Thin film batteries are used for several applications across a broad range of industries. A few examples include cosmetic and drug delivery patches, smart packaging, and wearable electronics.
The flexibility and versatility of thin film batteries allows innovators across multiple industries to continue to develop innovative new products. If you are in the midst of creating a new product that can benefit from thin film batteries, or if you are considering going down that path, it’s useful to know what to look for as you start your search for a low-profile, reliable power supply.
What to Look for in a Thin Film Battery
Although every application is different and the specifications will vary from product to product, here are some considerations when trying to find the right thin film battery:
Energy density – Like any type of battery you might use, it’s crucial to have an understanding of how much energy it can store so you know how long it can power your device. The energy density, typically expressed in Watt-hours per liter liter (or sometimes in Watt-hours per square centimeter), tells you how much energy the battery can store per unit of volume. When you calculate the energy demands of your device, you can determine the energy density requirement by dividing the energy by the battery volume.
Power density – The power density of a thin film battery goes hand in hand with the energy density. Measured in Watts per liter, the power density of a thin film battery tells you how much power it can deliver in a given volume. In general, as the power density increases, the energy density decreases, and vice versa for a given design. Factors that influence power density include electrode composition and thickness, and whether the power is discharged in a pulsed or continuous manner.
Safety – Battery safety is a priority no matter what technology you use. Thin film batteries must be able to safely withstand both routine use of the product and unexpected occurrences such as breaking, puncturing, or ingestion. All of these considerations limit the choice of chemistry for a thin film battery, which does not necessarily have the robustness of conventional cylindrical containers.
Form factor – When you envision a thin film battery, it is probably some version of a flat, flexible object, like a nicotine patch. While this is not incorrect, it is an oversimplified characterization of thin film batteries. Depending on the type of technology employed, thin film batteries can have a thickness at the micron or millimeter level and the size of the footprint can vary significantly depending on the end use, ranging from millimeters to centimeters. Thin film batteries can also be rigid or flexible depending on the battery chemistry and the casing.
Rechargeability– At first glance, this seems like a no-brainer. It seems logical that it’s always better to be able to recharge a battery than not to have that ability; none of our modern gadgets like smarphones, laptops, smartwatches, and so on would be practical without rechargeable batteries. The reality, however, is a bit more complicated. Rechargeable batteries generally cost more than comparable non-rechargeable batteries, and require added circuitry to enable recharging. For disposable products, such as drug delivery patches, RFID’s, or smart packaging the added cost of a rechargeable battery may not be necessary. Even if price is not a major consideration, rechargeable batteries will generally self-discharge more quickly than primary batteries, and all else equal will have lower capacity. Depending on the drain of the device you’re developing, it may make sense to provide a primary battery that lasts the life of the device instead of adding a rechargeable battery.
Shelf life – Is your product so specialized that it will be made to order, or will you mass produce inventory that will be stored for long periods of time? For most people, the latter scenario is most common, which means that you need a battery with a shelf life of at least two years. Make sure you select a thin film battery chemistry that will not self-discharge in the time between production and delivery to the customer.
Clearly, there are a lot of factors to consider when selecting a thin film battery for your application, and each of these also plays a role in the cost and scalability of your project. If you are looking for more information about thin film batteries, download our free white paper for more helpful tips.
Topics in this article: Thin Film Batteries