JPH10312796A - Electrode coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode coating apparatus which prevents a suspension liquid in which an electrode active material is dispersed from adhering to a non-coating part of a battery electrode without retarding the coating speed of the suspension liquid and which surely provides safety of and high productivity of batteries. SOLUTION: A blade 14 to lead a suspension liquid 4 to an aperture part 13 on the opposite to a metal foil 1 in a blade frame body 12 of a coater head 5 of this electrode coating apparatus is installed and the aperture part 3 is opened or closed by rotating a shutter 15 on a shutter axis 16. By the opening and closing control, the suspension liquid 4 is dripped on the metal foil 1 and due to the running movement of the foil, the suspension liquid 4 is applied to the metal foil 1 while being formed in a prescribed pattern. The blade 14 is made of a material having critical surface tension 40 dyn/cm or lower, preferably 25 dyn/cm or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode coating apparatus, and more particularly, to preventing a suspension in which an active material is dispersed from being formed on a non-coated part of an electrode, thereby ensuring safety and productivity of a coated battery. To a coated electrode coating apparatus.

[0002]

2. Description of the Related Art A secondary battery is used as a power source for driving a portable electronic device or the like for the purpose of economy and resource saving, and its use has been rapidly expanding in recent years. Also, with the miniaturization and high performance of electronic devices, batteries used are required to be small, light, and high in capacity.

Conventionally, lead batteries and nickel-cadmium batteries have been used as secondary batteries, but these batteries have insufficient energy density and are heavy. Therefore, in recent years, non-aqueous lithium secondary batteries having high energy density have been put to practical use. This lithium secondary battery is a coating type secondary battery, in which lithium in the positive electrode is occluded in the negative electrode via the electrolyte during charging, and lithium in the negative electrode is stored in the positive electrode through the electrolyte during discharging. It utilizes the electrochemical reversible reaction of being stored in the cell. That is,
Charge and discharge are performed by lithium flowing between the positive electrode and the negative electrode.

[0004] The source electrode of the lithium secondary battery is formed, for example, by disposing a suspension formed by dispersing a positive electrode active material or a negative electrode active material together with a binder on a foil-like current collector in a pattern. It is made by applying, drying and pressing together. After cutting the electrode material into a predetermined size, a lead wire is provided on an exposed portion of the current collector to form an electrode.

[0005] In order to perform pattern coating, a die or a coater, a kiss coater, a blade coater, or the like is provided with a shutter or the like so that intermittent coating can be performed, or a predetermined pattern is formed by partially closing a mesh. Screen coater etc.

[0006] However, when a pattern is applied by these devices, the suspension splash may adhere to a portion where the current collector is exposed (hereinafter, referred to as a “non-applied portion”). When this splash penetrates the separator, an internal short circuit occurs.
In addition, if the bonding of the lead wire in the non-applied portion is defective due to the splash, there is a possibility that a problem such as charging failure may occur, and further, if the charge and discharge are repeated in the state of the bonding failure of the lead wire, In addition, there is a fear that an internal short circuit occurs due to expansion and contraction of the electrode, and the lead wire is peeled off. In addition, splash is improved by slowing down the coating speed,
On the other hand, there is a problem that productivity is reduced.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent the suspension from splashing on the non-coated portion of the battery electrode.
Provided is an electrode coating device that prevents the coating speed without reducing the coating speed and ensures the safety and productivity of a coating type battery.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has been made in consideration of the above-described problems, and provides an electrode coating method in which a suspension in which an active material forming a battery electrode is dispersed is applied on a current collector in a predetermined pattern. In the apparatus, the application tip portion where the suspension of the electrode coating apparatus is dropped on the current collector is set at a critical surface tension of 40 dy.
It is composed of a member of n / cm or less. In addition, an organic polymer resin or a metal member whose surface is coated with the organic polymer resin is used as the constituent member.

[0009] The application tip portion where the suspension of the electrode coating device is dropped on the current collector is defined as having a critical surface tension of 25 dyn / c.
m or less. In addition, the above problem is solved by using a metal member whose surface is coated with an organic polymer resin or a glass member whose surface is surface-treated with a surfactant as the constituent member.

According to the configuration of the present invention, the suspension in which the active material is dispersed is prevented from adhering to the non-applied portion of the current collector, and the application is performed only at a predetermined position while securing the conventional application speed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a lithium secondary battery will be described with reference to FIGS. FIG. 1 is a schematic view of an electrode coating apparatus according to the present invention. FIG. 2 is a schematic diagram of a press slit device, and FIG. 3 is a schematic diagram of a coater head. FIG. 4 is a diagram for explaining the electrodes. FIG. 5 is a sectional view showing the structure of the secondary battery according to the present invention.

First, a process for manufacturing an electrode of a lithium secondary battery will be described. As shown in FIG. 1, the metal foil 1 is wound up from the unwinding roll 2 around which the metal foil 1 serving as the current collector is wound toward the winding roll 3. At a position where the metal foil 1 has been fed from the unwinding roll 2 by a predetermined distance, a suspension 4 in which an active material to be applied to the metal foil 1 is dispersed.
Is disposed, and the suspension 4 is dripped from the tip of the coater head 5 and is applied to the metal foil 1. In the case of double-sided application, the film is wound once on the take-up roll 3 and then dried if necessary, and is again mounted on the take-up roll 2 to apply the back surface. Then, it is dried by a drier 6 and wound up on a winding roll 3 as an electrode raw material 7.

Next, as shown in FIG.
The sheet is sent out from the unwinding roll 8 on which the raw electrode sheet 7 is newly mounted, pressed by the press 9, cut into a predetermined width by the slitter 10, and each is wound on the winding roll 11.

The structure of the coater head 5 is, as shown in FIG.
A blade 14 for guiding the suspension 4 is provided. The opening 13 has a shutter 15 which is a shutter shaft 1.
It is opened and closed by rotating in the R direction about the axis 6.
The suspension 4 is dropped on the metal foil 1 by this opening / closing control, and the traveling of the metal foil 1 causes the metal foil 1 to move in a predetermined pattern.
The suspension 4 is to be applied on the top.

The suspension 4 is formed on the metal foil 1 in a predetermined pattern.
The raw electrode 7 coated with is formed, for example, as shown in FIG. 4A, divided into a non-applied portion 21 and an applied portion 22. This is cut through the slitter 10 shown in FIG. 2 and, for example, as shown in FIG.
-1 to 23-n are produced.

However, conventionally, when the predetermined pattern is formed, the non-coated portion 21 is
In some cases, the suspension 4 may be spattered and adhered, causing the problem described above. In the present invention, the suspension 4
Is prevented from splashing and attaching, and a highly safe lithium secondary battery and its productivity are ensured.

Next, configurations and characteristics of Examples 1 to 4 and Comparative Examples 1 and 2 when the present invention is applied to a lithium secondary battery will be described.

The positive electrode is made of a lithium metal oxide compound represented by the general formula LiMxOy (where M, x, and y represent the type of metal, the composition ratio of the metal, and the composition ratio of oxygen) to increase the conductivity. Then, a conductive agent such as acetylene black is formed into a paint together with a binder such as polyvinylidene fluoride, and is formed by applying a thin film on an aluminum foil.

The negative electrode is a carbon material that absorbs lithium ions, and is formed by coating a carbon powder having a low degree of crystallinity or a graphite powder having a high degree of crystallinity with a binder such as polyvinylidene fluoride and forming a thin film on a copper foil. Apply and dry to form.

Examples of the electrolyte include ethylene carbonate, butylene carbonate, diethyl carbonate, and the like.
Dimethyl carbonate, methyl ethyl carbonate and the like are used. As the electrolyte, lithium salts such as lithium hexafluorophosphate, lithium perchlorate, and lithium tetrafluoroborate are used.

As a separator for separating the positive electrode and the negative electrode and holding the electrolytic solution, a microporous film such as polyethylene or polypropylene is used.

Example 1 A positive electrode was manufactured as follows. LiCoO ₂ (average particle size 1
0 μm), 100 parts by weight of polyvinylidene fluoride (average molecular weight 300,000), 5 parts by weight of carbon black (average particle size 15 μm), and 100 parts by weight of N-methyl-2-pyrrolidone. The mixture is mixed with a disper for 4 hours to form a positive electrode active material, which is applied to both sides of a 20 μm-thick aluminum foil so as to have a dry thickness of 250 μm. Then, it was rolled at a temperature of 100 ° C. and a linear pressure of 400 kg / cm, and then cut into a width of 50 mm and a length of 450 mm to produce a belt-shaped positive electrode.

The negative electrode was manufactured as follows. 100 parts by weight of artificial graphite (average particle size: 100 μm), 15 parts by weight of polyvinylidene fluoride (average molecular weight: 300,000), and 200 parts by weight of N-methyl-2-pyrrolidone were mixed by a disper for 4 hours. The negative electrode active material was applied to a copper foil having a thickness of 10 μm on both sides so that the dry thickness became 210 μm, and dried. Then, it was rolled at a temperature of 100 ° C. and a linear pressure of 400 kg / cm, and then cut into a width of 52 mm and a length of 450 mm to produce a strip-shaped negative electrode.

The blade 14 of the coater head 5 used for producing the above-mentioned positive electrode and negative electrode was obtained by coating the surface of SUS304 with polytetrafluoroethylene (PTFE). The critical surface tension of PTFE is 20 dyn /
cm.

A lithium secondary battery shown in FIG. 5 was constructed using the positive electrode and the negative electrode produced as described above. Positive electrode 31
A positive electrode lead 32 is welded to the positive electrode 31, a 25 μm thick microporous polyethylene separator 33a, a negative electrode 34,
25 μm thick microporous polyethylene separator 33
b were successively superimposed and wound in a roll with the positive electrode lead 32 as a core, to produce a battery element having an outer diameter of 15 mm. Further, the negative electrode lead 35 extracted from the battery element was
Welded to the bottom of a 5 mm steel plate negative electrode can 36,
An insulating plate 37 is provided on the bottom of the
To be stored. 1 mol / L of LiPF in the negative electrode can 36
₆ / Ethylene carbonate solution is injected as a non-aqueous electrolytic solution. Then, an insulating plate 38, a gasket 39, and a safety valve 40 are installed on the upper part of the battery element, and the positive electrode lead 32 is welded to the positive electrode cover 41, thereby fixing the positive electrode cover 41. Fit into the negative electrode can 36,
The edge was crimped to produce a battery having an outer shape of 18 mm.

Example 2 A battery was manufactured in the same manner as in Example 1 except that the blade 14 of the coater head 5 was used in which the surface of SUS304 was coated with a vinyl chloride resin. The critical surface tension of the vinyl chloride resin is 39 dyn / cm.

Example 3 The blade 14 of the coater head 5 is formed by molding glass, and the surface thereof is formed, for example, by the chemical formula C ₈ F ₁₇ C ₂ H ₄ Si.
A cyclohexane solution of a surfactant represented by Cl ₃ was applied, washed with cyclohexane, and then washed with water. A battery was produced in the same manner as in Example 1 except that this blade was used. Incidentally, the critical surface tension of this surfactant is 10 dyn /
cm.

Example 4 A battery was manufactured in the same manner as in Example 1 except that the blade 14 of the coater head 5 was formed of a vinyl chloride resin.

Comparative Example 1 A battery was manufactured in the same manner as in Example 1 except that the blade 14 of the coater head 5 was used as SUS304.
Incidentally, the critical surface tension of a metal in general is 1000 dyn / cm or more.

Comparative Example 2 A battery was manufactured in the same manner as in Example 1 except that the blade 14 of the coater head 5 was formed of glass. The critical surface tension of glass is approximately 250 dyn / cm.

Blades 1 of Examples 1-4 and Comparative Examples 1-2
Table 1 shows the material, surface treatment, and critical surface tension of No. 4.

[0032]

[Table 1]

With respect to Examples 1 to 4 and Comparative Examples 1 and 2 described above, lead wire adhesion evaluation and initial charge evaluation were performed.

[0034] In the stage of welding the lead wire to the lead wire bonding evaluation non-coating section, it was peeling operation of the lead wire. At this time, the lead wire that does not peel off and the foil serving as the base material of the electrode is torn is regarded as good, and the lead wire at least partially peeled is regarded as defective. Table 1 shows the results.

Initial Charging Evaluation The battery prepared as described above was left for 12 hours in a normal operating temperature and humidity environment, and then charged for 5 hours under the conditions of a constant current of 500 mA, 4.25 V and a constant voltage. 4 hours after charging,
After being left in an environment of normal use temperature and humidity, the voltage was measured, and a voltage which did not reach 4.2 V was determined to be defective. Table 2 shows the results.

[0036]

[Table 2]

Table 2 shows that Examples 1 to 4 are superior to Comparative Examples 1 and 2 in evaluation of lead wire adhesion and initial charge. That is, as the critical surface tension of the blade is smaller, the suspension of the active material dispersed on the non-coated portion of the electrode raw material is less likely to fly due to the splash, and the welding of the lead wire to the non-coated portion is performed better. I think that the.

The material, structure and manufacturing method of the lithium secondary battery according to the present invention are the same as those conventionally used except for the improvement of the coating apparatus described above. The coating device is not particularly limited as long as a target coating pattern can be obtained, such as a gravure coater or a blade coater.

[0039]

As is clear from the above description, according to the present invention, the blade of the electrode coating apparatus is made of a member having a small critical surface tension, so that the active material is dispersed in the non-coated portion of the electrode raw material. This can reduce the flying of the suspension, prevent the occurrence of an internal short circuit, and satisfactorily weld the lead wire to the non-coated portion. Therefore, it is possible to provide an electrode coating device for a lithium secondary battery that ensures safety and productivity without reducing the coating speed.

[Brief description of the drawings]

FIG. 1 is a schematic view of an electrode coating apparatus according to the present invention.

FIG. 2 is a schematic view of a press / slit device.

FIG. 3 is a schematic view of a coater head.

FIG. 4 is a diagram for explaining electrodes.

FIG. 5 is a cross-sectional view illustrating a structure of a secondary battery according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal foil, 2 ... Unwind roll, 3 ... Take-up roll, 4 ... Suspension, 5 ... Coater head, 6 ... Dryer, 7 ... Electrode raw material, 8 ... Unwind roll, 9 ... Press,
DESCRIPTION OF SYMBOLS 10 ... Slitter, 11 ... Take-up roll, 12 ... Blade frame, 13 ... Opening, 14 ... Blade, 15 ... Shutter, 16 ... Shutter shaft, 21 ... Non-coating part, 22 ...
Coating part, 23-1 to 23-n: electrode, 31: positive electrode, 32
... Positive electrode lead, 33a, 33b ... separator, 34 ... negative electrode, 35 ... negative electrode lead, 36 ... negative electrode can, 37, 38 ... insulating plate, 39 ... gasket, 40 ... safety valve, 41 ... positive electrode lid

Claims (6)

[Claims] An electrode coating device for applying a suspension in which an active material forming a battery electrode is dispersed on a current collector in a predetermined pattern, wherein the suspension of the electrode coating device is applied to the current collector. An electrode coating apparatus, wherein a coating tip portion to be dropped is formed of a member having a critical surface tension of 40 dyn / cm or less. 2. The electrode coating apparatus according to claim 1, wherein the coating tip portion is made of an organic polymer resin. 3. The method according to claim 1, wherein the tip portion of the coating is made of a metal member whose surface is coated with an organic polymer resin.
The electrode coating device according to claim 1. 4. A coating tip portion where the suspension of the electrode coating device is dropped on a current collector is provided with a critical surface tension of 25 dyn / d.
2. A member made of a member having a size of not more than 1 cm.
4. The electrode coating device according to claim 1. 5. The method according to claim 1, wherein the application tip portion is formed of a metal member whose surface is coated with an organic polymer resin.
The electrode coating device according to claim 4. 6. The electrode coating apparatus according to claim 4, wherein the coating tip portion is made of a glass member whose surface is surface-treated with a surfactant.