Effect of Ni Content on Anionic Redox Activity in Ru-Containing Li-Rich Cathode Material. Issue 7 (28th July 2021)

• Record Type: Journal Article
• Authors: Hu, Kai; Zheng, Feng; Zhu, Zi-Zhong; Wu, Shunqing
• Is Part Of: Journal of the Electrochemical Society. Volume 168:Issue 7(2021)
• Publication Date: 2021-07-28
• Subjects: Batteries Li-ion -- Energy Storage -- Theory and Modelling -- Solid-State Ionics; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/1945-7111/ac15ba
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : The high energy density of Li-rich layered oxides is associated with anionic redox reaction as it can deliver extra capacity. Herein, using first-principles calculations, we do a contrastive study of anionic redox mechanism in two Li-rich layered oxides, i.e., Li1.167 Ni0.167 Ru0.667 O2 (Li7 NiRu4 O12 ) and Li1.167 Ni0.333 Ru0.5 O2 (Li7 Ni2 Ru3 O12 ), which are marked as LNR4 O and LN2 R3 O, respectively. Our results reveal that the anionic oxidation potential is observed at around 3.95 V in LN2 R3 O, while, at around 4.31 V, oxygen oxidation reaction can only be achieved in LNR4 O. The difference of anionic redox activity can be attributed to the different local oxygen environments between these two materials. Due to the relatively higher content of Ni in the LN2 R3 O, there are two additional local environments around oxygen (O-Li4 NiRu and O-Li3 Ni2 Ru). Lattice oxygen is more easily oxidized in these two oxygen configurations, which explains the lower anionic oxidation potential in the LN2 R3 O. In addition, despite not containing linear Li-O-Li configuration, oxygen in the O-Li3 Ni2 Ru can still have anionic redox activity upon delithiation, which indicates that the anionic redox may not be only determined by linear Li-O-Li configuration. Our finding broadens the fundamental understanding of anionic redox mechanism in Li-rich oxides.