A new lithium vanadyl diphosphate Li<inf>2</inf>VOP<inf>2</inf>O<inf>7</inf>: Synthesis and electrochemical study

A new vanadium diphosphate, Li2VOP2O7, has been synthesized by ion exchange from Na2VOP2O7, using an eutectic mixture of {0.4LiOH·H2O-0.6LiNO3} at 200 °C. It crystallizes in space group P21/c, with the lattice parameters a = 7.4674(8) Å, b = 12.442(2) Å, c = 6.2105(7) Å and β = 97.79(1)°. The crystal structure of Li2VOP2O7, refined by powder X-ray diffraction data, shows that the structure of the parent Na-phase is retained but a prominent decrease in the layer spacing is observed. Li2VOP2O7 has been tested as a cathode material for Li-ion battery. One lithium is deintercalated by charging to 4.6 V, however, on discharge only about 0.5 Li is re-intercalated. © 2007 Elsevier Masson SAS. All rights reserved.