Revealing the Structural Stability and Na-Ion Mobility of 3D Superionic Conductor Na₃SbS₄ at Extremely Low Temperatures

Abstract

All-solid-state batteries that employ superionic solid conductor potentially enable the broadening of battery operation in harsh environments, such as under subzero temperatures and even lower. The solid electrolyte as the key component requires structural stability, high-efficiency of ion transportation channels, and low activation energy to maintain the fast-ionic conduction against temperature drop. Herein, we use 3D superionic conductor Na 3 SbS 4 as a model to investigate the structure and conductive mechanism at extremely low temperature. Cryogenic in situ neutron and X-ray diffractions reveal that Na 3 SbS 4 maintains a stable tetragonal crystal structure and the anisotropic lattice contraction upon cooling. The dimensions of the S-gate (represented by the S−S pair length) that Na ions hop through in the 3D transportation network is found to maintain open sizes in the xy-plane, contributing to the low activation energy and impressive ionic conductivity. The Na-ion transportation network is demonstrated to be directionally accessible at the extremely low temperature, which reveals the ion conductive mechanism at broadened temperature range in the view of structure. These findings provide valuable guidance in the search for materials as promising solid electrolyte in solidstate batteries to fulfill harsh environmental needs.

Synthesis and Properties of NaSICON‐type LATP and LAGP Solid Electrolytes

“…Ma et al employed aqueous-based sol-gelm ethod to prepare large batch LATP (Li 1.5 Al 0.5 Ti 1.5 (PO 4 ) 3 )s olid electrolytes (up to 1kg) with high purity,g reat ionic conductivity (6.9 10 À4 Scm À1 ), and high density (95 %). Kotobuki and Koishic ompared the LATP (Li 1.5 Al 0.5 Ti 1.5 (PO 4 ) 3 )s olid electrolytes by using Al(NO 3 ) 3 and Al(C 2 H 7 O) 3 (both water soluble) as Al sources, and found that AlPO 4 impurity was observed only in the sample produced from Al(NO 3 ) 3 and not from Al(C 2 H 7 O) 3 because of lower solubility in water. [72,73] To obtain pure phase and high ion conduction, these synthetic parameters (precursors, solvents, and temperatures) need to be well controlled.…”

“…[72,73] To obtain pure phase and high ion conduction, these synthetic parameters (precursors, solvents, and temperatures) need to be well controlled. Kotobuki and Koishic ompared the LATP (Li 1.5 Al 0.5 Ti 1.5 (PO 4 ) 3 )s olid electrolytes by using Al(NO 3 ) 3 and Al(C 2 H 7 O) 3 (both water soluble) as Al sources, and found that AlPO 4 impurity was observed only in the sample produced from Al(NO 3 ) 3 and not from Al(C 2 H 7 O) 3 because of lower solubility in water. [72] JimØneze tal.…”

“…In the solid-state synthesis of LAGP solid electrolytes, different phosphorous sources (NH 4 H 2 PO 4 ,H 3 PO 4 , P 2 O 5 ,H 3 PO 4 ,a nd Al(PO 3 ) 3 )w ere employed and compared. In the sol-gel method, different Al sources (Al(NO 3 ) 3 and Al(C 2 H 7 O) 3 )w ereu sed to comparet he obtained LATP (x = 0.5) samples. Through the melt-quenching method, Morimoto et al added an excess amount of Li 2 Op recursor to synthesize the LAGP glass ceramic and found that excess Li 2 Ow as beneficial for higheri onic conductivity.…”

“…For all-solid-state batteries, solide lectrolytes bring several advantages, [1][2][3][4][5][6] such as enhanced safety,i ncreased energy density,s olid device integration, and packaging;t hese expand the operation temperature range and potentially improve cycling stabilitya nd lifetime. For all-solid-state batteries, solide lectrolytes bring several advantages, [1][2][3][4][5][6] such as enhanced safety,i ncreased energy density,s olid device integration, and packaging;t hese expand the operation temperature range and potentially improve cycling stabilitya nd lifetime.…”

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Inorganic solid electrolytes, in comparison with their liquid counterparts, have more potential in varioust ypes of batteries due to their dual roles of ion transportation and separation. For all-solid-state batteries, solide lectrolytes bring several advantages, [1][2][3][4][5][6] such as enhanced safety,i ncreased energy density,s olid device integration, and packaging;t hese expand the operation temperature range and potentially improve cycling stabilitya nd lifetime. Moreover,i norganic solid electrolytes are also beneficial for lithium-ion batteries and lithium-air batteries, in which they functiona se ither surface modification layers or lithium-ion conductors.

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