|Title||Revealing and suppressing surface Mn(II) formation of Na0.44MnO2 electrodes for Na-ion batteries|
|Publication Type||Journal Article|
|Year of Publication||2015|
|Authors||Ruimin Qiao, Kehua Dai, Jing Mao, Tsu-Chien Weng, Dimosthenis Sokaras, Dennis Nordlund, Xiangyun Song, Vincent S Battaglia, Zahid Hussain, Gao Liu, Wanli Yang|
|Pagination||186 - 195|
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.
|Short Title||Nano Energy|