Carbon embedded α-MnO2@graphene nanosheet composite: A bifunctional catalyst for high performance lithium oxygen batteries

摘要

Carbon is essential for the oxygen electrode in non-aqueous lithium-oxygen (Li-O2) batteries for improving the electron conductivity of the electrode. However, it also leads to some side reactions when exposed to the Li2O2 product and the electrolyte, limiting the round-trip efficiency and coulombic efficiency of the batteries. In this paper, a carbon-embedded α-MnO2@graphene nanosheet (α-MnO2@GN) composite is introduced as a highly effective catalyst for Li-O2 batteries. X-ray photoelectron spectroscopy (XPS) analysis showed that the Li2CO3 by-product was significantly reduced due to the isolation of carbon with the electrolyte and Li2O2. Thus, the composite could deliver a reversible capacity of ～2413 mAh g-1 based on the total mass of the composite with an extremely high discharge voltage of ～2.92 V (only 40 mV lower than the thermodynamic potential) and a low charge voltage of ～3.72 V at a current density of 50 mA g-1. The round-trip efficiency is calculated to be ～78% with a coulombic efficiency of almost 100%. ? 2014 the Partner Organisations.