Guo Ying, Zhang Deyang, Yang Ya, Wang Yangbo, Bai Zuxue, Chu Paul K, Luo Yongsong
Key Laboratory of Microelectronics and Energy of Henan Province, Henan Joint International Research Laboratory of New Energy Storage Technology, Engineering Research Center for MXene Energy Storage Materials of Henan Province, Xinyang Normal University, Xinyang 464000, P. R. China.
Department of Physics, Department of Materials Science & Engineering, and Department of Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, China.
Nanoscale. 2021 Mar 4;13(8):4624-4633. doi: 10.1039/d0nr09228b.
Fe3O4 is one of the promising anode materials in Li-ion batteries and a potential alternative to graphite due to the high specific capacity, natural abundance, environmental benignity, non-flammability, and better safety. Nevertheless, the sluggish intrinsic reaction kinetics and huge volume variation severely limit the reversible capacity and cycling life. In order to overcome these hurdles and enhance the cycling life of Fe3O4, a one-dimensional (1D) nanochain structure composed of 2D Ti3C2-encapsulated hollow Fe3O4 nanospheres homogeneously embedded in N-doped carbon nanofibers (Fe3O4@MXene/CNFs) is designed and demonstrated as a high-performance anode in Li-ion batteries. The distinctive 1D nanochain structure not only inherits the high electrochemical activity of Fe3O4, but also exhibits excellent electron and ion conductivity. The Ti3C2 layer on the Fe3O4 hollow nanospheres forms the primary electron transport pathway and the N-doped carbon nanofiber network provides the secondary transport pathway. At the same time, Ti3C2 flakes partially accommodate the large volume change of Fe3O4 during Li+ insertion/extraction. Density functional theory (DFT) calculations demonstrate that the Fe3O4@MXene/CNFs electrode can efficiently enhance the adsorption of Li+ to promote Li+ storage. As a result of the electrospinning process, self-restacking of Ti3C2 flakes and aggregation of Fe3O4 nanospheres can be prevented resulting in a larger surface area and more accessible active sites on the flexible anode. The Fe3O4@MXene/CNFs anode has remarkable electrochemical properties at high current densities. For example, a reversible capacity of 806 mA h g-1 can be achieved at 2 A g-1 even after 500 cycles, corresponding to an area specific capacity of 1.612 mA h cm-2 at 4 mA cm-2 and a capacity as high as 613 mA h g-1 is retained at 5 A g-1, corresponding to an area capacity of 1.226 mA h cm-2 at 10 mA cm-2. The results indicate that the Fe3O4@MXene/CNFs anode has excellent properties for Li-ion storage.
Fe3O4是锂离子电池中很有前景的负极材料之一，由于其具有高比容量、天然丰度高、环境友好、不可燃以及安全性更好等特点，是石墨的潜在替代品。然而，其缓慢的本征反应动力学和巨大的体积变化严重限制了可逆容量和循环寿命。为了克服这些障碍并提高Fe3O4的循环寿命，设计并展示了一种由均匀嵌入N掺杂碳纳米纤维（Fe3O4@MXene/CNFs）中的二维Ti3C2封装空心Fe3O4纳米球组成的一维（1D）纳米链结构，作为锂离子电池中的高性能负极。独特的一维纳米链结构不仅继承了Fe3O4的高电化学活性，还表现出优异的电子和离子导电性。Fe3O4空心纳米球上的Ti3C2层形成了主要的电子传输途径，而N掺杂碳纳米纤维网络提供了次要的传输途径。同时，Ti3C2薄片部分地适应了Fe3O4在Li+嵌入/脱出过程中的大体积变化。密度泛函理论（DFT）计算表明，Fe3O4@MXene/CNFs电极可以有效地增强Li+的吸附以促进Li+存储。由于静电纺丝过程，可以防止Ti3C2薄片的自重新堆叠和Fe3O4纳米球的聚集，从而在柔性负极上产生更大的表面积和更多可及的活性位点。Fe3O4@MXene/CNFs负极在高电流密度下具有显著的电化学性能。例如，即使在500次循环后，在2 A g-1时仍可实现806 mA h g-1的可逆容量，对应于在4 mA cm-2时的面积比容量为1.612 mA h cm-2，在5 A g-1时仍保留高达613 mA h g-1的容量，对应于在10 mA cm-2时的面积容量为1.226 mA h cm-2。结果表明，Fe3O4@MXene/CNFs负极具有优异的锂离子存储性能。
