Licentiate seminar: Additives for Non-Flammable Electrolytes for Sodium-Ion Batteries

Supervisor: Assoc.Prof. Reza Younesi, Department of Chemistry - Ångström Laboratory, Structural chemistry

Please contact Jonas Welch if you would like a copy of the licentiate thesis.

Abstract

Batteries are an important technology for the energy transition away from the use of fossil fuels, both in electric vehicles and to balance weather-dependent energy sources like wind and solar power. Sodium-ion batteries are an attractive alternative to lithium-ion batteries, which can be manufactured based on abundant elements and without a need for copper, lithium, nickel or cobalt. Non-flammable and fluorine-free electrolytes increases safety and sustainability further. In this work, different electrolyte additives have been used to enable the use of the electrolyte sodium bis(oxalato)borate in triethyl phosphate in high mass-loading Prussian white – hard carbon full cells. Galvanostatic cycling at different temperatures was combined with resistance measurements with the Intermittent Current Interruption technique, pressure analysis, pause tests and rate tests to evaluate the battery performance. Solid electrolyte interface layers on negative electrodes were probed with X-ray photoelectron spectroscopy and the thermal stability of different electrolytes was studied by prolonged storage at elevated temperature, followed by characterization of degradation products with Nuclear Magnetic Resonance spectroscopy. The results highlight a viable alternative to the predominantly used carbonate-based electrolytes, and can provide a route forward to a successful commercialization of sodium-ion batteries.