Reaction Mechanism of a Ag36.4Sb15.6Sn48 Nanocomposite Electrode for Advanced Li-Ion Batteries

The phase transformations of an Ag 3 6 . 4 Sb 1 5 . 6 Sn 4 8 nanocomposite electrode, Ag 3 Sn/Sn/SnSb, were investigated during electrochemical lithium insertion/extraction. The high performance gives 410 mAh/g for 300 cycles. Electrodes were prepared at selected voltage points in the discharge-charge curves and high-energy synchrotron X-ray data was collected in order to study the reaction mechanism in detail. Both Ag 3 Sn and SbSn insert Li stepwise to form compounds with the partial compositions Ag 2 - x Li 1 + x Sn (0 ≤ x ≤ 1) and Li 2 + x Sn 1 - x Sb (x ≤ 1). At lower voltages, Li 7 Sn 2 , Li 2 2 Sn 5 , AgLi, and Ag 5 Li 8 could be observed. The intermetallic compounds before and after lithiation have a strong crystallographic relation.