Reconstructing the phase of vanadium oxides enables redox-catalysis manipulated reversible sulfur conversion for stable Zn–S batteries

Abstract

The naturally sluggish redox kinetics and limited utilization associated with the sulfur conversion in Zn/S electrochemistry hinder its real application. Herein, we report an in situ phase reconstruction strategy that activates the catalytic activity of vanadium oxides for invoking redox-catalysis to manipulate reversible sulfur conversion. It was identified that the V₂O₃@C/S precursor derived from metal organic frameworks could be transformed into V₂O_5−m·nH₂O@C/S by a facile electrochemical induction process. Vanadium oxides can realize a faster zinc ion storage process than sulfur components during the discharging process, thereby the pre-zincified Zn_xV₂O₅·nH₂O behaves as a redox medium to catalyze the sulfur reduction via a spontaneous reaction (Zn_x+1V₂O₅ + S = Zn_xV₂O₅ + ZnS, △G = −6.4 kJ mol⁻¹). For the reverse battery recharging, the electrodeposited ZnS around the active sites can be easily activated and the facile Zn²⁺ transport between Zn_xV₂O₅·nH₂O and ZnS enables the reversible conversion of ZnS back to S (Zn_xV₂O₅ + ZnS = Zn_x+1V₂O₅ + S, ΔG = −7.02 kJ mol⁻¹). Accordingly, the composite cathode delivers a high capacity of 1630.7 mA h g⁻¹ and maintains stable capacity retention after 150 cycles at 4 A g⁻¹. The proposed redox catalytic effect sheds light on the tunable Zn–S chemistry.