Electrochemical energy storage cell

The invention relates to an electrochemical energy storage cell, in particular to an energy store in a vehicle electrical system.

The automobile sector is increasingly using electrochemical energy stores, constructed of individual cells, preferably energy stores, constructed of double layer capacitors. When energy is stored and made available for use, these double layer capacitors offer the advantage that they may provide high performance for a short period of time. To arrive at the supply voltage required in a motor vehicle, the individual energy storage cells are connected in series. The technical aspects of double layer capacitors, such as their construction and manufacture, are comparable to those of batteries, especially lithium ion batteries. The materials that are used are similar to some extent. It involves predominantly monopolar arrangements, in which the electrodes are wound or stacked.

As a rule, the liquid electrolyte decomposes over the lifetime of the energy storage cells; and gaseous decomposition products are generated. This applies especially under the additional influence of higher temperatures, as is the case in motor vehicles. As a rule, the decomposition products are collected in the energy storage cell or an arrangement of several energy storage cells and vented to the atmosphere via a venting hose. Such a device has already been disclosed in DE 101 28 672 A1. Owing to the tolerances of the cells, the cell voltages diverge in the course of cyclic charging and discharging. This is critical, above all, when the maximum cell voltage is reached. The consequences extend from differential ageing of the cells up to the failure of individual cells. Furthermore, series-connected electrochemical energy storage cells exhibit a non-uniform distribution of voltage over the individual cells owing to the different internal resistances and/or the different capacities of the individual cells. Electronic circuits may be used to avoid overvoltages when charging and discharging. Such electronic circuits range from simple compensating resistors to totally active circuits, which are provided, as a rule, once per cell and once in an overreaching manner for a cell arrangement.

Both the electrical connection of the individual electrochemical energy storage cells and their respective monitoring logic, as well as the collection of the gaseous decomposition products and their venting into the atmosphere, represent a problem when a large number of electrochemical energy storage cells are wired together.

Therefore, the object of the invention is to provide an alternative construction of an electrochemical energy storage cell, which makes possible both a simple electrical connection as well as a simple venting of the resulting gaseous decomposition products in series-connected electrochemical energy storage cells.

The invention solves this problem by means of an electrochemical energy storage cell that exhibits a core tube, which passes through the energy storage cell and is open on its two ends.

As a consequence, the invention offers the possibility of integrating into the core tube not only one or more connections for supplying or dissipating energy and a databus structure for linking the individual cells together in an intelligent manner, but also provides a channel for siphoning off any electrolytes that may have become liberated. The result is that a simple cascading/series connection of the individual cells is possible.

Advantageous further developments and embodiments of the invention are described and claimed herein.

Preferably, the core tube forms a connection lead of the energy storage cell. In this case, the supply/dissipation of electric power and/or the databus structure may be realized by means of merely one additional lead to the core tube. To this end, the electrochemical energy storage cell exhibits preferably a conducting exterior housing, which is electrically insulated at least against the core tube, and/or at least one lead, which is arranged in the core tube and which also includes preferably at least one connection lead of the energy storage cell.

In the electrochemical energy storage cell, according to the invention, the core tube and/or at least one lead, arranged in the core tube, comprise/comprises at least one lead of a databus. The databus may also be integrated in the connection lead for supplying and dissipating energy.

The inventive electrochemical energy storage cell, which exhibits at least one lead, arranged in the core tube, includes preferably at least one guide element for the at least one lead, which is arranged in the core tube and by which the core tube is not closed. In this case, the electrochemical energy storage cell, according to the invention, may be cooled with air or liquid via the core tube. Furthermore, it is also possible to siphon off any electrolytes, which might have become liberated, through the core tube.

Preferably, the electrochemical energy storage cell, according to the invention, exhibits an electronic circuit for controlling, regulating and/or monitoring the energy storage cell. Owing to such an electronic circuit, which is also preferably an electronic slave, controlled by an electronic master, both the overvoltages and a diverging of the cell voltages during cyclic charging and discharging may be avoided. Furthermore, the consequence of such an electronic circuit is a temperature monitoring of the cell, the core tube and/or the channel, which is formed by said core tube; a voltage monitoring of the cell and/or the connection leads; and/or a current monitoring of the cell. Furthermore, it is also possible that the result of such an electronic circuit is a pressure monitoring of the cell and/or the core tube; a measurement of the throughflow of gas or a gas mixture, present in the core tube; and/or a monitoring of the occurrence of a (specific) gas or gas mixture, present in the core tube.

The electrochemical energy storage cell, according to the invention, exhibits preferably at least one overpressure valve, leading into the core tube. The consequence of this overpressure valve is that gaseous decomposition products of the electrochemical energy storage cell may be conveyed specifically into the core tube and vented safely and simply into the atmosphere. Furthermore, this venting into the atmosphere is done preferably by way of an activated charcoal filter and/or a molecular sieve for trapping at least a fraction of the decomposition products.

The inventive electrochemical energy storage cell exhibits preferably at least one cooling rib, arranged in the core tube. In the event that the inventive energy storage cell also exhibits a guide element for the at least one lead, arranged in the core tube, the at least one cooling rib is also formed in an integrated manner preferably with the guide element. The result of the at least one cooling rib, arranged in the core tube, is that the core tube may also be subdivided into a plurality of channels that may have different functions, for example, a channel for venting gaseous decomposition products of the energy storage cell, a channel for cooling the fluid, a channel for guiding the electrical lines, etc.

The electrochemical energy storage cell, according to the invention, includes preferably at least one sensor for measuring a cell temperature, a temperature in the core tube, a cell voltage, a voltage of the connection lead of the cell, a current taken from the cell, a pressure in the cell, a pressure in the core tube, a throughflow of a gas or a gas mixture present in the core tube, and/or a chemical composition or the occurrence of a (specific) gas or gas mixture present in the core tube.

The inventive energy storage cell is preferably an accumulator or a double layer capacitor.

Other details, advantages and features of the present invention are disclosed in the following description of the embodiments with reference to the drawings.

FIG. 1 is a schematic view of an electrochemical energy storage cell, according to a first preferred embodiment of the invention;

FIG. 2 is a schematic view of a cascading of electrochemical energy storage cells, shown in FIG. 1 ;

FIG. 3 is a top view of the core tube of the electrochemical energy storage cell, shown in FIG. 1 ;

FIG. 4 is a top view of the electrochemical energy storage cell, shown in FIG. 1 ; and

FIG. 5 is a view of an electrochemical energy storage cell, according to a second preferred embodiment of the invention.

FIG. 1 depicts an electrochemical energy storage cell 1 , according to a first preferred embodiment of the invention. In this case, the depicted energy storage cell consists of a double layer capacitor 4 , which is arranged in a two-part housing 2 , 3 . In particular, the housing 2 , 3 has an exterior section 3 , which includes an outer tube 3 a with an outer cover 3 b ; and an interior section 2 , which includes a core tube 2 a with an inner cover 2 b . The exterior section 3 and the interior section 2 are connected together in such a manner that the core tube 2 a is arranged coaxially inside the outer tube 3 a ; and the outer cover 3 b is connected by way of an inner seal 5 to that end of the core tube 2 a , on which the inner cover 2 b is not provided. The inner cover 2 b of the interior section 2 is connected by way of an outer seal 6 to that end of the outer tube 3 a , on which the outer cover 3 b is not arranged.

In this manner, the housing forms a double walled hollow cylinder, in which a cavity, which is closed by the outer cover 3 b and the inner cover 2 b and in which the double layer capacitor 4 is disposed, is formed between the walls. The inner seal 5 and the outer seal 6 also cause the interior section 2 to be electrically insulated from the exterior section 3 , the result of which is that connections for the supply of energy or dissipation of energy may be formed by means of the interior section 2 and the exterior section 3 . The core tube 2 a is open toward the outside; and the core tube 2 a has a lead 8 . Electronics 7 are mounted on the inner cover 2 b on the exterior. Owing to the electronics, the double layer capacitor may be controlled or regulated, charged or discharged. Moreover, the electronics monitor a number of different parameters of the double layer capacitor, such as the parameters of its temperature; of the temperature inside the core tube 2 a ; of the pressure inside the housing 2 , 3 ; a flow rate of a gas or a gas mixture, transported through the core tube 2 a ; a tightness of a channel, formed by way of the core tube 2 a and other elements attached to the core tube; etc. The electronics 7 may be accessed via a databus, which may also transfer information to the electronics 7 . With this information the electronics may check the line. Furthermore, the electronics 7 may also be connected to other energy storage cells by means of suitable connections, which may be disposed in the core tube 2 a , for the purpose of controlling, regulating and/or monitoring the energy storage cells.

FIG. 2 depicts a cascading of energy storage cells 1 , according to the first preferred embodiment of the invention. In this case, there are a series of four double layer capacitors la to id. Therefore, the exterior section of the housing forms a negative terminal; and the interior section of the housing forms a positive terminal of the energy storage cells. The individual cells 1 a to 1 d are arranged in a row or stacked one on top of the other such that a sealed channel is formed by way of the core tubes. Therefore, a core tube, forming a positive terminal of an individual cell, is connected to an outer cover 3 b , which forms a negative terminal of the individual cell and belongs to a neighboring individual cell. In this way the individual cells 1 a to 1 d are connected together in series. Therefore, an electrical insulation of the core tubes of the adjacent individual cells takes place via the inner seal 5 ; and an electrical insulation of the outer tubes of the adjacent individual cells takes place via the outer seal 6 . The tightness of the channel, formed by means of the core tubes, may be monitored by monitoring the pressure of the channel, which may ensue by use of the electronics of an individual cell. This may occur, for example, via a monitoring of an underpressure, which has built up in the channel. As an alternative, it is also possible, among other things, to monitor the tightness of the channel by way of determining the flow rate at the beginning and the end of the channel.

The individual electronics 7 a to 7 d of the individual cells 1 a to 1 d are constructed, for example, such that the electronics 7 a to 7 c of the individual cells 1 a to 1 c are slave circuits; and the electronics 7 d of the individual cell 1 d is a master circuit that controls the slave circuits 7 a to 7 c . A connection to the electrical system of a vehicle, for example to the supply voltage and a databus, may also ensue by way of the master circuit 7 d . As stated above, a slave circuit may also serve more than one individual cell.

FIG. 3 is a top view of the core tube 2 a of the energy storage cell, shown in FIG. 1 . The core tube 2 a , which in this case is constructed in a non-conducting manner, exhibits an outer lead 9 on its inside wall and an inner lead 8 , which is disposed coaxially to said outer lead and is held by way of the guide legs 10 , which in this embodiment also serve as the cooling ribs. The guide legs 10 may be disposed along the entire core tube 2 a or only in parts thereof. In the event that the guide legs 10 run along the entire core tube 2 a , the guide legs/cooling ribs 10 may form closed individual channels, for example a channel for conveying a cooling fluid, a channel for siphoning off gaseous decomposition products of the double layer capacitor, a channel for running other leads and a channel for accommodating sensors, for example temperature sensors.

FIG. 4 is a top view of the energy storage cell, including the electronics 7 , shown in FIG. 1 . From radially outward to inward one can see: the outer tube 3 a , the outer seal 6 , the electronics 7 , the core tube 2 a , the outer lead 9 , the guide legs/cooling ribs 10 and the inner lead 8 . Inside the outer lead 9 there is also a temperature sensor 14 , by which the temperature inside the core tube 2 a may be measured. On the electronics 7 there is another temperature sensor 13 , by which the temperature inside the energy storage cell (that is, the temperature of the double layer capacitor 4 ) may be measured. The electronics 7 are connected by way of a first connection lead 11 to the center lead 8 and by way of a second connection lead 12 to the outer lead 9 . These two leads form the databus, by which the electronics may be actuated.

FIG. 5 depicts an electrochemical energy storage cell, according to a second embodiment of the invention, which differs from the energy storage cell of the first embodiment in that there is an additional overpressure valve 15 . The overpressure valve 15 is arranged in such a manner that it vents an overpressure, generated in the closed interior of the housing, into the core tube 2 a . The overpressure valve 15 may comprise a valve, which automatically closes again after the overpressure has been reduced, or just merely a pressure relief joint.

The core tube 2 a may have a chemical sensor technology, which detects the gaseous decomposition products of a double layer capacitor, the decomposition products being vented into the core tube 2 a . Therefore, the electronics of the cell may indicate any necessary replacement.

Table of Reference Numerals

1 energy storage cell 2 a core tube 2 b inner cover 3 a outer tube 3 b outer cover 4 double layer capacitor 5 inner seal 6 outer seal 7 electronics 8 inner lead 9 outer lead 10 guide legs/cooling ribs 11 inner lead connection 12 outer lead connection 13 temperature sensor (cell) 14 temperature sensor (core tube) 15 overpressure valve

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.