Crystal structure refinement of Li2FeSiO4 cathode material

Abstract

Recently lithium iron orthosilicate, Li2FeSiO4, has been found to display attractive electrochemical properties when used as cathode material. Because its constituent elements are non-toxic, low-cost and abundant, it is also attractive system from the standpoint of environmental sustainability. Li2FeSiO4 compounds are known to exhibit a rich polymorphism and several crystal structures have been reported in the literature. Due to its complex polymorphism it is still a challenge obtaining a phase pure material. Here we report the properties of pure Li2FeSiO4 obtained by solid-state reaction at 750 °C. It was found that Li2FeSiO4 crystallizes in monoclinic P21/n space group. In this structure one set of LiO4 tetrahedra are arranged in edge sharing pairs with FeO4 tetrahedra, while the other set of LiO4 tetrahedra forms edge sharing pairs with itself. In addition, galvanostatically cycled material was characterized in terms of structural and transport properties.