The development of high-performance sodium-ion batteries (SIBs), as alternatives to lithium-ion batteries (LIBs), has surged in the past decade owing to the natural abundance of sodium resources [1, 2]. This is particularly important for large scale energy storage with the continuing integration of renewable energies such as wind, and solar into our powder grids [3, 4]. Current rechargeable battery technologies’ reliance on highly flammable liquid electrolytes presents major safety concerns [5]. To address these safety issues, the liquid electrolytes can be replaced by solid electrolytes to form all-solid-state batteries (ASSBs). As no liquid is used in ASSBs, their packing may be simplified resulting in smaller size and increased energy density. Importantly, the removal of highly flammable organic electrolytes allows for the safe operation of the battery over larger temperature ranges. Thus, the development of solid-state electrolytes with high ionic conductivity and structural stability is vital for the application of ASSBs.
Perovskite-type metal oxides are amongst the most promising candidates, owing to their vast chemical and structural flexibility. A new series of Nb doped A-site deficient sodium-ion perovskite-type metal oxide conductors were synthesised and characterised using high resolution synchrotron X-ray and neutron powder diffraction data as well as neutron PDF. All members of the series were found to adopt orthorhombic Pbnm space-group symmetry at room temperature. Members of the series were observed to undergo various phase transitions from orthorhombic to cubic upon heating. Detailed structural determinations for all members of the series as well as electrical conductivity measurements will be reported.
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