Powder neutron diffraction study of LiMnVO4

Abstract

Powder neutron diffraction data have been recorded for LiMnVO,. The crystal structure was determined by Rietveld analysis. The Rietveld refinement confirmed that the compound adopts an orthorhombic spinel-related structure. The framework structure of the compound is comprised of nearly regular, edge-sharing octahedra of MnO,. The lithium and vanadium atoms in LiMnVO, occupy, as partially mixed species, the two kinds of tetrahedral interstitial sites constructed by cubic close-packed oxygen atom arrays; this structural feature is quite similar to those of CrV0, and LiCuVO,. The magnetic susceptibility and the metal-oxygen bond distances estimated from the refined structure of LiMnVO, clearly indicate that the valence states for the transition-metal ions are divalent for manganese ions and pentavalent for vanadium ions.

Synthesis, Crystal Structure, Magnetic Properties, and Electronic Structure of the New Ternary Vanadate CuMnVO4

“…The extinction conditions observed for CuMnVO 4 agree with the Cmcm space group already used for the refinement of the homologous compound LiMnVO 4 . The starting atomic positions were those reported for LiMnVO 4 .…”

“…As shown in Table , the displacement of the Cu + ion from the tetrahedron center is twice as large as the one for the V 5+ ion. Such disproportionate cation displacements have also been found for LiMnVO 4 , CuCdVO 4 , and [Li 1/3 Cd 1/3 □ 1/ 3 ]CdVO 4 . , The reason that the shifts of the Cu + and Li + ions are large while the V 5+ ion remains close to the tetrahedron center in these compounds is discussed later (see section 5.1).

2 Perspective view of the CuVO 6 dimer of CuMnVO 4 .

…”

“…Several olivine-type compounds were successfully tested as positive electrodes (e.g., LiFePO 4 , , LiMnPO 4 , and LiCoPO 4 ). The vanadate compounds LiMVO 4 crystallize with different structural types, i.e., the Na 2 CrO 4 -type structure for LiMnVO 4 5 and the spinel-type structure for LiCoVO 4 , LiNiVO 4 , and LiCuVO 4 . , LiMnVO 4 is not a good positive electrode for lithium batteries, while, as negative electrodes, the LiMVO 4 (M = Co, Ni, Cd, Zn) series possesses a high capacity at low voltage and delivers a lower output voltage than carbon-based batteries . Compounds from the de-lithiated series, MVO 4 (M = In, Cr, Fe, Al, Y), were tested as negative electrodes, and FeVO 4 and InVO 4 were found to display a reversible capacity as high as 900 mAh g -1 …”

“…Only a few lithium vanadate compounds with the Na 2 CrO 4 -type structure are observed, i.e., LiMgVO 4 , LiMnVO 4 , LiCdVO 4 , and Li 0.9 (In 0.6 Li 0.3 )VO 4 . ,− The fact that the Na 2 CrO 4 -type structures are not as numerous as the olivine-type structures can be attributed to the strong strain associated with the short distance between V 5+ and Li + which results from the edge-sharing between the LiO 4 and VO 4 tetrahedra. One might speculate that substituting copper or sodium for the lithium in LiMnVO 4 may result in retention of that same structure, as found in NaCdVO 4 and CuCdVO 4 . , Thus, we have attempted to synthesize the homologous compounds NaMnVO 4 and CuMnVO 4 .…”

Vanadium‐Catalysed Aerobic Cleavage of C−C Bonds in Substituted Cyclohexanones To Afford Carboxylic Acids: Two Model Complexes with Tetrahedral Geometry around Vanadium(V)

“…With large metal cations such as Ba 2ϩ , the structures adopted by dinegative metavanadates, MV 2 O 6 , contains chains of vertex-shared VO 4 tetrahedra. [31,32] This structural motif is typically found in orthovanadates such as LiMnVO 4 [33] and LnVO 4 . [34] The [V 4 O 12 ] 4Ϫ ion has a cyclic tetrametaphosphate-like structure with an Ot-V-Ot angle of only 102.3(1)°, [35] the three others being 111°, while [V 5 O 14 ] 3Ϫ is pentanuclear with OϪVϪO angles ranging from 107.6(4) to 112.7(3)°.…”