Intermediate phase induced in situ self-reconstruction of amorphous NASICON for long-life solid-state sodium metal batteries†

Abstract

Solid-state sodium metal batteries (SSBs) have drawn significant attention as a low-cost alternative for post-lithium-ion energy storage systems. However, numerous challenges like poor grain-boundary conductivity and high interface resistance still stand in the way to realizing competitive SSBs. To address these issues, an in situ self-construction strategy of an intermediate phase in a solid-state electrolyte is proposed to regulate the ionic transfer in the grain boundary and stabilize the Na/SSE interface to alleviate dendrite growth. The intermediate phase induced amorphous NASICON enables sevenfold enhancement in grain-boundary conductivity. As a result, the room-temperature total ionic conductivity reaches up to 4.1 mS cm⁻¹. Benefiting from the kinetically stable, low-impedance and dendrite-free Na/amorphous NASICON interface with low interfacial formation energy, a high value of critical current density (1.3 mA cm⁻²) is obtained at room temperature, and a tenfold reduction in interfacial resistance is achieved before short-circuit. Stable Na plating/stripping cycles are rendered over 4000 h at 0.3 mA cm⁻² with restricted dendrite propagation. We highlight that the superior electrochemical performance is manifested in the Na|SSE|Na₃V₂(PO₄)₃ SSBs as remarkable cycling performance over 3000 cycles at 3C with a capacity retention of 92%. This work provides a widened way from the amorphous phase point of view without extra elements to address the issues of the large grain boundary and Na/SSE interfacial resistance, as well as Na dendrite deterioration of SSBs, which is expected to promote the development of long-lasting and fast-charging SSBs.