Reconstructing Hydrogen Bond Network Enables High Voltage Aqueous Zinc-Ion Supercapacitors

Abstract

High-voltage aqueous rechargeable energy storage devices with safety and high specific energy are hopeful candidates for the future energy storage system. However, the electrochemical stability window of aqueous electrolytes is a great challenge. Herein, inspired by density functional theory (DFT), polyethylene glycol (PEG) can interact strongly with water molecules, effectively reconstructing the hydrogen bond network. In addition, N, N-dimethylformamide (DMF) can coordinate with Zn2+, assisting in the rapid desolvation of Zn2+ and stable plating/stripping process. Remarkably, by introducing PEG400 and DMF as co-solvents into the electrolyte, a wide electrochemical window of 4.27 V can be achieved. The shift in spectra indicate the transformation in the number and strength of hydrogen bonds, verifying the reconstruction of hydrogen bond network, which can largely inhibit the activity of water molecule, according well with the molecular dynamics simulations (MD) and online electrochemical mass spectroscopy (OEMS). Based on this electrolyte, symmetric Zn cells survived up to 5000 h at 1 mA cm−2, and high voltage aqueous zinc ion supercapacitors assembled with Zn anode and activated carbon cathode achieved 800 cycles at 0.1 A g−1. This work provides a feasible approach for constructing high-voltage alkali metal ion supercapacitors through reconstruction strategy of hydrogen bond network.