The energy density of lithium-ion batteries can be raised by increasing the redox potential of the positive electrode. This can be done in principle by substituting oxygen in commonly used lithium transition metal oxides with the more electronegative fluorine. To synthesize the quaternary lithium transition metal fluoride LiMgFeF6 with triturile structure a sol–gel process without toxic chemicals was used. The as-synthesized LiMgFeF6 was ball milled with carbon and binder to characterize the electrochemical properties of the LiMgFeF6/carbon/binder nanocomposite against lithium metal. After 20 cycles of galvanostatic cycling a reversible specific capacity of 107 mAh g−1, which is 80% of the theoretical capacity (1 eq. Li = 133 mAh g−1), was retained. In a rate performance test up to a discharge rate of 1C the LiMgFeF6/carbon/binder nanocomposite provided a specific capacity of 64 mAh g−1. Moessbauer spectroscopy and cyclic voltammetry confirmed the electrochemically active redox couple Fe3+/Fe2+ during cycling against lithium metal. Structural changes of the trirutile structure after lithium insertion have been investigated by X-ray powder diffraction.