Electrochemical energy storage device

Abstract

The invention relates to an electrochemical energy storage device having at least one module (1), wherein each module (1) comprises a ply (2) having at least one cathode layer (3) and at least one anode layer (4). The cathode layer is formed of an electrically conductive nickel-containing material and interacts with an anode layer (4) via hydrogen as a reactant. The modules (1) are enclosed by a housing (13). The electrochemical energy storage device is characterised in that the cathode layer (3) is subdivided into segments, between which at least one connecting element (6) is arranged for creating a winding (8) of the ply (2), wherein the modules (1) are connected to one another via at least one component (9).

Description

[0001]

[0002] Electrochemical energy storage

[0003] Description

[0004] The invention relates to an electrochemical energy storage device with at least one module, wherein the module comprises a layer with at least one cathode layer and at least one anode layer, wherein the cathode layer is formed from an electrically conductive nickel-containing material which interacts with one of the anode layers via hydrogen as a reactant and the modules are surrounded by a housing.

[0005] Globally, the energy transition represents one of the central challenges of our time. The transformation towards a sustainable energy supply requires innovative technologies and forward-looking approaches, particularly in the field of energy storage. The need for efficient, durable, and cost-effective energy storage solutions is constantly increasing.

[0006] This high demand results, among other things, from the sometimes considerable fluctuations in supply and demand in the electricity grids. Rechargeable energy storage systems can play an important role as buffer storage in bridging these temporary discrepancies. Furthermore, energy storage technologies play a key role in the integration of renewable energies, since electricity production in this sector is generally neither continuous nor consistent due to the technologies' dependence on variable environmental conditions.

[0007] This development is of particular importance for small and medium-sized enterprises, but also for private households. Advanced energy storage technologies offer the opportunity to increase energy efficiency and reduce operating costs.

[0008]

[0009] 2

[0010] to reduce emissions and improve the environmental footprint. The increasing decentralization of energy supply also requires individually tailored storage solutions.

[0011] Advances in materials research, new design approaches, and innovative manufacturing methods have enabled the development of energy storage systems characterized by higher energy densities, improved cycle stability, reduced manufacturing costs, lighter weight, greater safety, and better environmental compatibility. These innovations have overcome many of the disadvantages of earlier battery storage systems.

[0012] The lead-acid battery (Gaston Plante, 1859), still used in motor vehicles today, marks the first large-scale application of electrochemical energy storage. This type of battery is characterized by its very high specific gravity, low storage efficiency, and the use of problematic substances such as lead and sulfuric acid.

[0013] The invention of the nickel-cadmium battery (Waldemar Jungner, 1899) subsequently represented an initial improvement in terms of energy density and longevity. The use of toxic cadmium and the so-called memory effect, i.e., the loss of capacity due to incomplete discharge, are the most significant disadvantages of this type of rechargeable battery.

[0014] It was only about 100 years later that the development of the nickel-metal hydride battery in the 1980s led to a further surge in innovation.

[0015]

[0016] 3

[0017] The energy density of this rechargeable battery has been further increased; nickel-metal hydride batteries have a larger capacity in the same size as nickel-cadmium batteries.

[0018] Further advantages of this battery type include the avoidance of environmentally hazardous cadmium, a significant reduction in the memory effect, and very low self-discharge. The minimal gas evolution inside nickel-metal hydride batteries also improves operational reliability.

[0019] A disadvantage of this battery type is its self-discharge during storage and the limited number of charge cycles, which is particularly caused by deep discharges. Another disadvantage is the limited availability and consequently high price of lanthanum or lanthanum compounds, which are essential for the production of this electrochemical energy storage device.

[0020] From the 1990s onwards, the lithium-ion battery was developed, and from 1996 a variant, the lithium-ion iron phosphate battery, was developed. These battery types currently dominate the market for rechargeable storage solutions in the small and medium-sized enterprise sector, in grid-stabilizing large-scale batteries, in private households, and in electric vehicles.

[0021] The advantages of this battery type are a significantly increased energy density, no occurrence of the memory effect, a considerable increase in possible charging cycles, increased operational reliability, and the avoidance of toxic heavy metals.

[0022]

[0023] 4

[0024] The main disadvantages of this type of battery are its sensitivity to overcharging and deep discharging, the higher manufacturing costs compared to lead-acid batteries and nickel-metal hydride batteries, as well as the limited availability of lithium and the environmental problems associated with lithium mining.

[0025] Recycling lithium-ion batteries is equally problematic.

[0026] The technological development of rechargeable energy storage systems outlined here in brief primarily concerns energy storage systems that can be mass-produced under market-oriented conditions and are suitable for a wide variety of applications.

[0027] In addition to these widely used battery storage systems, rechargeable energy storage devices have also been developed as niche products for specialized applications. These specialized storage solutions are better suited to the requirements of their respective applications than conventional battery storage systems. In certain areas, they are even superior. However, due to high manufacturing costs and sometimes low energy density, these storage solutions have not yet become established for mass-market applications.

[0028] The "Nickel Hydrogen Cell," developed in the 1970s and disclosed in patent US 38671991, is an example of one of these specialized batteries. At the time, the advantages of the nickel-hydrogen battery included a significantly increased service life, made possible in particular by its cycle stability of up to 50,000 charge cycles. Furthermore, the high energy density of the nickel-hydrogen battery, compared to alternative battery storage devices of the time, and its resistance to extreme temperatures and radiation were additional advantages of this type of storage device.

[0029]

[0030] 5

[0031] Therefore, nickel-hydrogen batteries were the preferred energy storage device in space stations, space probes, and satellites until the 2000s. Within these specific applications, the aforementioned advantages of this energy storage concept clearly outweighed its disadvantages.

[0032] A major disadvantage of this type of battery storage device was its high manufacturing cost. This resulted primarily from the complex design and the use of expensive materials, such as platinum, which was used in the early stages of nickel-hydrogen battery development.

[0033] Furthermore, the high weight of this type of battery storage system is also considered a disadvantage. This high weight resulted primarily from the use of steel for the casing. Steel as a construction material was necessary to withstand the high pressures occurring inside the battery and to minimize hydrogen leakage.

[0034] Another disadvantage was the low overall storage capacity relative to the battery casing's volume. This unfavorable ratio between the weight or volume of the nickel-hydrogen battery and the amount of energy it could store stemmed from the fact that, due to the high internal pressures, the casing had to be designed as a cylindrical steel body with rounded end caps, while the electrodes could only be manufactured using a plate-like structure. This plate-like construction was inherent to the sintered nickel hydroxide layer, which is very brittle. As a result, it was impossible to bend this electrode layer to conform to the casing's round cross-section. This led to a relatively large dead volume and a relatively small usable electrode area.

[0035]

[0036] 6

[0037] At the beginning of the new millennium, the development of lithium-ion battery types had progressed to such an extent that they increasingly replaced nickel-hydrogen batteries in space applications. This development meant, among other things, that technological improvements to the nickel-hydrogen battery concept were initially not a major focus.

[0038] However, this situation has recently changed due to global efforts to implement the energy transition. The demand for durable, safe, and robust energy storage systems is currently increasing steadily, making nickel-hydrogen battery technology attractive again, as the aforementioned requirements placed on modern energy storage solutions are among the genuine advantages of this battery type.

[0039] Accordingly, there are currently increasing efforts aimed at both technologically improving nickel-hydrogen batteries and making their production significantly more cost-effective. The underlying goal of these efforts is to introduce this battery type to the market on a large scale, making it competitive with established lithium-ion batteries. The improvements disclosed in patent specifications relate to a multitude of details. A few examples are listed below.

[0040] US patent 4115630 discloses a design in which a higher capacity is achieved through stacked electrodes with a round cross-section and a back-to-back arrangement of the electrodes. This addresses the fundamental problem of earlier embodiments, which was due to the unfavorable electrode / housing geometry and resulted in a relatively low storage capacity.

[0041]

[0042] 7

[0043] This idea, however, failed to gain traction because the difficulties encountered in the electrical wiring of the stacked electrode arrangement could not be satisfactorily resolved. Furthermore, short circuits caused by leakage of the liquid electrolyte were frequent. To address these problems, individual packaging of each double electrode with a waterproof but gas-permeable material became necessary. This measure, however, increased the manufacturing effort so significantly that widespread commercialization of this technology was no longer feasible.

[0044] Patent US 4395469A discloses a nickel-hydrogen battery that can operate at lower pressures. In conjunction with patent US 11855294B2, this invention was the starting point for the development of the nickel-metal hydride battery.

[0045] Furthermore, there are numerous suggestions for improvement, both regarding technological details of nickel-hydrogen battery technology and improvements to the manufacturing process. Examples include US 20200321621 A1 "Improvement of Charging Characteristics Across the Entire pH Range" and US 20170263942A1 "Composition of Catalyst Material".

[0046] The object of the invention is to provide an electrochemical energy storage device based on the nickel-hydrogen battery concept, largely eliminating the remaining disadvantages of this energy storage concept and unlocking the advantages of this battery type for broad application. In particular, the invention aims to provide an electrochemical energy storage device that allows for cost-effective storage of electrical energy with high cycle stability.

[0047]

[0048] 8

[0049] This problem is solved by the electrochemical energy storage device according to the main claim. Preferred embodiments of the invention are described in the dependent claims, the description, the figure description, or by the figures themselves.

[0050] According to the invention, the cathode layer of the energy storage device is subdivided into segments, between which at least one connecting element is arranged to generate a winding of the layer, wherein the modules are interconnected via at least one component.

[0051] In nickel-hydrogen batteries, gaseous hydrogen is used for the electrode reaction. This necessitates that the hydrogen transport layer, and consequently the nickel-hydrogen electrode, must be made thicker than required, precluding the coiling of the electrode as is possible in nickel-metal hydride batteries due to their thinner layer thickness. Because of the brittleness of the nickel hydroxide cathode at the required material thickness, it was and still is common practice to manufacture the cathode layer in the form of elongated sheets. However, this geometry does not optimally utilize the round cross-section of the casing, which is necessarily chosen due to the internal pressures of the battery.

[0052] The electrochemical energy storage device disclosed herein is based on the electrochemical principles described in detail in US patent 3,867, 1991, for the "Nickel Hydrogen Cell." The fundamental principles presented therein apply in full to the electrochemical energy storage device disclosed in the present patent. It is therefore unnecessary to repeat them here. The following discussion focuses exclusively on those aspects relevant to the invention.

[0053]

[0054] 9

[0055] Devices are appreciated. Furthermore, it should be noted that all materials and substances to be used according to the invention, such as, among others, the nickel hydroxide used as cathode material or the porous metallic material used as anode material, can be produced and used in any way.

[0056] By subdividing the cathode layer into segments according to the invention, the main disadvantage of the nickel-hydrogen battery, the unfavorable spatial geometry and the associated low energy density, is overcome.

[0057] By subdividing the cathode layer into segments, a winding can be constructed starting from a single layer, thus optimally utilizing the round cross-section of the battery's housing. This design, along with the resulting possibility of predominantly arranging the individual cathode layer segments in a back-to-back architecture, minimizes the dead volume within the housing and increases the electrode area by a factor of 3 to 4 compared to conventional plate-based electrode designs. This increase in usable electrode area relative to the given volume allows the nickel-hydrogen battery according to the invention to achieve an energy density comparable to that of lithium-ion batteries.

[0058] Despite the subdivision of the cathode layer into segments, an electrical connection exists between the segments, so that the cathode layer functions as a single, continuous electrode. This electrically conductive connection is established by a connecting element, preferably consisting of a metallic mesh.

[0059]

[0060] 10

[0061] Individual sections of this metallic mesh can, for this purpose, project at least partially into the nickel hydroxide layer. The metallic mesh is flexible enough to absorb the bending, notch, and shear stresses that occur during the winding of the layer.

[0062] This property is essential for constructing a winding adapted to the housing cross-section. Various metals can be used to construct the connecting element; in addition to copper and aluminum, stainless steel is particularly preferred.

[0063] As already mentioned, the generation of a winding, achieved by segmenting the cathode layer, and the potentially present back-to-back arrangement of the cathode and anode layers, are of paramount importance for increasing the energy density of the nickel-hydrogen battery according to the invention. This specific structure necessitates providing the layer as a cohesive unit within a module. However, the layer exhibits three different embodiments depending on its position within the winding.

[0064] In the first winding of the layer around the cathode contact, the metallic mesh of the connecting element can rest directly on the metallic cathode contact. In this layer section at the cathode contact, the layer, starting with the metallic mesh of the connecting element, can consist of the cathode layer sintered onto the metallic mesh, a subsequent (inner) separator, the following anode layer, and another (outer) separator.

[0065]

[0066] 11

[0067] From the second winding to the penultimate winding, the so-called central section of the layer can be structured as follows, progressing from the inside out: An (inner) cathode layer is followed by the metallic mesh of the connecting element, followed by another (outer) cathode layer (back-to-back arrangement), followed by an (inner) separator, the anode layer and another (outer) separator.

[0068] The final layer of the winding at the anode contact can be structured as follows: The bottom (inner) cathode layer is followed by the metallic mesh of the connecting element, followed by another (outer) cathode layer on which an (inner) separator is arranged. The anode layer forms the outermost layer of the winding. It is connected to the anode contacts.

[0069] The layer produced according to the invention can be mechanically wound around the cathode contact to create the winding. This possibility of mechanizing the manufacturing process keeps production costs low. This simplification of the manufacturing process is further supported by the fact that the modules produced in this way can be mechanically and electrically coupled to each other via a simple plug connection.

[0070] The structure with an inner cathode layer and an outer anode layer was described in detail above. In a further preferred embodiment, the anode layer is located on the inside and the cathode layer on the outside.

[0071] The component, which allows two modules to be directly connected mechanically and electrically, has an electrically conductive structure through which the anode side of a module is connected via an anode and a cathode contact.

[0072]

[0073] 12

[0074] The cathode side of the subsequent module is electrically connected, thus connecting the modules in series. To prevent short circuits, at least one insulating structure must also be installed in a suitable position.

[0075] For secure coupling and electrical connection of two adjacent modules, the component must have at least one connector. It is important to note that one part of the connector is made of an electrically conductive material and is connected to the component's conductor. The other part of the connector is made of a non-conductive material and is connected to the component's insulator. This design ensures a secure mechanical connection between the modules. Furthermore, this construction establishes the necessary electrical connections.

[0076] The arrangement described here connects the individual modules electrically in series. Since each module supplies approximately 1.5 volts, different total voltages of the electrochemical energy storage system can be achieved depending on the number of modules used. Starting with 3 volts when using two modules, any desired total voltage can be generated. Total voltages in the range of 12 volts (8 modules) are preferred.

[0077] 24 volts (16 modules). The modular design allows for different total voltages to be achieved without significant design complexity. This feature opens up the possibility of creating storage solutions for a wide variety of applications.

[0078] The anode layer, which consists of a metallic material suitable for electrochemical applications, exhibits a similar flexibility to the connecting element.

[0079]

[0080] 13

[0081] The hydrogen reaction is carried out in an alkaline medium. In a preferred embodiment, the anode layer consists of a nickel foam or, alternatively, a molybdenum-nickel foam. It has been shown that this novel nickel foam or molybdenum-nickel foam material is at least as suitable as a catalyst for the hydrogen reaction at the anode in an alkaline environment as the platinum used in this position in the original nickel-hydrogen battery design.

[0082] However, the suitability of nickel or molybdenum-nickel compounds was not yet known at that time. Furthermore, nickel foam or molybdenum-nickel foam was not yet available. Due to its good conductivity, high porosity, controllable pore size, and low weight, nickel or molybdenum-nickel foam is an ideal electrode material. Its use as an anode material according to the invention leads to a reduction in manufacturing costs, a weight reduction, and an increase in energy storage efficiency.

[0083] Electrochemical principles necessitate that the cathode layer be separated from the anode layer by a separator. This separator can be made from polypropylene, polyethylene, polysulfone, polyetheretherketone, polyvinyl alcohol, polyvinylidene fluoride, or perfluorosulfonate, depending on the specific requirements of different embodiments. The separator is preferably impregnated with a saturated potassium hydroxide solution. The separator has sufficient flexibility to absorb the bending, notch, and shear stresses that occur during winding assembly.

[0084]

[0085] 14

[0086] The connecting element consists of a metallic structure that projects at least partially into the cathode layer. In a preferred embodiment, this metallic structure consists of a stainless steel mesh. Nickel hydroxide coated with various additives is applied to this mesh in a thickness of at least 0.1 and at most 2.0 mm, preferably at least 0.5 and at most 1.5 mm, and particularly preferably at least 0.75 and at most 1.25 mm.

[0087] This task can be carried out unilaterally, e.g. in the area of ​​the layer section at the cathode contact, and bilaterally, e.g. in the area of ​​the central section of the layer to build a back-to-back architecture.

[0088] The nickel hydroxide layers, coated with additives, are firmly bonded to the metallic structure of the connecting element through a sintering process. Because at least some fragments of the metallic network protrude into the nickel hydroxide layer, a relatively strong, electrically conductive connection is formed.

[0089] This inventive structure makes it possible to build the cathode layer into a winding even with the high layer thickness of the nickel hydroxide layer required according to the invention.

[0090] In a preferred embodiment, the housing of the electrochemical energy storage device disclosed herein consists of a standard fourth-generation hydrogen pressure vessel. These modern pressure vessels are suitable for safely storing hydrogen up to a pressure of approximately 700 bar, depending on requirements. For the intended use here as a housing for a battery storage system, in which

[0091]

[0092] 15

[0093] Since pressures of up to 100 bar are expected, the design can be adapted economically. The use of this pressure vessel, which typically consists of an inner liner made of polyamide or polyethylene and a carbon fiber-reinforced epoxy coating, eliminates the need for a steel vessel.

[0094] The preferred use of a fourth-generation hydrogen pressure vessel results in savings in manufacturing costs and a significant reduction in the weight of the nickel-hydrogen battery according to the invention, while maintaining the required safety standards.

[0095] Since the pressure inside the casing is proportional to the amount of hydrogen released at the anode, the charge or discharge state of a nickel-hydrogen battery can be determined via this pressure. Standard wireless pressure sensors are available for pressure measurement. In a preferred embodiment, at least one pressure sensor is positioned inside the casing. It wirelessly transmits the pressure measurement results to an external unit.

[0096] Furthermore, in a preferred embodiment, the housing has an access point in the form of a valve. This valve allows the battery to be initially filled with hydrogen during production. Since minor gas losses occur during operation, it is necessary to compensate for these. This hydrogen refilling can be carried out via the valve as needed. This maintenance measure extends the overall operating time of the electrochemical energy storage device according to the invention.

[0097]

[0098] 16

[0099] The outdoor unit receives measurement data from the pressure sensor located inside the battery housing. Based on a stored control algorithm, the outdoor unit regulates how quickly and how deeply the electrochemical energy storage device can be discharged and when charging via an external power source is required. It can also determine whether the hydrogen supply in the battery needs to be replenished.

[0100] According to the invention, nickel hydroxide, which can be produced by any method, is preferably used as the material for constructing the cathode layer. To achieve electrical conductivity in the cathode layer, which is predominantly made of this material, it is common practice to modify the nickel hydroxide by adding various additive components.

[0101] According to the invention, these modifications, taking into account specific requirements in different application areas, can comprise the following individual measures or a combination of these measures: Introduction, embedding and / or doping of at least one foreign element from the group consisting of cobalt, iron or manganese. Introduction, embedding and / or doping of conductive structures in the form of particles and / or in the form of fine threads, e.g. in the form of metallic nanofibers.

[0102] These measures are of particular importance given that the efficiency of the electrochemical energy storage device according to the invention is significantly influenced by the thickness of the cathode layer. The particularly preferred thickness of the cathode layer disclosed here can only be used if the electrical conductivity is ensured by the structures listed.

[0103]

[0104] 17

[0105] To reliably prevent short circuits caused by escaping electrolyte, the winding of each module must be surrounded by a membrane. Therefore, the membrane material must be waterproof and resistant to potassium hydroxide. However, to allow the electrochemical processes to occur, it must also be permeable to hydrogen diffusion.

[0106] In a preferred embodiment, this membrane can be made of polytetrafluoroethylene, perfluorosulfone, or polyolefins.

[0107] In addition to the winding of the electrodes according to the invention, the storage efficiency of the electrochemical energy storage device is also largely determined by the back-to-back arrangement of the electrodes in at least one section of the layer. As already explained in detail, this specific embodiment significantly increases the usable area of ​​the electrodes that is crucial for the electrochemical reaction.

[0108]

[0109] 18

[0110] Reference symbol list:

[0111] (1) Module(s)

[0112] (2) location

[0113] (2.1) Position section at the cathode contact

[0114] (2.2) Central section of the situation

[0115] (2.3) Position section at the anode contact

[0116] (3) Cathode layer

[0117] (4) Anode layer

[0118] (5) Membran

[0119] (6) Connecting element

[0120] (7) Separator

[0121] (8) winding

[0122] (9) component

[0123] (10) Leader

[0124] (11) Insulator

[0125] (12) Connector

[0126] (13) Housing

[0127] (14) Pressure sensor

[0128] (15) Valve

[0129] (16) Outdoor unit

[0130] (17) Anode contact

[0131] (18) Cathode contact

[0132] (19) Positive terminal of the electrochemical energy storage device

[0133] (20) Negative terminal of the electrochemical energy storage device

[0134]

[0135] 19

[0136] Further features and advantages of the invention will become apparent from the description of exemplary embodiments with reference to the drawings and from the drawings themselves.

[0137] This shows:

[0138] Fig. 1 shows a schematic representation of a winding 8 of a module 1 in top view.

[0139] In the illustrated embodiment, module 1 comprises a centrally arranged cathode contact 18, on the outer wall of which the lowest layer of the layer section at the cathode contact 2.1, the connecting element 6, rests directly. The layer section at the cathode contact 2.1 resting on the cathode contact 18 comprises, in addition to the aforementioned connecting element 6, a cathode layer 3, an (inner) separator 7, an anode layer 4, and a further (outer) separator 7.

[0140] On the layer section at the cathode contact 2.1, the winding 8 is built up by repeatedly winding the central section of layer 2.2. The layer 2, built up in a back-to-back arrangement, comprises, from the inside out, an (inner) cathode layer 3, a connecting element 6, another (outer) cathode layer 3, an (inner) separator 7, an anode layer 4, and another (outer) separator 7 in the area of ​​the central section of layer 2.2.

[0141] This structure will be continued unchanged until the penultimate unfolding of layer 2 inclusive.

[0142]

[0143] 20

[0144] The single-layer winding that terminates winding 8 consists of the layer section at anode contact 2.3. This layer section at anode contact 2.3 consists, from the inside out, of the (inner) cathode layer 3, the connecting element 6 of the (outer) cathode layer 3, an (inner) separator 7, and the final anode layer 4. The anode layer 4 is partially connected to the anode contact 17. Since the anode layer 4 is electrically connected to the anode contact 17, the (outer) separator is missing in the area of ​​the layer section at anode contact 2.3.

[0145] For clarity, the winding of the central section of layer 2.2 in Fig. 1 is indicated by the curved, dashed lines with an unfilled arrow. The layer section at the anode contact 2.3 is also represented by the depiction of two segments.

[0146] Furthermore, Fig. 1 shows the insulator 11 and the membrane 5. These structures electrically insulate the module 1 from the subsequent module and seal it in a watertight manner, while allowing hydrogen to pass through.

[0147] Fig. 2 shows the schematic representation of the structure of layer 2 and its sections.

[0148] As can be seen in the figure, layer 2 consists of three subsections: the layer section at the cathode contact 2.1, the central section of layer 2.2, and the layer section at the anode contact 2.3. The sequence of the individual layers of layer 2 within these three sections was described in detail in the description of Fig. 1. The corresponding assignment to the designation list can be found here.

[0149]

[0150] 21

[0151] The figures for Fig. 2 can be adopted unchanged, making a repetition here unnecessary.

[0152] For reasons of clarity, the total length of each section of layer 2 in Fig. 2 cannot be shown to scale.

[0153] The diameter of the cathode contact 18 used is decisive for the length expansion of the layer section at the cathode contact 2.1.

[0154] The longitudinal extent of the central section of layer 2.2 and the layer section at the anode contact 2.3 depends on the selected housing diameter and the layer thickness of a layer of layer 2 in the central section of layer 2.2.

[0155] Furthermore, Fig. 2 shows that layer 2 in the area of ​​the layer section at the cathode contact 2.1 has a sintered segmented cathode layer 3 only on one side of the connecting element 6, while in the area of ​​the central section of layer 2.2, a segmented cathode layer 3 is applied to both sides of the connecting element 6. This preferred embodiment as a back-to-back arrangement also significantly increases the available cathode area, resulting not only in better space utilization due to the winding of the electrodes but also in a considerable increase in the energy density of the electrochemical energy storage device according to the invention.

[0156] Fig. 3 shows a schematic overview of the electrochemical energy storage system as a cross-sectional view along the longitudinal axis.

[0157]

[0158] 22

[0159] Due to the high pressures occurring during hydrogen storage, typically between 200 and 700 bar, and the associated stresses, standard hydrogen pressure vessels are cylindrical with rounded end caps. The wall of Type 4 hydrogen pressure vessels has a two-layer construction. It consists of an inner liner made of polyamide or polyethylene and a carbon fiber-reinforced epoxy coating.

[0160] Calculations have shown that pressures of up to a maximum of 100 bar occur in the electrochemical storage unit disclosed herein. This pressure load is therefore far below the load limits of the standard Type 4 hydrogen storage tanks and, in the selected embodiment, offers more than sufficient safety reserves. In an exemplary embodiment, the housing 13 of the electrochemical energy storage unit is approximately 200 cm long and has an inner diameter of approximately 20 cm. With a wall thickness of approximately 10 mm, this results in an outer diameter of approximately 22 mm. This embodiment is suitable for storing hydrogen up to a pressure of approximately 300 bar.

[0161] The modules 1 are centrally arranged in the housing 13 and are mechanically and electrically connected to each other via component 9. An exemplary embodiment with 16 modules 1 connected in series is shown. In the illustrated configuration, approximately 24 volts are present at the positive terminal of the electrochemical energy storage device 19, which exits the housing 13 at its uppermost point, when fully charged. The negative terminal 20 of the electrochemical energy storage device exits at the opposite apex of the housing 13. The stored electrical energy can be drawn from these two terminals during discharge.

[0162]

[0163] 23

[0164] During the charging process, the electrochemical energy storage device is recharged via these poles using a suitable energy source.

[0165] The state of charge of the electrochemical energy storage device directly affects the pressure inside the housing 13. This pressure is detected by a pressure sensor 14 located inside the housing 13 and, in a preferred embodiment, transmitted wirelessly to an outdoor unit 16. The outdoor unit 16 contains an algorithm that controls the charging and discharging processes based on the detected pressures. The electrochemical energy storage device receives an initial charge of hydrogen via a valve 15 located on the housing 13. This valve 15 can be used to compensate for any hydrogen losses that occur during operation.

[0166] Fig. 4 shows the schematic representation of the interaction of modules 1 and components 9 of the electrochemical energy storage system as a cross-sectional view along the longitudinal axis.

[0167] The schematic diagram clearly shows that module 1, or winding 8, is centrally connected to the cathode contact 18. The series connection is established via the anode contact 17, conductor 10, and the electrically conductive connector 12. The modules are electrically insulated by insulators 11. The non-conductive section of the connector 12 is connected to the lower insulator 11. At the ends of the stack of

[0168] Modules 1 each contain the positive terminal 19 and the negative terminal 20 of the electrochemical energy storage device. The individual modules 1 are sealed watertight by a membrane 5, the material of which is permeable to hydrogen.

[0169]

[0170] 24

[0171] Fig. 5 shows a schematic representation of a separate module 1 and a separate component 9 of the electrochemical energy storage device as a cross-sectional view along the longitudinal axis.

[0172] The schematic drawing shows the structure of module 1. It clearly shows that the cathode layer 3 is located in the center of the winding 8 and, when module 1 is joined with component 9, rests directly against the cathode contact 18. The anode layer 4 is located at the periphery of the winding 8. When module 1 is joined with component 9, this layer 4 rests directly against the anode contact 17. According to the invention, this structure can also be reversed, i.e., with the anode layer (4) on the inside and the cathode layer (3) on the outside.

[0173] Furthermore, it becomes clear that the conductor 10 following the anode contact 17 is connected to the electrically conductive part of the connector 12. Accordingly, the electrically non-conductive part of the connector 12 is connected to the lower layer of the insulator 11. The upper layer of the insulator 11 electrically isolates the successive modules 1 from one another. The individual modules 1 are sealed watertight by a membrane 5, the material of which is permeable to hydrogen.

Claims

Electrochemical energy storage Claims 1. Electrochemical energy storage device with at least one module (1), wherein the module (1) comprises a layer (2) with at least one cathode layer (3) and at least one anode layer (4), wherein the cathode layer (3) is formed from an electrically conductive nickel-containing material which interacts with an anode layer (4) via hydrogen as a reactant and the modules (1) are surrounded by a housing (13), characterized by that the cathode layer (3) is subdivided into segments, between which at least one connecting element (6) is arranged to generate a winding (8) of layer (2), wherein the modules (1 ) are connected to each other via at least one component (9).

2. Electrochemical energy storage device according to claim 1 , characterized by that the component (9) has at least one conductor (10) and at least one insulator (11).

3. Electrochemical energy storage device according to claim 1 or 2, characterized by 2 that the component (9) has at least one connecting piece (12) for coupling with the further module (1 ).

4. Electrochemical energy storage device according to one of claims 1 to 3, characterized by that the anode layer (4) consists of a metallic material designed for electrochemical hydrogen conversion in an alkaline medium.

5. Electrochemical energy storage device according to one of claims 1 to 4, characterized by that a separator (7) is arranged between the cathode layer (3) and the anode layer (4).

6. Electrochemical energy storage device according to one of claims 1 to 5, characterized by that the connecting element (6) is designed as a metallic structure which protrudes at least partially into the cathode layer (3). 3 7. Electrochemical energy storage device according to one of claims 1 to 6, characterized by that at least one pressure sensor (14) is arranged in the housing (13).

8. Electrochemical energy storage device according to one of claims 1 to 7, characterized by that at least one valve (15) is arranged on the housing (13).

9. Electrochemical energy storage device according to one of claims 1 to 8, characterized by that the state of charge of the electrochemical energy storage device can be monitored and controlled by an outdoor unit (16) based on the measured values ​​determined by the pressure sensor (14).

10. Electrochemical energy storage device according to one of claims 1 to 9, characterized by that the material for achieving electrical conductivity of the cathode layer (3) comprises at least one or more of the following measures: Embedding of a foreign element from the group consisting of cobalt, iron or manganese, Introduction of conductive particles or structures, Combination of doping and conductive structures, - Presence of conductive structures in the form of fine threads.

11. Electrochemical energy storage device according to one of claims 1 to 10, characterized by that the winding (8) of layer (2) of module (1) is surrounded by a membrane (5) which is impermeable to aqueous solutions but permeable to gases.

12. Electrochemical energy storage device according to one of claims 1 to 11 , characterized by that at least one layer (2) has a back-to-back arrangement of layers (3, 6, 3, 7, 4, 7).

Images