Insight into C, Ge and Sn substitution on structural and electronic properties of Li2FeSiO4: Spin density functional theory

Abstract

Abstract Li2FeSiO4 is the significant alternative cathode material for the further Li-ion batteries because of its high theoretical capacity. On the basis of spin density functional calculation, this manuscript comparatively studies the structural and electronic properties of Li2FeSiO4 with Si substituted by C, Ge and Sn atom using the Perdew-Burke-Ernzerhof (PBE) version of the generalized gradient approximation (GGA). These dopants significantly change the lattice parameters and corresponding volumes. The band gaps are reduced in the presence of the dopants, signifying the improvement of electro-conductive properties. Total and partial density of states establish that the impurity states induced by the modified atom are presented adjacent to the edge of the conduction band. As the results of Mulliken Population Investigation, the ionic character of Li-O pair is reduced in the presence of the dopants, indicating that lithium ion can loose and move easily. Interestingly, Ge and Sn doping in Li2FeSiO4 can improve the electronic conductivity because of volumetric expansion, narrow band gap and reduced ionic bond. Finally, I expect that the computational results elucidate the nature of doping in Li2FeSiO4 and are supportive for understanding the enhancement mechanism of Li2FeSiO4 and other cathode materials.