Published on 17 November 2011
A unique concept in energy storage using interlocking structural cells to contain a battery's chemicals could revolutionise design of road and racing vehicles. TWI's involvement in the design of batteries which also contribute structurally to the vehicle's chassis has been reviewed in hybrid vehicle designs and it looks likely to be taken up by commercial and competition vehicles.
The cells themselves could be plastics-based with a co-extruded conductive coating, or metal-based using aluminium. A battery requires chemicals, for example lead acid, lithium polymer or lithium iron in liquid or gel form. What is being done is taking those chemicals and incorporating them, not in a battery cell as a separate entity, but within the structural elements of the vehicle, such as the floor or loading bay.
A separate but related issue that has to be addressed is joining the individual cells together. These cells have to be tack welded or joined using some form of mechanical fastening. When assembling the cells, welding can cause serious harm to the battery chemistry because of localised heating, reducing their performance.
The Battrix concept was designed to increase the surface area of the anode and the cathode and provide a structural mechanical interlocking cell. Having a large interlocking surface area on the anode and cathode allows greater power (volts and amps) to be drawn out of the battery, without causing high electrical resistance therefore reducing heating.
If aluminium sandwich structures are used to make a large floor pan for a convertible car, one way of doing it, instead of actually bonding the honeycomb to the aluminium sheets, is to stake weld the sheets to the honeycomb or cells. Surface preparations on the aluminium need to be addressed otherwise the long term durability will be suspect and corrosion can occur.
The Battrix energy storage concept is modular. Once the issues of joining the skins to the core (cells) have been addressed, the unit can then be used as the structural chassis of the vehicle.
Ideally these batteries would be in the floor but could be in other sites of the vehicle, the roof, sides or wings, wherever there is space. It could even be put in the rear or the front wings of the vehicle where quite often the structure is built up using laminates on specialised vehicles.
The benefits of the Battrix concept for which TWI has applied for a patent include:
- High current transfer capability
- Exceptional thermal stability
- Environmentally friendly
- Easy recyclability
Battrix can be summarised as an electrical energy storage device such as an electromagnetic cell (battery) or a capacitor consisting of one or more inter-lockable structural cells that enables good current dissipation. This is achieved by way of increasing the surface area of the terminals of the device to enable a greater current flow and provide a structural element to a vehicle in the form of a chassis.