Direct-write Printed Flexible Batteries

Energy storage is required for many applications of flexible, printed electronics, and the ability to easily customize the power source is potentially useful. This is particularly true for disposable, mobile applications where flexibility is required. For these applications small capacities may be needed, but high driving voltages (~20 V) are often required due to the relatively thick, low k dielectric layers typically used in printed field-effect transistors. Since DC-to-DC up-conversion is presently non-trivial to achieve with printed electronics, in order to source these voltages many cells must be connected together in series. Using currently available products this would often lead to either a large footprint (if connected laterally) or result in a loss of flexibility (if cells are stacked vertically). As such, it is beneficial to tailor the battery properties, providing the necessary size, voltage and capacity for a particular application. Here, we show a method to achieve this using direct-write printing of batteries onto flexible substrates. A pressurized liquid dispensing system is used to drive a viscous solution through a fine needle in order to deposit the battery materials (current collector, electrodes and electrolyte). Using inks made from suspensions of metal(oxide) particles with polymer binders, an example of a printed zinc-manganese dioxide alkaline battery is shown.