Pressure‐ and Temperature‐Dependent Interface Kinetics in Na₃Zr₂Si₂PO₁₂‐Based All‐Solid‐State Na Metal Battery

Abstract

Ceramic Na superionic conductor (NASICON)‐type Na3Zr2Si2PO12 solid‐state electrolyte is one of the prime candidates for Na metal solid‐state batteries due to its high room‐temperature ionic conductivity and electrochemical stability. However, a major challenge lies in integration of NASICONs with a Na anode due to the solid‐solid nature of the interface. Herein, the ductility of Na metal is capitalized and the impact of stack pressure and temperature in improving the interfacial properties of Na|NASICON symmetric cells is investigated. At 100 MPa stack pressure and 50 °C, the voltage polarization of the cells is approximately 10 times lower than those tested at 25 °C. The improved Na+‐ion kinetics result in a higher critical current density and a stable Na cycling response over long durations. Postmortem studies confirm the presence of Na dendrites in the pores and along the grain boundary of the NASICON ceramic structure. The results demonstrate the dependence of interface kinetics on pressure and temperature in a Na3Zr2Si2PO12‐based all‐solid state Na metal battery and presents a strategy for enabling stable operation of high‐energy, solid‐state Na batteries.