JPH11176422A - Manufacture of electrode for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the manufacture of an electrode in which electrode active material layers on both sides of a collector do not exfoliate. SOLUTION: This manufacture of an electrode for a battery is constituted by sequentially applying electrode coating compositions including an electrode active material, a binder, a solvent and acid on both sides of a planar collector, and by respectively forming electrode active material layers on the both sides of the collector. Here, the manufacture has a front surface layer drying process, applying the electrode coating compositions on the surface of the collector, forming a coated layer and drying the coated layer, and a back surface layer drying process of the same kind. The drying processes of the front and the back surface layers include a first drying process performed at a temperature range T1 of 70-90 deg.C and a second drying process performed at a temperature range T2 of 120-200 deg.C, so that the temperature difference (T2-T1) is set to be more than 40 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrode for a battery, and more particularly to a method for manufacturing an electrode for a non-aqueous electrolyte battery, wherein an electrode active material layer is firmly provided on both surfaces of an electrode current collector. The present invention relates to a method for producing an electrode for a battery which can be used.

[0002]

2. Description of the Related Art An electrode of a lithium ion secondary battery is formed by applying a paint containing an electrode active material to both surfaces of an electrode current collector, respectively.
It is formed by drying. In particular, the coating for forming the negative electrode contains a negative electrode active material and a binder,
This negative electrode active material is appropriately dispersed within a range not to be destroyed. The paint for forming the negative electrode is first applied to one side of the electrode current collector made of a metal foil, dried, and then applied to the back side (the other side) in the same manner and dried. Thereby, the electrode active material layers are formed on both surfaces of the electrode current collector. The battery electrode in which the electrode active material layers are formed on both surfaces of the electrode current collector in this manner is then subjected to press working as necessary, and cut into a predetermined size for use.

Conventionally, when a coating film for forming a negative electrode is formed on a metal foil as an electrode current collector in this manner, the adhesiveness between the metal foil and the electrode active material layer is poor, and the electrode active material is poor. There has been a problem that the material layer may peel off.

[0004] In order to solve such a problem, there have been proposed a method of increasing the resin content in the electrode coating material and a method of adding an acid. Japanese Patent Application Laid-Open No. 2-68855 discloses that the addition of an acid to a paint improves the adhesion between an electrode current collector and a coated electrode active material layer.

[0005]

However, in the case where an acid is added to a paint in advance, the adhesion may not be improved unless the coating film is dried under appropriate drying conditions.

[0006] Also, compared to one side of the electrode current collector on which the electrode active material layer is formed first (hereinafter referred to as "A-side"), the back side of the electrode current collector on which the electrode active material layer is formed later ( Less than,
In “B side”, the adhesiveness of the electrode active material layer to the electrode current collector may be significantly reduced. Therefore, in the electrode manufactured in this manner, there is a problem that the electrode active material layer is easily peeled, particularly, the electrode current collector is easily peeled from the back surface (surface B). When the electrode active material layer is peeled off, the capacity of the battery using the electrode material is reduced, or the peeled electrode active material layer is sandwiched between the separator and, for example, the negative electrode, and the separator is broken and the negative electrode becomes a positive electrode. There is a risk of short circuit with the electrode.

Further, when an acid is previously added to the coating material, if the acid remains in the electrode active material layer, the characteristics may be adversely affected, and proper consideration should be given to the drying conditions. Had been requested.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electrode coating material containing an electrode active material, a binder, a solvent, and an acid, which is made of a flat electrode. In the method for manufacturing a battery electrode in which the electrode active material layer is formed on both surfaces of the electrode current collector by sequentially applying one surface and the other surface of the current collector, it is obvious that the productivity is good. It is an object of the present invention to provide a method for manufacturing a battery electrode in which the obtained electrode active material layer has extremely excellent adhesion between the electrode current collector and the electrode active material layer does not peel off on both surfaces of the electrode current collector. It is another object of the present invention to provide a method for manufacturing a battery electrode in which characteristics are not significantly deteriorated in consideration of the amount of acid remaining in the electrode active material layer.

[0009]

Means for Solving the Problems As a result of intensive studies by the inventors of the present application to solve the above-mentioned problems, the drying process of the coating film layer is divided into two stages, and the drying temperature conditions are appropriately adjusted. By setting, the adhesiveness between the electrode active material layer and the electrode current collector obtained regardless of the front side and the back side can be improved, and furthermore, it has been found that a battery electrode with extremely little deterioration in characteristics can be manufactured. The present invention has been reached.

That is, according to the present invention, an electrode paint containing an electrode active material, a binder, a solvent, and an acid is sequentially applied to one surface and the other surface of a flat electrode current collector.
In a method for manufacturing a battery electrode in which an electrode active material layer is formed on both surfaces of the electrode current collector, the method includes applying the electrode paint to one surface of the electrode current collector to form a coating layer. Forming and drying the coating layer, a surface layer drying step,
A back layer drying step of applying the electrode paint to the other surface of the electrode current collector to form a coating layer, and drying the coating layer, wherein the front layer drying step and the back layer drying step Is
Each includes a first drying step and a subsequent second drying step, wherein the first drying step is performed in a temperature range of 70 to 90 ° C., and the second drying step is performed in a temperature range of 120 to 20 ° C.
It is performed in a temperature range of 0 ° C., and the value of the temperature difference (T2−T1) between the drying temperature T2 in the second drying step and the drying temperature T1 in the first drying step is 40 ° C. or more. Be composed.

Further, the first drying step in the present invention is configured so that the applied coating layer is dried until touch drying.

According to the method for producing an electrode for a battery of the present invention, the drying step of the coating layer is divided into two steps, and by appropriately setting the drying temperature conditions, the coating layer can be obtained regardless of the front side and the back side. In addition, it is possible to improve the adhesion between the electrode active material layer and the electrode current collector, and to manufacture a battery electrode with very little deterioration in characteristics.

[0013]

Embodiments of the present invention will be described below in detail. FIGS. 1A and 1B show a state in which the electrode paint is sequentially applied to both surfaces 2a and 2b of the electrode current collector 2 and dried to form the electrode active material layers 51 and 55 sequentially. It is a drawing.

In the method of manufacturing a battery electrode according to the present invention, an electrode paint containing an electrode active material, a binder, a solvent, and an acid is applied to one surface 2a of a flat electrode current collector 2. After forming the coating layer, the coating layer is dried (surface layer drying step) to form the electrode active material layer 51 (FIG. 1).
(A)).

Next, in the same manner, an electrode paint is applied to the other surface 2b of the plate-shaped electrode current collector 2 to form a coating layer, and the coating layer is dried (a back layer drying step). ), And an electrode active material layer 55 is formed (FIG. 1B). In such a basic manufacturing process, the main part of the present invention is that the drying step (the front layer drying step and the back layer drying step) of each coating layer is divided into two stages in each case, The condition is set.

First, a step of preparing an electrode paint used in the present invention will be described.

The electrode paint used in the present invention contains an electrode active material, a binder, a solvent, and an acid.

As the electrode active material, various materials can be used without any particular limitation as long as they are conventionally used as an electrode active material. The material of the electrode active material differs depending on whether it is used as a negative electrode or a positive electrode.

As an electrode active material for forming a negative electrode, a carbonaceous material is usually used. As the carbonaceous material, any conventionally used carbonaceous material can be used without particular limitation. Examples thereof include amorphous carbon, acetylene black, petroleum coke, artificial graphite, natural graphite, and graphite-based carbon fiber. And non-graphitizable carbon.

On the other hand, as the electrode active material for forming the positive electrode, various types of positive electrode active materials can be used without any particular limitation as long as they are conventionally used. For example, various positive electrode active materials such as lithium cobaltate, lithium manganate, and lithium nickelate can be used.

The binder is not particularly limited as long as it is a conventionally used binder, and various binders can be used. For example, as the binder, polyacrylonitrile (PAN), polyethylene terephthalate, polyvinylidene fluoride (PVDF), polyvinyl fluoride, or the like can be used.

The binder is used in an amount of usually 1 to 40 parts by weight, preferably 2 to 25 parts by weight, based on 100 parts by weight of the electrode active material.
Used in parts by weight.

The solvent is not particularly limited as long as it is a solvent conventionally used in preparing an electrode paint.
Various solvents can be used. As such a solvent, for example, N-methylpyrrolidone (NMP), pyrrolidone, N-methylthiopyrrolidone, dimethylformamide (DMF), dimethylacetamide, hexamethylphosphamide, or the like can be used alone or in combination.

The solvent is usually used such that the solid content (non-volatile content) in the electrode paint is 10 to 60% by weight, preferably 30 to 50% by weight.

The acid contained in the electrode coating may be an organic acid or an inorganic acid. Among these acids, weak acids are preferred, and particularly weak acids of organic acids are preferred. Preferred examples of such weak organic acids include oxalic acid, formic acid, maleic acid, and hydrates of these acids.

The acid is usually used in an amount of 0.01 to 3 parts by weight based on all solids such as the electrode active material, the binder and the conductive agent.
Preferably, it is used in a ratio of 0.2 to 1.0 part by weight.

When the electric conductivity of the electrode active material is poor, a conductive agent may be added as needed. As such a conductive agent, the above-described carbonaceous materials and various types of metal fine powders can be used. When adding a conductive agent,
The content of the conductive agent is usually 1 to 25 parts by weight, preferably 3 to 15 parts by weight, based on 100 important parts of the active material.

The electrode current collector used in the present invention includes:
A flat plate, particularly a metal foil, is preferably used. The metal material of the electrode current collector is not particularly limited as long as it is conventionally used for the electrode current collector, and various metal materials can be used. Examples of such a metal material include copper, aluminum, stainless steel, nickel, iron and the like.

The electrode paint used in the present invention is prepared by mixing the above-mentioned components, and is a slurry-like mixture. In the electrode coating material, it is necessary that the electrode active material is appropriately dispersed within a range where the electrode active material is not destroyed. The electrode active material is mixed and dispersed using a planetary mixer, a ball mill, or the like.

The electrode paint thus prepared is applied to one surface of the electrode current collector to form a coating layer. The application of the electrode paint can be performed by a conventionally known method. For example, it can be applied to the electrode current collector by an application method such as an extrusion coat, a gravure coat, a reverse roll coat, a dip coat, a kiss coat, a doctor coat, a knife coat, a curtain coat, and a screen print.

In this manner, one surface 2 of the electrode current collector 2
The coating layer applied to a is dried in the next drying step (surface layer drying step). Next, in the same manner, the coating layer applied to the other surface 2b of the electrode current collector 2 is dried in the next drying step (surface layer drying step).

The present invention is characterized by specific operations in these drying steps. That is, in the present invention, the drying step (the front layer drying step and the back layer drying step)
In each case, the drying temperature conditions are set in two stages. That is, each of the front surface layer drying step and the back surface layer drying step has a first drying step and a second drying step performed subsequently.

In the first drying step performed first, the drying temperature T1 is 70 to 90 ° C., more preferably 80 to 9 ° C.
It is operated in a temperature range of 0 ° C. This temperature T1 is 70 ° C.
If it is less than this, it takes a very long time to dry the electrode paint applied to the electrode current collector, and the length of the drying furnace becomes very long, which is not preferable from the viewpoint of productivity. This temperature T
If the temperature exceeds 90 ° C., the initial drying time of the coating film layer will be short, and the acid contained in the electrode paint will not be able to sufficiently etch the oxide layer on the metal foil surface as the electrode current collector. In some cases, the adhesive strength of the layer is not sufficient. Also,
In the surface layer drying step performed first after the application, the excess acid that is not used for etching and evaporates increases, and this acid adheres to the back surface of the electrode current collector, and the other surface 2b (back surface)
This tends to lower the adhesive strength of the coating layer on the side.

In the first drying step, the coated film layer after application is
Drying treatment is performed until touch drying. The drying time may be appropriately set with the aim of the touch-drying state. here,
The state of touch-to-touch drying refers to a dry state in which a part of the coating film surface is touched with a finger in a drying oven during the first drying step, and the coating or solvent or the like does not reach the finger surface.

In the subsequent second drying step, the drying temperature T2 is operated in a temperature range of 120 to 200.degree. When the temperature T2 is lower than 120 ° C., drying of the coating film becomes insufficient, and after the electrode paint is dried,
After the electrode active material layer is formed, excess acid not used for etching the surface of the electrode current collector cannot evaporate, but remains in the electrode active material layer, and the amount of residual acid increases.
When the amount of the residual acid increases, the electric characteristics of the battery deteriorate.
The adhesion strength of the coating layer is not good. When the drying temperature T2 is 200
If the temperature exceeds ℃, oxidation of uncoated portions at both ends of the metal foil as an electrode current collector occurs, and furthermore, oxidation of the electrode current collector may occur between the electrode active material layer and the electrode current collector. For this reason, the adhesive strength of the coating layer is reduced. Therefore, it is necessary to dry the electrode active material layer at a drying temperature T2 of 120 to 200 ° C.

Further, in the present invention, the temperature difference (T2-T1) between the drying temperature T2 in the second drying step and the drying temperature T1 in the first drying step is 40 ° C. or more,
In particular, it is set at 40 to 110 ° C. This temperature difference (T2
When the value of -T1) is less than 40 ° C., a tendency that residual acid in the electrode active material layer tends to increase occurs.

By the predetermined drying operation in the present invention, it is possible to improve the adhesiveness of the electrode active material layer applied to one surface 2a (surface) of the electrode current collector, which is performed first, and also to perform the next operation. The adhesiveness of the electrode active material layer applied to the other surface 2b (back surface) of the electrode current collector can be greatly improved as compared with the related art. In the conventional method, it is not clearly understood why the adhesion deterioration on the other surface 2b (back surface) occurs more remarkably than on the first surface 2a applied first. There are several possible reasons, but the most probable reason is that the acid in the paint that evaporates or sublimates during drying adheres to the electrode current collector on the other surface 2b (back surface). It is considered that some compound that inhibits adhesion is formed between the attached acid and the metal of the electrode current collector.

The electrode having the electrode active material layers on both sides of the electrode current collector obtained by the production method of the present invention may be adjusted in thickness by a roller press or the like, if necessary.

Next, the obtained electrode material has a predetermined width,
Cut to length. Note that in order to obtain electrical contact between the electrode current collector and the outside, it is preferable to provide a portion of the electrode current collector where no electrode active material layer is formed. For example, as a method of not forming an electrode active material layer in such a portion, a method of forming an uncoated portion in advance of a coating operation,
After the formation of the electrode active material layer, a method of partially removing the electrode active material layer and the like can be given.

[0040]

The present invention will be described below in further detail with reference to specific examples.

(Example 1) Preparation of paint for negative electrode The composition of the paint for the negative electrode was set as follows, and a paint for the negative electrode was prepared in the following manner.

Mesocarbon microbeads (negative electrode active material) 87 parts by weight Acetylene black (conductive agent) 3 parts by weight Polyvinylidene fluoride (binder) 10 parts by weight N-methylpyrrolidone (solvent) 136 parts by weight Hydrate (acid) ... 0.5 parts by weight The negative electrode paint was specifically prepared as follows.

A lacquer was prepared by dissolving 10 parts by weight of a binder in 115 parts by weight of a solvent. 87 parts by weight of the negative electrode active material and 3 parts by weight of the conductive agent were mixed. This mixture was added to the lacquer and mixed, and oxalic acid dihydrate was further added to the solvent 2
A solution dissolved in 1 part by weight was added and mixed well to obtain a negative electrode paint.

Preparation of Negative Electrode One side 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm
After coating the above negative electrode paint by a nozzle coating method to form a coating layer (coating on one side 2a side), the drying temperature T
In a first drying step at 1 = 90 ° C., the coating layer was dried until touch drying. Next, in a second drying step at a drying temperature T2 of 130 ° C., the touch-dried coating film layer was completely dried.

In the same manner, the above negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step at a drying temperature T1 = 90 ° C., the coating film layer was subjected to drying treatment until touch drying. Next, in a second drying step at a drying temperature T2 of 130 ° C., the touch-dried coating film layer was completely dried.

The electrode current collector having the electrode active material layers thus obtained on both sides is compression-molded by a roller press, and then cut into a predetermined size to obtain a first embodiment.
Was prepared.

Example 2 A negative electrode paint used in Example 1 was applied to one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm by a nozzle coating method to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 90 ° C.
In the first drying step, the coating layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 160 ° C., the coating layer of the touch drying was completely dried.

In the same manner, the above-mentioned negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step at a drying temperature T1 = 90 ° C., the coating film layer was subjected to drying treatment until touch drying. Next, in the second drying step at a drying temperature T2 of 160 ° C., the coating layer of the touch drying was completely dried.

The thus obtained electrode current collector having electrode active material layers on both sides is compression-molded by roller pressing, and then cut into a predetermined size to obtain a second embodiment.
Was prepared.

Example 3 A negative electrode paint used in Example 1 was applied by a nozzle coating method on one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 90 ° C.
In the first drying step, the coating layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 190 ° C., the coating layer of touch drying was completely dried.

In the same procedure, the coating material for the negative electrode is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step at a drying temperature T1 = 90 ° C., the coating film layer was subjected to drying treatment until touch drying. Next, in the second drying step at a drying temperature T2 of 190 ° C., the coating layer of touch drying was completely dried.

The electrode current collector having the electrode active material layers thus obtained on both sides is compression-molded by a roller press, and then cut into a predetermined size.
Was prepared.

Example 4 The negative electrode paint used in Example 1 was applied by a nozzle coating method on one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm to form a coating film. After forming a layer (coating on one side 2a side), drying temperature T1 = 70 ° C.
In the first drying step, the coating layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 160 ° C., the coating layer of the touch drying was completely dried.

In the same procedure, the above negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step at a drying temperature T1 = 70 ° C., the coating film layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 160 ° C., the coating layer of the touch drying was completely dried.

The electrode current collector having the electrode active material layers thus obtained on both sides is compression-molded by a roller press, and then cut into a predetermined size to obtain a fourth embodiment.
Was prepared.

(Example 5) The negative electrode paint used in Example 1 was applied by a nozzle coating method onto one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 µm to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 80-
In a first drying step at a temperature of 90 ° C., the coating layer was dried until touch drying. Next, the drying temperature T2 = 120-
In the second drying step at a temperature of 130 ° C., the touch-dried coating film layer was completely dried.

In the same procedure, the above negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step in the range of drying temperature T1 = 80 to 90 ° C., the coating film layer was dried until touch drying. Next, in the second drying step in the range of drying temperature T2 = 120 to 130 ° C., the coating layer of touch drying was completely dried.

The electrode current collector having the electrode active material layers thus obtained on both sides is compression-molded by roller pressing, and then cut into a predetermined size to obtain a fifth embodiment.
Was prepared.

Example 6 The negative electrode paint used in Example 1 was applied by a nozzle coating method on one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 90 ° C.
In the first drying step, the coating layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 200 ° C., the coating layer of the touch drying was completely dried.

In the same manner, the above-mentioned negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step at a drying temperature T1 = 90 ° C., the coating film layer was subjected to drying treatment until touch drying. Next, in the second drying step at a drying temperature T2 of 200 ° C., the coating layer of the touch drying was completely dried.

The electrode current collector having the electrode active material layers thus obtained on both sides is compression-molded by a roller press, and then cut into a predetermined size to obtain a sixth embodiment.
Was prepared.

(Comparative Example 1) The negative electrode paint used in Example 1 was applied by a nozzle coating method on one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 130
In a first drying step at a temperature of 0 ° C., the coating layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 170 ° C., the coating layer of touch drying was completely dried.

In the same procedure, the coating material for the negative electrode was applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface). 2b side coating), in a first drying step at a drying temperature T1 = 130 ° C., the coating film layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 170 ° C., the coating layer of touch drying was completely dried.

The thus obtained electrode current collector having the electrode active material layers on both sides is compression-molded by roller pressing, and then cut into a predetermined size to obtain a negative electrode sample of Comparative Example 1. Was prepared.

(Comparative Example 2) A negative electrode paint used in Example 1 was applied by a nozzle coating method on one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 100
In a first drying step at a temperature of 0 ° C., the coating layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 170 ° C., the coating layer of touch drying was completely dried.

In the same procedure, the negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface). 2b side coating), in a first drying step at a drying temperature T1 = 100 ° C., the coating film layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 170 ° C., the coating layer of touch drying was completely dried.

The thus obtained electrode current collector having the electrode active material layers on both surfaces was compression-molded by roller pressing, and then cut into a predetermined size to obtain a negative electrode sample of Comparative Example 2. Was prepared.

(Comparative Example 3) The negative electrode paint used in Example 1 was applied by a nozzle coating method onto one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 60 ° C.
In the first drying step, the coating layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 120 ° C., the coating layer of touch drying was completely dried.

In the same manner, the above negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step at a drying temperature T1 = 60 ° C., the coating film layer was subjected to drying treatment until touch drying. Next, in the second drying step at a drying temperature T2 of 120 ° C., the coating layer of touch drying was completely dried.

The thus obtained electrode current collector having the electrode active material layers on both surfaces was compression-molded by roller pressing, and then cut into a predetermined size to obtain a negative electrode sample of Comparative Example 3. Was prepared.

(Comparative Example 4) A negative electrode paint used in Example 1 was applied to one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm by a nozzle coating method to form a coating film. After forming a layer (coating on one side 2a side), drying temperature T1 = 70 ° C.
In the first drying step, the coating layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 110 ° C., the coating layer of touch drying was completely dried.

In the same procedure, the above negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step at a drying temperature T1 = 70 ° C., the coating film layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 110 ° C., the coating layer of touch drying was completely dried.

The thus obtained electrode current collector having the electrode active material layers on both sides was compression-molded by roller pressing, and then cut into a predetermined size to obtain a negative electrode sample of Comparative Example 4. Was prepared.

(Comparative Example 5) The negative electrode paint used in Example 1 was applied by a nozzle coating method onto one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 90 ° C.
In the first drying step, the coating layer was dried until touch drying. Next, in the second drying step in the range of drying temperature T2 = 210 to 250 ° C., the coating layer of the touch drying was completely dried.

In the same procedure, the above negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step at a drying temperature T1 = 90 ° C., the coating film layer was subjected to drying treatment until touch drying. Next, in the second drying step in the range of drying temperature T2 = 210 to 250 ° C., the coating layer of the touch drying was completely dried.

The thus obtained electrode current collector having the electrode active material layers on both surfaces was compression-molded by roller pressing, and then cut into a predetermined size to obtain a negative electrode sample of Comparative Example 5. Was prepared.

Comparative Example 6 A negative electrode paint used in Example 1 was applied by a nozzle coating method on one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 90 ° C.
In the first drying step, the coating layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 of 120 ° C., the coating layer of touch drying was completely dried.

In the same manner, the above negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step at a drying temperature T1 = 90 ° C., the coating film layer was subjected to drying treatment until touch drying. Next, in the second drying step at a drying temperature T2 of 120 ° C., the coating layer of touch drying was completely dried.

The thus obtained electrode current collector having the electrode active material layers on both sides was compression-molded using a roller press, and then cut into a predetermined size to obtain a negative electrode sample of Comparative Example 6. Was prepared.

(Comparative Example 7) The negative electrode paint used in Example 1 was applied on one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm by a nozzle coating method to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 110
In a first drying step at a temperature of 0 ° C., the coating layer was dried until touch drying. Next, in a second drying step at a drying temperature T2 of 130 ° C., the touch-dried coating film layer was completely dried.

In the same procedure, the above negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), and in a first drying step at a drying temperature T1 = 110 ° C., the coating film layer was dried until touch drying. Next, in a second drying step at a drying temperature T2 of 130 ° C., the touch-dried coating film layer was completely dried.

The thus obtained electrode current collector having the electrode active material layers on both sides was compression-molded using a roller press, and then cut into a predetermined size to obtain a negative electrode sample of Comparative Example 7. Was prepared.

Comparative Example 8 The negative electrode paint used in Example 1 was applied to one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm by a nozzle coating method to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 90 ° C.
In the first drying step, the coating layer was dried until touch drying. Next, in a second drying step at a drying temperature T2 = 100 ° C., the coating layer of the touch drying was completely dried.

In the same procedure, the negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step at a drying temperature T1 = 90 ° C., the coating film layer was subjected to drying treatment until touch drying. Next, in the second drying step at a drying temperature T2 of 110 ° C., the coating layer of touch drying was completely dried.

The thus obtained electrode current collector having the electrode active material layers on both sides was compression-molded by applying a roller press, and then cut into a predetermined size to obtain a negative electrode sample of Comparative Example 8. Was prepared.

Comparative Example 9 The negative electrode paint used in Example 1 was applied by a nozzle coating method on one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 80 ° C.
In the first drying step, the coating layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 = 80 ° C., the touch-dried coating film layer was completely dried.

In the same procedure, the coating material for the negative electrode was applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), and in a first drying step at a drying temperature T1 = 80 ° C., the coating film layer was dried until touch drying. Next, in the second drying step at a drying temperature T2 = 80 ° C., the touch-dried coating film layer was completely dried.

The thus obtained electrode current collector having the electrode active material layers on both surfaces was compression-molded by applying a roller press, and then cut into a predetermined size to obtain a negative electrode sample of Comparative Example 9. Was prepared.

Comparative Example 10 The negative electrode paint used in Example 1 was applied by a nozzle coating method on one surface 2a of a rolled copper foil (electrode current collector) having a thickness of 18 μm to form a coating film. After forming the layer (coating on one side 2a side), drying temperature T1 = 1
In a first drying step at 50 ° C., the coating film layer was dried until touch drying. Next, the second drying temperature T2 = 150 ° C.
In the drying step, the coating layer of touch drying was completely dried.

In the same procedure, the above-mentioned negative electrode paint is applied on the other surface 2b of the rolled copper foil (electrode current collector) by a nozzle coating method to form a coating layer (the other surface 2b). Side coating), in a first drying step at a drying temperature T1 = 150 ° C., the coating film layer was subjected to drying treatment until touch drying. Next, in the second drying step at a drying temperature T2 = 150 ° C., the coating layer of the touch drying was completely dried.

The electrode current collector having the electrode active material layers thus obtained on both sides was compression-molded using a roller press, and then cut into a predetermined size to obtain a comparative example 10.
Was prepared.

Example 7 In Example 1, the concentration of the acid in the electrode paint was changed to 0.1% by weight. Otherwise in the same manner as in Example 1, a negative electrode sample of Example 7 was produced.

(Example 8) In Example 1, the concentration of the acid in the electrode paint was changed to 1.0% by weight. Otherwise in the same manner as in Example 1, a negative electrode sample of Example 8 was produced.

(Example 9) In Example 2, the concentration of the acid in the electrode paint was changed to 0.1% by weight. Otherwise in the same manner as in Example 2, a negative electrode sample of Example 9 was produced.

Example 10 In Example 2, the concentration of the acid in the electrode paint was changed to 1.0% by weight. Otherwise in the same manner as in Example 2, a negative electrode sample of Example 10 was produced.

The samples were evaluated for residual acid and adhesiveness in the following manner.

Measurement of Residual Acid 1.3 g of the electrode active material layer coating film was peeled off from the front and back surfaces of the electrode, respectively, and a total of 2.6 g of a coating film measurement sample was taken out.

The peeled coating film was placed in a styrene container for specifications (容器
1 inch x 3 inch: # 6134) and methacrylic ball for spec (Ф (3/8) inch: # 3112)
And two Spex mixers (# 800 for 10 minutes)
Grind in 0).

Take 2.5 g of the pulverized coating film and place in a 50 cc beaker. Add 5 ml of pure with a whole pipette and stir vigorously with a glass rod. When a black uniform paste is formed, the mixture is allowed to stand for 30 minutes, and filtered with a filter paper to prepare a sample solution. This sample solution is added to Dione
x The amount of acid was measured by a QIC ion chromatograph analyzer, and classified according to the measured values into the following ranks.

：: No effect on electric characteristics (less than 40 ppm) Δ: Small effect on electric characteristics (40 ppm or more and 100 ppm)
×): Large effect on electrical characteristics (100 ppm or more) Adhesive electrode sample was placed on a horizontal table, and the blade of a scratch tester (ERICHSEN MODE 295, 11 blades at 1 mm intervals) was 90 ° to the electrode And pull it evenly to the left and right to make a streak on the electrode surface. The depth of this streak is about the thickness of the electrode active material layer. Next, a 90-degree streak was attached to the first streak, and the strip was tested in a grid pattern (JIS K).
5400; cross-cut method with 8.5 adhesion). The degree of exposure of the copper foil was evaluated according to the following criteria.

The adhesiveness of both the electrode active material layer 51 applied first (for convenience, referred to as surface A) and the electrode active material layer 55 applied on the back surface (for convenience, referred to as surface B) are determined. Was measured for each.

：: No peeling of the electrode active material layer is observed. ：: The peeling area of the electrode active material layer is less than 20% of the entire square area. Δ: The peeling area of the electrode active material layer is 20% of the total square area. X: 50% or less ×: The peeling area of the electrode active material layer exceeds 50% of the area of the entire square. The results are shown in Table 1 below.

[0103]

[Table 1]

[0104]

The effects of the present invention are clear from the above results. That is, the present invention provides an electrode paint comprising an electrode active material, a binder, a solvent, and an acid, which is sequentially applied to one surface and the other surface of a flat electrode current collector. In the method for manufacturing a battery electrode in which the electrode active material layers are formed on both surfaces of the body, the drying step of the coating layer is divided into two stages, and the drying temperature conditions are appropriately set. Not only the adhesion of the coating film on one surface to be coated on the surface is good, but also the adhesion of the coating film on the other surface to be coated later (the so-called back surface) is extremely good without deteriorating. Quality can be guaranteed. In addition, the deterioration of the characteristics of the battery electrode is extremely small.

As a result, a decrease in battery capacity can be prevented, and a short circuit between the positive electrode and the negative electrode caused by peeling of the electrode active material layer can be prevented, and safety can be improved.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) show a state in which an electrode paint is sequentially applied to both surfaces 2a and 2b of an electrode current collector 2 and dried to form electrode active material layers 51 and 55 sequentially. FIG.

[Explanation of symbols]

2 ... Electrode current collector 2a ... One surface of the electrode current collector (the side on which the coating layer is first formed) 2b ... The other surface (back surface) of the electrode current collector 51, 55 ... Electrode active material layer

Claims (2)

[Claims] 1. An electrode active material, a binder, a solvent,
Production of an electrode for a battery in which an electrode paint containing an acid is sequentially applied to one surface and the other surface of a flat electrode current collector to form an electrode active material layer on both surfaces of the electrode current collector, respectively. In the method, the manufacturing method includes a step of applying the electrode paint to one surface of the electrode current collector to form a coating layer, and drying the coating layer. Forming a coating layer by applying the electrode paint to the other surface of the back surface layer, and a back layer drying step of drying the coating layer, the surface layer drying step and the back layer drying step, A first drying step and a subsequent second drying step, wherein the first drying step is performed in a temperature range of 70 to 90 ° C., and the second drying step is performed in a temperature range of 120 to 200 ° C. The drying temperature T in the second drying step.
2. A method for producing a battery electrode, wherein the temperature difference (T2−T1) between the drying temperature T1 and the drying temperature T1 in the first drying step is 40 ° C. or more. 2. The method for producing a battery electrode according to claim 1, wherein in the first drying step, the coating film layer after application is dried until touch drying.