Synthesis and morphology of metal Sn particles in SnO-P2O5 glasses and their battery anode performance

Tin-phosphate glasses with Sn metal crystals have been considered to be candidates of new anode materials for lithium and sodium ion batteries. A new route (not electro-chemical reaction) for the synthesis of Sn crystals in 72SnO·28P2O5 glass was proposed, in which aluminum nitride AlN powders were used as a reducing agent and reacted with SnO-P2O5 glass powders. Sn particles with sphere shapes were formed in the samples heat-treated for the mixture of glass and AlN powders (72SnO·28P2O5 + 48AlN) in 3%H2/Ar. The mean diameter of Sn particles was ~ 1.3 μm for the sample heat-treated at 550 °C for 3 h, and that was ~ 10 μm for the sample heat-treated at 600 °C. The formation of AlPO4 crystals besides Sn metals was detected in the samples obtained in the present reaction. It was also found that AlPO4 crystals transform into amorphous AlPO4 by a planetary ball milling. It was demonstrated that the samples with Sn particles work as anode materials for Li+ ion batteries, in which the irreversible capacity observed in the first charging process is becoming small.