Eutectic electrolytes with leveling effects achieving high depth-of-discharge of rechargeable zinc batteries

Abstract

Non-compact zinc (Zn) electrodeposition prevents homogeneous Zn dissolution and irreversibly depletes active Zn sources, which possess major hurdles to the practical realization of deep cycling Zn batteries. Although anionic surfactants are widely used as leveling additives to induce uniform Zn coating in Zn electroplating industry, their applications in rechargeable Zn batteries are restricted due to their readily precipitation in divalent Zn2+ electrolytes and continuous loss during long-term cycling. Herein, we report a newly designed eutectic electrolyte with an anionic surfactant, zinc dodecylbenzenesulfonate (Zn(DBS)2) as Zn salt in a mixture of acetamide and water. Due to the high binding energy of amphiphilic DBS− with Zn2+, DBS− enters the primary solvation shell of Zn2+, which slows down the kinetics of Zn2+ electroreduction and alleviates the concentration polarization. Consequently, uniform and compact Zn deposition with shiny metallic appearance can be achieved, which enables cycling of Zn anodes with a cumulative capacity of ∼600 mAh cm−2 at 50% depth of discharge and represents a 23-fold enhancement compared to the analogue Zn(TFSI)2-based electrolyte. This electrolyte also allows the operation of a Zn//Na3V2(PO4)3 full cell under the harsh conditions of limited Zn supply (N/P ratio of 2) with 79.7% capacity retention after 100 cycles.