Sodium-ion battery researchers find defects actually slow ion movement
Scientists studying sodium-ion conductors discovered an unexpected trap: adding defects to widen ion pathways paradoxically slows down ion flow. The finding, published in Sustainable Energy & Fuels, challenges conventional battery design wisdom and could reshape how researchers engineer faster sodium-ion batteries for cheaper energy storage.
Originaltitel: Na-ion dynamics in the solid solution Na<sub><em>x</em></sub>Ca<sub>1−<em>x</em></sub>Cr<sub>2</sub>O<sub>4</sub> studied by muon spin rotation and neutron diffraction
<p>In this work we present a systematic set of measurements carried out by muon spin rotation/relaxation (mu+SR) and neutron powder diffraction (NPD) on the solid solution NaxCa1-xCr2O4. This study investigates Na-ion dynamics in the quasi-1D (Q1D) diffusion channels created by the honeycomb-like arrangement of CrO6 octahedra, in the presence of defects introduced by Ca substitution. With increasing Ca content, the size of the diffusion channels is enlarged; however, this effect does not enhance the Na ion mobility. Instead the overall diffusivity is hampered by the local defects and the Na hopping probability is lowered. The diffusion mechanism in NaxCa1-xCr2O4 is proposed to be interstitial and the activation energy as well as diffusion coefficient are determined for all the members of the solid solution.</p>