Electrochemically Exfoliated Graphene Additive‐Free Inks for 3D Printing Customizable Monolithic Integrated Micro‐Supercapacitors on a Large Scale

Three-dimensional (3D) printing technology with enhanced fidelity can achieve multiple functionalities and boost electrochemical performance of customizable planar micro-supercapacitors (MSCs), however, precise structural control of additive-free graphene-based macro-assembly electrode for monolithic integrated MSCs (MIMSCs) remains challenging. Here, the large-scale 3D printing fabrication of customizable planar MIMSCs is reported utilizing additive-free, high-quality electrochemically exfoliated graphene inks, which is not required the conventional cryogenic assistance during the printing process and any post-processing reduction. The resulting MSCs reveal an extremely small engineering footprint of 0.025 cm², exceptionally high areal capacitance of 4900 mF cm^-2, volumetric capacitance of 195.6 F cm^-3, areal energy density of 2.1 mWh cm^-2, and unprecedented volumetric energy density of 23 mWh cm^-3 for a single cell, surpassing most previously reported 3D printed MSCs. The 3D printed MIMSC pack is further demonstrated, with the maximum areal cell count density of 16 cell cm^-2, the highest output voltage of 192.5 V and the largest output voltage per unit area of 56 V cm^-2 up to date are achieved. This work presents an innovative solution for processing high-performance additive-free graphene ink and realizing the large-scale production of 3D printed MIMSCs for planar energy storage.