JPH113701A - Manufacture of battery electrode and equipment thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery electrode with high bulk density and a smooth surface through less pressing number and light pressing by preheating a laminate prepared by applying an electrode mix to one side or both sides of a metal foil current collector, before it is pressed or heat-roll pressed. SOLUTION: A laminate 7 is successively fed from a winding out roll 1, where the laminate 7 is wound and stacked, and sent to a preheating part 3 through a guide 2. The laminate 7 is passed on a plurality of small diameter heating drums or on a large diameter heating drum, having the dimension capable of entering the preheating part 3, heated once, then sent to a heat press roll 4, without the temperature is not being lowered much. The laminate 7 is heated and at the same time pressed with the heat press roll 4 comprising two heating rolls and a hydraulic cylinder 6. The heated and pressed laminate 7 is wound with a winding roll 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for manufacturing an electrode for a battery, and more particularly to a technique for easily increasing the density of a laminate obtained by applying an electrode mixture onto a metal foil current collector formed by lamination. The present invention relates to a method for manufacturing a battery electrode and an apparatus for manufacturing the same. Particularly, the present invention relates to a battery used for a lithium battery and a lithium ion secondary battery.

[0002]

2. Description of the Related Art Conventionally, for a battery electrode, after applying an electrode mixture on a metal foil current collector, the bulk density has been increased by performing a pressure press at room temperature. In this method, in order to obtain a higher bulk density, the pressure is increased, and further pressing is performed. As a result, excessive pressing is performed, so that the active material is destroyed, the current collector foil is destroyed, and the particles fall off And other problems. Therefore, by increasing the bulk density by applying pressure while heating and fluidizing the binder added for the purpose of bonding between the active materials and between the active material and the current collector, that is, a heating roll press using a heating roll is used. Proposed.
However, heat transfer is not sufficient only by a heated roll press, and a desired bulk density cannot be easily obtained. On the other hand, if the pressing speed is reduced in order to obtain a sufficient heat transfer, there is a problem that productivity is deteriorated.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in order to solve such a problem, and it is intended that a laminate obtained by applying an electrode mixture onto a metal foil current collector be preheated. , A pressure press, more preferably this pressure press is a heated roll press, by using this in combination, a small number of presses, a battery electrode having a high bulk density and a smooth surface with a light press pressure The purpose is to provide.

[0004]

A method of manufacturing a battery electrode according to the present invention is directed to a general laminated wound battery comprising an electrode mixture applied to one or both sides of a strip-shaped metal foil current collector. The method for producing a battery electrode according to any one of claims 1 to 3, characterized in that the metal foil current collector and a laminate obtained by applying the electrode mixture to one or both surfaces thereof are preheated before pressing or hot roll pressing. .

As the preheating device of the present invention, a general heating device may be used, but the temperature of the coating film can be raised in a short time, and the fluidity of the electrode mixture is not lost until the moment of roll pressing. From the viewpoint that the temperature of the coating film can be maintained, it is preferable to arrange one large drum or several small drums in the preheating constant temperature layer. The preheating temperature is preferably set to be lower by about 50 ° C. than the melting point of the electrode mixture.

[0006] With this configuration, the number of press times is small.
With a small pressing pressure, an electrode with a smooth surface with a high bulk density
A pond electrode is obtained. The electrode used in the present invention is a positive electrode active material.
Examples include oxides represented by the following chemical composition formula (I).
Can be Chemical composition formula (I): Li_xM_yN_zO_Two(M is the transition metal
N represents at least one of the non-transition metals
Represents the species,_XYZAre 0.05 <X <1.10 and 0.8, respectively.
5 <Y ≦ 1.00, 0 ≦ Z <0.10. An oxide preferably used for the active material of the positive electrode of the present invention
The chemical composition formula Li _xM_yN_zO_Two(M is cobalt, d
One of nickel, manganese and other transition metals, or
N represents less of Al, In and Sn.
Both represent a kind,_XYZAre 0.05 <X <1.10.
0.85 <Y ≦ 1.00, 0 ≦ Z <0.10).
More preferably LiCoSnO_Two, LiNiSnz
O_Two, LiNiSnzO_Two, LiMnSn_zO_TwoAnd these
Is a mixture of (However, 0 ≦ Z <0.10
You. The inorganic compounds defined by the above chemical composition formula include Li
_0.5MnO_TwoIe, generally LiMn_TwoO_FourDescribed as
Also includes compounds of the composition. Z = 0, that is, Al, I
The case where n and Sn are not included is also within the scope of the present invention.

[0007] The active material of the negative electrode combined with the positive electrode of the present invention is not particularly limited as long as it can be charged and discharged. For example, various carbon materials described in JP-A-62-90863, having a true specific gravity of 1.3 to 1.8 g
/ Cm ³ , and various types of highly crystalline carbon materials, such as natural and artificial graphites. For example, coke as such a carbon material,
Examples include acetylene black, activated carbon, needle coke, mesophase microbeads, various carbon fibers, pyrolytic carbon, and fluid coke.

[0008] The material of the conductive auxiliary agent according to the present invention includes:
There is no particular limitation as long as the conductivity is high. For example, carbon or the like is a material often added as a conductive additive, but the type of carbon is not particularly limited, and activated carbon, various cokes, natural and artificial graphite, and the like can be used.
Of these carbons, various natural and artificial graphites are preferred because of their good electrical conductivity.

The shape of the conductive additive of the present invention is not particularly limited, but is preferably spherical or crushed. The electrode mixture used for the battery electrode of the present invention is not particularly limited, but the active material and the conductive auxiliary are mixed in a gas by various methods regardless of the positive electrode or the negative electrode, and then dispersed in a liquid containing a binder. To prepare a slurry. After that, it is applied and dried on the metal foil current collector to form a laminate. However, a conductive auxiliary may not be used for the negative electrode in some cases.

It is preferable that aluminum is used for the positive electrode and copper is used for the negative electrode for the current collector to which the slurry is applied. Teflon, polyethylene, nitrile rubber, polybutadiene, butyl rubber, polystyrene, styrene / butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethylcellulose, various latexes and acrylonitrile, vinyl fluoride, vinylidene fluoride, propylene fluoride And polymers such as chloroprene fluoride and mixtures thereof. Among them, polymers such as vinylidene fluoride, propylene fluoride, and chloroprene fluoride are preferred. The temperature of the pressure press is not particularly limited, but in order to increase the bulk density efficiently, around the melting point of the binder used,
The temperature is preferably in the range of melting point + 20 ° C. to melting point −20 ° C., more preferably in the range of melting point −20 ° C.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. FIG. 1 shows an example of a press machine, and FIG. 2 shows an example of a preheating portion in FIG. FIG. 2 is an example of the inside of the preheating unit 3 in FIG. It is important for the small diameter heating drum 8 to have a plurality of diameters, and for the large diameter heating drum 9 to have a diameter large enough to enter the preheating section. By raising the temperature of the body to the target temperature in a short time and further setting the drum diameter and the number, the time required for the laminated body to come into contact with the heating drum can be lengthened, so that the temperature decrease before reaching the heating press roll 4 is minimized. It is possible to suppress.

As shown in FIG. 1, the laminate 7 is sequentially sent out from the unwinding roll 1 on which the laminate 7 is wound and laminated, and sent to the preheating unit 3 via the guide 2. Preheating unit 3
Inside, the laminated body 7 passes over the drum 8, the temperature of the laminated body 7 is raised once, and thereafter, the laminated body 7 is sent to the heating press roll 4 with a small temperature decrease. The heating press roll 4 includes two heating rolls and a hydraulic cylinder 6. The fed laminate 7 is sandwiched between the heating rolls 4, and is pressed by the hydraulic cylinder 6 while being heated. The heat-pressed laminate 7 is then wound by winding means 5 (roll).

The laminate 7 thus formed is a battery electrode having a high bulk density and a smooth surface with a small number of presses and a small press pressure. The present invention is not limited to these devices, and the smaller the temperature drop from the preheating portion to the heated press roll, the better.

[0014]

Example 1 A carbon negative electrode active material was prepared so that polyvinylidene fluoride was 10 parts by weight with respect to the active material.
It was added to a solution dissolved in 2-pyrrolidone to obtain a slurry. This slurry was applied to one surface of a 15 μm copper foil and dried and solidified to obtain a 130 μm coating film.

The coating film was preheated by a press machine shown in FIG. 1 and pressed a total of seven times with the temperature of a heated press roll set at 120 ° C. FIG. 3 shows changes in the bulk density of the active material for each press.

[0016]

Example 2 FIG. 3 shows a change in the bulk density of the active material as a result of pressing in the same manner as in Example 1 except that the heated press roll of the press machine shown in FIG. 1 was used at room temperature.

[0017]

Example 3 A compound was prepared by adding 2.5 parts by weight of flaky graphite and acetylene black as conductive agents to a cobalt oxide composite oxide of lithium as a positive electrode active material. Next, a solution of vinylidene fluoride in N-methyl-2-pyrrolidone was added so as to be 3 parts by weight with respect to this compound to obtain a slurry. This slurry is 15 μm
And coated and dried and solidified to obtain a coating film of 240 μm. The obtained coating film was pre-heated by the press shown in FIG. 1 and the temperature of the heated press roll was set to 120 ° C., and the linear pressure was set to 100 kg / cm, 200 kg / cm, and 300 kg / cm.
Pressing was performed three times under four levels of pressing pressure of kg / cm and 400 kg / cm. FIG. 4 shows the change in the bulk density of the positive electrode active material at that time.

[0018]

EXAMPLE 4 FIG. 3 shows the change in the bulk density of the positive electrode active material as a result of pressing in the same manner as in Example 3 except that the heated press roll of the press shown in FIG. 1 was used at room temperature.

[0019]

Comparative Example 1 FIG. 3 shows the change in the bulk density of the active material as a result of pressing in the same manner as in Example 1 except that the preheating section of the press machine shown in FIG. 1 was not used.

[0020]

Comparative Example 2 Changes in the bulk density of the active material as a result of pressing in the same manner as in Example 1 except that the preheating section of the press machine shown in FIG. 1 was not used and the roll press was used without heating. Is shown in FIG.

[0021]

Comparative Example 3 The bulk density of the positive electrode active material as a result of pressing in the same manner as in Example 3 except that the preheating section of the press machine shown in FIG. 1 was not used and the roll press was used without heating was used. The changes are shown in FIG.

[0022]

According to the present invention, a battery electrode having a high bulk density and a smooth surface can be easily obtained with a small number of presses and a small press pressure.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a battery electrode forming apparatus of the present invention.

FIG. 2 is a schematic cross-sectional view of a preheating unit included in the battery electrode forming apparatus.

FIG. 3 is a diagram showing a change in bulk density with the number of presses when using the battery electrode forming apparatus of the present invention.

FIG. 4 is a diagram showing a change in bulk density with pressing conditions when using the battery electrode forming apparatus of the present invention.

[Explanation of symbols]

 Reference Signs List 1 unwinding roll 2 guide 3 pre-heating unit 4 heating press roll 5 winding roll 6 hydraulic cylinder 7 laminated body 8 heating drum (small diameter) 9 heating drum (large diameter)

Claims (3)

[Claims] 1. A method for manufacturing a battery electrode, comprising forming an electrode mixture containing an active material and a binder on a current collector, wherein a preliminarily heated laminate is prepared by applying the electrode mixture onto the current collector.
Next, a method for manufacturing a battery electrode, which comprises pressing the laminate under pressure. 2. The method for manufacturing a battery electrode according to claim 1, wherein the pressure press is a heated roll press. 3. An apparatus for producing a battery electrode in which an electrode mixture having an active material and a binder is formed on a current collector,
Unwinding means for sending out the laminate coated with the electrode mixture on the current collector, and preheating means for preheating the laminate,
A device for manufacturing a battery electrode, comprising: a heating / pressurizing means for heating and pressurizing the preheated laminate.