Interfacial effect investigation of lithium perchlorate-interacted oxygen-containing carbon paper

Abstract

The lithium perchlorate-interacted oxygen-containing carbon paper (LiClO4-OCP) is designed to act as electroactive supercapacitor electrode substrates for the energy storage application. The OCP is fabricated through hydrothermal activation treatment of carbon paper in H2O2 reaction medium. The OCP is composed of graphite pitches with ultra-thin graphene structure of top layer, showing the improved graphitization degree. The LiClO4-OCP with the polarized electrostatic force-induced interfacial adsorption reveals much more intensive interaction than LiClO4-CP with van der Waals force-induced interfacial adsorption, contributing to promoting interfacial charge transfer of LiClO4-OCP. LiClO4-OCP reveals more effective interface charge transfer and more feasible electrolyte diffusion than LiClO4-CP, contributing to higher electrochemical double-layer capacitance. LiClO4-OCP with oxygen-containing groups conducts reversible redox process to supply additional Faradaic capacitance. Mean response current is increased from 0.10 ∼ 1.34 mA cm-2 for LiClO4-CP to 0.19 ∼ 2.31 mA cm-2 for LiClO4-OCP at scan rates of 5∼100 mV s-1, indicating the improved electrochemical activity of LiClO4-OCP. The cyclic voltammetry-based capacitance increases from 19.91 ∼ 13.01 mF cm-2 mF g-1 for LiClO4-CP to 37.76 ∼ 23.06 mF cm-2 for LiClO4-OCP. The galvanostatic charge/discharge-based capacitance decreases from 13.84 ∼ 3.97 mF cm-2 for LiClO4-CP to 29.71 ∼ 12.92 mF cm-2 for LiClO4-OCP. Density-functional theory-based simulation calculation proves LiClO4-OCP with such a short molecular distance is allowed to occur strong electrostatic interaction which is caused by the perchlorate ion-induced polarization of oxygen-containing groups. The LiClO4-OCP has lower interfacial energy, lower band gap and higher density of states at Fermi energy level than LiClO4-CP, indicating the improved interfacial interaction and electrical conductivity of LiClO4-OCP. The experimental measurement and theoretical calculation achieve the consistent results of higher electrochemical activity of LiClO4-OCP electrode substrate to present its superior capacitance performance.