Inkjet Printing of All Aqueous Inks to Flexible Microcapacitors for High-Energy Storage

Due to the low energy density of commercial printable dielectrics, printed capacitors occupy a significant printing area and weight in fully printed electronics. It has long remained challenging to develop novel dielectric materials with printability and high energy-storage density. Here, we present the inkjet printing of all aqueous colloidal inks to dielectric capacitors composed of carbon nanotube electrodes and polyvinylidene fluoride (PVDF)-based dielectrics. The formulated dielectric ink is composed of PVDF latex particles coated by protonated chitosan molecules. Beyond the isoelectric point, the ink demonstrates excellent printability and film-forming properties. Chitosan serves as a strong binder to largely improve the printed film quality yet it introduces charged species. To confine the transport of these mobile charges, the printed PVDF@Chitosan layer was interlayered by a boron nitride nanosheet nanolayer. This layer is perpendicular to the electric field and serves as an efficient barrier to block the transport and the avalanche of charges, eventually leading to a recoverable energy density of 15 J/cm3 at 610 MV/m. This energy density represents the highest value among the waterborne dielectrics. It is also superior to most of the state-of-the-art printed dielectric materials from solvent-based formulations.