Synthesis and properties of multi-porous multi-doped nano-Na₃V₂(PO₄)₃@C materials from electroless nickel plating wastewater

Electroless nickel plating technology displays exuberant vitality in the field of surface treatment, nevertheless accompanying with its spent plating solution for environmental pollution and resource waste. Therefore, it is of great significance how to realize the high efficient utilization of various waste ions in the electroless nickel plating wastewater (ENPW). Herein, after transforming nickel and sulfur elements in ENPW into nickel hydroxide and barium sulfate, the remaining elements serve as primary raw materials for the synthesis of multi-porous multi-doped nano-Na₃V₂(PO₄)₃@C materials (D-NVP). This is achieved by integrating the sol–gel method with the carbon thermal reduction method. The as-synthesized D-NVP displays a 3D porous skeleton structure, where the pores with different nano-micron sizes are interlinked by the skeletons with the thickness of 40–200 nm. The unique structure, combined with Mg-Ca-Fe doping, contributes to D-NVP’s excellent electrochemical properties, with the initial discharge capacities of 108, 107, 104.3, 101.5, 98.6, and 95.3 mAh·g⁻¹ at 0.2, 0.5, 1, 2, 5, and 10 C, and the capacity retention rates of 99.2% and 98.9% at 1 and 5 C after 200 cycles, respectively.