3D Printing Engineered Multi-porous Cu Microelectrodes with In Situ Electro-Oxidation Growth of CuO Nanosheets for Long Cycle, High Capacity and Large Rate Supercapacitors

Abstract

Developing excellent pseudocapacitive electrodes with long cycle, high areal capacity and large rate has been challenged. 3D printing is an additive manufacture technique that has been explored to construct microelectrodes of arbitrary geometries for high-energy–density supercapacitors. In comparison with conventional electrodes with uncontrollable geometries and architectures, 3D-printed electrodes possess unique advantage in geometrical shape, mechanical properties, surface area, especially in ion transport and charge transfer. Thus, a desirable 3D electrode with ordered porous structures can be elaborately designed by 3D printing technology for improving electrochemical capacitance and rate capability. In this work, a designed, monolithic and ordered multi-porous 3D Cu conductive skeleton was manufactured through 3D direct ink writing technique and coated with CuO nanosheet arrays by an in situ electro-oxidation treatment. Benefiting from the highly ordered multi-porous nature, the 3D-structured skeleton can effectively enlarge the surface area, enhance the penetration of electrolyte and facilitate fast electron and ion transport. As a result, the 3D-printed Cu deposited with electro-oxidation-generated CuO (3DP Cu@CuO) electrodes demonstrates an ultrahigh areal capacitance of 1.690 F cm⁻² (38.79 F cm⁻³) at a large current density of 30 mA cm⁻² (688.59 mA cm⁻³), excellent lifespan of 88.20% capacitance retention after 10,000 cycles at 30 mA cm⁻² and superior rate capability (94.31% retention, 2-30 mA cm⁻²). This design concept of 3D printing multi-porous current collector with hierarchical active materials provides a novel way to build high-performance 3D microelectrodes.