No fully electric car has won the 24 Hours of Le Mans overall; the race has been won by internal-combustion and hybrid prototypes.
The famous endurance event has included electrically assisted racing cars, but hybrid systems combine electric motors with internal-combustion engines. Audi’s R18 e-tron quattro, Porsche’s 919 Hybrid, and Toyota’s TS050 Hybrid all used hybrid powertrains rather than being battery-electric vehicles.
This distinction matters because “electric” is often used loosely for any car with an electric motor. A battery-electric vehicle stores its driving energy mainly in a rechargeable battery and has no combustion engine. A hybrid can recover energy electrically while still relying on fuel and an engine.
Le Mans regulations have evolved to encourage efficiency and new powertrain technology. Fully electric prototypes may appear in future forms, but a hybrid victory is not the same as an all-electric overall win. The correct answer to the question as phrased is therefore none.