Spiro-OMeTAD as redox mediator and singlet oxygen scavenger in lithium-oxygen batteries

Abstract

Lithium-oxygen batteries (LOBs) are considered one of the new alternatives to lithium-ion batteries mainly due to its high energy density. Several strategies are pursued in order to avoid parasitic reactions that fade the battery capacity. In this work, it was carried out a photochemical and electrochemical characterization of Spiro-OMeTAD working as a redox mediator (RM) in the LOBs. By using the Time Resolved Phosphorescence Detection (TRPD) technique together with Rose Bengal, we demonstrate that RM can deactivate the singlet oxygen produced in the cell, decreasing its performance. A concentration of 5 mM Spiro-OMeTAD in the electrolyte avoids solubility problems, maximizes its catalytic effects during the charge, and is still enough to act as a singlet oxygen scavenger. Finally, lithium nitrate was added to the electrolyte to passivate the metallic lithium anode with the aim to prevent the RM decomposition and the increase of LOBs performance.