Elucidation of the Conversion Reaction of CoMnFeO4 Nanoparticles in Lithium Ion Battery Anode via Operando Studies

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• 作者：Stefan Permien ; Sylvio Indris ; Anna-Lena Hansen ; Marco Scheuermann ; Dirk Zahn ; Ulrich Schürmann ; Gero Neubüser ; Lorenz Kienle ; Eugen Yegudin ; Wolfgang Bensch
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：June 22, 2016
• 年：2016
• 卷：8
• 期：24
• 页码：15320-15332
• 全文大小：859K
• 年卷期：0
• ISSN：1944-8252

文摘

Conversion reactions deliver much higher capacities than intercalation/deintercalation reactions of commercial Li ion batteries. However, the complex reaction pathways of conversion reactions occurring during Li uptake and release are not entirely understood, especially the irreversible capacity loss of Mn(III)-containing oxidic spinels. Here, we report for the first time on the electrochemical Li uptake and release of Co^IIMn^IIIFe^IIIO₄ spinel nanoparticles and the conversion reaction mechanisms elucidated by combined operando X-ray diffraction, operando and ex-situ X-ray absorption spectroscopy, transmission electron microscopy, ⁷Li NMR, and molecular dynamics simulation. The combination of these techniques enabled uncovering the pronounced electronic changes and structural alterations on different length scales in a unique way. The spinel nanoparticles undergo a successive phase transition into a mixed monoxide caused by a movement of the reduced cations from tetrahedral to octahedral positions. While the redox reactions Fe³⁺ ↔ Fe⁰ and Co²⁺ ↔ Co⁰ occur for many charge/discharge cycles, metallic Mn nanoparticles formed during the first discharge can only be oxidized to Mn²⁺ during charge. This finding explains the partial capacity loss reported for Mn(III)-based spinels. Furthermore, the results of the investigations evidence that the reaction mechanisms on the nanoscale are very different from pathways of microcrystalline materials.