Considering water is common and a typically heavy substance, that gives about 89,876,000 MJ/cc. Uranium is about 19x heavier, giving a hard practical upper limi

Considering water is common and a typically heavy substance, that gives about 89,876,000 MJ/cc. Uranium is about 19x heavier, giving a hard practical upper limit (natural occurring) of 1,710,340,280 MJ/cc ... but is much harder to come by and maintain safely. Chemically, seems XeF2 has the upper bound on energy density, but I can't find the energy per volume (which, from molecular structure, looks astoundingly high). ...not that you want pure Fluorine as exhaust...