Nonequilibrium Structural Dynamics of Nanoparticles in LiNi1/2Mn3/2O4 Cathode under Operando Conditions

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• 作者：Andrej Singer ; Andrew Ulvestad ; Hyung-Man Cho ; Jong Woo Kim ; J枚rg Maser ; Ross Harder ; Ying Shirley Meng ; Oleg G. Shpyrko
• 刊名：Nano Letters
• 出版年：2014
• 出版时间：September 10, 2014
• 年：2014
• 卷：14
• 期：9
• 页码：5295-5300
• 全文大小：356K
• ISSN：1530-6992

文摘

We study nonequilibrium structural dynamics in LiNi_1/2Mn_3/2O₄ spinel cathode material during fast charge/discharge under operando conditions using coherent X-rays. Our in situ measurements reveal a hysteretic behavior of the structure upon cycling and we directly observe the interplay between different transformation mechanisms: solid solution and two-phase reactions at the single nanoparticle level. For high lithium concentrations solid solution is observed upon both charge and discharge. For low lithium concentration, we find concurrent solid solution and two-phase reactions upon charge, while a pure two-phase reaction is found upon discharge. A delithiation model based on an ionic blockade layer on the particle surface is proposed to explain the distinct structural transformation mechanisms in nonequilibrium conditions. This study addresses the controversy of why two-phase materials show exemplary kinetics and opens new avenues to understand fundamental processes underlying charge transfer, which will be invaluable for developing the next generation battery materials.

Keywords:

Lithium ion batteries; operando; in situ; coherent X-rays; phase transformation; metastable solid solution