Jerng Sung Eun, Chang Barsa, Shin Hyuksoo, Kim Hyuntae, Lee Taegeun, Char Kookheon, Choi Jang Wook
School of Chemical and Biological Engineering and Institute of Chemical Processes, Seoul National University, Seoul 08826, Republic of Korea.
ACS Appl Mater Interfaces. 2020 Mar 4;12(9):10597-10606. doi: 10.1021/acsami.0c00643. Epub 2020 Feb 19.
The high specific capacity in excess of 200 mAh g and low dependence on cobalt have enhanced the research interest on nickel-rich layered metal oxides as cathode materials for lithium-ion batteries for electric vehicles. Nonetheless, their poor cycle life and thermal stability, resulting from the occurrence of cation mixing between the transition-metal (TM) and lithium ions, are yet to be fully addressed to enable the widespread and reliable use of these materials. Here, we report a two-dimensional (2D) pyrazine-linked covalent organic framework (namely, Pyr-2D) as a coating material for nickel-rich layered cathodes to mitigate unwanted TM dissolution and interfacial reactions. The Pyr-2D coating layer, especially the 2D planar morphology and conjugated atomic configuration of Pyr-2D, protects the electrode surface effectively during cycling without sacrificing the electric conductivity of the host material. As a result, Pyr-2D-coated nickel-rich layered cathodes exhibited superior cyclability, rate performance, and thermal stability. The present study highlights the potential ability of 2D conjugated covalent organic frameworks to improve the key electrochemical properties of emerging battery electrodes.
超过200 mAh g的高比容量以及对钴的低依赖性，增强了人们对富镍层状金属氧化物作为电动汽车锂离子电池阴极材料的研究兴趣。尽管如此，由于过渡金属（TM）离子与锂离子之间发生阳离子混合，导致它们的循环寿命和热稳定性较差，这一问题仍有待充分解决，以便能够广泛且可靠地使用这些材料。在此，我们报道了一种二维（2D）吡嗪连接的共价有机框架（即Pyr-2D）作为富镍层状阴极的涂层材料，以减轻不必要的TM溶解和界面反应。Pyr-2D涂层，特别是Pyr-2D的二维平面形态和共轭原子构型，在循环过程中有效地保护了电极表面，同时又不牺牲主体材料的电导率。因此，涂覆Pyr-2D的富镍层状阴极表现出优异的循环性能、倍率性能和热稳定性。本研究突出了二维共轭共价有机框架改善新兴电池电极关键电化学性能的潜在能力。
