Lithium insertion into the spinel LiFe 5O 8

Abstract

Lithium has been inserted into the spinel LiFe 5O 8 at both ambient and high temperature. At 50 °C two lithium ions per formula unit can be inserted into the structure; the inserted lithium ions displace the tetrahedral ferric ions of the spinel into neighbouring vacant octahedral sites to yield a rocksalt phase Li 3Fe 5O 8. The long-range order of the lithium and iron ions on the B-sites of the A tet[B 2] octX 4 spinel (Fe[Li 0.5Fe 1.5]O 4) is not affected by lithiation. At 400 °C electrochemical insertion of lithium is accompanied by iron extrusion from the oxide lattice. The reaction of two lithium ions per LiFe 5O 8 at this temperature results in a product consisting predominantly of a rocksalt phase of composition Li 2Fe 3O 5 in which the lithium and iron ions are randomly distributed over all the octahedral sites of the structure, and metallic iron.