JPH0734556U - Connection structure between plastic bipolar plate and metal collector - Google Patents

Abstract

(57) [Summary] (Modified) [Objective] The present invention provides a connection structure between a plastic bipolar plate and a metal collector electrode, which solves the effect of a plastic bipolar plate containing unstable chlorine ions on the metal collector electrode. provide. [Structure] This plastic bipolar plate 1 and the metal collector electrode 2 are connected to each other by connecting a chlorine electrode A conductor 3 having an ion content of 100 ppm or less is inserted.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a connection structure between a plastic bipolar plate used in an electrolytic solution circulation type secondary battery such as a redox flow type secondary battery and a zinc-halogen type secondary battery, and a metal collector electrode made of a copper plate or the like. .

[0002]

[Prior art]

The redox flow secondary battery is one of the most promising methods for new type secondary battery for power storage. As shown in FIG. 3, this secondary battery stores a hydrochloric acid aqueous solution of a metal ion whose valence changes by a redox reaction in a pair of left and right positive (negative) electrode electrolyte tanks 21 (21 '), respectively. The recirculation pumps 23, 23 of the paths 22, 22 supply the secondary battery cells 24 for charging and discharging. For the metal ions, iron ions (Fe ³⁺ , Fe ²⁺ ) are typically used as the positive electrode active material, and chromium ions (Cr ²⁺ , Cr ³⁺ ) are typically used as the negative electrode active material. The structure of the secondary battery cell 24 is composed of a metal collector electrode 25 / a bipolar plate 27 / a positive electrode reaction electrode 28 / a diaphragm (cation exchange membrane) 29 / a negative electrode reaction electrode 28 ′ / a bipolar plate 27 / a metal collector electrode 25. Electrons (e ⁻ ) due to the reduction reaction are exchanged with the charging / discharging DC power supply 30 through the metal collector electrode 25. Positive electrode Fe ³⁺ + e ⁻ ⇔ Fe ²⁺ Negative electrode Cr ²⁺ ⇔ Cr ³⁺ + e ⁻ However, in the case of this single cell, the output wattage is small, so for practical (industrial) stacking of more than 10 layers. Then, stack units are connected in series or in parallel to increase the output power.

Assuming that the stack unit is composed of a single cell of n layers, the metal collector electrode 25 / bipolar plate 27 (1) / positive electrode reaction electrode 28 (1) / diaphragm 29 (1) / negative electrode reaction electrode 28 ′ (1). / Bipolar plate 27 (2) / Positive electrode 28 (2) / Differential membrane 29 (2) / Negative electrode 28 '(2) / Bipolar plate 27 (3) .................. Bipolar plate 27 (n) / Positive electrode 28 (n) / diaphragm 29 (n) / negative electrode reaction electrode 28 '(n) / bipolar plate 27 (n + 1) / metal collector electrode 25 structure, n + 1 sheets of bipolar plate 27 are used, and the outermost metal collector is used. Two electrodes 25 are used. In this stack structure, the term bipolar plate is named because there are positive and negative reaction electrodes 28 and 28 'on both sides, but the required characteristic is that electrons move quickly. Therefore, it is highly conductive, it is not affected by the hydrochloric acid aqueous solution of the electrolyte (hydrochloric acid concentration of about 10% by weight), and the positive and negative electrode electrolytes do not mix with each other, that is, there is no leakage. For example, a glassy carbon plate called glassy carbon (manufacturing method is described later) has been used for the verification test. However, this glassy carbon bipolar plate satisfies the requirements of high conductivity (volume resistivity: approx. 5 × 10 ^-3 Ω · cm) and hydrochloric acid resistance, but is extremely expensive, and it has no microscopic holes due to the manufacturing method. However, due to its drawbacks such as difficulty in assembly and brittleness and easy cracking during battery assembly, the use of conductive plastic bipolar plates has recently been reconsidered.

Polyolefin was initially considered as the matrix resin for the conductive plastic bipolar plate, but since the resin of this system contains a large amount of crystalline lamella structure in the molecule, it is difficult for the filler to fill, and the volume resistivity 1 It is difficult to obtain high conductivity of × 10 ^-1 Ω · cm or less. By the way, according to the test results of the present inventors, it has been found that high conductivity with volume resistivity of 3 × 10 ⁻² Ω · cm or less is required to obtain high energy efficiency. In addition, as a result of investigations by the present inventors, a polymer matrix that can be highly filled with a filler has a large number of amorphous parts in its molecular structure and has a functional group in a side chain, which is bulky and causes a polymer spiral. However, as a result of various investigations, it was found that it is preferable to use a polymer matrix containing chlorine in the molecule such as polyvinyl chloride and chlorinated polyethylene in consideration of properties such as hydrochloric acid resistance. Got Incidentally, polyvinyl chloride has an industrial track record of being used for many years in salt water electrolysis equipment and hydrochloric acid production equipment, and chlorinated polyethylene is regarded as polyvinyl chloride with a low degree of chlorination and has almost the same hydrochloric acid resistance.

[0005]

[Problems to be solved by the device]

 However, the results of battery cell tests revealed that these polymer matrices had the following problems depending on the thermal history during molding. That is, these resins having a chlorine group in the side chain undergo a radical dehydrochlorination reaction called a zipper reaction when heated without radical stabilizer, leading to decomposition. In order to suppress this, stabilizers such as lead-based, organic tin-based, Ba-Zn-based, and Ca-Zn-based stabilizers are added to capture the desorbed hydrogen chloride to suppress the dehydrochlorination acceleration effect, and The zipper reaction that proceeds radically is stopped. However, when such a resin is used and subjected to a high temperature and long-term heat history by press molding or the like, the above-mentioned stabilizer may not completely capture hydrogen chloride. For example, when a conductive resin containing a carbon-based filler mixed with chlorinated polyethylene (3 parts by weight of an organic tin stabilizer was added in the test) was press-molded at 180 ° C for 30 minutes, the chlorine ion concentration of the raw material was increased. The chlorine ion concentration of the molded plate is about 500 ppm with respect to 50 to 100 ppm, and when the molded plate is brought into close contact with the copper plate, the copper plate surface turns whitish over time, and the contact resistance also changes to about 4 times the initial value. I found out that Therefore, an object of the present invention is to provide a connection structure between a plastic bipolar plate and a metal collector electrode, which solves the influence of a plastic bipolar plate containing unstable chlorine ions on the metal collector electrode.

[0006]

[Means for Solving the Problems]

 The connection structure between the plastic bipolar plate and the metal collector electrode according to the present invention has a chlorine ion content of 100 ppm between the plastic bipolar plate composed of a polymer matrix containing chlorine in the molecule and a carbon-based filler and the metal collector electrode. Below, preferably, 50 ppm or less, more preferably 30 ppm or less, 1 ppm or more of a conductor is inserted.

The connection structure between the plastic bipolar plate and the metal collector electrode according to the present invention will be described below with reference to FIGS. 1 and 2 showing specific embodiments thereof. FIG. 1 shows a connection structure of a plastic bipolar plate and a metal collector electrode according to the present invention, 1 is a plastic bipolar plate, 2 is a metal collector electrode, and 3 is a conductive material having a chlorine ion content of 100 ppm or less inserted between them. It is the body. FIG. 2 shows an embodiment of the above connection structure as an example of application to an electrolytic solution circulation type secondary battery. In the figure, 11 (11 ') is a pair of left and right positive (negative) electrode electrolyte tanks for storing a hydrochloric acid aqueous solution of metal ions whose valence changes due to oxidation-reduction reaction. It is supplied to the electrolytic solution circulation type secondary battery cell 14 by the circulation pumps 13 and 13 of the paths 12 and 12 and used for charging and discharging. The secondary battery cell 14 includes a metal collector electrode 15 / a conductor having a chloride ion content of 100 ppm or less 16 / a plastic bipolar plate 17 / a positive electrode reaction electrode 18 / a diaphragm (cation exchange membrane) 19 / a negative electrode reaction electrode 18 ′ / plastic It consists of a bipolar plate 17 / a conductor 16 with a chlorine ion content of 100 ppm or less / a metal collector electrode 15, and the electrons (e ⁻ ) due to the reduction reaction pass through the metal collector electrode 15 and a DC power source 20 for charging / discharging. Exchange between the two.

Next, each component of the connection structure of the present invention will be described. In the plastic bipolar plate 17, as the polymer containing chlorine in the molecule serving as a matrix, polyvinyl chloride, polyvinylidene chloride, chlorinated polyether, chlorinated polyethylene, chlorosulfonated polyethylene, ethylene-vinyl chloride copolymer is used. , Vinyl chloride-vinyl acetate copolymer, acrylic rubber (ACM), epichlorohydrin rubber, epichlorohydrin-ethylene oxide rubber and the like. Among these, hydrochloric acid resistance as well as high carbonaceous filler filling and filler Considering the moldability of the filled resin, it is preferable to use chlorinated polyethylene or chlorosulfonated polyethylene. These two resins can be made into a crosslinked rubber by peroxide vulcanization, but from the viewpoint of preventing dehydrochlorination as much as possible, it is preferable to use without crosslinking. On the other hand, natural graphite powder as the carbon filler, artificial graphite powder, expanded graphite powder, acetylene black, conductive oil furnace black, preferably alone or combined system such as Ketjen Black ^R EC, volume resistivity 3 × 10 ^-2 In order to obtain a high conductivity of Ω · cm or less, it is necessary to add 150 parts by weight or more of carbon-based filler to 100 parts by weight of the polymer matrix.

The conductor 16 having a chlorine ion content of 100 ppm or less inserted between the plastic bipolar plate 17 and the metal collector 15 such as a copper plate is a glassy carbon plate, a CC composite plate, a K sheet, or an expanded graphite sheet. , Graphite film and the like. The reason for limiting the numerical value of the chlorine ion content to 100 ppm or less is that a bipolar plate having a chlorine ion content of about 500 ppm as a matrix and a bipolar plate is adhered to the copper plate and left at 70 ° C. for 240 hours. While a change in contact resistance was detected, a bipolar plate with a chloride ion content of about 30-100 ppm chlorinated polyethylene as a matrix was brought into close contact with the copper plate, and the plate was left at 70 ° C for 240 hours to discolor or contact resistance of the copper plate. This was because there was no change in. For practical purposes, it is desirable to keep the chlorine ion content below 50 ppm for safety. The above-mentioned glassy carbon plate is a carbonized material that is made by forming a raw material molded product from a thermosetting resin and a suitable aggregate, and heating this at high temperature to carbonize it. Natural graphite powder is mixed with resin and thoroughly kneaded, and this is sheeted with a calender roll or a T-die extruder. After heating this sheet material to a temperature close to 180 ° C, a high temperature of 1000 ° C or higher in an inert atmosphere. It is a glassy carbon plate which is fired and carbonized, and has high conductivity of 3 × 10 ⁻³ to 4 × 10 ⁻³ Ω · cm. A CC composite plate (carbon fiber / carbon composite material) is a carbon fiber cloth impregnated with a resin or an organic binder such as petroleum / coal pitch, and fired at high temperature. Since the number of pores is reduced and voids are generated, a process called densification, in which a binder is impregnated again and re-baking is repeated, is repeated several times.

The K sheet is a sheet in which short carbon fibers and carbon powder are kneaded with a resin, sheeted by compression molding, and fired at about 2000 ° C., and the volume resistivity is 2 × 10 ⁻³ Ω. It has a high conductivity of cm. Expanded graphite sheet is a powder obtained by immersing natural graphite powder in a mixed acid of sulfuric acid and nitric acid for several minutes, washing it with water, and baking it at 700 to 800 ° C, which is expanded to a volume of 200 to 300 times. (Powder) is compression-molded, and is a graphite sheet with a mechanical strength low like a tanned leather. What is a graphite film? An aromatic polymer film containing a large amount of benzene nuclei in the molecule, such as a polyimide film or wholly aromatic polyamide film, which is formed so that the molecular crystals are aligned and then fired at 2000 ° C or higher. Is. This graphite film has high conductivity with a volume resistivity of about 5 × 10 ⁻⁴ Ω · cm. For conductors with chlorine ion content of 100 ppm or less, in addition to the above carbon-based plate materials or film materials, corrosion-resistant metal plates or foils such as gold foil and titanium plate, chloride ions such as polyester, polyurethane, epoxy resin, phenol resin, etc. Examples thereof include a carbon-based conductive resin plate having a resin content of 100 ppm or less as a matrix, a coating film of a conductive ink, and a corrosion-resistant metal plating film such as gold plating formed on the surface of a metal collector electrode plate.

[0011]

[Effect of device]

 The present invention very easily solves the influence of chlorine ions contained in the plastic bipolar plate on the metal collector by inserting a conductor with a chloride ion content of 100 ppm or less between the plastic bipolar plate and the metal collector. can do. Although a high-temperature firing type carbon plate was illustrated as the insertion conductor, it seems that there is a contradiction that an expensive plastic plate is used while an expensive one is used. Since two to several tens of sheets are used, the rate of cost increase can be kept to a very low level.

[0012]

【Example】

Next, the present invention will be described with reference to examples. Chlorinated polyethylene with a chlorination degree of 35%: Erasulene 351A (Showa Denko KK, trade name) 100 parts by weight and organic tin stabilizer: Greg TO-248E (Akishima Chemical Industry Co., Ltd. trade name) 3 parts by weight and natural 50 parts by weight of carbon-based filler 1 in which graphite powder and carbon black are mixed is dissolved and stirred in a xylene solvent to prepare a conductive coating material having a solid content of 12% by weight, and this is coated on a support film multiple times. A conductive resin layer having a dry film thickness of 0.3 mm was formed by coating. Next, the conductive resin layers were combined and press-molded to manufacture a conductive resin plate having a thickness of 0.6 mm. The molding conditions at this time were to set the press heating plate temperature to 180 ° C, place the conductive resin layers formed on the support film in close contact with each other and place them on the heating plate, and preheat for 15 minutes at a pressure of 0 kgf / cm ^2. After that, heat was applied at a molding pressure of 50 kgf / cm ² for 15 minutes, and then water was passed through the heating plate to wait for the temperature to drop to 30 ° C (approximately 30 minutes during this time), and then the pressure was released. The resin sheet has been exposed to a thermal history of 180 ° C for about 30 minutes.

When the chlorine ion concentration of this conductive resin plate was measured by ion chromatography, the chlorine ion concentration in the sample was 530 to 560 ppm. In this measurement, 1 g of the sample was extracted in 50 ml of distilled water at 60 ° C. for 2 hours, and the measured value of chlorine ion concentration was converted to the mass of the sample. When the chlorine ion concentration of the chlorinated polyethylene as the raw material was measured by the same method, it was 70 to 90 ppm. For confirmation, the chloride ion concentrations of stabilizers, carbonaceous fillers, solvents, and other auxiliary materials other than chlorinated polyethylene were measured by the same method. Is presumably due to the heat history during press forming. Insert this conductive resin plate between two sheets of pure electrolytic copper foil, seal it with a pressure of 1.5 kgf / cm ² and leave it in an atmosphere of 70 ° C for 2 weeks, then check the contact resistance per 1 cm ^2. As a result, the initial value was about 0.1Ω to about 0.4Ω, and the adhesion surface of the copper with the conductive resin plate was discolored whitish. Next, an expanded graphite powder: EXP-5 (manufactured by Maruyo Casting Mfg. Co., Ltd.) was pressed into a conductive sheet having a thickness of 0.3 mm under a molding pressure of 800 kgf / cm ² at room temperature for 10 minutes. The actual volume resistivity of this expanded graphite sheet was about 5 × 10 ⁻³ Ω · cm. This expanded graphite sheet was inserted between the above conductive resin plate and the electrolytic copper foil, adhered under a pressure of 1.5 kgf / cm ² and left in an atmosphere of 70 ° C. for 2 weeks to check the contact resistance. After that, when it was disassembled, the contact resistance per 1 cm ² was almost the same as the initial value (about 0.1 Ω), and discoloration of the contact surface of the expanded foil with the copper foil was not observed.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a connection structure between a plastic bipolar plate and a metal collector electrode according to the present invention.

FIG. 2 is an explanatory view showing an embodiment of a connection structure between a plastic bipolar plate and a metal collector electrode according to the present invention.

FIG. 3 is a schematic explanatory diagram of a conventional redox flow secondary battery.

[Explanation of symbols]

1 ... Plastic bipolar plate, 2 ... Metal collector electrode, 3 ... Conductor with chlorine ion content of 100 ppm or less. 11
(11 ') ... Positive (negative) electrode electrolyte tank, 12
… Route, 13… Circulation pump,
14 ... Secondary battery cell, 15 ... Metal collector electrode, 16 ... Conductor with chlorine ion content of 100 ppm or less, 17 ... Plastic bipolar plate, 18
(18 ')… Positive (negative) electrode, 19
... diaphragm, 20 ... DC power supply for charging and discharging. 21 (21 ') ... Positive (negative)
Electrolyte tank, 22 ... Path, 23 ... Circulation pump, 24 ... Secondary battery cell,
25 ... Metal collector electrode, 27 ... Bipolar plate, 28 (28 ') ... Positive (negative) electrode,
29 ... diaphragm, 30 ... DC power supply for charging / discharging.

Front page continued (72) Inventor Hiro Ohara, 1-406-1, Yoshino-cho, Omiya-shi, Saitama Prefecture Shin-Etsu Polymer Co., Ltd. Product Research Laboratory (72) Yoshiaki Nishijima 1-406-1, Yoshino-cho, Omiya-shi, Saitama Prefecture Shin-Etsu Polymer Co., Ltd. Product Research Laboratory (72) Inventor Toshio Shigematsu 1-3-3 Shimaya, Konohana-ku, Osaka City Sumitomo Electric Industries, Ltd. Osaka Works (72) Inventor Tetsuji Ito 1-3-1, Shimaya, Konohana-ku, Osaka City No. Sumitomo Electric Industries, Ltd. Osaka Works

Claims (2)

[Scope of utility model registration request] 1. A conductor having a chlorine ion content of 100 ppm or less is inserted between a metal bipolar electrode and a plastic bipolar plate composed of a polymer matrix containing chlorine in the molecule and a carbon-based filler. A connection structure between a plastic bipolar plate and a metal collector electrode. 2. An electrolyte circulating secondary battery using the connection structure according to claim 1.