Solid-state integrated micro-supercapacitor array construction with low-cost porous biochar

The scalable production of flexible integrated micro-supercapacitors (MSCs) with high performance and low cost is urgently required. Printing is a promising strategy to build MSCs with designable shapes. Here, one kind of cost-effective and universal conductive ink derived from the porous activated biochar has been introduced, which is used for the scalable fabrication of carbon-based planar MSCs on various flexible substrates by the simple fabrication process of screen printing and program-controlled writing methods. The MSCs using the screen printing method have exhibited a favorable areal capacitance of 116 mF cm−2 and a high areal energy density of 9.26 μW h cm−2, and the integrated MSCs connected seven cells in series can also output a voltage of 5.6 V. In addition, the MSC arrays in this work have also been used for storing unstable external energy from a hand dynamo. This study provides significant guidance to construct metal-free integrated MSCs and facilitates the progress towards self-sustainable energy in the future.