Authors: Jin Han, Alessandro Mariani, Maider Zarrabeitia, Zenonas Jusys, R. Jürgen Behm, Alberto Varzi, Stefano Passerini
Published: 2022-07-10
Source: Full article
AbstractHalide‐free, water‐in‐salt electrolytes (WiSEs) composed of potassium acetate (KAc) and zinc acetate (ZnAc2) are investigated as electrolytes in zinc‐ion hybrid supercapacitors (ZHSs). Molecular dynamics simulations demonstrate that water molecules are mostly non‐interacting with each other in the highly concentrated WiSEs, while “bulk‐like water” regions are present in the dilute electrolyte. Among the various concentrated electrolytes investigated, the 30 m KAc and 1 m ZnAc2 electrolyte (30K1Zn) grants the best performance in terms of reversibility and stability of Zn plating/stripping while the less concentrated electrolyte cannot suppress corrosion of Zn and hydrogen evolution. The ZHSs utilizing 30K1Zn, in combination with a commercial activated carbon (AC) positive electrode and Zn as the negative electrode, deliver a capacity of 65 mAh g−1 (based on the AC weight) at a current density of 5 A g−1. They also offer an excellent capacity retention over 10 000 cycles and an impressive coulombic efficiency (≈100%).