Engineering interfaces to facilitate charge transport pathways in electrospun scaffolds for high-performance, flexible supercapacitors

Abstract

Understanding and engineering the interface of a polymeric matrix with the ionic conductor offers important insights into the electrochemical charge polarization performance of flexible solid-state supercapacitors. These aspects are captured herewith utilizing chemically identical yet morphologically and interfacially different and distinct non-woven, electrospun polymeric membranes as scaffolds. Three distinct variations achieved through electrospinning namely, bilayered (PU/Ge) and core-shell geometries (PU@Ge and Ge@PU) with polyurethane (PU) and gelatin (Ge) are utilized in both conditions as polymeric electrolyte membranes for flexible supercapacitors. Equally important is the unique graphenic nanoplatelets (GNPs), fabricated through a single-step, template-driven approach, providing synergistic electrode/electrolyte interfaces. We unravel distinct changes in charge transport mechanism brought out by the interplay between surface chemistry and morphology of the electrospun scaffolds. The all-solid-state symmetric supercapacitor devices assembled with GNP@CC electrodes and PU/Ge, PU@Ge or Ge@PU polymeric membrane electrolyte of 1 M H3PO4 or EMIMBF4 are studied.Accordingly, the charge transport is protic and aprotic observed to switch from interfacial driven in the case of PU@Ge with H3PO4 to distinct phase separated ion transport channels in the case of PU/Ge with EMIMBF4. Thereby, a range of energy density (1.03–21.94 Wh kg−1), power density (0.049–99.97 kW kg−1) and scan rate operability (5–10,000 mV s−1) are demonstrated in such devices without any compromise on the cyclability. This study establishes rational design principles for tailoring the ion transport mechanism in a variety of matrices and thereby opens transformative possibilities for realizing high performance energy storage devices.