Polymer stabilized droplet templating towards tunable hierarchical porosity in single crystalline Na${}_3$V${}_2$(PO${}_4$)${}_3$ for enhanced Sodium-ion storage

Na${}_3$V${}_2$(PO${}_4$)${}_3$ (NVP) is regarded as a potential cathode material for sodium-ion batteries, whereas, its performance is usually limited by inherent low electronic conductivity and dense bulk structure. Herein, we develop a facile polymer stabilized droplet template strategy to synthesize porous single crystal structured NVP. The pore structures (macrostructures, hierarchically meso/macrostructures, and mesostructures), pore sizes (5-2000 nm), and specific surface areas (26-158 m${}^2$ g${}^{-1}$) of the samples can be readily controlled by tuning the sizes of droplet templates. The resultant hierarchically meso/macropores NVP demonstrates superior sodium storage performances, because its porous single crystal structure owns solid-liquid Na${}^{+}$ transmission mode, shortens ion diffusion distance and provides large electrode-electrolyte contact area, greatly facilitating fast ionic transport. We believe the presented method will supply a novel avenue to prepare porous single crystal structured materials for anticipative applications. (© 2021 Wiley-VCH GmbH)