With the aim of improving the electrochemical properties of the LiCoMnO4 high-voltage spinel for lithium ion battery applications, LiCoMnO4-y F y (y = 0, 0.05, 0.1) compounds were synthesized by a two-step solid-state reaction at 800 °C. The stoichiometry of the samples was verified by nuclear reaction analysis for the fluorine stoichiometry, inert gas fusion analysis for the oxygen stoichiometry, and inductively coupled plasma optical emission spectroscopy for the cation stoichiometry. X-ray diffraction analysis and scanning electron microscopy revealed increasing phase purity and changing microstructure upon fluorine incorporation. Electrochemical characterizations were carried out in battery test cells using a liquid electrolyte. The samples show poor coulombic efficiency, due to liquid electrolyte decomposition. However, fluorinated spinels demonstrated significantly improved capacities of up to 18% and improved cycling stability of up to 20%, compared to their non-fluorinated counterparts.