MXene interlayer anchored Fe3O4 nanocrystals for ultrafast Li-ion batteries

Balancing energy density and charging rate has been identified as a great challenge for Li-ion batteries (LIBs), which mainly hinges on developing high-performance electrode materials. Herein, we have developed nove Fe3O4@Ti3C2 hybrids, in which the Fe3O4 nanocrystals are well-anchored between Ti 3 C 2 interlayers with the assistance of the synergistic effects of 2D physical confinement and Ti-O-Fe covalent bonds. Such structural design can address the dispersion and volume change of nanocrystals during continuous charge/discharge with the enhancement of structural stability and the exposure of abundant active sites for each component. Meantime, the charge polarization caused by the Ti-O-Fe covalent bonds greatly accelerates the lithiation reaction kinetics and electrons transfer. These advantages endow the Fe3O4@Ti3C2 hybrids with a very high specific capacity of 1172 mAh g(-1) and a rapid charging capability of 366 mAh g(-1) in 66 s. A 90% capacity retention can be maintained even through 1000 cycles at 5 A g(-1). More impressively, we can also achieve a free-standing electrode by a simple vacuum filtering, exhibiting a high areal capacity of 4.2 mAh cm(-2) at 4.4 mg cm(-2) almost without sacrificing gravimetric capacity. The present 2D confined strategy provides a new notion to construct satisfactory electrodes for energy storage. (C) 2019 Elsevier Ltd. All rights reserved.