A novel method to produce LiMn2O4/carbon nanocomposites in a rapid, one-step and industrially scalable process is presented. A flame spray and a diffusion flame are combined to continuously produce LiMn2O4 nanoparticles and carbon black, respectively. Powder carbon content is varied by adjusting the diffusion flame conditions. The powders are characterized by X-ray diffraction (XRD), transmission electron microscopy, cyclic voltammetry and galvanostatic cycling for a range of current densities. These LiMn2O4/carbon nanocomposites retain over 80% of their initial galvanostatic discharge capacity for current densities ranging from 5 to 50C-rates, significantly better than pure LiMn2O4 nanoparticles mixed conventionally with commercial carbon blacks. The improved performance of the LiMn2O4/carbon nanocomposites is attributed to the carbon particle contact and/or film coating of the freshly-made LiMn2O4 nanoparticles. This additional well-distributed carbon provides an electrically conductive network that induces a more homogeneous charge transfer throughout the electrode. The suitability of these nanocomposites as a hybrid material is discussed by considering the layout of a thin-layer lithium-ion battery containing these flame-made nanocomposites as positive electrode and LiC6 as negative electrode. The battery’s specific energy is calculated to be 78Whkg−1 (50C-rate) based on the results of lithium-ion insertion capacity experiments and reasonable engineering assumptions on the lithium-ion battery design.