Tape Casting of NASICON-Based Separators with High Conductivity for Na All-Solid-State Batteries

Rosen, Melanie; Schwab, Christian; Mahioui, Samir; Dück, Gerald; Finsterbusch, Martin

doi:10.3390/electrochem6010005

Journal Article

FZJ-2026-00504

Tape Casting of NASICON-Based Separators with High Conductivity for Na All-Solid-State Batteries

Rosen, M.FZJ* ; Mahioui, S. ; Schwab, C.FZJ* ; Dück, G.FZJ* ; Finsterbusch, M. (Corresponding author)FZJ*

2025
MDPI Basel

Electrochem 6(1), 5 - (2025) [10.3390/electrochem6010005]

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Please use a persistent id in citations: doi:10.3390/electrochem6010005 doi:10.34734/FZJ-2026-00504

Abstract: Sodium–ion batteries are emerging as strong competition to lithium–ion batteries in certain market sections. While these cells do not use critical raw materials, they still feature a liquid electrolyte with all its inherent safety issues, like high flammability and toxicity. Alternative concepts like oxide-ceramic-based all-solid-state batteries feature the highest possible safety while still maintaining competitive electrochemical performance. However, production technologies are still in their infancy, especially for Na all-solid-state batteries, and need to be urgently developed to enable solid-state-battery technology using only abundant raw materials. In this study, the additive-free production of freestanding, undoped NaSICON separators via tape-casting is demonstrated, having an extremely high total Na-ion conductivity of up to 2.44 mS·cm−1 at room temperature. Nevertheless, a strong influence of sample thickness on phase purity as well as electrochemical performance is uncovered. Additionally, the effect of self-coating of NaSICON during high-temperature treatment was evaluated as a function of thickness. While advantageous for increasing the stability against Na-metal anodes, detrimental consequences are identified when separator thickness is reduced to industrially relevant values and mitigation measures are postulated.

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