Battery system and electric vehicle including improved cell cover

Abstract

A battery system and an electric vehicle are provided. The battery system includes: a plurality of battery cells each having an exhaust gas outlet for discharging an exhaust gas flow at an exhaust gas side thereof; a first cover sheet having a first thickness covering the exhaust side of the battery cells to protect the battery cells from exhaust airflow discharged from adjacent ones of the battery cells, and having an exhaust opening aligned with the exhaust outlet of the battery cells for passing the discharged exhaust airflow therethrough; and a second cover sheet having a second thickness disposed between the first cover sheet and the plurality of battery cells to cover the exhaust outlets of the battery cells. The second cover sheet is configured to rupture at a section opposite the exhaust outlet due to the discharged exhaust gas flow exiting the covered exhaust outlet, and the first thickness is greater than the second thickness.

Description

Technical Field

[0001] The embodiments of this disclosure relate to battery systems. Background Technology

[0002] Recently, vehicles using electricity as a power source for transporting goods and people have been developed. Such electric vehicles are automobiles that are permanently or temporarily propelled by an electric motor using energy stored in rechargeable batteries. Electric vehicles can be powered solely by batteries (so-called battery electric vehicles "BEVs"), or they can include a combination of an electric motor and, for example, a conventional internal combustion engine (so-called plug-in hybrid electric vehicles "PHEVs"). BEVs and PHEVs use high-capacity rechargeable batteries designed to provide propulsion for a continuous period of time.

[0003] Generally, a rechargeable (or secondary) battery cell includes an electrode assembly comprising a positive electrode, a negative electrode, and a separator interposed between the electrodes. A solid or liquid electrolyte allows ions to move during the charging and discharging of the battery cell. The electrode assembly is located (e.g., housed in) a casing, and electrode terminals located on the outside of the casing establish conductive connections to the electrodes. The casing may have, for example, a cylindrical or rectangular shape.

[0004] A battery module is formed by connecting multiple battery cells together in series or parallel. For example, a battery module is formed by interconnecting the electrode terminals of multiple battery cells in a number and configuration depending on the desired power amount to provide a high-power rechargeable battery.

[0005] Battery modules can be constructed using either a block design or a modular design. In a block design, each battery cell is integrated into a common current collector structure and a common battery management system, and the cells are arranged within a housing. In a modular design, multiple battery cells are connected together to form sub-modules, and several sub-modules are connected together to form a battery module. In automotive applications, battery systems typically consist of multiple battery modules connected in series to provide the desired voltage.

[0006] A battery pack is a group of any number (typically identical) battery modules or individual battery cells. Battery modules (or individual battery cells) can be configured in series, parallel, or a combination of both to provide desired voltage, capacity, and / or power density. The components of a battery pack include individual battery modules and interconnections that provide conductivity between the battery modules.

[0007] Active or passive thermal management systems can be included to provide thermal control of the battery pack and ensure safe operation of the battery module by effectively dissipating, releasing, and / or dissipating heat generated from its rechargeable cells. If heat dissipation / release / dissipation is not adequately performed, temperature deviations may occur between individual battery cells, causing the battery module to potentially fail to produce the desired (or designed) power output. Furthermore, increased internal temperatures may lead to abnormal reactions within the battery, thus potentially degrading the charging and discharging performance of the rechargeable battery and shortening its lifespan.

[0008] The exothermic decomposition of a single cell can lead to what is known as thermal runaway. Generally, thermal runaway describes a process accelerated by rising temperatures, releasing energy that further increases in temperature. Thermal runaway occurs when rising temperatures alter conditions in a way that causes further increases in temperature, often resulting in destructive consequences. In rechargeable battery systems, thermal runaway is associated with a strongly exothermic reaction accelerated by rising temperatures. During thermal runaway, the temperature of a single cell rises extremely rapidly, and the stored energy is released very suddenly. In extreme cases, thermal runaway can cause a single cell to explode and ignite a fire. In rare cases, it can damage a single cell beyond repair.

[0009] When a battery cell is heated above a critical temperature (e.g., above approximately 150°C), it can enter thermal runaway. Generally, temperatures outside the safe zone on the low or high side can cause irreversible damage to the battery cell, potentially triggering thermal runaway. Thermal runaway can also occur due to internal or external short circuits within the battery cell or due to poor battery maintenance. For example, overcharging or fast charging can lead to thermal runaway.

[0010] During thermal runaway, the faulty battery cell can reach temperatures exceeding approximately 700°C. Furthermore, large amounts of hot gases are ejected from the inside of the faulty cell through vents in the cell casing into the battery pack. The main components of the emitted gases are H2, CO2, CO, electrolyte vapor, and other hydrocarbons. Therefore, the emitted gases are flammable and potentially toxic. The emitted gases also cause an increase in internal gas pressure within the battery pack. In the worst-case scenario, the high temperature causes this process (e.g., thermal runaway) to spread to adjacent cells and lead to a fire within the battery pack. At this stage, the fire is difficult to extinguish.

[0011] The conventional venting design for battery modules involves allowing the exhaust gas from the individual battery cells to expand into the battery casing and escape to the outside (e.g., to the environment surrounding the battery casing) through a casing vent valve. However, this design causes the exhaust gas to heat components inside the battery casing, such as other battery cells. Furthermore, particles from the exhaust gas can deposit on the battery cells, which can lead to heat propagation and potentially trigger thermal runaway in adjacent battery cells. To protect the battery cells, a cover element can be provided that covers the venting side of the battery cells.

[0012] Such a cover element can have a through-hole-shaped vent opening aligned with the vent outlet of a battery cell to allow vent gas to pass through the cover element in the event of thermal runaway in one of the covered battery cells. After passing through the cover element, particles of the discharged vent gas can deposit on the cover element. However, particles of the vent gas can pass through another vent opening in the cover element aligned with the vent outlet of another battery cell and can come into contact with (or enter) said other battery cell. This can lead to heat propagation to said other battery cell and, in the worst case, trigger thermal runaway in said other battery cell. Summary of the Invention

[0013] Embodiments of this disclosure provide a battery system that can more safely handle thermal runaway in one or more of its individual cells.

[0014] This disclosure is defined by the appended claims and their equivalents. The following description is subject to this limitation. Any disclosure outside the scope of the claims and their equivalents is intended for illustrative and comparative purposes.

[0015] According to one embodiment of this disclosure, a battery system includes: a plurality of battery cells, each battery cell having an exhaust outlet for discharging an exhaust gas flow on its exhaust side; a first cover having a first thickness, covering the exhaust side of the battery cells to protect the battery cells from the exhaust gas flow emitted from adjacent battery cells, the first cover having an exhaust opening aligned with the exhaust outlet of the battery cells for allowing the discharged exhaust gas flow to pass through the first cover; and a second cover having a second thickness, disposed between the first cover and the plurality of battery cells. The second cover covers the exhaust outlet of the battery cells and is configured to rupture at a section opposite the exhaust outlet due to the discharged exhaust gas flow exiting the covered exhaust outlet. The first thickness is greater than the second thickness.

[0016] According to embodiments of this disclosure, the first cover and the second cover may include heat-resistant materials.

[0017] According to embodiments of this disclosure, the first cover sheet and the second cover sheet may be mica sheets.

[0018] According to embodiments of this disclosure, the first cover and the second cover can be made of the same material.

[0019] According to embodiments of this disclosure, the first thickness can be 3 to 20 times larger than the second thickness.

[0020] According to embodiments of this disclosure, the first thickness can be 5 to 10 times larger than the second thickness.

[0021] According to embodiments of this disclosure, the first thickness may be at least 2 mm, at least 3 mm, or at least 5 mm.

[0022] According to embodiments of this disclosure, the second thickness may be 0.2 mm or less, or 0.15 mm or less, or 0.1 mm or less.

[0023] According to embodiments of this disclosure, the second cover can be located directly on the battery cell.

[0024] According to embodiments of this disclosure, the second cover can be adhered to the battery cell.

[0025] Another embodiment of this disclosure provides a vehicle including the battery system described above.

[0026] Further aspects and features of this disclosure may be learned from the dependent claims and / or the following description. Attached Figure Description

[0027] The aspects and features of this disclosure will become apparent to those skilled in the art from the detailed description of embodiments thereof with reference to the accompanying drawings, in which:

[0028] Figure 1 This is a schematic cross-sectional view of a battery system according to an embodiment of the present disclosure.

[0029] Figure 2 yes Figure 1 A perspective view of a portion of the battery system shown.

[0030] Some figure labels

[0031] 11. Wall components of the battery casing

[0032] 12 battery cells

[0033] 12a battery cell that experienced thermal runaway

[0034] Top side of 13 battery cells

[0035] 14 exhaust outlets

[0036] 16 exhaust channels

[0037] 20 First cover plate

[0038] 22 exhaust openings

[0039] 30 Second cover plate

[0040] 32. The section of the second cover opposite the exhaust outlet

[0041] 100 battery system

[0042] V exhaust airflow

[0043] t1 first thickness

[0044] t2 second thickness Detailed Implementation

[0045] Description of embodiments will now be given in detail, examples of which are illustrated in the accompanying drawings. Aspects and features of this disclosure and methods of implementation thereof will be described with reference to the drawings. However, this disclosure may be embodied in various different forms and should not be construed as limited to the embodiments shown herein. Rather, these embodiments are provided as examples so that this disclosure will be thorough and complete and will fully convey to those skilled in the art the aspects and features of this disclosure.

[0046] Therefore, processes, elements, and techniques that are not considered necessary for a person skilled in the art to have a full understanding of the aspects and features of this disclosure may be omitted or only briefly described. It will be understood that when an element or layer is referred to as being "on" another element or layer, "connected" to another element or layer, or "bonded" to another element or layer, it may be directly on, directly connected to, or directly bonded to the other element or layer, or one or more intermediary elements or layers may be present. When an element or layer is referred to as being "directly on" another element or layer, "directly connected" to another element or layer, or "directly bonded" to another element or layer, there are no intermediary elements or layers. For example, when a first element is described as being "bonded" or "connected" to a second element, the first element may be directly bonded or connected to the second element, or the first element may be indirectly bonded or connected to the second element via one or more intermediary elements.

[0047] In the accompanying drawings, the dimensions of various elements, layers, etc., may be exaggerated for clarity of illustration. The same reference numerals denote the same elements. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. Furthermore, when describing embodiments of this disclosure, the use of "may" refers to "one or more embodiments of this disclosure." Expressions such as "at least one of" and "any one of" modify the entire list of elements when following it, without modifying any individual element of the list. For example, the expression "at least one of a, b, or c" means only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or variations thereof. As used herein, the terms "use," "using," and "being used" may be considered synonymous with the terms "utilize," "exploit," and "be exploited," respectively.

[0048] It will be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers, and / or segments, these elements, components, regions, layers, and / or segments should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or segment from another element, component, region, layer, or segment. Therefore, the first element, component, region, layer, or segment discussed below may be referred to as the second element, component, region, layer, or segment without departing from the teachings of the exemplary embodiments.

[0049] For ease of description, spatial relation terms such as “below,” “under,” “down,” “above,” and “above” are used herein to describe the relationship of an element or feature to other elements or features as shown in the figures. It will be understood that, in addition to the orientations depicted in the figures, the spatial relation terms are also intended to cover different orientations of the device in use or operation. For example, if the device in the figure is flipped, an element described as “below” or “under” other elements or features will be oriented “above” or “above” said other elements or features. Therefore, the term “below” can encompass both above and below orientations. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatial relation descriptions used herein should be interpreted accordingly.

[0050] The terminology used herein is for the purpose of describing embodiments of this disclosure and is not intended to be limiting of this disclosure. As used herein, the singular form “a” is also intended to include the plural form unless the context clearly indicates otherwise. It will also be understood that, when used in this specification, the terms “comprising,” “including,” “containing,” and / or “comprising” indicate the presence of the stated features, integrals, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof.

[0051] In view of the whole of this disclosure, those skilled in the art will understand that each suitable feature of the various embodiments of this disclosure may be combined in part or in whole, or combined with each other, and may be technically linked and operated in a variety of suitable ways, and each embodiment may be implemented independently of or in combination with each other in any suitable way, unless otherwise stated or implied.

[0052] As used herein, the terms “substantially,” “about,” and similar terms are used as approximate terms rather than as terms of degree, and are intended to describe the inherent deviations in measured or calculated values ​​that would be recognized by one of ordinary skill in the art. Furthermore, if the term “substantially” is used in combination with a feature that can be expressed numerically, the term “substantially” indicates a range of values ​​centered at + / - 5%.

[0053] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will also be understood that terms (such as those defined in common dictionaries) shall be interpreted as having the meaning consistent with their meaning in the context of the relevant field and / or in the context of this specification, and shall not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0054] According to one embodiment of this disclosure, a battery system includes a plurality of battery cells. The battery cells may be housed within a battery casing of the battery system. The battery cells may be arranged or stacked along a stacking direction to form one or more cell stacks. The battery cells may be interconnected via electrical connectors (e.g., busbars) contacting the respective electrode terminals of the battery cells to form one or more battery modules / packs. The battery cells may be arranged to form one or more battery packs. In a battery pack, the battery cells may be electrically interconnected, for example, in series and / or in parallel. Multiple battery packs may form a battery module. The battery cells may be, for example, prismatic or cylindrical cells.

[0055] Each battery cell has an exhaust outlet on the exhaust side of the battery cell, which may be the terminal side of the battery cell where the electrode terminals of the battery cell are located. Each exhaust outlet is configured to allow exhaust gas flow to be discharged from the respective battery cell during thermal runaway of the corresponding battery cell. An exhaust valve may be provided at (or in) the exhaust outlet, which may open (e.g., burst or rupture) when a reference pressure (e.g., a predetermined pressure) is exceeded.

[0056] The battery system further includes a first cover having a first thickness. The first cover is configured to cover the venting side of a plurality of battery cells. In some embodiments, the first cover covers all of the battery cells (e.g., the first cover extends above the venting side of all the battery cells). The venting side of a battery cell may be the top side of the battery cell. The first cover may, for example, cover the top side of the battery cell, and thus may form a first top cover. The top side of the battery cell is the side of the battery cell facing upwards at the intended use location of the battery system (e.g., the mounting location of the battery system inside an electric vehicle).

[0057] A first cover plate covers the battery cell to protect it from exhaust products that can be emitted by one or more exhaust gas streams from the battery cell during thermal runaway. For example, the first cover plate may completely cover the exhaust side of the battery cell (e.g., the entire top side) except for the exhaust outlet. The first cover plate has an exhaust opening aligned with each exhaust outlet of the battery cell. The first cover plate has an exhaust opening in the form of a through-hole, and each exhaust opening is aligned with one of the exhaust outlets of the battery cell, such that exhaust gas streams exiting one of the battery cells via its exhaust outlet can pass through the corresponding exhaust opening and thus through the first cover plate. The first cover plate may be a heat-resistant cover plate, allowing it to withstand the temperature of the exhaust gas streams. Particles from the exhaust gas streams can deposit on the first cover plate without damaging it. The first cover plate prevents heat transfer from the exhaust gas streams to the battery cell.

[0058] The battery system further includes a second cover having a second thickness. The second cover is disposed between the first cover and the venting sides of the plurality of battery cells. The second cover may be disposed directly on the venting side of the battery cells (e.g., it may be adhered to or sealed to the venting side of the battery cells). In some embodiments, the second cover covers all of the plurality of battery cells (e.g., the second cover extends over the venting sides of all of the plurality of battery cells). The second cover also covers the venting outlet of the battery cells. In other words, the second cover extends over the venting side (e.g., the top side) of the battery cell that includes the venting outlet. The second cover may form a second top cover. The second cover may completely cover the venting side (e.g., the entire top side) of the battery cell that includes the venting outlet. That is, while the first cover does not cover the venting outlet of the battery cell, the second cover covers the venting outlet.

[0059] The second cover is configured to rupture (e.g., burst or break) at a section opposite (e.g., aligned with) the exhaust outlet due to the pressure of the exhaust gas flow leaving the covered exhaust outlet. In other words, the second cover is configured such that it cannot withstand the pressure exerted on it by the exhaust gas flow leaving one of the covered battery cells. Therefore, when one of the battery cells experiences thermal runaway, the hot exhaust gas flow leaves the affected battery cell at its exhaust outlet and causes the second cover to rupture. The second cover may be configured to burst based on its material and / or thickness. For example, the second cover may have a thickness small enough that it ruptures when exhaust pressure is applied to it, but also large enough that it can withstand any particles deposited on it from the other side.

[0060] However, the first cover sheet must withstand these pressures. Therefore, the first thickness is greater than the second thickness. In other words, the second cover sheet has a thinner thickness than the first cover sheet. The second cover sheet can have a uniform thickness. That is, the second cover sheet can have the same thickness in the section opposite the exhaust outlet as in the surrounding sections and in any other sections besides the section opposite the exhaust outlet. The section of the second cover sheet opposite the exhaust outlet can be a portion (or multiple portions) of a uniform sheet aligned with the exhaust outlet and exhaust opening. The second cover sheet can be a heat-resistant cover sheet, allowing it to withstand particles deposited on the second cover sheet from the exhaust gas flow without damage. Furthermore, the second cover sheet covering the exhaust outlet prevents any external contaminants (such as moisture or other particles) from entering the battery cell through its exhaust outlet during normal operation.

[0061] The exhaust gas stream emitted by one of the battery cells that has experienced thermal runaway can exit (e.g., exit) the exhaust outlet of the affected battery cell, causing a corresponding section of the second cover plate opposite the exhaust outlet to rupture, pass through the second cover plate, enter and pass through the exhaust opening of the first cover plate, and thus pass through the first cover plate. The exhaust gas stream ejected in this manner is kept away from the other battery cells in the battery system by the first and second cover plates.

[0062] For example, the exhaust gas flow can contact the outer side of the first cover and, at the exhaust opening, contact the lower second cover (e.g., the section of the lower second cover opposite the exhaust outlet and facing the exhaust opening). However, the exhaust gas flow, even when passing through another exhaust opening, cannot enter another battery cell because the exhaust outlet of the battery cell is covered and sealed by the second cover. For example, particles from the exhaust gas flow can deposit on the first cover and at the exhaust opening of the first cover on the section of the second cover below the exhaust opening, but may not reach the battery cell below. The ruptured section of the second cover will only rupture under the high pressure that occurs during thermal runaway of the battery cell with its exhaust outlet aligned with it. This pressure can be increased because the second cover seals the exhaust outlet.

[0063] The two covers combine the protective advantages of a thicker cover in the section corresponding to the vent opening with the protective advantages of a thinner cover. The two covers provide a combined single-cell cover that is stable enough to protect the battery cell on the one hand, and fragile enough to allow venting on the other. Placing the thinner second cover on top of the thicker first cover risks the thinner second cover bending outwards, allowing vented gas to flow between the covers towards adjacent battery cells; however, placing the thinner second cover under the thicker first cover prevents this. Furthermore, placing the thinner second cover under the thicker first cover facilitates the breakage of the thinner second cover, as it can rest against (e.g., be guided by) the edge of the vent opening of the thicker first cover. That is, during breakage, the second cover can be held in place by the first cover.

[0064] According to an embodiment, the first cover sheet and / or the second cover sheet is a mica sheet. In other words, the first cover sheet and / or the second cover sheet may comprise mica silicate minerals. This mica sheet is heat-resistant. Furthermore, this mica material may be a suitable material for the second cover sheet because, within a suitable thickness range, the mica sheet or the second cover sheet comprising mica allows the second cover sheet to break as intended, while being able to withstand any particles deposited on the second cover sheet.

[0065] According to the embodiment, the first cover and the second cover are made of the same material. For example, the first cover and the second cover can be mica sheets. Choosing the same material (such as mica) for both the first cover and the second cover can provide the advantages of providing protection and allowing venting in a simple structural manner. As mentioned above, mica sheets are heat-resistant and therefore very suitable for use as the first cover and the second cover.

[0066] According to one embodiment, the first thickness is about 3 to about 20 times greater than the second thickness. According to another embodiment, the first thickness is about 5 to about 10 times greater than the second thickness. That is, the first cover can be about 3 to about 20 times thicker than the second cover, or about 5 to about 10 times thicker. This thickness difference between the cover pieces within this range can support the fracture of the thinner second cover piece because it can be adequately held in place so that when exposed to the high pressure of the exhaust gas flow, it can rest against the edge of the exhaust opening of the thicker first cover piece.

[0067] According to the implementation, the first thickness is at least about 2 mm, or at least about 3 mm, or at least about 5 mm. In other words, the first cover can have a thickness of at least about 2 mm, at least about 3 mm, or at least about 5 mm. The first cover can have a uniform thickness and therefore can have a thickness of at least about 2 mm, at least about 3 mm, or at least about 5 mm over its entire extension. A first cover with this thickness can provide the intended protection against exhaust gases and particles and can support the fracture of a thinner second cover.

[0068] According to the embodiment, the second thickness is about 0.2 mm or less, or about 0.15 mm or less, or about 0.1 mm or less. In other words, the second cover can have a thickness of about 0.2 mm or less, or about 0.15 mm or less, or about 0.1 mm or less. The first cover can have a uniform thickness, and therefore can have a thickness of at least about 2 mm, or at least about 3 mm, or at least about 5 mm over its entire extension. The second cover with this thickness can ensure the intended breakage of the second cover while reliably preventing exhaust gases and particles emitted by other battery cells from contacting adjacent battery cells.

[0069] According to one embodiment, the second cover is directly disposed on the battery cell on the venting side of the battery cell. In other words, the second cover can be directly disposed on the battery cell without any inserted sheets or elements. For example, according to one embodiment, the second cover is adhered to and thus sealed to the battery cell. For example, the second cover can be glued to the battery cell. Furthermore, the second cover can be pressed onto the battery cell by the first cover. The second cover, which is directly disposed on and / or adhered to and / or pressed onto the battery cell, can provide a suitable (or sufficient) pressure increase during thermal runaway, such that the section of the second cover opposite the venting outlet of the thermally runaway battery cell can rupture as intended.

[0070] Embodiments of this disclosure also provide an electric vehicle that includes a battery system as described herein, for example, as a traction battery.

[0071] Figure 1 and Figure 2 A battery system 100 according to an embodiment of the present disclosure is illustrated schematically.

[0072] The battery system 100 includes a plurality of battery cells 12 arranged to form a stack of cells. Each battery cell 12 includes, on its exhaust side, an exhaust outlet 14 for discharging an exhaust gas flow in the event of thermal runaway (e.g., if thermal runaway occurs). Each exhaust outlet 14 may include an exhaust valve. The exhaust side of the battery cell 12 may form (or may be) a top side 13 of the battery cell 12. The plurality of battery cells 12 may be arranged inside a battery housing, with only the wall member 11 of the battery housing shown. The wall member 11 is arranged opposite to (e.g., above and facing) the top side 13 of the battery cells and defines (e.g., defines or forms) an exhaust passage 16.

[0073] A heat-resistant first cover 20 of the battery system 100 is disposed on the top side 13 of the battery cell 12. The first cover 20 may be a mica sheet. The first cover 20 may have a uniform first thickness t1, for example, about 2 mm. The first cover 20 has a vent opening 22 in the form of a through hole, and the vent opening 22 is aligned with the vent outlet 14 of the battery cell 12 to allow exhaust gas flow from the vent outlet 14 to pass through the first cover 20. Except for the vent outlet 14 where the vent opening 22 is disposed (or except for the vent outlet 14 where the vent opening 22 is disposed), the first cover 20 may completely cover the top side 13 of the plurality of battery cells 12.

[0074] The battery system 100 further includes a heat-resistant second cover 30 disposed between the first cover 20 and the plurality of battery cells 12. The second cover 30 may be a mica sheet. The second cover 30 may have a uniform second thickness t2, for example, about 0.2 mm. The second cover 30 may completely cover the plurality of battery cells 12 on the top side 13 including the vent outlet 14. Therefore, the second cover 30 may be (or may be formed) a continuous layer. The second cover 30 may be adhered (e.g., glued) to the top side 13 of the battery cells 12 and / or may be pressed against the top side 13 of the battery cells 12. Thus, the second cover 30 seals the vent outlet 14 relative to the vent passage 16. The second cover 30 is configured to rupture at a section 32 opposite (e.g., aligned) to the vent outlet 14 in the event of thermal runaway due to the pressure of the discharged vent gas flow leaving the covered vent outlet 14.

[0075] exist Figure 1 In this process, one of the multiple battery cells 12, 12a, is experiencing (or undergoing) thermal runaway, and therefore, an exhaust gas flow V is released from its exhaust outlet 14. This causes an increase in pressure below the second cover 30, and consequently causes the section of the second cover 30 opposite (e.g., aligned with) the exhaust outlet 14 to rupture. Therefore, the seal provided by the second cover 30 is breached (or ruptured) above the affected battery cell 12, and the exhaust gas flow V can pass through the second cover 30. Figure 1 As indicated by the arrow, the exhaust airflow V then passes through the corresponding exhaust opening 22 in the first cover 20, and thus through the first cover 20 and into the exhaust passage 16. The exhaust airflow V can then be deflected by the opposing wall member 11 and can expand along the exhaust passage 16 (e.g., can flow along the exhaust passage 16).

[0076] During this process, the exhaust gas flow V can flow into the exhaust opening 22 aligned with other battery cells in the battery cell 12, but is blocked by the second cover 30. Therefore, the second cover 30 prevents the exhaust gas flow V from reaching other battery cells 12, and thereby prevents the thermal propagation of thermal runaway to adjacent battery cells 12.

[0077] The first cover 20 protects the top side 13 of the battery cell 12 from the exhaust products of the exhaust gas flow and can hold (or fix) the second cover 30 in place during breakage. For example, placing the thinner second cover 30 below the thicker first cover 20 helps (or guides or controls) the breakage of the thinner second cover 30 because it can rest against the edge of the exhaust opening 22 of the thicker first cover 20. The thicker first cover 20 prevents the thinner second cover 30 from being bent outward by the exhaust gas flow V, which would otherwise cause the exhaust gas to flow between the first cover 20 and the second cover 30 toward the adjacent battery cell 12. The first cover 20 has a first thickness t1, for example, about 2.0 mm, and the second cover 30 has a second thickness t2, for example, about 0.2 mm, and both the first cover 20 and the second cover 30 may include mica (or may be made of mica) to provide sufficient protection for the battery cell 12 from the exhaust gas flow V while allowing the second cover 30 to be broken by the exhaust gas pressure.

Claims

1. A battery system, comprising: Multiple battery cells, each of which has an exhaust outlet for discharging exhaust gas flow on its exhaust side; A first cover sheet having a first thickness covers the exhaust side of the battery cell to protect the battery cells in the battery cell from the exhaust airflow emitted from adjacent battery cells in the battery cell. The first cover sheet has an exhaust opening aligned with the exhaust outlet of the battery cell for allowing the emitted exhaust airflow to pass through the first cover sheet. as well as A second cover sheet having a second thickness is disposed between the first cover sheet and the plurality of battery cells, the second cover sheet covering the exhaust outlet of the battery cells, and the second cover sheet being configured to rupture at a section opposite the exhaust outlet due to the exhaust gas flow exiting the covered exhaust outlet. The first thickness is greater than the second thickness.

2. The battery system according to claim 1, wherein, The first cover and the second cover comprise heat-resistant materials.

3. The battery system according to claim 1, wherein, The first cover and the second cover are made of the same material.

4. The battery system according to claim 1, wherein, The first cover and the second cover are mica sheets.

5. The battery system according to claim 1, wherein, The first thickness is 3 to 20 times larger than the second thickness.

6. The battery system according to claim 5, wherein, The first thickness is 5 to 10 times larger than the second thickness.

7. The battery system according to claim 1, wherein, The first thickness is at least 2 mm.

8. The battery system according to claim 1, wherein, The second thickness is 0.2 mm or less.

9. The battery system according to claim 1, wherein, The second cover is located directly on the battery cell.

10. The battery system according to claim 1, wherein, The second cover is adhered to the battery cell.

11. An electric vehicle comprising a battery system according to any one of claims 1 to 10.

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