The collective fanon agrees about barrier reacting to the weapon's electrical and/or heat charge (plasma IS ionized particle). This is done to explain why ShenLong cannon is more powerful after it's diffused by microwave radiation, or the fact Gospel's weapon so OP that it BREAKS absolute defense.
But canon didn't specify that, only said that energy weapon do a better job, and that's about it.
EIDT: Either way, Ion sword will be solid blade with a quirk, and that's about it. Unless you channel Marvel or DC and made metal doing impossible stuff by nature, not engineering.