EP3602670A1

EP3602670A1 - Redox flow battery and method for operating a redox flow battery

Info

Publication number: EP3602670A1
Application number: EP18730266.6A
Authority: EP
Inventors: Robert Fleck; Jochen FRIEDL; Barbara Schricker; Holger WOLFSCHMIDT
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2017-06-09
Filing date: 2018-05-28
Publication date: 2020-02-05
Also published as: EP3413384A1; CN110710042A; US20200161689A1; US11769895B2; JP2020522842A; WO2018224346A1

Abstract

The invention relates to a rechargeable redox flow battery and to a method for operating an electrically rechargeable redox flow battery. A redox flow battery comprising a first and second chamber which are separated by a membrane, wherein the first chamber comprises a cathode and the second chamber comprises an anode, is initially provided. A first electrolyte is routed into the first chamber as catholyte and a second electrode is routed into the second chamber as anolyte, wherein the first and/or second electrolyte comprises a reduction-oxidation pair, and wherein the oxidation number of the reduction-oxidation pair is changed by adding a first component to the first and/or second electrolyte and/or the oxidation number is changed electrochemically.

Description

description

Redox flow battery and method for operating a redox flow battery

The invention relates to a redox flow battery and a Ver ^¬ drive for operating a redox flow battery.

Demand for electricity fluctuates strongly over the course of the day. Electricity generation also fluctuates with increasing share of electricity from renewable energies during the course of the day. To an oversupply of power at times with a lot of sun and strong winds at low demand for electricity to ausglei ^¬ chen, you need controlled power plants or storage rather to store this energy.

Batteries are stores for electrical energy on electro ^¬ chemical basis and suitable to store the excess energy. If it is a rechargeable supply, it is also called an accumulator. A single element is also a rechargeable storage secondary element ge Nannt ^¬.

In the case of redox flow batteries, unlike traditional secondary elements, the electrode-active material is liquid.

This liquid electrolyte is stored in a tank and pumped into a cathode compartment with a cathode and / or into an anode compartment with an anode. At the electrodes, the electrode active material is reduced or oxidized. The liquid electrolyte therefore expediently comprises a reduction-oxidation pair as the electrode-active material.

In particular, the electrolyte comprises oxides of transition metal ^¬ len as oxidation-reduction pair. The disadvantage production-oxidation pair at the beginning of the chemical reaction in the wrong, ie the opposite, reduction or oxidation state. Furthermore, the usable capacity can be obtained by unintended displacement of oxidation during operation of the flow battery due to undesirable side reactions adversely during the operation of sin ^¬ ken.

It is therefore an object of the invention to provide a method for operating a redox flow battery and a redox flow battery, which setting the reduction or Oxida ^¬ tion status of the reduction-oxidation pair at the beginning or during operation of the Allow redox flow battery. The object is achieved by a method according to claim 1 and egg ^¬ ner redox flow battery according to claim 14.

The method of operating an electrically rechargeable redox flow battery involves several steps. There is the provision of a redox flow battery comprising a first and a second chamber separated by a membrane, where ^¬ in the first chamber comprises a cathode and the second chamber comprises an anode. A first electrolyte is passed as a catholyte into the first chamber and a second electrolyte is conducted as anolyte in the second chamber, wherein the first and / or second electrolyte comprises a reduction-oxidation pair. The oxidation number of the reduction-oxidation pair is changed by adding a first component to the first and / or second electrolyte and / or the oxidation number of the reduction-oxidation-oxidation pair is changed electrochemically.

An electrically rechargeable redox flow battery according to the invention for carrying out the above-mentioned method comprises a first and a second chamber, separated by a Membrane, said first chamber having a cathode and the second chamber comprises an anode, and wherein the first chamber is geeig ^¬ net to include an electrolyte as catholyte and said second chamber is adapted to receive the electrolyte as the anolyte, the electrolyte is a Reduction-oxidation pair comprises. The redox flow battery further comprises a first pump for pumping the catholyte through the first chamber and ei ^¬ ne second pump for pumping the anolyte through the second Kam ^¬ mer. Furthermore, the redox flow battery comprises a supply device suitable for supplying a first component into the first and / or second chamber. Particularly advantageously, this feed is arranged at an inlet for the electrolyte. The method according to the invention and the invention Before ^¬ direction advantageously allow the start of operation of the rechargeable flow battery, or change its oxidation number during operation of the rechargeable flow battery. In particular, enabling a reduction-oxidation pair in the electrolyte prior to operation allows it to be reactivated or deactivated during operation.

Activating and reactivating is especially for the

Polyoxometalate PV14O40 possible. This polyoxometalate can be reduced by means of hydrazine as a reducing agent and thus activate ^¬ or reactivate, if the redox flow battery is already operated. The hydrazine addition can therefore take place before or during the operation of the redox flow battery.

According to the invention, the first electrolyte comprises a first re ^¬ duktions oxidation pair and the second electrolyte a second reduction-oxidation pair. According to the invention as the first and / or second reduction-oxidation pair

Polyoxometalat used. Advantageously, the chemical structure of the polyoxometalates can be adapted to specific application goals of a redox flow battery. In particular, polyoxometalates with a fast reaction kinetics and several possible electron transitions are advantageously suitable for use in redox flow batteries.

According to the invention, the oxidation number of the first and / or second reduction-oxidation pair is reduced. In particular, the oxidation number of the polyoxometalate is reduced. Before ^¬ geous it is possible with the inventive method to convert the polyoxometalate by the addition of a reducing agent or by an electrochemical reduction in an active state, so that the polyoxometalate as Redukti ^¬ ons oxidation pair in the first and / or second chamber the redox flow battery is present. In particular, can

Tetradecavanadophosphat [PV (V) 14O42] ^{9 ~,} wherein the vanadium has the oxidation number five (V), which is indicated in the parenthesis of the research mel, redu from this oxidized state are ^¬ sheet towards Re [PV (V) sV (IV) 6O42] ^{9 ~} , where 6 of 14 of the total vanadium atoms in this compound have the oxidation number four (IV). According to the invention is as a first component for reducing the oxidation number of the first and / or second reduction-oxidation pair of hydrazine, an alkali metal, a hydride, an aldehyde, sodium sulfite, sodium dithionite or

Sodium thiosulfate used. In particular, hydrazine is a strong reducing agent and thus advantageously effective in activating the reduction-oxidation pairs.

In a further advantageous embodiment and development of the invention, the oxidation number of the first and / or second reduction-oxidation pair. In particular ver ^¬ applies as oxidant hydrogen peroxide permanganate, oxygen, halogens or noble metal ions.

Especially when neutral reduction-oxidation pairs are present at the start of operation of the flow battery, it is oxidise one half of the reduction-oxidation couples before ^¬ geous. These are then fed to the cathode space, that is, the first chamber, to be reduced again there. The second half is reduced. This half is the second chamber, ie the anode compartment, fed and oxidized there. Reducing or oxidizing can advantageously take place in the reservoir tanks before the start of operation. During operation, it is also advisable to add directly into the first or second chamber.

In a further advantageous embodiment and development of the invention, the addition of the first component for reactivation of the battery takes place in the discharged state of

Flow battery. The addition of the first component can occur in any state of the battery, from fully charged to empty. However, the addition of the first component in the empty state is particularly advantageous, since then advantageously the amount of the first component to be added can be accurately determined and its addition thus takes place particularly effectively.

In a further advantageous embodiment and development of the invention, a residual capacity of the redox flow battery is measured for the reactivation of the battery and added a first amount of the first component in relation to the measured ^¬ nen residual capacity. The remaining capacity is the usable capacity remaining at a given time. Advantageously, 50-100% of the theoretical to activate the usable storage capacity of the redox flow battery in this way. The first amount of the first component to be added is determined in a portion of the theo retical ^¬ usable storage capacity of the flow battery. In particular, this proportion can be stated as a percentage.

In a further advantageous development and refinement of the invention, the change in the oxidation state of the oxidation-reduction pair is carried out electrochemically by ei ^¬ ner first activation electrode in the first chamber

and / or by means of a second activation electrode in the second chamber. Advantageously, these activation electrodes form a ^{pair of} electrodes. It is also conceivable that the anode and cathode of the first and second chambers are used as activation electrodes. Expediently the stability of the electrodes must consider when voltage to be applied for the electrochemical reduction or oxidation ^¬ to. Are the anode and the cathode at the applied clamping voltage ^¬ stable, so it is advantageous to use this, since then the use of a second pair of electrodes is avoided.

In a further advantageous embodiment and development of the invention, the electrochemically caused change in the oxidation number of the reduction-oxidation pair takes place by means of catalysts on the first and / or second activation electrode.

In a further advantageous embodiment and further development of the invention, the electrochemically induced change in the oxidation number of the reduction-oxidation pair takes place by means of additives on the first and / or second activation electrode. The additives are in particular at the electrodes and in the entire electrolyte. you can in particular also detached from the electrode and then consumed.

In a further advantageous embodiment of the invention and further extension, the first and / or second actuation electrode are applied with a voltage in dependence on the capacity of the Restka ^¬ flow battery. The control of the reaction of the redox flow battery is thus advantageously possible. Furthermore, advantageously over or under voltages can be avoided.

In an advantageous embodiment and development of the invention the first chamber comprises a first activation ^¬ electrode and the second electrode chamber a second activation. The first and second activation electrodes are adapted to effect an electrochemical change of the reduction-oxidation pair.

Further features, properties and advantages of the present invention will become apparent from the following description with reference to the accompanying figure.

The figure shows a rechargeable redox flow battery with a first component feeder.

The figure shows a rechargeable redox flow battery 1. The rechargeable redox flow battery comprises a redox flow unit 2. The redox flow unit 2 comprises a membrane 3, wherein the membrane 3, a first chamber 4 and a second chamber 5 separated from each other. In the first chamber 4, a cathode 15 is arranged. In the second chamber 5, an anode 16 is arranged. The cathode 15 and the anode 16 are connected via an electrical energy connection 12 to a power grid. The first chamber 4 further comprises a first activation Electrode 17. The second chamber 5 comprises a second Akti ^¬ vierungselektrode 18th

The first chamber 4 and the second chamber 5 are suitable for receiving an electrolyte. In this example, a first electrolyte 10 is present in the first chamber 4. In the second chamber 5, a second electrolyte 11 is present. The first

Electrolyte is pumped by means of the first pump 8 and the second electrolyte 11 by means of the second pump 9 in the redox flow unit 2. From the redox flow unit 2 is the

Electrolyte 10, 11 then led back into the tanks. The electrolyte is presented in a first tank 6 and a second tank 7. In this example, the first Elect ^¬ rolyt 10 and the second electrolyte 11 comprises a Polyoxymetallat. The polyoxymetalate is present in a non-active form at the beginning of the operation.

In this example, the polyoxometalate used in the first chamber, ie the cathode space, is the tetradecavanadophosphate [PV (V) 14O42] ^{9 ~} (abbreviated to PV14) in oxidized form.

By adding a first component through feed line 13 and feed line 14, the polyoxymetalate is converted into an active form which, in this example, is in the reduced form

H ₆ [PV (V) ₈ V (IV) ₆ 0 ₄ 2] ^{9 ~} transferred. It is also possible that the first component is added during operation to reactivate the polyoxymetalate. In particular, the first component, in particular hydrazine, is added as a function of a residual capacity of the redox flow unit 2. In particular, the residual capacity ranges from 60% to 90% when the first component of hydrazine is added. Alternatively or in addition to adding a first component, in particular hydrazine, the activation, in particular of the polyoxymetalate, can also be carried out electrochemically. consequences. It is possible that the first activation ^¬ electrode 17 and the second actuation electrode 18 convert the Polyoxymetallat of the non-active to the active form by ^¬. This conversion can be accelerated by additives and catalysts. Advantageously, it is possible

Use polyoxymetalate as a reduction-oxidation pair in redox flow batteries and activate and reactivate them depending on the operating mode.

Claims

claims

1. A method for operating an electrically rechargeable redox flow battery (1) with the following steps:

- Providing a redox flow battery (1) comprising a first and second chamber (4, 5), separated by a membrane (3), wherein the first chamber (4) has a cathode (15) and the second chamber (5) an anode (16) comprises

- Leading a first electrolyte (10) as a catholyte in the first chamber (4) and guiding a second electrolyte (11) as anolyte in the second chamber (5), wherein the first and / or second electrolyte (10, 11) is a reduction Oxidation pair comprises, characterized in that

- The oxidation number of the reduction-oxidation pair by adding a first component to the first and / or second

Electrolyte (10, 11) is changed and / or that the Oxidati ^¬ onszahl is changed electrochemically, wherein the first

Electrolyte (10) comprises a first reduction-oxidation pair and the second electrolyte comprises a second reduction-oxidation pair, wherein a polyoxometalate is used as the first and / or the second reduction-oxidation pair and wherein the oxidation number of the first and / or second reduction-oxidation pair is reduced, using as the first component hydrazine, an alkali metal, a hydride, an aldehyde, sodium sulfite, sodium dithionite or sodium thiosulfate.

2. The method according to any one of the preceding claims, wherein the addition of the first component in the discharged state of the redox flow battery (1).

3. The method according to any one of the preceding claims, wherein the residual capacity of the redox flow battery (1) is measured and a first amount of the first component is added in relation to the measured residual capacity.

4. The method according to any one of the preceding claims, wherein the electrochemically induced change in the oxidation number of the reduction-oxidation pair by means of a first Akti ^¬ vierungselektrode (17) in the first chamber (4) and / or by means of a second activation electrode (18) in the second chamber (5) takes place.

5. The method of claim 4, wherein the electrochemically induced change in the oxidation number of the reduction-oxidation pair by means of catalysts on the first

and / or second activation electrode (17, 18).

6. The method according to any one of claims 4 or 5, wherein the electrochemically induced change in the oxidation number of the reduction-oxidation pair by means of additives to the first and / or second activation electrode (17, 18).

7. The method according to any one of claims 4 to 6, wherein the first and / or second activation electrode (17, 18) are acted upon with egg ^¬ ner voltage as a function of the residual capacity of the redox flow battery.

8. Electrically rechargeable redox flow battery (1) for carrying out the method according to one of claims 1 to 7, comprising: - A first and second chamber (4, 5), separated by a membrane (3), wherein the first chamber (4) comprises a cathode (15) and the second chamber (5) comprises an anode (16), and the first chamber (4) is adapted to receive a first electrolyte (10) as a catholyte and the second chamber (5) is adapted to receive a second electrolyte (11) as anolyte, wherein the first and / or the second electrolyte comprises a reduction-oxidation pair,

a first pump (8) for pumping the catholyte through the first chamber (4),

a second pump (9) for pumping the anolyte through the second chamber (5),

- A supply device (13, 14) suitable for supplying a first component in the first and / or second chamber (4, 5).

9. redox flow battery (1) according to claim 8, wherein the first chamber (4) comprises a first activation electrode (17) and the second chamber (5) comprises a second activation electrode (18) and the first and second activation electrodes (17 , 18) are suitable for effecting an electrochemical change of the reduction-oxidation pair.