Structural composite battery with fluidic port for electrolyte

Abstract

According to the invention there is provided a fluidic port (8-9) for a refillable structural composite electrical energy storage device (1), and a method of producing same. The device may be a battery or supercapacitor with first and second electrodes (2,3) which are separated by a separator structure (6), wherein the device contains an electrolyte (4) which may further contain active electrochemical reagents. The fluidic port allows the addition, removal of electrolyte fluids, and venting of any outgassing by products.

Claims

1. A structural composite electrical energy storage device comprising: a first electrode structure; a second electrode structure; and a separator structure, said structures being encapsulated in a binder matrix to form a composite, wherein the separator structure separates the first and second electrode structures respectively, wherein said device comprises at least one void between said first and second electrode structures, said void being fillable with an electrolyte, wherein at least one of the first and second electrodes comprises at least one fluidic port, the fluidic port being integral with at least one ply of a fabric within the composite energy storage device.

2. A device according to claim 1, wherein the device comprises at least two fluidic ports.

3. A device according to claim 1, wherein the device comprises a vent system.

4. A device according to claim 3 wherein the vent system is a gas permeable membrane.

5. A device according to claim 1, wherein the separator structure is formed from a composite material which includes electrically insulating fibers in a binder matrix.

6. A device according to claim 1, wherein the electrolyte is a liquid or a gel.

7. A device according to claim 1, wherein the energy storage device is a composite battery or a composite supercapacitor.

8. A device according to claim 1, wherein the first and second electrode structures form anode and cathode structures to form a composite battery, and further comprise nickel-zinc, nickel-iron, nickel-cadmium, nickel metal hydride, lead acid or silver-zinc, or Li-ion electrochemically active materials.

9. A device according to claim 1, wherein one or more of the first and second electrode structures contains a porous additive which increases access of the electrolyte into said structure.

10. A device according to claim 9, wherein the separator structure contains a porous additive which increases access of the electrolyte into said structure.

11. A method of manufacturing a device, said method comprising: providing a first electrode structure, a second electrode structure, and a separator structure; providing a fluidic port in the separator structure, the fluidic port being integral with at least one ply of a fabric within the composite energy storage device; laying up on either side of the separator structure the first and second electrode structures, so that the separator structure separates the first and second electrode structures respectively, at least one void being provided between the first and second electrode structures, said void being fillable with an electrolyte through the fluidic port; curing the separator structure and electrode structures so that they are encapsulated in a binder matrix to form a composite; and filling the void with electrolyte via the fluidic port.

12. The method of claim 11, further comprising fitting a gas permeable membrane to the fluidic port.

13. A panel on a vehicle vessel or craft, said panel comprising a structural composite energy storage device, said structural composite energy storage device including: a first electrode structure; a second electrode structure; and a separator structure, said structures being encapsulated in a binder matrix to form a composite, wherein the separator structure separates the first and second electrode structures respectively, wherein said device comprises at least one void between said first and second electrode structures, said void capable of being filled with an electrolyte, wherein at least one of the first and second electrodes comprises at least one fluidic port, the fluidic port being integral with at least one ply of a fabric within the composite energy storage device.

Description

(1) Exemplary embodiments of the device in accordance with the invention will now be described with reference to the accompanying drawings in which:

(2) FIG. 1 shows a cross sectional side view of a composite energy storage device, with a fluid port.

(3) FIG. 2 shows a cross sectional side view of a rechargeable electrochemical cell.

(4) FIG. 3 shows a top view of a fluidic port, formed from a female threaded bonding fastener.

(5) FIG. 4 shows a test rig with two fluidic ports located in a fibre reinforced polymer composite

(6) FIG. 1 shows an example of an electrical energy storage device 1, comprising a first electrode structure 2 which is spaced apart from a second electrode structure 3 by a separator structure 6. The electrodes structures 2, 3 may be connected to suitable electrode contacts 5, 7 respectively to permit charging and discharging of the device.

(7) The electrodes 2, 3 have a fluidic ports 8, 9 respectively, to allow an electrolyte 4 to be charged in the partially bonded separator layer 6.

(8) FIG. 2 shows an example of a component integral with an alkaline rechargeable battery, depicted generally at 10, comprising an anode structure 12 which is spaced apart from a cathode structure 14 by a separator structure 16. A fluidic port 17 is located in the cathode layer 14, such that electrolyte may be flowed into the separator structure 16. The anode and cathode structures 12, 14 may be connected to suitable electrode contacts 18, 20 to permit charging and discharging of the cell in the usual manner, although, as explained in more detail below, the anode and cathode structures 12, 14 may act fully as current collectors.

(9) Each of the anode and cathode structures 12, 14 and the separator structure 16 are formed as a composite material comprising suitable fibres in a binder matrix 12b, 14b. The anode and cathode structures 12, 14 comprise electrically conductive fibres 12a, 14a in respective binder matrices 12b, and 14b. The separator structure 16 comprises electrically insulating fibres 16a in a binder matrix 16b.

(10) A representative example of a component of the invention integral with an alkaline battery in the form of a nickel-zinc battery will now be described, in which epoxy resin is used as the binder matrix throughout the device. The anode structure 12 is formed from a plain weave carbon fibre fabric 12a embedded in the binder matrix 12b. The binder matrix 12b also contains porous carbon powder and nickel hydroxide (Ni(OH).sub.2) powder, all of which is mixed thoroughly prior to use. The carbon fibre fabric forms a convenient current collector.

(11) The cathode structure 14 is formed from a plain weave carbon fibre fabric 14a embedded in the binder matrix 14b. The binder matrix 14b also contains porous carbon powder and zinc oxide (ZnO) powder, all of which is mixed thoroughly prior to use. Typically, the number of moles of zinc oxide used is approximately half that of the nickel hydroxide, in view of the stoichiometry of the electrochemical reaction. The electrochemistry of the nickel zinc battery will be well known to the skilled reader, and therefore further details are not provided herein. The carbon fibre fabric forms a convenient current collector.

(12) The active additives in the anode and cathode structures (the nickel hydroxide, zinc oxide and carbon powder) are typically present as fine powders having particle sizes in the range 1 to 10 m.

(13) The separator structure 16 is formed from a plain weave E-glass fabric 16a embedded in the binder matrix 16b. Other electrically insulating fibres such as silicon carbide which provide suitable structural reinforcement might be used instead. Other separators such as microporous polymer films may be used in combination with the glass fabric. The separator structure 16 contains an aqueous electrolyte consisting of 40% by weight potassium hydroxide in deionised water. Zinc oxide is dissolved in this solution until saturation or near saturation is achieved. The electrolyte is passed in via the fluidic port 17.

(14) The electrolyte can be accommodated in a number of ways. The separator structure may be partially bonded in order to provide spaces which can be filled by the electrolyte. The electrolyte is retained by capillary action between fibres. A 30 to 40% degree of bonding is suitable for this purpose. A porous additive, such as a silica or a silica gel, may be used to provide a more open cell structure or a microporous polymer film may be employed. The fluidic port may, after filling the device, be fitted with a vent system (not shown) to control the release of gases during overcharge conditions. The fluidic port 17 permits the ready introduction and removal of the aqueous electrolyte for maintenance or storage.

(15) FIG. 3 shows a top view of a female bonded fastener 21, which may be used as a fluidic port. The faster comprises a base portion 23 with a plurality of holes 24, which allow the fabric plys to be sewn or fastened to the holes 24, and further increase the surface area available for bonding with the binder. The collar portion 22 extends up from the base portion 23. The collar 22 serves as the chamber through which the electrolyte can pass. The collar 22 may optionally be threaded 25 such that sealing caps, filling attachments, vent systems can be easily engaged with the fluidic port 21.

(16) FIG. 4 shows a test rig 30, wherein a fibre reinforced polymer composite 32, is layered up with two fluidic ports 31a, 31b (of the type in FIG. 3), into a central cavity 33, such that fluid may be passed between fluidic ports 31a and 31b.

(17) The first and second electrodes and separator structures are not necessarily planar. Non-planar configurations may be employed, for example, to provide a curved or even a generally tubular device structure, or to provide devices which can be shaped to any currently existing shaped panel. The structures of the invention are well suited for such configurations.