Investigating the stability of sodium couple in the ionic liquid electrolytes and cathode materials

There is an urgent need for a high energy density rechargeable battery for applications such as portable electronics and electric vehicles. This work involved the characterization of a novel inorganic salt-based ionic liquid electrolyte and the explanation of mechanisms behind the loss of coulombs for both electrodes with the goal of developing a room temperature electrolyte for the sodium/copper(I) chloride battery. The stability of the sodium couple in this electrolyte was examined using electroanalytical techniques with an electrochemical quartz crystal nanobalance as the first part of the characterization. The second part was to investigate mechanisms behind the reactions at the copper cathode.; The mixture of methanesulfonyl chloride (MSC) and aluminum chloride was prepared and studied. The coulombic efficiency of the sodium couple in the MSC electrolyte was up to 97%, which implies 97% of the reduced sodium was recovered after the oxidation. Our work focused on the lost 3% of the sodium and explained the possible causes, one of which is the co-reduction of electrolyte. Without the co-reduction of electrolyte, 99% of the reduced alkali metal can be oxidized.; The copper cathode was oxidized to form cuprous chloride; however, the parasitic reactions followed to convert cuprous to cupric chloride. Shift in the local acidity due to depletion of chloride would cause these chain reactions and result in greater than 100% coulombic efficiency. Keeping the local acidity constant can control these parasitic reactions by providing an unbounded amount of chloride.