[0001 ] The present invention relates to a structural battery.

[0002] The Applicant has developed a composite structure for a structural battery. More specifically, the Applicant has developed a structural battery comprising a container of a first material; and a core of a second material for accommodating a plurality of electric cells provided within said container wherein the container and the core of the composite structure together form a structural member having resistance to shear forces, tension forces, compression forces, torsional forces and longitudinal and transverse bending forces imposed on said structural member by the application. A composite sandwich structure is especially effective in providing such resistance. Further description of this composite structure is provided in the Applicant’s co-pending International Patent Application No. PCT/AU2018/050832, filed 8 August 2018, the contents of which are hereby incorporated herein by reference.

[0003] Structurally, the core of the Applicant’s structural battery provides shear resistance and compressive strength while allowing weight reduction in applications including, but not limited to, vehicles. Electric cells and ancillary components (such as conductors, fuses and thermal control means) are included within the core which is desirably rigid and of low density.

[0004] It is an object of the present invention to provide a structural battery that comprises a core having a structure that provides both electric connectivity and strength to the battery, advantageously where prismatic or pouch type electric cells are used.

[0005] With this object in view, the present invention provides a structural battery comprising:

a container of a first material; and a core of a second material for accommodating a plurality of electric cells provided within said container;

wherein the container and the core together form a structural member having resistance to shear forces, compression forces, torsional forces and longitudinal and transverse bending forces imposed on said structural member by the application and wherein said core comprises a framework of structural core elements wherein said structural core elements cooperate with said electric cells to provide electrical and thermal connections and structural links between said structural core elements and said electric cells and wherein said electric cells comprise pouch cells or prismatic cells. Typically, an electric cell comprises a shell and so the structural elements, which are conveniently in sheet form, are shaped and /or bonded to connect with and structurally link the shells of included electric cells. A desired core has electric cells and structural elements arranged in tiers. Where structural core elements are sheets, these sheets may have a folded or concertina configuration to save space.

[0006] The electric cells are of prismatic or pouch type, including pouch cells of simple leaf, plate or folded type. In such cases, the anode plates, strips or sheets of a pouch or prismatic electric cell are conveniently connected or fixed together, and the cathode plates, strips or sheets of a pouch or prismatic electric cell are conveniently connected or fixed together for example by welding to form an anode contact and a cathode contact that are also placed in electrical and thermal communication with the structural core elements as described above. Such a configuration allows particularly efficient heat transfer away from electric cell(s) - especially through conductive heat transfer - and, through desirable inclusion of a thermal management system, ultimately away from the structural battery. In one embodiment, heat may substantially be transferred along a longitudinal axis of each electric cell rather than radially.

[0007] The core of the structural battery advantageously includes a core structure of a lightweight material such as a conductive light metal or light metal alloy; for example aluminium. Such a core structure has high strength and stiffness yet is cost effective to produce. In that case, accommodation for electric cells is provided by spaces formed by the arrangement of core elements forming the framework of the core structure. These core elements are structural elements and the noted spaces may be disposed between the core elements. It will be understood that each of the first and second materials may include a combination of materials.

[0008] Each structural core element of such a core structure desirably comprises a conductive layer or form, an electrically insulating layer or strip and optionally a further conductive layer, preferably as a laminate. The electrically insulating layer, for example of suitable electrically insulating but thermally conductive polymer, should also have sufficient strength to handle compression and shear loads generated in the core structure. The electrically insulating layer, could also take the form of an electrically insulating coating applied to the, or a further, conductive layer that has sufficient strength to handle compression and shear loads generated in the core structure. The conductive layer is conveniently laminated to the insulating layer in a manner to form a plurality of fluid passage means for fluid transport system(s) of the structural battery, for example as described in the Applicant’s co-pending International Patent Application No. PCT/AU2018/050537 filed 8 August 2018, the contents of which are hereby incorporated herein by reference. Spaces for accommodating the pouch or prismatic cells are disposed between the structural core elements, which are desirably arranged in a concertina or folded configuration.

[0009] Each structural core element of the core structure may have a plurality of regularly spaced longitudinally extending parallel splines, each spline conveniently corresponding with a fluid passage means. The core conveniently comprises a plurality of structural core elements having a laminated structure resistant to tension, compression and shear loads and comprising a first electrically and thermally conductive layer and a second electrically insulating layer, said first and second layers of each core element being relatively disposed to form a plurality of regularly spaced longitudinally extending parallel splines, each spline conveniently corresponding with a fluid passage means and also providing the core elements with structural rigidity. It will be understood that first or second layers may themselves comprise a plurality of sub-layers of material.

[0010] Any desired arrangement of conductive layer relative to laminated insulating layer in which fabrication of a structural core element leaves spaces to form the fluid passage means may also be used.

[001 1 ] As alluded to above, the structural battery may include a plurality of fluid transport systems, each requiring fluid passage means. In the above desired arrangement, a further fluid passage means may be formed as channels between the corrugations or splines of each core element. Such fluid passage means may form part of a second fluid transport system as described in the Applicant’s co pending International Patent Application No. PCT/AU2018/050537, filed 8 August 2018 and incorporated herein by reference.

[0012] The structural core elements forming the framework of the preferred core structure are also disposed to define spaces for accommodating electric cells. The core elements desirably substantially or fully enclose the electric cell(s) accommodated within the spaces. A plurality of electric cells may be accommodated within spaces between the core elements. The remaining space between electric cells may accommodate a material that can serve a plurality of functions selected from the group consisting of electric insulation, thermal management, for example by being an intumescent material that endothermically degrades with the object of avoiding thermal runaway, providing structural strength and bonding adjacent core elements. A preferred material, such as a filled epoxy resin could fill most of these functions though further structural elements such as rigid sheets may be incorporated or encapsulated within the material to increase structural strength, noting that the prismatic or pouch cells also provide structural strength. [0013] The number of electric cells is determined with reference to the electric power requirements of the application. A potentially very large number of electric cells, perhaps thousands, could be included within a vehicle or other power module, with a single structural battery or bank of structural batteries as described herein being used. Electric cell connections are preferably made in both series and parallel.

[0014] As described above, the structural battery can be used in a range of applications. Any application that can draw electric power from electric cells could adopt the composite structure as a structural battery which is well suited to modularisation to deliver a required power output. One potential application would be use of the structural battery in on or off-grid contexts including utility scale grid support systems, stand-alone power systems and stationary power systems (SPS systems) which may include off grid for remote area power systems (RAPS) or on grid or off grid‘behind the meter’ systems. In an on-grid application, appropriate battery storage assists grid stabilisation. Another potential application is to electric motor vehicles. In either case, the composite structure could accommodate a very large number of electric cells for example in the form of a floor pan for an electric motor vehicle or a storage battery forming part of a power system. In a vehicle floor pan, weight is focussed in the typically lowest point of the vehicle where it may provide a beam between front and rear wheels, left and right wheels (where provided) and a torsionally rigid member between all wheels.

[0015] The structural battery of the invention may be more fully understood from the following description of exemplary embodiments thereof made with reference to the drawings in which:

[0016] Fig. 1 shows a first schematic cutaway view of a structural battery with a core structure according to one embodiment of the present invention.

[0017] Fig. 2 shows a second schematic cutaway view of a structural battery with a core structure according to one embodiment of the present invention. [0018] Fig. 3A shows a first bottom view of the core structure of the structural battery shown in Figs. 1 and 2.

[0019] Fig. 3B shows a second bottom view of the core structure of the structural battery shown in Figs. 1 and 2.

[0020] Fig. 4 shows a detail bottom view of the core structure of Figs. 3A and 3B.

[0021 ] Fig. 5 is a partial orthogonal view of the core structure of Figs. 3A to 4.

[0022] Fig. 6 is a partial detail orthogonal view of the core structure taken from

Fig. 4.

[0023] Fig. 7 is a partial section showing a pouch type electric cell included in the core structure of Figs. 3A to 6.

[0024] Fig. 8 is schematic cutaway view of a structural battery with a core structure according to a second embodiment of the present invention.

[0025] Referring now to Figs. 1 and 2, there is shown a view of structural battery 10 for delivering electric power to an application requiring electric power such as an electric motor vehicle (not shown) but not limited to this. Structural battery 10 includes a container 12 of a first, fibre reinforced composite material such as CFRP or GRP or combinations thereof to both insulate and add strength; and a core structure 30 for accommodating a plurality of electric cells 34 provided within the container 12 in a manner schematically illustrated with reference to Figs. 1 to 6. The container 12 has top and bottom facing layers 12a; and 12b respectively of sufficient strength to treat tension and compression loads. The structural battery 10 therefore has a composite sandwich structure. Layer 12c is an adhesive layer that, when heated to the correct temperature, bonds the core structure 30 to bottom facing layer 12a.

[0026] The structural battery 10 forms a structural member having resistance to compressive, shear and longitudinal and transverse bending forces imposed on the structural member by the electric motor vehicle whether stationary or in operation.

[0027] Core structure 30 forms the core of the structural battery 10 and is electrically and thermally conductive being made up of a framework of suitably arranged core layers or core elements 31 which are structural elements with the required structural characteristics, particularly in terms of compressive strength and shear resistance, for the application. The concertina configuration of the core elements 31 improves the structural properties of the core structure.

[0028] Structural core elements 31 of core structure 30 each have a laminated structure comprising multiple plies of corrugated aluminium (or other conductive light or lightweight metal) to form an electrically and thermally conductive layer or form of approximately 50pm thickness which are bonded together with an insulating layer or coating to leave sufficient spaces 32, with a zig-zag shape, for accommodating electric cells 34 in a manner avoiding short circuiting and other electrical malfunctions. Each space 32 accommodates a number of prismatic cells 34. Core structure 30 has a tiered configuration with structural core elements 31 and electric cells 34 arranged in tiers. The configuration is a folded or concertina configuration.

[0029] Spaces 29 are not occupied by electric cells 34. Though such spaces 29 could be left vacant, each space is desirably filled with a material 130 that can serve a plurality of functions including electric insulation between electric cells 34, thermal management, for example by being an intumescent material that endothermically degrades with the object of avoiding thermal runaway, providing structural strength and bonding adjacent structural core elements 31. A preferred material 130 is a filled epoxy resin.

[0030] A plurality of fluid passage means for a first fluid transport system of the structural battery 10 are formed by sealed spaces formed within each structural core element 31 during fabrication. The sealed spaces form passages 35 of suitable dimension, for example 2mm width forming part of a first thermal control fluid transport system for structural battery 10. Coolant is circulated through passages 35 to maintain cell temperature in an optimal range.

[0031 ] Structural core elements 31 are splined along the length of the passages 35, with the parallel longitudinally splines 35a which also provide rigidity to the core elements 31. Two such splines 35a are provided for each structural core element 31 ,31 a, 31 b though this number can be varied as desired and with a view to efficient heat transfer and thermal management as well as structural properties. Heat transfer fluid is circulated through passages 35 for controlling the temperature of structural battery 10 through heat transfer contact between passages 35 and the electric cells 34. Thermal runaway is also guarded against by the material 130 described above.

[0032] Each electric cell accommodating space 32 is substantially defined between adjoining structural core elements 31 (more particularly structural core elements 31 a and 31 b as conveniently shown in Figs. 3B, 5 and 6) , and more particularly the conductive layers of the core elements 31 of core structure 30.

[0033] Electric cells 34 of prismatic cell type are selected for structural battery 10. Prismatic cells 34 of simple leaf, plate or folded type are known in the art and are included within spaces 32 of core structure 30. Pouch cells, also known in the art, could also be adopted and a structural battery 1 10 with core structure 1 130 including such pouch cells 134 is shown in Fig. 8. [0034] Prismatic cells 34 are fabricated using a jelly roll 34a, as shown in Fig. 7, including anode sheets, cathode sheets, separator layers and electrolyte. Fabrication techniques, with one exception, are not of present concern. The one exception is that the prismatic cells 34 have anode sheets or strips and cathode sheets or strips joined together at opposed ends of the prismatic cell to form respective anode and cathode contacts 34a and 34b as shown in Figs. 3A to 7. These contacts 34a and 34b are welded to different, but adjoining, structural core elements 31 a and 31 b but may desirably be first welded to a tab 37 which is both thermally and electrically conductive and of similar material to the anode or cathode plates respectively, said tabs 37 then being welded to different but adjoining core elements 31 a and 31 b.

[0035] During operation of battery 10, heat is generated and effectively transferred along a longitudinal axis L, of each electric cell 34. The welding and consequential bonding of contacts 34a and 34b to adjoining structural core elements 31 a and 31 b, which are cooled by the first fluid transport system and coolant passing through nearby fluid passages 35, allows further efficient heat transfer away from the electric cells 34 and ultimately the battery 10 itself. It will be understood that, through this arrangement, structural core elements 31 cooperate with the electric cells 34 to provide electrical and thermal connectivity as well as structural links between structural core elements 31 (including structural core elements 31 a and 31 b) and electric cells 34. The Applicant understands that the thermal management of battery 10 is superior to batteries currently including pouch cells. The same configuration and operating principles, with similar benefits, are expected for a structural battery 1 10 including pouch cells 134, as shown in Fig. 8.

[0036] Referring further to Fig. 8, structural battery 1 10 has a housing 112 with top and bottom facing layers 1 12a, 112c; and 112b the same as described for battery 10 shown in Figs. 1 and 2. The core structure 1 130 also comprises structural core elements 131 in a concertina configuration. Structural core elements 131 also include fluid passages 135a of a first fluid transport system for thermal management, typically through cooling. However, structural core elements 131 do not require splining to increase structural rigidity since the bodies of the pouch cells 134 provide this. Pouch cells 134 have conductive tabs

136 which, though serving the same function as contacts 34a and 34b of the prismatic cells 34 (and similarly involving anode and cathode strips of the pouch cells 134 respectively being fixed together), are of conventional design. The conductive tabs 136 for each pouch cell 134 are also connected to adjacent structural core elements 131 as schematically shown for tab 136a. Each pouch cell 134 is separated by an insulating spacer 137 of polyamide or epoxy resin to prevent undesirable connection of adjacent pouch cells 134. Insulating spacer

137 is in the form of a biscuit or sheet which also acts to increase structural rigidity. Again, during operation of battery 1 10, heat is generated and conducted away through conductive tabs 136 to the cooled structural core elements 131 and ultimately away from battery 1 10 itself.

[0037] The structural battery 10, 1 10 can be used in a range of applications including in fixed structures such as those used in power systems, such as utility scale grid support, SPS and RAPS systems (whether on or off grid), mobility devices and portable devices. One further potential application is to electric motor vehicles. In the case of an electric motor vehicle, the selected electrical cells 34 would enable the structural battery 10, while having the required structural properties as described herein and in incorporated references to act as a structural member, to have a relatively shallow depth in relation to length and breadth. In the electric vehicle case also, a bank of structural batteries 10, 1 10 could accommodate a very large number of electric cells 34, 134, potentially thousands, and form a floor pan for the electric motor vehicle. Weight, which is significantly lower than that involved with conventional metal and metal alloy battery containers or trays, would then be focussed in the lowest point of the vehicle where one or a bank of structural batteries provides a load bearing beam between front and rear wheels, left and right wheels (where provided) and a torsionally rigid member between all wheels. [0038] Structural battery 10, 1 10 is rechargeable and not intended for replacement under normal circumstances. However, it could be made replaceable if desired. This would depend on the application.

[0039] Modifications and variations to the structural battery and core structure described herein may be apparent to the skilled reader of this disclosure. Such modifications and variations are deemed within the scope of the present invention.