Substantial doping engineering in Na3V2-xFex(PO4)3 (0≤x≤0.15) as high-rate cathode for sodium-ion battery

Due to its high theoretical capacity and stable structure, Na3V2(PO4)3 has gained much attention as a potential cathode for sodium-ion batteries (SIBs) in large-scale energy storage applications. However, poor electronic conductivity usually results in the low rate capacity and poor cyclability, limiting its application. Herein, we successfully introduce Fe3+ to substitute V3+ through doping engineering. Compared with Na3V2(PO4)3/C, an excellent initial high-rate capacity of 91.2 mAhg−1 (77.5% of the theoretical capacity) at 20 C (2.35 A g−1) has been achieved in Na3V1.9Fe0.1(PO4)3/C + rGO due to the improved electronic conductivity introduced by Fe doping and rGO modification, and a stable cyclability with 88.7% capacity retention after 100 charge/discharge cycles, implying the perfect structural stability of the composite. It is expected that the results obtained will grasp new insights into designing the optimal cathode and realizing the commercial synthesis for the large-scale rechargeable sodium energy storage devices.