High Pressure Structural Research Of LiMVO₄（M=Cu, Ni, Mn） Type Lithium Ion Battery Materials

In modern times, solution of the energy shortage problem need to been workedout in hurry. Because of that, the development of lithium-ion batteries have also gotwidely attention. In the lithium ion cathode performance comparison, the negativeselection of carbon material technical standard both in theory and practicalapplications are already very mature, and the cathode material choice also needgreatly improvement. Recently, GT-K.Fey et al first synthesized by inverse spinelstructure of LiNiVO₄, the Li+intercalation and deintercalation process can reach4.8V,create a5V lithium ion battery cathode material of precedent. Since then has a spinelstructure of a class of cathode materials for lithium ion batteries into the scientificresearcher of vision. This paper selects three representative hotspot poly anion lithiumion battery cathode material LiMVO₄（M=Cu, Ni, Mn）. The ternary cuprate oxidematerial having an inverse spinel structure, but each has different structure symmetry.Firstly, a widely reported material LiCuVO₄。It is not only just5V cathode material,but also due to its orthorhombic inverse spinel structure in Cu-O-Cu special bondingproperties as well as the unit cell structure information, which has been the attentionof magnetism. We also selected the LiCuVO₄at ambient with orthorhombic inversespinel structure of the sample, and carries out the in situ high pressure Ramanspectroscopy experiment, found in the20GPa Raman peak partially disappeared, andwith the emergence of new peak. And the shift of peak position are also varyingdegrees of distortion. We can conclude that the occurrence of the structure phasetransition. Synchrotron radiation XRD research shows that20GPa occur structuralphase transition, is from the atmospheric orthorhombic phase transition forhigh-pressure monoclinic phase. At the same time we discovered that the LiCuVO₄has Jahn-Teller effect, the Cu ion in the CuO6octahedron synergistic effects inducedby. But by the increasing of pressure, distortion of the CuO6octahedron incline to normal octahedron, so we think, pressure can reduce the Jahn-Teller effect. Secondly,we study the most extensive and most representative LiNiVO₄by in situ Ramanspectroscopy studies, found in the position of20GPa Raman peak appeared distortion,there may be a structural phase transition. Then the samples were studied bysynchrotron radiation XRD, confirmed that the Raman spectrum of structural phasetransition of information. The use of XRD pattern we predict the structure phasetransition is from the ambient cubic phase transform to the high-pressureorthorhombic phase. Another spinel type Cathode material which has been paid closeattention is LiMnVO₄. On the basis of the in situ high pressure Raman spectroscopyexperiments and synchrotron radiation experiments, found in the high pressure alsooccurred under the structural phase transition, through the XRD refinement, we getthe rule of phase transition: orthorhombic Na₂CrO₄tpye Phase-â… â†'Cubic spinel tpyePhase-â…¡â†'Phase-â…¢â†'Phase-â…£. Among these three materials, the first two hasperformed a reversible phase transition, only LiMnVO₄can get a high pressure phasefrom decompression.