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The thermodynamic stability and lithiated/delithiated potentials of LiFexMn1-xPO4 were studied with density functional theorical calculations.The results show that the formation free energy of the LiFexMn1-xPO4 solid solution is slightly higher than that of the phase-separated mixture of LiFePO4 and LiMnPO4,and the two forms may co-exist in the actual LiFexMn1-xPO4 materials.The calculation manifests that the lithiated/delithiated potentials of LiFexMn1-xPO4 solid solutions vary via the Mn/Fe ratio and the spatial arrangements of the transition metal ions,and the result is used to explain the shape of capacity-voltage curves.Experimentally,we have synthesized the LiFexMn1-xPO4 materials by solid-phase reaction method.The existence of the LiFexMn1-xPO4 solid solution is thought to be responsible for the appearance of additional capacity-voltage plateau observed in the experiment.