Theoretical investigation of Li۲FeSiO۴ as a cathode material for Li-ion batteries: a DFT study

Transition metal lithium orthosilicates are under investigation for their potential use as cathode materials in lithium batteries. Using density functional theory (DFT) calculations, we analyzed the structure and electrochemical behavior of various forms (polymorphs) of Li۲FeSiO۴.In our computational studies, we have found that the Pmn۲۱ polymorph of Li۲FeSiO۴ exhibits superior properties even after the removal of two lithium ions per formula unit.We conclude that the observed shortcomings of Li۲FeSiO۴ as a cathode can be attributed to two mechanisms. Firstly, there is a noticeable switch in the magnetic state during the initial cycles. The subsequent transition, under delithiated conditions, from the Pmn۲۱ or Pmnb polymorphs to the electrochemically weakest P۲۱/n polymorph is the second mechanism that may gradually lead to electrochemical and structural collapse