Structural investigation of the Li+ ion insertion/extraction mechanism in Sn-based composite oxide glasses

Artikel i vetenskaplig tidskrift, 2001

The effect of lithium insertion for two Sn-based composite oxide glasses, Sn2BPO6 and Sn2P2O7, was examined during the first electrochemical discharge/charge cycle. Electrodes based on these glasses were analysed with micro-Raman spectroscopy at different steps during the cycle. In-situ X-ray diffraction has been used to confirm the amorphous state during the lithium insertion and extraction process. No alloy formation between Li and Sn could be discerned throughout the first cycle. It was found that when lithium enters the electrode, a reaction at the surface of the glass particles takes place resulting in Li3PO4, Li2O and SnO2 formation. The charge compensation mechanism is thought to be the reduction of Sn2+ to Sn. The formation of Li3PO4 is found to be irreversible and is as such partly responsible for the large observed capacity loss during the first cycle.