⁵⁷Fe Mössbauer Spectroscopy and Electron Microscopy Study of Metal Extraction from CuFe₂O₄ Electrodes in Lithium Cells

Abstract

Active CuFe(2)O(4) electrode materials for lithium cells are produced by thermal decomposition of a citrate precursor. The precipitation of the metal citrate is carried out by a freeze-drying procedure. A tetragonally distorted spinel structure is prepared by the decomposition of a citrate precursor. Samples free of impurities are obtained depending on the annealing temperature. The sample heated at 800 degrees C performed at 470 mAh g(-1) after 50 cycles. Electron microscopy is used as the ultimate technique to monitor the morphological changes upon the reversible conversion reaction. Detachment of metallic particles from the starting material, the formation of a polymeric organic film, and the subsequent removal on charging are discussed as determining factors in the electrochemical behaviour of this oxide as an electrode versus lithium. The growth of metallic iron aggregates is inferred from the (57)Fe Mössbauer spectra.

Unfolding the role of iron in Li-ion conversion electrode materials by 57Fe Mössbauer spectroscopy

“…Initially, the unexpected reversibility of the conversion process was reported for binary first-row transition metal oxides, while subsequently it was extended to mixed oxides [5][6][7][8][9][10][11][12]. More recently, we were able to extend the reversible conversion to transition metal oxysalts, such as oxalates and carbonates, in which new mechanisms of charge storage such as double layer capacitive effects were detected [13][14][15][16][17].…”

Beyond Intercalation‐Based Li‐Ion Batteries: The State of the Art and Challenges of Electrode Materials Reacting Through Conversion Reactions

“…Several oxide systems containing two transition metals and crystallizing in a spinel structure have been studied to date, namely, MMn 2 O 4 (M = Co [ 43 ] ), MFe 2 O 4 (M = Co, [ 282 , 289,290 ] Ni, [ 290 , 291 ] Cu [ 292 ] ), and MCo 2 O 4 (M = Mn, [ 43 ] Fe, [ 282 , 293 ] Ni, [ 294 , 295 ] Cu [ 296 ] ), which show an overall performance that is similar to that of simple oxides. It is interesting to note that in all the cases reported so far the signature of their reduction is, systematically, a single plateau instead of the two that could be expected from the different potentials at which the individual oxides react, suggesting that the occurrence of mixed states at the Fermi level results in simultaneous reduction to the metallic state.…”

Nanostructured MgFe2O4 as anode materials for lithium-ion batteries

“…Firstly, Chen and Greenblatt [8] have reported that the transition metal ferrites with spinel structure used for cathode materials for Li-ion batteries. Spinel-type ferrite anodes, like NiFe 2 O 4 [9], CuFe 2 O 4 [10], CoFe 2 O 4 [11], ZnFe 2 O 4 [2] and CaFe 2 O 4 [12] have gained in significance due to their high specific capacities and simplistic synthesis. The higher capacity observed for the latter materials (i.e.…”