What is the maximum electrochemical Li insertion capacity in anatase? Insights from Density Functional Theory

We present a detailed analysis of stability and voltages of Li insertion in anatase using screened-exchange hybrid DFT calculations. Li insertion is studied for a range of compositions in Li_xTiO₂ with 0⩽x⩽1. Our calculations indicate that while tetragonal LiTiO₂ exhibits a smaller binding energy than the orthorhombic symmetry, both are actually stable compositions with respect to pure Li metal and anatase. We show that although the orthorhombic symmetry can be maintained to achieve the theoretical maximum capacity of LiTiO₂, in this situation, the electrode will undergo a large volume expansion that will affect the cycling performance of the electrode. On the other hand, if the tetragonal symmetry is maintained in the experiment, only capacities of about x=0.5 will be achieved.