JPH0365625B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrolyte reflux type secondary battery that is charged or discharged while circulating an ion-conductive electrolyte.

[Conventional technology]

In recent years, with the aim of leveling out the negative electrodes of generators and reducing the capacity of thermal power plants, research and development have been conducted on methods for storing power generated during light loads. One such power storage device uses an electrolyte reflux type secondary battery that is charged and discharged by circulating an electrolyte having ionic conductivity. An example of this electrolyte reflux type secondary battery is shown in Figures 12 to 1.
Shown in Figure 4.

In FIG. 12, the electrolyte reflux type secondary battery is
The stack 10 has supply pipes 12, 14 and a return pipe 16,
Electrolyte solution tanks 20 and 22 in which electrolyte is stored are connected via 18. Each supply pipe 12, 14
are provided with circulation pumps 24 and 26, respectively, so that the ion conductive electrolyte in the electrolyte tanks 20 and 22 can be supplied to the stack 10 and refluxed to the electrolyte tanks 20 and 22. There is.

The stack 10 is constructed by stacking a plurality of single cells 28, and as shown in FIG. 13, the positive and negative terminals of each single cell 28 are connected in series. Each single cell 28 is divided into a negative electrode chamber 32 and a positive electrode chamber 34 by a separator 30 made of an ion exchange membrane, and the negative electrode chambers of each single cell and the positive electrodes are formed in each single cell. They communicate with each other through channels. Each negative electrode chamber 32 is supplied with the electrolyte in the electrolyte tank 20 by a circulation pump 24, and each positive electrode chamber 34 is supplied with an electrolyte from a circulation pump 26.
The electrolyte in the electrolyte tank 22 is supplied.

In the electrolyte reflux type secondary battery configured as described above, for example, in the case of a zinc-bromine battery whose electrolyte is a ZnBr ₂ aqueous solution, the negative electrode is connected to the negative electrode and the positive electrode is connected to the positive electrode when charging. Apply,
Zn is electrodeposited on the negative electrode, and Br ₂ is generated in the positive electrode chamber.
Furthermore, during discharge, Zn deposited on the negative electrode becomes Zn ⁺⁺ and becomes Br ₂ ⁻ in the positive electrode chamber, and ZnBr ₂ is generated from these reactions. The electromotive force per single cell at this time is 1.82V, and in order to obtain a high voltage, a stack 1 is made by connecting a large number of single cells 28 in series and stacking them.
It needs to be set to 0 before use.

[Problem that the invention seeks to solve]

However, as shown in FIG.
The negative electrode chambers 32 and positive electrode chambers 34 of No. 8 are in communication with each other through a flow path, and based on the potential difference between each single cell 28, leakage occurs through the ionic conductive electrolyte circulating through each flow path. A current i flows. This leakage current i increases as the number of stacked unit cells 28 increases and as the value of the potential difference V between the unit cells at both ends increases. As a result, energy loss occurs within the stack 10 due to the leakage current i. Since this energy loss increases in proportion to the square of the voltage, it is not possible to increase the voltage between the terminals of the stack 10, and it is not possible to create a high voltage battery. For this reason, in conventional electrolyte reflux type secondary batteries, the number of stacked single cells 28 is set to 20 to 30, and the voltage between the terminals of one stack is suppressed to several tens of volts, making it possible to maintain high voltage batteries. If this is desired, it is necessary to connect multiple stacks in series as shown in FIG. However, if the configuration shown in FIG. 14 is adopted, electrolyte tanks 20 and 22 and circulation pumps 24 and
6, which increases the cost of the battery. Moreover, it is necessary to insulate each stack and electrolyte tank from the ground, making the installation method complicated.

The present invention was made to improve the above-mentioned drawbacks, and an object of the present invention is to provide an electrolyte reflux type secondary battery that can prevent leakage current between each single cell.

[Means for solving problems]

The present invention comprises a stack in which a plurality of cells are stacked with an insulator separator in between, each having a positive electrode frame made of an insulator adjacent to a positive electrode and a negative electrode frame made of an insulator adjacent to a negative electrode; and an electrolyte tank for storing an electrolyte. a circulation pump that circulates the electrolyte in the electrolyte tank to each of the cells and the electrolyte tank; a circulation pump that is installed in each cell and that intermittently pumps the electrolyte between the cells; A leakage current prevention device for preventing current leakage; In an electrolyte reflux type secondary battery, the leakage current prevention device includes a gear pump made of an insulator installed in the positive electrode frame and the negative electrode frame; A hydraulic turbine installed inside the separator frame and driven by an electrolyte circulated between the electrolyte tank and each cell by the circulation pump, and an operating shaft connecting the hydraulic turbine and each of the gear pumps. We propose an electrolyte reflux type secondary battery characterized by:

[Effect]

The present invention configured as described above prevents each cell from being electrically connected via the electrolyte by intermittently supplying electrolyte with a leakage current prevention device, thereby preventing leakage current from occurring. It is composed of

〔Example〕

Preferred embodiments of the electrolyte reflux type secondary battery according to the present invention will be described in detail with reference to the accompanying drawings. Note that the same reference numerals are given to the parts corresponding to the parts explained in the prior art, and the explanation thereof will be omitted.

FIG. 2 is a diagram illustrating an embodiment of the present invention.
FIG. 1 is a schematic configuration diagram of a bromine battery.

In FIG. 2, in the single cell 28 constituting the stack 10, a negative electrode 36 is disposed in a negative electrode chamber 32, and a positive electrode 38 is disposed in a positive electrode chamber 34.
The negative electrode chamber 32 of each unit cell 28 has a negative electrode chamber inflow path 4.
0 and a negative electrode chamber outflow path 42, the negative electrode inflow manifold 44 and the negative electrode outflow manifold 46 are connected to each other. Further, each positive electrode chamber 34 has a positive electrode chamber inflow path 4.
The positive electrode inflow manifold 52 and the positive electrode outflow manifold 54 are connected to each other via the positive electrode chamber outflow path 50 and the positive electrode chamber outflow path 50 . Further, each single cell 28 is provided with a negative leakage current prevention device 56 and a positive leakage current prevention device 58, the details of which will be described later. Each leakage current prevention device 56, 58 has an inflow path 4 between the negative electrode chamber and the positive electrode chamber.
Leakage current prevention parts 60, 62, formed by gear pumps provided at 0, 48 and the outflow passages 42, 50,
64, 66 and hydraulic turbines 68, 70 that drive gear pumps. In addition, electrolyte tank 2
A ZnBr ₂ solution 72 is stored in the chambers 0 and 22. In addition, a _Br2 complex compound 74 generated during charging is precipitated in the electrolyte tank 22, and Zn7 is deposited in the negative electrode 36.
6 breaks out. The Br ₂ complex compound 74 is supplied to the positive electrode chamber 34 via the valve 75 as a ZnBr ₂ aqueous solution in which Br ₂ is highly dissolved.

The leakage current prevention device has a structure as shown in FIG. 3, taking the positive electrode side leakage current prevention device 58 as an example. That is, the positive electrode side leakage current prevention device 5
8 are gear pumps 78 and 80 and a hydraulic turbine 70 provided in the positive electrode chamber inflow path 48 and the positive electrode chamber outflow path 50.
It is made up of. The gear pumps 78, 80 each include a pair of gears 82, 84, 86, 88, and the gears 82, 86 are connected to the hydraulic turbine 70 via operating shafts 90, 92.

The hydraulic turbine 70 is disposed within a branch passage 94 that communicates the positive electrode chamber inflow passage 48 and the positive electrode chamber outflow passage 50, and is disposed within a casing 96 that is integrated with the branch passage 94 as shown in FIG. A rotary blade 98 is rotatably disposed at. In addition, the gear pump 78 is
As shown in FIG. 5, gears 82 and 84 are rotatably housed in a casing 100 formed integrally with the positive electrode chamber inflow path 48 in a meshed state. Then, the casing 100 and gears 82, 84
Water supply space 102 and narrow passage 104 that move due to
are formed to constitute the leakage current prevention section 62. This also applies to other gear pumps and leakage current prevention parts. Note that each of the above-mentioned flow paths, hydraulic turbine, gear pump, etc. is made of an organic or inorganic insulator.

The negative electrode chamber 32 formed in the single cell 28 has a negative electrode 36
The positive electrode chamber 34 is formed by a positive electrode frame placed adjacent to the positive electrode 38, and a separator made of an ion exchange membrane is provided between the negative electrode frame and the positive electrode frame. A separator frame provided with the separator frame is arranged. These negative electrode frame, positive electrode frame, and separator frame are made of an insulator, and each manifold through which an electrolyte flows, a flow path, and casings of a hydraulic turbine and a gear pump are formed in each of these frames. Examples of these negative electrode frames, positive electrode frames, and separator frames are shown in FIGS. 6 to 8.

FIG. 6 is a front view of the negative electrode frame, which has the same structure as the positive electrode frame shown in FIG.

As shown in FIG. 6, the negative electrode frame 106 includes a negative electrode inflow manifold 44, a negative electrode outflow manifold 46, a positive electrode inflow manifold 52, and a positive electrode outflow manifold 54.
is formed. A positive electrode chamber inflow path 48 branching from the positive electrode inflow manifold 52 is formed in the negative electrode frame 106 . A casing portion 108 that houses the gear pump 78 is provided in the middle of this positive electrode chamber inflow path 48, and a leakage current prevention portion 62 is configured. The positive electrode chamber inflow path 48 is the negative electrode chamber inflow path 4
0 and the negative electrode chamber outflow path 42, a groove is formed on the back side of the negative electrode frame 106 in FIG. 6, and the outflow end is formed in the separator frame 110 shown in FIG.
It communicates with a positive electrode chamber inflow path 48 formed in the.

The central part of the negative electrode frame 106 is a space that becomes the negative electrode chamber 32, and the negative electrode chamber outflow path 42 forms the negative electrode chamber 32.
It communicates with 2 at the top.

A separator 30 made of an ion exchange membrane is attached to the center of the separator frame 110. The separator frame 110 includes a branch passage 9 through which an electrolytic solution that drives the hydraulic turbine 70 on the positive electrode chamber side flows.
4 and a branch path 112 through which an electrolytic solution that drives the hydraulic turbine 68 on the negative electrode side flows.
In the center of each branch passage 94, 112, a casing part 114, 1 houses a hydraulic turbine 70, 68.
16 are formed. The branch paths 94 and 112 are each formed in a groove shape, and are connected to the casing portions 114 and 1.
One side (right side) of 16 is on the front side in Fig. 7,
The other side is formed on the back side in FIG.
The inflow portion of the branch path 94 corresponds to the upstream side of the gear pump 78 of the positive electrode chamber inflow path 48 shown in FIG. 6, and the outflow end corresponds to the positive electrode chamber outflow provided in the positive electrode frame 118 shown in FIG. It is formed at a position corresponding to the downstream side of the gear pump 80 in the passage 50 . Also, branch road 1
The outflow section 12 is formed corresponding to the downstream side of the gear pump 117 of the negative electrode chamber outflow path 42 formed in the negative electrode frame 106, and the inflow side corresponds to the upstream side of the gear pump 119 of the negative electrode chamber inflow path 40 shown in FIG. It is formed at a position corresponding to the side.

FIG. 1 shows an exploded view of each frame and electrode, and FIG. 9 shows the assembled state. As shown in FIG. 1, the electrode plate 120 is formed with a negative inflow manifold 44, a negative outflow manifold 46, a positive inflow manifold 52, and a positive outflow manifold 54, and each manifold has an insulating ring 12.
2 is inserted into the manifold to insulate the electrolytic solution flowing through the manifold from the electrode plate 120. In the assembled state of each unit cell 28, a gasket 126 is interposed between each frame and between the electrode 124 and the frame. The electrode 124 shown in FIG. 9 is composed of a negative electrode 36 and a positive electrode 38 that are integrally connected in series.

The operation of the embodiment configured as described above is as follows.

When the circulation pumps 24 and 26 are driven during charging or discharging, the ZnBr ₂ aqueous solution 72, which is an ion-conductive electrolyte, in the electrolyte tanks 20 and 22 flows into the negative electrode chamber 32 and the positive electrode chamber 34 as follows. Supplied. The ZnBr ₂ aqueous solution (electrolyte) 72 in the electrolyte tank 22 is
It enters the positive electrode chamber inflow path 48 formed in the negative electrode frame 106 from the positive electrode inflow manifold 52 . The electrolytic solution 72 in this positive electrode chamber inflow path 48 enters the gear pump 78 .
On the other hand, a part of the electrolyte in the positive electrode chamber inflow path 48 provided in the negative electrode frame 106 enters the branch path 94 formed in the separator frame 110, drives the hydraulic turbine 70, and enters the positive electrode chamber formed in the positive electrode frame 118. It exits to the gear pump 80 downstream side of the outflow path 50 and is discharged to the positive electrode outflow manifold 54 . When the hydraulic turbine 70 is driven and rotated by the electrolyte, the gear pump 78, which cannot be rotated by hydraulic pressure, receives a rotational force that exceeds the resistance in the rotation system of the gears 82 and 84, and rotates.

Therefore, the electrolyte 72 in the positive electrode chamber inflow path 48
As shown in FIG. 5, water is intermittently fed from the upstream side to the downstream side by a water feeding space 102 that is composed of gears 82, 84 and a casing part 108.
Since the gears 82 and 84 and the negative electrode frame 106 are made of an insulator, the narrow portion 104
An electrically high resistance portion is formed in the electrolytic solution 72, thereby preventing leakage current occurring through the electrolyte 72. That is, ρ is the volume resistivity of the electrolyte, S
If is the cross-sectional area of the electrolyte and l is the length of the electrolyte, then
Electrical resistance R is expressed by the following formula.

R=ρl/S Therefore, since the cross-sectional area of the electrolyte 72 in the narrow part of the leakage current prevention part is very small, the value of electrical resistance when looking from the inlet (upstream side) to the outlet (downstream side) is very small. It becomes something big. The value of the electrical resistance in the leakage current prevention section 62 has the same effect as if as many resistors as the number of narrow sections 104 were connected in series, and the structure is such that the leakage current prevention effect is enhanced.

Electrolyte 7 fed to the downstream side of gear pump 78
2 enters the positive electrode chamber inflow path 48 formed in the positive electrode frame 118 via the positive electrode chamber inflow path 48 formed in the separator frame 110 . After flowing down the positive electrode chamber inflow path 48 of the positive electrode frame 118, this electrolytic solution enters the positive electrode chamber 34, undergoes a reaction described below, and enters the positive electrode chamber outflow path 50 from the upper part of the positive electrode chamber 34. Positive electrode chamber outflow path 5
Water is intermittently supplied to the electrolyte 7 in the electrolyte 7 in the leakage current prevention section 66 by a gear pump 80, discharged to the positive electrode outflow manifold 54, and returned to the electrolyte tank 22 together with the electrolyte from the branch path 94. In the leakage current prevention section 66, leakage current is prevented similarly to the leakage current prevention section 62 described above.

On the other hand, the electrolytic solution 72 in the electrolytic solution tank 20 is pumped by the circulation pump 24 to the negative electrode inflow manifold 4.
4 to the negative electrode chamber inflow path 40 formed in the positive electrode frame 118
to go into. Electrolyte 7 that has entered this negative electrode chamber inflow path 40
2 is a separator frame 11 similar to the flow on the positive electrode chamber side.
0 into the negative electrode chamber inflow path 40 of the negative electrode frame 106 , passes through the negative electrode chamber 32 , is discharged from the negative electrode chamber outflow path 42 to the negative electrode outflow manifold 46 , and is returned to the electrolyte tank 20 .

The reaction in the negative electrode chamber 32 and the positive electrode chamber 34 during charging is as follows.

During charging, at the negative electrode 36 of the negative electrode chamber 32
Zn ⁺⁺ +2e ^- → Zn76 is deposited by the reaction of Zn. At the positive electrode of the positive electrode chamber 34, 2Br ^- →Br ₂ +
Br ₂ is generated by the reaction of 2e ^- . This Br ₂ is dissolved in the electrolyte in the positive electrode chamber 34, transported to the electrolyte tank 22, and stored in the form of a complex 74. That is,
Power is stored in the form of electrodeposited Zn 76 and Br ₂ complex 74. On the other hand, during discharge, the valve 75 is opened and a high amount of Br ₂ is dissolved from the electrolyte tank 22.ZnBr ₂
It is supplied to the positive electrode chamber 34 as an aqueous solution. and,
The reaction of Br ₂ +2e ^- →2Br ^- at the positive electrode 38 and the Zn→Zn ⁺⁺ + about the deposited Zn at the negative electrode 36
The reaction with 2e ^- generates Zn ⁺⁺ + 2Br ^- → ZnBr ₂ and an electromotive force of 1.82V per single cell.

By forming the leakage current prevention portion in the single cells as described above, leakage current between the single cells 28 can be prevented, and a high voltage and large capacity stack can be formed by stacking a large number of single cells. As a result, there is no need to connect low-voltage, small-capacity stacks in series to increase high-voltage and large-capacity stacks as in the past, and the number of circulation pumps and electrolyte tanks can be reduced. A reflux type secondary battery can be obtained.

FIG. 10 shows an example of a zinc-chlorine battery.

In this embodiment, unlike the zinc-bromine battery described above, the separator frame 110 includes a separator 3
0 is not attached, and a reaction chamber 128 in which a negative electrode chamber and a positive electrode chamber are integrated is formed in each single cell 28. The reaction chamber 128 communicates with an inflow manifold 132 via an inflow path 130 and an outflow path 13.
6 to an outflow manifold 138. Further, a chlorine gas collection path 140 is formed in the upper part of the reaction tank 128, and this chlorine gas collection path 14
0 is connected to a hydrate reservoir 144 via a valve 142. As will be described later, chlorine gas generated during charging is introduced into the hydrate tank 144, where it is precipitated and stored in the form of chlorine hydrate ( _Cl2.X.H2O ) ₁₄₆ . Further, a chlorine gas supply pipe 148 is connected to the upper part of the hydrate tank 144, and a valve 150
It communicates with the inlet manifold 132 via the inlet manifold 132 .
A circulation pump 152 is provided in the inflow manifold 132, and this circulation pump 152 supplies the ZnCl ₂ aqueous solution 156 in the electrolyte tank 154 to each unit cell 28.
At the same time, the ZnCl ₂ aqueous solution 156 is refluxed from each unit cell 28 to the electrolyte tank 154.

Each single cell 28 is provided with a leakage current prevention device 158 similar to that described above. That is, the leakage current prevention device 158 consists of leakage current prevention sections 160 and 162 of the inflow path 136 and the outflow path 136, which are configured by a gear pump, and a hydraulic turbine 164 that operates the gear pump.

In the zinc-chlorine battery configured as described above, valve 142 is opened during charging, and valve 150 is opened.
is closed, and the ZnCl ₂ aqueous solution in the electrolyte tank 154 is circulated by the circulation pump 152. At this time, Zn 76 is deposited at the negative electrode 36 due to the reaction of Zn ⁺⁺ +2e ^- →Zn. Further, at the positive electrode 38, Cl ₂ (chlorine gas) is generated by the reaction 2Cl ⁻ →Cl ₂ ↑+2e ⁻ . The generated Cl ₂ is introduced into the cold water of the hydrate tank 144 through the chlorine gas collection path 140 and stored in the form of chlorine hydrate 146 . That is, the electric power is generated by electrodeposited Zn76 and chlorine hydrate14
It is stored in the form of 6.

On the other hand, when discharging, the valve 150 is opened and the valve 14 is opened.
2 is closed and the inside of the hydrate tank 144 is heated to about 400°C, Cl ₂ gas is generated from the chlorine hydrate 146 and sent to the inflow path 132, and the inside of the hydrate tank 144 is heated to about 400°C.
Cl ₂ gas is dissolved in the ZnCl ₂ aqueous solution 156 and circulated. At this time, at the positive electrode 36, Cl ₂ +2C ^-
→2Cl ^- reaction occurs, and at the negative electrode 36 Zn→
A reaction of Zn ⁺⁺ +2e ^- occurs. As a result, Zn ⁺⁺ +
Due to the reaction of 2Cl ^- →ZnCl ₂ , the concentration of ZnCl ₂ aqueous solution in the electrolyte increases. The electromotive force of the single cell 28 at this time is 2.12V.

FIG. 11 shows an embodiment of a redox flow battery. This redox flow battery has a structure substantially similar to the zinc-bromine battery shown in FIG. However, the electrolytic solution tank 20 stores an HCl aqueous solution containing chromium ions, and the electrolytic tank 22 stores an HCl aqueous solution containing iron ions. During charging, this redox flow battery generates divalent chromium ions in the electrolyte tank 20 due to the reduction reaction of Cr ³⁺ +e ^- →Cr ²⁺ at the negative electrode 36.
By increasing Cr ²⁺ , Fe ²⁺ →Fe ³ + at the positive electrode 38
Due to the oxidation reaction of e ^- , the trivalent iron ion Fe ³⁺ in the electrolyte tank 22 is stored in an increased form. During discharge, trivalent iron ions are consumed at the positive electrode 38 through the reduction reaction of Fe ³⁺ +e ^- →Fe ²⁺ , and divalent chromium ions are consumed at the negative electrode through the reaction of Cr ²⁺ →Cr ³⁺ +e ^- . . The electromotive force of the single cell 28 at this time is 1.0V.

〔Effect of the invention〕

As explained above, according to the present invention, by providing a leakage current prevention device that intermittently supplies electrolyte to each cell, leakage current between each cell can be prevented, and leakage current to each cell can be prevented. Since the circulation pressure of the electrolyte can be averaged, single cells can be built in high-rise structures, and a high-voltage, large-capacity stack can be obtained.

[Brief explanation of drawings]

Fig. 1 is an exploded view of the main parts of the electrolyte reflux type secondary battery according to the present invention, and Fig. 2 is a schematic diagram of a zinc-bromine battery showing an embodiment of the electrolyte reflux type secondary battery according to the present invention. 3 is a perspective view showing the concept of the leakage current prevention device according to the present invention, FIG. 4 is an explanatory diagram of the hydraulic turbine of the leakage current prevention device, and FIG. 5 is the leakage current prevention device of the above embodiment. FIG. 6 is a front view of the negative electrode frame of the embodiment shown in FIG. 2, FIG. 7 is a front view of the separator frame of the embodiment shown in FIG. The figure is a front view of the positive electrode frame of the embodiment shown in Fig. 2, Fig. 9 is an explanatory diagram showing the assembled state of the unit cell of the embodiment shown in Fig. 2, and Fig. 10 is an electrolytic solution according to the present invention. FIG. 11 is a schematic diagram of a zinc-chlorine battery showing another embodiment of the reflux type secondary battery, FIG. 11 is a schematic diagram of a redox flow battery which is another embodiment of the present invention, and FIG. 12 is a conventional battery. Fig. 13 is a stack configuration diagram showing an example of a conventional electrolyte reflux type secondary battery, and Fig. 14 is a high-voltage diagram of a conventional electrolyte reflux type secondary battery. FIG. 3 is an explanatory diagram of a capacitance method. 10... Stack, 20, 22, 154... Electrolyte tank, 24, 26, 152... Circulation pump, 2
8...Single cell, 36...Negative electrode, 38...Positive electrode, 5
6...Negative electrode side leakage current prevention device, 58...Positive electrode side leakage current prevention device, 60, 62, 64, 66, 1
60,162...Leakage current prevention section, 68,70,
164...hydraulic turbine, 78, 80, 117,
119...gear pump, 90,92...operating shaft,
106...Negative electrode frame, 110...Separator frame, 1
18... Positive electrode frame, 158... Leakage current prevention device.

Claims (1)

[Claims] 1. A stack in which a plurality of cells are stacked with insulating separators in between, each having a positive electrode frame made of an insulator adjacent to a positive electrode and a negative electrode frame made of an insulator adjacent to a negative electrode; storing an electrolyte; an electrolytic solution tank; the electrolytic solution in this electrolytic solution tank is connected to each of the cells;
a circulation pump for circulating the electrolytic solution into the electrolytic solution tank; a leakage current prevention device provided in each of the cells to intermittently feed the electrolytic solution to prevent current leakage between the cells; In the type secondary battery, the leakage current prevention device includes a gear pump made of an insulator installed inside the positive electrode frame and the negative electrode frame, and installed inside the separator frame, and the circulation pump connects the electrolyte tank and each other. 1. An electrolyte reflux type secondary battery comprising: a hydraulic turbine driven by an electrolyte circulating through the cell; and an operating shaft connecting the hydraulic turbine and each of the gear pumps.