Anchored VN Quantum Dots Boosting High Capacity and Cycle Durability of NaV(PO)@NC Cathode for Aqueous Zinc-Ion Battery and Organic Sodium-Ion Battery.

NaV(PO) is a promising high-voltage cathode for aqueous zinc-ion batteries (ZIBs) and organic sodium-ion batteries (SIBs). However, the poor rate capability, specific capacity, and cycling stability severely hamper it from further development. In this work, NaV(PO) (NVP) with vanadium nitride (VN) quantum dots encapsulated by nitrogen-doped carbon (NC) nanoflowers (NVP/VN@NC) are manufactured as cathode using in situ nitridation, carbon coating, and structural adjustment. The outer NC layer increases the higher electronic conductivity of NVP. Furthermore, VN quantum dots with high theoretical capacity not only improve the specific capacity of pristine NVP, but also serve as abundant "pins" between NVP and NC to strengthen the stability of NVP/VN@NC heterostructure. For Zn-ion storage, these essential characteristics allow NVP/VN@NC to attain a high reversible capacity of 135.4 mAh g at 0.1 A g, and a capacity retention of 91% after 2000 cycles at 5 A g. Meanwhile, NVP/VN@NC also demonstrates to be a stable cathode material for SIBs, which can reach a high reversible capacity of 124.5 mAh g at 0.1 A g, and maintain 92% of initial capacity after 11000 cycles at 5 A g. This work presents a feasible path to create innovative high-voltage cathodes with excellent reaction kinetics and structural stability.