Circumneutral concentrated ammonium acetate solution as water-in-salt electrolyte

TL;DR

This study explores a water-in-salt electrolyte based on ammonium acetate for energy storage, analyzing its physical properties and electrochemical stability, and demonstrating its application in a supercapacitor across various temperatures.

Contribution

It provides a comprehensive chemical-physical characterization of circumneutral WiSE using ammonium acetate and evaluates its performance in a supercapacitor device.

Findings

High ionic conductivity and electrochemical stability observed.

Solution structure analyzed via IR and molecular dynamics.

Supercapacitor operates effectively from -10 to 80°C.

Abstract

The exponentially growing market of electrochemical energy storage devices requires substitution of flammable, volatile, and toxic electrolytes. The use of Water in salt solutions (WiSE) regarded as green electrolyte might be of interest thanks to an association of key features such as high safety, low cost, wide electrochemical stability, and high ionic conductivity. Here, we report comprehensive chemical-physical study of circumneutral WiSE based on ammonium acetate so as to investigate application in electrochemical energy storage systems, with focus on the effect of pH, density, viscosity, conductivity, and the ESW with salt concentration ranging from 1 to 30 mol/kg . Data are reported and discussed with respect to the structure of the solutions investigated by complemental IR and molecular dynamic study. The study is addressed through the showcase of an asymmetric supercapacitor based on Argan shell-derived carbon electrodes tested at temperatures ranging from -10 to 80 {\deg}C.