In the constant race for more efficient Li-ion batteries, extensive research has focused on the design of new, more competitive cathode materials, currently limiting the battery performance. The improvement of cathode materials demands the detailed understanding of the complex structural mechanisms at play during battery operation, that is, when Li⁺ ions are inserted and extracted from the cathode. Moreover, new cathode designs involve more and more disordered/nanosized materials for enhanced Li⁺ cation diffusion and larger specific surfaces. This trend poses new challenges for the structural investigation methods employed, which mostly rely on the periodic and long-range ordered nature of the compounds under study. This is specially the case of the recently discovered nanostructured Li₄Mn₂O₅ high capacity cathode material, which shows record reversible capacities superior to the state-of-the-art Li-Mn-O electrodes and displays a strongly disordered rock salt-type structure. This last feature, mainly due to its synthetic route involving high energy milling, prevented from reaching a full understanding of the lithium exchange mechanism of particular interest in this 3D framework compound. Here, we demonstrate that a thorough description of such a disordered structure can be achieved by a combination of near-edge X-ray absorption spectroscopy and pair distribution function analysis of neutron and X-ray total scattering data, which ultimately lead to the elucidation of the Li cation diffusion pathways.

中文翻译：

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全散射和XANES探测Li ₄ Mn ₂ O ₅高容量阴极中的局部结构和锂扩散途径

在不断寻求更高效的锂离子电池的竞赛中，广泛的研究集中在新型，更具竞争力的正极材料的设计上，目前限制了电池的性能。正极材料的改进要求对电池运行过程中正在起作用的复杂结构机理（即，当Li ⁺离子从正极插入和从负极提取时）的详细理解。此外，新的阴极设计涉及越来越多的无序/纳米尺寸材料，以增强Li ⁺阳离子扩散和较大的比表面积。这种趋势给所采用的结构研究方法带来了新的挑战，这些方法主要取决于所研究化合物的周期性和远距离有序性质。特别是最近发现的纳米结构Li ₄ Mn ₂ O _5的情况高容量阴极材料，其记录的可逆容量优于现有技术的Li-Mn-O电极，并显示出强烈无序的岩盐型结构。最后一个特征（主要是由于其涉及高能研磨的合成路线）无法完全理解此3D框架化合物中特别感兴趣的锂交换机制。在这里，我们证明可以通过近边缘X射线吸收光谱法和中子和X射线总散射数据的成对分布函数分析相结合来对这种无序结构进行详尽的描述，从而最终阐明锂离子的扩散途径。