Study to improve electrolytes in sodium batteries

Abstract

With increasing need for batteries and energy storage sodium batteries are of increasing demand. Lithium batteries are very popular but focus is being placed on sodium due to its higher abundance and subsequently, its lower cost. Sodium is also less poisonous to the human body than lithium for use in ingestible battery applications. The main focus of the study is to improve the electrolyte. We test the electrolyte in a coin cell battery with sodium as both the anode and cathode. Five different solvents mixts. for the electrolytes were tested in our lab: ethylene carbonate (EC)/propylene carbonate (PC), EC/PC/DEC (di-Et carbonate), EC/PC/DMC (di-Me carbonate), PC/EC/DME (dimethoxyethane), and EC/PC/dioxolane. We tested the batteries with Na/Na sym. cycling and impedance spectroscopy. The EC/PC electrolytes performed the best of all mixts. We thus shifted our focus to different ratios of EC/PC with different concns. of our electrolyte salts which were sodium perchlorate (NaClO4) and sodium hexafluorophosphate (NaPF6). Of the EC/PC electrolytes we tested, the best results were obtained from an EC/PC mixt. at a 7:3 ratio with a concn. of 1.2M NaClO4. Based on the performance of this electrolyte we tested sodium-ion battery cells with prussian blue as cathode with the EC/PC electrolyte.