WO2017220146A1

WO2017220146A1 - Metal-gas battery comprising at least two metal-gas battery cells arranged in a housing

Info

Publication number: WO2017220146A1
Application number: PCT/EP2016/064515
Authority: WO
Inventors: Simon Nuernberger; Nikolaos Tsiouvaras; Odysseas Paschos; Tokuhiko Handa; Peter Lamp; Hidetaka Nishikoori; Toshihiko Inoue
Original assignee: Bayerische Motoren Werke Aktiengesellschaft; Toyota Motor Corporation
Priority date: 2016-06-23
Filing date: 2016-06-23
Publication date: 2017-12-28
Also published as: DE112016006995T5

Abstract

The invention is directed to a metal-gas battery, particularly for a vehicle, comprising: at least two metal-gas battery cells (2a, 2b) arranged in a housing (3) of the metal-gas battery, wherein the metal-gas battery is configured such that reaction gas, in particular air or pure oxygen, is able to circulate convectively around the at least two metal-gas battery cells.

Description

METAL-GAS BATTERY COMPRISING AT LEAST TWO METAL-GAS BATTERY CELLS ARRANGED IN A HOUSING

The present invention relates to the field of vehicular metal-oxygen battery systems, in particular for electric or hybrid automobiles. Specifically, the invention is directed to a metal-gas battery comprising at least two metal-gas battery cells arranged in a housing of the metal-gas battery. Alternatively or additionally, the system can be used in stationary applications, particularly as second life reuse after primary utilization in a vehicle.

BACKGROUND

While traditionally most long-range vehicles, such as cars, trucks, buses, motorcycles, and non-electric railway locomotives, have been powered by gasoline or diesel engines, in recent years the development of electric or hybrid vehicles, in particular automobiles that are at least partially powered by electric motors has been steadily increasing. Particularly, a steady stream of advances in battery research has put large numbers of hybrid electric vehicles on city streets. Additional advances are having a similar effect on so-called plug-in hybrids, hybrid automobiles that can be recharged from the grid. Despite these successes for electrically propelled cars, both types of hybrid vehicles strongly depend on petroleum-fueled internal combus- tion engines for distance driving.

To that purpose various different battery systems have been developed as suitable storages for electric energy, including in particular lithium-ion batteries, which are used for most of today's electric and hybrid cars. One disadvantage of such lithium- ion batteries is their limited energy density, i.e. stored electrical energy per battery mass or per battery volume. This limitation is - amongst others - caused by the fact that all chemical components needed for the electrochemical reactions taking place in the battery cells are already contained in the charged battery, thus adding to its weight or volume.

In order to fully establish electric vehicles in the market, a storage battery of practical size and weight and affordable price is needed that can provide enough electrical energy in a single charge for a motorist to drive at least a few hundred kilome- ters. In light of this requirement, a focus of the electric vehicle industry in battery research is directed to so-called "metal-air battery" or "metal-oxygen battery", which are, for example, described in U.S. patent 5,510,209.

Such a battery comprises one or more electrochemical cells each having a first elec- trode - usually referred to as "anode" - made of or at least containing a suitable metal, and a second electrode - usually referred to as "cathode" - working with ambient air or oxygen, and a separator arranged between the two electrodes to electrically separate them. In particular, the anode can comprise an alloy having such metal as a first component and one or more further metal or non-metal components, such as carbon (C), tin (Sn) or silicon (Si), wherein the metal component in such anode remains available to participate in the electricity generating chemical reactions of electrochemical, i.e. galvanic cell. Instead of such alloy also a transition metal oxide may be used as an anode material. Furthermore, an electrolyte, which may in particular be of the aqueous or solid type, is present in cathode and optional- ly in the separator. In particular, it is known to use zinc, aluminum or lithium as the metal for the anode. At the cathode side, oxygen is the relevant electrochemical component and unlike in lithium-ion batteries it does not have to be present in the charged battery from the beginning, but can rather be taken from ambient air or be delivered to the battery in the form of an oxygenous gas or pure oxygen from a source such as a tank or other reservoir during discharging of the battery. In this way, batteries having a much higher energy density than traditional lithium-ion batteries become possible. These metal air batteries provide a high theoretical electrical capacity, particularly when the oxygen mass is excluded.

When generating power, this oxygen reacts at the cathode of a lithium air battery with lithium to Li0₂ and/or Li₂0₂ (lithium peroxide) as discharge (reaction) products. In this reaction, one mole 0₂ releases two moles electrons. Furthermore, when such a battery is re-charged, oxygen is generated at the cathode and can be re-used in a subsequent discharging cycle.

Document US 4,463,064 refers to a galvanic element in the form a flat, high power cell, especially a metal-air-cell, which is cooled with cooling water and can be assembled to a battery which comprises a plurality of cells. The flat cell comprises bipolar electrodes which have a consumable metal electrode in flat form as an an- ode, a cathode (oxygen electrode) and a liquid electrolyte. The bipolar electrodes are electrically interconnected and a gasket is arranged between them which forms a cooling chamber. As a result, the heat balance and temperature of not only the anode but also of the cathode can be controlled directly. Document US 201 1/0195321 A1 refers to a rechargeable metal-air battery including a negative electrode for storing and releasing metal ions, a positive electrode using oxygen as an active material and an electrolyte membrane placed between the negative electrode and the positive electrode. A flexible dimension-absorbing member is disposed on the negative electrode side, wherein the dimension-absorbing member is an elastic body formed of a substance which changes reversibly. The rechargeable metal-air battery may comprise a coolant flow path through which a cooling medium (cooling air, water, or the like) for removing heat generated in charge and discharge reactions can be made to pass.

SUMMARY OF THE INVENTION Against this background, the present invention is directed to the problem of providing an improved metal-gas battery or vehicle, in particular in view of an enhanced simplicity of design and in view of cooling of the battery.

A solution to this problem is provided by the teaching of the independent claim 1 , namely by a metal-gas battery with the inventive properties. Various preferred embodiments and further improvements of the invention are provided in the dependent claims.

A first aspect of the present invention is directed to a metal-gas battery, particularly for a vehicle, comprising at least two metal-gas battery cells in a housing of the metal-gas battery, wherein the metal-gas battery is configured such that reaction gas, in particular air or pure oxygen, is able to circulate convectively around the at least two metal-gas battery cells.

The term "gas", as used herein, relates to a gas that contains oxygen as one of its components. In particular, the oxygen component may comprise molecular oxygen, preferably 0₂. Also pure or substantially pure oxygen is a "gas" as used herein. The gas is selected in dependence from the chemical materials of the electrodes of the battery, in particular of its anode side, such that the necessary chemical reactions for the generation of electrical energy consumed oxygen in the gas during a discharge cycle can take place.

The term "metal-gas battery", as used herein, relates to a battery where the electro- chemically relevant chemical component of one of the electrodes is a gas, in particular oxygen or 0₂. To support the electrochemical reactions taking place in the battery pack, the gas is provided to the at least two galvanic battery cells of the battery, especially to the cathode side of the battery cells. In particular, the term "metal-gas battery" means a battery that uses oxygen as gas, being a metal-gas battery or a metal-oxygen battery.

The term "to circulate convectively", as used herein, relates to the movement of gas by convection. Preferably, the movement of the gas can be supported by additional means such as a fan. The movement of gas is streaming to the gas inlet.

The term "up", as used herein, refers to the convective movement of hot gas with respect to cold gas against gravitation.

The term "cooling device", as used herein, is any means which is able to transfer the energy from a first medium to a second medium, such as a heat exchanging device, cooling fins, etc.

The term "module", as used herein, refers to a self contained unit comprising a stack of battery cells.

The invention is particularly based on the approach that reaction gas can circulate freely around the battery cells in the metal-gas battery. By this, warmer areas of the battery cells exchange heat with colder areas of the battery cells. Also a heat exchange between the battery cells via the reaction gas is possible. Therefore, the invention supports the homogeneous distribution in the battery. Furthermore, since the battery cells are surrounded by the reaction gas only, the design of cells can be kept simple. Safety issues linked to other fluids in the vicinity of the battery cells, such as water, do not exist. Therefore, the cells can even be designed openly with no cell or module housings. In addition, a gas distribution apparatus or system for distributing the reaction gas is not needed.

Therefore, the effective electrical capacity with respect to volume and/or weight of the battery cells and the battery as such can be increased leading to an augmented energy density level.

In an advantageous embodiment of the metal-gas battery, cathodes of the at least two metal-gas battery cells are exposed to the interior of the housing, such that the reaction gas is able to come into direct contact with the cathodes. By this, the design of the battery is very simple and effective.

In a further advantageous embodiment of the inventive metal-gas battery, a cooling device is arranged at the housing of the metal-gas battery, in particular in an upper portion and/or outside thereof. By providing a cooling device in a certain portion of the housing, this portion of the housing can be cooled. In particular, the cooling de- vice is arranged in an upper portion of the housing. Cold reaction gas, cooled down at that upper portion of the housing, sinks to the ground of the housing while warm reaction gas rises upwards due to a natural convection inside the battery. Warmer reaction gas rises to the top of the housing and is then cooled down by the cooled upper portion of the housing. Hence it then sinks to the ground again. By these means, no additional gas distribution is needed to bring or pump the reaction device or the cooling device. Preferably, therefore, there exists at least in the upper portion a heat conductive material such as a metal.

In a further advantageous embodiment of the inventive metal-gas battery, the cooling device covers at least a segment of the housing, in particular one face side. If for example the face side at the upper portion of the housing is covered by the cooling device, a very homogeneous temperature distribution can be achieved in the planar direction of the cooling device. Furthermore, by these means, an easily accessible side with a large surface can be used to cool the battery.

In a further preferred embodiment of the inventive metal-gas battery, the cooling device comprises channels through which a cooling medium can flow. In a further preferred embodiment of the inventive metal-gas battery, the at least two metal-gas battery cells are arranged in a stack, in which adjacent battery cells adjoin each other either by their cathode or by their anode. By arranging the battery cells in stacks, an effective cell or battery design can be realized, where the stacks can be installed in modules.

In a further advantageous embodiment of the inventive metal-gas battery, the at least two metal-gas battery cells are arranged in a stack in which adjacent battery cells share a common cathode and/or a common anode. By this configuration, the construction of the stack can be further simplified and the amount of common com- ponents can be reduced.

In a further advantageous embodiment of the inventive metal-gas battery, a ground- line and/or a flow field is arranged between the cathodes or in the common cathode of adjacent battery cells.

The term "flow field", as used herein, is a device which is capable to supply the cathode with reaction gas. In particular, the flow field can be a gas diffusion line.

By arranging flow fields between the cathodes of adjacent battery cells, a particularly effective distribution of reaction gas to the cathodes can be realized.

In a further advantageous embodiment of the inventive metal-gas battery, anodes or a common anode of the at least two metal-gas battery cells are at least sealed with respect to the reaction gas.

In a further advantageous embodiment of the inventive metal-gas battery, the separators of the at least two metal-gas battery cells seal the anodes or the common anode. This enables a particularly simple design of a stack or module of at least two battery cells. In a further advantageous embodiment of the inventive metal-gas battery, the at least two metal-gas battery cells form a module and different modules are arranged spaced apart from each other in the housing. By forming modules of battery cells, single modules can be deactivated in the case of failure. Furthermore, the modules can be arranged such that the reaction gas can also flow around the modules, thereby providing an even more effective convection of the reaction gas in the housing.

In a further advantageous embodiment of the inventive metal-gas battery, the hous- ing has one gas port only and is otherwise gas-tight. This embodiment is particularly advantageous in an added configuration, where pure oxygen is supplied to the battery. The less openings the battery has with respect to the environment, the less the battery is endangered by harmful substances being able to enter into the housing of the battery, for example, water or dust. In a further advantageous embodiment of the inventive metal-gas battery, the housing is gas-tight and has a first gas port, in particular a gas inlet, and a second gas port, in particular an overpressure vent. This embodiment is particularly advantageous if the reaction gas is a mixture of gases, such as air, of which only one component, such as oxygen is consumed by the battery. The remaining "exhaust" gas can then be exhausted by the second gas port.

A second aspect of the invention is directed to a vehicle, in particular an electrical vehicle, comprising an inventive metal-gas battery.

The various embodiments, variants and advantages described above in relation to the first aspect of the invention apply similarly to the second and third aspects of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and applications of the present invention are provided in the following description in connection with the figures. The figures illustrate at least partially schematically: Figure 1 a sectional view of a metal-gas battery according to a first preferred working example of the present invention;

Figure 2 a sectional view of a metal-gas battery according to a second preferred working example of the present invention; Figures 3a, 3b spatial representations of two different forms of a metal-gas battery according to the preferred working example with a cooling device; and

Figure 4 a sectional view of a stack of metal-gas battery cells. Fig. 1 illustrates a first preferred working example of a metal-gas battery cell 1.

Four modules 13a, 13b, 13c, 13d comprising a stack 8 of a plurality battery cells 2a, 2b are arranged in a housing 3 of the battery 1. Furthermore, the housing comprises a gas port 14 by which reaction gas, in particular oxygen, can be fed to the battery 1 . In the upper portion of the surface of the housing 3, a cooling device 5 is ar- ranged. This cooling device 5 comprises channel 7, through which a coolant fluid, preferably air or water, can flow. The housing 3 is preferably, at least in the upper portion where the cooling device 5 is arranged, made of a heat conductive material, particularly a metal such as stainless steel. The cooling device 5 is preferably in direct contact with the housing 3, such that an optimal heat transfer is assured. The coolant fluid is preferably delivered to the cooling device 5 by a heat exchanger using for example the head wind of an electrical vehicle to cool down the coolant fluid. The oxygen flowing into the battery 1 via gas port 14 is delivered preferably from a tank, where compressed hydrogen is stored or is extracted from ambient air by a gas separator. In this case, the gas is preferably also dry and compressed be- fore being delivered to the battery 1.

Alternatively, the housing 3 preferably has no reaction gas inlet at all. In this case, the housing 3 also forms a gas reservoir for storing reaction gas.

During operation, the battery cells 2a, 2b in the modules 13a, 13b, 13c, 13d warm up due to galvanic reactions taking place during charge or discharge of the battery 1 . The battery cells 2a, 2b or the modules 13a, 13b, 13c, 13d warm up the reaction gas in the housing 3, in this case pure oxygen, which then rises to the portion of the housing 3. There, the warm oxygen comes into contact with the wall of the housing 3, cooled down by the cooling device 5. The cooled air then falls down in the housing 3 to the ground and is again warmed up by the battery cells 2a, 2b. Therefore, a natural convection process is taking place within the housing 3 and the battery cells 2a, 2b are cooled down by this convection process.

On the other hand, the configuration according to Fig. 1 can also be used to heat up the reaction air in the housing 3. In this case, the cooling medium is warmer than the reaction gas in the housing 3 and therefore raises the temperature 3 of the battery 1. In such a case, it is preferably to arrange cooling device 5 in a bottom section of the housing 3.

Fig. 2 illustrates a second preferred working example of an inventive battery 1. In contrast to the example according to Fig. 1 , the housing 3 comprises a second gas port 15, in particular an overpressure vent. In this case, a reaction gas having different components can be used as a reaction gas. While the component reacting at the cathode 4a, 4b of the battery cells 2a, 2b is consumed in the battery 1 , the remaining gas components can flow through the housing 3 and be exhausted via the second gas port 15. While in the arrangement in Fig. 1 , the reaction gas is consumed at the cathode, in Fig. 2, the nonreactive components of the reaction gas remain as an exhaust gas.

Fig. 3 illustrates two different possible spatial extents of the working example according to Fig. 1 and 2. In Fig. 3a, the battery 1 has the form of a cylinder. In this case, the cooling device 5 has also the form of a part of a cylinder and covers the upper portion of the housing 3. In Fig.3b, the battery 1 is rectangular such that in this case the cooling device 5 forms a laminar plane on the housing 3.

Fig. 4 exhibits a stack 8 for the working examples of the inventive battery 1 according to Fig. 1 and 2. Each of the battery cells 2a, 2b comprises an anode 9a, 9b, a separator 1 1 a, 1 1 b, and a cathode 4a, 4b. The cathode is supplied with reaction gas, in this case pure oxygen, by the flow field 10. Preferably, this flow field 10 has a conducting structure such that it can serve also as cathode current collector. On the other hand, an anode current collector is arranged at the anode such that a voltage can be tapped between the collectors in the case of discharging or a voltage can be applied in the case of charging a battery 1. In the shown configuration of a stack 8, adjacent battery cells 2a, 2b adjoin each other either by the cathode 4a, 4b or the anode 9a, 9b. Therefore, they dispose over a common anode collector 12 or a common flow field / cathode collector 10 between the cathodes. The anodes are enclosed by separators 1 1 a, 1 1 b of adjacent battery cells 2a, 2b. As it can be seen from Fig. 4, the cathodes are freely accessible for the reaction gas, preferably oxygen, surrounding a stack 8 in the housing 3 of an inventive battery 1. The anodes, which must not come into contact with the reaction gas, are protected by the separators 1 1 a, 1 1 b which form casings around the anodes of two adjacent battery cells 2a, 2b.

While the stack 8 in Fig. 4 comprises three full battery cells 2a, 2b, a stack in principle may have any number of battery cells and can therefore be adapted to the de- mands of the specific application/appliance in which the inventive battery cell is used as a power supply.

Reference signs

1 metal-gas battery

2a, 2b metal-gas battery cell

3 housing

4a, 4b cathodes

5 cooling device

6 segment / portion

7 channel

8 stack

9a, 9b anode

10 cathode current collector /flow field

1 1 a, 1 1 b separator

12 anode current collector

13a-13d module

14 first gas port

15 second gas port

Claims

Metal-gas battery (1 ), particularly for a vehicle, comprising at least two metal- gas battery cells (2a, 2b) arranged in a housing (3) of the metal-gas battery (1 ).

wherein the metal-gas battery (1 ) is configured such that reaction gas, in particular air or pure oxygen, is able to circulate convectively around the at least two metal-gas battery cells (2a, 2b).

Metal-gas battery (1 ) according to claim 1 , wherein cathodes (4a, 4b) of the at least two metal-gas battery cells (2a, 2b) are exposed to the interior of the housing (3), such that the reaction gas is able to come into direct contact with the cathodes (4a, 4b).

Metal-gas battery (1 ) according to claim 1 or 2, wherein a cooling device (5) is arranged at the housing (3) of the metal-gas battery (1 ), in particular in an upper portion and/or outside thereof.

Metal-gas battery (1 ) according to claim 3, wherein the cooling device (5) covers at least a segment (6) of the housing (3), in particular one face side.

Metal-gas battery (1 ) according to claim 3 or 4, wherein the cooling device (5) comprises channels (7) through which a cooling medium can flow.

Metal-gas battery (1 ) according to one of the preceding claims, wherein the at least two metal-gas battery cells (2a, 2b) are arranged in a stack (8) in which adjacent battery cells adjoin each other either by their cathode (4a, 4b) or by their anode (9a, 9b).

Metal-gas battery (1 ) according to one of the preceding claims, wherein the at least two metal-gas battery cells (2a, 2b) are arranged in a stack (8) in which adjacent battery cells share a common cathode or a common anode. Metal-gas battery (1 ) according to claim 6 or 7, wherein a cathode current collector and/or a flow field (10) is arranged between the cathodes (4a, 4b) or in the common cathode of first adjacent battery cells.

Metal-gas battery (1 ) according to one of claims 6 to 8, wherein anodes (9a, 9b) or a common anode of the at least two metal-gas battery cells (2a, 2b) are at least sealed with respect to the reaction gas.

Metal-gas battery (1 ) according to claim 9, wherein separators (1 1 a, 1 1 b) of the at least two metal-gas battery cells (2a, 2b) seal the anodes (9a, 9b) or the common anode.

Metal-gas battery (1 ) according to one of claims 6 to 10, wherein a current collector (12) is arranged between the anodes (9a, 9b) or in the common anode of second adjacent battery cells.

Metal-gas battery (1 ) according to one of the preceding claims, wherein the at least two metal-gas battery cells (2a, 2b) form a module (13a, 13b , 13c, 13d) and wherein different modules (13a, 13b , 13c, 13d) are arranged spaced apart from each other in the housing (3).

Metal-gas battery (1 ) according to one of the preceding claims, wherein the housing (3) has one gas port (14) only and is otherwise gastight.

Metal-gas battery (1 ) according to one of the preceding claims, wherein the housing (3) is gastight and has a first gas port (14), in particular a gas inlet, and a second gas port (15), in particular an overpressure vent.

Vehicle, in particular an electrical vehicle, comprising a metal-gas battery (1 ) according to one of claims 1 to 14.