Cycling behavior of a high voltage spinel using an original three electrodes Li1-xNi0.4Mn1.6O4//LiNi0.4Mn1.6O4 symmetric cell: application to LiNi0.4Mn1.6O4 electrolyte interface degradation studies

The interface between LiNi0.4Mn1.6O4 and alkylcarbonate-based electrolytes is investigated by ab initio calculations, ICP-AES measurements and electrochemical tests. Interface degradation is known to occur by both the electrolyte oxidation and the Mnn+ and Nin+ ion dissolution. Nevertheless, EC or PC oxidation, leading to a polymeric film formation, is able to contribute to the interface stabilization. Besides Li//LiNi0.4Mn1.6O4 half-cells, Li1-xNi0.4Mn1.6O4//LiNi0.4Mn1.6O4 symmetric cells are used in order to eliminate the effects from the strong reducing nature of lithium on the electrolyte. Systematic comparisons of fading and coulombic efficiency show that the main degradation mechanism in half-cells is the electrolyte oxidation, as a consequence of the continuous precipitation of metal ion-based compounds on the lithium electrode. The symmetric cell studies indicate that redox shuttles (Mn+ <-> M(n-1)+, M=Mn or Ni) are mainly responsible for the LiNi0.4Mn1.6O4/electrolyte interface degradation despite the possible presence of a polymeric film. Symmetric cells also confirm EC superiority over other alkylcarbonates at the LiNi0.4Mn1.6O4 interface.