Atomic structure and electrochemical potential of Li1+xV3O8

The atomic configurations and total energies of both monoclinic phases of Li1+xV3O8, a candidate electrode material in rechargeable Li batteries, are calculated as a function of x within local-density-functional theory, using the plane-wave pseudopotential method. The predicted structures at the most standard compositions, 1 + x = 1.2 and 1 + x = 4, agree closely with x-ray-diffraction measurements of atomic structure. As Li is inserted into the low-Li compound, Li(2) is half filled and then S-t(3) is half filled, where the Li sites are labeled as in de Picciotto et nl. This is followed by the onset of a two-phase region. Calculations of the electrochemical potential as a function of lithiation are in excellent overall agreement with experiment. [S0163-1829(99)00330-6].