Aqueous high-voltage all 3D-printed micro-supercapacitors with ultrahigh areal capacitance and energy density

With the rapid development of integrated and miniaturized electronics, the planar energy storage devices with high capacitance and energy density are in enormous demand. Hence, the advanced manufacture and fast fabrication of microscale planar energy units are of great significance. Herein, we develop aqueous planar micro-supercapacitors (MSCs) with ultrahigh areal capacitance and energy density via an efficient all-3D-printing strategy, which can directly extrude the active material ink and gel electrolyte onto the substrate to prepare electrochemical energy storage devices. Both the printed active carbon/exfoliated graphene (AC/EG) electrode ink and electrolyte gel are highly processable with outstanding conductivity (~97 S cm −1 of electrode; ~34.8 mS cm −1 of electrolyte), thus benefiting the corresponding shaping and electrochemical performances. Furthermore, the 3D-printed symmetric MSCs can be operated stably at a high voltage up to 2.0 V in water-in-salt gel electrolyte, displaying ultrahigh areal capacitance of 2381 mF cm −2 and exceptional energy density of 331 μWh cm −2 , superior to previous printed micro energy units. In addition, we can further tailor the integrated 3D-printed MSCs in parallel and series with various voltage and current outputs, enabling metal-free interconnection. Therefore, our all-3D-printed MSCs place a great potential in developing high-power micro-electronics fabrication and integration.