NL2020172B1 - Proton selective membrane - Google Patents

Abstract

The invention relates to a membrane for pure proton conduction, the membrane comprising a layer of water, wherein the layer of water is substantially entirely in a solid state. The invention 5 also relates to a device for storing and/or producing energy, the device comprising a housing that is fillable with fluid, a first compartment in the housing in which an electrode is positioned, a second compartment in the housing in which an electrode is positioned and a membrane according to the invention, wherein the membrane being configured for placement in the housing for forming the first and second compartments, and wherein the electrodes are connectable to an external power 10 source and/or a load for forming an electrical circuit.

Description

Patent center

Θ 2020172

(2?) Application number: 2020172 (22) Application submitted: December 22, 2017

Int. CL:

H01M 8/1016 (2018.01) H01M 8/18 (2018.01)

0 Priority: 0 Patent holder (s): 11 September 2017 NL 2019525 Wetsus Foundation, Center of Excellence for Sustainable Water Technology in Leeuwarden. 0 Application registered: March 19, 2019 0 Inventor (s): Willem Johannes van Egmond in Leeuwarden. 0 Request published: Machiel Saakes in Leeuwarden. - Harm van de Kooi in Leeuwarden. 0 Patent granted: March 19, 2019 0 Authorized representative: ir. P.J. Hylarides et al. In The Hague. 0 Patent issued: May 23, 2019

PROTON SELECTIVE MEMBRANE

Invention) The invention relates to a membrane for pure proton conduction, the membrane comprising a layer of water, the layer of water is essentially entirely in a solid state. The invention also relates to a device for failure and / or producing energy, the device including a housing that is fillable with fluid, a first compartment in the housing in which an electrode is positioned, a second compartment in the housing in which an electrode is positioned and a membrane according to the invention, according to the membrane being configured for placement in the housing for forming the first and second compartments, and being the electrodes are connectable to an external power source and / or a load for forming an electrical circuit.

NL B1 2020172

This patent has been granted regardless of the attached result of the research into the state of the art and written opinion. The patent corresponds to the documents originally submitted.

PROTON SELECTIVE MEMBRANE

The invention relates to a proton selective membrane and a system and method including a proton selective membrane.

Membranes for transferring cations are known from practice in the form of cationexchange membranes. Such membranes are used for example in (bio) electrochemical cells and (bio-based) fuel cells. Regardless of the system in which cation-exchange membranes are used, the membranes should be designed to have a high selectivity towards protons, especially in situations in which pure proton transport is desired. In other words, the efficiency of the membrane, and consequently the system in which membrane is used, depends on the membrane being able to effectively block other cations from passing, especially in situations in which pure proton transport is wanted.

A disadvantage of the known cation exchange, however, is the presence of co-ion transport, which is (unwanted) transport or anions across the membrane. This is a direct consequence of the fact that most cation-exchange membranes have an insufficiently high level of selectivity for protons. A consequence of the co-ion transport is that the efficiency of the system in which the membrane is used is reduced and the maintenance costs or such a system increase.

The membrane according to the invention is aimed at obviating or at least reducing the abovementioned disadvantage.

To that end, the invention provides a membrane for proton conduction, the membrane including a layer of water, being the layer of water is essentially entirely in a solid state.

It should be noted that, for the purpose of the invention, water in a solid state can also be read as "ice", frozen water and / or similarly known synonyms for waler in a solid state. Furthermore, the solid-phase water as referred to in the application may be formed of any one of the known crystalline phases of solid state water, such as the crystalline phases ice-I to ice-XV, a combination of or any other additional crystalline phase of solid-state water. The invention is not limited to any one or any combination of such crystalline phases. Furthermore, it should be noted that the term "membrane" should be in view of the invention and also be read as "proton conduction layer", which among other can be used in an (electro) chemical system. The invention therefore may alternatively be formulated as a device for substantially pure proton conduction including a layer of water, the layer of water is substantially entirely in a solid state. The advantages and possibilities as described below are also applicable to the device for pure proton conduction.

The membrane according to the invention provides several advantages about the prior art.

Contrary to conventional cation-exchange membranes, the membrane according to the invention has the surprising advantage that it is a substantially pure proton conduction membrane in which substantially no co-ion transport is present. Several tests that were conducted using solid state water membranes have proven that the membrane according to the invention is up to 100% selective with regard to proton conduction in an electrochemical cell. Up to 100% should be read as being at least 95% selective, preferably at least 99% selective and more preferably at least 99.5% selective. The use of the membrane as substantially pure proton conduction layer therewith provides a significant improvement over conventional cation-exchange membranes, which are less selective. The increased selectivity of the membrane according to the invention eliminates or at least significantly reduced the co-ion transport across the membrane and significantly improved the lifetime and stability of a system in which the membrane is used. This is, for example, useful in Vanadium redox flow batteries, which are known to be the disadvantage that unwanted co-ion transport takes place through the currently used anion-exchange membranes. The membrane according to the invention has the advantage that is substantially inhibits any transport save pure proton transport, therewith significantly improving the existing Vanadium-redox-flow batteries.

Another advantage of the membrane according to the invention is that the membrane is substantially impervious to water transport caused by the proton transport. As a result, the efficiency of the membrane is increased compared to known cation-exchange membranes, in which water transport is also an issue.

Another advantage of the membrane according to the invention is that the membrane is manufactured from low-cost materials, most notably waler, that is transferred from a gas state or a fluid state to a solid state. Furthermore, the manufacturing process to manufacture the membrane according to the invention is also relatively low-cost, therewith allowing the membrane according to the invention to be produced at relatively low cost. As a result, the cost of the membrane according to the invention is relatively low compared to the known cation-exchange membranes. Furthermore, the membrane according to the invention also drives out any foreign substances, such as salts during the formation or growing of the membrane.

Yet another advantage is that the membrane according to the invention can be used in existing systems, such as redox-recirculation devices or systems. The membrane according to the invention may also be used in novel applications (which may also include redox recirculation systems or devices.

Yet another advantage is that the membrane according to the invention can easily be replaced and / or recycled after use. The membrane may, for example when used in a (bio) electrochemical cell, melted down to liquid phase after use and further recycled into a new membrane. Alternatively, the water may be mixed with the fluids in the system in which the membrane is used, such as an electrochemical cell, and subsequently released with those fluids.

Yet another advantage of the membrane according to the invention is that the membrane is exceptionally environmentally friendly, since it does not contain any rare metals and / or transition metals and / or other rare or scarce raw materials and / or toxic materials. Instead, it contains a readily available source of material.

The membrane according to the invention is useable in a great variety of different applications, such as energy storage and / or energy backup for example for server parks, hospitals and banks, and may also be used in (large-scale) energy storage solutions.

In an embodiment according to the invention, the membrane may be manufactured from demineralised water, distilled water and / or sonicated water.

The advantage of manufacturing the membrane from demineralised or demi-water, distilled water and / or sonicated water is that the membrane has a reduced amount of minerals and / or gases and / or contaminations contained in the crystalline structure of the solid state water. As a result, the amount of impurities in the membrane is reduced and the performance of the membrane is increased. Alternatively, milli-Q water may also be used.

In an embodiment according to the invention, the membrane may be manufactured from boiled water that is transferred from a fluid state to the solid state.

The advantage of using boiled water, preferably boiled demi-water, is that boiled water is substantially devoid or oxygen, which reduces the formation or "bubbles" in the solid-state water or the membrane during formation. This provides a more stable crystalline structure and a more efficient membrane.

In an embodiment according to the invention, the membrane may be transparent.

It has been found that the membrane is more efficient in terms of conductivity and potential when it is transparent. Manufacturing a layer or block of transparent solid state water can be performed using various techniques. Preferably, the manufacturing includes the use of demi water and / or boiled water as raw material for growing the membrane layer to provide a transparent layer containing a relatively low amount of impurities. Furthermore, the layer of solid-state water is preferably formed under controlled conditions, which may include providing a closed space having low oxygen conditions or even a vacuum.

In an embodiment according to the invention, the membrane may have a thickness, the thickness is in the range or 1 pm to 20 cm, preferably in the range or 1 pm to 10 cm, and more preferably in the range or 1 pm to 1 cm.

An advantage of the membrane according to the invention is that the thickness of the membrane may be adapted to the specific use that is required. In most applications, the thickness of the membrane will be limited to a thickness in the range of 1 micrometre - 1 centimeter. Having a thickness in this particular range allows for a membrane having sufficient strength, while simultaneously requiring relatively low amount of space and allowing a high performance. Alternatively, the thickness may also be chosen to be larger in order to provide an increased resistance of the membrane due to osmotic pressure.

In an embodiment, the thickness of the membrane may vary across the surface of the membrane. Such variation may for example be used to provide an outer edge that is configured to cooperate with a system in which the membrane is placed to provide a substantially tight fit or the membrane in the system. In an example, the membrane may be formed as a square, rectangular or round membrane having relatively high thickness in a middle section and having a decreased thickness near the edges. Alternatively, a reduced thickness in a middle section and an increased thickness near an outer edge is also possible for a membrane according to the invention. However, it is preferred to have a substantially constant thickness over the entire surface area of the membrane.

In an embodiment according to the invention, the membrane may contain a support structure that is configured to support the solid state layer of water.

The advantage of a support structure is that it provides additional strength to the membrane, which reduces the risk of fracturing and / or breaking.

Additionally, the support structure may be used during manufacturing for providing a basis on which the solid-state layer or water is grown to form the membrane. Preferably, the support structure is reusable or at least recyclable. Preferably, the support structure and the membrane cooperate to provide a fluid-tight seal between the first and second compartment. In a preferred embodiment, the solid-state layer or water is melted during or after removal from the system in which the membrane is used, after which the support structure is re-used for growing a new layer or solid state water on the support structure. This allows a cost-effective and environmentally friendly manufacturing of the membrane. Additionally or alternatively, the support structure may also be manufactured from a recyclable material.

In an embodiment according to the invention, the support structure may be provided by a number of cooling pipes or tubes that extend parallel to each other in a horizontal or vertical direction. The cooling pipes may be metal pipes, such as copper or stainless steel pipes, having a predetermined inner and outer diameter and which are configured for guiding a cooling medium. In an elaboration of the embodiment, the cooling pipes may have an inner diameter in the range or 1-3 mm. In an elaboration of the embodiment, the cooling pipes may have an outer diameter in the range of 1 - 6 mm, and may preferably have an outer diameter in the range or 2 - 4 mm. Furthermore, the cooling pipes may extend horizontally or vertically and parallel to each other with a predetermined center-to-center distance. The center-to-center distance may for example be in the range or 2 - 8 mm, and preferably may be in the range or 3 - 5 mm. A suitable cooling fluid, such as glycol, may be chosen for forming the membrane. Preferably, the pipes are connected to an external source for cooling (i.e., discharging heat), which often results in the coolant being at substantially the same temperature.

In an embodiment according to the invention, the support structure may be and / or may be manufactured from a porous material, the porous structure is preferably configured for holding and / or incorporating solid state water.

A porous support structure may, in addition to having opening for the easy transfer of protons, also being advantageously used during the manufacturing of the membrane, in that it can be provided as a starting point for forming the layer of solid state water.

In an embodiment according to the invention, the support structure may be a mesh structure, preferably a mesh structure having a varied or relatively large opening.

A mesh structure provides the advantage that requires a relatively small amount of raw material and provides a relatively high degree of flexibility compared to a solid support structure. Furthermore, the mesh structure reduces or obviates the possibility of interference with regard to the transport of protons. The mesh structure is preferably made of an inert material, such as mentioned above. Preferably, the mesh structure is chosen to provide support during the formation and / or operation of the membrane, where it may be coupled with an active cooling function or the membrane.

In an embodiment, the support structure is manufactured from an electrically non-conducting and / or chemically inert material. An inert material for the support structure is a material that is chemically inactive and / or electrically non-conductive, such that the support structure does not interfere with the function of the membrane and does not promote and / or support any co-ion transport and / or leak currents.

In an embodiment according to the invention, the support structure may be connectable to a cooling device that is configured for cooling the membrane and / or forming the membrane from fluid-slate phase water.

The support structure may be used to provide cooling to the membrane during operation, which reduces melting and increases the life-time of the membrane. The support structure is preferably manufactured from a material capable of transporting and / or extracting heat from the layer of solid state water or the membrane in order to maintain the layer at cryogenic temperatures, preferably a temperature of a few degrees below 0 ° C, although other temperatures are possible as well. Preferably, the cooling device is provided with a control system or is connectable thereto for regulating the amount and / or intensity of cooling.

More preferably, the material of the support structure is chosen to be capable of heat transport and extraction, while simultaneously being chemically inactive and electrically nonconductive.

The support structure may be provided in any form that is suitable for use in or on the membrane and / or may be connectable to (part of) a device or system in which the membrane is useable.

In an embodiment according to the invention, the support structure may include a cooling device configured for forming a layer or solid state water to manufacture the membrane.

This embodiment provides a highly integrated membrane in that the support structure is used for supporting the layer of solid state water during operation as well as forming the layer of solid state water during manufacturing of the membrane. This for example allows the membrane to be formed in-silu rather than manufacturing the membrane off-site and therewith obviates transportation of the membrane to the location of use.

In an embodiment according to the invention, the membrane is substantially pure in that the water in the membrane contains less than 1 volume% of impurities, and preferably less than 0.1 volume% of impurities.

By reducing the amount of impurities in the layer or solid state water or the membrane, a high performance membrane can be formed. Especially the presence of minerals, oxygen and / or other gases reduced the purity of the membrane, therewith resulting in a reduced performance of the membrane. It is found that if the level of impurities, measures as a volume percentage or the layer of water in the membrane, is kept within the range as mentioned before, the performance of the membrane is not adversely affected.

In an embodiment according to the invention, the membrane may be configured for operation under cryogenic conditions, and may be preferably configured for operation in a temperature range between -15 ° C and 4 ° C, more preferably in a temperature range or -10 ° C and 2 ° C and most preferably in a temperature range or -6 ° C to -2 ° C.

The temperature range of the membrane is preferably kept at or just more preferably slightly below '0 ° C, which prevents melting of the membrane during use in a system, for example an (bio) electrochemical cell. Simultaneously, a temperature at or just slightly below 0 ° C avoid any fluids in the system, for example a (bio) electrochemical cell, from completely freezing up and reducing or obviating operation of the system.

The invention also relates to a device for failure and / or producing energy, the device including:

a housing that is fillable with fluid;

a first compartment in the housing in which an electrode is positioned;

a second compartment in the housing in which an electrode is positioned;

a membrane according to one of the preceding claims, the membrane being configured for placement in the housing for forming the first and second compartments; the electrodes are connectable to an external power source and / or a load for forming an electrical circuit.

The device according to the invention provides the same effects and advantages as the membrane according to the invention. The device according to the invention is usable in a wide variety of different devices, all or which fall within the scope of the application. In a preferred embodiment, the device according to the invention is configured for producing and / or storing energy. This includes capacitive devices in which only a proton gradient between the first and the second compartment is provided to store and / or generate energy, and also includes devices having electrochemical devices having reversible electrodes and / or electrochemical couples. It also includes fuel cells for generating energy.

It has been found in various tests that the device according to the invention advantageously provides a cost-effective, efficient and environmentally friendly device for failure and / or generating energy. The device according to the invention may be provided in various different forms and shapes, depending on the specific requirements of the device, such as storage capacity and size. Preferably, the housing is chosen from a material that is suitable for holding acids and / or bases in order to provide a reusable housing for the device. The housing may be provided with means, such as connectors, for holding the electrodes, the means are preferably electrically insulated from the housing. The device may be configured for coupling the device with a second and / or further device, the device may be provided between devices, or may the device may be coupled using bipolar stacking, in which different devices are connected using a bipolar plate for connecting a first compartment or a second device to a second compartment or a first device.

The device according to the invention preferably is a reversible device in that it can be used as a rechargeable battery. This is achievable by choosing a correct combination of electrolytes and / or redox reactants. The electrolytes and / or redox reactants are in such a situation configured to facilitate proton transport across the membrane in both directions, depending on the configuration of an electrical circuit attached to the device.

Preferably, the device is isolated in that it is provided in an encapsulating layer of insulation that prevents heating of the device (and therewith melting of the membrane). The isolation is preferably configured to retain the device, or at least the membrane therein, at a temperature below 0 C °.

Furthermore, the device, and specifically the walls, may be configured to be actively cooled in order to retain the device, or at least the membrane therein, at a temperature below 0 C °. A combination of active cooling and providing an encapsulating layer or isolation also falls within the scope of the invention as described in the application.

In a non-limiting example of the device that is used for illustration purposes only, the housing is a square or rectangular box that has four side walls that define an inner space, the housing is preferably formed of a suitable plastic. The inner space is divided into the first and the second compartment, which are at least partially separated from each other by the membrane. The membrane may be formed externally from the housing and provided into the housing prior to filling the first and second compartment with fluid. In such a situation, it is preferred that the side walls of the housing, at the location in which the membrane is inserted, are provided with a slit or vertical opening through which the membrane is slidable insertable in the housing. The membrane may also be formed in the housing before filling the compartments with fluid. This may for example be performed by providing a support structure which is connected to and / or slidable into the housing. Preferably, the support structure is connectable to a cooling device and / or is a part of a cooling device, which allows the membrane to be formed directly onto the support structure. In this situation, the membrane has grown from an inside to an outside of the membrane. Such a support structure may be a cooling element, a pipe structure or a wire structure in which the pipes or wires extend substantially parallel to each other, a mesh structure or any other suitable structure. Alternatively, two vertical plates may be provided that provide a space formed between the plates and the side walls of the housing. The space is fillable with water and can be provided with a freezing or cooling element, or one or both of the plates may be cooled, which allows the water to transfer from a fluid slate to a solid state for forming the membrane. The plates are subsequently removed from the housing, which makes the device ready to use. In yet another example, the device may be integrally formed from a block of ice, in which the membrane is "inherently" available. The block of ice may be formed into the device by creating two compartments having a layer of ice between them. The compartments may be provided for example by drilling, milling, grinding, sawing or even laser cutting, although other suitable means can be used as well.

In an embodiment of the device according to the invention, the fluid may be a compatible couple or an acid and base.

The device according to the invention may be provided using a couple of an acid and a base, the acid is provided in one of the first and second compartment, whereas the base is provided in the other of the first and second compartment.

In an embodiment of the device according to the invention, the electrodes may be capacitive electrodes.

By using capacitive electrodes in the device, the device may advantageously provide a relatively low-cost device for malfunctioning (electrical) energy. In this embodiment, both the membrane and the electrodes are low-cost materials that are abundantly available. The device according to this embodiment may therefore be manufactured relatively easy and the use of (expensive) electrodes is obviated.

In an embodiment of the device according to the invention, the electrodes may be reversible electrodes.

The device according to the invention may also be provided with reversible electrodes, which is, for example, advantageous when refitting existing devices to the device according to the invention. Existing devices for energy storage are often provided with a cation-exchange membrane and reversible electrodes. Such devices may easily be converted into devices according to the invention by exchanging the existing membranes with a membrane according to the invention as provided above. This reduces the cost of the devices and obviates to replace the entire device.

Furthermore, the device having reversible electrodes may in some cases provide additional advantages about the use of capacitive electrodes.

Reversible electrodes have the advantage that they can be chosen to match other substances that may be used in the device, which may for example include acids, bases and / or reversible redox couples. This allows the voltage across the cell to be increased. In addition, it allows a rechargeable cell to be manufactured.

In an embodiment of the device according to the invention, the first compartment may be filled with an acid and the second compartment may be filled with a base.

The device may be operated with an acid and a base as primary fluids for the storage of electrical energy, which electrical energy may be discharged from the device to a load.

In a currently preferred embodiment of the device according to the invention, the first compartment may be filled with an acid, the second compartment may be filled with an acid, and preferably preferably the pH of the acid in the first compartment preferably may differ from the pH of the acid in the second compartment.

An advantage of the embodiment according to the invention is that it allows a rechargeable device to be manufactured. The application of two different acids allows the proton transport to take place in either direction across the membrane. By providing a difference in the pH value between the different acids, the proton exchange is stimulated.

In an embodiment of the device according to the invention, at least one of the compartments may additionally be provided with a reversible redox couple, while each compartment is provided with a reversible redox couple, the reversible redox couples may be different reversible redox couples , the reversible redox couples are preferably chosen to be compatible.

The device may additionally include redox couples which are added to the compartments, which advantageously increase the voltage across the electrodes. The redox couples are chosen to be compatible, which means that they (at least) provide a cell voltage. Preferably, the redox couples are chosen to complement each other to provide the highest effect, i.e. the highest voltage and / or the most stable and cost-effective solution. Furthermore, the redox couples are preferably stable redox couples in at least one of an acid and a base. In the embodiment in which both compartments are provided with an acid, each of the redox couples is configured to be stable in an acid.

In the known devices, the number of redox couples that is useable is relatively limited due to the fact that cation-exchange membranes are unable to provide sufficient selectivity to prevent co-ion transport in the device and due to the fact that the cation-exchange membrane transports other cations than protons as well. The device according to the invention has the advantage that a wide range of redox couples can be used, because the membrane is exclusively configured for proton transport as well as because the membrane is not reactive and / or affected by the redox couples in the compartments.

In practice, several options for manufacturing and a device are available. An example or such a device is provided below, considering that this example is in no way limiting other options. In the example, a redox couple or Fe ' ⁺ / Fe ²⁺ in a solution or 1 M HCl and a redox couple or Zn / Zn ²⁺ in a solution or 1 M HCl is used. The voltage over the electrodes is provided by the difference in standard potential or both redox couples. The total voltage across the electrodes amounts to 1.57 V.

In an embodiment of the device according to the invention, the electrodes may be chosen from a group of activated carbon cloth, graphite, silver (Ag), anodised silver, lead (Pb), Zinc (Zn), Cadmium (Cd), Nickel (Ni), Platinum (Pt), Titanium (Ti), Iridium (Ir), Ruthenium (Ru), Tantalum (Ta), Indium (In) and mixed metal oxides, including Platinum-Iridium (Pt-lr), Ruthenium- lridium (Ru-Ir), Tantalum-lridium (Ta-Ir), Titanium-Ruthenium (Ti-Ru), Titanium-Tantalum (Ti-Ta), mixed metal oxides are preferably mixed metal oxides used in dimensionally stable anodes ( DSAs).

The device according to the invention may be provided with a great variety of different electrodes, both reversible and capacitive electrodes can be used. Preferably, capacitive electrodes are formed by activated carbon cloth, which is a cost-effective material. The electrode may also be a capacitive slurry or capacitive solution provided in the compartment.

In an embodiment of the device according to the invention, each of the redox couples may be chosen from a group of: Fe ²⁺ / Fe ³⁺ , Ce ⁴⁺ / Ce ³⁺ , Cr ²⁺ / Cr ³⁺ , V ³⁺ / V ²⁺ , Cu ²⁺ / Cu ³⁺ and V ⁴⁺ / V ⁵⁺ .

The device according to the invention can be used in conjunction with a large number of different redox couples, which includes redox couples that may not be usable or prove difficult to use in known devices.

This may for example include the use of V ³⁺ / V ²⁺ as redox couple, preferably in combination with O2 / H2O as bifunctional gas diffusion electrode. The use of this particular redox couple in the device according to the invention provides the advantage that both transport or V ²⁺ and V ³⁺ as well as the crossover or O2 through the membrane is substantially obviated.

In an embodiment of the device according to the invention, the reversible redox couple may be a solid / solid couple, a solid / liquid couple, a liquid / liquid couple or a gas / liquid couple.

An advantage of the device according to the invention is that it can be used in conjunction with substantially all types or reversible redox couples. It is preferred to use redox couples that are stable in an acidic medium. This increases the flexibility and effectiveness of the device, since the type of redox couple than is chosen may be adapted to the specific availability of substances in particular area, such as a geographic region.

In an embodiment of the device according to the invention, the fluid may be a solution or one or more salts.

In an embodiment of the device according to the invention, the fluid may be a solution of acid, the acid may be chosen from a group of HF, HCl, HBr, HI, CH ₃ SO ₃ H, HCIO 4, HNO ₃ , H ₂ SO ₄ . H ₃ PO ₄ , HCOOH or CH ₃ COOH.

Several acids may be used in the device, although preferably the acid is chosen to be compatible with the redox couples which are provided to the acid in the housing.

In an embodiment of the device according to the invention, the first compartment may include a solution of acid and the second compartment may contain a solution of acid, the acid in the first and second compartments may be different acids, preferably preferably the acids may selected from a group of HF, HCl, HBr, HI, CH ₃ SO ₃ H, HCl ₄ , HNO ₃ , H ₂ SO ₄ or H ₃ PO ₄ .

Several acids may be used in the device, although preferably the acid is chosen to be compatible with the redox couples which are provided to the acid in the housing. More preferably, each compartment in the housing is provided with a different acid, which may increase the voltage. In case a device having more than two compartments is provided, the adjacent compartments are preferred to contain different acids or a similar acid having different concentrations. Furthermore, also in a device having two compartments, the concentration of the acids may be different, which also allows a single type of acid in different concentrations to be used in the different compartments. The use of the device according to the invention, especially when using acid and / or a combination of acid with redox couples, provides a further additional advantage that a relatively high concentration difference of acid and / or redox couples can be used between the two compartments . In other words, the concentration in one of the first and second compartments may be significantly higher than the concentration in the other of the first and second compartment. In existing membranes the concentration difference must be kept limited due to the lack of resistance against the increasing osmotic pressure between the compartments. The device according to the invention, by virtue of the membrane, can be used with relatively high concentration differences due to the high resistance to the ensuing osmotic pressure. Furthermore, the membrane may be provided at a relatively high thickness to increase the resistance to the osmotic pressure and provide higher concentration differences. Therewith, the device according to the invention provides a more efficient and compact storage for electrical energy than existing devices.

Yet another advantage of the embodiment according to the invention is that the concentrations in the first and second compartment can be significantly higher than with existing conventional membranes. In conventional cation-exchange membranes the permeation selectivity decreases with increasing concentrations of the acid and / or redox couple. This does not occur in the device according to the invention, which allows the use of higher concentrations of acid and / or redox couples, leading to a more efficient and compact storage cell for (electrical) energy.

In an embodiment of the device according to the invention, each of the electrodes may be a reversible electrode and each of the first and second compartments is provided with an acid, in a charging state involving a charging operation, the reversible electrode in the first compartment is configured to be subjected to a reduction reaction and the reversible electrode in the second compartment is subject to an oxidation reaction and the reduction reaction and the oxidation reaction provide a conversion of electrical energy into chemical energy. Furthermore, in a discharging state involving a discharging operation, the reversible electrode in the first compartment is subject to an oxidation reaction and the reversible electrode in the second compartment is subject to a reduction reaction, and the oxidation reaction and the reduction reaction provide a conversion reaction for converting chemical energy into electrical energy.

The invention also relates to a system for failure and / or generating energy, including a number of devices according to any one of the preceding claims, where the devices are connected to each other.

The system according to the invention provides the same effects and advantages as the membrane according to the invention and the device according to the invention. A system for energy storage may be formed by a number of devices according to the invention. Depending on the specific need that is fulfilled, a number of devices may be chosen and connected with each other for increasing the energy storage capacity. As such, the number may include one, i.e. a single device, yet may also be two, three, four, five or more. Just ten or a hundred or more devices can be used to form a single system according to the invention. In essence, the system according to the invention can be scaled by using any number of devices to obtain the desired storage.

The invention also relates to a method for failure and / or discharging energy, the method including the steps of:

providing a device or a system according to the invention; filling the housing with a solution including a salt and / or an acid; providing the membrane to the housing for forming compartments in the housing; and applying a potential to the electrodes for charging the device or the system.

The method according to the invention provides the same effects and advantages as the membrane, the device and the system according to the invention.

It should be noted that providing the device according to the invention also includes manufacturing the membrane, which may be performed using various production techniques, including the boiled water method (regular freezing at -18 to -20 ° C), the top-down freezing method (freezing at -3 to -8 ° C). , the high-temperature freezing method (freezing at -1 ° C) and / or the bottom freezing method (using very cold saltwater inside a freezer).

In an embodiment of the method according to the invention, the step of filling the housing with a fluid may include filling the first compartment with a fluid, preferably an acid, and filling the second compartment with a fluid, preferably an acid, filling first and second compartment is performed after the membrane is provided to the housing.

In a preferred embodiment according to the method, the housing is provided with a membrane, after which the first and second compartments are filled with acid. This may contain the same type of acid or have different pH values or may differ with different acids for each compartment.

In an embodiment of the method according to the invention, the method additionally may comprise the steps of:

providing a redox couple to the first compartment; and providing a redox couple to the second compartment.

Further advantages, features and details of the invention are elucidated on the basis or preferred otherwise, where reference is made to the accompanying drawings, in which:

Figure 1 shows a schematic example of a device according to the invention;

Figure 2 shows a second schematic example of a device according to the invention;

Figure 3 shows a third schematic example of a device according to the invention;

Figure 4 shows a fourth schematic example of a device according to the invention;

Figure 5 shows a fifth schematic example of a device according to the invention;

The membrane according to the invention can advantageously be used in a device for energy storage, such as an electrochemical or bio-electrochemical cell. A schematic example of device 2 is an electrochemical cell having housing 4 and electrodes 6 (see figure 1). Electrodes 6 are connectable to an external load or power source 8 (not shown) for closing the electrical circuit and charging or discharging electrochemical cell 2. Furthermore, housing 4 is provided with first compartment 10, which is fillable with a fluid, and second compartment 12, which is fillable with a different fluid than first compartment 10. First compartment 10 and second compartment 12 are separated by membrane 14. Membrane 14 is provided with cooling device 16, which is used to cool membrane 14 during operation to a temperature that is preferably below 0 ° C.

In use, first compartment 10 or housing 4 is filled with a fluid, preferably an acid, and is additionally preferably provided with a redox couple. Second compartment 12 or housing 4 is filled with a fluid, preferably an acid, which is a different fluid than the fluid in first compartment 10 or is a similar fluid having a different pH. Preferably, a redox couple is provided to 12 as well as second compartment. Furthermore, the electrodes are connected by external power source or load 8 to form an electrical circuit.

During operation, an oxidation reaction takes place at one electrode, for example electrode 6 in first compartment 10, which produces electrons, whereas a reduction reaction takes place at electrode 6 in compartment 12 in which electrons are used. This process may be reversible, which allows electrochemical cell 2 to function as a rechargeable battery.

In a second example (see figure 2), device 102 is an electrochemical cell having housing 104 and reversible electrodes 106. Electrodes 106 are connected to an external load or power source 108 (not shown) for closing the electrical circuit. Housing 104 is provided with first compartment 110 and second compartment 112. First compartment 110 in this example is filled with a HCl solution having a redox couple of Zn / Zn ²⁺ and second compartment 112 is filled with a HCl / FeCL ₃ -solution having a redox couple or Fe ²⁺ / Fe ' ⁺ . First compartment 110 and second compartment 112 are separated by membrane 114, which is formed from crystalline ice and forms a fluid-tight seal between first compartment 110 and second compartment 112. Membrane 114 is provided with cooling device 116, which is used to cool membrane 114 during operation to a temperature that is preferably below 0 ° C.

During operation, when a load is provided to device 102, an oxidation reaction takes place at electrode 106 in first compartment 110, which oxidizes zinc (Zn) to zine-ions (Zn ²⁺ ), according to the formula Zn -> Zn ^{2 +} + 2nd, while protons (H ⁺ ) are transported at the same time. The protons migrate through membrane 114 to second compartment 112 in which a reduction reaction takes place, which reduces the iron ions according to the formula 2Fe ³⁺ + 2nd Fe ²⁺ . Conversely, when external power source 108 is provided to close the electrical circuit with electrodes 106, the reverse process, which is a charging process, takes place, in which Fe ²⁺ ions are oxidized and zinc-ions are reduced to metallic Zinc. This occurs according to the following formulas:

2Fe ²⁺ 2 (Fe ³⁺ + e)

Zn ²⁺ + 2nd - Zn

Zn ²⁺ + 2Fe ²⁺ - + 2Fe ³⁺ + Zn

In a third example (see figure 3), device 202 is an electrochemical cell having housing 204 and reversible electrodes 206. Electrodes 206 are connected to a (not shown) external load or power source 208 for closing the electrical circuit. Housing 204 is provided with first compartment 210 and second compartment 212. First compartment 210 in this example is filled with an acid provided with a redox couple of Fe ²⁺ / Fe ' ⁺ and second compartment 212 is filled with an acid with a redox couple or Cr ²⁺ / Cr ³⁺ . First compartment 210 and second compartment 212 are separated by membrane 214, which is formed from crystalline ice and forms a fluid-tight seal between first compartment 210 and second compartment 212. Membrane 214 is provided with cooling device 216, which is used to cool membrane 214 during operation to a temperature that is preferably below 0 ° C.

During operation, when a load is provided to device 202, an oxidation reaction takes place at electrode 206 in first compartment 210, which oxidizes Fe ²⁺ -ions to Fe ³⁺ -ions, while at the same time protons (H ⁺ ) are transported through membrane 214. The protons migrate through membrane 214 to second compartment 212 in which a reduction reaction takes place, which reduces the Cryions to Cr ²⁺ -ions. Conversely, when external power source 208 is provided to close the electrical circuit with electrodes 206, the reverse process takes place.

In a fourth example (see figure 4), device 302 is a known Vanadium / Vanadium electrochemical cell provided with ice membrane 314 according to the invention. Device 302 is provided with housing 304 and reversible electrodes 306. Electrodes 306 are connected to an external load or power source 308 (not shown) for closing the electrical circuit. Housing 304 is provided with first compartment 310 and second compartment 312. First compartment 310 in this example is an acid having a redox couple or V ³⁺ / V ²⁺ and second compartment 312 is filled with an acid having a redox couple or VO ^{2 +} / VO ₂ ⁺ . First compartment 310 and second compartment 312 are separated by membrane 314, which is formed from crystalline ice and forms a fluid-tight seal between first compartment 310 and second compartment 312. Membrane 314 is provided with cooling device 316, which is used to cool membrane 314 during operation to a temperature that is preferably below 0 ° C.

Membrane 314 is provided instead of the commonly used anion-exchange membranes in Vanadium redox flow batteries and have the advantage that they block substantially all unwanted anion and cation transport (other than so-called "proton hopping"). In this example, and in general for the invention, it is preferable to provide circulation for the redox fluid in a closed system. In an example of a device according to the invention (see figure 5), device 402 is formed by Plexiglas container 404 having side walls 404a and bottom wall 404b. Upper side 404c is closeable with container member 404d (not shown). Housing 404 or device 402 has inner length L, inner width W and inner height H. The outer side of housing 404 is provided with vacuum insulating layer 405 that envelopes device 402 to maintain cryogenic circumstances within device 402.

In this example container 404 is provided with separation wall 411 to form compartments 410, 412. In this example, separation wall 411 comprises a Plexiglas wall having height H, outer width W, inner width W _; and thickness D. More Further, separation wall 411 is, near a lower end thereof, provided with aperture 413 having width W and height H _{o o.} In this example, opening 413 has a height and width of approximately 10 - 15 cm. Opening 413 is closed off by membrane 414 that seals opening 413 and prevents fluids from compartments 410 and 412 from mixing. A number of horizontally placed copper tubes 416 is provided in the opening 413 for forming and following cooling membrane 414 in the opening. In this example, tubes are 416 copper tubes with an inner diameter or about 2 mm and an outer diameter or about 3 mm. Tubes 416 are placed at a center-to-center distance of about 3-4 mm and are in use, provided with a refrigerant having a temperature well below 0 ° C, for example -6 ° C. The refrigerant is circulated through tubes 416 for cooling membrane 414, which in this example has a thickness of about 1 cm. Furthermore, the amount and intensity of the cooling process may be regulated using control system 415.

In use, device 402 is first of all provided with water, preferably boiled and / or demi-water, for forming membrane 414 by circulating refrigerant through tubes 416. During a predetermined period of time, membrane 414 is grown inside Plexiglas container 404. When the growing of membrane 414 is complete, the water is removed from compartments 410, 412 and replaced with acid that has a temperature of at most 0 ° C, for example -4 ° C. The acid provided to compartment 410 is a different acid or an acid with a different pH than the acid in compartment 412. Furthermore, device 402 may be provided with a compatible redox couple, each of the compartments 410, 412 is provided with a reagent forming the compatible redox couple.

In a subsequent step the respective electrodes 406, which in this example are provided in container paragraph 404d (not shown), are placed respectively in compartment 410, 412 and connected to an electrical circuit for discharging and / or charging device 402.

An experiment was ormed using the setup of figure 5, in Which membrane 414 was a transparent ice membrane made of demi-water, having height H and width W _{o o.} Membrane 414 has thickness D _o of 1 cm and a surface, or Approximately 25 cm ^2. Membrane 414 was internally cooled with a set point of -6 ° C. Tubes 416 are copper tubes having an inner diameter or 2 mm and an outer diameter or 3 mm. First compartment 410 was filled with a 0.5 M HCl solution at 0 ° C having a Zn / Zn ²⁺ redox couple and second compartment 412 was filled with a 0.1 M FeCE / O.1 M FeCl _; solution at 0 ° C, thus providing a redox couple Fe ²⁺ / Fe ³⁺ . Electrodes 406 were formed by a Zinc-plate in first compartment 410 and a Titanium mesh provided with a Ru / Ir coating in second compartment 412. After measurement, it was established that the open circuit voltage was 1.46 V. During the experiment , a load was applied to device 402, which lead to the following reactions: oxidation reaction first compartment 410: Zn Zn ²⁺ + 2 e;

reduction reaction second compartment 412: 2Fe ³⁺ + 2e '-> Fe ²⁺ ;

total reaction device 402: Zn + 2 Fe ³⁺ -> Zn ²⁺ + 2 Fe ²⁺

The ion transfer consisted of pure proton (H ⁺ ) transfer by means of proton hopping in membrane 414.

Further tests were performed. The viability of the concept was proven in laboratory test 1 and test 2, or which a brief summary is provided below.

Test 1

The test comprised of preparing a layer of solid state water (i.e. ice) which was sufficiently thick to prepare two holes on opposite sides of the layer. The holes were positioned a few centimeters apart. In a first hole a solution of 1 M HCl was provided, whereas the second hole was provided with a solution of 1 M NaOH. Both holes were provided with electrode material, which in this test was activated carbon cloth. The activated carbon cloth was rolled like a wick in a conical tube, and subsequently prepared for insertion. The preparation involved dipping the wicks in respectively the HCL solution (first hole electrode) and the NaOH solution (second hole electrode).

After insertion, the voltage difference measured between the electrodes at 273 K was 0.392 Volts. The test was performed in a cooled chamber of 6 ° C. The calculated potential difference was 0.379 V if Nernst Law was used with T = 273K and a perm selectivity equal to 1 of the ice for the protons and a concentration of 1 M or protons of the acid-base-salt used. If a temperature of T = 279 K is used (current temperature of the climate room) a voltage difference of 0.387 V was calculated, which is substantially equal to the voltage difference measured.

Test 2

In a second test, the first compartment was provided with a solution of 0.1 M HCl and the second compartment was provided with a solution of 1 M NaOH, which were separated by a membrane according to the invention. Furthermore, each compartment was provided with a reversible Ag / AgCl electrode. The voltage measured over the electrodes was 0.35 Volts, which was the expected value.

The present invention is by no means limited to the above described preferred expend. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.

Claims (30)

CLAUSES 1. Membrane for pure proton conduction, the membrane including a layer of water, the layer of water is substantially entirely in a solid state. 2. Membrane according to clause 2, where the membrane is manufactured from demineralised water, distilled water and / or sonicated water. 3. Membrane according to any one of the preceding clauses, the membrane is manufactured from boiled water that is transferred from a fluid-state phase to the solid state. 4. Membrane according to any one of the preceding clauses, the membrane is substantially transparent. 5. Membrane according to any one of the preceding clauses, whether the membrane has a thickness, whether the thickness is in the range or 1 pm to 20 cm, preferably in the range or 1 pm to 10 cm, and more preferably in the range or 1 µm to 1 cm. 6. Membrane according to any one of the preceding clauses, the membrane including a support structure that is configured to support the layer of water in the solid state. 7. Membrane according to clause 6, the support structure is manufactured from an electrically non-conductive and / or chemically inert material. 8. Membrane according to clause 6 or 7, the support structure is a porous structure and / or is manufactured from a porous material, the porous structure is preferably configured for holding and / or incorporating ice. 9. Membrane according to any one of the clauses 6 - 8, where the support structure is a mesh structure, preferably a mesh structure having a varied or relatively large opening. 10. Membrane according to any one of the clauses 6-9, the support structure is connectable to a cooling device that is configured for cooling the membrane and / or forming the membrane from fluid-state water. 11. Membrane according to any one of the clauses 6-9, comprising the support structure comprises a cooling device configured for forming a layer or solid state water. 12. Membrane according to any one of the preceding clauses, the membrane is substantially pure in the water in the membrane contains less than 1 volume% of impurities, and preferably less than 0.1 volume% of impurities. 13. Membrane according to any of the preceding clauses, the membrane is configured for operation under cryogenic conditions, and is preferably configured for operation in a temperature range between -15 ° C and 4 ° C, more preferably in a temperature range or 10 ° C and 2 ° C and most preferably in a temperature range or -6 ° C to -2 ° C. 14. Device for failure and / or producing energy, the device including: a housing that is configured for receiving and holding a fluid; a first compartment in the housing in which a first electrode is positioned; a second compartment in the housing in which a second electrode is positioned; and a membrane according to one of the preceding clauses, the membrane being configured for placement in the housing for separating the first and second compartments; Where the electrodes are connectable to an external power source and / or a load for forming an electrical circuit. 15. Device according to clause 14, with the electrodes are capacitive electrodes. 16. Device according to any one of the clauses 14 - 15, the electrodes are reversible electrodes. 17. Device according to any one of the clauses 14 - 16, the first compartment is filled with an acid, and the second compartment is filled with a base. 18. Device according to any one of the clauses 14-16, the first compartment is filled with an acid, the second compartment is filled with an acid, and the pH of the acid in the first compartment preferably differs from the pH or the acid in the second compartment. 19. Device according to clause 17 or 18, at least one of the compartments is additionally provided with a reversible redox couple, when each compartment is provided with a reversible redox couple, the reversible redox couples are different reversible redox couples, the reversible redox couples are preferably chosen to be compatible. 20. Device according to any of the clauses 14-19, the electrodes are chosen from a group of mixed metal oxides, preferably mixed metal oxides based on dimensionally stable anodes (DSAs). 21. Device according to any one of the clauses 14 - 20, when dependent on clause 19, each of the reversible redox couples is chosen from a group of: Fe ²⁺ / Fe ³⁺ , Ce ⁴⁺ / Ce ³⁺ , Zn / Zn ^2+, V ³⁺ / V ^2+, Cu ²⁺ / Cu ^3+, Cr ²⁺ / Cr ^3+, VO ²⁺ / VO ₂ ⁺ and V ⁴⁺ / V ^5+. 22. Device according to any one of the clauses 14 - 16, when dependent on clause 19, requiring the reversible redox couple is a solid / solid couple, a solid / liquid couple, a liquid / liquid couple or a gas / liquid couple. 23. Device according to any one of the clauses 14 - 22, the fluid is a solution of one or more salts. Device according to any one of the clauses 14 - 23, the fluid is a solution of acid, the acid is chosen from a group of HF, HCl, HI, HBr, CH3 SO3 H, HCIO4, HNO3, H2SO4 or H3PO4. 25. Device according to any of the clauses, 14 - 23, the first compartment comprising a solution of acid and the second compartment comprising a solution of acid, the acid in the first and second compartments are different acids, preferably preferably the acids are chosen from a group of HF, HCl, H1, HBr, CH 3 SO 3 H, HCl ₄ , HNO 3, H ₂ SO ₄ or H ₃ PO ₄ . 26. Device according to any one of the clauses 14 - 25, each of the electrodes is a reversible electrode and each of the first and second compartments is provided with an acid, in a charging state involving a charging operation: the reversible electrode in the first compartment is configured to be subject to a reduction reaction; the reversible electrode in the second compartment is configured to be subjected to an oxidation reaction; in which the reduction reaction and the oxidation reaction provide a conversion of electrical energy into chemical energy; and in, in a discharging state involving a discharging operation: the reversible electrode in the first compartment is configured to be subjected to an oxidation reaction; the reversible electrode in the second compartment is configured to be subject to a reduction reaction; oxidation reaction and reduction reduction provide a conversion reaction for converting chemical energy into electrical energy. 27. System for energy failure, including a number of devices according to any one of the clauses 14 - 26, where the devices are connected to each other. 28. Method for failure and / or discharging energy, the method including the steps of: providing a device according to any one of the clauses 14 - 26 or a system according to clause 27; filling the housing with a solution including a salt and / or an acid; providing the membrane to the housing for forming compartments in the housing; and applying a potential to the electrodes for charging the device or the system. 29. Method according to clause 28, where the step of filling the housing with a solution comprises: filling the first compartment with a fluid, preferably an acid; filling the second compartment with a fluid, preferably an acid; Filling filling the first and second compartments is performed after the membrane is provided to the housing. 30. Method according to clause 28 or 29, the method including the steps of: - providing a redox couple to the first compartment; and - providing a redox couple to the second compartment. CONCLUSIONS A membrane for pure proton conduction, comprising a layer of water, the layer of water being substantially entirely in a solid state. Membrane according to claim 2, wherein the membrane is made from demineralized water, distilled water and / or sonicated water. A membrane according to any one of the preceding claims, wherein the membrane is made from boiled water that is transferred from a liquid state to a solid state. A membrane according to any one of the preceding claims, wherein the membrane is substantially transparent. A membrane according to any one of the preceding claims, wherein the membrane has a thickness, wherein the thickness is in the range of 1 µm to 20 cm, preferably in the range of 1 µm to 10 cm, and more preferably in the range of 1 µm to 1 cm. A membrane according to any one of the preceding claims, wherein the membrane comprises a support structure that is adapted to support the layer of water in the solid state. A membrane according to claim 6, wherein the support structure is made from electrically non-conductive and / or chemically inert material. A membrane according to claim 6 or 7, wherein the support structure is a porous structure and / or is made of a porous material, the porous structure preferably being non-directional for holding and / or taking up ice. A membrane according to any one of claims 6-8, wherein the support structure is a mesh structure, preferably a mesh structure provided with a plurality of relatively large openings. A membrane according to any one of claims 6-10, wherein the support structure can be connected to a cooling device which is adapted to cool the membrane and / or to form the membrane from water in the liquid state. A membrane according to any one of claims 6-9, wherein the support structure comprises a cooling device which is adapted to form a layer of water in the solid state. A membrane according to any one of the preceding claims, wherein the membrane is substantially pure, such that the water in the membrane contains less than 1 volume% of impurities, and preferably comprises less than 0.1 volume% of impurities. A membrane according to any one of the preceding claims, wherein the membrane is adapted to work under cryogenic conditions, and is preferably adapted to work in a temperature range of -15 ° C to 4 ° C, more preferably in a temperature range of - 10 ° C to 2 ° C, and most preferably in a temperature range of -6 ° C to -2 ° C. 14. Device for storing and / or producing energy, the device comprising: a housing adapted to receive and hold a liquid; a first compartment in the housing in which a first electrode is positioned; a second compartment in the housing in which a second electrode is positioned; and a membrane according to any one of the preceding claims, wherein the membrane is adapted for placement in the housing for separating the first and second compartment; the electrodes being connectable to an external power source and / or a consumer for forming an electrical circuit. The device of claim 14, wherein the electrodes are capacitive electrodes. Device as claimed in any of the claims 14-15, wherein the electrodes are reversible electrodes. The device of any one of claims 14-16, wherein the first compartment is filled with an acid, and wherein the second compartment is filled with a base. The device of any one of claims 14-16, wherein the first compartment is filled with an acid, the second compartment is filled with an acid, and wherein the pH of the acid in the first compartment is preferably different from the pH of the acid in the second compartment. A device according to claim 17 or 18, wherein at least one of the compartments is further provided with a reversible redox couple, wherein, if each compartment is provided with a reversible redox couple, the reversible redox couples have different reversible redox couples the reversible redox couples are preferably chosen to be compatible with each other. The device of any one of claims 14-19, wherein the electrodes are selected from a group of mixed metal oxides, preferably mixed metal oxides used in dimensionally stable anodes (DSAs). The device of any one of claims 14 to 20 when dependent on claim 19, wherein each of the reversible redox couples is selected from a group of: Fe ²⁺ / Fe ³⁺ , Ce ⁴⁺ / Ce ³⁺ , Zn / Zn ^2+, V ³⁺ / V ^2+, Cu ²⁺ / Cu ^3+, Cr ²⁺ / Cr ^3+, VO ²⁺ / VO ₂ ⁺ and V ⁴⁺ / V ^5+. The device of any one of claims 14-16 when dependent on claim 19, wherein the reversible redox couple is a solid state / solid state torque, a solid state / liquid couple, a liquid / liquid couple or a gas / fluid torque. The device of any one of claims 14 to 22, wherein the liquid is a solution of one or more salts. The device of any one of claims 14 to 23, wherein the liquid is an acid solution, the acid being selected from a group of HF, HCl, H1, HBr, CH ₃ SO ₃ H, HCl ₄ , HNO ₃ , H ₂ SO ₄ or H ₃ PO ₄ . The device of any one of claims 14 to 23, wherein the first compartment comprises an acid solution and the second compartment comprises an acid solution, wherein the acid in the first and second compartments involves different acids, the acids preferably being selected from a group of HF, HCl, H1, HBr, CH ₃ SO ₃ H, HCl ₄ , HNO ₃ , H ₂ SO ₄ or H ₃ PO ₄ . The device of any one of claims 14 to 25, wherein each of the electrodes is a reversible electrode and wherein each of the first and second compartments is provided with an acid, wherein, in a loading state including a charging operation: the reversible electrode in the first compartment is adapted to be subjected to a reduction reaction; the reversible electrode in the second compartment is adapted to be subjected to an oxidation reaction; wherein the reduction reaction and the oxidation reaction provide a conversion from electrical energy to chemical energy; and wherein, in a discharging state including a discharging operation: the reversible electrode in the first compartment is adapted to be subjected to an oxidation reaction; the reversible electrode in the second compartment is adapted to be subjected to a reduction reaction; and wherein the oxidation reaction and the reduction reaction provide a conversion reaction for converting chemical energy into electrical energy. A system for storing energy, comprising a number of devices according to any one of claims 14 to 26, wherein the devices are connected to each other. A method for storing and / or releasing energy, the method comprising the steps of: providing a device according to any of claims 14-26 or a system according to claim 27; filling the housing with a solution comprising a salt and / or an acid; providing the membrane to the housing to form the compartments in the housing; and applying a potential difference across the electrodes for charging the device or system. The method of claim 28, the step of filling the housing with a solution comprising: filling the first compartment with a liquid, preferably an acid; filling the second compartment with a liquid, preferably an acid; wherein the filling of the first and second compartments is performed after the membrane has been provided to the housing. The method of claim 28 or 29, the method comprising the steps of: - providing a redox couple to the first compartment; - providing a redox couple to the second compartment. 102