A GAS DISTRI BUTION APPARATUS

TECHNICAL FI ELD

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 battery system comprising at least one battery cell having a first gas port and a second gas port being interconnected in such a manner that gas can stream through the at least one battery cell and a gas distribution apparatus. 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 combustion 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 kilometers. 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 electrode - 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 am- bient air or oxygen, and a separator arranged between the two electrodes to electrically separate them. In particular, the anode can comprise of 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 reac- tions 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 organic, aqueous or solid type, is present in cathode and optionally 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 electrochem- ical 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 bat- teries 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 Li0 ₂ and/or Li ₂ 0 ₂ (lithium peroxide) as discharge (reaction) products. In this reaction, one mole 0 ₂ 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. US 2010/0190082 A1 refers to a fuel cell including a stack having fuel channels through which fuel flows and air channels through which air flows, the fuel channels and air channels being located at both sides of a reaction film, an actuator disposed to be involved in the air channels, the actuator allowing external air of the stack to affect the air channels, and a skirt extending from the stack communicating with the air channels. The actuator may render air flow both in a direction toward the air channels and in an opposite direction thereto, namely, make an oscillating flow (i.e., in adverse directions). Accordingly, the air within the air channels makes an oscillatory flow within the air channels, without rarely flowing out of the air channels, under the influence of external air, which makes an oscillatory flow. This becomes a factor of stably maintaining the temperature and humidity conditions of the internal air of the stack. In addition, the oscillating flow facilitates the water as the reaction byproduct to be removed from the stack.

SUMMARY OF THE INVENTION

Against this background, the present invention is directed to the problem of providing an improved metal-oxygen battery system for vehicles, in particular in view of homogeneity of performance and depth of discharge of the battery system. A solution to this problem is provided by the teaching of the appended independent claims, namely by a vehicular battery system according to claim 1 and a method of operating such battery system according to claim 1 1 or 12.

Various preferred embodiments and further improvements of the invention are pro- vided in the dependent claims.

A first aspect of the present invention is directed to a metal-gas battery system for supplying electrical energy, particularly for a vehicle, comprising a metal-gas battery pack configured to output electrical power and comprising at least one battery cells having a first gas port and a second gas port being interconnected in such a manner that gas can stream through the at least one battery cell. Preferably, the system further comprises a gas distribution apparatus configured to selectively control a gas supply of the metal-gas battery pack. Further preferably, the system has at least two operational states controlled by the gas distribution apparatus, wherein, in a first operational state, inflowing gas is distributed to the first gas port and, in a second operational state, inflowing gas is distributed to the second gas port.

The term "gas distribution apparatus", as used herein, is any means to distribute gas between different connections or leads. A gas distribution apparatus is preferably controlled by at least one actuator and a control algorithm.

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 0 ₂ . 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 pack, in particular of its anode side, such that the necessary chemical reactions for the generation of electrical energy consuming oxygen in the gas during a discharge cycle are possible.

The term "metal-gas battery pack", as used herein, relates to a battery pack where the electrochemically relevant chemical component of one of the electrodes is oxy- gen, in particular 0 ₂ . 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 pack, especially to the cathode side of the battery cells. In particular, the term "metal-gas battery" means a battery that uses oxygen as gas, is a metal-air battery or a metal-oxygen battery. The invention is particularly based on the approach that inflowing gas, particularly oxygen, supplied to the cathode of the battery cells during discharging, is evenly distributed to the first gas ports and to the second gas ports of the battery cells.

Since oxygen reacts from the moment that it enters into an inlet port of a battery cell, the partial gas pressure diminishes from the inlet port to an outlet port. Therefore, also the reaction rate decreases from the inlet port to the outlet port during discharging cycle. Particularly, if not pure oxygen but gas, comprising a multitude of different sorts of pure gases, such as air, is used, also the concentration of oxygen in this gas decreases continuously from the inlet port to the outlet port of a battery cell. This also lowers the reaction rate, being higher at the inlet port than at the outlet port. Furthermore, during the discharging cycle, the discharge products may form layers at the cathode isolating the oxygen from lithium cations and therefore inhibiting the discharging process. Additionally or alternatively, the discharge products may form blocks at the cathode inhibiting with augmenting discharge oxygen of circulating around the cathode.

Both forms of deposit of discharge products may have the effect that the chemical reaction necessary for the discharging process is reduced or even stopped. This may be caused either by the formed layers building an isolator between the oxygen/gas and the lithium cations or the formed blocks blocking the connection be- tween the inlet port and the outlet port, such that no further oxygen or gas can flow into the battery cell bringing the discharging process to a halt.

Even so, according to the inventive concept, an increased reaction rate will still be present at the respective inflow port, an even distribution of reactive products is attained between the first gas ports as inlet ports and the second gas ports as inlet ports. Therefore, the formation of reaction products at the first gas ports and the second gas ports as inlet ports is divided at least into half.

Consequently, the period until a certain reaction surface at the cathode of a battery pack of a battery cell is isolated or the connection between an inlet port and an outlet port of a battery cell is highly extended. In the following, advantageous embodiments and variants of the system for supplying electrical energy according to the invention will be described. Unless explicitly excluded or mutually exclusive, those advantageous embodiments and variants may be arbitrarily combined with each other and with the second and third aspect of the invention, as described thereafter. In an advantageous embodiment of the inventive system, the gas distribution apparatus comprises a first valve to switch the gas supply between the first gas port and the second gas port.

In a further advantageous embodiment of the inventive system, in the first operational state, outflowing gas leaves the at least one battery cell by the second gas port and, in a second operational state, outflowing gas leaves the at least one battery cell by the first gas port.

In a further advantageous embodiment, the inventive system comprises at least two battery cells each having a first gas port and a second gas port, wherein the first gas ports and the second gas ports of the at least two battery cells are interconnected by a first pipe having a first connection to the gas distribution apparatus and the second gas ports of the at least two battery cells are interconnected by a second pipe having a third connection to the gas distribution apparatus. By supplying pipes interconnecting the respective first and second gas ports of several battery cells, separate gas lines from the gas distribution apparatus to each battery cell can be replaced by a single pipe. Therefore, tubing and space requirements of the inventive system can be reduced.

In a further advantageous embodiment of the inventive system, the gas distribution apparatus comprises a second valve for the first connection and a third valve for the third connection to switch the respective connection between the operational states.

In a further advantageous embodiment of the inventive system, the first pipe has a second connection to the gas distribution apparatus, the first gas ports being arranged between the first and the second connection, and wherein the second pipe has a fourth connection to the gas distribution apparatus, the second gas ports be- ing arranged between the third and the fourth connection. By this advantageous configuration, for each of the first ports and the second ports, two lines are provided to supply these ports with inflowing gas. For the first gas ports, these lines are the first and the second connection, for the second gas ports, these lines are the third connection and the fourth connection. By these connections, there are also two al- ternative lines to evacuate gas from the first and second gas ports. By this, an even more homogenous gas distribution to the first and second gas ports can be realized. This enhances the reaction distribution and therefore also the heat distribution throughout the battery cell. "Hot spots" in the battery cell can be avoided in this manner. In a further advantageous embodiment, the inventive system has four operational states wherein, in the first operational state, inflowing gas is distributed to the first connection, in the second operational state, inflowing gas is distributed to the third connection, in a third operational state, inflowing gas is distributed to the second connection, and in a fourth operational state, inflowing gas is distributed to the fourth connection. By these four modes, the highest oxygen concentration and/or the high- est partial gas pressure is not only provided in an alternating mode to the first gas ports and to the second gas ports, but also to different sides of the first pipe and the second pipe supplying the gas ports with the inflowing gas. By this, the highest reaction rate is not only altered from the first gas port to the second gas port and inversely, but also the highest reaction rates are altered between the two or more bat- tery cells of a metal-gas battery pack to ensure an improved even build-up of discharged products at each side of each battery cell. Therefore, also between different battery cells, the high pressure/oxygen-ratio and thus the build-up of discharge products in the cathodes are evenly distributed. This ensures not only a maximum discharge of each cell in a discharge cycle, but also a maximum discharge of all cells before one of the battery cells fails due to an isolating layer of the discharge product or a blocking of the airflow by the discharge product.

In a further advantageous embodiment of the inventive system, in the first and third operational states, outflowing gas leaves the system by the third connection and in the second and fourth operational states, outflowing gas leaves the system by the first connection. Also by this, the amount of "used gas" leaving the battery cells remaining in the lines of the inventive system can be reduced to a maximum. Ideally, the first and third connections are therefore as short as possible.

According to a further advantageous embodiment of the inventive system, the second and third valves are further configured to switch the third and fourth operational states.

A second aspect of the invention is directed to the method for operating the inventive system, comprising the following steps in any order:

supplying inflowing gas to the first valve of the gas distribution apparatus;

switching the first valve that inflowing gas is supplied to the first gas port; and switching the first valve that inflowing gas is supplied to the second gas port. Another second aspect of the invention is directed to the method for operating the inventive system, comprising the following steps in any order:

supplying inflowing gas to the first valve of the gas distribution apparatus;

switching the first valve that inflowing gas is supplied to the second valve and switching the second valve that inflowing gas is supplied to the first connection; switching the first valve that inflowing gas is supplied to the second valve and switching the second valve that inflowing gas is supplied to the second connection; switching the first valve that inflowing gas is supplied to the third valve and switching the third valve that inflowing gas is supplied to the third connection; and

switching the first valve that inflowing gas is supplied to the third valve and switching the third valve that inflowing gas is supplied to the fourth connection.

The various embodiments and 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.

In an advantageous embodiment of the inventive method, the steps are repeated periodically.

In a further advantageous embodiment of the inventive method, each step has a period of about 10 seconds to 1 second, preferably of about 3 seconds to 8 seconds, more preferably of about 5 seconds to 6 seconds.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages, features and applications of the present invention are provided in the following detailed description in connection with the figures:

Figure 1 illustrates at least partially schematically a metal-gas battery system according to a first preferred working example of the present invention;

Figure 2 illustrates at least partially schematically a preferred working example of a sequence of operational states of the inventive system of Fig. 1 ; Figure 3 illustrates at least partially schematically a flow diagram representing a preferred working example of a method for operating an inventive system of Fig. 1 ;

Figure 4 illustrates at least partially schematically a metal-gas battery system

according to a second preferred working example of the present invention;

Figure 5 illustrates at least partially schematically a preferred working example of a sequence of operational states of the inventive system of Fig. 4; and

Figure 6 illustrates at least partially schematically a flow diagram representing a preferred working example of a method for operating an inventive system of Fig. 4.

Fig. 1 shows a first preferred working example of a system 1 for supplying electrical energy according to the first aspect of the invention. The oxygenous gas, in particular air or pure oxygen, is supplied via line 15 to the system 1 . The gas is thereby provided by a gas reservoir for holding oxygenous gas under pressure and/or a compressor for compressing such gas. Furthermore, the oxygenous gas may have been cleaned by a cleaning apparatus. The gas reservoir, the compressor and the cleaning apparatus are not shown in the Figures.

Line 15 is fluidly connected to a valve 6 which is configured to connect line 15 via line 17a to a first gas port 4a of the galvanic battery cell 3a. Furthermore, valve 6 is configured to alternatively connect line 15 to a second gas port 5a of the battery cell 3a. Optionally, a second valve 7 is arranged between line 17a and connection 1 1 to release used air coming out of the battery cell 3a. Preferably, such a valve is a oneway valve. Accordingly, a third valve 8 may be arranged optionally between line 17b and third connection 12 to release used gas coming out of the battery cell 3a via the second gas port 5a.

Oxygen, provided to the battery cell 3a in an oxygenous gas via the first gas port 4a, is consumed in the battery cell 3a such that pressure and/or oxygen concentration of the gas in the cell diminishes when the gas flows from first gas port 4a to second gas port 5a. The same applies if the gas is delivered to second gas port 5a.

If pure oxygen is used as reactant gas for the battery cell 3a, first and second valves 6, 7 are not absolutely necessary. On the other hand, if reactant oxygenous gas with other gas components is used, used gas flowing out of the battery cell 3a has preferably to be evacuated via first and second valves 6, 7. Otherwise, the oxygen concentration in the battery cell 3a would diminish bit by bit during a discharge cycle.

The used gas is preferably exhausted from the first and second valves 6, 7 via exhaust lines 16a, 16b. In this preferred working example, the gas distribution apparatus is formed by first valve 6 and, optionally, by second valve 7 and third valve 8.

Fig. 2 shows two operational states A, B which are possible with the system 1 for supplying electrical energy according to Fig. 1.

The direction of inflowing gas and used gas in the different components of system 1 at different operational states is indicated by arrows.

In operational state A, gas is provided via line 15, valve 7 and first gas port 4a to battery cell 3a. In the case that gas comprising not only pure oxygen is used, the gas is exhausted from system 1 by second valve 7.

In operational state B, gas is supplied via line 15, first valve 6, line 17b and connec- tion 12 to second gas port 5a. In the case that gas is used which is not pure oxygen, the used gas leaving the battery cell 3a by the first gas port 4a is exhausted via connection 1 1 and a first valve 6.

Fig. 3 shows a flow diagram for a method for operating a system according to the first preferred working example according to Fig. 1. The steps of this method prefer- ably consist in supplying inflowing gas to the gas distribution apparatus comprising a first valve 6, 101. Subsequently or at the same time, switching the first valve 6 that inflowing gas is supplied to the first gas port 4a, 102, and, subsequently, switching the first valve 6 that inflowing gas is supplied to the second gas port 5a, 103.

Fig. 4 shows a second preferred working example of the system 1 for supplying electrical energy according to the first aspect of the invention. In contrast to the pre- ferred first working example according to Fig. 1 , battery pack 2 of the preferred second working example according to Fig. 4 comprises at least two battery cells. In the shown working example, battery pack 2 comprises four battery cells 3a, 3b, 3c, 3d.

In the second working example, each battery cell 3a, 3b, 3c, 3d can be fluidly connected to line 15 via first valve 6, second valve 7, first connection 1 1 , pipe 9 and first gas ports 4a, 4b, 4c, 4d. Alternatively, the first gas ports 4a, 4b, 4c, 4d can be connected to the line 15 supplying inflowing gas via valve 6, valve 7, second connection 13 and first pipe 9. Furthermore, first gas ports 4a, 4b, 4c, 4d can be connected to exhaust pipe 16a via first pipe 9 and second valve 7. Hence, valve 7, which may comprise one or several sub-valves, is configured to establish a fluid connection between line 17a and first connection 1 1 , or a fluid connection between line 17a and second connection 13, or a fluid connection between first connection 1 1 and exhaust line 16a.

Accordingly, second gas inlets 5a, 5b, 5c, 5d may be fluidly connected to line 15, first valve 6 and line 17b, third valve 8, third connection 12 and second pipe 10. Al- ternatively, second gas ports 5a, 5b, 5c, 5d may be fluidly connected to first line 15 via first valve 6, second valve 7, fourth connection 14 and pipe 10. Furthermore, second gas ports 5a, 5b, 5c, 5d can be connected to exhaust line 16b via second pipe 10 and third valve 8. Correspondingly to second valve 7, third valve 8 is configured to connect line 17b to third connection 12, line 17b to fourth connection 14 and third connection 12 to exhaust line 16b. Also, valve 8 can comprise one or several sub-valves.

In this preferred working example, the gas distribution apparatus is formed by first valve 6, second valve 7 and third valve 8.

If pure oxygen is used as inflowing gas, second and third valve 7, 8 as well as sec- ond connection 13 and third connection 12 may be omitted. In this case, system 1 would not exhaust gas but only provide inflowing gas alternatively at different gas ports of each gas port of the battery cells 3a, 3b, 3c, 3d.

Fig. 5 shows an exemplary sequence of operational states A, B, C, D of the system 1 according to the second preferred working example of Fig. 4. In the first operational state A, inflowing gas is provided to the battery cells 4a, 4b, 4c, 4d via first valve 6, second valve 7, first connection 1 1 and first pipe 9 to first gas ports 4a, 4b, 4c, 4d. The gas is then again streaming through each of the battery cells 3a, 3b, 3c, 3d to the second gas ports 5a, 5b, 5c, 5d. On the way through each battery cell 3a, 3b, 3c, 3d, oxygen is consumed during the discharge process at the cathode. Used gas with a reduced oxygen ratio and/or a reduced partial pressure leaves the battery cells 3a, 3b, 3c, 3d via gas ports 5a, 5b, 5c, 5d, is collected in second pipe 10 and then led via third connection 12 and third valve 8 to exhaust line 16b.

In the second operational state B, inflowing gas flows to the second gas ports 5a, 5b, 5c, 5d of the battery pack 2 via third valve 8 and third connection 12. On the other side of the battery pack 2, used gas leaves the first gas ports 4a, 4b, 4c, 4d and is led via first connection 1 1 and the second valve 7 to the exhaust line 16a.

In a third operational state C, the inflowing gas is again distributed to the first gas ports 4a, 4b, 4c, 4d. In contrast to operational state A, the gas is supplied via sec- ond valve 7 and second connection 13 to the first pipe 9 and then to the battery cells 3a, 3b, 3c, 3d.

In operational state D, the inflowing gas is again supplied to second gas ports 5a, 5b, 5c, 5d of battery pack 2. According to operational state C and in contrast to operational state B, the inflowing gas is supplied to the battery pack 2 via third valve 8, fourth connection 14 and second pipe 10.

The sequence of operational states is not limited to the sequences A, B or A, B, C depicted in Fig. 2 and Fig. 5. In fact, any sequence of the depicted operational states A, B and A, B, C, D is possible and encompassed by the scope of the present invention. Fig. 6 shows a flow chart of a method to operate a system 1 for supplying electrical energy according to the third aspect of the invention. This method comprises the step of supplying inflowing gas to the first valve 6 of the gas distribution apparatus. Simultaneously or subsequently, first valve 6 is switched in such a manner, that in- flowing gas is supplied to the second valve 7. Simultaneously or subsequently, second valve 7 is switched in such a manner that inflowing gas is supplied to first connection 1 1. Subsequently, second valve 7 is switched in such a manner that inflowing gas is supplied to second connection 13. Subsequently, first valve 6 is switched in such a manner, that inflowing gas is supplied to third valve 8 and subse- quently or simultaneously, third valve 8 is switched in such a manner, that inflowing gas is supplied to third connection 12. Subsequently, third valve 8 is switched in such a manner that inflowing gas is supplied to fourth connection 14.

All of these steps are repeated periodically and may be performed in any order. The period of each step is preferably about 10 seconds to 1 second, preferably of about 3 seconds to 8 seconds and more preferably of about 5 seconds to 6 seconds.

REFERENCE SIGNS

1 system

2 metal-gas battery pack

3a, 3b, 3c, 3d battery cells

4a, 4b, 4c, 4d first gas port

5a, 5b, 5c, 5d second gas port

6, 7, 8 gas distribution apparatus

9 first pipe

10 second pipe

1 1 first connection

12 third connection

13 second connection

14 fourth connection

15 gas supply line

16 exhaust line

17 distribution line

A first operational state

B second operational state

C third operational state

D fourth operational state