Lithium Hexastannate: A Potential Material for Energy Storage

Abstract

The prediction of a new lithium compound, Li2Sn6O13, is made from a combined first‐principles and classical force‐field approach. The electronic, structural, and mechanical properties of monoclinic Li2SnO3, Li2Ti6O13, and Li2Sn6O13 are explored. The calculated results for the equilibrium lattice parameters are in agreement with the available experimental data. The thermodynamic stabilities of Li2Ti6O13 and Li2Sn6O13 are evaluated. Both compounds are demonstrated to be thermodynamically stable with standard molar formation enthalpies of −5553 and −6740 kJ mol−1, respectively. Reaction energies for delithiation of 6.41 and 6.90 eV atom−1 are also determined for Li2Sn6O13 and Li2Ti6O13, respectively. The predicted voltage of Li insertion/extraction process per Li+/Li is 1.6 V for Li2Sn6O13, comparable to its isostructural counterpart Li2Ti6O13. Electronic band structure calculations indicate the insulating character of Li2SnO3 with an indirect band gap of 4.4 eV, whereas both Li2Ti6O13 and Li2Sn6O13 appear to be semiconductor compounds with band gaps of 3.1 and 3.0 eV, respectivley. The energy barriers for Li+ migration amount to ≈0.5 eV for both materials. Elastic stiffness coefficients and bulk, shear and Young's moduli were also calculated. The Li2Sn6O13 derivative is mechanically stable and can be predicted to be a brittle compound that is more resistant to volume change than Li2Ti6O13. If the Li2Sn6O13 compound could experimentally be prepared by using ion exchange, it could potentially be an efficient material for anodes in lithium‐ion batteries.