Inkjet-printed transparent micro-supercapacitors with morphology tailored co-continuous mesoporous Mn3O4

Abstract

High energy density, flexible supercapacitors typically use various carbon allotropes and 2-dimensional metals as the electrode material. As an alternative, here we report, fully printed, bendable and high-capacity micro-supercapacitors (MSCs) from large surface-to-volume ratio co-continuous mesoporous manganese oxide (Mn₃O₄). The printed 3-electrode supercapacitors have shown gravimetric capacitance as high as 1201 F g⁻¹, whereas the printed and highly transparent micro-supercapacitors demonstrate a large potential window up to 2.6 V, and gravimetric and volumetric capacitances of 396 F g⁻¹ and 1406 F cm⁻³ with printed aqueous solid polymer electrolytes and 679 F g⁻¹ and 2411 F cm⁻³ with non-aqueous solid polymer electrolytes, respectively. The cyclic stability of these printed MSCs has been demonstrated up to 10 000 cycles with <2% reduction in initial capacitance. Flexible MSCs realized onto polyimide substrates also exhibit excellent gravimetric (653 F g⁻¹) and volumetric (2317 F cm⁻³) capacitance, and no measurable performance degradation with bending fatigue tests performed down to the bending radius of 2.5 mm. In addition, the printed MSCs are found to be highly transparent with >90% transparency at 550 nm. The observed high energy density (353 W h kg⁻¹), coupled with high transparency and adequate flexibility can make them ideally suitable for application in smart glasses and invisible electronics.