It is not the lithium that burns but the cathode material, there are very much safer alternatives, one well developed technology is
https://en.m.wikipedia.org/wiki/Lith...sphate_battery
There is a 14% power to weight cost BUT increased cycle life and nearly constant discharge voltage. These batteries dont burn!. However like any power source they to hold significant energy. Unlike the other chemistrys these one do not have "thermal runaway" so cell failures dont cascade. Fantastic batteries but unfortunatly currently the subject of multiple licensing litigations !