Li / β ‐  VOPO 4: A New 4 V System for Lithium Batteries

Abstract

Lithium intercalation into ␤-VOPO 4 has been performed, both chemically and electrochemically, with X-ray diffraction characterization of the resulting phases at various levels of intercalation-deintercalation. It is shown that intercalation occurs through a first-order transition at 3.98 V vs. Li ϩ /Li 0 , which leads to a ␤-LiVOPO 4 -like structure but with lithium ordering which doubles the a and b unit cell parameters. Starting from chemically intercalated ␤-Li 0.92 VOPO 4 , the reversible process involves 0.55 electron per transition metal, i.e., 90 mAh/g, at a C/50 rate which owing to the 3.95 V potential plateau, gives an attractive specific energy of 355 Wh/kg. Fundamentally, it is shown herein that the redox energy of V 5ϩ /V 4ϩ couple in an octahedral coordination involving (V ϭ O) mϩ unit is included between those observed in oxides and in M 2 (PO 4 ) 3 compounds with (PO 4 ) 3Ϫ oxo-anions.

51V magic angle spinning NMR in VOPO4 phases

“…Both the magnitudes and relative orientation of the quadrupole and chemical shift tensors can be determined from the analysis of the complete manifolds of ssbs. 1 -3 Vanadyl phosphates, VOPO 4 , present open 2D or 3D frameworks that are suitable for lithium intercalation processes and are good candidates for new cathode materials in lithium ion rechargeable batteries. Recently, the electrochemical behavior of the different phases of VOPO 4 has been investigated.…”

“…1 -3 Vanadyl phosphates, VOPO 4 , present open 2D or 3D frameworks that are suitable for lithium intercalation processes and are good candidates for new cathode materials in lithium ion rechargeable batteries. Recently, the electrochemical behavior of the different phases of VOPO 4 has been investigated. 4 -7 These studies confirmed that VOPO 4 is promising as a cathode material with an electrochemical potential close to 4 V and a theoretical specific capacity of 165 mA h g 1 .…”

“…In particular, the spin-echo mapping technique has been shown to be a powerful tool to quantify the amounts of V IV and V V species. 9 -11 In contrast, 51 V NMR has rarely been used on these compounds; Lapina et al 12 studied the individual phases (˛I,˛I I ,ˇ) of VOPO 4 by 51 V MAS NMR.…”

“…The x-ray diffraction pattern of -VOPO 4 has been indexed with a monoclinic lattice 15 and the hypothesis found in the literature about the structure of the form proposes a layered structure similar to that of the˛forms but in which˛I-type and˛I I -type [VO] chains alternate. 16 -18 In this work, we used 51 V MAS NMR in order to characterize the structure of the˛I I -,ˇ-and -phases of VOPO 4 . The experimental quadrupole and chemical shift coupling parameters obtained were compared with literature data for the˛I I -andˇ-phases and are related to structural hypotheses for the -phase.…”

The crystal structure of δ-VOPO4 and its relationship to ω-VOPO4

“…More recently, these materials were also investigated in the field of lithium battery research [13][14][15][16][17][18][19]. Up to now, seven polymorphs of this compound have been described:  I [20],  II [20,21],  [22],  [1,23],  [1],  [24,25], and  [26,27].…”