Sc/Mg Co‐doping in Na3Zr2Si2PO12 solid‐state electrolytes enables outstanding performance of sodium metal batteries

Abstract

All solid-state sodium metal batteries offer a transformative opportunity for more sustainable energy storage, with the potential to significantly improve both energy density and safety compared to conventional sodium-ion batteries. However, their practical application is hindered by challenges such as dendrite formation and limited ion conductivity. In this study, a novel strategy is proposed in which Sc3+ and Mg2+ dopants are directly introduced into the Na3Zr2Si2PO12 solid-state electrolyte (NZSP SSE) to optimize composition and regulate interfacial chemistry. The resulting co-doped electrolyte, Na3.7Zr1.45Sc0.4Mg0.15Si2PO12 (NSZSP-0.15Mg), exhibits a significantly enhanced ionic conductivity of 1.3 mS cm−1 at room temperature and improved interfacial compatibility. Moreover, symmetric Na//NSZSP-0.15Mg//Na cells demonstrate stable Na stripping/plating for over 400 h (0.5 mA cm−2, 0.5 mAh cm−2), attributed to the formation of a dynamically stable ScPO4/Mg3(PO4)2-rich interphase layer at the Na metal/SSE interface. Furthermore, Na//NSZSP-0.15Mg//Na3V2(PO4)3 full cell batteries exhibit excellent rate capability and long-term cycling stability, maintaining 75 mAh g−1 over 3000 cycles at 2 C at room temperature. This work presents a robust approach for enabling practical solid-state sodium metal batteries with high conductivity, enhanced interfacial stability, high energy density, and long-term cyclability, advancing the development of next-generation SSEs for high-performance sodium metal batteries. © 2025 The Author(s). Advanced Science published by Wiley-VCH GmbH. Open Access CC BY 4.0.