| Abstract: | A sodium‐ion battery operating at room temperature is of great interest for large‐scale stationary energy storage because of its intrinsic cost advantage. However, the development of a high capacity cathode with high energy density remains a great challenge. In this work, sodium super ionic conductor‐structured Na3V2?xCrx(PO4)3 is achieved through the sol–gel method; Na3V1.5Cr0.5(PO4)3 is demonstrated to have a capacity of 150 mAh g?1 with reversible three‐electron redox reactions after insertion of a Na+, consistent with the redox couples of V2+/3+, V3+/4+, and V4+/5+. Moreover, a symmetric sodium‐ion full cell utilizing Na3V1.5Cr0.5(PO4)3 as both the cathode and anode exhibits an excellent rate capability and cyclability with a capacity of 70 mAh g?1 at 1 A g?1. Ex situ X‐ray diffraction analysis and in situ impedance measurements are performed to reveal the sodium storage mechanism and the structural evolution during cycling. |
