'Duet-Insurance' Eutectic Electrolytes for Zinc-Ion Capacitor Pouch Cells

摘要

Eutectic electrolytes are emerging to be explored to meet the high demandfor aqueous zinc-ion capacitors (AZICs) due to their high electrochemical stabilityand environmental-friendly feature. Notably, a large-scale requirementfor a practical AZIC has been addressed to balance decent performance andincrease package size. Thus, a “duet-insurance” eutectic electrolyte (DIEE) isproposed by introducing successively heavy water (D_2O) and dimethyl sulfoxidein an aqueous chaotropic Zn salt solution, which hindered the severe irreversibilityof Zn anodes compared to that lacking this dual-solvent protection.For example, the optimal DIEE delivered a high capacitance of 352.9 F g~(?1) at0.5 A g~(?1) and excellent capacitance retention of ≈100 over 30,000 cycles at2 A g~(?1) implementing in pouch cells and showing the ability to operate at alow temperature. Besides, experimental (e.g., nuclear magnetic resonancespectroscopy, Raman spectroscopy, electric double-layer capacitance, etc.)and theoretical techniques (e.g., molecular dynamics simulation, densityfunctional theory) illustrate the vital presence of contact ion pairs and aggregatesion species. Ultimately, this efficient DIEE system employing “duetinsurance”protections provides a promising direction for designing noveleutectic electrolytes for AZICs chemistries.