Intermediate Phase In-situ Self-reconstruction of Amorphous NASICON for Long-life Solid-state Sodium Metal Batteries

Solid-state sodium metal batteries (SSBs) have drawn significant attention as a low-cost alternative for post-lithium-ion energy storage system. However, numerous challenges like poor grain-boundary conductivity and high interface resistance still stand in the way to realize competitive SSBs. To address these issues, an in-situ self-construction strategy of intermediate phase in solid-state electrolyte is proposed to regulate the ionic transfer in 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 with remarkable cycling performance over 3000 cycles at 3 C with capacity retention of 92%. This work provides a widen way from an amorphous view without extra element 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 SSBs that work in long-lasting and fast-charging field.