J.X. Ma, S.H. Zheng, Y.X. Cao, Y.Y. Zhu, P. Das, H. Wang, Y. Liu, J.M. Wang, L.P. Chi, S.Z. (Frank) Liu,* and Z.-S. Wu*

Advanced Energy Materials, 2021, 11, 2100746.

DOI: 10.1002/aenm.202100746 [PDF]

Despite intense development of inkjet printing for scalable and customizable fabrication of power sources, one major shortcoming is the lack of eco-friendly aqueous inks free ofadditives (e.g., toxic solvents, surfactants).Here, we demonstrate an aqueous printable MXene/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) (MP) hybrid ink with adjustable viscosity to directly inkjet-print micro-supercapacitors (MP-MSCs)with excellent performance, seamless integration and desirable customization, which is crucial for scalable industrialization of self-powered integrated systems.The MP-MSCs deliver unprecedented volumetric capacitance of 754 F cm^-3and remarkable energy density of 9.4 mWh cm^-3, superior to previously reported inkjet-printed MSCs. Such outstanding performance is partly attributed to highly conductive PH1000 which prevents restacking of MXene nanosheets, enabling fast electron and ion diffusion throughout the micro-electrode. Moreover, MP-MSCs presentexceptional miniaturization and superiormodularizationfeaturinghigh voltage output up to 36 V from 60 serially-connected cells and impressive areal voltage of 5.4 V cm^-2connected in tandem. Further, MP-MSCs integrated with a flexible solar cell and printable temperature sensor exhibit exceptional response of 2% and mechanical flexibility withoutany bias voltage input. Therefore, the MXene inks will create various opportunities for miniaturization and innovative construction of flexible, self-sustaining, energy harvesting-storing-consuming microsystems for printable electronics.