High‐Entropy Solid‐State Na‐Ion Conductor for Stable Sodium‐Metal Batteries

Abstract

Solid-state sodium-metal batteries (SSBs) hold great promise for their merits in low-cost, high energy density, and safety. However, developing solid electrolyte (SE) materials for SSBs with high performance is still a great challenge. In this study, high-entropy Na 4.9 Sm 0.3 Y 0.2 Gd 0.2 La 0.1 Al 0.1 Zr 0.1 Si 4 O 12 was synthesized at comparatively low sintering temperature of 950 °C with high room-temperature ionic conductivity of 6.7 × 10 À 4 S cm À 1 and a low activation energy of 0.22 eV. More importantly, the Na symmetric cells using high-entropy SE show a high critical current density of 0.6 mA cm À 2 , outstanding rate performance with fairly flat potential profiles at 0.5 mA cm À 2 and steady cycling over 700 h under 0.1 mA cm À 2 . Solid-state Na 3 V 2 (PO 4 ) 3 j j high-entropy SE j j Na batteries are further assembled manifesting a desirable cycling stability with almost no capacity decay after 600 cycles and high Columbic efficiency over 99.9 %. The findings present opportunities for the design of high-entropy Na-ion conductors toward the development of SSBs.

High Entropy Materials for Reversible Electrochemical Energy Storage Systems

“…Very recently, our group successfully synthesized hexagonal-prismatic high-entropy Na 4.9 Sm 0.3 Y 0.2 Gd 0.2 La 0.1 Al 0.1 Zr 0.1 Si 4 O 12 at a relatively low sintering temperature of 950 °C. [100] The high room-temperature ionic conductivity of 6.7×10 À 4 S cm À 1 and low activation energy of 0.22 eV indicate the potential of this material as a solid electrolyte. Additionally, the use of this highentropy solid electrolyte (SE) in Na symmetric cells shows promising results.…”

“…(d) Long-term cycle performance at 0.5 C-rate of NVP j HE-SYGLAZ j Na cell. Reproduced from ref [100]. Copyright (2023), with permission from Wiley-VCH.…”