Irreversible capacity of electrodeposited Sn thin film anode

Tin thin film anodes for lithium-ion cells were prepared by electroplating and morphology changes of the surface during alloying and de-alloying were investigated by in situ AFM to understand the origin of large irreversible capacity on Li-Sn alloy anodes. The results of cyclic voltammetry (CV) revealed that an irreversible reduction peak, which is assigned to solvent decomposition, was observed in the range 1.0-1.4 V not in the first cycle, but in the second cycle and later. AFM observation during CV revealed that surface roughening by alloying and de-alloying occurred significantly in the first and second cycles. This surface roughening destroyed existing surface film and brought about a large area of active surface, and therefore is the reason for the appearance of large irreversible capacities in the second and third cycles in constant current charge and discharge tests.