I think you're describing methane, the primary component of natural gas. Methane production from electricity is ~60% efficient, according to a 6.3MW plant that Audi and SolarFuel cobuilt in Germany. And then converting methane into electricity or movement will only be ~50% efficient, for total roundtrip efficiency of 30%. That may make sense for electrical storage if the price swings from low to high are 3x or more.