Extremely Pure Mg 2 FeH 6 as a Negative Electrode for Lithium Batteries

Sergio Brutti, Luca Farina, Francesco Trequattrini, Oriele Palumbo, Priscilla Reale, Laura Silvestri, Stefania Panero and Annalisa Paolone
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Sergio Brutti: Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Roma, Italy
Luca Farina: Dipartimento di Chimica, Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Roma, Italy
Francesco Trequattrini: Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Roma, Italy
Oriele Palumbo: Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Roma, Italy
Priscilla Reale: ENEA-Centro Ricerche Casaccia, via Anguillarese 301, 00123 Roma, Italy
Laura Silvestri: Dipartimento di Chimica, Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Roma, Italy
Stefania Panero: Dipartimento di Chimica, Sapienza Università di Roma, Piazzale A. Moro 5, 00185 Roma, Italy
Annalisa Paolone: Consiglio Nazionale delle Ricerche, Istituto dei Sistemi Complessi, U.O.S. La Sapienza, Piazzale A. Moro 5, 00185 Roma, Italy

Energies, 2018, vol. 11, issue 8, 1-14

Abstract: Nanocrystalline samples of Mg-Fe-H were synthesized by mixing of MgH 2 and Fe in a 2:1 molar ratio by hand grinding (MIX) or by reactive ball milling (RBM) in a high-pressure vial. Hydrogenation procedures were performed at various temperatures in order to promote the full conversion to Mg 2 FeH 6 . Pure Mg 2 FeH 6 was obtained only for the RBM material cycled at 485 °C. This extremely pure Mg 2 FeH 6 sample was investigated as an anode for lithium batteries. The reversible electrochemical lithium incorporation and de-incorporation reactions were analyzed in view of thermodynamic evaluations, potentiodynamic cycling with galvanostatic acceleration (PCGA), and ex situ X-ray Diffraction (XRD) tests. The Mg 2 FeH 6 phase underwent a conversion reaction; the Mg metal produced in this reaction was alloyed upon further reduction. The back conversion reaction in a lithium cell was here demonstrated for the first time in a stoichiometric extremely pure Mg 2 FeH 6 phase: the reversibility of the overall conversion process was only partial with an overall coulombic yield of 17% under quasi-thermodynamic control. Ex situ XRD analysis highlighted that the material after a full discharge/charge in a lithium cell was strongly amorphized. Under galvanostatic cycling at C/20, C/5 and 1 C, the Mg 2 FeH 6 electrodes were able to supply a reversible capacity with increasing coulombic efficiency and decreasing specific capacity as the current rate increased.

Keywords: Mg 2 FeH 6; reactive ball milling; high temperature hydrogenation; pressure-composition isotherms; discharge capacity (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
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