Flexible self-standing graphene–Se@CNT composite film as a binder-free cathode for rechargeable Li–Se batteries

• A flexible, self-standing graphene–Se@CNT composite film was synthesized.
• The film cathode delivered a high reversible discharge capacity.
• The performance is mainly attributed to synergistic effects of graphene and CNT.

A flexible, self-standing graphene–Se@CNT composite film has been synthesized by a facile two-step assembly process. The film is directly employed as cathode for rechargeable Li–Se batteries without extra binders and conductive additives. It exhibits much higher reversible capacity and cycling stability (315 mAh g−1 after 100 cycles at 0.1 C) than graphene–Se composite film. The improved electrochemical performance is mainly attributed to the synergistic effects of graphene and CNT, which not only function as a flexible scaffold for strains/stresses release and volume expansion, but also offer a three-dimensional conductive architecture with open channels for electron transfer and Li ion diffusion, as well as strong confinement of soluble polyselenides.