In view of abundant resource, low cost, and high safety performance, aluminum-ion batteries have been considered as a new-style storage approach for prospective energy supply. In this work, NiCo2S4 nanosheet with hexagonal architectures is synthesized through two-step hydrothermal process. When applied as a cathode material for rechargeable aluminum-ion battery, NiCo2S4 hexagonal nanosheet delivers a high initial specific capacity of 165.08 mA h g(-1) at 100 mA g(-1), and possesses an excellent cycling stability with a reversible capacity of 143.81 mA h g(-1) and coulombic efficiency of above 90% after 100 cycles. More importantly, the redox reaction mechanism of the NiCo2S4 cathode for aluminum-ion batteries reveals that Ni3+ and Co3+ in NiCo2S4 cathode are respectively converted to Ni2+ (NiS) and Co2+ (CoS) during the discharge process. Such NiCo2S4 nanosheet with hexagonal architectures would be of great significance for future applications for aluminum-ion batteries. (C) 2018 The Electrochemical Society.