Sodium-ion batteries (SIBs) are uniquely positioned to help supplement the growing demand as sodium is ~1100 times more abundant and cheaper to extract than lithium, thus reducing environmental and social concerns. A typical battery consists of a cathode, anode, and solid/liquid electrolyte. The ideal solid electrolyte is resistant to explosions and flammability upon being punctured and possesses high ionic conductivity, moisture resistance, and great electrochemical stability. Research into sodium electrolytes have primarily focused on oxide- and sulfur-based systems whereas halide derivatives are emerging on the frontier. While oxide electrolytes display exceptional thermal and electrochemical stability, their performance is significantly hindered by high grain boundary resistance, impeding the flow of electricity at the interface. Sulfide systems display high ionic conductivities and have mild synthetic conditions, but operate within a narrower electrochemical range and are moisture sensitive. Emerging studies suggest sodium halide electrolytes possess the benefits of both its oxide and sulfide analogues.

The objective is to explore novel sodium halide compositions consisting of targeted transition metal(s) and halides ranging from fluorine to bromine. These electroyles ideally possess the previously aforementioned desirable properties. The principles of green chemistry will be employed using mechanochemistry to synthesize candidate materials. The project will focus on modifying the composition to assess ionic conductivity, identify phase changes, and better comprehend how sodium-ions move within the material.

Understanding the physical and electrochemical properties of these materials are fundamental to identifying superior compositions that can then be tested in a prototypical solid-state battery. The advancement of SIB research can demonstrate their viability to help offset fossil-fuel dependency and meet the growing demand for grid-scale energy storage and small-scale applications.