Electrochemical impedance study of the solid electrolyte interphase in MnSn2 based anode for Li-ion batteries

This work reports the interfacial properties of nanostructured MnSn2 as anode material for Li-ion batteries in order to explain ageing phenomena. The impedance measurements show variations of the solid electrolyte interphase (SEI) resistance during the first cycle that are interpreted from changes in thickness and/or porosity of the SEI film. These changes are mainly due to the degradation of the electrolyte at the beginning of the first discharge and to the de-alloying reaction of Li7Sn2 operating during the first part of the charge that causes strong volume variations. However, a rather stable SEI was obtained during the reformation of MnSn2 in the second part of the charge, which is peculiar to this compound. Finally, capacity fading is related to the continuous growth of the SEI during cycling.