Electrochemical single cell and electrical energy storage

Abstract

The invention relates to an electrochemical single cell (1) with a cell housing (2) in which an electrochemically active material (3) is arranged and the cell housing (2) has a vent opening (E) closed by a burst membrane, wherein the burst membrane at least partially releases the vent opening (E) when a predetermined internal pressure in the cell housing (2) is exceeded. According to the invention, a gas guidance structure element (4) is arranged in a region below the vent opening (E) within the cell housing (2) for the controlled guidance of gas exiting from the vent opening (E). The gas guidance structure element (4) comprises two planes arranged one above the other and running parallel to a housing side (2.1) of the cell housing (2.1) into which the vent opening (E) is integrated. According to the invention, one plane of the gas guidance structure element (4) serves as a support element (4.1) for fixing and supporting the electrochemically active material (3) within the cell housing (2) and for guiding the gas (G) from a side wall region of the cell housing (2) towards the vent opening (E). According to the invention, the support element (4.1) has webs (4.1.2) projecting from a central part (4.1.1) towards the side wall regions of the cell housing (2), which are connected to an end opposite the central part (4.1.1) of a respective side web (4.2.2) of a further plane of the gas guiding structure element (4) designed as a gas guiding element (4.2). According to the invention, the gas guide element (4.2) has a central web (4.2.1) for reducing gas turbulence when gas escapes from the vent opening (E) and for supporting a venting grid (6), as well as two opposing side webs (4.2.) that abut opposite side wall areas of the cell housing (2).2) for gas flow and as heat protection serving the outside.

Description

The invention relates to an electrochemical single cell with a cell housing in which an electrochemically active material is arranged and the cell housing has a vent opening sealed with a burst membrane, wherein the burst membrane at least partially releases the vent opening when a predetermined internal pressure in the cell housing is exceeded. The invention further relates to an electrical energy storage device. From US 9,196,920 B2, an electrochemical single cell with a cell cup having a side wall is known. The side wall is connected to a first end of the cell cup, which has a vent opening at the first end. The vent opening is configured so that gases and wastewater can escape from the cell cup once the pressure in the cell cup reaches a predetermined value. CN 2 12 874 611 U describes a battery cover mounting, a battery cover assembly, and a battery. The battery cover mounting comprises a first and a second mounting. The first mounting consists of a first support, a first butt joint, and a first substrate. The first butt joint extends below the center of the first support, and the first substrate extends horizontally on both sides of the first support. The second mounting comprises a second support, a second butt joint, and a second base plate. The second butt joint extends below the center of the second support, and horizontal base plates extend on both sides of the second support. One of the butt joints and the second butt joint are each provided with an eyelet, and the other butt joint and the second butt joint are each provided with a bend groove.The expansion direction of the buckle groove runs parallel to the butt joint direction of the first and second butt joint parts. After the buckle engages in the buckle groove, the side wall of the first butt joint part is attached to the side wall of the second butt joint part, and the first and second base plates are spaced apart. JP H1O - 284 036 A describes a battery with an internal pressure release device which opens to the outside when an internal pressure of a battery with a predefined pressure is applied to a pressure-sensitive area. The invention is based on the objective of providing an electrochemical single cell with a cell housing and an electrical energy storage device. The object is achieved according to the invention by an electrochemical single cell which has the features specified in claim 1, and by an electrical energy storage device which has the features specified in claim 6. Advantageous embodiments of the invention are the subject of the dependent claims. An electrochemical single cell comprises a cell housing in which an electrochemically active material is arranged, and the cell housing has a vent opening sealed with a burst membrane, wherein the burst membrane at least partially releases the vent opening when a predetermined internal pressure in the cell housing is exceeded. According to the invention, a gas guidance element is arranged in a region below the vent opening within the cell housing for the controlled guidance of gas exiting from the vent opening. The gas guidance element, located below the vent opening, keeps the vent area of ​​the individual cell clear, allowing gas to escape unhindered from the cell housing through the vent opening, particularly in the event of thermal runaway. Furthermore, the gas guidance element essentially prevents, for example, burning electrochemically active material from blocking the vent opening, thereby increasing heat generation within the individual cell and potentially creating a fire hazard for adjacent cells. Specifically, the gas guidance element ensures that electrochemically active material is transported, and especially ejected, from the cell housing due to the comparatively high internal pressure. Such thermal runaway can occur due to a short circuit within the individual cell. A short-circuit current, passing through internal resistance, can heat the immediate vicinity of a fault, creating a direct path from the cathode to the anode, thus initiating the short circuit. This heating, i.e., the resulting thermal energy, within the cell casing expands and generates even more heat, resulting in a continuous temperature increase. If the internal pressure in the cell casing rises to such an extent that the predetermined internal pressure is exceeded, the rupture membrane bursts, releasing the vent and venting the individual cell, thereby releasing toxic and flammable gases.If a thermally continuous single cell is part of an electrical energy storage system with a large number of electrically interconnected individual cells, there is a risk of thermal propagation that is difficult or impossible to stop and triggers a cascade reaction. This means that a fire will spread from individual cell to individual cell, in particular until the entire electrical energy storage system is consumed by smoke and / or flames. According to the invention, the gas guidance structure element comprises two levels arranged one above the other and running parallel to a housing side in which the vent opening is integrated. The vent area of ​​the individual cell, extending across these two levels of the gas guidance structure element, is kept clear by means of the gas guidance structure element for the targeted venting of the individual cell. According to the invention, one plane of the gas guidance structure element is designed as a support element for fixing and supporting the electrochemically active material within the cell housing and for guiding the gas from a narrow sidewall region towards the vent opening. This means that the electrochemically active material, in particular an electrode foil arrangement, is fixed in a predetermined position by means of the support element, so that it is largely prevented that the electrochemically active material blocks the vent opening and thus reduces the risk of explosion of the individual cell. According to the invention, the support element has a number of webs projecting from a central section towards the side wall regions of the cell housing. These webs are connected to an end opposite the central section of a respective side web on a further plane of the gas guidance structure element, which is designed as a gas guidance element. The webs are arranged and spaced apart from one another in such a way that it is essentially impossible for any free space formed by the spacing of the webs to be blocked by released active material and thus prevent venting of the individual cell. The more gas can escape from the individual cell in a controlled manner, particularly by keeping the venting area clear using the gas guidance structure element, the less heat is transferred to any adjacent individual cells.Furthermore, the gas flows in a directed manner from the vent opening via the gas guidance structure element, thus reducing heat transfer to neighboring individual cells and thereby minimizing the risk of thermal propagation. In one embodiment of the electrochemical single cell, the gas guide element of the gas guide structure is designed to guide the gas from the support element to the vent opening. Specifically, the gas is guided by means of the gas guide element, through an electrochemically active material along the narrow sidewall areas, to the vent opening, so that the gas can escape through the vent opening and thus reduce the internal pressure in the cell housing. According to the invention, the gas guide element comprises a central web for reducing gas turbulence when gas exits the vent opening and for supporting a venting grid, as well as two opposing side webs located against opposite side wall regions of the cell housing for gas guidance and as outward heat protection. The gas is actively guided by the gas guide element to the vent opening, whereby the gas is guided with minimal turbulence, i.e., with little to no turbulence, out of the cell housing due to the central web. The side webs are designed in such a way that they extend to the point where the electrochemically active material is fixed, thereby creating a correspondingly large venting area.The side ribs serve as heat protection, in particular to protect a critical area of ​​a neighboring single cell from the heat effect emanating from the thermally continuous single cell. In one embodiment, the gas guidance element is made of a thermoset and / or polypropylene, thus ensuring, to a large extent, that the protective geometry formed by the gas guidance element below the vent opening is maintained even during thermal runaway of the individual cell. Blockage of the vent opening by electrochemically active material can therefore be prevented for the entire duration of the thermal runaway by means of the gas guidance element, so that outgassing of the individual cell can be essentially ensured. In another possible embodiment, the gas guidance element is arranged in a force-fit, form-fit, and / or material-fit manner on fixing elements for securing the electrochemically active material and / or on an inner surface of the housing side of the cell casing. By means of the gas guidance element positioned between the electrochemically active material and the housing side, impermissible upward movement of the electrochemically active material during the thermal runaway of the individual cell can be largely prevented, thereby also preventing the vent opening from being blocked by the gas guidance element. In one embodiment, the cell housing is prismatic, with the vent opening being arranged in particular in a housing wall pointing upwards in the direction of a vertical axis, so that it can be essentially ensured that a venting area is located outside the individual cell. Furthermore, the invention relates to an electrical energy storage device with a plurality of electrically interconnected individual cells, wherein a gas guidance structure element for targeted gas guidance with respect to the venting opening is arranged in the area below the vent opening within the respective cell housing. By means of the respective gas guidance structural element, the risk of fire spreading from a thermally continuous single cell to a neighboring single cell can be reduced by reducing the thermally active residual mass of the electrochemically active material present in the thermally continuous single cell, thus reducing conduction to a neighboring single cell. Exemplary embodiments of the invention are explained in more detail below with reference to drawings. Figure 1 schematically shows a perspective semi-transparent view of a section of an electrochemical single cell; Figure 2 schematically shows a perspective sectional view of an enlarged section of the electrochemical single cell; Figure 3 schematically shows the perspective semi-transparent view according to Figure 1 with targeted gas guidance; Figure 4 schematically shows a perspective view of a gas guidance structural element in an alternative embodiment; and Figure 5 schematically shows another perspective view of the gas guidance structural element in the alternative embodiment. Corresponding parts are marked with the same reference symbols in all figures. Fig. 1 shows a perspective semi-transparent view of a section of an electrochemical single cell 1 with a prismatic cell housing 2, wherein a vent opening E is integrated into a housing side 2.1, which in particular points upwards in the direction of a vertical axis. Fig. 2 shows a perspective sectional view of an enlarged section of the single cell 1, in particular in the area of ​​the vent opening E, and Fig. 3 shows the perspective semi-transparent view according to Fig. 1 with gas guidance specifically for venting. The vent opening E is closed by means of a burst membrane (not shown in detail), which bursts when the internal pressure of the cell housing 2 exceeds a predetermined internal pressure, thus releasing the vent opening E for venting, in particular for the outgassing of the cell housing 2. This predetermined internal pressure is exceeded in particular when the individual cell 1 experiences thermal runaway, especially due to a short circuit. In the cell housing 2, an electrochemically active material 3, for example in the form of an electrode foil arrangement, is arranged and positioned and fixed within the cell housing 2 by means of a number of fixing elements. The individual cell 1 can experience thermal runaway, particularly due to a short circuit within the individual cell 1. Such a short circuit can be caused by a defect in the electrochemically active material 3. Through this defect, for example due to a foreign body in the cell housing 2, a direct path from a cathode to an anode can be formed, resulting in a short circuit. Thermal runaway refers to the overheating of an exothermic chemical reaction taking place within the cell casing 2. The damaged area heats up to such an extent that its immediate surroundings also heat up, and this process spreads. The comparatively high thermal energy initially leads to the vaporization of the electrolyte within the individual cell 1, generating additional thermal energy and flammable gases G. If the internal pressure rises above a certain threshold, the flammable gases G are released and, in combination with air, form an ignitable mixture, causing flames to erupt outside the cell casing 2. There is a risk that, due to the thermal energy of the thermally runaway individual cell 1 and / or the flames at the thermally runaway individual cell 1, neighboring individual cells 1 will heat up to such an extent that a chain reaction occurs. To largely prevent thermal propagation, particularly in the event of thermal runaway in a single cell 1 of an electrical energy storage device, the single cell 1 has a vent opening E. Gases G, also known as venting gases, can escape from the cell housing 2 through this vent opening E. To ensure, among other things, that an area below the vent opening E of the cell housing 2 remains clear to allow the gas G to escape from the cell housing 2 through the vent opening E, a gas guidance element 4 is arranged in this area. This gas guidance structure element 4 is made of a thermoset and / or polypropylene, so that the gas guidance structure element 4 retains its protective geometry even if the individual cell 1 thermally breaks down and heat energy is released as a result. Thermosets, i.e., thermosets, are comparatively high-temperature resistant plastics. The gas guidance structure element 4 has two levels arranged one above the other and running parallel to the housing side 2.1 of the cell housing 2, into which the vent opening E is integrated. The gas guidance structure element 4 is arranged by means of force-fit, form-fit, and / or material-fit connections to fixing elements 5 for fixing the electrochemically active material 3 and / or to an inner surface of the housing side 2.1 of the cell housing 2. One plane is designed as a support element 4.1 and has a central part 4.1.1 from which a number of webs 4.1.2 project towards a side wall area of ​​a respective flat side of the cell housing 2. A further level of the gas guidance structure element 4 is formed by means of a gas guidance element 4.2, which has a central web 4.2.1 and two opposing side webs 4.2.2 arranged parallel to the central web 4.2.1 and abutting opposite side wall regions of the flat sides of the cell housing 2. Each end of the webs 4.1.2 of the support element 4.1, opposite the central section 4.1.1, is connected to one of the two side webs 4.2.2 of the gas guidance element 4.2, in particular by a material bond. The central web 4.2.1 and the two side webs 4.2.2 act as longitudinal guides to direct the gas G from a section of the support element 4.1 to the vent opening E. Each end of the central web 4.2.1 of the gas guiding element 4.2 is formed by sections arranged at a predetermined angle to one another. The ends of the central web 4.2.1 are, for example, split, or in particular, formed. Alternatively, the central web 4.2.1 may, as shown in an alternative embodiment of the gas guiding structural element 4 in Figures 4 and 5, not have these sections in order to optimize the directed gas flow. The support element 4.1 is designed to support the electrochemically active material 3, for example, the electrode foil arrangement, in the event of thermal runaway of the individual cell 1, so that upward movement of the electrochemically active material 3 during thermal runaway of the individual cell 1 is either impossible or at least limited. Thus, the electrochemically active material 3 remains largely in its position, as defined by the fixing elements 5, by means of the support element 4.1 and therefore cannot block the vent opening E for degassing of the cell housing 2. Furthermore, the support element 4.1 is designed to guide the gas G laterally from an exterior area of ​​the electrochemically active material 3, in particular via narrow sidewall regions, towards the vent opening E. For example, the gas guidance structure element 4 extends from one narrow sidewall region to an opposite narrow sidewall region of the cell housing 2 for optimized, targeted, and in particular directional, gas guidance. By means of the central web 4.2.1 of the gas guiding element 4.2, a reduction of turbulence of the gas G is achieved when it exits the vent opening E, wherein the central web 4.2.1 additionally provides stable support, in particular laterally, to a venting grid 6 arranged on it. The side webs 4.2.2 of the gas guide element 4.2, which abut the side wall areas of the flat sides of the cell housing 2 in sections, also serve, at least to a minor extent, to guide the gas, with the side webs 4.2.2 serving as heat protection, particularly on the outer sides. The side webs 4.2.2 extend along the corresponding side wall areas in such a way that a critical, particularly heat-sensitive, area of ​​an adjacent single cell 1 is protected from excessive heat exposure by means of the side webs 4.2.2. The gas guidance structure element 4 fixes the electrochemically active material 3, particularly in its intended position. The different configurations of the two levels of the gas guidance structure element 4 largely prevent the vent opening E from becoming blocked by fragments of the electrochemically active material 3. Furthermore, the gas guidance structure element 4 ensures that the gas G is actively guided to the vent opening E and is directed outside the cell housing 2 in a controlled manner with minimal turbulence. Furthermore, the venting area is enlarged, in particular by the fact that the gas guiding structural element 4 extends over an area from the housing side 2.1 to the electrochemically active material 3, especially in an area below the vent opening E. Furthermore, the side webs 4.2.2 of the gas guide element 4.2 serve as heat protection in a relevant upper area of ​​the cell housing 2, wherein the side webs 4.2.2 can be arranged directly in a welding area for the metallurgical connection of current collector tabs of the electrochemically active material 3 with pole contacts of the individual cell 1 arranged on a cell cover. Figures 4 and 5 each show a perspective view of an alternative embodiment of the gas guidance structure element 4'. In the alternative embodiment, the gas guidance structure element 4' extends from one narrow side of the cell housing 2 to an opposite narrow side, so that the gas G is directed in a controlled manner, the electrochemically active material is guided around the narrow side wall areas of the cell housing 2 to the vent opening E, and the gas G flows in a controlled direction from the vent opening. In the alternative embodiment of the gas guide structure element 4', the central web 4.2.1' extends over both planes, with a reduced number of webs 4.1.2' projecting from the central web 4.2.1' towards the side webs 4.2.2'. Furthermore, a connecting web 4.1.3 is arranged, and in particular configured, between the central web 4.2.1' and the respective projecting web 4.1.2'. The gas guidance structure element 4' shown in Fig. 4 and Fig. 5 has further shapes and openings to guide the gas G specifically to the vent opening E in order to reduce heat generation within the cell housing 2 and heat transfer to adjacent individual cells 1. Reference symbol list 1 Single cell 2 Cell housing 2.1 Housing side 3 Electrochemically active material 4, 4' Gas guiding structure element 4.1 Support element 4.1.1 Middle section 4.1.2, 4.1.2' Web 4.1.3 Connecting web 4.2 Gas guiding element 4.2.1, 4.2.1' Middle web 4.2.2, 4.2.2' Side web 5 Fixing element 6 Venting grid E Vent opening G Gas

Claims

Electrochemical single cell (1) with a cell housing (2) in which an electrochemically active material (3) is arranged and the cell housing (2) has a vent opening (E) closed with a burst membrane, wherein the burst membrane at least partially releases the vent opening (E) when a predetermined internal pressure in the cell housing (2) is exceeded, characterized in that a gas guidance structure element (4) for the targeted guidance of a gas exiting from the vent opening (E) is arranged in a region below the vent opening (E) within the cell housing (2), wherein the gas guidance structure element (4) comprises two levels arranged one above the other and running parallel to a housing side (2.1) of the cell housing (2) in which the vent opening (E) is integrated, wherein one level of the gas guidance structure element (4) serves as a support element (4.1) for fixing and supporting the electrochemically active material (3) within the cell housing (2) and for guiding the gas (G) from a side wall region of the cell housing (2) towards the vent opening (E), wherein the support element (4.1) has webs (4.1.2) projecting from a central part (4.1.1) towards the side wall regions of the cell housing (2), which are connected to an end opposite the central part (4.1.1) of a respective side web (4.2.2) of a further plane of the gas guiding structure element (4) designed as a gas guiding element (4.2), characterized in that the gas guiding element (4.2) has a central web (4.2.1) for reducing gas turbulence when gas escapes from the vent opening (E) and for supporting a venting grid (6) as well as two oppositely arranged webs on opposite side wall regions of the cell housing (2) adjacent side ribs (4.2.2) for gas guidance and as heat protection serving the outside. Electrochemical single cell (1) according to claim 1 , characterized in that the gas guiding element (4.2) is designed to guide the gas (G) from the support element (4.1) to the vent opening (E). Electrochemical single cell (1) according to one of the preceding claims, characterized in that the gas guiding structure element (4) is formed from a thermoset and / or polypropylene. Electrochemical single cell (1) according to one of claims 1 to 3, characterized in that the gas guiding structure element (4) is arranged force-fit and / or form-fit and / or material-fit on fixing elements (5) for fixing the electrochemically active material and / or on an inner surface of the housing side (2.1) of the cell housing (2). Electrochemical single cell (1) according to one of the preceding claims, characterized in that the cell housing (2) is prismatic. Electrical energy storage device comprising a plurality of electrically interconnected individual cells (1) which are designed according to one of the preceding claims.

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