Revealing and suppressing surface Mn(II) formation of Na0.44MnO2 electrodes for Na-ion batteries

Revealing and suppressing surface Mn(II) formation of Na0.44MnO2 electrodes for Na-ion batteries

TitleRevealing and suppressing surface Mn(II) formation of Na0.44MnO2 electrodes for Na-ion batteries
Publication TypeJournal Article
Year of Publication2015
AuthorsRuimin Qiao, Kehua Dai, Jing Mao, Tsu-Chien Weng, Dimosthenis Sokaras, Dennis Nordlund, Xiangyun Song, Vincent S Battaglia, Zahid Hussain, Gao Liu, Wanli Yang
JournalNano Energy
Volume16
Pagination186 - 195
Date Published01/2015
ISSN22112855
Abstract

Understanding and controlling the surface activities of electrode materials is critical for optimizing the battery performance, especially for nanoparticles with high surface area. Na0.44MnO2 is a promising positive electrode material for large-scale sodium-ion batteries. However, its application in grid-scale energy storage requires improvements in cycling stability at high rate. Here, we performed comprehensive surface-sensitive soft x-ray spectroscopic studies of the Na0.44MnO2 electrode. We are able to quantitatively determine the Mn evolution upon the potentials and cycle numbers. We reveal the Mn2+ formation on the top 10nm of Na0.44MnO2 particles when the electrochemical potential is below 2.6V, which does not occur in the bulk. A portion of the surface Mn2+ compounds become electrochemically inactive after extended cycles, contributing to the capacity fading. Based on the spectroscopic discoveries, we demonstrate that cycling Na0.44MnO2 above 3V could efficiently suppress the Mn2+ formation. 

DOI10.1016/j.nanoen.2015.06.024
Short TitleNano Energy
Refereed DesignationRefereed