Zhang Kaiqiang, Lee Tae Hyung, Bubach Bailey, Ostadhassan Mehdi, Jang Ho Won, Choi Ji-Won, Shokouhimehr Mohammadreza
Department of Materials Science and Engineering, Seoul National University Seoul 08826 Republic of Korea
Electronic Materials Center, Korea Institute of Science and Technology (KIST) Seoul 136-791 Republic of Korea
RSC Adv. 2019 Jul 9;9(37):21363-21370. doi: 10.1039/c9ra03975a. eCollection 2019 Jul 5.
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; FeNi(CN), MnNi(CN), FeNi(CN), CuNi(CN), CoNi(CN), ZnNi(CN), and NiNi(CN)), 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 system exhibited superior electrochemical properties compared to the others with a capacity of 137.9 mA h g at a current density of 100 mA g. Furthermore, after a 5000-cycle long-term repeated charge/discharge measurement, the Ni/Fe system displayed a capacity of 60.3 mA h g with a coulombic efficiency of 98.8% at a current density of 1000 mA g. In addition, the capacity of 86.1% was preserved at 1000 mA g as compared with that at 100 mA g, implying a good rate capability. These potential capacities can be ascribed to an reduction of Li in the interlayer of Ni/Fe instead of the formation of other compounds with the host material according to XRD characterization. These specially designed FF-PBAs are expected to inspire new concepts in electrochemistry and other applications requiring 2D materials.
由六氰化物连接基形成的普鲁士蓝类似物（PBAs）已经研究了数十年。PBAs的骨架晶体结构主要得益于六配位的氰基官能团。在本研究中，利用面内四氰基镍酸盐来设计有机连接基，并设计了一系列四配位的PBAs（FF-PBAs；FeNi(CN)、MnNi(CN)、FeNi(CN)、CuNi(CN)、CoNi(CN)、ZnNi(CN)和NiNi(CN)），它们呈现出有趣的二维（2D）晶体结构。研究发现，这些FF-PBAs可用作锂离子电池的阴极材料，与其他体系相比，Ni/Fe体系表现出优异的电化学性能，在100 mA g的电流密度下容量为137.9 mA h g。此外，经过5000次循环的长期重复充放电测试后，Ni/Fe体系在1000 mA g的电流密度下容量为60.3 mA h g，库仑效率为98.8%。另外，与100 mA g时相比，在1000 mA g时容量保持率为86.1%，这意味着其倍率性能良好。根据XRD表征，这些潜在的容量可归因于Ni/Fe层间Li的还原，而不是与主体材料形成其他化合物。这些经过特殊设计的FF-PBAs有望在电化学和其他需要二维材料的应用中激发新的概念。
