Flexible, long cycle-life micro-supercapacitor with polypyrrole@Ag-wall interdigitated electrodes fabricated by micro-3D printing and electrochemical polymerization

Conductive polymers (CPs) have been widely used as electrode materials in supercapacitors because of their facile synthesis, low cost, and high capacitance. However, their practical application in micro-supercapacitors (MSCs) has been hindered by the manufacturing complexity and dimensional limits due to their low processability, and the very poor cycle-life due to its volumetric change in the charge-discharge process. Here, we present CPs-based MSCs with a unique structure of polypyrrole (PPy)@Ag-wall interdigitated electrodes fabricated by combing micro-3D printing Ag-wall and electrochemical polymerization of PPy. Benefiting from the unique structure and effective interface of PPy@Ag-wall interdigitated electrodes, these all-solid-state MSCs (S < 0.25 cm2) offer an area capacitance (C/A) up to 90 mF cm−2, coupled with a long cycle-life (capacitance remains 109 % after 10,000 cycles), great flexibility (capacitance remains 95 % after bending for 1000 times), and a very low interfacial resistance (2.88 Ω). In conclusion, this unique design of the PPy@Ag-wall interdigitated electrode structure not only achieves the formation of the arbitrary structure of CPs, but also greatly improves its cycle-life, promoting the CPs-based MSCs for the future miniature energy storage device.