Stretchability enhancement of buckled polypyrrole electrodes for stretchable supercapacitors via engineering substrate surface roughness

Pre-straining the elastic substrate is a commonly used strategy to fabricate buckle-structured electrodes for stretchable supercapacitors, but suffers from limited stretchability due to the detachment issue from mismatched mechanical properties. To enhance the stretchability of buckled polypyrrole (PPy) electrode on elastic poly(dimethylsiloxane) (PDMS), a rough interface is employed between the substrate and deposited layers. The surface roughness of substrate is produced by a facile imprinting process from a template (e.g. sandpaper), and it is inherited in the successive sputter coated current collector (Au) and electropolymerized PPy layers. The produced buckled PPy electrode on PDMS with optimal roughness shows a stretchability of over 60%, much higher than 30% for that on smooth substrate. It can be explained by the generated inhomogeneous stress distribution under stretching preventing the propagation of cracks. The assembled stretchable supercapacitors with buckled PPy electrodes can retain 88% of its initial capacitance after being stretched for 1000 cycles at a high strain of 50%.