Metal fluorides (MFx) are one of the most attractive cathode candidates for Li-ion batteries (LIBs) due to their high conversion potentials with large capacities. However, only a limited number of synthetic method, generally involving highly toxic or inaccessible reagents, currently exist, which has made it difficult to produce well-designed nanostructures suitable for cathodes; consequently, harnessing their potential cathodic properties has been a challenge. Herein, we report a new bottom-up synthetic method utilizing ammonium fluoride (NH4F) for the preparation of anhydrous MFx(CuF2, FeF3, and CoF2)/mesoporous carbon(MSU-F-C) nanocomposites, whereby a series of metal precursor nanoparticles pre-confined in mesoporous carbon were readily converted to anhydrous MFx through simple heat treatment with NH4F under solventless conditions. We demonstrate the versatility, less-toxicity, and efficiency of this synthetic method, and, using XRD analysis, propose a mechanism for the reaction. All MFx/MSU-F-C prepared in this study exhibited superior electrochemical performances, through conversion reactions, as the cathode for LIBs. Especially, FeF3/MSU-F-C maintained a capacity of 650 mAh g−1,FeF3 across 50 cycles, which is ~90% of its initial capacity. We expect that this facile synthesis method will trigger further research into the development of various nanostructured MFx for use in energy storage and other applications.