Patent Description:
This invention relates generally to thermal and dielectric insulators, and more particularly to thermal and dielectric insulators for inhibiting flame propagation within and from a battery pack.

It is known to contain or shield battery packs, including those used in electric vehicle applications, in thermal insulation. A common material used to form such thermal insulation is a fiberglass fabric. Although the fiberglass fabric insulation provides an acceptable level of protection against contamination and environmental temperatures during normal use, the fiberglass fabric insulation does not provide a desired level of protection against flame propagation outwardly from the battery pack or between cells of the battery pack, such as may be experienced in a thermal runaway condition of one or more cells of the electric vehicle battery pack. It is desired to provide a thermal insulation that also offers dielectric protection to the battery pack, while inhibiting the propagation of flame from the battery pack and between cells of the battery pack.

<CIT> discloses a multilayer thermal insulator for an electric vehicle battery pack, comprising a structure comprising a non-woven core layer comprising non-meltable, flame-resistant polymeric fibers having opposite first and second major surfaces; and one or more scrims disposed on opposing major surfaces of the non-woven core layer. A layer of pressure sensitive adhesive may extend across and contact one or both scrims, or any other outward-facing surface of the thermal insulator.

It is an object of the present disclosure to provide a thermal insulator for use with an electric vehicle battery pack that addresses at least the desire to inhibit the propagation of flame from the battery pack and between cells of the battery pack.

It is a further object to inhibit the propagation of flame from the battery pack and between cells of the battery pack for <NUM> minutes at a temperature of <NUM>.

It is a further object to inhibit the propagation of flame from the battery pack and between cells of the battery pack for upwards to <NUM> minutes at a temperature of <NUM>.

It is a further object of the present disclosure to provide a thermal insulator for use with an electric vehicle battery pack that addresses at least the desire to provide dielectric protection to the battery pack and between cells of the battery pack.

It is a further object of the present disclosure to provide a thermal insulator for use with an electric vehicle battery pack that is flexible to facilitate conformability of the thermal insulator about the battery pack and between cells of the battery pack.

It is a further object of the present disclosure to facilitate the ease installation of a thermal insulator about the battery pack and between cells of the battery pack.

It is a further object of the present disclosure to provide a thermal insulator for an electric vehicle battery pack that is lightweight, that has a low profile to minimize the amount of space occupied by the thermal insulator, and that is economical in manufacture and in use.

One aspect of the invention provides a thermal insulator for an electric vehicle battery pack having a wall including a scrim reinforced, polyether ether ketone layer, a first pressure sensitive adhesive layer coated on a side of the scrim reinforced, polyether ether ketone layer, and a silica fabric bonded to the pressure sensitive adhesive.

In accordance with another aspect of the invention, a second pressure sensitive adhesive layer can be bonded on the silica fabric to facilitate fixing the thermal insulator in the desired location.

In accordance with another aspect of the invention, a release film can be releasably fixed to the first pressure sensitive adhesive layer, with the release film being configured to be removed to expose the underlying first pressure sensitive adhesive layer for fixation to a surface of electric vehicle battery pack and/or to a housing thereof.

In accordance with another aspect of the invention, the first pressure sensitive adhesive layer and the second pressure sensitive adhesive layer can be provided as an acrylic pressure sensitive adhesive.

In accordance with another aspect of the invention, the wall prevents flame propagation when exposed to <NUM> for <NUM> minutes.

In accordance with another aspect of the invention, the wall has an electrical insulation resistance of 4000Mohm or greater before and after being exposed to <NUM> for <NUM> minutes.

In accordance with another aspect of the invention, the wall has a maximum thickness of <NUM>, thereby having a low profile to enhance design options and reduce weight.

In accordance with another aspect of the invention, the wall has a maximum thickness of <NUM>, thereby having a minimized profile to enhance design options and minimize weight.

In accordance with another aspect of the invention, the wall has a dielectric strength of 2kV after being exposed to <NUM> for <NUM> minutes.

In accordance with another aspect of the invention, a flexible thermal insulator for an electric vehicle battery pack has a composite wall including a sheet of silica fabric having opposite first and second sides, and a first pressure sensitive adhesive layer bonded to the first side of the sheet of silica fabric.

In accordance with another aspect of the invention, a flexible thermal insulator for an electric vehicle battery pack is provided having a composite wall including a sheet of flame-resistant material having opposite first and second sides. A first pressure sensitive adhesive layer is bonded to the first side of the sheet of flame-resistant material. Further, one of a scrim reinforced, polyether ether ketone layer is bonded to the second side of the flame-resistant material, or a silicone rubber layer is bonded to the second side of the flame-resistant material.

In accordance with another aspect of the invention, a second pressure sensitive adhesive layer can be bonded to the scrim reinforced, polyether ether ketone layer.

In accordance with another aspect of the invention, the composite wall prevents flame propagation when exposed to <NUM> for <NUM> minutes.

In accordance with another aspect of the invention, the composite wall has an electrical insulation resistance of 4000Mohm or greater before and after being exposed to <NUM> for <NUM> minutes.

In accordance with another aspect of the invention, the composite wall has a maximum thickness of <NUM>.

In accordance with another aspect of the invention, the composite wall has a dielectric strength of 2kV after being exposed to <NUM> for <NUM> minutes.

In accordance with another aspect of the invention, the composite wall of the flexible thermal insulator includes a silicone layer bonded to the second side of the sheet of silica fabric.

In accordance with another aspect of the invention, an electric vehicle battery pack is provided. The electric vehicle battery pack includes a housing bounding a plurality of cells. Further, a composite wall overlies the plurality of cells. The composite wall includes: a sheet of silica fabric having opposite first and second sides and a first pressure sensitive adhesive layer bonded to the first side of the sheet of silica fabric.

In accordance with another aspect of the invention, the electric vehicle battery pack can further include a second pressure sensitive adhesive layer bonded to the scrim reinforced, polyether ether ketone layer.

In accordance with another aspect of the invention, the electric vehicle battery pack can further include a release film releasably fixed to the first pressure sensitive adhesive layer, with the release film being configured to be removed to expose the underlying first pressure sensitive adhesive layer for operable fixation to a surface of the housing.

In accordance with another aspect of the invention, the first pressure sensitive adhesive layer and the second pressure sensitive adhesive layer of the electric vehicle battery pack can be provided as an acrylic pressure sensitive adhesive.

In accordance with another aspect of the invention, the composite wall of the electric vehicle battery pack prevents flame propagation when exposed to <NUM> for <NUM> minutes.

In accordance with another aspect of the invention, the composite wall of the electric vehicle battery pack has an electrical insulation resistance of 4000Mohm or greater before and after being exposed to <NUM> for <NUM> minutes.

In accordance with another aspect of the invention, the composite wall of the electric vehicle battery pack has a maximum thickness of <NUM>.

In accordance with another aspect of the invention, the composite wall of the electric vehicle battery pack has a dielectric strength of 2kV after being exposed to <NUM> for <NUM> minutes.

In accordance with another aspect of the invention, the composite wall of the electric vehicle battery pack further includes a silicone layer bonded to the second side of the sheet of flame-resistant material, wherein the flame-resistant material is a silica fabric.

In accordance with another aspect of the invention, the silica fabric is woven from silica multifilament yarns.

These and other aspects, features and advantages will become readily apparent to those skilled in the art in view of the following detailed description of presently preferred embodiments and best mode, appended claims, and accompanying drawings, in which:.

Referring in more detail to the drawings, <FIG> illustrates a motor vehicle, shown as an electrically powered motor vehicle, also referred to as electric vehicle <NUM>, having a battery pack <NUM>, such as a lithium-ion battery pack, configured with at least one, and shown as a plurality of thermal insulators <NUM> in accordance with an aspect of the invention. The electric vehicle battery pack <NUM> includes a housing <NUM> comprising a plurality of battery modules <NUM>, with each battery module <NUM> bounding a plurality of cells <NUM>. During normal use, and including in non-normal situations, such as in a vehicle crash condition or some other condition causing an impact force to battery pack <NUM>, a thermal runaway condition originating in any one of the cells <NUM> is controlled and contained via the thermal insulator <NUM>, such that flame propagation (spread) between cells <NUM> and outwardly from the battery pack <NUM> is prevented for at least <NUM> minutes, and an outer surface temperature of the battery housing <NUM>, also referred to as case, is maintained to be less than <NUM>, as evidenced in testing performed at a temperature of <NUM> for <NUM> minutes (<FIG> illustrating the outer surface temperature <NUM> for a first embodiment of the thermal insulator <NUM> constructed in accordance with one aspect of the disclosure while exposed to a temperature indicated at <NUM> of <NUM> for <NUM> minutes and <FIG> illustrating the outer surface temperature <NUM> for a second embodiment of a thermal insulator <NUM> constructed in accordance with another aspect of the disclosure while exposed to a temperature indicated at <NUM> of <NUM> for <NUM> minutes, with the different thermal insulators <NUM>, <NUM> being discussed in further detail below).

As shown schematically in <FIG>, the thermal insulator <NUM> includes a generally planar composite sheet, also referred to as composite wall, laminated wall or wall <NUM>, which overlies the plurality of the cells <NUM> and extends between the cells <NUM> to effectively insulate each cell <NUM> from an adjacent cell <NUM>. The composite wall <NUM> includes a sheet of insulating fabric <NUM> having opposite first and second sides <NUM>, <NUM>. The insulating fabric <NUM> is formed of a flame-resistant material, such as a tightly woven flame-resistant filaments (also referred to as multifilament yarns), and in one preferred embodiment, insulating fabric <NUM> is formed entirely from tightly interlaced silica multifilament yarns <NUM>, wherein the multifilament yarns <NUM> are preferably woven using a tight plain weave pattern for maximum density. Further, a first pressure sensitive adhesive layer <NUM> can be bonded to the first side <NUM> of the sheet of silica fabric <NUM> to facilitate fixation of the composite wall <NUM> to the desire surface of the battery pack <NUM>, including between adjacent cells <NUM> and/or about an inner and/or outer surface of the housing <NUM>. Further, a silicone rubber layer <NUM> is coated or otherwise bonded to the second side <NUM> of the sheet of silica fabric <NUM>. The silicone rubber layer <NUM> is a fluid impervious layer, thereby enhancing protection against the ingress of contamination, while greatly enhancing the flame-resistant properties of the wall <NUM>, thereby further inhibiting flame propagation outwardly from and between adjacent cells <NUM>, thereby extending the useful life of the battery pack <NUM> during an emergency situation.

In accordance with another aspect of the invention, a composite wall <NUM> of the thermal insulator <NUM> of the electric vehicle battery pack <NUM>, as shown in <FIG>, in lieu of the silicone rubber layer <NUM>, as discussed above for thermal insulator <NUM>, can further include a second pressure sensitive adhesive layer <NUM> bonded to the second side <NUM> of the woven sheet of silica fabric <NUM> and further include a scrim reinforced, polyether ether ketone layer <NUM> bonded to the second pressure sensitive adhesive layer <NUM>, such that the second pressure sensitive adhesive layer <NUM> is sandwiched between the second side <NUM> of the sheet of silica fabric <NUM> and the scrim reinforced, polyether ether ketone layer <NUM>.

In accordance with another aspect of the invention, the electric vehicle battery pack can further include a release film <NUM> releasably fixed to the first pressure sensitive adhesive layer <NUM>, with the release film <NUM> being configured to be removed to expose the underlying first pressure sensitive adhesive layer <NUM> for operable fixation to a surface of the respective cell <NUM> and housing <NUM>.

In accordance with another aspect of the invention, the first pressure sensitive adhesive layer <NUM> and the second pressure sensitive adhesive layer <NUM> of the electric vehicle battery pack <NUM> can be provided as an acrylic pressure sensitive adhesive.

In accordance with another aspect of the invention, the composite wall <NUM>, <NUM> of the electric vehicle battery pack <NUM> prevents flame propagation when exposed to <NUM> for <NUM> minutes.

In accordance with another aspect of the invention, the composite wall <NUM>, <NUM> of the electric vehicle battery pack <NUM> has an electrical insulation resistance of 4000Mohm or greater before and after being exposed to <NUM> for <NUM> minutes.

In accordance with another aspect of the invention, the composite wall <NUM>, <NUM> of the electric vehicle battery pack <NUM> has a maximum thickness (t) of <NUM>.

In accordance with another aspect of the invention, the composite wall <NUM>, <NUM> of the electric vehicle battery pack <NUM> has a dielectric strength of 2kV after being exposed to <NUM> for <NUM> minutes.

Claim 1:
A flexible thermal insulator (<NUM>; <NUM>) for an electric vehicle battery pack (<NUM>), the flexible thermal insulator comprising a composite wall (<NUM>; <NUM>) including a sheet of flame-resistant material (<NUM>) having opposite first and second sides (<NUM>, <NUM>),
characterised in that said wall (<NUM>;<NUM>) further includes:
a first pressure sensitive adhesive layer (<NUM>) bonded to said first side (<NUM>) of said sheet of flame-resistant material (<NUM>); and
one of a scrim reinforced, polyether ether ketone layer (<NUM>) bonded to said second side (<NUM>) said flame-resistant material (<NUM>), or a silicone rubber layer (<NUM>) bonded to said second side of said flame-resistant material (<NUM>).