Simultaneous Effects of C-N-V Bonds and Multiple Sulfides Anchoring Active V and Na Enables Honeycomb-Like Porous Na3V2(PO4)3 with Non-Attenuation Characteristics for Na-Ion Batteries

For Na 3 V 2 (PO 4 ) 3 (NVP) cathode, the activity and utilization rate of Na and V is the key to affecting its electrochemical properties. However, few studies can simultaneously optimize both. Currently, a facile hydrothermal route is proposed to successfully synthesize the honeycomb-like porous NVP@CHSLS cathodes possessing anchoring effects to enhance the immobilization of active Na/V through in situ carbonation with chitosan and sodium lignosulfonate. DFT calculations demonstrate the N/S co-doped carbon skeleton gains more electrons and behaves with superior charge transfer capability. Accordingly, XAFS verifies the existence of hypervalent V 4+ for the charge balance, as well as a newly generated C-N-V bond inside the bulk, which significantly inhibits the dissolution of V in the electrolyte. Moreover, ex-situ and after-cycled XRD verifies beneficial electrochemical intermediums such as Na 2 S manifest extra sodium fixation characteristics, which not only enter into the CEI membrane to reduce the loss of Na + , but also participate in the de-intercalation of Na + . Furthermore, honeycomb-like porous morphology enriches the active sites for Na + migration and improves the wettability of electrolytes, demonstrated by contact Angle and AFM tests. Consequently, the optimized NVP@CHSLS-2 reveals a high postactivated capacity of 104.5 mAh g −1 at 60 C, and it remains at 98.8% after 10 000 cycles at 60 C.