Effects of surface compositions and interlayer distance on electrochemical performance of Mo2CTx MXene as anode of Li-ion batteries

Abstract

In this study, highly pure Mo2CTx MXene was made from Mo2Ga2C by hydrothermal method in five different etching solutions (LiF, NaF, KF, NH4F or HF). The as-prepared multi-layer MXene samples were furthered delaminated by tetrabutyl-ammonium hydroxide (TBAOH) to increase the interlayer distance. The c-lattice parameter (c-LP) was increased from 20.3 Å to 23.87 Å. Thereafter, the electrochemical properties of Mo2CTx MXene samples as anode of Li-ion batteries (LIBs) were investigated. The multilayer Mo2CTx MXene made by KF + HCl etching had some residual K+ on the surface and had higher discharge specific capacity (32.7 mA h/g at the current density of 800 mA/g) than the samples made by other etchants. This is because that the residual K+ on MXene surface pillar the multi-layer structure, which provides larger room for Li+ storage and immigration. The Mo2CTx MXene after delamination with the c-LP of 23.87 Å presented a high discharge specific capacity of 239 mA h/g at the current density of 800 mA/g, which was 7.3 times higher than the discharge specific capacity of Mo2CTx MXene before delamination. The final discharge specific capacity was 118.83 mA h/g at 2000 mA/g after 100 cycles. The superior electrochemical performance of delaminated Mo2CTx MXene was attributed to the more easily accessible ion active sites between layers and the lower resistance. Therefore, the increasing of interlayer distance is the main direction to improve the performance of Mo2CTx as anode of LIBs.