Aluminum-ion storage reversibility in a novel spinel Al2/3Li1/3Mn2O4 cathode for aqueous rechargeable aluminum batteries

Aqueous aluminum batteries (AABs) are a very promising supplementary energy storage device for lithium-ion batteries (LIBs) in large-scale energy storage, but the lack of cathode materials with high energy density and cycle stability greatly limits the development of AABs. Herein, a spinel Al2/3Li1/3Mn2O4 (ALMO) cathode material has been synthesized via an electrochemical conversion reaction using LiMn2O4 (LMO) as the precursor. The ALMO cathode releases a discharge capacity of 151.8 mA h g−1 under a current density of 100 mA g−1 and a capacity retention of 64.1% over 1000 cycles. The full cell fabricated using the ALMO cathode exhibits a high energy density of 183 W h kg−1 and an average operating voltage of about 1.31 V, demonstrating a promising device for large-scale energy storage. The Al ion storage mechanism of the ALMO cathode material is scrutinized by a series of ex-situ analysis techniques, indicating the Al3+ ions can reversibly extract/insert out/into the ALMO cathode material with the oxidation/reduction of Mn. This work is expected to boost the development of the cathode materials for the low-cost and high-performance AABs.