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

International audience ; Due to the low energy density of commercial printable dielectrics, printed capacitors occupy a significant printing area and weight in printed electronics. It has long remained challenging to develop novel dielectric materials with printability and high energy-storage density. Here, we present a novel strategy for 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 negatively charged PVDF latex nanoparticles complexed with cationic chitosan molecules. Beyond the isoelectric point, the PVDF@Chitosan particles demonstrate excellent printability and film-forming properties. Chitosan serves as a strong binder to improve the printed film quality yet it introduces charged species. To mitigate the transport of mobile charges, we interlayer the printed PVDF@Chitosan film with a layer of boron nitride nanosheets. 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 cm-3 at 610 MV m-1. This energy density represents the highest value among the waterborne dielectrics. It is also superior to most of the state-of-the-art dielectric materials printed from solvent-based formulations.