Ahn Wook, Seo Min-Ho, Pham Tuan Kiet, Nguyen Quoc Hung, Luu Van Tung, Cho Younghyun, Lee Young-Woo, Cho Namchul, Jeong Soon-Ki
Department of Energy Systems Engineering, Soonchunhyang University, Asan-si, South Korea.
New and Renewable Energy Research Division, Hydrogen and Fuel Cell Center, Korea Institute of Energy Research, Daejeon, South Korea.
Front Chem. 2019 May 28;7:361. doi: 10.3389/fchem.2019.00361. eCollection 2019.
In this work, we show an effective ultrasonication-assisted self-assembly method under surfactant solution for a high-rate capable rGO-wrapped LiNiCoMnO (Ni-rich cathode material) composite. Ultrasonication indicates the pulverization of the aggregated bulk material into primary nanoparticles, which is effectively beneficial for synthesizing a homogeneous wrapped composite with rGO. The cathode composite demonstrates a high initial capacity of 196.5 mAh/g and a stable capacity retention of 83% after 100 cycles at a current density of 20 mA/g. The high-rate capability shows 195 and 140 mAh/g at a current density of 50 and 500 mA/g, respectively. The high-rate capable performance is attributed to the rapid lithium ion diffusivity, which is confirmed by calculating the transformation kinetics of the lithium ion by galvanostatic intermittent titration technique (GITT) measurement. The lithium ion diffusion rate ( ) of the rGO-wrapped LiNiCoMnO composite is . 20 times higher than that of lithium metal plating on anode during the charge procedure, and this is demonstrated by the high interconnection of LiNiCoMnO and conductive rGO sheets in the composite. The unique transformation kinetics of the cathode composite presented in this study is an unprecedented verification example of a high-rate capable Ni-rich cathode material wrapped by highly conductive rGO sheets.
在本工作中，我们展示了一种在表面活性剂溶液下有效的超声辅助自组装方法，用于制备具有高倍率性能的rGO包覆的LiNiCoMnO（富镍正极材料）复合材料。超声处理意味着将团聚的块状材料粉碎成初级纳米颗粒，这对于合成与rGO均匀包覆的复合材料非常有效。该正极复合材料在20 mA/g的电流密度下，首次放电比容量高达196.5 mAh/g，100次循环后容量保持率稳定在83%。在50和500 mA/g的电流密度下，其高倍率性能分别为195和140 mAh/g。这种高倍率性能归因于快速的锂离子扩散率，这通过恒电流间歇滴定技术（GITT）测量计算锂离子的转变动力学得到证实。rGO包覆的LiNiCoMnO复合材料的锂离子扩散速率（ ）为 。在充电过程中，该速率比阳极上锂金属镀层的锂离子扩散速率高20倍，这通过复合材料中LiNiCoMnO与导电rGO片层的高度互连得到证明。本研究中提出的正极复合材料独特的转变动力学是由高导电rGO片层包覆的高倍率富镍正极材料的前所未有的验证实例。
