Battery cell

Abstract

The invention relates to a battery cell (10; 60) comprising at least one battery cell sub-element (30; 70), wherein a battery cell sub-element (30; 70) has two contact elements (32, 34; 72, 74), an anode contact (32; 72) and a cathode contact (34; 74), wherein the battery cell (10; 60) further comprises a cell housing (12; 62) in which an anode active material (36; 76) and a cathode active material (38; 78) are received, wherein the cathode active material (38; 78) is electrically connected to the cathode contact (34; 74) and the anode active material (36; 76) is electrically conductively connected to the anode contact (32; 72), wherein the anode active material (36; 76) and the cathode active material (38; 78) are electrically insulating but ionically conductive (electrolytically) connected are separated from each other, in particular by a separator. The invention is characterized in that at least one thermal separating element (40; 80) is arranged in the cell housing (12; 62), which separates the interior of the cell housing (12;62) divides into at least two receiving spaces (14, 18; 64, 68), each of the at least two receiving spaces (14, 18; 64, 68) comprising at least one battery cell sub-element (30; 70), wherein the respective anode contacts (32; 72) and the cathode contacts (34; 74) are connected to each other, wherein the thermal separator element (40; 80) has a higher temperature resistance and a higher thermal resistance than the separator.;

Description

The invention relates to a battery cell of the type specified in the preamble of claim 1. Battery cells contain an active cell material that, particularly at high energy densities, comprises substances capable of highly exothermic reactions. Upon reaching certain temperatures, a reaction cascade is initiated within the active cell material that cannot be stopped at the cell level. This process is also known as thermal runaway. The intense heating can lead to a pressure build-up and uncontrolled rupture of the cell casing. Especially in arrangements where several cells are positioned side by side, such as in a battery pack, the overheating of one cell can cause the cascade to spread to neighboring cells. According to current technology, the spread of such a thermal runaway to neighboring cells is prevented or slowed down by introducing separating materials between adjacent cells. This has the disadvantage that, for example in battery cells in the form of prismatic or cylindrical cells, the entire cell active material within the cell housing is affected by thermal runaway, releasing a correspondingly high thermal energy which, in most commonly used battery cells, must be dissipated in a complex manner to prevent transmission to neighboring battery cells. The object of the invention is to prevent, or significantly reduce the probability of, thermal runaway across multiple battery cells in a simplified arrangement of a plurality of adjacent battery cells. The problem is solved by the characterizing features of claim 1 in conjunction with its preamble features. The dependent claims constitute advantageous further developments of the invention. The invention is based on the finding that by reducing the amount of thermally bonded cell active material, the reaction energy that can be generated in a battery cell can be reduced. In a known manner, a battery cell comprises at least one battery cell sub-element, wherein a battery cell sub-element has two contact elements, an anode contact and a cathode contact. The battery cell further comprises a cell housing in which an anode active material and a cathode active material are accommodated. The cathode active material is electrically conductively connected to the cathode contact and the anode active material is electrically conductively connected to the anode contact, wherein the anode active material and the cathode active material are electrolytically connected and, in particular, separated from each other by an ion-permeable separator. The separator possesses temperature resistance and thermal resistance. According to the invention, the battery cell is designed such that at least one thermal break element is arranged in the cell housing, which divides the interior of the cell housing into at least two receiving spaces, each of the at least two receiving spaces containing at least one battery cell sub-element. The respective anode contacts and the cathode contacts of the battery cell sub-elements are connected to each other, the thermal break element having a temperature resistance and a thermal resistance that are each higher than the temperature resistance and the thermal resistance of the separator. This results in the battery cell having an energy density essentially corresponding to its volume, although the reaction energy achievable through exothermic reactions in the individual battery sub-elements is lower. This can potentially prevent thermal runaway between the battery cell sub-elements separated by the thermal break element within the cell housing. Consequently, the total thermal energy, and especially the maximum temperature generated by a battery cell, can also be reduced. This can reduce the reaction energy released simultaneously or extend the energy release period. This can prevent thermal runaway from propagating to a neighboring battery cell, as the locally generated thermal energy is too low or can be easily dissipated by existing cooling structures. According to a further advantageous embodiment, the thermal break element is located in the center of the cell housing, particularly in a plane of symmetry of the cell housing. This has the advantage that the battery sub-elements can dissipate thermal energy at their outer region via the cell's outer wall. In the inner region, where the most heat accumulates due to the location, adjacent battery sub-elements are separated from each other by the thermal break element. In an advantageous embodiment, the thermal break element has a temperature resistance that is greater than that of the separator, in particular a temperature resistance of more than 120°C. Preferably, the temperature resistance of the thermal break element can be above 150°C. The battery cell preferably has a cell housing with a cross-section formed by at least two semicircular areas. In particular, in a cross-section consisting of two semicircular areas formed by the overlap of two circles, the thermal break element runs along a line connecting the two points of intersection of the two circular areas. This reduces heat transfer, especially in the inner part of the cell housing, as seen in cross-section. In a further advantageous embodiment of the invention, the battery cell according to the invention can be designed as a prismatic battery cell. In this design, the battery cell components are arranged in layers. These components, in particular, comprise layers of superimposed cathode active material, separator, and anode active material. According to the invention, a thermal break element is incorporated between the superimposed battery cell component layers, at least in half of the battery cell components. This thermal break element is thus located in the plane of symmetry of the battery cell housing. According to an advantageous embodiment of the invention, the thermal separation element is compressible, in particular elastically compressible. In addition to thermal protection, the inclusion of the thermal break element offers the advantage that the temperature-, charge-cycle-, and age-dependent expansion of the cell active material (anode and cathode active material), known as "swelling" and "breathing," can be partially or completely compensated for by compressing the thermal break element. This reduces the mechanical stress on the cell casing. Cracking of the cell casing due to swelling stress can thus be advantageously delayed or prevented. This has a particularly positive effect on prismatic cell casings. Further advantages and application possibilities of the invention will become apparent from the following description in conjunction with the embodiment shown in the drawing. In the drawing: Fig. 1 represents a battery cell according to the invention as a prismatic battery cell; Fig. 2 represents a battery cell according to the invention based on a cylindrical cell. Fig. 1 shows a schematic sectional view of a battery cell 10 according to the invention. The battery cell 10 comprises a cell housing 12 in which a plurality of battery cell components 30 are accommodated. In the present embodiment, the battery cell 10 is designed in the form of a prismatic battery cell. A battery cell element 30 comprises two contact elements 32 and 34, namely an anode contact 32 and a cathode contact 34. Within the cell housing 12, a cathode active material 38 and an anode active material 36 are accommodated, the cathode active material 38 being conductively connected to the cathode contact 34 and the anode active material 36 being conductively connected to the anode contact 32, the anode active material 36 and the cathode active material 38 being separated from each other, in particular by an ion-permeable separator. The cell housing 12 is optionally filled with a liquid electrolyte in a known manner. In the prismatically designed battery cell 10 described here, the battery cell elements 30 are arranged in layers. According to the invention, a thermal break element 40 is provided within the cell housing 12, which is inserted between two battery cell sub-elements 30. In the exemplary embodiment described here, the thermal break element 40 is inserted in the middle of a stack of four layers of battery cell sub-elements 30. The thermal break element 40 thus thermally separates each pair of battery cell sub-elements 30 from each other. In this way, the energy density of the battery cell is not significantly reduced, but the thermal potential is, since only two battery cell sub-elements 30 at a time contribute to thermal runaway, as the other two battery cell sub-elements 30 are thermally insulated from them. Fig. 2 shows a schematic sectional view of a battery cell 60 according to the invention, which corresponds to a basic structure of a round or cylindrical battery cell. This embodiment of the battery cell 60 comprises a cell housing 62, which in cross-section corresponds to two superimposed circles. A thermal break element 80 connects the cell housing 62 along a line that connects the intersection points of the circles. The cell housing 62 is thus symmetrically divided into two equally sized receiving spaces 64, 68. Each receiving space 64, 68 has a battery cell sub-element 70, wherein the battery cell sub-elements 70 are largely thermally decoupled from one another by the thermal break element 80. Overheating of one battery cell sub-element 70 therefore does not lead to a transmission of thermal runaway to the second battery cell sub-element 70.The thermal energy released at a specific point in a battery cell according to the invention is correspondingly lower than without the thermal partition 80 according to the invention. Because the maximum temperature produced in the battery cell 60 during a thermal runaway is significantly lower compared to a battery cell with a comparable energy density, the probability of the battery cell bursting and the thermal runaway being transmitted to neighboring battery cells can be significantly reduced. A battery cell sub-element 70, as is typical for cylindrical cells, is formed by an anode active material 76 and a cathode active material 78, which are contacted via – shown here only schematically – an anode contact 76 and a cathode contact 78, respectively. The anode contacts 76 of the two battery cell sub-elements 70 are connected to form a cell anode contact.

Claims

Battery cell (10; 60), comprising at least one battery cell sub-element (30; 70), wherein a battery cell sub-element (30; 70) has two contact elements (32, 34; 72, 74), an anode contact (32; 72) and a cathode contact (34; 74), wherein the battery cell (10; 60) further comprises a cell housing (12; 62) in which an anode active material (36; 76) and a cathode active material (38; 78) are accommodated, wherein the cathode active material (38; 78) is electrically connected to the cathode contact (34; 74) and the anode active material (36; 76) is electrically connected to the anode contact (32; 72), wherein the anode active material (36; 76) and the cathode active material (38; 78) are electrically insulating but ionically conductive (electrolytically) connected, in particular by a separator, are separated from each other, characterized in that at least one thermal separating element (40; 80) is arranged in the cell housing (12; 62), which divides the interior of the cell housing (12; 62) into at least two receiving spaces (14, 18;64, 68) divides, wherein each of the at least two receiving spaces (14, 18; 64, 68) has at least one battery cell sub-element (30; 70), wherein the respective anode contacts (32; 72) and the cathode contacts (34; 74) are connected to each other, wherein the thermal separator element (40; 80) has a higher temperature resistance and a higher thermal resistance than the separator.; Battery cell according to claim 1, characterized in that the thermal separating element (40;80) is located in the middle, in particular in a plane of symmetry of the cell housing (12;62). Battery cell according to one of the preceding claims, characterized in that the thermal separation element (40, 80) has a temperature resistance that is greater than the temperature resistance of the separator, Battery cell according to one of the preceding claims, characterized in that the thermal separating element (40, 80) has a temperature resistance of more than 120°C, in particular more than 150°C. Battery cell according to one of the preceding claims, characterized in that the thermal separating element (40, 80) is compressible, in particular elastically compressible. Battery cell according to one of the preceding claims, characterized in that the cell housing (62) has a cross-section formed by at least two circular areas, wherein the thermal separating element (80) runs along the line connecting the two points of intersection of the two circular areas. Battery cell according to one of the preceding claims 1 to 5, characterized in that the battery cell is a prismatic battery cell, wherein the battery cell sub-elements (30) are formed in layers and a thermal separating element (80) is incorporated in at least half of the battery cell sub-elements (30).

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