This work investigates a series of novel boronium-bistriflimide [TFSI-] ionic liquids using electrochemical and physical characterization techniques such as cyclic voltammetry, broadband dielectric spectroscopy, shear rheology, and thermogravimetric analysis. Systematic variations in boronium cation structure were employed to help identify the structural motifs that lead to optimal electrochemical and physical properties. The best performing boronium-based ionic liquids were then tested for initial lithium stability to further probe their potential for use in battery applications.