WO2019028515A1

WO2019028515A1 - A structural battery

Info

Publication number: WO2019028515A1
Application number: PCT/AU2018/050836
Authority: WO
Inventors: Kim Schlunke; Peter BASKOVICH; Lindsay WOOD
Original assignee: Cape Bouvard Technologies Pty Ltd
Priority date: 2017-08-08
Filing date: 2018-08-08
Publication date: 2019-02-14

Abstract

A structural battery (10) comprising: a container (12) of a first material; and a core (30) of a second material for accommodating a plurality of electric cells (34) provided within said container (12); wherein the container (12) and the core (30) 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 (30) comprises a framework of structural elements (31) wherein said structural elements (31) cooperate with said electric cells (34) to provide electrical connections and structural links between said structural elements (31) and said electric cells (34).

Description

A STRUCTURAL BATTERY

[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, filed 9 August 2018 under Attorney Docket No. P42453PCAU, 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 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.

[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, tension 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 elements wherein said structural elements cooperate with said electric cells to provide electrical connections and structural links between said structural elements and said electric cells.

[0006] 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.

[0007] The container is of a first high strength material and advantageously includes facing layers of the high strength material which treat tension/compression loads. Suitable first materials include, for example, fibre reinforced polymer (such as CFRP: carbon fibre reinforced polymer), fibreglass or a metal, desirably a lightweight metal such as aluminium or aluminium alloy.

[0008] The core of the structural battery advantageously includes a core structure of a second 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 or lattice of core elements forming the framework of the core structure. These core elements are structural elements. It will be understood that each of the first and second materials may include a combination of materials.

[0009] Each 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. Ceramics may also be used for an electrically conductive insulating layer, for example being coated on to a layer of conductive material. 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 filed 8 August 2018 under Attorney Docket No. P43210PCAU, the contents of which are hereby incorporated herein by reference. In such case, a core element may be formed to have a corrugated shape with an approximately semi-circular regular alternating pattern (advantageously matching cylindrical electric cell geometry) so as to leave sealed spaces between the insulating layer and conductive layer that form a fluid passage means for a fluid transport system.

[0010] Each resulting 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. Accordingly, the present invention provides, in another aspect, a core for a structural battery comprising a plurality of 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. It will be understood that first or second layers may themselves comprise a plurality of sub-layers of material.

[001 1 ] Any desired arrangement of conductive layer relative to laminated insulating layer in which fabrication of a core element leaves spaces to form the fluid passage means may also be used.

[0012] 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 copending International Patent Application filed 8 August 2018 under Attorney Docket No. P43210PCAU incorporated herein by reference.

[0013] The 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 space, desirably in a manner so that the space has compatible shape to the external surface of an electric cell. Tight fitting with a high close packing factor for electric cells in the core structure is highly desirable. Conveniently, and for matching with cylindrically shaped electric cells, the core elements include walls of part circular, circular or arcuate shape. The electric cells should be packed with a high packing ratio, though are arranged in parallel banks, rows or tiers. The first and second fluid passage means as described above conveniently also run parallel to the parallel rows of electric cells and conveniently also to each other.

[0014] One or more electric cells may be accommodated per space though one electric cell per space is preferred. It will be appreciated that, in the desired core arrangement, the conductive layer elements of the core structure are in electrical contact with each adjoining electric cell on both sides of the layer, the negative terminal of the electric cells on one side, and the positive terminal of the electric cells on the other side of the layer. In order to achieve this electrical connectivity, conductive tabs may be run from the positive terminal of the cell through openings or cutouts in the insulating layer element of a laminated layer to the electrically conductive layer element and conductive bonds may be formed between the electric cell shells which are internally connected to the negative terminal of the electric cell and the electrically conductive layer element. Such conductive tabs and conductive bonds may take the form of fusible links where the cross section of the said tabs is such that it melts or fails to conduct when a pre-selected high current attempts to pass through it. In order to transfer shear stresses effectively, each electric cell should desirably be adhesively or mechanically bonded its adjoining layer, be it an electrically conductive layer element or an electrically insulating layer element.

[0015] Pitch of electric cells may be selected freely to accommodate the required number of electric cells into a given form factor. Hexagonal packing allows the closest packing and altering the pitch of the electric cells is equivalent to changing the inclination of the hexagonal closest packed pattern. Altering the pitch of an electric cell also affects the amount of core, for example elements of the above described core structure, in contact with the electric cell. This may usefully be employed to improve heat transfer and/or core strength.

[0016] The number of electric cells and number of spaces selected to accommodate such 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, with a single structural battery or bank of structural batteries as described herein being used. The electric cell type is not critical though suitable batteries could be selected from rechargeable batteries, such as from the lithium ion battery class, such as for example 18650 type batteries rated at 3.7v approximately or 2170 type batteries rated at a higher voltage. Electric cell connections are preferably made in both series and parallel so that a parallel bank, group, row or string of electric cells, for example as described above, are connected to an adjoining parallel bank, group, row or string of electric cells in series. Individual electric cells within a respective bank etc. are preferably made in parallel. Provision may be made to break up the connections at given intervals in order to limit voltages during assembly or during an accident.

[0017] 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. A potential application is to electric motor vehicles. In such case, the composite structure could accommodate a very large number of electric cells conveniently in the form of a floor pan for an electric motor vehicle. Weight is then 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.

[0018] 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:

[0019] Fig. 1 shows an orthogonal exploded cutaway view of a structural battery with a core structure according to one embodiment of the present invention.

[0020] Fig. 2 shows a schematic orthogonal cutaway view of the structural battery of Fig. 1 .

[0021 ] Fig. 3 shows a detail view of a core element of the core structure of Figs. 1 and 2.

[0022] Referring now to Figs. 1 and 2, there is shown a cutaway 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; and a core 30 for accommodating a plurality of electric cells 34 provided within the container 12. The first material may also include other materials resistant to longitudinal and transverse bending forces, preferably lightweight materials which may include light metals or metal alloys such as aluminium alloys. Container 12 includes facing layers 12a and 12b of CFRP or like material, a material having significantly lower electrical conductivity than conductive materials included within elements of core 30. Facing layer 12a is shown curved upward for clarity; in practice, it would be flat like facing layer 12b. Facing layers 12a and 12b are of sufficient strength to treat tension and compression loads. The structural battery 10 therefore has a composite sandwich structure.

[0023] 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. Further description of a structural battery 10 and its composite sandwich structure, which approximates an "I" beam, is provided in the Applicant's co-pending International Patent Application filed 8 August 2018 under Attorney Docket No. P42453PCAU, incorporated herein by reference.

[0024] 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 for the application. Core elements 31 of core structure 30 have a laminated structure comprising multiple plies of corrugated aluminium (or other conductive metal) to form an electrically and thermally conductive layer or form 31 a of approximately 50μιη thickness which are bonded together with an insulating layer 31 b in a corrugation moulding, rolling or pressing process in such a way as to leave generally cylindrical spaces 32 for accommodating electric cells 34 and their connecting tabs or electrodes (not shown) in a manner avoiding short circuiting and other electrical malfunctions. One electric cell 34 is accommodated by each space 32. Core structure 30 has a tiered configuration with core elements 31 and electric cells 34 arranged in tiers.

[0025] Core structure 30, as schematically illustrated in Figs. 1 and 2, enables close packing of electric cells 34, in parallel rows such as those shown as P1 , P2 and P3, preferably with a packing factor approaching ideal hexagonal packing. Such close packing is important, even essential, for most applications, especially in electric vehicles.

[0026] Insulating layer 31 b of core element 31 is electrically isolating and is of a material providing sufficient compressive strength and shear resistance to meet structural battery 10 requirements. A ceramic insulating material or a polymeric insulating material, such as polyamide, may be used for insulating layer 31 b. For reasons that will become apparent below, insulating layer 31 b of core element 31 is thermally conductive. [0027] A plurality of fluid passage means for a first fluid transport system of the structural battery 10 are formed by sealed spaces left between the insulating layer 31 a and conductive layer 31 b of each 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.

[0028] Core element 31 , one of which is shown in Fig. 3, is effectively splined along the length of the passages 35, with the parallel longitudinally splines 35a contacting electric cells 34. Three such splines are provided for each element 31 though this number can be varied as desired. Heat transfer fluid may be circulated through passages 35 from heat transfer fluid distribution means M1 for controlling the temperature of structural battery 10 through heat transfer contact between passages 35 and the shells of electric cells 34. Though not shown, M1 can be disposed relative to structural battery 10 in a manner to provide localised crush resistance in the event of an accident.

[0029] Between splines 35a are located channels 35b which form part of a second fluid transport system used for purging, venting or monitoring of the structural battery 10. Three channels 35b are provided for each core element 31 though this number may be varied as desired. Such monitoring may detect abnormal battery operating conditions such as thermal runaway with the second fluid transport system enabling corrective action by supply of a suitable cooling fluid from manifold M2. Further description of the first and second fluid transport systems embodiment is provided in the Applicant's International Patent Application filed 8 August 2018 under Attorney Docket No. P43210PCAU, the contents of which are incorporated herein by reference.

[0030] Each electric cell accommodating space 32 is substantially defined by adjoining core elements 31 , and more particularly the conductive layers or splines 35a of the core structure 30 which, to be compatible with or match the cylindrical shape of the accommodated electric cells 34, have a semi circular geometry as schematically indicated in Fig. 3. Each space 32 also has a generally cylindrical volume. In order to transfer shear stresses and heat effectively, a shell of each electric cell 34 is bonded to adjoining core elements 31 , including splines 35a, by a conductive polymer adhesive such as a fusible epoxy resin. Altering pitch of electric cells 34 may also assist in promoting shear resistance and heat transfer. By this arrangement, it will be understood that, through this arrangement, core elements 31 cooperate with the electric cells 34 to provide electrical and thermal connectivity as well as structural links between core elements 31 and electric cells 34.

[0031 ] Electric cells 34 of various types could be selected for structural battery 10 and this is not critical though suitable cylindrically shaped batteries could be selected from rechargeable batteries especially from the lithium ion battery class, such as for example 18650 or 2170 type batteries which have a cylindrical geometry and are rated at 3.7v per cell. 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.

[0032] The structural battery 10 can be used in a range of applications including in fixed structures, mobility devices and portability devices. A potential application is to electric motor vehicles. In such case, a bank of structural batteries 10 could accommodate a very large number of electric cells 34, potentially thousands, and form a floor pan for an 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.

[0033] Structural battery 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. [0034] Modifications and variations to the structural battery and core 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.

Claims

CLAIMS:

1 . 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 elements wherein said structural elements cooperate with said electric cells to provide electrical connections and structural links between said structural elements and said electric cells.

2. The structural battery as claimed in claim 1 wherein each structural element has a laminated structure.

3. The structural battery of claim 1 or 2, wherein said structural elements are electrically and thermally conductive.

4. The structural battery as claimed in claim 1 or 2 wherein each structural element comprises a first electrically and thermally conductive layer and a second electrically insulating layer.

5. The structural battery as claimed in any one of the preceding claims wherein said structural elements are multi-ply corrugated sheets.

6. The structural battery as claimed in any one of the preceding claims wherein structural elements include walls having circular, part circular or arcuate shape for matching with cylindrically shaped electric cells.

7. The structural battery as claimed in claim 4 wherein conductive layer elements of the core structure are in electrical contact with each adjoining electric cell on both sides of the layer, the negative terminal of the electric cells on one side, and the positive terminal of the electric cells on the other side of the layer.

8. The structural battery of claim 7 wherein conductive tabs are run from the positive terminal of the cell through openings or cutouts in the insulating layer element of a laminated layer to the electrically conductive layer element and conductive bonds are formed between electric cell shells which are internally connected to the negative terminal of the electric cell and the electrically conductive layer element.

9. The structural battery of claim 8, wherein said conductive tabs and said conductive bonds take the form of fusible links where the cross section of the said tabs and bonds melts or fails to conduct on attempt to pass a pre-selected high current through them.

10. The structural battery of claim 4, wherein each electric cell is adhesively or mechanically bonded to its adjoining layer, whether an electrically conductive layer element or an electrically insulating layer element.

13. The structural battery of any one of the preceding claims, wherein electric cells are close packed within the core, optionally with a packing factor approaching that for hexagonal geometry.

14. The structural battery of claim 13 wherein pitch of electric cells is selected freely to accommodate the required number of electric cells into a given form factor.

15. The structural battery of any one of the preceding claims wherein structural elements comprise a laminated structure resistant to tension, compression and shear loads comprising a first electrically and thermally conductive layer and a second electrically insulating layer, said first and second layers of each structural element being relatively disposed to form a plurality of regularly spaced longitudinally extending parallel splines.

16. The structural battery of claim 15 wherein each spline corresponds with a fluid passage means.

17. A core for a structural battery comprising a plurality of 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

18. The core of claim 17 wherein each spline corresponds with a fluid passage means.

19. An electric device comprising a structural battery as claimed in any one of claims 1 to 13 as a structural member within said electric device or comprising a core as claimed in claim 17 or 18.

20. The device of claim 19 selected from the group consisting of portable devices, mobility devices and electric vehicles.