Terminal Group-Oriented Self-Assembly to Controllably Synthesize a Layer-by-Layer SnSe 2 and MXene Heterostructure for Ultrastable Lithium Storage.

Heterostructured materials integrate the advantages of adjustable electronic structure, fast electron/ions transfer kinetics, and robust architectures, which have attracted considerable interest in the fields of rechargeable batteries, photo/electrocatalysis, and supercapacitors. However, the construction of heterostructures still faces some severe problems, such as inferior random packing of components and serious agglomeration. Herein, a terminal group-oriented self-assembly strategy to controllably synthesize a homogeneous layer-by-layer SnSe 2 and MXene heterostructure (LBL-SnSe 2 @MXene) is designed. Benefitting from the abundant polar terminal groups on the MXene surface, Sn 2+ is induced into the interlayer of MXene with large interlayer spacing, which is selenized in situ to obtain LBL-SnSe 2 @MXene. In the heterostructure, SnSe 2 layers and MXene layers are uniformly intercalated in each other, superior to other heterostructures formed by random stacking. As an anode for lithium-ion batteries, the LBL-SnSe 2 @MXene is revealed to possess strong lithium adsorption ability, the small activation energy for lithium diffusion, and excellent structure stability, thus achieving outstanding electrochemical performance, especially with high specific capacities (1311 and 839 mAh g -1 for initial discharge and charge respectively) and ultralong cycling stability (410 mAh g -1 at 5C even after 16 000 cycles). This work conveys an inspiration for the controllable design and construction of homogeneous layered heterostructures.