yes, there is some inefficiency (as there is with all energy transfer) in storing that energy, but compared to the inefficiency of ICEs, its a lot better. also, its easier to control emissions from a power plant than it is with millions of individual engines. the biggest problem is the batteries. but there is some promising research into batteries that dont require us to use up all our precious earth metals.

basically, instead of millions of individual combustion reactions. you have one huge combustion reaction where the energy loss due to heat can be controlled on an industrial scale