Chemical Tuning of NaSICON Surfaces for Fast-Charging Na Metal Solid-State Batteries
Solid-state batteries (SSBs) with alkali metal anodes hold great promise as energetically dense and safe alternatives to conventional Li-ion cells. Whilst, in principle, SSBs have the additional advantage of offering virtually unlimited plating current densities, fast charges have so far only been achieved through sophisticated interface engineering strategies. Here, we reveal that such interface engineering can be easily achieved by tuning the chemistry of NaSICON solid electrolytes (Na3.4Zr2Si2.4P0.6O12) and taking advantage of the thermodynamic stabilization of a Na3PO4 layer on their surface upon thermal activation. The optimized planar Na|NZSP interfaces are characterized by their exceptionally low interface resistances (down to 0.1 Ω cm2 at room temperature) and, more importantly, by their tolerance to large plating current densities (up to 10 mA cm-2) even for extended cycling periods of 30 minutes (corresponding to an areal capacity 5 mAh cm-2).