Highly Solubilized Urea as Effective Proton Donor-Acceptors for Durable Zinc-Ion Storage Beyond Single-Anion Selection Criteria

Abstract

Urea, as one of the most sustainable organic solutes, denies the high salt consumption in commercial electrolytes with its peculiar solubility in water. The bi-mixture of urea-H2O shows the eutectic feature for increased attention in aqueous Zn-ion electrochemical energy storage (AZEES) technologies. While the state-of-the-art aqueous electrolyte recipes are still pursuing the high-concentrated salt dosage with limited urea adoption and single-anion selection category. Here, a dual-anion urea-based (DAU) electrolyte composed of dual-Zn salts and urea-H2O-induced solutions is reported, contributing to a stable electric double-layer construction and in situ organic/inorganic SEI formation. The optimized ZT2S0.5-20U electrolytes show a high initial Coulombic efficiency of 93.2% and durable Zn-ion storage ≈4000 h regarding Zn//Cu and Zn//Zn stripping/plating procedures. The assembled Zn//activated carbon full cells maintain ≈100% capacitance over 50 000 cycles at 4 A g–1 in coin cell and ≈98% capacitance over 20 000 cycles at 1 A g–1 in pouch cell setups. A 12 × 12 cm2 pouch cell assembly illustrates the practicality of AZEES devices by designing the cheap, antifreezing, and nonflammable DAU electrolyte system coupling proton donor-acceptor molecule and multi-anion selection criteria, exterminating the critical technical barriers in commercialization.