LiMn(23/24)Mg(1/24)PO4.LiAlO2/C is synthesized by a co-hydrothermal method in water/PEG system using Li2CO3, AAO and Mn1-xMgxPO4 as raw material. The electronic structure and micromorphology of multi-component compound LiMn1-xMgxPO4/C (x = 0, 1/24, 1/12, 1/6) and nano-hybrid LiMn(23/24)Mg(1/24)PO4.LiAlO2/C cathode materials are studied by first-principles calculation and experimental research including XRD, SEM, TEM. The calculated band gap of LiMn(23/24)Mg(1/24)PO4.LiAlO2/C is 2.296 eV, which is lower than other percentages Mg2+ doping samples. Electrochemical tests exhibit LiMn(23/24)Mg(1/24)PO4.LiAlO2/C has better cycling performance and rate capability than other contents Mg2+ doping samples with the discharge capacity of 143.5 mAh/g, 141.5 mAh/g, 139.2 mAh/g and 136.3 mAh/g at 0.05C, 0.1C, 0.5C and 1C in order. After compositing and preparation of LiMn(23/24)Mg(1/24)PO4.LiAlO2/C composite material by co-hydrothermal route, the initial discharge capacity reaches up to 151.8 mAh/g, which suggests that co-modified with Mg2+ doping and LiAlO2 compositing material can improve the electronic conductivity of LiMnPO4/C by facilitating the lithium ion diffusion rate in the interior of the materials. (C) 2016 Elsevier B.V. All rights reserved.