Today's highly mobile world is very dependent upon portable power and portable power today is trending towards electric rather than gasoline, which means batteries or other electrochemical devices are the primary power source. The energy needed for many devices and applications leads to the batteries consuming a significant portion of the mass and volume allocated to the device, and also imposes significant constraints on the shape and size of the device. For example, a large portion of the mass of a laptop computer is contained in the battery, and the shape is fixed by the shape of the battery.
Because of the space and weight taken up by batteries, engineers often try to have batteries serve multiple purposes. For example, the lead acid batteries in forklifts serve as ballast for stability. There are however, more instances where added weight and or volume are not beneficial. In these cases, engineers would like to get electrochemical devices to provide additional functions besides power. There are many applications where “multi-functional” composites containing energy storage would find application. As batteries take up space, one of the most obvious approaches is to have them contribute to the mechanical aspects of the structure. As most batteries are delivered in cases, it is technically feasible to try to gain structural aspects from fastening them together. However, this after-the-fact approach is not optimal.
There have been efforts in the past to use the carbon fiber in composites as anode material for lithium ion batteries and turn the composite into a battery. However, due to numerous problems with the composite resin, the carbon mat thickness, the need for vapor barriers and electrolytes, the efforts were never commercially successful. A much more direct approach is to embed individual lithium ion cells into a composite or polymer.
Unmanned Arial Vehicles (UAVs), and especially Micro UAVs that have electric propulsion are excellent examples which are critically dependent on weight and where composite structural panels are common. Accordingly, there is interest in using advanced multi-functional composites. Bending modulus is critical to UAV panels and the mechanics of bending are well understood. Consumer electronics are additional examples that are dependent on mass and volume. Accordingly, it is desirable to use multi-functional cells in the structure of these devices to reduce the mass and volume associated with the power supply without reducing the capacity or safety.