NMR under rotation at the magic angle (NMR MAS) has established itself as a method of choice for the study of materials. Not only does it allow fine characterization of atomic structures but, in the case of paramagnetic compounds, it also provides valuable information on bond geometry, spin density and particle shapes. De by the complexity of the interactions involved, lParamagnetic NMR methods are, however, less established for quadrupole nuclei, present in many materials.
The work carried out at the Infranalytics center in Lyon for NMR and reported in the Journal of Magnetic Resonance (doi 10.1016/j.jmr.2022.107235) push the limits of paramagnetic MAS NMR for the study of paramagnetic materials of high capacity sodium-ion batteries. The structure of the studied system, the NaMnO2 without post-synthesis modification, is a mixture of different polymorphs with a high level of structural disorder. Using tailor-made paramagnetic NMR techniques, the authors were able to extract the parameters of chemical shifts and quadrupole interactions of sodium nuclei and thus quantify the phases and complex stacking faults of the material.
The advances presented in this report thus open up new possibilities for the NMR study of quadrupole nuclei in complex paramagnetic samples.