Highly Stable Anode-Free Solid-State Sodium Batteries Enabled by Electrostatic Shielding and Nitrogenated Interphase

Abstract

Anode-free Solid-state Sodium Batteries (AFSSBs) demonstrate high energy densities and low costs, but suffer from a critical challenge of severe Na dendrite growth for practical applications. Current strategies mainly focus on improving Na plating uniformity, which however show intrinsic limitations, because that Na dendrites are generally originated from the uneven Na surface in atomic level. Herein, we report a highly stable AFSSBs using Lithium azide (LiN3) as additive, by which Na dendrite growth can be primarily suppressed by the electrostatic shielding of Li+ and the in-situ formed high ionic conductive nitrogen-rich interphase. We unveil that, the Li+ from LiN3 accumulates at the tipside of Na whisker electrostatically shield Na+ aggregation, thus homogenizing Na nucleation. Meanwhile, the remaining azide-group readily forms a high ionic conductive and robust nitrogen rich interphase, thus simultaneously enhancing Na-ion transportation dynamics and the mechanical strength of the interphase. With the validity of electrostatic shielding effect with LiN3 additive, the optimized AFSSBs realized a remarkable energy density of 256.8 Wh/kg and a capacity retention of 81.6 % after 400 cycles, thus shedding new light on the development of high energy density sodium batteries.

Keywords: anode-free, solid-state, sodium dendrites, LiN3 additive, electrostatic shielding, interphase