Maisuradze Mariam, Li Min, Mullaliu Angelo, Sorrentino Andrea, Tonti Dino, Passerini Stefano, Giorgetti Marco
Department of Industrial Chemistry "Toso Montanari", University of Bologna, Viale del Risorgimento 4, Bologna, 40136, Italy.
Helmholtz Institute Ulm (HIU), Helmholtzstrasse 11, 89081, Ulm, Germany.
Small Methods. 2023 Nov;7(11):e2300718. doi: 10.1002/smtd.202300718. Epub 2023 Aug 22.
Manganese hexacyanoferrate is a promising cathode material for lithium and sodium ion batteries, however, it suffers of capacity fading during the cycling process. To access the structural and functional characteristics at the nanometer scale, fresh and cycled electrodes are extracted and investigated by transmission soft X-ray microscopy, which allows chemical characterization with spatial resolution from position-dependent x-ray spectra at the Mn L-, Fe L- and N K-edges. Furthermore, soft X-rays prove to show superior sensitivity toward Fe, compare to hard X-rays. Inhomogeneities within the samples are identified, increasing in the aged electrodes, more dramatically in the Li-ion system, which explains the poorer cycle life as Li-ion cathode material. Local spectra, revealing different oxidation states over the sample with strong correlation between the Fe L-edge, Mn L-edge, and N K-edge, imply a coupling between redox centers and an electron delocalization over the host framework.
六氰合铁酸锰是一种很有前景的锂和钠离子电池阴极材料，然而，它在循环过程中会出现容量衰减。为了在纳米尺度上研究其结构和功能特性，提取了新鲜的和循环后的电极，并通过透射软X射线显微镜进行研究，该显微镜可以通过锰L边、铁L边和氮K边的位置相关X射线光谱进行具有空间分辨率的化学表征。此外，与硬X射线相比，软X射线对铁表现出更高的灵敏度。识别出样品中的不均匀性，在老化电极中增加，在锂离子体系中更明显，这解释了其作为锂离子阴极材料较差的循环寿命。局部光谱揭示了样品上不同的氧化态，铁L边、锰L边和氮K边之间有很强的相关性，这意味着氧化还原中心之间存在耦合以及电子在主体框架上的离域。
