Panel for thermal insulation, in particular for insulating battery modules in a motor vehicle battery pack

Abstract

A panel (1) for thermal insulation, in particular for insulating adjacent battery modules in a motor vehicle battery pack, is provided with at least three layers, i.e., an intermediate layer (2) made of a thermal insulation material, and two outer layers (3,4) arranged on opposite sides of the intermediate layer (2); the latter has aann iinnnneerr ssllaabb (10) with the thermal insulation material, and a frame (8), having an annular shape and completely surrounding the inner slab (10) so as to define the perimeter of a housing (12) engaged by this inner slab (10); the material of the outer layers (3) is an electrically insulating material such as to give, ttoo tthhee ppaanneell (( 11 )),, a breakdown voltage at least equal to 3 kV / mm, aanndd tthhee tthheerrmmaall iinnssuullaattiioonn mmaatteerriiaall hhaass,, at temperatures greater than 150 °C, a thermal conductivity less than, or equal to (0.0015 * T + 0.04), where T is the temperature (K) to which an outer face of the panel (1) is subjected.

Description

[0001] "PANEL FOR THERMAL INSULATION , IN PARTICULAR FOR INSULATING BATTERY MODULES IN A MOTOR VEHICLE BATTERY PACK"

[0002] Cross-Reference to Related Applications

[0003] This Patent Application claims priority from Italian Patent Application No . 102023000006624 filed on April 4 , 2023 , the entire disclosure of which is incorporated herein by reference .

[0004] Technical Field

[0005] The present invention relates to a panel for thermal insulation, in particular for insulating battery modules in a motor vehicle battery pack .

[0006] Background Art

[0007] To thermally insulate battery modules in battery packs , solutions of two types are mainly known .

[0008] According to the first type , in the form of adhesive tape , the barriers or thermal insulations are applied to the battery modules before they are mounted to form battery packs . With the second type , de fined by sheets of foam, mica, glass wool , rockwool , etc..., they are arranged between adj acent battery modules after the battery pack has been mounted . In particular, these sheets are then held in place thanks to the compression of the adj acent battery modules , without the need for dedicated coupling or fixing devices .

[0009] The known solutions according to the types listed above are not particularly satis factory .

[0010] In fact , in the first case , it is not possible to apply thermal barriers of the type with adhesive tape after the battery modules have already been arranged in side-by-side positions in the battery pack, due to a general di f ficulty of access . In other words , the space between each battery module and the adj acent ones is relatively narrow, so that it is not possible to add the aforesaid adhesive tapes . The latter can only be applied along the production lines , in which these modules are formed starting from an assembly of battery cells .

[0011] Moreover, the adhesive tapes can include porous material , which can flake , disintegrate or detach during use , thereby forming particles or debris that can be the cause of pollution or dirt inside the battery pack . This debris tends to reduce the electrical insulation between adj acent battery modules , where there are relatively close points with electrical voltages of opposite sign . Therefore , this debris can be a source of risk for possible short circuits , owing to the general di f ficulty in maintaining high clearances in the couplings and in satis fying the requirements of electrical insulation, above all at high temperatures , with a wide margin .

[0012] In solutions of the second type , there is an even greater problem of flaking of the thermal insulation and dispersing of particles or debris into the battery pack, resulting in pollution and dirt that can generate risks of short circuits .

[0013] The obj ect of the invention is to solve the aforesaid drawbacks , preferably in a simple and / or ef fective and / or economical way . For example , it would be important to prevent the dispersion of particles ( such as micas or fibres , for example ) with a si ze greater than one millimetre .

[0014] In particular, there is the need to produce a thermal barrier in the form of a panel , which can be positioned between adj acent battery modules in a motor vehicle battery pack during assembly of this battery pack . In this regard, di f ferent solutions defined by multilayer elements have recently been devised, as shown, for example , in WO 2021 235189 Al .

[0015] Fig . 4 of the document US2022181716A1 shows a solution according to the preamble of claim 1 , wherein the thermal insulation is encapsulated . In particular, the two opposite faces of the thermal insulation are covered by respective materials made of glass-based fabric, fixed to one another by adhesive made of thermoplastic elastomer arranged along the edge of the thermal insulation . This solution does not seem to achieve the desired obj ectives of thermal and electrical insulation . Moreover, since the outer surfaces are essential ly made of glass fibre , this solution does not achieve the obj ectives of cleanliness required for high voltage batteries ; in fact , the higher the voltage , the more important it is to avoid metallic and non-metallic particulate inside the battery pack .

[0016] In the light of this prior art , there is the need to provide a panel which, in addition to performing the aforesaid function of thermal insulation and not giving rise to dirt and debris , also helps to improve the electrical insulation between adj acent battery modules .

[0017] Summary of the Invention

[0018] The aforesaid obj ect is achieved by a panel for thermal insulation, in particular for insulating battery modules in a motor vehicle battery pack, as defined in claim 1 .

[0019] The dependent claims define particular embodiments of the invention .

[0020] Brief Description of the Drawings

[0021] Hereinafter, for a better understanding of the present invention, preferred embodiments will be described by way of non-limiting example , with reference to the accompanying drawings , wherein :

[0022] Fig . 1 is a perspective view, with parts in an exploded view, showing an example of a panel for thermal insulation according to the dictates of the present invention .

[0023] Detailed Description of Preferred Embodiments of the Invention In Fig . 1 , the reference number 1 indicates a panel having, as main function, that of thermal insulation, in particular for insulating battery modules (not illustrated) arranged in side- by-side positions , one after another, in a motor vehicle battery pack, in order to obstruct the transmission of heat in case of an uncontrolled temperature increase in one of the battery modules . In fact , in these cases the panel 1 has the function of preventing this increase in temperature from propagating to the adj acent battery modules or, at least , the function of slowing down the phenomenon of propagation, to allow the driver and passengers suf ficient time to exit the motor vehicle safely .

[0024] The panel 1 comprises a multilayer element , having at least three layers . In detail , the panel 1 comprises an intermediate layer 2 and two outer layers 3 and 4 , which are arranged on opposite sides of the layer 2 and completely cover the opposite faces 5 and, respectively, 6 of the layer 2 . In particular, the layer 2 is directly in contact with the layers 3 and 4 . More in particular, the panel 1 comprises only three layers .

[0025] Preferably, the layers 3 and 4 are defined by respective sheets of electrically insulating material .

[0026] According to the present invention, the layer 2 comprises a frame 8 having an annular shape and arranged along the perimeter edge of the panel 1 and consequently along the perimeter edges of the layers 3 and 4 . The layer 2 further comprises an intermediate slab 10 , which de fines a barrier or thermal insulation, is coplanar with the frame 8 and is completely surrounded by the latter . In particular, the frame 8 extends along the perimeter edge 11 o f the slab 10 without the interposition of other elements . More in particular, the slab 10 , the frame 8 and consequently the panel 1 have a rectangular perimeter .

[0027] The assembly def ined by the layers 3 and 4 and by the frame 8 defines an inner housing 12, in which the slab 10 remains encapsulated and which therefore allows the thermal insulation material of the slab 10 to be protected, to prevent any particles of this material from disintegrating and dispersing into the battery pack during installation and during the operative life of the panel 1. In particular, the housing 12 is insulated with respect to the external environment, i.e., it is closed in a leak-proof manner, thanks to the coupling of the layers 3 and 4 on the frame 8. Preferably, the layers 3 and 4 have an adhesive face, so that they are glued to the frame 8.

[0028] According to an aspect of the present invention, the layers 3 and 4 are defined by tapes or sheets made of dielectric, i.e., electrical insulation, material: the material of the layers 3 and 4 is selected so as to provide the entire panel 1 with a dielectric strength or breakdown voltage greater than, or equal to 3 kV / mm, considering the thickness, i.e. in the direction orthogonal to the faces 5, 6.

[0029] In this way, the panel 1 performs the function of shield for the battery module on which it is arranged, preventing discharges, i.e. electrical arcs, which could be favoured by any ionized gases produced as a result of uncontrolled temperature increases in the battery modules.

[0030] Moreover, the material of the layers 3 and 4 is not flammable, i.e., it is fire-resistant: in particular, it comprises a thermoplastic material or a condensation polymer material which, on the basis of the UL94 classification, is chosen so as to have a flame-retardant rating at least of V-0.

[0031] For example, to obtain these technical requirements, the following families of materials can advantageously be chosen to define the layers 3 and 4:

[0032] - PET supported materials;

[0033] - silicon based materials; - polyimide based materials;

[0034] - fluoropolymer-coated polyimide.

[0035] In particular, the thickness of the layers 3 and 4 is greater than 0.1 mm. This thickness partially affects the electrical insulation, as the essential property is defined by the CTI (Comparative Tracking Index) , which must be such as to give the whole panel a breakdown voltage at least equal to 3 kV / mm.

[0036] More in particular, the thickness of the layers 3 and 4 is less than 0.5 mm, to reduce the total thickness of the panel 1 to a minimum.

[0037] With regard to the slab 10, the thermal insulation material is chosen so as to have, at temperatures higher than 150 °C, a thermal conductivity (in W / (m K) less than, or equal to: (0.0015 * T + 0.04) ; where T is the temperature (in K) to which an outer face of the panel 1 is subjected. The material of this face, subjected to high temperatures in case of deterioration of a battery module, could melt, but the slab 10 nonetheless ensures that the opposite face remains at low temperatures, below values that could compromise the adjacent battery modules in the battery pack.

[0038] In practice, below 150 °C the question is irrelevant for lithium ion battery cells.

[0039] Preferably, the thermal insulation material of the slab 10 is chosen so as to have a maximum operating temperature of at least 1000 °C.

[0040] Preferably, the thermal insulation material of the slab 10 is also chosen so as to be non-flammable, i.e., fire-resistant: in particular, on the basis of the UL94 classification, it is chosen so as to have a flame-retardant rating at least of V-0. Preferably, the material of the slab 10 is a porous material, so as to be compressible.

[0041] For example, to obtain these technical requirements, the following families of materials can advantageously be chosen to define the slab 10:

[0042] - ceramic fleece;

[0043] - mica-based material;

[0044] - melamine fleece;

[0045] - mineral wool, for example glass wool or rockwool;

[0046] - composite material made of resin and fibres, such as carbon fibres or similar, for example in the form of SMC (Sheet Moulding Compound) ;

[0047] - aerogel;

[0048] - calcium silicate;

[0049] - silicate fabric.

[0050] Even if the porous material of the slab 10 could disintegrate and form debris, this remains enclosed in the housing 12 without being dispersed into the battery pack during its operative life. This porosity is disadvantageous from the viewpoint of electrical insulation, but the insulation is in any case guaranteed by the layers 3 and 4, and preferably also by the frame 8.

[0051] Preferably, the thickness of the slab 10 is established in the design phase so as to guarantee the required thermal insulation.

[0052] In particular, the thickness of the layer 2 is uniform, and the frame 8 has the same thickness as the slab 10.

[0053] With regard to the frame 8, its material is chosen so as to have a compressive strength substantially equal to that of the slab 10, when the panel 1 is subjected to a compression directed orthogonally to the faces 5, 6. It is relatively important for the layer 2 to have a certain elasticity. In particular, it is advisable for the compression set to be less than 25% after the material has been subjected to a compressive load of 25 kPa, along the thickness, i.e., orthogonally to the faces 5, 6.

[0054] These compressive strength data are important to optimally protect the slab 10 in the housing 12 and to perform a mechanical support function in relation to the slab 10 arranged in the housing 12.

[0055] The material of the frame 8 is also chosen so as to be nonflammable, i.e., to be fire-resistant: in particular, it is chosen so as to satisfy the requirements of the standard FMVSS 302.

[0056] Preferably, the material of the frame 8 is porous, for example with open or semi-open cells, so as to be compressible. In practice, the material of the frame 8 is in the form of foam.

[0057] The material of the frame 8 also has thermal insulation properties, although these insulation properties can be lower with respect to those of the slab 10; the heat exchange from the face 5 to the face 6, or vice versa, through the frame 8 is in any case negligible, as the area occupied by the frame 8 is relatively low (typically less than 15 % of the whole area of each of the faces 5, 6) .

[0058] Preferably, the material of the frame 8 is a dielectric, i.e., an electrical insulation, material, similarly to the layers 3 and 4. Therefore, the housing 12 is electrically insulated on all sides. The choice of the material of the frame 8 is also guided by having a breakdown voltage at least equal to 3 kV / mm along the thickness of the panel 1.

[0059] Optionally, the panel 1 comprises a retainer 15, which is preferably defined by a tape 16 , adhesive on both its opposite faces , one of which is covered by a liner 17 ; the liner 17 is a protective sheet that can be made , for example , of paper and is detachable manually to free the underlying adhesive face of the tape 16 , which will then be attached to a support in order to be able to retain the panel 1 on this support in a fixed position . In the speci fic case of the battery pack, this support is defined by the outer face of a battery module arranged inside this pack .

[0060] In particular, the liner 17 has an area greater than that of the tape 16 , so as to protrude laterally with respect to the tape 16 , towards the outer perimeter edge of the panel 1 , so as to have a free end that rests on the layer 4 and can be grasped manually to then be pulled and removed, during or after positioning of the panel 1 between two adj acent battery modules .

[0061] Therefore , the tape 16 facilitates installation of the panel 1 in the battery pack and ensures ef fective fixing to the battery module to which it is attached . Preferably, the tape 16 is only applied on one of the two layers 3 , 4 , i . e . , only on one of the faces of the multilayer element .

[0062] Finally, preferably, the panel 1 comprises a reference 18 , arranged in fixed position on the opposite face to the one on which the retainer 15 is arranged, to orient the panel 1 correctly during the assembly operations in the battery pack . The reference 18 can be defined by an additional element ( flag) applied on this face , for example by gluing, as illustrated by way of example in Fig . 1 , or by a sign or marking drawn or traced on this face .

[0063] From the above description, the advantages of the panel 1 are evident .

[0064] In particular, the thermal insulation of the slab 10 is such as to slow down the transmission of heat between adj acent battery modules in case of uncontrolled temperature increases in a battery module , in order to impede the propagation of thermal energy to the adj acent battery modules , regardless of the voltage of the battery pack . Simultaneously, the thermal insulation of the slab 10 remains completely enclosed in the housing 12 , as well as being supported by the frame 8 , so as to obtain a clean solution, without the dispersion of particles or debris that could trigger electric arcs in the battery pack in the presence of the aforesaid uncontrolled temperature increases . Moreover, the panel 1 has electrical insulation properties in addition to thermal insulation properties .

[0065] As mentioned above , this dual function ( electrical and thermal insulation) can be guaranteed, in practice , for each battery pack and for any voltage level , by si zing the components of the panel appropriately and choosing suitable materials .

[0066] Besides the functions of electrical and thermal insulation, the present invention also integrates in a single element , i . e . , in the panel 1 , the requirements of spacing between adj acent battery modules , thanks to appropriate si zing of the thicknesses and of the compressibility of the layers that make up said panel 1 .

[0067] Moreover, positioning of the panel 1 in the battery pack is made stable by means o f the retainer 15 , which occupies a relatively limited space but is nonetheless ef fective and easy to use .

[0068] Finally, it is evident that modi fications and variations may be made to the panel 1 according to the present invention without departing from the scope of protection defined by the appended claims .

[0069] In particular, the panel 1 could include di f ferent materials to those indicated above by way of example , to ensure the electrical and thermal insulation.

[0070] Moreover, the retainer 15 could be missing, or could differ from the adhesive tape 16 described above.

Claims

CLAIMS1.- A panel (1) for thermal insulation, in particular for insulating adjacent battery modules in a motor vehicle battery pack; the panel comprising a multilayer element having at least three layers respectively defined by an intermediate layer (2) comprising a thermal insulation material, and two outer layers (3,4) arranged on opposite sides of said intermediate layer (2) ; said intermediate layer (2) comprising: an inner slab (10) comprising said thermal insulating material, and a frame (8) having an annular shape and completely surrounding said inner slab (10) so as to define the perimeter of a housing (12) which is engaged by said inner slab (10) ; characterized in that the material of said outer layers (2,3) is an electrically insulating material such as to give, to said panel (1) , a breakdown voltage at least equal to 3 kV / mm, the thermal insulation material of said inner slab (10) has, at temperatures higher than 150 °C, a thermal conductivity less than, or equal to: (0.0015 * T + 0.04) ; where T is the temperature in [K] and the thermal conductivity is in [W / (m K) ] .2.- The panel according to claim 1, wherein said frame (8) has a compressive strength substantially equal to that of said slab (10) , when subjected to a compressive action directed orthogonally to said layers.3.- The panel according to claim 1 or 2, wherein said intermediate layer (2) has a compression set of less than 25% after having been subjected to a compressive load of at least 25 kPa, orthogonally to said layers.4.- The panel according to any one of the preceding claims, wherein said electrical insulating material is a fire-resistant material .5.- The panel according to any one of the preceding claims, wherein said frame (8) is made of an electrical insulating material .6.- The panel according to any one of the preceding claims, wherein said housing (12) is leak-proof.7.- The panel according to any one of the preceding claims, wherein a retainer (15) is fixed to a face of one of said outer layers (3,4) .8.- The panel according to claim 7, wherein said retainer(15) comprises a bi-adhesive tape attached to said face.9.- The panel according to anyone of the previous claims, wherein said electrically insulating material, on the basis of the UL94 classification, has a flame-retardant rating at least of V-0.

Images