An arrangement and a method for collecting gas from a battery cell

Abstract

An arrangement (20) for collecting gas from a battery cell (1). The arrangement (20) comprises a first part (21), and a second part (22) configured to be threadably engaged with the first part (21). The first part (21) comprises a cover portion (31) configured to provide an enclosed chamber (25) when the arrangement (20) is mounted to a battery cell (1). The first part (21) further comprises a hollow cylindrical portion (36), extending upwards from an upper wall (34) of the cover portion (31), and comprising an internal thread (37). The second part (22) comprises a cylindrical inner wall member (42) having a threaded outer surface (47) adapted to engage with the internal thread (37) of the cylindrical portion of the first part. The second part (22) further comprises a cylindrical outer wall member (43) coaxially arranged with the inner wall member, a top wall member (44) arranged to connect the inner wall member (42) to the outer wall member (43), and a bottom wall member (45) connected to the inner wall member, the bottom wall member (45) fixedly supporting a hollow needle (40) or drill adapted for puncturing the battery cell (1).

Description

The present disclosure relates in general to an arrangement for collecting gas from a battery cell. The present disclosure also relates in general to a method for collecting gas from a battery cell.BACKGROUNDThe electrification of vehicles has led to a lot of research being focused on energy storage devices that may be used for powering electrical propulsion units of vehicles. One of the most important issues to consider is the service life of the energy storage device as it directly affects the total life cost of the vehicle.Energy storage devices for vehicles require many electrochemical cells to achieve the desired capacity. Energy storage devices for vehicles may for example comprise one or more battery packs. Each battery pack may in turn comprise a plurality of battery modules, and each battery module may comprise a plurality of battery cells, each comprising an electrochemical cell. The most frequently used electrochemical cells today in energy storage devices for vehicles are secondary lithium-ion electrochemical cells. The battery cells may be classified as cylindrical cells, prismatic cells or pouch cells depending e.g. on their geometrical configuration.In general, cylindrical cells can be produced faster and therefore at lower cost than prismatic battery cells. However, prismatic cells typically allows for higher capacity and a much more efficient use of space in view of their shape, which are factors that are very important within the automotive industry. Furthermore, prismatic cells have the advantage of higher capacity as they can be stacked up better in their rigid casings compared to pouch cells which have a flexible outer casing. Moreover, the prismatic cells are typically less susceptible to damage caused by high temperatures and humidity compared to pouch cells. Therefore, prismatic battery cells are often used in energy storage devices for vehicles, especially in heavy vehicles.The service life of a battery cell is dependent e.g., of the selection of constituent materials (such as electroactive materials and composition of electrolyte) and how the battery cell is structured (such as configuration of electrode assembly). The service life may also be affected by how the battery cell is arranged in an energy storage device, such as the compressional state of the battery cell or the ability to control temperature of the battery cell. Moreover, the service life of battery cell is also affected by how it is operated. For example, the charging / discharging rate, the state of charge range within which the battery cell is cycled, as well as temperature conditions during charging / discharging may affect aging of the electrochemical cell of the battery cell and thereby the service life.Post-mortem analysis of battery cells is important in order to gain insight for improving future battery designs, constituent materials, and / or usage strategies. Post-mortem analysis of a battery cell comprises examination and evaluation of a battery cell after it has failed or reached the end of its service life. The purpose of this analysis is to understand the underlying causes of aging / degradation, failure, or performance loss.Post-mortem analysis may typically comprise examination of the surfaces of the electrodes to study aging mechanisms like growth of solid-electrolyte interface (SEI)-layer, lithium plating or dendrite formation, irreversible loss of electroactive material, and / or formation of other unwanted surface compounds. Moreover, the electrolyte may be tested for chemical degradation, contamination, and / or decomposition products. To be able to perform post-mortem analysis, the battery cell firstly needs to be deactivated to prevent e.g., short circuits or electrical chocks. Thereafter, the battery cell can typically needs to be opened in an inert atmosphere (typically in an argon-filled glovebox) e.g., to prevent moisture and oxygen from reacting with the constituent materials / compounds of the electrochemical cell.In order to gain a fuller understanding of the mechanisms leading to loss of performance and / or failure of a battery cell, it would be desirable to also be able to analyze gas generated inside the battery cell during its service life. Gas may be generated inside a battery cell during cycling thereof due to electrolyte decomposition. Electrolyte decomposition may for example generate CO2, O2 and H2. The gas generated inside the battery cell leads to a pressure build-up, and can often lead to swelling of the battery cell can. Thus, analysis of the gas may for example provide further insight into aging mechanisms. Collection of gas generated in the battery cell during its lifetime is not an easy task. Opening of the battery cell in a glovebox inherently leads to the gas contained in the battery cell escaping into the glovebox atmosphere. Therefore, collection of the gas to be analyzed has to be performed before conducting the opening process of the battery cell can normally used for postmortem analysis. The collection of gas naturally has to be conducted under an inert atmosphere for safety reasons as well as to avoid contamination thereof, which would otherwise lead to inaccurate results during analysis. Therefore, collection of gas should be performed in a glovebox. It has previously been proposed to use gas bags for collection of the gas. However, these do typically not work as well, especially not with the relatively low volumes of gas generated, and often suffer from leakage problems.SUMMARYThe object of the present invention is to enable safely extracting and collecting gas from a used battery cell, in particular to allow analysis of said gas.The object is achieved by the subject-matter of the appended independent claim(s).The present disclosure relates to an arrangement for collecting gas from a battery cell. The arrangement comprises a first part, and a second part configured to be threadably engaged with the first part. The first part comprises a cover portion comprising an internal volume configured to provide an enclosed chamber when the arrangement is mounted to a battery cell, said cover portion comprising a peripheral bottom surface configured to face a surface of the battery cell. The first part further comprises a hollow cylindrical portion extending upwards from an upper wall of the cover portion, said hollow cylindrical portion comprising an internal thread and being in fluid communication with the internal volume of the cover portion. The second part comprises a cylindrical inner wall member having a threaded outer surface adapted to engage with the internal thread of the cylindrical portion of the first part. The second part further comprises a cylindrical outer wall member coaxially arranged with the inner wall member. Moreover, the second part comprises a top wall member arranged to connect a top end of the inner wall member to a top end of the outer wall member. The second part also comprises a bottom wall member connected to a bottom end of the inner wall member, the bottom wall member fixedly supporting a hollow needle or drill adapted for puncturing the battery cell.The herein described arrangement provides a glovebox friendly and robust solution for collection of gas from a used battery cell, and which is easy to use and install. More specifically, the herein described arrangement allows for controlled puncturing of a battery cell with a considerably reduced risk of leakage of the gas to be collected. This is inter alia achieved by allowing the punching of a battery cell, through the hollow needle or drill, to be controlled by screwing of the second part relative to the first part. More specifically, the fact that a threaded engagement between the first and second parts of the arrangement is utilized, the movement of the hollow needle or drill relative to a surface of the battery cell may be gradual and smooth. Furthermore, the fact that the first part provides an enclosed chamber when the arrangement is mounted to a battery cell reduces the risk of gas being lost to the surrounding atmosphere when the battery cell is punched.The cylindrical portion of the first part may further comprise an external tread. In such a case, the outer wall member of the second part may have a threaded inner surface adapter to engage with the external thread of the cylindrical portion of the first part. This facilitates screwing the second part of the arrangement on the first part of the arrangement, and thereby also improves the ability to accurately control movement of the hollow needle or drill relative to a battery cell for collection of gas from the interior of the battery cell.The first part may comprise a recess arranged in the peripheral bottom surface of the cover portion, and the arrangement further comprising a first sealing ring arranged in said recess. This further ensures that a gas-tight fit of the first part of the arrangement to a surface of the battery cell is achieved, and thus also that gas escaping from the interior of the battery cell into the enclosed chamber does not leak to the surrounding atmosphere.Additionally, or alternatively, the arrangement may comprise a second sealing ring arranged between the inner wall member and the outer wall member of the second part. This may further ensure that gas from the interior of the battery cell is not leaked, between the first part and the second part of the arrangement, to the surrounding atmosphere.The arrangement may additionally, or alternatively, further comprise a third sealing ring arranged on the upper wall of the cover portion so as to encircle the hollow cylindrical portion of the first part. Thereby, a gas-tight seal between the first and the second part of the arrangement may be achieved when the second part is fully threaded onto the first part, and thereby further reduces the risk of gas leakage to the surrounding atmosphere.The arrangement may further comprise a coupling device configured to be threadably engaged with the second part, said coupling device being configured to allow coupling the arrangement to a gas analysis apparatus. This e.g., allows the arrangement to easily be connected to a gas analysis apparatus such that the gas from the interior of the battery cell may be analyzed directly, if desired.The inner wall member of the second part may comprise a threaded inner surface adapted to allow the above described coupling device to be threadably engaged with the second part. This has the advantage of facilitating connection of the coupling device to the rest of the arrangement.The above mentioned coupling device may be a swivel connector. This has the advantage of allowing screwing the second part of the arrangement without also turning of an end of the coupling device, opposite to the end being connected to the second part, which could otherwise cause e.g., any tubing or the like used for connection to a gas analysis apparatus.The hollow needle or drill may extend through the inner wall member so as to protrude above the top wall member of the second part. In other words, the hollow needle or drill may be arranged so as both of its longitudinal ends extend out from the inner wall member. Thereby, the collection of gas may be further facilitated as the hollow needle or drill may extend into a coupling device connected to the second part of the arrangement.The hollow needle or drill may suitably have a length, between its tip and the bottom wall member of the second part, which ensures that the tip is arranged above a plane of the peripheral bottom surface of the first part at least until the second part has been threaded to 50 % of a maximum thread engagement length of the engagement of the internal thread of the cylindrical portion of the first part and the threaded outer surface of the inner wall member of the second part. This e.g., has the advantage of ensuring that the hollow needle or drill does not risk punching the battery cell before it is safe to do so and the punching process may be accurately controlled.The first part of the arrangement may suitably further comprise a safety valve configured to allow escape of gas from the enclosed chamber at a pressure exceeding a threshold, said safety valve being arranged in the cover portion. This increases the safety when using the arrangement for punching and collecting gas from a battery cell.The present disclosure also relates to a method for collecting gas from a battery cell. The method comprises mounting the above described arrangement on a surface of the battery cell such that the cover portion of the first part of the arrangement forms an enclosed chamber together with the surface of the battery cell and a tip of the hollow needle or drill is arranged at a distance from the surface of the battery cell. The method further comprises screwing the second part of the arrangement relative to the first part of the arrangement such that the tip of the hollow needle or drill is moved towards the surface of the battery cell and punches the batter cell, and collecting gas flowing through the hollow needle or drill.Suitably, the arrangement is mounted over a safety vent of the battery cell and the hollow needle or drill is controlled to punch said safety vent. It is typically considerably easier to punch the safety vent compared to the battery cell can, which means that less force needs to be used for punching the battery cell if punched at the safety vent. This in turn also improves the ability to accurately control the process and increases safety.BRIEF DESCRIPTION OF DRAWINGSFig. 1 illustrates a perspective view of an example of a battery cell,Fig. 2 illustrates a perspective view of an example of a previously known battery cell where a portion of the cell case has been omitted for the purpose of illustrating an electrode assembly of the battery cell,Fig. 3 illustrates an exploded perspective and cross sectional view of a first exemplifying embodiment of the herein described arrangement for collecting gas from a battery cell,Fig. 4 illustrates a cross sectional view of a second exemplifying embodiment of the herein described arrangement for collecting gas from a battery cell, when the arrangement is mounted to such a battery cell,Fig. 5 illustrates a cross sectional view of a third exemplifying embodiment of the herein described arrangement for collecting gas from a battery cell, when the arrangement is mounted to such a battery cell,Fig. 6 illustrates a top view of the first part of a fourth exemplifying embodiment of herein described arrangement for collecting gas from a battery cell, andFig. 7 represents a flowchart schematically illustrating one exemplifying embodiment of the herein described method for collecting gas from a battery cell.The invention will be described in more detail below with reference to exemplifying embodiments and the accompanying drawings. The invention is however not limited to the exemplifying embodiments discussed and / or shown in the drawings, but may be varied within the scope of the appended claims. Furthermore, the drawings shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate the invention or features thereof.In the present disclosure, directional terms (such as "upper", "bottom", "top", "upwards", "downwards", "above", etc.) are used for the purpose of describing a relative arrangement of various features as seen in relation to other features of the herein described arrangement. These directional terms shall however not be considered to be limiting to e.g., any orientation of the arrangement during usage thereof.The present disclosure relates to an arrangement for collecting gas from a battery cell. More specifically, the herein described arrangement is adapted for puncturing a battery cell to allow a controlled collection of gas from the interior of the battery cell, for example for allowing analysis of said gas. Such an analysis of the gas collected from the interior of the battery cell may be performed through any previously known technology, such as gas chromatography, various forms of spectrometry, or the like.It should here be noted that although the herein described arrangement has primarily been developed for the purpose of performing post-mortem analysis (i.e. be used for examination of a battery cell after failure or at the end of its service life), the arrangement may also be used when performing in operando (i.e. in situ) analysis. Such in operando may be performed by cycling the battery cell and continuously collecting gas generated inside the battery cell using the herein described arrangement for collecting gas to thereby enable analysis of the gas.The herein described arrangement comprises (or consists of) a first part and a second part, as will be described in more detail below. The first part and the second part of the arrangement are configured to be threadably engaged with each other. The arrangement may further comprise a coupling device configured to allow coupling of the arrangement to, for example, a gas analysis apparatus. Alternatively, in case the coupling device is not part of the arrangement as such, the arrangement may be used together with such a coupling device in order to fluidly connect the arrangement with, for example, a gas analysis apparatus. In any case, the second part of the arrangement may be configured to allow connection to the coupling device, suitably through a threaded engagement. The coupling device may suitably be a swivel connector since this may allow turning of the second part of the arrangement without turning an end of the coupling device, opposite to the end being connected to the second part of the arrangement, when coupling device is connected to the second part. The arrangement may further comprise one or more sealing rings, as will be exemplified below.The first part of the arrangement comprises, or consists of, a cover portion and a hollow cylindrical portion. The cover portion comprises an internal volume configured to provide an enclosed chamber when the arrangement is mounted to a battery cell, and a peripheral bottom surface configured to face a surface of said battery cell. The hollow cylindrical portion extends upwards from an upper wall of the cover portion, comprises an internal thread (i.e. the radially inner surface of the hollow cylindrical portion is threaded), and is in fluid communication with the internal volume of the cover portion. In other words, gas may flow from the internal volume of the cover portion into the hollow cylindrical portion of the first part.The second part of the arrangement comprises a cylindrical inner wall member and a cylindrical outer wall member coaxially arranged with the inner wall member. Said inner and outer wall members are connected to each other via a top wall member of the second part. The cylindrical inner wall member of the second part has a threaded outer surface adapted to engage with the internal thread of the hollow cylindrical portion of the first part of the arrangement. The second part further comprises a bottom wall member connected to a bottom end of the inner wall member. Moreover, the second part comprises a hollow needle or drill fixedly supported by the bottom wall member, said hollow needle or drill being adapted for puncturing the battery cell.Figure 1 illustrates a perspective view of an example of a battery cell 1. The battery cell 1 comprises a cell case 2 configured to encapsulate an electrochemical cell comprising an electrode assembly and an electrolyte. The cell case 2 of the exemplified battery cell 1 has a substantially rectangular configuration and is typically made of a rigid metallic material, e.g., an aluminum based material. Batteries of this type are typically referred to as prismatic cells in the art. Prismatic cells inter alia have the advantage of allowing the batteries to be closely stacked next to each other, such as in a battery module or a battery pack.A first battery terminal 3 and a second battery terminal 4 are shown to be arranged on one side of the cell case 2, more specifically at a top plate 2a of the cell case 2. It should however be noted that the first and second battery terminals 3, 4 may alternatively be arranged on opposing sides of the battery cell 1, if desired. The battery terminals 3, 4 are electrically connected to a respective electrode of an electrode assembly, arranged inside the cell case 2. The electrode assembly forms, together with a liquid electrolyte, the electrochemical cell. Such an electrolyte is typically introduced into the cell case 2, after the electrode assembly has been arranged therein and the cell case 2 welded together, via an electrolyte-injection hole 5 in the cell case 2. The electrolyte-injection hole 5 is thereafter permanently sealed.The battery cell 1 further comprise a safety vent 6 arranged in the cell case 2, such as in the top plate 2a of the cell case 2. Said safety vent 6 is configured to break in case the pressure inside the cell case 2 is increased above a critical threshold, whereby gas may be released from the interior of the cell case 2 to the surrounding atmosphere. The purpose of the safety vent 6 is primarily to avoid an explosion resulting from a considerable increase of pressure inside the cell case 2, for example due to a thermal runaway inside the cell case 2.Figure 2 illustrates a perspective view of an example of a battery cell, such as the battery cell 1 shown in Figure 1, but where an upper portion of the cell case 2, including the top plate 2a of the cell case 2, as well as the constituent components attached to or otherwise arranged at the top plate, have been removed so that the electrode assembly 8 of the electrochemical cell is visible. The electrode assembly 8 is in the figure shown to be rolled into a so called prismatic jelly roll. However, the electrode assembly could alternatively be a stacked electrode assembly or a Z-folded electrode assembly.At the right hand side of Figure 2, a schematical cross-sectional view of (a single turn) of the electrode assembly 8 according to the example is shown in more detail. The electrode assembly 8 comprises a plurality of layers that may be laminated or otherwise attached to each other so as to form a sandwich structure. More specifically, the electrode assembly 8 comprises, or consists of, a first electrode layer 9, a first separator layer 10, a second electrode layer 11, and a second separator layer 12. The first electrode layer 9 may be an anode and the second electrode layer 11 may be a cathode, or vice versa. The first separator layer 10 is arranged between the first electrode layer 9 and the second electrode layer 11. As shown in the figure, the second separator layer 12 may be arranged in the electrode assembly 8 outwardly of the second electrode layer 11. In other words, the second electrode layer 11 may be arranged between the first separator layer 10 and the second separator layer 12. Alternatively, the second separator layer 12 may be arranged outwardly of the first electrode layer 9 such that the first electrode layer 9 is arranged between the first separator layer 10 and the second separator layer 12.The first electrode layer 9 may in turn comprise two first sub-layers 9a and a second sublayer 9b bonded to each other. The second sublayer 9a, which constitutes a current collector, is arranged between the two first sub-layers 9a. Each of the first sub-layer 9a comprises a first electroactive material. Similarly, the second electrode layer 11 comprises two first sub-layers 11a, each of the second sub-layers 11a comprising a second electroactive material. The second electrode layer 11 further comprises a second sub-layer 11b bonded to each of the first sub-layers 11a. The second sublayer 11b of the second electrode layer constitutes a current collector.The first and second electrode layers 9, 11 are, at a respective longitudinal end of the electrode assembly, each attached to a respective electrode tap 13, 14 configured to electrically connect the corresponding electrode to its corresponding battery terminal (compare with battery terminals 3, 4 shown in Figure 1).Figure 3 illustrates an exploded perspective and cross sectional view of a first exemplifying embodiment of the herein described arrangement 20 for collecting gas from a battery cell, such as the battery cell 1 shown in Figure 1. The battery cell 1 (more specifically the top plate 2a of the cell can 2, together with the safety vent 6) is in the figure schematically illustrated with dotted lines in view of not being a part of the arrangement 20. The arrangement 20 comprises a first part 21 and a second part 22. The second part 22 is configured to be threadably engaged with the first part 21 as will be further described below.The first part 21 of the arrangement 20 comprises a cover portion 31. The cover portion 31 comprises an upper wall 34 from which a plurality of side walls 35 extend downwards. The upper wall 34 and the side walls 35 jointly forms an internal volume 30 in the cover portion 31, and the cover portion 31 is open at the bottom. When the arrangement 20 is mounted to a battery cell 1, said internal volume 30 forms an enclosed chamber defined by the cover portion and a surface of the battery cell 1. The cover portion 31 may have a substantially rectangular configuration, as shown in the figure, but is not limited thereto. For example, the cover portion 31 may alternatively have the shape of an elliptic cylinder or a cylinder, in which case the cover portion may be regarded to have a single side surface (a lateral surface) extending downwards from the upper wall 34 and circumscribing the internal volume 30 (instead of a plurality of side surfaces 35 as shown in the figure).The cover portion 31 comprises a peripheral bottom surface 32 configured to face a surface of the battery cell 1 when the arrangement is mounted to the battery cell 1. As shown in the figure, said surface of the battery cell 1 may be the surface of a top plate 2a of the battery cell, and the peripheral bottom surface 32 may be arranged so as circumscribe a safety vent 6 of the battery cell 1. The peripheral bottom surface 32 may be formed at a free end of the side walls 35 opposing the end at which the side wall 35 are connected to the upper wall 34. Moreover, a circumferential recess 33 may be formed in the peripheral bottom surface 32 of the cover portion 31. Said recess is intended to hold, or at least contain, a first sealing ring 26. In other words, a first sealing ring 26 may be arranged in the recess 33. Such a first sealing ring 26 may serve the purpose of preventing leakage of gas from the enclosed chamber formed by the internal volume 30 when the arrangement 20 is mounted to a battery cell 1. The first sealing ring 26 may be regarded as a constituent component of the herein described arrangement 20, or may be regarded as a component separate from the arrangement 20.The first part 21 of the arrangement 20 further comprises a hollow cylindrical portion 36 extending upwards from the upper wall 34 of the cover portion 31. In other words, the hollow cylindrical portion 36 extends from the upper wall 34 in a direction away from the peripheral bottom surface 32 configured to face a surface of a battery cell 1. Moreover, the hollow cylindrical portion 36 comprises an annular top surface 39. The interior of the hollow cylindrical portion 36 is in fluid communication with the internal volume 30 of the cover portion 31. The hollow cylindrical portion 36 of the first part 21 further comprises an internal thread 37 arranged on a radially inner side thereof. The hollow cylindrical portion 36 further comprises an external thread 38 arranged on a radially outer side thereof.The second part 22 of the arrangement 20 comprises a cylindrical inner wall member 42 and a cylindrical outer wall member 43. The cylindrical outer wall member 43 is coaxially arranged with the cylindrical inner wall member 42. Moreover, the cylindrical inner wall member 42 and the cylindrical outer wall member 43 are connected, at their respective top ends, by a top wall member 44 of the second part 22. Thus, the second part 22 of the arrangement 20 may be described to comprise a double-walled cylindrical portion, said double-walled cylindrical portion being formed by the inner and outer wall members 42, 43 together with the top wall member 44. Said double-walled cylindrical portion is adapted to be threaded over the hollow cylindrical portion 36 of the first part 21 of the arrangement such that the inner wall member 42 is arranged radially inwardly of, and the outer wall member 43 is arranged radially outwardly of, the hollow cylindrical portion 36 when gas is to be collected from the interior of a battery cell 1. More specifically, the inner wall member 42 of the second part 22 comprises a threaded outer surface 47 adapted to engage with the internal thread 37 of the hollow cylindrical portion 36 of the first part 21. Moreover, the outer wall member 43 of the second part 22 comprises a threaded inner surface 48 adapted to engage with the external thread 38 of the hollow cylindrical portion 36 of the first part 21.The inner wall member 42 of the second part 22 may further comprise a threaded inner surface 46 configured to allow a coupling device (compare with Figures 4 and 5) to be threadably engaged with the second part 22 of the arrangement 20. Such a coupling device may be a conventional coupling device configured to allow connection to for example a gas analysis apparatus, for example via a tubing. Thus, such a coupling device may, or may not, be considered to be part of the arrangement 20 as such. The coupling device may provide a port to any connection that might be required to for the purpose of connection to a gas analysis apparatus or the like.The second part 22 of the arrangement further comprises a bottom wall member 45 connected to a bottom end of the inner wall member 42. Said bottom wall member 45 may have a conical configuration as shown in the figure, but is not limited thereto. The second part 22 of the arrangement 20 further comprises a hollow needle 40, or alternatively a hollow drill (not shown), which is fixedly supported by the bottom wall member 45. Said hollow needle 40 or drill may be arranged coaxially with the inner wall member 42, and thus also with the outer wall member 43, of the second part 22. The hollow needle 40 or drill is adapted to punch a battery cell 1 (suitably a safety vent 6 of the battery cell 1) and to allow gas from the interior of the battery cell 1 to flow through the hollow needle or drill during collection of said gas. Thus, the hollow needle 40 or drill is arranged to extend at least downwards from the bottom wall member 45. Suitably, the hollow needle 40 or drill may be arranged so as to extend through the whole inner wall member 42, as shown in the figure, such that an upper end of the hollow needle 40 or drill, longitudinally opposite the tip 41 of the hollow needle 40 or drill, extends / protrudes above the top wall member 44 of the second part 22. This allows the hollow needle 40 or drill not only to punch the battery cell 1 when the arrangement is mounted to the battery cell but also to extend into the above described coupling device (even before the coupling device is fully threadably engaged with the second part 22 of the arrangement 22).Although the hollow needle 40 or drill is intended to punch the battery cell 1, it should not do so until it is suitable from a safety perspective and it can be ensured that the punching process may be controlled. In particular, it is important to be able to control the punching process so that the hollow needle 40 or drill does not risk damaging the interior components of the battery cell, such as the electrode assembly. Thus, the hollow needle 40 or drill should have a length between its tip 45 and the bottom wall member 45 which ensures that the second part 22 may start to be threaded on the first part 21 without the tip 41 reaching the surface of the battery cell 1. Therefore, the hollow needle 40 or drill may suitably has a length L between its tip 41 and the bottom wall member 45 of the second part 22 which ensures that the tip 41 is arranged above a plane of the peripheral bottom surface 32 of the first part 21 at least until the second part 22 has been threaded to 50% of a maximum thread engagement length of the engagement of the internal thread 37 of the cylindrical portion 36 and the threaded outer surface 47 of the inner wall member 42. A maximum thread engagement length is here considered to mean the maximum length of interaction (i.e. engagement) between threaded surfaces. In other words, the maximum thread engagement length corresponds to the length of the treaded engagement between the first part and the second part when the second part is fully screwed onto the first part.In the following, it will be described how the above described arrangement 20 may be used for, and functions during, collection of gas from the interior of a battery cell 1.The first part 21 of the arrangement 20 is mounted to a surface of a battery cell 1, suitably over the safety vent 6 of the battery cell, such that the internal volume 30 forms an enclosed chamber (except for the opening between the cover portion 31 and the hollow cylindrical portion 36 of the first part 21) with the surface of the battery cell 1. Before mounting the first part 21 to the battery cell, the first sealing ring 26 may be arranged in the recess 33, to facilitate achieving a gas-tight abutment of the first part 21 to the surface of the battery cell 1. The mounting of the first part 21 to the battery cell may be performed using a range of various techniques, such as through clamping or bolting, and will therefore not be further described herein. The second part 22 of the arrangement 20 is thereafter threaded onto the first part 21 to such an extent that the tip of the hollow needle 40 or drill remains a short distance above the surface of the battery cell to be punched. Moreover, the second part 22 of the arrangement is connected, via the above described coupling device, to for example a gas analysis apparatus. It should here be noted that the threading of the second part to the first part of the arrangement and / or the connection of the second part to the coupling device may be performed in any order, including before the first part of the arrangement being mounted to the battery cell 1, as long as it may be ensured that the tip of the hollow needle 40 or drill does not punch the battery cell 1 before the gas from the interior of the battery cell may be collected as intended.Before punching of the battery cell, it should be ensured that the enclosed chamber is evacuated and suitably also that a low pressure is introduced into the enclosed chamber. Therefore, at least part of the installation of the arrangement on the battery cell may suitably be performed in a glovebox, or the like, under inert atmosphere such that the enclosed chamber is inherently evacuated. Moreover, a pump may be used for creating a low pressure in the enclosed chamber. Such a pump may for example be connected to the arrangement via the coupling device. Alternatively, the arrangement may comprise a separate port configured to allow connection to a pump, if desired. A low pressure in the enclosed chamber formed by the arrangement and the surface of the battery cell facilitates collection of as much of the gas a possible from the interior of the battery cell. As an alternative to creating a low pressure in the enclosed chamber before punching of the battery cell and the following collection of gas, the collection of gas may naturally be performed by means of suction of the gas from the interior of the battery cell. This may in turn be achieved through usage of a pump arranged between the arrangement and the gas analysis apparatus.After the enclosed chamber has been evacuated (and optionally a low pressure has been created therein), the tip of the hollow needle 40 or drill is used to punch the battery cell. This is achieved by screwing the second part 22 further onto the first part 21 of the arrangement 20, thereby moving the tip of the hollow needle 40 or drill downwards to penetrate e.g. the safety vent 6 or another part of the battery cell can 2. As the hollow needle 40 or drill pierces the battery cell 1, gas from the interior of the battery cell 1 will start flowing through the hollow needle 40 or drill and may therefore be collected for analysis. When the gas from the interior of the battery cell 1 has been collected, the second part 22 of the arrangement 20 may thereafter be partly screwed off the first part 21 such that the tip 41 of the hollow needle 40 or drill is located in the enclosed chamber. This allows for collection of any gas that may be leaked from the interior of the battery cell into the enclosed chamber during punching of the battery cell to also be collected.Figure 4 illustrates a cross sectional view of a second exemplifying embodiment of the herein described arrangement 20 for collecting gas from a battery cell. The arrangement 20 is here shown when mounted to such a battery cell 1. More specifically, the arrangement 20 is shown to be mounted over a safety vent 6 of the battery cell 1. Moreover, the arrangement 20 is shown to be in a state prior to punching of the battery cell 1.Like in the first exemplifying embodiment shown in Figure 3, the second exemplifying embodiment of the arrangement 20 comprises a first part 21 and a second part 22 configured to be threadably engaged with each other. Each of the first part 21 and the second part 22 of the arrangement 20 shown in Figure 4 has a configuration as described above with reference to Figure 3. As shown in the figure, the internal volume of the cover portion 31, formed by the upper wall 34 and the side walls 35 thereof, provides an enclosed chamber 25 when the arrangement 20 is mounted to the battery cell 1. To ensure that gas may not leak from the enclosed chamber where the peripheral bottom surface 32 of the cover portion 31 abuts the surface of the battery cell 1, the arrangement 20 may comprise a first sealing ring 26 arranged in a recess 33 formed in said peripheral bottom surface 32.The arrangement 20 according to the second exemplifying embodiment further comprises a second sealing ring 51. Said second sealing ring 51 is arranged between the inner wall member 42 and the outer wall member 43 of the second part 22 of the arrangement. More specifically, the second sealing ring 51 is arranged closed to the top wall member 44 of the second part 22 such that it is positioned above the hollow cylindrical portion 36 of the first part 21 when the first and second parts 21, 22 of the arrangement 20 are threadably engaged to each other. The second sealing ring 51 serves the purpose of reducing the risk of leakage of gas between the first and second parts 21, 22 of the arrangement during (and after) punching of the battery cell 1. More specifically, the second sealing ring 51 provides a gas-tight seal between the top wall member 44 of the second part 22 and the annular top surface 39 (see Figure 3) of the hollow cylindrical portion 36 of the first part 21.As shown in the figure, the arrangement 20 may further comprise a third sealing ring 52 arranged on the upper wall 34 of the cover portion 31 so as to encircle the hollow cylindrical portion 36 of the first part 21. The third sealing ring 52 may further ensure that gas may not be leaked between the first part 21 and the second part 22 of the arrangement 20 when the battery cell 1 is punched. In other words, the third sealing ring 52 is arranged so as to provide a gas-tight seal between the outer wall member 43 of the second part 22 and the upper wall 34 of the first part 21 at least when the second part 22 is fully threaded on the first part 21.In Figure 4, the second part 22 of the arrangement 20 is shown to be partly threaded onto the first part 21 of the arrangement 20 such that the tip 41 of the hollow needle 40 or drill is arranged close to, but distanced from, the surface of the battery cell 1. Through screwing the second part 22 of the arrangement 20, the tip 41 may be moved further towards the battery cell so as to punch the battery cell 1. Suitably, the battery cell 1 may be punched, using the herein described arrangement 20, at the safety vent 6 of the battery cell 1. When the battery cell 1 is punched by the hollow needle 40 or drill, gas will start to flow through the hollow needle 40 or drill and may therefore be collected, e.g. for the purpose of performing analysis thereof.Moreover, the figure illustrates a coupling device 23, here illustrated as a swivel connector, which may be threadedly engaged with the second part 22 of the arrangement. As already described with reference to Figure 3, the inner wall member 42 of the second part 22 of the arrangement 20 may for this purpose comprise an inner threaded surface 46. The coupling device 23 may, but need not, be considered as a constituent component of the herein described arrangement 20 for collecting gas.Figure 5 illustrates a cross sectional view of a third exemplifying embodiment of the herein described arrangement 20 for collecting gas from a battery cell. The arrangement 20 according to the third exemplifying embodiment corresponds to the second exemplifying embodiment shown in Figure 4 except that the outer wall member 43 of the second part 22 is configured to be slidably arranged relative to the radially outer surface of the hollow cylindrical portion 36 of the first part 21 (as opposed to threadably arranged). Thus, the hollow cylindrical portion 36 of the first part 21 does not comprise any external thread (compare with external thread 38 shown Figure 3) and the outer wall member 43 does not comprise any threaded inner surface (compare with threaded inner surface 48 shown in Figure 3). Furthermore, as shown in the figure, the second sealing ring 51 may be arranged between the outer wall member 43 of the first part and the outer wall of the hollow cylindrical portion 36 of the first part 21. Thereby, the second sealing ring 51 may provide a gas-tight seal between the first and second parts 21, 22 of the arrangement 20 irrespectively of how far the second part 22 is screwed onto the first part 21.Although not shown in Figure 5, the arrangement 20 of the third exemplifying embodiment may naturally also comprise the third sealing ring 52 as shown in Figure 4 and / or an additional sealing ring arranged in the same way as the second sealing ring 51 as shown in Figure 4.Compared to the first and second exemplifying embodiments of the arrangement, the arrangement of the third exemplifying embodiment may reduce the manufacturing costs as it does not require all the treads. Flowever, the sliding arrangement of the first and second part may result in increased friction when screwing the second part on the first part, and thereby possibly slightly impair the control of the movement of the hollow needle or drill relative to the battery cell.Figure 6 illustrates a top view of the first part 21 according to a fourth exemplifying embodiment of the herein described arrangement 20 for collecting gas from a battery cell. The first part 21 has the same configuration as the first part shown in Figure 3, except that it further comprises a safety valve 54. The safety valve 54 is arranged in the cover portion 31 of the first part 21. In the figure, the safety valve 54 is shown to be arranged in the upper wall 34 of the cover portion 31. However, the safety valve 54 may alternatively be arranged in a side wall of the cover portion 31. The safety valve 54 is configured to allow escape of gas from the enclosed chamber, formed by the cover portion when the arrangement is mounted to a battery cell, in case the pressure in the enclosed chamber increases above a threshold. This in turn increases the safety when punching the battery cell and collecting gas from the interior thereof in case of, for example, causing damage to the interior of the battery cell leading to an undesired / unexpected pressure increase, e.g. due to thermal runaway or the like.It should here be noted that, although not illustrated in any one of Figure 3 to 5, the exemplifying embodiments of the herein described arrangement shown in said figures may naturally be supplemented with a safety wall 54 configured to allow escape of gas from the enclosed chamber at a pressure exceeding a threshold in the same way as shown in Figure 6.Figure 7 represents a flowchart schematically illustrating one exemplifying embodiment of a method for collecting gas from a battery cell in accordance with the present disclosure. The method comprises a step S101 of mounting the arrangement for collecting gas as described herein to a surface of a battery cell such that the cover portion of the first part of the arrangement forms an enclosed chamber together with the surface of the battery cell and the tip of the hollow needle or drill is arranged at a distance from the surface of the battery cell. The method further comprises a step S102 of screwing the second part of the arrangement relative to the first part of the arrangement such that the tip of the hollow needle or drill is moved towards the surface of the battery cell and punches the battery cell. The method further comprises a step S103 of collecting gas flowing through the hollow needle or drill.

Claims

1. Device (20) for collecting gas from a battery cell (1), the device (20) comprising a first part (21), and a second part (22) designed to be screwed to the first part (21);the first part (21) comprising:- a cover portion (31) comprising an internal volume designed to provide an enclosed chamber (25) when the device (20) is mounted on a battery cell (1), said cover portion (31) comprising a peripheral bottom surface (32) designed to face a surface of the battery cell (1), and- a hollow cylindrical portion (36) extending upwardly from an upper wall (34) of the cover portion (31), said hollow cylindrical portion (36) comprising an internal thread (37) and in fluid communication with the internal volume of the cover portion;the second part (22) comprising:- a cylindrical inner wall element (42) having a threaded outer surface (47) adapted to engage the internal thread (37) of the cylindrical portion of the first part,- a cylindrical outer wall element (43) coaxially arranged with the inner wall element,- an upper wall element (44) arranged to connect an upper end of the inner wall element (42) to an upper end of the outer wall element (43), and- a lower wall element (45) connected to a lower end of the inner wall element, the lower wall element (45) firmly supporting a hollow needle (40) or drill adapted to puncture the battery cell (1).

2. The device (20) of claim 1, wherein the cylindrical portion (36) of the first part (21) includes an external thread (38), and the outer wall element (43) of the second part (22) has a threaded internal surface (48) adapted to engage the external thread (38) of the cylindrical portion (36) of the first part (21).

3. Device (20) according to any one of claims 1 or 2, wherein the first part comprises a recess (33) arranged in the peripheral bottom surface of the cover portion, and wherein the device further comprises a first sealing ring (26) arranged in said recess.

4. Device (20) according to any one of the preceding claims, further comprising a second sealing ring (51) arranged between the inner wall element (42) and the outer wall element (43) of the second part (22).

5. The device (20) according to any one of the preceding claims, further comprising a third sealing ring (52) arranged on the upper wall (34) of the cover portion (31) to enclose the hollow cylindrical portion (36) of the first part (21).

6. Device (20) according to any one of the preceding claims, further comprising a coupling device (23) designed to be screwed into the second part (22), said coupling device (23) being designed to enable coupling of the device (20) to a gas analysis apparatus.

7. The device (20) of claim 6, wherein the inner wall element (42) of the second part (22) includes a threaded inner surface (46) adapted to enable the coupling device (23) to be screwed into the second part (22).

8. Device (20) according to any one of claims 6 or 7, wherein said coupling device (23) is a rotatable connector.

9. A device (20) according to any one of the preceding claims, wherein the hollow needle (40) or drill extends through the inner wall element (42) so as to project above the upper wall element (44) of the second part (22).

10. Device (20) according to any one of the preceding claims, wherein the hollow needle (40) or drill has a length (L) between its tip (41) and the lower wall element (45) of the second part (22), which ensures that the tip (41) is arranged above a plane of the peripheral bottom surface (32) of the first part (21) at least until the second part (22) has been screwed to 50% of a maximum thread contact of the contact of the internal thread (37) of the cylindrical portion (36) of the first part (21) and the threaded outer surface (47) of the inner wall element (42) of the second part (22).

11. Device (20) according to any one of the preceding claims, wherein the first part (21) further comprises a safety valve (54) designed to enable the release of gas from the enclosed chamber (25) at a pressure exceeding a threshold value, said safety valve being arranged in the cover portion.

12. Method for collecting gas from a battery cell (1), the method comprising: mounting (S101) a device (20) according to any one of the preceding claims on a surface of the battery cell (1) such that a cover portion (31) of a first part (21) of the device (20) forms an enclosed chamber (25) together with the surface of the battery cell (1) and a tip (41) of a hollow needle (40) or drill is arranged at a distance from the surface of the battery cell (1), screwing (S102) a second part (22) of the device (20) relative to the first part (21) of the device (20) in such a way that the tip (41) of the hollow needle (40) or drill is moved towards the surface of the battery cell (1) and pierces the battery cell (1), and collecting (S103) gas flowing through the hollow needle (40) or the drill.

13. Method according to claim 12, wherein the device (20) is mounted over a security opening (6) in the battery cell (1), and the hollow needle (40) or drill is controlled to punch said security opening (6).