Appearance of the 4 V signal without transformation to spinel-related oxides from loose-crystalline rock-salt LiMnO2

Manganese (Mn)-based positive electrode materials have attracted significant attention because of their low-risk resources, high valence ranges, and their ability to form polymorphs. Loose-crystalline rock-salt LiMnO2 (LCRSLMO) synthesized via a mechanochemical method exhibited a capacity of ca. 190 mAh g-1 with a potential range of 5.0?2.0 V. The potential curve of LCRS-LMO after 11 charge/discharge cycles exhibited a characteristic 4 V signal, which is similar to the 4 V plateau observed in the transition from layered LiMnO2 or orthorhombic LiMnO2 to the spinel Li-Mn oxide. However, no diffraction peaks corresponding to a spinel-related structure were detected by X-ray diffraction (XRD) measurements of the bulk structure. Furthermore, in situ XRD revealed for the first time that the lattice size of LCRS-LMO approached that of the spinel-related oxide as the charge/ discharge process progressed. The local structural changes of LCRS-LMO examined by in situ X-ray absorption fine structure measurements suggest that the local structure around the manganese ions tends to be aligned toward the spinel-related lattice.

Automated summary

Research on loose-crystalline rock-salt LiMnO2 synthesized via a mechanochemical method shows high capacity and characteristic signal similar to spinel Li-Mn oxide. In-situ measurements indicate that the lithium storage process of LCRS-LMO is related to spinel-related structure changes during charge/discharge cycles.