JPH01653A - Zinc/halogen battery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a liquid circulation type zinc-halogen battery, and in particular to a battery that improves battery efficiency by increasing and uniforming the liquid permeability of the positive electrode. It is.・ [Prior technology] In general, zinc-halogen batteries, especially zinc-chlorine batteries, are batteries that use chlorine as a positive electrode active material, zinc as a negative electrode active material, and an aqueous solution containing zinc chloride as the main component. It operates by an electrode reaction in which chlorine is generated at the positive electrode and metal zinc is precipitated at the negative electrode at the same time, and during discharge, chlorine is ionized at the positive electrode and at the same time metal zinc is ionized and eluted at the negative electrode.゛As shown in Figure 3, the configuration of such a battery consists of a battery section (1) in which the electrode reaction takes place, and an electrolyte tank (2) and a chlorine storage tank (3) provided outside the battery section (1). , these are connected through pipes to form a closed system, and a liquid pump (
4), the electrolyte is constantly transferred from the electrolyte tank (2) to the battery section (
1), and during charging i, the chlorine gas generated in the electrical section (1) is sent to the gas pump along with the circulating gas mainly consisting of inert gas.
The chlorine is sucked into the chlorine storage tank (3) by the pump (5) and stored.
The inert gas also passes through the electrolyte tank (2) and is returned to the battery section (1), where it is mixed with chlorine gas again as a circulating gas. Next, during discharge, chlorine gas generated from the chlorine storage tank (3) is sent to the electrolyte tank (2), increasing the chlorine concentration in the electrolyte circulating in the battery section (1) and promoting the positive electrode reaction. There is.

In the figure, (6) shows the valve that circulates the electrolyte to heat the chlorine storage tank (3) and generate chlorine, and (7) shows the valve that cools the chlorine storage tank (3) and stores chlorine. The refrigerator used for this purpose is shown.

In addition, in the battery section, as shown in FIG. 4, an electrolyte-permeable porous graphite positive electrode (9) and a liquid-impermeable hard graphite negative electrode (8) are connected to a frame via a current collector (10). (11) are held and placed opposite each other, and the chlorine chamber (12) is located inside.
A plurality of frames (11) are stacked to form each frame (11).
1) It has a structure in which an electrode chamber (13) is provided in between. Within this battery part (1), the electrolyte is supplied to the chlorine chamber (12) from an electrolyte supply port (14) opened at the bottom of the chlorine chamber (12),
The electrolyte passes through the positive electrode (9) and overflows from the electrolyte outlet (15) in the upper part of the electrode chamber (13), and is collected and sent to the electrolyte tank.

The porous graphite plate used for the positive electrode of the battery section is manufactured by compounding carbon fiber as a reinforcing material and then firing it, especially in the case of large batteries, and the key density is usually 0.5 g/c.
It has a1 or more.

[Problem that the invention seeks to solve]

60071111 for such electrodes! X700an
X2. In order to investigate the liquid permeability of a porous graphite plate with a size of Om, the graphite plate was divided into certain small squares, and the electrolytic solution was supplied from one side at a constant pressure, and the flow rate of the permeated liquid in each square was measured. The results are shown in a distribution diagram as shown in Figure 5, in which areas of the same flow rate are separated from areas of other flow rates by boundary lines (the numbers in the figure indicate the permeation flow ffl
(showing rn1/m1ll-cr/l >). As is clear from Fig. 5, the distribution of liquid permeation within the plane of the conventional graphite plate ranges from 9 to 13 d/m1n-ci.
It was thought that the electrolyte flow was non-uniform because of the large variation and large deviation, which had a negative effect on the charging and discharging efficiency of the battery, that is, the efficiency of zinc electrodeposition and dissolution.

Therefore, in order to improve efficiency, it has been required to improve and uniformize the amount of liquid permeation through the porous graphite plate.

[Means for solving problems]

In view of this, as a result of various studies, the present invention has developed a zinc-halogen battery using graphite electrodes with uniform liquid permeability, in which a liquid permeable porous graphite positive electrode and a hard graphite negative electrode are disposed opposite each other. In a battery in which an electrolytic solution is supplied through the positive electrode into an electrode chamber formed by the above process, and the electrolyte is circulated by overflowing from the upper part of the electrode chamber, the positive electrode is scraped at a density of 0.4.
It is characterized by being formed from a porous graphite plate with a density of 5 g/cd or less.

[For production]

The purpose of using a graphite plate with a small surface density as the positive electrode is to improve the air permeability of the entire positive electrode plate surface compared to conventional methods, thereby suppressing bias and variation in the amount of liquid permeation depending on location. This is because the analysis becomes uniform and the reaction on the electrode surface also becomes uniform. Also, set the density to 0
．． The reason why it is set to 45'J/c11 or less is because if this value is exceeded, the battery efficiency will be greatly reduced.

〔Example〕

In order to obtain an electrode plate with a low key density, the amounts of carbon fiber and binder added as reinforcing materials to the raw material were adjusted to a small amount, mixed with the graphite raw material, molded, and fired to achieve a key density of 0.45.0. 600 x 700 x 2.40 and 0.35 g/cd respectively. A porous graphite electrode plate with a size of O (7m111) was prepared, and the distribution of liquid permeation was examined for each bulk density plate under the same conditions as above, and the results are shown in Figure 1 (a) and (b). (C) (The numbers in the figure indicate the permeation flow rate (d/min - cd)).

As is clear from Fig. 1 (a), (b), and (c), the graphite plates according to the present invention all have a large range of the same liquid permeation flow rate, and the liquid permeability is biased compared to the conventional product shown in Fig. 5. is small.

Further, the above porous graphite plate was used as a positive electrode, and a 2 molar aqueous solution of zinc chloride was used as an electrolyte in an electrode chamber formed opposite to a normal hard graphite negative electrode plate, and the pH of the solution was set to 1. o, Liquid temperature: 30℃, chlorine concentration in the liquid 1.0g/j! Binding, 1
．． A battery was assembled in which the positive electrode was supplied at a flow rate of 5 me/min-cm, overflowed from the upper part of the electrode chamber and circulated through the battery section, and the battery was charged and discharged to determine the current efficiency as a battery characteristic. Table 1 shows the value of battery efficiency obtained by calculating the voltage efficiency and voltage efficiency, and roughly multiplying the results and the battery efficiency, and further shows the relationship between bulk density and battery efficiency in FIG. For comparison, a conventional porous graphite plate with a plating density of 0.559/cm was prepared, and the cell efficiency was determined in the same manner and is also shown in Table 1 and FIG.

As is clear from Table 1 and Figure 2, the gas density is 0.4.
5g/a1! The battery of the present invention is smaller than NQI.

Nα2 and Nα3 (respectively (a) in Fig. 2).

(b) and (C)) both have battery efficiency of 79
．． 5% or more, which is significantly superior to the conventional battery Nα4 (indicated by (d) in FIG. 2) having a bulk density of 0.55 g/cri1.

(Effects of the Invention) As described above, according to the present invention, in a zinc-halogen battery, the distribution of the permeate amount of the porous graphite electrode is made uniform, so that the voltage efficiency is improved and the reaction at the electrode interface is uniform. This brings about significant industrial effects such as improved current efficiency.

[Brief explanation of the drawing]

Figure 1 (a), (b), and (c) show the amount of liquid permeation through the electrode plate according to the present invention. 0.45g/cd
Figure 2 is an actual measurement diagram showing the relationship between grid density and battery efficiency, Figure 3 is an explanatory diagram showing the structure of the battery, Figure 4 is a side sectional view showing the battery part, and Figure 5 is a diagram showing the relationship between grid density and battery efficiency. FIG. 3 is a distribution diagram showing the amount of liquid permeation through the electrode plate of a conventional battery. G... Battery section 2... Electrolyte tank 3... Chlorine storage tank 4... Liquid pump 5... Gas pump 6... Valve 7... Freezer 8... Hard graphite negative electrode 9. ... Porous graphite positive electrode 10 ... Current collector 11 ... Frame 12 ... Chlorine chamber 13 ... Electrode chamber 14 ... Electrolyte supply port 15 ... Electrolyte discharge port a. ...Battery of the present invention Nα1 b...Battery of the present invention Nα2 C...Battery of the present invention Nα3 d...Conventional battery Nα4 Fig. 1 (a) Fig. 1 (b) Fig. 1 (l\) No. 2
Fig. s Density rL (Q/cm') Fig. 4 Fig. 5

Claims (1)

[Claims] In a battery in which an electrolyte is supplied through the positive electrode to an electrode chamber formed by arranging a liquid-permeable porous graphite positive electrode and a hard graphite negative electrode, and is circulated by overflowing from the upper part of the electrode chamber, the positive electrode has a bulk density. 0.45g/cm^
A zinc-halogen battery characterized by being formed from a porous graphite plate of 3 or less.