Synthesis of NaNiF3 and its composite with multi-walled carbon nanotubes as cathode materials for aqueous sodium-ion battery

Aqueous sodium-ion battery is a safe and efficient system for large-scale energy storage due to low cost, abundant sodium supply, non-flammable aqueous neutral electrolyte and quick charge–discharge performance. The use of fluoride-based material as electrode material has a certain advantage due to high potential window and energy density. Exploring perovskite materials has advantage of corner-sharing matrix structure which helps in easy ion and electron diffusion. Herein, we synthesized the perovskite-structured NaNiF₃ and its composite with multi-walled carbon nanotubes (MWCNT) by a simple and cost-effective approach by the combination of precipitation and hydrothermal route. The synthesized material is characterized by X-rays diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and Brunauer–Emmett–Teller analysis. Electrochemical performance for aqueous sodium-ion batteries is tested by cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy (EIS) in 1 M Na₂SO₄ electrolyte. XRD confirms the perovskite structure of NaNiF₃ and NaNiF₃ // MWCNT. SEM shows the orthorhombic cube and cubical structure of NaNiF₃ and NaNiF₃ // MWCNT. Electrochemical results demonstrate the excellent performance with a specific capacity of 33 mAh g⁻¹ and 57 mAh g⁻¹ at 0.1 A g⁻¹ and shows excellent cyclic stability up to 500 cycles, indicating NaNiF₃ // MWCNT as potential candidate among cathode material of aqueous sodium-ion battery.