Preparation and Performance Analysis of High Performance Cathode Material Graphene-Mesoporous Carbon Composites for Lithium-Ion Capacitor

Abstract

ObjectivesThe lithium-ion capacitor (LIC) composite cathode materials with both high mass activity and high volume activity were designed.MethodsBy scanning electron microscope, transmission electron microscope, Kanta fully automatic specific surface and pore size analyzer, and four-probe tester, the micromorphology, stacking mode, contact mode and interface characteristics between particles were analyzed for the impact of conductivity and electrical properties of composite electrodes.ResultsMesoporous activated carbon (MC) and monodisperse graphene/single-walled carbon nanotube hybrid (GNH) were mixed, followed by compressing tightly to prepare the lithium-ion capacitor cathode material. GNH were uniformly wrapped around the surface of MC particles with face-to-face connection, which increases the contact area. Then, the even 3D conductive network constructed by GNH among the individual MC particles provided high electrical conductivity and accelerated electron conduction. In addition, GNH were located at the high ion concentration side due to their exohedral surface structure. Meanwhile, a contact potential difference effect existed between GNH (the easy conductive one) and MC (the poor conductive one). This produced rapid ion and electron dual transport channels at the interface between GNH and MC, and boosted ion diffusion in the porous structure inside MC particles. It will help avoid the loss of capacity from slow ion diffusion at higher current densities.ConclusionsThe addition of 5% GNH brings about outstanding rate performance, and higher mass and volumetric energy density, but does not reduce the packing density.

Keywords

• electrochemical energy storage
• mesoporous activated carbon
• graphene
• lithium-ion capacitor
• contact potential difference