Structural and Electronic Properties of the Layered LiNi_0.5Mn_0.5O₂ Lithium Battery Material

Computational studies based upon density functional theory (DFT) have been carried out on the Li x Ni 0.5 Mn 0.5 O 2 system, a promising cathode material for rechargeable lithium batteries. Electronic structure calculations suggest that the nominal valence state distribution is given by the formula . Possible Ni−Mn cation ordering schemes in the layered structure have been examined including intralayer and interlayer configurations. The results on lithium deintercalation of Li x Ni 0.5 Mn 0.5 O 2 indicate that the electrochemical behavior is linked to the oxidation of Ni 2+ . Our calculated cell voltage range as a function of lithium content ( x ) is compatible with electrochemical measurements that generally show sloping voltage profiles. The calculated Mn−O bond length shows relative invariance with Li extraction, whereas the Ni−O bond shortens significantly, which accords well with the available structural data.