Ultra-High-Capacity and Dendrite-Free Zinc–Sulfur Conversion Batteries Based on a Low-Cost Deep Eutectic Solvent

Traditional cathodes for aqueous Zn-ion batteries are afflicted by a limited specific capacity and fearful Zn dendrites. Herein, these troubles are disposed of with a conversion-type Zn–S battery and low-cost deep eutectic solvent (DES). By utilizing the optimized electrolyte, the symmetrical Zn battery can stably cycle over 3920 h, which also confers on the Zn–S battery an ultrahigh specific capacity of ∼846 mA h g S –1 and energy density of 259 W h kg –1 at 0.5 A g –1 . Importantly, the conversion chemistry of S and ZnS is responsible for the superior anti-self-discharge behavior (capacity retention: 94.58 and 68.58% after standing for 72 and 288 h versus Zn//VO 2 battery: 76.82 and 47.80% after resting for 24 and 72 h versus Zn//MnO 2 battery: 95.96 and 91.57% after resting for 24 and 72 h, respectively). This work is the first authentication of Zn–S batteries based on a newly developed low-cost DES-based electrolyte, which meanwhile settles the deep-rooted low specific capacity and infamous Zn dendrite issues in conventional (de)intercalation Zn-ion batteries.