Sodium Ion

Fundamental Advances In Solid-State Electrolyte Engineering DESIGN OF SODIUM SUPERIONIC CONDUCTORS

DESIGN PRINCIPLES IN ANODEFREE APPROACH

Wang et al. 1 establish face-sharing high-coordination sites CN 5 as a critical structural feature for fast sodium-ion conduction, unveiling a chloride-based family of sodium superionic conductors NaxMyCl6) with the high ionic conductivity 1.4 mS/cm at room temperature).

Deysher et al. 2 achieve a breakthrough by enabling stable cycling of an anode-free sodium all-solid-state battery over 400 cycles at a Coulombic efficiency of 99.96% under 10 MPa stack pressure and 40°C.

Advanced computational screening identified 35 new structural candidates, including NaLa1.67Cl6, whose face-sharing octahedral pathways yielded low activation barriers 0.13 eV. This discovery surpasses the conductivity of previous materials like Na2ZrCl6 0.02 mS/cm) and also consolidates design principles that reconcile large bottleneck sizes with low diffusion barriers.

The use of a sodium borohydride Na4B10H10B12H12) solid electrolyte, with a dense morphology formed through cold pressing, allowed for cycling at current densities exceeding 6 mA/cm2. The study demonstrated uniform sodium plating and stripping with an areal capacity of 1 mAh/cm2, achieved via an innovative aluminium pellet current collector that improved solid-solid interfacial contact. This collector reduced interfacial resistance and enabled the deposition of dense sodium layers, a key requirement for mitigating dendritic growth and maintaining cell integrity.

Source: 1 Wang, S., Fu, J., Liu, Y. et al. Design principles for sodium superionic conductors. Nat Commun 14, 7615 2023 2 Deysher, G., Oh, J.A.S., Chen, YT. et al. Design principles for enabling an anode-free sodium all-solid-state battery. Nat Energy 9, 11611172 2024.

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