Negating Na‖Na₃Zr₂Si₂PO₁₂ interfacial resistance for dendrite-free and “Na-less” solid-state batteries

Abstract

Solid electrolytes hold promise in safely enabling high-energy metallic sodium (Na) anodes. However, the poor Na‖solid electrolyte interfacial contact can induce Na dendrite growth and limit Na utilization, plaguing the rate performance and energy density of current solid-state Na-metal batteries (SSSMBs). Herein, a simple and scalable Pb/C interlayer strategy is introduced to regulate the surface chemistry and improve Na wettability of Na₃Zr₂Si₂PO₁₂ (NZSP) solid electrolyte. The resulting NZSP exhibits a perfect Na wettability (0° contact angle) at a record-low temperature of 120 °C, a negligible room-temperature Na‖NZSP interfacial resistance of 1.5 Ω cm², along with an ultralong cycle life of over 1800 h under 0.5 mA cm^-2/0.5 mA h cm^-2 symmetric cell cycling at 55 °C. Furthermore, we unprecedentedly demonstrate <i>in situ</i> fabrication of weight-controlled Na anodes and explore the effect of the negative/positive capacity (N/P) ratio on the cyclability of SSSMBs. Both solid-state Na₃V₂(PO₄)₃ and S full cells show superior electrochemical performance at an optimal N/P ratio of 40.0. The Pb/C interlayer modification demonstrates dual functions of stabilizing the anode interface and improving Na utilization, making it a general strategy for implementing Na metal anodes in practical SSSMBs.