WO2019028516A1

WO2019028516A1 - A structural battery

Info

Publication number: WO2019028516A1
Application number: PCT/AU2018/050837
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 plurality of fluid passage means (35, 35b) forming part of at least one fluid transport system.

Description

A STRUCTURAL BATTERY

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

[0002] The Applicant has developed a composite sandwich 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 and longitudinal and transverse bending forces imposed on said structural member by the application. Further description of this composite structure is provided in the Applicant's co-pending International Patent Application, filed 8 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] The Applicant's structural battery desirably includes temperature control means for controlling structural battery and electric cell operating temperature to provide performance and lifespan benefits, for example as described in the Applicant's co-pending International Patent Application filed 8 August 2018 under Attorney Docket No. P42683PCAU, the contents of which are hereby incorporated by reference. In the case of lithium based electric cells, structural battery and electric cell operating temperature is desirably in the range of 15^QC to 35^QC. [0005] It is an object of the present invention to provide a structural battery that comprises a core adapted to provide thermal control and desirably other structural battery control functionality as well.

[0006] 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 at least one, more typically a plurality of, fluid passage means forming part of at least one fluid transport system. The fluid passage means may, without limitation, include channels, ducts or passages.

[0007] The structural battery may include a plurality of fluid transport systems, each of which may serve a different function. For example, the structural battery highly desirably includes means for controlling the battery operating temperature, for example as described in the Applicant's co-pending International Patent Application filed 8 August 2018 under Attorney Docket No. P42683PCAU, the contents of which are incorporated by reference. The temperature control means may comprise at least one fluid transport system conveniently including the fluid passage means for transport of fluids to facilitate heat transfer during operation of the structural battery. Suitable heat transfer fluids may be gaseous including air and refrigerants such as R134a (1 ,1 ,1 ,1 ,2-tetrafluoroethane) or liquids such as organic liquids suitable as heat transfer fluids in a battery application.

[0008] In addition, or alternatively, to a fluid transport system being used for temperature control, a fluid transport system may also be included to enable other battery functions including, but not limited to, venting, monitoring and detection of gas evolution (for example during electric cell thermal runaway or electric cell failure or rupture) and purging with an inert gas (such as carbon dioxide) for example during an abnormal operating condition or thermal runaway. Fluids such as inert gases, e.g carbon dioxide, may be supplied to such a fluid transport system to enable cooling under such conditions. Under normal operating conditions, a fluid may be circulated and its composition sensed with a sensor to obtain data about structural battery operation. If an abnormal operating condition, for example overheating or thermal runaway is sensed, corrective action such as supplying fluids, such as inert gases, to a fluid transport system can be conducted. Flooding or phase change cooling may be conducted by such fluid supply. A structural battery or electric cells in this condition may also be isolated and additional measures taken to prevent further failures. For example, an insulating intumescent material may be included or delivered to the structural battery to protect electric cells proximate failed electric cell(s).

[0009] Each fluid transport system includes fluid passage means for transport of fluids suitable for performing the required function. For thermal control, a first fluid transport system includes a plurality of first fluid passage means for transporting heat transfer fluids. A second fluid transport system, for example used in purging venting or monitoring during structural battery operation as described above, may include a plurality of second fluid passage means.

[0010] The structural battery may further comprise at least one fluid distribution means, such as a manifold, for distributing fluid to or from the fluid passage means of the at least one fluid transport system. Where a plurality of fluid transport systems are included in the structural battery, a plurality of fluid distribution means are also required though these may be integrated within a fluid distribution unit. The fluid distribution means preferably allows recirculation of fluids through a fluid transport system for temperature control, for example following heat exchange at a radiator, chiller or other suitable heat exchanger. Where a fluid transport system is used for purging or venting, for example in a thermal runaway situation the fluid distribution means may only allow fluid flow, if any, out of the battery through venting means under normal operating conditions. In this case, the venting means or fluid distribution means may include a sensor for detecting gases or other species diagnostic of thermal runaway or other battery operating condition requiring monitoring. Such a fluid distribution means may enable a purging fluid to be supplied to the structural battery as described above.

[001 1 ] 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 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. Manifolds, as above described, may also be disposed relative to the container to prevent localised crushing in case of an accident.

[0012] The core of the structural battery advantageously includes a structure of lightweight material such as a conductive light metal or light metal alloy; for example aluminium. Desirably, the core comprises a framework of structural elements wherein the structural elements cooperate with electric cells to provide electrical connections and structural links between the structural elements and the electric cells. 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 structural core elements forming the framework of the core structure. Core structures of this kind are also described in the Applicant's International Patent Applications filed 8 August 2018 under Attorney Docket Nos. P42453PCAU, P42682PCAU, P42683PCAU, P43209PCAU and P43190PCAU, the contents of which are hereby incorporated herein by reference.

[0013] 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. Such core elements may be in the form of sheets. 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.

[0014] The conductive layer of the core element is conveniently laminated to the insulating layer in a manner to form a plurality of fluid passage means for the fluid transport system(s) of the structural battery. Each core element sheet is desirably formed to have a corrugated shape with an approximately semi-circular regular alternating pattern so as to leave sealed spaces between the insulating layer and conductive layer that form a fluid passage means, especially a plurality of first fluid passage means of suitable dimension for effective use in a first thermal control fluid transport system.

[0015] Each resulting core element may have a plurality of regularly spaced longitudinally extending parallel splines, each spline conveniently corresponding with a fluid passage means of a fluid transport system, desirably a system for temperature control.

[0016] As described above, a second fluid transport system, for example used in purging, venting or monitoring of the structural battery as described above, includes a plurality of second fluid passage means. In the above desired arrangement the second fluid passage means are located between the splines, conveniently being formed as channels between the corrugations or splines of each core element.

[0017] The core elements forming the framework of the preferred core structure are also disposed to define spaces for accommodating electric cells. Core elements and electric cells accommodated between them may be arranged in tiers as described in the Applicant's International Patent Application filed 8 August 2018 under Attorney Docket No. P43209PCAU, incorporated herein by reference. The core elements may 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 is highly desirable. Conveniently, and for matching with cylindrically shaped electric cells, the walls are of part circular, circular or arcuate shape. The electric cells typically require a high packing ratio, though are arranged in parallel banks or rows. 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.

[0018] 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, core elements are in electrical contact with each adjoining electric cell on both sides of the layer, the negative terminal of the cells on one side, and the positive terminal of the 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 battery 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.

[0019] 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.

[0020] 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.

[0021 ] 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.

[0022] 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:

[0023] Fig. 1 shows an orthogonal exploded cutaway view of a structural battery including core elements having a plurality of fluid passage means forming part of at least one fluid transport system in accordance with one embodiment of the present invention . [0024] Fig. 2 shows a schematic orthogonal cutaway view of the structural battery of Fig.1 .

[0025] Fig. 3 shows a detail view of a core element of the structural battery of Figs. 1 and 2.

[0026] Referring now to Figs. 1 and 2, there is shown a cutaway view of a 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.

[0027] The structural battery 10 forms a structural member having resistance to compressive, tension, shear, torsional 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.

[0028] Core structure 30 forms the core of the structural battery 10 and is resistant to compressive and shear loads, is also electrically and thermally conductive being made up of suitably arranged core layers or core elements in the form of sheets 31 . 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 parallel tiers or rows.

[0029] Core structure 30, as schematically illustrated in Figs. 1 and 2, enables close packing of electric cells 34, in parallel tiers or rows such as those shown as P1 , P2 and P3, preferably with a packing factor approaching ideal hexagonal packing.

[0030] Insulating layer 31 b 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 is thermally conductive.

[0031 ] A plurality of fluid passage means for the fluid transport system(s) of the structural battery are formed by sealed spaces left between the insulating layer 31 a and conductive layer 31 b of each 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.

[0032] Each 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 including heat transfer manifold and fixed or variable speed pump for thermal control, the contact between parallel splines 35a and the electric cells 34 allowing efficient heat transfer to maintain battery operating temperature in a desired range of 15^QC to 35^QC. Heat transfer fluid, such as a refrigerant or other heat transfer fluid selected not to interfere with battery 10 operation, is recirculated through manifold M1 for thermal control. In the event electric cells 34 are cooled, heat transfer fluid exchanges heat gained from the electric cells 34 at heat exchanger such as a radiator (not shown). If electric cells 34 require heating, a further heat exchanger replaces heat lost in electric cell 34 heating. Though not shown, M1 can be disposed relative to structural battery 10 in a manner to provide localised crush resistance in case of accidents.

[0033] 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 element 31 though this number may be varied as desired. Such monitoring of composition of any gas flowing in channels 35b may detect abnormal battery operating conditions such as thermal runaway or electric cell rupture or failure with the second fluid transport system enabling corrective action by supply of a suitable cooling fluid from manifold M2 to flood the failure zone. An intumescent material may also be included or delivered to conduct phase change cooling. Failure zones can also be isolated and adjacent electric cells 34 protected.

[0034] Each electric cell accommodating space 32 is substantially defined by adjoining core element sheets 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, 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. [0035] 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.

[0036] 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.

[0037] 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.

[0038] Modifications and variations to the structural battery 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

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 plurality of fluid passage means forming part of at least one fluid transport system.

2. The structural battery of claim 1 wherein said at least one fluid transport system includes first fluid passage means for controlling battery operating temperature.

3. The structural battery of claim 1 wherein said at least one fluid transport system includes second fluid passage means for enabling a battery function selected from venting monitoring and detection of gas evolution during thermal runaway or electric cell failure or rupture; and/or purging with an inert gas during an abnormal operating condition or thermal runaway.

4. The structural battery of any one of the preceding claims comprising a plurality of fluid transport systems including a fluid transport system including first fluid passage means for controlling battery operating temperature; and at least.

5. The structural battery of any one of the preceding claims comprising at least one fluid distribution means, such as a manifold, for distributing fluid to or from the fluid passage means of said at least one fluid transport system.

6. The structural battery of claim 5 comprising a plurality of fluid distribution means for distributing fluid to or from said fluid transport systems.

7. The structural battery of any one of the preceding claims, 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.

8. The structural battery of claim 7, 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.

9. The structural battery of claim 8, wherein each spline corresponds with a fluid passage means.

10. The structural battery of claim 8 or 9, wherein fluid passage means, such as channels, are located between each spline.

1 1 . The structural battery of claim 10 wherein said fluid passage means is a second fluid passage means for enabling a battery function selected from venting monitoring and detection of gas evolution during thermal runaway or electric cell failure or rupture; and/or purging with an inert gas during an abnormal operating condition or thermal runaway.

12 The structural battery as claimed in any one of claims 8 to 1 1 , wherein each structural element has a laminated structure comprising a first electrically and thermally conductive layer and a second electrically insulating layer.

13. The structural battery as claimed in any one of claims 8 to 12, wherein said structural elements are multi-ply corrugated sheets.

14. The structural battery of claim 12, wherein each electric cell is adhesively or mechanically bonded to its adjoining layer, whether an electrically conductive layer or an electrically insulating layer.

15. 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.

16. An electric device comprising a structural battery as claimed in any one of claims 1 to 15 as a structural member within said electric device.

17. The device of claim 16 selected from the group consisting of portable devices, mobility devices and electric vehicles.