Electrochemical performance and structural change during charge–discharge reaction of SnO–P2O5 glassy electrodes in rechargeable lithium batteries

Abstract Using melt quenching, SnO–P 2 O 5 glasses were synthesized, and then characterized as negative electrode materials for lithium secondary batteries. The electrochemical cell Li/the 67SnO·33P 2 O 5 (mol%) glass maintained reversible capacity of about 400 mAh g −1 for 20 cycles. The cell’s cycle performance was better than those of cells using Sn-based crystals such as Sn, SnO, and SnO 2 as working electrodes. The local structure of the 67SnO·33P 2 O 5 glass after lithium insertion and extraction was analyzed. 7 Li MAS-NMR measurements revealed that the Li–Sn alloy was formed during the first lithium insertion to the glass and that alloying–dealloying of the Li–Sn domain occurred during charge–discharge cycling. The glassy matrix surrounding the alloy was investigated using 31 P MAS-NMR. The P 2 O 7 4 - group might be changed to PO 4 3 - and P 2 O 6 4 - groups by the first lithium insertion to the glass. The formed phosphate groups remained after the consecutive lithium extraction process. An all-solid-state cell with the 67SnO·33P 2 O 5 glass exhibited the discharge capacity of 750 mAh g −1 at the first cycle, which is greater than that of a cell with the 50SnO·50B 2 O 3 glass.