High voltage Mg-doped Na0.67Ni0.3-xMgxMn0.7O2 (x = 0.05, 0.1) Na-ion cathodes with enhanced stability and rate capability

Gurpreet Singh, Nuria Tapia-Ruiz, Juan Miguel Lopez Del Amo, Urmimala Maitra, James W. Somerville, A. Robert Armstrong, Jaione Martinez de Ilarduya, Teófilo Rojo*, Peter G. Bruce

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

242 Citations (Scopus)
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Abstract

Magnesium substituted P2-structure Na0.67Ni0.3Mn0.7O2 materials have been prepared by a facile solid-state method and investigated as cathodes in sodium-ion batteries. The Mg-doped materials described here were characterized by X-ray diffraction (XRD), 23Na solid-state nuclear magnetic resonance (SS-NMR), and scanning electron microscopy (SEM). The electrochemical performance of the samples was tested in half cells vs Na metal at room temperature. The Mg-doped materials operate at a high average voltage of ca. 3.3 V vs Na/Na+ delivering specific capacities of ∼120 mAh g-1, which remain stable up to 50 cycles. Mg doping suppresses the well-known P2-O2 phase transition observed in the undoped composition by stabilizing the reversible OP4 phase during charging (during Na removal). GITT measurements showed that the Na-ion mobility is improved by 2 orders of magnitude with respect to the parent P2-Na0.67Ni0.3Mn0.7O2 material. The fast Na-ion mobility may be the cause of the enhanced rate performance.

Original languageEnglish
Pages (from-to)5087-5094
Number of pages8
JournalChemistry of Materials
Volume28
Issue number14
Early online date27 Jun 2016
DOIs
Publication statusPublished - 26 Jul 2016

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