Crystal Facet Design in Layered Oxide Cathode Enables Low-Temperature Sodium-Ion Batteries

Layered transition metal oxides (LTMOs) have been identified as promising cathodes for alkali metal-ion batteries. However, their low-temperature performance is generally restricted by the sluggish ion diffusion kinetics within the LTMOs' host. Nanostructured materials have been developed to enhance ion diffusion kinetics but often significantly reduce the tap density. Herein, using NaCrO2 as a model cathode material, from the aspect of crystallography, we report a large-sized monocrystalline NaCrO2 with abundant Na+ active facets exposed by a straightforward acetate-assisted solid-state reaction, which addresses the dilemma between the volumetric energy density and ion diffusion kinetics and enables excellent low-temperature performance. Specifically, the synthesized NaCrO2 cathode showcases a high specific capacity of 94.7 mAh g–1 at a high rate of 20C under room temperature and displays good capacity retention of 97.2% after 100 cycles at 1C under −20 °C. Additionally, the full-cell device demonstrates a remarkable initial capacity of 113.0 mAh g–1 at a rate of 0.1C and exhibits excellent cyclic performance, retaining 84.2% of its capacity after 100 cycles at 0.2C under −10 °C. This study opens up new possibilities to design LTMOs with improved ion diffusion kinetics for alkali metal-ion batteries.