Peel the lemons, avoiding the white pith. Place the peels in a large jar and pour the vodka over them. Seal the jar and let it sit for 7 days at room temperature.
After 7 days, strain the lemon peels from the vodka using a fine mesh strainer. Set the infused vodka aside.
In a saucepan, combine the water and sugar. Heat until the sugar dissolves completely. Let the syrup cool to room temperature.
Mix the cooled syrup with the infused vodka. Pour the limoncello into bottles and seal. Store in the freezer until ready to serve.