Monolithic integration of flexible lithium-ion battery on a plastic substrate by printing methods

Energy storage devices with flexible form factor have become critical components of wearable electronic systems. Inspired by methods of monolithic integration in the microelectronics fabrication process, we propose a planar flexible full-solid-state lithium-ion battery (FSLB) architecture and a layer-by-layer stencil printing assembly method for fabricating batteries on polyethylene terephthalate (PET) substrate. FSLBs use quasi-solid electrolyte based on LiTFSI and ultraviolet (UV)-curable ethoxylated trimethylolpropane triacrylate (ETPTA) polymeric matrix in combination with Li₄Ti₅O₁₂ (LTO)/LiFePO₄ (LFP)-based electrodes. Excellent mechanical flexibility (< 10 mm bending radius) can be achieved. The electrochemical characteristics of electrolyte, including ion conductivity, physical stability during room-temperature and tender assembly processes, are promising. A complete thin film-shape FSLB demonstrated working operation both under planar and bending conditions. The unique architecture and assembly processes open new ways for planar flexible devices to be integrated with flexible energy devices.