Kinetics and Pore Formation of the Sodium Metal Anode on NASICON-Type Na_(3.4)Zr_2Si_(2.4)P_(0.6)O_(12) for Sodium Solid-State Batteries

摘要

In recent years, many efforts have been made to introduce reversible alkalimetal anodes using solid electrolytes in order to increase the energy densityof next-generation batteries. In this respect, Na_(3.4)Zr_2Si_(2.4)P_(0.6)O_(12) is a promisingsolid electrolyte for solid-state sodium batteries, due to its high ionic conductivityand apparent stability versus sodium metal. The formation of a kineticallystable interphase in contact with sodium metal is revealed by time-resolvedimpedance analysis, in situ X-ray photoelectron spectroscopy, and transmissionelectron microscopy. Based on pressure- and temperature-dependentimpedance analyses, it is concluded that the Na|Na_(3.4)Zr_2Si_(2.4)P_(0.6)O_(12) interfacekinetics is dominated by current constriction rather than by charge transfer.Cross-sections of the interface after anodic dissolution at various mechanicalloads visualize the formed pore structure due to the accumulation of vacanciesnear the interface. The temporal evolution of the pore morphology after anodicdissolution is monitored by time-resolved impedance analysis. Equilibration ofthe interface is observed even under extremely low external mechanical load,which is attributed to fast vacancy diffusion in sodium metal, while equilibrationis faster and mainly caused by creep at increased external load. The presentedinformation provides useful insights into a more profound evaluationof the sodium metal anode in solid-state batteries.