JP2931650B2 - Electrolyte circulation type secondary battery - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolyte circulating secondary battery, and more particularly, to an electrolyte circulating secondary battery improved to reduce shunt current. It relates to batteries.

[Prior Art] Power companies need to generate power in accordance with power loads in order to supply stable power to consumers. For this reason, electric power companies are constantly constructing power generation facilities that match the maximum load, and generating power in response to the load. However, as shown by the power demand curve A in FIG. 6, there is a large difference in power demand between daytime and nighttime. Similar phenomena occur during the week, month and season.

Therefore, if it is possible to efficiently store the electric power, the surplus electric power (corresponding to the portion indicated by the symbol X in FIG. 6) is stored at the off-peak time, and the surplus electric power is discharged at the peak time to obtain the sixth electric power. The portion indicated by the symbol Y in the figure can be covered. In this way, it is possible to cope with a change in load, and the power company always keeps a substantially constant power (the sixth power).
It is only necessary to generate electricity (the amount corresponding to the broken line Z in the figure). If such load leveling can be achieved, it is possible to reduce the number of power generation facilities, and to greatly contribute to energy saving and fuel saving such as oil.

Therefore, various power storage methods have been conventionally proposed. For example, pumped storage power generation has already been implemented, but in pumped storage power generation, facilities are installed far away from the consuming area. Therefore, this method has problems such as transmission and transformation loss and restrictions on location conditions. Therefore, the development of a new power storage technology replacing pumped storage power generation is desired, and as one of them, the development of an electrolyte circulation type secondary battery is being promoted.

FIG. 7 is a schematic configuration diagram of a conventionally proposed redox flow type secondary battery. The redox flow battery includes a cell 1, a positive electrode solution tank 6, and a negative electrode solution tank 5. The inside of the cell 1 is partitioned by a diaphragm 2 made of, for example, an ion exchange membrane, and one side constitutes a positive electrode cell 1a and the other side constitutes a negative electrode cell 1b. In the positive electrode cell 1a and the negative electrode cell 1b, a positive electrode 4 or a negative electrode 3 is provided as an electrode, respectively. The positive electrode cell 1a is provided with a positive electrode electrolyte introduction pipe 30 for introducing a positive electrode electrolyte. Further, the positive electrode cell 1a is provided with a positive electrode electrolyte outflow tube 31 for discharging the positive electrode electrolyte contained in the positive electrode cell 1a. One end of the positive electrode electrolyte inlet tube 30 and one end of the positive electrode electrolyte outlet tube 31 are connected to the positive electrode tank 6.

The negative electrode cell 1b is provided with a negative electrode electrolyte introduction tube 32 for introducing a negative electrode electrolyte. Also, the negative electrode cell 1b
Is provided with a negative electrode electrolyte outflow pipe 33 for discharging the negative electrode electrolyte contained in the negative electrode cell 1b. One end of the negative electrode electrolyte introduction pipe 32 and one end of the negative electrode electrolyte discharge pipe 33 are connected to the negative electrode liquid tank 5.

The redox flow cell shown in FIG. 7, for example iron ions, the cathode solution tank 6 an aqueous solution of ions of varying valence, such as chromium ions, and stored in a negative electrolyte tank 5, a pump P ₁ this pump P _The liquid is sent to the cell 1 by _{2 and} charge and discharge are performed by an oxidation-reduction reaction.

For example, when Fe ³⁺ / Fe ²⁺ is used as the positive electrode active material and Cr ²⁺ / Cr ³⁺ is used as the negative electrode active material, and the respective hydrochloric acid solutions are used, the battery reactions at both electrodes 3 and 4 of each redox system are as follows. It becomes like the formula of.

The electrochemical reaction of the above formula provides about 1 volt of superpower.

Meanwhile, in order to increase the generated voltage of a redox flow battery, a multi-stage connection type redox flow battery in which a plurality of cells are connected in series has been proposed. In FIG.
FIG. 1 is an exploded perspective view showing a cell structure of a one-cell redox flow battery.

Referring to FIG. 8, cell 1 has a bipolar plate from the left in the figure.
The components of the negative electrode plate 13, the diaphragm 12, the positive electrode plate 14, and the bipolar plate 16 are sequentially arranged. In the multi-stage connection type, a large number of these cells are stacked, that is, the bipolar plate 15, the negative plate 1
3. A large number of components including a diaphragm 12, a positive electrode plate 14, and a bipolar plate 16 are stacked, and both ends thereof are gripped by a terminal plate 17 and a terminal plate 18. A stack of many cells 1 is called a (cell) stack.

The bipolar plate 15 has a bipolar plate frame 15f, the negative plate 13 has a negative plate frame 13f, and the positive plate 14 has a positive plate frame 14f.
The bipolar plate 16 includes a bipolar plate frame 16f.
The bipolar plate frame 15f, the negative electrode plate frame 13f, the diaphragm 2, the positive electrode plate frame 14f and the bipolar plate frame 16f have holes, and when stacked, a passage serving as a pipe inside a cell called a manifold is formed. It is formed.
In the manifold, the manifold 20 for feeding the negative electrode liquid,
There are a manifold 21 for feeding the positive electrode solution, a manifold 22 for returning the negative electrode solution, and a manifold 23 for returning the positive electrode solution.

The cathode plate electrolyte intake slit 1 is
5a, a positive electrode electrolyte return slit 15b, a negative electrode electrolyte intake slit 15c, and a negative electrode electrolyte return slit 15d are provided. The positive electrode solution intake slit 15a is connected to the positive electrode solution feed manifold 21, the positive electrode solution return slit 15b is connected to the positive electrode solution return manifold 23, and the negative electrode solution intake slit 15c is connected to the negative electrode solution feed manifold 20. And the negative electrode electrolyte return slit 15d is connected to the negative electrode solution return manifold 22.

The bipolar plate frame 16f has a positive electrode electrolyte intake slit 16
a, a positive electrode electrolyte return slit 16b, a negative electrode electrolyte intake slit 16c, and a negative electrode electrolyte return slit 16d are provided.

The positive electrode electrolyte intake slit 16a is connected to the positive electrode solution feed manifold 21 and the positive electrode electrolyte return slit 16b
Is connected to the positive electrode liquid return manifold 23, the negative electrode liquid electrolyte intake slit 16c is connected to the negative electrode liquid supply manifold 20, and the negative electrode liquid electrolyte return slit 16d is connected to the negative electrode liquid return manifold 22.

At the time of charge / discharge operation, the positive electrode electrolyte passes through the positive electrode solution feed manifold 21 and is supplied into the positive electrode cell 1a from the positive electrode electrolyte intake slit 16a, and is charged and discharged at the positive electrode reaction electrode 14e. The liquid is sent out from the return slit 16b to the cathode solution return manifold 23. Further, the negative electrode electrolyte passes through the negative electrode feed manifold 20, is supplied into the negative electrode cell 1b from the negative electrode intake slit 15c, and is charged and discharged at the negative electrode reaction electrode 13e, and then returned to the negative electrode return slit 15d.
From the negative electrode solution return manifold 22. At this time, a voltage is generated between the terminals 17 and 18, and a current is extracted.

[Problems to be Solved by the Invention] As described above, the electrolyte circulation type secondary battery has been studied as a secondary battery for power storage, and in order to obtain a predetermined electric output (W), cells must be connected in series and in series. Must be combined in parallel. The problem in this case is that, when a series connection is made, a current flows according to the potential gradient through the electrolytic solution flow path. This current is called a shunt current. The shunt current is a current irrelevant to the charge and discharge of the battery (leakage current that merely flows through the electrolyte flow path and does not contribute to the charge or discharge of the battery). It becomes. This shunt current also flows in the stack of stacked cells, but also flows in the electrolyte channel connecting the stacks when the stacks are connected in series.

By the way, as a method of reducing the loss of the shunt current in the stack, the present applicant has referred to FIG.
A method has been proposed in which the slits (16a, 16b, 16c, 16d, 15a, 15b, 15c, 15d) are made thinner and longer, thereby increasing the electrical resistance of this portion and reducing the shunt current (Japanese Patent Application No. Hei 1 (1994)).
-73497). There is also known a method of reducing the shunt current by reducing the number of stacked cells in the stack and reducing the potential gradient in one stack.

However, in the latter case, it is necessary to connect a plurality of stacks in series in order to obtain a predetermined voltage. In this case, the number of cells in one stack is at least by connecting a plurality of stacks in series, so that when viewed as a whole, a large number of cells are connected in series, causing a problem that the shunt current increases. In the former case, that is, even if the electric resistance of the slit portion is increased, the shunt current in the stack can be reduced, but there is a problem that a large shunt current flows in the pipe connecting the stack. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide an electrolyte-circulating secondary battery improved so as to suppress a shunt current.

[Means for Solving the Problems] FIG. 9 is an example of a series connection of stacks, and FIG. 10 is an equivalent circuit diagram of the stack series circuit. Referring to FIG. 9, a plurality of stacks 40 are electrically connected in series (in the figure, reference numeral 49 indicates an electrical connection).

Each of the stacks 40 is connected to one end of a positive electrode solution inlet line 41, a positive electrode solution outlet line 42, a negative electrode solution inlet line 43, and a negative electrode solution outlet line 44. The other end of the positive electrode solution inlet line 41 is connected to the positive electrode solution supply line 45, the other end of the positive electrode solution outlet line 42 is connected to the positive electrode solution discharge line 47, and the other end of the negative electrode solution inlet line 43 is connected to the negative electrode solution. Connected to the supply line 46, the negative electrode solution outlet line 44
Is connected to the negative electrode liquid discharge line 48.

An object of the present invention is to reduce a shunt current flowing through an electrolyte flow path connecting between stacks indicated by I ₁ , I ₂ , I ₁ ′, and I ₂ ′.

These shunt currents cause the potential between the stacks to be short-circuited via the resistance Ra of the electrolyte inlet line, the resistance Ra of the electrolyte outlet line, the resistance Rb of the electrolyte supply line, and the resistance Rb of the electrolyte discharge line. Caused by that.

Now, as is clear from the equivalent circuit diagram shown in FIG.
In order to reduce I ₁ , I ₂ , I ₁ ′, I ₂ ′, the resistance values of Ra and Rb may be increased. The resistance is generally represented by the following equation.

In the formula, R is a resistance, ρ is a specific volume resistance of the electrolytic solution, l is a length of the conduit, and S is a cross-sectional area of the conduit. Therefore, if the length of the electrolyte supply / discharge line between the stacks is made longer and the cross-sectional area is made smaller, the length of the electrolyte inlet and outlet pipes of the stack is made longer and the cross-sectional area is made smaller. Then, R
The resistance of a, Rb will increase and the shunt current will decrease.

Here, it is difficult to increase the length of the electrolyte supply / discharge line between the stacks (in the case described above) because of the arrangement of the stacks. Difficult to secure. However, it becomes relatively easy when the number of stacks is large, and when not only series connection but also parallel connection are used. At that time, it is not necessary to lengthen the pipeline between all the stacks, and a means of increasing the pipeline in a certain unit, for example, every several stacks is effective. Based on this idea, the present inventors have completed the invention described in claim 1.

That is, according to the first aspect of the present invention, the first stack serial circuit in which a plurality of stacks are electrically connected in series, the second stack serial circuit, and the supply and discharge of the electrolyte to and from the stacks A first electrolyte supply and discharge line and a second electrolyte supply and discharge line, and the first stack series circuit and the second stack series circuit are electrically connected in parallel. And the first
The electrolyte supply / discharge line and the second electrolyte supply / discharge line are connected in parallel, and are related to an electrolyte circulation type secondary battery. The plurality of stacks in the first stack series circuit are divided into those belonging to a first section and those belonging to a second section. Then, in order to reduce the shunt current, an electrolyte is supplied and discharged from the first electrolyte supply and discharge line to the stack existing in the first section of the first stack series circuit, The second of the stacked series circuit
The first electrolyte supply and discharge line and the second electrolyte supply and discharge line are supplied to and discharged from the stack existing in the section.
Electrolyte supply and discharge lines. Each of the stacks present in the first section of the first stack series circuit and the first electrolyte supply and discharge line are connected to the first electrolyte supply and discharge line, It is connected by a branch line for supplying and discharging liquid. Each of the stacks present in the second section of the first stack series circuit and the second electrolyte supply and discharge lines are coupled to the second electrolyte supply and discharge lines, It is connected by a branch line for supplying and discharging liquid.

[Operation] According to the present invention, an electrolyte is supplied and discharged from the first electrolyte supply and discharge line to the stack existing in the first section of the first stack series circuit, and the first stack series circuit is provided. Stacks in the second section of
The first electrolytic solution supply and discharge line and the second electrolytic solution supply and discharge line are provided so that the electrolytic solution is supplied and discharged from the electrolytic solution supply and discharge lines of the stack. It is divided into at least two or more. As a result, the shunt current decreases.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of an embodiment of the present invention, and is a configuration diagram of 6 series × 3 parallel stacks. FIG. 2 is a diagram showing a conventional method for connecting electrolyte supply lines and a method for electrically connecting a stack of 6 series × 3 parallel configurations. In these figures, for the sake of simplicity, the cathode solution supply lines 54, 55, 56 as electrolyte solution supply lines and the cathode solution inlet line 57 are shown.
The illustration of the anode solution supply line, cathode solution discharge line, anode solution discharge line, cathode solution outlet line, anode solution inlet line, and anode solution outlet line is omitted, but the arrangement is the same. Have been.

1 and 2, reference numeral 51 denotes a first stack serial circuit, 52 denotes a second stack serial circuit, 53 denotes a third stack serial circuit, 54 denotes a first positive electrode solution supply line, and 55 denotes a second Reference numeral 56 denotes a third positive electrode solution supply line.

Referring to the conventional example shown in FIG. 2, a positive electrode solution supply line and a liquid inlet line to the stack are connected to a circuit in which six stacks are electrically connected in series so as to short-circuit each stack. Electric current flows.

The electrolyte circulation type secondary battery shown in FIG. 1 has a first stack series circuit 51, a second stack series circuit 52, and a third stack series circuit 52.
And a stack series circuit 53. The first stack series circuit 51, the second stack series circuit 52, and the third stack series circuit 53 are electrically connected in parallel. The electrolyte circulation type secondary battery includes a first positive electrode solution supply line 54 and a second positive electrode solution supply line 55. The first positive electrode solution supply line 54 and the second positive electrode solution supply line 55 are connected in parallel.

The first electrolyte supply line 54 enters the first stack series circuit 51 so as to bisect the first stack series circuit 51,
The positive electrode solution is sequentially supplied to the stack 1, then the positive electrode solution is sequentially supplied to the stack a, the stack b, and the stack c of the second stack serial circuit 52, and then the third stack serial circuit 53 is divided into two. , And the cathode, the stack, and the stack are sequentially supplied with the cathode solution. The second positive electrode solution supply line 55 is connected to the third stack series circuit 53.
The positive electrode solution is supplied to the stack, the stack, and the stack in this order, and then the stack f,
The positive electrode solution is supplied to the stack e and the stack d in order, and then the positive electrode solution is supplied to the stack 4, the stack 5, and the stack 6 of the first stack series circuit 51 in this order. Each stack and the cathode solution supply line are connected to the cathode solution inlet line
Connected at 57.

 Next, the effects of the embodiment shown in FIG. 1 will be described.

First stack series circuit 51, second stack series circuit
52, the third stack series circuit 53 is connected to the electrolyte supply lines 54, 5
Since it is bisected by 5, the number of stacks in series is 1/2, and the shunt current is reduced.

Further, these are arranged so that the first positive electrode solution supply line 54 enters the first stack series circuit 51 and the second positive electrode solution supply line 55 enters the third stack series circuit 53. , Two inlets of the electrolyte supply lines 54 and 55 (in the figure,
The distance between A and B (the distance between A and B) increases, and the electrical resistance of this part increases. as a result,
The shunt current is smaller.

Further, when the positive electrode solution supply lines 54 and 55 are shifted to the adjacent stack series circuit, they are arranged so as to connect the stacks of the same potential (part C in the figure), so that both ends of C have no potential gradient. Therefore, the shunt current stops flowing.

In this embodiment, the positive electrode solution inlet line 57, which is an example of the electrolytic solution passage, is bent as shown in FIG. 3 to increase the resistance of this portion and further suppress the shunt current. be able to.

FIG. 4 is a schematic configuration diagram of another embodiment of the present invention. The stack connection example shown in FIG. 4 has exactly the same configuration as that shown in FIG. The difference is that in FIG. 1, the electrolyte solution line is a complicated route, but in FIG. 4, the electrolyte solution line is simplified and the route of the flexible electrical connection is complicated. The effect is the same as that shown in FIG. In FIG. 4, members or elements denoted by the same reference numerals as those used in FIG. 1 are exactly the same as those described in FIG. 1, and the description thereof is omitted here.

FIG. 5 is a schematic configuration diagram of still another embodiment of the present invention. The electrolyte circulation type secondary battery includes a first stack series circuit 51 and a second stack series circuit 52 each composed of 20 stacks (each stack is composed of 15 cells), and a first positive electrode solution supply line 54. And a second positive electrode solution supply line 55. The first stack series circuit 51 and the second stack series circuit 52 are connected in parallel. The first positive electrode solution supply line 54 and the second positive electrode solution supply line 55 are connected in parallel. Then, the first of the first stack series circuits 51
The stack present in the section has a first catholyte supply line
The positive electrode solution is supplied from 54, and the second
The stack present in the section has a second catholyte supply line
A first positive electrode solution supply line 54 and a second positive electrode solution supply line 55 are provided so that the positive electrode solution is supplied from 55.
Even with such a configuration, the same effect as that of the above embodiment is realized.

Specific Example Next, FIG. 2 shows the effect of the embodiment shown in FIG. 5 (here, the bent electrolytic solution inlet and outlet lines shown in FIG. 3 are used). Table 1 shows a comparison with the conventional example shown.

In the above embodiment, the positive electrode liquid supply line is exemplified. However, the same effects can be obtained in the case of the negative electrode liquid supply line, the positive electrode liquid discharge line, and the negative electrode liquid discharge line.

Further, in the above-described embodiment, the cathode fluid inlet pipe is illustrated,
A similar effect can be obtained even in the case of a positive electrode solution outlet line, a negative electrode solution inlet line, and a negative electrode solution outlet line.

[Effects of the Invention] As described above, according to the present invention, the first stack in the first section of the first series circuit has the first stack.
The electrolyte is supplied and discharged from the electrolyte supply and discharge lines of the first stack, and the electrolyte existing in the second section of the first stack series circuit is supplied and discharged from the second electrolyte supply and discharge line. As described above, since the first electrolytic solution supply and discharge line and the second electrolytic solution supply and discharge line are provided, the number of stacks in series is divided into at least two or more. As a result, there is an effect that a shunt current is suppressed, and a recirculating electrolyte secondary battery having a higher charging / discharging effect can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an electrolyte circulation type secondary battery according to one embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a conventional electrolyte circulation type secondary battery. FIG. 3 is a schematic view of an electrolytic solution passage used in the present invention. FIG. 4 is a schematic configuration diagram of another embodiment of the present invention. FIG. 5 is a schematic configuration diagram of still another embodiment of the present invention. FIG. 6 is a diagram showing a power demand curve. FIG. 7 is a schematic configuration diagram showing an example of a conventional redox flow battery. FIG. 8 is an exploded perspective view of a conventional cell. FIG. 9 is a diagram showing an example of stack connection in series. FIG. 10 is an equivalent circuit diagram of the electrolyte circulation type secondary battery shown in FIG. In the figure, 51 is a first stack series circuit, 52 is a second stack series circuit, 54 is a first positive electrode solution supply line, and 55 is a second
Of the positive electrode solution supply line.

Continuation of the front page (56) References JP-A-1-149373 (JP, A) JP-A-62-108465 (JP, A) JP-A-59-127378 (JP, A) JP-A-63-213261 (JP) , A) Actually open sho 59-188677 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01M 8/00-8/24

Claims (1)

(57) [Claims] 1. A first stack series circuit comprising a plurality of stacks electrically connected in series, a second stack series circuit, and a first stack circuit for supplying and discharging an electrolyte to and from the stack.
And a second electrolytic solution supply and discharge line, and a second electrolytic solution supply and discharge line, wherein the first stack series circuit and the second stack series circuit are electrically connected in parallel, 1 in which the electrolyte supply and discharge lines and the second electrolyte supply and discharge lines are connected in parallel, wherein the plurality of stacks in the first stack series circuit are , Which belong to the first section and those which belong to the second section, and the first electrolytic solution supply and the stack existing in the first section of the first stack series circuit are Electrolyte is supplied and discharged from a discharge line, and the stack existing in the second section of the first stack series circuit is supplied and supplied with electrolyte from the second electrolyte supply and discharge line. The first electrolyte supply and discharge lines and the second electrolyte supply and discharge lines are disposed so as to be discharged from the first section in the first section of the first stacked series circuit. Each of the stacks to be connected to the first electrolyte supply and discharge lines are connected by a branch line for supplying and discharging the electrolyte, branched from the first electrolyte supply and discharge lines. Wherein each of the stacks present in the second section of the first stack series circuit and the second electrolyte supply and discharge line are branched from the second electrolyte supply and discharge line. An electrolyte-circulating secondary battery connected by a branch pipe for supplying and discharging the electrolyte.