High-Performance Rechargeable Zinc Sulfur Battery with Deep Eutectic Solvents

Zinc is an attractive anode material due to it possesses the merits of high theoretical capacity, proper redox potential (−0.76 V vs standard hydrogen electrode) and low cost. However, when used in a zinc–sulfur battery, polysulfide rapidly reacts with zinc to form a passivating zinc sulfide (ZnS) film on the zinc metal surface, leading to the capacity decays rapidly. Up to date, it remains challenging to develop high-performance Zn–S batteries. To overcome these issues, non-aqueous electrolyte system composed of deep eutectic solvent (DES), which is combined by choline chloride, ethylene glycol and zinc chloride, is developed in this study. This DES electrolyte provides a wide electrochemical window of 1.8 V, which can stabilize the side reaction during the charge–discharge process. By applying carbon nanotube (CNT)/sulfur composite as cathode material and zinc foil as anode, the battery delivers a specific capacity of 450 mAh g^-1 with a flat discharge voltage of 0.8 V and a long-term stability. <i>Ex-situ</i> characterization of XRD, XPS, Raman and SEM-EDS mapping reveal that the working mechanism based on the reversible conversion reaction of the Zn–S alloying processes. The utilization of DES on electrolyte for rechargeable battery system opens a new route for high-performance zinc-sulfur batteries.