Two-Dimensional Cr-Doped MoO(OH) Nanosheets: A Promising Anode Material for Lithium-Ion Batteries.

α-MoO has gained growing attention as an anode material of lithium-ion batteries (LIBs) because it has a high theoretical specific capacity of 1111 mA h g and unique layer structure. However, the electrochemical reactions of MoO exhibit sluggish kinetics and structural instability caused by pulverization during charge and discharge. Herein, we report new two-dimensional Cr-doped MoO(OH) (doped MoO(OH)) ultrathin nanosheets prepared by a facile hydrothermal process. The formation of the ultrathin nanosheets was clarified by a "doping-adsorption" model. Compared with doped MoO, doped MoO(OH) has larger expanded spacing of the {0 l0} crystal planes for fast Li storage. The electrodes after cycling were investigated by ex situ transmission electron microscopy in combination with X-ray photoelectron spectroscopy analysis to reveal the reversible conversion reaction mechanism of doped MoO(OH) nanosheets. Interestingly, for doped MoO(OH) nanosheet electrodes, it was found that the as-formed intermediate Li MoO nanodots were well-dispersed in the mesoporous amorphous matrix and had an expanded (040) crystal plane after 10 cycles. These unique structural features increased the effective surface of intermediate products Li MoO to react with Li and shortened the diffusion length and thus promoted the electrochemical reactions of doped MoO(OH). Additionally, the presence of Cr also played a critical role in the reversible decomposition of LiO and enhanced specific capacity. When employed as an anode in LIBs, doped MoO(OH) nanosheets show superior reversible capacity (294 mA h g at 10 A g after 2000 cycles). Moreover, the reversible capacity after electrochemical activation is quite stable throughout the cycling, thereby presenting a potential candidate anode material for LIBs.