Hollow selenium encapsulated into 3D graphene hydrogels for lithium–selenium batteries with high rate performance and cycling stability

Hollow selenium (Se) nanospheres encapsulated within 3D graphene hydrogels were prepared by a two-step solution process and researched as lithium–selenium (Li–Se) battery cathode materials. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the hollow Se nanospheres were coated by homogeneous graphene shells. Thermogravimetric analysis indicated that the Se content in the nanocomposite was about 70%. The nanocomposite, as a cathode, had excellent capacity and cycling stability (343 mA h g−1 after 50 cycles at 0.2C). The remarkable electrochemical performance was due to the high content of Se and the synergistic effects of graphene. It was shown that the structure, comprising hollow Se nanospheres encapsulated into graphene, was beneficial to the practical application of the nanocomposite in Li–Se batteries.