AUTHOR=Dück Gerald , Naqash Sahir , Finsterbusch Martin , Breuer Uwe , Guillon Olivier , Fattakhova-Rohlfing Dina 

TITLE=Co-Sintering Study of Na0.67[Ni0.1Fe0.1Mn0.8]O2 and NaSICON Electrolyte–Paving the way to High Energy Density All-Solid-State Batteries

JOURNAL=Frontiers in Energy Research

VOLUME=9

YEAR=2021

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2021.689416

DOI=10.3389/fenrg.2021.689416

ISSN=2296-598X

ABSTRACT=<p>Sodium is a promising candidate for stationary storage applications, especially when the demand for lithium-ion batteries increases due to electromobility applications. Even though its energy density is lower, Na-ion technology is estimated to lead to a cost reduction of 30% compared to Li-ion technology. To improve safety as well as energy density, Na-based all-solid-state-batteries featuring solid electrolytes such as beta-alumina and sodium superionic conductors and cathode materials such as Na<sub>3</sub>V<sub>2</sub>(PO4)<sub>3</sub> and Na<sub>x</sub>CoO<sub>2</sub> have been developed over the past years. However, the biggest challenge are mixed cathodes with highly conductive interfaces, especially when co-sintering the materials. For example, a promising sodium superionic conductor type Na<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub> electrolyte sinters at 1,250°C, whereas the corresponding Na<sub>3</sub>V<sub>2</sub>PO<sub>12</sub> cathode decomposes at temperatures higher than 900°C, posing a bottleneck. Thus in this paper, we synthesized Na<sub>0.62</sub> [Ni<sub>0.10</sub>Fe<sub>0.10</sub>Mn<sub>0.80</sub>]O<sub>2</sub> as cathode material for all-solid-state sodium-ion batteries <italic>via</italic> a relatively cheap and easy solution-assisted solid state reaction processing route. The thermal investigations of the pure cathode material found no degradation up to 1,260°C, making it a perfect match for Na<sub>3.4</sub>Zr<sub>2</sub>Si<sub>2.4</sub>P<sub>0.6</sub>O<sub>12</sub> electrolyte. In our aim to produce a co-sintered mixed cathode, electron microscopy investigation showed a highly dense microstructure and the elemental mapping performed <italic>via</italic> energy dispersive X-ray spectroscopy and secondary ion mass spectrometry confirm that Na<sub>3.4</sub>Zr<sub>2</sub>Si<sub>2.4</sub>P<sub>0.6</sub>O<sub>12</sub> and Na<sub>0.62</sub> [Ni<sub>0.10</sub>Fe<sub>0.10</sub>Mn<sub>0.80</sub>]O<sub>2</sub> do not react during sintering. However, the active cathode material forms a sodium rich and a sodium deficient phase which needs further investigation to understand the origin and its impact on the electrochemical performance.</p>