Defect, transport, and dopant properties of andradite garnet Ca3Fe2Si3O12

Abstract

There is growing interest to discover suitable calcium containing oxides that can be used as electrode materials in calcium ion batteries. A comprehensive computational investigation of ionic defects and Ca-ion diffusion in Ca-bearing oxide materials at the atomic level is important so as to predict their suitability for use in Ca-ion batteries. In this study, we apply atomistic simulation techniques to examine the energetics of defects, dopants, and Ca-ion diffusion in Ca3Fe2Si3O12. The calculations suggest that the Ca/Fe anti-site defect is the most favorable intrinsic defect causing such significant disorder, which would be sensitive to synthesis conditions. Diffusion of Ca2+ ions within Ca3Fe2Si3O12 is three-dimensional, with the activation energy of migration of 2.63 eV inferring slow ionic conductivity. The most favorable isovalent defects are Mn2+, Sc3+, and Ge4+ on Ca, Fe, and Si, respectively, for this process. The formation of extra calcium was considered to increase the capacity and diffusion of Ca in this material. It is found that Al3+ and Mn2+ are the candidate dopants on the Si and Fe sites, respectively, for this process and there is a reduction observed in the activation energies. The electronic structures of favorable dopant configurations are discussed using density functional theory simulations.

Defects, diffusion and dopants in the ceramic mineral “Lime- Feldspar”

“…Atomistic simulations based on the classical pair potentials can provide useful information on diffusion pathways and activation energies as this information is generally difficult from the experiment. The present methodology has been successfully applied to various ionic materials to calculate migration pathways together with activation energies [11,12,25,26]. For example, there is an excellent agreement between calculated and experimentally determined Li-ion diffusion pathway in LiFePO 4 [43,44].…”

“…Furthermore, calcium-bearing minerals are of interest in the development of electrode materials for rechargeable Ca-ion batteries [9]. Though CaAl 2 Si 2 O 8 was not studied for this purpose yet, theoretical investigation on other Ca-based minerals is available [10][11][12].…”

Defects and Calcium Diffusion in Wollastonite

“…In general, Ca ion diffusion in Ca-bearing oxide materials is expected to be sluggish due to its ions with double positive charge. In previous theoretical simulations based on the DFT and classical pair potentials, it was shown that activation energies of Ca ion diffusion in Ca-based minerals are high, confirming the slow diffusion [49][50][51][52].…”

Kinetics of Ions in Post-Lithium Batteries

“…Magnesium and calcium are interesting alternative ions to Li, which have the advantage of being divalent [17,45,[106][107][108][109][110][111][112][113][114][115][116][117][118][119]. Here we will consider Mg as a potential divalent ion to substitute Li as the diffusion of Ca ions in crystal lattices is plagued by its larger ionic radius.…”