The search for efficient anodic electrochromic materials is essential to the development of electrochromic devices, such as smart windows. Magnetron-sputtered lithium-nickel-tungsten mixed oxides are good candidates to tackle this issue; however, they display a complicated microstructure, making it difficult to pinpoint the origin of their electro-optical properties. Herein, by exploring the Li₂O–NiO–WO₃ phase diagram, we obtained a new phase, Li₂Ni₂W₂O₉, that crystallizes in the orthorhombic Pbcn space group. This material can reversibly uptake/release 0.75 Li⁺ (31 mA h·g^–1) when cycled between 2.5 and 5.0 V versus Li⁺/Li. Moreover, through operando optical microscopy, we show that this new phase is electrochromic, and crucial information can be accessed about the diffusion-limited insertion of lithium at the single-particle scale. This study sets the ground for future syntheses of electrochemically active materials crystallizing in the ramsayite structure and details how the electrochromic properties of battery materials can be used to shed some light on their electrochemical mechanisms.

中文翻译：

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基于可逆嵌锂的电致变色类刚玉化合物：Li2Ni2W2O9

寻找高效的阳极电致变色材料对于电致变色设备（例如智能窗）的开发至关重要。磁控溅射锂镍钨混合氧化物是解决这一问题的良好候选者；然而，它们显示出复杂的微观结构，因此很难确定其电光特性的来源。在此，通过探究 Li ₂ O–NiO–WO ₃相图，我们获得了一个新相 Li ₂ Ni ₂ W ₂ O ₉，它在正交晶系Pbcn空间群中结晶。这种材料可以可逆地吸收/释放 0.75 Li ⁺ (31 mA h·g ^–1) 当在 2.5 和 5.0 V 之间循环时，相对于 Li ⁺ /Li。此外，通过原位光学显微镜，我们表明这个新相是电致变色的，并且可以获取有关锂在单粒子尺度上的扩散限制插入的关键信息。这项研究为未来合成在拉姆齐石结构中结晶的电化学活性材料奠定了基础，并详细介绍了如何利用电池材料的电致变色特性来阐明其电化学机制。