The electrochemical properties of LiMn2O4 and LiAlxMn2-xO4 (where x = 0.125, 0.25, 0.375) were studied for variations in lithium-ion diffusion, The largest diffusion coefficient was shown for the undoped material, DLi+ = 2.7 X 10(-11) cm(2)/s. As the level of dopant was increased a concurrent decrease in diffusion coefficient is shown. This effect was attributed to a decrease in the lattice parameter caused by dopant addition.