Effect of Mn and Cu Addition on Lithiation and SEI Formation on Model Anode Electrodes

The effect of addition of Mn2+ to the electrolyte on the lithiation of a model battery anode was studied using voltammetry, electrochemical quartz crystal microbalance (EQCM), scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Cyclic voltammetry of a Au anode showed that the presence of one equivalent monolayer of Mn2+ in the electrolyte reduces the battery capacity by as much as 48%, a result which is recapitulated in SEM images of the anode surface after five cycles which show that the presence of Mn2+ blocks lithiation of the anode. AES demonstrates the presence or lack of Mn on the surface. EQCM analysis demonstrates greater initial mass gain on the anode with increasing concentration of Mn2+ in the electrolyte while MALDI-TOF MS shows no observable differences in the solid electrolyte interface (SEI) between the electrolyte with or without Mn2+. The addition of Cu2+ to the electrolyte exhibits an effect similar to Mn2+ addition. (C) 2014 The Electrochemical Society. All rights reserved.