JP2001210317A - Manufacturing method of electrode for nonaqueous electrolytic solution secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of nonaqueous electrolytic solution secondary battery in which charge-discharge properties such as discharge rate property, charge-discharge cycle life or the like and thermal stability are improved. SOLUTION: By using an electrode plate in which the temperature difference between a paste application face and a current collection body face is eliminated and in which a binder is treated so that it is uniformly dispersed in the mixture paste, the current collection effect of electrode plate increases, and charge- discharge property such as the discharge rate property, charge-discharge cycle life or the like and thermal stability are improved.

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 plate for a non-aqueous electrolyte secondary battery, in which a water-dispersible mixture paste can be uniformly applied on a current collector and dried. It is about the law.

[0002]

2. Description of the Related Art As a non-aqueous electrolyte secondary battery having a high discharge capacity, a lithium ion battery that inserts and releases lithium has recently been put to practical use.

The electrode plate used in this battery is prepared by dispersing a compound capable of occluding and releasing lithium together with a conductive agent and a binder in a dispersion medium using a disperser such as a homogenizer or a planetary mixer. Is prepared, and this dispersion paste is applied on a current collector and dried. A non-aqueous solvent is often selected as the dispersion medium, in order to avoid direct deterioration of the active material or the like due to water and deterioration of battery performance due to residual moisture when the battery is assembled. However, when an organic solvent is used, there are environmental problems such as a working environment and discharge, and it is required to handle it in an aqueous dispersion system.

[0004] Materials capable of absorbing and releasing lithium are not stable in water, and the rate characteristics of non-aqueous electrolyte secondary batteries,
This has adversely affected the charge / discharge cycle characteristics and thermal stability, and was a problem. JP-A-1-296567 and JP-A-3
JP-A-145071 and JP-A-3-64860 each disclose a method of previously washing an active material with water.

[0005]

However, even with the above method, the improvement of the discharge characteristics is not sufficient. The reason why the charge / discharge cycle deteriorates when a water-dispersible mixture paste is used has not been clarified yet, but in addition to the reasons described above, other factors that increase the internal resistance of the battery during cycling time include: It is suggested that there is.

According to the present invention, a charge / discharge characteristic such as a rate characteristic and a charge / discharge cycle life of a battery is improved by uniformly applying a water-dispersible mixture paste and obtaining a dried electrode plate.

[0007]

In order to solve the above-mentioned problems, the present invention applies a water-dispersed mixture paste containing a material capable of absorbing and releasing lithium and a binder onto a current collector and then drying the paste. When obtaining the electrode plate, the drying temperature is adjusted to uniformly disperse the binder in the mixture paste.
In particular, the drying temperature of the electrode plate is set to 85 ° C. to 120 ° C., the temperature difference between the current collector surface and the paste is eliminated, the binder can be uniformly dispersed in the mixture paste, and the rate characteristics of the battery, Charge / discharge cycle life characteristics and thermal stability can be improved.

[0008]

An embodiment of the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. The embodiment described below is an example embodying the present invention, and does not limit the technical scope of the present invention.

An electrode plate for a non-aqueous electrolyte secondary battery in which a water-dispersed mixture paste containing a main material capable of inserting and extracting lithium and at least one or more binders is applied to a current collector and dried. The production method, wherein the treatment temperature in the drying treatment after applying the water-dispersed mixture paste on the current collector is 85 ° C to 120 ° C.
° C, eliminating the temperature difference between the paste application surface and the current collector surface, and dispersing the binder uniformly in the mixture paste, the current collecting effect of the electrode plate is increased, the battery's rate characteristics,
The charge-discharge cycle life characteristics and thermal stability are improved.

[0010] The above-mentioned effect is obtained by applying a water-dispersed mixture paste on a current collector and then monitoring the temperature of the paste-applied surface of the electrode plate and the surface of the current collector by thermography in a drying treatment step. This is achieved by a manufacturing method in which the environmental temperature and the coating speed are set so that the temperature difference becomes infinitely zero, and drying is performed. On the other hand, when the drying temperature is lower than 85 ° C., water in the aqueous dispersion mixture paste remains, and the current collecting effect cannot be sufficiently enhanced. If the temperature exceeds 120 ° C., the temperature difference between the paste-coated surface and the current collector surface increases due to the difference in heat capacity between the paste and the current collector, and the mixture is cracked, which also sufficiently enhances the current collecting effect. Can not do.

[0011]

Next, specific examples of the present invention will be described.

The positive electrode plate was manufactured as follows.

An aqueous dispersion of positive electrode active material LiCoO ₂ , acetylene black as a conductive agent, and PTFE as a binder;
A carboxymethylcellulose aqueous solution was kneaded in a mixer as a thickener to obtain a positive electrode mixture-dispersed paste. The prepared positive electrode mixture paste was applied on both sides of the aluminum foil current collector and dried, and then compression molded by a roller press and cut into a predetermined size to obtain a belt-shaped positive electrode plate.

On the other hand, the negative electrode plate was manufactured as follows.

An artificial graphite capable of absorbing and releasing lithium, an aqueous SBR dispersion as a binder, and an aqueous carboxymethylcellulose solution as a thickener were kneaded in a mixer to obtain a negative electrode mixture-dispersed paste. After applying the prepared negative electrode mixture paste to both surfaces of the copper foil current collector, the drying was performed under different drying conditions.

The temperature in the thermostat was adjusted to 85 ° C., the temperature difference between the paste-coated surface and the current collector surface was adjusted to 1 ° C., and the dried product was adjusted to the negative electrode plate A of the present invention.
The negative electrode plate B of the present invention was adjusted and dried at a temperature difference between the paste-coated surface and the current collector surface of 2 ° C., the temperature in the thermostat was set at 50 ° C., and the temperature difference between the paste-coated surface and the current collector surface. Was adjusted to 0 ° C. and dried, and a negative electrode plate C of a comparative example was dried.
The temperature in the thermostat was adjusted to 200 ° C., the temperature difference between the paste-coated surface and the current collector surface was adjusted to 15 ° C., and the dried one was used as the negative electrode plate D of the comparative example. To produce a strip-shaped negative electrode plate.

The positive electrode plate and the negative electrode plate are spirally wound via a microporous polyethylene film separator to form an electrode plate group, and the electrode plate group is a bottomed iron cylindrical battery can also serving as a negative electrode terminal. Stored in.

Next, an electrolytic solution was injected into the battery can, and a sealing plate having a positive electrode terminal was caulked via a gasket to produce a cylindrical battery.

The batteries A and B of the present invention and the batteries C and D of the comparative examples corresponding to the negative plates A to D, respectively, were subjected to an initial rate capacity ratio and a charge / discharge cycle test. The capacity retention after 300 cycles, the maximum temperature of the battery surface when the UL temperature was raised (150 ° C.), and the composite material scratching strength of each negative electrode plate were evaluated, and the results are shown in Table 1.

[0020]

[Table 1]

Here, the definition of the mixture scratching strength of the negative electrode plate will be described. It is considered that peeling of the electrode plate is caused by minute cracks on the electrode plate surface. That is, it is sufficient to check how much force is applied to the electrode plate surface to cause cracks. Therefore, a device capable of applying a continuous load change on the electrode plate is used.

FIGS. 2A and 2B are schematic diagrams showing a scratch test of an electrode plate. The product of the load W [gf / cm] continuously applied to the scratching needle and the moving distance X [cm] due to the movement of the moving plate is the load required to cause a crack in the electrode plate, that is, the scratching strength F [ gf],
Digitized.

In the batteries A and B of the present invention, since the conductivity of lithium ions was improved, the initial rate capacity ratio was improved as compared with the batteries C and D of the comparative example. In addition, the capacity retention ratio is high in the cycle characteristics, which is considered to be due to the improved rate characteristics.

Further, in the UL temperature rise test (150 ° C.), the maximum temperature of the battery surface was lower than those of the batteries C and D of the comparative example, and the thermal stability was improved. This is presumably because lithium ions were uniformly absorbed in the graphite, lithium ions were not unevenly distributed on the negative electrode surface, and the exothermic reaction on the negative electrode surface was suppressed.

When the electrode plate is wound, it often causes a problem that the mixture of the negative electrode is peeled off from the core material. In the present invention, however, the binder is uniformly distributed and the scratching strength is improved.

Although the temperature difference between the paste-coated surface and the current collector surface was 0 ° C. in the battery C of the comparative example, the scratching strength was low because the temperature in the thermostat was low and moisture remained. It is. For this reason, the binding property with the core material is poor, and the current collection efficiency is reduced. As a result, the initial rate capacity ratio, the 300 cycle capacity retention rate is reduced, and the negative electrode scratching strength is also reduced.

[0027]

As described above, by using the method for producing an electrode plate for a non-aqueous electrolyte secondary battery of the present invention, the binder can be uniformly distributed in the negative electrode mixture paste, and Rate characteristics, charge / discharge cycle characteristics, and thermal stability can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a non-aqueous electrolyte secondary battery of the present invention.

2A is a diagram showing a state before a scratch test of a negative electrode plate. FIG. 2B is a diagram showing a state of the negative electrode plate after a scratch test.

[Description of Signs] 1 Battery case 2 Sealing plate 3 Electrode plate group 4 Positive electrode lead 5 Negative electrode lead 6 Insulating plate 7 Load 8 Scratch needle 9 Moving plate 10 Electrode plate

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Tatsuya Hashimoto 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Kenichi Oshima 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor I ▲ Saki ▼ Seigo 1006 Odakadoma, Kadoma City, Osaka Matsushita Electric Industrial Co. 5H029 AJ03 AJ05 AK03 AL06 AL07 BJ02 BJ14 BJ16 CJ02 CJ08 CJ22 CJ28 DJ08 EJ12 HJ00 HJ14 5H050 AA02 AA07 AA10 BA17 CA08 CB08 DA11 GA02 GA10 GA22 HA14

Claims (3)

[Claims] 1. A main material capable of inserting and extracting lithium,
A method for producing an electrode plate, comprising applying a water-dispersed mixture paste containing at least one or more binders on a current collector and drying, adjusting the drying temperature of the electrode plate, A method for manufacturing an electrode plate for a non-aqueous electrolyte secondary battery in which a binder is uniformly dispersed in a mixture paste by eliminating a temperature difference between a coating surface and a current collector surface. 2. The method for producing an electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the drying temperature is 85 ° C. to 120 ° C. 3. The method for producing an electrode plate for a non-aqueous electrolyte secondary battery according to claim 1, wherein at least one of the binders is a polyethylene resin or a Teflon resin.