Solution-Processed Hexagonal Boron Nitride Ionogel Electrolytes for Printed Electronics and Energy Storage

Ionogels, also known as ion gels or ionic liquid gels, are composite solid-state electrolytes, in which ionic liquids are immobilized by a gelling solid matrix. Ionic liquids offer several advantages as an electrolyte solution, including nonflammability, negligible vapor pressure, and high thermal stability. Moreover, combining ionic liquids with a gelling solid matrix leads to a solid-state electrolyte that is mechanically robust yet flexible without leakage problems, rendering it promising for flexible electronics and energy storage [1]. However, the key limitation of ionogels has historically been their weak mechanical properties, resulting in poor structural integrity. In this talk, a novel ionogel will be introduced based on exfoliated hexagonal boron nitride (hBN) nanoplatelets [2], which shows not only desirable mechanical and electrochemical properties (storage modulus > 1 MPa, room temperature ionic conductivity > 1 mS/cm) but also good printability [3]. hBN possesses several desirable attributes as a solid matrix material, including electrically insulating character, chemical inertness, thermal stability, and mechanical robustness. In addition to these intrinsic advantages, the exfoliated hBN nanoplatelets significantly enhance the mechanical strength of ionogels without compromising electrochemical properties, compared to conventional bulk hBN microparticles. This talk will discuss the ink formulation and screen/aerosol-jet printing of hBN ionogel electrolytes, and will also show their applications for fully-printed thin-film transistors, lithium-ion batteries, and supercapacitors. [1] W. J. Hyun, et al., Advanced Energy Materials, 10, 2002135 (2020). [2] W. J. Hyun, et al., ACS Nano, 13, 9664 (2019). [3] W. J. Hyun, et al., Faraday Discussions, DOI: 10.1039/C9FD00113A (2020).