Hydrothermal synthesis of Cu-doped SnSe2 nanostructure for efficient lithium storage

We develop a simple and effective strategy to synthesize Cu-doped SnSe2 nanoflakes composites. The Cu doping plays triple roles in electrode: to buffer the volume change of SnSe2, to improve the conductivity of the electrode system, and to provide a considerable electrochemical catalytic function. From overall performance point of view, the SnSe2/0.4Cu sample exhibits the best lithium-storage performance with both superior cycling stability as well as excellent rate performance. Remarkably, the as-obtained SnSe2/0.4Cu exhibits a high initial reversible capacity of 583 mAh g(-1) at a cycling rate of 0.1 C and 254 mAh g(-1) after 100 cycles, with a capacity retention rate of 45.6%. However, after 100 cycles at 0.1 C, the capacity retention rates are 11.2%, 14.9%, 17.1%, 23.4% and 12.0% for pure SnSe2, SnSe2/0.1Cu, SnSe2/0.2Cu, SnSe2/0.3Cu and SnSe2/0.5Cu electrode, respectively. Besides, at a higher cycling rate of 0.5 C, the SnSe2/0.4Cu electrode can still achieve a high capacity of 165 mAh g(-1), however, the value is just 36 mAh g(-1) for pure SnSe2 electrode. Our work sufficiently evidences the great promotion of the capacity and stability of SnSe2 after a moderate amount of Cu doping as an anode material for lithium ion batteries. The very effective and easy method developed in this study could be extended to other materials to improve their electrochemical performance through metal doping.