Lithium insertion into Fe 2( MO 4) 3 frameworks: Comparison of M = W with M = Mo
Abstract
Room-temperature lithium insertion into the title framework structures can be represented as Fe3+2( Mo6+O4) 3limit→2n- BuLiLi2Fe2+2( Mo6+O4) 3limit→6n- BuLi[ Li+8Fe2+2( Mo4+O4) 3] Li+2yMo4+yFe2+2O2+3y+ Li+8-2yMo4+3-yO10-3y with 0 < y < 1 and Fe3+2( W6+O4) 3limit→2n- BuLiLi2Fe2+2( W6+O4) 3limit→10n- BuLi[ Li+12Fe02( W4+O4) 3]6 Li2O+2 Fe+3 WO2 Electrochemical insertion/extraction is reversible for Li xFe 2(WO 4) 3, 0 ≤ x ≤ 2.0, as in the molybdate system, a two-phase region extending over the range 0 < x ≤ 1.7. Lithium insertion suppresses the ferroelastic deformation of the unlithiated framework, but is otherwise topotactic for 0 ≤ x ≤ 2.0. Chemical delithiation to x ≈ 0.7 is possible for the two-phase product [Li 8Fe 2(MoO 4) 3]. The Li 2Fe 2( MO 4) 3 orthorhombic ( Pbcn) phases are metastable; they transform to a stable orthorhombic ( Pnma) structure at 537 K for M = Mo, 579 K for M = W. Li 2Fe 2(WO 4) 3 disproportionates to FeWO 4 and Li 2WO 4 above 723 K.
- Publication:
-
Journal of Solid State Chemistry France
- Pub Date:
- December 1987
- DOI:
- 10.1016/0022-4596(87)90242-8
- Bibcode:
- 1987JSSCh..71..349M