High aluminum storage performance achieved through Ni2+ doped polyaniline accelerating the conversion of different N structures

Aluminum-ion batteries (AIBs) have garnered significant attention due to their high theoretical capacity, low cost, and high safety. However, finding suitable cathode materials is a challenge due to the complex energy storage mechanism of multivalent ions, which severely limits the practical applications of AIBs. Polyaniline (PANI) is widely used in rechargeable batteries, but its polymerization reaction causes several problems that limit its use in AIBs. To address the issue, PANI material coordinated with Ni 2+ (Ni-PANI) is synthesized by introducing NiCl 2 ·6H 2 O with chemical oxidation, compared with PANI as the cathode materials for AIBs. A better electrochemical performance with Ni-PANI cathode is displayed at a voltage range of 0.1–2.2 V in comparison with PANI. Furthermore, the effects of introducing Ni 2+ are investigated on the reaction mechanism through ex-situ characterization. The coordination of Ni element with N in PANI increases the interaction between the molecular chains of polyaniline, and improves the mechanical strength, thus affecting its cycling stability. At the same time, the conversion between different N structures increases and improves the adsorption of AlCl 2 + , presenting high electrochemical performance of AIBs. A new strategy is presented for the development of organic polymer cathode materials for AIBs.