NU 2020-018

INVENTORS
Woo Jin Hyun
Mark Hersam*

ABSTRACT
Due to its excellent chemical/thermal stability and mechanical robustness, hexagonal boron nitride (hBN) is a promising solid matrix material for ionogels. While bulk hBN ionogels have been employed in macroscopic applications such as lithium-ion batteries, hBN ionogel inks that are compatible with high-resolution printing have not yet been realized. Here, we describe aerosol-jet-printable ionogels using exfoliated hBN nanoplatelets as the solid matrix. The hBN nanoplatelets are produced from bulk hBN powders by liquid-phase exfoliation, allowing printable hBN ionogel inks to be formulated following the addition of an imidazolium ionic liquid and ethyl lactate. The resulting inks are reliably printed with variable patterns and controllable thicknesses by aerosol jet printing, resulting in hBN ionogels that possess high room-temperature ionic conductivities and storage moduli of > 3 mS cm–1and > 1 MPa, respectively. By integrating the hBN ionogel with printed semiconductors and electrical contacts, fully-printed thin-film transistors with operating voltages below 1 V are demonstrated on polyimide films. These devices exhibit desirable electrical performance and robust mechanical tolerance against repeated bending cycles, thus confirming the suitability of hBN ionogels for printed and flexible electronics.

APPLICATIONS  

• Lithium-ion batteries
• Supercapacitors
• Transistors
• Neuromorphic computing devices
• Flexible electronics
• Printed electronics

ADVANTAGES  

• Printability enables the production of electronic devices with minimal materials waste and low cost, and also renders the device fabrication process compatible with roll-to-roll production schemes for high-throughput manufacturing.
• Compared to conventional dielectrics(e.g., SiO2), the high double-layer capacitance of ionogel electrolytes enable slow-voltage  operation of transistors for  low-power  and  portable devices. Moreover,the ionogels are  a  favorable  dielectric  for  flexible  printed transistors because the  electrolytes  offer  high  tolerance  to thickness variations and desirable mechanical flexibility without leakage issues.
• Compared to common polymer solid matrices, the hBN solid matrix concurrently imparts high mechanical strength and ionic conductivity to printable ionogels.

PUBLICATIONS
Hyun WJ, Chaney L, Downing J, deMoraes A and Hersam (2021) Printable Hexagonal Boron Nitride Ionogels.  Faraday Discussions 227: 92-104.

IP STATUS
Provisional and PCT applications have been filed.