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β‑NaMnO2: A High-Performance Cathode for Sodium-Ion Batteries
journal contribution
posted on 2014-12-10, 00:00 authored by Juliette Billaud, Raphaële
J. Clément, A. Robert Armstrong, Jesús Canales-Vázquez, Patrick Rozier, Clare P. Grey, Peter G. BruceThere is much interest in Na-ion
batteries for grid storage because
of the lower projected cost compared with Li-ion. Identifying Earth-abundant,
low-cost, and safe materials that can function as intercalation cathodes
in Na-ion batteries is an important challenge facing the field. Here
we investigate such a material, β-NaMnO2, with a
different structure from that of NaMnO2 polymorphs and
other compounds studied extensively in the past. It exhibits a high
capacity (of ca. 190 mA h g–1 at a rate of C/20),
along with a good rate capability (142 mA h g–1 at
a rate of 2C) and a good capacity retention (100 mA h g–1after 100 Na extraction/insertion cycles at a rate of 2C). Powder
XRD, HRTEM, and 23Na NMR studies revealed that this compound
exhibits a complex structure consisting of intergrown regions of α-NaMnO2 and β-NaMnO2 domains. The collapse of the
long-range structure at low Na content is expected to compromise the
reversibility of the Na extraction and insertion processes occurring
upon charge and discharge of the cathode material, respectively. Yet
stable, reproducible, and reversible Na intercalation is observed.