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Synthesis and Electrochemical Activity of Some Na(Li)‐Rich Ruthenium Oxides with the Feasibility to Stabilize Ru 6+
Author(s) -
Otoyama Misae,
Jacquet Quentin,
Iadecola Antonella,
Saubanère Matthieu,
Rousse Gwenaëlle,
Tarascon JeanMarie
Publication year - 2019
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201803674
Subject(s) - electrochemistry , lithium (medication) , redox , cationic polymerization , alkali metal , ruthenium , materials science , density functional theory , oxidation state , ion , inorganic chemistry , cathode , chemistry , metal , electrode , catalysis , computational chemistry , medicine , biochemistry , organic chemistry , polymer chemistry , metallurgy , endocrinology
The capacity of Li‐ion cathode materials has recently been greatly improved by the feasibility to trigger both cationic and anionic redox reactions within the same material. This concept has rapidly been implemented to Na‐ion batteries to boost their energy density. The electrochemical properties of Na 3 RuO 4 with Li 3 RuO 4 are reported and compared herein. Strikingly, it is found that 3 Na can be extracted from Na 3 RuO 4 with the charge compensation mechanism enlisting first the oxidation of Ru 5+ to Ru 6+ , leading to Na 2 RuO 4 , and then the oxidation of oxygen during the rest of the charge. This drastically contrasts with the behavior of the Li counterpart since Ru never reaches that high oxidation state during lithium removal. By comparing the phase diagrams of A x RuO 4 (A being Li, Na, or K) together with density functional theory calculations, this finding is rationalized and it is demonstrated that this difference is mainly rooted in the size of the alkali cation. The bigger the alkali, the lower the coordination of Ru will be, stabilized by the same higher oxidation states. This work highlights the difference between Li and Na materials toward anionic redox and suggests the unusual coexistence of Ru 6+ and (O 2 ) n − , hence setting new challenges to theoreticians and opening opportunities for materials design.