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

For NaV(PO) (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 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 NaS 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 at 60 C, and it remains at 98.8% after 10 000 cycles at 60 C.