Cation-intercalation and conversion-type cathode materials for rechargeable aluminum batteries

Abstract

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 Al³⁺ 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 (Mo₆S₈) is the only proven intercalation material for RABs with unambiguous evidence, different understandings of the Al³⁺ intercalation mechanism in Mo₆S₈ 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.