Lithium insertion into Fe2(MO4)3 frameworks: Comparison of M = W with M = Mo

Abstract Room-temperature lithium insertion into the title framework structures can be represented as Fe 3+ 2 ( Mo 6+ O 4 ) 3 → 2n- BuLi Li 2 Fe 2+ 2 ( Mo 6+ O 4 ) 3 → 6n- BuLi [ Li + 8 Fe 2+ 2 ( Mo 4+ O 4 ) 3 ] Li + 2y Mo 4+ y Fe 2+ 2 O 2+3y + Li + 8-2y Mo 4+ 3−y O 10−3y with 0 Fe 3+ 2 ( W 6+ O 4 ) 3 → 2n- BuLi Li 2 Fe 2+ 2 ( W 6+ O 4 ) 3 → 10n- BuLi [ Li + 12 Fe 0 2 ( W 4+ O 4 ) 3 ]6 Li 2 O +2 Fe +3 WO 2 Electrochemical insertion/extraction is reversible for LixFe2(WO4)3, 0 ≤ x ≤ 2.0, as in the molybdate system, a two-phase region extending over the range 0