Unveiling the Kinetics of Ion Transport in 2D Potassium Niobate by Raman Spectroscopy

The development of advanced solid-state electrolytes is crucial for improving the performance of energy storage devices. Despite various research focusing on ionic conductivity and mobility, there is a critical gap in understanding the kinetic mechanisms of ion transport, especially at the nanoscale. This study analyzes the ion transport kinetics in 2D layered potassium niobate (K₄Nb₆O₁₇), a promising solid-state electrolyte, using Raman spectroscopy. A correlation between interlayer Nb─O bonds in two types of channels and Raman peaks is established. By monitoring changes in Nb─O bond vibrations within the nanochannels of K₄Nb₆O₁₇, it is revealed that alkali ions such as Na⁺ and Li⁺ follow pseudo-first-order transport kinetics. This kinetics model identifies distinct differences in the transport rates and activation energies between two types of nanochannels. Na⁺ and Li⁺ exhibit faster transport in type I channels due to lower energy barriers compared to type II channels. Additionally, the spatial distribution analysis reveals anisotropic ion transport in K₄Nb₆O₁₇, facilitating the tracking of ion locations and transport pathways within the material. This work introduces a kinetic model for real-time tracking of ion transport quantitatively in 2D materials, enhancing the understanding of ion transport kinetics in solid-state electrolytes.