Fully Printed Li-Ion Batteries Enabled by Printable Amphiphilic Long-Chain Polyamide Separators

Printed lithium-ion batteries (LIBs) are highly attractive for the Internet of Things (IoT), but their development is severely limited by the lack of printing-compatible separators. Herein, we report a printable separator based on amphiphilic long-chain polyamide using a “mixed ‘non-solvents’ evaporation-induced phase separation” (MNEIPS) strategy. Long-chain polyamide dissolves uniquely in high-polarity/low-polarity mixtures, and rapid phase separation during solvent evaporation generates uniform porous structures with high electrolyte wettability and a wide electrochemical stability window. Sequential layer-by-layer printing enables monolithically integrated cathode–separator–anode stacks with tight interfacial contact. Such printable separators are compatible with various electrode materials, supporting both Li-ion and Na-ion full cells. We further demonstrate a stand-alone, fully printed battery with printed current collectors and UV-curable encapsulation, which can power commercial electronic devices. This work provides a facile and scalable room-temperature route to printable separators for structurally integrated batteries.