A LiMnPO4-LiMn2O4 (LMP-LMO) nanocomposite cathode is synthesized by a one-step polyol-assisted pyro-synthesis followed by mild annealing for rechargeable lithium-ion batteries. The LMP-LMO cathode delivered an initial discharge capacity of 142 mA h g(-1) and also maintains about 90% capacity retention for over 50 electrochemical cycles.