Development and investigation of a NASICON‐type high‐voltage cathode material for high‐power sodium‐ion batteries

Herein, we introduce a 4.0 V class high‐voltage cathode material with a newly recognized sodium superionic conductor (NASICON)‐type structure with cubic symmetry (space group P2${}_1$3), Na${}_3$V(PO${}_3$)${}_3$N. We synthesize an N‐doped graphene oxide‐wrapped Na${}_3$V(PO${}_3$)${}_3$N composite with a uniform carbon coating layer, which shows excellent rate performance and outstanding cycling stability. Its air/water stability and all‐climate performance were carefully investigated. A near‐zero volume change (ca. 0.40 %) was observed for the first time based on in situ synchrotron X‐ray diffraction, and the in situ X‐ray absorption spectra revealed the V${}^{3.2+}$/V${}^{4.2+}$ redox reaction with high reversibility. Its 3D sodium diffusion pathways were demonstrated with distinctive low energy barriers. Our results indicate that this high‐voltage NASICON‐type Na${}_3$V(PO${}_3$)${}_3$N composite is a competitive cathode material for sodium‐ion batteries and will receive more attention and studies in the future. (© 2019 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)