JP2997537B2 - Battery electrode manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a method for manufacturing a battery electrode.

(Prior Art) For a thin battery such as a flat battery, a coin battery, and a button battery, an electrode obtained by pressure-forming a mixture obtained by mixing a binder or a conductive agent with an active material is used.

Conventionally, in the method of manufacturing an electrode, generally, after a surface of a press mold (a member for pressing a mixture) is washed with a volatile solvent such as alcohol, the mixture is pressure-formed by a press mold to form an electrode. Has been manufactured.

However, in the manufacturing method, when the electrode is continuously manufactured by repeatedly performing pressure molding of the mixture after washing the surface of the press mold with a volatile solvent, the mixture gradually becomes on the surface of the press mold. Since the electrodes are attached, when the formed electrode (mixture) is peeled from the press die, the electrode is cracked or chipped. In particular, when an electrode having a thickness of 0.5 mm or less is produced by press-molding the mixture, it is more remarkable that the electrode is cracked or the like. When an electrode having such a crack or the like is incorporated in a battery, a part of the electrode may be powdered to cause a short circuit.

(Problems to be Solved by the Invention) The present invention has been made to solve the conventional problems, and an object of the present invention is to provide a method capable of easily manufacturing a good battery electrode.

[Constitution of the Invention] (Means for Solving the Problems) According to the present invention, a mixture containing an electrode active material and a binder is pressure-formed by a pressing member having a fluorine-based release agent adhered to the surface. A method for producing a battery electrode, characterized in that:

Examples of the mixture include a cathode active material composed of a metal chalcogen compound such as manganese dioxide, vanadium pentoxide, and titanium oxide, a binder such as polyacrylic acid and polytetrafluoroethylene (PTFE), and a conductive material such as graphite. And the like. When the mixture is in the form of a paste, usually, the mixture is dried and formed into pellets, followed by pressure molding. On the other hand, when the mixture is in a powder form, the mixture is usually subjected to pressure molding as it is, or is formed into pellets and then subjected to pressure molding.

Examples of the pressing member (a member for pressing the mixture) include a mold, a roller, and a rotary expander.

As the fluorine-based release agent, a compound having a polyfluoroalkyl group can be used. In particular, it is desirable to use a fluorine-based release agent that firmly adheres to the pressing member via an oxygen atom and forms a film having a surface energy reduced by a polyfluoroalkyl group being oriented on the surface thereof. . Examples of such a fluorine-based release agent include a fluorine-based surface treatment agent SA manufactured by Showa Denko KK
Series.

To attach the fluorine-based release agent to the surface of the pressure member, a coating method such as spray coating or brush coating,
Alternatively, an immersion method such as dipping may be employed.

The method of the present invention is such that the thickness of the mixture after pressure molding is 0.5 mm.
It is particularly suitable for producing the following battery electrodes.

(Function) According to the production method of the present invention, the mixture containing the electrode active material is press-molded with the pressing member having the fluorine-based release agent adhered to the surface, thereby forming the molded electrode (mixture). However, the battery electrode is easily peeled off from the pressurizing member, so that the battery electrode can be easily manufactured without generating cracks, chips or the like. Moreover, even if the fluorine-based release agent adheres to the electrode and the electrode is incorporated into the battery, the fluorine-based resin component in the fluorine-based release agent is chemically inactive, so that the release may occur. Battery performance such as discharge characteristics and storage characteristics does not deteriorate due to the influence of the mold agent.

Furthermore, as a fluorine-based release agent attached to the pressing member, while firmly adhering to the pressing member via an oxygen atom, a polyfluoroalkyl group was oriented on the surface, and the surface energy was reduced. If a material that forms a film is used, the formed electrode is more easily peeled off from the pressing member. Therefore, even when a battery electrode having a thickness of 0.5 mm or less is manufactured by press-molding the mixture, the electrode can be easily formed from the pressing member without applying a force that causes cracking or chipping of the electrode. It can be removed and removed.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Embodiment 1 FIG. 1 is a perspective view showing a molding apparatus used in Embodiment 1. The outer die 1 is formed with a square through hole 1a. In the vertical direction of the through hole 1a of the outer die 1, the through hole
An upper punch 2 and a lower punch 3 inserted into 1a are arranged so as to face each other. Lower surface (opposing surface) 2a of the upper punch 2 and upper surface (opposing surface) 3a of the lower punch 3
After washing with alcohol, fluorinated surface treatment agent SA
-301 (a trade name of Showa Denko KK, a fluorine release agent containing a compound having a polyfluoroalkyl group) is spray-coated and dried to form a film having a thickness of about several hundred angstroms. . The coating is firmly adhered to the lower surface 2a of the upper punch 2 or the upper surface 3a of the lower punch 3 by a chemical bond via an oxygen atom, and a polyfluoroalkyl group is oriented on the surface. The surface energy is reduced, and it has better water repellency and oil repellency as compared with a film made of ordinary polytetrafluoroethylene.

Next, a method for producing a positive electrode sheet using the molding apparatus shown in FIG. 1 will be described.

First, 90% by weight of manganese dioxide and 10% by weight of graphite are mixed, and a dispersion of 1% by weight of polyacrylic acid, 3% by weight of PTFE, and water is mixed and stirred with the mixture, and a viscous paste-like positive electrode is mixed. Prepare a mixture. Subsequently, after pouring the paste-like positive electrode mixture into a mold, the paste is irradiated with far-infrared rays and dried to form a pellet.

Next, as shown in FIG. 2 (A), a positive electrode mixture 4 in the form of a pellet is placed on the upper surface 3a of the lower punch 3. Subsequently, as shown in FIG. 2 (B), the upper punch 2 is inserted into the through hole 1a of the outer die 1 from above, and the lower punch 3 is inserted into the through hole 1a from below. The positive electrode sheet 5 having a thickness of 0.25 mm, a width of 20 mm and a length of 20 mm is applied by sandwiching the agent 4 between the upper punch 2 and the lower punch 3 and applying a pressure of 10 tons.
Is molded. Subsequently, as shown in FIG. 2 (C),
The upper punch 2 and the lower punch 3 are pulled out from the through holes 1a of the outer die 1, respectively, and the formed positive electrode sheet 5 is taken out from the upper surface 3a of the lower punch 3. Such a positive electrode mixture 4
, The positive electrode mixture 4 was press-formed, and the positive electrode sheet 5 was taken out, whereby 100 positive electrode sheets 5 were produced.

Comparative Example 1 The lower surface 2a of the upper punch 2 and the upper surface 3a of the lower punch 3
100 positive electrode sheets 5 were produced in the same manner as in Example 1, except that a molding apparatus in which no fluorine-based release agent was spray-coated was used.

Using the positive electrode sheet 5 of Example 1 and Comparative Example 1, 100 flat batteries each having a thickness of 0.5 mm as shown in FIG. 3 were assembled. That is, the positive electrode sheet 5 is superposed on the negative electrode sheet 6 made of lithium with the separator 7 interposed therebetween. The positive electrode sheet 5, the negative electrode sheet 6, and the separator 7 are disposed between a positive electrode terminal plate 8 in contact with the upper surface of the positive electrode sheet 6 and a negative electrode terminal plate 9 in contact with the lower surface of the negative electrode sheet 6. A frame-shaped insulating sealing body 10 is fused to the peripheral portions of the terminal plates 8 and 9.

For these batteries, the discharge capacity was measured under the condition that the battery was continuously discharged to 2.5 V with a resistance of 30 kΩ, and the average value and the variation were obtained. Furthermore, the discharge capacity under the same conditions after storage at a temperature of 45 ° C. for 60 days was measured, and the average value was obtained. The results are shown in Table 1 below.

As is clear from Table 1, the battery using the positive electrode sheet of Example 1 has a higher discharge capacity and smaller variation than the battery using the positive electrode sheet of Comparative Example 1. This is because, in Example 1, no crack or chipping occurred in the positive electrode sheet, whereas in Comparative Example 1, the upper punch lower surface and the lower punch upper surface of the molding device were gradually formed as the positive electrode sheet was continuously produced. This is due to the fact that the positive electrode mixture gradually adhered, and the positive electrode sheet was broken or chipped.

Further, the battery using the positive electrode sheet of Example 1 had a temperature of 45 ° C.
The decrease in the discharge capacity after storage at 60 ° C. for 60 days is extremely small, and it can be seen that the storage characteristics as well as the discharge characteristics are good. Therefore, it was confirmed that the fluorine-based release agent spray-coated on the upper punch lower surface and the lower punch upper surface of the molding apparatus of Example 1 had no adverse effect on battery characteristics such as discharge characteristics and storage characteristics.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a method capable of easily producing a good battery electrode.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing a molding apparatus used in Example 1, and FIGS. 2 (A) to 2 (C) are partially cutouts showing a positive electrode sheet manufacturing process of Example 1. FIG. 3 is a sectional view showing a flat battery. 1 ... outer die, 1a ... through hole of outer die, 2 ... upper punch, 2a
... lower surface of upper punch, 3 ... lower punch, 3a ... upper surface of lower punch, 4 ... positive electrode mixture, 5 ... positive electrode sheet.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-130373 (JP, A) JP-A-62-145647 (JP, A) JP-A-50-103553 (JP, A) 186490 (JP, A) JP-A-1-151158 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01M 4/08

Claims (1)

(57) [Claims] 1. A method for producing a battery electrode, comprising: pressing a mixture containing an electrode active material and a binder with a pressing member having a fluorine-based release agent attached to the surface thereof.