Innovative Electrolytes and Electrodes for Sodium-Ion Batteries

Licentiate thesis, 2013

Batteries are expected to be masterpieces for future large-scale energy storage, but the emergence of ecological and financial concerns has forced us to think about complementary battery technologies to the today outstanding lithium-ion batteries (LIBs). Therefore, the sodium-ion battery (SIB) is a concept worth studying - especially for large-scale applications due to the abundance of sodium as an element, the overall low cost anticipated, and the similarities with LiBs, which should ease a technology change. SIB electrolytes can be based for example on organic solvents or ionic liquids (IL), both doped with the appropriate sodium salt. Several features and properties of IL-based electrolytes for SIBs are investigated in this thesis; the ionic conductivity of novel electrolytes chosen among the large number of IL available, complemented by Raman vibrational spectroscopy to understand the interaction within the electrolyte and the possible operation temperature range by differential scanning calorimetry. In addition, a significant part of the work is dedicated to the electrochemical compatibility of the electrolytes with SIB electrode materials. The stability and behaviour toward the electrodes are investigated to make possible a fully operative safer SIB in the future, possibly based on IL based electrolytes.