Powders of Li 2MMn 3O 8 (M = Fe, Co) were prepared by glycine nitrate combustion from the corresponding metal nitrates. The reaction products were pressed into pellets with the addition of 20 wt.% excess LiNO 3, which were used as targets for e-beam evaporation. A high-voltage all-solid-state thin-film lithium ion battery was demonstrated by the sequential deposition of spinel structured Li 2MMn 3O 8 (M = Co, Fe) as positive electrode by e-beam evaporation, LiPON as electrolyte, and metallic Al as negative electrode by sputtering in N 2 and Ar gas mixtures with specific power and gas flow rates. A lithium ion conductivity of ∼10 -6 S cm -1 was observed for the optimized thin-film LiPON electrolyte prepared under the condition of a chamber pressure of 2.6 × 10 -2 mbar and a power of 60-100 W. The chemical diffusion coefficient (D ∼) was found to be in the range 10 -13 to 10 -12 cm 2 s -1 for any composition x of Li 2- xMMn 3O 8 (M = Fe, Co) in the range from 0.1 to 1.6 by employing the galvanostatic intermittent titration technique (GITT). AC impedance studies revealed a charge transfer resistance of 260-290 Ω, a double layer capacity of ∼45-70 μF for an electrode area of 6.7 cm 2.