transition metal layer ordering?s role in oxygen activity in na0.8li0.12ni0.22mno.66o2 as a sodium ion cathode material

Department: NanoEngineering
Research Institute Affiliation: Sustainable Power and Energy Center
Faculty Advisor(s): Ying Shirley Meng

Primary Student
Name: Hayley Sarah Hirsh
Phone: 650-380-9727
Grad Year: 2021

P2 transition metal (TM) oxide cathodes for sodium ion batteries (NIBs) are a promising material for grid storage given the high capacity, cycling stability of the material and the natural abundance of sodium (Na). In NIBs, it has been shown that P2-Na0.78Li0.12Ni0.22MnO2 (CCP_NLNMO) synthesized through a conventional co-precipitation route, has a reversible capacity of ~115 mAh/g when cycled between 2.0 and 4.5 V. The CCP_NLNMO charge compensation only utilizes the Ni2+/4+ redox and therefore has a low energy density. In this research, P2-Na0.80Li0.12Ni0.22Mn0.66O2 (MCP_NLNMO), was synthesized via a modified co-precipitation method. On the first charge this new material shows extra charge capacity of ~165 mAh/g at C/50, versus the CCP_NLNMO initial charge of ~121 mAh/g. Soft XAS of MCP_NLNMO shows that the TM oxidation state in the material does not change between 4.2 and 4.4 V but there is a change in the oxygen?s oxidation state. This implies that MCP_NLNMO has oxygen activity during the first charge but CCP_NLNMO, stoichiometrically the same material, does not. CCP_NLNMO and MCP_NLNMO have the same ratio of elements, confirmed by ICP, and are the same phase, confirmed by lab XRD. Besides morphology, the only difference is superlattice peaks in the MCP_NLNMO XRD indicative of Li-TM ordering in the TM layer which has been shown to cause oxygen activity in Na cathode materials. For the first time in NLNMO, transition metal layer ordering is shown it cause oxygen capacity, increasing the materials first charge capacity.

Industry Application Area(s)
Energy/Clean technology | Materials

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