The cathode-active materials, Li1+yMxMn2-xO4 (M = Al, Co, Ni, Zn, y = 0.02, x = 0.02) powder, were synthesized by sol-gel method using LiOH, Mn(NO3)(2) as the starting materials, citric acid as a carrier and Al(NO3)(3)center dot 9H(2)O or Co(NO3)(2)c
