Nano-material synthesis (here: LiMn₂O₄) carried out in the presence of graphene nano-sheets is shown using a crystal shape algorithm to be preferentially oriented along the thermodynamically stable (400) direction, indicating that graphene controls the synthesis through a thermo-dynamical step. Electrochemical studies show that the cathode material with preferred orientation along the (400) direction possesses superior electrochemical properties in general and much better rate capability in particular.