JPH0451950B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a framed separator that is one of the components of a metal halide electrolyte circulation type stacked secondary battery. A metal-halogen battery, such as a zinc-halogen (halogen is chlorine or bromine), is an electrolyte circulation type, which consists of a battery body, an electrolyte tank, and a circulation system (including a pump) that connects these and circulates the electrolyte. ) is formed from three elements. In the battery main body, an ion-permeable separator is provided between the positive and negative electrodes in order to prevent contact between the negative electrode liquid and the positive electrode liquid. Generally, when a liquid circulation type zinc-halogen secondary battery is put into practical use, the electrodes in the battery main body are bipolar, and a plurality of the above-mentioned single cells are stacked. FIG. 1 is a schematic diagram of these laminated secondary batteries. As shown in FIG. 1, the terminal electrodes 1 are placed at both ends of the electrode stack b, the separator 2 is interposed between them, the framed electrode 3 is placed next, and the framed electrode 3 is placed again through the separator 2. A plurality of single cell portions a are stacked. Furthermore, a clamping plate 7 to which a packing 4, electrolyte inflow pipes 5, 5', and outflow pipes 6, 6' are attached is placed in this order on both outsides of the laminated part b, and the clamping plate 7 is connected to the separator 2, Electrodes 1, 3
Bolts 8 are inserted into the bolt through holes 2a and 3a, and the battery body is integrally formed by tightening them. The electrode 3 is formed symmetrically on the front and back, and the center part is formed of a conductive plastic material 32, and the frame part 3
It is formed more submerged than 1. Electrolyte (positive electrode)
enters the battery body from the electrolyte inflow pipe 5, and flows through the electrolyte inflow manifold 9 into the channel 31a and microchannel 31 formed in the frame 31 of the electrode 3.
b is uniformly supplied to the surface of each electrode part 32,
The electrolyte is discharged from the battery body through an electrolyte outflow manifold 10 and an electrolyte outflow pipe 6 . The negative electrode liquid enters the battery body through the inflow pipe 5', flows on the back surface of the electrode 3 in the same process as the positive electrode liquid, and is discharged through the outflow pipe 6'. In such a zinc-halogen battery, such as a zinc-bromine battery, zinc is deposited on the negative electrode during charging, and melts and diffuses into the electrolyte during discharging. On the other hand, bromine is generated at the positive electrode during charging, dissolves in the electrolyte, and becomes bromine ions during discharge through an electrochemical reaction that generates superpower. When assembling the metal-halogen electrolyte circulation type stacked secondary battery described above, a porous membrane made of a base polymer such as polyethylene as the separator 2 is cut into the same external dimensions as the framed electrode 3, and packed or shielded. etc., were interposed between the frame portion 31 of the electrode 3 and laminated as is. However, in this lamination method, when the electrolyte is circulated, the liquid permeates into the membrane and oozes out to the outside.
Corrosion or erosion of surrounding metal or resin parts may occur, and the manifolds 9, 9', 10,
Problems such as a short circuit of the liquid at the 10' portion caused damage to peripheral equipment and a decrease in efficiency. An object of the present invention is to provide a method for manufacturing a framed separator for a metal-halogen electrolyte circulation type stacked secondary battery that eliminates the above-mentioned drawbacks. The gist of the present invention is to fit an electrolyte-impermeable round plate made of polyolefin resin into a hole drilled in the outer edge of a porous membrane, and to cover the outer edge including the round plate with polyolefin resin. After sandwiching from both sides with electrolyte-impermeable frame members made of electrolyte-impermeable frame members and molding the frame integrally by heating and pressurizing, the frame is penetrated at a position corresponding to the inside of the round plate of the frame. A method of manufacturing a framed separator for a metal-halogen electrolyte circulation type stacked secondary battery, which is characterized by providing a manifold. The present invention will be described in detail below based on the accompanying drawings and the knowledge of the examples. FIG. 2 is an explanatory diagram showing the material structure of a framed separator of a metal-halogen electrolyte circulation type stacked secondary battery according to the present invention, and FIG. 3 is a longitudinal cross-section around the separator. As shown in FIG. 2, the framed separator of the present invention has holes 23 formed in the outer edge 21 of a porous membrane 21 made of polyethylene resin as a matrix.
A homogeneous and electrolyte-impermeable round plate 24 is fitted to the
A frame member 22 made of polyolefin resin of the same quality as the porous membrane and impermeable to electrolyte and cut into a picture frame shape is superimposed on the top and bottom of this porous membrane 21 and integrally formed by a heat press method, and then the round plate is formed. Manifolds 9, 9', 10, 1 at corresponding positions within 24
0' Furthermore, a bolt through hole 2a is formed. It should be noted that the manifold forming section is formed by forming the membrane 2 in advance.
A hole 23 approximately twice the diameter of the manifold is opened in the forming portion of 1, and a round hole 23 having the same diameter as the hole and made of the same material as the frame member 22, such as polyethylene resin, and impermeable to the electrolyte. A plate 24 is fitted and integrally formed with the frame member 22 to ensure insulation and impermeability of the manifold. When the frame member 22 is stacked to form a battery, the frame member 22 has a frame shape.
As shown in the figure, it is formed to cover the height of the frame portion 31 of the electrodes 1 and 3 and the microchannel 31b. That is, the thickness should be the same as the thickness of the packing or shielding material during conventional tightening. In heat press bonding using the heat press method used in the present invention, the compression surface is flat, and the gap during mold clamping is usually about 0.6 mm in thickness for the porous membrane and 0.3 mm for the picture frame. In this case, it is preferable to use a mold with a diameter of 0.5 mm. Furthermore, the molding conditions are as follows. That is, the melting point of the resin forming the frame member 22 is approximately
Since the temperature is 120℃, if the molding temperature is less than 118℃, the membrane 21 and the frame member ² will be compressed with a pressure of 50Kg/cm2.
2, not only complete fusion but also no adhesion and easily peeled off. On the other hand, when the molding temperature is increased beyond 128°C, wavy wrinkles occur at the corners of the separator part 21a (○ rating), and in addition, the melted resin of the frame member 22 flows out onto the surface of the separator part 21a. , the corner portion of the separator portion 21a is made of resin, and the porosity of the portion is lost (Δ evaluation).
For example, at a molding temperature of 130°C and a pressure of 100 kg/cm ² , the unfavorable results described above will expand around the corners, and furthermore, the effective separator part of the molded product will have a large wave-like deflection, making it difficult to put it into practical use. It becomes a state where it is not possible to obtain (× evaluation). In addition, the press pressure should be set to 50Kg/ ^cm2 or more, e.g. 100
When the molding temperature is set to Kg/cm ² , it is preferable to lower the molding temperature, and 130°C is not practical.
Furthermore, if the heating compression time is extended beyond 1 minute, it is preferable to lower the molding temperature, but it is 120 to 125℃.
This corresponds to the above-mentioned △ evaluation. From the above, the heat press conditions for a frame separator that can be used for practical purposes are a molding start temperature of 118 to 128℃,
Preferably, the press pressure is 50 to 100 kg/cm ² , the heating compression time is 0 (described later) to 1 minute, and the cooling pressure holding time is 2 minutes. Furthermore, in the material composition of the framed separator according to the present invention, if the thickness of the frame member 22 is 0.3 mm or more, the entire surface of the molded product will not be compressed, resulting in large deflection of the membrane surface 21a. In addition, instead of stacking two frame members 22 with a thickness of 0.3 mm above and below the membrane 21, the frame members 22 with a thickness of 0.6 mm are doubled.
If 2 is overlapped only on one side, uneven contact will occur and the molded product will be warped on one side, making it impossible to obtain a practical product. Furthermore, when a total of two frame members 22 with a thickness of 0.3 mm or less are stacked on top and bottom of a porous membrane 21 with a thickness of 0.6 mm, a relatively good molded product can be obtained, but the part sandwiched between the frame members 21 The film 21 becomes insufficiently resinated,
The insulation and impermeability are insufficient for practical use in lamination. The above is about the molding conditions when molding a framed separator using the porous membrane 21 with a film thickness of 0.6 mm, but almost the same molding conditions and resin material combinations are used for films with a film thickness of 0.1 to 2 mm. A framed separator can be obtained. In this case, generally, a good molded product can be obtained by setting the thickness of the frame members that are stacked above and below the membrane to about 1/2 that of the porous membrane. As described above, in the method for producing a framed separator of the present invention, holes are formed in the outer edge of a porous membrane, and electrolyte-impermeable rounds of polyethylene resin are fitted into the holes, and both sides of the outer edge including the round pieces are fitted. An electrolyte-impermeable frame member made of polyethylene resin is superimposed on the frame member and formed integrally using a heat press method.
It is possible to prevent electrolyte from leaking in the battery stacking direction of the frame and in the separator surface direction. Next, an example will be described. Example 1 As shown in Figure 2, this corresponds to the manifold forming part at the outer edge of a porous membrane (length 400 mm x width 360 mm, thickness 0.6 mm) made of polyolefin resin (polyethylene density 0.956 g/cm ³ MFR 0.80). hole (φ15
mm), and fit into these holes electrolyte-impermeable round plates with the same diameter and thickness as the holes and made of the same material as the porous membrane. Frame-like frame members with the same dimensions (inner dimensions)
300mm x width 300mm thickness 0.3mm) stack two sheets,
Using a mold with a flat compression surface and a gap of 0.5 mm during mold clamping, heat pressing was performed under the molding conditions shown in Table 1 below, and then a frame was placed in the position corresponding to the round plate part. A manifold was formed that penetrated the section.

[Table] * Immediately after putting the material into the preheated mold, clamp the mold, raise the pressure to 50Kg/cm ² by gauge pressure, and immediately start cooling while maintaining the pressure. The frame separator manufactured by this method is a good product, with the porous membrane and frame member completely fused together, without peeling, and with no wrinkles in the separator part, and is a good product with no wrinkles or the like in the metal-halogen electrolyte circulation type laminated layer. When used as a separator for secondary batteries, it was excellent in terms of insulation and impermeability. Example 2 Using the same porous membrane, circular plate, and frame-shaped frame member as in Example 1, a framed separator was manufactured in the same manner as in Table 2, with only the molding conditions changed to those shown in Table 2. As a result, the results shown in Table 2 A framed separator with evaluation as shown in is obtained. Evaluations in Table 2: ◎ indicates that the product is practically excellent, similar to the product obtained in Example 1. ○ indicates that it can be put to practical use, but △ indicates that it has wavy wrinkles at the corners of the separator. This is possible, but in addition to the above-mentioned wavy wrinkles, the molten frame member flows out into the part, and the separator part becomes resin, which causes the product to lose its porosity. The product marked with an "X" has a large wave-like deflection in the separator portion and cannot be put to practical use.

[Table] As mentioned above, the framed separator according to the present invention has (1) excellent flatness of the frame because it is compression molded in a semi-molten state. (2) Since the porous membrane sandwiched between the electrolyte-impermeable frame members is turned into a resin during molding, the permeability of the frame can be significantly reduced. (3) By arranging an electrolyte-impermeable round plate made of the same resin as the frame member at a portion corresponding to the manifold forming portion at the outer edge of the porous membrane, insulation inside the manifold can be ensured. As a result, it is possible to obtain a framed separator that is free from liquid leakage and liquid short circuit.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a stacked secondary battery, FIG. 2 is an explanatory diagram showing the material structure of a framed separator according to the present invention, and FIG. 3 is a longitudinal cross-sectional view of the vicinity of the separator. 2... Separator, 21... Porous membrane, 22
...Frame-shaped frame member, 23...Hole of manifold forming portion, 24...Round plate.

Claims (1)

[Claims] 1. In a method for manufacturing a framed separator for a metal-halogen electrolyte circulating type stacked secondary battery, the holes 23 are formed in the outer edge 21 of the porous membrane 21a.
An electrolyte-impermeable round plate 24 made of polyolefin resin is fitted onto the outer edge 21, and the outer edge 21 including the round plate 24 is covered with a frame member 22 made of polyolefin resin which is impermeable to electrolyte. After the frame is integrally molded by heating and pressing, a manifold 9, 9', 10, 1 that penetrates the frame is placed at a position corresponding to the inside of the round plate 24 of the frame.
1. A method for manufacturing a framed separator for a metal-halogen electrolyte circulation type stacked secondary battery, characterized in that a separator with a frame is provided with a 0'.