Direct ink writing of polyimide aerogels for battery thermal mitigation

Abstract

Aerogels, which are ultralightweight and highly porous materials, are excellent insulators with applications in thermal management, acoustic impedance, and vibration mitigation. Aerogels have huge potential in the aerospace industry as a lightweight solution for thermally insulating electronic components which are confined within a small volume. However, the application of aerogels is currently hampered by the primary processing method of molding, which is costly, time-consuming, requires tooling, and limits geometric complexity. The extrusion-based 3D printing method of direct ink writing (DIW) provides an avenue to move past these constraints. However, rheology modifying additives are commonly used to make a sol printable, which may negatively impact the performance of the product aerogel. Here, we report the DIW of pure polyimide aerogels by subjecting the sol to mild heating (60 °C for 5 min) to promote gelation and produce a printable ink. This approach yielded printed aerogels with comparable microstructural, mechanical, and thermal properties to cast aerogels. The printed aerogel is stable up to 500 °C and has potential for high temperature applications relevant to the aerospace industry. We highlight the utility of this system by printing a bespoke enclosure to insulate a heating plate as a model for batteries; even at a plate temperature of 120 °C, the surface of the 8 mm thick aerogel maintained ambient temperature, indicating excellent inhibition of heat transfer. Additionally, a printed aerogel casing for a solid-state electrolyte coin cell battery resulted in a tenfold increase in ionic conductivity sustained for 100 min. This novel, simple method for 3D printing aerogels opens exciting opportunities to move beyond the geometric limitations of molding to expand the application space of these ultralightweight materials.