Capillary force driven printing of asymmetric Na-ion micro-supercapacitors

Abstract

Micro-supercapacitors, are ideal power sources for the next generation of smart microelectronics because of their high power density and unique characteristic of easy integration with other functional electronics. However, the preparation of a high-resolution interdigital micro-electrode while achieving high-loading deposition of asymmetric electrode materials is still a crucial challenge for large-scale fabrication of high-performance micro-supercapacitors. Here, we developed a capillary force driven printing approach to assemble asymmetric micro-supercapacitors (AMSCs) with Na-ion aqueous electrolyte. With optimization of the composition of two electrode active materials, the Na-ion AMSCs achieved a stable capacitive voltage window of 2.1 V, exhibited an areal specific capacitance of 34 mF cm⁻², and also showed an excellent mechanical and electrochemical stability with various device deformation states (bending, rolling and folding). The hydromechanical simulation was performed by using COMSOL Multiphysics in a 2-dimensional model to theoretically verify the feasibility of the capillary force driven process. After in series and in parallel connection of 9 AMSCs, a 6.3 V overall stable output voltage was achieved with a specific capacitance of 25.5 mF cm⁻². This work may pave a new way for assembling multi-functional material based micro energy storage devices and beyond.