If I'm understanding this correctly, it's not the energy of compression that's being used to store energy, it's the altered chemical bonds. In the same way you can take graphite and pump energy into its bonds to make diamond. If you compress different compounds their properties sometimes change radically, even when back at normal pressure. Now since this is a relatively new area of experimentation, the scientists probably only have a vague idea what they can make. The problem is those who have the money want 'practical results' as opposed to interesting results. Hence the 'possible' application list.