TY - JOUR
T1 - Study of sodium manganese fluorides as positive electrodes for Na-ion batteries
AU - Nava-Avendaño, Jessica
AU - Arroyo-De Dompablo, M. Elena
AU - Frontera, Carlos
AU - Ayllón, José A.
AU - Palacín, M. Rosa
PY - 2015/6/22
Y1 - 2015/6/22
N2 - © 2015 Elsevier B.V. Abstract Na2MnF5 and NaMnF3 were prepared in aqueous media using Mn2O3 and NaMnO4·H2O as Mn precursors and characterized by XRPD, ATR-IR and ICP-OES/ICP-MS. Additionally, a new metastable hydrated oxyfluoride was prepared, with a diffraction pattern (neutron and SXRPD data) consistent with an orthorhombic cell with a = 4.07559 Å, b = 9.04090 Å and c = 6.77290 Å and Cccm space group which yielded NaMnF4 upon dehydration. The feasibility of Na+ deintercalation was experimentally tested in electrochemical cells against sodium metal counter electrodes under different conditions, and also investigated by first principles methods. Experimental results were confronted to blank experiments performed with electrodes containing only carbon black and allowed to conclude that the redox processes observed were not related to active materials but to electrolyte/carbon black reactivity. DFT results point at the electrochemical activity of such compounds taking place at high potential values, in some cases well outside the electrolyte stability window. In the case of NaMnF3, for which he calculated density of states predicts a bang gap of 2.7 eV, its insulating character induces significant cell polarization thus electrochemical activity cannot not practically reached with the available electrolytes.
AB - © 2015 Elsevier B.V. Abstract Na2MnF5 and NaMnF3 were prepared in aqueous media using Mn2O3 and NaMnO4·H2O as Mn precursors and characterized by XRPD, ATR-IR and ICP-OES/ICP-MS. Additionally, a new metastable hydrated oxyfluoride was prepared, with a diffraction pattern (neutron and SXRPD data) consistent with an orthorhombic cell with a = 4.07559 Å, b = 9.04090 Å and c = 6.77290 Å and Cccm space group which yielded NaMnF4 upon dehydration. The feasibility of Na+ deintercalation was experimentally tested in electrochemical cells against sodium metal counter electrodes under different conditions, and also investigated by first principles methods. Experimental results were confronted to blank experiments performed with electrodes containing only carbon black and allowed to conclude that the redox processes observed were not related to active materials but to electrolyte/carbon black reactivity. DFT results point at the electrochemical activity of such compounds taking place at high potential values, in some cases well outside the electrolyte stability window. In the case of NaMnF3, for which he calculated density of states predicts a bang gap of 2.7 eV, its insulating character induces significant cell polarization thus electrochemical activity cannot not practically reached with the available electrolytes.
KW - Na<inf>2</inf>MnF<inf>5</inf>
KW - NaMnF<inf>3</inf>
KW - NaMnF<inf>4</inf>
KW - Positive electrode materials
KW - Sodium batteries
KW - Sodium manganese fluorides
U2 - 10.1016/j.ssi.2015.05.023
DO - 10.1016/j.ssi.2015.05.023
M3 - Article
SN - 0167-2738
VL - 278
SP - 106
EP - 113
JO - Solid State Ionics
JF - Solid State Ionics
M1 - 13680
ER -