Electrochemical Reactions of Iron Borates with Lithium: Electrochemical and in Situ Mössbauer and X-ray Absorption Studies

Alejandro Ibarra-Palos , C. Darie (1) , Olivier Proux (2) , J. Hazemann (1) , L. Aldon (3) , C. Jumas (3) , Mathieu Morcrette (4) , P. Strobel (1)

1 Laboratoire de Cristallographie
2 OSUG - Observatoire des Sciences de l'Univers de Grenoble
3 LAMMI - Laboratoire des Agrégats Moléculaires et Matériaux Inorganiques
4 LRCS - Laboratoire réactivité et chimie des solides - UMR CNRS 7314

Upon electrochemical reduction in a lithium cell, crystalline FeBO3 and Fe3BO6 give amorphous compounds, which can be cycled reversibly at low potential (Rowsell, J. Power Sources2001, 97−98, 254). We report here capacities as high as 300 Ah/kg at the 14th cycle. The mechanism of reaction was investigated by step-potential electrochemical spectroscopy and in situ Mössbauer and X-ray absorption spectroscopies on electrochemical cells encapsulated in thin sealed plastic bags. These techniques confirm the reduction mechanism consisting of the early destruction of the crystallized borates and a direct FeIII−Fe0 multiphase reduction on first discharge. On recharge and subsequent cyclings, a reversible redox reaction occurs between Fe0 and FeII/III in an amorphous or nanocrystalline matrix.

Domaines: Instrumentations et Détecteurs [physics.ins-det]

Alejandro Ibarra-Palos, C. Darie, Olivier Proux, J. Hazemann, L. Aldon, et al.. Electrochemical Reactions of Iron Borates with Lithium: Electrochemical and in Situ Mössbauer and X-ray Absorption Studies. Chemistry of Materials, 2002, 14 (3), pp.1166-1173. ⟨10.1021/cm010694q⟩. ⟨hal-02177295⟩