Selective Synthesis of Lithium Ion-Conductive β-LiVOPO4 Crystals via Glass-Ceramic Processing

A glass-ceramic processing is applied to a glass with the composition of 33.3Li(2)O-33.3V(2)O(5)-33.3P(2)O(5) (mol%) in order to synthesize lithium ion-conductive beta-LiVOPO4 crystals being a potential candidate for cathode materials in lithium ion batteries. It is found that three crystalline phases of alpha-LiVOPO4, Li2VPO6, and beta-LiVOPO4 are formed during the crystallization and alpha-LiVOPO4 crystals formed initially transform into beta-LiVOPO4. The glass-ceramics consisting of almost mainly beta-LiVOPO4 crystals are successfully prepared by a heat treatment at around 600 degrees C in air. The glass-ceramics with beta-LiVOPO4 crystals show the electrical conductivity of 1.7 x 10(-7) S/cm at room temperature and the activation energy of 0.38 eV in the temperature range of 25 degrees-240 degrees C. The structure and electrical properties of the precursor glass are also examined. The present study proposes that the glass-ceramic processing has an advantage for the fabrication of beta-LiVOPO4 crystals, because it is difficult to synthesize beta-LiVOPO4 crystals using a conventional powder-sintering method.