Battery, energy storage device, and vehicle

Abstract

A battery (1) comprising an electrochemical cell and a cell case (2) encapsulating the electrochemical cell. The battery (1) further comprises a gas release device (15) configured to reduce a possible pressure difference between the interior of the cell case (2) and the atmosphere surrounding the cell case (2). The gas release device (15) comprises one or more membranes (18, 28), said one or more membranes (18, 28) having a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 3 at room temperature. The battery (1) may be comprised in an energy storage device (50) and / or in a vehicle (100).

Description

[0001] BATTERY, ENERGY STORAGE DEVICE, AND VEHICLE

[0002] TECHNICAL FIELD

[0003] The present disclosure relates in general to a battery. The present disclosure also relates in general to an energy storage device comprising a plurality of batteries. Moreover, the present disclosure further relates in general to a vehicle comprising the above described battery.

[0004] BACKGROUND

[0005] A battery comprises an electrochemical cell, which may be formed of an electrode assembly and a liquid electrolyte. The electrode assembly is typically produced by laminating or otherwise attaching a plurality of layers to each other. The plurality of layers comprises electrode layers; more specifically, at least one anode layer and at least one cathode layer. The anode and cathode layers are in turn separated from each other by a porous separator layer. The separator layer is configured to contain the electrolyte and to prevent short circuit between the electrode layers. Depending on the desired configuration of the battery, the electrode assembly may e.g., be winded, stacked, or folded to allow as much electrode surface of the electrochemical cell as possible given the available space therefore, and thereafter placed in cell case configured to protect the electrochemical cell from the surrounding atmosphere. The electrolyte is thereafter filled into the cell case via an electrolyte filling hole, which is ultimately sealed. The electrolyte is an electrically insulating, but ionically conducting electrolyte enabling ions to move through the electrochemical cell between the anode and the cathode.

[0006] An important part of the battery production is the final procedure which establishes the final electrochemical cell chemistry. This procedure is called Formation and Aging (F&A) and is performed after the battery has been constructed and filled with electrolyte. During this procedure, the electrochemical cell of the battery is slowly charged and discharged for the first time, followed by repeated charging / discharging cycles, usually at different rates and with resting times between charging and discharging (and vice versa). The F&A procedure is associated with high costs, e.g. for being time consuming, being performed for each battery individually, and requiring a highly controlled atmosphere (at least if the battery has not been entirely sealed in advance). The formation and aging procedure generates gas inside the case, which must be evacuated before final permanent sealing of the battery. The gas may be generated as a result of electrolyte decomposition as well as through chemical reaction of oxygen released from the material of at least one of the electrodes. Gas trapped in-between adjacent electrode assembly sheets may result in stresses on internal components of the battery, which in turn may result in higher internal resistances. Moreover, the generated gas contributes to higher internal pressure inside the case which in turn may result in faster capacity decay during usage. Thus, the generation of gas inside a battery may lead to a considerable reduction of lifetime and performance of a battery.

[0007] US 2013 / 0130079 Al proposes a solution to the problem of gas generated during the manufacturing process. An opening portion of the case of the battery is provided with a first sealing body, the first sealing body being displaced or deformed by a pressure difference between an inside and an outside of the case in such a manner that the first sealing body is pressed by internal pressure to allow outflow of inside air from the opening portion when the internal pressure in the case is higher than external pressure and that the first sealing body is pressed by the external pressure to prevent entry of outside air from the opening portion when the internal pressure in the case is lower than the external pressure. Pressure in a space surrounded by the case and the first sealing body is set to be lower than pressure outside the space. The first sealing body thus essentially acts as a one-way valve during final stages of production of the battery. After evacuation, the opening portion is completely and airtightly sealed.

[0008] However, gas may also be generated inside the case after production, i.e. during use of the battery. This has the same negative effects as described above with regard to the gas generated during the F&A procedure. Thus, it would be desirable to also enable evacuation of gas generated while the battery is in use, as well as potential remaining gas generated during the F&A procedure which may not have been sufficiently evacuated earlier.

[0009] Batteries today are generally equipped with a safety valve configured to rupture and release gas in case the internal pressure inside the battery becomes too high. This reduces the risk for explosion, and therefore improves safety. However, when the safety valve ruptures, the electrochemical cell is also destroyed, and the battery can no longer be used. Thus, such solutions cannot be used for the purpose of increasing the lifetime or preserving performance of batteries.

[0010] SUMMARY

[0011] The object of the present invention is to improve lifetime and performance of a battery. The object is achieved by the subject-matter of the appended independent claim(s).

[0012] The herein described battery comprises an electrochemical cell, which in turn comprises an electrode assembly and an electrolyte. The battery further comprises a cell case encapsulating the electrochemical cell. The battery further comprises a gas release device configured to reduce a pressure difference between the interior of the cell case and the atmosphere surrounding the cell case. The gas release device comprises one or more membranes, said one or more membranes having a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 3 at room temperature.

[0013] The gas release device of the battery according to the present disclosure enables a release of gases, not fully evacuated during manufacturing of the battery and / or generated during use of the battery, from the interior of the case while at the same time preventing air from entering into the cell case from the surrounding atmosphere. This is achieved by the gas release device comprising at least one membrane which has a considerably higher permeability to carbon dioxide compared to oxygen. Although the pressure inside the cell case is typically at least slightly higher than the pressure outside of the cell case, it is important to seek to minimize the risk of oxygen from the surrounding atmosphere being able to penetrate into the electrochemical cell inside the cell case. By allowing gas generated inside the cell case to escape to the surrounding atmosphere, the performance of the battery may be preserved for a longer period of time, and the lifetime is thereby extended.

[0014] The one or more membranes may suitably have a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 5, or even equal to or higher than 8, at room temperature. The ability of the one or more membranes to release carbon dioxide from the interior while preventing oxygen to enter the cell case increases with increasing ratio between the carbon dioxide permeability and the oxygen permeability. Thus, higher ratios of carbon dioxide permeability to oxygen permeability are desirable.

[0015] The one or more membranes may suitably have a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 3 at temperatures up to at least 100 °C; preferably at temperatures up to at least 150 °C. The temperature of a battery may often increase during a charging-discharging cycle and it is therefore desirable that the above described ratio is maintained also at higher temperatures. The gas release device may be arranged so as to extend over an electrolyte-injection hole of the cell case. This inter alia has the advantage of avoiding the need to form a separate hole in the cell case for the gas release device, which in turn could increase the risk of possible production errors that e.g., could risk leading to leakage of air into the interior of the cell case over time and therefore loss of the controlled atmosphere inside the electrochemical cell environment. Moreover, the production costs may be reduced by reducing the number of through-holes needed to be formed in the cell case. As stated above, by utilizing the electrolyte-injection hole there is no need to provide a separate hole for the gas release device. It is also avoided that a pre-existing hole which has a different dedicated function during the lifetime of the battery cell need to be used for dual functions which would reduce the effectiveness of both functions. For example, if the membrane would be incorporated in the burst-valve which is used as a safety valve and configured to open at a certain pressure the design would be complex and each function would suffer from sub-optimization.

[0016] The gas release device may be arranged in a sealing arrangement configured to seal the electrolyteinjection hole. The sealing arrangement may be arranged so as to extend over and / or at least partly extend into the electrolyte-injection hole. Thus, the sealing arrangement may be arranged in / inside the electrolyte-injection hole, or to extend into the electrolyte-injection hole. Alternatively the sealing arrangement is arranged to extend over the electrolyte-injection hole, i.e. such that it covers the electrolyte-injection hole. Alternatively, the sealing arrangement may be arranged both in the electrolyte-injection hole and to extend over the electrolyte-injection hole, i.e. such that it covers the electrolyte-injection hole. The sealing arrangement may comprise one or more sealing members. The sealing arrangement may e.g. comprise two sealing members, a first sealing member and a second sealing member. The first sealing member may e.g. be a sealing pin, a sealing ball, or a sealing plate. The second sealing member may e.g. be a sealing pin, a sealing ball, or a sealing plate.

[0017] This inter alia has the advantage that the production process is simplified since the gas release device may be arranged in the sealing arrangement before the sealing arrangement is arranged on the battery, e.g. in and / or over the electrolyte-injection hole.

[0018] The sealing arrangement may e.g. comprise a sealing pin arrangement. In this case the sealing pin arrangement may comprise the gas release device. The battery may thus comprise a sealing pin arrangement arranged in and / or over the electrolyte-injection hole. Thereby the function of the gas release device is provided in a convenient and efficient manner. The sealing pin arrangement may comprise a first sealing pin configured to be arranged in / inside the electrolyte-injection hole such that it seals the electrolyte-injection hole. The first sealing pin may comprise the gas release device. Thereby the function of the gas release device is provided in a first sealing pin which seals the electrolyte-injection hole, providing both the sealing function as well as the gas release function of the gas release device in a convenient and practical manner. This is also advantageous since gas-leakage testing may be possible to be performed on the first sealing pin thereby avoiding the use of redundant seals.

[0019] The sealing pin arrangement may additionally comprise a second sealing pin or sealing plate configured to cover the first sealing pin and to seal the electrolyte-injection hole. Thus, the second sealing pin or sealing plate may act as a redundant seal for the electrolyte-injection hole. In this case a gas release device may be arranged in the first sealing pin and in the second sealing pin or sealing plate. Thus, the first sealing pin may comprise a first gas release device and the second sealing pin or sealing plate may comprise a second gas release device. Thereby a redundant sealing is provided providing the gas release function described above in a convenient and practical manner.

[0020] Moreover, the gas release device may be at least partly arranged in a through-hole of the cell case. This e.g., enables arranging the one or more membranes closer to the electrolyte inside the cell case and thereby quicker pick-up of gaseous species from the interior of the cell case by surface absorption followed by transfer through the one or more membranes. Described differently, the gaseous species needs to travel a shorter distance before being picked-up by a surface of the one or more membranes. Optionally, the through-hole of the cell case may be an electrolyte-injection hole of the cell case.

[0021] The gas release device may further comprise a cover body configured to protect the one or more membranes against mechanical impact. This in turn e.g., facilitates handling of the battery, as well as installation of the battery in the intended application therefore, without risking damaging the one or more membranes.

[0022] At least one membrane of the one or more membranes may comprise polyvinylidene chloride or polytetrafluoroethylene. Both polyvinylidene chloride and polytetrafluoroethylene have the advantage of being able to be used as barriers to oxygen but having a higher permeability of carbon dioxide. Moreover, both polyvinylidene chloride and polytetrafluoroethylene are thermally stable within the operating temperature range of batteries and resistant to the chemical environment inside the cell case. Alternatively, at least one membrane of the one or more membranes may comprise perovskite. Membranes comprising perovskite may be associated with higher cost than membranes comprising polyvinylidene chloride or polytetrafluoroethylene. However, perovskites have the advantage of enabling a high degree of tailoring of the permeability properties and are in generally stable over a wide range of chemical environments and temperatures.

[0023] The gas release device may further comprise a moisture absorbent member, if desired. This reduces the risk of entrance of moisture, via the gas release device, into the cell case and the electrochemical cell environment, which may otherwise risk to damage the electrochemical cell and / or cause further generation of gases during charging / discharging.

[0024] The gas release device may according to one embodiment comprise two membranes. If so, the above mentioned moisture absorbent member may, if present, be interposed between the two membranes. This inter alia has the advantage of preventing moisture to reach the innermost of the two membranes as well as the interior of the cell case. Furthermore, the moisture absorbent member may serve as a support structure for one or both of the two membranes, if desired.

[0025] The battery may further comprise a safety valve configured to break when a pressure in the interior of the cell case is equal to or higher than a pressure threshold. This has the advantage of increasing the safety in case the gas release device would be unable to evacuate a sufficient amount of gas, e.g. during a thermal runaway.

[0026] The battery may for example be a lithium-ion battery, but is not limited thereto. When the battery is a lithium-ion battery, the electrode assembly may comprise a nickel containing electroactive material. Previously known lithium-ion batteries comprising nickel containing electroactive materials have the advantage of increased operating voltage and high energy density, making them highly suitable for use in e.g., the automotive industry. However, there is also a higher tendency for generation of gases during charging / discharging of lithium-ion batteries comprising such electroactive materials compared to other conventional lithium-ion batteries. However, by means of the herein described battery that allows for gas to be released by means of the gas release device, such electroactive materials may be used without risk of reduced performance and / or lifespan. Described differently, by means of the herein described battery, the performance and lifetime of a lithium-ion battery comprising a nickel containing electroactive material may be improved. In case the battery is a lithium-ion battery comprising a nickel containing electroactive material, the one or more membranes of the gas release device may for example have a total gas permeability with regard to carbon dioxide of from 1 to 12 mMol per year and liter of internal volume of cell case; preferably from 2 to 8 mMol per year and liter of internal volume of cell case.

[0027] The present disclosure further relates to an energy storage device comprising a plurality of batteries connected in series and / or in parallel, wherein at least one of the plurality of batteries constitutes a battery as described above. The energy storage device may for example be a battery module or a battery pack. According to yet an alternative, the energy storage device may comprise a plurality of battery packs connected in series and / or in parallel. In case the energy storage device is or comprises a battery pack, said battery pack may optionally comprise a plurality of battery modules connected in series and / or in parallel. A battery module may for example comprise at least 5 batteries, which may each be the herein described battery comprising the gas release device.

[0028] The energy storage device may for example be used for powering one or more propulsion units of a vehicle, each of said one or more propulsion units constituting an electrical machine.

[0029] The present disclosure further relates to a vehicle comprising the battery described above. The battery may for example be comprised in an energy storage device as described above. The vehicle may be a fully electrical vehicle, a hybrid vehicle, or a fuel cell vehicle. Moreover, the vehicle may be a land based heavy vehicle, such as a truck or a bus, but is not limited thereto. The vehicle may for example be a land-based medium-duty vehicle or a car. The vehicle could alternatively be a watercraft or an aircraft.

[0030] BRIEF DESCRIPTION OF DRAWINGS

[0031] Fig. 1 illustrates a perspective view of an example of a previously known battery,

[0032] Fig. 2 illustrates a perspective view of an example of a previously known battery where a portion of the cell case has been omitted for the purpose of illustrating an electrode assembly of the battery,

[0033] Fig. 3 illustrates a perspective view of an exemplifying embodiment of the battery according to the present disclosure, Fig. 4 schematically illustrates a cross sectional view of a first exemplifying embodiment of a gas release device of the battery according to the present disclosure,

[0034] Fig. 5 schematically illustrates a cross sectional view of a second exemplifying embodiment of a gas release device of the battery according to the present disclosure,

[0035] Fig. 6 schematically illustrates a cross sectional view of a third exemplifying embodiment of a gas release device of the battery according to the present disclosure,

[0036] Fig. 7 schematically illustrates a cross sectional view of a fourth exemplifying embodiment of a gas release device of the battery according to the present disclosure, and

[0037] Fig. 8 illustrates a side view of an example of a vehicle which may comprise the herein described battery.

[0038] DETAILED DESCRIPTION

[0039] 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.

[0040] When a range is given in the present disclosure, said range shall be considered to include the specified end values of the range, unless explicitly disclosed otherwise.

[0041] Energy storage devices for vehicles require many electrochemical cells to achieve the desired capacity. Energy storage devices for vehicles may therefore for example comprise one or more battery packs. Each battery pack may in turn comprise a plurality of battery modules, each comprising a plurality of individual batteries (sometimes also known as battery cells). The battery modules may be connected in series and / or in parallel. Within each module, the batteries may be arranged in two or three dimensional arrays, and may be connected in series and / or in parallel. Each battery in turn comprises an electrochemical cell. The most frequently used batteries today in energy storage devices for vehicles are secondary lithium-ion batteries. The batteries may be classified as cylindrical cells / batteries, prismatic cells / batteries, or pouch cells / batteries depending e.g., on the geometrical configuration of the electrochemical cells.

[0042] 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.

[0043] The present disclosure relates to a battery which may be incorporated in an energy storage device for a vehicle as described above. It should however be noted that the herein described battery may also be used in other applications. Examples of such applications include stationary energy storage devices, e.g., for storing solar or wind energy, or other off-grid energy storage solutions for various purposes. The battery may also be used in various consumer related applications, if desired.

[0044] The battery according to the present disclosure comprises an electrochemical cell, which in turn comprises an electrode assembly and an electrolyte. The electrolyte may be a liquid electrolyte. The electrode assembly comprises at least one anode, at least one cathode and a separator interposed between the anode and the cathode. The electrode assembly may for example be wounded into a so called jelly roll, or be folded. The battery may suitably be a prismatic battery, but could alternatively be a cylindrical battery or a pouch battery. The battery may suitably be a secondary battery, i.e. a rechargeable battery.

[0045] The battery further comprises a cell case arranged so as to encapsulate the electrochemical cell. At least a part of an interior surface of the cell case is typically in direct contact with the electrolyte. The battery further comprises battery terminals arranged on the exterior of the cell case, these battery terminals being electrically connected to the electrode assembly. The battery terminals allows the battery to be electrically connected to one or more adjacent batteries and / or a power consumer.

[0046] The herein described battery further comprises a gas release device configured to reduce a possible pressure difference between the interior of the cell case and an atmosphere surrounding the cell case. More specifically, the gas release device is configured to reduce said pressure difference through release of gas, generated during charging and / or discharging of the battery, from the electrochemical cell environment to the outside of the cell case. For said purpose, the gas release device comprises (or consists of) one or more membranes configured to allow gas to pass from the interior of the cell case to the surrounding atmosphere outside of the cell case. Gas generated during charging-discharging cycles of the battery comprises carbon dioxide, and it is therefore important for carbon dioxide to be able to pass the one or more membranes of the gas release device. Moreover, it is important to avoid entry of oxygen into the interior of the cell case as this could risk leading to an increased amount of gas generated inside the cell case due to chemical reactions during charging and discharging. Therefore, the one or more membranes of the gas release device are selected to have a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 3 at room temperature.

[0047] The ability of the one or more membranes to release carbon dioxide from the interior while inhibiting oxygen to enter the cell case increases with increasing ratio between the carbon dioxide permeability and the oxygen permeability. Therefore, the one or more membranes may suitably have a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 5 at room temperature, or even equal to or higher than 8 at room temperature.

[0048] The permeability of the one or more membranes to carbon dioxide and oxygen, respectively, is affected by selection of material, the surface area that is exposed to the interior of the cell case, as well as the thickness of the one or more membranes. A thickness of the one or more membranes is in the present disclosure considered to mean an extension of the one or more membranes in a direction perpendicular to a surface of the one or more membranes that is directly exposed to the environment inside the cell case. In case the gas release device comprises a plurality of membranes, these may suitably be arranged in parallel to each other. Furthermore, in case there is a plurality of membranes, each membrane may be arranged to be in direct contact with an adjacent membrane or may be arranged at a distance from an adjacent membrane.

[0049] Moreover, the temperature of the one or more membranes, which in turn may be affected by the temperature of the surroundings, may also affect the permeability. The temperature inside the cell case may be increased during charging and discharging, and temperatures up to about 60°C may relatively often occur in conventional Li-ion batteries used within the automative industry. Therefore, the one or more membranes may suitably be selected so as to have a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 3 at temperatures up to at least 100 °C, or even up to at least 150 °C. Suitably, the one or more membranes may suitably be selected so as to have a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 5 at temperatures up to at least 100 °C.

[0050] The gas release device may be arranged so as to extend over and / or, at least partly, in a through-hole of the cell case of the battery. In some cases, said through-hole may be an electrolyte-injection hole (sometimes also referred to as an electrolyte filling hole) of the cell case. Arranging the gas release device at an electrolyte-injection hole has the advantage of reducing the number of through-holes needed to be made in the cell case. This may reduce the risk of leakage of air into the cell case as a result of possible manufacturing faults during production of the battery. However, in some cases, it may be desirable to be able to mount the gas release device to the cell case before introduction of the electrolyte into the cell case during production of the battery, or it may be desired to have a smaller sized electrolyte-injection hole than needed for the membrane area that is to be exposed to the interior of the cell case. In such cases, a separate through-hole in the cell case for the gas release device may be needed.

[0051] The gas release device may be arranged in a sealing arrangement configured to seal the electrolyteinjection hole. The sealing arrangement may be configured to seal the electrolyte-injection hole after the electrolyte has been injected into the battery cell. The sealing arrangement may be arranged so as to extend over and / or at least partly extend into the electrolyte-injection hole. The sealing arrangement may alternatively or additionally be arranged inside the electrolyte-injection hole. The sealing arrangement may comprise one or more sealing members, e.g. two sealing members. The sealing arrangement may comprise one or more sealing members. The sealing arrangement may e.g. comprise two sealing members, a first sealing member and a second sealing member. The first sealing member may e.g. be a sealing pin, a sealing ball, or a sealing plate. The second sealing member may e.g. be a sealing pin, a sealing ball, or a sealing plate.

[0052] By providing the gas release device in a sealing arrangement configured to seal the electrolyteinjection hole the production process is greatly simplified.

[0053] The sealing arrangement may e.g. comprise a sealing pin arrangement. In this case the sealing pin arrangement may comprise the gas release device. The battery may thus comprise a sealing pin arrangement arranged in and / or extending over the electrolyte-injection hole. Thereby the function of the gas release device is provided in a convenient and efficient manner. The sealing pin arrangement may comprise a first sealing pin configured to be arranged inside the electrolyte-injection hole such that it seals the electrolyte-injection hole. Thus, the first sealing pin may be a first sealing member of the sealing arrangement. The first sealing pin may comprise the gas release device. Thereby the function of the gas release device is provided in a first sealing pin which seals the electrolyte-injection hole, providing both the sealing function as well as the gas release function of the gas release device in a convenient and practical manner. This may remove the need for a redundant sealing since it may improve or simplify gas-leakage testing.

[0054] The sealing pin arrangement may additionally comprise a second sealing pin or a sealing plate, configured to cover the first sealing pin and to seal the electrolyte-injection hole. Thus, the second sealing pin or sealing plate may act as a redundant seal for the electrolyte-injection hole. In this case a gas release device may be arranged in both the first and the second sealing pin or sealing plate. Thus, the first sealing pin may comprise a first gas release device and the second sealing pin or sealing plate may comprise a second gas release device. Thereby a redundant sealing is provided providing the gas release function described above in a convenient and practical manner.

[0055] The gas release device may, in addition to the one or more membranes, comprise a holding body to which the one or more membranes are joined or otherwise attached in an air-tight manner. Such a holding body may serve the purpose of facilitating the installation of the gas release device in the battery during production and / or providing structural stability to the one or more membranes during use of the battery, if needed. It should however be noted that the one or more membranes may alternatively be attached, e.g., by adhesive, directly to the cell case, if desired. In such a case, the gas release device may consist of the one or more membranes.

[0056] In order to protect the one or more membranes during production of the battery, handling of the battery, or installation and use of the battery in the intended application, the gas release device may further comprise a cover body configured to protect the one or more membranes against mechanical impact. Naturally, such a cover body may comprise one or more holes configured to allow gas to be released to the surrounding atmosphere. The cover body may suitably be made of a metallic material, for example the same material as used in the cell case.

[0057] The one or more membranes have an inner surface facing towards the interior of the cell case such that it is directly exposed to the internal atmosphere of the battery. Typically, said inner surface corresponds to an inner surface of a single membrane of the one or more membranes. The inner surface of the one or more membranes may for example have an area from 8 mm2to 35 mm2. Suitably, the inner surface may have an area of from 10 mm2to 30 mm2. Moreover, the one or more membranes may for example have a total thickness (i.e. total extension in a direction perpendicular to the inner surface of the one or more membranes) of from 2 mm to 10 mm. Suitably, the one or more membranes may have a total thickness of from 3 mm to 8 mm. The present disclosure is however not limited to the above exemplified area of inner surface and total thickness, and other dimensions are also plausible. As previously mentioned, the permeability is affected both by the area and thickness of the one or more membranes as well as the selection of material(s) of the one or more membranes. Therefore, the size of the one or more membranes should suitably be adapted in dependence of the material selected for the one or more membranes.

[0058] Each of the one or more membranes may be made of polymer-based material. For example, one or more of the membranes of the gas release device may suitably comprise, or consist of, polyvinylidene chloride. According to another alternative, one or more of the membranes may comprise, or consist of, polytetrafluoroethylene. Both polyvinylidene chloride and polytetrafluoroethylene enable a considerably higher permeability of carbon dioxide compared to oxygen and are able to be formed into membranes of appropriate sizes for the gas release device according to the present disclosure.

[0059] Alternatively, each of the one or more membranes may be formed of an inorganic material. For example, at least one of the one or more membranes may be a perovskite membrane. Perovskites may be described as mixed metal oxides with a well-defined cubic structure and a general formula of ABO3, where A is at least one alkaline earth or lanthanide element, and B is at least one transition metal. The permeability of perovskite to various gaseous compounds may be tailored by tuning of the metal sites of the structure.

[0060] In order to reduce the risk for moisture entering into the electrochemical cell environment, the gas release device may further comprise a moisture absorbent member, if desired. The moisture absorbent member may be in the form of a porous body comprising, or consisting of, zeolite, silica gel or activated alumina. The moisture absorbent member may for example be arranged so as to be interposed between two membranes of the gas release device, although other arrangements of the moisture absorbent member are also possible.

[0061] The permeability of oxygen and carbon dioxide, respectively, through the at least one membrane may for example be measured in accordance with ISO 15105 in case the membrane is formed of a polymer-based material, e.g. when comprising polyvinylidene chloride or polytetrafluoroethylene. The permeability of oxygen and carbon dioxide, respectively, may in case the at least one membrane comprises perovskite be determined through gas chromatography

[0062] Although the above described gas release device is configured to reduce pressure difference between the interior of the cell case and the surrounding atmosphere, there is a risk that the pressure inside the cell case may rapidly increase due to e.g. thermal runaway. Therefore, the herein described battery may suitably further comprise a safety valve configured to break when a pressure in the interior of the cell case is equal to or higher than a critical pressure threshold. Such safety valves are as such previously known and will therefore not be described in more detail in the present disclosure. When such a safety valve breaks, the internal pressure of the battery is quickly reduced and the safety is therefore improved. However, the battery may no longer be used in view of the electrochemical cell environment not being protected.

[0063] The battery according to the present disclosure may for example be a lithium-ion battery. The herein described battery may for example be a lithium-ion battery wherein the electrode assembly comprises a nickel containing electroactive material. Litium-ion batteries comprising nickel- containing electroactive materials in the cathodes are particularly interesting for the automotive industry in view of their high energy density and operating voltage. Examples of such nickel- containing electroactive materials include lithium nickel manganese cobalt oxides, often abbreviated NMC, having the general formula LiNixMnyCoi-x-yCh.

[0064] The generation of gas in an electrochemical cell of the battery is affected by several factors, such as the electroactive materials used (including composition and particle sizes thereof), composition of the electrolyte (including additives), size of battery, as well as the charging / discharging rates to which it is subjected. The total desirable permeability of the one or more membranes of the gas release device with regard to carbon dioxide may therefore vary. However, as an example in case of a lithium-ion battery comprising a nickel containing electroactive cathode material as described above, the total gas permeability of the one or more membranes with regard to carbon dioxide may be from 1 mMol per year and liter of internal volume of cell case to 12 mMol per year and liter of internal volume of cell case (at least at room temperature). Suitably, the total gas permeability of the one or more membranes with regard to carbon dioxide may be from 2 to 8 mMol per year and liter of internal volume of cell case (at least at room temperature). As gas evolution and resulting internal pressure is correlated to the total amount of electroactive material in the electrochemical cell and dead volume in the cell case the values above are normalized against internal volume of the cell case, being a measure against which total cell energy and electroactive material typically is optimized during cell design.

[0065] It should however be noted that the present disclosure is not limited to a lithium-ion battery. The herein described battery may for example alternatively be a sodium-ion battery or a potassium-ion battery.

[0066] The present disclosure further relates to an energy storage device comprising a plurality of batteries, wherein at least one of the plurality of batteries constitutes the battery according to the present disclosure. The plurality of batteries of the energy storage device may be connected in series and / or in parallel. In the energy storage device, the plurality of batteries may be arranged in one or more battery modules, if desired. Each such battery module may comprise a module housing, or another form of mechanical structure configured to hold the batteries in place within the module. When the energy storage device comprises a plurality of modules, these may be connected in series and / or in parallel.

[0067] Figure 1 illustrates a perspective view of an example of a previously known battery 1'. The battery 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 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 a 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.

[0068] 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, if desired.

[0069] 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 sealed. The exemplified battery 1' further comprise a safety valve 6 arranged in the cell case 2. Said safety valve 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. When the safety valve 6 has been ruptured, the electrochemical cell is no longer sealed from the surrounding atmosphere. This in turn means that the battery 1' may no longer be used. The purpose of the safety valve 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.

[0070] Figure 2 illustrates a perspective view of an example of a previously known battery, such as the battery 1' shown in Figure 1, but where an upper portion of the cell case 2, including the top plate 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.

[0071] 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.

[0072] 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 lib bonded to each of the first sub-layers 11a. The second sublayer lib of the second electrode layer constitutes a current collector.

[0073] 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).

[0074] Figure 3 illustrates a perspective view of an exemplifying embodiment of the herein described battery 1. The battery 1 corresponds to the battery 1' described above with reference to Figures 1 and 2, except that it further comprises a gas release device 15. The gas release device 15 is configured to reduce pressure difference between the interior of the cell case 2 and the atmosphere surrounding the battery 1.

[0075] The gas release device 15 may, as shown in the figure, be arranged at a top side of the cell case. The top side of the cell case 2 is here considered to mean in relation to the orientation of the battery when used in the intended application. The gas release device 15 may be arranged on the same side of the battery as the safety valve 6. The gas release device may however be arranged at another side of the battery, if desired.

[0076] Albeit not visible in the figure, the gas release device 15 is arranged at a though-hole in the cell case 2. The gas release device 15 is in the figure shown to be arranged at a distance from the electrolyteinjection hole 5. The gas release device 15 could however be arranged at the electrolyte-injection hole 5 according to other embodiments of the herein described battery 1.

[0077] The gas release device 15 could have a substantially circular configuration as shown in the figure. The present disclosure is however not limited thereto, and the gas release device 15 could thus have an oval configuration (compare with the shape of the safety valve 6 of the battery 1) or a rectangular configuration.

[0078] Figure 4 schematically illustrates a cross sectional view of a first exemplifying embodiment of a gas release device 15 of the battery according to the present disclosure, such as battery 1 shown in Figure 3, when arranged in the battery 1. More specifically, the gas release device 15 is arranged on an outer surface 2b of the cell case 2 and extends over a through-hole 22 of the cell case 2. The through-hole 22 may be an electrolyte-injection hole or another through-hole in the cell case 2. The gas release device 15 comprises a holding body 16, a cover body 17, and a membrane 18. The membrane 18 has a surface 18a facing towards the interior of the cell case 2, and a thickness t. The membrane 18 is configured to allow release of gas from the interior of the cell case 2 to the surrounding atmosphere outside the battery 1 when the pressure inside the cell case 2 is higher than the outside pressure while at the same time preventing entry of oxygen from the outside air. Therefore, the membrane has a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 3 at least at room temperature. Carbon dioxide from the interior of the cell case may thus permeate through the membrane from the surface 18a in the direction of the thickness 7 of the membrane 18.

[0079] The holding body 16 and the membrane 18 are arranged such that they together surround the outer opening of the through-hole 22 (i.e. the opening of the through-hole 22 as seen in a plane coinciding with the plane of the surface 2b). For said purpose, the membrane 18 may be attached, e.g. by an adhesive, to the holding body 16. The cover body 17 is configured to protect the membrane 18 against mechanical impact. Moreover, in the shown exemplifying embodiment, the cover body 17 is configured to, together with the holding body 16 and the membrane 18, form a structure completely covering the through-hole 22. The cover body 17 may therefore be attached to the holding body 16 as well as the membrane 18, e.g. by an adhesive. The holding body 16 as well as the cover body may for example be made of metallic material, but the present disclosure is not limited thereto.

[0080] Figure 5 schematically illustrates a cross sectional view of a second exemplifying embodiment of a gas release device 15 of the battery according to the present disclosure, when arranged in said battery 1. Like the first exemplifying embodiment shown in Figure 4, the gas release device 15 according to the second exemplifying embodiment is arranged on an outer surface 2b of the cell case 2 and extends over a through-hole 22 of the cell case 2. Furthermore, the gas release device 15 comprises a holding body 16, a membrane 18, and optionally a cover body 17. Like in the first exemplifying embodiment of the gas release device 15 described above, the membrane 18 has a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 3 at least at room temperature.

[0081] However, in contrast to the first exemplifying embodiment shown in Figure 4, the membrane 18 extends over the through-hole. The surface 18a of the membrane that is exposed to the environment inside the cell case 2 is therefore arranged substantially parallel with the outer surface 2b of the cell case 2 where the gas release device 15 is arranged. This also means that the membrane has a thickness t which is substantially perpendicular to the surface 2b of the cell case 2. Furthermore, the cover body 17 shown in Figure 5 is an optional feature and may therefore be omitted, if desired.

[0082] The holding body 16 is arranged so as to surround the outer opening of the through-hole 22 along the whole circumference thereof. The holding body 16 may be attached to the outer surface 2b of the cell case 2, e.g. by welding or using an adhesive. The membrane 18 may in turn be attached to the holding body 16, e.g. by using an adhesive. The cover body 17, if present, may be attached to the holding body 16 and / or the cell case 2, e.g. by welding or by means of an adhesive. The cover body 17, if present, encloses the holding body 16 and the membrane 18. Described differently, the cover body 17 may be described as forming a cap-like structure over the through-hole 22 as well as the membrane 18. Thereby, the membrane 18 may be protected against mechanical impact. The optional cover body 17 comprises at least one through-opening 19 configured to allow gases, released from the interior of the cell case 2 and having passed through the membrane 18, to be released from the gas release device 15 to the surrounding atmosphere outside the battery 1. Said through-opening 19 is in the figure illustrated to be arranged in a side wall 17a of the cover body 17, said side wall 17a extending from the outer surface 2b of the cell case 2 to a top surface 17b of the cover body 17.

[0083] The second exemplifying embodiment of the gas release device 15 may be modified by omitting the holding body 16, if desired. In such a case, the membrane 18 may be directly attached to the outer surface 2b of the cell case and / or attached to an internal surface of the cover body 17, e.g. by adhesive. In fact, the gas release device 15 may consist solely of the membrane 18, in which case the membrane 18 is attached directly to the cell case 2.

[0084] Figure 6 schematically illustrates a cross sectional view of a third exemplifying embodiment of a gas release device 15 of the battery 1 according to the present disclosure, when arranged in said battery 1. Like in the first and second exemplifying embodiments shown in Figures 4 and 5, respectively, the gas release device 15 according to the third exemplifying embodiment extends over a through-hole 22 of the cell case 2 and comprises a holding body 16, and a membrane 18, said membrane 18 having a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 3 at least at room temperature. The gas release device may optionally further comprise a cover body 17 as shown in the figure.

[0085] However, in contrast to the first and second exemplifying embodiments of the gas release device 15, the gas release device 15 is configured to be arranged not only so as to extend over the through-hole 22 but also in (at least a part of) said through-hole 22. More specifically, the membrane 18 and the holding body 16 are at least partly arranged in said through-hole 22 when the gas release device 15 is arranged in the battery 1. The holding body 16 may have the configuration of a flanged sleeve, with the flange extending along the outer surface 2b of the cell case 2, as shown in the figure. The membrane 18 may in turn be arranged inside the flanged sleeve.

[0086] As shown in the figure, the optional cover body 17 may have a dome-like configuration comprising a plurality of through-openings 19 through which gas, having passed from the interior of the cell case 2 through the membrane 18, may escape to the atmosphere surrounding the battery 1. The optional cover body 17 need however not have a dome-like configuration, but could instead have a substantially flat top surface 17b as shown in Figure 5. Similarly, the cover body 17 of the gas release device 15 shown in Figure 5 may be replaced with the dome-like cover body 17 shown in Figure 6.

[0087] Like the second exemplifying embodiment, the third exemplifying embodiment of the gas release device 15 may be modified by omittance of the holding body 16. In such a case, the membrane 18 may be directly attached to the cell case, e.g. along the circumferential surfaces of the through-hole 22.

[0088] Figure 7 schematically illustrates a cross sectional view of a fourth exemplifying embodiment of a gas release device 15 of the battery according to the present disclosure, when arranged in said battery 1. The gas release device 15 according to the fourth exemplifying embodiment corresponds to the gas release device 15 of the third exemplifying embodiment described above, except that it comprises a first membrane 18 and a second membrane 28. The first and second membranes 18, 28 may be arranged in parallel as shown in the figure. Furthermore, the gas release device 15 may further comprise a moisture absorbent member 24. Said moisture absorbent member 24 may be interposed between the first and second membranes 18, 28, as shown in the figure. It should however be noted that the moisture absorbent member 24 may alternatively be arranged outwardly or inwardly of the first and second membranes 18, 28 as seen in a direction relative to the interior of the cell case 2.

[0089] In case at least one of the first and second membranes 18, 28 comprises perovskite, the moisture absorbent member 24 may further serve as a support structure (in other words, a carrier) for the perovskite. In such a case, the perovskite may for example be adhered to the moisture absorbent member 24 using conventional sol-gel techniques. It should here be noted that although Figure 7 illustrates a gas release device 15 comprising two membranes (i.e. the first membrane 18 and the second membrane 28) and a moisture absorbent member 24, the gas release device 15 of the battery 1 according to the present disclosure need only comprise one of the first and second membranes 18, 28 even if comprising a moisture absorbent member 24.

[0090] Figure 8 illustrates a side view of an example of a vehicle 100, here illustrated as a trailer tractor.

[0091] The vehicle 100 may be a land-based heavy vehicle, such as a truck or a bus, but is not limited thereto. Furthermore, the vehicle may be a fully electrical vehicle or a hybrid vehicle.

[0092] The vehicle 100 may comprise one or more energy storage devices 50, as schematically illustrated by dashed boxes in the figure. The one or more energy storage devices 50 may each be a battery pack comprising a plurality of batteries, wherein one or more of the plurality of batteries may constitute a battery 1 in accordance with the present disclosure. Within an energy storage device 50, the plurality of batteries may be arranged in a plurality of battery modules 40, if desired. The herein described battery may be comprised in such a battery module 40.

Claims

CLAIMS1. A battery (1) comprising: an electrochemical cell comprising an electrode assembly (8) and an electrolyte, a cell case (2) encapsulating the electrochemical cell, and a gas release device (15) configured to reduce pressure difference between the interior of the cell case (2) and an atmosphere surrounding the cell case (2), wherein the gas release device (15) comprises one or more membranes (18, 28), said one or more membranes (18, 28) having a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 3 at room temperature.

2. The battery (1) according to claim 1, wherein the one or more membranes (18,28) have a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 5, preferably equal to or higher than 8, at room temperature.

3. The battery (1) according to any one of claims 1 or 2, wherein the one or more membranes (18, 28) have a ratio of carbon dioxide permeability to oxygen permeability of equal to or higher than 3 at temperatures up to at least 100 °C; preferably at temperatures up to at least 150 °C.

4. The battery (1) according to any one of the preceding claims, wherein the gas release device (15) is arranged so as to extend over an electrolyte-injection hole (5) of the cell case (2).

5. The battery (1) according to claim 4, wherein the gas release device (15) is arranged in a sealing arrangement configured to seal the electrolyte-injection hole (5).

6. The battery (1) according to any one of the preceding claims, wherein the gas release device (15) is at least partly arranged in a through-hole (22) of the cell case (2), optionally wherein said through-hole (22) constitutes an electrolyte-injection hole (5) of the cell case (2).

7. The battery (1) according to any one of the preceding claims, wherein the gas release device (15) further comprises a cover body (17) configured to protect said one or more membranes (18, 28) against mechanical impact.

8. The battery (1) according to any one of the preceding claims, wherein at least one membrane (18, 28) of the one or more membranes (18, 28) comprises polyvinylidene chloride or polytetrafluoroethylene.

9. The battery (1) according to any one of the preceding claims, wherein at least one membrane (18, 28) of the one or more membranes (18, 28) comprises perovskite.

10. The battery (1) according to any one of the preceding claims, wherein the gas release device (15) further comprises a moisture absorbent member (24).

11. The battery (1) according to claim 9, wherein the gas release device (15) comprises two membranes (18, 28) and the moisture absorbent member (24) is interposed between said two membranes (18, 28).

12. The battery (1) according to any one of the preceding claims, further comprising a safety valve (6) configured to break when a pressure in the interior of the cell case (2) is equal to or higher than a pressure threshold.

13. The battery (1) according to any one of the preceding claims, wherein the battery (1) is a lithium-ion battery.

14. The battery (1) according to claim 13, wherein the electrode assembly (8) comprises -nickel containing electroactive material.

15. The battery according to claim 14, wherein the one or more membranes (18, 28) have a total gas permeability with regard to carbon dioxide of from 1 to 12 mMol per year and liter of internal volume of cell case (2).

16. An energy storage device (50) comprising a plurality of batteries connected in series and / or in parallel, wherein at least one of the plurality of batteries constitutes a battery (1) according to any one of the preceding claims.

17. A vehicle (100) comprising a battery (1) according to any one of claims 1 to 14 or an energy storage device (50) according to claim 16.

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