 2 or 3, dried, and then pressed by a press (1). ~ 2ton
/ Cm ² ), the non-aqueous electrolyte secondary battery electrode according to claim 1, wherein the reversal portion is deformed by a pressing force. 5. A secondary battery comprising an electrode and an electrolytic solution, wherein the first surface of the electrode is coated, dried, and then inverted, so that the first surface is opposed to the second surface via a foil. Claims 1, 2, 3
A roller having a pin shape on the surface thereof, which has a hole, and an electrode material formed on the second surface so as to fill the hole by passing through between the opposing rollers that apply a reaction force via the electrode. A method for producing an electrode for a non-aqueous electrolyte secondary battery, which comprises applying, drying and compressing under pressure of 1 to ² ton / cm ² .