N/S Co-modified carbon/Na3V2(PO4)3 with high rate capability for Zn-ion storage

Abstract

Na₃V₂(PO₄)₃ (NVP) with a NASICON structure serves as one of the most promising cathode materials for aqueous zinc-ion batteries (AZIBs) due to its stable crystal structure and fast ion mobility. Nevertheless, its electrochemical properties are still unsatisfactory because of its poor electrical conductivity. A simple hydrothermal method is used to prepare carbon-coated NVP (NVP-C) and N/S co-doped carbon-coated NVP (NVP-C-NS) composites. The results demonstrate that the NVP-C-NS composite exhibits superior capacity and rate capability. After 100 cycles at a high current density of 1000 mA g⁻¹, the reversible capacity of the NVP-C-NS composite can reach 115 mA h g⁻¹, while pure NVP-C is capable of achieving only 83 mA h g⁻¹ at the same current density, and 94.8% of the capacity of the NVP-C-NS composite and only 90% of the NVP-C material are retained. The excellent electrochemical performance of the NVP-C-NS composite is mainly due to the high carbon content (13.08 wt% vs. NVP-C with 4.8 wt%.) and high conductivity (3.72 × 10⁻⁴ S cm⁻¹vs. NVP-C with 1.20 × 10⁻⁴ S cm⁻¹). The introduction of more active sites and defects after N/S doping and the increased specific surface area can provide a larger electrochemical contact surface for electrochemical reactions. Furthermore, the practicality of the NVP-C-NS//Zn battery is evaluated by lighting up LED bulbs. This work provides a reference for the development of Na₃V₂(PO₄)₃ as a cathode material for AZIBs.