Rechargeable aluminum batteries (RABs) are gaining widespread attention for large-scale energy storage applications as a result of their high energy densities, high security, and abundance. The key to sustain the progress of RABs lies in the quest for the proper cathode materials with prominent capacity and reversible cycle life. Herein, we propose a tremella-like VS4 as a cathode material aiming to tackle this problem. Obtained from a morphology modification process, VS4 with a unique nanosheet structure provides sufficient active sites for intercalation and conversion reactions, shortens the transport paths for charge carrier ions, and facilitates the infiltration process for electrolyte. The RAB with the VS4 cathode exhibits excellent electrochemical performance, including outstanding specific capacity (407.9 mAh g-1) and stable cycling performance (∼300 cycles at a high current density). The energy storage mechanism has been comprehensively investigated and is confirmed to be a combination of the intercalation/deintercalation of Al3+ and AlCl4- ions and conversion reaction by various techniques and DFT calculation. Our study not only provides a peculiar and simple strategy for the rational design of metal sulfide cathode materials with high capacity and long-term stability but also proposes a specific energy storage mechanism that guides the development of cathode materials of RABs in the future.
Keywords: energy storage mechanism; morphological modification; rechargeable aluminum battery; sulfide cathode; tremella-like morphology; vanadium tetrasulfide (VS4).