Water Confinement by a Zn2+-Conductive Aqueous/Inorganic Hybrid Electrolyte for High-Voltage Zinc-Ion Batteries

Abstract

Aqueous zinc-ion batteries (ZIBs) have received extensive attention owing to the intrinsic safety and high specific energy. However, the practical performance of the ZIBs is impacted by the water-induced complicated interfacial reactions, including the corrosion/dendrites of a Zn anode and the dissolution/degradation of a cathode. Herein, we developed a type of inorganic Zn2+-interlayered montmorillonite-based aqueous/inorganic hybrid electrolyte (ZM-30% HE) that not only realizes low water content but also shows a strong water confinement effect, which leads to a significantly weakened water activity and water solvation effect. Therefore, the side reactions between the Zn anode and free water molecules are effectively suppressed and the diffusion/insertion of zinc ions into the cathode is substantially facilitated. At the Zn anode side, ZM-30% HE can stabilize the symmetric cell for 2000 h at 1 mA cm–2. Moreover, low water content enables the application of the intercalation-type Zn-ion cathode. Based on the ZM-30% HE and Mn4[Fe(CN)6]2.84·11.8H2O cathode, record-high voltage (1.70 V vs Zn2+/Zn) and voltage efficiency (92%) among the reported Zn metal cells with hybrid electrolytes and Zn2+-storage cathodes were achieved. Meanwhile, the dissolution/degradation problem of the cathode in the traditional liquid electrolyte was solved using the HE. The Zn/ZM-30% HE/Mn4[Fe(CN)6]2.84·11.8H2O full cell shows stable cycling up to 400 cycles even at a low current density of 100 mA g–1. The development of the hybrid electrolyte with unique water confinement effect provides a solution to boost the performance of the current ZIBs.