Prussian blue analogs (PBAs) formed with hexacyanide linkers have been studied for decades. The framework crystal structure of PBAs mainly benefits from the six-fold coordinated cyano functional groups. In this study, in-plane tetracyanonickelate was utilized to engineer an organic linker and design a family of four-fold coordinated PBAs (FF-PBAs; Fe ~(2+) Ni(CN) _(4) , MnNi(CN) _(4) , Fe ~(3+) Ni(CN) _(4) , CuNi(CN) _(4) , CoNi(CN) _(4) , ZnNi(CN) _(4) , and NiNi(CN) _(4) ), which showed an interesting two-dimensional (2D) crystal structure. It was found that these FF-PBAs could be utilized as cathode materials of Li-ion batteries, and the Ni/Fe ~(2+) system exhibited superior electrochemical properties compared to the others with a capacity of 137.9 mA h g ~(?1) at a current density of 100 mA g ~(?1) . Furthermore, after a 5000-cycle long-term repeated charge/discharge measurement, the Ni/Fe ~(2+) system displayed a capacity of 60.3 mA h g ~(?1) with a coulombic efficiency of 98.8% at a current density of 1000 mA g ~(?1) . In addition, the capacity of 86.1% was preserved at 1000 mA g ~(?1) as compared with that at 100 mA g ~(?1) , implying a good rate capability. These potential capacities can be ascribed to an in situ reduction of Li ~(+) in the interlayer of Ni/Fe ~(2+) instead of the formation of other compounds with the host material according to ex situ XRD characterization. These specially designed FF-PBAs are expected to inspire new concepts in electrochemistry and other applications requiring 2D materials.
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机译：与六氰化物接头形成的普鲁士蓝类似物（PBA）已有数十年的研究历史。 PBA的骨架晶体结构主要得益于六重配位的氰基官能团。在这项研究中，利用平面四氰基甲酸酯来设计有机连接基并设计四族配位PBA（FF-PBAs; Fe〜（2+）Ni（CN）_（4），MnNi（CN）_家族。 （4），Fe〜（3+）Ni（CN）_（4），CuNi（CN）_（4），CoNi（CN）_（4），ZnNi（CN）_（4）和NiNi（CN ）_（4）），显示出有趣的二维（2D）晶体结构。已发现这些FF-PBA可用作锂离子电池的正极材料，Ni / Fe〜（2+）体系的电化学性能优于其他FF-PBA，容量为137.9 mA hg〜（？1）。电流密度为100 mA g〜（？1）。此外，在进行了5000次循环的长期重复充电/放电测量之后，Ni / Fe〜（2+）系统在电流密度为时显示出60.3 mA hg〜（？1）的容量，库仑效率为98.8％。 1000 mA g〜（？1）。另外，与100mA g〜（Δ1）相比，在1000mA g〜（Δ1）下保持86.1％的容量，这意味着良好的倍率能力。这些潜在的容量可以归因于Ni / Fe〜（2+）中间层中Li〜（+）的原位还原，而不是根据异位XRD表征与主体材料形成其他化合物。这些经过特殊设计的FF-PBA有望在电化学和其他需要2D材料的应用中激发新的概念。
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