Lithium Hexastannate: A Potential Material for Energy Storage

Abstract

The prediction of a new lithium compound, Li 2 Sn 6 O 13 , is made from a combined first‐principles and classical force‐field approach. The electronic, structural, and mechanical properties of monoclinic Li 2 SnO 3 , Li 2 Ti 6 O 13 , and Li 2 Sn 6 O 13 are explored. The calculated results for the equilibrium lattice parameters are in agreement with the available experimental data. The thermodynamic stabilities of Li 2 Ti 6 O 13 and Li 2 Sn 6 O 13 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 Li 2 Sn 6 O 13 and Li 2 Ti 6 O 13 , respectively. The predicted voltage of Li insertion/extraction process per Li + /Li is 1.6 V for Li 2 Sn 6 O 13 , comparable to its isostructural counterpart Li 2 Ti 6 O 13 . Electronic band structure calculations indicate the insulating character of Li 2 SnO 3 with an indirect band gap of 4.4 eV, whereas both Li 2 Ti 6 O 13 and Li 2 Sn 6 O 13 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 Li 2 Sn 6 O 13 derivative is mechanically stable and can be predicted to be a brittle compound that is more resistant to volume change than Li 2 Ti 6 O 13 . If the Li 2 Sn 6 O 13 compound could experimentally be prepared by using ion exchange, it could potentially be an efficient material for anodes in lithium‐ion batteries.