A Binder-Free and Free-Standing Cobalt Sulfide@Carbon Nanotube Cathode Material for Aluminum-Ion Batteries

Rechargeable aluminum-ion batteries (AIBs) are considered as a new generation of large-scale energy-storage devices due to their attractive features of abundant aluminum source, high specific capacity, and high energy density. However, AIBs suffer from a lack of suitable cathode materials with desirable capacity and long-term stability, which severely restricts the practical application of AIBs. Herein, a binder-free and self-standing cobalt sulfide encapsulated in carbon nanotubes is reported as a novel cathode material for AIBs. The resultant new electrode material exhibits not only high discharge capacity (315 mA h g^-1 at 100 mA g^-1 ) and enhanced rate performance (154 mA h g^-1 at 1 A g^-1 ), but also extraordinary cycling stability (maintains 87 mA h g^-1 after 6000 cycles at 1 A g^-1 ). The free-standing feature of the electrode also effectively suppresses the side reactions and material disintegrations in AIBs. The new findings reported here highlight the possibility for designing high-performance cathode materials for scalable and flexible AIBs.