Dual-Amide Strategy for Quaternary Aqueous Electrolytes

Abstract

Aqueous Li-ion batteries (LIBs) offer promising advantages in terms of safety, sustainability, and cost-effectiveness, however, their practical application is fundamentally limited by the narrow electrochemical stability window (~1.23 V) of water. To overcome this issue, solvation structure design is essential-not only for suppressing water reactivity but also for the formation of stable solid-electrolyte interphase (SEI) layers. Building on this concept, we introduce a dual-amide strategy through a quaternary aqueous electrolyte composed of LiTFSI, water, and two structurally complementary amide-based diluents-acetamide and ε-caprolactam. Their contrasting molecular characteristics enable modular tuning of Li + solvation, strengthening Li + -anion association that serve as a foundation for anion-derived SEI formation, without compromising Li + conductivity. The dual amide quaternary electrolyte retains 82% capacity after 1,200 cycles at 1C-the longest cycle life reported for aqueous LIBs.