Highly connected thin electrodes comprising Ag–Ni core–shell nanowires for flexible CNT/graphene Joule heaters

Ag nanomaterials are typically used in solar-cell electrodes, medical imaging optical devices, touchscreen sensors, air and water purification devices, light-emitting diodes, catalysts, conductive adhesives, and wearable heaters. Although relatively bulky and expensive, Ag paste is widely used as an electrode material in these applications. The lightweight Ag–Ni core–shell nanowires (AgNW–Ni) developed in this study exhibit excellent thermal and electrical properties, even at extremely low mass loadings, because of their excellent electrical network resembling a spider web. Because Ni possesses a higher melting temperature than Ag, AgNWs were electroplated with Ni to protect Ag from disintegration under high Joule heating conditions. Then, AgNW–Ni electrodes were installed at both ends of a flexible carbon nanotube/graphene heater. The AgNW–Ni and Ag-paste electrodes with thicknesses of 1 and 35 μm disintegrated at T_max = 303 and 286 °C, respectively, under high Joule heating. Owing to its lower thickness, AgNW–Ni electrode synthesis consumes less material than synthesizing Ag-paste electrodes; thus, AgNW–Ni is relatively cost-effective. In addition to being used in electrodes, AgNW–Ni can be used as an active heating material. The patternability of the AgNW–Ni films for heaters of various shapes was also investigated in this study.