Pair Distribution Function study of candidate lithium cathode materials with rock-salt related structures

Lithium rich rock salt materials deliver the highest galvanometric energy density, 900 Wh/kg, of any cathode material, but are unsuitable for practical application in lithium batteries due to problems of longevity and cycling stability. The exceptional charge storage is realised through a combination of cation and oxide redox activity. Developing these materials for practical application requires an understanding of the role of cation disorder and percolated path for Li+ conduction. We have prepared metastable, highly disordered materials of the prototypical example in this family, Li2MnO3, and partially reduced materials Li2MnO3-xFx. Analysis of the PDF via neutron scattering (in conjunction with X-ray techniques) is uniquely able to resolve the contribution of local ordering domains in cathode functionality and so enable the development of next generation cathode materials.