Combine the sugar, water, mint, and ½ of the lemon peels in a small pot. Bring the mixture to a simmer over medium high heat until the sugar dissolves. Allow to cool.
Mix the simple syrup, vodka, and lemon juice in a large pitcher. Allow it to set up for 3-5 days. But, the longer the limoncello sits the darker in color it will get and deeper the flavor will develop. Strain and serve.