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The current research on cation-intercalation and conversion-type cathode materials for rechargeable aluminum batteries (RABs) is discussed in this critical review. The experimental evidence for Al 3+ intercalation in transition metal oxides, chalcogenides, MXene, and Prussian blue analogues in both chloroaluminate ionic liquids and aqueous electrolytes is analyzed to identify the true reaction mechanisms. Chevrel phase molybdenum sulfide (Mo 6 S 8 ) is the only proven intercalation material for RABs with unambiguous evidence, different understandings of the Al 3+ intercalation mechanism in Mo 6 S 8 are discussed. For conversion-type cathode materials, the discussion is focused on the conversion mechanism of metal chalcogenides, and the unique reversible oxidation mechanism of sulfur and selenium enabled by the chloroaluminate ionic liquid electrolytes. The reaction mechanisms of organic cathode materials are also discussed. 

Abstract Herein, a self‐charging mechanism of rechargeable aluminum (Al) batteries with Chevrel phase molybdenum sulfide (Mo₆S₈) cathode is reported. The results unambiguously reveal that the self‐charging is a spontaneous disproportionation of Al intercalated Mo₆S₈originated from the dynamic shift of Al between occupied sites during Al intercalating and resting. The theoretical study indicates that the fully Al intercalated Mo₆S₈in the format of Al_4/3Mo₆S₈is kinetically accessible driven by electrochemical overpotential but thermodynamically unstable due to the repulsion between Al³⁺cations. This mechanism is a true self‐charging with no input of any form of energy, thus distinctly superior to the previously reported self‐charging mechanisms. Based on this discovery, a semi‐flow AlMo₆S₈battery is designed and demonstrated with long‐lasting discharge capability and high capacity.