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capacitors, coulombic efficiency, electrolytes, solvent effect, zinc, Activated carbon, Electrolytic capacitors, Molecular dynamics, Positive ions, Solvents, Supercapacitor, Coulombic efficiency, Dendrite formation, Depth of discharges, Dynamics simulation, Hybrid capacitor, Performance, Solvent effects, Zinc cations, Zinc ions, Zinc salts, Electrolytes
Abstract:
Zinc ion hybrid capacitors suffer from lack of reversibility and dendrite formation. An electrolyte, based on a solution of a zinc salt in acetonitrile and tetramethylene sulfone, allows smooth zinc deposition with high coulombic efficiency in a Zn||stainless steel cell (99.6% for 2880 cycles at 1.0 mA cm−2, 1.0 mAh cm−2). A Zn||Zn cell operates stably for at least 7940 h at 1.0 mA cm−2 with an area capacity of 10 mAh cm−2, or 648 h at 90% depth of discharge and 1 mA cm−2, 9.0 mAh cm−2. Molecular dynamics simulations reveal the reason for the excellent reversibility: The zinc cation is only weakly solvated than in pure tetramethylene sulfone with the closest atoms at 3.3 to 3.8 Å. With this electrolyte, a zinc||activated-carbon hybrid capacitor exhibits an operating voltage of 2.0 to 2.5 V, an energy-density of 135 Wh kg−1 and a power-density of 613 W kg−1 at 0.5 A g−1. At the very high current-density of 15 A g−1, 29.3 Wh kg−1 and 14 250 W kg−1 are achieved with 81.2% capacity retention over 9000 cycles. © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.
