LAUSR

Abstract The phase stability of the Li 2 MnSiO 4 during Li insertion/extraction, is a key requirement for acceptable cyclability and practical application as a cathode material for lithium batteries. Here we present first-principles calculations used to study the phase stability of Mg substituted Li 2 MnSiO 4 . The 137 structures of Li 2 Mn 1−x Mg x SiO 4 (x = 0.25–0.50) were calculated based on 5 known polymorphs of Li 2 MnSiO 4 . Using three different functionals (PBE, PW91 and PBEsol), it is shown that the total-energy vs. distance between layers in the layered Pmn 2 1 curve has a clear minimum and does not demonstrate the exfoliation of layers found previously. The amorphlization of Li 2 MnSiO 4 is explained by high value of energy above Hull of its fully delithiated form. Crystal orbital Hamiltonian populations (COHP) revealed that the strength of Mn O and Si O bonds unchanged during the substitution with Mg, thus eliminating the concern about the safety. The pure Li 2 MnSiO 4 in the P 2 1 / n form was suggested as the most stable upon cycling. In the Mg substituted Li 2−x MnSiO 4 case, the Mg substitution is more beneficial for x in the range (0.0–2.0) than in the range (0.0–1.0). The increase in the performance for the x = 0.0–1.0 region, can be explained by the small particle size and the uniformity of nanoparticles distribution rather than the enhancement of the thermodynamic stability.