Structure of nanocrystalline alkali metal manganese oxides by the atomic pair distribution function technique

The atomic scale structures of two nanocrystalline K-Li-Mn-O-I materials obtained through Chimie Douce route in aqueous and acetone solutions have been determined using X-ray diffraction and atomic Pair Distribution Function technique. Both samples have been found to possess a layered-type structure, where the layers are made of edge-shared MnO ₆ octahedra. With the sample prepared in aqueous solution, the layers are well separated and the interlayer space is occupied by both Li and K atoms. With the sample prepared in acetone solution the Mn-O layers are not so well separated and encapsulate mostly Li atoms. This material exhibits some Li/Mn substitutional disorder as well. The new structural information has been used to explain the electrochemical behavior of the two nanocrystalline materials. Some methodological aspects of the atomic pair distribution function technique and its applicability to study the structure of crystalline and nanocrystalline materials have been discussed as well.