JPS61230267A - Frame for electrode of stacked cell - Google Patents

Abstract

PURPOSE:To prevent warp of product and increase mechanical strength by forming a frame with a compound obtained by mixing glass fibers and mica flakes to thermoplastic resin and kneading the mixture. CONSTITUTION:An electrode frame 1 is formed with a compound obtained by mixing glass fibers or glass fibers and mica flakes to thermoplastic resin and kneading the mixture. High density polyethylene (HDPE) having a density of 0.94 or more, and an MFI of 8-40 is used as thermoplastic resin. 20-50wt% of glass fiber is mixed to the HDPE and the mixture is kneaded, then the electrode frame is molded. The mixing amount of glass fiber is preferably limited to 35-45wt%. The electrode with frame which is flat and free from deformation and has sufficient mechanical strength can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Industrial Field of Application The present invention relates to flat carbon plastic electrodes (hereinafter referred to as CP electrodes) (hereinafter referred to as CP electrodes) used in, for example, electrolyte circulation type laminated secondary batteries C made of a metal-halogen system. This invention relates to an insulating electrode frame that is integrally molded.

B. Summary of the Invention The present invention is based on thermoplastic resins (niglass fibers and carbon fibers).
2 Necessary C: By using a frame material containing mica as needed, the outer periphery of the carbon plastic electrode C: By providing an electrode frame, the difference in molding shrinkage rate between the frame material and the carbon plastic electrode is mainly caused. The present invention provides an electrode frame that prevents warping of the product and has t:PA mechanical strength.

C Conventional technology Electrolyte circulation type stacked secondary battery (: The frame for the CP electrode used is a conventional injection molding method with a density of 0.94
g/cd or higher polyethylene or density 0.90g/d
The above polypropylene C is kneaded with an inorganic filler such as carbon black to form a flat plate. The base resin used was high-density polyethylene (hereinafter referred to as HDPK) of about 0.94 gl or more, and about 30 to 50 mica flakes were blended therein by weight.

The main reason for achieving this kind of material and ratio C is to match the coefficient of linear expansion with that of the CP electrode as much as possible (
Problems to be Solved by the Invention By the way, as mentioned above, the electrode frame material formulated with Niji has a relatively large molding shrinkage rate and the Compared to the CP electrode C, the wall thickness C: When a framed electrode is formed and then cooled to room temperature, the amount of shrinkage of the frame portion is greater than that of the CP electrode material, causing warpage. was often recognized.

It is difficult to further increase the filling amount of mica flakes by C2 in order to suppress this warpage, both from the viewpoint of manufacturing the molding material (for example, pellets) and from the viewpoint of the molding operation. Annealing treatment has been performed as a post-treatment.

However, when forming a frame, for example, a separator (like a porous membrane used) can absorb some of the strain that occurs in a molded product, but it is much more rigid than a membrane (like a porous membrane used). With CP electrodes, it is not possible to completely remove strain, and in the case of a single molded product, deformation is not restrained and after a certain period of time, the residual strain is removed and relaxed, and warpage is inevitable. Furthermore, in the case of a laminated battery in the practical state of the battery, warpage is restrained and concentrated warp strain occurs.

For high-power batteries, for example, if the effective electrode area is 800-12 or more, special strain will appear, and if stress is concentrated at the weld line C, which is the weakest part of the frame, there is a probability of 5% or more in this area. The problem was that cracks would occur during the process, requiring replacement.

For this reason, in order to construct an electrolyte circulation type stacked secondary battery and maintain the Cg so that it can operate for a long period of time, it was necessary to improve at least the following two points.

(1) Use a thermoplastic resin material with as low a molding shrinkage rate as possible to suppress the amount of shrinkage of the final frame.

(2) Increasing the strength of the Feldline to a level that does not cause cracks even when subjected to annealing treatment, for example.

We will correct these problems that need to be improved (: When we conducted a preliminary study in advance, we focused on the adhesion and fusion properties between the CP electrode and the frame material as issues that need to be solved. .

In other words, when we studied the integration of the CP electrode and the frame material C:, we found that in the mu part shown in Figure 1 (:), the two fuse and become integrated, but in the 8 part, they come into close contact, but until the fusion (- Therefore, if the position of the CP electrode 2 with respect to the frame 1C2 is appropriate, the current biting depth t (usually about 2 parts) will not cause any problems, but (: If there is a slight deviation, the biting depth f will be uneven, resulting in c
The value of t was extreme C: there was a risk of failure and the mechanical strength exhibited by the fused portion was reduced.

E. Means for Solving the Problems As a result of various studies in order to solve the above-mentioned problems, the present invention has been developed by molding a thermoplastic resin (a compound obtained by mixing and kneading Niglass single fibers and mica flakes). The electrode frame of a laminated battery characterized by
10 scaled up from 0υ CP electrode
kv class battery C: effective area used 1300clII
The present invention provides an electrode frame that can also be used with FoCP electrodes.

Regarding the 2-function frame material, as a result of various preliminary studies, basic C:
It was confirmed that HDPK having a density of 0.94 or more and an MFI depth of 8 to 40 is most preferable in terms of compatibility with the CP electrode and ease of flow of the frame material.

A preferable product is obtained by adding 20 to 50 parts by weight of glass fiber to this HDPg and kneading the mixture to form an electrode frame.

If the amount of glass fiber is less than 20% by weight, the molding shrinkage rate of the frame material will be large, and if it is more than 50% by weight, the blending ratio of pace resin will decrease, resulting in a decrease in the strength of the frame, making it impractical. It is. In addition, more preferable results can be obtained when the amount of glass fiber added is 65 to 45% by weight.

Glass fibers having a diameter of 3 to 50 μm and a length of 5 W or less are used because the frame material is formed into a pellet shape with a length of about 3 to 5 cm and then injection molded.

In addition, it has been found that it is effective to adjust the molding shrinkage rate by adding up to 30 weights of an inorganic filler such as mica.

When molding this frame material integrally with the CP electrode, the CP electrode is naturally set in the mold at a predetermined position C: and then the frame material is melted, but it is more preferable to integrate the two. In order to achieve the condition C:, the resin temperature and mold temperature are set to a high value (:), and during the process of cooling the molded product temperature to room temperature at the time of taking out the molded product (linear expansion coefficient C: amount of shrinkage due to cp electrode) = (Amount of molding shrinkage of frame material) + (,・Coefficient of linear expansion of frame material [:
It is necessary to control the temperature setting of the mold so that the amount of shrinkage due to

At this time, if the mold temperature is made higher than necessary, the CP electrode may soften and the molding pressure C: of the frame material may become more deformed, so this should be avoided.

G Example density 0.94 g/al1MF I -52g/10-
30 parts by weight of HDPE C: 40 parts by weight of glass fiber of 16 μm diameter x 3 m were added and kneaded to make pellets. The MFI of this product was 6.41 g/10-.

In addition, separate C: pellets (M F I -4, 68 g/s*) consisting of 50 parts by weight of the above-mentioned HDPE, 40 parts by weight of glass fiber, and 10 parts by weight of mica flakes were also obtained.

On the other hand, 30℃: The set mold (:, JP-A-59-21
No. 7952C: Set the CP electrodes made of polyethylene, carbon black, and graphite as shown, and inject the pellets (resin temperature at the nozzle part is about 27°C).
0° C.) to form a framed electrode, and then allowed to cool naturally.

This product showed considerable flatness, and after being formed, it was sandwiched between aluminum plates and subjected to a simple annealing process, resulting in an extremely stable framed electrode.

In addition, the Feldline strength is considerably improved compared to the conventional one (:), and the flatness of the molded product is excellent, so Feldline C: the stress concentration due to such strain C2 is also sufficient (
; Result C: A highly reliable framed electrode having practically sufficient strength could be obtained.

Furthermore, when molding the framed electrode, the mold temperature at C: was studied, and although it varies somewhat depending on the physical properties of the CP electrode material, when the temperature exceeds 80°C, the CP electrode material itself softens.
; On the other hand, it was found that temperatures below 20° C. were unfavorable in terms of integration. Therefore, it is usually preferable to carry out the molding at a mold temperature of around 30 to 70°C.Special C: It has been found that the most stable framed electrode can be obtained when the molding operation is carried out at around 30°C.

Apart from this (=, uneven shape at the end of the CP electrode (Fig. 2),
Waveform (Fig. 3), sawtooth shape (Fig. 4), micro-crack shape (
(Fig. 5), roughened surface (Fig. 6) C: When various modifications were made and the bite strength was examined, it was found that the strength was improved in all cases compared to the one with a flat end surface.

Effects of the invention H By implementing the invention, the following effects can be expected.

(1) After taking out the molded product, simply sandwich it between flat plates and leave it there.
Perfect flatness can be obtained.

When the glass fiber filling amount is increased to 50% by weight (:), almost perfect flatness can be obtained by simply leaving it to cool naturally.

(21. Along with glass fiber (): By adding and kneading an appropriate amount of mica flakes, etc., the molding shrinkage rate and thermal expansion rate of the frame material can be controlled, so various CP electrode materials C
: Optimal combination can be selected.

(3) Since the molding shrinkage rate was reduced, the dimensional stability was significantly improved.

(4) Addition of glass fiber I: The strength of the feldline was improved to such an extent that it was not a practical problem, and the problem of cracking was almost completely resolved.

(The biting dimension l between the 51CP electrode and the frame material is 3
Not only was it possible to obtain the most preferable biting condition when the sheets were closed by ±15 squares, but also molding was possible without any trouble even if the CP electrode was slightly misaligned (:).

(6) C2 to increase integration between the CP electrode and the frame material
Fig. 6C: It is advantageous to provide an uneven surface as shown, and as a result, a practically sufficient biting strength can be obtained.

Because of the various effects mentioned above, it is possible to produce framed electrodes that are flat, do not deform, and have sufficient strength for practical use without the need for annealing, which conventionally required a long time, and at a yield that is half that of conventional methods. It can be manufactured in the following required time.

[Brief explanation of the drawing]

Fig. 1 is a partial cross-sectional view showing the bonding state of the frame body and the end of the CP electrode in the framed electrode (:), and Figs. 2 to 6 are partial perspective views showing the processing state of the end of the CP electrode. 1... Frame body, 2... CP electrode, L... Biting distance. Agent: Patent attorney Sanro Kimura

Claims (2)

[Claims] (1) A carbon plastic electrode made by kneading a conductive inorganic material such as carbon black into a thermoplastic resin, and a compound made by kneading a thermoplastic resin with glass single fibers or glass single fibers and mica flakes were used to form an electrode frame. A frame for electrodes of a laminated battery characterized by the following. (2) A compound in which high-density polyethylene with an MFI of 8 to 40 is used as a thermoplastic resin, and 20 to 50% by weight of single glass fibers and 0 to 30% by weight of mica flakes are kneaded and blended is used. The electrode frame described in item 1.