Dual Protection Strategy by Constructing MXene-Coated Cu2Se–Cu1.8Se Heterojunction and CMK-3 Modification for High-Performance Aluminum-Ion Batteries

The fabrication of cathode materials with ideal kinetic behavior is important to improve the electrochemical performance of aluminum-ion batteries (AIBs). Transition metal selenides have the advantages of abundant reserves and high discharge specific capacity and discharge voltage plateau, which makes them a promising material for rechargeable AIBs. It is well-known that the low structural stability and relatively poor reaction kinetics pose a considerable challenge to the development of AIBs. The cubic structure of Cu2Se-Cu1.8Se can adapt to the volume change of the active material during cycling and facilitate the intercalation and deintercalation of chloroaluminate anions in the cathode material. We created a two-fold protection mechanism for AIBs with a CMK-3 modified separator and a Cu2Se-Cu1.8Se heterojunction coated with MXene in order to better mitigate the detrimental impacts. In addition to offering numerous electronic transmission routes, MXene and CMK-3 help prevent the solubilization of active species. This novel design enables the Cu2Se-Cu1.8Se@MXene composite to have a high initial discharge capacity of 705.5 mAh g-1 at 1.0 A g-1. Even after 1500 cycles at 2.0 A g-1, the capacity is still maintained at 225.1 mAh g-1. Furthermore, the reaction mechanism of AlCl4- intercalated/deintercalated into Cu2Se-Cu1.8Se heterojunction is revealed during charge/discharge. This work to construct novel cathode materials has greatly improved the electrochemical performance of AIBs.