Binder-free cobalt sulfide@carbon nanofibers composite films as cathode for rechargeable aluminum-ion batteries

Rechargeable aluminum ion battery (AIB) is considered to be a promising next-generation battery system that can meet future needs for the large scale energy storage, because of its high energy density and low-cost. For the development of long life AIBs, the most urgent challenge is to explore suitable cathode and understand the exact Al charge/discharge mechanism. Herein, a novel binder-free cathode material, CoS2@carbon nanofibers, was synthetized by electrospinning and annealing process. As a result, a specific capacity of ~80 mAh g−1 was maintained after 500 cycles under a current density of 200 mA g−1, which was higher than that of AIBs using a normal CoS2 cathode with binder. Significantly, even at a high current density of 500 mA g−1, the battery can still retain 74 mAh g−1 after 1200 cycles. Furthermore, its working mechanism was explored in combination with ex-situ XRD, XPS and first-principles calculations, which revealed that the reversible conversion reaction of CoS2/AlCo2S4. The novel binder-free CoS2@Carbon nanofibers cathodes are meaningful for the further design of binder-free AIBs with low-cost and long cycling life.