Templating preparation of cannular congeries of MnO2 and porous spheres of carbon and their applications to high performance asymmetric supercapacitor and lithium-sulfur battery

Abstract

Cannular congeries of MnO2 (CC-MnO2) have been fabricated via the in situ chemical reaction using carbon tubes derived from polypyrrole as reductive agent and sacrificial template. Porous spheres of carbon (PSCs) are prepared by a one-step calcination and template removal method, in which silica/chitosan spheres obtained by spray-drying process are carbonized and the SiO2 templates have been etched by mixing PTFE powder as in-situ template removal agent. It has been demonstrated the porous character is beneficial to their electrochemical performance of CC-MnO2 and PSC when they are used as electrode materials for supercapacitors and lithium-sulfur batteries. The CC-MnO2//PSC asymmetric supercapacitor exhibits a high energy density of 22.5 Wh kg-1 with a power density of 237 W kg-1 in a stable potential window of 0-1.8 V and the lithium-sulfur using PSCs as sulfur host also shows excellent cycle performance with a retention of 703 mhA h-1 after 100 cycles at 0.2 C.