“Water-in-Salt” and Nasicon Electrolyte-Based Na-CO2 Battery

Abstract

Super concentrated electrolytes, referred to as “water-in-salt (WiS) electrolytes”, have been received attention due to their wide electrochemical stability window, cost-effectiveness, and non-flammability. However, the free water molecules present in WiS electrolytes prevent the use of Na-metal as the anode for Na-gas batteries.In this study, we develop a Na-CO2 battery with WiS and Na-super-ionic conductor (NASICON) electrolytes that were used as energy storage cells and CO2 gas utilization. The NASICON separator allowed us to fabricate a hybrid Na-CO2 battery comprising Na metal as the anode material and WiS as the cathode electrolyte without damage of Na metal. Additionally, linear sweep voltammetry (LSV) with corresponding differential electrochemical mass spectroscopy (DEMS) measurements rendered the direct observation of H2 evolution retardation with increasing WiS concentration. Furthermore, we introduced a nano-sized Ru catalyst onto the current collector using Joule heating method for reducing the overpotential gap. Consequently, the Na-CO2 batteries with Ru@carbon current collector reduced the overpotential gap and exhibited a cycling endurance of over 75 cycles.