Potassium-assisted carbonization of chlorobenzene in Ar/H2 to prepare porous carbon with low oxygen content for high withstanding voltage EDLCs

Abstract

Low energy density is a fatal disadvantage of electric double-layer capacitor (EDLC). The improvement of the operation voltage of EDLCs is a more effective method to increase the energy density of EDLCs. When the operation voltage of EDLCs is higher than 2.7 V, the oxygen-containing functional groups on the surface of electrode materials (porous carbon) will decompose or chemically react with the electrolyte, causing significant deterioration of EDLC performance. In this paper, porous carbon with low oxygen content is prepared by using the potassium-assisted carbonization of chlorobenzene in Ar/H2 mixed gas to improve withstanding voltage characteristic of porous carbon. By constructing a relatively closed and stable pyrolysis environment (employing the nickel crucible with a lid), using the carbonaceous precursor without oxygen atoms (chlorobenzene) and selecting reasonable carbonization operation atmosphere (Ar/H2), the oxygen content of the as-prepared porous carbon (PC-KC-1000) is only 4.02 wt%. When the PC-KC-1000 sample is used as the electrode material of EDLCs, the operation voltage of EDLCs in the TEABF4/PC and EMIMBF4 electrolytes is respectively 3.3 and 3.5 V, and the maximum energy density is respectively 53.5 and 64.4 Wh kg−1. This strategy provides a new idea for the preparation of porous carbon with low oxygen content.