A battery cell casing, a method of producing said casing and a battery cell comprising said casing

Abstract

The invention relates to a battery cell casing comprising a thermally conductive material, said casing comprising a bottom, one or more sides, and a top, where the one or more sides are perforated with a plurality of through holes and wherein the holes are sealed by a thermoplastic polymer. The invention further relates to a battery cell comprising the battery cell casing according to the first aspect filled with at least an anode, a cathode, one or more separators, a positive current collector, a negative current collector, and an electrolyte.

Description

TITLE A battery cell casing, a method of producing said casing and a battery cell comprising said casing.FIELD OF THE INVENTIONThe present invention relates to a battery cell casing and to a battery cell comprising the battery cell casing. The invention moreover relates to a method for manufacturing the battery cells and to a battery system comprising one or more trays for holding one or more battery cells and one or a plurality of battery cells of this disclosure.BackgroundBattery cells comprise several components, such as a battery cell casing that is used to encase the internal components of the battery cell. Components that are generally present inside of the battery cell casing are: an anode, a cathode, one or more separators, a positive current collector, a negative current collector, and an electrolyte. For example, an electric vehicle battery (EVB) is a rechargeable battery used to power the electric motors of a battery electric vehicle (BEV) or hybrid electric vehicle (HEV). An EVB is comprised of a plurality of battery cells or battery modules comprising battery cells. A tray is used to house the battery cells and to provide cooling.Generally, battery cells, such as lithium-ion battery cells, involve a substantial risk of thermal runaway in case of local failure of the battery cell. Such local failure may result from mechanical impact, for example during an electric vehicle crash or dendrite formation and internal short upon overcharge or impurities or imperfection of the cell or thermal abuse. In case of thermal runaway, the battery cell keeps re-igniting, which makes it very difficult and time-consuming to extinguish.The present invention is related to a battery cell casing that encases the internal components of a battery cell. In particular to a battery cell casing having improved cooling provisions.ObjectsIt is an object to provide casing for individual battery cells, having an improved cooling provision. It is another object of the invention to provide a battery cell casing forplacement in trays having an integrated cooling provision. It is a further object of the invention to provide a battery cell casing, in which the chance of a catastrophic thermal runaway in case of battery cell failure may effectively be reduced.STATEMENT OF THE INVENTIONOne or more of the above objects are achieved by the invention according to one or more of the following aspects.In a first aspect, the invention relates to a battery cell casing comprising a thermally conductive material, said casing comprising a bottom, one or more sides, and a top, where the one or more sides are perforated with a plurality of through holes and wherein the holes are sealed by a thermoplastic polymer.In a second aspect, the invention relates to a battery cell comprising the battery cell casing according to the first aspect filled with at least an anode, a cathode, one or more separators, a positive current collector, a negative current collector, and an electrolyte.In a third aspect, the invention relates to a method for manufacturing the battery cells casings according to the first aspect, comprising: * providing a perforated casing made of a thermally conductive material, said casing comprising a bottom, one or more sides, and a top, where the one or more sides are perforated with a plurality of through holes, and * applying a thermoplastic polymer to seal said plurality of through holes.In a fourth aspect, the invention relates to a battery system, comprising one or more trays for holding one or more battery cells, at least one battery cell according to the second aspect or prepared according to the method of the third aspect and optionally a cooling system.The invention further relates to a battery system comprising a battery cell comprising the battery cell casing according to the first aspect and a cooling system configured for cooling the battery cell.The invention further relates to a battery system, comprising a battery cell comprising the battery cell casing according to the first aspect, one or more tray for holding one or more battery cells and a cooling system comprising: i) a supply line connected to a coolant inlet of each of the one or more trays; ii) a discharge line connected to the coolant outlet of each of the one or more trays; and iii) a flow generating device, such as a pump, for generating a circulating flow of the coolant medium through the supply line, via the channel and the discharge line.In some embodiments, the thermoplastic polymer is present inside the through holes and the inside of the one or more sides are not covered with the thermoplastic polymer. An example of such embodiment is described below referring to Fig. 4A.Below several embodiments of the invention are disclosed. Corresponding embodiments of the first aspect are also applicable for the other aspects according to the present invention, unless specified otherwise.An effect of the battery cell casing, battery cell and battery system according to the invention is that because of the configuration of the sides with closed / sealed perforations, a local battery cell failure which leads to the (local) overheating of the battery cell concerned, results in a local melting of the thermoplastic closure / seal thereby creating the opening of the perforation(s) near the location of the failure of the cell. As a result, heat (and optionally effluent) can pass through the local opening outside of battery cell, reducing the temperature of said battery cell. This contributes to preventing further propagation of the thermal runaway within the cell and in turn to other cells.DETAILED DESCRIPTIONBrief description of drawingsThe present invention is described hereinafter with reference to the accompanying drawings in which embodiments of the present invention are shown and in which like reference numbers indicate the same or similar elements. However, the invention may be embodied in many different forms and should not be construed as limited to therepresentative embodiments set forth herein. The exemplary embodiments are provided so that this disclosure will be both thorough and complete, and will fully convey the scope of the invention and enable one of ordinary skill in the art to make, use and practice the invention.The following Figures are exemplary embodiments, which are provided to illustrate the present disclosure.Fig. 1 is a schematic perspective view of a battery system depicting a tray which is holding battery cells;Fig. 2 is a schematic perspective view of another tray for holding a battery cell depicting insertion of the battery cell into the tray during assembling a battery system; Fig. 3 is a schematic perspective view of a battery cell;Fig. 4A is a schematic perspective view of a battery cell casing for a prismatic battery cell and depicting in a schematic cross section the configuration of a portion of a side of the battery cell casing;Fig. 4B is a schematic perspective view of another battery cell casing for a prismatic battery cell and depicting in a schematic cross section the configuration of a portion of a side of this battery cell casing;Fig. 4C is a schematic perspective view of a further battery cell casing for a prismatic battery cell and depicting in a schematic cross section the configuration of a portion of a side of this battery cell casing;Fig. 5 is schematic perspective view of a battery cell casing for a cylindrical battery cell and depicting in a schematic cross section the configuration of a portion of a side of this cylindrical shaped battery cell casing;Fig. 6A is a schematic perspective view of a battery cell casing for a pouch-type battery cell and depicting in n schematic cross section the configuration of a portion of a side of this battery cell casing;Fig. 6B is a schematic perspective view of another battery cell casing for a pouch-type battery cell and depicting in a schematic cross section the configuration of a portion of a side of this battery cell casing;Fig. 7 shows schematically method steps for manufacturing a battery cell casing according to this disclosure;Fig. 8 shows a flowchart of the method for manufacturing a battery cell casing according to this disclosure;Fig. 9 shows a flowchart of a method for providing perforations (through holes) according to this disclosure;Fig. 10 shows a flowchart of a method for applying a thermoplastic polymer on perforations of a battery cell casing.The present invention is elucidated below with a detailed description. Unless otherwise defined or specified, all terms should be accorded a technical meaning consistent with the usual meaning in the art as understood by the skilled person.All parameter ranges include the endpoints of the ranges and all values in between the endpoints, unless otherwise specified. When used in these specification and claims, the terms "comprise" and "comprising" and variations thereof mean that the specified features, steps, or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps, or components.Battery systemThis disclosure relates to a battery system 50; 50’ as shown in Figs. 1 ; 2, comprising one or more trays 51 ; 51 ’ for holding one or more battery cells 101 , at least one battery cell 101 as shown in Fig. 3, and optionally a cooling system 53.Regarding the tray 51 ; 51 ’ and the cooling system 53 reference is made to four applications in the name of the present applicant all filed on April 14, 2023, all entitled “A tray and a system for housing a plurality of individual battery modules, and a method for cooling a plurality of battery modules housed in a tray of such a system” with filing numbers EP23168132.1 , EP23168131 .3, EP23168129.7, and EP23168130.5, each of which is incorporated herein by reference.The tray according to the above applications that may be used in conjunction with the present battery cells may be a tray for housing a plurality of individual battery modules such as the present battery cells, the tray comprising a bottom wall and side walls defining a receiving space for the plurality of individual battery modules, wherein thetray has one or more inner walls extending between opposite side walls and subdividing the receiving space in a plurality of individual battery module receiving chambers each bounded by a part of the bottom wall and by one or more side walls and / or inner wall or walls, and a coolant inlet and a coolant outlet,I) wherein at least one of the side walls and / or at least one of the one or more inner walls comprises:- a plate shaped base part made of a thermoplastic material and comprising a wall-channel for a flow of a coolant medium on at least one plate side of the base part, wherein the wall-channel is in connection with the coolant inlet and with the coolant outlet such that a coolant medium can flow through the wall-channel, and- a thermoplastic-based, preferably a polyolefin-based layer, particularly preferably a polyolefin-based film, bonded to the base part such that it covers and thereby closes off the wall-channel, wherein the wall concerned is oriented in the tray such that it faces one or more of the battery module receiving chambers with a plate side thereof having the layer bonded thereto; and / orII) wherein the bottom wall comprises:- a plate shaped base part made of a thermoplastic material and comprising a bottom-channel for a flow of a coolant medium on at least one plate side of the base part, wherein the bottom-channel is in connection with the coolant inlet and with the coolant outlet such that a coolant medium can flow through the bottomchannel, and- a thermal conductive layer, preferably a thermal conductive film, bonded to the base part such that it covers and thereby closes off the bottom-channel, wherein the bottom wall is oriented such that it faces the receiving space with an inner plate side thereof having the layer bonded thereto.The tray according to the above applications that may be used in conjunction with the present battery cells may be a tray for housing at least one battery module such as the present battery cell, the tray comprising a bottom wall and side walls defining a receiving space for the at least one battery module, and at least one coolant inlet and at least one coolant outlet, wherein at least one of the side walls and / or the bottom wall comprises:- a plate shaped base part;- a first thermoplastic-based layer, preferably a polyolefin-based layer, particularly preferably a polyolefin-based film, attached to or positioned against the base part, and a second thermoplastic-based layer, preferably a polyolefin-based layer, particularly preferably a polyolefin-based film, bonded to the first layer, wherein at least one channel is provided between the first layer and the second layer for a flow of a coolant medium, wherein the channel is in connection with the at least one coolant inlet and with the at least one coolant outlet such that a coolant medium can flow through the channel, wherein the wall concerned is oriented in the tray such that the second layer faces the receiving space.In addition to the above tray, the disclosure also relates to a system for housing at least one battery cell, comprising: one or more trays according to the above aspect filled with one or more battery cells according to this disclosure; and a cooling system comprising: i) a supply line connected to a coolant inlet of each of the one or more trays; ii) a discharge line connected to the coolant outlet of each of the one or more trays; and iii) a flow generating device, such as a pump, for generating a circulating flow of the coolant medium through the supply line, via the channel and the discharge line.The tray 51 (Fig. 1) is a tray for housing a plurality of individual battery modules, i.e. battery cells 101 . The tray 51 comprises a bottom wall 51 a and side walls 51 b defining a receiving space for at least one battery cell 101. The tray 51 has one or more inner walls 51 d extending between opposite side walls 51 b and subdividing the receiving space in a plurality of individual battery module receiving chambers each bounded by a part of the bottom wall 51 a and by one or more side walls 51 b and / or inner wall 51 d or walls 51 d, and a coolant system 53. In the side wall 51 b with the smallest dimensions the channel configuration of the channel of the coolant system as shown in Fig. 1 has a horizontal orientation, but this channel may also have a vertical orientation like the channel configuration of the coolant system 53 of the side wall with the largest dimensions as shown in Fig. 1.The tray 51 ’ (Fig. 2) is a tray 51 ’ for housing at least one battery module such as a single battery cell 101 , the tray comprising a bottom wall 51 a’ and side walls 51 b’ defining a receiving space as shown in Fig. 2 for the battery cell 101. At least one of the side walls 51 b’ of the tray 51 ’ is provided with a coolant system 53’. The channel configuration of the channels of the coolant system 53’ in the side walls 51 b’ as shown in Fig. 2 also have a horizontal orientation, but these channels may also be configured to have a vertical orientation (not shown in Fig. 2).The battery system may also comprise a tray or trays for holding one or more battery cells 101 and one or a plurality of battery cells 101 of this disclosure, without a cooling system in the tray (not shown).Battery cellThis disclosure also relates to a battery cell 101 comprising a battery cell casing of this disclosure to be discussed in more detail below, wherein the battery cell 101 may be further filled with at least an anode, a cathode, one or more separators, a positive current collector, a negative current collector, and an electrolyte. The battery cell 101 may further be equipped with other standard battery cell components such as battery terminals 102a, 102b.Battery cell casingFigs. 4A-6B show various embodiments of battery cell casings l-VI and Fig. 7 shows a method to produce the battery cell casing I as shown in Fig. 4A.Below several features of said battery cell casing are disclosed in more detail, being the structure, the thermally conductive material, and the thermoplastic polymer.Structure of battery cell casingThere are three basic types of battery cells that are currently being used in electric vehicles, namely cylindrical cells, prismatic cells, and pouch cells. Cylindrical cells are self-contained in a cylindrical casing; said casing is a solid / rigid casing providing cylindrical battery cells with resistance against mechanical shocks. This type of cells has been used for many years in the field of household batteries and they are cost-efficient and easy to manufacture. Because they can be limited in respect of power output, other shapes of battery cells are used. Prismatic cells use less material for the casing and thus can store more energy and deliver higher power. In addition, they are found to also be better at managing heat compared to cylindrical cells. The casing of prismatic cells is a solid / rigid casing providing prismatic battery cells with resistance against mechanical shocks. This shape of cell in growing in use over the last years. A third shape and type of battery cells are the so-called pouch cells. These cells differ from cylindrical and prismatic cells in that the casing is not solid / rigid but instead pouch cells are encased in a soft, flexible plastic-aluminium laminate casing. Pouch cells have the advantage that they are efficient in terms of space usage due to the flexible packaging and lower internal resistance due to the stacking of the electrodes instead of wound like in cylindrical and prismatic casings. However, their flexible casing is relatively fragile so that they generally require additional protection, e.g., in the form of a tray, to prevent mechanical damage to the cells.The casing of the disclosure may have several different shapes, some of which will be discussed in detail below.In a battery cell casing l-lll (Figs. 4A-C) for a prismatic battery cell the bottom 1 is a bottom wall 1 of a thermally conductive material, wherein the one or more sides 3 are side walls 3 of a thermally conductive material, and wherein the top 5 is a top cover 5 of a thermally conductive material. The casing l-lll is a rigid casing (viz. a box-type casing) comprised of a bottom wall 1 , side walls 3 and a top cover 5. The top cover 5 may be configured as or adapted for battery terminal(s) of the battery cell, for example by recesses (not shown) or by the configuration of the top cover. It is also possible that alternatively or in addition the bottom wall 1 may be configured as or adapted for battery terminal(s) of the battery cell. Battery terminals 102a, 102b of the battery cell 101 are for example shown in Figs. 1-3.A casing having a prismatic shape comprises a bottom wall having a polygonal shape, and at least three side walls, and a top cover having a polygonal shape. The battery cell casing l-lll (Figs. 4A-C) is an example of a prismatic shaped battery cell casing. The casing l-lll (Figs. 4A-C) has a cuboid shape comprising the bottom wall 1 havinga rectangular shape, and four side walls 3, and the top cover 5 having a rectangular shape. The bottom wall 1 may have a width of between 1 and 100 centimetres, and a length of between 5 and 100 cm, and wherein the side walls 3 may have a height of between 5 and 20 centimetres. The side walls 3 have a dimension corresponding to the length or width of the bottom wall 1. The width and the length of the bottom wall (and top cover) are determined depending on the polygonal shape according to standard geometry.It is possible to provide the prismatic casing l-lll for a battery cell 101 by producing the side walls 3 with the bottom 3 as one-piece, wherein the top cover 5 is connected to the side walls 3 in subsequent step. It is also possible to provide the side walls 3 as one-piece, as will be explained in more detail hereafter, wherein the bottom 3 and the top cover 5 are connected to the side walls 3 in a subsequent step or steps. These producing methods of the casing l-lll make it possible 19 to produce the battery cell 101 relatively easily by filling it with battery components before connecting the bottom wall 1 and / or the top cover 5 to the side walls 3.Several other embodiments of prismatic casings (not shown) are the following: i) a triangular prism casing (not shown) comprising a bottom wall having a triangular shape, and three side walls, and a top cover having a triangular shape, ii) a pentagonal prism casing (not shown) comprising a bottom wall having a pentagonal shape, and five side walls, and a top cover having a pentagonal shape, iii) a hexagonal prism casing (not shown) comprising a bottom wall having a hexagonal shape, and six side walls, and a top cover having a hexagonal shape, iv) a heptagonal prism casing (not shown) comprising a bottom wall having a heptagonal shape, and seven side walls, and a top cover having a heptagonal shape, and v) an octagonal casing (not shown) comprising a bottom wall having an octagonal shape, and eight side walls, and a top cover having an octagonal shape.In a battery cell casing IV (Fig. 5) for a cylindrical battery cell, the bottom is a circular bottom wall 11 , and the top cover is a circular top cover 17. The bottom wall 11 and / or the top cover 17 may be configured as or adapted for battery terminals of (not shown) the battery cell. Between the top cover 17 and the bottom wall a cylindrical side wall13 extends. The side wall 13 may have a height of between 60 and 130 millimetres, and bottom wall and top cover may each have a diameter of between 15 and 50 millimetres. The cylindrical battery cell casing IV may be produced by providing the cylindrical side wall 13 with or without the circular bottom wall 11 as explained above for the prismatic casing l-lll, wherein the circular top cover 17 and possibly the circular bottom wall 11 may be connected to the cylindrical side wall 13 in a subsequent step.Several specific embodiments of cylindrical casings are the following: i) a diameter of 18 millimetres and a height of 65 millimetres, also called a 1865 cylindrical casing; ii) a diameter of 21 millimetres and a height of 70 millimetres, also called a 2170 cylindrical casing; iii) a diameter of 46 millimetres and a height of 80 millimetres, also called a 4680 cylindrical casing; iv) a diameter of 46 millimetres and a height of 100 millimetres, also called a 46100 cylindrical casing; and v) a diameter of 46 millimetres and a height of 120 millimetres, also called a 46120 cylindrical casing. In another embodiment, the said casing has a cylindrical shape comprising an oval bottom wall, a cylindrical side wall, and an oval top cover, preferably wherein said side wall having a height of between 60 and 130 millimetres, and bottom wall and top cover each having a length of the major axis (major diameter) of 15 and 50 millimetres and having a length of the minor axis (minor diameter) of between 15 and 50 millimetres.In solid / rigid casings for prismatic and / or cylindrical battery cells l-IV, the bottom wall 1 ; 11 and the one or more side walls 3; 13 are made of a thermally conductive material, wherein the thermally conductive material may have a thickness of between 0.1 and 2 mm. More specifically, the bottom walls 1 ;11 and the one or more side walls 3; 13 may have a thickness of between 0.1 and 0.6 mm.The battery cell casing V; VI may be in the form of a pouch, formed of a laminate comprising a thermally conductive material that is covered on one or both sides by a thermoplastic polymer TP. The laminate of the bottom 21 and the one or more sides 23 may have a thickness of between 50 and 500 micrometres, more preferably between 100 and 200 micrometres. The top 25 of the casing V; VII may be provided by connecting, for example by heat sealing, end portions of the two pouch sides 23 together. The pouch-like casing V; VI is a flexible casing (viz. a pouch-type casing)comprised of a bottom 21 , sides 23 and a top 25. One of the differences with the rigid casings being that the thickness is less. The casings V; VI in the form of a pouch according to the present disclosure are made of pouch material, being a laminate of a thermally conductive material layer (e.g., a metal layer such as aluminium), covered on one or preferably on both sides with a thermoplastic polymer TP. The thickness T; T’ of said laminate is preferably between 100 and 200 micrometres.The figures 4A-7B show a battery cell casing l-VI comprising a thermally conductive material, said casing l-IV comprising a bottom 1 ; 1 1 ; 21 , at least one side 3; 13; 23, and a top 5; 15; 25, where the at least one side 3; 13; 23 is perforated with a plurality of through holes 7; 17; 27 and wherein the holes 7; 17; 27 are sealed by a thermoplastic polymer TP. A side 3; 13; 23 of the battery cell casing l-VI may comprise at least ten (10) through holes 7; 17; 27 to reduce the risk of a catastrophic thermal runaway TR (Fig. 2).The term “battery cell casing comprising a thermally conductive material” as used in the present description means to include a battery cell casing made of a thermally conductive material wherein a thermoplastic polymer is present in addition to said thermally conductive material.The term “sealed” as used in the present description means that the through holes are closed off by the thermoplastic polymer. This may, with reference to Figs. 4A-6B, be by the presence of sealing material (“plugs”) TP made of thermoplastic polymer inside the through holes 7 (Fig. 4A); 17, or by a sealing layer I film TP covering either the inside opening 7a; 17a; 27a and / or outside opening 7b; 17b; 27b of the through holes 7; 17; 27 (see Figs. 4B-6B) or a combination of a plug TP and sealing layer(s) / film(s) TP. For example, it is possible to use a polymer layer or film TP covering the inside of the sides of a casing, see for example casings ll-VI, e.g., all the inside walls may be covered by such a layer or film TP. This layer or film TP to the inside walls seals the through holes 7; 17; 27 and may also provide electric insulation to avoid shortcircuiting. The laminate of casing V; VI may comprise a perforated aluminium foil with through holes 27 which is provided on an inner side with a film TP of thermoplastic polymer to prepare a pouch-laminate. The laminate of casing VI may comprise aperforated aluminium foil with through holes 27 which is provided on both sides with a film TP of thermoplastic polymer to prepare a pouch-laminate. A bag-like structure V; VI is formed after which the battery cell is filled inside said bag-like structure which is then closed on the top to form the top and provide the battery cell, with the battery cell casing around it. The film TP has a thickness of between 10 and 40 micrometres, such as 20 to 30 micrometres. This thickness allows to achieve the electrical insulating effect but still allows for thermal conductivity.The through holes 7; 17; 27 (perforations) are provided in the thermally conductive material and extend through the thermally conductive material providing an outside opening and an inside opening. The distance between the outside opening and the inside opening corresponds to the length of the hole (perforation) 7; 17; 27 which corresponds to the thickness of the thermally conductive material layer as shown in figures 4A-6B. The through holes 7; 17; 27 (perforations) in the at least one side 3; 13; 23 may have a size of between 0.5 and 5 millimetres. The holes 7; 17; 27 may have any shape, such as a circular, oval, or polygonal. The size of the holes is determined as the width, which in case of a circular hole the diameter, for an oval hole, the average of the major and minor diameter, and for a polygonal shape the width determined according to standard geometry. The through holes 7; 17; 27 form openings in the side (wall)s 3; 13; 23 of the casing.The bottom wall 1 ; 11 and / or the top cover 5; 15 of the prismatic or cylindrical shaped casing l-IV may also be perforated with a plurality of through holes (not shown), wherein these holes are sealed by a thermoplastic polymer in a manner as disclosed in this disclosure for the sides 3; 13; 23.In an aspect, the holes have a spacing of between 1 and 10 millimetres. The spacing between the holes is preferably less than 10 mm but at least 1 mm. The position of the holes in the side(s) may be aligned with positioning of cooling channels that may be present in the tray holding the battery cells (including casing) during use. In an aspect, the holes will be more than 2 millimetres spaced away from any edges, such as the top or bottom edge of the side(s) or from side edges in the case of a prismatic shaped cell.Generally, battery cell casings are made without through holes. For reducing the risks of thermal runaway, the sides 3; 13; 23 of the battery cell casing l-VI according to this disclosure are not only perforated to provide a plurality of through holes 7; 17; 27, but these holes 7; 17; 27 are also sealed by a thermoplastic polymer TP. Hence, a battery casing l-VI sealing the internal components of the battery cell 101 is provided. In addition, the battery casing l-VI has an improved cooling provision, because a thermal runaway in the battery cell 101 results in a local melting of the thermoplastic closure / seal TP thereby creating the opening of the perforation(s) near the location of the failure of the cell. As a result, heat (and optionally effluent) can pass through the local opening outside of battery cell, reducing the temperature of said battery cell 101 . This contributes to preventing further propagation of the thermal runaway within the cell and in turn to other cells in a tray of battery system.Thermally conductive materialIn an embodiment, the thermally conductive material is a metal, preferably aluminium or steel or an alloy comprising aluminium and / or steel. Other options besides the use of a metal, are the use of filled polymeric materials, such as polymeric materials filled with thermally conductive fillers, such as carbon black, carbon fibres, carbon tubes, graphene, or conductive ceramic powders.Thermoplastic materialThe thermoplastic material may be a polyolefin material and is preferably a polyolefin-based film. The polyolefin may be for example be an ethylene-based polymer or a propylene- based polymer. Preferably, the polyolefin has a peak melting temperature (Tp,m) of at least 100°C, as determined in accordance with ASTM D3418 (2008), preferably of at least 120 or at least 140°C.The thermoplastic-based layer may be polyvinyl halide polymer-based layer, preferably a polyvinyl halide polymer-based film, such a polyvinyl chloride (PVC) material being a thermoplastic chloropolymer having a repeating vinyl chloride unit or a polyvinyl fluoride (PVF) material being a thermoplastic fluoropolymer having a repeating vinyl fluoride. The thermoplastic-based layer / film may also be of one or more of the following materials: i)polyetherimide (PEI) (e.g., ULTEM®), ii) a modified resin consisting of amorphous blends of polyphenylene oxides (PPO) or polyphenylene ether (PPE) resins with polystyrene (e.g., NORYL®), iii) a polycarbonate (PC) (e.g., LEXAN®), iv) a semi-crystalline material of polybutylene terephthalate (PBT) and / or polyethylene terephthalate (PET) optionally blended with polycarbonate (PC) (e.g., VALOX®); or v) polyamides (PA). Preferably, the thermoplastic material has a peak melting temperature (Tpm) of at least 100°C, as determined in accordance with ASTM D3418 (2008), preferably of at least 120 or at least 140°C. Preferably, the thermoplastic material has a peak melting temperature (Tpm) of at most 280 °C, at most 250 °C, at most 230 °C, at most 200°C, at most 180 °C, at most 160 °C or at most 155 °C, as determined in accordance with ASTM D3418 (2008). In some particularly preferred embodiments, the thermoplastic material has a peak melting temperature (Tpm) of 120 to 155 °C as determined in accordance with ASTM D3418 (2008).Preferably, the thermoplastic material comprises a polymer selected from polyolefin, polyvinyl halide polymer, polyetherimide, polyphenylene oxides, polyphenylene ether, polystyrene, polycarbonate, polybutylene terephthalate, polyethylene, terephthalate, polyamide and combinations thereof, wherein the amount of said polymer is at least 90 wt%, more preferably at least 95 wt%, with respect to the total thermoplastic material.In some preferred embodiments, the thermoplastic material comprises a polyolefin, wherein the amount of the polyolefin is at least 90 wt%, more preferably at least 95 wt%, with respect to the total thermoplastic material.According to the invention, the (local) overheating of the battery cell concerned results in a local melting of the thermoplastic material to create opening of the perforation(s) near the location of the failure of the cell. Accordingly, the thermoplastic material preferably does not comprise fire-resistant additive. Preferably, the amount of fire-resistant additive in the thermoplastic material is less than 30 wt% with respect to the total thermoplastic material. More preferably, the content of fire-resistant additive in the thermoplastic material is less than 25 wt%, more preferably less than 20 wt%, more preferably less than 15 wt%, more preferably less than 10 wt%, more preferably less than 7.0 wt%, more preferably less than 5.0 wt%, more preferably less than 3.0 wt%, more preferably less than 1.0 wt%, more preferably less than 0.5 wt%, more preferably less than 0.1 wt%, more preferably less than0.05 wt%, more preferably less than 0.01 wt% or 0.00 wt%, with respect to the total thermoplastic material. The fire-resistant additive is selected from the group consisting of an endothermic agent, a flame retardant, and a thermally expandable layered inorganic matter, e.g. mentioned in US2021013460A1 ,

[0115] -

[0141] , incorporated herein by reference.The polyolefin-based layer may be selected from the group consisting of a biaxially oriented polypropylene (BOPP) film, a biaxially oriented polyethylene (BOPE) film, or a film comprising one or more layers, preferably at least a core layer and two outer layers.The ethylene-based polymer may for example be a homopolymer of ethylene, or a copolymer of ethylene and one or more a-olefin, preferably wherein the a-olefin comprises 1-10 carbon atoms, more preferably wherein the a-olefin is selected from 1 -butene, 1- hexene, or 1 -octene. For example, the ethylene-based polymer may comprise > 80.0 wt.% of moieties derived from ethylene, preferably > 90.0 wt.%, more preferably > 95.0 wt.%, with regard to the total weight of the ethylene-based polymer. For example, the ethylene-based polymer may comprise < 20.0 wt.% of moieties derived from 1 -butene, 1 -hexene, or 1- octene, preferably < 10.0 wt.%, more preferably < 5.0 wt.%. The ethylene-based polymer may for example have a density of > 870 kg / m3, preferably of > 870 and < 975 kg / m3, more preferably of > 900 and < 975 kg / m3, even more preferably > 945 and < 970 kg / m3, as determined in accordance with ASTM D792 (2008). The ethylene-based polymer may for example have a melt mass-flow rate of > 0.1 and < 10.0 g / 10 min, preferably > 0.1 and < 5.0 g / 10 min, more preferably > 0.2 and < 3.5 g / 10 min, as determined in accordance with ASTM D1238 (2013), at 190°C under a load of 2.16 kg.The polypropylene-based film may comprise a propylene homopolymer, a propyleneethylene copolymer, or a propylene-ethylene-C4-terpolymer or a propylene-ethylene-C6- terpolymer, wherein the copolymer of terpolymers have an ethylene content of at most 4.0 wt.%, such as between 3.0 and 4.0 wt.% or in another embodiment at most 1 .5 wt.% based on the weight of the copolymer or terpolymer; wherein said homopolymer, copolymer or terpolymer has: i) a Mw / Mn in the range of 4.0 to 12, preferably 5.0 to 12 wherein Mw stands for the weight average molecular weight and Mn stands for the number average molecular weight and wherein Mw and Mn are measured according to ASTM D6474-12; ii) an XS in the range from 1 .0 to 8.0 wt.%, preferably from 1 .0 to 6.0 wt.%, wherein XS stands for theamount of xylene solubles which are measured according to ASTM D 5492-10; and iii) a melt flow rate in the range of 1 to 10 dg / min as measured according to IS01133-1 (2011) (2.16 kg / 230 °C).The polyolefin film may for example be a bidirectionally oriented film (BO film), wherein the orientation is introduced in the solid state. For example, the BO film may be oriented at a temperature of at least 10°C below T pm. The BO film may for example have a thickness of > 50 and < 500 pm, preferably > 50 and < 300 pm. The BO film may be oriented to a degree of orientation of > 5.0 and < 25.0 in the machine direction. The BO film may be oriented to a degree of orientation of > 5.0 and < 25.0 in the transverse direction. The BO film may be oriented to a degree of orientation of > 5.0 and < 25.0 in the machine direction and > 5.0 and < 25.0 in the transverse direction. In this context, the degree of orientation is defined as the ratio of the dimension of the film after being subjected to orientation over the dimension of the film prior to orientation, in each of the machine and the transverse direction. The BO film may be produced by cast melt extrusion of a film, cooling the film to a temperature of at least 10°C below Tpm followed by stretching the film in the machine direction and the transverse direction. The stretching may be performed simultaneously in both directions, or sequentially, first in the machine direction and then in the transverse direction, or first in the transverse direction and then in the machine direction.In the embodiment of the present disclosure wherein the casing is pouch-like, the laminate used may be a multilaminate film comprising a perforated thermally conductive core layer in between two polyolefin-based outer layers. Such a laminate has the advantage that the core layer provides excellent thermal conductivity to dissipate heat away from the local hotspot to prevent or delay local overheating and local melting of the outer thermoplasticbased layer. The thermoplastic-based layer will locally melt thereby opening up the perforations in the core layer to allow heat to pass out of the pouch. The thermoplastic outer layers in turn can be multilayer to embody different properties needed for chemical resistance and mechanical integrity under normal operations.Method of manufacturing batter cell casingIn a third aspect, the disclosure relates to a method as shown in figure 8 for manufacturing the battery cell casing l-VI as described above, comprising:S1 : providing a perforated casing made of a thermally conductive material, said casing comprising a bottom, one or more sides, and a top, where the one or more sides are perforated with a plurality of through holes, andS2 applying a thermoplastic polymer to seal said plurality of through holes.There are several specific methods falling under the scope of the invention to provide the plurality of through holes in the casing of above step S1 , such as a method as shown in Fig. 9, wherein the step of providing a casing of step S1 comprises:S1 i) providing a case extrudate and punching the plurality of through holes in said case extrudate to obtain a perforated casing; orS1 ii) providing a solid casing and applying the plurality of through holes, for example by means of a laser, to obtain a perforated casing; orS1 iii) providing a perforated sheet of thermally conductive material, and extrudate to obtain a perforated casing.There are several methods to provide the plurality of through holes in the side walls.A first method (method step S1 i) is to provide a solid (without holes) case extrudate, then punching the plurality of through holes in said case extrudate using a template to obtain a perforated casing.A second method (method step S1 ii) is to provide a solid casing, being in the context of the present invention a casing without perforations, then the plurality of through holes are made by means of laser using a laser perforation technique. A person skilled in the art will determine the parameters required to obtain the through holes, depending on the thermally conductive material used, the thickness thereof and the shape of the casing.A third method (method step S1 iii) is to first provide a perforated sheet of thermally conductive material, and extrudate or form that sheet into a perforated casing. With this method, is should be noted the size and distribution of the holes will differ from the perforated sheet to the perforated casing, because of the extrusion method. This must be considered when selecting the thickness of the perforated sheet as well asthe size and distribution of the holes in the perforated sheet. For example, when a perforated sheet is used with circular holes, the holes in the final perforated casing may either be larger circular holes or oval holes.There are several specific methods to provide the thermoplastic polymer in said plurality of through holes of said perforated casing as indicated by step S2, such as by at least one of the following method steps (Fig. 10), wherein the thermoplastic polymer is applied to said plurality of through holes of said perforated casing by:S2i) providing a perforated casing, adding a plug inside of said perforated casing, dipping the perforated casing with plug inside into molten thermoplastic polymer, and plunge into a negative to clean the molten thermoplastic polymer of the outside of the perforated casing to obtain a battery cell casing; and / orS2ii) providing a perforated casing, applying a film of a thermoplastic polymer on the inside of the casing and optionally on the outside of the casing.As indicated by dotted arrows in fig. 10, it is possible to perform step S2ii after step S2i orto perform step S2i after step S2ii applying the film TP to the inside of the casing, wherein after these steps S2i and S2ii, it is optionally possible to apply the film to the outside of the casing.There are several methods to seal the plurality of through holes in the side walls. Such a method (method S2i) is the following with reference to Fig. 7. First, a perforated casing I’ of a thermally conductive material (e.g., a metal) is provided. The perforated casing is identified with I’, in that the perforated casing comprises the four sides 3 of casing I as shown in Fig. 4a without bottom and top. This perforated casing I’ has the shape of the final battery cell casing I but the through holes 7 are open and need to be sealed. A plug 34 is provided. The plug may also have a different configuration for temporarily closing the inside openings of the holes 7. The plug 34 has the shape of the perforated casing I’ and preferably fits exactly into the inside of said casing I’ by moving it in the direction as indicated with arrow P1 . In this way, the inside opening of the through holes 7 are temporarily closed / sealed. Next, the perforated casing I’ with plug 34 inside is dipped as indicated by arrow P2 into a container 36 with molten thermoplastic polymer. In this way, the molten thermoplastic material can enter thethrough holes 7 from the outside and is blocked on the inside by the plug 34, preventing the inflow of molten thermoplastic polymer into the inside of the perforated casing I’. The perforated casing I’ with plug 34 inside is removed from the container 36 and is subsequently plunged into a negative 38 in a direction indicated by arrow P3 to clean the molten thermoplastic polymer of the outside of the perforated casing I’. The inside shape of the negative 38 preferably matches exactly with the outside shape of the perforated casing I’ to scrape away all excess of molten thermoplastic polymer from the outside of the perforated casing I’. This in essence, cleans the outside of the perforated casing, leading to a battery cell casing I’ in which the thermoplastic polymer has filled the through holes 7 in a manner as shown in Fig. 4A. Instead of closing the inside openings of the through holes first, fill the through hole with the thermoplastic polymer and optionally clean the outside of the perforated casing, it is also possible to reverse the process by closing the outside opening of the through holes first, fill the through hole with the thermoplastic polymer and then, optionally, clean the inside of the perforated casing. In a variation of this method, there may be a spacing between the perforated casing I’ and the plug 34 to allow for a polymer coating to form on the inside of the perforated casing in addition to filing the holes 7. The casing is then allowed to cool or actively cooled to provide the casing according to the invention. In a variation of this method, there may be a spacing between the perforated casing I’ and the negative 38 to allow for a polymer coating to form on the outside of the perforated casing I’ in addition to filing the holes 7. These two variations may be combined.A second method (method S2i) is the following. First, a perforated casing of a thermally conductive material (e.g., a metal) is provided. This perforated casing has the shape of the final battery cell casing but the through holes are open and need to be sealed. A film of a thermoplastic polymer is applied on the inside and / or on the outside of the perforated casing (see Fig. 10).For example, for applying a polymer to the internal side walls the inner side walls can be coated with a molten polymer which is then cooled to set in place. Otherwise, a polymer film may be cut to shape and adhered to the inner side walls by means of an adhesive, optionally using a block to press the film onto the side walls. Otherwise, ahot polymer film (e.g. in the form of a pouch / bag) could be inserted using a block of a shape corresponding to the inside of the battery cell casing, which block assists in pressing the film against the inner side walls after which the polymer film is cooled to set. Methods for applying an insulating film to a prismatic cell casing are for example disclosed in DE102017202540A1 , which is incorporated herein by reference, which methods may be used. Other ways of applying inside coating is through spray coating and that is commonly practiced for food and beverage cans.When an outside film is applied, shrink wrapping may be used. Methods for applying an insulating film to a prismatic cell casing are for example disclosed in DE102017202540A1 , which is incorporated herein by reference, which methods may be used. With this method the through holes may or may not be filled, in any they are sealed by covering the outside opening and / or the inside opening of the through hole. This method may be combined with the first method (method S2i) discussed above.Effects of the inventionThe battery cell casing according to the invention provides for an efficient way to allow heat (and hot effluent) to escape the battery cell in case of overheating, thereby contributing to a decrease in the severity of a thermal runaway and mitigate associated risks. The battery cell casing of the invention has an improved cooling provision. The battery cell according to the invention, comprising the inventive battery cell casing are optimally combined with the above disclosed inventive trays in order to have a fully integrated cooling provision. The battery cell casing of this disclosure in combination with controlled release of the coolant from the tray will dissipate the heat and prevent further propagation of the thermal runaway within the cell and / or reduces the rate of propagation. This will also reduce the propagation to neighboring cells.With the present battery cell casing the chance of a catastrophic thermal runaway in case of battery cell failure may effectively be reduced.Clauses1 . A battery cell casing comprising a thermally conductive material, said casing comprising a bottom, one or more sides, and a top, where the one or moresides are perforated with a plurality of through holes and wherein the holes are sealed by a thermoplastic polymer.2. The battery cell casing according to clause 1 , wherein the thermally conductive material is a metal.3. The battery cell casing according to clause 1 , wherein the thermally conductive material is aluminium or steel or an alloy comprising aluminium and / or steel.4. The battery cell casing according to clause 1 , wherein the bottom is a bottom wall of a thermally conductive material, wherein the one or more sides are side walls of a thermally conductive material, and wherein the top is a top cover of a thermally conductive material.5. The battery cell casing according to clause 4, wherein the bottom walls and the one or more side walls having a thickness of between 0.1 and 2 mm.6. The battery cell casing according to clause 4, wherein the bottom walls and the one or more side walls having a thickness of between 0.1 and 0.6 mm.7. The battery cell casing according to clause 4, wherein said casing has a cylindrical shape comprising a circular bottom wall, a cylindrical side wall, and a circular top cover.8. The battery cell casing according to clause 7, wherein said side wall having a height of between 60 and 130 millimetres, and bottom wall and top cover each having a diameter of between 15 and 50 millimetres.9. The battery cell casing according to clause 4 having a cuboid shape comprising a bottom wall having a rectangular shape, and four side walls, and a top cover having a rectangular shape.10. The battery cell casing according to clause 9, wherein said bottom wall has a width of between 1 and 100 centimetres, and a length of between 5 and 100 cm, and wherein the side walls have a height of between 5 and 20 centimetres.11 . The battery cell casing according to clause 4, where the inside of the one or more side walls are covered with a thermoplastic polymer.12. The battery cell casing according to clause 4, where the inside of the one or more side walls are covered with a thermoplastic film.13. The battery cell casing according to clause 12, where the inside of the one or more side walls are covered with a thermoplastic film having a thickness of between 10 and 40 micrometres.14. The battery cell casing according to clause 1 in the form of a pouch, formed of a laminate comprising a thermally conductive material that is covered on one or both sides by a thermoplastic polymer.15. The battery cell casing according to clause 14, wherein the bottom and the one or more sides of the pouch having a thickness of between 50 and 500 micrometres.16. The battery cell casing according to clause 14, wherein the bottom and the one or more sides of the pouch having a thickness of between 100 and 200 micrometres.17. The battery cell casing according to clause 1 , wherein the holes have a size of between 0.5 and 5 millimetres.18. The battery cell casing according to clause 1 , wherein the holes have a spacing of between 1 and 10 millimetres.19. A battery cell comprising the battery cell casing according to clause 1 filled with at least an anode, a cathode, one or more separators, a positive current collector, a negative current collector, and an electrolyte.20. A battery system, comprising:- one or more trays for holding one or more battery cells,- at least one battery cell according to clause 19, and- optionally a cooling system.21. A method for manufacturing the battery cell casing according to clause 1 , comprising:* providing a perforated casing made of a thermally conductive material, said casing comprising a bottom, one or more sides, and a top, where the one or more sides are perforated with a plurality of through holes, and* applying a thermoplastic polymer to seal said plurality of through holes.22. The method according to clause 21 , wherein the step of providing a casing comprises: i) providing a case extrudate and punching the plurality of through holes in said case extrudate to obtain a perforated casing; orii) providing a solid casing and applying the plurality of through holes, for example by means of a laser, to obtain a perforated casing; or iii) providing a perforated sheet of thermally conductive material, and extrudate to obtain a perforated casing.23. The method according to clause 21 or 22, wherein the thermoplastic polymer is applied to said plurality of through holes of said perforated casing by: a) providing a perforated casing, adding a plug inside of said perforated casing, dipping the perforated casing with plug inside into molten thermoplastic polymer, and plunge into a negative to clean the molten thermoplastic polymer of the outside of the perforated casing to obtain a battery cell casing; and / or b) providing a perforated casing and applying a film of a thermoplastic polymer on the inside of the casing and optionally on the outside of the casing.24. A battery cell casing comprising a thermally conductive material, said casing comprising a bottom, one or more sides, and a top, where the one or more sides are perforated with a plurality of through holes and wherein the holes are sealed by a thermoplastic polymer.25. The battery cell casing according to clause 1 , wherein the thermally conductive material is a metal, preferably aluminium or steel or an alloy comprising aluminium and / or steel.26. The battery cell casing according to clause 1 , wherein the bottom is a bottom wall of a thermally conductive material, wherein the one or more sides are side walls of a thermally conductive material, and wherein the top is a top cover of a thermally conductive material and wherein said casing has a cylindrical shape comprising a circular bottom wall, a cylindrical side wall, and a circular top cover, preferably wherein said side wall having a height of between 60 and 130 millimetres, and bottom wall and top cover each having a diameter of between 15 and 50 millimetres.27. The battery cell casing according to clause 1 or clause 2, wherein the bottom is a bottom wall of a thermally conductive material, wherein the one or more sides are side walls of a thermally conductive material, and wherein the top is a top cover of a thermally conductive material and wherein said casing has a prismatic shape comprising a bottom wall having a polygonal shape, and at least three side walls, and a top cover having a polygonal shape, preferably said casing having acuboid shape comprising a bottom wall having a rectangular shape, and four side walls, and a top cover having a rectangular shape.28. The battery cell casing according to clause 1 or clause 2, wherein the holes have a size of between 0.5 and 5 millimetres.29. The battery cell casing according to clause 26, where the inside of the one or more side walls are covered with a thermoplastic polymer, preferably with a thermoplastic film, more preferably the film having a thickness of between 10 and 40 micrometres, such as 20 to 30 micrometres.30. The battery cell casing according to clause 1 in the form of a pouch, formed of a laminate comprising a thermally conductive material that is covered on one or both sides by a thermoplastic polymer, preferably the bottom and the one or more sides having a thickness of between 50 and 500 micrometres, more preferably between 100 and 200 micrometres.31. A battery cell comprising the battery cell casing according to any one of the preceding clauses filled with at least an anode, a cathode, one or more separators, a positive current collector, a negative current collector, and an electrolyte.32. A method for manufacturing the battery cell casing according to clause 1 , comprising:* providing a perforated casing made of a thermally conductive material, said casing comprising a bottom, one or more sides, and a top, where the one or more sides are perforated with a plurality of through holes, and* applying a thermoplastic polymer to seal said plurality of through holes.33. A battery system, comprising:- one or more trays for holding one or more battery cells,- at least one battery cell according to clause 31 , and- optionally a cooling system.34. The battery cell casing according to clause 1 , wherein the thermoplastic polymer is present inside the through holes and the inside of the one or more sides are not covered with the thermoplastic polymer.35. The battery cell casing according to clause 1 , wherein the amount of fire-resistant additive in the thermoplastic material is less than 30 wt%, preferably less than 25 wt%, more preferably less than 20 wt%, more preferably less than 15 wt%, more preferably less than 10 wt%, more preferably less than 7.0 wt%, more preferablyless than 5.0 wt%, more preferably less than 3.0 wt%, more preferably less than 1.0 wt%, more preferably less than 0.5 wt%, more preferably less than 0.1 wt%, more preferably less than 0.05 wt%, more preferably less than 0.01 wt% or 0.00 wt%, with respect to the total thermoplastic material.36. The battery cell casing according to clause 1 , wherein the thermoplastic material has a peak melting temperature (Tpm) of at most 280 °C, at most 250 °C, at most 230 °C, at most 200°C, at most 180 °C, at most 160 °C or at most 155 °C, as determined in accordance with ASTM D3418 (2008)s.37. A battery system comprising a battery cell comprising the battery cell casing according to claim 1 and a cooling system configured for cooling the battery cell.Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. The scope of the present invention is defined by the appended claims. One or more of the objects of the invention are achieved by the appended claims.

Claims

CLAIMS (PCT)1 . A battery cell casing comprising a thermally conductive material, said casing comprising a bottom, one or more sides, and a top, where the one or more sides are perforated with a plurality of through holes and wherein the holes are sealed by a thermoplastic polymer.

2. The battery cell casing according to claim 1 , wherein the thermally conductive material is a metal, preferably aluminium or steel or an alloy comprising aluminium and / or steel.

3. The battery cell casing according to claim 1 or claim 2, wherein the bottom is a bottom wall of a thermally conductive material, wherein the one or more sides are side walls of a thermally conductive material, and wherein the top is a top cover of a thermally conductive material, preferably the bottom walls and the one or more side walls having a thickness of between 0.1 and 2 mm, more preferably between 0.1 and 0.6 mm.

4. The battery cell casing according to claim 3, wherein said casing has a cylindrical shape comprising a circular bottom wall, a cylindrical side wall, and a circular top cover, preferably wherein said side wall having a height of between 60 and 130 millimetres, and bottom wall and top cover each having a diameter of between 15 and 50 millimetres.

5. The battery cell casing according to claim 3, wherein said casing has a prismatic shape comprising a bottom wall having a polygonal shape, and at least three side walls, and a top cover having a polygonal shape, preferably said casing having a cuboid shape comprising a bottom wall having a rectangular shape, and four side walls, and a top cover having a rectangular shape.

6. The battery cell casing according to claim 5, wherein said bottom wall has a width of between 1 and 100 centimetres, and a length of between 5 and 100 cm, and wherein the side walls have a height of between 5 and 20 centimetres.

7. The battery cell casing according to any one of the claims 3-6, where the inside of the one or more side walls are covered with a thermoplastic polymer, preferably with a thermoplastic film, more preferably the film having a thickness of between 10 and 40 micrometres, such as 20 to 30 micrometres8. The battery cell casing according to claim 1 or claim 2, being in the form of a pouch, formed of a laminate comprising a thermally conductive material that is covered on one or both sides by a thermoplastic polymer, preferably the bottom and the one or more sides having a thickness of between 50 and 500 micrometres, more preferably between 100 and 200 micrometres.

9. The battery cell casing according to any one of claims 1-6, wherein the thermoplastic polymer is present inside the through holes and the inside of the one or more sides are not covered with the thermoplastic polymer.

10. The battery cell casing according to any one of claims 1 -9, wherein the amount of fire-resistant additive in the thermoplastic material is less than 30 wt%, preferably less than 25 wt%, more preferably less than 20 wt%, more preferably less than 15 wt%, more preferably less than 10 wt%, more preferably less than 7.0 wt%, more preferably less than 5.0 wt%, more preferably less than 3.0 wt%, more preferably less than 1.0 wt%, more preferably less than 0.5 wt%, more preferably less than 0.1 wt%, more preferably less than 0.05 wt%, more preferably less than 0.01 wt% or 0.00 wt%, with respect to the total thermoplastic material.11 . The battery cell casing according to any one of claims 1-10, wherein the thermoplastic material has a peak melting temperature (Tpm) of at most 280 °C, at most 250 °C, at most 230 °C, at most 200°C, at most 180 °C, at most 160 °C or at most 155 °C, as determined in accordance with ASTM D3418 (2008).

12. The battery cell casing according to any one of the preceding claims, wherein the holes have a size of between 0.5 and 5 millimetres.

13. The battery cell casing according to any one of the preceding claims, wherein the holes have a spacing of between 1 and 10 millimetres.

14. A battery cell comprising the battery cell casing according to any one of the preceding claims filled with at least an anode, a cathode, one or more separators, a positive current collector, a negative current collector, and an electrolyte.

15. A method for manufacturing the battery cell casing according to any one of the claims 1-13, comprising:* providing a perforated casing made of a thermally conductive material, said casing comprising a bottom, one or more sides, and a top, where the one or more sides are perforated with a plurality of through holes, and* applying a thermoplastic polymer to seal said plurality of through holes.

16. The method according to claim 15, wherein the step of providing a casing comprises: i) providing a case extrudate and punching the plurality of through holes in said case extrudate to obtain a perforated casing; or ii) providing a solid casing and applying the plurality of through holes, for example by means of a laser, to obtain a perforated casing; or iii) providing a perforated sheet of thermally conductive material, and extrudate to obtain a perforated casing.

17. The method according to claim 15 or claim 16, wherein the thermoplastic polymer is applied to said plurality of through holes of said perforated casing by: a) providing a perforated casing, adding a plug inside of said perforated casing, dipping the perforated casing with plug inside into molten thermoplastic polymer, and plunge into a negative to clean the molten thermoplastic polymer of the outside of the perforated casing to obtain a battery cell casing; and / or b) providing a perforated casing and applying a film of a thermoplastic polymer on the inside of the casing and optionally on the outside of the casing.

18. A battery system, comprising:- one or more trays for holding one or more battery cells,- at least one battery cell according to claim 14, and- optionally a cooling system.

19. A battery system comprising a battery cell comprising the battery cell casing according to any one of claims 1 to 13 and a cooling system configured for cooling the battery cell.

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