Hydrogen-bond enhanced urea-glycerol eutectic electrolyte to boost low-cost and long-lifespan aqueous sodium-ion batteries

Abstract

Aqueous sodium-ion batteries (ASIBs) have garnered significant attention as promising candidates for large-scale energy storage applications. This interest is primarily due to their abundant resource availability, environmental friendliness, cost-effectiveness, and high safety. However, their electrochemical performance is limited by the thermodynamic properties of water molecules, resulting in inadequate cycling stability and insufficient specific energy density. To address these challenges, this study developed a hydrogen-bond enhanced urea-glycerol eutectic electrolyte (UGE) to expand the electrochemical stability window (ESW) of the electrolyte and suppress corresponding side reactions. The eutectic component disrupts the original hydrogen bonding network in water, creating a new, enhanced network that reduces the activity of free water and forms a uniform, dense passivation layer on the anode. As a result, the optimized composition of UGE exhibits a broad ESW of up to 3 V (−1.44 to 1.6 V vs. Ag/AgCl). The Prussian blue (PB)/UGE/NaTi₂(PO₄)₃@C full cell exhibits an exceptionally long lifespan of 10,000 cycles at 10 C. This study introduces a low-cost, ultra-long-life ASIB system, utilizing a green and economical eutectic electrolyte, which expands the use of eutectic electrolytes in aqueous batteries and opens a new research horizon for constructing efficient electrochemical energy storage and conversion.