Insights into manganese and nickel co-doped Li2FeSiO4 cathodes for lithium-ion battery

Abstract

Few studies on two-cations co-doped orthosilicate cathodes have been reported to date. Here, Mn and Ni co-doped Li2Fe0.8-xMn0.2NixSiO4 (x = 0.05 and 0.1) were synthesized using a solid state route. Both Mn and Ni can successfully enter into the Li2FeSiO4 lattice. The X-ray photoelectron spectroscopy (XPS) results show some certain evidence about the participation of foreign Mn and Ni in the charge-discharge reaction. Furthermore, at the conduction band minimum, Ni 3d-orbital contribution can reduce the band gap to 1.13 eV. These improvements can promote the Li+ insertion/de-insertion behavior in the co-doped material; consequently, when x = 0.1, Li2Fe0.7Mn0.2Ni0.1SiO4 shows the initial discharge capacities of 164 mAh g−1 and the corresponding Coulombic efficiency of 87.2%. Even at a rate of 80 mA g−1, the first discharge capacity can reach to 71.2 mAh g−1.