Understanding structural stability of monoclinic LiMnO2 and NaMnO2 upon de-intercalation. Issue 26 (17th June 2016)

• Record Type: Journal Article
• Authors: Tian, Meng; Gao, Yurui; Wang, Zhaoxiang; Chen, Liquan
• Is Part Of: Physical chemistry chemical physics. Volume 18:Issue 26(2016)
• Page Start: 17345
• Page End: 17350
• Publication Date: 2016-06-17
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp02019d
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : First-principles calculations demonstrate that the distinction between LiMnO2 and NaMnO2 in structural stability upon de-intercalation is due to their difference in charge distribution and the strength of the Mn–O bonding. Abstract : Although many strategies for Li-ion batteries have been successfully transplanted in Na-ion batteries, distinctions between these two kinds of secondary batteries are still clear. For example, monoclinic-NaMnO2 demonstrates high structural stability during charging and discharging, but its iso-structured LiMnO2 transforms to a spinel upon de-lithiation and the specific capacity fades quickly with cycling. In this work, first-principles calculations were carried out to have a better understanding of their difference in structural stability upon de-intercalation. Our studies show that the Mn-ions migrate into the Li layer of LiMnO2 via an interstitial tetrahedral O atom when a triple-vacancy of the Li-ion is produced. This process follows a double-vacancy mechanism and results in blocking of the diffusion of other Li-ions. In contrast, it is very difficult for the Mn-ions to migrate into the Na layer in NaMnO2 even when triple-vacancies are generated. The drastic differences between LiMnO2 and NaMnO2 in charge distribution and in the length of the Mn–O bond are believed to be responsible for the Mn-ion migration in them. These findings provide revelations for understanding the de-intercalation behaviors of electrode materials for Li- and Na-ion batteries as well as insights into the structural stability of LiMnO2 vs. NaMnO2 upon alkali metal ion de-intercalation.