Prediction of feasibility of Li and Fe doped natural olivine Mg2SiO4 for Li ion battery applications using Density Functional Theory

Abstract

Li and Fe doped olivine Mg2SiO4 was studied using density functional theory. It was found that Li atom prefers to occupy M1 site to M2 site of Pbnm space group symmetry. Also, probability of Fe occupying M1 site over M2 site was also investigated and was observed, like Li, Fe also preferably occupies M1 site to M2 site. Two samples like Li2RLi2iMg6Si4O16 (R stands for replacement and i stands for interstitial site) and Li2RLi2iFe1Mg5Si4O16 were formulated by inserting Li at replacement site and interstitial site to maintain charge neutrality while Fe atom was inserted at replacement site. The probability of oxygen evolution during charging was minimized by incorporating redox active Fe+2 ion in Li doped Mg2SiO4. It was found that extraction of all the Li ions from Li2RLi2iMg6Si4O16 and Li2RLi2iFe1Mg5Si4O16 could be done at 3.68 V and 3.29 V with specific capacities of 198 mAh/g and 187 mAh/g respectively.