Probing dynamic degradation and mass transport in solid-state sodium-ion batteries using operando simultaneous dual-polarity SIMS

Abstract

Operando investigation of a solid-state battery is challenging due to sample conditions, such as electrode roughness and sensitivity to the atmosphere. In this work, we present an operando technique that combines electrochemistry with the simultaneous detection of secondary ions in a Hi-5 Secondary Ion Mass Spectrometer (SIMS). Sodium metal|NASICON solid electrolyte interfaces were formed through cycling at different current densities in a 1 μm² region, where the critical current density was found to be 0.04 μA μm⁻². Electrochemical Impedance Spectroscopy (EIS) determined that a solid electrolyte interphase (SEI), resistive to sodium-ion migration, formed at each sodium metal|NASICON interface. Dynamic dual-polarity SIMS identified the SEI to be composed of oxide species that formed along the sodium mass transport columns and degraded the grain boundaries, leading to dendrite formation at the sodium metal|NASICON interfaces. This work pioneers a new diagnostic tool, propelling interfacial and solid electrolyte engineering solutions to mitigate device failure, allowing the development of next-generation solid-state batteries.