It's not solid state,just non mechanical, lithium batteries do undergo a chemical and toacertain degree physical state change as ions move and covert compounds from one to another. True solid state would use so called "supper caps", which provide physical spaces for electrons to rest, until discharged, with at present no swelling or physical movement,though swelling might become apparent with high enough capacities, which on consideration seems like it could come with a whole new way for things to go suddenly and drasticaly wrong, where something goes from a solid to a completly disasociated plasma instantly. nothing that will surprise an experienced linesman as initialy it would probable sound alot like the insulation starting to break down just before something carrying a lot of current at very high voltages makes just befor it finds ground