One-step electrochemical deoxidation method to prepare Sb/multiple-wall carbon nanotubes as anodes for sodium-ion batteries in deep eutectic solvent

The extraction of metallic antimony directly from stibnite ore (Sb 2 O 3 and Sb 2 S 3 ) to prepare antimony-based anode for sodium-ion batteries (SIBs) represents a simple and cost-effective approach to advancing energy storage. The direct electrochemical deoxidation of solid Sb 2 O 3 /multiple-wall carbon nanotubes (MWCNTs) to Sb/MWCNTs as anodes for SIBs in deep eutectic solvent (DES) was reported for the first time. Cyclic voltammetry (CV) tests reveal that the electrochemical deoxidation of Sb 2 O 3 /MWCNTs is a single-step process. Using a solid Sb 2 O 3 /MWCNTs disc as cathode, constant voltage electrolysis measurements were carried out to investigate the sodium storage performance of the Sb/MWCNTs composites by varying experimental conditions, which included electrolysis voltage (2.2, 2.4, and 2.6 V), electrolysis duration (2, 4, and 6 h), and different Sb 2 O 3 /MWCNTs ratios (Sb 2 O 3 -1 MWCNTs, Sb 2 O 3 -2 MWCNTs, and Sb 2 O 3 -3 MWCNTs). X-ray diffraction (XRD) analysis confirms that the Sb 2 O 3 /MWCNTs composites can be fully reduced to Sb/MWCNTs, while scanning electron microscope (SEM) results reveal that the particle size decreases as the cell voltage increases. The electrolytic samples of Sb-1 MWCNTs obtained under 2.6 V at 363 K for 6 h deliver excellent sodium-storage performance. The capacity of the Sb-1 MWCNTs composites anode is measured as 574.9 mAh g −1  at a current density of 0.1 A g −1 and as 450.4 mAh g −1  at a current density of 0.5 A g −1 after 200 and 150 cycles, respectively. The direct electrochemical deoxidation method using DES provides a new approach from oxide ore for preparing other alloy-types anode materials for SIBs.